Patent Publication Number: US-7722445-B2

Title: Insertion tool for an angle grinder

Description:
CROSS-REFERENCE TO A RELATED APPLICATION 
   The invention described and claimed hereinbelow is also described in German Patent Application DE 103602248.8 filed on Dec. 20, 2003. This German Patent Application, whose subject matter is incorporated here by reference, provides the basis for a claim of priority of invention under 35 U.S.C. 119(a)-(d). 
   BACKGROUND INFORMATION 
   The present invention is directed to an insertion tool for an angle grinder. The present invention is also directed to a system composed of an insertion tool with a hub and a driving device for an angle grinder. 
   Publication WO 03/097299 makes known an insertion tool—which represents the general class—for an angle grinder that includes a hub with a plurality of fastening means in the form of recesses. The insertion tool can be advantageously clamped onto a driving device of the angle grinder using a keyless system, which is also known from the publication cited above. 
   SUMMARY OF THE INVENTION 
   The present invention is directed to an insertion tool for an angle grinder that has a hub with at least one fastening means for fastening the hub to a driving flange of the angle grinder. 
   The present invention is also directed to a system composed of an insertion tool with a hub and a driving device for an angle grinder, the hub including at least a first fastening means, and the driving device including at least a first fastening element for interacting with the first fastening means and for fastening the hub to the driving device. 
   It is provided that the first fastening means is located on a partial circle with a radius between 12 mm and 25 mm. 
   Due to the proposed dimension of the partial circle, an insertion tool can be obtained that is reliably and easily installable on an angle grinder, using a keyless system in particular. An insertion tool that is advantageously well-designed and matched to the driving flange can be obtained, and advantageous force distributions in the insertion tool and into the driving flange while working with the insertion tool can be achieved. 
   The means of achieving the object according to the present invention can be used with all insertion tools for angle grinders that appear suitable to one skilled in the art, such as rubber backing pads, cutting discs, rough grinding discs, grinding discs, etc. The hub can be made of a material out of which the abrasive body is made, or out of another material, such as sheet steel. 
   Further advantages result from the description of the drawing, below. An exemplary embodiment of the present invention is shown in the drawing. The description of the drawing contains numerous independent features, each of which independently improves the means of achieving the object according to the present invention. The means of achieving the object according to the present invention can be improved by one or more of these features without the need to add additional features from the description of the drawing. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  Shows an angle grinder with a cutting disc, 
       FIG. 2  Shows a hub of the cutting disc of the angle grinder, 
       FIG. 3  Shows a driving flange of the angle grinder, 
       FIG. 4  Shows a top view of the hub in  FIG. 2 , 
       FIG. 5  Shows a sectional illustration of the hub in  FIG. 2 , and 
       FIG. 6  Shows a top view of the driving flange in  FIG. 2 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows an angle grinder  2  from above with an electric motor (not shown) supported in a housing  4 . Angle grinder  2  is guidable using two handles  6 ,  8 . An insertion tool  12  is drivable in direction of rotation  14  via the electric motor, a not-shown transmission in a transmission housing  10 , and a drive shaft (not shown). 
   When angle grinder  2  is viewed not from the top, as in  FIG. 1 , but from the bottom, a hub  16  of insertion tool  12  can be seen. This hub is shown in a perspective view in  FIG. 2 . An abrasive body  18 , shown in  FIG. 1 , of insertion tool  12  is located around hub  16 , abrasive body being fastened to hub  16  with the aid of fastening means  20 . Fastening means  20  are located in a radially outer region of hub  16  on a second partial circle, the entirety of which extends in the region of hub material. There are therefore no recesses located between fastening means  20 , thereby allowing a stable outer region of hub  16  to be obtained. 
   Hub  16  of insertion tool  12  configured as a rough grinding disc is designed to be inserted on a driving device  22  of angle grinder  2 , which is shown in  FIG. 3 . Driving device  22  surrounds a centering collar  24 , onto which hub  16  with a centering opening  26  can be slid. After insertion, hub  16  rests with its radially innermost part on three encoding raised areas  28  that extend radially outwardly away from centering collar  24 . When resting on encoding raised areas  28 , hub  16  can be rotated in tangential direction  30  until three radial recesses  32  are aligned with three encoding raised areas  28 . In this position, hub  16 , and with it, entire insertion tool  12 , drops down slightly until it comes to rest with its inner plate  34  on three snap-in bolts  36 . 
   These three snap-in bolts  36  are spring-loaded and can be pressed downward by an operator of angle grinder  2  by pressing on insertion tool  12 . Hub  16  can now be pressed with its lower plate  34  until it reaches a base  38  of driving flange  22 . As a result, fastening elements  40  configured as hooks pass through openings  42  in lower plate  34  of hub  16 . 
   To fasten insertion tool  12  onto driving flange  22 , hub  16  can now be rotated in the clockwise direction, which allows a radially innermost region  44  of lower plate  34  to be guided underneath encoding raised areas  28 . At the same time, a retaining region  46  adjacent to openings  42  in lower plate  34  is slid under a slanted ramp element  48  of fastening element  40 , fastening element  40  being pulled slightly upward against the force of a non-shown, preloaded spring. An exact description of driving flange  22 , spring-loaded snap-in bolt  36  and fastening elements  40  is provided in publication WO 03/097299 described initially. 
   When insertion tool  12  is rotated further in the clockwise direction, retaining region  46  is slid under a retaining element  50  oriented parallel to base  38  of driving flange  22  that presses hub  16  onto base  38  with the aid of the preloaded, not-shown spring. When a fastening position is reached, snap-in bolts  36  are aligned with pot-shaped recesses  52  in hub  16  and engage into these recesses  52  by snapping upward. Recesses  52  are designed as deformations of lower plate  34 ; they are shown in  FIG. 2  as cylindrical raised areas. Hub  16  and, with it, entire insertion tool  12 , is now fixed in tangential direction  30  by snap-in bolts  36  in pot-shaped recesses  52 , and are retained in the axial direction by spring-loaded retaining elements  50 . 
     FIG. 4  shows a top view of hub  16  of insertion tool  12 . Hub  16  includes three identical first fastening means configured as pot-shaped recesses  52  that extend out of the plane of the drawing, as seen from above. Pot-shaped recesses  52  include a circular cross section, the center point of which is located on a partial circle  54  with a radius  56  of 16.7 mm. Pot-shaped recesses  52  have a circular cross section with an inner diameter  58  of 6 mm ( FIG. 5 ) and an inner depth  60  of 3.85 mm. 
   Hub  16  also includes three identically configured openings  42  as the second fastening means. These second fastening means are configured in the shape of two parallel slots oriented in tangential direction  30 . The slots are substantially right-angled and abut each other along part of one of their long sides. Openings  42  include a first retaining region  62  formed by the radially inward slot with a radial width  64  of 3.9 mm. In a releasing region  66  formed by the two slots, opening  42  has a radial width  68  of 7.1 mm. In a third region  70  which also belongs to retaining region  66 , radial width  72  of opening  42  is 3.4 mm. In the circumferential direction  30 , each of the three openings  42  extends across an angular range  74  of approximately 60°. Openings  42  also include blocking elements  76  designed as bulges, each of which abuts the radially inner slot and extends into releasing region  66 . Blocking elements  76 , in turn, include a stop  78  provided to limit a releasing motion of fastening element  40  in opening  42 . 
   Due to the fact that openings  42  are formed by two right-angled slots, a particularly stable retention of hub  16  on driving device  22  in the axial direction can be achieved using fastening elements  40  that are simple and economical to produce. In addition, with the dimensions indicated, a laterally-reversed installation of insertion tool  12  onto an identical driving flange without encoding raised areas  28  can be effectively prevented, since fastening element  40  cannot be inserted through a laterally-reversed opening  42  if it has the dimensions indicated below. 
   To release hub  16  from driving device  22  shown in  FIG. 6  in a top view, an actuating button  80  is pressed, by way of which snap-in bolts  36  are pressed downward and out of recesses  52 . Hub  16  is now rotatable in the counterclockwise direction, by way of which fastening elements  40  move in a release motion in tangential direction  30  away from retaining regions  62  toward releasing regions  66  of openings  42 . The release motion can be carried out by an operator of angle grinder  2  until a segment  82  of fastening element  40  hits stop  78  of opening  42  and/or blocking element  76 . The dimensions of opening  42  and its position relative to recesses  32  are designed such that, when segment  82  hits stop  78 , recesses  32  are flush with encoding raised areas  28 . In this position, hub  16  can be lifted off of driving device  22 . Due to the shape and dimensions of opening  42  with blocking element  76  and third region  70 , fastening element  40  can have retaining element  50  that extends further in the release direction than segment  82  of fastening element  40 . This enables a particularly simple and economical manufacture of a stable fastening element  40  and a stable retention of hub  16  on driving device  22 . 
   In its radially inward region, hub  16  is designed with a well-shaped recess  84  with a well depth  86  of approximately 6 mm and an inner diameter  92  of 47 mm. An inner well wall  88  is thereby formed, with openings  42  being located at minimum distance  90  of approximately 2 mm from inner well wall  88 . As a result of this relatively radially far outward positioning of openings  42  in hub  16 , a stable axial fixing of hub  16  on driving device  22  via retaining elements  50  can be obtained. 
   When snap-in bolts  36  designed as fastening elements engage in recesses  52 , snap-in bolts  36 —which have an outer diameter  94  of 5.5 mm—are located in recesses  52  with a play of 0.5 mm. This relatively large amount of play makes it possible for snap-in bolts  36  to also engage in recesses  52  when snap-in bolts  36  or recesses  52  are very dirty. As a result, a secure fixing of insertion tool  12  in tangential direction  30  can be ensured, even when insertion tool  12  is very dirty. 
   Due to the large amount of play—which serves to provide operational reliability—between snap-in bolts  36  and recesses  52 , hub  16  cannot be retained in a centered position on driving device  22  by snap-in bolts  36 . Centering of this type, which is necessary, is achieved by the dimensions of centering opening  26  and centering collar  24 , the play of which relative to each other is less—by a factor of approximately  17 —than the play between snap-in bolts  36  and recesses  52 . Inner radius  96  of centering collar  26  is 11.1 mm, while the outer radius  98  of centering collar  24  is 11.115 mm. Since centering collar  24  and centering opening  26  are circular in design, the play between centering collar  24  and centering opening  26  is 0.03 mm. 
   Due to the relatively large amount of play between snap-in bolts  36  and recesses  52 , the contact surface between snap-in bolts  36  and recesses  52  attainable via elastic deformation can be very small during operation of insertion tool  12 . So that the resultant wear of snap-in bolts  36  remains minimal, snap-in bolts  36  are made of a hardened steel, while recesses  52  in hub  16  are made of an unhardened metal, e.g., unhardened steel sheet. During operation of insertion tool  12 , snap-in bolts  36  can extend into recesses  52  and deform them slightly, so that a sufficiently large contact surface between snap-in bolts  36  and recess  52  results, which results in low wear of snap-in bolts  36  even when insertion tool  12  undergoes strong vibration.