GB2378579A

GB2378579A - Latching mechanism

Info

Publication number: GB2378579A
Application number: GB0217889A
Authority: GB
Inventors: Bogdan Zabrocki
Original assignee: Moeller GmbH
Current assignee: Eaton Industries GmbH
Priority date: 2001-08-10
Filing date: 2002-08-01
Publication date: 2003-02-12
Anticipated expiration: 2022-08-01
Also published as: GB0217889D0; GB2378579B; DE10139566C1; ITMI20021747A1; FR2828578A1; FR2828578B1

Abstract

A latching mechanism comprises a latch 10 with at least one latching surface 12 and a latch lever 20 with a respective latch lever nose 22 latchable with the latching surface 12 as a component of the switching lock of a low-voltage power switch. The problem to be resolved lies in permanent reliable operation in spite of inadequate resistance on the part of the material of the latching surface 12. For that purpose in the latched condition the latching surface 12 is completely on the latching lever nose 22.

Description

Improvements in and Relating to Latching Mechanisms The invention concerns a latching mechanism, in particular, although not exclusively, to a latching mechanism for a power switch. The latching mechanism is a component part of the switching lock of a low-voltage power switch.

US Patent No 3 614 685 discloses a power switch with a multi-pole contact system. The switching lock comprises a U-shaped drive lever which is supported with its outer legs tiltably in fixed side covers and which has an actuating lever, a bell crank mechanism with an upper bell crank, a lower bell crank and a spring force-storage means, and a support lever mounted pivotably between the side covers. The bell cranks are pivotably connected together by way of a bell crank axis. The spring force-storage means engages between the bell crank axis and the drive lever. The lower bell crank is pivotably connected to a switching shaft. The switching shaft carries movable contact arrangements with single-arm movable contacts which are pivotable against the action of contact pressure springs within the so-called transfer stroke movement. The support lever is pivotably connected to the upper bell crank. The switching lock can be reset after a tripping operation by a procedure whereby the support lever is to be moved by passing the drive lever beyond its off position into a condition of supporting connection, which is subjected to the action of the spring force-storage means, to a latching mechanism which is operatively connected to tripping means.

German patent application number 42 27 213-Al discloses a switching lock with a latching mechanism comprising a latch actuable by tripping means and a latch lever which is latchable thereby and which in turn locks the support lever in the nontripped condition. The latch and the latch lever can be inserted pivotably in the side covers and held therein by the force action of a latch spring which engages the latch and the latch lever. Provided on the latch lever is a latch lever nose which can be brought into operative relationship, directed in such a way as to increase the biasing of the latch spring, with a corresponding latching surface on the latch. The latch generally comprises a softer material, in particular plastic material, than the metal latch lever. In the course of the service life of the power switch the numerous co-operations of the latch lever nose and the latching surface mean that there is material abrasive wear and in part material displacement at the latching surface, whereby inter alia an irregular

surface portion occurs in the latching surface, which surface portion co-operates with the latch lever nose. The co-operation of the latch lever nose with the irregular surface portion which is formed in that way disadvantageously results in a displacement in the direction of the force which the latch lever applies to the latching surface under the influence of the latch spring. Due to the displacement in the direction of the force, an inwardly rotating or an outwardly rotating moment of force is increasingly exerted on the latch. The increasing displacement in the direction of the force results in the first case in a marked increase in the frictional force between the latch lever nose and the latching surface so that in the extreme situation the switching lock can no longer be tripped. In the second case the increasing displacement in the direction of the force results in a marked reduction in the frictional force between the latch lever nose and the latching surface so that in the extreme case the switching lock can no longer be transferred into the non-tripped condition.

European patent application number 0 555 158-Al discloses a latching mechanism of a switching lock with a spring force-storage means for low-voltage power switches, having a latch, a latch lever and a support lever which is supported on the latch lever. That latching mechanism also does not resolve the above-depicted problem.

The invention is therefore based on the problem of ensuring durable and reliable operation of the latching mechanism.

In accordance with preferred embodiments of the invention, that problem is solved by the characterising features of the independent claim, while advantageous developments of the invention are to be found in the appendant claims.

Preferred embodiments of the present invention relate to the type of latch mechanism of a switching lock, with spring force-storage means for low-voltage power switches, comprising a latch actuable by tripping means and pivotable about a first axis, a latch lever pivotable about a second axis, wherein the axes of the latch and the latch lever are mounted pivotably in side covers of the switching lock and the latch is mutually latchable with the latch lever, for which purposes provided on the latch lever is at least one latch lever nose which can be operatively connected to a corresponding latching surface on the latch.

The proposed configuration of the latching surface on the latch and the oppositely disposed operative surface, which is in relationship therewith, of the latch lever nose, and the choice of a material which is more resistant in terms of shape for the latch lever nose in relation to the material for the latching surface, prevents harmful surface portions being formed in the course of time due to changes in shape on the latching surface. This provides that there is also no displacement in the direction of the force exerted on the latching surface by the latch lever nose, with the detrimental consequences which occur in the state of the art. Usually the material for the latch lever nose-and thus generally for the entire latch lever-is steel while the material for the latching surface-and thus generally for the entire latch-is a usual plastic material, for example thermoplastic materials.

Further details and advantages of the invention will be apparent from the embodiment hereinafter described with reference to drawings in which: Figure 1 shows a switching lock with a latching mechanism according to the invention,

Figure 2 shows the latching mechanism of Figure 1 in the non-latched condition, Figure 3 shows the latching mechanism of Figure 1 in the latched condition, Figure 4 shows a detail IV from Figure 2 on a greatly enlarged scale, Figure 5a shows a detail V from Figure 3 on a greatly enlarged scale, Figure 5b shows the features of figure 5a in a used condition, Figure 6a shows a view of a detail on a greatly enlarged scale of a latching mechanism according to the state of the art, Figure 6b shows the features of figure 6a in a used condition, Figure 7a shows a view of a detail on a greatly enlarged scale of a further latching mechanism according to the state of the art, and Figure 7b shows the features of figure 7a in a used condition.

Referring to Figure 1, the switching lock 1 as a component of a multi-pole power switch (not shown) comprises a U-shaped drive lever 2 which is mounted with its outer limbs tiltably in fixed side covers 3 and has an actuating handle 4, a bell crank mechanism 5 (not shown in detail) with upper bell cranks, lower bell cranks and a spring forcestorage means, and a support lever 6 mounted pivotably between the side covers 3. The

support lever 6 is pivotably connected to the upper bell crank. The switching lock 1 can be reset after a tripping operation by a procedure whereby the support lever 6 is to be moved by passing the drive lever 2 beyond its off position into a condition of supporting connection, which is subjected to the action of the spring force-storage means, to a latching mechanism 7 which is operatively connected to tripping means (not shown). The latching mechanism 7 comprises a latch 10 actuable by tripping means and a latch lever 20 which is latchable thereby and which in turn locks the support lever 6 in the non-tripped condition. The latch 10 and the latch lever 20 are mounted pivotably in the side covers 3 by way of transversely disposed first and second mounting axes 11 and 21 respectively, and are mutually acted upon by the latching force engaging the same, which results from the force action of the spring force-storage means and further spring means (not shown).

Looking at Figures 1 and 3, provided on the latch lever 20 which is of a forked configuration at the end thereof are two latch lever noses 22 which can be brought into operative connection with corresponding latching surfaces 12 on the latch 10. In the tripped condition of the switching lock 1 the latch lever noses 22 and the associated latching surfaces 12 are at a spacing relative to each other, as shown in Figures 2 and 4. The latch lever 20 is in the form of a sheet metal member of steel and the latch 10 is in the form of a moulding of plastic material.

As shown in Figures 3,4 and 5a, in the latched condition, the lower edge 13 of each of the two latching surfaces 12, which lower edge is towards the second axis 21 and is in the form of an outer edge, is on the associated latching lever nose 22. In addition, in the latched condition, the upper edge 24 of each latch lever nose 22, which upper edge is remote from the second axis 21 and is in the form of an outer edge, is slightly further away from the second axis 21, in relation to the upper edge 14 of the associated latching surface 12, which upper edge 14 is remote from the second axis 21 and is also in the form of an outer edge. In order to eliminate disadvantageously sharp edges, the upper edges 24 of the latch lever noses 22 and the upper edges 14 and the lower edges 13 of the latching surfaces 12, are multiply chamfered or rounded off. In the latched condition the latch lever noses 22 act on the latching surfaces 12 with the normal component of the above-mentioned latching force in the direction of the arrow Fl perpendicularly to the latching surface 12.

Over the service life of the power switch, material abrasion wear phenomena and material displacement phenomena occur at the latching surfaces 12 due to the action of the latch lever noses 22 which are of more resistant material. In comparison with the new condition as shown in Figure 5a, Figure 5b shows by way of example the used condition which is characterised by a markedly advanced service life. The latching surfaces 12 have receded in the used condition so that the latch lever 20 bears with its latch lever noses 22 against the latching surfaces 12 in an angular position which is slightly increased in the clockwise direction, in comparison with the new condition.

However, fixing the spacings of the lower edge 13 and the upper edges 14,24 in accordance with the invention, as described hereinbefore, ensures that even in the used condition the latch lever noses 22 bear against a sufficiently flat surface portion of the latching surfaces 12 so that the direction of the force is maintained in the direction of the arrow Fl. By virtue of its forked configuration and by virtue of the use of steel sheet as the basic material for same the latch lever 20 has a certain elasticity which, when the latching surfaces 12 bear irregularly against the associated latch lever noses 22, results in elastic equalisation as between the two latch lever noses 22, thereby ensuring that the mechanical loading of the two latching surfaces 12 is as uniform as possible.

Figure 6 shows a latching mechanism in accordance with the state of the art, with a spacing of the upper edge 14'of the latching surface 12', which in comparison with the invention is further away from the second axis 21 than the upper edge 24'of the latch lever nose 22'. Figure 6a shows the new condition with the illustrated direction F2 of the force acting on the latching surface 12'. Due to material abrasive wear and material displacement at the latching surface 12, which has occurred as shown in Figure 6b in the used condition, in the region of the upper edge 24'of the latch lever nose 22' there is a force component in the direction of the arrow F2', which applies to the latch

10'an outwardly rotating moment of force M2'which in the most unfavourable case means that the latch 10'and the latch lever 20'no longer properly latch.

Figure 7 shows a further latching mechanism in accordance with the state of the art with a lower edge 13"of the latching surface 12"of the latch 10", with the lower edge 13"being in the form of an inner edge, in comparison with the invention. Figure 7a shows the new condition with the illustrated direction F3 of the force acting on the

latching surfaces 12". Due to material abrasive wear and material displacement at the latching surface 12", which has occurred as shown in Figure 7b in the used condition, in the region of the lower edge 23"of the latch lever nose 22"of the latch lever 20" there is a force component in the direction of the arrow F3", which applies to the latch 10"an inwardly rotating moment of force M3"which in the most unfavourable case means that the latch 10"and the latch lever 20"no longer properly unlatch.

List of references: 1 switching lock 2 drive lever 3 side covers 4 actuating handle 5 bell crank mechanism 6 support lever 7 latching mechanism 8 latch spring 10 latch 11 first axis 12 latching surface 13 latching surface lower edge 14 latching surface upper edge 20 latch lever 21 second axis 22 latch lever noses 24 latch lever nose upper edge

Claims

1. A latching mechanism of a switching lock with spring force-storage means for low-voltage power switches, comprising a latch actuable by tripping means and pivotable about a first axis, a latch lever pivotable about a second axis, wherein the axes of the latch and the latch lever are mounted pivotably in side covers of the switching lock and the latch is mutually latchable with the latch lever, for which purposes provided on the latch lever is at least one latch lever nose which can be operatively connected to a corresponding latching surface on the latch, wherein the latch lever nose comprises a material which is more resistant in shape in comparison with the latching surface, that the latching surface has an upper edge remote from the second axis and a lower edge towards the second axis and the latch lever nose has an upper edge remote from the second axis, that in the latched condition the lower edge of the latching surface is on the latch lever nose and that the upper edge of the latch lever nose is at least equally far from the second axis as the upper edge of the latching surface.

2. A latching mechanism according to claim 1, wherein the upper edge of the latch lever nose is slightly further away than the upper edge of the latching surface from the second axis.

3. A latching mechanism according to claim 1 or 2, wherein the upper edge of the latch lever nose and the upper edge and the lower edge of the latching surface are multiply chamfered or rounded.

4. A latching mechanism according to one of claims 1, 2 or 3, wherein the latch lever is of a forked configuration with two latch lever noses.

5. A latching mechanism according to claim 4, wherein the latch is provided with two latching surfaces.

6. A latching mechanism according to claim 5, wherein the latch lever is so elastic that it permits equalisation between latching surfaces which non-uniformly meet the latch lever noses.

7. A latching mechanism according to any one of the preceding claims, wherein in the latched condition, the latch lever nose acts on the latching surface such that the normal component of the latching force acts in a direction substantially perpendicular to the latching surface over substantially the whole service life of the mechanism.

8. A latching mechanism substantially as described herein and with reference to the drawings hereof.