Patent GB-1491775-A (GB)
Title: Position sensing system
IPC: G01B13/14
Filed: 1975-09-05
Abstract: 1491775 Fluidic gauges: Position sensing system INTERNATIONAL BUSINESS MACHINES CORP 5 sept 1975 [23 Dec 1974] 36722/75 Headings G1M and GIN An object 11, Fig.2 having parallel flat faces 14, 15 is supported for treatment in a receiving member 10, Fig.1, and its orientation with respect to the member 10 is checked by passing compressed air into holes 23, 26, 29, 31, 33, Figs.2 and 3, and so on communicating with ducts 22, 25, 28, 30 and 32 and holes 17-21, Fig.1, in the member 10. A pneumatic signal is given according to which one of the holes 17-21 coincides with a slot 12 in the under surface 14 of the object 11, and the signal is used to light one of a number of lamps. On Fig.4 the compressed air source 35 is connected through a needle valve pressure reducer 36 to the passage 22 and opening 17 and through similar equal pressure reducers 38, 40, 42 to the passage 25 and hole 19, whilst further passages 28, 30 are connected to holes 18 and 20 respectively. The pressure source 35 is also connected by reducers 47, 53 to proportioned amplifiers 44, 50 which have the pressures in the output lines 48, 49; 54, 55 respectively dependent on the pressures in their input lines. The output line 48 of the amplifier 44 is connected to a fluidic Schmitt trigger 60 having a reduced reference pressure 61 less than the value of a reduced supply pressure 62 but greater than the pressure in the line 48 unless the pressure in 48 is increased because of a decrease in the input line 46 relative to that of the input line 45. This decrease in the line 46 happens when the slot 12 is positioned over the passage 25 and hole 19 so that less resistance is offered to the flow through 19 than through passage 22 and hole 17. When the reference pressure from 61 is greater than the pressure in the input line 48 the pressure flows from 48 to atmosphere through line 63. If the pressure in 48 exceeds the reference pressure however, then the trigger 60 connects line 48 to line 64 and lights a lamp 65 to indicate that the slot 12 is disposed over hole 19 and passage 25. Another trigger 66 functions in the same way as the trigger 60 and operates when the slot 12 is over the hole 17 and passage 22 to supply pressure to a line 68 and a lamp 69. The other amplifier 50 operates triggers and indicator lamps when the slot is over one of the holes 20, 18. The hole 21 and its passage 32 are connected with a back pressure switch 80 which closes and operates a lamp 83 when the object 11 is in position in the member 10. An AND gate 85 and a NOR gate 87 are connected as shown as that if the object 11 is in position but does not have the surface 14, Fig.2, disposed next to the surface 16 then the indicators 83 and 91 are energized, the indicator 83 being energized anyway to show that the object 11 is in the member 10. In Fig.5 a Piezo-electric transducer 106 is connected as shown into a bridge type circuit with the pressure reducers 102, 104 forming one pair of legs, whilst opening 96 and its passage 99 and opening 97 and its passage 100 form the other legs. As long as the pressures in lines 107, 108 are the same a constant signal is produced, but when slot 12 is positioned over 96 or 97 then the signal decreases or increases respectively and is passed to amplifier 109.