EP1869753A1

EP1869753A1 - Linear actuator for an electric percussion tool

Info

Publication number: EP1869753A1
Application number: EP06723929A
Authority: EP
Inventors: Andreas GRÜNDL; Bernhard Hoffmann
Original assignee: Compact Dynamics GmbH
Current assignee: Compact Dynamics GmbH
Priority date: 2005-04-15
Filing date: 2006-03-31
Publication date: 2007-12-26
Also published as: WO2006108524A1; CN101204000A; DE102005017483A1; DE102005017483B4; JP2008536462A; US20080252150A1

Abstract

The invention relates to a linear actuator in an electric percussion tool, provided with an armature and a stator. The armature comprises at least two permanent magnetic bars, arranged in a stack one above the other at a given separation from each other, the stator is embodied at least partly from a soft-magnetic material and comprises at least two pairs of teeth with opposing teeth, each tooth pair of which accommodates one of the two stacks between them with formation of an air gap, whereby the stator comprises at least two magnetically-conducting inner regions between both stacks, arranged at a given separation from each other in the direction of movement of the armature and each at least partly enclosed by an essentially hollow cylindrical coil arrangement, the longitudinal mid-axis of which is oriented roughly perpendicular to the direction of movement of the armature and the armature comprises a drive body which can transmit a mechanical impulse to a tool of the electric percussion tool.

Description

LINEAR ACTUATOR FOR AN ELECTRIC IMPACT TOOL

description

Background of the invention

The present invention relates to an electrically operated linear actuator in an electric impact tool with a rotor and a stator, wherein the rotor is arranged to act on a tool of the electric impact tool. The fields of application of such electric impact hammers are, for example, civil engineering, plant construction, concrete plants, artificial stone factories, foundries, installation companies, the processing of natural and artificial stone and any type of masonry and concrete, the chiselling, chiselling, breaking up, digging, sticking, Knocking, pounding and deburring, breaking up concrete and asphalt as well as gravel-filled soil, breaking off concrete, masonry and other building materials, tearing roads and concrete, asphalt, tar, wood and stone paving, cutting off clay, clay, peat as well as salts, the comminution of stuck or mashed soils, or the driving in of piles and earthing rods.

State of the art

From the operational Paxis Aufbruchhämmer are known in which after actuation of a manual shift lever, an AC universal motor drives a crank mechanism through a gearbox. The resulting rotating movement of a crank pin of the crank mechanism is converted by means of a connecting rod and a guide piston for linear movement and passed through an air cushion to a percussion piston. The percussion piston then strikes directly on an attached to the breaker, depending on the application tool (pointed chisel, star profile chisel, flat chisel, wedge chisel, broad chisel, spade, asphalt cutter, ramming insert, tamping ram, Rammhaube for driving piles, or driving mandrel). A built-in electronics control ensures low inrush current and a constant speed of the drive motor.

From DE 10259566 Al a beating electric power tool is known, in which along a striking axis by an electric motor, a tool is hit. In this case, the electric motor has a rotor shaft arranged transversely to the impact axis with a rotor laminated core and a motor pinion which drives a striking mechanism assembly with an eccentric via a striking mechanism transmission. The rotor core is arranged completely diametrically to the percussion gear with respect to the striking axis. US 1,871,446 shows an electric hammer in which the stator coils are arranged in series and form separate non-cooperating magnetic circuits. In the rotor co-operating secondary coils are provided with the respective stator coils.

Scripts showing technological background are US Pat. No. 2,892,140, DE 10025 371 A1, DE 30 30 910 A1, and DE 102 04 8861 A1.

The invention underlying problem

For many applications, such as demolition and demolition of concrete, masonry and stone, but also in medium and heavy wall breakthroughs, wall crashes and rework, in building renovation and plumbing, as well as demolition work on the ground and breakthroughs on the ground required impact performance, single impact energy and stroke rate is difficult to achieve at relatively low weight of the electric percussion hammer. In addition, known arrangements require a lot of space.

Inventive solution

To overcome these disadvantages, the invention teaches an electrically operated linear actuator in an electric impact tool, which is defined by the features of claim 1.

Design, developments and advantages of the solution according to the invention According to the invention, the linear actuator in the electric percussion tool has a rotor and a stator, wherein the rotor has at least one stack of permanent-magnetic rods arranged one above the other. The stand is at least partially formed of a soft magnetic material and has at least one pair of teeth with opposing teeth, each pair of teeth receiving a stack between them to form a respective air gap. The stator has at least two magnetically conductive inner regions, which are arranged in the direction of movement of the rotor from each other at a predetermined distance and are each at least partially surrounded by a substantially hollow cylindrical coil arrangement whose central longitudinal axis is oriented approximately transversely to the direction of movement of the rotor. In its simplest embodiment, the rotor has a stack of superposed, permanent magnetic rods. Laterally next to it, the coil arrangement of the stator and the at least two magnetically conducting inner regions surrounded by the coil arrangements are arranged on one side of the rotor. In order to operate a tool of the electric impact tool, the rotor has a drive member which cooperates via a loose coupling with the tool of the electric impact tool to transmit a mechanical impulse thereto. In this case, the invention has recognized that in such an arrangement of the linear actuator, the two coil assemblies can be operated so that the magnetic flux through the one of the two magnetically conductive inner regions at any time substantially equal to the magnetic flux through the other magnetically conductive inner region is. Thus, the overall arrangement of the two coil assemblies with the associated stator assembly in conjunction with the permanent magnetic rotor bars forms a self-contained magnetic circuit. In other words, in the invention, the magnetic flux induced by the coil assembly in the one direction can be induced in the other direction from the other coil assembly at the same time, so that the circle closes.

According to the invention, the rotor may comprise two or more stacks of permanent-magnetic rods arranged at a predetermined distance from each other, and the magnetically conductive inner regions of the stator may be arranged between the stacks of the rotor.

A further concept on which the invention is based is to "separate out" the part of the stator causing the armature flux, namely the coil region with the stator coil arrangement spatially from the part forming the force of the linear actuator, namely the tooth region of the stator. This can be achieved in comparison to conventional linear motors in which the stator coils are each arranged between two teeth of the stator, a significantly higher anchor flux. This is due to the fact that the coil has considerably less spatial restrictions due to the design according to the invention and can therefore be optimized for minimal (ohmic) losses - and thus for maximum magnetic field induction. The arrangement of the stator coil arrangement whose central longitudinal axis is oriented transversely to the direction of movement of the rotor or, in other words, substantially aligned with the central longitudinal axis of two opposing teeth of a pair of teeth, is particularly magnetically efficient, since the magnetic flux induced by such a oriented coil passes through the two Ends of the coil located tooth pairs flows equally. Thus, a matching force is generated in two stacks of permanent magnetic rods. This avoids skewing of the rotor without any special measures.

The invention further provides that the hollow cylindrical coil arrangement has a substantially rectangular cross-section viewed along its central longitudinal axis M. In this way, a coil, which is substantially rectangular in the outer contour, also encloses the respective magnetically conductive inner regions of the stator with a likewise essentially rectangular recess. By the dimensions of the permanent-magnetic rods in the direction of movement of the rotor or the dimensions of a tooth of the stator in the direction of movement of the rotor, a pole pitch is defined which is smaller than the dimension of the stator coil in the longitudinal direction.

Likewise, the force inducing rotor magnetic pole / stator teeth assemblies are concentrated so that they are not interrupted by stator coil assemblies. This allows a very small pole pitch, which in turn causes a high power density. In addition, partial strokes of the rotor are possible with the arrangement according to the invention.

Another significant advantage of the invention ünearaktors is that virtually only the magnetically active components (the permanent magnets) contribute to the inertial mass of the rotor, while all other parts of the actuator (coils, magnetic return, etc.) are associated with the stand. Thus, a particularly high ratio of force exerted by the actuator to inert mass can be achieved.

Due to the very simple design (single-phase and hollow cylindrical, for example, rectangular in cross section) arrangement of Ständerspulenanordungen it is possible to keep the influence of the forces acting on the coil shaking forces low, so that vibration of the coil or friction of the coil on the wall of the stator coil chamber low are. This makes it possible to make do with minimal insulating material or lining material of the stator coil chamber. This also contributes to the compactness and reliability of the overall arrangement. In addition, the simple structure causes a high power density even with small linear actuators, since the achievable fill factor of the stator coil chamber (coil volume in the stator coil chamber based on the total volume of the stator coil chamber) is high.

Each tooth may according to the invention in the direction of movement of the rotor have a dimension which substantially coincides with the dimension of a permanent magnetic rod in the direction of movement of the rotor, so that in a predetermined position of the rotor at least one pair of teeth of the stator is aligned with a permanent magnet rod.

Preferably, in the direction of movement of the rotor, adjacent pairs of teeth of the stator are relative to the dimension of the permanent-magnetic rods in the direction of movement of the rotor so dimensioned that, between two permanent-magnetic rods, which are aligned with two adjacent tooth pairs of the stator, at least one further of the permanent-magnetic rods is arranged.

According to the invention, the magnetically conductive inner regions may have at least one of the teeth at their end facing the rotor. In the case of a rotor having two or more stacks, the magnetically conductive inner regions of the stator located between the two stacks have their teeth on their ends facing the stacks of the rotor.

Furthermore, the stator may have at least one magnetically conductive outer region lying outside the stack of the rotor and having at least one of the teeth at its end facing the stack of the rotor.

In the case of a runner having two stacks, the stand may also have two magnetically conductive outer portions lying outside the two stacks of the runner and having the teeth at their ends facing the stacks.

According to the invention, the outer region of the upright is designed to be essentially comb-shaped in cross-section, at least in one section. The teeth of the comb form the outer (outer) teeth of the tooth pairs.

Adjacent bars of a stack according to the invention have an alternating magnetic orientation, wherein the longitudinal axis of this orientation is substantially aligned with the central longitudinal axis of two opposing teeth of a pair of teeth.

According to the invention, the central longitudinal axis of the coil arrangement can be oriented approximately transversely to the direction of movement of the rotor. Likewise, according to the invention, the central longitudinal axis of the coil arrangement can be aligned approximately with the central longitudinal axis of two opposing teeth of a pair of teeth or at least partially oriented substantially parallel to it. This allows a cranked configuration of the inner regions of the stator, for example to obtain corresponding mounting space for the coil assemblies.

The predetermined distance between the two magnetically conductive inner regions may, in accordance with the invention, be dimensioned to substantially coincide with the Measurement of an even number of permanent magnetic rods of the two stacks in the direction of movement of the rotor coincides.

In each case two adjacent permanent magnetic rods of the two stacks of the rotor can be connected according to the invention by magnetically non-effective spacers at a predetermined distance from each other. These spacers may contain a magnetically non-effective lightweight material (aluminum, titanium, plastic - including glass fiber or carbon fiber deposits - or the like.) Contain. Thus, the inertial mass of the runner is low but its stability is high.

By the dimensions of the permanent-magnetic rods in the direction of movement of the rotor and the dimensions of the teeth of the stator in the direction of movement of the rotor can be defined according to the invention, a pole pitch, which is smaller than the dimension of the stator coil assembly in the direction of movement of the rotor.

According to the invention, the outer region (s) of the stator can have at least one stator coil in addition to or instead of the inner regions of the stator.

The dimension of the coil arrangement of the stator in the direction of movement of the rotor can be greater according to the invention than the distance between two adjacent tooth pairs of the stator.

The stator (the inner and / or the outer magnetically conductive region) is preferably made of electro-sheet metal parts because of the stator's practically exclusively two-dimensional magnetic flux profile. However, it is also possible to produce it at least partially as a soft-magnetic shaped body, preferably made of pressed and / or sintered metal powder.

According to the invention, the outer regions of the stator at least partially form a magnetic yoke body.

Due to the high power density of the arrangement according to the invention, the transverse dimensions of the linear actuator with the necessary performance data can be kept very small. This allows use in tight spaces.

For the loose coupling of the linear actuator according to the invention with the tool of the electric percussion tool for the transmission of the impact energy are the most diverse Ausgestal- possible. Thus, for example, the drive member with a percussion part in the direction of movement of the rotor longitudinally displaceable be coupled such gear that the impact part can transmit the mechanical impulse to the tool of the electric percussion tool substantially in the direction of movement of the rotor.

The coil assembly of the stator can be adapted to be energized by an electronic control such that the drive member decelerates before striking the impact member on the tool or a tool holder in the electric impact tool movement and the impact member travels a predetermined path in a free flight phase , Under free flight phase is understood a movement of the percussion part in the direction of movement of the rotor, in which the impact part is not or practically no longer transported by the drive member to the tool or a tool holder in the electric impact tool; rather, as a result of a previous acceleration exerted by the rotor on the striker by drive member, the striker "flies" toward the tool or tool receptacle without further drive coupling with the striker, in other words the impact member has disengaged from the propulsion member In the case of the striking part, a mechanical decoupling of the tool or of the tool holder from the rotor of the linear actuator is achieved at the moment when the impact part hits the tool or the tool holder.This loose coupling does not cause the individual components of the linear actuator, in particular its rotor, to do so are heavily loaded mechanically.

The stator coil assembly may be further configured to be energized by electronic control such that the drive member directs the impact member toward the tool or tool receptacle in the electric impact tool and away from the tool or tool receptacle moved back to the starting position.

To operate a tool of the electric percussion tool, the rotor may also include a driving ram, which cooperates with a working chamber in which a working piston is slidably received, which is adapted to strike the tool of the electric percussion hammer, wherein in the working chamber between the drive rod and the working piston is a working medium, so that when a movement of the drive rod in the direction of movement of the rotor of the working piston performs a corresponding movement. Bn difference of the arrangement according to the invention to the above-described known arrangement of a Aufbruchhammers is that by the use of the linear actuator according to the invention or its loose coupling to the tool of the electrical Schalgwerkzeuges required for the implementation of the rotational movement of the AC universal motor in a rectilinear motion components ( Transmission, crank mechanism with crank pin, and connecting rod) accounts.

In this case, the drive rod may protrude at least in sections into the, for example, a hollow cylindrical working chamber. In addition, the working medium is preferably a compressible medium, e.g. Air or another gas; however, it is also possible to use an incompressible medium, e.g. Oil, water or the like to use. Finally, at least one stop can be provided, with which the working piston cooperates to limit the movement of the working piston in one or both directions of its movement.

The working piston can be arranged in the working chamber such that the movement performed by it is oriented approximately along the direction of movement of the rotor. However, it is also possible that the direction of movement of the rotor and the direction of movement of the working piston or with this associated tool of the electric impact tool are not collinear but enclose an angle with each other.

By the working medium between the drive rod and the working piston in the working chamber, the energy is transferred from the linear actuator to the working piston or the tool. In this case, in the case of a compressible medium, a mechanical decoupling of the working piston or the tool is achieved by the rotor of the linear actuator. This decoupling has the consequence that the individual components of the linear actuator, in particular its rotor, are not so heavily mechanically loaded. If greater coupling is desired, this can be achieved by using an incompressible medium, e.g. by a spring-loaded pressure receiving vessel, the coupling is adjustable.

Other features, features, advantages, and possible modifications will become apparent from the following description in which reference is made to the accompanying drawings.

Brief description of the drawings

1 is an embodiment of a linear actuator according to the invention in an electric

Impact tool illustrated schematically in perspective longitudinal section. In Fig. Ia, an alternative embodiment of a loose gear coupling of an impact member to the rotor is illustrated schematically in perspective longitudinal section.

In FIG. 2, an embodiment of a coil arrangement of the linear actuator according to the invention in the electric impact tool is schematically illustrated in a perspective plan view.

In FIG. 3, an embodiment of a stator of the linear actuator according to the invention in the electric impact tool is schematically illustrated in a perspective plan view.

In FIG. 4, an embodiment of a stack of magnetic bars of the linear actuator according to the invention in the electric impact tool is schematically illustrated in a perspective plan view.

FIG. 5 schematically illustrates a further embodiment of a linear actuator according to the invention in the electric impact tool in a perspective longitudinal section.

Detailed Description of Presently Preferred Embodiments

FIG. 1 illustrates a first embodiment of an electric linear actuator 10 in an electric percussion tool having rotor 16 and a stator 18.

The rotor 16 has two mutually spaced at a distance L parallel stack 14, 14 'of a plurality of superimposed, permanent magnetic rods 30, 30' with a substantially parallelepiped shape.

The stator 18 is formed as a soft magnetic molded body made of sintered iron-metal powder or layered iron sheets. The stator 18 has a plurality of tooth pairs 22a, 22a '; 22b, 22b '; 22c, 22c '; 22d, 22d '; 22e, 22e '; 22f, 22f with opposing teeth 22. Between the teeth 22 of a pair of teeth each one of the two stacks 14, 14 'is added to form an air gap 24 or 24'.

Between the two stacks 14, 14 'of the rotor 16, the stator 18 has magnetically conductive inner regions 50, 50a, which are arranged in the direction of movement B of the rotor 16 from each other at a predetermined distance A. Each of the two inner regions 50, 50a of the stator 18 is in each case surrounded by a substantially hollow-cylindrical coil arrangement 60, 60a. The central longitudinal axis M of the respective coil arrangements 60, 60a runs approximately transversely to the direction of movement B of the rotor 16. The coil assembly 60, 60a is designed to achieve the highest possible filling factor as a copper tape coil.

The two coil assemblies 60, 60a are to be energized so that they each generate a magnetic field in the opposite direction. In Fig. 1, the upper coil assembly 60 in the position shown of the rotor 16 generates a magnetic field which is oriented substantially along the central longitudinal axis of the coil assembly 60 from left to right, while the lower coil assembly 60a generates a magnetic field in the illustrated position of the rotor 16 which is oriented substantially along the central longitudinal axis of the coil assembly 60 from right to left. This changes to drive the rotor 16 along the direction of movement B (up or down).

Since each coil arrangement 60, 60a completely surrounds the respective one of the two inner regions 50, 50a of the stator 18 over its entire extension, it can be filled with maximum winding space. As illustrated in FIGS. 1 and 2 by respective arrowheads and arrowheads, the two coil assemblies 60, 60a are each energized to current each in the middle portion 64 in which they abut one another Lead direction (see Fig. 2).

In the arrangement shown, the rotor 16 is formed of two parallel aligned stacks 14, 14 ', the magnetic rods of permanent magnetic material (for example, samarium cobalt) are formed. The individual magnetic bars 30 are arranged flush with one another, wherein the magnetic orientation of the magnetic bars 30 is aligned alternately (from the inner region of the stator 18 to the outside and vice versa). In addition, the magnetic rods 30 are dimensioned so that in a predetermined position of the rotor 16 of the magnetic bars 30 between two teeth 22 of a tooth pair of the stator 18 is aligned. Adjacent bars 30, 30 'of a stack 14, 14' have an alternating magnetic orientation N -> S, S <- N. Each of these bars is thus aligned in certain positions of the rotor 14 with teeth 22 of the stator 18, in these escape positions also coincides the central longitudinal axis Z of two opposing teeth 22 of a tooth pair substantially with the magnetic orientation of the respective aligned rod together. As can be seen, the central longitudinal axis M of the coil arrangement 60 is oriented approximately transversely to the direction of movement of the rotor 16 and is aligned approximately with the central longitudinal axis of two opposing teeth of a pair of teeth.

Between two adjacent magnetic bars 30 of a stack 14, 14 'are 16 to reduce the inertial mass of the rotor magnetically not effective, also cuboid Ab- Stand holder 34, 34 'made of plastic, for example, carbon fiber reinforced plastic inserted. The mutually adjacent permanent magnet rods 30 and the magnetically non-effective spacers 34, 34 'are fixedly connected to each other. In other words, in the moving part of the actuator (the rotor) are no magnetic flux conducting parts (such as flux guide pieces), but only permanent magnets, which are always optimally arranged in the magnetic field. This arrangement also has the advantage of weight saving. If cuboidal rods made of permanent magnetic material are not available with sufficient magnetic field strength, it is also possible according to the invention to assemble the rods of permanent magnet segments in such a way that a magnetic field (from inside to outside or vice versa) is generated transversely to the direction of movement of the rotor 16.

The stator 18 furthermore has two magnetically conductive outer regions 52, 52 'lying outside the two stacks 14, 14' of the rotor 16, which are preferably produced as iron sheet packages because of the virtually exclusively two-dimensional magnetic flux guide. However, it is also possible to form these as a soft magnetic molded body made of sintered iron metal powder. These outer areas 52, 52 'of the stator 18 are designed in cross-section substantially comb-shaped and have at their, the stacks 14, 14' of the rotor 16 facing ends of teeth 22, the teeth of the inner areas 50, 50a of the Stand 18 mirror image. correspond.

Between the magnetically conductive inner regions 50, 50a lies a predetermined distance A, which is dimensioned to be substantially equal to the dimension of an even number (in the illustrated embodiment, two) of permanent magnetic rods 30, 30 'of the two stacks 14 , 14 '(with associated spacers) in the direction of movement B of the rotor 16. The length of the outer, in cross-section comb-shaped regions 52, 52 'of the stator 18 is dimensioned so that the magnetic rods of the rotor 16 facing, corresponding teeth 22 facing at both ends in each case a magnetic rod of different orientation. In other words, in a certain position of the rotor, the teeth 22 of the pair of teeth 22d are aligned with an outwardly oriented magnetic bar while the teeth 22 of the corresponding pair of teeth 22c are aligned with an inwardly oriented magnetic bar. The same applies to the teeth 22 of the tooth pair 22e, which correspond to the teeth 22 of the tooth pair 22b, as well as to the teeth 22 of the tooth pair 22f, which correspond to the teeth 22 of the pair of teeth 22a. Thus, the outer regions 52 of the stator 18 form a magnetic yoke body. In Fig. 1, the comb-shaped portions of the outer portions 52, 52 'of the upright 18 are illustrated as three single nested C-shaped yokes. However, it is also possible, the two outer portions 52, 52 'of the stator 18 each as Package of one-piece soft magnetic comb-shaped sheets, each having the teeth to make. An essential advantage of the arrangement according to the invention of the outer region (s) of the stator 18 is that virtually no magnetic leakage flux is emitted into the environment.

For better illustration, the stator 18 with its inner 50, 50a and outer regions 52, 52 'is shown exempted in FIG. In this case, one of the outer regions 52 'and the upper inner region 50 is omitted. Not illustrated in the drawing, but within the scope of the invention is that the outer portions 52, 52 'of the stator 18 in addition to or instead of the inner portions 52 of the stator 18 have at least one stator coil. As can be seen, the dimension of the coil arrangement 60, 60a in the direction of movement of the rotor 16 is greater than the distance between two adjacent tooth pairs of the stator 18.

In Fig. 5, a second embodiment of an electric linear actuator 10 is illustrated. In this case, reference numerals used in the preceding paragraph designate parts or components with the same or comparable function or mode of operation and are therefore explained below only in so far as their specific design, function or mode of operation deviates from those described above.

In this embodiment, the rotor 16 has a stack 14 of a plurality of superposed, permanent magnetic rods 30 having a substantially cuboidal shape. The stator 18 is formed as a soft magnetic laminated core stack. The stator 18 has a plurality of tooth pairs 22a... 22f with opposing teeth 22. Between the teeth 22 of a pair of teeth, the stack 14 is received to form an air gap 24 or 24 ',

On one side of the stack 14 of the rotor 16 (in Rg. 5 on the right side) of the stator 18 has two magnetically conductive inner portions 50, 50 a, which are arranged in the direction of movement B of the rotor 16 from each other at a predetermined distance A. Each of the two inner regions 50, 50a of the stator 18 is in each case surrounded by a substantially hollow-cylindrical coil arrangement 60, 60a. These two inner regions 50, 50a of the stator 18 practically form the legs of a horizontal "U", the Verbindungsjoch- is formed by a magnetically conductive outer region 52 '. In other words, in this embodiment, the second stack of the rotor is omitted and the stator iron is continuously formed. The outboard portion 52 of the upright 18 located outside of the runner 16 is substantially comb-shaped in cross-section and has at its the stacking 14 of the rotor 16 end facing teeth 22 which correspond in shape to the teeth of the inner regions 50, 50a of the stator 18 mirror images.

Also in this embodiment, between the magnetically conductive inner regions 50, 50a is a predetermined distance A, which is dimensioned to be substantially equal to the dimension of an even number (in the embodiment shown, two) of permanent-magnetic rods 30, 30 '. the two stacks 14, 14 '(with associated spacers) in the direction of movement B of the rotor 16 matches. Likewise, the length of the cross-sectionally comb-shaped regions 52, 52 'of the stator 18 is dimensioned so that the magnetic rods of the rotor 16 facing, corresponding teeth 22 are opposite to a magnetic rod of different orientation at both ends.

The above describes single-phase linear actuators. However, it is also within the scope of the present invention to design a two- or multi-phase arrangement of the linear actuator to achieve a more uniform power consumption of the linear actuator. For this purpose, the teeth of a further stator system with associated coils are to be positioned offset geometrically along the magnet of the rotor in accordance with the intended phase offset of the electrical drive power.

The rotor 16 a rod-shaped drive member 15 which has a slot 15a at its free end (in Rg. 1 below). In the slot 15a engages in the direction of movement B of the rotor 16 longitudinally displaceable a rod 19 with a at its free end (in Rg. 1 below) trained, opposite same slot 19a. The rod 19 is connected to a circular cylindrical impact member 21 made of high-strength steel. Through the two with their slots 15a, 19a nested in the ends of the impact member 21 is coupled with the rotor 16 so geared that the impact member 21 can transmit a mechanical impulse to a direction indicated by reference numeral 23 tool of electric percussion hammer in the direction of movement B.

In this case, during a "pushing phase", a free end v of the drive member 15 and an inner portion u of its elongated hole 15a respectively at an inner point v 'of the slot 19a of the rod 19 and at a free end u' of the rod 19. Then by correspondingly driving the coil assembly of the stator 18 causes a slowing or deceleration of the rotor 16, so that the thrust contact between the rod 19 and the drive member 15 is released, the impact member is in a "free-flying phase" in which there is no more acceleration. The free flight phase is terminated when the accelerated by the rotor 16 in the direction of the tool 23 of the electric percussion hammer part 21st on the facing this end face 23a of the tool 23a. Thereby, the tool 23 of the electric percussion hammer in the direction of movement of the percussion part 21 (in Fig. 1 down) accelerated. Subsequently, the impact member 21 of the drive member

15 pulled back (in Rg. 1 up), in which case the respective opposite inner points w and w 'of the slots 15a and 19a abut each other.

The tool 23 of the electric percussion hammer and the impact member 21 are at least partially in a direction indicated by the reference numeral 25 guide tube - in the sliding seat - added. The path of the tool 23 of the electric percussion hammer is limited by a step 25a in the guide tube, so that during the retraction of the percussion part 21 of the tool 23, these two separate from each other spatially in the direction of movement of the rotor 16. Instead of the stepped guide tube 25, however, other configurations, for. B. guide rails with corresponding travel limit stops 25a for the tool 23 of the electric percussion hammer possible.

Instead of the illustrated in Fig. 1 embodiment of a loose gear coupling of the percussion part 21 with the rotor 16 via the drive member 15 and the rod 19 with its two interlocking ends, other embodiments are possible. For this purpose, a loose coupling is exemplified in Fig. Ia, which is also an acceleration of the percussion part 21 by the rotor 16 in the direction of the tool 23 and a tool holder, a free-flying phase of the percussion part 21 until its impact on the tool 23, as well a return of the sliding part 21 away from the tool 23 allows. With 1 matching or equivalent components bear the same reference numerals.

The coil assembly of the stator 18 is electrically connected to an electronic control not further illustrated and is energized by the latter so that the rotor

16 decelerates before striking the impact member 21 on the tool 23 or a tool holder in the electric percussion hammer movement and the impact member 21 travels a predetermined path in a free-flying phase.

After the pulse has been transmitted from the impact member 21 to the tool 23 or the tool holder in the electric impact tool so that the tool performs a feed in the direction of movement, the coil assembly 60, 60 a can be energized by electronic control such that the rotor 16 the striking member 21 in the opposite direction (back) pulls. In this case, the rotor 16 moves the impact member 21 on the tool or the tool holder in the electric impact tool out with a first speed, and with a second, lower speed of the tool 23 or the tool holder away.

The rotor in another, also exemplary embodiment of the loose coupling can also be provided with a driving rod, which projects into a substantially circular cylindrical working chamber and is slidable in this by a seal in the sealing seat in the direction of movement of the rotor. In the working chamber is also a working piston, which is also slidable in the direction of movement of the rotor. The working piston can thus strike a tool of the electric impact tool, which is in a tool holder -. by plugging, a catch, or the like - is held. In the working chamber is located between the drive rod and the working piston, a working fluid, for example in the form of air, so that upon movement of the drive rod in the direction of movement B of the rotor, the working piston performs a corresponding - albeit cushioned - longitudinal thrust movement on the tool holder. The "air cushion" between the drive ram and the working piston practically prevents an immediate reaction from a backlash of the tool on the runner.

The wall of the cylindrical working chamber may be provided with a stepped stop to limit the movement of the tool holder, so that during the retraction of the drive rod of the working piston from the tool in the direction of movement of the rotor spatially separate. Instead of a stepped tubular working chamber but other configurations, for. B. guide rails with corresponding Wegbegrenzungsanschlägen for the tool of the electric impact tool possible.

The illustrated embodiments are particularly suitable to realize the required stroke of the tool of about 10-200 mm with the required single impact energy of about 3 to about 150 joules and a stroke rate of about 150 to 3000 per minute in a relatively small space.

It is understood by a person skilled in the art that individual aspects or features of the different embodiments described above can also be combined with one another.

Claims

claims

1. Linear actuator for an electric impact tool, with

- A rotor (16) and a stator (18), wherein

the rotor (16) has at least one stack (14, 140 of superposed permanent-magnetic rods (30, 300)

- The stator (18) is at least partially formed of a soft magnetic material and at least one tooth pair (22a, 22a ', 22b, 22b', 22c, 22c ', 22d, 22d', 22e, 22e ', 22f, 22p) with each other opposing teeth (22), each of which pair of teeth receives a stack (14, 140 between them to form a respective air gap (24, 240)

- The stator (18) has at least two magnetically conductive inner portions (50, 50a) which are arranged in the direction of movement (B) of the rotor (16) from each other at a predetermined distance A and each at least partially of a substantially hollow cylindrical Coil arrangement (60, 60a) are surrounded, whose center longitudinal axis M is oriented approximately transversely to the direction of movement B of the rotor (16), and

- The rotor (16) has a drive member (15) which cooperates via a loose coupling with a tool (23) of the electric percussion tool to transmit a mechanical impulse to this.

2. A linear actuator for an electric percussion tool according to claim 1, characterized in that the rotor (16) has two or more spaced from each other at a predetermined distance stack (14, 140 permanent-magnetic rods (30, 300, and the magnetically conductive inner regions ( 50, 50a) of the stand (18) between the stacks (14, 140 of the rotor (16) are arranged.

3. Linear actuator for an electric percussion tool according to one of claims 1 or 2, characterized in that the hollow cylindrical coil arrangement (60, 60a) has a substantially rectangular cross-section.

4. A linear actuator for an electric percussion tool according to any one of claims 1-3, characterized in that each tooth (22) in the direction of movement (B) of the rotor (16) has a dimension substantially corresponding to the dimension of a permanent magnet rod ( 30, 300 in the direction of movement (B) of the rotor (16) coincides, so that in a predetermined position of the rotor (16) at least one pair of teeth of the stator (18) with a permanent magnetic rod (30, 300 is aligned.

5. linear actuator for an electric impact tool according to claim 4, characterized in that in the direction of movement (B) of the rotor (16) adjacent tooth pairs of the stator (18) relative to the dimension of the permanent-magnetic rods (30, 30 ⁷ ) in the Movement direction (B) of the rotor (16) are dimensioned such that, between two permanent-magnetic rods, which are aligned with two adjacent tooth pairs of the stator (18), at least one further of the permanent-magnetic rods (30, 3C) is arranged.

6. linear actuator for an electric impact tool according to one of claims 1-5, characterized in that the magnetically conductive inner regions (50, 50a) at their, the rotor (16) facing ends at least one of the teeth (22).

7. Linear actuator for an electric percussion tool according to one of claims 1 to 6, characterized in that the stator (18) has at least one outside of the stack (14, 140 of the rotor (16) lying magnetically conductive outer region (52) at its, the stack (14, W) of the rotor (16) facing the end of at least one of the teeth (22).

8. linear actuator for an electric percussion tool according to one of claims 1-7, characterized in that the outer region (52, 520 of ^the stator (18) is designed at least in a partial section in cross-section substantially comb-shaped.

A linear actuator for an electric impact tool according to any one of claims 1-8, characterized in that adjacent rods (30, 30 ^* ) of a stack have an alternating magnetic orientation (N -> S, S <- N) substantially is aligned with the central longitudinal axis (Z) of two opposing teeth (22) of a pair of teeth.

10. Linear actuator in an electric impact tool according to one of claims 1 - 9, characterized in that the central longitudinal axis (M) of the coil assembly (60) is oriented approximately transversely to the direction of movement of the rotor (16) or approximately with the central longitudinal axis of two opposing teeth a tooth pair is aligned or at least partially oriented substantially parallel to it.

A linear actuator in an electric percussion tool according to any one of claims 1-10, characterized in that the predetermined distance (A) between the magnetically conductive inner regions (50, 50a) is dimensioned to be substantially equal to the dimension of a straight line Number of permanent magnetic rods (30, 3O ⁷ ) of the two stacks (14, 140 in the direction of movement (B) of the rotor (16) matches.

12. linear actuator in an electric impact tool according to one of claims 1-11, characterized in that in each case two adjacent permanent magnetic rods (30, 300 of the two stacks (14, 140 of the rotor (16) by magnetically non-effective spacers (34, 340 are interconnected at a predetermined distance.

13. Linear actuator in an electric impact tool according to one of claims 1 - 12, characterized in that by the dimensions of the permanent-magnetic rods (30) in the direction of movement (B) of the rotor (16) and the teeth (22) of the stator (18 ) is defined a pole pitch which is smaller than the dimension of the stator coil (28) in the direction of movement B of the rotor (16).

14. Linear actuator in an electric impact tool according to one of claims 1-13, characterized in that the outer regions (52) of the stator (18) additionally or instead of the inner regions (52) of the stator (18) at least one stator coil ( 28).

15. Linear actuator in an electric percussion tool according to one of claims 1-14, characterized in that the dimension of the coil arrangement (60, 60a) in the direction of movement of the rotor (16) is greater than the distance between two adjacent tooth pairs of the stator (18). ,

16 linear actuator in an electric impact tool according to one of claims 1-15, characterized in that the stator (18) is at least partially a soft magnetic molded body, preferably made of pressed and / or sintered metal powder.

17. Linear actuator in an electric impact tool according to one of claims 1-16, characterized in that the outer regions (52) of the stator at least partially form a magnetic yoke body.

18. Electric percussion tool with a linear actuator according to one of claims 1 - 17.