Abstract:
A plug assist drive assembly is provided for a thermoforming press. The plug assist drive assembly includes a drive platen, a plug assist platen, a first elongated gear rack, a second elongated gear rack, a drive gear, a driven gear, and a drive source. The first elongated gear rack and the second elongated gear rack are carried by the plug assist platen in longitudinally extending and substantially parallel, spaced apart relation with a plurality of rack teeth extending on each gear rack between proximal and distal ends. The drive gear is carried by the drive platen and is operably communicating with the first elongated gear rack. The driven gear is carried by the drive platen and is operably communicating with the second elongated gear rack and the drive gear. The drive source is operably communicating with the drive gear to drive the assist platen in linearly reciprocating motion relative to the drive platen. A thermoforming machine having the plug assist drive assembly is also provided. A method is also provided.

Description:
TECHNICAL FIELD 
       [0001]    The disclosed embodiments pertain generally to thermoforming apparatus. More particularly, the disclosed embodiments relate to drive mechanisms for advancing plug assists, or male dies into female mold cavities to help stretch material into conformity with the mold cavity walls during a thermoforming operation. 
       BACKGROUND OF THE INVENTION 
       [0002]    The use of a third platen on a thermoforming machine is known in order to more quickly advance an array of plugs into female mold cavities of a thermoforming machine. One machine uses a plurality of ball screws. Another machine uses a single roller screw shaft. Both machines provide a compromise between providing sufficient torque, or forming pressure, and providing a sufficiently fast stroke. Improvements are needed in order to provide both sufficient torque and sufficiently fast stroke in order to optimize article formation and surface finish. 
       SUMMARY OF THE INVENTION 
       [0003]    A third motion platen is driven for movement relative to one of a pair of platens on a thermoforming machine to provide quick movement of plugs in combination with relatively high forming pressures on the thermoforming machine as the plugs move into mold cavities during a thermoforming operation. 
         [0004]    According to one aspect, a plug assist drive assembly is provided for a thermoforming press. The plug assist drive assembly includes a drive platen, a plug assist platen, a first elongated gear rack, a second elongated gear rack, a drive gear, a driven gear, and a drive source. The first elongated gear rack and the second elongated gear rack are carried by the plug assist platen in longitudinally extending and substantially parallel, spaced apart relation with a plurality of rack teeth extending on each gear rack between proximal and distal ends. The drive gear is carried by the drive platen and is operably communicating with the first elongated gear rack. The driven gear is carried by the drive platen and is operably communicating with the second elongated gear rack and the drive gear. The drive source is operably communicating with the drive gear to drive the assist platen in linearly reciprocating motion relative to the drive platen. 
         [0005]    According to another aspect, a thermoforming machine is provided having a frame, a first platen, a second platen, a plug assist platen, a first elongated gear rack, a second elongated gear rack, a drive gear, a driven gear, and a drive source. The first platen is supported by the frame and is operative to carry a female die. The second platen is supported by the frame for movement to and fro relative to the first platen. The plug assist platen is carried relative to the second platen and is operative to carry a plug for complementary interaction with the female die. The first elongated gear rack and the second elongated gear rack are carried by the plug assist platen in longitudinally extending and substantially parallel, spaced apart relation, or equi-spaced apart relation, with a plurality of rack teeth extending on each gear rack between proximal and distal ends. The drive gear is carried by the drive platen and is operably communicating with the first elongated gear rack. The driven gear is carried by the drive platen and is operably communicating with the second elongated gear rack and the drive gear. The drive source is carried by the second platen and is operably communicating with the drive gear to drive the assist platen in linearly reciprocating motion relative to the drive platen. 
         [0006]    According to yet another aspect, a method is provided for forming an article in a thermoformable web. The method includes: providing a thermoforming machine with a first platen, a second platen, a third motion platen having a plug, and a drive source having a drive motor, a bevel gearbox, a pair of elongated gear racks coupled to the third motion platen and a pair of gears operably communicating together, with each gear cooperating with a respective one of the elongated gear racks to impart linear reciprocation to the gear racks and the third motion platen from the motor through the gearbox; presenting the first platen proximate a heated thermoformable web; moving the second platen toward the web; and driving the gears in co-rotation with the drive motor through the gearbox to raise the elongated gear racks, the third motion platen, and the plug relative to the second platen to drive the plug into the heated thermoformable web. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Preferred embodiments of the disclosure are described below with reference to the following accompanying drawings. 
           [0008]      FIG. 1  is a side elevational view of a thermoforming machine with a third motion plug assist drive assembly in accordance with an embodiment. 
           [0009]      FIG. 2  is a vertical sectional view taken along line  2 - 2  of  FIG. 1 . 
           [0010]      FIG. 3  is an elevational component side view of the third motion plug assist drive assembly of  FIGS. 1-2  with a rack and pinion stroke assembly portion removed in order to show the drive gear box. 
           [0011]      FIG. 4  is an elevational component end view with a cover removed from the rack and pinion assembly showing one rack and pinion stroke assembly. 
           [0012]      FIG. 5  is an end view of the third motion plug assist drive assembly of  FIGS. 1-4 . 
           [0013]      FIG. 6  is a perspective view from below of the third motion plug assist drive assembly of  FIGS. 1-5 . 
           [0014]      FIG. 7  is vertical sectional view corresponding with that shown in  FIG. 2 , but showing the drive platen and plug assist platen retracted to a lowermost position and the upper platen elevated to a top-most position. 
           [0015]      FIG. 8  is a vertical sectional view corresponding with that shown in  FIG. 7 , but later in time and showing the drive platen raised into engagement with the lowered upper platen, with the plug assist platen still retracted to a lowest-most position. 
           [0016]      FIG. 9  is a vertical sectional view corresponding with that shown in  FIG. 8 , but later in time and showing the drive platen raised into engagement with the lowered upper platen, with the plug assist platen being raised and approaching a topmost position. 
           [0017]      FIG. 10  is vertical sectional view corresponding with that shown in  FIG. 9 , but later in time and showing the drive platen raised into engagement with the lowered upper platen, with the plug assist platen fully raised to a top-most position. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0018]    This disclosure is submitted in furtherance of the constitutional purposes of the U.S. Patent Laws “to promote the progress of science and useful arts” (Article 1, Section 8). 
         [0019]    As used herein, the term “co-rotation” is understood to mean the action or process of rotating jointly through operable communication, as with another rotating object or field, and includes counter-rotation, as well as rotation of two objects in the same direction. 
         [0020]    Attention is now directed towards embodiments of the device.  FIGS. 1 and 2  are front and side elevational views illustrating a thermoforming machine  10  with a third motion plug assist drive assembly, or tooling assembly  12  in accordance with an embodiment. More particularly, thermoforming machine  10  includes a structural frame  14 , stationary die posts  16  and  18  supported by frame  14 , an upper platen  32 , and a lower platen  34 . Upper platen  32  and lower platen  34  are supported for vertical reciprocation via pairs of respective bronze bushings  20 ,  21  and  22 ,  23 , respectively. A kinematic drive linkage  19  drives upper platen  32  and lower platen  23  using upper kinematic linkage assembly  33  and lower kinematic linkage assembly  35 , respectively, each driven by a respective servo motor  15  and  17  (see  FIG. 2 ). A third motion platen, or assist platen  36  is supported for movement relative to lower platen  34  by bushings  28 - 31  which slide over respective die posts  24 - 27 . 
         [0021]    As shown in  FIG. 2 , third motion platen  36  is carried for reciprocating movement relative to lower platen  34  on an array of drive shafts  38 - 41 . Drive shafts  39  and  41  are driven by a drive assembly  46  (see  FIG. 1 ), while drive shafts  38  and  40  are driven by another drive assembly  48 . A servo motor  58  drives drive assemblies  46  and  48  (see  FIG. 1 ) through a bevel gearbox  52  (see  FIG. 3 ) to provide a drive source  50  (see  FIG. 2 ). Drive source  50  operably communicates with the drive assemblies  46  and  48  through gearbox  52  to drive the assist platen  36  in linearly reciprocating motion relative to the drive platen  34 . According to one construction, bevel gearbox  52  is a Hub City Model 950 gearbox. 
         [0022]    As shown in  FIG. 1 , upper kinematic linkage assembly  33  and lower kinematic linkage assembly  35  of kinematic drive linkage  19  cooperate to drive upper and lower platens  32  and  34 , respectively. Respective modern rotary electric servo drive motors  15  and  17  (see  FIG. 2 ) independently drive linkages  33 ,  35  and platens  32 ,  34  respectively. Such motors are driven by a computer control system  100  (see  FIG. 2 ), as is presently understood in the art. Other kinematic linkages and drive motor arrangements can be used in the alternative. 
         [0023]    More particularly, kinematic linkages  33  and  35  of  FIG. 1  each comprise drive linkages that are formed from a pair of top and bottom crank arm assemblies, respectively. Each assembly is formed from a crank arm linkage and a four-bar linkage. The crank arm linkage drives the four-bar linkage in an oscillating motion. Each platen  32  and  34  is driven by kinematic linkage  33  and  35 , respectively, in substantially non-rotating linear, vertical motion. Guide posts  16  and  18  further limit such motion to vertical reciprocating motion. Kinematic linkages  33  and  35  are driven by servo drive motors  15  and  17  (see  FIG. 2 ). This action causes coacting engagement of female cavities, or female dies  44  on the upper platen with mating male dies or plugs  42  on opposed sides of thermoformable web, or sheet  112  (see  FIG. 7 ). 
         [0024]    More particularly, each drive system, including the motor and associated drive 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 in response to rotation of the drive. Accordingly, a single revolution of drive motors  15  and  17  will produce a corresponding complete press cycle of both the upper and lower platens, respectively. Hence, a complete cycle of each drive will return the press to a starting, or closed position. For example, when lower drive motor  17  is at an initial rotated position of zero degrees, the lower platen  34  is closed, or upwardly raised against the thermoformable sheet, or web. Similarly, when lower driven motor  17  is rotated to 180 degrees, the lower platen  34  is lowered, or completely opened. Likewise, the same holds true for upper drive motor  15  and upper platen  32 . 
         [0025]      FIG. 2  illustrates a control system  100  configured to move upper platen  32 , lower platen  34 , and third motion, or plug assist platen  36  via respective servo motors  15 ,  17  and  58 . According to one construction, upper platen  32  and lower platen  34  are each drive platens, and plug assist platen  36  is also a moving platen. Control system  100  includes a controller  102  comprising processing circuitry  104  and memory  106  configured to precisely regulate motion of platens  32 ,  34  and  36  in desired, timed synchronization such that individual plugs, or male dies  42  are driven upwardly with a greater combination of speed and force than would be capable by merely moving platens  32  and  34  together. In operation, platens  32  and  34  are driven together into a heated web of thermoformable material that is captured between upper platen  32  and lower platen  34  during a thermoforming operation. Third motion platen  36  is subsequently moved upwardly relative to moving platen  34  so as to cause forming of a thermoformed article in a heated plastic web between each individual pair of complementary male plugs  42  and female die cavities  44 . As shown, several rows of complementary, interacting male plugs  42  and female die cavities  44  are provided in platens  36  and  32 , respectively. Subsequently, platens  32 ,  34  and  36  are withdrawn, or retracted apart in order to start the cycle all over again, and third motion platen  36  is lowered relative to lower platen  34 . The cyclical process is then repeated. 
         [0026]    Preferably, a modern rotary electric servo drive motor, or actuating device, is used for drive motors  15  and  17  (see  FIG. 2 ). Such a drive 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 Machine Tools, Robots and Special-Purpose Machines, P.O. Box 31 AD, D-91050, Erlangen, Federal Republic of Germany. Additionally, one suitable servo drive motor controller is sold by Siemens as an analog feed drive system including the SIMO DRIVE 611-A Transistor PWM Inverters and Motors for AC FV Drives. Such a drive will provide a predictable motor device that can very accurately position a machine element to a desired position at a given time. Accordingly, the associated servo motor is a brushless servo motor. Using suitable control software, activation of associated machine components can also be triggered based on velocity or position of a drive, by using a velocity profile or an integrated displacement of the drive. Furthermore, one suitable servo drive motor used for servo drive motor  58  is also a Siemens AC servo motor, model number 1FT5132-OSC71-1-ZH27, also available from Siemens AG._Automation Group, Automation Systems for Machine Tools, Robots and Special-Purpose Machines, P.O. Box 31 AD, D-91050, Erlangen, Federal Republic of Germany. 
         [0027]    As shown in  FIG. 2 , plug assist drive assembly  12  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 can be mounted to upper platen  32 , with the third motion platen being driven in a downward direction while the upper platen is being driven downwardly. Further optionally, a third motion platen can be mounted to a stationary platen, when an opposing platen is moved to and fro. Further optionally, a third motion platen can be mounted for horizontal movement relative to a moving platen from a pair of opposed moving platens that move together and apart along a horizontal direction. Finally, 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. 
         [0028]      FIG. 3  shows orientation of drive source  50  on plug assist drive assembly  12  with a nearest drive assembly  48  (see  FIG. 4 ) removed to show bevel gearbox  52 . Servo motor  58  is configured to drive a transverse drive shaft  54  through a belt drive assembly  56 , which causes pairs of drive shafts  38 ,  40  and  39 ,  41  to axially extend and retract relative to lower platen  34 , as lower platen  34  is moved up and down, respectively. One suitable bevel gearbox  52  is a Hub City Model 950 bevel gear drive, having a 7.33:1 reduction ration with a 3.4375 bore, and sold by Hub City, Inc., Factory Sale, 2914 Industrial Ave., P.O. Box 1089, Aberdeen, S. Dak. 57402-1089. Optionally, other suitable types of gear drives and transfer cases can be used, as long as they impart a similar combination of speed and torque to drive assemblies  46  and  48  (see  FIG. 1 ), such as worm gear drives, helical bevel drives, spur gear drives, or any other suitable mechanism for providing and converting a drive input to a driven output. 
         [0029]      FIG. 4  illustrates plug assist drive assembly  12  and corresponds with the view depicted in  FIG. 3 , but includes drive assembly  48 . More particularly, drive assembly  48  (as well as drive assembly  50 , see  FIG. 2 ) of plug assist drive assembly  12  is driven by servo motor  58  through bevel gearbox  52  by rotating and counter-rotating shaft  54 . Shaft  54  drives an intermeshing drive gear  64  and driven gear  66  in rotation and counter-rotation, raising and lowering linear gear racks  68  and  70 , respectively. Gear  64  is affixed onto drive shaft  54 , while gear  66  is affixed onto idler shaft  76 . Each of gears  64 ,  66  and gear racks  68 ,  70  have an array of individual gear teeth  72  configured to impart coaction with a respective gear. 
         [0030]    Linear gear racks  68  and  70  are rigidly affixed together within a frame that is formed by bolting together a cross-frame member  74 , side plates  92  and  94 , and cross plate  60 , as shown in  FIG. 4 . Linear gear racks  68  and  70  are then bolted to side plates  92  and  94  with a plurality of threaded fasteners. A cross plate  60  is then bolted to the top end of each plate  92  and  94  to form a rectangular frame, within which linear gear racks  68  and  70  are secured to plates  92  and  94 . Drive assembly  46  (see  FIGS. 1 and 5 ) is constructed in mirror-image and substantially identical to drive assembly  48 , but on an opposite side of bevel gearbox  52 . Cross plate  62  closes out a top end of drive assembly  46  atop similar side plates  90  and  91  (see  FIG. 5 ). A cover plate is secured over the resulting frame on each drive assembly  46  and  48 , such as cover plate  96  on drive assembly  48  (see  FIG. 6 ) in order to form a housing  78  that protects the intermeshing gear teeth of gears  64  and  66 , and linear gear racks  68  and  70 . 
         [0031]    Although drive assemblies  46  and  48  use a pair of linear racks  68  and  70  with teeth  72  facing one another, and gears  64  and  66  stacked there between, it is understood that other alternative configurations are possible. For example, one optional construction uses two cylindrical gears that are spaced apart and each configured to drive a respective linear rack, using one or more intermediate gears (or gearboxes) to drive the cylindrical gears in co-rotation or counter-rotation. Further optionally, the teeth on each linear gear rack can be configured to face away from each other, or face a common direction, with separate cylindrical drive gears driving each respective linear rack, using one or more intermediate gears (or gearboxes) to drive the cylindrical gears in co-rotation or counter-rotation. Further optionally, such linear gear racks can be arcuate or elongate racks that are mounted in such a way to drive a third motion platen in a linearly reciprocation movement, with separate die posts guiding each platen. 
         [0032]    In operation, servo motor  58  drives drive assemblies  46  (see  FIG. 5) and 48  through belt drive assembly  56  and gearbox  52 , as shown in  FIGS. 4-6 . Shaft  54  rotates and counter rotates in response to control signals being delivered from control system  100  (see  FIG. 2 ), driving drive shafts  38 - 41  upward and downward relative to lower platen  34 . Bronze bushings  28 - 31 , each contained within a housing, mounted on cross plates  60  and  62  are axially reciprocated along die posts  24 - 27  to ensure accurate, guided reciprocation of third motion platen  36  and plugs  42  (see  FIG. 2 ) relative to platen  34 . 
         [0033]      FIG. 5  further illustrates construction of belt drive assembly  56  with belt drive cover  94  (see  FIG. 6 ) removed. More particularly, assembly  56  includes a drive pulley  82  that is driven by servo motor  58  (see  FIG. 6 ), a driven pulley  86 , and an idler, or tension pulley  84 . Pulleys  82 ,  84  and  86  have teeth that intermesh with a toothed drive belt  88  to drive pulley  86 , which is affixed onto an input shaft  87  (see  FIG. 3 ) of bevel gearbox  52  (see  FIG. 3 ) to drive assemblies  46  and  48  in up and down reciprocation. 
         [0034]      FIG. 6  illustrates plug assist drive assembly (with third motion  36  and plugs  42  removed, see  FIG. 2 ). More particularly, drive assembly cover plate, or panel  96  on drive assembly  48  is shown affixed to frame member  74  and side plates  92  and  93 . Additionally, an array of urethane bumpers are each secured to each cross plate  60  and  62 , such as bumpers  95  and  97  to prevent rigid impact of cross plates  60  and  62  (and respective housing  78 , see  FIG. 5 ) with a platen  34  as drive shafts  38 - 41  reciprocates through bores  98 - 99  in a top surface of platen  34 . 
         [0035]    As shown in  FIG. 6 , panels  80 ,  81  and  83  are rigidly secured to a bottom surface of platen  34 , supporting servo motor  58  and gearbox  52 , as shown in  FIG. 6 . In operation, housing  78  of drive assembly  48  moves up and down with cross plate  60  and rods  38 ,  40 , relative to stationary plate  80  and platen  34 . 
         [0036]    A linear array of third motion platen urethane bumpers  95  are each fixed with a central threaded, recessed bolt to a bottom surface of each cross plate, such as cross plate  60 . Similarly, two arrays of bumpers  95  are affixed atop a riser base  97  that is secured to a top surface of each cross plate, such as cross plate  60 . Each bumper  95  has a central through-bore with an end recess for receiving an enlarged head of a respective threaded bolt for securing bumper  95  to either cross plate  60  or riser base  97 . Each bumper  95  is constructed from a resilient material capable of providing shock absorption, such as urethane. Alternatively, any shock absorbing material can be utilized, such as rubber, synthetic rubber, or other suitable structural material having elastic rebound capabilities. Bumpers  95  atop each cross plate  60  and  62  absorb impacts with a bottom surface of platen  34  during each up and down cycle of operation. Likewise, bumpers  95  below each cross plate  60  and  62  absorb impacts with components of the kinematic drive linkage  19  (see  FIG. 1 ). 
         [0037]    As shown in  FIGS. 1-6 , gearbox  52  is provided in a medial position, between drive assemblies  46  and  48 . The linear racks, such as racks  68  and  70  on drive assembly  48 , form a rectangular array of racks inside of which gearbox  52  is provided. Such configuration is very compact and provides a desirable combination of speed and torque when driving plugs  42  upwardly into a heated thermoformable web during an article forming operation. Such a construction provides for structural integrity under substantial cyclical forming loads at each of four corners on a platen, and retains structural orientation even for situations where a material “jam-up” of mis-formed web and articles occurs between plugs  42  and female cavities  44 , causing structural overloads to the plug assist drive assembly  12 . 
         [0038]      FIGS. 7-10  illustrate progressive stages of operation for a thermoforming machine  10  having a plug assist drive assembly  12  with a moving third motion platen  36  shown in the same cross-sectional view as  FIG. 2  taken in  FIG. 1 . Additionally, a chain rail conveyor  110  is shown supporting a heated web  112  of thermoformable material for forming between plugs  42  and female dies  44 .  FIG. 7  shows the drive platen  34  and plug assist platen  36  retracted to a lowest-most position, and the upper platen  32  retracted to a highest-most position corresponding with a position at the beginning of a new thermoforming cycle. More particularly, a heated web of thermoformable material (not shown) is intermittently conveyed in a gap between platens  32  and  34  using a conveyor (not shown). Platens  32  and  34  are subsequently driven together and apart relative to such web in order to drive plugs  42  and cavities  44  together and apart, forming articles in such web. Web  112  is conveyed along a web travel path away from between platens  32  and  34  after being formed via the steps depicted in  FIGS. 7-10 . Pursuant to the steps depicted in  FIGS. 8-10 , third motion platen  36  is subsequently driven upwardly after lower platen  34  has been raised toward a heated web. 
         [0039]    As shown in  FIGS. 7-10 , lower platen  34  is first raised into contact with a web  112  while upper platen  32  is lowered into contact with web  112  to arrive at the platen positions shown in  FIG. 8 . Subsequently, third motion platen  36  is driven upwardly from the starting position shown in  FIG. 9  to the final fully raised position shown in  FIG. 10 . Optionally, third motion platen  36  can be moved at the same time lower platen  34  is being raised, thereby further increasing the speed with which plugs  42  are driven upwardly into a heated web  112 . 
         [0040]    Plug assist drive assembly  12  uses servo drive motor  12  in combination with belt drive assembly  56 , bevel gearbox  52  (see  FIGS. 3-4 ), and drive assemblies  46  and  48  (see  FIGS. 1 and 5 ) in order to drive plugs  42  upwardly with a combination of speed and force (or torque) previously not attainable. It is important to drive plugs  42  upwardly with both speed and torque in order to impart an improved finish to thermoformed articles. If web  112  is heated too much, it has been discovered that undesirable article surface blemishes can be imparted to clear plastic articles as they are formed. In order to reduce or eliminate these blemishes, it is desirable to form web  112  at relatively cooler temperatures. However, cooler temperatures, in combination with cooling of web  112  when plugs  42  contact web  112 , causes a need for increased forming pressures (torque at the drive motor) in order to form articles in web  112 . If the forming operation is slowed down, producing a slower plug speed, web  112  is further cooled by contact with each plug  42 , causing further forming difficulties and even greater forming pressures. By increasing upward speed of plugs  42 , web  112  can be formed at relatively lower temperatures, as there is less time for heat to dissipate from web  112  into local contact with plugs  42 . Even though cooler temperatures entail greater forming forces, plug assist drive assembly  12  is capable of realizing these forces with concomitant speed. Secondly, it has been found that increased forming speeds, made possibly through gearbox  52  and drive assemblies  48  and  48 , improves the manner in which web  112  is drawn up by each plug  42  into each female cavity  44 , reducing undesirable article surface blemishes, such as lines in the resulting formed article, as increased speeds provide less time for the web to cool during the forming operation. 
         [0041]    Drive assemblies  46  (see  FIG. 1) and 48  cooperate with bevel gearbox  52  (see  FIG. 3 ) to move plugs  42  into a bottom surface of the heated web  112  at a high rate in combination with large forces (high forming pressures), thereby improving article formation by speeding up the forming process. Such increase in speed is important as contact between each plug  42  and a heated web causes cooling of the web, which otherwise increases forces needed to drive platen  34  in an upward direction. Accordingly, platen  36  increases the upward speed of plugs  42  in order to speed forming of articles, which mitigates cooling of the web as it contacts each plug  42 . In operation, drive source  50  imparts up and down movement of platen  36  relative to platen  34  via drive assembly  48  (and drive assembly  46 , see  FIG. 1 ) through controlled operation of servo drive  48 , belt drive assembly  56 , and gearbox  52  (see  FIGS. 3-4  and  6 ). 
         [0042]      FIG. 8  is a vertical sectional view corresponding with that shown in  FIG. 7 , but later in time and showing the lower drive platen  34  raised into engagement with the web  112 , while the upper platen is lowered onto web  112 . Plug assist platen  36  is shown at a lowest position, prior to being raised to drive plugs into web  112 . 
         [0043]      FIG. 9  is a vertical sectional view corresponding with that shown in  FIG. 8 , but later in time and showing the drive platen raised into engagement with web  112 , upper platen  32  lowered into engagement with web  112 , and plug assist platen  36  being raised and shown in a mid position. 
         [0044]      FIG. 10  is vertical sectional view corresponding with that shown in  FIG. 9 , but later in time and showing bottom platen  34  raised into engagement with web  112 , upper platen  32  lowered into engagement with web  112 , and plug assist platen  36  raised to a topmost position, thereby fully forming articles in web  112 . After the step depicted in  FIG. 10 , platen  32  is raised and platens  34  and  36  are lowered, as the process proceeds back to the step depicted in  FIG. 7  to continue the cyclical forming operation. 
         [0045]    In compliance with the statute, embodiments of the invention have been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the entire invention is not limited to the specific features and/or embodiments shown and/or described, since the disclosed embodiments comprise forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted in accordance with the doctrine of equivalents.