GB2054982A - Electrical fittings - Google Patents

Abstract

An electrical lampholder has a terminal covering cap (50) retained irrotationally so as to require axial movement in removal thereof. In Figure 1 the cap (50) has ribs engaging on legs (40, 41) of a bridge piece (42) itself having ribs (44, 45) shown engaging recesses (52, 53) in the cap. The bridge piece has a threaded portion (46) and includes a cord grip (48) extension through the cap. A clamping nut (47) of lesser diameter than the cap secures the latter and operates the cord grip (48) when screwed to the threaded portion (46). In Figure 6, the cap (50') has apertures (78) to take spring upstands (72) from a spring ring (70) fitted about the lampholder body. <IMAGE>

Description

SPECIFICATION Electrical fittings The invention relates to electrical fittings and has particular reference to lampholders.

Lampholders often have screw-on caps over their terminals and there is a risk that such a cap may be disturbed and come off during fitting or removal of lamps with the consequent danger of electric shocks via hand or finger contact with the terminals. It is an object of this invention to eliminate this risk.

To that end, we propose that a lampholder have a terminal covering cap that is irrotationally interlocated with a mating part or parts of the lampholder body. We have particularly in mind that dismounting of such a cover from other lampholder body parts must involve rectilinear initial relative movement, usually along an axis of the lampholder body.

In some preferred embodiments, provision is made for simple separation to disengage cooperating lugs and recesses. The apparent paradox, of sacrificing the safety aspects of requiring a different direction or form of decoupling movement (e.g. rotation) from the actually direction of separation, is overcome by clamping of the cover or caps in place by a further part that may well, itself, have a screwed fitting.

However that further part can then be of very much smaller diameter than, even be inset into, the cover, or cap so that it will not, itself, be gripped during lamp fitting or removal.

One advantageous implementation of such embodiments utilises a part that we shall call a bridge piece having extensions, such as legs, arms or ends, irrotationally captive relative to a base part or parts of the lampholder (by which we mean a terminal, contact and/or lamp coupling bearing member or assembly), and a formation that will be accessible through, preferably itself pass through, a said cover or cap for engagement by said further part. That formation will normally be annular to accommodate a feed cable and may also include cable gripper extensions, for example such as will be compressed onto a sheathed electrical cable or cord on and by a fixing of said further part. The bridge piece will normally cooperate with cap or cover to prevent rotation of the latter, for example by lug/recess engagement at said formation and/or by ribs engaging the bridge arms.

Alternatively, a cable clamp or gripper may be simply screwed into the cover or cap, especially where the latter is irrotatably located directly on a lampholder base part rather than by some interposed member such as the said bridge piece, for example snap-fitted thereto.

In general, our clamping proposal affords a safe and elegant solution to the problem of avoiding inadvertent cap removal. Thus, the danger of failure of snap-interfitting parts for the cap is avoided and screwing is a well-known, conventional, and thus expected, activity in relation to disassembly of lampholders.

However, snap-fitting arrangements that have a low risk of failure are envisaged herein, specifically using spring means, say as a resilient part or parts that is or are non-integral with constituent moulded parts of the lampholder, so that different materials better suited to the task may be used, for example metals. Generally, a resilient part or parts will be anchored to a moulded lampholder part, for example as a spring ring in a groover but with one or more shape upstands. Then, a moulded cap or cover will usually be shaped to displace the resilient part or parts during fitting so that the latter finally return to engage in holes or recesses therein. Holes are preferred as access may then be given to a release tool, such as a screwdriver blade. Also the cap or cover and the moulded part preferably interengaged irrotatably on fitment together.

Two specific embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a longitudinal section through a lampholder; Figure 2 is a plan view from above of the lampholder of Figure 1 prior to fitting of its upper cover; Figure 3 is a side view of what is shown in Figure 2; Figure 4 is a plan view of one particular bridge piece; and Figures 5 and 6 are fragmentary plan and sectional views of an alternative "snap-fit" embodiment.

In the drawings, a lampholder 10 comprises component parts that will be dealt with in the order in which they are used in a preferred lampholder assembly process.

A first subassembly comprises a metal sleeve 12 and an inner body or base part 13. The sleeve 12 will serve for lamp retention, typically having Jslots extending from its free end 1 4 for a bayonet fitting. The innerbody part 13 will be a moulding of electrically insulating material carrying, at its side 1 5, lamp cap connection parts such as spring loaded plungers, and, at its other side 16, conductor connection terminals, such as the well known screw clamping type, and an integrally moulded upstanding conductor separator 17.

The sleeve 12 has outward end flanging 18, 19 and tabs 20, 21. Also the inner body part 13 has outward end flanging 22, 23 and recesses 24, 25 in its upper end surface between discrete portions or lobes 22 and 23 of its end flanging. The flanging 1 8, 1 9 of the sleeve 12 is conveniently interrupted in a manner congruent with that of the flanging 22,23 on their mutual assembly, but that is not essential so long as the two sets of flanging 18, 1 9 and 22, 23 have mutual abutment to prevent one direction of relative axial movement and do not interfere with subsequent assembly operation to be described.The tabs 20, 21 and recesses 24, 25 must register in the desired relative positions of the sleeve 12 and the inner body part 13 and, ideally, substantially prevent any relative rotation and lead to no obtrusion of the tabs 20, 21 after they are bent into the recesses 24, 25.

This subassembly of the sleeve 12 and inner body part 13 can be inserted from above into an annular outer body or base part 11 that may be coterminate with the sleeve end 1 4 or be short thereof as shown. The outer body part 11 is shown with an external thread 26 for a lampshade carrier ring. The outer body part has interior recessing at 27, 28 to seat the outward flanging or flanging 18, 19 of the sleeve 12. As shown, this recessing 27, 28 occurs at the position of an exterior flange 29 against which a lampshade carrier may act for clamping purposes.

Beyond the recessing 27, 28 the outer body part has an upstanding rim 29 of significantly greater depth than the combined thicknesses of the sleeve and outer body part flanging 18, 1 9 and 22, 23. Over arcs at least coextensive with the maxima of the flanging 18, 19,22,23 the rim 29 will accept such flanging. Between those arcs the rim 29 has inwardly extended capture formations in the form of ledges 30,31 above slots 32,33 that will closely accept the flanging 18, 19, 22, 23 substantially to prevent relative movement of the body parts 11 and 13 axially of the sleeve 12. At their one sides, 34, 35, the ledges 30, 31 have connections to the recessing 27, 28 which act as stops 6 in limiting one direction of relative rotation ofthebody parts 11 and 13.

The disposition of the capture formation parts 30 to 35 is so related to the flanging 22, 23 and the electrical connections of the body parts 13 that the latter are correctly positioned, say relative to J-slotting of the sleeve 12.

It will be appreciated that there may be more than two capture formations and corresponding interruptions of the flanging 1 8, 19, 22, 23. Also the mentioned subassembly of the sleeve 12 and inner body part 1 3 prior to insertion into the outer body part 11, may be unnecessary if the assembly process includes use of a tool that will bend the tabs 20, 21 into the recesses 24, 25 after positioning first the sleeve 12, then the inner body part 13, in the outer body part and usually individually rotating them against the stops 6 and 34, 35.

As thus far described features of the illustrated lampholder are the subject of another patent application.

Reverting to the description for features applicable to the present invention, the ledges 30, 31 of the capture formations are shown as bridging interruptions 36, 37 in the outer periphery of the rim 29. These interruptions 36, 37 are actually in the form of T-slots to receive in their cross pieces, end ribs or feet 38, 39 and, in their stems, legs 40, 41 of a moulded plastics bridge piece 42. These legs 40, 41 are resilient and extend from a central cylindrical part 43 having lugs 44, 45 that brace the legs 40, 41 and serve a further purpose to be described. Beyond the lugs 44, 45 and inwardly thereof the cylindrical part 43 is externally threaded at 46 to accept a nut 47.Beyond the threaded part 46 are resilient cord grippers 48 and the nut 47 has an inner taper 49 so that, as it is screwed onto the threaded part 46, the cord grippers have their ends forced inwardly towards each other so as to grip a cable entered through them.

As shown, an upper cap 50 fits over the bridge piece 42 and has a central aperture 51 that is a clearance fit past the threaded part 46. Also, however, the upper cap has inner edge recesses 52, 53 that fit closely on the lugs 44, 45 and thus prevent rotation of the cap 50 after fitting of the nut 47 as desired for altering the objects of this invention. Furthermore, a skirt part 54 of the upper cap 50 engages on the legs 40,41 of the bridge piece 42 to ensure that they are then firmly held in the T-slots 36, 37. Non-rotation of the cap 50 may be enhanced or provided for alternatively by arranging that interior slotting of the cap, or flanking ribbing 57,58, closely fits to the legs 40, 41 as shown.

We also prefer that the feet or end ribs 38, 39 of the bridge piece 42 have inner protrusions to engage in recesses of the flanging 22, 23 of the inner body part 13 so as to lock that part and the sleeve against rotation away from the stops 34, 35. Also, the form of the feet or end ribs 38,39 is conveniently such that they lock under the edges of the T-slots 36, 37 during assembly.

It will, of course, be appreciated that it is not essential for the T-slotting 36, 37 to be at the same positions as the capture formations. Also, anti-rotation of the upper cap 50 could be at least partially by reason of parts thereof straddling the capture formations or otherwise interlocating therewith. Furthermore, the cap 50 could snap fit to the inner body part, say at the capture formations, and that could allow the bridge piece to be omitted, with a cord grip then screwed into the cap 50 itself.Other modifications and variants will be readily devised by those skilled in the art, for example omission of the rim 29, at least between capture formations and/or bridge feet locators, with the upper cap then over-fitting flush to the flange 29 of the outer body part 11, at least at spaced positions about the lampholder, or the bridge piece could snap into locator formations from the interior of the lampholder.

In Figures 5 and 6, the bridge piece can be omitted and securement of the cap 50' to the outer body or base part 11' is by way of a one piece, but not necessarily endjoined, spring ring 70 mounted on an exterior groove 71 of the part 11' and having upstands 72 usually diametrically located, and with their free ends 74 bent outwardly to engage in holes 76 in the cap 50'.

The inner wall of the cap 50' may at the position of its holes 76 be grooved (or ribbed) 78 (79) to guard against rotations even after pressing in of the free ends 74 of the ring upstands 72 for release purposes, that latter will require a tool, such as a screw driver blade and access therefor is improved by exterior flatting or channelling 80 of the cap, which also facilitates moulding.

It will be noted that the upstands 72 of the spring ring 70 are readily displaced on simple slide-on fitment of the cap 50' effectively rotating about the spring ring 70 in the groove 71 and that the cap 50' is readily and conveniently provided with chamfered camming surfaces in the groove to 78 or between ribs 79 to assist and promote such action.

Further protection against rotation of the cap is provided for by engagement of lugs or teeth 84 on the cap with interruptions 86, of the flanging of the outer body part required to accommodate the upstands 72.

Also, accommodation of tolerances that must be allowed in making the outer body part and the cap may be accommodated with tight interfitment thereof by sloping the bent free ends 74 and/or their engagement surfaces within the holes 76.

Finally concerning the drawings, we draw attention to the provision of side notched labyrinth plates 60, 61 in Figures 2 and 3 as additional conductor retaining means. If desired, such retention can be aided or substituted by specific formations of or on legs of the bridge pieces 42, say as small lugs to restrain the insulated conductors between the terminals and the cord gripper.

It will be noted that the various proposals for preventing rotation of the upper cap 50 and secure gripping of an electric cable all contribute substantially to ensuring that the cap is not inadvertently displaced during lamp or shade fitting or removal, and thus reduces the danger of accident by unintended access to live terminals at such times.

Furthermore, the above noted capability of assembly of successive parts wholly from above the outer body part 11 is continued throughout the entire assembly process in a most convenient and advantageous manner.

It will be appreciated that the invention is equally applicable to Edison screw type lampholders, at least with suitable modification to the lamp cap holding skirt and contact arrangements therefor.

Claims (14)

1. An electrical lampholder whereof a terminal covering cap fits to a mating part or parts of the lampholder body so as then to be irrotational relative thereto and to require at least initial rectilinear movement to be disengaged from said mating part or parts.

2. An electrical lampholder according to claim 1, wherein the cap fits irrotationally to the mating part or parts by engagement of respective lugs and recesses.

3. An electrical lampholder according to claim 2, comprising a further part by which the cap is clamped in irrotational relation to said mating part or parts.

4. An electrical lampholder according to claim 3, wherein the further, clamping, part screws onto the lampholder but is of lesser diameter than the cap.

5. An electrical lampholder according to claim 3 or claim 4, comprising a bridge piece having a formation accessibly to said further clamping part through the cap and above terminals of the lampholder, the bridge piece further being irrotationally captive relative to a terminal carrying base part or parts of the lampholder body via extensions from said formation.

6. An electrical lampholder according to claim 5, wherein the bridge piece also serves as or affords said mating part or parts.

7. An electrical lampholder according to claim 6, wherein said mating part is at said formation.

8. An electrical lampholder according to claim 6 or claim 7, wherein a said mating part is at a said extension.

9. An electrical lampholder according to any one of claims 5 to 8, wherein the formation is annular to accommodate an electrical feed cable or cord.

10. An electrical lampholder according to claim 9, wherein the formation has cable or cord gripper extensions that are compressed by engagement with said further, clamping part.

11. An electrical lampholder according to claim 2, comprising spring means as said mating part or parts for snap fitting of the cap.

12. An electrical lampholder according to claim 11, wherein the spring means comprise one or more upstands from a spring ring captive in the lampholder body.

13. An electrical lampholder according to claim 12, wherein the upstands engage in holes through the cap giving access to the upstands for release purposes.

14. An electrical lampholder according to claim 12 or claim 13, wherein the spring ring extends round an outer body part under an outer ledge interrupted at said upstands.

1 5. An electrical lampholder according to claim 12, 13 or 14, wherein the ring is substantially continuous through said upstands and between its ends.

1 6. An electrical lampholder according to any one of claims 11 to 15, comprising a cord or cable grip screw-fitted to the cap at a hole therethrough for the cable or cord.

1 7. An electrical lampholder substantially as herein described with reference to and as shown in the accompanying drawings.