A hydraulic circuit for automatically switching the fast and slow back movements of a taphole drilling machine trolley and a control method thereof

Abstract

The application relates to a hydraulic circuit for automatically switching the fast and slow back of a taphole cutting machine trolley, which comprises an oil motor with a brake, a back oil throttle valve one, a back oil throttle valve two, a one-way sequence valve, a pilot pressure reducing valve, an overflow valve one, an overflow valve two, a three-position four-way electromagnetic reversing valve, a two-position four-way electromagnetic reversing valve, a one-way valve, a pressure reducing valve, a pressure main pipe, a back oil main pipe and an internal leakage main oil pipe; the pressure oil port P of the three-position four-way electromagnetic reversing valve is communicated with the pressure main pipe, and the back oil port T is communicated with the back oil main pipe; the three-position four-way electromagnetic reversing valve has two outlets, one of which A is firstly connected with one end of the overflow valve one through an oil path, then connected with one end of the pilot pressure reducing valve through an oil path, connected with one end of the one-way sequence valve, connected with the A cavity of the oil motor, and connected with the one-way sequence valve in parallel with the back oil throttle valve one, and the other end of the overflow valve one is connected with the other outlet B of the three-position four-way electromagnetic reversing valve.

Description

Technical Field

[0001] This invention relates to a hydraulic circuit, specifically a hydraulic circuit for automatically switching the fast and slow retraction of a taphole machine trolley, belonging to the fields of mechanical equipment and hydraulic control technology. Background Technology

[0002] Hydraulic rock drills are currently crucial taphole opening equipment in blast furnaces, providing functions such as forward and reverse rotation, forward and reverse drilling, and soot blowing. The forward movement of the taphole opening trolley provides the feed force for the drill rod and allows it to quickly retract from the taphole. To reduce drill rod wear during taphole opening, the blast furnace maximizes the trolley's retraction speed and pressure to prevent the drill rod from sticking to the molten iron and burning. While maximizing the retraction speed and pressure reduces drill rod wear, it also increases the impact force on the mechanical limit switches, frequently causing damage and even trolley trolley malfunctions such as falling into the molten iron trough. Furthermore, the drill rod is typically around 5 meters long with a diameter of only about 40mm. During drilling, the drill rod bends, necessitating adjustable pressure to match the pressure as the drill rod's length, diameter, and material change.

[0003] The patent application (patent number): CN202222652133.X, entitled "A Braking Control System for a Tape Opening Machine," discloses a braking control system for a tape opening machine, comprising: a hydraulic motor with a normally closed hydraulic brake inside; a braking circuit; a buffer circuit; and a control circuit. The hydraulic motor is a bidirectional fixed-displacement motor. The normally closed hydraulic brake brakes the hydraulic motor under the action of a spring and releases the hydraulic motor after pressurized oil is introduced. The braking circuit includes a pressure reducing valve, a safety valve, a solenoid directional valve, and a one-way throttle valve. The buffer circuit is a hydraulic bridge circuit composed of an overflow valve and a check valve, which provides bidirectional buffering for the hydraulic motor. This braking control system for a tape opening machine avoids sudden changes in positive and reverse pressure of external loads. In case of overload, it can absorb hydraulic shock, prevent pipeline rupture and hydraulic component oil leakage, thereby improving the working efficiency of the tape opening machine. The overflow bridge is used to achieve motor braking, and the low-pressure side check valve can replenish oil from the oil tank to the oil circuit, avoiding the phenomenon of air suction in the oil suction chamber during the reversing braking process of the motor.

[0004] Patent application number CN202120376374.9, entitled "A Pilot Control Circuit for a Fully Hydraulic Blast Furnace Opening Machine," discloses a pilot control circuit for a fully hydraulic blast furnace opening machine. The circuit includes an oil inlet manifold and an oil return manifold. The oil inlet manifold is connected to the inlets of a first and second directional valve via pipes. The first and second directional valves are connected to the opening machine's rotation control circuit via pipes. The outlets of the first and second directional valves are connected via connecting pipes and then via pipes to a check valve. The oil inlet manifold is also connected to the inlets of a third and fourth directional valve via pipes. The outlets of the third and fourth directional valves are connected via connecting pipes and then via pipes to the check valve. This pilot control circuit for a fully hydraulic blast furnace opening machine, through its overall structure and the use of check valves, reduces equipment failures, extends the service life of the fully hydraulic control circuit, lowers maintenance costs, and ensures smooth and stable blast furnace production.

[0005] The above-mentioned prior art does not involve a hydraulic circuit and its control method for automatically switching the fast and slow retraction of the trolley of the iron tapping machine, nor does it solve the technical problems existing in the prior art. Summary of the Invention

[0006] This invention addresses the technical problems existing in the prior art by providing a hydraulic circuit and its control method for automatically switching the fast and slow retraction of the taphole machine trolley. The trolley retracts at maximum speed upon startup; after startup, pressure changes automatically switch the hydraulic circuit to a low-speed retraction state, preventing the trolley from colliding with the mechanical limit switch at maximum speed. Simultaneously, the hydraulic control circuit allows for adjustable trolley feed pressure, preventing bending failures during drill pipe drilling. This invention is primarily used in taphole opening equipment for blast furnace smelting.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows: To solve the above technical problems, one of the technical solutions proposed by the present invention is: a hydraulic circuit for automatically switching the fast and slow retraction of a taphole machine trolley, wherein the taphole machine trolley is equipped with four wheels, driving the drill rod to reciprocate on the feed beam. The taphole machine trolley is driven by a hydraulic motor mechanism via a chain. The hydraulic motor mechanism is driven by a hydraulic motor hydraulic circuit. The hydraulic motor hydraulic circuit includes a hydraulic motor with a brake, a return oil throttle valve one, a return oil throttle valve two, a one-way sequence valve, a pilot-operated pressure reducing valve, a relief valve one, a relief valve two, a three-position four-way solenoid directional valve, a two-position four-way solenoid directional valve, a check valve, a pressure reducing valve, a pressure main pipe, a return oil main pipe, and an internal leakage main oil pipe; the pressure port P of the three-position four-way solenoid directional valve is connected to the pressure main pipe, and the return port T is connected to the return oil main pipe; the three-position four-way solenoid directional valve has two outlets, one of which, outlet A, is first connected to one end of the relief valve one via an oil circuit, and then connected to one end of the pilot-operated pressure reducing valve via an oil circuit. One end of the pilot-operated pressure reducing valve is connected to one end of the one-way sequence valve. One end of the one-way sequence valve is connected to chamber A of the oil motor. The return oil throttle valve is connected in parallel with the one-way sequence valve. The other end of the relief valve is connected to the other outlet B of the three-position four-way solenoid directional valve. The control port X of the one-way sequence valve is connected to the other outlet B of the three-position four-way solenoid directional valve. The other outlet B of the three-position four-way solenoid directional valve is connected to one end of the relief valve through an oil circuit, and then connected to one end of the return oil throttle valve through an oil circuit. The other end of the return oil throttle valve is connected to chamber B of the oil motor. The other end of the relief valve is connected to the other outlet A of the three-position four-way solenoid directional valve.

[0008] The two-position four-way solenoid directional valve has a pressure port P connected to a pressure reducing valve, which is connected to the main pressure pipe. Its return port T is connected to a check valve, which is connected to the main return pipe. The two-position four-way solenoid directional valve has two outlets, one of which, outlet A, is closed and not used. The other outlet is connected to the brake control port of the hydraulic motor.

[0009] To solve the above-mentioned technical problems, the second technical solution proposed by this invention is: a hydraulic circuit control method for automatically switching the fast and slow retraction of the trolley of the taphole machine, as detailed below:

[0010] Trolley forward movement: When the trolley feeding mechanism reaches the working position, the feed beam is at a 10° angle to the horizontal. When the command to open the trolley hydraulic motor brake is issued, the pressure oil overcomes the force of the brake plate spring, and the hydraulic motor brake opens; during this process, the two-position four-way solenoid directional valve reverses, the pressure oil P connects to the brake control port of the hydraulic motor, and the pressure reducing valve reduces the pressure of the main pressure oil pipe from 20MPa to 3MPa, and the hydraulic motor brake opens.

[0011] When the trolley forward command is issued, the three-position four-way solenoid directional valve switches, connecting the pressure port P of the three-position four-way solenoid directional valve with port A. 20MPa pressure oil flows through the three-position four-way solenoid directional valve to the pilot-operated pressure reducing valve. The pilot-operated pressure reducing valve reduces the pressure to 7MPa. The 7MPa pressure oil flows through the parallel one-way sequence valve and return oil throttle valve one to the oil motor A chamber. The oil motor output shaft begins to rotate, and the oil motor B chamber begins to output return oil. The return oil flows to the return oil throttle valve two, which throttles and regulates the speed of the oil, controlling the forward speed of the trolley. The throttled and regulated return oil flows to the return port T of the three-position four-way solenoid directional valve, and the system enters the feed state.

[0012] When the production demands of the blast furnace change, the diameter, length, and material of the drill rod need to be changed, which in turn changes the rigidity of the drill rod. During the feed process, the drill rod may bend and deform. This invention adds a pilot-operated pressure reducing valve to adjust the required feed pressure.

[0013] Since the brake of the hydraulic motor is controlled by a two-position four-way solenoid directional valve, due to the long standby time, most of the oil in the control oil circuit will flow back to the oil tank. Also, because the oil circuit is too long, the brake of the hydraulic motor takes too long to open during operation. Therefore, a check valve is designed on the oil return of the two-position four-way solenoid directional valve to fill the brake of the hydraulic motor with low-pressure oil, so that the hydraulic motor brake can respond sensitively when opening.

[0014] Trolley Reverse: When the drill rod of the trolley opens the iron hole, the trolley needs to retract. At this time, the drill rod is stuck to the molten iron in the iron hole, requiring high pressure and high flow to pull out the drill rod. After the command for the trolley to retract is issued, the three-position four-way solenoid directional valve reverses, connecting the pressure port P of the three-position four-way solenoid directional valve to port B. 20MPa pressure oil flows through the three-position four-way solenoid directional valve to the return oil throttle valve two, and then flows to the B chamber of the oil motor. The oil motor starts to rotate in reverse, and the A chamber of the oil motor starts to output return oil. The return oil flows to the one-way sequence valve. At this time, the pressure oil in the B chamber of the oil motor is 20MPa. The 20MPa pressure oil opens the one-way sequence valve through the control port X of the one-way sequence valve, and the return oil flows quickly to the pilot-operated pressure reducing valve, and then to the return oil port T of the three-position four-way solenoid directional valve. The system enters the drill rod pulling state, that is, the trolley rapid retraction state.

[0015] When the trolley pulls the drill pipe and begins to retreat rapidly, the oil pressure in chamber B of the hydraulic motor drops from 20MPa to below 15MPa. Simultaneously, the oil pressure in port X of the one-way sequence valve also drops to below 15MPa. The one-way sequence valve closes, and the return oil, after being throttled and speed-regulated by the parallel return oil throttle valve, slowly flows to the return oil port T of the three-position four-way solenoid directional valve. The system automatically enters the slow retreat state of the trolley.

[0016] Compared with existing technologies, this invention has the following advantages: the taphole machine automatically switches between fast and slow speeds during the trolley's rod retraction process, reducing drill rod consumption and preventing the taphole machine trolley from crashing into the mechanical limit switch at full speed due to operator error, thus preventing the trolley from falling into the molten iron ditch; the drill rod feed pressure is adjustable, generally between 50MPa and 80MPa, to adapt to changes in blast furnace production needs, as well as variations in drill rod diameter, length, and material, preventing bending and deformation of the drill rod; a one-way valve is designed on the return oil of the two-position four-way electromagnetic reversing valve, ensuring that the hydraulic motor brake is filled with low-pressure oil, making the hydraulic motor brake release more responsive, reducing the opening time from 30 seconds to 1-2 seconds. Attached Figure Description

[0017] Figure 1 The schematic diagram of the hydraulic circuit for automatically switching the fast and slow retraction of the trolley of the iron-opening machine in this invention.

[0018] In the diagram: 1. Three-position four-way solenoid directional valve, 2. Relief valve II, 3. Relief valve I, 4. Pilot-operated pressure reducing valve, 5. Return oil throttle valve I, 6. Return oil throttle valve II, 7. One-way sequence valve, 8. Hydraulic motor brake, 9. Hydraulic motor, 10. Two-position four-way solenoid directional valve, 11. Pressure reducing valve, 12. One-way valve, 13. Pressure main pipe, 14. Return oil main pipe, 15. Internal leakage main oil pipe. Detailed Implementation

[0019] To enhance understanding of the present invention, the embodiments will be described in detail below with reference to the accompanying drawings.

[0020] Example 1: See Figure 1 In this embodiment, the hydraulic circuit automatically switches between fast and slow retraction of the taphole machine trolley. The taphole machine trolley has four wheels, which drive the drill rod to reciprocate on the feed beam. The taphole machine trolley is driven by a hydraulic motor mechanism via a chain. The hydraulic motor mechanism is driven by a hydraulic motor circuit.

[0021] Hydraulic circuit for oil motor, see Figure 1 The hydraulic circuit of the oil motor includes the oil motor 9, the oil motor brake 8, the return oil throttle valve 1 5, the return oil throttle valve 2 6, the one-way sequence valve 7, the pilot-operated pressure reducing valve 4, the relief valve 1 3, the relief valve 2 2, the three-position four-way solenoid directional valve 1, the two-position four-way solenoid directional valve 10, the one-way valve 12, the pressure reducing valve 11, the pressure main pipe 13, the return oil main pipe 14, and the internal leakage main oil pipe 15.

[0022] The pressure port P of the three-position four-way solenoid directional valve 1 is connected to the pressure main pipe 13, and the return port T is connected to the return main pipe 14. The three-position four-way solenoid directional valve 1 has two outlets. One outlet A is first connected to one end of the relief valve 3 through an oil circuit, and then connected to one end of the pilot-operated pressure reducing valve 4 through an oil circuit. The other end of the pilot-operated pressure reducing valve 4 is connected to one end of the one-way sequence valve 7. One end of the one-way sequence valve 7 is connected to chamber A of the oil motor 9. The return oil throttle valve 5 is connected to the one-way sequence valve 7. The three-position four-way solenoid directional valve 1 is connected in parallel. The other end of the overflow valve 3 is connected to the other outlet B of the three-position four-way solenoid directional valve 1. The control port X of the one-way sequence valve 7 is connected to the other outlet B of the three-position four-way solenoid directional valve 1. The other outlet B of the three-position four-way solenoid directional valve 1 is connected to one end of the overflow valve 2 through an oil circuit, and then connected to one end of the return oil throttle valve 6 through an oil circuit. The other end of the return oil throttle valve 6 is connected to the B chamber of the oil motor 9. The other end of the overflow valve 2 is connected to the other outlet A of the three-position four-way solenoid directional valve 1.

[0023] The pressure port P of the two-position four-way solenoid directional valve 10 is connected to the pressure reducing valve 11, which is connected to the pressure main pipe 13. The return port T is connected to the check valve 12, which is connected to the return main pipe 14. The two-position four-way solenoid directional valve 10 has two outlets, one of which, outlet A, is closed and not used. The other outlet is connected to the control port of the hydraulic motor brake 8.

[0024] like Figure 1 As shown, when the trolley of the opening machine moves forward: the electromagnet of the two-position four-way solenoid valve 10 is energized and reversed, the pressure oil in the pressure oil main pipe 13 passes through the pressure reducing valve 11, the pressure reducing valve 11 reduces the pressure oil and connects it to the pressure oil port P of the two-position four-way solenoid valve 10, the pressure oil P connects to the brake control oil port of the oil motor, and the oil motor brake 8 is opened. When the left electromagnet of the three-position four-way solenoid directional valve 1 is energized and reversed, the pressure port P of the three-position four-way solenoid directional valve 1 is connected to the port A. The pressurized oil flows through the three-position four-way solenoid directional valve 1 to the pilot-operated pressure reducing valve 4. Then, the pressurized oil flows through the parallel one-way sequence valve 8 and the return oil throttle valve 5 to the A chamber of the oil motor 9. The output shaft of the oil motor 9 begins to rotate in the forward direction, and the B chamber of the oil motor 9 begins to output return oil. The return oil flows to the return oil throttle valve 6. The return oil throttle valve 6 throttles and regulates the speed of the oil, controlling the forward speed of the trolley. The return oil that has been throttled and regulated flows to the return port T of the three-position four-way solenoid directional valve 1, and the system enters the forward motion state of the trolley.

[0025] like Figure 1As shown, when the trolley of the opening machine moves backward: the solenoid of the two-position four-way solenoid valve 10 is energized and reversed, and the hydraulic motor brake 8 is opened. The right solenoid of the three-position four-way solenoid valve 1 is energized and reversed, and the pressure port P of the three-position four-way solenoid valve 1 is connected to the B port. The pressurized oil flows through the three-position four-way solenoid valve to the return oil throttle valve 6, and then flows to the B chamber of the hydraulic motor 9. The output shaft of the hydraulic motor 9 begins to rotate in reverse, and the A chamber of the hydraulic motor 9 begins to output return oil. The return oil flows to the one-way sequence valve 7. At this time, the pressurized oil 8 in the B chamber of the hydraulic motor opens the one-way sequence valve 7 through the control port X of the one-way sequence valve 7. The return oil flows to the pilot-operated pressure reducing valve 4, and then to the return port T of the three-position four-way solenoid valve 1. The system enters the trolley backward movement state.

[0026] In actual use, due to the excessively long oil circuit, the hydraulic motor brake 8 takes a long time to open, and there is a delay of about 10 seconds before it can operate after the command is issued; the drill rod of the iron tapping machine is generally about 5 meters long and only about 40 mm in diameter. When the trolley moves forward to drill, the drill rod will bend, and the pressure when the trolley moves forward needs to be adjusted according to the actual situation; the designed parallel return oil throttle valve 5 and one-way sequence valve 7 combine to realize the automatic switching of the trolley's backward speed. The control pressure of the one-way sequence valve 7 also needs to be adjusted according to the actual situation to reduce the wear of the drill rod and the failure of the trolley to crash into the mechanical limit and fall into the iron ditch.

[0027] To address the above issues, this embodiment also provides a hydraulic circuit control method for automatically switching the fast and slow retraction of the trolley of the taphole machine. This method includes an automatic switching control method for the fast and slow retraction of the trolley of the taphole machine, a control method for quickly opening the brake of the hydraulic motor 9, and a control method for preventing the drill rod of the taphole machine from bending when it rotates forward.

[0028] Trolley forward movement: When the trolley feeding mechanism reaches the working position, the feed beam is at a 10° angle to the horizontal.

[0029] When the command to open the hydraulic motor brake 8 is issued, the pressurized oil overcomes the spring force of the brake plate, and the hydraulic motor brake 8 opens. During this process, the solenoid of the two-position four-way solenoid valve 10 is energized and reversed, the pressurized oil P connects to the control port of the motor brake 8, and the pressure reducing valve 11 reduces the pressure of the main pressurized oil pipe from 20MPa to 3MPa, thus opening the hydraulic motor brake 8. The check valve 12 is positioned between the return port T of the two-position four-way solenoid valve 10 and the main return oil pipe 14 to prevent a delay of approximately 10 seconds. After the solenoid of the two-position four-way solenoid valve 10 is de-energized and reversed, the B port of the two-position four-way solenoid valve 10 connects with the T port, and all the oil in the oil pipe flows back to the oil tank. After the solenoid of the two-position four-way solenoid valve 10 is energized and reversed, the pressurized oil reaches the brake 8 slowly, causing a delay of approximately 10 seconds. The opening pressure of the check valve 12 is set to 1.6MPa to prevent the hydraulic motor brake 8 from not closing completely.

[0030] When the trolley forward command is issued, the left electromagnet of the three-position four-way solenoid valve 1 is energized and reversed, connecting the pressure port P of the three-position four-way solenoid valve 1 to port A. 20MPa pressure oil flows through the three-position four-way solenoid valve to the pilot-operated pressure reducing valve 3, which reduces the pressure to 7MPa. The 7MPa pressure oil then flows through the parallel one-way sequence valve 8 and the return oil throttle valve 5 to chamber A of the hydraulic motor 9. The output shaft of the hydraulic motor 9 begins to rotate, and chamber B of the hydraulic motor 9 begins to output return oil. The return oil flows to the return oil throttle valve 6, which throttles and regulates the speed of the oil flow. The opening of the return oil throttle valve is set to 50%, controlling the forward speed of the trolley. The throttled return oil flows to the return port T of the three-position four-way solenoid valve 1, and the system enters the forward state. The trolley forward pressure is adjusted from 20MPa to 7MPa to prevent the drill pipe from bending during rotation and causing malfunctions. Relief valve 1 (3) and relief valve 2 (2) act as safety valves to prevent hydraulic shock in the oil circuit.

[0031] Trolley retraction: When the drill rod of the trolley opens the iron hole, the trolley needs to retract. At this time, the drill rod is stuck to the molten iron in the iron hole, and large pressure and large flow are required to pull out the drill rod.

[0032] When the command to retract the trolley is issued, the right side of the three-position four-way solenoid valve 1 is energized and reversed. The pressure port P of the three-position four-way solenoid valve 1 is connected to the B port. The 20MPa pressure oil flows through the three-position four-way solenoid valve 1 to the return oil throttle valve 7, and then flows to the B chamber of the hydraulic motor. The hydraulic motor 9 starts to rotate in reverse, and the A chamber of the hydraulic motor 9 starts to output return oil. The return oil flows to the one-way sequence valve 8. At this time, the pressure oil in the B chamber of the hydraulic motor 9 is 20MPa. The 20MPa pressure oil opens the one-way sequence valve 8 through the control port X. The return oil flows quickly to the pilot pressure reducing valve 4, and then to the return port T of the three-position four-way solenoid valve 1. The system enters the drill rod pulling state, that is, the trolley fast retraction state.

[0033] When the trolley pulls the drill pipe and begins to retreat rapidly, the pressure oil in chamber B of the hydraulic motor 9 drops from 20MPa to below 15MPa. Simultaneously, the pressure oil at control port X of the one-way sequence valve 8 also drops below 15MPa, reaching the adjusted pressure of 15MPa. The one-way sequence valve 7 closes, and the return oil passes through the parallel return oil throttle valve 5. With the return oil throttle valve 5 at 30% opening, the return oil is throttled and its speed is regulated, flowing slowly to the return oil port T of the three-position four-way solenoid directional valve 1. The system automatically enters the slow retreat state of the trolley. This automatic switching between fast and slow retreat control of the trolley not only reduces drill pipe consumption but also prevents the trolley from damaging the mechanical limit switch and falling into the molten iron ditch.

[0034] This invention is not limited to the specific technical solutions of the above embodiments. Besides the above embodiments, this invention may have other implementation methods. For those skilled in the art, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the protection scope of this invention.

Claims

1. A hydraulic circuit for automatically switching the fast and slow retraction of a taphole machine trolley, characterized in that, The hydraulic circuit includes a hydraulic motor with a brake, a return oil throttle valve one, a return oil throttle valve two, a one-way sequence valve, a pilot-operated pressure reducing valve, a relief valve one, a relief valve two, a three-position four-way solenoid directional valve, a two-position four-way solenoid directional valve, a check valve, a pressure reducing valve, a pressure main pipe, a return oil main pipe, and an internal leakage main oil pipe; the pressure port P of the three-position four-way solenoid directional valve is connected to the pressure main pipe, and the return port T is connected to the return oil main pipe; the three-position four-way solenoid directional valve has two outlets, one of which, outlet A, is first connected to one end of the relief valve one through an oil circuit, and then connected to one end of the pilot-operated pressure reducing valve through an oil circuit. The other end of the pilot-operated pressure reducing valve is connected to one end of the one-way sequence valve, and one end of the one-way sequence valve is connected to the A chamber of the oil motor. The return oil throttle valve is connected in parallel with the one-way sequence valve. The other end of the relief valve is connected to the other outlet B of the three-position four-way solenoid directional valve. The control port X of the one-way sequence valve is connected to the other outlet B of the three-position four-way solenoid directional valve. The other outlet B of the three-position four-way solenoid directional valve is connected to one end of the relief valve through an oil circuit, and then connected to one end of the return oil throttle valve through an oil circuit. The other end of the return oil throttle valve is connected to the B chamber of the oil motor. The other end of the relief valve is connected to the other outlet A of the three-position four-way solenoid directional valve.

2. The hydraulic circuit for automatically switching the fast and slow retraction of the taphole machine trolley according to claim 1, characterized in that, The pressure port P of the two-position four-way solenoid directional valve is connected to the pressure reducing valve, which is connected to the pressure main pipe. The return port T is connected to the check valve, which is connected to the return main pipe. The two-position four-way solenoid directional valve has two outlets, one of which, outlet A, is closed and not used, and the other outlet is connected to the brake control port of the oil motor.

3. A hydraulic circuit control method for automatically switching the fast and slow retraction of the trolley of an iron-opening machine, characterized in that, The hydraulic circuit for automatically switching the fast and slow retraction of the trolley of the taphole opening machine as described in claim 1 or 2 is controlled as follows: Trolley Forward Movement: When the trolley feeding mechanism reaches the working position, the feed beam is at a 10° angle to the horizontal. When the command to open the trolley hydraulic motor brake is issued, the pressurized oil overcomes the brake plate spring force, and the hydraulic motor brake opens. During this process, the two-position four-way solenoid directional valve reverses, the pressurized oil P connects to the brake control port of the hydraulic motor, and the pressure reducing valve reduces the pressure in the main pressurized oil pipe from 20MPa to 3MPa, thus opening the hydraulic motor brake. When the trolley forward command is issued, the three-position four-way solenoid directional valve switches, connecting its pressure port P to port A. 20MPa pressure oil flows through the three-position four-way solenoid directional valve to the pilot-operated pressure reducing valve, which reduces the pressure to 7MPa. The 7MPa pressure oil then flows through the parallel one-way sequence valve and return oil throttle valve one to the hydraulic motor's A chamber. The hydraulic motor's output shaft begins to rotate, and the hydraulic motor's B chamber begins to output return oil. This return oil flows to the return oil throttle valve two, which throttles and regulates the oil flow, controlling the trolley's forward speed. The throttled return oil then flows to the return port T of the three-position four-way solenoid directional valve, and the system enters the feed state. When blast furnace production demands change, the diameter, length, and material of the drill rod need to be modified, leading to changes in the drill rod's rigidity and bending deformation during feed. This invention incorporates a pilot-operated pressure-reducing valve to regulate the required feed pressure. Because the hydraulic motor's brake is controlled by a 2-position 4-way solenoid directional valve, the long standby time causes most of the oil in the control circuit to flow back to the oil tank. Furthermore, the long oil circuit results in an excessively long brake opening time during operation. Therefore, a check valve is designed on the return oil line of the 2-position 4-way solenoid directional valve to ensure the brake is filled with low-pressure oil, allowing for a more sensitive brake opening response. Trolley Reverse: When the drill rod of the trolley opens the iron taphole, the trolley needs to retract. At this time, the drill rod is stuck to the molten iron at the taphole, requiring high pressure and high flow to pull it out. When the command to retract the trolley is issued, the three-position four-way solenoid directional valve switches, connecting the pressure port P of the three-position four-way solenoid directional valve to port B. 20MPa pressure oil flows through the three-position four-way solenoid directional valve to the return oil throttle valve two, and then flows to the B chamber of the hydraulic motor. The hydraulic motor starts to rotate in reverse, and the A chamber of the hydraulic motor starts to output return oil. The return oil flows to the one-way sequence valve. At this time, the pressure oil in the B chamber of the hydraulic motor is 20MPa. The 20MPa pressure oil opens the one-way sequence valve through the control port X, and the return oil quickly flows to the pilot-operated pressure reducing valve, and then to the return port T of the three-position four-way solenoid directional valve. The system enters the drill rod pulling state, i.e., the trolley rapid retraction state. When the trolley pulls the drill pipe and begins to retreat rapidly, the oil pressure in chamber B of the hydraulic motor drops from 20MPa to below 15MPa. Simultaneously, the oil pressure in port X of the one-way sequence valve also drops to below 15MPa. The one-way sequence valve closes, and the return oil, after being throttled and speed-regulated by the parallel return oil throttle valve, slowly flows to the return oil port T of the three-position four-way solenoid directional valve. The system automatically enters the slow retreat state of the trolley.

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