Apparatus and method for automatically counting and stacking trimmed molded articles

An apparatus for automatically stacking molded articles successively trimmed by a trim press from a web of thermoplastic material, the trim press having a stationary die member which includes a die plate and a die shoe, the apparatus comprising: (a) a frame; (b) a carriage mounted to the frame; (c) at least one stacking mechanism, the stacking mechanism comprising: (i) a plurality of stack rods rotatively mounted to the carriage, each of the stack rods having a stack dog located substantially perpendicular to a first end thereof the stack dog positionable within a corresponding aperture of the die shoe of the stationary die member; and (ii) mechanism for rotating the stack rods so that the stack dog engages an endmost article of a completed stack of articles, the stack of articles located at least partially within the die shoe of the stationary die member; and (d) mechanism for transporting the completed stack of articles from within the die shoe of the stationary die member to a position for removal from the apparatus.

FIELD OF THE INVENTION 
The present invention relates to the counting and stacking of molded 
articles and, more particularly, to an apparatus for the automatic 
counting and stacking of mass produced thermoformed articles. 
BACKGROUND OF THE INVENTION 
Many products produced by thermoforming, such as plates, bowls, trays, 
cups, lids, containers, and the like, often require the trimming away of 
excess material as a final step of the formation process. Various 
apparatus and methods are known and employed in industry for trimming or 
severing a plurality of thermoformed articles from a continuous web or 
sheet of thermoplastic material. Generally, the web of thermoplastic 
material with the thermoformed articles molded therein is transported from 
the thermoformer at relatively high rates of speed and throughputs and is 
then conducted to a trim press for the severing of the thermoformed 
articles from the web of thermoplastic material. Such trim presses are 
usually comprised of a stationary platen and a reciprocally movable platen 
for the mounting of a plurality of cooperating die members, or 
complementary punch and die members which are conformed to the outer or 
peripheral configuration of each of the thermoformed articles, and are 
adapted to provide for concurrent trimming of a number of individual 
articles from the web. 
As thermoforming technology has improved and thermoforming speeds increase, 
it has become necessary to run trim presses at higher rates of speed in 
order to continue to provide an in-line trimming operation. A number of 
patents are directed to improvements in trim press technology for the 
purpose of increasing the speed of trim press operations. Such patents 
include U. S. Pat. Nos. 4,313,358, 4,391,171, 4,526,074, and 4,890,524, to 
which reference is made for those details. 
While improvements have been made in operations related to the mass 
production of thermoformed articles, the counting and stacking of those 
articles is often performed manually. In those operations employing manual 
stacking, the article, after it is formed and trimmed, may pass into a 
receptacle or onto a conveyor where it is thereafter manually arranged 
into a stack. As can be appreciated, this often proves to be quite labor 
intensive, compared with the rest of the production operation. In such 
operations, excessive labor costs are often experienced, providing the 
motivation to automate. 
One improved apparatus is described in U. S. Pat. No. 4,526,074, issued to 
Johnson. U. S. Pat. No. 4,526,074 discloses a system to increase the speed 
of trim press operations wherein a male locator is adapted to be 
reciprocated toward and away from a stationary cutter. The locator forces 
the severed thermoformed article which has been captured by the cutter 
into a cavity, or die shoe, encompassed by the blade structure. Each 
subsequent severing operation, wherein a successive thermoformed article 
is aligned with the cutting blade structure and urged against the cutting 
edge thereof, upon the forward reciprocating stroke of the male locator, 
will cause the preceding severed thermoformed article to be forced further 
into and through the die shoe cavity, thereby producing a stack of trimmed 
thermoformed articles in a nested relationship which may then be removed 
for further handling. While U. S. Pat. No. 4,526,074 provides a system 
which produces a stack of nested articles, the articles must still be 
removed and counted before packaging for the customer. U. S. Pat. No. 
4,526,074 is incorporated by reference for all that it discloses. 
A variety of other specialized stackers are known to those skilled in the 
art. For example, U. S. Pat. No. 3,499,063 discloses an apparatus for 
collecting and stacking plastic articles received from a blow molding 
machine. The articles are stacked in a stacking frame which retains the 
stack by having the lowermost article rest on a spring loaded pawl which 
extends into the path of incoming articles at the opening. The incoming 
article moves into the opening, depresses the pawl, moves past the pawl 
and nests into the stack of articles, lifting the stack from the pawl in 
the process. Thereafter, the stack of articles is lowered back onto the 
pawl where it rests until the next article is inserted. 
U. S. Pat. No. 4,597,705 relates to an apparatus for the automatic stacking 
of a predetermined number of pie shells in nested relation for subsequent 
packaging. The automatic stacking machine disclosed includes an inverted 
U-shaped structure, the legs of which straddle a conveyor on which the 
items to be stacked are carried to a location between the legs of the 
stacker. The legs of the stacker house like means for engaging the item to 
be stacked on opposite sides and lifting the item to an elevated position 
where it is deposited on holding means to be retained while the lifting 
means is returned to the lower position for engaging and lifting the next 
item to be stacked. When the desired number of items are held in the 
stack, an automatic kicker means pushes the the stacked items off the 
holding means and onto means for delivering the stack for further 
processing. 
U. S. Pat. No. 4,802,808 discloses a stacking apparatus for deep-drawn 
plastic articles. The apparatus includes a removal station formed by a 
support plate forwardly moveable horizontally underneath the raised stack 
of formed articles, a pushing device arranged above the support plate and 
moveable parallel relative to the support plate, and a tilting frame 
located adjacent the support plate when the support plate is in the 
forwardly moved position. 
Although the aforementioned devices have generally performed their intended 
stacking functions in an acceptable manner, it is to be noted that they do 
not meet the needs which exist in the mass production of molded articles, 
such as containers, bowls, plates, trays cups, lids and the like, which 
require the subsequent trimming or severing of a plurality of the articles 
from a continuous web or sheet of thermoplastic material. None of the 
machines known in the art possess the type of utility required by the 
aforementioned operation. 
Therefore what is needed is an apparatus and method for automatically 
counting and stacking trimmed molded articles which provides the speed and 
accuracy required in the mass production of such articles. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, there is provided an apparatus 
for automatically stacking molded articles successively trimmed by a trim 
press from a surrounding web of thermoplastic material, the trim press 
having a stationary die member which includes a die plate and a die shoe, 
the apparatus comprising: (a) a frame; (b) a carriage means mounted to the 
frame; (c) at least one stacking mechanism, the stacking mechanism 
comprising: (i) a plurality of stack rods rotatively mounted to the 
carriage means, each of the stack rods having a stack dog located 
substantially perpendicular to a first end thereof, the stack dog 
positionable within a corresponding aperture of the die shoe of the 
stationary die member; and (ii) means for rotating the stack rods so that 
the stack dog engages an endmost article of a completed stack of articles, 
the stack of articles located at least partially within the die shoe of 
the stationary die member; and (d) means for transporting the completed 
stack of articles from within the die shoe of the stationary die member to 
a position for removal from the apparatus. 
Also provided is a method of automatically counting and stacking molded 
articles successively trimmed by a trim press from a web of thermoplastic 
material, the trim press having a stationary die member which includes a 
die plate and a die shoe, comprising the steps of: (a) establishing an 
article count value, the article count value equal to a completed stack of 
articles; (b) retaining articles successively trimmed by a trim press from 
a web of thermoplastic material within a cavity defined by the stationary 
die member of the trim press; (c) ejecting a stack of articles into a 
position for removal within the die shoe upon reaching the article count 
value established in step (a); (d) engaging the endmost article of the 
completed stack of articles by rotating a plurality of stack rods mounted 
to a carriage means of an apparatus for stacking trimmed molded articles, 
each of the stack rods having a stack dog located substantially 
perpendicular to a first end thereof, the stack dog positionable within a 
corresponding aperture of the die shoe of the stationary die member; and 
(e) removing a completed stack of articles from the die shoe. 
Therefore, it is an object of the present invention to provide an apparatus 
for automatically counting and stacking articles which is capable of 
operating in-line with a thermoforming operation. 
It is another object of the present invention to provide an apparatus for 
automatically counting and stacking articles which operates in cooperation 
with an article trimming operation. 
It is a further object of the present invention to provide an apparatus 
which receives articles trimmed from a sheet of thermoplastic material and 
automatically counts and stacks such articles at the high speeds required 
of mass production operations even when such articles are formed in a 
plurality of transversely disposed rows. 
It is yet another object of the present invention to provide an apparatus 
for automatically counting and stacking articles which operates at the 
high speeds required of mass production operations without crushing the 
articles so stacked. 
It is still a further object of the present invention to provide a method 
for automatically counting and stacking molded articles successively 
trimmed by a trim press from a web of thermoplastic material. 
Other objects and the several advantages of the present invention will 
become apparent to those skilled in the art upon a reading of the 
specification and the claims appended thereto.

DETAILED DESCRIPTION OF THE INVENTION 
The present invention is best understood by reference to the appended 
figures, which are given by way of example and not of limitation. 
Referring now to FIG. 1, one embodiment of an apparatus for automatically 
counting and stacking molded articles is shown installed in line with a 
trim press of substantially conventional design. As may be seen, a 
continuous web or sheet of a thermoplastic material 42 into which a 
succession of thermoplastic articles 40 have been molded in a thermoformer 
50 is conveyed in the direction of arrows A. The articles 40 may consist 
of moldings in the form of, for example, cups, trays, plates, lids, bowls, 
containers or the like. The web 42, with the thermoformed articles 40 
molded therein is conveyed in a predetermined intermittent manner through 
the intermediary of suitable feed or indexing devices, not shown, to trim 
press 32. 
Trim press 32, comprises a stationary support frame 56, including vertical 
support members 35 and 36 and horizontal support members 57 and 59. 
Supported by vertical support members 35 and 36 is a trimming arrangement 
19 for trimming or severing thermoformed articles 40 from thermoplastic 
web 42. As shown, the trimming arrangement 19 includes, supported by 
vertical support member 36 which forms a stationary platen, a stationary 
die member 15 and, supported by movable platen 58, a movable punch member 
33. Stationary die member 15 is comprised of die shoe 18, which defines a 
central cavity 16 having a shape in general conformance with the outer 
periphery of the articles 40 being severed from thermoplastic web 42, and 
die plate 20 also having a central cavity having a shape in general 
conformance with the outer periphery of the articles 40 being severed. 
Movable punch member 33 is comprised of punch plate 34 and punch 38, which 
is mounted upon punch plate 34. Also, in accordance with the present 
invention, movable punch member 33 includes a low mass article ejector 44, 
the operation of which will be described hereinbelow. 
Movable platen 58 includes side arms 45 adapted to be reciprocated along 
guide rods 48 through the action of crankarm 46 which may be, as is 
sometimes the case, activated by a rotatable flywheel (not shown). As can 
be appreciated by those skilled in the art, when a system employing a 
flywheel is used, the flywheel may be connected to a drive motor through a 
suitable drive belt or other connecting means to translate the rotary 
motion of the flywheel into a reciprocating movement. 
Still referring to FIG. 1, an embodiment of the article counting and 
stacking apparatus 10 of the present invention is shown positioned to 
cooperate with trim press 32. Counting and stacking apparatus 10 is 
comprised of frame 14, to which carriage means 12 is mounted in such a 
manner so as to permit machine-direction horizontal movement along frame 
14, casters 30 and, as is preferred, a plurality of hold-down mechanisms 
28. Also shown in FIG. 1 is an optional conveyor means 52 for transferring 
the counted stacks of thermoplastic articles to another location for 
further manual or automatic activity. Carriage means 12 is comprised of at 
least one stacking mechanism 25, stacking mechanism 25 itself including: a 
plurality of stack rods 22 rotatively mounted to carriage means 12, each 
of the stack rods 22 having a stack dog 54 (see FIG. 4) located 
substantially perpendicular to a first end of stack rod 22 and means for 
rotating stack rods 22, a part of which is identified on FIG. 1 as element 
68. Also as shown, stack rod 22 is positionable within a corresponding 
aperture 82 (see FIG. 4 for a detailed view thereof) of die shoe 18 of 
stationary die member 15. Additional details concerning carriage means 12 
will be discussed below. 
Positioned below trimming arrangement 19 is a scrap grinder 60 for 
receiving and processing the thermoplastic web material 42 remaining from 
the trimming operation conducted above. As can be appreciated, the use of 
grinder 60 is conventional in such thermoforming and trimming operations 
and forms no part of the present invention. 
In operation, thermoplastic material web 42, into which thermoformed 
articles 40 have been molded, is conveyed from thermoformer 50 by a 
suitable feeding or indexing device (not shown) into the gap which is 
present within the trimming arrangement 19 when movable platen 58 is in 
the retracted position. The feed device for the thermoplastic web material 
42 indexes the latter so as to position a thermoformed article 40 into 
alignment with the cavity 16 of die shoe 18 and the corresponding cavity 
present within die plate 20 of stationary die member 15. 
Concurrently, the flywheel, when present, or crankarm alone, of trim press 
32 is rotated in synchronism with the positioning of the article 40 to 
thereby advance the crankarm 46 forwardly so as cause the movable platen 
58 to slide along the guide rods 48 into engagement with trimming 
arrangement 19. The throw of the crankarm 46 during the rotation of the 
flywheel is calibrated so that the protrusions of punch 38 of movable 
punch member 33 will enter the thermoformed article 40 which is positioned 
within the gap in axial alignment therewith, and will urge the article 40 
onto the die plate 20 of the stationary die member 15, thereby causing the 
cutting edge of the punch 38 to trim or sever the article 40 from the 
thermoplastic web 42, with the thermoformed article 40 being retained 
within cavity 16. During the retractive movement of the movable platen 58 
away from the stationary platen 36, the thermoplastic web 42 from which 
the trimmed article 40 has been severed therefrom drops downwardly toward 
the grinder 60 and the next thermoformed article to be trimmed is advanced 
in the direction of arrows A into the gap into axial alignment, as 
described herein above. The article trimming sequence is then repeated, 
with the successively severed articles 40 advancing the previously trimmed 
articles 40 into the cavity 16, thereby causing the severed thermoformed 
articles 40 to produce a nested stack for handling by the counting and 
stacking apparatus 10 of the present invention. 
Referring now to FIGS. 2A through 2C, a schematic representation is 
presented of the operation of the apparatus for automatically counting and 
stacking molded articles 10 of the present invention. Referring first to 
FIG. 2A, a stack of thermoformed and trimmed articles 40, of appropriate 
and desired count, has just been formed. Low mass article ejector 44 is 
advanced forward from its retracted position within movable punch member 
33 (not shown) to push the completed stack of articles 40 past stack dogs 
54 of stack rods 22. Advantageously, low mass article ejector 44 is only 
required to advance the stack of articles a distance of approximately one 
inch or less, preferably only about 3/4 of an inch, compared with ejector 
mechanisms of conventional design, which often seek to advance the 
articles a distance of four inches or more, totally exiting the die shoe. 
This, plus the fact that the ejector 44 is designed to have the lowest 
mass possible, permits the speed of the trim press 32 (see FIG. 1) to 
operate at cycle speeds of over 125 cpm, compared to conventional cycle 
speeds on the order of 80 cpm, and also permits parts to be ejected on the 
trim stroke. As can be appreciated by those skilled in the art, most 
ejector mechanisms are not fast enough to feed new material down into the 
die, trim the part, and eject same before the beginning of the next 
sequence. After ejection, the stack rods 22 of carriage means 12 (not 
shown) are rotated so that stack dogs 54 engage the endmost article 40 of 
the completed stack of articles 40. 
With reference now to FIG. 2B, low mass article ejector 44 is retracted 
into movable punch member 33 (not shown) and carriage means 12 (also not 
shown) is advanced in the direction of arrow B away from stationary die 
member 15, thus causing stack dogs 54 of stack rods 22 to pull the 
completed stack of articles from cavity 16 of die shoe 18. As indicated 
schematically, while the completed stack of articles 40 is transported 
away from the stationary die member 15, additional articles 40 continue to 
be trimmed by trim press 32 and positioned within the cavity of stationary 
die member 15. 
Referring now to FIG. 2C, the stack rods 22 and stack of articles 40 are 
shown to have been rotated to a vertical position, located away from 
stationary die member 15. This rotation is optional since, as can be 
appreciated, some larger stacks of product may be too long to stack 
vertically. When this is the case, parts can be pulled from the die and 
left in a horizontal orientation. Stack rods 22 have been rotated about 
their respective axis so that stack dogs 54 no longer engage the endmost 
article 40, thus releasing the stack for further handling. As can be 
appreciated, the stack of articles may be released onto optional conveyor 
52, depicted in FIG. 1. As shown in FIG. 2C, articles 40 continue to 
accumulate within cavity 16 of die shoe 18. Stack rods 22 of carriage 
means -2 will be repositioned within apertures 82 of die shoe 18 in 
advance of the time at which another completed stack of articles 40 is 
formed. 
With reference now to FIG. 3A, a schematic representation of a prior art 
trimming arrangement 119 for forming a nested stack of trimmed 
thermoplastic articles 140 is shown in an end and a side view. What is 
shown in FIG. 3A may be seen to be similar to the arrangement disclosed 
within U. S. Pat. No. 4,526,074. As can be appreciated by those skilled in 
the art, articles 140, as they are successively severed from the 
thermoplastic web (not shown) by punch 138 and stationary die member 115 
are positioned within the cavity of die plate 120, advancing the 
previously severed articles 140 into the cavity of die plate 120 and 
cavity 116 of die shoe 118. This causes a nested stack of articles 140 to 
be formed which, when it extends beyond cavity 116 of die shoe 118, will 
slide onto a platform or a packing table (not shown) from which the stack 
may then be manually removed. As can be appreciated, no accurate count of 
the articles 140 residing in the stack is achieved. It is not uncommon in 
the art to place a visible demarcation at certain intervals in order to 
provide a means to enable a packer to achieve the desired article count. 
FIG. 3B schematically represents, also in an end and a side view, an 
embodiment of a trimming arrangement 19, in accordance with the present 
invention. As shown, apertures 82 are provided about the periphery of 
cavity 16 of die shoe 18 for the placement of stack rods 22 (not shown) 
therein. Low mass article ejector 44 is also shown. As can be appreciated 
from the end view of FIG. 3B, a plurality of cut-outs 45 contribute to the 
low mass feature of ejector 44. 
Referring now to FIG. 4, a generally schematic representation, in 
perspective, of the interaction of die shoe 18 and stack rods 22 of a 
preferred embodiment of the apparatus of the present invention is 
presented. As shown, apertures 82 traverse the entire width of die shoe 18 
and are formed so that one side thereof of each aperture breaks through 
into cavity 16 of die shoe 18. As can be appreciated, this permits stack 
dogs 54 to protrude into the cavity 16 so that stack dogs 54 may engage 
the endmost article 40 (not shown), permitting the stack to be removed 
from cavity 16 when the desired article count is achieved. Apertures 82, 
as is preferred, do not protrude into die plate 20. 
As can be appreciated by those skilled in the art, article count may be 
kept by reference to movable platen stroke count, using a sensor 
appropriate for that purpose. The signal from that sensor may be fed into 
a controller of a type discussed hereinbelow. 
Although only a single article trimming apparatus 32 and counting and 
stacking apparatus 10 have been described thusfar, when a web 42 is 
presented for trimming which includes a plurality of thermoformed articles 
40 molded therein in a side-by-side or tandem relationship, a trim press 
having a plurality of concurrently acting trimming arrangements 19 can be 
provided, as those skilled in the art recognize. Likewise, a plurality of 
concurrently acting stacking mechanisms 25 can be located upon a carriage 
means 12 of an article counting and stacking apparatus 10. Such an article 
counting and stacking apparatus 10 is depicted in FIGS. 5 through 9. 
Referring now to FIG. 5, a side view of a preferred embodiment of an 
article counting and stacking apparatus is presented, in accordance with 
the present invention. As may be seen, the apparatus of FIG. 5 is shown 
with its carriage means 12 in a position for receiving articles from a 
trim press 32 (not shown). 
Still referring to FIG. 5, the apparatus 10 may be seen to include frame 
14, which is made portable by the provision of casters 30. When brought 
into position, lock-down mechanisms 28 are utilized to prevent movement 
during operation. Carriage means 12 is shown having a two-tier stacking 
mechanism arrangement which is designed to mate with a corresponding 
two-tier trim press trimming arrangement 19. Such a two-tier arrangement 
is effectively utilized when smaller parts are being produced. When larger 
parts are produced, a single tier arrangement will often be required. 
Carriage means 12 is capable of horizontally traversing frame 14, such a 
capability enabling completed stacks of articles to be removed from die 
shoes 18 (not shown). Moreover, as is preferred, carriage means 12 is 
designed to pivot about pivot point 82 which enables a completed stack of 
articles 40 to be placed upright on a horizontally disposed conveyor 52, 
as shown in FIG. 1. The pivoting of carriage means 12 is accomplished by 
activating pneumatic cylinder 24 which maintains tight contact between a 
cam and follower arrangement so that carriage means 12 pivots from a 
substantially horizontal disposition, with respect to the axial 
orientation of stack rods 22, to a substantially vertical disposition. As 
can be appreciated, any means capable of causing carriage means 12 to 
pivot is considered to be within the scope of the present invention. FIG. 
6 presents a side view of the FIG. 5 embodiment, shown with carriage means 
12 in a fully retracted and vertically pivoted position. 
Reference is now made to FIG. 7, in which a top view of the FIG. 5 
embodiment of the present invention is shown with carriage means 12 in a 
position for receiving articles from a trim press 32. FIG. 7 also depicts 
the means for retracting carriage means 12 away from trim press 32 so that 
a completed stack of articles 40 may be removed from within a cavity 16 of 
die shoe 18 of stationary die member 15, to a position for removal from 
the apparatus. As is preferred, carriage means 12 is retracted away from 
trim press 32 through the use of a retraction belt 78 and a motor and 
pulley system 80, although other retraction means can be employed as those 
skilled in the art will recognize. Guide rods 72 are provided to aid in 
the smooth retraction of carriage means 12. 
FIG. 8 presents an enlarged side view of the carriage means 12 of the FIG. 
5 embodiment. As indicated above, carriage means 12 also includes means 
for rotating stack rods 22 so that stack dogs 54 can engage an endmost 
article 40 of a completed stack of articles. As is preferred, the means 
for rotating stack rods 22 is a belt driven motor and pulley arrangement 
in which each tier of stacking mechanisms has a dedicated 90.degree. 
rotating air cylinder 68. Each air cylinder 68 has a pulley 64 for 
engagement with belt 66. As can be appreciated, although a rotating air 
cylinder is preferred for use in the practice of the present invention, 
other means, including an electric motor, could be used in conjunction 
with proper controls. Each stack rod has a pulley 62, also for engagement 
with belt 66. Pulley 62 is mounted at an end of stack rod 22 which is 
opposite the stack dog 54. Carriage means 12 also includes side plates 70 
(one on each side of carriage means 12) which serve to hold the mechanism 
together. 
FIG. 9 presents a back view of carriage means 12 of the FIG. 5 embodiment, 
showing in detail the preferred means for rotating a plurality of stack 
bars 22 of the article stacking mechanisms 25. Note that a single drive 
belt 66 is capable of rotating all pulleys 62 of stack rods 22 present in 
a tier of stacking mechanisms 25. As shown, a total of 10 sets of stacking 
mechanisms are present in the two-tier arrangement depicted. As those 
skilled in the art will plainly recognize the counting and stacking 
apparatus of the present invention is capable of being configured in a 
wide variety of arrangements, with the present invention not to be limited 
to the configurations depicted in FIGS. 1 through 9. 
As can be appreciated by those skilled in the art, article counting, 
stacking and stack ejection operations, as well as other apparatus control 
functions can be controlled through the use of a microprocessor, as is 
preferred. Such control technology, being well known, requires no further 
explanation for a complete understanding of the present invention. Any of 
a number of commercially available controllers are considered to be 
suitable in the practice of the present invention. The controller utilized 
in apparatus 10 may be located within a cabinet mounted on frame 14 or 
remote from same. Additionally, to rapidly shut down apparatus 10 in the 
event of an article jam or safety related problem, stop buttons may be 
located at a plurality of locations about the unit. 
To prevent inadvertent operator contact during operation, additional safety 
guards (not shown) may be provided as needed. Guards may be optionally 
provided in locations where operator contact is likely. 
Although the present invention has been described with preferred 
embodiments, it is to be understood that modifications and variations may 
be utilized without departing from the spirit and scope of this invention, 
as those skilled in the art will readily understand. Such modifications 
and variations are considered to be within the purview and scope of the 
appended claims.