Electric machine and manual machine tool comprising the same

The invention is based on an electrical machine with a rotatable brush plate (10, 12), which is held in its end positions by means of at least one holding mechanism (16, 18) that acts in the circumference direction (14).The invention proposes that the holding mechanism (16, 18) have at least one device (20, 22) that loads the brush plate (10, 12) in the circumference direction (14).

BACKGROUND OF THE INVENTION

The invention is based on an electrical machine.

In electrical machines with a brush plate that can be rotated on a housing base of a housing part, it is known to hold this brush plate in its end positions by means of a holding mechanism that acts in the circumference direction. The holding mechanism has hooks formed onto the brush plate, which engage the housing base from behind and which are moved in the circumference direction along a radially outward pointing end of the housing base when the brush plate is rotated. The end has projections pointing radially outward that are formed onto the housing base, spaced apart from end stops in the circumference direction. The distances between the end stops and the corresponding projections are selected so that they correspond to one hook width. When the brush plate is rotated, the hook moves across the projection extending in the radial direction, and arrives in an end position between the corresponding end stop and the respective projection. The end stop and the radial projection secure the brush plate in the circumference direction.

SUMMARY OF THE INVENTION

The invention is based on an electric machine with a rotatable brush plate that is held in its end positions by means of at least one holding mechanism that acts in the circumference direction.

The invention proposes that the holding mechanism have at least one device that loads the brush plate in the circumference direction. The brush plate can advantageously be held in a constant, play-free manner in its respective end position counter to a rotation direction, and a wear on the holding mechanism, in particular by outwardly pointing radial projections, can be advantageously avoided. A contact between a strip conductor affixed to the housing and a carbon cartridge mounted onto the brush plate can always be assured in the end positions, which makes it possible to prevent contacts from being burned off and to prevent a burn off-induced failure of the electrical machine.

The device advantageously has a bistable position, at least when in the installed position. Two forces in opposite directions can be generated in a structurally simple fashion with a single device or with a small number of components. It is also possible to achieve a design in which the device always moves the brush plate from an intermediate region into one of its end positions.

The device can be comprised of various components deemed appropriate by one skilled in the art, which have a bistable position either intrinsically or as a result of their installation, for example a relay, a spring element, etc. If the device is comprised of a spring element, then this permits a structurally simple, durable, reasonably priced, and space-saving device to be produced.

The spring element can be comprised of various spring elements deemed appropriate by one skilled in the art, e.g. a disk spring, a leg spring, etc. If the spring element is comprised of a leg spring, then an inexpensive, space-saving spring can be used, whose legs can advantageously be guided into the corresponding recesses disposed in the brush plate and in a housing part. The leg spring can be supported with its first leg against the housing part and its second leg can exert a spring force on the brush plate in the direction of its end positions.

In another embodiment, the invention proposes that the leg spring be supported so that it can pivot around the first leg. A bistable position of the leg spring can be achieved in a structurally simple manner and a simple and rapidly mountable holding mechanism can be achieved.

The invention also proposes the possibility of the leg spring engaging in detent fashion with the brush plate by means of a detent element. The leg spring can advantageously be preinstalled onto the brush plate and secured to it in captive fashion. The brush plate and the leg spring can be simply installed and removed as a unit.

If the detent element is of one piece with the leg spring, then this permits savings with regard to additional components, space, and costs.

At least one leg of the leg spring advantageously has a part for preventing an incorrect installation. The part can be comprised of a separate component or can be formed onto one end of the leg and be of one piece with it. If the part is formed onto the end of the leg of the leg spring-by means of a bending procedure, then a structurally simple, inexpensive protection against incorrect installation can be achieved.

In another embodiment, the invention proposes that an actuating button be embodied of one piece with the brush plate. This permits savings with regard to additional components, space, weight, and assembly costs. It is also possible for an advantageous installation space for the device to be created, particularly in the vicinity of the actuating button.

The invention also proposes that the brush plate be held in its end positions by means of at least one detent mechanism. The action of the device can be assisted and an operator can be clearly notified that the respective end position has been reached by means of a detent engagement.

Other advantages ensue from the following description of the drawings. The drawings depict exemplary embodiments of the invention. The drawings, the specification, and the claims contain numerous features in combination. One skilled in the art will suitably also consider the features individually and will unite them in other meaningful combinations.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1shows a drill with a housing38that has an electric motor mounted in it, whose rotation direction40, or the rotation direction40of a drill bit44clamped in a tool holder42, can be selected by means of a reversing lever46. The reversing lever46is disposed above an actuating switch48of the drill so that with one hand, an operator can operate the actuating switch48, switch the drill on or off, and select the desired rotation direction40of the drill bit44by using the reversing lever46. On a side of the drill oriented toward the tool holder42, a first handle50extending perpendicular to the actuation direction is fastened to the housing38. On a side of the housing38oriented away from the tool holder42, a second handle52extending perpendicular to the actuating direction is provided, which constitutes a part of the housing38.

The reversing lever46has an engaging fork54, whose free end positively engages with an articulating pin56(FIGS. 2,3,4, and5). The articulating pin56is formed onto a brush plate10in a lower region close to the reversing lever46. The brush plate10, which is supported in rotary fashion on a housing base58, radially encloses an armature shaft60. The brush plate10is secured in the axial direction by means of stays88, which extend in the axial direction toward the tool holder42on a side of the brush plate10oriented away from the armature winding90and are formed onto an inside of the handle52.

Carbon cartridges80,80′ are disposed situated diagonally opposite from each other on the brush plate10(FIGS.4and5). The carbon cartridges80,80′ have recesses, not shown, for containing carbon brushes82,82′. Spring elements84,84′ press the carbon brushes82,82′ radially inward against a commutator86(FIG.2).

A holding mechanism16that acts in the circumference direction14holds the brush plate10in its end positions (FIGS. 3,4, and5). The holding mechanism16has a device20comprised of a leg spring that has a bistable position and that loads the brush plate10from a neutral, unstable, middle position, in the circumference direction14toward its respective end positions. The leg spring20has a first leg24and a second leg66, which are connected to each other by a coil108of the leg spring20.

The leg spring20is supported so that it can pivot around the longitudinal axis of the first leg24(FIG.3). The first leg24, whose end62points toward the tool holder42, engages in a longitudinal channel64that is formed into an outer circumference of a cup-shaped inner region of the housing38that is encompassed by the handle52. The armature shaft60of the electric motor is supported in the cup-shaped region of the housing38.

The second leg66of the leg spring20, which also points toward the tool holder42, has a region that is bent radially outward at its end68. With the bent region, the second leg66positively engages in a transverse channel70that is formed into a collar72on the radial outside of the brush plate10.

The leg spring20is supported with its first leg24in the longitudinal channel64on the housing38and with its second leg66, by means of the transverse channel70, presses the brush plate10in the circumference direction14, into its first end position (FIG.4). In the first end position, the brush plate10is also secured in the circumference direction by a detent mechanism36.

The detent mechanism36has two detent bolts74,74′ formed onto the housing38that are disposed diagonally opposite each other (FIG.4). In the first end position of the brush plate10, the detent bolts74,74′ positively engage in detent recesses76,76′ that are let into outwardly protruding projections that are formed onto the brush plate10.

If an operator actuates the reversing lever46, the brush plate10is rotated in the circumference direction14by means of the engaging fork54and the articulating pin56, and the detent bolts74,74′ and the detent recesses76,76′ disengage from one another. The leg spring20is compressed by means of its legs24,66until the neutral position is reached. After the neutral position is passed, the leg spring20expands and with its second leg66, presses the brush plate10in the circumference direction14, into its second end position and is supported with its first leg24in the longitudinal channel64of the housing38. When the second end position is reached, the detent bolts74,74′ engage with two other detent recesses78,78′ let into the frames92,92′ of the carbon cartridges80,80′. In addition to the leg spring20, the brush plate10is also secured in the circumference direction in its second end position by means of the detent bolts74,74′ and the detent recesses78,78′. In addition, a spring-loaded detent bolt104in a recess of the engaging fork54fixes the reversing lever46and the engaging fork54to the housing38in the respective end position of the brush plate10by engaging in recesses of the housing38in the end positions (FIG.2).

FIG. 6shows a detail of an exemplary embodiment with an alternative holding mechanism18. In principle, components that remain essentially the same are provided with the same reference numerals. Furthermore, for features and functions that remain the same, reference can be made to the description of the exemplary embodiment inFIGS. 1to5. The description below is essentially restricted to the differences from the exemplary embodiment inFIGS. 1to5.

The holding mechanism18has a device22comprised of a leg spring, which has a bistable position and loads the brush plate12from a neutral, unstable position, in the circumference direction14toward its respective end positions. The leg spring22has a first leg26and a second leg34, which are connected to each other by means of a coil106of the leg spring22.

The leg spring22is supported so that it can pivot around the longitudinal axis of the first leg26. The first leg26points in the direction oriented away from a tool holder42and engages in a longitudinal channel94that is formed into an outer circumference of a cup-shaped inner region of a housing38that is encompassed by the handle52. At its end100, the first leg26has a region that is bent radially outward, which constitutes a part30that prevents an incorrect installation.

At its end102, the second leg34of the leg spring22, which also points in the direction oriented away from the tool holder42, has a region that is bent radially inward, is embodied as a detent element28, and has a bent longitudinal axis. An actuating button32is formed onto a radially outer region of the brush plate12and protrudes outward from the housing38. The second leg34engages in a longitudinal channel96that is formed into the radially outer region of the brush plate12.

During installation, the second leg34of the leg spring22is inserted into the longitudinal channel96by means of a pocket98in the brush plate12, and is elastically deformed in the process. After the end102of the second leg34has crossed the longitudinal channel96and when the leg spring22engages with its coil106in the pocket98, the second leg34expands and the leg spring22is fastened to the brush plate12in captive fashion. The brush plate12can be installed in the housing38together with the preinstalled leg spring22. In this case, the first leg26of the leg spring22is inserted into the open longitudinal channel94.

In the installed position, the leg spring22is supported on the housing38with its first leg26in the longitudinal channel94and with its second leg34, by means of the longitudinal channel96, presses the brush plate12in the circumference direction14, into its first end position.

By means of the actuating button32protruding from the side of the housing38, an operator can rotate the brush plate12in the circumference direction14on a housing base58. The leg spring22is compressed by means of its legs26,34until the neutral position is reached. After the neutral position is passed, the leg spring22expands and with its second leg34, presses the brush plate12and the actuating button32in the circumference direction14, into their second end position and is supported with its first leg26in the longitudinal channel94of the housing38.

REFERENCE NUMERALS