CA1228963A - Heat resistant plastic molded articles - Google Patents
Heat resistant plastic molded articlesInfo
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- CA1228963A CA1228963A CA000449352A CA449352A CA1228963A CA 1228963 A CA1228963 A CA 1228963A CA 000449352 A CA000449352 A CA 000449352A CA 449352 A CA449352 A CA 449352A CA 1228963 A CA1228963 A CA 1228963A
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- brake shoe
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- piston
- plastic body
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Abstract
HEAT RESISTANT PLASTIC MOLDED ARTICLES
ABSTRACT OF THE DISCLOSURE
Plastic molded articles with improved heat resistance comprise a molded resin body having a metallic heat shield molded on the surface of the molded body that is exposed to elevate temperatures. The articles are useful in automotive, appliance, electrical, electronic and aerospace industries. A preferred embodiment is a phenolic resin piston for a disc brake assembly.
ABSTRACT OF THE DISCLOSURE
Plastic molded articles with improved heat resistance comprise a molded resin body having a metallic heat shield molded on the surface of the molded body that is exposed to elevate temperatures. The articles are useful in automotive, appliance, electrical, electronic and aerospace industries. A preferred embodiment is a phenolic resin piston for a disc brake assembly.
Description
Improved heat resistance is constantly in demand with respect to plastic articles used in the automotive, appliance, electrical and aero-space industries. Phenolic resins are typical polymers used in high temperature applications in these industries. Phenolic parts for high temperature applications have short-term heat resistance of about 300 to 500Fahrenheit, and long-term heat resistance of about 250 to 425Fahren-heit. Heat resistance improvements of up to about 100Fahrenheit would greatly enhance the utility of these materials.
Canadian Patents 1,187,424 issued May 21, 1985, and 1,198,379 issued 10 December 24, 1985, both John E. Emmett, are directed to improved plastic pistons used in automotive disc brake assemblies. The improved pistons have a metallic cap that is attached by various anchoring means to the open end of the piston which contacts the backing plate of the brake shoe and functions to drive the brake shoe against the rotor when stopping a moving vehicle. It was found in working with the improved pistons that the presence of the metallic caps greated reduced the thermal degradation of the surface of the piston which contacts the brake shoe, compared to use of the piston without the metal cap. It is believed that the metal cap serves to shield the surface of the plastic piston from the effects of oxygen at elevated temperatures caused by the braking action of the brake shoes during braking of a vehicle.
The object of this invention is to maximize the oxidative shielding of plastic molded articles or parts that are subjected to constant or intermittent high temperatures. The just described plastic pistons are just one example of a plastic part that can be improved by this invention. Many other embodiments of the invention will be described in this specification.
With respect to the plastic pistons, the present invention has a further advantage that the metallic cap does not require a means for securing the metallic cap to the plastic piston, such as the beads, threads and other anchoring means disclosed in the aforementioned Canadian patents. Moreover, metallic caps are less likely to become accidentally detached from the plastic parts such as a plastic piston while it is in service.
~:2896 Summary of the Invention In accordance with this invention, there are provided molded plastic articles with improved heat resistance comprising a molded resin body having a metallic heat shield molded in place on the surface of the molded body that is exposed to elevated temperatures. The articles of the invention are produced from plastic materials, preferably from thermosetting plastics, and more preferably from phenol-aldehyde resin molding materials.
A specific embodiment of the invention comprises a composite vehicular brake piston for activating a vehicu1ar brake shoe during braking oF a vehicle comprising a substantially cylindrical plastic body having an open end and a closed end and a metallic cap extending over the end wall of the open end and secured to the plastic body by molding of the resin body against at least one surface of the metallic cap. The metallic cap may have one or both of (1) means for attaching a vehicular brake shoe or brake shoe assembly so that the brake shoe moves in unison with the piston during braking and debraking of the vehicle, and (2) a means for receiving and holding a dust boot that is conventionally used in connection with disc brake pistons to prevent dust from accumulating between the outside wall of the piston and the caliper.
Other embodiments of the invention in the automot;ve and transportation industry include intake manifolds, automotive engine pistons engine heads and the like.
The invention also finds use in the appliance industry, such as in broilers, hot plates, toasters, and various other heated appliances that have points where the plastic part is in contact or close to heating elements and the like.
The invention also finds use in the electrical industry for articles and parts that come in contact with hot environments, such as in electrical light bulb sockets, light reflectors and shields and the like.
~=Z~3963 Detailed Embodiments of the lnvention _utomotive and Transportation Applications Although the invention will be described in terms of disc brakes particularly intended for motor vehicles, it will be understood that the present improved piston is equally adaptable to piston brakes utilized on aircraft, railroad vehicles and in industrial applications such as engines.
One type of brake assembly presently in use in motor vehicle disc brakes is the opposed piston type. In such type, a piston i5 positioned adjacent each opposite side of a brake disc and forces its respective brake shoe or lining against the disc to impact a braking action. Other types of brake assemblies to which the present invention is equally useful are those in which a single piston is utilized to rnove the brake shoe or lining into contact with both sides of the brake disc by utilizing a caliper slide to impart a braking action.
The improved disc brake plastic piston of the present invention has a metallic cap or face which provides a means of attaching a brake shoe or a brake shoe assembly, or provides a dust boot groove, or, in the most preferred mode, the metallic cap component provides both a brake shoe retaininy means and a dust boot groove.
The improved piston of this invention is comprised of a cylindrical resin body having an open end and a closed end. The "closed end" can be cored out for structural or other purposes and is deemed to be within the foregoing description. A metallic cap extends over the end wall of the open end of the cylindrical body and is secured to the body by the process of molding of the resin body against at least one surface of the metallic cap as will be described in greater detail hereinafter. The metallic cap is adapted to receive and hold a brake shoe clip, also referred to in the trade as a retainer clip, and also to provide a dust boDt groove. In the most preferred embodiments of the invention, the metallic cap prov;des both a brake shoe retain;ng means and a dust boot groove.
Thus the metallic caps of the invention have means for attaching a vehicular brake shoe assembly so that the brake shoe moves in unison with the piston during braking and debraking of the vehicle. The above described attachment is not a permanent bond such as created by welding or soldering.
Rather the brake shoe clip engages the cap as a result of the shaped sur-face thereof, and~is readily removable when it is desired to disassemble the piston from the braking mechanism.
3.~Z~3~36~
The improved plastic pistons of the invention are generally manufactured by placing the metallic cap, suitably shaped to accomplish the requirements of the application, in a mold shaped in the form of a piston. The meta11ic cap or heat shield can be a pre-shaped or pre-formed metal cap or a metallic foil or film that becomes shaped or formed to the contour of the mold during the subsequent molding steps.
The metal cap or foil can have a thickness from about 0.0005 to about 0.25 inch, preferably from about 0.001 to about 0.05 inch. Thereafter, plastic molding material, such as a phenolic resin molding material comprising resin and fillers, is placed in the body of the mold, the temperature is elevated and pressure is applied to the resinous material to fill out the mold and form the plastic piston against at least one of the surfaces of the metallic cap. The plastic molding material can be introduced into the mold in any of the conventional forms such as various particulate forms such as powders, nodules and the like, or in "pre-form"
slugs, and the like. The resinous material is heated and pressed by compression molding or other suitable processes and is composite molded to the inner surface of the metallic cap. When the molded article is removed from the mold, the plastic piston and metallic cap are integrally bonded together. The result is that the metallic cap is embedably molded to the plastic piston. These methods of manufacture have been described with respect to the plastic piston, but are also applicable for manufacturing the other embodiments of the invention described hereinafter.
In the various embodiments of the invention, the metallic caps or heat shields can be any suitable metal such as steel, aluminum, copper and alloy.
Other embodiments of the invention in the automotive and transportation industries includes automotive engine pistons made from phenolic resins and having a metal skin or cap (such as aluminum) on the piston head as a replacement for the present steel and aluminum engine pistons. Internal combustion engine heads and intake manifolds can be made with a thin metal inner skin and a molded phenolic resin outer shell to provide the required dimensional stability and to,que retention.
Automobile mufflers can be produced with a metal inner skin and an outer phenolic resin casing that will last the lifetime of the automobile.
~2139~i3 Appliance Applications Most hand-held, countertop and other heated appliances are limited by the fact that the materials of construction must stand up to UL and other industry standards at the operating temperatures. Phenolic resin molding compounds are often used for enclosures or current-carrying func-tional parts because of the good thermal properties of this thermosetting plastic. Such properties include short term heat resistance of about 300 to 500Fahrenheit and long term heat resistance of about 250 to 425Fah renheit, as well as high heat distortion temperatures of about 325 to 500F and low creep and retention of strength at elevated temperatures.
The use of the present invention to provide oxidative shielding of phenolic resin molding compound appliance parts at the "hot spot" or plastic surface that sees the highest temperature permit use of operating temperatures of up to 100 higher than those stated above. Thus the present invention finds use in heated appliances such as broilers, hot plates, toasters, heating ovens, frying pans, hamburger cookers, popcorn poppers, coffee makers, egg cookers and similiar appliances having hot spots or points where the plastic part is in contact with or close to heating elements or metallic heating surfaces. Use of this invention permits improved, smaller and lower cost appliances. When hot spot tem-peratures exceed the allowable limit of the plastic used in appliances, industry has been resorting to air-gapping, and using metallic or ceramic insulators or shields or combinations of the above, which requires large plastic housings. The plastic housings can be considerably reduced in size to accommodate the heat shielded plastic components of this inven-tion.
Other applications in the appliance industry include electric irons that use heated sole plates. Traditional "electric iron" designs use heated sole plates and metal housings with handles made with phenol resin molding materials, or a combination phenolic housing and phenolic handle. Newer designs use a metal sole plate, an air gap, a heat shield molded from a glass filled or other high heat resistant phenolic molding compound and a thermoplastic handle. The use of oxidative shielding for electric irons consists of a phenolic resin molding compound molded directly to the sole plate, then attached to a thermoplastic or thermoset handle. The use of the invention offers safer, more compact and economi-cal appliances.
~Z~8~363 In the cookware field, "stick handles", the presently employed phenolic resin molding compound handles used on metal cookware, such as frying pans and sauce pans present two inherent problems. First, the handles are subject to thermal degredation on long term useage, and loosen at the point of attachment. Second, since this type of cookware is used on gas burners or ranges, they can be in contact with a gas flame and temperatures exceeding the normal, exposure limit for phenolic resins. The cookware industry uses flameguards to reduce the potential premature handle Failure from a high gas flame. Flameguards are of two designs. One is a metal spacer that fits between the handle and the metal cookware. The second is a metal shield that covers all or the bottom half of the handle for the first inch or so from the point of attachment. These shields are usually not molded on or tight fitting.
The use of the present invention in the form of a molded in metal cap on the end of the phenolic resin handle provides an oxidative shield around the handle. This is an improved flameguard that greatly reduces the possiblility of thermal degradation at the point of assembly and the resulting loose, unsafe handle. For the knobs used on pot and pan covers or lids or in side handles for oven cookware, oxidative shielding increases the liFe of the handle or knob, which are the parts that often fail first in these appliances. In present appliances, knobs and side-handles are bolted through to the cookware. Long term exposure to normal oven temperatures cause the handles to shrink, providing exposure to air and oxidation in the threaded part section. Handles and knobs on contin-ued high temperature exposure fail by thermal degradation and the result-ing cracking from the attachment hole. Molded in attachment bolts and/or metal caps or shields in accordance with the present invention, prevent surface oxidation in the critical points and substantially increase the life ox the handle and knobs. The invention can also be used for handles and knobs for gas, charcoal, propane and electrical heated grills, broil-ers, smokers and the like.
~2~3~363 Electrical Applications Electrical applications, especially phenolic resin molding compoundlighting fixtures used in enclosed or poorly vented areas can benefit significantly by the use of the oxidative shielding provided by the present invention. At present, phenolic resin, ceramic and metal are used for electrical light bulb sockets, light reflectors and shields.
The problem with metal is that it is an electrical conductor, resulting in a potential safety hazard if the insulating system fails. Ceramic is heavy, difficult to manufacture to tolerance and subject to breakage.
Phenolic resins, even the highest heat resistant grades, are better thermal insulators but unacceptable for some designs due to thermal degradation. All systems present a potential fire or electrical hazard if a light bulb with a higher than recommended wattage is used. These problems can be eliminated or seduced by the use or a phenolic resin molding compound with the oxidative metallic cap or shield of the present invention in light bulb sockets and/or light reflectors. These provide improved heat resistance plus the desired thermal conductivity to control heat buildup. The oxidative shield can be achieved by a molded in inter-nal metal skin. The same method can be used for reflectors for halogen lights used for automotive and other uses.
Aerospace and Missile Industry Phenolic resin, ceramic and high temperature metal alloys are used for rocket nozzles, such as thrust nozzles, and for ablative nose cones.
In accordance with the present invention, these applications are ful-filled by a composite molded rocket nozzle with an inner skin of hightemperature metal and a shell made of phenolic resin molding material.
Another emobodiment uses several layers of high temperature metal with layers of phenolic resin molding compound in between in a sandwich type structure. The benefits include more controlled burning and accuracy, thinner walls, lighter weight and improved reliability. other uses include ablative reentry systems and nose cones.
~2~3 _ief Description of the Drawings Figures 1 through 4 are elevational views of composite pistons, partly in section, which illustrates various preferred embodiments of the invention.
Detailed Description of the Drawings Referring to Figure 1, cylindrical piston 11 has a closed end 13 and ar open end 15. The exterior surface 23 of closed end 13 is shown to be concave, but the surface can be more nearly slush with the bottom line of closed end 13 provided that there is a sufficient cavity to provide or a fluid reservoir behind the piston. Metallic cap 19, preferably of steel or aluminum, extends over and covers end wall 14 of opened end 15 of piston 11 and is secured on piston 11 by virtue of the fact that piston 11 is formed by molding the resinous molding material that forms the body of piston 11 against one surface of metallic cap 19. In the molding operation, the metallic cap 19 is placed in the mold first, and then the resinous molding material, preferably in some particulate form or as a "pre-form" is placed in the mold adjacent to one surface of the metallic cap 19. In the molding operation, the resinous molding material is melted and compressed against the surface of the metallic cap 19 so as to 2n form a firm bond therewith. The bond between the resin body of piston 11 and the metallic cap 19 can be improved by forming the metallic cap with one or more of its edges crimped such as shown in Figures 2 and 3 so that these edges become embedded in the molded resin body. In this embodiment, metallic cap 19 forms a heat shield to protect the end wall l against oxidation as a result of the heat generated when the plastic piston is in service. In this embodiment groove 17 has been machined to provide a means for retaining a brake shoe clip. A groove 21 has been machined in the outside wall of piston 11 to provide a means for retaining a dust boot.
Figure 2 illustrates an embodiment of the invention wherein piston 11 is provided with a metallic cap 19 which has a groove 27 on the inside wall of piston 11 which is adapted to receive and retain a brake shoe clip. In this embodiment a groove 21 is machined in the outside wall of piston 11 to provide means or retaining a dust boot.
g Figure 3 illustrates an embodiment of the invention wherein the metallic cap 19 is formed to provide a groove 29 in the narrowed portion of the outer wall of piston 11 as a means for retaining a dust boot. In this embodiment a groove 17 has been machined in the inside wall of 5 piston 11 to provide a means for retaining a brake shoe clip.
Figure 4 illustrates an embodiment of the invention wherein metallic cap 19 is formed to provide a groove 29 in the narrowed portion of the outer wall of piston 11 which serves as a means for retaining a dust boot 41. The metallic cap 19 is also formed to provide a groove 27 on the inside surface of the piston _. Groove 27 provides a means for retaining brake shoe clip 37. Brake shoe clip 37 has two or more bent prongs 39 which are joined to a base plate which is attached by bolts or rivets 43 to a brake shoe backing plate 33 to which is attached brake shoe 35. In operation, the face of the backing plate 33 touches the portion of metallic cap 19 which covers end wall 14, but it is through the prongs 39 that the brake shoe clip 37 is attached to piston 11 by means of the groove 27 wormed in the metallic cap 19. The manner of attachment of the brake shoe clip and dust boot shown in Figure 4 illustrates the manner of attachment contemplated with respect to previously described Figures 2 and 3.
The foregoing description of embodiments is intended to illustrate the invention without limiting it thereby. It will be understood that various modifications can be made in the invention without departing from the spirit or scope thereof.
Canadian Patents 1,187,424 issued May 21, 1985, and 1,198,379 issued 10 December 24, 1985, both John E. Emmett, are directed to improved plastic pistons used in automotive disc brake assemblies. The improved pistons have a metallic cap that is attached by various anchoring means to the open end of the piston which contacts the backing plate of the brake shoe and functions to drive the brake shoe against the rotor when stopping a moving vehicle. It was found in working with the improved pistons that the presence of the metallic caps greated reduced the thermal degradation of the surface of the piston which contacts the brake shoe, compared to use of the piston without the metal cap. It is believed that the metal cap serves to shield the surface of the plastic piston from the effects of oxygen at elevated temperatures caused by the braking action of the brake shoes during braking of a vehicle.
The object of this invention is to maximize the oxidative shielding of plastic molded articles or parts that are subjected to constant or intermittent high temperatures. The just described plastic pistons are just one example of a plastic part that can be improved by this invention. Many other embodiments of the invention will be described in this specification.
With respect to the plastic pistons, the present invention has a further advantage that the metallic cap does not require a means for securing the metallic cap to the plastic piston, such as the beads, threads and other anchoring means disclosed in the aforementioned Canadian patents. Moreover, metallic caps are less likely to become accidentally detached from the plastic parts such as a plastic piston while it is in service.
~:2896 Summary of the Invention In accordance with this invention, there are provided molded plastic articles with improved heat resistance comprising a molded resin body having a metallic heat shield molded in place on the surface of the molded body that is exposed to elevated temperatures. The articles of the invention are produced from plastic materials, preferably from thermosetting plastics, and more preferably from phenol-aldehyde resin molding materials.
A specific embodiment of the invention comprises a composite vehicular brake piston for activating a vehicu1ar brake shoe during braking oF a vehicle comprising a substantially cylindrical plastic body having an open end and a closed end and a metallic cap extending over the end wall of the open end and secured to the plastic body by molding of the resin body against at least one surface of the metallic cap. The metallic cap may have one or both of (1) means for attaching a vehicular brake shoe or brake shoe assembly so that the brake shoe moves in unison with the piston during braking and debraking of the vehicle, and (2) a means for receiving and holding a dust boot that is conventionally used in connection with disc brake pistons to prevent dust from accumulating between the outside wall of the piston and the caliper.
Other embodiments of the invention in the automot;ve and transportation industry include intake manifolds, automotive engine pistons engine heads and the like.
The invention also finds use in the appliance industry, such as in broilers, hot plates, toasters, and various other heated appliances that have points where the plastic part is in contact or close to heating elements and the like.
The invention also finds use in the electrical industry for articles and parts that come in contact with hot environments, such as in electrical light bulb sockets, light reflectors and shields and the like.
~=Z~3963 Detailed Embodiments of the lnvention _utomotive and Transportation Applications Although the invention will be described in terms of disc brakes particularly intended for motor vehicles, it will be understood that the present improved piston is equally adaptable to piston brakes utilized on aircraft, railroad vehicles and in industrial applications such as engines.
One type of brake assembly presently in use in motor vehicle disc brakes is the opposed piston type. In such type, a piston i5 positioned adjacent each opposite side of a brake disc and forces its respective brake shoe or lining against the disc to impact a braking action. Other types of brake assemblies to which the present invention is equally useful are those in which a single piston is utilized to rnove the brake shoe or lining into contact with both sides of the brake disc by utilizing a caliper slide to impart a braking action.
The improved disc brake plastic piston of the present invention has a metallic cap or face which provides a means of attaching a brake shoe or a brake shoe assembly, or provides a dust boot groove, or, in the most preferred mode, the metallic cap component provides both a brake shoe retaininy means and a dust boot groove.
The improved piston of this invention is comprised of a cylindrical resin body having an open end and a closed end. The "closed end" can be cored out for structural or other purposes and is deemed to be within the foregoing description. A metallic cap extends over the end wall of the open end of the cylindrical body and is secured to the body by the process of molding of the resin body against at least one surface of the metallic cap as will be described in greater detail hereinafter. The metallic cap is adapted to receive and hold a brake shoe clip, also referred to in the trade as a retainer clip, and also to provide a dust boDt groove. In the most preferred embodiments of the invention, the metallic cap prov;des both a brake shoe retain;ng means and a dust boot groove.
Thus the metallic caps of the invention have means for attaching a vehicular brake shoe assembly so that the brake shoe moves in unison with the piston during braking and debraking of the vehicle. The above described attachment is not a permanent bond such as created by welding or soldering.
Rather the brake shoe clip engages the cap as a result of the shaped sur-face thereof, and~is readily removable when it is desired to disassemble the piston from the braking mechanism.
3.~Z~3~36~
The improved plastic pistons of the invention are generally manufactured by placing the metallic cap, suitably shaped to accomplish the requirements of the application, in a mold shaped in the form of a piston. The meta11ic cap or heat shield can be a pre-shaped or pre-formed metal cap or a metallic foil or film that becomes shaped or formed to the contour of the mold during the subsequent molding steps.
The metal cap or foil can have a thickness from about 0.0005 to about 0.25 inch, preferably from about 0.001 to about 0.05 inch. Thereafter, plastic molding material, such as a phenolic resin molding material comprising resin and fillers, is placed in the body of the mold, the temperature is elevated and pressure is applied to the resinous material to fill out the mold and form the plastic piston against at least one of the surfaces of the metallic cap. The plastic molding material can be introduced into the mold in any of the conventional forms such as various particulate forms such as powders, nodules and the like, or in "pre-form"
slugs, and the like. The resinous material is heated and pressed by compression molding or other suitable processes and is composite molded to the inner surface of the metallic cap. When the molded article is removed from the mold, the plastic piston and metallic cap are integrally bonded together. The result is that the metallic cap is embedably molded to the plastic piston. These methods of manufacture have been described with respect to the plastic piston, but are also applicable for manufacturing the other embodiments of the invention described hereinafter.
In the various embodiments of the invention, the metallic caps or heat shields can be any suitable metal such as steel, aluminum, copper and alloy.
Other embodiments of the invention in the automotive and transportation industries includes automotive engine pistons made from phenolic resins and having a metal skin or cap (such as aluminum) on the piston head as a replacement for the present steel and aluminum engine pistons. Internal combustion engine heads and intake manifolds can be made with a thin metal inner skin and a molded phenolic resin outer shell to provide the required dimensional stability and to,que retention.
Automobile mufflers can be produced with a metal inner skin and an outer phenolic resin casing that will last the lifetime of the automobile.
~2139~i3 Appliance Applications Most hand-held, countertop and other heated appliances are limited by the fact that the materials of construction must stand up to UL and other industry standards at the operating temperatures. Phenolic resin molding compounds are often used for enclosures or current-carrying func-tional parts because of the good thermal properties of this thermosetting plastic. Such properties include short term heat resistance of about 300 to 500Fahrenheit and long term heat resistance of about 250 to 425Fah renheit, as well as high heat distortion temperatures of about 325 to 500F and low creep and retention of strength at elevated temperatures.
The use of the present invention to provide oxidative shielding of phenolic resin molding compound appliance parts at the "hot spot" or plastic surface that sees the highest temperature permit use of operating temperatures of up to 100 higher than those stated above. Thus the present invention finds use in heated appliances such as broilers, hot plates, toasters, heating ovens, frying pans, hamburger cookers, popcorn poppers, coffee makers, egg cookers and similiar appliances having hot spots or points where the plastic part is in contact with or close to heating elements or metallic heating surfaces. Use of this invention permits improved, smaller and lower cost appliances. When hot spot tem-peratures exceed the allowable limit of the plastic used in appliances, industry has been resorting to air-gapping, and using metallic or ceramic insulators or shields or combinations of the above, which requires large plastic housings. The plastic housings can be considerably reduced in size to accommodate the heat shielded plastic components of this inven-tion.
Other applications in the appliance industry include electric irons that use heated sole plates. Traditional "electric iron" designs use heated sole plates and metal housings with handles made with phenol resin molding materials, or a combination phenolic housing and phenolic handle. Newer designs use a metal sole plate, an air gap, a heat shield molded from a glass filled or other high heat resistant phenolic molding compound and a thermoplastic handle. The use of oxidative shielding for electric irons consists of a phenolic resin molding compound molded directly to the sole plate, then attached to a thermoplastic or thermoset handle. The use of the invention offers safer, more compact and economi-cal appliances.
~Z~8~363 In the cookware field, "stick handles", the presently employed phenolic resin molding compound handles used on metal cookware, such as frying pans and sauce pans present two inherent problems. First, the handles are subject to thermal degredation on long term useage, and loosen at the point of attachment. Second, since this type of cookware is used on gas burners or ranges, they can be in contact with a gas flame and temperatures exceeding the normal, exposure limit for phenolic resins. The cookware industry uses flameguards to reduce the potential premature handle Failure from a high gas flame. Flameguards are of two designs. One is a metal spacer that fits between the handle and the metal cookware. The second is a metal shield that covers all or the bottom half of the handle for the first inch or so from the point of attachment. These shields are usually not molded on or tight fitting.
The use of the present invention in the form of a molded in metal cap on the end of the phenolic resin handle provides an oxidative shield around the handle. This is an improved flameguard that greatly reduces the possiblility of thermal degradation at the point of assembly and the resulting loose, unsafe handle. For the knobs used on pot and pan covers or lids or in side handles for oven cookware, oxidative shielding increases the liFe of the handle or knob, which are the parts that often fail first in these appliances. In present appliances, knobs and side-handles are bolted through to the cookware. Long term exposure to normal oven temperatures cause the handles to shrink, providing exposure to air and oxidation in the threaded part section. Handles and knobs on contin-ued high temperature exposure fail by thermal degradation and the result-ing cracking from the attachment hole. Molded in attachment bolts and/or metal caps or shields in accordance with the present invention, prevent surface oxidation in the critical points and substantially increase the life ox the handle and knobs. The invention can also be used for handles and knobs for gas, charcoal, propane and electrical heated grills, broil-ers, smokers and the like.
~2~3~363 Electrical Applications Electrical applications, especially phenolic resin molding compoundlighting fixtures used in enclosed or poorly vented areas can benefit significantly by the use of the oxidative shielding provided by the present invention. At present, phenolic resin, ceramic and metal are used for electrical light bulb sockets, light reflectors and shields.
The problem with metal is that it is an electrical conductor, resulting in a potential safety hazard if the insulating system fails. Ceramic is heavy, difficult to manufacture to tolerance and subject to breakage.
Phenolic resins, even the highest heat resistant grades, are better thermal insulators but unacceptable for some designs due to thermal degradation. All systems present a potential fire or electrical hazard if a light bulb with a higher than recommended wattage is used. These problems can be eliminated or seduced by the use or a phenolic resin molding compound with the oxidative metallic cap or shield of the present invention in light bulb sockets and/or light reflectors. These provide improved heat resistance plus the desired thermal conductivity to control heat buildup. The oxidative shield can be achieved by a molded in inter-nal metal skin. The same method can be used for reflectors for halogen lights used for automotive and other uses.
Aerospace and Missile Industry Phenolic resin, ceramic and high temperature metal alloys are used for rocket nozzles, such as thrust nozzles, and for ablative nose cones.
In accordance with the present invention, these applications are ful-filled by a composite molded rocket nozzle with an inner skin of hightemperature metal and a shell made of phenolic resin molding material.
Another emobodiment uses several layers of high temperature metal with layers of phenolic resin molding compound in between in a sandwich type structure. The benefits include more controlled burning and accuracy, thinner walls, lighter weight and improved reliability. other uses include ablative reentry systems and nose cones.
~2~3 _ief Description of the Drawings Figures 1 through 4 are elevational views of composite pistons, partly in section, which illustrates various preferred embodiments of the invention.
Detailed Description of the Drawings Referring to Figure 1, cylindrical piston 11 has a closed end 13 and ar open end 15. The exterior surface 23 of closed end 13 is shown to be concave, but the surface can be more nearly slush with the bottom line of closed end 13 provided that there is a sufficient cavity to provide or a fluid reservoir behind the piston. Metallic cap 19, preferably of steel or aluminum, extends over and covers end wall 14 of opened end 15 of piston 11 and is secured on piston 11 by virtue of the fact that piston 11 is formed by molding the resinous molding material that forms the body of piston 11 against one surface of metallic cap 19. In the molding operation, the metallic cap 19 is placed in the mold first, and then the resinous molding material, preferably in some particulate form or as a "pre-form" is placed in the mold adjacent to one surface of the metallic cap 19. In the molding operation, the resinous molding material is melted and compressed against the surface of the metallic cap 19 so as to 2n form a firm bond therewith. The bond between the resin body of piston 11 and the metallic cap 19 can be improved by forming the metallic cap with one or more of its edges crimped such as shown in Figures 2 and 3 so that these edges become embedded in the molded resin body. In this embodiment, metallic cap 19 forms a heat shield to protect the end wall l against oxidation as a result of the heat generated when the plastic piston is in service. In this embodiment groove 17 has been machined to provide a means for retaining a brake shoe clip. A groove 21 has been machined in the outside wall of piston 11 to provide a means for retaining a dust boot.
Figure 2 illustrates an embodiment of the invention wherein piston 11 is provided with a metallic cap 19 which has a groove 27 on the inside wall of piston 11 which is adapted to receive and retain a brake shoe clip. In this embodiment a groove 21 is machined in the outside wall of piston 11 to provide means or retaining a dust boot.
g Figure 3 illustrates an embodiment of the invention wherein the metallic cap 19 is formed to provide a groove 29 in the narrowed portion of the outer wall of piston 11 as a means for retaining a dust boot. In this embodiment a groove 17 has been machined in the inside wall of 5 piston 11 to provide a means for retaining a brake shoe clip.
Figure 4 illustrates an embodiment of the invention wherein metallic cap 19 is formed to provide a groove 29 in the narrowed portion of the outer wall of piston 11 which serves as a means for retaining a dust boot 41. The metallic cap 19 is also formed to provide a groove 27 on the inside surface of the piston _. Groove 27 provides a means for retaining brake shoe clip 37. Brake shoe clip 37 has two or more bent prongs 39 which are joined to a base plate which is attached by bolts or rivets 43 to a brake shoe backing plate 33 to which is attached brake shoe 35. In operation, the face of the backing plate 33 touches the portion of metallic cap 19 which covers end wall 14, but it is through the prongs 39 that the brake shoe clip 37 is attached to piston 11 by means of the groove 27 wormed in the metallic cap 19. The manner of attachment of the brake shoe clip and dust boot shown in Figure 4 illustrates the manner of attachment contemplated with respect to previously described Figures 2 and 3.
The foregoing description of embodiments is intended to illustrate the invention without limiting it thereby. It will be understood that various modifications can be made in the invention without departing from the spirit or scope thereof.
Claims
The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:-A vehicular part that is subjected to elevated tempera-tures comprising a molded article with improved heat resistance comprising a plastic body and a metallic heat shield molded on the surface of the plastic body.
An automotive part that is subjected to elevated tempera-tures comprising a molded article with improved heat resistance comprising a plastic body and a metallic heat shield molded on the surface of the plastic body.
An automotive part comprising a molded article with improved heat resistance comprising a plastic body and a metallic heat shield molded on the surface of the plastic body, wherein the automotive part is selected from the group consist-ing of automotive brake pistons, automotive engine pistons, internal combustion engine heads, internal combustion intake manifolds, and automotive mufflers.
An automotive part according to Claim 1 wherein the metallic heat shield has a thickness in the range of about 0.0005 to about 0.25 inch.
A vehicular part according to Claim 1 wherein the plastic is a thermosetting resin.
A vehicular part according to Claim 5 wherein the thermo-setting resin is a phenol-aldehyde resin molding material.
A heating appliance comprising a molded article with improved heat resistance comprising a plastic body and a metallic heat shield molded on the surface of the plastic body.
An electrical fixture that develops heat comprising a molded article with improved heat resistance comprising a plastic body and a metallic heat shield molded on the surface of the plastic body.
An aerospace component comprising a molded article with improved heat resistance comprising a plastic body and a metallic heat shield molded on the surface of the plastic body, so that the metallic heat shield is exposed to heat before the plastic body.
Cookware comprising a molded article with improved heat resistance comprising a plastic body and a metallic heat shield molded on the surface of the plastic body.
A vehicular brake piston for activating a vehicular brake shoe during braking of a vehicle comprising a cylindrical resin body having an open end and a closed end and a metallic cap molded to the end wall of said open end.
A vehicular brake piston according to Claim 11, wherein said metallic cap has means for attaching a vehicular brake shoe or brake shoe assembly so that the brake shoe moves in unison with the piston during brake and debraking of the vehicle.
A vehicular brake piston according to Claim 11, wherein said body has a narrowed portion in the outer wall thereof contiguous to said open end, the end of said cap and the portion of said body adjacent said narrowed portion providing a groove adapted to receive a dust boot.
A vehicular brake piston according to Claim 11, wherein said metallic cap is adapted to receive and hold a brake shoe clip.
A vehicular brake piston according to Claim 14, wherein said body has a narrowed portion in the outer wall thereof contiguous to said open end, the end of said cap and the por-tion of said body adjacent said narrowed portion providing a groove adapted to receive a dust boot.
The piston of Claim 11, wherein the resin is a thermo-setting resin.
The piston of Claim 16, wherein the thermosetting resin is a phenol-aldehyde resin molding material.
Apparatus comprising:
(1) a vehicular brake piston for activating a vehicular brake shoe during braking of a vehicle comprising a cylindrical resin body having an open end and a closed end and a metallic cap molded to the end wall of said open end and secured to said body by molding of the resin body against at least one surface of the metallic cap, wherein said metallic cap has means for attaching a vehicular brake shoe or brake shoe assembly so that the brake shoe moves in unison with the piston during braking and debraking of the vehicle, and (2) a vehicular brake shoe or brake shoe assembly attached to said means for attaching.
The apparatus of Claim 18 wherein said metallic cap is joined to said brake shoe or said brake shoe assembly by a brake shoe clip.
The apparatus of Claim 18, wherein said body has a narrowed portion in the outer wall thereof contiguous to said open end, the end of said cap and the portion of said body adjacent said narrowed portion providing a groove adapted to receive a dust boot.
The apparatus of Claim 20, wherein said metallic cap is joined to said brake shoe or said brake shoe assembly by a brake shoe clip.
The apparatus of Claim 18, wherein the resin is a thermo-setting resin.
The apparatus of Claim 22, wherein the thermosetting resin is a phenol-aldehyde resin molding material.
An automotive part that is subjected to elevated tempera-tures comprising a molded article with improved heat resistance comprising a plastic body and a metallic heat shield molded on the surface of the plastic body.
An automotive part comprising a molded article with improved heat resistance comprising a plastic body and a metallic heat shield molded on the surface of the plastic body, wherein the automotive part is selected from the group consist-ing of automotive brake pistons, automotive engine pistons, internal combustion engine heads, internal combustion intake manifolds, and automotive mufflers.
An automotive part according to Claim 1 wherein the metallic heat shield has a thickness in the range of about 0.0005 to about 0.25 inch.
A vehicular part according to Claim 1 wherein the plastic is a thermosetting resin.
A vehicular part according to Claim 5 wherein the thermo-setting resin is a phenol-aldehyde resin molding material.
A heating appliance comprising a molded article with improved heat resistance comprising a plastic body and a metallic heat shield molded on the surface of the plastic body.
An electrical fixture that develops heat comprising a molded article with improved heat resistance comprising a plastic body and a metallic heat shield molded on the surface of the plastic body.
An aerospace component comprising a molded article with improved heat resistance comprising a plastic body and a metallic heat shield molded on the surface of the plastic body, so that the metallic heat shield is exposed to heat before the plastic body.
Cookware comprising a molded article with improved heat resistance comprising a plastic body and a metallic heat shield molded on the surface of the plastic body.
A vehicular brake piston for activating a vehicular brake shoe during braking of a vehicle comprising a cylindrical resin body having an open end and a closed end and a metallic cap molded to the end wall of said open end.
A vehicular brake piston according to Claim 11, wherein said metallic cap has means for attaching a vehicular brake shoe or brake shoe assembly so that the brake shoe moves in unison with the piston during brake and debraking of the vehicle.
A vehicular brake piston according to Claim 11, wherein said body has a narrowed portion in the outer wall thereof contiguous to said open end, the end of said cap and the portion of said body adjacent said narrowed portion providing a groove adapted to receive a dust boot.
A vehicular brake piston according to Claim 11, wherein said metallic cap is adapted to receive and hold a brake shoe clip.
A vehicular brake piston according to Claim 14, wherein said body has a narrowed portion in the outer wall thereof contiguous to said open end, the end of said cap and the por-tion of said body adjacent said narrowed portion providing a groove adapted to receive a dust boot.
The piston of Claim 11, wherein the resin is a thermo-setting resin.
The piston of Claim 16, wherein the thermosetting resin is a phenol-aldehyde resin molding material.
Apparatus comprising:
(1) a vehicular brake piston for activating a vehicular brake shoe during braking of a vehicle comprising a cylindrical resin body having an open end and a closed end and a metallic cap molded to the end wall of said open end and secured to said body by molding of the resin body against at least one surface of the metallic cap, wherein said metallic cap has means for attaching a vehicular brake shoe or brake shoe assembly so that the brake shoe moves in unison with the piston during braking and debraking of the vehicle, and (2) a vehicular brake shoe or brake shoe assembly attached to said means for attaching.
The apparatus of Claim 18 wherein said metallic cap is joined to said brake shoe or said brake shoe assembly by a brake shoe clip.
The apparatus of Claim 18, wherein said body has a narrowed portion in the outer wall thereof contiguous to said open end, the end of said cap and the portion of said body adjacent said narrowed portion providing a groove adapted to receive a dust boot.
The apparatus of Claim 20, wherein said metallic cap is joined to said brake shoe or said brake shoe assembly by a brake shoe clip.
The apparatus of Claim 18, wherein the resin is a thermo-setting resin.
The apparatus of Claim 22, wherein the thermosetting resin is a phenol-aldehyde resin molding material.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US48439383A | 1983-04-13 | 1983-04-13 | |
| US484,393 | 1983-04-13 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1228963A true CA1228963A (en) | 1987-11-10 |
Family
ID=23923988
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000449352A Expired CA1228963A (en) | 1983-04-13 | 1984-03-12 | Heat resistant plastic molded articles |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1228963A (en) |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5713435A (en) * | 1994-08-17 | 1998-02-03 | Kelsey-Hayes Company | Molded piston having metallic cover for disc brake assembly |
| EP0861383A1 (en) * | 1995-11-13 | 1998-09-02 | Kelsey Hayes Company | Molded piston having metallic cover for disc brake assembly |
| US5826686A (en) * | 1995-12-20 | 1998-10-27 | Dayton Walther Corporation | Piston with moisture-protective outer cover for use in disc brake assembly |
| US5845747A (en) * | 1995-11-13 | 1998-12-08 | Dayton Walther Corporation | Piston with extended outer cover for use in disc brake assembly |
| EP0934809A1 (en) * | 1998-02-05 | 1999-08-11 | H. Weidmann AG | Heat shield for a motor vehicle |
| US6401596B1 (en) | 2000-09-01 | 2002-06-11 | Court Holdings Limited | Metallic cap for molded plastic disc brake pistons |
-
1984
- 1984-03-12 CA CA000449352A patent/CA1228963A/en not_active Expired
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5713435A (en) * | 1994-08-17 | 1998-02-03 | Kelsey-Hayes Company | Molded piston having metallic cover for disc brake assembly |
| EP0861383A1 (en) * | 1995-11-13 | 1998-09-02 | Kelsey Hayes Company | Molded piston having metallic cover for disc brake assembly |
| US5845747A (en) * | 1995-11-13 | 1998-12-08 | Dayton Walther Corporation | Piston with extended outer cover for use in disc brake assembly |
| EP0861383A4 (en) * | 1995-11-13 | 2000-08-23 | Kelsey Hayes Co | Molded piston having metallic cover for disc brake assembly |
| US5826686A (en) * | 1995-12-20 | 1998-10-27 | Dayton Walther Corporation | Piston with moisture-protective outer cover for use in disc brake assembly |
| EP0934809A1 (en) * | 1998-02-05 | 1999-08-11 | H. Weidmann AG | Heat shield for a motor vehicle |
| US6401596B1 (en) | 2000-09-01 | 2002-06-11 | Court Holdings Limited | Metallic cap for molded plastic disc brake pistons |
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