WO1999042252A1 - Dynamometric key for tightening a threaded element with a defined torque - Google Patents

Abstract

The invention relates to a dynamometric key for tightening a threaded element with a defined torque. Said dynamometric key comprises a key body (2) on whose one axial end a coupling element (3) is carried. The coupling element is provided for connecting to the threaded element which is to be screwed down. A handle element (4) which is provided for turning the key body (2) is carried on the other axial end thereof. The handle element (4) can rotate around the key body axis (X) and is held on the key body (2) in such a way that it can be axially displaced. In addition, the handle element is axially pressed against a stop (7), said stop being provided on the key body (2), by an elastic element (6) in such a way that torque can be transmitted from the handle element (4) to the stop (7) and thus to the key body (2).

Description

 1 Description:

Torque wrench for tightening a threaded element with a defined torque

The present invention relates to a torque wrench for tightening a threaded element with a defined torque, with a key body which carries at its one axial end a coupling element for connection to the threaded element to be screwed down and at its other axial end a handle element for rotating the key body.

Torque wrenches of this type are known and are used to tighten screws, threaded bolts or the like with a defined tightening torque and in this way to connect two components with a defined clamping force. For this purpose, in the known torque wrenches, a friction clutch is usually provided between the key body and the handle element, which can transmit a specific, maximum torque from the handle element to the key body and slips when this maximum torque is exceeded.

The known torque wrenches have proven their worth in practice. The disadvantage, however, is that it is relative

REPLACEMENT BLUE (RULE 26) complicated in construction and therefore expensive.

The object of the invention is therefore to provide a torque wrench of the type mentioned, which is simple in construction and inexpensive to manufacture.

This object is achieved in that the handle element about the key body axis is rotatably and axially displaceably held on the key body, wherein it is pressed axially by an elastic element against a stop provided on the key body, so that a torque from the handle element to the stop and thus the key body can be transmitted, and that the contacting contact areas on the grip element and stop are designed and cooperate in such a way that when a threaded element is screwed on, a relative rotational movement of the grip element relative to the stop to an axial movement of the grip element on the key body against the spring force of the elastic element leads.

According to the invention there is thus a frictional connection between the handle element and the stop provided on the key body in a similar manner to the known torque wrenches, via which a torque can be transmitted from the handle element to the stop and thus to the key body, the amount of the transmissible torque of depends on the axial force with which the grip element is pressed against the stop by the elastic element.

If the maximum transferable torque is exceeded, the grip element leads a relative to the stop Rotational movement, which brings about an axial movement of the grip element against the spring force of the elastic element due to the positive guidance formed by the contact areas. If the elastic element is formed, for example, by a plate spring assembly, this is compressed by the axial movement of the handle element, with the result that its clamping force and thus also the torque which can be transmitted from the handle element to the key body is increased.

In other words, a rotation of the handle element relative to the key body causes a change in the maximum transmissible torque, the transmissible torque corresponding to the respective relative angular position between these two components being exactly determined.

To screw, for example, a threaded bolt into a threaded bore, the torque wrench according to the invention is first connected to the threaded bolt via its coupling element, so that the key body axis and the threaded element axis are aligned. The torque wrench is then rotated via the handle element, which assumes an initial position with respect to the key body, in which only a comparatively low torque can be transmitted from the handle element to the key body, as a result of which the threaded bolt is screwed into the threaded bore. If the frictional moment of resistance, which is opposed to the screwing process, exceeds the torque that can be transmitted from the grip element to the key body, this leads to the fact that only the grip element is rotated further and, due to the forced guidance through the contact areas, an axial movement against the spring force of the elastic see Elements, which increases the maximum transferable torque. This process continues until the grip element relative to the key body assumes the rotational position corresponding to the desired tightening torque, which can be read off, for example, by scaling. If you now let go of the grip element, it is returned to its starting position by the restoring force of the elastic element.

As a result, a threaded element with the desired tightening torque can be screwed tight with the torque wrench according to the invention, the torque wrench being simple in design, since only the contact areas on the grip element and stop need be designed accordingly. In the simplest case, a control curve can be provided on one of the two components, for example in the form of an inclined surface, which cooperates with a control edge on the other component. The torque wrench according to the invention is thus simple and inexpensive to manufacture.

According to one embodiment of the invention, it is provided that the contact areas on the handle element and stop which cooperate in each case to bring about an axial movement of the handle element are designed in such a way that they come into contact flatly. This results in a low surface pressure. In particular, the contact areas can be designed to be complementary to one another.

In a further embodiment of the invention it can be provided that the contact areas have an inclination which changes in the circumferential direction with respect to the key body axis. Hereby it is achieved that the size of the torque transferable from the handle element to the key body changes not only with the biasing force of the elastic element, but also from the respective angle of inclination, so that there is no linear relationship between the rotation of the handle element relative to the key body and the size of the transferable Torque exists. This configuration opens up the possibility of establishing a progressive or degressive relationship between the angular path of the grip element and the increase in the transmissible torque, in that the inclination of the contact areas becomes correspondingly steeper or flatter.

It is also possible to subdivide the contact areas on the handle element and stop in the circumferential direction into a plurality of contact area sections, the contact area sections each having different inclinations with respect to the key body axis within a contact area.

According to a preferred embodiment of the torque wrench according to the invention it is provided that a plurality of contact areas are provided on the handle element distributed over the circumference of the key body, which simultaneously engage with corresponding contact areas on the stop, so that a torque is distributed evenly over the circumference from the handle element to the stop becomes. For example, two diametrically opposed contact areas can be provided on the grip element, which simultaneously engage corresponding contact areas at the stop. In a further embodiment of the invention, it can be provided that the axial end of the key body opposite the coupling element is designed as a pin onto which the elastic element and the grip element are pushed, the arrangement of the grip element / elastic element by the stop which is at the free end attached to the pin, in particular welded to the pin or screwed onto the pin, is tensioned against a shoulder of the key body. This design ensures simple assembly of the torque wrench according to the invention.

With regard to further advantageous refinements of the invention, reference is made to the subclaims and the following description of an exemplary embodiment with reference to the accompanying drawing. In the drawing shows

FIG. 1 shows a front view of an embodiment of a torque wrench according to the invention in its starting position,

FIG. 2 shows the torque wrench from FIG. 1 with indicated inner contours,

FIG. 3a shows the torque wrench from FIG. 1 with the handle element rotated,

3b shows the forces which occur at the contact areas between the grip element and the stop of the torque wrench from FIG. 3a, FIG. 4 the torque wrench from FIG. 3 with indicated inner contours,

FIG. 5 shows the torque wrench from FIG. 1 with an attached panel,

Figure 6 is a perspective view of the stop of a torque wrench according to the invention with the contact areas and provided

7 shows a part of a grip element with contact areas provided thereon.

In the figures, an embodiment of a torque wrench 1 according to the invention is shown, which is intended for tightening threaded bolts etc. with a defined torque. The torque wrench 1 has a cylindrical key body 2, which carries at its one axial end a coupling element 3 in the form of an inner square for connection to the threaded element to be screwed down and at its other axial end a handle element 4 for rotating the key body 2. The grip element 4 is axially displaceable on a pin 5 of the key body 2 and rotatable about the key body axis X and is supported by a plate spring assembly 6 previously pushed onto the pin 5, which bears against a shoulder 2a of the key body 2. A stop 7 is screwed onto the free end of the pin 5 so that the grip element 4 is braced with the plate spring assembly 6 and thus the grip element under the pretensioning force of the plate spring assembly 6 against the Stop 7 is pressed. This creates a frictional connection between the grip element 4 and the stop 7, by means of which a torque of a certain size can be transmitted from the grip element 4 to the stop 7 and thus to the key body 2.

The contact areas 8, 9 that come into contact with one another on the grip element 4 and stop 7 are designed to be complementary to one another, so that they come into abutment against one another in each case and thus the surface pressure between the components 4, 7 is low, and they act in the manner of run-up slopes in this way together that when screwing a threaded element a relative rotational movement of the grip element 4 with respect to the stop 7 leads to an axial movement of the grip element from the starting position shown in FIG. 1 away from the stop 7, whereby the plate spring assembly 6 is compressed, as indicated in FIG. 3a. This has the consequence that the spring force F _F , with which the handle element 4 is pressed against the stop 7, increases, so that a greater torque can be transmitted from the handle element 4 to the stop 7 and thus the key body 2.

The mode of operation of the torque wrench 1 according to the invention is clear from the overview of FIGS. 1, 3 and 3a, in which the forces acting between the grip element 4 and the stop 7 are shown. In FIG. 3a, the spring force with which the gripping element 4 is pressed against the stop 7 by the plate spring assembly 6 is denoted by F _r . This spring force F _r can be divided into a component F _{ra which is} perpendicular to the press nip and a component F _rp which extends in the direction of the press nip. From the normal to the press The force component F _FN standing in the gap can be determined via the friction coefficient between the grip element 4 and the stop 7, the friction force F _R acting in the press gap, which counteracts a relative movement between the grip element 4 and the stop 7.

If a torque M is introduced into the grip element 4, this results in a force F _M directed perpendicular to the spring force F _r in the press nip, which force can also be divided into a component F _MN directed perpendicular to the press nip and a component F _HS directed parallel to the press nip. This force component F _MN is opposed to the frictional force F "and the spring force component F _rs with the result that the grip element 4 begins to rotate relative to the stop 7 on the pin 5 when the force component F _MN becomes greater than the sum of the Frictional force F _R and the spring force component F _FS acting in the direction of the press nip. The handle element 4 then rotates until the spring force F _r has increased to such an extent that the axial movement of the handle element 4, which is inevitably associated with the rotary movement, increases that the forces acting in the press nip plane are in equilibrium.

From the above explanation it is clear that the magnitude of the torque, which can be transmitted at most via the frictional engagement between the grip element 4 and the stop 7, depends on the spring force F _r with which the grip element 4 is pressed against the stop 7, and the mean Radius and the inclination of the contact areas 8, 9 coming into contact with one another with respect to the key body axis X. Each relative angle of rotation position between the grip element 4 and the stop 7 corresponds to a spring force F _F and the inclination of the contact areas 8, 9 coming into contact with one another on the grip element 4 and stop 7 exactly defined, maximum transferable torque. The relative angle of rotation position between the grip element 4 and the stop 7 and thus the maximum transferable torque M can be read, for example, using a scale 11 provided on the stop 7 and the grip element 4 or a cover 10 connected to the grip element 4, as shown in FIG 5 is shown.

In order to be able to introduce a torque as evenly as possible over the circumference into the key body 2, as shown in FIG. 7, two contact areas 8, which are diametrically opposite with respect to the key body axis X, are provided on the grip element 4, which simultaneously with corresponding contact areas 9 of the stop 7 are engaged. 6 and 7 that the contact areas 8 on the grip element 4 and the corresponding contact areas 9 on the stop 7 are each divided into three contact area sections 8a, 8c, 9a, 9c, only one contact area section 8a, 8c each each contact area 8 of the grip element 4 engages with a corresponding, at least partially complementary contact area section 9a, 9c of the associated contact area 9 on the stop 7.

To screw, for example, a threaded bolt into a threaded bore, the torque wrench 1 according to the invention is first connected to the threaded bolt via its coupling element 3, so that the key body axis X and the threaded element axis are aligned with one another. Then the torque Key 1 via the grip element 4, which, relative to the key body 1, assumes the starting position shown in FIG. 1, in which the contact area sections 8a, 8c of the grip element 4 and stop 7 engage with one another and only a comparatively low torque from the grip element 4 onto the key body 2 can be transferred, rotated, whereby the threaded bolt is screwed into the threaded bore. If the frictional moment of resistance, which is opposed to the screwing process, exceeds the torque that can be transmitted from the grip element 4 to the key body 2, this leads to the fact that only the grip element 4 is rotated further and, due to the forced guidance through the contact area sections 8a, 9a, simultaneously executes an axial movement , by which the plate wheel package 6 is compressed, with the result that its pretensioning force and thus also the maximum torque that can be transmitted from the grip element 4 to the key body 2 is increased. This process continues until the grip element 4 assumes the rotational position corresponding to the desired tightening torque relative to the key body 2, which can be read off via the scaling. The maximum spring travel of the plate spring assembly 6 is selected such that it runs on blocks before the contact surface sections 8a, 9a disengage, so that a high level of operational safety is ensured.

If one releases the grip element 4 after tightening the threaded element, it is returned to its starting position by the restoring force of the plate spring assembly 6.

Furthermore, contact area sections 8c, 9c are formed on the threaded element 4 and stop 7, which are used to release the cooperate with each other and for this purpose have a corresponding inclination, which is opposite to the inclination of the contact area sections 8a, 9a, which cooperate with each other for tightening the threaded element. In an optimal manner, the contact areas 8, 9 are each formed center symmetrically, so that the contact area sections 8a, 9a; 8c, 9c, for example, can be used both for tightening a right-hand thread element and for loosening a left-hand thread element.

Claims

13 Expectations: Torque wrench for tightening a threaded element with a defined torque Torque wrench for tightening a threaded element with a defined torque, with a key body (2), which has a coupling element (3) at one axial end for connection to the threaded element to be screwed and at its other axial end a handle element (4) for rotating the key body ( 2) carries, characterized in that the grip element (4) about the key body axis (X) is rotatably and axially displaceably held on the key body (2), wherein it is axially by an elastic element (6) against a stop provided on the key body (2) (7) is pressed so that a torque can be transmitted from the grip element (4) to the stop (7) and thus to the key body (2), and that the contact areas (8, 9) coming into contact with one another on the grip element (4 ) and stop (7) are designed and cooperate in such a way that when a threaded element is screwed on, a relative rotary movement of the grip element ( 4) with respect to the stop (7) to an axial movement 14 supply of the handle element (4) on the key body (2) against the spring force of the elastic element (6) leads. Torque wrench according to Claim 1, characterized in that the contact regions (8, 9) on the handle element (4) and stop (7) which cooperate in each case to bring about an axial movement of the handle element (4) are designed such that they come into contact flatly. Torque wrench according to Claim 2, characterized in that the contact regions (8, 9) on the handle element (4) and stop (7) which cooperate to bring about the axial movement of the handle element (4) are designed to be complementary to one another. Torque wrench according to one of claims 1 to 3, characterized in that the contact areas (8, 9) have an inclination which changes in the circumferential direction with respect to the key body axis (X). Torque wrench according to one of claims 2 to 4, characterized in that the contact areas (8, 9) on the grip element (4) and stop (7) are each divided in the circumferential direction into a plurality of contact area sections (8a, 8b, 8c, 9a, 9b, 9c ), the contact area sections (8a, 8b, 8c, 9a, 9b, 9c) each having different inclinations with respect to the key body axis (X) within a contact area (8, 9). 15 6. Torque wrench according to one of claims 1 to 5, characterized in that distributed over the circumference of the key body (2) a plurality of contact areas (8) on the handle element (4) are provided, which are simultaneously engaged with corresponding contact areas on the stop (7) , so that a torque evenly distributed over the circumference is transmitted from the grip element (4) to the stop (7). 7. Torque wrench according to claim 6, characterized in that on the grip element (4) and stop (9) two diametrically opposite with respect to the key body axis (X) opposite contact areas (8, 9) are provided. 8. Torque wrench according to one of the preceding claims, characterized in that the coupling element (3) opposite axial end of the key body (2) is designed as a pin (5) onto which the elastic element (6) and the handle element (4) are pushed are, the arrangement of the grip element / elastic element by the stop (7), which is detachably attached to the free end of the pin (6), in particular screwed onto the pin (5), against a shoulder of the key body (2). 9. Torque wrench according to one of claims 1 to 8, characterized in that the elastic element as 16 Spring element, in particular as a plate spring assembly (6).