GB2279825A

GB2279825A - Lampholder

Info

Publication number: GB2279825A
Application number: GB9413759A
Authority: GB
Inventors: Patrick James Doherty
Original assignee: Seapart Ltd
Current assignee: Seapart Ltd
Priority date: 1993-07-08
Filing date: 1994-07-07
Publication date: 1995-01-11
Anticipated expiration: 2014-07-07
Also published as: GB2279825B; GB9413759D0

Abstract

A safety lampholder for a bayonet bulb comprises a housing 10 defining slots 11 to receive the bayonet pins of a bulb. Contacts 57 are provided within the housing 10. Axially moveable and rotatable shutter means 20 are also provided for selectively obstructing access to the contacts 57 and are moveable between a first inoperative position, in which the contacts 57 are shielded by the shutter means 20, and a second operative position in which the contacts 57 extend through apertures in the shutter means 20 for bearing against pad electrodes 101 of a bulb. Axial displacement of the shutter means is inhibited by shutter stops 26 abutting ribs 59 on a terminal block 50. On axial insertion of a bulb into the lampholder, the bulb shoulder 100 pushes shutter driving means 40 inwardly of the housing to rotate the shutter means by cooperating cams 24, 42 or gears and to align shutter apertures with the contacts. This displaces the shutter stops 26 relative to the ribs 59, to allow displacement of the shutter means 20 axially inwardly of the housing to the second operative position. The bulb is subsequently rotated to secure its bayonet pins in slots 11. The shutter means can comprise shutter halves driven to rotate relative to one another to release the stops and align the apertures. <IMAGE>

Description

LAMPHOLDER The present invention relates to a shuttered safety lampholder for a bayonet bulb.

French Patent No. 2403665 discloses a so-called shuttered lampholder in which a shutter is interposed between contacts connected to a power supply and a bulb receiving socket. In use, when a bulb is inserted into the socket, the shutter is rotated by the bulb. This moves apertures in the shutter into alignment with telescopic spring loaded contacts supported by the lampholder. These contacts spring through the apertures in the shutter to engage pad electrodes on the end of the inserted bulb.

However, it has been found that, with the above shutter arrangement, the contacts can become embedded in the bulb pad electrodes. This results in the contacts passing through the apertures in the shutter to such an extent that they lock the shutter against rotation.

Thus, this prevents bulb removal. Furthermore, even in the absence of a bulb, it is still possible for a wire, nail or the like to be inserted through the apertures in the shutter by, for example, an inquisitive child. If an inquisitive child should move the shutter to its open position, the spring loaded contacts would spring through the apertures in the shutter, locking the shutter against rotation with no bulb present. Thus, the lampholder may then be left in a highly dangerous condition.

The present invention seeks to provide an improved shuttered safety lampholder in which the bulb engaging contacts cannot lock the shutter against rotation when no bulb is present in the lampholder and in which the apertures in the shutter are covered when a bulb is not present, and furthermore, the shutter may automatically assume its closed position if a bulb is not present.

Accordingly, the present invention provides a safety lampholder for a bayonet bulb comprising a housing defining slots to receive bayonet pins of an inserted bulb, contacts within the housing for electrical connection to a power source to supply electricity to the bulb, axially moveable and rotatable apertured shutter means in the housing for selectively obstructing access to the contacts and moveable between a first inoperative position in which the contacts are shielded by the shutter means and a second operative position in which the contacts extend through apertures in the shutter means for bearing against a bulb, locking means within the housing for selectively inhibiting axial displacement of the shutter means and means for driving rotation of the shutter means and arranged so that axial insertion of a bulb into the lampholder is effective to actuate rotation of the shutter means from the first position to align apertures in the shutter means with the contacts and to release the locking means to allow displacement of the shutter means axially inwardly of the housing to the second position.

Typically the housing has "J" type slots.

Preferably the locking means are engageable with an inserted bulb so as to be releasable as the bulb is initially inserted into the lampholder before rotation of the bulb to engage the bayonet pins in the circumferential portion of the J slots.

Suitably, the housing includes power supply terminals, supported in a terminal block which is secured in fixed relation to the housing and bulb engaging contacts electrically connected to the power supply terminals by flexible conducting elements. Preferred bulb engaging contacts each comprise a closed cylinder which accommodates a bridging spring.

Preferably the locking means are axially moveable within the housing and the means for driving rotation of the shutter means are actuable upon axial displacement of the locking means. Suitably formations, such as axially extending channels, are provided in the housing for guiding axial displacement of the locking means, and preventing rotation of the locking means about the axis of rotation of the shutter means.

In preferred embodiments the locking means includes an axially moveable locking member which extends to the open end of the lampholder housing to bear against a bulb and has formations which engage with shutter means formations to inhibit axial displacement of the shutter means until the locking member has first been displaced axially inwardly of the housing by an inserted bulb.

Preferably the housing also has formations to cooperate with locking member formations to inhibit rotation of the shutter means until the locking member has firstly been displaced inwardly of the housing.

Typically, the locking member is arranged so that it is not readily releasable by a person's finger inserted into the housing.

Preferably the locking member includes a body, especially of generally disc shape having apertures therein to receive the bulb engaging contacts and has one or more limbs extending alongside the internal walls of the housing and to the open end of the housing to engage an inserted bulb. Preferably the locking member includes two diametrically opposed limbs. Suitably the body of the locking member locates between the shutter means and the closed end of the housing and the limbs of the locking member extend through cut outs in the shutter means, preferably at the periphery thereof. Thus, the shutter means may be rotatable with respect to the locking member between a first (closed) position in which respective apertures in the locking member and shutter means are obstructed and a second (open) position in which they are aligned. Preferably, the locking member has formations which locate in or on the shutter apertures when in the first position, to further shield the contacts.

In preferred embodiments the locking member is biased outwardly of the housing, thereby biasing the lampholder to its inoperative position. Resilient bulb engaging contacts may act as a biasing means. Preferably additional biasing means are included, such as a compression spring, typically arranged on the axis of rotation of the shutter means.

Suitably, the locking member has formations arranged to interengage formations on the shutter means to drive rotation of the shutter means upon axial displacement of the locking member. Preferably the interengageable formations include an inclined surface and a follower for the surface. Suitably, one of the shutter means or locking member includes an inclined slot and the other includes a radially extending projection, typically generally circular, to engage the slot. In some embodiments the locking member is provided with diametrically opposed inclined channels or through holes to engage diametrically opposed peg formations extending radially outwardly from the shutter means. In other embodiments inclined slots are provided on the shutter means to engage formations on the locking member.

In some preferred embodiments the shutter means comprise two apertured members, capable of rotation about a common axis, between a first position in which apertures in the members are obstructed and a second position in which they are aligned. Preferably the shutter members are secured against relative axial movement. Conveniently the shutter members are contrarotatable.

In some embodiments, the shutter members may be provided with circumferentially spaced formations on opposing surfaces and a displaceable member, such as a paddle or wheel member having formations interengageable with shutter member formations is arranged therebetween to be rotatable about an axis generally perpendicular to the common axis of rotation of the shutter members to drive contrarotation of the shutter members.

Preferably a locking member has axially spaced formations engageable with wheel member/paddle formations such that axial displacement of the locking member actuates rotation of the wheel member to drive contrarotation of the shutter members. Alternatively, one of the shutter members may be arranged to engage a locking member such that axial movement of the locking member drives rotation of that shutter member and wheel member/paddle so that the wheel member/paddle actuates contrarotation of the second shutter member. In this regard, preferably the locking member includes an inclined surface and the shutter member has a follower for the inclined surface.

In other preferred embodiments the locking member has inclined ramp formations arranged to engage ramp formations on the shutter members to drive contrarotation thereof.

Embodiments of the present invention will now be described further by way of example only, with reference to the accompanying drawings, in which: Figs. 1 to 3 are cross-sectional views of an assembled lampholder according to a first embodiment.

Fig. 1 illustrates the position of the components prior to bulb insertion, Fig. 2 after partial axial insertion of a bulb, and Fig. 3 when a bulb has been fully axially inserted and rotated to rest in the "J" slot; Fig. 4 is a plan view looking into the housing of the lampholder of Figs. 1 to 3 from the end of the housing opposite the bulb receiving end; Figs. 5 & 6 are views of the shutter part of the lampholder of Figs. 1 to 3, Fig. 5 is a plan view and Fig. 6 is a perspective view of the shutter; Figs. 7 & 8 are views of the locking member of the lampholder of Figs. 1 to 3, Fig. 7 is a perspective view and Fig. 8 is a cross-sectional view; Figs. 9 & 10 are plan views showing the locking member/shutter sub-assembly of Figs. 1 to 3 located in the housing in their relative positions, Fig. 9 prior to bulb insertion and Fig. 10 their relative positions if a bulb had been fully inserted; Fig. 11 is a cross-sectional view of an alternative arrangement according to a second embodiment; Fig. 12 is a perspective view illustrating a shutter member modified for incorporation into the embodiment of Fig. 11; Figs. 13, 14 & 15 are cross-sectional views of a third embodiment, Fig. 13 shows the arrangement of the lampholder components prior to bulb insertion, Fig. 14 after partial axial insertion of a bulb and Fig. 15 when a bulb has been fully axially inserted and rotated to rest in the "J" slot; Fig. 16 is an inverted perspective view of the locking member part of the embodiment of Figs. 13 to 15; Fig. 17 is a perspective view of the shutter member of the embodiment of Figs. 13 to 15; Fig. 18 is a cross-sectional view of a fourth embodiment of the present invention, showing the arrangement of the components prior to bulb insertion; Fig. 19 is a plan view of an inner shutter plate of Fig. 18; Fig. 20 is a plan view of an outer shutter plate of Fig. 18; Fig. 21 is a plan view of the inner and outer shutter plates of Fig. 18 as a sub-assembly, secured together against relative axial movement and in the closed position, the position they would assume prior to bulb insertion, the pair of apertures in each shutter plate respectively being non-aligned; Fig. 22 is a plan view of the shutter plate assembly of Fig. 21 in the open position, in which position the pair of apertures respectively in the two shutter plates are aligned; Fig. 23 is a plan view showing the locking member and shutter plate sub-assembly of Fig. 18 located in the housing, with the components in their closed position which they assume prior to bulb insertion; Figs. 24 to 30 are views of a shutter plate and locking member sub-assembly according to a fifth embodiment, Fig. 24 is a perspective view of a locking member, Fig. 25 is a perspective view of the inner shutter plate, Fig. 26 is a perspective view of the wheel member, Fig. 27 is a perspective view of the outer shutter plate, Fig. 28 is a side perspective view of the shutter plate sub-assembly, Fig. 29 is a side perspective view of the shutter plate, locking member and toothed wheel member sub-assembly in the closed position and Fig.

30 is a view of the assembly of Fig. 29 with the components in the open position; Figs. 31 to 33 are views of components incorporated in a sixth alternative arrangement, Fig. 31 is a perspective view of a locking member, Fig. 32 is a side perspective view of the inner and outer shutter and geared wheel member sub-assembly and Fig. 33 is a plan view showing the locking member, shutter plates and geared wheel member sub-assembly located in the housing in their respective closed positions; Figs. 34 and 35 illustrate an alternative shutter plate and locking member arrangement for a seventh embodiment, Fig. 34 shows the components prior to relative axial movement of the locking member and Fig. 35 when the locking member has been moved axially relative to the shutter; Figs. 36 and 37 illustrate a further shutter plate and locking member arrangement. Fig. 36 shows the inner and outer shutter plates prior to relative axial movement of the locking member, and Fig. 37 shows the position of the shutter plates after relative axial movement of the locking member; and Figs. 38 to 40 illustrate part cross-sectional views of an example of shutter plate assembly showing the relative positions of the terminal contacts and shutters, "38" prior to bulb insertion, "39" after partial axial insertion of a bulb and "40" when a bulb has been fully, axially inserted.

Referring now to Figs. 1 to 3, there is illustrated a shuttered lampholder comprising a hollow generally cylindrical housing 10 into one end of which can be received the cap of a bayonet type bulb. The housing 10 is provided with the usual "J" slots 11 (comprising an axial limb 12 and a circumferential limb 13) to receive the respective bayonet pins of a bulb. The external surface of housing 10 is also provided with a screw thread 15 to retain a shade locking ring.

In use, a cover (not illustrated) would be secured to the top of the lampholder housing 10 so as to cover terminals 55 whilst providing an entry port for the power supply flex. The end of the housing opposite the bulb receiving end is closed by a terminal block 50 which is secured in fixed relation to the housing 10. The terminal block 50 supports a pair of resilient terminal contacts 54 which each comprise a flex engaging terminal 55, a bulb engaging contact 57 and a bridging spring 56.

The bridging springs 56 provide a resilient electrical connection between the flex engaging terminals 55 and the bulb engaging contacts 57 (Ref. Fig. 1). The bulb engaging contacts 57 are each generally cylindrical, having a closed free end 58 and a flared end 60 located on a step 52 in the terminal block 50. The terminal contacts 54 extend through the terminal block 50 so as to be accessible on opposite sides thereof. Stop ribs 59 are also defined on and depend from the periphery of the inner surface of the terminal block 50, the terminal block 50 being supported in the housing on ledges 18.

A shutter 20 is located in the bulb receiving end of the housing 10. In this embodiment, the shutter 20 comprises a generally flat disc shaped member. The inwardly facing surface of the shutter 20 is provided with a pair of elongate formations, each comprising a central through aperture 21, with recesses or shelf portions 22 & 23 alongside each aperture 21 provided by inclined or angled faces.

A central bore 31 is provided in the inner surface of the shutter 20. A central peg 30 is located in the central bore 31 and is arranged to support a compression spring 17. A pair of lateral peg formations 24 extend from the side of the shutter 30 in cutaway portions 25.

A pair of vertical ribs 26 extend from the inner surface of the shutter 20 and on the periphery thereof. The ribs 26 also extend beyond the periphery of the shutter to provide a step 27. The steps 27 are arranged to engage a support shelf 16 in the housing wall. This provides outward stop means for the shutter 20. Each respective rib 26 abuts against a limb 59 which depends from the inner surface of the terminal block 50 when the shutter is in its closed position.

A locking member 40 is located in the housing 10 in a gap defined between the terminal block 50 and shutter 20. The features of the locking member 40 are shown in more detail in Figs. 7 and 8. Its body is generally disc shaped with opposing cutaway portions 49. A pair of diametrically opposed limbs 41 extend from the periphery of the locking member 40. In use, the member 40 and shutter 20 would be arranged so that member limbs 41 extend from the cutouts in the shutter to adjacent the open end of the housing. The limbs 41 are partially engaged in the vertical slots 19 defined in the housing wall.

Inclined apertures/slots or keyways 42 are provided in the limbs 41 to receive the pegs 24 which extend from the shutter 20. The locking member 40 is arranged so that it can only move axially relative to the housing 10 and within the slots or keyways 19. The interengagement of the shutter pegs 24 and inclined locking member apertures 42 provide that axial movement imparted to the locking member 40 on bulb insertion is converted to linear or rotational movement of the shutter 20. A leadin 43 may be provided in the limbs 41 to facilitate assembly of the shutter 20 into the locking member 40.

A central bore 45 is also provided in the locking member 40, and has a step 46 to support one end of a central compression spring 17. The bore 45 has a reduced diameter part which defines an aperture 47, arranged to accept the centralising and support peg 30 defined on the shutter 20.

A pair of spaced, diametrically opposed contact receiving apertures 44 are also provided in the surface of the locking member 40. The locking member, in use, is free to move axially inwards of the housing relative to and around bulb engaging contacts 57. A pair of pegs 48 depend from the outer surface of the locking member 40, adjacent the apertures 44. The pegs 48 are arranged so that, prior to bulb insertion, they cover the apertures 21 in the shutter 20 when the shutter 20 is in its closed position. The shutter 20 may be moved by the locking member 40 between closed and open positions.

Prior to bulb insertion, the apertures 21 in the shutter are non-aligned with the apertures 44 in the locking member 40 and thereby the terminal contacts 54.

At this stage the bulb engaging ends 57 of the terminal contacts 54 are located behind the shelf portions 22 of the shutter. The depending pegs 48 in the locking member 40 cover the shutter apertures 21 and the central compression spring 17 is biasing the locking member, and thereby the shutter, outwards of the housing and against support ledges 16. The pegs 24 are also located at the top of the inclined slots or apertures 42. (For example, the slots may be at an angle of 45 .) The ends of the limbs 41 are adjacent the bulb receiving end of the housing and the shutter is in its closed position.

On bulb insertion, the shoulder 100 of the bulb engages the limbs 41 of the locking member 40, moving the member 40 inwardly of the housing 20. This action simultaneously actuates rotation of the shutter 20 from its closed to its open position, aligning the shutter apertures 21 with the locking member apertures 44 and the bulb engaging contacts 57. The pegs 48 are raised inwards of the housing and clear of shutter apertures 21.

The ribs 26 are rotated clear of the stop limbs 59 depending from the terminal block 50 to engage the stop faces 14A in the housing. The pegs 24 are also located at the bottom of the inclined slots or apertures 42 (ref Fig. 2).

On continued axial insertion, the pad electrodes 101 on the end of the bulb depress the shutter 20 and locking member 40 inwards of the housing 10. This causes the ends 58 of the loaded terminal contacts 54 to engage the pad electrodes 101. The terminal contacts 54 are depressed inwards of the housing 10 and further loaded as the flared ends 60 of the contacts are raised off steps 52 in the terminal block 50 as the bayonet pins of the bulb reach the end of the axial portion 12 of the "J" slot 11. The bulb is subsequently rotated to locate the bayonet pins in the resting recess at the end of the horizontal portion of said "J" slot 11 (ref Fig. 3).

As a bulb is axially removed from the lampholder, the central compression spring will move the locking member 40 and shutter 20 outwards of the housing until the shutter 20 locates on the support ledges 16 in the housing wall. The inclined slots or apertures 42 act on the respective pegs 24 to rotate the shutter, as the locking member 40 is moved fully outwards of the housing to abut against the shutter 20. The limbs 26 are relocated beneath the stop limbs 59 and the locking member pegs 48 cover the shutter apertures 21 as the shutter reassumes its closed position. The pegs 24 relocate at the top of the inclined apertures 42 and the shutter 20 is locked against axial movement by the locking member 40.

The extreme ends of the limbs 41 may be fashioned in such a manner as to make it as difficult as possible for a person to depress one of them with a finger. The interengagement of the pegs 48 in the apertures 21 may provide initial resistance to axial movement of the limbs 41 relative to the shutter 20. It will be appreciated that in the absence of a bulb the lampholder components will automatically assume their first shuttered position and that the lampholder as proposed cannot be left in an unsafe condition with no bulb present.

In use, with the lampholder of Figs. 1 to 10 assembled and with no bulb present, the lampholder components assume the position illustrated in Figs. 1 and 9. The live terminal contacts are located behind the shutter 20, which is biased to its closed position by the central compression spring 17 acting on the locking member 40. The apertures 21 in the shutter are nonaligned with the apertures 44 in the locking member 40 and the peg formations 48 cover the shutter apertures 21.

The shutter 20 is supported on the ledges 16 and the ends of the limbs 41 are adjacent the open end of the housing.

Axial bulb insertion may be divided into two stages, a first stage which moves the shutter from its closed to its open position unlocking it to be moved axially, and a second stage in which the shutter and locking member are moved axially inwards of the housing, so that the pad electrodes on the bulb may engage the live terminal contacts within the housing.

In the first stage, as a bulb is inserted axially into the lampholder, the shoulder 100 of the bayonet cap engages the limbs 41 of the locking member 40, moving the locking member 40 inwards of the housing 10, against the force of the spring 17. This action simultaneously rotates the shutter 20 from its closed to its open position due to the interengagement of the formations 24 and 42 on the shutter and locking member respectively.

This results in alignment of the two pairs of apertures 21 and 44 in the shutter and locking member. It also moves the ribs 26 on shutter 20 clear of the stop limbs 59. The pad electrodes 101 on the end of the bulb engage the outer surface of the shutter 20 which is now unlocked and free to be moved axially relative to the housing 10.

The bayonet pins move into the axial portion 12 of the "J" slot 11 and the lampholder components assume the position illustrated in Figs. 2 and 10 after this first stage of axial bulb insertion.

In the second stage of axial bulb insertion, as the bulb is moved fully into the housing 10 it moves the shutter 20 and locking member 40 axially with it, the pad electrodes 101 bearing against the ends 58 of the resilient terminal contacts 54, depressing them inwards of the housing 10 against the force of the springs 56 and the bayonet pins of the bulb reach the end of the slot 12. The bulb is then rotated to locate the bayonet pins in the resting point at the end of the slot 13 and the lampholder components assume the position illustrated in Fig. 3 when a bulb is fully inserted.

On removal of a bulb, the above procedure is reversed and the components reassume the position illustrated in Figs. 1 and 9.

Referring now to Figs. 11 and 12, there is illustrated an alternative embodiment of the present invention. Parts of the lampholder which correspond to those of the previous embodiment are indicated using the same reference numerals as before. This lampholder comprises a one-piece housing 10A supporting a pair of telescopic spring loaded terminal contacts 54. A shutter 20A and locking member 40A sub-assembly is inserted into the housing 10A from the bulb receiving end. The subassembly is retained in the housing 10 by a resilient hook member 71 defined in the housing wall which is arranged to engage ledges 72 in the limbs 41.

Alternatively, the sub-assembly may be retained in the housing 10A by formations in the housing wall which engage the shutter 20A. For this embodiment, the support means 27 defined on the shutter of Figs. 5 & 6 is not required.

On the modified shutter of Fig. 12 stops 59A defined in the housing wall engage the ribs 26 on the shutter 20A, locking it against axial movement inwards of the housing until it has first been rotated. The operational aspects of this embodiment are identical to that of the previous embodiment. Fig. 11 illustrates the position of the lampholder components prior to bulb insertion. The live terminal contacts 54 are located behind the shutter 20A which is biased to its closed position by the central compression spring acting on the locking member 40A.

Turning now to Figs. 13 to 17, there is illustrated a further embodiment of the present invention. This differs from the previous embodiments in that the interengaging formations defined between a shutter 80 locking member 90 have been reversed i.e. pegs 92 are defined internally on the locking member limbs 91 and inclined slots or keyways 86 are defined in the sides of the shutter 80. The operational aspects of this embodiment are identical to that of the previous embodiment.

In use, when the lampholder of Figs. 13 to 17 is assembled and with no bulb present, the lampholder components assume the position illustrated in Fig. 13.

The contacts 57 are located behind the shutter 80 which is biased outwards of the housing 10 to its closed position by the central compression spring 17 acting on the locking member 90. The apertures 81 in the shutter 80 are non-aligned with the apertures 94 in the locking member 90 and the formations 96 are covering said apertures 81, the shutter 80 is supported on the ledges 16 and the ends of the limbs 91 are adjacent the front end of the housing.

As a bulb is inserted into the lampholder, in the first stage of bulb insertion, the shoulder 100 of the bayonet cap engages the limbs 91. This moves the locking member 90 inwards of the housing 10, simultaneously rotating the shutter 80 from its closed to its open position as the pegs 92 are moved along the inclined slots 86 in the shutter. This also aligns the apertures 81 in the shutter 80 with the apertures 94 in the locking member 90. The pegs 96 are moved inwards of the housing 10 clear of the apertures 81. At this stage the terminal block stop limbs 59 are aligned with slots 89 in the shutter 80, the pegs 92 have moved to the top or open end 85 of the respective slots 86 and the pad electrodes 101 abut against the outer surface of the shutter 80. The shutter 80 is now in its unlocked position and free to be moved axially inwards of the housing 10. The bayonet pins are engaged in the slot 12 and the lampholder components assume the position illustrated in Fig. 14 after the first stage of partial bulb insertion.

As a bulb is inserted fully axially into the housing 10 it moves the shutter 80 and locking member 90 axially inwards of the housing 10, against the force of the central compression spring. The pad electrodes 101 bear against the ends 58 of the loaded resilient terminal contacts 54, depressing the contacts 57 inwards of the housing against the force of the bridging springs 56, until the bayonet pins reach the ends of slots 12. The bulb is then rotated to locate the bayonet pins in the resting point at the end of the slot 13 and the lampholder components assume the position illustrated in Fig. 15 when a bulb is fully inserted. On removal of a bulb the above procedure is reversed and the lampholder components resume the position shown in Fig. 13, in which position the live terminal contacts 54 are inaccessible and not visible behind the shutter.

Turning now to Figs. 18 to 23, there is illustrated a shuttered lampholder comprising a hollow cylindrical housing 10 having "J" slots 111 to receive the respective bayonet pins of a bulb. The housing 10 has an external screw thread 115 to retain a shade locking ring. Support means 116 in the housing wall retain shutter plates 120 and 200 and the locking member 140 as a sub-assembly in the housing. A pair of diametrically opposed keyways 119 are defined in the housing wall to accommodate limbs 141 of a locking member 140. The keyways 119 prevent relative rotation of the locking member 140 in the housing 10. Vertical stop faces 114 and 114A are also provided in the housing wall.

The end of the housing opposite the bulb receiving end is closed by a terminal block 150 which is secured in fixed relation to the housing 10 and supports a pair of resilient terminal contacts 154. As in previous embodiments, the terminal contacts each comprise a flex engaging terminal block 155, a bulb engaging contact 157 and a bridging compression spring 156. The terminal contacts 154 extend through the terminal block 150 so as to be accessible on opposite sides thereof. Stop ribs 159 are defined on and depend from the periphery of the inner surface of the terminal block 150, which is supported on the ledges 118.

A pair of shutter plates 120 and 200 from the inner surface of the plate 120. Features of shutter plate 120 are shown more clearly in Figs. 20 & 22.

The inner shutter plate 200 is provided with a pair of spaced apertures 201 and cutaway portions 203. A peg 202 also extends radially outwardly from its periphery.

A central boss 204 is provided on the inner surface of the plate 200, and has a bore 205 to receive a support peg 130 of the plate 120.

The shutter plates 120 and 200 are locked together on assembly. Fig. 21 best illustrates how the inner shutter plate 200 nests within the outer plate 120. The apertures 121 in the outer plate 120 are non-aligned with the apertures 201 in the inner plate 200. The pair of plates are thus in their respective closed or shuttered positions.

A locking member 140 locates in the housing 10 in the gap defined between the terminal block 150 and shutter plate assembly. The locking member 140 is provided with a pair of opposed apertures 144 and a central aperture 145. The locking member 140 also defines a pair of diametrically opposed limbs 141 depending from each end of its body. In use the limbs 141 extend through the shutter plate assembly and adjacent the housing wall. The ends of the limbs 141 locate adjacent the open end of the housing 10. The limbs 141 also partially engage in the vertical keyways 119 defined in the housing wall. Angled slots 142a and 142b are provided in the limbs 141 to receive the pegs 124 and 125 of the outer and inner shutter plates 120 and 200 respectively. Preferably, for manufacture the locking member 140 and shutter plates 120 and 200 would form a sub-assembly to be located in the housing. A central compression spring 117 is arranged to act between the housing 10 and locking member 140 to bias the locking member 140 outwards of the housing.

Fig. 18 illustrates the position of the lampholder components prior to bulb insertion. The locking member 140 is biased outwards of the housing 10 by the spring 117. The ends of limbs 141 are adjacent the open end of the housing 10. The peg 124 on the outer shutter plate is located at the top of the angled slots 142a and the peg 202 on the inner shutter plate 200 is located at the top of the angled slot 124b. Thus, the locking member is biasing the pair of shutter plates 120 and 200 outwards of the housing 10, and rotationally with respect to said housing, to their respective closed positions. The limbs 126 on the outer plate 120 abut against the stop ribs 159 to prevent axial movement of the shutter plate assembly until the shutter plates have been rotated relative to each other and the housing 10 from their closed to their open position, in which position the pair of apertures 121 are aligned with the pair of apertures 201.

Movement of the locking member 140 inwards of the housing 10 causes the angled slots 142a and 142b to move the respective pegs 124 and 202. This action rotates the shutter plates 120 and 200 with respect to each other from their closed to their open positions and thereby rotates the limbs 126 clear of the stop ribs 159. This frees the shutter plate assembly to be moved axially inwards of the housing 10 with the locking member 140.

Fig. 22 shows the relative positions of the shutter plates 120 and 200 in their respective open positions.

At this stage the apertures 121 and 201 are aligned and the ends 158 of the terminal contacts 157 may pass through the aligned apertures 121 and 201 to engage their respective pad electrodes 101 of the inserted bulb.

In use, when the lampholder of Figs. 18 to 23 is assembled and with no bulb present, the lampholder components assume the position illustrated in Figs. 18 and 38. The live terminal contacts 154 are located behind the shutter plates 120 and 200. The shutter plates, 120, 200 are biased to their relative closed position by the locking member 140, which is itself biased outwards of the housing 10 by a central compression spring 159. At this stage the apertures 121 in the outer shutter plate 120 are non-aligned with the apertures 201 in the inner shutter plate 200 and the limbs 126 abut against the stop ribs 159. The shutter plate and locking member sub-assembly is supported in the housing 10 on ledges 116 and the ends of the limbs 141 are adjacent the open end of the housing 10.

Bulb insertion may be divided into three states, two axial insertion stages and one rotational stage. A first axial stage of bulb insertion actuates rotation of the shutter plates 120 and 200 with respect to each other from their closed to their open positions. This also unlocks the shutters to be moved axially inwards of the housing 10. There is also a second axial stage in which the shutter plates 120 and 200 and locking member 140 are moved axially inwards of the housing 10 so that the ends 158 of the terminal contacts 157 extend through the aligned apertures 121 and 201 respectively to engage their respective pad electrodes 101 of a bulb. The rotational stage of bulb insertion follows, when the bulb is rotated in the housing 10 to locate the bayonet pins in the rest points at the end of the horizontal portion of the "j" slots 111.

In more detail, in the first stage of axial bulb insertion, the shoulder 100 of the bayonet cap engages the ends of the limbs 141 of the locking member 140, to move the locking member 140 inwards of the housing 10 against the force of the spring 117. This action simultaneously rotates the shutter plates 120 and 200 relative to each other from their closed to their respective open positions. Also, due to the interengagement of the pegs 124 and 202 in slots 142a and 142b respectively, to rotate the shutter plates, this moves the limbs 126 clear of the stop ribs 159 in the housing 10, freeing the shutter plates 120 and 200 to be moved axially inwards of the housing with the locking member 140. The pair of apertures 121 are aligned with the respective apertures 201 respectively and the bayonet pins of the bulb are located in the axial portion 112 of the "J" slots 111. The lampholder components assume the position illustrated in Fig. 39 after a first stage of axial bulb insertion.

In the second stage of bulb insertion, as the bulb is moved fully into the housing 10, it moves the shutter plates 120 and 200 and locking member 140 with it, the pad electrodes 101 bearing against the ends 158 of the resilient terminal contacts 157 which have passed through the aligned apertures 121 and 201. The contacts 157 are depressed inwards of the housing 10 by the pad electrodes 101 against the force of the springs 156. This raises the flared ends 160 of the contacts 157 off the steps 152 until the bayonet pins reach the end of the slots 112.

The lampholder components assume the position illustrated in Fig. 40 after a second stage of axial bulb insertion.

The bulb is then rotated in the housing 10 to located the bayonet pins in the resting points are the end of the slots 113.

On removal of a bulb from the lampholder the above procedure is reversed when the components reassume the position illustrated in Figs. 18 and 38.

Turning now to Figs. 24 to 30, there is illustrated an alternative shutter plate and locking member assembly.

In this embodiment the outer shutter plate 320 and inner shutter plate 300 are secured together against relative axial movement by means of a screw 309. A number of gear teeth 302 are defined in the surface of the inner shutter plate 300 facing the plate 320. The plate 320 also has a number of matching gear teeth 324 on its inner surface opposite the teeth 302.

A locking member 340 is located over the shutter plate assembly. The locking member 340 has two depending limbs 341, each limb being provided with an elongate vertical aperture 342. Gear teeth 344 are defined on one vertical face of an aperture 342, and a geared wheel member 326 is inserted through one aperture 342 in one of the limbs 341 and arranged so that its teeth 327 engage or mesh with the teeth 302 and 324 in the plates 300 and 320 respectively and with the teeth 344 in the one limb 341 of the locking member 340. A plain band 328 is provided on the geared wheel member 326 and is arranged to be a snug fit against the vertical sides of the apertures 342. This prevents the wheel 326 rotating relative to the housing 10. The wheel 326 is free to turn and move axially within the apertures 342 and to turn relative to the housing and shutter plates 300 and 320. A central compression spring (not illustrated) would locate on a peg 343 and act to bias the locking member 340, and thereby the shutter plates 300 and 320 and wheel 326, outwards of the housing 10 and the shutter plates 300 and 320 rotationally to their relative closed positions.

In use the above shutter plate, locking member and geared wheel assembly components would assume the position illustrated in Fig. 29 prior to bulb insertion.

As a bulb is inserted axially into the lampholder, the shoulder 100 of the bayonet cap engages the ends of the legs 341 of the locking member 340. This moves the locking member inwards of the housing 10 against the force of the springs 117. This action simultaneously turns the wheel 326, which rotates the shutter plates 300 and 320 relative to each other, (in opposite directions) from their closed to their open position. This aligns the two pairs of apertures 301 and 321 in the plates and rotates the limbs 307 clear of the stop ribs 159 in the housing 10. The shutter plate assembly is thus unlocked to be moved axially inwards of the housing 10. The subassembly components thus assume the position illustrated in Fig. 30 after a first stage of axial bulb insertion.

In the second stage of axial bulb insertion, the shutter plates 300 and 320 and locking member 340 are moved fully into the housing by the ends of the bulb.

The pad electrodes 101 engage the respective ends 158 of the contacts 157 which have passed through the aligned apertures 301 and 321 and depress the loaded contacts 157 against the force of the springs 156 (ref Fig. 40) until the bayonet pins reach the end of the slots 112 when the bulb is rotated in the housing 10. This locates the bayonet pins in the resting points at the end of the slots 113.

Referring now to Figs. 31 to 33, this illustrates a further alternative shutter and locking member and geared wheel assembly. As with the previous embodiment, an outer shutter plate 420 and inner shutter plate 400 are secured together against relative axial movement by, for example, screw means or snap engaging means. Gear teeth 402 and 424 are provided in the opposing surfaces of plates 400 and 420 respectively. A geared wheel member 426 is also engaged in mesh with the pair of shutter plates, arranged so that its teeth 427 engage the two sets of teeth 402 and 424. A plain band 428 of the wheel engages in a vertical slot or keyway in the housing wall, preventing the wheel 426 rotating relative to the housing 10. The wheel 426 is free to turn relative to the housing 10 and shutter plates 400 and 420 and to move axially relative to the housing within the keyway.

A pair of pegs 409 are defined on and extend outwardly from the inner plate 400. The pegs 409 engage angled slots 442 defined in limbs 441 of the locking member 440 and provide that, as the locking member 440 is moved inwards of the housing 10, the angled slots 442 move the pegs 409. This action rotates the inner plate 400 from its closed to its open position. The inner plate 400 simultaneously turns the geared wheel 426 to rotate the outer plate 420 in the opposite direction to the inner plate from its closed to its open position.

This aligns the two pairs of apertures 401 and 421 in the two shutter plates 400 and 420 respectively. Shutter limbs 407 are also rotated clear of stop ribs 159 in the housing 10, freeing the shutter assembly, geared wheel and locking member to be moved fully, axially inwards of the housing 10 by the end of the bulb. The pad electrodes 101 of the bulb engage the ends 158 of the resilient terminal contacts 157 which have passed through the aligned pairs of apertures 401 and 421 in the plates 400 and 420. The pad electrodes 101 depress the loaded contacts 157 further inwards of the housing against the force of the springs 156 (ref Fig. 40) until the bayonet pins reach the ends of the slots 112 when the bulb is rotated in the housing 10 to locate the bayonet pins in the resting points at the end of the slots 113.

A compression spring (not illustrated) would locate on the peg 443 and act to bias the locking member 440 and thereby the shutter plate and wheel assembly outwards of the housing 10 and the shutter plates 400 and 420 rotationally to their closed positions. It should be noted that more than one geared wheel may be used to act between the pair of shutter plates.

Referring now to Figs. 34 and 35, there is illustrated a further shutter and locking plate arrangement for insertion into a lampholder housing.

Again, a pair of shutter plates 500 and 520 are secured together against relative axial movement. Fig. 34 illustrates the relative, assembled position of the shutter plates 500 and 520 and locking member 540 in the position they would assume in the lampholder housing prior to bulb insertion. At this stage, the plates 500 and 520 are in their closed position, in which the two pairs of apertures 501 and 521 in said plates 500 and 520 are non-aligned. The locking member 540 defines formations 544A and 544B on one of its limbs 541A. These formations 544A,B co-operate with formations 545 and 524 in the side of the outer shutter plate 520. The other limb 541B of the locking member 540 defines similar formations (not visible) which co-operate with formations defined in the side of the inner plate 500. A compression spring (not illustrated) would locate on the peg 543 and be arranged to bias the locking member 540 outwards of the housing 10.

In use, as a bulb is inserted axially into the lampholder, the shoulders 100 of the bayonet cap engage the ends of the limbs 541A, B, moving the locking member 540 inwards of the housing 10 against the force of the biasing means. This action simultaneously causes the ramp formations 544A on the locking member limb 541A to engage the ramp formations 545 on the outer shutter plate 520. This rotates the shutter plate 520 from its closed to its open position. Simultaneously, formations 544C on the opposing locking member limb 541B engage co-operating formations on the inner shutter plate 500. This action rotates the inner shutter plate 500 in the opposite direction to the outer plate 520 from its closed to its open position. Thus, the two pairs of apertures in the plates 500 and 520 are aligned and the shutter stop limbs 507 have rotated clear of the stop ribs 159 in the housing 10 (ref Fig. 35). As with the previous embodiments, the pad electrodes engage the contacts 157, moving the plates 500 and 520 and locking member 540 inwards of the housing 10, depressing the loaded resilient contacts 157 until the bulb is fully axially inserted and rotated to locate the bayonet pins in the resting points in the slots 113.

As the bulb is removed axially from the lampholder, the central compression spring moves the locking member 540 and shutter plates 500 and 520 outwards of the housing 10, until the shutter plates abut against the support ledges 116 defined in the housing wall. The ramp formations 544B on the locking member limb 541A cooperate with the ramp formations 524 on the outer plate 520 to rotate the plate 520 from its open back to its closed position. Simultaneously, ramp formations (not visible) on the locking member limb 541B act on ramp formations (not visible) on the inner shutter plate 500 to move it from its open back to its closed position.

This results in non-alignment of the two pairs of apertures in the plates 500 and 520 respectively and relocates the limbs 507 beneath the stop ribs 159 in the housing 10. The locking member 540 locks the pair of shutter plates 500 and 520 in their respective closed positions and against axial movement inwards of the housing 10.

Turning now to Figs. 36 and 37, there is shown an arrangement similar to that of Figs. 34 and 35 in which formations 644A, defined on each limb 641 of the locking member 640, co-operate with formations 645 on the outer shutter plate 620, to rotate the plate 620 from its closed to its open position. Ramp formations 644B also defined on each limb 641 of the locking member 640, cooperate with formations 602 on the inner shutter plate 600 to rotate the plate 600 (in the opposite direction to the outer plate 620) from its closed to its open position. This aligns the two pairs of apertures in the plates 600 and 620 and unlocks the plates 600 and 620, permitting them to be moved inwards of the housing 10 by the bulb. The pad electrodes 101 engage the contacts 157 and move them inwards of the housing against the force of the springs 156, until the bulb is fully axially inserted and rotated to rest. In this embodiment a torsion spring (not visible) is arranged to act between the shutter plates 600 and 620 to bias them rotationally to their respective closed positions in the absence of a bulb.

The central compression spring will bias the locking member 640 and shutter plates 600 and 620 outwards of the housing 10 and against the support ledges 116 in the housing wall.

It will be appreciated that various modifications may be made to the illustrated embodiments.

Claims

A safety lampholder for a bayonet bulb comprising a housing defining slots to receive bayonet pins of an inserted bulb, contacts within the housing for electrical connection to a power source to supply electricity to the bulb, axially moveable and rotatable shutter means in the housing for selectively obstructing access to the contacts and moveable between a first inoperative position in which the contacts are shielded by the shutter means and a second operative position in which the contacts extend through apertures in the shutter means for bearing against a bulb, locking means within the housing for selectively inhibiting axial displacement of the shutter means and means for driving rotation of the shutter means and arranged so that axial insertion of a bulb into the lampholder is effective to actuate rotation of the shutter means from the first position to align apertures in the shutter means with the contacts and to release the locking means to displace the shutter means axially inwardly of the housing to the second operative position.
2. A lampholder according to Claim 1 wherein the locking means are axially moveable within the housing and the means for driving rotation of the shutter means are actuable upon axial displacement of the locking means.
3. A lampholder according to Claim 2 having means for guiding axial displacement of the locking means.
4. A lampholder according to Claim 2 or 3 wherein the locking means includes an axially moveable locking member which extends to the open end of the lampholder housing to bear against a bulb, the locking member having formations to engage with the shutter means to inhibit axial displacement of the shutter means until the locking member has first been displaced axially inwardly of the housing by an inserted bulb.
5. A lampholder according to Claim 4 wherein the housing has formations to cooperate with locking member formations to inhibit rotation of the shutter means until the locking member has first been displaced inwardly of the housing.
6. A lampholder according to Claim 4 or 5 wherein the locking member includes a body having apertures therein to receive the bulb engaging contacts and has one or more limbs extending from the body to the open end of the housing for engagement with an inserted bulb.
7. A lampholder according to any one of claims 4 to 6 wherein the locking member includes two diametrically opposed limbs arranged to extend to the open end of the housing.
8. A lampholder according to Claim 6 or 7 wherein the body of the locking member locates between the shutter means and the closed end of the housing and the limbs of the locking member extend through openings in the shutter means.
9. A lampholder according to any one of claims 6 to 8 wherein the shutter means are rotatable with respect to the locking member between a first position in which respective apertures in the locking member and shutter means are obstructed and a second position in which they are aligned.
10. A lampholder according to Claim 9 wherein the locking member has formations for location in shutter apertures when the locking member and shutter means are in the first position.
11. A lampholder according to any one of claims 4 to 10 wherein the locking member is biased outwardly of the housing.
12. A lampholder according to Claim 11 having resilient bulb engaging contacts which act to bias the locking member outwardly of the housing.
13. A lampholder according to any one of claims 4 to 12 wherein the locking member has formations arranged to interengage formations on the shutter means to drive rotation of the shutter means upon axial displacement of the locking member.
14. A lampholder according to Claim 13 wherein the interengageable formations on the locking member and shutter means include an inclined surface and a follower for the inclined surface.
15. A lampholder according to Claim 14 wherein one of the shutter means and locking member includes diametrically opposed inclined slots and the other includes diametrically opposed radially extending projections to engage said slots.
16. A lampholder according to any preceding claim wherein the shutter means comprises two apertured members, capable of rotation about a common axis, between a first position in which apertures in the members are obstructed and a second position in which they are aligned to receive the bulb engaging contacts.
17. A lampholder according to Claim 16 wherein the shutter members are secured against relative axial movement.
18. A lampholder according to Claim 16 or 17 wherein the shutter members are arranged for contrarotation.
19. A lampholder according to Claim 18 wherein the shutter members are provided with circumferentially spaced formations on opposing surfaces and a displaceable member having formations interengageable with shutter member formations is arranged therebetween to be rotatable about an axis generally perpendicular to the common axis of rotation of the shutter members so as to drive contrarotation of the shutter members.
20. A lampholder according to Claim 19 wherein the locking member has axially spaced formations, engageable with displaceable member formations such that axial displacement of the locking member actuates rotation of the displaceable member to drive contrarotation of the shutter members.
21. A lampholder according to Claim 19 wherein one of the shutter members is arranged to engage a locking member such that axial movement of the locking member drives rotation of that shutter member and the displaceable member so that the displaceable member actuates contrarotation of the second shutter member.
22. A lampholder according to Claim 18 wherein the locking member has inclined ramp formations arranged to engage ramp formations on the shutter members to drive contrarotation thereof.
23. A lampholder substantially as hereinbefore described with reference to, and as illustrated in, any one of the accompanying drawings.