GB2299367A - Assembly of electrical accessories - Google Patents

Abstract

In an electrical accessory a first or front part (2) is latched to a second or rear part (4) by means of a resilient latch (4',2) which engages a corresponding recess (20) the latch engaging the recess in a first direction, the arrangement being such that assembly of the parts require a protrusion (40) on one part to be firstly engaged with a further recess (10) before latching the latch (42) and recess (20) together.

Description

Assemblv of electrical accessories The present invention relates to the assembly of electrical accessories.

It is well known to manufacture an electrical accessory by assembling two or more plastics mouldings together by arranging part of one moulding to snap fit with a corresponding part of a second moulding so that when the two mouldings are placed together they become physically attached to each other. It is also known to utilise the natural resilience of plastic materials to obtain an arrangement whereby one of the interacting parts forms a latch that engages with a catch on the other interacting part. It is also known to make a tamper resistant fastening by arranging the latching components so that it is easy to assemble the two mouldings, but difficult or impossible to disassemble them once assembled. However in such a case once assembled, the only way to disassemble the mouldings is to destroy part of at least one of the mouldings.It is frequently necessary in electrical accessories to require that once assembled the user can not open the accessory without destroying it, as otherwise the user could after opening the accessory render it unsafe and then reassemble it forming a modified accessory that would be potentially hazardous.

It is often the case however that in the course of manufacture of such accessories it is desirable to be able to open them for inspection or modification.

However the nature of this tamper resistant fastening may make this uneconomic.

An object of this invention is to provide an improved tamper resistant latch for enabling the assembly of an electrical accessory comprising two or more parts.

According to the present invention there is provided an electrical accessory comprising a first part having a resilient latch arranged to interact with a corresponding portion of a second part such that when the two parts are assembled together the resilient latch engages the corresponding portion in both a first direction and in a second direction.

Preferably the first and second directions are perpendicular to each other and perpendicular to the relative direction of movement when the two parts, preferably mouldings, are assembled.

The benefit of this preferred embodiment is that unless the resilient latch is moved in both perpendicular directions, and the moulding is then moved in the relative direction it will be impossible to disassemble the two mouldings. A further embodiment is arranged so that movement must occur in one perpendicular direction before a force is applied in the other perpendicular direction. Hence the accessory as assembled will be more resistant to tampering.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 shows a part cross section of an assembly of two moulded parts forming front and rear parts of an electrical accessory, showing the features on the two parts that interact to physically attach the rear part to the front part; and Figure 2 shows a perspective view of a latch forming one of the features shown in Fig. 1; and Figure 3 shows a plan view of the rear part shown in Fig.

1 viewed in the direction of arrow R; and Figure 4 shows a similar cross section to that shown in Fig. 1, but with the two mouldings in a partially assembled state.

An electrical accessory 1 is shown in Fig. 1, comprising a front part 2 and a rear part 4 formed as mouldings of plastics material. The front part is formed with an first undercut 10 which engages with a protrusion 40, forming a non-resilient first engaging feature. A second undercut 12 is formed so that it faces in an opposing direction to the first undercut 10. The second undercut engages with a resilient latch 42, forming a resilient second engaging feature. The resilient latch 42 comprises a flexible arm 44 forming part of the moulding of the rear part 4 at a fixed end 46, and a free end 48.

Free end 48 is shaped to form an engaging surface 50 which when the two parts are assembled together abuts a corresponding engaging surface 14 of the undercut 12. It can be seen from Fig. 1 that the two engaging surfaces may be angled to improve the ability of the resilient engaging feature to resist forces acting to separate the two parts.

The perspective view of Fig. 2 shows the resilient latch 42 and for clarity omits the rest of the rear part 4. On the free end 48 may be seen a security latching feature 52, which has a latching surface 54 which engages with the internal surface 22 of a corresponding recess 20 which is visible in Fig. 4. When the latching surface 54 is engaged with the surface 22, it is not possible to move the resilient latch 42 in the direction of arrow P to disengage the engaging surfaces 50 and 14. To disengage the engaging surfaces 50 and 14 it is necessary to first move the flexible arm in the direction of arrow Q to disengage the security latch, the flexible arm is then free to move in the direction of arrow P disengaging the engaging surfaces 50 and 14 and hence allowing disassembly of the two parts.Fig. 2 shows how the resilient arm 44 is made with a larger dimension in the plane of arrow Q than in arrow P, hence a significantly higher force is required to disengage the security latch than to disengage the engaging surfaces.

The benefit of this is that once assembled it is not possible to see the security latching feature and hence someone trying to disassemble the parts will find it impossible to move the resilient arm in the direction P that it has to move to disengage the engaging surfaces.

Fig. 3 shows a scrap plan view seen from the direction of arrow R in Fig. 1 of one corner of the rear part 4 with a resilient latch 42. The side wall 16 of the rear part may be seen. Fig. 3 also shows that the latching surface 54 may be angled so that application of force in the direction of arrow P before movement in the direction of arrow Q acts to increase the force required to produce movement in the direction of arrow Q. This particular feature is beneficial in that it reduces the chance of a person discovering how to release the resilient latch.

From Fig. 4 it can be seen that the method of assembly is to first partially engage the protrusion 40 with the undercut 10 and then rotate the rear part in the direction of arrow S until the resilient latch 42 is displaced in the direction of arrow T when the radiused surfaces 24 and 56 come into contact. This allows the resilient latch to move to an assembled position as shown in Fig. 1 when the latch moves to the position where surfaces 50 and 14 are engaged. Note that the resilient latch 42 is also displaced in a direction perpendicular to arrow T when similar radiused surfaces (not shown) come into contact to allow the security latching feature 52 to operate.

The benefit of the arrangement of using a non-resilient first engaging feature is that such a feature may be constructed to have greater physical strength than a resilient engaging feature. It is also easy to locate the two mouldings together using such a feature, and the subsequent rotational movement to complete the assembly is a natural continuation of the movement required for the initial location. This ensures that components such as rockers and fuse holders (not shown) that have been assembled to the rear part forming a rear part assembly are located correctly with respect to their respective apertures in the front part, so that as the rear part assembly is fitted to the front part any such rockers and fuse holders pass through their apertures without restriction.

Claims (8)

1. An electrical accessory comprising a first part having a resilient latch arranged to interact with a corresponding portion of a second part such that when the two parts are assembled together the resilient latch engages the corresponding portion in both a first direction and in a second direction.

2. An electrical accessory as claimed in claim 1, wherein the first and second directions are perpendicular to each other.

3. An electrical accessory as claimed in claim 1, wherein both the first and second perpendicular directions are perpendicular to a direction of movement required to assemble the two mouldings.

4. An electrical accessory as claimed in claim 1, wherein the resilient latch requires movement in both the first and second directions to disengage it from the corresponding portion.

5. An electrical accessory as claimed in claim 4, wherein to disengage the resilient latch movement is required in the first direction to permit movement in the second direction.

6. An electrical accessory as claimed in claim 4, wherein greater force is required to move the resilient latch in the first direction than in the second direction.

7. An electrical accessory as claimed in claims 4, 5 and 6, wherein application of force in the second direction before movement in the first direction acts to increase the force required to produce movement in the first direction.

8. An electrical accessory substantially as described herein with reference to the accompanying drawings.

8. An electrical accessory substantially as described herein with reference to the accompanying drawings.

Amendments to the claims have been filed as follows CLAIMS 1. An electrical accessory comprising a first part having a resilient latch arranged to interact with a corresponding portion of a second part such that when the two parts are assembled together the resilient latch engages the corresponding portion in both a first direction and in a second direction and further comprising a protrusion on one said part and a recess to receive the protrusion on the other said part, the arrangment being such that assembly of the parts required the protrusion to be firstly engaged with the recess and secondly the latch of the first part to be engaged with the second part.

2. An electrical accessory as claimed in claim I, wherein the first and second directions are perpendicular to each other.

3. An electrical accessory as claimed in claim 1, wherein both the first and second perpendicular directions are perpendicular to a direction of movement required to assemble the two parts.

4. An electrical accessory as claimed in claim 1, wherein the resilient latch requires movement in both the first and second directions to disengage it from the corresponding portion.

5. An electrical accessory as claimed in claim A, wherein to disengage the resilient latch movement is required in the first direction to permit movement in the second direction.

6. An electrical accessory as claimed in claim 4, wherein greater force is required to move the resilient latch in the first direction than in the second direction.

7. An electrical accessory as claimed in claims 4, 5 and 6, wherein application of force in the second direction before movement in the first direction acts to increase the force required to produce movement in the first direction.