Patent GB-702322-A (GB)
Title: Improvements in the cutting of the followers of the cam and follower type of steering gear
IPC: B23F23/08
Filed: 1949-12-16
Abstract: 702,322. Copy-milling. BISHOP, R., KENT, Ltd., G., CAM GEARS, Ltd., and HORRIDGE, J. March 16, 1951 [Dec. 16, 1949; Dec. 16, 1949], Nos. 32401/49 and 32403/49. Class 83 (3). [Also in Groups XXIII and XXIV] A method for the production of followers 6, for use in cam-andfollower mechanism such as is used in steering gear, consists in using a rotary cutting tool 4 and in moving the tool and a follower blank 6 angularly relatively to one another, firstly in a tooth-forming operation about one axis and then, in an indexing operation, about a second axis 13 parallel with the first but displaced therefrom by an amount equivalent to the throw of the follower. Twin cutters 4, 4a are carried on a spindle 3, the axis of which is co-planar with the said first axis of an axially-adjustable drum 11. The drum 11 contains an eccentric shaft 13 constituting the second axis and carrying a spring- pressed centre 19. The threetooth follower blank 6 is supported between the centre 19 and a centre 20 adjusted by a pinion 23 and rack 24. The blank is clamped against a stop 15 by a manually-operated cam 16. The drum is oscillated by a rack-bar 34 engaging a gear segment 33 attached to the drum 11, the bar being reciprocated by a grooved cam 44. The cam 44 is rotated independently or from the cutterspindle 3 by change gearing 37-41 and is formed so that the motion of the drum in one direction is initially slow for the greater part of its angular motion and is completed at a fast speed, but, in the reverse direction, is initially fast and is completed slowly for the greater part of its motion. The shaft 13 carries an indexing disc 25 having recesses 26 pitched according to the teeth of the follower blank 6. The recesses are engaged by pins 29 on a ratchet wheel 28 having teeth 28a engaged by a recessed flat spring 31. The indexing disc 25 is also formed with recesses 64 which can be engaged by a pin 65, and carries adjustable feed stops 62 which, in turn, engage a limit stop 63. Engaged with the end of the shaft 13 is a yoke 50 which is urged forwardly by a spring-pressed rod 58 but which can be swung to move the work away from the cutters by a follower 52 co-operating with a cam-track 67. In operation, the blank 6 is mounted and clamped, the pin 65 is engaged with the first recess 64 and the ratchet wheel 28 is positioned with the second tooth 28a in the lower position. The machine is started and during the slow motion of the drum 11 (anti-clockwise in Fig. 4), the slide 7 is fed to the correct cutting-depth. The cutting depth is subsequently determined by the limit stops 62, 63. On the return swing of the drum the cam 67 pushes the roller 52 forwardly and withdraws the spindle 13, so disengaging the pin 65 and allowing the ratchet gear 28 to index the work and present the second tooth to the cutters. When all the teeth have been cut, the final swing of the drum 11 causes a stop 71 to engage a switch-operating lever 68 and stop the machine. The spindle 13 is re-set bv a handle 72. The cutters are formed concavely to give a convex tooth shape. In a modification, the cutters 4, 4a, Fig. 5, are separately mounted with electric motors on hydraulic cylinders 81 which are raised when the work is indexed. The depth of cut is determined initially by adjustment of screws 86 and subsequently by stepped bars 85 which are moved during indexing by a differential-gear 102-104. The work is carried on a table 78 rotatably mounted on a table 120 which is adjustable transversely, to accommodate followers of varying throw, on a member 121. The member 121 is carried on a drum 11 which is oscillated by a hydraulically-operated rack 91. The cutters operate in only one direction of swing of the drum 11, the opposite swing being combined with the rotational movement of the table 78 to index the blank when the cutters are withdrawn. The table 78 is rotated by a hydraulically-moved rack 94 acting through pinions 95, 97 and rack 98. A hydraulicallyoperated escapement mechanism (see Group XXIV), sets the blank in the correct indexed position. Specifications 502,035 and 536,183, [both in Group XXIV], are referred to.