Abstract:
A power tool has an electric motor that includes a commutator, with which at least one commutator brush is acted upon with spring force via at least one commutator spring in the direction of a non-rotatable collector of the commutator. At least one auxiliary tool for adjusting the commutator spring is located on a component of the power tool.

Description:
CROSS-REFERENCE TO A RELATED APPLICATION 
     The invention described and claimed hereinbelow is also described in German Patent Application DE 10 2007 010 494.6 filed on Mar. 5, 2007. 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 OF THE INVENTION 
     The present invention relates to a power tool with an electric motor. 
     With power tools operated using commutator motors (universal or direct-current motors), current is transferred to an armature winding via a commutator. To this end, (carbon) commutator brushes glide over the collector (contact roller) of the commutator. The collector is usually laminated, is non-rotatably mounted on an armature shaft, and is connected with the armature winding in an electrically conductive manner. During operation of the power tool, the commutator brushes undergo frictional wear due to the sliding motion. With high-quality power tools in particular, worn commutator brushes may be replaced with new commutator brushes. To accomplish this, a spring that presses the worn commutator brush against the collector of the commutator must first be displaced, i.e., lifted, usually. 
     To ensure easy access to the spring and the worn commutator brush, it is known to integrate a brush cover in the housing above the commutator brush, so that the power tool need not be fully disassembled in order to replace the commutator brush. An auxiliary tool that is typically filigree and hook-shaped is required to displace the spring. An auxiliary tool of this type is often a piece of wire, cable, or the like that has been bent into the necessary shape. If material of this type is unavailable for manufacturing the auxiliary tool, operators often try to remove the spring using other, unsuitable tools, such as a screwdriver, which often results in damage to the power tool. 
     SUMMARY OF THE INVENTION 
     The object of the present invention, therefore, is to refine a power tool such that the commutator brush may be replaced as conveniently as possible. 
     In keeping with these objects and with others which will become apparent hereinafter, one feature of the present invention resides, briefly stated, in a power tool, comprising an electric motor that includes a commutator with a collector and at least one commutator brush; at least one commutator spring acting upon said at least one commutator brush with a spring force in a direction of said collector of said commutator; and at least one auxiliary tool configured for adjusting said commutator spring and located on a component of the power tool. 
     The present invention is based on the idea of integrating the auxiliary tool required to displace the spring that acts on the commutator brush in the power tool, i.e., to assign it to a component of the power tool, and/or to locate it on this component. Due to the inventive design of the power tool with an integrated auxiliary tool, an operator no longer needs to create an auxiliary tool out of wire, cable, etc. The defined positioning of the auxiliary tool on a component of the power tool also ensures that the auxiliary tool will not become misplaced and that the operator will not have to spend time looking for it. In addition, damage to the power tool that could occur when the commutator brushes are replaced is prevented, since unsuitable tools such as screwdrivers, etc., will not be used. 
     For special device designs that require that the spring that acts on the worn commutator brush be removed, it may be reasonable to design the auxiliary tool with special shapes, or to provide several auxiliary tools on one or more power tool components. In the context of the present invention, the expression “displacing the spring” refers to disassembling and/or assembling the spring entirely, i.e., removing or installing the spring entirely, and to any motion of the spring that is required to gain access to the commutator brush, in particular displacing the spring into a “park” position and removing it from the park position after the new commutator brush has been installed. 
     In a refinement of the present invention, it is advantageously provided that the component on which the auxiliary tool is located is a housing component in particular. The housing component is preferably a brush cover, which must be removed before the commutator brush may be replaced. The component—the housing component in particular, on which the auxiliary tool is installed—preferably also serves as a functional part of the auxiliary tool and, e.g., as a handle. 
     According to an advantageous refinement of the present invention, the auxiliary tool is detachably connected to the component, i.e., it may be removed from the component in order to displace the spring from the component. Once the commutator brush has been replaced, the auxiliary tool may be reconnected with the component. 
     With some power tool designs, to protect the power tool components, it may be advantageous to provide a cover for the auxiliary tool in its secured (retained) position. The cover would prevent damage to the power tool components. Highly diverse types of covers may be used, e.g., rotary covers, telescoping covers, folding covers, swivel covers, or removable covers, etc. 
     In addition or as an alternative to a detachable connection of the auxiliary tool on the component of the power tool, it is advantageous to locate the auxiliary tool such that it may be displaced between a retained position or a connection position, in which the auxiliary tool is supported (exclusively) on the power tool, and a working position, in which the auxiliary tool may be used as intended, to displace the spring. In the working position, the auxiliary tool preferably extends beyond the circumferential contour of the component on which it is mounted, and particular in the direction of its longitudinal extension, so that it may interact with the spring without restriction. 
     Various displacement mechanisms—which may be used in combination—are realizable in order to displace the auxiliary tool between its retained position and its working position. It is possible, e.g., to mount the auxiliary tool such that it is rotatable or swivelable around an axis using a pivot or swivel joint, and to therefore displace the auxiliary tool between the positions stated, in particular by hand. 
     It is also feasible to support the auxiliary tool on the component of the power tool such that it may be extended, and preferably pulled out. Preferably, the auxiliary tool may be pulled out of a cover, which is designed as a retaining pocket. The cover serves the purpose of protecting the auxiliary tool and other power tool components from damage. 
     With an extendable design of the power tool in particular, it is advantageous when the auxiliary power tool catches in the device when the power tool component that accommodates it—a housing cover, in particular—is pulled off or removed, and is therefore automatically pulled out of its retained position and into its working position when the component is removed from its retained position. After removal, in particular when the power tool component is pulled out, the auxiliary tool is therefore advantageously ready for use immediately. 
     It is also feasible to design the auxiliary tool such that it may be folded out or pulled out in a telescoping manner. An embodiment of this type is extremely advantageous due to the small amount of space it requires. 
     To provide the operator with better control of the auxiliary tool during operation, it is advantageous when the auxiliary tool may be fixed in the working position in particular, and when it is snapped in place, in particular. 
     According to an embodiment of the present invention that is particularly cost-favorable to manufacture, the auxiliary tool is designed as a single piece with a power tool component. For example, the power tool component may be formed together with the auxiliary tool using an injection-moulding procedure. 
     The auxiliary tool is preferably designed such that a form-fit connection may be created between it and the commutator spring, so that the displacement forces to be applied may be transferred in a suitable manner. 
     For a large number of power tool configurations, it is advantageous when the auxiliary tool is designed as a type of hook for this purpose, in particular so that it may interact with a spring leg for displacing the commutator brush into a park position or out of the park position. In the park position, the commutator brush may be easily replaced. As an alternative, it is feasible to design the auxiliary tool as tongs, with which the commutator spring may be displaced. 
     The auxiliary tool is preferably made of metal, and is designed as a bent wire part in particular. To prevent current from passing through the auxiliary tool and, therefore, to protect the operator from harm, an insulator is provided, e.g., in the form of a shrink tube or a jacket. 
     The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view showing a schematic depiction of a power tool, 
         FIG. 2  is a view showing a first embodiment of a component with an auxiliary tool installed thereon such that it may be swiveled, in its retained position, 
         FIG. 3  is a view showing an exemplary embodiment in  FIG. 2 , with the auxiliary tool swiveled into its working position, 
         FIG. 4  is a view showing an alternative location of an auxiliary tool on a component of the power tool, in its retained position, 
         FIG. 5  is a view showing an exemplary embodiment in  FIG. 4 , with an auxiliary tool that may be extended out of its retained position. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Identical components and components with the same functionality are labeled with the same reference numerals in the figures. 
       FIG. 1  shows, as an example and in a schematic depiction, a power tool  1  designed as a grinding tool, with a rotationally driven grinding disk  2 . Grinding disk  2  is located directly on an armature shaft  3  (motor shaft), which is rotatably mounted inside a housing  4 . A collector  5  of a commutator  6  of an electric motor  7  is located on armature shaft  3 . Electric motor  7  includes commutator  6  and an armature stack  8  with a not-shown armature winding. The armature stack and/or its armature winding, which are non-rotatably located on armature shaft  3 , are connected with collector  5  in an electrically conductive manner. Armature stack  8  is located radially inside two separated permanent magnets  9 ,  10 . 
     In addition to collector  5 , commutator  6  also includes two commutator brushes  11 ,  12 , which are made of graphite in particular, which are acted upon with spring force in the radially inward direction on collector  5  using a schematically depicted commutator spring  13 ,  14 . Commutator brushes  11 ,  12  are guided in displaceable brush holders  15 ,  16 . Commutator brushes  11 ,  12  are electrically contacted (not shown) and supply collector  5  and, therefore, the armature winding of armature stack  8  with electrical energy. 
     To replace commutator brushes  11 ,  12  when they become worn, associated commutator spring  13 ,  14  must first be moved into a park position or removed. To this end, brush covers  17 ,  18  (housing cover) are removed from housing  4 , to gain access to commutator springs  13 ,  14 . Commutator springs  13 ,  14  are then displaced using a hook-shaped auxiliary tool  19  shown in  FIGS. 2 through 5 , which is located on a power tool component. 
     With the exemplary embodiment shown in  FIGS. 2 and 3 , hook-shaped auxiliary tool  19  is designed as a bent-wire part and is secured to an underside  21  of a brush cover  17  using a pivot  20 . Brush cover  17  is removed from housing  4  of power tool  1  to remove the commutator spring. To this end, a fastening screw—which has been guided through a screw hole  22  and screwed into an inner thread of power tool  1 —is unscrewed, then brush cover  17  and insertion tabs  23  integrally formed thereon may be removed from power tool  1 . 
     Pivot  20  serves to swivel auxiliary tool  19  from the retained (park) position shown in FIG.  2 —in which it bears against underside  21  of brush cover  17  and does not extend beyond the circumferential contour of brush cover  17 —into the working position shown in  FIG. 3 , in which it extends beyond the circumferential contour of brush cover  17  in the direction of its longitudinal extension and may therefore be used. 
       FIGS. 4 and 5  show a further exemplary embodiment, in which auxiliary tool  19  is not installed on a brush cover  17 , but on a housing pot  24  of a power tool  1  with a pot-shaped design. Auxiliary tool  19  is extendable out of the retained position shown in  FIG. 4  and into the working position shown in  FIG. 5 . A longitudinal guide  25  for the auxiliary tool  19  is provided. An axial stop  26  on the left—according to the plane of the drawing—end of auxiliary tool  19  prevents auxiliary tool  19  from sliding out of longitudinal guide  25 , thereby retaining it permanently on power tool  1 . 
     It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the type described above. 
     While the invention has been illustrated and described as embodied in a power tool with an integrated auxiliary tool for replacing brushes, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention. 
     Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, be applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.