GB467096A - Improvements in or relating to pneumatic tyres for vehicle wheels - Google Patents

Abstract

467,096. Pneumatic tyres. STEVENSON, A. C. Dec. 7, 1935, No. 33934. [Class 144 (ii)] [Also in Group XXVIII] Means for automatically inflating pneumatic tyres whilst running comprise one or more reciprocating pumps carried by the wheel and operated, against spring resistance, by alteration of centrifugal forces due to variation of speed of the vehicle. The pumping-devices may be housed in a hollow wheel structure forming a chamber in communication with the tyre ; and, an additional pumping-device may be fitted for actuation by the flexing of the tyre in road-contact. In the form shown in Fig. 2, a cylinder 14 carried by a movable block 1 cooperates with a fixed piston 2 which is fitted with a lubricating-bush 12 and is screwed into a bracket 3 clamped to the wheel. The block 1 is fitted with inlet and blow-off valves 16, 17 respectively, an inlet valve 19 being fitted at the inner end of a bore 18 in the piston which communicates through pipe 20 with the airchamber of the tyre. A helical spring 15 is fitted between the piston and the cylinder-block 1 to force the latter towards the wheel-centre. A dust-excluding cover 21 may be fitted as shown. With the parts in the position shown, if the speed of rotation of the wheel decreases, the spring 15 overcomes the centrifugal thrust of the block 1 and air is drawn into the cylinder 14, to be forced past the valve 19 into the tyre on subsequent acceleration of the wheel. For balancing purposes, a second pumping-device, or an appropriate weight, may be fitted at the diametrically-opposite side of the wheel. In a modification, a device such as that shown in Fig. 2 is fitted directly on the valve-stem of the tyre. Figs. 7 and 8 show a modification in which the wheel body, of the kind described in Specification 380,163, constitutes an air-chamber 50 and the tyre 54 encloses an emergency load-supporting rim 53. Valve-controlled openings 58, 59 connect the chamber 50 with the atmosphere and the tyre respectively, and a pair of pistons 57 normally retracted by springs 61 operate in diametrically-opposed cylinders 55. Fig. 11 shows a further modification in which the centrifugally-actuated pump is combined with a pump actuated by the flexing of the tyre in road contact. In this form, the outward throw of the piston 72 and sleeve 75 due to centrifugal force, against the resistance of the spring 76, draws air into the cylinder 71 through the valve 79, 80 being a blow-off valve. On decrease in speed of the wheel, the piston 72 is retracted thereby forcing air trapped in cylinder 71 past valve 81 into cylinder 73 and through bore 82 of piston 74 into the tyre. The piston 74 is rigidly secured to the casing 75 whereby on undue flattening of the tyre under load the parts 74, 75, 72 are moved radially inwards to force air from the cylinder 71 into the tyre. A grub-screw 83 is fitted to limit the movement of the piston 74 in its cylinder 73, and a buffer-spring 78 is provided to cushion the travel of the sleeve 75 after the piston 72 has reached the end of cylinder 71.