Apparatus and method for heat-sealing a film cover to open ended containers

A film cover is heat-sealed to the open end of containers and cut from a film stock by a cam-actuated, orbitally moving knife blade which severs the film stock along a circumferential region closely adjacent the container's open end. A major extent of the orbital movement of the cam-actuated knife blade about the open-ended container is preferably substantially circular (to closely conform to the circular cross-sectional geometry of open-ended containers to be film-covered). However, a minor segment of the knife blade's orbital movement is cam-actuated so as to follow a segment of an arcuate non-circular (e.g., elliptical) path to form a protruding tab on the film cover so as to allow a consumer to more easily grasp and remove the same. The film is preferably continuously supplied to the sealing and cutting zone, while the waste web (i.e., the film remaining after the film cover has been cut from the film stock) is continuously retrieved from the sealig and cutting zone at substantially constant rates. Meanwhile, discrete sections of the film stock are sequentially indexed into the momentarily stopped within the zone to allow for sealing of the film cover to the open-ended container. During such momentary stoppages, a dancer roll assembly accommodates the continuous supply and retrieval of film stock and waste web to and from the sealing and treating zone, respectively.

FIELD OF INVENTION 
The present invention relates generally to packaging apparatus and methods. 
More specifically, the present invention relates to methods and apparatus 
which apply a film covering onto the open ends of containers of the type 
which are used to package edible products (e.g., dairy products and the 
like). 
BACKGROUND AND SUMMARY OF THE INVENTION 
Numerous edible products, such as dairy products (e.g., yogurt, ice cream, 
cottage cheese, and the like), are packaged for retail sales in open-ended 
containers which are closed by a resealable lid. Resealable lids have for 
many years been employed in the food-packaging industry as a means to 
ensure that the consumer is provided with sanitary, unadulterated edible 
products. However, due to several well publicized criminal events that 
involved the intentional adulteration of packaged products, there has been 
an increased effort to provide enhanced tamperproof and/or tamper-evident 
packaging to supplement the protection which is afforded by resealable 
lids alone. 
One proposal that has gained industry acceptance in terms of its enhanced 
tamperproof and/or tamper-evident functions is to heat-seal a film barrier 
of plastics material (preferably transparent) onto the upper 
circumferential edge of open-ended foodstuff containers. A resealable lid 
may then be placed onto the now film-sealed end of the container so that 
the lid/film seal collectively provide enhanced protection of the 
container contents. Moreover, a consumer may more easily be alerted to the 
possibility of the contents possibly being adulterated simply by visually 
inspecting the integrity of the film seal upon removal of the lid. If no 
visual evidence of film breakage, tearing or the like can be discerned, 
the consumer can have a greater level of confidence that the contained 
product will not have been illegally tampered with. 
As can be appreciated, the advent of film seals in conjunction with 
conventional resealable lids has presented the packaging industry with 
special problems in terms of economically mass producing product-filled 
containers having both a heat-sealed film barrier and a conventional 
resealable lid. For example, U.S. Pat. Nos. 3,838,550 and 4,065,908 each 
issued to Martin Mueller, disclose heat-sealing a generally rectangularly 
shaped film barrier to the upper edge of open ended containers. The 
rectangularly shaped film barriers are, according to the techniques of the 
'550 Patent, preferably cut along mutually orthogonal longitudinal and 
latitudinal lines from a continuous web of film material. Once heat-sealed 
to the upper edge of the container, the four corners of the film extend 
below the upper container edge (see FIG. 1 in each of the '550 and '908 
Patents) so as to provide gripping mechanisms which allow a consumer to 
more easily remove the film seal when access to the product contents is 
desired. 
While the techniques disclosed in the '550 and '908 Patents certainly 
provide a measure of enhanced tamperproof and/or tamper-evident 
characteristics to the container, there are some improvements that could 
be made. For example, the rectangular configuration of the film 
necessarily forms four corners which, when applied to a generally 
cylindrical or slightly conical container, are each visible below the 
resealable lid (e.g., as shown in FIG. 1 in the '908 Patent). Visibility 
of the four corners on the exterior of the container may not always be 
aesthetically desirable and thus may detract from a consumer selecting a 
particular manufacturer's product in favor of a competitor's product. 
One more aesthetically acceptable solution that has been proposed is to 
provide the film seal with a single tab element as represented by U.S. 
Pat. No. 4,176,507 to Derek V. Mancini. According to the technique 
disclosed in the '507 Patent, a preformed "daisy-chain" series of tabbed 
lids are fed to a heat-sealing station, where they are momentarily 
positioned in registry with an open end of a container (e.g., a 
single-serve condiment container), heat-sealed to the container end, and 
then severed from the adjacent tabbed lid. The resulting film-sealed 
container thus has an integral single tab which provides a consumer with a 
means to grip and remove the film so as to enjoy the contents of the 
container. 
The technique disclosed in the '507 Patent, however, necessarily depends 
upon the formation and supply of an especially configured "daisy-chain" 
series of tabbed film lids. Thus, an especially adapted upstream 
fabrication apparatus which forms the series of such "daisy-chain" series 
of tabbed film lids from stock film sheets is needed, thereby increasing 
production costs. 
It would therefore be highly desirable if standard film stock could be 
employed during packaging operations so as to produce economically 
product-filled containers with a heat-sealed barrier film cover having an 
integral pull tab. It is towards providing such a technique that the 
present invention is directed. 
According to the present invention, methods and apparatus are provided for 
applying tamper-evident film seals onto the open ends of containers using 
a continuously advancing film stock. More particularly, the present 
invention provides packaging methods and apparatus which simultaneously 
heat-seals a film to a container and then circumferentially cuts the film 
around the container's upper edge. As a result, the perimeter of the 
heat-sealed film closely conforms to the circumferential geometry of the 
open container end. 
The circumferential cut is performed using a cam-articulated orbiting 
cutting blade. The orbital path of the cutting blade around the 
circumference of the container's upper edge (i.e., an orbit about the 
longutidinal central axis of the container) is controlled by a camming 
mechanism which preferably forms a generally elliptical protrusion near 
the end of the blade's orbit. This protrusion thus forms a convenient pull 
tab for the tamper-evident film which more easily permits a consumer to 
access the container's contents. 
The film stock is advanced into registry with the containers using a novel 
film-advancing system according to the present invention. In this regard, 
the film stock is supplied to a heat-sealing station by means of a 
continuously driven supply roll. On the other hand, the waste film (e.g., 
the webbing that remains after removal of the tamper-evident film seals) 
is taken up by means of a continuously driven take-up roll. 
Discrete sections of the supplied film stock are synchronously indexed with 
an advancing group of containers by means of a dancer roll system which 
serves as a mechanical buffer between the continuously advancing film 
stock from the supply roll and the continuously retreating waste web onto 
the take-up roll. That is, the continuously advancing film stock is 
temporarily accommodated by means of a substantially horizontally moving 
supply dancer roll which essentially allows the advancing film to 
accumulate. At the same time, however, previously accumulated waste film 
webbing is continuously being paid-out at the same rate by means of a 
substantially horizontally moving discharge dancer roll. The net effect of 
these dancer rolls is to allow a length of film stock therebetween to be 
stopped momentarily in a registered positioned above a stationary set of 
open containers that have been indexed into position. During this 
momentary stoppage, the heat sealing and film-cutting functions can be 
accomplished, after which the now heat-sealed containers are advanced and 
the cycle repeats itself. 
Thus, the present invention provides economical techniques for providing 
open-ended product-filled containers with heat-sealed film covers that are 
well suited for implementation on a mass production scale. Further aspects 
and advantages of this invention will, however, become more clear after 
careful consideration is given to the detailed description of the 
preferred exemplary embodiments which follow.

DETAILED DESCRIPTION OF THE PREFERRED EXEMPLARY EMBODIMENTS 
A preferred embodiment of the apparatus 10 according to the present 
invention is depicted in accompanying FIGS. 1 and 2. AS is seen 
particularly from accompanying FIG. 1, the apparatus 10 is generally 
comprised of a frame 12 which itself may be supported vertically above the 
ground in operative relationship to a conveyor C by any suitable rigid 
structural supports (not shown). 
The apparatus 10 necessarily includes a supply roll SR and take-up roll TR 
for respectively supplying film stock to, and taking-up waste film web 
from, the sealing and cutting zone SCZ (see FIG. 2). The supply and 
take-up rolls SR, TR are journally supported at a terminal end between 
paired roll support arms 14, 16, respectively. The proximal ends of the 
support arms 14, 16 are, in turn, pivotally coupled to an upper support 
block 18 so as to allow the arm pairs 14, 16 to pivot as the diameter of 
the film which is rolled upon the supply roll SR and take-up roll TR 
respectively decreases and increases as shown in phantom line in FIG. 1. 
The lower end of the frame 12 journally supports a transverse indexing 
shaft 20 (see FIG. 2) which includes an indexing sprocket 22 at its 
terminal end engaged with an endless drive chain 24 as can be seen more 
clearly in FIG. 1. 
As can also be observed in FIG. 1, the endless drive chain 24 is 
operatively coupled to a set of rollers 30a-30d associated with the film 
supply side of the apparatus 10, and a set of rollers 32a-32d associated 
with the waste web take-up side of the apparatus 10. The rollers 30a-30d 
and 32a-32d each transversely extends in the cross-machine direction 
(i.e., perpendicular relative to the conveyance direction --arrow P5 in 
FIG. 1 --of the conveyor C). 
The rollers 30a, 32a are journally supported by the frame 12 and are each 
respectively in contact with the circumferential surface of the film stock 
and waste web which is wound upon the supply and take-up rollers SR and 
TR. Driven motivation to rotate the rollers 30a, 32a in a counterclockwise 
direction may be supplied an output shaft (not shown) associated with the 
gear box 31 which receives its drive power from a motor M (see FIG. 2). 
Thus, since continuous driven motivation is supplied to each of the 
rollers 30a, 32a, this continuous driven motivation will be transferred to 
the rollers 30b, 32b by means of the endless drive chain 24 being 
intermeshed with their respective roller sprockets 30b', 32b'. 
The shaft 20 is coupled to a mechanical indexer 33 as shown in FIG. 2 which 
operates periodically in a timed relationship to be described below to 
cause a fresh section of film stock FS to be advanced into the sealing and 
cutting zone SCZ. Thus, during the operation of the indexer 33, the 
rollers 30d, 32d will each be incrementally rotated due to their being 
operatively coupled by endless drive chain 24 to the indexing sprocket 22 
of shaft 20 via sprockets 30d', 32d', respectively, and idler sprockets 
30e', 32e'. Driven motivation for the indexer 33 is provided by power 
take-off shafts 20a, 20b coupled to the output drive of motor M via gear 
boxes GB1 and GB2. 
The contact between the continuously rotating rollers 30a, 32a and the 
supply and take-up rolls SR and TR, respectively, will cause the latter to 
rotate in a clockwise direction as viewed in FIG. 1. As a result, the 
rollers 30a, 32a provide an indirect drive for the rolls SR and TR, 
respectively, so as to continuously unwind the film stock from the roll SR 
and continuously wind the waste film web onto the roll TR. Of course, when 
the supply of film stock on roll SR is exhausted, the operation of 
apparatus 10 must temporarily be suspended so that the exhausted supply 
roll SR can be interchanged with a replenished supply roll SR having a 
fresh supply of film stock may be provided. At that time, an empty take-up 
roll TR may also interchanged for the take-up roll TR having its full 
complement of waste web wound thereon. A quick-change fitting 35 (see FIG. 
2) is most preferably provided for each of the supply and take-up rolls SR 
and TR, respectively. 
The vertically paired rollers 30b, 30d and 32b, 32d are each stationary and 
journally coupled to the frame 12, respectively. The roller pairs 30b, 30d 
and 32b, 32d thus serve as guide rollers for the supply dancer roller 30c 
and take-up dancer roller 32c, respectively. The supply and take-up dancer 
rollers 30c and 32c, respectively, are each pendulously supported at the 
terminal ends of arm pairs 34, 36, respectively (only one arm of each arm 
pair 34 and 36 being seen in FIG. 1) so as to allow the arms 34, 36 to 
pivotally move relative to the frame 12 (arrows P1 and P2 in FIG. 1) 
which, in turn, responsively causes the rollers 30c and 30c to move 
reciprocally in forwardly and rearwardly directions substantially 
horizontally parallel (arrows P3 and P4 in FIG. 1) to the travel direction 
of the conveyor C (arrow P5 in FIG. 1). Synchronous pendulous movement of 
the arms 34, 36 (and hence the rollers 30c, 32c, respectively) is provided 
by a rigid tie rod 38 which is pivotally coupled at each of its ends to 
the arms 34 and 36, respectively. 
The length of the arms 34 and 36 is such that the movement of the dancer 
rollers 30c, 32c is along a very shallow arc so as to substantially be 
rectilinear between their travel extents. Thus, although the dancer 
rollers 30c, 32c are shown as being supported for pendulous movement, they 
could likewise be supported in a functionally equivalent manner by 
providing a slide rail assembly 38a'which supports a tie rod 38' connected 
at each of its ends to the rollers 30c, 32c for reciprocal rectilinear 
movements (see the double dash line representation thereof in FIG. 1). In 
both structural arrangements described above, however, the dancer rollers 
30c, 32c move in concert with one another due to the the mechanical 
interconnection provided by the tie rod. 
The rollers 30b-30d constitute the dancer roll assembly associated with the 
film supply side of the apparatus 10, whereas the roller 32b-32d 
constitute the dancer roll assembly associated with the waste web take-up 
side of the apparatus 10, the purpose and function of which will become 
evident from the discussion which follows. Suffice it to say here, 
however, that since the rollers 30b, 32b are each being continuously 
rotated, whereas the rollers 30d, 32d are each intermittently rotated 
during operation of the indexer 33 as described above, the dancer rolls 
30c, 32c, due to their simultaneous reciprocal motions, will serve as a 
mechanical buffer or lost motion assembly for the endless chain 24 and the 
film stock FS. As a result, the film stock FS is allowed to momentarily 
stop within the sealing and cutting zone SCZ. 
The idler sprockets 30e' and 32e' serve to guide the endless chain 24 to 
and from the driven indexing sprocket 22 associated with the indexing 
shaft 20. The drive chain 24 is further intermeshed with a tensioning 
sprocket 40 located substantially centrally between and below the 
sprockets 30a' and 32a'. The tension sprocket 40 may be selectively 
adjusted so that the proper tension is maintained on the endless chain 24. 
The path of the film after being unwound from the supply roll SR is hidden 
in FIG. 1 due to the presence of the frame 12. However, the path follows 
generally that taken by the drive chain 24 around the rollers 30a-30d on 
the opposite (hidden) side of the frame 12. Similarly the path taken by 
the waste web on the take-up side of the apparatus 10 generally follows 
that taken by the drive chain 24 around the rollers 32d-32a. Thus, a 
linear section of the film stock is tensioned between the roller 30d on 
the one hand and roller 32d on the other hand within the sealing and 
cutting zone SCZ. 
The sealing and cutting zone SCZ is essentially comprised of one or more 
sealing and cutting assemblies. In the embodiment shown in FIGS. 1 and 2 a 
pair of side-by-side sealing and cutting assemblies 50, 52 are depicted 
since the apparatus 10 shown in the accompanying FIGURES is especially 
adapted to sealing and cutting a film stock simultaneously with respect to 
a pair of containers C1 and C2 being conveyed on the conveyor C. However, 
it should be recognized that the principals of the present invention could 
similarly be embodied in apparatus using a single sealing and cutting 
assembly, or a greater number of sealing and cutting assemblies than are 
depicted in the accompanying FIGURES. 
When a number of sealing and cutting assemblies are provided, they each 
preferably operate substantially simultaneously so that a corresponding 
number of containers may simultaneously be provided with a heat-sealed 
film cover. However, for purposes of discussion and clarity of 
understanding, the sealing and cutting assembly 50 is depicted in FIG. 2 
in a "ready" state, whereas the sealing and cutting assembly 52 is 
depicted in an "operational" state. 
The sealing and cutting assemblies 50, 52 include a heat-sealing head 50a, 
52a, each of which is sized and configured to conform to the circumference 
of the upper edge of the containers C1 and C2, respectively. The 
heat-sealing heads 50a, 52a are heated by any suitable means (e.g., 
electrical resistance heaters) so as to cause a circumferential portion of 
the film stock FS in registry with the upper edge defining the open end of 
the containers C1 and C2 to be at least partially plasticized. As a 
result, the circumferential regions of the film stock are heat-sealed to 
the upper edge of the containers C1 and C2. Since heat-sealing of plastics 
film is in and of itself well known, further discussion as to the manner 
in which the film adheres to the upper circumferential edge of the 
containers C1 and C2 is believed unnecessary for a full understanding of 
this invention by those skilled in the plastics film heat-sealing art. 
The sealing and cutting assemblies 50, 52 also include respective cutting 
subassemblies 50b, 52b. These cutting subassemblies are, in turn, 
comprised of a rotatable drive plate 50b.sub.1 52b.sub.1 which dependently 
carries a radially opposed pair of blade-holders 50b.sub.2, 52b.sub.2 
holding respective knife blades 50b.sub.3, 52b.sub.3. The drive plates 
50b.sub.1, 52b.sub.2 are coupled to sleeve shafts 50b.sub.4, 52b.sub.4 
which, in turn, are splined via gears 50b.sub.5, 52b.sub.5, respectively, 
to pinion gear 54. The pinion gear 54 is operatively coupled to a pulley 
54a on a shaft 54b. Drive belts 56 connect the continuously rotating 
output pulley 56a (associated with a power take-off shaft 56b of gear box 
31) to the pulley 54a so as to, in turn, continuously drive the pinion 
gear 54. In such a manner, constant rotational motion is imparted to the 
plates 50b.sub.1, 52b.sub.1 to thereby cause the knife holders 50b.sub. 2, 
52b.sub.2 and their respective knife blades 50b.sub.3, 52b.sub.3 to orbit 
continuously the circumference of the cups C1 and C2, respectively. 
The knife holders 50b.sub.2, 52b.sub.2 are mounted to the plates 50b.sub.1, 
52b.sub.1 so as to be reciprocally radially displaceable towards and away 
from the longitudinal axis of the shafts 50b.sub.4, 52b.sub.4, 
respectively. The upper ends of the knife holders 50b.sub.2, 52b.sub.2 are 
respectively positioned within an endless race (not shown) defined by the 
cam plates 50b.sub.6, 52b.sub.6. The cam plates 50b.sub.6, 52b.sub.6, are 
respectively coupled to the shafts 50b.sub.4, 52b.sub.4 so as to be 
stationary relative to the orbital movements of the knife holders 
50b.sub.2, 52b.sub.2 as was described previously. 
The races defined in the cam plates 50b.sub.6, 52b.sub.6 are such that the 
upper end of the knife holders 50b.sub.2, 52b.sub.2 follow a substantially 
circular orbit to responsively cause their respective knife blades 
50b.sub.3, 52b.sub.3 to orbit circularly adjacent the upper edges of the 
containers C1 and C2, respectively. However, a minor portion of the race 
is preferably comprised of a non-circular (e.g., elliptical) segment so 
that the knife holders 50b.sub.2, 52b.sub.2 will follow a corresponding 
non-circular (e.g., elliptical) segment during their orbit. As a result of 
this non-circular (e.g., elliptical) segment being defined in the race, 
the knife blades 50b.sub.3, 52b.sub.3 will cut a non-circular (e.g., 
elliptical) tab from the film stock FS which extends outwardly from the 
upper edge of the containers C1 and C2, respectively. Thus, the tab that 
results provides a convenient member which a consumer may grip to more 
easily remove the film cover when access to the container contents is 
desired. 
As mentioned briefly above, the sealing and cutting assemblies 50, 52 are 
respectively shown in "ready" and "operational" states. The difference 
between these states is that in the former, the sealing and cutting 
assembly is raised relative to the film stock FS, whereas in the latter, 
the sealing and cutting assembly is lowered into operative engagement with 
the film stock FS. Raising and lowering of the sealing and cutting 
assemblies 50, 52 is accomplished by means of pneumatically controlled 
loaded air cylinder actuators 50b.sub.7, 52b.sub.7, as well as main 
pneumatic actuators 50b.sub.8, 52b.sub.8. 
Compression springs 50b.sub.9, 52b.sub.9 serve to ensure that the cam 
plates 50b.sub.6, 52b.sub.6 are properly positioned relative to the knife 
holders 50b.sub.2, 52b.sub.2 of the plates 50b.sub.1, 52b.sub.1 so that 
the upper ends of the knife holders 50b.sub.2, 52b.sub.2 reliably follow 
the race defined in the cam plates 50b.sub.6, 52b.sub.6. Furthermore, the 
compression springs 50b.sub.9, 52b.sub.9 allow the cam plates 50b.sub.6, 
52b.sub.6 to be moved vertically relative to their associated plates 
50b.sub.1, 52b.sub.1 to permit positional adjustment and/or replacement of 
the knife holders 50b.sub.2, 52b.sub.2 and their associated knife blades 
50b.sub.3, 52b.sub.3. 
As mentioned briefly above, the knife blades 50b.sub.3, 52b.sub.3 
continuously orbit relative to the longitudinal axes of the sealing and 
cutting assemblies 50b, 52b, respectively. Therefore, operation of the 
actuators 50b.sub.7, 52b.sub.7 and 50b.sub.8, 52b.sub.8 is controllably 
timed by any suitable pneumatic control system well known to those skilled 
in the art. In this regard, the assemblies 50b, 52b are controllably moved 
between their "ready" state (i.e., when the film stock FS is not capable 
of being cut by the orbiting knife blades 50b.sub.3, 52b.sub.3) and their 
"operational" state (i.e., when cutting of the film stock FS occurs due to 
the orbiting knife blades 50b.sub.3, 52b.sub.3) synchronously with 
movement of the containers C1 and C2 into registry therewith. 
The operation of the apparatus 10 as described above, particularly the 
manner in which the film stock FS is supplied and taken-up from the 
sealing and cutting zone SCZ will be described with reference to the 
accompanying FIGS. 3a-3c. It will, of course, be understood that FIGS. 
3a-3c depict the apparatus 10 schematically and, moreover, show only 
sealing and cutting assembly 50 for ease of discussion. Sealing and 
cutting assembly 52 (or any other sealing and cutting assembly that may be 
provided with the apparatus) would thus function in a manner similar to 
that described below with reference to sealing and cutting assembly 50. 
Accompanying FIG. 3a depicts the apparatus 10 in a state whereby a 
container C1 has been conveyed via the conveyor C (not shown in FIGS. 
3a-3c, but see FIGS. 1 and 2) so that its upper open end is in registry 
with the sealing and cutting assembly 50. In this connection, the conveyor 
C is preferably driven by its own indexing system which is controllably 
synchronized with the operation of the apparatus 10 according to this 
invention to ensure that containers will be sequentially advanced into the 
sealing and cutting zone in timed relationship to the operation of the 
sealing and cutting assembly 50. 
The container C1 rests upon a pneumatically actuated container support CS1 
(a similar container support CS2 being provided for container C2, see FIG. 
2) which is movable vertically between a retracted position as shown in 
FIG. 3a (i.e., so that the upper edge of container C1 is spaced from the 
film stock in the sealing and cutting zone CSZ) to an extended position as 
shown in FIG. 3b (i.e., so that the upper edge of container C1 is in 
contact with the film stock in the sealing and cutting zone SCZ --see 
also, the phantom line representation for cup C2 in FIG. 2). 
At the time the cup C1 is advanced into registry with the sealing and 
cutting assembly 50 (i.e., by an indexing mechanism associated with the 
conveyor C), a fresh length of film stock FS will have been advanced by 
means of the driven indexer 33 coupled operatively to the endless chain 24 
via the sprocket 22 (see FIG. 2). Thus, as was described previously, the 
rollers 30d, 32d will each be rotated counterclockwise (in the direction 
viewed in FIG. 3a) during the time that the indexer 33 operates thereby 
advancing a fresh section of the film stock FS into the sealing and 
cutting zone SCZ. 
It will be remembered that the rollers 30a, 32a and 30b, 32b are 
continuously being rotated in a counterclockwise direction. As a result, 
the film stock FS is continuously being paid out from the supply wound 
upon the supply roll SR, whereas the waste web WW is continuously being 
taken up by the take-up roll TR. However, the film stock FS in the sealing 
and cutting zone SCZ (i.e., between the rollers 30d, 32d) is momentarily 
stationary to allow heat-sealing and cutting by means of the sealing and 
cutting assembly 50. To accomplish this, the dancer rolls 30c, 32c will 
begin simultaneously to move substantially horizontally in a rightward 
direction as viewed in FIG. 3a due to the accumulated amount of waste web 
being drivenly taken-up by the take-up roll TR. The take-up dancer roll 
32c is thus responsively moved rightwardly as viewed in FIG. 3a. While 
this is occurring, the fresh film stock FS is being continuously supplied 
to the feed dancer roll 30c. However, since the feed dancer roll 30c is 
slaved to the take-up dancer roll 32c during this phase of the operation, 
the fresh film stock is accumulated by movement of the feed dancer roll 
30c in a rightward direction as viewed in FIG. 3c. 
With a fresh section of film stock FS in registry with the upper edge of 
the container C1, the container support CS1 is actuated so as to move the 
upper end of the container C1 up to the film line. The sealing and cutting 
assembly 50 is then lowered into an operational state as shown in FIG. 3b. 
In this connection, the movement of the cup upwardly toward the film line 
occurs just prior to movement of the sealing and cutting assembly 50 so as 
to provide support for the film when the heat sealing head 50a is moved 
into contact with the film. As a result, the film is prevented from bowing 
and/or stretching under the weight of the heat sealing head 50a. 
It will be observed, for example, in FIG. 2, that the knife blades 
50b.sub.3 are vertically raised relative to the heat sealing head 50a when 
the sealing and cutting head 50 is in a "ready" state but are extended 
below the bottom edge of the heat sealing head 50a when in an 
"operational" state so as to cut the film stock FS. Thus, when the sealing 
and cutting head 50 is lowered, the actuators 50b.sub.7, 50b.sub.8 will 
respectively cause the heat sealing head 50a and the knife blades 
50b.sub.3 to be lowered substantially concurrently until the the heat 
sealing head 50a comes into pressing contact with the film stock FS 
against the upper edge of the raised container C1. At this time, the 
actuator 50b.sub.7 maintains the pressure of the heat sealing head 50a 
against the upper edge of the container C1 so as to positionally restrain 
the film stock. Meanwhile, the knife blades 50b.sub.3 continue to be 
lowered by the actuator 50b.sub.8 (i.e., by lowering the plates 50b and 
50b.sub.6) until they penetrate through the film stock FS. 
Since the knife blades 50b.sub.3 continuously orbit in the manner described 
above, the film will begin to be cut closely adjacent to the circumference 
of the open end of container C1. Thus, the sealing and cutting assembly 50 
is maintained in its "operational" state as shown in FIG. 3b (i.e,. due to 
controllably timing the functioning of the actuators 50b.sub.7 and 
50b.sub.8) for a time such that each of the blades 50b.sub.3 travels at 
least one-half the circumferential distance around the container C1 so as 
to ensure a complete orbital severance of the now heat-sealed film cover 
from the remaining waste web WW. 
It will be appreciated that during the operation described above with 
reference to FIG. 3b, the feed and take-up dancer rolls 30c, 32c, 
respectively, continue to move rightwardly due to the continuously driven 
paying-out of fresh film stock FS at the supply roll SR and the continuous 
driven retrieval of the waste web WW at the take-up roll TR. Thus, at the 
time when heat-sealing and cutting is finished such that the sealing and 
cutting assembly 50 is returned to its "ready" state, the dancer rolls 
30c, 32c will have traveled to their rightwardmost extent. Such a state 
during the operation is depicted in accompanying FIG. 3c. 
At this time, the indexer 33 is operated at a rate faster than the rate 
which film stock is being paid out at the supply roll SR and being 
retrieved at the take-up roll TR. This operational rate difference results 
in the feed dancer roll 30c being moved leftwardly, which then slaves the 
take-up dancer roll 32c (due to the interconnection therebetween via tie 
rod 38) so that it likewise moves leftwardly. The differential rate of 
movement of the feed stock FS by virtue of the indexer 33 thereby causes 
the film stock FS accumulated by means of the feed dancer roll assembly 
30b-30d to be diminished, while simultaneously allowing the waste web WW 
to be accumulated by means of the take-up dancer roll assembly 32b-32d. 
The indexer 33 operates until the feed dancer roll 30c has moved to its 
leftwardmost extent as viewed in FIG. 3a, whereby the film stock FS that 
had been accumulated within the supply dancer roll assembly 30b-30d is 
substantially completely paid out, but the waste web WW that is 
accumulated within the take-up dancer roll assembly 32b-32d is 
substantially at a maximum. At this time, the indexer 33 stops the shaft 
20 thereby again momentarily stopping advancement of the film stock within 
the sealing and cutting zone. As a result, the apparatus 10 returns to the 
state of operation depicted in FIG. 3a, at which time the cycle described 
above repeats. 
Although the heat sealing and cutting assembly 50 has been shown and 
described above in connection with structures which enable substantially 
simultaneous heat-sealing of a film cover to an upper edge of a container 
and cutting of the cover from the film stock, the structures and functions 
attributable to the heat-sealing head 50a and the cutting assembly 50b 
could, however, be separated. That is, it is entirely conceivable (and 
within the scope of this invention) to provide the heat sealing head at a 
heat sealing station upstream of the cutting assembly positioned at a 
cutting station within the sealing and cutting zone SCZ. In such a case, 
the conveyor C would be controllably indexed by any suitable control 
scheme so that the containers are sequentially moved into position at each 
of the sealing and cutting stations during the momentary stoppage of the 
film stock FS within the sealing and cutting zone SCZ. 
It will thus now be appreciated that the present invention provides several 
advantages in terms of flexibility during manufacture of filled containers 
to provide a heat-sealed film cover. That is, the cam plates can easily be 
exchanged quickly so that different container sizes can be accommodated 
without significant modification occurring to the apparatus. In addition, 
the individual knife blades can easily be exchanged when dulled after 
repeated cutting operations. Furthermore, the dancer roll assemblies 
allows substantially constant tension to be maintained on the film stock 
while, at the same time, permitting smooth momentary stoppages of a film 
stock section in registry with the next containers to be heat-sealed. 
Therefore, while the invention has been described in connection with what 
is presently considered to be the most practical and preferred embodiment, 
it is to be understood that the invention is not to be limited to the 
disclosed embodiment, but on the contrary, is intended to cover various 
modifications and equivalent arrangements included within the spirit and 
scope of the appended claims.