Patent GB-713354-A (GB)
Title: Improvements in or relating to mechanically operated presses
IPC: F16P3/04
Filed: 1951-11-27
Abstract: 713,354. Machinery guards. SPIERTZ SOC. ANON. Nov. 27, 1951 [July 30, 1951],No.27755/51. Class 80 (4) [Also in Group V] A tiltable or other mechanicallyoperated crankshaft, eccentric or toggle press having electro-pneumatic means interconnecting a clutch-brake mechanism and a front guard is operated by a pedal switch 21 according to the settling of a manual switch 34 having four positions- (O) "Off", (1) "Adjustment", (2) "Step-by-step" and (3) "Continu. ous." The press comprises a crankshaft linked to a ram having W- shaped guides, and the front guard consists off interlinked shutters 11, 12 respectively pivoted to, and slidable in, a frame 13 which it self is pivoted to the press frame 1. In addition side shutters, Fig. 1 (not shown), are hinged respectively to the frame 13 and the frame 1. The shutters 11, 12 are gently closed, against a spring or gravity, by a ,piston 20 supplied with compressed air from a reservoir 23 through a pressure reducer 24 and a valve 25. The brake is released and the clutch engaged by pneumatic means connected to the reservoir 23 through a valve 26 which, except when the switch 34 is in position (1), is only opened when the shutter 12 has closed and operated a contact 22. When this has happened the bake and clutch are operated and at the same time air ds admitted at full pressure through the valve 26, pipes 31. 28 and a by-pass to hold the shutters closed whether or not the valve 25 remains open. The valves 25, 2G are operated, respectively by relays 25<SP>1</SP>, ER (Fig. 4). A switch 35 is held closed by the air of the system so that the press ms only operative if the air is at the required pressure. In the drawing the three arms of switch 34 are in the "Off" position. When it is required to adjust the press parts the switch 34 is turned to position (1) and the frame 13, together with the shutters, is swung down thereby rendering the guard inoperative and opening the contact 22. Then referring to Fig 4, on depression of the pedal 21 current passes through the switch 34 and through the normally-closed contact N2 of a relay N to energize the relay ER, which thereupon opens the valve 26 and starts the press. As the press reaches ,the top of its stroke a double-contact cam-operated switch 33 is closed; the upper contacts maintain the relay ER energized, while the lower contacts energize the relay N which closes a hold-on contact N1 and opens the contact N2. As the cam continues to rotate the switch 33 is opened again, thereby de-energizing the relay ER and stopping the press, since the relay N still holds the contact N2 open. The next cycle can be introduced only by temporarily releasing the pedal 21 so that the contacts N1, N2 resume their normal position. For "Step-by-step" press operation, with the switch 34 in position (2), the frame 13 is raised to the guard-operative position. On depression of the pedal 21, the relay 25<SP>1</SP> closes the valve 25, the piston 20 closes the shutters 11, 12. the contact 2,2 is. closed and energizes the relay ER and the press is started. At the top of the stroke the switch 33 is closed and opened as above and the press is stopped. The pedal 21 must be temporarily released before the press will start again. For continuous press operation with the switch 34 in position (3) and the frame 13 raised, depression of the pedal 21 closes.the guard and starts the press as under (2) above. Whether or not the pedal is then released the press will operate continuously, since the relay N does not become energized when the switch 33 closes. Depression of a "Stop" button 36, however, closes contacts S1 and S2 so that when next the switch 33 closes, the relay N is energized and as the switch opens again the press is stopped. The press will also be stopped should an attempt be made to open the shutters 11. 12, since this will open the contact 22.