Patent GB-662095-A (GB)
Title: Improvements relating to devices for indicating the maximum value of a variable force
IPC: G01L7/06
Filed: 1949-06-01
Abstract: 662,095. Pressure gauges; measuring forces; accelerometers; indicating-apparatus. SULZER FRERES SOC. ANON. June 1, 1949 [Oct. 28, 1948; March 16, 1949], Nos. 14667/49 and 14668/49. Classes 106 (ii), 106 (iii) and 106 (iv). A device for indicating the maximum value of a force, in which the force is measured by' the deflection of a spring, has a member moved in accordance with the deflection of the spring, which member is rotatable relatively to an indicating element, the latter being urged by an auxiliary force in the sense of an increase in indication but being normally locked by screw-thread means which release the element when the said member moves beyond its previous position of maximum displacement. A fluid pressure or force, of which the maximum value is to be indicated, is applied to a piston 4, Fig. 1, slidable in a cylinder 3 and restrained against rotation by pins 6. The force on the piston is balanced by a spring 12 and the movement of the piston is indicated by a pointer 9 in a nut 8 on a threaded extension 5 of the piston. The nut is urged to rotate to increase the indication of the pointer by a pretensioned spring 14 but frictional forces in the screw-thread and between the nut and the spring housing 11 normally hold the pointer stationary. When, however, the previous maximum is exceeded, the piston is moved further upwardly, the frictional forces are decreased, and the spring rotates the pointer to indicate the new maximum. The pointer and piston may be restored by rotating a knob 18 or nut 17. In a modification, Fig. 7 (not shown), for indicating the maximum value of an acceleration or deceleration according to the direction in which the instrument is arranged, the extension 5 is fast to a mass slidable, but not rotatable, upon ball bearings in a cylindrical casing. In a further modification, Fig. 6 (not shown), the extension 5 is on the end of a bellows mounted in a casing open to the atmosphere so that the minimum ambient pressure is indicated. To indicate the maximim ambient pressure, the bellows 23, Fig. 4, which may be evacuated or contain a fluid, is closed by a threaded member 28 held against rotation by a pin 29 and slidable on a spigot 39 fast to the base 26 of the casing. The member 28 is urged upwardly by a spring 25 and is engaged by a nut 31 carrying the pointer 34 and a re-setting nut 33a. The nut 31 is normally held against rotation by the friction between a conical surface thereon and a stationary conical seating 38 but when the bellows contracts beyond its previous maximum contraction, a spring 37 is able to rotate the nut. The indication may be damped by lubricating the conical surfaces through passages 42, by grooving these surfaces and, when the bellows contains a fluid, by forming the spigot 39 with a groove 41. In a different embodiment, Fig. 9, the force or pressure is applied to a piston 66 in which a pin 71, fast to a threaded rod 69, is rotatable. The balancing spring 72 has its ends secured in the casing and in a flange of the rod 69 respectively and so tends to rotate the rod which carries a scale 77 and resetting nut 81. A nut 74, on the rod 69 and non-rotatably housed in the casing, normally locks the rod against rotation but frees it, as before, when a previous maximum is exceeded. The apparatus may be used to determine a periodically repeating maximum, e.g. the maximum pressure in the piston of an internal combustion engine, and in this case, to prevent overthrow of the indicator, the indicator is allowed slowly to approach the maximum, the movement of the nut 74 being limited by an adjustable stop 79, locked in its adjusted position by a screw 82.