The present invention relates to a closure apparatus. It is particularly, but not exclusively, concerned with closure apparatuses for use in telecommunications and CATV installations.

The well established closure for use in the telecommunications field comprises a generally barrel- shaped enclosure, open at one end. At the open end, there is circumferential lip on the outer face and an angled compression surface on the inner face. This barrel is then closed with a lid comprising a disc adapted to lie against the exterior lip and a corresponding ramp face adapted to face the compression surface of the barrel. An O-ring is sandwiched between the ramp face and compression surface. Thus, the two parts are pressed together by an operator prior to a clamp being attached around the lip and disc. This clamp is then tightened, providing an acceptable seal.

This arrangement provides an acceptable seal but can be considered commercially disadvantageous in that the price of the complete system is somewhat high given the engineering tolerances required of the clamp.

More recently, there has been suggested an arrangement in which the exterior lip and the compression surface of the barrel member are omitted. In this arrangement, the lid has a gently sloping frusto-conical part about which is based an O-ring. As this frusto-conical part is inserted into the barrel member, the O-ring contacts the inner surface of the barrel and is forced by friction up the conical section and into closer contact with the barrel. The barrel is provided with a pair of resilient clips to hold the lid in place once it is inserted to a sufficient degree.

This arrangement is structurally simpler and can therefore be manufactured at lower cost, but it has been found in use that the mechanical integrity is insufficient. Often it is necessary to add a further clamp around the exterior of the closure, thus obviating some of its cost advantages.

It is also known to provide a screw-top lid, within whose screw portion can be provided an O-ring. However, it is not certain that sufficient mechanical strength would be provided in this fashion. There would also be a cost penalty.

The present invention provides a seal arrangement for a closure, comprising two corresponding parts to be sealed, each part having a sealing ring comprising an outer ridge and an inner recess, the respective ridge and recess being provided on the inner surface of one sealing ring and the outer surface of the other sealing ring, one sealing ring

including within its recess an O-ring.

One or both of the recesses can be defined by the ridge, or vice-versa. Preferably, the sealing rings are circular. It is also preferred if at least the recesses and preferably also the ridges extend about the entire circumference of the sealing rings.

Preferably, the O-ring is in included in the recess that is on the outer surface of a sealing ring. This reduces the possibility of accidental loss of the O-ring.

It is also preferred if the recess which includes the O-ring is sufficiently deep to accommodate the O-ring without the O-ring extending radially higher than the ridge. That is, the depth of the recess underneath the ridge is greater than the thickness of the O-ring.

There are known engineering design procedures for "snap rings", and it is preferred if the ridge and recess of each sealing ring conform to those known procedures.

Snap rings are joined by engaging the ridge of one part within the recess of the other at a single point on the circumference thereof, thereby placing the two sealing rings at an angle to each other, and relatively rotating the two rings so as to reduce that angle and thereby bring the whole circumference gradually into register. By this method, the outer sealing ring is only stretched at two points at any one time, and this enables the sealing rings to be joined with relatively little force. Thus, a join can be designed which is easy to make yet which can resist a very large separation pressure.

The present inventor has discovered that during the process of this joining operation, the ridge of the outer sealing ring will "fall" into the recess of the other sealing ring in a substantially radial direction. Thus, by placing an O-ring within that recess, the corresponding ridge will grip that O-ring in a purely radially direction as the seal is made. Therefore, there is little or no frictional rolling or sliding of the O-ring as is the case in the second-mentioned known example. This should lead to an increased life for the O-ring and to a more secure seal. Thus, by the present invention, a seal is provided which has very good mechanical integrity through the use of a snap-ring or similar design, and yet which provides adequate sealing by the novel application of an O-ring to a snap-ring and the resultant unexpectedly good sealing of that O-ring.

An embodiment of the present invention will now be described with reference to the accompanying Figures, in which:

Figure 1 is a longitudinal cross-section through a closure apparatus being an embodiment of the present invention and comprising a container part and a lid part;

Figure 2 is a similar cross-section through the container part only;

Figure 3 is an enlarged cross-sectional view of the sealing ring of the container part;

Figure 4 is a cross-sectional view showing the relevant parts of the lid portion;

Figure 5 is an enlarged cross-section through the sealing ring of the lid.

Figure 1 shows an overall view of the embodiment. This comprises a generally barrel-shaped body portion 10 which is open at one end. That open end is closed by a lid 12. The lid 12 is generally circular to correspond to the open end of the container 10. Thus, there is defined an internal space 14 in which can be placed items to be sealed from the outside, for example telecommunications connections.

The lid 12 has a number of through passages 16 which are bounded with suitable sealing elements. This is to allow cables to be brought through the lid 12 to the interior space 14 for connection to items within that space. The design of the sealing devices is known per se and conventional in this art.

Around the circular open end of the container 10 is a first sealing ring 18 and an outer ring 20. As can be seen more clearly in Figures 2 and 3, the inner face of the first sealing ring 18 has a circumferential recess 22 behind a circumferential ridge 24. The leading edge 25 of the ridge 24 is gently sloping, to assist assembly of the closure.

Similarly, the lid 12 has a radial flange 26 around a second sealing ring 28 which has on its outer surface a circumferential recess 30 behind a circumferential ridge 32. This can be seen most clearly in Figures 4 and 5. As can be seen in Figure 1, an O-ring 34 is provided within

the circumferential recess 30. The recess 30 is sufficiently deep to accommodate the O-ring 34 without it extending radially outwardly of the ridge 32.

In use, wires or optical fibres cables will be fitted through the seal holes 16 of the lid 12, and the apparatus to be sealed fitted to the ends of both wires. The container part 10 will then be placed over its intended contents, and the first sealing ring 18 of the container 10 offered up to the second sealing ring 28 of the lid 12. The ridge 24 of the first sealing ring 18 will be placed behind the ridge 32 of the second sealing ring 28 at one point on its circumference only, leaving the container 10 and lid 12 axially misaligned. The two parts can then be rotated relatively to bring them to alignment, and the first sealing ring 18 of the container 10 will then be forced up and over the ridge 32 of the sealing ring 28 gradually. As each individual circumferential part of the first sealing ring 18 of the container 10 is forced up and over the ridge 32, it will snap into place in the recess 30 behind the ridge 32 in a radial direction. Thus, the O- ring 34 will be clamped into place within the recess 30.

The outer ring 20 provides simple mechanical protection for the first sealing ring 18.

To remove the container 10 from the lid 12, a screwdriver blade can be inserted in the gap between the flange 26 and outer ring 20 and rotated. This will locally disengage the first sealing ring 18 from the recess 30 at a single point, whereupon the container 10 and lid 12 can

be rotated relatively to reverse the sealing action. This assembly and parting forces can be varied by altering the depths and angles of the ridges and ridge slopes respectively.

If desired, the outer ring 20 could be provided with an axially projecting ring into which a screwdriver blade could be inserted to provide leverage behind the flange 26 to enhance the closing force for the container 10. This will enable a deeper ridge and recess arrangement or a thicker wall to be employed, giving a stronger mechanical joint. Also, resilient lugs could be provided on the outer ring 20 which deform during sealing and eventually clip into place behind the flange 26.

The above-described embodiment has been tested to an external pressure of 5 metre head of water pressure for 100 hours, and no detectable leakage was observed. From this, it can be ascertained that this embodiment has levels of mechanical integrity and sealing that are at least as good as the previously described known examples for external pressures. This is nevertheless achieved through use of a simpler design which will therefore be less expensive to manufacture.

It will be appreciated by those skilled in the art that the above-described embodiment is purely illustrative of the invention, and many variations could be made thereto without departing from the scope of the present invention. In particular, it is not essential that the O-ring is in the recess 30 of the lid and only relatively simple

adjustment of the design would be necessary to accommodate the O-ring in the recess 22 of the barrel sections . Also , for further mechanical strength, additional internal grooves and lips or an external support ring could be provided .