Patent GB-143279-A (GB)
Title: Improvements in or relating to intermittent driving mechanism
IPC: F16H29/08
Filed: 1918-06-19
Abstract: 143,279. Vickers, Ltd., and Francis, C. E. June 19, 1918. Sewing-machines; needles, vibrating.-Ratchet gearing is employed to convert reciprocating strokes in one direction of a driving-member into intermittent rotary motion of a driven member in either direction, the forward and reverse movements of the driven member being similarly timed with respect to the driving strokes. The device is applicable for producing stitches of a varying lateral length and direction in a sewing-machine for embroidery &c. The character of the stitch is controlled by a cam carried by a driven drum F, Fig. 1, which is driven intermittently by frictional gripping-devices or clutches E actuated by reciprocating movements of a rod A produced by a driving cam a<7>. A roller a<1> on the rod A engages an arc-shaped groove in a pivoted member a, which is inclined more or less to impart varying longitudinal movement to the lower end of the rod A. As shown in Fig. 1, the gearing is in the neutral position and the rod A oscillates without conveying any drive. The lower end of the rod A is pivoted to the bar a<4> connected by links a<3> to studs at the back of each clutch E, only one of which operates, the other being held stationary by a fixed seat G, Fig. 10, co-operating with the upper end of a slot f in an arm F pivoted on the axis of the drum B. The two arms F are pivoted to a bent lever f<1> having a roller f<5> running in a guide slot f<6> and operated by a hand-lever D. In the neutral position shown in Fig. 1, the roller occupies the central position of the slot and both clutches E are held against the seats G. By moving the lever in one direction or the other, one of the clutches becomes free to operate in its slot f. Each clutch has two gripping-rollers e guided by spring-pressed arms e<2> and co-operating with inclined walls e<4>. To stop the reciprocations of the rod A when the gearing is in the neutral position, a link pivoted to the lever f<1> is connected to a pivoted controlling- device H, which through a link h<2> alters the inclination of the member a.. By adjusting the link h<2> in an arc-shaped groove h<1> in the device H, the degree of tilt of the member a, and therefore the length of the driving-stroke, is varied. To prevent the rollers e of the clutch which is not operating from retarding the movement of the drum B, a pivoted spring-pressed abutment I is arranged to bear against the base of the clutch when in its lowest position and raise the rollers against the springs e<5>, a pin i on the arm F moving the abutment into the desired position. A light band-brake surrounds the drum B to prevent accidental back-lash. The hand-lever D carries a spring-pressed pin to engage recesses in a plate K in the central and two extreme positions. A partial movement of the lever D results in a partial movement of one of the slots f and therefore a limited movement of the corresponding clutch E. By this means the length of the stitch on either side of the neutral is controlled. Adjustable stops may be mounted on the plate K at equal distances from the centre when it is desired to form stitches of the same length on reversal. The speed of movement of the lever D is used to vary the pattern produced by the stitches. In a modification, the cam a<7> is provided with an eccentric strap connected to the member a, in which the upper end of the rod A is adjustably mounted. A control member such as H moves the end of the rod A towards or from the pivot of the member a and so varies the extent of the reciprocation of the lower end of the rod A. Fig. 14 shows a modification in which the gripping rollers are replaced by tilting dogs E operated by arms L against the action of springs l<1>. Back-lash is prevented by grooved dogs J held in operation by springs j<2> and released by projections i<1> on the pivoted members I, which have a similar function to those shown in Fig. 1. Instead of acting on the same driven drum B, the two clutches may drive each a separate drum, or they may be arranged horizontally so as to impart intermittent movements in both directions to a straight rod. This reciprocating movement may be reversed automatically by a stop on the driven member engaging the lever f<1>. To vary the leverage of the links driving the clutches E, the lower end of the rod A, Fig. 1, may be moved along the cross-bar a<4> under the control of the lever f<1>, stops being provided to limit the movement. As described in the Provisional Specification, the gripping-rollers are replaced by pairs of pins mounted on members with lever extensions and pivoted at points midway between the pins.