GB2201303A - Lampholders - Google Patents

Abstract

The lampholder has a barrel (1) engaging a bulb (not shown), the upper barrel having an integral cover (17) and an aperture allowing passage of wires, and a terminal holder inserted in the barrel from its lower end. The wire ends are clamped inside the cover (17) between a terminal body and a cable grip member (61) which may be urged away from a plunger pin by a compression spring. <IMAGE>

Description

LAMPHOLDERS This invention relates to lampholders for holding lamp bulbs of the kind in common domestic use.

Conventional lampholders are generally suspended from the ceiling by the wires conducting electric current to the bulb. A lampholder of the bayonet fitting type comprises a generally cylindrical barrel having an open lower end provided with J-slots to allow the cap of a bulb to be fitted in the open end. A pair of resiliently biased plungers to make electrical contract with corresponding contact elements of the cap is located within the barrel and the upper end of the barrel is generally provided with screw terminals, electrically connected to the plungers, to receive the bare ends of the wires. The upper part of the barrel has a cylindrical or dome-shaped cover which is secured to the barrel either by means of respective internal and external screw-threads extending around the lower edge of the cover and the cylindrical body of the barrel, or by a snap fit.The cover surrounds and protects the terminals and has a central hole to allow passage of the wires. The exterior surface of the barrel is generally provided with an outwardly extending flange and an adjacent screw thread to receive a clamping ring for clamping the centre of a lampshade against the flange.

This screw thread may also receive the upper end of a circular shroud which extends below the bottom of the barrel to conceal and protect the part of the barrel provided with the J-slots.

Use of such a lampholder gives several problems. When a bulb is removed or fitted the user normally holds the bulb in one hand and the cover in the other, and as the bulb is rotated there is then a substantial risk of the cover being removed from the barrel to expose the terminals, which are electrically live when the lamp is switched on. The cover may also be unintentionally removed when a lampshade is fitted or removed. When the lampholder is installed in a room attachment of the wire ends to the screw terminals may be an awkward operation, especially when the clearance between the lampholder and the ceiling is small.

According to one aspect of the invention, a lampholder comprises a barrel having an open lower end to receive and engage the cap of a lamp bulb, the upper end of the barrel comprising a cover integral with the remainder of the barrel and having an aperture allowing passage of wires into the cover, and a terminal holder inserted into the barrel from said lower end and retained in the barrel so that the terminals are within the cover, means being provided within the lampholder for electrically connecting the terminals to the bulb.

The means connecting the terminals to the bulb may be spring-loaded plunger pins carried by the terminal holder, the pins projecting downwardly to engage corresponding contact surfaces on the bulb cap. The lower end of the barrel may be provided with diametrically opposed J-slots to allow fitting of a bayonet-type bulb in known manner.

In one embodiment of the invention the cover has a pair of opposed longitudinal slots forming gaps in the cover and the part of the terminal holder extending into the cover has a pair of corresponding leg portions which occupy the slots when the terminal holder is inserted in the barrel and, together with the cover, completely enclose the terminals (apart from the aperture allowing entry of the wires).

The terminal holder may be retained in the barrel by snap fittings, screw retention or by any other fixing means.

The exterior of the barrel may be provided with an outstanding flange and a screw thread, preferably a twin-start screw thread, in order to allow fitting of a shroud surrounding the lower part of the barrel and/or of a lampshade in known manner.

As the cover is integral with the part of the barrel holding the bulb there is no risk of the cover being displaced when a bulb or a lampshade is being fitted to or removed from the lampholder and the risk of the terminals being accidentally exposed is very small.

However, access to the terminals for connecting or disconnecting the wires may be obtained by removing the terminal holder through the lower end of the barrel.

The terminal holder is preferably made in two identical halves which are joined together face-to-face, in a plane containing the longitudinal axis of the lampholder. Each half may be moulded from insulating plastics material and shaped so as to allow mounting, in the assembled terminal holder, of the plunger pins, terminals and members connecting the terminals to the pins. The terminal holder halves may be joined together by means of hooked prongs entering and snap-fitting into corresponding slots in the opposite half.

According to another aspect of the invention, a lampholder is provided with terminals for connect-ion to wires for feeding electric current to a bulb held by the lampholder, each terminal comprising a terminal body held within the lampholder and a cable grip member resiliently urged against the terminal body to clamp the wire against the terminal body. The cable grip member is preferably urged upwardly against the terminal body by a compression spring which also urges a plunger pin, for conducting current from the terminal to a bulb held by the lampholder, downwardly against the bulb. When a bulb is fitted the spring is compressed by the bulb and the clamping force applied to the cable grip member is then increased.

It has been found that this clamping arrangement attaches the wire ends to the lampholder sufficiently securely to enable the wires to sustain the weight of the lampholder, bulb and any lampshade attached to it.

The wires may be attached to the terminals simply by positioning the wire end between the terminal body and clamping member while the latter is depressed against its spring, and releasing the clamping member. This procedure is much less awkward than attaching the wires to the lampholder using screw terminals.

A lampholder according to one embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a longitudinal cross-section of the lampholder, Figure 2 shows a barrel fdrming part of the lampholder, Figure 3 is an exploded view of terminal holder forming part of the lampholder, Figure 4 is a longitudinal cross-section of the lampholder perpendicular to Figure 1.

The -lampholder shown in Figs. 1 and d comprises a barrel 1, a terminal holder 3 within the barrel and a shroud 5 surrounding the lower part of the barrel.

The barrel is shown in Fig. 2 and is a one-piece moulding of plastics material comprising a lower cylindrical open end 7 forming a socket which is provided with diametrically opposed J-shaped slots 9 so that an- ordinary bayonet-type electric bulb may be fitted in the lampholder in the usual manner. The middle of the barrel is provided with an exterior screw-thre-ad 11, preferably of the twin-start type on to which the shroud 5 may be screwed by means of an internal screw-thread- on- the upper end of the shroud.

The shroud is a frusto-conical moulding of plastics material, flares outwardly in the downwards direction and extends downwardly beyond the lower end 7 of the barrel. The purpose of the shroud is to conceal and protect end 7 and the end of the bulb inserted in the lampholder. The shroud is dimensioned so that, when fitted to the barrel, it does not obstruct the bulb when the bulb is fitted to or removed from the lampholder.

Lower end 7 is separated from the upper part of the barrel by outwardly extending radial flange 15 which abuts the narrower end of the shroud when the shroud is fitted. The upper- part of the barrel comprises a pair of similar, diametrically opposed cover members 17 which are separated by axially extending gaps 19 and which are joined at their upper ends by a ring 21 through which wires may pass into the barrel. The ring 21, cover member 17, flange 15 and lower end 7 are integrally moulded as a single member.

The terminal holder comprises a pair of identical halves shown in Fig. 3, which may be joined together to form an assembly to fit inside the barrel. Each half comprises a pair of legs 25 connected part-way along their length by a generally semicircular base 27. The legs are shaped and dimensioned so that their outer surfaces define part of a cylinder to fit within the barrel 1.

The bases 27 of the halves are provided with upstanding members, which form retaining means for terminal members in the terminal holder and also form a slot 31 and an outstanding prong 33 terminating in a hook 35 dimensioned to enter the slot 31 of the opposite half when the halves are joined together. One of the legs of the halves is provided with locating pegs 37 arranged to enter locating holes 39 on a leg of the opposite half.

The two halves are identical and when they are assembled together, in the manner indicated in Fig. 3, pegs 37 enter the holes 39 of the opposite half and prongs 33 enter slot 31 of the opposite half so that hook 35 extends beyond the respective slot and forms a snap fit behind surface 41 which defines the rear edge of the slot. The two halves are thus permanently joined together.

The terminal holder is intended to accommodate current-carrying plungers which engage the lamp bulb, when fitted in the lampholder, to supply the bulb with electric current in the usual manner used for bayonet-fitting bulbs. The terminal holder also accommodates the terminals, electrically connected to the plungers, for receiving the wires which supply the current. The plungers to engage the bulb comprise tubular metal pins 43 having a closed lower end and an open upper end provided with a flange 45. The plungers are slideably mounted in circular holes in base 27 defined by opposed semicircular holes 47 in the bases of the two halves. The upper ends of the plungers are contained in metal terminal bodies 49 contained in the terminal holder.Terminal bodies 49 are. accommodated in sockets 51 and held in place by flanges 53, shown in Fig. 3, which enter slots 55 to prevent movement of the terminal bodies in the assembled terminal holder in the axial direction.

The terminal bodies are formed from metal sheet as tubes of square cross-section which are open at the bottom to receive the upper ends of plungers 45 above holes 47.

The upper ends of the terminal bodies comprise apertures 57 bounded by cross-members 59.

Each terminal is provided with a cord grip bracket 61 comprising a metal plate 63 and upstanding wings 65 which are turned inwardly to provide a gap between their opposite edges. The cord grip bracket is dimensioned to fit iside the terminal body 49 with plate 63 abutting the inside surfaces of cross-members 59 and wings 65 passing through the aperture 57 to extend above the terminal body.

Each terminal also comprises a compression spring 67 which extends within the plunger 43 and the terminal body 49 to urge the plunger downwardly and the cord grip bracket 61 upwardly.

The complete terminal holder is easily assembled by locating the plungers, springs, terminal bodies and brackets within respective halves of the holder and joining the halves together as described above.

The terminal- holder is dimensioned so that it may be slid into the barrel from the barrel lower end to take the position shown in Figs. 1 and 4. In this position the legs 25 of the terminal holder, arranged side-by-side in pairs after assembly of the terminal holder, occupy the gaps 19 between the cove members 17 of the barrel so that the upper part of the barrel is effectively closed, apart from the aperture in ring 21, the legs having inwardly turned flanges 69 at their upper ends to fit below ring 21. The external surface of the terminal holder, and the internal surface of the barrel may be provided with cooperating guides to ensure correct positioning of the terminal holder in the barrel.The edges of flanges 69 may extend peripherally beyond legs 25 to form a projection forming a snap fit on to shoulders 73 of the members 17 to retain the terminal older within the barrel after insertion.

In order to install the lampholder in a room of a building the ends of the two wires for supplying electric current, normally hanging from the ceiling, may be threaded through the aperture in ring 21 of tile barrel before insertion of the terminal holder in the barrel and attached to the terminals before the holder is inserted. The exposed ends of the wires may be attached simply by inserting them between the abutting surfaces of cross-pieces 59 and plate 63, which are urged together by spring 67 so that the wires are clamped to the terminal. An exposed wire end ma be clamped against plate 63 by both cross-pieces 59 of a terminal and one or both of the abutting surfaces may be roughened to ensure adequate retention of the wire end.

When a lamp bulb is fitted to the lampholder the springs 67, urging the plunger downwardly, hold the bulb in place and ensure good electrical contact with the bulb conducting surfaces: also fitting of the bulb has the effect of compressing springs 67, increasing the clamping force applied to the wire ends at the terminals 49. It is found that, even when a heavy lampshade is fitted to the lampholder, the clamping force at the terminals 49 exerted by the springs is sufficient to hold the wires in place securely.

Claims (9)

1. A lampholder comprising a barrel having an open lower end to receive and engage the cap of a lamp bulb, the upper end of the barrel comprising a cover integral with the remainder of the barrel and having an aperture allowing passage of wires into the cover, and a terminal holder inserted into the barrel from said lower end and retained in the barrel so that the terminals are within the cover, means being provided within the lampholder for electrically connecting the terminals to the bulb.

2. A lampholder according to claim 1, in which the means connecting the terminals to the bulb are springloaded plunger pins carried by the terminal holder, the pins projecting downwardly to engage corresponding contact surfaces of the bulb cap.

3. A lampholder according to claim 1 or 2, in which the lower end of the barrel is provided with diametrically opposed J-slots to allow fitting of a bayonet-type bulb.

4. A lampholder according to claim 1, 2 or 3 in which the cover has a pair of opposed longitudinal slots forming gaps in the cover and the part of the terminal holder extending into the cover has a pair of corresponding leg portions which occupy the slots when the terminal holder is inserted in the barrel.

5. A lampholder according to any preceding claim, in which the barrel exterior is provided with an outstanding flange and a screw thread to allow fitting of a shade.

6. A lampholder according to any preceding claim, in which the terminal holder is made in two identical halves which are joined together in a plane containing the longitudinal axis of the lampholder.

7. A lampholder provided with terminals for connection to wires for feeding electric current to a bulb held by the lampholder, each terminal comprising a terminal body held within the lampholder and a cable grip member resiliently urged against the terminal body to clamp the wire against the terminal body.

8. A lampholder according to claim 8, in which the cable grip member is urged upwardly against the terminal body a compression spring which also urges a plunger pin for conducting current from the terminal to the bulb downwardly against the bulb.

9. A lampholder, substantially as described with reference to the accompanying drawings.