Patent GB-297111-A (GB)
Title: Power actuators or servo-motors particularly for operating brakes
IPC: B60T15/04
Filed: 1928-08-30
Abstract: 297,111. Bragg, C. S., and Kliesrath, V. W. Sept. 16, 1927, [Convention date]. Fluid-pressure; hand actuation. -Valve mechanism for controlling the pressure in the operating cylinder of vehicle brake mechanism comprises a disc or diaphragm connected to the operator's handle and forming the seating for one or more valves by which air or other higher pressure fluid is admitted to the cylinder, the piston or diaphragm being subject on its opposite faces respectively to the higher pressure fluid and the pressure in the brake cylinder and on one face also to the pressure of a spring in such a manner that the resistance of the spring which is felt by the operator in opening the valve is an indication of the resultant pressure acting in the cylinder. As shown in Fig. 2, the mechanism comprises a casing 10 connected at 14 to the brake cylinder, at 18 to the source of lower pressure which may be the induction pipe of the engine of the vehicle and at 36 to the source of higher pressure which, as shown, is the atmosphere. A slidable rod 21 provided with a handle 47 has freely mounted thereon a valve 25 engageable with a ring on the rod and a socket 32 forming part of a disc 30 which carries a plate 39 engageable with a sleeve 21<b> secured to the rod 21. The socket 32 slides in a cylindrical part of the fixed partition 34. The disc 30 is provided with a series of concentrically arranged small passages 42 each forming the seat of a valve 43 the stems of which are of varying lengths and carry stops 46. Springs 41 which offer a substantial resistance to the movement of the disc 30 are disposed between it and the casing and a light spring 24 is arranged between the disc and the valve 20. In. the application of the valve to a system in which the chamber on one side of the brake piston is permanently exhausted and in which the chamber on the other side is normally exhausted, the pipe 14 is connected to the latter chamber and the valve parts are normally in the position shown with the valve 25 unseated so that this chamber is connected with the suction pipe 18. To apply the brakes, the valve rod 21 is pulled to the right seating the valve 25 and withdrawing the disc 30 from the valves 43 which become unseated in succession by reason of the varying length of the valve stems thus permitting the admission of air at an adjustable rate through the strainer 37, openings 34a, passages 42 and pipe 14 to the brake cylinder. As the pressure in the valve chamber 11 and on the corresponding face of the disc 30 rises, the pressure exerted by the operator against the springs 41 to hold the disc in the open position also rises and an indication of the pressure acting on the brake piston is thus given. When the handle 47 is released, the disc 30 moves back to seat the valves 43 and the valve 20 remains seated to hold the brakes applied. A brake svstem for a motor tractor vehicle and a trailer is shown comprising one or two brake cylinders and a cylinder on the trailer, in which connection is made with the induction pipe of the engine for producing the vacuum and control of all the cylinders is effected by a single valve mechanism as above described. In a modification of the valve mechanism, the disc 30 is replaced by a diaphragm secured to the casing at its outer periphery. As shown in Fig. 6, the valve mechanism may be mounted upon the hand lever 50 of an emergency brake which is not actuated by the brake cylinders controlled by the valve so that when the rod 21 has been withdrawn from the casing to the limit determined by a projection 40, Fig. 2, thereon, the casing and the hand lever will be moved and the emergency brake applied. The inlet 36 for atmospheric air may be connected to a source of higher pressure in which case the pipe 18 may be connected either to the atmosphere or to suction.