Abstract:
A food pan cover for use with a food pan having a flange extending from the walls and substantially surrounding the periphery of the walls. A plurality of protuberances and depressions are formed on the underside of the flange; on the cover under and adjacent to the walls, and a plurality of dovetail members are formed on the periphery of the walls. An elastomeric seal is formed on the protuberances, and depressions and dovetails of a polyurethane having a usable temperature after molding of 212° fahrenheit and a hardness of 60 to 120 shore A, with a plurality of ribs, and terminates in a downwardly curved projection defining a groove around the periphery of the seal.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The field of this invention resides within the food pan art. In particular, it resides within the food pan art with respect to institutional food service such as in restaurants, schools, hospitals, and hotels that rely upon storage of food in a well maintained container. More specifically, it resides within the plastic food pan art related to sealing plastic food containers where the lid or cover can be removed and replaced over an extended period of time in order to maintain pure and clean food for service.  
           [0003]    2. Prior Art of this Invention  
           [0004]    The prior art with regard to food pans for food service relates to food pans having covers. Such food pans with a covers, are utilized for restaurants, fast food service, hotels, banquet facilities, hospitals, schools, and prisons. When referring to food pans of this invention as to the prior art, the general prior art is relevant with regard to food pans which are made of plastic with covers thereover.  
           [0005]    When reviewing the prior art food pans that are made of plastic with covers thereover, it is seen that certain food pans are made with a lid or cover with a flange, groove, or other means for sealing the cover to a food pan. The sealing of such covers to a food pan is such wherein the resiliency of the plastic is utilized for engaging the cover with regard to such structures as flanges, grooves, and related seals.  
           [0006]    In the utilization of seals such as flanges and grooves, or other catching means, a sufficiently tight seal is usually not maintained. This is because of the fact that the nature of the plastic will not yield sufficiently to allow for a close proximate sealing of the food pan with the cover thereover. As a consequence, the cleanliness, integrity, and maintenance of the food can not be provided without a degree of possible contamination.  
           [0007]    This invention specifically incorporates an elastomeric seal which is preferably affixed, secured, bonded or molded to the cover or lid. The elastomeric seal when secured or bonded to the cover or lid is such where it can be placed on the pan and retained in a tightened sealed relationship.  
           [0008]    Alternately, the elastomeric seal can be bonded to the pan so that the cover or lid can be placed on the pan and retained in a tightly sealed manner.  
           [0009]    The elastomeric nature allows for a flexing and tightly juxtaposed fitting of the cover or lid on the pan. This helps to accommodate a seal which prevents intrusion of contaminants and foreign substances which are deleterious to the food once prepared.  
           [0010]    It should be understood that the food once prepared is oftentimes retained for an extended period of time either in a heated or semi-heated condition or in the alternative a cooled condition. Thus, a desire to eliminate contaminants in the pan with the cover or lid thereover is extremely well sought after. However, there has not been a superior solution in the prior art for such seals to prevent food contamination within the pan.  
           [0011]    This invention provides for an elastomeric seal on a cover or lid or on a pan which is compatible with food and at the same time seals the cover or lid and pan together in a firm manner to substantially eliminate contamination.  
         SUMMARY OF THE INVENTION  
         [0012]    In summation, this invention comprises a food pan and a cover or lid with an elastomeric seal having various portions which are firmly fixed to the cover or pan which respectively seat within a food pan or cover for sealing thereof.  
           [0013]    More specifically, the invention comprises a food pan and cover having an elastomeric seal. The elastomeric seal has plural flanges externally surrounding the cover or pan. One of the flanges incorporates a substantially concave portion which flexes inwardly to allow for a flexibly improved seal.  
           [0014]    Further to this extent, the cover with the pan provides for a seal which is retained in a tightened condition over an extended period of time. This elastomeric seal is based upon utilization of plastics which are compatible with the food pan and cover while at the same time being acceptable for food service.  
           [0015]    The cover or pan has numerous indentations, openings, and notches for receipt of the molded elastomeric seal. The seating of the elastomeric seal and affixing, securing, bonding, or molding to the cover or pan is enhanced so that the configuration of the notches and openings allow for a mechanical retention of the seal. Also, the seal is most preferably of a chemical composition which is compatible with the plastic material to which it is secured or molded.  
           [0016]    The net result is to provide a seal which is compatible and molded or otherwise secured to the plastic cover or to the pan while at the same time being held and supplemented for retention by grooves, notches and openings for the securement thereof on the cover or pan respectively.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    [0017]FIG. 1 shows a perspective view of the food pan and cover overlying the pan showing the elastomeric seal surrounding it.  
         [0018]    [0018]FIG. 2 shows a perspective view of the cover partially in place and partially withdrawn from the pan.  
         [0019]    [0019]FIG. 3 shows a fragmented side elevation view of the cover prior to receiving by molding the elastomeric seal thereto.  
         [0020]    [0020]FIG. 4 shows a fragmented side elevation view of the cover after the seal has been bonded thereto.  
         [0021]    [0021]FIG. 5 shows a bottom plan view looking upwardly at the corner of the cover prior to the elastomeric seal being molded thereto.  
         [0022]    [0022]FIG. 6 shows a sectional view in the direction of lines  6 - 6  of FIG. 5.  
         [0023]    [0023]FIG. 7 shows a sectional view through lines  7 - 7  of FIG. 4 wherein the elastomeric seal is shown bonded to the cover.  
         [0024]    [0024]FIG. 8 shows a sectional view of the seal of FIG.  7  as it is emplaced and held by the side walls of the pan.  
         [0025]    [0025]FIG. 9 shows an enlarged detailed plan view of the dovetailed edges of the pan with the specific under cuts and draft lines as well as other relieved and protruding portions.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0026]    While the invention is primarily described with respect to the preferred embodiment wherein the elastomeric seal is adhered, secured, bonded or molded onto the lid or cover for sealing with the pan, it should be understood that the invention is also intended to include placement of the elastomeric seal on the pan for sealing with the cover.  
         [0027]    Looking more specifically at the figures, it can be seen that the invention comprises a cover or lid  10  which is suitable for placement over, and substantially in sealed relationship with a pan or dish  12 . The pan  12  has exterior side walls  14  and  16  with end walls  18  and  20 . These respective walls  14 ,  16 ,  18 , and  20  define a bottom portion  22 .  
         [0028]    The walls  14  through  20  terminate upwardly into an area that is set outwardly of the edge by a band or bead  24 . The band or bead  24  can be seen in FIG. 8. The band  24  has an interior stepped area  25  having an interiorly flared surface  27  which tapers into the band  24  and the wall  18  and has an outward step  29 .  
         [0029]    The band or bead  24  as stepped from the walls  14  through  20  also provides reinforcement. On the top edge of the pan  12  a flange or web  26  is provided which circumscribes the pan  12 . The flange or web  26  has a compound curved portion  28  providing a concavity which terminates at the edge region in a lip  30  circumscribing the pan  12 .  
         [0030]    The reinforced edge or band  24  serves to provide for a degree of strength as well as receiving the seal of the cover  10 . This strength enhances the overall features to allow for a seal to be maintained by avoiding untoward flexure outwardly. The flange  26  with the lip  30  also reinforces the edge region while at the same time providing a seating surface upon which the cover  10  can be placed. The depending or lowered lip  30  allows a space between the cover  10  and the pan for gripping and removing of the cover.  
         [0031]    Looking more specifically at the cover  10 , it can be seen that a top portion  34  is provided with ribs  36  and  38  which help to provide rigidity. The top portion  34  of the cover  10  is recessed, indented or depressed by virtue of a wall  40  surrounding the interior portions. The wall  40  extends upwardly to a surrounding lip, flange, or edge region  42 . The upper lip or flange  42  is spaced upwardly from the surface of the top  34  by the distance of the wall  40 .  
         [0032]    As shown in FIG. 3, the flange or edge region  42  has an underside or lower portion  44  which tapers at a tapered region  46  in order to fair into the edge of the flange  42 . This slightly tapered portion allows for removal of the cover  10  in a more facile manner by providing for a grip.  
         [0033]    In order to secure the cover  10  in a relatively and substantially sealed condition to the pan  12 , a seal, gasket, or closure  50  is provided around the edge of the cover  10 . This seal, gasket or closure  50  is flexible and extends downwardly below the major portion of the cover  10 . The seal  50  is sufficiently flexible as can be seen in FIGS. 7 and 8 to permit the placement of the seal  50  interiorly of the pan  12 .  
         [0034]    Looking more specifically at FIG. 8, it can be seen wherein the seal  50  is displaced slightly inwardly to the point of sealing the cover  10  to the pan  12  at the interface thereof. This interface shows wherein the band  24  is reduced at a step  25  which has a tapered surface  27  circumscribing the interior portion of the pan  12 .  
         [0035]    The seal  50  is in the form of an elastomeric material which is preferably a thermoplastic polyurethane as provided by Bayer Corporation Plastics Division. An aromatic polyether-based elastomeric plastic or other elastomeric plastic meeting the requirements which will be set forth hereinafter can also be used.  
         [0036]    When adhering, bonding and molding the seal  50  to the cover  10 , the bond is made preferably to a polycarbonate which provides for a strong bond, particularly when a thermoplastic polyurethane is the material of the seal. However, other types of plastics other than a polycarbonate for the cover  10  and for the pan  12  can be utilized. The substitution of various materials for the seal  50  will be expanded upon hereinafter.  
         [0037]    Looking more specifically at the seal  50 , it can be seen where it comprises an interior expanded lip or flange portion  60  which has been molded around the edge as seen in FIGS. 4, 7, and  8 . This molded edge portion seats within a recess as will be detailed hereinafter within the cover  10 . The seal  50  has a plurality of longitudinal ribs or protruding bands  62 ,  64 ,  66 , and  68 . The protruding bands  62  through  68  although four in number can be of other plural numbers depending upon the amount of resiliency seal and tightness that is required in seating the cover  10  within the pan  12 . In some measure, these ribs or circumscribing bands  62  through  68  can be seen in a relatively collapsed condition when sealed as shown in FIG. 8.  
         [0038]    Circumscribing the seal  50  at the base portion thereof is a convex arcuate trough  70  with a terminal edge portion extension or finger  72 . The arcuate portion  70  is preferably outside of the general line or dimension extending downwardly along the edge of the seal defining the area between the ribs  62  through  68 . In this manner, when impressed into the pan  12  interior, it can be seen as collapsing inwardly to provide a seal in conjunction with the rounded or sloped edge  27  of the step  25  surrounding the interior of the pan  12 . This substantially helps to seal the interface between the seal  50  and the pan  12 .  
         [0039]    Various configurations to provide the arcuate convex configuration  70  terminating in the terminal portion  72  can be utilized. In effect, it can constitute a protuberance, rib, finger, expansion, or land  80  which flexes inwardly and outwardly in its cross-section. The finger or extension  80  when displaced by the side walls of the pan  12  creates somewhat of a seal. As can be seen in FIG. 8, the inward flexure creates an up bending channelized portion  72  which creates an improved seal with significant resilience as well as sealing continuity.  
         [0040]    Looking more specifically at the cover  10  without the seal  50 , it can be seen that the cover  10  in FIGS. 3, 5,  6  and  9  has been shown in detail. A plan view of the underside of the seal  50  has been shown in FIG. 5 with a highly enlarged view as taken within a curved portion of the bottom of the cover  10  in FIG. 9.  
         [0041]    The cover  10  without the seal as seen in FIG. 3 shows the lip  42  having its sloped faired portion  46  terminating in the lower edge  44 . Extending therefrom are a number of dovetail like portions  80 . The dovetail like portions  80  are such where they extend downwardly toward the lower portion of the cover. The dovetails  80  are relieved between them with relief portions, insets, indentations, depressions, and channels  82  between the dovetails. The insets  82  are configured so as to provide for a gripping of the seal in the manner to be described.  
         [0042]    As shown in FIG. 5, the upper portion of the dovetails  80  and relief portions  82  terminate in a channel  86  formed as a slight depression on the underside  44  of the flange  42  for receiving the seal  50  therein. In the lower area, the dovetails  80  terminate at an interior portion, or relieved surface forming a shallow channel  88  with a step  90  surrounding the interior periphery or underside of the top portion  34  of the cover  10 . This channel  88  with the step  90  allows for a retention of the seal  50  in a more secure position than without it.  
         [0043]    Enhancing the overall mechanical adhesion of the seal  50  to the cover  10  are a plurality of circular depressions  100  in the channel  86  and relatively smaller depressions  102 . Also, a plurality of angular tabs or insets  104  can be seen. The angular tabs or insets  104  allow for a further gripping of the seal  50 .  
         [0044]    On the interior channel  88  with the step or ledge  90 , it can be seen that there is a second grouping of round depressions  110  and smaller depressions  112 . These respective depressions  110  and  112  allow for a further griping of the seal  50 .  
         [0045]    When the top or cover  10  without the seal  50  is first injection molded, or formed in any other particular way it must be withdrawn from the mold. Accordingly, a draft angle  130  can be seen on the insets  82  and the dovetails  80  as shown in FIG. 3. This draft angle  130  can be a reduction in exterior dimensions. As the part is withdrawn from the mold, it comes off freely without binding on the mold. The draft angle can be anywhere from 1° to 9° or more depending upon the type of mold.  
         [0046]    In order to provide for a dovetail mechanical engagement of the seal  50  into the insets  82  and the dovetails  80 , the dovetails have an angular inset  134  which creates a grip on the seal  50 . This angle can be approximately anywhere from 1° to 30° from where it intersects the peripheral arch of the inset  82  and the edge of the inset along the periphery. This angle A can be seen in FIG. 9 as expanded upon and is the angle which helps to mechanically secure the seal  50 .  
         [0047]    The draft angle  130  of the edge region, and the insets  82  and dovetails  80 , can be seen in FIG. 3. This further enhances the withdrawal of the cover  10  from the mold.  
         [0048]    When the seal  50  is molded in place, the draft angle  130  of the edge region provides for a tightened relationship on the mechanical interface between the round openings  100 ,  102 ,  110  and  112 . Also, the stepped relationship of the seal  50  on the indentations  82  and the dovetails  80  with the notches  134  provides for a locking and securement of the seal. Accordingly, a mechanical linkage takes place between the cover  10  and the seal  50 .  
         [0049]    In order to enhance the linkage, the elastomeric material forming the seal  50  is preferably chemically compatible with the plastic forming the pan  12  and the cover  10 . For example, when the cover  10  is made from a polycarbonate, then the seal  50  is preferably made from a thermoplastic polyurethane generally referred to as an aromatic polyether-based grade polyurethane plastic.  
         [0050]    This combination of a polycarbonate lid and a polyurethane elastomer seal  50  provides a bond with a great degree of adhesion. The polyurethane elastomer with its resilience and bonding capacity to the polycarbonate provides for a strong bond while at the same time a significant flexibility for sealing as seen in the cross-section of FIG. 8.  
         [0051]    In order to provide for sufficient flexibility, a shore A rating of between 60 and 120 of the finally molded seal  50  should be provided. This provides sufficient sealing, resilience and deformation for allowing the seal to resiliently deform while at the same time maintaining sufficient stiffness to provide a seal.  
         [0052]    The plastic material for the seal  50  which is most preferred is an aromatic polyether-based thermoplastic polyurethane sold by Bayer Corporation Plastics Division under the mark TEXIN®. TEXIN® is an aromatic polyether-based polyurethane. It can be processed by injection molding, extrusion or blow molding. The resin exhibits an inherent resistance to hydrolysis and the attack of fungi and provides abrasion resistance and impact strength with flexibility.  
         [0053]    Polyetherimides such as ULTEM® provided by General Electric can also be utilized for the seal  50 . This polyetherimide material provides a high level of heat resistance, chemical resistance, high dielectric strength, good mechanical properties and ease of fabrication coupled with good bonding ability.  
         [0054]    The use of TEXIN® for the seal  50  with polycarbonate for the cover  10  and the pan  12  is helpful in complying with FDA, NSF, USDA, and SPSC regulations for food service. This being the case, health and safety for the food service is maintained.  
         [0055]    Inasmuch as the pan  12  and cover  10  of this invention must be food compatible and meet with FDA food-contact regulations, polycarbonate is deemed desirable and is well received. Polycarbonate is further desirable because of its clarity.  
         [0056]    Other preferred plastics for the food pan  12  and the cover  10  can be utilized. For example, other preferred plastics for the food pan  12  and for the cover  10  include among others polyethylenes, polypropylenes, and styrenic resins, in particular, styrene-acrylonitrile (SAN) and acrylonitrile-butadiene-styrene (ABS). The above mentioned plastics or resins are preferred for their clarity, ease of fabrication, thermal stability, relatively high modulus and low cost.  
         [0057]    The food pan  12 , the cover or lid  10  and the seal  50  according to the invention can be made from many other plastic materials besides those preferred plastic materials mentioned above. When intended for food use, any of the resins and polymers approved for food use by the Food and Drug Administration can be used keeping in mind that chemically compatible material provide a better bond. Examples of such plastic materials can include among others the homopolymers, copolymers, polymers and mixtures thereof containing:  
         [0058]    Acrylic and modified acrylic plastics;  
         [0059]    Acrylonitrile/butadiene/styrene copolymers;  
         [0060]    Acrylonitrile/butadiene/styrene/methyl methacrylate copolymers;  
         [0061]    Acrylonitrile/styrene copolymers;  
         [0062]    Acrylonitrile/styrene copolymer modified with butadiene/styrene elastomers;  
         [0063]    n-Alkylglutarimide/acrylic copolymers;  
         [0064]    Cellophanes;  
         [0065]    Cross-linked polyacrylate copolymers;  
         [0066]    1,4-Cyclohexylene dimethylene terephthalate and 1,4-Cyclohexylene dimethylene isophthalate copolymers;  
         [0067]    Ethylene-acrylic acid copolymers;  
         [0068]    Ethylene-carbon monoxide copolymers.  
         [0069]    Ethylene-1, 4-cyclohexylene dimethylene terephthalate copolymers;  
         [0070]    Ethylene-ethyl acrylate copolymers.  
         [0071]    Ionomeric resins;  
         [0072]    Ethylene-methyl acrylate copolymer resins;  
         [0073]    Ethylene/1,3-phenylene oxyethylene isophthalate/terephthalate copolymers;  
         [0074]    Ethylene-vinyl acetate copolymers;  
         [0075]    Ethylene-vinyl acetate-vinyl alcohol copolymers;  
         [0076]    Fluorocarbon resins;  
         [0077]    Isobutylene polymers;  
         [0078]    Isobutylene-butene copolymers;  
         [0079]    Melamine-formaldehyde resins;  
         [0080]    Nitrile rubber modified acrylonitrile-methyl acrylate copolymers;  
         [0081]    Nylon resins;  
         [0082]    Olefin polymers;  
         [0083]    Perfluorocarbon resins;  
         [0084]    Polyarylate resins;  
         [0085]    Polyaryletherketone resins;  
         [0086]    Polyarylsulfone resins;  
         [0087]    Poly-1-butene resins and butene/ethylene copolymers;  
         [0088]    Polycarbonate resins;  
         [0089]    Polyestercarbonate resins;  
         [0090]    Polyester elastomers;  
         [0091]    Polyetherimide resins;  
         [0092]    Polyethylene resins, carboxyl modified;  
         [0093]    Polyethylenes, chlorinated;  
         [0094]    Polyethylenes, fluorinated;  
         [0095]    Polyethylenes, oxidized;  
         [0096]    Polyethylene phthalate polymers;  
         [0097]    Poly(phenyleneterephthalamide)resins;  
         [0098]    Poly(p-methylstyrenes) and rubber-modified poly(p-methylstyrenes);  
         [0099]    Poly(oxy-1,2-ethanediyloxycarbonyl-2,6-naphthalenediylcarbonyl) resins;  
         [0100]    Polystyrenes and rubber-modified polystyrenes;  
         [0101]    Polysulfide polymer-polyepoxy resins;  
         [0102]    Polysulfone resins;  
         [0103]    Poly(tetramethylene terephthalates);  
         [0104]    Polyurethane resins;  
         [0105]    Styrene block polymers;  
         [0106]    Styrene-maleic anhydride copolymers;  
         [0107]    Styrene-methyl methacrylate copolymers;  
         [0108]    Textryls;  
         [0109]    Urea-formaldehyde resins;  
         [0110]    Vinyl chloride-ethylene copolymers;  
         [0111]    Vinyl chloride-hexene-1 copolymers;  
         [0112]    Vinyl chloride-lauryl vinyl ether copolymers;  
         [0113]    Vinyl chloride-propylene copolymers;  
         [0114]    Vinylidene chloride/methyl acrylate copolymers; and,  
         [0115]    Vinylidene chloride/methyl acrylate/methyl methacrylate polymers.  
         [0116]    The above list is only intended to be illustrative of the plastics which can be used and is not intended to constitute a limitation thereof. Other plastic materials and mixtures thereof will be apparent to one skilled in the art and can be used without departing from the spirit and scope of the invention.  
         [0117]    In addition to the foregoing, food is sometimes served at elevated temperatures. Accordingly, preferred elastomers and plastics including polycarbonates should have a temperature of deformation which is greater than or equal to about 212° fahrenheit. In most uses, the foregoing elastomers as noted are such where they exceed the temperature requirements for food service.  
         [0118]    Based upon the foregoing, it can be seen that this invention is a substantial step over the prior art in providing a sealed relationship between a cover  10  that can be easily removed yet provide a sufficient seal over a pan  12  containing food which is to be served.