GB2101406A

GB2101406A - Contact member and blade assembly and method of making same

Info

Publication number: GB2101406A
Application number: GB08213200A
Authority: GB
Inventors: Janez Rizman; Jurica Zadravec
Original assignee: ISKRA SOZD ELEKTRO INDUS
Current assignee: ISKRA SOZD ELEKTRO INDUS
Priority date: 1981-05-11
Filing date: 1982-05-07
Publication date: 1983-01-12
Also published as: YU39887B; DD209042A5; YU119681A; DE3217657A1; JPS5832316A; FR2505549A1; IT8267620A0; IT1155345B; IT8253266V0

Abstract

A contact member and blade assembly has a first and optionally a second contact member, (1, 1') in the form of a hollow cap. The contact member (1, 1') can be made of a hard, e.g. sintered material or of a softer contact material which can be deformed. The member (1) has a peripheral groove engageable in an aperture formed in the blade (2). The aperture has an edge raised out of the plane of the blade (2) which forms a flange (3') for abutting in the groove in the member (1) to hold it in place. A second contact member (1') may be provided located on the opposite side of the blade (2) to the first contact member (1) to provide bilateral contacts, or the member (1) may be bent through 180 DEG to provide bilateral contacts. <IMAGE>

Description

SPECIFICATION Contact member and blade assembly and method of making same This invention relates to a contact member and blade assembly for use in the switching part of a relay or other switching component, and also concerns a method of making such an assembly.

An assembly of a contact member and a blade is known, in which the contact member is made of solid material, especially of a noble metal. Such an assembly has a high operational quality, but has at least two disadvantages. One is the high price of the compiete switching element and the relay, respectively, an essential part of which is the price of the noble metal of the contact members. The second disadvantage is the increased mass of the moving part of the switching component and the relay, respectively, which has an influence upon the switching time.

An assembly of a contact member with a blade also is known, in which the solid contact member is replaced by a bimetal or trimetal contact member, which is embodied in such manner than onto a supporting piece made of a common metal, e.g. copper, a thin layer of a noble contact material is deposited on one side or on both sides thereof. The thickness of such a layer is between 0.1 and 0.6mm, which depends.upon the desired lifetime and the electrode loading of the contact itself. The disadvantage of such a solution first of all lies in a relatively short lifetime of such an assembly in which a qualitative contact is established by the member.The electric arc on the contact causes relatively fast wearing of the contact material at the point at which the arc appears so that the arc causes a formation of an alloy of the noble metal with the material of the supporting piece which highly increases the contact resistance. In assemblies in which the contact member is made of sintered material, the contact member must be fitted to the blade as a solid; member, as a thin layer deposition is not possible, The attachment of sintered members is technoiogically different, which means that-the manufacturer requires extra equipment, which additionally influences the production- cost.

There is thus a need for a generally improved assembly of contact member and blade, which minimises the disadvantages of known assemblies.

According to one aspect of the present invention there is provided a contact member and blade assembly, including a first contact member in the form of a hollow cap with a circumferential groove insertable into an aperture in the blade, the edge of the blade defining the-aperture being raised out ofthe plane of the blade to form a flange for abutting against the circumferential groove in the first contact member under pressure.

According-to another aspect of the present invention there is provided a method of making an assembly as he rein before described, in which a first contact member in the form of a hollow cap with a circumferential groove is pressed into a flanged aperture in the blade so that the flange abuts against the groove of the first contact member, whereafter the flange is squeezed into the groove.

An assembly of the invention does not require the use of large amounts of a noble material for the contact member thereby reducing the mass of the whole assembly and preventing the formation of alloys between the material of the contact member and substrate to which the member is fixed. Additionally, an assembly of the invention permits, to a great extent, similar technological treatment for contact members made of usual contact material and-for contact members made of sintered material. The method of the invention allows the production of assemblies with bilateral contact members.

Four a better understanding of the present invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings in which: Figure 1 shows a blade with an inserted, but not fixed contact member, in cross-section, according to one embodiment of the invention.

Figure 2 shows the contact member of Figure 1 fixed in the blade, in cross-section; Figure 3 shows a second embodiment of the invention having a blade with contact member positioned on-both sides, in cross-section; Figure 4a shows the starting form of a blade with two contact members of a third embodiment, in cross-section: Figure 4b shows the final form of Figure 4a with the blade with contact members positioned on both sides; and Figure 5 shows a fourth embodiment of the invention having a blade with a bent contact member.

As is shown in the accompanying drawings a contact member and blade assembly of the invention has a blade 2 in which an aperture is made with an edge 3 of which is slightly raised out of the plane of the blade to form a flange 3'.

Into this aperture a contact member 1 is inserted, which may be made of a very hard, e.g. sintered material, and has the form of a cap with a circumferential groove, which is shown in the upper part of Figure 1. If the member 1 is made of softer material which can be deformed, it has the form of a cap with an edge slightly bent outwards to form the groove, as shown in the lower part of Figure 1. The diameter of the member 1 is such that it can be forced into the aperture in the blade 2 so that the edge 3 of the aperture of the blade 2 abuts the groove or snaps into the groove.

To ensure a rigid junction of the contact member 1 with the blade 2 and to form a reliable and durable contact assembly, in the case that the member 1 is made of sintered material, the edge 3 of the aperture of the blade 2 has to be pressed against the circumferential groove of the member 1 whereby a contact assembly as shown in cross section in Figure 2 is attained.

From this Figure it is evident that by said treatment the flanged edge 3' is pressed into the groove of the member 1, whereby, because of the relatively large abutting area between the member 1 and the blade 2, an extremely good and at the same time a durable and mechanically firm contact is achieved. In the case that the contact member 1 is drawn from sheet-metal, i.e.

of soft material, this member 1 is pressed with the aid of a proper tool from both sides so that the member 1 is deformed and close contact with the raised edge 3 of the aperture of the blade 2 is established.

Figure 3 shows an embodiment with a contact member positioned on both sides, in crosssection From this Figure it is evident that the contact member is positioned first in the blade 2 and fixed therein in the above described manner.

From the other side a contact member 1' is pressed into the cavity of the contact member 1.

This contact member 1' is also a cap which need not have a circumferential groove nor an outwardly bent edge so that its wall forms a cylinder in the axial direction, the outer diameter of the member 1' being equal to the diameter of the member 1 at that place where the member 1 abuts against the blade 2. The member 1' is pressed into the member 1 so far that the outer part of the wall of the member 1' where the diameter enlarges abuts against the inner part of the wall of the member 1 at its edge. Because of the high friction between both members 1, 1' it can be considered that cold weiding takes place between the members 1. 1' ensuring durability of the contact between the members 1, 1' as well as with the blade 2.

In Figure 4b a further embodiment is shown with the blade 2 having a contact member positioned on both sides. As is evident from Figure 4a, two members 1 are fixed to the blade 2 one beside the other, in the longitudinal direction of the blade 1. By bending the blade 2 about an axis 4 in the middle between both members 1, symmetrical positioning of the contact members on both sides is attained, with this embodiment additionally yielding the advantage that falling out of the members 1 from the blade 2 is impossible.

In Figure 5 an embodiment of the assembly is shown in which the member 1 is such that the bending about the axis 4 is executed in its middle.

Thereby with one single contact member a bilateral contact area is attained. In a simplified embodiment instead of a member a layer of contact material of a restricted length is deposited on the blade, the bending being executed in the middle of this layer: this embodiment is not shown in the drawing.

The free end 5 of the bent part of the blade 2' is connected to the other part of the blade 2, e.g.

by welding.

With the assembly of the invention very little contact material is needed for the contact member so that the member is cheap and light in weight.

Eventualiy with high current and prolonged usage the electric arc formed at each switching-on and off may cause an aperture to form in the member of the assembly according to the invention, but this does not disturb the operation of the device using the assembly according to the invention.

After the formation of the aperture the contact place slightly shifts, but in spite of this the composition of the material of the contact itself does not change so that also practically the same contact resistance is ensured as existed in the original new contact assembly.

Claims

1. Contact member and blade assembly, including a first contact member in the form of a hollow cap with a circumferential groove insertable into an aperture in the blade. the edge of the blade defining the aperture being raised out of the plane of the blade to form a flange for abutting against the circumferential groove in the first contact member under pressure.

2. Assembly according to claim 1, including a second contact member in the form of a hollow cap engageable in the open mouth of the first contact member from the opposite side of the blade to the first contact member such that a contact is formed on both sides of the blade by the contact members.

3. Assembly according to claim 1, in which the blade has two such apertures and is bent so that the two apertures are coaxial, a second contact member in the form of a hollow cap being engageable in the second aperture so that contacts are formed by the cap members on opposite sides of the blade.

4. Assembly according to claim 1, in which the blade is bent back on itself about an axis passing through the aperture so that the first contact member encloses the bent axis.

5. Method of making an assembly according to claim 1 in which a first contact member in the form of a hollow cap with a circumferential groove is pressed into a flanged aperture in the blaze so that the flange abuts against the groove of the first contact member, whereafter the flange is squeezed into the groove.

6. Method of making an assembly according to claim 1, in which a first contact member in the form of a hollow cap is inserted into a flanged apart, e in the blade, and the first contact member is flanged over against the raised edge of the o ade forming the flange of the aperture of the blade.

7. Method according to claim 5, in which a second contact member in the form of a hollow cap is pressed into the cavity of the first contact member so that the outer wall of a widened part of the second contact member abuts against the widened inner wall of the edge of the first contact member and thereby cold welds thereto.

8. Method of making an assembly according to claim 3 in which first and second contact members in the form of hollow caps are engaged in respective apertures formed side by side in the longitudinal direction of a blade, the blade is bent symmetrically between the two contact members through 1800 so that the contact members are coaxially positioned, and the bent over part of the blade is at its free end connected to the other part of the blade.

9. Method according to claim 5, in which after the first contact member has been fixed to the blade the blade and first contact member are bent in the middle of the contact member through 1800, and the bent over part of the blade is at its free end connected to the other part of the blade.

10. Contact member and blade assembly, substantially as hereinbefore described with reference to Figures 1 and 2, Figure 3, Figures 4a and 4b, or Figure 5 of the accompanying drawings.