Tractor hydraulic system control device

Abstract

The invention discloses a control device for a tractor hydraulic system, which includes a hydraulic system. A hydraulic cylinder in the hydraulic system is hinged to a connecting rod with a hinge shaft, and a lifting arm is installed through the led-out hinge shaft. Among them, a lifting control mechanism and a floating descent control mechanism of the hydraulic system are installed on one side of the lifting arm. Therefore, by manipulating the handle control panel wire to control the travel switch turntable and the two travel switches thereon to change positions relative to the convex and concave surface sections of the limit contact disc, the mutual conduction or cut-off of the two travel switches is controlled, so that the hydraulic solenoid valve acts, realizing the synchronous action of the position of the tractor hydraulic cylinder and the rotation position of the handle control panel, controlling the telescopic action of the hydraulic cylinder to lift and lower the lifting arm, and the floating descent control mechanism can also be set to control the hydraulic cylinder to rely on the self-weight of the lifting arm to drain and compress back. It has the characteristics of forced and precise lifting control function, simple operability and maintainability.

Description

Technical Field

[0001] The present invention relates to the field of agricultural machinery, and more specifically to a control device for the hydraulic system of a tractor. Background Art

[0002] As a widely used agricultural machine, tractors play an important role in China's agricultural production. In agricultural operations, the hydraulic hitch system of a tractor must frequently adjust its operation to control the attached agricultural implements. There are two ways for the hydraulic hitch system of a tractor. One is through a hydraulic distributor, and the control of the hydraulic cylinder is achieved by moving a joystick up and down. Its disadvantage is that the hydraulic rod is in a neutral position, and the hydraulic cylinder only moves when the joystick is manually moved. When the hand is released, the hydraulic cylinder moves, so the hydraulic cylinder cannot maintain position synchronization with the joystick. At the same time, the driver needs to control the steering wheel with one hand and the joystick with the other hand, resulting in frequent operations for the driver. The other is through the operating handle of the hydraulic distributor in the cab. Changing the position of the handle can only lift the hydraulic cylinder unidirectionally, but the lowering of the hydraulic cylinder depends on the self-weight of the agricultural implement, that is, there is no strong pressure device for the hydraulic cylinder to lower, which affects the performance of the tractor. After comprehensively analyzing the above technologies, they can be classified into strong pressure type and non-strong pressure type. Strong pressure type: It has the function of forced lifting and lowering, but no precise control function for lifting and lowering, and the controllability and maintainability are complex. Non-strong pressure type: It has the function of forced lifting, no forced lowering function, has a precise control function for lifting, no precise control function for lowering, the controllability is simple, and the maintainability is complex. Summary of the Invention

[0003] In view of the above situation, the present invention provides a control device for the hydraulic system of a tractor, which has the characteristics of forcibly and precisely controlling the telescopic movement of the hydraulic cylinder, as well as simple controllability and maintainability.

[0004] The technical solution of the present invention is: A control device for the hydraulic system of a tractor, including a hydraulic system installed on a frame. The hydraulic cylinder in this hydraulic system is hinged to a connecting rod, and the hinge shafts on the connecting rod extend out of both sides of the frame. Lifting arms are symmetrically installed on the hinge shafts extending out on both sides. Among them, on one side of the lifting arm, there is an up-and-down control mechanism and a floating-down control mechanism for the hydraulic system.

[0005] The up-and-down control mechanism includes a shaft pin and a limit touch disk and a travel switch turntable installed thereon. The limit touch disk is connected to the lifting arm through the shaft pin, and the travel switch turntable is connected to the handle control disk through a wire. Two travel switches are provided on the travel switch turntable and are electrically connected to the corresponding hydraulic solenoid valve, relay, and electromagnetic overflow valve in the hydraulic system. By pushing or pulling the handle control disk, the travel switch turntable is rotated to any position and stopped. The hydraulic cylinder is started to expand and contract, causing the lifting arm and the limit touch disk to rotate up and down. When the touch point on the limit touch disk contacts or disengages from the travel switch turntable, the expansion and contraction of the hydraulic cylinder are controlled to stop.

[0006] The floating descending control mechanism includes a floating travel switch. The No. 3 travel switch is electrically connected to the electromagnetic hydraulic valve and the relay. When the floating travel switch contacts the contact pin on the travel switch turntable, it controls the hydraulic cylinder to release pressure and retract. Therefore, by controlling the relative rotation between the travel switch turntable and the limit contact disc through the cable of the handle operating disc to change the contact position, it controls the conduction or power-off of the travel switch turntable, the hydraulic solenoid valve, and the relay, so as to realize the synchronous displacement of the telescopic position of the tractor hydraulic cylinder and the rotation position of the handle operating disc.

[0007] In the present invention, the limit contact disc includes a circular disc and a central shaft hole. Along the radial direction, there is a limit interval section formed by a convex-concave surface, and a touch point for the travel switch turntable to be powered on or off is formed at the transition edge of the convex-concave surface.

[0008] In the present invention, the travel switch turntable includes a circular disc and a central shaft hole. It is provided with the No. 1 and No. 2 travel switches, contacts, a second cable connection pin, and a floating contact. Therefore, after the contact on the travel switch turntable contacts the contact rod of the No. 3 travel switch and gets powered on, the No. 2 overflow valve is opened to release the pressure of the hydraulic cylinder, and the lifting arm floats and descends by its own weight.

[0009] In the present invention, the handle operating disc includes a circular disc and a central shaft hole. A handle, a first cable connection pin, and a cable guide frame are fixed on it. The circular disc is connected to the rotating shaft on the fixed seat through the central shaft hole and is installed in the cab through the screw on the fixed seat.

[0010] In the present invention, the travel switch is connected to a relay, a hydraulic solenoid valve, an electromagnetic overflow valve, and a power supply circuit; the circuit includes a 1# relay J1, a 2# relay J2, and a 3# relay J3; the 1# relay J1 has two normally open contacts J1-1, J1-2 and a normally closed contact J1-3 of the 1# travel switch. One end of the normally open contact J1-1 of the 1# relay J1 is connected to the power supply, and the other end is connected to the coil of the rising electromagnetic overflow valve; one end of the normally open contact J1-2 is connected to the power supply through the normally open contact J1-1, and the other end is connected to the coil of the rising hydraulic solenoid valve; the 2# relay J2 has two normally open contacts J2-1, J2-2 and a normally closed contact J2-3 of the 1# travel switch. One end of the normally open contact J2-1 of the 2# relay J2 is connected to the power supply, and the other end is connected to the coil of the descending electromagnetic overflow valve; one end of the normally open contact J2-2 is connected to the power supply through the normally open contact J2-1, and the other end is connected to the coil of the descending hydraulic solenoid valve; the 3# relay J3 has a normally open contact J3-1. One end of the normally open contact J3-1 is connected to the power supply, and the other end is connected to the coil of the descending hydraulic solenoid valve; one end of the 1# relay J1 is connected to the power supply, and the other end is connected to one end of the normally closed contact J1-3 of the 1# travel switch. The normally closed contact J1-3 is respectively connected to one ends of the 2# travel switch and the normally closed contacts J2-3, J3-2 of the 3# travel switch; one end of the 2# relay is connected to the power supply, and the other end is connected to one end of the normally closed contact J2-3 of the 2# travel switch. The other end of the normally closed contact J2-3 is respectively connected to one ends of the normally closed contact J1-3 and the normally closed contact J3-2; one end of the 3# relay is connected to the power supply, and the other end is connected to one end of the normally closed contact J3-2 of the 3# travel switch. The other end of the normally closed contact J3-2 is connected to the power supply.

[0011] The hydraulic system of the present invention includes an oil pump, a double-acting hydraulic cylinder, a relay, a hydraulic solenoid valve, an electromagnetic overflow valve, and a fuel tank.

[0012] The beneficial effects of the present invention are as follows: By controlling the travel switch turntable and the two travel switches thereon to change positions in the convex and concave surface intervals of the limit contact plate through the control cable of the control handle, the mutual conduction or disconnection of the two travel switches is controlled, so that the hydraulic solenoid valve operates, and the position of the hydraulic cylinder of the tractor and the rotation position of the control handle are kept synchronized. Therefore, it has the characteristics of forced and precise lifting control, and simple operation and maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a schematic diagram of the present invention;

[0014] Figure 2 is Figure 1 a schematic diagram of the lifting control mechanism and the floating descent control mechanism;

[0015] Figure 3 is Figure 2 the top view of

[0016] Figure 4 is Figure 1 Exploded schematic diagram of the lifting control mechanism;

[0017] Figure 5 is Figure 1 Schematic circuit diagram of the travel switch control;

[0018] Figure 6 is Figure 1 Schematic diagram of the hydraulic system connection. Specific implementation manners

[0019] The present invention will be further described below in conjunction with the embodiments with reference to the drawings.

[0020] See Figures 1 to 3A control device for a tractor hydraulic system as shown includes a hydraulic system installed on the rear frame 2 of the tractor 1. The piston rod of the hydraulic cylinder 3 in this hydraulic system is hinged to a connecting rod 14, and is led out from both sides of the frame 2 through the hinge shaft 23 on the connecting rod 14. Lifting arms 8 are symmetrically installed on the hinge shafts 23 led out from both sides of the frame 2. In this embodiment, a lifting control mechanism of the hydraulic system and a floating descent control mechanism installed on the frame 2 are installed on one side of the lifting arm 8. The lifting control mechanism in this embodiment includes a limit contact disk 7 and a travel switch turntable 6 installed on a pin 9. The limit contact disk 7 is connected to the lifting arm 8 through the pin 9, and the travel switch turntable 6 is connected to the handle control panel 13 through a wire 15. The travel switch turntable 6 is electrically connected to a 1# travel switch 4, a 2# travel switch 5 and corresponding hydraulic solenoid valves, relays, and electromagnetic overflow valves (not shown in the figure) in the hydraulic system. By pushing or pulling the handle control panel 13 to control the travel switch turntable 6 to rotate to any position and stop (relative to the limit contact disk 7), the piston rod of the hydraulic cylinder 3 is started to extend and retract, causing the lifting arm 8 and the limit contact disk 7 to rotate up and down until the contact point a on the limit contact disk 7 contacts the contact head of the 1# travel switch 4 or the 2# travel switch 5 on the travel switch turntable 6, and the extension and retraction of the hydraulic cylinder are controlled to stop. The floating descent control mechanism in this embodiment includes a 3# travel switch 12 installed on the frame. The 3# travel switch 12 is electrically connected to a hydraulic solenoid valve and a relay. When the 3# travel switch 12 contacts the contact pin 10 on the travel switch turntable 6, the hydraulic cylinder is forced to release pressure and retract. Therefore, by controlling the relative rotation and position contact between the travel switch turntable 6 and the limit contact disk 7 through the wire 15 on the handle control panel 13, the conduction or power-off of the travel switch turntable 6, the hydraulic solenoid valve, and the relay is controlled, so as to realize the synchronous displacement of the extension and retraction position of the hydraulic cylinder 3 of the tractor 1 and the rotation position of the handle control panel 13. In this embodiment, the limit contact disk 7 includes a circular disk and a central shaft hole. Along the radial direction, there is a limit interval section formed by a convex and concave surface, and a contact point a for controlling the energization or power-off of the travel switch turntable 6 is formed at the transition edge of the convex and concave surface limit interval section. The travel switch turntable 6 in this embodiment includes a circular disk and a central shaft hole, and is provided with a 1#, 2# travel switch and contact heads, a second wire connection pin 11 and a floating contact 10. Therefore, after the floating contact 10 on the travel switch turntable 6 contacts the contact rod of the 3# travel switch 12 and gets energized, the 2# overflow valve is opened to release the pressure of the hydraulic cylinder 3, and the lifting arm 8 floats and descends by its own weight. The handle control panel 13 in this embodiment includes a circular disk 18 and a central shaft hole, and a handle 19, a first wire connection pin 17, and a wire guiding frame 16 are fixed thereon. The circular disk 18 is fixedly connected to a fixed shaft 24 on a fixed seat 20 through the central shaft hole, and is installed in the cab of the tractor 1 through a screw on the fixed seat 20.In this embodiment, one end of the wire rope 15 is connected to the first wire rope connecting pin 17 on the handle control panel 18, and then passes through the wire rope guide frame 16 and is connected to the second wire rope connecting pin 11 on the travel switch turntable 6. The actuating handle 19 acts on the travel switch turntable 6 through the wire rope 15 to rotate in the forward and reverse directions.

[0021] See Figure 5 The circuit schematic diagram of the connection between the travel switch, relay, hydraulic solenoid valve, electromagnetic overflow valve, and power supply is given. The circuit includes relay J1 of No. 1, relay J2 of No. 2, and relay J3 of No. 3; relay J1 of No. 1 has two normally open contacts J1-1, J1-2 and the normally closed contact J1-3 of the travel switch of No. 1. One end of the normally open contact J1-1 of relay J1 of No. 1 is connected to the power supply, and the other end is connected to the coil of the rising electromagnetic overflow valve; one end of the normally open contact J1-2 is connected to the normally open contact J1-1 to connect to the power supply, and the other end is connected to the coil of the rising hydraulic solenoid valve; relay J2 of No. 2 has two normally open contacts J2-1, J2-2 and the normally closed contact J2-3 of the travel switch of No. 1. One end of the normally open contact J2-1 of relay J2 of No. 2 is connected to the power supply, and the other end is connected to the coil of the descending electromagnetic overflow valve; one end of the normally open contact J2-2 is connected to the normally open contact J2-1 to connect to the power supply, and the other end is connected to the coil of the descending hydraulic solenoid valve; relay J3 of No. 3 has a normally open contact J3-1. One end of this normally open contact J3-1 is connected to the power supply, and the other end is connected to the coil of the descending hydraulic solenoid valve; one end of the relay J1 of No. 1 and the power supply, and the other end is connected to one end of the normally closed contact J1-3 of the travel switch of No. 1. The normally closed contact J1-3 is respectively connected to one end of the travel switch of No. 2, the normally closed contact J2-3 of the travel switch of No. 3, and the normally closed contact J3-2; one end of the relay J2 of No. 2 is connected to the power supply, and the other end is connected to one end of the normally closed contact J2-3 of the travel switch of No. 2. The other end of the normally closed contact J2-3 is respectively connected to one end of the normally closed contact J1-3 and the normally closed contact J3-2; one end of the relay J3 of No. 3 is connected to the power supply, and the other end is connected to one end of the normally closed contact J3-2 of the travel switch of No. 3. The other end of the normally closed contact J3-2 is connected to the power supply.

[0022] See Figure 6 Schematic diagram of the hydraulic system connection. It includes the hydraulic solenoid valve C, and this hydraulic solenoid valve C is respectively connected to the coil D of the hydraulic solenoid valve of No. 1, the coil E of the hydraulic solenoid valve of No. 2, and the coils F of the electromagnetic overflow valves of No. 1 and No. 2. There are ports A0, B0, oil supply port P, and oil return port T on the hydraulic solenoid valve C. The ports A0 and B0 are respectively connected to the A chamber and the B chamber of the hydraulic cylinder 3.

[0023] This embodiment combines Figure 5 、 Figure 6 to describe the specific working process:

[0024] I. Process from rising to rising stop:

[0025] When the handle 19 on the operating handle turntable 13 is pushed forward, the travel switch turntable 6 is driven to rotate clockwise through the wire 15. The contact on the 1# travel switch turntable 6 is in the concave position of the limit turntable 7, and the contact of the 1# travel switch turntable 6 does not contact the convex and concave surfaces of the limit turntable 7. The normally closed contacts J1-3 and J2-3 of the 1# and 2# relays are in the conducting state. At this time, the 1# relay J1 and the normally closed contact of the 1# travel switch 4 are energized, so that the two normally open contacts J1-1 and J1-2 of the 1# relay J1 are closed and energized, respectively energizing the 1# electromagnetic overflow valve coil F and the 1# hydraulic solenoid valve coil D. The hydraulic system forms a normal working pressure. At this time, the oil supply port P of the hydraulic solenoid valve C communicates with the A0 port of the hydraulic solenoid valve C after commutation, and the oil return port T of the electro-hydraulic valve C communicates with the B0 port. The pressure oil supplied by the hydraulic pump enters the A chamber of the hydraulic cylinder through the A0 port of the hydraulic solenoid valve C through the oil supply port P, and the oil in the B chamber of the hydraulic cylinder flows back to the fuel tank through the B0 port of the hydraulic solenoid valve C. The piston rod of the hydraulic cylinder 3 extends to act on and control Figure 4 the lifting arm in

[0026] to rotate upward (rise). While the lifting arm rotates upward, the limit contact disc 7 rotates accordingly. When the convex and concave transition edge touch point a on the limit contact disc 7 touches the contact of the 1# travel switch 4 on the travel switch turntable 6, the normally closed contact of the 1# travel switch 4 is disconnected. At the same time that the 1# relay J1 is de-energized, the 1# electromagnetic overflow valve coil F and the 1# hydraulic solenoid valve coil D are de-energized. The 1# hydraulic solenoid valve returns to the neutral position, and the A0 port and B0 port of the hydraulic solenoid valve C are closed. The hydraulic cylinder 3 stops acting and remains stationary. The hydraulic oil flows back to the fuel tank from the A0 port of the hydraulic solenoid valve C through the oil circuit of the 1# electromagnetic overflow valve in the de-energized state through the oil return port T of the electro-hydraulic valve C. When rising, the 2# travel switch does not work.

[0027] When the handle 19 on the control handle turntable 13 is pulled backward, it drives the travel switch turntable 6 to rotate counterclockwise through the wire 15. The contact of the No. 2 travel switch 5 is in the convex position of the limit contact disc 7. The contact of the No. 2 travel switch 5 presses on the convex and concave limit contact disc 7. The normally open contacts of the No. 1 and No. 2 relays are closed and conducted. At this time, the normally open contacts of the No. 2 relay J2 and the No. 2 relay are closed and energized. The No. 2 relay J2 is closed. The No. 2 electromagnetic overflow valve coil F and the No. 2 hydraulic solenoid valve coil E are energized. The hydraulic system is under normal working pressure. At this time, the oil supply port P of the hydraulic solenoid valve C is communicated with the B0 port of the No. 1 hydraulic solenoid valve and the hydraulic solenoid valve C. The oil return port T is communicated with the A0 port. The hydraulic oil supplied by the hydraulic pump enters the B chamber of the hydraulic cylinder through the oil supply port P of the hydraulic solenoid valve C and the B0 port. The oil in the A chamber of the hydraulic cylinder flows back to the fuel tank through the A0 port of the hydraulic solenoid valve C and the oil return port T. The piston rod of the hydraulic cylinder retracts, controlling the lifting arm to rotate downward (lower). When the convex and concave transition touch point a on the limit contact disc 7 on the lifting arm rotates to the contact position on the travel switch turntable 6, when the contact of the No. 2 travel switch 5 starts to relax to a certain extent, the two normally open contacts J2-1 and J2-2 on the No. 2 travel switch 5 are disconnected. The No. 2 relay J2 is de-energized. At this time, the normally closed contact J2-3 of the No. 2 relay d is disconnected. The No. 2 electromagnetic overflow valve coil F and the hydraulic solenoid valve C are de-energized. The No. 2 hydraulic solenoid valve returns to the neutral position. The A0 port and the B0 port of the hydraulic solenoid valve group C are closed. The hydraulic oil cylinder stops descending and remains stationary. The hydraulic oil flows back to the fuel tank through the oil return port T through the oil path of the No. 2 electromagnetic overflow valve when the No. 2 hydraulic solenoid valve is de-energized from the oil supply port P of the hydraulic solenoid valve C. When descending, the No. 1 travel switch does not work.

[0028] III. Floating condition:

[0029] When the operating vertical handle 19 is pulled down to the lowest position, the travel switch turntable 6 is driven by the wire 15 to rotate counterclockwise, and the contact rod on the 3# travel switch 12 is triggered to make the 3# travel switch 12 act. The normally closed contact J3-2 of the 3# travel switch 12 is disconnected, and the normally open contact J3-1 is closed and conducts. After the normally closed contact J3-2 is disconnected, the power supplies of the 1# and 2# travel switches 4 and 5 are cut off, and the 1# and 2# travel switches 4 and 5 do not work. After the normally open contacts J1-1, J1-2, J2-1, and J2-2 are closed and conduct, the 3# relay coil 12 is energized. The normally closed contact J3-3 of the 3# relay J3 is closed and conducts, making the hydraulic solenoid valve energized and work. At this time, because the 1# and 2# electromagnetic overflow valves are de-energized, there is no pressure in the hydraulic system. The oil supply port P of the hydraulic solenoid valve C is connected to the oil return port T through the electromagnetic overflow valve. The oil supply port P is connected to the A0 port through the down hydraulic solenoid valve, and the B0 port is connected to the oil return port T. The A0 port and the B0 port of the hydraulic cylinder are in a state of being connected without oil pressure. Therefore, the piston rod of the hydraulic cylinder 3 can automatically extend or contract according to the external force it receives, that is, the lifting arm connected to the piston rod of the hydraulic cylinder 3 automatically extends or contracts. At this time, it is the floating function of the tractor hydraulic system.

[0030] The feature of implementing the present invention is to adopt a dynamically rotating travel switch that actively rotates to control the hydraulic cylinder of the hydraulic system to drive the lifting arm and the limit contact plate thereon to rotate in the same direction until they contact the travel switch, so as to adjust and control the up and down swing (lifting) of the lifting arm.

[0031] Travel switch description:

[0032] The 1# and 2# travel switches are switches of the same model LXW5-11Q1.

[0033] There is a time difference in the action time of the 1# and 2# travel switches. The 1# travel switch acts first when lifting; the 2# travel switch acts first when descending. The position of the time difference in the action time of the 1# and 2# travel switches is the neutral position of the controlled hydraulic cylinder.

Claims

1. Control device for a tractor hydraulic system, comprising a hydraulic system mounted on a frame, the piston rod of a hydraulic cylinder in the hydraulic system being hinged to a connecting rod, the connecting rod being led out of both sides of the frame through a hinge shaft on the connecting rod, and lifting arms being symmetrically mounted on the hinge shafts led out on both sides; characterized in that, On one side of the lifting arm, a lifting control mechanism and a floating lowering control mechanism of the hydraulic system are installed: The lifting control mechanism includes a shaft pin, a limit contact disc and a travel switch turntable mounted on the shaft pin. The limit contact disc is connected to the lifting arm through the shaft pin, and the travel switch turntable is connected to the handle control disc through a wire rope. The limit contact disc includes a first circular disc with a first central shaft hole provided thereon. The first circular disc is provided with a limit interval section formed by a concave surface along the radial direction, and a touch point for the travel switch turntable to be powered on or off is formed at the transition edge of the concave surface. The travel switch turntable includes a second circular disc with a second central shaft hole provided thereon. The second circular disc is provided with a first travel switch, a second travel switch, a contact head, a second wire rope connection pin and a floating contact head. The first travel switch and the second travel switch are electrically connected to a hydraulic solenoid valve, a relay and an electromagnetic overflow valve in the hydraulic system. The handle control disc includes a third circular disc with a third central shaft hole provided thereon. The third circular disc is fixedly provided with a handle, a first wire rope connection pin and a wire rope guide frame. The third circular disc is connected to a rotating shaft on a fixed seat through the third central shaft hole, and the fixed seat is installed in the cab through a screw rod. By pushing or pulling the handle control disc, the travel switch turntable is controlled to rotate, and the hydraulic cylinder is started, so that the lifting arm and the limit contact disc rotate upward or downward until the touch point on the limit contact disc contacts the contact head of the first travel switch or the contact head of the second travel switch, and the telescopic movement of the hydraulic cylinder is controlled to stop; The floating lowering control mechanism includes a third travel switch, which is electrically connected to a hydraulic solenoid valve and a relay. When the contact rod of the third travel switch contacts the floating contact head on the travel switch turntable, the hydraulic cylinder is forced to release pressure and retract, and the lifting arm floats and descends by its own weight.

2. The control device for the tractor hydraulic system according to claim 1, characterized in that, The first travel switch, the second travel switch, and the third travel switch are connected to a relay, a hydraulic solenoid valve, an electromagnetic overflow valve, and a power supply through a connection circuit. The connection circuit includes a first relay J1, a second relay J2, and a third relay J3. The first relay J1 includes a normally open contact J1-1, a normally open contact J1-2, and a normally closed contact J1-3 of the first travel switch. One end of the normally open contact J1-1 of the first relay J1 is connected to the power supply, and the other end is connected to the rising electromagnetic overflow valve coil. One end of the normally open contact J1-2 is connected to the normally open contact J1-1 and the power supply, and the other end is connected to the rising hydraulic solenoid valve coil. The second relay J2 includes a normally open contact J2-1, a normally open contact J2-2, and a normally closed contact J2-3 of the first travel switch. One end of the normally open contact J2-1 of the second relay J2 is connected to the power supply, and the other end is connected to the falling electromagnetic overflow valve coil. One end of the normally open contact J2-2 is connected to the normally open contact J2-1 and the power supply, and the other end is connected to the falling hydraulic solenoid valve coil. The third relay J3 includes a normally open contact J3-1. One end of the normally open contact J3-1 is connected to the power supply, and the other end is connected to the falling hydraulic solenoid valve coil. One end of the first relay J1 is connected to the power supply, and the other end is connected to one end of the normally closed contact J1-3 of the first travel switch. The other end of the normally closed contact J1-3 is respectively connected to the normally closed contact J2-3 of the second travel switch and the normally closed contact J3-2 of the third travel switch. One end of the second relay J2 is connected to the power supply, and the other end is connected to one end of the normally closed contact J2-3 of the second travel switch. The other end of the normally closed contact J2-3 is respectively connected to the normally closed contact J1-3 and one end of the normally closed contact J3-2. One end of the third relay J3 is connected to the power supply, and the other end is connected to one end of the normally closed contact J3-2 of the third travel switch. The other end of the normally closed contact J3-2 is connected to the power supply.

Images