METAL STRAP FOR HOLDING CYLINDRICAL LAMP

Abstract: A lamp is provided with a mounting arrangement for achieving a precise alignment. The lamp includes a double-ended light source (12), a metal strap (16) clamping one end of the light source at two locations, and a plastic base (14) having an internal opening (36) wherein the metal strap (16) is engaged. The metal strap (16) includes two clamping members (38) between which the light source (12) is clamped and a cap member (40) attached to the clamping members (38). The cap member (40) has tabs (60) adapted for engaging the internal opening (36) of the plastic base (14) and gimbaling the light source (12) to align the light source (12) with respect to the plastic base (14). The clamping members (38) are joined together at a point (64) between the two clamping locations such that a spring force clamps the light source (12). The clamping members (38) are also oriented at an angle of about 45 degrees from vertical to better withstand both vertical and horizontal loads.

Description: METAL STRAP FOR HOLDING CYLINDRICAL LAMP BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The present invention generally relates to a replaceable bulb for automotive headlamps and more particularly to such a replaceable bulb having a metal strap for aligning and locking a light source in a fixed position with respect to a base. DESCRIPTION OF RELATED ART With automotive designs tending to require smaller headlamp packaging, smaller light bulbs must be utilized which operate at higher temperatures, up to 700 degrees centigrade, due to their small size. These light sources are typically, but not limited to, the double-ended type. The light sources is typically fixed in a plastic base to form a replaceable bulb which is installed within the headlamp assembly. Proper alignment and stability of the light source inside the headlamp assembly are important requirements for the performance of the headlamp. Therefore, the light source is aligned in a specific position with respect to the plastic base to ensure alignment of the light source in the headlamp assembly. A gi bal device is one of the mechanisms typically used to align the light source with respect to the plastic base. The gimbal device, which serves as a holder for the light source, generally extends into a cylindrical opening of the plastic base from which the light source can be aligned. After alignment, the gimbal device is attached to the plastic base by either thermal or mechanical means so as to secure the light bulb in the aligned position. Once installed in the headlamp assembly, the replaceable bulb must conform to Federal Motor Vehicle Safety Standard 108. The standard demands that the replaceable bulb mounted inside the headlamp assembly does not permanently deflect beyond a specified distance of 0.005 inches in response to a 4 pound force applied perpendicular to its longitudinal axis. A tight reliable joint between the gimbal device and the plastic base is critical tp ensure that the replaceable bulb meets this deflection specification. Typical gimbal devices include a glass or ceramic member in order to insulate the plastic base from the heated light source. For example, see U.S. Patent No. 5,386,173, the disclosure of which is hereby expressly incorporated herein by reference in its entirety, which discloses a gimbal device having glass-mica member. The ceramic members, however, may cause cracks which penetrate the light source tube due to a thermal mismatch between the ceramic member and the quartz tube. Additionally, the ceramic members are relatively brittle and may be easily damaged by mechanical shocks or impacts. Accordingly, there is a need in the art for a replaceable bulb for ah automobile headlamp with improved thermal and mechanical shock resistance. SUMMARY OF THE INVENTION The present invention provides a lamp with a mounting arrangement for achieving a precise alignment that overcomes at least some of the above noted problems. The lamp includes a double-ended light source, a metal strap clamping one end of the light source at two locations, and a plastic base having an internal opening wherein the metal strap is engaged. The metal strap deflects during shock impacts and thereby enables the lamp to be more durable during handling and use. However, because the light source is clamped at two locations, the lamp can meet the deflection specification. Additionally, the metal strap reduces the thermal mismatch with the light source. Furthermore, the metal strap takes significantly less time and energy attach to the plastic base than prior art gimbal devices. BRIEF DESCRIPTION OF THE DRAWINGS These, and other features and advantages of the present invention will be apparent with reference to the following description taken in conjunction with the accompanying drawings, wherein: FIG. 1 is a top plan view of a replaceable bulb for an automotive headlamp having a metal strap according to the present invention; FIG. 2 is a side view of the replaceable bulb of FIG. 1; FIG. 3 is a bottom plan view of the replaceable bulb of FIG. 1; FIG. 4 is an end view of the replaceable bulb of FIG. l; FIG. 5 is an enlarged fragmented view, in partial cross-section, of the replaceable bulb taken along line 5-5 of FIG. 4; FIG. 6 is a side view of a clamping member of the metal strap; FIG. 7 is a plan view of the clamping member of FIG. 6; FIG. 8 is an end view of the clamping member of FIG. 6; FIG. 9 is an end view of a cap member of the metal strap; FIG. 10 is a side view of the cap member of FIG. 9; FIG. 11 is a perspective view of a variation of the metal strap of FIG. 1; and FIG. 12 is a perspective view of another variation of the metal strap of FIG. 1. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS FIGS. 1-5 illustrate a replaceable bulb 10 of an automotive headlamp according to the invention. An old bulb is replaced by installing a new bulb into a headlamp fixture (not shown) in a manner that is standard for this type of replaceable headlamp bulb 10. The replaceable bulb 10 includes a light source 12, a plastic base 14, and a metal strap or gimbal device 16. The light source 12 of the illustrated embodiment is of the double-ended type having an outer envelope 18 made of quartz material. The light source 12 can be of other types. The light source is a high-temperature light source, that is, it operates at temperatures in the range of about 200 degrees centigrade to about 900 degrees centigrade. The envelope 18 has a central bulbous section 22 and a pair of generally cylindrically-shaped inner and outer neck sections 22, 24 longitudinally extending from the bulbous section 20. Inner and outer lead wires 26, 28 emerge from the respective neck sections 22, 24 and are encapsulated by the neck sections 22, 24. The outer lead wire 28 is connected to an external conductor wire 30 that longitudinally extends into the plastic base 14. The inner lead 26 is connected to an internal conductor wire 32 within the plastic base 14. Within the plastic base 14, the conductor wires 30, 32 are connected to terminals 34 such that the light source 12 can be connected to an electrical source (not shown) in a conventional manner. The plastic base 14 is constructed from a high temperature plastic and contains a cylindrically-shaped internal space or opening 36 into which an inner end of the light source 12 extends and is supported by the metal strap 16. • The plastic base 14 is of a configuration that it can be mounted into the headlamp fixture in a manner that is consistent with industry practice. As best shown in FIG. 5, the metal strap 16 includes a pair of clamping members 38 and a cap member 40. The clamping members 38 and the cap member 40 are each formed from a suitable metal such as, for example, stainless steel, steel-Ni alloy, or Ni-Ag alloy. As best shown in FIGS. 6-8,. each clamping member 38 includes inner and outer clamping straps 44, 46, two connecting arms 48 and two attachment tabs 50 which are all integrally formed. The clamping straps 44, 46 each have a central arcuate portion 52 and rectangularly-shaped legs 54 extending outwardly therefrom. The arcuate portion 52 is sized such that, when joined with an associated clamping strap of another clamping member 38, a cylindrically-shaped nest is formed for the inner neck section 22 of the light source 12. The connecting arms 48 are generally coplanar with and connect the legs 54 of the inner and outer clamping straps 44, 46 and the arcuate portions 52 of the connecting straps 44, 46 are generally coaxial. The connecting arms 48 are sized such that the inner and outer clamping straps 44, 46 are longitudinally spaced apart to adequately supports the light source 12. A central opening 56 is formed between the clamping straps 44, 46. The attachment tabs 50 are generally rectangularly-shaped and perpendicularly extend outwardly from the legs 54 of the inner clamping strap 44. As best shown in FIGS 9 and 10, the cap member 40 includes a planar base 58 and four connecting tabs 60 extending from the base 58. The base 58 has a central circular opening 62 sized for allowing the inner neck section 22 to pass therethrough with clearance. The connecting tabs 60 are generally rectangularly-shaped and are equally spaced about the periphery of the base 58. Outer surfaces of the connecting tabs each have a radius which corresponds to the diameter of the internal opening 36 of the plastic base 14. Preferably, the connecting tabs 60 angle forwardly and outwardly from the base 58 as best shown in FIG. 10. As best shown in FIG. 5, the metal strap 16 clamps the inner neck section 22 of the light source 12 between the two clamping members 38. The clamping members 38 clamp the.neck section 22 at each of the spaced apart pairs of clamping straps 44, 46. The two clamping members 38 are attached together by welds 64. Preferably, the welds 64 are located near the center of the clamping members, that is, on the connecting arms 48 between the clamping straps 44, 46. Welding in this manner allows the clamping members 38 to deflect outwardly at the ends, as best shown in FIG. 5, so that a spring force clamps the neck section 22 at both locations of the clamping straps 44, 46. Accordingly, the arcuate sections 52 of the clamping members 44, 46 are sized such that they do not fully encircle the neck section 22 of the light source 12. Clamping with a spring force enables relatively large variations in the diameter of the neck section 22 to be accommodated. The spring force also enables the metal strap 16 to have more flexibility or "give" so that the lamp 10 can tolerate larger impact forces while still meeting the deflection specification. Alternatively, the welds 64 can be located on the clamping straps 44, 46 for more strength. However, the metal strap 16 would be more rigid and the tolerance of the neck section 22 must be more closely controlled. The clamping members 38 are attached to the cap member 40 by welding the attachment tabs 50 to the outer side of the base 58 as best shown in FIG. 5. The clamping members 38 are preferably oriented such that the interface between the two clamping members 38 is generally perpendicular to two of the connecting tabs 60 of the cap member 40 as best shown in FIG. 4. The cap member 40 of the metal strap 16 is inserted into the opening 36 of the plastic base 14 so that the outer surfaces of the connecting tabs 60 are in contact with the inner surface of the internal opening 36 as shown in FIG. 5. Preferably, the cap member 40 is sized such that the connecting tabs 60 engage the inner surface of the opening 36 with a spring force. In the illustrated embodiment, the metal strap 16 is oriented such that the interface between the clamping members 38 is about 45 degrees from vertical. Such an orientation enables the replacement lamp 10 to better withstand both vertical and horizontal loading. Once inserted in the plastic base 14, the metal strap 16 is free to gimbal, that is, free to slide axially along the longitudinal axis 66 and to rotate about the longitudinal axis 66 and the two axes perpendicular thereto. The gimbaling of the metal strap 16 enables the light source 12 to be properly oriented with respect to the plastic base 14 so that it will be in focus when assembled into the headlight fixture. Once the light source 12 is properly oriented with respect to the plastic base 14 the metal strap 16 is heated by application of Radio-Frequency (RF) energy whereupon the heat causes softening of the plastic base 14 near the connecting tabs 60 of the metal strap cap member 40. The metal strap cap member 40 expands and plastic of the plastic base 14 flows around the edges of the connecting tabs 60 thus interlocking the metal strap 16 to the plastic base 14 to form a rigid reliable joint. Contact between the metal strap 16 and the light source 12 is minimized because of the high thermal conductivity of the metal strap 16. Heat output from the light source 12 could overheat the plastic base 14 if enough heat is transferred through the metal strap 16. Accordingly, the metal strap 16 is adapted to minimize contact with the light source. The clamping straps 44, 46 are sized effective to both minimize contact with the neck section 22 of the light source 12 and to provide enough clamping force to meet the deflection specification. Contact between the metal strap 16 and the plastic base 14 is also minimized. The connecting tabs 60 are sized effective to minimize contact with the plastic base 14, to adequately gimbal to align the light source 12, and to provide an adequate joint to meet the deflection specification. It is noted that the only contact between the metal strap 16 and the plastic base 14 is at the connecting tabs 60. FIG. 11 illustrates a metal strap 68 which is a variation of the metal strap 16 of FIGS 1-10 wherein like numbers are used to identify like structure. The metal strap 68 illustrates that the inner and outer clamping straps 44, 46 can be oriented in different directions. In the illustrated embodiment, the outer clamping straps 46 are oriented about 45 degrees relative to the inner clamping straps 44. To obtain this orientation, the connector arms 48 of the metal strap 16 are twisted in a generally helical manner about the longitudinal axis 66. As shown in FIG. 11, the interface between the inner clamping straps 44 is generally vertical while the interface between the outer clamping straps 46 is generally about 45 degrees from vertical. Twisted in this manner the metal strap is able to better withstand loads in various directions. FIG. 12 illustrates a metal strap 70 which is another variation of the metal strap 16 of FIGS 1-10 wherein like numbers are used to identify like structure. The metal strap 70 illustrates that the inner and outer clamping straps 44, 46 can be unconnected. The inner clamping straps 44 are attached to a cap member 72 which has two connecting tabs 60. The outer connecting straps 46 are integrally formed with two additional connecting tabs 74 which longitudinally extend from the outer clamping straps 46 to a position in which they cooperate with the connecting tabs 60 of the cap member 72 to engage the plastic base 14 as described above. in the illustrated embodiment, the interface between the outer clamping straps 46 is oriented generally horizontal and the outer clamping straps 46 are connected to the top and bottom connecting tabs 74 while the interface between the inner clamping straps 44 is generally vertical and the inner clamping straps 44 are attached to the side connecting tabs 60. Although a particular embodiment of the invention has been described in detail, it will be understood that the invention is not limited correspondingly in scope, but includes all changes and modifications coming within the spirit and terms of the claims appended hereto.

Claims: WHAT IS CLAIMED IS: 1. A lamp with a mounting arrangement for achieving a precise alignment, said lamp comprising: a light source having a generally cylindrically- shaped neck portion; a metal strap clamping said light source at two longitudinally spaced apart locations on said neck portion; and a plastic base having an internal opening wherein said metal strap is engaged. 2. The lamp according to claim 1, wherein said light source and said metal strap are movable within said internal opening during an alignment stage to achieve the precise alignment of said light source with respect to said plastic base. 3. The lamp according to claim 1, wherein said plastic base is of a plastic material that softens upon generation of heat to lock said metal strap to said plastic base. 4. The lamp according to claim 1, wherein a periphery of said metal strap engaging said internal opening is generally spherically-shaped to allow said metal strap the freedom to move inside said plastic base, thereby aligning said light source. 5. The lamp according to claim 1, wherein said light source is a high temperature light source including discharge, halogen, and halogen IR. 6. The lamp according to claim 1, wherein said metal strap includes clamping straps connected by arms extending between the clamping straps. 7. The lamp according to claim 6, wherein said arms are joined together between said clamping straps such that said clamping straps clamp with a spring force. 8. The Lamp according to claim 6, wherein said arms are twisted. 9. The lamp according to claim 6, wherein said arms are oriented about 45 degrees from vertical. 10. The lamp according to claim 1, wherein said metal strap clamps said light source with a spring force. 11. The lamp according to claim 1, wherein said metal strap includes two clamping members between which the light source is clamped. 12. The lamp according to claim 11 wherein said metal strap includes a cap member attached to the clamping members and having tabs for engaging said internal opening of the plastic base. 13. The lamp according to claim 12, wherein said tabs have an outer surface arcuate both circumferentially and longitudinally. 14. The lamp according to claim 12, wherein said clamping members have integral attachment tabs for joining said clamping members to said cap member. 15. The lamp according to claim 11, wherein said clamping members are joined at a point between the two clamping locations such that a spring force clamps said light source. 16. The lamp according to claim 11, wherein said clamping members are oriented at an angle of about 45 degrees from vertical. 17. The lamp according to claim 1, wherein said light source is a double-ended type light source. 18. The lamp according to claim 17. wherein said metal strap clamps one end of said light source.

Inventors: NORRIS THOMAS RAINER, SAVARINO GINO, SEREDICH DOUGLAS GEORGE, STEWART JOHN JOSEPH, YU THOMAS HUEI-CHUNG, NORRIS, THOMAS, RAINER, SAVARINO, GINO, SEREDICH, DOUGLAS, GEORGE, STEWART, JOHN, JOSEPH, YU, THOMAS, HUEI-CHUNG
Applicants: GEN ELECTRIC, GENERAL ELECTRIC COMPANY
Application year: 1996
Main classification: F21M7
IPC codes: F21S8, F21V15, F21V17, F21V19, H01J5