GB2235831A - Improvements in and relating to switched electrical connectors - Google Patents

Abstract

An electrical connector, for example a lampholder comprises an on/off switch mechanism including a pushbar 22. The switch cannot be switched ON when the lamp is not in position. Removal of the lamp either causes the switch to be turned OFF, or is precluded until the switch is OFF. The locking arrangement includes an interlock tube 2 having an arm 8 and rotated by insertion of the lamp into the holder 1, causing the arm to move out of co-operation with a locking slot 37 in the pushbar 22. Lamp insertion also depresses contacts 13, 14, moving contact flanges 15, 16 within guides 17, 18 and out of blocking alignment with a pushbar projection 32. The pushbar 22 must be returned to an OFF position before tube 2 can be rotated to free the lamp, or alternatively the pushbar includes a camming surface (50, 54) arranged such that the switch mechanism will be switched off when the cooperating device is removed from the connector. The pushbar supports contacts 25, 26 engaging the lamp contacts 13, 14 via electrically conducting springs 20, 21 and movable to engage terminals 27, 28. The pushbar is positioned by stops 35a, 35b. <IMAGE>

Description

IMPROVEMENTS IN AND RELATING TO ELECTRICAL CONNECTORS The invention relates to electrical connectors and is particularly, though not exclusively, related to electrical lampholders.

Lampholders generally comprise a securing arrangement by which a lamp may be secured in the lampholder and at least one contact through which electrical power can be delivered to the lamp; the securing arrangement may provide the other electrical connection to the lamp. The securing arrangement may be for example the so-called edison screw connection in which a screw threaded cap at one end of a light bulb or other lamp co-operates with a similarly threaded member on the lampholder. Alternatively, the securing arrangement may be a bayonet connection in which a cap at one end of a light bulb includes a number of lugs, for example two lugs which co-operate with suitably formed slots in a cap receiving member in the lampholder.

Some light fittings include an on/off switch mechanism by which electrical power to the lamp can be switched on and off by a user. The switch mechanism switches power to at least one pin or plunger which acts as the contact and which is normally spring biassed to accommodate the insertion and the removal of a lamp from the lampholder.

In hitherto known light fittings it has been possible to switch the switch mechanism to an on position irrespective of whether or not there is a lamp in the lampholder. Thus it is possible for the contact, i.e. the pin or plunger, to be electrically live even when there is no lamp in the lampholder.

This is a potentially dangerous situation, because for example it is possible for a person to insert his or her fingers into the lampholder and to touch the pin.

If the pin is live this will result in electrocution of that person.

The present invention aims to overcome the abovementioned and associated problems.

The invention therefore includes an electrical connector having an off switch mechanism and wherein a locking means is provided between the on/off switch mechanism and the connector such that the on/off switch mechansim cannot be switched to its on position when the connector is disconnected from a cooperating device.

In preferred embodiments of the invention, as will be described in greater detail hereinafter, the locking means is arranged such that the co-operating device cannot be removed from the connector when the switch mechanism is in its on position. Thus, the preferred embodiments include a double safety feature in that the connector cannot be switched on when there is no co-operating device, which for example may be a light bulb or other lamp in the connector and the light bulb cannot be removed from the connector when the switch mechanism is on.

In the preferred arrangements, to be described in greater detail hereinafter, the locking means is arranged such that when the co-operating device is removed from the connector the switch mechanism is switched to its off position.

In the exemplary practice of the invention an electrical connection is made to the co-operating device, i.e. the lamp for example, via at least one biassed plunger member. That is to say, a pin biassed by a spring for example is arranged to contact a cooperating terminal on the light bulb or lamp.

Furthermore, the switching means preferably comprises a switching pushbar switchable between an on and an off position and at least one terminal contactor on the pushbar is arranged to make electrical contact with at least one electrical terminal connectable to an electrical supply. In practice, the terminal connector can be electrically connected to the pin by way of the spring which biasses the pin. In this way, the number of separate components which constitute the connector can be minimised.

In order to lock the switch mechanism in its off position when there is no lamp or other co-operating device in the connector, one preferred embodiment includes an interlock member which co-operates with the switch mechanism and with the co-operating member, the interlock member including an elongate member and being movable between a first position at which movement of the switch mechanism is prevented by the elongate member and a second position at which movement of the switch mechanism to its on position can be effected.

The elongate member or arm may be arranged tooperate with a slot cut or otherwise formed in, say, one side of the switching pushbar to prevent the pushbar from being switched to its on position when there is no lamp or other fitting in the connector.

The relationship between the slot and the arm can be arranged such that the connector will also prevent the co-operating device, i.e. the lamp, from being removed when the pushbar is in its on position. Thus, in the preferred embodiment to be described, when the switch mechanism is in its on position, the elongate member is prevented from being moved from its said second position to its said first position, thereby preventing disconnection of said co-operating device from said connector.

The abovementioned locking means may alternatively comprise, or indeed may further comprise, a guiding member associated with the switching mechanism, which guiding member extends into a channel defined in the connector, and said at least one plunger member is adapted for restricting the channel when the connector is disconnected from a cooperating device.

In the preferred embodiments the guiding member and the switch pushbar are integrally formed from a plastics material and the abovementioned terminal contactor is mounted to the pushbar to contact the electrical terminal which is mounted to an insulating backing plate. The backing plate may also include camming portions which co-operate with projections or ridges on the switch pushbar to provide a positive switching action.

Instead of arranging the locking means so that it prevents removal of the lamp or other co-operating device, the locking means may be arranged such that the elongate member co-operates with the switch mechanism to urge the switch mechanism to its off position. Thus in a second preferred embodiment the connector can be arranged so that when the switch mechanism is in its on position and said co-operating device is being disconnected from the connector, the elongate member co-operates with the switch mechanism as the elongate member moves from said second position to said first position to urge the switch mechanism to its off position.

In one version of the second preferred embodiment the elongate member or arm co-operates with a curved camming surface on the pushbar. In another version of the second embodiment, the arm co-operates with an angled surface on the pushbar.

In the preferred embodiments the connector is a push and turn type bayonet connector and the locking means is responsive to the pushing and turning of a co-operating device in the connector.

The above and other features are set forth with particularity in the appended claims.

In order that the invention may be understood embodiments will be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a perspective exploded view of the major components of a first embodiment of a lampholder; Figure 2 is a section view of the lampholder without a lamp therein; Figure 3 is a detail view showing a guiding member defining a channel and other components associated therewith; Figure 4 is a section view of the lampholder with a lamp therein; Figure 5 is a detail view of the first embodiment illustrating the action of a retainer member and an interlock tube; Figure 6 is a detail view of the first embodiment showing the relationship between an arm and a pushbar; Figure 7 is a detail view of a second embodiment showing a first modification to a pushbar; and Figure 8 is a detail view of the second embodiment showing a second modification to the pushbar.

Referring now to Figure 1 of the accompanying drawings, which shows a perspective exploded view of the major components of a first embodiment of a lampholder, it will be seen that the lampholder comprises a retainer member 1, an interlock tube 2, and a main body 3.

Considering each of these components in turn, the retainer member 1 may be made from a conducting material, such as brass for example. Bayonet lug retaining slots 4,5 are formed in the retainer 1, and co-operate in use with bayonet lugs on a lamp (not shown) to retain the lamp in the lampholder. The interlock tube 2 is made from an electrically insulating plastics material and is dimensioned to fit snugly, whilst being slidingly rotatable, within the retainer member 1. Since the interlock tube 2 fits coaxially within the retainer member 1, and for other reasons which will be explained in greater detail hereinafter, slots 6, 7 are provided to enable the bayonet lugs of a lamp to co-operate with the lug retaining slots 4,5 in the retainer member 1.

The interlock tube 2 may be made from an insulating plastics material and also includes an arm 8 which may be integrally formed. When the lampholder is assembled, the arm 8 extends through an arcuate slot 9 in the end plate 10 of the main body 3. The arcuate slot 9 is dimensioned to allow for movement of the arm 8 when a lamp is connected to the lampholder, i.e. the lamp is pushed and turned to an engaging position in the reatiner member 1.

Two apertures 11,12 are also defined in the end plate 10 and receive respective plungers 13,14 of brass for example, which make an electrical connection with a lamp engaged in the retainer member 1.

Respective collars 15,16 prevent the plungers 13,14 from passing through the end plate 10 and co-operate with plunger guiding bores 17,18 defined in a retainer sleeve 19 which upon assembly abuts the inner face (not shown) of the end plate 10. The plungers 13,14 are biassed by compression springs 20,21 which extend from the plungers to a switch pushbar 22. The springs 20,21 are held in position in receiving apertures 23,24 provided in the switch pushbar 22 by way of terminal contactors 25,26.

When the pushbar 22 is in an on position, the terminal contactors 25,26 make electrical contact with terminals 27,28 on a backing plate 29. The terminals 27,28 are adapted by means, not shown in Figure 1, to be connectable to an electrical power supply and when the pushbar 22 is in the on position an electrical connection is made between each terminal 27,28 and its respective plunger 13,14 via the springs 20,21.

The pushbar 22 includes a tee member 30 which, when the lampholder is assembled, extends into a guiding channel 31 also defined in the retainer sleeve 19, with the top surface 32 thereof slidingly contacting the inner face of the end plate 10.

When the lampholder is assembled, the backing plate 29 engages with a supporting lip 33 on the main body 3 and encloses the pushbar 22, the retainer sleeve 19, the plungers 13,14, etc., within the main body 3. The pushbar 22 also includes two ridges 34, one of which can be seen in Figure 1, and these ridges co-operate with respective cams 35a,35b on the backing plate 29. When the pushbar 22 is moved between on and off positions, the ridges 34 ride over the respective cam 35a,35b and in this way a positive switching action is obtained. Two further ridges 36a,36b on the pushbar 22 co-operate with edge portions within the main housing 3 to limit movement of the pushbar 22 to that between its open and its closed positions.

A slot 37 is cut or otherwise defined in one limb 38 of the pushbar 22 such that, when the lampholder is assembled and the pushbar 22 is in its off position with no lamp in the lampholder, the arm 8 will extend into the slot 37 thereby to lock the pushbar 22 in the off position. The limb 38 extends through a slot 39 in the main body 3 and limb 40 extends through another slot (not shown in Figure 1) in the main body 3 and opposite to slot 39.

Turning now to Figure 2 of the accompanying drawings, which shows a section view of the first embodiment of the lampholder without a lamp therein, it can be seen that when there is no lamp in the lampholder the plungers 13,14, of which one is shown, are urged upward by their respective biassing spring 20,21 (shown partially by broken lines). In this position, the collars 15,16 abut the end panel 10 of the main body 3 and restrict the width of the channel 31 in the retainer sleeve 19. It should be noted that in this position the terminal contactors 25,26 are spaced well away from their respective terminals 27,28 and therefore no electrical connection is made between terminals 27,28 and plungers 13,14.

The ridge 36b abuts inner wall 41 of the main body 3 to limit lateral movement of the pushbar 22 in the direction of its limb 40. Similarly the ridges 34a,34b will co-operate with the respective cams 35a,35b on the backing plate 29 to provide a positive switching action between on and off positions of the pushbar.

As can be more clearly seen in Figure 3 of the accompanying drawings, the abovementioned restriction in the width of the channel 31 is sufficient to prevent the top 32 of the tee member 30 from moving past the collars 15,16. In this way, the pushbar 22 is locked in the off position shown in Figure 2 and is prevented from being moved to any other position.

Thus, the retainer sleeve 19 in combination with the collars 15,16 co-operate with the tee member 30 to provide one means for locking the switch pushbar in its off position.

Returning now to Figure 2, it can be seen that, when there is no lamp in the lampholder, the interlock arm 8 extends into the slot 37 in the pushbar 22. With the arm 8 in this position the slot 37 cooperates with the arm 8 to prevent lateral movement of the pushbar 22.

Figure 2 also illustrates further components of the lampholder. A dome 3a is mounted to the main body 3 by way of for example a click fit arrangement or a screwthread arrangement. The dome 3a together with the main body 3 form a housing for the terminals 27,28 (one of which is shown in Figure 2). Wires (not shown) can be passed through an access bore 3b in the dome 3b for connection to the terminals 27,28. Means, such as the gripping clip arrangement 27a shown in the drawing, are also provided to enable wires to be connected to the terminals 27,28.

Turning now to Figure 4 of the accompanying drawings, it may be seen that when a lamp (as represented by part of a lamp connector 41 in the drawing) is inserted into the lampholder, terminals 42,43 of the connector 41 contact the respective plungers 13,14. The plungers 13,14 are urged into the main body 3 against the force of the springs 20,21.

With the lamp 41 fully inserted in the lampholder, the plungers are positioned such that collars 15,16 are spaced from the end plate 10. In this way the abovementioned restriction in the width of the channel 31 (see Figure 3) is removed and the top 32 of the tee member 30 is free to be moved along the channel 31.

When a lamp is inserted into the lampholder, lugs on the lamp connector 41 engage with the bayonet lug retaining slots 4,5 on the retainer member 1.

In Figure 5 of the drawings it can be seen that as lamp 43 (not shown) is inserted into the retainer 1, the lug 44 moves along the path defined by the slot 6 and illustrated as a broken line 45. It should be noted that before the lamp 43 is inserted to the retainer 1, the slots 6,7 of the interlock tube 2 and the slots 4,5 of the retainer 1 are aligned. As the lamp is twisted, the lug 44 moves. from position A to position B. During this movemebt the lug 44 cooperates with the slot 6 to move the slot to position 6'. A similar lug opposite to lug 44 co-operates with slot 7 to move that slot in a similar manner. In this way, the interlock tube is rotated and the arm 8 is moved to position 8'. The lamp is retained in the retainer by the frce of the springs 20,21 which urge the respective plungers 13,14 and thus the lug 8' against the upper edge 46 of the slot 4.

As a lamp is being inserted into the lampholder, the arm 8 is rotated out of engagement with slot 37 in the pushbar 22 thereby freeing the pushbar 22 for switching to its on position. Figure 6 is a detail view showing the relationship between the arm 8 and the pushbar 22. It will be seen from this drawing that when the arm 8 and the switch pushbar 22 are in the position illustrated as broken lines, the arm 8 prevents the pushbar 22 from being moved in the direction of the arrow ON. The terminal contactors 25,26 and the terminals 27,28 (not shown in Figure 6) are positioned such that they do not make electrical contact until the pushbar is switched in the direction of the arrow ON to the position illustrated by the unbroken line 22'.Since the pushbar cannot be moved to the unbroken line ON position 22' until the arm is in its unbroken line position 8', and since the arm will not be in this position unless a lamp is mounted in the lampholder, the pushbar cannot be switched to its on position when there is no lamp in the lampholder.

Similarly, when the pushbar is switched to is unbroken line ON position 22' the edge 47 of the switch blocks the path of the arm 8' thereby preventing the arm from being moved into its broken line position 8. It will be recalled from Figure 5 of the drawings that movement of the arm is effected by a lamp being turned in the lampholder to an engaged position. When the pushbar is in its on position the interlock tube 2 cannot be rotated (because movement of the arm is prevented by the edge of the pushbar) and the lamp cannot be removed from the lampholder.

Thus, the arm 8 in co-operation with the slot 37 in the pushbar 22 provides a second means for locking the pushbar 22 in its off position. Furthermore, in this first embodiment, the arm 8 in co-operation with the edge 47 of the pushbar 22 provides a means by which a lamp is locked in the lampholder when the pushar 22 is in its on position.

In a second embodiment, which will now be described, the pushbar is modified such that when it is in its on position removal of the lamp from the lampholder will cause the pushbar to be moved to its off position.

Figure 7 shows a first modification to a pushbar 48 which enables the lampholder to function in accordance with the second embodiment. A slot 49 and a camming surface 50 are defined in the pushbar 48.

The slot 49 includes an edge 51 which co-operates with the arm 8 to prevent the pushbar 48 from being switched to an on position when there is no lamp in the lampholder. The edge 51 and the arm 8 function in much the same way as that described hereinabove with respect to the first embodiment.

When a lamp is placed in the 1dmpholder the arm is moved out of the path of the pushbar 48 thus allowing the pushbar 48 to be switched between its on and off positions. If the lamp is removed from the lampholder when the pushbar is in its on position, the arm 8 is moved by way of the lamp being rotated which causes the interlock tube (not shown) to be rotated.

As the arm 8 moves toward the pushbar 48, a corner portion 52 of the arm 8 co-operates with the camming surface 50 to urge the pushbar 48 towards its off position in the direction of the arrow OFF.

The exact form of the camming surface 50 is dependent upon the required length of travel of the pushbar and this in turn is dictated by the relationship between the terminal contactors 25,26 and the terminals 27,28 (see Figure 1 or 2 for example).

In the example shown in Figure 7 the camming surface is a curved surface having for example a radius of curvature of between 6mm and 7.5mm which will cause the pushbar 48 to move axially by about 4.5mm to 5mm.

Figure 8 shows a second modification to a pushbar 53 which also enables the lampholder to function in accordance with the abovementioned second embodiment.

In this pushbar 53 the camming surface is defined by a planar surface 54 which is inclined at an angle from the axis of the pushbar 53. The angle of the camming surface 54 may for example be between 390 and 320 to move the pushbar axially by about 3.5 to 4.5mm in the direction of the arrow OFF.

Embodiments have been described and it will be apparent to those possessed of the appropriate skills that many modifications are possible. For example, the lampholders described herein include two means for locking the pushbar in its off position. although these means have been described herein in combination in a single lampholder, it should be appreciated that either of these two means can be used alone in a lampholder to prevent a pushbar from being moved to its on position when there is no lamp in the lampholder.

Moreover, whilst the exemplary embodiments are of lampholders, it is not intended that the invention be limited to such devices. Indeed it is envisaged that the invention may be applicable to any electrical connector having an on/off switch mechanism.

The ambit of the invention is intended to cover all such modifications and is limited in scope only by the terms of the appended claims.

Claims (18)

CLAIMS:

1. An electrical connector having an on/off push bar switch mechanism and wherein a locking means is provided between the switch mechanism and the connector such that the switch mechanism cannot be switched to its on position when the connector is disconnected from a co-operating device and such that when the co-operating device is removed from the connector the switch mechanism is urged to its off position.

2. An electrical connector according to claim 1, wherein the locking means is arranged such that the co-operating device cannot be removed from the connector when the switch mechanism is in its on position.

3. A connector according to any preceding claim, wherein an electrical connection is made to the cooperating device via at least one biassed plunger member.

4. A connector according to any preceding claim, wherein the pushbar includes at least one terminal contactor arranged to make electrical contact with at least one electrical terminal connectable to an electrical supply.

5. A connector according to claim 4 as dependent on claim 3, wherein the said at least one terminal contactor is electrically connected to the said at least one biassed plunger member by way of a plunger biassing spring.

6. A connector according to any of claims 3 to 5, wherein the locking means comprises a guiding member associated with the switching mechanism, which guiding member extends into a channel defined in the connector, and said at least one plunger member is adapted for restricting the channel when the connector is disconnected from a co-operating device.

7. A connector according to any preceding claim, wherein the locking means comprises an interlock member which co-operates with the switch mechanism and with the co-operating member, the interlock member including an elongate member and being movable between a first position at which movement of the switch mechanism is prevented by the elongate member and a second position at which movement of the switch mechanism to its on position can be effected.

8. A connector according to claim 7, in which, when the switch mechanism is in its on position and said co-operating device is being disconnected from the connector, the elongate member co-operates with the switch mechanism as the elongate member moves from said second position to said first position to urge the switch mechanism to its off position.

9. A connector according to any -preceding claim, wherein the connector is a push and turn type bayonet connector and the locking means is responsive to the pushing and turning of a co-operating device in the connector.

10. An electrical connector having an on/off switch mechanism, wherein: a locking means is provided between the on/off switch mechanism and the connector such that the on/off switch mechanism cannot be switched to its on position when the connector is disconnected from a co-operating device; an electrical connection is made to the co-operating device via at least one biassed plunger member; and the locking means comprises a guiding member associated with the switching mechanism, which guiding member extends into a channel defined in the connector, and said at least one plunger member is adapted for restricting the channel when the connector is disconnected from a co-operating device.

11. A connector according to claim 10, wherein the switching means comprises a switching pushbar switchable between an on and an off position and at least one terminal contactor on the pushbar is arranged to make electrical contact with at least one electrical terminal connectable to an electrical supply.

12. A connector according to claim 10 or 11, wherein the locking means comprises an interlock member which co-operates with the switch mechanism and with the cooperating member, the interlock member including an elongate member and being movable between a first position at which movement of the switch mechanism is prevented by the elongate member and a second position at which movement of the switch mechanism to its on position can be effected.

13. A connector according to claim 12, in which, when the switch mechanism is in its on position, the elongate member is prevented from being moved from its said second position to its said first position, thereby preventing disconnection of said co-operating device from said connector.

14. A connector according to claim 12, in which, when the switch mechanism is in its on position and said co-operating device is being disconnected from the connector, the elongate member co-operates with the switch mechanism as the elongate member moves from said second position to said first position to urge the switch mechanism to its off position.

15. A connector according to any. of claims 10 to 14, wherein the connector is a push and turn type bayonet connector and the locking means is responsive to the pushing and turning of a co-operating device in the connector.

16. An electrical connector for supplying power to a device connected thereto, the connector comprising at least one terminal to which power can be supplied via a manually operable switch mechanism and a locking arrangement which co-operates with said connected device to ensure that the switch mechanism is in a position at which power is not supplied to the terminal when said device is removed from the connector.

17. An electrical connector for supplying power to a device connected thereto, the connector comprising at least one biassed terminal to which power can be supplied via a manually operable switch mechanism, the biassed terminal being arranged to co-operate with the connected device to move between a position at which movement of the switch mechanism is obstructed thereby and a position at which movement of the switch mechanism is not obstructed thereby.

18. A connector substantially as herein described with reference to the accompanying drawings.