Apparatus for thermoforming hollow articles

An apparatus for thermoforming hollow articles including forming molds and die cutting molds disposed in spaced-apart relationship wherein the web or sheet of thermoplastic material is sequentially moved or indexed in an integrated operation whereby an article formed in the forming molds is advanced into proper alignment with respect to the die cutting molds and die cut, and subsequently withdrawn to an appropriate storage assembly. The forming molds and die cutting molds being positioned on upper and lower platens.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a process and apparatus for thermoforming hollow 
articles, such as cups, dishes or lids, and more particularly to an 
improved process and apparatus for thermoforming hollow articles including 
concomitant die cutting of the thus formed hollow article. 
2. Description of the Prior Art 
This invention is particularly concerned with thermoforming operations in 
which a web or sheet of thermoplastic material is first softened by heat 
and then formed or shaped while in this stretchable plastic state by being 
drawn or pressed against the contours of a mold or die under the influence 
of a fluid pressure differential. The former may be exemplified by the 
application of pressure within a pressure box or female mold assembly 
produced by compressed air or the like, to press the softened material 
against the countours of a male mold or core pin. Alternately, a vacuum 
may be applied from within a female mold while allowing atmospheric 
pressure to shape the heat softened thermoplastic material against the 
surface of the female mold. For many purposes, a combination of these two 
techniques is preferred with the softened sheet material being subjected 
to vacuum on the face contacting the mold surfaces and to a substantial 
positive pressure on its other face as such combination provides greater 
versatility and better control in the forming operations. 
Apparatus for effecting thermoforming operations, in general, is comprised 
of a press having upper and lower platens on which are mounted a male mold 
assembly and female mold or pressure box assembly. In this regard, the 
male mold is generally mounted on the lower platen, however, this is 
normally a matter of choice. Prior to forming of the sheet of 
thermoplastic material as hereinabove discussed, a clamping assembly 
normally constituting a part of the male mold assembly is first caused to 
trap the sheet of thermoplastic material about the entrance into the 
female mold or the pressure box assembly including a cooperating clamping 
grid. Thereafter, the male mold of the male mold assembly is caused to 
pass through the plane of the thermoplastic material and eventually form 
the hollow article, as hereinabove discussed. Relative movement of the 
male and female mold assemblies is effected by hydraulic cylinder or 
electric motor assemblies together with associated cams, gears, support 
arms, etc., to move the platens whereas movement of a clamping assembly is 
effected by an associated cylinder assembly. 
The hydraulic cylinder or electric motor assemblies are large even for 
small thermoforming apparatus and have large energy requirements. In this 
application the term fluid cylinder assembly is to be interpreted as the 
combination of a cylinder, piston and rod which is operated by a 
pressurized fluid, i.e. a gas or a liquid. 
Die cutting of the hollow article is generally effected in another 
apparatus including die cutting elements into which is introduced the web 
or sheet of thermplastic material including thus formed hollow articles. 
Die cutting in a separate operation suffers from alignment problems as 
well as problems associated with die cutting of cooled thermoplastic 
materials, e.g. splitting and the like, as well as cost considerations, 
i.e. a separate assembly. 
Other known assemblies include the thermoforming and die cutting of the 
hollow article without indexing of the heated sheet of thermoplastic 
material, with the article being laterally drawn off and moved upwardly to 
a stacking device. 
In many assemblies, the hollow articles are subjected to further finishing 
operations in a corresponding appropriate finishing device, e.g. punching, 
embossing, printing, testing or the like. Such finishing devices are 
expensive, require space, are time consuming and result in the manufacture 
of a certain number of unacceptable products. 
OBJECTS OF THE INVENTION 
It is an object of the present invention to provide an improved process and 
apparatus for thermoforming hollow articles which overcome the problems of 
the prior art. 
Another object of the present invention is to provide an improved process 
and apparatus for thermoforming hollow articles wherein molding and die 
cutting of the hollow articles are sequentially performed in the same 
apparatus. 
Still another object of the present invention is to provide an improved 
process and apparatus for thermoforming hollow articles permitting of 
facile die cutting of the thus formed articles. 
SUMMARY OF THE INVENTION 
These and other objects of the present invention are achieved in a 
thermoforming apparatus including forming molds and die cutting molds 
disposed in spaced-apart relationship wherein the web or sheet of 
thermoplastic material is sequentially moved or indexed in an integrated 
operation whereby an article formed in the forming molds is advanced into 
proper alignment with respect to the die cutting molds and die cut, and 
subsequently withdrawn to an appropriate storage assembly.

DETAILED DESCRIPTION OF THE INVENTION 
It will be appreciated that the type of thermoplastic or thermoelastically 
deformable material employed in the present process is generally 
determined by the economics and duty in which the hollow article will 
eventually be placed. Among the many thermoplastic resins suitable for 
various purposes and adaptable to thermoforming are high-impact 
polystyrene, polybutadiene, styrene-butadiene blends or copolymers, 
polyvinylchloride and related vinyl polymers, polyallomers, nylon, 
formaldehyde polymers, polyethylene, polypropylene, nitrocellulose, 
cellulose acetate, cellulose propionate, cellulose acetate, acetate 
butyrate, polymethylmethacrylate, ethyl cellulose, benzyl cellulose and 
ethylesters of cellulose. 
Referring now to the drawings and particularly FIGS. 1 to 5, and more 
particularly to FIG. 1, there is illustrated a portion of a thermoforming 
machine comprised of an upper tool member 2 and a lower tool member 3 
mounted to an upper and lower platen 4 and 5, respectively. The lower tool 
member 3 is mounted via an intermediate plate member 6 to the lower platen 
5. The upper and lower platens 4 and 5 are constructed and arranged for 
vertical movement in the thermoforming machine by suitable mechanism M for 
thermoforming a sheet 11 of thermoplastic material. 
The upper tool member 2 is formed with a substantially cylindrically-shaped 
recess 7 and a spaced-apart cylindrically-shaped channel 12 defining a 
circularly-shaped sealing edge 8 and a circularly-shaped cutting edge 13 
of a tool portion 2a of the upper tool member 2, respectively, referring 
particularly to FIG. 5 with the spacing between the recess 7 and the 
channel 12 being in conformity with indexing distances of the sheet of 
thermoplastic material. The upper tool member 2 is formed with a 
cylindrically-shaped channel in coaxial alignment with the recess 7 in 
which is disposed a cross-hole die member 9 mounted for reciprocal 
movement to a fluid cylinder 10 mounted to the upper platen 4. As 
illustrated in FIG. 1, the cross-hole die member 9 is withdrawn within the 
cylindrically-shaped channel therefor and does not come into contact with 
the heated sheet 11 of thermoplastic material during forming of the hollow 
article thereby preventing tempering marks from being formed thereon. The 
upper platen 4 is provided with a cylindrically-shaped channel 14 in 
coaxial alignment with the channel 12. Above the channels 12 and 14 there 
is provided stacking plate members 16 including stacking orifices 15 also 
in coaxial alignment with the channels 12 and 14 as more fully hereinafter 
disclosed. 
The lower tool member 3 is formed with a recess defining a 
circularly-shaped ring portion 17 and a circular scoring edge 18 extending 
upward-y and in coaxial alignment with the recess 7 of the upper tool 
member 2, with the scoring edge 18 cooperating with the sealing edge 8 of 
the upper tool member 2, as more fully hereinafter discussed. In the 
recess of lower tool member 3, there is disposed a deforming male mold 19 
including a cylindrically-shaped recess 20 mounted to or formed as a part 
of a guide rod 21 mounted to a plate member 22 mounted to a fluid cylinder 
23 for reciprocal movement through the lower platen member 5. On the 
intermediate plate member 6, there is disposed a cylindrically-shaped tool 
24 including circularly-shaped cutting edge 25 (FIG. 5) in coaxial 
alignment with the channel 12 of the upper tool member 2 for cooperating 
with the cutting edge 13 of tool portion 2a of the upper tool member 2. 
The cylindrically-shaped tool 24, intermediate plate member 6 and the 
lower platen 5 are formed with cylindrically-shaped channels for receiving 
an ejection member including an ejection rod 26 mounted for reciprocal 
movement to a suitable fluid cylinder (not shown). 
The following description in conjunction with FIGS. 1 to 4 describes the 
sequence of steps in the formation of a hollow article in accordance with 
the present invention. As is known to one skilled in the art, the upper 
and lower platens 4 and 5 in an initial position are above and below the 
sheet 11 of thermoplastic material to allow unimpeded horizontal passage 
of the formed article through the apparatus upon horizontal advancement 
(left to right) of the sheet 11 of thermoplastic material. 
In operation, the sheet 11 of thermoplastic material softened to an optimum 
forming temperature by suitable means, such as radiant heaters H, infrared 
lamps, etc., is advanced or indexed by advancing assembly A into a 
position between the upper and lower platens 4 and 5, referring 
specifically to FIG. 1. The upper platen 4 is caused to be lowered by 
upper mechanism M to a point where the upper tool member 2 contacts the 
sheet 11 of thermoplastic material with the lower platen 5 being caused to 
be moved upwardly by lower mechanism M to a point where the 
circularly-shaped ring portion 17 of the lower tool member 3 passes 
through the plane of the sheet 11 of thermoplastic material, as 
illustrated in FIG. 2. The scoring edge 18 of the lower tool member 3 
cooperates with the sealing edge 8 of the upper tool member 2, as 
illustrated in FIG. 5, to form a circularly-shaped scored portion about 
the hollow article 1 being formed between the recess 7 of the upper tool 
member 2 and the lower tool member 3. In the position illustrated in FIG. 
2, the cross-hole die member 9 is lowered into the cylindrically-shaped 
recess 20 and cooperates with the deforming male mold portion 19 of the 
lower tool member 3 to form a cross cut. 
During such cooperative lowering and raising of the upper and lower platens 
4 and 5, the scored hollow article 1 formed in the forming station and 
indexed laterally therefrom is now positioned between tool portion 2a 
including channel 12 of the upper tool member 2 and the lower die cutting 
cylindrically-shaped tool 24 whereby the scored portion of the thus formed 
hollow article 1 is completely cut by cooperation of the cutting edge 13 
of the tool portion 2a with the circularly-shaped cutting edge 25 of the 
cylindrically-shaped tool 24, referring again to FIG. 5. The relative 
diameter between the edges 13 and 25 is smaller than the relative diameter 
between the edges 8 and 18 since slight cutting irregularities may be 
tolerated. 
After a predetermined time period, the fluid cylinder associated with the 
ejecting member and ejection rod 26 is activated to cause upward movement 
thereof to a point where the severed hollow article 1 engages an article 
orifice 15 of the stacking plate members 16, as illustrated in FIG. 3. The 
article orifices 15 are designed to retain the hollow article therein 
during retraction of the ejection rod 26. 
Upon the ejection rod 26 reaching a lowered position, the upper platen 4 is 
raised as illustrated in FIG. 4. To ensure that the thus formed article is 
separated from the circularly-shaped ring portion 17 prior to indexing of 
the heated sheet 11 of thermoplastic material, the fluid cylinder 23 is 
activated to cause the guide rod 21 and related deforming male mold 
portion 19 to be simultaneously raised during lowering of the lower platen 
5 eventually to the position illustrated in FIG. 1, thereby lifting the 
thus formed hollow article 1 and the heated sheet 11 of thermoplastic 
material. Once the platens have assumed the position illustrated in FIG. 1 
and guide rod 21 and related deforming male mold portion 19 lowered, the 
heated sheet 11 of thermoplastic material is indexed or moved (from left 
to right), referring to FIGS. 1 to 4, and the thermoforming cycle 
repeated. 
In the embodiment of the present invention, as illustrated in FIGS. 1 to 4, 
it will be understood that the cylindrically-shaped tool 24 may be 
integrally formed with the tool member 3. Additionally, it will be 
understood that a further tool may be provided, e.g. a further finishing 
operation or a leakage test, between the forming molds and die cutting 
tools. Still further, while the present invention is illustrated with only 
one recess 7 in upper tool member 2 and cooperating channels 12 and 14 and 
die cutting tools 2a and 24 (i.e. "one-up"), it will be understood that a 
plurality of such items may be provided essentially in a plane vertical to 
the plane of the drawings. The thus formed hollow article is described as 
being circularly-shaped, however, hollow articles formed in accordance 
with the present invention may be square-shaped, rectangularly-shaped, 
etc., with appropriate modification to the tools. 
The basic structure and mode of operation of the thermoforming assembly for 
forming hollow articles illustrated in FIG. 6 are substantially the same 
as those for the thermoforming assembly of FIGS. 1 to 5, with numeral 
designations, however, being prefixed by 100. 
Referring now to FIG. 6, the upper tool member 102 is formed with channels 
127 for the passage of a cooling fluid, e.g. cooling water, introduced 
into the channels 127 by a conduit 128, and with a conduit 132 in fluid 
communication with a source of compressed air. The upper tool member 102 
is formed with a frame-like rib portion 129 maintained at a temperature 
considerably below the temperature of heated sheet 11 of thermoplastic 
material by the cooling medium flowing through the channels 127 therein. 
The lower tool member 103 is formed with an internal chamber 130 for 
positioning a heating cartridge, or for the introduction of a heating 
medium, e.g. hot water via conduit 131 to maintain the lower tool member 
103 at optimum forming temperatures to minimize any problems in the 
forming of the hollow article 101. The frame-like rib portion 129 of the 
upper tool member 102 engages an edge area 101a of the thermoplastic sheet 
111 about the lower tool member 103 during lowering and raising of the 
platens to permit compressed air to be introduced therebetween via conduit 
132 to force the heated sheet 111 of thermoplastic material against the 
contours of the lower tool member 103. The lower tool member 103 is 
provided with a conduit 133 to vent to the atmosphere the lower tool 
member 103. It will be understood by one skilled in the art that 
conversely, conduit 133 may be placed on the suction side of a pump with 
conduit 132 being in fluid communication with the atmosphere to form the 
hollow article. 
The upper cutting tool 102a is separate from the upper tool member 102 and 
is mounted to the upper platen 104 and is formed with channels 134 for the 
passage of a cooling fluid, e.g. cooling water introduced into the 
channels 134 by a conduit 135. The lower die member 124 is similarly 
formed with channels 136 for the passage of a cooling fluid, e.g. cooling 
water, introduced into the channels 136 via conduit 137. The ejection 
plate and piston member 126 are provided with channels 138 and 139 for 
passage of a cooling fluid, e.g. cooling water. 
The upper platen 104 is provided with a slide plate 140 to place channels 
112 and 114 in a sealed airtight relationship after lowering and raising 
of the upper and lower platens 10 and 105, respectively, with the lower 
die member 124 provided with channels 141 in fluid communication to the 
atmosphere. 
In operation of the apparatus of FIG. 6 with the platens 104 and 105 in an 
opened position, the sheet of thermoplastic material 111 is heated in a 
stepwise manner to a forming temperature, e.g. 120.degree. C. The heated 
sheet of thermoplastic material 111 is advanced or indexed into the 
thermoforming assembly. The platens 104 and 105 are lowered and raised, 
respectively, with the frame-like rib portion 129 of the upper tool member 
102 contacting the heated sheet 111 of thermoplastic material about the 
area 101a thereof and against the lower tool member 103. Compressed air is 
introduced via conduit 132 through upper tool member 102 to force the 
heated sheet 111 of thermoplastic material against the contours of the 
lower tool member 103 maintained at forming temperatures by the heating 
fluid introduced via conduit 131 into the internal chamber 130 during 
formation of the hollow article 101. A peripheral edge portion 101a of the 
hollow article 101 is cooled by contact with the cooled frame-like rib 
portion 129 of the upper tool member 102. 
After a predetermined time period, the platens 104 and 105 are raised and 
lowered, respectively, with platen 105 being lowered to the extent 
necessary to permit free passage of the thus formed hollow article 101 
upon subsequent indexing or advancement (left to right) of the heated 
sheet 111 of thermoplastic material. Upon indexing of the heated sheet 111 
of thermoplastic material, the hollow article 101 is positioned between 
the upper and lower die cutting die cutting tools 102a and 124, 
respectively, with the peripheral edge portion 101a being aligned with the 
cutting edges 113 and 125 of the upper and lower cutting dies 102a and 
124, respectively. Upon lowering and raising of the upper and lower 
platens 104 and 105, respectively, the cutting edge 125 of the lower 
cutting die 124 is caused to partially penetrate throughout a major 
portion of a thickness of the sheet 111 of thermoplastic material. The 
thus formed hollow article 101 is cooled by contact with the cooled 
contours of the lower cutting die 124 and ejection plate and rod member 
126, assisted by compressed air via a conduit (not shown) through 
cooperation of the slide plate 140 endorsing channels 112 and 114. 
Thereafter, the lower platen 105 is raised slightly further whereby the 
cutting edge 125 of the lower cutting die 124 completely severs the hollow 
article 101 from the sheet 111 of thermoplastic material. To permit such 
operation without interfering with the operation of the molding tool 
members 102 and 103, the upper tool member 102 is resiliently mounted to 
the upper platen 104 by members 142. 
The lower platen 105 is provided with cam discs (not shown) permitting for 
problem free adjustable movement of the lower platen 105 wherein the cam 
discs are shaped to permit initial partial cutting followed by complete 
cutting of the hollow article 101. After complete die cutting of the 
hollow article 101, the ejection plate and rod member 126 is raised to 
thereby transport the thus cut hollow article to the stacking orifices 115 
of the stacking member 116. 
The apparatus illustrated in FIG. 6 is particularly advantageously used for 
thermoforming hollow articles from PET plastic sheets or films. 
The basic structure and mode of operation of the thermoforming assembly for 
forming hollow articles illustrated in FIG. 7 are substantially the same 
as those for the thermoforming assembly of FIGS. 1 to 5, with numeral 
designations, however, being prefixed by 200, and similarly may 
advantageously process PET plastic sheets or films. 
Referring now to FIG. 7, the upper tool member 202 and upper cutting die 
member 202a are mounted to upper platen 104 whereas cooperating lower tool 
member 203 and lower cutting die member 224 are mounted to lower platen 
205. The upper tool member 202 is provided with a plug assist member 209 
mounted for vertical movement to fluid cylinder 210 by a rod member. The 
lower tool member 203 is provided with a deforming head 219 mounted on a 
guide rod 221 for vertical movement by a fluid cylinder (not shown) 
mounted on the lower platen 205. The lower die cutting member 224 is 
provided with an ejection plate and rod member 226 for vertical movement 
by a fluid cylinder (not shown) mounted on the lower platen 205. 
A heated sheet 211 of thermoplastic material is advanced or indexed into 
the thermoforming assembly including upper and lower platens 204 and 205 
disposed in an opened position. Thereupon, the upper and lower platens 204 
and 205 are lowered and raised, respectively, and the heated sheet 211 of 
thermoplastic material captured between the upper and lower tool members 
202 and 203. The plug assist member 209 is caused by the fluid cylinder 
210 to be lowered to stretch the heated thermoplastic sheet 211 to ensure 
for more uniform wall thickness distribution of the thermoplastic material 
with the thermoforming process for forming hollow article 201 being 
completed by use of compressed air or vacuum introduced or withdrawn, 
respectively, as hereinabove discussed. 
After a predetermined time period for formation of the hollow article 201, 
the lower platen 205 is lowered with concomitant raising of the deforming 
head 219 by the fluid cylinder 210 cooperating with the guide rod 221 
thereby supporting the deep drawn hollow article 201. Thereafter, the 
deforming head 219 is lowered to permit advancement or indexing of the 
heated sheet 211 of thermoplastic material including the hollow article 
201, as hereinabove discussed, to the point where the hollow article 201 
is in coaxial alignment with the upper and lower cutting dies 202a and 
224. 
Initiation of another operational cycle, including the raising of the lower 
platen 205, permits the thus formed hollow article 201 to assume the 
contours of the lower die 224 wherein the hollow article 201 is supported 
on the ejection plate and rod member 226 with concomitant initial cutting 
of the hollow article 201 about an edged area thereof from the sheet 211 
of the thermoplastic material by cooperation of the cutting edges 213 and 
225 of the upper and lower cutting dies 202a and 224, respectively. 
Thereafter, complete cutting of the hollow article 201 is effected by the 
raising of the ejection plate and rod member 226 eventually to the 
position illustrated by the dotted-dashed lines through the channels 212 
and 214 to a point proximate an article orifice 242 cooperating with an 
article passage 243 for passage laterally of the hollow 201 article to a 
stacking chute 244 including a stacking piston assembly, generally 
indicated as 245. 
It will be appreciated by one skilled in the art that the apparatuses of 
the present invention advantaegously permit operation thereof at fast 
cycling speeds as a result of the small distances, i.e. one indexing of 
the sheet of thermoplastic material between thermoforming of the hollow 
article and die cutting of the hollow article from the heated 
thermoplastic sheet. Additionally, the apparatus of the present invention 
is significantly less expensive than thermoforming apparatus of the prior 
art since the upper and lower platens of the present invention support 
thermoforming molds and the cutting dies and the like, as distinguished 
from prior art assemblies requiring separate feeding assemblies resulting 
in improper cutting of the hollow article. Cooling of the cutting dies, as 
described and illustrated in FIG. 6, substantially improves effectiveness 
of the cutting edges thereof, thereby minimizing any heating effect of the 
heated thermoplastic material being processed, while permitting of die 
cutting while the thermoplastic material is still warm. 
As hereinabove discussed in one embodiment of the present invention, an 
edge area of the thermoplastic sheet about the thus formed hollow article 
is cooled during thermoforming to permit more efficacious cutting about 
such cooled edge area. This type of process provides the advantageous 
possibility to punch or cut out the total thickness of the cooled down 
sheet, because the mold edge area which surrounds the given hollow article 
is approximately at the temperature, already during the thermoforming, 
which assures an effectiveness of the immediately subsequent punching 
process. Furthermore, it offers the advantageous opportunity of a more 
rapid cycle succession, because molding is effected in the first tool 
section with punching and stacking performed in a second tool section. 
This thermoforming process is particularly advantageous when applied to the 
forming of composite foils of thermoplastic materials, for example, a 
composite foil having layer distribution of PP/PYDC/PP. Such composites 
would have to be deformed at least in the crystalline melting point if 
deep drawing parts should be made for sterile packaging, and the processes 
of the present invention are particularly advantageous in lengthening 
service life of the cutting edges since the sheet may be heated to 
temperatures of up to 170.degree. C. (at which temperature the 
thermoplastic material crystallizes) and initially scored in a hot stage 
and cutting of the hollow article completed at a lower temperature in a 
manner to maintain the cutting edge clean and to minimize splintering 
thereof. 
While the present invention has been described in connection with several 
exemplary embodiments thereof, it will be understood that many 
modifications will be apparent to those of ordinary skill in the art; and 
that this application is intended to cover any adaptations or variations 
thereof. Therefore, it is manifestly intended that this invention be only 
limited by the claims and the equivalents thereof.