Abstract:
Hot melt thermoplastic adhesive is predeposited on a carrier strip having front and back release surfaces. The carrier strip is rolled into a coil compressing the thermoplastic hot melt into disks which may later be removed for use. The disks are spaced so that the carrier strip may be deformed to expose a single disk to a planar surface permitting simplified dispensing of the disks.

Description:
IDENTIFICATION OF RELATED APPLICATIONS  
       [0001]    This patent application is a continuation of U.S. patent application Ser. No. 10/125,012, filed on Apr. 18, 2002, entitled “Thermoplastic Adhesive Dispensing Method and Apparatus,” which is a continuation of U.S. patent application Ser. No. 09/998,950, filed on Nov. 15, 2001, entitled “Thermoplastic Adhesive Dispensing Method and Apparatus,” which is in turn a continuation of U.S. patent application Ser. No. 09/363,200, filed on Jul. 29, 1999, now U.S. Pat. No. 6,319,442, entitled “Process of Making a Thermoplastic Adhesive Dispensing Tape,” which is in turn a continuation-in-part of U.S. patent application Ser. No. 08/909,189, filed on Aug. 11, 1997, now U.S. Pat. No. 5,935,670, entitled “Thermoplastic Adhesive Dispensing Method and Apparatus,” which is in turn based upon U.S. Provisional Patent Application No. 60/036,896, filed on Feb. 6, 1997, all of which are assigned to the assignee of the present invention. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    In the preparation of mass mailings, for example, it is often desired to attach a card, such as a credit card or the like, to a carrier document so that the former can be peeled easily from the carrier document for use by a consumer. One method of making such an attachment uses a pressure-sensitive, thermoplastic adhesive. During the printing or collating process, a portion of the thermoplastic adhesive is metered onto the carrier document and the card pressed against this material. The equipment for this process includes a heating container for the thermoplastic adhesive and a metering pump that may be electrically actuated.  
           [0003]    Thermoplastic adhesive can be difficult to work with. Its high melting temperature and adhesive properties present some risk of burn to untrained operators. The price of the equipment for dispensing the thermoplastic adhesive and positioning and placing the attachments makes such equipment impractical for low volume mailings.  
         SUMMARY OF THE INVENTION  
         [0004]    The present invention provides a method and apparatus allowing thermoplastic pressure-sensitive adhesives to be used simply and safely by those who have low-volume requirements. In the present invention, pressure-sensitive thermoplastic adhesive is pre-metered onto a release strip which may be rolled into coil. The size and spacing of the metered dots of thermoplastic adhesive allows one dot to be exposed at a time across an anvil plate which may be used to press the dot against a card or the like. The carrier strip may be advanced between the pressing operation to bring a new dot into position.  
           [0005]    The spacing of the dots along the strip provides simple methods of dispensing the dots including the use of a specially constructed cardboard dispenser box or the like or various automated metering systems and mechanisms to be described.  
           [0006]    Specifically, the present invention provides a thermoplastic adhesive dispensing tape having a flexible carrier tape extending longitudinally and having a transverse width and having opposed first and second release surfaces. Thermoplastic adhesive dots are arrayed longitudinally along the first release surface so that the carrier tape may be curved about an axis to expose a single adhesive dot to an abutting planar surface.  
           [0007]    Thus, it is one object of the invention to provide a simple means for dispensing thermal plastic adhesive dots without requiring the expense or hazard of molten thermoplastic adhesive.  
           [0008]    The second release surface may adhere less strongly to the thermoplastic adhesive dot than does the first release surface.  
           [0009]    Thus, it is another object of the invention to provide a thermoplastic adhesive dispensing tape that may be unwound from a coil with the thermoplastic adhesive dots being retained on the first release surface.  
           [0010]    The invention includes a method of manufacturing the thermoplastic adhesive dispensing tape by unrolling the flexible carrier strip from a first reel to expose the first release surface and dispensing molten thermoplastic adhesive at periodic intervals on the unrolled carrier strip. The carrier strip is then rerolled to compress the dispensed molten thermoplastic adhesive into flat disks.  
           [0011]    Thus, it is another object of the invention to provide for adhesive disks that approximate the size and area that would be provided by an automatic dispensing equipment directly on the surfaces to be adhered together. The action of adjacent coils of the carrier strip mimics that of a card or other planar surface pressing against a molten portion of thermoplastic adhesives.  
           [0012]    The rerolling of the flexible carrier strip may be delayed until the thermoplastic adhesive has skinned over.  
           [0013]    Thus, it is yet another object of the invention to ensure that the thermoplastic adhesive dots are retained by the first release surface which receives the thermoplastic adhesive in a molten state prior to it skinning over and therefore adheres to it more strongly.  
           [0014]    The step of dispensing molten thermoplastic adhesive may simultaneously dispense at least two separate portions of thermoplastic adhesive at transversely separated locations. The method may include the further step of longitudinally slitting the flexible carrier strip between separate portions of the thermoplastic adhesive prior to rerolling the flexible carrier strip.  
           [0015]    Thus, it is another object of the invention to provide for a high throughput manufacture of adhesive dots with a single dispensing unit without jeopardizing the cooling of the dots as is necessary to allow them to skin over.  
           [0016]    The invention also includes a dispensing apparatus for the thermoplastic adhesive dispensing tape, including a reel support, for holding the thermoplastic adhesive dispensing tape in coiled configuration, and a guide for receiving the carrier tape after adhesive dots have been removed. An anvil surface is positioned between the reel and the guide to receive the thermoplastic adhesive dispensing tape as unreeled from the coil and deform the thermoplastic adhesive dispensing tape to expose a single adhesive dot to a planar surface.  
           [0017]    Thus, it is another object of the invention to provide a rapid application technique for the thermoplastic adhesive dots on the tape of the present invention. The positioning of the dots so that a single dot may be exposed to a planar surface allows the dots to be readily applied to planar surfaces by a proper incrementing of the tape over a correctly sized anvil surface.  
           [0018]    The foregoing and other objects and advantages of the invention will appear from the following description. In this description, reference is made to the accompanying drawings which form a part hereof and in which there is shown by way of illustration, a preferred embodiment of the invention. Such embodiment does not necessarily represent the full scope of the invention, however, and reference must be made therefore to the claims for interpreting the scope of the invention.  
       
    
    
     DESCRIPTION OF THE DRAWINGS  
       [0019]    [0019]FIG. 1 is a schematic view of a manufacturing system for the present invention showing the dispensing of thermoplastic pressure-sensitive dots onto a carrier strip and the winding of the strip into coils;  
         [0020]    [0020]FIG. 2 is a plan view of a section of a strip of the present invention showing the ultimate spacing of the dots when flattened;  
         [0021]    [0021]FIG. 3 is a cross section through a coil of FIG. 1 showing the compression of the dots by adjacent coils of the release strip;  
         [0022]    [0022]FIG. 4 is a perspective cut-away view of a container for dispensing the coils of FIG. 1 showing the spacing of the dots which permits a single dot to be exposed over an anvil surface for attachment to a card;  
         [0023]    [0023]FIG. 5 is a perspective view of the container of FIG. 4 placed in an automatic tape advancing apparatus to pull the release strip a predetermined amount at the pressing of a palm button;  
         [0024]    [0024]FIG. 6 is a simplified fragmentary cross section of a semi-automatic dispensing machine positioned for dispensing an adhesive dot on a carrier sheet prior to dispensing;  
         [0025]    [0025]FIG. 7 is a view similar to that of FIG. 6 showing a downward activation of the apparatus of FIG. 6 advancing a dot from the carrier strip over a movable anvil surface to be pressed against the carrier sheet; and  
         [0026]    [0026]FIG. 8 is a figure similar to that of FIGS. 6 and 7 showing the upward return of the apparatus after dispensing, the return causing a tensioning of the used carrier strip in preparation of a second stroke.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0027]    Referring to FIG. 1, an adhesive dot manufacturing machine  10  provides a back tensioned reel  12  holding a differential release carrier strip  14 . The carrier strip  14  is a paper that has a silicon release material on opposed first and second surfaces  16  and  18  selectively applied so that surface  16  provides less release than surface  18 .  
         [0028]    The carrier strip  14  is dispensed from the tensioned reel  12  with surface  16  facing upward to move beneath a pair of thermoplastic glue metering nozzles  20  (only one of which is visible in FIG. 1) supplied by a metering pump not shown, to dispense side-by-side glue dots  22  onto surface  16  as surface  16  moves past nozzle  20 . Air jet  24  directed on surface  16  then cools the glue dots  22  which are also cooled by natural convection as the carrier strip  14  moves along.  
         [0029]    A slitting knife  26  divides the carrier strip  14  into multiple strips, each of which are then wound into coils  30  on take-up reels  28  under controlled tensioning. Capstan and idler wheels may also be provided so that the tension on reels  28  may be controlled independently of the tension provided by reel  12 .  
         [0030]    Referring now to FIG. 3, the glue dots  22  are initially mounded high on the surface  16  of the carrier strip  14 , but as they are wound about the reel  28 , each glue dot  22 ′ is compressed beneath surface  18  of the carrier strip  14  of the next succeeding layer of carrier strip  14  and the surface  18  of the layer of the carrier strip  14  on which it was deposited so as to flatten the glue dots  22 ′ into circular disks.  
         [0031]    The differential release properties of surfaces  16  and  18 , the fact that the glue dots  22  were initially applied in a hot state to surface  16  causing better adherence, and the fact that there is some cooling and hence “skinning over” of the glue dots  22  prior to the winding on reel  28 , all ensure that the glue dots  22  remain adhered to surfaces  16  as the coil  30  is unwound.  
         [0032]    Referring now to FIG. 2, the spacing of the glue dots  22 ′ after flattening on the carrier strip  14  is such that the glue dots  22 ′ do not overlap in the dimension defined by the extent of carrier strip  14 . This ensures that there is a margin  32  in that dimension such that an individual glue dot  22  may be exposed for adhering to a card or the like without the risk of the card picking up multiple glue dots  22 . Dots  22  and  22 ′ of a preferred embodiment may be separated by three times their diameter.  
         [0033]    Referring now to FIG. 4, the coil  30  may be inserted within a dispensing container  34  having generally rectangular configuration with top, side, and bottom walls  36  and a spanning vertical wall  38 . Vertical wall  38  includes a coil support hub  40  extending laterally into the volume of the container  34  from the vertical wall  38  about which the coil  30  may be positioned. As positioned, the coil  30  is free to rotate along a horizontal axis with the outer surfaces of the coil containing the glue dots  22 ′ being removed from the inner surfaces of the walls  36 .  
         [0034]    A slot  43  at one end of the upper wall  36  allows a portion of the carrier strip  14  to be threaded from within the container  34  out of the slot  43  and across the upper wall  36  with the glue dots  22 ′ exposed on the upper surface of the carrier strip  14 . The upper wall  36  provides an anvil surface supporting the carrier strip  14  against pressure when a card  42  or the like is pressed down as indicated by arrow  44  against the upper surface of the carrier strip  14  to receive a glue dot  22 ′.  
         [0035]    As a result of the earlier removal of the glue dots  22 ′ on the carrier strip  14 , only a single dot  22 ′ will be exposed on the upper surface of the container  34  at a time simplifying this attachment process.  
         [0036]    The portion of the carrier strip  14  previously having its dots  22 ′ removed may be received within a slot  46  in a side wall  36  adjacent to the top wall  36  and then threaded out of a similar slot  48  positioned below slot  46  to permit sliding of the carrier strip  14  for the dispensing of additional dots  22  while preventing general looseness of the carrier strip  14  such as would promote unwinding of the coil  30  unintentionally.  
         [0037]    Referring to FIG. 5, the container  34  may be used for manual dispensing or may be placed within an automatic dispensing system  50 . Such a system includes a rigid container sleeve  52 , holding the lower portion of the container  34 , and a motor drive unit  54  receiving the carrier strip  14  after dots have been removed and incrementing the tape by a predetermined amount with a pressing of a palm sized push button  56 . With each pressing of the button  56 , the motor drive unit  54  increments the carrier strip  14  by the interdot spacing so as to expose a single dot  22 ′ at the top of the container  34 .  
         [0038]    Referring now to FIG. 6 in an alternative dispensing method, the coil  30  may be carried on a semi-automatic affixing tool  58 . A foot portion  60  of the tool  58  is placed at the top of a carrier sheet  63  where an adhesive dot will be placed. A plunger assembly  62  attached to slide up and down with respect to the foot portion  60  and biased upward with helical tension springs (not shown) so as to normally be held away from the carrier sheet  63  prior to the dispensing action. Plunger assembly  62  has a handle  64  exposed above the coil  30  and connected to a hanger  66  holding the coil for rotation about hanger  66 . A lower portion of the plunger assembly  62  includes a convex elastomeric anvil surface  68  flanked by rollers  70 . The rollers  70  guide the carrier strip  14  downward across the lower surface of the anvil  68  which contacts the inner surface  18  of the carrier strip and up between pinch rollers  72  which grasp the portion of the carrier strip  14  after dots have been removed.  
         [0039]    Referring now to FIG. 7, the handle  64  may be grasped and pressed downward toward the carrier sheet  63  as indicated by arrow  74 . The pinch rollers  72  are mounted to be fixed in height with respect to the foot portion  60  and to rotate only in a manner that would pull tape from the coil  30 . Hence, with downward motion of the plunger assembly  62 , the anvil  68  moves towards the carrier sheet  63  simultaneously causing the unwinding of carrier strip  14  from the coil  30  such that at the moment the anvil  68  strikes the carrier sheet  63 , a glue dot  22 ′ is positioned immediately beneath the anvil  68  to be attached to the carrier sheet  63 .  
         [0040]    Referring now to FIG. 8, the handle  64  may be pulled upward aided by the springs (not shown) between the foot portions  60  and the plunger assembly  62 , at which time a ratchet lever (not shown) interconnecting the plunger assembly  62  and the foot portion  60  causes a partial rotation of the pinch rollers  72  in response to the movement of the plunger assembly  62  with respect to the foot portion  60 . This rotation of the pinch rollers  72  advances the carrier strip  14  to remove slack and cause it to remain abutted to the anvil  68  in preparation for a new actuation sequence.  
         [0041]    Thus the tape of the present invention provides a simple method for dispensing dots of glue for joining materials together without the need for complex equipment or exposure to heated thermoplastic materials.  
         [0042]    The above description has been that of a preferred embodiment of the present invention. It will occur to those that practice the art that many modifications may be made without departing from the spirit and scope of the invention. For example, a separate release strip may be wound into the coils of the dots to avoid the need for a carrier strip having opposed release surfaces. Glue dots having shapes other than disks may be produced by the appropriate dispensing nozzles. In order to apprise the public of the various embodiments that may fall within the scope of the invention, the following claims are made.