Patent GB-875490-A (GB)
Title: Improvements in screw thread cutting devices
IPC: F16D43/206
Filed: 1958-01-24
Abstract: 875,490. Positive clutches friction gear; shaft couplings. SVENSKA PRECISIONSVERKTYG A.B. Jan. 24, 1958 [Jan. 26, 1957], No. 2399/58. Classes 80 (1) and 80 (2). [Also in Group XXII] In a screw-thread cutting device, the driving member 22 drives the tool-carrying shaft 120 through yielding means comprising coaxial rings 62, 64, 56, abutments 196, Fig. 3, on the ring 62 and coupling elements 72, 80, the abutments 196 sliding over the elements 72 and the ring 64 being displaced axially by the elements 80 when a predetermined torque is exceeded, thus rendering inoperative the elements 72 and permitting ring 62 to rotate without interruption in contact with ring 64. The rings are housed in a casing 12 connected to the member 22, which has a driving socket 24. The drive between member 22 and ring 62 is by pins 34 in passages in member 22 and pockets 66 in the ring, the pins being loaded by cup springs 32 adjusted by a screw-threaded sleeve 10 and engaging a flange 30 bearing against the pins. A spring-pressed ball 42 in the member 22 engages slots 44 in sleeve 10 to secure the sleeve after adjustment. Driving dogs 88 on the ring 56 contact driven dogs 90 on a sleeve 92 having radial driving projections 104, Fig. 5, engaging driven projections 110 on an inner sleeve 94. The inner sleeve and shaft 120 have opposed axial grooves 110, 122 housing alternately balls 126, keying the shaft to the inner sleeve, and springs 128 located between abutments 112, 124 and a cup spring 114 on the shaft and sleeves respectively, to cause the sleeves to follow movements of the shaft, as described below. Balls 60, in opposed annular grooves in member 22 and an annular extension of ring 56, locate the ring axially, and further balls 98, in radial passages in the ring and projected by spring 100 into one of two annular grooves 96 in the sleeve 92, locate the sleeves axially. Operation; reversing mechanism.-Upon a tap preventing further rotation of shaft 120, the clutch rings move from the drive position of Figs. 1 and 3 into the slipping position of Fig. 4, inclined tracks 74, 76 assisting movement of the balls 72 along the ring 56 and ring 64 over balls 80 from a position in which pockets 78 in the ring receive the balls. Pins 84, projecting from ring 64 into slots 86 in ring 56, restrict movement between these rings, which are locked to the shaft while ring 62 continues to rotate. The drive is reversed by raising the attachment and thus sleeve 92, against the action of springs 128 and a return spring 194. Movement of the sleeve is arrested by pressure of the balls 126 against the cup spring 114, causing the balls 98 to release the sleeve 92 and move suddenly into the upper groove 96. In this setting, the sleeve dogs 90 are driven in the reverse direction by driving dogs 178 on a ring 170 coupled by balls 168 to a member 158 which is driven from the casing 12 by tapered rollers 156. The rollers are located in pockets in a cage 157 fixed to a cover 138 which is prevented from rotating with the casing 12 by an arm 140. A cup spring 186, acting on the ring 170 through a ball-race 180, 184, presses the rollers against the casing and member 158. To release the tap, the rollers rotate member 158 relatively to the ring 170, which is held by the tap, thus camming the balls 168 along tracks 167, 171, Fig. 6. This separates the ring 170 and member 158 and increases the axial pressure on the rollers until the reverse torque transmitted to the ring 170 is sufficient to overcome the resistance of the sleeve 92 and thus of the tap. Instead of forming the grooves 96 in the sleeve 92 and housing the balls 98 in the ring 56, the dogs 90 on sleeve 92 may house balls 206, Fig. 7, co-operating with grooves 202 in an additional ring 204. Specifications 830,332, 875,488 and 875,489 are referred to.