Hydraulic circuitry for an excavator

• US 3,922,855 A
• Filed: 09/03/1974
• Issued: 12/02/1975
• Est. Priority Date: 12/13/1971
• Status: Expired due to Term

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Donald L. Hopkins, John W. Bridwell, Kenneth R. Lohbauer
• Inventors: Bridwell, John W., Hopkins, Donald L., Lohbauer, Kenneth R.
• Primary Examiner(s): Geoghegan, Edgar W.
• Application Number:
  US05/502,829
• Time in Patent Office: 455 Days
• Field of Search: 60/421,428,484,486 91/414 214/138R
• US Class Current: 60/421
• CPC Class Codes: B62D 11/183 Control systems therefor
• CPC Class Codes: E02F 3/42 Drives for dippers, buckets, dipper-arms or bucket-arms
• CPC Class Codes: E02F 9/2221 Control of flow rate; Load sensing arrangements E02F9/2203 take precedence over E02F9/2221
• CPC Class Codes: E02F 9/2239 using two or more pumps with cross-assistance
• CPC Class Codes: E02F 9/2282 Systems using center bypass type changeover valves
• CPC Class Codes: E02F 9/2292 Systems with two or more pumps
• CPC Class Codes: E02F 9/2296 Systems with a variable displacement pump
• CPC Class Codes: F15B 11/17 using two or more pumps
• CPC Class Codes: F15B 2211/3051 Cross-check valves
• CPC Class Codes: F15B 2211/30595 with additional valves between the groups of valves 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 2211/67 Methods for controlling pilot pressure
• CPC Class Codes: F15B 2211/7142 the output members being arranged in multiple groups
• CPC Class Codes: F15B 2211/78 Control of multiple output members

Abstract

A hydraulic circuit is provided for powering a wheel-type excavator with a plurality of pumps supplying pressurized fluid for the circuit. The circuit is arranged so that fluid is provided from a plurality of pumps in a sequence manner to permit maximum utilization of pump volume for translation of the machine. A unique sequence of the distributor valves also provides positive independent control of the various implement motors of the machine, with means provided so that fluid may also be combined to operate selected implement motors for faster operation and maximum efficiency of the machine.

Claims

1. A hydraulic circuit for a hydraulic excavator comprising:

a first and a second variable displacement pump for supplying pressurized fluid to said circuit;

a first series of series-connected distributor valves operatively connected for directing fluid from said first pump to a translation motor and to a first pair of implement control motors;

a second series of series-connected distributor valves operatively connected for directing fluid from said second pump to said translation motor and at least another implement control motor;

pilot control means for shifting said distributor valves for said translation motor in sequence;

said pilot control means including a source of pressurized pilot control fluid;

drive control means including pilot valve means operative to direct said pilot fluid for shifting said distributor valves controlling said translation motor and operative to vary the pressure of said pilot pressure over a wide range of pressures;

anD, the first of said distributor valves being operative to shift progressively over a first range of pilot fluid pressures and the second of said distributor valves being operative to progressively shift over a second range of pilot fluid pressures so that the first pump is operative to supply fluid for low speed operation and fluid from said second pump is added to said first pump fluid for high speed operation.

2. The hydraulic system of claim 1 wherein said drive control means comprises a first distributor valve for directing fluid from a first of said pumps to said translation motor;

a second distributor valve operative to direct fluid from a second of said pumps to said translation motor;

pilot control means for operating said distributor valves;

said pilot control means including a valve operative to provide a variable pilot pressure signal to said distributor valves;

said first distributor valve being responsive to a first range of pressures of said pilot signal; and

said second distributor valve being responsive to a second range of pressures of said pilot signal.

3. The hydraulic system of claim 2 wherein said drive control means includes a directional control valve for selecting the direction of shifting of said distributor valves.

4. The hydraulic system of claim 3 wherein said first distributor valve includes means for restrictively communicating fluid from both sides of said translation motor to the sump when said distributor valve is in a neutral position.

5. The hydraulic circuit of claim 1 including dual-pressure relief valve means having a first relief pressure when said translation motor is in operation, and a second relief pressure when said implement motors are in operation.

6. The hydraulic circuit of claim 4 wherein said circuit includes diverter valve means at the end of each of said series of distributors operative to direct fluid from downstream of each of said series to the last distributor in the other of said series.

7. The hydraulic circuit of claim 6 wherein said circuit includes a pair of distributor valves downstream from said diverter valves for directing fluid for operation of a pair of outrigger jacks.

8. The hydraulic circuit of claim 6 wherein said circuit includes a third pump and a distributor for separately supplying fluid for operation of a slewing motor for said excavator, and a pair of distributor valves downstream of said slewing distributor for directing fluid to a pair of outrigger jacks.

9. The hydraulic circuit of claim 6 wherein said circuit includes a dual relief valve assembly having a first relief valve operative when said translation motor is in operation, and a second relief valve operative when said translation motor is not in operation.

10. The hydraulic circuit of claim 9 wherein said relief valve assembly includes a shuttle valve that is responsive to said pilot valve means to bypass said second relief valve and said second relief valve has a lower relief setting than said first relief valve.

11. The hydraulic circuit of claim 9 wherein said first range of pilot fluid pressures is from 35 to 155 psi, and said second range of pilot fluid pressure is from 145 to 218 psi.

12. A hydraulic system for powering the translation motor and implements of an excavator having a boom, a stick, and a bucket supported on a rotatable platform, said system comprising:

a first and a second variable displacement pump driven by an internal combustion engine;

a single translation motor for propelling the vehicle;

a slew drive motor for controlling the movement of the platform;

a boom control motor;

a stick control motor;

a bucket control motor;

a first series of interrupted series-connected distributors connecting said first pump first to the translation motor and lastly to said stick control motor; and

a second series of interrupted series-connected distributors connecting the second pump first to the transLation motor, then to said bucket control motor, and lastly to said boom control motor;

the first distributor in each of said series being operated by single pilot control means operative to shift the first of said first distributors over a first range of pilot control pressure and to shift the second of said first distributors over a second range of pilot control pressure so that said translation motor operates from said first pump over said first range and from both pumps over said second range; and

the last distributor in at least one of said series being operative to combine fluid available from the other series for operation of its respective control motor.

13. The invention of claim 12 comprising a third pump and a distributor valve operative to direct fluid from said third pump to said slew control motor independent of said translation motor.

14. The invention of claim 13 wherein the slew control circuit is completely independent of the other circuits of said systems.

15. The hydraulic system of claim 13 including dual-pressure relief valve means having a first relief pressure when said translation motor is operating, and having a second relief pressure when said implement control motors are in operation.

16. The hydraulic system of claim 15 wherein said first range of pilot control pressure is from 35 to 155 psi and said second range of pilot control pressure is from 155 to 218 psi.