Patent GB-778002-A (GB)
Title: Improvements in or relating to pressure responsive apparatus
IPC: G05D23/275
Filed: 1955-04-22
Abstract: 778,002. Measuring pressure. GIANNINI & CO., Inc., G. M. April 22, 1955 [April 22, 1954] No. 11768/55. Class 40 (1). [Also in Group XXXVII] In a system in which two fluid pressure-responsive transducers respond respectively, e.g. to static and stagnation pressure, a switch actuated mechanically by the transducers at a given difference between the pressures modifies the response of the circuits to the transducer outputs. In Fig. 1 capsule 44 is evacuated and capsule 40 and housing 30 are supplied with fluid at stagnation or total (Pt) and static (Ps) pressures respectively; capsule 40 operates through flexure pivoted lever 60 (see Figs. 3 and 7) to move brush 116 along potentiometer winding 110 whereby the latter has an output proportional to Pt-Ps; capsule 44 operates through flexure pivoted lever 80 to move brushes 134, 144 (see Fig. 2) along potentiometer windings 130, 140, whereby each of the latter has an output proportional to Ps altitude. Circuiting and switch operation.-An output voltage representing altitude is taken from one Ps variable potentiometer 140/ 144 (see Fig. 3) the potentiometer windings 110, 130 with brushes 116, 134 operate as Ps altitude and Pt-Ps variable resistors respectively, Fig. 5, with windings 110, 130 in series so that output (E1) across winding 110 (terminals 155, 156) is a definite function of Mach number independent of altitude. The values of fixed resistors 160, 162 in series across windings 110, 130 are so selected that the voltage (E2) across the 160, 162 and 110, 130 junctions (terminals 156, 157) is zero for a predetermined value of Mach number. If the input voltage (E) across terminals 152, 153 is D.C., the output voltage E2 changes polarity at the predetermined value of Mach number; if E is A.C. a change of phase takes place. The levers 60, 80 comprise flexible switch contacts 202, 212 (see Fig. 7) connected across terminals 156, 157 and these contacts may close at the selected Mach number at which E2 is zero so that at higher Mach numbers E2 remains zero. Constructional details.-The capsules 40, 44 mounted on frame 20 within housing 30 cooperate with respective levers 60, 80 generally triangular in shape (see Fig. 3 for lever 50) and each mounted on frame 20 by flexure pivot pairs 61, 62 (for lever 60) and 81, 82 (for lever 80). The apex of lever 60 is opposite the base of lever 80 and each is connected by a flexure pivot 70, 90 to its respective capsule 40, 44 so that axial movement of capsules 40, 44 produces angular movement of levers 60, 80 (see Fig. 7). Each flexure pivot comprises a pair of spaced blocks connected by two crossed leaf springs. The potentiometers constructed as described in Specification 765,987, [Group XXXVI], may have different or the same non- linear responses and with their brushes may be mounted by adjustable brackets whereby the ratio of amplification between capsule movement and movement of the corresponding potentiometer brush or brushes may be adjusted. Fluid at stagnation pressure is fed via conduit 56 into capsule 40 and housing 30 receives fluid under static pressure through conduit 57 so that capsule 44 vacuum-saled the exterior of both capsules 40, 44 is exposed to static pressure.