GB1249799A - Improvements in and relating to machine controls - Google Patents

Abstract

1,249,799. Controlling clutches. GULF & WESTERN INDUSTRIAL PRODUCTS CO. 25 Feb., 1970 [17 April, 1969], No. 9044/70. Headings F2J and F2L. The clutch L of a reciprocating press is actuated by compressed air controlled by two solenoid-actuated valves A, B arranged so that when the valves are de-energized air flow to the clutch is prevented even if one of the valves is stuck in its open position, each valve A, B being associated with a proximity switch or, as shown a fluid pressure switch E, F in the energizing circuit of the solenoid coils 74, 76 so as to prevent starting of the press if one of the valves is stuck in its open position. As shown, the compressed air C is delivered to the clutch L through the valve A and a valve 46 positioned by compressed air delivered via valve B, both valves A and B having to be open to engage the clutch. The switches E, F have respective contacts 68, 72 and 66, 70 in the run and hold circuits, K and H, of the press. Initially, current flows in run line 78 through run button contacts 82, 84 and normally closed switches 66, 68 to the anti-repeat relay 1CR closes contacts 1CR1 in line 80. On depressing the run buttons to close contacts 86, 88, (requiring both hands of the operator), relays 2CR, 3CR are energized closing contacts 2CR-1, 3CR-1 and 2CR-2, 3CR-2 to energize the coils 74 and 76 respectively. Valves A and B open, actuating switches E and F to open contacts 66, 68 and close contacts 70, 72 in the hold circuit H. A switch RLS-1 in the hold circuit is then closed by a cam on the press crankshaft to maintain current flow there through to the coils to allow the run buttons to be released. The press is then stopped at the end of its cycle by the camoperated switch. Should either valve A or B be stuck open, one of the contacts 66 or 68 would be open to prevent initial energization of relay 1CR. The valves A and B are formed as poppet valves, Fig. 1, (not shown), the valve A being formed in an integral housing with the valve 46, and both valves E and F being actuated by the output compressed air from the valves A and B. Again, Figs. 3 and 4, (not shown), the valves A and B are arranged in series, valve 46 being omitted. The first valve A again has a fluid pressure actuated switch associated therewith, whereas the second valve B has a proximity switch (116) associated with it. When the valve is opened, a pin (118) is moved so that a mass (120) thereon passes in to the field of the switch to open it. Also, Figs. 5, 5A, (not shown), the two solenoid-actuated valves (134), (136) are connected in parallel, (or in series), and are mechanically linked to three-way valves (138), (140) which, when valves (134), (136) are open, direct compressed air to pressure sensitive switches (154), (156) in the electrical control circuit. Should either valve (134), (136) be stuck open, it breaks the electrical circuit, and compressed air passing through the open valve is exhausted through the closed valve providing an audible signal to the operator.