Note: Descriptions are shown in the official language in which they were submitted.
_IELD_OF I7iE ~ rION ~4 ~ S L5
Ihis invention relates to ~ethod and ap~aratus for packaging goods.
In p~rticular, the invention Fertains to vacuum packaging food in heat
shrinkable plastic bags.
BACKGRD~D
Specifically, this invention pertains to improvements in the nethod
and apparatus of the patent of T~T. Day, W.S. No. 4,132,048 issued on
January 2, 1979. In the Day patent, which is owned ~y W.R~ Grace & Co.,
the assignee of ~e present invention, the bag inside the chamber and
the chamber are both evacuated to a relatively low reduced pressure, at
which time the bag is sealed inside the chamber. Continued evacuation
of the air in the chan~er outside the bag causes the bag to balloon out
due to the residual air left therein, and move towards heaters on the
inside of the chan~er. m e bag is thus h~ated, and, ~subsequently, the
chan~er is vented whereby the bag collapses and shrir~s onto the product.
The Day apparatus ~ld process operate well, and an object of the
present invention is to improve its operation further. Among these
desired improven~nts are better control of the bag shrir~age. As the bag
is heated to a tempexature at which the plastic of the bag material
begins contracting, the bag will tend to shrink regardless of wnether or
not it is the rn~st opportune time in relation to the degree of evacuation
of the surro~mding chamber. S~me uneven shrinkage r~y therefore, occur;
and it is thus an object of the present invention to provide a process
in whic'n the bag is more evenly shrunk.
Other objects of the present invention are to provide a process and
apparatus in ~nich lawer shrink ten~eratures are used and in which the
bag can be heated m~re quickly thus increasing the nun~er of packaging
cycles per minute for the apparatus.
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~ oth th~ preY~nt invention and the a~xlatus of the
above n~ntioned Day patent cvercome numerous problems present in the
prior are where hot water baths are used to shrink evacuated shrink
bags. It has been heretofore known to use pre-formed packaging such as
bags for relatively large meat products such as whole rounds of beef
or whole pork loins, but heretofore the practive has been to shrink thes~
bags using a hot water bath. There are many disadvantages with hot water
systems, including very poor utilization of the energy in the hot water.
It has been est~nat~d that as low as 3% of the heat energy in the water
goes into the useful work of bag shrinkage, and the rest is wasted. In
addition, handling of the hot water itself is a great problem sin oe this
work is done in meat packing cold r3oms. Ihese cold rooms consume enormous
amounts of ener~y to keep them refrigerated and thus floor spa oe is very
valuable. The present invention is a dry process, which saves all of
the slu~iness and n~ss and safety hazards associated with water getting
on the floor, and in addition it utilizes much less valuable floor spa oe
than is utilized ~y hot water systems.
qhe present invention is related somewhat to general ooncepts in
the field of vacuum skin packaging. Re~erence can be had to U.S.
Patent 3,950,919 which issued April 20, 1976 to the present inventor and
is assigned to the same assignee for a more detailed explanation of vacuum
skin packaging. An idea in U.S. Pat. No. 3,950,919 is the use of a
separate vacuum system for controlling the packaging material, which in
the vacuum skin packaging art is a sheet of plastic and in the present
invention is a bag. Thus, at a general con oeptual level only, the present
invention might be characterized as a hybrid of the vacuum skin packaging
technology of U.S. Patent 3,950,919 with the vacuum chamber heating of
shrink plastic bags as taught in the Day patent 4,132,048. However,
it is believed that no such combination has been made heretofore.
751~i
Another feature of the present invention pertains to
apparatus means to permit interchan~ing platens so that
different sizes and shapes of food products or other goods can
be accommodated in one machine with minimal changes.
There are many different sizes and shapes of large
cuts of beef and there are many different sizes of processed
meat such as salami, thus interchangeability of platens is an
important advantage of the present invention over the prior art
in general.
Another important advantage of the invention resides
in its utilization of a rack in the chamber between the heated
platen, and the filled bag resting thereon. By controlling the
size and the spacing of the wlres or other material making up
the rack the amount of heat imparted ~o the product by the
heated platen can be well controlled. Thls ls very lmportant
with aertain proclu~ts, such a cheese and certain processecl
~oods, whereln more than a predetermined small amount of heat
would be unacceptable.
STATEMENT OF INVENTION
The present invention relates to an improvement in an
apparatus for vacuum packaylng goods in heat shrinkable plastic
bags, which apparatus generally comprises a vacuum chamber, a
pump for evacuating the chamber, a platform for holding a
product in a heat shrinkable bag so that the bag may be
evacuated through its unsealed mouth as the chamber is
evacuated, radiant heaters or movable contact heaters within
the chamber for heating the bag when the bag has ballooned
outwardly from the product as the chamber is evacuated, and
seal bars ~or sealing the bag after it has been evacuated.
~;~4~7~i~5
The said improvement is characterized by the fact that the seal
bars can close and clamp the mouth of the bag without sealing
the bag while the chamber is evacuated so that the bag will
balloon outwardly. The improvement is further characterized by
a heated platen generally conforming to the shape of the
ballooned bag so that when the bag balloons outwardly it
conta~ts the heated platen which impar~s heat to the bag so
that it will shrink after which the heater bars are opened so
that the shrinking force of the bag will force the air out
through the now unclamped bag mouth and evacuate the hag as the
bag collapses and shrlnlcs tightly around the product. The
improvement is characterized still further in that electrical
resistance heate.rs are included in the seal bars which can be
activated as the seal bars again close, thus sealing the bag.
DESCRIPTION Ok' THE DRAWINGS
The above and other advantages of the lnvention wlll
be pointed out or will become evident in the following summary
of the lnvention, detalled descripti.on, and clalms, and in the
accompanying drawing also forming a part of the disclosure, in
which,
Figures 1 to 4 lnclusive are a series of views
illustrating the method of the invention as used in a first
embodiment of the apparatus according to the invention; and
Figures 5 and 6 are vlews similar to certain ones of Flgures 1
to ~ lllustratlng the method applied to second embodiment of
apparatus.
-4a-
B
SU~RY OF THE lNVENTION
In one aspect the present invention i5 a ~ethod of vacuum
packing gcods in a heat shrinkable bag comprising the steps of:
(1) causing the bag to balloon outwardly from the g~ods
by creating a pressure differential between the outside of the bag
and the inside of the bag;
(2) using said pressure differential to ~ositively hold said
bag in its ballooned condition and in contact with a heating
means;
t3) heating said bag to its shrinking temperature while held
in contact with the heating means;
(4) evacuating said bag around the gocds therein; and,
(5) closing a~ sealing the bag shut.
In another aspect the present invention is a machine for vacuum
packing goods in heat shrinkable b~gs, the combination comprising vac~lum
chamber means, heated plat~n menas in said chamber means for receiving
pre-bagged goods, mr~ns to cause the bag to balloon outwardly from the
goods into contact with said heated platen means, means to cre~te a
pressure diffe~ential to hold the bag in its ballooned condition in
contact with said heating means, means to evacuate the inside of the bay
ar~und the gcods, means to oontrol the evacuating means, the heating
means and the pressure differential holding said ballooned bag in order
to cause said kag to collapse and to shrink onto said goods in a controlled
manner; and means to close and seal the bag.
DE~AILED DE RIPTION ~L24 7515
Referring now in detail to the drawings, Figs~ 1 through 4 show
a first form of the apparatus comprising an outer vacuum chanber made up
of an upper half 10 and a lower half 12. Other means not shown are
provided to form air tight seals and the like, all as is well knc~n to
those skilled in these arts. An upper double walled platen 14 is mounted
in the upper half 10, and a lower double walled platen 16 is mDunted
in the lower half 12. ~unting means, which may comprise yokes, nuts
and bolts and the like, are provided to removably mount the platens 14
and 16 in the upper halves, and these means also permit interchanging
sizes of the platens as is well known to those skilled in these arts.
The inside surfaces of the platens 14 and 16 are provided with a plurality
of air access cpenings 20, throught which vacuum pressure can be drawn
via conduits 22 which connect to suitable sleeve~s 24 in the upper and
lower chamber halves 10 and 12~
Ihe bag, B, is evacuated by vac~lum applied through oonduit 26
when its mouth is placed within closure and sealing means 30. Of course,
the sealing halves of the closure mean 30 are not closed upon the bag
mouth when vacuum V~ is applied. The assemblage of the p rts 22 and 24
also facilitates interchanging of different sized platens in the machine
halves lC and 12.
By way of example, the drawings show a turkey "T" which has ~een
pre-~acka~ed in a bag "B" and has been put inside the chamber. A rack
28 is provided on the inside surface of the bottom platen 16 on which
the turkey "T" or other food product rests.
Ihe rack 28 will create an unheated section in the bag and will also
control the heating of the food product thereon. With, for example,
cheese, and certain other products, heat must be very closely controlled
or the product`'s esthetics or even its fitness as food can ke adversely
effected. Ihe invention contemplates making racks of different sizes
and types to control the degree to which the food product is heated lower
platen 16. FDr example, if the bars or other elements used to fabricate
rack 28 were made thicker and/or Fositioned closer together, then the food
515
prGduct resting thereon would be heated less by the heat frGm the lo~er
platen 16. However, 2 concurrent disadvantage is that that portion of
the bag cn the rack is not heated as much as other portions of the kag.
This will cause an irregularity in the n~nner in which the bag shrinks
arGund the product as is explained below.
It is anticipated that this problem can be overcome in a nwmber
of ways. Firstly, for oe rtain products, this irregular area may not
matter, i.e., products ~hich have top and bottom surfaces. For exam~le,
if a quantity of chicken Farts were to be shrink wrapped on a flat tray
or cardboard or the like, the underside of the tray or cardboard does
not matter and its contact with the rack and any resultant irregularity
of the shrink has no effect. However, in some products this oould make
a difference, i.e., whole poultry. This problem can be overcome, as
one Fossible solution, by providing a very large degree of shrink. Ihat
is~ if t~,e VariOIlS parameters of the bag both before and after shrinking are
controlled such that the bag will have to shrink a great deal, then this
large amount of shrinkage can literally "cverpcwer" any Fossible irregu-
larity created by the rack.
muS~ the advantage of controlling the heat imparted to the foGd
so that no adverse effect is experienced by the f3cd is obtained. Any
problem of irregular shrink of the bag, if there is any, is overccme by
other aspects of the teaching of the invention.
In general, the present invention solves the problems of exoe ssive
wrinkling of the bag, excessive non-uniform fitting of the bag mateiral
onto the goods, and limitations of the size of the g~od relative to the
chamber size which can be accon~odated.
The bag may ~e made of any suitable packaging material including
but not limited to thermoplastics such as Folyethylene, cross-linked
et~ lene Folymers and ccpolymers, ~olypropylene, saran, ethylene vinyl
alc~hol oopolymers, nylon, Folyvinyl fluoride, polyester and the like, and
laminates of these materials. 0~ course, other materials known to those
skilled in the art can also be used.
~Z~
It is conventional in this art to provide means inside the vacuum
chamber to close, to seal, and to cut off exoe ss b~g material outboard
of the seal. Ihese means are well developed and can be found, for
example, in the description of the above identified patent, and all of
these means are indicated herein by reerence numeral 30. So far as
pertinent to this invention, these means 30 include the ability to close
in an air tight manner, but not to seal the bag, and to later re-open
and then seal the bag. As an ex~mple these means can ~e a pair of
opposed electrically heated ~eal bars or clipping means to apply a metal
closure clip. Both means are well known in the art.
Means are also provided to heat the upper and lower platens 14 and
16. Ib this end a platen heater energy source means 32 is provided and
is shown connected by wires 34 to the two platens. Heating of platens
is known in this art, referen oe may be had to these Day and Perdue
patents referenced above as needed. m e energy source 32 may be electric
cul~ent supplied throught wires 34 to an electrically resistant wire
mesh or strips on the cuter surface of the platens which are preferably
constructed of a highly conductive material and as aluminum to transfer
heat to their inner surfaces in close proximity to the bagged product.
It is sufficient to say that the heating means can deliver enough heat
to shrink the bag.
Ihe method of the invention ooTprises the following steps, which
will ke acooTpanied by references to Figs. 1, 2, 3 and 4 as they appear
in the sequence of steps:
(1) The preloaded bag "B~ with the turkey "T" is placed on the rack
28 in the open machine, with the mDuth of the bag positioned over the
closing, æ aling, and cutting means 30. ~his is the oondition shown in
Fig. 1.
(2) In Fig. 2 the machine is closed onto the bag and the means 30
are closed on the uth of the bag, but the bag is not sealed.
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7~:~5
3) me platen heaters are activated to begin heating. (the
platen heaters, once activated, may be continuously heated, particularly
if quick cycle time is desired.)
4) Vacuum pressure is provided to the perforated double wall platens
to cause the bag to balloon out into contact with the heated platens. This
condition is shown in Fig. 2.
5) In Fig. 3, means 30 are separated to oQen the bag mouth to the
environment inside the closed chamber defined by the halves 30a and 30b
which is evacuated through conduit 26 as indicated by V .
6) The vacuum pressure at the platen V is stopp~d while the vacuum
pressure in the chamber Vc continues. This causes a controlled collapsing
of the bag onto the product and is the condition shown in Fig. 3.
7) me bag is then permanently sealed or clipped shut. Clipping
means are well known in this art, see U. S. patent 3,832,824 which issued
on September 3, 1974 to Burrell and is assigned to the same assignee as the
present invention. In fact tho~e clipping means are particularly adapted
for use in the second embodLment of this invention shown in Figs. 5
and 6 and described in detail below.
8) V is turned off and the chamber vented to the atmosphere which
causes an additional final tight collapse of the bag onto the product.
9) The chamber is open and the package may be removed as shown in
Fig. 4.
It is important to note that a great deal of the flexibility of the
invention is provided at step 6). The time at which V is turned off
controls the amount of build up of shrink force within the plastic of the
bag created by the heating which in turn is an important factor in controlling
the speed and uniformity of the shrinkage. Likewise, the continued application
~'2,,~75i5
of V to the ~ag interior after V is re]eased and ~ented also has a
c P
large effect on this con~rol. V can be totally or partially released
giving precise control over film shrinkage. Thus, the invetnion provides
several separate paranE~ters which can be controlled to contxol the shrinXing
of the bag to the product without any wrinkles or aix pockets or the like
is achieved. lrnese E~xaneters are: a) the tern2erature to which the platen
is heated; b) the time the bag is alla~ed to re~ain in contact with the
heated platens; c) the timing of the turning off of Vp; d) the value of Vc
at this point; and, 3) the rate of increase of Vc after the heater and V
are t~lrned off.
Referring now to Figs. 5 and 6, there is shown a second embodLm~nt
of apparatus ada~ted to carry out the method. T~lis apparatus is a rr~dification
of a machine currently marketed by the assignee of the present invention and is
described and clain~d in the aforementioned U. S. patent 3,832,824. Commexcially,
in the form shown in the Fatent but not as r~dified as in Figs. 5 and 6 of this
application, this rnachine is known as the CRYOVAC* ~lodel 8200 dual charr~er
vacuumizing machine. One of its principal uses is for large cuts of beef,
large t~rkeys and the like. Tb the extent parts in this apparatus 40 are the
s~ne as or similar to parts described above in regard to the first e~kodiment,
such parts are indicated by the same reference nun~rals followed by "An.
Fig. 5 corresponds to Fig. 1, the beginning of a process wherein the
turkey "T" already positioned within the bag "B" is placed within the rnachine
40, with the neck portion of the bag extending across a pair of walls 42 and
44 and into a second chamber on the right hand side of the walls. me
clipping or æaling means 30A are provided between the walls 42 and 44. As
can be readily appreciated ~y those skilled in the art, and by looking at
Fig. 6, the only conceptual difference ~etween the second eTbodim~nt and the
first embodiment of Fi~s. 1 through 4 is that the entire left hand chamber
to the left of the wall 42 is subject to the vacuum pressure V , and the
*Reg. U. S. Patent & Tradernark Office
--10--
~4~7S~ S
entire right hand chamber is conceptually identical to the overall chamber
outside the double walls of the first form, and is subject to the vacuum
pres Æ e V . Otherwise, the method is implemented identically in this
second form as it is in the fixst, with only minor changes being necessary
to accommodate this slight difference in the form of the apparatus.
Fig. 6 corresponds most closely to a step just prior to the
end of the step shown in Fig. 2, that is the use of V to balloon the
bag after the bag has been shut but not sealed. For this purpose, the
arrow indicated Vc in Fig. 6 is shown dotted, that is, it is not yet active.
Mbunting means 18A are also provided so that here again this
apparatus can have interchangeable platens. The major structural difference
is in the uppex and lowex platens 14A and 16A which are formed with openings
20A. thus, the dual chamb~x machine is more economical to mcdify for use
with the invention in that the platens are of simpler construction, i.e.,
they are single walled rather than the double walled platen structures
reguired in the first embc~lin~nt of the invention in Figs. l through 4.
This form also uses the rack 28A as in the first embcdim~nt to achieve those
same advantages.
The word "platen" as used in tlle specification and claims herein
shall be understood to include various sizes and shapes of such means useful
in the invention and note be limited to flat devices as the word is sometimes
defined in dictionaries.
While the invention has been described in detail above, it is to
be undexstood that this detailed description is by way of example only, and
the protection granted is to be limited only within the spirit of the
invention and the scope of the following claims.
