GB2247715A - Closure fastener for an electrical connector - Google Patents

Abstract

A two-part moulded plastics enclosure for an electrical connector in which the first part (1) has at least one tongue (5) projecting from it which is provided with a latching foot-portion (17) which engages with latching means (10) provided on the second part (7). A post (13) is spaced laterally from the latching means (10) by a distance substantially equal to the thickness of the or each tongue (5) to prevent the latching foot portion (17) of the tongue (15) from being laterally displaced and disengaged from the latching means (10). <IMAGE>

Description

METHOD AND MEANS FOR SECURING TWO MOULDED PLASTIC ENCLOSURE HALVES TOGETHER DESCRIPTION This invention relates to a method and means for securing two moulded plastic enclosure halves together.

Many products require the housing enclosing the components to be made in two halves to facilitate assembly and also to permit the housing or enclosure to be opened for servicing or repair. In the past, where two enclosure parts have to be separated, it has been common practice to retain them together by means of a screw. This has several disadvantages in that an additional assembly step is needed during manufacture and also the screw can be undone by a customer which may not be desirable if it is intended that the enclosure be sealed for life Two enclosure halves which snap together are known in which tongues on one shell half engage in means located on the other shell half.If the enclosure is moulded of a relatively thin plastics material, it is possible to torsionally twist the enclosure and thereby release the tongues from engagement with their retaining means so the two enclosure parts become separated. This can be highly undesirable, particularly with electrical fittings such as plugs or adaptors.

It is an object of the present invention therefore to provide a two-part moulded plastics enclosure which, once assembled, cannot be separated by exerting a lateral pressure on the tongues and locating means holding the two enclosure halves together.

According to the invention, there is provided a two-part moulded plastics enclosure wherein the first part has at least one tongue projecting therefrom provided with a latching portion which engages with latching means provided on the second part and retaining means associated with said latching means to prevent the latching portion of the tongue from being displaced laterally and thereby becoming disengaged from the latching means.

Preferably the retaining means are located directly opposite the latching means to prevent lateral movement of the tongue but they could be located elsewhere.

In one embodiment, the or each tongue is L-shaped, the latching portion on the tongue comprising the laterally extending foot portion. In another embodiment, the free end of the or each tongue is T-shaped, the latching portion comprising the pair of laterally extending feet. Alternatively, the or each tongue has a hole in its free end to provide the latchning portion.

Conveniently, the latching means comprises a nib which engages with the latching portion when the two enclosure halves are fitted together. In a preferred embodiment, the or each nib includes a cam surface terminating in a returned or rebated latching surface.

Suitably, the retaining means comprises a projection or post spaced from the latching means by a distance substantially equal to the thickness of the or each tongue. Conveniently the or each post includes a bevelled surface which, in use, initially applies a lateral pressure to the tongue as it is inserted into the space between the latching means and the post so that the or each foot portion thereon snaps into latching engagement with the latching surface on the or each nib, the post also having a second surface which retains said tongue and latching surface in latching engagement regardless of any lateral force applied to the tongue.

In a preferred embodiment, both halves of the enclosure are shells with four sides and a bottom, at least one tongue being provided on each side wall of a parallel pair of said sides. Preferably at least one tongue is also provided on one or both the other two sides.

Conveniently, the or each tongue is of a thickness less than that of the walls of the enclosure.

The invention is applicable to any product which requires two shell halves to be non-releasably connected together but is particularly applicable to electrical components. A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a rear view of the front shell half of an electrical adaptor, Figure 2 is a side view of the shell half shown in Figure 1, Figure 3 is an end view of the shell half shown in Figures 1 and 2, Figure 4 is a rear view of the rear shell half to be fitted to the electrical adaptor shown in Figures 1-3, Figure 5 is a cross section along the lines V-V in Figure 4, Figure 6 is a cross section along the lines V1-V1 in Figure 4 and, Figure 7 is a cross section along the lines V11-V11 in Figure 4 on an enlarged scale.

Referring to Figures 1-3 of the drawings, there is shown a front shell half 1 which is rectangular in shape and has a wall 2 extending around a base 3. Holes 4a-4c are provided in the base 2 to receive the connector pins of an electrical plug when inserted therein. Tongues 5 project from the wall 2 generally coplanar therewith . In the illustrated embodiment, two pairs of tongues 5 are provided along each side of the shell half and it can be seen from Figure 2 that the free end of these tongues is generally T-shaped for reasons which will be explained hereafter. An additional tongue 5 is provided on a rib 6 extending across the width of the shell half adjacent the socket holes 4a-4c. The free end of each tongue 5 has a bevelled edge 6.It should be noted, that the tongues 5 are considerably thinner than the thickness of the wall 2 and thus they are flexible and can be readily deflected laterally with respect to the longitudal axis of the shell half.

Referring now to Figures 4-6, there is shown a rear shell half 7 which is also rectangular in shape and comprises a base 8 surrounded by a wall 9. The base 8 is provided with apertures 9a-9c through which the adaptors electrical pins (not shown) project when assembled in the shell half 7.

Pairs of nibs 10 are provided on the wall 9 around its periphery. In the illustrated embodiment, two pairs of nibs 10a, lOb are provided on one side wall of the shell half and two pairs of nibs 10c, lOd are provided on the opposite parallel side wall . A third pair of nibs 10e are provided across the bottom of the shell or rib 20 . As can be seen more clearly from Figure 7, each nib 10 comprises an inclined surface 11 terminating in a rebate or undercut 12.

In the illustrated embodiment, retaining means in the form of a projection or post 13 is provided intermediate the nib pairs 10a and lOc. However, additional posts 13 may be provided opposite pairs of nibs lOb and lOd and also opposite the pair of nibs 10e.

The configuration of each post 13 can be seen more clearly in Figure 7 to comprise a base portion 14 which tapers at 15 to an apex. The upper end of the front edge of the post 13 facing the nibs 10 is bevelled at 16 for reasons which will be explained hereafter.

In order to assemble the two shell halves 1 and 7 together, the front shell half 1 with its tongues 5 is offered up to the rear shell half 7. As pressure continues to be applied to the shell half 1 in a direction towards the shell half 7, the tongues 5 slide inside the walls 9 and over the inclined surfaces 11 of the nibs 10. This movement is assisted by means of the bevelled edge 6 on each tongue and the bevelled surface 16 on each retaining post 13. It will be appreciated that when the tongues 5 are pushed fully home, each lateral foot portion 17 (see Figure 2) will snap under the rebate or undercut 12 on a nib 10 to engage therewith. The tongue will be maintained locked in this position by means of upright surface 18 on the post 13 so it cannot readily be disengaged from its nib 10. It will be appreciated that the thickness of the tongues 6 is subtantially equal to the space between the part of the wall 9 underneath the nib 10 and the front face 18 of the respective retaining post.

This combination of a T-shaped tongue and retaining post 13 located between the nibs provides excellent snap-engagement and stability as each post 13 bends the base of the tongue slightly inwardly towards the nibs to tension it and thereby ensure that the feet 17 are tensioned in a direction towards the nibs at all times.

Once the tongues 5 have engaged with the nibs 10, it is virtually impossible to separate the shell halves. It was found in the prior art arrangement that without the retaining posts 13, if the side wall 9 was squeezed in the region of the nibs 10, the tongues 5 would disengage from the nibs. This could also happen if the shell 7 was torsionally twisted about its longitudal axis. The addition of the retaining posts 13 overcame this problems and provided a convenient means for preventing disengagement of the tongues 5 from the nibs 10 which is easy to mould and provides a very effective way of holding the shell halves together so that they cannot be separated and no additional retaining means such as a screw is needed.

Claims (13)

1. A two-part moulded plastics enclosure wherein the first part has at least one tongue projecting therefrom provided with a latching portion which engages with latching means provided on the second part and retaining means associated with said latching means to prevent the latching portion of the tongue from being displaced laterally and thereby becoming disengaged from the latching means.

2. An enclosure as claimed in Claim 1 wherein the retaining means are located opposite the latching means to prevent lateral movement of the tongue.

3. An enclosure as claimed in Claim 1 or Claim 2 wherein the or each tongue is L-shaped, the latching portion on the tongue comprising the laterally extending foot portion thereof.

4. An enclosure as claimed in Claim 2 wherein the free end of the or each tongue is T-shaped, the latching portion comprising the pair of laterally extending feet.

5. An enclosure as claimed in Claim 1 or Claim 2 wherein the or each tongue has a hole in its free end to provide the latching portion.

6. An enclosure as claimed in Claim 3 or Claim 4 wherein the latching means comprises a nib which engages with the latching portion when the two enclosure halves are fitted together.

7. An enclosure as claimed in Claim 6 wherein the or each nib includes a cam surface terminating in a returned or rebated latching surface.

8. An enclosure as claimed in any of Claims 2-7 wherein the retaining means comprises a projection or post spaced from the latching means by a distance substantially equal to the thickness of the or each tongue.

9. An enclosure as claimed in Claim 8 wherein the or each post includes a bevelled surface which, in use, initially applies a lateral pressure to the tongue as it is inserted into the space between the latching means and the post so that the or each foot portion thereon snaps into latching engagement with the latching surface on the or each nib, the post also having a second surface which retains said tongue and latching surface in latching engagement regardless of any lateral force applied to the tongue.

10. An enclosure as claimed in any preceding claim wherein both halves of the enclosure are shells with four sides and a bottom, at least one tongue being provided on each side wall of a parallel pair of said sides.

11. An enclosure as claimed in Claim 10 wherein at least one tongue is also provided on one or both the other two sides.

12. An enclosure as claimed in any preceding claim wherein the or each tongue is of a thickness less than that of the walls of the enclosure.

13. An enclosure substantially as herein described with reference to the accompanying drawings.