The present invention relates to a metal element adapted for securing another element in a through going hole in the metal element. Moreover, the invention relates to a method of making such a joint.

More specifically the invention relates to the joining of two elements, of which at least one is a metal element, for inst- anse of light metal'. The invention may be applied in a number of technical fields, but a particular application is in cases where the two elements are subjected to repeated loading, in such a manner that it represents a problem how to avoid that the elements are separated or loosened from each other.

As an example of such a joint is mentioned a steel bolt attached in a hole for instance in a rod and subjected to transverse forces, i.e. bending and/or shear, which, causes compressive strains between the 'bolt and the hole, If the rod is made of steel, it is normally not a severe problem to avoid that the surface of the hole does not withstand the strains, but if the rod is of metal the problem is worse because of the different mechanicalproperties, as for instance less material strength of the metal.

A known principle for the solution of this problem is to pro¬ vide a bushing in the hole, for instance a steel bushing which is pressed into place. The bushing may be provided with an abutment collar in one end. Experience has, however, shown that the bushing may overload the surface in the hole. in the same manner as a steel rod. Moreover, temperature changes may lead to a clearance between the bushing and the hole surface, because of mutually different temperature coefficents for the metal and the steel. This is particularly a problem when the metal is a light metal or light metal alloy having a*-large temperature coefficient.

The main object of the present invention is to achieve an improvement of the above circumstances.

In accordance with the invention this is achieved with a metal element and a method, respectively, as defined in the succeeding patent claims.

Because the hole diverges, for instance conically, towards the ends, a favourable distribution of the stresses iϊ , achieved. When the second element, i.e. the element attached in the hole through the metal element, is subjected to bend¬ ing and/or shear, the hole surface will be ^' subjected to forces which increase towards the hole ends. In the end areas of the hole the circumference of the hole, however, is largest, and also the unit area per hole unit length,- and the hole surface, hence, has a substantially greater ability to withstand load¬ ings, compared with the surface of a cylindrical hole having diameter corresponding to the smallest diameter of the hole in the metal element in accordance with the present invention, i.e. a hole which diverges towards both ends.

Another advantage is the shape of the hole efficiently pre¬ vents that the second element can loosen from the hole.

According to an advantageous embodiment of the invention at least one of the frusto-conical surfaces inside the hole ends in a bevelled portion at the end of the hole, i.e. the conical surface ends in a conical surface having a substantially in¬ creased conus angle or in a double curved, circumferential surface. Such a bevelled portion is particularly advantageous for the purpose of avoiding clearance between the metal ele¬ ment and the second element when the second element is made cf a material having a less temperature coefficient than the metal. As an example is mentioned the combination of aluminium and steel, v/here the ratio between the temperature coefficients is about 2:1. By means of the bevelled surface or surfaces it- can be achieved that the two materials "follow" each other during temerature ^" changes. The reason for this is that the oevelled portion or portions compensate for the difference

3 with respect to the coefficients.

In many applications it is of substantial importance to avoid clearances between the elements. If a clearance occurs,there may occur impacts, i.e. a kind of "hammering" of the metal.

In order to achieve the advantageous effect of the bevelled portion or portions it or they should be conical and have a conus angle which is correctly chosen.

The invention will hereinafter be described more in detail, with reference to the accompanying drawin, which shows two embodiments of a metal element according to the invention.

Fig. 1 shows a section through a part of a metal element, in which is attached a second element, in the example in the form of a shaft which may for instance be an extension of a wheel spindle for an automobile or a waggon."

Fig. 2 also shows a section through a part of a metal element in which is attached a second element in the form of a bushing or sleeve. Moreover, it is indicated a conical shaft attached to the bushing by means of a nut.

Fig. 1 shows a metal element 1, which in the example shown is a part of a vehicle wheel suspension, to which element is attach¬ ed a wheel spindle 6. On the wheel spindle 6, of which only a fraction is shown, may be mounted a ball or roller bearing for a wheel. The spindle 6 has a flange 7, which usually is used as a sliding surface for a sealing ring. The spindle 6 is attached to the metal element 1 by means of a stud 2, being deformed in such a manner that it completely fills the hole in the element ^' 1. The stud 2 may, as shown, be integral with the spindle 6, and is usually made of steel. In accordance with the invention the stud may initially be cylindrical, and has been pressed axially in such a manner that it finally fills the hole. The stud 2, however, may alternatively have been given such an initial shape that the half of the stud nearest

to the spindle 6 mainly is complementary to the shape of the corresponding half of the hole, the other half of the stud being cylindrical. This is advantageous in case the stud is not accessible to be pressed by means of a tool on the half nearest to the spindle, as in the example shown.

The hole in the element 1 comprises two conical surfaces 3 which adjoin each other in the middle of the hole. Each end of the hole has a widened portion completely occupied by corresponding portions of the stud 2. In the example shown the widened portions 4 have a conus angle of about 90 .

Fig 2 also shows an element, which in this embodiment may be a bar, and the second element is a sleeve having a conical hole. Also indicated is a conical pin 8 which has been pulled into the sleeve 2 by means of a nut 9 resting against a washer 10, shown in dotted lines.

The hole i^ the -element 1- has in this embodiment mainly the same shape as shown in Fig. 1,comprising conical surfaces 3 and bevelled portions 4. The hole, however, comprises a cylindrical middle portion 5. This may be an advantage with respect to the making of the hole, because the axial length of said cylindrical portion constitutes a measure indicating whether the conical milling tool has come to the appropriate depth in the hole.

The sleeve 2 shown in Fig. 2 may initially be manufactured with a cylindrical outer surface. The sleeve may have a hole, but it may also be massive all through, i.e. being in fact a massive cylinder, because the conical hole must under all circumstances be machined after being deformed by pressing. Because the sleeve 2 is accessible from both ends, a cylindri¬ cal sleeve can be pressed from both ends by means of a suit¬ able tool, until it completely fills the hole in the element 1.

S^r ^;

The stud 2 shown in Fig. 1 and the sleeve 2 shown in Fig. 2, respectively, making what is called the second element in this specification, will usually not have its end surface or surfaces completely coplanar with the surface or surfaces of the element 1 after the pressing operation. When it is desired that said surfaces are coplanar, the end or ends of the stud or sleeve may of course be machined, for instance by milling in order to achieve coplanar surfaces.

The present invention is in particular useful in cases where it is desirable to achieve a weight reduction compared with making the element 1 of steel, and in particular when the joint between the elements must be able to transfer large ^' dynamic forces. Fig. 1 shows an embodiment which, as already mentioned, may be used to secure a wheel spindle in a carrying element, while Fig. 2 shows an embodiment in which the element ^' 1 may be an arm in the wheel suspension of a vehicle, and the pin 8 may be provided with a ball, for instance Cf the type used in order to permit the turning movement of the front wheel and the springing movement of the chassis. By making such suspension arms from for instance light metal it is achieved a reduction of the weight of the automobile and improved road performance (less unsprung masses) , compared with the use of steel arms.