KR102254780B1 - Hydraulic cylinder with built-in locking device - Google Patents

Abstract

The present invention relates to a hydraulic cylinder with a built-in locking apparatus, which comprises: a cylinder tube having a certain diameter and extended straight in a longitudinal direction; an end cap engaged with an end unit of the cylinder tube, having a locking unit providing a support force; a reciprocating rod slidably inserted into the cylinder tube and extended to the outside of the other end unit of the cylinder tube; and a locking end placed on an end unit of the reciprocating rod to be fixed on the locking unit by meeting the locking unit with the reciprocating rod completely inserted into the cylinder tube. As such, in accordance with the present invention, the hydraulic cylinder with the built-in locking apparatus is able to support the piston rod inserted completely into the cylinder tube to be firmly engaged and fixed by the built-in locking apparatus, prevent the piston rod from abnormally deviating by a load applied from outside including its own weight, have a good motion reliability, secure and increase a buffer volume in the cylinder body for preventing the piston from rapidly colliding with an end plug, and secure flexibility and stability in the operation of the cylinder. In addition, since the locking apparatus supporting the piston rod is placed inside the cylinder tube, the external structure is not complex and can be simply maintained.

Description

Hydraulic cylinder with built-in locking device

The present invention relates to a hydraulic cylinder applied to various industrial equipment, and more particularly, to a hydraulic cylinder having a built-in locking device that has good operational reliability by preventing abnormal pulling out of a piston rod due to external force.

Hydraulic cylinders, which are widely used in various industrial fields, are important output equipment that converts the pressure energy of incompressible hydraulic oil into mechanical force.

The hydraulic cylinder includes a hollow cylinder tube extending in the longitudinal direction, a hydraulic pump for pressurizing hydraulic oil into the cylinder tube, and a piston rod inserted into the cylinder tube and linearly reciprocating under pressure of hydraulic oil. In addition, a valve for controlling the flow rate of hydraulic oil pressed into the cylinder tube and preventing reverse flow, and a control device for controlling the valve are installed outside the cylinder tube.

These hydraulic cylinders have features that can output a large force and can easily adjust the length of the piston rod, and are essentially used in almost all heavy equipment for civil engineering construction. For example, it is applied to excavators, blowers, cranes, dump trucks, and forklifts.

1 is a view showing a conventional hydraulic cylinder 19 connected to a boom 11 of an excavator.

As shown, the adapter 13 is linked to the end of the boom stand 11, and the bucket 15 and the tongs 17 are attached to the adapter 13 together. The adapter 13 rotates in the direction of an arrow a or the opposite direction by the main hydraulic cylinder 16 basically installed on the boom stand 11.

The bucket 15 is mounted on the adapter 13 and operated by the operation of the main hydraulic cylinder 16 to perform excavation. In addition, the tongs 17 are attachments fastened for the tongs operation, and are connected to the link bracket 11a of the boom through the hydraulic actuator 19.

The tongs 17 rotate by the operation of the hydraulic actuator 19 and serve to support and support the heavy object to be transported toward the bucket 15 side. For example, by rotating in the direction of arrow b, wood or waste materials of a size that cannot be stored in the bucket 15 are supported by the bucket 15.

These tongs 17 are lowered and used only when in use, and when not in use, they are rotated in the direction of the arrow c so as to be as close as possible to the side of the boom stand 11.

By the way, the tongs 17 are obviously an attachment for heavy equipment, and since their weight is heavy, they often rotate downward due to their own weight. That is, even though the operator did not lower the tongs 17, it goes down by itself.

The phenomenon that the tongs naturally descend occurs because the piston rod 19b is pulled out from the cylinder tube 19a downward. That is, the piston rod 19b, which has been completely upwardly inserted into the cylinder tube 19a, is lowered by receiving the load of the tongs 17. In order to solve this problem, a check valve to block the reverse flow of hydraulic oil may be installed on the outside of the cylinder tube 19a, but there is a limitation in solving the above problem with only the check valve, but rather, another problem that heat is generated from the check valve. Occurs.

As a background technology related to a hydraulic cylinder, Korean Patent Publication No. 10-1151377 (hydraulic cylinder with a built-in check valve) has been disclosed. The disclosed hydraulic cylinder includes a cylindrical cylinder tube with an empty inside, a piston for maintaining hydraulic pressure by dividing a large chamber and a small chamber inside the cylinder tube, a cylinder rod for linearly reciprocating the piston in the cylinder tube, and a cylinder tube. A head cover and an end cover fixed to both ends to prevent leakage of hydraulic oil from the stroke end, a cushion ring and a cushion plunger respectively mounted on the outer surface and one end of the cylinder rod to absorb mechanical shock at the stroke end, Including a flow path formed in the head cover to communicate with the hydraulic oil port of the head cover, and a check valve installed to open and close the flow path, the flow path is closed at the stroke end to secure a cushioning function, and during initial movement after direction change at the stroke end In a hydraulic cylinder having a built-in check valve that secures a first thrust to pressurize the cushion ring and a second thrust to pressurize the piston by hydraulic oil supplied through a flow path that is opened during initial movement after direction change at the stroke end: , A seating portion extending at one end of the flow path to which a check valve is installed, a body coupled to the seating portion and forming a through hole communicating with the flow passage, a check ball opening and closing the through hole, and a pusher supporting the check ball under pressure And an elastic member for elastically biasing the through hole closed by a check ball by pressing the pusher in an initial state, and a plug screwed to the seating portion to support the elastic member.

Korean Patent Registration No. 10-1151377 (hydraulic cylinder with built-in check valve)

The present invention has been created to solve the above problem, and the piston rod completely inserted into the cylinder tube is not abnormally removed by the load applied from the outside, so that the operation reliability is good, and the piston suddenly collides with the end plug. In order to prevent it, the purpose of the purpose is to provide a hydraulic cylinder with a built-in locking device that secures the flexibility and stability of the cylinder operation by securing the amount of buffering inside the cylinder body and increasing the buffering force.

In order to achieve the above object, a hydraulic cylinder with a locking device according to the present invention includes: a cylinder tube having a predetermined diameter and extending straight in a longitudinal direction; An end cap coupled to one end of the cylinder tube and having a locking portion providing a support force; A reciprocating rod inserted into the cylinder tube so as to be slidably movable and extending outside the other end of the cylinder tube; And a locking end provided at an end of the reciprocating rod and fixedly supported by the locking unit by meeting the locking unit in a state in which the reciprocating rod is completely inserted into the cylinder tube,

The reciprocating rod and the locking end constitute a piston rod, and the end cap includes a center hole receiving and receiving the locking end, a chamber communicating with the center hole and providing a passage through which hydraulic oil passes, and the chamber is external And a connection port to which the hydraulic hose is connected, and the locking unit includes a pressing ball accommodated in each locking unit mounting hole and having a diameter larger than the diameter of the opening hole, and a ball for elastically pressing the pressing ball toward the locking groove. It has a pressing part, and in the locking part mounting hole, it is opened to the center hole through the opening hole, the inner diameter is expanded as the distance from the center hole increases, and an inclined passage for accommodating the pressure ball, and an end cap connected to the inclined passage A female screw hole opened in the radial direction of is formed, and the ball pressing unit is inserted into the inclined passage along with the pressing ball and elastically supports the pressing ball, and is screwed to the female threaded hole and supports the spring toward the pressing ball. The hydraulic oil provided with a support cap and pressurized through the hydraulic hose pushes the piston rod to the outside of the cylinder tube while being discharged to the center hole through the chamber, and the spring corresponds to the shape of the inclined passage. It is provided in a form in which the diameter gradually expands toward the support cap, and an entrance inclined portion is formed on the outer circumferential surface of the tip of the locking end to contact the pressing ball when the locking end is inserted into the center hole and to spread the pressing ball in a radial direction, and the locking end It is characterized in that a cushion bush that is provided in a form surrounding the outer circumferential surface from the outer circumferential surface of the front end of the entry slope to buffer the impact when inserted into the end cap of the locking end is provided so as to be slidable back and forth.

Here, the cushion bush is composed of a cylindrical body, a rounding portion is formed at a corner portion of the front end of the body, a tapered section is formed with a predetermined length on the rear side of the rounding portion, and the rear side of the tapered section has a predetermined length. It is preferable that a buffer section having a diameter smaller than that of the body is formed, and a rounded step portion is formed between the buffer section and the body.

In addition, a plurality of locking portions are disposed at an equal angle around the center hole, and a plurality of locking portion mounting holes opened to the center hole through the opening hole are formed symmetrically around the center hole, and the pressing ball is formed of the spring. It is preferable to maintain a state partially protruding toward the center hole through the open hole by the action.

In the hydraulic cylinder with the locking device of the present invention as described above, the piston rod completely inserted into the cylinder tube is tightly engaged and fixedly supported by the built-in locking device, so that it is supported by loads applied from the outside including its own weight. Since it does not fall out abnormally, the operation reliability is good, and in order to prevent the piston from suddenly colliding with the end plug, it is possible to secure the flexibility and stability of the cylinder operation by securing the buffer amount inside the cylinder body and increasing the buffering force.

In addition, since the locking device for supporting the piston rod is located inside the cylinder tube, the external structure is not complicated and maintenance is concise.

1 is a view for explaining the problem of a conventional hydraulic cylinder,
2 and 3 are partial cross-sectional views for explaining the internal structure and operation method of a hydraulic cylinder with a built-in locking device according to an embodiment of the present invention;
Figure 4 is a view showing a separate piston rod shown in Figure 2,
Figure 5 is a partial cross-sectional view of the end cap shown in Figure 2,
FIG. 6 is a view showing the end cap of FIG. 5 viewed from a different angle;
7 is a view showing another embodiment of FIG. 2;
FIG. 8 is a perspective view showing a state in which a cushion bush is provided on an outer circumferential surface of the front end of the locking end of FIG. 7 and an exploded state, respectively;
9 is a side view, a front view, and an enlarged view of an area “A” in which a part of the cushion bush according to the present invention is cut.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The hydraulic cylinder with a built-in locking device of the present invention has a configuration in which the piston rod completely inserted into the cylinder tube is not removed from the cylinder tube by force other than normal hydraulic pressure, and has a constant diameter and is a straight line in the longitudinal direction. An extended cylinder tube; An end cap coupled to one end of the cylinder tube and having a locking portion providing a support force; A reciprocating rod inserted into the cylinder tube so as to be slidably movable and extending outside the other end of the cylinder tube; It is provided at the end of the reciprocating rod, and has a basic configuration of a locking end fixedly supported by the locking portion by meeting the locking portion while the reciprocating rod is completely inserted into the cylinder tube.

2 and 3 are partial cross-sectional views for explaining the internal structure and operation method of the hydraulic cylinder 30 with a built-in locking device according to an embodiment of the present invention, and FIG. 4 is a separate piston rod shown in FIG. It is a drawing shown. In addition, FIG. 5 is a partial cross-sectional view of the end cap shown in FIG. 2, and FIG. 6 is a view showing the end cap of FIG. 5 viewed from a different angle.

FIG. 2 shows a state in which the piston rod 60 has been removed from the cylinder tube 40 to some extent, and FIG. 3 shows a state in which the piston rod 60 is completely inserted into the cylinder tube 40.

As shown, the hydraulic cylinder 30 with a built-in locking device according to the present embodiment, a cylinder tube 40, an end cap 45, a reciprocating rod 63, a locking end 65, a rod connecting portion 67 ).

The cylinder tube 40 provides an inner space 40a as a hollow pipe-shaped member having a predetermined diameter and extending linearly in the longitudinal direction. The inner space 40a is a space for accommodating the reciprocating rod 63 in a reciprocating manner. The size of the cylinder tube 40 may vary.

The end cap 45 is a member that is coupled to one end (right end in the drawing) of the cylinder tube 40 and incorporates a locking portion 45u. The locking part 45u accommodates and fixes a locking end 65, which will be described later, as shown in FIG. 3.

The locking part 45u together with the locking end 65 constitutes one locking device. In the locking device, in a state in which the reciprocating rod 63 is completely inserted into the cylinder tube 40 (the state of Fig. 3), the reciprocating rod 63 is moved to the cylinder tube 40 by a force other than hydraulic pressure. It is to prevent it from falling outside. Referring to FIG. 1 as a reference, it is to prevent the tongs 17 folded upward from being unfolded back to the bottom.

The end cap 45 is manufactured by cutting one metal block, and has an insertion fixing portion 45c inserted into the inside of one end of the cylinder tube 40. The insertion fixing part 45c is in close contact with the inner circumferential surface of the cylinder tube 40 while being inserted into the cylinder tube 40. The end cap 45 may be fixed to the cylinder tube 40 by a welding method in a state in which the insertion fixing part 45c is fitted to the cylinder tube 40.

Further, in the end cap 45, a center hole 45k, a chamber 45m, a connection port 45n, six locking part mounting ports 45g, and a pin hole 45b are formed.

The center hole 45k is a hole opened into the inner space 40a of the cylinder tube 40 and receives and accommodates the locking end 65 entering in the direction of the arrow m in FIG. 2. In addition, the chamber (45m) is a space provided behind the center hole, and is opened to the outside through the connection port (45n). The connection port 45n is a hole to which the hydraulic hose is connected.

The hydraulic oil pressurized through the hydraulic hose pushes the piston rod 60 to the outside of the cylinder tube 40 while being discharged to the center hole 45k via the chamber 45m. In addition, when the piston rod 60 moves in the direction of the arrow m due to the hydraulic oil being pressed into the opposite connection port 41, the hydraulic oil flowing in through the center hole 45k is passed and guided to the connection port 45n. The piston rod 60 is a combination of the reciprocating rod 63, the piston 61, and the locking end 65, which will be described later.

The pin hole 45b is a hole into which a link pin connecting the hydraulic cylinder 30 to the excavator is inserted.

The locking part mounting hole 45g is a hole for accommodating the locking part 45u, and as shown in Figs. 5 and 6, about 6 to 12 are equiangularly arranged around the center hole 45k. In addition, the locking part mounting hole (45g) is located in the insertion fixing portion (45c).

Inside each locking part mounting port 45g, an inclined passage 45e and a female screw port 45d are provided. The inclined passage 45e is a hole opened to the center hole 45k through the opening hole 45f, and accommodates the pressing ball 45t.

The inner diameter of the inclined passage 45e expands as it moves away from the center hole 45k. In addition, the inner diameter of the opening hole (45f) is smaller than the diameter of the pressing ball (45t). Therefore, as shown in Figure 5, the pressing ball (45t) is accommodated in the inclined passage (45e) and is caught in the open hole (45f) and a part of it protrudes into the center hole (45k).

The female screw hole 45d is a hole connected to the inclined passage 45e and opened in the radial direction of the end cap, and a female screw thread is formed on the inner circumferential surface. The support cap (45q) is screwed to the female screw hole (45d).

A locking part 45u is installed inside each locking part mounting hole 45g. The locking portion 45u includes a pressing ball 45t and a ball pressing portion. The ball pressing unit serves to elastically fit the pressing ball (45t) into the locking groove (65b) and has a spring (45s) and a support cap (45q).

The pressing ball 45t is a spherical member made of steel and, as shown in FIG. 3, presses the locking groove 65b in the direction of the arrow f. In addition, the spring (45s) is inserted into the inclined passage (45e) together with the pressure ball (45t) and elastically presses the pressure ball toward the engaging groove (65b).

At this time, the spring (45s) is preferably provided in the shape of a conical shape gradually expanding toward the support cap (45q) to correspond to the shape of the inclined passage (45e).

When the hydraulic oil pressurized through the hydraulic hose is discharged to the center hole (45k) via the chamber (45m), the lock is released and the piston rod (60) is pushed to the outside of the cylinder tube (40), with less hydraulic pressure. Also, the operation efficiency can be further improved by allowing smooth unlocking of the lock, and separation of the spring 45s and the pressure ball 45t can be prevented even when used for a long period of time, so that the durability of the device can be further strengthened.

The support cap (45q) is a component that is screwed to the female threaded hole (45d) to support the spring (45s) to the pressure ball (45t) side. Of course, it is possible to adjust the force by which the spring 45s presses the pressure ball 45t by adjusting the degree of coupling of the support cap 45q to the female screw hole 45d.

Meanwhile, as shown in FIGS. 3 and 4, the piston rod 60 includes a reciprocating rod 63, a locking end 65, a piston 61, and a rod connecting portion 67.

The reciprocating rod 63 is a round bar-shaped member having a constant diameter and extending straight in the longitudinal direction, accommodated in the cylinder tube 40, and reciprocates by the action of hydraulic pressure. It is a linear motion by hydraulic pressure pressed through the connection ports (41,45n).

The locking end 65 is provided at the right end of the drawing of the reciprocating rod 63, has a substantially cylindrical shape, and has an entrance inclined portion 65a and a locking groove 65b on the outer circumferential surface.

When the locking end 65 enters the center hole 45k, the entry slope 65a is an inclined surface that contacts the pressing ball 45t and spreads the pressing ball 45t in the radial direction. In addition, the engaging groove (65b) is a groove for accommodating and restraining the pressing ball (45t). The pressing ball (45t) elastically presses the locking groove (65b) by the action of the spring (45s) in a state inserted into the locking groove (65b). The pressing ball (45t) is to maintain a state that is fitted into the locking groove (65b) by the elastic force of the spring (45s). The spring 45s is compressed by the action of hydraulic pressure when hydraulic pressure is pressed through the connection port 45n, and causes the pressure ball 45t to retreat into the inclined passage 45e.

The entrance inclined portion 65a and the locking groove portion 65b take a shape extending in the circumferential direction of the locking end 65. In other words, it extends in the circumferential direction of the locking end 65 and has a shape where both ends meet after rotating one turn.

This locking end 65, in a state in which the reciprocating rod 63 is completely inserted into the cylinder tube 40, meets the locking portion 45u and is fixed to the locking portion, as shown in FIG. It does not come out from the end cap 45 by the force of.

Reference numeral 65d denotes a piston coupling part. The piston coupling portion 65d is a portion in which a male thread is formed on the outer circumferential surface, and is screwed with the coupling screw portion 61a of the piston 61. The piston 61 is in close contact with the inner circumferential surface of the cylinder tube 40 and prevents leakage of hydraulic oil. The rod connection 67 has a pin hole 67a and serves to connect the hydraulic cylinder 30 to the excavator.

In the end, the hydraulic cylinder 30 with the locking device according to the present embodiment configured as described above, the piston rod 60 in a state that is completely inserted into the cylinder tube 40, by a force other than the hydraulic pressure, the cylinder It has a structure that does not come out from the tube 40. In the case of replacing the hydraulic cylinder 19 shown in FIG. 1, the tongs 17 folded upwards do not fall to the bottom by their own weight.

On the other hand, as shown in Figures 7 and 8, the front end of the entrance inclined portion (65a) from the outer peripheral surface of the front end of the locking end (65) is provided in a form surrounding the outer peripheral surface of the locking end (65) to the end cap (45). It is preferable that the cushion bush 70 is provided so as to be slidable back and forth to buffer the impact upon insertion engagement.

Accordingly, when the piston rod 60 is completely inserted into the cylinder tube 40, the locking end 65 of the piston rod 60 is cushioned inside the cylinder body in order to prevent it from suddenly colliding with the end cap 45. Since the bush 70 is provided to be slidable back and forth, it is possible to secure the flexibility and stability of cylinder operation by securing the amount of buffering by the cushion bushing 70 and increasing the buffering force.

9, the cushion bush 70 is composed of a cylindrical body 71, a rounding portion 73 is formed at the edge portion of the front end of the body 71, the rounding portion 73 A tapered section 75 is formed on the rear side with a predetermined length, and a buffer section 77 having a diameter smaller than the body 71 is formed at a predetermined length on the rear side of the tapered section 75, and the buffer section 77 and the body It is preferable that the rounded step portion 79 is formed between (71).

Accordingly, the cushion bush 70 provided in a form surrounding the outer circumferential surface at the front end of the entry slope 65a from the outer circumferential surface of the distal end of the locking end 65 slides back and forth on the outer circumferential surface of the distal end of the locking end 65 and the locking end 65 It is possible to achieve a structure in which the impact is buffered when inserted into the end cap 45 of.

If this is described in more detail with dimensions, as shown in FIG. 9, the body 71 is formed of a cylindrical body having an inner diameter of ø27.2mm and an outer diameter of ø37mm and a length of 38mm. The outer diameter is formed from the rear side of the body 71 to the front side of 23 mm. In addition, a buffer section 77 and a tapered section 75 are formed on the outer periphery of the body 71 having a length of 15 mm except for 23 mm out of the total length of 38 mm. The buffer section 77 is formed with an outer diameter of ø36.9mm with a length of 10mm excluding 5mm from the length of 15mm, and the stepped part 79 is formed with a height difference of ø0.1mm between the body 71 and the buffer section 77. It is formed to generate a gap through which the fluid passes, and the remaining 5mm section is formed as a tapered section 75 tapered to 10°, and a rounding section 73 of R1 is formed at the edge of the tip of the tapered section 75. will be.

The cushion bush 70 of the hydraulic cylinder according to the present invention configured as described above has an initial buffering function by the tapered section 75 having the rounding part 73, and the fluid passing through the tapered section 75 is again After passing through the gap formed around the outer circumference of the body 71 and the buffer section 77 having a height difference of ø0.1 mm by the step portion 79, it passes along the outer surface of the body 71. At this time, the fluid passing through the tapered section 75 having the rounding part 73 resists the fluid while passing through the gap between the body 71 and the buffer section 77 having a length of 10 mm stepped by ø0.1 mm. By being able to secure a sufficient amount of buffering according to the decrease in speed, it is possible to further increase the buffering capacity.

In this way, the present invention provides precise processing of step-by-section steps in a tapered section having a rounding portion at the tip of the cylinder body and a buffer section slightly larger in diameter than the body in order to prevent the piston from suddenly colliding with the end plug. Thus, by reducing the buffering speed, not only can the buffering amount be sufficiently secured, but also the flexibility and stability of cylinder operation according to the increase of the buffering force can be improved.

Although the technical aspects have been described above and in the accompanying drawings, the technical idea of the present invention is for the purpose of explanation, and is not limited thereto, and those having ordinary technical knowledge in the technical field of the present invention It will be appreciated that the present invention can be variously modified and changed without departing from the technical scope of the claims to be described later.

11: Boom stand 11a: Link bracket 13: Adapter
15: bucket 16: main hydraulic cylinder 17: tongs
19: additional hydraulic cylinder 19a: cylinder tube 19b: piston rod
30: hydraulic cylinder 40: cylinder tube 40a: internal space
41: connection port 45: end cap 45b: pin hole
45c: Insertion fixing portion 45d: Female threaded port 45e: Inclined passage
45f: Open hole 45g: Locking part mounting port 45k: Center hole
45m: Chamber 45n: Connection port 45q: Support cap
45s: spring 45t: pressurized ball 45u: locking part
60: piston rod 61: piston 61a: coupling screw portion
63: reciprocating rod 65: locking end 65a: entrance slope
65b: engaging groove 65d: piston coupling portion 67: rod connection portion
67a: pin hole 70: cushion bush

Claims (3)

A cylinder tube 40 having a constant diameter and extending straight in the longitudinal direction;
An end cap (45) coupled to one end of the cylinder tube (40) and having a locking part (45u) providing a support force;
A reciprocating rod 63 inserted into the cylinder tube 40 so as to be slidably movable and extending outside the other end of the cylinder tube 40; And
A locking end 65 provided at an end of the reciprocating rod 63 and fixedly supported by the locking portion 45u by meeting the locking portion 45u while the reciprocating rod 63 is completely inserted into the cylinder tube 40; Including,
The reciprocating rod 63 and the locking end 65 constitute a piston rod 60,
The end cap 45 is a center hole 45k for receiving and receiving the locking end 65, a chamber 45m communicating with the center hole 45k and providing a passage for passing hydraulic oil, and the chamber ( 45m) to the outside and equipped with a connection port (45n) to which the hydraulic hose is connected,
The locking part (45u) is accommodated in each locking part mounting hole (45g) and has a diameter larger than the diameter of the opening hole (45f) a pressing ball (45t), and the pressing ball (45t) locking groove (65b) It has a ball pressing portion that elastically presses the side
In the locking part mounting hole (45g), it is opened to the center hole (45k) through the opening hole (45f), the inner diameter is expanded as the distance from the center hole (45k) and accommodates the pressing ball (45t) An inclined passage 45e and a female screw hole 45d connected to the inclined passage 45e and opened in the radial direction of the end cap 45 are formed,
The ball pressing unit is inserted into the inclined passageway (45e) together with the pressing ball (45t), a spring (45s) for elastically supporting the pressing ball (45t), and screwed to the female screw hole (45d), and a spring (45s) It is provided with a support cap (45q) to support the pressure ball (45t) side,
The hydraulic oil press-in through the hydraulic hose pushes the piston rod 60 to the outside of the cylinder tube 40 while being discharged to the center hole 45k via the chamber 45m,
The spring (45s) is provided in a shape that gradually expands in diameter toward the support cap (45q) to correspond to the shape of the inclined passage (45e),
On the outer circumferential surface of the front end of the locking end 65, when the locking end 65 is inserted into the center hole 45k, there is an entry slope 65a that contacts the pressing ball 45t and spreads the pressing ball 45t in the radial direction. Formed,
A cushion bush that is provided in a form surrounding the outer circumferential surface at the front end of the entry slope 65a on the outer circumferential surface of the front end of the locking end 65 to buffer the impact when inserted into the end cap 45 of the locking end 65 (70) A hydraulic cylinder with a built-in locking device, characterized in that provided to be slidable back and forth. The method of claim 1,
The cushion bush 70 is composed of a cylindrical body 71, a rounding portion 73 is formed at a corner portion of the front end of the body 71, and a tapered to a predetermined length at the rear side of the rounding portion 73. A section 75 is formed, and a buffer section 77 having a diameter smaller than the body 71 with a predetermined length is formed on the rear side of the tapered section 75, and A hydraulic cylinder with a locking device, characterized in that the rounded step portion 79 is formed therebetween. The method according to claim 1 or 2,
A plurality of the locking portions 45u are equiangularly arranged around the center hole 45k,
A plurality of locking part mounting holes 45g opened to the center hole 45k through the opening hole 45f are formed symmetrically around the center hole 45k,
The pressure ball (45t) is a hydraulic cylinder with a built-in locking device, characterized in that maintaining a state partially protruded toward the center hole (45k) through the opening hole (45f) by the action of the spring (45s).

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