GB2097486A

GB2097486A - Bearings

Info

Publication number: GB2097486A
Application number: GB8209810A
Authority: GB
Original assignee: Kamatics Corp
Current assignee: Kamatics Corp
Priority date: 1981-04-20
Filing date: 1982-04-02
Publication date: 1982-11-03
Also published as: IT1210477B; DE3214250C3; FR2504218A1; IT8220726A0; DE3214250C2; JPH0461205B2; DE3214250A1; JPS57184721A; FR2504218B1; GB2097486B

Abstract

A self-lubricating bearing overcomes a debilitating ploughing action, by having the lubricating material 31 disposed on the inner race 23 instead of on the outer race 25. The lubricating material is in the form of solid, organic lubricant which may be in the form of one or more of a solid polyester, a polyamide, polyphenylene sulphide, polyarylsulphone, a polyfluorocarbon, a cured acrylate, or a woven fibre matrix impregnated with a cured acrylate. <IMAGE>

Description

SPECIFICATION Bearings The present invention relates to bearings and particularly to a self-lubricating bearing.

Conventional track roller bearings are constructed of rolling elements positioned between inner and outer races, lubricated by grease. Periodic lubrication is required to maintain operational performance with added resistance to corrosion. Such bearings are subject to failure upon fracture of the rolling elements and spalling of the inner race. The performance of these known track roller bearings also depends on the effectiveness of the sealing of the bearing which not only ensures that the grease lubrication is kept within the bearing but also that contamination from the outside is avoided.

An alternative bearing incorporates a self-lubricating liner system fixed to the inner surface of an outer race which operates against the bearing surface of a hardened inner race. These bearings do not require periodic lubrication and they generally have higher rolling load capacity than the first mentioned roller bearings. Also, the static radial load capacity of the alternative bearings is substantially higher than the roller bearings due to the use of the separate self-lubricating liner system.

Such an alternative self-lubricating type bearing assembly is disclosed for instance in U.S. Patents Nos.

4,048,370 and 4,134,842.

It has been found, however, that the self-lubricating material or liner on the inner bearing surface of the outer race in such bearings is subject to a ploughing action, as defined hereinafter, by induced liner deflection when loaded by the inner race during rotation of the outer race. This adversely affects the liner bond of the self-lubricating liner to the inner bearing surface of the outer race, which fails and the liner system is pinched between the inner and outer races without any support and is squeezed out.

Known track rollers are constructed utilizing a self-lubricating liner system attached to the inside diameter of the outer race with the belief that the wear experienced during the life of the bearing system would be distributed over the full circumference of the liner system and thus result in extended service life expectancy. However, it has been observed that due to the rotation of the outer race selflubricating liner in relation to the stationary inner race and the unidirectional load application, liner systems with compression modulus up to 1,000,000 psi are subjected to material deflection. The mismatch of the inner race circumferential surface to the outer race by differential tolerances and the thickness of the liner system provide the mechanism which permits local deflection of the liner system as the outer race translates to the stationary inner race when loaded.Therefore, liner systems when applied with a steady load, while moving in relation to the inner race, impose high shearing action and tensile forces on the liner immediately in front of the progressing load action of the inner race; this action is known as ploughing. When combined with fluid contamination, the liner system is further distressed due to the wedging action of the fluid in front of the advancing inner race slider.

It is an object of the present invention to avoid liner bond failure occasioned by the abovedescribed ploughing action and obtain a significantly extended wear life.

According to this invention, we propose a bearing comprising an inner race member cooperative within and relatively angularly movable with an outer race member wherein means for lubricating the bearing is attached to the outer, bearing surface of the inner race.

In the bearing assembly of the present invention the self-lubricating bearing material is provided on the outer bearing surface of the inner race member rather than, as in prior art bearings, on the inner bearing surface of the outer race. This construction ensures positive contact between liner system and mating surface, so that fluid contamination does not become a mechanical wedging tool as it does in known self-lubricating roller bearings. The present invention precludes the deflection of the liner system which creates a shear lip thereby causing high shearing forces within the liner. The liner system adhered to the outside diameter of the liner race does not permit hydraulic wedging due to fluid contamination.The limited wear surface of this configuration allows a number of additional wear surfaces which can be positioned by reindexing the inner race in relation to the primary load application.

An embodiment of the invention is described by way of example with reference to the drawings, in which: Figure 1 a is an exploded sectional view of a prior art bearing assembly; Figure 1 b is a fragmentary exploded view showing the bearing assembly of the present invention; Figure 2 is a view of the whole bearing assembly of this invention; (the shaft is omitted for clarity in Figures 1 a, 1 b and 2); and Figure 3 is a view taken along line 3-3 of Figure 2 to illustrate the relative position of the selflubricating bearing material secured to the outer surface of the inner race with respect to the bearing surface of the outer race.

Figure 1 a shows a prior art bearing assembly such as disclosed in U.S. Patent 4,134,842 (Orkin et al). The bearing assembly includes an inner race 11 which may, for example, be a bushing which is locked in place. An outer race 13 is engageable with the inner race 11 and is rotatable relative thereto.

A lubricating material 1 5 is fixedly secured to the inner bearing surface 1 7 of the outer race 13, said bearing material 1 5 being engageable with and movable relative to the outer bearing surface 1 9 of the inner race 11. An annular closure 21 is secured to the inner race 11 to maintain the outer race 13 fixed with respect to the inner race 11 in the axial direction. Techniques for securing the bearing material 1 5 to the inner bearing surface 1 7 of the outer race 1 3 are known, as disclosed for example in the aforementioned U.S. Patent 4,134,842.

A bearing assembly according to this invention comprises inner race 23 which may, for example, be a bushing. An outer race 25 is located so that it is engageable with the inner race 23 and is rotatable relative thereto. An annular locking member 27 prevents axial movement of the outer race 25 which respect to the inner race 23. In the bearing assembly of the present invention, the outer surface 29 of the inner race 23 carries a lubricating material 31 in any conventional manner. The bearing material 31 is engageable with and movable relative to the inner bearing surface 33 of the outer race 25.

The self-lubricating bearing material 31 is also fixed to the side walls 35 of the outer race 25 in order to provide low-friction engagement of the outer race 25 with respect to the complementary and co-engaging surface 37 of annular locking member 27 and the co-engaging surface 39 of a flange portion 41 of the inner race 23.

Now referring to Figure 3, which show the lubricating material 31 secured to outer surface 29 of the inner race 23 with respect to the bearing surface 33 of outer race 25. In a typical mode of operation, the applied bearing load is directed vertically as indicated by the arrow, thus causing the bearing surface 33 of the outer race 25 to bear against the self-lubricating bearing material 31 of inner race 23 in the illustrated wear zone. Thus, if the inner race 23 is fixed in position, only the bearing material 31 in the wear zone will be subjected to wear. The inner race 23 may be indexed to vary the portion of the bearing material 31 subjected to wear, thereby extending the life of the bearing assembly.

The outer race 25 is made of metal, preferably stainless steel (wrought or powder metallurgical) such as 440C, 1 7-4PH and 304, and more preferably 440C, although other metal such as high carbon steel 52100 as well as case-hardened titanium, anodized aluminum, Inconel and Hastelloy can also be employed, so as to provide a metal inner bearing surface 33. The side walls 35 of outer race 25 have fixedly secured thereto a lubricating material 31.

The inner race 23 of the bearing assembly of the present invention can also be made of a metal as given above, and more preferably stainless steel 17-4PH. The outer surface 21 thereof has fixedly secured thereto the lubricating material 31.

The lubricating material 31 is a solid, organic lubricant. Examples of solid organic lubricant are given as follows: a solid polyester, polyamine, polyphenylene sulphide, polyarylsulphone, a polyfluorocarbon or, a cured acrylate as disclosed in U.S. Patent 4,048,370 or even a woven fibre matrix impregnated with a cured acrylate composition as disclosed in U.S. Patent 4,134,842. The lubricating material 31 can be attached to the outer surface 29 of inner race 23 and to the side walls 35 of the outer race 25 by known methods.

Polyesters which can be used include aromatic poiyesters such as p-oxybenzoyl polyester which is commercially available, for instance, under the tradename Ekanol and sold by the Carborundum Co.

This polyester material has a density ranging from 1.44-1.48 gcc and a melting point of about 8000F.

Polyamides usefully employed in the present invention include, for instance, Nylon-6 and Nylon-6,6 although other nylon formulations can also be employed. Aromatic poly p-phenylene sulphides can also be employed and such polymers can have a molecular weight range as high as about 1 3,000.

They are available, commercially, under the tradename of Ryton by Phillips Petroleum Company, having a specific gravity of about 1.34, a density of about 0.0485 Ibs/in3 and a melting point of about 5500C.

Polyfluorocarbons which can be used include polytetrafluoroethylene. Included in the polyaryl sulphones suitable for use in the present invention are those which have a molecular weight ranging from about 30,000 to 60,000. One convenient polyaryl sulphone is that sold commercially under the tradename Polymer 360-3M Astrel 360 having a specific gravity of 1.36, a density of 0.049 Ibs/in3, a compressive strength at 730F of 17,900 psi and a melting point of about 5500 F.

Polyamides which are available commercially under, for instance, the tradenames of Vespel SP-1 (DuPont) which has a specific gravity ranging from about 1.41--1.43, a density of about 0.052 Ibs/in3, a compressive strength at 730F of about 24,000 psi and a heat distortion temperature at 264 psi of about 6800 F. A modified Vespel SP-1 polyamide is Vespel SP-21 which contains 15 weight percent graphite, has a specific gravity of about 1.51, a density of about 0.0546 Ibs/in3 and a compressive strength at 730F of about 18,000 psi. Other polyamides include one available commercially as XPI 1 82 by American Cyanamid which has a specific gravity of about 1.28, a density of about 0.046 Ibs/in3, a compressive strength at 730F of about 25,000 psi and a heat distortion temperature at 264 psi of about 4400 F. Another polyamide commercially available is that sold under the tradename of Genom 3010 by General Electric and has a specific gravity of about 1.90, a density of about 0.068 Ibs/in3, a compressive strength at 730F of about 41,900 psi and a heat distortion temperature at 264 psi of about 6600 F. Polyamides containing polytetrafluoroethylene or graphite fibres can also be used.

If the self-lubricating material is a cured mixture of an acrylate composition and a particulate solid lubricant, such as polytetrafluoroethylene, the acrylate composition can be selected from a group consisting of (a) a mixture of a major amount of a liquid acrylic ester selected from the group consisting of di-, tri-, and tetraesters of an acrylic acid and an a polyhydric alcohol, a minor amount of a low molecular weight prepolymer of an ester of a low molecular weight prepolymer of an ester of a low molecular weight alcohol having a terminal vinyl group and an aromatic polycarboxylic acid in solution in said acrylic ester and an organic amide of the formula

wherein R is selected from the group consisting of hydrogen and aliphatic hydrocarbon of 1-20 carbon atoms in an amount sufficient to copolymerize said acrylic ester and prepolymer, (b) a mixture of acrylic ester monomer, a peroxidic initiator in an amount sufficient to initiate polymerization of said monomer and an aminoalkoxyalkylamine of the formula R,-N(H)R,[OR,],(H)R, wherein x is an integer of 1-6 inclusive, each of R1 and R4 is selected from the group consisting of hydrogen and lower alkyl and each of R2 and R3 is a lower alkyl linking bridge between N and 0, in an amount sufficient to accelerate the polymerization of said monomer, (c) a mixture of an acrylic ester of an alkyl amino alkyl alcohol and an effective amount of hydroperoxide catalyst, said acrylic ester having the formula

wherein x is an integer of 0--5 inclusive, y is an integer of 1-6 inclusive, R is selected from the group consisting of hydrogen, halogen, hydroxy, cyano and lower alkyl and R, is selected from the group consisting of hydrogen and alkyl having 1-6 carbon atoms, (d) a mixture of a liquid acrylic ester monomer selected from the group consisting of diesters of an acrylic acid and a polyhydric alcohol, acrylic esters of cyclic ether alcohols, acrylic esters of amino alcohols and mixtures thereof, a peroxidic initiator and an oxyalkylamine of the formula (H)mN[(CH2)x(OR1)yOR2]n wherein m and n are each integers of 1 to 2 inclusive, the total of m and n is 3, x is an integer of 1 to 6 inclusive, y is an integer of O to 6 inclusive, R1 is lower alkyl and R3 is selected from hydrogen and lower alkyl, (e) a mixture of an acrylic ester monomer selected from the group consisting of di-, tri- and tetraesters of an acrylic acid and a polyhydric alcohol, acrylic esters of cyclic ether alcohols, acrylic esters of amino alcohols and mixtures thereof, a peroxidic initiator of an amount sufficient to initiate polymerization of said monomer and a member selected from the group consisting of rhodanine and a hydrazide of the formula

wherein R and R' are selected from separate groups and an interconnected group forming a cyclic ring, R is further selected from the group consisting of hydrogen, alkyl, cycloalkyl, aryl and alkoxy and R' is selected from the group consisting of hydrogen, alkyl, cycloalkyl, acyl, and dithiocarbonyl in an amount sufficient to accelerate the polymerization of said monomer; and (f) a mixture of a monomer of the formula

wherein R, and R2 are selected from the group consisting of hydrogen and lower alkyl and R3 is selected from the group consisting of lower alkyl, lower hydroxyalkyl, cyano and lower cyanoalkyl; at least one equivalent of an acid for each equivalent of said monomer, said acid being selected from the group consisting of acrylic acid and lower alkyl acrylic acids; and initiator selected from the group consisting of t-butyl perbenzoate, t-butyl peracetate and di-t-butyl diperphthalate, said initiator being present in an amount sufficient to initiate the polymerization of said monomer; a trihydroxy benzene inhibitor and an accelerator selected from the group consisting of benzyhydrazide and Naminorhodanine.

If the self-lubricating material is a woven fibre matrix impregnated with a cured acrylate composition, the woven fibre matrix can comprise a material woven from a mixture of fibres, one face of the woven material comprising lubricating fibres and the other comprising reinforcing fibres.

Conveniently the woven fibre matrix can be fabricated from polytetrafluoroethylene fibre, as the lubricating fibre; and from such reinforcing fibres as Kevlarfibres, polyethylene terephthalate (Dacron) fibres as well as fibreglass and graphite fibres. Preferably, the reinforcing fibres are Kevlar fibres, available commercially under the tradename Kevlar PRD 49 from DuPont. Kevlar is an organic polymeric compound known as an aromatic polyamide, i.e. an aramide. it is a high strength, high modulus fibre made from long chain synthetic polyamides wherein at least 85 percent of the amide linkages are attached directly to two aromatic rings. Keviar fibre is extremely stable, has high strength, toughness and stiffness characteristics. The density of Kevlar PRD 49 is 1.45 g/cc and its mechanical properties lie between the values of glass and graphite filament. The curable acrylate, which can be any of those defined above at (a) to (f) is present in an amount sufficient to impregnate the woven fibre matrix and to bond the same to the outer surface of the inner race.

Claims

1. A bearing comprising an inner race member cooperative within and relatively angularly movable with an outer race member wherein means for lubricating the bearing is attached to the outer, bearing surface of the inner race.

2. A bearing according to claim 1 , wherein the lubricating means is a solid, organic lubricant.

3. A bearing according to claim 1 or claim 2, wherein the race members are made of metal.

4. A bearing according to claim 3, wherein the race members are made of stainless steel.

5. A bearing according to claim 3, wherein lubricating material is also attached to side walls of the outer race cooperable with portions extending from the inner race.

6. A bearing according to any preceding claim, wherein the lubricant is one or more of a solid polyester, a polyamide, polyphenylene sulphide, polyarylsulphone, a polyfluorocarbon, a cured acrylate, or a woven fibre matrix impregnated with a cured acrylate.

7. A bearing according to claim 6, wherein the polyester is aromatic.

8. A bearing according to claim 6, wherein the polyamide includes nylon.

9. A bearing according to claim 6, wherein the polyamide contains polytetrafluoroethylene or fibres of graphite.

10. A bearing according to claim 6, wherein the polyphenylene sulphide has a maximum molecular weight of 13 x103.

11. A bearing according to claim 6, wherein the polyaryl sulphone has a molecular weight in the range 3-6x 104.

12. A bearing according to claim 6, wherein the polyfluorocarbon includes polytetrafluoroethylene.

13. A bearing according to claim 6, wherein the acrylate is selected from: (a) a mixture of a major amount of a liquid acrylic esters selected from the group consisting of di-, tri-, and tetra-esters of an acrylic acid and a polyhydric alcohol, a minor amount of a low molecular weight prepolymer of an ester of a low molecular weight alcohol having a terminal vinyl group and an aromatic polycarboxylic acid in solution in said acrylic ester and an organic amide of the formula

wherein R is selected from the group consisting of hydrogen and aliphatic hydrocarbon of 1-20 carbon atoms in an amount sufficient to copolymerize said acrylic ester and prepolymer, (b) a mixture of acrylic ester monomer, a peroxidic initiator in an amount sufficient to initiate polymerization of said monomer and an aminoalkoxyalkylamine of the formula R1N(H)R2[0R3]X(H)R4 wherein x is an integer of ? 1-6 inclusive, each of R1 and R4 is selected from the group consisting of hydrogen and lower alkyl and each of R2 and R3 is a lower alkyl linking bridge between N and 0, in an amount sufficient to accelerate the polymerization of said monomer, (c) a mixture of an acrylic ester of an alkyl amino alkyl alcohol and an effective amount of hydroperoxide catalyst, said acrylic ester having the formula

wherein x is an integer of 0--5 inclusive, y is an integer of 1-6 inclusive, R is selected from the group consisting of hydrogen, halogen, hydroxy, cyano and lower alkyl and R1 is selected from the group consisting of hydrogen and alkyl having 1-6 carbon atoms, (d) a mixture of a liquid acrylic ester monomer selected from the group consisting of diesters of an acrylic acid and a polyhydric alcohol, acrylic esters of cyclic ether alcohols, acrylic esters of amino alcohols and mixtures thereof, a peroxidic initiator and an oxyalkylamine of the formula (H)mN[(CH2)x(OR1)yOR2]n wherein m and n are each integers of 1 to 2 inclusive, the total of m and n is 3, x is an integer of 1 to 6 inclusive, y is an integer of O to 6 inclusive, R1 is lower alkyl and R2 is selected from hydrogen and lower alkyl, (e) a mixture of an acrylic ester monomer selected from the group consisting of di-, tri- and tetraesters of an acrylic acid and a polyhydric alcohol, acrylic esters of cyclic ether alcohols, acrylic esters of amino alcohols and mixtures thereof, a peroxidic initiator of an amount sufficient to initiate polymerization of said monomer and a member selected from the group consisting of rhodanine and a hydrazide of the formula

wherein R and R' are selected from separate groups and an interconnected group forming a cyclic ring, R is further selected from the group consisting of hydrogen, alkyl, cycloalkyl, aryl and alkoxy and R' is selected from the group consisting of hydrogen, alkyl, cycloalkyl, acyl and dithiocarbonyl in an amount sufficient to accelerate the polymerization of said monomer; and (f) a mixture of a monomer of the formula

wherein R1 and R2 are selected from the group consisting of hydrogen and lower alkyl and R3 is selected from the group consisting of lower alkyl, lower hydroxyalkyl, cyano and lower cyanoalkyl; at least one equivalent of an acid for each equivalent of said monomer, said acid being selected from the group consisting of acrylic acid and lower alkyl acrylic acids; an initiator selected from the group consisting of t-butyl perbenzoate, t-butyl peracetate and di-t-butyl diperphthalate, said initiator being present in an amount sufficient to initiate the polymerization of said monomer; a trihydroxy benzene inhibitor and an accelerator selected from the group consisting of benzyhydrazide and Naminorhodanine.

14. A bearing according to claim 6, wherein the woven fibre matrix comprises a material woven from a mixture of fibres, one face of the woven material comprising lubricating fibres and the other comprising reinforcing fibres.

1 5. A bearing according to claim 14, wherein the lubricating fibres consist of polytetrafluoroethylene.

1 6. A bearing according to claim 14, wherein the reinforcing fibres are made from one or more of an aromatic polyamide, polyethylene terephthalate, fibreglass and graphite.

17. A bearing comprising an inner race member cooperative with an outer race member angularly movable relative to one another said inner race having an outer bearing surface carrying lubricating material which is engageable with and movable relative to the bearing surface of said outer race member.

1 8. A bearing comprising a metal inner race member, the outer surface of which constitutes a bearing surface to which is fixedly secured a self-lubricating bearing material, and a metal outer race member having a metal inner bearing surface coengaging and movable relative to said self-lubricating bearing material.

1 9. A bearing constructed and arranged substantially as herein described with reference to and as illustrated in Figures 1 b, 2 and 3 of the drawings.

20. A bearing according to claim 1, having solid organic lubricant according to any one of the examples herein described.