Patent Publication Number: US-9421670-B2

Title: Safety guard device

Description:
This application is a 35 U.S.C. §371 National Stage Application of PCT/EP2013/058623, filed on Apr. 25, 2013, which claims the benefit of priority to Serial No. DE 10 2012 210 771.1, filed on Jun. 25, 2012 in Germany, the disclosures of which are incorporated herein by reference in their entirety. 
     BACKGROUND 
     Guard devices are already known. 
     SUMMARY 
     The disclosure is based on a guard device, having at least one basic element, and having at least one guard anti-twist device, which has at least one braking element that, in at least one operating state of a portable power tool, is provided at least for a frictional anti-twist locking of the basic element relative to a portable power tool. 
     It is proposed that the guard anti-twist device comprises at least one self-energizing unit which is designed for increasing a braking force between at least one part of the portable power tool and the at least one braking element in a braking state. The basic element preferably forms a guard, which is designed for fastening to a portable power tool, in particular to a right angle grinder. By a “braking element” should in this context be understood, in particular, an element which is designed to, in particular in a fitted state, apply a braking force to a further, corresponding element. Preferably, the braking force, in particular in an operating state of a force which in an operating state acts on the guard device, in particular on the basic element, is at least partially, preferably fully, oppositely directed. The braking force is preferably at least partially, preferably at least almost completely, formed by a friction force. It is also conceivable, however, for the braking force to be formed, at least partially, by a form closure. It is further conceivable for the braking element to be designed to fulfill further functions and/or tasks which appear sensible to a person skilled in the art, such as, for example, a loss prevention of the guard device on a portable power tool, in particular in the axial direction, and/or a coding. By an “operating state” should in this context particularly be understood be understood, by an operator, a controlled and normal working and/or usage state of the portable power tool to which the guard device is coupled. 
     By a “self-energizing unit” should in this context be understood, in particular, a unit for increasing at least one braking force between at least one part of the portable power tool, in particular a collar, and the at least one braking element in a braking state by at least 25%, preferably by at least 50% and preferably by at least 100%, in particular in relation to a normal operating state and/or a braking state without a self-energizing unit. By “movably relative to the basic element” should be understood in this context, in particular, that the braking element can execute at least one motion in which a position of the braking element relative to the basic element changes. By a “braking state” should in this context be understood, in particular, an extraordinary operating state of the portable power tool to which the guard device is coupled. A braking state can be induced, in particular, by the rupturing of an insert tool, connected to the portable power tool, in an operating state. 
     A preferably secure anti-twist locking of the guard device on a portable power tool can thereby be achieved by the inventive configuration of the guard device. An advantageously high operator safety can thereby be achieved. 
     In addition it is proposed that the guard anti-twist device comprises at least one bearing unit, which is designed to movably support the braking element at least in a braking state. By a “bearing unit” should in this context be understood, in particular, a unit which is designed to absorb forces of at least one mounted element. The bearing unit is preferably designed to movably support at least one mounted element. The bearing unit can comprise a roller bearing and/or slide bearing element. 
     An advantageously high increase in the braking force in a braking state can thereby be achieved. 
     It is further proposed that the at least one self-energizing unit at least partially comprises the at least one braking element. In a particularly preferred illustratative embodiment, the self-energizing unit and the braking element are formed integrally. A simple and advantageously compact embodiment of the self-reinforcing unit can thereby be achieved. 
     Furthermore, it is proposed that the at least one braking element has a contour which is designed for increasing a braking force between at least one part of the portable power tool and the at least one braking element in a braking state. The contour of the braking element is preferably of curved configuration. A preferably high braking force, in particular friction force, can thereby be achieved in a structurally simple manner. By the force being applied radially to the braking element, the latter is clamped against the collar of the portable power tool in a fitted state. The small support surface and the shaping of the braking element enable the guard device to exhibit very high clamping forces against contact surfaces on the collar in a fitted state, and therefore the guard device can be fixed in a manner locked against twisting. 
     Alternatively, the bearing surface of the braking element could be subsequently treated, for example also mechanically, thus increasing the delay in angular momentum. 
     In addition, it is proposed that the bearing unit and the self-energizing unit are configured at least partially in one piece. By “in one piece” should be understood, in particular, at least integrally connected, for example by a welding process, a gluing process, an spray-on process and/or another process which appears sensible to a person skilled in the art, and/or advantageously formed in one piece, such as, for example, by manufacture from a casting and/or by manufacture in a single or multicomponent spraying process and advantageously from a single blank. A constructively simple and advantageously compact embodiment of the self-energizing unit can thereby be achieved. 
     It is further proposed that the bearing unit is designed to support the at least one braking element such that this is tiltable about at least one axis. By “tiltable” should in this context be understood, in particular, pivotable about at least one axis through a specific angular range. It is also conceivable for the bearing unit to be designed to fulfill at least one further function and/or task which appears sensible to a person skilled in the art. In a constructively simple manner, a preferably reliable and secure anti-twist locking of the guard device, and thus an advantageously high operator safety, can thereby be achieved. 
     Furthermore, it is proposed that the at least one axis extends at least substantially perpendicularly to a radial direction. In this context, “at least substantially perpendicularly” is intended to be understood as meaning, in particular, that a deviation of an angle which the axis encloses with the radial direction deviates from a right angle, i.e. from 90°, in particular by less than 15°, preferably less than 10° and particularly preferably less than 5°. A preferably high braking force of the braking element can thereby be achieved in a braking state. 
     In addition, it is proposed that the at least one axis extends at least substantially parallel to a radial direction. In this context, “at least substantially parallel” is intended to be understood as meaning, in particular, that a deviation of the axis from the radial direction is in particular less than 15°, preferably less than 10° and particularly preferably less than 5°. A preferably high braking force of the braking element can thereby be achieved in a braking state. 
     The disclosure is based on a portable power tool with a collar which is designed for receiving the guard device according to the disclosure. 
     It is proposed that the portable power tool has a braking region which has at least one tilting element which is designed to correspond with at least one braking element of the guard device in a braking state. The collar preferably has a circular cross section. However, it is also conceivable for the cross section of the collar to be formed by a regular polygon or by another geometrical shape appearing expedient to a person skilled in the art. In this context, a “tilting element” is intended to be understood as meaning, in particular, an element which is provided in particular to at least partially tilt the at least one braking element of the guard device in a fitted state during a movement of the guard device relative to the collar of the portable power tool, in particular in a braking state. A preferably high braking force of the braking element in a braking state and an advantageously high operator safety can thereby be achieved. 
     In addition, it is proposed that the braking region comprises at least one braking groove in which the at least one braking element engages in a fitted state. In this context, a “braking groove” is intended to be understood as meaning in particular an in particular annular or ring-segment-shaped recess on the collar, which recess extends inward at least partially in the radial direction from an outer circumferential surface of the collar. An additional, preferably reliable securing of the guard device in the axial direction in a fitted state can thereby be achieved in a structurally simple manner. 
     Furthermore, it is proposed that the at least one tilting element is disposed on a groove bottom of the at least one braking groove. In this context, a “groove bottom” is intended to be understood as meaning in particular a surface of the braking groove that extends at least partially parallel to the outer circumferential surface of the collar and the surface normal of which is arranged parallel to the radial direction. A preferably high braking force of the braking element in a braking state and an advantageously high operator safety can thereby be achieved in a structurally simple manner. In addition, a structurally simple embodiment of the tilting element can be achieved. 
     Furthermore, it is proposed that the at least one tilting element is arranged on at least one groove wall of the at least one braking groove. In this context, a “groove wall” is intended to be understood as meaning in particular a surface of the braking groove that extends at least partially perpendicularly to the outer circumferential surface of the collar and the surface normal of which is arranged perpendicularly to the radial direction. A preferably high braking force of the braking element in a braking state and an advantageously high operator safety can thereby be achieved in a structurally simple manner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further advantages emerge from the following drawing description. In the drawing, a plurality of illustrative embodiments of the disclosure is represented. The drawing, the description and the claims contain numerous features in combination. The person skilled in the art will expediently consider the features also individually and will combine these into sensible further combinations. 
       In the drawing: 
         FIG. 1 a    shows a portable power tool having an inventive guard device in a perspective representation, 
         FIG. 1 b    shows a detail of the portable machine tool in the region of a collar in a schematic, perspective representation, 
         FIG. 1 c    shows the collar of the portable power tool in a schematic sectional representation, 
         FIG. 2 a    shows a detail of the inventive guard device having a guard anti-twist device in a schematic representation, 
         FIG. 2 b    shows the detail of the inventive guard device having a guard anti-twist device in a sectional representation, 
         FIG. 3 a    shows a detail of an alternative guard device having a guard anti-twist device in a schematic sectional representation, 
         FIG. 3 b    shows the detail of the alternative guard device having the guard anti-twist device in a state fitted to the portable power tool, 
         FIG. 4 a    shows a detail of an alternative guard device having a guard anti-twist device in a schematic representation, 
         FIG. 4 b    shows the alternative guard device in a state fitted to the portable power tool in a perspective representation, 
         FIG. 5  shows a detail of an alternative guard device having a guard anti-twist device in a schematic representation, 
         FIG. 6  shows a detail of an alternative guard device having a guard anti-twist device in a schematic representation, 
         FIG. 7  shows a detail of an alternative guard device having a guard anti-twist device in a schematic representation, 
         FIG. 8  shows a detail of an alternative guard device having a guard anti-twist device in a schematic representation, 
         FIG. 9 a    shows a detail of the portable power tool in the region of a collar in a schematic, perspective representation, and 
         FIG. 9 b    shows the collar of the portable power tool in a schematic sectional representation. 
     
    
    
     DETAILED DESCRIPTION 
     In  FIG. 1 a   , a portable power tool formed by a right angle grinder is represented. The portable power tool has a housing  56 . The housing  56  is of cylindrical configuration and serves as a handle  58  for an operator. The housing  56  encloses a drive unit (not represented) formed by an electric motor. The housing  56  is formed of a plastic. At one end of the housing  56 , the portable power tool has a power cable  60 , which is designed to supply the drive unit with electric power. At an end of the housing  56  which is facing away from the drive unit, an actuating element  62  is disposed on the housing  56 . The actuating element  62  is formed by a slide switch and is designed to actuate, i.e. switch on and off, the drive unit. 
     Adjoining that end of the housing  56  which is facing away from the drive unit is a gear casing  64 . The gear casing  64  encloses a gear unit (not represented). The gear casing  64  is fixedly connected to the housing  56 . The gear casing  64  is screwed to the housing  56 . The gear casing  64  is formed of a metal. In a region in which the housing  56  and the gear casing  64  are connected to each other, an additional handle  66  is arranged. The additional handle  66  extends perpendicularly to a drive output axis  68  of the drive unit. 
     Projecting from the gear casing  64 , perpendicularly to the drive output axis  68  of the drive unit and perpendicularly to the additional handle  66 , is a tool holder  70 . The tool holder  70  is designed to receive an insert tool  72  and drive it in an operating state. The tool holder  70  is connected to a power take-off shaft  86 . The power take-off shaft  86  is enclosed in the peripheral direction  74  by a collar  20 . 
     In  FIGS. 1 b  and 1 c   , the collar  20  of the portable power tool is shown in detailed representation. The collar  20  of the portable power tool is designed to receive a guard device. The insert tool  72  is formed by a grinding or cutting-off wheel. In a fitted state, the guard device extends around the tool holder  70 . The collar  20  is disposed between the tool holder  70  and the gear casing  64 . The collar  20  comprises a braking region  22 , in which a braking groove  28  is disposed. The braking groove  28  extends from the outer peripheral surface of the collar  20  inward in the radial direction  18 . The guard device is fastened in a fitted state in the braking region  22  of the collar  20 . In a fitted state, a braking element  114  of the guard anti-twist device  112  engages in the braking groove  28 . The braking groove  28  comprises a groove bottom  30 , and two groove walls  32  extending perpendicular thereto. 
     The guard device comprises a basic element  110  formed by a guard, a fastening element  140  formed by a clamping band, and a guard anti-twist device  112  ( FIG. 2 a   ). The guard device can be fastened by the fastening element  140  to the collar  20  of the portable power tool steplessly in an angular position desired by an operator. The basic element  110  encloses the insert tool  72 , in a state connected to the tool holder  70 , within an angular range of about 180°. The basic element  110  is fixedly connected to the fastening element  140 . The basic element  110  is integrally connected to the fastening element  140 . The basic element  110  is welded to the fastening element  140 . In a fitted state, the fastening element  140  bears against the collar  20  of the portable power tool and encloses the same. 
     In  FIGS. 2 a  and 2 b    is a first illustrative embodiment of the guard anti-twist device  112 . In order to be able to securely prevent unwanted twisting of the basic element  110  relative to the tool holder  70 , particularly if the insert tool  72 , in an operating state, were to rupture, the guard anti-twist device  112  has a braking element  114 . The braking element  114  of the guard anti-twist device  112  is, in an operating state of the portable power tool, designed for frictional anti-twist locking of the basic element  110  relative to the portable power tool. The braking element  114  is formed by a sliding block. The braking element  114  is formed of a metal. 
     The guard anti-twist device  112  further comprises a bearing unit  116 , which is designed to support the braking element  114 , in an operating state of the portable power tool, movably relative to the basic element  110 . The bearing unit  116  comprises a cutout  176 , which extends in the radial direction  18  through the fastening element  140 . The braking element  114  extends in a fitted state through the cutout  176  in the fastening element  140 . The braking element  114  is movably mounted. The bearing unit  116  is designed to support the braking element  114  tiltably about an axis. The axis extends perpendicularly to the radial direction  18 . In addition, the bearing unit  116  is designed to support the braking element  114  tiltably about a further axis. The further axis extends parallelly to the radial direction  18 . 
     The braking element  114  has a pot-shaped cross section. An outer contour of the braking element  114 , which outer contour faces inward in the radial direction  18 , has a step-shaped region  178 . On a side facing away from the step-shaped region  178 , the inward facing outer contour of the braking element  114  has a beveled corner. The braking element  114  is configured such that it is laterally open between the step-shaped region  178  and the corner. The braking element  114  is mounted with play in the cutout  176  of the fastening element  140  of the guard device. The braking element  114  is mounted such that it is displaceable and tiltable within the cutout  176  in the peripheral direction  74  and in the radial direction  18 . The braking element  114  has a frictional engagement surface  180 , which extends parallelly to the peripheral direction  74 . The frictional engagement surface  180  is of curved configuration. The frictional engagement surface  180  is designed to, in a fitted state, form a frictional engagement between the braking element  114  and a groove of the collar  20 . Alternatively, it is also conceivable for the braking element  114  to act on an outer peripheral surface of the collar  20  and, in a braking state, form a frictional engagement therewith. 
     A center point of this curved frictional engagement surface  180  here lies offset to a center point of the collar  20 . The center point of the curved frictional engagement surface  180  is arranged displaced in at least one direction, preferably in two directions, in relation to the center point of the collar  20 . If the center point of the curved frictional engagement surface  180  of the braking element  114  is placed in an X-Y system of coordinates, with the braking element  114  lying on a negative Y-axis, then this center point is negatively displaced in the X direction and in the Y direction. In connection with the mounted installation position, this shaping is of particular importance and has great influence on a delay in angular momentum in respect of a basic element  110  of the guard device in a braking state, which basic element has been abruptly set in rotation. The shaping of the curved frictional engagement surface  180  of the braking element  114  further causes the guard device to be strongly fixed to the collar  20  in the working position. In additional, a diameter of the curved frictional engagement surface  180  of the braking element  114  is smaller than a diameter of the collar  20 , whereby a twisting of the basic element  110  relative to the portable power tool can be prevented and an angular momentum delay in a braking situation can be improved. It is also conceivable, however, for the frictional engagement surface  180  of the braking element  114 , as shown in dashed representation in  FIG. 2 a   , to have a significantly stronger curvature than the collar, whereby, in a fitted state, a linear contact of one edge of the braking element  114  against the collar and thus, in a braking state, an advantageous entrenchment of the edge of the braking element  114  into the groove bottom  30  can be achieved. 
     In a braking state, which can arise as a result of rupturing of the insert tool  72  during an operating state of the portable power tool, large forces act on the basic element  110  of the guard device as a result of flying splinters of the insert tool  72 . These large forces can induce twisting of the basic element  110  relative to the portable power tool. In order to prevent, or at least reduce, this twisting of the basic element  110  relative to the portable power tool in the braking state, the guard device has a self-energizing unit  134 , which is designed to increase a braking force between the collar  20  of the portable power tool and the braking element  114  in a braking state. The braking state is brought about by twisting of the guard device, in a state fitted to the collar  20 , relative to the portable power tool. The self-energizing unit  134  comprises the braking element  114 . A contour of the braking element  114 , which forms the frictional engagement surface  180 , is designed to increase the braking force between the collar  20  of the portable power tool and the braking element  114  in a braking state. Moreover, a position of the axis about which the braking element is tiltably mounted impacts on the increase in braking force of the braking element  114  in a braking state by the self-energizing unit  134 . The bearing unit  116  and the self-energizing unit  134  are thus configured partially in one piece. 
     The guard anti-twist device  112  comprises an actuating unit  142 , which is designed to displace the braking element  114  in a clamping operation for fastening of the guard device to the portable power tool. The actuating unit  142  comprises a screwing element  144 . 
     The screwing element  144  has an external thread  182 . The screwing element  144  is formed by a screw. The screwing element  144  is designed to act on the braking element  114  in the radial direction  18 . The screw element  144  is designed to directly contact the braking element  114 . The screwing element  144  has a screw head  184 , which comprises an actuating contour. The screw element  144  can be actuated and turned with a screwdriver by an operator. 
     The actuating unit  142  further comprises a receiving element  146 , which is designed to correspond with the screwing element  144 . The receiving element  146  is likewise formed by a screw element. The receiving element  146  comprises an internal thread  148 . The receiving element is formed by a screw nut. The external thread  182  of the screwing element  144  and the internal thread  148  of the receiving element  146  are of mutually corresponding configuration. The screwing element  144  and the receiving element  146  are designed to be screwed together. The receiving element  146  is fixedly connected to the fastening element  140 . The receiving element  146  is integrally connected to the fastening element  140 . The receiving element  146  is welded to the fastening element  140 . The receiving element  146  is welded to the outside of the fastening element  140  in the radial direction  18 . 
     The screwing element  144  is, in a fitted state, screwed into the receiving element  146  and extends parallelly to the radial direction  18  through the receiving element  146 . In a fitted state, the screw head  184  forms an outermost point of the screwing element  144 , viewed in the radial direction  18 . An end of the screwing element  144 , which end faces away from the screw head  184 , bears against a surface of the braking element  114  which runs parallelly to the frictional engagement surface  180  ( FIG. 2 b   ). Turning of the screwing element  144  is translated by the internal thread  148  of the receiving element  146  into a linear motion of the screwing element  144  in the radial direction  18 . The braking element  114  is thereby displaced inward in the radial direction  18  and presses in a fitted state against the collar  20  of the portable power tool. An abutment shoulder  117  of the braking element  114  bears against the fastening element  140 . Further screwing in of the screwing element  144  causes the braking element  114  to tilt about an outer edge of the abutment shoulder  117 , whereby an opposite edge of the frictional engagement surface  180  is pressed against the braking groove  128 . 
     Alternatively or additionally, a surface which lies opposite the frictional engagement surface  180  and against which the screwing element  144 , in a fitted state of the guard device, rests, can be configured obliquely to the peripheral direction  74 , whereby a tilting of the braking element  114  as the screwing element  144  is screwed in can advantageously be reinforced. 
     It is also conceivable, however, for the screwing element  144  to be designed for screwing directly into a recess (not represented) of the fastening element, which recess can have an internal thread, whereby the receiving element as a separate component can advantageously be dispensed with. 
     When the screwing element  144  is screwed in, a first edge of the braking element  114  first of all touches the groove bottom  30  of the braking groove  28 . Upon further screwing in, a force in the radial direction  18  increases, which force acts via the screwing element  144  on the braking element  114 , and the braking element  144  tilts about an axis running perpendicularly to the radial direction  18 . The axis corresponds to the first edge of the braking element  114 . The braking element  114  tilts to the point where a further edge of the braking element  114  likewise bears against the groove bottom  30  of the braking groove  28  of the collar  20 . This tilting characteristic is of particular importance especially in the case of a basic element  110  of the guard device which is abruptly set in rotation relative to the portable power tool, and is comparable to the effect of a primary brake. In a braking state, the braking element  114  tends to come to bear against the collar  20 . Self-energization of the braking force, configured as friction force, of the braking element  114  in a braking state is thereby obtained. As a result of the herein formed frictional engagement between the braking element  114  and the collar  20 , unwanted twisting of the basic element  110  relative to the portable power tool in an operating state is prevented. 
     The guard device further comprises a coding element  138 , which is designed to correspond with a coding element  36  of the collar  20  of the portable power tool ( FIGS. 1 b  and 1 c   ). The coding element  36  of the collar  20  is formed by the braking groove  28  which is made in the collar  20 . The coding element  138  of the guard device is configured in one piece with the braking element  114 . The coding element  36  of the collar  20  is configured in one piece with the braking groove  28 . It is also conceivable, however, for the coding element  136  of the collar  20  to be configured separately from the braking groove  28  and/or for the coding element  138  of the guard device to be configured separately from the braking element  114 . The guard device is designed for the portable power tool. 
     A further guard device (not represented) is designed for a further portable power tool (not represented). The further portable power tool is configured similarly to the portable power tool already described. The further portable power tool is likewise formed by a right-angle grinder. The further portable power tool has less power and is configured smaller than the portable power tool already described. The further guard device corresponds in its function to the guard device already described. The further guard device likewise has a coding element formed by a braking element. The coding element of the further guard device is configured larger than the coding element  138  of the guard device already described. The further portable power tool has a collar having a braking region in which a braking groove is disposed. The braking element of the further guard device is designed to, in a fitted state, engage in the braking groove. The braking groove of the collar of the portable power tool is configured larger than the braking groove  28  of the collar  20  of the portable power tool already described. The coding element, formed by the braking element, of the further guard device cannot therefore correspond with the coding element  36 , formed by the braking groove  28 , of the portable power tool and engage in the braking groove  28 . The coding element of the further guard device locks with the coding element  36  of the portable power tool. A fitting of the further guard device to the portable power tool for which the further guard device is not designed can thus be prevented. By contrast, the guard device can be fitted to the further portable power tool, since the guard device is overdimensioned in design, yet, in an operating or braking state, represents no danger for an operator of the further portable power tool. 
     The following descriptions and the drawings of the further illustrative embodiments are substantially restricted to the differences between the illustrative embodiments, wherein, in relation to like-denoted components, in particular in relation to components with same reference symbols, reference can also fundamentally be made to the drawings and/or the description of the other illustrative embodiments. In order to differentiate between the illustrative embodiments, the numerals 1 to 9 are prefixed to the relevant reference symbols of the further illustrative embodiments. 
     In  FIGS. 3 a  and 3 b   , a guard device is represented. The alternative guard device corresponds to the guard device already described and is designed for coupling to an alternatively configured collar  320  of the portable power tool already described. The collar  320  has on an outer peripheral surface a braking region  322 . In the braking region  322  of the collar  320  is disposed a braking groove  328 ′. The braking groove  328 ′ extends from the outer peripheral surface of the collar  320  inward in the radial direction  18 . The braking groove  328 ′ is formed by a vertical groove, which extends parallelly to the power take-off shaft  86  of the portable power tool. In the course of mounting of the guard device, the braking element  114  is guided in the braking groove  328 ′ in the axial direction. The braking groove  328 ′ forms a coding element  336 , which is designed to correspond with the coding element  138  formed by the braking element  114 . In addition, a braking groove  328  (not represented in detail), which extends in the peripheral direction  74  along the collar  320  and overlaps with the braking groove  328 ′ ( FIGS. 1 b  and 1 c   ), is provided. 
     In  FIGS. 4 a  and 4 b   , a detail of an alternative guard device is represented. The alternative guard device corresponds in large part to the guard device already described and is designed for coupling to the portable power tool already described. The alternative guard device comprises a basic element  210 , a fastening element  240  and a guard anti-twist device  212 . The guard anti-twist device  212  has a braking element  214 , which, in an operating state of the portable power tool, is designed for frictional anti-twist locking of the basic element  210  relative to the portable power tool. The guard anti-twist device  212  additionally has an actuating unit  242 , which is designed for displacement of the braking element  214 . The actuating unit  242  comprises a screwing element  244 . The screwing element  244  corresponds to the screwing element  144  already described. The actuating unit  242  further comprises a receiving element  246 , which is designed to correspond with the screw element  244 . The receiving element  246  is likewise formed by a screw element. The receiving element  246  corresponds to the receiving element  146  already described. 
     The actuating unit  242  further has a reinforcing element  288 , which is designed to reinforce and stabilize the actuating unit  242 . The reinforcing element  288  is formed by an arcuate sheet metal element. The reinforcing element  288  is fixedly and integrally connected to the fastening element  240 . The reinforcing element  288  is welded onto the fastening element  240 . The reinforcing element  288  extends over the receiving element  246 . In a fitted state, the screwing element  244  rests with a screw head  284  partially against the reinforcing element  288 . Alternatively or additionally, the reinforcing element  288  can be designed to serve in a braking state as a stop against the gear casing  64  of the portable power tool and thus form a further, positive anti-twist locking mechanism of the guard device. 
     In  FIG. 5 , an alternative guard device is represented. The alternative guard device corresponds in large part to the guard device already described and is designed for coupling to the portable power tool already described. The alternative guard device comprises a basic element  410 , a fastening element  440  and a guard anti-twist device  412 . The guard anti-twist device  412  comprises a braking element  414 . The guard anti-twist device  412  comprises an actuating unit  442 , which is designed to displace the braking element  414  in the radial direction  18 . The braking element  414  has a polygonal base. The braking element  414  has a pentagonal, mirror-symmetrical base. The base is interrupted by rectangular incision  490 , which is made in mirror-symmetrical arrangement in the base. The incision  490  is designed to, in the peripheral direction  74 , engage in a recess  476  of the fastening element  440 , which recess forms a bearing unit  416 , and to guide the braking element  414  tangentially to the fastening element  440 . An axis of mirror symmetry of the base of the braking element  414  is arranged tangentially to the fastening element  440 . 
     The actuating unit  442  comprises a screwing element  444 , which extends tangentially to the fastening element  440 . The screwing element  444  has an external thread  482 . The screwing element  444  is formed by a screw. Attached to the fastening element  440  is a reinforcing element  488 . The reinforcing element  488  is welded onto the fastening element  440 . The reinforcing element  488  is formed of a metal sheet. On the reinforcing element  488  is disposed a receiving element  446 . The receiving element  446  has an internal thread  448 . The internal thread  448  of the receiving element  446  corresponds to the external thread  482  of the screwing element  444 . The receiving element  446  is formed by a screw nut. The receiving element  446  is welded onto the reinforcing element  488 . Alternatively or additionally, the reinforcing element  488  can be designed to serve in a braking state as a stop against the gear casing  64  of the portable power tool and thus to form a further, positive anti-twist locking mechanism of the guard device. 
     If the screwing element  444  is screwed into the receiving element  446 , an end of the screwing element  444 , which end lies opposite a screw head  484 , is displaced tangentially to the fastening element  440  along an ascending side face  492  of the braking element  414 . The braking element  414  is thereby displaced tangentially to the peripheral direction  74  in the same direction as the screw element  444  and inward in the radial direction  18 . A radially outer edge of the ascending side face  492  of the braking element  214  here slides along a descending face of the reinforcing element  488 , whereby the braking element  414  is likewise displaced inward in the radial direction  18 . An edge  492  of the braking element  414 , which edge lies innermost in the radial direction  18 , is here pressed against the collar  20  of the portable power tool already described and thus forms a frictional anti-twist locking mechanism. The braking element  414  is, in a braking state, tiltably mounted. 
     In  FIG. 6 , a detail of an alternative guard device is represented. The alternative guard device corresponds in large part to the guard device already described and is designed for coupling to the portable power tool already described. The alternative guard device comprises a basic element  610 , a fastening element  640  and a guard anti-twist device  612 . The guard anti-twist device  612  has a braking element  614 , which, in an operating state of the portable power tool, is designed for frictional anti-twist locking of the basic element  610  relative to the portable power tool. The guard anti-twist device  612  additionally has an actuating unit  642 , which is designed for displacement of the braking element  614 . 
     The actuating unit  642  comprises a lever element  650 . The guard anti-twist device  612  comprises a bearing unit  654 , which is designed to pivotably support the lever element  650 . The bearing unit  654  is further designed to support the braking element  614 , in a braking state, movably relative to the braking element  640 . The braking element  614  comprises an eccentric  652 . The lever element  650  is designed to act on the braking element  614  in the radial direction  18 . The lever element  650  is designed to directly contact the braking element  614 . The lever element  650  and the braking element  614  are fixedly connected to each other. The lever element  650  and the braking element  614  are integrally connected to each other. The lever element  650  and the braking element  614  are configured in one piece. 
     The bearing unit  654  comprises a bearing pin, which forms a pivot axis of the lever element  650  and of the braking element  614 . The bearing pin is connected in a rotationally secure manner to the lever element  650 . The bearing pin is held by a bearing element  694  and is mounted rotatably relative to the fastening element  640  of the guard device. The bearing element  694  is formed by a sheet metal element, which is fixedly connected to the fastening element  640  and forms an eyelet. The bearing element  694  is welded to the fastening element  640 . The bearing pin engages in the eyelet formed by the bearing element  694 . 
     In  FIG. 7 , a detail of an alternative guard device is represented. The alternative guard device corresponds in large part to the guard device already described and is designed for coupling to the portable power tool already described. The alternative guard device comprises a basic element  710 , a fastening element  740  and a guard anti-twist device  712 . The guard anti-twist device  712  has a braking element  714 , which, in an operating state of the portable power tool, is designed for frictional anti-twist locking of the basic element  710  relative to the portable power tool. The guard anti-twist device  712  additionally has an actuating unit  742 , which is designed for displacement of the braking element  714 . 
     The actuating unit  742  comprises a lever element  750 . The guard anti-twist device  712  comprises a bearing unit  754 , which is designed to support the lever element  750 . The bearing unit  754  comprises a bearing pin, which extends perpendicularly to the radial direction  18 . The bearing pin is connected in a rotationally secure manner to the lever element  750 . The bearing pin is held by a bearing element  794  and is mounted rotatably relative to the fastening element  740  of the guard device. The bearing element  794  is formed by a sheet metal element, which is fixedly connected to the fastening element  740  and forms a lug having a cutout. The bearing element  794  is welded to the fastening element  740 . The bearing pin engages in the cutout of the bearing element  794  formed by the tab. 
     The guard anti-twist device  712  comprises a further bearing unit  716 , which is designed to support the braking element  714 , in a braking state, movably relative to the basic element  710 . The bearing unit  716  comprises a further bearing pin  755 , which extends perpendicularly to the radial direction  18  and tangentially to the fastening element  740 . The further bearing pin  755  is connected to the lever element  750  and is movably mounted. A screwing element (not represented in detail) is movably connected by a screw connection to the bearing unit  716  and to the braking element  714 . The bearing pin  755  is rotatably connected to the braking element  714  and extends through a cutout  796  of the braking element  714 . The bearing unit  716  is designed to support the braking element  714  tiltably about an axis which extends perpendicularly to the radial direction  18  and tangentially to the fastening element  740 . 
     In  FIG. 8 , a detail of an alternative guard device is represented. The alternative guard device corresponds in large part to the guard device already described and is designed for coupling to the portable power tool already described. The alternative guard device comprises a basic element  810 , a fastening element  840  and a guard anti-twist device  812 . The guard anti-twist device  812  has a braking element  814 , which, in an operating state of the portable power tool, is designed for frictional anti-twist locking of the basic element  810  relative to the portable power tool. The guard anti-twist device  812  additionally has an actuating unit  842 , which is designed for displacement of the braking element  814 . 
     The actuating unit  842  comprises a lever element  850 . The guard anti-twist device  812  comprises an eccentric  852 , which is connected in a rotationally secure manner to the lever element  850 . The lever element  850  is supported by means of a bearing unit  854  pivotably relative to the fastening element  840 . Also provided is a braking element  814 , which in large part corresponds to the braking element  114  already described. The braking element  814  is of cup-shaped configuration. The eccentric  852  contacts the braking element  814 . By pivoting of the lever element  850 , the braking element  814  is displaced by means of the eccentric  852  inward in the radial direction  18  and is pressed against the collar  20 . A braking force formed by a friction force is thereby generated. 
     In  FIGS. 9 a  and 9 b   , a detail of an alternative collar  920  of the portable power tool already described is represented in greater detail. The alternative collar  920  corresponds in large part to the collar  20  already described. The collar  920  has on an outer peripheral surface a braking region  922 . In the braking region  922  of the collar  920  is disposed a braking groove  928 . The braking groove  928  extends from the outer peripheral surface of the collar  920  inward in the radial direction  18 . The braking region  922  of the collar  920  has a tilting element. The braking region  922  of the collar  920  has a plurality of tilting elements  924 ,  926 , which are evenly distributed in the peripheral direction  74 . 
     The braking region  922  of the collar  920  has different tilting elements  924 ,  926 . The tilting elements  924 ,  926  are designed to, in a braking state, correspond with the braking element already described (not represented here) of the guard device in a fitted state. The first tilting element  924  is disposed on a groove bottom  930  of the braking groove  928  and extends in the radial direction  18  outward from the groove bottom  930  of the braking groove  928 . The further tilting element  926  is disposed on a groove wall  932  of the braking groove  928  and extends perpendicularly to the radial direction  18  from the groove wall  930  of the braking groove  928  into the braking groove  928 . Alternatively or additionally, it is also conceivable for the groove bottom  930  and/or the groove wall  932  to have as the tilting element a depression (not represented), into which the braking element in a braking state tips, and/or a predetermined breaking point (shown in dashed representation) ( FIG. 9 b   ), into which the braking element in a braking state breaks, is thereby tilted, so that a frictional engagement or an entrenchment of the braking element in the braking groove  928  can be reinforced. 
     In a braking situation in which the guard device twists relative to the portable power tool, the braking element brushes over at least one of the tilting elements  924 ,  926  of the braking groove  928  and leads to a tilting of the braking element, whereby the braking element digs into the braking groove and a friction force is increased sufficiently far to brake or halt the twisting of the guard device relative to the portable power tool. It is conceivable to provide in the braking groove  928  just a single tilting element  924 ,  926 , or only similar tilting elements  924 ,  926 , or a plurality of different tilting elements  924 ,  926 .