GB1417697A - Master cylinder units - Google Patents

Abstract

1417697 Master cylinders; clutch control AUTOMOTIVE PRODUCTS Ltd 19 Dec 1972 [5 Jan 1972] 465/72 Headings F2F and F2L A master cylinder unit for use in an hydraulic motor vehicle clutch control system comprises ports 16, 17, 18 for connection respectively to a slave cylinder unit 66 of a clutch release mechanism 67, a pump 68 and a reservoir 69, pressurization of the unit being brought about by operation of a plunger 20 and an associated valve spool 54 which causes port 16 to be cut off from port 18 and pressurized liquid from port 17 to be introduced into a space 32 where it acts to urge a piston 11 leftwardly to displace liquid from the master cylinder bore 12 through port 16 to unit 66 to release the clutch. As shown, plunger 20, which is operable by a push rod 13, slides in an annular stud 19 and has a spigot 64 received in a cavity 65 in spool 54. The spool 54 slides in a portion 40 of a through bore of piston 11, and in a larger diameter portion 39 is received a cup-shaped plunger 46 carrying a sealing ring 48 for engagement with a ring 43 fixed at the mouth of the piston through bore to close the central aperture 49 of ring 43. In the unactuated condition of the master cylinder unit the port 16 communicates with port 18 via aperture 49, a diametral drilling 51 in plunger 46, an axial bore 60 and a radial passage 61 in spool 54 and portion 38 of the piston through bore. The space 32 communicates with bore 60 via a drilling 63 in spool 54, a recess 62 and a passage 42 in piston 11. When clutch pedal 70 is operated, the resultant movement of spool 54 compresses a spring 59 and this movement is initially transmitted to cup-shaped plunger 46 via a washer 55 and a spring 57 to compress a light spring 50 and bring ring 48 into engagement with aperture 49: at the same time radial passage 61 is moved out of portion 38 so that the axial bore 60 and port 16 are both cut off from port 18. Further movement of the plunger 20 compresses spring 57 and further compresses spring 59 until annular recess 62 places the passage 42 in communication with another passage 41 in piston 11 which communicates with port 17 via an annular recess 34. Thus liquid under pressure introduced into space 32 moves piston 11 leftwardly to displace liquid through port 16. The amount of movement imparted to piston 11 is dependent on the amount of movement of spool 54. Should pump 68 fail, the piston 11 may be moved mechanically by engagement of washer 55 with the end of an annular recess 52 in plunger 46. When the clutch pedal 70 is released port 16 is again connected to port 18.