| 摘要 |
1. A hydraulic circuit breaker comprising a housing (12) having an inlet orifice (13) for connecting to the outlet of a hydraulic pump, a first outlet orifice (14) for connecting to the pressure chamber of a hydraulic accumulator, and a second outlet orifice (16) for connecting to an open-centre hydraulic circuit, a stepped bore (20) formed in the housing (12) receiving a differential piston (30) which defines an inlet chamber (28) therein in communication with the inlet orifice (13) and a control chamber (26), a constriction orifice (32) having a cross-section which varies in dependence of the position of the differential piston (30) being disposed between the inlet chamber (28) and the second outlet orifice (16), the inlet chamber (28) communicating with the control chamber (26) via a first passage (34, 36) comprising a first constriction (38) and also communicating with the first outlet orifice (14) via a connection (34) comprising a check valve (40), the circuit breaker also comprising a resilient vessel having a variable-volume compartment connected to the control chamber (26), said vessel being adapted to connect the compartment with a leak passage forming a constriction when the pressure in the compartment reaches a first predetermined value, and the communication with the leak passage being interrupted when the pressure in the compartment falls below a second predetermined value, characterized in that said resilient vessel is comprised of an interchangeable capsule (50) placed coaxially in the large-diameter or control-chamber portion (26) of the stepped bore (20), said capsule containing a second piston (64) slidably mounted therein sealing-tight manner and dividing its interior into a first compartment (66) defining said variable-volume compartment and a second compartment (68), said second piston (64) being urged towards the end of said first compartment (66) by resilient means (70) disposed in said second compartment (68), an axial passage (72) for connecting the two compartments being provided in said piston (64) and opening into the first compartment (66) to define a valve seat (74) which cooperates with a valve element (76) from its seat (74) so that fluid can flow in the leak passage (72) when the second piston (64) has moved a given distance corresponding to said first predetermined pressure in said first compartment (64), the leak passage (72) then comprising the space defined between said push-rod element and said axial passage, and said second compartment (68) being connected by a leak orifice (60) to a low-pressure fluid tank. |
