US3598368A

US3598368A - Wire-tensioning apparatus for use in stressing concrete structures

Info

Publication number: US3598368A
Application number: US827790A
Authority: US
Inventors: Antonio Brandestini; Hans Rudolf Siegwart
Original assignee: Individual
Current assignee: Individual
Priority date: 1968-05-27
Filing date: 1969-05-26
Publication date: 1971-08-10
Anticipated expiration: 1988-08-10
Also published as: DE1924561A1; CH475453A; NL6907984A; SE341677B; JPS5111419B1; ES367652A1

Abstract

Apparatus for tensioning members in a concrete structure including an anchor head receiving the stressing members comprises a housing adapted to be supported against the concrete structure, a hydraulically or pneumatically operated traction member adapted to reciprocate within the housing for stressing the tensioning members, a coupling device arranged at the free end of the traction member for connecting the traction member to the anchor head, means for holding the housing in position against the concrete structure, means for axial alignment of the traction member with the anchor head, and motor-driven means for rotating the coupling device when the traction member and the anchor head are aligned to produce engagement of the coupling device with the anchor head.

Description

United States Patent WIRE-TENSIONING APPARATUS FOR USE IN STRESSING CONCRETE STRUCTURES 8 Claims, 5 Drawing Figs.

U.S. CI 254/29 Int. Cl E2lb 19/00 Field of Search 254/29, 29 A Primary Examiner-Othell M. Simpson Assistant Examiner-David R. Melton Attorney-Werner W. Kleeman ABSTRACT: Apparatus for tensioning members in a concrete structure including an anchor head receiving the stressing members comprises a housing adapted to be supported against the concrete structure, a hydraulically or pneumatically operated traction member adapted to reciprocate within the housing for stressing the tensioning members, a coupling device arranged at the free end of the traction member for connecting the traction member to the anchor head, means for holding the housing in position against the concrete structure, means for axial alignment of the traction member with the anchor head, and motor-driven means for rotating the coupling device when the traction member and the anchor head are aligned to produce engagement of the coupling device with the anchor head.

PATENTEU AUG] 0 an SHEET 1 UF 2 WIRE-TENSIONING APPARATUS FOR USE 1N STRESSING CONCRETE STRUCTURES The present invention relates to an apparatus for tensioning wires in a concrete structure.

Apparatus of this type usually consist of a hydraulic working cylinder having a piston with a continuous central bore through which the actual traction member leads to the anchoring place. The whole apparatus is brought to the place of use and arranged at the end of a concrete structure as precisely as possible over an anchor head of a bundle of wires to be stressed. Thereafter the traction member is connected by hand to the anchor head, the wire or bundle of wires is stressed and the anchor head is then supported on suitable supporting members.

The present invention has for its object to provide an improved wire-tensioning apparatus which is easy to manipulate, which operates automatically to a large degree and permits a rapid and safe operation, while being particularly suitable for stressing large bundles of wires.

The wire-tensioning apparatus according to the present invention comprises a housing adapted to be supported against one end of a concrete structure, a tensioning unit in said housing, a traction member extending from one end of said tensioning unit into said housing, a coupling device arranged at the free end of said traction member for connecting said traction member to an anchor head of a wire bundle, centering means provided at said end of the traction member for axial alignment of the traction member with said anchor head, means for temporarily connecting said housing to the concrete structure, said connecting means including tensioning members arranged at the outside of said housing, the tensioning force of said tensioning members being adjustable, and coupling members for said tensioning members adapted to connect the tensioning members to the concrete structure.

In a particularly advantageous embodiment of the apparatus, the tensioning unit and the tensioning members serving as connecting means are hydraulically or pneumatically operating working cylinders and the coupling device for connecting the traction member to the anchor head is also hydraulically or pneumatically operable. A central control device provided with control valves is advantageously provided for controlling the operation of the apparatus.

The invention will be described in greater detail with reference to the accompanying drawings, in which:

FIG. 1 is a longitudinal section through an apparatus according to the invention mounted on the end of a concrete construction, wherein the connecting means attached to the outside of the housing have been omitted for the sake of clearness of the drawing.

FIG. 1A is a view of one of the connecting means, here in the form ofa hydraulic cylinder, which is shown in the correct position with respect to the apparatus according to FIG. 1.

FIG. 2 is a section along the line lI-II of FIG. 1, with the connecting means in position.

FIG. 3 is a longitudinal sectional view of the front end of a modification of the apparatus according to FIG. 1, and

FIG. 4 is a diagram of the hydraulic control means of an apparatus according to FIG. 1.

FIGS. 1, 1A and 2 of the drawing show different views of a wire-tensioning apparatus, according to the present invention.

The main part of the apparatus consists of a housing 1, provided with lateral openings 2,3. The apparatus may be suspended on a suspension device 6 of a crane cable by means of one or more links 4 and bolts 5, in order to be brought to the place of anchorage of a bundle of wires 7 at the end of a concrete construction 8 to be prestressed. The base portion of the housing 1 is supported on a thrust plate 9 at the place of anchorage. The above-mentioned link 4 may also be formed as a ring rotatably mounted on the outside of the housing 1 and provided with bores for the bolt (see FIG. 1). The rear part of the housing 1 consists of a hydraulic working cylinder 10, which is closed by two screwed-on end plates 11 and 12. A piston 13 can reciprocate inside the cylinder 10. The piston rod 14 forms the traction member for the tensioning device and extends through a bore 15 in the end plate 11 forwardly to the front part of the housing 1. The piston 13 as well as the bore 15 are provided with suitable packing means 16 and 17. Two

ports

18 and 19, to which pressure fluid conduits (not shown) are connected, selectively admit pressure fluid to one or the other side of the piston 13 to move the piston in one or the other direction.

The front end of the traction member 14 is supported and guided axially inside the housing 1 by a guide member 20. The guide member consists of a ring 21 mounted on the traction member 14 and of a forwardly projecting cylindrical sleeve 22 secured to the outer edge of the ring 21. The ring 21 is provided with a projection 66 engaging an axial slot 67 in the housing 1 for axially guiding the member 20 and preventing any movement of rotation thereof and of the piston rod 14 to which it is secured.

At its front end, the traction member 14 has a part 23 of enlarged diameter forming a shoulder 23. A coupling sleeve 24 is rotatably mounted on the traction member 14 at the rear of the shoulder 23'. When sleeve 24 abuts on the shoulder 23', it projects with its cylindrical part 25, whose front end is provided with an internal thread 26, in the direction of the bundle of wires to be stressed. This sleeve 24 is screwed onto the anchor head 27 of the bundle of wires 7 to be stressed. In the illustrated embodiment the sleeve 24 is shown in the position screwed on the anchor head.

A centering bolt 28 is screwed into the front end of the part 22 of the traction rod 14. This bolt cooperates with a corresponding bore 29 in the anchor head 27 in order to bring the wire bundle 7 into the exact axial alignment with the direction of traction.

Behind the coupling sleeve 24, a gear ring 30 and a spring washer 31 are secured to the sleeve 24. The spring washer 31 is screwed to the sleeve 24 by means of pins 32 which pass through bores 33 in the gear ring 30, whilst the gear ring 30 itself is secured with some axial clearance between sleeve 24 and spring washer 31. The coupling sleeve 24, the gear ring 30 and the spring washer are consequently connected together and may be rotated together about the traction member 14 and are axially shiftable within certain limits. One of these limits is formed by the shoulder 23' of the part 23 of the traction member 14, whilst the other limit is formed by the guide member 20. A helical spring 34 is arranged between the front side of the guide ring 21 and the spring washer 31. The helical spring only comes into effect when the sleeve 24 is not yet screwed onto the anchor head 27; for example when the front end of the traction member 14 is moved into contact with the anchor head 27, the spring 34 will abut against a baseplate 35 on the ring 21 and at the same time against the spring washer 31, and will thereby press the coupling sleeve 24 with a predetermined force against the anchor head 27 provided with an external thread 36. When the sleeve 24 is now correctly rotated, the two threads 26, 36 can engage one another and the sleeve 24 may be screwed on the head 27. As soon as the thread of the sleeve 24 has engaged the thread of the head 27, the function of the spring 34 is terminated.

In the represented apparatus the coupling sleeve 24 is screwed onto the anchor head 27 automatically by means of a motor. To this end the gear ring 30 is driven by a pinion 37. The pinion 37 is mounted on a splined shaft 38 for rotation therewith and axial movement along the shaft which is mounted in the housing and is driven in one or the other direction by an oil engine 39 via a chain and chain wheels 40, 41. The pinion 37 penetrates through a recess 68 in thesleeve 22 of the guide member 20 which is secured against rotation. Due to the axial mobility the pinion 37 can move together with the gear ring 30 and the traction member 14, to any position along the path of reciprocation of the traction member 14.

A pointer 42 projects outwardly through the housing 1 from the sleeve 22 and moves along a graduated scale 43. This enables the position of the traction member 14 to be ascertained or the path of stress applied to the wire bundle to be read at any time.

In order to secure the apparatus to the concrete construction, four

hydraulic anchoring cylinders

44, 45, 46, 47 are, in the embodiment shown, mounted on the outside of the housing 1 between

suitable bearing plates

48, 49, 50 and 51 and four identical bearing plates of which only the plate 48 is visible in FIG. 1A.

Holding pins 52 are screwed into the thrust plate 9 on the concrete construction 8. A front plate 53 of the housing 1 provided with openings 69 is pushed over the pins 52. The piston rod 54 projects from the cylinder 44 towards the pin 52 and carries a coupling sleeve 55 at its front end. For connecting the piston rod to the pin 52, the sleeve 55 is pushed over the pin 52 up to a shoulder 56, and then a key 55 is pushed through corresponding perforations in sleeve 55 and pin 52.

Due to the holding cylinders 4447, at least two of which should be provided, the stressing apparatus may be applied and securely attached to the concrete construction 8 before starting a stressing operation. When the traction member 14 is pressed against the anchor head 27, before effecting coupling of the sleeve 25 with the anchor head 27, the holding force of the cylinders .44 to 47 may be overcome, and the apparatus may be aligned with respect to the anchor head 27 which is inclined as the case may be, so that the sleeve 24 may be screwed onto the head 27. As the wire bundles are being stressed, the apparatus then straightens up again. The same applies when the sleeve 24 is released for the purpose of disconnecting the sleeve 24 from the anchor head 27.

FIG. 3 f the drawing shows diagrammatically a modification of the coupling device at the front end of the traction member 14. An extension 60 is screwed into the coupling sleeve 57, which abuts on the shoulders 58 of a stop ring 59 screwed onto the traction member 14. The extension 60, formed as a sleeve, has such an external diameter that it can engage through the bore 61 of the thrust plate 9 into a recess 62 provided in the concrete construction 8 in order to grip the anchor head 63 of a bundle of wires located in the recess. Here, too, the traction member 14, has a centering bolt 64, which may penetrate into a bore 65 of the head 63.

The extension 60 is internally threaded at its front end and may be screwed onto the anchor head 63 by rotating the sleeve 57. The sleeve 57 is driven in exactly the same way as the sleeve 24 of the apparatus shown in FIG. 1.

FIG. 4 of the drawing shows a hydraulic diagram, in zero position, for the automatic drive of a stressing apparatus according to the invention.

A high-pressure pump unit 101 comprises an electromotor 102 for a high-pressure pump 103, a relief valve 104, a relief valve 105, and an oil filter 106 with associated conduits. A and B are pressure fluid connections, T is a return conduit, S a suction pipe and 133 a check valve.

107 designates the actual control device with the

different control valves

108, 109, 110 and 111. Each control valve may be brought into one of the three schematically indicated operating positions, as desired.

Relief valves

112, 113, 114, 115, 116 and 117, pressure gauges 118, 119, 120, 121, 122 and 123, as well as

nonreturn valves

124 and 125 whose functions may be seen from the diagram are provided in the various conduits.

134 indicates the actual stressing device which is provided with two holding presses or

cylinders

126, 126, as well as with a stressing press or cylinder 127. The stressing cylinder is associated with a throttle valve 128, a check valve 129 and a pressure gauge 130. 132 is a relief valve. Finally, 131 designates the oil engine for rotation in one or the other direction of the coupling sleeve of the traction member of the stressing apparatus.

An operating cycle of the automatic stressing apparatus is explained in detail hereinbelow:

The stressing apparatus together with the control device 107 is suspended from a cable and is brought near the place of anchoring of the wire bundle in the concrete construction 8 to be prestressed.

The control device 107 is brought into a position from which the stressing procedure can easily be controlled and supervised. The pressure gauge 130 as well as the

path indicator

42, 43 must be easily visible.

The various conduits of the pump unit 101 are connected to the control device 107 and the pump 103 is set into operation.

The four holding pins 52 are screwed into the thrust plate 9. The housing 1 of the stressing apparatus is pushed over the holding pins 52 and provisionally secured.

The pistons 54 of the four holding cylinders 4447 are extended until they abut on the shoulders 56 of the pins 52. Then the keys 55 are inserted and the holding cylinders are pressurized until the housing 1 abuts tightly on the thrust plate 9.

The traction member 14 is moved forwards and pressed against the anchor head 27. Indicator 42 and scale 43 are set to 0 (zero).

The coupling sleeve 24 is then screwed onto the head 27 until it abuts against the head.

The throttle valve 128 is then closed and the actual stressing of the wire bundle is begun. Up to a certain pressure, operation can be effected via the rapid oil feed, then a switchover takes place to the lower speed. The oil pressure in the stressing cylinder may be read on the pressure gauge 130, and by means of a calibration curve, the tensional force can be determined.

The pressure gauge 121 in the control device serves thereby as control, so long as oil is pumped into the cylinder.

The elongation may be read directly from the scale 43.

After the maximum tensional force is reached, the necessary size or height of the supports for the anchor head 27 may be read from the scale.

Fixing clamps are placed in the housing 1 in predetermined positions and the support members are arranged by means of electromagnetic grippers.

By opening the throttle valve 128, the anchor head 27 is placed on the support members.

Then the holding cylinders 4447 are briefly placed under pressure in abutting pressure direction, the traction member 14 is applied against the anchor head 27 and the coupling sleeve 24 is released and unscrewed.

The fixing clamps for the support members are removed.

Then the traction member 14 is withdrawn until this latter is fully disconnected from the anchor head 27, and the holding cylinders 4447 are released from the holding pins 52.

The stressing apparatus is now ready for the next stressing operation.

When the stressing apparatus is to be used for stressing the wire bundle above the normal stressing path, it will become necessary to use extensions for positioning the housing 1 further away from the concrete construction.

To this end, the anchor head 27 will be temporarily supported.

Then the holding cylinders 4447 are released from the pins 52. By urging the traction member 14 forwardly, the housing 1 of the apparatus moves away from the concrete construction. The housing is moved for such a distance that a gap will be formed between the front end of the housing 1 and the thrust plate 9, which gap is somewhat greater than the extensions to be inserted.

Now the said extensions are placed on the four pins 52.

The housing is then pressed against the extensions and the fixing clamps for the support members are arranged in position.

The holding cylinders 4447 are again attached and the second stage of the stressing operation may begin.

The temporarily arranged support members for the anchor head 27 are removed and replaced by the final, longer support members.

We claim:

1. Wire-tensioning apparatus for use in stressing concrete structures comprising a housing adapted to be supported against one end of a concrete structure, a tensioning unit in ranged at the free end of said traction member for connecting said traction member to an anchor head of a wire bundle, centering means provided at said end of the traction member for axial alignment of the traction member with said anchor head, means for temporarily connecting said housing to the concrete structure, said connecting means including tensioning members arranged at the outside of said housing, the tensioning force of said tensioning members being adjustable, and coupling members for said tensioning members adapted to connect the tensioning members to the concrete structure.

2. Apparatus according to claim 1, in which said stressing unit comprises a hydraulic or pneumatic working cylinder, a piston reciprocating in the cylinder, and a piston rod forming a traction member projecting into said housing, said coupling device arranged at the free end of the traction member including an internally threaded coupling sleeve mounted to rotate on the traction member.

3. Apparatus according to claim 1, in which means are provided for the remote control of said coupling device connecting the anchor head of a wire bundle to said traction member.

4. Apparatus according to claim 3 and comprising motordriven means for selectively rotating said coupling sleeve in one or the other direction.

1 said anchor head.

5. Apparatus according to claim 4, in which said motordriven means comprises a gear'ring which may be brought into driving connection with said coupling sleeve, a driving pinion for said gear ring, said pinion being mounted for rotation on a shaft and axially movable therealong, which shaft extends parallel to the traction member of said tensioning unit, and a driving motor for said shaft.

6. Apparatus according to claim 1, in which said tensioning members attached to the outside of the housing comprise hydraulic or pneumatic working cylinders, having pistons to transmit the tensioning force.

:7. Apparatus according to claim 1, in which said centering means comprise a forwardly projecting centering pin arranged in the center of the front end of said traction member, said centering pin being adapted to engage a central opening in 8. Apparatus according to claim 1, in which said tensioning unit and said tensioning members arranges at the outside of the housing are hydraulically or pneumatically operated working cylinders, said coupling device for the anchor head being also hydraulically or pneumatically operable, and a central control device provided with control valves being provided for controlling the operation of the apparatus.

Claims

1. Wire-tensioning apparatus for use in stressing concrete structures comprising a housing adapted to be supported against one end of a concrete structure, a tensioning unit in said housing, a traction member extending from one end of said tensioning unit into said housing, a coupling device arranged at the free end of said traction member for connecting said traction member to an anchor head of a wire bundle, centering means provided at said end of the traction member for axial alignment of the traction member with said anchor head, means for temporarily connecting said housing to the concrete structure, said connecting means including tensioning members arranged at the outside of said housing, the tensioning force of said tensioning members being adjustable, and coupling members for said tensioning members adapted to connect the tensioning members to the concrete structure.

4. Apparatus according to claim 3 and comprising motor-driven means for selectively rotating said coupling sleeve in one or the other direction.

5. Apparatus according to claim 4, in which said motor-driven means comprises a gear ring which may be brought into driving connection with said coupling sleeve, a driving pinion for said gear ring, said pinion being mounted for rotation on a shaft and axially movable therealong, which shaft extends parallel to the traction member of said tensioning unit, and a driving motor for said shaft.

7. Apparatus according to claim 1, in which said centering means comprise a forwardly projecting centering pin arranged in the center of the front end of said traction member, said centering pin being adapted to engage a central opening in said anchor head.

8. Apparatus according to claim 1, in which said tensionIng unit and said tensioning members arranges at the outside of the housing are hydraulically or pneumatically operated working cylinders, said coupling device for the anchor head being also hydraulically or pneumatically operable, and a central control device provided with control valves being provided for controlling the operation of the apparatus.