Patent GB-979290-A (GB)
Title: Apparatus for compensating the deflection of a sliding spindle having a non-vertical axis
IPC: B23Q11/00
Filed: 1963-11-18
Abstract: 979,290. Bearings. SOC. GENEVOISE D'lNSTRUMENTS DE PHYSIQUE. Nov 18, 1963 [Dec. 7, 1962], No. 45499/63. Heading F2A. [Also in Division B3] A device for compensating for the deflection of an axially sliding spindle having a non- vertical axis, comprises a movable bearing, the movement of which is controlled by the overhanging length of the spindle, and by the weight of a tool at the free end of the spindle, in such a way that the axis of the tool is always on the theoretical axis of the spindle. The deflection of spindle 1, e.g. a boring spindle, Fig. 2, due to its weight Q, is fp= constant x L<SP>4</SP>, and the deflection due to the weight P of the tool, Fig. 3, is fo = constant x L<SP>3</SP>, where L equals the overhang of the spindle. The spindle has a theoretical axis X, Fig. 5, the thin line Y indicates the actual axis of the spindle whilst supported in bearings 2, 3, and line Z indicates the axis of the spindle when deflection fp +fo is compensated by moving a bearing 4 through a distance a. Spindle 1, Fig. 6, slides in fixed bearings 2, 3, and the compensating bearing 4 is movable in a direction normal to the spindle axis. A detector 5 delivers a signal ip, which is a function of the axial position of the spindle proportional to L<SP>4</SP>, and proportional to the weight of the spindle. A second detector 6 delivers a signal io<SP>1</SP> proportional to L<SP>3</SP> and to a tool of unit weight. Signal io<SP>1</SP> is multiplied at 8 by a constant, depending on the weight of tool P, and signals io, ip are added at 9, and the combined signal passes to a comparator 11. A detector 10 delivers a signal ir, which is a function of the position of bearing 4, and this signal is compared with signal ie, at 11, and an error signal i passes through an amplifier 12. The amplified signal I passes to an electric motor 13, which displaces bearing 4 so that the axis of tool 7 is located on the theoretical axis of the spindle. Spindle 1, Figs. 7-9, slides in a quill 14, rotated from a motor 19 through a belt 20 and gears 22, 23. The spindle is axially displaced by a screw and nut drive 26, 27, the screw being driven from a motor 24, through a belt 25, and the nut having a non- rotary but axially slidable connection with headstock 15 at 30, 31. The movable bearing assembly comprises a bearing 35, the outer cage of which has an outer periphery 36 which is eccentric, an intermediate ring 37, the bore of which is concentric with surface 36, and the outer periphery of which is eccentric with the bore, the ring being located in a bore 36a, concentric to the axis of bearing 35. Ring 37, and the outer cage of bearing 35, are connected by links 39 to a nut 40, the connecting points being located at the same radial distance by a bracket 41 on the outer cage. A screw 43 which co-operates with nut 40, is driven by a reversible motor 13, through a worm and wheel 44, 45, the motor being controlled by signal I, Fig. 6. Detector 5, Fig. 6, comprises a cam 46, Fig. 8, fixed on headstock 15, and a feeler 47 radially displaceable in nut 2. The rubbing contact 48 of a linear potentiometer 49, is displaced in proportion to L<SP>4</SP> by the cam, thus delivering signal Fig. 6. The rubbing contact 52 of detector 6 is displaced in proportion to L<SP>3</SP>, thus delivering signal io<SP>1</SP>. Detector 10 comprises a potentiometer 54, Fig. 7, having a rubbing contact 55, movable when screw 43 rotates. Multiplier 8 comprises a rod 57, sliding in a bore 59, Fig. 7, and urged into contact with tool 7 by a spring 60. Each tool has a bore 59, the depth of which is a function of the weight of the tool, so that the position of rod 57 determines the position of the rubbing contact 65 of a non-linear potentiometer 64 and signal io<SP>1</SP>, Fig. 6, is multiplied by a coefficient corresponding to the weight of the tool to produce a signal io. Detectors 5, 6 may be of optical, pneumatic, or mechanical types, supplying signals to a computer. Multiplier 8 may be constituted by a transformer, transducer, or magnetic amplifier, the windings of which could be fed by a current depending on the tool, or alternatively by a Hall generator.