Fluid handling – Systems – With selective motion for plural valve actuator
Patent
1995-04-10
1996-09-24
Michalsky, Gerald A.
Fluid handling
Systems
With selective motion for plural valve actuator
1375961, 251285, F15B 1308
Patent
active
055581277
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a hydraulic pilot valve for executing a directional changeover of control valves, or the like, feeding hydraulic oil to cylinders for driving a working unit mounted on construction machinery such as a hydraulic excavator, a wheel-mounted loader, a dump truck, a bulldozer, and the like.
BACKGROUND ART
A pilot operated control valve is known as a control valve to feed hydraulic oil to cylinders of a working unit of a construction machine. A spool, slidable freely between a neutral position and a hydraulic oil feed position, is provided in a main body of such pilot operated control valve. The spool is held at the neutral position by a spring, and pilot hydraulic oil fed to a pilot cylinder causes the spool to slide to the hydraulic oil feed position. For a directional changeover of the pilot operated control valve, a hydraulic pilot valve feeds hydraulic oil to the pilot cylinder of the control valve. Diverse constructions are known for such a hydraulic pilot valve. For example, Japanese Utility Model Registration Application Laid-Open No. 101379/1988 discloses a hydraulic pilot valve wherein a main body thereof is provided with pressure-reducing elements, pistons to actuate the pressure-reducing elements, and a swinging member swingable freely by an operating lever for pressing the pistons, and wherein swinging the operating lever causes the swinging member to press a piston for establishing the state of feeding pilot hydraulic oil to a pilot cylinder of a control valve. In such a hydraulic pilot valve, a stroke end position of the operating lever is determined by the contact of a member with magnetic material, provided on the operating lever and serving as a stopper, with a solenoid. However, when there is an error in a mounting position of the member with magnetic material and the solenoid, the stroke end position of the operating lever is not fixed but varies. This causes the operator to have an unstable sense of operation and a resultant rough operation. Furthermore, since the stroke end position of the operating lever is substantially determined by the stopper, a maximum stroke from the neutral position is fixed. Thus, the maximum strokes of the pistons of the pressure-reducing elements are also fixed, causing the maximum pressures of pilot hydraulic oil being outputted with a plurality of pressure-reducing elements to become the same. This involves a drawback in that it is impossible to change the maximum pressures of pilot hydraulic oil outputted from the pressure-reducing elements as desired.
Furthermore, according to the prior art, in a hydraulic pilot valve which includes a shaft pivotally mounted on a main body of the valve, an arm fixed to the shaft and extending right and left therefrom, and pressure-reducing valves located at the right and left of the shaft and formed in the main body of the valve, the pressure-reducing valves having a pressure-reducing element between input and output ports thereof and including a spool biased by a spring so as to establish a normally shut-off state between the input and output ports, and which further includes pistons, an end of which comes into contact with the arm to press each spool, the arm is locked onto the shaft by means of a knock-pin, so that the operation of the operating lever causes the arm to swing about the shaft and to come into contact with a stopper. However, according to the construction described above, since an operating force of the operating lever is transmitted to the arm through the shaft and the knock-pin, operating the operating lever with a large force causes the knock-pin to fracture. Therefore, the construction described above had a drawback in that if the diameter of the knock-pin is increased to avoid such a problem, the diameter of the shaft is also increased, with a resultant increase in the size of the hydraulic pilot valve. Furthermore, according to the construction described above, a hydraulic pilot valve for a traveling circuit of a hydraulic excavator or the like
REFERENCES:
patent: 3800615 (1974-04-01), Pilch
patent: 4296773 (1981-10-01), Harshman et al.
patent: 5184646 (1993-02-01), Hori et al.
Hayashi Seita
Hori Suji
Karakama Tadao
Maruyama Jun
Kabushiki Kaisha Komatsu Seisakusho
Michalsky Gerald A.
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