Jack

Abstract

The jack comprises a cylinder body, a piston rod and a throttling element, the cylinder body is provided with a cavity, a throttling cavity, a first liquid hole and a second liquid hole, and the second liquid hole is communicated with the throttling cavity; the piston rod is movably connected with the cylinder body so that the piston rod can be switched between an extending state and a retracting state, the piston rod comprises a piston part and a rod part which are connected with each other, the piston part is arranged in the cavity and divides the cavity into a first cavity and a second cavity, the rod part penetrates through the cavity wall of the first cavity, the first cavity is communicated with the first liquid hole, and the second cavity is communicated with the second liquid hole. The second cavity is communicated with the throttling cavity; the throttling element is connected with the piston part, when the piston rod is switched from the stretching-out state to the retracting state, the throttling element is inserted into the throttling cavity, and a liquid inlet and return channel is defined by the outer wall of the throttling element and the cavity wall of the throttling cavity. According to the jack disclosed by the embodiment of the utility model, the retraction process of the piston rod has the characteristic of fast front and slow back, so that the stroke of the piston rod can be more accurately controlled, and the stroke of a load connected with the jack can be accurately controlled.

Description

Technical Field

[0001] This utility model relates to the technical field of lifting equipment, specifically to a jack. Background Technology

[0002] Jacks are commonly used support and moving equipment in mining operations. For example, they are used for roadway support, working face support, moving hydraulic supports forward, and relocating auxiliary coal mining machines. Mining jacks operate at high pressures, generally no less than 30 MPa, resulting in rapid piston rod extension and retraction, making precise control of their stroke difficult. Consequently, the movement speed of the load connected to the jack is also difficult to control precisely. Utility Model Content

[0003] This utility model aims to at least partially solve one of the technical problems in the related art.

[0004] Therefore, embodiments of this utility model propose a jack in which the piston rod retraction process is characterized by a fast initial movement followed by a slower retraction, which allows for more precise control of the piston rod's stroke, thereby enabling precise control of the stroke of the load connected to the jack.

[0005] The jack of this utility model embodiment includes a cylinder, a piston rod, and a throttling device. The cylinder has a cavity, a throttling chamber, a first liquid hole, and a second liquid hole. The cross-section of the throttling chamber is smaller than the cross-section of the cavity. The second liquid hole communicates with the throttling chamber. The piston rod is movably connected to the cylinder to switch between an extended state and a retracted state. The piston rod includes a piston portion and a rod portion connected to each other. The piston portion is disposed in the cavity and divides the cavity into a first chamber and a second chamber. The rod portion passes through the cavity wall of the first chamber. The first chamber communicates with the first liquid hole, and the second chamber communicates with the throttling chamber. The throttling device is disposed on the side of the piston portion facing the throttling chamber and is connected to the piston portion. When the piston rod switches from the extended state to the retracted state, the throttling device is inserted into the throttling chamber. The outer wall of the throttling device and the cavity wall of the throttling chamber form an inlet and outlet liquid channel.

[0006] In some embodiments, the throttling element is a throttling column arranged along the extension direction of the throttling cavity. The outer wall of the throttling element includes a fitting portion and a groove portion. In the retracted state, the fitting portion fits against the cavity wall of the throttling cavity, and the groove portion and the cavity wall of the throttling cavity form the inlet and outlet liquid channel.

[0007] In some embodiments, the outer wall of the throttling column has a plurality of grooves, the plurality of grooves being arranged at circumferential intervals along the throttling column, and the groove walls forming the groove portions.

[0008] In some embodiments, the throttling column includes a throttling section and a conical section, the throttling section being connected to the piston portion, and the cross-section of the conical section gradually decreasing in the direction away from the piston portion.

[0009] In some embodiments, the first chamber has a first chamber wall arranged toward the piston portion, and the second chamber has a second chamber wall arranged toward the piston portion; in the extended state, the piston portion is in contact with the first chamber wall, and in the retracted state, the piston portion is in contact with the second chamber wall.

[0010] In some embodiments, the piston portion has a boss on the side facing the first cavity wall, and the outer wall of the boss and the cavity wall of the first cavity form a first liquid inlet groove, which communicates with the first liquid hole.

[0011] In some embodiments, the piston portion has a second liquid inlet groove on the side facing the second cavity wall, and the second liquid inlet groove communicates with the groove.

[0012] In some embodiments, the second liquid inlet groove includes an annular groove and a plurality of grooves, the annular groove being arranged circumferentially along the piston portion, the plurality of grooves being arranged at intervals circumferentially along the piston portion, and both the grooves and the recesses communicating with the annular groove.

[0013] In some embodiments, the projections of the groove and the recess on the cross-section of the throttling column do not coincide.

[0014] In some embodiments, the wall of the first chamber has a through hole, the rod passes through the through hole, a seal is provided between the rod and the wall of the through hole, the seal is connected to the wall of the through hole, and the side of the seal facing the piston forms the first chamber wall.

[0015] In this embodiment of the jack, during the process of switching the rod from the extended state to the retracted state, the piston drives the throttling element to move closer to the throttling cavity, compressing the second chamber. Before the throttling element is inserted into the throttling cavity, the liquid in the second chamber flows back through the throttling cavity and the second liquid hole in sequence. The liquid backflow speed is relatively fast, which makes the piston rod retract quickly. This process is the rapid retraction process of the piston rod. After the throttling element is inserted into the throttling cavity, the liquid in the second chamber flows back through the inlet and outlet liquid channels and the second liquid hole in sequence. Since the cross-section of the inlet and outlet liquid channels is much smaller than the cross-section of the throttling cavity, the liquid backflow resistance increases, the liquid backflow speed slows down, which slows down the retraction speed of the piston rod. This process is the slow retraction process of the piston rod.

[0016] Therefore, the piston rod retraction process exhibits a characteristic of being fast at the beginning and slow at the end. During the slow retraction, the piston rod's stroke can be more precisely controlled, thereby precisely controlling the stroke of the load connected to the jack, ensuring the load accurately reaches the predetermined position. Furthermore, during the rapid retraction, the piston rod moves quickly, maintaining its overall movement speed. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of a jack according to an embodiment of the present invention.

[0018] Figure 2 This is a schematic diagram of the piston rod of a jack in the extended state according to an embodiment of the present invention.

[0019] Figure 3 This is a schematic diagram of the piston rod of the jack in the retracted state according to an embodiment of the present invention.

[0020] Figure 4 This is a schematic diagram of the piston rod and throttling column of a jack according to an embodiment of the present invention.

[0021] Figure 5 This is a schematic projection of the groove and slot of the jack in one embodiment of the present invention onto the cross-section of the throttling column.

[0022] Figure label:

[0023] 100. Jack;

[0024] 1. Cylinder block; 11. First chamber; 111. First chamber wall; 112. Through hole; 12. Second chamber; 121. Second chamber wall; 13. Throttling chamber; 131. Third chamber wall; 14. First liquid hole; 15. Second liquid hole; 16. Second connecting end;

[0025] 2. Piston rod; 21. Piston part; 211. Boss; 212. First liquid inlet groove; 213. Second liquid inlet groove; 2131. Annular groove; 2132. Groove; 22. Rod part; 221. First connecting end;

[0026] 3. Throttling column; 31. Groove; 311. Inlet / outlet channel; 312. Groove section; 313. Fitting section; 32. Throttling section; 33. Conical section;

[0027] 4. Sealing components. Detailed Implementation

[0028] The embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0029] like Figures 1 to 3 As shown, the jack 100 of this utility model embodiment includes a cylinder body 1, a piston rod 2, and a throttling element; the cylinder body 1 has a cavity, a throttling cavity 13, a first liquid hole 14, and a second liquid hole 15. The cross-section of the throttling cavity 13 is smaller than the cross-section of the cavity body, and the second liquid hole 15 communicates with the throttling cavity 13; the piston rod 2 is movably connected to the cylinder body 1 so that the piston rod 2 can switch between an extended state and a retracted state. The piston rod 2 includes a piston portion 21 and a rod portion 22 connected to each other. 21 is located in the cavity, dividing the cavity into a first chamber 11 and a second chamber 12. The rod 22 passes through the cavity wall of the first chamber 11. The first chamber 11 is connected to the first liquid hole 14, and the second chamber 12 is connected to the throttling cavity 13. The throttling element is located on the side of the piston 21 facing the throttling cavity 13 and is connected to the piston 21. When the piston rod 2 switches from the extended state to the retracted state, the throttling element is inserted into the throttling cavity 13. The outer wall of the throttling element and the cavity wall of the throttling cavity 13 form a liquid inlet and outlet channel.

[0030] In this embodiment of the jack 100, during the process of switching the rod 22 from the extended state to the retracted state, the piston 21 drives the throttling element to move closer to the throttling cavity 13, and the second chamber 12 is compressed. Before the throttling element is inserted into the throttling cavity 13, the liquid in the second chamber 12 flows back through the throttling cavity 13 and the second liquid hole 15 in sequence. The liquid backflow speed is relatively fast, which makes the piston rod 2 retract at a relatively fast speed. This process is the rapid retraction process of the piston rod 2. After the throttling element is inserted into the throttling cavity 13, the liquid in the second chamber flows back through the inlet and outlet liquid channels and the second liquid hole 15 in sequence. Since the cross-section of the inlet and outlet liquid channels is much smaller than the cross-section of the throttling cavity 13, the liquid backflow resistance increases, the liquid backflow speed slows down, which slows down the retraction speed of the piston rod 2. This process is the slow retraction process of the piston rod 2.

[0031] Therefore, the retraction process of piston rod 2 exhibits a characteristic of being fast at the beginning and slow at the end. During the slow retraction process, the stroke of piston rod 2 can be more precisely controlled, thereby precisely controlling the stroke of the load connected to jack 100, ensuring that the load accurately reaches the predetermined position. In addition, during the rapid retraction process of piston rod 2, the movement of piston rod 2 is faster, ensuring the overall movement speed of piston rod 2.

[0032] Similarly, the process of piston rod 2 switching from the extended state to the retracted state includes a slow extension process and a fast extension process; therefore, the piston rod 2 starts slowly when it extends, which can reduce the impact caused by the fast start, so that the jack 100 can operate smoothly, and thus it is easier to achieve precise control during the movement of the telescopic rod.

[0033] Alternatively, the liquid medium can be water or hydraulic oil.

[0034] like Figures 1 to 3 As shown, the cylinder body 1 is cylindrical, forming a cylindrical cavity and a cylindrical throttling chamber 13 inside it. The diameter of the throttling chamber 13 is smaller than the diameter of the cavity. The piston portion 21 is slidably disposed in the cavity. The piston is sealed to the cavity by a sealing structure (e.g., a sealing ring) to prevent leakage between the liquid in the first chamber 11 and the liquid in the second chamber 12. The first end of the rod portion 22 passes through the cavity wall of the first chamber 11 and extends to the outside of the cylinder body 1. The second end of the rod portion 22 is connected to the piston portion 21. The first end of the rod portion 22 forms a first connecting end 221. The side of the cylinder body 1 away from the rod portion 22 has a second connecting end 16. The first connecting end 221 and the second connecting end 16 are used to connect the load and the base, respectively, so that the movement of the load can be controlled by the extension and retraction of the piston rod 2.

[0035] The first liquid hole 14 and the second liquid hole 15 are both arranged through the side wall of the cylinder body 1. The first liquid hole 14 and the second liquid hole 15 are arranged close to both ends of the cylinder body 1 along the length direction of the cylinder body 1. The first liquid hole 14 is connected to the first chamber 11, and the second liquid hole 15 is connected to the throttling chamber 13. When the piston rod 2 switches from the extended state to the retracted state, liquid enters through the first liquid hole 14 and liquid returns through the second liquid hole 15. When the piston rod 2 switches from the retracted state to the extended state, liquid enters through the second liquid hole 15 and liquid returns through the first liquid hole 14.

[0036] like Figure 2 As shown, with the piston rod 2 extended, the throttling element is located in the second chamber 12; as Figure 3 As shown, when the piston rod 2 is in the retracted state, the throttling element is inserted into the throttling cavity 13. At this time, there is a gap between the end face of the throttling element away from the piston part 21 and the cavity wall of the throttling cavity 13 facing the piston part 21, so as to prevent the throttling element from colliding with the cavity wall of the throttling cavity 13 and causing damage to the throttling element.

[0037] The stroke of piston rod 2 during rapid retraction is called the rapid traverse stroke, and the stroke during slow retraction is called the slow traverse stroke. The rapid traverse stroke and the slow traverse stroke together constitute the total stroke of piston rod 2. It can be understood that the size of the rapid traverse stroke is determined by the length of the cavity, and the size of the slow traverse stroke is determined by the length of the throttling cavity 13. Those skilled in the art can make reasonable settings for the length of the cavity and the length of the throttling cavity 13 according to their needs.

[0038] In some embodiments, such as Figures 1 to 3 As shown, the throttling device is a throttling column 3 arranged along the extension direction of the throttling cavity 13. The outer wall of the throttling device includes a fitting part 313 and a groove part 312. In the retracted state, the fitting part 313 fits against the cavity wall of the throttling cavity 13, and the groove part 312 and the cavity wall of the throttling cavity 13 form an inlet and outlet liquid channel.

[0039] With the above settings, after the throttling column 3 is inserted into the throttling cavity 13, the fitting part 313 fits against the cavity wall of the throttling cavity 13, making the sliding of the throttling column 3 more stable. At the same time, the liquid can flow back through the groove part 312 and the second liquid hole 15 in sequence, thereby slowing down the retraction speed of the piston rod 2.

[0040] In some embodiments, such as Figure 4 and Figure 5 As shown, the outer wall of the throttling column 3 has a plurality of grooves 31, which are arranged at intervals along the circumference of the throttling column 3, and the groove wall of the groove 31 forms a groove portion 312.

[0041] Multiple grooves 312 can form multiple inlet and return liquid channels arranged circumferentially along the throttling column 3 between the cavity wall of the throttling chamber 13 and the grooves 312. The liquid can return through the multiple inlet and return channels 311, making the force on the throttling column 3 more uniform, thereby improving the stability of the throttling column 3.

[0042] Optionally, multiple grooves 31 are evenly arranged along the circumference of the throttling column 3.

[0043] Therefore, when the liquid flows back through multiple grooves 31, the force on the throttling column 3 is more uniform, which can further improve the stability of the cooperation between the throttling column 3 and the throttling cavity 13.

[0044] In some embodiments, such as Figures 1 to 3 As shown, the throttling column 3 includes a throttling section 32 and a cone section 33. The throttling section 32 is connected to the piston section 21, and the cross-section of the cone section 33 gradually decreases in the direction away from the piston section 21.

[0045] Through the above configuration, the cone segment 33 can act as a transition when the piston rod 2 switches from a rapid retraction process to a slow retraction process, so that the retraction speed of the piston rod 2 decreases gradually. Specifically, during the process of the throttling column 3 inserting into the throttling cavity 13, the cone segment 33 first enters the throttling cavity 13. During the insertion of the cone segment 33 into the throttling cavity 13, a gap is formed between the outer surface of the cone segment 33 and the cavity wall of the throttling cavity 13. As the cone segment 33 moves, this gap gradually decreases. The liquid in the second chamber 12 flows back through this gap, the throttling cavity 13, and the second liquid hole 15 in sequence, so that the liquid backflow speed gradually slows down, avoiding the liquid impacting the cylinder 1 due to a sudden decrease in the liquid backflow speed, improving the stability of the liquid backflow process, and thus improving the stability of the piston rod 2 during the retraction process.

[0046] Furthermore, by setting the conical section 33, the outer diameter of the end of the throttling column 3 facing the throttling cavity 13 is smaller, making it easier for the throttling column 3 to be inserted into the throttling cavity 13. The outer wall of the conical section 33 can guide the insertion of the throttling column 3 into the throttling cavity 13, making the throttling column 3 inserted into the throttling cavity 13 more smoothly.

[0047] Optionally, such as Figure 3 As shown, the throttle column 3, piston section 21 and rod section 22 are integrally formed.

[0048] This results in higher strength for the piston rod 2 and the throttling column 3.

[0049] Of course, in other embodiments, the piston portion 21 can also be fixedly connected to the throttling column 3 or the rod portion 22 by other connection methods, such as welding or threaded connection.

[0050] As an example, such as Figure 4 and Figure 5 The throttling section 32 is cylindrical, the conical section 33 is conical, and the cross-section of the groove 31 is semi-circular. The groove 31 extends through the length of the throttling column 3. In other words, the groove 31 extends from the throttling section 32 to the conical section 33, and the groove 31 on the outer side of the conical section 33 extends obliquely along the inclined direction of the outer side of the conical section 33.

[0051] In some embodiments, such as Figure 1 As shown, the first chamber 11 has a first chamber wall 111 arranged toward the piston portion 21, and the second chamber 12 has a second chamber wall 121 arranged toward the piston portion 21; in the extended state, the piston portion 21 is in contact with the first chamber wall 111, and in the retracted state, the piston portion 21 is in contact with the second chamber wall 121.

[0052] The first cavity wall 111 and the second cavity wall 121 can limit the sliding of the piston part 21, preventing the piston rod 2 from moving excessively and causing damage.

[0053] like Figure 1 and Figure 3 As shown, the first end of the rod 22 passes through the first cavity wall 111 and forms the first connecting end 221. In the extended state of the piston rod 2, the piston part 21 is in contact with the first cavity wall 111. The throttling chamber 13 has a third cavity wall 131 arranged towards the piston part 21. In the retracted state of the piston rod 2, the piston part 21 is in contact with the second cavity wall 121, and the throttling column 3 passes through the second cavity 12. At the same time, there is a gap between the end face of the throttling column 3 away from the piston part 21 and the third cavity wall 131 to prevent the throttling column 3 from colliding with the third cavity wall 131.

[0054] In some embodiments, such as Figure 2 and Figure 3 As shown, the piston part 21 has a boss 211 on the side facing the first cavity wall 111. The outer wall of the boss 211 and the cavity wall of the first cavity 11 form a first liquid inlet groove 212, which is connected to the first liquid hole 14.

[0055] When the piston rod 2 is in the extended state, the end face of the boss 211 facing the first cavity wall 111 is attached to the first cavity wall 111, and the first liquid inlet groove 212 is connected to the first liquid hole 14. When the piston rod 2 switches from the extended state to the retracted state, liquid enters the first liquid inlet groove 212 through the first liquid hole 14, which can apply pressure to the piston part 21 toward the second cavity 12 to push the piston part 21 to move toward the second cavity 12, thereby causing the piston rod 2 to switch from the extended state to the retracted state.

[0056] Optionally, such as Figure 2 and Figure 3 As shown, the boss 211 is cylindrical and is arranged coaxially with the piston part 21.

[0057] As a result, the first liquid inlet groove 212 surrounds the boss 211, and the liquid surrounds the boss 211 along the first liquid inlet groove 212, which can apply a more uniform pressure to the piston part 21, so that the piston part 21 moves towards the second chamber 12.

[0058] In some embodiments, such as Figure 3 As shown, the piston part 21 has a second liquid inlet groove 213 on the side facing the second cavity wall 121, and the second liquid inlet groove 213 is connected to the groove 31.

[0059] When the piston rod 2 is in the retracted state, the piston part 21 fits against the second cavity wall 121, and the groove part 312 and the cavity wall of the throttling cavity 13 form the above-mentioned liquid inlet and return channel. The second liquid inlet groove 213 is connected to the liquid inlet and return channel. When the piston rod 2 switches from the retracted state to the extended state, the liquid enters the gap formed between the outer surface of the cone section 33 and the cavity wall of the throttling cavity 13 through the second liquid hole 15. Then, it flows through multiple liquid inlet and return channels and enters the second liquid inlet groove 213. The liquid in the second liquid inlet groove 213 can directly apply pressure to the piston part 21 toward the first cavity 11, pushing the piston part 21 to move toward the first cavity 11, thereby causing the piston rod 2 to switch from the retracted state to the extended state.

[0060] In some embodiments, the second liquid inlet groove 213 includes an annular groove 2131 and a plurality of grooves 2132. The annular groove 2131 is arranged circumferentially along the piston portion 21, and the plurality of grooves 2132 are arranged at intervals circumferentially along the piston portion 21. Both the grooves 2132 and the recesses 31 are in communication with the annular groove 2131.

[0061] With the above settings, when switching from the retracted state to the extended state, the liquid enters the annular groove 2131 through multiple inlet and outlet channels, and then enters the multiple grooves 2132. This allows the liquid to contact the piston part 21 through the annular groove 2131 and the multiple grooves 2132, thereby applying a more uniform pressure to the piston part 21, improving the sliding stability of the piston part 21, and thus improving the smoothness of the piston rod 2's start-up.

[0062] like Figure 3 and Figure 4 As shown, the annular groove 2131 surrounds the throttling column 3, and multiple grooves 2132 are arranged on the outside of the annular groove 2131. The grooves 2132 extend radially along the piston part 21, and the cross-section of the grooves 2132 is semi-circular. The end of the groove 2132 near the axis of the piston part 21 is connected to the annular groove 2131, and the end away from the axis of the piston part 21 is open, so that multiple grooves 2132 can be connected to the annular groove 2131.

[0063] The diameter of the inner ring wall of the annular groove 2131 is equal to the outer diameter of the throttling section 32. Multiple grooves 31 extend along the length of the throttling section 32 to the piston part 21 and are all connected to the annular groove 2131, thereby enabling the grooves 31 to connect with the second liquid inlet groove 213.

[0064] In some embodiments, such as Figure 4 and Figure 5 As shown, the projections of the grooves 2132 and the recesses 31 onto the cross-section of the throttling column 3 do not overlap.

[0065] Liquid enters multiple inlet and outlet channels through the second liquid hole 15. It is understood that the liquid flow rate in the inlet and outlet channels closer to the second liquid hole 15 is relatively fast, while the liquid flow rate in the inlet and outlet channels farther away from the second liquid hole 15 is relatively slow.

[0066] With the above settings, the liquid in the multiple inlet and outlet channels cannot directly pass through the annular groove 2131 into the groove 2132. The liquid in the multiple inlet and outlet channels first mixes together in the annular groove 2131, and then is evenly distributed to each groove 2132, so that the liquid flow rate in each groove 2132 is equal. This can further improve the uniformity of liquid distribution on one side of the piston section 21, thereby making the starting process of the piston rod 2 switching from the retracted state to the extended state more stable.

[0067] As an example, such as Figure 5 As shown, there are six grooves 31 and six channels 2132, and the projections of multiple grooves 31 and channels 2132 on the cross-section of the throttling column 3 are arranged alternately.

[0068] In some embodiments, such as Figure 2 As shown, the first chamber 11 has a through hole 112 in its cavity wall. The rod 22 passes through the through hole 112. A seal 4 is provided between the rod 22 and the cavity wall of the through hole 112. The seal 4 is connected to the cavity wall of the through hole 112. The side of the seal 4 facing the piston 21 forms the first cavity wall 111 described above.

[0069] By setting the seal 4, the sealing performance of the connection between the rod 22 and the cylinder 1 can be increased, preventing liquid leakage from the connection between the rod 22 and the cylinder 1.

[0070] Optionally, seal 4 is a sealing ring.

[0071] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. A jack (100), characterized in that, include: The cylinder body (1) has a cavity, a throttling cavity (13), a first liquid hole (14) and a second liquid hole (15). The cross-section of the throttling cavity (13) is smaller than the cross-section of the cavity. The second liquid hole (15) is connected to the throttling cavity (13). A piston rod (2) is movably connected to the cylinder (1) so that the piston rod (2) can switch between an extended state and a retracted state. The piston rod (2) includes a piston part (21) and a rod part (22) connected to each other. The piston part (21) is disposed in the cavity and divides the cavity into a first chamber (11) and a second chamber (12). The rod part (22) passes through the cavity wall of the first chamber (11). The first chamber (11) communicates with the first liquid hole (14). The second chamber (12) communicates with the throttling chamber (13). A throttling device is provided on the side of the piston part (21) facing the throttling cavity (13) and connected to the piston part (21). When the piston rod (2) switches from the extended state to the retracted state, the throttling device is inserted into the throttling cavity (13). The outer wall of the throttling device and the cavity wall of the throttling cavity (13) form an inlet and outlet liquid channel.

2. The jack (100) according to claim 1, characterized in that, The throttling element is a throttling column (3) arranged along the extension direction of the throttling cavity (13). The outer wall of the throttling element includes a fitting part (313) and a groove part (312). In the retracted state, the fitting part (313) fits against the cavity wall of the throttling cavity (13), and the groove part (312) and the cavity wall of the throttling cavity (13) form the inlet and outlet liquid channel.

3. The jack (100) according to claim 2, characterized in that, The outer wall of the throttling column (3) has a plurality of grooves (31), which are arranged at intervals along the circumference of the throttling column (3), and the groove wall of the groove (31) forms the groove portion (312).

4. The jack (100) according to claim 2, characterized in that, The throttling column (3) includes a throttling section (32) and a conical section (33). The throttling section (32) is connected to the piston part (21), and the cross-section of the conical section (33) gradually decreases in the direction away from the piston part (21).

5. The jack (100) according to claim 3, characterized in that, The first chamber (11) has a first chamber wall (111) arranged toward the piston portion (21), and the second chamber (12) has a second chamber wall (121) arranged toward the piston portion (21); in the extended state, the piston portion (21) is in contact with the first chamber wall (111), and in the retracted state, the piston portion (21) is in contact with the second chamber wall (121).

6. The jack (100) according to claim 5, characterized in that, The piston part (21) has a boss (211) on the side facing the first cavity wall (111). The outer wall of the boss (211) and the cavity wall of the first cavity (11) form a first liquid inlet groove (212). The first liquid inlet groove (212) is connected to the first liquid hole (14).

7. The jack (100) according to claim 5, characterized in that, The piston portion (21) has a second liquid inlet groove (213) on the side facing the second cavity wall (121), and the second liquid inlet groove (213) communicates with the groove (31).

8. The jack (100) according to claim 7, characterized in that, The second liquid inlet groove (213) includes an annular groove (2131) and a plurality of grooves (2132). The annular groove (2131) is arranged circumferentially along the piston portion (21), and the plurality of grooves (2132) are arranged at intervals circumferentially along the piston portion (21). The grooves (2132) and the recesses (31) are both connected to the annular groove (2131).

9. The jack (100) according to claim 8, characterized in that, The projections of the groove (2132) and the recess (31) on the cross-section of the throttling column (3) do not coincide.

10. The jack (100) according to claim 5, characterized in that, The first chamber (11) has a through hole (112) in its cavity wall. The rod (22) passes through the through hole (112). A sealing element (4) is provided between the rod (22) and the cavity wall of the through hole (112). The sealing element (4) is connected to the cavity wall of the through hole (112). The sealing element (4) forms the first cavity wall (111) on the side facing the piston (21).

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