EP1632313B1 - Screwdriving tool with axially working hammering mechanism - Google Patents

Description

The invention relates to a screwdriver with a housing and a hollow spindle which is rotatably mounted in the housing and driven by a, in particular electric, motor. In addition, the screwdriver has a coupling which rotatably couples the hollow spindle in an engaged position with the motor, rotatably decoupled from the motor in a disconnected position and which is biased by a clutch spring into the disconnected position. A driving spindle is axially displaceable relative to the hollow spindle and rotatably mounted, wherein the driving spindle with a tool holder for attaching a tool rotationally coupled and the clutch can be moved by pressure on the drive spindle against the clutch spring in the engaged position. Furthermore, the screwing device has a striking mechanism, by means of which the driving spindle can be acted upon by a pulse-like axial force.

In screwdrivers of this type, the screwdriver can be impulsively displaced in the direction of insertion when screwing through the axial-striking mechanism. As a result, for example, a drywall screw when attaching soft material elements, such as plasterboard, are screwed to a metal frame after drilling through the soft material without stronger pressing the screwdriver into the hard metal frame. In this case, the axial forces generated by the Axialschlagmechanismus extend as far as possible pressing forces to screw the screw into the metal.

From the DE 100 32 949 is a screwdriver with an axial striking mechanism for generating pulse-like axial forces on a driving spindle according to the preamble of the independent claim 1 known. For this purpose, the driving spindle is held by spherical locking elements limited axially displaceable on the hollow spindle. The spherical locking elements are rotatably mounted in radial receiving bores of the hollow spindle and project permanently into axially aligned grooves on the surface of the driving spindle. To transmit the rotational movement, the drive-in spindle must be moved against the housing by pressing the screwdriver against the workpiece to be screwed against the screwing-in direction.

At a certain point, the hollow spindle is also displaced by the insertion spindle until a coupling part mounted on the hollow spindle engages with a housing-mounted coupling part.

This known procedure results in a compact screwdriving device, with which a good screwing quality can be achieved with reduced contact forces.

However, it may happen during operation of the known Schraubgerätes that generated by the Axialschlagmechanismus axial displacement of Eindrehspindel sufficient in the screwing to disconnect the clutch for a short time. On the one hand, this can result in lower work progress and, on the other hand, higher wear. In addition, the slidable mounting of the screw drive makes it difficult to attach and remove the tool on the tool holder as well as the placement of a screw on the tool.

The present invention has for its object to avoid in a screwdriver with Axialschlagmechanismus said disadvantages and to extend the lifetime with good handling.

According to the invention the object is achieved in that a locking mechanism is provided for locking the clutch, wherein the clutch can be locked in the engaged position. This makes it possible to keep the clutch largely independent of the position of the screw drive in engagement. Thus, a torque can be transmitted from the drive via the coupling and the hollow spindle on the driving spindle and the tool holder even with a disengaged in the screw-driving drive. In this way, a separation of the clutch due to the axial displacement of the screw drive by the Axialschlagmechanismus is avoided, which in turn reduces the wear of the clutch.

Advantageously, it is provided the locking mechanism in response to the position of the screw drive relative to the hollow spindle actuated. As a result, the locking mechanism can be automatically activated and deactivated in a simple manner.

Preferably, the coupling has a movable coupling part which can be fixed in the engaged position by means of the locking mechanism on the housing. In this way, the clutch can be kept particularly stable in the engaged position, whereby an unintentional adjustment is avoided in the disconnected position.

In a particularly preferred embodiment, the drive-in spindle can be fixed in the disconnected position by means of the locking mechanism in the axial direction on the hollow spindle. As a result, the driving spindle is fixed in the disconnected position of the coupling via the hollow spindle and the spring force of the coupling spring in the axial direction relative to the housing. In this way, attachment or detachment of a tool on the tool holder is substantially simplified, since the screw-in spindle can no longer move freely freely.

Advantageously, the locking mechanism has at least one locking body, which is displaceable in a radial transverse bore of the hollow spindle between an engagement position in which it partially protrudes into a longitudinal bore of the hollow spindle and a disengagement position in which it is positioned outside the longitudinal bore. As a result, a releasable engagement with the guided in the longitudinal bore Eindrehspindel can be produced at low production costs.

It is advantageous if the screw drive has a recess whose axial extent is matched to the engageable in the longitudinal bore part of the locking body. As a result, the drive-in spindle can be fixed in the axial direction substantially free of play relative to the hollow spindle.

It is advantageous if the recess is formed by an annular groove, whereby the manufacturing cost can be reduced.

Advantageously, the movable coupling part is firmly connected to the hollow spindle. In addition, an axial stop is formed on the housing, to which the locking body in the release position in the axial direction can be applied. As a result, the movable coupling part via the hollow spindle and the disengaged locking body against the spring force of the clutch spring are supported on the housing to hold the clutch stable in the engaged position.

Further, it is advantageous if the locking body is spherical, to allow by avoiding tilting a smooth change between the engagement and disengagement of the locking body.

Advantageously, the axial stop is formed by a guide sleeve having formed thereon, circumferential shoulder. This allows the axial stop separately from the housing especially hard material to extend the life of the screwdriver.

Fig. 1

eine teilweise geschnittene Ansicht eines vorderen Teils eines erfindungsgemässen Schraubgerätes vor einem Einschraubvorgang,

Fig. 2

eine teilweise geschnittene Ansicht des Schraubgerätes nach Fig. 1 während eines Einschraubvorganges bei Anlage an einem harten Werkstück und

Fig. 3

eine teilweise geschnittene Ansicht des Schraubgerätes nach Fig. 2 unmittelbar nach Durchdringen des harten Werkstückes.

The invention will be explained in more detail below with reference to an embodiment. Show it:

Fig. 1

a partially sectioned view of a front part of an inventive screwdriver before a screwing,

Fig. 2

a partially sectioned view of the screwdriver after Fig. 1 during a Einschraubvorganges when resting on a hard workpiece and

Fig. 3

a partially sectioned view of the screwdriver after Fig. 2 immediately after penetration of the hard workpiece.

Fig. 1 shows the working side part of an electrically operated, hand-held screwdriver 2, which has a housing 4. In the housing 4, a driving spindle 6 is slidably mounted along its axis A but rotatably mounted in a hollow spindle 8. On a driven-side end of the insertion spindle 6, a tool holder 10 is attached in the form of a bit holder, which serves for releasably receiving a tool 12, in particular in the form of screwdriver bits.

At a drive-side end of the driving spindle 6 facing away from the output-side end, the screwdriving device 2 has an impact mechanism designated as a whole by 14. This consists essentially of one of a schematically illustrated control unit 16 actuated electromagnet 18 and a striking mass 20 which is pressed by a return spring 22 in an initial position in which most of the impact mass 20 is disposed outside of the electromagnet 18.

In the axial extension of the driving spindle 6, the impact mass 20 has a hardened insert 24, via which the drive-side end of the insertion spindle 6 can be acted upon by a pulse-like axial force. For this purpose, a coil, not shown, of the electromagnet 18 is supplied by the control unit 16 for a predetermined period of time with a predetermined voltage. As a result of the resulting magnetic force, the magnetizable impact mass 20 is accelerated against the force of the return spring 22 in the direction of the insertion spindle 6. In this way, blows can be generated on the drive-side end of the insertion spindle 6, which cause this pulse-like acting axial impacts.

The control unit 16 may be formed, for example, as a switch or sensor-controlled electronics.

To generate a torque at the drive spindle 6, the screwdriver 2 has an electric motor 26, which is rotationally coupled in a manner not shown with a drive wheel 28 in the form of a toothed belt pulley. The drive wheel 28 is rotatably connected to a first coupling part 32 of a total of 30 designated coupling. The first coupling part 32 is rotatably mounted on the hollow spindle 8. A second coupling part 34 of the coupling 30 is freely rotatable and axially displaceable on the hollow spindle 8. A third coupling part 36 is fixedly connected to the hollow spindle 8.

The first coupling part 32 and the second coupling part 34 are biased by a first clutch spring 40 into an illustrated disconnected position in which cam-shaped first engagement means 38 formed thereon are spaced from each other. The second coupling part 34 and the third coupling part 36 are biased by a second clutch spring 44 in the release position in which cam-shaped second engagement means 42 formed thereon are spaced from each other.

By moving the hollow spindle 8, the clutch 30 can be brought into an engaged position, in which the engagement means 38, 42 are engaged, as explained later.

Further, a generally designated 46 locking mechanism is provided which has two spherical locking body 48 which are held radially movable in opposite radial transverse bores 50 of the hollow spindle 8.

In the in Fig. 1 illustrated initial position of the screwdriver 2 protrude the locking body 48 partially into a longitudinal bore 52 of the hollow spindle 8 and thereby engage in a matched to the shape of the locking body 48 groove-shaped recess 54 which is embedded in the surface of the drive spindle 6. On the side remote from the driving spindle 6 side, the locking body 48 are located on an inner side of a guide sleeve 55 which is fixedly connected to the housing 4 and which is penetrated by the hollow spindle 8. By the guide sleeve 55, the locking body 48 are held radially immovable in the engagement position shown with respect to the longitudinal bore 52.

As a result, the insertion spindle 6 is fixed in the axial direction via the locking body 48 to the hollow spindle 8, which in turn via the clutch springs 40, 44 and the coupling parts 34, 36 is pressed in the position shown on the housing 4. By this definition on the housing 4, the tool 12 can be easily attached to the tool holder 10 or detached from it.

Fig. 2 shows the screwdriver 2 when screwing a fastener 56 in the form of a drywall screw for mounting a soft component 58 in the form of a plasterboard to a hard component 60 in the form of a metal frame.

In the situation illustrated, the fastener 56, which is pressed against the hard component 60 by an operator (not shown) of the screwdriver 2, exerts a counter-pressure on the screw-in spindle 6 via the tool 12 and the tool holder 10. About a shaft shoulder 62, this back pressure is also delivered to the output side end of the hollow spindle 8 so that it is displaced together with the screw 6 relative to the housing 4 against a direction of insertion E. As a result, the clutch 30, as shown, changes to the engagement position, in which both the first engagement means 38 and the second engagement means 42 are engaged.

In addition, while the locking body 48 are displaced in the axial direction relative to the guide sleeve 55 fixed to the housing and are now at the level of expansion 66 of the guide sleeve 55. In the region of this expansion 66 gives the guide sleeve 55, the locking body 48 a radial play between the inside of the guide sleeve 55 and the Recess 54.

At the same time, the drive-side end of the insertion spindle 6 is displaced into a hammering space 64 formed by the electromagnet 18. Upon activation of the impact mechanism 14, the hardened insert 24 thus encounters the driving spindle 6 protruding into the striking space 64, whereby it is acted upon in the insertion direction E by a pulse-like axial force which drives the fastening means 56 through the hard component 60, as in FIG Fig. 3 shown.

How out Fig. 3 Further, the locking body 48 are moved out of the recess 54 and moved into a disengaged position by the displacement of the drive spindle 6 relative to the hollow spindle 8, in which they no longer protrude into the longitudinal bore 52. Rather, the locking body 48 are now in the region of the expansion 66 on the inside of the guide sleeve 55 at. Thus, there is now between the drive spindle 6 and the hollow spindle 8 only acting in the direction of rotation positive engagement, while the axial positive engagement is canceled.

At the same time the locking body 48 are in the disengaged position in the axial direction of a circumferential shoulder 68 of the guide sleeve 55, which limits the expansion 66 in the axial direction. As a result, the second coupling part 34 and the third coupling part 36 are supported against the spring forces of the clutch springs 40 and 44 via the locking body 48 and the guide sleeve 55 on the housing 4. In this way, the clutch 30 is in the in Fig. 3 shown moment immediately after a blow of the impact mechanism 14 locks on the drive spindle 6 by the locking mechanism 46 in the engaged position. Thus, a permanent torque transmission from the motor 26 via the coupling 30 on the hollow spindle 8 and further on the drive-in spindle 6 is ensured during the driving-in, even when the impact mechanism 14 is switched on.

By tracking the rest of the screwdriver 2 against the accelerated in the screwing E Eindrehspindel 6 by the operator, the locking body 48 come back to the height of the recess 54, where they can migrate radially inward, and the spring forces of the clutch 30 are again through the hard component 60th supported, as shown in Fig. 2 ,

Upon reaching a set on a depth stop screw 70, the hollow spindle 8 is moved by the clutch springs 40, 44 in the direction of insertion E. In this case, the locking body 48 are brought via the shoulder 68 again in the area located outside of the expansion 66 of the guide sleeve 55, where they are held radially immovably between the inside of the guide sleeve 55 and the drive spindle 6. This takes the screwdriver 2 again in Fig. 1 shown starting position.

Claims (10)

1. A power screwdriver (2) comprising:

   a housing (4);

   a rotatable hollow spindle (8) accommodated in the housing (4) and driven by a motor (26);

   a clutch (30) which in an engaged position rotationally connects the hollow spindle (8) to the motor (26) and in a disengaged position rotationally disconnects said hollow spindle (8) from said motor (26) and which is urged by a preloaded clutch spring (40, 44) into the disengaged position;

   a screwing-in spindle (6), which is twist-locked to a chuck (10) for the attachment of a bit (12) and which is carried for joint rotation with the hollow spindle (8) and so as to be axially displaceable relative to said hollow spindle (8), the clutch (30) being brought into the engaged position against the action of the clutch spring (40, 44) via the screwing-in spindle (6); as well as

   a hammer mechanism (14), by means of which a pulsed axial force can be applied to the screwing-in spindle (6);

   characterized in that a locking mechanism (46) is provided by means of which the clutch (30) can be locked in the engaged position.
2. A power screwdriver according to Claim 1, characterized in that the locking mechanism (46) is actuated as a function of the position of the screwing-in spindle (6) relative to the hollow spindle (8).
3. A power screwdriver according to Claim 2, characterized in that the clutch (30) has a movable clutch component (34, 36) which in the engaged position can be secured to the housing (4) by means of the locking mechanism (46).
4. A power screwdriver according to Claim 2 or 3, characterized in that in the disengaged position the screwing-in spindle (6) can be secured to the hollow spindle (8) in axial direction by means of the locking mechanism (46).
5. A power screwdriver according to one of Claims 2 to 4, characterized in that the locking mechanism (46) has at least one locking member (48), which is displaceable in a radial transverse bore (50) in the hollow spindle (8) between an engaged position, in which it partly projects into a longitudinal bore (52) in the hollow spindle (8), and a released position, in which it is positioned outside of said longitudinal bore (52).
6. A power screwdriver according to Claim 5, characterized in that the screwing-in spindle (6) has a recess (54), the axial dimension of which is adapted to the part of the locking member (48) which engages in the longitudinal bore (52).
7. A power screwdriver according to Claim 6, characterized in that the recess (54) takes the form of an annular groove.
8. A power screwdriver according to one of Claims 5 to 7, characterized in that the movable clutch component (34, 36) is firmly attached to the hollow spindle (8), and an axial stop is formed on the housing (4), against which the locking member (48) rests in the released position.
9. A power screwdriver according to one of Claims 5 to 8, characterized in that the locking member (48) is spherical in form.
10. A power screwdriver according to Claim 8 or 9, characterized in that the axial stop takes the form of a circumferential shoulder (68) formed on a guide sleeve (55).

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