Patent GB-593746-A (GB)
Title: Improvement in automatic duplicating milling-machines
IPC: B23Q35/12
Filed: 1944-08-08
Abstract: 593,746. Copying by milling. NILES-BEMENT-POND CO. Aug. 8, 1944, No. 15065. Convention date, Jan. 28. [Class 83 (iii)] [Also in Group XXXVIII] In a milling-machine wherein a tool or work slide is movable along two perpendicular axes by means of four electromagnetic clutches under control of an electric tracer engaging a pattern, relays for operating the clutches are actuated by tracer-controlled contacts and also by an automatic relay to cause resultant movement of the slide in a NE, SE, SW or NW direction, and an arm which is rotated by movement of the tracer around the pattern operates switches to select the relays required in order to steer the tracer completely round the pattern. The tracer 10, which is similar to that described in Specification 233,747, [Class 83 (iii)], is mounted for universal movement in a sleeve 11 rigidly supported in a head 12 and carries a button 13 engageable with the laminer pattern 14. The head 12 is carried by a slide which also carries the cutter and is moved in perpendicular directions by screws operated respectively by reversely running electromagnetic clutches S, N and E, W, Fig. 5. A plate 15 rotatable on the head 12 carries a gear 16 meshing with a gear 20 mounted on a spindle 21 rotatable on the head. An arm 17 projects radially from the plate 15 and has a slot 18 engaging a pin 19 attached to the pattern near the centre thereof, so that as the head moves round the pattern the gear 20 and shaft 21 will be rotated. An arm 22 on the shaft is thus caused to rotate and engage in succession with switches C1-C4 and 23-26 adjustably mounted on the head. The rear conical end of the tracer engages a depression in a lever 29 carrying contacts 32 cooperating with contacts 33, 34 on a slide 35 normally pressed by a spring to cause contacts 32, 33 to engage. In operation with the tracer 13 to the NW of the pattern as shown in Fig. 6, a push-button 1, Fig. 5, is momentarily depressed to energize a relay 50 from an earthed generator 57. This closes the contacts IS ; IN ; IE and IX against contacts Ic. ; Id ; Ie and If, whereof contacts Ix, If close a holding circuit for the relay. Contact IS establishes a circuit to relay RS to energize clutch S and cause a " South " feed of the tracer &c., this circuit passing through tracer contacts 32, 33 which are maintained closed by a spring 31 acting on lever 29. Contacts IN, IE would close circuits to relays RN, RE for actuating the " North " and " East " clutches N and E, but the circuits are broken by the separated contacts 32, 34 and by a solenoid TS respectively, the latter being energized by contacts 32, 33 and acting to open the switch 91. The " South " feed continues until the tracer engages the pattern, whereupon it rocks lever 29 to separate contacts 32, 33, thus de-energizing clutch S and solenoid TS. Switch 91 may then close under spring pressure to complete the circuit to relay RE and start the " East " feed which increases pressure of the pattern on the tracer and rocks lever 29 further until contacts 32, 34 are closed. This completes the circuit to relay RN, energizing clutch N for a " North " feed and simultaneously energizes relay TS to actuate switch 91 and cut out the " East " feed, until pressure on the tracer is relieved sufficiently to allow contacts 32, 34 to open and restore East " feed instead of " North." The " East and " North " feeds will alternate to carry the tracer round the pattern and when this resultant NE feed becomes tangential to the pattern the arm 22 will have been rotated into a position to engage switch C1 the closing of whose contacts c, d will complete a circuit to energize a magnet 39 and to energize a solenoid CS2 which closes holding circuits for' magnet 39 and for itself. Contacts a, b, c of switch C1 close an additional holding circuit for relay R1. Magnet 39 draws slide 35 to the left against an adjustable stop 38 so that lever 29 will, in its neutral position, maintain contacts 32 out of engagement with contacts 33, 34 instead of in engagement with contact 33, and the N and E feeds will continue to alternate due to intermittent engagement of contacts 32, 34, the holding circuit for relay R1 now being maintained by switch C1. When the tracer reaches the northern extremity of the pattern, arm 22 will be in position to close switch 24 which energizes a solenoid CS1. This solenoid opens switch 108 to out out solenoid CS2 and thus de-energize magnet 39 so that a spring may return slide 35 to its former position against an adjustable stop 36, and close contacts 32, 33. The circuit to relay RS is thereby reestablished and the circuit to relay RE is broken by energization of relay TS so that a " South " feed takes place until contacts 32, 33 are opened by pressure on the tracer. This de-energizes relays RS and TS, allowing switch 91 to close and energize relay RE for an " East " feed. " North " and " East " feeds will then alternate due to intermittent closing of con.- tacts 32, 33 until the " NE " feed becomes tangential to the pattern, at which point arm 22 closes the contacts of switch C2, which energizes magnet 39 to move slide 35 to the left, energizes relay R5 to cut out relay R1, and completes the circuit to energize relay R2. Relay R5 is again de-energized by relay R6 which establishes a holding circuit for relay R2 and the latter operates to connect relays RW and RE to contacts 33, 34 and relay RS to switch 91. " South " and " East " feeds will then alternate due to opening and closing of contacts 32, 34 until the resultant path is again tangential to the pattern and arm 22 closes switch 25 to restore slide 35 to the right-hand position in which case " South " and " West " feeds alternate due to opening and closing of contacts 32, 33. In a similar manner the switches C3, C4, 26, 23 are successively closed by arm 22 to alter the clutch relays RE, RS, RW, RN which are controlled by contacts 33, 34 and relay TS so that the tracer will be caused to circumscribe the pattern. If the pattern has re-entrant curves, further switches 23, C1 must be spaced on the head 12 to co-operate with the arm 22 and change the clutch relay circuits controlled by the tracer contacts in accordance with the change in direction of the pattern, curve. Push-button switches 2, 3 or 4 are used in starting the machine to cause the tracer to approach the pattern-from a NE, SE or SW position respectively.