Abstract:
An external mirror for motor vehicles includes a housing having a one-piece foam core and a reinforcing layer enveloping the core, at least one mirror plate, and a swivelling mechanism secured to the mirror plate and the core of the housing for movably positioning the mirror plate relative to the housing. Method for manufacturing an external mirror for vehicles includes the steps of molding a housing, embedding at least one swivelling mechanism in the housing during the molding step, and attaching a mirror plate to the swivelling mechanism.

Description:
BACKGROUND OF THE INVENTION 
     The invention is generally related to an external mirror for motor vehicles, especially for trucks or buses. The invention is more particularly related to an external mirror having unitary housing design to which various elements are readily secured. 
     External mirrors of various constructions have been made. Typically, external mirrors include a housing integrated with a vehicle body in some way, a mirror plate, and a swivelling mechanism inserted between the mirror plate and the housing for positioning and securing the mirror plate in an adjustable manner relative to the housing. The housing is typically an injection molded part made of heavy plastic, which is generally shaped as a trough, to which mirror elements are installed over corresponding mounting points. In order to provide the housing with necessary stability, expensive ribs and reinforcements are necessary. Moreover, the mounting points—for instance, screw collets, entry borings, and the like—are installed for additional mirror parts by means of relatively costly molding tool work on the housing. 
     For large trucks and bus mirrors, very often tubular or plate designs are employed for the support means of the external mirrors, which are directly integrated with the mirror holder extending from the vehicle body (see, for example, EP 0 590 510 A1). The housing serves in this case only not as a cover for the back side of the mirror plate and the swivelling mechanism, but also as an aerodynamic sheathing for the external mirror. Such designs are extremely expensive and heavy. 
     Known multiple unit mirrors employ a complex grating type tube design, upon which the housing is simply set as a sheathing thereover. The mirror, is thus weighty and can only be produced at a high cost. In particular, the molding equipment for the production of the sheathing portion is very complex and hence expensive. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     It is accordingly an object of the invention to provide an external mirror addressing and solving the above drawbacks and others of the prior art. 
     It is an additional object of the invention to create an external mirror that is simple and inexpensive to manufacture and assemble, and a corresponding method of assembling the external mirror. 
     It is another object of the invention to provide a mirror that is stable and resistant to vibration. 
     These objects and others are achieved by the features and corresponding method steps described and explained below. The invention provides a housing that is a self supporting, integral shaped piece from a single foam core with a reinforcing layer that covers the core. The invention provides a simple manufacture, high shape stability, minimum vibration sensitivity, and low weight. Very complex basic housing shapes can be made, as well as very large housings. These advantages will be discussed in detail below with reference to particular preferred embodiments. 
     Polyurethane material has been selected as a preferred plastic substance for the foam core and the reinforcing layer which is applied thereon. It suffices for the installation of the mirrors and for the related swivelling mechanism, generally, to allow for a basin shaped reception recess in the housing. In this design, the mirror plate is installed with the swivelling mechanism and, for example, affixed to the housing for a long term period by plastic tapping screws or an appropriate adhesive. Special screw collets or penetrating borings, as used in conventional devices, are not necessary, substantially reducing the technical forming process. 
     Due to the filling of the housing by foam material, it is possible, even during the formation of the housing, to embed within the foam core, for instance, fittings for the attachment of the housing on to the body of the motor vehicle, holder bases for the fastening of the swivelling mechanism to the housing, and cable and/or empty tubing for the electrical system, the positioning control, and the heating of the mirror plates. This too reduces the amount of the production costs for the external mirror itself and the expense of the final mounting on the vehicle. The housing can also be penetrated by an opening through the foam core, so that the housing is mountable on a retaining arm for the mirror. 
     The multiple unit mirror embodiment according to the present invention includes a self supporting housing, which not only serves as the support structure, but also as the sheathing of the mirror plates within the respective swivelling mechanism. The housing can be made with a relatively simple molding set up, whereby the molding costs are substantially reduced. Because of its integral structure and the stability of shape along with low response to vibration provided by the integral structure, the corresponding multiple unit mirror is well-suited for use on vehicles such as busses. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further features, details, and advantages of the invention can be inferred from the following description in which preferred embodiments of the invention are discussed with reference to the following figures: 
     FIG. 1 is a side view of the external mirror according to a first embodiment of the invention. 
     FIG. 2 is a horizontal section through the mirror along line II—II of FIG.  1 . 
     FIG. 3 is a longitudinal section through a multiple unit mirror according to a second embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the presently preferred embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. 
     The exterior mirror presented in FIGS. 1 and 2 includes a housing  1 , the outside contour of which exhibits the convexly cambered profile common to truck mirrors. The housing  1  is designed as a self supporting, integrally shaped piece, which is made out of a one-piece foamcore  2  and a reinforcing layer  3  which totally envelopes the foam core  2 . The foam core  2 , which is preferably a polyurethane substance, is expressed out of an appropriate molding apparatus, and subsequently the reinforcing layer  3  (also preferably polyurethane) is sprayed thereon. The reinforcing layer  3  congeals into a smooth outer skin of a few millimeters thickness, which, together with the foam core  2 , lends the necessary stability to the housing and makes it weather resistant. At the same time, the reinforcing layer  3  can be lacquered or painted to conform with the outer color of the vehicle which is being provided with the mirror. The foam core  2  and the reinforcing layer  3  are preferably comprised of polyurethane substances which can be easily chosen by persons skilled in the art. 
     As is particularly made clear in FIG. 2, the housing  1  includes on side  4 , which is turned away from the direction of travel “F, ” a receiving recess S having an opening  6  in which the mirror plate  7  is installed with an all-around clearance “a ” from the stiffening surface of collar  8  of the housing which lines the recess  5 . The mirror plate  7  is affixed to a plate shaped mirror carrier  9 , for example, by mechanically locking or securing with adhesive. The mirror carrier  9  is fastened to a holding plate  11  by a clamping connection, as is described in the German Patent Application P 43 02 950.7 (which corresponds to U.S. patent application Ser. No. 08/245,952 now U.S. Pat, No. 5,615,054). The holding plate is bound to the housing  1  by means of a swivelling mechanism denoted generally by  12 , whereby the mirror plate  7  is installed in the housing  1  in a swivelable manner. 
     The swivelling mechanism  12  is designed as a ball joint, whereby a bearing shell  13  of the ball joint is integrally formed as part of a socket piece  14 . A side wall portion  15  of the socket piece  14  extends from the bearing shell  13  with a conical frustum shape that terminates in a ring shaped, encircling collar  16 . As shown in FIG. 2, the collar  16  and the adjacent portions of walls  15  of the socket  14  are embedded within the foam core  2  of the housing  1 , whereby a firm connection between the socket  14  and the housing  1  is achieved. The foam material, in this arrangement, completely fills the inner volume of the socket  14 . 
     The bearing shell  13  includes in its one-piece construction a centrally located, axially protruding threaded sheath  17  within which a securing screw  18  holds a thrust bearing cap  19  in place on the end of the threaded sheath  17 . In the interior of the thrust bearing cap  19  is compressed a spring  20 , which acts against a spherical segment shaped detent element  21  in the direction of the bearing shell  13  of the swivelling mechanism  12 . Between the detent element  21  and the bearing shell  13  is a hemispherical opposed bearing shell  22  fitted on the holding plate  11  for the mirror holder  9 . The opposed bearing shell  22  includes a central opening  23  through which, with some play, the threaded sheath  17  penetrates. 
     As may further be made clear from FIG. 2, the housing  1  includes a vertical opening  24  extending through the housing by means of which the housing  1  can be mounted on a tubular holding arm  25 . The housing  1  can be stably bound to the holding arm  25  by screws which are not shown. 
     The exterior mirror depicted in FIG. 3 is designed as a multiple unit mirror, the housing  1 ′ of which runs in a somewhat quarter-circular arc, viewed in a plane parallel to the ground, and with substantially vertical surfaces (vertical to the drawing plane of FIG.  3 ). The housing  1 ′ is made from a foam core  2  and a reinforcing layer  3  which envelopes the foam core  2 . In the concave inner side  26  of the housing  1 ′ are three mirror assemblies  27  arranged next to one another covering some ⅔ of the length of the arc of the housing  1 ′. Extending from this section, called the “mirror zone  28 , ” of the housing  1 ′ is found an anchoring segment  29 , the end  30  of which, i.e. the end of the exterior mirror, is affixed to a bus. To make clear this installation of the exterior mirror on the bus, the latter is indicated by dotted lines, whereby in FIG. 3 the forward roof end  31 , the so-called A-column  32  of the bus body, and the front pane  33  are recognizable. 
     The mirror assemblies  27  are placed once again in the respective receiving recess  5  in the housing  1 ′. Each mirror assembly  27  includes swivelling modules  34  held respectively in place on the innermost wall  35  of the recess  5  by means of plastic self tapping screws  36 . The swivelling modules  34  are of conventional construction and possess integrated swivelling motors. On the side of the swivelling module  34  remote from the back plate  35 , a holding plate is installed as before, upon which the mirror carrier  9  of the mirror plate  7  is fastened by means of the mentioned clamping connection  10 . The mirror plates  7  lie again in the area of the opening  6  of the receiving recess  5 . 
     In the anchoring segment  29  of the housing  1 ′, a gable shaped fitting base  37  is embedded in the foam core  2  of the housing  1 ′, whereby an anchoring plate of the fitting base  37  is enveloped by the foam core  2  on all sides, and by means of the openings  39  is penetrated by the foam core  2 . In this way, an intimate connection between the fitting base  37  and the foam core  2  is achieved. Extending from an anchoring plate  38  are two side bars  40 ,  41 , which are surrounded by the foam core on the outer surfaces. Between the opposing inner sides of bars  40 ,  41 , the foam core is excised (cut-out  43 ) so that the two side bars  40 ,  41  of the fitting base  37  can be pushed on to a support bracket  42  on the forward roof end  31  of the bus body and subsequently affixed this with screws. Thus, a simple yet stable securement of the external mirror to the body is guaranteed. 
     As is further made clear from FIG. 3, in the foam core  2  of the housing  1 ′, empty tubes  44  made of thin, stable shaped hose are embedded, which generally run from the cutout  43  to the receptacle recesses  5  with the terminal end opening in the area of the back plate  35 . Electrical power lines and control cables can be run through these tubes  44  to serve the swivelling module  34  and possibly a mirror heating means if such is provided. Again the wiring of these electrical components can be carried out with ease. As an alternative, the cables can be embedded directly in the foam core  2  by laying the cables in the molding equipment. 
     It should be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope and spirit of the invention. It is intended that the present invention includes such modifications and variations as come within the scope of the appended claims and their equivalents.