Electrical Connectors

Abstract

An electrical connector comprising a base of plastics material with a contact carrier upstanding therefrom, and a lid of plastics material hinged to the base and arranged for snap-acting locking closure over the contact carrier, the hinge of the lid embodying a lost-motion mechanism enabling the lid to move bodily in a direction at right-angles to the base during closure. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to electrical connectors, and more particularly to connectors having a protective hinged lid. 2. Description of the Prior Art In supplying gas, electricity and sometimes water to domestic and industrial premises, it is usual for each supplier to install a meter which provides on a dial or set of dials a measure of the amount supplied. Meter readers visit each of the premises at regular intervals -- usually every 3 months -- and record the meter readings in a record book. The book is used by accountants to calculate the charges to be made to the occupiers of the premises. Frequently, however, when a meter reader calls upon premises to read a meter therein he is unable to gain access. This is particularly the case with the domestic premises. This causes delay and adds considerably to the cost of accounting. In addition even when access can be gained to premises the time taken to make each meter reading can be several minutes. In order to simplify the operation of recording meter readings, and to enable meter readings to be recorded whether or not access can be gained to the premises concerned, it has been proposed to provide for each meter an adaptor whereby the meter reading can be provided in electrical form. A cable is provided from the adaptor to a connector on the outside of the premises whereby a meter reader equipped with an electrical recorder, such as a magnetic tape recorder, can connect the recorder to the adaptor and record the meter reading automatically. It will be appreciated that the connector to be fitted to the outside of premises must be suitable for withstanding rigorous conditions both as to environment and handling. For example it must be able without deterioration to withstand dry heat, moist heat, low temperatures, driving rain, driving dust, driving sand, corrosive atmospheres, freezing moisture such as freezing fog and ultra-violet radiation all over a long period of time. In addition it must be tamper-proof at least by young children, but readily accessible to meter readers. Finally it must not be unduly expensive in view of its wide application to domestic premises. Prior to the present invention, there were no available connectors which could provide such characteristics. SUMMARY OF THE INVENTION It is the object of this invention to provide a connector which can meet the above-noted conditions. According to the invention there is provided an electrical connector comprising a base of plastics material with a contact carrier upstanding therefrom, and a lid of plastics material hinged to the base and arranged for snap-acting locking closure over the contact carrier, the hinge of the lid embodying a lost-motion mechanism enabling the lid to move bodily in a direction at right-angles to the base during closure.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described, by way of example, with reference to the accompanying drawings in which:

FIG. 1 shows schematically one example of the proposed arrangement whereby a meter inside premises can be read without the need for gaining access to the premises,

FIG. 2 is a perspective view of a connector according to the invention together with a tool for opening a lid thereof,

FIG. 3 is a further perspective view similar to FIG. 2 but with the lid loosened and ready for lifting by hand,

FIG. 4 shows the lid of the connector of FIGS. 2 and 3 lifted to its vertical position and the connector ready to receive a plug,

FIG. 5 is a side view of the connector of FIG. 4,

FIG. 6 is a further perspective view of the second connector embodiment with a tool inserted for releasing the lid thereof,

FIG. 7 is a perspective view of the base of the second connector embodiment with the lid removed therefrom,

FIG. 8 is a perspective view of the lid of the second connector embodiment detached from the base,

FIG. 9 is a cross-section of the second connector embodiment with the lid in a position in which it is ready for closure,

FIG. 10 is a similar cross-section to that of FIG. 9 but with the lid locked in the closed position, and

FIG. 11 is a cross-section of the second connector embodiment with the lid opened wide.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1, premises 10 have a gas meter 11 therein and the meter 11 has an adaptor 12, whereby the reading on the meter 11 can be derived in electrical form. The adaptor 12 is connected by a cable 13 to a connector 14 mounted on the outside of a wall 15 of the premises 10. The connector 14 enables a meter reader (not shown) with a magnetic tape recorder 16 provided with a carrying strap 17 and a plug 18 to record the meter reading on the meter 11. To make the record, the plug 18 is merely inserted into the connector 14 for a period of, say, five seconds.

The present invention is concerned with the connector 14 which is shown in FIG. 2. The connector 14 is, as shown, arranged for flush mounting and has a hinged lid 19 which can readily be opened by means of a two-pronged tool carried by the meter reader but as described later cannot otherwise be opened easily.

FIG. 3 shows the lid 19 after it has been loosened by the tool 20, and FIG. 4 shows the lid 19 hinged to a vertical position and the connector 14 ready to receive the plug 18. It will be seen in FIG. 4 that the lid 19 has two recesses 21 and 22 to receive the two prongs of the tool 20.

It will also be seen that the connector 14 has an upstanding circular boss 23 with contacts 24, whereby connections can be made to the plug 18.

Referring now to FIGS. 4 and 5 the connector 14 is shown with the lid 19 in an open position. The lid is hinged to two posts 25 and 26 by means of hinge pins, of which one is shown at 27, there being one hinge pin for each post. The hinge pins are secured to the lid and engage substantially triangular recesses in the posts, one such recess being shown in dotted lines at 28 in FIG. 5.

By using the triangular recesses 28 in the posts 25 and 26, the lid can move substantially parallel to the base 29 of the connector and to a lesser extent it can move parallel to the surface of the base 29. Thus, when the lid is closed, it can locate itself over the upstanding boss 23.

As seen in FIG. 4, the lid has three inwardly directed nibs 30, 31 and 32 lying on a circle for locating the lid on the boss 23. The inner diameter of the nibs in less than the outer diameter of the boss, and the nibs are undercut whereby the lid can snap into position over the boss. The boss has for this purpose a flange 33 seen in FIGS. 4 and 5. By this snap action the lid is urged firmly against the base to form a close and tight joint between the lid and the base.

In using the tool 20 to loosen the lid, the two prongs are inserted into the two recesses 21 and 22 and is rocked as a lever to snap open the lid. A cranked lever with two prongs is necessary for this, and as the connector is fitted flush to a wall, a straight tool such as a slender screwdriver or rod is not adequate.

The contacts 24 are preferably headed and extend rearwardly through the boss 23. The rear shanks of the contact may be of square cross-section, whereby a wire-wrapping technique can be used for making connections thereto.

The inside of the lid is provided with a pad 34 of resilient insulating material, such as foamed plastics materials which is compressed over the contacts 24 to complete the seal and protect them against ingress of moisture and grit.

As shown in FIG. 4, the boss 23 is provided with two bayonet slots 35 and 36 for receiving bayonet pins on the plug 18. The slots 35 and 36 do not lie on a diameter and this asymmetry ensures that the mating plug which has correspondingly staggered bayonet pins can fit in only one position.

In order to provide adequate toughness with sufficient resilience for the snap-action of the lid, a tough plastics material is used for the base and lid of the connector 14. The preferred material is that sold as DELRIN 507 (Registered Trademark) which is an acetal thermoplastic polymer. This also has excellent resistance to moisture, low temperatures and ultra-violet radiation.

In use, to close the lid it is brought down from the position shown in FIG. 4 to the position shown in FIG. 3 where it hangs loosely over the boss 23 where, from FIG. 3, it will be seen to be parallel to the base. The triangular recesses in the posts 25 and 26 allow this to occur. The lid is then given a sharp blow with the hand snapping the nibs 30, 31 and 32 over the flange 33 and forcing the rim of the lid hard and snugly against the base. At the same time, the pad 34 is compressed over the boss 23 thereby sealing the connector against the ingress of dust, grit and moisture.

To open the lid the prongs of the tool 20 are inserted into the recesses 21 and 22 and the lid is opened by leverage. The lid opens with a snap-action and the triangular recesses in the posts permit the lid to snap into a vertically upright position, at which it stands as shown in FIG. 4.

Referring now to FIGS. 6 to 11, these show a further embodiment of the invention.

In FIG. 6, the connector 14 is of the same material as the other embodiment and is shown fitted to the wall 15 with the lid 19 closed. Two blind cavities 21 and 22 are shown to be provided in the lid 19 to receive prongs of the tool 20 for opening the lid 19.

The tool 20 is shown with its two prongs in the two cavities 21 and 22 ready for opening the lid. In this embodiment, the lid is opened by lowering the handle of the tool 20 upwardly as shown by the arrow 40 instead of downwardly as in the other embodiment.

Referring now to FIGS. 6 to 11, the connector shown comprises a circular boss 23 upstanding from the base, the boss carrying the contacts 24, as in the other embodiment. The lid 19 contains a circular recess 41 into which the resilient pad 34 of foamed plastics material is fitted. As shown in FIG. 10, the upper end of the boss 23 fits into the recess 41 when the lid 19 is closed and the pad 34 completes the seal over the contacts 24, as in the previous embodiment.

The snap-action closure is effected in this embodiment directly between the lid and the base instead of between the lid and the boss. For this purpose the base has an inclined undercut 42 adjacent the hinge and extending between the two hinge-posts 25 and 26. On the side of the base remote from the hinge, there is a further inclined undercut 43 with a gap 44 (FIG. 7).

The lid 19 has, adjacent the hinge, two inwardly directed projections 45 and 46 each of which has an inclined face 47 in which the inclination is complementary to the inclination of the undercut 42. Each of the projections 45 and 46 has a further inclined face 48 of an inclination complementary to that of a face 49 on the base extending between the hinge-posts 25 and 26.

Remote from the hinge, the lid 19 has three inwardly directed projections 50, 51 and 52 respectively shown most clearly in FIG. 8. Each of these projections has an inclined face 53 with an inclination complementary to the inclination of the inclined face of the undercut 43. In addition each of the projections 50, 51 and 52 has a further inclined face 54 of which the inclination is complementary to the inclination of a face 55 extending from the face 43 on the base.

With the lid placed initially as shown in FIG. 9 ready for closure, the faces 48 are in contact with the faces 49 and the faces 54 are in contact with the faces 55.

The lid is then given a sharp blow with the hand to move it parallel to the base (as shown by the arrow 56) and snap it into locked engagement with the base. The locked position is as shown in FIG. 10.

When the sharp blow is given the resilience of the plastics material of the lid permits yielding and deflection of the projections 46, 47 and 50, 51 and 52. Their deflection is facilitated and encouraged by the complementary inclinations of the faces 48, 49 and 54, 55 whereby the projections snap into position with the faces 42, 47 and 53, 43 of complementary inclinations in engagement with one another. The inclinations of the latter faces also cause the lid to slide down to a position in which its rim 57 firmly engages the rim 58 of the base as shown in FIG. 10.

The rim 57 contains a V-shaped groove along its length as shown, and this engages over an inverted-V-shaped projection along the rim of the base as shown.

Lost-motion for the hinge in this embodiment is provided by two slots 59 (FIG. 7) in the hinge-posts 25 and 26, the lid 19 being provided with hinge-pins 60, which are a loose fit in the slots 59. It will be seen that the slots 59 are open at their bottom ends which, in use, fit against a wall which serves to make the hinge pins captive in the slots.

By virtue of the sliding action provided by the inclinations of the faces 42, 47 and 53, 43, the V-shaped groove in the rim of the lid and the inverted-V-shaped projection on the rim of the base, an extremely closely fitting, tamper-proof and sealing joint is provided between the lid and the base. Final sealing of the contacts against the environment is provided by the pad 34 which is squeezed under pressure against the upper face of the contact-carrying boss 23.

To open the lid the two prongs of the tool 20 are inserted into the cavities 21 and 22 in the lid, and as previously explained the tool is levered upwardly. The effect of this is to bend the end of the lid carrying the projections 50, 51 and 52 outwardly from the base enabling these projections to snap out of the undercut 43 and release the lid. Leverage in the opposite direction will not release the lid and it will be appreciated that with blind cavities 21 and 22 in the lid, the prongs of the tool have to be a close fit in the cavities to enable the lid to be snapped open. In addition to the further measure of security so provided, it has been found necessary to have a two-pronged tool. Attempts to snap open the lid with a single-pronged tool with its one-sided distortion of the lid have failed.

Thus attempts to tamper with the lid using an instrument such as a screwdriver fail to open the lid.

It has been found that a small connector can be engineered to provide up to 5 amps current-carrying capacity for each contact with D.C. insulation of 1,000 megohms at 500 volts D.C. The D.C. resistance of each contact-to-plunger connection can readily be made less than 50 milliohms.

Connectors made in accordance with this invention have withstood dry heat tests at 55.degree. C. for 16 hours without deterioration of its electrical characteristics. Samples have likewise withstood long term damp heat tests without undue reduction of insulation. Cyclic damp heat tests have also been applied without noticeable deterioration. Subjection of the connector to a temperature of -25.degree. C. for 24 hours has not caused deterioration either mechanically or electrically. Driving rain, driving dust and driving sand have not caused loss of insulation or mechanical deterioration. Salt mist tests produced no corrosion or deterioration of insulation or contact resistance. Mould growth tests with spores of Aspergillus terreus, Penicillium funiculosum, Scopulariopsis brevicaulis and Trichoderma virid have shown no signs of mould growth. Industrial-atmosphere tests with different concentrations of sulphur dioxide caused no deterioration. Similarly exposure to freezing fog and ultra-violet radiation over long term tests have caused no deterioration.

Thus the connector is of simple construction but capable of withstanding harsh environmental conditions without deterioration. In addition it is proof against normal tampering, for example by children not equipped with a suitable tool for opening the lid.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An electrical connector comprising a base of plastics material with a contact carrier upstanding therefrom, and a lid of plastics material pivotably hinged to the base and arranged for snap acting locking closure over the contact carrier, the hinge of the lid embodying a loss motion mechanism enabling the lid to bodily move simultaneously or independently in directions both parallel to and at right angles to the base during closure, said lid embodying a pad of resilient material which engages the contact carrier when closed and seals the contacts against the environment.

2. A connector according to claim 1, wherein the contact carrier has a flange thereon and the lid has a plurality of co-operating resilient projections which yield during closure of the lid and snap into locking engagement with the flange on the contact carrier.

3. A connector according to claim 1, wherein the lost-motion mechanism comprises two hinge-posts with slots therein extending in a direction normal to the base, and hinge pins projecting from the lid into the slots.

4. A connector according to claim 1, wherein the lid embodies a recess on the inner face thereof which fits over the contact-carrying upper face of the contact carrier when the lid is closed, the recess including containing said pad of resilient material which is compressed against the said upper face when the lid is closed.

5. A connector according to claim 1, wherein, for opening the lid, there are provided two cavities in the rim of the lid on the side thereof remote from the hinge, whereby a two-pronged lever can be inserted to snap the lid out of locking engagement with the base.

6. An electrical connector comprising a base of plastics material with a contact carrier upstanding therefrom, and a lid of plastics material hinged to the base and arranged for snap acting locking closure over the contact carrier, the hinge of the lid embodying a lost motion mechanism enabling the lid to move bodily in directions both parallel to and at right angles to the base during closure, said base having a first undercut portion adjacent to the hinge of the lid, and the second undercut portion remote from the hinge, said lid having at least two resiliently inwardly directed cooperating projections which yield and snap into locking engagement with the base on closure of the lid, said undercut portions on the base and the cooperating projections on the lid having faces with complimentary inclinations which cause the lid and base to be urged towards one another when the lid is closed.

7. A connector according to claim 6, wherein the rims of the base and lid have grooves of complementary cross-sections which engage one another in the closed position.

8. An electrical connector comprising a base of plastics material with a contact carrier upstanding therefrom, said contact carrier having a plurality of spaced apart contact elements protruding from the fact thereof, and a lid of plastics material pivotally hinged to the base and arranged for snap acting locking closure over the contact carrier, said lid embodying a pad of resilient material which engages the face of said contact carrier when closed and seals both the contacts and the surface of the face between said contacts against the environment.