US3310702A

US3310702A - Vehicle headlamp with improved filament mounting structure

Info

Publication number: US3310702A
Application number: US463608A
Authority: US
Inventors: Robert N Falge
Original assignee: Individual
Current assignee: Individual
Priority date: 1965-06-14
Filing date: 1965-06-14
Publication date: 1967-03-21
Anticipated expiration: 1984-03-21

Description

R. N. FALGE March 21, 1967 VEHICLE HEADLAMP WITH IMPROVED FILAMENT MOUNTING STRUCTURE Filed June 14, 1965 United States Patent 3,310,702 VEHICLE HEADLAMP WITH IMPROVED FILAMENT MOUNTING STRUCTURE Robert N. Falge, RR. 2, Box 305, Anderson, Ind. 46011 Filed June 14, 1965, Ser. No. 463,608 3 Claims. (Cl. 313113) The subject matter of the present invention is an improved lamp and more particularly an improved filamentlead structure for sealed beam lamps of the type used for headlamps in automotive vehicles.

The conventional lighting element structure in sealed beam automotive vehicle headlamps consists of a generally U-shaped tungsten filament having a coil portion which forms the bottom of the U and an integral leg portion extending from each end of the coil. The filament legs are secured by staking, welding or both, to the ends of straight lead wires, the filament legs being generally parallel to each other and forming extensions of the generally parallel ends of the two lead wires.

The present invention provides an improvement in such structure and has as its principal object the provision of a filament-to-lead structure for vehicle headlamps and the like which assures better and more uniform headlamp quality, longer headlamp life and improved lighting characteristics and efficiency. More specifically, it is an object of the invention to provide a lamp having a filament-tolead structure which avoids mounting strains at the filament-to-lead joints thereby improving electrical connections between filament and leads and avoiding coil distortion and coil mislocation due to mounting strains.

Briefly, these objects are accomplished in accordance with the invention by a filament having a coil portion with an integral leg at one end thereof extending at an angle to the longitudinal axis of the coil portion and secured to the end of one lead wire, and an integral leg extending from the other end of the coil generally parallel to longitudinal axis of the coil and secured to the end of the other lead wire. Preferably the end of the lead wire to which the second-mentioned filament leg is secured extends transversely to the optical axis of the lamp and at about right angles to the end of the other lead wire such that each filament leg is coaxial with the end of the lead wire to which it is secured. One of the chief advantages of such structure is that it greatly reduces the tendency of the filament legs to separate from the leads due to strains generated in the junctions during lamp manufacture or during lamp operation. With conventional filament structure, for example, due to manufacturing inaccuracies in forming the filaments it frequently occurs that the two legs instead of extending parallel to each other, as is necessary to provide an unstrained condition when the legs are initially secured to the leads, the legs in fact are at an angle to each other about the longitudinal axis of the coil. Hence, when the legs are secured to the leads in lamp manufacture, there is immediately a strain tending to cause the legs to pull free of the leads. Also, since the leads are fixed the result is that the filament coil twists and moves thereby destroying the accurate filament location provided by fixtures in the mounting operation. To prevent such a condition of initial strain it is essential, with the conventional filament-to-lead structure, to use and precisely attain fully complete coil turns in the filament coiling operation in order to provide precise parallelism between the legs. Such precision is difiicult to attain in the coiling operation and where it is not attained it leaves a choice of either scrapping those filaments which have partial turns and hence lack the desired leg parallelism or using such filaments with resultant inferiority .due to strains in the lamp filament-tolead joints. With the structure of the present invention, since one filament leg extends from one end of the coil coaxially With the longitudinal axis of the coil, its precise angular orientation with respect to the coil and with respect to the other filament leg will be the same irrespective of Whether there are partial turns imparted to the coil in the coiling operation. Hence, the possibilities of the legs being in an initially strained condition during lamp manufacture are minimized. Further, as the coil heats during lamp operation there is minimum tendency for the legs to change their orientation with respect to each other and hence minimum strain on the leg-to-lead joints.

Other objects, advantages and features of the invention will be apparent from the following detailed description of a preferred embodiment thereof made With reference to the accompanying drawings in which:

FIGURE 1 is a side view, with parts broken away, of a sealed beam headlamp embodying the invention;

FIGURE 2 is a top view in enlarged scale of one of the filament-to-lead elements of the lamp shown in FIG- URE l; and

FIGURE 3 is a partial perspective view in enlarged scale of the lamp shown in FIGURE 1 and shows the filament-to-lead structure.

Referring now to the drawings, there is shown an auto motive vehicle sealed beam headlamp having a conventional hermetically sealed glass envelope including a glass parabolic reflector 2 which has an aluminized front surface 4 (see FIGURE 3) and which is sealed by fusion at its periphery 6 to a glass lens 8 having the desired flutes and prisms (not shown) on the inner surface thereof to provide the desired beam pattern. Extending into the lamp through the reflector in sealed relationship therewith are three lead wires 10, 12 and 14, each having its own electrical connector exterior of the reflector as shown for example at 16. The lead wire 12 has a lead wire 18 welded thereto within the lamp, wires 10 and 12 being for one filament and wires 14 and 18 being for the other filament. This structure which is shown is, of course, for a lamp having a high beam filament and a low beam filament, it being understood that the invention is also applicable to a one filament type lamp in which instance only two lead wires are required. Also, it will be understood that the precise arrangement of the lead wires as they enter the glass envelope and the shape of the lead wires remote from the free ends thereof can vary from what is shown. In some instances, for example, the lead structure adjacent the envelope is modified to support a filament cap or shield positioned in front of the filaments and such can, if desired, be used with the present invention.

Referring now to the spaced pair of lead wires 10 and 12, the latter has an end portion 20 which extends parallel to the optical axis of the lamp (i.e., the axis which extends through the focal point of the reflector parallel to the light rays from the reflector) and the wire 10 has an end portion 22 which is bent to extend in a direction transverse to the optical axis of the lamp and hence at about a right angle to the end portion 20 of the other lead wire 12. Bridging these two leads is a tungsten filament 24 having an elongated coil portion 26 which extends transversely to the optical axis of the lamp' and which has integral legs 28 and 30 extending from the ends thereof. Filament leg 28 extends from the coil at a right angle to the longitudinal axis of the coil and is secured by staking or welding to the end 20 of the lead wire 12, the leg 28 being positioned coaxially with the lead wire end portion 20. The other leg of the filament, leg 30, is staked or welded into and coaxially with the end portion 22 of the lead wire 10.

Filament 32 which is substantially the same as filament 24 is secured across leads l4 and 16 in the same manner.

It will be noted that with the structure shown the angular orientation of the filament leg 30 with respect to the leg 28 is not dependent upon the turns in the filament coil portion 26; leg 30 will always extend at the same angle with respect to leg 28. Hence, the structure shown greatly increases lamp durability with lessened possibilities of disconnection of the filament to one of the leads. Additionally, the filament-to-lead structure shown and described improves the efficiency and lighting characteristics particularly of the low or city driving beam. The low beam hot spot is made up of filament images from the reflector transmitted through the lens. The best images for optimizing the low beam are those in and near the vertical plane through the reflector which bisects the low beam filament transversely through its longitudinal axis. The filament legs of the convention U-shaped filament are directed upward from the upper half of the reflector and are incandescent in decreasing degree from the coil to the lead wire thereby tending to dull the low beam cut off. With the improved filament structure of the present invention wherein the right leg is coaxial with the filament coil, this dulling of the beam cut off is eliminated on the left side and the stray light is directed to the left instead of upward. Further, by using a short coaxial filament leg as shown at 30, the extent to which the stray light is directed to the left can be kept to a minimum. Also, by suing the short coaxial filament leg 30, as shown, eificiency is increased since less heat is dissipated through the short leg.

As alluded to above, the invention reduces the need for precision in the coiling of the filaments in order to attain optimum lamp durability and lighting characteristics. Hence, there need be little scrap loss in the filament coiling operation. Since a filament-to-lead strain condition will not result from slight inaccuracies in the coiling operation, it is not necessary to set the filament wire so much in the winding and this in turn permits the use of a larger mandrel with fewer turns. Springback in the cooling operation is less a problem.

For optimum efiiciency and lighting characteristics, the filament must be precisely located on the focal point of the parabolic reflector. Of course on a two filament lamp as shown, only one filament can be so located. In a two headlamp vehicle lighting system the high beam filament is located on the focal point. For a four lamp system as is now commonly used, the low beam filaments of one pair of lamps is located on focus and the single high beam filament of the other pair of lamps is located on focus. In either case, however, it is always desirable to have one filament or the other precisely located on the focal point. With the conventional U-shaped filament, strains resulting from filament heating have a tendency to twist the filament off focus. Such twisting also causes the turns of the coil to change pitch; the turns which are closed up and brought closer together have an increased tendency to overheat and reduce the life of the unit, and the turns which are stretched will operate at lower temperature with resultant reduced light output. With the structure of the present invention there is lesser tendency for the filament coil to undergo such twisting due to strains thereby better assuring that the filament remains on focus and provides optimum lighting performance and durability. Further, the invention affords greater discretion in filament design since with the old U-shaped filament structure an even number of coil turns was necessary to attain the required parallelism between filament legs whereas with the present structure partial coil turns can be used if desired without effect on the orientation of one filament leg to the other.

Whereas in the two-filament lamp structure shown in the drawings, the bent leads 10 and 14 are both located on the same side of the lamp, it may be desirable to locate the bent lead for one filament on one side and the bent lead for the other filament on the other side as, for ex ample, by reversing the locations of leads 10 and 12 for filament 26.

It will be understood therefore that whereas the invention has been described in detail with reference to a particular embodiment thereof, various changes and modifications may be made all within the full and intended scope of the claims which follow.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A vehicle headlamp comprising; an envelope having a reflector and a lens, an electrical lead wire in said envelope having an end portion extending parallel to the optical axis of the lamp, an electrical lead wire in said envelope having an end portion extending transversely to the optical axis of the lamp, and a filament having a coil with a leg extending from one end thereof at an angle to the axis of said coil and secured to the end portion of said first-mentioned lead wire and with a leg extending parallel to the axis of said coil and secured to the end portion of said second-mentioned lead wire the axis of said coil extending transversely to the optical axis of said headlamp adjacent the focal point thereof.

2. A vehicle headlamp as set forth in claim 1 wherein the length of said second-mentioned leg between the end of said first-mentioned lead and said coil is shorter than the length of said first-mentioned leg between the end of said second-mentioned lead and said coil.

3. A vehicle headlamp comprising; an envelope having a reflector and a lens, a pair of spaced lead wires extending into said envelope through said reflector and having straight free end portions positioned at a right angle to each other, and a filament having an elongated coil with a leg extending from one end thereof at a right angle to the axis of said coil and secured to the end portion of one of said lead wires coaxially therewith and a leg extending from the other end of said coil coaxially with said coil and secured to the end portion of the other of said lead wires coaxially therewith, the axis of said coil extending transversely to the optical axis of said headlamp adjacent the focal point thereof.

References Cited by the Examiner UNITED STATES PATENTS 1,121,802 12/1914 Clark 316-4 2,131,897 10/1938 Malter 3l3272 2,359,302 10/1944 Curtis 2925.l5

2,795,722 6/1957 Burgener et al. 313-117 JAMES W. LAWRENCE, Primary Examiner.

v, LAFRANCHI, Assistant Examiner,