Field of the disclosure

The disclosure relates to a brake for linear movement, e.g. for a linear electric motor. Furthermore, disclosure relates to hammer device comprising a brake for linear movement and connectable to an excavator or a to working machine of another kind.

Background

In many applications, there is a need for linear movement that can be generated with for example a linear electric machine or with hydraulic means. Furthermore, there can be a need to keep the linear movement within an allowed range with the aid of a brake that smoothly stops the linear movement instead of abruptly stopping the linear movement. For example, a brake for linear movement may be useful in a hammer device that 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. A hammer device of the kind mentioned above is often hydraulically driven, allowing it to be connected to the hydraulic system of an excavator or another working machine. The hydraulic hammer device comprises a percussion mechanism capable of delivering impacts to an actuator member, e.g. a chisel, whose end forms a tip which transmits the impacts to material to be broken up. If there are no means for smoothly stopping a linear movement, the hammer device might get damaged in a situation in which an impact is directed to the actuator member when the tip of the actuator member is not against any external material such as stone or concrete, because mechanical structures supporting the actuator receive impacts that would be received by the external material when the external material is being hammered. The impacts directed to the mechanical structures supporting the actuator may cause e.g. material fatigue that may lead to damages.

Braking force generated with a brake for linear movement is advantageously progressive so that the braking force increases along with the linear movement being braked. The progressive braking force makes it possible that a movement range on which the brake is active is short but still the linear movement can be stopped smoothly. For example, in conjunction with a hammer device, a non-progressive brake generating a substantially constant braking force along a linear movement would lead to a compromise between the mechanical length of the construction, smoothness of braking, and power losses which would occur if the movement range on which the brake is active overlaps with the normal operating movement range.

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 brake for linear movement.

A brake according to the invention comprises:

- a frame structure,

- an annular element linearly movable with respect to the frame structure, the annular element constituting a wall of an annular chamber for damper fluid e.g. oil, a center element surrounded by the annular element and linearly movable with respect to the frame structure and the annular element, and - a spring configured to move the annular element with respect to the frame structure in a first direction in which the volume of the annular chamber is increasing.

The above-mentioned center element comprises a collar configured to abut to a contact portion of the annular element and to move the annular element together with the center element in a second direction opposite to the first direction and against a spring force of the spring. A portion of the annular element surrounding the contact portion comprises apertures configured to conduct the damper fluid to flow to and from the annular chamber. The above-mentioned spring is a plate spring, i.e. a disc spring, configured to gradually close the apertures in response to a situation in which the annular element is moved in the second direction against the spring force, where a plate of the spring gets gradually parallel with a surface of the annular element around the apertures in response to a situation in which the spring is compressed.

When the above-mentioned plate of the spring gets gradually parallel with the surface of the annular element around the apertures, an ability of the plate to inhibit a flow of the damper fluid via the apertures gradually increases and thereby the braking force increases along with a linear movement. Thus, there is no need for separate valves for controlling the flow of the damper fluid.

In accordance with the invention, there is provided also a new hammer device connectable 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, 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 linearly movably supported with respect to the frame, - a linear electric machine comprising a mover configured to direct impacts to the actuator member and a stator connected to the frame and provided with windings configured to generate a magnetic force directed to the mover in response to electric current supplied to the windings, and

- a brake according to the invention and configured to brake movement of the mover of the linear electric machine.

In a hammer device according to an exemplifying and non-limiting embodiment, the mover of the linear electric machine is the center element of the brake. In a hammer device according to another exemplifying and non-limiting embodiment, the actuator member is the center element of the brake.

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 nonlimiting 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: figure 1 illustrates a brake according to an exemplifying and non-limiting embodiment, figure 2 illustrates a brake according to an exemplifying and non-limiting embodiment, figures 3a, 3b, 3c, 3d, 3e, and 3f illustrate a hammer device according to an exemplifying and non-limiting embodiment, and figure 4 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 shows a section view of a brake 101 according to an exemplifying and nonlimiting embodiment. The geometric section plane is parallel with the geometric yz- plane of the coordinate system 199. The brake 101 comprises a frame structure 102 and an annular element 103 that is linearly movable with respect to the frame structure 102. The brake 101 comprises a center element 104 that is surrounded by the annular element 103 and linearly movable with respect to the frame structure 102 and the annular element 103. The frame structure 102, the annular element 103, and the center element 104 constitute an annular chamber 105 for damper fluid e.g. oil. The center element 104 can be for example rotationally symmetric with respect to geometric line 128. It is however also possible that the center element 104 has a non-circular cross-sectional shape. The brake 101 comprises a spring 106 configured to move the annular element 103 with respect to the frame structure 102 in a first direction, i.e. in the positive z-direction of the coordinate system 199, in which the volume of the annular chamber 105 is increasing. The center element 104 comprises a collar 107 configured to abut to a contact portion 108 of the annular element 103 and to move the annular element 103 together with the center element 104 in a second direction, i.e. in the negative z-direction of the coordinate system 199, opposite to the first direction and against the spring force of the spring 106. A portion of the annular element 103 surrounding the contact portion 108 comprises apertures 109 configured to conduct the damper fluid to and from the annular chamber 105. The spring 106 is a plate spring configured to gradually close the apertures 109 in response to a situation in which the annular element 103 is moved in the second direction against the spring force, i.e. in the negative z-direction of the coordinate system 199. A plate 110 of the spring 106 gets gradually parallel with a surface of the annular element 103 around the apertures 109 in response to a situation in which the spring 106 is compressed. When the plate 110 of the spring 106 gets gradually parallel with the surface of the annular element 103 around the apertures 109, an ability of the plate 110 to inhibit a flow of the damper fluid via the apertures 109 gradually increases and thereby the braking force increases along with a linear movement in the negative z-direction of the coordinate system 199. Thus, there is no need for separate valves for controlling the flow of the damper fluid.

In the exemplifying brake 101 illustrated in figure 1 , the contact portion 108 of the annular element 103 comprises other apertures 111 which are configured to be closed by the collar 107 of the center element 104 in response to a situation in which the collar 107 moves the annular element 103 in the second direction in which the volume of the annular chamber 105 is decreasing. The apertures 111 are configured to conduct the damper fluid into the annular chamber 105 in response to a situation in which the collar 107 is a distance away from the contact portion 108 and the spring 106 moves the annular element 103 in the first direction in which the volume of the annular chamber 105 is increasing. Thus, the apertures 111 do not reduce the braking force since they are closed by the collar 107 when the collar 107 moves the annular element 103 in the second direction. On the other hand, the apertures 111 allow the damper fluid to flow into the annular chamber 105 when the collar 107 is a distance away from the contact portion 108. Thus, the apertures 111 make the brake 101 faster to recover into a position in which the spring 106 is not compressed and the brake 101 is ready to operate.

Figure 2 shows a section view of a brake 201 according to an exemplifying and nonlimiting embodiment. The geometric section plane is parallel with the geometric yz- plane of the coordinate system 299. The brake 201 comprises a frame structure 202 and an annular element 203 that is linearly movable with respect to the frame structure 202. The brake 201 comprises a center element 204 that is surrounded by the annular element 203 and linearly movable with respect to the frame structure 202 and the annular element 203. The annular element 203 constitutes a wall of an annular chamber 205 for damper fluid e.g. oil. The center element 204 can be for example rotationally symmetric with respect to geometric line 228. It is however also possible that the center element 204 has a non-circular cross-sectional shape. The brake 201 comprises a spring 206 configured to move the annular element 203 with respect to the frame structure 202 in a first direction, i.e. in the positive z-direction of the coordinate system 299, in which the volume of the annular chamber 205 is increasing. The center element 204 comprises a collar 207 configured to abut to a contact portion 208 of the annular element 203 and to move the annular element 203 together with the center element 204 in a second direction, i.e. in the negative z-direction of the coordinate system 299, opposite to the first direction and against a spring force of the spring 206. A portion of the annular element 203 surrounding the contact portion 208 comprises apertures 209 configured to conduct the damper fluid to and from the annular chamber 205. The spring 206 is a plate spring configured to gradually close the apertures 209 in response to a situation in which the annular element 203 is moved in the second direction against the spring force. A plate 210 of the spring 206 gets gradually parallel with a surface of the annular element 203 around the apertures 209 when the spring 206 is compressed. When the plate 210 of the spring 206 gets gradually parallel with the surface of the annular element 203 around the apertures 209, an ability of the plate 210 to inhibit a flow of the damper fluid via the apertures 209 gradually increases and thereby the braking force increases along with a linear movement in the negative z-direction of the coordinate system 299.

Figure 3a shows a hammer device 312 according to an exemplifying and non-limiting embodiment. Figures 3b and 3c show section views taken along a line A-A shown in Figure 3a in two different situations. The geometric section plane is parallel with the yz-plane of a coordinate system 399. Figure 3d shows a magnification of a part B of figures 3b and 3c. The hammer device 312 comprises a frame 313 attachable to a working machine, e.g. such as to the boom of an excavator in place of a bucket. The frame 313 comprises attachment members 314 for attaching to the working machine so that the frame is nondestructively detachable from the working machine. The hammer device 312 comprises an actuator member 315, e.g. a chisel, linearly movably supported by the frame 313. An end of the actuator member 315 is shaped to constitute a tip for breaking material e.g. stone or concrete.

The hammer device 312 comprises a linear electric machine 316 having a mover 317 and a stator 318. The mover 317 is configured to direct impacts to the actuator member 315 in the negative z-direction of the coordinate system 399. Figure 3b shows a situation in which the mover 317 is in its lowest position and in contact with the actuator member 315. Figure 3c shows a situation in which the mover 317 is in an upper position. The stator 318 is attached to the frame 313 and comprises windings for generating a magnetic force directed to the mover 317 in response to electric current supplied to the windings. The windings may constitute for example a multi-phase winding, e.g. a two- or three-phase winding. In the exemplifying hammer device 312 illustrated in figures 3a-3d, the linear electric machine 316 is a tubular linear electric machine in which the conductor coils of the windings are configured to surround the mover 317. Figures 3b, 3c, and 3d show cross-sectional views of the conductor coils of the windings. In figures 3b and 3c, the cross-sections of the conductor coils are depicted by black rectangular patterns. In figure 3d, two of the conductor coils of the windings are denoted with references 319 and 320. The mover 317 can be, for example, substantially rotationally symmetric with respect to a geometric line 328 shown in figure 3d.

The hammer device 312 comprises a brake 301 according to an exemplifying and non-limiting embodiment of the invention. The brake 301 can be for example like the brake 101 illustrated in figure 1. In this exemplifying hammer device 312, the mover 317 of the linear electric machine 316 is the center element of the brake 301 . The brake 301 inhibits a linear movement of the mover 317 in the negative z-direction of the coordinate system 399 when a collar 307 of the mover 317 is in contact with an annular element 303 of the brake 301 . In the exemplifying hammer device 312 illustrated in figures 3a-3d, the mover 317 comprises annular permanent magnets provided one after another in the longitudinal direction of the mover 317, i.e. in the direction of the z-axis of the coordinate system 399. The axial direction of the annular shape of each permanent magnet coincides with the longitudinal direction of the mover 317. In figure 3d, two of the annular permanent magnets are denoted with references 321 and 322. The magnetizing directions of the permanent magnets coincide with the longitudinal direction of the mover 317, and the magnetizing directions of successive permanent magnets are opposite to each other. The magnetizing directions of the permanent magnets are indicated with arrows in figure 3d. Exemplifying magnetic flux lines are depicted with dashed lines. In this exemplifying case, the mover 317 comprises a center rod 325 and annular ferromagnetic elements provided around the center rod 325 to form a ferromagnetic core structure of the mover 317. In figure 3d, two of the annular ferromagnetic elements of the mover 317 are denoted with references 326 and 327. As shown in figure 3d, each annular permanent magnet is situated between two successive annular ferromagnetic elements.

Advantageously, the center rod 325 of the mover 317 is made of non-ferromagnetic material in order to maximize a magnetic coupling between the permanent magnets and the windings of the stator 318, i.e. to minimize a leakage flux via the center rod 325. The center rod 325 can be made of for example austenitic steel or some other suitable non-ferromagnetic and sufficiently strong material.

In a hammer device according to an exemplifying and non-limiting embodiment, the above-mentioned annular ferromagnetic elements of the mover 317 are made of solid steel and provided with slits extending from an air-gap surface of the mover towards, but without reaching, a surface of a yoke section of a ferromagnetic corestructure of the mover and extending longitudinally through the annular ferromagnetic elements. Figure 3f shows the annular ferromagnetic element 326 when seen along the negative z-direction of the coordinate system 399. In figure 3f, one of the slits is denoted with a reference 335 and the air-gap surface of the mover is denoted with a reference 334. The solid steel provided with the slits emulates a laminated structure and thus eddy currents induced in the ferromagnetic core-structure are reduced. Despite the slits, each annular ferromagnetic element is a single piece of material since the slits do not reach the surface of the annular ferromagnetic element constituting a part of the surface of the above-mentioned yoke section. The strongest magnetic flux variations take place near the airgap and thus the slits are more important in areas near the airgap than in areas near the surface of the yoke section.

In a hammer device according to an exemplifying and non-limiting embodiment, the above-mentioned slits are filled with electrically insulating solid material that can be for example resin. The electrically insulating solid material in the slits can be useful e.g. for dampening vibrations of the steel portions between the slits.

In a hammer device according to an exemplifying and non-limiting embodiment, the slits of the annular ferromagnetic elements of the mover comprise first slits and second slits so that the first slits are shorter in a radial direction than the second slits. In the exemplifying case illustrated in figure 3f, an angle between adjacent slits is 2.5 degrees on the area where there are both the longer slits and the shorter slits and an angle between adjacent slits is 5 degrees on the area where there are only the longer slits.

It is to be noted that hammer devices according to exemplifying and non-limiting embodiments may have different ferromagnetic core structures of the mover, and thus hammer devices according to exemplifying and non-limiting embodiments are not limited to any specific ferromagnetic core structures of the mover.

In the exemplifying hammer device 312 illustrated in figures 3a-3d, the ferromagnetic core structure (331 ) of the stator 318 comprises annular ferromagnetic elements which surround the mover 317 and which are stacked one after another in the longitudinal direction of the mover and form slots for conductor coils of the stator windings. In figure 3d, two of the annular ferromagnetic elements of the stator 318 are denoted with references 323 and 324. An exemplifying way of implementing the windings of the stator 318 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 example, with two conductor coils belonging either to a same phase of the windings or to two different phases of the windings. The stator 318 comprises also a stator frame 329 having cooling channels for conducting cooling fluid, e.g. water or air. In figure 3d, one of the cooling channels is denoted with a reference 330.

In a hammer device according to an exemplifying and non-limiting embodiment, the above-mentioned annular ferromagnetic elements of the stator 318 are made of solid steel and provided with slits extending from an air-gap surface of the stator towards, but without reaching, a surface of a yoke section of the ferromagnetic corestructure and extending longitudinally through the annular ferromagnetic elements. Figure 3e shows the annular ferromagnetic element 323 when seen along the negative z-direction of the coordinate system 399. In figure 3e, one of the slits is denoted with a reference 332 and the air-gap surface of the stator is denoted with a reference 333. The solid steel provided with the slits emulates a laminated structure and thus eddy currents induced in the ferromagnetic core-structure are reduced. Despite the slits, each annular ferromagnetic element is a single piece of material since the slits do not reach the surface of the annular ferromagnetic element constituting a part of the surface of the above-mentioned yoke section. The strongest magnetic flux variations take place near the airgap and thus the slits are more important in areas near the airgap than in areas near the surface of the yoke section.

In a hammer device according to an exemplifying and non-limiting embodiment, the above-mentioned slits are filled with electrically insulating solid material that can be for example resin. The electrically insulating solid material in the slits can be useful e.g. for dampening vibrations of the steel portions between the slits.

It is to be noted that hammer devices according to exemplifying and non-limiting embodiments may have different ferromagnetic core structures of the stator, and thus hammer devices according to exemplifying and non-limiting embodiments are not limited to any specific ferromagnetic core structures of the stator.

The mover 317 can be moved in a controlled way for example with a power electronic converter coupled to the windings of the stator 318. In many cases, it is advantageous for the control by the power electronic converter to know the position of the mover 317 with respect to the stator 318. For example, the position of the mover 317 can be measured with a mechanical position sensor comprising a sensor rod fixed to the mover. The position of the mover 317 can be measured also in a contactless way, for example with a laser measurement arrangement. It is also possible to provide the mover 317 and the stator 318 with structures operable as an inductive or capacitive position sensor. Hammer devices according to certain embodiments may comprise any suitable means for position measurement and/or estimation, and hammer devices according to other embodiments can be without any means for position measurement and/or estimation.

It is to be noted that hammer devices according to embodiments of the invention are not limited to any specific type of a linear electric machine. For example, the linear electric machine of a hammer device according to an exemplifying and non-limiting embodiment can be a flux switching permanent magnet synchronous machine "FSPMSM” where permanent magnets are located in a stator. It is also possible that a hammer device according to an exemplifying and non-limiting embodiment comprises a reluctance linear electric machine in which no permanent magnets are needed. In a reluctance linear electric machine, all magnetic flux is produced by electric currents and 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 lower power density, i.e. a larger machine is needed to produce the same power, and lower efficiency because all magnetic flux is produced by electric currents, 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.

Figure 4 shows a section view of a hammer device 412 according to an exemplifying and non-limiting embodiment. The geometric section plane is parallel with the yz- plane of a coordinate system 499. The hammer device 412 comprises a frame 413 attachable to a working machine. The frame 413 comprises attachment members 414 for attaching to the working machine so that the frame is nondestructively detachable from the working machine. The hammer device 412 comprises an actuator member 415, e.g. a chisel, linearly movably supported by the frame 413. An end of the actuator member 415 is shaped to constitute a tip for breaking material e.g. stone or concrete. The hammer device 412 comprises a linear electric machine 416 having a mover 417 and a stator 418. The mover 417 is configured to direct impacts to the actuator member 415 in the negative z-direction of the coordinate system 499. The stator 418 is attached to the frame 413 and comprises windings for generating a magnetic force directed to the mover 417 in response to electric current supplied to the windings. The windings may constitute for example a multi-phase winding, e.g. a two- or three-phase winding.

The hammer device 412 comprises a brake 401 according to an exemplifying and non-limiting embodiment of the invention. The brake 401 can be for example like the brake 201 illustrated in figure 2. In this exemplifying hammer device 412, the actuator member 415 is the center element of the brake 401. The brake 401 inhibits a linear movement of the actuator member 415 in the negative z-direction of the coordinate system 499 when a collar 407 of the actuator member 415 is in contact with an annular element 403 of the brake 401 .

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.