WO2012055599A1

WO2012055599A1 - Device for limiting torque

Info

Publication number: WO2012055599A1
Application number: PCT/EP2011/064502
Authority: WO
Inventors: Andreas Eckstein; Mathias Goldt; Marc Schäffer; Arjen Detmer Dijkhuis
Original assignee: Hilti Aktiengesellschaft
Priority date: 2010-10-29
Filing date: 2011-08-24
Publication date: 2012-05-03
Also published as: DE102010043167A1

Abstract

The invention relates to a device for limiting torque, having a head part (10) comprising a rotary engagement means (12) for a setting tool, a threaded part (30) comprising at least one thread (32), and means (40) that transfer torque from the head part to the threaded part and connect the head part to the threaded part, wherein the means for torque transfer fracture at a limit torque, eliminating the connection between the head part and the threaded part. According to the invention, means (50) are provided for the rotationally decoupled transfer of axial forces from the head part to the threaded part.

Description

Principality of Liechtenstein

Device for torque limitation

The invention relates to a device for torque limiting, in particular a tear-off nut or tear-off screw, according to the preamble of claim 1.

There are known tear-off or tear-off screws with a head part and a threaded part, which are connected to each other via a welded connection. When attaching these nuts or screws, a torque is applied to the head part by means of a fastening tool, wherein the torque is transmitted at the beginning of the fastening operation via the welded connection to the threaded portion. If a predetermined limit torque is reached at the end of the fastening process, the head part shears off the threaded part at the welded joint. By this shearing the maximum acting on the threaded part torque is limited.

For example, a breakaway nut is disclosed in US 2002/076295 A1.

Tear off nuts are used in particular for connecting metal parts. By contrast, when using such nuts in concrete anchors reliability problems may arise. In particular, it has been observed that the tear-off nut can prematurely break off when used on concrete anchors.

The object of the invention is to provide a particularly reliable device for the limited transmission of torque.

The object is achieved according to the invention by a device having the features of claim 1. Preferred embodiments are given in the dependent claims. The device according to the invention is characterized in that means are provided for the rotationally coupled transmission of axial forces from the head part to the threaded part.

The invention is based on the recognition that the difficulties encountered in the use of prior art breakaway nuts on concrete anchors are due to the hammering action often required when placing concrete anchors. When hammering in, high impact forces act on the headboard. In the known Abreissmuttern these impact forces but also act on the means for torque transmission. Therefore, the impact forces can damage or at least weaken the means for transmitting torque. This may in particular mean that the means for transmitting torque already break before reaching the limit torque, so that a correct control of the bias voltage when tightening the armature is no longer possible.

This is where the invention starts and provides, in addition to the means for transmitting torque, means for rotationally coupled transmission of axial forces from the head part to the threaded part. These means for transmitting axial forces are connected in terms of power in parallel with the means for transmitting torque. They therefore pass on at least part of the axially directed impact forces from the head part on the threaded part and thus relieve the means for transmitting torque in appropriate mass. The means for the transmission of axial forces are provided for dreenktkoppelten power transmission, that is, in contrast to the means for transmitting torque transmitted at most a fraction of the torque acting on the head part on the threaded part. Thus, substantially all of the torque continues to act on the torque transmitting means, so that the limit torque at which the torque transmitting means breaks continues to apply to the entire device.

Thus, according to the invention, the means for torque transmission are protected from axial forces without substantially changing the torque transmission characteristic of the device. The device according to the invention can therefore also be used, in particular, for concrete anchors in which hammering with corresponding axial forces is frequently required for setting.

Insofar as an axial direction and torques are mentioned here, these details can relate in particular to the same direction, ie the torque relates to a rotation about an axis extending in the axial direction. In particular, that can Drehmomerit and / or refer to the axial direction on a longitudinal and / or axis of symmetry of the device.

The rotary handle can, for example, be an external polygon, in particular an external hexagon.

For example, it can be provided that the means for the rotationally coupled transmission of axial forces have at least one axial stop arranged on the head part for the threaded part. Such an axial stop can transmit axial forces as soon as the threaded part abuts against it. In particular, when the threaded part is a nut, the axial stop may have an annular stop surface for the threaded portion, wherein the annular stop surface is preferably arranged coaxially to the passage opening of the nut.

According to the invention, it can be provided that the threaded part rests against the axial stop already in the axially unloaded state of the device. In this case, the means for the rotationally coupled transmission of axial forces already contribute to the transmission of very small axial forces. But it can also be provided that the threaded portion is spaced from the axial stop in the axially unloaded state. In this case, a particularly good rotational decoupling of the head part and threaded part is given because there is a gap between threaded part and stop. The Axialkraftübertragung takes place in this case only when the axial forces are sufficiently high to deform the device so far that the gap between the threaded part and stop is closed.

A further preferred embodiment of the invention is that the means for transmitting torque have at least one web which connects the head part and the threaded part. Such a web can form a predetermined breaking point, which breaks when the limit torque is reached. Preferably, a plurality of webs are provided, which may be arranged in particular around the longitudinal axis of the device around. With regard to the force symmetry, it is advantageous that the webs are arranged equidistantly.

In principle, the means for torque transmission can be formed by any type of connection between the head part and the threaded part. In particular, the means may be formed by a welded connection. For example, with regard to the design effort, it may be advantageous for the means for transmitting torque to the head part to be arranged radially further outside than the means for rotationally coupled transmission of axial forces. The radial direction may relate in particular to the longitudinal axis of the device. For example, a stop surface may be provided for the transmission of axial forces, which is surrounded in the plan view of webs for transmitting torque.

Furthermore, it is preferred in terms of design complexity that the device comprises a, preferably crown-shaped, holding element, which comprises the head part, the means for transmitting torque and a receptacle for the threaded portion, wherein the means for transmitting torque connect the head portion and the receptacle. In such an embodiment, the head part, the means for transmitting torque and the receptacle which can receive the threaded part together form a unit, the so-called holding element. The device can thus be formed in two parts in a particularly simple manner.

It is particularly preferred that the threaded part is received in the receptacle at least positively. Alternatively or additionally, however, the receptacle can also receive the threaded part frictionally and / or cohesively. For example, the receptacle may have an internal polygon, in particular a hexagon socket, and the threaded part has a corresponding external polygon, in particular hexagon.

For example, the device according to the invention can be designed as a tear-off nut. Accordingly, it is preferable that the thread of the thread part is an internal thread. The inventive device can also be designed as a departure screw, in which case the thread of the threaded part is an external thread.

The invention will be explained in more detail below with reference to preferred embodiments, which are shown schematically in the accompanying figures. They show schematically:

Fig. 1 is a side view of an embodiment of an inventive device;

Fig. 2 is a view of the device of Figure 1 from above. a cross-sectional view A-A 'according to FIG. 2 of the device of FIG. 1;

Fig. 4 is a view of the device of Figure 1 from below. and Fig. 5 is a view of the device of FIG. 1 from below, wherein in contrast to Fig. 4, the threaded portion is not shown.

An exemplary embodiment of a device according to the invention designed as a tear-off nut for torque limiting is shown in FIGS. 1 to 5.

As the figures show, the device has a crown-shaped holding element 1, which comprises a head part 10, a foot-side receptacle 60 and at least one web 43. The at least one web 43 connects the head part 10 and the receptacle 60 and thereby forms means 40 for transmitting torque. The head part 10, the at least one web 43 and the receptacle 60 may in particular be integrally formed and / or have a metal material.

As is shown in particular in FIGS. 1, 3, 4 and 5, a receiving opening 63 is formed in the receptacle 60, in which, when the device is assembled, a threaded part 30 designed as a hexagon nut is received in a form-fitting manner with a thread 32 designed as an internal thread. For the positive torque transmission from the receptacle 60 to the threaded portion 30, the receiving opening 63 has a hexagon socket, which corresponds to an external hexagon formed as a hexagon threaded part 30. Instead of a hexagon, another polygonal structure can also be provided. Additionally or alternatively, a non-positive connection may be present.

As FIG. 2 shows in particular, the head part 10 has a rotary engagement means 12 designed as an external hexagon, by means of which a torque can be transmitted form-fittingly to the head part 10 by a setting tool, not shown. As particularly shown in FIG 2, a plurality of webs 43 are provided for transmitting torque from the head portion 10 on the receptacle 60 and thus on the threaded portion 30 between the head portion 10 and receptacle 60, wherein in the illustrated embodiment, each web of the rotary control means 12, a web 43 is omitted. Thus, a total of six webs 43 are present in the example shown.

The threaded part 30 and the head part 10 are arranged coaxially and define a common longitudinal axis 5 of the device. The head part 10 has a through hole 15, which is aligned with the threaded bore 35 of the threaded part 30, so that the device seen in the longitudinal direction (see Fig .. 2) is continuous.

As can be seen in particular in FIG. 3, the head part 10 has an annular axial stop 51, which permits an axial movement in the receiving opening 63 recorded threaded part 30 is limited relative to the head part 10. The axial stop 51 forms means 50 for the rotationally coupled transmission of axial forces from the head part 10 to the threaded part 30.

During operation, a torque is exerted on the head part 10 by means of a setting tool via the rotary control means 12. This torque is transmitted via the webs 43 to the receptacle 60 and from the receptacle 60 in turn to the threaded portion 30. On the other hand, the means 50 for rotationally coupled axial force transmission formed as an axial stop 51 do not appreciably participate in the torque transmission.

Act during operation axial forces, i. Forces with a component in the direction of the longitudinal axis 5, on the head part 10, for example due to hammer blows on the head part 10, these axial forces are primarily on the axial stop 51, i. the means 50 for torsionally coupled axial force transmission, transmitted to the threaded portion 30. On the other hand, the webs 43 take on the power transmission at most insignificantly, due to frictional forces on the inner wall of the receiving opening 63, part. The webs 43 and thus the means 40 for torque transmission are consequently not significantly affected by axial forces according to the invention.

If the torque applied to the head part 10 reaches a predetermined limit torque, the webs 43 tear, with the result that the head part 10 is separated from the receptacle 60 and no further torque transmission takes place on the threaded part 30. The device therefore acts as a torque limiting Abreissmutter.

Claims

cLAIMS

1 . Device for torque limiting, with

a head part (10) which has a rotational support means (12) for a setting tool, a threaded part (30) which has at least one thread (32), and

Means (40) for transmitting torque from the head part (10) to the threaded part (30) connecting the head part (10) and the threaded part (30), the means (40) for

Torque transmission at a limit torque canceling the connection between the head part (10) and threaded part (30) break,

characterized,

in that means (50) for the rotational coupling of axial forces from the head part (10) to the threaded part (30) are provided.

2. Apparatus according to claim 1, characterized in that

in that the means (50) for rotationally coupled transmission of axial forces have at least one axial stop (51) for the threaded part (30) arranged on the head part (10).

3. Device according to one of the preceding claims, characterized

in that the means (40) for transmitting torque comprise at least one web (43) connecting the head part (10) and the threaded part (30).

4. Device according to one of the preceding claims, characterized

in that the means (40) for transmitting torque to the head part (10) are arranged radially further outward than the means (50) for the rotational coupling of axial forces.

5. Device according to one of the preceding claims, characterized

in that it comprises a crown-shaped holding element (1) which comprises the head part (10), the means (40) for transmitting torque and a receptacle (60) for the threaded part (30), the means (40) for transmitting torque to the head part (10 ) and connect the receptacle (60).

6. Apparatus according to claim 5, characterized in that

that the threaded part (30) is received in the receptacle (60) at least positively.

7. Device according to one of the preceding claims, characterized

that the thread (32) of the threaded part (30) is an internal thread.