US3567892A

US3567892A - Electric switches of large power comprising axially movable switching rods and resilient annular fixed contacts which are in permanent contact with said switching rods and contact strips for such fixed contacts

Info

Publication number: US3567892A
Application number: US867796A
Authority: US
Inventors: Rintje Boersma; Gijsbert W Irik
Original assignee: COQ NV
Current assignee: COQ NV
Priority date: 1969-04-15
Filing date: 1969-10-20
Publication date: 1971-03-02
Anticipated expiration: 1988-03-02
Also published as: DE1945895A1; NL135150C; FR2039174A1; JPS502068B1; NL6905749A; BE738895A; AT295640B; SE367731B; GB1222919A; DE1945895B2

Abstract

An electric switch having an axially movable switching rod and a fixed contact which is in permanent contact with said switching contact. The fixed contact comprising a zigzag folded metal contact strip which is bent in the shape of an uninterrupted ring. The inner circumference of said ring is bent in the shape of longitudinally split tubes extending in the direction of the width of said strip and interconnecting the parts of the folded strip that adjoin each other at said inner circumference.

Description

United States Patent [7 21 Inventors Rintje Boersma Harmelen; Gijsbert W. Irik, Bilthoven, Netherlands 21] Appl. No. 867,796 [22] Filed Oct. 20, 1969 [45] Patented Mar. 2, 1971 [73] Assignee N.V. COQ

Utrecht Kanaalweg, Netherlands [32] Priority Apr. 15, 1969 [33 Netherlands 3 l 1 69.05749 [54] ELECTRIC SWITCHES OF LARGE POWER COMPRISING AXIALLY MOVABLE SWITCHING RODS AND RESILIENT ANNULAR FIXED CONTACTS WHICH ARE IN PERMANENT CONTACT WITH SAID SWITCHING RODS AND CONTACT STRIPS FOR SUCH FIXED CONTACTS 6 Claims, 5 Drawing Figs.

[52] US. Cl

[51] Int. Cl .6 Htllh l/10 [50] Field of Search 200/166 (B1), 166 (B8) [56] References Cited UNITED STATES PATENTS 2,975,254 3/1961 Yanagisawa ...200/l66(B1)(X) 3,087,038 4/1963 Bethke 200/166(Bl) Primary Examiner-4i. 0. Jones Attorney-Snyder and Butrum ABSTRACT: An electric switch having an axially movable switching rod and a fixed contact which is in permanent contact with said switching contact. The fixed contact comprising a zigzag folded metal contact strip which is bent in the shape of an uninterrupted ring. The inner circumference of said ring is bent in the shape of longitudinally split tubes extending in the direction of the width of said strip and interconnecting the parts of the folded strip that adjoin each other at said inner circumference.

3; 567,892 PATENTEB "AR 2 I97! INVENTORQ RiNra'E 805R A eia'sssnr w. K

BY9 Www ATTORNEYS The invention relates to an electric switch of large power comprising an axially movable switching rod and a resilient annular fixed contact which is in permanent contact with said switching rod and is adapted to connect said switching rod electrically conductively with the circuit to be closed and opened by said switch, said fixed contacts consisting of a zigzag folded metal contact strip which is surrounded and supported by an annular holder and is bent in the shape of an uninterrupted ring, which snugly encloses the switching contact.

Annular fixed contacts of this kind are known in many shapes. If the folded contact strip of such a fixed contact is arranged, as is usual, with the bisectors of the angles, enclosed between its adjacent parts diverging in V-shape, in radial direction to the switching rod, the resilience of the strip is very tough and there is the risk that the contact strip does not lie with all folds at the inner circumference of the ring formed by said strip against the switching rod with substantially equal pressure and that some of said folds do not touch the switching rod at all. More over, the number of contact places between the contact strip and the switching rod and between said rod and the holder of said strip is restricted, which may lead at large currents, e.g. short circuit currents, to the burning-out of said strip. If the contact strip is directed with its parts in more tangential directions to the switching rod the resilience is more elastic and the number of contact places between the strip and the switching rod and between said strip and the holder can be increased, but then the cooling of the strip in the contact places appears to be worse, which may also lead to burning-out at short circuit. The parts of the strip must then still join each other at the inner circumference of the contact ring somewhat in V-shape, so that the possible number of contact places is decreased again. In the fixed contacts of the described kind the best arrangement is always a comprise between the resilience, the number of contact places and the cooling.

The invention has for its object to provide a switch comprising a switching rod and a fixed contact consisting of a folded contact strip and being in permanent contact with said rod, in which the parts of the contact strip lie against the switching rod with well reproducible resilience,'the number of contact places can be large and s satisfactory cooling of said contact places is obtained. The invention consists in that the said contact strip is folded in such a manner, that the parts of each individual pair of adjacent parts thereof are interconnected at the inner circumference of said ring by a portion of the contact strip which is bent in the shape of a split tube extending in the direction of the width of said strip. Consequently, the strip is bent tubularly in the contact places. Owing thereto not only the resisting moment of the contact strip is increased in the contact places but also a satisfactory cooling in said places becomes possible. Due to this better cooling it becomes possible to lay two parts of the strip interconnected by such a tubular portion very close or even completely one against the other, which means that, considering that the parts of the strip have to extend tangentially to the switching rod, a reproducible well-elastic resilience of said parts is obtained and the number of contact places an be relatively large. Load tests have proved that the fixed contact manufactured in accordance with the invention is resistant to considerably larger currents than the fixed contact, of which the folded strip does not have the tubular portions in the contact places.

Advantageously, the fixed contact of the switch may be constructed in such a manner, that one part of each pair of adjacent parts interconnected by a tubular portion of the contact strip merges smoothly and the 7 other part thereof merges through a fold extending in the direction of the width of said strip into said tubular portion. In this construction the parts of the strip come to lie near the contact places, a bit farther from the switching rod, whereby the cooling is still further improved.

Preferably, each tubular portion interconnecting two adjacent parts of the contact strip and at least the end portions of said parts adjoining said tubular portion are curved both in the direction of the width of said strip and in a plane at right angles with the plane of said strip. This prevents that the switching rod is scraped by edges of the strip, when said rod is moved through the fixed contact. Thereby the movement of the switching rod through the fixed contact is facilitated and the'risk that the switching rod takes the strip along during its movement, whereby the latter is deformed in cross direction, is reduced practically to mil.

The invention also relates to a contact strip for the mentioned fixed contact of the described switch, said co'ntact strip being constructed in such a manner, that the parts of each individual pair of adjacent parts of the contact strip are interconnected by a portion of said strip which is bent in the shape of a split tube extending in the direction of the width of said strip. If necessary, each tubular portion interconnecting two adjacent parts of the contact strip and at least the end portions of said parts adjoining said tubular portion may be curved both in the direction of the width and in a plane at right angles with the plane of said strip.

The invention will be elucidated with the aid of the drawing. Therein is:

FIG. 1 partly an axial sectional view, partly an elevational view of a switching rod and a fixed contact which is permanently in contact with said rod of a switch of large power according to the invention;

FIG. 2 a cross sectional view taken on the line Il-Il in FIG.

FIG. 3 in perspective a portion of a contact strip for the mentioned fixed contact of such a switch;

FIG. 4 in perspective a portion of a variant of the contact strip shown in FIG. 3 and used in the fixed contact shown in FIGS. 1 and 2; and

FIG. 5 in perspective a portion of a variant of the contact strip shown in FIG. 4.

ln FIGS. 1 and 2 an axially movable switching rod of an electric switch of large power is designated by 1. Provided for the permanent connection of the switching rod 1 with the outer circuit is a fixed contact which consists of an annular metal holder 2 and a contact strip 3 supported by said holder. The contact strip 3 consists of a zigzag folded metal strip which is bent in the shape of a ring snugly enclosing the switching rod 1. The

parts

3, 3" of the folded strip 3 extends closely and almost parallel to each other in pairs and they are directed nealy tangentially to the switching rod 1 (see FIG. 2).

The two parts 3', 3 of each pair of substantially parallel parts are interconnected at the inner circumference of the ring formed by the strip 3 by a portion 4 of the strip which is bent in the shape of a split tube. The strip 3 is resiliently forced against the switching rod 1 with the tubular portions 4. The tubular shape of the strip 3 in the contact places between the fixed

contact

2, 3 and the switching rod 1 improves the cooling in said places.

In the embodiment shown in FIG. 3 the tubular portion 4 of the strip 3 is symmetrically positioned in respect of the parts 33" interconnected by said portion 4. In FIGS. 2 and 4 the tubular portion 4' is asymmetrically positioned in such a manner, that the part 3' merges smoothly and the part 3" merges through a fold 5 extending in the direction of the width of said strip into said tubular portion 4'. Due to this construction a somewhat better cooling of the contact places is obtained.

In the variant shown in FIG. 5 the tubular portion 4" and the end portion of the parts 3', 3" of the contact strip adjoining said portion 4" are somewhat curved in the direction of the width and transversely to the plane of the strip. Owing thereto the edges of the strip come to lie against the switching rod 1 with little or no pressure, so that it is avoided, that during the movement of the switching rod said edges of the strip scrape over the surface of said rod, whereby the switching rod could be damaged and the contact strip could be taken along with the switching rod through a small distance.

We claim:

1. An electric switch of large power comprising an axially movable switching rod, a resilient annular fixed contact which is in permanent contact with said switching rod to connect same with the circuit to be closed and opened by the switch, an annular holder and a zigzag folded metal contact strip which is surrounded and supported by said holder and bent in the shape of an uninterrupted ring that snugly encloses said switching rod, said holder and said contact strip constituting together said fixed contact, the parts of each individual pair of adjacent parts of sad contact strip interconnected at the inner circumference of said ring by a portion of said contact strip which is bent in the shape of a longitudinally split tube extending in the direction of the width of said contact strip.

2. An electric switch as claimed in claim 1, in which one part of each pair of adjacent parts interconnected by a tubular portion of said contact strip merges smoothly and the other part thereof merges through a fold extending in the direction of the width of said contact strip into said tubular portion.

3. An electric switch as claimed in claim 1, in which the parts of each pair of adjacent parts interconnected by a tubular portion of the contact strip lie practically against each other.

4. An electric switch as claimed in claim 1, in which each tubular portion interconnecting two adjacent parts of said contact strip and at least the end portions of said parts adjoining said tubular portion are curved both in the direction of the width of and at right angles with said parts.

5. A zigzag folded metal contact strip for a fixed contact of the electric switch claimed in claim 1, in which the parts of each individual pair of adjacent parts of said contact strip are interconnected by a portion of said strip which is bent in the shape of a longitudinally split tube extending in the direction of the width of the contact strip.

6. A zigzag folded metal contact strip as claimed in claim 5, in which each tubular portion interconnecting two adjacent parts adjoining said tubular portion are curved both in the direction of the width and at right angles with said parts.