TECHNICAL FIELD: The present invention relates to a grounding element for making possible an electrical connection between a structural element and an electrical connector according to the preamble to claim 1 and a method for creating a ground connection.

BACKGROUND ART : There are a number of different ways of making a ground connection to, for example, the frame of a heavy goods vehicle, all of which are well-known to experts within this field.

Normally, ground connections on vehicles do not cause any problem. A sufficient number of grounding points are mounted during production in predetermined positions on the vehicle so that all equipment that is installed during production or that can be ordered as manufacturer-specific extra equipment has a prepared grounding point. Normally, the grounding points consist either of a ground plate where spade terminals or ring terminals can be mounted or of a bolt to which ring terminals can be attached. Ground plates can, for example, be screwed or riveted onto the chassis and the bolt can, for example, consist of a spot-welded stud.

An example of a spot-welded stud is known through EP- 0641944-Al, in which a stud for grounding purposes in mass production is described. The described stud is provided with a weld lug, a middle section and a threaded shank. A nut is mounted on the shank. The stud is spot-welded onto the untreated vehicle. The vehicle is then surface-treated and after this the nut is loosend, in order to be able to mount the ground

terminal. This ensures that there is no paint on the contact surfaces of the ground terminal.

Problems with ground connections arise, however, for body builders who mount extra equipment on heavy goods vehicles. When this extra equipment is mounted, the frame of the vehicle has already been surface-treated.

It is therefore not possible to utilize the abovementioned ways of creating a ground terminal in a simple way. As there are so many different types of equipment and combinations of equipment that can be retrofitted on heavy goods vehicles, it is not possible nor desirable to equip the vehicle with grounding points for all variants of extra equipment during production.

The most common way of providing a grounding point for extra equipment on a heavy goods vehicle is to attach a ground plate onto the vehicle. This is often attached to the frame of the vehicle. A ground terminal can then be attached to this ground plate. The ground plate is usually screwed on, either with a self-tapping screw, a through bolt or with a bolt in a threaded hole in the frame. The ground plate can also be riveted on. Another way of providing a grounding point is to spot-weld a stud onto the frame.

Even though the abovementioned ways of retrofitting a grounding point work technically, they all have several disadvantages.

It is important that the ground plate makes electrical contact with the frame. In order to ensure a reliable electrical contact, the contact surface between the ground plate and the frame must be thoroughly clean of paint, anti-corrosion coatings and other insulating material. This terminal must then be protected, so that it does not start to corrode. In addition, the attachment of the ground plate must be sufficiently

strong mechanically, so that it can withstand the forces to which it is subjected.

In order to obtain sufficient strength and to prevent the ground plate rotating, a ground plate needs to be attached by two fixing elements. As it is desirable to utilize existing groups of holes, this means that the ground plate is relatively large. At the same time, it can be difficult to find a free group of holes.

Sometimes new holes must be made, which is time-consuming.

Self-tapping screws or a bolt that is screwed into a threaded hole in the frame do not provide sufficient strength. A frame element on, for example, a lorry can have various thicknesses, depending upon the type of lorry and the location. A frame element can, for example, be as thin as 7 mm, which provides too small an attachment surface for providing these fixing elements with a sufficiently strong fixing. This means that the electrical contact is not reliable. In addition, existing holes can not be used for these types of fixing element, but new holes must be made. In order to rivet the plate on, expensive and complicated equipment is required and it is often difficult to access the area concerned with a riveting tool.

Spot-welding studs onto the frame also requires expensive and complicated equipment and, in addition, electrical equipment on the vehicle must be disconnected when carrying out spot-welding, which is time-consuming.

In addition, for all these methods, the problem remains of removing paint and other insulating material from the contact surface, which is labour-intensive as the frame has been subjected to many different surface treatments.

DISCLOSURE OF INVENTION:

The object of the invention is therefore to provide a grounding element that makes possible an electrical connection between a structural element and an electrical terminal, which can be mounted in a way that is as simple, quick and cheap as possible, which takes up little space and at the same time provides as a reliable an electrical terminal as possible, and also a method for achieving a reliable ground connection in a simple and quick way.

The solution to this task according to the invention is described in the characterizing part of claim 1 for the grounding element and in claim 8 for the method. The other claims contain advantageous. embodiments and further developments of the grounding element according to the invention and the method.

With a grounding element that comprises a first part and a second part, with the first part comprising a first contact surface in the plane where the first part is connected to the second part and an opposing second contact surface, the task of the invention is solved by the second part comprising a section with at least one projecting tooth and by the grounding element comprising a central through-hole that is parallel to the center line of the grounding element.

The method according to the invention consists of a grounding element and a ground terminal being mounted at the same time.

By means of this first embodiment of the grounding element according to the invention, a grounding element is obtained which can be mounted in a simple way, for example, on the frame of, for example, a heavy goods vehicle, so that an electrical contact is created between the frame and the grounding element. The teeth create the electrical contact by cutting through paint

and other surface coatings on the frame and also by deforming the mounting hole so that a metallic contact is created between the grounding element and the frame.

A ground terminal can then be mounted on the grounding element. The advantage of this is that a reliable grounding point is obtained in a simple and cheap way.

In an advantageous first further development of the grounding element according to the invention, the second part of the grounding element is tapered. The advantage of this is that greater tolerances can be accepted for the mounting hole while still making electrical contact.

In an advantageous second further development of the grounding element according to the invention, the outer contact surface of the grounding element is provided with one projection or a plurality of projections. The advantage of this is that the electrical contact between the contact surface and the electrical terminal is improved, and also that the electrical terminal is prevented from rotating when it is being mounted.

BRIEF DESCRIPTION OF DRAWINGS The invention will be described in greater detail in the following, with reference to the embodiments that are shown in the attached drawings, in which Fig. 1 shows an advantageous first embodiment of a grounding element according to the invention, Fig. 2 shows the grounding element according to Figure 1 in a mounted state, and Fig. 3 shows an advantageous second embodiment of a grounding element according to the invention.

MODE (S) FOR CARRYING OUT THE INVENTION The following described embodiments of the invention and further developments are only to be regarded as examples and are in no way to restrict the extent of the

protection provided by the claims. In the embodiments described here, the same reference numerals in the different figures refer to the same components. Each component is therefore not described in detail in all the embodiments.

The first embodiment of a grounding element 1 according to the invention shown in Figure 1 comprises a first part 2 and a second part 3. The first part 2 has a first contact surface 4 facing towards the second part 3 and a second contact surface 5 facing in the opposite direction. The contact surfaces 4 and 5 are parallel and at right angles to the center line 6 of the grounding element. The second part 3 comprises a part 3a with a plurality of projecting teeth 7 and a lead-in 3b, here in the form of a chamfer. The lead-in 3b is shaped to facilitate the insertion of the grounding element 1 into a mounting hole and can be a plurality of different shapes, known to experts in the field. The grounding element 1 also comprises a central through-hole 10 which is parallel to the center line 6. The central hole 10 is intended for the straight shank of a bolt and is therefore unthreaded. The grounding element 1 is advantageously rotationally symmetrical around the center line 6.

The diameter of the first part 2 exceeds the diameter of the second part 3. The first contact surface 4 of the first part is designed to make contact with a structural element when the grounding element is mounted. The second contact surface 5 of the first part is designed to make contact with the ground terminal. The diameter of the first part is therefore selected so that strength requirements and electrical requirements are met. The second part 3 is designed to make electrical contact with a structural element through the walls of a mounting hole in the structural element. The diameter of the second part is therefore selected so that a good

electrical connection is achieved, taking into account the tolerances of the mounting hole and the size of the teeth 7. The length of the teeth is also selected so that a good electrical contact is guaranteed, taking into account, among other things, tolerances and the surface treatment of the structural element.

The grounding element is designed to be mounted in a mounting hole in a structural element, for example on the frame of a lorry. The second part 3 must therefore have a length that is less than the thickness of the structural element so that the whole second part is inside the mounting hole when the grounding element is mounted. This ensures a good contact between the first contact surface 4 of the first part and the structural element.

The center hole 10 is selected to fit the selected mounting bolt. In order to increase the mounting strength and guarantee a good electrical contact between the grounding element and the structural element, the center hole can be selected so that its internal diameter corresponds to the diameter of the shank of the mounting bolt, which is unthreaded. In this way, a press fit is obtained between the grounding element and the mounting bolt, which increases the pressure between the teeth of the grounding element and the structural element. It is also possible to provide the center hole 10 of the grounding element with teeth 9, in order to increase the contact between the grounding element 1 and the mounting bolt.

The grounding element 1 is manufactured of a material which is electrically conductive, preferably a metal such as steel. It is advantageous if the material of the grounding element 1 is harder than the material of the structural element in which the grounding element 1 is to be mounted, so that the teeth 7 can cut into the

edge surfaces of the mounting hole and provide a reliable electrical contact between the grounding element 1 and the structural element. As a result, the grounding element will not be deformed when it is mounted. As far as manufacture is concerned, it is advantageous to manufacture the grounding element 1 from a solid circular blank, so that the grounding element 1 is circular and so that the first part 2 and the second part 3 are centred around a common center line 6, but other methods of manufacture and designs are also possible.

In the first embodiment, the grounding element 1 is intended for mounting in the frame of, for example, a heavy goods vehicle. In this example, the grounding element 1 is manufactured of a relatively high-strength steel, so that the teeth 7 can cut through the surface coating on the frame and also deform the mounting hole in the frame. The grounding element 1 is here surface-coated with, for example, nickel or chrome as protection against corrosion.

The grounding element 1 is mounted in a hole in the frame of the vehicle. As the grounding element 1 only requires one hole in order to be mounted, in most cases it is possible to use an existing hole in the frame. If there is no free hole in the vicinity of the place where a grounding point is required, a hole must be made in a suitable place.

The grounding element 1 is pressed into a mounting hole in a suitable way. This can, for example, be carried out using a press that presses in the grounding element 1 by pressing on the contact surface 5. When the grounding element 1 has been mounted, a ground terminal is attached by means of a bolt and a nut. A mounted grounding element 1 with a ground terminal is shown in Figure 2, where the grounding element 1 is pressed into

a mounting hole 14 in a frame 15 of a lorry. It shows clearly here that the grounding element is pressed through a large part of the mounting hole, but does not extend beyond the hole. The grounding element extends advantageously through at least half of the structural element in order to ensure a good ground connection.

For a lorry frame that is 8 mm thick, the second part extends suitably 4-6 mm into the mounting hole. The ground terminal consists here of a ground cable, in this case mounted by a ring terminal 13, but other types of terminal, which are attached by a bolt 11 and a nut 12, are also possible. By this means, the ring terminal 13 is pressed against the second contact surface 5 so that a good electrical contact is obtained. The ground terminal will then have two contact surfaces, one between the ring terminal and the contact surface 5 and also one between the ring terminal and the bolt 11. It is important that the nut is tightened with a suitable torque so that the ring terminal is not deformed more than is desirable.

An alternative way of mounting the grounding element 1 is to mount the grounding element 1 and the ground terminal at the same time. In this case, the ring terminal 13 is placed on the bolt 11, after which the grounding element 1 is threaded onto the bolt 11. The bolt 11 is then passed through the mounting hole 14 and secured by the nut 12. When the nut is tightened, the grounding element 1 will be drawn into the mounting hole 14 until the first contact surface 4 is in contact with the frame 15 of the lorry. It is advantageous to hold the bolt 11 still while it is tightened, so that it cannot rotate. This can be carried out either by means of the head 17 of the bolt or by means of a square section 16 integrated into the bolt.

The design of the teeth 7 is important for the function of the grounding element 1. The teeth 7 are dimensioned

so that they can cut sufficiently into the material into which the grounding element 1 is to be mounted.

Each tooth 7 is advantageously designed with a pointed cross section and a sharp tip, the length of the base can, for example, be between half and the whole height of the tooth, but other shapes that provide a good cut are also possible. With the right design of the teeth 7, where a tooth 7 deforms the frame, the material will cold-flow, which provides an airtight connection between the grounding element 1 and the frame. This provides protection against possible corrosion of the connection surfaces. The connection can, of course, be protected in addition by a suitable anti-corrosion agent. The teeth are advantageously arranged parallel to the center line 6 of the grounding element, but teeth arranged in a spiral design are also possible.

In a second embodiment of a grounding element according to the invention, the second part 3 is tapered in shape, as shown in Figure 3. This can facilitate the mounting of the grounding element, while at the same time the grounding element can accept greater tolerances of the mounting hole. The height and length of the teeth 7 are dimensioned to be certain to be able to cut into the edge surfaces of the mounting hole, taking into account the tolerances of the mounting hole. The cutting is also dependent upon the materials of which the grounding element and the structural element are constructed.

In a third embodiment of a grounding element according to the invention, the second contact surface 5 is provided with one projection or a plurality of projections 8. The projections 8 can be designed in many different ways. The purpose of the projections is to improve the electrical contact between the contact surface and the electrical terminal. In addition, the projections 8 prevent the electrical terminal from

rotating when it is being mounted. The projections 8 should therefore be low and relatively sharp so that they can deform the contact surface of the terminal element. There should also be many projections so that as many contact points are created as possible. For example, the surface can be roughly abraded. By this means, many small projections are created which facilitate a good electrical contact. The surface can also be, for example, pimpled or can be provided with a number of teeth.

In the method according to the invention for connecting a ground terminal to a structural element, the grounding element and the ground terminal are mounted at the same time. This is carried out by the ground terminal and the grounding element being secured in the same mounting hole at the same time by the same bolt. When the nut is tightened, the grounding element 1 will be drawn into the mounting hole 14 until the first contact surface 4 is in contact with the frame 15 of the lorry.

At the same time, the ground terminal 13 is secured to the grounding element 1. It is advantageous to hold the bolt 11 still while it is tightened, so that it cannot rotate. This can be carried out either by means of the head 17 of the bolt or by means of a square section 16 integrated into the bolt. The advantage of this method is that the grounding element, ground terminal and bolt can be applied from the inside of the frame of the lorry. The securing can then be carried out from the outside of the frame, which simplifies the mounting considerably.

The invention is not to be considered to be limited to the embodiments and further developments described above, a number of additional variants and modifications being possible within the framework of the following claims. The grounding element can, for example, be used on all types of vehicle and also on practically any electrical apparatus where an electrical connection between a metallic structure and an electrical terminal is required.