Abstract:
A mounting mechanism for an adjustable component that is to be held against an abutment surface of a housing, especially for the guide bar of a power chain saw, is provided. The mechanism includes at least two bolts that are provided on the housing, are spaced from one another, and project beyond the abutment surface of the housing and into an elongated opening of the component. At least one device is provided that extends into a gap between one of the bolts and at least one of the longitudinal edges of the elongated opening for engaging such at least one longitudinal edge.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a mounting mechanism for an adjustable component that is to be held, especially for the guide bar of a power chain saw. The component is adapted to be held against an abutment surface of a housing. 
     DE 25 09 518 A1 discloses the arresting of a guide bar or rail on motor driven hand saws, especially power chain saw, whereby the sword-shaped guide rail is provided with a guide groove that extends in the longitudinal direction. This guide rail can be secured relative to an abutment transverse to the plane of the rail. The guide rail is furthermore associated with a counter guide that cooperates with the sides of the guide groove and that is formed by at least one support element for at least one of the groove sides. When the rail is secured against the abutment, for example the motor housing, this support element is automatically securable in abutment against the groove side. The support element can be a swivel bar, a swivel lever, or a spring element. 
     With the known arrangement the support element is disposed between two bolts provided for screwing on tightening nuts and is hence disposed approximately in the middle of the guide groove. As a result, the support element forms merely one defined abutment point on the side of the guide groove, whereby the support points required on the opposite side of the guide groove respectively result from the shaft of the bolts for receiving the tightening nuts. Since the support elements can compensate only for a slight tolerance transverse to the longitudinal axis of the guide groove, not only the width of the guide groove but also a radial shoulder on the bolts for receiving the tightening nuts must be manufactured with relatively close tolerances in order to always ensure an abutment without play against the side of the guide groove. 
     It is therefore an object of the present invention to provide a mounting mechanism of the aforementioned general type that is simpler in construction and can compensate greater tolerances with respect to the opening in the component. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     This object, and other objects and advantages of the present invention, will appear more clearly from the following specification in conjunction with accompanying schematic drawings, in which: 
     FIG. 1 schematically illustrates a power chain saw with a guide bar for a saw chain mounted on the housing of the power chain saw; 
     FIG. 2 shows that end of the guide bar that is to be secured to the housing along with one exemplary embodiment of the inventive mounting mechanism; 
     FIG. 3 is a longitudinal cross-sectional view through the arrangement of FIG. 2 with the bolts received therein; 
     FIG. 4 is an exploded view of a bolt, collar and the housing taken along the line IV—IV in FIG. 2; 
     FIG. 5 is a cross-sectional view through another exemplary embodiment of an inventive mounting mechanism with a plate section for compensating for tolerance; 
     FIG. 6 is a cross-sectional view through a modified mounting mechanism having compensating means formed on a bolt head; and 
     FIG. 7 is a modification of the embodiment of FIG. 2 with a guide element. 
    
    
     SUMMARY OF THE INVENTION 
     The mounting mechanism of the present invention is characterized primarily by at least two bolts that are provided on the housing, are spaced from one another and project beyond the abutment surface of the housing and into an elongated opening of the component, and by at least one means that extends into a gap between one of the bolts and at least one of the longitudinal edges of the elongated opening for engaging such at least one longitudinal edge. 
     The essential advantages of the present invention are that the means for compensating the dimensional tolerances are not susceptible to becoming clogged and due to their shape offer the possibility of also being able to compensate for alternations in the dimensions caused by wear. 
     The bolts are preferably screws that are received in threaded bores of the housing. It is particularly expedient if the means for compensating the dimensional gap between the edge of the elongated opening and the bolt is a sleeve or collar that is disposed in the opening, and the outer cross-sectional shape of which in at least one dimension is greater than the width of the elongated opening. It is particularly advantageous to form the outer surfaces of the collar from two circular arc sections having preferably equal radii and two parallel chords of the circle that extend between the arcs. 
     If the collar is configured in this manner, it has the advantage that upon rotation about the collar axis, it comes to rest against both edges of the elongated opening, so that an absolutely play-free support against both longitudinal edges of the opening is achieved by a single component, namely the collar. In order to bring the collar into contact against the edges of the elongated opening, means are provided for the positive or frictional connection of the bolt and sleeve in the direction of rotation of the bolt. These means work by carrying along the collar in the direction of rotation by rotating the bolt until contact against the edges of the elongated opening is achieved, and subsequently a limited further rotation of the bolt is still possible in order to fix the collar in this rotational position. In this connection, it is particularly expedient to provide a respective conical section in a bore of the collar and on the bolt, with the cone angles being coordinated with one another. 
     A further bolt is expediently provided between the spaced-apart bolts for the means for compensating for the tolerances. This further bolt projects through the component that is to be held, and on its free end has a threaded portion upon which can be screwed the tightening element that fixes the component against the abutment surface of the housing. So that the abutment of this tightening element against the surface of the component is possible independent of the shape of the tightening element, no projections should extend out of the plane of the component, for example the guide bar. It is therefore advantageous that the cone on the bolt be formed on the head of the bolt so that this head is disposed within the collar and the axial length of the bolt head corresponds approximately to the axial length of the collar. In this way, the collar and bolt head are flush and do not exceed the thickness of the guide bar. To rotate the bolt, a hexagonal recess is provided in the bolt head into which can be inserted an Allen wrench. So that the shape of the collar can be maintained regardless of how frequently and how long it is used, and so that is does not undergo wear, it is expedient for the collar to be made out of very hard carbon steel. 
     Depending upon the material of the housing, a metal plate is provided on the abutment surface of the housing for supporting the component. This metal plate is provided with an opening through which extends the bolt or its head. If such a metal plate is present, the means for compensating for the tolerances can be formed by a section of the metal plate that is disposed on the rim of the opening and extends at an angle to the longitudinal axis of the bolt. In this way, the leading end of this section extends into the gap between the head of the bolt and the longitudinal edge of the opening in the guide bar. As an alternative, it is also possible for the head of the bolt to have an essentially circular cross-sectional shape and to be provided on the outer surface over a portion of the periphery with a radially widened portion having a surface that extends at an angle to the longitudinal axis. Not only with an inclined section of the metal plate but also with the described radially widened portion of the bolt head, when the guide bar is pressed against the metal plate or the abutment of the housing, the opening of the guide bar is brought into a position in which the two longitudinal edges of the elongated opening are held without play against support points of the bolt head or of the plate. 
     Further specific features of the present invention will be described in detail subsequently. 
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring now to the drawings in detail, FIG. 1 is a schematic side view of a power chain saw  1 , which comprises a housing  2  in which is accommodated an internal combustion engine  3 , and a guide bar  5  that is secured to the housing  2  and is provided for a saw chain  6 . Furthermore, disposed on the housing  2  is a rear handle  4 , a forward handle  7 , and a hand guard  8 . The rear end  9  of the guide bar  5  is secured to the housing  2 , whereby a mounting mechanism  10  is provided that has means for adjustment in the longitudinal direction of the guide bar  5  and for holding the after in position on the housing; to facilitate illustration, such means are not shown in detail in FIG.  1 . 
     FIG. 2 is an enlarged view of the rear end  9  of the guide bar  5  as well as of the mounting and securing mechanism  10 . Provided in the rear end  9  of the guide bar  5  is an elongated opening  11  that extends in the longitudinal direction of the guide bar and which has two parallel longitudinal edges  12  and  13 . Disposed in this elongated opening  11  is a central bolt  14  as well as two screws  15  and  17  that also serve as bolts and that are disposed at different distances from the central bolt  14 . The plan view of the screws  15  and  17  of FIG. 2 shows the heads  15 ″ and  17 ″, in each of which is provided a respective hexagonal recess (Allen head)  16  or  18 . The Allen head  16 ,  18  serves for receiving a key or Allen wrench for turning the screws  15 ,  17 . 
     Disposed in the elongated opening  11  is a sleeve or collar  20  that surrounds the head  15 ″ of the screw  15 , as well as a sleeve or collar  21  that surrounds the head  17 ″ of the screw  17 . These collars  20 ,  21  have the same cross-sectional shapes, whereby the cross-sectional shape of the collar  20  comprises two arcs  22 ,  22 ″ and two chords  23 ,  23 ′ of the circle. The cross-sectional shape of the collar  21  is formed from two arcs  24 ,  24 ′ and two chords  25 ,  25 ′. As a consequence of this cross-sectional shape, at least one of the dimensions of the collars  20 ,  21  is greater than the spacing A between the parallel longitudinal edges  12  and  13  of the elongated opening  11 . By rotating the collars  20 ,  21  about the longitudinal axis, each of the collars  20 ,  21  can be brought into contact not only with the longitudinal edge  12  but also with the longitudinal edge  13  of the elongated opening  11 . 
     FIG. 3 shows a longitudinal cross-sectional view through the mounting mechanism  10 , whereby a securing means that can be screwed onto a threaded portion  14 ″ of the bolt  14 , and which fixes the guide bar  5  against an abutment surface  19  of the housing  2 , has been omitted from the drawing. Provided in the housing  2  are threaded bores  26 ,  27 ,  28  for respectively receiving a threaded shaft  14 ′,  15 ′,  17 ′ of the bolts and screws. The collar  20  is disposed on the screw head  15 ″, with the respective upper edges of the head  15 ″ and of the collar  20  being flush with one another. The configuration of the collar  21  and the head  17 ″ of the screws  17  are comparable to this, so that these components are also flush with one another. Since the thickness D of the guide bar  5  is somewhat greater than the axial length of the collars  20 ,  21 , the heads  15 ″,  17 ″ of the screws  15 ,  17 , and the collars  20 ,  21 , therefore do not project beyond the upper edge of the guide bar  5 . Pursuant to an alternative embodiment, the central bolt can be used in place of one of the lateral bolts, so that altogether only two bolts are provided, one of which is embodied as a screw having a collar. 
     FIG. 4 is an exploded view of the screw  17 , the collar  21 , and that portion of housing  2  in which the threaded bore  28  is disposed. From the illustration of FIG. 4 it can be seen that a stepped bore  29  is provided in the collar  21 , whereby a conical portion  30  is provided between the two steps of the bore. The screw head  17 ″ is also provided with a conical portion  31  that has the same conical angle and thus serves as a cooperating cone for the conical portion  30  that is provided in the bore  29 . In this manner, when the two conical portions rest against one another, a frictional connection results between the screw  17  and the collar  21 , so that when the screw  17  is tightened, the collar  21  is carried along until the collar  21  rests against the longitudinal edges  12  and  13  of the elongated opening  11 , as shown in FIG.  2 . 
     Alternatively, it is also possible to provide a smooth-walled bore in the housing  2  through which extends a shaft of the screw, whereby one end of the screw has a head and the other end has a threaded portion. By means of this threaded portion the screw can be rotatable in a threaded bore of the collar. 
     FIG. 5 is an enlarged view of a further exemplary embodiment of the present invention; in this embodiment, a bolt  33  is rotated into the threaded bore  28  of the housing  2  via the threaded shaft  33 ′ of the bolt. The bolt  33  furthermore has a head  33 ″ having smooth walls in the axial direction. A metal plate  32  is disposed against the abutment surface  19  of the housing  2 , and the metal plate is provided with an opening  32 ′ through which the head  33 ″ of the bolt  33  extends. At the rim of the opening  32 ′, a metal plate  32  is provided with a bent-away section  34  that extends at an acute angle relative to the longitudinal axis of the bolt  33  and rests against the side surface of the bolt head  33 ″. As a consequence of this configuration, when the end  9  of the guide bar  5  is pressed against the metal plate  32 , the end  9  is displaced by the inclined section  34  transverse to the longitudinal axis of the bolt  33  until the longitudinal edge  13  of the elongated opening  11  rests against the bolt head  33 ″. The longitudinal edge  12  of the end  9  of the guide bar  5  is supported against the section  34 , so that there is no play available for a movement directed transverse to the longitudinal axis of the bolt  33 . Although only one section  34  is shown in FIG. 5, it is to be understood that two or more sections could also be provided. 
     A variation of the embodiment of FIG. 5 is illustrated in FIG.  6 . In this embodiment, a bolt  35  is shown, the threaded shaft  35 ′ of which is received in the threaded bore  28 , and the head  35 ″ of which is provided on at least one portion of its periphery with a radially widened portion  36  that is provided with a surface  37  that extends at an angle to the longitudinal axis of the bolt  35 . This inclined surface  37  performs the same function as does the inclined section  34  in FIG. 5, whereby reference is made to the foregoing description of such function. Two or more widened portions  36  could be provided. Furthermore, instead of the bolt head  35 ″, a correspondingly shaped collar having a bolt shaft or threaded section disposed inwardly of the collar could also be provided. 
     It is to be understood that the angle shown in FIGS. 5 and 6 between the metal plate  32  and the rear end  9  of the guide bar  5  is exaggerated in order to explain the functioning of the inventive mounting mechanism. In actuality, when the guide bar is mounted and secured, the guide bar rests against the metal plate  32  on both sides of the bolt head  33 ″ or  35 ″. 
     Pursuant to the further exemplary embodiment illustrated in FIG. 7, a molded part in the form of the guide element  38  is disposed in the elongated opening  11 ; a bolt  14  projects into this guide element  38 . With an appropriate length two bolts or screws  15 ,  17  can also extend into or pass through the guide element  38 . The peripheral surface of the guide element  38  is provided with at least one abutment for the longitudinal edges  12 ,  13  of the elongated opening  11 ; however, a number of such abutments can also be provided. For this purpose, inclined surfaces can also be provided. Identical components are provided with the same reference symbols in FIG. 7 as they are in FIG.  2 . 
     The specification incorporates by reference the disclosure of German priority document 298 12 098.4 of Jul. 8 1998. 
     The present invention is, of course, in no way restricted to the specific disclosure of the specification and drawings, but also encompasses any modifications within the scope of the appended claims.