AU700240B2 - Lampholder - Google Patents

Description

0 6 0 *9O10 I Regulation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Ineto Tte LAPODR Th folwn sttmn safl ecipino hsivnin Theolowing tebstmethisdafl desriptmin ofknwt thisenin Applicant:la

LAMPHOLDER

The present invention relates to a safety lampholder to receive a bayonet type bulb and in particular to a shuttered safety lampholder.

Shuttered lampholders have been proposed, for example, in US 4461523, French 2403665, GB'2267607 and GB 2269270. Such lampholders are generally required to allow 3.5mm diameter bulb engaging contacts to pass through a shutter mechanism to engage the pad electrodes E of a bulb. To achieve this the holders typically require a large degree of rotation of the bulb in the customary slots provided in the lampholder body. The horizontal portion of the slots are thus long and i prone to fracture in use.

e A further problem arises in that, in order to comply with requirements such as defined in British Standard I 20 BS5042, which concerns lampholder construction, a bulb should be rotated in a lampholder by no more than a certain predetermined amount. In addition, the I requirements set a minimum diameter of the bulb engaging contacts. The above prior art shutter designd are I' i expected to be unsatisfactory in that they would not comply with British, and possibly, International I standards. This is on the grounds that they would J, j J 2 require rotation of a bulb far in excess of the limit to provide aperturing in the shutter adequate to allow contacts of appropriate diameter to extend therethrough.

The present invention aims to provide an improved shuttered safety lampholder. Embodiments of the invention also seek to provide a lampholder which will readily convert from a switching type to a non-switching type and using common components.

Accordingly, the present invention provides a safety 'lampholder for a bayonet bulb comprising a body defining slots to receive bayonet pins of an inserted bulb, bulb engaging contacts within the body for electrical connection to a power source to supply electricity to the r bulb and shutter means in the body for selectively Qw obstructing access to the contacts, the shutter means comprising apertured shutter members capable of relative rotation about a common axis between a first position in 20 which their apertures are obstructed and a second position in which they are aligned and arranged so that rotation of an inserted bulb actuates rotation of a first shutter member, wherein means are provided on the first and second shutter members for actuating contrarotation of the second shutter member upon rotation of the first shutter member between a first inoperative position in which the contacts are shielded by at least one of the i'

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aas--- rr u~ .4 4Y 4 4, 44r~ *i 44.4 4 4) 4 44 4 4 44 i 4 4~ 944 44 *4 4i_ 3 shutter members and a second operative position in which they extend through aligned apertures in both shutter members for bearing against a bulb, which means comprise hump formations on the first and second shutter members, which hump formations have respective ramp faces which ride over one another on rotation of the first shutter members thereby to cause axial movement and contrarotation of the second shutter member.

The present invention may thus permit, for example, for a 30" rotation of a bulb in the slots to allow apertures to be opened in the shutter means which is equivalent to a 45" rotation of a bulb in prior lampholders. Thus using this simple contramotion principle the horizontal portion of the slots may be 15 much shorter than in prior lampholders and therefore less lightly to fracture. Also, the proposed lampholder may comply more readily with existing British Standards on lampholder construction.

Typically, a lampholder according to the present invention may include first and second apertured shutter members which are both axially moveable within the lampholder body. Suitably contrarotation of the first and second shutter members also involves relative axial displacement of the two members.

25 Suitably, in the present lampholders, power supply terminals are supported in a terminal block which closes the end of the lampholder body or housing opposite the bulb receiving end. Such a terminal block is typically fixedly mounted therein and acts to retain other 4 components in the housing. The power supply terminals may take various forms as discussed in more detail below.

Most preferably one of the shutter members, suitably the second shutter member, acts as a contact carrier to support the bulb engaging contacts in the lampholder body. The contact carrier may also act as a shutter member by shielding at least part of the contacts from apertures in the other shutter member. Preferably, a first rotatable shutter member is biased outwardly of the housing by such a contact carrier via bulb engaging S. contacts which most preferably include resilient spring t: means. The first shutter member is preferably biased against formations n the wall of the lampholder body to its first position in which it is locked against rotation relative to the housing, and axial insertion of a bulb is p capable of displacingthe first shutter member inwardly of the housing to an unlocked portion.

20 Preferably, the bulb engaging contacts are in the form of hollow metal cylinders, closed at one end and flared at an open end and by means of which flared ends they are retained in stepped apertures in a contact carrier provided by the second shutter member.

Compression springs may in a known manner provide a resilient bridging connection between the pair of bulb engaging contacts and bridging contacts supported by a ean. Th fist suttr meberis pefeablybiaed contact plate which is fixed in relation to the lampholder body. Such bridging springs may allow the bulb engaging contacts to move axially/rotationally when supported within the carrier and relative to the bridging contacts.

The most preferred means for actuating contrarotation of the second shutter member comprise circumferentially spaced formations on opposing surfaces of the first and second shutter members. Suitably such :.surface formations take the form of interengagable hump formations, each respective hump formation comprising oppos ng ramp surfaces. Preferably the ramp surfaces in each hump formation are of different respective lengths.

1 Prefe rably, the interengaging hump surface formations, such as ramps, are defined on and between the first hutter member and carrier and are located on the .e periery of each component. Most preferably each I 20 component is provided with two circumferentially spaced ad diametrically opposed hump formations, the pair of kump formations on the contact carrier acting as cam followers to follow the profile of the humps defined on the first shutter member.

Preferably, each hump formation on the first shutter member comprises first and second ramp surfaces, the /1' u 1 6 first .'off' ramp surface most preferably inclined at about and the second 'on' ramp surface extending to a lower level than the foot of ths 'off' ramp.

Preferably, formations' are also defined between various selected components to ensure that the rotatable components rotate about a common axis.

Examples of shuttered lampholders according to w ;embodiments of the invention will now be described further by way of example, only, with reference to the accompanying drawings, in which:- Fig. 1 is an exploded view of a lampholder according to a first embodiment of the present invention; S" Figs. 2 to 4 are cross-sectional views of an assembled lampholder of Fig. 1 showing the relative 20 position of the components, Fig, 2. prior to bulb insertion, Fig. 3 when a bulb has been fully inserted and Fig. 4 when the transverse switchbar has been moved to its 'on' position.

Fig. 5 is a cross sectional view of a lampholder corresponding to that of Fig. 1 from which the transverse S switchbar has been omitted thus converting it to a nonr 7 switching type. The components are illustrated in the 'on' position.

Fig, 6 is a cross-sectional view of a lampholder according to a further embodiment similar to that of Fig.

from which has been omitted that support plate and its bridging contacts, and in this embodiment the bridging springs locate directly onto modified flex terminals.

Figs. 7 to 12 are part cross-sectional views Sillustrating the relationship between the hump formations i t on the shutter member and contact carrier at various stages of bulb insertion.

a Fig. 13 is an exploded view of a lampholder according to a further embodiment similar to that of Fig.

a 1 and provided with a modified terminal block supporting o insulation displacement terminal assemblies.

*o i :7 20 Fig. 14 is a cross-sectional view of an assembled lampholder incorporating the modified terminal block of Fig. 13, showing the position of the components prior to bulb insertion.

Figs. 15 and 16 are top and bottom views of the screwle 3 a screwless terminal block of Figs. 13 and 14. 1 1 8 Fig. 17 is a perspective view of the assembled lampholder of Figs. 13 and 14 illustrating the relative position of the components prior to bulb insertion.

Fig. 18 is an exploded view of a further alternative lampholder.

Fep ease of reference the same numerals have been used throughout to denote similar components.

Referring now to Fig.s 1 to 4 and 7 to 12 there is :42 illustrated a shuttered lampholder according to a first aspect of the present invention. The lampholder comprises a hollow cy~.ndrical body or housing 1 into one end of which can be received the cap of a bayonet type bulb. The housing 1 is provided with two slots 2, each to receive the bayonet pins of an inserted bulb.

The slots include an axial portion 3 and a circumferential portion 4. The housing 1 is also 20 provided with a screw thread 6 to retain a shade locking ring and a further screw thread to retain a cover (not shown) to cover the screw terminals 99 whilst providing an entry port for the power supply flex.

i 25 In this embodiment shutter means is made up of first and second rotatable shutter members w.lch may

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r selectively obstruct the bulb engaging contacts of the !1i, i- 4,.

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#4 .9.l *94 9 .9P 9 lampholder. In this case the first shutter member forms the principal shield for the contacts. A second shutter member 40 in use shields an extent of the bulb engaging contacts and also acts as a contact carrier. In the following description, for brevity, the first member will be referred to as the "shutter 20" and second member as "carrier Annular support ledges 12 are provided internally in the housing wall to support the limbs 21 of shutter S and by means of which the shutter is retained in the housing. Vertical stop faces 14 and 14A are also defined in the housing wall to limit relative rotation of the shutter 20 and carrier 40. Ledges 13 are defined 15 adjacent switchbar cutouts 8 to support a contact plate and four circumferentially spaced vertical ribs 10 are provided to support the terminal block within the housing 1. Preferably, the terminal block snap-engages the housing to the secured therein in fixed relation. Two 20 pairs of diametrically opposed apertures 11 are also provided in the housing wall adjacent its closed end.

The function of apertures 11 will be described at a later stage.

Rotational stop faces 18 are also defined internally in the housing wall. The end of the housing opposite the ,bulb receiving end is closed by a terminal block 90 i t

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i e r k- r AI supporting a pair of flex engaging terminals 99 "which extend through the terminal block so as to be accessible on both sides thereof.

The shutter 20 locates in the bulb receiving end of the housing 1 and comprises a disc shaped body portion with a pair of limbs 21 extending therefrom. The limbs 1 extend to the housing slots and locate on the support ledges 12. The limbs 21 are also provided with slots 22 for engagement with the bayonet pins of an inserted bulb. i Rotational stop faces 28 are provided on the sides of the S: shutter 20 to engage the vertical stop faces 18 in the housing as described above. The stop faces 18 require that the shutter 20 is moved inwards of the housing 1 to clear the stop faces 28 in order to unlock it to be rotated relative to the housing 1 and carrier S

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A pair of stepped elongated apertures 23 are e provided in the surface of the body portion of the 20 shutter 20 and a vertically extending centralising peg 24 also extends from the inner surface of shutter 20. Two i diametrically opposed hump formations 25 are defined on and extend from the inner surface of the shutter facing the carrier 40. Each hump formation 25 comprises i 23 a first 'off' ramp 27 and a second 'on' ramp 26. Preferably, the 'off' ramp 27 is inclined at 400 and the ramp 26 is inclined at 45*. Also the 'on' ramp 26 i: n 11 is preferably longer than the 'off' ramp 27 to extend to below the level of the bottom of the 'off' ramp 27. In use the shutter 20 is arranged so as to be movable axially and rotationally with respect to the housing 1.

The contact carrier 40 is located in the housing 1 and supported on the shutter 20. The contact carrier comprises a generally disc shaped member having a central aperture 41 to accommodate the peg 24 of the shutter A pair of spaced apertures 42 are also provided in the Ssurface of the carrier 40 to receive bulb engaging contacts 50. The apertures 42 are stepped to retain bulb engaging contacts 50 therein by means of their flared -ends 52. The ends of the bulb engaging contacts 50 in use, are capable of protruding imm past the outer surface of the shutter 20 when in their operative position.

4 A pair of surface formations in the form of bosses S" 47 depend from the outer surface of the carrier 40 and 20 act to shutter a main body portion of the contacts 50. i In this respect the carrier also acts as a shutter member. The free ends of the contacts (approximately protrude from the bosses 47 and are shuttered in recess 23A in the inner surface of the shutter 20 when I said contacts are in the inoperative position of the 4 Ilampholder (see Fig. A pair of diametrically opposed i hump formations 44 are defined on the periphery of the 6.-1 4' 12 outer surface of the carrier 40 to interengage respective hump formations 25 on the shutter 20. The hump formations 44 act as cam followers to follow the contour of the humps 25 as the shutter 20 and carrier 40 are moved relative to each other on bulb insertion. The carrier 40 is arranged so as to be movable axially/rotationally with respect to the housing 1.

A contact support plate 60 locates in the housing 1 I on support ledges 13 and comprises a generally flat ;rectangular plate provided with a pair of spaced apertures 63 to receive bridging contacts 56. Bridging springs 55 are also arranged to act between the bridging contacts 56 and bulb engaging contacts 50. One end of each spring 55 locates within a contact 56 the other end of the spring locates on or within a bulb engaging contact 50. In this respect the springs 55 provide a 1 suitable, electrical bridging connection between the two pairs of contacts 50, 56. The springs 55 also S""i 20 accommodate approximately 150 rotational movement of the .4 bulb engaging contacts 50 relative to the bridging contacts 56. The contact plate 60 is in fixed relation to the housing 1 and simply acts to support the bridging contacts 56. The contacts 56 are also free to be moved axially against the force of the springs 55. A transversely movable switchbar 70 is mounted in i j 13 the housing 1 between the terminal block 90 and support plate 60. The switchbar is slidably mounted in the housing for movement between a first inoperative position and a second operative position. The switchbar 70 is also provided with a pair of stepped, spaced contact receiving apertures 73. Stop faces 75 limit transverse movement of the switchbar 70 and its end portions 71 and 72 are adapted to pass through slots 8 in the housing wall. A pair of switching humps 74 are also provided on 10 the surface of the switchbar facing the contact plate i In use, the humps 74 engage the respective bridging contacts 56 displacing said contacts 56 outwards of the Shousing against the force of the springs $5 are thereby providing a snap-action switch mechanism. A further pair 15 of bridging contacts 80 locate in stepped apertures 73 and provide an electrical bridging connection between the flex terminals 99 in the terminal block 90 and the bridging contacts 56 in the support plate 60 when the switchbar 70 is in its second operative position. The electrical connection is broken when the switchbar 70 is in its first inoperative position.

In the alternative to the illustrated embodiment, a snap-action switch mechanism may be achieved in a conventional manner by providing bridging contacts 56 with flared ends. Such contacts would bias a contact plate 60 via the springs 55 inwards of the housing 1.

it 14 and support-plate 60. The.plate 60 would be free to be moved outwards of the housing 1, such that transverse movement of the switchbar 70 between its two positions causes the plate 60 to be moved axially of the housing against the force of the contacts 56 and their biasing springs 55 as the pairs of humps on the switch are forced past the humps on the plate 10 Returning to the illustrated embodiment, the shutter i 20 is rotatable between a closed position in which the i contacts 50 are non-aligned with the apertures 23 and the extreme ends of the contacts 50 are located in recesses 23A in the stepped apertures 23. Rotation of the bulb in T: 15 the housing 1 causes the shutter 20 to rotate with it from its closed to its open position 30" rotation ref Figs. 7 to The action causes the carrier 40 to be moved inwards of the housing 1 as its humps 44 ride up t respective ramp faces 27 on the shutter 20. The carrier i 40 moves outwards of the housing 1 as the humps 44 move part way down the ramps 26 to a position illustrated in Fig. 8. The bulb has now finished driving the shutter as it has moved its 30 in the slots. The carrier 40 i is now rotated a further 150 axially in the opposite i direction to the shutter 20 by the force of the loaded contact 50 and outwards of the housing 1. The humps 44 move to the foot of the ramps 26 and this action causes r ji r the contacts 50 to extend through the now formed apertures in the shutter means to engage respective pad electrodes 100 of an inserted bulb.

Removal of a bulb causes the shutter 20 to rotate from its open back to its closed position (ref Figs. to 12) and the humps 44 to ride up the ramp faces 26.

This moves the carrier 40 inwards of the housing 1 and thereby the contacts 50 back through the apertures in the shutter means. When the bulb has been rotated fully in j the slots (ref Fig. 11) the humps 44 have moved over the apex of the humps 25 and are part way down the ramp I faces 127. At this stage the loaded contacts 50 will automatically move the carrier 40 back to its first 15 position in which position the humps 44 are located at o the foot of the ramps 27.

Upon axial removal of a bulb the loaded contacts move the carrier 40 and thereby the shutter 20 outwards of the housing 1. The limbs 21 of the shutter 20 locate on the support ledges 12 and the stop faces 28 on the shutter located behind the vertical stop faces 18 in the i housing wall thereby locking the shutter 20 against rotation relative to the housing 1 and in its first position. 17- i ia In use with the lampholder of Figs. 1 to 4 assembled

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16 and with no bulb present the lampholder components assume the position illustrated in Fig. 2, where the slots 22 are aligned with the axial portion 3 of the slots 2.

The contacts 50 are located behind the inner surface of the shutter 20 and the ends of said contacts 50 are shielded in the recesses 23A'defined in the inner surface of the shutter 20 and so as to be not visible or accessible from the open end of the housing. The carrier 40 is biased outwards of the housing 1 by the contacts 10 and their biasing springs 55, and the humps 44 on the carrier 40 are biasing the shutter 20 outwards of the housing 1 and against the support ledges 12. The humps S" 44 are located at the foot of the ramps 27 and the shutter 20 is therefore in its closed position and locked 0S .00.

15 against rotation relative to the housing 1. The transverse switchbar 70 is in its first inoperative position, the contacts 80 being non-aligned with the contacts 56 and terminals 99.

Insertion of a bulb is done in two stages, an axial stage and a rotational stage. As a bulb is inserted axially into the lampholder the bayonet pins engaqe the aligned slots 3 and 22 and the pad electrodes 100 on the bulb engage the outer surface of the shutter 20. This I moves the shutter 20 and thereby the carrier 40 inwards of the housing 1 against the force of the loaded contacts raising the stop faces 28 on the shutter clear of the 17 stop faces 18 in the housing 1 and unlocking the shutter to be rotated relative to the housing 1 and carrier As the shutter 20 is rotated by the bulb the humps 44 move up the ramps 27 over the apex and part way down ,the ramps 26, at which stage the loaded contacts 50 take over moving the carrier 40 further outwards of the 4 chousing 1, the humps 44 moving further down the ramps 26 and the contacts 50 passing through apertures in the shutter 20 to engage respective pad electrodes of the einserted bulb. The lampholder components then assume the position shown in Fig. 3 when a bulb is fully inserted.

I: 15 The switchbar 70 may now be moved manually transversely of the housing 1 from its inoperative position to its operative position (ref Fig. 4) in which p position the contacts 80 bridge the terminals 99 and contacts 56 and energise the inserted bulb. The switchbar 70 may be moved between its two positions in conventional manner in order to switch the lampholder 'on'l and 'off' making and breaking the electrical connection between the terminals 99 and bridging contacts 56.

As the shutter 20 is rotated by the bulb on bulb removal the humps 44 -move up the ramps 26 and over the I tt 18 apex of the humps 25 and part way down the ramps 27.

This moves the contacts 50.back through apertures in the shutter 20 (ref Fig. 11) when the loaded contacts 50 take over moving the carrier 40 such that the humps 44 locate at the foot of the ramps 27.

As the bulb is removed axially from the lampholder the loaded contacts 50 move the carrier 40 and thereby the shutter 20 outwards of the housing 1. The limbs 21 10 locate on support ledges 12 and the lampholder components assume their first position illustrated in Fig. 2 in which the shutter is locked against rotation and the

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contacts 50 are located behind the shutter means are inaccessible and not visible.

Referring now to Fig. 5, this illustrates an alternative to the lampholder of Figs. 1 to 4 in which the switchbar 70 has been omitted. The terminal block has also been rotated 90* such that the vertical ribs defined in the housing wall locate within cutouts 94 in the terminal block 90. Thus allows the terminal block to be fixedly mounted in the housing 1 at a lower level than in the previous embodiment such that the terminals 99 may engage the bridging contacts 56. Thus, the switching lampholder of Figs. 1 to 4 isisimply converted to a nonswitching type. All other features of this embodiment correspond to those of Figs. 1 to 4.

19 Referring now to Fig. 6, in this embodiment a switchbar 70, contacts 80,.support plate 60 and bridging contacts 56 have been omitted. Modified screw terminals 99A are fixed in the terminal block 90m, the terminals 99A defining, bosses 99C onto which one end of bridging springs 55 locate. The other ends of the springs 55 are supported on or in the bulb engaging contacts 50 to provide a lampholder of non-switching type. All other features of this embodiment are identical to those of o* 10 Figs. 1 to 4.

Referring now to Figs. 13 to 17 there is illustrated a further embodiment of the present invention in which a modified terminal block 200 is provided which fixedly snap-engages the housing 1 and is supported on the ledges 13. The terminal block 200 is provided with a pair of screwless terminals 160 of the guillotine type which have apertures 162 with intersecting slots 163 and deflected opposing edges 161. The terminals are slidably mounted in horizontal slots 209 for transverse movement relative to the housing 1. Hollow metal cylinders 150 closed at one end and with the other end flared, which are generally similar to the contacts 50, locate within the springs 55. The cylinders 150 are supported by their flared end 152 which engage the ends of springs 55. The ends of the respective springs 55 with the metal cylinders 150 mounted therein locate in apertures 220 in the terminal block 200. The springs 55 urge the cylinders 50 against the terminals 160 to provide a good electrical connection between said terminals and the bulb engaging contacts 50 in the carrier 40. The terminals 160 are slidably mounted on and transversely movable with respect to the cylinders 150.

In use, an insulated conductor is inserted through the aperture 205 such that it passes through the aligned 10 hole 162 in the terminal 160 and to the bottom of the cylinder 150, said cylinder 150 providing a stop for the insulated conductor. The guillotine terminal 160 may now I be moved transversely relative to the housing and terminal block by means of a screwdriver which is S 15 inserted through one of the apertures 11 provided in the housing wall (ref Fig. i17). Angled faces 216 on the terminal block act. ,torMide the screwdriver tip to the centre of the end of the terminal 160. In a known manner, as a terminal 160 is moved transversely to its operative position, it displaces the insulation on a conductor forcing the conductor tightly into the narrow slot 163 to make an acceptable electrical connection j between the insulated conductor and terminal 160. This electrical connection is made from the terminal 160 through to the bulb engaging contacts 50 via the cylinders 150 and springs L j 21 The vertical surfaces 215 on the underside of the terminal block 200 act as screwdriver stops controlling transverse movement of the terminals 160 in the slots 209. To remove a conductor which has been guillotined to, for example, re-wire the lampholder, it is simply necessary for a screwdriver to be inserted through the aperture 11 in the opposite side of the housing to move the terminal 160 back to the opposite side of the housing |o to move the terminal 160 back to the position illustrated t 10 in Figs. 15 and 16. At this stage the conductor may be ft withdrawn from the aperture 205.

Screwless terminals of this type are becoming increasingly more popular as they provide a cheap and :r 15 convenient alternative to conventional screw type pillar terminals.

S' In this embodiment the individual insulated conductors and also the outer sheath of the flex are gripped by an elaborate lex, restraining means. The insulated conductors are first trapped by the sharp edges 21 1 at the mouth of the apertures 205 as they are bent downwards and turned at 90' to be forced beneath the cutaway trap 208, the outer sheath then being forced into tP base of the vertical housing 210 and between the barbs, 207.

V 22 The housing 1, 'shutter 20, contact carrier contacts 50 and bridging springs 55 are components common to this embodiment and the previous embodiments, the shutter means and functioning of this aspect is identical to that of Figs. 1 to 6.

Fig. 18 illustrates a simplified lampholder construction which may be preferred in terms of ease of manufacture. In this case the lampholder body 1 houses io0 a first shutter member 20 which is rotatable by an inserted bulb so as to drive contrarotation of a second e shutter member or contact carrier 40. As in previous embodiments the contrarotation is driven by the opposing members, as explained in relation to Figs. 10 to 12.

In this embodime-t the bulb engaging contacts 509 comprise hollow cylinders 51 closed at one end and which accommodate springs 55. The respective springs 55 are also secured to flex engaging terminals in a terminal S 20 block 90, for supplying electricity to the cylinders 51.

The springs 55 permit axial and angular displacement of cylinders 51 in accordance with displacement of the carrier It will be appreciated that various modifications omay be made to the illustrated embodiments. In I particular the lamholder may accommodate bulb engaging 'm ho er 23 contacts of a host of forms. Also, first and second shutter members may interengage in various ways to ef fect the contrarotation. It is, however, a particular advantage of the present invention in that it provides for one shutter member to drive directly the contrarotation of another shutter member.

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Claims (12)

1. A safety lampholder for a bayonet bulb comprising a body defining slots to receive bayonet pins of an inserted bulb, bulb engaging contacts within the body for electrical connection to a power source to supply 'electricity to the bulb and shutter means in the body for selectively obstructing access to the contacts, the 10 shutter means comprising apertured shutter members capable of relative rotation about a common axis between a first position in which their apertures are obstructed and a second position in which they are aligned and arranged so that rotation of an inserted bulb actuates rotation of a first shutter member, wherein means are provided on the first and second shutter members for actuating contrarotation of the second shutter member upon rotation of the first shutter member between a first inoperative position in which the contacts are shielded by at least one of the shutter members and a second operative position in which they extend through aligned apertures in both shutter members for bearing against a bulb, which means comprise hump formations on the first and second shutter members, which hump formations have respective ramp faces which ride over one -another on rotation of the first shutter members thereby to cause axial movement and coltrarotation of the second shutter 4 444 Ce4 n C ll~i~-I~-~P~W member.

2. A safety lampholder according to claim 1 wherein the first and second apertured shutter members are both axially movable within the lampholder body.

3. A safety lampholder according to claim 2 wherein locking means are provided for inhibiting rotation of at least the first shutter member until it has been displaced axially inwardly of the lampholder body.

4. A safety lampholder according to claim 3 wherein the locking means comprise interengageable surface formations provided in the lampholder body and on the first shutter member.

5. A safety lampholder according to any one of claims 1 to 4 wherein means are provided for biasing the first loop and/or second shutter member outwardly of the lampholder 20 body.

6. A safety lampholder according to any preceding claim wherein means are provided for rotationally biasing the first and/or second shutter member to the first position.

7. A safety lampholder according to claim 5 or claim 6 having resilient bulb engaging contacts which provide a I 1- 26 biasing means.

8. A safety lampholder according to any preceding claim wherein the means for actuating contrarotation of the second shutter member comprise circumferentially spaced formations on opposing surfaces of said first and second shutter members.

9. A safety lampholder according to any one of the preceding claims wherein the second rotatable shutter member acts as a contact carrier.

S.10. A safety lampholder according to any preceding claim t o wherein power supply terminals and bulb engaging contacts are supported in the lampholder body and a pair of bridging contacts are arranged to effect an electrical connection between the terminals and bulb engaging contacts, a transversely movable member being provided in the housing and having limbs which extend laterally 20 beyond the lampholder body, the transversely movable member providing a manually operable switch bar by being displaceable to displace the bridging contacts to make and break the electrical connection between the terminals i and the bulb engaging contacts.

11. A safety lampholder according to any preceding claim wherein the first shutter member has recesss alongside 4 27 its apertures for accommodating the contacts when the lampholder is in the first inoperative position.

12. A safety lampholder substantially as hereinbefore described with reference to, and as illustrated in, any one of the accompanying Figures 1 to 18. DATED: 21 OCTOBER 1998 CARTER SMITH BEADLE Patent Attorneys for the Applicant: PATRICK JAMES DOHERTY 4t 'I"I' 4 s A i 'r'4 IABSTRACT LAMPHOLDER A safety lampholder for a bayonet bulb comprises a body which defines slots to receive the bayonet pins of an inserted bulb. Resilient bulb engaging contacts (50) are provided within the body for electrical connection to a power source to supply electricity to the bulb. Shutter means are also provided for selectively obstructing access to the contacts in the absence of a bulb. The shutter means include two Sapertured shutter members (20, 42) which are rotatable 15 about a common axis between a first (inoperative) ;O 9 Vposition in which their apertures (23, 42) are obstructed and a second (operative) position in which the apertures are aligned to permit the bulb engaging contacts (50) to bear against a bulb. One shutter member (20) is 20 rotatable by an inserted bulb (via slots (22). Formations (25, 44) are provided on opposing surfaces of the shutter members (20, 40) and arranged such that rotation of the first member (20) directly drives contrarotation of the second member 25 Fig 18 i° i