EP0969948B1 - Screwing element - Google Patents

Abstract

In a screwing element (1) for accommodation of a fastener head (5) of a fastener (6) there are provided jaws (3, 4) for seizing the fastener head. The jaws (3, 4) can be axially inserted into or withdrawn from the holder (2), wherein the jaws in the withdrawn position can be pivotably forced apart into open position. At their free end the jaws are provided with incisions (15, 16) and, adjoining these, with gripper-like parts (17, 18) jutting outwardly toward the central axis for the purpose of engaging mechanically and/or frictionally with the fastener head (5) from behind.

Description

The invention relates to a screwdriver element for holding and rotating a fastener with several successive beacons in the circumferential direction for gripping the fastener, wherein the jaws engage in a sleeve-like holder and in cooperation with this holder in a first end position for holding the fastener in the radial direction can be pressed apart and in a second end position with axial and / or radial force by positive action of the holder in the radial direction against each other are pushable.

Such screwdriver elements have become known in various versions. In As a rule, such screwdriver elements have a recess for receiving the fastener head on, the recess seen in the axial direction in cross-section on the Cross section of the fastener head is adjusted so that the torque when screwing in Fastener can be transferred. A fastener is therefore with its head in the recess guided in such a screwdriver element in the axial direction. By additional Arrangement of resilient pins or balls can be prevented, for example the head of a fastener automatically detaches after insertion into the screwdriver element. A loss protection is thus guaranteed at least temporarily. But if such Fastener is to be driven into a corresponding workpiece, then one is also required axial power transmission, so that in a screwdriver element again corresponding Stop elements must be provided to limit movement in the direction of To effect screwdriver element. Because the diameter of the threaded Shank of the fastener is usually much smaller than the diameter of the fastener head, As a rule, even a centering for the shaft has to be created, at all to be able to properly attach the fastener.

A handling device for a drilling process is also known (FR 15.845 E), at which the free end of a drill shank is to be clamped around a rotary drive effect and to be able to hold the drill accordingly. Between the swiveling ones Jaws and the free end of the drill shank are additional holding parts. To the Tightening the drill between the jaws requires a wheel to be twisted, causing a Screw spindle is moved in the axial direction. By withdrawing one Middle part of the cheeks are pushed apart in the rear area, so that they are in the front, freely projecting area are pressed against each other. Such a construction can possibly be used if a drill is used for a large number of holes should be clamped, but not if a large number of screws are in order have to be screwed in.

Furthermore, an arrangement for holding a threaded bolt is known (US 2,434,354 A) which corresponds to the preamble of claim 1. at this construction gives no possibility to shape and / or a fastener head To be able to record non-positively and then also a proper rotary drive to effect. A rotary drive with such a construction is only possible if either We captured entire thread from the jaws so that the threaded bolt no longer in the jaws can be screwed in, or if there is a kind between the jaws There is a stop for the threaded bolt.

The present invention has therefore set itself the task of a screwdriver element of the beginning to create mentioned type, which has a fastener head or sections of a fastener head secured when placing a fastener in the axial direction and in the radial direction quickly captured and holds behind, until the final tightening of the Fastener.

According to the invention this is achieved in that incisions or at the free end region of the jaws Recesses for the positive and / or non-positive reception of one on the fastener arranged fastener head are formed, and that at the free end of the jaws to the Incisions or recesses then towards or away from the central axis cantilevered, claw-like parts for additional positive and / or non-positive, up to for the final screwing in of the fastener effective detection of sections of the Fastener head are formed, and that on the inside of the bracket and / or on the The outer surface of the jaws is formed with ramp surfaces running at an acute angle to the central axis are, the jaws by axial pressing into the holder due to the ramp surfaces are automatically pushable against each other.

With the screwdriver element according to the invention, the fasteners to be used are in the area of the fastener head so clamped that they are in the axial direction. can no longer be moved can that during the entire setting process in the axial direction with the screwdriver element stay aligned and thus enable optimal driving of a screwing tool becomes. As a result of the radial compression of corresponding jaws, not only can Fastener head can be grasped exactly, but also a corresponding reaching behind the Fastener head is possible without additional stop elements and spring-return Bolts or balls are needed.

The invention allows the jaws to be forced to close with simple means only by axially pushing in the fastener, the fastener head acts accordingly on the cheeks. If then even more axially during the setting process If pressure comes from the insertion tool, the acute-angled ones Ramp surfaces an additional radial force component, so that the fastener head when Fastening process of the fastener is clamped even more powerfully.

To ensure a particularly good alignment between the screwdriver element and the fastener and to allow an exact clamping of the fastener head, it is provided that the Incisions or recesses on the jaws at least approximately the cross section of the Edge area of the fastener head to be detected or a collar formed on it correspond. The screwdriver element or the jaws of the same can be particularly attached to one trained fasteners are adjusted so that a for a particular application very special screwdriver element is available, with which the fasteners are also optimal can be placed.

To do a drilling process, a thread forming process or simply screwing in a Fastener to also ensure proper torque transmission, it is proposed that on the jaws in the area of the incisions or recesses or in Axial direction offset to these or openings on the gripper-like parts or profiles for attacking the fastener head or on sections thereof are provided. Thus, in addition to the form-fitting holders through the jaws causes an optimal transmission of the torque, namely in the particular Areas of the jaw formations of a tool can be provided.

In this context, it is advantageous that the jaws in the direction of their open position are spring loaded. This means that the jaws are always in the open position the pivoted position so that no problems with the insertion of the next fastener occur.

To ensure that the jaws are not in place until a fastener is ready come into engagement on the surface of the workpiece, it is provided that the thickness of the gripper-like parts seen in the axial direction of the screwdriver element is smaller than the axial Length of a section on a fastener head, the shaft side to a circumferential on the fastener head trained covenant. The bottom end of the jaws and thus the gripper-like parts are therefore still at an appropriate distance from the Surface of the workpiece so that the fastener head to the immediate final Setting can be held without scratching the workpiece surface.

So that a perfect power transmission can take place, it is advantageous if both at the Bracket as well as on the jaws acute-angled ramp surfaces are provided.

In a special constructive variant it is further provided that the jaws on their in the ends of the sleeve-like holder protrude radially inwards, which in a radially circumferential groove of one in the screwdriver element axially displaceable and in engage different locking positions fixable bolt, this bolt through axial pressure and / or tensile action on the jaws is adjustable together with these. The Jaws are not only secured in the axial direction and are therefore held captive, in cooperation with the bolt, this can also result in a concrete End opening position and end closing position are brought. Because the cheeks in her remain an end position in the closed position, the fastener head after Do not reinsert between the jaws even when mounting downwards fall out. In this context, it is advantageous that the bolt at least is locked in place in the two end positions of the jaws.

For this purpose, it is proposed that the bolt have at least two through circumferential grooves Has formed locking points, with a spring-loaded on the sleeve-like holder Pen or ball is held, which or which in the corresponding circumferential Engages groove. This creates safe rest areas that prevent unwanted adjustment prevent the jaws from opening and closing.

To achieve an optimal interaction between the bolt and the form and / or non-positively interacting jaws with the bolt is proposed that the bolt on its to the groove for engagement of the cams formed on the jaws adjoining section adapted to the inner cross section of the jaws in the closed state is, the transition between the groove and the end part of the bolt and the corresponding Areas of the jaws are spherical. This is not only an exact guidance between the pin and the jaws, but also an exact pivoting possibility guaranteed without causing canting and thus malfunctions can come with the screwdriver element.

The construction of a screwdriver element according to the invention results in still more technical possibilities. So it is possible with a special embodiment that in A tool for an internal attack is formed in the center between the jaws. In one in such cases, the jaws are practically only for holding and for axial alignment of the fastener is required, whereas the drive for screwing in takes place via an internal attack can. With such a construction, it is particularly advantageous if the tool for an internal attack at the free end of the movable in the sleeve-shaped holder Bolzens is formed or arranged. This bolt moves together with the Bake and always takes the same axial position with respect to the jaws, so it is very it is easy to equip the free end of this bolt with the corresponding internal attack. Since the fastener head is held in the axial direction, the internal attack cannot be pressed out of the corresponding recess on the fastener head. Thereby a relatively high torque can be transmitted, even if the measure of the axial Intervention of the internal attack is relatively small.

In an advantageous embodiment, it is proposed that the jaws be replaced by a in a groove on the outer circumference of the jaws in the area of the inwardly projecting cams inserted O-ring are resiliently pressed against each other, so that the jaws in their out Bracket extended position are pressed apart in the open position. In order to a structurally very simple variant is created, which on the one hand has the resilient effect causes and on the other hand a corresponding mounting of the jaws against the Produces bolts.

Another embodiment provides that between the jaws in the area of their free ends Compression springs are used so that the jaws are guided out of the holder Are pressed apart into the open position. Through these measures practically the same effect is achieved, since the aim of both versions is to achieve that the protruding into the holder ends of the jaws or their cams constantly remain pressed against the bolt.

In order to achieve an optimal mounting of a fastener head used, it is proposed that that the gripper-like parts each run over the entire sector of the jaws are. It is therefore the broadest possible bracket on the circumference of the fastener head guaranteed. An optimal and very simple construction is also given if two approximately jaws are provided over an angular range of 180 °.

Fig. 1

einen Schnitt durch ein Schrauberelement, wobei die Backen in geschlossenem Zustand dargestellt sind;

Fig. 2

das gleiche Schrauberelement, ebenfalls in einem Längsschnitt dargestellt, wobei sich die Backen in ihrer Öffnungsstellung befinden;

Fig. 3

eine Ansicht eines Befestigers, welcher mit einem erfindungsgemäßen Schrauberelement gesetzt werden kann;

Fig. 4 und Fig. 6 bis Fig. 9

jeweils Längsschnitte durch ein Schrauberelement gemäß den Fig. 1 und 2 mit einem eingesetzten Befestiger, wobei verschiedene Stellungen der Backen innerhalb des Schrauberelementes aufgezeigt sind;

Fig. 5 und Fig. 10

Schnitte nach den Linien V-V bzw. X-X in den Fig. 4 und 9;

Fig. 11

ein Schrauberelement gemäß einer anderen Ausführungsvariante, wobei gegenüber der Ausführung nach den Fig. 1 und 2 lediglich die Federmittel zur Halterung in der Öffnungsstellung geändert sind.

Further features according to the invention and special advantages are explained in more detail in the following description with reference to the drawings. Show it:

Fig. 1

a section through a screwdriver element, wherein the jaws are shown in the closed state;

Fig. 2

the same screwdriver element, also shown in a longitudinal section, with the jaws in their open position;

Fig. 3

a view of a fastener which can be set with a screwdriver element according to the invention;

4 and 6 to 9

in each case longitudinal sections through a screwdriver element according to FIGS. 1 and 2 with an inserted fastener, different positions of the jaws being shown within the screwdriver element;

5 and 10

Sections along lines VV and XX in Figures 4 and 9;

Fig. 11

a screwdriver element according to another embodiment variant, with only the spring means for holding in the open position being changed compared to the embodiment according to FIGS. 1 and 2.

The screwdriver element 1 according to FIGS. 1 and 2 consists essentially of a sleeve-like Bracket 2 and two jaws 3 and 4 and is used to hold a fastener head 5 and for holding the same or for driving the same and thus for screwing in a Fastener 6. The fastener 6 is with a corresponding shaft 7 and a thread 8 and can optionally also be equipped with a drilling part 9. The fastener head 5 has a collar 10 which extends from the support surface 11 by the length B. of the head is spaced. In the example of a fastener shown here is below the Federal 10 a section 12 is provided, which is smaller in size than that Bund 10 and is practically completely covered by this. Section 12 is with a Tool attack 13 provided, here for example with a hexagon.

With the screwdriver element 1 according to the invention, a possibility should now be created a fastener 6 during a drilling and / or thread forming process and / or during of a screwing process to keep it firmly and axially aligned and the corresponding To transmit torque from the screwdriver element to the fastener 6.

As already mentioned, two jaws 3 and 4 are present, being within the scope of the invention also several successive jaws in the circumferential direction for gripping the fastener head 5 can be provided. The jaws 3, 4 engage in the sleeve-like holder 2 and can be closed or pushed apart in cooperation with the same.

The jaws 3, 4 are in their one end position (FIG. 2) for inserting a fastener head 5 can be pressed apart in the radial direction. With axial force on the Baking 3, 4 in the direction of arrow 14 is due to the positive action between the holder 2 and jaws 3, 4 achieved that the jaws 3, 4 are forced against each other in the radial direction are pressed (position according to FIG. 1). At the free end of the Jaws 3, 4 are provided with cuts 15, 16 with which the shape and / or non-positive reception of a fastener head 5 or sections of one Fastener head can be effected. 3, only the the collar 10 forming section of the fastener head 5 in the incisions 15, 16 of the Jaws 3, 4 added. The incisions or corresponding recesses of others Close the mold at the free end of the jaws 3, 4, projecting towards the central axis, gripper-like parts 17, 18 to thereby create a possibility of fastening head 5 or sections thereof, e.g. the federal government 10, positive and / or non-positive engage behind.

The incisions 15, 16 on the jaws 3, 4 correspond at least approximately to the cross section the edge region of the fastener head 5 to be detected or that formed on it Federal 10. On the gripper-like parts 17, 18 are training 19, 20 one Tool provided for attacking the fastener head 5 or the tool attack 13 in the area of section 12.

4 and 5 can be seen in this connection, the fastener head 5 in the position of the screwdriver element 1, as is also shown in FIG. 1, firmly clamped between the two jaws 3 and 4, the gripper-like parts 17, 18th reach behind or reach under the collar 10 and with these gripper-like parts on the Support tool attack 13 of fastener head 5. In this way clamped the fastener 6 until it is finally screwed into the workpiece by the screwdriver element are kept clamped, since the part of the fastener head 5 engages below gripper-like parts 17, 18 do not come to rest on the workpiece surface can. If then after setting the fastener 5, the screwdriver element 1 in the direction of the arrow 21 is pulled away from the fastener 6 or from the fastener head 5, the Jaws 3, 4 pulled out of the holder 2 and finally come into a position as shown in Figs. 9 and 10. The two jaws 3 and 4 are in this position so far apart in their open position that the fastener head 5 is released becomes. Now the screwdriver element can be lifted upwards in the direction of arrow 21 and is thus for receiving the next fastener 6, which is only with the fastener head 5 must first be pressed into the screwdriver element, prepared. Through the axial load on the jaws 3, 4 they are pushed into the holder 2, so that the jaws 3, 4 finally reach the closed position in which the fastener head 5 is recorded.

The jaws 3, 4 are thus shaped and / or by an axial movement in the sleeve-like holder 2 non-positively pivotable in its closed or open position. The easiest is the version when a positive locking is achieved in the closed position and in the open position next to the positive connection by a corresponding spring a frictional connection is also provided. The jaws 3, 4 are therefore in the direction of their open position expediently carried spring-loaded, the jaws 3, 4 in the examples 1 and 2 by a inserted in a groove on the outer circumference of the jaws 3, 4 O-ring 22 are pressed resiliently against each other, in the area of their in Bracket 2 protruding ends. This will cause the jaws to move over with their Bracket protruding ends are pressed apart in the open position.

The only difference between the embodiment according to FIG. 11 and the embodiment variant 1 and 2 is that between the jaws, in the area of their free Ends, compression springs 23 are inserted so that the jaws are guided out of the holder 2 Position in the open position.

On the inside of the holder 2 and on the outside of the jaws 3, 4 are acute angles Running surfaces 25, 26 extending to the central axis 24 of the screwdriver element are provided, so that the jaws 3, 4 against each other when they are axially pressed in in the direction of the arrow 14 be pressed. Appropriately, both on the bracket 2 and on the Cheeks 3, 4 corresponding ramp surfaces 25, 26 are provided. But it would also be conceivable only on the bracket 2 or on the jaws 3, 4 corresponding acute-angled ramp surfaces perform. However, it is for proper and trouble-free function sensible, corresponding ramp surfaces corresponding to both mutually facing areas train.

The jaws 3, 4 point radially at their ends projecting into the sleeve-like holder 2 inwardly directed cams 27, 28, which in a radially circumferential groove 29 in a Engage screwdriver element 1 axially displaceable bolt 30. The bolt 30 is on his to the groove 29 for engagement of the cams 27, 28, the section 31 adjoining the inner cross section the jaws 3, 4 adapted in the closed state. The transition between The section 31 forming the groove 29 and the end part 32 of the bolt 30 is advantageously spherical executed, the inner regions of the jaws 3, 4 are designed accordingly. Thus, between the bolt 30 and Jaws 3, 4 practically created a kind of ball socket and ball connection, so that Bolts and jaws can slide on each other in an optimal way and optimal pivotability from the closed position of the jaws 3, 4 to the open position of the same is guaranteed.

The bolt 30 is adjusted together with the jaws in the direction of the axis 24 by a corresponding axial pressure and / or tensile action on the jaws 3, 4. At its end protruding into the holder 2, the bolt 30 has circumferential grooves 33 and 34, in which a pin 36 or a corresponding ball, which is spring-loaded for example by an O-ring 35, can engage. The spring-loaded pin 36 thus engages at least in the region of the two end positions of the bolt 30 in one of the grooves 33 and 34, so that additionally a non-positive mounting of the bolt 30 and thus the jaws is ensured in the two end positions. Instead of a spring-loaded pin 36, of course, correspondingly spring-loaded balls or the like could also be provided, which engage in the corresponding circumferential groove 33 or 34.

At the free end, the bolt 30 has a circumferential collar 37, which has a diameter is greater than the section of the bolt 30 having the two grooves 33 and 34 the holder 2 is a ball 38, which partially in the region of the bore 39 in the holder 2 protrudes and thus prevents the bolt 30 from being pulled out completely axial displacement held securely. The circumferential collar 37 is in the bore 39 protruding ball 38 prevented from further adjustment.

But if a sleeve 40 overlapping the sleeve-like holder 2 against the force of a Coil spring 41 is pulled up, the ball 38 is also released to a certain extent, so that the bolt 30 can be completely pulled out of the bore 39. It it is also easily possible to replace the jaws 3, 4 and the bolt 30 or can also be dismantled and reassembled for other purposes.

The gripper-like parts 17, 18 are expedient over the entire sector area of the Jaws 3, 4 guided. But it is quite conceivable here only individual projecting parts or webs, which form the gripper-like parts 17, 18 to provide. Instead of the towards cantilever-like parts 17, 18 projecting towards the central axis would also be so possible to provide openings or profiles leading away from the central axis, if appropriately designed fasteners 6 or designed accordingly Fastener heads 5 are to be detected. In this case, the fastener heads would then be 5th corresponding protruding elevations, cones or the like are available. Would be conceivable it also that the bumps, cones or the like over the scope of a federal government 10 protrude from the fastener head 5.

In the above description it was mentioned that on the gripper-like parts 17, 18th or training of a tool attack at corresponding openings or profiles are provided. In the context of the invention, it is also possible to provide such a training Tool attack in the area of the incisions 15, 16, recesses or the like or alternatively in the axial direction to train them afterwards. Of course it is conceivable, seen in the axial direction on the jaws two or more incisions 15, 16 To provide, a fastener head 5, for example, two or more in the axial direction Have spaced consecutive frets 10.

In this context, it would also be conceivable that the gripper-like parts or accordingly pins directed towards the central axis or openings leading away from this central axis or profiles are provided directly in the area of the incisions 15, 16, so that then fasteners 6 can also be held on the fastener head 5, which only a kind of collar 10, on which projections or depressions or pins and holes directly are provided. With such a configuration, the jaws would then be the Correspond to the shape of the collar 10 of the fastener head 5, the positive and / or non-positive connection is created by the interlocking elevations or projections. In this case, too, is a holder of a fastener head that can be fixed in the axial direction 5 possible in the screwdriver element. If the gripper-like parts 17, 18 are present and these parts engage the collar 10 of a fastener head 5, then must be in any Form a corresponding section 12 to be present, determined by the length B. Distance between the support of the fastener head 5 and the beginning of the federal government 10 manufacture. Instead of section 12, a corresponding one can of course also be used here the collar 10 with a smaller washer in diameter, so that a fastener head then also clamped in a screwdriver element according to the invention can be.

Especially with such a version, but also with versions with one one-piece screw head as shown in Fig. 3, it is conceivable, in addition to the Fastener head 5 holding jaws 3, 4 in the center between the jaws 3, 4 a tool to train for an internal attack. Then there would be a corresponding one in the fastener head 5 Internal attack, the corresponding tool, for example, also on the free End of the bolt 30 which is displaceable in the sleeve-shaped holder 2 is arranged or arranged can be.

In the above description, exemplary embodiments were explained in which the Jaws 3 and 4 are axially displaceable in a sleeve-like holder 2, and from an open position to a closed position, due to the axial displacement - if necessary together with a corresponding bolt 30 - also the shape and / or non-positive adjustment of the jaws 3, 4 is achieved. Within the scope of the invention but it is also conceivable that the jaws 3, 4 in a different embodiment of a sleeve-like Arrange bracket 2, the jaws 3, 4 then no longer opposite in the axial direction the bracket 2 would be slidable. The opening position would then be radial Bring about force or by releasing the radial mobility of the jaws 3, 4, or the jaws 3, 4 could be rotated by, for example, sleeve parts be brought into the closed position. In this context it would also be conceivable, the jaws 3, 4 axially relative to a pin 43 which can be inserted into a screwdriver to keep immovable, the sleeve-like holder 2 then just in the direction of arrow 14 could be withdrawn, thereby pivoting the jaws 3, 4 into the open position. In terms of design, there are therefore a wide variety of design options given.

Claims (16)

1. A screwdriver element for the retention and for the rotary drive of a fastener (6), having a plurality of jaws (3,4) following one another in a peripheral direction for gripping the fastener (6), wherein the jaws (3,4) engage in a sleeve-like mounting (2) and in co-operation with this mounting (2) they can be forced apart in a first end position for retaining the fastener (6) in a radial direction and in a second end position they can be constrained to be pressed towards one another in a radial direction under the action of axial and/or radial force by a form-locking action of the mounting (2), characterised in that indentations or recesses (15,16) are formed at the free end portion of the jaws (3,4) for receiving in a form-locking and/or force-locking manner a fastener head (5) provided on the fastener (6), and in that projecting gripper-like parts (17,18) for the additional form-locking and/or force-locking gripping of portions of the fastener head (5) and acting up to the final screwing-in of the fastener are formed at the free end of the jaws (3,4) adjacent the indentations or recesses (15,16) towards the centre axis (24) or directed away therefrom, and in that on the inside of the mounting (2) and/or on the outer surface of the jaws (3,4) abutting surfaces (25,26) extending at an acute angle to the centre axis (24) are formed, wherein the jaws (3,4) can be automatically pressed towards one another by axial pressing into the mounting (2) as a result of the abutting surfaces (25,26).
2. A screwdriver element according to Claim 1, characterised in that the indentations or recesses (15,16) in the jaws (3,4) correspond at least approximately to the cross-section of the marginal region of the fastener head (5) to be gripped or of a flange (10) formed thereon.
3. A screwdriver element according to Claim 1 or 2, characterised in that openings or profiled portions for engagement on the fastener head (5) or on portions thereof are provided in the jaws (3,4) in the vicinity of the indentations or recesses (15,16) or offset in axial direction adjacent thereto or else on the gripper-like parts (17,18).
4. A screwdriver element according to Claim 1, characterised in that the jaws (3,4) are spring-loaded in the direction of their opening position.
5. A screwdriver element according to any one of Claims 1 to 4, characterised in that the thickness of the gripper-like parts (17,18) viewed in the axial direction of the screwdriver element (1) is smaller than the axial length (B) of a portion (12) on a fastener head () which, on the shank side, is adjacent a flange (10) formed circumferentially on the fastener head (5).
6. A screwdriver element according to Claim 1, characterised in that abutting surfaces (25,26) extending at an acute angle are provided both on the mounting (2) and on the jaws (3,4).
7. A screwdriver element according to Claim 1 and any one of the preceding Claims, characterised in that the jaws (3,4) have at their end protruding into the sleeve-like mounting (2) radially inward directed cams (27,28) which engage in a radially circumferential groove (29) of a stud (30) which is axially displaceable in the screwdriver element (1) and which can be located in different engagement positions, wherein by axial pressure and/or tension acting on the jaws (3,4) this stud (30) can be adjusted together with the latter.
8. A screwdriver element according to Claim 7, characterised in that the stud (30) is engageably located at least in both end positions of the jaws (3,4).
9. A screwdriver element according to Claims 7 and 8, characterised in that the stud (30) has at least two engagement positions formed by circumferential grooves (33,34), wherein a spring-loaded pin (36) or a sphere is retained on the sleeve-like mounting (2), which engages in the corresponding circumferential groove (33,34).
10. A screwdriver element according to Claim 7, characterised in that in its portion (31) adjacent the groove (29) for engagement of the cams (27,28) formed on the jaws (3,4) the stud (30) is adapted to the inner cross-section of the jaws (3,4) in the closed position, wherein the transition between the groove (29) and the end part (32) of the stud (30) and the corresponding zones of the jaws (3,4) are of spherical segment shape.
11. A screwdriver element according to Claim 1 and any one of the preceding Claims, characterised in that a tool for an internal engagement is formed in the centre between the jaws (3,4).
12. A screwdriver element according to Claims 1 and 11, characterised in that the tool for an internal engagement is formed or arranged on the free end of the stud (30) displaceable in the sleeve-like mounting (2).
13. A screwdriver element according to Claim 1 and any one of the preceding Claims, characterised in that the jaws (3,4) are pressed resiliently towards one another by an O-ring (22) inserted in a groove on the outer circumference of the jaws (3,4) in the vicinity of the inwardly projecting cams (27,28) so that in their position extended out of the mounting the jaws (3,4) are forced apart into the open position.
14. A screwdriver element according to Claim 1 and any one of the preceding Claims, characterised in that compression springs (23) are inserted between the jaws (3,4) in the vicinity of the their free ends so that in their position extended out of the mounting (2) the jaws (3,4) are forced apart into the open position.
15. A screwdriver element according to Claim 1 and any one of the preceding Claims, characterised in that the gripper-like parts (17,18) are each guided over the sector zone of the jaws (3,4).
16. A screwdriver element according to Claim 1 and any one of the preceding Claims, characterised in that two jaws (3,4) are provided extended approximately over an angular range of 180°.

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