GB2140221A - Electrical connectors - Google Patents

Abstract

An electrical connector (1) which is particularly suitable for use in a component (A) for a telephone main distribution frame comprises a cylindrical portion (2) having an axial wire-receiving slit (3) and a resilient contact clip (4) which includes wiping portion or blade (6). The connector is located in a housing (10) such that part of the wiping blade is exposed to the exterior through an aperture (12) in the housing. The component (A) consists of two pairs of such cylinders in housings assembled with a protection module (17) having two input and two output surface contacts (18a, 18b) such that each of the surface contacts touches the exposed part of a connector. Any desired number of components A may be used as a standard frame to build up a complete system with the incoming and outgoing lines terminating in a simple compact stacked array having a high density of terminations for a given area. <IMAGE>

Description

SPECIFICATION Electrical connectors This invention relates to electrical connectors, and is particularly concerned with connectors for use in telecommunications applications, for example in telephone exchanges.

One of the functions of a telephone exchange is to sort incoming lines from individual subscribers or groups of subscribers into strict numerical order. This operation is carried out on a main distribution frame (MDF). The signal from each pair of incoming wires is passed through a protection unit on the MDF which acts in much the same way as a fuse to isolate the incoming wires from the remainder of the exchange if they should, for any reason, be carrying a dangerously high current. The output from the protection unit is also sorted so that the incoming lines are in numerical order and the outputs from the MDF may then be cross-patched into the exchange proper.

Conventionally, the incoming wires have terminated at the protection units in a more or less permanent connection such as a soldered or wire wrap connection, and the protection units have been separately wired to the MDF outputs. This has resulted in a bulky construction, particularly since access to all parts of the MDF has been required.

The current move towards digital telephone exchanges has meant that the MDF in an exchange has become the largest and most cumbersome component of the exchange. However, digital equipment has a lower tolerance to signal variation than conventional equipment and so the importance of the protective function of the MDF has increased. Consequently, development of a new MDF construction and components therefor have been investigated.

This invention provides an electrical connector comprising a cylindrical portion having a slit defining an insulation displacement contact section and a resilient contact clip, the clip having an intermediate portion which extends away from one end of the cylinder and a contact portion which extends from the end of the intermediate portion remote from the cylinder back towards the cylinder and terminates in a free end.

The connector is used to terminate a wire which is received and gripped by the slit of the cylinder and is to be connected via the two portions of the contact clip to an opposed contact member. The dimensions of the cylinder and, in particular, of the wire receiving slit therein are chosen with regard to the wire to be received.

The invention further extends to a connector block comprising such a connector in an insulating housing having a first aperture in one face thereof for introduction of a wire and a second aperture in another face thereof through which a part of the contact portion is exposed to the exterior.

Such connector blocks may conveniently be used in components for an MDF in a telephone exchange.

The invention further extends to a component for a telecommunications main distribution frame comprising an arrangement of four such connector blocks and a protection module having two input and two output surface contacts, the arrangement being such that each contact of the protection module is in contact with the exposed part of a connector.

Preferably, the contacts of the protection module take the form of pads standing slightly proud of the protection module surface.

The invention will now be further described by way of example with reference to the drawings, in which: Figure 1 shows a perspective view of a connector embodying the invention; Figure 2 shows, in vertical section, a component for a telephone main distribution frame incorporating the connectors of Figure 1; Figure 3 shows an end view of the component of Figure 2 as part of a telephone main distribution frame; and Figure 4 shows, schematically, a perspective view of part of a telephone main distribution frame incorporating a plurality of the components shown in Figures 2 and 3.

Referring to Figure 1, the connector 1 includes a barrel terminal consisting of a metal split cylinder 2 having an axial wire-receiving slit 3. A resilient contact clip indicated generally at 4 is formed integrally with the cylinder at one end thereof. The clip 4 has an intermediate portion 5 extending away from the cylinder joined to a wiping contact portion or blade 6 which extends back towards the cylinder and terminates in a free end 7 provided with a cross-piece 8. The split cylinder 2 is formed with an outwardly projecting retaining tag 9 (see Figure 25.

The split cylinder 2 provides an insulation displacement device in which the slit 3 acts to displace the wire insulation and cut into the conductor of the wire as the wire is inserted into the slit to form a conductive connection. The cylinder may also be provided with a formation at the end remote from the contact clip to cut off excess wire. No soldering or internal wiring is necessary, and the nature of the connection between wire and connector allows the wire to be temporarily removed if this is necessary for testing etc. Although conventionally termed an insulation displacement contact, the cylinder can also be used with uninsulated conductors.

Figure 2 shows a component (indicated generally at A) for a main distribution frame including four connector blocks of which only two can be seen. Each block comprises a connector 1 arranged in a moulded insulating housing 10.

Opposing faces of each housing 10 are formed with apertures 11 and 12. One wire 1 3a of a pair incoming from, for example, a telephone, passes through the aperture 11 of the right-hand housing and is received and gripped by the slit 3 in the appropriate connector. One wire 1 3b of a pair going out to, for example, a telephone exchange proper, passes from the slit 3 of the left-hand connector out through the appropriate aperture 11. The apertures 11 are designed to provide strain relief for the wire terminations.

The apertures 1 2 are arranged so that, when the connectors are in position in their housings, small portions of the wiping blades are exposed to the exterior through the apertures 12. Each housing is also formed with a retaining aperture 14 and a seating arrangement indicated generally at 15. Each connector block is assembled by slightly compressing the cross-piece 8 towards the split cylinder 2 and inserting the connector into the housing in the direction indicated by arrow X. The retaining tag 9 is forced inwards by the adjacent housing wall until the cylinder is seated on seat 1 5a of arrangement 1 5 when it can spring outward into retaining aperture 14 thus locating the connector in the housing.At the same time, the cross-piece 8 is engaged by a mechanical stop 1 6. The connector may be removed from the housing by the reverse procedure, i.e. by pushing the tag 9 through the aperture 14 towards the body of the cylinder, and sliding the connector out of the housing.

Connectors may easily be replaced in this way if desired.

The four connector blocks are assembled in a unit (not shown) with a protection module indicated generally at 1 7. The protection module may contain various safety devices which are not central to the present invention and so will not be described in detail. The protection module has two input contact pads, one of which is shown at 1 8a and two output contact pads, one of which is shown at 1 8b. The module also has an earth contact (not shown). The nature of the connection between the connector blocks and protection module is such that they are brought into contact by relative movement in the direction of arrow X effectively to plug in the protection module so that the contact pads make wiping cdntact with the exposed portions of the wiping blades.

The connector blocks and protection module are held in registry by means of spring-loaded latches 19.

The mechanical stop 1 6 in each connector block is designed so as to exert a specified preload on the wiping blade so as to ensure that the contact pressure applied to the relevant contact pad of the protection module when the component is assembled is neither too low (which might result in a poor contact) or too high (which might lead to overstressing of the contact). The wiping blade is arranged by means of the preload in a position such that, as the protection module is moved in the direction shown by the arrow X, the exposed portion of the blade only makes contact with the contact pads and not with the surface of the protection module surrounding the pads.This means that the contact surface of the wiping blades does not become contaminated by foreign particles which might be the case if it rubbed along the surface of the protection module itself during assembly. This feature is particularly advantageous for telecommunications applications where clean contacts are most important. The contact may also be improved by plating a gold strike on to the exposed area of the wiping blade.

Figure 3 shows a plan view of the left-hand end of the component of Figure 2 as part of a telephone MDF. The two output connectors are indicated at 1.

Figure 4 shows parts of an MCF, the whole of which would consist of 100 of the components shown in Figure 2 arranged in ten vertically stacked rows of ten components each of which four rows 19 are shown. The rows of components are supported on a frame 20. As is shown in more detail in Figure 3, the two output connectors of each component are arranged at the front with the two input connectors being hidden from view behind them. The wiring of the MDF has been omitted from the drawing for the sake of clarity, but the incoming wires would be fed in from the back of the frame 20 and the-outgoing wires would leave from the front via guide channels 21.

It will be seen that any particular subscriber may easily be isolated from the exchange proper by simply moving the appropriate protection module outwards to disengage the spring latches and break the contacts as shown at Y. It is not, therefore, necessary to use an isolation member (which might contaminate the contacts) to break the contact. Additionally, a quick glance at the frame will show which incoming lines are isolated at any one time. Similarly, if it is desired to test a faulty incoming line to see whether the fault is on the exchange or telephone side by insertion of a test jack, this may also be achieved from the front of the frame by insertion of the jack via opening 22 of the particular component to break the output contact.The rest of the exchange will still, however, be protected from freak currents on the line in question as the input contacts of the protection module remain undisturbed.

It will be understood from the foregoing description that the present invention provides, inter alia, a component for a telephone MDF, any desired number of which may be used on a standard frame to build up a complete system with the incoming and outgoing wires terminating in a simple compact stacked array having a high density of terminations for a given area. The components include split cylinder or barrel terminal insulation displacement devices and so require no internal wiring. Termination of incoming and outgoing wires is also facilitated. If a protection module blows, it may simply be replaced by a new one without involving any complex rewiring.

It will further be appreciated that the operations ordinarily regarded as necessary for maintenance of the frame can be carried out from the front and so the frame itself may be fixed to a wall and thus will take up a relatively small amount of space.

If it is desired to simplify access from the front of the frame to the input connectors, this may be achieved by making the input connector blocks bigger than the output blocks leaving a series of spaces at the front of the frame through which access can be gained past the output connectors to the input connectors at the back of the frame.

Alternatively, the protection module may be designed with input and output contacts on opposing surfaces and the connectors blocks arranged accordingly.

It will be understood that connectors and connector blocks according to the invention can be used without protection modules in private exchanges.

Claims (3)

1. An electrical connector comprising a cylindrical portion having a slit defining an insulation displacement contact section and a resilient contact clip, the clip having an intermediate portion which extends away from one end of the cylinder and a contact portion which extends from the end of the intermediate portion remote from the cylinder back towards the cylinder and terminates in a free end.

2. A connector block comprising an electrical connector including a cylindrical portion having a slit defining an insulation displacement contact section and a resilient contact clip, the clip having an intermediate portion which extends away from one end of the cylinder and a contact portion which extends from the end of the intermediate cylinder remote from the cylinder back towards the cylinder and terminates in a free end, in an insulating housing having a first aperture in one face thereof for introduction of a wire and a second aperture in another face thereof through which a part of the contact portion is exposed to the exterior.

3. A component for a telecommunications main distribution frame comprising an arrangement of four connector blocks as claimed in claim 2, and a protection module having two input and two output surface contacts, the arrangement being such that each contact of the protection module is in contact with the exposed part of a connector.