Cutting and sealing apparatus

A die assembly and machine incorporating the die assembly are disclosed which are operable to cut and hermetically seal irregularly shaped unstripped receptacles in overlying sheets of polyethylene material. The die assembly includes a first die means having a body portion and a cutting edge surface projecting therefrom which defines an irregular shape. An access opening extends through the body portion and is substantially encompassed by the cutting edge surface. A second die means has an external contour conforming to the irregular shape and is positioned within the cutting edge surface. The second die means is operable by means extending through the access opening of the body portion and includes a projecting sealing edge surface which is juxtaposed to the cutting edge surface. The body portion may be provided with cartridge heaters that provide the source of heat for both the cutting and the sealing operations. In operation the second die means is guided vertically by the cutting edge surface of the first die means. The cutting edge surface is heated by conduction from the body portion; similarly, the sealing edge surface is heated by conduction from the body portion. However, the sealing edge surface is only heated while the second die means is in a heat receiving position with the first die means.

BACKGROUND OF THE INVENTION 
This invention relates to apparatus for cutting receptacles from sheets of 
heat weldable material. More particularly, this invention concerns the 
unstripped cutting and hermetic sealing of irregularly shaped receptacles 
from sheets of heat weldable material. 
In the past, receptacles fabricated from heat sealable synthetic resinous 
materials, such as polyethylene, have been widely used to package and 
store various objects and commodities. Some receptacles are generally 
rectangular and are fabricated from a tubular piece of heat sealable 
material. Other generally rectangular receptacles are fashioned from 
overlying sheets of heat sealable material. 
To fabricate the generally rectangular receptacles, an essentially straight 
heated blade is often used. The heated blade first seals a straight edge 
of the receptacle and, when all the necessary edges are formed, a separate 
guilotine apparatus severs each receptacle from the substantially 
continuous sheets of material. 
Typically, the heated blade has an internal heat source that is not easily 
shaped in complex contours. Accordingly, the heated blades are ordinarily 
linear. Moreover, each heated blade is usually provided with a separate 
heat source to provide control of its temperature. 
Irregularly configured receptacles, as opposed to circular or rectangular 
receptacles, are used, for example, as novelty items and as liners in 
irregularly contoured vessels. Because of the irregular shape, known 
heated blades are not truly suitable for fabrication of these complex 
shapes. 
One approach used in the cutting of irregularly shaped receptacles from 
sheet material is to mount a resistance wire on a plywood support. The 
supported wire is placed in contact with the sheets of heat weldable 
material. Then an electrical pulse is passed through the wire thereby 
heating it and allowing the heated wire to cut through the sheets of 
material. 
With the hot wire apparatus, precise dimensional tolerances are difficult 
to obtain since the hot wire undergoes thermally induced linear expansion 
when the wire is pulsed. Moreover, the wire wears out quickly. A 
particularly disadvantageous feature of the hot wire apparatus concerns 
the fact that it actually strips or cuts out an irregular shape from the 
sheet material. In this fashion, each of the irregular shapes, as well as 
the parent sheet material, must be handled during fabrication and a 
concurrent expense is experienced. Additionally, the hot wire gives a 
receptacle an erractic edge configuration which typically has 
imperfections such as pin holes through which fluids can escape from the 
receptacle. 
In the tire packaging art, concentric annular members have been used to 
separately cut and seal plastic packaging material around annular object 
prior to heat shrinking of the material to the object. An example is 
illustrated by U.S. Pat. No. 3,868,291 issued to Benz et al on Feb. 25, 
1975. Apparatus for packaging solid objects is not concerned with 
providing an hermetic seal. Moreover, annular heating elements are not 
readily deformed to complex irregular shapes. 
Where separate sealing and cutting operations are provided, they are 
ordinarily independent, rather than interdependent. Moreover, the sealing 
operation is not guided by the cutting operation to allow precise control 
of the spacing between the cut and seal lines. Accordingly, indexing of 
the separate cutting and sealing operations is required. 
With known apparatus for simultaneously cutting and sealing, such as hot 
wire and heated blades, pin holes and similar imperfections occur along 
the cut line. Thus, an hermetic seal is not present. These pin holes are 
particularly objectionable as fluids may leak from the receptacle thereby 
rendering the receptacles unsuitable for use with fluids or, for that 
matter, sterile objects. 
Thus, it will be seen that the need continues to exist for a truly 
effective apparatus capable of fabricating unstripped hermetically sealed 
irregular objects from heat sealable plastic materials. 
Objects and Summary of the Invention 
It is a general object of the present invention to provide a novel die 
assembly for the fabrication of irregularly shaped hermetically sealed 
receptacles from overlying sheets of synthetic resinous material. 
It is a more specific object of the present invention to provide a novel 
two part die assembly for the fabrication of irregularly shaped 
receptacles from overlying sheets of synthetic resinous material in which 
a single source of heat is used for both cutting and sealing the overlying 
sheets. 
Yet another object of the present invention is to provide a novel two part 
die assembly for the fabrication of irregularly shaped hermetically sealed 
receptacles in which an hermetic sealing portion is dependent from and 
guided by a cutting portion. 
The above and many other objects of the present invention are substantially 
accomplished by the use of a die assembly comprising a first die member 
and a second die member. Preferably the first die member includes a body 
portion which is heated by a heat source that provides all the heat 
necessary for the die assembly. The body portion is thermally conductive 
so as to distribute and store heat. 
To sever the material from which a receptacle or article is to be formed, a 
generally planar cutting edge surface projects from the body portion. The 
cutting edge surface may be located on a cutting bar projecting from the 
body portion so that a recess is defined thereby to receive the second die 
member. Preferably, the cutting bar is integrally connected to the body 
portion to provide good thermal conduction from the body portion to the 
cutting edge. 
The cutting bar may be machined from the body portion so as to define an 
irregularly shaped outline conforming to the desired receptacle. The body 
portion is preferably provided with an access opening communicating with 
the recess, essentially circumscribed by the cutting bar and operable to 
receive an operating means for the second die member. 
Disposed within the recess defined by the cutting bar is the second die 
member. The second die member has a perimeter which is shaped similarly to 
the irregular outline defined by the cutting bar. In this manner the 
second die member is positively positioned rotationally relative to the 
first die member. The second die member includes an outwardly projecting 
sealing edge surface juxtaposed with the cutting edge surface and having a 
width substantially exceeding the width of the cutting edge. The sealing 
edge surface creates an hermetic seal within the irregular outline defined 
by the cutting edge. Preferably, the sealing edge surface is carried by a 
sealing bar and is closer to the body portion than the cutting edge 
surface so that the first and second die members may be independently 
actuated. 
The operating means extends through the access opening of the first die 
member and engages the second die member. The operating means moves the 
second die member from a heat receiving position in which it is in general 
surface contact with the body portion and a heat sealing position in which 
the sealing edge surface is in generally coplanar relation with the 
cutting edge surface. 
The first die is preferably controlled such that the cutting edge does not 
completely sever a receptacle from parent material of the overlying 
sheets. In this manner, the irregularly shaped object is not stripped from 
the parent material and subsequent handling is facilitated. 
In order to assure accurate positioning of the sealing edge surface member 
with respect to the cutting edge surface, the perimeter of the second die 
member is guided between the heat sealing and heat receiving positions by 
the cutting bar of the first die member. Accordingly, when the sealing 
edge surface is advanced into heat sealing relationship with sheet 
material, effective rotational as well as axial control is provided to 
permit accurate positioning and regulation of spacing between the cutting 
line and the sealing line. 
To reduce the energy required to maintain the die assembly at operating 
temperature, as well as to reduce the expense of the overall die assembly, 
the sole heat source may comprise a plurality of cartridge heaters 
positioned in the body portion of the first die member. The cartridge 
heaters heat the cutting edge surface directly by conduction and, when the 
second die member is in the heat receiving position, supply heat by 
conduction to the second die member and thus the sealing edge surface. 
The first and second dies are preferably fabricated of easily machined heat 
conducting material such as steel so that the dies have an extremely long 
useful life in comparison with cutting apparatus fabricated of less 
durable material. 
By using the die assembly to form unstripped irregular receptacles, the die 
assembly is well adapted for use in machinery that intermittently advances 
sheets of heat weldable material to a position between the platen assembly 
and a die assembly. Accordingly, rapid automated production with minimal 
human supervision is accomplished.

Description of the Preferred Embodiment 
Turning now to FIG. 1, automated apparatus is disclosed for the fabrication 
of irregularly shaped hermetically sealed receptacles or articles from two 
superposed sheets of heat weldable synthetic resinous material. The 
apparatus preferably includes a frame structure 10 which supports various 
components in the proper spatial relationship. 
Mounted at one end of the frame 10 are two or more rolls 12, 14 of heat 
weldable synthetic resinous material. Connection of the rolls 12, 14 to 
the frame 10 may be accomplished in any suitable conventional manner that 
permits easy replacement of an empty roll with a full roll. A particularly 
suitable synthetic resinous material for use with apparatus of the present 
type is polyethylene. 
One or both of the rolls of material 12, 14 may be printed as generally 
indicated at 16 with instructions for use, advertising material, or other 
desired information. The material from each roll 12, 14 is withdrawn in a 
sheet 18, 20, respectively, that may pass between a pair of guide rollers 
22, 24 which are suitably mounted to portions of the frame 10. The guide 
rollers 22, 24 serve to orient the sheets 18, 20 in overlying or 
superposed relationship for delivery to the receptacle forming apparatus 
26. 
The receptacle forming apparatus 26 preferably includes a die assembly 28 
and a platen assembly 30. The platen assembly 30 is suitably connected to 
portions of the frame 10 in a generally rigid manner. In addition, the 
film is supported, and carried over the platen assembly 30, by a resilient 
rubberized, continuous belt 31 which underlies the sheets 18, 20 during 
article formation. The die assembly 28 is preferably suspended from 
actuating means 32 which may be securely directly to the frame 10. For the 
purpose of clarity, portions of the frame 10 have been deleted from FIG. 
1. 
After passing the guide rolls 22, 24, the superposed sheets 18, 20 pass a 
forming station positioned between the die assembly 28 and the platen 
assembly 30. At the forming station, the die assembly 28 fashions an 
unstripped irregularly shaped hermetically sealed receptacle 34 in the 
parent material of the sheets 18, 20. 
The superposed sheets 18, 20 with the unstripped receptacles 34 therein are 
subsequently advanced and wound up on a take-up roll 36 mounted at the 
second end of the frame 10. The take-up roll 36 may be intermittently 
advanced by a suitable sprocket drive assembly having a driven sprocket 44 
on the take-up roll, a driving sprocket 40 driven by a motor 38 and a 
chain 42 interconnecting sprockets 40, 44. 
With reference now to FIG. 2, the die assembly 28 is illustrated in greater 
detail. The die assembly 28 includes a first die member having a body 
portion 46 which may be generally rectangular in shape, as illustrated. 
The first die member is fabricated from a thermally conductive easily 
machined material such as aluminum or steel. A suitable conventional heat 
source may be used to heat the first die member to operating temperature. 
The relatively large mass of the body portion serves as a heat storage 
member and aids the maintenance of a uniform temperature. 
The body portion 46 may include a plurality of generally parallel 
internally disposed openings, such as bores 48, each of which is adapted 
to receive a cartridge heater 49 (see FIG. 1). Preferably the bores 48 are 
spaced uniformly from one another and spaced by a uniform distance from a 
surface 52 (FIG. 2) of the body portion 46 so that the temperature 
distribution thereof is reasonably uniform. 
The body portion 46 preferably includes a generally planar bottom surface 
52 from which a cutting bar 54 projects. The cutting bar 54 is preferably 
integral with the body portion 46 and is heated by conduction therefrom. 
By machining material from a surface of the body portion 46, the cutting 
bar and a recess are defined. The cutting bar 54 essentially circumscribes 
the recess and defines a substantial portion of the perimeter of an 
irregularly shaped object. 
Positioned within the recess and the contour delineated by the cutting bar 
54 is a second die member 56. The external perimeter 58 of the second die 
member 56 is similar and generally conforms to the irregular shape defined 
by the cutting bar 54. By virtue of the similar shape, the absence of 
rotational symmetry and the interfitting relationship of the first and 
second die members, relative rotation therebetween is effectively 
controlled. 
The second die member 56 includes an integral sealing bar 60 which may 
project from the peripheral edge thereof in a generally parallel relation 
to the cutting bar 54. The sealing bar 60 may be formed by machining away 
portions of the second die member 56. Preferably, the second die member 56 
and the sealing bar are fabricated from the same easily machined thermally 
conductive material as the first die member. 
Turning now to FIG. 3, the second die member 56 includes an upper generally 
planar surface 62 which can be moved into contact with the generally 
planar surface 52 of the body portion 46. With the second die member 56 in 
surface contact with the first die member, the second die member 56 is in 
a heat receiving position where heat is conductively transferred thereto 
from the first die member. Thus, only a single source of heat, the 
cartridge heaters 49, is required for both the first and second die 
members. 
The body portion 46 (see FIG. 2) includes at least one, but preferably two, 
access openings 50 that extend therethrough and communicate with the 
bottom surface 52 in the recess. The second die member 56 is engaged by an 
operating means, such as the rods 64, 66 which project through the 
corresponding access openings 50 (FIG. 1). By providing two rods 64, 66, 
the second die member 56 is more easily controlled so as to be parallel to 
the surface 52. The operating means moves the second die member 56 
generally perpendicularly to the surface 52 between the heat receiving 
position and a heat sealing position. 
As seen in FIG. 3, the first die member may have a polytetrafluoroethylene 
sheet 68 connected thereto and extending across the plane defined by the 
cutting edge surface of the cutting bar 54. The polytetrafluoroethylene 
sheet is approximately 3 mils thick and provides a means for releasing the 
die assembly 28 from the polyethylene sheets 18, 20 at the end of a 
cutting and sealing cycle. 
Returning briefly to FIG. 1, it will be seen that the die assembly 28 is 
suspended below the housing of the actuating means 32 by a suitable 
support 70 which may comprise a bar. Moreover, the second die member 56 is 
also suspended and controlled from the actuating means by the rods 64, 66 
which extend through the access openings 50. 
The entire die assembly 28 may be moved by any conventional means between a 
remote position, as illustrated in FIG. 1, in which the sheets 18, 20 are 
positioned on the platen assembly 30 and a cutting sealing position in 
which the die assembly 28 and the platen assembly 30 cooperate to form an 
unstripped receptacle in the sheets 18, 20. One suitable conventional 
means is the double acting fluid pressure cylinder 72 schematically 
illustrated in FIG. 4. One end of the cylinder 72 is connected to a 
support 33 of the actuating means 32 and the other end is connected to the 
bar 70. With this operating arrangement, a bracket 74 is carried by the 
actuating rod 70 and is provided with a pair of guide openings 76. Each 
guide opening 76 slidably receives one of the actuating rods 64, 66. 
Vertically spaced from the first bracket 74 is a second bracket 78 which is 
suitably connected to each of the actuating rods 64, 66 of the second die 
member. The second bracket 78 has a guide opening 80 which slidably 
receives the shaft 70. In order to independently operate and control the 
second die member with respect to the first die member, one or more double 
acting fluid pressure cylinders 82 may be provided between and attached to 
the brackets 74, 78. 
It should be apparent that extension of the cylinder 72 will cause the 
entire die assembly 28 to move toward the cutting sealing position 
adjacent the platen assembly 30 whereas contraction of the cylinder 72 
will cause the die assembly 28 to move away from the platen assembly 30 to 
permit advancement of the polyethylene sheets. Similarly, extension of the 
power cylinders 82 will cause the second die member to move with respect 
to the first die member. 
The fabrication of an irregularly shaped receptacle from a pair of 
superposed sheets of polyethylene material will now be described in 
greater detail in connection with FIGS. 5, 6 and 7. When the polyethylene 
sheets 18, 20 (FIG. 5) are positioned in superposed relationship on the 
platen assembly 30, the power cylinder 72 (see FIG. 4) is actuated and the 
die assembly 28 is moved vertically downwardly to the heating sealing 
position (FIG. 6). At this time the polytetrafluoroethylene sheet 68 
contacts the uppermost polyethylene sheet 18. Heat is conducted from the 
body portion 46 to the cutting bar 54 and to the cutting edge surface 84. 
Typically the cutting edge surface 84 has a uniform width of about 1/32 
inch. 
While the second die member 56 is in the heat receiving position (FIG. 5), 
intimate contact between the generally planar surface 62 of the second die 
member 56 and the generally planar surface 52 of the body portion 46 
allows conductive heat transfer to occur. In this manner the second die 
member 56 is maintained at its operating temperature. 
After the cutting operation has begun, the second power fluid cylinders 82 
(FIG. 4) are actuated to advance the second die member 56 toward the 
polytetrafluoroethylene sheet 68 and the heat sealing position (FIG. 7) to 
provide an hermetic seal in the superposed sheets 18, 20. The hermetic 
seal is positioned closely adjacent to the cutline formed by the cutting 
edge surface 84. 
The sealing bar 60 has a sealing edge surface 86 with a generally uniform 
width approximately four times the width of the cutting edge surface 84, 
i.e., approximately 1/8 inch. With the second die member 56 in the heat 
sealing position (FIG. 7) both the first and second die members remain in 
contact with the polytetrafluoroethylene sheet 68 until the polyethylene 
sheets 18, 20 have been substantially cut and sealed. 
It will be seen in FIG. 7 that the cutting edge surface 84 has penetrated 
approximately 90% of the combined thickness of the polyethylene sheets 18, 
20. As the cutting edge surface 84 penetrates the polyethylene sheets, the 
polyethylene material recedes from the heated edge in an erratic manner 
and forms an imperfect seal. The hermetic seal is effected by the sealing 
edge surface 86 carried by the second die member 56. During sealing, the 
sealing edge surface 86 penetrates approximately 50% of the combined 
thickness of the sheets 18, 20. 
When the die assembly 28 is retracted from its final position (FIG. 5), the 
irregular receptacle defined by the cutting bar 54 is not stripped from 
the superposed sheets 18, 20 of polyethylene material. Accordingly, the 
receptacles and parent material may be readily wound on the roll 36 (see 
FIG. 1) for ease in further handling. 
The die assembly 28 illustrated in FIGS. 1 through 7 is but one of a 
multitude of irregular configurations which may be fabricated using the 
two piece die assembly of the present invention. More particularly, (FIG. 
8) a die assembly may be easily constructed for fabrication of a complexly 
contoured receptacle defined by the cutting edge surface 90 carried by a 
first die member 92. A second die member 94 with a correspondingly 
contoured perimeter and a sealing edge surface is vertically movable with 
respect to the first die member 92. 
Several characteristics of the types of irregular shapes which may be 
readily fashioned with the two piece die assembly of the present invention 
are depicted in FIG. 8. For example, acute angular junctions, illustrated 
at 96, between a bulbous curve 98 and generally straight portions 100, 102 
are easily made. In fact, it will be appreciated that virtually the only 
constraint on any desired cnfiguration is the ability to machine the 
cutting edge surface and the sealing edge surface. 
From FIGS. 5 and 6 it will be noted that when the second die member 56 is 
guided during advancement from the heat receiving position of FIG. 5 to 
the heat sealing position of FIG. 6 by the cooperation and close spacing 
between the peripheral edge 58 and the cutting bar 54. In this manner, the 
positioning of the cutting and sealing surface 84, 86 can be accurately 
controlled and only a minimal waste of material occurs. 
In addition, with the two part cutting and sealing die assembly of the 
present invention, indexing of the material sheets between successive 
operations is avoided. 
By using the die assembly of the present invention in combination with 
material advancing apparatus it is possible for a single operator to 
simultaneously oversee the operation of several machines. Quite obviously 
this results in a substantial reduction in the cost of labor during 
production of irregularly shaped objects. Moreover, a high level of 
dimensional precision as well as reproducible consistency between 
sequentially fabricated receptacles is attainable, in contrast to 
heretofore known apparatus. 
A particular advantage of the present invention is the provision of an 
hermetic seal positioned adjacent to the cut edge of the receptacle. The 
hermetic seal allows receptacles fabricated in accordance with the present 
invention to be used as containers for liquids without danger of leakage. 
Moreover, the use of heat to perform both the cutting and sealing 
operations provides a redundancy that improves reliability. 
It should now be apparent that there has been provided in accordance with 
the present invention a novel die assembly for use in the fabrication of 
irregularly shaped receptacles from heat sealable synthetic resinous 
materials. It will be apparent to those skilled in the art that numerous 
modifications, variations, substitutions and equivalents exist for 
features of the invention which do not depart from the scope of the 
invention. Accordingly, it is expressly intended that all such 
modifications, variations, substitutions and equivalents which fall within 
the spirit and scope of the invention as defined in the appended claims be 
embraced thereby.