EP3227056A1

EP3227056A1 - Hand-held power tool

Info

Publication number: EP3227056A1
Application number: EP15802103.0A
Authority: EP
Inventors: Oliver Ohlendorf
Original assignee: Hilti AG
Current assignee: Hilti AG
Priority date: 2014-12-03
Filing date: 2015-12-01
Publication date: 2017-10-11
Anticipated expiration: 2035-12-01
Also published as: CN107000181A; US10414035B2; CN107000181B; WO2016087399A1; EP3227056B1; EP3028818A1; US20170355070A1

Abstract

The invention relates to a hand-held power tool comprising a tool-receiving section (2) for holding a tool (4) on a working axis (3), a pneumatic striking mechanism (6) for striking said tool (4), and an absorber (27) which consists of a mass body (28) and a bending spring (29) arranged transversely to said working axis (3). A countershaft (11) is driven, by said motor (5), about a rotational axis (12) which runs parallel to the working axis (3). A swash drive (14) for driving the pneumatic striking mechanism (6) is arranged on said countershaft (11). In addition, a cam disc (36) is arranged on the countershaft (11) and comprises a cam (39) which projects into an advancement direction that runs parallel to said working axis (3). The bending spring (29) comprises a counterpiece (46) provided relative to the cam (39). The cam (39), lying against said counterpiece (46), preloads the bending spring (29) into the advancement direction.

Description

Hand tool

FIELD OF THE INVENTION

The present invention relates to a chisel hand tool containing a damper for reducing vibrations.

DISCLOSURE OF THE INVENTION

The hand tool has a tool holder for holding a tool on a working axis, a pneumatic impact mechanism for applying shocks to the tool and a damper from a transverse to the working axis bending spring and a mass body. A countershaft is driven by a rotation axis parallel to the working axis through the motor. On the countershaft a wobble drive for driving the pneumatic impact mechanism is arranged. In addition, a cam disc with a cam extending in a direction parallel to the working direction of the starting cam is arranged on the countershaft. The spiral spring has provided counterpart to the cam. The cam biases adjacent to the counterpart of the spiral spring in the direction of advance.

The absorber is triggered by the rotating cam. The abutment takes place at the resting position of the spiral spring when the absorber is at a standstill or when the absorber has not yet completely settled. The cam periodically forces a minimum deflection of the absorber. However, the absorber excited by the vibrations and the hand tool can deflect more. The abutment is synchronized with the movement of the striking mechanism and thus the vibrations of the power tool.

One embodiment provides that the cam disc is non-contact with the bending spring when the cam and the counterpart are in diametrical angular position relative to the axis of rotation. The cam disc dissolves with each revolution of the cam about the axis of rotation once by the spiral spring, so that the absorber can oscillate freely at least during this phase. Preferably, the absorber releases for at least 50% of an oscillation, ie, without contact with the cam and only driven by the inertia of the mass. An embodiment provides that the mass body is guided by the spiral spring on a curved path. The flexure spring may be attached to the machine housing at a first end and secured to a second end of the mass body, wherein the first end and the second end are diametrically disposed from the countershaft. The projection may be at a distance from the first end which corresponds to between 30% and 50% of the distance of the first end to the second end.

An embodiment provides that a maximum deflection of the spiral spring from a rest position by the voltage applied to the counterpart cam between 1 degree and 5 degrees.

One embodiment provides that the cam has a helix-shaped flank facing the spiral spring, which rises in the starting direction via a central angle between 30 degrees and 90 degrees. The counterpart can have a helix-shaped flank facing the cam, which rises over a central angle between 30 degrees and 90 degrees counter to the starting direction. The force applied to the absorber during abutment force is preferably kept low. This avoids suggestions of higher harmonic oscillations in the spiral spring. The pneumatic chamber of the striking mechanism is maximally compressed when the countershaft angle is set. The cam at the time assumes a specific position relative to the projection, which depends on the arrangement of the cam before or after the bending spring. If the cam is in front of the spiral spring, the cam and the projection are in the same angular position with respect to the axis of rotation, i. The cam can maximally deflect the projection. When the cam is positioned after the bending spring, the cam and projection are diametrically opposed to the axis of rotation, i. offset by 180 degrees. The absorber is optimally tuned to the movement of the impact mechanism.

The wobble drive is at a first angular position of the countershaft in a dead center away from the tool. The cam is at a second angular position in a bending spring maximally deflecting angular position. If the cam is arranged on the side facing away from the tool of the bending spring, the second angular position can advantageously follow between 95 degrees and 1 15 degrees to the first angular position. If the cam is arranged on the tool facing side of the spiral spring, the first angular position can advantageously follow between 65 degrees and 85 degrees to the second angular position. BRIEF DESCRIPTION OF THE FIGURES

The following description explains the invention with reference to exemplary embodiments and figures. In the figures show:

Fig. 1 a hammer drill

Fig. 2 the absorber of the hammer drill in rest position Fig. 3 the absorber of the hammer drill deflected in the direction of impact

Fig. 4 the absorber of the rotary hammer deflected against the direction of impact

Fig. 5, the bending spring of the absorber

Fig. 6, the cam disc for abutment of the absorber

Fig. 7 shows the relative movement of the absorber and a cam of the cam disc Fig. 8 synchronous to Fig. 7 movement of the striking mechanism

Identical or functionally identical elements are indicated by the same reference numerals in the figures, unless stated otherwise. EMBODIMENTS OF THE INVENTION

1 shows an exemplary hammer drill 1. The hammer drill 1 has a tool holder 2, which can accommodate along a working axis 3 a drill bit 4, a chisel or other tool. A motor 5 can drive the tool holder 2 in rotation about the working axis 3. A striking mechanism 6 can also exert on the lying in the tool holder 2 tool periodically blows in the direction of impact 7 along the working axis 3 for chiseling operation. The striking mechanism 6 is driven by the motor 5. The user takes the motor 5 with a main switch 8 in operation. The motor 5 and the striking mechanism 6 are arranged in a machine housing 9. A battery pack or a power line provide the motor 5 with electrical power. The user can guide the hammer drill 1 with a handle 10 which is fixed to the machine housing 9. The hammer drill 1 has a shiftable transmission with a countershaft 11. The countershaft 11 is rotatably mounted about an axis of rotation 12. The axis of rotation 12 is parallel to the working axis 3. The motor 5 meshes with a drive pinion 13 on the countershaft 11 and drives the countershaft 11 permanently. The countershaft 11 transmits the torque to a wobble drive 14 for the striking mechanism 6 and a rotary drive 15 for the tool holder 2. The exemplary transmission allows the rotary drive of the tool holder 2 on and off. A shift sleeve 16 is axially movable on the countershaft 11 between a first position and a second position. In the first illustrated position engages an internal toothing of the shift sleeve 16 in a toothing 17 of the countershaft 11, in a second position, the shift sleeve 16 is disengaged. The shift sleeve 16 is in permanent engagement with a ring gear 18, which is coupled to the rotary drive 15 and the tool holder 2. A shift knob allows the user to move the shift sleeve 16 between the two positions. An analog shift sleeve can be arranged on the countershaft 11 for connecting and disconnecting the wobble drive.

The wobble drive 14 converts the rotational movement of the countershaft 11 into a periodic, linear movement for the striking mechanism 6. The wobble drive 14 includes a swash plate 19 and a wobble finger 20. The exemplary swash plate 19 includes a rolling bearing having an inner race driven by the countershaft 11 and an outer race connected to the wobble finger 20. The outer ring is rotatable relative to the inner ring about an axis inclined to the axis of rotation 12, but inhibited by the applied to the hammer mechanism 6 tumble 20 against rotation about the axis of rotation 12. The driven inner ring forces the outer ring and the wobble finger 20 to a periodic pivotal movement in a plane E spanned by the axis of rotation 12 of the countershaft 11 and the working axis 3 about a pivot axis which passes through the axis of rotation 12 and perpendicular to the plane spanned E. The pneumatic percussion 6 has an exciter piston 21 and a racket 22, both of which are guided in a guide tube 23 of the impact mechanism 6 coaxial with the working axis 3. The exciter piston 21 is connected to the wobble finger 20. The pivoting movement of the wobble finger 20 translates into a periodic linear movement of the excitation piston 21. An air spring formed by a pneumatic chamber 24 between the excitation piston 21 and the racket 22 couples a movement of the racket 22 to the movement of the exciter piston 21 (FIG. 8). , The racket 22 may strike directly on a rear end of the drill 4 or indirectly via a substantially resting intermediate racket 25 transmit a portion of its pulse to the drill 4. The stroke rate of the impact mechanism 6 is equal to the speed of the countershaft eleventh

The periodically striking mechanism 6 generates vibrations in the machine housing 9, which the user perceives as vibrations of the handle 10. The vibrations lead to early fatigue of the user and can cause damage to health under excessive load. The handle 10 may be connected to the vibration reduction via damping elements 26 to the machine housing 9. The damping elements 26 in particular reduce high-frequency components of the vibrations and convert them into heat. The damping elements 26 are preferably made of open-cell polymer foams. The effectiveness of the damping elements 26 are limited. The guiding of the power tool 1 requires a stable and rigid connection of the handle 10 to the machine housing 9, while for an ideal damping a loose and soft connection would be advantageous.

The exemplary hammer drill 1 has a damper 27 to reduce the vibration. The damper 27 has a mass body 28 and a bending spring 29. The mass body 28 is held only by the bending spring 29 and is preferably unguided otherwise. The mass body 28 can move along the working axis 3 on a curved path, approximately a circular path, back and forth. The curved path preferably lies in a plane E spanned by the working axis 3 and the axis of rotation 12 of the countershaft 11 (image plane of FIG. 2). The absorber 27 has a rest position 30 (shown in Fig. 2), in which the mass body 28 and the bending spring 29 return when no force is applied to the absorber 27. The mass body 28 can be deflected out of the rest position 30 on the curved path (compare FIGS. 3 and 4). The bending spring 29 is elastically bent and exerts a force driving back into the rest position 30 on the mass body 28. The absorber 27 oscillates after a deflection 31 from the rest position 30 about the same with its natural frequency. The natural frequency of the mass-spring system is determined by the rigidity of the spiral spring 29 and the mass of the mass body 28.

The absorber 27 is tuned to the percussion 6. The natural frequency is approximately equal to the stroke rate of the striking mechanism 6 selected, for example, between 100% and 105% of the stroke rate. The only coupled via the spiral spring 29 to the machine housing 9, inert mass body 28 dynamically counteracts the vibrations of the impact mechanism 6, whereby the force acting on the handle 10 vibrations of the machine housing 9 are reduced. The inertial mass body 28 begins to move due to its inertia by itself relative to the machine housing 9, as soon as the impact mechanism. 6 is switched on and vibrations occur. Excited by the impact mechanism 6, the mass body 28 oscillates between two reversal points, which are shown in FIGS. 3 and 4. The amplitude of the deflection 31 depends on the load of the hammer drill 1. The deflection is known for typical applications, eg when working with reinforced concrete, from test series. The deflection 31 subsequently designates the angle of inclination of the bending spring 29 with respect to its rest position 30.

FIG. 2 shows the exemplary absorber 27 in its rest position 30. In the rest position, the bending spring 29 is arranged substantially perpendicular to the working axis 3. One end of the bending spring 29 is configured as the suspension 32 and fixed to the machine housing 9. The mass body 28 is attached to the distal end of the suspension 32 end 33 of the spiral spring 29. The distance of the distal end 33 to the suspension 32 is the largest dimension or length 34 of the bending spring 29. A thickness 35 of the bending spring 29, i. whose dimension along the working axis 3, is at least an order of magnitude smaller than the length 34. The bending spring 29 is elastically bendable along the working axis 3. The mass body 28 moves on the curved path around the suspension 32. The length 34 of the spiral spring 29 provides the distance to the suspension 32. The curved path corresponds in good approximation to a circular arc with a radius equal to the length 34. The bending spring 29 curves with increasing deflection, whereby the radius is shortened. Preferably, the spiral spring 29 is stiff in the third spatial direction. The curved path runs in the plane defined by the working axis 3 and the axis of rotation 12 of the countershaft 11 level E (image plane of Fig. 2). The mass body 28 and the suspension 32 are arranged symmetrically to the plane E. The absorber 27 is preferably arranged in a sufficiently large cavity in the machine housing 9, so that the mass body 28 in typical vibrations, no element, except for the bending spring 29, in the machine housing 9 touches.

A cam 36 facilitates the settling of the damper 27, in particular when initially the striking mechanism 6 is still accelerated to the intended number of strokes. The cam disc 36 deflects the absorber 27 in a direction of start 37 on one side of its rest position 30; the arranged for example in the direction of impact 7 in front of the absorber 27 cam 36 deflects the absorber 27 on the side facing away in the direction of impact 7 of the rest position 30 from. The cam 36 does not touch the damper 27 when the damper 27 swings to the other side of the rest position 30 (FIG. 4). Advantageously, the typical deflection 30 of the damper 27 in the steady state and in an active hammer mechanism 6 is greater than the possible of the cam 36 possible forced deflection 38 of the damper 27. The damper 27 vibrates freely according to its natural frequency, ie alone given by the inertia of the mass body 28 and stiffness of the spiral spring 29th

The cam plate 36 is disposed on the countershaft 11 adjacent to the bending spring 29. The cam 36 may be integrated in the drive sprocket 13, integrated in the swash plate 19, or formed as a discrete disk. The countershaft 11 drives the cam plate 36 at the same speed as the swash plate 19, whereby the wobble of the swash plate 19 and the rotation cam 36 have a constant angular displacement. The cam plate 36 can be coupled or decoupled from the countershaft 11 together with the swash plate 19 in order to activate or deactivate the impact mechanism 6.

The cam disc 36 has a single cam 39, which projects in a direction parallel to the working axis 3 starting direction 37 to the bending spring 29 out. The exemplary cam 39 has a vertex 40, a rising in the circumferential direction 41 to the apex 40 flank

42 and after the apex 40 falling edge 43 (Fig. 6). The helical flanks 42,

43 rise in the starting direction 37 or fall off in the starting direction 37. The flanks 42 can increase linearly with the angle of rotation about the axis of rotation 12. A center angle 44 of the rising flank 42 is for example in the range between 45 degrees and 90 degrees. The falling edge 43 is preferably formed symmetrically to the rising edge 42. The entire cam 39 covers a maximum of a central angle of 180 degrees. Outside the cam 39, at the same radial distance from the axis of rotation 12, the exemplary cam disk 36 has a recess 45. The cam disk 36 can touch the bending spring 29 with only one cam 39. Driven by the countershaft 11, the cam 39 passes over a coaxial to the rotational axis 12, annular rotational volume.

The bending spring 29 has a cam 46 toward the direction of advancement 37 projecting projection 46, on which the cam 39 can strike. The projection 46 protrudes, when the bending spring 29 is in the rest position, into the rotational volume swept by the cam 39. The projection 46 may be formed the same as the cam 39. The exemplary projection 46 has a vertex 47 projecting toward the cam 36. The projection 46 has a flank 48 rising in the direction of rotation to the apex 47 and a flank 49 descending to the apex 47. A center angle 50 of the rising flank 48 is, for example, in the range between 45 degrees and 90 degrees. Of the Vertex 47 is preferably in the plane E and between the mass body 28 and the countershaft 11th

Fig. 7 illustrates the abutment of the damper 27 by the cam 36. The ordinate shows the position of the cam 36 and the bending spring 29 along the working axis 3 in the plane E. The position is plotted against the cyclic angular position 51 of the countershaft 11. The angular position 51 at 0 degrees lies in plane E and faces the mass body 28. The movement of the damper 27 is represented by the projection 46 or its vertex 47. The movement of the damper 27 is shown for the following explanations without excitation by vibrations, with which typically sets a greater deflection. The dashed line indicates the position of the apex 47 in the rest position 30.

The cam 36 rotates driven by the countershaft 11 about the rotation axis 12. The cam 39 approaches the projection 46 of the spiral spring 29. The cam 39 exceeds in the direction of start 37 with the rising edge 42, the rest position 30 of the projection 46. By way of example, the cam exceeds 39, the rest position 30 at an angular position 52 of -45 degrees. If the absorber 27 is stationary and thus the projection 46 in the rest position 30, the cam 39 begins to deflect the absorber 27 in the direction of start 37 and to brace. The deflection 38 forced by the cam 39 is maximum when the apex 40 of the cam 39 has an angular position 53 which is aligned identically with the apex 47 of the projection 46. For example, the equi-aligned peaks 40, 47 are both at 0 degrees. The two vertices 40, 47 lie in the plane E with the mass body 28 and the vibration plane of the damper 27. The maximum forced deflection 38 is in the range between 1 degree and 5 degrees.

Subsequent to the maximum forced deflection 38, the cam 39 moves away with the falling edge 43 of the projection 46. The cam 39 no longer exerts force in the direction of start 37 on the bending spring 29 from. Accordingly, the spiral spring 29 relaxes and accelerates the mass body 28 against the starting direction 37 in the direction of the rest position 30. The projection 46 moves with increasing speed against the starting direction 37. The rate of increase of the falling edge 48 at the speed of the countershaft 11 is greater than that Speed of the projection 46 is selected. Accordingly, 36 opens a gap between the spiral spring 29 and the cam plate. The movement of the damper 27 is now solely by the inertia of the mass body 28 and the Stiffness of the bending spring 29 predetermined. The free movement lasts at least 75% of one revolution of the countershaft 11 (270 degrees).

The absorber 27 oscillates on the rest position 30 and reaches its greatest deflection 31 counter to the starting direction 37 when the cam 39 is at about 180 degrees. The cam 39 is again in the plane E, but on the suspension 32 of the spiral spring 29 facing side of the countershaft 11. The cam 39 and the projection 46 are relative to the axis of rotation 12 diametrically. The cam 39 is preferably arranged along the axis of rotation 12 a recess 54 of the spiral spring 29 against the projection 46 is preferably along the axis of rotation 12, the recess 45 of the cam plate 36 against. The cam 36 and the bending spring 29 do not touch each other in the diametrical angular position 55, regardless of the amplitude of the deflection 31 of the spiral spring 29. The amplitude 38 shown in FIG. 7 includes only the excitation by the cam 36, wherein the chiselling hammer 1 is the deflection 38 is at least 20% larger in typical applications.

The maximum forced deflection 38 of the damper 27 is preferably carried out simultaneously with the maximum compression of the pneumatic chamber 24. The countershaft 11 drives synchronously the wobble finger 20, thus indirectly the impact mechanism 6, and also the cam 36 at. The wobble finger 20 periodically reaches its tool-remote dead center 56 at an angular position 57, for example at 255 degrees (-105 degrees). The wobble finger 20 moves and the excitation piston 21 subsequently in the direction of impact 7. The pneumatic chamber 24 of the striking mechanism 6 is compressed. The maximum compression is achieved between 95 degrees and 15 degrees after dead center 56. The fixed angular offset of the wobble drive 14 to the cam 36 is selected such that the rectified angular position 53 of the cam 39 to the projection 46 between 95 degrees and 1 15 degrees to the tool away from the dead center 56 of the wobble drive 14. The angular offset shifts by 180 degrees when the cam plate 36 is arranged on the tool side of the bending spring 29.

The already oscillating absorber 27 should be disturbed as little as possible by the cam 39. The projection 46 is designed to leave the area swept by the cam 39 quickly. The apex 47 lies on a side facing away from the suspension 32 of the countershaft 11. The distance of the apex 47 to the suspension 32 is between 30% and 50% of the length 34 of the spiral spring 29th The spiral spring 29 may be stiffened perpendicular to the plane. The width 58 of the spiral spring 29 is preferably greater than its thickness 35 and less than its length 34. The exemplary bending spring 29 is formed as a plate-shaped leaf spring (Fig. 5). The bending spring 29 surrounds the countershaft 11. The suspension 32 of the spiral spring 29 and the distal end 33 with the mass body 28 are on diametrically opposite sides of the countershaft 11. The spiral spring 29 has, for example, a recess 59 through which the countershaft 11 is guided. The bending spring 29 may have a further recess 54 through which the impact mechanism 6 arranged parallel to the countershaft 11 is guided. The recesses 54, 59 are sufficiently dimensioned so that the bending spring 29 does not abut against the countershaft 11 and the percussion mechanism 6 when it is deflected by the mass body 28. The bending spring 29 is for example made of spring steel or a fiber composite.

Claims

1 . Hand tool with

a tool holder (2) for holding a tool (4) on a working axis

(3),

a motor (5),

a pneumatic striking mechanism (6) for applying blows to the tool

(4),

a damper (27) comprising a bending spring (29) arranged transversely to the working axis (3) and a mass body (28),

a countershaft (1 1), which is driven by a to the working axis (3) parallel axis of rotation (12) by the motor (5),

one on the countershaft (1 1) arranged wobble drive (14) for driving the pneumatic impact mechanism (6),

a cam disc (36) arranged on the countershaft (1 1) with a cam (39) projecting in a direction of origin (37) parallel to the working axis (3), a counterpart (46) provided on the bending spring (29) to the cam ( 39), wherein the cam (39) adjacent to the counterpart (46) biases the bending spring (29) in the direction of start (37).

2. Hand tool (1) according to claim 2, characterized in that the cam disc (36) is non-contact with the spiral spring (29) when the cam (39) and the counterpart (46) relative to the axis of rotation (12) in diametrical angular position (55) are.

3. Hand tool (1) according to claim 1 or 2, characterized in that the cam disc (36) is for at least 75% of a rotation about the axis of rotation (12) without contact with the spiral spring (29).

4. Hand tool (1) according to one of the preceding claims, characterized in that the mass body (28) is guided by the spiral spring (29) on a curved path.

5. Hand tool (1) according to one of the preceding claims, characterized in that the bending spring (29) with a first end (32) fixed to the machine housing (9) and at a second end (33) of the mass body is fixed, wherein the first end (32) and the second end (33) diametrically from the countershaft (1 1) are arranged.

Hand tool (1) according to claim 5, characterized in that the counterpart (46) of the cam (39) from the first end (32) at a distance which is between 30% and 50% of the distance (34) of the first end ( 32) corresponds to the second end (33).

Powered hand tool (1) according to one of the preceding claims, characterized in that a maximum forced deflection (38) of the spiral spring (29) from a rest position (30) by the counterpart (46) fitting cam (39) between 1 degree and 5 Degree is.

Hand tool (1) according to one of the preceding claims, characterized in that the cam (39) has a bending spring (29) facing helical flank (42) via a central angle (44) between 30 degrees and 90 degrees in the direction of start ( 37) increases.

Powered hand tool (1) according to one of the preceding claims, characterized in that the counterpart (46) has a helical flank (48) facing the cam (39), which has a center angle (50) of between 30 degrees and 90 degrees counter to the starting direction (FIG. 37) increases.

0. Hand tool (1) according to any one of the preceding claims, characterized in that a pneumatic chamber (24) of the impact mechanism (6) at an angular position (54) of the countershaft (1 1) is maximally compressed and wherein the cam (39) in the angular position (53) of the countershaft (1 1) and in an arrangement of the cam (39) on a side facing away from the tool (4) of the spiral spring (29) with respect to the axis of rotation (12) in the same angular position (53) Counterpart (46) is or wherein the cam (39) in the angular position (53) and in an arrangement of the cam (39) on a tool (4) facing side of the bending spring (29), relative to the axis of rotation (12) diametrically to the counterpart (46) lies.

1 . Hand tool (1) according to one of the preceding claims, characterized in that the wobble drive (14) at a first angular position (57) of the countershaft (1 1) in a tool (4) facing away from dead center (56) and the cam (39 ) at a second angular position (53) in a bending spring (29) maximum is deflecting angular position, and wherein in an arrangement of the cam (39) on the tool (4) facing away from the bending spring (29), the second angular position (53) between 95 degrees and 1 15 degrees to the first angular position (57), and wherein in an arrangement of the cam (39) on the tool (4) side facing the bending spring (29) the first angular position (57) between 65 degrees and 85 degrees to the second angular position (53) follows.