Abstract:
The invention relates to a protective hood anti-rotation lock for a portable power tool ( 12   a - k ), especially for an angle grinder, for providing anti-rotational locking between the portable power tool ( 12   a - k ) and a protective hood unit ( 14   a - k ). According to the invention, the protective hood anti-rotation lock has a form-fit unit ( 16   a - k ) which is provided for anti-rotational locking of the protective hood unit ( 14   a - k ) in relation to the portable power tool ( 12   a - k ) in the event of a tool ( 18   a - k ) breakage.

Description:
CROSS-REFERENCE TO A RELATED APPLICATION 
     The invention described and claimed hereinbelow is also described in German Patent Application DE 10 2006 053 305.4 filed on Nov. 13, 2006. This German Patent Applications, whose subject matter is incorporated here by reference, provide the basis for a claim of priority of invention under 35 U.S.C. 119(a)-(d). 
     BACKGROUND OF THE INVENTION 
     An angle grinder with an adjustable guard is made known in EP 812 657 A1. In that case, the guard is adjustable in a rotating manner on a connection piece of a flange of the angle grinder, and is supported such that it may be detachably attached using a single form-fit locking means. The spindle of the angle grinder passes through the center of the flange. A cutting disk and/or grinding disk are/is installed on the free end of the spindle in a clampable, rotationally drivable manner for cutting and machining work pieces, which are partially enclosed by the guard. The guard must be positioned in a rotationally adjustable manner on the hand-held power tool such that the region of the grinding disk that faces the user is enclosed by the guard. At the same time, a region of the grinding disk that points away from the user extends past the flange, radially relative to the region of engagement with the work piece. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a guard anti-rotation lock device for a hand-held power tool, in particular for an angle grinder, which is provided to prevent rotation between the hand-held power tool and a guard unit. 
     It is provided that the anti-rotation lock device includes a form-fit connection unit, which is provided to prevent rotation between the hand-held power tool and the guard unit if a tool should burst. The guard unit is preferably provided to protect an operator—during regular operation of the hand-held power tool—from a tool, in particular from a disk-shaped, rotatably drivable tool, and/or from machining residue that is slung in the direction of the operator, and it is attached to the hand-held power tool in a working position. A “form-fit connection unit” refers, in particular, to a unit that is provided to establish a form-fit connection—that acts in the circumferential direction—between the guard unit and the hand-held power tool, and which is designed to absorb forces of an outwardly-slung tool piece that could occur if a tool should burst. The guard anti-rotation lock device, which in an anti-rotation lock position, is designed to absorb a force of at least 1000 N, advantageously at least 2500 N, and particularly advantageously at least 4500N. To realize an anti-rotation lock of the guard unit on the hand-held power tool, the guard unit, which is attached to the hand-held power tool, may be moved into an anti-rotation lock position by absorbing impulses and/or forces of outwardly-slung pieces of the burst tool. “Provided” is intended to mean, in particular, specially equipped and/or designed. Due to the inventive design of the guard anti-rotation lock device, it is possible to effectively protect an operator of the hand-held power tool from a tool that rotates during operation of the hand-held power tool, and, in particular, from pieces of the tool that are slung in the direction of the operator if the tool becomes damaged, e.g., if the tool should burst. 
     It is furthermore provided that the form-fit connection unit includes at least one form-fit connection element, which is movably supported on the guard unit and/or the hand-held power tool, thereby enabling the form-fit element to be moved and/or brought into an anti-rotation lock position if a tool should burst, and enabling an anti-rotation lock to be realized between the guard unit and the hand-held power tool via the form-fit connection unit. Removal may also be simplified by designing the form-fit connection unit to be movable out of the anti-rotation lock position so that it may be removed. 
     It is also provided that the form-fit connection unit is supported on the guard unit such that it is movable around a pivot axis, thereby making it possible to advantageously utilize a transfer of an impulse of an outwardly-slung piece of a burst tool, in order to attain an anti-rotation lock position of the form-fit connection element and/or the guard unit. The form-fit connection element is preferably deflected from its neutral position by an impulse of a tool piece that is transferred to the guard unit, and is moved into an anti-rotation lock position. This may be attained in a particularly advantageous manner when the form-fit connection element is located on a guard of the guard unit, in particular on a side of the guard that faces the tool when in the installed state. 
     In an advantageous refinement of the present invention, it is provided that the form-fit connection unit includes a guide element in which the form-fit connection element is movably supported, thereby making it possible to realize a particularly specific motion into an anti-rotation lock position, and to realize a low-wear motion of the form-fit connection element. 
     Additional components, installation space, assembly effort and costs may be advantageously saved when the form-fit connection element is designed at least partially as a single piece with the guard unit and/or the hand-held power tool. In this context, the term “single piece” is intended to mean, in particular, one piece, cast, and/or designed as one component. 
     If, in addition, the form-fit connection element is formed at least partially by a detent element, it is advantageously possible to prevent the guard unit from rotating, in particular if a tool should burst, and in particular when the detent element is provided to block a motion of the guard unit in at least one direction. A blocking direction of the detent element preferably refers to a direction of rotation of a tool. 
     In an advantageous refinement of the present invention, it is provided that the form-fit connection unit is movable—together with the guard unit—into an anti-rotation lock position, thereby making it possible to utilize energy from a piece of a burst tool that was transferred to the guard to change the position of the form-fit connection element to the anti-rotation lock position. An “anti-rotation lock position” refers, in particular, to a position of the guard unit relative to the hand-held power tool in which the guard unit is oriented opposite to a rotation, in particular a direction of rotation of the tool on the hand-held power tool, in particular on a receiving flange. This may be attained in a particularly advantageous manner when the form-fit connection element is provided to couple to the guard unit in an at least partially non-positive manner. A coupling may take place directly, or indirectly via a driving element and/or further components that appear reasonable to one skilled in the technical art. 
     It is also provided that the form-fit connection element includes at least one driving element, which is provided to drive at least one form-fit connection element into an anti-rotation lock position together with the guard unit, thereby making it possible to attain a deliberate change of position of the form-fit connection element into an anti-rotation lock position if a tool should burst. 
     It is possible to advantageously realize a driving of the form-fit connection element via the driving element into an anti-rotation lock position if a tool should burst when the driving element is provided to couple at least partially to the guard unit in a circumferential direction, the guard unit preferably undergoing a motion into an anti-rotation lock position along a direction of rotation of the tool due to a transfer of kinetic energy of an outwardly-slung piece of a burst tool. This may be attained using a simple design when the driving element is designed as an intermediate ring located between the guard unit and the hand-held power tool, and/or by a rolling element, and/or by further driving elements that appear reasonable to one skilled in the technical art. 
     It is furthermore provided that the form-fit connection unit includes at least one release-prevention mechanism, which is provided to fix at least one driving element and/or one form-fit element in a neutral position before an anti-rotation lock, thereby making it advantageously possible to prevent and/or block an installation procedure and/or a removal procedure of the guard unit using the form-fit connection element during installation or removal of the guard unit on the hand-held power tool. In this context, a “release-prevention mechanism” refers, in particular, to a securing of a form-fit element and/or a driving element that is provided to fix the form-fit element or the form-fit element together with the driving element in a neutral position during regular operation of the hand-held power tool system, and/or in a switched-off operating mode of the hand-held power tool, and, when a stronger force is applied, in particular by a piece of a tool that has burst during operation of the hand-held power tool and that strikes the guard unit, a motion of the form-fit connection element is released out of its neutral position and into an anti-rotation lock position. 
     An advantageous and, in particular, exact starting position of the form-fit element before an anti-rotation lock if a tool should burst may be advantageously attained when the form-fit connection unit includes at least one retaining element, which is provided to secure the form-fit connection element in a position in front of the anti-rotation lock. This may be attained in a manner with a particularly simple design when the retaining element is designed as a spring element. 
     In a further embodiment of the present invention, a hand-held power tool system is provided that includes a hand-held power tool, in particular an angle grinder, a guard unit, and a guard anti-rotation lock device, in which case the guard anti-rotation lock device includes a form-fit connection unit, which is provided to prevent the guard unit from rotating relative to the hand-held power tool if a tool should burst. As a result, it is possible to effectively protect an operator of the hand-held power tool from a tool that rotates during operation of the hand-held power tool, and/or, in particular, from pieces of the tool that are slung in the direction of the operator if the tool becomes damaged, e.g., if the tool should burst. To attain an anti-rotation lock of the guard unit on the hand-held power tool, the guard unit, which is attached to the hand-held power tool, may be moved into the anti-rotation lock position by absorbing forces of impulses and/or forces of outwardly-slung pieces of the burst tool. 
     It is furthermore provided that the hand-held power tool includes a receiving unit, which is provided at least partially to movably support the form-fit connection element, thereby making it possible to at least partially realize a particularly compact positioning of the form-fit connection unit. 
     It is also provided that the hand-held power tool includes a receiving unit with an intermediate ring on which the form-fit connection element is at least partially located, thereby making it possible to replace the form-fit connection element—using a simple design—if deformation should occur after a form-fit connection is established between the guard unit and the hand-held power tool if a tool should burst. 
     When the form-fit connection unit includes at least two form-fit connection elements, which are located one after the other in the circumferential direction on a receiving unit of the hand-held power tool and/or the guard unit, it is possible to realize a reusable form-fit and/or non-positive connection between the guard unit and the receiving unit, and/or the guard unit may be installed on the receiving unit in different positions along the circumferential direction in a non-rotating manner, in particular if a tool should burst. The term “circumferential direction” is intended to mean, in particular, a circumferential direction of the guard unit, which is oriented essentially parallel to a direction of rotation of the tool when the guard unit is in an installed state. 
     Particularly advantageously, the present invention includes a hand-held power tool for a rotating, preferably disk-shaped tool, with a machine housing that includes a flange and/or a machine neck, on which a guard—that is composed of sheet metal in particular—is detachably clampable in order to cover the tool. The guard includes a guard body, which is composed of a circular, disk-shaped piece, in particular with an outer edge located at a right angle thereto, and with a central, circular recess, on the edge of which a guard connection piece and/or collar is formed and that includes an annular clamping band that may be tightened using a clamping means. An anti-rotation lock that acts between the machine neck and the guard is located between the guard and the machine neck and is designed as a profiled structure. The guard may be repeatedly coupled via the clamping band and/or the clamping means in its clamping position in a form-fit and/or non-positive manner with the machine neck, and is therefore capable of being fixed in a non-rotatable position and, to attain a release position, may be disengaged from the form-fit and/or non-positive connection, so that the guard may then be adjusted in a rotational manner. 
     Further advantages result from the description of the drawing, below. Exemplary embodiments of the present invention are shown in the drawing. The drawing, the description, and the claims contain numerous features in combination. One skilled in the art will also advantageously consider the features individually and combine them to form further reasonable combinations. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an exploded view of an inventive hand-held power tool system, 
         FIG. 2  shows a guard anti-rotation lock device with a form-fit connection element, in a schematic, partial cross-sectional view, 
         FIG. 3  shows a guard anti-rotation lock device with a form-fit connection element that is an alternative to that shown in  FIG. 2 , in a schematic, partial cross-sectional view, 
         FIG. 4  shows a guard anti-rotation lock device with a form-fit connection element that is movably supported in a guide element, in a schematic, partial cross-sectional view, 
         FIG. 5  shows a guard anti-rotation lock device with a form-fit connection element designed as a chain, in a schematic, partial cross-sectional view, 
         FIG. 6  shows a guard anti-rotation lock device with a folded form-fit connection element, in a schematic, partial cross-sectional view, 
         FIG. 7  shows a guard anti-rotation lock device with a pivotably supported form-fit connection element, in a schematic, partial cross-sectional view, 
         FIGS. 8   a  and  8   b  show a guard anti-rotation lock unit with an intermediate ring and a form-fit connection element, in a schematic side view ( FIG. 8   a ), and in a perspective view ( FIG. 8   b ), 
         FIG. 9  shows a guard anti-rotation lock device with a driving element designed as an intermediate ring, in a schematic, partial cross-sectional view, 
         FIG. 10  shows a guard anti-rotation lock device with a form-fit connection element designed as a single piece with an intermediate ring, in a schematic, partial cross-sectional view, 
         FIGS. 11   a  and  11   b  show a guard anti-rotation lock unit with a form-fit connection element that is movable perpendicularly to a direction of rotation, in a first schematic, partial cross-sectional view ( FIG. 11   a ), and in a second, schematic partial cross-sectional view ( FIG. 11   b ), and 
         FIG. 12  shows a guard anti-rotation lock device with a form-fit connection element designed as a single piece with a receiving unit, in an exploded view. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a hand-held power tool system  50   a  with a hand-held power tool  12   a  designed as an angle grinder and shown only partially here, and with a guard unit  14   a  and a guard anti-rotation lock device  10   a . Hand-held power tool  12   a  includes a hand-held power tool housing  54   a , and a receiving unit  48   a  for receiving guard unit  14  and/or a tool  18   a  designed as a cutting disk, receiving unit  24   a  being screwed together with hand-held power tool housing  54   a . A drive shaft  58   a  extends out of receiving unit  48   a  on a side  56   a  facing away from hand-held power tool housing  54   a . Drive shaft  50   a  is connectable at its free end  60   a  with disk-shaped tool  18   a  and is rotationally drivable around an axis  62   a . Guard unit  14   a  includes a guard  52   a  and a closing unit  64   a . When hand-held power tool system  50   a  is in an installed state, guard  52   a  extends around an angular range of tool  18   a  of approximately 180° and, to this end, includes a semi-disk shaped guard body  66   a  and a guard edge  68   a , which is initially oriented perpendicularly to semi-disk shaped body  66   a  and is finally oriented parallel to semi-disk shaped guard body  66   a , inwardly in a radial direction  70   a.    
     Guard unit  52   a  also includes a guard collar  72   a , which is oriented essentially perpendicularly to semi-disk shaped guard body  66   a . Guard collar  72   a  is enclosed outwardly in radial direction  70   a  by a clamping band  74   a  of closing unit  64   a . Guard collar  72   a  and clamping band  74   a  are interconnected via a welded connection. Guard collar  72   a —together with clamping band  74   a —is provided to attach guard unit  14   a  to hand-held power tool  12   a  and/or to receiving unit  48   a , which includes a cylindrical receiving flange  76   a  for this purpose. Along a circumferential direction  36   a ,  38   a  of clamping band  74   a , clamping band  28   a  includes two end regions  78   a ,  80   a  in a region that faces away from guard  52   a  and extends outwardly in radial direction  70   a . End regions  78   a ,  80   a  each include a recess  82   a , through which a closing element  84   a —designed as a clamping screw—of closing unit  64   a  extends (see  FIG. 2 ). The clamping screw may be fastened in recesses  82   a  of clamping band  74   a  using a nut  86   a . Guard  52   a  is attached in a working position to receiving unit  48   a  and/or on receiving flange  76   a  via closing unit  64   a  using a frictional connection between guard collar  72   a  and clamping band  74   a  and receiving flange  76   a , so that guard unit  14   a  is positioned in a non-rotatable manner during regular operation of hand-held power tool  12   a . In an alternative design of closing unit  64   a , it is basically feasible to use—instead of the clamping screw—further closing elements, e.g., a clamping lever and/or form-fit elements, etc. 
     Hand-held power tool system  50   a  also includes a coding device  88   a , which is provided to prevent tools  18   a  and/or tools  18   a  together with guard unit  14   a  from being installed on unsuitable hand-held power tools  12   a . To this end, clamping band  74   a  includes a coding element  90   a  of coding device  88   a , which is designed as a single piece with clamping band  74   a . Coding element  90   a  is designed as a pressed-out region that extends inwardly in radial direction  70   a  and has a rectangular shape. Correspondingly, receiving flange  76   a  includes a coding element  92   a  of coding device  88   a , which is designed as a recess into which coding element  90   a  of clamping band  74   a  may be inserted when guard unit  14   a  is installed on hand-held power tool  12   a . After guard unit  14   a  has been inserted onto receiving unit  48   a , guard unit  14   a  may be rotated into a working position. To this end, receiving flange  76   a  includes a groove  94   a  that extends in circumferential direction  36   a ,  38   a , in which coding element  90   a  is guided when guard unit  14   a  is rotated into the working position. 
       FIG. 2  shows guard anti-rotation lock device  10   a  in  FIG. 1  in greater detail. Guard anti-rotation lock device  10   a  is provided to prevent rotation between guard unit  14   a  and hand-held power tool  12   a  and/or receiving unit  48   a  during a breakdown of tool  18   a , e.g., when a tool  18   a  bursts. To this end, anti-rotation lock device  10   a  includes a form-fit connection unit  16   a , which is provided to prevent rotation in a form-fit manner between hand-held power tool  12   a  and guard unit  14   a  if a tool  18   a  should burst. Form-fit connection unit  16   a  includes a form-fit connection element  20   a , which is located inside receiving flange  76   a , and several form-fit connection elements  24   a ,  26   a , which are located one after the other in circumferential direction  36   a ,  38   a  on clamping band  74   a  and/or guard collar  72   a  of guard unit  14   a . Form-fit connecting elements  24   a ,  26   a  of guard unit  14   a  are designed as recesses. 
     Form-fit connecting element  20   a  of receiving flange  76   a  includes a hook element  96   a  and a subregion  98   a , which is designed as a rolling element  100   a . In addition, form-fit connection element  20   a  is located on an edge region  102 —located outwardly in radial direction  70   a —of receiving flange  76   a  such that it may rotate around rotation axis  104   a . When guard unit  14   a  is in a working position, subregion  98   a  of form-fit connection element  20   a  designed as rolling element  100   a  bears against a surface  106   a —that faces inwardly in radial direction  70   a —of clamping band  74   a  and/or guard collar  72   a . Form-fit connection element  20   a  couples in a non-positive manner to clamping band  74   a  and/or guard collar  72   a . Form-fit connection element  16   a  also includes a retaining element  46   a , which is designed as a spring element and holds form-fit connection element  20   a  in a position before an anti-rotation lock. It is also feasible for form-fit connection element  20   a  to be located—due to its design in radial direction  70   a —in receiving unit  48   a  in a form-fit manner. 
     If a tool  18   a  should burst during operation of hand-held power tool  12   a , tool pieces are slung outwardly in a rotation direction  108   a  of tool  18   a . If one of these tool pieces strikes guard unit  14   a , the kinetic energy of the tool piece transferred to guard unit  14   a  exceeds the attachment energy of the frictional connection of closing unit  64   a  between guard unit  14   a  and hand-held power tool  12   a . Guard unit  14   a  is then rotated out of its working position and in rotation direction  108   a  of tool  18   a . Form-fit connection element  20   a , which couples on surface  106   a —which faces inward in radial direction  70   a —of clamping band  74   a  and/or guard collar  72   a  in a non-positive manner, is rotated around rotation axis  104   a  in rotation direction  108   a . Due to a motion of guard unit  14   a , form-fit connection element  20   a  and/or subregion  98   a  of form-fit connection unit  20   a  designed as rolling element  100   a  walk(s) around clamping band  74   a  and/or guard collar  72   a , so that form-fit connection element  20   a  is moved together with guard unit  14   a . In addition, it is also feasible for surface  106   a —which faces inward in radial direction  70   a —of clamping band  74   a  and/or guard collar  72   a , and/or an outer surface  110   a  of subregion  98   a  designed as rolling element  100   a  to have a high friction coefficient in order to increase a non-positive connection between form-fit connection element  20   a  and clamping band  74   a  and/or guard collar  72   a  due to a special material selection and/or a special surface treatment. 
     Due to the rotation of form-fit connection element  20   a , hook element  96   a  is rotated outwardly, and thereby extends through one of the recesses in clamping band  74   a  and/or guard collar  72   a . As soon as a form-fit connection is established between form-fit connection element  20   a  supported in receiving unit  48   a  and one of the form-fit connection elements  24   a ,  26   a  of clamping band  74   a  and/or guard collar  72   a , guard unit  14   a  is located in an anti-rotation lock position relative to hand-held power tool  12   a . In a further embodiment of the present invention, it is feasible to increase the number of form-fit connection elements  20   a ,  24   a ,  26   a  and/or to change a location of form-fit connection element  20   a  within receiving unit  48   a  in a manner that appears reasonable to one skilled in the technical art. 
     Alternative exemplary embodiments are shown in  FIGS. 3 through 12   b . Components, features, and functions that are essentially the same are labelled with the same reference numerals. To distinguish the exemplary embodiments from each other, the reference numerals of the exemplary embodiments are appended with the letters a through k. The description below is essentially limited to the differences from the exemplary embodiment in  FIGS. 1 and 2 . With regard for the components, features, and functions that remain the same, reference is made to the description of the exemplary embodiment in  FIGS. 1 and 2 . 
       FIG. 3  shows an alternative embodiment of guard anti-rotation lock device  10   b  Guard anti-rotation lock device  10   b  includes a form-fit connection unit  16   b , which is provided to prevent rotation between a guard unit and a receiving unit  48   b  of a hand-held power tool if a tool should burst. Form-fit connection unit  16   b  includes a form-fit connection element  20   b , which is rotatably supported inside receiving unit  48   b . Form-fit connection element  20   b  differs from the embodiments shown in  FIG. 2  in that a hook element  96   b  for establishing a form-fit connection between the hand-held power tool and the guard unit is reinforced in this case, thereby resulting in earlier engagement in a form-fit connection element  24   b ,  26   b  of the guard unit. A further embodiment of form-fit connection unit  16   b  and/or the guard anti-rotation lock device, and a mode of operation of guard anti-rotation lock device  10   b  are similar to those described with reference to  FIG. 2 . 
       FIG. 4  shows an alternative embodiment of guard anti-rotation lock device  10   c . Guard anti-rotation lock device  10   c  includes a form-fit connection unit  16   c , which is provided to prevent rotation between a guard unit and a receiving unit  48   c  of a hand-held power tool if a tool should burst. Form-fit connection unit  16   c  includes a form-fit connection element  20   c  that is movably supported in receiving unit  48   c , and several form-fit connection elements  24   c ,  26   c  located one after the other in a circumferential direction  36   c ,  38   c . Form-fit connection element  20   c  of receiving unit  48   c  is designed as a single piece with driving element  34   c . Form-fit connection element  20   c  in located in a rotation direction  108   c  of a tool, downstream of driving element  34   c . Driving element  34   c —together with form-fit connection element  20   c —is also fixed in a neutral position—before an anti-rotation lock is implemented—relative to receiving unit  48   c  via a release-prevention mechanism  44   c , only a portion of which is shown. Driving element  34   c  couples in a non-positive manner to a clamping band  74   c  and/or a guard collar of guard unit if the guard unit should rotate when in an installed state. In addition, receiving unit  48   c  includes a guide element  32   c —which is tapered in rotation direction  108   c —of form-fit connection unit  16   c , in which form-fit connection element  20   c  is movably supported. Guide element  32   c  is designed as a guide groove and is located in an outer—in radial direction  70   c —edge region  102   c  of a receiving flange  76   c . If a tool should burst, the guard unit is rotated out of its working position and in rotation direction  108   c . An impulse of the guard unit in rotation direction  108   c  is greater than a force of release-prevention mechanism  44   c , thereby enabling form-fit connection element  20   c  to be moved together with driving element  34   c  and the guard unit, also in rotation direction  108   c . Due to the tapered design of guide element  32   c , form-fit connection element  20   c  is also moved outwardly in radial direction  70   c  and engages in one of the form-fit connection elements  24   c ,  26   c  of the guard unit. 
       FIG. 5  shows an alternative embodiment of guard anti-rotation lock device  10   d . Guard anti-rotation lock device  10   d  includes a form-fit connection unit  16   d , which is provided to prevent rotation between a guard unit and a receiving unit  48   d  of a hand-held power tool if a tool should burst. Form-fit connection unit  16   d  includes several form-fit connection elements  24   d ,  26   d , which are located one after the other in a circumferential direction  36   d ,  38   d , each of which is formed by a recess that extends outwardly in a radial direction  70   d  and is located on a clamping band  74   d  and/or a guard collar of the guard unit. Moreover, receiving unit  48   d  includes a further form-fit connection element  20   d  of form-fit connection unit  16   d , which is movably supported in a guide element  32   d —designed as a guide groove—of receiving unit  48   d . The guide groove is located in an outer—in radial direction  70   d —edge region  102   d  of a receiving flange  76   d . Form-fit connection element  20   d  is designed as a chain and is fixedly located on a driving element  34   d  designed as a sliding carriage. Driving element  34   d  is fixed in a neutral position—before an anti-rotation lock is implemented—relative to receiving unit  48   d  via a release-prevention mechanism  44   d , only a portion of which is shown. Moreover, a link of the chain is fixed in position in an end region  114   d  facing away from driving element  34   d , so that the chain—together with driving element  34   d —extends along circumferential direction  36   d ,  38   d  along the entire length of the guide groove. If a tool should burst, driving element  34   d  couples in a non-positive manner to clamping band  74   d  and/or the guard collar, and is moved—together with the guard unit—when rotation occurs in rotation direction  108   d  due to a piece of a burst tool striking the guard unit, as described with reference to  FIG. 4 . As a result, a region  112   d  that is present within the guide groove of the chain is reduced along rotation direction  108   d , so that individual links in the chain move toward each other and thereby fold up relative to each other. Individual links engage in form-fit connection elements  24   d ,  26   d —designed as recesses—of the guard unit and bring about an anti-rotation lock of the guard unit. 
       FIG. 6  shows an alternative embodiment of guard anti-rotation lock device  10   e . Guard anti-rotation lock device  10   e  includes a form-fit connection unit  16   e , which is provided to prevent rotation between a guard unit and a receiving unit  48   e  of a hand-held power tool if a tool should burst. Form-fit connection unit  16   e  includes several form-fit connection elements  24   e ,  26   e , which are located one after the other in a circumferential direction  36   e ,  38   e , each of which is formed by a detent recess and is located on a clamping band  74   e  and/or a guard collar of the guard unit. The detent recesses include a detent bevel, which extends outwardly away from a surface  106   e —which faces inwardly, in radial direction  70   e —of clamping band  74   e  and/or the guard collar, and opposite to a rotation direction  108   e  of a tool. Receiving unit  48   e  also includes several form-fit connection elements  20   e ,  22   e  located one after the other in circumferential direction  36   e ,  38   e , each of which is designed as a detent element  28   e ,  30   e . Detent elements  28   e ,  30   e  are designed as single pieces with a folded sheet-metal element  116   e , and they are located in an outer—in radial direction  70   e —fold region  118   e  of sheet-metal element  116   e . Sheet-metal element  116   e  includes a driving element  34   e  and fold region  118   e , and extends along circumferential direction  36   e ,  38   e  over an entire length of a guide element  32   e  of receiving unit  48   e . Moreover, detent elements  28   e ,  30   e  extend diagonally in radial direction  70   e , outwardly and opposite to rotation direction  108   e , so that they may engage in the detent recesses in a form-fit manner and block a motion of the guard unit relative to the hand-held power tool in rotation direction  108   e  if a tool should burst. An anti-rotation lock brought about using form-fit connection elements  20   e ,  22   e ,  24   e ,  26   e  and driving element  34   e  if a tool should burst takes place as described with reference to  FIG. 5 . 
       FIG. 7  shows an alternative embodiment of guard anti-rotation lock device  10   f . Guard anti-rotation lock device  10   f  includes a form-fit connection unit  16   f , which is provided to prevent rotation between a guard unit and a receiving unit  48   f  of a hand-held power tool if a tool should burst. Form-fit connection unit  16   f  includes several form-fit connection elements  20   f ,  22   f , which are located one after the other in a circumferential direction  36   f ,  38   f , and each of which is formed by a recess and extends inwardly in a radial direction  70   f  away from an outwardly oriented surface  120   f  of a receiving flange  76   f  of receiving unit  48   f . In addition, form-fit connection element  16   f  includes two further form-fit connection elements  24   f ,  26   f , which are designed as single pieces with a driving element  34   f —which is designed as an oscillating element—and which are supported together with driving element  34   f  on guard unit  14   f  such that they may oscillate around a pivot axis  122   f . Form-fit connection elements  24   f ,  26   f  are located on a radially inwardly facing side  124   f  of the oscillating element, which—in an installed state of the hand-held power tool system—is located on a surface  126   f —which faces a tool—of a guard body  66   f . Form-fit connection elements  24   f ,  26   f  extend inwardly in radial direction  70   f , away from the oscillating element. The oscillating element includes—on a side  128   f  facing away from form-fit connection elements  24 ,  26   f —an oscillating weight  130   f , and is secured in a position—before an anti-rotation lock is implemented—in a central subregion  132   f  via two retaining elements  46   f ,  134   f  designed as spring elements. When guard unit  14   f  is struck by an outwardly-slung tool piece when a tool bursts, guard unit  14   f  is affected by an impulse in a rotation direction  108   f  of the tool. The oscillating element is deflected out of its neutral position, and one of the two form-fit connection elements  24   f ,  26   f  engages in one of the recesses in receiving unit  48   f , thereby preventing guard unit  14   f  from rotating further. 
     An alternative design of a guard anti-rotation lock  10   g  is shown in  FIGS. 8   a  and  8   b . Guard anti-rotation lock device  10   g  includes a form-fit connection unit  16   g , which is provided to prevent rotation between a guard unit and a receiving unit  48   g  of a hand-held power tool if a tool should burst. Form-fit connection unit  16   g  includes two form-fit connection elements  20   g ,  22   g , each of which is formed by a detent element  28   g ,  30   g , and which are movably located within receiving unit  48   g  on edge regions  102   g ,  136   g  which are diametrically opposed in circumferential direction  36   g ,  38   g . Detent elements  28   g ,  30   g  are designed as spring elements, and, in a neutral position before an anti-rotation lock is implemented, are located inside receiving unit  48   g  and are preloaded against a spring force. To this end, receiving unit  48   g  includes an intermediate ring  40   g  designed as a retaining element  46   g , which is rotatably located on a radially outwardly oriented surface  120   g  of a receiving flange  76   g . Intermediate ring  40   g  is secured via a not-shown release-prevention mechanism from accidentally rotating on receiving flange  76   g . Further form-fit connection elements  24   g ,  26   g  are located on a clamping band  74   g  and/or a guard collar, and they are designed as recesses. Intermediate ring  40   g  couples in a non-positive manner to clamping band  74   g  and/or the guard collar, so that, if a tool should burst, it releases an anti-rotation lock position of form-fit connection elements  20   g ,  22   g . To this end, intermediate ring  40   g  also includes recesses  138   g ,  140   g , via which detent elements  28   g ,  30   g  extend into the recesses in clamping band  74   g  and/or the guard collar. 
       FIG. 9  shows an alternative embodiment of guard anti-rotation lock device  10   h . Guard anti-rotation lock device  10   h  includes a form-fit connection unit  16   h , which is provided to prevent rotation between a guard unit and a receiving unit  48   h  of a hand-held power tool  12   h  if a tool should burst. Form-fit connection unit  16   h  includes a form-fit connection element  20   h , which is movably supported inside receiving unit  48   h  and is designed as a bolt. Form-fit connection element  20   h  is movable in an outward direction into an anti-rotation lock position of receiving unit  48   h  via a driving element  34   h , which is designed as an intermediate ring  40   h . A moving direction  142   h  of form-fit connection element  20   h  extends diagonally to radial direction  70   h  in a rotation direction  108   h  of the tool. A maximum angle of inclination of form-fit connection element  20   h  relative to radial direction  70   h  is 45°. To this end, intermediate ring  40   h  includes a peg-shaped element  144   h  that is bent inwardly in radial direction  70   h , which moves form-fit connection element  20   h  into an anti-rotation lock position when intermediate ring  40   h  rotates in rotation direction  108   h . Intermediate ring  40   h  is also held in a neutral position—before an anti-rotation lock is implemented—relative to receiving unit  48   h  via a release-prevention mechanism  44   h . Release-prevention mechanism  44   h  includes a securing element  146   h —which is designed as a recess—on intermediate ring  40   h , in which a securing element  148   h —designed as a raised area—of receiving unit  48   h  is supported. Intermediate ring  40   h  is driven via a motion of the guard unit into an anti-rotation lock position in the manner described with reference to  FIG. 8 , and an anti-rotation lock with the guard unit is implemented via form-fit connection element  20   h  in a manner described with reference to  FIG. 2 . 
       FIG. 10  shows an alternative embodiment of guard anti-rotation lock device  10   i . Guard anti-rotation lock device  10   i  includes a form-fit connection unit  16   i , which is provided to prevent rotation between a guard unit and a receiving unit  48   i  of a hand-held power tool if a tool should burst. Form-fit connection unit  16   i  includes a form-fit connection element  20   i , which is designed as a single piece with an intermediate ring  40   i  of receiving unit  48   i . Form-fit connection element  20   i  is designed as a tab, which projects outwardly from a side  150   i —which faces inwardly in radial direction  70   i —of intermediate ring  40   i , and which extends away from intermediate ring  40   i  opposite to a rotation direction  108   i  of a tool. On an end  152   i  facing away from intermediate ring  40   i , the tab includes a hook element  154   i , which is designed as a single piece with the tab. Hook element  154   i  extends diagonally outward. Furthermore, form-fit connection unit  16   i  includes a driving element  34   i , which is designed as a rolling element  42   i  that is rotatable in circumferential direction  36   i ,  38   i , and which is located inside receiving unit  48   i  on inwardly-facing side  150   i  of intermediate ring  40   i . Rolling element  42   i  bears along circumferential direction  36   i ,  38   i  in a region  156   i  of intermediate ring  40   i , on which form-fit connection element  20   i  is located. Intermediate ring  40   i  couples in a form-fit manner with a clamping band  74   i  and/or a guard collar of the guard unit. To this end, intermediate ring  40   i  includes—on a surface  158   i  that faces outward in radial direction  70   i —several coupling elements  160   i  designed as notches. Correspondingly, clamping band  74   i  and/or the guard collar include(s) a coupling element  162   i  that is designed as a raised area that extends inwardly in radial direction  70   i . When the guard unit is in an installed working position on the hand-held power tool, coupling elements  160   i ,  162   i  engage in each other in a form-fit manner. If the guard unit is struck by an outwardly-slung tool piece when a tool bursts, and the guard unit is moved together with intermediate ring  40   i  in rotation direction  108   i , rolling element  42   i  walks around intermediate ring  40   i  and the tab is pressed outwardly in radial direction  70   i  and extends through a recess  138   i  in intermediate ring  40   i  in one of several form-fit connection elements  24   i ,  26   i  which are designed as recesses in the guard unit. 
     An alternative design of a guard anti-rotation lock  10   j  is shown in  FIGS. 11   a  and  11   b . Guard anti-rotation lock device  10   j  includes a form-fit connection unit  16   j , which is provided to prevent rotation between a guard unit and a receiving unit  48   j  of a hand-held power tool if a tool should burst. Receiving unit  48   j  includes a form-fit connection element  20   j  of form-fit connection unit  16   j , which is designed as a bolt and is located inside a main element  164   j  of receiving flange  76   j . The bolt is supported such that it is movable along a direction  166   j  away from main element  164   j  in the direction of a free end of a drive shaft  58   j  in main element  164   j . In addition, receiving unit  48   j  includes an intermediate ring  40   j , which is located in circumferential direction  36   j ,  38   j  around a receiving flange  76   j , and is fixed in a neutral position—before an anti-rotation lock is implemented—on receiving flange  76   j  via a release-prevention mechanism  44   h , which is designed as described with reference to  FIG. 9 . A clamping band  74   j  and/or a guard collar of the guard unit are located around intermediate ring  40   j  in a non-positive manner. Intermediate ring  40   j  and clamping band  74   j  and/or the guard collar include form-fit connection elements  24   j ,  26   j  of form-fit connection unit  16   j —designed as recesses—on a side  168   j  facing main element  164   j . When the guard unit is in an installed working position, the bolt is supported by a recess-free subregion  170   j  of clamping band  74   j  and/or the guard collar together with intermediate ring  40   j  in main element  164   j  against a spring force of a driving element  34   j , which is designed as a spring element. When the guard unit is rotated out of its working position together with intermediate ring  40   j , as is the case when a tool bursts, recess-free subregion  170   j  is rotated away from the bolt, and the bolt moves due to spring force in direction  166   j  and engages in one of the form-fit connection elements  24   j ,  26   j , thereby halting a rotation between the guard unit and the hand-held power tool. 
       FIG. 12  shows an alternative embodiment of guard anti-rotation lock device  10   k  of a hand-held power tool system  50   k . Guard anti-rotation lock device  10   k  includes a form-fit connection unit  16   k , which is provided to prevent rotation between a guard unit  14   k  and a receiving unit  48   k  of a hand-held power tool  12   k  if a tool should burst. Form-fit connection unit  16   k  includes several form-fit connection elements  20   k ,  22   k , which are designed as single pieces with receiving unit  48   k , and several form-fit connection elements  24   k ,  26   k , which are designed as single pieces with a clamping band  74   k  of guard unit  14   k . Form-fit connection elements  20   k ,  22   k ,  24   k ,  26   k  are designed as detent elements  28   k ,  30   k    172   k ,  174   k , which, when engaged, prevent guard unit  14   k  from rotating relative to hand-held power tool  12   k  in a rotation direction  108   k  of the tool. Form-fit connection elements  20   k ,  22   k  of receiving unit  48   k  are located in radial direction  70   k  downstream of an outwardly directed side  124   k  of a receiving flange  76   k  in a main element  164   k  of receiving unit  48   k . Form-fit connection elements  24   k ,  26   k  are located on clamping band  74   k  on a side  168   k  facing main element  164   k  and away from clamping band  74   k  in a direction  176   k  away from guard body  66   k  and toward main element  164   k . Direction  176   k  is oriented parallel to an axis  62   k  of a drive shaft  58   k . Receiving unit  48   k  includes an intermediate ring  40   k , which is connected with receiving flange  76   k  in a form-fit manner. To this end, receiving flange  76   k  includes several bolt-shaped coupling elements  178   k , which are distributed in circumferential direction  36   k ,  38   k  and are supported in corresponding slots  180   k  in intermediate ring  40   k . Slots  180   k  include—in rotation direction  108   k —a bevel that points in direction  176   k , which has a maximum angle of inclination to rotation direction  108   k  of  450 . When guard unit  14   k  rotates, together with intermediate ring  40   k , in rotation direction  108   k , intermediate ring  40   k  is moved together with guard unit  14   k  in direction  176   k  of main element  164   k , and form-fit connection elements  20   k ,  22   k ,  24   k ,  26   k  of receiving unit  48   k  and guard unit  14   k  engage in each other, thereby preventing guard unit  14   k  from rotating.