Patent GB-711581-A (GB)
Title: Improvements relating to integrating apparatus
IPC: G01D1/04
Filed: 1952-05-29
Abstract: 711,581. Integrating-apparatus. WALLACE & TIERNAN CO., Inc. May 29, 1952 [June 8, 1951], No. 13716/52. Class 106 (4). [Also in Group XXIX] Apparatus for integrating the value of a physical quantity represented by a force or pressure, in which a rotor driven under the control of a member responsive to the force or pressure and to the opposing effect of a force dependent on the speed of the rotor, with the result that the speed is caused to vary with the quantity and the total number of revolutions in a given time provides a measure of the required integral. In the embodiment described the quantity to be integrated is represented by the pressure of a fluid which is communicated to a cylinder 8, Fig. 1, to act on a piston 10 which positions, through linkwork, an arm 11 which swings a jet nozzle 12 about a pivot 13 toward and away from the bladed edge of a turbine wheel 14. Rotating with the wheel 14 is a disc 15 of copper exerting a magnetic drag on a magnet 16 carried by an arm 17 mounted to move with the arm 11 about a pivot 18. An increase in pressure swings the nozzle 12 nearer the wheel 14 and the consequent increase in speed increases the magnetic drag which tends to swing the nozzle 12 away from the wheel 14, a state of balance being reached when the speed is proportional to the pressure. Means such as a counter 20 driven by the wheel 14 is provided to count the revolutions of the wheel 14 and thus give the required integral. To avoid a long path of swing for the nozzle 12 as the pressure falls toward zero a positive cut-off is provided in the form of a deflection plate 19 below which the nozzle swings to a position representative of zero pressure and where the drive to the wheel 14 is interrupted. The cylinder 8 is secured to a back plate 21, the piston 10, Fig. 4, has external circumferential grooves 22 and inside a swivel element 23 supports a vertical rod 25, pointed at the top 24 to engage a conical seat in the element 23 and at its lower end pivoted to a lever 26, Fig. 1, which is pivoted at 27 to a fixed arm 28. The other end of lever 26 is pivotally connected to the arms 11, 17 through a rod 30 pivoted at the top 31 of the lever 26 and at the bottom to a transverse portion 33 of a U-shaped bi-metallic strip 32, Fig. 3, which extends upwards, with the rod 30 moving between its limbs, to be pivoted near the pivot 31 to a bracket 35 secured to the arm 17. The wheel 14 is preferably mounted on a shaft 38 seated in anti-friction bearings 39, Fig. 3, and the wheel is preferably of light weight construction to minimize inertia. The magnet 16 preferably comprises a pair of permanent magnets 16a, 15b on opposite sides of the disc 15 bridged by a supporting element 41 and for the small displacements of the arm 17 involved the drag force is substantially independent of the position of the magnet. A portion of the element 41 engages fixed stops outside the normal range of movement to prevent damage to the lever assembly. The jet nozzle 12 is mounted in a bracket 49 pivoted on the axis 13 in a support 50 carried by a plate 46 adjustably secured by screws to the back plate 21. Flexible tubing joins the nozzle tube 12 and air inlet 52 and a depending foot 54 rests on the arm 11, the weight of the nozzle 12 and bracket 49 being sufficient to maintain the contact, though a spring may be provided in some cases. The point of contact of the foot 54 and arm 11 is preferably in line with the pivot points 13, 18 to avoid lateral displacement and consequent friction. If it is desired to reach a predetermined minimum pressure above atmospheric in the cylinder 8 before the apparatus is responsive to actuate the wheel 14, a coil spring 56 may be attached to the lever 26 and to a rod 57 adjustable in a collar 58 and locked by a set screw 60. To achieve a static balance about the pivot 18 a coarse adjustment is provided by a screw 65 in the base of arm 17 which bears against a spring-loaded arm 64 fixed in a block 62 in which the bi-metal 32 is also fixed and which block 62 is pivoted at the point 63 to the bracket 35. Fine adjustment for attaining static balance when running at a low pressure is obtained by shifting weights 68, 69 on a beam 67 projecting from the arm 17. To counteract the torque due to gravity set up when the lever assembly pivots a light spring 70 is tensioned between the top of the arm 17 and a fixed support 71. Preferably the centre of gravity is vertically above the pivot 18 when the jet nozzle 12 just reaches the point of cut-off. Since an increase of temperature decreases the magnetic drag, the bi-metal 32 is arranged to move the pivot 33 nearer the pivot 18 thus reducing the effective lever arm and maintaining constant the relation between pressure and speed. However, this compensating movement upsets the static balance which is connected by a second bi-metal 74 fixed to the arm 17 and carrying weights 75 which it is arranged to move toward the strip 32 upon an increase of temperature. A spirit level 77 may be provided. The counter 20 for counting the number of revolutions of the shaft 38 of the wheel 14 is mounted on a plate 80 spaced apart from the plate 21 and movement is transmitted through gearing 81 to a shaft 82 and through bevel gearing 83 to a shaft 84 thence to the counter shaft 78 by a pair of gears 85, 86. To facilitate calibration the counter 20 may be adjustably mounted by means of slots 88 in order to accommodate different sets of gears 85, 86 in different gear ratios. Special regulation of the air flow to the nozzle 12 is unnecessary since, e.g. a decrease tending to reduce the speed of the wheel 14 would tend to reduce the magnetic drag and move the nozzle 12 nearer to the wheel to increase its speed and a balance would be maintained with the same relation between speed and pressure.