Patent GB-1477618-A (GB)
Title: Apparatus for converting continuous rotary motion into angular oscillatory motion
IPC: D05B27/02
Filed: 1975-12-01
Abstract: 1477618 Sewing machine W SHIMO'- KAWA 1 Dec 1975 [29 Nov 1974 21 Oct 1975] 49199/75 Heading D1G [Also in Division F2]  Rotation of a driving shaft 4 of a zig-zag sewing machine, is converted to oscillation of a driven shaft 2 (for operating a cloth feeding mechanism 35, and/or a needle rod or bobbin carrying shuttle (not shown) of the sewing machine) by a pair of parallel non-extensible flexible and/or articulated links 3 the ends of which are connected at one end to a stationary frame member 50a or 50 and at the other end to the driven shaft 2, the links 3 forming a loop the inner sides of which respectively engage the opposing sides of an axially variable contour cam 5 (Fig. 4) rotatably fast with but axially slidably arranged on the driving shaft 4, the arrangement being such that as the driving shaft 4 rotates, the cam 5 deflects first one side (Fig. 3a) and then the other side (Fig. 3c) of the flexible link loop 3 whereby continuous rotation of the cam 5 oscillates the driven shaft 2 about its axis. The cam 5 may have its transverse crosssection varying along its axial length (Fig. 4) from a circular cross-section at the centre point 51 to a varying radiused triangular form at 52, 53 each side of the central i.e. mid point 51, the triangular shape at any section 52L, 53L to the left of the mid point 51 being a mirror image but 180‹ out of phase with the corresponding section 52R, 53R to the right of the mid point 51. In this manner, when the rotating cam 5 engages the flexible link loop 3 at its mid point 51 the driven shaft 2 will remain stationary. As the cam 5 is axially moved by a selector 1, 7, via a manual knob 33 (Fig. 5) in one or other direction the driven shaft 2 is oscillated about its axis, the amplitude and phase of oscillation being dependent on the extent, and direction i.e. left or right, of movement of the cam 5 from its mid point 51. The radii of the corners at each triangular cross-section are generated from the axis of the driven shaft 2 to provide a dwell at the ends of each oscillating movement of the driven shaft 2. The flexible links 3 may be formed from a single continuous flexible elongate non-extensible member with both ends secured to the stationary member 50 and the central portion encircling the driven shaft 2, and secured thereto, to form the cam engaging loop (Figs. 1 and 3). Alternately, each of the links 3 may comprise a single continuous flexible cord or cable (Fig. 2) connected at one end to the stationary member 50 and at the other end to the opposite ends of a link 9 secured to the driven shaft 2. The flexible cord or cable links 3 may, in the cam 5 engaging regions, have a wear protective and replaceable wire coil sleeve (8) (Fig. 6 not shown) or a solid intermediate cam engaging link (13, 14) (Figs 7 and 8 not shown) whilst in Figs. 9 and 10 (not shown) the flexible links 3 are formed from articulated rigid links (17). Alternatively the flexible links 3 may be arranged as a cord or chain which passes around a pulley or sprocket on the driven shaft 2. As shown in Fig. 5 the oscillatory movement of the driven shaft 2 is transmitted to the cloth feeding mechanism 35 by a belt 31 and shaft 30 which oscillates to horizontally reciprocate the cloth feeding mechanism 35 by arms 29 on the shaft 30, the cloth feeding mechanism 35 being also simultaneously vertically reciprocated from the driving shaft 4 by a connecting rod 42 and cranked rods 41, 40 and 45, 37, 36, 34, whereby the teeth 35 are moved in a parallelogram motion such that the teeth 35 are moved forwardly in a horizontal direction whilst they are raised, lowered and then moved backwardly whereby the repeated cycle of motion forwardly feeds the cloth. Adjustment of the amplitude of oscillation of the driven shaft 2 effects corresponding adjustment of rate of feed, whilst reversal of the phase effects reversal of the direction of feed of the cloth.