GB2242790A - Lampholder terminals - Google Patents

Abstract

A lampholder comprises one or two conductors (62) are each formed as a strip of resilient conductive material with a terminal formed as an aperture (70) in the strip which by the resilience of the strip grips the bared end (75) of a supply wire: a terminal operating means or plunger (50) movable in a direction parallel to the holder axis (x) is arranged to deform the or each conductor to open the or each terminal when it is depressed. <IMAGE>

Description

IMPROVED LAMPHOLDER The present invention relates to lampholders.

Lampholders commonly comprise a body having at one axial end a lamp socket and at the other end a terminal chamber in which a pair of terminals are provided which receive supply cable wires. A cover to the terminal chamber is provided with a central entry hole for the supply cable.

The terminals form part of or are connected to conductors which terminate in the socket with contacts which contact the lamp contacts.

These known holders are troublesome to wire up to a supply cable particularly as this often hangs down from a ceiling. The terminals are usually provided with small screws which have little threaded engagement with the terminal blocks and frequently when unscrewed to fit a wire drop out of the terminal blocks. Screwless terminals are known but these are often too bulky to be used for lampholders or else are inconvenient to operate when the operative is on a ladder wiring up a ceiling fitting.

A lampholder according to the invention comprises a body with a lamp socket for removably holding a lamp, electrical conductors mounted in the body so as to provide a connection between an electrical supply cable and the lamp, the or each conductor formed as a strip of resilient conductive material with a terminal for the supply cable formed as an aperture in the strip, and a cable grip provided in a cable entry chamber in the body remote from the socket so as to hold the cable in a central axis of the holder characterised by terminal operating means for deforming the or each conductor to open the or each terminal, the operating means being mounted for movement parallel to the holder axis.

The provision of the terminal operating means for opening the or each terminal movable in the axial direction enables the operative to very conveniently grasp the holder in his or her hand with a finger controlling the operating means whilst the other hand is used to insert the wires of the supply cable easily and quickly into the holder. Preferably one or more passages are formed between the chamber and conductor through the body so that the cable wire or wires are inserted into the terminals in a direction across the holder axis. This ensures the cable is kept clear of operating means during wiring up so that wiring up is easier. Furthermore this final alignment by the wire or wires enables suitable lead for the supply cable to ensure it is locked securely in the holder.

Suitably the operating means comprises a pair of plungers each having a finger plate at its outer end away from the socket. These plates facilitate operation of the plungers and assist in the convenience of wiring up. Furthermore by suitably matching their radially extending shape they can support a cover over the entry chamber. A fixed plate between the grip and socket in the chamber can be provided to improve the run of the supply cable wires along a labyrinthine path to improve cable location and security.

The or each conductor may be formed into a substantially double 'S' formation in which the central portion grips the body of the holder whilst the inner 'S' portion forms a resilient terminal and the outer 'S' portion forms a contact for the lamp. The cable wire gripping function in this arrangement is carried out by the aperture in the strip being formed as a hole with a 'V' shaped edge on one side of the hole away from the entry chamber. The inner 'S' portion is deformed by the terminal operating means to align the hole with a guide passage in the body and an under surface of the conductor in the central portion. The supply cable wire is poked through the passage, the hole in the conductor until it lies along the central portion. On releasing the operating means, the resilience of the inner S portion causes the wire to be trapped between the two portions of the conductor.

The 'V' shape makes the entrapment more secure. Pockets opening into the socket assist in guiding the conductor as it flexes.

Preferably a guide is provided in the entry chamber a part of which is formed into the cable grip and a part of which may form a guide for the cover of the entry chamber which has an axial cable entry slot along its length to enable the cover to be fitted over the chamber after the supply cable is wired up.

An embodiment of the invention will now be described with reference to the accompanying drawing in which: Figure 1 shows an elevation of a lamp holder according to the invention with its cover and shade ring removed, Figure 2 is a partly broken side elevation of the holder of Figure 1 as seen from II of Figure 1, Figure 3 is an enlarged cross-section of part of the holder body of Figure 1 taken at III of Figure 1 with the supply cable removed, Figure 4 shows the part of the cross-section of Figure 3 with the terminal portion of the conductor depressed to open the terminal, Figure 5 shows a similar view to Figure 4 with a supply cable wire trapped in the terminal and Figure 6 shows a view from VI of Figure 5 of the terminal with a supply cable wire trapped in the terminal.

In Figures 1 and 2 there is shown a lampholder according to an embodiment of the invention with a body 1, a lamp socket 2, a cable entry chamber 3 covered by a cover 4.

The socket has outside it an interrupted thread 5 on which may be screwed a shade ring 6.

A twin cored supply cable 10 is led into the entry chamber 3 through a cable grip 12 formed as two opposing sets of teeth 13 formed on the inside of a guide 14. The upper part of the guide is formed with near semicircular edge 15 which forms part of the cable entry hole into the entry chamber.

The other part of the entry hole is formed by an edge 16 in an axial cable entry slot 18 in the cover along its length so that it only partly surrounds the supply cable 10 at its entry into the holder. This enables the cover to be placed onto the entry chamber after the holder has been wired up without first threading the cover over the cable. The cover is held in place on the holder by means of internal projections 20 which engage in recesses 22 on the central part of the body. The sides 23 of guide 14 help support the cover whilst a flange 24 and the guide 14 complete the closure of the entry chamber.

The shade ring 6 is provided with an internal thread at 26 which engages with interrupted thread 5 on the exterior of the socket 2. The inner exterior face 28 cooperates with flange 24 to hold shades on the holder.

Within the entry chamber 3 are guide protrusions 30 which extend in a direction at right angles to the holder axis X and a plate 32 which is fixed to and indeed forms a part of the body moulding. The plate 32 extends in a plane at right angles to the holder axis X. The protrusions 30 and plate 32 assist in forming a labyrinthine passage for the two conductor wires 34 and 35 of the supply cable 10 so that they can hitch on the lower edges 36 of the protrusions and rear edge 37 of the plate 32 before entering passages formed as holes 38 and 39 in the central part of the body. This ensures good location for the cable wires and helps to securely lock the wires into the entry chamber.

The holes 38 and 39 in the central part of the body are aligned so as to be at right angles to the holder axis X which increases the facility and convenience of wiring up the holder as will be described. Referring to Figures 3 to 6 it will be seen that hole 38 (hole 39 is formed in the same way) enters one of a pair of pockets 40 which extend from socket 2 towards the entry chamber but are closed therefrom by a wall 42 at the upper end of which is a pair of passages 44 contained in wall portions 46 either side of guide 14. Each passage 44 slidably receives a stem 48 for one of a pair of plungers 50 at the entry chamber end of each of which is a finger plate 52 formed outwards with a part circular edge 54 (see Figure 1) to conform with the inner conical surface of cover 4. A straight edge 55 of each plate 52 slidably abuts guide 14 in part.

Centrally and aligned in the axial direction X on each side of each pocket are lands 60 which act to guide terminal portions 64 of each strip conductor 62 and to enable a central gripping portion 66 of the conductor to fixedly engage with the body to which it is held by pairs of sprags 67 engaging with the opposed lands 60.

The conductors 62 are each formed in a double 'S' shape with each 'S' shape extending from the central gripping portion 66 so that the terminal portion 64 comprises a first leg 68 extending in a direction across the holder axis X towards the entry hole 38, thence in a double loop to the foot 47 of stem 48 of plunger 50 and then down with a leg 69 again past hole 38. An aperture 70 (see particularly Figure 6) is provided at the end of leg 69 which can be open at one side or formed as a hole as shown. The hole 70 has a V shaped edge 72 which assist in gripping the bared end 75 of supply wire.

The other 'S' shaped part 80 of strip conductor 62 is formed from the central fixed part 66 into an 'S' shaped double loop with its end 82 tucked into the respective pocket 40 so as to be guided by wall 83 of the pocket.

The outer leg 84 of part 80 of the conductor forms a contact with a lamp contact.

The conductor strip 62 is made from a suitable spring quality stainless steel.

Although a bayonet type fitting is shown it is possible to provide only a single strip conductor 62 for a screw type lamp fitting.

In order to wire up the holder the supply cable is divided into its two conductor wires which are bared as shown in Figure 5. The holder cover is removed and placed to one side. The holder is grasped in the palm of the hand with the socket towards the operative and two of the operative's fingers on the finger plates and the thumb on the central part of the holder body on or near the flange 24. The plungers 50 are depressed to deform the upper parts 64 of the conductors as shown in Figure 5. Ends 75 of conductor wires 34 and 35 are inserted in holes 38 and 39 and pushed home until they extend along first legs 68. The plungers are released. The 'S' shaped part 64 springs back to trap wire 75 between leg 68 and 'V' shaped edge 72 as can be seen in Figures 5 and 6. The insulated wires 34 and 35 are then wound round edges 37 of plate 32 and protrusions 30 and the final dual sheathed part of cable 10 is inserted in grip 12.

The cable entry slot 18 in the cover is placed around the supply cable and the cover is slid axially onto the entry chamber until clipped in position. The holder is then ready for use.

Claims (10)

1. A lampholder comprising a body with a lamp socket for removably holding a lamp, electrical conductors mounted in the body so as to provide a connection between an electrical supply cable and the lamp, the or each conductor formed as a strip of resilient conductive material with a terminal for the supply cable formed as a aperture in the strip, and a cable grip provided in a cable entry chamber in the body remote from the socket so as to hold the cable in a central axis of the holder characterised by terminal operating means for deforming the or each conductor to open the or each terminal, the operating means being mounted for movement parallel to the holder axis.

2. A lampholder according to claim 1 wherein one or more passages is or are formed between the chamber and the conductor(s) in a direction across the direction of the holder axis so that a wire or wires of the cable enter the or each terminal in the direction across the direction of the holder axis.

3. A lampholder according to claim 1 or 2 wherein the terminal operating means comprises a pair of plungers each having a finger plate at its outer end away from the socket.

4. A lampholder according to any one of claims 1 to 3 wherein a fixed plate extends in a plane at right angles to the holder axis within the entry chamber between the grip and socket so as to guide the wires of the supply cable along a labyrinthine path after the grip.

5. A lampholder according to any one of claims 1 to 4 wherein the or each conductor is formed into a substantially double 'S' formation having a central gripping portion for gripping the body, a terminal portion extending from the gripping portion in a direction across the holder axis toward a supply cable wire entry and thence to a loop adjacent the terminal operating means and thence back to the wire entry where the conductor is provided with a wire receiving hole forming a terminal, a contact portion of the conductor extending in a 'S' shape from the gripping portion to make an abutment contact with a contact on the lamp.

6. A lampholder as claimed in claim 5 wherein a pair of conductors are provided each in a respective pocket opening into the socket and extending from the lamp socket inwardly toward the entry chamber, the central gripping portion of each conductor engaging with a portion of a side wall of its respective pocket for retention of the conductor therein.

7. A lampholder as claimed in claim 5 or 6 wherein the or each conductor has its terminal aperture formed as a hole with a 'V' shaped edge on one side of the hole away from the entry chamber.

8. A lampholder as claimed in. any one of claims 1 to 7 wherein the cable grip is formed on a guide extending in a direction parallel to the holder axis from a central portion of the body through the entry chamber, the guide being so arranged as to guide an axially movable cover into a closed position over the entry chamber.

9. A lampholder as claimed in any one of claims 1 to 8 wherein the cover is provided with an axial cable entry slot along its length so that it only partly surrounds the supply cable at its entry into the holder, and wherein a part of the- holder body surrounds the other part of the cable.

10. A lampholder substantially as shown and described in and with reference to the accompanying drawings.