DE69317263T2 - Tight-fitting sliding arrangement made of a metal component and a plastic composite component - Google Patents

Description

The present invention relates generally to combinations of machine parts for a movable connection with low friction and small play, and in particular to a motion transmission combination with a metal part and a polymer composite part, which can be connected with low friction and small play, and to methods for producing motion transmission combinations. An arrangement according to the preamble of claim 1 and a method according to the preamble of claim 20 are disclosed in US-A-3 081 644. It is also known from DE-A-2 101 262 to provide an impregnated porous sintered body which slides with respect to a polymer sleeve with, for example, a lubricant as filler. An anodized porous layer filled with PTFE is known from NL-A-6 805 392.

Other known methods for producing tight-fitting, low-friction, low-wear machine parts include the steps of casting a self-lubricating composite material onto a mating part. For example, an axle bearing can be made by casting an epoxy containing a dry lubricant such as graphite onto a polished shaft coated with a release composition to facilitate separation of the parts after the epoxy/lubricant mixture has cured. After the epoxy has cured to a hard solid, the bearing can be removed from the shaft and machined with a lapping composition so that it runs freely on the shaft but with very little clearance. After the shaft and bearing are cleaned of the lapping composition, the resulting pair exhibits low friction and a low wear rate.

Bearing friction and wear can be further reduced by applying a dry lubricant coating to the shaft, usually by spraying and oven drying. Despite the reduced friction and wear achieved by applying the dry lubricant coating to the shaft, there are significant disadvantages associated with its use. If the dry lubricant coating is applied after the lapping operation, the clearance between the two mating parts is altered. The resulting fit is either too tight or too overlapping to allow for tolerance of the dry lubricant coating after its application. If the dry lubricant coating is applied before the lapping step, most of the coating is removed by the abrasive lapping composition, reducing or negating its friction and wear reducing effect.

According to one aspect of the present invention, there is provided a motion transmission arrangement comprising a metal part and a polymeric composite part, wherein the polymeric composite part is mounted in movable clamping engagement with a surface area of the metal part, wherein

the metal part has a self-lubricating surface with a first self-lubricating composition,

the polymeric composite part is a self-lubricating polymer composite material comprising a thermosetting thermoplastic or a thermosetting/thermoplastic polymer and a second self-lubricating composition, the polymeric composite part being molded in contact with the surface of the metal part, cured in situ and encased in a metal housing, and

where there is a small clearance between the metal part and the polymer composite part,

characterized in that

the self-lubricating surface of the metal part is a wear-resistant self-lubricating surface consisting of a porous metal oxide layer or a porous electrolyzed metal layer and the first self-lubricating composition impregnated into the pores of the metal oxide or electrolyzed metal layer.

According to another aspect of the present invention, there is provided a method of manufacturing an assembly having a polymeric composite part movably connected to a metal part, the method comprising the following steps:

(a) providing the metal part;

(b) providing a first self-lubricating composition on the metal part to form a self-lubricating surface;

(c) bringing the self-lubricating surface of the metal part into contact with a moldable mixture of a polymer and a second self-lubricating composition; and

(d) curing the moldable mixture to form the polymeric composite part,

characterized in that the first self-lubricating composition is applied to the metal part by creating a wear-resistant, porous surface layer on the metal part and by impregnating the wear-resistant, porous surface layer of the metal part with the first self-lubricating composition, and that the polymeric composite part is lapped to the metal part to achieve a predetermined small clearance between the cast polymeric composite part and the metal part.

Embodiments of the invention provide machine parts and methods for forming matching machine parts which, in combination with one another, closely lie against each other, but are considerably less sensitive to friction and wear than previously available combinations of machine parts.

Such embodiments may provide combinations of low friction, low wear and self-lubricating machine parts, such as shaft/pivot bearing combinations, shaft/linear bearing combinations, screw/nut combinations and the like, and methods for manufacturing the same.

Machine part combinations according to the invention can be used in a wide range of ambient conditions, can be manufactured with high precision and can have low friction and low wear in continuous, intensive industrial use.

For a better understanding of the present invention and to clarify the implementation of the same, reference is made by way of example to the accompanying drawings, which show:

Figure 1 - a longitudinal section of a metal screw with a clamping and sleeve arrangement to illustrate a first step in producing a combination of screw and nut according to the invention for transmitting motion, as described below in Example 1.

Figure 2 - a longitudinal section of the screw of Figure 1 with a polymeric composite nut and sleeve assembly showing a second step in the manufacture of the screw and nut combination.

Figure 3 - a longitudinal section taken along line 3-3 in Figure 4 of a metal rail with a slider sleeve and clamping assembly for illustrating the first step in the manufacture of an alternative embodiment of the invention according to Example 2 described below.

Figure 4 - a cross-section through the rail and a finished sliding device with a polymer composite part taken along line 4-4 in Fig. 3.

Figure 5 - a longitudinal section through a round shaft with a bushing and clamping arrangement to illustrate a first step in the manufacture of a second alternative embodiment of the invention according to the following description of Example 3.

Fig. 6 - a cross-section of the shaft and the finished bushing with a polymeric composite part taken along line 6-6 of Fig. 5.

Detailed description of the invention I. Motion transfer combinations

The above-described objects are achieved by the motion transmission combination of the present invention, which comprises a polymeric composite part suitable for movably connecting to a metal part. The metal part consists of at least one metal, a metal alloy or a metal mixture and has a wear-resistant porous surface layer. A coating of a self-lubricating composition applied to the metal part impregnates or extends into the pores of the porous surface layer. The coated metal part and the polymeric composite part operate with little play.

In the context of the present invention, the term "motion transmission" refers to a combination of parts, elements or individual parts in which movement is transmitted by one part of the combination, while the other part primarily maintains the spatial arrangement of the combination. Although one part of a combination according to the invention can be absolutely stationary, both parts are nevertheless in motion relative to one another and thus "motion transmitting". Inventive Combinations are also those in which forces are transferred between the parts.

The motion transmitting combination of the invention can be adapted to any physical embodiment that has one or more mechanical contacts through which motion and/or force is transmitted through or between the parts. Examples of motion transmitting mechanical contacts are bearing/shaft combinations, including plain bearings such as journal bearings, and rolling element bearings such as ball bearings, roller bearings and needle bearings; combinations of threaded fastening and locking devices such as screws and nuts, bolts and washers; gears such as meshing or intermeshing spur gears and worms; clutches such as friction clutches with two opposing surfaces in frictional contact, axial clutches with discs and plates perpendicular to a shaft, and one-way clutches in which an inner and an outer member are keyed together by concentric rollers running in a cage; Chain drives such as roller chains consisting of a series of interconnected axle bearings forming a flexible track; cam mechanisms; load-bearing rails or tracks and wheels of moving vehicles such as railroad cars or automatic guided vehicle systems traveling on the rail or track; and the like.

In each of these embodiments, at least one of the parts of the motion transmission combination forms the polymer composite part, at least one other part forms the metal part, and the polymer composite part is designed to be movably connected to the metal part. In this context, the expression "suitable for movably connecting" means that one part is movable relative to another part when both parts are connected to one another. For example, a motion transmission combination according to the invention can have a (completely) stationary metal shaft and a polymer composite bearing that rotates about the shaft. Alternatively, both parts can be movable, as in the case of two meshing spur gears, or the polymer The composite part can be (absolutely) stationary and the metal part can be movable, such as in a combination of a metal ball bearing and a housing made of polymer composite material.

The metal part of the present combination, which has a wear-resistant, porous surface layer coated with a self-lubricating composition, contacts the polymeric composite part with little clearance. All or part of the total surface of the metal part may contact the polymeric composite part, but at least that portion of the metal surface contacting the polymeric composite part is wear-resistant, porous and impregnated with a self-lubricating composition. "Impregnated" in the present context means that the self-lubricating composition extends into the pores of the porous surface layer of the metal part. As previously mentioned, mechanical contacts of conventional combinations of machine parts have suffered from significant friction and high wear, resulting in unacceptable deviations from the intended dimensions of the machine parts. In the context of the present invention, the term "small clearance" means that when the impregnated wear resistant porous surface of the metal part is in contact with the polymeric composite part and when one or both parts move relative to the other or to each other, the wear resistance and friction provided by the inventive combination are such that the parts fit snugly and tightly together, but are freely movable relative to each other. Preferably, the clearance between the metal part and the polymeric composite part is between about 2.5 µm or 0.0001 inch and about 100 µm or 0.004 inch, and most preferably between about 5 µm or 0.0002 inch and about 50 µm or 0.002 inch.

The present invention is not limited to two-part combinations, but also includes motion transmission combinations with multiple polymer composite parts and a single metal part, a single composite part and multiple metal parts, or multiple polymer composite parts and multiple metal parts. For example, in a typical ball bearing application, a plurality of rolling elements or balls are evenly spaced in a circular channel or track formed by two rings or cage members. When a load is applied to the bearing, the load is distributed unevenly across the race to some or all of the rolling elements. The present invention also places no restrictions on which part or parts transmit motion to one or more other parts. Although power is usually transmitted from the metal part to the polymer composite part, power can also be transmitted from the polymer composite part to the metal part.

II. The polymer composite part

At least a portion of the present power transmission combination is comprised of a self-lubricating polymeric composite material. Preferably, the composite material comprises a substantially homogeneous mixture of a polymer and a self-lubricating composition.

The polymer of the self-lubricating polymeric composite material can be any organic polymer which forms a substantially uniform mixture with the self-lubricating composition. Suitable polymers are essentially infusible and insoluble once cast and cured, or are not substantially melted, reshaped, dissolved or deformed in any way by the application of heat at normal operating temperatures encountered in industrial use up to 315°C (600°F). The starting polymer materials suitable for the composite material of the invention can be solid such as powders, granules, preformed materials such as pills, tablets, cakes or preformed parts; they can be bulk molding compositions such as premixes, gel, putty, dough or slurry; or they can be sheet molding compositions such as spray or molded mats. Alternatively, the starting polymer materials can be a fluid, a semi-fluid or a liquid, as in the case of a liquid resin.

The polymer properties can be selected as desired to achieve properties such as plasticity, flexibility, strength, stiffness, high or low density, temperature resistance, elasticity, deformability, adhesion, tackiness, polymeric bonding, crystallinity or non-crystallinity, and/or high or low molecular weight. Preferred values for these properties are:

Tensile strength greater than approximately 28 MPa (4000 PSI)

Tensile modulus greater than approximately 5500 MPa (3x10&sup5; PSI)

Flexural strength greater than approximately 55 MPa (3000 PSI)

Flexural modulus greater than approximately 4800 MPa (7x10&sup5; PSI)

Compressive strength greater than approximately 90 MPa (13000 PSI)

Impact strength greater than approximately 0.026 J/mm (0.5 ft-lb/in)

Rockwell hardness greater than approximately E 60.

The polymers having one or a suitably combined number of these properties and the processes for their preparation are known to the person skilled in the art of polymers.

Generally, polymers suitable for the present invention include, but are not limited to, thermosetting polymers or polymers having both thermosetting and thermoplastic properties. Suitable thermosetting polymers include, but are not limited to, cross-linked or network polymers such as epoxy resins, for example bisphenol A epoxy resins; allyl esters such as those formed from the monomers diallyl phthalate (DAP), diallyl isophthalate (DAIP) and allyl diglycol carbonate; amino polymers such as urea formaldehyde (UF) and melamine formaldehyde (MF); phenols or phenol formaldehyde (PF) polymers; polyesters, including network polyesters such as alkyds; polyimides; cyanoacrylates; polyurethanes; silicones such as silicone resins; and blends thereof. For a general discussion of thermosetting polymers, see T. Richardson, Composites: A Design Guide, 65-81 (Industrial Press, Inc., 1987). Casting epoxies suitable as engineering materials for mechanical designs are described by J. M. Wilson, "Cast Epoxies Replace Metals in Mechanical Designs," Materials Engineering (April 1983). Various commercially available epoxies are described in "Materials of Construction: Current Literature," Chemical Engineering, 69-83, (October 24, 1988).

Thermoplastics and linear plastics that do not soften to any significant degree at temperatures that are used in the motion transfer combination of the invention may also be suitable for the present invention, for example polystyrene, polyethylene, polyvinyl chloride and polyethylene terephthalate. Polymers that can be described as both thermosetting and thermoplastic may also be suitable for the present invention. For example, modified polyethylene and polyvinyl chloride polymers with cross-linked molecules are available that have improved dimensional stability under load and at high temperatures. For example, see A. Rudin, The Elements of Polymer Science and Engineering, 23-24 (1982).

The amount of polymer in the self-lubricating polymeric composite material of the present invention can range from about 30 weight percent to about 99 weight percent based on the total weight of the composite material, and is preferably about 70-80 weight percent.

Self-lubricating compositions suitable for use in the polymeric self-lubricating composition of the invention are those capable of forming a substantially uniform mixture with the polymer. These self-lubricating compositions may be solid lubricants such as graphite, molybdenum disulfide (MoS₂) and tungsten disulfide (WS₂) which are suitable for use in the polymeric self-lubricating composition of the invention because of their lamellar structure consisting of loosely bonded layers held together by weak intermolecular forces, have a low shear strength and a low coefficient of friction. Suitable self-lubricating compositions may also comprise intercalated solids, for example intercalating compositions of graphite or dichalcogenides, or oxides such as silver oxide, lead oxide, cadmium oxide or zinc oxide. Alternatively, the self-lubricating compositions may comprise a plastic lubricant such as a perhaloolefin, preferably a perfluoroolefin, for example polytetrafluoroethylene (PTFE) available under the trade names Teflon, Fluon and Fluoroflex, or a similar non-sticky material may be used. The self-lubricating composition of the invention may further comprise a suitable carrier, an additive, a filler and the like.

The amount of self-lubricating composition in the self-lubricating polymeric composite material of the invention can be between about 1 and about 70 weight percent, preferably between about 20 and about 30 weight percent, based on the total weight of the composite material.

Suitable commercially available and suitable compositions of self-lubricating polymeric composite materials include SKC 3, an epoxy material from Gleitbelag-Technik GmbH, Germany; Moglice P500, another epoxy material from Diamant MetallPlastic GmbH, Germany; Super Alloy-Black 1500 LF, also an epoxy material from ITW Philadelphia Resins Corporation, Montgomeryville, Pennsylvania; and INTERCAL EP 28, EP 66 and EP 49, which are embedded graphite materials, all available from Intercal, Port Huron, Michigan. The INTERCAL products are organic matrix composite materials reinforced with embedded graphite. The manufacture of these products is described in US-A-4,414,142.

III. The metal part

The motion transmission combination according to the invention further comprises at least one metal part. The metal part can consist of any material or alloy whose strength is sufficient to withstand and transmit the movements and/or forces occurring in the given application. Suitable metals are generally aluminum, chromium, copper, iron, titanium, nickel, tungsten, vanadium, zinc, zirconium, or alloys or mixtures thereof. Specifically selected metals from the above list can only be suitable for use in alloys or mixtures. Preferred alloys are steels and aluminum alloys. Metal mixtures suitable for the present invention can contain non-metallic materials such as carbon.

The metal, metal alloy or metal mixture can be chosen at will to achieve properties such as corrosion resistance, yield strength, tensile strength, elongation, hardness, malleability, density, specific gravity, melting point, thermal conductivity, electrical resistance, tensile modulus of elasticity and formability. The suitable metals, metal alloys or metal mixtures with one or a suitable mixture of the above properties are known to those skilled in the art of metallurgy. The choice of values for these properties depends on the specific application. Under common requirements for transmitting mechanical movement or force, examples of such values are:

Flexural strength 55-275 MPa (8000 - 40000 PSI)

Tensile strength 210-1035 MPa (30000 - 150000 PSI)

Compressive strength 275-1380 MPa (40000 - 200000 PSI)

Impact strength 13.6 - 32 J (10-150 ft-lbs) (measured using the Charpy V-notch test)

Hardness Rockwell H 50-C60

The surface of the metal part according to the invention is porous. In this context, the word "porous" means that the surface layer on the metal has sufficient porous structure or porosity to permit penetration of an effective amount of a self-lubricating composition applied to the surface of the metal. Preferably, the porosity percentage of the surface layer of the metal part prior to impregnation is between about 1 and about 35 volume percent, most preferably between about 10 and about 15 volume percent.

The porous surface layer of the metal part according to the invention is also wear-resistant. Wear resistance can be an inherent feature of the metal, metal alloy or metal mixture used to form the metal part, or it can be artificially created in any known way, for example by anodizing or by applying an external autocatalytic coating. In this regard, reference is made to the following detailed description of the production of the wear-resistant porous layer in connection with the description of the method.

A self-lubricating composition is applied to the wear-resistant porous surface layer of the metal part of the motion transmission combination of the invention to provide reduced friction and abrasion and wear resistance beyond the wear resistance inherent in the nature of the metal surface prior to application of the coating. Any of the self-lubricating compositions previously described as suitable in connection with the self-lubricating polymeric composite part can also be used as the self-lubricating composition of the coating of the metal part.

A preferred formation of the coated metal part results from impregnating or penetrating the self-lubricating composition coating into the pores of the surface of the metal part. In this way, a suitable bond between the metal surface and the coating can be achieved.

The coating having a self-lubricating composition may be a fluoropolymite telomer powder. My suitable commercially available spray of this powder is GP 1589, sold by Acheson Colloids Co., Port Huron, Michigan.

The coating having a self-lubricating composition may be one of the commercially available "synergistic" coatings such as Tufram®, sold by General Magnaplate Corporation, Linden, New Jersey. A synergistic coating may be defined as a coating in which the base metal, the intermediate bond layer, and the incorporated or impregnated polymer become an integral material having properties different from those of the original components. The product brochure "Tufram: The Synergistic Coating for Improving Corrosion Resistance, Hardness and Lubricity of Aluminum," General Magnaplate Corp.; the article "Tough, Slick Hide Expands Markets for Aluminum Parts," Modern Metals, 46 (May 1976), and the article "A Coating that Makes Aluminum Hard and Corrosion/Erosion Resistant," Manufacturing Engineering. 56 (August 1977), disclose that a coating of Tufram on aluminum provides an impregnating penetration of tetrafluoroethylene (TFE) into the aluminum surface, which may or may not be anodized prior to coating. The coating preferably provides increased wear resistance and permanent dry lubrication. Another commercially available synergistic coating is Lectrofluor, also developed by General Magnaplate Corporation, which incorporates Allied Chemical's Halar fluoropolymer into ferrous and nonferrous metals. The Lectrofluor product is described in the product brochure "Synergistic Times," General Magnaplate Corporation; and in "New Synergistic Fluoropolymer Coating for Metal," Chemical Equipment, 36 (February 1965). A third synergistic coating is commercially available under the trade designation NEDOX from General Magnaplate, and is described in "Magnaplate News," Magnaplate Corp. (1978). The product Hardlube, available from Pioneer-Norelkote, Green Bay, Wisconsin, is another coating used for anodizing aluminum and suitable for treatment with polytetrafluoroethylene (PTFE) in order to provide the treated part with the desired friction, wear and abrasion resistance.

IV. Manufacturing process

The present invention further relates to methods for producing a motion transmission combination with a polymer composite part for movable connection to a metal part.

As a first step of the process, a metal part is provided with a wear-resistant porous surface. This type of surface may be inherent in the metal part. If not, such a surface may be produced by anodizing the surface of the metal part. Anodizing, a process well known in the field of surface treatment of metals, involves immersing the metal part in an electrolytic bath, such as a 50% sulfuric acid solution, and passing an electric current through the bath. The metal part to be anodized forms the positive terminal. The current density is preferably about 270 amps/m² (25 amps/ft²) and the immersion time is preferably at least about 1 hour.

Anodizing is also a method of obtaining an oxide surface on a metal part according to the present method. For example, an aluminum part can be anodized to form an oxide layer on the surface of the part. This layer has a wear-resistant, porous structure suitable for impregnation with a self-lubricating composition as described above.

Alternatively, the wear-resistant porous surface layer on the metal part can be produced by applying an electrolytic layer of nickel or chromium. Chromium is particularly suitable in this respect because of its hardness. Alternatively, a porous zinc phosphate layer can be bonded to the metal surface.

The wear-resistant porous surface layer of the metal part can also be achieved by appropriate selection of metals from which the part is to be formed. For example, sintered metal powders with a porosity of 1-35 percent are known and suitable for forming a porous surface.

The next step of the process of the invention involves impregnating the porous surface of the metal part with a self-lubricating composition. Self-lubricating compositions suitable for use in the polymeric self-lubricating composition of the invention are those capable of forming a substantially uniform mixture with the polymer. These self-lubricating compositions may be solid lubricants such as graphite, molybdenum disulfide (MoS2) and tungsten disulfide (WS2) which have low shear strength and a low coefficient of friction due to their lamellar structure consisting of loosely bonded layers held together by weak intermolecular forces. Suitable self-lubricating compositions may also comprise intercalated solids, for example intercalated compositions of graphite or dichalcogenides, or oxides such as silver oxide, lead oxide, cadmium oxide or zinc oxide. Alternatively, the self-lubricating compositions may comprise a plastic lubricant such as a perhaloolefin, preferably a perfluoroolefin, for example polytetrafluoroethylene (PTFE) available under the trade names Teflon, Fluon and Fluoroflex, or a similar non-sticky material may be used. The self-lubricating composition of the invention may further comprise a suitable carrier, an additive, a filler and the like.

The self-lubricating composition coating may be applied in any manner that ensures that the self-lubricating composition is impregnated into or extends into the pores of the porous surface of the metal part. For example, the coating may be sprayed onto the surface layer or applied with a brush or roller, or the metal part may be tank or container containing the self-lubricating composition. After application of the self-lubricating composition, the coated metal part should be allowed to stand for a period of time sufficient to allow the coating to dry or cure in the pores of the porous surface layer of the metal part, followed by oven drying at at least 93-149º C (200-300º F) for at least about one hour to cure the coating.

The next step of the method of the invention consists of applying a moldable mixture of a polymer and a self-lubricating composition to the impregnated surface of the metal part, and curing the resulting composite material to form the polymeric composite part. In this context, "moldable mixture" means any fluid, semi-fluid, solid or semi-solid mixture of a polymer and a self-lubricating composition which, when applied to the metal part, is sufficiently pourable, moldable, injection moldable or malleable to conform to the shape of the metal part upon curing. Suitable polymers of the moldable mixture include, for example, the thermosetting polymers, the thermoplastic polymers and the polymers which are both thermosetting and thermoplastic, as previously described. The moldable mixture to be cured can be kept in contact with the coated surface of the metal part by enclosing it in a sleeve or other housing that can form the outer surface of the polymeric composite part and serve as a mold for pouring the moldable mixture. Alternatively, the moldable mixture can be sprayed, brushed or rolled onto the metal part.

Once formed, the composite material can be cured by any known method suitable for the curing reaction of the polymer chosen. For example, if the polymer is a polyolefin with pendant olefin groups and an internal catalyst or a blocked polyisocyanate, the composite material can be cured by placing the polymeric composite mixture in the sleeve and the metal part (surrounded by the sleeve) in a curing oven. The curing oven may provide infrared, convection or conduction heat. Typical operating temperatures for curing ovens are between about 149º C and 204º C (300º F and 400º F). Curing ovens are commercially available from Glenro, Inc., Peterson, New Jersey; Radiation Systems, Inc., Wyckoff, New Jersey; and BGK, Inc., Minneapolis, Minnesota. If the polymer comprises one or more polymers having pendant glycidyl and acid groups, the moldable mixture may also be cured by leaving the material at room temperature for at least about 24 hours to effect curing of the mixture. Preferably, additional post-curing may be performed after the room temperature residence to ensure that the composite material is fully cured.

Once the composite material is cured, the next step of the inventive method involves machining the cured composite material at the metal surface with a lapping composition to provide a suitable clearance between the polymeric composite part and the metal part. Lapping compositions and their use are well known to those skilled in the metalworking art. Suitable available lapping compositions include the TimeSaver line of lapping compositions from TimeSaver Products Company, Franklin Park, Illinois, and the Clover line of lapping compositions from Fel-Pro Incorporated, Skokie, Illinois.

After lapping the polymeric composite part in conjunction with the metal part, both parts may be washed with soap and water or a suitable solvent, such as acetone, to remove residual lapping composition. The surfaces of the metal part and the polymeric composite part may, if desired, be coated with grease or other liquid lubricant prior to use.

The invention is now described using the following detailed examples.

example 1 Anodized aluminum screw with polymer composite nut

An ACME threaded screw with a diameter of 25.4 mm (1"), a length of 300 mm (12"), and a front end of 6.35 mm (0.25") was made from an extruded round bar of 6061 aluminum alloy. The screw was lapped to a medium finish (0.15 µm to 0.3 µm (6 to 12 micro-inches) RMS) using a mixture of light machine oil and a 60N lapping compound manufactured by TimeSaver Products Company, Franklin Park, Illinois. The screw was then thoroughly cleaned with soap and water and anodized to provide a 0.05 µm (0.002") thick hard oxide coating using the proprietary process of BTM Corporation, Marysville, Michigan. The anodized screw was then treated with PTFE manufactured by BTM Corporation to provide a self-lubricating surface. The construction of the polymeric composite part is shown in Figures 1 and 2. As shown in Figure 1, construction began with an extruded 6061 aluminum alloy sleeve 10 having an inner diameter (ID) of 31.75 mm (1.25") and an outer diameter (OD) of 38.11 mm (1.50") and a cut length of 50.8 mm (2"). A steel jig 12 had an ID at one end that closely matched the major diameter of the anodized aluminum screw and an OD that closely matched the ID of the 50.8 mm (2") long extruded aluminum sleeve. The other end of the jig had a widened cross-section so that the ID fit closely over the OD of the aluminum sleeve. This jig was then used to center the screw 14 in the sleeve while a soft rubber mold 16 was molded around the lower end of the combination. The soft mold was made of molding material using SC-131 silicone from Thermoset, Indianapolis, Indiana with a Dow Corning 1 catalyst.

The material used to cast the internally threaded nut in the sleeve was a product of ITW Philadelphia Resins Corporation under the designation Super Alloy Black 1500 L.F. It was applied following the manufacturer's recommended steps, namely: (1) all metal surfaces were washed with trichloroethylene to remove dirt and grease; (2) the surface of the screw in the sleeve 10 was sprayed with a release agent (MS-122 from Miller Stephenson Chemical Company, Danbury, Connecticut), and (3) the two components of the polymeric composite composition were mixed in the specified amounts by pouring the designated curing agent into the resin and stirring for 3 minutes.

Prior to mixing the polymeric composite resin, the bolt was placed in the soft mold. As shown in Figure 2, the polymeric composite composition 18 was poured into the cavity between the nut shell and the bolt. After filling the cavity, the wide end of the jig was positioned in the upper end of the nut shell to center the bolt. The polymeric composite was then left overnight at room temperature to cure into a solid part. After curing, the nut was removed from the bolt for lapping.

Lapping was accomplished by applying a mixture of 50 weight percent each of light machine oil and 60N lapping compound from Timeaver Products Company, Franklin Park, Illinois, to the bolt and rotating the nut up and down until it ran freely. The lapping compound/oil mixture was then washed from the bolt and nut with acetone. At this point the process was complete and the nut ran freely on the bolt. The nut on the bolt had approximately 13um (0.0005 inches) of play.

Example 2

Anodized aluminum rail with polymer composite sliding device As shown in Figures 3 and 4, the track 21 used in this example, a #155 Hi Beam Track from Harken Yacht Fittings, Pewaukee, Wisconsin, was an extruded aluminum alloy part of rectangular cross-section. It was treated with a suitable coating treatment available as Hardlube from Pioneer-Norelkote, Green Bay, Wisconsin. The Hardlube treatment consists of anodizing the aluminum part to give it a hard wear resistant surface 22 followed by a PTFE treatment to make that surface self-lubricating. Before molding the slider 23 onto the track, the track was sprayed with a release composition MS-122 from Miller Stephenson Chemical Company, Danbury, Connecticut.

Fabrication of the polymer composite began with a stainless steel sleeve 24, which formed the outer surface of the slide and served as a mold for pouring the polymer composite. The sleeve 24 was held in place by polyurethane retainers 25, which were made similar to the soft rubber mold of Example 1. The polyurethane retainers 25 positioned the sleeve 24 and closed the ends of the sleeve around the rail to hold the liquid polymer composite mixture therein.

INTERCAL EP 28 self-lubricating two-component epoxy resin from Intercal, Port Huron, Michigan, was mixed in the manufacturer's recommended proportions and poured into the sleeve. The poured mixture was then allowed to cure overnight at room temperature (21º C (70º F)). The next day, the polymeric composite was post-cured for two hours at 180º C (356º F) after which the polymeric composite member 26, now a slider or linear bearing slidable along the rail, was removed by sliding it over the end of the rail. The inner surface of the polymeric composite member 26 contacting the metal rail was coated with an oil mixture of 60N medium lapping composition from TimeSaver Products Company, Franklin Park, Illinois, and the slider was lubricated on the rail for an accumulated distance of 15m (50 feet) to provide sufficient clearance for unhindered movement.

After lapping was completed, the parts were separated, washed with acetone to remove the lapping compound/oil mixture, and the contact surfaces were coated with a thin coating of Greadag 740, a grease from Acheson Colloids Company, Port Huron, Michigan. Although aluminum alloys have a silvery-white color, the Hardlube anodized coating was a smooth, uniform dark gray color. After lapping, there were no signs of wear on the Hardlube aluminum alloy surface, i.e., no changes in the color density of the coating of the lapped areas compared to other areas not in contact with the polymer composite surface, no streaking of the surface, or other signs of minor metal removal.

Example 3 Hard chrome plated round hollow shaft with Moglice polymer composite bushing

As shown in Fig. 5, the shaft 31 used in this example was a 25.4 mm (1") diameter and 300 mm (12") long SAE cold rolled steel shaft. Electrogalvanization was used to provide the shaft surface with a wear-resistant coating of chromium. This coating was modified hard electrogalvanized chromium with a thickness of 0.025 to 0.05 mm (1/1000 to 2/1000 inch) and a Rockwell hardness of C72. This semiporous coating was impregnated with PTFE to create a wear-resistant surface layer 32 impregnated with a self-lubricating composition.

Fabrication of the slide bushing 33 began with the manufacture of a circular cylinder that served as a sleeve 34 for molding a self-lubricating polymeric composite 35 (see Fig. 6). The cylinder had an inner diameter of 31.75 mm (1-1/4"), an outer diameter of 44.5 mm (1-3/4"), and a length of 50.8 mm (2"). The inside of the sleeve 34 was roughened to assist in the adhesion of the molded liner.

A jig 36 for centering the shaft 31 in the sleeve 34 consisted of a cylinder having an inside diameter of 25.4 mm to fit snugly into the sleeve. A soft mold 37 was formed to cover one end of the shaft/sleeve combination by holding the shaft and sleeve in a vertical position with the shaft 31 approximately 3.175 mm (1/8 inch) below the bottom edge of the sleeve 34 and the jig 36 between the sleeve 34 and the shaft 31. The assembly was held in the vertical position in a container 38 measuring 76.2 mm (3") in diameter and 76.2 mm (3") in depth. A silastic molding composition, available from Thermoset Plastics, Inc., Indianapolis, Indiana, was molded around the lower end of the assembly to a depth of 50.8 mm (2"). The silastic was cured overnight and the jig 36 was removed from the annular space between the sleeve 34 and the shaft 31.

The cast lining of bushing 33 was made of Moglice PL500, a two-component, self-lubricating, epoxy-based polymer composite material manufactured in Germany by Diamant and imported to the United States by Devitt Machinery Company. According to the manufacturer's instructions, the epoxy-based material was mixed by pouring the pre-measured ingredients together and mixing for three minutes. During this time, shaft 31 was removed from mold 37, sprayed with MS-122 release agent, and returned to mold 37. Once the shaft was in place, the Moglice PL500 Mixture is poured into the cavity between the shaft and the sleeve and cured for 16 hours at room temperature.

After the cast self-lubricating polymer composite part 35 was fully cured, the shaft and bushing assembly was removed from the Silastic mold and the bushing was released by sliding it along the shaft. At this point, the bushing was difficult to move along the shaft because there was essentially no clearance between the parts. The appropriate clearance to allow the bushing to move freely on the shaft was achieved by lapping with a mixture of 60N medium lapping composition from TimeSaver Products Company, Franklin Park, Illinois.

The present invention has been described in connection with various specific and preferred embodiments and methods. It should be understood, however, that numerous changes and modifications may be made without departing from the scope of the invention as defined by the claims.

Claims (29)

1. A motion transmission arrangement comprising a metal part (14, 21, 31) and a polymer composite part (18, 26, 35), the polymer composite part being mounted in movable clamping engagement with a surface area of the metal part, the metal part (14, 21, 31) has a self-lubricating surface with a first self-lubricating composition, the polymeric composite part (18, 26, 35) is a self-lubricating polymer composite material comprising a thermosetting thermoplastic or a thermosetting/thermoplastic polymer and a second self-lubricating composition, the polymeric composite part being molded in contact with the surface of the metal part, cured in situ and encased in a metal housing (10, 24, 34), and wherein there is a slight clearance between the metal part (14, 21, 31) and the polymer composite part (18, 26, 35), characterized in that the self-lubricating surface of the metal part (14, 21, 31) is a wear-resistant self-lubricating surface (22, 32) consisting of a porous metal oxide layer or a porous electrolyzed metal layer and the first self-lubricating composition impregnated into the pores of the metal oxide or the electrolyzed metal layer. 2. An assembly according to claim 1, characterized in that the slight clearance is between about 2.5 µm (0.0001 inch) and about 100 µm (0.004 inch). 3. Arrangement according to claim 1, characterized in that the first self-lubricating composition comprises graphite, intercalated graphite, molybdenum disulfide, tungsten disulfide, a perhabolefin, silver oxide, lead oxide, cadmium oxide, zinc oxide or a mixture thereof. 4. Arrangement according to claim 3, characterized in that the first self-lubricating composition comprises a perhabolefin. 5. Arrangement according to claim 4, characterized in that the perhaloolefin is polytetrafluoroethylene. 6. Arrangement according to claim 1, characterized in that the polymeric composite part is a bearing (26, 35). 7. Arrangement according to claim 6, characterized in that the bearing is a plain bearing. 8. Arrangement according to claim 1, characterized in that the metal part is a rod (14) with an external thread and the polymeric part is a nut (18) with an internal thread. 9. Arrangement according to claim 1, characterized in that the polymeric part is a sleeve (35). 10. Arrangement according to claim 1, characterized in that the metal part is a shaft (31). 11. Arrangement according to claim 1, characterized in that the metal part is a load-bearing part (21). 12. Arrangement according to claim 11, characterized in that the load-bearing part (21) is a rail or a track. 13. Arrangement according to claim 1, characterized in that the polymer is thermosetting and is an epoxy resin, an allyl ester, an amino polymer, a phenolic resin, a polyester, a polyimide, a polyurethane, a silicone or a mixture thereof. 14. The assembly of claim 1, characterized in that the polymer comprises approximately 30-99 weight percent of the self-lubricating polymer composite material (18, 26, 35). 15. An assembly according to claim 1, characterized in that the polymer constitutes approximately 70-80 weight percent of the self-lubricating polymer composite material (18, 26, 35). 16. The assembly of claim 1, characterized in that the second self-lubricating polymer composition comprises approximately 1-70 weight percent of the self-lubricating polymer composite material (18, 26, 35). 17. The assembly of claim 1, characterized in that the second self-lubricating polymer composition comprises approximately 20-30 weight percent of the self-lubricating polymer composite material (18, 26, 35). 18. Arrangement according to claim 1, characterized in that the metal of the metal part (14, 21, 31) is aluminum, chromium, copper, iron, titanium, nickel, tungsten, vanadium, zinc, zirconium or an alloy or mixture thereof. 19. Arrangement combination according to claim 1, characterized in that the porosity of the porous surface of the metal part (14, 21, 31) is approximately 1-35 vol.%. 20. A method for producing an assembly with a polymer composite part (18, 26, 35) which is movably connected to a metal part (14, 21, 31), the method comprising the following steps: (a) providing the metal part (14, 21, 31); (b) providing a first self-lubricating composition on the metal part (14, 21, 31) to form a self-lubricating surface; (c) bringing the self-lubricating surface of the metal part (14, 21, 31) into contact with a moldable mixture of a polymer and a second self-lubricating composition; and (d) curing the moldable mixture to form the polymeric composite part (18, 26, 35), characterized in that the first self-lubricating composition is applied to the metal part (14, 21, 31) by creating a wear-resistant, porous surface layer (22, 32) on the metal part and by impregnating the wear-resistant, porous surface layer of the metal part with the first self-lubricating composition, and in that the polymeric composite part (18, 26, 35) is lapped to the metal part to achieve a predetermined small clearance between the cast polymeric composite part and the metal part (14, 21, 31). 21. Method according to claim 20, characterized in that the wear-resistant, porous surface of the metal part (14, 21, 31) has a metal oxide layer. 22. Method according to claim 20, characterized in that the wear-resistant, porous surface of the metal part (14, 21, 31) is produced by anodizing the metal part. 23. Method according to claim 20, characterized in that the wear-resistant, porous surface of the metal part (14, 21, 31) has a coating of chromium or a coating of zinc phosphate. 24. The method of claim 20 wherein the moldable mixture is cured at a temperature of from about 300°F to about 400°F. 25. A method according to claim 20, characterized in that the moldable mixture is cured by applying infrared, convection or conduction heat. 26. A method according to claim 20, characterized in that the moldable mixture is cured by a chemical reaction at or slightly above about room temperature. 27. The method according to claim 20, characterized in that the polymeric composite part (18, 26, 35) is lapped to the metal part (14, 21, 31) by means of a lapping composition. 28. The method of claim 27, further comprising the step of removing the lapping composition by washing with a solvent. 29. The method of claim 20, further comprising the step of applying a coating of a liquid lubricant to the metal part (14, 21, 31) and the polymeric composite part (18, 26, 35).