GB2259414A

GB2259414A - Electrical connector with test terminal

Info

Publication number: GB2259414A
Application number: GB9118421A
Authority: GB
Inventors: Colin Mckenzie Elliott
Original assignee: Individual
Current assignee: Individual
Priority date: 1991-08-28
Filing date: 1991-08-28
Publication date: 1993-03-10
Also published as: GB9118421D0

Abstract

A testable connector is provided for attachment to a single insulated wire (Figure 5) or for joining two insulated wires (Figure 1). The connector includes a connector casing (10) or (50) in which there is insulation piercing means (12, 14) or (52) for receiving and making electrical contact with the wire(s). The connector also includes a test terminal (30) or (54) to which external test equipment can be connected. The test terminal is electrically coupled in the casing to the insulation piercing means. The arrangement is such that the test terminal can be concealed in the casing (10) (as shown) when the test terminal is not in use, and exposed (32) when it is required to connect test equipment to the terminal for coupling to one or two wires without having to bare a portion of the or each wire. In figure 1, the test terminal (30), which may be telescopic, is released by a catch (36) for spring biassing to its exposed position; contacts (40a, b) make sliding contact with tracks (44, 46). An led (48) indicates current flow through wires inserted in casing holes (22) into piercing slots of (12 and 14). A casing part (10b) supports ribs for forcing the wires into the slots. In figure 5, casing (50) is flexed to insert a single wire into terminal (52), which is connected to terminal (54). The latter is flexed outwardly for probing. in an alternative, the test terminal is protected by a cover. <IMAGE>

Description

CONNECTOR This invention relates to a testable connector for attachment to one or more wires to enable test equipment to be coupled to the wires. The invention relates especially but not exclusively to a connector for attachment to wires in a telephone or other telecommunication system.

In such an application, it is often required to connect test equipment to a telephone wire in situ to measure, for example the voltage or current, to test whether a fault has occured in the wire. A known method for making the connection is to strip a portion of the insulation sleeving from the wire, and to attach a crocodile clip to the exposed core. However, this technique can cause long term damage to the wire, which may cause a later fault in the telephone line. For example, the wire core can be weakened by the indentations from the teeth of the crocodile clip and this can lead to the wire breaking. This is especially important in the field of telecommunications, where wires of very small diameter are used to occupy less space.

After the test equipment has been disconnected, the bare portion of the wire could cause a short circuit if it came into contact with other exposed metal contacts. The insulation sleeving is also significantly weakened, and may begin to wear.

In order to avoid damage to the wire, it is also known to use metal crimps for joining wires. The crimps provide points to which the test equipment can be connected. However, the metal crimps are prone to rusting, and they can also cause short circuits if they come into contact with other metal contacts.

The present invention has been devised with the aim of overcoming these problems.

In a first aspect, the invention is directed to a testable connector for attachment to an insulated wire. The connector includes a connector casing in which there is insulation piercing means for receiving the wire and for making electrical contact with the wire. The connector also includes a test terminal to which external test equipment can be connected. The test terminal is electrically coupled in the casing to the insulation piercing means. The arrangement is such that the test terminal can be concealed in the casing when the test terminal is not in use, and exposed when it is required to connect test equipment to the terminal.

With such an arrangement, test equipment can be coupled to the wire without having to bare a portion of the wire.

Furthermore, the test terminal only need be exposed when it is desired to make an external connection to the terminal. At other times, the test terminal can be concealed in the casing to prevent the occurence of short circuits.

Preferably, the test terminal is in the form of a probe which can project from the casing to enable external connections to made, and which can be fully retracted into the casing when the terminal is not use. Preferably, the tip of the probe is insulated, so that external electrical contact cannot be made with the probe when it is retracted. This prevents a short circuit occuring if, for example, the connector touches another external contact.

In the preferred embodiment, the probe is of fixed length, and slidable in a bore in the casing. Alternatively, an extendable probe may be used, such as a telescopic probe.

Preferably, the connector includes biasing means to urge the probe outwardly towards its projecting position, and a catch on the casing to hold the probe in its retracted position when the probe is not in use. To activate the probe, the catch is released allowing the biasing means to push the probe into its projecting position. After the probe has been used, it can be pushed back into the connector casing by hand, and secured with the catch.

Preferably, the catch is "self-locking" so that it will automatically lock against the probe when the probe is retracted fully. The biasing means may, for example, be a spring acting on the end of the probe.

Preferably, the casing is made substantially of insulating material, for example, moulded plastics. This prevents short circuits occuring if the connector is accidently brought into contact with another electrical contact.

Preferably, the casing substantially covers the insulation piercing means. This protects the insulation piercing means and the wire cones from corrosion and damage which might otherwise be caused, for example, by moisture.

Preferably, the connector is intended to be permanently fixed to a wire. In such an arrangement, the casing and/or the insulation piercing means provide a secure attachment of the connector on the wire.

Preferably, the insulation piercing means comprises at least one metal plate in which there is a V-shaped slot, and into which slot the wire is pressed. The edges of the slot are sufficiently sharp to break through the insulation, and make contact with the wire core.

Preferably, a circular cut-out is formed at the base of the V-shaped slot, the cut-out being of substantially the same diameter as the wire core. With this arrangement, when the wire is pushed fully into the slot the wire core will be recieved in the circular cut-out. This prevents the sharp edges of the V-shaped slot from damaging the core of the wire, and ensures good electrical contact between the plate and the wire core.

Preferably, the connector can be attached to the wire without having to first break the wire. For example, the connector can be in the form of a deformable or flexible C-shaped sleeve which can be fitted around the wire, and squeezed so that the insulation piercing means will cut through the insulation of the wire.

In a second aspect, the invention is directed to a testable connector for joining two or more insulated wires. The connector includes a connector casing, and insulation piercing means in the casing for receiving the wires and making electrical contact with the wire cores. The connector also includes a test terminal to which external test equipment can be connected. The test terminal is electrically coupled in the casing to the insulation piercing means. The arrangement is such that the test terminal can be concealed in the casing when the test terminal is not in use, and exposed to allow external test equipment to be connected.

This connector offers the same advantages as the connector described previously, but also allows two or more wires to be connected together. The connector can therefore be used as a standard connector for joining two or more wires together, and at the same time, the connector provides a test point to enable test equipment to be coupled to the wire without having to break the connection between the wires, or strip insulation from the wires.

Preferably, the insulation piercing means includes a first insulation piercing means for receiving and contacting the first of the wires, and a separate second insulation piercing means for receiving and connecting a second of the wires.

When the retractable probe is used as the test terminal, the electrical connection between the first and second insulation piercing means is preferably made across the probe. A visual indicator such as a minature light emitting diode (LED) can be incorporated in the probe to indicate current flow across the probe between the first and second insulation piercing means.

The arrangement is preferably such that current flow across the probe is maintained when the probe is in its retracted or projecting positions and is not interrupted when the probe is moved between these positions.

Preferably, the connector is adapted to connect together the ends of two or more wires. In the embodiment described below, the ends of the wires are inserted in holes in the connector casing, and the connector casing is then squeezed or "crimped" to force the wires in engagement with the insulation piercing means.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which: Fig. 1 shows is plan view of the lower half of a connector; Fig. 2 shows an underside view of the upper half of the connector; Fig. 3 shows a sectional view from the front of the upper and lower connector halves together; Fig. 4 shows a sectional view along the line IV - IV of Fig. 3; Fig. 5 shows a perspective view of an alternative design of connector; Fig. 6 shows a side view of the connector of fig. 5; and Fig. 7 shows a top view of the connector of fig. 5 in an extended position.

Figures 1 to 4 show a testable connector for joining together the ends of two insulated wires. The connector comprises a lower half 10a and an upper half 10b of a moulded plastics casing. The upper casing half 10b fits inside the lower casing half 10b as shown by the dotted line in Fig. 1.

First and second pairs of insulation piercing blades, 12 and 14 respectively, are located in the lower casing half 10a for receiving the wires and piercing the insulation to make electrical contact with the wire cores. Each pair of blades comprises a U-shaped metal plate 16, the uprights of which are formed with V-shaped slots 18. The edges of the slot are sharp so that they can cut through the insulation of the wires. A circular cut-out 20 is formed at the base of each V-shaped slot 18 to accomodate the core of the wire when it is secured in the connector.

The upper half 10b is formed with two holes 22 for receiving the ends of the wires. Three transverse ribs 24a, 24b and 24c are integrally moulded on the underside of the upper casing half 10b.

Two slots 26 are formed in the ribs 24 to guide the ends of the wires as they are inserted into the casing. Referring especially to Figs. 3 and 4, the positioning of the holes 22, the ribs 24 and the slots 26 is such that the portions of the wires within the casing are held above the respective V-shaped slots 18 the blades 12 an 14.

To secure the wires in the connector, the upper casing half 10b is "crimped" by pressing it into the lower casing half 10a, in the direction of the arrow 28. This might be done by hand, or by using a suitable tool such as a pair of pliers.

As the upper casing half 10b is pressed down, the ribs 24 locate around the blades. The central rib 24b fits between the blades of each pair, and the outer ribs 24a and 24c fit outside each pair of blades. The wires in the slots are pressed firmly into the V-shaped slots 18, until the wire cores locate in the circular cut-outs 20. The penetration of the blades holds the wires firmly so that they cannot be pulled out from the connector.

The lower casing half 10a is also formed with a passage in which a probe 30 is received. The probe 30 is slidable between a retracted position (as shown in Fig. 1) in which it is concealed in the casing, and a projecting position (shown dotted as 32) in which it is substantially exposed. The probe is biased outwardly towards its projecting position by a coil spring 34 which bears against the inner end of the probe. The probe is prevented by means of a projecting contacts 40a and 40b from being completely removed from the casing.

A catch 36 holds the probe 30 in its retracted postion when the probe is not in use. To access the probe 30, the catch 36 is pushed inwardly by hand, which releases the probe 30, whereupon the probe 30 is pushed outwardly by the spring 30. Once the probe has been used, it can be pushed back into the casing by hand. The catch 36 is self-locking so that it will automatically lock against the probe 30 when the probe 30 is pushed back into its fully retracted position.

The contacts 40a and 40b on the probe 30 bear against respective contact strips 42a and 42b arranged axially on the wall of the passage. A first conductive track 44 connects the first pair of blades 12 with one of the strips 42a, and a second conductive track 46 connects the second pair of blades 14 with the other strip 42b.

A permanent electrical connection is made from the first pair of blades 12 across the contacts 40a and 40b of the probe to the second pair of blades 14. The connection is maintained when the probe 30 is in its retracted or projecting positions, and when it is being moved between these positions.

A minature LED indicator 48 is fitted to the tip of the probe 30.

The LED is coupled between the first and second contacts 40a and 40b such that the LED is illuminated whenever a current flows in the wires. The transparent plastics body of the LED also acts as an insulator to insulate the tip of the probe 30. This ensures that when the probe is retracted, it will not cause a short circuit if the connector is accidently brought into contact with another metal contact. A resistor (not shown) is arranged between the walls of the probe to prevent the conductance of the probe short circuiting the potential difference between contacts 40a and 40b.

Fig. 5, 6 and 7 shows an alternative design for a connector for attachment to a single insulated wire in situ, without breaking the wire. The main difference lies in the design of the casing.

Instead of using holes to receive the ends of the wires, the casing consists of a bendable C-shaped sleeve 50 which can be fitted around the wire. The connector includes at least one insulation piercing blade 52 as described above, and is attached to the wire by squeezing the casing so that the blade penetrates the wires insulation, and contacts the core. The connector may include a retractable probe as described above.

As can be seen from the figures, the connector includes a connecting portion 54 separate from the main connector body and pivotable around a hinge between a retracted position (figure 5) and an extended position (figure 7). This connecting portion 54 may be used as an alternative to probe 30 described previously.

The connecting portion 54 is electrically connected to the insulation piercing blade 52 (here two blades are used) by a contact portion 56. A chip 58 is provided at the free end of connecting portion 54 to retain the portion 54 in its normally closed position.

The connectors described when installed greatly facilitates the testing of the wires using external test equipment without causing damage to the wire or the wires, and without interrupting the current flow in the wires. When the probe 30 or connector portion 54 are in their projecting positions, a crocodile clip can easily be attached. When the portion 54 or probe 30 are in their retracted positions, they are concealed to prevent accidental short circuits occuring.

Other forms of test terminal can be used with other techniques for concealing the terminal when its is not in use. For example, in an alternative embodiment, the terminal might be fixed to the casing, and normally concealed by a removable or openable cover.

Claims

1. A testable electrical connector comprising a connector casing housing insulation piercing means arranged to receive an insulated wire and make electrical contact with the core thereof, and a test terminal electrically coupled in the casing to the insulation piercing means, the test terminal being concealable within the casing and exposable to allow connection of test equipment thereto.

2. A connector according to claim 1, in which the test terminal is a probe which projects from the casing to allow connection thereto and is fully retractable into the casing.

3. A connector according to claim 2, in which the tip of the probe is electrically insulated.

4. A connector according to claim 2 or claim 3, in which the probe is of a fixed length and is slidably received in a bore in the casing.

5. A connector according to claim 2 or claim 3, n which the probe is telescopically extendable.

6. A connector according to any of claims 2 to 5, including biasing means urging the probe towards the projecting position.

7. A connector according to any of claims 2 to 6, in which the casing includes a catch operable to releasably hold the probe in the retracted position.

8. A connector according to any preceding claim, in which the insulation piercing means comprises at least one metal plate having a V-shaped slot therein for receiving a wire.

9. A connector according to claim 8, in which the or each metal plate has a circular cut-out at the base of the V-shaped slot, the diameter of the circular cut-out being substantially the same as the diameter of the core of a wire to be received.

10. A connector according to any preceding claim, in which the insulation piercing means are arranged to receive two insulated wires and make electrical contact with the core of each, and including means electrically coupling two cores so received.

11. A connector according to claim 10, in which the insulation piercing means includes first and second insulation piercing means arranged to receive respective ones of the said two insulated wires, and'the test terminal provides the said means electrically coupling two cores.

12. A connector according to claim 10 or claim 11, including visual indicator means operable to indicate when an electric current flows between the cores of two received wires.

13. A connector according to any preceding claim in which the casing is deformable and the insulation piercing means is arranged to pierce the insulation of a received wire on compression of the casing.

14. A connector according to any preceding claim, in which substantially the whole of the connector casing is formed from electrically insulating material.

15. A connector according to claim 1, in which a part of the casing is movable relative to the remainder of the casing to expose or conceal the test terminal.

16. A method of testing, comprising the steps of providing an electrical connector which comprises a connector casing which houses insulation piercing means and a test terminal electrically coupled to the insulation piercing means and concealed within the casing, the insulating piercing means receiving an insulated wire and making contact with the conductor thereof; exposing the test terminal; and connecting test equipment to the exposed test terminal.

17. A method according to claim 16, in which the test terminal comprises a concealable probe which is exposed by being caused to project from the casing.

18. A method according to claim 16, in which the test terminal is exposed by replaceably moving a moveable part of the casing relative to the remainder of the casing.

19. A testable electrical connector substantially as hereinbefore described with reference to Figures 1 to 4 of the accompanying drawings.

20. A testable electrical connector substantially as hereinbefore described with reference to Figures 5 to 7 of the accompanying drawings.