AU590053B2

AU590053B2 - Safety lampholder

Info

Publication number: AU590053B2
Application number: AU69351/87A
Authority: AU
Inventors: Patrick John Doherty
Original assignee: KUDOS LIGHTING Ltd
Current assignee: KUDOS LIGHTING Ltd
Priority date: 1986-02-06
Filing date: 1987-02-02
Publication date: 1989-10-26
Anticipated expiration: 2007-02-02
Also published as: GB8817744D0; NZ219176A; GB2207819B; AU6935187A; WO1987004867A1; GB2207819A

Description

LAMPHOLDER

The present invention relates to a safety lampholder for receiving a bayonet bulb. Various lampholder structures have been proposed which are intended to prevent contact with electrical terminals supported by the lampholder when the lampholder does not have a bulb inserted therein. Examples of such proposals are described in European Patent Specification EP 101257 and French Patent Specification No. 2403665.

European Patent Specification EP 101257 describes a safety lampholder in which contacts that are intended to bear against an inserted bulb are supported on a carrier. A latch mechanism is provided which causes the carrier to rotate when a bulb is inserted, the rotation freeing the carrier so that it can move axially with an inserted bulb. The lampholder contacts are isolated from power supply terminals supported in the lampholder when a bulb is removed and are only electrically connected to the terminals after a combined rotation and axial movement resulting from insertion of a bulb.

The structures described in the abovementioned specification are inherently very safe as it is difficult even when using a tool such as a screw driver to cause the carrier to make the required rotational and axial movements. A spring-loaded return mechanism is required however to ensure that the carrier returns to its ^■■safe" position when a bulb is removed and this adds to the cost and complexity of the lampholder. In addition, as the carrier must be capable of moving axially the minimum axial length of the lampholder is increased. For some applications, e.g. decorative chandeliers, it is highly desirable to be able to provide a very compact lampholder structure.

French Patent Specification No. FR2403665 describes a different safety lampholder structure which relies upon a shutter interposed between power supply terminals mounted in the lampholder body and the base of a socket into which a bulb is inserted. When no bulb is present in the lampholder the shutter obstructs access to the terminals. When a bulb is inserted however the shutter rotates with the bulb until the terminals are aligned with the apertures in the shutter. The terminals are spring-loaded and accordingly extend through the shutter apertures and contact the inserted bulb. When the bulb is removed the shutter is rotated with the bulb to its original position and the spring loaded terminals ride up inclined surfaces defined on the rear surface of the shutter. The shutter is caused to rotate by engagement between the pins of the inserted bulb and a sleeve which defines slots into which the bulb pins are received. Thus the shutter is directly driven by the bulb.

The abovementioned arrangement works effectively but is difficult to produce in a compact form. This is because the lampholder terminals must have sufficient resilience in the axial direction to accommodate retraction behind the shutter and extension through the shutter apertures. The resilient force in the extended condition of the terminals must be sufficient to provide adequate contact pressure on the bulb. Furthermore, there is a risk that the lampholder terminals will become embedded in the bulb contacts, locking the shutter against rotation and thus preventing bulb removal. In addition, the apertures in the shutter can be penetrated by an inserted wire or the like so that the shutter does not provide absolute security against an inquisitive child.

It is an object of the present invention to provide an improved safety lampholder.

According to the present invention there is provided a safety lampholder for receiving a bayonet bulb, the lampholder comprising a body defining slots each of which has two mutually inclined limbs along which the bayonet pins of a bulb slide during insertion and removal of the bulb, a contact carrier mounted within the body and movable relative to the body between first and second positions, power supply terminals supported by the body and defining surfaces facing the carrier, direct access to the terminal surfaces being obstructed by the contact carrier, and contacts supported by and extending on both sides of the carrier, the contacts moving with the carrier so as to be spaced from the terminal surfaces when the carrier is in the first position and so as to bear against the terminal surfaces when the carrier is in the second position, wherein the carrier comprises a sleeve extending to the body slots and defining slots for engagement with the pins of an inserted bulb, the body slots and sleeve slots being arranged such that as a bulb is inserted its pins slide along one limb of the body slots and enter the sleeve slots and then slide along the other limb of the body slots whilst bearing against the edges of the sleeve slots so as to rotate the carrier with the bulb to the second position, and such that as a bulb is removed its pins slide along the said other limb of the body slots whilst bearing against the edges of the sleeve slots so as to rotate the carrier with the bulb from the second position and then slide along the said one limb of the body slots and out of the sleeve slots to leave the carrier in the first position.

The carrier contacts may be in the form of resilient strips extending through and along opposed sides of the carrier. The carrier may comprise an insulating base, and the sleeve may be in the form of a sheet metal member supported by that base or an integral tubular extension of the base. The carrier may comprise a spring member which is biased to engage a slot defined within the lampholder body, a predetermined force being required to disengage the spring member from the slot when the carrier is moved from the first position towards the second position.

The body may comprise a moulded element defining a socket at one end and closed at the other end. The power supply terminals may be mounted on a terminal support member which is a snap-fit within the socket, and the carrier may be a snap-fit in the terminal support member. The terminal support member and carrier may be inserted through the open end of the socket. The single moulded element may define recesses into which spring arms extending from the terminal support member snap engage and the support member may define an aperture into which an arm extending from the carrier snap engages.

In an alternative arrangement the body may comprise a moulded element with a removable cap at one end and defining a socket at the other. The carrier may be inserted through the said one end of the body moulding and retained within the socket by a flange against which the carrier sleeve bears. A terminal support member may also be inserted into the body via the said one end.

Each sleeve slot may extend parallel to the said one limb of a respective body slot such that each of the bayonet pins of an inserted bulb enters the respective sleeve slot during movement of the bulb pin along the said one limb of the body slot without causing rotation of the sleeve relative to the body. Alternatively, each sleeve slot may be inclined to the said one limb of a respective body slot such that the sleeve is caused to rotate as each of the bayonet pins of an inserted bulb moves along the said one limb of the body slot. The carrier may be movable axially relative to the body, the carrier being moved axially with an inserted bulb as a result of engagement between the bayonet pins of the bulb and the edges of the sleeve slots. The carrier and body may comprise interengaging formations which prevent rotation of the carrier to the second position unless the carrier has been moved axially relative to the body.

The body may define a support surface upon which the sleeve rests when the carrier is in the second position, the body and sleeve slots being arranged such that the bayonet pins of an inserted bulb are supported by edges of the sleeve slots when the carrier is in the second position.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which :-

Fig. 1 is a sectional view through a first embodiment of the invention;

Figs. 2 and 3 are respectively perspective and sectional views through the body of the embodiment of Fig. 1;

Figs. 4 and 5 are sectional views through the carrier assembly shown in Fig. 1 before insertion of a bulb (Fig. 4) and after insertion of a bulb (Fig. 5) ; Figs. 6 and 7 are side elevations taken on lines 6-6 and 7-7 of Figs. 4 and 5 respectively;

Fig. 8 is a section through a portion of a second embodiment of the present invention; Fig. 9 is a perspective view of a sleeve incorporated in the embodiment of Fig. 8;

Fig. 10 illustrates an alternative sleeve to that of Fig. 9.

Figs. 11 and 12 are sections through a further embodiment of the present invention;

Fig. 13 is a perspective view of a carrier of the embodiment of Figs. 11 and 12;

Figs. 14 and 15 are respectively end views of the carrier and body of the embodiment of Figs. 11 and 12, the orientations of the sections shown in

Figs. 11 and 12 being indicated by lines 11-11 and

12-12 respectively;

Fig. 16 is a sectional view of a further lampholder embodying the present invention, the components of the lampholder being in the relative positions which they adopt when no bulb has been inserted;

Fig. 17 is a sectional view of the lampholder of Fig. 16 with the lampholder components being in the positions that they assume after a bulb has been inserted;

Fig. 18 is an exploded view of the components of the lampholder illustrated in Figs. 16 and 17;

Figs. 19 to 24 illustrate the relative orientations of the lampholder housing and shell in the embodiment of Figs. 16 to 18 as a bulb is inserted into the lampholder;

Fig. 25 is a sectional view through a modified embodiment of the present invention which in many respects in similar to that of Figs. 16 to 18 but which incorporates an alternative slot formation;

Fig. 26 is a perspective view of a flex grip shown in Fig. 25;

Fig. 27 is a perspective view of the carrier contacts of the embodiment of Fig. 25;

Fig. 28 is an underside view of the flex terminal structure of the embodiment of Fig. 25;

Figs. 29 and 30 are respectively a perspective view of the carrier shell illustrated in Fig. 25 and a section view of the main housing body of the embodiment shown in Fig. 25;

Fig. 31 is a perspective view of an alternative lampholder housing in which the housing slots incorporate an angled entry portion so as to increase the rotation of the carrier shell as a bulb is inserted; and

Figs. 32 to 35 illustrate the relative orientations of ^' the components of the embodiment illustrated in Fig. 25 as a bulb is inserted. Referring to Figs. 1 to 7, the illustrated lampholder comprises a one piece integrally moulded body 1 defining a socket 2 at one end and supporting an integrally moulded cap 3 at the other. A pair of apertures 4 are defined on either side of the cap 3. The cap also defines a threaded aperture 5 through which a power supply cable (not shown) can be fed. A threaded sleeve (not shown) can be screwed into the aperture 5 so as to clamp the cable in position. The body defines a pair of L-shaped slots 6 along which the pins of an inserted bulb (not shown) slide during insertion and removal of that bulb.

The body socket receives an assembly comprising a terminal support member 7 and a carrier defined by a carrier base 8 and a carrier sleeve 9. The terminal support member 7 supports a pair of power supply terminals 10 to which a cable fed through the aperture 5 is connected. The terminals 10 define surfaces 11 which are exposed on the side of the terminal support member 7 remote from the aperture 5. The carrier base 8 supports a pair of contacts in the form of spring strips 12.

The terminal support member comprises resilient arms 13 terminating in hooks 14. The terminal support member 7 also defines a central aperture 15. The underside of the terminal support member 7 defines an annular flat surface surrounding the aperture 15, the terminal surfaces 11 being coplanar with this annular surface.

The carrier base 8 supports an upwardly extending arm 16 with an enlarged head 17. The terminal support member 7 and carrier base 8 are assembled together by forcing the head 17 of the arm 16 through the aperture 15. The carrier base 8 can not then become detached from the terminal support member 7 although it can rotate relative thereto. The carrier base 8 defines a flange 18 and a recess 19. The sheet metal sleeve 9 has an upper flange 20 which engages over the flange 18 so that the sleeve cannot be pulled downwards away from the carrier base 8. In addition, the sleeve 9 supports a resilient arm 21 which projects radially outwards beyond the rest of the sleeve. The arm 21 can be depressed however into the space provided by the recess 19. The lower edge of the sleeve 9 has two slots 22 formed therein. The upper ends of the spring strip contacts 12 are free to slide around the annular surface a part of which is formed by the surfaces 11 defined by the terminal blocks 10.

As can be seen from Figs. 1 and 3, the body 1 defines axially extending slots 23. When the lampholder is assembled, a cable is threaded through aperture 5 and connected to the terminals 10, the carrier and terminal support member are interengaged as shown in Figs. 4 to 7, and the assembly is pushed into the body so that the hooks 14 and the resilient arm 21 slide in the slots 23. The terminal support member and carrier assembly is pushed in until the hooks 14 engage in the apertures 4 and the terminal support member and carrier assembly can not then be withdrawn unless the hooks 14 are disengaged using a suitable " tool such as a small screwdriver. The lampholder assembly is then in the condition illustrated in Fig. 1 with the terminal support member and carrier sub-assembly being in the condition shown in Figs. 4 and 6.

When a bulb (not shown) is inserted, its pins initially slide along the axially extending limb of the L-shaped slots 6 until the pins engage in the sleeve slots 22. This partially depresses the contacts 12 so that the terminals of the bulb are in good electrical contact therewith. The bulb pins are then slid along the circumferentially extending limbs of the L-shaped slots 6 and the sleeve is rotated with the bulb pins so that the terminal support member and carrier assembly assume the relative positions illustrated in Figs. 5 and 7. In this position the contact strips 12 bear against the surfaces 11 on the underside of the terminal blocks 10. When the bulb is withdrawn its pins rotate the sleeve 9 back to the position shown in Fig. 1 and the bulb can then be withdrawn from the lampholder. Rotation of the carrier from the position shown in Fig. 1 is resisted by the interengage ent of the resilient arm 21 with the slot 23. If an attempt is made to rotate the carrier relative to the lampholder assembly using for example a finger a considerable rotational force must be applied to disengage the resilient arm 21 from the groove 23. This cannot be done accidentally. The maximum rotation of the carrier relative to the terminal support member is limited by a projecting arm 24 which is integral with the carrier base 8 and is received within a cut-out

25 defined in the terminal support member 7.

The spring strip contacts 12 extend through the carrier base 8 and because of their resilience are pressed firmly against the annular surface defined on the underside of the terminal support member 7 but nevertheless can slide easily relative thereto because of the resilience of the contacts 12.. There is no axial movement of the carrier and therefore the axial dimensions of the contacts can be relatively limited. Accordingly, the entire assembly can be manufactured in a very compact form. In addition only three moulded components are required with the result that manufacturing and assembly costs are limited.

It will be noted that there is no spring return mechanism in the lampholder. The carrier structure is .such however that a bulb can only be removed if in the process the carrier is returned to its "safe" position. The safety mechanism accordingly corresponds to a double pole switch. There is no tendency for the carrier contacts to become welded to the terminal blocks 10. Figs. 8 and 9 illustrate an alternative structure to that illustrated in Figs. 1 to 7. In the arrangement of Figs. 8 and 9, a lampholder body

26 is provided which does not have an integrally moulded cap. A separate cap (not shown) would be required to cover the upper end of the body as shown in Fig. 8.

In the arrangement of Figs. 8 and 9 a terminal support member 27 is secured against rotation by cooperating ^' projections and grooves (not shown) and terminal blocks (not shown) are supported by the terminal support body 27 so as to form surfaces which are coplanar with the undersurface 28 of the member 27. A carrier base 29 is positioned beneath the terminal support member 27 and in turn supports contacts 30. A sleeve 31 is secured against rotation relative to the carrier base 29 and is provided with slots 32 which are engaged by the pins of an inserted bulb, the pins being inserted into L-shaped slots 33 defined by the body 26. The carrier is rotated by engagement of the pins of an inserted buib in the slots 32 in exactly the same manner as in the case of the equivalent components in the embodiment of Figs. 1 to 7.

Fig. 9 illustrates the structure of the sleeve 31. The sleeve has cut-outs 34 in its upper edge which engage around mating projections (not shown) defined by the carrier base 29.

Fig. 10 illustrates an alterative sleeve structure. The same reference numerals are used for the same features as in Fig. 9. In the case of Fig.

10 however the sleeve is split so as to define a gap 35 between the two ends of the sleeve. This simplifies manufacture. In addition the cut-outs 34 define inwardly extending ears 36 which are intended to engage in appropriately shaped cut-outs in the carrier base 29.

The lampholder is assembled by interengaging the sleeve 31 and the carrier base 29 and dropping these into the body 26 so that they rest on a flange 37 defined by the body. The terminal support member 27 is then inserted on top of the carrier assembly. The sleeve 31 does not extend to the end of the socket defined by the lampholder and accordingly the radial thickness of the portion of the body beneath the L-shaped slots 33 can be increased as compared with the corresponding portions of the body in the embodiment of Figs. 1 to 7. This increases the strength of the body moulding in those regions relied upon to support the weight of a bulb. in the embodiment illustrated in Figs. 1 to 7, resistance to rotation of the carrier is provided by the resilient arm 21 which projects radially outwards beyond the body of the sleeve. This resistance to turning of the carrier can be provided in alternative ways however. For example it may be achieved by interengagement between a resilient member supported by the carrier base and engaging in slots in the lampholder body or a terminal block secured in that body. The carrier base may be generally disc shape in form and comprise a circumferentially extending arm -which in its free state projects above the surface of the disc. The arm can be positioned so as to engage in a first depression in the lampholder body when the lampholder supports a bulb and a second depression when the bulb is removed. The first and second depressions are separated by an axially extending projection so that rotation of the carrier with an inserted bulb requires the displacement of the resilient arm as it passes over the projection. in the embodiment of Figs. 1 to 7 the sleeve supported by the carrier base does not extend to the end of the lampholder socket and provides no support to a bulb supported in the lampholder. This means that the moulded material around the opening of the lampholder socket must be sufficiently thick to provide the necessary support for a bulb inserted into the lampholder. The sleeve may be designed however so as to provide such support by replacing the simple U-shaped slot in the sleeve as shown in 5 Fig. 4 by a J-shaped slot the dimensions of which are such that, after rotation of the carrier by an inserted bulb, the bulb is supported by engagement between its pins and the J slot in the carrier sleeve. The sleeve is of course supported by the

10 carrier base which in turn is supported by the lampholder body.

The lampholder of Figs. 1 to 10 comprise a body of relatively small outside diameter to enable a lampshade support ring to 'be slipped over the

*L5 lampholder body and secured thereon. The lampholder body is moulded and must have a radial thickness sufficient to provide the required strength. The internal diameter of the sleeve must be greater t an the bulb diameter. Thus the radial thickness of the

20 sleeve is preferably as small as possible,, and this makes the use of a thin metal sleeve preferable. Where radial dimensions are not critical however, as for example in the case of landholders not intended to directly support lampshades,, the lampholder sleeve

25 can be an integral part of the carrier. Such an arrangement is shown in Figs. 11 to 15.

Referring to Figs. II to 14, the illustrated lampholder comprises a body 38 and a carrier 39 both of moulded plastics material. The carrier supports

30 contacts 40 and 41. The carrier comprises a sleeve 42 in which sleeve slots 43 are defined, transverse axially extending walls 44, 45 and 46, spring fingers 47, and transverse radially extending walls 48 and 49. As best seen from Fig. 12, the contacts 40 and 5 41 are generally S-shaped and are slipped over the walls 48 and 49, each contact defining an aperture and being retained in position by engagement of a projection 50 in that aperture.

The body defines conventional L-shaped slots 51 and a radial inwards extending flange 52 against which the end of the sleeve 42 bears. The body slots 51 penetrate the flange 52 as shown in Fig. 15. The^' body also defines axially extending slots 53 separated by ribs 54, and ribs 55. When the carrier is inserted into the body, the slots 43 are aligned with the slots 51 as shown in Fig. 15. The spring fingers 47 are received in the slots 53 and if the carrier is rotated relative to the body the spring fingers 47 must ride up over the ribs 54. The ribs 55 limit the rotation of the carrier.

The body also receives a terminal support plate 56 which is retained in the body by internally projecting ribs 57. The plate 56 supports flex terminals 58 which extend through the full thickness of the plate. A cover (not shown) is provided to extend over the top of the lampholder.

When a bulb is inserted, the components are as shown in the drawings. The pins of the inserted bulb engage the sleeve slots 43 and the sleeve is then rotated with the bulb. The torque applied to the bulb pushes the fingers 47 over the projections 57, and the contacts 41 and 42 slide over the underside of the plate 56 into contact with the terminals 58. When the bulb is removed, the bulb pins again rotate the carrier, effectively switching off the lampholder.

In the above described embodiment of the invention, the carrier executes a simple rotational movement when a bulb is inserted. It is possible however to arrange the carrier such that both axial and rotational movements of the carrier are required. Such an arrangement makes it even more difficult to move the carrier except as a result of insertion of a bulb, but does require increased axial dimensions. Arrangements requiring both axial and rotational carrier movements are described below with reference to Figs. 16 to 35.

Referring to Figs. 16 to 18, the illustrated lampholder comprises a housing 101 defining a socket 102 into which a carrier comprising a sleeve 103 and body 104 is inserted. As is best appreciated from Fig. 18, the sleeve 103 receives the carrier body 104, a key 105 on the carrier body 104 engaging in a slot 106 in the carrier sleeve. The sleeve and body are then dropped into the housing 101 and are retained therein by a lip 107 defined around the socket opening.

The sleeve 103 is a relatively tight fit in the housing so that it cannot be easily moved by an inserted finger. The carrier body 104 is a relatively loose fit.

A terminal support 108 supporting terminals 109 is engaged over the top of the housing, resilient arms 110 snap-engaging over latent formations around the outer periphery of the top of the housing 101. Resilient contacts 111 (not shown in Fig. 18) are received in slots 112 in the carrier body 104. When no bulb has been inserted into the lampholder the carrier assumes the position shown in Fig. 16 and the contacts 111 are as a result isolated from the terminals 109. When a bulb is inserted however the carrier rotates and moves axially upwards towards the terminals 109 so that the contacts 111 bear against the terminals 109 as shown in Fig. 17.

The housing 101 defines J-slots intended to receive the bayonets of an inserted bulb. These J-slots comprise an axially extending entry portion 113, a circumferentially extending portion 114 and a recess 115. A projection 116 located on a resilient arm extending adjacent the J-slot gives a positive indication of the bayonet pin being twisted fully home, and prevents the bayonet pin being accidentally released.

The lip 107 around the opening of the lampholder socket has a thickened portion 117 and the edge of the carrier sleeve 103 adjacent the socket opening is cut away to form a recess 118. When no bulb has been inserted into the lampholder (Fig. 16) the thickened portion 117 of the lip 107 is received in the recess 118. When a bulb has been inserted however the thickened portion 117 bears against the edge of the carrier shelf 103 to one side of the recess 118.

Referring now to Figs. 19 to 24, the movement of the carrier sleeve 103 relative to the housing 101 when a bulb is inserted is illustrated. With the carrier in the position shown in Fig. 16, when the bulb is first pushed into the lampholder socket the bayonet pins 119 assume the position shown in Fig. 19. As the bulb is pushed axially into the lampholder the carrier 103 is forced to rotate to the position shown in Fig. 20 as a result of engagement between the pins 119 and a surface 120 defined by J-slots formed in the carrier sleeve 103. The J-slots in the carrier 103 are best seen in Fig. 18 and comprise an inclined entry portion 121 one side of which is defined by the surface 120 and a circumferentially extending slot portion 122. Axial movement of the carrier relative to the housing is prevented until the rotation illustrated by the differences between Figs. 19 and 20 has been accomplished. After the bayonet pins 119 have reached the position illustrated in Fig. 20, further axial movement of the bulb moves the pins axially further into the socket to the position shown in Fig. 21 and the pins 119 engage the J-slots in the carrier sleeve 103 so that the carrier sleeve 103 and the carrier body 104 move axially also. Once the pins 119 have reached the position shown in Fig. 21 the bulb can then be rotated firstly to the position shown in Fig. 22 and then to the position shown in Fig. 23 beyond the projection 116. Rotation of the bulb from the position shown in Fig. 22 to the position shown in Fig. 23 causes the sleeve 103 to rotate within the housing 101. Release of the bulb when the carrier is in the position illustrated in Fig. 23 causes the pins 119 to drop downwards towards the recess 115 defined by the J-slots in the housing 101. The pins 119 do not reach the bottom of the recess 115 however as they are prevented from doing so by the lower edge of the circumferential portion 122 of the J-slot in the carrier sleeve 103. As seen in Fig. 17 when the bulb is in the position illustrated in Fig. 24 the lower edge of the carrier sleeve 103 rests on the thickened portion 117 of the lip 107. Thus the load on the bulb pins 119 is transferred through the sleeve 103 to the relatively strong lip on the housing around the socket opening. No load is applied to the housing in the region of the socket recess 115 in which region the housing is relatively weak.

When the carrier sleeve 103 executes the rotations illustrated in Figs. 19 to 24 the contacts

111 slide along moulded ramps 123 (Fig. 18) onto the end surfaces of the terminals 109 and thus the contacts become live. If however in the absence of a bulb in the lampholder an attempt is made with an inserted finger to move the carrier from the position shown in Fig. 16 to the position shown in Fig. 17 this cannot be done as the smooth inner surface of the carrier sleeve 103 is difficult to engage and the sleeve 103 is a relatively tight fit. Should the carrier body 104 be pushed down it simply slides axially against the force resulting from the contacts 111 bearing against the ramps 123 and no rotation of the carrier occurs. The carrier sleeve 103 will not move axially as the fit between the carrier sleeve 103 and the housing 101 is tighter than the fit between the carrier sleeve 103 and the carrier body 104. Referring now to Figs. 25 to 30, an alternative arrangement to that of Fig. 16 to 18 is illustrated, the main difference being that in the embodiment of Figs. 25 to 30 the J-slots in the carrier sleeve 103 comprise an axially extending entry portion 121 (Fig. 29) . Thus as the bulb is pushed into the lampholder there is no initial rotation of the carrier sleeve relative to the housing. The same reference numerals are used in Figs. 25 to 30 as have been used in Figs. 16 to 18 for equivalent components and accordingly the significance of those equivalent components can be appreciated from the full description of the embodiment illustrated in Figs. 16 to 18.

Fig. 25 illustrates a knurled cover 124 and a flex clamp 125 of the type which may also be used in the embodiment of Figs. 16 to 18 to secure a flex to the lampholder and prevent access to the proper side of the terminal support 108. The cover has a threaded portion 126 which engages on a threaded portion 127 on the terminal support. Fig. 31 illustrates the structure of a housing 101 which is similar to that of Fig. 25 except for the fact that the entry portion 113 of the slots defined by the housing is inclined to the lampholder axis so as to increase the rotation of the sleeve 103 as a bulb is inserted. If such an arrangement was used in for example a lampholder of the general type illustrated in Figs. 25 to 30, it would be necessary to enable the sleeve 103 to rotate as the bulb pins move along the slots 113. This would require reshaping of the portion 117 of the lampholder socket and the recess 118 in the sleeve 103.

Referring now to Figs. 32 to 35, the movement of the sleeve 103 relative to the housing 101 of the embodiment illustrated in Fig. 110 is illustrated. When the bulb is first inserted the bayonet pins 119 move up to the position shown in Fig. 32. Further axial movement of the bulb causes the carrier sleeve 103 to move up with the bulb until the lower edge of the carrier sleeve 103 clears the thickened portion 117 of the lip 107 around the socket opening. The bulb can then be rotated from the position shown in Fig. 33 to the position shown in Fig. 34. Release of the bulb causes the pins 119 to drop down to the position shown in Fig. 35 in which position the pins 119 are supported by the sleeve resting against the thickened portion 117. The resilient contacts 111 provide the necessary spring force to maintain the pins 119 in the position shown in Fig. 35.

In the embodiment of Figs. 16 to 18 the carrier sleeve 103 rotates in two stages, that is a first stage as the bulb is pushed in axially and a second stage as the bulb is rotated. In the embodiment of Fig. 25 all the rotation is caused as the bulb is twisted after its axial insertion. Accordingly, the circumferentially extending portion 114 of the slots in the housing is longer in the case of the Fig. 25 embodiment as compared with the Fig. 16 embodiment. In the case of the Fig. 31 embodiment rotation of the carrier sleeve again occurs in two stages, that is a first stage during insertion of the bayonet pins into the entry portion 113 and a second stage as the bulb is further rotated and the pins move along the circumferential portion 114.

A particular advantage of all the described embodiments is that if the contacts and flex terminals become fixed together, the bulb cannot be removed, and the lampholder cannot therefore be left in an unsafe condition.

Claims

CLAIMS :

1. A safety lampholder for receiving a bayonet bulb, the lampholder comprising a body defining slots each of which has two mutually inclined limbs along which the bayonet pins of a bulb slide during insertion and removal of the bulb, a contact carrier mounted within the body and movable relative to the body between first and second positions, power supply terminals supported by the body and defining surfaces facing the carrier, direct access to the terminal surfaces being obstructed by the contact carrier, and contacts supported by and extending on both sides of the carrier, the contacts moving with the carrier so as to be spaced from the terminal surfaces when the carrier is in the first position and so as to bear against the terminal surfaces when the carrier is in the second position, wherein the carrier comprises a sleeve extending to the body slots and defining slots for engagement with the pins of an inserted bulb, the body slots and sleeve slots being arranged such that as a bulb is inserted its pins slide along one limb of the body slots and enter the sleeve slots and then slide along the other limb of the body slots whilst bearing against the edges of the sleeve slots so as to rotate the carrier with the bulb to the second position, and such that as a bulb is removed its pins slide along the said other limb of the body slots whilst bearing against the edges of the sleeve slots so as to rotate the carrier with the bulb from the second position and then slide along the said one limb of the body slots and out of the sleeve slots to leave the carrier in the first position.

2. A safety lampholder according to claim 1, wherein each sleeve slot extends parallel to the said one limb of a respective body slot such that each of the bayonet pins of an inserted bulb enters the respective sleeve slot during movement of the bulb pin along the said one limb of the body slot without causing rotation of the sleeve relative to the body.

3. A safety lampholder according to claim 1, wherein each sleeve slot is inclined to the said one limb of a respective body slot such that the sleeve is caused to rotate as each of the bayonet pins of an inserted bulb moves along the said one limb of the body slot.

4. A safety lampholder according to claim 1, 2 or 3, wherein the carrier is movable axially relative to the body, the carrier being moved axially with an inserted bulb as a result of engagement between the bayonet pins of the bulb and the edges of the sleeve slots.

5. A safety lampholder according to claim 4, wherein the carrier and body- comprise interengaging formations which prevent rotation of the carrier to the second position unless the carrier has been moved axially relative to the body.

6. A safety lampholder according to any preceding claim, wherein the carrier comprises an electrically insulating base and the sleeve comprises a sheet metal member supported on the carrier base.

7. A safety lampholder according to claim 6, wherein the body defines a support surface upon which the sleeve rests when the carrier is in the second position, the body and sleeve slots being arranged such that the bayonet pins of an inserted bulb are supported by edges of the sleeve slots when the carrier is in the second position.

8. A safety lampholder according to any one of claims 1 to 5, wherein the carrier is a moulded member and the sleeve is an integrally moulded part of the moulded member.

9. A safety lampholder according to any preceding claim, wherein the body comprises a moulded element defining a socket at one end and closed at the other end, the power supply terminals are mounted on a terminal support member which is a snap fit within the socket, and the carrier is a snap fit on the terminal support member, the carrier and terminal support member being insertable through the open end of the socket.

10. A safety lampholder according to any one of claims 1 to 8, wherein the body comprises a moulded element with a removable cap at one end and defining a socket at the other, the carrier is insertable through the said one end of the body to engage a flange which retains the carrier within the socket, and a terminal support member is insertable through the said one end of the body to be positioned on the side of the carrier remote from the socket.

11. A safety lampholder according to any preceding claim, wherein the carrier contacts comprise resilient strips extending along opposed sides of the carrier.

12. A safety lampholder according to claim 11, wherein the carrier defines transverse walls which obstruct access to the terminal surfaces, and the resilient strips are slipped onto the transverse walls from one end thereof.

13. A safety lampholder according to any preceding claim, comprising at least one spring member which interengages the carrier and body to provide a predetermined resistance to rotation of the sleeve towards the second position.