GB371164A - Improved method of and machine for producing irregular or noncircular arcuate surfaces - Google Patents

Abstract

371,164. Milling arcuate surfaces. FORD MOTOR CO., Ltd., 88, Regent Street, London.-(Assignees of Pioch, W. F. ; 2960, Clairmont Avenue, Detroit, Michigan, U.S.A.) April 20, 1931, No. 11716. Convention date, May 16, 1930. [Class 83 (iii).] Milling-cutter.-In a method of machining arcuate surfaces such as the cams of an internalcombustion engine the work is rotated about an axis and a rotary end-milling cutter is simultaneously moved to and from the work and also transversely to the work axis, the transverse movement being such as to maintain the cutting region in a constant position relatively to the cutter. The box-shaped frame 10 is provided with transverse vertical webs between which the cam shaft 14 having cams 13 is mounted. An inclined trough 102 extends beneath the work and serves to receive cuttings and lubricant. Each cam is shaped by a separate end-milling cutter 33, which are arranged in two groups of four, one group being vertically disposed while the other group are inclined as shown in Fig. 2. Alternate cams are machined by the vertical cutters and the remainder by the horizontal cutters. A greater number of cutters may be similarly arranged for machining the cam shafts of six- or eightcylinder engines. Each group of cutters is driven through spiral gearing 36 from a shaft 19, each spindle being mounted in ball bearings 32 in a carriage 22 which slides in a bracket 20 pivotally movable about the shaft 19. A master cam shaft 15 arranged parallel to the work is provided with a number of cams 16, each of which actuates one vertical and one inclined cutter spindle. The peripheral cam portion 17 acts through a pivoted lever 29 to reciprocate the cutter-spindle carriages axially against the resistance of springs 52 while a side cam groove 18 acts through an arm 37 to oscillate the cutter carriages about the axis of the shaft 19. The first movement serves to give the cam the required peripheral contour while the second movement serves to move the cutter so that it operates with substantially the same part of its end face throughout the operation as shown in Figs. 12 and 14. The cutter driving-shafts 19 are driven from an electric motor 40 through belt and spur gearing. The master cam shaft is also driven through reducing gearing from the gear train which drives the shafts 19. The work is mounted at each end in collet chucks which are driven simultaneously by means of gears 105 engaging gears 107 on a shaft 106 which is enclosed in a protecting tube. The work is held stationary during the time required to withdraw the tools, substitute a fresh work-piece in the collets and restore the tools to cutting position. For this purpose the gear 72 forming part of the master cam-shaft driving-train is integral with a gear 108 having a gap 109, and a toothed sector 110 rotatably mounted on the shaft 71 has a movement limited by the radial boundaries of the gap against a spring 111 which normally urges the segment in the direction of rotation of the gear 108. Thus when, during the rotation of the shaft 71, the gap 109 comes opposite the wheel 107, the positive drive to the latter wheel is interrupted while the sector 110 traverses across the gap. At this time the wheel 107 is braked to bring the work to rest by means of a friction pad 113 which is allowed to engage with a drum on wheel 107 by a cam on the shaft 74 acting through a lever 115. Means are attached to the master cam shaft for stopping the motor in the position shown in Fig. 5 during each revolution of the master cam shaft. This is effected by means of a dog 120 engaging a lever operating the switch of the driving motor 40. A manually -operated starting-switch is provided for restarting the machine after a fresh work-piece has been chucked. The operative part of the end mill during the milling operation is indicated by the lines 130 in Fig. 15, three or four radial teeth of the tool being continuously operative. In a modification, the transverse shifting of the milling spindles is produced by means of an eccentric on the master cam shaft. Chucks.-The split collets 86, Fig. 6, which carry the work are secured by means of a member 85 and cross-pin 84 to a tubular housing 78 rotatable in bearings 76, 77. The collet is closed by a sleeve 80 which forms an extension of a piston-rod 81 carrying a piston which works in a cylindrical part of the housing 78. Fluid to reciprocate the collet sleeve is supplied by pipes 96, 97, and both collets are controlled by a single valve 98. A locating pin 89 secured to the collet coacts with a drilled hole in the cam shaft to ensure correct mounting of the work. A ball bearing is provided at 94 to permit the rotation of the hydraulic cylinder with the work. Alternatively, the collets may be operated by compressed air.