Patent GB-678918-A (GB)
Title: Improvements in tool-holding capstans for machine-tools
IPC: B23Q16/10
Filed: 1948-10-22
Abstract: 678,918. Machine tool details. CAYERE, P. E. A., and PICAND, R. Oct. 22, 1948 [Oct. 22, 1947; July 30, 1948; Sept. 6, 1948], No. 27577/48. Class 83 (iii). A tool turret is supported on its carriage in any selected one of a number of positions by means which are disposed between the turret and carriage and have respectively a one-point contact, a two-point contact, and a three-point contact with surfaces on the turret or carriage, the six points being so disposed that, when the turret and carriage are held against movement bodily one away from the other, the turret is maintained against all other movement out of the selected working position. As shown in Figs. 1 and 2, three balls B1 ... B3 are mounted on the carriage C and the underside of the turret T has (a) four sockets P, Pa, Pb, Pc, fir co-operation with the ball B1 and each having line contact with the ball so as to provide at least three points of contact therewith; (b) four grooves Q, Qa, Qb, Qc for co-operation with the ball B2 and providing two contact points, and (c) plane surfaces p, pa, pb, pc, each providing a single point with the ball B3. The sockets may be conical or pyramidal, and both these and the grooves may have curved sides. If desired,. the balls may be replaced by the part-spherical head U of a bolt as shown in Fig. 10, co-operating with the plane underface of the turret, or it may be of ovoid shape as shown at M, Fig. 11. In another form, the balls may be replaced by members provided with three curved bosses d, Fig. 13, or having the rounded form shown in Fig. 14. The undersurface of the turret may be formed in the shape of a surface of revolution. An alternative form of the supports consists of a number of sockets P, Figs. 16 and 17, uniformly arranged on the underside of the turret, and fingers Bal, Ba2, Ba3 on the carriage. In each working position, the finger Bal engages a socket P so as to provide a three-point contact, the finger Ba2, which is cut away as shown at Fig. 16, engages another socket with a two-point contact, and the third finger Ba3 engages a plane surface between two sockets P. The finger Ba1 may have three flat parts machined on it to provide three points of contact with the sockets. In a modification, the projections or fingers may be provided on the turret, and the co-operating holes on the carriage. In the construction shown in Fig. 4, the nut E for locking the turret is operated by a handle L which, to tighten the nut, acts solely through fibre washers R1 and a spring washer R2 and, to unscrew it, acts through a one-way clutch or ratchet disposed between the nut and handle. The turret, which may have a spring 4, Fig. 2, between it and the carriage, may be set in each of its working positions by two spring- pressed plungers mounted in the turret shaft A for engaging grooves in the turret; alternatively, the plungers may be mounted on the turret and the grooves in the shaft, or one or more plungers may be mounted on either the top surface of the carriage or under face of the turret for engaging grooves in the other surface. Dust is excluded from the bearing parts by a depending flange Ta, Fig. 4, on the turret enclosing the edge a of the carriage, with an intervening felt joint F, or a sheath H, Fig. 17, of leather &c., may be secured to the turret. In a modified form of locking device for the turret, Fig. 15 (not shown), the clamping nut is graduated for co-operation with corresponding marks on the top of the turret, and spring washers are inserted between the nut and turret. The Specification as open to inspection under Sect. 91, describes the use of the turret as a work support and the formation of the projecting elements and co-operating surfaces as standard elements for fitting sockets in the carriage and turret. This subject-matter does not appear in the Specification as accepted.