Patent GB-533667-A (GB)
Title: Improvements in or relating to fluid pressure remote control systems
IPC: B64C25/22
Filed: 1939-11-08
Abstract: 533,667. Pneumatic single stroke apparatus. AUTOMOTIVE PRODUCTS CO., Ltd., and THORNHILL, P. W. Nov. 8, 1939, No. 29672. [Class 8 (ii)] [Also in Group XXIX] A fluid pressure remote control system which is especially applicable for actuating fluid motors such as the jacks 20, 21, Fig. 1, on aircraft for controlling wing flaps, under-carriages &c. is constructed with a series of selector valves 28 ... 33, each operable by a handle 61 to control the pressure in pipe lines 36, 37, 38 leading to separate control valves 23, 24, for controlling the supply of the fluid to the motors 20, 21, the control valves being adapted to operate the motors in either direction or to leave the motor inoperative according to the setting of the appropriate handle 61. The liquid control shown comprises a pump 11 fed from a reservoir 13 and supplying liquid to an accumulator 10 connected to the pressure supply line 18. The return line 19 is connected to the reservoir 13 as is the overflow from the accumulator 10. The control valves 23, 24 are connected by pipes 25, 26, to the lines 18, 19, and by pipes 22 to the motors 20, 21, and one pressure line 36, 37, 38 leads from each selector valve to each control valve. One of the selector valves is shown in Fig. 2 in the " off " position with the handle 61 in a mid-position which enables a spring-pressed plunger 53 to assume its extreme position towards the right. In this position a pipe 35 connects the pipe 36 to the pipe 19 so that there is no operative pressure in pipe 36. Connection between the pipe 35, 36 takes place through the hollow stem of a valve 42 and radial ports 51. The valve 42 which can be set to connect the pressure inlet pipe 34 to the pipe 36 is pressed on its seat by the pressure of fluid entering the port 34a and acting upon an annular washer 47 attached to a secondary plunger 46 which draws the valve 42 to its seat by acting upon a shoulder 49 of an enlarged part of the valve stem. When the handle 61 is raised to engage a stop 72 so that a pivot 63 acts on a thrust plate 65 to move the plunger 53 to the left, the connection to the pipe 35 is closed by the engagement of a sleeve 57 with a washer 58 on the secondary plunger 46, and the plunger 46 is finally moved to the left and so releases the pressure on the valve stem which can then open partially under the fluid pressure, the valve acting as a pressure reducing valve to reduce the pressure in pipe line 36 to a predetermined proportion, say one-half, of the pressure of pipe 18. If the pressure exceeds this the secondary plunger is moved to the right and the fluid can pass to the pipe 35 leading to the reservoir 13. The sleeve 57 is formed with a flange 59 which engages the end surface 60 of the plunger 46 to permit a thrust to be transmitted without damage to the plunger 46. By moving the handle 61 over to its extreme clockwise position a pivot 64 causes a further movement of the plunger 53 towards the left, and the valve 42 opens fully and the pressure transmitted to the pipe 36 is equal to the full pressure of the pipe 18. The valve mechanism for controlling the fluid supply to the motors 20 is shown in Fig. 6 in the position which the valves E, P : E<SP>1</SP>, P<SP>1</SP> occupy when the selector valve is in the " off " position. In this position the motors are connected to the exhaust lines by valves E, E<SP>1</SP> so that compensation for temperature variation can take place. To operate the motor in one direction the selector valve is set to the half-pressure position and the pressure in pipe 36 then causes a small plunger 104 to move to the left and actuate a lever 96 which opens a valve P<SP>1</SP> leading to the inlet of one end of the motor 20, and closes the valve E<SP>1</SP>, the exhaust then being through connection 22a, passage 114, valve E pipe 26. When the pressure in pipe 36 is raised to full pressure a large plunger 99 is moved to the right with a pressure which corresponds to the same as that which moved the small plunger 104 to the left. The plunger 104 which has a lost motion connection 107 with the large one is at the same time withdrawn. The valve P is now opened and the valve E shut, the valves E<SP>1</SP>, P<SP>1</SP> are returned to their original position by a spring 92. The operation of the motor is thus reversed. The pressure on the face of plunger 99 due to fluid admitted to port 36b is opposed by pressure admitted to a space 110 from the main pressure line. When the pressure in pipe 36 is half that of the pressure line these forces balance. When the pressure in pipe 36 is made equal to that of the pressure line the resultant force acting on the lever 95 is the same as that which previously acted upon the lever 96. In a modified form of selector valve, Fig. 7, the handle 61 is arranged when in mid-position to set the valve for half pressure, and the control valve is so arranged that the motors are inoperative when the valve is in this position, and are operative in opposed directions according as the pressure in the pipe line 36 is connected to the pressure line 18 or the return line 19. The handle 61 operates a cam with recesses 122, 123, 124 which engages a ball on the plunger 53 the end of which is of frusto-conical shape to act as a valve with the end of a sleeve 126 which has an aperture 128 leading to the reservoir passage 35a. In the position shown, which is the half-pressure position, the valve 44 opens against the action of a light-spring under fluid pressure from a conduit 34a. If the pressure exceeds the half pressure it acts on the end of the sleeve 126 which is moved to permit of escape of fluid by conduit 35a. When the handle 61 is raised to position 61a the valve 57a opens under spring action and the fluid is connected by conduit 35a to the reservoir. In the 61b position the valve 44 is held fully open. In a simpler form of valve the handle 61 is arranged to have two operative positions only, and a valve similar to 57a, Fig. 7, is arranged to move to two positions which permit of the fluid which enters the conduit 34a having access to the conduit 35a or the pipe 36, the valve 44 being fully open in the latter case. The form of the valve E, P, E<SP>1</SP>, P<SP>1</SP> is varied to suit the pressure control system described in connection with Fig. 7.