Patent Publication Number: US-6669542-B1

Title: Angle grinder

Description:
PRIOR ART 
     The invention is based on an angle grinder as generically defined by the preamble to claim  1 . 
     An angle grinder with such a housing is known from German Patent Disclosure DE 43 44 128. The housing in this case is in one piece and is screwed onto a cup-shaped motor housing. A spindle bearing receptacle in which the bearing for a work spindle is received is embodied integrally with the housing. For changing a tool that is mounted on the work spindle, the work spindle has to be fixed. This is done by providing that a spindle lock, by means of a hand lever and counter to the force of a restoring spring, presses a detent cam into an indentation that is embodied on a clamping flange, which in turn is connected to the work spindle in such a way that it rotates with it. In the operation of the work spindle and when the tool secured to it is changed, major forces, or clamping forces, occur. It is therefore necessary that both the spindle bearing receptacle and the locking device comprise a high-quality, wear-resistant material. Since the spindle bearing receptacle is embodied integrally with the housing, the entire housing must be made from such a high-quality, expensive material. 
     ADVANTAGES OF THE INVENTION 
     The angle grinder of the invention as defined by the characteristics of claim  1  has the advantage over the prior art that the entire housing can be made by shell construction and can be fabricated from an economical material; only the insert part to be inserted separately into the housing has to comprise especially high-quality material. The possibility is thus afforded of producing a less expensive product than was previously possible. This is made possible by the fact that the entire housing is made of shell construction, that is, with a mounting shell and a cap shell, between which the insert part is inserted. Because the insert part is fixed with its first and second fixation device between the mounting shell and the cap shell, the spindle bearing receptacle and the spindle locking receptacle, also disposed in the insert part, always remain stationary in their position relative to the housing. 
     It is advantageous if the spindle bearing receptacle and the spindle locking receptacle are disposed parallel to one another in a base body of the insert part, and if this base body has an aperture oriented perpendicular to the spindle locking receptacle, which is embodied as a through hole. As a result, it is possible for the insert part to be well fixed in its position between the mounting shell and the cap shell, each of which have a screw dome that is disposed in a line with the through hole. 
     It is also advantageous if the insert part has an outrigger, on which a first fixation device is disposed, the cross section of the outrigger being in the form of a double T. The first fixation means of the mounting shell and second fixation means of the cap shell can easily engage the resultant indentations on both sides of the outrigger, thus assuring good fixation of the angular position of the insert part in the housing between the two shells. 
     It is also advantageous if the insert part comprises a high-quality, wear-resistant material, while conversely the mounting shell and the cap shell are of an inexpensive material. This is made possible because only the spindle bearing receptacle and the spindle locking bolt experience heavy loads, while the remaining points of the housing experience hardly any load. As material for the insert part, Grivory or a similar material is used. This is a glass-fiber-reinforced, heavy-duty polyamide plastic, such as PA 6-66 GF. 
     An advantageous fixation of the insert part in the housing is achieved by the provision that the outrigger of the insert part rests over a large surface area on first and second bearing faces of the mounting shell and cap shell, respectively. 
     Advantageously, in the region of its through hole, the insert part has first and second centering devices, oriented toward each of the screw domes, that can be brought into engagement with first and second centering means of the screw domes. As a result, centering and thus correct insertion of the insert part between the mounting shell and the cap shell are assured. 
     Further advantageous features of the invention will become apparent from the other dependent claims. 
    
    
     DRAWINGS 
     The invention is explained in further detail in the ensuing description of an exemplary embodiment shown in the drawings. Shown are: 
     FIG. 1, a perspective view of an insert part; 
     FIG. 2, the plan view on the insert part of FIG. 1 in the direction II; 
     FIG. 3, a cross section through the insert part taken along the plane III—III of FIG. 2; 
     FIG. 4, a plan view on the inside face of a mounting shell; 
     FIG. 5, a plan view on the inside of a cap shell; 
     FIG. 6, a section through a fully assembled housing taken along the plane VI—VI of FIG. 4; and 
     FIG. 7, a section through a fully assembled housing taken along the plane VII—VII of FIG.  6 . 
    
    
     DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
     FIGS. 1 and 2 show views of an insert part  1 . Identical parts are identified by the same reference numerals. The insert part  1  has a base body  14  and an outrigger  15 . A spindle bearing receptacle  13 , spindle locking receptacle  12 , and second fixation device  11  are embodied on the base body  14 . The spindle bearing receptacle  13  is embodied as a blind bore  130  (shown in dashed lines in FIG.  2 ). The spindle locking receptacle  12  is designed as a through hole  120  (shown in dashed lines in FIG.  2 ). The longitudinal center axes of the through hole  120  and the blind bore  130  are oriented parallel. The second fixation device  11  has an aperture  140 , which is oriented perpendicular to the plane defined by the two longitudinal center axes of the through hole  120  and the blind bore  130 . A first centering device  16  (see FIG. 6) and a second centering device  17  are embodied in the region around each of the two openings of the through hole  120 . 
     Fins  110 ,  111  are provided laterally on the base body  14 . The fin  111  is embodied as a rib protruding from the base body  14 . The fin  110  is located symmetrically on the opposite side of the base body  14 . These fins  110 ,  111  are provided in order to fix the insert part in the installed state and in particular to prevent torsion about the axis of the motor. 
     The outrigger  15  of the insert part  1  is embodied integrally with the base body  14  and extends outward from the spindle bearing receptacle  13 . A first fixation device  10  is embodied on the end of the outrigger  15  remote from the base body  14 . The entire outrigger  15  is embodied in the shape of a double T. The shape of the outrigger  15  is illustrated by the first fixation device  10 , in the cross section shown in FIG.  3 . Because of the double T shape, there are two indentations  100 ,  101 , separated from one another by a wall  102 . The wall  102  extends in the plane defined by the center longitudinal axes of the blind bore  130  and the through hole  120 . The first indentation  100  and the second indentation  101  are U-shaped in cross section. In the plan view of FIG. 2, they have an oval shape. It is shown in suggested fashion in FIG. 2 how a second fixation means  40 , in the form of a second rib  400  which is embodied on a cap shell  4  (see FIG.  5 ), engages the second indentation  101 . 
     FIG. 4 shows the inside of a mounting shell  3  of a housing  2  (see FIGS.  6  and  7 ). Below, only those parts of the mounting shell  3  essential to the invention will be described. The mounting shell  3  has a first rib  300 , which in the installed state of the housing  2  engages the first indentation  100  of the outrigger  15  (see FIG. 3) in such a way that the insert part  1  (see FIGS. 1-3) is fixed with its first fixation device  10  in its angular position relative to the mounting shell  3 . In this position the outrigger  15  (see FIGS. 1-3) rests with a large surface area on the first bearing face  301 . The mounting shell  3  also has a first screw dome  31 . A first centering means  32 , which is in engagement with the first centering device  16  (see FIG. 6) in the installed state of the housing  2 , is embodied on the first screw dome  31 , around an opening that serves to receive a screw. The mounting shell  3  also has a first receiving opening  33 , through which a spindle locking bolt  6  (see FIG. 7) can be introduced through the through hole  120  (see FIGS. 1,  2 ,  6  and  7 ) into the spindle locking receptacle  12  of the base body  14  of the insert part  1 . The mounting shell  3  furthermore has a first rib  310  and a second rib  320  with recesses  311  and  321 , respectively, for receiving the fin  110 . Further details of the relative position between the mounting shell  3  and the insert part  1  will be described in conjunction with FIGS. 6 and 7. 
     FIG. 5 shows the inside of the cap shell  4 , which in the state in which it is assembled with the mounting shell  3  is attained by folding it upward about the center axis between FIGS. 4 and 5. Once again, only those parts essential to the invention will be described below. A second bearing face  401  assures that the insert part  1  with its outrigger  15 , in the installed state of the housing  2 , will also rest over a large surface area on the cap shell  4 , in addition to the above-described large-area contact with the mounting shell  3 . On the inside of the cap shell  4  as well, a second rib  400  also engages the second indentation  101  of the first fixation device  10  of the insert part  1  (see FIG.  2 ). The cap shell  4  also has a second screw dome  41 , which in the installed state is aligned with the first screw dome  31  of the mounting shell  3 . The second screw dome, around its opening, has a second centering means  42 , which in the installed state of the housing  2  is in engagement with the second centering device  17  of the second fixation device  11  of the insert part  1  (see FIGS.  1  and  2 ). In addition, the cap shell  4  has a second receiving opening  43 , which in the installed state of the housing  2  has a receiving opening, cohesive with the first receiving opening  33  of the mounting shell  3 , into which the spindle locking bolt  6  (see FIG. 7) can be introduced. A first rib  410  and a second rib  420  with respective recesses  411  and  421  are also provided for receiving the fin  111 . 
     FIG. 6 shows the front region of the housing  2  in its fully assembled state, once the insert part  1  has been placed between the mounting shell  3  and the cap shell  4 . The blind bore  130 , in which a spindle bearing  8  for receiving the work spindle  7  (not shown) is disposed, can be seen on the insert part  1 . The through hole  120  embodied parallel to the blind bore  130  can also be clearly seen. The aperture  140  oriented perpendicular to the plane that is defined by the longitudinal center axes of the through hole  120  and the blind bore  130  is disposed in alignment with the first screw dome  31  of the mounting shell  3  and the second screw dome  41  of the cap shell  4 . For the sake of simple centering of the insert part  1  between the mounting shell  3  and the cap shell  4 , a first centering means  32  on the first screw dome  31  engages a first centering device  16  on the insert part  1 . In addition, a second centering device  17  on the insert part  1  also engages a second centering means  42  on the second screw dome  41  of the cap shell  4 . For secure positional fixation of the individual parts of the housing  2  relative to one another, a screw  5  is passed through the second screw dome  41 , the aperture  140 , and this screw engages the first screw dome  31  and thus brings about secure fixation. 
     FIG. 7 shows the three-dimensional disposition of the insert part  1  in the mounting shell  3 . The outrigger  15  with its first fixation device  10  rests over a large surface on the first bearing face  301  (see FIG. 4) of the mounting shell  3 . The first rib  300  of the first fixation means  30  on the mounting shell  3  engages the first indentation  100  of the first fixation device  10 , as described in conjunction with FIG.  4 . As a result, a fixation of the angular position of the insert part  1  relative to the mounting shell  3  is achieved. To prevent torsion of the insert part  1  in the mounting shell  3  and thus in the housing  2 , there is not only the fixation just described by means of the first fixation device  10  but also the second fixation device  11  as described in conjunction with FIG.  4 . In the blind bore  130 , the work spindle  7  is supported in the spindle bearing  8  rotatably relative to the insert part  1 . To fix the work spindle  7  so a tool can be changed, a spindle locking bolt  6  is introduced through the first receiving opening  33  in the through hole  120 . 
     The mounting of the housing  2  is effected as follows: 
     The insert part  1  is placed in the mounting shell  3  in such a way that the position described in conjunction with FIGS. 1-7 is reached. This essentially means that the first fixation device  10  is made to engage the first fixation means  30 , and the second fixation device  11  is centered relative to the first screw dome  31  such that the aperture  140  is oriented in alignment with the first screw dome  31 . The fin  110  of the insert part  1  comes to rest in the recess  311  of the first rib  310  and in the recess  321  of the second rib  320 . The cap shell  4  is thereupon placed on the mounting shell  3  in such a way the second fixation means  40  engages the first fixation device  10 , and the second screw dome  41  is oriented in alignment with the aperture  140  and the first screw dome  31 . This also causes the fin  111  to engage the recess  411  of the first rib  410  and the recess  421  of the second rib  420 . This assures an additional security against torsion of the insert part  1 , in particular longitudinally to the motor axis. After that, the cap shell  4  is screwed to the mounting shell  3  by means of the screw  5 , as described above.