Patent GB-701116-A (GB)
Title: Measuring devices
IPC: G01L9/00
Filed: 1951-02-23
Abstract: 701,116. Electric indicating systems. TANDLER, W. S. Feb. 23, 1951 [Feb. 25, 1950], No. 4379/51. Class 40 (1). The distance between one or more articles and a reference plane is measured by displacing a plurality of probes mounted on a carriage towards the reference plane and the articles, and measuring electrically the carriage displacement between impingement of a probe against the reference plane and successive impingements of other probes with the respective articles. As shown, for recording the linear displacement of the end 12 of a Bourdon tube 10 relative to a reference plane member 26 two electrically insulated resilient probes 18, 19 are mounted on a carriage 20 adapted to be reciprocated periodically by a synchronous motor 73 through a screw and nut mechanism. A further carriage 66 carrying recording styluses 55, 60 is also reciprocated by a motor 81 in synchronism with the carriage 20. Cyclic operation of the apparatus is effected by a continuously driven timing motor 97 which through a cam 98 closes contacts 99, 100, periodically e.g. every three seconds to energise a relay 91. The relay 91 locks and starts both the motors 37, 81 to drive their respective carriages 20, 66 to the left. , At the same time the relay 91 by opening contacts 94, 95 de-energises the magnet 67, whereby the stylus 55, 60 carried on pivotal arms 63a, 63b, drop into contact with a conducting record strip 61. When the probe 29 engages the reference plane contact arm 26, a circuit is completed through an amplifier 50 causing current to pass through the stylus 60 and record 'a mark 127, Fig. 2, on the strip 61. Subsequently, when the probe 18 engages the portion 12 of the Bourdon tube 10 a circuit is closed through an amplifier 44 to cause the stylus 55 to record a mark 128 on the strip 61 so that the distance between the record marks 127, 128 is a measure of the displacement between the tube end 12 and the reference plane 26, and hence a measure of the pressure deviation registered by the Bourdon tube from some predetermined value. The carriages continue to move to the left stressing the resilient probes until the motor circuits are broken by limit switches 38-40, 115-116 on the carriages, when the relay 91 is de-energised, the magnet 67 is energised to raise the styluses from the record strip 61, a stepper magnet 90 is energised to advance the record strip 61 and the motors are energised to drive their carriages in the reverse direction until their circuits are broken by the right hand limit switches 39-41, initiated by the next closure of the contacts 99-100 by the timing motor. In this way a succession of records are made as shown in Fig. 2. Modifications. A plurality of pressure measurements could be recorded by means of further Bourdon tubes, and providing for each such additional tube a co-operating probe on the carriage 20 and a stylus such as 55. In such a case two reference probes 29 may be used to produce a datum line on the record strip rather than a datum point. To determine differential pressures two separate groups of styluses driven with their carriages in opposite directions relative to the record strip may be provided. Instead of recording dots, the recorder may draw a line of length proportional to the pressure variation, or a counter could be operated proportionally to the pressure variation. The probes may alternatively be fixed and the Bourdon tube (s) moved towards and away therefrom. Reference has been directed by the Comptroller to Specification 662,073, [Group XIX].