This application claims priority under 35 U.S.C. §119 to German patent application no. DE 10 2011 078 082.3, filed Jun. 27, 2011 in Germany, the disclosure of which is incorporated herein by reference in its entirety.
The disclosure relates to a handheld power tool, in particular to a power drill or screwdriver, e.g. a battery-operated drill or screwdriver.
U.S. Pat. No. 5,557,990 describes a battery-operated screwdriver having an electric drive motor, which drives a tool holder for holding a tool. The battery-operated screwdriver has a push-start mechanism for switching on the drive motor automatically as soon as the tool held in the tool holder is placed with pressure on the screw to be screwed in or unscrewed and the tool holder is moved axially backward into the housing. During this process, a radially projecting actuating element is moved axially by the tool holder and pressed against a microswitch, which switches the electric motor on and off.
The tool holder is urged into its initial position by the force of a spring element, with the result that the tool holder returns to its initial position as soon as the screwdriver is removed from the screw.
It is the underlying object of the disclosure to provide a handheld power tool, such as a power drill or screwdriver, with a starting mechanism of structurally simple design which is intuitive to operate.
According to the disclosure, this object is achieved by the features set forth below. Expedient developments are also set forth below.
The handheld power tool, which is preferably a power drill or screwdriver, in particular a battery-operated screwdriver, has a tool holder for holding a tool, and a grip housing for holding and guiding the handheld power tool. A relative motion of the tool holder and the grip housing is possible and this can be transmitted as a switching motion to a microswitch, by means of which a drive unit can be switched on and off The drive unit is preferably an electric drive motor, which is accommodated in a housing of the handheld power tool. In the case of a battery-operated screwdriver, the electric drive motor is supplied with power by a battery, which is likewise accommodated in the housing of the handheld power tool. Generally, the housing furthermore also contains an electronic system for controlling the drive motor.
The relative motion of the tool holder and the grip housing comprises a relative rotary motion. The grip housing can be twisted relative to the tool holder or to a component connected to the tool holder about the longitudinal axis of the housing, which coincides, in particular, with the tool holder axis; this rotary motion is part of the switching motion for switching the microswitch on and off.
According to an expedient embodiment, the relative motion of the tool holder and the grip housing is made up of an axial component and of a component in a direction of rotation, in each case in relation to the longitudinal axis of the handheld power tool or tool holder axis, along which or about which the relative motion takes place. The switching motion for switching the drive unit on and off by means of the microswitch is thus also made up of the two component motions, namely the motion in an axial direction and the motion in a direction of rotation.
The combination of an axial and a rotary actuating motion allows the drive unit to be switched on in an intuitive manner since, after the tool held in the tool holder has been placed on the workpiece or screw to be worked upon, the grip housing is twisted relative to the tool holder in a direction of rotation by actuating the grip housing, and the axial spacing of the grip housing relative to the tool holder is shortened. By means of the rotation, the direction of rotation of the drive motor can be specified, while the axial motion switches the microswitch on and off. According to a preferred embodiment, the direction of rotation of the drive motor coincides with the direction of rotation of the grip housing, and therefore the rotary motion of the grip sleeve to the right or to the left also determines the direction of rotation of the drive motor in the corresponding direction.
When the electric drive motor is switched on, the two-part actuating motion is advantageously carried out in a predetermined order. First of all, the grip housing is twisted in order to specify the direction of rotation of the drive motor. However, the direction of rotation alone does not start the drive motor. The grip housing is then pushed forwards axially, thus shortening the axial spacing between the grip housing and the tool holder; the axial forward motion starts the drive motor in the desired direction of rotation by acting upon the microswitch. When switching off, the actuating motion of the grip housing takes place in a corresponding manner in the opposite direction.
In principle, a switching on motion in the reverse order is also possible, so that the grip housing is pushed forwards axially first and then moved in a direction of rotation. Moreover, superimposed axial and rotary actuating motions may also be considered.
This embodiment of the handheld power tool has the advantage that neither a sensor device for detecting the relative motion of the handle nor an ON/OFF switch on the housing of the handheld power tool is required to switch the drive motor on and off. Only the relative motion of the grip housing and the tool holder is responsible for switching the drive motor on and off and for specifying the direction of rotation of the drive motor.
In order to be able to produce both anticlockwise rotation and clockwise rotation of the tool holder through appropriate activation of the drive unit, it is expedient if, in relation to a neutral or initial position, the grip housing can be moved in opposite directions of rotation relative to the tool holder. The neutral position can be produced by means of a spring element, which urges the grip housing into the neutral position. In principle, an embodiment in which a spring element urging the grip housing in the direction of rotation is dispensed with, is also possible, ensuring that the grip housing remains in its twisted position even without intervention by the user.
It is advantageous if a spring element which urges the grip housing into the neutral or initial position in an axial direction is provided. The spring element counteracts the forward motion of the grip housing relative to the tool holder, with the result that the grip housing is moved back axially into its neutral or initial position by the force of the spring element as soon as the user is no longer applying any forward-acting force on the grip housing. During this axial return motion, the microswitch is switched off.
It is advantageous if the tool holder is held on an inner shell, which houses the drive unit and with respect to which the grip housing can perform the relative motion. The inner shell is at least partially surrounded by the grip housing.
According to another expedient embodiment, a latching element, which, in the driving position, is in engagement with a mating latching element, which is arranged on the tool holder or a component connected to the tool holder, is arranged on the grip housing. The latching element on the grip housing is designed as a pin on the inside of the grip housing, for example. The mating latching element on the tool holder or on the component connected thereto—generally the inner shell—is embodied in a corresponding manner as a groove, into which the pin can be engaged in the driving position. The latching engagement of the latching elements ensures that, in the driving position with the drive motor running, the grip housing is not inadvertently moved into a position in which the drive motor is unintentionally switched off or set to the opposite direction of running. The latching element and the mating latching element are accordingly embodied in such a way that inadvertent twisting of the grip housing and the tool holder relative to one another is prevented in the driving position. The groove on the component connected to the tool holder extends in an axial direction.
During a switch-on motion involving the twisting of the grip housing followed by an axial forward motion of the grip housing, the pin is, after the twisting motion, initially moved into the position in which axial entry of the pin into the groove is possible. With the axial forward motion that follows the twisting motion, the pin enters the groove, thus securing the relative twist of the grip housing and preventing the grip housing from accidentally leaving this rotational position.
The relative twist of the grip housing preferably ranges over a limited angular segment of, for example, plus/minus 10° in relation to the neutral or initial position.
Further advantages and expedient embodiments can be found below, the description of the figures and the drawings, in which:
In the figures, identical components are provided with identical reference signs.
As can be seen from the illustration in
In relation to the longitudinal axis 6 of the handheld power tool 1, which coincides with the tool holder axis, the grip housing 5 can perform a relative rotary motion in direction of rotation 7 and a relative axial movement in axial direction 8 with respect to the inner shell 4, including the tool holder 2. The relative motion of the grip housing 5 with respect to the inner shell 4 can be used as a switching motion for actuating a microswitch, by means of which the electric drive motor can be switched on and off.
As can be seen from the longitudinal section in
Mounted on the circumferential surface of the inner shell 4 is a spring element 12 in the form of a helical spring, which is held under preload between ribs on the circumferential surface of the inner shell 4. The spring element 12 urges the grip housing 5 into a neutral or initial position in an axial direction. If the grip housing 5 is moved axially towards the inner shell 4 or tool holder 2, as indicated in arrow direction 8 in
As can be seen from the sectional representation in
As can be seen from the sectional representation in
The microswitches 16 and 17 are actuated by means of an actuating element 18, which is embodied as a leaf spring and is secured on the inside of the grip housing 5. During a relative rotary motion of the grip housing 5 with respect to the inner shell 4, the leaf spring 18 also moves relative to the inner shell 4 and hence also to the microswitches 16 and 17 mounted on the inner shell 4. Depending on the direction of rotation of the grip housing 5, one or the other end of the leaf spring 18 comes into contact with one of the microswitches 16 or 17 and switches it on, with the result that the drive motor too is put into operation. The ON state is illustrated in
The switch-on operation proceeds as follows:
First of all, the user specifies the direction of rotation in which the electric motor is to revolve by twisting the grip housing 5 about the longitudinal axis 6. With respect to an initial or neutral position, the grip housing 5 can be twisted over a limited angular range of, for example, plus/minus 10° in relation to the inner shell 4. The grip housing 5 is then moved axially towards the inner shell 4, as a result of which the relevant microswitch 16 or 17 is switched on by one end of the leaf spring 18, whereupon the motor begins to run in the desired direction of rotation. The axial setting motion takes place counter to the force of the spring element 12. With the axial motion, the latching pin 15 on the inside of the grip housing 5 enters one of grooves 13 and 14 on the outer circumference of the inner shell 4, each of the grooves 13 and 14 being assigned to one direction of rotation of the electric drive motor. This prevents the grip housing 5 from twisting in relation to the inner shell 4 during operation, something which could otherwise lead to accidental reversal of the direction of rotation of the drive motor.
On completion of the working process, a reduction in the holding force allows the grip housing 5 to return axially into the retracted position thereof by virtue of the action upon it of the spring element 12, thereby ensuring that the leaf spring 18 disengages from the respective microswitch 16 or 17 and the motor is switched off. Simultaneously with the axial return motion, the latching pin 15 disengages from the associated groove 13 or 14, thus allowing the grip housing 5 to then be twisted back in the direction of the initial or neutral position about the longitudinal axis.
Number | Date | Country | Kind |
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10 2011 078 082.3 | Jun 2011 | DE | national |