Patent Publication Number: US-6902471-B2

Title: Heavy-duty tool with a rotationally driven, disk-shaped hub

Description:
BACKGROUND OF THE INVENTION 
   A disk-shaped insertable tool, e.g., a grinding disk or a cutoff disk for angle grinders, are usually composed entirely of bound grinding means and have a center, circular recess, via which the insertable tool can be secured on an angle grinder spindle with a clamping nut in non-positive fashion in the circumferential direction and in positive fashion in the axial direction. Insertable tools are known that have a reinforcement made of sheet metal in the region of the recess, and some are known that do not have a reinforcement. 
   SUMMARY OF THE INVENTION 
   The invention is based on an insertable tool having a rotationally drivable, disk-shaped hub on which a grinding means forming a cutoff disk, grinding disk, roughing disk, or abrasive disk is secured in the radially outer region. 
   It is proposed that the grinding means and the hub are joined via joining means in positive fashion at least in the direction of rotation. An advantageous connection can be achieved via which high drive torques can be transmitted securely from the hub to the grinding means. In addition to a positive connection in the direction of rotation, a positive connection in the axial direction is also feasible, e.g., by means of projections that are angled and/or bent at right angles. The positive connection can be realized with simple design means without additional components with projections on the hub extending in the axial direction and forming the joining means, which said projections grip axially in or through the grinding means and can be advantageously integrally molded on the hub in a stamping process, e.g., jointly with other recesses. An axial positive connection can take place—in the case of thin grinding means, in particular—by outwardly or inwardly bending integrally molded projections or borders gripping through the grinding means in a cost-effective fashion when the grinding means are pressed. 
   It is furthermore proposed that the hub is designed with a flexural strength that changes in the radial direction. An advantageous transition can be achieved between the grinding means and a harmonious bending line overall can be obtained. An advantageous coherence between the grinding means and the hub can be achieved and detachment can be securely prevented when attaching the insertable tool, e.g., on a spindle of an angle grinder, and during operation. Axial forces and resultant bending torques can be securely supported via a harmonious bending line. 
   A flexural strength and/or bending line can be specifically adapted to a desired course using simple design means by the shape of recesses installed in the radially outer region of the hub. The flexural strength of the hub can be specifically weakened in individual areas. The recesses can have various shapes that appear reasonable to one skilled in the art. The recesses can be designed as slits having a uniform width and/or with a width that decreases radially inwardly in continuous fashion or in stages, by way of which the flexural strength decreases radially outwardly due to the hub material that decreases radially outwardly. 
   In a further embodiment of the invention it is proposed that at least one recess has a greater width in the radially inward region than in the radially outward region, by way of which an advantageously large fastening area is provided in the radially outer region and, in the adjacent radially inner region, a type of spring area can be obtained. The recesses are advantageously designed open in the radially outward direction, by way of which segments can be advantageously obtained that can be deflected largely independent of each other. Basically, however, the recesses could also be designed closed in the radially outward direction. 
   Instead of recesses, other design embodiments appearing reasonable to one skilled in the art are feasible for achieving a certain bending line, such as embodiments having material strengths that increase or decrease radially outwardly, different numbers of material layers, different materials with different stiffness and/or with reinforcement ribs for setting a desired bending line. Furthermore, materials are feasible that were subjected to different material treatments radially outwardly. 
   The hub is advantageously produced in cost-effective and environmentally-friendly fashion out of sheet metal, preferably steel sheet. The grinding means, which is often difficult to recycle, can be used up completely, and the hub can simply be recycled. Basically, however, other hub materials are feasible as well, such as plastics, ceramic materials, etc. 
   In a further embodiment of the invention it is proposed that the hub is covered at least partially on both sides with at least one layer of the grinding means, e.g., with a fabric layer carrying an abrasive substance, or fiberglass mats, etc., by way of which the connection between the hub and the grinding means can be improved. A positive connection can be achieved in both axial directions. 
   A connection between the hub and the grinding means can be further improved by jointly subjecting the grinding means and the hub—during a production process of the grinding means—to at least one heating process, and/or by connecting the grinding means with the hub via a bonded connection in addition to a non-positive and/or positive connection, e.g., via an adhesive connection in particular. The bonded connection can be created after or during the production process of the grinding means. If the production process of the grinding means is used to join the hub and the grinding means, additional working steps can be spared, and a production process of the insertable tool that is more streamlined overall can be obtained. A bonding process in particular can be easily integrated in the production process of the grinding means, whereby other bonded connections are feasible as well, however, such as soldered and/or welded connections, etc. 
   The means of attaining the object according to the invention can be used with insertable tools that are secured on the spindle via a clamping nut, and particularly advantageously with hubs that have—in addition to a center recess—recesses for fixation via a quick-release system. During installation on a spindle, any installation forces that occur in the axial direction can be advantageously absorbed via a harmonious bending line. 
   Further advantages result from the following description of the drawings. Exemplary embodiments of the invention are presented in the drawings. The drawing, the description, and the claims contain numerous features in combination. One skilled in the art will advantageously consider them individually as well and combine them into reasonable further combinations. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a schematic illustration of an angle grinder from above, 
       FIG. 2  shows an insertable tool according to the invention, 
       FIG. 3  shows an enlarged drawing of a hub without the grinding means, from above, 
       FIG. 4  shows the hub in  FIG. 3  in a side view, and 
       FIG. 5  shows an alternative to FIG.  3 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows an angle grinder  36  from above with an electric motor supported in a housing  38  and not shown in further detail. The angle grinder  36  is capable of being guided via a first handle  40  integrated on the side furthest away from the insertable tool and extending in the longitudinal direction, and via a second handle  44  attached to a gearbox housing  42  in the region of the insertable tool and extending transversely to the longitudinal direction. 
     FIG. 2  shows the insertable tool in  FIG. 1  in the removed state. The insertable tool has a rotationally drivable, disk-shaped hub  10  made of steel sheet to which a grinding means  14  forming a grinding disk is attached in the radially outward region. The grinding means  14  is essentially composed of fiberglass mats, grinding means and binding means that are pressed together to form a solid disk, whereby the binding means were set in a heating process. 
   The hub  10  is designed with a changing flexural strength in the radial direction, whereby the hub  10  is specifically weakened in its radially outward region to adjust the flexural strength using slit-shaped recesses  16 . The recesses  16  are designed open in the radially outward direction, by way of which segments that can be deflected advantageously largely independently of each other are produced. The recesses  16  have a uniform width and project radially inwardly until shortly before a region in which recesses  30 ,  32  are installed to secure the insertable tool to an angle grinder spindle via a quick-release system. A circular recess  28  is installed in the center region of the hub  10  to center the insertable tool. 
   The hub  10  is covered on both sides by at least one layer  22 ,  24  of the grinding means  14 , whereby the grinding means  14 —with essentially its entire thickness—are located in an annular indentation on a side  48  facing the angle grinder, so that the hub  10  and the grinding means  14  advantageously meet in a common plane in the direction of the angle grinder  36 . If the grinding means  14  should detach from the hub  10  during operation, they are still secured by the hub  10  against coming loose in the direction away from the angle grinder  36  (FIGS.  2  and  4 ). On a side  34  facing away from the angle grinder  36 , a layer  22 —formed by a fiberglass mat—of the grinding means  14  covers the hub  10  radially inwardly. 
   The grinding means  14  and the hub  10  are joined in the manner of a positive connection via joining means  26  in the direction of rotation (FIG.  4 ). The joining means  26  are formed by projections integrally molded on the hub  10  and extending in the axial direction, which said projections grip into and/or through the grinding means  14 . The projections forming the joining means  26  are integrally molded with the recesses  16 ,  28 ,  30 ,  32  in a common stamping process. 
   During the production process of the grinding means  14 , the hub  10  and the grinding means  14  are subjected to a joint heating process, whereby a bonded connection between the grinding means  14  and the hub  10 —in fact, an adhesive connection—is set. 
   An alternative hub  12  is shown in FIG.  5 . Components that essentially remain the same are basically labelled with the same reference numerals. Moreover, the description of the exemplary embodiment in  FIGS. 2 and 3  can be referred to with regard for identical features and functions. 
   The hub  12  has recesses  18 ,  20  that are designed open in the radially outward direction and that have different widths in the radial direction. The recesses  18  are designed in the shape of a tee and have a greater width in the radially inner region than in the radially outward region. In contrast, the recesses  20  are designed in the shape of a vee and have a width that decreases radially inwardly. 
   In  FIG. 5  the recesses  18  and  20  are combined, whereby it is also feasible, however, to provide the recesses  18  or  20  each on just one hub.