Patent GB-742825-A (GB)
Title: Improvements in scanning type recording meters
IPC: G01D9/28
Filed: 1953-10-21
Abstract: 742,825. Automate control systems. BENDIX AVIATION CORPORATION. Oct. 21, 1953 [Nov. 3,1952], No. 29086/53. Class 38 (4). [Also in Groups XXXVIII and XL (b)] In a device for recording the angular position of a master element such as the shaft of a thermocouple driven D.C. meter a stylus is moved regularly and repeatedly at right angles to the path of a continuously driven record and caused to mark the record when the position of the master element is located by a pick-up rotatable coaxially with the master element. As shown, the pointer 12 the position of which is to be recorded on a continuously driven record sheet 28 is positioned by the output of a thermocouple 50, the output of which may be backed off by means of voltages tapped from a potentiometer 65 thereby altering the range of the instrument. The stylus 16 progresses regularly and repeatedly across the record driven by a shaft 20 and is of known form as described in U.S.A. Specification 2,593,068. Also driven by a shaft 20 is a scanning device comprising a mirror 35 which rotates in a circle about a second mirror 36 carried on the instrument shaft. When these two mirrors are in a correct relative position light from a source 37 is reflected to mirror 36 back to mirror 35, again to mirror 36 and finally to photo-cell 38. When this occurs photo-cell 38 triggers a gas-discharge tube 45 which sends a pulse to the stylus to mark the record sheet. If the output of the thermocouple is such as to drive pointer 12 past the end of the meter range the pulse from photo-cell 38 is delivered after stylus 16 has left the recording sheet. At this instant a contact 76 is connected by a rotating switch, also on shaft 20 to one of amplifiers 80 or 84 according as the instrument is at the bottom of the top end of its scale. The contact 76 also receives the photo-cell output pulse and steps by means of solenoids 70 or 86 and associated ratchet and pawl mechanism a shaft 64. This shaft drives rotating switches 57 and 90 which back off the thermocouple voltage with a preset voltage from potentiometer 65 and energize one of a number of auxiliary styli to mark the edge of the record sheet and indicate the range being recorded. To take account of the fact that the reflected angle of the beam from mirror 36 in the scanning devices is twice that of the mirror the switches on shaft 20 may be arranged instead on an auxiliary shaft geared with appropriate ratio to shaft 20 (Fig. 4, not shown). Automatic control of furnace temperature is provided by means of a further switch 100 operated by shaft 20 in synchronism with the scanning mechanism and receiving the amplified output pulse from cell 38. This switch has a conductive segment which is between but not bridging contacts 103, 104 when a pulseis produced by the scanner provided temperature is within appropriate limits. Otherwise the pulse is fed through one of contacts 103, 104 (which may be angularly preset) to energize either a solenoid 108 to close contacts 108a, 108b and increase furnace temperature or to allow these contacts to separate by energizing solenoid 106. The temperature range in which control is to be exercised may be set by means of a switch 110 which ensures that the earth circuit of coils 106, 108 is not complete unless shaft 64 has been stepped to the appropriate temperature range. Specifications 666,263 and 675,867, [both in Group XXXVIII], are referred to.