Patent Publication Number: US-8523640-B2

Title: Guard hood torsion preventer

Description:
CROSS-REFERENCE TO RELATE APPLICATION 
     This application is based on German Patent Application 10 2008 040 372.5 filed Jul. 11, 2008. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention is based on a guard hood torsion preventer. 
     2. Description of the Prior Art 
     A guard hood torsion preventer for a right-angle power sander is already known that is intended for preventing torsion of a guard hood on the handheld power tool in the event of damage to a tool. 
     OBJECT AND SUMMARY OF THE INVENTION 
     The invention is based on a guard hood torsion preventer for a handheld power tool, in particular for a right-angle power sander, which is intended for preventing torsion of a guard hood on the handheld power tool, in particular in the event of damage to a tool, of a guard hood on the handheld power tool, in particular in the event of damage to a tool, having at least one torsion-prevention unit. 
     It is proposed that the torsion-prevention unit has a longitudinal axis, about which the torsion-prevention unit is rotatably supported. In this connection, the term “intended” should be understood in particular to mean especially equipped and/or especially designed. Moreover, the term “damage to a tool” should be understood in particular to mean a tool that bursts during operation of the handheld power tool, where individual pieces of the tool are spun outward because of a rotation of the tool. The term “preventing torsion” or “torsion prevention” should furthermore mean securing against unwanted torsion, particularly in the event of damage to a tool, of a guard hood unit out of its guard position relative to a handheld power tool, so that the guard hood always remains in a guard position that is advantageous for a user. Preferably, the guard hood together with the guard hood torsion preventer is designed so that in the event of a bursting tool, the guard hood is rotated, in response to transmission of an linear momentum from a fragment of a burst tool that has spun outward onto the guard hood, the guard hood is rotated by a maximum of 90°, and the user is shielded from the tool fragments by the guard hood, and in particular energy of the tool fragments is dissipated by the guard hood and/or by the guard hood torsion preventer while preserving a guard function for the user, and/or the tool fragments are conducted in a direction leading away from the user. The term “longitudinal axis” should also be understood in particular to mean an axis along a lengthwise direction and/or a primary direction in which the torsion-prevention unit extends. Preferably, the longitudinal axis is oriented essentially perpendicular to an axis of rotation of a tool. Advantageously, the torsion-prevention unit is intended in at least one position for securing, and in particular preventing rotation of, the guard hood. By means of the design according to the invention, advantageous protection of a user in a mode of operation of the handheld power tool, in particular the right-angle power sander, against tool fragments flying around and in particular being spun outward by a force of rotation, is achieved in the event of a bursting tool, and in particular the guard hood can advantageously be kept in a guarding position. 
     It is furthermore proposed that the guard hood torsion preventer has at least one bearing point, by means of which the torsion-prevention unit is braced on the handheld power tool. Preferably, the bearing point is secured or braced directly on a housing and/or a receiving unit for receiving a tool, such as a receiving flange. By means of this design, an advantageous, and in particular secure, fastening of the torsion-prevention unit can be attained via the bearing point, which is intended for secure bracing of the guard hood along with the torsion-prevention unit in the presence of strong forces and/or torques acting on the torsion-prevention unit, as in the case for example of a bursting tool. 
     In an embodiment of the invention, it is proposed that the torsion-prevention unit has at least one shaft, as a result of which a space-saving torsion-preventing motion can be attained, such as a rotation of the shaft, in particular about the longitudinal axis, in the torsion-prevention unit. The shaft is preferably formed by a force-locking shaft or a form-locking shaft. 
     It is furthermore proposed that the torsion-prevention unit is intended, by means of a rotation about its longitudinal axis, for varying the guard hood in its position. The term “varying a position” should be understood to mean in particular that for positioning when mounting of the guard hood, a plurality of different guarding positions are available, and the guard hood can be changed from one guarding position to a further guarding position upon a rotation of the torsion-prevention unit about its longitudinal axis. A change from one guarding position to a further guarding position can especially advantageously be effected in a continuously variable manner. An advantageous adaptation of the guard hood, and in particular of a guarding position of the guard hood, to a work situation, particularly by a user, can be achieved and hence a high degree of protection, in particular individual protection, for the user can be attained. 
     If the torsion-prevention unit has at least one actuation element that is intended for rotating the torsion-prevention unit about its longitudinal axis, then advantageously a position can be adapted to a work situation by means of a change of position of the guard hood performed by a user, and thus a high degree of user comfort and convenience can be attained. The actuation element is preferably designed for operation by a user of the handheld power tool. An especially space-saving embodiment of the actuation element can be attained if the actuation element is formed by a set screw. In principle, in an alternative embodiment of the invention, the actuation element can also be formed by a switch element that can be operated by a user, by which element a motor for rotating the torsion-prevention unit can be controlled, and/or can be formed by a further actuation element that appears useful to one skilled in the art, such as a crank, rotary knob, and so forth. 
     It is furthermore proposed that the torsion-prevention unit is formed at least partly by a form-locking unit, as a result of which structurally simple torsion prevention, particularly of the guard hood in a guarding position, can be attained during operation of the right-angle power sander. 
     Especially advantageous torsion prevention of the guard hood when mounted in a guarding position on the power tool can be attained if the torsion-prevention unit is formed at least partly by a set of teeth. The term “set of teeth” should be understood in particular to mean a component and/or element that because of its shape is intended for transmitting a force and/or torque and in the process engages a further, complementary component and/or element. 
     In a further embodiment of the invention, it is proposed that the torsion-prevention unit is formed at least partly by a rolling-contact worm gear. In this connection, the term “rolling-contact worm gear” should in particular be understood to mean a gear which has at least one worm shaft and/or threaded shaft for transmitting and/or converting a force and/or a torque, and axes of rotation of transmission elements of the rolling-contact worm gear, which transmit a force and/or a torque to one another, are disposed such that they are rotated, in particular skewed, by approximately 90° relative to one another. Structurally simple securing of the guard hood in a guarding position can be attained because it is advantageously possible to use self-locking of the rolling-contact worm gear in at least one direction of rotation for securing the guard hood against torsion. Additional securing elements for securing the guarding position of the guard hood, such as a detent element or other securing elements that appear appropriate to one skilled in the art, are conceivable at any time in an alternative embodiment. Especially advantageously, the torsion-prevention unit has at least one threaded shaft. 
     It is furthermore proposed that the torsion-prevention unit is formed at least partly by a force-locking unit, as a result of which a torsion-prevention unit can be attained that is economical in terms of material and in particular is inexpensive. 
     In an advantageous refinement of the invention, it is proposed that at least one further torsion-prevention unit and a guard hood, the torsion-prevention unit having at least two torsion-prevention elements, which are disposed in succession in a circumferential direction on the guard hood. In this connection, the term “disposed” should be understood in particular to mean that the torsion-prevention elements are secured directly on the guard hood and/or a force of gravity of the torsion-prevention elements is braced via the guard hood. Furthermore, the torsion-prevention elements may also be embodied in one piece with the guard hood, the term “in one piece” being understood to mean in particular one-piece and/or made in one casting and/or embodied as a single component. Moreover, the term “circumferential direction” should be understood in particular to mean a direction which extends around the guard hood in a longitudinal direction of a neck of the guard hood and/or in a mounted state of the guard hood extends about an axis of rotation of a tool. The torsion-prevention elements may be formed by form-locking elements and/or force-locking elements. By the embodiment according to the invention, structurally simple securing of the guard hood in a guarding position can advantageously be attained. Moreover, a flow of force and/or torque transmitted to the guard hood can advantageously be dissipated by way of a plurality of torsion-prevention elements, so that even if strong torques and/or linear momentums are operative on the guard hood, especially in the case of a tool that bursts during operation of the right-angle power sander, securing of the guard hood in a guarding position can be provided. 
     Especially advantageously, at least one of the torsion-prevention elements is formed at least partly by a set of teeth, so that especially secure prevention of torsion of the guard hood in operation of the handheld power tool can be attained. Advantageously, the torsion-prevention elements or the set of teeth forms a contrary contour to a set of teeth that is braced and/or supported on a housing and/or a receiving unit of the right-angle power sander. In principle, the form-locking element, in an alternative embodiment of the invention, can also be formed by a recess and/or further form-locking elements, which appear useful to one skilled in the art, and/or the torsion-prevention unit can be formed by a force-locking unit. 
     Furthermore, it is proposed that the torsion-prevention unit is disposed at least partly on a side of the guard hood facing away from a receiving region of the guard hood for a tool and/or on a side of the guard hood facing away from a receiving region of the guard hood for fastening. In this connection, the term “receiving region of the guard hood for a tool” should be understood in particular to mean a region of the guard hood that is intended for receiving a tool, where the guard hood, in particular a disklike guard hood body, shields the user from the tool receiving region. Moreover, the term “receiving region of the guard hood for fastening” should be understood in particular to mean a region of the guard hood that is surrounded by a guard hood neck and/or a tightening strap and that is intended for receiving a receiving flange of the right-angle power sander. An especially space-saving disposition of the torsion-prevention unit on the guard hood can be attained here, and moreover an advantageously large securing area for the torsion-prevention unit in the event of damage to the tool. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be better understood and further objects and advantages thereof will become more apparent from the ensuing detailed description of preferred embodiments taken in conjunction with the drawings, in which: 
         FIG. 1  shows a right-angle power sander, having a guard hood torsion preventer according to the invention, in a schematic illustration; 
         FIG. 2  shows the guard hood torsion preventer with a form-locking unit, in a schematic illustration; 
         FIG. 3  shows a guard hood of the guard hood torsion preventer of  FIG. 2  in a schematic illustration; 
         FIG. 4  shows an alternative embodiment to  FIG. 3  of a guard hood in a schematic illustration; 
         FIG. 5  shows an alternative embodiment to  FIG. 3  of a guard hood with a flat collar, in a schematic illustration; 
         FIG. 6  shows an alternative embodiment to  FIG. 2  of the guard hood torsion preventer, with a splined shaft, in a schematic illustration; and 
         FIG. 7  shows a guard hood torsion preventer with a force-locking unit, in a schematic illustration. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In  FIG. 1 , a handheld power tool  12   a , formed by a right-angle power sander  14   a , is shown, along with a guard hood unit  56   a  and a guard hood torsion preventer  10   a . The right-angle power sander  14   a  includes a handheld power tool housing  58   a  and a primary hand grip  60   a  that is integrated with the handheld power tool housing  58   a . The handheld power tool housing  58   a  includes a motor housing  62   a  and a gearbox  64   a . The right-angle power sander  14   a  also has a receiving unit  66   a , for receiving the guard hood unit  56   a  or a tool  18   a  fowled by a cutting disk, and the receiving unit is screwed to the handheld power tool housing  58   a . The guard hood unit  56   a  includes a guard hood  16   a  and a locking unit  68   a . The guard hood  16   a , in a mounted state, covers an angular range of approximately 180° of the tool  18   a . An additional hand grip  72   a  is disposed on the gearbox  64   a  of the right-angle power sander  14   a . The guard hood torsion preventer  10   a  is intended for torsion prevention of the guard hood  16   a  on the right-angle power sander  14   a  to counter unwanted torsion of the guard hood  16   a , in particular as in the case of a tool  18   a  that is bursting. 
     In  FIG. 2 , the guard hood torsion preventer  10   a  of  FIG. 1  is shown in greater detail. For the sake of simplicity, a guard hood of the guard hood unit  56   a  is not shown in  FIG. 2 . The guard hood torsion preventer  10   a  has two torsion-prevention units  20   a ,  38   a . The first torsion-prevention unit  20   a  is braced or secured to the receiving unit  66   a  by means of a bearing point  24   a . In principle, it is furthermore conceivable that the bearing point  24   a  is disposed or secured on the gearbox  64   a  and/or other housing components that appear appropriate to one skilled in the art. The first torsion-prevention unit  20   a  has a longitudinal axis  22   a , about which the torsion-prevention unit  20   a  is rotatably secured by means of the bearing point  24   a . The bearing point  24   a  has two bearing elements  74   a ,  76   a , which are disposed along the longitudinal axis  22   a  on opposed end regions  78   a ,  80   a  of the first torsion-prevention unit  20   a  on the receiving unit  66   a . The two bearing elements  74   a ,  76   a  are screwed to the receiving unit  66   a , each via a respective screw connection  82   a , and by means of the two screw connections  82   a  and two further screw connections  84   a , the receiving unit  66   a  is secured to the gearbox  64   a . The torsion-prevention unit  20   a  is disposed on a region  86   a , oriented toward the gearbox  64   a , of the receiving unit  66   a  next to a flange neck  88   a  for fastening the tool  18   a  and the guard hood unit  56   a . The longitudinal axis  22   a  is embodied essentially transversely to an axis of rotation  90   a  of a drive shaft of the right-angle power sander  14   a  for driving the tool  18   a.    
     The torsion-prevention unit  20   a  is formed by a form-locking unit  26   a , which is formed at least partly by a rolling-contact worm gear  30   a . The torsion-prevention unit  20   a  furthermore has a shaft  92   a , which is rotatably supported by its end regions  94   a ,  96   a  along the longitudinal axis  22   a  in the bearing elements  74   a ,  76   a . Along the longitudinal axis  22   a , in a middle region  98   a , the shaft  92   a  has a threaded shaft  32   a , embodied as a set of teeth  28   a , which is intended for form locking to the second torsion-prevention unit  38   a . The shaft  92   a  is supported by its end regions  94   a ,  96   a  in recesses of the bearing elements  74   a ,  76   a  that are formed as angular components, and the shaft  92   a  is supported immovably along the longitudinal axis  22   a  via two securing rings  100   a , which are disposed fixedly on the end regions  94   a ,  96   a  of the shaft  92   a . The torsion-prevention unit  20   a  furthermore has an actuation element  36   a , which is embodied in one piece with the shaft  92   a  and is disposed on one of the two end regions  94   a ,  96   a  of the shaft  92   a . The actuation element  36   a  is embodied in the form of the head of a screw, so that for adjusting or rotating the torsion-prevention unit  20   a  in a direction of rotation  102   a  about the longitudinal axis  22   a , this actuation element can be rotated or adjusted by a user using a screwdriver. 
     The guard hood torsion preventer  10   a  furthermore has the guard hood  16   a , on which the second torsion-prevention unit  38   a  is disposed, and the torsion-prevention unit  38   a  is embodied in one piece with the guard hood  16   a  (see  FIGS. 2 and 3 ). The guard hood  16   a  has a guard hood neck  104   a , by means of which the guard hood  16   a  can be secured to the flange neck  88   a . For that purpose, the guard hood neck  104   a  surrounds a receiving region  52   a  of the guard hood  16   a . The guard hood neck  104   a  has a coding element  106   a , which is formed by a coding lug oriented inward from the guard hood neck  104   a  in a radial direction  108   a  of the guard hood  16   a . The coding element  106   a , together with a coding element, not shown in further detail, of the flange neck  88   a , is intended for preventing the mounting of the guard hood unit  56   a  on handheld power tools  12   a  that are unsuitable for it. 
     The torsion-prevention unit  38   a  is disposed on the guard hood  16   a  on a side  54   a  of the guard hood neck  104   a  facing away from the receiving region  52   a  in the radial direction  108   a , and the torsion-prevention unit  38   a  is formed by a form-locking unit  110   a . The torsion-prevention unit  38   a  has a plurality of torsion-prevention elements  40   a ,  42   a , disposed in succession in a circumferential direction  44   a , which are formed by form-locking elements  146   a ,  148   a  and form a set of teeth  46   a . The form-locking elements  146   a ,  148   a  embodied by teeth extend, together with a guard hood body  112   a  of the guard hood  16   a , over an angular range of approximately 180° of the tool  18   a  in the circumferential direction  44   a , so that mounting the guard hood  16   a  in an unprotected position that is dangerous to a user is advantageously prevented. Fundamentally, however, it is also conceivable for the form-locking elements  146   a ,  148   a  to cover an angular range in the circumferential direction  44   a  of nearly 360° on the guard hood neck  104   a . The teeth extend in the radial direction  108   a  outward from the guard hood neck  104   a . It is also conceivable for the form-locking elements  146   a ,  148   a  to be formed by recesses, indentations, and/or other form-locking elements  146   a ,  148   a , disposed in the guard hood neck  104   a , the form-locking elements being of a kind that would be appropriate to one skilled in the art. 
     Moreover, between the flange neck  88   a  and the guard hood  16   a  or the guard hood neck  104   a , a compensation element  118   a  ( FIG. 2 ) is also disposed in the radial direction  108   a . The compensation element  118   a  is formed from a rubberlike material and embodied cylindrically. The compensation element  118   a  is intended to counteract or prevent play between the flange neck  88   a  and the guard hood neck  104   a.    
     In an already-mounted state of the guard hood unit  56   a  on the right-angle power sander  14   a  ( FIGS. 1 and 2 ), the two torsion-prevention units  20   a ,  38   a  are in engagement with one another. In this situation, the form-locking elements  146   a ,  148   a  of the guard hood  16   a , which are formed by teeth, mesh with a threaded profile of the threaded shaft  32   a . Rotation of the actuation element  36   a  along with the threaded shaft  32   a  in a direction of rotation  102   a  about the longitudinal axis  22   a  exerts a force  116   a , because of the set of teeth  28   a , embodied as a thread, of the threaded shaft  32   a , along the longitudinal axis  22   a , on the form-locking elements  146   a ,  148   a , meshing between the thread, of the guard hood  16   a , and this force is transmitted via a threaded flank  114   a  to the form-locking elements  146   a ,  148   a  and thus to the guard hood  16   a . As a result of this force, a rotation of the guard hood  16   a  in the circumferential direction  44   a  from a first guarding position to a second guarding position is effected. A change from one guarding position to a further guarding position of the guard hood can be accomplished in continuously variable fashion here by means of the rolling-contact worm gear  30   a . Because of self-locking of the rolling-contact worm gear  30   a , a rotation of the guard hood  16   a  with transmission of linear momentum and/or force from the guard hood  16   a  to the threaded shaft  32   a  is prevented. For that purpose, a pitch of the threaded flank  114   a  of the threaded shaft  32   a  is embodied such that even at extremely strong linear momentums and/or torques, acting on the guard hood  16   a  or on the guard hood torsion preventer  10   a , as in the case in particular of fragments of a bursting tool  18   a  that strike the guard hood  16   a , a rotation of the guard hood  16   a  out of the guarding position is prevented. 
     Alternatively or in addition, in a further embodiment, an adjustment of a guarding position of the guard hood  16   a  can moreover be effected by way of a switching unit which is operable or adjustable by the user and by which a motor for rotating the torsion-prevention unit  20   a  can be controlled. The switch unit may have one control element for coarse positioning and one control element for fine positioning of the guarding position of the guard hood  16   a.    
     In  FIGS. 4 through 7 , alternative exemplary embodiments are shown. Components, characteristics and functions that remain essentially the same are identified by the same reference numerals throughout. However, to distinguish the various exemplary embodiments, the letters a through e are added to the reference numerals in the exemplary embodiments. The ensuing description is limited essentially to the differences from the exemplary embodiment in  FIGS. 1 through 3 , and the description of the exemplary embodiment of  FIGS. 1 through 3  can be referred to for components, characteristics and functions that remain the same. 
     In  FIG. 4 , an alternative embodiment to  FIG. 3  of a torsion-prevention unit  38   b  of the guard hood torsion preventer  10   b  is shown. The torsion-prevention unit  38   b  is disposed on a guard hood  16   b  and embodied in one piece with it. Moreover, the torsion-prevention unit  38   b  is formed by a form-locking unit  110   b  and has a plurality of torsion-prevention elements  40   b ,  42   b , which are formed by form-locking elements  146   b ,  148   b . The form-locking elements  146   b ,  148   b  are disposed along a semi-circular path  120   b  on a guard hood body  112   b , on a side  50   b  of the guard hood body  112   b  facing away from a receiving region  48   b  for a tool. The form-locking elements  146   b ,  148   b  are embodied as a set of teeth  46   b , which extend away from the guard hood body  112   b  in the direction of the side  50   b  facing away from the receiving region  48   b . A form-locking connection to a further torsion-prevention unit of a guard hood torsion preventer  10   b  is effected analogously to the exemplary embodiment in  FIG. 2 . Analogously to the exemplary embodiment in  FIGS. 1 through 3 , here as well the form-locking elements  146   b ,  148   b , in an alternative embodiment, may be formed by recesses and/or indentations that can be engaged by a set of teeth of a threaded shaft. 
     In  FIG. 5 , a guard hood unit  56   c  that is an alternative to  FIGS. 3 and 4  is shown, with a guard hood  16   c . Instead of a guard hood neck, the guard hood  16   c  has a guard hood collar  122   c , which extends essentially parallel to an extension face  124   c  of a guard hood body  112   c  of the guard hood  16   c . The guard hood collar  122   c  is intended for securing the guard hood  16   c  to a receiving unit of a right-angle power sander, and for that purpose, by means of a disk not shown in detail that can be screwed to the receiving unit, it can be clamped between the disk and the receiving unit. For torsion prevention, the guard hood collar  122   c  has a torsion-prevention unit  38   c  of a guard hood torsion preventer  10   c . The torsion-prevention unit  38   c  has a plurality of torsion-prevention elements  40   c ,  42   c , which are formed by form-locking elements  146   c ,  148   c , and the form-locking elements  146   c ,  148   c  are disposed in a radial direction  108   c  outside a clamping region  150   c  for securing the receiving unit to the guard hood collar  122   c . The form-locking elements  146   c ,  148   c  are disposed in a circumferential direction  44   c  on the guard hood collar  122   c  on a side  50   c  facing away from a receiving region  48   c  for a tool, and they extend away from the guard hood collar  122   c  in the direction of the side  50   c  facing away from the receiving region  48   c . The form-locking elements  146   c ,  148   c  are formed by a set of teeth  46   c , analogously to  FIGS. 3 and 4 . Analogously to the exemplary embodiment in  FIGS. 1 through 3 , here as well the form-locking elements  146   c ,  148   c , in an alternative embodiment, may be formed by recesses and/or indentations that can be engaged by a set of teeth of a threaded shaft. 
     In  FIG. 6 , an embodiment of a torsion-prevention unit  20   d , as an alternative to  FIG. 2 , of a guard hood torsion preventer  10   d  is shown. The torsion-prevention unit  20   d  is braced via a bearing point  24   d  on a receiving unit  66   d  for receiving a tool and a guard hood unit  56   d  of a right-angle power sander  14   d . The torsion-prevention unit  20   d  has a longitudinal axis  22   d , about which the torsion-prevention unit  20   d  is rotatably supported. The torsion-prevention unit  20   d , in a middle region  98   d  along the longitudinal axis  22   d , has a splined shaft  126   d , which has a set of teeth  28   d  formed by splines  128   d . The set of teeth  28   d  has three splines  128   d , extending in the circumferential direction or the direction of rotation  102   d  around the splined shaft  126   d , and the splines are embodied asymmetrically in the direction of rotation  102   d  of the splined shaft  126   d , and a portion  130   d  of the set of teeth  28   d  or splines  128   d  in the direction of rotation  102   d  is disposed with a maximum spline height in a radial direction of the splined shaft  126   d , while another portion  132   d  of the set of teeth  28   d  or of the splines  128   d  is disposed with a /minimum spline height. By a rotation of the torsion-prevention unit  20   d  or of the splined shaft  126   d , the splines  128   d  engage a set of teeth  46   d  of a torsion-prevention unit  38   d  on a guard hood  16   d , the torsion-prevention unit  38   d  and the guard hood  16   d  being embodied analogously to the exemplary embodiment in  FIG. 3 . Alternatively, it is also conceivable for the torsion-prevention unit  38   d  to have torsion-prevention elements  40   d ,  42   d , formed by recesses, with the splines  128   d  of the splined shaft  126   d , for torsion prevention or form-locking connection mesh with the torsion-prevention unit  38   d  in indentations intended for the purpose of the torsion-prevention unit  38   d , which indentations are disposed on a radially outward-oriented surface of the flange neck  88   d.    
     By means of the splined shaft  126   d , the guard hood  16   d  is securely held, as a result of the two meshing torsion-prevention units  20   d ,  38   d  of the guard hood torsion preventer  10   d , in a guarding position by a spline clamping action between the splined shaft  126   d  and the guard hood  16   d . By rotation of the splined shaft  126   d  by 180° in the direction of rotation  102   d  about its longitudinal axis  22   d , a form-locking connection or spline clamping action between the two torsion-prevention units  20   d ,  38   d  is undone, and the guard hood  16   d  can be changed in its position or lifted from the flange neck  88   d  by a user of the right-angle power sander  14   d . It is moreover conceivable for the splined shaft  126   d  to be prestressed or preclamped in a wedging position by means of a spring element and/or a detent element and/or other components that appear appropriate to one skilled in the art. 
     In  FIG. 7 , an embodiment of a guard hood torsion preventer  10   e  is shown that is an alternative to  FIG. 2 . The guard hood torsion preventer  10   e  has two torsion-prevention units  20   e ,  38   e , which are each formed by a respective force-locking unit  34   e ,  134   e . The first torsion-prevention unit  20   e  is braced via a bearing point  24   e  on a receiving unit  66   e  of a right-angle power sander  14   e , and the torsion-prevention unit  20   e  is supported rotatably about its longitudinal axis  22   e  in the bearing point  24   e . The torsion-prevention unit  20   e  has a shaft  92   e , formed by a force-locking shaft  136   e , which in its middle region along the longitudinal axis  22   e  has a force-locking element  138   e , and for attaining a force lock with a guard hood  16   e , the force-locking element  138   e  is disposed asymmetrically about the longitudinal axis  22   e , and an axis of rotation  144   e  extends eccentrically through the force-locking element  138   e . For assuring a force lock, the force-locking shaft  136   e  can be fixed in its position by a user, via fixation elements not shown in further detail. The second torsion-prevention unit  38   e  is embodied in one piece with a guard hood neck  104   e  of the guard hood  16   e . The torsion-prevention unit  38   e  has torsion-prevention elements  40   e ,  42   e , disposed in succession in the circumferential direction  44   e  and formed by force-locking elements  140   e , which are formed by ramps that rise counter to a direction of rotation  142   e  of a tool. In a mounted position or guarding position of the guard hood  16   e  on the right-angle power sander  14   e , a static friction is operative between the two torsion-prevention units  20   e ,  38   e , or between the force-locking shaft  136   e  and the ramps of the guard hood  16   e , and this friction counteracts rotation of the guard hood  16   e  out of the guarding position. Moreover, by means of the ramps, a static friction force between the ramps and the force-locking shaft  136   e  upon a rotation of the guard hood  16   e  in the direction of rotation  142   e  is additionally increased, so that even at strong rotary linear momentums and/or torques, as in the case for instance of tool fragments, spun outward and striking the guard hood  16   e , from a tool that has burst in operation of the right-angle power sander  14   e , rotation of the guard hood  16   e  out of its guarding position is advantageously prevented. 
     The foregoing relates to preferred exemplary embodiments of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.