Patent GB-403160-A (GB)
Title: Improvements in fluid-pressure measuring devices
IPC: B60C23/00
Filed: 1932-07-18
Abstract: 403,160. Pressure gauges. HENRY, L. E. V. J., 40, Rue Trebois Levallois-Perret, Seine, France. July 18, 1932, No. 20322. [Class 106 (ii).] The pressure in an air chamber, particularly a pneumatic automobile tyre, is indicated continuously by a manometer, means being provided between the manometer and the chamber which automatically closes a valve of the latter to cut off the air supply to the manometer should a leak occur in the tubes between the chamber and manometer or between the chamber and an independent inflating valve therefor. An electric signal is given when the manometer indication reaches a predetermined minimum. The manometer comprises a rigid casing 2, Figs. 2 and 3, housing an extensible sealed chamber 4, variations in the volume of which under the pressure of air entering at 14 are imparted through a tube 5, plates 6, 8 and racks 7, 9, Fig. 3, carried by the plates 6, 8 to the pinion 11 of the indicating pointer 13. The plates 6, 8 are connected at a point diametrically opposite to the racks which are thereby sprung to take up any play in the drive to the pinion. The glass cover 19 is made air tight by a gasket 18 and the pointer spindle is provided with a conical portion 21 which forms an air tight joint with its seating should the glass cover be broken. The pinion 11 may drive the pointer 13 through a temperature compensating spiral, as the manometer normally indicates correctly only at the temperature at which it was calibrated. The manometer, the inflating valve 46, Fig. 7, and the tubes 14, 47, leading to the manometer and inner tube respectively, are carried in a casing 48 which may be secured to an automobile wheel by the usual wheel securing bolts. The tube 14 is made smaller at 14<1> to damp the air pulsations to the manometer during inflation, and the tube 47 is protected and secured, by tubular elastic pieces 49 and metal spirals 50, to casing 48 the cover of which forms a hub shield. When the manometer indication falls to a predetermined minimum the tube 5, Fig. 2, contacts with an adjustable conducting rod 24, 27 insulated at 26, 28. The circuit from terminal 25 is led through an insulated conducting ring, carried by the brake drum of the wheel, and a spring pressed brush contacting therewith and carried by any suitable fixed part of the brake, to operate a luminous or audible signal on the dash board. Alternatively, the alarm circuit may be made by the pointer 13 and an adjustable contact at the predetermined minimum pressure. The means for closing the air chamber valve when a leakage occurs in the connecting tubes comprises a casing 59, Fig. 8, housing a membrane 57 carrying a perforated piston 58 and forming a chamber 54 communicating with the atmosphere through ducts 55. A sleeve 62 is formed at 621 with a seating for a valve 60 freely mounted on a rod 61 and biassed by a spring 60<1>. The sleeve 68 is screwed on the valve stem of the inner tube or air chamber. During inflation the incoming air through tube 47, Figs. 7 and 8, depresses piston 58 which depresses the rod 61 to open the tyre valve. The valve 60 is also depressed allowing free access of air to the tyre. When inflation is completed valve 60 returns to its seat and communication between the tyre and manometer, which is also connected to tube 47 (see Fig. 7), is maintained solely by a slight leakage between valve 60 and the rod 61. Should a leak occur in tube 47 or 14 or at the manometer, the atmospheric pressure on membrane 57, 58 causes the latter to rise and release rod 61 thereby closing the tyre valve. In a modification the membrane is replaced by a piston 69, Fig. 9, connected to the valve operating rod 61 through links 70, 71 the latter being pivoted at 72. Normally with the tyre valve held open by rod 61 the elastic ring 75 abuts against cylinder 76, but should the pressure in tube 47 fall, the atmospheric pressure plus that of a spring 78 forces piston 69 to the left when the tyre valve is released. In another embodiment the casing 59, Fig. 15, is secured to the valve stem 113<1> by a nut 107, collar 106 and gasket 67. The tyre valve 113 is normally maintained open by a link plate 71, pivoted at 72 and held, abutting against a disc 97 on the end of the valve operating rod 61, by a link 70 pivoted to a rod 89 which moves with a diaphragm 84 corresponding to 57 in Fig. 8. The downward movement of rod 89 is limited by a sleeve 90 fixed thereto abutting against the member 88 and upward movement thereof is limited by a plate 86 fixed to rod 89 abutting against a ring 87. Normally the air pressure in the tube 47, Fig. 7, connected to the inlet 109 maintains the membrane 84 in the position shown. When a leakage occurs, the pressure on the underside of membrane 84, due to the atmosphere and a spring 85 coacting with an adjustable thrust block 92, elevates the rod 89 whereupon the plate 71 releases the rod 61 to release the tyre valve. A deflating push button 100 fitted in a membrane 98 is provided, depression thereof rocking the plate 71 until the rod 61 is displaced sufficiently to open the valve 60 when the air escapes through 109. As the rod 89 moves according to the air pressure its movements may be used to actuate a pointer indicating pressure. Modifications. The apparatus may be used as a pressure equaliser between two air chambers, functioning in this case only at the pressure for which it has been set.