Abstract:
An electrical tool, in particular drill and chiselling hammer, including a drive shaft and two driven members. The drive shaft is operatively connectable with the driven members by a respective one of a pair of coupling sleeves. The coupling sleeves are actuatable by a rotatable and mechanical actuating element, in particular a mechanical rotary switch. The actuating element of the electrical tool includes a transmission means or a transmission portion that is stationary with respect to the actuating element and which is contactable directly with the respective coupling sleeve for actuating the coupling sleeves.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority to European Patent Application No. EP-08 161 170.9, filed Jul. 25, 2008, entitled ELECTRICAL TOOL WITH GEAR SWITCHING, the entirety of which is incorporated by reference herein. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention is directed towards an electrical tool, in particular a drill and chipping hammer having a drive shaft and two driven members, wherein the drive shaft can be operatively connected with the individual driven members by means of a coupling sleeve. The coupling sleeve can be operated by a mechanical actuating element, in particular by a mechanical rotary switch. 
         [0004]    2. Description of the Related Art 
         [0005]    Electrical tools, such as drill and chipping hammers, in which a motion of the drive shaft is transmitted to driven members are mostly provided with a coupling device that enables coupling and decoupling between the drive shaft and the driven members in order to transmit power. For example, the driven members should not be coupled with the drive shaft in every operating condition of the electrical tool. In this case it is also necessary that the flow of force (power transmission) between the drive shaft and the corresponding driven member can be interrupted. 
         [0006]    In order to operate corresponding coupling elements, rotary switches are often used to allow a user to choose between two or three operating modes of the electrical tool. As the coupling elements are mostly operated by a translational motion, a diverting mechanism is necessary in this case, which translates the rotational motion of the rotary switch into a translational motion of the coupling elements. 
         [0007]    In a drill and chiselling hammer, a corresponding diverting mechanism is usually formed by means of a switching slider that it movable by corresponding guide rails along the actuating direction of the coupling elements. In order to allow a plurality of operating modes of an electrical tool having two separate couplings, the mentioned switching slider is often based upon a complicated mechanical structure which translates the rotational motion of the rotary switch in corresponding translational motions and directions of the corresponding coupling elements. 
         [0008]    A disadvantage of such a configuration of an electrical tool consists in the switching slider being formed by a complex component or arrangement. Moreover, the additional component requires a certain amount of space. in the housing and renders more complicated the manufacture of the electrical tool. 
       SUMMARY OF THE INVENTION 
       [0009]    It is an object of the present invention to design an electrical tool of the above-mentioned technical field, comprising a straight-forward mechanism for actuating the coupling and allowing a simple locking of at least one of the driven members. 
         [0010]    A solution to one or more of the above problems is provided by the features of the claimed electrical tools. According to embodiments of the present invention, the actuating element comprises a transmission means stationary with respect to the actuating elements and which is directly contactable with the corresponding coupling sleeve for actuation thereof. The transmission means is, thus, an element fixedly installed on the actuating elements and acting immediately, that is without additional diverting or guiding mechanisms, onto the coupling sleeve. In such a configuration of the actuating element, in which a transmission means comprising the above features is provided, a complicated structure of the switching slider or similar components may be dispensed with. By omitting such a component, the entire electrical tool may be constructed in a simpler manner and the housing may be made slimmer. 
         [0011]    Moreover, there is no further need for a guiding rail or other guiding element for the switching slider, and the electrical tool is operatively more secure in the direct transmission of the actuation of the gear switching mechanism on the coupling sleeve as compared to an electrical tool having a switching slider. In a corresponding configuration of the actuating element it is further possible to implement the actuating element as mechanical rotary switch so that the operability of the electrical tool in comparison to common electrical tools is maintained. 
         [0012]    Preferably, the coupling sleeves are supported in an axially displaceable manner on the drive shaft. In such an embodiment, an additional guide for each of the coupling sleeves can be dispensed with. Moreover, the coupling sleeves, which are supported on the drive shaft in an axially displaceable manner, on the one hand allow a simpler force transmission by means of a direct coupling between the coupling sleeves and the drive shaft, and on the other hand this coupling can also be easily interrupted by an axial displacement relative to the drive shaft. The coupling mechanism between the drive shaft and the corresponding driven member by means of the coupling sleeve is, thus, particularly easy to realize with a correspondingly supported coupling sleeve. 
         [0013]    Advantageously, the driven members are supported on the drive shaft in a free-wheeling manner so that the drive shaft can move independently of and is surrounded by the driven members. Moreover, in this way it is particularly straight-forward to allow the flow of force to arise between the coupling sleeves and the driven members if also the coupling sleeves are supported on the drive shaft. 
         [0014]    Preferably, the coupling sleeves are formed for creating a form-fit operative connection (e.g., an interlocking connection) between the drive shaft and the driven members. Thus, a particularly secure and low-wear force transmission between the drive shaft and the individual driven member is ensured. Alternatively, it is also possible for the coupling sleeves to create a force-fit connection (e.g., a friction connection) between the drive shaft and the individual driven member. In the preferred embodiments, the flow of force runs, however, both from the drive shaft to the coupling sleeve and from the coupling sleeve to the individual driven member by means of form-fit. This force transmission is particularly low-wear. 
         [0015]    In a further preferred embodiment, the coupling sleeves are loaded in the direction of a respective first position, in which the drive shaft and the individual driven member are operatively connected to each other, preferably by a spring load, wherein the respective first positions are preferably axially opposite to each other. In this preferred embodiment a spring load, for example, thus acts upon each of the coupling sleeves and presses these in a direction of the coupled position in which the drive shaft is coupled with the individual driven elements. This means that a force opposed to the load has to be applied to the coupling sleeves to be operated by means of the actuating element and via the transmission means. Thus, in this preferred embodiment, a decoupling of the coupling sleeve is caused by the actuating element, which otherwise would always remain coupled due to the load. In the particularly preferred embodiment, in which the respective first positions of the coupling sleeve are axially opposite to each other, a single spring member extending between the coupling sleeves may be used for loading both coupling sleeves. In this case, each of the coupling sleeves is supported against the other one of the coupling sleeves by the spring member. Consequently, this results in a further simplification of the housing as no separate stopper for the spring member needs to be present. 
         [0016]    Further it is preferred that the coupling sleeves are each positionable, via the transmission means through the actuation elements, in a second position in which the drive shaft and the corresponding driven member are not operatively connected. In this preferred embodiment, the coupling sleeve may thus each be brought into a position by means of the actuating element so that the coupling sleeve interrupts the flow of force between the drive shaft and the corresponding driven member. This second position in which the corresponding driven member is thus decoupled may in a particularly preferred manner be occupied by shifting a first coupling sleeve in direction of the second coupling sleeve. 
         [0017]    Preferably, the transmission means may selectively be brought in direct contact with one of the coupling sleeves. For example, this may be rendered possible by having a single transmission means in a first position directly contact the first coupling sleeve and, in a second position, be in direct contact with the second coupling sleeve. To that end, the coupling means may, for example, establish a sliding contact with the corresponding coupling sleeve. Thereby, the coupling sleeve can be displaced in a first direction by means of the transmission means, and may be displaceable relative to the transmission means in a second direction not parallel to the first one. In particular it is possible that the coupling sleeve rotates relative to the transmission means. A direct contact of the transmission means with the coupling sleeve may for example be already achieved by directly abutting the transmission means to the corresponding coupling sleeve. 
         [0018]    In a preferred embodiment, the transmission means is formed by at least one projection, preferably two projections, wherein the projection preferably extends in a direction parallel to the rotational axis of the actuating element. Such a projection is a particularly simple embodiment of a transmission means, wherein the projection advantageously extends on the rotatable mechanic actuating element over an arc of an angle range of at least 45°, or in the preferred case of two projections, a first projection is attached at a first angle portion of the actuating element and a second projection is attached at a second angle portion of the actuating element, wherein the second angle portion is angularly distanced from the first angle portion by at least 45°. In the preferred case of forming the transmission means by two projections, each of the two projections can be brought into contact with one of the coupling sleeves and, thus, the path around which the mechanical actuating element rotates in order to contact a respective coupling sleeve is shortened. Advantageously, the projection extends in a direction parallel to the rotational axis of the actuating element so that upon operating the actuating element it is moved in constant alignment around the rotational axis of the actuating element. 
         [0019]    Preferably, the projection is formed by a pin which, in a particularly preferred manner, is integrally formed with the actuating element. A pin in the actuating element is a particularly simple embodiment of the projection, but alternatively an elongated arc portion may be provided as continuous projection, too. If the projection is realized by a pin, this may be connected with the actuating element in a particularly simple manner. A separate pin, for instance made of metal, may very preferably be incorporated into a corresponding actuating element, for example pressed, screwed or otherwise fitted therein. In contrast, in the case of an integral (unitary) implementation of the projection with the actuating element, there is the advantage that the number of parts to be used is reduced and the production effort as well as the associated costs may further be reduced. However, it is to be observed that due to the high frictional force between the projection and the coupling sleeve a heat-resistant implementation of both components is important in order to avoid rapid wear of these elements. 
         [0020]    At least one of the driven members is, according to the invention, lockable against a rotational motion by means of a locking device. If the respective driven member is decoupled from the motion of the drive shaft by means of the actuating element, it is possibly not desired that the decoupled driven member may freely move around its rotational axis. In order to restrict such a movement, the locking device is provided which locks the driven member against rotational motion. The locking device is utilized in the above-mentioned case in which the driven member is decoupled from the motion of the drive shaft. 
         [0021]    Preferably, the actuating element is formed so as to select from three different coupling states between the drive shaft and the two driven members. The three different coupling states may consist in that, on the one hand, only the first driven member is driven by the drive shaft, further that only the second member is driven by the drive shaft, and moreover that both driven members are concurrently driven by the drive shaft. However, it is also conceivable that the actuating element may be utilized for choosing only two different coupling states. 
         [0022]    Preferably, the rotational axis of the actuating element runs substantially in parallel to the radial axis of the drive shaft. By this alignment of the rotational axis of the actuating element a particularly space-saving and efficient combination of the actuating element with the transmission means and the coupling sleeves to be contacted is possible. Here, it is preferred that the rotational axis of the actuating element is not exactly situated on a radial axis of the drive shaft but is displaced running in parallel thereto. The precision of the parallelism between the rotational axis of the actuating element and the respective radial axis of the drive shaft may be in a range of ±10°. 
         [0023]    In a preferred embodiment in which the projection extends in parallel to the rotational axis of the actuating element, the projection further extends in one of the contact positions with one of the coupling sleeves substantially along an axis running radially with respect to the drive shaft. In such an embodiment and in this state, the projection of the actuating element occupying one of the contact positions is situated on an axis running radially with respect to the drive shaft. This arrangement of the projection allows for a particularly advantageous actuation of the respective coupling sleeve by means of the projection of the actuating element. The precision of alignment of the projection with respect to the axis running radially with respect to the drive shaft may also be in a range of ±10°, wherein the position of the projection with respect to the axis running radially to the drive shaft has to be maintained with a precision of two diameters of the projection on both sides of the axis, respectively. 
         [0024]    Advantageously, the driven members are a countershaft (layshaft) gear and a tumble drive. 
         [0025]    Preferably, the actuating element alternatively switches between a first state in which the electrical tool performs a rotational motion of the countershaft gear, and a second state in which the electrical tool performs a motion of the tumble drive, wherein the countershaft gear is rotationally fixed, and a third state in which the electrical tool performs a simultaneous motion of the countershaft gear and the tumble drive. Here, it is not necessary that the countershaft gear is rotationally fixed. In the second state, it can also rotate freely. However, it is preferred that the countershaft gear is rotationally fixed in this state. 
         [0026]    In the electrical tool according to embodiments of the invention, the mechanical actuating element is in contrast to an electronic actuating device. However, it is also possible that a mechanical actuating element having the inventive features is moved by means of an electronic actuating device. However, it is preferred that the actuating element is actuated directly, that is immediately by hand, by a user. The actuation of the coupling sleeves by means of the mechanical actuating element means that each of the couplings is decoupled upon actuation. In the not actuated state each of the couplings ensures a flow of force from the drive shaft to the respective driven member; this flow of force is only interrupted upon actuation. The property of the transmission means to be stationary with respect to the actuating elements means in particular that the transmission means is fixed on the actuating element. As an example for a corresponding transmission means a pin fitted into the actuating element is mentioned, although other elements may be suitable as transmission means, too. The central feature of the transmission means to be directly, that is immediately, contactable with the respective coupling sleeve for actuating a coupling sleeve, means that there is no rodding (linkage), deflecting (bypass) element or similar intermediate elements such as guides etc. between the transmission means situated stationary on the actuating element and the respective coupling sleeve. Rather, the transmission means directly contacts the respective coupling sleeve. 
         [0027]    Apart from the mentioned form-fit operative connection between the drive shaft and the driven members, a (partial) force-fit operative connection between the mentioned elements is possible, too. It is also conceivable that only one power transmission at the respective coupling sleeve is effected by force-fit, and the other power transmission occurs by form-fit. For example, the power transmission between the drive shaft and the respective coupling sleeve may be effected by a form-fit connection and, simultaneously, the power transmission between the coupling sleeve and the respective driven member may be effected by force-fit. 
         [0028]    The circumstance, that the transmission means is selectively contactable directly with one of the coupling sleeves means that the transmission means may be brought into contact with the first, the second or none of the two coupling sleeves. Thus, there is no fixed contact between the transmission means an one or both of the coupling sleeves, but the transmission means contacts the respective coupling sleeve in the case of actuation and disengages completely therefrom if the coupling sleeve has to establish a force-fit between the drive shaft and the respective driven member. 
         [0029]    As described above, due to the creation of high temperatures caused by the possibly large frictional heat between a coupling sleeve and the transmission means, care should be taken to manufacture the transmission means from a temperature-resistant material. In particular, a metal or a temperature-resistant plastic may serve this purpose. The latter is to be utilized in particular in the preferred embodiment in which, as the transmission means, the projection is integrally formed with the actuating element. 
         [0030]    Regarding the coupling sleeves it is to be observed that they advantageously comprise a surface which the transmission means of the actuating element may come in contact with. Preferably, this contact surface is directly contactable from a housing-side direction of the electrical tool. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0031]      FIG. 1  shows a section of a gear switcher of an electrical tool in a preferred embodiment of the present invention, seen in a side sectional view. 
           [0032]      FIG. 2  shows a sectional view of the preferred electrical tool, wherein the section is made perpendicular to the alignment of the electrical tool along the sectional plane S 1  and is shown from behind, along the drive shaft. 
           [0033]      FIG. 3  shows a side sectional view of the electrical tool in a state in which the drive shaft is coupled with both driven members. 
           [0034]      FIG. 4  shows a top sectional view along the sectional plane S 2  of the electrical tool of  FIG. 3 . 
           [0035]      FIG. 5  shows the electrical tool of  FIG. 3  in a side sectional view, wherein a flow of force between the drive shaft and a tumble drive is interrupted. 
           [0036]      FIG. 6  shows the electrical tool of  FIG. 5  in a top sectional view along sectional plane S 2 . 
           [0037]      FIG. 7  shows the electrical tools of  FIGS. 3 and 5  in a side sectional view, wherein a flow of force between the drive shaft and a counter shaft is interrupted. 
           [0038]      FIG. 8  shows a top sectional tool along sectional plane S 2  of the electrical tool of  FIG. 7 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0039]      FIG. 1  shows a gear shift mechanism in a preferred embodiment of an electrical tool according to the present invention in a side sectional view. A tumble drive hub  16 , a countershaft gear  14 , a first coupling sleeve  18  and a second coupling sleeve  20  are free-wheelingly supported on a horizontally arranged drive shaft  12 . The two coupling sleeves  18 ,  20  are pressed apart and into engagement with the countershaft gear  14  and the tumble drive hub  16 , respectively, by means of a biasing member, such as a helical spring  28 . The helical spring  28  is free-wheelingly supported on the drive shaft  12  between the two coupling sleeves  18 ,  20 . 
         [0040]    Thus, the spring  28  engages the coupling sleeves  18 ,  20  and applies a force to the sleeves  18 ,  20  in opposite directions. In contrast to the countershaft gear  14  and the tumble drive hub  16 , the coupling sleeves  18 ,  20  are form-fittingly connected to the drive shaft  12  through a splined connection or pinion contour  30 ,  32  of the drive shaft  12 . A rotation of the drive shaft  12  thus directly leads to a rotation of both coupling sleeves  18 ,  20 .  FIG. 1  shows a state in which the coupling sleeves  18 ,  20  are, moreover, in form-fitting engagement with the countershaft gear  14  and the tumble drive hub  16 , respectively. 
         [0041]    In this state, in which the coupling sleeves  18 ,  20  are pressed by the helical spring  28 , a rotation of the drive shaft  12  simultaneously leads to a rotation of the countershaft gear  14  and the tumble drive hub  16 , too. An outer ring having a radially extending journal  34  is supported via a ball-bearing  36  on the tumble drive hub  16 . 
         [0042]    Upon rotation of the tumble drive hub  16 , the journal  34  of the tumble drive, which is arranged in a linear guide, is moved backward and forward and effects an impact motion onto a tool clamped within a drill spindle  44  ( FIG. 3 ,  5 ,  7 ). The countershaft gear  14  is rotationally coupled with the drill spindle  44  of the electrical tool  10  so that a rotation of the drive shaft  12  transferred to the countershaft gear  14  by means of the coupling sleeve  18  results in a rotation of the drill spindle  44 . 
         [0043]      FIG. 2  shows a further sectional view of the electrical tool according to the preferred embodiment of  FIG. 1 . The section is made perpendicular to the drive shaft  12  at the height of the coupling sleeve  20  along the sectional plane S 1 , and is illustrated as a projection from behind, that is from the coupling sleeve  20  in direction of the coupling sleeve  18 . Apart from the drive shaft  12  and the coupling sleeve  20 , in this sectional view of the electrical tool  10 , a stationary gear  26  can be seen which engages the countershaft gear  14  and transmits the rotational motion of the countershaft gear  14  onto the drill spindle  44 . 
         [0044]    This stationary gear  26  surrounds an axis Ax 1  ( FIG. 3 ,  5 ,  7 ) along which also the impact motion of the tumble drive is transmitted via an impact cylinder  40  to the tool chucked in the drill spindle  44 , and around which the drill spindle  44  rotates. Moreover,  FIG. 2  shows an actuating element  22  present in form of a rotary switch. 
         [0045]    The rotary switch  22  comprises two pins  24 . 1 ,  24 . 2  which can be brought into contact with respective ones of the coupling sleeves  18 ,  20 . In the state of the rotary switch  22  shown in  FIG. 2 , the first pin  24 . 1  is in contact with the coupling sleeve  20  by hitting against the overhanging region of the coupling sleeve  20  in a direction of the drive shaft  12  and thus displacing the coupling sleeve  20  along the drive shaft  12 . The overhanging region of the coupling sleeve  20  is realized in rotational symmetry around the drive shaft  12  and constitutes a contact surface for pin  24 . 1 . Due to the annular shape of the contact surface of the coupling sleeve  20 , the coupling sleeve  20  can also rotate around drive shaft  12  without changing the contact between pin  24 . 1  and coupling sleeve  20 . 
         [0046]    The pin  24 . 1  is arranged and aligned such that it projects in a direction substantially parallel to rotational axis Ax 2  of the rotary switch  22  and defines an axis Ax 3 . 1  running substantially radially to the drive shaft  12 . The same is true for the second pin  24 . 2 , wherein the axis Ax 3 . 2  defined by this pin is radially arranged to the drive shaft  12  only in a state of engagement with the coupling sleeve  18 , not shown in  FIG. 2 . In the state shown in  FIG. 2 , the axis Ax 3 . 2  runs in parallel to the rotational axis Ax 2  of rotary switch  22  and the axis Ax 3 . 1  defined by the first pin. The pins  24 . 1  and  24 . 2  together operate as a transmission portion of the rotary switch  22 . That is, the pins  24 . 1  and  24 . 2  are configured to contact the sleeves  18 ,  20  and selectively move the sleeves  18 ,  20  to a desired position. Suitable alternative structures to the pins  24 . 1  and  24 . 2  can also be used to contact the sleeves  18 ,  20 , as well. 
         [0047]      FIG. 3  shows a side sectional view of the electrical tool of  FIGS. 1 and 2 . The shifting gear of  FIG. 1  can be seen in the lower part of the electrical tool. The shifting gear is in the same state as  FIG. 1  so that a detailed description of the elements used is unnecessary here. In addition to  FIG. 1 ,  FIG. 3  shows a further flow of force from the tumble drive hub  16  and the countershaft gear  14 , respectively. 
         [0048]    Further, a locking plate  38  can be seen which, however, does not serve a locking function in the state shown in  FIG. 3 . In the state shown in  FIG. 3 , the drive shaft  12  serves both for driving the tumble drive hub  16  and for driving the countershaft gear  14 . Upon its rotation, the tumble drive hub  16  causes a forward and backward impact motion of the tumble drive journal  34 , which is supported on the tumble drive hub  16  via ball bearing  36  and is guided in a linear guide running parallel to the drive shaft  12 . The forward and backward motion of journal  34  is propagated to an impact cylinder  40  guided in an impact guide, wherein the impact guide extends in a direction parallel to drive axis  12  along axis Ax 1 . Upon forward motion of the tumble drive journal  34  the impact cylinder  40  hits upon a snap die  42  which in turn transmits the impact force onto a tool chucked within a drill spindle  44 . 
         [0049]    In parallel to this impact motion of the tumble drive journal  34 , the impact cylinder  40  and the snap die  42 , the rotation of the drive shaft  12  leads to a rotation of the countershaft gear  14  which engages the stationary gear  26 . The stationary gear  26  surrounds an impact axis Ax 1  of the electrical tool  10  and the impact cylinder  40  and snap die  42  arranged therein. The drill spindle  44  is wedged with the stationary gear  26  so that the rotational motion of the gear  26  also rotates the drill spindle  44  and the tool chucked therein, independent from the tool in the drill spindle  44  being acted upon by the impact cylinder  40  and the snap die  42 . 
         [0050]    The state of the electrical tool  10  shown in  FIG. 3  thus corresponds to the combined drill and chisel operation of the electrical tool  10  in which a tool chucked within the drill spindle  44  is, on the one hand, driven to perform a drill motion and, on the other hand, acted upon by impact forces from behind. 
         [0051]      FIG. 4  shows a further sectional view along a sectional plane S 2  in  FIG. 3 . Thus, a top view of a sectional representation is shown, wherein the section runs along the drive shaft  12 . Just as in  FIGS. 1 and 3 , the drive shaft  12 , the countershaft gear  14 , the tumble drive hub  16  and the coupling sleeves  18  and  20  are shown in  FIG. 4 , too. In addition to what is illustrated in  FIG. 3 ,  FIG. 4  shows the rotary switch  22  already shown in  FIG. 2 . 
         [0052]    The rotary switch  22  is provided with two pins  24 . 1 ,  24 . 2  which are both disengaged from the respective coupling sleeves  20 ,  18 . In the state of the electrical tool  10  illustrated in  FIGS. 3 and 4 , the coupling sleeves  18 ,  20  are also engaged with their corresponding driven member, the countershaft gear  14  and the tumble drive hub  16 , respectively, since none of the pins  24 . 1 ,  24 . 2  of the rotary switch  22  is in contact with one of the coupling sleeves  18 ,  20  and contrasts the force acting upon coupling sleeves  18 ,  20 .  FIG. 4  thus shows the position of the rotary switch  22 , which allows a combined drill and chiselling operation of the electrical tool  10 . 
         [0053]      FIG. 5  shows the view of  FIG. 3  of the electrical tool  10  according to the preferred embodiment of the invention. In contrast to  FIG. 3  however,  FIG. 5  shows a state in which the coupling sleeve  20  provided for transmitting the drive force of the drive shaft  12  onto the tumble drive hub  16  is decoupled. In the state illustrated in  FIG. 5 , the coupling sleeve  20  is displaced to the left, in a direction towards the coupling sleeve  18 . 
         [0054]    In this way, the coupling sleeve  20  is still in form-fitting connection with the drive shaft  12 , but the tumble drive hub  16  is not connected with the coupling sleeve  20  and thus lies free-wheelingly on the drive shaft  12 . This means that the rotation of the drive shaft  12  results in a rotational motion of the countershaft gear  14  and, thus, the stationary gear  26  and the drill spindle  44 ; but apart from this motion employed for the drill operation of the electrical tool  10 , no impact motion of the tumble drive journal  34 , the impact cylinder  40  and the snap die  42  is effected. If the coupling sleeve  20  is decoupled, the electrical tool  10  is thus in a pure drill mode without simultaneously performing a chiselling function. 
         [0055]      FIG. 6  corresponds to the view of  FIG. 4  of the electrical tool  10 , in a state as shown in  FIG. 5 . It can be clearly seen that the rotary switch  22  acts onto the coupling sleeve  20  through pin  24 . 1  which is fixed on the rotary switch  22 . Here, the second pin  24 . 2  of the rotary switch  22  is not in engagement with the coupling sleeve  18  so that the force transmission between the drive shaft  12  and the countershaft gear  14  via coupling sleeve  18  is ensured. The state of the electrical tool shown in  FIGS. 5 and 6  corresponds to a rotation of rotary switch  22  from the combined drill and chiselling position by 90° to the right and, thus, deactivates the chiselling function of the electrical tool. 
         [0056]      FIG. 7  shows the electrical tool  10  in the same view as  FIGS. 3 and 5 , but in a state in which the coupling sleeve  20  is in engagement with the tumble drive hub  16 , but the coupling sleeve  18  is disengaged from the countershaft gear  14 . In the state illustrated in  FIG. 7 , the coupling sleeve  18  is displaced to the right, in a direction towards the coupling sleeve  20 . 
         [0057]    In this way, the coupling sleeve  18  is still form-fittingly connected with the drive shaft  12 , but the countershaft gear  14  is not connected with the coupling sleeve  18  and is, thus, arranged free-wheelingly on the drive shaft  12 . Moreover, in the state of the electrical tool  10  shown in  FIG. 7 , the locking plate  38  is in engagement with the countershaft gear  14  in order to lock it. The locking plate  38  is acted upon by a biasing member such as a spring (not shown) in direction of the coupling sleeve  20 . 
         [0058]    The locking plate constitutes a third coupling element in analogy to the two coupling sleeves  18  and  20 . Thus, by means of the actuating element  22 , three coupling elements  18 ,  20  and  38  are brought directly into engagement, without a further intermediate switching element, in order to realize the three operating modes of the electrical tool. 
         [0059]    The rotary switch  22 , not shown in  FIG. 7 , keeps the locking plate  38  disengaged from the countershaft gear  14 , both in the combined drill and chiselling operating mode and in the pure drill mode of the electrical tool, and allows a locking of the countershaft gear  14  only in the case of decoupling the coupling sleeve  18 . In the case of this decoupling of the coupling sleeve  18 , the countershaft gear  14  is decoupled from the rotational motion of the drive shaft  12  so that the drive shaft  12  is rotatable independently of the locking of the countershaft gear  14 . By locking the countershaft gear  14  through the locking plate  38 , a rotation of the drill spindle  44  is prevented, too, so that a tool chucked within the drill spindle  44  cannot be rotated around axis Ax 1 . However,  FIG. 7  also shows that the coupling sleeve  20  is engaged with tumble drive hub  16 . Thus, in the state of the electrical tool  10  shown in  FIG. 7 , the tumble drive operation is effected by means of tumble drive hub  16 , ball-bearing  36  and tumble drive journal  34  and results in an impact motion of the impact cylinder  40  and the snap die  42  onto the tool chucked within drill spindle  44 . Consequently,  FIG. 7  shows a pure chiselling mode of the electrical tool  10 . 
         [0060]    Similarly, in  FIG. 8  which corresponds to the view of  FIGS. 4 and 6 , a rotary switch  22  is shown, the second pin  24 . 2  of which is in contact with coupling sleeve  18 . In analogy to the state of the electrical tool  10  shown in  FIG. 6 , the coupling sleeve  18  is disengaged from the countershaft gear  14  by the contact between pin  24 . 2  and the overhanging portion of the coupling sleeve  18 . Here, coupling sleeve  20  is not contacted by pin  24 . 1  of rotary knob  22  and is, thus, in engagement with tumble drive hub  16 . 
         [0061]    Apart from the embodiment shown in  FIGS. 1 through 8 , an electrical tool is conceivable, which merely comprises one coupling sleeve. In this case it is sufficient if the rotary switch  22  comprises a single pin which is contactable with the coupling sleeve. Besides, in an embodiment of the electrical tool having two coupling sleeves, it is also possible to provide merely one projection instead of two pins  24 . 1 ,  24 . 2 , which extends between the two positions of pins  24 . 1 ,  24 . 2 . 
         [0062]    As can be seen in  FIGS. 4 ,  6  and  8 , the rotary switch  22  is implemented as a substantially circular element which has a grip portion on its outwardly directed part for rotating the rotary switch. The two pins  24 . 1 ,  24 . 2  are provided on the inwardly projecting part of the rotary switch  22  on its innermost surface. 
         [0063]    In the embodiment illustrated here, these pins are fitted into the body of the rotary switch  22 . In contrast and preferably, it is also possible to form the pins  24 . 1 ,  24 . 2  integrally with the rotary switch  22 . Moreover, the inward facing part of the rotary switch  22  has a substantially cylindrical form, wherein a part of the cylindrical portion is cut away in the shape of a secant. In this way, a flat contact surface is created which is formed on a side of the inwardly protruding part of the rotary knob  22 . In this angle range, the peripheral surface of the inwardly projecting part of the rotary switch  22  does not have the form of a cylinder barrel but is planar. In the state of the electrical tool shown in  FIGS. 7 and 8 , that is upon decoupling the coupling sleeve  18 , this planar surface faces the locking plate  38  such that this locking plate  38  acted upon by a spring force is displaceable to the right, that is in direction of coupling sleeves  18  and  20 , since the locking plate  38  would otherwise abut against the cylinder barrel-shaped part of the rotary switch  22 , not present in the angle range of the secant-shaped plane. In this way, it is ensured that an engagement of the locking plate  38  with the countershaft gear  14  only occurs in the decoupled state of the countershaft gear  14 .