Apparatus for sealing packaging for foodstuffs

An overwrap machine for sealing packaging for a foodstuff comprises a conveyor belt, heating elements, and pluralities of modules holding rollers which contact the packaging as individual foodstuffs are conveyed by the modules. The modules, and thus the rollers, are heated by the heating elements. There are two different roller types, which are the cylindrical first rollers and the ellipsoidal second rollers. The pluralities of rollers include substantial numbers of the first rollers with fewer numbers of the second rollers interspersed therein. The ellipsoidal second rollers are effective to insure the sealing of the ends of the foodstuff being overwrapped by bearing against the unsealed ends as each foodstuff traverses the gap between opposing second rollers.

FIELD OF THE INVENTION 
The present invention relates to the field of food packaging, and 
particularly to shrinkwrap and overwrap machines for packaging resilient 
foodstuffs such as bread. 
BACKGROUND OF THE INVENTION 
Commercial bakeries often package baked bread in an overwrap, which is a 
plastic package that contains the bread. This overwrap may be the sole 
airtight packaging for the bread or it may be contained within a plastic 
bag tied with a twist tie or other closure. 
The bread overwrap typically comprises a sheet of transparent polypropylene 
which must be sealed at both ends to retain freshness. In the past, the 
ends of an overwrap have been folded to a desired closure and then sealed 
in place by a bread overwrap machine. The loaves of bread are conveyed 
sideways through such an overwrap machine such that the wrap at the ends 
of the loaves would be sealed as the loaves were conveyed through the 
machine. Traditionally, the overwrap machine has used a heated mesh belt 
to contact the ends of the bread and packaging to fuse and seal the ends. 
More recently, the inventor herein has developed an overwrap machine in 
which uniformly cylindrical rollers have been used in place of the mesh 
belt to obtain a sealing of the ends. 
SUMMARY OF THE INVENTION 
It is an object of the invention to provide an apparatus for sealing the 
overwrap packaging of foodstuffs such as bread. It is an object of the 
invention to provide such an apparatus which improves the reliability and 
effectiveness of sealing. It is an object of the invention to provide an 
apparatus which is readily cleanable--an important consideration in the 
making and packaging of foodstuffs. 
The invention, in one embodiment, generally comprises means for conveying a 
foodstuff; means for heating; a first plurality of uniform diameter 
generally cylindrical first rollers heated by the heating means such that 
the first rollers are sufficiently heated to seal the packaging of the 
foodstuff; and a second plurality of second rollers, at least a portion of 
the second rollers having a diameter which is larger than the diameter of 
the first rollers, heated by the heating means such that the second 
rollers are sufficiently heated to seal the packaging of the foodstuff. 
Preferably, the diameter of the second rollers is variable over the length 
of the second roller, and most preferably they are generally ellipsoidal 
in shape. 
There are preferably groups of from about four to about twenty of the first 
rollers separated by groups of from about one to about four of the second 
rollers. Most preferably, there are groups of about twelve of the first 
rollers separated by groups of two of the second rollers. There are 
preferably pluralities of such first and second rollers which face each 
other across the conveying means, with the first rollers facing the first 
rollers, and the second rollers facing the second rollers. 
The first rollers are preferably contained in modules each having no more 
than about four rollers, and the second rollers are similarly contained in 
modules containing no more than two second rollers. 
The modules containing the rollers act as heat sinks, and are heated by the 
heating means. Heat is transferred from the module to the roller by 
conduction and radiative heating. The rollers preferably include a jacket 
of a non-stick thermally conductive material. The modules are separately 
removable from the apparatus for cleaning. 
In another embodiment, the invention comprises an apparatus having arrays 
of said ellipsoidal rollers to seal the packaging of a foodstuff. 
Other objects, aspects and features of the present invention in addition to 
those mentioned above will be pointed out in detail or will be understood 
from the following detailed description provided in conjunction with the 
accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION 
Referring now to FIGS. 1-3, an apparatus 10 for sealing packaging of 
foodstuffs is shown. Apparatus 10 has a means 12 for conveying a foodstuff 
14 wrapped in a packaging 16 thereon. Means 12 may comprise a moving bed 
of support bars, or a conveyor belt, or an array of rollers, or other 
types of food carrying devices, and preferably also includes pushing arms 
supported above the moving bed or belt and synchronized therewith. 
Foodstuff 14 is typically a baked product such as a loaf of bread. 
Packaging 16 is an overwrap formed of transparent polypropylene. Conveying 
means 12 has two lateral sides 18 and 20. 
Disposed on each lateral side 18 and 20 are pluralities of first rollers 30 
and second rollers 50. As used herein, "plurality" includes a single 
element as well as multiple elements, unless otherwise defined. First 
rollers 30 are uniform diameter cylindrical rollers. First rollers 30 are 
mounted in a module 36 adapted to hold a plurality, preferably four, of 
the first rollers 30. Module 36 has a substantial heat capacity and is 
made from aluminum. First rollers 30 comprise an inner roller 32 made of 
aluminum and an outer jacket 34 made from a thermally conductive yet 
non-stick material, preferably "Rulon". Rulon is a trademark for a 
fluoropolymer (TFE) made by Dixon Corporation and available through 
distributors such as AIN Plastics, Mount Vernon, N.Y. Rulon has the 
property of relatively high thermal conductivity, in the range of 2.3 
B.T.U./hr./sq.ft./.degree.F./in., combined with a very low coefficient of 
friction, in the range of 0.04-0.16 for static dry friction, and in the 
range of 0.12-0.19 for dynamic dry coefficient of friction against steel. 
The combination of thermally conductive and non-stick properties is highly 
effective to seal packaging such as polypropylene sheet while minimizing 
undesirable accumulation or sticking of the packaging to the rollers. 
First rollers 30 are mounted in module 36 by steel pins 38 fitting into 
apertures 40 in steel flanges 42 of module 36. The face of module 36 has a 
plurality of channels 44 for receiving the rollers 30. Preferably, the 
channels 44 are semi-cylindrical and are sized such that the rollers 30 
fit with close clearance therein. The close fit and enclosure of the 
channels 44 about rollers 30 is desirable to increase heat transfer from 
the module 36 to the rollers 30. Heat also is transferred to the rollers 
30 from module 36 through the pins 38. 
Second rollers 50 have a diameter, at least a portion of which is greater 
than the diameter of the first rollers. Preferably, the second rollers 50 
are ellipsoidal. As used herein "ellipsoidal" encompasses a variety of 
shapes having a larger diameter cross-sectional central portion and 
smaller diameter cross-sectional end portions with a tapering diameter 
between those central and end portions, and includes, inter alia, 
generally football shaped rollers, as well as cylindrical central sections 
joined to conical or conical frustum end portions such as shown in FIG. 1. 
Second rollers 50 are mounted in a module 56 adapted to hold a plurality, 
preferably two, of the second rollers 50. Module 56 has a substantial heat 
capacity and is made from aluminum. Second rollers 50 comprise an inner 
roller 52 made of aluminum and an outer jacket 54 made from Rulon. Second 
rollers 50 are mounted in module 56 by steel pins 58 fitting into 
apertures 60 in steel flanges 62 of module 56. The face of module 56 has a 
plurality of channels 64 for receiving the rollers 50. Preferably, the 
channels 64 are semi-cylindrical and are sized such that the rollers 50 
fit with close clearance therein. 
As can be seen in FIG. 2, the modules 36 and 56 are disposed on both 
lateral sides 18 and 20 of the conveying means 12, with pluralities of the 
first rollers 30 facing each other on opposite lateral sides 18 and 20 of 
the conveying means 12. Pluralities of second rollers 50 preferably also 
face each other on opposite lateral sides 18 and 20 of the conveying means 
12. 
Means for heating the heat sealing modules 36 and 56 are provided as shown 
in FIG. 1 and preferably comprise an electrical resistance heating bar 70. 
Heating bar 70 is preferably sized to match notches 66 and 67 in the 
modules 36 and 56 respectively. Heating bar 70 is thus in thermally 
conductive contact with the modules 36 and 56 to heat the modules, and 
thereby heat the rollers 30 and 50. 
In order for the rollers 30 and 50 to be maintained at a desired 
temperature, a temperature control unit is provided to control the current 
provided to electrical heating bar 70. The temperature control unit senses 
the temperature at the modules 36 and 56 and controls the temperature to 
be between about 260.degree.-300.degree. F. 
In the apparatus of the invention, a foodstuff to be packaged is wrapped in 
a sheet of packaging material, in which the ends are folded up to a 
desired wrap. The foodstuff is then passed through the apparatus 10. The 
first and second pluralities of rollers 30 and 50 are disposed on both 
lateral sides of the conveying means 20 at a distance apart sufficient to 
permit the heated rollers 30 and 50 to contact two ends of the packaging 
and foodstuff conveyed in the conveying means and to thereby seal the ends 
of the packaging. 
As shown in FIG. 3, the second rollers 50 of the present invention are 
particularly useful to seal packaging 16 of a resilient foodstuff 14 such 
as a loaf of bread. The second rollers 50 press against the end of the 
foodstuff 14 to cause the packaging 16 to press on and seal against 
itself. 
If desired, the second module 56 and/or the mountings for the second 
rollers 50 may be provided with spring resilient means to permit the 
second rollers 50 to resiliently bear against the foodstuff without 
crushing the foodstuff. 
Preferably the modules 36 and 56 are suspended above the conveying means 12 
and arrays of such modules located on opposite sides 18 and 20 of the 
conveying means 12 are movable towards and away from each other, to 
accommodate foodstuffs of varying lengths and size. The movable modules 36 
and 56 permit the sealing rollers 30 and 50 to be precisely located for 
optimum sealing effectiveness. 
In the apparatus 10 there are preferably a sufficient number of first 
modules 36 to form pluralities of about four to about twenty of the first 
rollers 30. These pluralities of first rollers 30 are separated by a 
sufficient number of second modules 56 to form a plurality of from about 
one to about four of the second rollers 50 between the pluralities of the 
first rollers 30. More preferably, there are pluralities of about twelve 
of the first rollers 30 separated by a plurality of two of the second 
rollers 50. 
In an alternative embodiment of the invention, the first cylindrical 
rollers are omitted and the sealing is effected by pluralities of second 
rollers 150 having the characteristics of the rollers 50 described above. 
Accordingly, the present invention provides an improved and effective 
apparatus for sealing the ends of packaging in a foodstuff such as a loaf 
of bread. The modular design permits simple disassembly for cleaning, and 
subsequent reassembly.