Abstract:
A six station rotary thermoforming machine includes a first oading station for first or upper panels, a second loading station for second or lower panels, two adjacent stations for heating the panels, a thermoforming station, an unloading station and a carousel for transferring thermoformable panels between such stations. The carousel includes a rotating circular frame which is driven by a centrally disposed drive assembly. The circular frame carries and supports six carrier assemblies having peripheral clamping members which receive panels of thermoformable material and rotates to sequentially move them from one station to the next. The two heating stations each include upper and lower radiant heaters. The thermoforming station includes a pair of opposed, vertically translatable platens which receive respective molds which engage and form the panels and may include a device for loading performs or inserts. The number of stations and the residence time of the plastic panels to be formed in each optimizes production output of twin sheet thermoformed products.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates generally to multiple station forming machines for thermoformable panels and more particularly to a six station thermoforming machine having loading, heating, forming and unloading stations and a carousel for transporting thermoformable panels between such stations. 
     The technology of relatively large scale thermoforming of thermoplastic or thermosetting sheets has developed in response to continuing demands from various industries such as the automotive industry. Thermoformed panels are used as tonneau covers, floor panels, body panels, sound insulating partitions and the like in both motor vehicles and a wide variety of other products where relatively rigid, weather resistant, lightweight, tough, strong and non-rusting components are required. 
     The demand for such products has encouraged research and development of processes and manufacturing machines. One such machine is disclosed in U.S. Pat. No. 4,769,106, which is directed to an apparatus which assembles a pair of plastic sheets into a unitary device by welding about the peripheries of the sheets. The device includes a welding station, a cutting station and a conveying apparatus which transports the plastic sheets through the assembling stations. The conveying apparatus includes a moving carriage with grasping devices which engage the periphery of the plastic sheets. A cam arrangement operates to move the grasping devices from a first position in which they engage the plastic sheets to a second position in which the plastic sheets are released. Due to the linear construction of this machine and the use of a single device at each station, the overall maximum speed of the machine is limited by the maximum speed of the slowest station. This situation, which is a common manufacturing problem, adversely effects production efficiency. 
     A rotary thermoforming machine is disclosed in U.S. Pat. No. 4,555,377. In this machine, a rotating, substantially circular frame includes four sub frames having peripheral clamping members, which may be engaged or released to retain or release plastic sheets. The frame which carries the four carriages rotates and indexes them from a loading station through two heating stations to a mold station where the thermoformed product is produced. 
     A review of the foregoing two patent references as well as other references and prior art devices reveals that certain design choices and machine configurations limit production speed and interfere with both production throughput and product quality. The present invention is directed to an improvement in such thermoforming machines which address the foregoing and other shortcomings of the prior art. 
     SUMMARY OF THE INVENTION 
     A six station rotary thermoforming machine includes a carousel and a first loading station for first or upper panels, a second loading station for second or lower panels, two adjacent stations for heating the panels, a thermoforming station and an unloading station. The carousel includes a rotating circular frame which is driven by a centrally disposed drive assembly. The frame carries and supports six carrier frame assemblies having peripheral clamping members which receive panels of thermoformable material and rotate to sequentially move them from one station to the next. The two heating stations each include upper and lower radiant heaters. The thermoforming station includes a pair of opposed, vertically translatable platens which receive respective molds which engage and form the panels. Adjacent the thermoforming station is an insert or preform loader which places a preform into the mold during fabrication of the product. The number of stations and the residence time of the plastic panels to be formed in each optimizes production output of twin sheet thermoformed products. 
     Thus is an object of the present invention to provide a six station rotary thermoforming machine. 
     It is a further object of the present invention to provide a six station rotary thermoforming machine having two heating stations and one forming station. 
     It is a still further object of the present invention to provide a six station rotary thermoforming machine having two loading stations and one thermoforming station. 
     It is a still further object of the present invention to provide a six station rotary thermoforming machine having a carousel containing six panel engaging carrier frame assemblies and a centrally disposed drive unit. 
    
    
     Further objects and advantages of the present invention will become apparent by reference to the following description of the preferred embodiment and appended drawings wherein like reference numbers refer to the same component, element or feature. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic, top plan view of a six station rotary thermoforming machine according to the present invention; 
     FIG. 2 is a side, elevational view of a six station rotary thermoforming machine according to the present Invention illustrating the heating stations; 
     FIG. 3, is a top plan view of a carousel assembly containing six panel receiving carrier frames in a six station rotary thermoforming machine according to the present invention; 
     FIG. 4 is a full, sectional view of one of the carrier frame assemblies on the carousel assembly having clamps in their open or disengaged positions taken along line  4 — 4  of FIG. 3; 
     FIG. 5 is a full, sectional view of one of the carrier frame assemblies on the carousel assembly having clamps in their locked or engaged positions taken along line  4 — 4  of FIG. 3; 
     FIG. 6 is a front, elevational view of the thermoforming station of a six station rotary thermoforming machine according to the present invention with platens in an open position; 
     FIG. 7 is a side elevational view of the thermoforming, station illustrating a mechanism for translating platens of a six station rotary thermoforming machine according to the present invention; 
     FIG. 8 is an enlarged, perspective view of a portion of the platen translating drive assembly of a six station rotary thermoforming machine according to the present invention; 
     FIG. 9 is a fragmentary, sectional view of a bayonet drive assembly on the thermoforming station of a six station rotary thermoforming machine according to the present invention taken along line  9 — 9  of FIG. 7; 
     FIG. 10 is a side, elevational view of a core or insert loading mechanism of a six station rotary thermoforming machine according to the present invention; 
     FIG. 11 is a side, elevational view of an unloading station of a six station rotary thermoforming machine according to the present invention; 
     FIG. 12 is a front, elevational view of a thermoforming station of six station rotary thermoforming machine according to the present invention with a bottom panel loaded onto a lower mold section; 
     FIG. 13 is a front, elevational view of the thermoforming station of six station rotary thermoforming machine according to the present invention with a bottom panel formed in the lower mold section; 
     FIG. 14 is a front, elevational view of the thermoforming station of six station rotary thermoforming machine according to the present invention with a top panel loaded onto a top mold section; 
     FIG. 15 is a front, elevational view of the thermoforming station of six station rotary thermoforming machine according to the present invention with a top panel formed in the top mold section and a reinforcing core disposed in the bottom panel in the lower mold section; and 
     FIG. 16 is a front, elevational view of the thermoforming station of a six station rotary thermoforming machine according to the present invention illustrating a final thermoforming and sealing operation. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Apparatus 
     Referring now to FIGS. 1,  2  and  3 , a rotary thermoforming machine according to the present invention is illustrated and generally designated by the reference number  10 . The rotary thermoforming machine  10  includes a rigid superstructure or frame  12  having a plurality of vertical supports  14  and a pair of horizontal rails or beams  16 . The rotary thermoforming machine  10  also includes a rotating, generally circular frame or carousel assembly  18  which is supported about its periphery on a plurality of rollers  22  secured to the vertical supports  14 . The carousel assembly  18  is also supported by a center column  24  which is rotatably received within and supported by a suitable bearings  26  attached to cross members  28  secured to the frame  12 . The center column  24  includes a large driven chain sprocket  32  which receives a chain  34  which also engages a small chain drive sprocket  36  driven by the output of a speed reduction unit  38 . The speed reduction unit  38  is, in turn, driven by an electric motor  40 . In operation, the electric motor  40  is intermittently activated such that the carousel assembly  18  indexes, that is, rotates in 60° increments or arcs, ceases rotation or dwells for a fixed period of time while certain process steps are performed and then repeats the indexed rotation cycle. Alternatively, a clutch (not illustrated) disposed in operable relationship with the speed reduction unit  38  may be engaged and disengaged to effect such intermittent rotation of the carousel assembly  18 . The carousel assembly  18  includes an outer circular box beam frame  42  and an inner hexagonal box beam frame  44  and suitable chordal and radial braces  46 . The outer circular frame  42  and the inner hexagonal frame  44  support and receive a plurality, preferably six, carrier frame assemblies  48 . 
     The rotary thermoforming machine  10  also includes a plurality of operating or process stations disposed generally concentrically about the center support column  24  of the carousel assembly  18 . There is a first loading station  50  at which, as will be described subsequently, a first or upper panel is loaded into a carrier frame assembly  48 , a second loading station  52  wherein in a second or lower panel is loaded onto another carrier frame assembly  48 , a first heating station  54  which provides radiant heat to an adjacent panel in the carousel assembly  18 , and a second heating station  56  which likewise provides heat to a panel in the carousel assembly  18 , a molding station  60  wherein the product fabricated in the rotary thermoforming machine  10  is assembled. A robot loading assembly  62  cooperates with the molding station  60  to supply preforms or inserts into the products fabricated therein. Finally, the rotary thermoforming machine  10  includes an unloading station  64  which removes finished product from the thermoforming machine  10  and specifically the carrier frame assemblies  48  of the carousel assembly  18 . 
     Turning now to FIGS. 2,  3  and  4 , the second loading station  52  will now be described. At the outset, it should be understood that the first loading station  50  loads only first or upper thermoformable sheets or panels  66 A into the carousel assembly  18  and that the second loading station  52  loads only second or lower thermoformable sheets or panels  66 B into the carousel assembly  18 . The thermoformable sheets or panels  66 A and  66 B are preferably high density polyethylene (HDPE) but may be any similar rugged and durable thermoplastic or thermosetting material. The first loading station  50  and the second loading station  52  are disposed adjacent one another in the rotary thermoforming machine  10  and are identical in operation and design. Accordingly, only the second loading station  52 , illustrated in FIG. 2 will be described, it being understood that the following description relating thereto applies fully and accurately to the first loading station  50 . 
     The second loading station  52  is provided with a plurality of second or lower thermoformable panels  66 B disposed in an aligned, vertical stack  68 . A loading assembly  70  transfers individual lower thermoformable panels  66 B from the stack  68  to the carrier frame assemblies  48 . The loading assembly  70  includes a moveable frame  72  attached to a vertical jack or lead screw  74  which is vertically raised and lowered by an associated drive assembly  76 . Pneumatic cylinders and analogous bi-directional linear translating devices are all suitable alternative motive devices. Depending from the frame  72  are a plurality of suction (vacuum) lift cups  78 . The suction lift cups  78  are in fluid communication with a controllable vacuum source (not illustrated). As the frame  72  is lowered through action of the drive assembly  76  and the jack or lead screw  74 , the suction lift cups  78  engage the uppermost lower thermoformable panel  66 B on the stack  68  and, when a vacuum is present in the suction lift cups  78 , the lower thermoformable panel  66 B is engaged and lifted. The lower thermoformable panel  66 B may be readily released from the suction lift cups  78  by terminating the vacuum therein in accordance with conventional practice. 
     Turning now to FIGS. 2,  3 ,  4  and  5 , the loading assembly  70  individually transfers one of the lower thermoformable panels  66 B to one of the carrier frame assemblies  48 . Each of the frame assemblies  48  includes a peripheral rectangular mounting frame  82  upon which are pivotally mounted a plurality of air piston and cylinder assemblies  84 . The pistons of the assemblies  84  activate an elongate pivoting clamp  86  which pivots toward an inner rectangular frame surface  88  which extends about the interior of the frame  82 . Generally speaking, the configuration of the inner frame surface  88  defines a rectangular shape slightly larger than the rectangular shape of the thermoformable panels  66 A and  66 B. When the loading assembly  70  lifts one of the lower thermformable panels  66 B from the stack  68 , one of the carrier frame assemblies  48  is accurately aligned thereover and the lower thermoformable panel  66 B is raised until it engages the inner rectangular frame surface  88 . At this time, the piston and cylinder assemblies  84  are activated and the pivoting clamps  86  engage and retain the lower thermoformable panel  66 B on the surface  88  as illustrated in FIG.  5 . After the first loading station  50  has loaded the first or upper thermoformable panel  66 A into one of the carrier frame assemblies  48  and the second loading station  52  has loaded a second or lower thermoformable panel  66 B into an adjacent one of the carrier frame assemblies  48 , the electric motor  40  is activated and the carousel assembly is rotated 60°. 
     It should be appreciated that by utilizing separate loading stations  50  and  52  for the upper and lower thermoformable panels  66 A and  668 , specific exterior surface treatments or features such as designs, graining, logos and the like may be readily located on the outer surfaces of a product while alleviating the necessity of providing such surface treatment or logo on both surfaces of the thermoformable panels  66 A and  66 B. Alternatively, it may be desirable that the graining or other surface treatment be on the Inner surface in order to aid bonding or adhesion of produce elements. In either event, because the machine  10  utilizes two separate stacks  68  of thermoformable panels  66 A and  66 B and the locations of the thermoformable panels  66 A and  66 B in the carrier frame assemblies  48  are effectively tracked, the thermoformable panels  66 A loaded at the first station  50  with such surface treatment or logo facing up or down are always utilized as an upper panel in the product such that any surface treatment or logo Is located as desired, i.e., either on the exposed, upper face of the product or the interior surface of the upper panel  66 A and the thermoformable panels  66 B loaded at the second station  52  with such surface treatment or logo facing down or up are always utilized as the bottom panel of the product such that any logo or desired surface treatment is located either on the visible, i.e., exposed, lower face of the product or the interior surface of the lower panel. 
     Referring again to FIGS. 1 and 2, the first heating station  54  and the second heating station  56  will next be described. It should be understood that the heating stations  54  and  56  are identical and that incorporation of two heating stations, among other things, improves process cycle time. Inasmuch as the two heating stations  54  and  56  are substantially identical in structure, only the first heating station  54  will be described, it being understood that generally only operational and process differences such as electrical input or heating element to product spacing will vary between the two stations  54  and  56 . 
     The first heating station  54  includes a first or upper radiant heating assembly  92  having a plurality of electrical resistance heating elements  94  disposed in a conventional, spaced-apart array. Preferably, the upper heating assembly  92  is disposed several inches above the carousel assembly  18  and is relatively fixedly secured to the horizontal rails or beams  16  of the frame  12 . By “relatively fixedly secured,” it is meant that while the radiant heating assembly  92  is not mounted in a fashion which readily permits height adjustment relative to the carousel assembly  18 , it may, nevertheless, be raised or lowered relative thereto, if necessary, and its mounting configuration should not preclude such adjustment. 
     A second or lower radiant heating assembly  98  is disposed vertically beneath the upper heating assembly  92  and beneath the carousel assembly  18 . The second or lower heating radiant assembly  98  likewise includes a plurality of electrical resistance heating elements  102  in a spaced-apart array. The second or lower radiant heating assembly  98 , is, however, readily adjustable and is supported upon a scissor lift assembly  104  having a conventional pantograph type configuration and an actuator such as a hydraulic piston and cylinder assembly  106  or an electrically driven motor and lead screw which, when activated, raises and lowers the second or lower radiant heating assembly  98  as will be readily appreciated. Accordingly, the amount of heat provided by both radiation and convection from the second or lower heating assembly  98  to the thermoformable panels  66 A and  66 B retained in the frame assemblies  48  of the carousel assembly  18  may thus be readily adjusted in order to achieve proper heating and thus flexibility and formability of the panels  66 A and  66 B when they arrive at the thermoforming station  60 . 
     The second heating station  56  is substantially identical to the first heating station  54  and thus includes an upper radiant heating assembly  92  having a plurality of electrical resistance heating elements  94  disposed in a spaced-apart array. The second heating station  56  also includes a second or lower radiant heating assembly  98  vertically aligned with the upper radiant heating assembly  92  and having a plurality of electrical resistance heating elements  102  in a spaced-apart array. The second radiant heating assembly  98  is likewise mounted upon a scissor lift assembly  104  which is driven by a hydraulic piston and cylinder assembly  106 . 
     Optionally, photoelectric sag sensors  108  utilized in conjunction with a light source (not illustrated) may be disposed below the plane of the carousel assembly  18  adjacent both the first heating station  54  and the second heating station  56  in order to detect sag of the thermoformable panels  66 A and  66 B in each of the stations  54  and  56  as they are heated. Depending upon the selected vertical location of the sag sensors  108  above the lower heating assemblies  98 , a signal from one of the sag sensors  108  indicating that it has sensed sag of one of the panels  66 A or  66 B may be utilized in various ways. For example, If the sag sensors  108  are relatively close to the plane of the carousel assembly  18  and the carrier frame assemblies  48 , a sag signal may be used as an operational signal indicating that the thermoformable panel  66 A or  66 B is sufficiently heated and flexible and that the carousel assembly  18  may be indexed and that thermoforming may proceed. If the sag signal is utilized to index the carousel assembly  18 , it is necessary, of course, that the heating cycle at an individual heating station  54  or  56  generally occupy more time than that of the steps of the thermoforming cycle such that when sag is detected, the carousel assembly  18  can be promptly indexed. Alternatively, when sag is sensed, electrical energy to the electrical heating elements  94  and  102  may be limited or reduced to maintain the temperature of, but not further heat, the thermoformable panels  66 A and  66 B. As a further alternative, if the sag sensors  108  are disposed relatively proximate the second or lower radiant heating assemblies  98 , sag sensing may be utilized to trip an alarm or provide a control signal alerting an operator that further sag of the thermoformable panels  66 A and  66 B may result in contact between the panels  66 A and  66 B and the electrical resistance heating elements  102 . As a final alternative, multiple sag sensors  108  may be utilized at multiple vertical locations to provide both operating signals and limit or alarm signals, if desired. 
     Referring now to FIGS. 2,  6 ,  7  and  8 , the thermoforming station  60  of the rotary thermoforming machine  10  according to the present invention will now be described. The thermoforming station  60  includes an upper mold assembly  110  located within and positioned by the vertical supports  14 , the horizontal supports  16 , upper frame members  112  and upper horizontal frame members  114 . The upper mold assembly  110  includes a plurality of gear racks  118 . The gear racks  118  are stationary, disposed vertically and depend from cantilever support plates  122 , which, in turn, are attached to the horizontal frame members  114 . The gear racks  118  are slidably received within bushings or journal bearings  124  secured to an upper platen  126 . As illustrated in FIG. 6, preferably at least four of the gear racks  118  and associated journal bearings or bushings  124  are utilized with the upper platen  126 . 
     As best illustrated in FIGS. 6,  7  and  8 , each of the gear racks  118  is driven by a complementarily configured spur gear  128  which engage the gear rack  118  through a suitable opening in the journal bearing or bushing  124 . Each of the spur gears  128  is, in turn, secured to one of a pair of transverse shafts  132  supported in suitable bearings such as pillow blocks  134 . Secured to each of the shafts  132  is a driven chain sprocket  136 . A pair of chains  138  engage a respective one of the driven chain sprockets  136  and in turn, engage one of a pair of chain drive sprockets  142  disposed on the output shaft  144  of a speed reduction assembly  146 . The speed reduction assembly  146  is driven by a bi-directional electric motor  148  mounted upon the upper platen  126 . As illustrated in FIGS. 6 and 7, it will be appreciated that the pair of chain drive sprockets  142  are disposed upon the output shaft  144  of the gear reduction assembly  146  and receive a respective one of the drive chains  138  which engage, at both the front and rear of the upper platen  126 , the drive chain sprockets  136  disposed upon the transverse shafts  132 . That is, the drive chains  138  extend to both the front and rear of the platen assembly  136  and drive the transverse shafts  132  and the spur gears  128  at each end which engage the vertically disposed gear racks  118 . Thus, as the output shaft  144  and the chain drive sprockets  142  rotate, such motion is transmitted through the components just recited and elevates or lowers the upper platen  126 , maintaining its horizontal disposition as illustrated in the drawing figures. 
     The thermoforming station  60  also includes a lower mold assembly  160  which is vertically aligned with and disposed below the upper mold assembly  110 . The lower mold assembly  160  is similar in many respects to the upper mold assembly  110  and includes a similar configuration of mechanical components which raise and lower a lower platen  162 . The lower mold assembly  160  thus includes a plurality, preferably four, gear racks  164  which are slidably received within bushings or journal bearings  166  secured to the lower platen  162 . A like plurality of spur gears  168  disposed upon two transverse shafts  172  engage the gear racks  164  and, upon rotation, raise and lower the lower platen  162 . The shafts  172  each include a chain drive sprocket  174  driven by a chain  176  which, in turn, is driven by a pair of chain sprockets  178  disposed upon the output shaft  182  of a gear reduction assembly  184 . The gear reduction assembly  184  is, in turn, driven by a bi-directional electric motor  186 . It will be appreciated that rotation of the electric motor  186  in a first direction will result in raising the lower platen  162  and vice versa. It will also be appreciated that both the bi-directional drive motors  148  and  186  as well as the associated mechanical linkages are capable of moving the upper platen  126  downward into, proximity with the top side of the carousel assembly  18 , specifically the carrier frames  48 , and the lower platen  162  upward into proximity with the underside of the carousel assembly  18 , specifically the carrier frames  48 . 
     Referring now to FIGS. 6,  7  and  9 , the thermoforming station  60  and specifically both the upper mold assembly  110  and the lower mold assembly  160  also include interlockable assemblies  190  which tightly and positively secure and retain the upper platen  126  and the lower platen  162  in a defined, proximate relationship during thermoforming activity. These assemblies  190  include a plurality of, preferably four, bayonets  192  which define elongate rods having male threads  194  disposed thereabout. The bayonets  192  are received within threaded locking collars  196  which may be rotated and secured to permit axial adjustment of the positions of the bayonets  192 . Each of the bayonets  192  also includes an axial keyway  198  which each receives a key  200  or similar radially inwardly projecting component which extends from the inner wall of a drive collar  202 . The drive collars  202  each also include radially oriented crank arms  204  which are pivotally, secured to a drive linkage  206 . The drive linkage  206  is pivotally coupled to a piston shaft  208  of a double acting piston and cylinder assembly  210 . Activation of the double acting piston and cylinder assembly  210  rotates the collars  202  and thus also rotates the bayonets  192  through an acute angle from a first angular position to a second angular position. Adjacent the lower termini of the bayonets  192  are a pair of opposed, radially extending bayonet pins  212 . 
     The bayonets  192  and specifically the bayonet pins  212  are received within a respective one of a complementarily disposed like plurality of aligned bayonet sockets  216 . Each of the bayonet sockets  216  includes a vertically, axially extending passageway  218  generally complementary to the bayonets  192 . On the walls of the bayonet sockets  216  are suitably formed bayonet lock passages  222  which, in conventional bayonet operating fashion, receive the bayonet pins  212  axially and, upon rotation of the bayonets  192 , lock the bayonet pins  212  and, thus the bayonets  192  into a fixed, axial position relative to the bayonet sockets  216 . Such rotation of the bayonets  192  is, of course, accomplished by the piston and cylinder assemblies  210  illustrated in FIG.  9 . 
     Referring now to FIGS. 1 and 10, a mechanical or robot loading assembly  62  is disposed adjacent the thermoforming station  60 . The mechanical or robot loading assembly  62  includes a plurality of vertical track or frame members  226  having horizontal cross members  228  which, with the vertical track or frame members  226 , define a rectangular frame. A first carriage  230  translates vertically and bi-directionally along the vertical track or frame members  226  and includes friction reducing members such as guides or slides  232 , a plurality of rollers or equivalent devices which both retain the carriage  230  in the frame and guide it vertically along the path defined thereby. The first carriage  230  is vertically, bi-directionally translated by a pneumatic piston and cylinder assembly  234  or other linear actuator such as a lead or ball screw device. The piston and cylinder assembly  234  or other device is preferably double acting and thus positively drives the first carriage  230  both up and down but may be single acting, its force being provided only to raise the first carriage  230 , the lowering of the first carriage  230  accomplished by either gravity or a biasing spring which may be disposed within the piston and cylinder assembly  234 . 
     Translating with the first carriage assembly  230  is a horizontally extensible arm or member  240  disposed upon a supporting slide  242  or similar friction reducing device such as a plurality of rollers. The horizontally extensible member  240  is driven by a bi-directional actuator  244  which may be, as described above, a double acting pneumatic cylinder or an electrically operated linear actuator, ball screw or the like. The extensible member  240  includes a plurality of, preferably two suction (vacuum) lift cups  246 . The suction lift cups  246  and the extensible member  240 , illustrated in a loading position in FIG. 10, engage an uppermost insert  250  in a vertically aligned stack of inserts  252  disposed adjacent the thermoforming station  60 . At the appropriate time, a vacuum is supplied to the suction lift cups  246 , the uppermost insert  250  is engaged, the actuators  234  and  244  are activated and the insert  250  is translated into the thermoforming station  60  as will be more fully described subsequently. 
     Turning now to FIGS. 1 and 11, the unloading station  64  will be described. The unloading station  64  includes a tiltable table  256  which is generally vertically aligned with the carousel assembly  18 , and specifically one of the carrier frame assemblies  48 , when it is in one of its six, indexed positions. The table  256  is disposed upon one or a pair of vertically oriented, bi-directionally translatable members such as a gear rack  258 . The gear rack  258  is bi-directionally translated by a drive, actuator  260  and both are supported by a rectangular frame assembly  262 . A tilt stop  264  extends upwardly from the frame assembly  262  on the side of the gear racks  258  opposite the desired direction of discharge of product from the table  256 . The drive actuator  260  may be selectively activated to raise the table  256  in timed relation to the other operations of the thermoforming machine  10  and engage a formed product  266  contained within one of the carrier frame assemblies  48  of the carousel assembly  18 . The formed product  266  is released to the table  256 , the actuator  260  is activated in the opposite direction and the table  256  lowers. As the bottom side of the table  256  engages the tilt stop  264 , the table  256  tilts, discharging the formed product  266  onto an adjacent conveyor assembly  270 . 
     Operation 
     Referring now to FIGS. 1,  2 ,  5 ,  12  and  13 , operation of, and the processes performed by, the thermoforming machine  10  will now be described. All such operation is keyed in time to indexed or intermittent rotation of the carousel  18  and the carrier frame assemblies  48 . Operation of the thermoforming machine  10  will thus be correspondingly described. Starting with a fully empty carousel assembly  18 , i.e., six empty carrier frame assemblies  48 , which are disposed in alignment with the six operating stations of the thermoforming machine  10  as illustrated in FIG. 1, the loading assembly  70  associated with the first loading station  50  loads a first or, upper thermoformable panel  66 A into the carrier frame  48  and the piston and cylinder assemblies  84  are activated to engage the pivoting clamps  86  against the thermoformable panel  66 A to retain the thermoformable panel  66 A therein. At the same time or during the same cycle of the index cycle, the loading assembly  70  associated with the second loading station  52  undertakes and achieves a similar function by loading a second or lower thermoformable panel  66 B into the carrier frame  48  currently disposed in a second position as illustrated in FIG.  5 . 
     As noted previously, since the stacks  68  associated with the first loading station  50  and the second loading station  52  are separate and independent, the upper and lower thermoformable panels  66 A and  66 B, respectively, may include position specific surface treatment or indicia, i.e., graining or logos, for example, intended for the visible (exposed) upper or lower surface of the finished product  266  or the hidden (interior) panel surfaces and the thermoforming machine  10  handles these panels  66 A and  66 B in a manner which ensures that the surface treatment is located as desired in the formed product  266 . The electric motor  40  may then be activated to index the carousel assembly  18  another 60° such that each carrier frame  48  moves clockwise from one station to the next (adjacent) station. At this time, the lower thermoformable panel  66 B resides in the first heating station  54 . After a dwell time determined for example, by the time consumed by operation of the thermoforming station  60  or first stage heating of the panel  66 B in the first heating station  54 , the electric motor  40  is again activated and the carousel assembly  18  again indexes 60°. Now the lower thermoformable panel  66 B resides in the second heating station  56 , the top thermoformable panel  66 A resides in the first heating station  54  and the two carrier frames  48  resident in the first loading station  50  and the second loading station  52  are empty and may be loaded as previously described. 
     When the lower thermoformable panel  66 B has been heated sufficiently as either determined by elapse of a predetermined time period or indicated by the sag sensors  108 , the carousel assembly  18  is again indexed and rotated 60°, the lower thermoformable panel  66 B is disposed and aligned with the thermoforming station  60  directly over a lower vacuum mold  280  as illustrated in FIG.  12 . At this time, the electric motor  186  is activated to raise the lower platen  162  and a lower mold  280  into contact with the lower surface of the thermoformable panel  66 B residing in the carrier frame  48  currently disposed within the thermoforming station  60 . A vacuum is drawn within a lower mold cavity  282  of the lower mold  280  according to conventional practice and, as illustrated in FIG. 13, the thermoformable panel  66 B takes the shape of the lower mold cavity  282 . At this time, the piston and cylinder assemblies  84  are deactivated and the pivoting clamps  86  release the lower thermoformable panel  66 B. 
     Turning now to FIGS. 14 and 15, the electric drive motor  186  is then activated to lower the lower platen  162  preparatory to activating the electric motor  40  to cause another 60° step of indexed rotation of the carousel assembly  18 . Such indexed rotation of the carousel assembly  18  then provides and aligns the upper thermoformable panel  66 A with an upper vacuum mold  290  secured to and carried by the upper platen  126 . In a fashion similar to the action of the lower mold assembly  160 , the electric motor  148  is activated to lower the upper platen  126  and the upper mold  290  such that an upper mold cavity  292  is adjacent the upper thermoformable panel  66 A. A vacuum is drawn within the upper mold cavity  292  and, as illustrated in FIG. 15, the upper thermoformable panel  66 A conforms to the surface of the upper mold cavity  292 . 
     Next, and as illustrated in FIG. 16, or during this previously described activity, and as illustrated in FIGS. 10 and 15, the robot loading assembly  62  is activated to transfer a preform or insert  250  from the stack  252  into the interior of the lower thermoformable panel  66 B. The preform or insert  250  may be selected from a wide variety of reinforcing materials and may be wood, aluminum, honeycomb, plastic foams and multilayer sandwiches of fibers or resin impregnated fibers and foam layers of polyurethane, polyethylene or Styrofoam, for example. 
     Next, the electric motor  186  is once again activated to raise the lower platen  162  and the associated lower mold  280  such that the opposing faces of the thermoformable panels  66 A and  66 B engage one another. The same raising of the lower platen  162  engages the bayonets  192  and the radially extending bayonet pins  212  into the passageways  218  and the bayonet lock passages  222 . At this time, the piston and cylinder assemblies  210  are activated to rotate the bayonets  192  such that the bayonet pins  212  engage and lock in the bayonet lock passageways  222  thereby preventing relative vertical motion between the upper platen  126  and the lower platen  162 . The upper thermoformable panel  66 A and the lower thermoformable panel  66 B and the insert or perform  250  are secured together within the molds  280  and  290  by compressive force generated by a plurality of air bladders  300  disposed between the lower platen  162  and the lower mold  280 . The air bladders  300  preferably occupy substantially the entire lower surface of the lower platen  126  and are filled with compressed air at a pressure of at least about 100 p.s.i. Significant compressive force, on the order of 75 to 100 tons or more depending upon the air pressure and surface areas of the bladders  300  and the lower platen  162 , is typically generated and applied to the molds  280  and  290 . 
     Upon completion of the forming and sealing steps wherein the peripheries of the thermoformable panels.  66 A and  668  are secured together, air pressure within the bladders  300  is released, the piston and cylinder assemblies  210  are activated in the reverse direction such that the bayonet pins  212  release from the bayonet lock passages  222 . Then the electric drive motors  148  and  186  are activated to raise and lower, respectively, the upper platen  126  and associated upper mold  290  and the lower platen  162  and the associated lower mold  280 . 
     Once again and as illustrated in FIGS. 1 and 11, the electric drive motor  40  is activated and indexes the carousel assembly  18  another 60° such that the formed product  266  is now aligned with the unloading station  64 . At this time, the product  266  is released from the carrier frame  48  by deactivating the piston and cylinder assemblies  84  and releasing the pivoting clamps  86 . The formed product  266  then drops and is engaged by the table  256  which has been elevated to a position directly underneath the product  266  such that it does not drop a significant distance. The drive actuator  260  is then activated to lower the table  256  and the product  266 . The tilt stop  264  engages the bottom of the table  256  tilting it and the product  266  slides onto the conveyor  270 . The formed product  266  is then removed from the conveyor  270  such that final trimming and other post production processes may be completed prior to storage and shipment. 
     Although the foregoing description relates to the operation and sequencing of two adjacent carrier frames  48  as they receive the upper and lower thermoformable panels  66 A and  66 B, are heated in the adjacent heating stations  54  and  56 , are formed and combined into the completed product  266  in the forming station  60  and finally unloaded from the rotary thermoforming machine  10  at the unloading station  64 , it should be appreciated that the upper and lower thermoformable panels  66 A and  66 B are continuously and alternately loaded into the carrier frames  48  such that a formed product  266  is produced upon or after every two indexed cycles, i.e., 120° of rotation, of the carousel assembly  18 . 
     The foregoing disclosure is the best mode devised by the inventors for practicing this invention. It is apparent, however, that apparatus and methods incorporating modifications and variations will be obvious to one skilled in the art of rotary thermoforming machines. Inasmuch as the foregoing disclosure presents the best mode contemplated by the inventors for carrying out the invention and is Intended to enable any person skilled in the pertinent art to practice this invention, it should not be construed to be limited thereby but should be construed to include such aforementioned obvious variations and be limited only by the spirit and scope of the following claims.