GB2092736A

GB2092736A - Device for Fixing a Bulb on to the Reflector of a Headlamp

Info

Publication number: GB2092736A
Application number: GB8203590A
Authority: GB
Original assignee: Cibie Projecteurs SA
Current assignee: Cibie Projecteurs SA
Priority date: 1981-02-09
Filing date: 1982-02-08
Publication date: 1982-08-18
Also published as: DE3204248A1; ES509414A0; JPS57148802A; IT8219532A0; DE3204248C2; GB2092736B; ES8302258A2; SE8200040L; IT1149571B

Abstract

The device incorporates a fixing collar (13) independent of the reflector (1) and capable of being mounted on the latter in two different positions in which, respectively, it provides a support for standardised means (12) on the base (6) of a bulb (4) of differing types. The collar (13) is fixed on the reflector (1) by snap engagement of catches (40, 41, 42) in anchoring holes (35, 36, 38, 39) on the reflector (1). A plug (45) locked on the collar (13) by a bayonet mounting (51, 52, 53, 54, 55) ensures the immobilisation of the bulb (4) with reference to the collar (13), and the whole assembly is dimensioned so that the plug cannot be locked on the collar (13) if the bulb (4) does not occupy a desired predetermined position with reference to it. <IMAGE>

Description

SPECIFICATION Device for Fixing a Bulb on to the Reflector of a Headlamp The present invention relates to improvements in a device for fixing a bulb on to the reflector of a headlamp, particularly for an automobile.

It has been proposed to provide such a device incorporating fixing collar with two faces for supporting standardised means on the base of a bulb and a central aperture for the bulb to pass through, means for fixing a bulb on the collar so that its base rests on one or other face of the collar, and means arranged around the collar and adapted to engage complementary means around an aperture in the reflector to permit mounting of the collar on the reflector in a predetermined position with either face turned towards the exterior of the reflector.

Such a design is advantageous in that it makes it possible to use a single reflector of standard type and a single collar also of standard type to produce headlamps capable of receiving a bulb of one type or a bulb of another type, according to the sense in which the collar is fixed on to the reflector. It is also possible to use the same standard reflector and collar to make provision for driving on the right or driving on the left. This is a particularly interesting possibility when the headlamp is intended to emit an asymmetric beam, for example as in the case of dipped headlights.

It is an object of the present invention to provide such a device, which is capable of use with two types of bulb and which is also capable of providing for driving on the right and left.

According to the present invention there is provided a device for fixing a bulb of the type having a base with standardised reference means on to the reflector of a headlamp, the reflector including an aperture arranged to receive the bulb, the device comprising a fixing collar independent of the reflector and having two faces each of which has support means for the standardised means on the bulb base and a central aperture permitting the bulb to pass through it when the base of the bulb is resting on the support means of one or other face; means for fixing the bulb on the collar, in a position where the bulb passes through this collar and its base rests on the support means of one or other face of the collar, mounting means arranged around the collar adapted to engage the reflector to permit mounting of the collar on the reflector with either one or the other face facing towards the reflector, in such a position that a bulb which passes through the collar and has its base resting against the support means of this face occupies a predetermined position in the interior of the reflector, the mounting means including a peripheral ring around the faces of the collar, having two surfaces to support the collar on the reflector, in orientations which substantially correspond respectively to those of one and the other of the faces of the collar, and further including two sets of resiliently deformable catches, one set of catches projecting from each of the two support surfaces of the ring, the catches of the two sets occupying identical relative positions and each of the catches having one end attached to the ring and one end in the form of a hook, the two hooks of each set having opposite orientations, the hooks being adapted to engage and form a snap fit in corresponding holes in the reflector when the corresponding support surface of the ring is resting against the reflector.

Preferably, the means for fixing a bulb on to the collar incorporate a plug having two surfaces, either of which can be placed facing the collar, and means for fixing the plug on to the collar in these two positions, trapping the standardised means on the base of the bulb between the plug and the face of the collar facing it. Preferably, these means for fixing on the plug on the collar comprise complementary reliefs respectively around the external periphery of the faces of the collar and on the plug, thus defining a bayonet fitting.

Means are preferably also provided to prevent the plug being fixed on the collar if the base of the bulb is resting on the support means of one face of the collar in such a position that the standardised means on the base of the bulb occupy a position relative to the support means which is different from a predetermined relative position corresponding to a desired predetermined position of the bulb in the interior of the reflector.

The invention may be carried into practice in various ways and one embodiment will be described by way of example with reference to the accompanying drawings in which the single figure shows, in an exploded perspective view, the mounting of a bulb on to the reflector of a headlamp by means of a device according to the invention.

The reflector 1 is generally paraboloidal, having an axis of revolution 2 and an outer surface 3, only the zone closest to the top being shown in the Figure. A bulb 4 of the H4 type, this type being chosen by way of example, is located with respect to the reflector 1 by means of a single part 5 which assembles all the parts permitting mounting of the bulb 4 in its predetermined position.

Reference should be made to standard texts for precise details of the dimensional characteristics and positioning relative to the reflector of H4 bulbs.

As illustrated, the base 6 of such bulbs has a collar 7 generally perpendicular to the axis of the bulb (co-axial herewith the axis 2). This collar 7 has a peripheral zone 11 in the form of a flat ring perpendicular to the axis of the bulb and having a circular external rim which extends radially away from the axis of the bulb, in the form of three radial tongues such as 12, (reference tongues) which are distributed irregularly about the axis of the bulb.

The part 5 has a complementary mounting collar 13 the axis of which coincides with the axis 2 when mounting has been achieved, one face 14 of which is perpendicular to this axis and has a shape complementary to that of the face of the collar 7 situated at the side of the globe 10 of the bulb 4. Thus, with reference to the axis, the face 14 has the shape of a substantially flat transversely oriented crown defined by an inner rim 15 and an outer rim 16 both of which are circular and centered upon the axis.The rim 1 5 has a diameter close to the external diameter of the zone 11 of the collar 7, and three radial slots such as 1 7 are cut in the face 14 and distributed irregularly about the axis, in positions corresponding respectively to each of the tongues 1 2 in such a way that the collar 7 can be engaged with precision and in a unique relative position in the collar 13 by means of the face 14.

At the level of the rim 15 a cylindrical face 18 about the axis of the collar 13 is connected to the face 14, the face 18 linking the face 14 to an analogous face spaced from the face 14 along the axis of the collar 13, parallel to the face 14 and in an inverse orientation with reference to this axis.

This face, which cannot be seen in the figure, is defined externally by the face 1 8 and internally by a coaxial cylindrical face 21 which together with the face 1 8 defines a central aperture 22 passing through the collar 13 from one side to the other.

These elements of the collar 1 3 are dimensioned in such a way that they do not present any obstacie to the tongues 12 coming to rest at the bottom of the slots 17 and in fact the aperture 22 permits the globe 10 of the bulb and the part of the base 6 on the same side of the collar 7 as the globe 10, to pass right through the collar 13.

In addition, the depth of the slots 1 7, measured parallel to the axis 2, is substantially equal to, or very slightly greater than, the corresponding overall thickness of the tongues 12 so that, when the tongues 12 rest on the bottom of the slots 17, they are flush with the face 14 or form a projection of the order of some tenths of millimeters at the maximum above this face 14.

On the opposite side to the face 14, the collar 13 has another transverse face, not shown, the shape of which is complementary to that of a collar on the base of a bulb other than an H4 bulb, for example a bulb of the type known as "European standard beam". Again, reference should be made to the standard documents relating to this type of bulb in order to determine its precise characteristics. This transverse face of the collar 1 3 is constructed so that the collar of the bulb can rest on this face in a direction towards the face 14 along the axis of the collar, with relative immobilisation of the two collars to rotation about this axis when support is achieved, the globe of the bulb then being situated on the same side of the collar 13 as the face 14.

Naturally, a collar 13 according to the invention could be provided for mounting bulbs other than the said "H4" and "European standard beam" bulbs, in a unique respective relative position.

The face 14 by its rim 16, and the other transverse face (not shown) are connected to a radially outer peripheral face 23 which is cylindrical about the axis of the mounting collar 1 3. Approximately halfway along axially, this peripheral face 23 has an annular flange 24 which is perpendicular to this axis and which connects the face 23 to an external peripheral ring 25. The ring 25 has a radially inner and a radially outer face, 26 and 27 respectively which are cylindrical about the axis of the mounting collar 13, and perpendicularly to this axis, the ring 25 is defined by annular faces such as 28.Of these faces such as 28, the face which is oriented in the opposite direction to the face 14 which is intended to engage the complementary standardised means on the base of the bulb which is intended to be used, is required to come into contact with the face 3 of the reflector 1 when mounting of the collar on the reflector is effected. The annular flange 24 is integral with the peripheral ring 25 between the two transverse faces 28 and is located approximately halfway between them.

It will be noted that the mounting collar 13 is also required to come into contact with the external face 3 of the reflector 1 at the junction of the face 23 and the annular rim 24, and the term "support face of the peripheral rim of the collar for mounting on the reflector" will be understood to mean a real or virtual face joining a transverse face such as 28 of the external peripheral rim 25 to the connecting edge such as 29 between the face 23 and the face such as 30 of the annular rim 24 having an orientation in the axial direction analogous to that of the transverse face such as 28 under consideration.This "support face of the peripheral rim" can be formed either only by the face such as 28 and the edge such as 29, as in the illustrated example, or can be formed by reliefs (not shown) arranged at the bottom of the groove such as 31 defined by the face 23 and the faces such as 30 and 26, these reliefs having a shape complementary to that of the zone of the external face 3 of the reflector 1 to which the support face thus defined is required to correspond.

In order to receive the part 5, and particularly the mounting collar 13, the reflector 1 has an opening 32 in its zone corresponding to the top of the paraboloid the periphery 33 of which is generally circular and centered upon the axis 2.

The opening 32 has a diameter close to that of the face 23 of the collar 13 so that the part of the latter defined by the two transverse faces such as 14, the faces 18 and 21, and the face 23 can be located in the opening 32 in a position where the axis of the collar 13 coincides with the axis 2, with a minimum clearance between the face 23 and the periphery 33 of the opening 32.

In a region close to the periphery 33 of the opening 32, the reflector 1 has two identical anchoring holes 35 and 36 which are diametrically opposite on diameter 34 and are equidistant from the axis 2. The holes 34, 36 are approximately square, and are defined by two approximately radial edges and by two circumferential edges.

On a second diameter 37, two other anchoring holes 38 and 39 are provided, which are identical to the holes 35 and 36 and occupy the same relative position with reference to the axis 2. The set of anchoring holes 35, 36 and the set of anchoring holes 38, 39 can both be used for mounting the collar 1 3 on the reflector, and the angular stagger of the diameters 34 and 37 with reference to the axis 2 is such that the use of one or the other set corresponds to a particular angular positioning of the collar 13 with reference to the axis 2. The particular positioning corresponds, by means of the relationship between the face 14 and the collar 7 of the bulb 4, to an orientation of the bulb about its axis with a view to driving on the right or left respectively.

It should be recalled that there are provided either in the interior of the bulb, or in a form attached to its exterior, and for example on the collar 13 (in a manner which is not shown), means such as a cover which is opaque to the light and so cuts the beam emitted by the bulb along a broken line when the beam is to be dipped so as to limit the level of illumination towards the road whilst retaining a greater level of illumination towards the roadside.Various standards call for cutting the beam at the horizontal on the offside and cutting at a 1 50 angle above the horizontal towards the nearside, from a vertical plane passing through the focal centre of the reflector, and thus an angular stagger sg of 1 50 is provided between the two diameters 34 and 37, these figures being given by way of non-limiting example since other standards could be imposed.

The collar 13 has means to engage one or the other set of anchoring holes 35, 36 or 38, 39 permitting it to be mounted on the reflector 1 with either of its faces such as 14, having support means for the complementary standardised means on the base of a bulb, turned towards the exterior of the reflector. Thus the bulb which passes through the collar and has its base resting against the support means of this face such as 14 may occupy a predetermined position in the interior of the reflector 1.

These means include two sets of two resiliently deformable catches projecting respectively from each support face of the peripheral rim of the collar, the two catches of each set occuping positions corresponding to those of the anchoring holes of one set, that is to say those of the holes 35 and 36 or those of the holes 38 and 39. Thus the drawing shows one set of two catches 40 and 41 which occupy with reference to each other and with reference to the axis of the collar 13 positions corresponding to the positions which the holes 35 and 36 or the holes 38 and 39 occupy relative to each other and relative to the axis 2.One end of each of these two catches 40 and 41 is integral with the annular rim 24 defining the base of the groove 31, while the other end is in the form of a hook projecting beyond the support face of the peripheral rim of the collar 13 defined by the face 28 and the edge 29, the two hooks being oriented towards one another In the same way a set of two projecting catches such as 42 is provided on the second support face of the peripheral rim of the collar for mounting on the reflector, itself defined by the transverse face of the rim 25 other than the face 28 and by the edge for connection of the face 23 to the rim 24 other than the edge 29. These two catches occupy positions relative to each other and to the axis of the collar 13 which are identical to those of the two catches 40 and 41.Like the catches 40 and 41, these two catches such as 42 are resiliently deformable and each have one end integral with the rim 24, in the groove corresponding to the groove 31 but on the other side of this rim 24, and the other end in the form of a hook projecting beyond the support face of the peripheral rim of the collar for mounting the collar 13 on the reflector by means of a support face other than the support face defined by the face 28 and the edge 29.

The shapes, dimensions and respective relative positions of the catches 40 and 41, or the catches such as 42, and those of the anchoring holes of one set such as 35 and 36 or 38 and 39 are such that the hooked ends of the catches engage in the anchoring holes and snap in position. In the embodiment shown, the hooks engage the internal face 43 of the reflector 1 when the corresponding support face of the peripheral rim of the collar for mounting on the reflector is located against the outer face 3 of the reflector 1 on the periphery of the opening 32.

The anchoring holes 35, 36, 38, 39 on the one hand and the different catches 40, 41 , 42 on the other hand are situated respectively the same distance form the axis 2 and the axis of the collar 1 3 and are regularly distributed about this respective axis, and error-prevention means are provided on the collar 13 and on the reflector which only permit the set of catches 40 or 41, or the set of catches such as 42, to snap in in a predetermined angular position with reference to the set of anchoring holes 35-36, or the set of anchoring holes 38-39, so preventing engagement in any other relative angular position likely to correspond to an alignment of the catches with the anchoring holes. Thus, in the illustrated example, in order to ensure correct positioning of the bulb by the collar 13, it is the catch 42 or the catch 40 which must engage in the hole 39 or 30, depending upon whether the headlamp is intended for driving on the left or driving on the right, and the other catch of the same set, such as 41, which must engage respectively in the anchoring hole 38 or in the anchoring hole 35.

In the illustrated embodiment, these error prevention means consists on the reflector 1, of a slot 44 in the circular periphery 33 of the opening 32 arranged in the immediate proximity of the two neighbouring anchoring holes 36 and 39. The slot 44 is defined by a circular base centred upon the axis 2, with a diameter slightly greater than that of the rest of the periphery 33, and by two radial edges which are staggered angularly with reference to each other by an angle slightly greater than the angle . In addition, the face 23 of the collar 1 3 is provided with four projections such as 45, two being on each side of the rim 24.

These projections are located near the catches 40 and 42 intended to engage in the hole 36 or in the hole 39. The two projections situated on the same side of the annular rim 24 are displaced angularly relative to one another with reference to the axis of the collar 13, by an angle which is close to the angular development of the slot 44 diminished by the angle .

Thus, the projections such as 45 do not oppose the engagement of the catch 42 or the catch 40 in the interior of the hole 36 or the hole 39, nor the engagement of the other catch of the same set respectively in the hole 35 or in the hole 38 which constitute the only desired possibiiities for locating the collar 13 on the reflector 1, since these projections such as 45 engage in the slot 44 as the collar 13 and the reflector 1 are brought closer together along the axis 2. If, on the other hand, one attempts to engage the catch 42 or the catch 40 in one of the anchoring holes 35 and 38, the projections such as 45 are out of alignment with the slot 44, and butt against the face 3 of the reflector 1 on the circular periphery 33 of the opening 32, so preventing engagement.

In addition to the means for its location on the reflector, the collar 1 3 has means for fixing a bulb on it in a position where the bulb passes through the collar 1 3 and the base of the bulb rests with the tongues 12 on the support means such as 17 of one or other of the faces such as 14. These means for fixing a bulb on the collar include a plug 45, preferably made in one piece from plastics material with the collar 13 to which it is connected by one or several members which form flexible connections, two of these being provided in this embodiment and designated by the reference numerals 48 and 49. These connectors 48, 49 permit the plug 45 to be positioned facing either of the faces such as 14 whilst at the same time ensuring that the plug cannot be lost.

The part of the plug 45 complementary to the faces such as 14 is essentially in the form of a crown 46 which has a central opening 50 through which the base 6 of the bulb can pass for connection to the electrical circuit of the vehicle by means of its pin or pins. The crown 46 has two plane parallel annular faces, only one of which is visible in the drawing where it is designated by the reference numeral 47. One or the other of these faces is intended to trap the standardised means on the base of the bulb, such as 12, in position on the collar 13 depending upon which of the faces such as 14 is used, that is to say depending upon the direction of mounting of the collar 1 3 on the reflector.For this purpose, the two faces such as 47 are so dimensioned that they can cover the face 14 or the second analogous face of the collar 1 3, in a position where the axis of the crown 46 coincides with that of the collar 13. Thus, the crown 46 can trap, by means of its face analogous to the face 47 but of reverse orientation, the tongues such as 12 in the slots 17 by resting on these tongues. If the tongues 12 are flush with the face 14, the crown rests on this face 14 itself.

Means are provided for fixing the plug 45 on the collar 13 in one or other of the two positions in which it traps standardised means on the base of the bulb against the face such as 14 of the collar.

In the illustrated embodiment, these means incorporate complementary reliefs defining a bayonet fitting respectively around the external periphery of the faces such as 14 of the collar and on the external periphery of the crown 46.

Means are also provided to prevent fixing of the plug 45 on the collar 13 if the base of the bulb is resting on the support means of one face of the collar in such a position that the tongues 12'on this base of the bulb are not all located within the slots 1 7 and the bulb is in a position other than one of its predetermined positions in the interior of the reflector. This is achieved by an appropriate dimensioning of the reliefs defining the bayonet fitting.Thus, if one refers to the mounting of a bulb of the "H4" type which is illustrated, the reliefs defining the bayonet mounting have shapes and dimensions such that they only lock mutually when the plug 45 and the collar 13 occupy relative positions in which the plane face (not visible in the drawing) of the crown 46 parallel to the face 47 and the face 14 of the collar 13, outside the slots 17, are spaced by a distance less than the overall thickness of a tongue 12. Thus, locking can only be effected if all the tongues such as 12 are correctly engaged in the slots such as 1 7.

It will be noted that this condition occurs at the commencement of locking, the end of the locking corresponding to a position of the plug 45 and the collar 13 such that the face of the plug 45 analogous to the face 47 but parallel to it is in contact with the tongues 12 resting in the slots 1 7 and, if the tongues 12 are flush with the face 14, in contact with this face 14 itself.

The locking reliefs include two helical grooves 51 and 52, at diametrically opposite positions in the face 27 of the peripheral rim 25 of the collar the axis of each of which is the axis of the collar 13. These two grooves 51 and 52 open both in the face 28 of the rim 25 and in its other transverse face.

The plug 45 has a set of two lugs 53 and 54 around the external periphery of the crown 46 occupying positions diametrically opposed with reference to the axis of the crown 46 and projecting from the face 47. The lugs 53, 54 have hook-shaped ends remote from the face 47 the relative positions of which are the same to those of the grooves 51 and 52, in such a way as to engage respectively in the groove 51 and in the groove 52 of the collar by way of the transverse face of the rim 25 opposed to the face 28 when the face 47 is placed facing the face of the collar 1 3 analogous to the face 14, when the collar is used in the opposite position to that illustrated.

The plug 45 also has a second set of two lugs such as 55 on the periphery of the crown 46 which occupy positions diametrically opposed with reference to the axis of the plug 45 and which project from the face of the crown 46 parallel to the face 47 but of reverse orientation.

These two lugs such as 55 also have hook-shaped ends in relative positions identical to those of the grooves 51 and 52 in order to engage in the grooves by way of the face 28 of the peripheral rim 25 when the collar 13 is mounted on the reflector 1 in the position illustrated, for the use of a bulb 4 of the H4 type.

The angular development of the hook-shaped ends of the lugs 53 to 55, with reference to the axis of the crown 46, is less than the angular development of the grooves 51 and 52 with reference to the axis of the collar 13, in such a way that after the lugs 53 and 54 respectively have been engaged in the grooves 51 and 52, or the lug 55 and the other lug of the same set have been engaged in these same grooves, it is possible to transmit to the plug 45 a rotation relative to the collar 1 3 about their common axis in order to bring the hooked end of the lugs progressively into engagement with the twist defined by the corresponding grooves. Preferably, the hooked ends of the lugs such as 53 to 55 are themselves twisted in a way complementary to that of the grooves 51 and 52.

Thus the lugs 53 to 55 and the grooves 51 and 52 are shaped and dimensioned in order that locking of the plug 45 on the collar 13 is reliably prevented if the bulb is not correctly positioned. In addition, the length of the connection 48 and 49 is chosen so that it is sufficiently small to prevent the plug being located the wrong way round if the connections are crossed.

In order to avoid accidental unlocking of the plug 45, by accidental rotation of the plug relative to the mounting collar 13, means are provided to prevent this. These means consist of teeth such as 56 oriented parallel to the axis of the collar 13 on the face 26 of the peripheral rim 25 of the collar 13 and on the other face (not visible in the drawing) of this rim 25 also facing towards the face 23 of the collar, in the interior of the groove 31 and the corresponding groove on the other side of the annular rim 24.

The plug 45 has lugs 57, 58, 59, 60 which are flexibly connected around the external periphery of the crown 46 with which they are advantageously made in one piece from moulded plastics material. These lugs are capable of engaging in one of the sets of grooves 31 depending on the direction of use of the collar in order to come into resilient engagement with the teeth such as 56 when, by rotation of the plug 45 on the collar 13 about their common axis, the hooked ends of the lugs such as 53 to 55 are brought into engagement with the twist of the grooves 51 and 52.

In the illustrated embodiment, each of the lugs 57, 58, 59, 60 is flexibly connected to the crown 46 by a tab 61, 62, 63, 64 respectively, oriented from its connection to the crown in a circumferential direction with reference to the axis of this crown, in a direction opposite that of the rotation of the plug 45 with reference to the collar 13 leading to the engagement of the hooked ends of the lugs such as 53 to 55 in the grooves 51 and 52, on locking. Thus, rotation of the plug 45 with reference to the collar 13 in the direction of unlocking causes jamming of the tabs such as 61 to 64 which then tend to oppose the disengagement of the lugs such as 57 to 60 from the teeth such as 56, but do not completely oppose it. Thus, the force which needs to be exerted on the plug 45 in order to turn it with reference to the collar 13 with a view to unlocking is greater than the force which is necessary in order to turn it with a view to locking. The two lugs 57 and 58 project from the face of the crown 46 opposed to the face 47 in order to engage with the teeth such as 56 of the groove 31 when it is the face 14 of the collar which receives the standardised support means such as the tongues 12 on the base of the bulb, and the two lugs 59 and 60 projecting from the face 47 of the crown 46 are intended to come into engagement in the teeth of the other groove of the collar 13 when the collar is used the other way up.

Claims

1. A device for fixing a bulb of the type having a base with standardised reference means on to the reflector of a headlamp, the reflector including an aperture arranged to receive the bulb, the device comprising a fixing collar independent of the reflector and having two faces each of which has support means for the standardised means on the bulb base and a central aperture permitting the bulb to pass through it when the base of the bulb is resting on the support means of one or other face; means for fixing the bulb on the collar, in a position where the bulb passes through this collar and its base rests on the support means of one or other face of the collar, mounting means arranged around the collar adapted to engage the reflector to permit mounting of the collar on the reflector with either one or the other face facing towards the reflector, in such a position that a bulb which passes through the collar and has its base resting against the support means of this face occupies a predetermined position in the interior of the reflector, the mounting means including a peripheral ring around the faces of the collar having two surfaces to support the collar on the reflector in orientations which substantially correspond respectively to those of one and the other of the faces of the collar and further including two sets of resiliently deformable catches, one set of catches projecting from each of the two support surfaces of the ring the catches of the two sets occupying identical relative positions and each of the catches having one end attached to the ring and one end in the form of a hook, the two hooks of each set having opposite orientations, the hooks being adapted to engage and form a snap fit in corresponding holes in the reflector when the corresponding support surface of the ring is resting against the reflector.

2. A device as claimed in Claim 1 in which the means for fixing the bulb on the collar incorporate a plug which can be placed facing one or other of the faces of the collar, and means for fixing the plug on to the collar in these two positions and trapping the standardised means on the base of the bulb between the plug and the face of the collar.

3. A device as claimed in Claim 2 in which the means for fixing the plug on to the collar comprises complementary reliefs around the external periphery of the faces of the collar and on the plug defining a bayonet fitting.

4. A device as claimed in Claim 3 in which the locking reliefs comprise at least two helical grooves formed in a peripheral surface around the external periphery of the faces of the collar the grooves having a common axis, being oriented transversely with reference to the faces of the collar and opening respectively towards one or the other of the faces of the collar, the locking reliefs further comprising two sets of lugs projecting respectively from two faces of the plug on one and the other, the two sets of lugs having hooks in relative positions identical to those of the helical grooves and capable of engaging in the latter by way of the faces of the collar.

5. A device as claimed in Claim 4 in which each hook has an angular development which is less than that of the grooves with reference to their axis and to a locking position.

6. A device as claimed in Claim 4 or Claim 5 in which the hooks of the lugs of the plug are twisted in a way which is complementary to the grooves of the collar.

7. A device as claimed in any preceding Claim further including means for mutual immobilisation of the collar and the plug to prevent relative rotation about their common axis.

8. A device as claimed in Claim 7 in which the immobilisation means comprises teeth on the collar, and on the plug complementary resilient fingers which engage the teeth.

9. A device as claimed in Claim 8 in which the teeth are arranged in an annular groove between each face of the collar and the peripheral surface of the collar.

10. A device as claimed in Claim 9 in which the teeth are arranged on the back of the peripheral surface of the collar, facing radially inwards.

11. A device as claimed in any of Claims 8 to 10 in which each of the fingers is connected to the plug by a resilient tab oriented generally circumferentially from the plug towards the corresponding finger in the opposite direction to the direction of rotation of the plug with reference to the collar on locking.

1 2. A device as claimed in any preceding Claim further incorporating means to prevent fixing of the plug on the collar if the base of the bulb is resting on the support means of one face of the collar in such a position that the standardised means on the base of the bulb occupy with reference to the support means a position different from the predetermined relative position corresponding to a desired predetermined position of the bulb in the interior of the reflector.

13. A device as claimed in Claim 12 in which, when the said standardised means on the base of a bulb include at least one tongue, the support means of one face of the collar for the complementary standardised means on the base of the bulb comprise a slot in this face intended to receive the tongue on the base of the bulb, and in which the depth of the slot is at most equal to the overall thickness of the tongue, so that the tongue rests in the slot in such a way that it is flush with the face or forms a slight projection when it is engaged in the slot, the face of the collar otherwise being plane, and in which the plug has a plane surface complementary to the face of the collar and in which the means for fixing the plug on the collar include complementary locking reliefs on the plug and on the collar, these reliefs having shapes and dimensions such that they lock mutually only when the plug and the collar occupy a relative position in which the plane surface of the plug is placed at a distance from the face of the collar less than the overall thickness of the tongue.

14. A device as claimed in any preceding claim in which the plug is made in one piece with the collar to which it is connected by flexible connecting means.

1 5. A device for fixing a bulb on to the reflector of a headlamp constructed and arranged substantially as herein specifically described with reference to and as shown in the accompanying drawing.

16. A device as claimed in any preceding claim in combination with a reflector, the reflector including an aperture arranged to receive the bulb and having, around the aperture, a set of anchoring holes which occupy relative positions corresponding to those of the catches of a set of catches, the shapes, dimensions, respective relative positions of the catches and the anchoring holes being such that the hook-shaped ends of the catches engage in the anchoring holes and snap resiliently into the interior of the reflector when the corresponding support surfaces of the ring is resting against the reflector.