Patent GB-682608-A (GB)
Title: Improvements in or relating to pneumatic gauging apparatus
IPC: G01B13/02
Filed: 1950-02-01
Abstract: 682,608. Pneumatic gauging apparatus. ETAVEX SOC. ANON. Feb. 1, 1950 [Feb. 22, 1949], No. 2601/50. Class 106 (ii). The invention relates to pneumatic gauging apparatus for channelled parts, the apparatus being such that the gauging operation is not influenced by the presence of such channels. Compressed air is supplied to a control chamber 17 having a first branch leading to an orifice 19 at the surface of a channelled part 26 and a second branch leading to a chamber containing a diaphragm 21. The diaphragm 21 is connected on one face to a flexible electric terminal 25 and on its other face it carries a contact 22. When a projection on the channelled part 26 is opposite the orifice 19 the pressure in the control chamber 17 rises and the diaphragm 21 is deflected downwards, causing the contact 22 to engage a contact 23. This completes an electric circuit AB to the dimension gauging part of the apparatus. When a channel in the part 26 is opposite the orifice 19, the pressure in the control chamber 17 falls and the diaphragm 21 moves upwards to break the electric supply AB. The electrical supply AB is thus made available to the dimension gauging part of the apparatus, only when a projection on the part 26 is opposite the orifice 19. Around the channelled part 26 are two other orifices 8 and 9 arranged such that they are opposite projecting portions of the part 26 during the same periods that projecting portions of the part 26 are opposite the orifice 19. Air supplied to a measuring chamber 3, communicating with the orifices 8 and 9, influences a flexible diaphragm 11 such that if the dimension of the projecting portions of the part 26 is too great the pressure in the chamber 3 causes an upper signalling means 15 to be operated through contacts 12 and 13. If the part 26 is slowly reduced in diameter the flow of air from the orifices 8 and 9 increases until the contacts 12 and 13 are opened and contacts 12 and 14 are closed to operate a lower signalling means 16 indicating that the part 26 has been reduced to the desired diameter. The apparatus is calibrated by revolving a standard part 26 between the orifices 8, 9 and 19, and slowly closing an air-escape orifice 6 of an adjusting chamber above the diaphragm 11 until the signalling system 16 is operated. As the electrical supply from AB is broken every time a channel is presented to the orifice 19 and hence when channels are presented to the orifices 8 and 9, the signalling means 15 and 16 register only when projecting portions are presented to the three orifices. The signalling means 15 and 16 may be lamps. In a modified arrangement, Fig. 2, the control chamber 17 is associated with an adjusting chamber 30 having an airescape orifice 32. Those parts of the apparatus that are the same as in Fig. 1, have the previously used reference numerals. During machining, the channelled part 26 is rotated between the orifices 8, 9 and 19 by a three-phase motor M. At the commencement of the machining operation, each time a projection of the part 26 is opposite the orifice 19 the rise of pressure in the control chamber 17 causes contacts 22 and 23 to engage so that phase S of the supply is connected to the contact 12. At the same time, the rise of pressure in the measuring chamber 3, due to projections of the member 26 being also opposite the orifices 8 and 9, causes the contacts 12 and 13 to close, thus energizing a measuring winding C<SP>1</SP> connected to phase R. A contact piece 38, attracted by the measuring winding C<SP>1</SP>, bridges contacts 34 and 35, causing a lamp L to light. As the part 26 is rotated further to present a channel to the three orifices, the contacts 22 and 25 engage at the instant that the supply to the measuring winding C<SP>1</SP> is interrupted by the opening of the contacts 12 and 13. A holding winding m<SP>1</SP> is thus energized, there not being sufficient time for the contacts 34 and 35 to be opened before the winding m<SP>1</SP> is energized. The lamp L therefore continues to be illuminated. As the part 26 is reduced in diameter, a point is reached when the pressure in the measuring chamber 3 no longer rises to a value sufficient to close the contacts 12 and 13 as the part 26 rotates. The measuring winding C<SP>1</SP> is consequently no longer energized every time a projection of the part 26 is presented to the orifices 8 and 9, and as a result the contacts 34 and 35 are opened and the lamp L is extinguished, the continued closing of the contacts 22 and 25 every time a channel of the part 26 is presented to the orifice 19 having no effect on the holding winding m<SP>1</SP> since the contacts 34 and 35 are now open. The extinction of the lamp L indicates to the operator that the machining will soon be ended. When the machining has progressed so far that the pressure in the measuring chamber 3 no longer rises to a value sufficient to separate the contacts 12 and 14, a measuring winding C<SP>2</SP> is energized when the contacts 22 and 23 are closed upon the passing of a projecting portion of the part 26 past the orifice 19. When energized, the winding C<SP>2</SP> causes contacts 36 and 37 to close, the contacts 36 and 37 remaining closed, thereafter by the consequent alternate energization of the measuring winding C<SP>2</SP> and a holding winding m<SP>2</SP> as first projections and then channels of the part 26 are presented to the orifices 8, 9 and 19. The closing of the contacts 36 and 37 cause a solenoid A to be energized to break the supply to the electric motor M and stop the machining operation on the part 26. Specification 638,209 is referred to.