Pilot valve

• US 6,125,886 A
• Filed: 11/18/1998
• Issued: 10/03/2000
• Est. Priority Date: 05/22/1997
• Status: Expired due to Term

• Current Assignee: Kawasaki Jukogyo Kabushiki Kaisha
• Original Assignee: Kawasaki Jukogyo Kabushiki Kaisha
• Inventors: Sagawa, Toyoaki, Fujiyama, Kazuto, Togashi, Yoshio, Sakashita, Koji
• Primary Examiner(s): Michalsky, Gerald A.
• Application Number:
  US09/195,214
• Time in Patent Office: 685 Days
• Field of Search: 137/596.1, 137/625.69, 137/636.1, 137/636.2, 251/50
• US Class Current: 137/625.69
• CPC Class Codes: F15B 13/0422 with manually-operated pilot valves, e.g. joysticks
• CPC Class Codes: F16K 11/168 only swings
• CPC Class Codes: Y10T 137/8671 With annular passage [e.g., spool]
• CPC Class Codes: Y10T 137/87064 Oppositely movable cam surfaces
• CPC Class Codes: Y10T 137/87233 Biased exhaust valve

Abstract

In order to obtain great damper effects with a comparatively simple structure and fully control a hunting phenomenon, a pilot valve comprises push rods attached to a valve body, spools attached to spools holes of the valve body, spring bearing members provided in spring chambers of the valve body, first spring members provided between the valve body and the spring bearing members, second spring members provided between the spring bearing members and the spools, and an operation level for pressing the push rods. A fluid chamber is provided on an outside of one of ends of each of the spool holes. The fluid chamber communicates with a drain passage through a throttle passage having a throttle portion.

Claims

1. A pilot valve comprising:

a valve body having a spring chamber and a spool hole communicating therewith;

a push rod movably attached to the valve body;

a fluid chamber, at least a part of which is formed in the valve body;

a spool movably attached to the spool hole, one end surface of the spool forming a portion of an interior surface of the fluid chamber;

a spring bearing member movably provided in the spring chamber relatively to the valve body;

a first spring member provided between the valve body and the spring bearing member for elastically biasing the push rod in a projecting position through the spring bearing member;

a second spring member provided between the spring bearing member and the spool for elastically biasing the spool in a direction apart from the push rod; and

an operation lever for pressing the push rod,

the spool including;

a first spool portion having a small pressure receiving area of a pressure receiving part;

a second spool portion having a large pressure receiving area of a pressure receiving part; and

a notch provided between the first spool portion and the second spool portion,

the pilot valve having a structure in which when the push rod is set in the projecting position, the first spool portion of the spool blocks communication of a primary pressure side passage with a secondary pressure side passage and the notch of the spool causes the secondary pressure side passage to communicate with a tank passage, and when the push rod is pressed by the operation lever, the spool is moved by action of the second spring member, the notch of the spool causes the primary pressure side passage to communicate with the secondary pressure side passage, and a pressure fluid flowing in the secondary pressure side passage acts on the pressure receiving parts of the first and second spool portions,

wherein the fluid chamber is provided on an outside of one end of the spool, the fluid chamber communicating with a tank line through a throttle passage having a throttle portion.

2. A pilot valve comprising:

a valve body having a spring chamber and a spool hole communicating therewith;

a push rod movably attached to the valve body;

a spool movably attached to the spool hole;

a spring bearing member movably provided in the spring chamber relatively to the valve body;

a first spring member provided between the valve body and the spring bearing member for elastically biasing the push rod in a projecting position through the spring bearing member;

a second spring member provided between the spring bearing member and the spool for elastically biasing the spool in a direction apart from the push rod; and

an operation lever for pressing the push rod,

the spool including;

a first spool portion having a small pressure receiving area of a pressure receiving part;

a second spool portion having a large pressure receiving area of a pressure receiving part; and

a notch provided between the first spool portion and the second spool portion,

the pilot valve having a structure in which when the push rod is set in the projecting position, the first spool portion of the spool blocks communication of a primary pressure side passage with a secondary pressure side passage and the notch of the spool causes the secondary pressure side passage to communicate with a tank passage, and when the push rod is pressed by the operation lever the spool is moved by action of the second spring member, the notch of the spool causes the primary pressure side passage to communicate with the secondary pressure side passage, and a pressure fluid flowing in the secondary pressure side passage acts on the pressure receiving parts of the first and second spool portions,

wherein a fluid chamber is provided on an outside of one end of the spool, the fluid chamber communicating with a tank line through a throttle passage having a throttle portion and a drain passage extending from the spring chamber is provided on the valve body, the throttle passage is provided in the first spool portion of the spool, and the fluid chamber is caused to communicate with the drain passage.

3. A pilot valve comprising:

a valve body having a spring chamber and a spool hole communicating therewith;

a push rod movably attached to the valve body;

a spool movably attached to the spool hole;

a spring bearing member movably provided in the spring chamber relatively to the valve body;

a first spring member provided between the valve body and the spring bearing member for elastically biasing the push rod in a projecting position through the spring bearing member;

a second spring member provided between the spring bearing member and the spool for elastically biasing the spool in a direction apart from the push rod; and

an operation lever for pressing the push rod,

the spool including;

a first spool portion having a small pressure receiving area of a pressure receiving part;

a second spool portion having a large pressure receiving area of a pressure receiving part; and

a notch provided between the first spool portion and the second spool portion,

the pilot valve having a structure in which when the push rod is set in the projecting position, the first spool portion of the spool blocks communication of a primary pressure side passage with a secondary pressure side passage and the notch of the spool causes the secondary pressure side passage to communicate with a tank passage, and when the push rod is pressed by the operation lever, the spool is moved by action of the second spring member, the notch of the spool causes the primary pressure side passage to communicate with the secondary pressure side passage, and a pressure fluid flowing in the secondary pressure side passage acts on the pressure receiving parts of the first and second spool portions,

wherein a fluid chamber is provided on an outside of one end of the spool, the fluid chamber communicating with a tank line through a throttle passage having a throttle portion and the throttle passage extends from one of the ends of the spool in an axial direction through the first and second spool portions, and the fluid chamber is caused to communicate with the spring chamber.

4. A pilot valve comprising:

a valve body having a spring chamber and a spool hole communicating therewith;

a push rod movably attached to the valve body;

a spool movably attached to the spool hole;

a spring bearing member movably provided in the spring chamber relatively to the valve body;

a first spring member provided between the valve body and the spring bearing member for elastically biasing the push rod in a projecting position through the spring bearing member;

a second spring member provided between the spring bearing member and the spool for elastically biasing the spool in a direction apart from the push rod; and

an operation lever for pressing the push rod,

the spool including;

a first spool portion having a small pressure receiving area of a pressure receiving part;

a second spool portion having a large pressure receiving area of a pressure receiving part; and

a notch provided between the first spool portion and the second spool portion,

the pilot valve having a structure in which when the push rod is set in the protecting position, the first spool portion of the spool blocks communication of a primary pressure side passage with a secondary pressure side passage and the notch of the spool causes the secondary pressure side passage to communicate with a tank passage, and when the push rod is pressed by the operation lever, the spool is moved by action of the second spring member, the notch of the spool causes the primary pressure side passage to communicate with the secondary pressure side passage, and a pressure fluid flowing in the secondary pressure side passage acts on the pressure receiving parts of the first and second spool portions,

wherein a fluid chamber is provided on an outside of one end of the spool, the fluid chamber communicating with a tank line through a throttle passage having a throttle portion and the spool hole is opened on one end of the valve body, a cover member for blocking an opening of the spool hole to form the fluid chamber is attached to the end of the valve body, a drain passage extending from the spring chamber is provided on the valve body and the cover member, the throttle passage is provided on a junction face of the valve body and the cover member, and the fluid chamber is caused to communicate with the drain passage.