Abstract:
A container and lid sealing apparatus comprising a frame structure including a sealing position, support beams, a shiftable container support which includes a container retainer and shiftable on drawer rails from a position for loading and unloading a container into and out of the retainer, to the sealing position for sealing a lid on the tray, an upper heater platen suspended above the tray support, and an actuator actuable to force the upper heater platen downwardly with force onto a container and lid on the support. The force is equally distributed on all portions of the platen to seal a lid onto a container. The actuator may be either a manual actuator or an air actuator. The actuator is multi-axially pivotally coupled to the platen to thereby allow the platen to rock and seek and obtain a parallel relation with the container flange and lid.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of U.S. patent application Ser. No. 09/389,202 filed on Sep. 2, 1999 now abandoned, entitled DRAWER ACTION TRAY SEALING MACHINE, which is a continuation-in-part of U.S. patent application Ser. No. 09/103,859 filed on Jun. 24, 1998, entitled DRAWER ACTION TRAY SEALING MACHINE, now U.S. Pat. No. 5,946,887, which is a continuation of U.S. patent application Ser. No. 08/629,269 filed on Apr. 8, 1996, entitled DRAWER ACTION TRAY SEALING MACHINE, now U.S. Pat. No. 5,784,858. Priority under 35 U.S.C. §120 is claimed to the filing dates of the &#39;202, &#39;859 and &#39;269 applications and the entire disclosures of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to a machine for sealing a lid on a container, and more particularly for sealing food or the like in the container. 
     Food containers used by fast food establishments, grocery stores, delicatessens and the like, when filled on site, commonly employ a tray-type container integrally connected to a cover or lid. These containers are handy but do not seal the food in or seal air out. Consequently spillage readily occurs and retention of freshness is not possible. Another type of common container is that which has a separate lid which is snapped into place between the specially formed lid and container. Some containers of this type are leak resistant, but do not totally seal the contents. In large food processing establishments, containers can be completely sealed utilizing sealing machines which are presently known, but these typically are complex apparatuses, not suitable for on-site use in fast food restaurants, grocery stores, and the like. Persons employed at fast food establishments and the like are frequently young, relatively unskilled persons who work at a rapid pace. Turnover rate of employees is generally high, resulting in a high level of inexperience. Therefore, any mechanical devices to be used to close and seal containers at these establishments should be simple, easy and safe to use. There is needed an apparatus which meets these criteria as well as providing a leakproof or leak resistant container which also preserves freshness of the food item as well as assists in retaining heat with the food item. 
     One type of known apparatus usable in grocery stores, to seal a polymeric film lid onto the top rim of a container for containing and transporting food, uses a heated platen. If the tray is plastic, it can be made leakproof and airtight. If it is paperboard, it can be made leak resistant. The apparatus involves a fixed lower support serving as a tray carrier and having a well or cavity to receive and retain a container therein, and the upper heated platen pivotally mounted to shift to a closed position on the. container and lid between the platen and the lower support. The heated platen is manually forced down and held down by the weight of the human operator onto the container and lid during a time period while heat is applied to seal the lid to the container. 
     However, in order to provide sufficient force on the container and lid to fully compress the periphery of the two together, the heated upper platen must be manually forced down by the operator with a significant force which is usually about 20-40 pounds. By using leverage-type mechanical advantage, the force applied to the container and lid can be about 75 pounds. This exertion is required for each tray and lid, and for a set time period, in order to force the platen and tray carrier fully together. Establishments which would use these units frequently employ teenage persons or ladies, so that applying this significant amount of force steadily on the platen is difficult, requiring considerable exertion, and is particularly tiring. Moreover, it has been determined that even the application of this much force is sometimes not sufficient to assure a complete seal of the lid periphery to the container periphery. To be certain of sealing, the force should actually be several times this amount. One of the variables that can prevent total sealing is the fact that the flange of the tray might not be of uniform thickness around its periphery, resulting in a poor seal at the thinner areas. 
     SUMMARY OF THE INVENTION 
     An object of this invention is to provide a container sealing device which is rapid in operation, simple to use, requires little skill and is safe. The sealing device is particularly suitable for fast food restaurants, grocery stores, delicatessens, meat markets, senior meals programs and the like, to seal the contents of the container against leakage from the container, and preferably against air entry into the container. It rockingly adjusts automatically to apply equal pressure to all areas of the tray flange. 
     The sealing machine has a slide drawer which serves as a tray carrier on which a container and lid are placed and retained, the tray carrier being readily slidable on drawer rails into a sealing position from a load-unload position. An upper heated platen is shiftable downwardly by an actuator to apply a great force to the center of the heated platen and hence to the container and lid. The platen is suspended from a horizontal beam of a support structure so as to be able to swing as necessary to seek a parallel relationship with the container and lid flanges and thereby apply uniform pressure to the peripheral sealing regions of the container and lid. The actuator may be manual or be an inflatable air actuator. 
     These and other features, advantages, and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims, and appended drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
     FIG. 1 is a side elevational view of an apparatus constructed in accordance with a first embodiment of the present invention; 
     FIG. 2 is a top plan view of the apparatus of the first embodiment; 
     FIG. 3 is a front end elevational view of the apparatus of the first embodiment; 
     FIG. 4 is another front elevational view showing internal components of the first embodiment; 
     FIG. 5 is a bottom view of the upper platen of the first embodiment; 
     FIG. 6 is a sectional plan view of the apparatus of the first embodiment; 
     FIG. 7 is a front end elevational view of the lower portion of the apparatus of the first embodiment; 
     FIG. 8 is a front elevational view showing internal components of the first embodiment; 
     FIG. 9 is a side elevational view of an apparatus constructed in accordance with a second embodiment of the present invention; 
     FIG. 10 is a top plan view of the apparatus of the second embodiment; 
     FIG. 11 is a front elevational view showing internal components of the second embodiment; 
     FIG. 12 is an enlarged cross-sectional view of the platen of the second embodiment shown in open and closed positions; 
     FIG. 13 is a cross-sectional view of an upper plate of the platen of the second embodiment, taken through line XIII—XIII, of FIG. 11; 
     FIG. 14 is a front end elevational view of an apparatus constructed in accordance with a third embodiment of the present invention; 
     FIG. 15 is a front end elevational view showing internal components of the third embodiment; 
     FIG. 16 is a top perspective view of an apparatus constructed in accordance with a fourth embodiment of the present invention; and 
     FIG. 17 is an enlarged top perspective view of the apparatus of the fourth embodiment. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     For purposes of description herein, the terms “upper,” “lower,” “right,” “left,” “rear,” “front,” “vertical,” “horizontal,” and derivatives thereof shall relate to the invention as oriented in FIG.  1 . However, it is to be understood that the invention may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings and described in the following specification are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise. 
     The reference numbered  10  generally designates a first embodiment of the novel sealing apparatus. The sealing apparatus  10  is shown having a support frame  14  which defines a sealing location or position  16  into which and out of which a lower tray support  18  can be moved. Tray holder  18  is indirectly mounted on a pair of drawer rails  20  (FIGS. 6 and 7) which telescopically cooperate with fixed case rails  22  for movement between the two positions, i.e., sealing position and load-unload position (FIG.  1 ). The drawer rails  22  are actually attached to the inside faces of a pair of elongated bars  24 . Tray holder  18  is mounted above and on bars  24  with upstanding pins or studs  26  (FIG.  7 ), resting on compression springs  28  around the pins. Downward force on tray holder  18  depresses it against the bias of springs  28 , with movement on pins  26 , until the tray holder abuts the top surfaces of stops in the form of a pair of elongated, upstanding, fixed, rigid beams  30  mounted to frame  14  and located at the sealing position  16 . Beams  30  are parallel to bars  24 . With this arrangement, the tray holder  18  can be readily moved into and out of the sealing position  16  on the drawer rails  22  but, under significant downward force applied to the tray holder by the upper platen, the tray holder will be depressed against the bias of springs  28  onto these laterally spaced, parallel beams  30  which will supply support so as to prevent damage to the drawer rail assembly. 
     Tray holder  18  (FIG. 6) defines a desired number of container receiving cavities, shown here to be two, each cavity being surrounded by a peripheral ledge which is surrounded by a plurality of depressible locator pins  32 . When a container having a peripheral shape like that of the cavity is placed therein, its peripheral, horizontal flange will rest on the peripheral ledge around the cavity, bounded by the pins  32 . A lid of configuration like that of the container flange is placed thereon, also retained within locator pins  32  for alignment. 
     At the sealing position  16  is a heated upper platen  40  suspended on two laterally spaced rods  42 . These rods  42  are loosely fit within sleeves  44  (FIG. 4) and are vertically slidable in sleeves  44  to allow vertical movement of platen  40 . As shown in FIG. 8, rods  42  are attached to platen  40  using spherical washers  98 , which allows platen  40  to multi-axially pivot freely front to back and side to side relative to rods  42 . 
     Downward movement of the platen  40  and rods  42  is against the bias of compression springs  46  around rods  42 . The bottom ends of the springs  46  are on a top  102  of a fixed, elongated, horizontal member  17  forming part of support structure  14  and extending transversely of the structure. Member  17  is located at the top of a pair of upstanding support columns  15  (FIG. 4) above the upper platen  40 . Springs  46  are trapped between support  17  and washers  48  on the upper end of rods  42 , the washers being held in position by bolts  50  threaded into rods  42 . Downward pressure on platen  40  thus will compress springs  46  against the bias thereof, this downward pressure being applied by an actuator  51  that includes an air actuator  54  mounted between support  17  and platen  40 . Inflation of the air actuator  54  by injection of air under pressure lowers upper platen  40  down onto lidded trays on tray holder  18 . As shown in FIG. 8, air actuator  54  includes a flexible rubber baffle  53  positioned between two rigid plates  56  and  57 . Because plates  56  and  57  are flexibly joined by only baffle  53 , plates  56  and  57 , and hence, support  17  and platen  40 , may move into non-parallel positions relative to one another and “rock” as needed to allow platen  40  to seek and obtain a parallel relation with the container flange and lid. 
     Actuator  51  has a centrally positioned rod  55  engaging the top center of platen  40 . Therefore, downward pressure of actuator  54  on rod  55  creates a balanced pressure by all portions of platen  40  against all portions of the tray and lid even when plates  56  and  57  of actuator  51  are not parallel, since platen  40  can rock (i.e., pivot or swing) due to the manner in which it is suspended from horizontal member  17  and air actuator  54 , as necessary to always seek a parallel relationship to the support and a container flange and lid thereon. This ability of the platen to rock enables the platen to place uniform pressure on all parts of the flange and contacting lid areas. The upper platen includes a plurality of resistance heater elements  41  (FIG.  4 ), so that heat and pressure can be applied to the lid and the peripheral rim of the tray in cavity  34 , to seal the lid to the tray container. 
     Support  17  is mounted at one of its ends to one column  15  with a pivot pin  60  (FIG.  3 ), and at the other end to the other column  15  by a removable lock pin  62 . Lock pin  62  extends through a pair of rigid mounting ears  64 , as well as through the one end of support  17 . Removal of the lock pin  62  allows support  17  and the upper platen to be pivoted laterally on pin  60  for cleaning, repair or the like. The lower support  18  is also removable for cleaning, substitution of a support with a different size and/or shape recess, or otherwise, simply by releasing the drawer rails in a conventional manner. 
     The frame structure also includes a pair of upper roller bars  70  extending transversely of the apparatus and parallel to each other, for mounting a roll R of interconnected lids thereon. These lids are separable along perforations (not shown) so that the operator can grasp the endmost portion of the roll, pull it beneath a retaining bar  72  and detach the end lid portion from the roll along the perforations, then place the lid on a container in cavity  34 , and aligned within the pins  32 . A friction brake on retaining bar  72  prevents the film from moving in reverse on the roll. These pins are depressible into support  18  when upper platen  40  is lowered by air actuator  54 . The lids are normally of plastic material with a heat sealable layer, or a material such as paperboard coated with a heat sensitive sealable layer, to bond to the container flange when heated and pressed. 
     On the front end of tray support  18  is a rotational knob  43  for manual actuation to eject the finished tray from cavity  34  for grasping the tray. Specifically, by rotating knob  43 , rod  92  and transverse element  90  are rotated, the latter engaging and lifting the tray. Also on the front face of tray support  18  is an upright protector panel  45  which closes adjacent the vertical panel on the front face of platen  40  when the support is moved inwardly to the sealing position, to close off the front face of the sealing apparatus and prevent injury to persons during vertical movement of heated upper platen  40 . 
     A gas spring  76  for shifting the container support from its sealing position back to the extended load-unload position is attached between frame  14  and a pivotal link  78  (FIG.  6 ). More specifically, one end  76 A of gas spring  76  is pivotally attached to frame  14 , with the extended end of its piston rod  76 B (FIG. 6) being pivotally connected at  76 C intermediate the ends of link  78 . One end of link  78  is pivotally connected at  78 A to frame  14  while the opposite end  78 B has a roller cam engaging tray support  18 , such that extension of the gas spring shifts the link and tray support from the sealing position to the load-unload outer position, such movement being shown by the three successive positions depicted in FIG.  6 . 
     Downward movement of air actuator  54  of actuator  51  is controlled by opening of a valve  80  (FIG. 4) with a pneumatic cam valve switch  82  engaged by the inner end of one of the drawer supports  24  when the tray holder is moved into the sealing position. The force of air actuator  54  lowers upper platen  40  down against the container and lid on the tray support  18 , forcing the lower platen down against the bias of springs  46  until it engages support beams  30 . The time interval of actuation of the constant force air actuator  54  is controlled by a timer  83  (FIG.  10 ). At the end of this interval, timer  83  actuates a quick exhaust, i.e., air dump, valve  96  which instantly dumps the air from the air actuator  54  to immediately cause it to retract vertically upwardly under the bias of compression springs  46 . Upon release of the downward pressure by the upper platen, gas spring  76  extends its piston rod to pivotally shift link  78  and thereby horizontally shift tray support  18  out of the sealing position to the extended load-unload position. 
     In operation, therefore, with the tray support in the extended load-unload position, a person places in cavity  34  an open top container having a peripheral flange (FIG. 1) to rest on the tray support. The container can be filled in place or can have contents already in it when so placed. The operator then pulls the end portion of roll R and separates the endmost lid from the roll, placing it on top of the container and flange, within the confines of pins  32 . The lid and/or container flange have heat responsive sealing material thereon. The tray support, tray, contents and lid are then pushed into the sealing position, riding on the drawer rails. At this point the tray support engages cam  82  of pneumatic cam valve  80  to actuate the air logic system and cause air to enter air actuator  54 . This lowers, i.e., depresses, the heated upper platen  40  against the bias of compression springs  46 , down against the lid, container and tray support, forcing the tray support down against the bias of compression springs  28 , onto the upper surfaces of rigid support beams  30 . Heat and pressure are held for the preset time interval necessary to seal the lids to the containers. The actuator  51  causes a balancing of pressure to all portions of the tray flange and engaging lid by the floating, i.e., multi-axial rocking/pivoting, action of the platen  40  beneath actuator  54 . Upon timed release of the air actuator  54 , compressed air is discharged from the air actuator  54 , the upper platen is vertically retracted by spring bias, allowing gas spring  76  to horizontally eject the tray support along with its sealed container and contents from the sealing position to the load-unload position. At this point, the container can be made to partially protrude above tray support  18  by manual rotation by the operator of knob  43  and thus element  90  (FIG. 7) on pivot shaft  92 , enabling the operator to grasp the sealed container. The unit is then ready for reloading. The operation is quick, simple and easy to learn. The sides and front of the unit are provided with guards to prevent the operator&#39;s hands from entering the sealing position area. Although the apparatus has been largely described using a tray type flanged container, other containers than trays could be sealed. 
     The reference  100  (FIG. 9) generally designates a second embodiment of the novel sealing apparatus. The sealing apparatus  100  is shown having a support frame  102  which defines a sealing location or position  104  into which and out of which a lower tray support or holder  106  (FIG. 10) can be moved. Tray holder  106  is supported on a pair of rails  108  which are attached to the inside faces of support frame  102 . A handle  110  is fixedly attached to tray support  106 , thereby allowing easy manipulation of tray support  106  along rails  108 . With this arrangement, the tray holder  106  can be readily moved into and out of the sealing position  104  on drawer rails  108 . 
     Each tray holder  106  defines a desired number of container receiving cavities  111 , shown here to be two, each cavity being surrounded by a peripheral ledge  113  which is surrounded by a plurality of depressible locator pins  112 . It should be noted that while in the illustrated example each tray holder  106  is configured to hold a container within two cavities  111 , containers having varied numbers of cavities in numerous arrangements may be used. When a container having a peripheral shape like that of the cavity  111  it is placed therein, its peripheral, horizontal flange will rest on the peripheral ledge  113  around the cavity  111 , bounded by locator pins  112 . A lid of configuration like that of the container flange is placed thereon, also retained within locator pins  112  for alignment. 
     At the sealing position  104  is a heated platen  114  (FIG. 11) suspended on two laterally spaced rods  116 . These rods  116  loosely fit within sleeves  118  and are vertically slideable in sleeves  118  to allow vertical movement of platen  114 . The rods  1   16  are attached to an upper plate  120  of platen  114  using spherical washers  122 , which allows upper plate  120  to multiaxially pivot freely from front to back and side to side relative to rods  116 . 
     Downward movement of the platen  114  and rods  116  is against the bias of compression springs  124  around rods  116 . The bottom ends of the springs  124  are on the top of a fixed, elongated, horizontal member  126  forming part of support frame  102  and extending transversely of the structure. Member  126  is located at the top of a pair of upstanding support columns  128 . Springs  124  are trapped between member  126  and washers  130  on the upper end of rods  116 , the washers being held in position by bolts  132  threaded into rods  116 . Downward pressure on platen  114  thus will compress springs  124  against the bias thereof, this downward pressure being applied by an actuator  133  that includes a manual actuator  134  mounted on member  126  and mechanically linked to platen  114 . Manual actuator  134  of actuator  133  includes a handle  136  movable between an open position wherein platen  114  is raised and tray support  106  may be moved between the sealing position  104  and the load/unload position, and a closed position, as shown in phantom line in FIG. 9, wherein platen  114  is in a lowered position for sealing. Handle  136  is mechanically linked to upper plate  120  of platen  114  by a reciprocating actuator rod  138  that is loosely fit within a sleeve (not shown) similar to sleeves  118 . A cammed mechanical linkage  140  connects handle  136  to actuator rod  138  such that movement of handle  136  between open and closed positions moves actuator rod  138  in a reciprocating linear manner. 
     Platen  114  further includes a lower plate  140  that includes a heating element  142  (FIG.  12 ). Lower plate . 140  is connected to upper plate  120  by a pair of bolts  144  that loosely fit within a pair of apertures  146  within upper plate  120  and are threadably engaged within lower plate  140 . Actuator  133  further includes a plurality of springs  148  that are located within a plurality of recesses  149  within plates  120  and  140  and bias plates  120  and  140  away from one another. In the example illustrated in FIG. 13, springs  148  are placed in two concentric, circular patterns, however, springs  148  may be placed between plates  120  and  140  in other arrangements. Because plates  120  and  140  are flexibly joined by bolts  144  that loosely fit within apertures  146  of plate  120 , upper plate  120  and lower plate  140  may move into non-parallel positions relative to one another, and “rock” as needed to allow the heating element  142  to seek and obtain a parallel relation with the container flange and lid. 
     The plurality of springs  148  create the only force exerted on lower plate  140  and hence heating element  142 . Therefore, downward pressure of actuator  133  creates a balanced pressure by all portions of heating element  142  against all portions of the tray and lid even when upper plate  120  and lower plate  140  are not parallel, since lower plate  140  can rock (i.e. pivot or swing) as necessary to always seek a parallel relationship to the tray support  106  and a container flange and lid thereon due to the manner in which it is suspended from upper plate  120  and manual actuator  134 . This ability of the platen to rock enables the platen to place uniform pressure on all parts of the flange and contacting lid areas. 
     The reference  100 A (FIG. 14) generally designates another embodiment of the novel sealing apparatus. Since sealing apparatus  100 A is similar to previously described sealing apparatus  100 , similar parts appearing in FIGS. 14 and 15 and FIG. 11 are represented by the same, corresponding reference numeral, except for the suffix (A) in the numerals of the latter. In sealing apparatus  100 A, a pair of springs  150  are used in place of rods  116  (FIG.  11 ), sleeves  118 , and springs  124 . Springs  150  (FIG. 15) are fixedly attached to support columns  128 A of support frame  102 A, and eyelets  152  fixedly attached to the top of heating element  142 A. Because upper plate  120 A and lower plate  140 A are flexibly joined by loosely fitting bolts (not shown) similar to plates  120  and  140  (FIG.  12 ), plates  120 A and  140 A, and hence, heating element  142 A and upper plate  120 A may move into non-parallel positions relative to one another and “rock” is needed to allow heating element  142 A to seek and obtain a parallel relationship with the container flange and lid. A downward pressure of manual actuator  134 A on actuator rod  138 A creates a balanced pressure by all portions of heating element  142 A against all portions of the tray and lid, even when upper plate  120 A and lower plate  140 A are not parallel, since lower plate  140 A can rock (i.e., pivot or swing) due to the manner in which it is suspended from upper plate  120 A, thereby allowing heating element  142 A to always seek parallel relationship with a support and container flange and lid thereon. This ability of the platen to rock enables the platen to place uniform pressure on all parts of the flange and the contacting lid areas. 
     The present inventive sealing apparatus that includes air actuator  53  (FIG. 8) and/or actuator  133  plates  120  and  140  and springs  148  (FIG. 11) positioned therebetween, may also be utilized within an auto-feed tray sealer  154 , as shown in FIG.  16 . The tray sealer  154  includes an elongated supporting frame  156  and a sealing apparatus  158  positioned along supporting frame  156  to define a sealing location or position  160  therebetween. Supporting frame  156  is supported above the ground by a plurality of legs  162  that each may include a roller or wheel  164  attached thereto. Supporting frame  156  is trough-shaped and defines an open top  166 . A plurality of tray supports or holders  168  each define a desired number of container receiving cavities.  169 , shown here to be two. As previously noted, although the illustrated example is for use with containers which each contain two separate food compartments or cavities, numerous constructions and layouts may be used. When a container having a peripheral shape like that of the cavities  169  is placed therein, its peripheral, horizontal flange will rest on the peripheral ledge around the cavities  169 . The tray supports  168  are driven along opening  166  and through sealing position  160  by a pair of drive chains (not shown) juxtaposed across supporting frame  156 . The drive chains are supported and driven by a plurality of drive gears that are in turn supported and driven by a first rotating shaft  170  and a second rotating shaft  172  positioned at opposite ends of supporting frame  56 . 
     As illustrated, the sealing apparatus  158  is constructed similarly to sealing apparatus  10  (FIG. 4) and includes an actuator  173  that includes an air actuator  174  mounted between a horizontal support member  176  which is supported by vertical support members  178 , and a platen  180 . Alternatively, sealing apparatus  158  may also include a dual plate and spring assembly similar to actuator  133  and plates  120  and  140  and springs  148  (FIG. 11) as discussed above. As discussed above, the sealing apparatus  158  is constructed to have a platen that rocks and thereby uniformly engages a peripheral region of the container. 
     The tray supports  168 .are driven along supporting frame  156  by a pneumatic cylinder  184  which is. mechanically linked to shaft  170 , and hence the drive chains (not shown). More specifically, pneumatic cylinder  184  (FIG. 17) is pivotally attached at a first end  185  to an air logic circuit block  182  which form a portion of an air logic circuit  183 , and pivotally attached at a second end  187  to crank  186 . The crank  186  is fixedly attached to shaft  170  such that rotation of crank  186  about shaft  170  causes shaft  170  to rotate, thereby causing the drive chains and tray supports  168  to move along supporting frame  156 . 
     A disc-shaped stop block  188  is attached to shaft  170  to prohibit tray supports  168  “over-advanced” or “under-advanced,” thereby ensuring proper alignment of each tray support  168  within sealing position  160 . More specifically, stop block  188  is provided with a first notch  190  and a second notch  192 . A first stop tab  194  and a second stop tab  196  are pivotally attached to supporting frame  156  and are adapted to engage first notch  190  and second notch  192 . 
     In operation, as air cylinder  184  advances, crank  186  is rotated in a clockwise direction  198  until first stop tab  194  engages first notch  190  within stop block  188 , thereby prohibiting stop block  188  and shaft  170  from rotating, thus ensuring that tray supports  168  cannot advance beyond a certain point along supporting frame  156 . Through experimentation it has been discovered that the impact force between stop block  188  and first stop tab  194  can cause shaft  170  to recoil or react in a counter-clockwise motion, thereby moving tray support  168  out of the desired location within sealing position  160 . Second stop tab  196  engages second notch  192 , thereby prohibiting shaft  170  from reversing its rotation due to the impact, thus ensuring proper locating of each tray support  168  within sealing position  160 . 
     The pneumatic cylinder  84  receives pressurized air through the pneumatic circuit block  182  which receives air via an air hose  200 . The air logic circuit  183  is adapted to adjustably control the cycle time of the air cylinder, as well as to control the dwell time of the platen  180  within sealing apparatus  158 . Air logic circuit  183  is provided with a variable control switch  202  which controls the cycle time of air cylinder  184 , thus controlling the cycle time that each individual tray support  168  is located within sealing position  160 , as well as the dwell time of the platen  180 . 
     The above description is considered that of the preferred embodiments only. Modifications of the invention will occur to those skilled in the art and to those who make or use the invention. Therefore, it is understood that the embodiments shown in the drawings and described above are merely for illustrative purposes and not intended to limit the scope of the invention, which is defined by the following claims as interpreted according to the principles of patent law, including the Doctrine of Equivalents.