GB600435A - Automatic signalling-apparatus for street-crossings and the like - Google Patents

Abstract

600,435. Road signals for controlling traffic. NAERBO, D. Nov. 7, 1945, No. 29619. [Class 118 (ii)] A hydraulic traffic signal system comprises a padoperated piston and cylinder in communication with a second cylinder whose piston has attached to it a switch-member adapted to close circuits for a " clear " and a "stop '' signal. A hinged plate 1 (Fig. 1) fitted into the roadway is pressed in an upward direction by a spring 3. Depression of this plate by a passing vehicle forces down a piston 4, against the pressure of springs 24, to impel liquid along a pipe 6 and past a non-return valve 9 to raise a second piston 8 against the pressure of a return spring 25. On an extension rod 12 (Fig. 2) of this second piston 8 is an electrically-insulated cross-piece 13 on which are pivoted at 29, 29<SP>1</SP> two arms 14, 14<SP>1</SP>, carrying contact rollers 16, 16<SP>1</SP>, which are urged outwards by a spring 15 against fixed contact members 17, 18, 19 and 17', 18<SP>1</SP>, 19<SP>1</SP>. As the piston 8 rises, the contact rollers 16, 16<SP>1</SP> leave contacts 17, 17<SP>1</SP>, extinguishing a " clear " signal 22 and connect contacts 19, 19<SP>1</SP> to light a " stop " signal 23. When the actuating vehicle leaves the plate 1, the springs 24, 25 begin to restore the pistons 4, 8 to normal. The return of piston 8 and its contact rollers 16, 16<SP>1</SP>, however, is slowed down since the operating liquid has to byepass the non-return valve 9 by means of a small adjustable outlet 10. Thus, the " stop " signal 23 remains alight for a predetermined time. As the piston 8 and contact rollers 16, 16<SP>1</SP> continue to fall, they leave contacts 19, 19<SP>1</SP> and the " stop " circuit is momentarily broken, contacts 18, 18<SP>1</SP> momentarily re-establish it, it is again broken, and contacts 17, 17<SP>1</SP> then establish the " clear " circuit.