Forklift lifting buffer hydraulic circuit

Abstract

This invention discloses a forklift lifting buffer pressure circuit, comprising: a main control valve connected to a lifting cylinder; a pilot control valve connected to the main control valve; an electro-proportional relief valve and a second relief valve connected in sequence to the main control valve, the electro-proportional relief valve being connected to the lifting cylinder, the second relief valve having a third port connected to the pilot control valve; the electro-proportional relief valve having a first port and a second port, the first port being connected to a fifth port of the second relief valve; the second port being connected to a fourth port of the second relief valve; the lifting cylinder having a proximity switch controlling the conduction of the first and second ports, when the first and second ports are conducted, the fifth port is depressurized, thus conducting the third and fourth ports; by shifting the valve core of the second relief valve through the electromagnetic relief valve, pressure relief buffering can be performed on different working states of the pilot control valve, so that in addition to critical limit buffering, the hydraulic process can be buffered to any degree at any time.

Description

Technical Field

[0001] This invention relates to the field of hydraulic press control circuit technology, and more particularly to a forklift lifting buffer hydraulic circuit. Background Technology

[0002] In a typical forklift hydraulic system, the actuator is a hydraulic cylinder. When the piston of the hydraulic cylinder reaches the end position, it will impact the cylinder barrel. However, since the inner mast is rigidly connected to the piston rod of the lifting cylinder, when the lifting cylinder drives the mast to the top and is under heavy load, the impact will cause a huge safety hazard.

[0003] For example, a hydraulic control system integrating drive and buffer, disclosed in Chinese patent literature (publication number CN115306799A), includes a power circuit, a drive and buffer control circuit, and an actuator. The power circuit includes a ball valve, an oil tank, a level sensor, and a temperature sensor. The oil tank is equipped with a level sensor, a temperature sensor, and a level thermometer in sequence. The oil inlet of the ball valve is connected to the oil outlet of the oil tank. The output of the motor is connected to a plunger pump, and the oil inlet of the plunger pump is connected to the oil outlet of the oil tank. However, this solution requires an additional pressure relief system and relies on the status detection of the hydraulic oil tank for buffering. Summary of the Invention

[0004] To address the problem of hydraulic oil pressure relief and buffering in existing technologies, this invention provides a forklift lifting buffer pressure circuit. By releasing pilot control oil through an electro-proportional relief valve, the valve core of the main control valve is displaced, thereby achieving lifting buffering of the mast.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A forklift lifting buffer pressure circuit includes: a main control valve connected to a lifting cylinder, the main control valve controlling the flow of pressure oil to the lifting cylinder; and a pilot control valve connected to a pilot control valve controlling pilot control oil.

[0007] The main control valve is connected to an electro-proportional relief valve and a second relief valve connected in sequence. The electro-proportional relief valve is connected to the lifting cylinder. The second relief valve has a third port connected to the pilot control valve.

[0008] The electro-proportional overflow valve is provided with a first port and a second port. The first port is connected to the fifth port of the second overflow valve. The second port is connected to the fourth port of the second overflow valve.

[0009] The lifting cylinder is equipped with a proximity switch that controls the conduction of the first and second ports. When the first and second ports are connected, the pressure at the fifth port is released, which in turn connects the third and fourth ports. Under normal conditions, the pressure between the third and fourth ports of the second relief valve is balanced. During pressure relief, the valve core of the second relief valve is shifted via the electromagnetic relief valve, allowing the third and fourth ports of the second relief valve to provide pressure relief and buffering for different operating states of the pilot control valve. This enables pressure buffering of the hydraulic process at any time and to any degree, in addition to critical limit buffering.

[0010] Preferably, the proximity switch includes an upper proximity switch and a lower proximity switch arranged sequentially. The upper proximity switch emits a first proximity signal, and the lower proximity switch emits a second proximity signal. Buffer control is achieved by the upper and lower proximity switches at different positions.

[0011] Preferably, the main control valve is connected to an overflow control unit, which controls the flow of pilot control oil to the valve core inside the main control valve; the overflow control unit controls the release of pilot control oil based on a signal from a proximity switch. The overflow control unit enables the control of the valve core position of the main control valve via pilot control oil.

[0012] Preferably, the pilot control valve is located in the overflow control section. The pilot control valve includes a first pilot control valve and a second pilot control valve, each connected to the main control valve. The first and second pilot control valves control the pilot control oil to enter the valve core of the main control valve from different directions. By using the first and second pilot control valves, the valve core of the main control valve can be moved in different directions, thereby enabling different operating modes.

[0013] Preferably, the overflow control unit includes an overflow path connected to the main control valve, the overflow path connected to a second overflow valve, and the overflow path connected to both a first pilot control valve and a second pilot control valve. The overflow path releases pilot control oil from the hydraulic circuit, thereby adjusting the spool position of the main control valve.

[0014] Preferably, the second relief valve opens different relief paths according to different signals from the proximity switch; when the relief path is opened, the pilot control oil in the pilot control valve is released. This allows for different releases for different hydraulic processes.

[0015] Preferably, a pilot oil source valve is included, which is connected to both the pilot control valve and the second relief valve, and outputs pilot control oil. Pilot control oil is obtained through the pilot oil source valve.

[0016] Preferably, the main control valve is connected to a hydraulic oil supply unit, which supplies hydraulic oil to the valve core inside the main control valve. The main control valve has a PD port connected to the hydraulic oil supply unit, and the hydraulic oil supply unit supplies pressurized oil from the PD port to the main control valve. Hydraulic oil is then supplied to the valve core of the main control valve through the hydraulic oil supply unit.

[0017] Preferably, the hydraulic oil unit includes an oil pump that supplies hydraulic oil to the main control valve. The oil pump is connected to a hydraulic oil tank, which stores pressurized oil. The hydraulic oil is obtained through the oil pump.

[0018] Preferably, the lifting cylinder is connected to a mast, and the mast is rigidly connected to the piston rod inside the lifting cylinder; the proximity switch detects the position of the mast and sends a signal when a threshold is reached. By relying on the mast to lift to the top for cushioning, safety and comfort during operation are improved, the service life of the cylinder is extended, and hydraulic cushioning is achieved during forklift operation.

[0019] The present invention has the following advantages:

[0020] (1) Under normal conditions, the pressure between the third and fourth ports of the second relief valve is balanced. When depressurizing, the valve core of the second relief valve is moved by the electromagnetic relief valve, so that the third and fourth ports of the second relief valve can respectively depressurize and buffer the different working states of the pilot control valve, so that in addition to the limit buffer, the hydraulic process can be buffered at any time and to any degree; (2) Reduce parts and improve versatility; (3) Buffer by lifting the mast to the top, improve safety and comfort during operation, extend the working life of the cylinder, and realize hydraulic buffering during the operation of the forklift. Attached Figure Description

[0021] The accompanying drawings described below are merely exemplary. Those skilled in the art can derive other embodiments based on the provided drawings without any inventive effort.

[0022] Figure 1 This is a schematic diagram of the loop structure in the embodiment.

[0023] Figure 2 This is a schematic diagram of the loop operation logic in the embodiment.

[0024] In the picture:

[0025] 1-Electro-proportional relief valve; 2-Second relief valve; 3-Pilot control valve; 4-Main control valve; 5-Lifting cylinder; 6-Proximity switch; 7-Pilot oil source valve; 8-Oil pump; 9-Hydraulic oil tank. Detailed Implementation

[0026] Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] like Figure 1-2 As shown, in a preferred embodiment, the present invention discloses a forklift lifting buffer hydraulic circuit, including: a main control valve 4, which realizes the hydraulic action of the system in which the circuit is located through the main control valve. The main control valve is provided with a valve core. When the position of the valve core in the main control valve changes, the system in which the circuit is located performs different hydraulic actions. When performing different hydraulic actions, the main control valve outputs different hydraulic power.

[0028] The main control valve 4 is connected to a lifting cylinder 5, which provides power output to the circuit. The lifting cylinder controls the lifting and lowering actions under different hydraulic power outputs. The lifting cylinder includes a piston rod and a lifting cylinder cavity. A piston is mounted on the piston rod, dividing the lifting cylinder cavity into a rodless chamber and a rod chamber. The rodless chamber contains hydraulic oil, and the piston rod is located in the rod chamber. When the piston and piston rod move within the lifting cylinder cavity, the volumes of the rodless and rod chambers change accordingly. This change in volume causes corresponding displacement of the piston and piston rod within the lifting cylinder cavity, thereby controlling the lifting and lowering power through the piston rod.

[0029] The main control valve 4 controls the flow of pressurized oil to the lifting cylinder 5; the main control valve is used to output and retract the pressurized oil. The rodless chamber of the lifting cylinder is connected to the main control valve. The rodless chamber contains pressurized oil from the main control valve. When pressurized oil enters the rodless chamber from the main control valve, the volume of the rodless chamber increases, pushing the piston in the lifting cylinder towards the rod chamber, thus extending the piston rod. When the pressurized oil leaves the lifting cylinder and returns to the main control valve, the volume of the rodless chamber decreases, pushing the piston in the lifting cylinder towards the rodless chamber, thus retracting the piston rod. This achieves the pushing of the piston rod.

[0030] The main control valve 4 is connected to a pilot control valve 3, which outputs pilot control oil to the main control valve. The pilot control valve outputs pilot control oil, which in turn controls the valve core position of the main control valve, thereby changing the state of the main control valve. The pilot control valve has different input modes; when the pilot control valve is in different input modes, the operating mode of the main control valve is changed.

[0031] A pilot control valve controls pilot control oil; when the pilot control valve is open, the pilot control oil enters the main control valve through the pilot control valve, thereby causing the valve spool in the main control valve to move in the corresponding direction. The pilot control oil controls the oil input and output by changing the position of the valve spool.

[0032] The main control valve 4 is connected in sequence to an electro-proportional relief valve 1 and a second relief valve 2. The electro-proportional relief valve receives a signal indicating the need to open the buffer. When the electro-proportional relief valve receives the corresponding signal indicating the need to open the buffer, it is activated. The electro-proportional relief valve is normally closed, and its closed state does not affect the pilot control valve's control of the pilot control oil. When the electro-proportional relief valve is activated, it adjusts the state of the second relief valve.

[0033] The electro-proportional relief valve 1 is connected to the lifting cylinder 5. A signal indicating the need for buffering is received from the lifting cylinder via the electro-proportional relief valve, thus achieving buffering during the lifting and lowering process. Furthermore, the lifting cylinder can send its own operating status as a signal to the electro-proportional relief valve, or send the corresponding movement distance as a signal. The electro-proportional relief valve operates based on the signal from the lifting cylinder as a start signal. When the electro-proportional relief valve receives a signal, it internally conducts. When the electro-proportional relief valve is internally conducting, it opens to release pressure from the second relief valve.

[0034] The second relief valve 2 is provided with a third port connected to the pilot control valve 3; when the second relief valve is depressurized, pilot control oil returning from the pilot control valve is input through the third port. Through the third port, the pilot control oil in the pilot control valve is released, thereby slowing down the hydraulic action.

[0035] The electro-proportional relief valve 1 is provided with a first port and a second port. The electro-proportional relief valve is also provided with an energized coil. When the energized coil is energized, the first port and the second port are connected; when the energized coil is de-energized, the first port and the second port are in a closed state.

[0036] The first port is connected to the fifth port of the second relief valve; the first port is connected to the fifth port of the second relief valve. When the first port and the second port are connected, the pilot control oil is unloaded from the second port through the fifth port, so that the third port and the fourth port in the second relief valve are connected, thereby realizing the release of the pilot control oil of the pilot control valve from the third port or the fourth port. When the pilot control oil in the pilot control valve is released, the pilot control oil in the main control valve is reduced, which in turn reduces the valve core movement speed of the main control valve, and finally reduces the pressure oil input rate of the lifting cylinder, thus completing the buffering of the pressure action process.

[0037] The second port is connected to the fourth port of the second overflow valve; when the first port and the second port are connected, after the second overflow valve is opened, the pilot control oil flows from the third port to the fourth port, and the pilot control oil in the fourth port gradually balances with the pilot control oil in the second port, thereby stopping the buffer discharge.

[0038] The lifting cylinder is equipped with a proximity switch 6 that controls the conduction of the first and second ports. The proximity switch 6 obtains the hydraulic operation status of the lifting cylinder 5. The proximity switch detects the distance between the lifting cylinder and a fixed reference object. When the lifting cylinder moves to a position relative to the fixed reference object, the proximity switch sends a signal. The proximity switch sends the signal to the electro-proportional relief valve. Upon receiving the signal, the coil in the electro-proportional relief valve is energized, thereby connecting the first and second ports.

[0039] When the first and second ports are connected, the fifth port releases pressure, which in turn connects the third and fourth ports. Under normal conditions, the pressure between the third and fourth ports of the second relief valve is balanced. During pressure relief, the valve core of the second relief valve is shifted through the electromagnetic relief valve, allowing the third and fourth ports of the second relief valve to provide pressure relief and buffering for different operating states of the pilot control valve. This enables pressure buffering of the hydraulic process at any time and to any degree, in addition to critical limit buffering.

[0040] In other embodiments, the proximity switch of this solution includes an upper proximity switch and a lower proximity switch arranged sequentially. The upper and lower proximity switches detect the positions corresponding to different working states of the lifting cylinder, respectively. The upper proximity switch detects the position during lifting, and the lower proximity switch detects the position during lowering. When the upper or lower proximity switch detects its corresponding position, it sends out its respective signal.

[0041] The upper proximity switch sends a first proximity signal; the first proximity signal is sent to the electro-proportional relief valve, and upon receiving the first proximity signal, the coil of the electro-proportional relief valve is energized, causing the first port and the second port to conduct. When the first proximity signal is received, it indicates that the hydraulic process corresponding to the lifting cylinder has reached the limit position.

[0042] The lower proximity switch sends a second proximity signal. Buffer control is achieved by using the upper and lower proximity switches at different positions.

[0043] In other embodiments, the main control valve of this solution is connected to an overflow control unit, which controls the overflow of the pilot control oil in the main control valve, thereby achieving the release and buffering of the pilot control oil during the hydraulic control process.

[0044] The overflow control unit controls the flow of pilot control oil to the valve core inside the main control valve; when a venting buffer is required, the overflow control unit reduces the input of pilot control oil; when performing normal hydraulic operations, the overflow control unit controls the input and adjustment of pilot control oil to the main control valve.

[0045] The overflow control unit controls the release of pilot control oil based on the signal from the proximity switch. The overflow control unit enables the control of the main control valve's spool position via the pilot control oil.

[0046] In other embodiments, the pilot control valve of this solution is located in the overflow control unit. The overflow control unit controls the pilot control oil in the main control valve through the pilot control valve to achieve normal hydraulic operation. The pilot control valve includes a first pilot control valve and a second pilot control valve, which are respectively connected to the main control valve. The two pilot control valves control the pilot control oil for different hydraulic operation processes.

[0047] In use, the first pilot control valve and the second pilot control valve respectively control the pilot control oil to enter the valve core of the main control valve from different directions. The first pilot control valve and the second pilot control valve respectively realize the displacement of the valve core of the main control valve in different directions, thereby performing different working modes.

[0048] In other embodiments, the overflow control unit of this solution includes an overflow path connected to the main control valve, the overflow path being connected to a second overflow valve, and the overflow path being connected to both a first pilot control valve and a second pilot control valve. The overflow path releases pilot control oil from the hydraulic circuit, thereby adjusting the valve core position of the main control valve.

[0049] In other embodiments, the second overflow valve of this solution opens different overflow paths based on different signals from the proximity switches; the proximity switches emit different signals for different positions. When multiple proximity switches are present, each proximity switch emits a different signal based on its respective position threshold. Each proximity switch is directly connected to the electro-proportional overflow valve. When a proximity switch emits a signal, the electro-proportional overflow valve opens, thereby opening different circuits of the second overflow valve and achieving venting at different ports of the overflow path.

[0050] When the overflow path is open, the pilot control oil in the pilot control valve is released. This allows for different release methods for different hydraulic processes. When the overflow path releases oil through different ports, the corresponding pilot control oil in the pilot control valve is reduced at each port, thus achieving buffering under different hydraulic actions.

[0051] In other embodiments, this solution includes a pilot oil supply valve 7, which is connected to both the pilot control valve 3 and the second relief valve 2, providing pilot control oil. The pilot oil supply valve simultaneously inputs pilot control oil to both the second relief valve and the pilot control valve, and stops at the second relief valve, but continuously inputs oil to the pilot control valve to provide all the pilot control oil required to complete the hydraulic action.

[0052] The pilot oil source valve outputs pilot control oil. Pilot control oil is obtained through the pilot oil source valve.

[0053] In other embodiments, the main control valve of this solution is connected to a hydraulic oil supply unit, which supplies hydraulic oil to the valve core inside the main control valve; the hydraulic oil supply unit supplies hydraulic oil to the main control valve and pilot control oil to the overflow control unit, thus providing fluid for the hydraulic operation process.

[0054] The main control valve is equipped with a PD port connected to the hydraulic oil section, through which the hydraulic oil section inputs pressurized oil to the main control valve. Hydraulic oil is then supplied to the valve core of the main control valve via the hydraulic oil section.

[0055] In other embodiments, the hydraulic oil section of this solution includes an oil pump 8 that supplies hydraulic oil to the main control valve. The oil pump 8 is connected to a hydraulic oil tank 9, which stores pressurized oil. The hydraulic oil is obtained through the oil pump.

[0056] In other embodiments, the lifting cylinder of this solution is connected to a mast, which is rigidly connected to the piston rod inside the lifting cylinder. The mast provides cushioning during lifting, improving safety and comfort during operation, extending the cylinder's lifespan, and achieving hydraulic cushioning during forklift operation. The proximity switch detects the mast's position and sends a signal when a threshold is reached.

[0057] In other embodiments, this solution includes an electro-proportional relief valve 1, which is connected to a second relief valve 2. The electro-proportional relief valve 1 and the second relief valve 2 are connected to a pilot control valve 3, which is connected to a main control valve 4. The main control valve 4 is connected to a lifting cylinder 5. The lifting cylinder is equipped with an upper proximity switch and a lower proximity switch.

[0058] During operation, the oil pump draws oil from the hydraulic oil tank, pumping pressurized oil into the system. A portion of the pressurized oil reaches the PD port of the main control valve, while the other portion enters from the P1 port of the pilot oil source valve, undergoes pressure reduction, and then enters the accumulator. The pilot control oil then flows out from the V2 port of the pilot oil source valve, with a portion reaching the third port of the second relief valve and the other portion reaching the PK port of the pilot control valve.

[0059] In other embodiments, the first port of the electro-proportional relief valve is connected to the fifth port of the second relief valve. Since the coil of the electro-proportional relief valve is not energized, the electro-proportional relief valve remains closed. The relief valve also remains closed under the action of the pilot oil pressure on both sides and the spring, so that the pilot control oil is cut off at the third port of the second relief valve.

[0060] When the pilot control valve does not operate, the pilot control oil is cut off at its PK port, and at this time the main control valve and the lifting cylinder do not operate.

[0061] When the pilot control valve does not operate, the pilot control oil is cut off at its PK port, and at this time the main control valve and the lifting cylinder do not operate.

[0062] When the pilot control valve's C1 port actuates, its internal oil circuit is opened. Pilot control oil flows in from the PK port, then through the pilot control valve and out from its C1 port, reaching the main control valve's A1 port. The main control valve's spool moves to the left position. Pressure oil at the pilot control valve's PD port enters the main control valve, passes through its spool, and flows out from its A1 port to the rodless chamber of the lifting cylinder, causing the piston rod to extend and the gantry to lift. When the gantry is close to the top, i.e., when the gantry is about to complete its lifting stroke, the upper proximity switch detects the gantry's approach, causing the electro-proportional relief valve to reach a high level, energizing its coil. At this time, the electro-proportional relief valve opens, connecting its first and second ports. Control pressure oil at the fifth port of the second relief valve is unloaded through the relief valve. With the second relief valve open, pilot control oil in the pipeline is unloaded through it. As the valve core of the main control valve 4 gradually moves to the neutral position, the extension of the piston rod in the lifting cylinder 5 gradually stops, thus stopping the lifting of the gantry.

[0063] When the pilot control valve 3's C2 port actuates, its internal oil circuit is opened, and pilot control oil flows in from the PK port, flows out through the pilot control valve 3's C2 port, and reaches the main control valve 4's B1 port. Then, the valve core of the main control valve 4 moves to the right position, and the pressure oil at the PD port enters the main control valve 4, is cut off at the valve core, and controls the system pressure through the relief valve in the main control valve 4. The pressure oil in the rodless chamber of the lifting cylinder 5 returns to the main control valve 4 through the A1 port, and returns oil from the TD port through the valve core, causing the piston rod of the lifting cylinder 5 to retract and the gantry to descend. When the gantry descends to near the bottom, the lower proximity switch detects a signal, causing the electro-proportional relief valve 1 to receive a high level, energizing the coil. At this time, the electro-proportional relief valve 1 opens, making the first port and the second port of the electro-proportional relief valve 1 connected, and the control pressure oil at the fifth port of the second relief valve is unloaded through the second relief valve. As the valve core of the main control valve 4 gradually moves to the neutral position, the retraction of the piston rod in the lifting cylinder 5 gradually stops, thereby stopping the gantry from descending.

[0064] Any modifications or improvements made based on this invention without departing from its spirit are within the scope of protection claimed by this invention.

Claims

1. A forklift lifting buffer pressure circuit, characterized in that, include: The main control valve is connected to a lifting cylinder and controls the pressure oil to the lifting cylinder; the main control valve is also connected to a pilot control valve and controls the pilot control oil. The main control valve is connected to an electro-proportional relief valve and a second relief valve connected in sequence. The electro-proportional relief valve is connected to the lifting cylinder. The second relief valve has a third port connected to the pilot control valve. The electro-proportional overflow valve is provided with a first port and a second port. The first port is connected to the fifth port of the second overflow valve. The second port is connected to the fourth port of the second overflow valve. The lifting cylinder is equipped with a proximity switch that controls the conduction of the first port and the second port. When the first port and the second port are conducted, the pressure in the fifth port is released, which will conduct the third port and the fourth port. Under normal conditions, the pressure between the third and fourth ports of the second relief valve is balanced. When depressurization is performed, the valve core of the second relief valve is moved by the electromagnetic relief valve, so that the third and fourth ports of the second relief valve can respectively provide pressure relief and buffer for different working states of the pilot control valve. Except for the critical limit buffer, it can buffer the hydraulic process to any degree at any time.

2. The forklift lifting buffer pressure circuit according to claim 1, characterized in that, The proximity switch includes an upper proximity switch and a lower proximity switch arranged in sequence. The upper proximity switch emits a first proximity signal, and the lower proximity switch emits a second proximity signal.

3. A forklift lifting buffer pressure circuit according to claim 1 or 2, characterized in that, The main control valve is connected to an overflow control unit, which controls the flow of pilot control oil to the valve core inside the main control valve; the overflow control unit controls the release of pilot control oil according to the signal from the proximity switch.

4. The forklift lifting buffer pressure circuit according to claim 3, characterized in that, The pilot control valve is located in the overflow control section. The pilot control valve includes a first pilot control valve and a second pilot control valve that are respectively connected to the main control valve. The first pilot control valve and the second pilot control valve respectively control the pilot control oil to enter the valve core of the main control valve from different directions.

5. The forklift lifting buffer pressure circuit according to claim 3, characterized in that, The overflow control unit includes an overflow path connected to the main control valve, the overflow path connected to the second overflow valve, and the overflow path connected to the first pilot control valve and the second pilot control valve respectively.

6. The forklift lifting buffer pressure circuit according to claim 5, characterized in that, The second overflow valve opens different overflow paths according to different signals from the proximity switch; when the overflow path is opened, the pilot control oil in the pilot control valve is released.

7. A forklift lifting buffer pressure circuit according to claim 1 or 2, characterized in that, It includes a pilot oil source valve, which is connected to a pilot control valve and a second relief valve, and outputs pilot control oil.

8. The forklift lifting buffer pressure circuit according to claim 1, characterized in that, The main control valve is connected to a hydraulic oil section, which supplies hydraulic oil to the valve core inside the main control valve. The main control valve is provided with a PD port connected to the hydraulic oil section, and the hydraulic oil section supplies pressurized oil from the PD port to the main control valve.

9. A forklift lifting buffer pressure circuit according to claim 8, characterized in that, The hydraulic oil section includes an oil pump that supplies hydraulic oil to the main control valve, the oil pump being connected to a hydraulic oil tank, and the hydraulic oil tank storing pressurized oil.

10. A forklift lifting buffer pressure circuit according to claim 1 or 2, characterized in that, The lifting cylinder is connected to a gantry, and the gantry is rigidly connected to the piston rod inside the lifting cylinder; the proximity switch detects the position of the gantry and sends a signal when a threshold is reached.

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