Abstract:
A device for monitoring vehicles surroundings includes a sensor, a sensor holder and a fastener. Due to manufacturing tolerances, the sensor axis that passes through the head of the sensor deviates from the axis of the sensor main body. The sensor head passes into an opening in the sensor holder centered around a sensor holding axis. When the sensor is mounted into a receiver niche in the sensor holder, the sensor holding axis and the sensor axis are aligned. The fastener fastens the sensor to the sensor holder and compensates for the sensor axis deviating from the main body axis. Screws pass through bore holes in the fastener and into screw holes in the sensor holder. The bore holes have a larger diameter than do the screw holes, allowing the sensor axis to be aligned with the sensor holding axis despite the sensor axis deviating from the main body axis.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application is based on and hereby claims the benefit under 35 U.S.C. §119 from German Patent Application No. DE 102014205505.9, filed on Mar. 25, 2014, in the German Patent Office. This application is a continuation-in-part of German Patent Application No. DE 102014205505.9, the contents of which are incorporated herein by reference. 
       TECHNICAL FIELD 
       [0002]    The invention relates to a sensor arrangement for monitoring a vehicle&#39;s surroundings, and in particular to sensors that are attached outside of the vehicle. 
       BACKGROUND 
       [0003]    In motor vehicles, sensors of the widest variety are continually used for monitoring a vehicle&#39;s surroundings. Ultrasound sensors are used for parking assistance systems, radar sensors for distance monitoring systems, cameras for indirect viewing systems and thermal imaging cameras for detecting persons in the vicinity of the vehicle. 
         [0004]      FIG. 1  (prior art) shows a sensor  10  that includes a sensor main body  11  from which a sensor head  12  protrudes. The sensor  10  is held in a sensor holder  13 . The sensor holder  13  includes a sensor head receiver niche  14  with a sensor head opening  15  and two screw receivers  16  and  17  that extend on the left and on the right of the sensor head opening  15  in a direction parallel to the sensor main body  11 . The sensor main body  11  includes two fastening clips  18  and  19  with screw holes  20 ,  21  located on the left and right away from the sensor main body  11 . The sensor  10  is inserted into the sensor holder  13 , and the two fastening clips  18  and  19  come to rest on the upper ends of the two screw receivers  16  and  17 . Sensor  10  and sensor holder  13  are screwed together using screws that are not shown in  FIG. 1 . The height of the two screw receivers  16  and  17  is selected so that the sensor head  12  is aligned with the outside surface  22  of the sensor holder  13 . 
         [0005]    The sensor  10  is oriented along a sensor axis  23 . The sensor main body  11  has a main body center axis  24  that deviates from the sensor axis  23  due to a manufacturing tolerance  25 . The sensor head receiver niche  14  and the sensor head opening  15  have a sensor holding axis  26  that passes through the center of the opening  15 . Because the sensor  10  is mounted by the fastening clips  18  and  19  arranged symmetrically on the sensor holder  13  relative to the sensor main body  11 , the manufacturing tolerance  25  between sensor axis  23  and main body center axis  24  must be taken into consideration in the dimensioning the sensor head opening  15 . Therefore, in the assembled state of sensor  10  and sensor holder  13 , gap widths varying between 27 and 28 result between the margin of the sensor head opening  15  and the sensor head  12 . These gap widths varying between 27 and 28 lead to a visually unsatisfactory result because the human eye is sensitive to such variations in gap width. 
         [0006]    A sensor arrangement is sought that improves upon the current manner in which the heads of sensors and cameras protrude from sensor holders outside of vehicles so as to avoid any large variation in the gap width between the sensor head and the opening in the sensor holder. 
       SUMMARY 
       [0007]    A sensor arrangement is provided, in particular for sensors to be attached outside of a motor vehicle, for monitoring the vehicle surroundings. Small manufacturing tolerances between the sensor head and the sensor main body can lead to unequal gap widths. Because the sensor head receiver niche is designed so that, in the mounted state of the sensor in the sensor holder, the sensor holding axis and the sensor axis are aligned, the result is a joint gap with constant gap width between the margin of the sensor head opening and the sensor head. The gap width variations that are perceived as visually unappealing are thus prevented, and the visual quality of the component group is increased. The constant gap width also decreases wind noises and soiling in the interior area. In spite of the constant gap width, the mounting of the sensor in the sensor holder does not become more difficult. The outside surface of the sensor holder is preferably designed as a visible component. Alternatively, an additional transparent cover is also possible. 
         [0008]    In one embodiment, a device for monitoring the surroundings of motor vehicles includes a sensor, a sensor holder and a fastener. The sensor includes a sensor main body and a sensor head. The sensor axis passes through the center of the sensor head, and the main body center axis passes through the center of the sensor main body. Due to manufacturing tolerances, the sensor axis deviates from the main body center axis. The sensor holder includes a sensor head receiver niche and a sensor head opening into which the sensor head is received. The sensor holding axis passes through the center of the sensor head opening. The sensor head receiver niche is formed so that when the sensor is mounted in the sensor holder, the sensor holding axis and the sensor axis are aligned. The fastener fastens the sensor to the sensor holder and compensates for the sensor axis deviating from the main body central axis. Aligning the sensor axis of the sensor head with the sensor holding axis of the opening achieves a constant gap width between the sensor head and the edge of the sensor head opening. This avoids gap width variations that are visually unappealing. 
         [0009]    In one aspect, the fastener includes bore holes in holding clips attached to the sensor. Screws pass through the bore holes and into screw holes in the sensor holder. The bore holes have a larger diameter than do the screw holes, which allows the sensor axis to be aligned with the sensor holding axis despite the sensor axis deviating from the main body center axis. In another aspect, the sensor head includes a sensor head collar that rests on the sensor holder so as to align the sensor axis with the sensor holding axis. The sensor head collar has an annular ridge that fits in an annular groove in the sensor holder. In yet another aspect, the sensor and the sensor holder are integrated into a holding arm that is attached to the vehicle. The sensor holder is attached to the holding arm by an annular collar of the sensor holder that mates with a complementary annular step of the holding arm. A flexible heating foil is wrapped around the sensor head inside the holding arm. 
         [0010]    In another embodiment, a sensor arrangement on a vehicle includes a sensor, a sensor holder and a fastener. The sensor includes a sensor main body and a cylindrical sensor head. The sensor axis passes through the center of the sensor head, and the main body center axis passes through the center of the sensor main body. The sensor axis deviates from the main body center axis due to manufacturing tolerances. A sensor holder includes a circular sensor head opening into which the sensor head passes. The sensor holding axis passes through the center of the sensor head opening. The fastener attaches the sensor to the sensor holder such that the sensor holding axis and the sensor axis are aligned. The fastener compensates for the sensor axis deviating from the main body central axis by centering the sensor head in the sensor head opening. The sensor is a thermal imaging camera, an infrared sensor, a radar sensor, or an ultrasound sensor. 
         [0011]    Other embodiments and advantages are described in the detailed description below. This summary does not purport to define the invention. The invention is defined by the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The accompanying drawings, where like numerals indicate like components, illustrate embodiments of the invention. 
           [0013]      FIG. 1  (prior art) is a schematic diagram of a sensor arrangement according to the prior art. 
           [0014]      FIG. 2  is an exploded view of a first embodiment of the invention. 
           [0015]      FIG. 3  is an exploded view of a second embodiment of the invention. 
           [0016]      FIG. 4  shows a schematic diagram of a third embodiment of the invention. 
           [0017]      FIG. 5  shows a schematic diagram of a fourth embodiment of the invention. 
           [0018]      FIG. 6  is a cross-sectional diagram of a fifth embodiment of the invention. 
           [0019]      FIG. 7  is a cross-sectional diagram of a sixth embodiment of the invention. 
           [0020]      FIG. 8  is a cross-sectional diagram of a seventh embodiment of the invention. 
           [0021]      FIG. 9  is a cross-sectional diagram of an eighth embodiment of the invention. 
           [0022]      FIG. 10  is a cross-sectional diagram of a ninth embodiment of the invention. 
           [0023]      FIG. 11  is a cross-sectional diagram of a tenth embodiment of the invention. 
           [0024]      FIG. 12  is a cross-sectional diagram of an eleventh embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    Reference will now be made in detail to some embodiments of the invention, examples of which are illustrated in the accompanying drawings. 
         [0026]      FIG. 2  shows a sensor arrangement according to a first embodiment in which the sensor axis  23  and the sensor holding axis  26  are aligned in the mounted state of the sensor  30  in the sensor holder  31 . 
         [0027]    The sensor axis  23  passes through the center of the sensor head  12 , and the sensor holding axis  26  passes through the center of the sensor head opening  15 . The sensor  30  fits into the sensor head receiver niche  14 . By forming the sensor head receiver niche  14  so that the sensor axis  23  and the sensor holding axis  26  are aligned, a joint gap with a constant gap width is achieved between the margin of the sensor head opening  15  and the sensor head  12 . Variations in the gap width, which are perceived as visually unappealing, are prevented, and the visual quality of the component group is improved. A constant gap width also decreases wind noises and soiling in the interior area of the sensor holder  31 . In spite of the constant gap width, however, it does not become more difficult to mount the sensor  30  in the sensor holder  31 . The outside surface  32  of the sensor holder  31  is preferably designed as a visible component. Alternatively, an additional transparent cover is also possible. The fastening means can include one or more screws, clamps and the like. 
         [0028]    The sensor head  12  is preferably secured in the sensor head opening  15 . This is achieved either by a clamping seat of the sensor head  12  in the sensor head opening  15  or by a peripheral collar on the sensor head, which rests on the sensor holder  31 . The sensor head opening  15  is surrounded by a cover  33  with a cover opening  34 . The sensor head  12  protrudes through the sensor head opening  15  and into the cover opening  34 . As a result, the gap width between the sensor head  12  and the margin of the cover opening  34  that is visible from the outside can be set based on external specifications. 
         [0029]    By providing the centering means on the sensor head  12  and the sensor head receiver niche  14 , it is reliably ensured that the sensor axis  23  and the sensor holding axis  26  are aligned with one another. The manufacturing tolerances between the main body center axis  24  and the sensor axis  23  are compensated by appropriate dimensioning of the fastening means in a manner that is not visible from the outside. The sensor  30  and the sensor holder  31  can be attached to or integrated into a holding arm  35 . 
         [0030]    The gap width between the sensor head  12  and the opening  15  in the sensor holder  31  can be adapted to external requirements. In addition, the distance of the gap that has a predefined gap width is increased and is thereby made visually more apparent. The sensor holder  31 , the holding arm  35  and/or the holding arm cover can be used as a cooling body for the sensor  30 . 
         [0031]    Fogging up of the sensor surface that is accessible only from the outside is prevented. This is particularly important in the case of cameras and their lenses. Indirect viewing is enabled with mirror-substitute cameras in order to detect legally required fields of vision. Here, the sensor axis  23  is the optical axis of the camera lens. Undesired reflections in the sensor are avoided or reduced by applying a matte coating to the outside surface of the sensor holder  31 . The sensor arrangement preferably can be integrated into components such as indicator lamps, exterior mirrors and the like, which are already mounted outside the vehicle. 
         [0032]      FIG. 2  is a cross-sectional, exploded view of the first embodiment of the sensor arrangement. The sensor arrangement includes the sensor  30  with a sensor main body  36  from which the sensor head  12  protrudes. The sensor  30  is held in the sensor holder  31 . The sensor holder  31  includes the sensor head receiver niche  14  with the sensor head opening  15  and two screw receivers  37  and  38 , which are located on the left and on the right of the sensor head opening  15  and extend in a direction parallel to the sensor main body  36 . The sensor main body  36  includes two fastening clips  39  and  40  that extend away on the left and on the right from the sensor main body  36 . Each of the fastening clips  39 ,  40  has a screw hole  41 ,  42 . The sensor  30  is inserted into the sensor holder  31 , and the two fastening clips  39  and  40  come to rest on the upper ends of the two screw receivers  37  and  38 . The sensor  30  and the sensor holder  31  are screwed together using screws or bolts. The height of the two screw receivers  37  and  38  is chosen so that the end of the sensor head  12  is aligned with the outside surface  32  of the sensor holder  31 . 
         [0033]    The sensor axis  23  passes through the center of the sensor head  12  of the sensor  30 . The main body center axis  24  passes through the center of the sensor main body  36 , which deviates or can deviate from the sensor axis  23  due to the manufacturing tolerance  25 . The sensor holding axis  26  passes through the center of the sensor head opening  15  at the end of the sensor head receiver niche  14 . In contrast to the prior art shown in  FIG. 1 , the orientation and mounting of the sensor  30  is carried out in such a manner that it is not the main body center axis  24  that is aligned with the sensor holding axis  26 , but instead the sensor axis  23  that is aligned with the sensor holding axis  26 . Therefore, in comparison with the prior art, the bore holes  41 ,  42  in the holding clips  39  and  40  have to be made slightly larger so that the manufacturing tolerance  25 , i.e., the deviation between the main body center axis  24  and the sensor axis  23 , can be compensated. By appropriately dimensioning the sensor head opening  15 , a precisely defined gap width  43  results between the margin of the sensor head opening  15  and the sensor head  12 . The gap width  43  can therefore be adapted to the requirements of the given site of application. The manufacturing tolerance  25  is no longer represented in the drawings in the embodiments described below for the sake of simplifying the representation. 
         [0034]      FIG. 3  shows a second embodiment that differs from the first embodiment of  FIG. 2  in that the sensor head  12  protrudes past the sensor head opening  15  and in that the sensor head  12  is held in the sensor head opening  15  by press fitting. The sensor head opening  15  is surrounded by a cover  33  that includes a cover opening  34  into which the sensor head  12  protrudes. The free end of the sensor head  12  is aligned with the outside surface  32  of the cover  33 . The distance from the margin of the cover opening  34  to the sensor head  12  can be adjusted to a desired gap width  44 . 
         [0035]      FIG. 4  shows a third embodiment that differs from the embodiment of  FIG. 3  only in that the sensor head  12  includes a peripheral sensor head collar  45 . The peripheral sensor head collar  45  has a peripheral annular ridge  46  with a rectangular cross section that engages in a corresponding annular groove  47  on the inside surface of the sensor holder  31 . The annular ridge  46  and annular groove  47  are a centering means that provide the desired orientation of the sensor axis  23  with the sensor holding axis  26 . 
         [0036]      FIG. 5  shows a fourth embodiment in which the sensor  30  and sensor holder  31  are mounted on a holding arm  35 . In this manner, the sensor  30  can be mounted, for example, on the outside of a motor vehicle. The holding arm  35  is formed at least partially as a hollow profile and has a sensor opening  48  at the end  49  of the arm opposite the vehicle. The sensor opening  48  extends transversely to the longitudinal direction of the holding arm  35 . 
         [0037]    The holding arm  35  is covered by a first holding arm cover  50  and a second holding arm cover  51 . The first holding arm cover  50  has a sensor holder opening  52  into which the sensor holder  31  is inserted. 
         [0038]    The sensor holder  31  includes an annular peripheral, step-shaped collar  53  that engages with an overlap into a corresponding annular peripheral step  54  in the first holding arm cover  50 . On the inside surface, the step-shaped collar  53  and the corresponding step  54  are put in contact, and on the outside surface they are spaced apart by a predefined gap width  55 . Again, the gap width  55  can be adapted to external specifications. 
         [0039]    The sensor opening  48  in the hollow area of the holding arm  35  is delimited by a flat margin section  56 . Screw holes  41 ,  42  are provided in the margin section  56 . An annular fastening collar  57  of the first holding arm cover  50  extends along the outside surface of the flat margin section  56  of the holding arm  35 . The fastening collar  57  also has screw holes  41 ,  42 . Within the annular collar  53 , the left and right screw receivers  37  and  38  extend inward in the direction of the holding arm  35 . Between the two screw receivers  37  and  38 , the sensor head opening  15  opens in the middle of a flat margin section  58 . The margin section  58  also has screw holes  41 ,  42 . A left fastening clip  39  and a right fastening clip  40  extend away from the sensor main body  36  to the sides. The fastening clips  39  and  40  are associated with the left and right screw receivers  37  and  38 . The two fastening clips  39  and  40  rest on the inner surface on the flat margin section  56 . 
         [0040]    Two fastening screws  59  first pass through the screw holes  41 ,  42  in the fastening clips  39  and  40 , then through the screw holes in the flat margin section  56  of the holding arm  35 , through the screw holes in the fastening collar  57  and finally engage in the screw receivers  37  and  38 . As a result, the sensor  30 , the sensor holder  31  and the first holding arm cover  50  are secured to one another and to the holding arm  35 . The individual components are dimensioned so that the end of the sensor head  12  is approximately aligned with the outside surface  32  of the sensor head opening  15 . 
         [0041]    The sensor head  12  sits in the sensor head opening  15 , resulting merely in a peripheral joint gap with gap width  43  between the margin of the sensor head opening  15  and the sensor head  12 . The mating edge or overlap connection between the annular collar  53  and the complementary annular step  54  is designed so that an annular closed gap  60 , which is visible from the outside surface  32 , results with a predefined gap width  55 . 
         [0042]    The left side of the annular collar  53  protrudes past the end of the sensor head  12 , while the right side of the annular collar  53  is slightly set back relative to the sensor head  12 . As a result of this design, a visually constant impression is achieved, and the risk is decreased of soiling due to entry of foreign objects from the side. 
         [0043]      FIG. 6  shows a fifth embodiment that differs from the embodiment of  FIG. 5  in that the sensor main body  36  includes no fastening clips. The sensor opening  48  in the holding arm  35  is dimensioned so that the lower edge of the sensor main body  36  facing the sensor head  12  sits on the flat margin section  56 . The end of the sensor main body  36  facing away from the sensor head  12  is covered by an upper holding cap or an upper holding bracket  61  from which the left and right fastening clips  62  and  63  extend away on the sides. 
         [0044]      FIG. 7  shows a sixth embodiment that differs from the embodiment of  FIG. 6  in that the sensor main body  36  includes no fastening clips. The left and right screw receivers  37  and  38  have an inwardly broadening design so that the lower edge of the sensor main body  36  facing the sensor head  12  sits on the upper ends of the two screw receivers  37  and  38 . The other end of sensor main body  36  facing away from the sensor head  12  contacts the inside surface of the holding arm  35  so that the sensor main body  36  and thus the sensor  30  are wedged in between the inside surface of the holding arm  35  and the upper surface of the two screw receivers  37  and  38 . The fastening screws  59  pass through the screw holes  41 ,  42  in the flat margin section  56 , through the screw holes in the annular fastening collar  57  and engage in the screw receivers  37  and  38 . 
         [0045]      FIG. 8  shows a seventh embodiment that differs from the embodiment of  FIG. 7  in that the lower edge of the sensor main body  36  facing the sensor head  12  is not supported on broadened screw receivers  37  and  38 . Instead, the lower surface of the sensor main body  36  facing the sensor head  12  is covered by a lower holding cap or lower holding bracket  64 . On the side, the left and the right fastening clips  65  and  66  extend away from the lower holding cap  64 . The sensor main body  36  and thus the sensor  30  are wedged in between the lower holding cap  64  and the inner surface of the holding arm  35  and secured to the holding arm  35 . 
         [0046]      FIG. 9  shows an eighth embodiment that differs from the embodiment of  FIG. 5  in that the sensor holder  31  and the first holding arm cover  50  are formed as a single piece. As a result of this design, the fastening collar  57  provided in the embodiments of  FIGS. 5-7  can be dispensed with. The fastening screws  59  pass through the screw holes in the fastening clips  39  and  40 , through the screw holes  41 ,  42  in the flat margin section  56  and then engage in the two screw receivers of 37 and 38. 
         [0047]      FIG. 10  shows a ninth embodiment that differs from the preceding embodiments primarily in that the sensor holder  31  includes no screw receivers. The flat margin section  56  in the holding arm  35  is provided with a cylindrical attachment  67  that extends outward. In the same way, a cylindrical attachment  68  extends from the margin section  58  of the sensor holder  31  in the direction of the sensor main body  36 . The outer diameter of the cylindrical attachment  68  corresponds to the inner diameter of the cylindrical attachment  67 . The upper end of the cylindrical attachment  68  engages in the lower end of the cylindrical attachment  67 , and the cylindrical attachment  68  is wedged in between the sensor head  12  and the cylindrical attachment  67 . In the embodiments of  FIGS. 10 and 6 , the lower edge of the sensor main body  36  facing the sensor head  12  sits on the inner surface of the flat margin section  56 . The surface of the sensor main body  36  facing away from the sensor head  12  is covered by an upper holder cap  61 , from which the two fastening clips  62  and  63  extend away to the sides. The screw holes  41 ,  42  in the flat margin section  56  are provided with threads so that the fastening screws  59  pass through the screw holes  41 ,  42  in the fastening clips  62  and  63  and are secured in the threaded screw holes in the flat margin section  56 . 
         [0048]      FIG. 11  shows a tenth embodiment that differs from the embodiment of  FIG. 10  in that the sensor main body  36  and thus the sensor  30  are wedged inside the holding arm  35 . For this purpose, the sensor main body  36  again sits with the lower edge facing the sensor head  12  on the flat margin section  56 . A spring element  69  is provided on the upper surface of the sensor main body  36  or on the surface of the sensor main body facing away from the sensor head  12 . The spring element  69  presses against the inner surface of the holding arm  35  and secures the sensor main body  36  and thus the sensor  30  to the holding arm  35 . 
         [0049]      FIG. 12  shows an eleventh embodiment that differs from the preceding embodiments in that the holding arm  35  itself is designed as a sensor holder  31  and in that the sensor holder  31  is an integral component of the holding arm  35 . The holding arm  35  is designed with a hollow profile at least in the area in which the sensor  30  is located. The holding arm  35  includes the sensor head opening  15 . The sensor head  12  is fitted into the sensor head opening  15  with a minimal gap width  43 . The fastening clips  39  and  40  extend away from the sensor main body  36  on the left and on the right. On the side, the left and the right screw receivers  37  and  38  extend away from the sensor head opening  15  inward in the direction of the sensor main body  36 . Fastening screws  59  pass through the screw holes  41 ,  42  into the two fastening clips  39  and  40  and engage the two screw receivers  37  and  38 , thus securing the sensor  30  in the holding arm  35 . 
         [0050]    The portion of the sensor head  12  located inside the holding arm  35  is enclosed annularly by a heating element  70 . For example, the heating element  70  is a flexible heating foil that is wrapped around the sensor head  12  on the inside of the holding arm  35 . Such heating foil can be obtained from the company Flextem GmbH in Bobenheim-Roxheim, Germany. This heating element  70  prevents condensate from precipitating on the side of the sensor  30  that is accessible from the outside. The heating element  70  can also be used with all the above-described embodiments. 
         [0051]    In addition, the outside surface of the holding arm  35  has a matte implementation in the area of the sensor holder  31  or is provided with a matte coating  71  in order to prevent reflections towards the sensor. This is particularly important when the sensor  30  is a camera and the sensor head  12  is the lens of a camera. The coating  71  can naturally also be provided in all of the other above-described embodiments. 
         [0052]    To the extent that screw receivers are provided in the above-described embodiments, reference is always made to two screw receivers. Of course, it is also possible to provide only one screw receiver or more than two screw receivers. 
         [0053]    In the above-described embodiments, the sensor head  12  is inserted snuggly into the sensor head opening  15  in the sensor holder  31 . The sensor head  12  can also be inserted through force fitting or press fitting into the sensor head opening  15 . 
       LIST OF REFERENCE NUMERALS 
       [0000]    
       
         
           
               10  prior art sensor 
               11  sensor main body 
               12  sensor head 
               13  sensor holder 
               14  sensor head receiver niche 
               15  sensor head opening 
               16  left screw receiver 
               17  right screw receiver 
               18  left fastening clip 
               19  right fastening clip 
               20  screw hole 
               21  screw hole 
               22  outside surface of sensor holder 
               23  sensor axis 
               24  main body center axis 
               25  manufacturing tolerance, deviation between sensor axis and main body center axis 
               26  sensor holding axis 
               27  gap width 
               28  gap width 
               30  sensor 
               31  sensor holder 
               32  outside surface of sensor holder 
               33  cover 
               34  cover opening 
               35  holding arm 
               36  sensor main body 
               37  left screw receiver 
               38  right screw receiver 
               39  left fastening clip 
               40  right fastening clip 
               41  left screw hole 
               42  right screw hole 
               43  gap width 
               44  gap width 
               45  sensor head collar 
               46  annular ridge 
               47  annular groove 
               48  sensor opening in arm 
               49  end of arm away from vehicle 
               50  first holding arm cover 
               51  second holding arm cover 
               52  sensor holder opening in holding arm cover 
               53  annular, step-shaped collar on sensor holder 
               54  step in arm cover 
               55  gap width 
               56  flat margin section around sensor opening 
               57  annular fastening collar on arm cover 
               58  flat margin section around sensor head 
               59  fastening screws 
               60  annular gap around sensor holder 
               61  upper holding cap or upper holding bracket 
               62  left fastening clip 
               63  right fastening clip 
               64  lower holding cap or lower holding bracket 
               65  left fastening clip 
               66  right fastening clip 
               67  cylindrical attachment on collar 
               68  cylindrical attachment on flat margin section 
               69  spring element 
               70  heating element 
               71  coating 
           
         
       
     
         [0115]    Although the present invention has been described in connection with certain specific embodiments for instructional purposes, the present invention is not limited thereto. Accordingly, various modifications, adaptations, and combinations of various features of the described embodiments can be practiced without departing from the scope of the invention as set forth in the claims.