Abstract:
The welding arrangement for plastic components comprises a base member ( 1 ), a primary member ( 12 ) abutting onto the base member, the primary member being provided with a first positioning feature ( 21, 22 ) that engages a corresponding first positioning feature ( 61   a,    62   a ) provided on the base member and a secondary member ( 13 ) vibration welded to the base member so as to at least partly interpose the primary member between the secondary member and base member. Because the welding is performed between the base member and the secondary member while the primary member is properly positioned relative to the base member on account of the first positioning feature cooperating with the corresponding first positioning feature, the welding can be favorably performed without being obstructed of the oscillatory movement required for the welding process while the positional precision of the primary member is ensured. The primary member may be additionally provided with a second positioning feature ( 81 ) that engages a corresponding second positioning feature ( 82 ) provided on the secondary member so as to permit positional adjustment between them in a prescribed direction corresponding to a direction of vibration of the vibration welding.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a welding arrangement for plastic components, and in particular to a welding arrangement for attaching two component parts by using frictional heat produced by oscillating at least one of the components. 
       BACKGROUND OF THE INVENTION 
       [0002]    It is known to attach a plastic component such as a bracket to a plastic base member such as an automotive instrument panel by the vibration welding. As the vibration welding allows the component to be attached to any part of the base member, it is necessary to provide a means for positioning the component to the base member at the time of welding. In the welding arrangement disclosed in Japanese patent laid open publication No. 2004-90697, projections that can resiliently deform in a prescribed direction project from an instrument panel of a motor vehicle, and mating grooves corresponding to the projections are formed in the component so that the two parts may be properly positioned relative to each other by fitting the projections into the corresponding mating grooves and vibration welding the two parts to each other by oscillating the component in the prescribed direction by using a vibration welder. 
         [0003]    However, according to this proposal, during the welding process, the projections inevitably deflect to a certain extent as a result of the relative movement caused by the welding process, and the component may shift in position relative to the instrument panel during the welding process. When a high positional precision is required, such a positional shifting is not tolerable. 
         [0004]    Also, when a large number of component parts are required to be attached, a correspondingly large number of projections are required to be formed on the side of the instrument panel. However, because the instrument panel is a relatively large plastic component, it is not desirable to complicate the shape of the instrument panel in view of minimizing the manufacturing cost. 
       BRIEF SUMMARY OF THE INVENTION 
       [0005]    In view of such a problem of the prior art, a primary object of the present invention is to provide a welding arrangement for plastic components that ensures a proper positioning between the two plastic components that are welded to each other. 
         [0006]    A second object of the present invention is to provide a welding arrangement for plastic components that ensures a proper positioning without interfering with the vibration welding process. 
         [0007]    These and other objects of the present invention can be at least partly accomplished by providing a welding arrangement for plastic components, comprising: a base member at least partly made of thermoplastic plastic material; a primary member abutting onto the base member, the primary member being provided with a first positioning feature that engages a corresponding first positioning feature provided on the base member; and a secondary member at least partly made of thermoplastic plastic material and vibration welded to the base member so as to at least partly interpose the primary member between the secondary member and base member. 
         [0008]    Because the welding is performed between the base member and the secondary member while the primary member is properly positioned relative to the base member on account of the first positioning feature cooperating with the corresponding first positioning feature, the welding can be favorably performed while the positional precision of the primary member is ensured. The positioning features may consist of a combination of a projection and a corresponding opening or recess as can be readily appreciated by a person skilled in the art. Also, in such a case, the projection may be provided on either the primary member or the base member while the remaining member is provided with the corresponding opening. 
         [0009]    According to a preferred embodiment of the present invention, the primary member is provided with a second positioning feature that engages a corresponding second positioning feature provided on the secondary member so as to permit positional adjustment between them in a prescribed direction corresponding to a direction of vibration of the vibration welding. It is particularly preferable if the second positioning feature of the primary member comprises a positioning projection configured to be resiliently readily deformable in the prescribed direction, and the corresponding second positioning feature of the secondary member comprises a positioning opening that closely receives the positioning projection. 
         [0010]    Thereby, the positional precision can be positively ensured while the secondary member is allowed to accommodate the oscillation in the direction of the vibration welding. 
         [0011]    The primary member may comprise a mounting feature for attaching another component to the base member. Thereby, the primary member which may be of a relatively small size may be used as a support bracket for a larger component part so that the positional accuracy of the large component can be achieved while improving the work efficiency of the welding process. 
         [0012]    Typically, the primary member is provided with at least one opening through which a welding piece of the secondary member is welded to the base member so that the secondary member is enabled to evenly apply a force required to secure the primary member to the base member. For added integrity of the entire assembly, the secondary member may be additionally vibration welded to the primary member. The base member may comprise an automotive instrument panel among other possibilities. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    Now the present invention is described in the following with reference to the appended drawings, in which: 
           [0014]      FIG. 1  is a perspective view of an automotive instrument panel embodying the present invention; 
           [0015]      FIG. 2  is an exploded perspective view of the mounting bracket  11  as seen from the rear side (remote from the vehicle operator) of the instrument panel which is inverted from the normal orientation for the convenience of illustration; 
           [0016]      FIG. 3  is a perspective a view showing the mounting bracket  11  at an intermediate step of the assembling process of the mounting bracket  11  as seen from the front side (from under the instrument panel); 
           [0017]      FIG. 4  is a perspective view showing the mounting bracket  11  at an intermediate step of the assembling process of the mounting bracket  11  as seen from the rear side (from above the instrument panel); 
           [0018]      FIGS. 5   a ,  5   b  and  5   c  are sectional views taken along line V-V of  FIG. 3  illustrating different stages of the process of mounting the mounting bracket of the first embodiment to the instrument panel  1 ; 
           [0019]      FIG. 6  is a view similar to  FIG. 2  showing a second embodiment of the present invention; 
           [0020]      FIG. 7  is a view similar to  FIG. 3  showing the second embodiment of the present invention; and 
           [0021]      FIGS. 8   a ,  8   b  and  8   c  are sectional views taken along line VIII-VIII of  FIG. 7  illustrating different stages of the process of mounting the mounting bracket of the second embodiment to the instrument panel  1 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0022]      FIG. 1  is a perspective view of an automotive instrument panel embodying the present invention. In particular, the present invention is applied to a bracket for mounting a display visor that surrounds a display located in a central part of the instrument panel for displaying car navigation and other information. 
         [0023]    The instrument panel  1  is provided with a plurality of openings  2  one above another in a central part thereof for a display and switch consoles for a car navigation system, an audio system and an air conditioning system. Other openings provided in the instrument panel  1  include an opening  3  on the left hand side thereof for such instruments as a speedometer, a fuel gage and a tachometer, and an opening  4  on the right hand side thereof for defining a glove box. The instrument panel  1  is at least partly made of an integrally molded thermoplastic plastic member. In this case, the entire instrument panel  1  is made of an integrally molded thermoplastic plastic member. 
         [0024]    The display visor  5  is a separate component that surrounds a display unit typically including an LCD panel not shown in the drawings. The display visor  5  is generally fitted into one of the central openings  6  of the instrument panel  1 , and is secured in position by using a mounting arrangement that includes a mounting bracket  11  interposed between the upper edge of the opening  6  defining a mounting surface  7  and the opposing upper edge of the display visor  5  as shown in  FIG. 1 . Along the upper edge of the display visor  5  are provided a plurality of mounting claws  8  at a regular interval for engaging the mounting bracket  11 . 
         [0025]      FIG. 2  is an exploded perspective view of the mounting bracket  11  as seen from the rear side (remote from the vehicle operator) of the instrument panel which is inverted from the normal orientation for the convenience of illustration.  FIGS. 3 and 4  are perspective views showing the mounting bracket  11  at an intermediate step of the assembling process of the mounting bracket  11  as seen from the front side (from under the instrument panel) and from the rear side (from above the instrument panel), respectively. 
         [0026]    The mounting bracket  11  consists of two parts, a primary bracket part  12  defining a mounting surface configured have the display visor  5  attached thereto, and a secondary bracket part  13  configured to be vibration welded to the instrument panel  1  with the primary bracket part  12  interposed between the instrument panel  1  and secondary bracket part  13 . The primary and secondary bracket parts  12  and  13  are each integrally molded with thermoplastic plastic material in the illustrated embodiment, but are only required to be at least partly made of material suitable for vibration welding. 
         [0027]    Prior to vibration welding the secondary bracket part  13  to the instrument panel  1  as will be described hereinafter, as shown in  FIGS. 3 and 4 , the primary and secondary bracket parts  12  and  13  are temporarily joined to each other (in a laterally moveable manner relative to each other), and the primary bracket part  12  is properly positioned relative to the instrument panel  1 . 
         [0028]    For the purpose of positioning the primary bracket part  12  with respect to the instrument panel  1 , the primary bracket part  12  is provided with a pair of engagement portions  21  and a pair of projections  22 . The primary bracket part  12  is additionally provided with openings  23  to  25  for exposing the welding portions of the mounting surface  7  of the instrument panel  1  with respect to the corresponding welding portions  51  to  53  of the secondary bracket part  13 , a pair of openings  26  ( FIG. 4 ) and a pair of engagement pieces  27  ( FIG. 3 ) for temporarily joining the primary bracket part  12  and secondary bracket part  13  to each other and a pair of mounting holes  28  for mounting the display visor  5  to the instrument panel  1 . 
         [0029]    Referring to  FIG. 2 , the engagement portions  21  extend forward (toward the vehicle operator) from lower parts of the primary bracket part  12  on either lateral end thereof, and each comprise a resiliently deformable engagement claw  31  projecting laterally in both directions, an abutting projection  32  projecting laterally in both directions at a small distance from the rear end  31   a  of the engagement claw  31  and a pair of rigid wall sections  33  extending along upper and lower sides of the engagement portion  21 . Each rigid wall section  33  is provided with a rib  33  extending along the length of the engagement portion  21 . The projections  22  project laterally outwardly from upper parts of the lateral sides of the primary bracket part  12 . 
         [0030]    The secondary bracket part  13  is provided with welding portions  41  to  43  which are to be welded to the instrument panel  1  and openings  44  ( FIG. 3 ) for receiving the corresponding engagement pieces  27  of the primary bracket part  12  and engagement pieces  45  ( FIG. 4 ) configured to be fitted into the corresponding openings  26  of the primary bracket part  12  for temporary attachment with the primary bracket part  12 . The engagement pieces  45  and/or engagement pieces  27  may consist of simple tabs or may be at least partly provided with barbs so that a snap fit engagement may be achieved. Any other known arrangements can be used for temporarily retaining the two bracket parts  12  and  13  as long as the two parts can be joined or retained until the welding is completed, but it is desirable that the arrangement for retaining the two bracket parts  12  and  13  does not involve friction or any other mutual constraint that interferes with the vibration welding of the secondary bracket part  13  to the instrument panel. The secondary bracket part  13  is oscillated in the lateral direction as indicated by arrows in  FIG. 2  at the time of the vibration welding. The secondary bracket part  13  has the function to attach the primary bracket part  12  to the instrument panel  1 , but may be provided with a feature such as an opening for mounting a component part that does not require a high positional precision. 
         [0031]    The welding portions  41  to  43  are provided on the side of the secondary bracket part  13  facing the primary bracket part  12  at positions corresponding to the openings  23  to  25  of the primary bracket part  12 . Each welding portion  41 ,  42 ,  43  is provided with a pair of first welding pieces  51 ,  52 ,  53  extending substantially perpendicularly to a major plane of the secondary bracket part  13 , and a pair of second welding pieces  54 ,  55 ,  56  ( FIGS. 5   a  to  5   c ) extending in parallel with the corresponding first welding pieces by a significantly smaller distance and flanking the corresponding first welding pieces. The openings  44  and engagement pieces  45  of the secondary bracket part  13  are located so as to correspond to the corresponding engagement pieces  27  and openings  26  of the primary bracket part  12 , respectively. However, it suffices if the welding portions  41  to  43  are configured to be welded to the instrument panel  1  via the first welding pieces  51  to  53 , but they may also be additionally configured to be welded to the primary bracket part  12  as well via the second welding pieces  54  to  56  so that the primary bracket part  12  may be more firmly attached to the instrument panel  1 . 
         [0032]    The openings  23  to  25  of the primary bracket part  12  are provided for the purpose of exposing the instrument panel  1  to the corresponding welding portions  41  to  43  of the secondary bracket part  13 , and may be formed in various different manners. For instance, the number of the openings, and the shape and size of each opening may be changed as desired as long as they correspond to the corresponding welding portion of the primary bracket part  12 . At least one of the openings may consist of a notch formed along a peripheral part of the secondary bracket part  13 . It is also possible that at least one of the welding portions is welded to the instrument panel  1  at a part outwardly adjacent to a peripheral part of the secondary bracket part  13 . 
         [0033]    When temporarily joining the primary bracket part  12  and secondary bracket part  13  to each other, first of all, the engagement pieces  27  of the primary bracket part  12  are fitted into the corresponding openings  44  of the secondary bracket part  13  as shown in  FIG. 3 . This causes the first welding pieces  51  to  53  of the secondary bracket part  13  to be passed into the openings  23  to  25  of the primary bracket part  12 , and the engagement pieces  45  of the secondary bracket part  13  to be passed into the openings  26  of the primary bracket part  12  as shown in  FIG. 4 . 
         [0034]    As shown in  FIG. 4 , the lateral width of each opening  23 ,  24 ,  25  of the primary bracket part  12  (along the direction indicated by arrows which correspond to the direction of the oscillation at the time of the welding) is somewhat greater than the width of the corresponding first welding piece  51 ,  52 ,  53 . In other words, a gap G 1  is defined between each side edge  52   a ,  52   b  of the first welding piece  52  and the opposing edge  24   a ,  24   b  of the corresponding opening  24 . The same is true with the remaining first welding pieces  51  and  53 . Similarly, a gap G 2  is defined between each side edge of each engagement piece  45  and the opposing edge of the corresponding opening  26  of the secondary bracket part  13 . Further, a gap G 3  is defined between each side edge of each engagement piece  27  of the primary bracket part  12  and the opposing edge of the corresponding opening  44  of the secondary bracket part  13 . The size of each of these gaps G 1  to G 3  may be suitably selected by taking into account the amplitude of the oscillations caused during the vibration welding process. 
         [0035]    Owing to the presence of these gaps G 1  to G 3 , the necessary relative movement in the direction of the oscillation between the primary bracket part  12  and secondary bracket part  13  is accommodated so that the vibration welding process can be performed in a favorable manner. Also, because the primary bracket part  12  and secondary bracket part  13  are joined to each other prior to the vibration welding process, the work efficiency at the time of attaching the mounting bracket  11  to the instrument panel  1  can be improved. 
         [0036]    When positioning the primary bracket part  12  with respect to the instrument panel  1 , the engagement portions  21  of the primary bracket part  12  are inserted in openings  61  formed in the instrument panel  1  on either lateral side of the mounting opening  6  of the instrument panel  1 . At the same time, the projections  22  projecting laterally from either side edge of the primary bracket part  12  are fitted into openings  62   a  formed in a wall  62  of the mounting surface  7  of the instrument panel  1 . 
         [0037]    At this time, the rear end  31   a  of each engagement claw  31  is engaged by the side edges  61   a  and  61   b  of the corresponding opening  61  while the corresponding abutting projection  32  is engaged by the side edges  61   a  and  61   b  of the corresponding opening  61  from the opposite side of the wall of the instrument panel  1 . Thereby, each side edge  61   a ,  61   b  of each opening  15  is interposed between the corresponding engagement claw  31  and abutting projection  32  for secure attachment, and this also ensure an accurate positioning of the primary bracket part  12  with respect to the instrument panel  1  in the direction perpendicular to a plane defined by the opening  6 . The bead  33   a  on each rigid wall section  33  closely contacts the corresponding upper or lower edge  61   c ,  61   d  of the corresponding opening  61 . Thereby, the primary bracket part  12  is accurately positioned with respect to the instrument panel  1  in a direction perpendicular to a major plane of the mounting surface  7  by being thus prevented from moving in this direction relative to the instrument panel  1 . At this time, each projection  22  is fitted into the corresponding opening  62   a  formed in the wall  62 , the movement of the primary bracket part  12  with respect to the instrument panel  12  (in the direction of the oscillation) is prevented, and this also contributes to an accurate positioning of the primary bracket part  12  with respect to the instrument panel  1 . 
         [0038]      FIGS. 5   a ,  5   b  and  5   c  are sectional views illustrating the process of mounting the mounting bracket of the first embodiment to the instrument panel  1 . The plane of the section of each of these sectional views including the section of the instrument panel  1  corresponds to line V-V in  FIG. 3 . 
         [0039]    First of all, referring to  FIG. 5   a , the secondary bracket part  13  is moved toward the primary bracket part  12  as indicated by the arrow. 
         [0040]    The secondary bracket part  13  is then pushed against the primary bracket part  12  until the secondary bracket part  13  rests upon an opposing surface  71  of a selected area of the primary bracket part  12 . As a result, the engagement pieces  27  and  45  become engaged to the corresponding openings  44  and  26 . At this time, the first welding pieces  52  of the secondary bracket part  13  are received in the corresponding opening  24  of the primary bracket part  12 , and the free end of each first welding piece  52  slightly projects from the surface of the surrounding part of the primary bracket part  12  facing away from the secondary bracket part  13  while the second welding pieces  55  abut the surface of the surrounding part of the primary bracket part  12  facing the secondary bracket part  13  as shown in  FIG. 5   b . The same is true with the remaining first welding pieces  51  and  53  and second welding pieces  54  and  56 . 
         [0041]    Once the primary bracket part  12  is properly positioned with respect to the instrument panel  1 , a welding tip  72  of a vibration welding device is applied to each welding portion from a side facing away from the instrument panel  1  as shown in  FIG. 5   c , and the secondary bracket part  13  is oscillated in the direction perpendicular to the plane of the drawing while the secondary bracket part  13  is pushed onto the instrument panel  1 . The vibration welding device may consist of a known vibration welding device which uses the frictional heat generated by oscillating the object to be welded. The frequency of this oscillating movement may be selected freely depending on the property of the object to be welded. 
         [0042]    The frictional heat generated between each first welding piece  52  of the secondary bracket part  13  and the opposing surface  7  of the instrument panel  1  melts the surrounding part, and this causes the tip  52   c  of the first welding piece  52  to be welded to the opposing surface  7  of the instrument panel  1 . Likewise, the frictional heat generated between each second welding piece  55  of the secondary bracket part  13  and the opposing surface  71  of the primary bracket part  12  melts the surrounding part, and this causes the tip  55   c  of the second welding piece  53  to be welded to the opposing surface  71  of the primary bracket part  12 . 
         [0043]    When mounting the display visor  5  to the mounting bracket  11 , the mounting claws  8  of the display visor  5  are fitted into the corresponding mounting holes  28  of the primary bracket part  12  which is fixedly attached to the instrument panel  1 . Thus, the display visor  5  can be mounted to the instrument panel  1  accurately, firmly and easily. 
         [0044]      FIG. 6  is an exploded perspective view of a second embodiment of the mounting bracket according to the present invention, again shown in an inverted orientation, and  FIG. 7  is a perspective view of the mounting bracket as see from below. In the description of the second embodiment, the parts corresponding to those of the previous embodiment are denoted with like numerals without repeating the description of such parts. 
         [0045]    In this embodiment, the surface of the primary bracket part  12  opposing the secondary bracket part  13  is provided with a positioning projection  81 , and the secondary bracket part  13  is provided with a corresponding opening  82  that receives the positioning projection  81  when temporarily joining the two bracket parts  12  and  13  for positioning them to each other. 
         [0046]    The positioning projection  81  consists of a triangular, relatively thin plate member having a base thereof connected to the opposing surface  71  and the apex opposing this base projecting upward. The major surface of the positioning projection  81  is substantially perpendicular to the lateral direction of the mounting bracket  11  which coincides with the direction of the oscillation of the vibration welding. Owing to the small thickness of the positioning projection  81 , the positioning projection  81  is allowed to elastically deform in the direction of the oscillation of the vibration welding or the lateral direction so that the two bracket parts  12  and  13  can be accurately positioned to each other without obstructing the relative oscillation between them at the time of the vibration welding. The thickness of the positioning projection  81  may be selected so as not to obstruct the vibration welding process, and the opening  82  is required to receive at least a part of the positioning projection  81 . 
         [0047]    When temporarily joining the two bracket parts  12  and  13  to each other, the positioning projection  81  is fitted into the opening  82  as shown in  FIG. 7 . This positively positions the two bracket parts  12  and  13  in the lateral direction and maintains the gaps G 1  to G 3  mentioned in relation with  FIG. 4  properly without fail so that the vibration welding can be performed without being interfered, and a favorable welding result can be ensured. The shapes and sizes of the positioning projection  81  and corresponding opening  82  can be selected at will. To take advantage of the resiliency of the positioning projection  81 , it may be arranged such that only a free end of the positioning projection  81  is received by the opening  82 . 
         [0048]      FIG. 8  is a simplified sectional view, including the section of the instrument panel, taken along line VIII-VIII of  FIG. 7  showing the mode of joining the mounting bracket of the second embodiment to the instrument panel. 
         [0049]    First of all, the secondary bracket part  13  is moved toward the primary bracket part  12  causing the positioning projection  81  to be received in the corresponding opening  82  as indicated by the arrow in  FIG. 8   a , and is then pushed against the primary bracket part  12  until the secondary bracket  12  rests upon an opposing surface  71  of a selected area of the primary bracket part  12  as shown in  FIG. 8   b . Thereby, the two bracket parts  12  and  13  are temporarily joined to each other in a similar manner as in the previous embodiment. 
         [0050]    Once the primary bracket part  12  is positioned with respect to the instrument panel  1 , the vibration welding may be started. Because the positioning projection  81  can be readily deformed in an elastic manner in the direction of the welding oscillation (perpendicular to the plane of the drawing) as shown in  FIG. 8   c , the vibration welding may be performed in a favorable manner while effectively preventing a positional error between the two bracket parts  12  and  13 . 
         [0051]    Although the present invention has been described in terms of preferred embodiments thereof, it is obvious to a person skilled in the art that various alterations and modifications are possible without departing from the scope of the present invention which is set forth in the appended claims. 
         [0052]    The contents of the original Japanese patent applications on which the Paris Convention priority claim is made for the present application are incorporated in this application by reference.