Method and apparatus for heat shrinking film around a product

An apparatus for heat shrinking an envelope of heat shrinkable film into close conformity to a product enclosed within the film envelope includes a housing; a first assembly disposed within the housing for directed heated air to at least a first portion of the film envelope; a second assembly disposed with the housing and operable subsequent to the first assembly for directing heated water onto at least a second portion of the envelope, both causing the envelope to shrink into conformity with the product; an arrangement for drying the product after water has been applied thereto; and an arrangement for circulating the hot water into heat transfer relation with a moving stream of the hot air for enhanced water heating prior to its application to the product.

BACKGROUND OF THE INVENTION 
The present invention relates generally to methods and apparatus for heat 
shrinking an envelope of heat shrinkable film into close conformity with a 
product and more particularly to a method and apparatus using hot air and 
hot water in combination as the shrinking medium to shrink the film. 
It is well known to employ various flexible, heat shrinkable sheet 
materials for packaging products, including food products. These heat 
shrinkable materials provide an inexpensive, substantially airtight 
package which will prevent contamination of the product when properly heat 
sealed and which will maintain perishable items in a state of freshness 
for a relatively long period of time. In addition, these films enhance the 
appearance of the product and conform to the contours of the product due 
to their transparency and shrinking characteristics respectively. 
Typically, chicken pieces and other refrigerated meat items are packaged 
for sale to the public in heat shrinkable wrappers. 
Heretofore, these packages were wrapped with heat shrinkable film with the 
film being caused to shrink in so-called "shrink-tunnels" wherein hot air 
is applied to the package, causing the film to shrink therearound. 
However, problems with this method have arisen when packaging cold food 
products since once the film contacts the cold food, shrinking stops even 
in the presence of hot moving air. The result is a package which may or 
may not be sealed properly and which presents an unsightly appearance. 
Other methods of heat shrinking film around a product include subjecting 
the product package to immersion in a water bath or passage through a 
water curtain. This substantial application of water is enough to overcome 
the problem of the film ceasing to shrink when contacting the cold food 
product. However, a relatively large amount of energy is required to 
initially heat the water and maintain the necessary temperature to provide 
proper shrink wrapping of a product. It is therefore desirable to provide 
a heat shrinking apparatus which will more efficiently heat shrink 
wrappers around cold products. 
SUMMARY OF THE INVENTION 
It is accordingly an object of the present invention to provide a heat 
shrinking apparatus which solves the aforementioned problems by using hot 
air and hot water in combination as the film shrinking medium. More 
particularly, it is an object of the present invention to provide an 
apparatus for heat shrinking an envelope of heat shrinkable film around a 
chilled food product which uses hot water to cause shrinking of portions 
of the film envelope adjacent the chilled food product and uses hot air to 
cause the remainder of film shrinking. A further object is to improve 
efficiency of the heat shrinking apparatus by recirculating a portion of 
the hot water into the hot air stream for supplemental heating thereof. 
Briefly summarized, the present invention basically provides an apparatus 
and method for heat shrinking an envelope of heat shrinkable film into 
close conformity to a product enclosed within the film envelope by 
subjecting at least a first portion of the film envelope to heated air 
from a first heated air directing assembly for causing that portion of the 
film envelope to shrink into conformity with an adjacent first portion of 
the product and by subjecting at least a second portion of the envelope to 
heated water from a second, heated water directing assembly for causing at 
least the second portion of the envelope to shrink into conformity with an 
adjacent second portion of the product. The first directing assembly is 
disposed at a first shrinking station and the second directing assembly is 
disposed at a second shrinking station and the apparatus further includes 
an assembly, preferably an endless conveyor, for conveying the package 
from the first shrinking station to the second shrinking station. 
According to the present invention, the heated air is at a greater 
temperature than the heated water and an arrangement is included for 
circulating the heated water into heat transfer relation with the heated 
air for using the heated air to increase the temperature of the heated 
water prior to application thereof to the film envelope. It is preferred 
that the circulating arrangement includes a hot water coil in 
communication with the heated water supply reservoir and an apparatus for 
circulating heated water to the coil, the coil being arranged in heat 
transfer relation with the first directing assembly for flow of the heated 
air across the coil for the transfer of heat from the heated air to the 
heated water. 
It is preferred that the heat shrink apparatus of the present invention 
further includes a third assembly disposed within the housing and operable 
subsequent to the second assembly for directing heated air onto the 
envelope for drying the envelope after the application thereto of heated 
water by the second directing assembly. 
Preferably the first directing assembly includes an arrangement disposed 
beneath the conveyor for directing the heated air against a bottom portion 
of the envelope to shrink the envelope bottom portion into conformity with 
an underside of the product and the second directing assembly includes an 
arrangement disposed above the conveyor for directing the heated water 
against a top portion of the envelope to shrink the envelope top portion 
into conformity with a top side of the product. 
According to the preferred embodiment of the present invention, the product 
is a chilled food product of a non-uniform shape supported in an open top 
tray and the first directing assembly is disposed for directing the heated 
air against a bottom portion of the envelope adjacent the tray and the 
second directing assembly is disposed for directing the heated water 
against a top portion of the envelope adjacent the chilled food product. 
Here, the second directing assembly is operable subsequently to the first 
directing assembly. 
It is further preferred that the second directing assembly include a spray 
arrangement for directing a spray of water at the product. The spray 
arrangement is controlled to direct the spray of heated water in an amount 
just sufficient to complete the shrinkage of the film envelope into close 
conformity with the product.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to FIG. 1, an apparatus for heat shrinking an envelope of 
heat shrinkable film into close conformity to a product enclosed within 
the film envelope is shown generally at 10. In the preferred embodiment of 
the present invention, the apparatus 10 is particularly suited to 
shrinking film around a chilled food product disposed in an open-topped 
tray. However, those persons skilled in the art will recognize that the 
present invention is not limited to use with food products. 
The apparatus basically includes a housing 12 configured for an upright 
floor standing disposition. The housing 12 primarily consists of a frame 
14 having a plurality of spaced apart, upright frame members 18 
interconnected by cross members 16 which extend laterally between the 
upright frame members 18 forming a generally cage-like structure. A 
plurality of foot members 22 project outwardly from the lowermost portions 
of the upright frame members 18 providing a surface upon which the 
apparatus 10 can rest. The frame 14 has a plurality of generally 
rectangular, planar wall panels 20 covering the skeletal frame 14, the 
panels 20 being attached to the frame members 16,18, thereby enclosing the 
structure and forming the housing 12. 
The frame 12 is basically divided into two operationally defined portions, 
a hot air treatment portion 24 and a hot water treatment portion 26, each 
portion 24,26 comprising approximately one half of the entire apparatus 10 
and being arranged in a side-by-side relation. The housing 12 includes 
rectangular hood 30 defining a first tunnel 30' through which a product 
may pass for hot air shrink wrap treatment. A first heating station is 
defined by the hot air treatment portion 24 of the apparatus 10. 
A second heating station is defined by the hot water treatment portion 26 
of the housing 12 which includes a second generally rectangular hood 32 
defining a second tunnel 32' aligned with the first tunnel 30' through 
which a product may pass for hot water treatment. 
In order to transport the product to be shrink wrapped through the 
apparatus 10, a pair of conveyors are provided. The first conveyor 34, 
which is shown in broken lines in FIG. 1, extends lengthwise through the 
hot air treatment portion 24 of the housing 12 and is disposed immediately 
below the first tunnel 30'. The first conveyor 34 is preferably in the 
form of an endless open-work link or belt loop member 35 trained around 
two guide rollers 36, one of which is driven, the loop member 35 thereby 
having sufficient openings formed therein over its length and width for 
generally unrestricted flow of air therethrough. Alternatively, the 
conveyor 34 may be formed by a series of spaced rollers providing openings 
through which hot air may pass, as will be described in greater detail 
hereinafter. The second conveyor 38 extends lengthwise through the hot 
water treatment portion 26 of the housing 12 and is disposed immediately 
below the second tunnel 32'. The second conveyor 38 is disposed adjacent 
the end of the first conveyor 34 so that a product traveling on the first 
conveyor 34 will be picked up and transported by the second conveyor 38 
when it reaches the junction of the two conveyors 34,38. The second 
conveyor 38 is configured similarly to the first conveyor 34 and is driven 
by a drive belt or chain 39 which extends between the drive roller 37 and 
a drive motor 40 which is mounted to the frame 14. 
In order to effect efficient heat shrinkage of the heat shrinkable film 
surrounding a product, a two stage heat shrinking process is provided by 
the apparatus 10 of the present invention. Specifically, the hot air 
treatment portion 24 contains an arrangement for directing heated air to 
at least a portion of the film envelope and comprises a first shrinking 
station. The hot water treatment portion 26 contains an assembly for 
directing hot water to at least the remaining portion of the film envelope 
and comprises a second shrinking station. 
With regard to the hot air treatment portion 24, a heater 42 is disposed 
within the housing 12 across which air is forced by a fan 44 which is also 
disposed within the housing 12. The heater 42 is typically a fifteen 
kilowatt electric heater providing heated air at a temperature of 
approximately 300.degree. F. The heated air is routed to a variety of 
locations for a variety of purposes. Hot air is routed through a conduit 
or ductwork system 48 disposed within the lower portion of the hot air 
treatment portion 24 of the housing 12, shown schematically by broken 
lines in FIG. 1, to a plurality of nozzles 49 which are disposed 
underneath the upper run of the first conveyor 34 for application of hot 
air to the underside of the product as the first conveyor 34 carries it 
over the nozzles 49. As previously stated, openings are formed in the 
first conveyor 34 for the passage of air therethrough. Hot air is also 
routed through another conduit or ductwork system 50 disposed within the 
upper portion of the hood 30 of the hot air treatment portion 24 of the 
housing 12, also shown schematically by broken lines in FIG. 1, to a 
plurality of nozzles 51 which are suspended from the upper portion of the 
hot air hood 30 to direct air downwardly to the top of the package P as it 
passes through the hot air treatment portion 24. A portion of the hot air 
is diverted from the upper ductwork 50 through a branch duct 72 for 
direction to a drying nozzle 70 which will be explained in greater detail 
hereinafter. Finally, hot air is routed to the side portions of the hot 
air hood 30 through a conduit or ductwork system 52 disposed along the two 
laterally opposed sides of the hot air hood 30 which directs hot air to 
the sides of the package P as it passes through the hot air hood 30 as 
well as directing air across a hot water heat exchanger 60 as shown in 
arrows in FIG. 1, as will also be explained in greater detail hereinafter. 
By the above, it can be seen that hot air is directed to the package P 
from all four sides of the rectangular hot air hood 30 as the package P 
passes therethrough. 
Turning now to the hot water treatment portion 26, a water reservoir 54 is 
disposed within the hot water portion 26 of the housing 12 beneath the 
conveyor 38 providing a water supply and a basin for recovery of water W 
applied to the package P. An application pump 56 is mounted to the frame 
14 beneath the reservoir 54 to deliver water through piping 57 from the 
reservoir 54 to a plurality of nozzles 58 which are disposed within the 
hot water hood 32 and directed generally downwardly to apply hot water to 
the upper portions of the package P as it passes through the hot water 
hood 32. Conventional electric heating coils 62 are disposed within the 
reservoir 54 to heat the water to approximately 180.degree. F. 
As the product P emerges from the hot water hood 32 it will still be wet 
from application of hot water thereto. In that regard and as previously 
stated, an assembly for drying the packages is provided which includes a 
drying nozzle 70 disposed at the outlet of the hot water hood 32 and 
communicated with the air heater 42 through the ductwork 72 branching from 
the upper ductwork 50. The drying nozzle 70 emits a downwardly directed 
stream of hot air for drying the package P after the water is applied 
thereto. 
Enhanced efficiency of the shrink wrapping operation is provided by 
recirculating a portion of the water W contained within the reservoir 54 
into heat transfer relation with the hot air. For this purpose, 
recirculation pump 64 is disposed underneath the reservoir 54, adjacent 
the application pump 56. As previously mentioned, a heat exchanger 60 is 
disposed within the hot air hood 30 through which the hot water is 
circulated into heat transfer relation with the hot air. The heat 
exchanger 60, depicted schematically in FIG. 1, is a conventional 
generally sinuous coil of piping for circulating water therethrough. 
Substantially identical heat exchangers 60 are disposed on either lateral 
side of the hot air hood 30, however, only one is shown in FIG. 1 for 
clarity. The recirculation pump 64 communicates with the heat exchanger 60 
through conventional piping 66. A return pipe 67 returns water heated in 
the heat exchanger 60 to the reservoir 54. As previously mentioned, the 
intermediate ductwork 52 directs hot air across the coils of the heat 
exchanger 60 for heat transfer, as shown by arrows in FIG. 1. Water 
circulated from the reservoir 54 by the recirculation pump 64 into the 
heat exchanger 60 is returned at an elevated temperature to the reservoir 
54 for application to the package P through the aforesaid hot water 
directing assembly. Typically, hot air at 300.degree. F will increase the 
water temperature from 180.degree. F. to 200.degree. F. for application to 
the package P. In this manner, hot air is used to elevate the temperature 
of the hot water, thereby eliminating the need for large capacity steam or 
electric hot water heaters and enhancing the efficiency of the heat 
shrinking process. 
Operation of the apparatus of the present invention is basically as 
follows. According to the method of the present invention, an envelope of 
heat shrinkable film may be caused to shrink into close conformity to a 
product by placing the product on the first conveyor 34 which causes the 
product P to be transported through the hot air hood 30 wherein it is 
subjected to hot air from the lower hot air nozzles 49, the upper hot air 
nozzles 51 and air exiting the heat exchanger 60 which is at a slightly 
reduced temperature due to the hot air giving up some of its energy to the 
water passing through the coils thereof. This application of hot air 
causes the shrink wrap film to shrink into generally close conformity with 
the configuration of the package P. However, when the upper portion of the 
shrink wrap film contacts the cold food product contained within the 
package P, shrinking stops and the package P retains a rough, unfinished 
appearance as it exits the hot air hood 30, still being transported on the 
first conveyor 34. 
The first conveyor 34 then deposits the package P onto the second conveyor 
38 for transport through the hot water hood 32. Within the hot water hood 
32 the aforesaid water nozzles 58 discharge onto the package P a stream of 
hot water on the top and sides thereof. This hot water application causes 
the heat shrink film to complete the heat shrinking process, even in the 
region of the cold food product due to the direct, prolonged contact 
between the hot water and the film. Water that is applied to the package P 
drains off and reenters the reservoir 54 through the openings in the 
second conveyor 38. 
From the reservoir 54 the hot water is circulated by the recirculating pump 
64 through the heat exchanger 60 where the aforesaid water temperature 
elevation process is performed with the resulting hotter water returning 
to the reservoir 54. 
As the package emerges from the hot water hood 32 it is still wet from the 
application of hot water thereto. Therefore, at the end of the process, 
hot air is directed to the package P through the drying nozzle 70 which 
effectively dries the package P, completing the shrink wrap process. 
By the above, a method and apparatus for heat shrinking an envelope of heat 
shrinkable film into close conformity to a product enclosed within the 
envelope provides a final packaged product of enhanced appearance and does 
so in a simple and efficient process. 
It will therefore be readily understood by those persons skilled in the art 
that the present invention is susceptible of a broad utility and 
application. Many embodiments and adaptations of the present invention 
other than those herein described, as well as many variations, 
modifications and equivalent arrangements will be apparent from or 
reasonably suggested by the present invention and the foregoing 
description thereof, without departing from the substance or scope of the 
present invention. Accordingly, while the present invention has been 
described herein in detail in relation to its preferred embodiment, it is 
to be understood that this disclosure is only illustrative and exemplary 
of the present invention and is made merely for purposes of providing a 
full and enabling disclosure of the invention. The foregoing disclosure is 
not intended or to be construed to limit the present invention or 
otherwise to exclude any such other embodiments, adaptations, variations, 
modifications and equivalent arrangements, the present invention being 
limited only by the claims appended hereto and the equivalents thereof.