WO2005007492A1

WO2005007492A1 - Telescopic locking

Info

Publication number: WO2005007492A1
Application number: PCT/SE2004/001098
Authority: WO
Inventors: Ingemar Melander
Original assignee: Kongsberg Automotive AB
Current assignee: Kongsberg Automotive AB
Priority date: 2003-07-15
Filing date: 2004-07-06
Publication date: 2005-01-27
Anticipated expiration: 2006-01-15
Also published as: SE0302071L; SE525532C2; SE0302071D0

Abstract

The present invention relates to an adjustable locking arrangement for releasably locking together a gear shift lever (1) and a gear shift rod (5) in a motor vehicle (40) having a preferably forward-tipping cab (41), in which arrangement the gear shift lever (1) is articulated in the cab (41) by way of a universal joint (10) and is furthermore provided with a gear shift movement-transmitting section (15) having a shaft (14) which pivotally supports a moveable locking part (17). The gear shift movement-transmitting section (15) is designed to interact with the gear shift rod (5), which is connected to the gearbox and to which a fixed locking part (20) is secured, and on the end of which, facing the gear shift movement-transmitting section (15), seating surfaces (31) are arranged. The gear shift rod (5) is further provided with a flexible extension element (16), which is further connected to the gear shift movement-transmitting section (15) for guiding the gear shift rod towards the gear shift movement-transmitting section (15) when returning the tipped cab to a working position, the shaft (14) being designed to interact with the seating surfaces (31) so that a gear shift movement-transmitting engagement is obtained when the cab (41) is in the working position.

Description

Telescopic locking

TECHNICAL FIELD

The present invention relates to an adjustable locking arrangement for releasably locking together a gear shift lever and a gear shift rod in a motor vehicle having a preferably forward-tipping cab, under which cab an engine for propelling the motor vehicle and driving the motor vehicle gearbox is located. The gear shift lever is articulated in the cab by way of a universal joint and is furthermore provided with a gear shift movement-transmitting section having a shaft which pivotally supports a moveable locking part, the gear shift movement-transmitting section being designed to interact with the gear shift rod, which is connected to the gearbox and on which a fixed locking part is arranged, and on the end of which, facing the gear shift movement-transmitting section, seating surfaces are arranged that determine the position in relation to the gear shift movement-transmitting section. The gear shift rod is further provided with a flexible extension element, which is connected to the gear shift movement-transmitting section for guiding the gear shift rod towards the gear shift movement-transmitting section when returning the tipped cab to a working position.

PRIOR ART

In conventional operating elements such as gear shift mechanisms in motor vehicles a gear shift lever is very often mechanically connected to a gearbox. This mechanical connection usually comprises a gear shift rod which transmits both longitudinal movements and rotational movements. In instances where the part of the vehicle in which the gear shift lever is situated is moved relative to the gearbox, there is a need to release the locking of the gear shift rod to the gear shift lever. When the part of the vehicle in which the gear shift lever is situated is returned to the original position, there is furthermore a need to restore the locking of the gear shift rod to the gear shift lever. This is the case, for example, in that type of truck which is fitted with a tipping cab, in which the truck cab can be tipped in order to allow access to the engine of the truck. When the truck cab is returned, the coupling of the gear shift rod to the gear shift lever must be restored.

The conventional solution to this problem is to design the gear shift rod with a telescopic section which can be extended. This means that mechanical contact between the gear shift lever and the gear shift rod exists at all times by way of the telescopic section. The telescopic section, however, only constitutes a mechanical guide linkage between the gear shift lever and the gear shift rod. The engagement coupling transmitting the shift movement of the gear shift lever to the gear shift rod is disengaged when the truck cab is raised and the telescopic section is extended. When the truck cab is lowered, the telescopic part is compressed, and the engagement coupling transmitting the shift movement of the gear shift lever to the gear shift rod is guided so that engagement is restored. Here it is desirable for the engagement coupling transmitting the movement of the gear shift lever to the gear shift rod to be locked in such a way that movements of the gear shift lever are transmitted to the gearbox via the gear shift rod without any play. This locking must be releasable each time the truck cab is raised, so that the engagement coupling transmitting the movement of the gear shift lever to the gear shift rod is disengaged, and locking must be restored when the truck cab is lowered, so that said coupling is again locked in the engaged position.

These guides and locking arrangements have hitherto been achieved, for example, by some type of spring-loaded locking tongue, which is supported so that it can pivot about one shaft, whilst the locking tongue release arrangement is supported so that it can pivot about a further shaft. In order to obtain guide surfaces, a metal component is usually cast with guide faces, said metal component then being welded to the gear shift rod, which usually comprises a tube.

The gear shift lever is normally fixed to a lower part of the vehicle cab by way of a ball joint or other type of universal joint which will permit gear shift movements. The gear shift lever extends further down to the gear shift rod, by means of which the gear shift lever is joined to a mechanism which allows a reciprocating gear shift movement of the gear shift lever to be translated into a largely longitudinal reciprocating movement of the gear shift rod, and a lateral movement of the gear shift lever to be translated into a rotational movement of the gear shift rod.

The prior art is therefore of a design construction which involves not only a number of pivot axes, which in turn results in a large number of components, but also welding of cast iron components to tubular components.

SUMMARY OF THE INVENTION

It is an object of the present invention to minimize the number of components and pivot axes, and at the same time to provide a simple and tolerance- accommodating solution. It is also an object of the invention to provide a solution which does not involve welding cast components to tubular components.

The invention thereby provides an adjustable locking arrangement of the aforementioned type, in which the shaft is designed to interact with the seating surfaces so that a gear shift movement-transmitting engagement is obtained when the cab is in the working position and the locking parts are in an interlocking position.

Preferred embodiments are set forth in the dependent claims. The present invention affords a number of advantages over the locking arrangements used hitherto.

- Use is primarily made here of just one shaft which is a pre-existing shaft for transmitting movements from the gear shift lever to the gear shift rod, which means that the locking arrangement has a very simple design construction.

- Guide means are furthermore integrated into the locking arrangement instead of fitting special guide means at suitable points. The locking elements are furthermore designed with a constrictive engagement such that problems with play due to manufacturing tolerances and wear do not arise. - Nor does the locking arrangement according to the invention need complicated cast components that have to be fixed to the tubular components, use being made solely of metal blanks punched and formed from sheet metal, which results in a simple and inexpensive design construction.

DESCRIPTION OF THE DRAWINGS

The invention will be described in more detail below on the basis of an example of an embodiment and with reference to drawings attached in which:

Fig. 1 shows a schematic side view of a vehicle for which the invention is intended; Fig. 2 shows a schematic side view of a joined and locked arrangement according to the invention; Fig. 3 shows a schematic front view of an arrangement according to the invention; Fig. 4 shows a schematic view of a locking heel according to one embodiment of the invention; Fig. 5 shows a detailed schematic side view of a joined and locked locking arrangement according to the invention; Fig. 6 shows a schematic side view of a joined and unlocked arrangement according to the invention; Fig. 7 shows a schematic side view of an at least partially separated and unlocked arrangement according to the invention; and Fig. 8 shows a schematic side view of the engagement of the shaft in seating recesses of the gear shift rod.

PREFERRED EMBODIMENTS

Referring firstly to Fig. 1 , the present invention relates to a locking arrangement intended for a vehicle, a truck 40, having a so-called forward cab 41 , which has a gear shift lever 1 , which is rotatably fixed in the cab 41 and which by way of a gear shift rod 5 controls a gearbox 4 positioned further back in the vehicle. This gearbox 4 is in turn coupled to an engine 42 positioned under the vehicle cab for propelling the vehicle 40. The vehicle cab 41 is furthermore capable of tipping forwards from its working position in a known manner, as shown in Fig. 1 , allowing easy access to the engine 42 located under the cab 41. When tipping or returning the cab 41 , this means that the part of vehicle 40 in which the gear shift lever 1 is fixed is moved relative to the gearbox 4. There is therefore a need here firstly to release the gear shift lever 1 from the gear shift rod 5. When the cab 41 is being returned to the working position there is secondly a need to bring the gear shift lever 1 and the gear shift rod 5 correctly together.

The construction of a gear shift mechanism will be described schematically with reference to Fig. 2. The gear shift lever 1 is pivotally fitted in a lever control console 2. The gear shift lever 1 is conventionally provided with an ergonomically designed lever knob 3 or lever head, designed to be manually gripped by a driver of the truck for operating a gearbox 4. In its interaction with the gearbox 4 the lever 1 is moveable, according to a specific pattern of movements, between various shift positions, partly through forwards/backwards movements and partly through lateral movements. By means of such movements the gearbox 4, by way of the gear shift rod 5, is shifted between the various gear shift positions via an operating shaft 6 belonging to the gearbox 4. The choice of gear shift position is therefore a combination of rotational position and axial displacement position of the gear shift rod 5 and the operating shaft 6. The gear shift rod 5 is coupled to the operating shaft 6 via a ball joint coupling 7. The ball joint coupling 7 is fixed to a tube 8 which is slipped on over the end of the gear shift rod, which tube 8 is flattened at the end where the ball joint coupling 7 is fixed. The tube 8 is slotted and is clamped by means of an adjustable clamping element 9 to the gear shift rod 5, so that it cannot perform any movements in relation to the gear shift rod 5. The aim of this arrangement is to allow the position of the operating shaft 6 to be adjusted relative to a certain position of the gear shift lever 1 , so that the pattern of movements of the gear shift lever is correctly transmitted to the gearbox 4. The clamping element 9 is provided in a known manner with a projection, to which a reaction strut is fixed (not shown).

The gear shift lever 1 is pivotally supported by means of a joint 10, which of itself affords free articulation in all directions, but which is limited by other factors such as the gearbox operating shaft 6, which is controlled by the gearbox 4 to allow it to assume certain specific positions as described above. The joint 10 of the gear shift lever, hereinafter called the lever joint, is a universal joint which in the example shown consists of a ball joint with a joint ball 11 , which is fitted around the lever and is pivotally supported in a spherical ball socket 12, which forms part of the lever console 2. The ball socket is integrally formed with a fixing plate 13, forming part of the console, for fixing the gear shift lever to a fixed part of the vehicle, such as an element of the lower part or bottom of the cab (not shown).

An embodiment of the locking arrangement according to the invention will be further described in more detail with continued reference to Fig. 2 and also to Fig. 3. A swivel joint in the form of a shaft 14, which is involved in gear shift movements of the lever, that is to say swivel movements about the lever joint 10, is coupled to the lever 1. The shaft 14 is fed through a holder housing 15 formed as an upturned and downturned U-shape, which is fixed to the lower part of the lever 1. The holder housing 15 is symmetrical about the line C and constitutes a gear shift movement-transmitting section. The shaft 14 is further taken through the outermost part 16a of an extending element, introduced and fixed into the gear shift lever 5, in the form of a telescopically extending tube 16, which telescopic tube 16 is in a known manner fixed onto and capable of extending out of the gear shift rod 5 (see also Fig. 7). Note that Fig. 3 shows the short end of the outermost part 16a of the telescopic tube 16 that faces the gear shift lever 1. Other components which in the figure are situated further into the plane of projection than the outermost part of the telescopic section 16 are not shown in the simplified Fig. 3, nor is the gear shift rod 5, which is nevertheless shown schematically in Fig. 1. When the telescopic section 16 is fixed to the gear shift rod and to the gear shift lever 1 by way of the shaft 14 and the holder housing 15, it will constitute a mechanical connection between these parts, even when the telescopic section 16 is extended, that is to say when the cab 41 is tipped. The shaft 14 is also led though a hooked section 17, which will constitute a first locking part, situated between the outermost part of the telescopic section 16 and the holder housing 15. For the sake of clarity, Fig. 3 shows the hooked section 17 partially broken open. The hooked section 17 is described in more detail below. Both the holder housing 15, the hooked section 17 and the outermost part of the telescopic section 16 are supported so that they can swivel about the shaft 14, which is led through these parts. The hooked section 17 is further acted upon by a spring plate 18, which strives to maintain the hooked section 17 in a normal position in which the longitudinal extent of the hook legs largely coincides with the gear shift rod. In the normal position the hook legs 19a, 19b are preferably directed somewhat downwards in relation to a transverse plane to the gear shift lever 1. The spring plate 18 is either fixed around the shaft 14 in a known manner or clamped in the telescopic section 16, to which the spring plate 18 can be fixed, for example, by means of a rivet or the like (not shown). Both the hooked section 17 and the holder housing 15 preferably comprise punched and bent metal components. The fact that the shaft 14 joins the telescopic section 16 to the gear shift lever 1 means that when necessary the telescopic section 16 can be released from the gear shift lever 1 by removing the shaft 14. Since the telescopic section 16 is not connected to the gear shaft lever 1 via cast components welded thereto, as is usual in known mechanisms of this type, the parts of the telescopic section 16 may be suitably surface treated, for example anodized, beforehand, free of the gear shift lever, if so required.

Fastened to the gear shift rod 5, at the end facing the gear shift lever, is a locking heel 20, which constitutes a second locking part. The locking heel 20 preferably comprises a punched and bent metal component which, likewise with reference to Fig., 4 a), is punched so that it has a pre-existing trapezoidal shape with four edges 21 , 22, 23, 24. After punching, the locking heel 20 is further formed so that it largely conforms to the rounding of the gear shift rod 5, which is shown in Fig. 4b)-d). the locking heel is suitably fixed to the gear shift rod 5 by welding. The locking heel 20, as is shown in Fig. 4 d), has two locking surfaces 25, 26 which are formed by a first edge 21 of the locking heel 20 remote from the gear shift lever, said locking surfaces 25, 26 coming to be situated on either side of the gear shift lever 5. These locking surfaces 25, 26 will extend largely at right angles to the longitudinal direction of the gear shift lever. The locking heel 20 is further designed with guide surfaces 27, 28 which are formed by a second edge 22 and a third opposing edge 23. The guide surfaces 27, 28 are angled in relation to the longitudinal direction of the gear shift rod, in such a way that a fourth edge 24 facing the gear shift lever is shorter than the first edge 21. Their function will be described in more detail below.

Continuing to refer to Fig. 2 and 3, and also the more detailed Fig. 5, the hooked section 17 is designed as a U-shape which is symmetrical about the line C, in which the legs of the U-shape each form a hook 19a, 19b, each hook 19a, 19b being designed to grip against the respective locking surface 25, 26 of the locking heel (the locking surfaces 25, 26 are obscured in Fig. 5). The U-shape of the hooked section is designed so that it can grip around the end of the gear shift rod 5 where the locking heel 20 is applied, but also, on the other hand, so that it cannot grip around the locking heel 20 but comes to rest against it in the locked position. In the locked position the engaging surface 29 of each hook 19a, 19b will lie, broadly speaking, parallel to the respective locking surface 26 of the locking heel, but with a small angle of engagement φ between these surfaces, which is shown most clearly in the detailed Fig. 5. This angle of engagement φ is designed so that each hook 19a, 19b does not come into full engagement with the respective locking surface 25, 26, that is to say the locking heel 20 does not reach the bottom of the respective hook 19a, 19b. Instead, in the locked position, only a small part of the engaging surface 29 of each hook will be in contact with the respective locking surface 26, so that a constrictive engagement is obtained. This eliminates any loose fit and play that might otherwise occur due to manufacturing tolerances and wear.

The locking arrangement according to the invention has a release mechanism as described below. If, in the position according to Fig. 2, 3 and 5, the gear shift lever, as the cab 41 starts to tip, is angled so that the lever knob 3 is moved away from the gearbox 4, the holder housing 15 will correspondingly follow the angling movement so that its one end 15a comes into contact with a bearing surface 30 of the hooked section 17, and against the spring force of the spring 18 will depress the hooked section 17, so that its opposing legs 19a, 19b will be brought out of engagement with the locking heel 20, as is shown in Fig. 6. In this position the gear shift lever 1 can be moved away from the gearbox 4 without the mechanical contact between the gear shift lever 1 and the gear shift rod 5 being broken, when the telescopic section 16, which is fixed to the shaft 14 at this stage, is telescopically drawn out of the gear shift rod 5. The telescopic section 16 will further function as a guide when the gear shift lever 1 and the gear shift rod 5 are to be brought together again. The lock-releasing angling of the gear shift lever illustrated in Fig. 6 normally occurs automatically when the truck cab according to Fig. 1 is tipped, so that the hook engagement release mechanism will thereby function quite automatically at the start of the tipping sequence, in which the gear shift lever 1 is lifted largely at right angles to the longitudinal direction of the gear shift rod.

Fig. 7 shows the telescopic section 16 at least partially drawn out of the gear shift rod 5, the gear shift lever 1 here being shown returned to an upright position, which need not be the case, however. Owing to the spring force of the spring 18, the hooked section 17 has here returned to a normal position, since it is no longer depressed by the holder housing 15. Fig. 7 also shows one of two engagement recesses 31 made in the gear shift rod 5 which function as seating surfaces for the pivot shaft 14 of the gear shift lever. An opposing engagement recess is arranged in the gear shift rod 5, hidden on the other side of the telescopic section 16. Fig. 8 shows the shaft 14 when it is in engagement with the engagement recesses 31. Fig. 8 is a schematic side view of the engagement of the shaft 14 in seating recess 31 in the gear shift rod 5 with other parts shown by dashed lines for the sake of clarity. These engagement recesses 31 are designed as convergent boundary surfaces, these surfaces converging so that the shaft 14 is not allowed to touch the bottom of the engagement recesses 31 when it is introduced into these. In this way, in the joined position according to Fig. 2, 3 and 5, a contact is achieved between the shaft 14 and the engagement recesses 31 that is free of play and not susceptible to tolerances. The convergent surfaces of the engagement recesses are also designed with an opening angle such that when the gear shift lever is brought towards the joined position according to Fig. 2, 3 and 5 the shaft 14 will be guided into the engagement recesses 31 via the opposing upper recess guide surface 33 and lower recess guide surface 34 thereby created, the lower recess guide surface 34 projecting in relation to the upper recess guide surface 33, since the end of the lower part of the gear shift rod consists of a lip part 35.

In the joined position according to Fig. 2, 3 and 5, in which the hooks 19a, 19b are in engagement with the locking surfaces 25, 26 of the locking heel, movements of the gear shift lever 1 are transmitted to the gear shift rod 5 via the shaft 14, which is here in engagement with the engagement recesses 31. Because no play exists either between the hooks 19a, 19b and the locking surfaces 25, 26 or between the shaft 14 and the engagement recesses 31 , transmission of the gear shift lever movements to the gear shift rod 5 and on to the gearbox 4 is stable and free from play.

Looking at Fig. 7 again, it may be noted that the hooks 19a, 19b are provided outside their respective engagement surfaces 29 with hook guide surfaces 32 (see also Fig. 5), which are designed to interact with guide surfaces 27, 28 of the locking heel when the gear shift lever 1 is brought towards the joined position with the gear shift rod 5 according to Fig. 2, 3 and 5. Each hook guide surface 32 will then slide on the respective guide surface 27, 28 of the locking heel, so that the hooked section 17 is bent up against the force of the spring 18. When each hook guide surface 32 leaves the respective guide surface 27, 28 of the locking heel , the hooked section 17 is depressed due to the spring force so that the hooks 19a, 19b come into engagement with locking surfaces 26, 27 of the locking heel as shown in Fig. 2, 3 and 5. At the same time that they are being brought together, the shaft 14 is therefore also being guided in towards the engagement recesses 31 in the gear shift rod 5 in the manner described above. In order that the locking achieved in the joined position may be free from play, the dimension T in Fig. 7 must meet a relatively precise tolerance. The dimension T extends between the transition of each locking heel guide surface 27, 28 to the respective locking surface 25, 26 and the shaft contact points when it is in full engagement in the respective recess 31 , see also Fig. 5. The recesses 31 , which serve as seating surfaces, are thus also reference points for the dimension T. Otherwise the tolerance-accommodating characteristics of the design construction mean that no other such dimension susceptible to tolerances exists in the locking arrangement according to the invention.

All guide surfaces are designed so that guiding occurs regardless of the angular position of the gearshift rod 5 in relation to the gear shift lever 1 in the extended position. It is in fact feasible for the gear shift rod 5 to be in such a position that on parting the gearbox was set to gear 1 , whilst the gearshift lever has ended up in a position corresponding to some other gear.

The locking heel and the interacting hooked section may be designed in a number of ways without sacrificing the function described above. The telescopic section may be fixed to the shaft 4 by way of a shaft piece (not shown) which may be a more substantial tubular element through which the shaft is fed. The telescopic section may be fixed to the shaft piece by a pin or the like. The telescopic section 16 can thereby be removed, as required, by removing the pin instead of the shaft.

The telescopic section 16 may furthermore be designed so that it runs on the outside of the gear shift rod 5 instead of inside the gear shift rod, as described above.

The invention is not limited to the example of embodiment described above and shown in the drawings but may be modified within the scope of the following patent claims. The core of the invention therefore resides in the fact that a single point of articulation in the form of the shaft 14 described is needed for locking and a gear shift movement-transmitting connection between the gear shift lever 1 and the gear shift rod 5, in which the shaft 14 transmits all gear shift lever movements to the gear shift rod 5. The invention is furthermore equipped with interacting guide surfaces which ensure that coupling together is as easy as possible. Here the precise appearance of the guide surfaces as described above is not important but must only be regarded as an example of how such interacting guide surfaces might be realized. The guide surfaces must be formed so that they assume the various possible relative positions that may occur between the engagement 31 of the gear shift rod and the shaft 14. There are also several ways (not shown) of making the engagement recesses 31. For example, they may be more semi-circular.

Nor do the mechanical embodiments of the constituent parts limit the invention. For example the hooked section may comprise two independent legs which are each spring-loaded and which are each provided with a bearing surface 30 which is depressed by the holder housing 15 when the gear shift lever 1 is angled by tipping of the cab 41.

The position and design of constituent parts, such as the gear shift rod and the gearbox, are only schematic and are indicated only in order to explain the invention, and must not be regarded as limiting the invention.

The invention is not limited to truck tipping cabs but may also be applied to other types of vehicle in which that part of the body in which the gear shift lever is supported is moved away to allow access to otherwise hidden components.

Claims

1. Adjustable locking arrangement for releasably locking together a gear shift lever (1 ) and a gear shift rod (5) in a motor vehicle (40) having a preferably forward-tipping cab (41 ), under which cab an engine (42) for propelling the motor vehicle (40) and driving the motor vehicle gearbox (4) is located, in which arrangement the gear shift lever (1 ) is articulated in the cab (41 ) by way of a universal joint (10) and is furthermore provided with a gear shift movement-transmitting section (15) having a shaft (14) which pivotally supports a moveable locking part (17), the gear shift movement-transmitting section (15) being designed to interact with the gear shift rod (5), which is connected to the gearbox and on which a fixed locking part (20) is arranged, and on the end of which, facing the gear shift movement-transmitting section (15), seating surfaces (31) are arranged that determine the position in relation to the gear shift movement-transmitting section (15), the gear shift rod (5) being further provided with a flexible extension element (16), which is further connected to the gear shift movement-transmitting section (15) for guiding the gear shift rod towards the gear shift movement-transmitting section (15) when returning the tipped cab to a working position, characterized in that the shaft (14) is designed to interact with the seating surfaces (31 ) so that a gear shift movement-transmitting engagement is obtained when the cab (41 ) is in the working position and the locking parts (17, 20) are in an interlocking position.

2. Locking arrangement according to Claim 1 , characterized in that the shaft (14), in the locking stage, is designed to interact with the seating surfaces (31) for guiding the gear shift lever (1) and the gear shift rod (5) into the locked position.

3. Locking arrangement according to either of the preceding Claims, characterized in that the extending element (16) is connected to the gear shift movement-transmitting section (15) by way of the shaft (14).

4. Locking arrangement according to any one of the preceding Claims, characterized in that the gear shift movement-transmitting section (15) comprises a holder housing for the shaft (14), which holder housing (15) has a first bearing surface (15a) which is designed, on tipping of the cab, to interact with a corresponding bearing surface (30) of the moveable locking part (17) in order to bring the latter to an opened position, it being possible to remove the moveable locking part (17) and the gear shift lever (1 ) from the fixed locking part (20) and the gear shift rod (5), while the extending connecting element (16) is designed to maintain mechanical contact between them.

5. Locking arrangement according to any one of the preceding Claims, characterized in that said locking parts (17, 20) are formed with interacting guides (27, 32) which are designed to correct relative angular deviations between the shaft (14) and the seating surfaces (31 ) when these are to be brought into engagement as the cab is brought down from the raised position to the working position.

6. Locking arrangement according to any one of the preceding Claims, characterized in that the seating surfaces (31 ) in the gear shift rod (5) are provided with guide surfaces (33, 34, 35) for receiving the shaft (14) when the gear shift rod (5) and the seating surfaces (31) are brought together as the cab is brought down from the raised position to the working position.

7. Locking arrangement according to any one of the preceding Claims, characterized in that a spring element (18), which is designed to bias the moveable locking part (17) towards a locking position, is arranged on the shaft (14).