Title:
INTEGRAL, THIN-WALL TRAY
United States Patent 3583623
Abstract:
A thin-wall plastic tray comprising a rectangular bottom wall and outwardly extending integral sidewalls defining a shallow compartment, said sidewall edges defining a flared, peripheral skirt of arcuate cross section, said bottom wall including a rectangular protuberance extending into said compartment defining a recessed border, said protuberance having a concave surface, a plurality of upraised ribs in said recessed border, diagonally extending corrugated braces disposed in said protuberance and upraised corner gussets.
US Patent References:
Service plate or tray
Hill - December 1962 - 3067922
/3104776.html
Bostrom - September 1963 - 3104776
Packaging tray
Engles et al. - October 1964 - 3151799
Article package convertible to a container
Collie - October 1968 - 3405858
Service plate or tray
Hill - December 1962 - 3067922
/3104776.html
Bostrom - September 1963 - 3104776
Packaging tray
Engles et al. - October 1964 - 3151799
Article package convertible to a container
Collie - October 1968 - 3405858
Inventors:
Golner, Jerold Julius (Lowell, MA)
Alroy, John D. (Union City, NJ)
Alroy, John D. (Union City, NJ)
Application Number:
04/858347
Publication Date:
06/08/1971
Filing Date:
09/16/1969
View Patent Images:
Export Citation:
Primary Class:
Other Classes:
D09/425, 220/675, 220/608
International Classes:
B65D1/34; B65D1/00
Field of Search:
229/2.5 220/72,97 99/171,174
Primary Examiner:
Bockenek, David M.
Claims:
What I claim is
1. An integral, thin-wall plastic tray for comestibles or the like comprising a generally rectangular bottom wall and upwardly extending sidewalls at each edge thereof, said sidewalls defining a relatively shallow tray compartment adapted to receive said comestibles said sidewall edges extending outwardly and downwardly to define a flared, peripheral skirt of arcuate cross section, said bottom wall including a generally rectangular protuberance extending into said compartment defining a recessed border on the periphery adjacent said sidewalls, said protuberance having a concave surface, a plurality of upraised ribs in said recessed border, said rectangular protuberance including diagonally extending braces upraised and intersecting at the center from said concave surface, the recessed border of said tray including upraised corner gussets.
2. A tray according to claim 1 wherein said gussets terminate in upraised ribs for additional reinforcement, said border corners being provided with staggered upraised bottoms to facilitate separation between trays in nested relation to promote easy removal from the stack.
3. A tray according to claim 1 wherein said protuberance includes planar border, said concave surface being formed with said border, said intersecting diagonal braces defining merging triangles, the base of each triangle being the planar border of said protuberance.
1. An integral, thin-wall plastic tray for comestibles or the like comprising a generally rectangular bottom wall and upwardly extending sidewalls at each edge thereof, said sidewalls defining a relatively shallow tray compartment adapted to receive said comestibles said sidewall edges extending outwardly and downwardly to define a flared, peripheral skirt of arcuate cross section, said bottom wall including a generally rectangular protuberance extending into said compartment defining a recessed border on the periphery adjacent said sidewalls, said protuberance having a concave surface, a plurality of upraised ribs in said recessed border, said rectangular protuberance including diagonally extending braces upraised and intersecting at the center from said concave surface, the recessed border of said tray including upraised corner gussets.
2. A tray according to claim 1 wherein said gussets terminate in upraised ribs for additional reinforcement, said border corners being provided with staggered upraised bottoms to facilitate separation between trays in nested relation to promote easy removal from the stack.
3. A tray according to claim 1 wherein said protuberance includes planar border, said concave surface being formed with said border, said intersecting diagonal braces defining merging triangles, the base of each triangle being the planar border of said protuberance.
Description:
BACKGROUND OF THE INVENTION
Heretofore, numerous transparent, thin-wall, thermoplastic trays, have been used in the purveyance of meat, vegetables, or other comestibles and noncomestibles; the tray and contents are enrobed in a transparent film which is heat-shrunk or stretch-wrapped to display the contents in a neatly wrapped package in grocery stores and other retail outlets. The transparent trays permit consumers to fully inspect the product; this is especially advantageous where inconsistent properties may appear in comestible surface juxtaposed with tray bottom wall. In many communities, recent legislation has required that such transparent trays be used.
The known transparent trays which comply with the legislative standards have, in many instances, proven commercially unsuitable because they buckle and crack under the wrapping stresses normally encountered. In addition, horizontal, thin-wall flanges having sharp edges on the sidewalls often puncture the tightly drawn film permitting escape of exudate from the sealed comestibles which is both unsightly and unsanitary. The users often cut their hands on the sharp flange edges as individual trays are manually removed from a nested stack and during the wrapping operation. Moreover, the flange edge presents a narrow surface area difficult to grasp with the fingers.
To date, virtually no imagination has been exercised in the design of thin-wall, plastic trays to overcome the aforementioned shortcomings of the prior art. Generally, when the longitudinal, transverse and diagonal compressive stresses are applied to the tray by heat shrinkage or stretch-wrapping of the enrobing plastic film, inventors have simply added additional plastic to the points of greatest stress concentration to withstand these forces. This has resulted in increased cost per unit for the additional plastic, reduced area of usage in the tray compartment and increased protuberances which cause unsightly impressions in the foodstuff. Conventionally, tray manufacturers have provided tray bottom walls with upraised, reinforcing ribs, in a trial and error fashion, completely disregarding esthetic appeal. These reinforcing ribs leave unsightly imprints in the comestibles which becomes highly objectionable in rewrapping of comestibles where the comestible has to be inverted for rewrapping.
One known plastic comestible tray is disclosed in the patent to Donovan, U.S. Pat. No. 3,420,431. This tray has prompted numerous improvements, foremost of which is the construction of a bottom wall which is sufficiently strong to withstand buckling, but eliminates the many upraised ribs which impress the comestible as well as requiring costly plastic.
SUMMARY OF THE INVENTION
The present invention overcomes the stated deficiencies of the prior art and has as its primary objective an improved, integral thin-wall, plastic tray whose bottom wall withstands the application of longitudinal, transverse and diagonally compressive stresses normally encountered when plastic film enrobing the tray is heat-shrunk or stretch-wrapped to form a tight package. In particular, the tray comprises a rectangular bottom wall having integral, shallow, upstanding walls along each edge thereof and a centrally disposed, generally rectangular protuberance projecting into the tray compartment whose upper surface is concave. The protuberance defines a recessed border along its periphery adjacent the sidewalls and includes diagonal upraised corrugations for tray sizes where required. The recessed border is provided with spaced upraised reinforcing ribs; each corner is provided with an upraised gusset to positively withstand diagonally applied compressive stresses.
The sidewalls extend upwardly and outwardly of the bottom to define a shallow compartment and terminate in an outwardly flared skirt having an arcuate cross section to increase the surface area of contact between the film and tray: the film-skirt interface establishes a seal to retain comestible exudate within the tray compartment.
BRIEF DESCRIPTION OF THE DRAWING
The various features of the apparatus of this invention will become apparent from the following detailed description set forth in connection with the accompanying drawing which relates to the preferred embodiment of the present invention and is given by way of illustration.
FIG. 1 is an isometric view of the preferred embodiment of the present invention.
FIG. 2 is a top view of the present invention.
FIG. 3 is a cross section view of a stack of trays taken along line--III of FIG. 2, illustrating the spacing of uncompressed trays to improve the denesting features of this invention.
DETAILED DESCRIPTION OF THE INVENTION
Referring to the preferred embodiment in FIG. 1, an integral, thin-wall transparent plastic tray 10 is illustrated. The tray comprises a generally rectangular bottom wall 11, lying in a horizontal plane, and upstanding, low-height sidewalls 12 joined by rounded corners to define the shallow tray compartment 13. The sidewalls 12 are disposed at an angle to bottom wall 11, extending upwardly and outwardly and terminating in a downwardly and outwardly, flared rim 14 defining an arcuate cross section, seen in FIG. 3. The tray is enrobed in a transparent, plastic film 15 by conventional wrapping apparatus and subjected to a heated environment: this heat-shrinks the plastic film to form a sealed, tightly drawn neatly wrapped package. Alternatively, a stretch-wrapper may be used requiring no shrinkage. The interface of film 15 with flared rim 14 forms a peripheral seal to retain the comestible exudate and juices with the compartment. Moreover, the rim presents a broad, readily graspable surface to facilitate manual removal of individually nested trays in a stack. Additionally, the down-turned skirt eliminates sharp, horizontal edges which often cut operator's fingers as the trays are removed from stacks for insertion into the wrapping apparatus.
The angular disposition of sidewalls 12 transmits the compressive stresses applied thereon directly to the bottom wall. By this construction, if a bottom wall design can be achieved capable of withstanding longitudinal, transverse and diagonally applied compressive stresses, enrobing with the film can be performed without tray buckling: buckling creates unsightly packages which are not readily saleable. To date, no such design has been achieved; the buckling of tray walls during film enrobing has persistently plagued production: this interruption is costly, in terms of both time and labor.
The bottom wall 11 includes a centrally disposed, rectangular protuberance 16 projecting into the tray compartment defining a peripheral recessed border 17 adjacent the sidewalls 12. By this construction, the bottom wall is reinforced against longitudinal and transverse compressive stresses. The surface of the protuberance 16 is concave to provide additional reinforcing against buckling.
The surface of protuberance 16 includes flat peripheral border 18 and concave, central portion 19; the lowermost contour of the concave portion 19 lies in the plane as the horizontal border 17: this configuration provides additional reinforcing against bottom wall buckling. Diagonal, upraised corrugations 20 especially required in larger tray sizes extend from the corners of the border 19 and intersect at the midpoint of portion 19 to define four triangles 29, 30, 31, and 32; the base of each is one edge of the border. The corrugation walls 21 are inclined downwardly and outwardly from the flat, horizontal surface of the corrugation exposed to the tray compartment: the merging wall 21 and concave portion form an angular bent to withstand buckling from compressive stresses.
The flat horizontal border 19 surmounts, along each edge, outwardly and downwardly inclined wall 22 which merges with recessed border 17 and inwardly and downwardly inclined wall 23 which merges with concave portion 19.
The recessed border 17 is provided with a plurality of corrugated, upraised spaced ribs 24 comprise inclined walls 33. The ribs include a horizontal leg 34 and an inclined leg 35 disposed in inclined sidewalls 12; the horizontal leg 34 projects into and above the border 19. When a comestible is disposed within the tray, the spacing of legs 34 permits the circulation beneath the lower surface of the comestibles into the recessed triangles to preserve the blood of meat, the preferred foodstuff in this invention. The generally planar surface of the inclined triangles substantially eliminates any impressions on the surface of the juxtaposed foodstuff.
The application of diagonal stresses occurs on the bottom wall 11 as stress of film 15 occurs at the corners. Trays otherwise capable of withstanding stresses have buckled under these forces. Conventionally, tray manufacturers have simply added more plastic to the tray corners or otherwise redesigned expensive molding apparatus to provide elaborate corner shoulders. Unfortunately, these shoulder modifications have interferred with denesting of trays: the tray corners in nested stacks often wedge together. One of the novel features of the present invention is the provision of integral, upraised corrugated gussets 25 at each corner disposed in border 17. The gussets merge into ribs 26, similar to spaced ribs 24, which serves to reinforce sidewalls 12 at each corner. The midportion of the gussets merge with the corner of protuberance 16; inclined, angular bents 36 formed at the intersection reinforce the bottom wall against diagonally applied compressive stresses.
Each corner in the border 17 is provided with an integral, upraised button 28 spaced from the sidewalls in staggered relation. Before the product to be wrapped is inserted, the trays are stacked, in nesting relation, so that the upper contour of each button abuts a flat surface on the underside of a juxtaposed tray: this spaces the trays eliminating wedging and trapped air therebetween that would interfere with separation upon removal of individual trays. The trays may be compressed in a tight stack to minimize space occupancy during storage and transport, but as soon as the compressive force on the stack is released, the trays "spring back" to the spaced position illustrated in FIG. 3. Easy grasping of the skirt 14 on the space defined between individual trays by the buttons 28 promotes easy removal during use.
Any moldable thermoplastic material may be used in accordance with the present invention so long as it is crack-resistant under ordinary circumstances, nonporous to comestible exudate and contains sufficient strength to be fabricated to form the thin-layered corners and contours and is economical. Naturally, the tray may be reused by the consumer after the comestible is removed. Ordinarily, construction of the tray may be performed by thermoforming or stamping the plastic into the desired shape at a molden stage: gauge thickness of the walls should be between 2 80 mils with about 10 mils preferred. Selection should be based on ability to withstand refrigerated temperatures below 32° F. for protracted periods: the plastic must not be brittle or fracturable at these temperatures.
In practice, the most rigid, commercially successful trays have included the following critical rations: the length of the bottom wall 11 to the sidewall height h varies from between 3/1 to about 30/1; the rim extension e to the wall height h ranges from about 1/20 to about 1/2. The spacing s of the rim extension equals the dimension e; all of the above letters are best seen in FIG. 3.
Heretofore, numerous transparent, thin-wall, thermoplastic trays, have been used in the purveyance of meat, vegetables, or other comestibles and noncomestibles; the tray and contents are enrobed in a transparent film which is heat-shrunk or stretch-wrapped to display the contents in a neatly wrapped package in grocery stores and other retail outlets. The transparent trays permit consumers to fully inspect the product; this is especially advantageous where inconsistent properties may appear in comestible surface juxtaposed with tray bottom wall. In many communities, recent legislation has required that such transparent trays be used.
The known transparent trays which comply with the legislative standards have, in many instances, proven commercially unsuitable because they buckle and crack under the wrapping stresses normally encountered. In addition, horizontal, thin-wall flanges having sharp edges on the sidewalls often puncture the tightly drawn film permitting escape of exudate from the sealed comestibles which is both unsightly and unsanitary. The users often cut their hands on the sharp flange edges as individual trays are manually removed from a nested stack and during the wrapping operation. Moreover, the flange edge presents a narrow surface area difficult to grasp with the fingers.
To date, virtually no imagination has been exercised in the design of thin-wall, plastic trays to overcome the aforementioned shortcomings of the prior art. Generally, when the longitudinal, transverse and diagonal compressive stresses are applied to the tray by heat shrinkage or stretch-wrapping of the enrobing plastic film, inventors have simply added additional plastic to the points of greatest stress concentration to withstand these forces. This has resulted in increased cost per unit for the additional plastic, reduced area of usage in the tray compartment and increased protuberances which cause unsightly impressions in the foodstuff. Conventionally, tray manufacturers have provided tray bottom walls with upraised, reinforcing ribs, in a trial and error fashion, completely disregarding esthetic appeal. These reinforcing ribs leave unsightly imprints in the comestibles which becomes highly objectionable in rewrapping of comestibles where the comestible has to be inverted for rewrapping.
One known plastic comestible tray is disclosed in the patent to Donovan, U.S. Pat. No. 3,420,431. This tray has prompted numerous improvements, foremost of which is the construction of a bottom wall which is sufficiently strong to withstand buckling, but eliminates the many upraised ribs which impress the comestible as well as requiring costly plastic.
SUMMARY OF THE INVENTION
The present invention overcomes the stated deficiencies of the prior art and has as its primary objective an improved, integral thin-wall, plastic tray whose bottom wall withstands the application of longitudinal, transverse and diagonally compressive stresses normally encountered when plastic film enrobing the tray is heat-shrunk or stretch-wrapped to form a tight package. In particular, the tray comprises a rectangular bottom wall having integral, shallow, upstanding walls along each edge thereof and a centrally disposed, generally rectangular protuberance projecting into the tray compartment whose upper surface is concave. The protuberance defines a recessed border along its periphery adjacent the sidewalls and includes diagonal upraised corrugations for tray sizes where required. The recessed border is provided with spaced upraised reinforcing ribs; each corner is provided with an upraised gusset to positively withstand diagonally applied compressive stresses.
The sidewalls extend upwardly and outwardly of the bottom to define a shallow compartment and terminate in an outwardly flared skirt having an arcuate cross section to increase the surface area of contact between the film and tray: the film-skirt interface establishes a seal to retain comestible exudate within the tray compartment.
BRIEF DESCRIPTION OF THE DRAWING
The various features of the apparatus of this invention will become apparent from the following detailed description set forth in connection with the accompanying drawing which relates to the preferred embodiment of the present invention and is given by way of illustration.
FIG. 1 is an isometric view of the preferred embodiment of the present invention.
FIG. 2 is a top view of the present invention.
FIG. 3 is a cross section view of a stack of trays taken along line--III of FIG. 2, illustrating the spacing of uncompressed trays to improve the denesting features of this invention.
DETAILED DESCRIPTION OF THE INVENTION
Referring to the preferred embodiment in FIG. 1, an integral, thin-wall transparent plastic tray 10 is illustrated. The tray comprises a generally rectangular bottom wall 11, lying in a horizontal plane, and upstanding, low-height sidewalls 12 joined by rounded corners to define the shallow tray compartment 13. The sidewalls 12 are disposed at an angle to bottom wall 11, extending upwardly and outwardly and terminating in a downwardly and outwardly, flared rim 14 defining an arcuate cross section, seen in FIG. 3. The tray is enrobed in a transparent, plastic film 15 by conventional wrapping apparatus and subjected to a heated environment: this heat-shrinks the plastic film to form a sealed, tightly drawn neatly wrapped package. Alternatively, a stretch-wrapper may be used requiring no shrinkage. The interface of film 15 with flared rim 14 forms a peripheral seal to retain the comestible exudate and juices with the compartment. Moreover, the rim presents a broad, readily graspable surface to facilitate manual removal of individually nested trays in a stack. Additionally, the down-turned skirt eliminates sharp, horizontal edges which often cut operator's fingers as the trays are removed from stacks for insertion into the wrapping apparatus.
The angular disposition of sidewalls 12 transmits the compressive stresses applied thereon directly to the bottom wall. By this construction, if a bottom wall design can be achieved capable of withstanding longitudinal, transverse and diagonally applied compressive stresses, enrobing with the film can be performed without tray buckling: buckling creates unsightly packages which are not readily saleable. To date, no such design has been achieved; the buckling of tray walls during film enrobing has persistently plagued production: this interruption is costly, in terms of both time and labor.
The bottom wall 11 includes a centrally disposed, rectangular protuberance 16 projecting into the tray compartment defining a peripheral recessed border 17 adjacent the sidewalls 12. By this construction, the bottom wall is reinforced against longitudinal and transverse compressive stresses. The surface of the protuberance 16 is concave to provide additional reinforcing against buckling.
The surface of protuberance 16 includes flat peripheral border 18 and concave, central portion 19; the lowermost contour of the concave portion 19 lies in the plane as the horizontal border 17: this configuration provides additional reinforcing against bottom wall buckling. Diagonal, upraised corrugations 20 especially required in larger tray sizes extend from the corners of the border 19 and intersect at the midpoint of portion 19 to define four triangles 29, 30, 31, and 32; the base of each is one edge of the border. The corrugation walls 21 are inclined downwardly and outwardly from the flat, horizontal surface of the corrugation exposed to the tray compartment: the merging wall 21 and concave portion form an angular bent to withstand buckling from compressive stresses.
The flat horizontal border 19 surmounts, along each edge, outwardly and downwardly inclined wall 22 which merges with recessed border 17 and inwardly and downwardly inclined wall 23 which merges with concave portion 19.
The recessed border 17 is provided with a plurality of corrugated, upraised spaced ribs 24 comprise inclined walls 33. The ribs include a horizontal leg 34 and an inclined leg 35 disposed in inclined sidewalls 12; the horizontal leg 34 projects into and above the border 19. When a comestible is disposed within the tray, the spacing of legs 34 permits the circulation beneath the lower surface of the comestibles into the recessed triangles to preserve the blood of meat, the preferred foodstuff in this invention. The generally planar surface of the inclined triangles substantially eliminates any impressions on the surface of the juxtaposed foodstuff.
The application of diagonal stresses occurs on the bottom wall 11 as stress of film 15 occurs at the corners. Trays otherwise capable of withstanding stresses have buckled under these forces. Conventionally, tray manufacturers have simply added more plastic to the tray corners or otherwise redesigned expensive molding apparatus to provide elaborate corner shoulders. Unfortunately, these shoulder modifications have interferred with denesting of trays: the tray corners in nested stacks often wedge together. One of the novel features of the present invention is the provision of integral, upraised corrugated gussets 25 at each corner disposed in border 17. The gussets merge into ribs 26, similar to spaced ribs 24, which serves to reinforce sidewalls 12 at each corner. The midportion of the gussets merge with the corner of protuberance 16; inclined, angular bents 36 formed at the intersection reinforce the bottom wall against diagonally applied compressive stresses.
Each corner in the border 17 is provided with an integral, upraised button 28 spaced from the sidewalls in staggered relation. Before the product to be wrapped is inserted, the trays are stacked, in nesting relation, so that the upper contour of each button abuts a flat surface on the underside of a juxtaposed tray: this spaces the trays eliminating wedging and trapped air therebetween that would interfere with separation upon removal of individual trays. The trays may be compressed in a tight stack to minimize space occupancy during storage and transport, but as soon as the compressive force on the stack is released, the trays "spring back" to the spaced position illustrated in FIG. 3. Easy grasping of the skirt 14 on the space defined between individual trays by the buttons 28 promotes easy removal during use.
Any moldable thermoplastic material may be used in accordance with the present invention so long as it is crack-resistant under ordinary circumstances, nonporous to comestible exudate and contains sufficient strength to be fabricated to form the thin-layered corners and contours and is economical. Naturally, the tray may be reused by the consumer after the comestible is removed. Ordinarily, construction of the tray may be performed by thermoforming or stamping the plastic into the desired shape at a molden stage: gauge thickness of the walls should be between 2 80 mils with about 10 mils preferred. Selection should be based on ability to withstand refrigerated temperatures below 32° F. for protracted periods: the plastic must not be brittle or fracturable at these temperatures.
In practice, the most rigid, commercially successful trays have included the following critical rations: the length of the bottom wall 11 to the sidewall height h varies from between 3/1 to about 30/1; the rim extension e to the wall height h ranges from about 1/20 to about 1/2. The spacing s of the rim extension equals the dimension e; all of the above letters are best seen in FIG. 3.