CN110375139B

CN110375139B - Hydraulic pipeline joint

Info

Publication number: CN110375139B
Application number: CN201910657132.4A
Authority: CN
Inventors: 余果; 杨倩倩; 金结娥
Original assignee: Ningbo Xingming Hydraulic Equipment Co ltd
Current assignee: NINGBO XINGMING HYDRAULIC EQUIPMENT Co.,Ltd.
Priority date: 2019-07-19
Filing date: 2019-07-19
Publication date: 2021-08-17
Anticipated expiration: 2039-07-19
Also published as: CN110375139A

Abstract

The invention belongs to the technical field of hydraulic engineering, and particularly relates to a hydraulic pipeline joint which comprises a bent pipe; the two ends of the bent pipe are fixedly connected with oil pipes through nuts; the nut is in threaded connection with the bent pipe; a boss at the outer edge of the turning part of the bent pipe is internally provided with a sliding hole, the sliding hole is communicated with the bent pipe through a communication hole, and the diameter of the sliding hole is larger than that of the communication hole; a slip ring is connected in the slip hole in a sliding manner, and a buffer film is fixedly connected on the slip ring; a group of springs is fixedly connected between one side of the slip ring, which is far away from the communicating hole, and the bottom of the slip hole; the sliding ring is pushed to move through the communicating hole and the buffer membrane deforms, the buffer membrane deforms to absorb a part of impact energy, the sliding ring slides in the sliding hole and is matched with the spring to compress, so that the impact energy in the hydraulic oil way is further absorbed, the impact of the water hammer action in the hydraulic oil way on the valve body and the pipeline connecting piece is reduced, the service life of the valve body is prolonged, and the probability that the pipeline connecting piece is broken and falls off under the impact is reduced.

Description

Hydraulic pipeline joint

Technical Field

The invention belongs to the technical field of hydraulic engineering, and particularly relates to a hydraulic pipeline joint.

Background

When the hydraulic system is suddenly started, stopped, shifted or reversed, the valve port is suddenly closed or the action is suddenly stopped, and due to the action of flowing liquid and inertia of moving parts, high peak pressure is formed in the system instantaneously, and the phenomenon is called hydraulic shock. The occurrence of hydraulic shock can cause significant damage to the hydraulic system, with more serious consequences in high pressure, high speed and high flow systems. Efforts are therefore made to avoid the formation of hydraulic shocks during operation.

Hazard of hydraulic shock in hydraulic systems:

1. many components in hydraulic system such as pipeline, instrument can suffer destruction because of receiving too high hydraulic pressure impact force, and the peak pressure that hydraulic pressure impact produced generally speaking can be as high as 3 ~ 4 times normal operating pressure. If heavy, the pipeline is broken, the hydraulic components and the measuring instrument are damaged, and if light, the precision of the instrument is reduced.

2. The reliability and stability of the hydraulic system may also be affected by hydraulic shocks. For example, a pressure relay may send an error signal due to hydraulic shock, which may interfere with the proper operation of the hydraulic system.

3. When the hydraulic system is impacted by hydraulic pressure, the temperature of the hydraulic system can be raised, vibration and noise are generated, the connecting piece is loosened, oil is leaked, and the adjusting pressure (set value) of the pressure valve is changed.

The hydraulic actuating element easily causes pipeline blockage due to fatigue damage during operation, and can seriously damage a connecting pipeline, a hydraulic valve and a hydraulic pump when the pressure in the pipeline is too high, and a large amount of hydraulic oil can be leaked at the same time, so that huge cost can be caused when the environment is polluted.

Disclosure of Invention

The invention provides a hydraulic pipeline joint, which aims to make up for the defects of the prior art and solve the problems that a pipeline of a hydraulic system is broken due to hydraulic impact, a hydraulic element and a measuring instrument are damaged, a hydraulic actuating element is easy to block due to fatigue damage when in work, a connecting pipeline can be seriously damaged when the pressure in the pipeline is overlarge, a hydraulic valve and a hydraulic pump can leak a large amount of hydraulic oil, the environment is polluted, and the huge cost is caused.

The technical scheme adopted by the invention for solving the technical problems is as follows: the invention relates to a hydraulic pipeline joint, which comprises a bent pipe; the two ends of the bent pipe are fixedly connected with oil pipes through nuts; the nut is in threaded connection with the bent pipe; a boss at the outer edge of the turning part of the bent pipe is internally provided with a sliding hole, the sliding hole is communicated with the bent pipe through a communication hole, and the diameter of the sliding hole is larger than that of the communication hole; a sliding ring is connected in the sliding hole in a sliding manner, and a buffer film is fixedly connected on the sliding ring; a group of springs is fixedly connected between one side of the slip ring, which is far away from the communicating hole, and the bottom of the slip hole; when pressure impact is caused by the opening and closing of the communicating valve in the hydraulic oil path, local pressure is transmitted to the bent pipe, the communicating hole pushes the sliding ring to move and the buffer membrane to deform, the buffer membrane deforms to absorb a part of impact energy, the sliding ring is in sliding fit with the spring in the sliding hole to compress so as to further absorb the impact energy in the hydraulic oil path, the impact of a water hammer effect in the hydraulic oil path on the valve body and the pipeline connecting piece is reduced, the service life of the valve body is prolonged, and the probability that the pipeline connecting piece is broken and falls off due to impact is reduced.

Preferably, an overflow hole is formed in the bottom of the sliding hole, which is far away from the sliding ring, and the overflow hole is communicated with the first cavity in the boss; a second cavity is arranged below the first cavity, an opening is formed in the bottom of the second cavity, an elastic folding oil bag is arranged in the second cavity, and the folding oil bag is communicated with the overflow hole through the first cavity; when the working machine is damaged or an oil circuit is blocked due to other reasons, the pressure of hydraulic oil in the bent pipe or the oil pipe is too high, the hydraulic oil in the bent pipe breaks through the buffer membrane and then enters the folding oil bag through the first cavity, the folding oil bag is opened after oil is filled, waste after the high-pressure oil is sprayed out after the high-pressure oil breaks through the joint of the bent pipe and the nut is prevented, rush-repair reaction time is provided for a driver, and pipeline damage and hydraulic oil waste are reduced.

Preferably, the buffer film is made of elastic rubber, and the thickness of the buffer film is gradually increased from the middle part to the outer edge; a group of steel rings with sequentially increased diameters for increasing the strength of the buffer film are arranged at the positions far away from the center in the buffer film; the strength of the buffer film close to the outer edge can be increased through the steel ring arranged in the buffer film, the service life of the buffer film is further prolonged, and the absorption capacity of pipeline hydraulic oil pressure impact is further increased; meanwhile, the thickness of the buffer membrane is gradually increased from the middle part to the outer edge, so that the buffer membrane is preferentially deformed and broken from the middle part to form an oil drainage channel when the hydraulic pipeline is blocked, and the whole buffer membrane is prevented from being flushed away from the blocked overflow hole and the folded oil bag.

Preferably, an impeller is rotatably connected to a position, close to the overflow hole, in the first cavity, and hydraulic oil sprayed from the overflow hole can drive the impeller to rotate; a boss above the impeller is provided with a movable hole; a swing rod is hinged to a rotating pin fixedly connected to the position, close to the outer edge, of the impeller, the swing rod penetrates through the movable hole and extends out of the boss, and the middle of the swing rod is hinged to a rotating shaft in the movable hole; one end of the swing rod, which is positioned outside the boss, is connected with a small ball; the position of the boss corresponding to the small ball is fixedly connected with an alarm clock through a bracket; the part of the swing rod positioned in the movable hole is sleeved with an elastic sealing sleeve; when the pipeline is blocked, hydraulic oil breaks through the buffer film and then is sprayed out from the overflow hole to push the impeller to rotate, and then the swing rod is driven by the rotating pin to swing, the swing rod drives the small ball to strike the alarm clock, so that an alarm sound is given out, a driver is reminded that the pipeline breaks down, the machine is stopped for maintenance in time, hydraulic oil is reduced from spilling or a hydraulic element is damaged more, and economic loss is further reduced.

Preferably, a rotating shaft of the impeller is wound with a steel rope, the other end of the steel rope is fixedly connected to the bottom of the folding oil bag, and the steel rope is used for accelerating the rotating speed of the impeller; when hydraulic oil is filled into the folding oil bag after breaking the buffer film, the folding oil bag is filled with oil and expands, the expanded folding oil bag pulls the steel rope, and then the impeller is accelerated to rotate, so that the frequency of hitting the alarm clock by a small ball is increased, a driver is more quickly reminded to stop, inspect and maintain, the damage aggravation of a hydraulic element is avoided, and the maintenance cost is increased.

Preferably, a piston rod is connected in the piston cylinder in the boss above the sliding hole in a sliding manner, and the piston rod is pushed to move when the sliding ring slides; the piston cylinder rodless cavity is filled with fastening rubber and is communicated with the threaded connection part of the bent pipe and the nut through a pipeline; when the water hammer effect of hydraulic oil in the elbow is large, the joint of the elbow and the oil pipe is subjected to large impact force, the hydraulic oil pushes the sliding ring and the buffer membrane to perform reciprocating sliding with a large stroke so as to absorb the impact force, the sliding ring pushes the piston rod to move when moving, and then a fastening agent in a rodless cavity of the piston cylinder enters a thread gap between the nut and the elbow after being extruded through a pipeline, so that the connection strength of the nut and the elbow is increased, and the phenomenon that the elbow is loosened due to pressure impact of an oil way to influence the normal work of a hydraulic element is further reduced.

The invention has the following beneficial effects:

1. according to the hydraulic pipeline joint, the communicating hole pushes the sliding ring to move and the buffer film to deform, the buffer film deforms to absorb a part of impact energy, the sliding ring slides in the sliding hole and is matched with the spring to compress, so that the impact of a water hammer in a hydraulic oil circuit on the valve body and the pipeline connecting piece is further absorbed, the service life of the valve body is prolonged, and the probability that the pipeline connecting piece is broken and falls off under the impact is reduced.

2. According to the hydraulic pipeline joint, when an oil way is blocked, high-pressure hydraulic oil in a pipeline breaks through the buffer film and then enters the folding oil bag through the first cavity, the folding oil bag is opened after being filled with oil, waste after the high-pressure oil breaks through the joint of the elbow and the nut and is sprayed out is prevented, rush repair reaction time is provided for a driver, and pipeline damage and hydraulic oil waste are reduced.

Drawings

The invention will be further explained with reference to the drawings.

FIG. 1 is a perspective view of the present invention;

FIG. 2 is a front view of the present invention;

FIG. 3 is a cross-sectional view of the present invention;

FIG. 4 is an enlarged view of a portion of FIG. 3 at A;

in the figure: the device comprises a bent pipe 1, a nut 11, an oil pipe 12, a boss 13, a sliding hole 2, a communication hole 21, a sliding ring 22, a buffer film 23, a spring 24, an overflow hole 3, a first cavity 31, a second cavity 32, a folding oil bag 33, a steel ring 25, an impeller 34, a movable hole 35, a swing rod 36, a small ball 37, a warning clock 38, a sealing sleeve 39, a steel rope 310, a piston cylinder 4, a piston rod 41 and a pipeline 42.

Detailed Description

In order to make the technical means, the creation characteristics, the achievement purposes and the effects of the invention easy to understand, the invention is further described with the specific embodiments.

As shown in fig. 1 to 4, a hydraulic line joint according to the present invention includes an elbow 1; two ends of the bent pipe 1 are fixedly connected with an oil pipe 12 through nuts 11; the nut 11 is in threaded connection with the elbow 1; a boss 13 at the outer edge of the turning part of the elbow 1 is internally provided with a sliding hole 2, the sliding hole 2 is communicated with the elbow 1 through a communication hole 21, and the diameter of the sliding hole 2 is larger than that of the communication hole 21; a slip ring 22 is connected in the slip hole 2 in a sliding manner, and a buffer film 23 is fixedly connected to the slip ring 22; a group of springs 24 are fixedly connected between one side of the slip ring 22 far away from the communication hole 21 and the bottom of the slip hole 2; when pressure impact is caused by the opening and closing of the communicating valve in the hydraulic oil path, local pressure is transmitted to the elbow 1, the communicating hole 21 pushes the sliding ring 22 to move and the buffer film 23 to deform, the buffer film 23 deforms to absorb a part of impact energy, the sliding ring 22 is in sliding fit with the spring 24 in the sliding hole 2 to compress to further absorb the impact energy in the hydraulic oil path, the impact of a water hammer action in the hydraulic oil path on the valve body and a pipeline 42 connecting piece is reduced, the service life of the valve body is prolonged, and the probability that the pipeline 42 connecting piece is broken and falls off due to impact is reduced.

As an embodiment of the invention, an overflow hole 3 is formed in the bottom of the slide hole 2 far away from the slide ring 22, and the overflow hole 3 is communicated with a first cavity 31 in the boss 13; a second cavity 32 is arranged below the first cavity 31, an opening is formed in the bottom of the second cavity 32, an elastic folding oil bag 33 is arranged in the second cavity 32, and the folding oil bag 33 is communicated with the overflow hole 3 through the first cavity 31; when the working machine is damaged or an oil circuit is blocked due to other reasons, the pressure of hydraulic oil in the elbow 1 or the oil pipe 12 is too high, the hydraulic oil in the elbow 1 breaks through the buffer film 23 and then enters the folding oil bag 33 through the first cavity 31, the folding oil bag 33 is opened after oil is filled, waste after the high-pressure oil is sprayed out after the high-pressure oil breaks through the joint of the elbow 1 and the nut 11 is prevented, rush-repair reaction time is provided for a driver, and pipeline damage and hydraulic oil waste are reduced.

As an embodiment of the present invention, the buffer film 23 is made of elastic rubber, and the thickness of the buffer film 23 gradually increases from the middle portion to the outer edge; a group of steel rings 25 with sequentially increased diameters for increasing the strength of the buffer film 23 are arranged in the buffer film 23 at positions far away from the center; the strength of the buffer film 23 close to the outer edge can be increased through the steel ring 25 arranged in the buffer film 23, the service life of the buffer film 23 is further prolonged, and the absorption capacity of pipeline hydraulic oil pressure impact is further increased; meanwhile, the thickness of the buffer film 23 is gradually increased from the middle part to the outer edge, so that the buffer film 23 is preferentially deformed and broken from the middle part to form an oil drainage channel when the hydraulic pipeline is blocked, and the whole buffer film 23 is prevented from being flushed away from the blocked overflow hole 3 and the folded oil bag 33.

As an embodiment of the invention, an impeller 34 is rotatably connected to a position, close to the overflow hole 3, in the first cavity 31, and hydraulic oil ejected from the overflow hole 3 can drive the impeller 34 to rotate; a movable hole 35 is formed in the boss 13 above the impeller 34; a swing rod 36 is hinged to a rotating pin fixedly connected to the position, close to the outer edge, of the impeller 34, the swing rod 36 penetrates through the movable hole 35 and extends out of the boss 13, and the middle of the swing rod 36 is hinged to a rotating shaft in the movable hole 35; one end of the swing rod 36 positioned outside the boss 13 is connected with a small ball 37; the position on the boss 13 corresponding to the small ball 37 is fixedly connected with an alarm clock 38 through a bracket; the part of the swing rod 36 positioned in the movable hole 35 is sleeved with an elastic sealing sleeve 39; when the pipeline is blocked, hydraulic oil breaks through the buffer film 23 and then is sprayed out from the overflow hole 3 to push the impeller 34 to rotate, the swing rod 36 is driven by the rotating pin to swing, the swing rod 36 drives the small ball 37 to knock the alarm clock 38 to give an alarm sound, a driver is reminded that the pipeline has a fault, the machine is stopped for maintenance in time, hydraulic oil is prevented from being spilled or hydraulic elements are damaged more, and economic loss is further reduced.

As an embodiment of the present invention, a steel cable 310 is wound around a rotating shaft of the impeller 34, the other end of the steel cable 310 is fixedly connected to the bottom of the folded oil pocket 33, and the steel cable 310 is used for increasing the rotating speed of the impeller 34; when the hydraulic oil is filled into the folding oil bag 33 after breaking the buffer film 23, the folding oil bag 33 is filled with the oil and expands, the expanded folding oil bag 33 pulls the steel rope 310, and further the impeller 34 is accelerated to rotate, so that the frequency of hitting the alarm clock 38 by the small ball 37 is increased, a driver is reminded to stop, inspect and maintain more quickly, the damage aggravation of hydraulic elements is avoided, and the maintenance cost is increased.

As an embodiment of the present invention, a piston rod 41 is slidably connected in the piston cylinder 4 in the boss 13 above the sliding hole 2, and the sliding ring 22 pushes the piston rod 41 to move when sliding; the rodless cavity of the piston cylinder 4 is filled with fastening rubber, and the rodless cavity of the piston cylinder 4 is communicated with the threaded connection part of the elbow 1 and the nut 11 through a pipeline 42; when the water hammer effect of hydraulic oil in the elbow 1 is large, the joint of the elbow 1 and the oil pipe 12 is subjected to large impact force, at the moment, the hydraulic oil pushes the sliding ring 22 and the buffer membrane 23 to perform reciprocating sliding with a large stroke so as to absorb the impact force, the sliding ring 22 pushes the piston rod 41 to move when moving, then a fastening agent in a rodless cavity of the piston cylinder 4 enters a thread gap between the nut 11 and the elbow 1 after being extruded through the pipeline 42, the connection strength between the nut 11 and the elbow 1 is increased, and the phenomenon that the elbow 1 is loosened due to pressure impact of an oil way to influence the normal work of a hydraulic element is further reduced.

When the hydraulic oil way works, when pressure impact is caused by the opening and closing of the communicating valve in the hydraulic oil way, local pressure is transmitted to the bent pipe 1, the communicating hole 21 pushes the sliding ring 22 to move and the buffer membrane 23 to deform, the buffer membrane 23 deforms to absorb a part of impact energy, the sliding ring 22 slides in the sliding hole 2 and is matched with the spring 24 to compress so as to further absorb the impact energy in the hydraulic oil way, the impact of the water hammer action in the hydraulic oil way on the valve body and the connecting piece of the pipeline 42 is reduced, the service life of the valve body is prolonged, and the probability that the connecting piece of the pipeline 42 is broken and falls off under the impact is reduced; when the working machine is damaged or an oil circuit is blocked due to other reasons, the pressure of hydraulic oil in the elbow 1 or the oil pipe 12 is too high, the hydraulic oil in the elbow 1 breaks through the buffer film 23 and then enters the folded oil bag 33 through the first cavity 31, and the folded oil bag 33 is opened after oil is filled, so that waste after the high-pressure oil is ejected after the high-pressure oil breaks through the joint of the elbow 1 and the nut 11 is prevented, rush-repair reaction time is provided for a driver, and pipeline damage and hydraulic oil waste are reduced; the strength of the buffer film 23 close to the outer edge can be increased through the steel ring 25 arranged in the buffer film 23, the service life of the buffer film 23 is further prolonged, and the absorption capacity of pipeline hydraulic oil pressure impact is further increased; meanwhile, the thickness of the buffer film 23 is gradually increased from the middle part to the outer edge, so that the buffer film 23 is preferentially deformed and broken from the middle part to form an oil drainage channel when the hydraulic pipeline is blocked, and the whole buffer film 23 is prevented from being washed away from the blocked overflow hole 3 and the folded oil bag 33; when the pipeline is blocked, hydraulic oil breaks through the buffer film 23 and then is sprayed out from the overflow hole 3 to push the impeller 34 to rotate, and then the swing rod 36 is driven by the rotating pin to swing, the swing rod 36 drives the small ball 37 to strike the alarm clock 38 to give out an alarm sound, so that a driver is reminded of the fault of the pipeline and the shutdown maintenance is carried out in time, hydraulic oil is reduced from being scattered or hydraulic elements are damaged more, and the economic loss is further reduced; when the hydraulic oil is filled into the folding oil bag 33 after breaking the buffer film 23, the folding oil bag 33 is filled with the oil and expands, the expanded folding oil bag 33 pulls the steel rope 310, and further the impeller 34 is accelerated to rotate, so that the frequency of hitting the alarm clock 38 by the small ball 37 is increased, a driver is reminded to stop, inspect and maintain more quickly, the damage of hydraulic elements is avoided being aggravated, and the maintenance cost is increased; when the water hammer effect of hydraulic oil in the elbow 1 is large, the joint of the elbow 1 and the oil pipe 12 is subjected to large impact force, at the moment, the hydraulic oil pushes the sliding ring 22 and the buffer membrane 23 to perform reciprocating sliding with a large stroke so as to absorb the impact force, the sliding ring 22 pushes the piston rod 41 to move when moving, then a fastening agent in a rodless cavity of the piston cylinder 4 enters a thread gap between the nut 11 and the elbow 1 after being extruded through the pipeline 42, the connection strength between the nut 11 and the elbow 1 is increased, and the phenomenon that the elbow 1 is loosened due to pressure impact of an oil way to influence the normal work of a hydraulic element is further reduced.

The front, the back, the left, the right, the upper and the lower are all based on figure 1 in the attached drawings of the specification, according to the standard of the observation angle of a person, the side of the device facing an observer is defined as the front, the left side of the observer is defined as the left, and the like.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate orientations or positional relationships based on those shown in the drawings, and are used merely for convenience in describing the present invention and for simplifying the description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the scope of the present invention.

The foregoing illustrates and describes the principles, general features, and advantages of the present invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims

1. A hydraulic line coupling, characterized by: comprises a bent pipe (1); two ends of the bent pipe (1) are fixedly connected with an oil pipe (12) through nuts (11); the nut (11) is in threaded connection with the elbow (1); a boss (13) at the outer edge of the turning part of the bent pipe (1) is internally provided with a sliding hole (2), the sliding hole (2) is communicated with the bent pipe (1) through a communication hole (21), and the diameter of the sliding hole (2) is larger than that of the communication hole (21); a slip ring (22) is connected in the slip hole (2) in a sliding manner, and a buffer film (23) is fixedly connected to the slip ring (22); a group of springs (24) are fixedly connected between one side of the slip ring (22) far away from the communicating hole (21) and the bottom of the slip hole (2);

an overflow hole (3) is formed in the bottom of the sliding hole (2) far away from the sliding ring (22), and the overflow hole (3) is communicated with a first cavity (31) in the boss (13); a second cavity (32) is arranged below the first cavity (31), an opening is formed in the bottom of the second cavity (32), an elastic folding oil bag (33) is arranged in the second cavity (32), and the folding oil bag (33) is communicated with the overflow hole (3) through the first cavity (31);

an impeller (34) is rotatably connected to a position, close to the overflow hole (3), in the first cavity (31), and hydraulic oil sprayed from the overflow hole (3) can drive the impeller (34) to rotate; a movable hole (35) is formed in the boss (13) above the impeller (34); a swing rod (36) is hinged to a rotating pin fixedly connected to the position, close to the outer edge, of the impeller (34), the swing rod (36) penetrates through the movable hole (35) and extends out of the boss (13), and the middle of the swing rod (36) is hinged to a rotating shaft in the movable hole (35); one end of the swing rod (36) positioned outside the boss (13) is connected with a small ball (37); the position, corresponding to the small ball (37), on the boss (13) is fixedly connected with an alarm clock (38) through a support; the part of the swing rod (36) positioned in the movable hole (35) is sleeved with an elastic sealing sleeve (39).

2. A hydraulic line coupling as claimed in claim 1, wherein: the buffer film (23) is made of elastic rubber, and the thickness of the buffer film (23) is gradually increased from the middle part to the outer edge; and a group of steel rings (25) with the diameters sequentially increased and used for increasing the strength of the buffer film (23) are arranged in the buffer film (23) at positions far away from the center.

3. A hydraulic line coupling as claimed in claim 1, wherein: a steel rope (310) is wound on a rotating shaft of the impeller (34), the other end of the steel rope (310) is fixedly connected to the bottom of the folding oil bag (33), and the steel rope (310) is used for accelerating the rotating speed of the impeller (34).

4. A hydraulic line coupling as claimed in claim 1, wherein: a piston rod (41) is connected in a piston cylinder (4) in a boss (13) above the sliding hole (2) in a sliding mode, and the piston rod (41) is pushed to move when the sliding ring (22) slides; and a rodless cavity of the piston cylinder (4) is filled with fastening rubber, and the rodless cavity of the piston cylinder (4) is communicated with the threaded connection part of the elbow pipe (1) and the nut (11) through a pipeline (42).