Abstract:
A protective cover of a hand-held cut-off machine has a bracket that is secured on the exterior side of the protective cover. The bracket is locked in at least one locked position with at least one locking projection in at least one receptacle of the protective cover. The bracket is releasable from the locked position by a movement of the bracket in the release direction. A simple release of the bracket can be achieved in that the protective cover has means that move the locking projection upon movement of the bracket in the release direction at least partially out of the receptacle.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The invention concerns a protective cover of a hand-held cut-off machine wherein the protective cover comprises a bracket secured on the exterior side of the protective cover. The bracket in at least one locked position is locked with at least one locking projection in at least one receptacle of the protective cover. The bracket, by a movement of the bracket in a release direction, is releasable from the locked position. 
         [0002]    U.S. 2006/0128289 A1 discloses a protective cover of a hand-held cut-off machine that is provided with a bracket. The bracket serves in particular for supplying a liquid, such as water, to the cutting disc. The liquid (water) supplied through the hollow bracket serves primarily for binding dust produced during cutting as well as for cooling and lubricating the cutting disc. The protective cover can be secured on the extension arm of the cut-off machine in different positions, i.e., on both sides of the extension arm of the cut-off machine. For this purpose, the position of the bracket must be changed on the protective cover. 
         [0003]    The bracket is exposed to high thermal stress on the protective cover. Moreover in operation strong vibrations act on the bracket. In order to ensure that the locked bracket will not be released in operation and in order to avoid thermal overload, the bracket is advantageously comprised of a strong and brittle material. When releasing the bracket from the locking means, this brittle material must be bent. This can cause overload of the material and thus breakage of the bracket. 
       SUMMARY OF THE INVENTION 
       [0004]    The invention has the object to provide a protective cover of the aforementioned kind whose bracket is releasable in a simple and safe way. 
         [0005]    This object is solved by a protective cover that has means that move the locking projection at least partially out of the receptacle upon movement of the bracket in the release direction. 
         [0006]    In that the protective cover itself has means that effect the movement of the bracket out of the receptacle, the operator must only move the bracket in the release direction. An additional spreading of the bracket for releasing it from the receptacle is no longer required. The means provided on the protective cover determines by constructive measures how far the bracket can be spread apart. In this way, by constructive measures an overloading of the bracket can be avoided. In a simple way a safe release of the bracket is enabled and at the same time overloading of the bracket is prevented. 
         [0007]    Advantageously, the means are arranged on the exterior side of the protective cover adjacent to the bracket in the release direction. Already for a minimal movement of the bracket from the locked position in the release direction, the bracket contacts the means and is released. A simple configuration results when the means comprise at least one guide ramp formed integrally on the protective cover. The guide ramp effects a gradual spreading and causes only a minimal mechanical loading of the bracket. In order to ensure that the bracket can be released easily from the receptacle, it is provided that the height of the guide ramp corresponds at least approximately to the engagement depth of the locking projection in the receptacle. 
         [0008]    Advantageously, the bracket has two legs that extend on opposite sidewalls of the protective cover wherein both legs of the bracket in the locked position are locked in one receptacle of the protective cover, respectively. Advantageously, each sidewall of the protective cover has at least one guide ramp. In this way, simultaneous release of both legs of the bracket is achieved. Advantageously, the guide ramps are formed symmetrically to one another on both sidewalls. In this connection, the guide ramps are advantageously mirror-symmetrical to a plane extending between the sidewalls. In this way, the two legs of the bracket are moved and spread apart in the outward direction uniformly and symmetrically. A one-sided spreading that would lead to overloading of one of the legs is thus prevented. 
         [0009]    The bracket can be released in a simple way when the bracket is pivotable about the receptacle for release from the locked position. The pivot movement can be carried out easily. Upon pivoting, the guide ramps effect a forced guiding action of the legs of the bracket in the outward direction and thus cause an automatic release of the bracket. 
         [0010]    Advantageously, the protective cover comprises at least one spray nozzle and at least one supply conduit connected to the spray nozzle. The spray nozzle serves for supplying a cooling liquid, in particular cooling water, to the cutting disc of the cut-off machine. 
         [0011]    Advantageously, one conduit section of the supply conduit passes through the bracket. A simple configuration of the protective cover results when the bracket has two legs and each leg has a spray nozzle arranged there at and when the conduit section passing through the bracket completely extends within the interior of the bracket and connects the two spray nozzles with one another. An additional connecting conduit of the two spray nozzles can thus be eliminated. Advantageously, the receptacle is an opening and the locking projection is provided on a hollow pin in which the spray nozzle is secured. The spray nozzle can supply cooling liquid through the opening to the cutting disc. The opening thus serves as a securing means for the locking projection of the bracket and as a passage for the cooling liquid. In this way, a simple configuration of the protective cover is provided. 
         [0012]    Advantageously, the bracket has a support section that is arranged in the locked position on the outer circumference of the protective cover. In this way, the rotational position of the bracket on the outer circumference of the protective cover can be determined in a simple way. Expediently, the support section in the locked position is secured by a locking device on the circumference of the protective cover. Accordingly, in a simple way the position of the bracket can be secured wherein the bracket advantageously is locked at both ends and on the circumference of the protective cover so that a three-point support action for the bracket is provided. Expediently, the bracket is secured in the locked position by a securing means. The securing means is advantageously a securing screw. In this way, even at strong vibrations of the protective cover it is ensured that the bracket cannot become detached accidentally. 
         [0013]    In order to achieve a minimal weight of the cut-off machine, it is provided that the protective cover is comprised of magnesium. The protective cover is advantageously produced by magnesium die casting. The bracket is comprised advantageously of fiberglass-reinforced plastic material. In particular, the bracket is comprised of fiberglass-reinforced polyphthalamide. In this way, a satisfactory temperature resistance of the bracket and at the same time a satisfactory strength can be achieved. The embodiment made from plastic material moreover provides a minimal weight of the bracket. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    One embodiment of the invention will be explained in the following with the aid of the drawing. 
           [0015]      FIG. 1  shows a side view of a cut-off machine. 
           [0016]      FIG. 2  is a schematic section illustration of the cut-off machine of  FIG. 1 . 
           [0017]      FIG. 3  is a perspective illustration of the protective cover of the cut-off machine of  FIG. 1 . 
           [0018]      FIG. 4  is a side view of the protective cover of  FIG. 3 . 
           [0019]      FIG. 5  shows a section of the protective cover along section line V-V of  FIG. 4 . 
           [0020]      FIG. 6  is a section view of a detail of the protective cover along the line VI-VI of  FIG. 4 . 
           [0021]      FIG. 7  is a perspective illustration of the protective cover when releasing the bracket. 
           [0022]      FIG. 8  is a side view of the protective cover when releasing the bracket. 
           [0023]      FIG. 9  is a sectioned illustration of a detail along the line IX-IX of  FIG. 8 . 
           [0024]      FIG. 10  is a sectioned illustration of a detail along the line X-X of  FIG. 8 . 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0025]    The cut-off machine  1  illustrated in  FIG. 1  is a hand-held portable cut-off machine. The cut-off machine  1  can also be secured on a guide carriage. The cut-off machine  1  has a housing  2  on which a rear handle  3  is arranged. On the rear handle  3  a throttle lever  4  is pivotably arranged for operating a drive motor  6  arranged in the housing  2 . On the housing  2 , on the side facing away from the rear handle, there is a grip pipe  5  that extends across the housing  2 . A starter handle  7  of a starter device  8  of the drive motor  6 , shown in  FIG. 2 , projects from the housing  2 . On the housing  2  an extension arm  14  is secured that projects forwardly; on it a cutting disc  15  is supported so as to rotate about axis of rotation  17 . The cut-off disc  15  is surrounded about part of its circumference by a protective cover  16 . The protective cover  16  can extend, for example, about half the circumference of the cutting disc  15 . 
         [0026]    A supply conduit  19  is provided on the cut-off machine  1  for supplying the cutting disc  15  with cooling liquid, for example, cooling water. The supply conduit  19  has a hose coupling  20  at the end neighboring the housing  2  for connecting it to a cooling medium tank. The supply conduit  19  is connected on the protective cover  16  to the bracket  18 . Adjacent to the bracket  18  a guide ramp  28  is formed integrally on the protective cover  16  whose function will be explained in the following in more detail. 
         [0027]    As shown in  FIG. 2 , the drive motor  6  is embodied as an internal combustion engine and comprises a piston  11  that drives in rotation a crankshaft  10 . Between the starter device  8  and the drive motor  6  there is a fan wheel  9  for conveying cooling air to the internal combustion engine  6 . On the opposite side of the drive motor  6  there is a centrifugal clutch  12  that connects the crankshaft  10 , after starting the internal combustion engine  6  and after surpassing a limit engine speed, to a shaft section  48  that drives a drive belt  13 . The drive belt  13  couples the crankshaft  11  to a bearing shaft of the cutting disc  15 . The drive belt  13  is guided within the extension arm  14 . 
         [0028]    As shown in  FIG. 3 , the protective cover  16  has a hub  21  and fastening projections  45  for fixing and positionally securing the protective cover  16  on the extension arm  14 . The bracket  18  has a first leg  38  shown in front in  FIG. 3  that is provided with a hollow pin  26  at the end facing the axis of rotation  17 . In the area of the circumference of the protective cover  16  the bracket  18  has a grip section  22  by means of which an operator can actuate the bracket  18 . Between the bracket  18  and the protective cover  16  a support section  23  is arranged on the circumference of the protective cover  16 . The support section  23  has a transverse opening that, in the locked position  46  of the bracket  18  shown in  FIG. 3 , is aligned with the fastening opening  25  of the protective cover  16 . A securing means in the form of a securing screw  24  is pushed through the fastening opening  25  and provides a positive-locking positional securing action for the bracket  18 . On the opposite end of the protective cover  16  a projecting portion  33  is shown in  FIG. 3  and is provided with a fastening opening  25 . The protective cover  16  is symmetrically designed so that the fastening opening  25  matches the fastening opening through which the securing screw  24  is pushed in the locked position  46  shown in  FIG. 3 . The hollow pin  26  projects through an opening  27  that in  FIG. 3  is also shown for the second locked position (not shown) of the bracket  18 . As shown in  FIG. 3 , the first leg  38  extends on the first sidewall  40  of the protective cover  16 . 
         [0029]    In  FIG. 4 , the symmetry plane  49  of the protective cover  16  is illustrated. The symmetry plane  49  contains the axis of rotation  17  of the cutting disc  15 . In  FIG. 4 , the second locked position  47  of the bracket  18  is also illustrated in dashed lines. In this second locked position the bracket  18  is arranged relative to the symmetry plane  49  mirror-symmetrical to the locked position  46 . 
         [0030]    The protective cover can be secured at both sides of the extension arm  14 . Because the protective cover  14  is provided with a hub  21  and fastening projections  45  only at the first sidewall  40  shown in front in  FIG. 3  and  FIG. 4 , the protective cover is rotated when it is to be mounted in reverse. In this connection, the position of the bracket  18  must be changed also. The bracket  18  is adjusted from the first locked position  46  shown in  FIG. 4  to the second locked position  47  schematically illustrated in  FIG. 4 . For this purpose, the bracket  18  is pivoted in the release direction  42  about the opening  27  and the hollow pin  26  that is arranged in the opening  27 . 
         [0031]    As shown in the section illustration of  FIG. 5 , a conduit section  34  of the supply line  19  is formed integrally on the bracket  18 . The bracket  18  has two legs  38 ,  39  that are formed symmetrical to a symmetry plane  50 . The symmetry plane  50  extends between the two sidewalls  40  and  41  of the protective cover  16  parallel to the plane of the cutting disc  15 , in particular in the plane of the cutting disc  15 . Each leg  38 ,  39  of the bracket  18  has at its end a hollow pin  26  on which a locking projection  43  is integrally formed. The locking projection  43  of the hollow pin  26  projects into the two openings  27 . The interior of the two hollow pins  26  is connected by the conduit section  34 . 
         [0032]    In the interior of the protective cover  16  webs  44  are provided on both sidewalls  40 ,  41 ; the webs are formed as thicker portions of the sidewalls  40 ,  41 . In the two hollow pins  26  a spray nozzle  45  is arranged, respectively. For simplifying the drawing, in  FIG. 5  only one spray nozzle  35  on the leg  39  is shown. The spray nozzle  35  connects the cavity formed between the hollow pin  26  and the spray nozzle  35  with the interior of the protective cover  16 . In this connection, the spray nozzle  35  extends through the receiving opening  27 . For fixation, the spray nozzle  45  is screwed into a square nut  36  that is fixedly secured between the two webs  44  so as not to rotate. On the opposite side, on the first leg  38  a connecting member, not shown, is provided at the hollow pin  26  for connecting it to the supply conduit  19 . 
         [0033]    As shown in the section illustration of  FIG. 6 , the guide ramps  28  are embodied to project outwardly beginning at the legs  38  and  39  of the bracket  18 . The guide ramp  28  extends at an angle to the sidewalls  40  and  41 ; the angle is advantageously approximately 5° 0  up to approximately 30°. 
         [0034]    For releasing the bracket  18 , the bracket  18  is moved in the release direction  42 . This is illustrated in  FIG. 7 . For this purpose, first the screw  24  is released. The support section  23  is locked in locked positions  46 ,  47  on a locking device in the form of projecting portion  33  on the outer circumference of the protective cover  16 . This locking action is released by movement of the bracket  18  in the release direction  42 . When pivoting the bracket  18  in the release direction  42 , the legs  38 ,  39  of the bracket  18  reach the area of the guide ramps  28 . This is shown in  FIG. 10 . The legs of the bracket  18  glide on the guide ramps  28  that are provided on either side of the protective cover  16  symmetrical to the symmetry plane  50  ( FIG. 5 ). In this way, the legs  38 ,  39  are moved outwardly and spread apart. This has the effect that the locking projections  43  are lifted out of the receiving openings  27 . This is shown in  FIG. 9  for the leg  38  of the bracket  18 . The guide ramps  28  in the embodiment are arranged close to the openings  27 . In order to achieve complete lifting of the locking projection  43 , the height a of the guide ramp  28 , measured perpendicular to the symmetry plane  50 , matches at least the engagement depth b of the locking projection  43  illustrated in  FIG. 9 . The guide ramps  28  integrally formed symmetrically on both sidewalls  40 ,  41  effect a uniform spreading of the legs  38  and  39  of the bracket  18  so that an excessive loading of one leg is prevented. 
         [0035]    As shown in  FIG. 4 , the protective cover  16  has steps  37  that extend approximately in the direction of the bracket  18  when in the locked position  46 ,  47 ; one step is shown in  FIG. 4 . As shown in  FIG. 6  for the locked position  46 , the legs  38 ,  39  are positioned adjacent to the steps  37  formed integrally on the two sidewalls  40 ,  41 . In this way, an additional positional securing action of the bracket  18  is provided. 
         [0036]    Instead of the guide ramps  28  other means for releasing the locking projections  43  from the openings  27  can be provided. 
         [0037]    It is provided that the protective cover  16  is comprised of magnesium and is produced in particular by magnesium die casting. The bracket  18  is comprised advantageously of fiberglass-reinforced plastic material so that a satisfactory temperature resistance and a satisfactory strength are provided. Advantageously, the bracket  18  is comprised of fiberglass-reinforced polyphthalamide (PPA). 
         [0038]    The specification incorporates by reference the entire disclosure of German priority document 10 2007 032 672.8 having a filing date of 13 Jul. 2007. 
         [0039]    While specific embodiments of the invention have been shown and described in detail to illustrate the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.