Field of the disclosure

The disclosure relates to a hammer device connectable to an excavator or a to working machine of another kind.

Background

Typically, a hammer device is used as an attachment to an excavator or another working machine where the intention is to break up for example stone, concrete, or some other material. The hammer device can be attached e.g. to the boom of an excavator, in place of a bucket. The hammer device is often hydraulically driven, allowing it to be connected to the hydraulic system of the excavator or the other working machine. The hydraulic hammer device incorporates a percussion mechanism capable of delivering impacts to a tip member forming part of the hammer device. A first end the tip member forms a tip which transmits the impacts to the ma- terial to be broken up. The percussion mechanism comprises a percussion piston having a reciprocating linear movement and striking and impact face on a second end of the tip member. At the same time as the percussion piston delivers the impacts, the hammer device is pushed against material to be broken up. Thus, the above-mentioned tip penetrates, due to the impacts and the pushing, into the mate- rial to be broken up, and, consequently, breaks up the material.

However, a hydraulic hammer device of the kind described above has its own challenges. One of the challenges encountered with hydraulic hammer devices is their tendency to cause pressure shocks which can be destructive to the hydraulic system of the working machine. These pressure shocks can be smoothed, but to some ex- tent only, by means of a pressure accumulator. Another challenge of a hydraulic hammer device is that it has relatively high power consumption. The hydraulic system contains, in the energy flow direction, a plurality of energy-loss producing elements one after another, causing a reduction of the efficiency of the whole. The energy-loss producing elements include, for instance, an engine that drives a hy- draulic pump, the hydraulic pump, a piping and valve system that produces a flow resistance. Any heating up of the hydraulic oil in the hydraulic hammer device may also pose its own challenges to the hydraulic system of the working machine.

Summary

The following presents a simplified summary to provide a basic understanding of some aspects of various invention embodiments. The summary is not an extensive overview of the invention. It is neither intended to identify key or critical elements of the invention nor to delineate the scope of the invention. The following summary merely presents some concepts of the invention in a simplified form as a prelude to a more detailed description of exemplifying embodiments of the invention. In this document, the word "geometric" when used as a prefix means a geometric concept that is not necessarily a part of any physical object. The geometric concept can be for example a geometric point, a straight or curved geometric line, a geometric plane, a non-planar geometric surface, a geometric space, or any other geometric entity that is zero, one, two, or three dimensional. In accordance with the invention, there is provided a new hammer device connect- able to e.g. an excavator or another working machine. A working machine, such as e.g. an excavator, is typically called an off-road machine. However, to emphasize that an ability for off-road operation is possible but not necessary, the broader term "working machine" is used in this document. A hammer device according to the invention comprises:

- a frame attachable to a working machine e.g. to the boom of an excavator, the frame comprising attachment members for attaching to the working machine so that the frame is nondestructively detachable from the working machine, - an actuator member linearly movably supported by the frame and forming a tip member to transmit impacts to target material, or, capable of accommodating a separate tip member, and a linear electric machine comprising : - a mover for moving the actuator member in a linear manner, and

- a stator connected to the frame and provided with windings for producing a magnetic force directed to the mover in response to electric current supplied to the windings. An inherent advantage of the above-described electrically driven hammer device is that it does not cause pressure shocks to a hydraulic system of an excavator or another working machine. Furthermore, the efficiency of electrically implemented energy transmission and processing is typically higher than that of hydraulically implemented energy transmission and processing. Thus, the electrically driven ham- mer device typically has a lower energy consumption than a hydraulic hammer device of equal power. An advantage of the electrically driven hammer device is that its operating electrical energy can be taken, in many instances, from the common electrical grid. The unit price, such as the kilowatt hour price, of the electrical energy provided by the common electrical grid is often lower than the unit price of hydraulic energy generated locally e.g. with a diesel-driven pump.

Exemplifying and non-limiting embodiments are described in accompanied dependent claims.

Various exemplifying and non-limiting embodiments both as to constructions and to methods of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific exemplifying and non- limiting embodiments when read in conjunction with the accompanying drawings.

The verbs "to comprise" and "to include" are used in this document as open limitations that neither exclude nor require the existence of un-recited features. The features recited in dependent claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of "a" or "an", i.e. a singular form, throughout this document does not exclude a plurality. Brief description of the drawings

Exemplifying and non-limiting embodiments and their advantages are explained in greater detail below in the sense of examples and with reference to the accompanying drawings, in which: Figures 1 a, 1 b, and 1 c illustrate a hammer device according to an exemplifying and non-limiting embodiment,

Figure 2 illustrates a linear electric machine of a hammer device according to an exemplifying and non-limiting embodiment,

Figures 3a, 3b, and 3c illustrate a linear electric machine of a hammer device ac- cording to an exemplifying and non-limiting embodiment,

Figure 4 illustrates a detail of a linear electric machine of a hammer device according to an exemplifying and non-limiting embodiment, and

Figure 5 illustrates a hammer device according to an exemplifying and non-limiting embodiment. Description of exemplifying and non-limiting embodiments

The invention and the embodiments thereof are not limited to the exemplifying and non-limiting embodiments described below. Thus, the specific examples provided in the description given below should not be construed as limiting the scope and/or the applicability of the appended claims. Lists and groups of examples provided in the description given below are not exhaustive unless otherwise explicitly stated.

Figure 1 a shows a hammer device 100 according to an exemplifying and non-limiting embodiment. Figure 1 b shows a section view taken along a line A-A shown in Figure 1 a. The section plane is parallel with the yz-plane of a coordinate system 199. Figure 1 c shows a magnification of a part B of Figure 1 b. The hammer device 100 has a frame 101 attachable to a working machine, such as to the boom of an excavator in place of a bucket. The frame 101 has attachment members 102 for attaching to the working machine so that the frame is nondestructively detachable from the working machine. The hammer device 100 comprises an actuator member 1 03 linearly movably supported by the frame 1 01 . An end 1 1 5 of the actuator member 1 03 is shaped to allow a separate tip member 1 1 6 to be attached as an extension of the actuator member. The hammer device 1 00 comprises a linear electric machine having a mover 1 04. The mover 1 04 is arranged to move the actuator member 1 03 in a linear manner, parallel to the z-axis of the coordinate system 1 99. The linear electric machine comprises a stator 1 05 attached to the frame 1 01 and comprising windings 1 06 for generating a magnetic force directed to the mover 1 04 in response to electric current supplied to the windings. The windings 1 06 may constitute for example a multi-phase winding, e.g. a two- or three-phase winding. In the exemplifying hammer device 1 00 illustrated in Figures 1 a-1 c, the linear electric machine is a tubular linear electric machine in which the conductor coils of the windings 1 06 are arranged to surround the mover 104. Figures 1 b and 1 c show cross-sectional views of the conductor coils of the windings. In Figure 1 b, the cross-sections of the conductor coils are depicted by black rectangular patterns. In Figure 1 c, two of the conductor coils of the windings are denoted with figure references 1 25 and 1 26. The mover 1 04 can be, for example, substantially rotationally symmetric with respect to a geometric line 1 20 shown in Figure 1 c.

The mover 1 04 comprises annular permanent magnets provided one after another in the longitudinal direction of the mover, i.e. in the direction of the z-axis of the coordinate system 1 99, the axial direction of the annular shape of each permanent magnet coinciding with the longitudinal direction of the mover. In Figure 1 c, two of the annular permanent magnets are denoted with figure references 1 07 and 1 08. The magnetizing directions of the permanent magnets coincide with the longitudinal direction of the mover, the magnetizing directions of the successive permanent mag- nets being opposite to each other. The magnetizing directions of the permanent magnets are indicated with arrows in Figure 1 c. Exemplifying magnetic flux lines are depicted with dashed lines. The mover 1 04 has a center rod 1 1 1 and annular ferromagnetic elements provided around it form a ferromagnetic core structure for the mover 1 04. In Figure 1 c, two of the annular ferromagnetic elements of the mover are denoted with figure references 1 1 2 and 1 1 3. Each annular permanent magnet is situated between two successive annular ferromagnetic elements. Preferably, the center rod 1 1 1 is made of a non-ferromagnetic material to allow a portion as large possible of the magnetic flux generated by the permanent magnets to travel through the stator 1 05. The center rod can be made of for example austenitic steel or some other non-ferromagnetic and sufficiently strong material.

The core structure of the stator 1 05 comprises annular ferromagnetic elements which surround the mover 1 04 and which, being stacked one after another in the longitudinal direction of the mover, form slots for conductor coils of the stator windings. In Figure 1 c, two of the annular ferromagnetic elements are denoted with figure references 1 09 and 1 10. An exemplifying way of implementing the windings of the stator 1 05 is that each slot is provided with only one conductor coil belonging to one phase of the windings. It is also possible to provide each slot, for instance, with two conductor turns belonging either to the same phase of the windings or to two different phases of the windings. The stator 1 05 also comprises a stator frame 1 1 7 having cooling channels for a cooling medium flow. The cooling medium can be for example oil or water. In Figure 1 c, one of the cooling channels is denoted with a figure refer- ence 1 14.

The mover 1 04 can be moved in a controlled way for example with a power electronic converter coupled to the windings of the stator. It is often advantageous for the control by the power electronic converter to know the position of the mover 104 with respect to the stator 1 05. For example, the position of the mover can be meas- ured with a mechanical position sensor comprising a sensor rod fixed to the mover. The position of the mover can also be measured in a contactless way, for example with a laser measurement arrangement. It is also possible provide the mover and the stator with structures operable as an inductive position sensor. Hammer devices according to different embodiments allow for the use of any applicable position measurement and/or estimation methods known in the prior art. The invention is not limited any specific position measurement and/or position estimation method.

Figure 2 illustrates a part of a linear electric machine of a hammer device according to an exemplifying and non-limiting embodiment. The linear electric machine comprises a mover 204 and a stator 205. The mover 204 is movably supported relative to the stator 205, the direction of movement of the mover 204 being parallel to the z-axis of a coordinate system 299. Figure 2 shows a section view in which the section plane is parallel to yz-plane of the coordinate system 299. The stator 205 comprises windings for generating a magnetic force directed to the mover 204 in response to electric current supplied to the windings. In the exemplifying case shown in Figure 2, the windings constitute a three-phase winding whose phases are denoted with figure references U, V and W. The linear electric machine is a tubular linear electric machine in which the conductor coils of the stator windings are arranged to surround the mover 204. The mover 204 and the electromagnetically active parts of the stator 205 can be, for instance, rotationally symmetric with respect to a geometric line 220 shown in Figure 2. In Figure 2, the cross-sections of the conductor coils of the windings of the stator 205 are presented as cross-hatched areas. Figure 2 uses a notation in which the left side of an area representing a cross- section of each conductor coil is provided with a phase-indicating figure reference U, V or W, and with "+" if the direction of electric current in the conductor coil cross- section under consideration is the positive x-direction of the coordinate system 299 when the electric current of this phase U, V or W is positive, or with "-" if the direction of the electric current in the conductor coil cross-section under consideration is the negative x-direction of the coordinate system 299 when the electric current of this phase U, V or W is positive. The stator 205 has annular permanent magnets provided one after another in the longitudinal direction of the mover 204, wherein the axial direction of the annular shape of each permanent magnet coincides with the longitudinal direction of the mover, i.e. is parallel with the z-axis of the coordinate system 299. In Figure 2, two of the annular permanent magnets are denoted with figure references 207 and 208. The magnetizing directions of the permanent magnets coincide with the longitudinal direction of the mover 204, the magnetizing directions of the successive permanent magnets being opposite to each other. The magnetizing directions of the permanent magnets are indicated with arrows in Figure 2. An exemplifying magnetic flux line is depicted with a dashed line. The core structure of the stator 205 comprises annular ferromagnetic elements surrounding the mover 204 and forming slots for the conductor coils of the windings. In Figure 2, two of the annular ferromagnetic elements are denoted with figure references 209 and 210. The annular ferromagnetic elements and the permanent magnets of the stator are provided in the longitudinal direction of the mover 204 so that there is one of the slots between successive permanent magnets. In this exemplifying case, two conductor coils are provided in each stator slot. For example, conductor coils with designations +V and -W are provided in the slot formed by the ferromagnetic elements 209 and 210. The stator 205 may also comprise a stator frame 217, possibly equipped with cooling channels for a cooling medium flow. The stator frame 217 is advantageously made of a non-ferromagnetic material to allow a portion as large possible of the magnetic flux generated by the permanent magnets to travel through the mover 204. The stator frame 217 can be made of for example aluminum.

The mover 204 has a center rod 21 1 and annular ferromagnetic elements provided around the center rod to form a ferromagnetic core structure of the mover. In Figure 2, two of the annular ferromagnetic elements of the mover are denoted with figure references 212 and 213. The annular elements of the mover 204 are shaped to form, on the outer surface of the mover, ridges oriented in the circumferential direction of the mover and causing a reluctance variation which enables the stator 205 to generate the magnetic force directed to the mover. Figure 2 only shows a portion of the linear electric machine concerned. In total, the slots of the stator 205 can be 12 in number, for example, and the ridges can be provided on the mover 204 so that there are 13 mover ridges in the area covered by the stator. The mover 204 must have such a length that there is a sufficient number of ridges in the area covered by the stator within the entire range of movement of the mover.

The linear electric machine illustrated in Figure 2, having permanent magnets on its stator, is often referred to by the term a Flux switching permanent magnet synchronous machine, abbreviated as "FSPMSM".

Figure 3a shows a section view of a linear electric machine of a hammer device according to an exemplifying and non-limiting embodiment. The section plane is parallel with the yz-plane of a coordinate system 399. Figure 3b shows a magnifica- tion of a part B1 of Figure 3a, and Figure 3c shows a magnification of a part B2 of Figure 3a. The linear electric machine comprises a mover 304 and a stator 305. Figure 3a shows a part of the mover 304 also separately for the sake of clarity. The mover 304 comprises an active part 321 that contains permanent magnets provided one after another in the longitudinal direction of the linear electric machine. The longitudinal direction is parallel with the z-axis of the coordinate system 399. In Fig- ures 3a and 3b, two of the permanent magnets are denoted with figure references 307 and 308. The stator 305 comprises a ferromagnetic core-structure and windings for generating magnetic force acting on the mover 304 in response to supplying electric current to the windings. In Figure 3b, the ferromagnetic core-structure of the stator is denoted with a figure reference 322 and cross-sections of two conductor coils of the windings are denoted with figure references 335 and 336. As shown in Figure 3b, the ferromagnetic core-structure 322 constitutes stator slots for the conductor coils of the windings. Typically, the windings are arranged to constitute a multi-phase winding, e.g. a three-phase winding, and the windings can be implemented for example so that each stator slot contains only one conductor coil which belongs to one phase of the windings. It is, however, also possible that each stator slot contains for example two conductor coils which can belong to different phases of the windings or to a same phase of the windings.

The exemplifying linear electric machine illustrated in Figures 3a-3c comprises first and second support structures 323 and 324 on both sides of the ferromagnetic core- structure of the stator in the longitudinal direction of the linear electric machine. The first and second support structures 323 and 324 are arranged to support the mover 304 to be linearly movable with respect to the stator 305 in the longitudinal direction of the mover. As shown in Figure 3a, the active part 321 of the mover 304 is longer than the ferromagnetic core-structure of the stator 305 in the longitudinal direction of the mover. Thus, during a reciprocating linear movement of the mover 304, some of the permanent magnets of the mover 304 are temporarily inside a frame-portion 325 of the support structure 323. The frame-portion 325 is made of solid metal, e.g. solid steel, to achieve a sufficient mechanical strength. The support structure 323 further comprises a support element 326 arranged to keep the mover 304 a distance away from the solid metal of the frame-portion 325. In Figure 3c, the above-mentioned distance is denoted with D. The support element 326 constitutes a sliding surface 327 that is against the mover 304 and supports the mover in transversal directions, i.e. in directions perpendicular to the longitudinal direction of the linear electric machine. The support element 326 comprises material whose electrical conductivity, S/m, is less than that of the solid metal of the frame-portion 325. The electrical conductivity of the material of the support element 326 can be e.g. less than 50%, 40%, 30%, 20%, 1 0%, or 5% of the electrical conductivity of the solid metal of the frame-portion 326. As the mover 304 is kept the distance D away from the solid metal of the frame-portion 326, eddy currents induced by the moving permanent magnets of the mover to the solid metal are reduced. As a corollary, losses of the linear electric machine are reduced and thereby the efficiency of the hammer device is improved. The distance D can be e.g. at least 5 mm, at least 10 mm, at least 1 5 mm, at least 20 mm, at least 25 mm, or at least 30 mm.

The support element 326 may comprise for example polymer material or some other suitable material having low electrical conductivity and suitable mechanical properties. The polymer material can be e.g. polytetrafluoroethylene, known as Teflon. In a linear electric machine according to an exemplifying and non-limiting embodiment, the support element 326 comprises a coating constituting the sliding surface that is against the mover 304. In Figure 3c, the coating is denoted with a figure reference 330. The coating improves the wear resistance of the sliding surface of the support element 326. The coating can be for example a layer of chrome. In cases, where the coating is made of electrically conductive material, the coating is advantageously thin to reduce eddy current losses in the coating. In Figure 3c, the thickness of the coating 330 is exaggerated for the sake of clarity.

The exemplifying linear electric machine illustrated in Figures 3a-3c is a tubular linear electric machine where the ferromagnetic core-structure of the stator 305 is ar- ranged to surround the mover 304 and the windings of the stator are arranged to surround the mover 304 and conduct electric currents in a circumferential direction. The mover 304 can be, for example but not necessarily, substantially rotationally symmetric with respect to a geometric line 320 shown in Figure 3b. In this exemplifying case, the mover 304 comprises annular ferromagnetic elements that are alter- nately with the permanent magnets in the longitudinal direction of the mover. In Figure 3b, two of the annular ferromagnetic elements of the mover 304 are denoted with figure references 31 2 and 31 3. In this exemplifying case, the magnetization directions of the permanent magnets of the mover 304 are parallel with the longitudinal direction, and longitudinally neighboring ones of the permanent magnets have magnetization directions opposite to each other. In Figure 3b, the magnetization directions of the permanent magnets are depicted with arrows. Exemplifying mag- netic flux lines are denoted with curved dashed lines. In this exemplifying case, the mover 304 comprises a center rod 31 1 that mechanically supports the permanent magnets and the annular ferromagnetic elements of the mover 304. The center rod 31 1 is advantageously made of non-ferromagnetic material in order that as much as possible of the magnetic fluxes generated by the permanent magnets of the mover 304 would flow via the stator 305. The center rod 31 1 can be made of for example austenitic steel or some other sufficiently strong non-ferromagnetic material. In this exemplifying case, the ferromagnetic core-structure of the stator 305 comprises annular ferromagnetic elements surrounding the mover 304 and forming slots for the conductor coils of the windings. In Figure 3b, two of annular ferromagnetic elements of the stator 305 are denoted with figure references 309 and 310.

In the exemplifying linear electric machine illustrated in Figures 3a-3c, the support element 326 is tubular and arranged to surround an end-portion 328 of the mover 304. An end-portion 329 of the support structure 323 is closed, and the end-portion 328 of the mover 304 is arranged to operate as a piston for compressing gas, e.g. air, when the mover 304 moves towards the closed end-portion 329 of the support structure 323. The gas in the room limited by the tubular support element 326, the end portion 329 of the support structure 323, and the end-portion 328 of the mover 304 acts as a gas spring that intensifies the movement of the mover 304 in the negative z-direction of the coordinate system 399 and acts against the movement of the mover 304 in the positive z-direction of the coordinate system 399.

Figure 4 shows a section view of a part of a linear electric machine of a hammer device according to an exemplifying and non-limiting embodiment. The section plane is parallel with the yz-plane of a coordinate system 499. Figure 4 illustrates a part of a support structure 423 of the linear electric machine and a part of a mover 404 of the linear electric machine. The support structure 423 is arranged to support the mover 404 in the same way as the support structure 323 is arranged to support the mover 304 in the linear electric machine illustrated in Figures 3a-3c. The support structure 423 comprises a support element 426 that comprises material whose electrical conductivity is less than that of solid metal constituting a frame-portion 425 of the support structure 423. In this exemplifying linear electric machine, the support element 426 comprises ferromagnetic material 431 whose electrical conductivity is less than that the solid metal constituting the frame-portion 425, e.g. at most half of the electrical conductivity of the solid metal. The ferromagnetic material 431 provides low reluctance paths for magnetic fluxes generated by permanent magnets of the mover 404, and thereby the ferromagnetic material 431 reduces magnetic stray fluxes directed to the frame-portion 425 of the support structure 423. Furthermore, the ferromagnetic material 431 reduces the flux variation taking place in the permanent magnets and thereby the ferromagnetic material reduces losses of the permanent magnets. The ferromagnetic material 431 can be for example ferrite or iron powder composite such as e.g. SOMALOY® Soft Magnetic Composite. The support element 426 further comprises a coating 430 on a surface of the ferromagnetic ma- terial and constituting a sliding surface that is against the mover 404. The coating 430 can be for example a layer of chrome.

Figure 5 shows a section view of a hammer device 500 according to an exemplifying and non-limiting embodiment. The section plane is parallel with the yz-plane of a coordinate system 599. The hammer device comprises a frame 501 that comprises attachment members 502 for attaching to the working machine, e.g. an excavator, so that the frame 501 is nondestructively detachable from the working machine. The hammer device 500 comprises an actuator member 503 linearly supported to the frame 501 and linearly movable with respect to the frame. In this exemplifying case, an end of the actuator member 503 is shaped to allow a separate tip member to be attached as an extension of the actuator member. The hammer device 500 comprises a linear electric machine according to an embodiment of the invention. A sta- tor 505 of the linear electric machine is attached to the frame 501 , and a mover 504 of the linear electric machine is arranged to move actuator member 503. The linear electric machine can be for example such as illustrated in Figures 3a-3c or such as illustrated in Figure 4.

A linear electric machine of a hammer device according to an exemplifying and non- limiting embodiment is a reluctance machine in which no permanent magnets are needed, but, in which all magnetic flux is induced by an electric current, and, in which the magnetic force directed to the mover is generated by reluctance variation based on the design of the mover. In comparison to a permanent magnet machine, the drawbacks of a reluctance machine are a lower power density, i.e. a larger ma- chine is needed to produce the same power, and a lower efficiency because all magnetic flux is induced by an electric current, resulting in higher resistive l ² R losses in the electric machine, and, in addition, higher losses in the power electronics feeding the electric machine.

The invention and the embodiments thereof are not limited to the exemplifying and non-limiting embodiments described above. Thus, the specific examples provided in the description given above should not be construed as limiting the scope and/or the applicability of the appended claims. Lists and groups of examples provided in the description given above are not exhaustive unless otherwise explicitly stated.