GB2263202A - Coil-spring contact for lampholder - Google Patents

Abstract

An electrical connection (10) to a conductor wire (12) is made by clenching the wire between consecutive electrical connection-making turns (18X, Y) of an helical spring (16) of electrically conducting strip or wire without significant disturbance of the axis of the spring. The close electrical connection-making turns (18X, Y) are spaced along the spring (16) from other turns (18A) that are wider spaced for conductor (12) entry purposes prior to relative rotation of the spring (16) and the conductor (12) about the axis of the spring (16) to achieve connection-making clenching. The conductor (12) can have its insulation removed from between clenching turns (18X, Y) after such relative rotation by using heat or ultrasound. Both conductor wires of an electrical cord can be so connected within a lampholder (fig 8B). The connection may be made by apparatus including a holder for the wire and a turner and a guide for the spring. <IMAGE>

Description

ELECTRICAL CONNECTIONS This invention relates to making electrical connections.

We have commercial interests in mains electrical accessories, including but not limited to lampholders. All such electrical accessories require electrical connections to be made to wire conductors, whether of mains supply wiring, usually single strand insulated wires, going between consumer units and outlets or switches or junction or spur units; or of subsidiary wiring, usually multistrand cord or flex, going from mains wired units to subsidiary units as from ceiling roses to lampholders or from spur units or plugs to electrical goods. The two most common ways of making electrical connections for wires are by way of screw clamp terminals or crimped connections.

Alternatives include insulation disrupting devices usually intended to save costs of baring insulated wires for connection purposes. Pursuit of reduced costs of making electrical connections is a significant general exercise, including for provision of ready-wired accessories, for example lampholders with cord or flex drops, even further complete with ceiling roses; and has influenced growth of overall market share for non-rewirable accessories.

Specific origin of this invention lies with lampholders, particularly non-rewirable lampholders produced complete with cord or flex drops. For our home market of the United Kingdom, lampholders are most commonly of bayonet type having spring-loaded plungers to engage with lamp cap contacts. In considering low cost alternatives to rewirable screw-clamp terminal blocks for bayonet lampholders, we have looked carefully at all variants known to us, obviously including crimping and insulation disruptors. A particular concern has been for quality of connection so that undue heat is not generated, and we believe there is room for improvement particularly for reliable repeatability in volume production.As far as we are aware, no one has looked seriously at making direct connections to springs by which the plunger contacts are loaded, despite springs long having normally been electrically conductive parts of the lampholder, and the fact that success could dispense also with otherwise necessary connection making abutments for such springs. No doubt that reflects the profound problems involved, including reliably soldering to spring wire. This invention reflects a radically different approach.

According to one aspect of this invention an electrical connection to a conductor wire comprises clenching that wire between consecutive turns of an helical spring itself of electrically conducting strip or wire without significant disturbance of the axis of the spring.

We are, of course, aware of light-duty, low voltage and current connections (as used in educational and like kits introducing children and other students to electronics) made by bending a spring and allowing it to relax onto a conductor placed between its turns as openedup by its bending. However, such connections are inherently temporary and wholly unsuitable for mains wiring purposes, including for voltages concerned and for even lightest of current loadings involved in lighting (rather than power) circuits. The term "clenching" as used herein is intended to convey a meaning of far greater contact/connection force than available simply from bending a spaced turns spring from its normal relaxed axial orientation and its recovery therefrom.

Surprisingly, first experiments involving making electrical connections to bared multi-strand cord or flex wires have produced better and repeatable connection quality, in terms of heat production and temperature generation, than provided reliably by insulation interrupting plates. That was first shown to be the case where clenching between spring turns spreads the strands of multi-strand wire bared of its insulation.

Even more surprisingly, entry into the spring turns of a wire complete with its insulation can also be made effective by the simple expedient of applying a welding tool to the adjacent end of the spring. Both of heated welding tools and ultrasonic welding tools have proved effective in causing insulation to move from between clenching spring turns and the wire itself, thus achieving electrical connection at both sides of the spring turns concerned.

In one embodiment of this invention, the electrical connection is with the wire between spring turns then held further apart than would otherwise be the case, i.e. representing localised extension of the spring and relying on consequent spring return forces. That is preferably achieved within an helical compression type of spring that is compressed overall in its required action in establishing electrical connection between the wire and abutment for at least one end of the spring. It is particularly effective if connection is within a closeturned spring region that is adjacent another spring region having wider spaced turns into which the wire can be introduced easily and the spring turned on the wire and about its axis until the wire moves axially of the spring in getting clenched between the close turns.A compression spring with medial open turns and closed end turns is particularly suitable.

In principle, of course, the wire could be turned round the spring axis in order to translate along that axis from relatively wide to relatively close spaced turns having clenching action. However, turning the spring about its axis with the wire held steady is much more convenient and practical, and constitutes a particular aspect of invention. Indeed, a related aspect concerns a tool having an end drivingly to engage a spring and rotatable to turn the spring relative to a wire, and a preferred tool does so at one end of the spring and has a further extension into the spring for release of driving engagement automatically when that further extension is engaged.by the wire.

Such method and use-of-tool aspects are readily implemented whether at a wire insulation removal station or without such insulation removal or within a spring housing bore of a body part of an accessory itself, in each case with provision for holding the wire steady, whether at said station or some other attachment station or in or against formations of the accessory body part.

It is also the case that, in principle, clenching of the wire between spring turns can be achieved solely by compression of the spring concerned as installed in an electrical accessory, though advantages of wires with springs retained thereon would then be foregone.

Specific implementation for this invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figures 1A and 1B show side and end views of an electrical connection; Figure 2 shows a tool and indicates its use in making the electrical connection of Figure 1; Figures 2A and 2B show use of welding type ool to make connections through insulation; Figures 3A and 3B indicate making electrical connections for bared wires; Figure 4 is a perspective view of a lampholder body part; Figures 5A and 5B are sections at right angles on lines VA and VB of Figure 4; Figures 6A and 6B are perspective views of a lampholder cap; Figures 7A and 7B are sections at right angles on lines VIIA and VIIB of Figure 6; and Figures 8A and 8B are assembled and exploded views of the lampholder as a whole.

Referring first to Figures 1A and 1B, electrical connection indicated generally at 10 is shown made between conductor wire 12 bared of insulation 14 and a spring 16 of electrically conductive material, specifically an helical compression spring having relatively spaced or open medial turns at 18A and relatively close or closed end turns at 18B and 18C. The connection 10 is shown made between adjacent relatively close or closed turns 18X,Y at one end 18B by clenching of the bared wire 12 between those adjacent turns 18X,Y.

The spring 16 is typical of springs we make for biassing plunger contacts of bayonet type lampholders.

Having a few closed-up turns at ends facilitates handling for automatic feed purposes during assembly. The illustrated electrical connection 10 effectively and advantageously exploits provision of such closed-up turns, whose number is unimportant other than that there should be at least two sufficiently adjacent to clench on electrically conducting wire.

The wire 12 with insulation 14 is typical of what is used for drops from ceiling roses to lampholders, normally as a double-insulation cord -or flex with two insulated wires within an outer insulating sheath. Such wire 12 is usually of multi-strand type and its strands can spread out to a maximum extent represented by a minimum of one component strand thickness between the adjacent turns 18X,Y as indicated in Figures 1A and 1B.The electrical connection then formed is of high quality and of high repeatability in volume production, especially when made as preferred herein by effectively winding the spring 16 down onto the wire 12, from an easy entry position between medial wider spaced turns, conveniently spaced at least by the normal diameter of the wire 12, to the connection position shown with the wire 12 clenched between closer turns 18X,Y, and during which winding a multi-strand wire 12 will be progressively spread.

It will be appreciated that wherever a spring is provided in an electrical accessory, its compressibility is an important feature of the accessory concerned. Clearly, wherever such compression is, as it is with bayonet lampholder plungers, an accompaniment to electrical contact for functional purposes, the clenching illustrated in Figures 1A and 1B will have its force if anything increased when most needed.

A consistent variation on what is shown in Figures 1A and 1B would, of course, be to pre-spread bared ends of multi-strand wires, if desired consolidated in that state by solder or whatever; or to flatten the end of a single-strand conductor. However, good electrical connection can result for single-strand wires without such flattening and with toleration of extra distortion of the closed-up spring windings or adjustment of the spacing to give little or no distortion, but still adequate clenching, or with some acceptable optimisation of distortion and clenching. Logical extension to achieving clenching by closing up spring turn spacing by coaction of two other parts of the lampholder in compressing the spring is not ruled out, even though it does not produce an electrical connection advantageously self-supporting as a subassembly, i.e. with spring attached to wire.

Turning to Figure 2, first entry of bared wire 12 between relatively spaced medial turns 18A of the spring 16 is shown. Figure 2 also shows a highly advantageous tool 20 with an operative end 22 having an annular peripheral end surface 23 stepped at 24 snugly to engage the end of the spring 16, including the free spring wire end referenced 18F. When the operative tool end 22 engaged with the end of the spring 16, particularly at 18F, and is rotated, see arrow R (for the indicated direction of spring winding), axial rotation of the spring 16 as a whole will result. If the wire 12,14 is held steady the spring will travel down the bare wire 12, which will correspondingly effectively travel up into the closed-up windings 18B of the spring 16.

Highly advantageously, the operative tool end 22 has a central projection 25 within the annular spring end engaging surface 23. That projection 25 then serves not only to assist in spring end engagement by the tool end 22 but also in automatic release of that engagement-by the simple expedient of the wire 12 within the spring 16 engaging the projection 25 and lifting the tool end 22 off the spring end, at least so long as the tool 20 is biassed into such engagement by a force less than the minimum clenching force of the spring turns 18X,Y at either side of their engagement with the wire 12.

Holding the wire 12 steady is readily achieved by locating means that may engage it from below, or from above, or sideways, or some combination that may be the same or different to each side of the spring 16. A guide hole or recess for the spring 16 is preferred and the whole operation can conveniently take place either separately from electrical accessory assembly or as part of accessory assembly relative to an axis of movement for the spring 16 into the accessory. For that reason the operative end 22 of the tool 20 is shown on a shank or spindle 26 of a length suiting both of driving the spring 16 onto the wire and subsequent pushing of the achieved connection further into the accessory concerned. Drive application end 28 of the tool 20 may be of any desired configuration whether for fitting to a chuck or for band drive or for geared drive or whatever.

Turning to Figures 2A and 2B, making connection to wires without removing insulation is indicated as being processed generally as before but for wire 12 complete with insulation as between the clenching spring turns 18X,Y.

Then, however, a suitable heated or ultrasonically actuated tool 30 is shown going to touch the end of the spring 16 and caused removal or retraction of the insulation 14 at clenching between the turns 18X,Y. This is highly advantageous in avoiding specific insulation removal, though that will now be described.

Figure 3A indicates connection making operation at a wire insulation stripping station, see blade pairs 32A,B and 34A,B, and with the spring 16 brought onto the wire by a pusher 36 also cooperating with an abutment surface 38 to guide the spring 16 when it is rotated.

Figure 3B also indicates operation that could be at a wire insulation stripping station, but involves bringing the wire 12 into the spring by a pusher 42 movable over a surface 44 apertured at 46 for spring guidance purposes.

Turning now to Figures 4 to 7 for a specific application of electrical connections hereof to a lampholder of non-rewirable bayonet type, Figures 4 and 5 concern the lampholder body 50 and Figures 6 and 7 concern the lampholder cap 80.

In Figures 4 and 5, the lampholder body 50 has a conventional lamp receiving skirt 52 with shade retention threading 54 below locally enlarged flanging 56 and a pair of diametrically opposed J-slots 58A,B. A central barrier 60 is apertured at 62A,B for plunger contacts (not shown) to be inserted from above as shown and retained by flanging engaging bottoms of wells 64A,B about the apertures 62A,B, and to be biassed by springs within the plungers and the wells 64A,B.

The wells 64A,B are preferably of- circular section and extend from arcuate formations 66A,B of a central upstand 67 and 68A,B of flanking shorter upstands 69A,B. Confronting ones of arcuate formations 66,68 form slots 70A,B above the wells 64 proper. The slots 70A,B will accept connecting wires, such as 12,14 above, and the wells 64A,B will accept plunger bias springs, such as 16 above. Self-evidently, making of the wire-spring connections could take place in the lampholder body 50, though it is preferred to do so separately and along with insulation stripping.

The central upstand 67 is shown with a further larger and deeper slot 72 that is sized to accept cord or flex sheathing, and has cord grip provisions by way of confronting teeth 74A,B at its free end. Below the shorter flanking upstands 69A,B is a circumferential outwardly facing toothed formation 76.

Turning to Figure 6, the lampholder cap 80 is of generally conventional outer shape from its cable entry aperture 82. Internally, however, the lampholder cap 80 has two outwardly open box-like formations 84A,B capable of fitting about the shorter upstands 69A,B of the body part 50, including entering the slots 70A,B. In fact, those slots together with an appropriate clearance at their bottoms for wires 12 and their insulation 14 in electrical connections near ends of the plunger springs, effectively define the extent of the box-like formations 84A,B, particularly their open ends.

Additionally, the lamp cap cover 80 has internal toothed formations 86A,B that engage over the circumferential toothing 76 of the body part 50 in a strong snap-fit arrangement for the cap 80 on the body part 50 with the mouth of the cap 80 then in substantially flush abutment with the flanging 56 (other than for protuberances thereof for gripping purposes).

This lampholder 50,80 represents substantial advances at least in terms of achieving low-cost pre-wired products. Notably, of course, it dispenses entirely with customary terminal block or equivalent upper abutment fittings to the body part for the springs of its plungers.

However, other features have individual and collective merit, including the fact that all assembly can be from the top of the body part as illustrated, and that linear action snap-fitting secures the assembled and pre-wired product, and that cord grip provision is of such an inherently simple nature as engagement in a slotted upstand lying immediately below cord entry of the cap.

An assembled lampholder 100 is shown in Figure 8A complete with fragmentarily indicated drop cord 102, commonly known as a pre-wired lampholder.

Figure 8B is an exploded view of the pre-wired lampholder showing its body part 50 of bayonet type and its snap-on cap 80, also conventional shade ring 104, and plunger type lamp-cap contacts 106A,B with upper capture flanging 108A,B and bias springs 11OA,B. Upper ends of the bias springs 11OA,B have closer turns and serve as before described for wire clenching and connection-making purposes to individual wires 1I'2A,B of the drop cord 102. It is feasible for those wires 112A,B to be entered into wider spaced spring turns and for the springs 11OA,B to be turned by a tool or tools after insertion into body part wells, if not done before presentation to the body part 50, and for the cap 80 to be threaded on and snap fitted afterwards (then assuring bias spring action, of course).

Claims (35)

1. An electrical connection to a conductor wire comprising clenching the wire between consecutive electrical connection-making turns of an helical spring itself of electrically conducting strip or wire, and without significant disturbance of the axis of the spring, the electrical connection-making turns being spaced along the spring from other turns that are wider spaced for conductor entry purposes prior to relative rotation of the spring and the conductor about the axis of the spring to achieve connection-making clenching.

2. An electrical connection according to claim 1, wherein bared multi-strand cord or flex wire is clenched between said consecutive connection-making turns and with its component strands spread by the clenching.

3. An electrical connection according to claim 1, wherein wire first clenched between said consecutive connectionmaking turns complete with its insulation has had its insulation moved from between those clenching spring turns so as to achieve electrical connection at clench positions of the spring turns concerned.

4. An electrical connection according to any preceding claim, wherein the wire is clenched within a close-turned spring region at one end of the spring that is adjacent another spring region having wider spaced turns into which the wire can be introduced easily before relative turning of the spring and the wire until the wire reaches desired clenching between turns in the end region.

5. An electrical connection between wire and a spring substantially as herein described with reference to and as shown in the accompanying drawings.

6. A method of making an electrical connection wherein a conductor wire is inserted between first spaced turns of an helical spring, and the spring and the conductor wire are relatively rotated about the axis of the spring so that the wire is relatively translated axially of the spring into clenching relation with consecutive closer spaced turns of the spring.

7. A method according to claim 6, wherein the spring is axially rotated on the wire.

8. A method according to claim 7, wherein said rotation of the spring is done using a turning tool with its end stepped to engage an end of the spring.

9. A method according to claim 6, 7 or 8, wherein a welding tool is applied to the spring at its end to achieve movement of insulation on the wire from between clenching turns of the spring.

10. A method according to claim 6, 7 or 8, wherein the wire is bare of insulation where entrant then clenched between turns of the spring.

11. A method according to claim 10, wherein multiple strands of the wire are spread by the clenching of the bared wire.

12. A method of making an electrical connection wire between turns of a spring substantially as herein described with reference to the drawings.

13. Apparatus for making an electrical connection, comprising a holder for conductor wire, a guide for a spring to extend transversely of conductor wire when in the holder and entered between turns of the spring, and a turning tool for causing axial rotation of the spring on the conductor wire to bring the wire from its entry between wider spaced turns of the spring to clenching between closer spaced turns of the spring for electrical connection making purposes.

14. Apparatus according to claim 13, wherein the turning tool serves directly to engage the spring for rotation thereof.

15. Apparatus according to claim 14, wherein the tool has a step formation to engage an end of the spring at its last turn at that end.

16. Apparatus according to claim 15, wherein the step formation of the tool is in a ledge about a spring entrant end of the tool.

17. Apparatus according to claim 15 or 16, wherein the step formation will engage a spring end adjacent said closer spaced clenching turns.

18. Apparatus for making electrical connections between wire and turns of a spring arranged and adapted to operate substantially as herein described with reference to and as shown in the accompanying drawings.

19. An electrical accessory having at least one electrical connection according to any one of claims 1 to 5.

20. An electrical accessory, wherein each of electrical connections to conductor wires of a service cord, flex or cable is in accordance with any one of claims 1 to 5.

21. An electrical accessory according to claim 19 or claim 20, comprising a lampholder wherein the or each said electrical connection is to conductor wire of a cord suitable for connection to a ceiling rose.

22. A lampholder according to claim 21, wherein the or each spring of the or each said electrical connection serves as a bias and electrical supply to a lamp-cap contact of the lampholder.

23. A lampholder according to claim 22, of bayonet type, wherein a body part has two parallel wells for captively retaining respective plungers constituting its lamp-cap contacts and a respective one of two said springs having end parts making said electrical connections.

24. A lampholder according to claim 23, wherein the body part has for said end parts respective shielding upstands flanking entries to those end parts for conductor wires of said electrical connections.

25. A lampholder according to claim 24, wherein the body part has another upstand between said shielding upstands.

26. A lampholder according to claim 25, wherein said other up stand has grooves facing said shielding upstands and permitting entry to said wells for said plungers and springs.

27. A lampholder according to claim 24 or claim 25, wherein said other upstand has a deep slot or groove sized to accept sheathing of a cord or flex whose conductor wires are to go to said electrical connections.

28. A lampholder according to claim 26, wherein said deep slot or groove has internally projecting teeth formations for gripping said sheathing.

29. A lampholder according to any one of claims 24 to 28, wherein a lampholder cap has open ended box-like formations to surround said shielding upstands above said conductor wires at said entries therefor.

30. A lampholder according to claim 29, wherein said boxlike formations engage the springs as bias abutments there for.

31. A lampholder according to claim 29 to claim 30, wherein said body -part and said lampholder cap have cooperating snap-fit formations.

32. A lampholder having a body part and a cap substantially as herein described with reference to and as shown in Figures 4 to 8B of the accompanying drawings.

33. A method of assembling a lampholder according to claim 31 or claim 32, comprising the steps of making electrical connections between conductor wires of electrical cord or flex and contact bias springs, inserting into wells of the lampholder body part from above its plunger type lamp-cap contacts and said springs, engaging sheathing of the cord in said other upstand and with gripping teeth formations thereof, and snapping the lampholder's cap onto its body part.

34. A method according to claim 33, wherein the electrical connections are made between the bias springs and the conductor wires before the springs are entered into the wells.

35. A method of pre-wiring and assembling a lampholder substantially as herein described with reference to and as shown in the accompanying drawings.