Eck, Steven (3274 S. Oak, Springfield, MO, 65804, US)
|1.||An idler pulley with an integral bearing carrier insert characterized by: a pulley body (12) having a peripheral surface for accepting and retaining an endless belt ; and a tubular bearing carrier insert (14) for housing a bearing (16), said insert forming a central hub along a perpendicular axis of said idler pulley body (12), said hub having an inner circumferential surface and an outer circumferential surface.|
|2.||The idler pulley of claim 1, characterized in that said idler pulley body (12) is manufactured from a moldable polymeric material, such as a polyamide, phenolic resin, epoxy resin, polyester, polyurethane, high density polyolefin, or a blend thereof, especially a polyamide or a polyphthalamide, if said polymeric material is a polyamide, said polyamide is a nylon selected from the group consisting of nylon6 ; nylon 6,6 ; nylon 4,6 ; nylon 6,10 ; nylon 9; nylon 11; or nylon 12, especially nylon 6, nylon 6,6 or nylon 4,6.|
|3.||The idler pulley of claim 1 or 2, characterized in that said moldable material further includes at least one of a modifier, a filler, a reinforcing agent and an adhesion promoter, such as a modifier selected from the group consisting of polytetrafluoroethylene, ultra high molecular weight polyethylene, silicone, molybdenum disulfide, graphite and rubber, or a filler selected from the group consisting of glass beads, carbon black, calcium carbonate, wollastonite, mica, clay and talc, or a reinforcing agent selected from the group consisting of glass fiber, long glass fiber, aramid fiber, steel fiber and carbon fiber, or an adhesion promoter selected from the group consisting of sulfur, silica, acrylates, vinyl acetates and low molecular weight polyamides.|
|4.||The idler pulley of any of claims 14, characterized in that said outer circumferential surface of said pulley body (12) is coated with a metallic coating, such as of steel or aluminum.|
|5.||The idler pulley of any of claims 14, characterized in that said tubular bearing carrier insert (14) is manufactured from a metal material, such as a metal selected from the group consisting of steel, aluminum, zinc, brass or a combination thereof, wherein if said tubular bearing carrier insert (14) is manufactured from steel, said steel tubular bearing carrier insert may be coated with zinc or brass.|
|6.||The idler pulley of any of claims 15, characterized by a bearing member having an outer bearing race surface fitted within said central hub such that said outer race surface of said bearing member is circumferentially adjacent the inner circumferential surface of said hub, wherein said central hub may include locating means for locating said bearing member during assembly, wherein said locating means may be one of a stepped profile or detents.|
|7.||The idler pulley of any of claims 16, characterized in that said outer circumferential surface of said tubular insert (14) further includes means to enhance interlocking between said tubular insert and said pulley main body (12).|
|8.||An idler pulley assembly with an integral bearing carrier insert characterized by: a moldable polymeric pulley body (12) having an outer circumferential surface for accepting and retaining an endless belt ; a tubular metal or ceramic bearing carrier insert (14) forming a central hub along a perpendicular axis of said pulley body (12), said hub having an outer circumferential surface shaped to enhance interlocking between said bearing insert (14) and said moldable polymeric pulley body (12), and having an inner circumferential surface provided with one or more bearing member locating means selected from the group consisting of stepped profiles and detents; and a bearing member (16) having an outer bearing race surface, said bearing member being fitted within said hub such that said outer race surface of said bearing member is circumferentially adjacent the inner circumferential surface of said hub.|
|9.||A method for manufacturing a moldable polymeric idler pulley having an integrally formed metal or ceramic bearing insert characterized by the steps of: (a) providing a mold (26) having a cavity, the inner surface of said cavity being shaped to form an outer surface of a pulley body (12) having a desired configuration and dimension; (b) inserting a tubular metal bearing carrier insert (14) having an outer circumferential surface and an inner circumferential surface defining an open interior space for accepting a bearing member (16) within said cavity, said insert (14) configured to provide a hub along a perpendicular axis of a pulley body (12) formed in said mold (26), said outer circumferential surface of said insert (14) having an outer surface shaped to enhance interlocking between said hub and said pulley body (12) and said hub further including a stepped profile or detents to locate said bearing member (16); (c) closing said mold (26); (d) introducing a freeflowing moldable polymeric material into said cavity such that said freeflowing moldable polymeric material fills said cavity around said outer circumferential surface of said insert (14) leaving said open interior space of said insert free of said freeflowing moldable polymeric material; (e) subjecting said mold (26) containing said free flowing material and said tubular metal bearing carrier insert (14) to conditions of heat and pressure to form an idler pulley (10) with an integral bearing carrier insert (14); (f) cooling said mold (26) to provide a molded idler pulley (10) with integral bearing carrier insert (14) formed along a perpendicular axis of said idler pulley body (12); (g) opening said mold (26); and (h) recovering said molded idler pulley (10) with integral bearing carrier insert (14).|
|10.||The method of claim 9, characterized in that said step (b) further includes inserting a bearing member (16) in said open interior space, or by a further step (i) of inserting a bearing member (16) into said open interior space.|
Background Art Plastic idler pulleys are known in the art as taught by U. S.
Pat. Nos. 6,220, 635; 6,200, 513; 6,181, 239; 6,120, 401; 6,102, 822; 6,090, 001; 6, 086, 809; 6,032, 635; 5,830, 046; 5,782, 709; 5,725, 448; 5,724, 930 and 5,176, 580. Such plastic idler pulleys have heretofore been made by either molding-in a bearing, incorporated as an insert in the molding process, or by force fitting a bearing into a molded bore in the plastic part. For example, U. S. Pat. Nos. 4,468, 210 and 4,473, 363 describe examples of a plastic outer pulley body molded on a metal disc; and U. S. Pat. Nos. 4,913, 688 and 5,476, 423 describe examples of a two-step assembly wherein first a plastic outer pulley body is molded and then the metal insert is placed into the already molded pulley body.
Traditionally, when a pulley is produced by the one-step process of compression molding the plastic pulley body about the metal insert, the insert is physically altered to include one or more projections such as radially extending scallops or knurls on the outer periphery of the insert.
Pulleys are also produced by the two-step process wherein a metal insert is attached to a molded plastic outer pulley by forcing the insert into the bore of the pulley. An adhesive, such as epoxy, is generally applied between the outer metal surface of the insert and the inner surface of the plastic pulley body to assist in bonding the insert to the pulley body. In each of the methods, the bearing retention is less than desirable since the clamping force which secures the bearing is
dependent upon the modulus of the plastic material and upon the surface of the outer bearing race. Typically, the outer bearing is smooth and made from material having relatively little affinity for the plastic pulley. Furthermore, asymmetric forces which may occur during the molding process can distort the bearing to an out-of-round condition, thereby shortening its useful life. For example, when an idler pulley is subjected to a heavy radial load from a belt, such as a timing belt, entrained therearound, the pulley and the bearing are slightly deformed and, since the deformation patterns of the plastic pulley and the insert are different, a slight clearance is defined between the inner surface of the pulley and the outer surface of the bearing. This clearance becomes wider as the radial force from the belt increases and over time, results in the wear of the fit surfaces of the pulley and the outer surface of the bearing, thus decreasing the joining force between the pulley and the bearing. The process of bonding with an adhesive presents undesirable clean-up and environmental problems. Accordingly, there is a need, particularly in the area of an endless drive belt of a vehicle accessories drive system, for a plastic pulley with a metal insert that may be easily manufactured without the problems associated with prior art pulleys.
Disclosure of the Invention In accordance with the present invention, there is provided an idler pulley having a moldable pulley body with a rigid bearing carrier insert integrally formed in the pulley body for accepting a bearing member. The bearing member may be fitted into the rigid bearing carrier insert either before or after molding.
In one aspect of the invention, the bearing member is installed into the integrally formed moldable idler pulley body and rigid tubular bearing insert before molding.
In another aspect of the invention, the bearing member is fitted into the tubular bearing carrier insert of the molded idler pulley after the idler pulley is formed.
In yet another aspect of the invention, the metal bearing insert is fitted into the bore of the tubular shell and the tubular shell having the bearing insert fitted therein is inserted into the bore of the plastic pulley body.
The material selected for the construction of the tubular shell is a suitably strong and rigid material which is compatible with the plastic material of the pulley body and with the metal bearing insert.
The tubular shell may be adapted to provide a hoop/clamping force sufficient to afford superior bearing retention and to resist unbalanced forces during molding and maintain bearing concentricity.
Brief Description of the Drawings The features of the invention, and its technical advantages, can be seen from the following description of the preferred embodiments together with the claims and the accompanying drawings, in which: FIG. 1 illustrates one embodiment of the idler pulley with an integral bearing carrier insert of the present invention; FIG. 2 is a cross-section of the idler pulley of FIG. 1 taken along lines 2-2 of FIG. 1; FIG. 3 is a cross-sectional view of a mold which may be used to make an idler pulley having an integral barrier carrier insert; FIG. 4 is a cross-section taken along lines 4-4 of FIG. 3; and FIG. 5 is a cross-sectional view of the mold of FIG. 3 after a plastic material has been inserted into the mold cavity to make the idler pulley of the invention.
Description of Preferred Embodiments Referring to the drawings, FIGS. 1 and 2 illustrate an idler pulley 10 comprising a molded plastic body 12 having an integral tubular bearing carrier insert 14 centrally positioned in the pulley body 12. The tubular bearing carrier insert 14 is incorporated between the plastic body
of the pulley and an outer bearing race. The bearing 16 may be fitted into the insert either before or after molding.
The idler pulley 10 of the invention may be made from a wide variety of polymeric materials, provided that they are distortion resistant at ambient and higher temperatures. It also is generally desirable, particularly for automotive applications, that the polymeric material used to make the pulley 10 have a low-temperature resiliency.
Suitable polymeric materials include thermoplastic and thermosetting materials, such as polyamides, e. g., polyphthalamides, nylons, particularly, nylon-6, nylon-6, 6, nylon and nylon 4,6 ; polyesters, epoxy resins; phenolic resins; polyurethanes ; high density polyolefins, e. g., polyethylene ; and the like. The polymeric material used to manufacture the body 12 of the pulley 10 may be compounded with additional fillers, modifiers or reinforcing agents as determined for a particular application.
In a preferred aspect of the invention the polymeric material contains a reinforcing material, such as a fibrous glass reinforcing material.
The outer peripheral surface of the pulley 10 comprises a plurality of protrusions 20 and recesses 22. The protrusions may be in the form of V-shaped projections and recesses, truncated V-shaped projections and recesses, and any other useful design. In a preferred aspect of the invention, the peripheral surface of the pulley 10 comprises a metal or ceramic liner 18 to provide enhanced abrasion resistance.
The liner 18 may be of any suitable material which has the desired resistance to abrasion, and is sufficiently deformable so that it can be used in the practice of the invention. Steel or aluminum having a thickness in the approximate range of about 0.0254-0. 127 cm (0.010- 0.050 inch) is preferred.
The tubular insert 14 may be manufactured from steel, aluminum, zinc, brass, or any other suitably rigid and strong material and may contain additives such as one or more modifiers, fillers, reinforcing agents, adhesion promoters, and the like. Useful modifiers include
lubricants such as polytetrafluoroethylene, silicone, graphite, molybdenum disulfide, ultra high molecular weight polyethylene. Other suitable modifiers include thermoplastic materials, rubber, etc. Fillers may be glass beads, carbon black, minerals such as calcium carbonate, wollastonite, mica, clay, talc, etc. The reinforcing agent may be glass fibers, long glass fibers, aramid, carbon fibers, etc. The insert 14 may also be coated or plated to enhance adhesion to the particular polymeric material selected for the body 12 of the idler pulley 10. For example, a brass or zinc plating over a steel tubular insert shell increases the chemical affinity of the insert for a thermoplastic phenolic material, especially if the phenolic material also incorporates any of several classes of adhesion-enhancing ingredients such as sulfur, silica, acrylates, vinyl acetates, low molecular weight polyamides, etc. The outer surface of the tubular insert 14 may be knurled, splined, or <BR> <BR> otherwise shaped, e. g. , it may contain holes, to provide a rough surface for the purpose of enhancing the mechanical interlock of the insert 14 with the plastic body 12. The inner surface of the tubular insert 14 may be provided with means 24, such as a stepped profile or detents, to accurately locate and align the bearing 16 during assembly, or the surface of the insert during molding.
Referring now to FIGS. 3-5, the idler pulley 10 is formed using a three-section mold (or a two-section mold for flat pulleys), designated generally by the reference numeral 26. The first, or base section 28 has a cylindrical center portion 30 having an outside diameter approximately equal to the inside diameter of the tubular insert 14. The second section 32 has at least two segmented sections 34 so that the completed pulley can be easily removed. The segments 34, when in the molding position, form an annular opening. The inner periphery of the segments 34 has a plurality of projections 36 and recesses 38 corresponding to the shape of the recesses 22 and projections 20, respectively, of the peripheral surface of the pulley 10. The third section
40 has a central opening 42 which has an inside diameter approximately equal to the outside diameter of the tubular insert 14. The third section 40 also has at least one injection port 44 through which the plastic material is injected into the mold 26. The mold sections may be clamped together by any suitable clamping means, such as bolts 45, as illustrated.
To make the pulley 10, the second section 32 is assembled on the first section 28 and the tubular insert 14 is inserted over the cylindrical center portion 30 of the first portion 28 and the third section 40 is assembled on the top of the second section 32 and the mold 26 is clamped together by the clamping means.
The pulley 10 is made by injecting a suitable polymeric material through the injection port (s) 44 under sufficient pressure, e. g., about 500-30,000 psi, to fill the cavity and, if present, to deform the metal liner 18, causing it to conform to the projections 36 and recesses 38 in the segments 34.
Various changes and modifications may be made to the idler pulley having an integral bearing carrier insert of the present invention, and to the method of manufacturing such idler pulley, in light of the above disclosure without departing from the scope and spirit of the appended claims.
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