Abstract:
The invention relates to a protective hood for a hand tool, in particular for an electrical hand tool which has a support area for the attachment of a flange of the hand tool, and with a clamping device for fastening the protective hood to the flange as well as an anti-twist device to secure the angle position of the protective hood relative to the hand tool. It is provided that the support area ( 9 ) has at least one anti-twist device element ( 18 ) working in conjunction with at least one anti-twist device mating element ( 47 ) of the flange ( 34 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The invention described and claimed hereinbelow is also described in German Patent Application, DE 10 2006 022 386.1 filed on May. 12, 2006. This German patent Application, whose subject matter is incorporated here by reference, provides the basis for a claim of priority of invention under 35 U.S.C. 119(a)-(d). 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a guard for a hand-held power tool, in particular for an electric hand-held power tool, which includes a support surface for placement against a flange of the hand-held power tool, with a clamping device for fastening the guard to the flange, and with a rotation lock for fixing the angular position of the guard relative to the hand-held power tool. 
     Hand-held power tools, in particular electric hand-held power tools, with rapidly rotating disks, e.g., angle grinders, are equipped with a guard to protect the user from sparks, fragments, grinding particles, etc. The known guards are composed of a hood body and a clamping element. The clamping element is used to enclose a flange of the hand-held power tool, in particular an electric hand-held power tool. The flange encloses an axis that is the rotation axis of the rapidly rotating disk or the like. Screw connections or clamping levers are typically used to clamp the clamping element. The clamping produces a frictional connection between the flange and the guard, which fixes the guard in position and prevents it from rotating. To adjust the guard, the clamping element is released, thereby enabling the guard to be repositioned (i.e., to change its angular position). Once the guard has been repositioned, the clamping element is tightened once more. Guards are also known that realize the aforementioned frictional connection as well as a form-fit connection in order to fix the guard in place. This form-fit connection between the guard and the hand-held power tool is created by the fact that a lever installed on the hood or the hand-held power tool creates a form-fit connection with the electric hand-held power tool or the hood when in the neutral position, thereby providing reliable rotational locking. 
     SUMMARY OF THE INVENTION 
     With the inventive guard of the type described initially, it is provided that the support surface includes at least one rotation lock element, which is capable of interacting with a rotation lock counter-element of the flange. To this end, the contact surface between the hood and the flange, i.e., the support surface mentioned, includes at least one rotation lock element, which may interact with a rotation lock counter-element of the flange. The support surface is formed on the guard and is provided with the rotation lock element, thereby resulting in a very simple, effective design. The support surface is assigned directly to a hood body of the guard, and therefore lies in the zone of the hood body and not in a zone that belongs only to the clamping device. The inventive embodiment fulfills the requirements for increased safety, and fulfills the requirements of proposed standards, according to which fragments may not strike the user if the rotating disk breaks into four fragments of equal size, but are instead directed by the guard in the forward direction, e.g., away from the user. With the inventive design, a frictional connection is realized, as is a form-fit connection between the guard and the flange, so that extremely large forces may be absorbed. The guard is prevented from rotating out of a defined position, or it may be rotated by a maximum angle of 90°, thereby also complying with this standard. Via the rotation lock element, which interacts with the rotation lock counter-element, a type of profile is produced, which creates at least one latching position in which the guard is latched in place. When the guard is installed, this profile ensures that, when the clamping device is clamped, the hood remains in the desired position and does not slide as a result of the clamping procedure and move into an undesired position. 
     According to a refinement of the present invention, it is provided that the guard includes a hood body, and that the rotation lock element is designed/located on the hood body. As a result, the guard rests with its hood body directly on the flange of the hand-held power tool. 
     As an alternative, it is possible to locate the rotation lock element on a part of the clamping device assigned to the hood body. As a result, the rotation lock element is not located on just any part of the clamping device, but precisely in the zone that is assigned to the hood body, and it is overlapped by the hood body in particular. 
     It may be provided, in particular, that the rotation lock element is designed as a stamped element and/or a deep-drawn element. With stamping, no additional material is required. When stamping is carried out, a profile is created, which may interact with a counter-profile of the rotation lock counter-element. 
     It is provided in particular that the rotation lock element is designed as one piece with the component on which is it provided, or it is designed as a separate component, and it is attached to the hood body or the clamping device. 
     The support surface is preferably curved, and it is semicircular in shape in particular. Several rotation lock elements may be located along the curve. The rotation axis of the tool fitting of the hand-held power tool, in particular the electric hand-held power tool, is located in the center of the semicircle described above. 
     It is advantageous when the rotation lock elements are separated by the distance covered in one latching, or by a multiple thereof. A profile therefore results that has the same “pattern” around the circumference or a partial circumference of the support surface, thereby making it possible to attach the guard in this circumferential zone in form-fit positions with angular offsets relative to each other. The support surface may be semicylindrical or semiconical in design. The prefix “semi . . . ” means that the support surface is assigned to the guard and may therefore not be full-sized in the circumferential direction (360°), since open space must remain for a working region in which the tool is not covered by the guard. The rotation lock element is not located in this open space. An axial lock between the guard and the flange may be formed by the semiconical shape. Another possibility is to design the support surface convex and/or concave in shape, as viewed in the axial direction. Preferably, this may also serve to form the axial lock mentioned above. 
     The flange is preferably designed as an annular flange. The rotation lock element is preferably designed as one piece with the flange, and the flange is preferably curved in design, in particular semicircular or circular in design. It is advantageous when several rotation lock counter-elements are located along the curve or semicircle or the circular design of the flange. 
     The rotation lock counter-elements may be separated by the distance covered in one latching, or by a multiple thereof. It is also possible for the flange to be cylindrical or conical in design, as mentioned above with regard for the support surface. The support surface and flange are always designed with matching shapes. It is also advantageous when the rotation lock element and the rotation lock counter-element engage in each other with matching shapes. 
     To form an axial lock, it is particularly advantageous when at least one guide projection is formed on the support surface or the flange, which engages in a circumferential recess or semicircumferential recess of the flange or support surface. The circumferential recess or semicircumferential recess may be designed as a circumferential groove or semicircumferential groove. 
     A clamping band is preferably provided as the clamping device. The clamping band may be separate from the guard, and it may extend over a section of the guard, i.e., a region of the hood body, or it is a clamping band attached to the hood body. The rotation lock element may be located on the zone of the clamping band that extends over the region of the hood body. It is advantageous, in particular, when the clamping band is designed as one piece with the guard. This is realized, e.g., by designing the guard with at least one and preferably two clamping strips that are formed as one piece with the hood body. The clamping band is preferably clamped using a clamping closure, which may be designed as a screw connection in particular. 
     The present invention also relates to a hand-held power tool, in particular an electric hand-held power tool, with a guard and a flange as described above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The drawing serves to explain the present invention, with reference to exemplary embodiments. 
         FIGS. 1 and 2  show a guard with a clamping band located on the outside, 
         FIGS. 3 and 4  show a guard with a clamping band located on the inside, 
         FIGS. 5 and 6  show a guard with an integrated clamping band that is formed as one piece with the hood, 
         FIG. 7  shows a guard attached to a flange of a not-shown hand-held power tool, in particular an electric hand-held power tool, 
         FIG. 8  shows a perspective view of a flange, 
         FIG. 9  shows a detailed view of a profiled support surface of the guard in a form-fit position on a flange with a counter-profile, 
         FIGS. 10   a  through  10   e  show various designs of support surfaces, i.e., semi-/cylindrical (a), semi-/conical (b), semi-/conical (c), convex (d), concave (e), 
         FIGS. 11   a  through  11   f  show combination shapes of the support surface, 
         FIGS. 12   a  through  12   c  show profile shapes of the rotation lock (rotation lock element and/or rotation lock counter-element), in different variants, 
         FIGS. 13   a  through  13   e  show combination forms of profiles according to  FIG. 12 , and 
         FIG. 14  shows a top view of the guard attached to the flange. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a guard  1  for a not-shown hand-held power tool, in particular an electric hand-held power tool, e.g., an angle grinder, with a rapidly rotating disk. Guard  1  includes a hood body  2  with an axial surface  2 ′, which is designed as a semicircular surface (180°) and from which a semicircumferential surface  4  extends, in outer region  3 . Axial surface  2 ′ and semicircumferential surface  4  are preferably located at right angles to each other. End edge  5  of semicircumferential surface  4  is curved radially inwardly, as shown in  FIG. 7  in particular. Radially inwardly drawn edge  5  forms an overreaching protective edge  6  for a rapidly rotating disk—which is not shown in the figures—of the electric hand-held power tool. 
     Axial surface  2 ′ transitions into a conical surface  8  toward inner region  7 . Support surface  9  extends outwardly from conical surface  8 , and it extends cylindrically relative to a rotation axis  10 —shown in FIG.  2 —of the not-shown rotating disk and forms support surface  9  for placement on a flange—not shown in FIGS.  1  and  2 —of the electric hand-held power tool. Axial surface  2 ′, semicircumferential surface  4 , overreaching protective edge  6 , conical surface  8 , and support surface  9  are formed as one piece with each other, preferably as a sheet-metal piece, in particular as a one-pieced hood body  2 . 
     Support surface  9  forms a semiannular surface  11 , with which the circumferential angle preferably extends around 180°, as is the case with the other surfaces mentioned. Support surface  9 , i.e., the entire sheet-metal region that forms support surface  9 , is profiled in design, i.e., it has a profile  12 . The cross-sectional structure of support surface—as shown in FIG.  2 —therefore does not mathematically form a semicircle, but rather a superposed zig-zag structure  13 , thereby resulting in tooth-like raised areas  14  with recesses  15  between them, as viewed around the partial circumference. As shown in  FIG. 9 , the raised areas  14  have peak lines  16 , which extend axially. Recesses  15  have base lines  17 , which also extend axially, i.e., in the direction of rotation axis  10 . Individual raised areas  14  form rotation lock elements  18  that interact with matching rotation lock counter-elements of the abovementioned flange of the hand-held power tool, as is described in greater detail below. 
     According to  FIGS. 1 and 2 , outer side  19  of support surface  9  is overlapped by a clamping device  20 , which is designed as clamping band  21 . Clamping band  21  is separate from hood body  2 , although it is attached to hood body  2  using suitable means, in particular to outside  19  of support surface  9 . The attachment is preferably carried out using welding. Clamping band  21  has a circular cross section and includes a clamping closure  22  in the form of angled clamping band ends  23  and  24 . Clamping band end  23  includes a thread receptacle  25 , and clamping band end  24  includes a through-bore  26 , thereby enabling the diameter of clamping band  21  to be reduced using a not-shown threaded screw that is inserted into through-bore  26  and crewed into thread receptacle  25 . Clamping therefore takes place on the aforementioned flange of the hand-held power tool, in particular an electric hand-held power tool. 
     Inner side  27  of clamping band  21  is provided with a guide projection  28 , which may be created, in particular, by creating two parallel separating sections of clamping band  21 —which is made of sheet metal—and designing the sheet-metal region located between the separating sections to extend radially inwardly. 
     The exemplary embodiment shown in  FIGS. 3 and 4  differ from the exemplary embodiment shown in  FIGS. 1 and 2  only in that clamping band  21  is not designed as a clamping band on the outside, but rather as clamping band  21  on the inside, i.e., outside  29  of clamping band  21  bears against inner side  30  of the corresponding part of hood body  2 , so that support surface  9  is formed by the inner side of clamping band  21  in the zone that overlaps the aforementioned part of hood body  2 . A semicircular section ( FIG. 4 ) of clamping band  21 , i.e., support surface  9 , includes a profile  12  with a zig-zag structure  13 . Hood body  2  is welded with outside  29  of clamping band  21 . Hood body  2  may also include a profile, thereby enabling the two profiles of hood body  2  and clamping band  21  to engage in each other in a form-fit manner. The profile of support surface  9  forms at least one rotation lock element  18  toward a not-shown flange. 
     With the exemplary embodiment shown in  FIGS. 5 and 6 , the only difference from the exemplary embodiment shown in  FIGS. 1 and 2  is that clamping band  21  is not designed as a separate part, but rather as one piece with hood body  2 , i.e., support surface  9  of hood body  2  with zig-zag structure  13  transitions as one piece into two clamping strips  32  and  33 , thereby also resulting in one clamping band  21  with a clamping closure  22 . 
     In all, it should be noted that profile  12 , i.e., rotation lock elements  18  formed as a result, have the same shape, i.e., lock rotation elements  18  are separated by the distance of one latching or by a multiple thereof. 
       FIG. 8  shows flange  34  of the hand-held power tool, in particular an electric hand-held power tool, which is designed as annular body  35  with fastening segment  36 . A ball bearing may be inserted in an inner opening  37  of annular body  30  to support a shaft—on which a tool is mounted—which rotates around rotation axis  10  ( FIG. 9 ). Outer side  38  of annular body  35  of flange  34  is provided with a counter-profile  39  for interacting with profile  12  of guard  1 . Counter-profile  39  includes tooth-like raised areas  40  and recesses  41  located between them. Raised areas  40  have peak lines  42 , and recesses  41  have base lines  43 . Peak lines  42  and base lines  43  extend axially, i.e., parallel, to the direction of rotation axis  10 . 
     Outer side  38  of annular body  35  is provided with a circumferential recess  41  in the form of a circumferential groove  45  in the region of counter-profile  39 . Moreover, annular body  35 —as shown in FIG.  9 —includes an insertion recess  46  on its outer side  38  for guide projection  28  of clamping band  21 . 
     Due to counter-profile  39 , rotation lock counter-elements  47  are formed on flange  34 , which may interact with rotation lock elements  18  of guard  1  in a form-fit manner and via their matching shapes, thereby forming a rotation lock of guard  1  on flange  34 . Counter-profile  39  has an even design, as does profile  12 . Individual rotation lock counter-elements  47  are therefore separated by the distance of one latching, or by a multiple thereof. The distance of one latching of rotation lock elements  18  corresponds to the distance of one latching of rotation lock counter-elements  47 , thereby enabling guard  1  to be fastened to flange  34  in desired angles of rotation in accordance with the latch-in distance, by installing it axially and then clamping the clamping device  20 , as shown in  FIGS. 7 and 9 . When installing guard  1  on flange  34  axially, an angular position of the two parts must first be selected, and in such a manner that guide projection  28  may enter insertion recess  46 . When guard  1  has been slid entirely onto annular body  35  of flange  34 , guide projection  28  lies inside circumferential groove  45 , thereby forming an axial lock. If clamping band  21  has not been tightened, guard  1  may be rotated relative to flange  34 . Once the desired rotational position of these parts has been attained, clamping band  21  is tightened by closing clamping closure  22 , thereby reducing its diameter. A frictional connection and a form-fit connection are thereby formed between guard  1  and flange  34 . The form-fit connection is created via the meshed rotation lock elements  18  and rotation lock counter-elements  47 . Profile  12 , which is assigned to hood body  2 , preferably extends around only a portion of the circumference; counter-profile  39  of flange  34  preferably extends around the entire circumference. 
     Very strong forces of the type that may occur if the rotating disk were to break may be absorbed by the form-fit connection—created according to the present invention—between guard  1  and flange  34 . Profile  12 , in interplay with counter-profile  39 , also creates latching positions, which allow guard  1  to latch into position when it is adjusted, thereby ensuring that the selected position is maintained when clamping device  20  is clamped. 
     The following possibilities and advantages also result from the present invention: The clamping band may be designed as an annular band, in particular as a smooth ring. As an alternative, the clamping band is not circumferential, but rather is designed as a one-piece extension of the guard neck (support surface  9 ). Flange  34  of electric hand-held power tool forms an interface with guard  1 . Due to profile  12  and counter-profile  39 , guard  1  may be fastened on flange  34  in a frictional and non-positive manner in a large number of angular positions. Profile  12  and counter-profile  39  extend parallel with rotation axis  10 , as mentioned above. Other profile shapes are also feasible, however, e.g., with a pitch, similar to a thread pitch of a screw, a herringbone profile, similar to herringbone teeth in gears, or a profile shape with variable pitch. The profile and/or counter-profile may be designed to extend 360° or to extend only around a semicircle or part of a curve. Different cross-sectional configurations between the supporting surface and the flange are feasible in order to form an axial lock, e.g., truncated cone shapes and/or concave and/or convex contact surfaces. 
     As described above, the contact surface, in particular the support surface, between guard  1  and flange  34  may be cylindrical or semicylindrical, and/or conical or semiconical, and/or convex and/Or concave. Combined forms of these shapes are also possible, i.e.,—as viewed along the axial length—cylindrical or semicylindrical, and conical or semiconical. It is also possible to select, e.g., conical or semiconical shapes, it being possible to form necks or angular shapes using two conical sections that are slanted toward each other. The rotation lock, which is formed by the at least one rotation lock element  18  in combination with the at least one rotation lock counter-element  47 , may also have a profiled shape, i.e., it may extend axially as a straight line or at a diagonal to rotation axis  10 , it may be curved or be a combination of the profile shapes described. When the shape is beveled, angled sections may also be specified. 
     When clamping band  21  is connected with the neck of hood body  2  by welding, in particular spot welding, profiling is preferably not provided or stamped in the region of the spot welding sites, in order to attain the best possible contact zones.  FIG. 10  shows various support surface designs.  FIG. 11  shows combination shapes of support surface designs,  FIG. 12  shows profile shapes of the rotation lock, and  FIG. 13  shows combination shapes of profiles. 
     It is important in particular to design the profiles of the rotation lock such that flange  34  and guard  1  do not form an undercut in a certain direction, which is indicated in  FIG. 14  with an arrow. During adjustment, guard  1  moves automatically via accumulation of forces in support surface  9  in this direction and disengages the profile, thereby making it possible for guard  1  to rotate relative to flange  34 . As a result, comfortable handling with a minimal amount of force is made possible. Based on the description provided above, it is clear that the profile assigned to the guard must be capable of moving over the profile of the flange in a latching manner when the clamping device has not been tightened. This rotational capability is only given, however, when the profile of guard  1  extends only around an angular range that is less than 180° and therefore does not require that the guard neck or the like expand during rotation. Rather, when rotated, the guard moves in the direction of the arrow shown in  FIG. 14 , without guard  1  undergoing plastic deformation. If the profile assigned to guard were 180° or nearly 180°, undercuts would be formed, i.e., a motion in the direction of the arrow shown in  FIG. 14  would not be possible without guard  1  or its neck being expanded. Since guard  1  is preferably composed of a relatively stiff sheet-metal material, however, an expansion of this type should be prevented. It is also possible, of course, as an alternative, to manufacture the guard out of a resilient material, so that expansion may occur. The profile of the guard could then definitely have an angular range of 180°. It is also feasible, of course, as an alternative, for the undercuts described to be permitted with unflexible hoods. As a consequence, however, the handling would be less comfortable when adjustments are made, since it would then be necessary to always remove guard  1  axially from the flange, to adjust the new angular settings, and to then insert the guard axially onto the flange once more in the new position. It would not be possible to perform adjustments in a convenient, latching manner.