US 3438896 A
Abstract available in
Claims available in
Description (OCR text may contain errors)
April 15, 1969 B. E. COUNCIL ET AL 3,438,896
LUBRICANT COMPOSITION AND METHOD OF USING SAME Filed Sept. 9, 1965 TLEZ INVENTORS' a BY VVAPQE-M M Woo/.75
United States Patent 3,433,896 LUBRICANT COMPOSTTION AND METHOD OF USING SAME Bill E. Council and Warren W. Woods, Ponca City, Okla, assignors to Continental Oil Company, Ponca City, Okla, a corporation of Delaware Filed Sept. 9, 1965, Ser. No. 486,173 Int. Cl. ClGm 7/26, 3/22; Flori 17/00 US. Cl. 25212 4 Claims ABSTRACT OF THE DISCLOSURE Lubricant composition comprising wax, wax-extendible copolymer and an extreme pressure solid lubricant.
In one aspect the invention relates to a method of lubricating a railroad center plate assembly employing the above-described composition in the form of solid pellets.
This invention relates to a lubricant composition for lubricating two metallic parts which move relatively to each other, and which include two opposed, relatively large bearing areas which are pressed against each other with a high compressive force. More particularly, but not by way of limitation, this invention relates to a method of lubricating such parts, including especially, the method of lubricating the pivotal connection between railroad cars and the trucks upon which the cars are mounted, and to the lubricant composition used in such method.
In the rail transport industry, certain standards have been adopted for railroad car construction. In this standard construction, a center bearing assembly is utilized to connect each of the railroad cars with the trucks upon which the cars are mounted so as to permit the trucks to move pivotally with respect to the cars, and thus to follow the curvature of the tracks despite the inability of each of the cars to exactly follow or conform to such curvature. The center bearing assembly now in substantially universal use includes a truck center plate having a pivot pin extending vertically upward therefrom, and a body center plate attached to the railroad car on the longitudinal centerline thereof. The body center plate of the car acts as the load support for the entire weight of the car, and this plate contacts the truck center plate carried by the truck with the pivot pin functioning as the connecting member and post about which the relative rotary motion between the car and the truck occurs.
The large contacting areas of the truck center plate and the body center plate conjunctively wtih the heavy loading which is imposed upon the center bearing assembly results in a lubrication problem which has not heretofore been satisfactorily solved. The extent to which the car body is pivoted on the trucks in normal operation of the railroads is from about 3 to about dependent on the radius of curvature of the railroad track curve, and the pivotal movement of the car on the truck is relatively slow. Thus, no opportunity is presented for conventional oil or grease type lubricants to enter between the body center plate and the truck center plate and form a separating wedge of lubricant therebetween. In other words, no occasion is afforded for the lubricant to penetrate between the two plates, and any lubricant which does enter into this zone, or which has been initially placed there, is soon extruded from between the two plates and becomes ineffective for lubricating purposes.
A generally similar problem is frequently encountered in metal drawing, a process by which metal in its solid state is shaped by pressing it against a metal surface of nonc0nforming or differing configuration from the metal being shaped.
The present invention provides an improved method of ice lubricating the opposed surfaces of two metal members which move relatively to each other, and which are pressed against each other under loads of large magnitude. More specifically, the method of the invention has particular and special utility in the lubrication of center hearing assemblies of the type used on railway cars. The type of lubricating composition utilized in practicing the method of the invention is believed to be a novel lubricant.
Broadly described, the method of the invention comprises positioning between two substantially monoplanar surfaces which are in bearing contact with each other over a relatively large area, a lubricant composition which consists essentially of from about 20 to about weight percent of a petroleum derived wax, from about 5 to about 50 weight percent of a wax extendible copolymer, and from about 3 to about 40 percent of an extreme pressure solid lubricant material, such as graphite, molybdenum disulfide, or vermiculite. In a preferred method of practicing the invention, small solid particles of the lubricant composition are disposed between the contacting metal surfaces to be lubricated at a time When the metal surfaces are spaced relatively far from each other, and prior to the positioning of these surfaces in bearing contact with each other. It is also preferred to position between the metal bearing surfaces, an amount of the lubricant composition which exceeds the amount required to fill the void spaces between the surfaces and to form a film between the surfaces during operation of the bearing. The use of the excess lubricant permits a portion of the lubricant to be extruded from between the contacting bearing surfaces when the opposing metallic members are fully loaded, and the extruded portion of the lubricant solidifies adjacent the edges of the plates which are in bearing contact, and this serves to form an encasing shield around the joint which prevents infiltration of dirt, water and other deleterious materials between the bearing surfaces.
Important broad objects of the invention are to provide a new lubricant composition and an improved method of lubrication.
Another, more specific object of the invention is to provide a lubricant composition which functions superiorly to other lubricants in lubricating opposed metal surfaces in instances where the surfaces are each of relatively large surface area, and are pressed against each other :by
' forces of large magnitude.
A further object of the invention is to provide a method of lubrication by which an effective lubricant may be interp'osed between two bearing surfaces, and a sealing film or shield substantially simultaneously formed around the junction line of the bearing surfaces so as to exclude dust, water and other deleterious materials from between the bearing surfaces.
A more specific object of the invention is to provide an improved method of lubricating the center plate assembly used to support railroad cars on their respective trucks.
Another object of the invention is to improve the ease with which metal drawing can be accomplished, such improvement being effected through the use of the new lubricant of this invention.
Additional objects and advantages will become apparent as the following detailed description of the invention is read in conjunction with the accompanying drawing which illustrates certain aspects of the invention.
In the drawing:
FIGURE 1 is a plan view of a railroad car and illustrating in dashed lines, the position of the trucks and the center plate assemblies beneath the car.
FIGURE 2 is a sectional view taken along line 2-2 of FIGURE 1.
Before referring specifically to the drawings which depict a center plate assembly to which the method of the invention can be especially beneficially applied, the lubricant composition utilized in the method of the invention will be discussed. The composition is basically a threecomponent system and consists essentially of a petroleumderived wax, a wax compatible copolymer and an extreme pressure solid lubricant. The petroleum-derived wax utilized may be, for example, a paratfin wax or a microcrystalline wax prepared by any of the methods now in use and well understood in the petroleum refining industry. Excellent results have been obtained utilizing a crude scale paraffin wax having a melting point of from about 125 F. to 135 F. and a maximum oil content of about 1.5 percent. Parafiin waxes of widely varying melting points and oil contents can be utilized successfully, however, and microcrystalline waxes are also suitable, though generally less desirable, for use in the lubricant composition. The amount of the wax employed can vary widely, and will depend upon the chemical character and the quantity of the other materials used in the composition. In general, however, from about 20 weight percent to about 80 weight percent of the wax should be utilized in the composition. An amount of from about 40 to about 70 weight percent is preferred.
The second major ingredient of the composition is a copolymeric material which is compatible with the wax, and which is a so-called wax extendible material. Examples of copolymers of this type are ethylene-vinyl acetate, ethylene-ethyl acrylate, and ethylene-isobutyl acrylate. The preferred copolymer for use in the lubricant composition is an ethylene-vinyl acetate copolymer, such as that sold under the tradename Elvax by the E. I. du Pont de Nemours Company, of Wilmington, Del. The copolymer functions in the composition as a plasticizing agent to give the proper retention properties to the solid extreme pressure lubricant material hereinafter described, and to form a cohesive mixture of the wax with the solid lubricant. The quantity of the wax extendible copolymer utilized can vary widely, but in general, should be at least a sufficient amount to prevent the composition from having an oily texture. From about 5 weight percent to about 50 weight percent of the copolymer can generally be employed in the composition, with weight percent to about weight percent usually being preferred.
The third major ingredient of the lubricant composition is an extreme pressure solid lubricant material. Materials of this type are well known in the art and include, for example, graphite, molybdenum disulfide and vermiculite. The amount of solid lubricant used may range from 3 to weight percent and is preferably from about 10 to about 30 weight percent. In general, it is preferable to use about 5 to about 10 weight percent less vermiculite in lubricants containing this material than the amount of graphite or molybdenum disulfide which would be optimum in the same composition.
In preparing the lubricant composition, the wax and copolymer are heated so as to convert these materials to a molten state and the liquids are then blended together in any suitable mixing device. The solid extreme pressure lubricant is reduced to a finely divided or powdered state and is thoroughly dispersed in the molten wax-copolymer blend so as to achieve an evenly distributed dispersed phase in the blend. The composition is then permitted to solidify and is pelletized into small solid pellets. The lubricant is applied in most lubricating applications in the pellet form, as will be hereinafter described in greater detail, but it should also be noted that, in some instances, such as in metal drawing, it will be preferable to lubricate bearing surfaces by heating the lubricant composition to a molten state and painting or covering the contacting surfaces with the molten composition and then permitting it to solidify in situ. It should also be pointed out that in a metal drawing operation involving stamping, the lubricant has been effectively used by casting a thin film of the lubricant (10 to 20 mils in thickness) and placing the film between the plate to be stamped and the female die of the stamping machine.
As has been previously indicated herein, an important specific aspect of the present invention is the utilization of the method of the invention in lubricating the center plate assemblies used to connect railroad cars to their respective supporting trucks. A typical center plate assembly is depicted by the accompanying drawings. A railroad car 10 is supported on a forward truck assembly 12 and a rear truck assembly 14. As illustrated in FIG- URE 2, the car body It} carries a body center plate 16 at each end thereof. The respective body center plates 16 rest upon a car truck center plate 18 which is mounted on a truck bolster 20. The truck bolster 20 extends between and is connected to a pair of parallel wheel supporting frame members 22. Each body center plate 16 is connected to its respective truck center plate 18 by a pivot pin 24 which is either connected to the truck center plate and extends upwardly through an aperture in the body center plate, or is extended through aligned apertures in both of the plates to pivotally interconnect the two plates. When the car body 10 is connected to the truck assemblies 12 and 14, the entire weight of the car and its cargo is transmitted to the truck wheels 26- through the body center plate 16 and the truck center plate 1 8 which are in bearing contact with each other. As the train negotiates a curve, the car body 10 and its associated body center plates 16 pivot with respect to the truck assemblies 12 and 14. In general, each of the body center plates 16 will rotate through an angle of up to about 10 about the pivot pin 24.
In using the method of the present invention to lubricate a center plate assembly, a number of the lubricant pellets formed as hereinbefore described are placed upon the upwardly facing truck center plate 18 while the car 10 is removed from the trucks. In general, about one pound of the lubricant pellets will be adequate for the lubrication of each of the standard center plate assemblies. After the pellets have been evenly distributed on the upwardly facing surface of the truck center plate 18, the car 10 islowered into position so that the body center plate 16 carried by the car is centered on the truck center plate and is connected thereto by the upwardly extending pivot pin.
As the weight of the car 10 is brought to bear on the center plate assembly, the pressure generated in the assembly by the weight of the car body is sufficient to cause the lubricant to have plastic flow properties and t0 fill all of the voids between the opposed or facing surfaces of the truck center plate 18 and the body center plate 16. The slight excess of lubricant which is preferably provided is extruded around the edges of the center plates and resolidifies after extrusion to form a surrounding shield which protects the space between the plates against the entry thereinto of dirt, Water and other deleterious materials.
The lubricant composition of the invention has been markedly more effective in lubricating center plate assemblies of the type described than conventional lubricants which have heretofore been employed in this environment. The effectiveness of the lubricant is due to the collective role played by each of the major constituents of the composition in the overall lubricating function. It appears that the wax lubricates the assembly in substantially the same manner as grease or oil interposed between the bearing surfaces. The solid extreme pressure lubricant, such as graphite or molybdenum disulfide, lubricates the high pressure metal-to-metal points which exist between the metal faces due to non-conformites and asperities. Although the copolymer may have some lubricating properties, its primary role is as a plasticizing agent functioning to give the proper retention properties of the lubricant in the bearing.
An example of the use of the lubricant of the invention in lubricating the center plate assembly of railroad cars will serve to further clarify the manner in which the invention is to be practiced. 56 weight percent of a parraffin Wax of crude scale wax grade and having a melting point of 128 F. and a maximum oil content of 1.5 Weight percent was blended in the molten state with 14 weight percent of an ethylene-vinyl acetate copolymer having the following properties:
Wt. percent ratio, ethylene: vinyl acetate 72:28 Melt index (A'STM D l238-57T 22 to 28 Refractive index, N 1.485 Density at 30 'C., grams/cc. 0.95 Softening point (ring and ball), F 307 Inherent viscosity, cp. 30 C. 0.78
After thoroughly mixing the wax and ethylene-vinyl acetate, 30 weight percent of finely divided lubrication grade graphite was thoroughly dispersed in the molten waxcopolymer blend. The composition was then permitted to solidify and was pelletized int-o pellets having a diameter of about lit; inch and an indiscriminate length which was usually between about A inch and /3 inch.
About one pound of the pelletized lubricant was placed on the truck center plate of a railroad car center plate assembly and the car then lowered into position on the truck. A small amount of the lubricant was extruded between the opposed surfaces of the body center plate carried by the car and the truck center plate carried by the truck. This extruded portion of the lubricant solidified outside the bearing and formed a protective shield preventing entry of dirt and water into the bearing. The lubricant thoroughly lubricated the center plate assembly over an extended period of time and, in general, performed more satisfactorily than conventional lubricants of the type previously used in the lubrication of center plate assemblies.
The same lubricating composition used in the example of the lubrication of a railroad center plate assembly as described above was used in a metal drawing operation where a fatty type conventional lubricant had previously been used without success. The operation involved stamping 4 inch pipe caps from inch steel plate using a 93- ton Bliss side-crank press. When the conventional lubricant was used the caps were unsymmetrical and were excessively scufied and scarred. When the lubricant of the present invention was used, symmetrical stampings were obtained which displayed very little scufiing.
From the foregoing description of the invention, it will have become apparent that the invention provides an improved method of lubrication utilizing a novel lubricant composition. The eifectiveness of the lubricant for lubricating the center plate assemblies of railroad cars is particularly marked.
Although certain specific embodiments of the invention have been herein described in order to provide examples of its practice as guidelines suflicient for those having skill in the art to which the invention appertains, it will be apparent that other materials in addition to those specifically mentioned can be included in, and made a part of, the lubricating composition, and that other steps may be included in the lubricating method without departure from the basic principles herein enunciated and which constitute the foundation of the invention. Therefore, modifications and innovations in the practice of the invention which continue to rely on the basic principles underlying the invention are deemed to be circumscribed by the spirit and scope of the invention except as the same may be necessarily limited by the appended claims or reasonable equivalents thereof.
What is claimed is:
1. A solid lubricant composition in the form of solid pellets and consisting essentially of from about 20 to about weight percent of a petroleum derived wax, from about 5 to about 50 weight percent of a wax-extendible copolymer selected from the group consisting of ethylene-vinyl acetate copolymers, ethylene-ethyl acrylate copolymers and ethylene-isobutyl acrylate copolymers, and from about 3 to about 40 weight percent of an extreme pressure solid lubricant, selected from the group consisting of graphite molybdenum disulfide and vermiculite.
2. A solid lubricant composition as claimed in claim 1 wherein said composition consists essentially of from about 40 to about 70 weight percent petroleum derived wax, from about 10 to about 25 weight percent of Wax extendible copolymer, and from about 10 to about 30 weight percent of extreme pressure solid lubricant.
3. A lubricant composition as claimed in claim 1 wherein said wax is paraffin wax, said wax extendible copolymer is ethylene-vinyl acetate and said solid lubricant is graphite.
4. A solid lubricant composition consisting of about 56 weight percent of a paraffin wax having a melting point of from about F. to about F. and an oil content not exceeding 1.5 weight percent; about 1'4 weight percent of an ethylene-vinyl acetate copolymer having a vinyl acetate content of about 2'8 Weight percent and a melt index of from 22 to 28; and about 30 weight percent of graphite.
References Cited UNITED STATES PATENTS 3,097,'169 7/ 1963 Hall '10238 3,213,024 10/1965 Blake et a1 252-18 3358,6 19 6/ 1966 'Cox 2'5Q59 3,264,215 8/1966 Smith et a1 252- 12 DANIEL E. WYMAN, Primary Examiner.
I. VAUGHN, Assistant Examiner.
US. Cl. X.R.