US 3898451 A
A type 2 rectangular sealed beam headlamp unit wherein the ferrule bosses are positioned off the geometric center of the reflector to obtain equal ferrule boss heights by compensating for the inclination of the optical axis relative to the mechanical axis thereby greatly reducing reflector distortion caused by heat sinks in the molding of the reflector which result from varying glass thickness. The ferrule bosses are rotated with respect to the geometric axis such that the ferrule boss openings and surrounding distorted surfaces are removed from selected portions of the reflector surface to provide better selection of hot spot fluting.
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Description (OCR text may contain errors)
United States Patent 1 1 1 3,898,451
Murphy et al. Aug. 5, 1975 [5 RECTANGULAR SEALED BEAM 2.890920 6/1959 Falge 313/113 x HEADLAMP UNIT 3,343,021 9/1967 Burnett et :11 i 3 l 3/l 13 X 3,752,976 8/1973 DiSulvo et al 1. 240/8.l R  Inventors: Joe W. Murphy; Thomas E. Persing;
z Harwell an of Anderson Primary ExaminerRichard L. Moses n Attorney, Agent, or FirmPeter D. Sachtjen  Assignee: General Motors Corporation,
D t 't, M' h.
e 57 ABSTRACT  Filed: July 29, 1974 A type 2 rectangular sealed beam headlamp unit pp 492,546 wherein the ferrule bosses are positioned off the geometric center of the reflector to obtain equal ferrule  us CL 240/41 240/7 1 240/4125. boss heights by compensating for the inclination of the 1 313/115 optical axis relative to the mechanical axis thereby 51 Int. (:1. FilM 3/00 greatly reducing reflector distortion caused by heat  Field of Search 240/41 SB 41 R R sinks in the molding of the reflector which result from R R E 41:25. 13 varying glass thickness. The ferrule bosses are rotated 1 1 with respect to the geometric axis such that the ferrule boss openings and surrounding distorted surfaces are  References Cited removed from selected portions of the reflector sur- UNITED STATES PATENTS face to provide better selection of hot spot fluting.
2,858,467 10/1958 Meese et al 313/115 X 4 Claims, 7 Drawing Figures PATENTEU AUG 5W5 SHEET PATENTEU AUB 51975 SHEET RECTANGULAR SEALED BEAM HEADLAMP UNIT The present invention relates to lighting units, and, in particular, to a rectangular sealed beam headlamp unit for use on motor vehicles.
Currently. motor vehicles are provided with forward lighting systems comprising one or more sealed beam headlamp units. Each of these units, circular in profile, is an integral all-glass reflector and lens assembly having filaments disposed in the interior thereof. The filaments provide an upper beam illumination intended primarily for distant illumination and a lower beam illumination for use in congested areas. The filaments are supported on lead wires which extend through openings in ferrule bosses at the reflector base. The lead wires are fixedly attached to metal ferrules fusion sealed to the bosses. Such units are of two basic types; a type 1 unit having a single filament and a type 2 unit having dual filaments providing the aforementioned upper and lower beam illumination. Therein, the ferrule bosses are equally spaced on the rear surface about the geometric center of the unit. For both units two of the ferrule bosses are located on the mechanical horizontal plane through the unit. In the type 2, a third ferrule and boss is located above center on the vertical plane of the unit.
In the type 2 unit, the paraboloidal or optical axis is inclined downwardly and to the right of the units mechanical axis. Accordingly, mechanical axis and the paraboloidal axis are not coincident at the rear surface of the reflector. Therefore, placing the ferrule bosses uniformly about mechanical axis and terminating them in a common plane normal thereto produces unequal ferrule boss heights. The bosses closest to the optical axis have the thinner sections and those most remote from the paraboloidal axis have the thickest sections. In the reflector molding process the different amount of glass mass resulting from the different ferrule boss heights cause sinks and reflector distortion in the areas immediately adjacent thereto and impairs the optical performance of the reflector. In the type 2 unit, the distorted ferrule areas are located at portions of the reflector which, if not distorted, would produce optically efficient hot spot images of the filament. The present location of these bosses requires that the illumination pattern be synthesized from less efficient portions of the reflecting surface.
The aforementioned problem of reduced optical efficiency due to heat sinks and the ferrule positions is especially acute in rectangular units. Therein, the frontal profile of the unit is basically rectangular. To accommodate such a profile, the upper and lower margins and, to a lesser extent the side margins, of the paraboloidal reflector are removed and connected to the lens by non-reflecting side walls. Removal of these reflecting areas dictates an increase in reflector area and, to prevent excessively large units, requires that optimum use be made of the remaining area if overall unit performance comparable to that of the round units is to be achieved.
A rectangular sealed beam unit made in accordance with the present invention overcomes the deficiencies of prior sealed beam headlamp unit design by positioning the ferrule bosses at locations which provide minimal interferencewith hot spot illumination and which additionally provide equal ferrule boss heights. More particularly, the ferrule bosses are positioned off the mechanical axis at a location which will provide equal ferrule boss heights with the axes parallel to the mechanical or casting axis of the reflector. This compensates for the unequal boss heights occasioned by the optical axis not being coincident with the mechanical axis. The resulting equal glass masses enables the reflector to be molded with minimal distortion around the ferrule bosses. The ferrule bosses are further rotated through an angle relative to the present round type 2 units to provide ferrule positions having minimal interference with favorable hot spot illumination. These two improvements allow rectangular sealed beam units to be designed with minimal reflector area and still provide optical performance comparable to circular units.
The above and other features of the present invention will be apparent to one skilled in the art upon reading the following detailed description, reference being made to the accompanying drawings illustrating a preferred embodiment of the present invention in which:
FIG. I is a partially section front elevational view of a rectangular sealed beam unit made in accordance with the present invention;
FIG. 2 is a view taken along line 22 of FIG. I showing the connection of the filament with the ferrules;
FIG. 3 is a rear elevational view of the rectangular sealed beam headlamp unit of FIG. I showing the location of the ferrules and ferrule bosses with respect to the mechanical axis of the unit;
FIG. 4 is a fragmentary cross-sectional view showing the disposition of the ferrule with respect to the exhaust tube;
FIG. 5 is a front elevational view of the reflector;
FIG. 6 is a view taken along line 66 of FIG. 5; and
FIG. 7 is a fragmentary perspective view of the reflector and filament assembly.
Referring to the drawings and as shown in FIG. 2, a rectangular sealed beam headlamp unit 10 made in accordance with the present invention comprises a glass reflector 12, a glass lens 14, and a plurality of electrically conductive metal ferrules 16 carrying electrical terminals 18. .The reflector l2 and the lens 14 are molded and all surfaces thereon have a positive draft angle.
A filament assembly I9 is disposed interior of the unit I0 and fixedly supported on the ferrules 16.
The unit 10 is an integral and indivisible optical assembly which. when combined with one or more additional units, constitutes a major lighting device for providing general illumination ahead of a motor vehicle. In such an application, the unit 10 is mounted on a suitable adjustable headlamp assembly which can be precisely aimed to project illumination in a desired direction. However, the total headlamp assembly does not form a part of the present invention and further discussion will proceed with reference to the construction of the headlamp unit per se.
The lens 14 has a slightly spherical front lens section 20 bounded by a slightly flared generally rectangular peripheral rim 22. The lens 14 includes an optical gridwork including a plurality of flutes or facets, generally represented by numeral 24. The facets serve to redirect illumination reflected light from the reflector 12 in a desired illumination pattern forwardly of the unit. The exact prescription for the lens forms no part of the present invention and it should be sufficient to note that only a portion of the gridwork may be fluted to provide the necessary lens prescription for a given application. The rim 22 terminates with a peripheral rearwardly extending lip 26 which is fusion sealed to a mating flange on the reflector 12.
The reflector 12 comprises a paraboloidal rear section 30, an upper wall 32, a lower wall 34, and side walls 36 and 38. The walls 32, 34, 36 and 38 diverge frontally terminate with a continuous peripheral flange 40 which is fusion sealed to the lip 26 of the lens 14. The rear section 30 has a paraboloidal front reflecting surface 42 having an optical axis 44 and a focal point 46. A plurality of raised ferrule bosses, numbered 50a, 50b, and 50c, are formed on the rear surface of the section 30 and are equally radially and circumferentially about an exhaust tube 51. The bosses have openings 52 extending therethrough. The metal ferrules 16 are con ventionally fusion sealed to the rear surfaces of the bosses 50 over the openings 52 (FIG. 4).
The filament assembly 19 comprises helically coiled major and minor filaments 60 and 62 respectively. The major filament 60 is located at the focal point 46 in a horizontal plane therethrough. The minor filament 62 is located slightly below and parallel to the major filament 60. The major filament 60 has rearwardly extending legs connected to filament support leads 64 and 66 which respectively extend through the openings of the ferrule bosses 50a and 500 and are brazed to the ferrules 16 associated therewith. The minor filament 62 has rearwardly extending legs connected to filament support leads 74, 76 similarly brazed to ferrules 50b and 500 respectively. A supplemental support leg 78 is brazed to ferrule 50a and supports a glare shield 80 at its front end thereof. The shield 80 is positioned with respect to filament 60 to prevent direct filament glare in a conventional manner. When the terminals 18 are attached to suitable electrical connector in the headlamp circuit, the filaments 60 and 62 will be selectively energized in accordance with switching devices therein.
The reflector 12 further includes four seating pads 81 on the rear reflector surface adjacent flange 40 (FIG. 3). These define a plane normal to the mechanical axis through the geometric center of the unit and are adapted to engage complementary seating surfaces on the headlamp assembly. The upper left hand pad 81 is larger than the others to provide indexing of the unit. The lens 14 further includes three aiming pads 82. The pads 82 are ground to compensate for optical variations in the units and are nominally parallel to the pads 81. When positioned in a known plane, the unit will direct illumination in a desired direction.
In conventional units, the ferrules 16 are equally radially disposed with respect to the mechanical axis on the horizontal mechanical center line 100 and the vertical mechanical line 102 (FIGS. 1, 3 and 5). This places two of the ferrule bosses on the horizontal center line and one above on the vertical center line. Thus, a considerable portion of the reflector surface, i.e. the openings 52 and surrounding areas, suitable for producing acceptable images for senthisizing the hot spot portion of the desired illumination pattern, are badly distorted and are not optically functional such that the overall pattern must be senthisized by controlling il lumination from less desirable portions of the reflector. This is particularly true with regard to the major filament 60 which most effectively uses the upper center and upper right sectors of the reflecting surface.
Referring to FIG; 3, the ferrule bosses 50 are rotated clockwise an angle (phi) from their conventional position with respect to horizontal mechanical center line and are evenly spaced with respect to the exhaust tube 51. The rotation of ferrules by the angle 4) (phi) locates the ferrule bosses 52'at portions 'of the reflecting surface which are least effective in senthisizing the desired illumination pattern and removes all bosses from the upper right and upper center sectors. While in the present application an angle of approximately 155 has been found effective; several factors affect this angle namely, reflector focal length, vertical and horizontal reflector dimensions, reflector tilt, type of filament design and the type of light distribution and cutoffs required.
The type 2 unit thus far described the plural filaments provide dual lighting modes. Further, the paraboloidal axis 44 is not coincident with a longitudinal mechanical axis 104 which is perpendicular to the horizontal mechanical center line 100 and the vertical mechanical center line 102, both of which pass through the geometric center of the lens 14. The type 2 unit has the parabolic axis 44 directed three degrees downwardly and three degrees rightwardly of the mechanical axis 104. Theoptical axis 44 intersects the rear surface at point 96.
Because these two axes are not coincident, ferrules equally spaced with respect to the mechanical axis, as in conventional units, will have unequal heights. Such unequal heights leads to unequal ferrule masses, and during the molding of the reflector the differences in glass mass cause considerable reflector distortion immediately adjacent to the ferrules due to different material filling and cooling temperatures.
While equal ferrule heights and masses could be achieved by uniformly spacing theferrules with respect to the optical axis 44, this is not easily accomplished with an all-glass unit. The molds used in casting such a reflector must have positive draft angles and must be separable along a mechanical axis perpendicular to the flange '40. It also must have sufficient drafts to permit full withdrawal and proper mold filling characteristics. It is therefore necessary that the axes of the bosses 50 be substantially parallel to the mechanical axis 104 to fulfill'these conditions.
Accordingly, in satisfying the above criteria, the present invention provides equal ferrule heights with the ferrule bosses having axes parallel to the mechanical axis and located with respect to the optical axis and mechanical axis at locations compensating for the relative inclination therebetween. In the present invention, the ferrule bosses 50a, 50b and 500 are equally radially spaced about the exhaust tube 51 which is located offcenter of the mechanical center of the unit.
This is accomplished by first determining the relative spacings desirable for the ferrules. In this connection the customary standard spacing is used wherein the terminals are located 0.670 inches about the exhaust tube 51. Two are located on a line through the exhaust tube 51 and the other along a line perpendicular thereto. lnitially two ferrulepositions, i.e. 50b, 500 are first coordinated relative to a selected base ferrule, i.e. 50a. These positions arethen translated to a coordinate system normal to the paraboloidal optical axis 44. The three equations are then solved for the locations of the ferrules which place them in a common plane perpendicular to the'mechanical axis. This yields a solution which places the prescribed ferrule spacings at a common distance measured parallel to the mechanical axis 44 with respect to the reflecting surface. This solution is then translated back to the mechanical axis to yield the relative positions of the ferrules. The exhaust tube 51 is then located at a position constituting the origin of a circle drawn through the three points.
In the present instance where a three degrees down and three degrees right inclination is used for the optical axis, the axis as viewed parallel to the mechanical axis will be at a 45 angle. The exhaust tube 51 is located 0.120 left and 0.120 up along this line for a paraboloidal reflecting surface having a focal length of 1.25 inches. With this technique, it is thus possible to prescribe equal ferrule boss heights for any random location and number of ferrules keeping in mind that equal boss heights can be achieved independently of the number of ferrules and any rotation of the ferrules with respect to any of the planes.
The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
l. A reflector for a lighting unit comprising: a molded member having all surfaces thereon with a positive draft angle with respect to a mechanical axis substantially through the center of the unit; a paraboloidal reflecting surface on the member having an optical axis inclined with respect to the mechanical axis; means on said member defining a plane normal to said mechanical axis; a plurality of raised ferrule bosses formed on the rear surface of said member, said ferrule bosses having axes parallel to said mechanical axis and being offset with respect to the mechanical axis and said paraboloidal axis to provide equal ferrule boss heights as measured from said plane to compensate for the inclination between said axes thereby provide equal masses and prevent distortion due to differing cooling rates thereat.
2. A lighting unit comprising: a paraboloidal reflector member having a paraboloidal axis; a lens memberr secured to said reflector; means on one of said members defining a plane wherein a normal thereto is inclined a predetermined amount with respect to said paraboloidal axis; a plurality of raised ferrule bosses formed on the rear surface of said reflector, said ferrule bosses having axes parallel to said normal and being offset with respect to the paraboloidal axis to provide equal ferrule boss heights as measured from said plane, said equal ferrule boss heights reducing reflector distortion caused by heat sinks in the molding of the reflector caused by varying glass thickness; ferrules sealed to said ferrule bosses; filament means fixedly electrically connected to said ferrules; and terminal means attached to said ferrules adapted to be connected to a power source for providing energization of said filament means.
3. A type 2 sealed beam headlamp unit for a motor vehicle comprising; a molded glass reflector, all surfaces of said reflector being formed with a positive draft angle with respect to a mechanical axis substantially longitudinally through the center of the reflector; a glass lens sealed to the reflector; a paraboloidal reflecting surface on said reflector, said reflecting surface having an optical axis inclined a predetermined amount with respect to said mechanical axis; a filament adapted to be positioned horizontally through the optical axis at the focal point of the paraboloidal reflecting surface,
the portions of the reflecting surface above the horizontal plane through the center of the unit redirecting illumination from the filament to produce optically efficient'images ofthc latter; three raised ferrule bosses formed on the rear surface of said reflector, said ferrule bosses having openings therein, theareas surrounding said'openings being subject to distortion during the molding process, said opening having axes parallel to said mechanical axis and being offset with respect to both axes to provide substantially equal ferrule boss heights as measured from said rear surface and along said axes, said equal ferrule boss heights compensating for the inclination between said axes to thereby provide equal glass masses and prevent distortion due to differing cooling rates during the molding of said reflector; an exhaust tube located at the origin of a circle drawn through the three ferrule bosses, the openings being rotated with respect to said exhaust tube to place the distorted areas of the ferrule bosses at portions of the reflecting surface having minimal interference with the optimum hot spot illumination; metal ferrules sealed to each of said bosses; and lead wires fixedly supporting said filament from said ferrules with the lead wires extending through said openings.
4. A rectangular sealed beam headlamp unit for a motor vehicle comprising: a molded glass reflector having a substantially rectangular frontal profile, said reflector having all surfaces thereon formed with a positive draft angle with respect to a mechanical axis substantially longitudinally through the center of the reflector; a paraboloidal reflecting surface on said reflector having substantially forwardly projecting planar side walls terminating with a rectangular peripheral flange; a first filament adapted to be supported at a horizontally position on the optical axis at the focal point of the reflecting surface; a second filament adapted to be supported at a position parallel to the first filament; said paraboloidal reflecting surface having an optical axis inclined with respect to said mechanical axis, said reflecting surface receiving illumination from the filament for redirection therefrom with the portions of the reflecting surface lying above horizontal plane through the center of the unit producing optically efficient hot spot images of the first filament; a generally rectangular glass lens having a rectangular peripheral lip sealed to said peripheral flange of said reflector, said lens distributing illumination from the reflecting surface outwardly in a desired illumination pattern; an exhaust tube formed in the rear surface of the reflector; a plurality of ferrule bosses formed on said rear surface and equally radially spaced with respect to said exhaust tube, said ferrule bosses having openings therein surrounded by distorted reflecting surfaces, said exhaust tube being positioned with respect to said rear surface at a location that establishes equal ferrule boss heights as measured in a plane normal to said mechanical axis to thereby provide equal glass masses and prevent distortion due to different cooling rates of the masses during molding of the reflector, said openings of said ferrule bosses having axes parallel to the mechanical axis, two of the openings being located on a line through said exhaust tube and rotated substantially 25 from a horizontal plane through said exhaust tube and the third opening being located substantially 25 from the vertical plane through said exhaust tube along a line perpendicular to and below the line joining the first twomentioned openings whereby said distorted areas are 8 whereby rotating the openings and providing equal ferrule boss masses provides a rectangular reflecting surface having minimal distortion and interference with the production controlled hot spot images of the filament.