Fixing system for lighting fixture parts, especially automobile lights

A fixing system for lighting fixture parts, especially the lights of an automobile, includes a thermoplastic outer lens (2), which is installed in a thermoplastic encircling housing (3) by means of a sealing adhesive (4) and secured by fastening elements. The fixing element is a brad pin (1) which is shot through a groove (31) of the encircling housing (3) and a lug (21) of the outer lens (2), with a profile in the shape of a circle flattened at least at two diametrically opposite places, having a longitudinally smooth brad pin shank (14) along its entire length, which is covered by an adhesive (112) to hold the brad pins (1) together.

FIELD OF TECHNOLOGY

The invention concerns a Fixing system for lighting fixture parts, especially automobile lights.

PRIOR ART

From the specification of U.S. Pat. No. 5,267,386 there is known a design describing a method of securing an outer lens to a housing, where a hot rolled wire is forced through a plastic housing and the ribs of the plastic outer lens with total plasticization of the plastic material. The drawback of this solution is its low production effectiveness and limited possibility of automation.

From the specification of DE Patent No. 4310048 there is further known a method of using nails of circular cross section, by which the outer lens and the housing are joined together with the use of partial ultrasound plasticization of their material. This method is not sufficiently effective, since mechanical loading during the process produces deformation of the joined parts, and the circular cross section of the nail enables a rotation about its lengthwise axis. Moreover, the additional operation of predrilling produces dust particles inside the lighting appliance.

There is also known from the specification of CZ Patent No. 296 970 a fastening means, being a clip in the shape of the letter U or the letter J. This complicated shape with two feet creates an internal stress between the contact points of the feet in the joined plastic parts, which leads to the formation of stress cracks under the influence of a corrosive environment. There is also known a solution (specification DE No. 10 2008 025 609) describing a method of primary fastening of two plastic parts in a mutual joint, performed without the use of adhesive, in which they are preheated by hot air, laser, or infrared light, before inserting a fastening nail in order to bring about a partial plasticization of the joined parts. In this case, the drawback is the risk of producing flaws in the appearance of the product in the heated region, due to the high temperature.

A solution is also known from specification of EP No. 2,223,794, enabling a primary fixing of three or more plastic parts, such as a outer lens, a housing, and another part (frame, interior optical part, filter, reflector, socket, etc.), all of which are joined without the use of adhesive. A fastening element of nail type contains a head and a shaft. The fastening element has a profile of square shape, with a rectangular head and locking grooves situated along the entire length of the shaft. The drawback of this solution is less accuracy of the external shape of the lighting appliance, due to the greater number of joined parts, all of which are in the required contact position, and the creation of cracks under stress due to the corrosive environment in the shell and the lens, as a result of deformation caused by the head.

ESSENCE OF THE INVENTION

The aforementioned drawbacks of the known designs are eliminated to a substantial degree by a fixing system of lighting fixture parts, especially the lights of an automobile, including a thermoplastic outer lens, which is installed in a thermoplastic encircling housing by means of a sealing adhesive and secured by fastening elements according to the invention, the essence of which lies in the fact that the fixing element is a brad pin which is shot through a groove of the encircling housing and a lug of the outer lens, with a profile in the shape of a circle flattened at least at two diametrically opposite places, having a longitudinally smooth brad pin shank along its entire length, which is covered by an adhesive to hold the brad pins together in the lug.

Another essence of this solution is the fact that the width of the brad pin is greater than the distance between the parallel lines of its two flat areas.

In an advantageous embodiment, the profile of the brad pin has four flattened areas, each of which is oriented perpendicular with respect to the two neighboring flats.

Another essence of this solution is the fact that the brad pin is made from a material which is harder than the material of the lug of the outer lens and the groove of the encircling housing, and the adhesive for holding together the brad pins in the lug is based on nitrolack.

The advantage of this solution is that the material of the outer lens and the housing remains constantly cold and is not plasticized by the hot air or by some other medium, or otherwise heated. The brad pin is shot through the lug of the outer lens and a flange of the housing, while its circular profile is bounded by at least two parallel flattened areas, situated at two diametrically opposite places, to prevent rotation of the brad pin about its lengthwise axis. Moreover, the side or corner arcs produced by the flattening reduce the stress in the joined parts and the formation of stress cracks under the action of the corrosive environment, both for the outer lens and for the housing.

The adhesive on the surface of the brad pins acts as a sliding layer when they are shot in, and this furthermore creates a sealing joint between the surface of the brad pin and the outer lens and housing.

SAMPLE EMBODIMENTS OF THE INVENTION

The fixing system for the parts of lighting fixtures for automobile lighting that is illustrated inFIG. 1aandFIG. 1bincludes a thermoplastic outer lens2and a thermoplastic housing3. The outer lens2and the housing3are glued/sealed by a sealing adhesive4and joined together by brad pins1through a lug21of the outer lens2and a groove31of the housing3. The groove31of the housing3includes the outer flange33of the housing3and the inner flange32of the housing3. The brad pin1has a length which prevents its full penetration through the wall of the inner flange32of the housing3.

The primary fastening is accomplished by the sealing adhesive4, which is applied as a first fastening element and upon hardening forms the basic joint between the outer lens2and the housing3. The brad pin1serves as a second fastening element to ensure the position until the sealing adhesive4hardens.

The main advantage of the fastening system is the higher precision in fixing the outer lens2to the housing3before the primary fastening system of the sealing adhesive4begins to function after hardening. Another benefit is the more simple design of these parts.

The fastening is accomplished by at least three brad pins1in order to ensure the required stability of position of the outer lens2and the housing3, and in order to achieve their expected positional tolerance on the vehicle.

The fastening is done on the cold parts, not heated either by hot air or by infrared light or by laser or by some other heating that is used for the thermal plasticization of the materials of the installed parts. The brad pins1, shown inFIG. 2andFIG. 3, consist of a brad pin shank14and a tip15. The angle of the brad pin point15of the brad pin1can be 60° to 120°, in order to facilitate the installation. The brad pin shank14is longitudinally smooth, without locking grooves, and the brad pin1does not have a head, and its side parts are blunt.

One alternative profile of the brad pin1is shown inFIG. 4. The circular shape is bounded by parallel cut lines12, which have a spacing from each other less than the width of the brad pin1.

Another alternative profile of the brad pin1is shown inFIG. 5. The circular shape is bounded by two horizontal parallel lines12and two vertical parallel lines12, joined by corner radii. The advantage of these profiles is a more robust fabrication of the strip111of the brad pins1and fewer stress cracks due to the corrosive environment of the lug21of the outer lens2and the inner flange32of the housing3.

The brad pin1is made from a material which is harder than the material used for the lug21of the outer lens2and the groove31of the housing3. The brad pins1are coated with an adhesive11to increase the adhesion between the brad pin1and the inner flange32of the housing3and the outer flange33of the housing3and the lug21of the outer lens2. The material forming the joint adhesive11is based on epoxy.

The brad pins1, prior to the fastening process, are joined together within the strip111of brad pins1by the joint adhesive11,112, for easier handling when filling them into the brad pin gun. These strips111of brad pins, illustrated inFIG. 6andFIG. 7, facilitate the automating of the production process.

A stapling device is used for the application of the brad pins1. There are various systems for creating the required mechanical energy for shooting the brad pins1: mechanical, pneumatic, or electrical. The system predominantly used is a pneumatic stapling machine with electrical control. The impact force of the air of the pneumatic stapler helps in driving the brad pin into the surface. The great force produced by the compressed air of the pneumatic stapler is able to force the brad pin into a material like plastic extremely quickly.

This fastening system for the parts of an automotive lighting system is simple, economical, and efficient.

LIST OF REFERENCE SYMBOLS USED