EP0025472B2 - Switch box door lock fixing nut for mounting a metal lock on a door of an electrical switch box - Google Patents

Abstract

1. Fastening nut (34) to fasten closures (10) consisting of metal for switch cabinet doors, in which the closure (10) that is passed through a metal panel (26) is earthed by electrical contact with the metal panel (26), characterised in that the fastening nut (34) is at the same time an earthing nut, that both lateral surfaces (50) of the fastening nut (34) are provided with teeth (40) that are sharp in the direction of tightening with their point projecting above the contact surface (50), for the purpose of scraping off non-conducting layers (74), more particularly layers of paint and oxide, on the metal panel (26), in order to create an electrical contact between the lateral contact surface (50) of the fastening nut (34) and the metal panel (26) and thereby to render separate earthing measures unnecessary, each tooth (40) being of smaller width (54) than the cross-sectional width (56) of the contact surface (50) of the fastening nut (34).

Description

The invention relates to a control cabinet door fastening nut for fastening metal closures for control cabinet doors, in which the closure passed through a metallic wall is grounded by electrical contact with the metallic wall.

Such a switch cabinet door lock fastening nut, also called simply fastening nut below, is already known from DE-U-76 21 270.

Control cabinets are mostly made of sheet metal for safety reasons, the control cabinet door e.g. is provided with a rod lock or twist lock closure, as is already known from the aforementioned DE-U-76 21 270. To actuate this rod lock or another lock that has a grater, an opening is punched into the sheet metal of the door leaf, through which a screw provided with an axial bore is passed, which forms a bearing for the cabinet door closing device and even by means of a nut in the Die cut can be firmly attached. These locking devices can also have a square arranged within the bore, which can be rotated with a handle or key that can be plugged onto this square.

For safety reasons it is now necessary that the lock is always in electrical contact with the metallic and thus electrically conductive door leaf, i.e. is grounded. For this purpose, the screw provided with the hole or the associated fastening nut must be in electrical contact with the sheet metal of the door leaf.

In order to achieve this electrical contact with certainty, it has previously been customary to leave the area of the door leaf around the punched-out area unpainted during production or, since this can sometimes cause considerable problems in terms of production technology, to remove this paint from the area after painting, for example by grinding. However, this means an additional work step, which increases the cost of the manufacturing process, and it is not ensured that only the surface that will come into contact with the screw or nut is removed from the paint, but also areas beyond that, which can look unattractive, and also these surfaces susceptible to rust, since the material of the control cabinets is mostly sheet steel.

If you leave the sheet unpainted in advance, there is a further disadvantage that it cannot be ensured that oxide residues and contaminants that have arisen during the rolling of the steel sheet are removed so securely that not by high contact resistance between the fastening nut and the door leaf is poorly grounded.

It has been helped in many ways that a serrated lock washer was arranged between the nut and the door leaf surface, which through its fan when the nut is moved back and forth during the tightening process penetrate any paint and oxide layers of the steel sheet and possibly the fastening nut and thereby Establish a perfect earth contact, see e.g. the 1970 VDE 0660 publication, page 35, penultimate paragraph.

Another possibility is the use of Nomel disks, which are fan-shaped and have on their outer edges in the one axial direction protrusions, while on the contact surface for the mother have radial, in the other axial direction protruding corrugations, which also to secure the Serve mother.

A disadvantage of the use of serrated lock washers and Nomel washers, however, is the fact that an additional part is required which, on the one hand, increases the costs and, on the other hand, may be incorrectly inserted or even forgotten during assembly, so that the purpose of securing is not achieved.

From US-A-21 12 494 and DE-A-26 41 177 a screw nut (ratchet nut) is provided on both sides with teeth and depressions associated with these teeth, in which the teeth serve to secure the screws. When tightening (US-A-21 12 494) or loosening (DE-A-26 41 177), the teeth should dig into the material of the workpiece and get caught in the process. In US-A-21 12 494 it is mentioned that the indentations from the workpiece should partially absorb material cut off by the cutting action of the teeth as a compacted mass, in order to thereby secure the "clamping device" against movement (see page 2, right column, lines 59 to 64). An suggestion in the sense that a trough must be placed in front of each tooth with regard to the tightening direction, in order to ensure that scraped-off material does not get stuck between the actual contact surface of the nut and the contact surface of the door leaf and thereby deteriorate the ground contact and the gas tightness not in these publications. On the contrary, the person skilled in the art will be informed, for example, in DE-A-26 41 177 that this trough. "Do not disturb", not encouraged to consciously provide this trough for the fulfillment of certain purposes (here the establishment of a grounding contact and the establishment of a gas tightness), rather he will take a closer look at this advice in the following, in which such troughs do not even occur arise. In the US-A-21 12 494 there is also the indication that a considerable pressure is necessary so that the cutting into the workpiece material can take place, see page 2, right Column, lines 39 to 48. This is a feature in the case of fastening nuts for switchgear closures with their limited strength, which likewise cannot inspire the average person skilled in the art to provide the fastening screw in switchgear door closures with teeth that require considerable pressure. It follows from all of this that these two documents can provide the average person skilled in the art with no suggestions whatsoever which lead to the subject of the invention. Rather, both publications relate only to measures for securing screws against loosening and are therefore not relevant to the subject matter of the present invention.

The etz-a (Elektrotechnische Zeitschrift), vol. 99, number 2, pages 89 to 92, furthermore DE-C-319 339 and JP-U-11031/76 each disclose toothed screws for the electrically conductive connection of two painted sheets over the paint scraping screws. The etz-a mentions in the summary immediately after the title that the screw connection serves to ground the components.

Insofar as only screws (and no nuts) are mentioned in the publications described above, it should be said that screws are not at all suitable for fastening a control cabinet door lock of the type described at the outset, since this control cabinet door lock has no openings or openings, through which the screws are inserted and can be used to attach the closure.

Of all the documents, a mother with teeth on the side surfaces for earthing purposes ultimately only shows DE-C-319 339, as well as a publication by Bulten-Kanthal AB, Hallstahammar, Sweden, from February 1979, with the designation PI No. 7905 E. , from DE-C-319 339 a nut for producing an electrical contact has become known, which scratches oxide layers on the contact surfaces due to its "elevations" f located on the two pressure surfaces or due to scratching parts. However, this nut is again unsuitable for fastening closures for control cabinet doors, since it requires relatively high compressive forces for the scratch effect to take effect, which a control cabinet door lock does not allow due to its special design, since on the one hand its wall thickness is much too small for this, and on the other hand only the space available allow very narrow fastening nuts, which therefore contain only a few threads and therefore can only absorb relatively low compressive forces. In addition, in order to be able to use the known nut at all for fastening the door lock in question, the grater must first be dismantled. In some embodiments this can be done by removing a screw, but in other embodiments with a fixed grater this is not possible, so that the known fastening nut cannot be used there.

In addition, it is not known from DE-C-319 339 to provide both contact surfaces with teeth which are sharp in the tightening direction and have their tips protruding beyond the contact surface for scratching non-conductive layers (such as oxide layers) on the metallic wall.

Rather, it can be seen from the overall context that the "teeth" mentioned in the publication are milling strips which do not protrude beyond the contact surface of the mother. Since these milling strips also extend across the entire cross-sectional width of the contact surface of the nut, the required compressive force is increased even more and, in addition, an often undesired leakage path is created by these milling strips, which from the one door leaf level through the milling strip impressions, along the outer circumference of the closure housing to the opposite Door leaf surface leads. This leakage path allows moisture to enter the control cabinet, or even aggressive or potentially explosive gases, provided the control cabinet is used in appropriate environments.

The nut described in the Bulten-Kanthal publication, on the other hand, has sharp edges arranged on the outer edge, which also protrude beyond the clamping surface, but has the shape of a normal machine screw and would only be a fastening screw for a control cabinet door lock according to the preamble after it has been greatly flattened. or according to DE-U-76 21 270) operational, as already described above. In particular, however, there is a lack of the important feature of the depression receiving the scraped-off material provided in front of each tooth in the tightening direction. Scratched material can therefore get stuck between the actual contact surface of the nut and the door leaf and thereby worsen the grounding contact.

It is also conceivable that such scraped-off material in some places prevents the mother from resting snugly against the door leaf surface, thereby resulting in the risk of an increase in the earth resistance.

The object of the invention is to provide a cabinet door lock fastening nut of the type mentioned, which certainly makes an earth contact to the metallic door leaf surface, is billing in production, and cannot be incorrectly assembled or forgotten.

The object is achieved in that the control cabinet door fastening nut is also a grounding nut that both side surfaces of the Cabinet door lock fastening nut with teeth sharp in the tightening direction, with their tips protruding beyond the contact surface for scratching non-conductive layers, in particular lacquer and oxide layers on the metallic wall, in order to make electrical contact between the lateral contact surface of the control cabinet door fastening nut and the metallic wall In order to make separate grounding measures unnecessary, each tooth having a width which is substantially smaller than the cross-sectional width of the contact surface of the control cabinet door lock fastening nut, so that a scratched-in material receiving recess is provided in front of each tooth with respect to the tightening direction of rotation, so that each tooth is formed by a material expression that the depression occurred during the production of the material expression, and that the material expression for the simultaneous formation of the teeth and the egg Reductions are generated by a tool that can be applied obliquely in the direction of the sharpness of the tooth to be formed in the material penetrating the side surfaces of the cabinet door lock fastening nut, and that several teeth in a different radial distance (R ₁ , R ₂ , R ₃ ) are arranged from the nut axis.

This combination of features makes the above Task solved.

The fact that the cabinet door locking nut is also the grounding means avoids the need for additional grounding means, e.g. Serrated lock washers, Nomel washers and the like, which on the one hand leads to a cheaper grounding measure, and on the other hand makes it particularly impossible to forget the grounding means.

Due to the fact that both side surfaces of the fastening nut are provided with teeth, incorrect assembly of the earthing nut and thus prevention of the proper earthing are prevented, and the manufacture is facilitated and therefore cheaper, as will be explained.

Characterized in that the teeth are sharp in the tightening direction and in particular protrude beyond the contact surface, as well as in that the tooth has a smaller width than the cross-sectional width of the contact surface of the fastening nut, the pressing pressure required for the scratching process can be reduced, whereby the fastening nut for The grounding fastening of control cabinet door locks is suitable because such mounting nuts have to be kept very flat for space reasons and therefore have only a few threads and the thin-walled lock housing of conventional control cabinet door locks is often made from non-tensile die-cast material, so that the compressive forces available for the scratching process are only limited are.

Due to the feature that each tooth has a smaller width than the cross-sectional width of the contact surface of the fastening nut, the occurrence of unfavorable leakage paths is also prevented, since an annular cross-sectional area is always left, which creates a sealing effect in connection with, for example, the door coating.

Characterized in that a scraped material receiving depression is provided in front of each tooth with respect to the tightening direction of rotation, this scraped material cannot get stuck between the actual contact surface of the nut and the door leaf and thereby deteriorate, for example, the grounding contact or due to the contact surface of the nut not properly fitting against the Door leaf surface in turn result in a leak.

It is particularly cost-effective to form the tooth with the aid of material squeezing, which pushing out could simultaneously lead to the formation of a depression in relation to the tightening direction of rotation in front of the tooth, which depression serves to receive scraped-off material. The fact that scraped material can be included in this depression, it can not get stuck between the actual contact surface of the mother and the door leaf and thereby deteriorate the grounding contact. The material expressions are created for the simultaneous formation of the teeth and the depressions by a tool which can be applied obliquely in the direction of the sharpness of the tooth to be formed in the material penetrating the side surfaces of the fastening nut. Such fastening nuts can be produced in a single operation, although a tangential force (torque) arises due to the tangential component of the pressure force acting obliquely in the direction of sharpness, that is to say in the tangential direction, on the side surface during tooth production (oblique pressing in of tool tips) onto the fastening nut to be machined or manufactured. This torque can namely be easily compensated for by the corresponding torque forces which are generated by the tool tips placed on the other side of the nut. This applies in particular if an equal number of teeth of approximately the same dimensions are produced on both sides of the nut in approximately the same or a symmetrical radial spacing arrangement. The mother then does not need to be held particularly tight (e.g. on its circumference), while the tooling devices engage the two sides of the nut (e.g. while simultaneously pressing and slightly twisting the tool halves against one another), thereby producing the teeth and indentations.

The material expressions are for the simultaneous formation of the teeth and the sinking gene generated by a tool that can be applied obliquely in the direction of the sharpness of the tooth to be formed penetrating into the material on the side surfaces of the fastening nut. Such fastening nuts can be produced in a single operation, although a tangential force (torque) arises on the fastening nut to be machined or manufactured during tooth production (oblique pressing in of tool tips) due to the tangential component of the pressure force acting obliquely in the direction of sharpness, that is to say in the tangential direction on the side surface . This torque can namely be easily compensated for by the corresponding torque forces generated by the tool tips placed on the other side of the nut. This applies in particular if an equal number of teeth of approximately the same dimensions are produced on both sides of the nut in approximately the same or a symmetrical radial spacing arrangement. The nut then does not need to be held particularly tight (for example, at its circumference), while the tool devices engage the two sides of the nut (for example, with simultaneous pressing and slight mutual twisting of the tool halves) and thereby produce the teeth or indentations.

It is also advantageous not only to give the individual tooth a smaller width than the cross-sectional width of the contact surface of the fastening nut, but to make this width considerably smaller, and then to arrange several teeth at a different radial distance from the nut axis. This arrangement of the teeth scrapes the insulating layer with a greater width than the width of the individual tooth, which enables an even better ground contact to be made.

According to an advantageous development of the invention, radially opposite teeth are provided in the fastening nut. This is cheap because it makes the load on the nut more uniform. With the hexagon circumference of the fastening nut, it is particularly advantageous to arrange one tooth in the area of each corner.

The height of the tooth must be greater than the thickness of the lacquer or oxide layer, which is, for example, 50 x 10- ⁶ m. In addition, since the tooth may be partially blunted during tightening, it is advisable to design the tooth so that it is after it Production protrudes by about 0.2 to 0.4 mm beyond the contact surface of the fastening nut.

According to yet another development of the invention, the teeth are arranged spirally with a larger radial distance from tooth to tooth over at least part of the support circumference of the fastening nut, the distance differences being approximately the same or slightly smaller than the tooth width.

A fastening nut which has been stamped from sheet metal and / or deep-drawn has proven to be particularly advantageous.

The invention is explained in more detail below on the basis of exemplary embodiments which are illustrated in the drawings.

• Fig. 1 in einer Seitenansicht einen Schaltschranktürverschluß, der in der Blechwand des Türblattes mittels einer Befestigungsmutter gehalten ist;
• Fig. 2 eine Schnittansicht durch eine in einer Blechwand mit einer Befestigungsmutter befestigte Türverschlußlagerung ;
• Fig. 3 eine Befestigungsmutter in Draufsicht gemäß einer Ausführungsform der Erfindung ;
• Fig. 4 eine vergrößerte Teilansicht der Befestigungsmutter der Fig. 3 ;
• Fig. 5a eine Detailschnittansicht längs der Linie V-V der Fig. 4 zur Darstellung der Schabewirkung des Zahnes auf das mit Lack beschichtete Blech;
• Fig. 5b eine ähnliche Ansicht wie Fig. 5a, jedoch mit durch die Schabewirkung abgestumpftem Zahn und mit durch abgeschabtes Material gefüllter Einsenkung; und
• Fig. 6 eine weitere Ausführunqsform der erfindungsgemäßen Befestigungsmutter mit spiralförmig angeordneten Zähnen.

It shows :

• Figure 1 is a side view of a cabinet door lock, which is held in the sheet metal wall of the door leaf by means of a fastening nut.
• 2 shows a sectional view through a door lock bearing fastened in a sheet metal wall with a fastening nut;
• 3 shows a fastening nut in plan view according to an embodiment of the invention;
• Fig. 4 is an enlarged partial view of the mounting nut of Fig. 3;
• 5a shows a detailed sectional view along the line VV of FIG. 4 to show the scraping effect of the tooth on the sheet coated with lacquer;
• 5b shows a view similar to FIG. 5a, but with a tooth blunted by the scraping action and with a depression filled with scraped material; and
• Fig. 6 shows a further embodiment of the fastening nut according to the invention with spirally arranged teeth.

In Fig. 1 is a side view of a so-called rotary bolt or friction door lock, as it is often used in electrical cabinets. It consists of a lock bearing 10, in which an actuating shaft 14 having a toggle handle 12 at its free end is rotatably supported by 90 °. The angle of rotation is limited by a nose 16, which is attached to the actual grater 18 and strikes a stop at two stop surfaces 20 at the end of the bearing cylinder 10 to limit the angle of rotation.

The grater is fastened to the actuating shaft 14 by means of a screw 22 and slides with its grater surface 24 on a corresponding path of the door frame when the control cabinet door is closed. The handle can also be removable, for example by providing a square on the actuating shaft 14 within the bearing 10, onto which a key provided with a corresponding square recess can be attached. Other embodiments such as triangular, double beard, etc. are also possible.

For safety reasons, the bearing 10 and handle 12, if these consist mostly of metal, must be electrically connected to the wall panel 26 of the door leaf, so that this is not caused by a wire that is torn off inside the cabinet and is under tension, for example touching the grater 18 Bearing 10 and the handle 12 under Get tense.

In order to establish a secure earth connection between the bearing 10 and the handle 12 and the door surface 26, it was previously customary to scrape the door panel 26 in the area of the support plates 28 of the flange 30 of the bearing 10, see FIG. 2, before installation, so that a safe ground contact with a low transition resistance is obtained.

Alternatively, the opposite surface 32 of the sheet 26 was scraped bare, on which the bearing surface of a fastening nut 34 comes to rest, in which the overall arrangement after being pushed through is fixed by a corresponding punching in the wall sheet 26 by screwing the nut 34 onto a corresponding thread 36 is, the bearing 10 is secured against rotation by flattenings 38 within the punched.

The scratching off of the paint before the assembly of the closure device as well as the use of additional devices such as Nomel disks, serrated lock washers or the like can be avoided if a fastening nut 34 is used for fastening the closure device, as will be described in more detail below.

3 shows a fastening nut 34, the two side surfaces 50 of which are provided with teeth 40 which are sharp in the tightening direction and whose tip protrudes beyond the bearing surface 50 for scratching on non-conductive layers 74 (see FIGS. 4, 5a and 5b), and so on to establish an electrical contact between the lateral contact surface 50 of the fastening nut 34 and the metallic wall, here the door leaf 26. One of the several teeth 40 that are sharp in the tightening direction (usually a clockwise direction of rotation) is shown in an enlarged top view. As can be seen from this Fig. 4 and from Fig. 5a, which shows a section through Fig. 4 along the lines VV, the tooth is arranged so that it with its tip 42 when tightening the nut 34 what leads to a movement of the tooth tip 42 with respect to the sheet 26 to the right, scrapes the lacquer layer or oxide layer 44 down to the bare metal of the sheet 26, the scraped-off lacquer or oxide chips 46 expediently being able to collect in a depression 48, which is in front of the tooth tip 42 is provided, as can also be seen in FIG. 5b.

Tooth tip 42 and countersink 48 can be formed in a particularly favorable manner at the same time that material is thrown up with a suitable tool by pressing into the surface 50 of the nut 34 in such a way that the tip 42 results. For this purpose, for example, the tool could be placed obliquely in the direction of the sharpness of the tooth 42 to be formed in the surface 50 and brought to penetrate into the material, the tool simultaneously forming the depression 48 and the material throw-up 42, which automatically indicates a certain sharpness receives its top position if a suitable material is selected for nut 34. Brass, hard bronze or steel are particularly suitable for this purpose.

As a tool, a simple grain or chisel can be used, but for the cheapest possible production, a machine specially designed for this purpose is of course preferable, with which the teeth and the corresponding depressions on both sides of the fastening nut are produced simultaneously by using appropriate tools the side surfaces of the fastening nut act in, for example, only a single operation.

Depending on the pitch of the thread of the screw 34 and depending on the thickness and strength of the layer 44, a full turn or more than a full turn is required to tighten the nut 34.

If the layer 44 of varnish or oxide thin, however, it has for example a thickness of less than 50 x 10- ^e m, also includes the nut 34, the normally standard threaded and the other parts are made accurately, there is less than one revolution between the beginning of the scratching and the final tightening of the screw 34. Here, it is advantageous that several teeth are provided on the contact surface of the nut 34, as shown in FIG. 3. This also ensures in this case that the entire circular arc of the contact surface 32 of the sheet 26 for the nut 34 is covered by at least one tooth 42 and is thus at least partially freed from its insulating layer 44. As the fastening nut is tightened, the side surface 50 of the fastening nut 34 approaches the surface 52 of the sheet 26 more and more, while at the same time the apex 42a becomes blunt, as shown in FIG. 5b, while the chips 46, if not in any case, move fall out of the area of the fastening nut 34 because of the vertical arrangement of the metal wall 26, collect in the depression 48. At the end of the tightening, the remaining blunted tip 42a will press a little into the material of the sheet 26 and not only bring about an even closer electrical contact with an even lower contact resistance, but also a locking of the fastening nut 34.

For the reasons described in the introduction, each tooth 40 has a smaller width 54 than the cross-sectional width 56 on the bearing surface 50 of the fastening nut 34. After all, a relatively wide area of the sheet 26 is still scratched free. For particularly hard materials, however, it may be cheaper to make the tooth 40 considerably narrower than the full width 56 of the contact surface 50 of the fastening nut 34, in order to make it even sharper Get scratching effect. In this case, it may be advantageous to arrange a plurality of teeth at radially different distances R from the axis of the nut 34, the difference in distance in each case corresponding approximately to the width 54 of the individual teeth 40 or also being slightly smaller. Due to this staggered arrangement of the teeth 40, the insulating layer 44 would be removed in strips from the individual teeth, so that after, for example, one full turn of the nut 34, the lacquer would be scraped off in a manner that would correspond to the staggered width of the teeth 40.

The fastening nut shown in FIG. 3 can be solid, but, as will be explained in more detail below, it can also be punched out of sheet metal and / or deep-drawn. result in considerable material savings. Preferably, the fastening nut will then be made of sheet steel, because steel can be machined particularly well in the form specified and sufficient stability is ensured even when thin-walled material is used.

The toothed fastening nut can be formed by deep drawing or pressing in one or at most two working steps. The deep-drawing tools required for this are complex, but allow simple and extremely inexpensive manufacture.

Thus, a fastening nut according to the invention with teeth which have the shape shown in FIG. 4 can be produced simultaneously with an appropriate tool in a single operation by obliquely pressing in tool tips on both side surfaces, the tooth groups which are sharp in the tightening direction being produced simultaneously. The torques created by the oblique placement essentially compensate each other, so that holding the blank is either unnecessary or requires only slight holding forces. The machining forces are rather applied in that the opposing tool parts, which grip the two sides of the fastening nut, engage the fastening nut while simultaneously pressing and slightly rotating the tool halves, while simultaneously pressing out the material 42 and the depression 48 on both sides for all effect teeth to be generated simultaneously.

Claims (6)

1. Switch box door lock fixing nut (34) for mounting metal locks (10) for switch box doors, wherein the lock (10) which is passed through a metal panel (26) is earthed by electrical contact with the metal panel (26), characterised in that the switch box door lock fixing nut (34) is at the same time an earthing nut, in that both lateral surfaces (50) of the switch box door lock fixing nut (34) are provided with teeth (40) that are sharp in the direction of tightening with their point projecting above the contact surface (50), for the purpose of scraping off non-conducting layers (24), more particularly layers of paint and oxide, on the metal panel (26), in order to create an electrical contact between the lateral contact surface (50) of the switch box door lock fixing nut (34) and the metal panel (26) and thereby to render separate earthing measures unnecessary, each tooth (40) being of considerably smaller width (54) than the cross-sectional width (56) of the contact surface (50) of the switch box door lock fixing nut (34), in that in front of each tooth (42) relative to the direction of tightening a depression (48) is provided which receives scraped off material (46), in that each tooth (40) is formed from material that is forced outwards, in that the depression (48) is produced when the material is forced outwards (42), and in that the forcing outwards of material for the simultaneous formation of the teeth (14) and depressions (48) is carried out by a tool that can be applied to the lateral surfaces (50) of the fixing nut, penetrating the material obliquely in the direction of the point of each tooth (42) to be formed and in that several teeth (40) are each positioned at a different radial distance (R_i, R₂, R₃) from the axis of the nut.

2. Switch box door lock fixing nut according to Claim 1, characterised in that teeth (40) lying radially opposite one another are provided.

3. Switch box door lock fixing nut according to Claim 2, characterised in that where the periphery of the switch box door lock fixing nut is hexagonal, one tooth respectively is positioned in the area of each corner (Fig. 3).

4. Switch box door lock fixing nut according to Claim 1, characterised in that each tooth (40) after its fabrication projects approximately 0.2 to 0.4 mm above the contact surface (50) of the switch box door lock fixing nut (34).

5. Switch box door lockfixing nut according to one of Claims 1 to 4, characterised in that over at least a part of the contact extent of the switch box door lock fixing nut (34) the teeth (40) are arranged spirally (Fig. 6) with the radial distance R_i, R₂, R₃ increasing from tooth to tooth, the differences between the distances r = R₂ - R₁ = R₃ - R2... being approximately equal to or somewhat less than the width (54) of the tooth.

6. Switch box door lock fixing nut according to one of Claims 1 to 5, characterised in that the switch box door lock fixing nut (34) is stamped and/or deep drawn from sheet metal.

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