Method

CROSS REFERENCE TO RELATED APPLICATION This application claims priority to U.S. Provisional Patent

Application Serial No.61/559,212 which was filed on November 14, 2011, the entirety of which is incorporated by reference herein.

TECHNICAL FIELD

The disclosure pertains generally to thermoforming apparatus. More particularly, this disclosure relates to thermoforming machines having adjustable length load shafts for securing together opposed platens and dies of a thermoforming apparatus.

BACKGROUND OF THE INVENTION

The use of large tonnage thermoforming frames and drive mechanisms is known where pneumatic pressure is being applied to a heated sheet of thermoformable material during an article forming operation. Where large arrays of articles are provided on die plates on a platen, the surface area subject to pneumatic pressure and/or vacuum generates very large loads on the kinematic drive linkages and frame of a thermoforming machine. Improvements are needed in order to enable forming using very large loads without requiring further increases in the size and strength of traditional frames and linkages of a thermoforming machine, particularly when forming newer plastic sheet materials and/or article geometries that require greater forming pressures and loads. SUMMARY OF THE INVENTION

A thermoforming machine is provided with a plurality of load shaft end adjustment assemblies. Each load shaft is adjustable in length using the respective load shaft end adjustment assemblies to enable alignment of the mating mold surfaces on respective platens of a thermoforming

IR1-060 P01.doc 1 machine when i n a locked, closed position , providing for the capability of handli ng i ncreased thermoforming pressures on the thermoformi ng machine duri ng a thermoforming operation. A preload can be applied to the end adjustment assemblies i n order to prevent damage to mating threaded assembly components due to platen formi ng loads.

According to one aspect, a thermoforming machine load shaft length adjustment apparatus is provided. The apparatus i ncludes a load shaft, a structural support, a length adjustment nut, a collar, and at least one fastener. The load shaft has a threaded segment, and is configu red to engage between a pai r of thermoforming platens of a thermoformi ng machine and carry formi ng loads between the pair of platens du ri ng a thermoforming operation . The structural support is provided on the load shaft proxi mate the th readed segment. The length adjustment nut is threaded onto the threaded segment of the load shaft proxi mate the structu ral support and is movable to effect length adjustment of the load shaft as engaged between the pai r of platens. The collar is mounted onto a platen of the thermoformi ng machi ne and is configured to receive the length adjustment nut for relative rotation. At least one fastener extends between the structu ral support and the collar and is configured to secure together the structural support and the collar with the length adjustment nut interposed there between and engaged i n threaded relationship to impart a preload that urges the heig ht adjustment nut agai nst the collar that is greater than a load received by the load shaft as thermoforming pressu re is applied between the platens. Accordi ng to another aspect, a length-adjustable thermoforming machi ne load shaft apparatus is provided having a load shaft, a load- beari ng support, an adjustment nut, a collar, and a preload fastener. The load shaft has a th readed seg ment and spaced-apart engagement portions for releasably engaging together a pair of thermoformi ng platens of a thermoforming machine and is operative to carry pneumatically- induced thermoforming loads imparted between forming dies on the pair

IR 1-060 P01.doc 2 of platens during a thermoforming operation. The load-bearing support is provided on the load shaft proxi mate the th readed segment. The adjustment nut is threaded onto the threaded seg ment proxi mate the load-bearing support and is movable to effect length adjustment of the load shaft as engaged between the pair of platens. The collar is mou nted onto a platen of the thermoformi ng machi ne and is configured to mate in engagement with the adjustment nut. The preload fastener extends between the structural support and the collar and is configured to draw together the structural support and the collar so as to u rge the collar i nto engagement with the adjustment nut so as to preload threads on the adjustment nut with complementary threads on the load shaft such that the resulti ng preload is greater than a load received by the load shaft as forming pressure is applied between the platens.

Accordi ng to yet another aspect, a method is provided for adjusting lengths of load shafts on a platen of a thermoforming apparatus. The method includes providing : a first platen with a first die mold , a second platen with a second die mold, a drive linkage for moving together and apart the fi rst platen and the second platen, and a plurality of load shafts extendi ng between the first platen and the second platen operative to secure together u nder thermoformi ng loads the first die mold and the second die mold during a thermoforming operation ; urgi ng together the fi rst platen and the second platen such that the first die mold and the second die mold are held together i n engagement; ascertaini ng any loose fit-up along respective die surfaces between the first die mold and the second die mold ; and adjusting length on one of the load shafts to eliminate the ascertained loose fit-up between the first die mold and the second die mold when the die molds are held together in engagement.

BRI E F D ESC RI PTION OF TH E D RAWI NGS

Preferred embodiments of the disclosure are described below with reference to the followi ng accompanyi ng drawings.

IR 1-060 P01.doc 3 Fig. 1 is a perspective view from above of a thermoforming machine with a platen lock assembly taken from a drive motor side in accordance with an embodiment.

Fig. 2 is a perspective view from above of the thermoforming machine of Fig. 1 taken from a kinematic drive linkage side, and with the die plates removed.

Fig. 3 is an elevational side view of the thermoforming machine of Figs. 1-2 showing the upper and lower platens locked together in a fully closed position (but with the forming die plates omitted). Fig. 4 is a perspective view from below of the thermoforming machine of Figs. 1-3 taken from a kinematic drive linkage side.

Fig. 5 is an elevational side view of the thermoforming machine of Fig. 3 showing the upper and lower platens unlocked and in a fully open, or separated position (but with the forming die plates omitted). Fig.6 is a component view from below taken along line 6-6 of Fig.5 and showing one side of the platen lock assembly.

Fig. 7 is a component view taken along line 7-7 of Fig. 5 and showing one lock plate assembly and load shaft in an unlocked and separated position corresponding with separation of the upper platen and lower platen.

Fig.8 is a vertical sectional component view taken along line 8-8 of Fig. 5 and showing a pair of load shafts and corresponding lock plate in the unlocked and separated position depicted in Fig.7.

Fig.9 is a vertical side view of the thermoforming machine of Fig.3, but later in time and showing the upper platen lowered and the lower platen raised to positions that correspond with a position where die plates (not shown) would be fully engaged during a thermoforming operation.

IR1-060 P01.doc 4 Fig. 10 is a component view from below taken along line 10-10 of Fig. 9 and showing one side of the platen lock assembly in a locked position.

Fig. 11 is a component view taken along line 11-11 of Fig. 9 and showing one lock plate assembly and load shaft in a locked position corresponding with movement of the upper platen and lower platen to a position where die plates (not shown) would be fully engaged during a thermoforming operation.

Fig. 12 is a vertical sectional component view taken along line 12- 12 of Fig. 10 and showing a pair of load shafts and corresponding lock plate in the locked and closed together die position (die plates not shown) depicted in Fig.9.

Fig. 13 is a vertical side view of the thermoforming machine taken on an opposite side of the view in Fig.3 and corresponding with the same time and showing the upper platen lowered and the lower platen raised to positions that correspond with a position where die plates (not shown) would be fully engaged during a thermoforming operation.

Fig. 14 is a vertical sectional view taken along line 14-14 of Fig. 13.

Fig. 15 is a perspective view from above of the thermoforming machine of Fig. 1 with upper and lower servo drive motors, gearboxes, and die plates removed.

Fig. 16 is a fragmentary component perspective view of one corner of lower platen 26 with a respective pair of load shafts and lock plate assembly depicting the load shafts locked with the lock plate assembly corresponding with a closed platen position.

Fig. 17 is an enlarged view of a top end portion of the load shaft end adjustment assembly of Figs. 1-2, 12 and 15.

Fig. 18 is a vertical sectional view taken along line 18-18 of Fig. 17.

IR1-060 P01.doc 5 Fig. 19 is an enlarged perspective view of the load shaft end adjustment assembly of Figs. 17-18.

Fig.20 is a vertical sectional view taken along line 20-20 of Fig. 19. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Attention is now directed towards embodiments of the device.

Figures 1 and 2 are left and right perspective views illustrating a thermoforming machine 10 with a platen lock assembly 12 and a load shaft end adjustment apparatus 14 in accordance with an embodiment. More particularly, thermoforming machine 10 includes a structural frame 18, stationary die posts 20 and 22 supported by frame 18, an upper platen 24, and a lower platen 26. Upper platen 24 and lower platen 26 are supported for vertical reciprocation via pairs of bronze bushings 28, 29 and 30, 31, respectively. A kinematic drive linkage drives upper platen 24 and lower platen 23 using upper kinematic linkage assembly 34 and lower kinematic linkage assembly 36, respectively, each driven by a respective servo motor 38 and 40 (see Fig. 1) via gearboxes 39 and 41, respectively. A third motion platen, or assist platen 16 is supported for movement relative to lower platen 26 by bushings that slide over respective die posts. A set of platen load shafts 48-51 and 52-55 are provided on either side of mold plates, or die plates 44 and 46, extending between upper platen 24 and lower platen 26. More particularly, platen lock assembly 12 comprises set of shafts 48-51 attached to platen 24 along a top end and lock plate assemblies 70 and 71 (see Fig.9), as well as set of shafts 52- 55 attached to platen 24 along a top end and lock plate assemblies 72 and 73 (see Fig. 13). A top end of each shaft 48-55 is mounted in vertically, or axial lengthwise adjustable relation relative to top platen 24 with an adjustable rod end assembly 14, thereby enabling adjustment of each shaft when locked to lock plate assemblies 70-73 to obtain uniform engagement and fit-up between contact surfaces (and realize a

IR1-060 P01.doc 6 pneu matic seal) between upper die plate 44 and lower die plate 46 when broug ht together and locked via platens 24 and 26. Accordi ng to one construction , load shafts 48-55 are constructed from pre-heat treated 41 40 steel, having 40 Rockwell C-scale hard ness. Backlash nut 1 1 4 and adjustment nut 1 1 6 are also constructed from heat treated 41 40 steel, having 40 Rockwell C-scale hardness, also accordi ng to one construction. Shafts 48-55 and nuts 1 1 4 and 1 1 6 can alternatively be made from any suitable structural material , such as any steel , composite, or other suitable structural load-beari ng material . As shown in Figu re 2, third motion platen 27 of plug assist drive assembly 1 6 is carried for reciprocati ng movement relative to lower platen 26 on an array of drive shafts (not shown) . Optionally, features of the present lock rods can be implemented on a thermoformi ng machine that does not use a third motion platen. As shown in Figu re 1 , upper kinematic linkage assembly 34 and lower kinematic linkage assembly 35 cooperate to drive upper and lower platens 32 and 34, respectively. Respective modern rotary electric servo drive motors 38 and 40 (see Fig. 2) i ndependently drive li nkages 34 and 36 via gearboxes 39 and 41 to reciprocate platens 24 and 26 respectively. Such motors are driven by a computer control system, as is presently understood in the art. Linkage position i nformation can also be implemented on the gearboxes usi ng electric position sensors (not shown) that send sig nals to the control system in order to validate absolute position of respective ki nematic linkages. Other kinematic linkages and drive motor arrangements can be used in the alternative.

More particularly, kinematic linkages 34 and 36 of Figure 3 each comprise d rive linkages that are formed from a pair of top and bottom crank arm assemblies, respectively. Each assembly is formed from a crank arm li nkage and a four-bar li nkage. The crank arm li nkage drives the fou r-bar li nkage i n an oscillating motion . Each ki nematic linkage 34 and 36 is driven via servo motor 38 and 40 and respective gearbox 39

IR 1-060 P01.doc 7 and 41 th rough a rotary cross shaft 56 and 58, respectively. Each platen 24 and 26 is driven by kinematic li nkage 34 and 36, respectively, i n substantially non-rotating li near, vertical motion . Guide posts 20 and 22 further li mit such motion to vertical reciprocating motion . This vertical reciprocating motion causes co-acting engagement of female cavities, or female dies 45 i n an upper die plate 44 mou nted on the upper platen 24 with mating male dies or plugs 47 i n a lower die plate 46 mounted on the lower platen 26 on opposed sides of thermoformable web, or sheet 21 (see Fig . 1 ) . I n some constructions, a resilient rubber seal is provided around the cavities and plugs and between the die plates. I n other constructions, a heated sheet of thermoformable web provides a seal between the die plates.

More particularly, each drive system , including the motor and associated d rive controller, forms the motor of an associated rotary press. This rotary press attaches to a rotating crank arm assembly that moves the associated four-bar linkage. The linkage causes the attached platen to move up and down i n response to rotation of the drive. Accordingly, a single revolution of shafts 56 and 58 caused by d rive motors 38 and 40 and gearboxes 39 and 41 will produce a correspondi ng complete press cycle of both the upper and lower platens 24 and 26, respectively. Hence, a complete cycle of each drive will return the press to a starting , or closed position. For example, when lower d rive motor 40 is at an initial rotated position of zero deg rees, the lower platen 26 is closed , or upwardly raised against the thermoformable sheet, or web. Si milarly, when lower driven motor 40 is rotated to 1 80 degrees, the lower platen 26 is lowered, or completely opened. Likewise, the same holds true for upper drive motor 38 and upper platen 24.

A control system is configu red to move upper platen 24, lower platen 26, and third motion, or plug assist platen 27 via respective servo motors, such as servo motors 38, 40. Accordi ng to one construction , upper platen 24 and lower platen 26 are each drive platens, and plug

IR 1-060 P01.doc 8 assist platen 27 is also a movi ng platen . The control system includes a controller comprisi ng processing circuitry and memory configured to precisely regulate motion of platens 24, 26 and 27 i n desired, timed synchronization such that individual plugs, or male dies 47 are d riven upwardly with a greater combination of speed and force than would be capable by merely moving platens 24 and 26 together. I n operation, platens 24 and 26 are d riven together into a heated web of thermoformable material that is captu red between upper platen 24 and lower platen 26 duri ng a thermoformi ng operation . According to Figure 1 , a seal 65 is provided around each male plug

47, while a vacuu m is applied to the bottom of mold plate 44 (top of the thermoformable web) via a vacuu m source through vacuum ports 69, and pneu matic form pressure is applied along the top of mold plate 46 (bottom of the thermoformable web) to help form the web. However, this generates considerable loads, which are countered by usi ng platen lock assembly 1 2. For the case of some mold designs, an entire periphery along top su rface of mold plate 46 is encircled by a seal , which generates considerable loads when vacuu m and pressu re are applied to respective top and bottom surfaces of a thermoformable web, or sheet 21 . Thi rd motion platen 27 is subsequently moved upwardly relative to movi ng platen 26, so as to cause formi ng of a thermoformed article in a heated plastic web between each i ndividual pair of complementary male plugs 47 and female die cavities 45, while platen lock assembly 1 2 is locked.

As shown in Figure 1 , numerous rows of complementary, interacting male plugs 47 and female die cavities 45 are provided in die plates 46 and 44 affixed to respective platens 26 and 24, respectively. Subsequently, platens 24, 26 and 27 are withd rawn , or retracted apart in order to start the cycle all over again , and thi rd motion platen 27 is lowered relative to lower platen 26. The cyclical process is then repeated.

IR 1-060 P01.doc 9 Preferably, a modern rotary electric servo drive motor, or actuating device, is used for drive motors 1 5 and 1 7 (see FIG. 2) . Such a d rive includes an AC servo motor and an associated servo drive motor controller. For example, one suitable AC motor is sold by Siemens AG , Automation Group, Automation Systems for Machi ne Tools, Robots and Special- Purpose Machi nes, P.O. Box 31 AD, D-91 050, Erlangen, Federal Republic of Germany. Additionally, one suitable servo drive motor controller is sold by Siemens as an analog feed drive system including the SI MO D RIVE 61 1 -A Transistor PWM I nverters and Motors for AC FV Drives. Such a drive will provide a predictable motor device that can very accurately position a machi ne element to a desired position at a given time. Accordingly, the associated servo motor is a brushless servo motor. Usi ng suitable control software, activation of associated machi ne components can also be triggered based on velocity or position of a drive, by using a velocity profile or an integ rated displacement of the drive. Fu rthermore, one suitable servo drive motor used for servo drive motor 58 is also a Siemens AC servo motor, model number 1 FT51 32- OSC71 - 1 -ZH27, also available from Siemens AG. Automation G roup, Automation Systems for Machine Tools, Robots and Special- Purpose Machines, P.O. Box 31 AD, D-91 050, Erlangen, Federal Republic of Germany.

As shown i n Figure 2, plug assist drive assembly 1 2 reciprocates third motion platen 36 up and down relative to lower platen 34. Platen 36 is guided for axial reciprocation by a rectangular array of bronze bushings 28-31 , each contained within a housing, that are slidably received over respective cylindrical die posts 24-27 mounted rigidly to lower platen 34. Optionally, plug assist drive assembly 1 2 can be mounted to upper platen 32, with the third motion platen being driven in a downward direction while the upper platen is being d riven downwardly. Further optionally, a third motion platen can be mou nted to a stationary platen, when an opposi ng platen is moved to and fro. Fu rther optionally, a thi rd motion platen can be mounted for horizontal movement relative to a moving

IR 1-060 P01.doc 1 0 platen from a pai r of opposed moving platens that move together and apart along a horizontal direction . Fi nally, a third motion platen can be affixed to any one of a pair of platens that move together and apart along a contact plane in any angular orientation. As shown in Figures 3-4, a servo motor 60 drives a cross shaft 61 via a gearbox 62, usi ng a connecti ng rod 64 that is eccentrically mounted onto each end of cross shaft 61 to drive a respective drive bar 74 and 75 (see Fig. 5) to-and-fro so as to lock and u nlock platen lock assembly 1 2. Accordingly, load shafts 48-55 of Figure 3 lock together platens 24 and 26 while vacuum and pressu re are respectively applied to top and bottom surfaces of a thermoformable web presented between respective mold plates (see Fig . 1 ) . For example, a pneumatic differential pressure of 1 20 PSI can be imparted between die plates 44 and 46 (see Fig. 1 ) where the sealed area between die plates 44 and 46 is 50" by 50", which imparts 1 50 tons of load on load shafts 48-55 duri ng formi ng of the web. A pneumatic cyli nder 43, on each side, is pressurized so as to counterbalance gravitational pull on lower platen 26. Additionally, or optionally, similar pneumatic cylinders can be added to the top platen i n order to counterbalance g ravitational pull on upper platen 24. Figu re 5 illustrates platens 24 and 26 i n a fully open state via positioni ng of kinematic li nkages 34 and 36, with lock plate assemblies 70-73 of platen lock assembly 1 2 placed in an unlocked position via servo motor 60, shaft 61 , gearbox 62, rods 64 and d rive bars 74 and 75. Figu re 6 further illustrates the open , or u nlocked position between load shafts 48-51 relative to lock plate assemblies 70 and 71 . Likewise, Figure 7 further illustrates the position of load shaft 51 relative to lock plate assembly 71 when u nlocked with the platens opened (or moved apart) , and showing reduced diameter portion, or lock ledge 66 having a horizontal engagement su rface, or ci rcu mferential shelf 68. Fu rthermore, Figu re 8 shows load shafts 50 and 51 in the u nlocked and open position

IR 1-060 P01.doc 1 1 relative to lock plate assembly 71, with lock ledges 66 raised relative to lock plate assembly 71.

Figures 9 and 15 illustrate thermoforming machine 10 on opposite sides, with Figure 13 showing the configuration of servo motors 38 and 40 with respective gearboxes 39 and 41. An eccentric mount on each end of shaft 61 is positioned to place drive bars 74 and 75 in forward positions, locking each lock plate assembly 70-73 onto each respective load shaft 48-55. In such locked configuration, load shafts 48-55 counter, or resist, forming pressures imparted when applying vacuum and pressure to respective top and bottom surfaces of a thermoforming web during an article thermoforming operation.

Figure 10 depicts lock plate assemblies 70 and 71 in a locked position on load shafts 48-49 and 50-51, respectively. Figure 11 further illustrates load shaft 51 secured by lock plate assembly 71 along lock ledge 66. Finally, Figure 12 illustrates load shafts 50 and 51 locked by lock plate assembly 71 while platens 24 and 26 are held in a closed position corresponding with respective mold plates (not shown) being urged together in sealed relationship.

Figures 13 and 14 further illustrate platen lock assembly 12 of thermoforming machine 10 in a locked, or closed position. Figure 14 depicts third motion plug assist drive assembly 16 in a retracted position, corresponding with male plugs retracted before they are extended into a web during a forming operation.

Figure 16 depicts in component view exemplary load shafts 54 and 55 in a locked position relative to lock plate assembly 73. Figure 17 further illustrates the configuration of lock plate assembly 73 in a closed, or locked position relative to lock ledges 66 and circumferential shelves 68 on load shafts 54 and 55. A pair of apertures, or key slots 80 and 82 each have an elongate, narrow portion and an enlarged clearance portion. The narrowed portion locks onto ledges 66.

IR1-060 P01.doc 12 As shown in Figure 16, lock plate assembly 73 comprises a stationary beveled clearance plate 76 and a movable beveled key plate 78. Plates 76 and 78 each have top and bottom surfaces that are beveled at 2 degrees such that motion of plate 78 relative to plate 76 increases and decreases total thickness of lock plate assembly 73. When locked, the total thickness increases. The ability to adjust thickness ensures that proper sealing occurs between the top and bottom mold plates when pressed together while applying vacuum and pressure. Threaded fasteners secure plate 76 to platen 26, while threaded fasteners secure retainer plates 84 and 86 onto plate 76. Finally, threaded fasteners 92 secure drive bar 75 onto plate 78. A pair of parallel elongate grooves 88 provide a sliding surface along plates 84 and 86, facilitating sliding to-and-fro of plate 78 relative to stationary plate 76 when locking and unlocking lock plate assembly 73 relative to load shafts 54 and 55.

Figure 17 illustrates a thermoforming machine load shaft end adjustment apparatus 14 used on thermoforming machine 10 of Figures 1-16. More particularly, load shaft end adjustment apparatus 14 comprises a cylindrical backlash nut 114 that is received onto a threaded end portion of load shaft 54, a height adjustment nut 166 that is also received onto the same threaded end portion of load shaft 54, and a cylindrical collar 118 that receives a lower, reduced diameter portion of nut 116 for rotatable engagement. Nut 114 provides a structural support. Optionally, a structural support can be provided by any integrally formed, attached, or mounted frame member, arm, clamp, or suitable structural support provided on or adjacent the load shafts 54 that enables one to impart a preload to the adjustment nut and shaft so as to prevent thread wear during pneumatic loading and unloading. A plurality of circumferentially spaced apart threaded hex head bolts 122 and respective washers 123 are threaded into respective threaded bores in a radially outwardly extending flange of collar 118 for fixing the relative position of nut 114 and collar 118 when height adjustment nut 116 has

IR1-060 P01.doc 13 been rotated to a desired threaded position along load shaft 54, using one of a circumferential array of radially extending bores 130 for receiving a turning tool, or shaft. A plurality of circumferentially spaced apart threaded hex head cap screws, or bolts (not shown) are received within respective bores 125 in a radially outwardly extending flange of collar 118. Flats 129 are provided on opposite sides of the flange of collar 118 to enable adjacent positioning together of adjacent pairs of assemblies 144 onto respective apertures within upper platen 14 (see Fig. 1). Alternatively, load shafts 54 can be mounted upside down (relative to what is shown in Fig.1), between the upper and lower platen.

One or more of load shafts 54 can be adjusted in length in order to eliminate any pneumatic leakage between die plates during thermoforming. A visual inspection with feeler gauges can detect a local gap requiring one or more load shafts to be adjusted in length, when die plates are engaged together and a pneumatic source and/or vacuum are applied across the web (while engaged between the die plates and locked together with load shafts 54). An audible inspection can also be used in order to identify where pressurized air, or gas is leaking through a seal between engaged die plates, then adjacent load shafts can be adjusted in length so as to reduce or eliminate any leakage of pneumatic air/vacuum during a thermoforming operation.

As shown in Figures 17-19, a key 120 is affixed into a receiving aperture in collar 118 using a pair of threaded machine screws, or bolts 126. Key 120 includes a radially extending threaded bore 127 provided to receive a threaded tool end (not shown) used to extract key 120 during assembly and disassembly. Key 120 is received in axially sliding relation within key slot 128 in assembly in order to ensure that nut 114, nut 116, and collar 118 do not rotate relative to load shaft 54 when secured and tightened together in a desired position via bolts 122. In this manner, nut 116 is rotated via bore 130 (using a cylindrical rod tool) to a desired threaded position along load shaft 54 in order to impart a desired length

IR1-060 P01.doc 14 to assembly 14 by nut 114, nut 116, and collar 118, after which bolts 122 are tightened in order to retain the desired combined length of assembly 14. A scale 138 extends around a circumferential outer surface of collar 118 to enable determination of relative rotation of nut 116 and collar 118 via a reference mark, or notch (not shown) atop collar 118. According to one construction, load shaft 54 is threaded from a distal end to a topmost portion of a key slot 128 on load shaft 54 by a continuous thread segment 110 that is complementary to respective threaded female thread segments 111 and 112 within nuts 114 and 116, respectively. As shown in Figure 20, a circumferential array of threaded fasteners, or bolts 125 secure collar 118 to platen 24 within bore 90. More particularly, a circumferential shoulder 134 of flange 132 seats against a complementary shoulder 136 on platen 24. In order to eliminate cyclical loading between threads 110 and threads 111 and 112, fasteners 122 are torqued to a level that forces a shoulder 141 on nut 116 into forceable engagement with a shoulder 142 on cylindrical collar 118. Bolts 122 are torqued to a level that generates an axial force between nut 116 and collar 118 that exceeds any axial load on shaft 54 that is generated during a thermoforming cycle. This preload (above maximum shaft loads) prevents any "erosion" between threads 110 and threads 111 and 112 due to movement there between, which would result in wear and damage to the threads, and eventually failure of the structural integrity. Accordingly, the load shaft adjustment apparatus 14 is a preloaded assembly that enables lengthening and shortening of shaft 54 on a thermoforming machine in order to get good fit-up, or sealing between die assemblies of platens. In one case, bolts 122 are torqued to 80 ft. lbs., and bolt 122 is a Grade 8 bolt. In such one exemplary case, the die plates seal together an area 50" by 50", and a differential pneumatic forming pressure of 120 psi will impart 150 tons of load to the load shafts. Larger areas are also possible, requiring greater torque on bolts 122. Smaller areas are also possible.

IR1-060 P01.doc 15 According to one implementation , a method is provided for adjusting lengths of load shafts on a platen of a thermoforming apparatus. The method i ncludes providi ng : a first platen with a first die mold , a second platen with a second die mold, a drive linkage for movi ng together and apart the fi rst platen and the second platen, and a plurality of load shafts extendi ng between the fi rst platen and the second platen operative to secure together u nder thermoforming loads the first die mold and the second die mold during a thermoforming operation ; urgi ng together the first platen and the second platen such that the fi rst die mold and the second die mold are held together in engagement; ascertaini ng any loose fit-up along respective die surfaces between the first die mold and the second die mold ; and adjusting length on one of the load shafts to elimi nate the ascertai ned loose fit-up between the first die mold and the second die mold when the die molds are held together in engagement.

According to another implementation , a method is fu rther provided for adjusting lengths of load shafts on a platen of a thermoformi ng apparatus, or machi ne. A first load shaft is adjusted in length while molds on dies of a thermoformi ng machi ne are held together in engagement. A second load shaft, spaced apart from the first load shaft is also adjusted in length while the molds are held together in engagement. Subsequent load shafts are also adjusted in length so as to ensure seali ng fit-up of a seal that is i nterposed between the mati ng molds on each of a pai r of platens on the thermoforming machine.

IR 1-060 P01.doc 1 6