Control method of electric hydraulic jack with safety protection function

Abstract

The invention discloses a control method of an electric hydraulic jack with a safety protection function, which is characterized in that when the jack is controlled to ascend, an ascending button of a positioning button area is pressed, and a main control module controls the jack to perform jacking; the current and the temperature of the motor are monitored in the jacking process, when it is monitored that the current of the motor exceeds a preset current parameter during positioning, the main control module controls an ascending button and a descending button in the positioning button area to be locked, and at the moment, the ascending button and the descending button in the positioning button area both lose efficacy; when the jack is continuously controlled to jack, the motor is controlled to be started by pressing an ascending button of the safety button area, the motor drives the electric pump to be started, and hydraulic oil is pumped into the jack to enable the jack to continuously jack. Through the arrangement, a worker can conveniently operate the electric jack to lift a vehicle or other heavy objects, meanwhile, the operation process of the jack is monitored and safely protected, and therefore the using safety of the electric jack is improved, and potential safety hazards are reduced.

Description

Technical Field

[0001] The invention relates to an electric hydraulic jack, and in particular to a control method of the electric hydraulic jack with a safety protection function. Background Art

[0002] An electric hydraulic jack is a jack that uses an electric motor as a power element to drive the jack for lifting. When the jack is lowered, the oil is released by opening the oil release valve, thereby achieving the lifting and lowering functions of the car.

[0003] The existing technology includes a technical solution of using a push-pull electromagnet to drive the oil drain valve to open and close, a technical solution of controlling the opening and closing of the oil drain valve by a solenoid valve, and a solution of controlling the rise and fall of the jack by controlling the forward and reverse rotation of the motor and gear pump.

[0004] In the above three control methods, when the operator presses the corresponding button, the main control module controls the corresponding motor, pushes and pulls the electromagnet or solenoid valve to drive the jack to lift and lower.

[0005] In the prior art, the drive of the electric jack can be controlled by pressing the switch button on the handle without manual pressing. For safety reasons, the switch on the handle is generally set at the far end of the jack handle, away from the lifting component of the jack, so that the operator can keep a certain safe distance from the lifted car as much as possible. However, in the actual lifting of the car, since it is necessary to ensure that the lifting component of the jack can correctly contact the lifting point of the vehicle, the operator usually lies down at the bottom of the lifted car to observe closely whether the jack correctly contacts the lifting point of the vehicle. However, since the operating button of the existing electric jack is at the far end of the handle, the operator's arm length cannot be used to observe and operate the handle switch at the same time, so the operator needs to climb in and out from the bottom of the lifted car from time to time, while operating the jack and observing whether the lifting component of the jack correctly contacts the lifting point of the lifted vehicle. Such an operation method is time-consuming and labor-intensive, inconvenient and unsafe. Therefore, it is necessary to provide the operator with a jack and vehicle lifting positioning method to facilitate the operator to operate the jack while observing that the jack arm can correctly contact the lifting point of the lifted vehicle, while ensuring the personal safety of the operator. To this end, a control method for an electric hydraulic jack with a safety protection function is proposed. Summary of the invention

[0006] The purpose of the present invention is to solve the above problems and to provide a control method for an electric hydraulic jack with a safety protection function.

[0007] In order to achieve the above object, the present invention provides the following technical solution: a control method of an electric hydraulic jack with a safety protection function, characterized in that: When controlling the positioning of the jack and the object to be lifted, press the rising button in the positioning button area to send a signal to the main control module, which controls the motor to start, and the motor drives the electric pump to start, and the hydraulic oil is pumped into the jack to lift it; During the positioning and lifting process, the motor current acquisition module collects and monitors the motor current. The motor current will increase after the jack contacts the object being lifted. When the motor current acquisition module detects that the motor current exceeds the preset current parameters during positioning and then feeds back to the main control module, the main control module no longer receives the command signals of the up button and the down button in the positioning button area, or no longer outputs control commands after receiving the command signals of the up button and the down button in the positioning button area. At this time, the up button and the down button in the positioning button area are temporarily invalid and in a locked state. At this time, if it is necessary to continue to control the lifting of the jack, the operator must send a signal to the main control module by pressing the up button in the safety button area. The main control module controls the motor to start, and the motor drives the electric pump to start, and then hydraulic oil is pumped into the jack to continue lifting.

[0008] Further preferably, a control method for controlling the descent of the jack by a descent button in the positioning button area is included; the method includes: when the jack is not in contact with the object to be lifted, directly pressing the descent button in the positioning button area sends a signal to the main control module, and the main control module controls the electromagnet to be energized, thereby opening the oil release valve to return oil and lowering the jack; When the up button and down button in the positioning button area of ​​the lifted object are in a locked state, first press the down button or up button in the safety button area to send a command to the main control module. After receiving the command, the main control module controls the electromagnet 1 or the motor to work, thereby unlocking the up button in the positioning button area; then continue to press the up button in the positioning button area for a set time. If the motor current exceeds the set current parameter during positioning, the main control module controls the up button in the positioning button area to lock it again. When the motor current does not exceed the set current parameter during positioning within the set time, the down button in the positioning button area is unlocked. After unlocking, press the down button in the positioning button area to send a signal to the main control module. The main control module controls the electromagnet 1 to be energized, thereby opening the oil release valve to return oil, so that the jack is lowered.

[0009] Further preferably, the process of controlling the jack to continue to rise by the rising button in the safety button area is also included, and the motor current acquisition module collects and monitors the motor current. When the motor current exceeds the set value, the main control module controls the motor to stop working; after the motor stops working for a set time, the rising button in the safety button area is pressed again to control the jack to rise. If the jack rises normally and the motor current does not exceed the set value, normal work is performed; if the motor current exceeds the set value again, the main control module continues to control the motor to stop working; When controlling the jack to descend, by pressing the descending button in the safety button area, a signal is sent to the main control module, and the main control module controls the electromagnet to be energized, thereby opening the oil release valve to return oil and lowering the jack.

[0010] Further preferably, the motor temperature is collected and monitored during the operation of the motor through a temperature collection module. When the motor temperature collection module detects that the motor temperature exceeds the set value, it sends a signal to the main control module. The main control module controls the motor to stop working. The motor can only be started again after the motor temperature is lower than the set value.

[0011] Further preferably, the up button and down button in the positioning button area are set at any position of the jack or on a control terminal that establishes a communication connection with the jack main control module through wired or wireless communication; the up button and down button in the safety button area are set on the handle of the jack and at one end far away from the jack and the object being lifted.

[0012] Further preferably, when controlling the movement of electromagnet one to open the oil drain valve and lower the jack, the main control module controls the power-on of electromagnet one, which, after being energized, drives the transmission component used to push the oil drain valve to open the oil drain valve to return oil, thereby lowering the jack. Then the main control module controls the power-on of electromagnet two, which, after being energized, is magnetically connected to a metal component, so that the transmission component maintains the position of pushing the oil drain valve to open, and then the main control module controls the power-off of electromagnet one.

[0013] Further preferably, the temperature and current of electromagnet one and electromagnet two are detected in real time during the descent process. When the temperature and current of electromagnet one and electromagnet two are within the set range, they continue to work normally. When the temperature and current exceed the set range, the main control module controls to cut off the power to electromagnet one and electromagnet two.

[0014] Further preferably, when the single continuous working time of the second electromagnet exceeds the set value, the main control module actively cuts off the current output and the jack stops descending.

[0015] Further preferably, it also includes a display module controlled by the main control module for displaying the jack status and battery pack status.

[0016] Further preferably, the method of lowering the jack by controlling the electromagnet and the oil drain valve through the main control module is replaced by controlling the solenoid valve through the main control module to switch the return oil circuit to lower the jack, or by controlling the rotation direction of the motor and the gear pump through the main control module to switch the flow direction of the hydraulic oil to lower the jack.

[0017] Beneficial effects of the present invention: Through the configuration of the present invention, it is convenient for workers to operate the electric jack to lift vehicles or other heavy objects, and at the same time, the operation process of the jack can be monitored and protected, thereby improving the safety of the electric jack when in use and reducing potential safety hazards; By setting the rising button and the falling button in the positioning button area, the rising button is used to drive the jack to rise when it is unloaded, and the falling button is used to drive the jack to fall when it is unloaded. The rising button and the falling button in the positioning button area are used to adjust the lifting position of the jack. After the jack contacts the object to be lifted, the rising button and the falling button in the positioning button area are locked after the motor current exceeds the current parameter set during positioning. At this time, the locking of the rising button and the falling button fails. At this time, the user can only climb out of the object to be lifted or leave the vicinity of the object to be lifted, and then press the rising button set in the safety button area after being in a safe position to drive the jack to continue lifting. The rising button and the falling button in the positioning button area can be unlocked only after the rising button in the safety button area is pressed, and the rising button in the positioning button area can be pressed to control the jack to rise after unlocking. Before pressing the down button in the positioning button area to control the jack to descend, you must first keep pressing the up button in the positioning button area for a set time to ensure that the jack is in a no-load state. Only then can you control the jack to descend by pressing the down button in the positioning button area. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the local structure of the jack using the present invention; Figure 2 This is a schematic diagram of the first position of the positioning button area and the safety button area in the jack using the present invention; Figure 3 It is a schematic diagram of the second position of the positioning button area and the safety button area in the jack of the present invention; Figure 4 It is a schematic diagram of the third position of the positioning button area and the safety button area in the jack using the present invention; Figure 5 It is a fourth position schematic diagram of the positioning button area and the safety button area in the jack using the present invention.

[0019] Description of the drawings: 1. Jack; 2. Motor; 3. Electromagnet 1; 4. Transmission part; 5. Electromagnet 2; A. Positioning button area; B. Safety button area. DETAILED DESCRIPTION

[0020] Hereinafter, we will further illustrate the control method of the electric hydraulic jack with safety protection function described in the present invention in conjunction with the accompanying drawings.

[0021] It should be noted that all directional indications such as up, down, left, right, front, back, etc. in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture as shown in the accompanying drawings. If the specific posture changes, the directional indication will also change accordingly.

[0022] In the present invention, unless otherwise clearly defined and limited, the terms "connection", "fixation" and the like should be understood in a broad sense; they can be mechanical connection or electrical connection; they can be directly connected or indirectly connected through an intermediate medium; they can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0023] See also Figure 1-Figure 5 As shown in, a control method of an electric hydraulic jack 1 with a safety protection function is characterized by: When the jack 1 is moved to the bottom of the object to be lifted for lifting, the operator is located under the object to be lifted and observes the lifting positions of the jack 1 and the object to be lifted. First, the jack 1 is controlled to perform no-load lifting until the jack 1 contacts the lifting position of the object to be lifted. When controlling the positioning of the jack 1 and the object to be lifted, press the rising button in the positioning button area to send a signal to the main control module, and the main control module controls the motor to start, and the motor drives the electric pump to start, and the hydraulic oil is pumped into the jack 1 to lift it; During the positioning and lifting process, the motor current acquisition module collects and monitors the motor current. After the jack 1 contacts the object being lifted, the motor current will increase. When the motor current acquisition module collects that the motor current exceeds the preset current parameter during positioning, it will feed back to the main control module. Then, the main control module will no longer receive the command signals of the up button and down button in the positioning button area, or will no longer output control commands after receiving the command signals of the up button and down button in the positioning button area. At this time, the up button and down button in the positioning button area are temporarily invalid and in a locked state. At this time, if it is necessary to continue to control the lifting of jack 1, the operator must press the rising button in the safety button area to send a signal to the main control module, and the main control module controls the motor to start, and the motor drives the electric pump to start, and the hydraulic oil is pumped into jack 1 to continue lifting; During the continuous lifting process of the jack 1, the motor current and temperature are monitored by the motor current acquisition module and the motor temperature acquisition module. When the motor current or temperature exceeds the set value, the control module controls the motor to stop working and controls the display module to light up a red light. When the motor current exceeds the set value, the main control module controls the motor to stop working; after the motor stops working for the set time, press the up button in the safety button area again to control the jack 1 to rise. If the jack 1 rises normally and the motor current does not exceed the set value, it will work normally; if the motor current exceeds the set value again, the main control module controls the motor to stop working; When the motor temperature acquisition module detects that the motor temperature exceeds the set value, it sends a signal to the main control module, and the main control module controls the motor to stop working. The motor can only be started again when the motor temperature is lower than the set value; When controlling the jack 1 to descend, by pressing the descending button in the safety button area, a signal is sent to the main control module, and the main control module controls the electromagnet 1 3 to be energized. After the electromagnet 1 3 is energized, it drives the transmission part 4 used to push the oil drain valve to open the oil drain valve to return oil, so that the jack 1 is lowered. The electromagnet 1 3 adopts a push-pull electromagnet or other push electromagnet; then the main control module controls the electromagnet 2 5 to be energized. After the electromagnet 2 5 is energized, it is magnetically connected with a metal part, so that the transmission part 4 keeps pushing the oil drain valve to open position, and then the main control module controls the electromagnet 1 3 to be de-energized; During the descent process, the temperature and current of the electromagnet 1 3 and the electromagnet 2 5 are detected in real time. When the temperature and current of the electromagnet 1 3 and the electromagnet 2 5 are within the set range, they continue to work normally. When the temperature and current exceed the set range, the main control module controls the display module to light up a red light and control the power off of the electromagnet 1 3 and the electromagnet 2 5. After waiting for the temperature to drop below the set value, it can be restarted; after the interruption set time, the electromagnet 1 3 and the electromagnet 2 5 are powered on again. If the current is lower than the set value, it works normally. If it is still higher than the set value, it will be powered off again and stop working. After pressing the down button or up button in the safety button area, the main control module controls the up button in the positioning button area to be unlocked; after unlocking, the jack 1 can be driven to lift by pressing the up button in the positioning button area; After the up button in the positioning button area is unlocked, when the up button in the positioning button area is pressed, if the motor current is lower than the current parameter set during positioning, the jack 1 is driven normally to lift up; if the motor current exceeds the current parameter set during positioning, the main control module controls the up button and down button in the positioning button area to be locked again; When the jack 1 is not in contact with the object to be lifted and the jack 1 is controlled to descend, the descending button in the positioning button area is directly pressed to send a signal to the main control module, and the main control module controls the electromagnet 1 3 to be energized, thereby opening the oil release valve to return oil and causing the jack 1 to descend; When the rising button and the falling button in the positioning button area of ​​the lifted object are in a locked state, when controlling the jack 1 to descend, first press the falling button or the rising button in the safety button area to send a command to the main control module. After receiving the command, the main control module controls the electromagnet 1 or the motor to work, and unlocks the rising button in the positioning button area. After unlocking, continue to press the rising button in the positioning button area for a set time. If the motor current exceeds the set current parameter during positioning, the main control module controls the rising button in the positioning button area to lock again. When the motor current does not exceed the set current parameter during positioning within the set time, the falling button in the positioning button area is unlocked. After unlocking, press the falling button in the positioning button area to send a signal to the main control module. The main control module controls the electromagnet 1 to be energized, thereby opening the oil release valve to return oil, so that the jack descends. During the whole use process of the jack 1, the battery pack of the jack 1 is monitored in real time. When the voltage of the battery pack is lower than the set value, the main control module controls the yellow light in the display module to flash, informing the user that the battery voltage is too low. At this time, the voltage of the battery pack cannot start the motor, and only the electromagnet 1 3 and the electromagnet 2 5 can be started to drive the jack 1 to descend; Through the setting and control of electromagnet 1 3 and electromagnet 2 5, electromagnet 1 3 is used to drive the transmission part 4 to push the oil drain valve to open, and electromagnet 2 5 is used to maintain the position of the transmission part 4, so as to keep the oil drain valve in an open state; after controlling the electromagnet 1 3 to drive the oil drain valve to open, the electromagnet 2 5 is controlled to move to maintain the position of the electromagnet 1 3 in place, and then the electromagnet 1 3 is powered off, and only the electromagnet 2 5 is relied on to maintain the electromagnet 1 3 and the transmission part 4 in place; compared with electromagnet 1 3, the energy consumption required for electromagnet 2 5 when working is lower than that of electromagnet 1 3. It is relatively low and generates less heat, and can work effectively for a long time. Therefore, through the setting and control of electromagnet 25, while ensuring the realization of the oil drain valve function, the overall working energy consumption of the electromagnet is reduced, and at the same time, it is avoided that the electromagnet 3 is in a high-power state for a long time, causing the temperature of the electromagnet 3 to reach the set high temperature value too quickly, thereby avoiding the jack 1 from stopping working after the temperature of the electromagnet 3 exceeds the set temperature value limit when the jack 1 is not completely lowered, causing the jack 1 to stop descending. It is necessary to wait for the temperature of the electromagnet 3 to drop before working again, affecting the work efficiency.

[0024] In one embodiment, in order to better control the temperature of electromagnet 25, when the single continuous working time of electromagnet 25 exceeds the set value, the main control module actively cuts off the current output, and the jack stops descending. When controlling the descent again, the descending button in the positioning button area or the safety button area is pressed again to send a signal to the main control module. The main control module controls the electromagnet 3 to be energized. After the electromagnet 3 is energized, it drives the transmission part 4 used to push the oil drain valve to open the oil drain valve to return oil, so that the jack 1 descends; then the main control module controls the electromagnet 25 to be energized. After the electromagnet 25 is energized, it is magnetically connected to a metal part, so that the transmission part 4 keeps pushing the oil drain valve to open the position, and then the main control module controls the electromagnet 3 to be powered off to control the jack to continue to descend.

[0025] In one embodiment, the up button and down button of the positioning button area are arranged at the handle of the jack 1 near the main body of the jack 1 or at any position on the main body of the jack 1, or are arranged on a control terminal connected to the main control module of the jack 1 by wire or wireless; the up button and down button of the safety button area are arranged on the handle of the jack 1 and on one end away from the jack 1; The control terminal and the main control module are connected by wire or wirelessly; when a wireless connection is adopted, the control terminal and the main control module are connected by a communication module, and the communication module is selected from any one of a Bluetooth communication module, an RF wireless control module or a network communication module; In one embodiment, it also includes a display module controlled by the main control module for displaying different conditions of the jack 1 and the battery pack condition. The display module is used to display green light, red light and yellow light. The yellow light is used to display that the battery pack voltage is lower than the set value, the red light is used to display that the temperature and current parameters of the electromagnet 1 3, the electromagnet 2 5 and the motor exceed the set value, and the green light is used to display that the power is on and working normally; the machine can work normally when the green light is on, and stop working when the red light is on. When the yellow light flashes, the motor cannot be started, and the jack 1 can only be started to descend.

[0026] In one embodiment, the main control module controls the electromagnet 3 and the oil drain valve to lower the jack 1, and the main control module controls the solenoid valve to switch the return oil circuit to lower the jack 1, or controls the rotation direction of the motor 2 and the gear pump to switch the flow direction of the hydraulic oil to lower the jack 1; When the solenoid valve is used, the main control module controls the opening and closing of the solenoid valve to realize the opening and closing of the oil return line, thereby realizing the lowering or stopping of the jack 1; When the motor 2 and the gear pump are used, the main control module is used to control the change of the rotation direction of the motor 2 and the gear pump to switch the lifting and lowering of the jack 1, thereby realizing the lifting or lowering of the jack 1.

[0027] The protection scope of the present invention is not limited to the above embodiments and their variations. Conventional modifications and replacements made by those skilled in the art based on the contents of this embodiment all fall within the protection scope of the present invention.

Claims

1. A control method for an electric hydraulic jack with a safety protection function, characterized in that: When controlling the positioning of the jack and the object to be lifted, press the rising button in the positioning button area to send a signal to the main control module, which controls the motor to start, and the motor drives the electric pump to start, and the hydraulic oil is pumped into the jack to lift it; During the positioning and lifting process, the motor current acquisition module collects and monitors the motor current. The motor current will increase after the jack contacts the object being lifted. When the motor current acquisition module detects that the motor current exceeds the preset current parameters during positioning and then feeds back to the main control module, the main control module no longer receives the command signals of the up button and the down button in the positioning button area, or no longer outputs control commands after receiving the command signals of the up button and the down button in the positioning button area. At this time, the up button and the down button in the positioning button area are temporarily invalid and in a locked state. At this time, if it is necessary to continue to control the lifting of the jack, the operator must send a signal to the main control module by pressing the up button in the safety button area. The main control module controls the motor to start, and the motor drives the electric pump to start, and then hydraulic oil is pumped into the jack to continue lifting.

2. The control method of the electric hydraulic jack with safety protection function according to claim 1 is characterized in that: Also included is a control method for controlling the jack to descend by using a descending button in the positioning button area; It includes that when the rising button and the descending button in the positioning button area are not in a locked state, a signal is directly sent to the main control module by pressing the descending button in the positioning button area, and the main control module controls the electromagnet to be energized, thereby opening the oil release valve to return oil and lowering the jack; When the up button and down button in the positioning button area of ​​the lifted object are in a locked state, first press the down button or up button in the safety button area to send a command to the main control module. After receiving the command, the main control module controls the electromagnet 1 or the motor to work, thereby unlocking the up button in the positioning button area; then continue to press the up button in the positioning button area for a set time. If the motor current exceeds the set current parameter during positioning, the main control module controls the up button in the positioning button area to lock it again. When the motor current does not exceed the set current parameter during positioning within the set time, the down button in the positioning button area is unlocked. After unlocking, press the down button in the positioning button area to send a signal to the main control module. The main control module controls the electromagnet 1 to be energized, thereby opening the oil release valve to return oil, so that the jack is lowered.

3. The control method of the electric hydraulic jack with safety protection function according to claim 1 is characterized in that: It also includes controlling the jack to continue to rise through the rising button in the safety button area, and the motor current acquisition module collects and monitors the motor current. When the motor current exceeds the set value, the main control module controls the motor to stop working; after the motor stops working for a set time, the rising button in the safety button area is pressed again to control the jack to rise. If the jack rises normally and the motor current does not exceed the set value, it will work normally; if the motor current exceeds the set value again, the main control module continues to control the motor to stop working; When controlling the jack to descend, by pressing the descending button in the safety button area, a signal is sent to the main control module, and the main control module controls the electromagnet to be energized, thereby opening the oil release valve to return oil and lowering the jack.

4. A control method for an electric hydraulic jack with a safety protection function as described in claims 1 to 3, characterized in that: It also includes collecting and monitoring the motor temperature during the operation of the motor through a temperature collection module. When the motor temperature collection module detects that the motor temperature exceeds the set value, it sends a signal to the main control module. The main control module controls the motor to stop working. The motor can only be controlled to start again after the motor temperature is lower than the set value.

5. The control method of the electric hydraulic jack with safety protection function according to claim 2 is characterized in that: The up button and down button in the positioning button area are set at any position of the jack or on a control terminal that establishes a communication connection with the jack main control module through wired or wireless; the up button and down button in the safety button area are set on the handle of the jack and at one end far away from the jack and the object being lifted.

6. A control method for an electric hydraulic jack with a safety protection function according to claim 2 or 3, characterized in that: When the oil drain valve is opened by controlling the action of electromagnet one to lower the jack, the main control module controls the power supply to electromagnet one. After the power supply of electromagnet one, it drives the transmission part used to push the action of the oil drain valve to open the oil drain valve to return oil, so that the jack is lowered. Then the main control module controls the power supply to electromagnet two. After the power supply of electromagnet two, it is magnetically connected with a metal part, so that the transmission part keeps pushing the oil drain valve to open position. Then the main control module controls the power supply to electromagnet one.

7. The control method of the electric hydraulic jack with safety protection function according to claim 6 is characterized in that: During the descent process, the temperature and current of electromagnet 1 and electromagnet 2 are detected in real time. When the temperature and current of electromagnet 1 and electromagnet 2 are within the set range, they continue to work normally. When the temperature and current exceed the set range, the main control module controls the power supply to electromagnet 1 and electromagnet 2 to be cut off.

8. The control method of the electric hydraulic jack with safety protection function according to claim 7 is characterized in that: It also includes that when the single continuous working time of the electromagnet 2 exceeds the set value, the main control module actively cuts off the current output and the jack stops descending.

9. The control method of the electric hydraulic jack with safety protection function according to claim 1, characterized in that: It also includes a display module controlled by the main control module for displaying the status of the jack and the battery pack.

10. A control method for an electric hydraulic jack with a safety protection function according to claim 2 or 3, characterized in that: The method of lowering the jack by controlling the electromagnet and the oil drain valve through the main control module is replaced by controlling the solenoid valve through the main control module to switch the return oil circuit to lower the jack, or by controlling the rotation direction of the motor and gear pump through the main control module to switch the flow direction of the hydraulic oil to lower the jack.

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