cylinder

Abstract

A cylinder (10) is provided with: a cylinder bore (12); a first cover (18); a second cover (20); a piston (14); a first port (70) that supplies and discharges compressed air to a first pressure chamber (30); a first buffer chamber (58) formed in the first cover (18); a first buffer projection (44) that protrudes from the piston (14) and cuts off the first internal flow path (62) and the first pressure chamber (30) at the end of stroke; a first internal flow path (62) that connects the first buffer chamber (58) and the first port (70); and a first throttle flow path (64) that has a smaller effective cross-sectional area than the first internal flow path (62) and connects the first pressure chamber (30) and the first port (70), the first throttle flow path (64) being connected to the first internal flow path (62) inside the first cover (18).

Description

Technical Field

[0001] This utility model relates to a cylinder with an air buffer mechanism. Background Technology

[0002] Description of related technologies:

[0003] In cylinders, air buffer mechanisms are sometimes used to mitigate the impact of inertia when the piston stops at the end of its stroke. For example, Japanese Patent Application Publication No. 2000-199503 discloses an air buffer mechanism that includes a main flow path for a large flow through the cylinder barrel and a throttling flow path equipped with a throttle valve. When the piston is near the end of its stroke, the main flow path is closed, the exhaust flow is throttled, and the piston is decelerated.

[0004] In conventional air buffer mechanisms, a main flow path, a throttling flow path, and a throttle valve are required for each port. To efficiently manufacture these structures in the cylinder, the throttling flow path extends along the axial direction, and the throttle valves are arranged in a row along the axial direction relative to the port.

[0005] However, when the axial length of the cylinder is shortened, there is sometimes insufficient space for the throttle valve and ports. For example, when the piston stroke is short, to ensure sufficient space for the throttle valve, a pair of ports need to be positioned close together axially, causing interference between the interfaces and making connection difficult. Therefore, conventional air buffer mechanisms have the technical limitation of only being able to be mounted on cylinders with a certain stroke length. Utility Model Content

[0006] The purpose of this invention is to solve the aforementioned technical problems.

[0007] This utility model relates to a cylinder comprising: a cylinder barrel having a through hole extending along an axial direction; a first cover closing an end of the through hole in a first direction; a second cover closing an end of the through hole in a second direction, forming a cylinder chamber between the second cover and the first cover; a piston dividing the cylinder chamber into a first pressure chamber and a second pressure chamber; a first port formed in the cylinder barrel for supplying and discharging compressed air to the first pressure chamber; and a first buffer chamber formed in the first cover and communicating with the first pressure chamber. A protrusion, the first buffer protrusion protruding from the piston in the first direction, preventing communication between the first pressure chamber and the first buffer chamber when the first buffer protrusion is inserted into the first buffer chamber; a first internal flow path connecting the first buffer chamber and the first port; and a first throttling flow path formed in the first cover, having an effective cross-sectional area smaller than the first internal flow path, and connecting the first pressure chamber and the first port, the first throttling flow path being formed in the first cover and connected to the first internal flow path inside the first cover.

[0008] According to this invention, a first throttling flow path that throttles the exhaust gas at the end of the stroke is built into the first cover. Therefore, the cylinder described above does not need to be equipped with a throttle valve in the cylinder barrel, and an air buffer mechanism that throttles the exhaust gas can be installed even when the stroke length is short.

[0009] The above-described objects, features, and advantages will be readily understood through the following description of embodiments with reference to the accompanying drawings. Attached Figure Description

[0010] Figure 1 This is a cross-sectional view of the cylinder according to the embodiment, showing the state where the piston is at the end of its stroke in the first direction.

[0011] Figure 2A yes Figure 1 A magnified sectional view of the area near the first cover. Figure 2B yes Figure 1 A magnified sectional view of the area near the second cover.

[0012] Figure 3 yes Figure 1 A cross-sectional view of the cylinder at the midpoint of its stroke.

[0013] Figure 4 yes Figure 1 A cross-sectional view of the cylinder at the end of its second stroke. Detailed Implementation

[0014] Figure 1The cylinder 10 shown in this embodiment is a double-acting cylinder that operates by the supply and exhaust of compressed air. The cylinder 10 is used, for example, in automated production lines in factories. In the following description, the direction along the central axis C of the cylinder barrel 12 of the cylinder 10 will be referred to as the axial direction (first direction and second direction). Furthermore, the direction perpendicular to the axial direction will be referred to as radially outward or outward, and the direction perpendicular to and approaching the axial direction will be referred to as radially inward or inward. In the radial direction, the direction in which the port is formed will be referred to as the upward direction, and the opposite direction will be referred to as the downward direction. Furthermore, in the following description, the terms "upward" and "downward" are used to describe the relative positional relationship of the components of the cylinder 10 and are not intended to limit the arrangement direction of the cylinder 10.

[0015] The cylinder 10 includes a cylinder barrel 12, a piston 14, a piston rod 16, a first cover 18 (top side cover), a second cover 20 (rod side cover), a first air buffer mechanism 22, and a second air buffer mechanism 24. A through hole 26 extending linearly is formed inside the cylinder barrel 12. The first cover 18 is inserted near the end of the through hole 26 in a first direction, and the second cover 20 is inserted near the end of the through hole 26 in a second direction. The first cover 18 and the second cover 20 close the two ends of the through hole 26, forming a cylinder chamber 28 inside.

[0016] The first cover 18 and the second cover 20 are integrally disposed inside the through hole 26 in the axial direction, and are installed in a manner that does not protrude from the cylinder barrel 12 in the axial direction. Therefore, the axial dimension of the part of the cylinder 10, excluding the piston rod 16, is equal to the length of the cylinder barrel 12. Such a cylinder 10 can achieve miniaturization in the axial direction.

[0017] Piston 14 is housed in cylinder chamber 28. Piston 14 hermetically divides cylinder chamber 28 into a first pressure chamber 30 in a first direction and a second pressure chamber 32 in a second direction. While hermetically dividing cylinder chamber 28, piston 14 slides along the axial direction inside cylinder barrel 12.

[0018] A piston liner 34, a magnet 36, and a wear ring 38 are installed on the outer periphery of the piston 14. The piston liner 34 hermetically isolates the first pressure chamber 30 and the second pressure chamber 32 by preventing leakage of compressed air along the gap between the piston 14 and the cylinder 12. The magnet 36 enables the detection of the piston position using a magnetic sensor (not shown). The wear ring 38 prevents the piston 14 from wobbling and stabilizes the axial displacement of the piston 14.

[0019] A first annular damper 40 is installed on the end face 14a of the piston 14 in a first direction. The first damper 40 is formed of an elastic material and mitigates the impact caused by the collision between the piston 14 and the first cover 18. A second annular damper 42 is installed on the end face 14b of the piston 14 in a second direction. The second damper 42 mitigates the impact caused by the collision between the piston 14 and the second cover 20.

[0020] The first buffer joint 44 protrudes from the end face 14a of the piston 14 in the first direction toward the first direction. The first buffer joint 44 is formed in the first rod portion 48 that constitutes part of the piston rod 16 in the first direction. The first buffer joint 44 is a cylindrical component with an outer diameter smaller than that of the piston 14, and its top end is tapered.

[0021] The first buffer spring 44 forms part of the first air buffer mechanism 22. That is, the first buffer spring 44 is inserted into the first buffer chamber 58 (described later) at the end of the first direction of the piston 14's stroke, preventing compressed air from being exhausted through the first internal flow path 62.

[0022] The piston 14 has a second buffer protrusion 46 protruding from its end face 14b in a second direction. The second buffer protrusion 46 is integrally formed with the piston 14. The second buffer protrusion 46 is formed to have a diameter larger than that of the piston rod 16. A portion of the second buffer protrusion 46 covers the outer peripheral surface of the piston rod 16.

[0023] The second buffer spring 46 forms part of the second air buffer mechanism 24. That is, the second buffer spring 46 is inserted into the second buffer chamber 72 (described later) at the end of its stroke in the second direction, preventing the exhaust of compressed air through the second internal flow path 76.

[0024] The piston rod 16 is connected to the piston 14 and extends along the axial direction. The piston rod 16 has a first rod portion 48 that holds the piston 14 from a first direction and a second rod portion 50 that holds the piston 14 from a second direction. The first rod portion 48 has a first cushioning protrusion 44 that protrudes in the first direction relative to the piston 14, a through portion 52 that inserts into the center hole 14c of the piston 14, and a connecting portion 54 that connects to the second rod portion 50. The connecting portion 54 is inserted into the connecting hole 56 of the second rod portion 50 and thus connects to the second rod portion 50.

[0025] The second rod portion 50 is received in the receiving hole 14d of the piston 14, holding the piston 14 in a second direction. The piston 14 is held by the first rod portion 48 and the second rod portion 50 along the axial direction and connected to the piston rod 16. The second rod portion 50 is inserted through the insertion hole 20a of the second cover 20 and protrudes from the second cover 20 in a first direction. The piston rod 16 and the piston 14 are integrally displaced along the axial direction.

[0026] The first cover 18 has a first buffer chamber 58, a first buffer liner 60, a first internal flow path 62, and a first throttling flow path 64.

[0027] The first buffer chamber 58 is formed by recessing from the second-direction end of the first cover 18 in the first direction. The first buffer chamber 58 is located at the center of the first cover 18 and opens into the first pressure chamber 30. The first buffer chamber 58 has an inner diameter and axial dimension larger than the first buffer protrusion 44, and is capable of accommodating the first buffer protrusion 44.

[0028] A first pad receiving groove 58a is formed near the second end of the first buffer chamber 58. A first buffer pad 60 is installed in the first pad receiving groove 58a. When the first buffer contact 44 is inserted into the first buffer chamber 58, the first buffer pad 60 makes airtight contact with the first buffer contact 44, preventing communication between the first buffer chamber 58 and the first pressure chamber 30. That is, the first buffer pad 60 prevents compressed air from being exhausted through the first internal flow path 62 by abutting against the first buffer contact 44.

[0029] like Figure 1 and Figure 2A As shown, the first internal flow path 62 extends vertically and radially through the first cover 18. The central portion of the first internal flow path 62 opens into and communicates with the first buffer chamber 58. That is, the first internal flow path 62 communicates with the first pressure chamber 30 via the first buffer chamber 58. The outer peripheral end of the first internal flow path 62 communicates with the first port 70 formed on the upper part of the cylinder 12. The first internal flow path 62 has a relatively large effective cross-sectional area, enabling rapid supply and discharge of compressed air to the first pressure chamber 30.

[0030] The first throttling flow path 64 is located radially outward of the first buffer chamber 58. The first throttling flow path 64 extends along its axial direction, with its first end connected to the first internal flow path 62 inside the first cover 18. The second end of the first throttling flow path 64 opens into the first pressure chamber 30. The effective cross-sectional area of ​​the first throttling flow path 64 is smaller than that of the first internal flow path 62. Therefore, the first throttling flow path 64 delays the discharge of compressed air from the first pressure chamber 30. The first throttling flow path 64 is arranged to overlap with the first buffer chamber 58 radially. That is, since the axial position of the first throttling flow path 64 overlaps with the axial positions of the first buffer chamber 58 and the first port 70, it can be configured in the cylinder 10 without increasing its axial length.

[0031] A first peripheral gasket 66a, a second peripheral gasket 66b, and a first positioning ring 68 are installed on the outer periphery of the first cover 18. The first peripheral gasket 66a is located on the first direction side of the first internal flow path 62, and the second peripheral gasket 66b is located on the second direction side of the first internal flow path 62. These first peripheral gaskets 66a and second peripheral gaskets 66b prevent compressed air from leaking through the gap between the first cover 18 and the cylinder 12.

[0032] The first positioning ring 68 fixes the first cover 18 to the cylinder 12. The first positioning ring 68 engages with the groove-shaped recess formed in the first cover 18 and the cylinder 12, preventing the first cover 18 from displacing relative to the axial direction of the cylinder 12.

[0033] like Figure 1 As shown, the second cover 20 has an insertion hole 20a, a second buffer chamber 72, a second buffer gasket 74, a second internal flow path 76, and a second throttling flow path 78. The insertion hole 20a extends through the center of the second cover 20 along the axial direction. The insertion hole 20a allows the piston rod 16 to be inserted. A rod gasket 80 is installed at a designated location in the insertion hole 20a. The rod gasket 80 prevents compressed air from leaking through the gap between the piston rod 16 and the second cover 20.

[0034] The second buffer chamber 72 is formed in a concave shape, such that the end of the second cover 20 in the first direction is recessed in the second direction. The second buffer chamber 72 opens in the first direction and communicates with the second pressure chamber 32. The second buffer chamber 72 is located at the center of the second cover 20 and has an inner diameter and axial length larger than the second buffer protrusion 46. The second buffer chamber 72 accommodates the second buffer protrusion 46 when the piston 14 is displaced to near the end of its stroke in the second direction.

[0035] like Figure 2B and Figure 4 As shown, a second pad receiving groove 72a is formed near the end of the second buffer chamber 72 in the first direction. A second buffer pad 74 is installed in the second pad receiving groove 72a. When the second buffer joint 46 is inserted into the second buffer chamber 72, the second buffer pad 74 makes airtight contact with the second buffer joint 46, preventing communication between the second buffer chamber 72 and the second pressure chamber 32. That is, the second buffer pad 74 makes airtight contact with the second buffer joint 46 near the end of its stroke in the second direction, cutting off the exhaust of compressed air from the second pressure chamber 32 through the second internal flow path 76.

[0036] The second internal flow path 76 extends vertically and radially through the second cover 20. The central portion of the second internal flow path 76 opens into and communicates with the second buffer chamber 72. The outer peripheral end of the second internal flow path 76 communicates with the second port 82 formed on the upper part of the cylinder 12. The second internal flow path 76 has a relatively large effective cross-sectional area, enabling rapid supply and discharge of compressed air to the second pressure chamber 32.

[0037] like Figure 2B As shown, the second throttling flow path 78 is located radially outward of the second buffer chamber 72. The second throttling flow path 78 extends along its axial direction. The first end of the second throttling flow path 78 opens into the second pressure chamber 32. The second end of the second throttling flow path 78 connects to the second internal flow path 76 inside the second cover 20. The second throttling flow path 78 has a smaller effective cross-sectional area than the second internal flow path 76. The axial position of the second throttling flow path 78 overlaps with the axial positions of the second buffer chamber 72 and the second port 82, allowing it to be configured without extending the axial length of the cylinder 10.

[0038] A third peripheral gasket 84a and a fourth peripheral gasket 84b are installed on the outer periphery of the second cover 20. The third peripheral gasket 84a is located on the first direction side of the second internal flow path 76, and the fourth peripheral gasket 84b is located on the second direction side of the second internal flow path 76. The third peripheral gasket 84a and the fourth peripheral gasket 84b prevent compressed air from leaking through the gap between the second cover 20 and the cylinder 12.

[0039] A second positioning ring 86 is installed at the second end of the second cover 20 in a second direction. The second positioning ring 86 fixes the second cover 20 to the cylinder 12. The second positioning ring 86 is a C-shaped metal component that fits into a groove-shaped recess formed in the cylinder 12, preventing the second cover 20 from displacing relative to the axial direction of the cylinder 12.

[0040] like Figure 1 and Figure 2A As shown, the first air buffer mechanism 22 comprises a first buffer contact 44, a first buffer chamber 58, a first buffer pad 60, a first internal flow path 62, and a first throttling flow path 64. At the end of the stroke in the first direction, the first buffer contact 44 of the first air buffer mechanism 22 contacts the first buffer pad 60, isolating the first buffer chamber 58 from the first pressure chamber 30. The first air buffer mechanism 22 reduces the moving speed of the piston 14 by cutting off the first internal flow path 62 and the first pressure chamber 30 and throttling the compressed air from the first pressure chamber 30 in the first throttling flow path 64.

[0041] like Figure 1As shown, a first port 70 and a second port 82 are formed in the cylinder 12. The first port 70 is located near the end of the cylinder 12 in a first direction. The first port 70 is configured such that its axial position overlaps with the axial positions of the first buffer chamber 58 and the first throttling flow path 64, thereby shortening the axial direction of the cylinder 10. Compressed air is supplied to and discharged to the first pressure chamber 30 by connecting a compressed air pipe (not shown) to the first port 70. The second port 82 is located near the end of the cylinder 12 in a second direction. The second port 82 is configured such that its axial position overlaps with the axial positions of the second buffer chamber 72 and the second throttling flow path 78, thereby shortening the axial direction of the cylinder 10. Compressed air is supplied to and discharged to the second pressure chamber 32 by connecting a compressed air pipe (not shown) to the second port 82.

[0042] Cylinder 10 is configured as described above. The operation of cylinder 10 will be explained below.

[0043] exist Figure 1 In the cylinder 10 shown, the piston 14 is located at the end of its stroke in the first direction. When a compressed air supply source is connected to the first port 70 and an exhaust port is connected to the second port 82, compressed air is supplied to the first pressure chamber 30 through the first throttling flow path 64. This creates a pressure difference between the first pressure chamber 30 and the second pressure chamber 32, and the piston 14 begins its stroke in the second direction. When the first buffer actuation 44 disengages from the first buffer pad 60, the first buffer chamber 58 and the first pressure chamber 30 connect, and a larger flow of compressed air is supplied to the first pressure chamber 30 through the first internal flow path 62. This increases the speed of the piston 14's movement in the second direction.

[0044] like Figure 3 As shown, at the middle position of the stroke, the first internal flow path 62 and the first throttling flow path 64 are connected to the first pressure chamber 30, and the second internal flow path 76 and the second throttling flow path 78 are connected to the second pressure chamber 32. Because the exhaust of compressed air from the second pressure chamber 32 proceeds rapidly through the second internal flow path 76 and the second throttling flow path 78, the piston 14 moves rapidly.

[0045] like Figure 4As shown, when the piston 14 displaces near the end of its stroke in the second direction, the second damping contact 46 inserts into the second buffer chamber 72. As a result, the second buffer pad 74 comes into airtight contact with the second damping contact 46, and the second buffer chamber 72 is isolated from the second pressure chamber 32. The second internal flow path 76 is also isolated from the second pressure chamber 32. The subsequent exhaust of compressed air from the second pressure chamber 32 is carried out through the second throttling flow path 78. The second throttling flow path 78 reduces the movement speed of the piston 14 to a range where the impact can be absorbed by the second damper 42 by throttling the exhaust flow of compressed air. As described above, the second air buffer mechanism 24 mitigates the impact at the end of its stroke in the second direction.

[0046] Subsequently, when the first port 70 is connected to the exhaust port and the second port 82 is connected to the compressed air supply source, compressed air is supplied to the second pressure chamber 32 through the second internal flow path 76 and the second throttling flow path 78. As a result, the piston 14 performs a stroke in the first direction.

[0047] During the stroke in the first direction, piston 14 passes through... Figure 3 The middle position of the journey towards Figure 1 The displacement at the end of the stroke in the first direction is shown. Near the end of the stroke in the first direction, the first buffer joint 44 is inserted into the first buffer chamber 58. As a result, the first buffer pad 60 is in airtight contact with the first buffer joint 44, and the first buffer chamber 58 and the first pressure chamber 30 are isolated. The first internal flow path 62 is cut off from the first pressure chamber 30. The subsequent discharge of compressed air from the first pressure chamber 30 is carried out through the first throttling flow path 64. The first throttling flow path 64 reduces the speed of the piston 14 to a range where the impact can be absorbed by the first damper 40 by throttling the flow rate of the discharged compressed air. As described above, the first air buffer mechanism 22 mitigates the impact at the end of the stroke in the first direction.

[0048] In the cylinder 10 described above, the first air buffer mechanism 22 is formed inside the first cover 18, and the second air buffer mechanism 24 is formed inside the second cover 20. Therefore, it is not necessary to install a throttle valve or a throttle flow path in the cylinder barrel 12. As a result, the overall length of the cylinder barrel 12 can be shortened, and the axial dimensions of the cylinder 10 can be miniaturized.

[0049] Regarding the above-described embodiments, the following notes are further disclosed.

[0050] (Postscript 1)

[0051] The cylinder 10 of this utility model comprises: a cylinder barrel 12 having a through hole 26 extending along an axial direction; a first cover 18 closing the end of the through hole in a first direction; a second cover 20 closing the end of the through hole in a second direction, forming a cylinder chamber 28 between the second cover and the first cover; a piston 14 dividing the cylinder chamber into a first pressure chamber 30 and a second pressure chamber 32; a first port 70 formed in the cylinder barrel for supplying and discharging compressed air to the first pressure chamber; and a first buffer chamber 58 formed in the first cover and connected to the first pressure chamber. The system includes: a first buffer protrusion 44, which protrudes from the piston in the first direction and prevents communication between the first pressure chamber and the first buffer chamber when the first buffer protrusion is inserted into the first buffer chamber; a first internal flow path 62, which connects the first buffer chamber and the first port; and a first throttling flow path 64, which is formed in the first cover, has a smaller effective cross-sectional area than the first internal flow path, and connects the first pressure chamber and the first port. The first throttling flow path is formed in the first cover and is connected to the first internal flow path inside the first cover.

[0052] The cylinders described above do not require throttle valves or similar components in the cylinder barrel, thus shortening the overall length of the cylinder.

[0053] (Postscript 2)

[0054] In the cylinder described in Appendix 1, the first internal flow path may extend radially inside the first cover, intersecting the axial direction, and the first throttling flow path may extend inside the first cover along the axial direction and connect to the first internal flow path. This cylinder can simply and compactly form an air buffer mechanism within the first cover.

[0055] (Note 3)

[0056] In the cylinder described in Appendix 1 or 2, the first throttling flow path may also be arranged parallel to the first buffer chamber outside the first buffer chamber. This cylinder is capable of suppressing the axial dimension of the first cover.

[0057] (Postscript 4)

[0058] In the cylinder described in Appendix 1, the first throttling flow path, the first buffer chamber, and the first port may also be arranged in a radially overlapping manner intersecting the axial direction. This cylinder can efficiently arrange the first throttling flow path, the first buffer chamber, and the first port along the axial direction, and can suppress dimensional changes in the axial direction.

[0059] (Note 5)

[0060] In any of the cylinders described in Appendices 1 to 4, the cylinder may further include: a second port 82 formed in the cylinder barrel for supplying or discharging compressed air to the second pressure chamber; a second buffer chamber 72 formed in the second cover and communicating with the second pressure chamber; a second internal flow path 76 connecting the second buffer chamber and the second port; a second buffer protrusion 46 protruding from the piston in the second direction, which, when inserted into the second buffer chamber, prevents communication between the second internal flow path and the second pressure chamber; and a second throttling flow path 78 formed in the second cover, having a smaller effective cross-sectional area than the second internal flow path, and connecting the second pressure chamber and the second port, wherein the second throttling flow path is connected to the second internal flow path inside the second cover. This cylinder can suppress dimensional changes in the axial direction while also providing an air buffer mechanism at the end on the second port side.

[0061] Although the present invention has been described in detail, it is not limited to the various embodiments described above. These embodiments may involve various additions, substitutions, modifications, partial deletions, etc., without departing from the spirit of the present invention, or from the spirit of the present invention derived from the content described in the claimed scope and its equivalents. Furthermore, these embodiments may also be implemented in combination. For example, in the embodiments described above, the order of each action and the order of each process are shown as an example and are not limited thereto. The same applies to the use of numerical values ​​or formulas in the description of the above embodiments.

Claims

1. A cylinder, characterized in that, have: A cylinder barrel having a through hole extending along the axial direction; A first cover, which closes the end of the through hole in a first direction; A second cover closes the second end of the through hole in a second direction, forming a cylinder chamber between the second cover and the first cover; A piston that divides the cylinder chamber into a first pressure chamber and a second pressure chamber; A first port, formed in the cylinder, supplies or discharges compressed air to the first pressure chamber; A first buffer chamber is formed in the first cover and communicates with the first pressure chamber; A first buffer engagement protrudes from the piston in the first direction, and when the first buffer engagement is inserted into the first buffer chamber, it prevents communication between the first pressure chamber and the first buffer chamber. A first internal flow path connects the first buffer chamber and the first port; as well as A first sectional flow path, formed in the first cover, has a smaller effective cross-sectional area than the first internal flow path, and connects the first pressure chamber and the first port. The first throttling flow path is formed in the first cover and is connected to the first internal flow path inside the first cover.

2. The cylinder according to claim 1, characterized in that, The first internal flow path extends radially inside the first cover along a direction intersecting the axis, and the first throttling flow path extends inside the first cover along the axis and is connected to the first internal flow path.

3. The cylinder according to claim 1, characterized in that, The first throttling flow path is configured outside the first buffer chamber and parallel to the first buffer chamber.

4. The cylinder according to claim 1, characterized in that, The first throttling flow path, the first buffer chamber, and the first port are arranged to overlap radially in a direction intersecting the axis.

5. The cylinder according to any one of claims 1 to 4, characterized in that, It also has: A second port, formed in the cylinder, supplies or discharges compressed air to the second pressure chamber; A second buffer chamber is formed in the second cover and communicates with the second pressure chamber; A second internal flow path connects the second buffer chamber and the second port; A second buffer protrusion protrudes from the piston in the second direction, and when the second buffer protrusion is inserted into the second buffer chamber, it prevents the communication between the second internal flow path and the second pressure chamber. as well as A second flow path, formed in the second cover, has a smaller effective cross-sectional area than the second internal flow path, and connects the second pressure chamber and the second port. The second throttling flow path is connected to the second internal flow path inside the second cover.

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