Patent GB-766497-A (GB)
Title: Improvements in and relating to a device enabling the needles of sewing machines to be stopped in their top or bottom dead centre position
IPC: D05B69/22
Filed: 1954-12-13
Abstract: 766,497. Sewing machines. GERBAUD, A. H. Dec. 13, 1954 [Dec. 15, 1953; Nov. 3, 1954], No. 36055/54. Class 112. [Also in Groups XXXV and XXXVII] Starting and stopping: driving. An arrangement for enabling a sewing- machine to be stopped in a predetermined position comprises a pair of driving motors, integral with one another or coupled together at least at the moment of stopping, at which time one of them is reversely energized, with a clutch and brake arranged between the motors and the machine. In the embodiments described, both motors take part in the normal drive and their rotors are rigid with one another, the clutch and brake being alternatively engaged under the control of the usual lever, and a slow-speed gear drive can be connected by partial operation of this lever ; when this control lever is released to stop the machine and an auxiliary control is actuated, the connections to one of the motors are reversed, whereby the stator of this motor is moved slightly to cause engagement of the slow drive until a contact-breaker opens the circuit of this motor at the required position of the machine, provision being made for alternative positions. In a modification the motors are connected by a clutch ; the second motor may be used only to brake the first, in which case it is energized only at the moment of stopping. In the form shown, a casing 1 enclosing both motors has a central tube 3 rigid with it, a rotor structure 11 being carried on bearings on this tube and the stator 5 of one motor being fixed thereon while the stator 10 of the second motor is mounted on a sleeve 6 having limited rotation on the tube 3 ; a cooling fan 52 is fixed on the end of the rotor 11. A non-rotatable shaft 23 slidable in the tube 3 carries bearings for the sewing-machine drive pulley 29, rigid with clutch disc 32, and for an epicyclic gear planet-carrier 25, rigid with a braking disc 24; the planet-pinion 37 meshes with a pinion 26 fixed on the shaft 23 and with a pinion 30 mounted by a free-wheel 31 on an extension sleeve of the pulley 29. The shaft 23 is moved to the right, against springs, either by a control lever 47 moving balls 45 out of recesses in discs 42, 44 and thereby moving the latter to the right or by rotation of the stator 10 on the tube 3 forcing balls 39 in a fixed holder 38 out of recesses in a disc 8 and thereby moving to the right a disc 40 and, through rods 41, the assembly 42, 45, 44. The first movement of the shaft moves the clutch disc 32 out of braking engagement with the end of the casing 1 and the disc 24 out of engagement with a braking member 18 fixed on the tube 3, and moves the planetcarrier 25 into engagement with a slidable spring-pressed clutch element on the rotor 11, whereby the pulley 29 is driven slowly through the epicyclic gear; further movement of the shaft 23 to the right brings the clutch disc 32 into engagement with an extension 11a of the rotor 11, to transmit direct high-speed drive to the pulley, the free-wheel 31 then being in action. The sewing-machine shaft carries a contact-breaker with pairs of contacts in parallel opened when the needle is in its top and bottom positions respectively; the circuit also contains an inertia switch closed when the machine is nearly stopped, a switch which is closed when the clutch control lever is in the stopping position, and a switch actuated by an auxiliary control lever to connect one or other of the pairs of contact-breaker contacts. When the machine is stopped or nearly stopped and the auxiliary control lever is actuated, a relay is energized by this circuit to reverse the connections to the stator 10, which is thereby shifted angularly on the tube 3 to cause engagement of the slow drive to the machine whereby it is driven until the circuit is opened by the contact-breaker, whereupon the parts are restored to their initial position ; the action of the relay may be delayed by a dash-pot. In a modification of the slow-speed gearing, Fig. 6 (not shown), the rotor extension 11a, the braking arrangement 18, 24, and the pinion 30 are dispensed with, the pinion 26 is made free on the shaft 23 and provided with a clutch flange for engagement with the disc 32, and the planet pinion 37 is replaced by a helicoidal idler gear, on a carrier fixed on the shaft 23, meshing with the pinion 26 and with helical teeth on the interior of a drum having clutch engagement with the disc 32 and the rotor 11 : partial displacement of the shaft 23 carries the disc 32 away from the casing 1 and the drum into engagement with the rotor, the pinion 26 being in driving connection with the disc 32 for slow drive, while further movement of the shaft breaks this driving connection and brings the disc 32 into engagement with the drum for direct drive.