GB608797A - Improvements in or relating to fluid-pressure-actuated electric switches - Google Patents

Abstract

608,797. Engine stop-gear. TAYLOR, J. L., and TAYLOR, A. E. March 1, 1946, No. 6341. [Class 122 (iv)] [Also in Groups XVIII, XXVII and XXXVII] A double-throw switch for closing a circuit to sound an alarm and to give a visual signal on the failure of the cooling or lubricating system of an engine or when liquid in a tank falls below or rises above a predetermined level, is actuated by the movement of a diaphragm and piston which are normally subjected to the fluid pressure of the system. Fig. 6 shows the switch actuating means and Fig. 7 a view of the switch. An inlet 21 leads from the cooling or lubricating system &c. to the lower compartment of a chamber 18 which. is divided by a diaphragm 20. Resting on the diaphragm is a piston 24, the rod 26 of which passes loosely through a sleeve 27 which engages the dolly 38 of the switch. A washer 30 and spring 31 are placed over the lower end of the rod which is pressed downwards by an adjustable spring 28. A manually-operated trigger 51 is provided. The fluid pressure under the diaphragm 20 keeps the piston and steove 27 in the raised position, whereby one moving contact of the switch is maintained in engagement with the corresponding fixed contact and a circuit is closed which illuminates a green lamp. When the fluid pressure fails, the diaphragm and piston are lowered and the switch is closed by a permanent magnet 41 which attracts an armature 40 on the movable member of the switch. The contacts controlling the green lamp are thus opened and a second pair closed to complete a circuit through an electromagnetically operated horn and through a red lamp. Fig. 7 shows the switch which consists of a pivoted arm 37 carrying a flexible crosspiece 42 carrying a contact at each end. The contact 43 at one end is on the top surface of the cross-piece and engages a fixed contact 45 when the dolly 38 is lowered. The contact at the other end of the cross-piece is on its lower surface and engages a second fixed contact when the contacts 43, 45 are separated. The arm 37 carries an extension in the form of an iron plate 40 which is attracted and held by a permanent magnet 41 when the dolly 38 is not held in its raised position by the sleeve 27. The magnet also causes the switch to operate with a snap action when the dolly is raised. Fig. 3 shows the circuits when three switches 17 are used, of which one is inserted in the lubricating system, the other two being in fresh water and salt water cooling systems. When the three systems are in normal operation, three green lamps 13, 14, 15 are illuminated. Failure of any one system causes the corresponding green lamp to go out and a red lamp 12 to be lit, a horn 11 being sounded at the same time. A separate switch 16 is provided to disconnect the horn.