EP0904191A1

EP0904191A1 - Apparatus for two-stage fusion of face-to-face polymeric sheets

Info

Publication number: EP0904191A1
Application number: EP97922708A
Authority: EP
Inventors: Paul V. Corpus; Gary Field; Douglas K. Fossum
Original assignee: Atlantek Inc; Minnesota Mining and Manufacturing Co
Current assignee: Atlantek Inc; 3M Co
Priority date: 1996-05-13
Filing date: 1997-05-07
Publication date: 1999-03-31
Also published as: AR007107A1; AU2831097A; AU717865B2; CA2254876A1; BR9709235A; KR20000011135A; JP2000510066A; WO1997043110A1

Abstract

Apparatus (117) operative for fusing an amorphous copolyester sheet (14) with a polyvinyl chloride sheet (16) includes a belt assembly (118) having an endless belt (122) received around first and second rollers (124, 126). The apparatus (117) further includes a third roller (158) mounted in cooperation with the first roller (124) to form an input nip with the first roller (124) such that the rollers (124, 158) press the sheets (14, 16) together to define a two-piece structure (12) having a polyvinyl chloride side and an opposing amorphous copolyester side. The polyvinyl chloride side is positioned adjacent to the first roller (124). The apparatus (117) still further includes a cartridge heater (154) for heating the first roller (124) such that the polyvinyl chloride side of the two-piece structure (12) is heated as the sheets (14, 16) pass through the nip. The third roller (158) is cooled by a fan means (164) so that the amorphous copolyester side is cooled while the polyvinyl chloride side is heated. The apparatus (117) even further includes a heated platen (180) for applying additional heat to the polyvinyl chloride side of the two-piece structure (12). The heated platen (180) is in thermal communication with an underside of the belt (122) wherein further heat is applied to the polyvinyl chloride side of the two-piece structure as the belt (122) carries the two-piece structure over the platen (180). Finally, the apparatus includes fan cooled heat sinks (194, 202) positioned above and below the belt (122) for cooling both sides of the two-piece structure (12) as the two-piece structure is transported away from the heated platen (180).

Description

APPARATUS FOR TWO-STAGE FUSION OF FACE-TO-FACE POLYMERIC SHEETS

cross-reference to Related Applications: This application is a continuation-in-part of co- pending U.S. Application No. 08/419,457 commonly assigned with the present application.

Background and Summary of the Invention: The instant invention relates to the fusion of an amorphous copolyester backing sheet and a polyvinyl chloride sheet to form a two-piece card structure, such as an identification card, and more particularly to belt- type transport apparatus for transporting the facing sheets through successive fusing and cooling stages.

Belt-type transport apparatus of the general type contemplated herein have heretofore been known in the lamination art. In general, the prior art apparatus typically include only a single heating station for applying heat to the surfaces of the thermoplastic sheets while maintaining the sheets in face-to-face relation. These apparatus are known as single-stage laminators and they are effective for laminating many types of thermoplastic sheet materials. However, there are certain types of thermoplastic sheet materials, such as the above-noted amorphous copolyester and polyvinyl chloride materials, which have specific heating and cooling characteristics which are not met by the prior art devices. It has thus been found that there is a need in the industry for an apparatus which is effective for the fusion of these new card materials. A first embodiment of the instant invention provides a two-stage fusing apparatus comprising upper and lower belt assemblies which are supported in closely spaced adjacent relation. The lower belt assembly comprises a stainless steel belt received around first and second rollers, and the upper belt assembly comprises a fiberglass belt received around third and fourth rollers. The belt assemblies are supported in a frame structure such that the first and third rollers form an input nip, and the second and fourth rollers form an output nip, with the endless belts in facing relation. The first and second rollers are fixed in position, with the third and fourth rollers being slidably suspended relative to the first and second rollers. The third and fourth rollers are biased downwardly from their suspended position toward the first and second rollers to form spaced, but pressurized input and output nips. The first, or lower, input roller is heated by an internal cartridge heater to a temperature of about 200°C. The heated input nip is operative for pressing the copolyester sheet and the polyvinyl chloride sheet together to initially fuse the two facing sheets into a two piece structure. A heating platen, positioned in abutting relation with an upper portion of the metallic belt adjacent to the first roller is heated to a temperature of about 160°C to define a full fusing stage. Fan cooled heat sinks are positioned in abutting relation adjacent to the output nip for cooling the metallic and fiberglass belts passing therebetween and removing heat from the card after fusion. A second embodiment of the apparatus includes a single belt assembly having an endless belt received around first and second rollers. The apparatus further includes a third roller mounted in cooperation with the first roller to form an input nip with the first roller such that the rollers press the sheets together to define a two-piece structure having a polyvinyl chloride side and an opposing amorphous copolyester side. The polyvinyl chloride side is positioned adjacent to the first roller. The apparatus still further includes a cartridge heater for heating the first roller such that the polyvinyl chloride side of the two piece structure is heated as the facing sheets pass through the nip. The third roller is actively cooled by a fan means so that the amorphous copolyester side is cooled while the polyvinyl chloride side is heated. The roller fan actively removes heat from the amorphous copolyester sheet during the initial fusion to prevent the copolyester -from deforming under the nip pressure. The apparatus further includes a heated platen downstream of the input nip for applying additional heat to the polyvinyl chloride side of the two piece structure to effect a full fusion of the sheets. The heated platen is in thermal communication with an underside of the belt wherein further heat is applied to the polyvinyl chloride side of said two-piece structure as the belt carries the two piece structure over the platen. Finally, the apparatus includes fan-cooled heat sinks positioned above and below the transport belt for cooling both sides of the two-piece card structure as the two-piece card structure is transported away from the heated platen. Accordingly, among the objects of the instant invention are the provision of a two-stage fusing device wherein two thermoplastic sheets are initially fused under heat and pressure, fully fused under heat alone, and then cooled; the provision of a fusing device including an endless belt for transporting sheet materials through an initial fusing station, a full fusing station, and a cooling station; and the provision of a fusing device including a heated input nip, a heated platen and fan cooled heat sinks. Other objects, features and advantages of the invention shall become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawings.

Description of the Drawings: In the drawings which illustrate the best mode presently contemplated for carrying out the present invention: Fig. 1 is a front view of the first embodiment of the apparatus of the instant invention; Fig. 2 is a rear view thereof; Fig. 3 is a top view thereof; Fig. 4 is a cross-sectional view thereof taken along line 4-4 of Fig. 3; Fig. 5 is a perspective view of a second embodiment of the apparatus; Fig. 6 is a front view thereof; Fig. 7 is a rear view thereof; Fig. 8 is a top view thereof; Fig. 9 is a right side view thereof; and Fig. 10 is a cross-sectional view thereof taken along line 10-10 of Fig. 9

Description of the Preferred Embodiment: Referring now to the drawings, a first embodiment of the apparatus of the instant invention is illustrated and generally indicated at 10 in Figs. 1-4. As will hereinafter be more fully described, the instant apparatus 10 is operative for fusing face-to-face thermoplastic sheet materials, such as those types of sheet materials used in constructing security cards. More specifically, the instant invention 10 has been found to be particularly useful in fusing a security card system developed by Minnesota Mining and Manufacturing Company of Saint Paul Minnesota, and described in PCT Publication No. WO95/09084 which is incorporated herein by reference. The subject security card system generally indicated at 12 in Fig. 4, comprises a backing sheet 14, a cover sheet 16, and a security image (not shown), with the security image preferably being reverse printed on the inner surface 18 of the cover sheet 16 so that it is located between the fused sheets 14, 16 when secured together. When viewed through the upper side of the cover sheet, the reverse printed security image appears in its correct orientation. The backing and cover sheets 14, 16 are fused directly together without an intermediate layer of adhesive, wherein the backing sheet 14 preferably comprises an amorphous copolyester film, and the cover sheet 16 comprises a rigid polyvinyl chloride film. The amorphous copolyester backing sheet 14 is preferably pigmented with titanium dioxide so that it is opaque white, while the PVC cover sheet 16 is preferably transparent, although other color schemes and arrangements are also suitable. In most instances, the backing sheet 14 is considerably thicker than the cover sheet as it is intended to provide most of the rigidity and strength of the assembled card 12. For example, the backing sheet 14 preferably has a thickness of between about 20 and 22 mils, and the cover sheet 16 preferably has a thickness of between about 7 and 10 mils for a total card thickness of between about 27 and 32 mils. The particular advantage of the subject security card system 12 is that good adhesion can be achieved between PVC and amorphous copolyesters at relatively low temperatures, e.g. , at temperatures of about 150°C. The fusion can be effectively achieved because both amorphous copolyesters and PVC are softened during the fusion process, and both contract on cooling at about the same rate, thereby reducing warping problems encountered with other existing card materials. The first embodiment of the apparatus 10 comprises upper and lower belt assemblies generally indicated at 20 and 22, which are supported in closely spaced adjacent relation by a frame assembly comprising a bottom wall 24, and parallel front and rear walls, 26 and 28 respectively. The lower belt assembly 22 comprises a stainless steel belt generally indicated at 30 received around first and second metallic rollers 32, 34 respectively, and the upper belt assembly 20 comprises a fiberglass belt generally indicated at 36 received around third and fourth metallic rollers, 38 and 40 respectively. Both the stainless steel belt 30 and the fiberglass belt 36 preferably have thicknesses of about .003 inches. The steel belt 30 is commercially available from Belt Technologies of Agawam, MA, and the fiberglass belt 36 is available from Greenbelt Industries, Inc. of Buffalo, NY. The rollers 32, 34, 38, 40 preferably comprise aluminum rollers having shafts 32S, 34S, 38S, 40S. It is pointed out that shafts 32S and 38S are hollow, while shafts 34S and 4OS are solid. The belt assemblies 20, 22 are supported in the frame such that the first and third rollers 32, 38 from an input nip, and the second and fourth rollers 34, 40 form an output nip, with the endless belts 30, 36 in facing relation. The first and second rollers 32, 34 are fixed in position, with the third and fourth rollers 38, 40 being slidably movable relative to the first and second rollers 32, 34. More specifically, the shaft of each roller is received through a pair of spaced bearing mounts generally indicated at 42A, 42B, 42C, and 42D. Each bearing mount 42 comprises a bearing 44A, 44B, 44C, 44D which is supported in a bearing holder 46. Bearings 44A and 44C each comprise a roller-type bearing, while bearings 44B and 44D comprise sleeve-type bearings. Furthermore, the sleeve bearings 44B and 44D are mounted in a hardened outer sleeve 45. Each bearing holder 46 includes a recess 48 for receiving the bearing 44 therein, and further includes grooves 50 in the side edges thereof. The grooves 50 of the bearing mounts 42 are slidably received in respective slots 52 in the front and rear walls 26, 28 of the frame assembly so that the bearing holder 46 engages both the inner and outer surfaces of the walls 26, 28. The bearing mounts 42A and 42B rest against the bottom of their respective slots 52, and thus maintain the first and second rollers 32, 34 in a fixed vertical position. It is pointed out that the recesses 48B in the bearing mounts 42B (second roller 34) are elongated in a horizontal direction to allow sliding horizontal movement of the axis of the second roller 34 with respect to the first roller 32. In this connection, a set 54 is extended through a threaded opening in the side wall of the bearing mount 46B and engaged with the hardened outer sleeve 45 to adjust the distance between the axis of the first roller 32 and the axis of the second roller 34. This set screw arrangement is operative for adjusting the parallelism of the first and second roller axes as well as for taking up or tightening slack in the steel belt 30. The bearing mounts 42D for the fourth roller 40 have the same elongated recess 48D and set screw 54 for adjustment of the fourth roller axis with respect to the third roller axis. The bearing mounts 42C, 42D for the third and fourth rollers 38, 40 are suspended in the frame assembly by screws 56 which extend downwardly through spaced suspension bars 58 attached to the front and rear walls 26, 28. The head 60 of the screw 56 rests on top of the bar while the shaft 62 passes through an opening (not shown) in the bar 58 and extends into a threaded bore (no shown) in the top of the respective bearing holder 46. A compression spring 64 is received around each screw 56 and captured between the top of the respective bearing holder 46 and the bottom of the respective suspension bar 58 to bias the third and fourth rollers 38, 40 downwardly from their suspended position toward the first and second rollers 32, 34. Rotation of the screw 56 permits adjustment of the vertical spacing between the third and first rollers 38, 32 (input nip rollers) and the fourth and second rollers 40, 34 (output nip rollers). In this regard, the belt assemblies 20, 22 are adjusted so that there is at 25 mil spacing between the input rollers 32, 38 and between the output rollers 34, 40, the spacing being slightly smaller than the combined thickness of the security card sheets (27-33 mils) . Since the third and fourth rollers 38, 40 are biased downwardly toward the first and second roller 32, 34, the roller pairs form spaced, but pressurized input and output nips. The first, or lower, input roller 32 is heated by a conventional cartridge heater 66 to a temperature of between about 190°C and about 215°C, but more preferably to a temperature of about 200^CC. The cartridge heater 66 is slidably received in the center of the hollow roller shaft 32S and is energized by a conventional electric source (not shown). The input nip (rollers 32, 38) thus defines an initial fusing stage for fusing the cover and backing sheets 14, 16 together under pressure and heat. Referring now to Fig. 4, a full fusing stage is defined by a 1/2 inch thick aluminum heating platen 68, positioned in abutting relation with an upper portion of the steel belt 30 adjacent to the first roller 32. The platen 68 is preferably heated to a temperature between about 150°C and about 170^CC, and more preferably to a temperature of about 160°C. Heating of the platen 68 is accomplished by means of a rubber plate heater 70 glued to the bottom surface of the platen 68. A rubber plate heater 70 of the type contemplated is available from Hotset, Inc. of Battle Creek, MI. Alternatively, other beating devices, such as cartridge-type heaters, could be used to heat the platen 68. In order to cool the belts 30, 36 and the fused sheets 14, 16 held therebetween, first and second fan cooled heat sinks generally indicated at 72, 74 respectfully, are positioned in abutting relation adjacent to the output nip (rollers 34, 40). More specifically, a first aluminum heat sink 72 is positioned between the front and rear walls 26, 28 of the frame, with the body portion 72B in abutting relation with the upper portion of the steel belt 30. Fasteners 76 extend through the front and rear walls 26, 28 of the frame and into openings (not shown) in the heat sink 72 to fixedly secure the heat sink 72 in position. A second heat sink 74 is positioned between the front and rear walls 26, 28 of the frame assembly with the body portion thereof 74B in abutting relation with the lower portion of the fiberglass belt 36. A second set of fasteners 78 extend through vertical slots 80 in the frame walls 26, 28 and into the second heat sink 74. Springs 82 are secured between the fastener pairs to draw the second movable heat sink 74 downwardly into compressing relationship with the first fixed heat sink 72. The fins 72F, 74F of the heat sinks 72, 74 extend perpendicular to the direction of travel of the belts 30, 36 wherein first and second fans 83, 84 mounted to the rear wall of the frame respectively blow air over the fin surfaces 72F, 74F in a direction perpendicular to the direction of belt travel. To facilitate rapid air movement and optimize cooling, the air is moved through openings 86, 88 in the front and rear walls 26, 28 of the frame assembly. In use, the belts 30, 36 are rotated simultaneously in opposite directions for transporting the overlapping cover and backing sheets 14, 16 between the endless belts from the input nip to the output nip. Rotation of the belts 30, 36 is accomplished via an electric motor generally indicated at 90 and gear system. The body 92 of the electric motor 90 is mounted to a bracket 94 attached to the rear wall 28 of the frame assembly. The drive shaft 96 of the motor 90 includes a worm gear portion 98 for rotating a drive gear 100 mounted on the rear end of the shaft 34S of the second roller 34 (Fig. 2, 3). Rotation of the lower belt assembly 22 is transferred to the upper belt assembly 20 by a pair of intermeshing transfer gears 102, 104 mounted on the front ends of the shaft 34S, 4OS of the second and fourth rollers 34, 40 (Fig. 1). The motor 90 and gear assembly are preferably timed for transporting cards through the apparatus at a rate of about 0.25 inches per second. The instant device is thus operative for transporting a conventional size ID card through the apparatus at a rate of about 1 card per minute. The apparatus 10 further includes upper and lower steering assemblies generally indicated at 106 and 108 for maintaining proper alignment and rotation of the belts 30, 36 on their respective rollers. Each steering assembly 106, 108 comprises a shaft 110 mounted between the front and rear walls 26, 28 of the frame. The shaft 110U of the upper steering assembly 108 extends immediately beneath the upper portion of the fiberglass belt 36 adjacent the input nip, and the shaft 110L of the lower steering assembly extends immediately above the lower portion of the steel belt 30 adjacent to the input nip (Fig. 4) . Mounted on each of the shafts 110 is a mating pair of truncated cone rollers 112 with the larger diameter ends of the roller 112 facing toward the outer ends of the shafts 110. In this regard, as the belts 30, 36 rotate, if either belt should skew toward one side or the other, the belt will ride upwardly on the corresponding truncated roller 112, wherein it will be urged back downwardly into its normal rotating position. The apparatus 10 is intended to be used with the cover sheet 16 of the card system facing downwardly and the backing sheet facing 14 upwardly. As the overlying sheets 14, 16 are fed into the input nip, the backing and cover sheets 14, 16 are pressed together under the pressure of the nip while the cover and backing sheets 14, 16 are heated by the heated lower roller 32 of the input nip. The pressure of the input nip squeezes out air bubbles from between the sheets 14, 16 prior to fusion, and further maintains the cover and backing sheets 14, 16 in proper registration during initial heating by the roller 32. Maintaining the sheets 14, 16 in proper registration during the initial heating is extremely important, since the plastic materials become somewhat soft, and movement of the sheets at their interface while in a molten state will cause smudging or smearing of the security image printed on the inner side 18 of the cover sheet 16. After the initial fusion, the sheets 14, 16 are transported over the heated platen 68 which further heats the sheets for a longer duration while in a fixed position wherein they are able to fully fuse together. It is noted that the longer exposure to heat over the platen 68 significantly softens the upper backing sheet 14 to a point wherein the surface grain or texture of the fiberglass belt 36 can be unwantedly imprinted on the back surface 114 of the backing sheet 14. In this connection, a lower portion of the fiberglass belt 36 directly above the heating platen 68 is cooled by a fan 116. The air directed across the fiberglass belt 36 keeps the back surface 114 of the backing card 14 sufficiently cool and rigid so as not to be imprinted with the surface texture of the fiberglass belt 36. The fused sheets 14, 16 are thereafter cooled to almost room temperature by passage between the fan-cooled heat sinks 72, 74. The sinks 72, 74 effectively remove almost all of the heat from the sheets 14, 16 prior to exiting from the apparatus between the output nip. Referring now to Figs. 5-10, a second embodiment of the apparatus is illustrated and generally indicated at 117. The second emobidment 117 is generally similar to the apparatus 10 with the exceptions that there is only a single transport belt, and the upper input roller is cooled. More specifically, the second embodiment 117 comprises a belt assembly generally indicated at 118 which is supported in a frame assembly comprising front and rear spaced walls, 119, 120 respectively. The belt assembly comprises a Teflon coated .005 inch thick stainless steel belt 122 received around first and second rollers 124, 126 respectively. The rollers 124, 126 are preferably fabricated from aluminum for good heat conduction. The rollers 124, 126 are rotatably mounted on shafts 128, 130 respectively wherein shaft 128 is hollow while shaft 130 is solid (See Fig. 10) . The opposing ends of the shafts 128, 130 are rotatably mounted in respective fixed bearing mounts 132 received in the spaced front and rear walls 119, 120 of the frame such that the rollers 124, 126 are maintained in fixed parallel relation at all times. The belt assembly 118 is rotated by an electric drive motor 134 having a drive shaft 136 with a worm gear surface 138 which intermeshes with a corresponding drive gear 140 on the shaft 130 of the second roller 126. The motor 134 and gears 138, 140 cooperate to rotate roller 126 at an appropriate speed to transport a card received on top of the belt 122 through the various heating and cooling stages of the apparatus 117. During rotation, the belt 122 is tensioned around the first and second rollers 124, 126 by a spring-biased tension roller assembly generally indicated at 142 (See Fig. 10) . The assembly 142 comprises a roller 144 rotatably mounted on a shaft 146. The shaft 146 is slidably mounted in a pair of opposing guide slots 148 in the front and rear frame walls 119, 120. The shaft 146 is normally biased upwardly by a pair of springs 150 each having one end received around an end of the roller shaft 146, and the opposite end received around a fixed post 152 mounted on the respective front and rear frame walls 119, 120. The first roller 124 is heated by a conventional cartridge heater 154 which is slidably received into the hollow shaft 128 of the first roller 124. The cartridge heater 154 is energized by a conventional electric source (not shown) and is effective for heating the roller 124 to a temperature between about 190°C and about 215°C. The apparatus 117 further includes a third roller assembly generally indicated at 156 mounted in cooperation with the first roller 124 to form an input nip with the first roller 124 such that the sheets 14, 16 (See Fig. 4) together to define a two-piece structure having a polyvinyl chloride side 16 and an opposing amorphous copolyester side 14. The roller assembly 156 generally comprises a roller 158, front and rear retaining walls 160, 162, and a fan 164. More specifically, the roller 158 is preferably fabricated from aluminum for good heat conduction, and is further formed with a plurality of lateral bores 166 (Fig. 10) extending parallel to the turning axis and spaced around the circumference of the roller 158. The bores 166 are intended to allow an air stream from the fan 164 to travel through the roller 158 to remove heat from the roller 158. The roller 158 is rotatably mounted on a shaft 168 which is received in fixed bearing mounts 170 which are secured in the front and rear retaining walls 160, 162. The retaining walls 160, 162 are attached by flanges 172, 174 respectively to the respective front and rear frame walls 119, 120. The roller 158 is positioned in the assembly 156 to provide approximately a 25 mil spacing between the rollers 124, 158 so that the nip has adequate clearance to accept the combined thicknesses of the facing sheets 14, 16. The front and rear retaining walls 160, 162 each include a plurality of apertures 176 to permit air flow from the fan 164 to pass through the retaining walls 160, 162 and the bores 166 in the roller 58. The fan 162 is a conventional electrically powered fan, which is mounted on four spaced stanchions 178 affixed to the outside surface of the front retaining wall 160. The input nip (rollers 124, 158) is intended to function as an initial fusing stage wherein the two facing sheets 14, 16 are initially fused together under temperature and pressure. In operation, the sheets 14, 16 are fed into the input nip with the polyvinyl chloride side 16 facing the first roller 124 and the amorphous copolyester side 14 facing the third roller 158. In this manner, only the polyvinyl chloride side 16 is heated. The heat provided by the heated roller 124 is sufficient to soften the entire polyvinyl chloride sheet 16 and at least the lowermost facing surface of the amorphous copolyester sheet 14. However, it has been found by experimentation, that the heat from the roller 124 often is conducted completely through the copolyester backing 14 thereby softening the backing 14 and causing deformation the entire card structure. This was sometimes a problem in the first embodiment 10 because the softening of the backing sheet 14 allowed the texture of the fiberglass belt 36 to be imprinted into the back surface of the card during passage through the nip. Obviously, if a user wanted to print on the rear surface of the card, the imprinting of the texture would be unacceptable. The key aspect in the initial fusion of the instant card structure is to retain the stability of the backing 14, i.e. to heat the polyvinyl chloride cover sheet 16 and only the facing surface of the copolyester sheet 14 while maintaining the back surface of the copolyester sheet 14 at room temperature. Accordingly, this second embodiment 117 has been provided with a means for actively cooling the upper, i.e. third roller 158 to actively remove heat from the back surface of the copolyester sheet 14 during fusion. In operation, the fan 164 creates an air flow which passes through the bores 166 in the roller 158 to remove heat from the roller 158, and the copolyester sheet 14. By removing the heat provided by the roller 124, the back surface of the copolyester backing sheet 14 remains rigid and the fused card is not deformed. The apparatus 117 further includes a heated platen 180 (Fig. 10) for applying additional concentrated heat to the polyvinyl chloride side 16 of the two piece structure to achieve a complete fusion of the two sheets 14, 160. The platen 180 comprises an aluminum body which is positioned in thermal communication with an underside of the belt 122 adjacent to the first roller 124. More specifically, the platen 180 is mounted between the front and rear frame walls 119, 120. The platen 180 is heated to a temperature of between 150°C to 170°C by a cartridge heater 182 inserted into a bore in the body platen 180. As the fused two-piece structure exits the input nip it is transported over the surface of the heated platen 180 by the belt 122. In order to maintain the card in intimate thermal contact with the belt 122 and platen 180, the apparatus includes a plurality of pivotally linked rollers 184 which rest on the top surface of the belt 122. As the two-piece card structure passes under the rollers 184, the rollers 184 hold the card in contact with the belt 122. It is noted that the rollers are free floating and are not affixed to the frame so that they can move up and down as the card structure passes beneath each roller 184. However, the rollers 184 are disposed within an upper housing 186 which maintains the rollers 184 in position on top of the belt 122. In this regard, the rollers 184 are pivotably linked together by link elements 188, and the link elements 188 are slidably pinned to the upper housing 186 by a pin 190. Pin 190 rides in a slot 192 in the housing 186 to permit upward movement of the roller assembly while restricting longitudinal movement of the rollers 184 with respect to the belt 122. While the rollers 184 do exert some downward pressure due to gravitational forces, they are not intended exert any positive pressure onto the card. Accordingly, as the two-piece card structure card passes over the platen 180, the card structure is heated to a sufficient temperature to fully fuse the polyvinyl chloride and copolyester materials together. It is to be understood that the second heating of the card by the platen 180 will not deform the card because there is no positive pressure exerted on the card to cause deformation. In order to cool the two-piece card structure back to room temperature, the apparatus 117 includes a lower fan-cooled heat sink 194 (See Figs. 7 and 10) positioned in abutting relationship with the underside of the belt 122. The heat sink 194 is mounted between the front and rear frame walls 119, 120 and is cooled by a fan 196 mounted to the front frame wall 119. The front and rear frame walls 119 are provided with appropriate apertures 198, 200 respectively, to permit an air flow from the fan 196 to pass through the front frame wall 119, through the fins of the heat sink 194 and outwardly through the rear frame wall 120. The apparatus 117 further includes a second upper heat sink 202 which is pivotably linked at its upstream end to the rollers 184. The heat sink 202 also includes a chamfered corner 204 at its upstream end to permit the fused card structure to easily slide underneath the heat sink 202 during transport. It is noted that the heat sink 202 is captured within the upper housing 186 and is permitted to float upwardly so that the upper surface of the backing sheet 14 is maintained in intimate contact with the lower surface of the heat sink 202. The heat sink 202 is cooled by another fan 206 which is mounted on the upper wall of the upper housing 186. In operation, air passes downwardly through the upper housing 186, over the heat sink 202 and outwardly through openings at the sides and ends of the housing 186. Before the cooled card is output to the operator, the card passes through an output nip formed by the lower belt roller 126, and a fourth roller 208 mounted in cooperation with the lower belt roller 126. The roller 208 is rotatably mounted on a shaft 210 having ends which are received in shaft blocks 212. The shaft blocks 212 are slidably received in openings 214 in the sidewalls of the upper housing 186. The blocks 212 are biased in a downward direction by springs 216 captured between the upper housing 186 and the shaft blocks 212. The springs 216 bias the roller 208 downwardly to form a pressurized output nip for output of the card. It can therefore be seen that the instant invention provides apparatus 10 and 117 which are effective for initially fusing a pair of sheet materials under pressure and heat, further heating the fused sheets without pressure to achieve a full bond, and then cooling the fused sheets prior to exiting the apparatus. The apparatus achieve these objectives by providing a pressurized input nip having a heated roller. Sheet materials passed through the input nip are fused under the pressure and heat of the nip. The fused materials are then passed over a heated platen for further heating of the sheets materials to achieve a full bonding of the materials. The fully fused sheets are then cooled by fan cooled heat sinks prior to passage out of the apparatus. For these reasons, the instant invention is believed to represent a significant advancement in the art which has substantial commercial merit. While there is shown and described herein certain specific structure embodying the invention, it will be manifest to those skilled in the art that various modifications and rearrangements of the parts may be made without departing from the spirit and scope of the underlying inventive concept and that the same is not limited to the particular forms herein shown and described except insofar as indicated by the scope of the appended claims.

Claims

Claims : 1. Apparatus for fusing a first polymeric sheet in face-to-face relation with a second polymeric sheet, the apparatus comprising: means for pressing said sheets together in face-to- face relation to define a two-piece structure; first means for applying heat only to the first polymeric sheet while said sheets are being pressed together, said pressure and heat achieving an initial fusing of said first and second polymeric sheets; means for cooling said second polymeric sheet while said sheets are being pressed together; and second means for applying heat only to said first polymeric sheet under ambient pressure to achieve a full fusion of the first and second polymeric sheets to each other.

2. In the apparatus of claim 7, said means for pressing said sheets together comprising an input nip having first and second rollers.

3. In the apparatus of claim 8 said first polymeric sheet being received adjacent to said first roller and said second polymeric sheet being received adjacent to said second roller while said sheets are being pressed together, said first means for applying heat to said first polymeric sheet comprising means for heating said first roller.

4. In the apparatus of claim 9, said means for cooling said second polymeric sheet while said sheets are being pressed together comprising means for cooling said second roller.

5. The apparatus of claim 7 further comprising a second cooling means downstream of said second heating means for cooling said sheets.

6. The apparatus of claim 8 further comprising a second cooling means downstream of said second heating means for cooling said sheets.

7. The apparatus of claim 9 further comprising a second cooling means downstream of said second heating means for cooling said sheets.

8. Apparatus for fusing a first polymeric sheet in face-to-face relation with a second polymeric sheet comprising; a first belt assembly including a first endless belt received around first and second rollers; a third roller mounted in cooperation with said first roller to form an input nip with said first roller, said first and third rollers pressing said sheets together in face-to-face relation to define a two-piece structure, said first polymeric sheet being received adjacent said first roller and said second polymeric sheet being received adjacent said second roller while said sheets are being pressed together; means for heating said first roller such that only said first polymeric sheet is heated, said pressure and said heat achieving an initial fusing of said first and second polymeric sheets; means for cooling said third roller such that said second polymeric sheet is cooled while said first polymeric sheet is heated; and heated platen means for applying heat to said first polymeric sheet, said heated platen means being in thermal communication with an underside of said belt, said two piece structure being supported on an upper side of said belt and being transported from said input nip over the surface of said heated platen means wherein further heat is applied under ambient pressure to said first polymeric sheet.

9. The apparatus of claim 14 further comprising a second cooling means downstream of said heated platen means for cooling said sheets.

10. A method of making an identification card in an apparatus as claimed in claim 7 comprising the steps of: providing first and second polymeric sheets; arranging said first and second polymeric sheets in face-to-face relation to define a two-piece card structure; applying pressure to said face-to-face sheets to press said sheets together; preheating only the second polymeric sheet while said sheets are being pressed together, said pressure and heat achieving an initial fusing of the sheets; removing the applied pressure from the initially fused sheets; and then applying heat to only said second polymeric sheet of the initially fused two-piece card structure to achieve full fusion of the first and second polymeric sheets to each other.

11. The method of claim 16 further comprising the step of cooling said fused sheets of said two-piece structure.

12. A method for fusing a first polymeric sheet in face- to-face relation with a second polymeric sheet, comprising the steps of; arranging said first and second polymeric sheets in face-to-face relation to define a two-piece card structure; applying pressure to said face-to-face sheets to press said sheets together; preheating only the second polymeric sheet while said sheets are being pressed together, said pressure and heat achieving an initial fusing of the sheets; removing the applied pressure from the initially fused sheets; and then applying heat to only said second polymeric sheet of the initially fused two-piece card structure to achieve full fusion of the first and second polymeric sheets to each other.

13. The method of claim 18 further comprising the step of cooling said fused sheets of said two-piece structure.