Patent GB-549882-A (GB)
Title: Measuring instruments
IPC: G01L19/08
Filed: 1941-06-09
Abstract: 549,882. Indicating instruments. SQUARE D CO. June 9, 1941, No. 7243. Convention date, June 8, 1940. [Classes 106 (ii) and 106 (iv)] Comprises the combination with an element movable in response to the magnitude of a physical condition, of a threaded spindle connected to be moved in proportion to the rotation of the element, said spindle having portions of different diameters, a roller, a movable member supporting said roller for rotative and axial movement, means for urging said roller against the spindle and a pair of contacts actuable by the movement of the said member. An instrument casing 10 comprises a rear part 11 and a front ring 12 secured thereto through which the indicating means are visible. To a mounting support 13 inside the casing is secured a member, illustrated as a set of barometer capsules 16, responsive to the magnitude of a physical condition under measurement, for instance atmospheric pressure. Movement of the member 16 is transmitted by link 18, arm 19, shaft 20, and segment 21 to a gear 23 and through further gears 24, 28 to a threaded spindle 29 mounted in bearings 30, 31. A hair spring 25 takes up lost motion in the mechanism. A pointer shaft 32 is secured to the spindle 29 and carries a long pointer 33 moving over a dial 34. A short pointer 35 moving over the same dial is carried by a sleeve 37 driven from the shaft 32 through a 1:10 reduction gear 40, 39, 38, 36. A cage 41 is secured to the support 13 and the whole mechanism may be rotated by a gear 43 operated by a knob 46 and pinion 48 and held by a large spring washer 44 bearing between the gear 43 and a shoulder 45 on the casing. The knob 46 on shaft 47 drives two pinions 48, 53. When the knob and pinions are in the lowest position, pinion 48 gears with wheel 43 and the pinion 53 with a gear 54 carrying a gear 55 meshing with a gear 56 carrying a dial 57 graduated in barometric units and readable through a window 58 in the dial 34 provided with a reference marker 59. By rotating the wheel 43 and instrument the latter is adjusted for barometric pressure at sea level which is read at 59. A rotatable support 61 held by ears 62 against a flange 60 of the cage carries part of the contact mechanism for setting adjustment relatively to the spindle 29. A part 64 is riveted at 65 to the support 61 and has arms 66, 67 furnished with pivoting screws 69, 70 defining an axis about which is pivoted a frame 68. A roller 71 is mounted on a thin spindle or wire 72 in the frame 68 and may turn about its axis, be displaced along it and move in a plane normal to it by reason of being pivoted about an axis displaced from the axis 69, 70 of the frame. The frame 68 is insulated by insulating studs 73, 74 bearing against contact springs 75, 76 cooperating with contact screws 77, 78. The spring 75 rests against stud 73 and urges the frame and roller towards spindle 29. When the roller is moved away from spindle 29 the frame 68 tilts and spring 75 contacts screw 77 permitting separation of contacts 76, 78. These are connected up in an electric circuit shown in Fig. 5 provided with a three pole plug 101 having prongs 102, 103, 104 connected through fuses 106, 109, capacitances 89, 90 and a reactance 91 with terminals 82, 83 for the contact springs. The spindle 29 is threaded and has two portions either of different diameters or of the same diameter but with threads of different depths with which the roller 71 engages. At the join of these two portions the spindle is provided with a cam. When the roller engages the cam, the frame 68 is swung about its pivot to break contact at 76 and make it at 75. To preset the contact device, the plate 61 is rotated to cause the roller to be rotated about the cam. This is accomplished by moving the pinion 48 into gear with a toothed gear 112 on plate 61, and turning the button 46. The setting position is indicated by reference markers 113, 114 movable relatively to the dial and interconnected to move in the same ratio as pointers 33, 35. The marker 113 is carried by an annular gear 115 meshing with pinion 53 and driving a second annular gear 116 having the marker 114 thereon through reduction gears 117, 118. The gear 115 moves with gear 112.