CA1274748A - Balanced hydraulic propulsion system - Google Patents

Balanced hydraulic propulsion system

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Publication number
CA1274748A
CA1274748A CA000557948A CA557948A CA1274748A CA 1274748 A CA1274748 A CA 1274748A CA 000557948 A CA000557948 A CA 000557948A CA 557948 A CA557948 A CA 557948A CA 1274748 A CA1274748 A CA 1274748A
Authority
CA
Canada
Prior art keywords
hydraulic
valve assembly
hydraulic fluid
compensating valve
pressurized
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related
Application number
CA000557948A
Other languages
French (fr)
Inventor
Steven Harold Johnson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Deere and Co
Original Assignee
Deere and Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Deere and Co filed Critical Deere and Co
Application granted granted Critical
Publication of CA1274748A publication Critical patent/CA1274748A/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

Links

Classifications

    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20—Drives; Control devices
    • E02F9/22—Hydraulic or pneumatic drives
    • E02F9/2253—Controlling the travelling speed of vehicles, e.g. adjusting travelling speed according to implement loads, control of hydrostatic transmission
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
    • F15B11/02—Systems essentially incorporating special features for controlling the speed or actuating force of an output member
    • F15B11/04—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the speed
    • F15B11/044—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the speed by means in the return line, i.e. "meter out"
    • F15B11/0445—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the speed by means in the return line, i.e. "meter out" with counterbalance valves, e.g. to prevent overrunning or for braking
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
    • F15B11/16—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
    • F15B11/16—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors
    • F15B11/22—Synchronisation of the movement of two or more servomotors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B13/00—Details of servomotor systems ; Valves for servomotor systems
    • F15B13/02—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors
    • F15B13/022—Flow-dividers; Priority valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/305—Directional control characterised by the type of valves
    • F15B2211/30525—Directional control valves, e.g. 4/3-directional control valve
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/305—Directional control characterised by the type of valves
    • F15B2211/3056—Assemblies of multiple valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/50—Pressure control
    • F15B2211/505—Pressure control characterised by the type of pressure control means
    • F15B2211/50509—Pressure control characterised by the type of pressure control means the pressure control means controlling a pressure upstream of the pressure control means
    • F15B2211/50545—Pressure control characterised by the type of pressure control means the pressure control means controlling a pressure upstream of the pressure control means using braking valves to maintain a back pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/605—Load sensing circuits
    • F15B2211/6051—Load sensing circuits having valve means between output member and the load sensing circuit
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/705—Output members, e.g. hydraulic motors or cylinders or control therefor characterised by the type of output members or actuators
    • F15B2211/7058—Rotary output members
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/71—Multiple output members, e.g. multiple hydraulic motors or cylinders
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/78—Control of multiple output members
    • F15B2211/782—Concurrent control, e.g. synchronisation of two or more actuators

Landscapes

  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • Mining & Mineral Resources (AREA)
  • Civil Engineering (AREA)
  • Structural Engineering (AREA)
  • Fluid-Pressure Circuits (AREA)
  • Operation Control Of Excavators (AREA)
  • Non-Deflectable Wheels, Steering Of Trailers, Or Other Steering (AREA)

Abstract

BALANCED HYDRAULIC PROPULSION SYSTEM
Abstract of the Disclosure A large industrial earthmoving machine having a hydraulic propulsion system comprising at least two hydraulic motors which are powered from a source of hydraulic fluid to drive a common load. Each motor of the hydraulic propulsion system is provided with two compensating valve assemblies. Each compensating valve assembly is provided with a compensating spool and a shuttle spool to provide accurate control of the hydraulic motors. In each pair of compensating valve assemblies, there is a forward compensating valve assembly and a backward valve assembly respectively controlling forward and backward movement of the hydraulic motor. Between the both forward compensating valve assemblies and the respective hydraulic motors, the compensating valve assemblies are fluidically coupled to one another by a small hydraulic communication line that better equalizes hydraulic fluid flow to the motors and prevents domination of one forward compensating valve assembly over the other.
Similarly, the backward compensating valve assemblies are provided with an identical small hydraulic communication line accomplising the same results.

Description

~74~

BALF~NCED HYDRAULI C PROPULS ION S YSTEM
B k~round of the Inventio 1. Field of the Invention:
The invention is directed to a hydraulic propulsion system for a large industrial machine such as an excavator. The machine having at least two hydraulic propulsion motors which are driven from the same source of hydraulic pressure.
2. Description of the Prior Art:
Large industrial machines are propelled many times by 1~ hydraulic motors. Typically, such machines are provided with internal combustion engines that are used to drive hydraulic pumps. The hydraulic pumps draw hydraulic fluid from a sump and pump the hydraulic fluid into hydraulic lines where it is directed tG the propulsion motors and other operating members.
Individual three-position directional control valves are used to control the flow of hydraulic fluid to each of the mo~ors, thereby controlling the propulsion motors and other hydraulic motor6 used for driving the operating members.
In simple hydraulic systems, hydraulic fluid takes the path 20 of least resista~ce and flows to the area requiring the lowest pressure. This is especially troublesome wherein two hydraulic motors are being used to move a common load, for example two crawler tracks of a crawler excavator, because the low pressure motor will command more hydraulic fluid resulting in an uneven operation of the two motors. To overcome this natural tendency of the hydraulic fluid, compensator valve assemblies are provided to better balance the flow between the two motors by having the high pressure compensator valve assembly meter the low pressure side to even the pressure between the two assemblies.
Although c~mpensator systems work well in most instances, another problem develops when the loads are equal or close to being equal. This situation is noticeable when a crawler operator wants to go in a straight line wherein the tracks need to move equally to accomplish this task. The crawler operator would notice that the crawler would tend to turn to one side or the other as it moves. Therefore, the operator has to continually adjust for this turning movement in the crawler.
This situation arises because one of the compensator valve assemblies is dominating the other compensator valve assemb 1 efectively reducing flow tllrough one of the hydraulic motors.
This typically happens because the directional control valves are never opened simultaneously and the directional control valve that is opened irst creates a dominating compensator valve assembly as it becomes the high pressure compensator valve. The compensator valve assembly associated with the latter opening directional control valve becomes dominated by earlier opening and now high pressure compensator valve assembly and tends to reduce flow to the hydraulic motor to which it is associated. Therefore, the hydraulic motor associated with the firs~ opening directional control valve moves faster than the motor associated with the latter opening directional control valve resulting in a ~urning movement by the crawler.
Summary of the Invention The present invention is designed to overcome this problem with compensator valve assemblies by providing a small communication hydraulic line between the downstream hydraulic paths of the two compensator valve assemblies~ A source of hydraulic fluid supplies hydraulic fluid to two directional control valves each of which direct pressurized hydraulic fluid to a pair of downstream compensator valve as~emblies. Each pair of compensator valve assemblies is provided with a forward compensator valve assembly for controlling forward movement of the crawler and a backward compensator valve assembly for controlling the backward movement of the crawler. The position of the directional control valve determines which one of the compensator valve assemblies in each pair of compensator valves the hydraulic fluid is directed to, thereby controlling the movement of the crawler. Two small communLcation hydraulic lines are provided for transmitting hydraulic fluid between the two forward compensator valve assemblies and the two backward compensator valve assemblies.
~rief Descrintion of the Drawinas .~ ~
FIG. 1 is a side view of a crawler excavator.
FIG. 2 is a hydraulic schematic of a hydraulic propulsion system for an excavator crawler without the small communication line.
FIG~ 3 is a hydraulic schematic of a hydraulic propulsion system for an excavator crawler with the small communication line.

.

1Detailed Descrlption FIG. 1 illustrates an excavator crawler to which the present hydraulic propulsion is particularly well suited. Excavator 10 is provided with a movable boom 12, dipper 14 and bucket 16.
The boom, dipper and bucket are controlled by linear hydraulic motors 18, 20, and 22, respectively. Excavator crawler 10 is a self-propelled excavator being supported on two ground engaging tracks 24 ~only one shown) which are used to drive and position the excavator at a work site, 10The tracks are independently driven by rotary hydraulic motors 26 and 28 which are coupled through compensator valve assemblies 30, 32, 34 and 36 to directional control valves 38 and 40. ~ydraulic fluid is pumped to the directional control valves 38 and 40 from 8ump 42 by hydraulic pump 44. The hydraulic pump is driven by an internal combustion engine mounted in the excavator. The operator in cab 46 can move or position the excavator by manipulating the directional control valves to propel the excavator forward or backward, or turning the e~cavator by operating hydraulic motors 26 and 28 in different directions.
It should be noted that although the invention is being described with regards to an excavator crawler propulsion ~ystem, the present invention could be utilized in a number of hydraulic applications wherein two independently controlled hydraulic motors drive a common load from a single source of pressurized hydraulic fluid.
FIG. 2 is the hydraulic schematic of the hydraulic propulsion system without the small balancing communication line between the downstream output of the compensator valve assemblies. Each compensator valve assembly is provided with a metering compensator spool 48, 50, 52 and 54, a shuttle spool 56, 58, 60 and 62, and a return flow check valve 64, 66, 68 and 70. For forwardly driving motor 26 hydraulic pump 44 pumps hydraulic fluid into hydraulic pumping line 72 to directional control valve 38. The directional control valve 38 directs the fluid to forward compensator valve assembly 30 and specifically to metering two-position compensator ~pool 48 having a restricted orifice position and a checked position. SPOG1 48 is spring biased into a closed position by spring 74 which is overcome by hydraulic pressure in sensing line 76 which pushes 74~

1 the valve into the open position. Hydraulic pressure Erom line 72 is also directed through hydraulic line 77 to shuttle spool 56 into compensation communication line 78. Shuttle spool 56 is hydraulically balanced by the hydraulic pressure in line 78 and the pressure downstream of compensator spool 48 as transmitted through line 80. The hydraulic fluid in line 80 is used both for balancing spool 56 and for flowing thrvugh spool 56 to line 82 to ~alance spool 48 by adding to the biasing force of spring ~ .
10Hydraulic fluid passing through valve 48 into line B4 i5 directed to motor 26 driving one of the crawler tracks of ~he excavator. The exhausted hydraulic fluid then passes into line 86 where it is directed to backward compensator valve assembly 32. As shuttle spool 58 is shifted into the closed position by the hydraulic pressure in compensator communication line 78, and : spool 50 is closed by the biasing force of spring 88 and the hydraulic pressure in line 90 which i5 fluidically coupled to compensator communication line 78 by the closed position of spool 58; the exhausted fluid passes through check valve 66 and into exhaust hydraulic line 92 wherein it is directed into sump 42, Hydraulic fluid does not pass through check valve 64 of compensator valve assembly 30 because of the pressure drop across the restricted orifice of spool 480 In FIG. 2, both motors are being driven in the same forward direction as determined by directional control valves 38 and 40. However, compensator valve assembly 30 has become dominant, either because it was triggered first by the operator or because of shorter hydraulic line connections when compared with compensator valve assembly 34. Compensator valve assembly 34 works in an identical manner to that of compensator valve assembly 30 except that because of the hydraulic pressure in compensation communication line 78 shuttle spool 60 tends to be biased into a closed position which in turn directs hydraulic pressure from line 78 through shuttle spool 60 and hydraulic line 94 to aid spring 96 in biasing compensator spool 52 closed.
It should be noted that the shuttle and compensating spools are two-position metering spools which are hydraulically balanced. As such, the spools are reciprocated between the each of the two positions during operation and they do not normally 4 _ ~2~7~13 1 maintain a fixed position. There~ore ;n viewing FIG. 2, it should be noted that dominatiny compensa~ g spool 48 in compensating valve assembly 30 is opened and transmits more hydraulic fluid because of its higher pressure, if it is the dominating valve assembly, and compensating spool 52, of compensating valve assembly 34 transmits less hydraulic fluid because of its lower hYdraulic pressure when compared to dominating compensating valve assembly 30.
As with compensating valve assemblies 30 and 32, hydraulic fluid from pump ~4 flows through pumping line 72 to directional control valve 40 where it is transmitted to compensating spool 52. ~ydraulic fluid passes through the restricted orifice in compensating spool 52 and is directed to pump 28 from which it is exhausted to compensating valve assembly 36. As with lS compensating valve assembly 32, hydraulic fluid is prevented from passing through compensating spool 54 and instead passes through check valve 70 and back to sump 42. The balancing hydraulic lines for all of the compensating-spools and shuttles spools of compensating valve assemblies 32, 34 and 36 are identical to those explained with regards to compensating valve assembly 30 and function in the same manner.
If the excavator crawler is to be reversed, directional control valves 38 and 40 are moved to the left to direct pumping fluid to backward compensating valve assemblies 32 and 36. In this situation, the pumps exhaust hydraulic fluid through check valves 64 and 68, respectively. ~o pivot the machine, one hydraulic motor is operated in the forward direction and the other in a reverse direction. The excavator itself can be pivoted on the tracks which means that since the hydraulic motors are adjacent to the tracks, the hydraulic lines leading from the pump to the motors must pass through a hydraulic line swivel (not shown) which is well known ln the art.
FIG. 3 illustrates the small communication hydraulic lines used for overcoming the problem illustrated in FIG. 2.
Hydraulic lines 98 and 100 fluidically couple hydraulic line 84 to line 102, and line 86 to line 104, respectively. When the excavator crawler is moving forward, line 98 tends to equalize the hydraulic pressure between compensating valve assembly 30 and compensating valve assembly 34. As compensating valve assembly 30 tries to dominate valve assembly 34, hydraulic fluid l pressure increases in line 84 increasing the pressure in line 98 and line 102 which in turn increases pressure in line 106 causing metering shuttle spool 60 to remain open for transmitting pre~sure through line 108 ~o help bias compensating spool 52 open, and better equalizing the hydraulic flow to both motors During forward movement, exhaust lines 86 and 104 are joined by line lO0, but this does not effect the operation of the system because the hydraulic pressure in compensating li~e 78 serves to maintain compensating valve assemblies 32 and 36 closed except for the normal exhaust flow through check valves 66 and 70.
In reversing the excavator crawler, communication line lO0 would prevent either compensating valve assembly 32 or 36 from dominating one another. As with the forward operation, exhaust lines 84 and 102, even through coupled through line 98, would ; not effect operation of the compensating valve assemblies.
To prevent inexact operation~, lines 98 and lO0 must be guite small when compared to hydraulic lines 84, 86~ 102 and 104 which are used to transfer hydraulic fluid to the pumps. For example, li~es 84, 86, 102 and 104 can be 0.75 inches in diameter and in accordance therewith communication lines 98 and lO0 should be 0.~5 inches in diameter. In addition, lines 98 and lO0 should be provided with an orifice further restricting flow. This orifice should be 0.004 inches in diameter to further reduce the cross flow between the pumping lines.
Compensating communication line 78 serves an additional function as indicated by arrow llO and that is to provide a pressure sensing circuit with a hydraulic feedback to better control the operation of the hydraulic pump.
The presen~ invention described above should not be limited by the above described embodiments, but should be limited solely by the claims that follow.

Claims (17)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A hydraulic system for operating a plurality of hydraulic motors from a source of hydraulic pressure, the system comprising:
a source of pressurized hydraulic fluid;
a first hydraulic motor;
a first compensating valve assembly fluidically coupled to the source of pressurized hydraulic fluid therefrom;
a first hydraulic line located between the first compensating valve assembly and the first hydraulic motor for directing pressurized hydraulic fluid from the first compensating valve assembly to the first hydraulic motor;
a second hydraulic motor;
a second compensating valve assembly fluidically coupled to the source of pressurized hydraulic fluid for receiving pressurized hydraulic fluid therefrom;
a second hydraulic line located between the second compensating valve assembly and the second hydraulic motor for directing pressurized hydraulic fluid from the second compensating valve assembly to the second hydraulic motor;
a communication hydraulic line fluidically coupling the first hydraulic line to the second hydraulic line to better balance the flow of pressurized hydraulic fluid from the source of pressurized hydraulic fluid to the first and second hydraulic motors;
a third compensating valve assembly fluidically coupled to the source of pressurized hydraulic fluid for receiving pressurized hydraulic fluid therefrom;
a third hydraulic line located between the third compensating valve assembly and the first hydraulic motor for directing pressurized hydraulic fluid from the third compensating valve assembly to the first hydraulic motor;
a fourth compensating valve assembly fluidically coupled to the source of pressurized hydraulic fluid for receiving pressurized hydraulic fluid therefrom;
a fourth hydraulic line located between the fourth compensating valve assembly and the second hydraulic motor for directing pressurized hydraulic fluid from the fourth compensating valve assembly to the second hydraulic motor; and a second communication hydraulic line fluidically coupling the third hydraulic line to the fourth hydraulic line to better balance the flow of pressurized hydraulic fluid to the first and second hydraulic motors.
2. A hydraulic system as defined by claim 1 wherein the first, second, third and fourth compensating valve assemblies are respectively provided with a first, second, third and fourth bypass hydraulic lines which permit the return of hydraulic fluid from the first and second hydraulic motors to the source of pressurized hydraulic fluid, each of the bypass hydraulic lines are provided with at least one check valve which permits the flow of hydraulic fluid in only one direction, that is from the hydraulic motors to the source of pressurized hydraulic fluid.
3. A hydraulic system as defined by claim 2 further comprising first and second three-position directional control valves which are respectively positioned fluidically between the first and third, and second and fourth compensating valve assemblies and the source of pressurized fluid.
4. A hydraulic system as defined by claim 3 wherein each of the compensator valve assemblies are fluidically coupled to one another by a compensating communication hydraulic line.
5. A hydraulic system as defined by claim 4 wherein each compensator valve assembly is provided with a metering two-position compensator spool and a metering two-position shuttle spool.
6. A propulsion system for an industrial machine having a hydraulic system for operating a plurality of hydraulic propulsion motors for moving the machine, the machine comprising:
a source of pressurized fluid;
a first hydraulic propulsion motor operatively coupled to an operative member adapted and constructed to move the machine;

a first compensating valve assembly fluidically coupled to the source of pressurized hydraulic fluid for receiving pressurized hydraulic fluid therefrom;
a first hydraulic line located between the first compensating valve assembly and the first hydraulic motor for directing pressurized hydraulic fluid from the first compensating valve assembly to the first hydraulic motor;
a second hydraulic propulsion motor operatively coupled to an operative member adapted and constructed to move the machine;
a second compensating valve assembly fluidically coupled to the source of pressurized hydraulic fluid for receiving pressurized hydraulic fluid therefrom;
a second hydraulic line located between the second compensating valve assembly and the second hydraulic motor for directing pressurized hydraulic fluid from the second compensating valve assembly to the second hydraulic motor;
a communication hydraulic line fluidically coupling the first hydraulic line to the second hydraulic line to better balance the flow of pressurized hydraulic fluid from the source of pressurized hydraulic fluid to the first and second hydraulic motors;
a third compensating valve assembly fluidically coupled to the source of pressurized hydraulic fluid for receiving pressurized hydraulic fluid therefrom;
a third hydraulic line located between the third compensating valve assembly and the first hydraulic motor for directing pressurized hydraulic fluid from the third compensating valve assembly to the first hydraulic motor;
a fourth compensating valve assembly fluidically coupled to the source of pressurized hydraulic fluid for receiving pressurized hydraulic fluid therefrom;
a fourth hydraulic line located between the fourth compensating valve assembly and the second hydraulic motor for directing pressurized hydraulic fluid from the fourth compensating valve assembly to the second hydraulic motor; and a second communication hydraulic line fluidically coupling the third hydraulic line to the fourth hydraulic line to better balance the flow of pressurized hydraulic fluid to the first and second hydraulic motors.
7. A propulsion system as defined by claim 6 wherein the first, second, third and fourth compensating valve assemblies are respectively provided with a first, second, third and fourth bypass hydraulic lines which permit the return of hydraulic fluid from the first and second hydraulic motors to the source, of pressurized hydraulic fluid, each of the bypass hydraulic lines are provided with at least one check valve which permits the flow of hydraulic fluid in only direction, that is from the hydraulic motors to the source of pressurized hydraulic fluid.
8. A propulsion system as defined by claim 7 further comprising first and second three-position directional control valves which are respectively positioned fluidically between the first and third, and second and fourth compensating valve assemblies and the source of pressurized fluid.
9. A propulsion system as defined by claim 8 wherein each of the compensator valve assemblies are fluidically coupled to one another by a compensation communication hydraulic line.
10. A propulsion system as defined by claim 9 wherein each compensator valve assembly is provided with a metering two-position compensator spool and a metering two-position shuttle spool.
11. A self-propelled excavator having a hydraulic propulsion system, the excavator is provided with a frame on which is mounted a digging arm having a movable boom member, a movable dipper member and a movable bucket each of which are moved by independent linear hydraulic moors, the frame is also provided with ground engaging means for supporting the excavator and on which the excavator is propelled over the ground, the improvement comprising:
a source of pressurized hydraulic fluid;

a first hydraulic propulsion motor operatively coupled to the ground engaging means for propelling the excavator;
a first compensating valve assembly fluidically coupled to the source of pressurized hydraulic fluid for receiving pressurized hydraulic fluid therefrom;
a first hydraulic line located between the first compensating valve assembly and the first hydraulic motor for directing pressurized hydraulic fluid from the first compensating valve assembly to the first hydraulic motor;
a second hydraulic propulsion motor operatively coupled to the ground engaging means for propelling the excavator;
a second compensating valve assembly fluidically coupled to the source of pressurized hydraulic fluid for receiving pressurized hydraulic fluid therefrom;
a second hydraulic line located between the second compensating valve assembly and the second hydraulic motor for directing pressurized hydraulic fluid from the second compensating valve assembly to the second hydraulic motor;
a communication hydraulic line fluidically coupling the first hydraulic line to the second hydraulic line to better balance the flow of pressurized hydraulic fluid from the source of pressurized hydraulic fluid to the first and second hydraulic motors;
a third compensating valve assembly fluidically coupled to the source of pressurized hydraulic fluid for receiving pressurized hydraulic fluid therefrom;
a third hydraulic line located between the third compensating valve assembly and the first hydraulic motor for directing pressurized hydraulic fluid from the third compensating valve assembly to the first hydraulic motor;
a fourth compensating valve assembly fluidically coupled to the source of pressurized hydraulic fluid for receiving pressurized hydraulic fluid therefrom;
a fourth hydraulic line located between the fourth compensating valve assembly and the second hydraulic motor for directing pressurized hydraulic fluid from the fourth compensating valve assembly to the second hydraulic motor; and a second communication hydraulic line fluidically coupling the third hydraulic line to the fourth hydraulic line to better balance the flow of pressurized hydraulic fluid from the source of pressurized hydraulic fluid to the first and second hydraulic motors.
12. An excavator as defined by claim 11 wherein the first, second, third and fourth compensating valve assemblies are respectively provided with a first, second, third and fourth bypass hydraulic lines which permit the return of hydraulic fluid from the first and second hydraulic motors to the source of pressurized hydraulic fluid, each of the bypass hydraulic lines are provided with at least one check valve which permits the flow of hydraulic fluid in only one direction, that is from the hydraulic motors to the source of pressurized hydraulic fluid.
13. An excavator as defined by claim 12 further comprising first and second three-position directional control valves which are respectively positioned fluidically between the first and third, and second and fourth compensating valve assemblies and the source of pressurized fluid.
14. An excavator as defined by claim 13 wherein each of the compensator valve assemblies are fluidically coupled to one another by a compensation communication hydraulic line.
15. An excavator as defined by claim 14 wherein each compensator valve assembly is provided with a metering two-position compensator spool and a metering two-position shuttle spool.
16. An excavator as defined by claim 15 wherein all of the compensator spools are hydraulic balanced between the source of pressurized hydraulic fluid and the pressurized hydraulic fluid located in the respective hydraulic line of the respective compensator valve assembly as metered by the respective shuttle spool.
17. An excavator as defined by claim 12 wherein the cross sectional area of the first and second communication hydraulic lines are smaller than the cross sectional area of the first, second, third and fourth hydraulic lines.
CA000557948A 1987-02-19 1988-02-02 Balanced hydraulic propulsion system Expired - Fee Related CA1274748A (en)

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US1631887A 1987-02-19 1987-02-19
US016,318 1987-02-19

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JP (1) JP2604399B2 (en)
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Publication number Priority date Publication date Assignee Title
WO1990014519A1 (en) * 1989-05-24 1990-11-29 Kabushiki Kaisha Komatsu Seisakusho Hydraulic circuit apparatus
US5209063A (en) * 1989-05-24 1993-05-11 Kabushiki Kaisha Komatsu Seisakusho Hydraulic circuit utilizing a compensator pressure selecting value
US6715402B2 (en) * 2002-02-26 2004-04-06 Husco International, Inc. Hydraulic control circuit for operating a split actuator mechanical mechanism

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US2912131A (en) * 1957-10-01 1959-11-10 Demag Baggerfabrik Gmbh Hydraulically operated machines
FR1400491A (en) * 1964-04-14 1965-05-28 Auxitra Hydraulic distribution system for excavator
GB1035141A (en) * 1964-05-07 1966-07-06 Priestman Brothers Improvements relating to civil engineering machines
LU52175A1 (en) * 1965-10-21 1966-12-19
US3960284A (en) * 1972-10-02 1976-06-01 American Hoist & Derrick Company Hydraulic backhoe circuitry
JPS6244849Y2 (en) * 1981-02-02 1987-11-28
JPS5897030U (en) * 1981-12-24 1983-07-01 株式会社小松製作所 Hydraulic circuit for driving hydraulically driven vehicles
DE3525823A1 (en) * 1985-07-19 1987-01-29 Schmitz Soehne Gmbh Maschf Path-dependent synchronous pressure control for double-acting presses, in particular laminating presses

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JPS63215467A (en) 1988-09-07
JP2604399B2 (en) 1997-04-30
EP0279362B1 (en) 1990-12-05
EP0279362A1 (en) 1988-08-24
DE3861194D1 (en) 1991-01-17

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