Title:
Apparatus and method for braking folding sheet material
Kind Code:
A1


Abstract:
Preferred embodiments of the present invention have brake heads located at a circumferential position with respect to a folding roll in a web folder or interfolder. In some preferred embodiments, the brake heads and vacuum lines running thereto are stationary with respect to the folding roll and are recessed within circumferential folding roll grooves permitting folding roll rotation relative to the brake heads and lines. The brake heads are preferably located downstream of the nip between the rolls and upstream of a point at which vacuum is cut off to vacuum ports in the roll to release the web material being folded. When vacuum is supplied to the brake heads, passing web material is attracted thereto and is thereby braked. Preferably, the times at which vacuum is drawn through ports in the brake heads to brake the passing web can be controlled by a valve connected to the vacuum lines.



Inventors:
Couturier, Dennis P. (Washburn, WI, US)
Application Number:
09/812245
Publication Date:
10/03/2002
Filing Date:
03/19/2001
Assignee:
COUTURIER DENNIS P.
Primary Class:
International Classes:
B65H23/24; B65H45/101; (IPC1-7): B65H33/04
View Patent Images:
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Primary Examiner:
TAWFIK, SAMEH
Attorney, Agent or Firm:
MICHAEL BEST & FRIEDRICH LLP (Mke) (MILWAUKEE, WI, US)
Claims:

I claim:



1. A braking device for a vacuum roll having a roll surface upon which web material is conveyed, comprising: a vacuum source; a brake head having: a brake head position at a circumferential location with respect to the vacuum roll; and at least one vacuum port defined in the brake head, the brake head located substantially beneath the roll surface and over which the web material can pass; and a vacuum line, the vacuum source and the brake head in fluid communication with one another via the vacuum line.

2. The braking device as claimed in claim 1, wherein the vacuum line passes to and below the roll surface at a circumferential position of the roll and passes at least partially around the roll substantially beneath the roll surface.

3. The braking device as claimed in claim 1, wherein the vacuum roll has a circumferential groove defined therein within which the brake head is received.

4. The braking device as claimed in claim 3, wherein the vacuum line runs from the brake head at least partially around the roll substantially beneath the roll surface.

5. The braking device as claimed in claim 1, further comprising a rotary valve coupled to the vacuum line, the rotary valve configured and arranged to open and close the vacuum line in substantial synchronicity with vacuum roll rotation.

6. The braking device as claimed in claim 5, wherein the rotary valve has a plurality of apertures, the valve rotatable in substantial synchronicity with the vacuum roll to bring the plurality of apertures successively into fluid communication with and between the vacuum line and vacuum source.

7. The braking device as claimed in claim 1, wherein the vacuum line is coupled to the brake head and thereby at least partially supports the brake head in the brake head position.

8. The braking device as claimed in claim 1, further comprising: a vacuum port in the vacuum roll through which vacuum is supplied to the roll surface; and a sensor positioned to sense vacuum pressure of vacuum supplied to the vacuum port.

9. The braking device as claimed in claim 8, further comprising a valve coupled to the sensor and between the vacuum source and the brake head, wherein the valve is periodically actuatable between opened and closed positions at times determined at least partially by pressure sensed by the sensor.

10. The braking device as claimed in claim 9, wherein the valve is actuated by a motor driving the valve and wherein the intervals are adjustable by temporarily adjusting motor speed.

11. The braking device as claimed in claim 9, further comprising a valve coupled to the sensor, to the brake head, and to the vacuum source, wherein the valve has a valve timing in which the valve is periodically opened and closed to open and close fluid communication between the vacuum source and brake head, wherein the valve timing is adjustable responsive to the sensor.

12. A folding roll for use in a folding apparatus for folding web material, the folding roll comprising: a brake head having at least one vacuum port defined therein; a folding roll surface for conveying web material, the folding roll rotatable about a folding roll axis to rotate the folding roll surface with respect to the brake head; a vacuum source; and a vacuum line, the at least one vacuum port in the brake head in fluid communication with the vacuum source via the vacuum line; wherein the brake head is sufficiently recessed within the folding roll surface to permit web material conveyed on the folding roll surface to pass over the brake head.

13. The folding roll as claimed in claim 12, further comprising a circumferential groove in the folding roll surface within which the brake head is received.

14. The folding roll as claimed in claim 12, further comprising a circumferential groove in the folding roll surface within which the vacuum line is received.

15. The folding roll as claimed in claim 12, further comprising a vacuum port defined in the folding roll surface and rotatable with the folding roll surface for transmitting vacuum to the folding roll surface.

16. The folding roll as claimed in claim 12, wherein the brake head is substantially stationary in a circumferential location with respect to the folding roll.

17. The folding roll as claimed in claim 16, wherein the vacuum line is coupled to the brake head and at least partially supports the brake head in the circumferential location.

18. The folding roll as claimed in claim 12, further comprising a valve coupled to the vacuum line for opening and closing vacuum supplied to the brake head in substantial synchronicity with folding roll rotation.

19. The folding roll as claimed in claim 18, wherein the valve is a rotary valve.

20. The folding roll as claimed in claim 18, further comprising: a vacuum port in the folding roll surface for transmitting vacuum to the folding roll surface; and a sensor positioned to detect vacuum pressure transmitted to the folding roll via the vacuum port.

21. The folding roll as claimed in claim 20, wherein the valve is timed to open and close in substantial synchronicity with folding roll rotation, and wherein valve timing is adjustable responsive to vacuum pressures detected by the sensor.

22. The folding roll as claimed in claim 21, further comprising a motor coupled to the valve for driving the valve, wherein the motor is coupled to the sensor, and wherein valve timing is adjustable by temporarily adjusting motor speed responsive to vacuum pressures detected by the sensor.

23. The folding roll as claimed in claim 18, wherein the valve is adjustable to open and close at different times in substantial synchronicity with folding roll rotation.

24. A method of braking a sheet of folding web material, comprising: conveying web material upon a surface of a rotating roll in a rotational direction; retaining the web material against the surface of the rotating roll while conveying the web material thereon; passing the web material over a brake head at least partially recessed within the roll; drawing the web material toward the brake head to exert a braking force upon the web in a direction substantially opposite to the first rotational direction; and releasing the web material from the surface of the rotating roll.

25. The method as claimed in claim 24, wherein retaining the web material against the surface of the rotating roll includes supplying vacuum through a vacuum port defined in the surface of the rotating roll to exert a vacuum force upon the web material.

26. The method as claimed in claim 25, wherein drawing the web material toward the brake head includes supplying vacuum to a vacuum port defined in the brake head to exert a vacuum force upon the web material.

27. The method as claimed in claim 26, further comprising: detecting vacuum pressure of vacuum supplied to the vacuum port defined in the surface of the rotating roll; and adjusting when vacuum is supplied to the vacuum port defined in the brake head based at least partially upon the vacuum pressure detected.

28. The method as claimed in claim 24, wherein releasing the web material includes reducing vacuum supply to the surface of the rotating roll to reduce vacuum force exerted upon the web material.

29. The method as claimed in claim 24, wherein drawing the web material toward the brake head occurs at least partially while releasing the web material from the surface of the rotating roll.

30. The method as claimed in claim 24, wherein drawing the web material toward the brake head begins after releasing the web material from the surface of the rotating roll has begun.

31. The method as claimed in claim 24, wherein drawing the web material toward the brake head begins after releasing the web material from the surface of the rotating roll is substantially complete.

32. The method as claimed in claim 24, wherein drawing the web material toward the brake head begins before releasing the web material from the surface of the rotating roll has begun.

33. The method as claimed in claim 24, wherein releasing the web material from the surface of the rotating roll is substantially complete before drawing the web material toward the brake head is substantially complete.

34. The method as claimed in claim 24, wherein releasing the web material from the surface of the rotating roll is substantially complete after drawing the web material toward the brake head is substantially complete.

35. The method as claimed in claim 24, further comprising opening and closing a valve to periodically supply vacuum to the brake head to draw the web material toward the brake head.

36. The method as claimed in claim 35, wherein the valve is a rotary valve.

37. The method as claimed in claim 35, wherein the valve is opened and closed in substantial synchronicity with rotation of the roll.

38. The method as claimed in claim 35, wherein retaining the web material against the surface of the rotating roll includes supplying vacuum to the surface of the rotating roll, the method further comprising: sensing pressure of vacuum supplied to the surface of the rotating roll; and adjusting timing of valve opening and closing based upon the pressure sensed.

39. A method of folding web material, comprising: rotating a vacuum roll in a first direction; exerting a suction force through a surface of the vacuum roll and upon the web material; drawing the web over a brake head that is substantially stationary with respect to the roll; reducing the suction force downstream of the brake head after drawing the web over the brake head; and exerting a suction force through the brake head and upon the web material drawn thereover to brake the web material in a direction substantially opposite to the first direction.

40. The method as claimed in claim 39, wherein the brake head is at least partially recessed within a groove in the vacuum roll.

41. The method as claimed in claim 39, further comprising supplying vacuum to the brake head via a vacuum line.

42. The method as claimed in claim 41, wherein the vacuum line is at least partially recessed beneath the surface of the vacuum roll.

43. The method as claimed in claim 39, wherein exerting a suction force through the brake head includes opening a valve to supply vacuum to the brake head.

44. The method as claimed in claim 43, wherein the valve opens and closes in substantial synchronicity with rotation of the vacuum roll.

45. The method as claimed in claim 44, further comprising: sensing pressure of vacuum exerted through the surface of the vacuum roll; and adjusting timing of valve opening and closing based upon pressure sensed.

46. The method as claimed in claim 43, wherein the valve is a rotary valve.

47. The method as claimed in claim 39, wherein reducing the suction force downstream of the brake head occurs at least partially during exertion of the suction force through the brake head.

48. The method as claimed in claim 39, wherein exerting the suction force through the brake head occurs after reducing the suction force downstream of the brake head.

49. The method as claimed in claim 39, wherein reducing the suction force downstream of the brake head includes substantially eliminating the suction force downstream of the brake head.

50. The method as claimed in claim 39, further comprising: supplying vacuum to the surface of the vacuum roll to exert the suction force through the surface of the vacuum roll; sensing vacuum pressure supplied to the surface of the vacuum roll; and timing exertion of suction force through the brake head at least partially upon the vacuum pressure sensed.

51. The method as claimed in claim 39, further comprising: maintaining the suction force through the brake head for a period of time; and then reducing the suction force through the brake head to stop braking the web material.

Description:

FIELD OF THE INVENTION

[0001] The present invention relates to systems and methods for folding material, and more specifically to systems and methods for controlling folding operations of material in sheet form.

BACKGROUND OF THE INVENTION

[0002] Advancements in web processing technology have enabled web materials to be processed at much higher speeds than ever before. As a result, relatively new problems have arisen relating to the control of web material at high speeds. In web folding and interfolding equipment, a challenging problem regarding high web speeds can occur as the folded or interfolded web is being stacked. Specifically, the inertia of even a relatively lightweight web material can be significant enough to generate web stopping problems when the folded web is brought to a stop as it is stacked.

[0003] The problem just described is best understood with reference to FIGS. 1 and 2, which show the relevant area of a conventional web interfolding machine. As is well known to those skilled in the art, conventional interfolders typically have a pair of rolls 1, 2 mounted for rotation adjacent to one another and defining a nip 3 therebetween. Streams of web material W are brought together by being conveyed on the surfaces of the rolls 1, 2, which counter-rotate with respect to one another as indicated by the arrows on the rolls 1, 2. As used herein and in the appended claims, the term “surface” is not restricted to a continuous or unbroken surface, but includes in its meaning the collective surfaces defining the exterior of the roll upon which the streams of web material W are conveyed. Also, reference to areas or elements “above” or “below” such a surface does not necessarily indicate that the areas or elements are over or under the surface, but only that they are at a higher or lower elevation than that of the surface.

[0004] Usually (but not necessarily), the streams of web material W are held against the rolls 1, 2 by vacuum force exerted through the surfaces of the rolls 1, 2. Specifically, the surfaces of the rolls 1, 2 are typically provided with vacuum ports which are supplied with vacuum from a vacuum source. The vacuum source can be a vacuum pump or other vacuum device connected to the rolls 1, 2. The vacuum source is commonly attached at one or both ends of the rolls 1, 2, although other manners of supplying vacuum to the rolls 1, 2 exist. A rotary valve or other conventional vacuum porting structure or device on one or both ends of the rolls 1, 2 permits the rolls 1, 2 to rotate while vacuum is selectively ported to desired portions of the rolls 1, 2.

[0005] In most common arrangements such as that illustrated in FIGS. 1 and 2, multiple vacuum lines 4, 5 run in the vacuum rolls 1, 2, and are in fluid communication with vacuum ports 6, 7 in the surfaces of the vacuum rolls 1, 2. By operating the vacuum valve or other such vacuum porting structure or device connected to the rolls 1, 2, vacuum can be supplied to any combination of vacuum lines 4, 5 and corresponding vacuum ports 6, 7 desired. Such controlled vacuum supply is useful for manipulating the web material W (e.g., to “grasp” the web material fed to the roll 1, 2 at one desired circumferential location and to “release” the web material from the roll 1, 2 at another desired circumferential location). In the prior art embodiment shown in FIGS. 1 and 2, web material W is fed to each of the rolls 1, 2 at desired circumferential locations, at which vacuum is preferably already supplied to one or both roll surfaces to hold one or both webs W against the rolls 1, 2.

[0006] The web material W on each roll 1, 2 is preferably cut in any conventional manner into individual items to be folded and stacked. For example, the web material W can be cut by retractable blades in the rolls 1, 2, by being pressed in the nip 3 by cooperating elements on the rolls 1, 2, and the like. After being conveyed through the nip 3 preferably while being held to the surface of the rolls 1, 2 by at least one vacuum port 6, 7, vacuum to the roll surface 8 of a first vacuum roll 1 is preferably cut off, thereby permitting the second vacuum roll 2 to retain both streams of web material W against its surface. As shown in FIGS. 1 and 2, both streams of web material W are then conveyed to a point where the web streams W are adjacent to the surface upon which the web material W is to be stacked or to a stack of earlier-stacked product. At about this time, the vacuum supplied to that surface 9 of the second vacuum roll 2 carrying both web streams W is preferably cut off, thereby permitting the web material W to drop upon the stack building surface or stack of web material W. As the next break, perforation, or other location in the web material W (where the next fold is to be made) passes through the nip 3, vacuum to the roll surface 9 of the second vacuum roll 2 is instead preferably cut off, thereby permitting the first vacuum roll 1 to retain both streams of web material W against its surface 8 downstream of the nip 3.

[0007] Further rotation of the first vacuum roll 1 brings the web material adjacent to the surface upon which the web material W is to be stacked or to a stack of earlier-stacked product. At about this time, the vacuum supplied to that surface 9 of the first vacuum roll 1 is cut off, thereby permitting the web material to drop upon the stack building surface or stack of web material W to complete the fold. During this second stage of motion, it is desirable to hold the first portion of the web 10 (laid earlier) while the second portion of the web 11 is laid for purposes of better web control. To perform this task, count fingers 12, 13 are often mounted for reciprocating motion into and out of contact with the stack being built to hold alternating sides of the stack down. The separation fingers 12, 13 are typically mounted for reciprocating rotation about respective pivots, although other types of separation finger motion are possible. In FIGS. 1 and 2, one finger 12 is shown rotated to a position in which it is holding the first portion 10 of the web W while the second portion 11 of the web W is being laid. The other finger 13 is shown in a retracted position in FIG. 1 (ready for performing this same function on the opposite side of the stack in the next fold) and in a descending position in FIG. 2. Although much less common, other conventional mechanisms and elements for holding the web upon the stack during folding (for better web control) are possible.

[0008] At low speeds, the above-mentioned folding operations work adequately well to produce a quality stack of web product. However at higher speeds, the web material W being conveyed to the stack building surface or to the stack being built has higher inertia and therefore may not stop in a desired location when the vacuum ports 6, 7 moved downstream of the nip 3 release the web material W. Specifically, the folded areas of the web material W (e.g., at the edges of the stack of web product being built) can experience web rollout, in which the web material released from the vacuum roll surfaces 8, 9 downstream of the nip 3 shoots past its proper stacking location, continuing in a trajectory substantially tangent or adjacent to the roll 1, 2. Such web rollout is shown in the right side of the built stack of web product shown in FIG. 2.

[0009] Web rollout generates an unpleasant appearance for the final product, can cause product damage, increases the potential for equipment misfeeds and jams, and can even result in damage to the folding or interfolding machine. Accordingly, conventional folding and interfolding equipment is run at lower speeds than would otherwise be possible, thereby reducing product output and system productivity.

[0010] For several reasons, the web control problem described above has long remained a performance-limiting factor for web folding and interfolding equipment. First, the area within which this problem occurs is typically relatively small. The ability to install devices, structure, or elements within this area to address the problem is therefore very limited. Also, the area within which this problem occurs is usually substantially enclosed by moving elements, thereby making access to the area difficult regardless of the devices, structure, or elements used. With reference for example to the prior art interfolder illustrated in FIGS. 1 and 2, the subject area is substantially enclosed by the rotating rolls 1, 2 on the top and sides and by the moving stack-building surface or stack being built below.

[0011] In addition to the problems of space and access just described, conventional systems do not provide any manner in which folding web material can be slowed, restrained, or blocked from rolling out of a desired folded position when processed at high speeds. Such interaction with the web material W is made more difficult because the web W is on or closely adjacent to the surfaces of the rolls 1, 2 and is conveyed thereby at high speed until immediately before it is released to the stack building surface or stack below. Also, because the necessary braking forces upon the web W vary depending upon the type of web (e.g., weight, thicknesses, porosity, etc.) and upon the speed of the web W, further design difficulties arise in attempting to make the braking device, structure, or element adjustable.

[0012] To be practical and cost-effective, a solution to the problem of high-speed web roll-out should be simple and easy to install, and could preferably be readily employed even in existing folding and interfolding machinery. Prior to the present invention, such a relatively inexpensive and simple solution had not been discovered.

[0013] In light of the above design requirements and limitations, a need exists for an apparatus and method for braking folding sheet material which can be used in relatively small and enclosed areas, can be adjusted to brake different web materials running at different web speeds, is relatively inexpensive, does not add significant complexity to web processing machinery, and can be installed in existing web folders and interfolders. Each preferred embodiment of the present invention achieves one or more of these results.

SUMMARY OF THE INVENTION

[0014] The present invention employs braking action upon passing web material to slow the web material during the creation of a fold or interfold. By exerting a braking force countering the inertial forces of a web as it is being folded or interfolded, fold or interfold “roll-out” is prevented and the resulting stack of material has a regular, more uniform appearance.

[0015] The present invention can be employed in any system or apparatus used for folding web material. Therefore, while the disclosure of the present invention is presented with reference to use in an interfolder, this application is presented by way of example only. Also, the term “web” is used herein and in the appended claims with reference to the material being folded. The present invention can be employed in any equipment operating to fold any type of sheet material. Although often used to refer to porous or semi-porous paper product in sheet form (e.g., napkin stock, paper toweling, tissue paper, toilet paper, and the like), the term “web” as used herein and in the appended claims therefore refers to any material that is found in sheet form and that can be folded. Examples of such material include without limitation fabric, textiles, foils, synthetic sheeting, and the like.

[0016] Preferred embodiments of the present invention have one or more brake heads located at a circumferential position with respect to a folding roll in a web folder or interfolder. The brake heads are preferably stationary or substantially stationary with respect to the folding roll. Also preferably, the brake heads are recessed within circumferential grooves or other recesses within the folding roll to permit the webs being folded or interfolded to pass without interference over the brake heads when no braking is being performed. The grooves or other recesses permit rotation of the folding roll relative to the stationary brake heads.

[0017] Vacuum is preferably supplied to the brake heads by respective vacuum lines. Like the brake heads, the vacuum lines are preferably recessed within the folding roll to avoid interference with passing web material. To this end, the vacuum lines can also be recessed within circumferential grooves in the folding roll and can pass around a portion of the folding roll to a position where the vacuum lines exit the folding roll and run to a vacuum source.

[0018] The folding roll is preferably a vacuum roll having a plurality of vacuum ports on the conveying surface thereof. As the folding roll rotates, the vacuum ports are rotated through a nip between the folding roll and an adjacent folding roll, and then through a distance in which a fold in the web material is created. At the end of this distance, vacuum to the vacuum ports passing therethrough is reduced (preferably to an extent where no vacuum is exerted through the vacuum ports), thereby releasing the folding web to a stack building surface or stack of already-folded web material. Control of vacuum to the vacuum ports is performed in any conventional manner, whereby vacuum is supplied to ports passing a desired sector of the roll's circumference and is cut off to ports in adjacent sectors.

[0019] The brake heads are preferably located between the nip of the roll and the point at which vacuum is reduced (e.g., cut off) to the vacuum ports in the roll to release the web material being folded. The brake heads can be supported in their locations by the vacuum lines, which can be made of a resilient material capable of bearing the weight of the brake heads. Preferably, the brake heads have one or more vacuum ports through which vacuum can be drawn to attract passing web and thereby to exert a braking force thereon. To control the time at which vacuum is drawn through the vacuum ports in the brake head, a valve is preferably connected to the vacuum lines supplying vacuum to the brake heads. The valve is preferably timed to rotation of the roll so that the valve is open when braking action is desired and is closed when braking action is not desired. More specifically, at or near the time vacuum is reduced to those roll vacuum ports conveying the web material past the nip, vacuum is supplied to the brake heads to brake the web material. Vacuum is preferably supplied to the brake heads temporarily, and is supplied for a long enough time to slow the web material but not so long as to interfere with the fold being created.

[0020] The valve can take a number of different conventional forms, but most preferably is a rotary valve driven by a motor having a speed that is controllable (e.g., a servo motor). In highly preferred embodiments, the motor drives the valve in synchronicity or substantial synchronicity with the corresponding folding roll. The valve preferably has one or more apertures therein that are rotated into fluid communication with an upstream vacuum source and the downstream vacuum lines leading to the brake heads. In this manner, the valve regularly and temporarily provides vacuum to the brake heads for regular and temporary braking actions synchronously or substantially synchronously with vacuum cutoff to the roll ports as described above.

[0021] In some preferred embodiments, the timing of the valve is adjustable to change the braking time of the brake heads relative to the release time of the roll vacuum ports. This is useful particularly for making operational adjustments, where different web materials are processed that respond differently to vacuum brakings, and where different web speeds call for different braking times. Most preferably, one or more pressure sensors are mounted to detect the pressure in the vacuum lines, and respond to a reduced detected pressure (e.g., vacuum being reduced to release the web in a fold) by sending a signal to the valve motor controller. If the valve is being opened too early or too late to generate braking earlier or later than desired, the valve motor controller can then automatically adjust the valve to a correct timing.

[0022] Preferably, vacuum lines, brake heads, and a valve substantially the same as those described above are provided on another folding roll adjacent to the first folding roll. Both rolls and their associated braking assemblies are preferably operated in an alternating fashion to exert braking force upon web material on one roll in one fold and then to exert braking force upon the web material on another roll in the next fold. Accordingly, braking actions can be performed for each fold made as a stack of web material is being built.

[0023] Because the brake heads and vacuum lines can be recessed within existing folding roll grooves used for packer fingers (commonly used in interfolding and folding equipment), the brake heads and vacuum lines of the present invention can be installed on existing folding and interfolding equipment with relative ease. The brake heads and vacuum lines take up little space in existing equipment, especially in those embodiments in which they are recessed within the folding rolls. Also, the present invention does not add significant complexity to folding and interfolding equipment, and presents a cost-effective manner in which such equipment can be run at faster speeds for increased product output without sacrificing product quality.

[0024] More information and a better understanding of the present invention can be achieved by reference to the following drawings and detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention is further described with reference to the accompanying drawings, which show a preferred embodiment of the present invention. However, it should be noted that the invention as disclosed in the accompanying drawings is illustrated by way of example only. The various elements and combinations of elements described below and illustrated in the drawings can be arranged and organized differently to result in embodiments which are still within the spirit and scope of the present invention. In the drawings, wherein like reference numerals indicate like parts:

[0026] FIG. 1 is an elevational end view of a portion of a web interfolder according to the prior art, shown in the process of making a web fold;

[0027] FIG. 2 is an elevational end view of the web interfolder illustrated in FIG. 1, shown at the end of making a fold;

[0028] FIG. 3 is a perspective view of a portion of a web interfolder according to a preferred embodiment of the present invention, with only one of two vacuum rolls and only two of several vacuum line and brake head assemblies shown for clarity;

[0029] FIG. 4 is an elevational end view of a the web interfolder illustrated in FIG. 3, shown with both vacuum rolls;

[0030] FIG. 5 is an enlarged perspective view of the vacuum valve illustrated in FIG. 4;

[0031] FIG. 6 is a graph illustrating the timing relationship between vacuum supplied to the vacuum roll and vacuum supplied to the brake head according to a preferred embodiment of the present invention;

[0032] FIG. 7 is a perspective cross sectional view of a vacuum line and brake head assembly shown in FIG. 3, taken along lines 7-7 of FIG. 3; and

[0033] FIG. 8 is a perspective cross sectional view of the vacuum roll illustrated in FIG. 3, taken along lines 8-8 of FIG. 3.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0034] With reference to FIGS. 3 and 4, a preferred application of the present invention is in a web interfolding machine, although numerous other applications exist. As described above, an interfolder typically has two adjacent rolls 20, 22 mounted for counter-rotation about their respective axes 24, 26. The rolls 20, 22 are driven for such rotation in any conventional manner, such as by one or more motors (not shown) drivably connected to the rolls 20, 22 by belts, gearboxes, and the like. To interfold two webs of material W′, W″, each web W′, W″ is conveyed to a respective roll 20, 22 in any conventional manner and is thereafter conveyed by the rotating roll 20, 22 into the nip 24 between the rolls 20, 22. In other embodiments, both webs W′, W″ are conveyed directly to the nip 24 rather than being conveyed into the nip 24 upon the surfaces 26, 28 of the rolls 20, 22.

[0035] To better control the webs W′, W″ as they are conveyed to the nip 24, the rolls 20, 22 are preferably provided with one or more vacuum ports 30, 32 in the surfaces 26, 28 thereof. Vacuum is supplied to these ports 30, 32 to hold the webs W′, W″ against the rolls 20, 22 as the webs W′, W″ are conveyed to the nip 24. At some point (whether at the nip 24 or before reaching the nip 24), the webs W′, W″ are preferably cut on the rolls 20, 22 in any conventional manner to be later interfolded in a stack of separate elements. Numerous mechanisms exist for cutting the webs W′, W″ in this manner, including without limitation extendable and retractable blades in the surfaces 26, 28 of the rolls 20, 22, cutoff rolls mounted for rotation adjacent to the rolls 20, 22 and having blades or anvils interacting with anvils or blades (respectively) on the surfaces 26, 28 of the rolls 20, 22, etc. Still other mechanisms for cutting the webs W′, W″ are well known to those skilled in the art and are not therefore described further herein.

[0036] As the webs W′, W″ pass through the nip 24 between the rolls 20, 22, the rolls 20, 22 are preferably controlled to pass the webs W′, W″ in an alternating fashion between the rolls 20, 22. Specifically, both overlapping webs W′, W″ preferably continue moving along with one of the rolls 20, 22 for a period of time, after which both overlapping webs W′, W″ are transferred to the other roll 22, 20 to move therewith for a period of time. This process continues during web stacking to produce a folded stack of interfolded web product 38. Although web transfer back and forth between the rolls 20, 22 can be accomplished in many different manners (e.g., via electrostatic charge of the roll surfaces 26, 28 exerting repelling and/or attracting forces upon the webs W′, W″, by blasts of air from air jets blowing the webs W′, W″ against the surfaces 26, 28 of the rolls 20, 22 in an alternating fashion, etc.), web transfer preferably occurs by control of vacuum through vacuum ports 30 in the roll surfaces 26, 28. Specifically, vacuum is preferably supplied to the portion of one roll 20, 22 downstream of the nip 24 for a period of time, after which time vacuum supply thereto is cut and is instead supplied to the portion of the other roll 22, 20 downstream of the nip 24. Such web transfer occurs back and forth between the rolls 20, 22 for each fold of the webs W′, W″ as the webs W′, W″ are stacked. Alternatively or in addition (as shown in the illustrated preferred embodiment), the vacuum ports 30 can be arranged so that only one roll's vacuum ports 30 are downstream of the nip 24 and upstream of the stack building surface 38 at a time. In such a manner, vacuum can be continually and simultaneously supplied to those portions of the vacuum rolls 20, 22 upstream of the nip 24.

[0037] To selectively supply vacuum to the vacuum rolls 20, 22, the rolls 20, 22 are preferably provided with vacuum lines 40 in fluid communication with one or more vacuum ports 30, 32 on the rolls 20, 22. These vacuum lines 40 can take any shape or form, but preferably are a number of longitudinal bores or apertures running along the rolls 20, 22 beneath the roll surfaces 26, 28. As the rolls 20, 22 rotate about their axes 24, 26, the vacuum lines 40 orbit about the roll axes 24, 26 and are preferably brought into and out of fluid communication with a vacuum supply through at least a portion of the rolls' rotation downstream of the nip 24. Most preferably, one or more vacuum valves 42 at the end(s) of the rolls 20, 22 are substantially stationary and are connected to a vacuum source such as a vacuum tank, vacuum pump, and the like (not shown).

[0038] Rotation of the rolls 20, 22 successively brings the vacuum lines 40 into alignment with ports 44 in the vacuum valves 42. The vacuum lines 40 remain in fluid communication with the ports 44 through at least a portion of each roll's rotation, thereby providing vacuum to the associated vacuum ports 30, 32 as they rotate through those portions. In other words, as the vacuum lines pass the nip 24, they are brought into fluid communication with the vacuum source by the vacuum valves 42, and remain in fluid communication for some phase angle of each roll's rotation. With particular reference to FIG. 4, this phase angle preferably runs from the nip 24 to a location adjacent the edge of the stack 38 (or the surface upon which the stack 38 will be built in the case of a new stack). The ending locations of this phase angle in the illustrated preferred embodiment is indicated at 46 and 48 in FIG. 4. Preferably, when a vacuum line 40 of one roll 20 is in the phase angle and thereby is supplying vacuum ports 30 therein with vacuum to hold the webs W′, W″ against the roll surface 26, the vacuum lines 40 in the other roll 22 are not in the phase angle and so do not exert such a vacuum. In this manner, vacuum force upon the webs W′, W″ alternates between the rotating rolls 20, 22 to generate the desired web folding action.

[0039] More information regarding the preferred manner in which to supply vacuum in an alternating fashion to the surfaces of rotating rolls 20, 22 can be found with reference to U.S. Pat. No. 4,778,441 issued to Couturier, the disclosure of which is hereby incorporated by reference insofar as it relates to vacuum rolls, related equipment, and the manner of folding web material by the control of vacuum supplied to vacuum rolls. Vacuum rolls and their operation in folding webs are well known to those skilled in the art and are not therefore described further herein. However, it should be noted that a number of conventional manners exist for intermittently supplying vacuum to vacuum lines 40 in rotating vacuum rolls 20, 22 and, more generally, for interfolding webs passing through rolls upstream of a stack or stacking surface, each of which falls within the spirit and scope of the present invention.

[0040] For example, vacuum can be supplied in a controlled manner to desired portions of rolls 20, 22 in a number of well known ways (whether by rotary valves or otherwise). As another example, vacuum need not necessarily be supplied to the roll ends 20, 22, and can instead be supplied at any location along the length of the rolls 20, 22 using conventional valve assemblies. As indicated above, alternative manners of interfolding webs using the rolls 20, 22 need not necessarily employ vacuum force to hold, transfer, and otherwise control the webs W′, W″.

[0041] Therefore, although the present invention can be employed in an interfolder such as the one illustrated in the figures and described herein, the present invention is not limited thereto and finds application in many other conventional interfolding devices and systems.

[0042] To assist in the web folding process, it can be necessary in some devices and systems to hold part of the web W′, W″ as it is being folded in any of the manners described above. Specifically, as the web W′, W″ is drawn by a roll 20, 22 from the nip 24 to a location adjacent to the stack or stack building surface 38, it can be necessary to hold the web W′, W″ at a downstream location to prevent movement of the downstream web portion while the new fold is being made. To accomplish this task, a common practice is to employ a series of packer fingers 50, 52 associated with each roll 20, 22. The packer fingers 50, 52 are commonly mounted for pivotal movement upon and away from the edges of the stack 38 being built, and typically move in this manner for each fold created upon the adjacent stack edge. To provide sufficient room for the packer fingers 50, 52 to move in this manner, the rolls 20, 22 can be provided with circumferential grooves 54, 56 within which the packer fingers 50, 52 can move as they are rotated toward and away from the stack 38 being built. Any number of grooves 54, 56 and packer fingers 50, 52 can be used as desired.

[0043] Packer fingers 50, 52 and their manner of operation are well known to those skilled in the art and are not therefore described further herein. For more information on packer fingers 50, 52 and their operation, reference is hereby made to U.S. Pat. No. 4,778,441 issued to Couturier and U.S. Pat. No. 4,770,402 issued to Couturier, the disclosures of which are incorporated herein by reference insofar as they relate to this subject matter. One having ordinary skill in the art will appreciate that packer fingers 50, 52 are only one of many devices and elements that can be used to hold the downstream web W′, W″ during folding operations. Accordingly, use of such devices and elements in conjunction with the present invention falls within the spirit and scope of the present invention.

[0044] With continued reference to FIGS. 3 and 4, each roll 20, 22 is preferably provided with one or more brake heads 58 located at a circumferential position of the roll 20, 22 downstream of the nip 24. The brake heads 58 each have at least one vacuum port 60 through which vacuum can be drawn to exert a suction force upon nearby webs W′, W″ . The brake heads 58 are preferably recessed below the surfaces 26, 28 of the rolls 20, 22 so as not to disturb, interrupt, or otherwise interfere with movement of the webs W′, W″ as they are drawn over the brake heads 58 by the vacuum ports 30, 32 on the roll surfaces 26, 28. Although the brake heads 58 are most preferably fully recessed or have some portion that is at most substantially flush with the rolls surfaces 26, 28, in other embodiments some portion of each brake head 58 projects past the roll surfaces 26, 28, and is shaped (e.g., has a leading edge that is tapered, curved, ramped, and the like) to readily permit the webs W′, W″ to pass thereover without substantial interference. As used herein and in the appended claims, brake heads 58 that are fully or partially recessed below the roll surfaces 26, 28 are said to be located “substantially beneath” the roll surfaces 26, 28. In still other embodiments, no part of the brake head 58 is recessed below the roll surfaces 26, 28. To also avoid any substantial web interference, these brake heads 58 are preferably thin in profile and have leading edges that are shaped as described above.

[0045] In most preferred embodiments of the present invention, each brake head 58 has a plurality of vacuum ports 60, although any number can be employed as desired. These vacuum ports 60 preferably open radially outward from the rolls 20, 22 for best suction upon passing webs W′, W″ when vacuum is exerted through the vacuum ports 60. However, the vacuum ports 60 can be oriented in any manner with respect to the periphery of the rolls 20, 22 so long as adequate suction can be generated to exert force against passing webs W′, W″ as will be described below.

[0046] To address the difficulty of providing vacuum to the stationary brake heads 58 recessed within or immediately adjacent to the moving rolls 20, 22 without disturbing web conveyance, a vacuum line 62 preferably runs from each brake head 58, around at least a portion of the respective roll 20, 22, and then away to a vacuum source (described below). The vacuum lines 62 can be any cross sectional shape or size desired, including without limitation square, rectangular, round, oval, polygonal, and the like. The vacuum lines 62 are connected to the brake heads 58 in any conventional manner, such as by welding, brazing, gluing, fastening with one or more fasteners, and by any conventional fitting such as a press fitting, threaded connection, and the like. The vacuum lines 62 are preferably in the form of ducts, pipes, tubes, or other conduits capable of transmitting vacuum, and can be made of any material desired. In most preferred embodiments such as the one illustrated in FIGS. 3-8, the brake heads 58 are supported in their circumferential positions recessed or immediately adjacent to the rolls 20, 22 by the vacuum lines 62. Therefore, the vacuum lines 62 are preferably made of a resilient material such as steel, aluminum, plastic, and the like capable of bearing the weight of the brake heads 58 without substantial bending or other deformation.

[0047] In alternative embodiments, the brake heads 58 can also or instead be supported in their positions relative to the rolls 20, 22 by a series of fingers, rods, bars, a frame, and the like extending to the rolls 20, 22 and connected to the brake heads 58 by passing at least partially around the rolls 20, 22 as the vacuum lines 62 do in the illustrated preferred embodiment. In still other embodiments, the brake heads 58 can be connected to a series of fingers, rods, bars, a frame, and the like coupled to and supported by an axle or pivot shaft (not shown) about which each roll 20, 22 rotates. In such embodiments, the fingers, rods, bars, or frame can be journaled to the axle or pivot shaft, connected thereto by a conventional bearing, etc. In those embodiments where the brake heads 58 are supported in their positions by structure other than the vacuum lines 62, the vacuum lines 62 can be made of non-rigid material such as hose, tubing, and the like. Regardless of how the brake heads 58 are supported in their positions relative to the vacuum rolls 20, 22, the brake heads 58 are preferably capable of remaining stationary despite roll movement and vibration, or at least remain substantially stationary so that the brake heads 58 do not move into an interfering relationship with the passing webs W′, W″.

[0048] The vacuum lines 62 are preferably at least partially recessed within the rolls 20, 22 to avoid interference with the moving webs W′, W″, and are more preferably fully recessed therein for this purpose. Therefore, the vacuum lines 62 are preferably appropriately shaped and sized to be received within recesses in the rolls 20, 22. To permit roll rotation with the vacuum lines 62 and brake heads 58 recessed therein, the recesses are preferably the same grooves 54, 56 within which the packer fingers 50, 52 move as described above. Even if packer fingers 50, 52 are not used or do not move into roll recesses 54, 56, the vacuum lines 62 and brake heads 58 are most preferably recessed within such circumferential grooves 54, 56. The grooves 54, 56 can be any depth or width desired, but preferably are not so deep as to compromise roll strength and not so wide as to leave insufficient surface area on the roll surfaces 26, 28 for retaining and conveying the webs W′, W″. It should also be noted that other types of recesses capable of receiving the vacuum lines 62 and brake heads 58 are possible and fall within the spirit and scope of the present invention. Also, in other embodiments, the vacuum lines 62 are not recessed within the rolls 20, 22, but are relatively flat and thin to generate as little interference with the running webs W′, W″ as possible. Such vacuum lines can run to brake heads that are either recessed or not recessed within the rolls 20, 22. In still other embodiments, multiple brake heads 58 and/or vacuum lines 62 can run within each roll recess 56. Additionally, multiple brake heads 58 can be supplied with vacuum by the same vacuum line 62.

[0049] With reference again to FIGS. 3 and 4 of the present application, the vacuum lines 62 preferable run from the brake heads 58 and around a substantial portion of the rolls 20, 22 prior to leaving the rolls 20, 22 so as not to interfere with movement of the webs W′, W″ on the rolls 20, 22 and into the nip 24. Depending at least partially upon which angle the webs W′, W″ approach the rolls 20, 22, the vacuum lines 62 can pass around any amount of the rolls 20, 22 desired.

[0050] Although vacuum is preferably supplied to the brake heads 58 by vacuum lines 62 as described above, it is possible to supply vacuum to the brake heads 58 in other manners. For example, vacuum can be supplied from within the rolls 20, 22 rather than through the circumference of the rolls 20, 22 as in the illustrated preferred embodiment. In such cases, vacuum can be supplied to the interior of the roll 20, 22 in any conventional manner, such as by a conventional rotary vacuum valve (located on either or both ends of the rolls 20, 22 and/or at one or more locations along the length of the rolls 20, 22) in fluid communication with one or more vacuum lines running along some portion of the rolls 20, 22, by a vacuum line passing through the axle or pivot about which the rolls 20, 22 rotate, and the like. Vacuum can then be supplied from such vacuum lines to the brake heads 58 by one or more conventional connecting vacuum lines, ports, and the like within the rolls 20, 22. Still other manners of supplying vacuum to the brake heads 58 exist and fall within the spirit and scope of the present invention.

[0051] Vacuum is preferably supplied to the vacuum lines 62 from a vacuum source such as a vacuum pump, evacuated tank, and the like. In the illustrated preferred embodiment, the vacuum source is a vacuum pump (not shown) connected to the vacuum lines 62 by a manifold 64. The vacuum pump is conventional in nature and is not therefore described further herein. To control the time and duration of braking by the brake heads 58, the supply of vacuum from the vacuum pump is preferably controlled. Preferably, this is performed by a valve 66 connected between the vacuum pump and the brake heads 58. Although separate valves 66 can be connected to each vacuum line 62 or to groups of brake heads 58, one valve 66 more preferably controls vacuum supply to all brake heads 58 on a roll 20, 22.

[0052] Preferably, the valve 66 is operated automatically by a conventional controller, although it is possible in less preferred embodiments to control the valve 66 manually. The valve 66 can be of any conventional type capable of rapidly opening and closing vacuum supply to the vacuum lines 62. The valve 66 is preferably controllable to control the duration of the valve's opened and closed states and to open and close at regular times substantially coinciding with desired braking times of the brake heads 58. A number of conventional valve types can be employed to perform this function. However, the valve 66 illustrated in FIGS. 3 and 5 is most preferred.

[0053] The valve 66 is preferably a rotary valve mounted for rotation about an axis, such as by being rotatably mounted upon and with respect to a pivot, by being coupled to a pivot that is rotatably mounted within one or more bearings, and the like. The pivot can be a separate element as shown in the figures or can be a pivot about which an associated roll 20, 22 pivots. The valve 66 can be driven in any manner, such as by a motor turning a pivot upon which the valve 66 is mounted, by a gear assembly having one or more drive gears engaged with a toothed circumference of the valve 66, or (most preferably) by a belt and pulley arrangement as shown in FIGS. 3 and 5. In any of these embodiments, the driving device can be an electric motor, hydraulic motor, engine, or any other type of driving device. With regard to the illustrated preferred embodiment in which the valve 66 is driven by a belt and pulley arrangement, the belt 68 preferably runs around the circumference of the valve 66 and about a pulley on an electric servo motor 70 controlled by a conventional controller. Accordingly, the valve 66 can be rotated at desired speeds by the motor 70. In alternative embodiments of the present invention, the belt and pulley assembly can be replaced by other assemblies such as a chain and sprocket assembly, a cable and pulley assembly, and the like (in which case the valve 66 and the pulley on the motor 70 are preferably shaped for driving engagement with the chain, cable, or other driving element.

[0054] The valve 66 in the illustrated preferred embodiment has at least one vacuum aperture 72 therein for opening the upstream vacuum pump to the downstream vacuum lines 62. Specifically, the vacuum apertures 72 are located in the valve 66 so that rotation of the valve 66 brings the vacuum apertures 72 successively into and out of fluid communication with the vacuum pump 64 and vacuum lines 62. Any number of apertures 72 located in any positions, arranged in any regular or irregular fashion, and capable of operating in this manner are possible. Also, the vacuum apertures 72 can be any shape and size desired (preferably defined at least in part by the anticipated ranges of braking duration for the brake heads 58 and valve speeds of the valve 66 as described in more detail below). By way of example, the valve 66 in the illustrated preferred embodiment has three equally-spaced vacuum apertures 72 each having a generally trapezoidal shape.

[0055] When the valve 66 is rotated by the motor 70, the apertures 72 successively establish temporary fluid communication with the upstream vacuum pump and the downstream vacuum lines 62. The duration of each temporary fluid communication is determined by the size of the subject aperture 72 and the rotational speed of the valve 66. For example, the duration of each braking action can be extended by slowing the vacuum valve 66 and/or by shaping the apertures 72 (e.g., enlarging, elongating in a circumferential direction, and the like) so that they are in fluid communication with the vacuum pump and the vacuum lines 62 for a longer rotational distance of the valve 66. Similarly, the duration of each braking action can be shortened by accelerating the vacuum valve 66 and/or by reducing the apertures 72 (e.g., making the apertures smaller, shortening their circumferential length, and the like) so that they are in fluid communication with the vacuum pump and the vacuum lines 62 for a shorter rotational distance of the valve 66. Also, the frequency of the braking actions can be increased by changing the number of apertures 72 in the valve 66 and/or by changing the speed of the valve 66. Because the motor speed is preferably controlled by a conventional controller, the valve 66 can therefore be controlled to increase or decrease the frequency of braking actions and to increase or decrease the duration of the braking actions. Further structural and operational features of the valve 66 are conventional in nature and are not therefore described in greater detail herein.

[0056] In operation, the rolls 20, 22 rotate as described above to convey webs W′, W″ to the nip 24 therebetween. Preferably, the webs W′, W″ are introduced to their respective rolls 20, 22 at a circumferential distance from the nip 24, and are conveyed thereto while being held on the surfaces 26, 28 of the rolls 20, 22 by vacuum exerted through the vacuum ports 30, 32 in the roll surfaces 26, 28. As described above, when the webs W′, W″ pass the nip 24, they are preferably held by the vacuum force against only one of the rolls 20, 22 by the fact that vacuum ports 30, 32 on only one of the rolls 20, 22 are located downstream of the nip 24 at any given time (and/or by shutting vacuum off to the vacuum ports 30, 32 in the opposing vacuum roll 22, 20 near and downstream of the nip 24). The webs W′, W″ are then conveyed on the surface of the first roll 20, 22 preferably until a web fold is located in its proper stacked position on the stack building surface or upon the stack 38 thereon. At this point (ending location 46 or 48), vacuum to the vacuum ports 30, 32 conveying the web W′, W″ downstream of the nip 24 is cut off. The webs W′, W″ are thereafter conveyed on the opposite roll 22, 20 by vacuum ports 32, 30 passing through or past the nip 24 and/or by turning vacuum on to those ports 32, 30 in the opposing roll 22, 20 until the next fold is made. To prevent roll-out of the first fold described above, vacuum is supplied to the brake head 58 for a period of time just prior to, during, or just after vacuum to the vacuum ports 30, 32 downstream of the nip 58 is cut off.

[0057] For purposes of description only, the vacuum port shown in FIG. 4 and designated with reference numeral 74 is illustrated at the point where vacuum thereto is preferably in or near the process of being cut off, thereby releasing the fold 76 to the stack 38 below. At this time or near this time, vacuum is introduced to the brake head 58, thereby exerting an attractive force upon the webs W′, W″ adjacent to the brake head 58 and generating a retarding force (indicated by arrow F) upon the webs W′, W″ in a direction opposite to or substantially opposite to the direction of roll rotation. In this way, inertia of the webs W′, W″ which could otherwise cause the fold being created to “roll out” is counteracted, and the fold can be located in its correct position on the stack building surface or stack 38.

[0058] Preferably, the opposing roll 22 has a series of brake heads 58 whose circumferential location is a mirror image to those on the roll 20 just described. The following fold cycle is therefore preferably performed in a similar manner in which the webs W′, W″ move in a mirror image to that described above and illustrated in FIG. 4.

[0059] The strength of each braking action is preferably controlled by controlling the vacuum pump supplying vacuum to the manifold 64 and vacuum lines 62 (which can be performed manually or automatically in any number of manners well known to those skilled in the art). With reference to the above description of the valve 66, the duration of each braking action is a function of the valve speed and the valve aperture shapes and sizes, while the frequency of the braking actions is a function of the valve speed and the number of apertures 72 in the valve 66. The valve 66 is preferably driven in synchronicity (or substantial synchronicity) with rotation of its corresponding roll 20, 22. Preferably, the valve 66 is driven at a speed and the apertures 72 therein are numbered and arranged so that an aperture 72 comes into fluid communication with the upstream vacuum pump and the downstream vacuum lines 62 each time the vacuum port 74 conveying the webs W′, W″ past the nip 24 reaches the position 46 shown in FIG. 4. Therefore, at or near the time when vacuum to the vacuum port 74 is cut off, vacuum is supplied to the vacuum port 60 in the brake head 58 to brake the webs W′, W″ as folding is completed.

[0060] Recognizing that the braking needed will likely vary depending upon a number of factors such as the type of material being folded and the speed at which the material is run, the valve 66 is preferably adjustable to change the time at which vacuum is supplied to the brake heads 58 relative to when vacuum to the vacuum ports 30, 32 is cut off. The valve 66 can be timed to lag slightly behind the roll 20, 22 so that braking force is exerted at a later time during each fold, such as for lighter web materials or for slower roll speeds. Alternatively, the valve 66 can be timed in advance of the roll 20, 22 so that braking force is exerted at an earlier time during each fold, such as for heavier web materials or for higher roll speeds. The phase difference between rotation of the valve 66 and rotation of the roll 20, 22 can be controlled by controlling the speed of the motor 70 driving the valve 66 or by controlling the speed of the roll 20, 22 (e.g., temporarily speeding or slowing the valve 66 and/or roll 20, 22 to change the phase angle between the valve 66 and roll 20, 22). This control can be performed by temporarily changing valve 66 or motor speed manually or by any number of conventional controllers. Such controllers are well known to those skilled in the art and are not therefore described further herein.

[0061] To illustrate the relationship between vacuum introduced to the brake heads 58 and vacuum cut off from the vacuum ports 30, 32 during a braking action, FIG. 6 illustrates the respective levels of vacuum at the vacuum ports 30, 32 and brake heads 58 as a function of time during a braking action. With reference to the solid lines in the graph, the amount of vacuum at the vacuum ports 30, 32 typically drops rapidly over a relatively short period of time when vacuum to the vacuum ports 30, 32 is cut off. Similarly, the amount of vacuum at the brake heads 58 typically rises rapidly over a relatively short period of time when the valve 66 is opened. In preferred operation of the present invention, the dark lines overlap to some degree, meaning that some degree of vacuum is always exerted upon the webs W′, W″ during the time when vacuum to the vacuum ports 30, 32 is cut off and vacuum is introduced to the brake heads 58. Therefore, control of the webs W′, W″ by vacuum is transferred from the vacuum ports 30, 32 to the brake heads 58. In such preferred operation, the amount of vacuum to the vacuum ports 30, 32 can begin to drop prior to, at the same time as, or after initial introduction of vacuum to the brake heads 58. Similarly, suction through the vacuum ports 30, 32 can end prior to, at the same time as, or after full suction through the brake heads 58 is achieved.

[0062] By advancing or delaying the timing of valve opening with respect to roll rotation as described above, more or less overlap of the lines on FIG. 6 results (either or both of the lines are moved horizontally and with respect to one another). For example, by temporarily increasing the speed of the valve 66 with respect to the roll 20, 22, the brake heads 58 exert vacuum braking force at an earlier time represented by a shift of the brake head vacuum profile in FIG. 6 to the left and resulting in more time during which greater vacuum forces are exerted simultaneously by the vacuum ports 30, 32 and the vacuum heads 58. As another example, by temporarily increasing the speed of the roll 20, 22 with respect to the valve 66, the brake heads 58 exert vacuum braking force at a later time represented by a shift of the brake head vacuum profile in FIG. 6 to the right and resulting in less time during which the web W′, W″ is simultaneously attracted to the surface of the vacuum roll 20, 22 and to the brake heads 58.

[0063] It is even possible to change the phase between the valve 66 and the vacuum roll 20, 22 to a point where the profiles in FIG. 6 do not overlap (indicating no suction force upon the web W′, W″ exists from the vacuum ports 30, 32 prior to generating suction through the brake heads 58) or completely overlap (indicating suction force upon the web W′, W″ is fully exerted by the brake heads 58 before any reduction of suction force upon the web W′, W″ by the vacuum ports 30, 32). Although both manners of control fall within the spirit and scope of the present invention, the former manner of control is less preferred because the web W′, W″ is temporarily released prior to braking, while the latter manner of control is less preferred because the web W′, W″ experiences relatively heavy braking while still being pulled by the roll 20, 22.

[0064] In highly preferred embodiments, the speed of the valve 66 and/or the speed of the rolls 20, 22 can be automatically controlled as a function of vacuum in the vacuum ports 30, 32 on the surfaces of the rolls 20, 22. By measuring the amount of vacuum in the vacuum ports 30, 32, the time at which vacuum to the brake heads 58 is introduced and at which braking is begun can be controlled. In the illustrated preferred embodiment for example, pressure sensors 76 such as pressure transducers or other conventional pressure detection devices are mounted within the vacuum lines 40 and detect the amount of vacuum in the vacuum lines 40. Alternatively, the pressure sensors 76 can be mounted at any point preferably near the vacuum ports 30, 32 for detecting the amount of vacuum at, near, or upstream of the vacuum ports 30, 32. Although a pressure sensor 76 is mounted in each vacuum line 40 shown in FIGS. 4 and 8, not all vacuum lines 40 need to have a pressure sensor 76 for proper operation. In one preferred embodiment, only one vacuum line 40 in a roll 20, 22 having multiple vacuum lines 40 is provided with a pressure sensor 76.

[0065] Preferably, upon detecting a sufficient drop in vacuum pressure, the pressure sensors 76 send one or more signals to the system controller (not shown) which directly or indirectly controls the speed of the motor 70 driving the valve 66 and/or the speed of the rolls 20, 22. If the valve 66 has not yet rotated the desired amount to open vacuum to the brake heads 58, the system controller causes the motor 70 to temporarily increase in speed relative to the rolls 20, 22 or the rolls 20, 22 to temporarily decrease in speed relative to the valve 66. If the valve 66 has already rotated too far and has thereby opened vacuum to the brake heads 58 too early, the system controller causes the motor 70 to temporarily reduce in speed relative to the rolls 20, 22 or the rolls 20, 22 to temporarily increase in speed relative to the valve 66. This vacuum detecting and resulting valve speed control process preferably occurs constantly to ensure proper synchronicity and timing between the rolls 20, 22, the valve 66, and brake heads 58.

[0066] The embodiments described above and illustrated in the drawings are presented by way of example only and are not intended as a limitation upon the concepts and principles of the present invention. As such, it will be appreciated by one having ordinary skill in the art that various changes in the elements and their configuration and arrangement are possible without departing from the spirit and scope of the present invention as set forth in the appended claims.

[0067] For example, each roll 20, 22 can have any number of grooves 54, brake heads 58, vacuum lines 62, and vacuum ports 30, 32. Accordingly, reference in the appended claims to any of these elements in the singular does not preclude the existence of others in the subject apparatus or method.