Abstract:
A method for fabricating a lid for attachment to a vessel having an open top surrounded by a peripheral edge portion, includes injection molding from a molten plastic material a first shot structure defining a web portion, a peripheral portion surrounding the web portion; in a second shot procedure, over-molding an elastomeric material different from said plastic material onto the first short structure to form a seal structure portion integrated with the lid portion to form a unitary lid-seal structure, wherein the seal structure portion is permanently adhered to the peripheral portion of the first shot structure, and wherein the seal structure portion is configured to provide an air-tight seal between the lid and a sealing surface portion of the peripheral edge of the vessel when the lid is attached to the vessel.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional application of U.S. application Ser. No. 13/193,456, filed Jul. 28, 2011, now U.S. Pat. No. 8,678,230, which in turn claimed priority from provisional U.S. Application No. 61/449,563, filed Mar. 4, 2011, and from provisional U.S. Application 61/369,644, filed Jul. 30, 2010; the entire contents of which applications are hereby incorporated by reference. 
    
    
     BACKGROUND 
     Vessels for holding food items may include a separate lid, but are often not provided with an air-tight seal. This is particularly the case for glass bakeware vessels for example. Air-tight containers-lid systems are typically fabricated from a rigid plastic material, and typically utilize a separate seal member disposed between the lid and container. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features and advantages of the disclosure will readily be appreciated by persons skilled in the art from the following detailed description when read in conjunction with the drawing wherein: 
         FIG. 1A  is an isometric view of an exemplary embodiment of a vessel and lid in an attached configuration to provide an air-tight seal.  FIG. 1B  is a side view of the vessel-lid combination of  FIG. 1A .  FIG. 1C  is a front view of the vessel-lid combination of  FIG. 1A .  FIG. 1D  is an exploded view of the vessel and lid. 
         FIG. 2A  is an isometric view of the exemplary lid of the combination of  FIG. 1A , with the latches in a latch position.  FIG. 2B  is a front view of the lid of  FIG. 2A .  FIG. 2C  is a top view of the lid of  FIG. 2A .  FIG. 2D  is a bottom view of the lid of  FIG. 2A . 
         FIG. 3A  is a top view of an embodiment of a first mold shot structure for an exemplary embodiment of a lid for the combination of  FIG. 1A .  FIG. 3B  is a cross-sectional view taken along line  3 B- 3 B of  FIG. 3A .  FIG. 3C  is an enlarged portion of  FIG. 3B , within circle  3 C of  FIG. 3B .  FIG. 3D  is a cross-sectional view taken along line  3 D- 3 D of  FIG. 3A .  FIG. 3E  is an enlarged portion of  FIG. 3D , within circle  3 E of  FIG. 3D . 
         FIG. 4A  is a top view of an embodiment of a first mold shot structure for an exemplary embodiment of a lid, positioned in place on a vessel.  FIG. 4B  is a cross-sectional view taken along line  4 B- 4 B of  FIG. 4A .  FIG. 4C  is an enlarged portion of  FIG. 4B , within circle  4 C of  FIG. 4B .  FIG. 4D  is an isometric view of a portion of the first mold shot structure. 
         FIG. 5A  is a top view of an embodiment of the lid of  FIG. 1A .  FIG. 5B  is a cross-sectional illustration of the lid of  FIG. 5A , taken along line  5 B- 5 B of  FIG. 5A .  FIG. 5C  is an enlarged portion of  FIG. 5B , within circle  5 C of  FIG. 5B .  FIG. 5D  is an enlarged portion of  FIG. 5B , within circle  5 D of  FIG. 5B .  FIG. 5E  is an enlarged portion of  FIG. 5B , within circle  5 E of  FIG. 5B .  FIG. 5F  is a cross-section view taken along line  5 F- 5 F of  FIG. 5A , as latched onto a vessel as in  FIG. 1A . 
         FIG. 6A  is another top view of the lid of  FIG. 1A .  FIG. 6B  is a cutaway view, taken along line  6 B- 6 B of  FIG. 6A .  FIG. 6C  is an enlarged view of the portion of  FIG. 6B  within circuit  6 C. 
         FIG. 7A  is a top view of an exemplary embodiment of a vessel-lid combination as in  FIG. 1A , but with the latches in an opened position.  FIG. 7B  is a cutaway view, taken along line  7 B- 7 B of  FIG. 7A .  FIG. 7C  is an enlarged view of the portion of  FIG. 7B  within circle  7 C. 
         FIG. 8  is an isometric view showing an exemplary embodiment of a vessel-lid combination as in  FIG. 1A , with another like vessel in a stacked configuration.  FIG. 8A  is a top view of the stacked configuration of  FIG. 8 .  FIG. 8B  is a cutaway view taken along line  8 B- 8 B of  FIG. 8A .  FIG. 8C  is an enlarged view of the portion of  FIG. 8C  within circle  8 C. 
         FIG. 9A  is a top view of an alternate embodiment of a lid.  FIG. 9B  is a cross-sectional view of the lid of  FIG. 9A , taken along line  9 B- 9 B of  FIG. 9A .  FIG. 9C  is an enlarged view of the portion of  FIG. 9B  within circle  9 C. 
         FIGS. 10A and 10B  are respective isometric views of alternate embodiments of a vessel-lid combination. 
         FIGS. 11A, 11B and 11C  are respective isometric, bottom and end views of another exemplary embodiment of a vessel-lid combination. 
         FIG. 12A  is a top view of the lid of the combination of  FIG. 11A , with the latches in an open position.  FIGS. 12B and 12C  are respective bottom views of a lid as in  FIG. 11A , without the seal (a first shot structure) and with the seal after a second molding shot. 
         FIG. 13A  is a top view of a lid as in the vessel-lid combination of  FIG. 11A .  FIGS. 13B, 13C, 13D, 13E and 13F  are respective cross-sections taken along cross-sectional lines indicated in  FIG. 13A .  FIG. 13G  is an enlarged fragmentary view of the portion of  FIG. 13F  within circle  13 G. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description and in the several figures of the drawing, like elements are identified with like reference numerals. 
     An exemplary embodiment of a vessel-lid combination includes a glass, ceramic or metal vessel having an open top surrounded by a peripheral edge, a lid fabricated of a plastic material, and a seal structure integrated with the lid to form a unitary structure. The lid is configured to attach to the open top by means of a latch or set of latches integrated with the lid, and the seal structure is configured to provide an air-tight seal between the lid and the peripheral edge of the vessel when the lid is attached to the vessel. In one exemplary embodiment, the vessel is a container fabricated of a glass suitable for baking or oven heating applications. In a general sense the vessel could be any container with a suitable locking lip to engage the lid latches, including plastic, ceramic or other containers. 
       FIGS. 1-8C  illustrate an exemplary embodiment of a vessel and lid system  50 , which includes a vessel  60  and a lid  70  with an integral seal structure and latches  80 . The vessel  60  in one embodiment is a glass bakeware container, suitable for heating or baking food items in a hot oven. In this embodiment, the vessel  60  is made from a material which can withstand oven temperatures and cooling stresses, such as, by way of example only, borosilicate glass, which provides advantageous thermal properties for safe use under baking and cooling conditions. Other types of glass, metal or ceramic vessels can be configured for use with the lid  70 , such that the vessels are formed with a sealing edge and latch engagement lip, as described more fully below. 
     The cutaway view of  FIG. 7B  illustrates the construction of the exemplary vessel  60  in further detail. The vessel  60  is a unitary structure, having an open top region  60 A, defined by a bottom portion  62 A, a sidewall portion  62 B and a peripheral rim portion  64 . A sealing edge portion  62 C is defined by the sidewall portion at or adjacent the open top region. In this example, the sidewall portion  60 B is angled outwardly from the bottom region, defining a  15  angle relative to the bottom portion. This particular angular arrangement is but one example, other configurations of the sidewall and bottom portions of the vessel may alternately be employed. The rim portion  64  includes a generally flat top edge portion  64 A and a latch engagement lip portion  64 B. 
     Referring to  FIGS. 1A-1D , the lid  70  is attached to the vessel  60  and latched in place to cover the open vessel top, using latches  80  connected by living hinges to the lid proper on opposite sides of the lid. The latches have latch hook features  82 A which engage the latch engagement lip portion  64 B of the vessel when the lid is placed on the vessel and the latches rotated about the hinges to the latched position shown in  FIGS. 1A-1C , for example. A seal portion  90 D engages a seal surface on the vessel as the lid is latched in place. 
     The lid  70  in an exemplary embodiment is fabricated by injection molding using a two shot molding technique, in which a first shot structure is fabricated of a first plastic material, and then the lid structure is completed in a second shot in which a second plastic material is overmolded to a portion of the first shot structure. In an exemplary embodiment, the primary, first shot lid structure is formed from a clear polymer such as polypropylene or similar structurally rigid polymer material. An exemplary over-mold material used in the second shot is a thermoplastic elastomer (TPE) material. 
       FIGS. 2A-2D  illustrate the lid  70  in a completed form, i.e. after the overmolding process is completed to form the second plastic material to the first shot structure. 
       FIGS. 3A-3E and 4A-4D  illustrate an exemplary first shot structure  70 - 1  for the lid  70 . The first shot structure  70 - 1  defines a web portion  70 - 1 A which is generally flat and is configured to extend over the open top region of the vessel when the lid is attached. The first shot structure  70 - 1  includes a peripheral region  70 - 1 B extending around the periphery of the lid, and opposed end regions  70 - 1 C at the longitudinal ends of the lid, adjacent the sides of the lid which do not support latches  80 . Slot openings or channels  70 - 1 D are formed in the first shot structure  70 - 1  at spaced locations around the peripheral region  70 - 1 B and in the end portions  70 - 1 C. In this exemplary embodiment, there are eight slots  70 - 1 D in the first shot structure, and this number can be increased or decreased, depending on the configuration and size of the first shot structure. The slots  70 - 1 D pass through the first shot structure from the top surface to the bottom surface of the peripheral region of the first shot structure. The structure  70 - 1  further includes a downwardly protruding outer peripheral sidewall portion  70 - 1 E, and an inner peripheral rib portion  70 - 1 F defining a lower bonding ring portion  70 - 1 F 1 . Transverse rib portions  70 - 1 G are formed between the inner rib portion and the outer sidewall portion at spaced intervals around the periphery of the first shot structure. 
     Once the first shot structure  70 - 1  has been formed, the second shot process is performed. The over-mold material applied to the first shot structure  70 - 1  in an exemplary embodiment is a thermoplastic elastomer material. In an exemplary embodiment, this material is molded in an injection molding process similar to that of the formation of the first shot structure  70 - 1 , except that the first shot structure is already in the mold cavity and thereby the second shot material attaches to the first shot structure as the hot second shot material enters into the mold and onto the first shot structure. The second shot material is located preferentially based of the design of the mold to fill the desired locations. The two shot process in a general sense is widely used. The second shot material is selected to provide good adhesion to the material of the first shot structure  70 - 1 . The second shot material, in an exemplary embodiment, may also be selected to provide appropriate bending characteristics, and a high coefficient of friction with the vessel material to ensure a high quality seal. The second shot material may also be selected to have good tear strength so as to retain good sealing over time. For the exemplary embodiment in which the vessel is fabricated of borosilicate glass, the first shot structure may be polypropylene or similar structurally rigid polymer material, and the over-mold material used in the second shot is a thermoplastic elastomer (TPE) material. 
     In an exemplary embodiment, the second shot material covers at least the peripheral top edge portion  70 - 1 B of the first shot structure, and flows through flow channels to the peripheral underside of the first shot structure. A first portion of each flow channel is formed by the slots or channels  70 - 1 D formed in the first shot structure  70 - 1 . The flow channels provide a path for the second shot material to flow through the top surface of the lid, down the height of the vertical rib  70 - 1 F to reach the sealing area  70 - 1 I, where the second shot material defines a peripheral flexible seal portion. The flow channels include vertical path portions  70 - 1 H below each slot  70 - 1 D, which are recessed into the rib portion  701 -F. 
     In an exemplary embodiment, there are three main parts to the flow channels for the molten second shot materials. The first part is the opening or through holes  70 - 1 D in the lid top. The second part is the vertical flow path portions  70 - 1 H defined by the recesses in the inner rib  70 - 1 F. The third portion of the flow path is provided by the bonding ring portion  70 - 1 F 1  of the inner rib portion. The bonding ring portion  70 - 1 F 1  provides additional adhesion surface area all around the sealing area  70 - 1 I, where the second shot material will experience stress from repeated opening and closing of lid. 
     The ribs  70 - 1 G are formed at multiple locations around the periphery of the lid providing rigidity to the lid and a stop for the application of the lid to the vessel. The cross-section of the rib shows how the rib provides a stop surface  70 - 1 G 1  for the consumer to know when the lid is in place and when it is appropriate to engage the latch with the vessel. 
     An exemplary embodiment of the lid  70  after completion of the second shot is illustrated in  FIGS. 5A-7C . In  FIGS. 5A and 5B , the stippled areas designate second shot material. The second shot material produces layers or features generally indicated by reference “ 90 _”, including the top peripheral layer  90 A, a layer  90 B on each vertical flow channel portion  70 - 1 H, a layer  90 C formed on the bonding ring portion  70 - 1 F 1 , which extends around the bottom edge of the bonding ring portion to form the peripheral seal portion  90 D. It is the circumferential seal portion  90 D, extending about the entire periphery of the bonding ring portion, that engages the sealing surface  62 C of the vessel  60  to create an air-tight seal. The seal portion  90 D forms a flexible flap which bends as the lid is placed in position on the vessel, and is bent upwardly as the lid is latched, as shown, for example, in  FIGS. 5F, 8B and 8C . In this exemplary embodiment, the second shot material includes layers  90 E and  90 F formed on the latches  80 . 
     The lid web surface portion  70 - 1 A in this exemplary embodiment is substantially flat or planar to receive a like vessel or any other item that would require stacking. The peripheral portion  70 - 1 B is generally raised with respect to the web surface portion, and portion  70 - 1 B and end portions  70 - 1 C are covered with the second shot or over-mold material layer  90 A. The over-mold layer  90 A covering the raised peripheral portion  70 - 1 B provides a peripheral retention surface  90 A- 1 . The over-mold layer  90 A, as previously mentioned, is preferentially made of a material (such as TPE) with a high coefficient of friction with glass and other materials to aid in the retention of the stacking items. The retention surface  90 A- 1  is designed to fit a like vessel appropriately snugly with sufficient manufacturing tolerance for a glass vessel manufacturing process. The stacking of a vessel on the lid of a vessel-lid system is illustrated in  FIGS. 8A-8C . 
     In the exemplary embodiment of the lid  70  depicted in  FIGS. 1A-5F , the hinges  82  are molded in a living hinge arrangement as part of the first shot structure  70 - 1 , and are fabricated of the same material as the first shot, e.g. polypropylene or similar structurally rigid polymer material. A living hinge is typically made from a polymer having long chains where the thinning out of the cross section allows for the chains to align parallel to the hinge allowing the chains to bend or hinge but due to the length of the chains reaching both thicker sections of plastic on both sides the chains connect the two sides. The chains are very strong in tension. The second shot material, e.g. TPE, or over-mold does not cover the hinge  82  in this exemplary embodiment, but covers the first shot material on both sides of the hinge area. 
     In this exemplary embodiment, the ends  82 A,  82 B of the hinges  82  are enclosed by a thickness of (TPE) or over-mold, e.g. as illustrated in  FIGS. 6A-6C . This accomplishes two things. First the living hinge ends act as a tear strip. Typically living hinges are subject to tearing off once a tear has been initiated at one of the ends. The highly elastic over-mold material at either end of the hinge acts to protect the hinge from tearing. In addition the hinge ends act as another flow channel for the second shot or over-mold to flow from the main body of the lid onto the latch area. This can also be achieved by placing additional gates on each location where the second material is desired. However in this embodiment the tooling and manufacturing process is much simplified allowing fewer simpler gates and far more process control. 
     In an alternate embodiment, the hinge  82 ′ is formed by the second shot, not the first. The latch is attached by the second shot. Through holes are provided in the latch body to allow for improved bonding with mechanical bond with both materials.  FIGS. 9A-9C  illustrate this alternate embodiment of a hinge  80 ′ for the lid  70 ′ in which the latch  80 ′ is attached to the lid body proper by the second shot layer forming a living hinge  82 ′. 
     The vessel and lid air-tight seal configuration may be employed on vessels of different sizes and configurations. For example,  FIG. 10A  a square vessel and lid configuration  50 ″.  FIG. 10B  shows another rectilinear vessel and lid configuration  50 ′″. 
     A further embodiment  50 ″″ of a vessel and air-tight lid combination is illustrated in  FIGS. 11A-13F . This exemplary embodiment includes a vessel  60  and lid  170 . The exemplary vessel  60  may be identical to the vessel described above regarding the exemplary embodiment of  FIG. 1A , for example. The lid  170  differs from the lid  70  of  FIG. 1A  in several respects. The lid  170  has a peripheral downwardly extending skirt or outer peripheral edge, defining a lid perimeter which is slightly larger than the perimeter of the vessel, so that the skirt facilitates alignment of the lid onto the vessel. The lid skirt may be provided with a lead-in chamfer or angle to further facilitate alignment of the lid onto the vessel. In this exemplary embodiment, no second shot material is molded onto the top surface of the lid, providing a cost reduction advantage relative to the embodiment of  FIG. 1A . Relatively thick second shot flow leaders are formed on the underside of the lid peripheral region to facilitate each of injection of the molten material of the second shot. Stop ribs are formed in the underside of the lid peripheral region to define a correct latched position of the lid on the vessel, even though the lid perimeter is larger than the vessel perimeter. These features are illustrated in  FIGS. 11A-13G . 
       FIGS. 11A-11C  are respective isometric, bottom and end views of the vessel and air-tight lid combination  50 ″″ including the vessel  60  and with the lid  170  in a latched condition on the vessel. The constituent materials of the vessel and the lid, both the first shot material and the second shot material, may be identical to those of the embodiments of  FIGS. 1-11 . 
       FIG. 12A  is a top view of the lid  170 . In this exemplary embodiment, no second shot material is molded onto the top surfaces of the lid, visible in this top view.  FIG. 12B  is a bottom view of the first shot structure  170 - 1 , with the latches  180  rotated about the living hinges to an unlatched configuration. The first shot structure  170 - 1  includes a downwardly protruding outer peripheral sidewall portion  70 - 1  E, and an inner peripheral rib portion  170 - 1 F. Transverse rib portions  170 - 1 G are formed between the inner rib portion and the outer sidewall portion at spaced intervals on the longitudinal sides of the first shot structure, three on each longitudinal side in this example. In this embodiment, the rib portions  170 - 1 G provide attachment bosses for injection leader portions of the second shot material. The first shot structure  170 - 1  also includes stop ribs  170 - 1 H at the transverse end portions of the second shot structure, in this example, two on each transverse end portion. These stop ribs have a depth sufficient to prevent the lid from being inserted too far into the vessel during an attachment. 
       FIG. 12C  is a bottom view, showing the lid  170  in its completed form, after the second shot material has been overmolded onto the first shot structure. The second shot material includes a region overmolded onto the inner rib  170 - 1 F of the first shot structure, and defining the peripheral seal  190 D. The overmolded second shot material is shown as the stippled regions in  FIG. 12C . It is noted that, during the second shot molding process, the second shot material is injected at injection leader regions  190 F on the transverse rib or boss portions  170 - 1 G, and on narrow portions of the underside of the lid peripheral edge at the transverse end portions, as injection leaders  190 G. The bosses  170 - 1 G provide support for the second shot material, and provide crush force tending to compress the injection leader regions  190 F as the lid is latched onto the vessel. 
     The peripheral seal  190 D is dimensioned to provide appropriate seal force on the vessel and to accommodate the dimensional variations in the vessel due to manufacturing tolerances. The thickness of the seal may be selected to provide an appropriate flexing as the lid is positioned on the vessel and latched. In one example, the seal may have a width in a range of about 2.5 to 4 mm and a thickness at its thickest dimension on the order of 1 mm or so. The dimensions of the seal  190 D including its width and also its elevation position may vary spatially around the perimeter of the lid. This variation in dimensions can accommodate spatial variations in the vessel tolerance. For example, the tolerances in a rectangular vessel are typically greater in its corners, and the seal may be wider in the corners to accommodate wider dimensional variations. Also the elevation of the seal may vary, with the seal positioned lower in the corners relative to the vessel top edge. 
       FIGS. 13A-13G  illustrate the features of the lid  170  and vessel-lid combination  50 ″″ in further detail. The lateral cross-sectional view of  FIG. 13B , taken through line  13 B- 13 B of  FIG. 13A , is taken through one of the ribs or bosses  170 - 1 G, and shows the second shot leader portion  190 B, with terminal portion  190 B- 1  at a crush region, being compressed between the edge of the vessel and the shoulder defined by the rib  170 - 1 G.  FIG. 13B  also shows the second shot region  190 C formed on the outer side of the inner peripheral rib  170 - 1 F, around the rib tip and partially up the inner side of the rib, also forming the seal  190 D. 
       FIG. 13C  is a lateral cross-section taken along line  13 C- 13 C of  FIG. 13A  through the combination  50 ″″, away from the ribs  170 - 1 G, and shows the tapered edge  170 - 1 E 1  of the outer peripheral rib of the lid  170 .  FIG. 13C  also illustrates the oversize of the lid outer peripheral rib  170 - 1 E relative to the outer edge of the vessel  60 , with a small gap  188  between the rib and the vessel edge. 
       FIG. 13D  is a longitudinal cross-sectional view taken along line  13 D- 13 D of  FIG. 13A , through a second shot injection leader region  190 G at each lateral or end region of the lid  170 . The injection leader region  190 G, the second shot region  190 C and the seal  190 D are shown in  FIG. 13D . 
       FIG. 13E  is a longitudinal cross-sectional view taken along line  13 E- 13 E of  FIG. 13A , through the stop ribs  170 - 1 H at either end of the lid.  FIG. 13E  shows the base of the stop ribs resting on the upper surface of the vessel edge, supporting the lid from further downward movement of the lid. 
       FIG. 13F  is another longitudinal cross-sectional view, this one along line  13 F- 13 F of  FIG. 13A , and offset from the stop ribs and the injection leader regions.  FIG. 13G  is an enlarged view of a fragment of  FIG. 13F  within the phantom circle  13 G. These views illustrate an exemplary variation in the elevation of the seal  190 D around the periphery of the lid, showing the transition in height of the seal  190  in a corner of the lid, to accommodate variations in the dimensions of the vessel, which typically has larger manufacturing tolerances in the vessel corners. In  FIG. 13G , the seal portion  190 D- 1  along the longitudinal side of the lid transitions in elevation to seal portion  190 D- 2  approaching the lid corner, and to a lower elevation for corner seal portion  190 D- 3 . The inner peripheral rib  170 - 1 F also transitions in elevation, to position the seal at the appropriate elevation. 
     Although the foregoing has been a description and illustration of specific embodiments of the subject matter, various modifications and changes thereto can be made by persons skilled in the art without departing from the scope and spirit of the invention.