Patent Abstract:
A rearview mirror assembly blowmolded carrier for vehicles and method of blowmolding the carrier are provided. The mirror assembly has a blowmolded carrier with a hollow space and a recess to affix a mirror element.

Full Description:
BACKGROUND OF THE INVENTION  
         [0001]    The invention concerns a rearview mirror arrangement, especially a lightweight mirror assembly for commercial vehicles.  
           [0002]    Outside mirrors of this kind and of variously different construction are already known in the present state of the technology. A mirror pane is adjustably affixed by a pivoting mechanism to a housing part, which part is appropriately connected to the body of the vehicle, allowing the mirror to swing in reference to the housing part. The housing part is, as a rule, a solid plastic part, produced by injection molding. It is generally of a basin-like construction in which further mirror components or corresponding connection points for additions are installed. In particular, for large truck and bus mirrors, the carrying structure for outside mirrors is based on tubing or plates, which are affixed directly to the mirror holder which projects toward the vehicle body. This construction is disclosed by EP-A-0 590 510. The housing part serves then as a covering of the back side of the mirror plate and supports the pivoting mechanism. The housing also provides a streamlined sheathing of the outside mirror. Such construction is extremely expensive and heavy.  
           [0003]    A problem with this tube and plate construction is that relatively strong vibrations occur in the rearview mirror assembly during the operation of the vehicle. In order to reduce these vibrations, EP 0 865 967 A2 proposes a carrying tube structure encased in a foamed molded part. Again, the disadvantage of this is that the entire carrying structure is heavy.  
           [0004]    A very light design, which is adaptable to smaller mirrors, is taught by DE 44 29 604 A1. In this case, the tube construction is fully dispensed with and the foam element itself remains as the support structure. For this purpose, a gradiated foam is employed as a one-piece element or the element can be composed of several shells.  
         OBJECTIVES AND SUMMARY OF THE INVENTION  
         [0005]    It is thus the objective of the present invention to make available a sufficiently stable rearview mirror which also offers the greatest possible reduction in vibration.  
           [0006]    The achievement of this objective is accomplished by the features of the invention.  
           [0007]    Since a blown, hollow plastic body, originating from a plastic blank, is used as a carrier, the result is a very light structure so that even in the case of a cantilevered mirror, or outboard carrier construction, the basic rigidity of the plastic hollow body assures a sufficient stability. At first, it appears doubtful that a blown plastic hollow body would exhibit sufficient stability to be used as a carrier for a rearview mirror arrangement for commercial vehicles. However, by means of the substantial reduction in the weight, the demands for achieving stability are likewise reduced, so that a blown plastic hollow body does indeed offer sufficient stability.  
           [0008]    Because of the fact that the plastic blank is made with varying wall thicknesses, the corresponding wall thickness of the finished carrier, that is, the plastic hollow body, can be controlled to specification for location and thickness. That is, the wall thicknesses of the carrier is increased in locations of high stress, i.e. at the point of juncture with the vehicle body, while the thicknesses in zones of lesser stress may be reduced. Also, a grid-like rib structuring on the inner side of the plastic hollow body may be used to increase rigidity.  
           [0009]    In accord with a further advantageous embodiment of the invention, the plastic hollow body encompasses a multitude of hollow spaces, which are enhanced by, for instance, inset pieces or correspondingly designed bubble formations. By these measures, the stability is additionally increased and also the possibility exists to fill specified hollow spaces with filling materials.  
           [0010]    In accord with another advantageous embodiment of the present invention, the plastic hollow body is constructed in multiple layers, whereby, first, an increased stability is achieved, and second, outer layers can be provided, which are especially smooth and/or acceptable for high quality lacquering.  
           [0011]    In accord with a further advantageous embodiment of the invention, the possibility exists of introducing, either in or to the hollow spaces, a stiffening structure whereby the rigidity of the carrier is additionally increased.  
           [0012]    In accord with a further advantageous embodiment of the invention, a filling material for the hollow spaces comprises plastic foam, such as polyurethane (PU) foam, a gradient foam or a multi-component hard foam, which binds itself firmly to the inside wall of the hollow spaces and thus increases the stability of the carrier. Moreover, the harmonic vibratory properties of the carrier can be advantageously addressed by the appropriate choice of foam density or its degree of softness, so that during commercial driving the unavoidable vibrations are strongly damped and also as a result, less wear on the mirror assembly is incurred.  
           [0013]    Additionally or alternatively, there may be injected into a portion of the hollow spaces, or into various hollow spaces, a viscous fluid mass, for instance a gel or a gelatinous filling material which will also favorably affect specific vibratory and damping characteristics.  
           [0014]    In accord with a further advantageous embodiment of the invention, a granulate and/or sand may additionally or alternatively be placed in the hollow spaces. In this way, the fill material can comprise exclusively sand or granulate, or a mixture thereof, or yet a mixture with the above described gel, gelatine or foam. Once again, the stability is favored in a positive way and again the specific vibratory and damping characteristics can be advantageously controlled with attention to specifics. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    Further details, features and advantages of the invention will become evident from the following description of a preferred embodiment. The description is made with the aid of the drawings. There is shown in:  
         [0016]    [0016]FIG. 1 a  a schematic sideview of a first embodiment of the invention with a carrier in the form of a blown plastic hollow body with a single, continuous hollow space,  
         [0017]    [0017]FIG. 1 b  a sectional view along the line A-A of FIG. 1 a ,  
         [0018]    [0018]FIG. 2 a  a perspective view of a second embodiment of the invention, with a rearview mirror, which possesses a carrier in the form of two bearing arms,  
         [0019]    [0019]FIG. 2 b  a sectional view along the line B-B of FIG. 2 a,    
         [0020]    [0020]FIG. 3 a schematic sideview of a third embodiment of the invention with a carrier in the form of a plastic, hollow body with a multitude of hollow spaces, and  
         [0021]    [0021]FIG. 4 a partial sectional view of a fourth embodiment of the invention with a carrier comprised of a blown plastic hollow body with added elements for rigidity. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0022]    Reference will now be made in detail to the presently preferred embodiment of the present invention, examples of which are illustrated in the drawings. The examples are provided by way of explanation of the invention and are not meant as a limitations of the invention. For example, features illustrated or described as part of one embodiment can be used on another embodiment to yield yet a third embodiment. Accordingly, it is intended that the present invention include such modifications and variations.  
         [0023]    [0023]FIGS. 1 a  and  1   b  schematically present a first embodiment of the invention. The rearview mirror arrangement encompasses a carrier  2  in the form of a plastic hollow body  2 , blown from an extruded plastic blank and having a closed wall  3 . On the vehicle end of the plastic hollow body  2 , screw holes  4  are provided, in order to affix the carrier  2 , i.e., the rearview mirror arrangement, to the vehicle body. On the distal end of the plastic hollow body  2  remote from the vehicle, a first mirror  6  and a second mirror  8  are mounted in respective recesses  7  and  9 . Both mirrors,  6  and  8  include, respectively, an adjusting mechanism  10  and  12 , by means of which the mirrors are secured to the plastic hollow body  2 . The wall  3  of the plastic hollow body  2  is thicker at locations of higher stress than at locations of more moderate stress (not shown).  
         [0024]    The FIGS. 2 a  and  2   b  show a second embodiment of the invention with a carrier  20  in the form of a hollow plastic body. The hollow plastic body  20  includes a shell shaped mirror housing  22  and two carrier arms, respectively  24  and  26 , which are of one piece with the mirror housing  22 . The two carrier arms  24  and  26  are hollow, and exhibit respectively a hollow space  28  which is filled with filling material  27 . Preferably polyester urethane foam, gradient foam, multi-component foam and the like may be used as the filling material  27 . The carrier  20  possesses, on the distal end of the mirror housing remote from the vehicle, an additional hollow space  29 , the interior of which, likewise is filled with foam  27 . By filling the hollow spaces  28  and  29  with foam  27 , first, the stability is improved, since the foam binds itself to the interiors of the walls in the hollow spaces  28  and  29 , that is, adheres to the walls. Second, because of the foam the vibratory characteristics are positively influenced, that is, the vibration is damped.  
         [0025]    [0025]FIG. 3 shows a third embodiment of the invention with a carrier  30  in the form of a hollow plastic body, wherein the hollow plastic body exhibits a plurality of bubble shaped hollow spaces  32  and  34 . In this case, the bubble shaped hollow spaces  32  are empty, while the bubble shaped hollow spaces  34  are at least partially filled with a filling material  36 . Because of the plurality of the hollow spaces  32 ,  34 , first, the weight is reduced and second, by means of the dividing walls  33  between the hollow spaces  32 ,  34 , the stability is increased. By filling of a portion of the hollow spaces, namely the hollow spaces  34 , with a filling material  36 , the vibratory properties of the mirror assembly are influenced in such a way, that less vibration occurs, that is to say, the vibrations are damped. Additionally, in the case of the third embodiment, carrier arms  38  are constructed of metal, by means of which the stability of the carrier  30  is additionally increased.  
         [0026]    [0026]FIG. 4 shows a fourth embodiment of the invention, with a carrier  40  in the form of a plastic hollow body, by which on the interior walls of the plastic hollow body  40 , grid type stiffening ribs  42  are provided. These grid shaped, stiffening ribs  42  can be made by providing correspondingly different wall thicknesses in the plastic blank before the blowing of body in the blow mold. The grid shaped stiffening ribs  42  also contribute to the increase of the stability of the carrier  30 .  
         [0027]    It will 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.

Technology Classification (CPC): 1