GB2178240A

GB2178240A - Overcentre locking device

Info

Publication number: GB2178240A
Application number: GB08616282A
Authority: GB
Inventors: Joachim Freyermuth
Original assignee: Licentia Patent Verwaltungs GmbH
Current assignee: Licentia Patent Verwaltungs GmbH
Priority date: 1985-07-20
Filing date: 1986-07-03
Publication date: 1987-02-04
Also published as: FR2585176A1; GB8616282D0; IT8621150A0; IT1196505B; DE3526034C1; GB2178240B

Abstract

A locking device for a resiliently biased actuating member (10), e.g. a switch lever, comprises a blocking member (14, 15) and a trip element (19), through the rotation of which the blocking member (14, 15) can be moved into an unlocking position. In the locking position, a radially outer surface (16) of the blocking member (14, 15) is engaged by the actuating member (10) and a radially inner surface (17) of the blocking member engages a recess (22) in the trip element (19). The axis (13a) of the blocking member (14, 15) is coincident with the rotational axis (20) of the trip element (19). During rotation of the trip element (19) and after passing beyond a certain point, the blocking member (14, 15) slides out of the recess (22) so as to unlock the actuating member (10). <IMAGE>

Description

SPECIFICATION Overcentre locking device The present invention relates to a locking device.

In a locking device disclosed in, for example, DE-PS 25 02 091, a blocking member is supported by way of an outer annular surface of a bolt of the trip element and by way of an inner annular surface of an actuating member to be locked. The trip element is arranged to be rotatable about the bolt. In the known construction, three system points are arranged in such a manner one relative to the other that they lie, as in a toggle lever, in over-extended position. In that case, the axis of the blocking member in the locking setting lies on the same side of a notional dead point line which extends through the contact points of the blocking member with the actuating element and the trip element. In this mode of construction, the blocking member is thereby held by the locking force itself in locking setting, i.e. with increasing security at increasing locking pressure.In order to unlock this device, the three mentioned system points must first be brought into the straight position. In that case, the actuating member must be lifted. The supporting force, which increases during the unlocking, thus necessitates a required turning moment that increases with the unlocking. As soon as the axis of the blocking member has reached or passed beyond the dead centre line, unlocking takes place.

There is, however, scope for improving the locking arrangement in simple and reliable mannr so that only a relatively small amount of energy is required for the unlocking.

According to the present invention there is provided a locking device comprising a trip element pivotable about a first axis and defining a recess, a locking body movable in the recess into and out of a locking setting and having a radially inner and a radially outer cylindrical surface which are rotationally symmetrical about a second axis coincident with the first axis in the locking setting of the body, and a displaceable member so engageable under a resilient bias with the outer surface in the locking setting of the body as to exert on the body a first force along a line passing through the coincident axes and to cause a second force opposing the first force to be generated through engagement of the inner surface with wall means of the recess, the trip element being pivotable in a given direction to so displace a boundary edge of the recess out of a position ahead of the line with respect to the given direction as to permit the force exerted by the member on the body to overcome the opposing force and al low the member to displace by movement of the body of the locking setting.

In a preferred embodiment the locking device comprises an actuating member under spring pressure, for example a switch lever of an electrical switching device, and a blocking member which is movably held in a trip element. The blocking member in locking setting is supported by way of at least two coaxial annular surfaces beteen the actuating member and the trip element and is movable into an unlocked setting through rotational movement of the trip element. The blocking member and the trip element in locking setting have a common rotational axis and the blocking member in its locking setting is supported by way of at least one outer annular surface at the actuating member and by way of at least one inner annular surface at at least one undercut groove of the trip element.One boundary edge of the groove, seen in rotational direction of the trip element, in locking setting lies in front of a line which passes through the centre of the blocking member and is defined by the force engagement place of the actuating element.

In a mode of construction of that kind, the setting of the spring-loaded actuating member and thereby the required unlocking moment remain unchanged during the unlocking operation. Even in the case of changing support forces of the actuating member, the locking can be released securely and with relatively little effort. Due to the fact that the blocking member and the trip element in the locking setting possess a common rotational axis, the trip element can be turned in the tripping direction without the actuating member being lifted. Thus, the required unlocking torque remains constant during the unlocking. The boundary edge of the undercut groove, seen in the direction of rotation of the trip member in the locking setting lies in front of the line which extends through the centre of the blocking member and is defined by the force engagement place of the actuating member.

Consequently, the blocking member cannot slide out of the undercut groove even in the case of substantial application of force. Only when the boundary edge passes beyond the mentioned line does the blocking member slide out of the undercut groove and thus initiate the unlatching.

An embodiment of the present invention will now be more particulary described by way of example with reference to the accompanying drawings, in which: Figure 1 is a schematic view of a locking device embodying the invention, showing the device in locked setting; Figure 2 is a view similar to Fig. 1 but showing the device during unlocking; Figure 3 is a view similar to Fig. 1 but showing the device in unlocked setting; Figure 4 is a view similar to Fig. 1 but showing the device in unlocked intermediate setting; Figure 5 is a view similar to Fig. 1 but showing the device in actuation end setting; and Figure 6 is a side and end view of a blocking member of the device.

Referring now to the drawings, there is shown in Figs. 1 to 5, a switch lever 10 of an electrical switching device, the lever being rotatable about an axis 11 and being biassed by a tension spring 12 suspended at a locally fixed point. The free end of the lever 10 is supported against a blocking member 13, which is illustrated more closely in two views in Fig. 6. The blocking member consists of a roller bearing 14, which is splined on a shaft 15. The bearing 14 has an annular surface 16 lying radially outwardly, and the shaft 15 has on either side of the bearing 14 inner annular surfaces 17 lying radially inwardly.

The blocking member 13 sits in a trip element 18, which comprises two gates 19 arranged at a spacing from each other and connected together by, for example, a yoke. The trip element 18 with the gates 19 is rotatably mounted at a fixed axis 20. The gates 19 define entry openings 21, which at their closed ends are each provided with a respective undercut groove 22 having a boundary edge 23. The lever 10 engages the blocking member 13 at the point 24. Designated by 25 is an abutment for the lever 10, which during unlatching turns in the direction 26. The direction of rotation of the trip element 18 is designated by 27.

As shown in Fig. 1, the blocking member 13 lies by its surfaces 17 in the undercut grooves 22 of both gates 19 of the trip element 18. The mechanical energy stored in the tension spring 12 introduces a normal force 28, perpendicular to the tangent of contact, at point 24 by way of the lever 10. The arrangement is so designed that the rotational axis 13a of the blocking member 13 in the locking setting illustrated in Fig. 1 coincides with the rotational axis 20 of the rotatable trip element 18. The force 28 acting at point 24 thus brings about an equally great, oppositely acting reaction force 30 at point 29 on the opposite side. Since the blocking member 13 in the locking setting shown in Figs. 1 and 2 is disposed coaxially with the axis 20 and is constructed to be rotationally symmetrical, no turning moment about the axes 13a and 20 arises.Thereby, secure locking is ensured even in the case of variabie supporting forces 28 arising in operation. To compensate for production tolerances for reasons of safety, the boundary edge 23 of the undercut groove 22 lies in the rotational direction 27 in front of the action line 31, extending through the points 24, 20 and 29, of the forces 28 and 30. The corresponding angle opposite this line of action is designated by a.

During the unlocking operation shown in Fig.

2, the trip element 18 is turned in direction 27 by a force acting 33 acting at point 32.

Thereby, the boundary edge 23 is positioned at the point 29. The forces 28 and 30, however, still lie on the same line 31, which extends through the points 24, 20 and 29/23. If the force 33 decays at this instant, a restoring spring (not shown) restores the trip element 18 into the initial position. During all restorations of the trip element between the initial position according to Fig. 1 and the position illustrated in Fig. 2, the unlocking operation can thus be broken off at any time without the lever 10 being unlatched.

On continuing action of the force 33 on the point 32, the setting of the trip element 18 shown in Fig. 3 results. The boundary edge 23 is now disposed on the other side of the line 31 of the force 28. As a result, the force 30 resolves into the forces 30' and 30". In consequence thereof, the blocking member 13 deviates as illustrated in Fig. 4. The lever 10 can now perform a rotational movement, accelerated by the spring 12, about the axis 11 in direction 26 until it bears against the abutment 25 as shown in Fig. 5. The blocking member 13 and the trip element 18 are reset into their initial positions according to Fig. 1 by restoring springs (not shown).

For unlocking, energy thus needs to be brought into the system only until it has attained the setting according to Fig. 2. Continuation of the rotary movement of the trip element 18 through a differentially small angle causes a force resolution according to Fig. 3.

The energy supply, which drives the unlocking forward, is now contested by the tension spring 12 and thereby from a significantly higher level. After passing beyond the setting shown in Fig. 2, the unlocking of the device can no longer be held up, not even by the cancellation of the force 33.

The locking device can be applied with advantage to switches. Usually, excess current trips are constructed as components which are supplied with energy by way of transformers. However, the space requirement permits only a limited power output. This necessitates use of thermal and magnetic trip units with small power absorption. In spite of high demands on the efficiency of the transmission mechanism, the transmission and thereby the need of mechanical energy of the force storage remains the component determining all. If the energy requirement remains small, then the upstream components from transformer through the bimetallic element to the S-magnet can be smaller and thereby cheaper.

Use of the device is not, however, restricted to switches, and many other uses are possible.

Claims

1. A locking device comprising a trip element pivotable about a first axis and defining a recess, a locking body movable in the recess into and out of a locking setting and having a radially inner and a radially outer cylindrical surface which are rotationally symmetrical about a second axis coincident with the first axis in the locking setting of the body, and a displaceable member so engageable under a resilient bias with the outer surface in the locking setting of the body as to exert on the body a first force along a line passing through the coincident axes and to cause a second force opposing the first force to be generated through engagement of the inner surface with wall means of the recess, the trip element being pivotable in a given direction to so displace a boundary edge of the recess out of a position ahead of the line with respect to the given direction as to permit the force exerted by the member on the body to overcome the opposing force and allow the member to displace by movement of the body out of the locking setting.

2 A device as claimed in claim 1, wherein the inner surface and the outer surface are provided on, respectively, two relatively rotatable parts of the body.

3. A device as claimed in either claim 1 or claim 2, wherein the body has two such inner surfaces respectively disposed at the two axial ends of the outer surface.

4. A device as claimed in claim 3, wherein the inner surfaces are provided by circumferential surface portions of a shaft and the outer surface by the circumferential surface of a rotationally symmetrical element mounted on the shaft.

5. A device as claimed in claim 4, wherein the rotationally symmetrical element is a roller bearing mounted on the shaft by splines.

6. A device as claimed in claim 4, wherein the rotationally symmetrical element is a roller slidably mounted on the shaft.

7. A device as claimed in claim 3, wherein the body is a one-piece element formed with the inner and the outer surface.

8. A device as claimed in any one of the preceding claims, wherein the recess is circularly arcuate in shape in a region of contact thereof with the inner surface or inner surfaces, as the case may be, of the body.

9. A device as claimed in any one of claims 1 to 7, wherein the recess is angular in shape in a region of contact thereof with the inner surface or inner surfaces, as the case may be, of the body.

10. A device as claimed in either claim 8 or claim 9, wherein the region of contact extends over an angle of substantially 90".

11. A device as claimed in any one of the preceding claims, comprising a restoring spring biassing the locking body into its locking setting.

12. A device as claimed in any one of the preceding claims, comprising a restoring spring biassing the trip element in a direction opposite to the given direction.

13. A device as claimed in any one of claims 3 to 7, wherein the trip element comprises two mutually parallel arms which each define a respective such recess and which are interconnected at a fixed spacing by connecting means, each recess receiving one of the inner surfaces of the locking body.

14. A device as claimed in any one of the preceding claims, wherein the movable member is a switch lever of an electrical switching device.

15. A locking device substantially as hereinbefore described with reference to the accompanying drawings.