Patent GB-834257-A (GB)
Title: Position indicating device
IPC: G01G23/42
Filed: 1956-08-17
Abstract: 834,257. Electric selective signalling systems. INTERNATIONAL BUSINESS MACHINES CORPORATION. Aug. 17, 1956 [Aug. 22, 1955], No. 25280/56. Class 40 (1). In a device for producing digital electric signals representative of the position of a shaft 5, Fig. 1, by means of a fixed commutator type disc 20 and radially arranged brushes B, the pattern of conductive areas on the disc includes a so-called check pattern which by providing, or not providing, a signal to its associated brush indicates whether the shaft is in one of _1000 discrete angular ranges or whether it is on the boundary of the adjacent ranges in which position the other. brushes-the position sensing brushes-may provide indeterminate outputs by virtue of the fact that at least one of them will be on the boundary of both a conducting and a non-conducting region. If the brushes are in an indeterminate position they are given a small displacement through an angle (approximately one half that of each of the 1000 angular ranges) before notice is taken of the signals produced by the position sensing brushes. As described the indicating shaft of a weighing machine carries an arm 17, Figs. 1, 3, which houses a brush holder 65, Fig. 3, normally held clear of the fixed commutator disc 20. After an article has been placed on the weighing machine and the shaft 5 has come to rest, the shaft is locked in position by a solenoid BKM, Fig. 1, and a collar 51, Figs. 1, 3, is moved axially above the shaft, by a solenoid BDM to force the brushes into contact with the commutator disc. A test is then made, by sensing the check pattern brush, and if the brushes are in an indeterminate position a solenoid BRM is energized rotating the collar 51 slightly which by virtue of the friction between the collar and the brush holder and the free-play in the brush holder mounting, causes the brushes to be displaced slightly to a determinate position. Sensing of the position indicating brushes then follows to control for example a printing device. Sensing arrangement.-The brushes are connected together in pairs, Fig. 5, and fixed connections D0, D1 ... D9, U, OZ, H, T, TC, TP are taken from various conductive regions on the disc. A test, or check, to determine whether the disc is in an indeterminate position or not is effected by applying a voltage to terminal TC and observing whether or not it is transmitted via brushes 13 and 14 to terminal TP. Sensing of the position indicating brushes is achieved by applying a voltage, in turn, to terminals H, T, U and OZ whereupon one of-the terminals D0 to D9 will be marked when a voltage is applied to terminal H, which marking will represent the hundreds digit of the weight, one will be marked when a voltage is applied to terminal T to represent the tens digit of the weight, and so on for the other terminals, the H, T and U terminals giving the pounds component of the weight and the terminal OZ the ounces component of the weight, except that as the lowest increment recognized by the device is 2 oz., the markings on terminals D0 to D9, when a voltage is applied to terminal OZ, represent units of 2 oz.