GB2239827A - Method for joining conductor parts of an electric switch component - Google Patents

Abstract

For the simplified and more rapid production of a switch component 1 having a bimetallic element 3 and a switch 6 which can be actuated by the bimetallic element via a transfer element 15, the conductor parts 4 are joined to contact parts 5 by welding. For this purpose, each conductor pan 4 has a vertical welding section 8 which is partly exposed to the outside of the ceramic body 2. A contact part 5 is then placed on the exposed section 8 and is welded thereto. <IMAGE>

Description

METHOD FOR JOINING CONDUCTOR PARTS OF AN ELECTRIC SWITCH COMPONENT The invention relates to a method for joining conductor parts of an electric switch component, at least one of which conductor parts is surrounded at least over an area by an element of ceramic or similar high-temperature-resistant material.

According to DE-OS 3,538,537, it is already known to rivet current-conducting conductors of electric switch components to one another. For this purpose, a metal part provided as rivet is passed through a hole in a ceramic body, heated by the passage of current and deformed under pressure in the heated state. Such joints have the disadvantage, particularly when used in high environmental temperatures, that they become loose in the course of time and thus considerably impair the current transfer. In addition, such mechanical joints have the disadvantage of high contact resistances which can increase further by the formation of oxide or similar during operation. In addition, the disadvantage of an additional work step required for inserting the rivets is given with this known rivet joint.

The invention then has the object of creating such joints of conductor parts of an electric switch component which are essentially free of electric contact resistances and, in addition, provide the possibility of advantageous more rapid production.

According to the invention, the object is achieved by the fact that the conductor parts are joined to one another by welding. After the optimum welding duration and current density has been set, such a joint can be particularly rapidly and durably produced, in which connection, in particular, even an environmental temperature which is increased during operation of the switch component does not have any deleterious effect on the contact resistance in the area of the weld. Another advantage of such a joint can also be seen in the fact that the area of deformation is restricted to a very short, essentially small part area of the conductor part to be joined.

The invention also relates to an electric switch component having an insulation body, preferably of ceramic, a switch unit attached to a carrying or supply part which is passed through the insulation body, and a contact part joined to the carrying or supply part. The invention is characterized by the fact that the carrying or supply part exhibits in its welding section passed through the insulation body a cross-sectional area whizz is smaller in comparison with the remain i r.g carrying section, the transition area between the two sections being constructed to be step-shaped, forming a support shoulder which is intended to rest against the insulation body, and that the end of the welding section projecting from the insulation body is joined to the contact part by welding.Due to the construction of a wider and of a narrower section, it is ensured that only the section to be joined to the contact part is heated during the welding process. Due to the formation of the support shoulder, exact placement of the end of the welding section to be welded at the intended place is ensured when the support shoulder rests against the insulation body. It is suitable in this connection to allow the end which is to be welded to project over the insulation body by exactly the length of the intended distance of deformation, as a result of which the movement of the contact part pressed with pressure against the melting end of the welding section is automatically stopped by coming to rest against the insulation body after the deformation distance has reached its end. An accurate joint can be particularly rapidly produced in this manner.

Due to the fact that the deformation of the carrying or supply part with the welding is restricted to its end area, a durable joint is produced even after a brief action of current whilst avoiding inadmissibly high mechanical stressing of the insulation body.

Another preferred embodiment of the invention consists in the fact that the carrying or support part is constructed to be U-shaped and the two legs, which extend parallel to one another, exhibit in each case a carrying section which adjoins thecentre vertical leg and a welding section which is passed through the insulation body.

Such a U-shaped construction of the carrying or support part ensures a particularly firm connection with the contact part, in which arrangement virtually no contact resistances occur due to the two contact points.

According to another advantageous embodiment of the invention, the welding section of the carrying or support part exhibits in front of the welding joint with the contact part, a circular cross-section having a conical tip provided in the end area. Due to the pointed construction of the welding section, a particularly rapid and point-shaped melting can be achieved due to high current density, as a result of which the contact part is immediately fixed in location.

The end of the welding section of the carrying or support part provided for the joint with the contact part can exhibit another preferably wedge-shaped step according to a further preferred embodiment of the invention. With a flat construction of the carrying or supply part, such a wedge-shaped step enables high current density to be formed for a linear and stable welding joint.

Another preferred embodiment of the invention consists in the fact that the end of the welding section of the carrying or support part provided for the joint with the contact part exhibits a centre U-shaped recess, form ing two spaced-apart welding webs. The construct ion of welding webs results in a reduction in the cross-section of the welding section so that a rapid melting and stable two-point joint can be achieved.

Finally, another advantageous embodiment of the invention also consists in the fact that indentations in the insulation body are arranged in the area of the end of the welding section provided for the joint with the contact part. The welding material of the welding section displaced by the pressing-on of the contact part can be accommodated by these indentations in the insulation body.

In the text which follows, the invention is described in greater detail with the aid of several illustrative embodiments shown in the drawing, in which: Figure 1 shows a cross-section through a switch component constructed in accordance with the invention, Figure 2 shows a top view of the switch component accord ing to Figure 1, Figures 3 show enlarged illustrative embodiments of a to 8 carrying or supply part constructed in accordance with the invention and Figure 9 shows a greatly magnified cross-section through another embodiment of a switch component accord ing to the invention.

A switch component (1), which can be seen in Figure 1, essentially consists of a cylindrical insulation body (2) of ceramic, a bimetallic element (3), two bow - or U-shaped carrying or supply parts (4) and contact parts (5) arranged at the top side of the insuLation body (2).

Each carrying or supply part (4) exhibits a wide carrying section (7) provided for accommodating a switch (6) and a narrower welding section (8) which is passed through a corresponding rectangular opening (9) in the insulation body (2). This welding section (8) of the carrying or supply part (4) is welded to the contact part with its free end projecting over the plane (11) of the insulation body (2). The said switch (6) essentially consists of a current-conducting bridge (12) which connects the two carrying or supply parts (4) to one another, having an end-side contact (13) and a spring (14) connected to the bridge (12). A transfer element (15) of electrically insulating material, for example ceramic, is carried between the bimetallic element (3) and the bridge (12).

The switch component (1) is produced in such a manner that, after insertion of the bridge (12) with the spring (4) into the insulation body (2), the two carrying or supply parts (4) with their four welding sections (8) are introduced into the openings (9) of the insulation body (2) until the support shoulders (16) located between the carrying and the welding section (7) and (8), respectively, rest against the underside (17) of the insulation body (2). The carrying or supply parts (4) are oressed against the underside (17) of the insulation body (2) by a tool which, at the same time, is constructed as electrode of a welding device. As a next step, the two contact parts (5) are pressed against the ends of the welding sections (8) projecting over the plane 11, also with the aid of a tool constructed as electrode, a current of high current density flowing through the two electrodes.

During this process, the welding section ends melt and are firmly joined to the contact parts (5). The welding material laterally displaced during the melting flows into an indentation (18) in the insulation body (2) which adjoins the opening (9).

The switch component (1) operates as follows. As soon as high heating occurs in the area of the bimetallic element (3), it is arched up in the direction of the switch (6), during which process the transfer element (15) leads to a Lifting of the bridge (12) which is directed against the action of the spring (14). During this process, the contact (13) is lifted away from the corresponding carrying or supply part (4), as a result of which the contact between the two carrying or supply parts (4.) and the associated contact parts (5), which are in each case connected to a current-conducting conductor, is interrupted.

As soon as the bimetallic element (3), after having cooled off, bends back into the initial position shown in Figure 1, the contact (13) stops against the associated carrying or supply part (4) due to the action of the spring (14), as a result of which the contact between the two contact parts (5) is restored and thus current- can flow.

In Figure 3, the carrying or supply part (4) is shown in a slightly smaller side view.

In Figure 4, the end of a welding section (8-), which exhibits a wedge-shaped tapering (19) is shown enlarged. The narrow longitudinal web (20) formed as a result comes into contact with the contact part (5) during the welding process and is melted by the high current density occurring during the welding process.

In Figure 5, the end of the welding section, designated by (19), is also constructed to be wedge-shaped.

In Figure 6, the end of the welding section is constructed to be forked.

The switch component shown in Figure 9, corresponding in its operation to that of Figure 1, exhibits a U-shaped carrying or supply part (4) and a carrying or supply part (4) which is constructed to be rod-shaped and which can be seen in a side view in Figure 7.

The welding section (8) of a carrying or supply part (4) shown in Figure 8 consists of two cylindrical bodies having a different diameter, one end being constructed as conical tip (21).

The construction of the welding section is not restricted to the examples listed.

Claims (1)

1. Method for welding conductor parts of an electric switch component (1), having a ceramic body (2), characterised by: providing a first conductor part (4) inside the ceramic body (2), said first conductor part (4) being partly surrounded by the ceramic body (2) and partly exposed (8) to the outside of the ceramic body (2) of the electric switch component (1); placing a second conductor part (5) on the exposed section (8) of the first conductor part; and welding the second conductor part (5) thereto.