CN217557055U

CN217557055U - Electrically-controlled full-variable hydraulic system and loader

Info

Publication number: CN217557055U
Application number: CN202221599877.3U
Authority: CN
Inventors: 梁洪铭; 范武德; 王允; 罗远鹏; 李泽华; 李祖杰
Original assignee: Guangxi Liugong Machinery Co Ltd
Current assignee: Guangxi Liugong Machinery Co Ltd
Priority date: 2022-06-24
Filing date: 2022-06-24
Publication date: 2022-10-11
Anticipated expiration: 2032-06-24

Abstract

The utility model relates to a loader hydraulic system, for solving the problem that the current loader can not control pressure according to respective load when carrying out the combined action, the utility model discloses construct an automatically controlled full variable hydraulic system and loader, wherein hydraulic system includes first, second variable pressure oil source, distribution valve includes the first, second main valve and two four-way solenoid valve of automatically controlled and closed meso position, first variable pressure oil source communicates with the work oil inlet of first main valve and the meso position oil-out of second main valve simultaneously, second variable pressure oil source communicates with the work oil inlet of second main valve and the meso position oil-out of first main valve simultaneously; the LS1 port and the LS2 port are connected through flow control ports of a first variable pressure oil source and a second variable pressure oil source of the two-position four-way electromagnetic valve. The utility model discloses when hydraulic system carries out equipment combined action, first main valve and second main valve independent fuel feeding separately, the load pressure signal according to corresponding separately control flow respectively separately realizes that pressure controls respectively.

Description

Electric control full-variable hydraulic system and loader

Technical Field

The utility model relates to a loader hydraulic system, more specifically say, relate to an automatically controlled full variable hydraulic system and loader.

Background

The hydraulic system of the loader comprises a steering hydraulic system and a working hydraulic system, and the steering hydraulic system and the working hydraulic system are made into a confluence oil supply hydraulic system for saving energy and fully utilizing. In the steering hydraulic system, the excess flow of the steering pump is supplied to the working hydraulic system via the priority valve.

In the working hydraulic system, a distribution valve includes a boom linkage valve and a bucket linkage valve for driving a boom cylinder and a bucket cylinder, respectively, to perform a boom raising and lowering operation and a bucket retracting and releasing operation. At a certain moment in the operation process of the loader, only one or two actions of the boom lifting action and the bucket retracting action may occur, so that a compound action is formed.

In the prior art, for example, in the technical solution disclosed in chinese patent document CN103085865A, when only a single action of lifting a boom or retracting a bucket is performed, a main valve of a boom linkage or a bucket linkage in a distribution valve is opened, a valve rod moves, an LS signal passing through the valve rod is transmitted to a flow control valve of a work pump and a steering pump through a shuttle valve network to control the pump displacement, and the steering pump oil is merged with the work pump oil through an EF port of a flow amplification valve and flows into a boom or a bucket cylinder through the distribution valve. When the control handle carries out compound action, because the two couples of loads are different, but only one LS signal is led out from the distribution valve, so that the two variable pumps can not output flow according to the loads of the corresponding couples respectively, the two variable pumps can not separately control pressure, in addition, the LS signal needs to be suppressed high by the pressure compensation valve with lower pressure of the two couples of loads, so that the two couples of pressures are equal, the pressure difference of the two couples of different loads during the compound action is compensated, the compound action of the whole machine is realized, and certain pressure loss can be caused.

SUMMERY OF THE UTILITY MODEL

The to-be-solved technical problem of the utility model is that current loader can not be according to the problem of respective load separately controlled pressure when carrying out the combined action, and provides an automatically controlled full variable hydraulic system and loader.

The utility model discloses a realize that the technical scheme of its purpose is like: the electric control fully variable hydraulic system is characterized by comprising a first variable pressure oil source, a second variable pressure oil source, a distribution valve and a two-position four-way electromagnetic valve, wherein the distribution valve comprises a first main valve and a second main valve which are electrically controlled and close to a middle position, the middle position oil inlets of the first main valve and the second main valve are communicated with a working oil inlet, the middle position oil inlets of the first main valve and the second main valve are communicated with a middle position oil outlet when the first main valve and the second main valve are in the middle position, and the middle position oil inlets and the middle position oil outlet are closed when the first main valve and the second main valve are not in the middle position; the first variable pressure oil source is simultaneously communicated with a middle oil inlet of the first main valve and a middle oil outlet of the second main valve, and the second variable pressure oil source is simultaneously communicated with a middle oil inlet of the second main valve and a middle oil outlet of the first main valve; the LS1 port of the first main valve and the LS2 port of the second main valve are correspondingly connected with the S1 port and the S2 port of the two-position four-way electromagnetic valve, and the S3 port and the S4 port of the two-position four-way electromagnetic valve are correspondingly connected with the flow control port of the first variable pressure oil source and the flow control port of the second variable pressure oil source; the two-position four-way electromagnetic valve can be switched between a first working position and a second working position, the S1 port and the S2 port are correspondingly communicated with the S3 port and the S4 port when the two-position four-way electromagnetic valve is in the first working position, the S1 port and the S2 port are correspondingly connected with two oil inlet ends of the first shuttle valve when the two-position four-way electromagnetic valve is in the second working position, and the S3 port and the S4 port are simultaneously connected with an oil outlet end of the first shuttle valve.

The utility model discloses in, when only a switching-over of first main valve and second main valve left the meso position, first variable pressure oil source, the confluence fuel feeding of second variable pressure oil source, two four-way solenoid valve are in the second work position, and the load pressure signal warp of first main valve or second main valve output the shuttle valve transmission of the second work position of two four-way solenoid valve is to first variable pressure oil source and second variable pressure oil source. When the first main valve and the second main valve are reversed and leave the middle position to perform composite action, the first variable pressure oil source supplies oil to the first main valve, the second variable pressure oil source supplies oil to the second main valve, the two-position four-way solenoid valve is positioned at a first working position, a load pressure signal output by the first main valve is transmitted to the first variable pressure oil source through the first working position of the two-position four-way solenoid valve, a load pressure signal output by the second main valve is transmitted to the second variable pressure oil source through the first working position of the two-position four-way solenoid valve, and the first variable pressure oil source and the second variable pressure oil source respectively control flow according to the load pressure signals corresponding to the first main valve and the second main valve, so that pressure is respectively controlled.

In the above electrically controlled fully variable hydraulic system, the first variable pressure oil source includes a first variable pump, a steering mechanism having an oil inlet connected to a pump port of the first variable pump, and a second shuttle valve; the first oil inlet end of the second shuttle valve is connected with the LS port of the steering mechanism, the second oil inlet end of the second shuttle valve is connected with the S3 port of the two-position four-way electromagnetic valve, the oil outlet end of the second shuttle valve is connected with the flow control valve of the first variable displacement pump, and the EF port of the priority valve in the steering mechanism is connected with the working oil inlet of the first main valve.

In the above electrically controlled fully variable hydraulic system, the first variable pressure oil source further includes a one-way damping valve, and the oil outlet end of the second shuttle valve is connected to the flow control valve of the first variable pump via the one-way damping valve.

In the above-mentioned electrically controlled fully variable hydraulic system, the hydraulic system further includes a pilot oil supply valve, the first main valve and the second main valve both include an electric proportional pilot valve for controlling the position of the valve rod thereof, the oil inlet end of the pilot oil supply valve is connected with the pump port of the second variable displacement pump, and the oil outlet end is connected with the oil inlet end of each electric proportional pilot valve.

In the electric control fully-variable hydraulic system, overflow valves are arranged between the LS1 port and the LS2 port and a T port on the distribution valve, which is used for connecting a hydraulic oil tank.

In the above electrically controlled fully variable hydraulic system, the hydraulic system further includes a main overflow valve, an oil outlet end of the main overflow valve is communicated with a T port of the distribution valve, which is used for connecting the hydraulic oil tank, and an oil inlet end of the main overflow valve is communicated with a working oil inlet of the first main valve or a working oil inlet of the second main valve.

In the above electrically controlled fully variable hydraulic system, the second variable pressure oil source is a second variable pump.

In the above-mentioned electrically controlled fully variable hydraulic system, the first main valve and the second main valve are nine-way directional valves, and the nine corresponding oil ports thereof are respectively a neutral oil inlet, a neutral oil outlet, an oil return port, a working oil inlet, a first working oil port, a second working oil port, a first load signal output port, a second load signal output port, and a main valve oil supplementing port.

The utility model discloses a realize that the technical scheme of its purpose is like: the loader is characterized by comprising the electrically controlled full-variable hydraulic system.

The loader further comprises a controller and an electric control handle, wherein the controller is electrically connected with the first main valve, the second main valve and the electric control end of the two-position four-way electromagnetic valve, and the electric control handle is electrically connected with the controller and used for inputting a first main valve reversing signal and a second main valve reversing signal.

Compared with the prior art, the utility model, have the utility model discloses well automatically controlled full variable hydraulic system is when carrying out equipment composite action, and two variable pressure oil sources are respectively to first main valve and second main valve fuel feeding, and the load pressure signal difference control flow of first main valve and the second main valve that just corresponds is separately according to, realizes that pressure controls respectively.

Drawings

Fig. 1 is a hydraulic schematic diagram of an electric control full-variable hydraulic system in the loader of the utility model.

Fig. 2 is an electrical control schematic diagram of the hydraulic system of the loader of the present invention.

Part names and serial numbers in the figure:

the hydraulic control system comprises a hydraulic oil tank 1, a second variable pump 3, a pilot oil supply valve 3, a movable arm oil cylinder 4 and a rotary bucket oil cylinder 5.

A first variable displacement pump 10, a steering mechanism 11, a second shuttle valve 12 and a one-way throttle valve 13.

The main overflow valve comprises a distribution valve 20, a first main valve 21, a second main valve 22, a main overflow valve 23, a first overflow valve 24, a first main valve middle position oil inlet 25, a first main valve middle position oil outlet 26, a second main valve middle position oil inlet 27, a second main valve middle position oil outlet 28 and a second overflow valve 29.

A two-position four-way solenoid valve 30, a first shuttle valve 31.

Controller 90, automatically controlled handle 91.

Detailed Description

The following description of the embodiments refers to the accompanying drawings.

Fig. 1 shows the hydraulic principle of the hydraulic system of the loader in this example. The hydraulic system is an electric control full-variable hydraulic system and comprises a steering hydraulic system and a working hydraulic system.

The steering hydraulic system comprises a first variable pump 10 with an oil suction port connected with a hydraulic oil tank 1, a steering mechanism 11 connected with the pump port of the first variable pump 10, a second shuttle valve 12, a one-way throttle valve 13 and the like. The steering mechanism 11 includes a steering gear, a flow amplifying valve, a steering cylinder and the like (not shown in the figure), the steering gear is connected with the flow amplifying valve, the flow amplifying valve is controlled to output hydraulic oil to drive the steering cylinder, a priority valve in the flow amplifying valve is connected with a pump port of a first variable displacement pump, and an EF port of the priority valve is connected with a working hydraulic system to supply oil to the working hydraulic system. The LS port of the steering mechanism 11 is connected to a first oil inlet end of the second shuttle valve 12, and transmits the steering load pressure of the steering mechanism 11 to the second shuttle valve 12. The steering hydraulic system constitutes a first variable pressure oil source that supplies oil to the working hydraulic system. The oil outlet end of the second shuttle valve 12 is connected with the X port of the first variable pump 10 through a one-way throttle valve 13, so as to realize the connection with the flow control valve of the first variable pump.

The working hydraulic system comprises a second variable pump 2 with an oil suction port connected with a hydraulic oil tank, a distribution valve 20, a movable arm oil cylinder 4, a rotating bucket oil cylinder 5 and a pilot oil supply valve 3.

The distribution valve 20 includes a first main valve 21, a second main valve 22, a first relief valve 24, a second relief valve 29, and a main relief valve 23.

The first main valve 21 and the second main valve 22 are both nine-way valves, and oil ports thereof are respectively a middle oil inlet, a middle oil outlet, an oil return port, a working oil inlet, a first and a second working oil ports, a first and a second load pressure signal output ports, and a main valve oil supplementing port. In each main valve, a working oil inlet is communicated with a middle oil inlet, a main valve oil supplementing port is connected with an oil inlet end of a back pressure valve, an oil return port is connected with a T port, and a first load pressure signal output port and a second load pressure signal output port are communicated with each other to form an LS port corresponding to the main valve. The oil outlet of the back pressure valve is connected with the T port.

The first main valve 21 and the second main valve 22 are both in a closed middle position function, when the valve rod of each main valve is in a middle position, a middle position oil inlet 25 of the first main valve is communicated with a middle position oil outlet 26 of the first main valve, and a middle position oil inlet 27 of the second main valve is communicated with a middle position oil outlet 28 of the second main valve; when the valve rod leaves the middle position, the middle position oil inlet and the middle position oil outlet of each main valve are cut off.

The first main valve 21 and the second main valve 22 are both electric control valves, and the hydraulic control ends at both ends of the valve rod of each main valve are both provided with electric proportional pilot valves which output pilot pressure oil with corresponding pressure according to control current to push the valve rod to move and change direction.

The first main valve 21 is a boom linkage main valve, first and second working oil ports A1 and B1 of the first main valve are connected with the boom cylinder 4, and a first main valve working oil inlet 25 is communicated with a middle oil outlet 28 of the second main valve. The second main valve 22 is a rotating bucket joint main valve, first and second working oil ports A2 and B2 of the second main valve are connected with a rotating bucket oil cylinder, and a working oil inlet 27 of the second main valve is communicated with a middle oil outlet 26 of the first main valve.

The first relief valve 24 is connected between the LS1 port and the T port of the first main valve 21, and is used to set the maximum pressure of the LS1 port, the distribution valve 20 is connected to the hydraulic tank 1 through the T port, and the LS1 port is a load pressure feedback port of the first main valve 21 and is used to feed back a load pressure signal of the boom cylinder. The second relief valve 29 is connected between the LS2 port and the T port of the second main valve 22, and is used for setting the highest pressure of the LS2 port, and the LS2 port is a load feedback port of the second main valve 22 and is used for feeding back a load pressure signal of the bucket cylinder. A primary spill valve 23 is provided between the working oil inlet and the T port of the first main valve 21 for defining the highest pressure of the system.

The two-position four-way solenoid valve 30 is provided with an S1 port, an S2 port, an S3 port and an S4 port and comprises a first shuttle valve 31, the two-position four-way solenoid valve 30 is provided with two working positions, when the two-position four-way solenoid valve is in the first working position, the S1 port is communicated with the S3 port, and the S2 port is communicated with the S4 port; when the two-position four-way solenoid valve 30 is located at the second working position, the port S1 and the port S2 are respectively communicated with the two oil inlet ends of the first shuttle valve 31, and the port S3 and the port S4 are simultaneously connected with the oil outlet end of the first shuttle valve 31. The S1 port of the two-position four-way electromagnetic valve 30 is connected with the LS1 port, the S2 port is connected with the LS2 port, the S3 port is connected with the second oil inlet end of the second shuttle valve 12, and the S4 port is connected with the X port of the second variable pump 2, so that the connection with the flow control valve of the second variable pump 2 is realized.

The oil inlet of the pilot oil supply valve 3 is connected with the pump port of the first variable pump 10, the oil outlet is connected with the Pst port on the distributing valve 20 through an oil filter, so that the pilot oil supply is connected with the oil inlet of each electric proportional pilot valve on the distributing valve 20 and provides pilot pressure oil source for pilot control of each main valve.

The EF port of the priority valve in the steering mechanism 11 is connected to the P1 port of the distribution valve 20, and is communicated with the first main valve working oil inlet 25 through the P1 port. The pump port of the second variable displacement pump 2 is connected with the port P2 of the distribution valve 20, and is communicated with the second main control valve working oil inlet 27 through the port P2.

The working hydraulic system part in the hydraulic system of the loader is controlled in an electric control mode, and a control device comprises a controller 90 and an electric control handle 91. As shown in fig. 2, the electric control handle 91 is connected to the controller 90, and is used to control the work implement, and outputs a boom raising/lowering operation signal and/or a bucket retracting/extending operation signal to the controller 90 when the electric control handle is controlled by an operator. The electromagnets XDA1, XDB1, XDA2, XDB2 of the electric proportional pilot valves of the main valves and the electromagnets SDKZ1 of the two-position four-way electromagnetic valves are all connected with the controller 90, the controller 90 outputs corresponding control current to the electromagnets of the corresponding electric proportional pilot valves according to operation signals input by the electric control handle, and the electromagnets SDKZ1 of the two-position four-way electromagnetic valves are controlled to work at a first working position or a second working position by electrifying or powering off, and the working principle is as follows:

1. the working device is not active.

The electric control handle 91 is operated, no operation signal is output to the controller 90, the controller 90 does not output control current to the electromagnets of the electric proportional pilot valves of the first main valve and the second main valve and the electromagnets of the two-position four-way solenoid valve, the first main valve 21 and the second main valve 22 are both in the middle position, no load pressure signal is output to the ports LS1 and LS2, so that no load pressure exists at the second oil inlet end of the second shuttle valve 12 and the port X of the second variable pump 2, and the second variable pump 2 is at the minimum displacement. If the steering mechanism 11 does not perform steering action, the load pressure transmitted by the steering mechanism 11 to the first oil inlet end of the second shuttle valve 12 is also zero, the port X of the first variable displacement pump 10 does not have load pressure, and the first variable displacement pump 10 is at the minimum displacement. If the steering mechanism 11 has a steering action, the steering load pressure signal is transmitted to the X port of the first variable displacement pump 10 through the second shuttle valve 12, and the first variable displacement pump 10 outputs the pressure oil with a corresponding flow rate according to the load pressure signal of the steering mechanism 11.

2. The working device is single-acting.

The electric control handle 91 is operated to output only a boom operation signal or a turning motion operation signal to the controller 90, and the controller 90 outputs a control current of a corresponding magnitude to the electromagnet of the electric proportional pilot valve of the first main valve and the second main valve corresponding to the main valve to perform power-off control on the electromagnetic valve of the two-position four-way electromagnetic valve. The main valve to which the control current is input in the first main valve 21 and the second main valve 22 is away from the middle position, and the other main valve is still in the middle position, so that the working oil inlet of the main valve in the middle position is communicated with the middle oil outlet, and the pressure oil from the port P1 and the pressure oil from the port P2 are converged. The two-position four-way solenoid valve 30 is in the second working position, the load pressure from the main valve to which the control current is input is transmitted to the second oil inlet end of the second shuttle valve 12 and the X port of the second variable pump 2 through the first shuttle valve 31 in the second working position of the two-position four-way solenoid valve 30, and the second variable pump 2 outputs the corresponding flow according to the pressure signal of the X port. The pressure at the second oil inlet end of the second shuttle valve 12 is compared with the pressure at the first oil inlet end of the second shuttle valve 12 and then transmitted from the oil outlet end to the port X of the first variable pump 10, and the first variable pump 10 outputs corresponding flow according to the pressure signal at the port X. In the work apparatus single-action operation, the first variable pump 10 and the second variable pump 2 merge to supply oil.

3. The working devices perform compound actions.

The electric control handle 91 is operated to simultaneously output a boom operation signal and a turning motion operation signal to the controller 90, and the controller 90 outputs control currents of corresponding magnitudes to the electromagnets of the electric proportional pilot valves of the first main valve 21 and the second main valve 21, respectively, to energize and control the electromagnet of the two-position four-way solenoid valve 30. The first main valve 21 and the second main valve 22 are separated from the middle position, the working oil inlet and the middle oil outlet of the two main valves are cut off, the port P1 is not communicated with the port P2, the pressure oil from the first variable displacement pump 10 is only supplied to the first main valve 21, and the pressure oil from the port P2 is only supplied to the second main valve 22. Under the control of pilot pressure oil output by the respective electric proportional pilot valves, the first main valve 21 and the second main valve 22 open corresponding valve port openings, and the boom cylinder 4 and the swing bucket cylinder 5 respectively extend and retract to push the bucket to turn over and lift or lower the boom, thereby realizing the compound action of the working device.

The electromagnet of the two-position four-way electromagnetic valve 30 is electrified to be at a first working position, the load pressure output by the first main valve 21 is transmitted to the second oil inlet end of the second shuttle valve 12 through the LS1 port, the S1 port and the S3 port of the two-position four-way electromagnetic valve 30, and is transmitted to the X port of the first variable pump 10 after being compared with the pressure signal of the first oil inlet end of the second shuttle valve 12, and the first variable pump 10 outputs corresponding flow according to the pressure signal of the X port. The load pressure output by the second main valve 22 is transmitted to the X port of the second variable pump 2 through the LS2 port, the S2 port and the S4 port of the two-position four-way solenoid valve 30, and the second variable pump 2 outputs a corresponding flow rate according to a pressure signal of the X port thereof. Therefore, when the loader working device performs a combined action, the boom cylinder and the bucket cylinder are respectively and independently supplied with oil by the first variable pump and the second variable pump, and the two variable pumps perform flow control according to respective corresponding load pressures.

Claims

1. An electric control fully variable hydraulic system is characterized by comprising a first variable pressure oil source, a second variable pressure oil source, a distribution valve and a two-position four-way electromagnetic valve, wherein the distribution valve comprises a first main valve and a second main valve which are electrically controlled and close to a middle position, the middle position oil inlets of the first main valve and the second main valve are communicated with a working oil inlet, the middle position oil inlets of the first main valve and the second main valve are communicated with a middle position oil outlet when the first main valve and the second main valve are in the middle position, and the middle position oil inlets and the middle position oil outlet are closed when the first main valve and the second main valve are not in the middle position; the first variable pressure oil source is simultaneously communicated with a middle oil inlet of the first main valve and a middle oil outlet of the second main valve, and the second variable pressure oil source is simultaneously communicated with a middle oil inlet of the second main valve and a middle oil outlet of the first main valve; the LS1 port of the first main valve and the LS2 port of the second main valve are correspondingly connected with the S1 port and the S2 port of the two-position four-way electromagnetic valve, and the S3 port and the S4 port of the two-position four-way electromagnetic valve are correspondingly connected with the flow control port of the first variable pressure oil source and the flow control port of the second variable pressure oil source; the two-position four-way electromagnetic valve can be switched between a first working position and a second working position, the S1 port and the S2 port are correspondingly communicated with the S3 port and the S4 port when the two-position four-way electromagnetic valve is at the first working position, the S1 port and the S2 port are correspondingly connected with two oil inlet ends of the first shuttle valve when the two-position four-way electromagnetic valve is at the second working position, and the S3 port and the S4 port are simultaneously connected with an oil outlet end of the first shuttle valve.

2. The electrically controlled fully variable hydraulic system of claim 1, wherein the first variable pressure oil source comprises a first variable pump, a steering mechanism having an oil inlet connected to a pump port of the first variable pump, and a second shuttle valve; the first oil inlet end of the second shuttle valve is connected with the LS port of the steering mechanism, the second oil inlet end of the second shuttle valve is connected with the S3 port of the two-position four-way electromagnetic valve, the oil outlet end of the second shuttle valve is connected with the flow control valve of the first variable pump, and the EF port of the priority valve in the steering mechanism is connected with the working oil inlet of the first main valve.

3. The electrically controlled fully variable hydraulic system of claim 2, wherein said first variable pressure source further comprises a one-way damper valve, and said second shuttle valve outlet port is connected to said first variable pump flow control valve through said one-way damper valve.

4. The electrically controlled fully variable hydraulic system according to claim 2, further comprising a pilot supply valve, wherein the first main valve and the second main valve each comprise an electric proportional pilot valve for controlling a valve rod position thereof, an oil inlet end of the pilot supply valve is connected to the pump port of the first variable pump, and an oil outlet end of the pilot supply valve is connected to an oil inlet end of each of the electric proportional pilot valves.

5. An electrically controlled fully variable hydraulic system according to any one of claims 1 to 4, characterised in that relief valves are provided between the LS1 and LS2 ports and the T port of the distribution valve for connection to a hydraulic tank.

6. The electrically controlled hydraulic system according to any one of claims 1 to 4, further comprising a main overflow valve, wherein an oil outlet end of the main overflow valve is communicated with a T-port of the distribution valve for connecting the hydraulic oil tank, and an oil inlet end of the main overflow valve is communicated with the working oil inlet of the first main valve or the working oil inlet of the second main valve.

7. An electrically controlled fully variable hydraulic system according to any of claims 1 to 4, characterised in that the second source of variable pressure oil is a second variable pump.

8. The electrically controlled fully variable hydraulic system according to any one of claims 1 to 4, wherein the first main valve and the second main valve are both nine-way directional valves, and the corresponding nine oil ports are respectively a middle oil inlet, a middle oil outlet, an oil return port, a working oil inlet, a first working oil port, a second working oil port, a first load signal output port, a second load signal output port, and a main valve oil supplementing port.

9. A loader characterized by an electrically controlled all variable hydraulic system according to any one of claims 1 to 8.

10. The loader of claim 9, further comprising a controller electrically connected to the first main valve, the second main valve, and the electrical control end of the two-position, four-way solenoid valve, and an electrical control handle electrically connected to the controller for inputting the first main valve reversing signal and the second main valve reversing signal.