Pressure booster

A booster for increasing the pressure in a hydraulic fluid by means of a pressure gas, such as compressed air, especially for use in connection with an operating device for clutches for vehicles,

• comprising a housing (11,11′) with an inlet (14,14′) for low-pressure fluid, an outlet (15,15′) for high-pressure fluid, an inlet (16,16′) and an outlet (17,17′) for compressed air and a main piston (22,22′) mounted in the housing (11,11′) with an end portion (22b,79) with a relatively small diameter and a portion (23,23′) with an enlarged diameter, where the small end portion (22b,79) together with the housing (11,11′) define a second cylinder space (27,27′), which is connected to the high-pressure fluid outlet (15,15′), and the large portion (23,23′) together with the housing (11) define a third cylinder space (26,26′), which can be connected to the compressed air inlet (16,16′) or the outlet (17,17′), the third cylinder space (26,26′) being located on one side of the main piston (22,22′) and the second cylinder space (27,27′) located on the other side of the main piston (22,22′), viewed in the main piston's (22) axial direction,
• and there is provided a first passage (29,29′) which connects the second cylinder space (27,27′) with the low-pressure fluid inlet (14,14′) and in this passage (29) there is provided a check valve (30,30′), which can be influenced by a body (28,28′), which, when no low-pressure fluid impulse exists in the low-pressure fluid inlet (14,14′), influences the check valve (30,30′) in such a manner that it is located in a first position, wherein a fluid flow is permitted in both directions through the first passage (29), and which when such an impulse exists, brings the check valve (30) into a second position, wherein it permits a flow only from the low-pressure fluid inlet (14,14′) to the second cylinder space (27),
• and in the housing there is provided a shut-off valve (48,52;48′,52′) which in a first position prevents a connection between the third cylinder space (26,26′) and the compressed air inlet (16,16′) and provides a connection between the third cylinder space (26,26′) and the compressed air outlet (17,17′), and in a second position provides a connection between the third cylinder space (26,26′) and the compressed air inlet (16,16′), preventing a connection between the third cylinder space (26,26′) and the compressed air outlet (17,17′),
• characterized in that the body is in the form of a valve piston (28,28′), which is sealingly and slidably mounted in the housing (11,11′), and which has a first end portion (34,34′) which is arranged to influence the check valve (30,30′), and a second end portion (55,55′) which is arranged to influence the shut-off valve (48,52;48′,52′), whereby the valve piston (28,28′) is arranged to be moved in a first direction, bringing both valves (30,30′ and 48,52;48′,52′respectively) to their second positions when a pressure impulse occurs in the low-pressure fluid inlet (14,14′) and to be moved in the opposite direction, bringing both valves (30,30′ and 48,52;48′,52′ respectively) to their first positions when no pressure impulse occurs in the low-pressure fluid inlet (14,14′).