WO2025032098A1 - A mover for a tubular linear induction machine - Google Patents

A mover for a tubular linear induction machine Download PDF

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Publication number
WO2025032098A1
WO2025032098A1 PCT/EP2024/072275 EP2024072275W WO2025032098A1 WO 2025032098 A1 WO2025032098 A1 WO 2025032098A1 EP 2024072275 W EP2024072275 W EP 2024072275W WO 2025032098 A1 WO2025032098 A1 WO 2025032098A1
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WO
WIPO (PCT)
Prior art keywords
mover
ferromagnetic
ferromagnetic core
stator
longitudinal direction
Prior art date
Application number
PCT/EP2024/072275
Other languages
French (fr)
Inventor
Jyri PELTOLA
Tuomo Peltola
Juha PYRHÖNEN
Original Assignee
Lekatech Oy
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Lekatech Oy filed Critical Lekatech Oy
Publication of WO2025032098A1 publication Critical patent/WO2025032098A1/en

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K41/00—Propulsion systems in which a rigid body is moved along a path due to dynamo-electric interaction between the body and a magnetic field travelling along the path
    • H02K41/02—Linear motors; Sectional motors
    • H02K41/025—Asynchronous motors
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25D—PERCUSSIVE TOOLS
    • B25D11/00—Portable percussive tools with electromotor or other motor drive
    • B25D11/06—Means for driving the impulse member
    • B25D11/064—Means for driving the impulse member using an electromagnetic drive
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B1/00—Percussion drilling
    • E21B1/12—Percussion drilling with a reciprocating impulse member
    • E21B1/22—Percussion drilling with a reciprocating impulse member driven by electromagnets
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K33/00—Motors with reciprocating, oscillating or vibrating magnet, armature or coil system

Definitions

  • the disclosure relates generally to linear electric machines. More particularly, the disclosure relates to a mover for a tubular linear induction machine. Furthermore, the disclosure relates to a tubular linear induction machine. Furthermore, the disclosure relates to an electric percussion device that comprises a tubular linear induction machine.
  • a linear electric machine comprises a stator and a mover which is linearly movable with respect to the stator in the longitudinal direction of the linear electric machine.
  • the mover and the stator are provided with magnetically operating means for converting electric energy into linear movement of the mover when the linear electric machine operates as a linear motor, and for converting linear movement of the mover into electric energy when the linear electric machine operates as a linear generator.
  • the magnetically operating means may comprise for example multiphase windings for generating a magnetic field moving with respect to the multiphase windings when alternating currents are supplied to the multiphase windings.
  • the magnetically operating means may comprise equipment for generating force in response to the moving magnetic field generated with the multiphase windings.
  • the above-mentioned equipment may comprise for example permanent magnets, electromagnets, electrically conductive structures, and/or mechanical structures providing a spatial reluctance variation.
  • the multiphase windings can be located in the stator and the equipment for generating force in response to a moving magnetic field can be located in the mover. It is also possible that the multiphase windings are located in the mover and the equipment for generating the force in response to the moving magnetic field is located in the stator.
  • a mover of a linear electric machine of an electric percussion device is configured to direct impacts to an actuator member, e.g. a chisel, of the electric percussion device.
  • an actuator member e.g. a chisel
  • the electric percussion device is pushed against material, e.g. stone, to be broken up.
  • material e.g. stone
  • a tip of the actuator member penetrates, due to the impacts and the pushing, into the material to be broken up, and, consequently, breaks up the material. Therefore, the mover of the linear electric machine of an electric percussion device is subjected to strong mechanical impacts and this imposes a requirement for a sufficient mechanical strength of the mover.
  • 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.
  • a mover comprises a ferromagnetic core having a rodlike shape elongated in the longitudinal direction of the mover.
  • the ferromagnetic core is made of ferromagnetic steel and has annular grooves on a surface of the ferromagnetic core so that the annular grooves are successively in the longitudinal direction of the mover and the annular grooves surround a longitudinal geometric center line of the ferromagnetic core.
  • the mover further comprises conductor rings placed in the annular grooves of the ferromagnetic core.
  • the conductor rings are made of electrically conductive material, e.g. copper, aluminum, copper alloy, or aluminum alloy, whose electric conductivity, 1/(Qm), is greater than the electric conductivity of the ferromagnetic steel of the ferromagnetic core.
  • the ferromagnetic core is a single piece of ferromagnetic steel to provide high mechanical strength against impacts directed to the mover.
  • a mover according to this exemplifying and non-limiting embodiment is suitable for e.g. an electric percussion device.
  • a new tubular linear induction machine that comprises:
  • stator comprising a stator core structure and stator windings configured to generate a magnetic field moving with respect to the stator core structure when alternating currents are supplied to the stator windings
  • a new electric percussion device that comprises:
  • a frame attachable to a working machine such as e.g. an excavator
  • the frame comprising attachment members configured to attach to the working machine so that the frame is nondestructively detachable from the working machine
  • an actuator member e.g. a chisel, linearly movably supported with respect to the frame
  • the stator of the tubular linear induction machine is attached to the frame and the mover of the tubular linear induction machine is configured to direct impacts to the actuator member.
  • An electric percussion device can be for example a hammer for breaking and demolition, a hammer of a piling machine, a hammer of a rock drill, or some other percussion device.
  • figures 1 a and 1 b illustrate a linear induction machine according to an exemplifying and non-limiting embodiment
  • figure 2 illustrates a percussion device that comprises a linear induction machine according to an exemplifying and non-limiting embodiment
  • figure 3 illustrates a percussion device that comprises a linear induction machine according to an exemplifying and non-limiting embodiment.
  • Figure 1 a shows a section view of a part of a tubular linear induction machine 105 according to an exemplifying and non-limiting embodiment.
  • the section plane is parallel with the yz-plane of a coordinate system 199.
  • the tubular linear induction machine comprises a stator 106 and a mover 101.
  • the mover 101 is linearly movable with respect to the stator 106 in the longitudinal direction of the tubular linear electric machine.
  • the longitudinal direction is parallel with the z-axis of the coordinate system 199.
  • Figurel b shows a magnification of a part of the section view of the mover 101 shown in figure 1 a.
  • the mover 101 comprises a ferromagnetic core 102 having a rod-like shape elongated in the longitudinal direction of the mover, i.e. in a direction parallel with the z-axis of the coordinate system 199.
  • the ferromagnetic core 102 is a single piece of ferromagnetic steel and has annular grooves on a surface of the ferromagnetic core so that the annular grooves are successively in the longitudinal direction of the mover 101 and the annular grooves surround a longitudinal geometric center line 198 of the ferromagnetic core.
  • the mover 101 comprises conductor rings placed in the annular grooves of the ferromagnetic core. In figure 1 a, one of the conductor rings is denoted with reference 103.
  • the conductor rings are made of electrically conductive material, e.g. copper, aluminum, copper alloy, or aluminum alloy, whose electric conductivity, 1/(Qm), is greater than the electric conductivity of the ferromagnetic steel of the ferromagnetic core 102.
  • the electric conductor rings can be made for example by casting the electrically conductive material into the grooves of the ferromagnetic core 102 and thereafter by machining outer surfaces, i.e. airgap surfaces, of the conductor rings by turning.
  • the exemplifying mover 101 illustrated in figures 1 a and 1 b comprises a tubular band 104 surrounding the ferromagnetic core 102 and the conductor rings. As shown in figure 1 b, the tubular band 104 has a mechanical contact with areas of an outer surface of the ferromagnetic core 102 between the annular grooves. The purpose of the tubular band 104 is to provide a smooth surface of the mover 101 , which facilitates arranging a mechanical support for supporting the mover 101 linearly moveably with respect to the stator 106.
  • the tubular band 104 can be made of for example steel or some other material whose coefficient of thermal expansion is sufficiently close to that of the steel of the ferromagnetic core 102.
  • the coefficient of thermal expansion of the electrically conductive material, e.g. copper, aluminum, copper alloy, or aluminum alloy, of the conductor rings is greater than the coefficient of thermal expansion of the steel of the ferromagnetic core 102.
  • the outer surfaces of the conductor rings are advantageously nearer to the longitudinal geometric center line 198 of the ferromagnetic core 102 than areas of the outer surface of the ferromagnetic core 102 between the annular grooves, i.e. R1 ⁇ R2, and thus there are safety gaps between the conductor rings and the inner surface of the tubular band 104.
  • the safety gaps make it possible to avoid a situation in which the outer surfaces of the conductor rings get farther from the longitudinal geometric center line 198 than the areas of the outer surface of the ferromagnetic core 102 between the annular grooves because of thermal expansion of the conductor rings greater than thermal expansion of the ferromagnetic core 102. In this unwanted situation, the tubular band 104 might be deformed and thus its outer surface might become uneven.
  • the safety gaps may contain e.g. air. In a mover according to another exemplifying embodiment, there is no tubular band and outer surfaces of the conductor rings and the areas of the outer surface of the ferromagnetic core between the annular grooves are in flush.
  • a mover according to this exemplifying embodiment is suitable for cases in which temperature changes are so small that a possible difference between the coefficient of thermal expansion of the steel of the ferromagnetic core and the coefficient of thermal expansion of the material of the conductor rings does not make the outer surface of the mover too uneven.
  • the outer surface of the mover can be provided with a suitable coating.
  • the coating material can be e.g. chrome or some other suitable material.
  • the stator 106 comprises a stator core-structure 107 and windings surrounding the mover 101 and configured to generate a magnetic force directed to the mover 101 in response to electric currents supplied to the windings.
  • FIG 1 a crosssections of two coils of the windings are denoted with references 108 and 109.
  • the windings of the stator 106 may constitute for example a multi-phase winding, e.g. a two- or three-phase winding.
  • the stator 106 also comprises a stator frame 112 having cooling channels for conducting cooling fluid, e.g. water or air. In figure 1 a, one of the cooling channels is denoted with a reference 113.
  • the stator core structure 107 comprises ring-shaped stator elements stacked in the longitudinal direction of the mover 101 , i.e. in a direction parallel with the z-axis of the coordinate system 199.
  • two of the ring-shaped stator elements are denoted with references 110 and 111.
  • the ring-shaped stator elements can be made of for example sintered ferromagnetic and electrically weakly conducting material such as ferrite or soft magnetic composite “SMC” material, e.g. Somaloy®.
  • a section of each of the ring-shaped stator elements along a geometric section plane coinciding with the longitudinal geometric center line 198 is T-shaped so that annular stator slots for the stator windings are formed between the ring-shaped stator elements which are stacked in the longitudinal direction.
  • the above-mentioned section of each of the ring-shaped stator elements along a geometric section plane of the kind mentioned above is L- shaped so that annular stator slots for stator windings are formed between the ring- shaped stator elements stacked in the longitudinal direction.
  • the slot pitch of the stator is advantageously different from the slot pitch of the mover to avoid reluctance forces which tend to keep the mover in place relative to the stator.
  • the slot pitches are measured in the longitudinal direction of the mover i.e. in the z-direction of the coordinate system.
  • FIG. 2 shows a section view of an electric percussion device 220 according to an exemplifying and non-limiting embodiment.
  • the section plane is parallel with the yz- plane of a coordinate system 299.
  • the electric percussion device 220 comprises a frame 221 that comprises attachment members 222 for connecting to a working machine such as e.g. an excavator so that the frame 221 is nondestructively detachable from the working machine.
  • the electric percussion device 220 comprises an actuator member 223, e.g. a chisel, supported with respect to the frame 221 and linearly movable with respect to the frame 221.
  • the electric percussion device 220 comprises a tubular linear electric machine 205 according to an embodiment of the invention.
  • a stator 206 of the tubular linear electric machine is attached to the frame 221 , and a mover 201 of the tubular linear electric machine is configured to direct impacts to the actuator member 223.
  • the mover 201 comprises a ferromagnetic core 202 that is a single piece of ferromagnetic steel. Furthermore, the mover comprises conductor rings in annular grooves of the ferromagnetic core 202. In figure 2, one of the conductor rings is denoted with a reference 203.
  • the tubular linear electric machine 205 can be for example such as the tubular linear electric machine 105 illustrated in figures 1 a andl b.
  • an end portion of the ferromagnetic core 202 that is closer to the actuator member 223 has a first region 230 that is free from annular grooves and from conductor rings and is thicker than second regions of the ferromagnetic core 202 surrounded by the conductor rings.
  • the length of the first region 230 in the longitudinal direction of the mover 201 i.e. in the z-direction of the coordinate system 299, is from 5 % to 30 % of a whole length of the ferromagnetic core 202 in the longitudinal direction of the mover.
  • the region 230 that is free from annular grooves and conductor rings is advantageous from the viewpoint of mechanical strength of the mover 201 which is configured to direct impacts to the actuator member 223.
  • Figure 3 shows a section view of an electric percussion device 320 according to an exemplifying and non-limiting embodiment.
  • the section plane is parallel with the yz- plane of a coordinate system 399.
  • the electric percussion device 320 comprises a frame 321 that comprises attachment members 322.
  • the electric percussion device 320 comprises an actuator member 323, e.g. a chisel, supported with respect to the frame 321 and linearly movable with respect to the frame 321.
  • the electric percussion device 320 comprises a tubular linear electric machine 305 according to an embodiment of the invention.
  • a stator 306 of the tubular linear electric machine is attached to the frame 321 , and a mover 301 of the tubular linear electric machine is configured to direct impacts to the actuator member 323.
  • the mover 301 comprises a ferromagnetic core 302 that comprises a center rod 331 made of the ferromagnetic steel and annular ferromagnetic elements 332 made of the ferromagnetic steel and surrounding the center rod 331 .
  • the annular ferromagnetic elements are successively in the longitudinal direction of the mover 301 , i.e. in the z-direction of the coordinate system 399, so that gaps between the annular ferromagnetic elements constitute annular grooves containing conductor rings.
  • one of the conductor rings is denoted with a reference 303 and one of the annular ferromagnetic elements is denoted with a reference 332.
  • an end portion of the center rod 331 that is closer to the actuator member 323 has a first region 330 that is free from the annular ferromagnetic elements and from the conductor rings and is thicker than second regions of the center rod surrounded by the conductor rings.
  • the length of the first region 330 in the longitudinal direction of the mover 301 i.e. in the z-direction of the coordinate system 399, is from 5 % to 30 % of the whole length of the ferromagnetic core 302 in the longitudinal direction of the mover.

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Abstract

A mover (103) for a tubular linear induction machine comprises a ferromagnetic core (102) having a rod-like shape elongated in the longitudinal direction (z) of the mover The ferromagnetic core is a single piece of ferromagnetic steel and has annular grooves on a surface of the ferromagnetic core so that the annular grooves are successively in the longitudinal direction of the mover and the annular grooves surround a longitudinal geometric center line (198) of the ferromagnetic core. The mover comprises conductor rings (103) made of electrically conductive material and placed in the annular grooves of the ferromagnetic core. As the ferromagnetic core is the single piece of ferromagnetic steel, it provides mechanical strength against impacts directed to the mover. Thus, the mover is suitable for an electric percussion device.

Description

A mover for a tubular linear induction machine
Field of the disclosure
The disclosure relates generally to linear electric machines. More particularly, the disclosure relates to a mover for a tubular linear induction machine. Furthermore, the disclosure relates to a tubular linear induction machine. Furthermore, the disclosure relates to an electric percussion device that comprises a tubular linear induction machine.
Background
A linear electric machine comprises a stator and a mover which is linearly movable with respect to the stator in the longitudinal direction of the linear electric machine. The mover and the stator are provided with magnetically operating means for converting electric energy into linear movement of the mover when the linear electric machine operates as a linear motor, and for converting linear movement of the mover into electric energy when the linear electric machine operates as a linear generator. The magnetically operating means may comprise for example multiphase windings for generating a magnetic field moving with respect to the multiphase windings when alternating currents are supplied to the multiphase windings. Furthermore, the magnetically operating means may comprise equipment for generating force in response to the moving magnetic field generated with the multiphase windings. The above-mentioned equipment may comprise for example permanent magnets, electromagnets, electrically conductive structures, and/or mechanical structures providing a spatial reluctance variation. The multiphase windings can be located in the stator and the equipment for generating force in response to a moving magnetic field can be located in the mover. It is also possible that the multiphase windings are located in the mover and the equipment for generating the force in response to the moving magnetic field is located in the stator.
Requirements for a linear electric machine are strongly dependent on an application in which the linear electric machine is used. For example, a mover of a linear electric machine of an electric percussion device, such as a hammer or a rock drill, is configured to direct impacts to an actuator member, e.g. a chisel, of the electric percussion device. At the same time as impacts are directed to the actuator member, the electric percussion device is pushed against material, e.g. stone, to be broken up. Thus, a tip of the actuator member penetrates, due to the impacts and the pushing, into the material to be broken up, and, consequently, breaks up the material. Therefore, the mover of the linear electric machine of an electric percussion device is subjected to strong mechanical impacts and this imposes a requirement for a sufficient mechanical strength of the mover.
Summary
The following presents a simplified summary to provide 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.
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 mover for a tubular linear induction machine.
A mover according to the invention comprises a ferromagnetic core having a rodlike shape elongated in the longitudinal direction of the mover. The ferromagnetic core is made of ferromagnetic steel and has annular grooves on a surface of the ferromagnetic core so that the annular grooves are successively in the longitudinal direction of the mover and the annular grooves surround a longitudinal geometric center line of the ferromagnetic core. The mover further comprises conductor rings placed in the annular grooves of the ferromagnetic core. The conductor rings are made of electrically conductive material, e.g. copper, aluminum, copper alloy, or aluminum alloy, whose electric conductivity, 1/(Qm), is greater than the electric conductivity of the ferromagnetic steel of the ferromagnetic core.
In a mover according to an exemplifying and non-limiting embodiment, the ferromagnetic core is a single piece of ferromagnetic steel to provide high mechanical strength against impacts directed to the mover. Thus, a mover according to this exemplifying and non-limiting embodiment is suitable for e.g. an electric percussion device.
In accordance with the invention, there is also provided a new tubular linear induction machine that comprises:
- a stator comprising a stator core structure and stator windings configured to generate a magnetic field moving with respect to the stator core structure when alternating currents are supplied to the stator windings, and
- a mover according to the invention and linearly movable with respect to the stator in the longitudinal direction of the mover.
In accordance with the invention, there is also provided a new electric percussion device that comprises:
- a frame attachable to a working machine such as e.g. an excavator, the frame comprising attachment members configured to attach to the working machine so that the frame is nondestructively detachable from the working machine,
- an actuator member, e.g. a chisel, linearly movably supported with respect to the frame, and
- a tubular linear induction machine according to the invention.
The stator of the tubular linear induction machine is attached to the frame and the mover of the tubular linear induction machine is configured to direct impacts to the actuator member. An electric percussion device according to an embodiment of the invention can be for example a hammer for breaking and demolition, a hammer of a piling machine, a hammer of a rock drill, or some other percussion device.
Exemplifying and non-limiting embodiments are described in accompanied dependent claims.
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 figures
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 and 1 b illustrate a linear induction machine according to an exemplifying and non-limiting embodiment, figure 2 illustrates a percussion device that comprises a linear induction machine according to an exemplifying and non-limiting embodiment, and figure 3 illustrates a percussion device that comprises a linear induction machine according to an exemplifying and non-limiting embodiment. Description of exemplifying embodiments
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 section view of a part of a tubular linear induction machine 105 according to an exemplifying and non-limiting embodiment. The section plane is parallel with the yz-plane of a coordinate system 199. The tubular linear induction machine comprises a stator 106 and a mover 101. The mover 101 is linearly movable with respect to the stator 106 in the longitudinal direction of the tubular linear electric machine. The longitudinal direction is parallel with the z-axis of the coordinate system 199. Figurel b shows a magnification of a part of the section view of the mover 101 shown in figure 1 a.
The mover 101 comprises a ferromagnetic core 102 having a rod-like shape elongated in the longitudinal direction of the mover, i.e. in a direction parallel with the z-axis of the coordinate system 199. The ferromagnetic core 102 is a single piece of ferromagnetic steel and has annular grooves on a surface of the ferromagnetic core so that the annular grooves are successively in the longitudinal direction of the mover 101 and the annular grooves surround a longitudinal geometric center line 198 of the ferromagnetic core. The mover 101 comprises conductor rings placed in the annular grooves of the ferromagnetic core. In figure 1 a, one of the conductor rings is denoted with reference 103. The conductor rings are made of electrically conductive material, e.g. copper, aluminum, copper alloy, or aluminum alloy, whose electric conductivity, 1/(Qm), is greater than the electric conductivity of the ferromagnetic steel of the ferromagnetic core 102. The electric conductor rings can be made for example by casting the electrically conductive material into the grooves of the ferromagnetic core 102 and thereafter by machining outer surfaces, i.e. airgap surfaces, of the conductor rings by turning.
The exemplifying mover 101 illustrated in figures 1 a and 1 b comprises a tubular band 104 surrounding the ferromagnetic core 102 and the conductor rings. As shown in figure 1 b, the tubular band 104 has a mechanical contact with areas of an outer surface of the ferromagnetic core 102 between the annular grooves. The purpose of the tubular band 104 is to provide a smooth surface of the mover 101 , which facilitates arranging a mechanical support for supporting the mover 101 linearly moveably with respect to the stator 106. The tubular band 104 can be made of for example steel or some other material whose coefficient of thermal expansion is sufficiently close to that of the steel of the ferromagnetic core 102.
Typically, the coefficient of thermal expansion of the electrically conductive material, e.g. copper, aluminum, copper alloy, or aluminum alloy, of the conductor rings is greater than the coefficient of thermal expansion of the steel of the ferromagnetic core 102. In this case, the outer surfaces of the conductor rings are advantageously nearer to the longitudinal geometric center line 198 of the ferromagnetic core 102 than areas of the outer surface of the ferromagnetic core 102 between the annular grooves, i.e. R1 < R2, and thus there are safety gaps between the conductor rings and the inner surface of the tubular band 104. The safety gaps make it possible to avoid a situation in which the outer surfaces of the conductor rings get farther from the longitudinal geometric center line 198 than the areas of the outer surface of the ferromagnetic core 102 between the annular grooves because of thermal expansion of the conductor rings greater than thermal expansion of the ferromagnetic core 102. In this unwanted situation, the tubular band 104 might be deformed and thus its outer surface might become uneven. The safety gaps may contain e.g. air. In a mover according to another exemplifying embodiment, there is no tubular band and outer surfaces of the conductor rings and the areas of the outer surface of the ferromagnetic core between the annular grooves are in flush. A mover according to this exemplifying embodiment is suitable for cases in which temperature changes are so small that a possible difference between the coefficient of thermal expansion of the steel of the ferromagnetic core and the coefficient of thermal expansion of the material of the conductor rings does not make the outer surface of the mover too uneven. In a mover according to this exemplifying embodiment, the outer surface of the mover can be provided with a suitable coating. The coating material can be e.g. chrome or some other suitable material.
In the exemplifying tubular linear induction machine 105 illustrated in figures 1 a and 1 b, the stator 106 comprises a stator core-structure 107 and windings surrounding the mover 101 and configured to generate a magnetic force directed to the mover 101 in response to electric currents supplied to the windings. In figure 1 a, crosssections of two coils of the windings are denoted with references 108 and 109. The windings of the stator 106 may constitute for example a multi-phase winding, e.g. a two- or three-phase winding. In this exemplifying tubular linear induction machine 105, the stator 106 also comprises a stator frame 112 having cooling channels for conducting cooling fluid, e.g. water or air. In figure 1 a, one of the cooling channels is denoted with a reference 113.
In the exemplifying tubular linear induction machine 105 illustrated in figures 1 a and 1 b, the stator core structure 107 comprises ring-shaped stator elements stacked in the longitudinal direction of the mover 101 , i.e. in a direction parallel with the z-axis of the coordinate system 199. In figure 1 a, two of the ring-shaped stator elements are denoted with references 110 and 111. The ring-shaped stator elements can be made of for example sintered ferromagnetic and electrically weakly conducting material such as ferrite or soft magnetic composite “SMC” material, e.g. Somaloy®. As illustrated in figure 1 a, a section of each of the ring-shaped stator elements along a geometric section plane coinciding with the longitudinal geometric center line 198 is T-shaped so that annular stator slots for the stator windings are formed between the ring-shaped stator elements which are stacked in the longitudinal direction. It is however also possible that the above-mentioned section of each of the ring-shaped stator elements along a geometric section plane of the kind mentioned above is L- shaped so that annular stator slots for stator windings are formed between the ring- shaped stator elements stacked in the longitudinal direction. The slot pitch of the stator is advantageously different from the slot pitch of the mover to avoid reluctance forces which tend to keep the mover in place relative to the stator. The slot pitches are measured in the longitudinal direction of the mover i.e. in the z-direction of the coordinate system.
Figure 2 shows a section view of an electric percussion device 220 according to an exemplifying and non-limiting embodiment. The section plane is parallel with the yz- plane of a coordinate system 299. The electric percussion device 220 comprises a frame 221 that comprises attachment members 222 for connecting to a working machine such as e.g. an excavator so that the frame 221 is nondestructively detachable from the working machine. The electric percussion device 220 comprises an actuator member 223, e.g. a chisel, supported with respect to the frame 221 and linearly movable with respect to the frame 221. The electric percussion device 220 comprises a tubular linear electric machine 205 according to an embodiment of the invention. A stator 206 of the tubular linear electric machine is attached to the frame 221 , and a mover 201 of the tubular linear electric machine is configured to direct impacts to the actuator member 223. The mover 201 comprises a ferromagnetic core 202 that is a single piece of ferromagnetic steel. Furthermore, the mover comprises conductor rings in annular grooves of the ferromagnetic core 202. In figure 2, one of the conductor rings is denoted with a reference 203. The tubular linear electric machine 205 can be for example such as the tubular linear electric machine 105 illustrated in figures 1 a andl b.
As illustrated in figure 2, an end portion of the ferromagnetic core 202 that is closer to the actuator member 223 has a first region 230 that is free from annular grooves and from conductor rings and is thicker than second regions of the ferromagnetic core 202 surrounded by the conductor rings. The length of the first region 230 in the longitudinal direction of the mover 201 , i.e. in the z-direction of the coordinate system 299, is from 5 % to 30 % of a whole length of the ferromagnetic core 202 in the longitudinal direction of the mover. The region 230 that is free from annular grooves and conductor rings is advantageous from the viewpoint of mechanical strength of the mover 201 which is configured to direct impacts to the actuator member 223.
Figure 3 shows a section view of an electric percussion device 320 according to an exemplifying and non-limiting embodiment. The section plane is parallel with the yz- plane of a coordinate system 399. The electric percussion device 320 comprises a frame 321 that comprises attachment members 322. The electric percussion device 320 comprises an actuator member 323, e.g. a chisel, supported with respect to the frame 321 and linearly movable with respect to the frame 321. The electric percussion device 320 comprises a tubular linear electric machine 305 according to an embodiment of the invention. A stator 306 of the tubular linear electric machine is attached to the frame 321 , and a mover 301 of the tubular linear electric machine is configured to direct impacts to the actuator member 323. The mover 301 comprises a ferromagnetic core 302 that comprises a center rod 331 made of the ferromagnetic steel and annular ferromagnetic elements 332 made of the ferromagnetic steel and surrounding the center rod 331 . The annular ferromagnetic elements are successively in the longitudinal direction of the mover 301 , i.e. in the z-direction of the coordinate system 399, so that gaps between the annular ferromagnetic elements constitute annular grooves containing conductor rings. In figure 3, one of the conductor rings is denoted with a reference 303 and one of the annular ferromagnetic elements is denoted with a reference 332.
As illustrated in figure 3, an end portion of the center rod 331 that is closer to the actuator member 323 has a first region 330 that is free from the annular ferromagnetic elements and from the conductor rings and is thicker than second regions of the center rod surrounded by the conductor rings. The length of the first region 330 in the longitudinal direction of the mover 301 , i.e. in the z-direction of the coordinate system 399, is from 5 % to 30 % of the whole length of the ferromagnetic core 302 in the longitudinal direction of the mover.
It is, however, worth noting that an electric percussion device of the kind described above is only one exemplifying application for a tubular linear induction machine according to an embodiment of the invention, but linear induction machines according to embodiments of the invention can be used in many other applications, too.
The specific examples provided in the description given above should not be construed as limiting the applicability and/or the interpretation of the appended claims. Lists and groups of examples provided in the description given above are not exhaustive unless otherwise explicitly stated.

Claims

What is claimed is:
1. A mover (101 , 201 , 301 ) for a tubular linear induction machine, the mover comprising a ferromagnetic core (102, 202, 302) having a rod-like shape elongated in a longitudinal direction (z) of the mover, characterized in that the ferromagnetic core is made of ferromagnetic steel and has annular grooves on a surface of the ferromagnetic core so that the annular grooves are successively in the longitudinal direction of the mover and the annular grooves surround a longitudinal geometric center line (198) of the ferromagnetic core, and the mover comprises conductor rings (103, 203, 303) made of electrically conductive material and placed in the annular grooves of the ferromagnetic core, electric conductivity of the electrically conductive material of the conductor rings being greater than electric conductivity of the ferromagnetic steel of the ferromagnetic core.
2. A mover according to claim 1 , wherein the ferromagnetic core (102, 202) is a single piece of the ferromagnetic steel.
3. A mover according to claim 2, wherein an end portion of the ferromagnetic core (202) has a first region (230) that is free from the annular grooves and from the conductor rings (203) and is thicker than second regions of the ferromagnetic core surrounded by the conductor rings (203), a length of the first region (230) in the longitudinal direction of the mover is from 5 % to 30 % of a whole length of the ferromagnetic core (202) in the longitudinal direction of the mover.
4. A mover according to claim 1 , wherein the ferromagnetic core (302) comprises a center rod (331 ) made of the ferromagnetic steel and annular ferromagnetic elements (332) made of the ferromagnetic steel and surrounding the center rod, the annular ferromagnetic elements being successively in the longitudinal direction (z) of the mover so that gaps between the annular ferromagnetic elements constitute the annular grooves containing the conductor rings (303).
5. A mover according to claim 4, wherein an end portion of the center rod (331 ) has a first region (330) that is free from the annular ferromagnetic elements and from the conductor rings and is thicker than second regions of the center rod surrounded by the conductor rings, a length of the first region (330) in the longitudinal direction of the mover is from 5 % to 30 % of a whole length of the ferromagnetic core (302) in the longitudinal direction of the mover.
6. A mover according to any one of claims 1-5, wherein the mover comprises a tubular band (104) surrounding the ferromagnetic core and the conductor rings, the tubular band having a mechanical contact with areas of an outer surface of the ferromagnetic core between the annular grooves.
7. A mover according to any one of claims 1 -6, wherein outer surfaces of the conductor rings are nearer to the longitudinal geometric center line (198) of the ferromagnetic core than areas of an outer surface of the ferromagnetic core between the annular grooves (R1 < R2).
8. A mover according to any one of claims 1 -7, wherein the electrically conductive material of the conductor rings is copper, aluminum, copper alloy, or aluminum alloy.
9. A tubular linear induction machine (105, 205) comprising:
- a stator (106, 206) comprising a stator core structure (107) and stator windings (108, 109) configured to generate a magnetic field moving with respect to the stator core structure when alternating currents are supplied to the stator windings, and
- a mover (101 , 201 ) according to any one of claims 1 -8 and linearly movable with respect to the stator in the longitudinal direction (z) of the mover.
10. A tubular linear induction machine according to claim 9, wherein the stator core structure (107) comprises ring-shaped stator elements (110, 111 ) stacked in the longitudinal direction (z) of the mover.
11. A tubular linear induction machine according to claim 10, wherein the ring- shaped stator elements are made of ferrite or soft magnetic composite material.
12. A tubular linear induction machine according to claim 11 , wherein the soft magnetic composite material is Somaloy®.
13. A tubular linear induction machine according to any one of claims 9-12, wherein a section of each of the ring-shaped stator elements (110, 111 ) along a geometric section plane coinciding with the longitudinal geometric center line (198) of the mover is T-shaped so that annular stator slots for stator windings are formed between the ring-shaped stator elements stacked in the longitudinal direction.
14. An electric percussion device (220, 330) comprising:
- a frame (221 , 321 ) attachable to a working machine, the frame comprising attachment members (222, 322) configured to attach to the working machine so that the frame is nondestructively detachable from the working machine,
- an actuator member (223, 323) linearly movably supported with respect to the frame, and
- a tubular linear induction machine (205, 305) according to any one of claims 9-13, wherein the stator (206, 306) of the tubular linear induction machine is attached to the frame and the mover (201 , 301 ) of the tubular linear induction machine is configured to direct impacts to the actuator member (223, 323).
15. An electric percussion device (220, 330) according to claim 14, wherein the mover (201 , 301 ) of the tubular linear induction machine (205, 305) is according to claim 3 or 5, and the first region (230, 330) is at an end of the mover that is closer to the actuator member (223, 323) than another end of the mover.
PCT/EP2024/072275 2023-08-09 2024-08-06 A mover for a tubular linear induction machine WO2025032098A1 (en)

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US3135879A (en) * 1958-08-04 1964-06-02 Gen Electric Linear motor
WO2022129680A1 (en) * 2020-12-15 2022-06-23 Lekatech Oy A brake for linear movement and a hammer device comprising the same

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ATE167597T1 (en) * 1991-07-12 1998-07-15 Denne Dev Ltd ELECTROMAGNETIC DEVICE FOR GENERATING LINEAR MOTION
JP2019122072A (en) * 2017-12-28 2019-07-22 Ｋｙｂ株式会社 Cylindrical linear motor
FI130138B (en) * 2018-09-21 2023-03-10 Lekatech Oy A linear electric machine
JP2020065412A (en) * 2018-10-19 2020-04-23 Ｋｙｂ株式会社 Cylindrical linear motor
DE202018005390U1 (en) * 2018-11-21 2019-01-24 Helmut Rempel induction launcher

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US3135879A (en) * 1958-08-04 1964-06-02 Gen Electric Linear motor
WO2022129680A1 (en) * 2020-12-15 2022-06-23 Lekatech Oy A brake for linear movement and a hammer device comprising the same

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