Patent GB-524520-A (GB)
Title: Improvements in or relating to the finishing of surfaces by abrading
IPC: B24B35/00
Filed: 1939-01-31
Abstract: 524,520. Grinding and polishing surfaces. CHRYSLER CORPORATION. Jan. 31, 1939, No. 3289. Convention date, Sept. 23, 1938. [A Specification was laid open to inspection under Sect. 91 of the Acts Jan. 17, 1940.] [Class 60] In a method of and apparatus for finishing a surface such as that shown in Fig. 1, having a number of minute projections thereon lying above a base line 12, a film of lubricating coolant is maintained on the surface and an abrading element is moved over the work under sufficient pressure to cause the abrading element to break the film and wear away the projections until the surface is reduced to the condition shown in Fig. 2, at which point the pressure, distributed over an increased area, is insufficient to rupture the film and no further abrading action occurs. No appreciable dimensional changes are produced by the operation. In order that the film strength of the oil or other film-forming medium may be exactly determined, the oil &c. is preferably maintained at a uniform temperature. The abrading tool preferably has a combined relative rotary and reciprocatory movement with regard to the work, cyclic variations in the movements being introduced to vary continuously the direction of the resultant finishing movement. In finishing a roll 14 such as that used in rolling mills, the roll-necks 22 are supported on jacks 17 through rollers 21 and the roll may be mounted between centres 23, 34 and driven by a chuck 27 connected to a motor 38 through worm gearing 29 and further gearing including elliptical wheels or motor-circuit control mechanism for cyclically varying the rotational speed of the work. A pair of upper guide rails 41 support the rollers 47, 48 of a tool carriage 44 which is fed along the rails by screws 49 driven in unison by a reversing motor 53 which: may also have cyclically varying speed. The tool support has bearings for three radiallyarranged lapping tools 60. One of these tools is shown in Fig. 5 and includes a rectangular casing 62 carrying a pair of levers 63 which are oscillated on a common pin 64 by crank pins 73 engaging slots in the upper ends of the levers. The crank pins are driven from a motor 69 through eccentric gearing or other speed-varying means and gearing 70, 71. The lower end of each lever carries pivoted rollers 74 for a pair of abrading blocks 75 which are yieldably urged towards the work against the pressure of a spring 76 by a fluid link 79 which transmits the pressure on a piston 81 derived from a spring 84. The spring 84 may exert a constant pressure through the fluid link or the pressure may be cyclically varied by a cam 85 driven from a motor 87. The periods and stroke lengths of the tools may be altered by altering the sizes of pinions 71 and the eccentricity of the crank pins 73. The central tool has only a single oscillating lever. In a modification, one element 75 may be associated with a spring to control the pressure of this tool on the work and to maintain such pressure different from the pressure of the other tool. Lubricant may be discharged on the work from nozzles 97 (not shown). In one example the five tool elements carried by the members 60 may have stroke lengths of # inch, 3/16 inch, “ inch # inch and ¢ inch respectively and be moved at 500, 400, 300, 250 and 200 reciprocations per minute with or without cyclic variations. The abrading elements may be of 500 mesh grit. For cast iron, steel, or aluminium the pressure may be 15-16 lb. per square inch or may be varied up to 30 lb. per square inch. The relative rotational speed may be 35-50 feet per minute and the reciprocatory speed from 15-25 feet per minute. The oil may have a viscosity of 460 seconds Saybolt at 100‹F. In a modification, the apparatus may be permanently secured to a roll stand, the tool carriage being similar to that described above and being moved along a roll by a longitudinal shaft. Vertical adjustment is effected by a screw. A device for varying the speeds of any of the driving motors is shown in Fig. 8. A rheostat 121 in one of the supply means to the motor is controlled by an arm 122 actuated by a cam 128 on a disc driven by a motor 129. In some cases the action may be stopped before the ridges have been entirely removed. Any depressions such as 11 which are left after the base line 12 is reached serve as lubricant reservoirs for a lubricated surface in use.