Patent Publication Number: US-4732493-A

Title: Autolubricating bearing

Description:
The present application is a continuation-in-part of my previously-copending application Ser. No. 756,090, filed July 17, 1985 and now U.S. Pat. No. 4,636,096, Jan. 13, 1987. 
    
    
     The present invention relates to an autolubricating bearing simultaneously constituting an end abutment which can be used in very special applications imposing extreme working conditions, a total lack of maintenance, a great solidity and a great longevity. These bearings are particularly intended to equip measuring apparatuses included in control panels of airplanes such as artificial horizons, altimeters and barometers and so on. 
     For these very particular applications, it is necessary to reduce the driving torque of the movable parts as much as possible, to ensure a good working in a range of temperature from -60° C. to +80° C., that the working characteristics be independent of the relative humidity of the environment in which the device works. 
     The bearings which are now used in this type of applications present generally contact surfaces which are provided with graphite so that during their storage before the mounting in the instruments and apparatus and during that assembly particular precautions have to be taken to prevent dust from being occluded on the sliding surfaces, which damages the working conditions. Further the graphite is sensible to the degree of humidity so that the characteristics, in particular the driving torque of the apparatus thus equipped vary as a function of the ambiant humidity. 
     The present invention has the object to provide an autolubricating bearing avoiding the precited drawbacks and permitting a reduction of the driving torque, a greater durability, a total absence of maintenance, a perfect working in a range of temperature from -60° C. to +80° C. and which is insensible to humidity. 
     The autolubricating bearing according to the invention is characterized in that it comprises a brass body provided with a central through passage presenting a first cylindrical surface in which a hard natural or synthetic stone disc is driven, and a second cylindrical surface, of greater diameter than the first one, in which a steel ring is driven, which is provided with a central hole having a diameter less than that of the first cylindrical surface and one of the annular faces of which is in contact with one of the faces of the hard stone disc; by the fact that a cylindrical part of synthetic resin is fixed in the steel ring, this part presenting a median internal cylindrical surface intended to receive a pivot and two conical surfaces widening from that median cylindrical surface up to the frontal surfaces of that part defining thus a central void having a longitudinal cross section the general shape of a diabolo, and by the fact that the internal frontal face of the part of synthetic resin is in contact with the face of the hard stone disc which is itself in contact with the steel ring. 
    
    
     The attached drawing shows schematically and by way of example two embodiments of the autolubricating bearing according to the invention. 
     FIG. 1 is an axial cross section of a first embodiment of the bearing. 
     FIG. 2 is an axial cross section of a second embodiment of the bearing. 
     FIG. 3 is a variant of the bearing. 
    
    
     The autolubricating bearing shown on a greatly enlarged scale in FIG. 1 has in its actual size an external diameter of about 1 to 3 mm and a thickness of about 0.6 to 1.8 mm, that is to say that these bearings are of very small dimensions. 
     This bearing is intended to equip measuring instruments and apparatuses intended for aeronautics such as altimeters and barometers for example, which have to be insensible to aging, to humidity, to variations of temperature in a range of -60° C. to +80° C. and which require no maintenance, lubrication, cleaning or like. 
     To obtain such a result the material used for the realization of the different parts of the bearing is naturally important, but it is also necessary to realize a combination of parts and to determine the shape of each of these parts so that the characteristics of the realized bearing be optimal. 
     The bearing shown in FIG. 1 comprises a body 1 having a generally cylindrical shape, the edges of which have been chamfered to facilitate its assembly in an apparatus or instrument which is generally made by insertion in a calibrated hole. 
     This body 1 has a central through passage 2, presenting a first cylindrical surface 3 and a second cylindrical surface 4, having a greater diameter defining thus a shoulder 5. A third cylindrical surface 6 of smaller diameter than the first one 3 defines a second shoulder 7. The ends of the central passage emerging on the frontal faces of the body 1 are chamfered at 8 respectively 9. 
     A disc of ruby 10, synthetic or natural, presents a diameter corresponding to that of the first cylindrical surface 3 in order to be fixed in the body 1 by driving or by friction in said cylindrical surface 3. The height h of this disc 10 is equal to the height H of the said cylindrical surface 3 so that when the rubis disc 10 is in service position, abutting against the shoulder 7, its other face will be located in the plane of the shoulder 5. The circular edges of the disc 10 are chamfered to facilitate its introduction into the body 1. 
     It is evident that this disc of rubis 10 could be in variants realized in an other synthetic or natural stones generally used for industrial bearings. 
     This disc 10 in hard stone is maintained in service position as shown by a steel ring 11 driven, fitted or fixed in the second cylindrical surface 4 of the body 1, which rests against the shoulder 5 and which thus enters into contact with the frontal face of the disc 10. The circular internal edges of this ring 11 are chamfered to facilitate its introduction into the body 1. 
     This steel ring 11 houses a part 12 made of a synthetic resin denominated &#34;Hostaform&#34;, made by the firm HOECHST AKTIENGESELLSCHAFT, FRANKFURT A/MAIN-HOECHST, with which it is fastened by any means, setting, driving in, gluing etc. The thickness of this part 12 is equal to that of the ring, it presents a central hole 13 of a diameter corresponding to that of a pivot having to cooperate with this bearing. This hole 13 is extended on either side by conical surfaces 14,15 widening towards the frontal faces of the part 12. The hollow housing of this part 12 has thus in axial cross section the general shape of a diabolo. 
     This synthetic resin &#34;Hostaform&#34; is autolubricating and does not necessitate any graphite or any other external lubrication. 
     Tests made with these bearings have proved that they are very simple to assemble, do not necessitate any lubricating operation, that they need PG,7 no maintenance, that they correspond to the working conditions required and enumerated above and that the driving torque is reduced by about 50% with respect to a normal bearing and that on top of all this driving torque diminishes after a certain time of utilization without introducing any play or other negative consequences. This bearing has thus mechanical characteristics which improve as a function of its duration of use. 
     The second embodiment of the bearing shown in FIG. 2 is a double bearing in which the shoulder 7 against which the disc 10 rests is replaced by a second ring 11a driven into a cylindrical surface 4a which the body 1a presents and housing a part 12a. Thus, the same disc of hard stone 10 is used as abutment for inline bearings cooperating with two distinct coaxial pivots. The other elements of this bearing are the same as those described in reference to FIG. 1. 
     In variants the design of the bearing can be modified to facilitate its manufacturing and reduce its cost. 
     For example the metallic body 1 can have a through hole of constant diameter in which the disc 10 as well as the part 12 can be mounted directly without the use of a ring 11. Furthermore the inside surface of revolution of the autolubricating part 12 can have in cross section the general shape of two curves with opposite curvatures defining a central area of minimum diameter. 
     Finally the disc 10 can also be made in an autolubricating material as the part 12.