GB2128041A - A screwless electrical coupling device - Google Patents

Abstract

An electrical coupling device (10) comprises a first member (11) having an electrically conductive first conductor clamping surface (18), locating means (12) for locating an end portion of a stranded electrical conductor (22) adjacent the first conductor clamping surface (18), a second member (13) having a second conductor clamping surface (17), and means (14, 15) mounting the first and second members (11, 13) to enable the second member (13) to slide over the locating means (12). In use of the device (10), relative sliding movement of the first and second members (11, 13), so that the second conductor clamping surface (17) is moved relatively over the locating means (12) and the first clamping surface (18), causes an end portion of a stranded electrical conductor (22) located by the locating means (12) to be moved against the first conductor clamping surface (18) and to be deformed into an at least partly flattened configuration clamped between the first and second clamping surface (18, 17). <IMAGE>

Description

SPECIFICATION A screwless electrical coupling device This invention relates to an electrical coupling device for connecting a stranded electrical conductor to an electrically conductive member, e.g. a switch contact or terminal. More particularly the invention relates to a screwless coupling device enabling the quick-connection of a stranded electrical conductor to an electrically conductive member.

One known type of screwless terminal device comprises a recessed member of electrically insulating plastics material. The walls of the recess support a fixed electrical contact and a metallic leaf spring, the latter being positioned so as to converge towards, and to make resilient contact with, the fixed electrical contact. In order to connect a stranded electrical conductor to this known terminal device, an end portion of the conductor is first treated, e.g.

tinned or fitted with a crimped ferrule, to stiffen the conductor end. The conductor end portion is then inserted through an access opening of the recess into the converging gap defined between the fixed electrical contact and the leaf spring. On continued insertion of the stiffened end portion of the conductor through the access opening, the end portion of the conductor through the access opening, the end portion of the leaf spring is deflected, against the spring force provided by the leaf spring, out of mechanical contact with the fixed contact and the end of the stranded electrical conductor is clamped between the fixed contact and the end portion of the leaf spring.The end portion of the leaf spring is resiliently urged against the clamped end portion of the stranded electrical conductor and, since it contacts the conductor at an acute angle, resists any attempt to withdraw the conductor from the recess through the access opening.

One disadvantage of this known type of screwless terminal is that the walls of the recess are made of a plastic material which yields in use thereby reducing the effective clamping force applied by the leaf spring resulting in a relatively poor electrical connection between the stranded electrical conductor and the fixed contact.

The present invention aims to provide an improved electrical coupling device capable of making a good, screwless connection between a stranded electrical conductor and an electrically conductive member.

According to the present invention an electrical coupling device comprises a first member having an electrically conductive first conductor clamping surface, locating means for locating an end portion of a stranded electrical conductor adjacent the said first conductor clamping surface, a second member having a second conductor clamping surface, and means mounting said first and second members to enable the second member to be slid relatively over said locating means and to enable the said second conductor clamping surface to be slid relatively over the said first conductor clamping surface in confronting relationship thereto, whereby in use of the device, on relative sliding of the first and second members so that the second conductor clamping surface is moved relatively over said locating means and the said first clamping surface, an end portion of a stranded electrical conductor located by said locating means is moved against said first conductor clamping surface and is deformed into an at least partly flattened configuration clamped between said first and second conductor clamping surfaces.

Suitably the said locating means comprises an aperture formed in the said first member.

Typically the said second member is directly slidably mounted on the first member. In this case the first member may comprise a flat elongate metal strip and the second member may be of channel section having a pair of spaced apart flanges connected by a flat connecting web defining the said second surface, the said flanges being positioned along opposite side edges of the elongate metal strip and having their free edges turned over towards the side of the metal strip remote from said first surface.

Preferably the said second member is formed of spring metal and typically has a loose sliding fit on the first member.

Detent means may be provided for locating the first and second members relative to each other in a conductor clamping position.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a sectional view of a known screwless electrical coupling device, Figure 2 is a schematic sectional view of an electrical coupling device according to the invention showing its parts in positions ready to couple thereto a stranded electrical conductor, Figure 3 is a schematic sectional side view of the electrical coupling device shown in Figure 2 but showing its parts in positions clamping the stranded electrical conductor thereto, Figure 4 is a view taken on the line IV-IV of Figure 2, Figure 5 is a view taken on the line V-V of Figure 3 but not showing the insulation on the stranded electrical conductor, and Figure 6 is a view taken on the line VI-VI of Figure 2.

In Figure 1 there is shown a known form of a screwless electrical coupling device, generally designated by the reference numeral 1. The device 1 comprises a member 2 of electrically insulating thermoplastics material having a recess 3 formed therein. The walls of the recess 3 support a fixed terminal 4 and a metallic leaf spring 5, the latter being positioned to converge towards the fixed terminal 4. An access opening 6 opens into the recess 3 to permit an insulated stranded electrical conductor 7, with its insulation bared or stripped from one end, to be inserted into the recess 3 between the fixed terminal 4 and the leaf spring 5 (as shown in Figure 1). In order to provide the bared end of the conductor with sufficient stiffness to deflect the leaf spring 5, it is conventional to treat the bared end of the conductor prior to its insertion into the recess 3.Suitably this treatment involves tinning the bared conductor end or crimping a ferrule thereto.

When so inserted, the end of the conductor 7 is clamped against the terminal 4 by the resilient clamping force applied by the leaf spring 5. As shown, the end of the leaf spring 5 bites into the bared end of the conductor 7 and, by virtue of the angle and resilience of the spring 5, resists any attempts to withdraw the conductor from the recess 3. However, as mentioned previously, the effective operation of this known device 1 depends on the walls of the recess 3 being made of a non-yielding material. In practice the walls of the recess tend to yield in use resulting in a less effective clamping force being exerted by the leaf spring 5.

In Figures 2 to 6 there is shown a screwless electrical coupling device according to the invention and generally designated by the reference numeral 10. The device 10 comprises an electrically conductive strip 11, typically the end of a switch contact or terminal, having an aperture 12 formed therein, and a slide member 13 mounted on the strip 11 with a loose sliding fit. Although not essential it is preferred that the slide member 13 is made of spring metal.

As can be most clearly seen in Figure 6, the slide member 13 is of generally channel section having a pair of spaced apart side flanges 14, 15 connected by afat connecting web 16. The flanges 14 and 15 are curled over inwardly towards each other with their free ends remaining spaced apart from the connecting web 16 and defining therewith a gap in which the strip 11 is received. In this manner the slide member is slidable along the strip 11 with a surface 17 oftheweb 16 being spaced apart from, in confronting relationship to, a clamping surface 18 of the strip 11. A pair of end flanges 19, 20 extending in the opposite direction to the flanges 14, 15 are provided at the opposite ends of the connecting web 16.

In use of the coupling device 10, insulation 21 is stripped from one end of a stranded conductor 22 and the individual strands are twisted together so as to have a substantially circular cross-section. The bared end of the insulated conductor 22 is then inserted through the aperture 12 with the slide member 13 in a position (see Figures 2 and 4)50 as not to cover the aperture 12. The slide member 13 is then slid along the strip 11 in the direction indicated by the arrow X in Figure 2 until it is moved into the position shown in Figures 3 and 5. During the course of this movement, the end flange 19 first contacts the end of the conductor 22. Continued movement of the slide member 13 causes the end of the conductor 22 to be moved against the walls of the aperture 12 and to be subsequently turned against the clamping surface 18 of the strip 11.Finally, as the slide member 13 is moved into its final clamping position, the surface 17 is moved over the aperture 12 and the bared strands at the end of the conductor 22 are deformed from a generally cylindrical configuration into a flattened, flared configuration (see Figure 5) calmped between the confronting surfaces 17 and 18.

In the position shown in Figures 3 and 5, the end of the conductor 22 is held firmly clamped by the slide member 13 against the strip 11. Stop members 23, 24 of electrically insulting plastics material are positioned to prevent undue bending of the strip 11 if the conductor 22 is pulled in the direction indicated by the arrow Y in Figure 3. The stop member 24 also prevents the slide member 13 from being slid off the end of the strip 11; movement of the slide member 13 along the strip 11 in the opposite direction being limited by a widened portion 25 (see Figures 4 and 5) of the strip 11. If desired the end of the conductor 22 can be released from its clamped position by sliding the slide member 13 back along the strip 11 in the direction opposite to that indicated by arrow X.

Alternatively, if it is desired to permanently clamp the conductor end, the slide member 13 may be locked on the strip 11 in its conductor clamping position.

It will be appreciated that in the embodiment described, the effective working of the device 10 is not dependent on the stability of plastics materials.

Thus easily mouldable thermoplastics material may be used for housing or mounting the coupling device without affecting its calmping effectiveness.

Stripped conductors for coupling to the device 10 do not require any special preparation, (other than twisting the conductor ends together), making the device suitable for permanent and rewirable situations without the need for special tools.

Furthermore when trapped, the bared strands of a conductor spread out in a fan shape, increasing the area of contact giving an improved and consistent mechanical and electrical connection.

The device 10 may be modified in many ways within the scope of the present invention. For instance cooperating detent means (not shown) may be provided on the slide member 13 and the strip 11 for locating the slide member 13 in either of its operative positions shown in Figures 2 and 3.

Claims (11)

1. An electrical coupling device comprising a first member having an electrically conductive first conductor clamping surface, locating means for locating an end portion of a stranded electrical conductor adjacent the said first conductor clamping surface, a second member having a second conductor clamping surface, and means mounting said first and second members to enable the second member to be slid relatively over said locating means and to enable the said second conductor clamping surface to be slid relatively over the said first conductor clamping surface in confronting relationship thereto, whereby in use of the device, on relative sliding of the first and second members so that the second conductor clamping surface is moved realtively over said locating means and the said first clamping surface, an end portion t a stranded electrical conductor located by said locating means is moved against said first conductor clamping surface and is deformed into an at least partly flattened configuration clamped between said first and second conductor clamping surfaces.

2. An electrical coupling device according to claim 1, in which the said locating means comprises an aperture formed in the said first member.

3. An electrical coupling device according to claim 1 or 2, in which the said second member is directly slidably mounted on the first member.

4. An electrical coupling device according to claim 3, in which the first member comprises a flat elongate metal strip and the second member is of channel section having a pair of spaced apart flanges connected by a flat connecting web defining the said second surface, the said flanges being positioned along opposite side edges of the elongate metal strip and having their free edges turned over towards the side of the metal strip remote from said first surface.

5. An electrical coupling device according to claim 3 or 4, in which the said second member is formed of spring metal.

6. An electrical coupling device according to claim 3,4 or 5, in which the said second member has a loose sliding fit on the first member.

7. An electrical coupling device according to any of claims 3 to 6, in which detent means are provided for locating the first and second members relative to each other in a conductor clamping position.

8. An electrical coupling device according to any of the preceding claims, including electrically insulating plastics material for housing and /or mounting the first and second members.

9. An electrical coupling device according to claim 8, in which said plastics material comprises a thermoplastics material.

10. An electrical coupling device constructed and arranged substantially as herein described with reference to , and as illustrated in, Figures 2 to 6 of the accompanying drawings.

11. Electrical apparatus having at least one electrical coupling device according to any of the preceding claims.