EP2919946B1 - Power tool - Google Patents

Description

FIELD OF THE INVENTION

The present invention relates to a chiseling hand tool according to the preamble of claim 1 and as shown in CH 662 978 A5 known.

Another chiseling hand tool is eg from the US 5,111,890 known. A pneumatic percussion mechanism has an exciter piston which is constantly reciprocally moved by a motor along an axis. An air spring couples a racket formed as a piston to the movement of the exciter piston. The hammer mechanism should switch off when the club hits a stop instead of hitting an intermediate club. For this purpose ventilation openings are provided, which releases the racket to the attack fitting. The air spring is vented through the ventilation openings and thus deactivated. Once the racket is pushed back over the vents, the percussion begins to strike again. The racket can already slide back by a rebound from the stop sufficiently for closing over the ventilation openings. In this case, disadvantageously, no automatic deactivation of the percussion mechanism takes place.

DISCLOSURE OF THE INVENTION

The hand tool of the invention according to claim 1 has a tool holder for holding a chiseling tool. A pneumatic percussion of the power tool has a racket, a pathogen and a guide tube. The racket is designed to apply impact blows to the tool. The pathogen is motor driven. The racket is coupled to the reciprocal movement of the exciter by means of an air spring. The racket is guided adjacent to the guide tube along a working axis. The racket is guided at a movement between a stroke position and the exciter with a constant guide length of the guide tube and when the impact position in the direction of impact is exceeded, the guide length is reduced. The hand tool is provided with a slanted guide, in which the racket is introduced after exceeding the impact position and which tilts the racket relative to the working axis.

During operation, the bat flies in the direction of impact up to the impact position and strikes there on the tool or an intermediate beater (striker). If the user does not work with the hand tool, ie not the tool to a Underground presses, the racket can slide beyond the stroke position. The axial guidance of the racket is deliberately reduced in order to provoke an inclined position of the racket relative to the working axis. The inclination can promote a sticking of the racket to favor the shutdown of the percussion. The racket runs into the inclined guide only after exceeding the impact position. The racket reaches at the latest with an axial stop in the inclined guide. The normal way while working carefully coaxial with the working axis guided racket is tilted targeted. The tilting inhibits the movement of the racket and favors the staying in a position to stop the percussion mechanism, eg behind the ventilation openings.

One embodiment provides that ventilation openings are provided for ventilating the air spring. The ventilation openings are arranged such that the racket isolates the air spring from the ventilation openings when the racket is in the direction of impact before the impact position, and otherwise releases the ventilation openings. The air spring can thus be preferably ventilated as soon as the racket slides beyond the impact position.

The oblique guide can have a bearing surface pointing to the radial axis, and the racket have a bearing surface contacting radial sliding surface. One, preferably exactly one, of the bearing surface or sliding surface is formed asymmetrically to the working axis. The oblique guide causes a resultant force in an angular direction on the racket, which is not compensated for lack of rotational symmetry. As a result, the racket tilts. The racket is advantageously guided with its rear end in the direction of impact in the guide tube.

The bearing surface or the sliding surface may have a radially protruding projection in only one angular direction. An axis of the bearing surface or an axis of the sliding surface may be offset parallel to the working axis or tilted relative to the working axis.

The racket may comprise a piston and a plunger. The piston terminates in the guide tube from the pneumatic chamber and is positively guided by the guide tube. The plunger is in the direction of impact after the piston and forms the striking surface, which strikes the intermediate beater or the tool. The plunger may have a smaller diameter than the piston and is preferably not guided by the guide tube. The slanted guide guides the ram, provided the racket over the impact position has advanced. The subdivision of the racket in the piston and plunger is to be understood only in terms of their function or geometry. Pistons and clubs are a monolithic body; Pistons and clubs can not be separated from each other or moved to each other.

The plunger may have an asymmetric radial surface formed to the axis of the piston. A center of the contour of the radial surface is not on the axis.

BRIEF DESCRIPTION OF THE FIGURES

Fig. 1

einen Bohrhammer in Schlagstellung

Fig. 2

einen Detailansicht von Fig. 1

Fig. 3

einen Querschnitt in der Ebene III-III von Fig. 2

Fig. 4

den Bohrhammer in einer Leerlaufstellung

Fig. 5

eine Detailansicht von Fig. 4

Fig. 6

eine Querschnitt in der Ebene VI-VI von Fig. 5

Fig. 7

einen beispielhaften Schläger des Bohrhammers

Fig. 8

einen beispielhaften Prellbock des Bohrhammers

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

Fig. 1

a hammer drill in striking position

Fig. 2

a detailed view of Fig. 1

Fig. 3

a cross section in the plane III-III of Fig. 2

Fig. 4

the hammer drill in an idle position

Fig. 5

a detailed view of Fig. 4

Fig. 6

a cross section in the plane VI-VI of Fig. 5

Fig. 7

an exemplary mallet of the hammer drill

Fig. 8

an exemplary buffer of the hammer drill

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

EMBODIMENTS OF THE INVENTION

Fig. 1 schematically shows a hammer drill 1 as an example of a chiseling hand tool . The hammer drill 1 has a tool holder 2, in which a shank end 3 of a tool, for example one of the drill bit 4, can be used. a primary drive of the hammer drill 1 forms a motor 5, which drives a striking mechanism 6 and an output shaft 7 . A user can guide the hammer drill 1 by means of a handle 8 and take means of a system switch 9, the hammer drill 1 is in operation. In operation, the hammer drill 1 rotates the drill bit 4 continuously about a working axis 10 and can beat the drill bit 4 in the direction of impact 11 along the working axis 10 in a substrate. The striking mechanism 6 and preferably the further drive components are arranged within a machine housing 12 .

The percussion 6 is a motor-driven, pneumatic percussion 6. An exciter 13 and a racket 14 are movably guided in the striking mechanism 6 along the working axis 10 . The exciter 13 is coupled via an eccentric 15 or a wobble finger to the motor 5 and forced to a periodic, linear movement along the working axis 10 . An air spring formed by a pneumatic chamber 16 between exciter 13 and racket 14 couples a movement of the racket 14 to the movement of the exciter 13 . The bat 14 can strike directly on a rear end of the drill bit 4 or indirectly transfer part of its pulse to the drill bit 4 via a substantially resting intermediate beater 17 .

When dismantling a wall or a substrate, ie in working mode, press the user or the weight of the hammer drill 1 the drill bit 4 and the intermediate beater 17 against the direction of impact 11 to a stop 18. The working position of the drill bit 4 and the intermediate beater 17 is thus before Beat defined. The bat 14 thus hits in a defined position (hereinafter impact position, Fig. 1 ) along the working axis 10 on the intermediate racket 17. The racket 14 moves during working in the direction of impact 11 only to the impact position. Contrary to the direction of impact 11 , the movement of the racket 14 is limited by the air spring and the exciter 13 .

The stop 18 is formed, for example, by an annular buffer 19 , which is arranged between the racket 14 and the intermediate racket 17 . The buffer 19, in particular the cavity, is preferably rotationally symmetrical and coaxial with the working axis 10 . The coaxial with the working axis 10 guided intermediate beater 17 can be supported against the direction of impact 11 on the buffer 19 for the impact position. The rear end of the intermediate beater 17 with the impact surface 20 preferably enters the cavity of the buffer 19, for example, the impact surface 20 reaches at least up to the direction of impact 11 front side of the buffer 19. The buffer 19 preferably includes an axially movable metal ring 21, which against the direction of impact 11 rests against an elastic rubber ring 22 for damping the rebound of the intermediate beater 17 .

The user can stop working by lifting the tool off the wall or the ground. The percussion 6 should switch off automatically, as now no longer blows on the drill bit 4 introduced into the wall but must be collected in the tool holder 2 . The bat 14 is decoupled from the exciter 13 by aerating the pneumatic chamber 16 . The motor 5 can thus continue to rotate without shocks are generated. The hammer drill 1 automatically goes into an idling operation. The bat 14 can slide in the off-hook tool 4 in the direction of impact 11 on the impact position, the now ingestable position (eg Fig. 3 ) are referred to collectively as idle position. The venting of the pneumatic chamber 16 is coupled to the assumption of the neutral position, therefore, the bat 14 should stay with lifted tool 4 as possible in the idle position.

The exemplary racket 14 consists of a piston 23 and a plunger 24. The piston 23 terminates with an end face 25, the pneumatic chamber 16 in the direction of impact 11 from pressure-tight. In operation, the racket 14 is forcibly guided by a guide tube 26 coaxial with the working axis 10 . The guide is made by a lateral surface 27 of the piston 23, which bears flush against a cylindrical, inner guide surface 28 of the guide tube 26 . The axis 29 of the piston 23, which defines the axis of the racket 14 , is located on the working axis 10. A diameter 30 of the piston 23 is equal to the inner diameter of the guide surface 28 except for a slight play for the sliding movement. The clearance is typically less than zero ,1 mm. A tilting of the racket 14 relative to the guide surface 28 is counteracted by the ratio of the guided length 31 (dimension along the working axis 10 ) of the lateral surface 27 to diameter 30 of the piston 23 . The guided length 31 or guide length is preferably at least a quarter, eg at least half of the diameter 30. The lateral surface 27 may be interrupted along the working axis 10 by grooves 32 or other structures, as in the illustrated racket 14. Essentially for the guide length 31 are along the working axis 10 furthest away from each other surface portions which lie on the snugly against the racket cylinder 14 , ie the guide surface 28 .

The striking surface 33 of the racket 14 is adapted to the diameter of the tool 4 and typically smaller than the diameter 30 of the racket 14 and its end closing the air spring 25. An annular shoulder 34 forms a transition of the piston 23 on the plunger 24. The plunger 24th is a substantially cylindrical Main body, which is coaxial with the axis 29 of the piston 23 . The main body forms the majority of the radial surface 35 of the plunger 24. One or more annular grooves can be introduced into the base body. The end face of the plunger 24 forms the striking surface 33, which is perpendicular to the axis 29 . The impact surface 33 is preferably rotationally symmetrical and coaxial with the axis 29. When impact, ie in impact position, the impact surface 33 is located centrally on the working axis 10. The impact can be introduced into the intermediate beater 17 with minimal losses and with minimal transverse and radial forces. The intermediate beater 17 preferably also has a co-axial and vertical striking surface 20 to the working axis 10 .

The radial surface 35 of the plunger 24 is formed asymmetrically to the working axis 10 . When in the cross section in Fig. 3 exemplified and drawn plunger 24 is radially in front of a tooth 36 in a single angular direction. In the absence of another tooth at 180 degrees, two further teeth at 120 degrees and 240 degrees or a larger tooth arranged at equidistant angles, the radial surface 35 lacks rotational symmetry. The impact surface 33 striking the intermediate beater 17 is nevertheless rotationally symmetrical or at least rotationally symmetrical. For example, the end face of the plunger 24 is slightly larger than the striking surface 20 of the intermediate beater 17, whereby the tooth 36 has no influence on the striking surface 33 .

The height 37, measured to the axis 29 of the racket 14, of the tooth 36 may be up to between 5% and 20% greater than the outer radius 38 of the ram 24 . The outer radius 38 is the radial dimension of the substantially cylindrical base body, for. B. the distance of the radial surface 35 to the axis 29 away from the tooth 36th

The plunger 24 may be provided with a plurality of teeth, without giving the plunger 24 a rotational symmetry. For example, no tooth is provided over an angular range of at least 180 degrees about the working axis 10 . A cross section perpendicular to the axis 29 through the plunger 39 shows an area whose center or center of gravity lies outside the axis 29 .

The idling operation is achieved by radial ventilation openings 40 which are only opened when the racket 14 slides in the direction of impact 11 beyond the impact position into the idling position ( Fig. 4 ). In the embodiment shown by way of example, the ventilation openings 40 are blocked or opened by the pneumatic chamber 16 final end face 25 of the racket 14 . The end face 25 is just in front of the ventilation openings 40 when the racket 14 is in the impact position, and the Face 25 is located in the direction of impact 11 behind the ventilation openings 40 when the racket 14 is in the neutral position. Via the ventilation openings 40 , the air moved by the exciter 13 in the pneumatic chamber 16 can flow in and out to at least a large extent. The exciter 13 can no longer suck the bat 14 , whereby it remains in a position after the impact position.

The strict forced guidance of the racket 14 by the guide tube 26 is limited to the working operation. The guide surface 28 ends substantially beyond the impact position. An edge 41 of the guide surface 28 is approximately at the axial position of the edge of the lateral surface 27 for the bat 14 in the impact position . The piston 23 and its lateral surface 27 are beyond the guide surface 28 in the direction of impact 11 when the bat 14 passes over the impact position and is in the neutral position. The guide length 31 is thereby shortened at least by the distance 42, by which the racket 14 has overtaken the impact position. The inner surface 43 adjoining the guide surface 28 in the direction of impact 11 has a larger diameter 44 than the piston 23. Preferably, the diameter increases by at least 0.5 mm and preferably by at most 5 mm. The projecting part of the lateral surface 27 is therefore not performed or with much greater play. The racket 14 can tilt with respect to the working axis 10 .

The racket 14 may preferably extend at least as far in the direction of impact 11 over the impact position, that the lateral surface 27 rests against the guide surface 28 with less than half its length 31 . For example, the racquet 14 can be at least half the length of guide 31, that is, the length 31 of the casing 27, also move in the direction of impact 11 on the impact position. In the exemplified piston 23 is already a small distance 42 is sufficient. The groove 32 arranged approximately in the middle of the lateral surface 27 subdivides the lateral surface 27 into a front section and a rear section 45. The piston 23 need only be displaced by a distance 42 equal to the length of the rear section 45 in order to guide it as desired reduce.

The racket 14 is stopped in the direction of impact 11 by the buffer 19 . The annular shoulder 34 of the racket 14 is supported on the buffer 19 from. The plunger 24 dips into the cavity and pushes if necessary the intermediate beater 17 out of the cavity. The racket 14 can not completely escape from the guide surface 28 due to the buffer 19 , preferably remains at least one-tenth of the length 31 of the Jacket surface 27 adjacent to the guide surface 28 . The racket 14 can be safely pushed back by the intermediate racket 17 in the impact position.

The plunger 24 is unguided during the working operation. The coaxial alignment of the racket 14 is carried out only by the leadership of the piston 23 on the guide surface 28 of the guide tube 26. In the blank strike position, at least when the bat 14 on the buffer 19, the plunger 24 is guided. The plunger 24 is, in contrast to the piston 23, guided on a tilted to the working axis 10 path. The oblique guide is made by the plunger 24 radial surface 35, which slides on the inner surface 46 of the annular bumper 19 . The cylindrical inner surface 46 , for example, is coaxial with the working axis 10. At least the portion that projects asymmetrically in the radial direction, for example the tooth 36, is guided through the inner surface 46 . The tooth 36 has a height 37 which is measured in the radial direction from the axis 29 of the racket 14 . The height 37 is slightly larger than an inner radius 47 of the inner surface 46. The plunger 24 is offset according to the difference of the height 37 to the inner radius 47 perpendicular to the axis 29 . The bat 14 , which is still partly located in the guide tube 26 , tilts relative to the working axis 10.

The plunger 24 may be guided on a stiff, unyielding inner surface 46 of the bumper 19 at the Leerschlagstellung. The inner surface 46 may be formed, for example, by a steel ring 48 of the buffer 19 . In this case, the inner radius 47 is at least as great as the mean of the height 37 of the tooth 36 and the outer radius 38. In the embodiment illustrated by way of example, the elastic rubber ring 21 forms at least part or all of the inner surface 46. The inner radius 47 can be less than the mean of the height 37 of the tooth 36 and the outer radius 38 of the plunger 24. The rubber ring is more strongly squeezed by the tooth 36 in the radial direction than in the diametrically opposite angular direction (see. Fig. 6 ). This results in a resultant force, which deflects the plunger 24 in the diametrically opposite angular direction and tilts the bat 14 relative to the working axis 10 .

Another embodiment of the impact mechanism 6 has a racket 14 according to the Fig. 7 , The piston 23 defines the axis 29 of the racket 14 and provides for its positive guidance in the guide tube 26 coaxial with the working axis 10. The plunger 49 is a substantially cylindrical body whose longitudinal axis 50 is tilted relative to the axis 29 of the racket 14 to a Asymmetry of its radial surface 51 relative to the working axis 10 to effect. The buffer 19 is formed coaxially and symmetrically to the working axis 10 . The inner radius 47 of the buffer 19 is selected such that the radial surface 51 of the plunger 24 bears against the inner surface 46 . An outer radius 52 of the plunger 24 is for example, equal to or slightly larger than the inner radius 47. The tilting results from the tilted axis longitudinal axis 50 of the plunger 49th

The impact surface 33 forming part of the end face 25 is preferably formed perpendicular and coaxial with the axis 29 of the racket 14 . The impact of the bat 14 thus takes place centrally on the working axis 10. For example, the end face is elliptical and the smaller radius is equal to the radius of the circular striking surface 33rd

A further embodiment of the striking mechanism 6 provides to provide the racket 14 with a rotationally symmetrical radial surface 53 of the plunger 39 ( Fig. 8 ). In this case, the inner surface 54 of the buffer 19 is asymmetrical to the working axis 10. For example, the rubber ring 55 has a larger cord diameter 56 at one point .

Claims (6)

1. Hand-held power tool (1), comprising
   a tool holder (2) for supporting a chiselling tool (4),
   a pneumatic striking mechanism (6) having a striker (14) for imparting blows to the tool (4) in the impact direction (11), a motor-driven exciter (13) to the reciprocating motion of which the striker (14) is coupled by means of an air spring, and a guide tube (26) bearing against which the striker (14) is guided along a working axis (10), the striker (14) being guided on the guide tube (26) for a constant guide length (31) when it moves between an impact position and the exciter (13) and the guide length (31) being reduced when the striker goes beyond the impact position in the impact direction (11), and
   an inclined guide into which the striker (14) is introduced once it goes beyond the impact position, characterised in that the inclined guide tilts the striker (14) in relation to the working axis (10).
2. Hand-held power tool according to claim 1, characterised in that vent openings (40) for venting the air spring are arranged in such a manner that the striker (14) isolates the air spring in relation to the vent openings (40) when the striker (14) is upstream of the impact position in the impact direction (11) and otherwise opens the vent openings (40).
3. Hand-held power tool according to claim 1 or claim 2, characterised in that the inclined guide has a radial inner surface (46) directed towards the working axis (10) and the striker (14) has a radial surface (35) contacting the inner surface (46), one of the inner surface (46) and the radial surface (35) being designed asymmetrically relative to the working axis (10).
4. Hand-held power tool according to claim 3, characterised in that the inner surface (46) or the radial surface (35) has a projection (36) projecting in the radial direction in only one angular direction.
5. Hand-held power tool according to one of the preceding claims, characterised in that the striker (14) has a piston (23) guided by the guide tube (26) and a plunger (24) forming an impact surface (33), the inclined guide guiding the plunger (24).
6. Hand-held power tool according to claim 5, characterised in that the plunger (24) has a radial surface (35) designed asymmetrically relative to the axis (29) of the piston (23).

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