Countable Hydraulic Bolt Tensioner and Its Assembly Method

Abstract

The present invention relates to the field of hydraulic technology, and in particular provides a countable hydraulic bolt stretcher and an assembly method thereof. A countable hydraulic bolt stretcher includes a housing assembly, a piston assembly, an oil circuit assembly, and a sleeve pulling assembly. By cooperating the piston assembly with the oil circuit assembly, the present invention enables the sleeve pulling assembly to smoothly stretch the bolt through an external high-pressure oil pump, while counting and recording at the same time, reducing manual operation, making the hydraulic stretching process more convenient, and avoiding the situation of counting when the stretcher is idling, accurately evaluating the performance state of the stretcher. At the same time, through the close cooperation of the housing assembly and the piston assembly, the stretching process is safer, the vertical force is more concentrated, avoiding insufficient bolt stretching or distortion caused by force dispersion, with simple operation and strong practicability.

Description

Technical Field

[0001] The invention relates to the field of hydraulic technology, and in particular to a countable hydraulic bolt tensioner and an assembling method thereof. Background Art

[0002] The hydraulic tensioner is a hydraulic source provided by a hydraulic booster pump. The tensile force is determined according to the tensile strength, yield coefficient and elongation of the material. The tensile force generated by the ultra-high pressure oil pump is used to stretch the bolt to which the force is applied in its elastic deformation zone, causing the bolt diameter to deform slightly, making it easy to loosen or tighten the nut. There is no torsional shear force and no friction damage to the contact surface of the connection. It is widely used in petrochemical, nuclear power, wind power, hydropower, thermal power, shipbuilding, railways, aerospace, mining, heavy machinery and other fields.

[0003] At present, the service life of hydraulic tensioners in the industry is generally 8,000 times. When in use, it is necessary to monitor its performance by counting to avoid safety accidents during operation. Most of the existing hydraulic tensioners are counted and recorded by manual counting during operation, which is very inefficient. Although a few hydraulic tensioners are equipped with life counters, they will also count in the case of human misoperation and when the tensioner is unloaded, which will shorten the service life of the hydraulic tensioner and make it impossible to accurately evaluate the performance status of the tensioner. When the tensioner is unloaded, it is easy for a single piston to run too fast, resulting in direct impact on the hydraulic tensioner, causing damage to the equipment, and even threatening the life of the operator. At the same time, the pulling of a single piston is also prone to produce lateral stress / unidirectional impact force, causing the bolt to twist and deform, affecting the subsequent loosening or tightening of the nut. Summary of the invention

[0004] Based on this, it is necessary to provide a countable hydraulic bolt tensioner and an assembly method thereof to solve at least one technical problem in the background technology.

[0005] A countable hydraulic bolt tensioner includes: a shell assembly, a piston assembly, an oil circuit assembly and a sleeve pulling assembly. The shell assembly includes a support cylinder and a dual oil circuit connecting cylinder. The interior of the support cylinder is hollow to form a hollow cavity. The bottom of the dual oil circuit connecting cylinder is fixedly installed on the top of the support cylinder. The interior of the dual oil circuit connecting cylinder is hollow to form a piston mounting cavity, and the piston mounting cavity is connected to the hollow cavity. The side wall of the dual oil circuit connecting cylinder is penetrated by a plurality of oil circuit holes, and the plurality of oil circuit holes are connected to the piston mounting cavity. The piston assembly is slidably installed in the piston mounting cavity. The oil circuit assembly is fixedly installed on a side wall of the dual oil circuit connecting cylinder. The upper portion of the sleeve pulling assembly is fixedly installed in the piston assembly, and the lower portion of the sleeve pulling assembly is penetrated into the hollow cavity.

[0006] As a further improvement of the present invention, a working groove is formed through the side wall of the support cylinder, and the working groove communicates with the hollow cavity. An annular mounting seat protrudes from the inner side of the top of the support cylinder; the double-oil-way connection cylinder includes a connection cylinder body and a disc spring pressing cover. An annular connection protrusion protrudes from the top of the connection cylinder body. The bottom of the disc spring pressing cover is hollow and is threadedly connected to the connection protrusion. A central hole is formed through the center of the top surface of the disc spring pressing cover. The piston installation cavity is formed in the connection cylinder body. The piston installation cavity includes an installation cavity, a first sliding cavity, a first connection cavity, a second sliding cavity, and a second connection cavity that are sequentially communicated from bottom to top. The second connection cavity communicates with the upper piston installation cavity. The inner diameter of the installation cavity is equal to the outer diameter of the mounting seat. The double-oil-way connection cylinder is sleeved and installed on the mounting seat through the installation cavity and is fixedly installed on the support cylinder by bolts. The first sliding cavity is located above the mounting seat. The inner diameter of the first sliding cavity is equal to the inner diameter of the second sliding cavity. Annular flow blocking grooves are recessed in the middle of the inner walls of the first sliding cavity and the second sliding cavity. The inner diameter of the first connection cavity is equal to the inner diameter of the second connection cavity, and the inner diameter of the first connection cavity is larger than the inner diameter of the first sliding cavity. The central hole communicates with the second connection cavity. L-shaped oil-way holes are formed in the side walls of the first connection cavity and the second connection cavity. The two oil-way holes communicate with the oil-way assembly.

[0007] As a further improvement of the present invention, the piston assembly includes a lower piston element, an upper piston element, and a buffer element. The lower piston element is slidably installed in the first sliding cavity and the first connection cavity. The upper piston element is slidably installed in the first connection cavity, the second sliding cavity, and the second connection cavity. The buffer element is fixedly installed in the second connection cavity.

[0008] As a further improvement of the present invention, the lower piston element includes a lower piston body and a lower piston platform. The lower piston body is slidably installed in the first sliding cavity and the first connection cavity. The lower piston platform protrudes from the outer peripheral wall of the top of the lower piston body, and the bottom surface of the lower piston platform abuts against the bottom surface of the first connection cavity. A lower piston hole is formed through the lower piston body. An annular lower flow-through groove is recessed at the bottom of the outer peripheral surface of the lower piston platform. An annular lower bypass groove is recessed along the radial direction of the lower piston body at the top of the bottom wall of the lower flow-through groove. Both the lower flow-through groove and the lower bypass groove communicate with the oil-way hole of the first connection cavity. The bottom wall of the lower bypass groove and the side wall of the first connection cavity jointly form an annular lower flow-through space. A lower conductive sheet is arranged on one side of the top surface of the lower piston platform. The lower conductive sheet is electrically connected to the oil-way assembly.

[0009] As a further improvement of the present invention, the upper piston element includes a spring, an upper piston body, and an upper piston platform that are connected in sequence from bottom to top. The bottom surface of the spring abuts against the top surface of the lower piston platform. The top surface of the spring is fixedly connected to the bottom surface of the upper piston body. The spring is located in the first connection cavity. The upper piston body is axially slidably installed in the second sliding cavity. The upper piston platform is slidably installed in the second connection cavity. The bottom surface of the upper piston platform abuts against the bottom surface of the second connection cavity. One side of the outer peripheral surface of the upper piston body protrudes outward to form an upper conductive sheet. The upper conductive sheet is electrically connected to the oil circuit assembly. The upper conductive sheet and the lower conductive sheet are arranged opposite to each other up and down. The diameter of the upper piston platform is greater than the diameter of the upper piston body, and the inner diameter of the upper piston platform is equal to that of the second connection cavity. An annular upper flow channel is recessed at the bottom of the outer peripheral wall of the upper piston platform. An annular upper bypass channel is recessed along the radial direction of the upper piston body at the top of the bottom wall of the upper flow channel. The upper flow channel and the upper bypass channel communicate with the oil circuit holes of the second connection cavity. The bottom wall of the upper flow channel and the side wall of the second connection cavity jointly form an annular upper flow space. An upper piston hole is penetrated through the top surface of the upper piston platform. An annular positioning groove is recessed at the top of the inner wall of the upper piston hole. An annular inclined surface is recessed between the positioning groove and the upper piston hole.

[0010] As a further improvement of the present invention, the buffer element includes a disc spring and a support conductive member. The bottom surface of the disc spring is fixedly installed on the top surface of the upper piston platform. The top surface of the disc spring is fixedly installed on the top surface of the inner wall of the disc spring cover. The support conductive member includes an upper support portion and a lower support portion. The top surface of the upper support portion is fixedly installed on one side of the top surface of the inner wall of the disc spring cover. The bottom surface of the lower support conductive portion is fixedly installed on the top surface of the upper piston platform. The upper support portion includes an upper conductive platform and conductive columns protruding from both sides of the upper conductive platform. Resistance sheets are arranged inside both conductive columns. The lower support conductive portion includes a mounting platform, a lower conductive platform, and two conductive plates. The bottom of the mounting platform is fixedly installed on one side of the top surface of the upper piston platform adjacent to the oil circuit assembly. The bottom surface of the lower conductive platform is fixedly installed in the middle of the top of the mounting platform. The two conductive plates are respectively rotatably installed on the top of the side walls on both sides of the lower conductive platform through torsion springs. The upper support portion and the lower support portion are in corresponding positions.

[0011] As a further improvement of the present invention, the oil circuit assembly includes an oil circuit element and a pressure relief display element. One side wall of the oil circuit element is fixedly installed on the side wall of the double oil circuit connection cylinder. The bottom of the pressure relief display element is fixedly installed on the top of the oil circuit element. The oil circuit element includes a lower oil pipeline, an upper oil pipeline, a connecting oil pipeline, and a connecting oil valve. The lower oil pipeline and the upper oil pipeline are parallel to each other. One end of each of them is connected and communicated with the oil circuit hole of the first connection cavity and the oil circuit hole of the second connection cavity respectively. The other end of each of them is connected and communicated with the upper and lower ends of the connecting oil pipeline respectively. A connecting through hole is penetrated through the side wall of the connecting oil pipeline away from the double oil circuit connection cylinder. One end of the connecting oil valve is fixedly installed in the connecting through hole, and the other end is connected to an external high-pressure oil pump. A pressure relief hole is penetrated through the top of the connecting oil pipeline. The pressure relief display element is connected and communicated with the pressure relief hole.

[0012] As a further improvement of the present invention, the pressure relief display element includes a pressure relief body and a control display member. The control display member is fixedly installed on the side wall of the pressure relief body away from the double oil circuit connection cylinder. The bottom of the pressure relief body is hollow to form a pressure relief cavity. A pressure relief valve is installed at the bottom of the inner wall of the pressure relief cavity. The pressure relief cavity is communicated with the pressure relief hole through the pressure relief valve. An explosion-proof valve hole is formed through the top of the pressure relief cavity, and an explosion-proof valve is arranged in the explosion-proof valve hole. The control display member includes a display, a control unit, and a storage battery connected in sequence from top to bottom. The side wall of the storage battery is fixedly connected to the side wall of the pressure relief body. The top of the storage battery is fixedly connected to the bottom of the control unit, and the storage battery is electrically connected to the control unit and the display. The control unit is electrically connected to the display, the support conductive member, the upper conductive sheet, and the lower conductive sheet.

[0013] As a further improvement of the present invention, the sleeved pulling assembly includes a threaded sleeve, a fastening nut, and a positioning nut. The threaded sleeve passes through the upper piston hole and the lower piston hole and is installed in the hollow cavity and the piston installation cavity. The fastening nut is rotatably installed in the hollow cavity of the support cylinder. The positioning nut is slidably installed in the upper piston element. A threaded hole is formed at the bottom of the threaded sleeve. A rotating shaft protrudes from the center of the top surface of the threaded sleeve, and the rotating shaft is fitted through the center hole. A knob hole is formed at the top of the rotating shaft. External threads are formed on the outer peripheral surface of the top of the threaded sleeve, and the external threads are in threaded cooperation with the positioning nut. A fastening groove is recessed at the top of the outer peripheral surface of the fastening nut, and the fastening groove is connected and communicated with the working groove in the support cylinder. A nut groove is recessed at the bottom of the inner wall of the fastening nut. A snap ring protrudes outward from the top of the outer peripheral surface of the positioning nut, and an inclined transition sliding surface protrudes between the snap ring and the bottom surface of the positioning nut, and the transition sliding surface abuts against the inclined surface.

[0014] The present invention provides an assembly method for a countable hydraulic bolt stretcher, and the assembly method includes the following steps:

[0015] Step S: Threadedly connect the threaded sleeve to the bolt to be stretched through the threaded hole, and pass the support cylinder through the threaded sleeve so that the bottom surface of the support cylinder abuts against the working surface of the bolt to be stretched;

[0016] Step S: Install the piston assembly in the double oil circuit connection cylinder, and pass the double oil circuit connection cylinder through the threaded sleeve so that the positioning nut is in threaded cooperation with the external threads of the threaded sleeve. At the same time, the double oil circuit connection cylinder is sleeved and installed on the mounting seat through the installation cavity, and the rotating shaft is fitted through the center hole;

[0017] Step S: Fix the side wall of the oil circuit assembly to the side wall of the double oil circuit connection cylinder, and connect and communicate one end of the lower oil pipeline and the upper oil pipeline with the oil circuit holes of the first connection cavity and the second connection cavity.

[0018] The beneficial effects of the present invention are as follows:

[0019] 1. If the threaded hole of the threaded sleeve is not connected to the thread of the bolt to be stretched due to human error during operation, when the stretcher runs without load, the spring, the upper piston body, and the upper piston platform will move upward synchronously under the hydraulic push of the external high-pressure oil pump. The lower flow space and the upper flow space will expand upward synchronously, causing the disc spring to compress until the two conductive plates of the lower support conductive part contact the conductive column of the upper support part, sending an electrical signal to the control unit. The control unit controls the closing of the connecting oil valve and pauses the hydraulic push. At the same time, since the spring, the upper piston body, and the upper piston platform move upward synchronously, the upper conductive sheet and the lower conductive sheet do not contact, and the control unit does not count this operation. The total number of uses displayed on the monitor does not change, preventing the stretcher from being counted when running without load, which may shorten the service life of the hydraulic stretcher and make it impossible to accurately evaluate the performance state of the stretcher. At the same time, the disc spring relieves the impact force when the stretcher runs without load, ensuring the use efficiency of the stretcher, prolonging the service life of the stretcher, and protecting the safety of the operator during work.

[0020] 2. When the positioning nut provided on the upper piston element and the threaded sleeve move upward, since the upward expansion speed of the upper flow space in the upper piston element is less than the upward expansion speed of the lower flow space in the lower piston element, the spring compresses, the upper conductive sheet contacts the lower conductive sheet, and an electrical signal is sent to the control unit. The control unit sends a signal to the monitor, resulting in an increase in the number of uses displayed on the monitor. At the same time, the lower piston element will increase the upward driving force of the upper piston element, increasing the upward force of the threaded sleeve. At the same time, due to the outer peripheral wall of the threaded sleeve abutting against the inner walls of the upper piston hole and the lower piston hole, increasing the contact area, the upward stress from the lower piston element and the upper piston element is dispersed to synchronously push the threaded sleeve upward, avoiding concentrated stress and side stress that may cause the bolt to twist and deform, affecting the subsequent loosening or tightening of the nut.

[0021] 3. When the bolt needs to be stretched again, the operator manually opens the connecting oil valve again, pushing the lower piston element and the upper piston element to continue rising, causing the disc spring to compress further. The two conductive plates are pressed to rotate around the torsion spring until the top of the lower conductive platform abuts against the bottom of the upper conductive platform, and the tops of the two conductive plates abut against the resistance sheets on the side walls of the two conductive columns, resulting in an increase in the resistance in the circuit and sending an electrical signal to the control unit. The control unit controls the closing of the connecting oil valve and makes it impossible for the operator to open it again, ensuring the safety performance of the stretcher. At the same time, the control unit will open the pressure relief valve, allowing the high-pressure liquid to flow into the pressure relief chamber, ensuring that the stretcher is not affected by overpressure and reducing the service life of the stretcher. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a sectional view of the present invention.

[0023] Figure 2 This is a sectional view of the support cylinder in the present invention.

[0024] Figure 3This is the cross-sectional view of the dual oil circuit connecting cylinder in the present invention.

[0025] Figure 4 This is the cross-sectional view of the lower piston element in the present invention.

[0026] Figure 5 This is the cross-sectional view of the upper piston element in the present invention.

[0027] Figure 6 This is the front view of the buffer element in the present invention.

[0028] Figure 7 This is the cross-sectional view of the oil circuit assembly in the present invention.

[0029] Figure 8 This is the cross-sectional view of the threaded sleeve in the present invention.

[0030] Figure 9 This is the cross-sectional view of the fastening nut in the present invention.

[0031] Figure 10 This is the cross-sectional view of the positioning nut in the present invention. Detailed implementation

[0032] For ease of understanding the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. The preferred embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of the present invention more thorough and comprehensive.

[0033] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0035] Please refer to Figures 1 to 10, A countable hydraulic bolt tensioner, comprising a housing assembly 10, a piston assembly 20, an oil circuit assembly 30 and a sleeved drawing assembly 40. The housing assembly 10 includes a support cylinder 11 and a double-oil-circuit connection cylinder 12. The interior of the support cylinder 11 is hollow to form a hollow cavity 13. The bottom of the double-oil-circuit connection cylinder 12 is fixedly installed on the top of the support cylinder 11. The interior of the double-oil-circuit connection cylinder 12 is hollow to form a piston installation cavity 14, and the piston installation cavity 14 communicates with the hollow cavity 13. A plurality of oil holes 127 are formed through the side wall of the double-oil-circuit connection cylinder 12, and the plurality of oil holes 127 communicate with the piston installation cavity 14. The piston assembly 20 is slidably installed in the piston installation cavity 14. The oil circuit assembly 30 is fixedly installed on one side wall of the double-oil-circuit connection cylinder 12. The upper part of the sleeved drawing assembly 40 is fixedly installed in the piston assembly 20, and the lower part of the sleeved drawing assembly 40 passes through the hollow cavity 13.

[0036] As Figure 2 , 3 shown, a working groove 15 is formed through the side wall of the support cylinder 11, and the working groove 15 communicates with the hollow cavity 13. An annular mounting seat 111 protrudes from the inner side of the top of the support cylinder 11; the double-oil-circuit connection cylinder 12 includes a connection cylinder body 16 and a disc spring pressing cover 17. An annular connection protrusion 18 protrudes from the top of the connection cylinder body 16. The bottom of the disc spring pressing cover 17 is hollow and is threadedly connected to the connection protrusion 18. A central hole 128 is formed through the center of the top surface of the disc spring pressing cover 17. The piston installation cavity 14 is formed in the connection cylinder body 16. The piston installation cavity 14 includes an installation cavity 121, a first sliding cavity 122, a first connection cavity 123, a second sliding cavity 124 and a second connection cavity 125 that are connected in sequence from bottom to top. The second connection cavity 125 communicates with the upper piston installation cavity 14. The inner diameter of the installation cavity 121 is equal to the outer diameter of the mounting seat 111. The double-oil-circuit connection cylinder 12 is sleeved and installed on the mounting seat 111 through the installation cavity 121 and is fixedly installed on the support cylinder 11 by bolts. The first sliding cavity 122 is located above the mounting seat 111. The inner diameter of the first sliding cavity 122 is equal to the inner diameter of the second sliding cavity 124. Annular flow blocking grooves 126 are recessed in the middle of the inner walls of the first sliding cavity 122 and the second sliding cavity 124. The inner diameter of the first connection cavity 123 is equal to the inner diameter of the second connection cavity 125, and the inner diameter of the first connection cavity 123 is larger than the inner diameter of the first sliding cavity 122. The central hole 128 communicates with the second connection cavity 125. L-shaped oil holes 127 are formed in the side walls of the first connection cavity 123 and the second connection cavity 125. The two oil holes 127 communicate with the oil circuit assembly 30.

[0037] As Figure 1 and Figures 4 - 6As shown, the piston assembly 20 includes a lower piston element 21, an upper piston element 22, and a buffer element 23. The lower piston element 21 is slidably mounted in the first sliding cavity 122 and the first connection cavity 123. The upper piston element 22 is slidably mounted in the first connection cavity 123, the second sliding cavity 124, and the second connection cavity 125. The buffer element 23 is fixedly mounted in the second connection cavity 125.

[0038] The lower piston element 21 includes a lower piston body 211 and a lower piston platform 212. The lower piston body 211 is slidably mounted in the first sliding cavity 122 and the first connection cavity 123. The lower piston platform 212 protrudes from the outer peripheral wall of the top of the lower piston body 211, and the bottom surface of the lower piston platform 212 abuts against the bottom surface of the first connection cavity 123. A lower piston hole 213 is formed through the lower piston body 211. An annular lower flow-through groove 214 is recessed in the bottom of the outer peripheral surface of the lower piston platform 212. An annular lower bypass groove 215 is recessed in the top of the bottom wall of the lower flow-through groove 214 along the radial direction of the lower piston body 211. Both the lower flow-through groove 214 and the lower bypass groove 215 communicate with the oil passage hole 127 of the first connection cavity 123. The bottom wall of the lower bypass groove 215 and the side wall of the first connection cavity 123 together enclose an annular lower flow-through space 216. A lower conductive sheet 217 is provided on one side of the top surface of the lower piston platform 212, and the lower conductive sheet 217 is electrically connected to the oil passage assembly 30.

[0039] The upper piston element 22 includes a spring 220, an upper piston body 221, and an upper piston platform 222 that are connected in sequence from bottom to top. The bottom surface of the spring 220 abuts against the top surface of the lower piston platform 212. The top surface of the spring 220 is fixedly connected to the bottom surface of the upper piston body 221. And the spring 220 is located in the first connection cavity 123. The spring 220 is made of an insulating elastic material. The upper piston body 221 is axially slidably installed in the second sliding cavity 124. The upper piston platform 222 is slidably installed in the second connection cavity 125. And the bottom surface of the upper piston platform 222 abuts against the bottom surface of the second connection cavity 125. On one side of the outer peripheral surface of the upper piston body 221, an upper conductive sheet 226 protrudes outward. The upper conductive sheet 226 is electrically connected to the oil circuit assembly 30. And the upper conductive sheet 226 and the lower conductive sheet 217 are arranged opposite to each other vertically. The diameter of the upper piston platform 222 is larger than that of the upper piston body 221. And the inner diameter of the upper piston platform 222 is equal to that of the second connection cavity 125. At the bottom of the outer peripheral wall of the upper piston platform 222, an annular upper flow-through groove 223 is recessed. At the top of the bottom wall of the upper flow-through groove 223, an annular upper flow-around groove 224 is recessed along the radial direction of the upper piston body 221. The upper flow-through groove 223 and the upper flow-around groove 224 communicate with the oil circuit hole 127 of the second connection cavity 125. The bottom wall of the upper flow-through groove 223 and the side wall of the second connection cavity 125 together surround an annular upper flow-through space 225. An upper piston hole 227 is penetrated through the top surface of the upper piston platform 222. At the top of the inner wall of the upper piston hole 227, an annular positioning groove 228 is recessed. An annular inclined surface 229 is recessed between the positioning groove 228 and the upper piston hole 227.

[0040] The buffer element 23 includes a disc spring 231 and a support conductive member 232. The bottom surface of the disc spring 231 is fixedly installed on the top surface of the upper piston platform 222. The top surface of the disc spring 231 is fixedly installed on the top surface of the inner wall of the disc spring cover 17. The support conductive member 232 includes an upper support portion 233 and a lower support portion 234. The top surface of the upper support portion 233 is fixedly installed on one side of the top surface of the inner wall of the disc spring cover 17. The bottom surface of the lower support conductive portion 234 is fixedly installed on the top surface of the upper piston platform 222. The upper support portion 233 includes an upper conductive platform 235 and conductive columns 236 protruding from both sides of the upper conductive platform 235 respectively. Resistance sheets 230 are arranged inside both of the two conductive columns 236. The lower support conductive portion 234 includes a mounting platform 237, a lower conductive platform 238, and two conductive plates 239. The bottom of the mounting platform 237 is fixedly installed on one side of the top surface of the upper piston platform 222 adjacent to the oil circuit assembly 30. The bottom surface of the lower conductive platform 238 is fixedly installed in the middle of the top of the mounting platform 237. The two conductive plates 239 are respectively rotatably installed on the top of the side walls on both sides of the lower conductive platform 238 through torsion springs. And the upper support portion 233 and the lower support portion 234 are corresponding to each other in position.

[0041] As Figure 1 、 7As shown, the oil circuit assembly 30 includes an oil circuit element 31 and a pressure relief display element 32. One side wall of the oil circuit element 31 is fixedly installed on the side wall of the double oil circuit connection cylinder 12, and the bottom of the pressure relief display element 32 is fixedly installed on the top of the oil circuit element 31. The oil circuit element 31 includes a lower oil pipeline 311, an upper oil pipeline 314, a connecting oil pipeline 312 and a connecting oil valve 313. The lower oil pipeline 311 and the upper oil pipeline 314 are parallel to each other, and one end of each of them is connected and communicated with the oil circuit hole 127 of the first connection cavity 123 and the oil circuit hole 127 of the second connection cavity 125 respectively, and the other end is connected and communicated with the upper and lower ends of the connecting oil pipeline 312 respectively. A connecting through hole 315 is formed through one side wall of the connecting oil pipeline 312 away from the double oil circuit connection cylinder 12. One end of the connecting oil valve 313 is fixedly installed in the connecting through hole 315, and the other end is connected to an external high-pressure oil pump. A pressure relief hole 316 is formed through the top of the connecting oil pipeline 312, and the pressure relief display element 32 is connected and communicated with the pressure relief hole 316.

[0042] The pressure relief display element 32 includes a pressure relief body 321 and a control display part 322. The control display part 322 is fixedly installed on the side wall of the pressure relief body 321 away from the double oil circuit connection cylinder 12. A pressure relief cavity 323 is formed by hollowing out the bottom of the pressure relief body 321. A pressure relief valve 324 is installed at the bottom of the inner wall of the pressure relief cavity 323. The pressure relief cavity 323 is communicated with the pressure relief hole 316 through the pressure relief valve 324. An explosion-proof valve hole 325 is formed through the top of the pressure relief cavity 323, and an explosion-proof valve 326 is arranged in the explosion-proof valve hole 325. The control display part 322 includes a display 327, a control unit 328 and a storage battery 329 which are connected in sequence from top to bottom. The side wall of the storage battery 329 is fixedly connected to the side wall of the pressure relief body 321. The top of the storage battery 329 is fixedly connected to the bottom of the control unit 328, and the storage battery 329 is electrically connected to the control unit 328 and the display 327. The control unit 328 is electrically connected to the display 327, the support conductive part 232, the upper conductive sheet 226 and the lower conductive sheet 217.

[0043] As Figure 1 and Figures 8 - 10As shown, the nested drawing assembly 40 includes a threaded sleeve 41, a fastening nut 43 and a positioning nut 42. The threaded sleeve 41 passes through the upper piston hole 227 and the lower piston hole 213 and is installed in the hollow cavity 13 and the piston installation cavity 14. The fastening nut 43 is rotatably installed in the hollow cavity 13 of the support cylinder 11, and the positioning nut 42 is slidably installed in the upper piston element 22. A threaded hole 411 is formed at the bottom of the threaded sleeve 41, a rotating shaft 413 protrudes from the center of the top surface of the threaded sleeve 41, and the rotating shaft 413 is fitted through the central hole 128. A knob hole 414 is formed at the top of the rotating shaft 413, and an external thread 412 is formed on the outer peripheral surface of the top of the threaded sleeve 41. The external thread 412 is in threaded cooperation with the positioning nut 42. A fastening groove 431 is recessed at the top of the outer peripheral surface of the fastening nut 43, and the fastening groove 431 is connected and communicated with the working groove 15 in the support cylinder 11. A nut groove 432 is recessed at the bottom of the inner wall of the fastening nut 43. A snap ring 421 protrudes outward from the top of the outer peripheral surface of the positioning nut 42, and an inclined transition sliding surface 422 protrudes between the snap ring 421 and the bottom surface of the positioning nut 42, and the transition sliding surface 422 abuts against the inclined surface 229.

[0044] The present invention also provides an assembly method for a countable hydraulic bolt stretcher. The assembly method is applied to the countable hydraulic bolt stretcher described above, and includes the following steps:

[0045] Step S1: Threadedly connect the threaded sleeve 41 with the bolt to be stretched through the threaded hole 411, and pass the support cylinder 11 through the threaded sleeve 41 so that the bottom surface of the support cylinder 11 abuts against the working surface of the bolt to be stretched.

[0046] Step S2: Install the piston assembly 20 in the double-oil-way connection cylinder 12, and pass the double-oil-way connection cylinder 12 through the threaded sleeve 41 so that the positioning nut 42 is in threaded cooperation with the external thread 412 of the threaded sleeve 41. At the same time, the double-oil-way connection cylinder 12 is sleeved and installed on the mounting seat 111 through the installation cavity 121, and the rotating shaft 413 is fitted through the central hole 128.

[0047] Step S3: Fix the side wall of the oil-way assembly 30 to the side wall of the double-oil-way connection cylinder 12, and connect and communicate one end of the lower oil pipeline 311 and the upper oil pipeline 314 with the oil-way holes 127 in the first connection cavity 123 and the second connection cavity 125.

[0048] For example, in one embodiment: due to human error, the threaded hole 411 of the threaded sleeve 41 is not threadedly mated with the bolt to be stretched, resulting in the stretcher running without load. The lower piston element 21 and the upper piston element 22 will run synchronously upward under the hydraulic push of an externally connected high-pressure oil pump. The lower flow space 216 and the upper flow space 225 will expand synchronously upward, causing the disc spring 231 to be compressed until the two conductive plates 239 of the lower support conductive part 234 contact the conductive column 236 of the upper support part 233, sending an electrical signal to the control unit 328. The control unit 328 controls the closing of the connecting oil valve 313 to suspend the hydraulic push. At the same time, since the spring 220, the upper piston body 221, and the upper piston platform 222 run synchronously upward, the upper conductive sheet 226 and the lower conductive sheet 217 do not contact each other, and the control unit 328 does not count this operation. The total usage times value of the display 327 does not change, preventing the stretcher from being counted when it runs without load, resulting in a shortened service life of the hydraulic stretcher and an inability to accurately evaluate the performance state of the stretcher. At the same time, the disc spring 231 alleviates the impact force when the stretcher runs without load, ensuring the service efficiency of the stretcher, extending the service life of the stretcher, and protecting the safety of the operator.

[0049] For example, in one embodiment: The operator threadedly mates the threaded hole 411 of the threaded sleeve 41 with the bolt to be stretched. The fastening nut 43 is sleeved on the outer side of the bottom of the threaded sleeve 41, and after the nut groove 432 of the fastening nut 43 is threadedly mated with the nut of the bolt to be stretched, the externally connected high-pressure oil pump is started, causing the lower piston element 21 and the upper piston element 22 to rise. However, since the positioning nut 42 is connected to the external thread 412 at the top of the threaded sleeve 41 and the positioning nut 42 is slidably installed in the upper piston element 22, the upper piston element 22 needs to push the positioning nut 42 and the threaded sleeve 41 upward, resulting in the upward expansion speed of the upper flow space 225 in the upper piston element 22 being less than the upward expansion speed of the lower flow space 216 in the lower piston element 21, causing the spring 220 to be compressed. The upper conductive sheet 226 contacts the lower conductive sheet 217 and sends an electrical signal to the control unit 328. The control unit 328 sends a signal to the display 327, resulting in an increase in the number of uses of the display 327. At the same time, the lower piston element 21 will increase the upward driving force of the upper piston element 22, increasing the upward force of the threaded sleeve 41. At the same time, since the threaded sleeve 41 passes through the upper piston hole 227 and the lower piston hole 213, the outer peripheral wall of the threaded sleeve 41 abuts against the inner walls of the upper piston hole 227 and the lower piston hole 213, increasing the contact area, so that the upward stress from the lower piston element 21 and the upper piston element 22 dispersedly and synchronously pushes the threaded sleeve 41 upward, avoiding concentrated stress and side stress from causing the bolt to twist and deform, which affects the subsequent loosening or tightening of the nut. At the same time, during the process of the upper piston element 22 stretching the positioning nut 42 and the threaded sleeve 41 upward, the disc spring 231 is compressed until the two conductive plates 239 of the lower support conductive part 234 contact the conductive column 236 of the upper support part 233, sending an electrical signal to the control unit 328. The control unit 328 controls the closing of the connecting oil valve 313 and pauses the hydraulic push to complete the first bolt extension and stretching.

[0050] When the bolt needs to be stretched again, the operator manually opens the connecting oil valve 313 again, pushing the lower piston element 21 and the upper piston element 22 to continue rising, causing the disc spring 231 to be further compressed, causing the two conductive plates 239 to be pressed to rotate around the torsion spring until the top of the lower conductive platform 238 abuts against the bottom of the upper conductive platform 235, and the tops of the two conductive plates 239 abut against the resistance sheets 230 on the side walls of the two conductive columns 236, resulting in an increase in the resistance in the circuit and sending an electrical signal to the control unit 328. The control unit 328 controls the closing of the connecting oil valve 313 and makes it impossible for the operator to open it again to ensure the safety performance of the stretcher. At the same time, the control unit 328 will open the pressure relief valve 324, causing the high-pressure liquid to flow into the pressure relief chamber 323 to ensure that the stretcher is not affected by overpressure and reduce the service life of the stretcher.

[0051] Installation process:

[0052] The lower piston element 21 is slidably mounted in the first sliding cavity 122 and the first connecting cavity 123, and the bottom surface of the lower piston platform 212 abuts against the bottom surface of the first connecting cavity 123. The bottom surface of the spring 220 abuts against the top surface of the lower piston platform 212. The top surface of the spring 220 is fixedly connected to the bottom surface of the upper piston body 221, and the spring 220 is located in the first connecting cavity 123. The upper piston body 221 is axially slidably mounted in the second sliding cavity 124, and the upper piston platform 222 is slidably mounted in the second connecting cavity 125. The bottom surface of the upper piston platform 222 abuts against the bottom surface of the second connecting cavity 125, and the upper conductive sheet 226 and the lower conductive sheet 217 are arranged opposite to each other vertically. The double-oil-way connecting cylinder 12 is sleeved and mounted on the mounting seat 111 through the mounting cavity 121. The fastening nut 43 is rotatably mounted in the hollow cavity 13 of the support cylinder 11, and the nut groove 432 of the fastening nut 43 is in mating connection with the nut of the bolt to be stretched. The threaded sleeve 41 is passed through the fastening nut 43, the lower piston hole 213, and the upper piston hole 227, so that the threaded sleeve 41 is mounted in the hollow cavity 13 and the piston mounting cavity 14. The positioning nut 42 is threadedly mated and mounted with the external thread 412 on the outer peripheral surface of the top of the threaded sleeve 41, and the transition sliding surface 422 of the positioning nut 42 abuts against the inclined surface 229. The bottom surface of the lower support conductive part 234 is fixedly mounted on the top surface of the upper piston platform 222. The bottom surface of the disc spring 231 is fixedly mounted on the top surface of the upper piston platform 222. The top surface of the disc spring 231 is fixedly mounted on the top surface of the inner wall of the disc spring pressing cover 17. The top surface of the upper support part 233 is fixedly mounted on one side of the top surface of the inner wall of the disc spring pressing cover 17, and the upper support part 233 and the lower support part 234 are in corresponding positions. It is threadedly connected to the connecting protrusion 18, and the rotation axis 413 of the threaded sleeve 41 passes through the central hole 128. One side side wall of the oil-way element 31 is fixedly mounted on the side wall of the double-oil-way connecting cylinder 12. The bottom of the pressure relief display element 32 is fixedly mounted on the top of the oil-way element 31, and one ends of the lower oil pipeline 311 and the upper oil pipeline 314 are respectively connected and communicated with the oil-way holes 127 of the first connecting cavity 123 and the second connecting cavity 125.

[0053] Beneficial effects:

[0054] 1. Due to human error, the threaded hole 411 of the threaded sleeve 41 is not threadedly mated with the bolt to be stretched. When the stretcher runs without load, the spring 220, the upper piston body 221, and the upper piston platform 222 will move upward synchronously under the hydraulic push of the externally connected high-pressure oil pump. The lower flow space 216 and the upper flow space 225 will expand upward synchronously, causing the disc spring 231 to be compressed until the two conductive plates 239 of the lower support conductive part 234 contact the conductive column 236 of the upper support part 233, sending an electrical signal to the control unit 328. The control unit 328 controls the closing of the connecting oil valve 313 to pause the hydraulic push. At the same time, since the spring 220, the upper piston body 221, and the upper piston platform 222 move upward synchronously, the upper conductive sheet 226 and the lower conductive sheet 217 do not contact, and the control unit 328 does not count this operation. The total usage times value of the display 327 does not change, preventing the stretcher from being counted when it runs without load, resulting in a shortened service life of the hydraulic stretcher and an inability to accurately evaluate the performance status of the stretcher. At the same time, the disc spring 231 alleviates the impact force when the stretcher runs without load, ensuring the service efficiency of the stretcher, extending the service life of the stretcher, and protecting the safety of the operator's work.

[0055] 2. When the positioning nut 42 provided on the upper piston element 22 and the threaded sleeve 41 move upward, since the upward expansion speed of the upper flow space 225 in the upper piston element 22 is less than the upward expansion speed of the lower flow space 216 in the lower piston element 21, the spring 220 is compressed, the upper conductive sheet 226 contacts the lower conductive sheet 217, and an electrical signal is sent to the control unit 328. The control unit 328 sends a signal to the display 327, resulting in an increase in the usage times of the display 327. At the same time, the lower piston element 21 will increase the upward driving force of the upper piston element 22, increasing the upward force of the threaded sleeve 41. At the same time, since the outer peripheral wall of the threaded sleeve 41 abuts against the inner walls of the upper piston hole 227 and the lower piston hole 213, increasing the contact area, the upward stress from the lower piston element 21 and the upper piston element 22 is dispersed to synchronously push the threaded sleeve 41 upward, avoiding concentrated stress and side stress that may cause the bolt to twist and deform, affecting subsequent nut loosening or tightening.

[0056] 3. When the bolt needs to be stretched again, manually open the connecting oil valve 313 again. The external high-pressure oil pump pushes the lower piston element 21 and the upper piston element 22 to continue rising, causing the disc spring 231 to be further compressed, so that the two conductive plates 239 are pressed to rotate around the torsion spring until the top of the lower conductive platform 238 abuts against the bottom of the upper conductive platform 235, and the tops of the two conductive plates 239 abut against the side wall surfaces of the resistance sheets 230 on the side walls of the two conductive columns 236. At this time, the resistance sheet 230 causes the resistance in the circuit to increase and sends an electrical signal to the control unit 328. The control unit 328 controls to close the connecting oil valve 313 and makes it impossible for manual operation to open it again, ensuring the safety performance of the stretcher. At the same time, the control unit 328 will open the pressure relief valve 324, so that the high-pressure liquid flows to the pressure relief chamber 323, ensuring that the stretcher is not affected by overpressure and reducing the service life of the stretcher.

[0057] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0058] The above-described embodiments only represent several embodiments of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent for the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent for the present invention should be subject to the appended claims.

Claims

1. A countable hydraulic bolt tensioner, characterized in that: It includes a housing assembly, a piston assembly, an oil circuit assembly, and a fitting and pulling assembly. The housing assembly includes a support cylinder and a double-oil-circuit connection cylinder. The interior of the support cylinder is hollow to form a hollow cavity. The bottom of the double-oil-circuit connection cylinder is fixedly installed on the top of the support cylinder. The interior of the double-oil-circuit connection cylinder is hollow to form a piston installation cavity, and the piston installation cavity communicates with the hollow cavity. A plurality of oil holes are penetrated through the side wall of the double-oil-circuit connection cylinder, and the plurality of oil holes communicate with the piston installation cavity. The piston assembly is slidably installed in the piston installation cavity. The piston assembly includes a lower piston element, an upper piston element, and a buffer element. The lower piston element includes a lower piston body and a lower piston platform. The lower piston platform protrudes from the outer peripheral wall of the top of the lower piston body. One side of the top surface of the lower piston platform is provided with a lower conductive sheet, and the lower conductive sheet is electrically connected to the oil circuit assembly. The upper piston element includes a spring, an upper piston body, and an upper piston platform that are connected in sequence from bottom to top. The bottom surface of the spring abuts against the top surface of the lower piston platform, and the top surface of the spring is fixedly connected to the bottom surface of the upper piston body. One side of the outer peripheral surface of the upper piston body protrudes outward to form an upper conductive sheet, and the upper conductive sheet is electrically connected to the oil circuit assembly, and the upper conductive sheet and the lower conductive sheet are arranged opposite to each other vertically. The oil circuit assembly is fixedly installed on one side wall of the double-oil-circuit connection cylinder. The upper part of the fitting and pulling assembly is fixedly installed in the upper piston element of the piston assembly through a positioning nut, and the lower part of the fitting and pulling assembly penetrates through the hollow cavity. A working groove is penetrated through the side wall of the support cylinder, and the working groove communicates with the hollow cavity. An annular mounting seat protrudes from the inner side of the top of the support cylinder; the double-oil-circuit connection cylinder includes a connection cylinder body and a disc spring pressing cover. An annular connection protrusion protrudes from the top of the connection cylinder body. The bottom of the disc spring pressing cover is hollow and is threadedly connected to the connection protrusion. A central hole is penetrated through the center of the top surface of the disc spring pressing cover. The piston installation cavity is opened in the connection cylinder body. The buffer element includes a disc spring and a support conductive member. The bottom surface of the disc spring is fixedly installed on the top surface of the upper piston platform. The top surface of the disc spring is fixedly installed on the top surface of the inner wall of the disc spring pressing cover. The support conductive member includes an upper support part and a lower support conductive part. The top surface of the upper support part is fixedly installed on one side of the top surface of the inner wall of the disc spring pressing cover. The bottom surface of the lower support conductive part is fixedly installed on the top surface of the upper piston platform. The upper support part includes an upper conductive platform and conductive columns protruding from both sides of the upper conductive platform. Resistance sheets are arranged inside both conductive columns. The lower support conductive part includes a mounting table, a lower conductive platform, and two conductive plates. The bottom of the mounting table is fixedly installed on one side of the top surface of the upper piston platform adjacent to the oil circuit assembly. The bottom surface of the lower conductive platform is fixedly installed in the middle of the top of the mounting table. The two conductive plates are rotatably installed on the top of the side walls on both sides of the lower conductive platform through torsion springs respectively, and the upper support part and the lower support conductive part are correspondingly positioned.

2. The countable hydraulic bolt tensioner according to claim 1, wherein: The piston installation cavity includes an installation cavity, a first sliding cavity, a first connection cavity, a second sliding cavity, and a second connection cavity that are sequentially connected from bottom to top. The second connection cavity communicates with the piston installation cavity on the upper side. The inner diameter of the installation cavity is equal to the outer diameter of the installation seat. The double-oil-circuit connection cylinder is sleeved and installed on the installation seat through the installation cavity and is fixedly installed with the support cylinder by bolts. The first sliding cavity is located above the installation seat. The inner diameter of the first sliding cavity is equal to the inner diameter of the second sliding cavity. An annular flow-blocking groove is recessed in the middle of the inner walls of the first sliding cavity and the second sliding cavity. The inner diameter of the first connection cavity is equal to the inner diameter of the second connection cavity, and the inner diameter of the first connection cavity is larger than the inner diameter of the first sliding cavity. The central hole communicates with the second connection cavity. L-shaped oil holes are opened on the side walls of the first connection cavity and the second connection cavity. The two oil holes communicate with the oil circuit assembly.

3. The countable hydraulic bolt tensioner according to claim 2, wherein: The lower piston element is slidably installed in the first sliding cavity and the first connection cavity. The upper piston element is slidably installed in the first connection cavity, the second sliding cavity, and the second connection cavity. The buffer element is fixedly installed in the second connection cavity.

4. The countable hydraulic bolt tensioner according to claim 3, wherein: The lower piston body is slidably installed in the first sliding cavity and the first connection cavity. The bottom surface of the lower piston platform abuts against the bottom surface of the first connection cavity. A lower piston hole is penetrated through the lower piston body. An annular lower flow-through groove is recessed at the bottom of the outer peripheral surface of the lower piston platform. An annular lower bypass groove is recessed along the radial direction of the lower piston body at the top of the bottom wall of the lower flow-through groove. Both the lower flow-through groove and the lower bypass groove communicate with the oil hole of the first connection cavity. The bottom wall of the lower bypass groove and the side wall of the first connection cavity jointly form an annular lower flow-through space.

5. The countable hydraulic bolt tensioner according to claim 4, wherein: The spring is located in the first connection cavity. The upper piston body is axially slidably installed in the second sliding cavity. The upper piston platform is slidably installed in the second connection cavity, and the bottom surface of the upper piston platform abuts against the bottom surface of the second connection cavity. The diameter of the upper piston platform is larger than the diameter of the upper piston body, and the inner diameter of the upper piston platform is equal to the inner diameter of the second connection cavity. An annular upper flow-through groove is recessed at the bottom of the outer peripheral wall of the upper piston platform. An annular upper bypass groove is recessed along the radial direction of the upper piston body at the top of the bottom wall of the upper flow-through groove. The upper flow-through groove and the upper bypass groove communicate with the oil hole of the second connection cavity. The bottom wall of the upper flow-through groove and the side wall of the second connection cavity jointly form an annular upper flow-through space. An upper piston hole is penetrated through the top surface of the upper piston platform. An annular positioning groove is recessed at the top of the inner wall of the upper piston hole. An annular inclined surface is recessed between the positioning groove and the upper piston hole.

6. The countable hydraulic bolt tensioner according to claim 5, characterized in that: The oil circuit assembly includes an oil circuit element and a pressure relief display element. One side wall of the oil circuit element is fixedly installed on the side wall of the double oil circuit connection cylinder, and the bottom of the pressure relief display element is fixedly installed on the top of the oil circuit element. The oil circuit element includes a lower oil pipeline, an upper oil pipeline, a connecting oil pipeline and a connecting oil valve. The lower oil pipeline and the upper oil pipeline are parallel to each other, and one ends of the two are respectively connected and communicated with the oil circuit holes of the first connection cavity and the second connection cavity, and the other ends are respectively connected and communicated with the upper and lower ends of the connecting oil pipeline. A connecting through hole is penetrated and opened on the side wall of the connecting oil pipeline away from the double oil circuit connection cylinder. One end of the connecting oil valve is fixedly installed in the connecting through hole, and the other end is connected to an external high-pressure oil pump. A pressure relief hole is penetrated and opened on the top of the connecting oil pipeline, and the pressure relief display element is connected and communicated with the pressure relief hole.

7. The countable hydraulic bolt tensioner according to claim 6, characterized in that: The pressure relief display element includes a pressure relief body and a control display part. The control display part is fixedly installed on the side wall of the pressure relief body away from the double oil circuit connection cylinder. A pressure relief cavity is formed by hollowing out the bottom of the pressure relief body. A pressure relief valve is installed at the bottom of the inner wall of the pressure relief cavity. The pressure relief cavity is communicated with the pressure relief hole through the pressure relief valve. An explosion-proof valve hole is penetrated and opened on the top of the pressure relief cavity, and an explosion-proof valve is arranged in the explosion-proof valve hole. The control display part includes a display, a control unit and a storage battery connected in sequence from top to bottom. The side wall of the storage battery is fixedly connected to the side wall of the pressure relief body. The top of the storage battery is fixedly connected to the bottom of the control unit, and the storage battery is electrically connected to the control unit and the display. The control unit is electrically connected to the display, a support conductive part, an upper conductive sheet and a lower conductive sheet.

8. The countable hydraulic bolt tensioner according to claim 7, characterized in that: The sleeve pulling and drawing assembly includes a threaded sleeve, a fastening nut and a positioning nut. The threaded sleeve passes through the upper piston hole and the lower piston hole and is installed in the hollow cavity and the piston installation cavity. The fastening nut is rotatably installed in the hollow cavity of the support cylinder. The positioning nut is slidably installed in the upper piston element. A threaded hole is opened at the bottom of the threaded sleeve. A rotating shaft protrudes from the center of the top surface of the threaded sleeve, and the rotating shaft is fitted and passed through the center hole. A knob hole is opened at the top of the rotating shaft. External threads are opened on the outer peripheral surface of the top of the threaded sleeve, and the external threads are in threaded cooperation with the positioning nut. A fastening groove is recessed at the top of the outer peripheral surface of the fastening nut, and the fastening groove is connected and communicated with the working groove in the support cylinder. A nut groove is recessed at the bottom of the inner wall of the fastening nut. A snap ring protrudes outward from the top of the outer peripheral surface of the positioning nut, and an inclined transition sliding surface protrudes between the snap ring and the bottom surface of the positioning nut, and the transition sliding surface abuts against the inclined surface.

9. An assembling method of a countable hydraulic bolt tensioner, characterized in that, For assembling the countable hydraulic bolt stretcher as described in claim 8, the assembling method includes the following steps: Step S1: Threadedly connect the threaded sleeve with the bolt to be stretched through the threaded hole. Pass the support cylinder through the threaded sleeve so that the bottom surface of the support cylinder abuts against the working surface of the bolt to be stretched. Rotatably install the fastening nut in the hollow cavity of the support cylinder and make the nut in the bolt to be stretched be clamped in the nut groove; Step S2: Install the piston assembly in the double oil circuit connection cylinder. Pass the double oil circuit connection cylinder through the threaded sleeve so that the positioning nut is in threaded cooperation with the external threads of the threaded sleeve. At the same time, make the double oil circuit connection cylinder be sleeved and installed on the mounting seat through the installation cavity, and make the rotating shaft be fitted and passed through the center hole; Step S3: Fix the side wall of the oil circuit component to the side wall of the double oil circuit connecting cylinder, and connect one end of the lower oil pipeline and the upper oil pipeline to the oil circuit holes of the first connection cavity and the second connection cavity.

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