CN219793649U - Automatic tensioning and locking equipment for prestressed low-retraction anchor - Google Patents

Abstract

The utility model provides an automatic stretch-draw locking equipment of prestressing force low-retraction ground tackle, includes tension rod (1), its characterized in that: the automatic tensioning device is reasonable in structure, capable of automatically tensioning and locking, capable of accurately measuring displacement and tension values in real time, capable of avoiding the breakage of a prestressed steel rod during tensioning construction, safe and efficient in tensioning process, high in anchoring efficiency and small in prestress loss.

Description

Automatic tensioning and locking equipment for prestressed low-retraction anchor

Technical Field

The utility model relates to prestress tensioning and locking equipment, in particular to prestress low-retraction anchor automatic tensioning and locking equipment, and belongs to the technical field of prestress construction.

Background

Along with the progress of bridge technology, the application of large-span concrete makes bridge span bigger and bigger, on one hand mainly benefits from the use of bridge prestress technology, namely, the low-retraction anchoring of penetrating unbonded prestress steel strands in the concrete applies pressure to the concrete, so that partial tensile work load of the concrete is counteracted, and the strength of the concrete is improved by a plurality of times. However, in the early-built prestressed concrete bridge, many adverse phenomena such as beam cracking, downdisturbance and the like already occur, and one of the factors is that the prestress loss is large, so that the safety use of the bridge is greatly hidden danger.

The prior advanced bridge prestress technology needs to use a prestress steel strand and a low-retraction anchoring system, and the common low-retraction anchoring system technology mainly comprises finish rolling threaded steel, high-strength threaded steel bars, round nut clamping piece type low-retraction anchoring and the like, and the common low-retraction anchoring structure has the problems of complex structure, large prestress loss, easy fracture of prestress ribs, easy corrosion, difficult construction, nonstandard construction and the like, so that the service life and the use safety of the low-retraction anchoring structure are seriously influenced.

The prestress steel strand is a key stress component in a prestress bridge structure, and the use safety of the bridge is seriously affected by prestress loss, so that the prestress of the steel strand is extremely important to maintain. The grouting-free low-retraction anchoring system mainly solves the problems of complex structure, large prestress loss, high prestress rib fracture, easiness in corrosion, difficult construction, nonstandard construction and the like in short-bundle prestress, but when the low-retraction anchoring device is adopted for prestress tensioning, manual operation tensioning equipment is generally adopted, and because standard equipment tools are not used for carrying out refined operation on the low-retraction anchoring device, tensioning stress cannot be accurately controlled, data record is not available, and the prestress steel bar fracture occurs during tensioning construction. In addition, the prestress construction is manually operated, the prestress is different from person to person, the stress loss is large, the discreteness is also large, cracks can be caused to the prestress beam body structure, and the safety cannot be guaranteed. In general, it is difficult to meet the set technical requirements, and the above technical problems have not been solved effectively.

Disclosure of Invention

The utility model aims at solving the defects that the existing common tensioning equipment cannot accurately control the tensioning stress, the pre-stressed steel bar is broken during the tensioning construction, the pre-tightening force is greatly affected by human factors due to the adoption of manual tensioning operation, the stress loss is large, the discreteness is also large, and the pre-stressed beam structure is easy to crack.

In order to achieve the purposes of the application, the technical solution of the utility model is as follows: the utility model provides a prestressing force low anchor automatic tensioning locking equipment that contracts, includes the tension rod, install the pressure-bearing section of thick bamboo on the middle part outer circumference of tension rod, the tensioning jack is installed to the upper end of pressure-bearing section of thick bamboo, be provided with adjustable mounting after the upper portion tensioning end of tension rod passes the inner chamber of tensioning jack, the lower extreme coaxial fixed with backing plate support piece of pressure-bearing section of thick bamboo, the outer end of backing plate support piece is provided with the supporting terminal surface that extrudees the laminating with the support backing plate, backing plate support piece is both ends open-ended tubular structure, the inside of backing plate support piece is the stand pipe cavity, coaxial mounting has the automatic locking device of flexible function in the stand pipe cavity, the outer end of automatic locking device is provided with the nut fastening link by automatic locking device drive.

Further, the automatic locking device comprises a bearing pressure cylinder, a hollow shaft, a guide pipe, a torsion sleeve, a bearing support, a thrust bearing, a worm and a worm wheel, wherein the bearing pressure cylinder is coaxially arranged at the lower end of the bearing pressure cylinder, the hollow shaft is arranged in the bearing pressure cylinder, the worm wheel is coaxially and fixedly arranged on the bearing pressure cylinder, the worm is arranged on the outer side of the worm wheel through the bearing support and the thrust bearing, the worm is matched with the worm wheel, the guide pipe is fixedly arranged in a cavity of the guide pipe, the torsion sleeve is coaxially arranged in the guide pipe, the torsion sleeve is connected with the worm wheel through a movable connecting piece, and a nut connecting hole corresponding to a locking nut is formed in the bottom end of the torsion sleeve.

Further, the automatic locking device is provided with a through hole along the axial lead, the lower end of the tension rod penetrates through the through hole of the automatic locking device, the lower end of the tension rod is provided with an anchor connector, and the upper tensioning end of the tension rod penetrates through the inner cavity of the tensioning jack and then is provided with a tensioning nut through external threads.

Further, the movable connecting piece comprises a cylindrical spring, a sliding groove and a guide sliding block, one or more sliding grooves are formed in the outer wall of the guide tube along the axial direction, the guide sliding block is movably installed in the sliding groove and fixed on the outer wall of the torsion sleeve, the cylindrical spring is installed on the inner wall of the guide tube close to the inner wall of the guide tube, and the cylindrical spring is arranged between the inner cavity of the guide tube and the upper end of the torsion sleeve in an extrusion mode.

Further, a protective cover is arranged on the periphery of the bearing support, the protective cover is fixed on the outer surface of the pressure-bearing cylinder or the backing plate support piece, the worm is installed on the bearing support through a thrust bearing, the outer end of the worm is provided with a driving device connecting end, the driving device connecting end is connected with a rotary driving device, and a bearing cover is installed at the outer end of the bearing support.

Further, a piston capable of reciprocating is arranged at the outer end of the tensioning jack, and the piston is located between the tensioning nut and the outer end of the tensioning jack.

Further, an outer shell of the tensioning jack is arranged on the pressure-bearing cylinder through a fixing screw, and a displacement sensor is arranged on the tensioning jack.

Further, the tension jack and/or the automatic locking device are/is provided with a force transducer.

Further, a bearing is arranged on the outer circumference of the hollow shaft, and a tension rod penetrates into an inner hole of the hollow shaft.

Further, a handle is fixedly arranged on the outer wall of the pressure-bearing cylinder or the tensioning jack.

The beneficial effects of the utility model are as follows:

1. the utility model adopts a tensioning and locking integrated structure, the tensioning jack is utilized to drive the tensioning rod to carry out tensioning, and an automatic locking device is adopted to effectively lock the tensioned anchorage, so that the tensioning and the locking are effectively connected and synchronously carried out.

2. The automatic locking device is adopted, the automatic locking device drives the locking nut to automatically lock through the torsion sleeve, the automatic locking device has a telescopic function, can perform elastic adjustment in a certain range under the action of the guide mechanism, and has good adaptability.

3. The utility model can automatically control the tension in a grading way, can automatically maintain the pressure according to the set time after reaching the preset tension value of each grade, can accurately measure the displacement and the tension value in the tensioning process, and can be uploaded to a system for analysis and storage in real time.

4. The utility model has reasonable structure, avoids the condition of fracture of the prestress steel bar during the tensioning construction, has safe and efficient tensioning process, high anchoring efficiency and small prestress loss.

Drawings

Fig. 1 is a schematic structural view of the present utility model.

Fig. 2 is a cross-sectional view of the present utility model.

Fig. 3 is a schematic structural view of the automatic locking device of the present utility model.

Fig. 4 is a schematic structural view of the tension rod of the present utility model.

In the figure: tension rod 1, tension nut 2, anchor connector 3, lock nut 4, pressure-bearing cylinder 5, backing plate support 6, tension jack 7, piston 8, bearing pressure cylinder 9, hollow shaft 10, guide tube cavity 11, guide tube 12, cylindrical spring 13, torsion sleeve 14, chute 15, guide slider 16, set screw 17, bearing 18, shield 19, bearing support 20, thrust bearing 21, turbine driving motor 22, worm 23, worm wheel 24, driving device connection end 25, displacement sensor 26, load cell 27, handle 28, anchor 29, support backing plate 30, concrete beam 31, tension rod driving device 32.

Description of the embodiments

The utility model is described in further detail below with reference to the accompanying drawings and detailed description.

Referring to fig. 1 to 4, the automatic tensioning and locking device for the prestressed low-retraction anchor, disclosed by the utility model, comprises a tensioning rod 1, and is characterized in that: the middle part of stretching rod 1 is equipped with pressure-bearing section of thick bamboo 5 on the outer circumference, stretch-draw jack 7 is installed to pressure-bearing section of thick bamboo 5's upper end, be provided with adjustable mounting after stretch-draw jack 7's the upper portion stretch-draw end of stretching rod 1 passes the inner chamber of stretch-draw jack, pressure-bearing section of thick bamboo 5's lower extreme coaxial fixation has backing plate support 6, backing plate support 6's outer end is provided with the supporting end face that extrudees the laminating with supporting backing plate 30, backing plate support 6 is both ends open-ended tubular structure, backing plate support 6's inside is stand pipe cavity 11, stand pipe cavity 11 interior coaxial mounting has the automatic locking device of flexible function, automatic locking device's outer end is provided with the nut fastening link by automatic locking device drive.

The automatic locking device comprises a bearing pressure cylinder 9, a hollow shaft 10, a guide pipe 12, a torsion sleeve 14, a bearing support 20, a thrust bearing 21, a worm 23 and a worm wheel 24, wherein the bearing pressure cylinder 9 is coaxially arranged at the lower end of the pressure cylinder 5, the hollow shaft 10 is arranged in the bearing pressure cylinder 9, the worm wheel 24 is coaxially and fixedly arranged on the bearing pressure cylinder 9, the worm 23 is arranged on the outer side of the worm wheel 24 through the bearing support 20 and the thrust bearing 21 and matched with the worm wheel 24, the guide pipe 12 is fixedly arranged in a cavity 11 of the guide pipe, the torsion sleeve 14 is coaxially arranged in the guide pipe 12, the torsion sleeve 14 is connected with the worm wheel 24 through a movable connecting piece, and a nut connecting hole corresponding to the locking nut 4 is arranged at the bottom end of the torsion sleeve 14.

The automatic locking device is provided with a through hole along the axial lead, the lower end of the tension rod 1 passes through the through hole of the automatic locking device, the lower end of the tension rod 1 is provided with an anchorage connector 3, and the tensioning nut 2 is arranged at the upper tensioning end of the tension rod 1 through external threads after passing through the inner cavity of the tensioning jack 7.

The movable connecting piece comprises a cylindrical spring 13, a sliding groove 15 and a guide sliding block 16, one or more sliding grooves 15 are formed in the outer wall of the guide tube 12 along the axial direction, the guide sliding block 16 is movably installed in the sliding groove 15, the guide sliding block 16 is fixed on the outer wall of the torsion sleeve 14, the cylindrical spring 13 is installed on the inner wall of the guide tube 12 close to the inner wall of the guide tube 12, and the cylindrical spring 13 is arranged between the inner cavity of the guide tube 12 and the upper end of the torsion sleeve 14 in an extrusion mode.

The periphery of the bearing support 20 is provided with a protective cover 19, the protective cover 19 is fixed on the outer surface of the pressure-bearing cylinder 5 or the backing plate support 6, a worm 23 is installed on the bearing support 20 through a thrust bearing 21, the outer end of the worm 23 is provided with a driving device connecting end 25, the driving device connecting end 25 is connected with a rotary driving device, and a bearing cover 22 is installed at the outer end of the bearing support 20.

The outer end of the tensioning jack 7 is provided with a piston 8 capable of reciprocating, and the piston 8 is positioned between the tensioning nut 2 and the outer end of the tensioning jack 7.

The outer shell of the tensioning jack 7 is arranged on the pressure-bearing cylinder 5 through a fixing screw 17, and a displacement sensor 26 is arranged on the tensioning jack 7.

The tensioning jack 7 and/or the automatic locking device are/is provided with a load cell 27.

The bearing 18 is arranged on the outer circumference of the hollow shaft 10, and a tension rod 1 is arranged in an inner hole of the hollow shaft 10 in a penetrating way.

A handle 28 is fixedly arranged on the outer wall of the pressure-bearing cylinder 5 or the tensioning jack 7.

Referring to the attached drawings, the utility model is different from the traditional prestress tensioning device, adopts a tensioning and locking integrated structure, can realize automatic locking when tensioning an anchor for a low-retraction anchoring system, and has safe and efficient tensioning process, high anchoring efficiency and small prestress loss. Before tensioning, the support base plate 30 is pre-buried to be arranged on the beam body concrete 31, an anchor 29 is installed in a mounting hole formed in the support base plate 30, the anchor 29 is fixed on the support base plate 30, external threads are formed at the outer end of the anchor 29, and the threaded end is convenient for installing a locking nut 4 to lock the anchor after tensioning.

The axle center of the automatic tensioning and locking device is provided with a tensioning rod 1 in a penetrating way, the lower end of the tensioning rod 1 is provided with an anchor connector 3 which is used for being connected with a threaded end on the outer side of an anchor 29, and meanwhile the tensioning rod 1 can be used as an important force transmission component for tensioning. The middle part outer circumference of the tension rod 1 is provided with a pressure-bearing cylinder 5, the upper end of the pressure-bearing cylinder 5 is provided with a tension jack 7, the outer shell of the tension jack 7 is arranged on the pressure-bearing cylinder 5 through a fixing screw 17, the upper tension end of the tension rod 1 passes through the inner cavity of the tension jack 7, and the upper end of the tension rod 1 is provided with external threads for installing a tension nut 2. The tensioning jack 7 is driven by hydraulic pressure, a piston 8 capable of reciprocating is arranged at the outer end of the tensioning jack 7, the piston 8 can reciprocate under the action of a hydraulic cylinder, the piston 8 is located between the tensioning nut 2 and the outer end of the tensioning jack 7, and tensioning action is achieved by extruding the tensioning nut 2 through the piston 8.

The lower end of the pressure-bearing cylinder 5 is coaxially fixed with a pad support piece 6, the pad support piece 6 is fixedly connected with the pressure-bearing cylinder 5 through a flange plate or an ear plate, and the pad support piece 6 is of a cylindrical structure with two open ends. The inside of the backing plate support 6 is a guide tube cavity 11, an automatic locking device with a telescopic function is coaxially arranged in the guide tube cavity 11, and the automatic locking device can provide preset torsion to automatically screw after being in butt joint with the locking nut 4, so that the support backing plate 30 is locked. The automatic locking device may take various forms, for example: the automatic locking device comprises a bearing pressure cylinder 9, a hollow shaft 10, a guide tube 12, a torsion sleeve 14, a bearing support 20, a thrust bearing 21, a worm 23 and a worm wheel 24, wherein the bearing pressure cylinder 9 is coaxially arranged at the lower end of the pressure cylinder 5, the hollow shaft 10 is arranged in the bearing pressure cylinder 9, the worm wheel 24 is coaxially and fixedly arranged on the bearing pressure cylinder 9, the worm 23 is arranged on the outer side of the worm wheel 24 through the bearing support 20 and the thrust bearing 21, the worm 23 is matched with the worm wheel 24, the guide tube 12 is fixedly arranged in a guide tube cavity 11, the torsion sleeve 14 is coaxially arranged in the guide tube 12, the torsion sleeve 14 is connected with the worm wheel 24 through a movable connecting piece, and a nut connecting hole corresponding to the locking nut 4 is arranged at the bottom end of the torsion sleeve 14.

In addition, the automatic locking device adopted by the utility model also has a telescopic function so as to adapt to different screwing connection depths between the tension rod 1 and the anchorage 29, in particular to adopt a movable connecting piece which is used for connecting the torsion sleeve 14 and the worm wheel 24. The movable connecting piece comprises a cylindrical spring 13, a sliding groove 15 and a guide sliding block 16, one or more sliding grooves 15 are formed in the outer wall of the guide tube 12 along the axial direction, the guide sliding block 16 is movably installed in the sliding groove 15, the guide sliding block 16 can slide up and down along the axial direction in the sliding groove 15, the guide sliding block 16 is fixed on the outer wall of the torsion sleeve 14, the cylindrical spring 13 is installed on the inner wall, close to the guide tube 12, of the guide tube 12, and the cylindrical spring 13 is arranged between the inner cavity of the guide tube 12 and the upper end of the torsion sleeve 14 in an extrusion mode. In the process of aligning the bottom end of the torsion sleeve 14 with the lock nut 4, the torsion sleeve 14 can be elastically adjusted to a certain extent under the action of the cylindrical spring 13 and the guide mechanism, so that the tension-type adjustable locking device can be well adapted to the change of the height position after tensioning.

The periphery of the bearing support 20 is provided with a protective cover 19, and the protective cover 19 is used for placing the bearing support 20, the thrust bearing 21 and the worm 23 in a protective cover shell to play a role in protection of dust prevention, water prevention and the like. The protection casing 19 is fixed on the surface of pressure-bearing section of thick bamboo 5 or backing plate support 6, and worm 23 passes through thrust bearing 21 and installs on bearing support 20, and the outer end of worm 23 is provided with drive arrangement link 25, and drive arrangement link 25 is connected with turbine driving motor 22, and turbine driving motor 22 can adopt servo motor.

According to the utility model, the displacement sensor 26 is arranged on the tensioning jack 7, the tensioned displacement is accurately measured through the displacement sensor 26, measurement data are sent to the data acquisition device, and the extension value is automatically checked by the monitoring system in the tensioning process. Meanwhile, a force transducer 27 is arranged between the tensioning jack 7 and the piston 8 and used for detecting the pulling force or the extrusion force in the tensioning process, and the force transducer 27 can be arranged on the automatic locking device and used for detecting the torque in the locking process.

The tensioning and locking method comprises the following steps: firstly, an anchor box is reserved or pre-buried, one or more steering gears 29 are installed, then, a middle supporting base plate 30 is inserted into the steering gears 29 in a partitioned mode, firstly, the concrete beam body 31 is pre-buried, meanwhile, an anchor 29 is installed in a central hole of the supporting base plate 30 and fixed, and a locking nut 4 is initially installed on a threaded connector at the outer end of the anchor 29. The automatic tension locking device is then held by a handle 28 and aligned with the anchor 29, the lower end of the pad support 6 is pushed against the outer surface of the support pad 30, the anchor connector 3 at the lower end of the tension rod 1 of the automatic tension locking device is connected with the anchor 29, and the nut connecting hole at the bottom end of the torsion sleeve 14 is aligned with the locking nut 4. Then the rotating connection end of the driving device is connected with the upper end of the tension rod 1, and the tension rod driving device 32 is operated to drive the tension rod 1 to rotate, so that the anchor connector 3 at the lower end of the tension rod 1 is screwed into the threaded connector at the outer end of the anchor 29. The tensioning nut 2 is arranged on the upper part of the tensioning rod 1 and is adjusted to a proper position, so that the outer end of the piston 8 is propped against the inner side end surface of the tensioning nut 2.

Then, the tensioning jack 7 is started again, the piston 8 extends outwards and extrudes the lock nut 4 so as to realize tensioning of the tensioning rod 1, tensioning data of the anchor 29 are monitored and recorded, and pressure is maintained for a certain time after the tensioning reaches a preset tension. The automatic locking device is started while the constant stress is ensured in the tensioning and pressure maintaining process, the torsion sleeve 14 drives the locking nut 4 to rotate at the threaded end on the anchor 29, the support backing plate 30 is screwed, the small retraction amount of the anchor is ensured, and the tensioning and locking operation is completed.

The foregoing is a further detailed description of the utility model in connection with the specific embodiments, and it is not to be construed as limited to the specific embodiments of the utility model, but it is to be understood that the utility model is capable of modification and substitution in accordance with the utility model without departing from the spirit of the utility model.

Claims (10)

1. The utility model provides an automatic stretch-draw locking equipment of prestressing force low-retraction ground tackle, includes tension rod (1), its characterized in that: the automatic locking device is characterized in that a pressure-bearing cylinder (5) is mounted on the outer circumference of the middle of the tension rod (1), a tension jack (7) is mounted at the upper end of the pressure-bearing cylinder (5), a tension nut (2) is mounted through external threads after the upper tension end of the tension rod (1) passes through the inner cavity of the tension jack (7), a backing plate supporting piece (6) is coaxially fixed at the lower end of the pressure-bearing cylinder (5), a supporting end face which is in extrusion fit with a supporting backing plate (30) is arranged at the outer end of the backing plate supporting piece (6), the backing plate supporting piece (6) is of a cylindrical structure with two open ends, an automatic locking device with a telescopic function is coaxially mounted in the guide tube cavity (11), a nut fastening connecting end driven by the automatic locking device is arranged at the outer end of the automatic locking device, the automatic locking device is arranged to be a through hole along a core wire, the lower end of the tension rod (1) passes through the through hole of the automatic locking device, and an anchor connector (3) is arranged at the lower end of the tension rod (1).

2. The automatic tensioning and locking device of a prestressed low-retraction anchor of claim 1 wherein: the automatic locking device comprises a bearing cylinder (9), a hollow shaft (10), a guide tube (12), a torsion sleeve (14), a bearing support (20), a thrust bearing (21), a worm (23) and a worm wheel (24), wherein the bearing cylinder (9) is coaxially arranged at the lower end of the bearing cylinder (5), the hollow shaft (10) is arranged in the bearing cylinder (9), the worm wheel (24) is coaxially and fixedly arranged on the bearing cylinder (9), the worm (23) is arranged on the outer side of the worm wheel (24) through the bearing support (20) and the thrust bearing (21), the worm (23) is matched with the worm wheel (24), the guide tube (12) is fixedly arranged in a guide tube cavity (11), the torsion sleeve (14) is coaxially arranged in the guide tube (12), the torsion sleeve (14) is connected with the worm wheel (24) through a movable connecting piece, and a nut connecting hole corresponding to a locking nut (4) is arranged at the bottom end of the torsion sleeve (14).

3. The automatic tensioning and locking device of a prestressed low-retraction anchor of claim 1 wherein: the automatic locking device is provided with a through hole along the axial lead, the lower end of the tension rod (1) passes through the through hole of the automatic locking device, the lower end of the tension rod (1) is provided with an anchor connector (3), and the tensioning nut (2) is arranged on the upper tensioning end of the tension rod (1) through external threads after passing through the inner cavity of the tensioning jack (7).

4. The automatic tensioning and locking device of a prestressed low-retraction anchor of claim 2 wherein: the movable connecting piece comprises a cylindrical spring (13), a sliding groove (15) and a guide sliding block (16), one or more sliding grooves (15) are formed in the outer wall of the guide tube (12) along the axial direction, the guide sliding block (16) is movably installed in the sliding groove (15), the guide sliding block (16) is fixed on the outer wall of the torsion sleeve (14), the cylindrical spring (13) is installed on the inner wall of the guide tube (12) close to the inner wall of the guide tube (12), and the cylindrical spring (13) is arranged between the inner cavity of the guide tube (12) and the upper end of the torsion sleeve (14) in an extrusion mode.

5. The automatic tensioning and locking device of a prestressed low-retraction anchor of claim 2 wherein: the periphery of the bearing support (20) is provided with a protective cover (19), the protective cover (19) is fixed on the outer surface of the pressure-bearing cylinder (5) or the backing plate support piece (6), the worm (23) is installed on the bearing support (20) through the thrust bearing (21), the outer end of the worm (23) is provided with a driving device connecting end (25), and the driving device connecting end (25) is connected with the rotary driving device.

6. The automatic tensioning and locking device of a prestressed low-retraction anchor of claim 1 wherein: the outer end of the tensioning jack (7) is provided with a piston (8) capable of reciprocating, and the piston (8) is located between the tensioning nut (2) and the outer end of the tensioning jack (7).

7. The automatic tensioning and locking device of a prestressed low-retraction anchor of claim 1 wherein: the outer shell of the tensioning jack (7) is arranged on the pressure-bearing cylinder (5) through a fixing screw (17), and a displacement sensor (26) is arranged on the tensioning jack (7).

8. The automatic tensioning and locking device of a prestressed low-retraction anchor of claim 1 wherein: and a force transducer (27) is arranged on the tensioning jack (7) and/or the automatic locking device.

9. The automatic tensioning and locking device of a prestressed low-retraction anchor of claim 2 wherein: the bearing (18) is arranged on the outer circumference of the hollow shaft (10), and a tension rod (1) penetrates into an inner hole of the hollow shaft (10).

10. The automatic tensioning and locking device of a prestressed low-retraction anchor of claim 1 wherein: a handle (28) is fixedly arranged on the outer wall of the pressure-bearing cylinder (5) or the tensioning jack (7).