US3820257A

US3820257A - Self loading scraper hydraulic control system with automatic load relieving circuit

Info

Publication number: US3820257A
Application number: US00211218A
Authority: US
Inventors: J Junck; J Scheidt
Original assignee: J Junck; J Scheidt
Current assignee: Caterpillar Inc
Priority date: 1971-12-23
Filing date: 1971-12-23
Publication date: 1974-06-28
Anticipated expiration: 1991-06-28

Abstract

A hydraulic circuit is described for driving the bowl positioning and ejector mechanisms of an earth scraper vehicle, as well as for driving a scraper elevator mechanism at three different speeds. The circuit includes four hydraulic pumps driven by the scraper tractor engine providing sources of fluid pressure to operate the various mechanisms, and a composite control valve for selectively directing fluid pressure to each of the mechanisms when it is desired to actuate the same. A diverter valve is also provided for diverting from the elevator mechanism the fluid pressure of one of the pumps whenever the elevator is operating at its highest speed and either the bowl or ejector mechanism is actuated. The tractor engine is therefore not required to drive all four pumps against back pressure at the same time.

Description

United States Patent [191 Junck et al.

[ SELF-LOADING SCRAPER HYDRAULIC CONTROL SYSTEM WITH AUTOMATIC LOAD RELIEVING CIRCUIT 76] Inventors: John A. Junck, 904 Allan Dr.;

James E. Scheidt, 100 Olympia St., both of Joliet, 111. 60435 [22] Filed: Dec. 23, 1971 '[21] Appl. No.: 211,218

[52] US. Cl 37/8, 37/124, 91/412 [51] Int. CL... B60p 1/36 [58] Field of Search 37/8, 124; 91/411-414; 60/52 [56] References Cited, 4

UNITED STATES PATENTS 2,659,206 11/1953 Carlson 91/411 2,785,789 3/1957 Slomer 91/412 X 3,350,986 11/1967 Berta et al. 91/414 3,469,501 9/1969 Middleton 91/411 R 3,478,647 11/1969 Gerber et a1 91/414 X 3,486,418 12/1969 Cryder ct al. 91/411 R 3,535,877 10/1970 Becker et a1 91/412 X June 28, 1974 12/1970 Treichel 12/1970 Gardenhour Primary Examiner-Robert E. Pulfrey Assistant Examiner-Eugene H. Eickholt Attorney, Agent, or Firm-Phillips, Moore, Weissenberger, Lempio & Strabala I [57] ABSTRACT A hydraulic circuit is described for driving the bowl positioning and ejector mechanisms of an earth the same. A diverter valve is also provided for diverting from the elevator mechanism the fluid pressure of one of the pumps whenever the elevator is operating at its highest speed and either the bowl or ejector mechanism is actuated. The tractor engine is therefore not required to drive all four pumps against back pressure at the same time.

' 6 Claims, 1 Drawing Figure RESERVOIR PATENTEDJUH28 1914 3820.257

RESERVOIR INVENTORS JOHN A. JUNCK JAMES E. QCHYJDT 1 SELF-LOADING SCRAPER HYDRAULIC CONTROL SYSTEM WITH AUTOMATIC LOAD RELIEVING CIRCUIT BACKGROUND OF THE INVENTION The present invention relates to a fluid control system and, more particularly, to such a system which is especially adapted for preventing the overloading of a common power source for several independent fluid pumps of the system by the simultaneous application of load to the several pumps.

Fluid control systems, especially hydraulic control systems, are extensively used to control and operate mechanical equipment. For example, hydraulic control systems have been found to be particularly well suited for operating the major mechanical components of earth scraper vehicles. In this connection, a hydraulic system is often used to raise and lower theearth carrying bowl of such a scraperto adjust the depth in the earth of the cutting edge on the front of the bowl, and also to control and motivate the ejector mechanism for emptying the bowl. Some types of scrapers also have an elevator mechanism at the front of the bowl which is,

the bowl. Such elevator mechanisms are also most de-.

sirably driven by the hydraulic system of the scraper. One reason for this is that for high production work, a scraper elevator mechanism should have a number of different elevator drive speeds. Not only are different speeds desirable for loading different types of materials, but the provision of multiple speeds also allows the velocity of the individual flights of the elevator to be matched to the forward speed of the vehicle and the speed at which material is flowing over the scraper cutting edge.

It will be appreciated that for a hydraulic control system to be capable of operating the various components of an earth scraper, a'plurality of sources of hydraulic pressure, e.g., pumps, must be provided. On this connection, at least one pump must be provided for operating the hydrauilc jacks which raise and lower the bowl of the vehicle. Since the bowl is not normally being raised or lowered at the same time earth is being ejected from it, the pump used for controlling the bowl movement can also be used to control the ejector. However, since the bowl is often raised or lowered at the same time at which it is being filled, i.e., at the time at which the elevators are working, the one pump cannot as a practical matter be used to provide operation of the elevator mechanism as well unless the pump is made unusually large in capacityfl'hus, at least one separate pump is generally provided to drive the eleva tor motor. As mentioned before, though, it is desirable to be able to drive the elevator at different speeds. In order to provide the elevator with this versatility, additional pumps are required.

The operation of each of the various pumps of a scraper hydraulic control system against back pressure provided by a load on its driven mechanism requires a substantial amount of power. And for practical reasons, the power sources for the pumps is the tractor engine. When a plurality of pumps in a scraper control system are simultaneously required to provide pressure sources for the various operations of a scraper, the

' amount of power drained from the tractor engine can be so great as to deleteriously affect its operation. For

example, it has been found that when a scraper has a three speed elevator mechanism which is operating at its high speed and thus is consuming large amounts of power, and one attempts to operate either the ejector or bowl positioning mechanism by activating an addi tional pump, it is not unusual for the power drain on the engine to be so high that the engine is incapable of driving the wheels of the vehicle and stalling occurs. This has posed a major problem in the art in view of the im portance of being able to drive the elevator at least three different speeds to enable efficient operation of the scraper under various conditions, while yet not affecting the ability of the operator to also operate the bowl positioning and ejector mechanisms.

SUMMARY OF THE INVENTION The present invention is a fluid control system which can have more pumps or other sources of fluid pressure than are able to be simultaneously operated against back pressure by a common power source, and yet which assures that the common power source is not overloaded. The control system is designed for the operation of at least two fluid driven mechanisms and, in its basic aspects, includes two separate sources of fluid pressure each associated with a corresponding one of the fluid driven mechanisms. Means, such as a pressure line and a control valve, are provided for directing fluid pressure from a first one of the sources to its associated fluid driven mechanism, and a valve is actuatable to selectively direct fluid pressure from the second source to its associated driven mechanism.

As a particular salient feature of the invention, the combination includes a diverter means which is responsive to the actuation of the valve between the second source and its associated fluid mechanism to automatically relieve any back pressure which is caused on the first source of fluid pressure by its associated fluid driven mechanism. The provision of such diverter means enables the fluid control system of the invention to be used to automatically assure that the system does not overload a common source of power for its various sources of fluid pressure. It does this by relieving the back pressure on a first one of the sources or pumps whenever back pressure is applied to the other so that the common power source is not subjected to the combined back pressure on both pumps at the same time.

The fluid system of the invention has been found to be most advantageous when combined with a scraper vehicle. In such a combination it enables the use of a three speed elevator mechanism while yet assuring that the high speed operation of the same will not cause the vehicle engine to stall. For example, when the fluid control system for the various mechanical components of the scraper has at least four different pumps, one for selective operation of the bowl positioning or ejector mechanism, and three to provide the three different speeds for the elevator mechanism, the invention can be combined with the same to release the back pressure on one of the three elevator pumps whenever the pump for the bowl positioning and ejector mechanisms has back pressure applied against it. That is, when the elevator mechanism is operating at high speed with all three elevator motor pumps working against pressure, upon the bowl positioning or ejector mechanism being activated, one of the elevator pumps is relieved of its The invention includes other features and advantages which become apparent from the following detailed detaile description.

BRIEF DESCRIPTION OF THE DRAWING The single FIGURE of the accompanying sheet of drawing is a schematic illustration of a preferred embodiment of a scraper hydraulic control system of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to the drawing, a valve body 11 is provided housing together a bowl control valve 12, an ejector control valve 13, and a multiple speed elevator control valve 14. The bowl and ejector control valves 12 and 13 act as means for delivering fluid pressure from a source of fluid pressure to bowl positioning hydraulic jacks 16 and an ejector hydrauic jack 17, respectively. More particularly, a source of fluid pressure in the form of a pump 18 delivers fluid pressure from a reservoir 19 via conduit 21 to an inlet 22 for the valve body. When the valve spools 23, 24, and 26 of the bowl, ejector, and elevator valves, respectively, are in the neutral positions illustrated, fluid flowing into valve body 11 via inlet 22 passes successively through

port chambers

27, 28, and 29 to an outlet passage chamber 31 in the valve body. Fluid in passage 31 flows through a valve body outlet 32 for return to the reservoir 19 via

conduits

33 and 34. I v

The bowl of the scraper is either raised or lowered by translationally moving the spool 23 of the bowl control valve to the R or L positions to communicate the fluid pressure of pump 18 with the raising and lowering jacks 16 via

conduits

36 and 37, respectively.

Such conduits

36 and 37 act in the alternative as return con.- duits for hydraulic fluid forced out of the. bowl jacks 16. The exhausted fluid is passed through the valve body and ultimately to the reservoir 19 through outlet passage chamber 31, outlet 32, and

conduits

33, 34.

Hydraulic pressure from pump 18 can also be communicated via the ejector control valve 24 with the ejector jack '17 to cause operation of the ejector. More particularly, fluid pressure in port chamber 28 from pump 18 is made to communicate with either the upperor lower portion of jack 17 through

conduits

38 or 36 respectively, by properly positioning the ejector valve spool 24 in the R" and E positions. Each of the

conduits

36 and 38 aso acts as a return path for fluid exhausted from the ejector jack 17 when it is evacuated.

Further details of the operation of the bowl position control and ejector control circuits will not be included as they are conventional and do not comprise any portion of the present invention except insofar as they represent means for providing a back pressure on the pump 18 whenever the bowl or ejector is energized.

More complete details on the operation of similar bowl and ejector control circuits may be obtained from US. Pat. No. 3,258,926 issued July 5, 1966 for Hydraulic Control Circuit for Self-Loading Scrapers.

The elevator control mechanism of this preferred embodiment is adapted to drive the elevator at three different speeds. For this purpose, the control system of the invention includes three separate pumps for delivering to the elevator motor three different fluid pressures for providing the various speeds. However, in

keeping with the invention, diverter means are pro-- vided for diverting to the reservoir 19 pressure from one of such pumps when either of the valves 12 or 13 are actuated to operate the bowl or ejector and, thus, provide a back pressure on Pump 18.

A multiple speed hydraulic motor for driving the elevator at the desired three different speeds is diagramatically depicted at 41. Motor 41 is selectively driven by one or more of the hydraulic pumps 42, 43, and 44. That is, motor 41 is in a hydraulic circuit with the reservoir 19 and each of the pumps 42-44 in such a manner that the elevator control valve 14 can selectively control the application to the motor of the fluid pressure provided by one or more of the pumps.

When the spool 26 of the elevator control valve 14 is in the neutral or N position shown, each of the pumps 42 -44 communicates with the reservoir, and does not drive the elevator. That is, the pump 42 draws fluid through conduit 46 from the reservoir 19 and delivers the same to the control valve via conduit 47. The conduit 47 communicates with an annulus 48 about spool 26 in the control valve 14, and when the spool is in the neutral position, annulus 48 communicates via bore portion 49 with the outlet passage 31. Thus, with the spool 26 in the neutral position, fluid from pump 42 passes through the control valve 14 and is exhausted via conduits 33and 34 back to the reservoir.

Pump 43 draws fluid through conduit 51 from reservoir 19 and delivers the same when the spool is in the neutralposition through

conduits

52 and 53 to control valve 14. Such fluid flows through an annulus 54 to a bore portion 56 in the control valve for communication with the passage 31, and thence, communicates back with the reservoir 19 through

conduits

33 and 34.

Pumpj44 draws fluid from reservoir 19 through conduit 57 and delivers the same to a diverter valve 58 which will be described in more detail hereinafter. When the piston or spool 59 of the diverter valve is in the position illustrated, the fluid from pump 44 is directed by the valve through a conduit 61 which communicates with the conduit 33 for exhausting the fluid back to reservoir 19.

By appropriatelypositioning spool 26 of elevator control valve 14, the elevator motor 41 can be selectively driven at low, intermediate and high speeds. For low speed operation, the control spool is moved' to the left as viewed in the FIGURE to cause land 62 on spool linkage not shown, the elevator itself to move at a first, low speed.

When it is desired to drive the elevator at an intermediate speed, the spool 26 is moved to the right to the M position to drive the motor 41 with the combined fluid pressure of pumps 42 and 43. More particularly, upon the spool being moved to the M position, the land 67 on the spool will block communication between annulus 54 and the bore portion 56 while the land 68 will simultaneously block communication between the bore portion 49 and the passage 31. When communication between the annulus 54 and the bore portion 56 is thus blocked, fluid from pump 43 can no longer flow through the control valve for return to the reservoir and hence is forced through a check valve 69 to the conduit 64 for driving motor 41. At the same time, fluid flow from pump 42, also cannot pass through the controlvalve in view of the blockage of bore portion 49 by land 68 so that the fluid from such pump is also forced into conduit 64 for driving motor 41. Thus motor 41 is driven by the combined fluid pressure or flow from both pumps 42-and 43 and is driven at an intermediate speed faster than the slow speed at which it was driven when communicated only with the fluid flow from pump 42.

For high speed operation, the elevator motor 41 is driven not only by fluid flow from pumps 42 and 43 but also by the fluid flow from pump 44. More particularly, spool 26 is moved further to the right as viewed in the drawing to the H position where the lands 68 and 67 continue to block respectively the

bore portions

49 and 56. In such position, however, an internal bore 71 in spool 26 is additionally communicated with the fluid pressure in annulus 54 and transmits the same to an annulus 72 circumferentially surrounding land 73 of the spool. Annulus 72 is in communication via a small diameter bore 74 in the valve body with a conduit 76 having a similar small diameter. As is illustrated, conduit 76 communicates through one end of the body of diverter valve 58 with the end face of a reduced diameter portion 77 of diverter valve spool 59.

When the spool 26 is in the H" position and the fluid pressure of pump 43 is therefore applied to the end face of reduced diameter portion 77 of spool 59, such pressure is sufficient to move piston spool 59 against the force of compression spring 78 to a far right location within the diverter valve 58. With the spool at such location, land 79 thereof blocks flow of fluid from pump 44 into exhaust conduit 61, while at the same time land 81 thereof is moved free of the inlet to a conduit 82. Thus, flow from pump 44 is directed into conduit 82 rather than conduit 61. Conduit 82 is in communication with conduit 47 so that upon the spool 26 being moved to the 11" position, the fluid from pump 44 is combined with the flow of pump 42 through the elevator motor 41. The result is that motor 41 is simultaneously driven by the combined flow of all three pumps and is therefore driven at a speed higher than either the low or intermediate speeds described above.

Means are provided for protecting the elevator motor and elevator mechanism from damageif for some reason the load on the elevator should become too high. More particularly a conduit 86 is provided connecting conduits 64 and 66 at a location bypassing motor 41. A pressure relief valve 87 in conduit 86 is designed to permit flow directly between conduits 64 and 66 with out passage through motor 41 if the pressure in conduit 64 and, hence on motor 41, should become greater than a predetermined, safe value.

As has been mentioned previously, the four pumps 18, 42, 43 and 44 are all driven by the engine of the scraper tractor. However, each pump presents a substantial load to the engine when such pump is operating its associated mechanism. That is, when any one of the described scraper mechanisms is calling on a pump for fluid flow or pressure, the mechanism applies a back pressure to the pump resisting the driving of the pump by the engine. In fact, even though the tractor engine of a scraper is quite powerful, such an engine is often incapable of driving all four pumps of the described hydraulic circuit simultaneously against back pressure, as well as drive the wheels of the vehicle and other power requiring components of the vehicle, such as a hydraulic steering mechanism.

As a particularly salient feature of the invention, therefore, means are included for automatically relieving the back pressure on one of the pumps when the back pressure on another is increased due to activation of its associated driven mechanism. In the particular embodiment being described, this is accomplished by assuring that the flow from one of the elevator drive motors is prevented from being directed to the elevator motor whenever the pump 18 is subjected to a back pressure because of the operation of either the bowl or ejector mechanism.

More particularly, it will be noted that the end face of the land 81 on the piston spool 59 of diverter valve 58 is in communication via a conduit 83 with the conduit 21 leading from pump 18. Whenever pump 18 is operating against pressure provided by either the bowl or ejector, the end face of piston spool 50 adjacent the land 81 is subjected to such pressure via conduit 83. Because the end face of the piston spool subjected to this pressure has a greater surface area than the end face of reduced diameter portion 77 of the spool, the pressure from pump 18, with the aid of compression spring 78, will positively position the position spool 59 in the far left position illustrated. Upon the spool being so positioned, fluid flow from pump 44 is directed into the reservoir l9 via

conduits

61 and 34, rather than to the elevator motor 41 through conduits 82, 47 and 64.

The result is that when the elevator is being run at high speed, i.e., the output of pump 44 is being used to aid in driving the motor, and either the ejector or the bow] mechanism is activated, the fluid from pump 44 will be diverted to resevoir 19 and, hence, the back pressure on such pump will be relieved. in such circumstance the elevator motor will be driven at the intermediate speed provided by the combined outputs of pumps 42 and 43, rather than at the high speed provided by the combined outputs of all three pumps. Thus, at the same time the tractor engine must provide the power necessary to drive the bowl or ejector mechanisms, the elevator can only be driven at intermediate speed and the control system of the invention will assure that the tractor engine is not forced to drive all four pumps against back pressure at the same time.

As another particularly salient feature of the invention, the diverter valve automatically restores the application of the fluid pressure from pump 44 to the elevator motor 41 after back pressure on the pump 18 is relieved by the de-actuation of the mechanism responsirelease of pressure through conduit 83 on the larger end face of the piston spool 59, the pressure applied to the smaller end face through conduit 76 can again move the spool 59 to the right to direct the flow from the pump 44 to the elevator motor. This will result in the motor again being driven at its fastest speed. It should be noted that no special manipulation by the operator of the vehicle is required to cause restoring of the faster speed, other than the de-actuation of the bowl or ejector mechanism producing the back pressure on pump 18.

It will be appreciated that not only will the mechanism of the inventioncause reduction of the elevator motor from its high speed to its intermediate speed whenever either the bowl or ejector is actuated, it will also prevent the elevator motor from being actuated from its intermediate to its high speed mode whenever the ejector or bowl is being operated. That is, when the elevator motor is operating at, for example, its interme-' diate speed and the piston spool 59 of diverter valve 58 is in the left hand position illustrated, back pressure communicated to the piston spool through conduit 83 by operation'of either the bowl or'ejector will prevent the spool from moving to the right to effect operation of the elevator motor at its high speed.

While the invention has been described with respect to a preferred embodiment thereof, it will be apparent to those skilled in the art that various changes can be made without departing from its scope. Therefore, it is intended that the scope of coverage afforded the invention be limited only by the claims.

What is claimed is:

l. A fluid control system for a selfloading earth scraper vehicle having at least a fluid operated jack for selectively raising and'lowering the earth carrying bowl thereof and a fluid motor for controlling the speed of operation of a bowl filling elevator mechanism; said control system including a fluid reservoir and further including a first source of fluid pressure communicable with said motor for driving said elevator mechanism at a first speed, a second source of fluid pressure communicable through a control valve with said jack for selectively raising and lowering said bowl, and a diverter valve for diverting fluid back to said reservoir, said diverter valve being responsive to back pressure on said second source of fluid pressure caused by operation of 7 first source caused by said elevator motor.

2. The fluid control system of claim 1 wherein said diverter valve is responsive to therelief of back pressure on said second source of fluid pressure by restoring back pressure on said first source caused by said elevator motor.

3. The fluid control system of claim 1 wherein said diverter valve relieves back pressure on said first source caused by said fluid motor by diverting flow of fluid pressure from said first source to a fluid reservoir.

4. The fluid control system of claim 3 wherein said fluid motor is a multiple speed motor for operation of said elevator mechanism at different speeds and a third separate source of fluid pressure is communicable with said fluid motor, both said first and third sources being communicablewith said motor by way of a control valve movable between a position at which one of said first and third sources is in communication with said fluid motor for driving the same at a first speed and a second position at which both of said first and third sources are in communication'with said fluid motor for driving the same at a second, faster speed; said diverter valve diverting only the fluid from said first source of fluid pressure when said motor control valve is in said second position whereby said motor remains subjected to the fluid pressure from said third source for driving at said first speed upon sensing by said diverter valve of back pressure on said second source of fluid pressure caused by operation of its associated jack.

5. The fluid control system of claim 4 wherein said first, second, and third sources of fluid pressure are hydraulic pumps all of which are driven by the tractor engine of said scraper, said diverter valve assuring that said tractor engine is freed from having to drive all three of said pumps against back pressure provided by their associated driven mechanisms at the same time.

6. The fluid control system of claim 5 wherein a fourth source of hydraulic pressure is selectively communicable with said fluid motor by way of said motor control valve for the combination of its pressure with one of said first and third sources for drivingsaid motor and, hence, said elevator mechanism at a third, intermediate speed.

Claims

1. A fluid control system for a selfloading earth scraper vehicle having at least a fluid operated jack for selectively raising and lowering the eaRth carrying bowl thereof and a fluid motor for controlling the speed of operation of a bowl filling elevator mechanism; said control system including a fluid reservoir and further including a first source of fluid pressure communicable with said motor for driving said elevator mechanism at a first speed, a second source of fluid pressure communicable through a control valve with said jack for selectively raising and lowering said bowl, and a diverter valve for diverting fluid back to said reservoir, said diverter valve being responsive to back pressure on said second source of fluid pressure caused by operation of its associated jack by relieving back pressure on said first source caused by said elevator motor.

2. The fluid control system of claim 1 wherein said diverter valve is responsive to the relief of back pressure on said second source of fluid pressure by restoring back pressure on said first source caused by said elevator motor.

4. The fluid control system of claim 3 wherein said fluid motor is a multiple speed motor for operation of said elevator mechanism at different speeds and a third separate source of fluid pressure is communicable with said fluid motor, both said first and third sources being communicable with said motor by way of a control valve movable between a position at which one of said first and third sources is in communication with said fluid motor for driving the same at a first speed and a second position at which both of said first and third sources are in communication with said fluid motor for driving the same at a second, faster speed; said diverter valve diverting only the fluid from said first source of fluid pressure when said motor control valve is in said second position whereby said motor remains subjected to the fluid pressure from said third source for driving at said first speed upon sensing by said diverter valve of back pressure on said second source of fluid pressure caused by operation of its associated jack.

6. The fluid control system of claim 5 wherein a fourth source of hydraulic pressure is selectively communicable with said fluid motor by way of said motor control valve for the combination of its pressure with one of said first and third sources for driving said motor and, hence, said elevator mechanism at a third, intermediate speed.