Patent GB-469302-A (GB)
Title: Improvements in and relating to work-holding mandrels for lathes and like machine tools
IPC: B23B31/40
Filed: 1936-11-25
Abstract: 469,302. Lathe &c. mandrels. HASSE & WREDE GES., C., and STUDINGER, E. Nov. 25, 1936, No. 32248. [Class 83 (iii)] A mandrel has the axially spaced gripping devices operated by an axially sliding member which is actuated by a mechanical source of power, such as an electric motor, and means are provided for disconnecting the power when the required pressure has been applied to the gripping devices or when they have been released. The mandrel body 1, secured to a lathe &c. spindle 3, has two sets of grippers 10, 11 spaced circumferentially and held inwards by spring bands 12. The grippers are expanded by separate plungers 4, 6, the former having an enlargement 5 attached to a draw-spindle 17 and the latter being attached to a rod 7 carrying an adjustable abutment 15. A head 16 on the rod 7 engages the end of the body 1 to limit the rearward position of the plunger 6 and a spring 13 is placed between the abutment 15 and a shoulder on the enlargement 5 so as to tend to draw the plungers 4, 6 together. The draw-spindle 17 carries a plunger 56, Fig. 2, which is splined at 57 within a bush 51 attached to the lathe spindle 3 and is threaded at 55 to screw within a sleeve 52. The sleeve 52 is keyed at 53 within a sleeve 46 which is prevented from moving axially by a collar 47 thereon engaging thrust bearings 48, 49 located respectively by a sleeve 33 secured at 32 to the spindle 3, and the bush 51. A further sleeve 44 is keyed at 45 to the sleeve 46 and is secured to the boss 43 of a gear wheel 42. Differential pinions 39, 40 having slightly different numbers of teeth engage the gear 42 and a gear 41 formed on the sleeve 33 attached to the spindle 3, and are carried by a pin 38 extending between flanges 35, 37 on a sleeve 36, which is mounted by roller bearings 34, 59 on the sleeves 33, 43. A double conical friction gear 24 may be engaged by a conical gear 23 driven by an electric motor 20 which is mounted eccentrically at 22 so that rotation of the motor casing by a lever 25 will cause the gear 24 to be rotated in one direction or the other or remain stationary. Axial movement of the gear 24 is prevented by ball bearings 60 engaging a shoulder on a bush 58 within the sleeve 36 and a nut 64 screwing within the bush, the bearings 60 embracing a collar 62 on the sleeve 44. Adjustable nuts 65, 67 on the sleeves 44, 52 receive the pressure of strong springs 68, 69 which tend to draw the sleeve 52, plunger 56 and plunger 4 into the releasing position. In operation, with a work-piece such as a projectile x on the body 1, a lever 30 is rocked by hand to rotate the motor casing through the lever 25 and engage the gear 23 with the gear 24 so as to rotate the latter in the closing direction. The pinions 39, 40 are thereby rolled round the stationary gear 41 and cause the sleeves 43, 44, 46 and 52 to be rotated, and since the latter is held axially by the springs 68, 69, the plunger 56 is drawn to the left. This moves the plungers 4, 6 axially and expands the grippers 10, 11, which are arranged so that the grippers 11 make contact with the work first to centre it. The plunger 4 then moves further to expand the grippers 10 and compresses the spring 13. The drive may then be disconnected by rocking the lever 30 by hand, or for automatic operation, as soon as the plunger 56 is prevented from moving by the grippers engaging the work, the sleeve 52 will screw itself to the right against the pressure of springs 68, 69, and cause a slide 87 engaged by a groove 86 in the nut 67 to be moved. The slide 87 carries with it a bush 81 in which is screwed a rod 72, whereby the rod is pushed against a yoke 80 embracing the spindle 3 and engaging the lever 25 with its lower end. The lever 25 is thus rocked to disengage the drive, the pressure of the grippers on the work at which disengagement takes place being adjusted by screwing the rod 72 in or out of the bush 81 by means of a hand wheel 83, or by varying the compression of the springs 68, 69. In order to release the grippers the lever 30 is rocked by hand to engage the gear 23 with the opposite side of the gear 24 and the sleeve 52 is rotated slowly in the opposite direction. The sleeve first moves to the left, assisted by the springs 68, 69, until stopped by a shoulder 88 thereon engaging the axially fixed sleeve 46, whereupon the plunger 56 is moved to the right to release the grippers. A rod 54 is attached to the plunger 56 to move therewith and carries an adjustable flange 79 against a lever 76 which is rocked counterclockwise. A toothed segment 74 on the lever engages rack teeth on a sleeve 71 surrounding the bush 81 and carrying the yoke 80 whereby the yoke is carried to the left to rock the lever 25 and stop the drive to gear 24. Adjustment of the flange 79 determines the time of disengagement. The grippers 10, 11 may be replaced by other gripping devices operated by a draw-spindle.