Fluid pressure cylinder unit

Abstract

To effectively use high pressure gas to be discharged from a first chamber of a fluid pressure cylinder.SOLUTION: Each of fluid pressure cylinder units 101, 201, 301, 401 includes: lift cylinders 100, 400 having cylinder tubes 1 and piston rods 10, 310; accumulators 40, 340 having gas chambers 41 in which gas can be filled and liquid chambers 42 in which liquid can be filled; and first passages 30 communicating the first chambers with the gas chambers 41 of the accumulators 40, 340. Gas is filled in the first chambers and hydraulic fluid is supplied / discharged to / from second chambers to cause piston rods 10, 310 to reciprocate. In the first passages 30, check valves 50 are provided as valves allowing the flow only of the gas from the first chambers to the gas chambers 41 of the accumulators 40, 340.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a fluid pressure cylinder unit.

Background Art

[0002] Patent Document 1 discloses a fluid pressure cylinder having a bottomed cylindrical cylinder tube having an opening at one end, a rod inserted into the cylinder tube, a piston connected to the tip of the rod and partitioning the inside of the cylinder tube into a rod side chamber filled with gas and a bottom side chamber for supplying and discharging working fluid. The rod side chamber is filled with gas, and the bottom side chamber is supplied and discharged with hydraulic oil. The fluid pressure cylinder extends by the hydraulic pressure of the working oil guided from the hydraulic source to the bottom side chamber.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the fluid pressure cylinder as described in Patent Document 1 extends, the gas in the rod side chamber is pressurized and discharged to a tank or the like. The high-pressure gas is only discharged to a tank or the like and is not effectively utilized.

[0005] The present invention has been made in view of the above problems, and an object thereof is to effectively utilize the high-pressure gas discharged from the first chamber of the fluid pressure cylinder.

Means for Solving the Problems

[0006] The present invention relates to a fluid pressure cylinder unit comprising: a fluid pressure cylinder having a cylinder tube; a piston rod reciprocally mounted within the cylinder tube and dividing the inside of the cylinder tube into a first chamber and a second chamber; an accumulator having an air chamber that can be filled with gas and a liquid chamber that can be filled with liquid; and a first passage connecting the first chamber and the air chamber of the accumulator, wherein the first chamber is filled with gas and the piston rod reciprocates as working fluid is supplied to and discharged from the second chamber. The second chamber and the liquid chamber of the accumulator are in constant communication. The first passage is characterized by being equipped with a valve that allows only the flow of gas from the first chamber to the gas chamber of the accumulator.

[0007] In this invention, when the fluid pressure cylinder extends, the gas filled in the first chamber is pressurized and guided through the first passage and valve to fill the gas chamber of the accumulator. This allows the high-pressure gas discharged from the first chamber to be effectively utilized as the gas to fill the gas chamber of the accumulator. Furthermore, in this invention, the second chamber and the liquid chamber of the accumulator are in communication. Therefore, vibrations of the object driven by the fluid pressure cylinder can be absorbed by the accumulator.

[0010] Furthermore, the present invention further comprises a second passage connected between the first chamber and the valve in the first passage and communicating with the atmosphere, and the second passage is provided with a check valve that allows only the flow of gas from the atmosphere to the first passage.

[0011] This invention prevents a decrease in pressure within the accumulator's air chamber.

[0012] Furthermore, the present invention further comprises a third passage connected between the first chamber and the valve in the first passage, and the third passage is provided with a relief valve that opens when the pressure in the first passage reaches a predetermined pressure.

[0013] This invention prevents the pressure inside the accumulator's air chamber from exceeding a set pressure.

[0014] Furthermore, the present invention is characterized in that the accumulator further has a partitioning member that separates the air chamber and the liquid chamber, and a first passage, a valve, and a partitioning member are provided inside the piston rod.

[0015] This invention makes the fluid pressure cylinder unit more compact.

[0016] Furthermore, the present invention is characterized in that, after the fluid pressure cylinder and the accumulator are connected, when the fluid pressure cylinder is extended or retracted for the first time, the gas in the first chamber is pressurized and filled into the gas chamber of the accumulator.

[0017] In this invention, the gas chamber is not filled with high-pressure gas before the fluid pressure cylinder is operated. Therefore, the accumulator can be handled safely and easily. [Effects of the Invention]

[0018] According to the present invention, the high-pressure gas discharged from the first chamber of the fluid pressure cylinder can be effectively utilized. [Brief explanation of the drawing]

[0019] [Figure 1] This is a circuit diagram of a fluid pressure cylinder unit according to an embodiment of the present invention. [Figure 2] This figure shows the operation of the fluid pressure cylinder unit according to an embodiment of the present invention and the process of filling the accumulator with gas. [Figure 3] This is a circuit diagram of a fluid pressure cylinder unit according to a modified example 1 of the present invention. [Figure 4] This is a circuit diagram of a fluid pressure cylinder unit according to a modified example 2 of the present invention. [Figure 5] This is a circuit diagram of a fluid pressure cylinder unit according to a modified example 3 of the present invention. [Modes for carrying out the invention]

[0020] Referring to the drawings, the fluid pressure cylinder unit 101 according to an embodiment of the present invention will be described. The fluid pressure cylinder unit 101 includes a fluid pressure cylinder and an accumulator 40 connected to the fluid pressure cylinder. In the present embodiment, the case where the fluid pressure cylinder is a lift cylinder 100 for raising and lowering the fork of a forklift will be described.

[0021] The lift cylinder 100 is a single-acting hydraulic cylinder. As shown in FIG. 1, the lift cylinder 100 includes a cylinder tube 1, a piston rod 10 provided reciprocally in the cylinder tube 1 and partitioning the inside of the cylinder tube 1 into a rod-side chamber 2 as a first chamber and a rodless-side chamber 3 as a second chamber, a first passage 30 connected to the rod-side chamber 2, and a main passage 20 connected to the rodless-side chamber 3.

[0022] The piston rod 10 has a piston 11 slidably provided along the inner peripheral surface of the cylinder tube 1, and a rod 12 having the piston 11 connected to one end and extending to the outside of the cylinder tube 1 and reciprocating. The rod-side chamber 2 is filled with a gas such as air. Note that "filling" includes actively injecting gas into the rod-side chamber 2 using a cylinder or the like, or gas being mixed into the rod-side chamber 2 during the assembly of the lift cylinder 100. The gas is discharged from the rod-side chamber 2 through the first passage 30. Working oil as a working fluid is supplied and discharged to and from the rodless-side chamber 3 through the main passage 20. Note that a liquid such as water other than the working oil may be used as the working fluid.

[0023] The main passage 20 is provided with a switching valve (not shown), and by switching the switching valve, the main passage 20 is connected to a pump (not shown) or a tank (not shown). In the lift cylinder 100, the hydraulic oil is supplied and discharged to and from the counter-rod side chamber 3 through the main passage 20, whereby the piston rod 10 reciprocates. Specifically, when the hydraulic oil is supplied from the hydraulic pressure source to the counter-rod side chamber 3, the piston rod 10 moves upward (the upper side in FIG. 1), the lift cylinder 100 extends, and the fork and the load placed on the fork rise. When the hydraulic oil is discharged from the counter-rod side chamber 3 to the tank due to the self-weights of the fork, the load, and the piston rod 10, the piston rod 10 moves downward (the lower side in FIG. 1), the lift cylinder 100 contracts, and the fork and the load descend.

[0024] Further, the accumulator 40 has a gas chamber 41 capable of being filled with gas and a liquid chamber 42 capable of being filled with liquid. The accumulator 40 is provided separately from the lift cylinder 100. The gas chamber 41 and the liquid chamber 42 may be partitioned by a partitioning member such as a free piston or a bladder. The gas chamber 41 is connected to the first passage 30, and the liquid chamber 42 is connected to a branch passage 21 branched from the main passage 20. Thus, the rod side chamber 2 and the gas chamber 41 communicate with each other through the first passage 30, and the counter-rod side chamber 3 and the liquid chamber 42 communicate with each other through the main passage 20 and the branch passage 21. A check valve 50 as a valve that allows only the flow of gas from the rod side chamber 2 to the gas chamber 41 of the accumulator 40 is provided in the first passage 30. Instead of the check valve 50, a solenoid valve, a manual valve, or the like may be provided. Further, the counter-rod side chamber 3 and the liquid chamber 42 may be communicated with each other through a passage provided in parallel with the main passage 20.

[0025] The fluid pressure cylinder unit 101 of the present embodiment is assembled by connecting the lift cylinder 100 and the accumulator 40 in the atmosphere. Before the connection between the lift cylinder 100 and the accumulator 40, the gas chamber 41 of the accumulator 40 is at atmospheric pressure and is not filled with high-pressure gas. The gas chamber 41 of the accumulator 40 is filled with high-pressure gas by the initial operation of the lift cylinder 100 after the connection between the lift cylinder 100 and the accumulator 40.

[0026] Next, the filling of the gas chamber 41 of the accumulator 40 with high-pressure gas will be described in detail.

[0027] Figures 2(a)-(c) show the initial operation of the lift cylinder 100, with Figure 2(a) showing the state before the initial operation of the lift cylinder 100 (in other words, immediately after the connection of the lift cylinder 100 and the accumulator 40). In this state, the lift cylinder 100 is in its most retracted state due to the weight of the piston rod 10. The rod side chamber 2 and the air chamber 41 of the accumulator 40 are at atmospheric pressure, and the air chamber 41 is not filled with high-pressure gas.

[0028] The initial operation of the lift cylinder 100 is performed by supplying hydraulic fluid from the hydraulic source to the anti-rod side chamber 3 through the main passage 20, as shown in Figure 2(b), thereby extending the lift cylinder 100 (specifically, to its maximum extension). This pressurizes the gas in the rod side chamber 2, which is then guided to the gas chamber 41 of the accumulator 40 through the first passage 30 and the check valve 50, as indicated by the arrow on the right side of Figure 2(b). The gas chamber 41 is then filled with high-pressure gas until the pressure in the gas chamber 41 reaches the set pressure.

[0029] Subsequently, when the hydraulic fluid is discharged from the anti-rod side chamber 3, the lift cylinder 100 fully retracts due to the weight of the piston rod 10, as shown in Figure 2(c), and the initial operation of the lift cylinder 100 ends. In this state, the volume of the rod side chamber 2 increases compared to the state shown in Figure 2(b), so the pressure inside the rod side chamber 2 decreases. However, since a check valve 50 is provided in the first passage 30, the gas filled in the air chamber 41 of the accumulator 40 is not guided into the rod side chamber 2 through the first passage 30. Therefore, the pressure inside the air chamber 41 of the accumulator 40 is maintained at the set pressure. Note that the operations shown in Figures 2(a)-(c) described above may be performed before or after mounting the fluid pressure cylinder unit 101 onto the forklift. Also, the operations shown in Figures 2(a)-(c) may be performed during the operation test of the lift cylinder 100 or when bleeding air from the anti-rod side chamber 3. Furthermore, if a solenoid valve or manual valve is provided instead of the check valve 50, it is sufficient that when the lift cylinder 100 is extended, the rod side chamber 2 and the air chamber 41 of the accumulator 40 communicate through the first passage 30, and when the lift cylinder 100 is retracted, the communication between the rod side chamber 2 and the air chamber 41 of the accumulator 40 is blocked. Even with this configuration, the solenoid valve or manual valve can only allow the flow of gas from the rod side chamber 2 to the air chamber 41 of the accumulator 40.

[0030] When the fluid pressure cylinder unit 101 is mounted on a forklift and cargo is transported and handled, during the normal operation of the lift cylinder 100, the pressure in the rod side chamber 2 is lower than the pressure in the air chamber 41 of the accumulator 40 until the lift cylinder 100 is fully extended. However, the check valve 50 maintains the pressure in the air chamber 41 of the accumulator 40. When the lift cylinder 100 is fully extended, the pressure in the rod side chamber 2 becomes the same as shown in Figure 2(b), and is equivalent to the pressure in the air chamber 41 of the accumulator 40. Thus, during the normal operation of the lift cylinder 100, the gas in the rod side chamber 2 is not introduced into the air chamber 41 of the accumulator 40. In other words, in the fluid pressure cylinder unit 101, after the lift cylinder 100 and the accumulator 40 are connected, the gas in the rod side chamber 2 is pressurized and filled into the gas chamber 41 of the accumulator 40 only when the lift cylinder 100 is first extended (specifically, fully extended).

[0031] Thus, in the lift cylinder 100, during the initial operation of the lift cylinder 100, when the lift cylinder 100 extends, the gas filled in the rod side chamber 2 is pressurized and guided through the first passage 30 and the check valve 50 to the gas chamber 41 of the accumulator 40 and filled. This allows the high-pressure gas discharged from the rod side chamber 2 to be effectively utilized as the gas that fills the gas chamber 41 of the accumulator 40.

[0032] Furthermore, since the accumulator 40 is only filled with high-pressure gas in its air chamber 41 during the initial operation of the lift cylinder 100, the air chamber 41 is not filled with high-pressure gas before the lift cylinder 100 operates. Therefore, the accumulator 40 can be handled safely and easily. In addition, the accumulator 40 can be transported safely and easily. Moreover, since the gas in the rod-side chamber 2 is pressurized and filled into the air chamber 41 of the accumulator 40, there is no need to use gas cylinders or the like to fill the air chamber 41 with high-pressure gas. Therefore, compared to cases where gas cylinders or the like are used, the accumulator 40 can be handled safely and easily, and manufacturing costs are reduced.

[0033] Furthermore, in the fluid pressure cylinder unit 101, the anti-rod side chamber 3 and the liquid chamber 42 of the accumulator 40 are in communication through the main passage 20 and the branch passage 21, so that pressure fluctuations in the main passage 20 and the anti-rod side chamber 3 are absorbed by the accumulator 40. Therefore, even if, for example, an impact from the road surface acts on the lift cylinder 100 during the transport of goods by forklift, the vibration of the goods can be absorbed by the accumulator 40. Thus, it is possible to prevent goods from collapsing during transport.

[0034] According to the above embodiments, the following effects and advantages are achieved.

[0035] In the lift cylinder 100, when the lift cylinder 100 extends, the gas filled in the rod side chamber 2 is pressurized and guided through the first passage 30 and the check valve 50 to the gas chamber 41 of the accumulator 40, where it is filled. This allows the high-pressure gas discharged from the rod side chamber 2 to be effectively utilized as the gas that fills the gas chamber 41 of the accumulator 40.

[0036] In the lift cylinder 100, the anti-rod side chamber 3 and the liquid chamber 42 of the accumulator 40 are connected by the main passage 20. Therefore, vibrations of the object driven by the lift cylinder 100, such as a load, can be absorbed by the accumulator 40.

[0037] In the fluid pressure cylinder unit 101, after the lift cylinder 100 and the accumulator 40 are connected, high-pressure gas is only filled into the gas chamber 41 of the accumulator 40 during the initial operation of the lift cylinder 100. Therefore, before the operation of the lift cylinder 100, the gas chamber 41 is not filled with high-pressure gas. As a result, the accumulator 40 can be handled safely and easily. Furthermore, the accumulator 40 can be transported safely and easily.

[0038] The following modifications are also within the scope of the present invention, and it is possible to combine the configurations shown in the modifications with the configurations described in the embodiments described above, or to combine the configurations described in the following different modifications.

[0039] <Example 1> In the above embodiment, the fluid pressure cylinder unit 101 includes a first passage 30 that connects the rod side chamber 2 and the air chamber 41 of the accumulator 40. In addition, as shown in Figure 3, the fluid pressure cylinder unit 201 according to Modification 1 includes a second passage 31 that is connected between the rod side chamber 2 and the check valve 50 in the first passage 30 and communicates with the atmosphere.

[0040] The second passage 31 communicates with the atmosphere through the filter 60. The second passage 31 is equipped with a check valve 51 that allows only the flow of gas from the atmosphere to the first passage 30. Therefore, when the lift cylinder 100 is retracted, the pressure in the rod side chamber 2 and the first passage 30 decreases (specifically, falls below atmospheric pressure), and gas is supplied to the rod side chamber 2 and the first passage 30 through the filter 60, the second passage 31, and the check valve 51. This allows the gas in the rod side chamber 2 to be repeatedly filled into the gas chamber 41 of the accumulator 40 each time the lift cylinder 100 extends. Thus, a decrease in the pressure in the gas chamber 41 is prevented.

[0041] Furthermore, the fluid pressure cylinder unit 201 includes a third passage 33 connected between the rod side chamber 2 and the check valve 50 in the first passage 30. The third passage 33 communicates with the atmosphere through a silencer 61. The third passage 33 is provided with a relief valve 52 that opens when the pressure in the first passage 30 reaches a predetermined pressure. When the relief valve 52 opens, the gas in the rod side chamber 2 and the first passage 30 is discharged to the atmosphere through the third passage 33 and the silencer 61. The pressure at which the relief valve 52 opens is set, for example, to be equivalent to the set pressure of the accumulator 40. Therefore, the pressure in the rod side chamber 2 and the first passage 30 does not exceed the set pressure of the accumulator 40. In other words, during the operation of the lift cylinder 100, it is prevented that the gas chamber 41 of the accumulator 40 is filled with gas beyond the set pressure, and the pressure in the gas chamber 41 is prevented from exceeding the set pressure.

[0042] Furthermore, the third passage 33 may communicate with a tank instead of the atmosphere. Also, it is not necessary for both the second passage 31 and the third passage 33 to be provided; only one may be provided. In addition, the filter 60 and silencer 61 are not mandatory and may not be provided.

[0043] <Modification 2> In the above embodiment, the fluid pressure cylinder unit 101 has the anti-rod side chamber 3 and the liquid chamber 42 of the accumulator 40 communicating through the main passage 20 and the branch passage 21. In contrast, as shown in Figure 4, in the fluid pressure cylinder unit 301, the anti-rod side chamber 3 and the liquid chamber 42 of the accumulator 40 are not communicating, and the liquid chamber 42 of the accumulator 40 is connected to another device (not shown) separate from the lift cylinder 100 through the passage 221. Even with this configuration, the high-pressure gas discharged from the rod side chamber 2 can be effectively utilized as the gas that fills the gas chamber 41 of the accumulator 40. Furthermore, the accumulator 40 can absorb vibrations of the other device to which it is connected.

[0044] <Variation 3> In the above embodiment, the accumulator 40 is provided separately from the lift cylinder 100. In contrast, in the fluid pressure cylinder unit 401 according to Modification 3, the accumulator 40 is provided inside the piston rod 10. Specifically, as shown in Figure 5, the accumulator 240 has a free piston 43 as a partitioning member that separates the air chamber 41 and the liquid chamber 42, and the piston rod 310 is provided with a first passage 30, a check valve 50, the free piston 43, and a passage 321 that connects the anti-rod side chamber 3 and the liquid chamber 42. Even with this configuration, when hydraulic fluid is supplied from the hydraulic source to the anti-rod side chamber 3 and the lift cylinder 400 is extended, the gas in the rod side chamber 2 is pressurized and guided through the first passage 30 and the check valve 50 to the air chamber 41 of the accumulator 340 and filled. Furthermore, since the anti-rod side chamber 3 and the liquid chamber 42 of the accumulator 340 are connected by the passage 321, pressure fluctuations in the main passage 20 and the anti-rod side chamber 3 are absorbed by the accumulator 340, preventing cargo collapse during transport. In this way, by providing the accumulator 340 inside the piston rod 310, the fluid pressure cylinder unit 401 can be made more compact.

[0045] <Modification 4> In the above embodiment, the fluid pressure cylinder unit 101 is configured such that the rod side chamber 2 is filled with gas and the rod side chamber 2 and the gas chamber 41 are in communication. In addition, the non-rod side chamber 3 and the liquid chamber 42 are in communication and hydraulic fluid is supplied to and discharged from the non-rod side chamber 3. However, the fluid pressure cylinder unit 101 may also be configured such that the non-rod side chamber 3 is filled with gas and the non-rod side chamber 3 and the gas chamber 41 are in communication, and the rod side chamber 2 and the liquid chamber 42 are in communication and hydraulic fluid is supplied to and discharged from the rod side chamber 2. In this configuration, after the lift cylinder 100 and the accumulator 40 are connected, when the lift cylinder 100 is first contracted (specifically, fully contracted), the gas in the non-rod side chamber 3 is pressurized and filled into the gas chamber 41 of the accumulator 40. Furthermore, the fluid pressure cylinder unit 101 may be used in the opposite orientation to that shown in Figure 1.

[0046] <Modification 5> In the above embodiment, the case where the fluid pressure cylinder is a lift cylinder 100 that raises and lowers the forks of a forklift was described. However, the fluid pressure cylinder is not limited to this, and may be any other cylinder other than the one mounted on the forklift, as long as gas is filled in one of the rod side chambers 2 or the anti-rod side chamber 3 and working fluid is supplied and discharged to the other, causing the piston rod 10 to reciprocate. Furthermore, the fluid pressure cylinder may be a double-rod type cylinder.

[0047] The configuration, operation, and effects of the embodiment of the present invention configured as described above will be summarized below.

[0048] The fluid pressure cylinder units 101, 201, 301, and 401 each include a lift cylinder 100, 400 as a fluid pressure cylinder having a cylinder tube 1 and piston rods 10, 310 provided to reciprocate within the cylinder tube 1 and dividing the inside of the cylinder tube 1 into a first chamber and a second chamber, an accumulator 40, 240 having a gas chamber 41 that can be filled with gas and a liquid chamber 42 that can be filled with liquid, and a first passage 30 connecting the first chamber and the gas chamber 41 of the accumulator 40, 340, wherein the first chamber is filled with gas and the piston rods 10, 310 reciprocate as working fluid is supplied to and discharged from the second chamber, and the first passage 30 is provided with a check valve 50 that allows only the flow of gas from the first chamber to the gas chamber 41 of the accumulator 40, 340.

[0049] In this configuration, when the lift cylinders 100 and 400 extend, the gas filled in the first chamber is pressurized and guided through the first passage 30 and the check valve 50 to the gas chamber 41 of the accumulators 40 and 340, where it is filled. This allows the high-pressure gas discharged from the first chamber to be effectively utilized as the gas that fills the gas chamber 41 of the accumulators 40 and 340.

[0050] Furthermore, in the fluid pressure cylinder units 101, 201, and 401, the second chamber is in communication with the liquid chamber 42 of the accumulators 40 and 340.

[0051] In this configuration, the second chamber and the liquid chamber 42 of the accumulators 40 and 340 are in communication. Therefore, vibrations of the object driven by the lift cylinders 100 and 400 can be absorbed by the accumulators 40 and 340.

[0052] Furthermore, the fluid pressure cylinder unit 201 is further provided with a second passage 31 connected between the first chamber in the first passage 30 and the check valve 50, and which communicates with the atmosphere. The second passage 31 is equipped with a check valve 51 that allows only the flow of gas from the atmosphere to the first passage 30.

[0053] In this configuration, a drop in pressure within the air chamber 41 of the accumulator 40 is prevented.

[0054] Furthermore, the fluid pressure cylinder unit 201 further includes a third passage 33 connected between the first chamber in the first passage 30 and the check valve 50, and the third passage 33 is provided with a relief valve 52 that opens when the pressure in the first passage 30 reaches a predetermined pressure.

[0055] In this configuration, the pressure inside the air chamber 41 of the accumulator 40 is prevented from exceeding the set pressure.

[0056] Furthermore, in the fluid pressure cylinder unit 401, the accumulator 340 further has a free piston 43 as a partitioning member that separates the air chamber 41 and the liquid chamber 42, and a first passage 30, a check valve 50, and the free piston 43 are provided inside the piston rod 310.

[0057] This configuration allows for a more compact fluid pressure cylinder unit 401.

[0058] Furthermore, in the fluid pressure cylinder units 101, 201, 301, and 400, after the lift cylinders 100 and 400 are connected to the accumulators 40 and 340, when the lift cylinders 100 and 400 are first extended or retracted, the gas in the first chamber is pressurized and filled into the gas chamber 41 of the accumulators 40 and 340.

[0059] In this configuration, the gas chamber 41 is not filled with high-pressure gas before the lift cylinders 100 and 400 are operated. Therefore, the accumulators 40 and 340 can be handled safely and easily.

[0060] Although embodiments of the present invention have been described above, these embodiments only represent a part of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments. [Explanation of Symbols]

[0061] 1...Cylinder, 2...Rod-side chambers (first chamber, second chamber), 3...Non-rod-side chambers (first chamber, second chamber), 10, 310...Piston rod, 30...First passage, 31...Second passage, 32...Third passage, 40, 340...Accumulator, 41...Air chamber, 42...Liquid chamber, 43...Free piston (partition member), 50...Check valve (valve), 51...Check valve, 52...Relief valve, 100, 400...Lift cylinder (fluid pressure cylinder), 101, 201, 301, 401...Fluid pressure cylinder unit

Claims

1. A fluid pressure cylinder unit, A fluid pressure cylinder having a cylinder tube and a piston rod that is reciprocally mounted within the cylinder tube and divides the inside of the cylinder tube into a first chamber and a second chamber, An accumulator having an air chamber that can be filled with gas and a liquid chamber that can be filled with liquid, It comprises a first passage connecting the first chamber and the air chamber of the accumulator, The first chamber is filled with gas, The piston rod reciprocates as the working fluid is supplied to and discharged from the second chamber. The second chamber and the liquid chamber of the accumulator are in constant communication. A fluid pressure cylinder unit characterized in that the first passage is provided with a valve capable of allowing only the flow of gas from the first chamber to the air chamber of the accumulator.

2. A fluid pressure cylinder unit according to Claim 1, The first passage further comprises a second passage connected between the first chamber and the valve, which communicates with the atmosphere, A fluid pressure cylinder unit characterized in that the second passage is provided with a check valve that allows only the flow of gas from the atmosphere to the first passage.

3. A fluid pressure cylinder unit according to Claim 1, The system further comprises a third passage connected between the first chamber and the valve in the first passage, A fluid pressure cylinder unit characterized in that the third passage is provided with a relief valve that opens when the pressure in the first passage reaches a predetermined pressure.

4. A fluid pressure cylinder unit according to claim 1, The accumulator further includes a partitioning member that separates the air chamber and the liquid chamber, A fluid pressure cylinder unit characterized in that the first passage, the valve, and the partition member are provided within the piston rod.

5. A fluid pressure cylinder unit according to claim 1, A fluid pressure cylinder unit characterized in that, after the fluid pressure cylinder and the accumulator are connected, when the fluid pressure cylinder is extended or retracted for the first time, the gas in the first chamber is pressurized and filled into the gas chamber of the accumulator.

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