AU5511386A - Lampholder - Google Patents

Description

LAMPHOLDER

The present invention relates to lampholders, and in particular to lampholders in which terminals exposed within a socket defined by the lampholder are isolated from terminals located within the lampholder body to which electrical cables are connected whenever a bulb is not in position within the lampholder socket. European Patent Specification No. 0101257 describes various safety lampholders including a lampholder in which a carrier is movable from a first position to a second position when a bulb is inserted into the lampholder, contacts supported by the carrier and arranged to engage with the contacts of an inserted bulb being isolated from flex terminals when the carrier is in the first position. A latch is provided ^'against which an inserted bulb engages, axial movement of the latch being necessary before the carrier is free to move from the first to the second positions.

In the abovementioned arrangement three relatively movable components are required to form the basic contact isolating structure of the lampholder, that is a housing defining the lampholder socket, a carrier, and a latch.

It is an object of the present invention to provide a safety lampholder in which the relatively movable carrier and latch referred to above are replaced by a single component.

According to the present invention there is provided a bayonet lampholder comprising a housing supporting fixed terminals to which in use electrical cables are connected, the housing defining a socket for receiving an inserted bulb and slots for receiving the bayonet pins of an inserted bulb, a carrier mounted within the housing and supporting contacts arranged to electrically contact a bulb inserted into the lampholder, the carrier being movable between a first position in which the contacts are isolated from the terminals and a second position in which the contacts electrically contact respective terminals, and means for biasing the carrier from the second position to the first position, wherein the carrier supports surfaces which extend adjacent the slots so as to be engaged by the bayonets of an inserted bulb, the carrier and housing define interacting formations such that for the carrier to be moved from the first position to the second position it must initially execute a turning movement within the housing and then an axial movement relative to the housing, and the said carrier surfaces are positioned such that the bayonets of an inserted bulb slide along the said surfaces as the bayonets are pushed into the slots, the slots being inclined to the said surfaces such that the sliding contact between the bayonet and the surfaces causes the carrier to execute the said turning movement. The said carrier surfaces may be defined by the ends of legs supported by the corner and extending along the inside of the socket wall. Alternatively, the said carrier surfaces may be defined by a metal shell which is slidable and rotatable within the socket and into which an inserted bulb is received.

As the said carrier surfaces are arranged around the periphery of the lampholder socket adjacent the slots they are difficult to engage with an inserted finger to accidentally cause the carrier to turn within the housing. It is thus difficult for, for example, a child to accidentally move the carrier to

^• \ a position in which the contacts exposed within the lampholder are connected to the flex supplying power to the lampholder. 5 The slots may extend generally parallel to the direction of insertion of a bulb or may be inclined to the said direction to positively push the carrier around within the socket.

The carrier may be a simple snap inserted fit 10 within the housing. The housing may be in one or two parts for example.

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which: 15 Fig, 1 is a sectional view of a first embodiment of the present invention;

Fig. 2 is a view of the embodiment of^' Fig. 1 but with the carrier moved to the position it will adopt when a bulb is inserted (the bulb being omitted from 20 Fig. 2);

Fig. 3 illustrates the rotation of the carrier which occurs when a bulb is inserted in the embodiment of Figs. 1 to 2;

Figs. 4, 5 and 6 are respectively perspective

25 views of the carrier of the embodiment of Fig. 1, a sectional view through the carrier of Fig. 4, and an illustration of the spring engaged between the carrier and the housing of Fig. 1;

Fig. 7 illustrates an alternative means for 30 connecting the carrier and the housing in the embodiment of Fig. 1;

Figs. 8 and 9 respectively show sectional views of a second embodiment of the invention with the carrier in the position when no bulb is pushed into

35 the housing and the carrier in the position when a bulb has been inserted into the housing (the bulb not being shown in Fig. 9);

Fig. 10 shows four views of a main housing component of the embodiment of Figs. 8 and 9; Figs. 11 and 12 show details of the other component of the housing of the embodiment of Figs. 8 and 9;

Fig. 13 illustrates the structure of a flex terminal provided in the embodiment of Figs. 8 and 9; Figs. 14 and 15 show alternative slot arrangements for incorporation in embodiments of the present invention;

Fig. 16 shows in section a bar switch arrangement for incorporation in an embodiment of the invention such as that illustrated in Fig. 8; and

Figs. 17 to 22 illustrate detailed features of components of the arrangement illustrated in Fig. 16.

Figs. 23 to 25 illustrate an alternative embodiment of the invention in which the carrier comprises a metal shell which is slidable within the socket and which is engaged by the bayonet pins of an inserted bulb; and

Figs. 26 to 31 illustrate the movement of the shell relative to the lampholder housing in the embodibment of Figs. 23 to 25.

Referring to Figs. 1 and 2, the illustrated arrangement comprises a housing 1 within which a carrier 2 is movable from the position shown in Fig. 1 to the position shown in Fig. 2 as a result of the insertion of a bulb (not shown) into the housing 1. The housing supports a pair of flex terminals 3 defining slots into which the wires of the flex are inserted. In a conventional manner the terminals 3 are then pushed down so that the insulation on the wires is cut to obtain a good electrical contact between the wire and the terminal 3. Conventional screw terminals could be used however.

A compression spring 4 is arranged between the housing 1 and the carrier 2 so as to bias the carrier towards the position shown in Fig. 1. The spring imparts axial force to the carrier 2 and also twists the carrier in a clockwise direction relative to the housing when viewed from the open end of the housing into which a bulb is to be inserted. The carrier 2 supports a pair of carrier contacts 5 which are electrically isolated from the terminals 3 when the carrier is in the position shown in Fig. 1 but which electrically contact the terminals 3 when the carrier is in the position of Fig. 2. The housing 1 defines a key 6 intended to run within a keyway 7 provided in the carrier. With the carrier in the position shown in Fig. 1 the key. and keyway are misaligned so that axial movement of the carrier relative to the housing is not possible. When the carrier has been twisted against the force of the spring 4 so as to align the key and keyway the carrier can then be moved axially to the position shown in Fig. 2.

The carrier supports legs defining inclined surfaces 8 which extend across bayonet slots 9 in the housing. When a bulb is inserted a respective bayonet on the bulb contacts each of the inclined surfaces 8. When an axial force is applied to the bulb so as to push it into the housing the bayonets slide down the inclined surfaces 8 and the carrier is thus caused to rotate against the force of the spring 4. This aligns the key 6 and the keyway 7 so that further axial force applied to the bulb moves the bulb and carrier as a body upwards until the carrier contacts 5 engage the flex terminals 3. Fig. 3 is a schematic illustration of the interaction between the slot 9, a bulb bayonet 10 and the inclined surface 8 defined by a leg of the carrier. In the position shown in full line the 5 bayonet 10 is just engaging the inclined surface 8 but the carrier is still in the position illustrated in Fig. 1. In the position shown in dotted lines the carrier has been rotated by the distance indicated by arrow 11 as a result of the bayonet 10 sliding along 0 the surface 8. Further axial movement of the bayonet 10 causes the bulb to engage the carrier contacts and move the carrier axially so as to achieve contact between the flex terminals 3 and the carrier contacts 5.

_]_5 Figs. 4 and 5 illustrate the carrier 2 in greater detail. It will be seen that the carrier supports a central pin 12 around which the spring -4 is engaged. The inclined surfaces 8 define an angle of approximately 45° relative to a line drawn through

20 that surface parallel to the axis of the pin 12.

Fig. 6 illustrates the spring 4. The ends 13 of the spring engage in a slot in the housing (not shown) and against a formation 14 defined by the carrier so as to support the carrier contacts. The

25 orientation of the spring ends 13 and the positions in which they engage the housing and the carrier are such that it is necessary to pretension the spring by twisting the carrier relative to the housing prior to its insertion. The carrier is retained within the

3₀ housing by a lip 15 (Fig. 2) defined around the opening of the socket in the housing. Thus a very simple assembly process is all that is required to engage the carrier within the housing.

Fig. 7 shows an alternative arrangement for

₃5 securing the carrier within the housing. Rather than relying upon a lip 15 around the socket opening in the housing the pin 12 has a deformable enlarged head 16 which is a snap fit within a socket 17. A tapered rim 18 around the opening of the socket 17 prevents withdrawal of the head of the pin 12 from the socket 17.

Figs. 8 and 9 illustrate an alternative embodiment of the invention which is very similar to that of Figs. 1 and 2 except for the fact that the housing is in two parts. The housing comprises a main component 19 and a upper component 20 which is a snap-fit within the main component. The operation of the device is substantially the same as that of the device of Figs. 1 and 2. Fig. 10 shows various views of the main housing component 19 and Figs. 11 and 12 show two views of the upper housing ' component 20. Fig. 13 is a perspective view of the flex terminal 3 of the type used in the embodiments of Figs. 8 and 9 and also the embodiment of Figs. 1 and 2.

Figs. 14 and 15 show two alternative arrangements to the conventional axial slot provided in normal bayonet lampholders. In the arrangement of Figs. 14 and 15 the lead into the slots are inclined so that the bulb must be simultaneously twisted and moved axially as it is inserted into the lampholder. In each of the drawings circles 21, 22, 23 and 24 show the positions adopted by the bayonet pins of an inserted bulb as it is progressively moved into final engagement with the end of the J slots. In position 21 the edge 25 of the carrier arm is in its normal rest position. In position 22 the edge 25 of the carrier arm has to be displaced and this can only be as a result of rotation of the carrier relative to the housing of the lampholder. No axial movement of the carrier is at this stage possible. In position 23 the carrier arm has rotated sufficiently to enable axial movement of the carrier and the contacts on the bulb will be in contact with the contacts supported by the carrier, the carrier contacts being resiliently supported. In position 24 the bulb is fully engaged in the lampholder. In the case of the arrangement of Fig. 14 twisting of the carrier continues as the pins move from position 23 to 24. There is thus a considerable displacement of the carrier in rotation relative to the housing. In the arrangement of Fig. 15, no further rotation of the carrier occurs as the pins move from position 23 to 24. The arrows 26 indicate the total rotation of the carrier relative to the housing.

Turning now to Fig. 16, the illustrated arrangement is similar to that of Fig. 9 except ' for the fact that a plastics switch stud 27 is supported on top of the central spring 28 so as to project into a cavity defined in the head 29 of the lampholder housing. A bar switch member 30 is slidable within the cavity defined in the housing head 29.

Referring now to Figs. 17, 18 and 19, Fig. 17 is a top view of the head of the lampholder housing 29 showing terminals 31 and 32 and Figs. 18 and 19 illustrate the structure of terminals 31 and 32 respectively. Terminal 31 is provided with an aperture 33 having a narrowed neck portion 34. As shown in Fig. 17 the live conductor of a power supply flex (not shown) is inserted into a channel 35 extending across the position of the terminal 31. The live conductor is pushed through the aperture 33 and the terminal 31 is then pushed down into the housing member so that the edges of the narrowed neck portion 34 cut through the insulation on the conductor. Terminal 31 is thus connected to the live conductor. The neutral conductor is received in a channel 36 and connected to a neutral terminal 37 in an equivalent manner to that of terminal 31. The terminal 32 is thus isolated from the live terminal 31. The terminal 31 is not connected to the terminals within the lampholder housing and accordingly the contacts on the carrier make contact with the neutral terminal 37 and the other terminal 32.

The bar switch member 30 supports a resilient leaf spring 38 which can be moved from a position in which it interconnects terminals 31 and 32 to a position in which the terminals 31 and 32 are isolated from each other. On the underside of the switch member 30 is a cavity 39 divided into two sections by a raised portion 40. This is best seen from Fig. 22. The sloping sides of the raised portion 40 serve to resist accidental movement of the bar switch from the on to the off position. Thus the described arrangement in a very simple manner enables a lampholder to incorporate an on/off switch without in any way affecting the reliability of the carrier mechanism within the lampholder housing proper. Referring now to Figs. 23 to 25, an alternative carrier structure to that of the preceding embodiments will now be described.

In the arrangement of Figs. 23 to 25, the carrier comprises a moulded body 41 which supports carrier contacts 42 that as illustrated may be in the form of resilient metallic members inserted into slots 43 defined by the carrier. The lampholder housing comprises a main body 44 into which a flex terminal support 45 is a snap fit, the flex terminal support 45 supporting flex terminals 46 and 47. When no bulb is supported by the lampholder the carrier 41 assumes the position shown in Fig. 23 with the contacts 42 spaced from the terminals 46 and 47. When a bulb is inserted the carrier moves to the position shown in Fig. 24. Movement of the carrier body 41 from the position shown in Fig. 23 to the position shown in Fig. 24 requires rotation of the carrier body 21 about the axis of the housing and^' then an axial movement of the carrier body 41 'towards the flex terminals 46 and 47.

The carrier body 41 fixedly supports a metal shelf 48 which is positioned so as to. be slidable and rotatable within the socket defined by the housing body 44 and into which the end of an inserted bulb is received. The carrier body 41 and its attached shelf 48 are prevented from being forced out of the socket- by a lip 49 which has a thickened portion '50 that in^"* the position of the carrier shown in Fig. 23 is received within a cooperating slot 51 in the edge of the shell 48. The housing body 44 defines a J-shaped slot comprising a first portion 52 extending axially relative to the lampholder housing and a second portion 53 terminating in a recess 54. The shell 48 also defines J-slots but these are formed so as to have a first portion 55 which extends in a direction that is inclined to the axis of the shell and a second portion 56 which does not terminate in a recess. Thus the slots in the shell 48 define surfaces 57 which extend across the inner surface of the slot portions 52 in the lampholder housing when no bulb is inserted into the lampholder (Fig. 23).

Referring to Figs. 26 to 31, the interaction between the bayonet pins and the inserted bulb and the slots in the lampholder housing body 44 and the carrier shell 48 will now be described. As shown in Fig. 26, when the bayonet pins 58 of a bulb are inserted into the open ends of the slot portions 52 in the lampholder housing, they come into contact with the surfaces 57. As the bulb is pushed into the lampholder the pins 58 slide along the surfaces 57 causing the carrier shell to rotate relative to the lampholder housing until the bayonet pins 58 assume the position shown in Fig. 27. The shell does not rotate back to its initial position as there is no return force acting in that direction. Once the shell has executed the turning movement represented by the change in position between Figs. 26 and 27 the shell can then be pushed axially by the pins to the position shown in Fig. 28. The bulb can then be turned so that the bayonet pins 58 move along to the ends of • the slot portions 56 (Fig. 29) and then carry the shell 48 through a further rotational movement until the pins 28 come to the end of the slot portion 53 (Fig. 30). The bulb is then released and the pins 58 drop back into the recesses 54 (Fig. 31). The bulb can then only be removed by first pushing it in so that the pins 58 clear the recesses 54, secondly turning the bulb about the axis of the lampholder so that the pins 58 move to the position shown in Fig. 28, and then pulling the bulb out of the lampholder so that the pins 58 rotate the carrier shell back to the position shown in Fig. 26.

When a bulb is inserted into the lampholder the carrier shell is in the position shown in Fig. 24. It will be seen that in that position the lower edge of the carrier shell rests on the thicker portion 50 of the lip 49 around the opening of the housing socket. This means that the weight of the bulb is supported by the carrier shell and the lip around the socket opening rather than by the edge of the recess 54 in the J-slot defined by the lampholder housing. This considerably increases the strength of the assembly.

Claims (7)

CLAIMS :

1. A bayonet lampholder comprising a housing supporting fixed terminals to which in use electrical cables are connected, the housing defining a socket for receiving an inserted bulb and slots for receiving the bayonet pins of an inserted bulb, a carrier mounted within the housing and supporting contacts arranged to electrically contact a bulb inserted into the lampholder, the carrier being movable between a first position in which the contacts are isolated from the terminals and a second position in which the contacts electrically contact respective terminals, and means for biasing the carrier from the second position to the first position, wherein the carrier supports surfaces which extend adjacent the slots so as to be engage'd by the bayonet^'s of an inserted bulb, the carrier and housing define interacting formations such that for the carrier to be moved from the first position to the second position it must initially execute a turning movement within the housing and then an axial movement relative to the housing, and the said carrier surfaces are positioned such that the bayonets of an inserted bulb slide along the said surfaces as the bayonets are pushed into the slots, the slots being inclined to the said surfaces such that the sliding contact between the bayonet and the surfaces causes the carrier to execute the said turning movement.

2. A bayonet lampholder according to claim 1, wherein the said carrier surfaces are defined by the ends of legs supported by the carrier and extending along the inside of the sockets.

3. A bayonet lampholder according to claim 1, wherein the said carrier surfaces are defined by a metal shell which is slidable and rotatable within the socket and into which an inserted bulb is received.

4. A bayonet lampholder according to claim 1, wherein the slots comprise a- first portion extending generally parallel to the direction of insertion of a bulb.

5. A bayonet lampholder according to claim 1, wherein the slots define a first portion which is inclined to the direction of insertion of a bulb.

6. A bayonet lampholder according to claim 1, wherein the carrier is a snap fit within the housing.

7. A bayonet lampholder substantially as herein described, with reference to the accompanying drawings.