GB600570A - Improvements in or relating to clamping fixtures for holding work pieces during machining operations - Google Patents

Abstract

600,570. Work-holders. WOODWORTH CO., N. A. Feb. 1, 1945, No. 2562. Convention date, March 19, 1943. [Class 83 (iii)] In a work-holding fixture the movable part for clamping the work is actuated by a rotatable member which is locked in the clamping position by the engagement of a friction surface rotatable therewith with a fixed friction surface. In one form, a base 20 having a supporting surface 22 for the work 26 has elongated sockets 38 for guiding two rods 28 secured to the clamp 24 by collars 30 and nuts 32. Racks 46 on the rods 28 having teeth inclined in the same direction engage helical pinions 44 on a shaft 42 which is mounted in bearings 40 on the base and is rotatable by a handle 48. When resistance to rotation of the shaft 42 is increased by the clamp 24 engaging the work, the helical pinions cause the shaft to be moved endways to bring a conical surface 52 thereon into contact with a similar surface 54 on the bearing 40, thus locking the shaft in clamping position until reverse rotation causes axial motion of the shaft in the opposite direction to release the surfaces 52, 54. The motion in this direction is limited by a washer 64 keyed to the shaft by deformed tongues 66 and secured by a bolt 60 and spring washer 62, and upward movement of the rods 28 is limited by washers 70 secured to the lower ends thereof by screws 72. To prevent falling of the clamp 24 under gravity from a released position the washer 64 may be replaced by a hollow cone 90, Fig. 7, keyed at 68 to the shaft and secured thereto by a bolt 88 so that when the washers 70 prevent further upward movement of the clamp the shaft 42 will move'to the right in Fig. 7 to engage the cone 90 with a conical surface on a boss 80 prevented from rotating on the bearing 40 by a shoulder 84, thus locking the clamp in its uppermost position. In modifications, the cone 52 on shaft 42 may be replaced by a cone on the opposite end of the shaft which is forced into a conical recess in the left-hand bearing 40 of Fig. 1 when the clamp is applied, or a collar 112, Fig. 10, having an internal conical surface may be keyed to the shaft and secured by the handle 48 and a nut 118 so as to engage a conical surface 110 on the bearing 40b. In a further modification, a conical sleeve 120, Fig. 11, keyed to shaft 42 coacts with a conically seated bracket 124 attached by screws 126 to the bearing 40c, the helical pinions 44c being of opposite hand to the previous constructions. In another modification, the clamp 24d, Fig. 13, is guided by two cylindrical rods 28d and is actuated by a third rod 132 located behind the others and having rack teeth engaging a helical pinion on the shaft 42d. Conical surfaces 52d, 136 formed on the shaft and on a sleeve 138 respectively coact with similar surfaces formed in the ends of a continuous bearing 40d for the shaft to lock the latter at the end of its rotation in either direction. The sleeve 138 is keyed to the shaft by dogs thereon engaging a flattened portion 140 of the shaft and is secured by nuts 142 screwing on the shaft and a spring 147 which serves to maintain slight pressure between the sleeve and bearing at all times, but permits axial motion of the shaft for locking as above. Cylindrical surfaces 148 on the cones 52d, 136 prevent ingress of dirt &c. and in this construction the shaft 42d may be turned end for end for operation at either side by the handle 48d. The handle may be secured in a transverse cylindrical hole in the shaft by an axial grubscrew in the shaft end, or a short tapered pin may be secured transversely in the shaft by the grub-screw and a removable handle fitted thereto. Alternatively, a short cylindrical pin 172, Fig. 16, may be secured by a set-screw 136 and engaged in any one of a number of different angular positions by a slotted removable socket 174 having a transverse handle 180. The helical pinions may be formed separately from the shaft 42 and may have one of the conical friction surfaces formed thereon, the pinions moving axially with the shaft or being splined thereon, and where more than one pinion is used, only one need be helical. In order to apply a yielding clamping pressure to the work, springs may be fitted between tubular nuts which replace the nuts 32 and enclosing sleeves engaging the clamp 24.