CN115956164A - Multi-stage fluid pressure cylinder - Google Patents

Abstract

A multistage fluid pressure cylinder (100) is provided with: a cylinder (10); a first rod assembly (30); a second rod assembly (40); and a snap ring (35) that is housed in an annular recessed portion (30 b) formed in the first rod assembly (30), wherein at least one of the first rod assembly (30) and the second rod assembly (40) is provided with communication passages (32 c, 42 d) that communicate a gap (G1) with the rod-opposite-side chamber (5), and wherein the gap (G1) is defined by the snap ring (35), an outer peripheral surface (42 a) of the first inner piston portion (42), and an inner peripheral surface (30 a) of the first rod assembly (30) in a state in which the snap ring (35) is housed in the housing recessed portion (42 c).

Description

Multi-stage fluid pressure cylinder

Technical Field

The present invention relates to a multistage fluid pressure cylinder.

Background

In japanese patent laid-open No. JPH4-254005A, there is disclosed a multistage fluid pressure cylinder including: an outer rod member having an end provided with an outer piston portion that slides along an inner circumferential surface of the cylinder tube and divides the inside of the cylinder tube into a rod side chamber and a rod opposite side chamber; an inner rod member having an end provided with an inner piston part sliding along an inner circumferential surface of the outer rod member; and a snap ring that is provided on an inner peripheral surface of the outer rod member and restricts movement of the inner rod member in a contraction direction.

Disclosure of Invention

In the inner piston portion of the multi-stage fluid pressure cylinder described in japanese patent laid-open No. JPH4-254005A, an accommodation recess portion is formed in which the inner diameter side of the snap ring is accommodated when the inner rod member contracts. When the multistage fluid pressure cylinder having such a configuration is in the most contracted state and the working fluid is not supplied to or discharged from the rod side chamber and the rod opposite side chamber, if an external force such as forcibly extending the multistage fluid pressure cylinder acts rapidly, the pressure of the rod opposite side chamber decreases, while the pressure of the rod side chamber increases. When the pressure in the rod side chamber rises in this way, the outer rod member is displaced in the extending direction together with the cylinder tube, and therefore the snap ring provided in the outer rod member is separated from the accommodating recess of the inner piston portion.

When the retainer ring is separated from the accommodating recess portion and the volume of the gap defined by the outer peripheral surface of the inner piston portion, the inner peripheral surface of the outer rod member, and the retainer ring is rapidly increased, the pressure in the gap and around the accommodating recess portion is reduced as compared with the pressure in the chamber on the rod side. When the pressure in the region where the inner diameter side of the snap ring faces is reduced in this way, a fluid force acting in the diameter expansion direction of the snap ring is generated on the inner diameter side of the snap ring so as to overcome the elastic force of the snap ring acting in the diameter expansion direction, and the outer diameter of the snap ring is reduced, and as a result, the snap ring may be detached from the outer rod member.

The invention aims to prevent a snap ring from falling off.

According to one aspect of the present invention, a multistage fluid pressure cylinder includes: a cylinder barrel; a cylindrical outer rod member having an outer piston portion at an end thereof, the outer piston portion sliding along an inner peripheral surface of the cylinder and dividing the inside of the cylinder into a rod side chamber and a rod opposite side chamber; an inner rod member having an end provided with an inner piston portion that slides along an inner peripheral surface of the outer rod member; and a snap ring having an outer diameter side that is accommodated in an annular recess formed in the inner peripheral surface of the outer rod member and that restricts movement of the inner rod member in a contraction direction, wherein the inner piston portion is provided with an accommodating recess that accommodates the inner diameter side of the snap ring when the inner rod member contracts, at least one of the outer rod member and the inner rod member is provided with a communication passage that communicates a gap with the rod-opposite-side chamber or a fluid chamber, the gap being defined by the snap ring, an outer peripheral surface of the inner piston portion, and the inner peripheral surface of the outer rod member in a state where the snap ring is accommodated in the accommodating recess and is in contact with the inner piston portion, and the fluid chamber is communicated with the rod-opposite-side chamber by relative movement of the cylinder tube with respect to the outer rod member.

Drawings

Fig. 1 is a cross-sectional view of a fluid pressure cylinder according to an embodiment of the present invention, which is a view showing a most contracted state.

Fig. 2 is a cross-sectional view of the fluid pressure cylinder according to the embodiment of the present invention, which shows a state in which the first rod assembly is located at the extended position, and the second rod assembly and the third rod assembly are located at the retracted position.

Fig. 3 is a cross-sectional view of the fluid pressure cylinder according to the embodiment of the present invention, showing a state in which the first rod assembly and the second rod assembly are in the extended position and the third rod assembly is in the retracted position.

Fig. 4 is a cross-sectional view of a fluid pressure cylinder according to an embodiment of the present invention, which is a view showing the most extended state.

Fig. 5A is an enlarged view of a portion a of fig. 1, which is a view for explaining a conventional problem.

Fig. 5B is a diagram for explaining a related art problem, which is a diagram of a state subsequent to fig. 5A.

Fig. 5C is a diagram for explaining a related art problem, which is a diagram of a state subsequent to fig. 5B.

Fig. 6 is an enlarged view showing a portion B of fig. 1 in an enlarged manner.

Fig. 7 is a diagram showing a first modification of the fluid pressure cylinder according to the embodiment of the present invention, and is a diagram showing a portion corresponding to fig. 6.

Fig. 8 is a diagram showing a second modification of the fluid pressure cylinder according to the embodiment of the present invention, and is a diagram showing a portion corresponding to fig. 6.

Fig. 9 is a diagram showing a third modification of the fluid pressure cylinder according to the embodiment of the present invention, and is a diagram showing a portion corresponding to fig. 6.

Fig. 10 is a diagram showing a fourth modification of the fluid pressure cylinder according to the embodiment of the present invention, and is a diagram showing a portion corresponding to fig. 6.

Detailed Description

Hereinafter, a multistage fluid pressure cylinder 100 according to an embodiment of the present invention will be described with reference to the drawings. Hereinafter, a case where the multi-stage fluid pressure cylinder 100 is a multi-stage fluid pressure cylinder 100 (hereinafter, simply referred to as "fluid pressure cylinder 100") that drives the hydraulic fluid as the working fluid will be described.

As shown in fig. 1, the hydraulic cylinder 100 includes: a bottomed cylindrical cylinder tube 10; a first rod assembly 30 as an outer rod member inserted into the cylinder 10 so as to be slidable; a second rod assembly 40 as an inner rod member inserted into the first rod assembly 30 so as to be slidable in a central axis direction (hereinafter, simply referred to as an axial direction) of the cylinder 10; a third rod assembly 50 as a second inner rod member is inserted into the inner side of the second rod assembly 40 so as to be freely slidable in the axial direction. Fig. 1 is a cross-sectional view showing a most contracted state of the hydraulic cylinder 100.

The hydraulic cylinder 100 is attached to the drive target apparatus such that the cylinder tube 10 is positioned on the upper side in the vertical direction and the third rod assembly 50 is positioned on the lower side in the vertical direction, by a first attachment portion 61 provided at the bottom of the cylinder tube 10 and a second attachment portion 62 provided at an end portion of the third rod assembly 50 protruding from the cylinder tube 10. That is, the hydraulic cylinder 100 is attached to the driving target equipment such that the first attachment portion 61 is displaced in a substantially vertical direction, that is, in the vertical direction, with respect to the second attachment portion 62. The direction in which the hydraulic cylinder 100 is attached is not limited to this, and the hydraulic cylinder may be attached such that the cylinder tube 10 is positioned on the vertically lower side and the third cylinder assembly 50 is positioned on the vertically upper side. The hydraulic cylinder 100 is attached to the driving target equipment such that the first attachment portion 61 is displaced in the horizontal direction with respect to the second attachment portion 62.

The first rod assembly 30 has: a cylindrical outer rod part 31; an annular outer piston portion 32 which is provided at one end portion of the outer rod portion 31, slides along the inner peripheral surface 10a of the cylinder 10, and divides the inside of the cylinder 10 into a rod side chamber 2 and a rod opposite side chamber 5; and a cylindrical first support portion 33 formed to protrude radially inward from the other end portion of the outer rod portion 31, and supported slidably by the second rod assembly 40.

An annular recess 30b to which a first snap ring 35 serving as a snap ring is attached is formed in an inner peripheral surface 30a of the first rod assembly 30 on the outer piston portion 32 side. The first snap ring 35 is a metal wire rod formed in a substantially annular shape with a circular cross-sectional shape, and has an unillustrated mouth portion partially divided. The first snap ring 35 is inserted into the first rod assembly 30 in a reduced diameter state, and is fitted into the annular recess 30b by being pressed on the outer diameter side by the inner peripheral surface 30a by an elastic force acting in the diameter expansion direction. In this way, in a state where the first snap ring 35 is assembled to the first rod assembly 30, the inner diameter side of the first snap ring 35 is in a state of protruding radially inward from the inner peripheral surface 30a of the first rod assembly 30. In addition, the installation of the first snap ring 35 is performed after the second rod assembly 40 is inserted into the first rod assembly 30.

The second rod assembly 40 has the same shape as the first rod assembly 30, and has: a first cylindrical inner rod 41 inserted into the outer rod 31; an annular first inner piston section 42 as an inner piston section provided at one end of the first inner rod section 41 and sliding along the inner peripheral surface 30a of the first rod assembly 30; and a cylindrical second support portion 43 formed to protrude radially inward from the other end portion of the first inner rod portion 41, and supporting the third rod assembly 50 to be slidable.

A second annular recess 40b to which a second snap ring 45 is attached is formed in an inner peripheral surface 40a of the second rod assembly 40 on the first inner piston portion 42 side. The second snap ring 45 is a metal wire rod formed into a substantially annular shape with a circular cross-sectional shape, similarly to the first snap ring 35, and has a mouthpiece portion, not shown, a part of which is divided. The second snap ring 45 is inserted into the second rod assembly 40 in a reduced diameter state, and is fitted into the second annular recess 40b by being pressed on the outer diameter side by the inner peripheral surface 40a by an elastic force acting in the diameter expansion direction. In this way, in a state where the second snap ring 45 is assembled to the second rod assembly 40, the inner diameter side of the second snap ring 45 is in a state of protruding radially inward from the inner peripheral surface 40a of the second rod assembly 40. Additionally, the installation of the second snap ring 45 is performed after the third rod assembly 50 is inserted into the second rod assembly 40.

The third rod assembly 50 has: a second inner lever portion 51 inserted into the first inner lever portion 41; and an annular second inner piston portion 52 coupled to one end of the second inner rod portion 51 and sliding along the inner circumferential surface 40a of the second rod assembly 40. The second inner rod portion 51 and the second inner piston portion 52 are coupled by bolts, not shown.

Thus, three rod members, i.e., the first rod assembly 30, the second rod assembly 40, and the third rod assembly 50, are inserted into the cylinder tube 10.

A cylinder head 11 that slidably supports the outer rod portion 31 of the first rod assembly 30 is provided at an opening portion of the cylinder tube 10, and a recess 10b that is recessed toward the first mounting portion 61 is formed at a bottom portion of the cylinder head 10 that faces the respective piston portions 32, 42, and 52 in the axial direction. The inner diameter of the recess 10b is set to be larger than the inner diameter of the outer piston portion 32 of the first rod assembly 30.

The most contracted position of the first rod assembly 30 inserted into the cylinder head 10 is defined by the outer piston portion 32 abutting against the bottom of the cylinder liner 10, and the most extended position is defined by the outer piston portion 32 abutting against the cylinder head 11. Further, a seal member, not shown, that closes a gap between the inner peripheral surface of the cylinder head 11 and the outer peripheral surface of the outer rod portion 31 is provided on the inner peripheral surface of the cylinder head 11 to prevent leakage of the hydraulic oil to the outside.

The most contracted position of the second rod assembly 40 inserted into the first rod assembly 30 is defined by the first inner piston portion 42 abutting against the first snap ring 35 attached to the first rod assembly 30, and the most extended position is defined by the first inner piston portion 42 abutting against the first support portion 33. In addition, the first snap ring 35 restricts movement of the second rod assembly 40 in the contraction direction, and prevents the first rod assembly 30 from being detached from the cylinder liner 10 when the hydraulic cylinder 10 contracts.

Further, a seal member, not shown, that closes a gap between the inner peripheral surface of the first support portion 33 and the outer peripheral surface of the first inner rod portion 41 is provided on the inner peripheral surface of the first support portion 33 in order to prevent leakage of the working oil to the outside.

The most contracted position of the third rod assembly 50 inserted into the second rod assembly 40 is defined by the second inner piston portion 52 abutting against the second snap ring 45 attached to the second rod assembly 40, and the most extended position is defined by the second inner piston portion 52 abutting against the second support portion 43. In addition, the second snap ring 45 restricts the movement of the third rod assembly 50 in the contraction direction, and prevents the second rod assembly 40 from being detached from the cylinder liner 10 when the hydraulic cylinder 100 contracts.

Further, a seal member, not shown, that closes a gap between the inner peripheral surface of the second support portion 43 and the outer peripheral surface of the second inner rod portion 51 is provided on the inner peripheral surface of the second support portion 43 to prevent leakage of the working oil to the outside. Further, an annular recess 43a is formed in the inner peripheral surface of the second support portion 43 so as to be faced by an opening of a communication hole 51b, which will be described later, formed in the second inner rod portion 51 when the third rod assembly 50 is maximally extended. The annular recess 43a is formed to open into a second inside rod side chamber 4 described later.

In the cylinder tube 10 into which the first rod assembly 30, the second rod assembly 40, and the third rod assembly 50 having the above-described shapes are inserted, a rod side chamber 2 defined by the cylinder tube 10, the cylinder head 11, the outer rod portion 31, and the outer piston portion 32, a first inner side chamber 3 defined by the outer rod portion 31, the first support portion 33, the first inner rod portion 41, and the first inner piston portion 42, a second inner side chamber 4 defined by the first inner rod portion 41, the second support portion 43, the second inner rod portion 51, and the second inner piston portion 52, and a rod opposite side chamber 5 defined by the cylinder tube 10, the outer piston portion 32, the first inner piston portion 42, and the second inner piston portion 52 are formed.

A first seal member 34 is provided on an outer peripheral surface 32a of the outer piston portion 32 of the first rod assembly 30, and communication between the rod side chamber 2 and the rod opposite side chamber 5 via a gap between the outer peripheral surface 32a of the outer piston portion 32 and the inner peripheral surface 10a of the cylinder 10 is blocked by the first seal member 34.

Further, a plurality of supply/discharge ports 32b for supplying/discharging the hydraulic oil to/from the rod side chamber 2 are formed in the outer piston portion 32 of the first rod assembly 30 so as to penetrate in the radial direction.

A second seal member 44 is provided on an outer peripheral surface 42a of the first inner piston portion 42 of the second rod assembly 40, and communication between the first inner rod side chamber 3 and the rod opposite side chamber 5 via a gap between the outer peripheral surface 42a of the first inner piston portion 42 and the inner peripheral surface 30a of the first rod assembly 30 is blocked by the second seal member 44.

Further, a plurality of inner supply/discharge ports 42b for supplying/discharging the working oil to/from the first inner rod side chamber 3 are formed in the first inner piston portion 42 of the second rod assembly 40 so as to penetrate in the radial direction.

A third seal member 54 is provided on an outer peripheral surface 52a of the second inner piston portion 52 of the third rod assembly 50, and communication between the second inner rod side chamber 4 and the rod opposite side chamber 5 via a gap between the outer peripheral surface 52a of the second inner piston portion 52 and the inner peripheral surface 40a of the second rod assembly 40 is blocked by the third seal member 54.

The second inner rod portion 51 of the third rod assembly 50 is formed with a supply/discharge passage 51a for supplying/discharging hydraulic oil to/from the hydraulic cylinder 100 and connected to an external device not shown, and a communication hole 51b for communicating the supply/discharge passage 51a with the second inner rod side chamber 4. In addition, the second inner lever portion 51 is formed with a connection passage 51c that connects the passage 64 formed in the second mounting portion 62 and the supply and discharge passage 51 a.

The supply/discharge passage 51a communicates with the second inside chamber 4 via the communication hole 51b, communicates with the first inside chamber 3 via the inside supply/discharge port 42b and the communication hole 51b, and communicates with the rod side chamber 2 via the supply/discharge port 32b, the inside supply/discharge port 42b, and the communication hole 51b.

That is, the supply of the working oil to the rod side chamber 2, the first inside rod side chamber 3, and the second inside rod side chamber 4, and the discharge of the working oil from the rod side chamber 2, the first inside rod side chamber 3, and the second inside rod side chamber 4 are performed via the supply and discharge passage 51a formed in the second inside rod portion 51.

Further, the second inner rod 51 is provided with a pipe-shaped supply/discharge pipe 55 for supplying/discharging the hydraulic oil to/from the hydraulic cylinder 100 and connecting to an external device. The supply and discharge pipe 55 is assembled to the second inner rod 51 so that one end thereof opens into the rod-opposite-side chamber 5, and specifically, is joined to the second inner rod 51 so as to penetrate the supply and discharge passage 51a in the axial direction. The second inner lever portion 51 is formed with a connection passage 51d that connects the passage 63 formed in the second attachment portion 62 and the other end of the supply/discharge pipe 55.

Since the supply/discharge pipe 55 is provided so that one end thereof opens into the rod side opposite chamber 5, the supply of the hydraulic oil to the rod side opposite chamber 5 and the discharge of the hydraulic oil from the rod side opposite chamber 5 are performed via the supply/discharge pipe 55.

Next, the operation of the hydraulic cylinder 100 will be described with reference to fig. 1 to 4. Hereinafter, a case will be described in which the hydraulic cylinder 100 is attached to the driving target equipment such that the first attachment portion 61 is located on the upper side in the vertical direction and the second attachment portion 62 is located on the lower side in the vertical direction.

When the hydraulic cylinder 100 is extended, hydraulic oil is supplied to the rod-side opposite chamber 5 from a hydraulic source such as a pump, not shown, via the supply/discharge pipe 55, and the hydraulic oil in the rod-side chamber 2, the first inside rod-side chamber 3, and the second inside rod-side chamber 4 is discharged to a tank, not shown, via the supply/discharge passage 51 a.

When the hydraulic cylinder 100 extends from the most contracted state shown in fig. 1, hydraulic oil is supplied to the rod-side chamber 5 through the supply/discharge pipe 55. Here, the pressure receiving area of the rod opposite side chamber 5 that receives the pressure is largest when the first rod assembly 30 is elongated and smallest when the third rod assembly 50 is elongated. Thus, when the hydraulic cylinder 100 performs an extension operation from the most contracted state, first, the cylinder tube 10 moves relative to the first rod assembly 30. Specifically, as shown in fig. 2, the cylinder 10 moves upward (upward in fig. 2) with respect to the first rod assembly 30. Further, since the recess 10b formed in the bottom of the cylinder tube 10 has an inner diameter larger than that of the outer piston portion 32 of the first rod assembly 30, the pressure of the working oil guided to the rod opposing side chamber 5 acts on the outer piston portion 32 via the recess 10b.

When the cylinder 10 moves relative to the first rod assembly 30, the hydraulic oil in the rod side chamber 2 is guided to the supply/discharge passage 51a via the supply/discharge port 32b, the inner supply/discharge port 42b, and the communication hole 51b, and is discharged to the outside.

As shown in fig. 2, when the cylinder tube 10 is in the most extended state with respect to the first rod assembly 30, that is, the cylinder tube 10 is moved upward until the cylinder head 11 abuts against the outer piston portion 32 of the first rod assembly 30, then the cylinder tube 10 and the first rod assembly 30 are relatively moved with respect to the second rod assembly 40 by the pressure of the opposite-rod side chamber 5. Specifically, as shown in fig. 3, the cylinder 10 and the first rod assembly 30 move upward (upward in fig. 3) with respect to the second rod assembly 40.

When the first rod assembly 30 moves relative to the second rod assembly 40, the working oil in the first inside rod side chamber 3 is guided to the supply/discharge passage 51a through the inside supply/discharge port 42b and the communication hole 51b, and is discharged to the outside.

As shown in fig. 3, when the first rod assembly 30 is in a state of being most extended with respect to the second rod assembly 40, that is, the cylinder 10 and the first rod assembly 30 are moved upward until the first support portion 33 of the first rod assembly 30 comes into contact with the first inner piston portion 42 of the second rod assembly 40, the cylinder 10, the first rod assembly 30, and the second rod assembly 40 are then moved relative to the third rod assembly 50 by the pressure of the rod-opposite-side chamber 5. Specifically, as shown in fig. 4, the cylinder 10, the first rod assembly 30, and the second rod assembly 40 move upward (upward in fig. 4) with respect to the third rod assembly 50.

When the second rod assembly 40 moves relative to the third rod assembly 50, the working oil in the second inside rod side chamber 4 is guided to the supply/discharge passage 51a via the communication hole 51b and discharged to the outside.

As shown in fig. 4, when the second rod assembly 40 is in the most extended state with respect to the third rod assembly 50, that is, the cylinder tube 10, the first rod assembly 30, and the second rod assembly 40 are moved upward until the second support portion 43 of the second rod assembly 40 comes into contact with the second inner piston portion 52 of the third rod assembly 50, the hydraulic cylinder 100 is in the most extended state.

On the other hand, when the hydraulic cylinder 100 performs the contraction operation, the hydraulic oil is supplied from the hydraulic source to the rod side chamber 2, the first inside rod side chamber 3, and the second inside rod side chamber 4 via the supply/discharge passage 51a, and the hydraulic oil in the rod side chamber 5 is discharged to the tank via the supply/discharge pipe 55. The retraction operation of the hydraulic cylinder 100 may be performed by the weight of the driving target equipment coupled to the first mounting portion 61. In this case, the working oil does not need to be supplied to the rod side chamber 2, the first inside side chamber 3, and the second inside side chamber 4, and the working oil is sucked from the tank into the rod side chamber 2, the first inside side chamber 3, and the second inside side chamber 4.

When the hydraulic cylinder 100 performs the retracting operation from the most extended state, the cylinder 10, the first rod assembly 30, and the second rod assembly 40 are first moved relative to the third rod assembly 50 from the state shown in fig. 4 to the state shown in fig. 3, and then the cylinder 10 and the first rod assembly 30 are moved relative to the second rod assembly 40 from the state shown in fig. 3 to the state shown in fig. 2. Further, the cylinder tube 10 is moved relative to the first rod assembly 30 from the state shown in fig. 2 to the state shown in fig. 1, whereby the hydraulic cylinder 100 is brought into the most contracted state.

As shown in fig. 5, the first inner piston portion 42 of the second rod assembly 40 of the hydraulic cylinder 100 configured as described above is provided with an accommodating recess portion 42c that accommodates the inner diameter side of the first snap ring 35 in the most contracted state of the second rod assembly 40. The accommodation recess 42c is provided to limit deformation of the first snap ring 35 on the radially inner side, and is configured to prevent the first snap ring 35 from being disengaged from the first rod assembly 30 by the first inner piston portion 42 coming into contact with the first snap ring 35 when the second rod assembly 40 contracts. Fig. 5A is an enlarged view of a portion enclosed by a broken line indicated by an arrow a in fig. 1 showing the hydraulic cylinder 100 in the most contracted state.

Further, as shown in fig. 5A, in a state where the first snap ring 35 is accommodated in the accommodation recess portion 42c and the first snap ring 35 is in contact with the first inner piston portion 42, a gap G1 defined by the outer peripheral surface 42a of the first inner piston portion 42, the inner peripheral surface 30a of the first rod assembly 30, and the first snap ring 35 is formed on the opposite side of the rod-opposite side chamber 5 with the first snap ring 35 interposed therebetween.

Here, when the hydraulic cylinder 100 configured as described above is in the most contracted state and the hydraulic oil is not supplied to and discharged from the rod side chamber 2 and the rod opposite side chamber 5, if an external force such as forcibly extending the hydraulic cylinder 100 acts rapidly, the hydraulic oil is not supplied to the rod opposite side chamber 5 having an enlarged volume, and therefore the pressure in the chamber decreases, while the hydraulic oil is not discharged to the rod side chamber 2 having a reduced volume, and therefore the pressure in the chamber increases.

When the pressure in the rod side chamber 2 increases in this manner, the first rod assembly 30 is displaced in the extending direction together with the cylinder tube 10, and the first rod assembly 30 is displaced relative to the second rod assembly 40. Therefore, as shown in fig. 5B, the first snap ring 35 provided in the first rod assembly 30 is separated from the housing recess 42c of the first inner piston portion 42.

As shown in fig. 5B, when the first snap ring 35 is instantaneously separated from the housing recess 42c, the volume of the gap G defined by the outer peripheral surface 42a of the first inner piston portion 42, the inner peripheral surface 30a of the first rod assembly 30, and the first snap ring 35 is rapidly increased, and therefore, the pressure in the gap G1 is lower than that in the rod opposite side chamber 5, and a flow of the hydraulic oil from the rod opposite side chamber 5 to the gap G1 as shown by an arrow F in fig. 5B is generated.

Further, the flow of the hydraulic oil from the rod side chamber 5 toward the gap G1 passes through a small gap between the radially inner side of the first snap ring 35 and the housing concave portion 42c, and therefore the pressure on the inner diameter side of the first snap ring 35 is significantly reduced by the so-called venturi effect.

When the pressure in the region that the inner diameter side of the first snap ring 35 faces is reduced in this way, a fluid force that acts in the direction of reducing the diameter of the first snap ring 35 against the elastic force of the first snap ring 35 that acts in the diameter expansion direction is generated on the inner diameter side of the first snap ring 35, and the outer diameter of the first snap ring 35 is reduced, and as a result, as shown in fig. 5C, the outer diameter side of the first snap ring 35 separates from the annular recessed portion 30b, and the first snap ring 35 may separate from the first rod assembly 30.

In contrast, in the hydraulic cylinder 100 of the present embodiment, as shown in fig. 6, through holes 32c, 42d as communication passages that communicate a gap G1 with the rod opposite side chamber 5, the gap G1 being defined by the outer peripheral surface 42a of the first inner piston portion 42, the inner peripheral surface 30a of the first rod assembly 30, and the first snap ring 35, are provided in the first rod assembly 30 and the second rod assembly 40, respectively.

The through hole 32c provided as the communication passage in the first rod assembly 30 is a cut hole formed such that one end opens in the rod opposite side chamber 5 and the other end opens in the gap G1, and a plurality of through holes are provided at intervals in the circumferential direction in the outer piston portion 32 of the first rod assembly 30.

The through-hole 42d provided in the second rod assembly 40 as a communication passage is a cut hole formed so that one end opens into the rod-opposite-side chamber 5 and the other end opens into the gap G1, similarly to the through-hole 32c, and a plurality of through-holes are provided at intervals in the circumferential direction in the first inner piston portion 42 of the second rod assembly 40.

Since the gap G1 and the rod opposite side chamber 5 are communicated with each other through the through holes 32c and 42d, as described above, even if the volume of the gap G1 rapidly increases, the pressure difference between the gap G1 and the rod opposite side chamber 5 is suppressed from increasing, and therefore, the flow of the working oil from the rod opposite side chamber 5 to the gap G1 through the radially inner side of the first snap ring 35 becomes small.

Further, since the working oil flows into the gap G1 from the rod-opposite-side chamber 5 not only through the gap between the radially inner side of the first snap ring 35 and the housing recess 42c but also through the through- holes 32c, 42d, the degree of decrease in the pressure in the gap G1 is alleviated, and the pressure in the region facing the inner diameter side of the first snap ring 35 is suppressed from extremely decreasing.

With this, the fluid force acting in the direction of reducing the diameter of the first snap ring 35 so as to overcome the elastic force of the first snap ring 35 acting in the diameter expansion direction is suppressed from being generated on the inner diameter side of the first snap ring 35, and as a result, the first snap ring 35 can be prevented from coming off from the first rod assembly 30.

Although the through holes 32c and 42d are provided in the first rod assembly 30 and the second rod assembly 40, respectively, they may be provided only in one of the first rod assembly 30 and the second rod assembly 40.

In order to prevent the second snap ring 45, which is accommodated in the second annular recess on the outer diameter side and the second accommodating recess 52b on the inner diameter side, from being detached from the second rod assembly 40 in addition to the first snap ring 35, as shown in fig. 6, a through hole 52c, which is a communication passage, may be provided in the third rod assembly 50 to communicate a second gap G2 with the rod-opposite-side chamber 5, the second gap G2 being defined by the outer circumferential surface 52a of the second inner piston portion 52, the inner circumferential surface 40a of the second rod assembly 40, and the second snap ring 45.

The through-hole 52c provided in the third rod assembly 50 as a communication passage is a cut hole formed such that one end opens into the rod-opposite-side chamber 5 and the other end opens into the second gap G2, and a plurality of through-holes are provided at intervals in the circumferential direction in the second inner piston portion 52 of the third rod assembly 50. In addition, not only the third rod assembly 50 but also the second rod assembly 40 may be provided with a through hole as a communication path that communicates the second gap G2 with the rod-opposite-side chamber 5.

According to the above embodiment, the following effects are obtained.

In the hydraulic cylinder 100 having the above-described configuration, the through- holes 32c and 42d that communicate the gap G1 defined by the outer peripheral surface 42a of the first inner piston portion 42, the inner peripheral surface 30a of the first rod assembly 30, and the first snap ring 35 with the rod-opposite-side chamber 5 are provided in at least one of the first rod assembly 30 and the second rod assembly 40.

As described above, by communicating the gap G1 and the rod side chamber 5 through the through holes 32c and 42d, when the hydraulic cylinder 100 is in the most contracted state, an external force such as forcibly extending the hydraulic cylinder 100 acts rapidly, the first rod assembly 30 is displaced in the extending direction together with the cylinder tube 10, the first snap ring 35 is instantaneously separated from the housing recess 42c, and even if the volume of the gap G1 rapidly increases, the pressure difference between the gap G1 and the rod side chamber 5 is suppressed from increasing.

This alleviates the degree of decrease in the pressure in the gap G1, and suppresses the pressure in the region where the inner diameter side of the first snap ring 35 faces from extremely decreasing, and therefore, suppresses the fluid force acting in the direction of reducing the diameter of the first snap ring 35 so as to overcome the elastic force of the first snap ring 35 acting in the diameter expansion direction from being generated on the inner diameter side of the first snap ring 35. As a result, the first snap ring 35 can be prevented from being detached from the first rod assembly 30.

In addition, the following modifications are also within the scope of the present invention, and the configurations described in the modifications and the configurations described in the above embodiments may be combined, or the configurations described in the following different modifications may be combined with each other.

In the above embodiment, the communication paths are through- holes 32c and 42d having one end opening into the rod-opposite-side chamber 5 and the other end opening into the gap G1. In addition, as in the first modification shown in fig. 7, the communication path may be a cut-out groove 32d formed by cutting the inner peripheral surface 30a of the first rod assembly 30 in the axial direction and a cut-out groove 42e formed by cutting the outer peripheral surface 42a of the first inner piston portion 42 in the axial direction. Fig. 7 is a view showing a modification of the above embodiment, and shows a portion corresponding to fig. 6.

The notch groove 32d provided as the communication passage in the first rod assembly 30 is a groove having a width of a predetermined magnitude in the circumferential direction of the outer diameter piston portion 32 and formed in the axial direction so as to go over the annular recess 30b from the end surface of the first rod assembly 30 facing the rod-opposite-side chamber 5, and a plurality of notches are provided in the outer diameter piston portion 32 of the first rod assembly 30 with intervals in the circumferential direction. The depth of the notch groove 32d from the inner peripheral surface 30a of the first lever assembly 30 is formed to be deeper than the annular recessed portion 30b. In this way, when viewed in cross section as shown in fig. 7, the notch groove 32d is formed so as to surround the annular recessed portion 30b, whereby the rod-opposite-side chamber 5 and the gap G1 are always communicated with each other via the notch groove 32 d.

The notch groove 32d may be formed so as to communicate the rod side chamber 5 with the gap G1, and may not be formed so as to reach the end surface of the first rod assembly 30 facing the rod side chamber 5 in the axial direction, but is preferably formed so as to open to the end surface of the first rod assembly 30 as described above in order to facilitate workability.

The notch groove 42e provided in the second rod assembly 40 as the communication passage has a width of a predetermined size in the circumferential direction of the first inner piston portion 42, and is formed in the axial direction so as to extend from the end surface of the second rod assembly 40 facing the rod opposite side chamber 5 beyond the housing recess 42c, and a plurality of notches are provided in the first inner piston portion 42 of the second rod assembly 40 at intervals in the circumferential direction. The notch groove 42e is opened in the radial direction on the outer peripheral surface 42a of the first inner piston portion 42 and the inner peripheral surface 40a of the second rod assembly 40. As described above, in the sectional view shown in fig. 7, the notch groove 42e is formed so as to surround the housing recess 42c, so that the lever-opposite-side chamber 5 and the gap G1 are always communicated with each other through the notch groove 42e. The notch groove 42e may be formed so as to communicate the rod-opposite-side chamber 5 with the gap G1, and may not be formed so as to reach the inner peripheral surface 40a of the second rod assembly 40 in the radial direction.

In this way, in the first modification as well, the gap G1 and the rod-opposite-side chamber 5 communicate via the notched grooves 32d, 42e, and therefore, similarly to the above-described embodiment, it is possible to prevent the first snap ring 35 from being disengaged from the first rod assembly 30.

In the first modification, in order to prevent the second snap ring 45 provided in the second rod assembly 40 from coming off as well as the first snap ring 35 from coming off, a notch groove 52d serving as a communication passage that communicates the second gap G2 with the rod-opposite-side chamber 5 may be provided in the third rod assembly 50.

The notch groove 52d provided as the communication passage in the third rod assembly 50 is a groove having a predetermined width in the circumferential direction of the second inner piston portion 52 and formed in the axial direction so as to extend from the end surface of the third rod assembly 50 facing the rod-opposite-side chamber 5 beyond the second receiving recess 52b, and a plurality of notches are provided in the second inner piston portion 52 of the third rod assembly 50 with a gap in the circumferential direction. In addition, a notch groove that communicates the second gap G2 with the rod-opposite-side chamber 5 may be formed not only in the third rod assembly 50 but also in the second rod assembly 40.

In the above embodiment, the communication passages are through holes 32c and 42d newly formed in the first rod assembly 30. In addition, as in the second modification shown in fig. 8, the communication path may be a threaded hole 32e into which the jig is screwed when the first snap ring 35 is removed from the first rod assembly 30, or a threaded hole 42f into which the jig is screwed when the second snap ring 45 is removed from the second rod assembly 40. Fig. 8 is a view showing a modification of the above embodiment, and shows a portion corresponding to fig. 6.

The screw hole 32e formed in the first rod assembly 30 as the communication passage is a female screw hole formed to penetrate the first rod assembly 30 in the radial direction so that one end thereof opens in the outer peripheral surface 32a of the outer piston portion 32 and the other end thereof opens in the annular recess 30b formed in the inner peripheral surface 30a of the first rod assembly 30, and a plurality of screw holes are provided in the outer piston portion 32 of the first rod assembly 30 at intervals in the circumferential direction. The female screw inner diameter of the screw hole 32e is set to be larger than the wire diameter of the first snap ring 35, that is, the width of the annular recessed portion 30b in the axial direction. Therefore, the opening end of the screw hole 32e opened in the inner peripheral surface 30a of the first rod assembly 30 is divided into two by the first snap ring 35 accommodated in the annular recess 30b, one of which opens in the rod-opposite-side chamber 5 and the other of which opens in the gap G1. Therefore, the rod-opposite-side chamber 5 and the gap G1 are always in communication with each other through the inside of the screw hole 32e.

The threaded hole 42f formed in the second rod assembly 40 as the communication passage is a female threaded hole formed radially through the second rod assembly 40 so that one end opens in the outer peripheral surface 42a of the first inner piston portion 42 and the other end opens in the second annular recess 40b formed in the inner peripheral surface 40a of the second rod assembly 40, and a plurality of threaded holes are provided in the first inner piston portion 42 of the second rod assembly 40 at intervals in the circumferential direction. The female screw inner diameter of the screw hole 42f is set to be larger than the wire diameter of the second snap ring 45, that is, the width of the second annular recessed portion 40b in the axial direction. Therefore, the opening end of the screw hole 42f opened in the inner peripheral surface 40a of the second rod assembly 40 is divided into two by the second snap ring 45 accommodated in the second annular recess 40b, one of which opens in the rod-opposite-side chamber 5 and the other of which opens in the second gap G2. Further, since the screw hole 42f also opens to the outer peripheral surface 42a of the first inner piston portion 42 defining the gap G1, the rod-side chamber 5 and the gap G1 are always in communication with each other through the inside of the screw hole 42f.

In this way, in the second modification, since the gap G1 and the rod opposite side chamber 5 communicate with each other through the screw holes 32e and 42f, the first snap ring 35 can be prevented from being disengaged from the first rod assembly 30, as in the above-described embodiment. Further, by using the holes used when the snap rings 35, 45 are removed as the communication passages like the screw holes 32e, 42f, the manufacturing cost of the hydraulic cylinder 100 can be reduced as compared with the case where the communication passages are separately formed.

In the second modification, since the rod opposite side chamber 5 and the second gap G2 are always communicated with each other through the inside of the screw hole 42f, it is possible to prevent not only the first snap ring 35 from being disengaged but also the second snap ring 45 provided in the second rod assembly 40 from being disengaged.

In the second modification, the holes formed as the communication passages are the screw holes 32e and 42f, but the communication passages may be simple through holes having an inner diameter of a size that allows the gap G1 to communicate with the rod side chamber 5.

Specifically, when a through-hole is provided in the first rod assembly 30 in place of the screw hole 32e, the inner diameter of the through-hole is set to be larger than the wire diameter of the first snap ring 35, that is, the width of the annular recess 30b in the axial direction. In the case where a through-hole is provided in the second rod assembly 40 in place of the screw hole 42f, the inner diameter of the through-hole is set to be larger than the wire diameter of the second snap ring 45, that is, the width of the second annular recessed portion 40b in the axial direction.

Such a through-hole is freely formed in the direction if one end is opened to the outer peripheral surface 32a and the other end is opened to the annular recess 30b, but preferably, in the case where the through-hole is used as an insertion hole of a jig for removing the snap rings 35, 45, the through-hole is formed in the radial direction while being orthogonal to the axial direction.

In the above embodiment, the communication path provided in the first rod assembly 30 is a single through-hole 32c formed in the first rod assembly 30. Alternatively, as in a third modification shown in fig. 9, the communication path may be constituted by a plurality of communication paths (32 f, 32 g) formed in the first rod assembly 30. Fig. 9 is a diagram showing a modification of the above embodiment, and shows a portion corresponding to fig. 6.

The through-hole 32f provided as a communication passage in the first rod assembly 30 is a cut hole formed such that one end thereof opens in the outer peripheral surface 32a of the outer piston portion 32 and the other end thereof opens in the gap G1, and a plurality of through-holes are provided in the outer piston portion 32 of the first rod assembly 30 with a gap therebetween in the circumferential direction. The notch groove 32g provided as a communication passage in the first rod assembly 30 is a groove in the end surface of the first rod assembly 30 facing the rod-opposite-side chamber 5, and is formed so as to reach the outer peripheral surface 32a of the outer piston portion 32 along the radial direction of the outer piston portion 32. The plurality of notch grooves 32g are provided at intervals in the circumferential direction in the outer piston portion 32 of the first rod assembly 30.

The through hole 32f and the notch groove 32G formed in this way form a communication passage that constantly communicates the rod-opposite-side chamber 5 and the gap G1 via a third gap G3 defined by the outer peripheral surface 32a of the outer piston portion 32 and the inner peripheral surface 10a of the cylinder 10. In this way, in the third modification, since the gap G1 and the rod opposite side chamber 5 are communicated through the through hole 32f and the cutout groove 32G, the first snap ring 35 can be prevented from being detached from the first rod assembly 30, as in the above-described embodiment.

In the above embodiment, the communication path provided in the first rod assembly 30 always communicates the rod-opposite-side chamber 5 and the gap G1. In addition, as in the fourth modification shown in fig. 10, the communication path may communicate the opposite-rod side chamber 5 with the gap G1 when the cylinder 10 slightly moves relative to the first rod assembly 30, that is, when the end surface 30c of the first rod assembly 30 that abuts the step portion 10c formed between the inner circumferential surface 10a of the cylinder 10 and the recess 10b is slightly separated from the step portion 10 c. Fig. 10 is a view showing a modification of the above embodiment, and shows a portion corresponding to fig. 6.

The through-hole 32h provided in the first rod assembly 30 as a communication passage is a cut hole formed such that one end thereof opens to the outer peripheral surface 32a of the outer piston portion 32 and the other end thereof opens to the gap G1, and a plurality of through-holes are provided in the outer piston portion 32 of the first rod assembly 30 with a gap therebetween in the circumferential direction.

When the cylinder 10 moves relative to the first rod assembly 30 and the end surface 30c of the first rod assembly 30 is separated from the step portion 10c, the through-hole 32h formed in this way communicates the gap G1 with a third gap G3 as a fluid chamber that communicates with the rod-opposite-side chamber 5 via the gap formed between the end surface 30c and the step portion 10 c. That is, the through-hole 32h communicates the rod side chamber 5 with the gap G1 via a gap formed between the end surface 30c and the stepped portion 10c and a third gap G3 defined by the outer peripheral surface 32a of the outer piston portion 32 and the inner peripheral surface 10a of the cylinder 10.

In this way, in the fourth modification, the gap G1 and the rod-opposite-side chamber 5 communicate with each other through the through-hole 32h, and therefore, as in the above-described embodiment, the first snap ring 35 can be prevented from being detached from the first rod assembly 30.

In the above embodiment, the cross-sectional shape of each snap ring 35, 45 is circular. The cross-sectional shape of each snap ring 35, 45 is not limited to a circle, and may be an ellipse or a rectangle.

In the above embodiment, the hydraulic cylinder 100 is a three-stage hydraulic cylinder 100 in which three rod members (the first rod assembly 30, the second rod assembly 40, and the third rod assembly 50) are provided so as to overlap in the cylinder tube 10 in the radial direction. In contrast, the hydraulic cylinder 100 may be a two-stage hydraulic cylinder in which two rod members are provided so as to overlap in the radial direction in the cylinder tube 10, or may be a hydraulic cylinder in which four or more rod members are provided so as to overlap in the radial direction.

Hereinafter, the structure, operation, and effects of the embodiments of the present invention will be summarized.

The hydraulic cylinder 100 includes: a cylinder barrel 10; a first cylindrical rod assembly 30 having an outer piston 32 provided at an end thereof, the outer piston 32 sliding along an inner peripheral surface 10a of the cylinder 10 and dividing the inside of the cylinder 10 into a rod side chamber 2 and a rod opposite side chamber 5; a second rod assembly 40 having a first inner piston 42 sliding along the inner circumferential surface 30a of the first rod assembly 30 at an end thereof; and a snap ring 35 having an outer diameter side accommodated in an annular recessed portion 30b formed in an inner peripheral surface 30a of the first rod assembly 30 and restricting movement of the second rod assembly 40 in a contraction direction, wherein the first inner piston portion 42 is provided with an accommodating recessed portion 42c accommodating the inner diameter side of the snap ring 35 when the second rod assembly 40 contracts, at least one of the first rod assembly 30 and the second rod assembly 40 is provided with communication passages (32 c, 32d, 32e, 32f, 32G, 32h, 42d, 42e, 42 f) communicating a gap G1 with the rod opposite side chamber 5 or a third gap G3, the gap G1 being defined by the snap ring 35, the outer peripheral surface 42a of the first inner piston portion 42 and the inner peripheral surface 30a of the first rod assembly 30 in a state where the snap ring 35 is accommodated in the accommodating recessed portion 42c and abuts the first inner piston portion 42, and the third gap G3 is communicated with the rod opposite side chamber 5 by moving the snap ring 35 relative to the first rod assembly 30 through the cylinder 10.

In this configuration, communication passages (32 c, 32d, 32e, 32f, 32G, 32h, 42d, 42e, and 42 f) that communicate with the rod opposite side chamber 5 or a third gap G3 that communicates with the rod opposite side chamber 5 are provided in at least one of the first rod assembly 30 and the second rod assembly 40, the gap G1 defined by the outer peripheral surface 42a of the first inner piston portion 42, the inner peripheral surface 30a of the first rod assembly 30, and the first snap ring 35.

As described above, since the gap G1 and the rod side opposite chamber 5 are communicated via the communication passages (32 c, 32d, 32e, 32f, 32G, 42d, 42e, 42 f), or the third gap G3 is communicated via the communication passage (32 h) with the gap G1, and the third gap G3 is communicated with the rod side opposite chamber 5 by the relative movement of the cylinder tube 10 with respect to the first rod assembly 30, when the hydraulic cylinder 100 is in the most contracted state, an external force such as forcibly extending the hydraulic cylinder 100 acts abruptly, the first rod assembly 30 is displaced in the extending direction together with the cylinder tube 10, the first snap ring 35 is instantaneously separated from the housing recess 42c, and even if the volume of the gap G1 is rapidly increased, the pressure difference between the gap G1 and the rod side opposite chamber 5 is suppressed from increasing.

This alleviates the degree of decrease in the pressure in the gap G1, and also suppresses extreme decrease in the pressure in the region facing the inner diameter side of the first snap ring 35, so that the fluid force acting in the direction of reducing the diameter of the first snap ring 35 against the elastic force of the first snap ring 35 acting in the diameter expansion direction is suppressed from being generated on the inner diameter side of the first snap ring 35. As a result, the first snap ring 35 can be prevented from being detached from the first rod assembly 30.

The communication passages are through holes 32c and 42d formed in at least one of the first rod assembly 30 and the second rod assembly 40, and one ends of the through holes 32c and 42d open to the rod-opposite-side chamber 5 and the other ends open to the gap G1.

In this configuration, the communication passages are through- holes 32c and 42d formed so that one end opens into the rod-opposite-side chamber 5 and the other end opens into the gap G1. By using the through holes 32c, 42d that can be easily formed in the first rod assembly 30 and the second rod assembly 40 as communication passages that communicate the gap G1 with the rod-opposite-side chamber 5 in this way, it is possible to prevent the first snap ring 35 from coming off the first rod assembly 30 without increasing the manufacturing cost of the hydraulic cylinder 100.

The communication passages are cut-out grooves 32d and 42e cut in the axial direction in at least one of the inner peripheral surface 30a of the first rod assembly 30 and the outer peripheral surface 42a of the first inner piston portion 42.

In this configuration, the communication passages are the notch grooves 32d, 42e cut in the axial direction on the inner peripheral surface 30a of the first rod assembly 30 and the outer peripheral surface 42a of the first inner piston portion 42. By using the through holes 32d, 42e that can be easily formed in the first rod assembly 30 and the second rod assembly 40 as communication passages for communicating the gap G1 with the rod opposite side chamber 5, it is possible to prevent the first snap ring 35 from being detached from the first rod assembly 30 without increasing the manufacturing cost of the hydraulic cylinder 100.

Further, the notch grooves 32d, 42e are formed in the axial direction from at least one of the end surface of the first rod assembly 30 and the end surface of the second rod assembly 40 facing the rod-opposite-side chamber 5.

In this configuration, the notch grooves 32d and 42e are formed in the axial direction from the end surface of the first rod assembly 30 facing the rod opposite side chamber 5 and the end surface of the second rod assembly 40. By forming the notch grooves 32d, 42e in the axial direction from the end surface of the first rod assembly 30 facing the rod opposite side chamber 5 and the end surface of the second rod assembly 40 in this way, a communication path through which the gap G1 and the rod opposite side chamber 5 can communicate can be easily formed.

The communication passage is a threaded hole 32e having one end opened to the outer peripheral surface 32a of the outer piston portion 32 and the other end opened to the annular recess 30b, and the female-thread inner diameter of the threaded hole 32e is larger than the wire path of the snap ring 35.

In this configuration, the communication passage is a screw hole 32e having one end opening to the outer peripheral surface 32a of the outer piston portion 32 and the other end opening to the annular recess 30b. By using the screw hole 32e into which the jig is screwed when the clamp ring 35 is detached from the annular recessed portion 30b as the communication passage in this way, it is possible to prevent the first clamp ring 35 from being detached from the first rod assembly 30 without increasing the manufacturing cost of the hydraulic cylinder 100.

Further, the hydraulic cylinder 100 includes: a third rod assembly 50 having a second inner piston portion 52 provided at an end thereof to slide along the inner circumferential surface 40a of the second rod assembly 40; and a second snap ring 45 that is accommodated in a second annular recess 40b formed in an inner peripheral surface 40a of the second rod assembly 40 on the outer diameter side thereof, and that restricts movement of the third rod assembly 50 in the contraction direction, wherein the communication passage is a threaded hole 42f having one end opening in the outer peripheral surface 42a of the first inner piston portion 42 and the other end opening in the second annular recess 40b, and the threaded hole 42f has a female thread inner diameter larger than the thread diameter of the second snap ring 45.

In this configuration, the communication passage is a screw hole 42f having one end opening to the outer peripheral surface 42a of the first inner piston portion 42 and the other end opening to the second annular recess 40b. By using the threaded hole 42f into which the jig is screwed when the second snap ring 45 is removed from the second annular recessed portion 40b as the communication passage in this way, it is possible to prevent the first snap ring 35 from being detached from the first rod assembly 30 without increasing the manufacturing cost of the hydraulic cylinder 100.

Although the embodiments of the present invention have been described above, the above embodiments are merely some of application examples of the present invention, and the technical scope of the present invention is not limited to the specific configurations of the above embodiments.

This application claims priority based on Japanese patent application 2020-141111, filed to the patent office on 8/24/2020 and is incorporated herein by reference in its entirety.

Claims (6)

1. A multi-stage fluid pressure cylinder is provided with:

a cylinder barrel;

a cylindrical outer rod member having an outer piston portion at an end thereof, the outer piston portion sliding along an inner peripheral surface of the cylinder and dividing the inside of the cylinder into a rod side chamber and a rod opposite side chamber;

an inner rod member having an end provided with an inner piston part that slides along an inner circumferential surface of the outer rod member;

a snap ring, the outer diameter side of which is accommodated in an annular recess formed in the inner peripheral surface of the outer rod member, and which restricts movement of the inner rod member in a contraction direction,

the inner piston portion is provided with an accommodation recess portion for accommodating an inner diameter side of the snap ring when the inner rod member contracts,

a communication passage is provided in at least one of the outer rod member and the inner rod member, the communication passage communicating with the rod opposite side chamber or a fluid chamber, the communication passage being defined by the snap ring, an outer peripheral surface of the inner piston portion, and the inner peripheral surface of the outer rod member in a state where the snap ring is accommodated in the accommodation recess and is in contact with the inner piston portion, and the fluid chamber communicating with the rod opposite side chamber by relative movement of the cylinder tube with respect to the outer rod member.

2. The multiple stage fluid pressure cylinder as claimed in claim 1,

the communication passage is a through hole formed in at least one of the outer rod member and the inner rod member,

one end of the through hole opens in the chamber on the opposite side of the rod, and the other end opens in the gap.

3. The multiple stage fluid pressure cylinder as claimed in claim 1,

the communication passage is a notch groove cut in an axial direction in at least one of the inner peripheral surface of the outer rod member and the outer peripheral surface of the inner piston portion.

4. The multiple stage fluid pressure cylinder as claimed in claim 3,

the notch groove is formed in the axial direction from at least one of an end surface of the outer rod member and an end surface of the inner rod member facing the chamber on the opposite side of the rod.

5. The multiple stage fluid pressure cylinder as claimed in claim 1,

the communication passage is a threaded hole having one end opening to the outer peripheral surface of the outer piston portion and the other end opening to the annular recess,

the internal diameter of the female thread of the threaded hole is larger than the line diameter of the clamping ring.

6. The multi-stage fluid pressure cylinder as claimed in claim 1, further comprising:

a second inner rod member having a second inner piston part provided at an end thereof to slide along an inner circumferential surface of the inner rod member;

a second snap ring whose outer diameter side is accommodated in a second annular recess portion formed in the inner peripheral surface of the inner rod member and which restricts movement of the second inner rod member in a contraction direction,

the communication passage is a threaded hole having one end opening to the outer peripheral surface of the inner piston portion and the other end opening to the second annular recess,

the inner diameter of the female thread of the threaded hole is larger than the line diameter of the second clamping ring.

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