Back to results
US 4,787,293 AGranted
Hydraulic system for working vehicles
AssigneeHonda Giken Kogyo Kabushiki Kaisha
InventorsYuji Kishizawa, Sadanori Nishimura
Life of this patent
Estimating the term…
Abstract
A hydraulic system for raising and lowering a working machine in a working vehicle such as agricultural tractors, which comprises a hydraulic cylinder, a hydraulic pump, an oil tank, a manual valve shiftable between three positions: a stationary position in which a working oil discharged from said hydraulic pump is released into the oil tank; a raised position in which the working oil is supplied into the hydraulic cylinder; and a lowered position in which the working oil supplied into the hydraulic cylinder is passed back into the oil tank, and a check valve for permitting only a flow of the working oil from the manual valve toward the hydraulic cylinder.
Claims14
A hydraulic system for a working vehicle comprising:
- a hydraulic cylinder on the working vehicle and operable to raise and lower a working machine;
- a hydraulic pump;
- an oil tank;
- a manual valve constructed to be shiftable to a stationary position in which a working oil discharged from said hydraulic pump is released into said oil tank, a raised position in which the working oil is supplied into said hydraulic cylinder, and a lowered position in which the working oil supplied into the hydraulic cylinder is passed back into the oil tank;
- and
- a check valve interposed in an oil passage between said manual valve and said hydraulic cylinder for permitting a flow of the working oil in a normal direction from said manual valve toward said hydraulic cylinder and blocking a flow of the working oil in a reverse direction, wherein said check valve comprises a main valve seat interposed within the oil passage between said manual valve and said hydraulic cylinder to permit the flowing of the working oil therethrough, a main valve cooperating with said main valve seat to permit flowing of the working oil in said normal direction and to block flowing of the working oil in said reverse direction;
- a sub-valve seat formed in said main valve to permit flowing of the working oil therethrough;
- a sub-valve having a pressure-receiving area smaller than that of said main valve seat and cooperating with said sub-valve seat to permit flowing of the working oil in said normal direction and to block flowing of the working oil in said reverse direction;
- and a valve-opening rod mounted in an opposed relation to said main and sub valves and operable to open said sub-valve prior to said main valve, said valve opening rod being operatively connected to said manual valve such that the rod operates in the course of shifting of said manual valve from the stationary position to the lowered position;
- said manual valve including a spool slidable in a valve bore in a casing to which bore are opened a discharge port of said hydraulic pump, an exit port connected to said oil tank and a feed port connected to said hydraulic cylinder, said manual valve being operable to permit said feed port to selectively communicate with said discharge port and said exit port;
- and wherein an oil passage is provided in said manual valve for interconnecting said discharge port and said oil tank and a relief valve is interposed in said oil passage in the manual valve to open when a pressure discharged from said hydraulic pump reaches not less than a specified value.
8 more elements
A hydraulic system for a working vehicle comprising:
- a plurality of hydraulic cylinders on the working vehicle each hydraulic cylinder of said plurality of hydraulic cylinders being operable to raise and lower a selected one working machine of a plurality of working machines on said vehicle;
- a hydraulic pump;
- an oil tank;
- a manual valve constructed to be shiftable to a stationary position in which a working oil discharged from the hydraulic pump is released into the oil tank, a raised position in which the working oil is supplied into the hydraulic cylinder of a selected one working machine of said plurality of working machines, and a lowered position in which the working oil supplied into said hydraulic cylinder is passed back into the oil tank;
- a switch valve interposed in an oil passage between said manual valve and said hydraulic cylinders for permitting an output side of said manual valve to selectively communicate with each cylinder of said plurality of hydraulic cylinders;
- a pressure control valve which is opened upon application of an overload to said hydraulic cylinder selectively put into communication by said switch valve, thereby escaping the overload working oil within said hydraulic cylinder into the oil tank;
- and
- a throttle valve between said switch valve and said pressure control valve for throttling the oil passage to limit the operational speed of the hydraulic cylinder selectively put into communication by said switch valve and for closing said oil passage.
5 more elements
A hydraulic system for a working vehicle comprising:
- a hydraulic cylinder on the working vehicle and operable to raise and lower a working machine;
- a hydraulic pump;
- an oil tank;
- a manual valve constructed to be shiftable to a stationary position in which a working oil discharged from said hydraulic pump is released into said oil tank, a raised position in which the working oil is supplied into said hydraulic cylinder, and a lowered position in which the working oil supplied into the hydraulic cylinder is passed back into the oil tank;
- and
- a check valve interposed in an oil passage between said manual valve and said hydraulic cylinder for permitting a flow of the working oil in a normal direction from said manual valve toward said hydraulic cylinder and blocking a flow of the working oil in a reverse direction, wherein said check valve comprises a main valve seat interposed within the oil passage between said manual valve and said hydraulic cylinder to permit the flowing of the working oil therethrough;
- a main valve cooperating with said main valve seat to permit flowing of the working oil in said normal direction and to block flowing of the working oil in said reverse direction;
- a sub-valve seat formed in said main valve to permit flowing of the working oil therethrough;
- a sub-valve having a pressure-receiving area smaller than that of said main valve seat and cooperating with said sub-valve seat to permit flowing of the working oil in said normal direction and to block flowing of the working oil in said reverse direction;
- and a valve-opening rod mounted in an opposed relation to said main and sub valves and operable to open said sub-valve prior to said main valve, said valve opening rod being operatively connected to said manual valve such that the rod operates in the course of shifting of said manual valve from the stationary position to the lowered position, main and sub valve seats of said check valve being formed to have a larger opening and a smaller opening, respectively;
- wherein a throttle valve is interposed in series to said check valve in the oil passage between said manual valve and said hydraulic cylinder, and wherein first and second smaller grooves are formed in said manual valve for providing a throttling resistance to the working oil passing through said manual valve at positions of the manual valve intermediate between the stationary position and the raised position and between the stationary position and the lowered position, respectively.
8 more elements
Dependencies are inferred from the claim text.