Title:
STRIP ADHESIVE APPLICATION MECHANISM
United States Patent 3765992


Abstract:
A mechanism for transferring predetermined lengths of pressure-sensitive strip adhesive to objects from a supply of strip adhesive carried on a releasable liner. The device includes means for severing the supply of strip adhesive to form a predetermined length of adhesive, for positioning the length of adhesive on an application surface of a pressure foot, for providing relative movement between the pressure foot and a support surface to press the length of adhesive into contact with an object positioned on the support surface, and for transferring the length of adhesive from the liner to the object.



Inventors:
STAGEBERG W
Application Number:
05/213958
Publication Date:
10/16/1973
Filing Date:
12/30/1971
Assignee:
MINNESOTA MINING MFG CO,US
Primary Class:
Other Classes:
156/248, 156/767
International Classes:
B65H35/00; B65H37/00; (IPC1-7): B32B31/00
Field of Search:
156/521,584,230,238,248,249,540,355,523
View Patent Images:
US Patent References:
3676266N/A1972-07-11Jensen et al.
3649413N/A1972-03-14Way
3625799DEVICE FOR DISPENSING AND APPLYING LENGTHS OF ADHESIVE TAPE1971-12-07Way
2543004Machine for cutting short lengths of tape from a strip and applying the same to articles1951-02-27Dewyer



Primary Examiner:
Drummond, Douglas J.
Assistant Examiner:
Wityshyn M. G.
Claims:
Having thus described the present invention, what is claimed is

1. A mechanism useful for transferring a predetermined length of pressure-sensitive strip adhesive to an object from a supply of strip adhesive carried on a releasable liner, said mechanism comprising:

2. the mechanism of claim 1 further including:

3. The mechanism of claim 1 wherein said severing means comprises:

4. The mechanism of claim 1 wherein said holding means comprises:

5. The mechanism of claim 1 wherein said advancing means includes tensioning means adapted for tensioning said liner across said application surface.

6. The mechanism of claim 1 wherein said advancing means comprises:

Description:
BACKGROUND OF THE INVENTION

This invention relates to a mechanism for applying predetermined lengths of pressure-sensitive strip adhesive seriatim to a series of objects.

The use of pressure-sensitive adhesive rather than heat sealing to seal the flap to the body of a polyethylene envelope affords potential customers the opportunity to inspect merchandise such as lingerie contained within the envelope while allowing subsequent resealing of the envelope. The exterior surface of the envelope typically is treated to be oleophillic facilitating printing thereon while the interior surface of the envelope (including the inner surface of the flap) is untreated and remains oleophobic. Pressure-sensitive adhesive pressed between the interior surface of the flap and the exterior surface of the envelope will have a stronger adhesion to the oleophillic exterior surface of the envelope than to the oleophobic inner surface of the flap, and will have sufficient internal strength to separate cleanly from the interior surface of the flap when the flap is pulled away from the adhesive. The adhesive retains sufficient adhesion for the flap to reseal the envelope after the adhesive seal has been broken several times.

Prior art methods, for applying strip adhesive to such envelopes, have had certain disadvantages. The methods include using conventional tape severing and application equipment to apply to the envelope a length of strip adhesive mounted on a length of releasable liner. The liner must then be manually removed from the strip adhesive to afford sealing the flap against the adhesive. This manual operation precludes the high envelope sealing rates attainable from the more automated heat sealing mechanisms. Thus there has been a tendency to heat seal merchandise within polyethylene envelopes even where the merchandisers would prefer a reclosable adhesive type of envelope seal.

SUMMARY OF THE INVENTION

The present invention provides an automated mechanism for transferring a predetermined length of pressure-sensitive strip adhesive from a releasable liner to an object such as a polyethylene envelope, thus eliminating hand removal of the releasable liner. The present invention provides unique means for cutting a predetermined length of adhesive from a supply of strip adhesive carried on a releasable liner, for pressing the length of adhesive into contact with the envelope, and for insuring transfer of the length of adhesive from the releasable liner to the envelope.

According to the present invention there is provided a mechanism useful for transferring a predetermined length of pressure-sensitive strip adhesive to an object from a supply of strip adhesive carried on a releasable liner. The mechanism includes path means for guiding the releasable liner carrying the strip adhesive along a predetermined path, comprising a pressure foot having an application surface defining a length of said path and adapted to contact the liner. The severing means are mounted along the path for severing the strip adhesive on the liner in advance of the application surface to form a said predetermined length of strip adhesive, and advancing means are provided for advancing the liner and the strip adhesive along the path to position the predetermined length of strip adhesive on the application surface. The mechanism also includes means defining a support surface for supporting an object in a predetermined relationship with respect to the application surface; and moving means for providing relative motion between the application surface and the support surface from a first position with the application surface spaced from the support surface to afford insertion of a said object therebetween to a second position to press the predetermined length of strip adhesive on the application surface into contact with an object positioned on the support surface. Holding means are also provided for maintaining the object on the support surface until after the moving means has begun movement of the surface from the second toward the first position.

BRIEF DESCRIPTION OF THE DRAWING

The advantages and novel features of this invention will become more apparent upon a careful reading of the following description which refers to the accompanying drawing wherein:

FIG. 1 is an elevational partially fragmented front view of a mechanism constructed in accordance with the present invention;

FIG. 2 is a top plan view of the mechanism of FIG. 1;

FIG. 3 is a top plan view of a polyethylene envelope having a predetermined length of adhesive applied thereto as by the mechanism of the present invention;

FIG. 4 is an elevational rear view of the mechanism of FIG. 1;

FIG. 5 is a fragmentary elevational front view of the mechanism of FIG. 1 showing the position at which the strip adhesive is pressed into contact with an envelope;

FIG. 6 is a fragmentary detailed view taken approximately along line 6--6 of FIG. 1;

FIG. 7 is an enlarged fragmentary elevational detailed view of the adhesive cutting device also shown in FIGS. 1 and 5; and

FIG. 8 is a perspective view of the control means for the present invention .

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawing, there is shown a mechanism generally designated by the numeral 10 which is adapted for transferring a predetermined length of pressure-sensitive strip adhesive 12 (herein called length of adhesive 12) to an object such as a polyethylene bag or envelope 14 from a supply of tape comprising a coating a pressure-sensitive adhesive 16 on a liner 18 having a release coating on the surface coated by the adhesive as well as the backside.

The mechanism will apply lengths of adhesive 12 seriatim to a series of polyethylene envelopes 14 fed as by a conveyor belt 22 into position at a support surface 20 on the mechanism 10 illustrated as the surface of the conveyor belt 22 beneath a pressure foot 26. The mechanism 10 includes means for forming lengths of adhesive 12, for positioning a length of adhesive 12 on an application surface 24 of the pressure foot 26, for providing relative movement between the pressure foot and the support surface 20 to press the length of adhesive 12 on the application surface 24 into contact with an envelope 14 on the support surface 20, and for transferring the length of adhesive 12 from the liner 18 to the envelope 14 on the support surface 20.

The envelope 14 for which the mechanism 10 is adapted is best seen in FIG. 3. The envelope 14 is formed of a length of polyethylene sheet material transversely folded 180° to form unequally extending portions with aligned edges 25. Both edges 25 are seamed as by heat sealing to form the envelope 14 with a flap 27. The flap 27 may be folded to contact the exterior surface of the envelope 14 and essentially close the opening of the envelope 14. The envelope 14 shown in FIG. 3 has had a transversely extending length of adhesive 12 adhered thereto as by the mechanism 10 of the present invention. The length of adhesive 12 is positioned on the exterior surface of the envelope 14 so as to afford attachment of the flap 27 thereto to seal the envelope 14. The exterior surface of the envelope may be treated as by an electronic corona to be oleophillic and thus provide preferred adhesion of the length of adhesive 12 thereto as compared to the untreated oleophobic contacting surface of the flap 27 so that opening of the flap 27 subsequent to sealing will leave all of the length of adhesive 12 adhered to the exterior surface of the envelope 14.

The mechanism 10 includes a first main support frame 28 through which may pass the conveyor belt 22 for spaced seriatim delivery of envelopes 14 from a source (not shown) to the support surface 20. A second frame 30, to which the pressure foot 26 is affixed, is mounted to afford relative movement between the frames 28 and 30 or frame 28 and pressure foot 26 via movement of the second frame 30 between a first position at which the application surface 24 is spaced from the support surface 20 to afford movement of the polyethylene envelopes 14 on the conveyor belt 22 beneath the pressure foot 26, and a second position to press a length of adhesive 12 on the application surface 24 into contact with a polyethylene envelope 14 positioned on the support surface 20. The mounting means for the frame 30 comprises a pair of vertically extending rods 32 mounted on the first frame 28 and slidably engaged with a pair of bearings 33 attached to the second frame 30.

Movement of the second frame 30 between the first and second position is afforded by means comprising a double acting air cylinder 36 attached to the first frame 28 and having its piston 38 coupled to the second frame 30. The double acting cylinder 36 is operated by control means later to be explained. The first position of the second frame 30 is established by the limit of upward travel of the piston 38 within the cylinder 36. The second position of the frame 30 is defined by engagement of the support surface 20 and the application surface 24 about an envelope 14 and a length of adhesive 12 on the liner 18 positioned on the application surface 24, so that force exerted by the air cylinder 36 will be distributed over the application surface 24 to press the length of adhesive 12 into firm contact with the envelope 14.

Means is provided for separating the predetermined length of adhesive 12 from the liner 18 to transfer the length of adhesive 12 from the liner 18 to the envelope 14 when the frame 30 is moved from its second to its first position. This means comprises holding means for holding the envelope 14 against the support surface 20 while the length of adhesive 12 is separated from the liner 18 on the application surface 24, and air pressure means for directing a high pressure jet of air between the liner 18 and the length of adhesive 12 on the envelope 14 to aid in effecting separation therebetween.

Referring now to FIGS. 1, 4, 5, 6 and 7, the holding means comprises a pressure plate 40 having a holding surface 42 adapted for contact with an envelope 14 positioned on the support surface 20. The pressure plate 40 is formed with a slotted opening 44 sized to closely conform with the perimeter of the application surface 24 on the pressure foot 26, and to allow the pressure foot 26 to move through the opening 44 to position the application surface 24 essentially in alignment with the holding surface 42 on the plate 40 to press a length of adhesive 12 into contact with the envelope 14. The plate 40 is mounted on the second frame 30 via a pair of mounting brackets 46 formed with parallel slots 48 extending perpendicular to the holding surface 42 and sized to afford slidable engagement of the brackets 46 about a pair of pins 50 on the second frame 30. This mounting affords movement of the pressure plate 40 between a first position relative to the second frame 30 to which the pressure plate 40 is urged by a pair of springs 52 mounted between the second frame 30 and the pressure plate 40 and at which the holding surface 42 of the pressure plate 40 projects beyond the application surface 24 of the pressure foot 26 toward the support surface 20; and a second position relative to the second frame 30 at which the holding surface 42 is generally aligned with the application surface 24 on the pressure foot 26. This second position is attained against the bias of the springs 52 upon movement of the second frame 30 to its second position.

Movement of the second frame 30 from its first toward its second position will first bring the holding surface 42 of the pressure plate 40 into contact with the envelope 14 on the conveyor. Movement of the pressure plate 40 is then stopped and further movement of the frame 30 will increase holding pressure between the holding surface 42 and the envelope 14 under the influence of the springs 52. The further movement of the second frame 30 toward its second position will move the pressure foot 26 through the opening 44 to press the predetermined length of adhesive 12 on the application surface 24 into contact with the envelope 14 thereby positioning both the second frame 30 and the pressure plate 40 in their second positions. Subsequently, when the second frame 30 begins to move from its second toward its first position, the holding surface 42 will remain in contact with the envelope 14 under the influence of the springs 52 until the pins 50 contact the end of the slots 48 at the first position of the pressure plate 40 to again move the pressure plate 40 with the second frame 30 toward the first position of the second frame 30. During the interval in which the pressure plate 40 moves from its second to its first position relative to the second frame 30, the holding surface 42 will maintain the envelope 14 against the support surface 20 while the liner 18 on the application surface 24 separates from the length of strip adhesive 12 adhered to the envelope 14.

The air pressure means for directing a high pressure jet of air between the liner 18 on the application surface 24 and the length of adhesive 12 at the time of separation therebetween comprises a pair of flexible hoses 54 attached to a regulated air supply through a control valve 55 (FIG. 8) operated by control means later to be explained. The hoses 54 are connected to a pair of orifices 56 formed in the plate 40 which communicate with the opening 44 for the pressure foot 26 via a pair of slots 58 (best seen in FIG. 6) formed along the holding surface 42 in the pressure plate 40. The air is directed along the slots 58 toward the application surface 24 as the frame 30 begins to move from its second to its first position to separate the length of adhesive 12 from the releasable liner 18 on the application surface 24. The air serves to cut between the length of adhesive 12 and the liner 18 positioned on the application surface 24 to insure a clean separation or removal of the adhesive from the liner.

The means for forming the lengths of adhesive 12 and for positioning a length of adhesive 12 on the application surface 26 functions between successive applications of a length of adhesive 12 to an envelope 14 by a cycle of the second frame 30 between its first and second positions. This means includes path means for the liner 18 and the supply of strip adhesive 16 on the liner 18 including the application surface 24; severing means mounted along the path means for severing the strip adhesive 16 to form the predetermined lengths of adhesive 12 without severing the liner 18; and advancing means engaging the liner 18 and the strip adhesive 16 for advancing the severed lengths of adhesive 12 onto the application surface 26.

The path means for the liner 18 and supply of strip adhesive 16 includes a pair of flanged rollers 60 rotatably attached to the second frame 30 over which may be positioned a core 62 supporting a supply roll of tape including the adhesive 16 on a releasable liner 18. A pin 64 projects through an arcuate slot 66 in the second frame 30 from an arm 68 mounted on the second frame 30 for pivotal movement about an end 70. The liner 18 is drawn about 180° of the periphery of the pin 64 to provide abrupt separation of the pressure-sensitive strip adhesive 16 from the back of the inner coil of liner 18 onto which it has been wound. This abrupt separation has been found to provide a clean separation of the strip adhesive 16 from the inner coil. Pivotable mounting of the arm 68 allows the pin 64 to follow the outside diameter of the supply roll as its size changes. From the pin 64, the liner 18 and the pressure-sensitive strip adhesive is threaded around a flanged guide roller 72 contacted by the liner 18, and between a roller 74 formed of silicone rubber and contacted by the strip adhesive 16, and a floating roller 76 contacting the liner 18 and mounted on an arm 78 biased to press the floating roller 76 into engagement with the liner 18 to facilitate drive means later to be explained. The liner 18 and strip adhesive 16 are then threaded past the severing means for forming the predetermined lengths of adhesive 12 as will later be explained, and around the application surface 24 of the pressure foot 26. As the lengths of adhesive 12 formed by the severing means are applied to the envelopes 14 from the application surface 24, (as has already been explained) the liner 18 alone continues past the application surface 24 around the periphery of the pressure foot 26 and between a drive roller 80 and the floating roller 76.

The severing means generally designated by the numeral 82 for severing the predetermined lengths of strip adhesive is best seen in FIG. 7. The severing means 82 comprises a blade 84 such as a portion of a razor blade, firmly attached to an arm 86 rotatably mounted about a pin 88 on the second frame 30. The surface of the pressure foot 26 adjacent the blade 84 serves as an anvil 90 along the path of the liner 18 and strip adhesive 16. The blade 84 is spaced along the path from an edge 92 of the application surface 24 a distance equal to the length of the predetermined length of adhesive 12 to be formed, and the advancing means later to be explained will advance the liner 18 and the strip adhesive 16 this distance to position the juncture between the strip adhesive 16 and the length of adhesive 12 at the edge 92 between successive applications of the length of adhesive 12. Alternately, the blade 84 could be spaced a distance equal to a multiple of this distance (other than one) from the edge 92.

The blade 84 is mounted for pivotal movement between a first position with the edge thereof spaced from the anvil 90 to afford movement of the liner 18 carrying the strip adhesive 16 along the path, and a second position affording engagement of the edge of the blade 84 with the liner 18 positioned on the anvil 90. Biasing means or a spring 94 attached between a projection on the arm 86 and the second frame 30 is provided for urging the blade 84 toward the second position. The spring 94 is adapted to provide a sufficient static pressure at the edge of the blade 84 to sever or "drift through" the strip adhesive 16 without severing or notching the liner 18. Surprisingly, this static pressure between the edge of the blade 84 and the liner 18 may be quite high. A 0.003 inch thick liner 18 of silicone treated paper will not be cut or notched by static pressures as high as 10 pounds per inch of blade length, while much lower pressures will quickly sever a pressure-sensitive strip adhesive 16 such as that supplied in 465 Adhesive Transfer Tape available from Minnesota Mining and Manufacturing Company of St. Paul, Minnesota. With a spring 94 capable of providing these pressures, however, it is important that the blade 84 is not allowed to impact the liner 18 as such impact force would be sufficient to sever the liner 18 as well as the adhesive.

Means are provided for moving the blade 84 from the second to the first position in opposition to the spring 94 to afford operation of the advancing means for advancing the liner 18 and strip adhesive 16 along the path and for subsequently affording controlled, gentle repositioning of the blade 84 against the strip adhesive 16 and the liner 18.

The blade moving means best seen in FIG. 4 comprises a double-acting air cylinder 96 having the piston thereof attached to an arm 98 guided by a pair of pins 100 and formed at its distal end with a cam surface 102. The cam surface 102 is formed to engage a follower 104 attached to the pin 88 on the arm 86. The cam surface 102 has a gradual slope affording relatively slight rotational movement of the blade 84 between its first and its second position. Additionally, a regulating valve (not shown) is provided in the air supply line to the cylinder 96 to afford regulation of the rate at which air may be introduced to operate the cylinder 96. By these means, the edge of the blade 84 may be positioned in a controlled impact free manner against the strip adhesive 16 and the liner 18 to afford "drifting" of the blade 84 through the strip adhesive 16 and retention of the edge of the blade 84 against the surface of the liner 18 without severing thereof upon operation of the severing means.

The advancing means generally designated by the numeral 106 and best seen in FIG. 4, comprises a spring return air cylinder 108 mounted on the second frame 30 with its piston attached to a rack 110 to provide reciprocal motion thereof. The rack 110 engages a pinion 112 coupled to a sprocket 114 by a one-way clutch 116 to afford driving contact with the sprocket 114 only upon outward movement of the piston in the air cylinder 108. A braking strap 118 is tensioned about the hub of sprocket 114 by a spring to prevent coasting. The sprocket 114 engages a chain 120 extending from the sprocket 114 past an idler pulley 122 and around a pair of equally sized sprockets 124 and 126. The sprockets 124 and 126 are respectively attached to the rollers 80 and 74. Outward movement of the air cylinder 108 provides means for rotating the sprockets 124 and 126 in a counter-clockwise direction as viewed in FIG. 4 to advance the strip adhesive 16 and liner 18 along the path. The length of stroke of the piston in the air cylinder 108 is adjustable to cause sufficient movement of the rollers 74 and 80 to advance the length of adhesive 12 newly formed by the severing means (as previously described) to position the juncture between the adhesive supply 16 and the length of adhesive 12 at the edge 92 of the application surface 24. Driving contact of the roller 74 with the strip adhesive 16 and the roller 80 with the liner 18 is insured by the freely rotatable floating roller 76 pressed into the nip between the rollers 74 and 80. The roller 76 is mounted on the arm 78, which arm is slidably mounted about a pin positioned in a slot 128 formed in the arm 78 so that the roller will be accurately centered between the pulleys 74 and 80. The arm 78 is biased by a spring 130 attached between an end thereof and the second frame 30 to insure the proper driving pressure between the rollers 74 and 80 and the liner 18 or strip adhesive 16.

The advancing means includes means for tensioning the liner 18 and length of adhesive 12 across the application surface 24. While the sprockets 124 and 126 are of the same size, the roller 80 is slightly larger in diameter than the roller 74, therefore providing a slightly higher peripheral speed for the roller 80. This slight difference in peripheral speed between the rollers 80 and 74 requires a slight slippage in the drive coupling between the strip adhesive 16 and the roller 74 or between the liner 18 and the roller 80, thus affording the tensioning of the liner 18 about the pressure foot 26. The control means for the mechanism 10 comprises a series of air control valves each coupled to a source of air under pressure (not shown) and each operated by a separate cam mounted for simultaneous rotation on a common shaft 132. The shaft 132 is driven by drive means timed with the conveyor drive to complete a 360° rotation for each cycle of the conveyor 22 during which the conveyor 22 advances to position a successive envelope 14 on the support surface 20 and the movement of the conveyor 22 pauses to afford application of a length of adhesive 12 to the envelope 14. An operating cycle of the control means in conjunction with the conveyor 22 will be explained starting at the point at which the second frame 30 has just returned to its first position subsequent to application of a length of adhesive 12 to an envelope 14. As the conveyor 22 advances the position a new envelope 14 on the support surface 20, a cam 134 engaging the control valve 136 for the cylinder 96 activates the cylinder 96 to move the blade 84 to its second position spaced from the anvil 90. The cam 134 is shaped to maintain the valve 136 in this position thereby maintaining the blade 84 in the second position while a valve 138 actuating the cylinder 108 is cycled by a cam 140 to advance the strip adhesive 16 and liner 18 along the path to position the juncture between the strip adhesive 16 and the length of adhesive 12 at the edge 92 of the application surface 24. The cam 134 then operates the control valve 136 to return the blade 84 gently to its second position against the strip adhesive 16. After the conveyor 22 has advanced the predetermined distance to position a new envelope 14 on the support surface 20, movement of the conveyor 22 is stopped while continuing rotation of the shaft 132 by the drive means rotates a cam 142 to operate a control valve 144 to cycle the cylinder 36 thereby moving the second frame 30 between its first and second position to apply the length of adhesive 12 on the application surface 24 to the envelope 14, while a cam 146 is rotated to operate the control valve 55 to direct a jet of air between the liner 18 and the length of adhesive 12 thereby aiding in separating the length of adhesive 12 from the liner 18 as has previously been described. Upon return of the second frame 30 to its first position the cycles are complete.

Alternatively, the mechanism 10 may be operated for semi-manual application of lengths of adhesive 12 to objects or envelopes 14 manually positioned on the supporting surface 20. For a system of this type, the shaft 132 may be driven by a motor (not shown). A cycle may be initiated by operation of a switch to start the motor which will operate the cams through one cycle for the control means as previously described and reset the mechanism 10 for future operations via reactivation of the switch.