GB2167250A - Watertight electrical connector - Google Patents

Abstract

The watertight electrical connector has an external body (10) which houses an electrical connector block in the center (12). At one end there is a collar (19). At both ends there is a rubber compression ring (24 & 25) and metal washers (26 & 27) which are held in position by screwed nuts (30) Each nut has twin wedges (34) which can be screwed in by a pressure plate (40) and two screws (46 & 47) When in use the nuts (30) compress the rubber compression rings (24 & 25) on to the electrical cables sealing the chamber (60) from the entry of water. Then by screwing in the pressure plates (40) with the screws (46 & 47) the wedges (34) put pressure on the electrical cables thus preventing external stresses pulling the electrical cables out of the connector (12). <IMAGE>

Description

SPECIFICATION Watertight electrical connectors This invention relates to watertight electrical connectors.

Such connectors comprise a terminal block by means of which appropriate electrical connections are made between the electrical conductors of first and second water proof electrical cables brought to the terminal block. The terminal block itself is necessarily located in an air-filled chamber within the connector.

Two further conditions must then be met in a practical connector. Firstly the cable entries to the terminal block chamber must be watertight, and secondly each cable must be securely clamped to the body of the connector.

The clamping means serves to prevent mechanical strain being applied by the conductors to the terminal connections, and in addition serves to prevent or minimise movement or mechanical strain between the cable and the cable entries so as to maintain the entries watertight. This second function of the clamping means is of particular importance for an effective watertight electrical connector.

In one form of commercially available connector the clamping means consists of a clamping bridge of a form well known in the electrical connector art. The cable to be clamped passes through a tubular member which has a deep transverse slot cut therein to receive a clamping bridge. Screws pass through bores at opposite end of the bridge and engage in threaded bores in the walls of the tubular member at the base of the slot.

When the screws are tightened they urge the bridge to move down the slot perpendicular to the axis of the tubular member and thus the cable is clamped between the bridge and the bottom inner surface of the tubular member.

This conventional clamping means is found to have a number of disadvantages in practice.

Firstly, the existing clamp is one-sided in construction and in action. As it tightens it necessarily moves the cable laterally just outside the watertight cable entry thereby causing the cable to curve into a double bend and simultaneously deforming the cable cross-section from a circle into an irregular oval as it is squeezed between the bridge and the curved wall of the tubular member. This renders the cable entry liable to leak and the effect is greater the more the clamp is tightened.

Secondly the existing clamp bridge is short in its dimension along the cable and therefore does not provide sufficient clamping force unless tightened to the point where the cable is significantly pinched. This amplifies the double-bend effect explained in the previous paragraph. The bridge cannot be broadened without further weakening of the structural integrity of the tubular member, already weakened by the necessity of cutting a slot substantially half way across the tubular member to accommodate the clamp bridge and by the presence of the threaded bores for the clamp screws in the weakened section of the tubular member.

An object of the present invention is to provide an improved watertight electrical connector which mitigates the above explained technical disadvantages.

According to the present invention there is provided a watertight electrical connector comprising a connector body having first and second cable entries communicating with a chamber containing a terminal block, seal means associated with each cable entry operable to render the entries watertight in use, and cable clamping means associated with each cable entry and located outside the seal means for clamping a cable with respect to the connector body, each said clamping means comprising a ring member generally coaxial with its associated cable entry and having inner surface portions inclined relative to the ring axis and disposed on opposite sides of said axis, first and second wedge members in sliding contact with the respective inner surface portions of the ring member, said wedge members defining a cable passage therebetween, and means operable to urge said wedge members and said ring member axially relative to one another to cause said wedge members to clamp a cable substantially symmetrically of said ring axis.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a longitudinal section of the body of a connector according to the invention; Figure 2 is a cross-section of Fig. 1 on line 2-2; Figure 3 is a longitudinal section of a clamp for the connector of Figs. 1 and 2; Figure 4 is a section on line 4-4 of Fig. 3; and Figure 5 is a right hand end view of the clamp of Fig. 3.

The drawings show a watertight electrical connector. By watertight is meant that the connector is designed to prevent the entry of water into the terminal block chamber. Details of construction and materials of an actual connector will determine the precise conditions, for example water depths or pressure, under which and for how long a particular connector is fully watertight. The connector comprises a generally tubular body 10 having a central chamber 11 receiving a terminal block 12. The block 12 typically comprises an insulating carrier 13 mounting two conductive sleeves 14, 15 each provided with a pair of spaced metal screws 16, 17. The terminal block is located in the chamber 11 by means of collars 18 and 19. The collar 18 is fixed, i.e. is moulded integrally with the body 10, and collar 19 is a separate component inserted into body 10 after insertion of the terminal block.

The tubular body 10 has opposite end portions 20, 21 forming cable entries to the terminal block chamber 11. Each end portion 20, 21 is internally threaded at 22, 23. Seal means is located in each entry. The seals comprise rubber grommets 24, 25 each having an outer diameter dimensioned for sliding reception within the cable entry 20, 21, and an inner diameter substantially equal to that of the cable to be used with the connector. The grommets may have concentric cylindrical cuts to enhance their sealing capabilities.

The grommets seat against the collars 18, 19, and metal washers 26, 27 in turn seat against the grommets 24, 25. Axial compression of the grommets in use serves to seat them tightly between the washers 26, 27 and the collars 18, 19 and simultaneously to expand the grommets radially both outwardly in sealing contact with the cable entries 20, 21 and inwardly against the sheath of the cable which in use passes through each grommet.

The connector further comprises two end pieces shown in Fig. 3, one for each cable entry 20, 21. Each end piece serves both as clamping means for the cable and as the means operable to apply the above described axial compressive force on the grommets to seal the cable entries against water penetration to the chamber 11.

Each end piece comprises a ring member 30 having a tubular extension 31 with an external thread 32 for threaded engagement with the internal threads 22, 23 of the cable entries.

The ring member has a frusto-conical inner surface 33 coaxial with the ring member axis.

First and second wedge members 34, 35 each take the form of less than one half of an axially split frustum of a cone with a central axial cylindrical bore. Each wedge member thus has an external conical surface portion 36 complementary to the inner surface 33 and an inner cylindrical surface portion 37 of diameter substantially equal to that of a cable to be clamped.

An end plate 40 serves as means operable to urge the wedge members in unison axially relative to and within the ring member. The end plate has a central aperture 41 of greater diameter than a cable to be clamped but with a substantial overlap on the outer end surfaces 42 of the wedges to provide a sufficient area for transmission of axial driving force.

The end plate has opposed lobes 43 provided with openings 44 registering with threaded bores 45 in the ring member. Screws 46, 47 are received in the openings 44 and engage bores 45.

It will be seen from Fig. 3 that the action of tightening the screws 46, 47 drives the wedges axially towards the connector body 10. The conical surface portions 36 slide down the inner conical surfaces 33 and this urges the two wedges progressively towards one another. A cable located between the edges is thereby progressively clamped between the wedges.

The ring members 30 are each provided with an integrally formed hexagonal nut configuration 50 and the central portion of connector body 10 is similarly provided with a hexagonal nut configuration 51.

In use of the connector, first and second cables to be connected are threaded through the respective end pieces of Fig. 3. One cable is also threaded through washer 27, grommet 25 and connector body 10, and the other cable is threaded through washer 26, grommet 24 and collar 19. The conductors of the two cables are then dielectrically connected by the screws and sleeves of the terminal block 12, and the body 10 moved to locate the block 12 within chamber 11, the collar 19 within entry 20, and grommets and washers in the respective cable entries.

The end pieces are then threaded into the cable entries and tightened by opposite torque applied to nuts 50 and 51. The extensions 31 engage the respective washers 26 and 27 and thereby apply axial compressive force to the grommets to achieve the appropriate degree of watertight sealing of the cable entries as explained above.

When the end pieces are sufficiently tight and the seals effective, the screws 46 and 47 are tightened in each end piece. This action serves to clamp each cable tightly between the two opposed surfaces 37 of the two wedge members 34, 35. It will be appreciated that the clamping action is substantially symmetrical with respect to the longitudinal axis of the cable and the connector. The doublebend problem described above is thereby solved. It will also be appreciated that the cable is gripped over an extended axial length and around a substantial proportion of its circumference over the whole of that axial length, i.e. the length of surface 37 of wedges 34, 35. The clamping is therefore very secure and the localised pressure on the cable is low because pressure equals force per unit area. The problem of cable deformation or kinking due to high or uneven localised clamping pressure is thereby also solved.

In addition the clamp avoids the necessity for deep transverse cuts in the ring member or other structurally weakening features and has an overall balanced structural strength and integrity with regard to the forces initiated and applied by tightening the screws 46 and 47.

Moreover the clamping action of the wedges proceeds by moving the wedges axially towards the terminal block 11. A cable gripped by the wedge is thus moved slightly axially inwardly towards the block 11 as it is progressively clamped thereby relieving any tension that might have existed between the conductors of the cable and the terminal screws 16, 17.

Claims (4)

1. A watertight cable connector box comprising a hollow body in which the two cableends are joined with a nut at each end into which two conical wedges are screwed into the nut by means of a clamp-plate and two screws.

2. A watertight cable connector box as described in Claim 1 where the end conical wedges, when tightened by the two screws, will exert a completely uniform pressure on the cables to be joined and thus prevent the cables from being damaged and bent to one side which is the case with existing cable connectors.

3. A watertight cable connector box as described in Claims 1 & 2 which because of the large surface area of the two wedge pieces screwed into the end nuts will distribute the pull on the cables to be joined evenly, thus making the cable connector box watertight and the cables and their insulation less liable to damage.

4. A watertight cable connector box as described substantially herein with reference to Figs. 1 to 6 of the accompanying drawings.