Patent GB-172631-A (GB)
Title: Apparatus for the measurement of speeds
IPC: G01P3/12
Filed: 1921-12-05
Abstract: 172,631. Seguin, A. Dec. 11, 1920, [Convention date]. Impulse and momentum speedindicators.-Consists in an instrument having a driving-member continuously rotated at a speed proportional to that to be measured, and a comparison-member having a fixed speed relatively to the driving-member, and released at uniform intervals of movement of the driving- member, indication of the speed being furnished by the intersection of the path of the comparison-member with a fixed curve, or by the direction of the path at a fixed point. The driving-member comprises an arm 13, Fig. 1, fast on an horizontal shaft 5 driven by the machine to which the instrument is attached through pinion-wheels 8, 9, and carrying at one end a counterpoise 14 and at the other a spring- strip 16 having a projecting stud 18 which comprises the comparison-member, and is pressed by the spring against a fixed snail-cam 20. On leaving the cam at the point 19, Fig. 5, of greatest radius the stud describes a curved path such as 39, 40, or 41, characteristic of the speed of rotation of the arm 13, until it again meets the cam at a point such as 35, 36, or 37. During this movement, the stud drives the upper advanced part of a pointer 23 attached to a pulley 25, both freely mounted on the shaft 5 normally driven slowly at a speed proportional to that of the machine 'out in the opposite direction to the arm 13 by a pulley and belt system, until it passes under a bent portion 24, the position of which at the intersection of the path of the stud with the circle 42 described by the bent portion during rotation determines the speed to be measured. If the speed is constant, the pointer 23 will swing between two determined positions, the angle between them being constant for all speeds. The indicating pointer 28, Fig. 1, is rigidly connected to a frictionally-mounted fork 26, the arms 26<a>, 26<b> of which are bent at right-angles to engage with the pointer 23, the .angle of the arms being made equal to the angle between the end positions of the pointer, so that the indicating pointer is stationary for a constant speed. For high speeds, a centrifugal force compensator may be applied to the spring strip. The Specification describes modifications in which, for the spring strip, a balance-wheel is substituted provided with a spiral spring, and having an arm carrying the stud 18, the whole being mounted on the arm 13, and in which other means effect the back movement of the pointer 23, namely, (1) a gearing system, (2) an independent spring, and (3) the action of the stud against teeth on a wheel carrying or geared with the pointer before it strikes the pointer itself. The pointer 23 may alternatively have movement of translation along a straight rod. Optical indication may be employed by a coloured disc or lamp on the stud 18 passing a slot in the side frame. Fig. 16 shows a method of indication by the direction of the path of the stud, in which, on leaving the cam, the stud engages in a path 75 formed by the upturned edges 76, 77 of a disc 78 connected by a shaft 79 pivoted in the side plate 2 to the indicating pointer, which is thus set in a direction tangential to the path.