US3526978A - Elevator motor reversing valve control system - Google Patents

Description

Sept. 8, 1970 I D. H. JORDAN 3,526,978

I ELEVATOR MOTOR REVERSING VALVE CONTROL SYSTEM Filed March 1, 1968 2 Sheets-Sheet 1 P 8, 1970 I D. H. JORDAN 3,526,978

ELEVATOR MOTOR REVERSING VALVE CONTROL SYSTEM Filed March 1, 1968 2 Sheets-sheet z Patented Sept. 8, 1970 3,526,978 ELEVATOR MOTOR REVERSING VALVE CONTROL SYSTEM David H. Jordan, Cedar Rapids, Iowa, assignor to Allis- Chalmers Manufacturing Company, Milwaukee, WIS.

Filed Mar. 1, 1968, Ser. No. 709,635 Int. Cl. B60p 1/36 U.S. Cl. 37-8 5 Claims ABSTRACT OF THE DISCLOSURE A control system for a hydraulic motor driving the elevating mechanism of a motor scraper which avoids excessive pressures when reversing the direction of operation. This is achieved by delaying the delivery of high pressure fluid to the motor for reverse operation thereof for a sufficient time to permit the elevating mechanism to substantially stop movement in its initial direction.

This invention relates to a control system for the hydraulic motor driving and elevating mechanism of an earth mover and more particularly relates to providing means in such control system for delaying the delivery of reverse direction pressure fluid to the hydaulic motor when it is desired to reverse the operation of the elevating mechanism.

Heretofore it has been possible to reverse the delivery of pressure fluid to the hydraulic motor driving the scraper elevating mechanism very quickly and this has resulted in excessive pressures in the hydraulic motor and associated hydraulic system components because the motor and elevating mechanism will continue to operate in the same direction that it was traveling initially due to the inertia of the elevating mechanism and its drive means. Accordingly, the present invention is concerned with the provision of means to permit the elevating mechanism to slow down to a substantial degree before subjecting the hydraulic motor to reverse pressure fluid flow.

It is a further object of this invention to provide means in the hydraulic control system for the hydraulic motor driving the elevating mechanism of an earthmover to prevent delivery of high pressure fluid to the hydraulic motor for a predetermined period of time during the condi1 tioning of the control system from one direction of operation to the other.

It is a further object of this invention to provide a control system of the type hereinbefore outlined wherein a plurality of manual control elements must beoperated by the earthmover operator in order to reverse the direction of the elevating mechanism.

It is a further object of this invention to provide means in the elevating mechanism control system which retards shifting movement of the reversing valve from one operating position to another.

These and other objects and advantages of this invention will be apparent to those familiar with the art when the following description is read in conjunction with the drawings in which:

FIG. 1 is a top view of an earthmover in which the present invention is incorporated; and

FIG. 2 is a schematic showing of the control system of the present invention with some parts shown in section.

Referring to FIG. 1, the earthmover 11 includes a twowheel tractor unit 13 articulatively connected on a vertical steering axis 14 to the draft frame 17 of a two-wheel scraper unit 16. The draft frame 17 has a pair of rearwardly extending legs 18, 19 pivotally connected on a transverse axis 20 to the side walls 21, 22 of the scraper unit 16. An elevating mechanism 23 is provided in the forward end of the scraper 16, the forward end of which is disposed above the cutting edge, not shown. The elevating mechanism 23 includes a frame 24 which extends upwardly and rearwardly and has rearwardly extending arms 26, 27 pivotally connected to side walls 21, 22, respectively, for vertical swinging movement about a trans- Verse axis 28. The elevating mechanism 23 also includes a conveyor 31 which includes a pair of chains 32, 33 and a plurality of transverse slats 34 secured to the chains. The endless conveyor 31 is driven by a hydraulic motor 36 through a speed reducer 37 and sprockets, not shown, engaging the chains 32, 33. A flywheel 35 is provided on the motor output shaft to minimize pressure rises in the motor when the conveyor encounters large objects such as boulders. A control system is provided for the hydraulic motor 36 which includes a delayed action reversing valve 41 having a shiftable flow control member 42 which is operated by an air actuator 43. Air is supplied from a suitable source such as storage tank 44 to the air actuator 43 through conduit 48 under the control of electrically operated valves in the form of solenoid valves 46, 47

A pair of motor conduits 51, 52 interconnect the reversing valve 41 and the hydraulic motor 36. Pressure fluid is supplied to the reversing valve by a hydraulic pump 53 through supply conduit 54. The pump 53 draws hydraulic fluid from reservoir 56 through its intake conduit 57 and an exhaust conduit 58 connects the reversing valve 41 to the reservoir 56.

The reversing valve 41 has only forward and reverse operating positions, and in order to stop operation of the elevating mechanism a dumping valve 61 is provided in a bypass passageway or conduit 62, extending between the supply conduit 54 and reservoir 56. The dumping valve 61 is operated by a pilot valve 66 in pilot conduit 68 which has a manually shiftable control member 67 disposed in a bore 81. The electric energy for operating solenoid valves 46, 47 is supplied by a battery 71 which is connected to the solenoid valves 46, 47 through circuits 72, 73, respectively. Operation of solenoid valve 46 is controlled by manually operable switch in circuit 72 and solenoid valve 47 is controlled by the manually operated pilot valve switch 74 in circuit 73. The switch lever 70' and valve element 67 constitute manual control members which are positioned on the tractor unit 13 at the operators station 75. The control system components within dash lines 63 are mounted on the tractor unit 13, the dumping valve 61 being in close proximity to the pump and reservoir to minimize circulating flow power loss.

Referring to FIG. 2 the operation of the control system for the hydraulic motor 36 will now be described. In the illustrated condition of the control system, the reversing valve 41 is in its forward operating position, in which the elevating motor 36 drives the elevating mechanism 23 in a direction to load the earthmover. In this forward condition, the hydraulic pump 53 delivers fluid" under pressure to motor conduit 51 by way of supply conduit 54 since the bypass passage 62 isblocked by the shiftable fluid flow control element 76 in dumping valve 61 which, as shown in FIG. 2, is in its closed position. The element 76 is prevented from shifting downwardly to its open position by the pressure fluid in chamber 77 which enters through orifice 78. Escape of fluid from chamber 77 is blocked by land 80 on spool member 67 of pilot valve 66. The switch 74 is open and thus the normally closed, electrically operated valve 47 is closed preventing air delivery to actuator 43 even if reversing switch 70 should be closed.

If the elevating mechanism becomes overloaded to such an extent that the fluid pressure in the hydraulic passage 54 becomes excessive, a pilot relief valve 79 interposed in a passage 90 interconnecting pilot passage 68 and bypass passageway 62 will open. Upon opening of the pilot relief valve 79, the pressure in chamber 77 will drop to such an extent that the flow control element 76 will move downwardly against the biasing action of spring 98 to its open position and relief flow from conduit 54 will pass to reservoir 56 through the bypass passageway 62. Thus the dumping valve 61 in conjunction with pilot relief valve 90 acts as a relief valve for pump 53.

On occasion, it is desirable to reverse the direction of the elevating mechanism 23. To achieve a reverse direction, the operator first moves the manual control member 67 upwardly to place the reduced diameter portion 82 in bridging relation to ports 83, 84, of pilot valve 66, thus opening the bypass passage 68 to reservoir. This will cause the chamber 77 to be placed at substantially reservoir pressure and the fluid delivery from the pump will pass back to the reservoir through the bypass passage 62 at a very low pressure. The pressure in the conduit 54 will not be suflicient to operate the motor 36 and thus the motor and the elevating mechanism will slow to a stop. The inertia of the elevating mechanism 23, flywheel 35 and speed reducer 37 will tend to prevent the motor 36 from coming to an instantaneous stop. The upward movement of the manual control member 67 to its open position will close the switch 74 in the circuit 73 thus energizing solenoid valve 47 causing its armature and flow control element 86 carried thereby to be moved from its illustrated closed position to an open position in which passage 88 is unblocked. At this point the actuating chamber of actuator 43 is in communication with the atmosphere through exhaust port 91 in the deenergized solenoid valve 46. In order to expand the air actuator 43 to shift the reversing valve to its reverse position, it is necessary for the operator to close switch 70 in circuit 72 thereby energizing solenoid valve 46 causing its armature to move to the right closing exhaust port 91 and opening passage 92 to place the source of air pressure 44 in communication with the actuator 43. The

actuator 43 will expand and shift the flow control element 42 of reversing valve 41 to its reverse operating position. The shifting movement of valve element 42 is relatively slow because of a restriction 87 provided in passage 88 in solenoid valve 47. The restriction 87 insures slow movement of the reversing valve in both directions. As soon as the reversing valve has been shifted to its reverse position, the operator will move the control member 67 to its closed position thereby blocking the pilot passage 68 and closing the dumping valve 61. At the same time switch 74 will be opened and valve element 86 closed thus trapping air in the expanded actuator 43. With the bypass passage 62 closed, the pressure will build up in supply passage 54 and motor conduit 52 and the motor 36 will operate in its reverse direction.

When it is desired to stop operation of the elevating mechanism, the dumping valve is placed in its open position by movement of valve member 67 to its open position.

When it is desired to shift from reverse driving condition of the elevating mechanism to forward driving condition, the dumping valve 66 is placed in its open position to place the supply conduit 54 at a reduced pressure thereby stopping operation of the motor 36. Switch 70 is opened to place solenoid valve 46 in its exhaust or deenergized position and thus air will escape from actuator 43 permitting its piston to retract slowly as air passes through restriction 87. The restriction is proportioned so the valve will shift from one operating position to another in about the same time as the elevating mechanism will coast to a stop. After the reversing valve has been shifted back to its forward position, the operator shifts manual control member 67 of pilot valve 66 to its closed position to close the dumping valve 61 and cause delivery of pressure fluid to motor conduit 51.

From the foregoing description it is apparent that the control system for the motor will not quickly shift hyraulic pressure delivery from one motor conduit to the other. The delay is suflicient to permit the motor 36 and elevating mechanism to come to a stop when changing their direction of operation. This avoids excessive pressure buildup in the motor and other control system components. Even though a pressure relief is provided in the control system momentary excessive pressures can be created in the system in absence of the delay afforded by this invention. The circuit 73 forms an interlock between the reversing and dumping valves preventing operation of the actuator 43 when the flow control element 76 of dumping valve 61 is in its closed position.

The embodiments of the invention in which an exclusive property or privilege is claimed and are defined as follows:

1. In a control system for the hydraulic drive motor for operating an elevating mechanism of an earthmover in forward and reverse directions including a hydraulic pump and a hydraulic reservoir, the combination comprismg:

a reversing valve shiftable between forward and reverse operating positions,

a supply conduit interconnecting said reversing valve and pump,

an exhaust conduit interconnecting said reversing valve and reservoir,

a pair of motor conduits interconnecting said reversing valve and motor,

a bypass passageway connected to said supply conduit intermediate said reversing valve and pump for bypassing hydraulic fluid to said reservoir,

a dumping valve in said bypass passageway including a fluid flow control element shiftable between open and closed positions in which said bypass passageway is open and closed, respectively,

first means for shifting said fluid flow control element including a first manual control member,

second means for operating said reversing valve including a second manual control member, and

third means preventing shifting of said reversing valve when said flow control element is in its closed position.

2. The invention of claim 1 wherein the direction of travel of said elevating mechanism is changed from forward to reverse only by placing said dumping valve flow control element in its open position and operating said manual control member and then placing said dumping valve flow control element in its closed position.

3. The invention of claim 2 wherein said second means includes an actuator operatively associated with said second manual control member and operable to shift said reversing valve and wherein said third means includes an interlock preventing operation of said actuator when said flow control element of said dumping valve is in its closed position.

4. The invention of claim 3 wherein said actuator is a fluid actuator connected to said reversing valve, wherein said second means includes a source of pressure fluid, a passage connecting said actuator and source and valve means in said passage and wherein said interlock operatively interconnects said first means and said valve means.

5. The invention of claim 4 wherein said valve means is an electrically operated valve controlled by an electric circuit and wherein said interlock includes an electric switch in said circuit operated by said first manual control member.

References Cited UNITED STATES PATENTS Lane n 60-52 Tyler 60-52 Vander Kaay 1.- 91-420 Hipple 91-459 X Junck et a1 37-8 X Hein et al 37-129 6 Slator et a1. 91-420 X Blattry 91-420 Byers 91-414 X Tennis 60-52 Linz 91-420 ROBERT E. PULFREY, Primary Examiner E. H. EICKHOLT, Assistant Examiner US. Cl. X.R.

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