Patent GB-789376-A (GB)
Title: Device for the conversion of measuring values into electric impulses
IPC: G01D5/26
Filed: 1954-07-09
Abstract: 789,376. Electric control systems. AVERY, Ltd., W. & T. (Schenck Maschinenfabrik Ges., C.). July 9, 1954, No. 20094/54. Class 40 (1). [Also in Group XL (b)] The reading of a meter is converted into impulses the number of which is proportional to the pointer movement by means of a photo-cell which detects the pointer position and controls the production of the appropriate number of impulses. As shown (Fig. 1) a watt-meter pointer 1 carrying a flag 3 takes up its position when the current is applied. A time delay relay then switches on a motor 13 which drives a member 7 on which are mounted a light source 10 and photo-cell 11. A mirror 4 beneath the instrument pointer reflects light to the photocell until the member 7 is so positioned that flag 3 interrupts the light beams. The current impulse thus produced by 11 reverses the motor drive and energizes a counting circuit 19 so that as member 7 is returned to its zero position a cam 15 geared to motor 14 operates a contact 16 to produce pulses which are counted at 19a and the number of which is proportional to the pointer movement. When member 7 has reached its starting position a cam (not shown) which it carries operates a control to disconnect motor 3. If the part of the scale beyond the pointer is to be measured the photo-electric pulse may be used to energize the counter but not to reverse the drive. If the meter is of the centre zero type two members 7 may be used, one examining the positive direction of the pointer movement and one the negative. In the arrangement of Fig. 3 the pointer carries the mirror 20 which reflects light to the cell 11. In this device the photo-cell does not chase the pointer. The pointer is allowed to take up its final position; lamp 10 is then switched on and motor 13 runs to introduce resistance 21 into the meter circuit and to operate a counter 19a by cam-driven contact 19. Then the count continues until the pointer is back to zero when photo-cell 11 receives a light pulse to stop motor 13. In the arrangement of Figs. 4 and 5 (Fig. 5, not shown), a mirror 20 in the pointer reflects light from a source 22 through an apertured shield 27 to a concave mirror 25 and thence to cell 26. After the pointer has moved to its rest position the light source is switched on and motor 13 backs off the meter supply so that the meter falls back generating photo-electric impulses as it does so because of the light beam traversing the apertures in shield 27. Application of invention to dynamic polarising machine.-Inductive pick-offs 65, 66 detect, oscillations at the bearings of the rotor 61. The output of one pick-off or the other is applied through switch 81 to the moving coils of wattmeters 82, 83 while the field coils are fed respectively with one of the phases of a twophase generator 67, rotated in synchronism with the work by motor 63. Thus meters 82 and 83 indicate the horizontal and vertical components of the unbalance at selected planes. Meter 83 incorporates a photo-electric device for sensing the pointer position similar to that already described with reference to Fig. 3, the arrangement being that the cell energizes a relay 94 to drive motor 69 if the cell is not illuminated. Motor 69 rotates the housing of the phase generator until meter 83 is again at zero when the photo-cell interrupts the circuit of the motor and energizes motor 13. Meter 82 is of the type already described with reference to Fig. 1 and runs to produce pulses which are "plus" or "minus" according to the direction of pointer deviation from a centre zero and which indicate the degree of unbalance in one or the other of a pair of compensation planes depending on the position of switch 80. In order to control boring-machines 75, 76 which remove excess material in the compensation planes, a pair of brushes 70, 71 are provided, either of which may be coupled to the housing of phase generator 67 so as to be rotated with its housing by motor 69. The circuit of the appropriate drilling machine is completed when the workpiece is so rotated that the appropriate bush and conductive portion of the slip-ring are aligned.