LAMP FOR A LIGHT SYSTEM AND CLAMPING PLATE

The invention relates to a lamp for a light system, which lamp comprises at least a lamp envelope in which at least one electrical radiant source is enclosed and that has a pinch seal, the pinch seal having a plurality of (at least two) fixing members that, in relation to the longitudinal axis of the lamp, are arranged radially and in opposed positions on the outside contour of the pinch seal, and at least a lamp cap, this latter having at least one clamping plate having at least two fixing members that, by means of at least two corresponding fixing members, can be used to fix the pinch seal to the lamp cap, and the clamping plate having a main body in plate form that is arranged approximately perpendicularly to the longitudinal axis of the lamp and that has an opening into which the at least two fixing members project.

Such lamps are for example halogen automobile lamps made of quartz glass or hard glass, e.g. what are called H4 or H7 lamps.

At the present time, lamps of this kind, which have at least one lamp envelope in which at least one electrical radiant source is enclosed and that have a pinch seal, are used in vast quantities and are manufactured by industrial mass production.

On the pinch seal there are two fixing members that, in relation to the longitudinal axis of the lamp, are arranged radially and in opposed positions on the outside contour of the pinch seal. The lamp cap has a clamping plate having two fixing members corresponding to the fixing members on the pinch seal, by which clamping plate the pinch seal is fixed to the lamp cap by means of the total of four fixing members, principally by means of a force fit. The clamping plate has a circular main body in plate form that, in the fitted position, is arranged approximately perpendicularly to the longitudinal axis of the lamp. The opening in the clamping plate is approximately symmetrical about its longitudinal axis and is positioned approximately centrally in the circular plane of the clamping plate. The two fixing members of the clamping plate are in the form of clamping fingers and are arranged symmetrically and in opposed positions in relation to the longitudinal axis of the opening. The free end of each clamping finger projects into the opening in the clamping plate and does not lie in the plane of the clamping plate. The clamping finger is solidly connected to the

clamping plate only by its other end, which is arranged in an opposite position from the free end.

The clamping plate is made of metal and is usually a stamping, i.e. is produced by a stamping operation. It is in the stamping operation that the surrounding flanged rim, the lugs, the opening and the clamping fingers are, in particular, produced, these latter being pressed downwards, i.e. out of the plane of the clamping plate.

The maximum length of the clamping finger that is stamped out is thus limited in this arrangement, because a limit is always set to the lengthwise extent of the clamping finger, at its free end, by the centerline of the clamping plate, which is also the longitudinal axis of the opening.

To make the fixing between the lamp envelope and the lamp cap, the bottom part of the pinch seal is inserted in the opening in the clamping plate. When this is done, the clamping plate is fixed in place by latching into engagement with the two glass lugs arranged on the pinch seal, which it does by means of the two metal fingers stamped out in symmetrical positions, which are used for the clamping and which form two fixing members. In the latched-together state, the total of four fixing members produces a clamped fit resulting from two-point support.

Acting as stabilizing abutments are four stamped-in lugs that project above the main face of the clamping plate and that are supported in the region of the pinch seal in the latched-together state.

The two metal fingers that are stamped out, and the corresponding fixing members, allow only a short length of the pinch seal of the lamp envelope to be clamped in place and thus enable the lamp-fixing system as a whole to be of only limited stiffness. Particularly in the case of lamps whose overall dimensions are small, such as H7 lamps for example, the length available for clamping-in is, for functional reasons, especially short.

When the clamping plate is, as described above, "forced" onto the pinch seal, there is also only a limited width available for the purposes of the process. With this kind of symmetrical configuration there is, due to the narrow rectangular shape of the pinch seal in cross-section and the circular main face of the clamping plate, only a limited amount of material available and for certain applications, insufficient material available. In this case, the maximum length of the clamping fingers is also determined by the thickness of the pinch, and thus by the width of the opening that is stamped out. However, the maximum length of the clamping fingers is a measure of whether there is secure fixing in a defined position in space, secure fixing being achievable to only a limited degree with clamping fingers that are short in

the way described. Even quite small deviations from the desired fixed positions of the pinch seal and the clamping plate thus have an adverse effect on the quality of the light system.

Also, due to the short inelastic clamping fingers, damage often occurs to the surface of the pinch seal when the clamping plate is being forced on, and this results in the lamp concerned being rejected in the course of the quality control applied during the industrial manufacturing process.

The manner of fixing employed hitherto, which has been in use for many years, allows no, or only slight, possible variations with regard to the structural design of such lamps.

It is the object of the invention to provide a clamping plate, or a lamp having such a clamping plate, which allows improved fixing and can be manufactured efficiently in industrial mass production. This object of the invention is achieved by virtue of the features of a lamp for a light system as defined in claim 1.

The essence of the invention is that the pinch seal and the clamping plate each have at least three fixing members that correspond to one another, with three fixing members that correspond to one another producing three-point support. Compared with fixing and positioning by two-point support, three-point support of known dimensions is more stable and thus more secure and more reliable. Because of the three-point clamping-in, the system as a whole is unambiguously located and more stiffly clamped in place. The size of the resulting bending moment or the resulting moment of resistance is zero, and central positioning is thus ensured. Rather than two as has been the case hitherto, the new clamping plate has three clamping fingers, which can also be arranged in such a way that appreciably longer fingers can be produced by the stamping process.

An arrangement having three abutment lugs may be used for certain applications. By making the clamping fingers longer, the four abutment lugs may be made more elastic and the clamping-in forces can then be transmitted to the glass pinch more efficiently, without any deformation.

Also, because of the changed geometrical conditions, the possibility exists of reducing the clamping-in forces but still obtaining a secure fit.

In the context of industrial mass production, this solution can be put into practice inexpensively and can be adjusted to suit the standard of the given product.

The manner of fixing according to the invention can be applied in all similar glass-to-metal connections in which there is, in particular, a narrow, rectangular pinch cross- section, such as in halogen automobile lamps or CDM applications.

Dependent claims 2 to 4 describe advantageous embodiments of the lamp according to the invention, though without constituting a full and final listing of such embodiments.

It is preferable for the pinch seal and the clamping plate each to have three fixing members that correspond to one another and that produce a clamped fit. What is specified in this way is a solution that is very simple in design but very effective and that replaces a solution that has remained unchanged for many years.

It is also preferable for the base area of the cross-section of the pinch seal perpendicular to the longitudinal axis of the lamp to be rectangular and for the length of at least one of the clamping fingers to be greater than the width of the base area of the cross- section of the pinch seal. With this extended length for at least one of the clamping fingers, it is possible to achieve more exact positioning due to a longer distance over which the desired position can be approached. Also, the clamping-in forces can be selected to be lower, thus greatly reducing the risk of damage to the pinch seal. The object of the invention is also achieved by virtue of the features of a clamping plate for fixing the pinch seal of a lamp, as defined in claim 5.

Dependent claims 6 to 10 specify advantageous embodiments of the clamping plate according to the invention, though without constituting a full and final listing of such embodiments. It is preferable for the clamping plate to have four abutment lugs that are arranged opposite one another in pairs about the longitudinal axis of the opening and for respective ones of two of the clamping fingers to be arranged next to two of the four abutment lugs, on the right and left respectively of the longitudinal axis of the opening, and for the third clamping finger to be arranged between the other two abutment lugs. This arrangement, which differs from the prior art and in which the two clamping fingers are arranged between the abutment lugs, gives the designer new opportunities.

It is also preferable for the length of at least one of the clamping fingers to be larger than the width of the base area of the cross-section of the pinch seal. Alternatively, two, three or all the clamping fingers may be larger in this respect.

These and other aspects of the invention are apparent from and will be elucidated with reference to the embodiments described hereinafter.

In the drawings:

Fig. 1 is a schematic view from the side of a lamp according to the invention for a motor vehicle headlamp system.

Fig. 2 is a plan view of a clamping plate according to the invention for fixing a lamp envelope of a lamp as shown in Fig. 1, and, Fig. 3 is a view from the side, in section, of a clamping plate 10 for fixing a lamp envelope 1 of a lamp as shown in Fig. 2.

The preferred embodiment of the invention that is shown in Fig. 1 is a twin- filament incandescent halogen lamp that is intended for use in a motor vehicle headlamp.

The lamp has a substantially cylindrical glass envelope 1 containing two incandescent filaments 2, 3 that are arranged in the usual way approximately parallel to the longitudinal axis of the lamp. Three current supply means 5, 6 and 7, that project out of the end of the lamp envelope 1 adjacent the cap, namely out of the pinch seal 4, serve to hold the two incandescent filaments 2, 3 in position and to supply current to them. The pinch seal 4 has three fixing members 8, 9.1 and 9.2 that, relative to the longitudinal axis of the lamp, are arranged radially on the outer contour of the pinch seal 4. The pinch seal 4 is of approximately rectangular cross-section, one fixing member 8 being situated on one long side of the outer contour and the other two fixing members 9.1 and 9.2 (not visible in Fig. 1) being situated on the other long side.

The metal clamping plate 10 is a stamping and is a component of the lamp cap 11.

Fig. 2 is a plan view of a clamping plate 10 for fixing an envelope 1 of a lamp as shown in Fig. 1. The clamping plate 10 has a circular main body in the form of a plate that, in the fitted position (shown in Fig. 1) is arranged approximately perpendicularly to the longitudinal axis of the lamp. The opening 12 in the clamping plate 10 is of a symmetrical configuration about a second axis that extends perpendicularly to the longitudinal axis of the opening 12 and that is located in the center of the circular plane of the clamping plate. The three fixing members 8, 9.1 and 9.2 of the clamping plate 10 are in the form of clamping

fingers. The four abutment lugs 13 on the clamping plate 10 are arranged opposite one another in pairs about the longitudinal axis of the opening 12. Respective ones of the two clamping fingers 9.1 and 9.2 are arranged next to two of the four abutment lugs 13, on the right and left respectively of the longitudinal axis of the opening, and the third clamping finger 8 is arranged between the other two abutment lugs 13. The length of each of all three of the clamping fingers 8, 9.1 and 9.2 is greater than the width of the base area of the cross- section of the pinch seal 4. The clamping fingers 8, 9.1 and 9.9 are so formed and arranged that they correspond to the fixing members on the pinch seal (not shown in Fig. 2) and in the fitted position produce three-point support. Fig. 3 is a view from the side, in section, of a clamping plate 10 as shown in

Fig. 2 for fixing an envelope 1 of a lamp. The clamping plate 10 is a stamping of metal. It is in the stamping operation that, in particular, the surrounding flanged rim 14, the lugs 13, the opening 12 and the clamping fingers 8, 9.1 and 9.2 are produced, these latter being pressed downwards, i.e. out of the plane of the clamping plate. The angle between the perpendicular through the plane of the clamping plate and the angled clamping fingers is less than 45°.