Machine for molding a peripherally encapsulated product

Details Machine for molding a peripherally encapsulated product Machine for molding a peripherally encapsulated product

2003-03-25

2004-08-31

Davis, Robert B. (Department: 1722)

Plastic article or earthenware shaping or treating: apparatus

Distinct means to feed, support or manipulate preform stock...

Female mold type means

C425S128000, C425S443000, C264S252000

Reexamination Certificate

active

06783347

ABSTRACT:

BACKGROUND OF THE INVENTION
It is conventional to insert a small panel or piece of glass into a cavity of a multi-part mold and inject therein under elevated temperature and pressure polymeric/copolymeric material which peripherally encapsulates a peripheral edge of the glass. An early injection molding system of this type was used, for example, to manufacture lens mounts, as disclosed in U.S. Pat. No. 2,266,169 in the name of Chester W. Crumrine which granted on Dec. 16, 1941. A lens element is clamped between two centering plungers which hold the lens with a peripheral edge thereof projecting into an annular cavity into which hot plastic is injected under pressure, cools and is subsequently removed from the mold cavity in the form of a lens mount. Similar injection molding to form peripherally encapsulated pieces of glass are found in U.S. Pat. Nos. 2,559,860 and 3,971,841 issued to Howard G. Fay and Leon Rubinstein, respectively, on Jul. 10, 1951 and Jul. 27, 1976, respectively. Each of these two patents relate to lens systems for photographic apparatus.
Larger pieces of glass have also been similarly provided with an injection molded rim, encapsulation, or frame, as in U.S. Pat. Nos. 4,626,185; 4,695,420 and 5,676,894 in the respective names of Bernard Monnet, Charles E. Grawey et al. and Paul Specht, which issued respectively on Dec. 2, 1986; Sep. 2, 1987 and Oct. 14, 1997. Such larger encapsulated glass structures are typically used as curved automobile glass panels, printed circuit boards, window panes, structural paneling, and the like.
Another approach toward the manufacture of a frame member which encapsulates a peripheral edge of a panel is found in U.S. Pat. No. 5,329,686 in the name of Maurice A. Kildal et al. issued on Jul. 19, 1994. In this patent a panel is placed between a frame member with an edge thereof being located in a recess while an integral lip of the frame member can be bent a distance sufficient to allow the panel to be peripherally clamped to the frame. Heretofore eye glass rims were so constructed, as is evidenced by U.S. Pat. No. 3,399,018 in the name of Conrad L. Leblanc issued on Aug. 27, 1968.
Well prior to the latter disclosures, powdered material was placed in an annular cavity of a mold into which was inserted a piece of tempered glass, and upon the closing of the mold with the glass clamped and centered therein, the powdered material melted and fused to a periphery of the glass. Typical of this process was the utilization of “Bakelite” powder in the manner disclosed in U.S. Pat. No. 2,137,472 granted to Lewis Jex-Blake Forbes on Nov. 22, 1938.
In lieu of powder which can be molded under heat and pressure, as defined in the aforementioned patent, it had been common for years to utilize a ring or ring-like member of elastomeric material to form a seal for bearings or the like by placing the elastomeric member and a metal reinforcing member in a mold and closing the same under heat and pressure, as disclosed in U.S. Pat. No. 3,341,647 granted on Sep. 12, 1967 to Douglas J. Aberle. The seal is extruded about an inner periphery of the reinforcing member and is appropriately contoured to provide dual-lip seals with excess material being squeezed radially outwardly into a cavity for collecting excess unwanted elastomer.
Somewhat similar to the latter process is that of manufacturing such items as loudspeaker diaphragms between a pair of mating molds by inserting therein the diaphragm and, adjacent an edge thereof, a strip-shaped base material consisting of rubber as a main composition with an associated foaming agent. During heat and pressure molding in the cavity of the close mold the rubber is vulcanized and defines a foamed edge self-adhered to the outer periphery of the diaphragm, as disclosed in U.S. Pat. No. 5,705,108 issued Jan. 6, 1998 to A. Nonogaki.
The assignee of the present invention has expertise in the injection molded encapsulation of tempered glass which is used primarily for shelving, particularly for refrigerators, as is evidenced by U.S. Pat. Nos. 5,273,354; 5,362,145; 5,403,084; 5,429,433; 5,441,338 and 5,454,638 issued respectively on Dec. 28, 1993; Nov. 8, 1994; Apr. 4, 1995; Jul. 4, 1995; Aug. 15, 1995 and Oct. 3, 1995, all assigned to the assignee of the present application.
Typically, such encapsulated shelves are manufactured in an injection mold of the type disclosed in pending application Ser. No. 08/303,200 filed on Sep. 8, 1994 in the names of Max Meier et al. In the latter disclosure a tempered glass plate or panel has its peripheral edge located in a peripheral or annular cavity into which highly pressurized, hot, synthetic plastic polymeric/copolymeric material is injected and, upon subsequent cooling, the peripheral edge of the panel is bounded by a polymeric frame, rim or encapsulation which, since intended for use as a refrigerator shelf, has also integrally unitized thereto during molding opposite metallic shelf brackets.
A cooktop can be manufactured in much the same manner as that described immediately above, and a full disclosure thereof is found in commonly assigned pending U.S. application Ser. No. 08/890,651 filed on Jul. 9, 1997.
SUMMARY OF THE INVENTION
In keeping with the foregoing, a primary object of the present invention is to provide a novel and unobvious method of manufacturing a peripherally encapsulated unit, such as a range oven door, which in use is subject to relatively high temperatures, particularly when an oven is being automatically cleaned under elevated temperatures. Range oven doors are presently manufactured from metal which has a high degree of rigidity and temperature stability, resist distortion, can withstand abuse, etc. However, conventional range oven doors are made of many different pieces requiring separate formation, fabrication and assembly. Most commonly, such conventional range oven doors include a multipiece, inner, metal door frame assembly and a multipiece, oven door outer shell assembly. The latter are individually manufactured to include an oven door inner metal frame and an oven door outer shell, each of which has a tempered glass viewing panel or window. A separate metallic connecting flange through which fasteners, pass is utilized for securing each glass panel to its associated frame and/or shell. The outer shell is also necessarily primed and painted to match or complement the color of the range/oven. All of this is extremely time consuming and costly.
The prior art patents referenced earlier herein suggest the manufacture of a range oven door by injection molding polymeric/copolymeric material under heat and pressure to encapsulate a peripheral edge of a tempered glass sheet. Unfortunately, the polymeric/copolymeric plastic materials available for injection molding cannot maintain tolerances, particularly if heated to relatively high temperatures. In other words, such materials generally lack relatively high hot rigidity at temperatures associated with baking, and even under relatively low temperatures the strength to weight ratio is relatively low i.e., the polymeric material is relatively weak and lacks the necessary strength, toughness and rigidity to withstand normal range oven door usage. Furthermore, while smaller products can be formed by injection molding polymeric material about the edge of a piece of glass, larger products create additional manufacturing problems, such as the control, reduction or elimination of product shrinkage. Absent non-shrink or low-shrink characteristics, it would be essentially impractical, if not impossible, to form an injection molded encapsulated polymeric/copolymeric oven door, be it an oven door outer shell or an oven door inner frame or both and connect the two together with repetitive accuracy. The individual shrinkage of each and the effects thereof one upon the other would essentially preclude either (a) inner and outer encapsulated units from being matchingly connected together or (b) either such encapsulated units from being matchingly connected to its multipart metal counterpart to form a commercially acceptable

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