Control system for hydraulic actuator

• US 4,367,624 A
• Filed: 02/15/1980
• Issued: 01/11/1983
• Est. Priority Date: 02/20/1979
• Status: Expired due to Term

• Current Assignee: Kabushiki Kaisha Komatsu Seisakusho (Komatsu Ltd.)
• Original Assignee: Kabushiki Kaisha Komatsu Seisakusho (Komatsu Ltd.)
• Inventors: Ogata, Yasuhiro, Mutou, Norishige
• Primary Examiner(s): Hershkovitz, Abraham
• Application Number:
  US06/121,735
• Time in Patent Office: 1,061 Days
• Field of Search: 91/6, 91/509, 91/519, 91/521, 91/523, 91/529, 91/461, 60/486, 60/484
• US Class Current: 60/484
• CPC Class Codes: E02F 3/844 for positioning the blade, e.g. hydraulically
• CPC Class Codes: E02F 9/2239 using two or more pumps with cross-assistance
• CPC Class Codes: E02F 9/2285 Pilot-operated systems
• CPC Class Codes: E02F 9/2292 Systems with two or more pumps
• CPC Class Codes: F15B 11/17 using two or more pumps
• CPC Class Codes: F15B 2211/20584 Combinations of pumps with high and low capacity
• CPC Class Codes: F15B 2211/30585 having a single valve for multiple output members
• CPC Class Codes: F15B 2211/3116 the pump port being open in the centre position, e.g. so-called open centre
• CPC Class Codes: F15B 2211/329 actuated by fluid pressure
• CPC Class Codes: F15B 2211/6355 having valve means
• CPC Class Codes: F15B 2211/67 Methods for controlling pilot pressure
• CPC Class Codes: F15B 2211/7128 the chambers being connected in parallel
• CPC Class Codes: F15B 2211/7142 the output members being arranged in multiple groups

Abstract

A control system for a hydraulic actuator comprising a first pump with large displacement capacity, a second pump with small displacement capacity, a pilot pump, a first pilot operated spring centered control valve connected at the input side thereof to the first pump, the output side of which is selectively connected to the hydraulic actuator and drain, a second pilot operated spring centered control valve connected at the input side thereof to the second pump, the output side of which is selectively connected to the hydraulic actuator and drain, and a third control valve for pilot pressure connected at the input side thereof to the pilot pump, the output side of which is connected to the first and second control valves wherein the second control valve is adapted to be actuated by a pilot pressure lower than a pilot pressure which actuates the first control valve.

Claims

1. A control system for controlling a hydraulic actuator during full stroke operations and inching operations, said control system comprising:

an engine;

a first hydraulic pump with a large displacement capacity driven by said engine;

a second hydraulic pump with a small displacement capacity driven by said engine;

a pilot pump driven by said engine;

first pilot operated control valve means connected at the input side thereof to said first pump, the output side thereof being selectively connected to said hydraulic actuator and a drain;

second pilot operated control valve means connected at the input side thereof to said second pump, the output side thereof being selectively connected to said hydraulic actuator and a drain wherein said second pilot operated control valve means is actuated by a lower pilot pressure than said first pilot operated control valve means; and

third control valve means for pilot pressure connected at the input side thereof to said pilot pump, the output side thereof being connected to said first and second pilot operated control valve means for controlling the actuation thereof, such that, during full stroke operations, said first and second pilot operated control valve means are actuated by said third control valve means such that said hydraulic actuator is operated by hydraulic fluid from said first and second hydraulic pumps and during inching operations, only said second pilot operated control valve means is operated by said third control valve means such that said hydraulic actuator is operated by hydraulic fluid from only said second hydraulic pump, wherein each of said first and second pilot operated control valve means has two pilot ports formed therein one of which is connected to said third control valve means for pilot pressure through a first conduit, the other port being connected to said third control valve means for pilot pressure through a second conduit and wherein adjustable restrictor means is provided between said first and second conduits, said restrictor means being interlocked with lever means for operating said third control valve means for pilot pressure.

2. A control system for a hydraulic actuator as recited in claim 1 wherein said first pilot operated control valve means is spring centered type and has four positions formed therein and said second pilot operated control valve means is also spring centered type and has three positions formed therein.

3. A control system for a hydraulic actuator as recited in claim 1 further comprising another hydraulic actuator;

fourth pilot operated control valve means connected at the input side thereof to said second pump, the output side thereof being selectively connected to said another actuator and drain; and

fifth control valve means for pilot pressure connected at the input side thereof to said pilot pump, the output side thereof being connected to said fourth pilot operated control valve means.