Patent GB-1022067-A (GB)
Title: Automatically controlled sewing unit for making seams according to predetermined patterns
IPC: D05B39/00
Filed: 1963-07-05
Abstract: 1,022,067. Sewing machines. NECCHI S.p.A. July 5, 1963 [July 25,1962], No. 26674/63. Heading D1G. A sewing machine is driven via an electromagnetic clutch, the output shaft of which is provided with an electromagnetic brake, and a work holder is moved relatively to the needle by means of the co-operation of a follower or followers with a pattern-generating surface, the arrangement also being such that at the beginning of a sewing cycle the clutch is fully energised, and at the end of a sewing cycle the clutch is connected to a direct current generator driven by the sewing machine, whereby the clutch and brake co-operate to reduce the machine speed to a predetermined value controlled by said generator through a potentiometer, the clutch being subsequently de-energized and the brake being fully energized through timing means arranged in predetermined angular position relatively to a shaft of the machine. A sewing machine 1, mounted on a table 3, is driven by an electric motor A through an electromagnetic clutch B, the output shaft of which is provided with an electromagnetic brake C. A work holder 2 is rigid with a mounting 8 movable on guides 9 rigid with a mounting 10, the latter being movable on fixed guides 11. Mounting 8 carries a motor D which drives, via reduction gearing 7, a spindle 5 held against a fixed pattern surface 6 by an electromagnet E and thereby adapted to travel along surface 6 from a starting position 12 to a finishing position 12<SP>1</SP>. The main shaft of the sewing machine carries three conductively interconnected discs 69, 70, 71, a brush 72 engaging disc 69, and brushes 75, 81 engaging conductive segments 74, 80 on discs 70 and 71 respectively when the needle 4 is fully raised. The positive terminals of bridge rectifiers 36, 38 are interconnected at a terminal x via a rectifier 45. Rectifier 38 is connected to a potentiometer U, the sliding contact 50 of which is connected to the negative terminal of a D.C. generator R driven by the sewing machine. The positive terminal of generator R is connected to terminal x via a rectifier 53. Rectifier 36 is connected to clutch B, brake C, brush 72, brush 81 via normally open contacts TT, a relay coil Z, a relay coil W via normally open contacts ZW, and the field coil S of generator R. The collector and emitter of a transistor U are connected across normally open contacts HB in the circuit of clutch B. The base of transistor U is connected to the positive terminal of generator R via a rectifier 60. The circuit of brake C passes through the collector and emitter of a transistor V, the base of which is connected via a resistance 67 and rectifier 68 to the positive terminal of rectifier 38, and is also connected via normally open contacts TC to the junction of resistances 76, 78 connected in series in the circuit of brush 75. Closing a main switch 15 energizes the motor A and the rectifiers 36, 38. Relay Z is thereby energized, and, after a delay caused by a condenser 91, closes contacts ZT in the circuit of relay T, and the contacts ZW, a contact ZZ also shifting to short circuit condenser 91. Relay T is then energized, if the needle is raised, to close its latching contacts TT and the contacts TC, and to open a contact TB in the circuit of clutch B. Relay W is also energized to open contacts WC in the circuit of brake C, after a delay caused by a condenser 94, and also to shift a contact WW for short circuiting the latter. The work holder is then moved to the starting position 12 to close a limit switch F1. A relay coil G is thereby energised to close its latching contacts GG, contacts GE for energizing electromagnet E via a bridge rectifier 31, and contacts GD in the circuit of motor D. Sewing is then initiated by operating a pressbutton P to close contacts PH. A relay H is thereby energized to open contacts HC in the circuit of brake C, contacts HS in the circuit of field winding S, and the contacts HZ thereby de-energizing first relay Z and then relay W. Relay H closes its latching contacts HH, contacts HB for energizing the clutch B, and contacts HD for energising the motor D. Spindle 5 on reaching the end 12<SP>1</SP> of surface 6 closes a limit switch F2 to energize a relay L. Contacts LG and LH are thereby opened to de-energize the relays G and H. Electromagnet E and motor D are thus de-energised, field winding S is energized, clutch B is connected in circuit via the transistor U, and brake C is connected in circuit via the transistor V. The speed of the machine then falls to a uniform low value which is determined by the selective energization and de-energization of the clutch and brake as governed by the voltages Vr and Vj developed by the generator R and potentiometer U respectively. Energization of relay Z is delayed by condenser 91 until the low uniform speed is attained, when contacts ZT close to energize relay T when the needle is raised and brush 81 engages segment 80. Contacts TB then open to de-energize clutch B, and contacts TC close to effect full energization of brake C. Energisation of relay W is delayed by condenser 94 until the machine has stopped, when contacts WC open to de-energize the brake. Emergency stopping may be effected during sewing by operating a pressbutton Q to close contacts QM. Relay M is thus energized to close its latching contacts MM via the closed contacts PM of the pressbutton P, and to close contacts ML which shunt the limit switch F2. The machine may thus be re-started by operating pressbutton P. In a modification in which the pattern surface 6 is continuous, a single limit switch is used, said switch being connected, via a double-pole switch, in the position of switch F1 when relay H is deenergised, and in the position of switch F2 when relay H is energized. It is stated that, alternatively, the pattern surface may be movable, the movements then being controlled by driving means constituted by an electromagnetic clutch connecting said surface to the motor A.