Title:
LIQUID EXTRACTING APPARATUS AND METHOD
United States Patent 3841910


Abstract:
Apparatus and method, for extracting liquid from a traveling porous web such as a paper machine felt, direct a jet of gas at a surface of the web at an angle to the surface of the web inclined oppositely to the direction of travel, the angle and force of the jet being such that the jet penetrates the web and is reflected back into a collecting chamber, carrying liquid and dirt with it. A wall member is arranged to engage the surface of the web between the chamber and the jet mouth to form a seal to insure the desired web penetration by the jet.



Inventors:
BAKER D
Application Number:
05/339972
Publication Date:
10/15/1974
Filing Date:
03/12/1973
Assignee:
BIRD MACHINE CO INC,US
Primary Class:
Other Classes:
15/306.1, 15/345, 34/414, 134/21, 134/37, 162/199, 162/274
International Classes:
D21F1/32; (IPC1-7): B08B5/02; D21F1/32
Field of Search:
134/15,21,37 162
View Patent Images:
US Patent References:



Primary Examiner:
Wolk, Morris O.
Assistant Examiner:
Turk, Arnozo
Attorney, Agent or Firm:
Kent, Edgar H.
Parent Case Data:


This application is a continuation of my applications Ser. No. 27,714, filed Apr. 13, 1970 and Ser. No. 266,124, filed June 26, 1972, both now abandoned.
Claims:
I claim

1. A method for extracting liquid from a traveling porous web comprising the steps of:

2. A method according to claim 1 wherein said wall forms one side of a nozzle for said jet and of said chamber.

3. A method according to claim 1 wherein said jet has a width in the direction of travel of the web of the order of 0.004 to 0.005 inch.

4. A method according to claim 1 wherein said jet is formed of a plurality of separate gas streams spaced longitudinally of said jet.

5. A method according to claim 1 which includes the further step of applying suction to said chamber.

6. A method according to claim 5 wherein said suction produces a vacuum of the order of from 2 to 10 inches Hg.

7. A method according to claim 1 wherein said jet is directed into said web at an acute angle to the plane of the web between about 25° and 85°.

8. A method according to claim 7 wherein said angle is between about 70° and 75°.

9. A method according to claim 1 wherein the pressure of said gas jet is at least 10 p.s.i. gage.

10. A method according to claim 9 wherein said pressure is at least 30 p.s.i. gage.

11. A method according to claim 1 wherein the other face of the web is supported opposite said jet and chamber.

12. A method according to claim 11 wherein said other face of the web is supported on an impervious rotating surface.

Description:
This invention relates to apparatus and method for extracting liquid from traveling porous webs, particularly to such apparatus and method which are useful for conditioning paper machine felts.

A primary object of the invention is to provide such apparatus and method which utilize a stream of gas under pressure to eject from the web contained water and with it dirt more effectively than has heretofore been possible. Further objects are to provide such apparatus which is not expensive to construct or to operate as compared with existing equipment, which will operate effectively at high speeds of travel of the web, and which is particularly useful for conditioning the felts of paper-making machines; and to provide a method which utilizes such apparatus.

It has been discovered that water (and dirt with it) can be effectively removed from a wet porous traveling web by an apparatus and method wherein a jet of gas under pressure is directed into one face of the web at a backward angle to the direction of travel of the web and the web-penetrating portion of the jet is reflected back at an opposite angle from adjacent the opposite face of the web to and out said one face thereof into a collecting chamber, the chamber being preferably under a vacuum. In order that the jet may operate effectively in this manner, there is provided between the jet and the chamber a wall with an edge engaging the felt continuously across the web and against which the web is sufficiently tensioned to form therewith a seal, the seal preventing short-circuiting of the jet to the chamber and providing access of the jet to the chamber only by penetration of and reflectance from within the web.

Preferred apparatus of the invention includes, opposite a face of the web being treated, a trough-like, moisture collecting chamber extending transversely across the web and having front and rear walls with edges arranged to engage the said face of the web. The rearward one of these walls in the direction of travel of the web comprises or is adjacent to a chamber connected to a source of gas (normally air or steam) under pressure and having a nozzle outlet extending across the web. The nozzle is arranged to discharge the jet into the web at a backward angle to the direction of travel of the web and rearwardly of the web-engaging edge of the rear wall of the chamber, the pressure and angle being such that the jet penetrates the web and is reflected back outward at an opposite angle into the collecting chamber, carrying the liquid with it as a spray or stream. The collecting chamber is preferably under vacuum which may be of the order of about 2 to 10 inches Hg. However, the jet can operate, although not as effectively, with the collecting chamber at atmospheric pressure. The rearward wall of the chamber engages the web between the jet outlet and chamber with sufficient force to provide the requisite seal between jet and chamber mentioned above.

A support for the opposite face of the web may or may not be provided. If the web being treated is relatively thin and highly porous an impervious support opposite the described equipment may be needed to insure adequate reflectance of the jet but with thick, dense webs such as paper machine felts adequate reflectance can ordinarily be obtained from within the body of the web without such a support. When the web is traveling at high speeds as in the case of the felts of high speed paper machines, a rotary support opposite the jet and chamber may be advantageous to assist, by centrifugal force, the removal of liquid into the chamber.

Optimum jet thickness and pressure are variables depending on such factors as nature and porosity of the material being treated, its thickness and the extent of liquid removal desired. In general it has been found that the jet should be between about 0.002 to 0.007 inches wide, a width of about 0.004 to 0.005 inch being preferred when the gas is compressed air, a lesser width impairing effectiveness in most cases while greater width does not usually materially improve performance while increasing compression requirements. Within limits and with other variables fixed it has been found that free liquid removal increases approximately proportionally to increase of pressure of the jet. For example, the extent of water removal from a felt with apparatus as described above having a 0.005 inch wide slit forming an air jet, was increased from about 40 percent at 10 p.s.i. (gage), to 65-70 percent at 20 p.s.i. to 80-85 percent at 30 p.s.i., to about 90 percent at 40 p.s.i., other conditions remaining the same. Similar results were obtained using steam as the gas but with lower percentages removal at each p.s.i. level. Since these lower percentages of removal roughly correspond to the lower density of steam as compared with air, results indicate that jet density as well as pressure and speed is an important factor, which should be kept in mind when correlating results obtained with air to other gaseous media.

The angularity of the jet should be such that its angle of reflectance from within the web lies substantially entirely within the confines of the collecting chamber. In part, the degree of angularity will depend on the distance between the adjacent edges of the jet and this chamber, which is preferably as small as possible consistent with the provision of sealing engagement of the web with the edge of the rear wall of the chamber between the chamber and the jet to prevent short-circuiting of any substantial part of the jet over the material being treated into the chamber. With this limitation in mind, the most effective angle is a function of various factors such as the thickness of the web being treated, its porosity, and the speed of its movement past the jet. The acute angle to the surface of the web should not exceed about 85° nor be less than about 25°, 70°-75° being preferred.

One particularly useful application of the apparatus and method according to the invention is in the so-called "conditioning" of felts of pulp and paper-forming machines. In such practice, the felts, which transport the wet sheet to and through the press rolls, are relied upon to remove by absorption much of the water from the sheet. To keep the felts absorbent, they are treated by felt conditioners after a certain amount of travel or on a continuous basis to remove the water that has been absorbed and with it fibres and dirt which the felt picks up from its contact with the fibrous web and which interfere with operability of the felt. Felt conditioners have conventionally been vacuum boxes with slotted covers which engage the sheet-contacting face of the felt to suck the water and foreign matter from it. In some cases these boxes are oscillated.

My apparatus and method, used for felt conditioning and working on the sheet engaging face of the felt, have important advantages over conditioning with these prior devices. With proper control over the variables as indicated in the foregoing, they can be made to extract more water and to remove more fibre and dirt. The entire width of the felt can be treated at each cycle whereas oscillating vacuum boxes treat only part of the felt at each cycle. The treatment may be uniform across the felt, or it may be made different in different zones as may be desirable by compartmenting the jet supply passage to correspond to such zones and varying the gas pressure as desired between compartments. Treatment by my apparatus and method desirably fluffs the sheet contacting surface of the felt rather than matting it as vacuum boxes tend to do, and makes that surface dried. Yet equipment cost and operating cost are at least comparable with, if not lower than, these prior devices. The apparatus and method are fully effective at the high speeds at which paper machine felts are operated.

Similar advantages may be realized when my apparatus and method are utilized for extracting liquid from porous webs other than felts, such as pile or other fabrics after bleaching, washing or other treatment.

The invention will be further described in connection with the accompanying drawings which show several preferred forms of the apparatus and of the practice of the method. In the drawings:

FIG. 1 is a cross-section view of such apparatus for use in, and for applying the method to, felt conditioning, the cross-section being taken on line 1--1 of FIG. 2 looking in the direction of the arrows;

FIG. 2 is a top plan view of the apparatus shown in FIG. 1, centrally broken away;

FIG. 3 is a section view similar to FIG. 1 showing a modification of the apparatus according to FIGS. 1 and 2.

Referring to FIGS. 1 and 2, the apparatus therein shown comprises a manifold 10 which is of greater length than the width of the felt F and is mounted adjacent its ends in clamps 12 opposite the working face of the felt (i.e., the face that contacts the paper on the machine). Clamps 12 have upper and lower clamping members 14 and 16 and are held together by bolts 18 which extend rotatably through lugs at the sides of member 14 and are received in threaded sockets 20 at opposite sides of member 16. Member 16 is provided at its base with laterally projecting slotted feet 22 through which extend bolts 24 fastening the apparatus to a suitable base B which may be a part of the paper machine frame or a separate base as convenient.

Provided manifold 10 is under suction to remove the extracted liquid therefrom as is preferred, the apparatus is not dependent on gravity and may be mounted beneath the felt or above it or at one side or the other of a vertical or angular run. In the drawings it is assumed that the apparatus is mounted below a substantially horizontal run of the felt having its working face the lower one. Clamps 12 rotatably embrace manifold 10 so that when the bolts 18 are loose, manifold 10 may be rotated therein about its axis for position adjustment purposes.

Manifold 10 is preferably provided with suitable connections 26 (one or more, two shown, one at each end) to a source of suction (not shown) capable of maintaining a desired vacuum in the manifold, connections 26 extending through end closures 28 of the manifold. Secured to the outer face of manifold 10 between the manifold and the felt is a pressure manifold 30, which may conveniently be formed as shown of two angle irons welded together and has suitable connections 32 (one or more, two shown, one at each end) to a source of gas under pressure (not shown) capable of maintaining the desired gas pressure in manifold 30.

Secured to the outer surface of manifold 10 by bolts 34 is a bracket arm 36 extending the full width of the felt and having an outwardly extending portion generally parallel to and spaced from one side of manifold 30. Secured to arm 36 by bolts 38 and overlying its outer end is a shoe 40 which defines the leading edge of a slot 42, the opposite edge of which is defined by a second shoe or bar 44 secured by bolts 46 to the adjacent side of manifold 30. Slot 42 forms the mouth of a collecting chamber between shoe 40, bar 44, arm 36 and manifold 30 from which the liquid collected therein flows through a slot 48 in the wall of manifold 10 into the manifold. As indicated on the drawing, shoe 40 is formed, preferably, of plastic over which the felt readily slips, such as high density polypropylene.

Bar 44 is beveled on both its forward and rearward faces to taper its outer end to a narrow edge 50 which defines the leading edge of a pressure jet nozzle, the opposite edge of which is formed by a bar 52 which is fastened to the outer side of manifold 30 by bolts 54. The forward edge of bar 52 is beveled to provide, with the contiguous beveled end of bar 44, the nozzle outlet for directing the gas into the felt at the desired backward angle to the direction of travel of the felt. Preferably, the forward edge of bar 52 is serrated so that it forms with bar 44 a series of spaced slots 56 (FIG. 2) rather than a continuous slit, as I have found that the jet produced by such slots is as effective as one that is continuous, requires less pressure and also effectively reduces the noise level. For ease in fabrication, bar 52 may be formed in sections which are butted at their ends. Gas from manifold 30 flows through a series of holes 58 in the manifold wall into a space below bar 52 and thence out the nozzle as indicated by the arrows in FIG. 1.

As shown in FIG. 1 the outer surfaces of shoe 40 and bar 52 are smooth and in line with each other and with the edge 50 of bar 44 so that the felt contacts and rides smoothly on these surfaces and edge. Also, it will be seen that suction in slot 42 pulls the felt inwardly as it passes thereover which has a beneficial effect in opening up the working face of the felt on the suction side and closing the opposite face and also in insuring sealing engagement of edge 50 with the felt between the jet and the chamber to which slot 42 is the inlet. If suction is not applied to slot 42, to obtain a similar sealing engagement of the felt with edge 50 the web should be tensioned against that edge throughout its width. Escape of the gas entering the felt from its outer surface or by short-circuiting directly into slot 42 is thus inhibited whereas the desired angular reflection of the jet from within the felt forwardly into slot 42 carrying the liquid and dirt from the working face, is assisted. To permit adjustment in length of slot 42 to correspond exactly to the felt width when suction is applied thereto adjustable stop bars 60 are provided at each end thereof (FIG. 2), slidable in ways 62 mounted on manifold 10 and extending through end walls 64 of the structure mounted on manifold 10 into the opposite ends of slot 42. Bars 60 fill the space between shoe 40, arm 36 and bar 44 to confine the suction to the space between their ends.

It will be appreciated that the usual equipment for wetting the felt, normally on the working face, preceding the conditioner, though not shown herein, will normally be provided.

In the modification of FIG. 3 the web W being treated is supported on its back side by a roll R rotating in the direction of the arrow. Such a support is desirable where the web W is more porous than the usual dense paper machine felts and so porous as to permit enough of the jet to escape from its outer surface if unsupported to impair the desired ejection action by the jet into slot 42. A roll is desirable as a support because the wrap of the web about the roll opens its exposed face facilitating extraction. It should be appreciated, however, that the modified apparatus of FIG. 3 may be also applied to unsupported felts or other webs as in FIG. 1.

The modification of FIG. 3 adds a suction slot 70 which follows slot 42 and the jet nozzle in the direction of travel of the web for removing residual moisture passing the jet. To provide slot 70, bracket arm 36 with shoe 40, manifold 30 with bar 44 and slot 48 have been moved laterally of the axis of manifold 10, to the left as viewed in FIGS. 1 and 3. A rearward extension 72 on bar 52 defines the leading edge of slot 70, the opposite edge of which is defined by a shoe 74 mounted by bolts 76 on bracket arm 78 attached to the rear surface of manifold 10 by bolts 80. Slot 70 opens into a collecting chamber formed between extension 72, shoe 74, manifold 30 and arm 78 which in turn opens into manifold 10 through slot 82 in its wall. The apparatus is otherwise the same as in the FIGS. 1 and 2 embodiment.

Separate manifolds in place of the single manifold 10 may of course be provided for slots 42 and 70 and this will necessarily be done if slot 42 is not to be placed under suction. Provision for applying suction to the web following its treatment by the jet is more important if suction is not applied to slot 42 which makes the jet less effective, and in such case the ensuing suction may be applied by a conventional Uhle box which follows the jet applying equipment in the direction of travel of the web.