CN116600940A - Hammer apparatus - Google Patents

Abstract

The present invention relates to a hammer apparatus comprising a hammer body, a hammer piston and an electrically operated piston drive. The piston drive includes a stator fixedly positioned within the hammer body and at least partially surrounding a translator configured to act on the hammer piston. The stator includes a plurality of circumferential windings embedded in an inner surface of the stator, and the stator is configured to cause reciprocating linear motion of the translator. The translator includes an elongated rod surrounded by peripheral, outwardly extending teeth integrally formed in the elongated rod along a longitudinal extension of the translator. The translator is made of a material with a relative permeability >10 at a magnetic flux density of 0.2 tesla.

Description

Hammer apparatus

Technical Field

The present disclosure relates to a hammer apparatus including an electrically operated piston drive. The present disclosure also relates to an electrically operated piston drive for a hammer apparatus.

Background

In rock drills, drills and other impact mechanisms, hereinafter collectively referred to as hammer devices, a hammer piston performs a reciprocating motion in a barrel housing and repeatedly impacts on a shank adapter or other type of anvil. Hammer devices, such as impact hammers, are configured to perform an iterative process of transmitting force to a material by means of high frequency and energy intensive movements. The impact hammer comprises a piston and a translator/distributor axially arranged in the housing relative to each other, the piston being arranged to move axially in a reciprocating manner between a first position and a second position. During operation, a large amount of kinetic energy is transferred to the tool to which the piston is attached; kinetic energy is transferred in each stroke. After each stroke, the piston will move back to a position that can provide the next stroke, repeatedly providing the same kinetic energy transfer during operation. Thus, the piston is subjected to high impact and high energy acceleration/deceleration at each hammer strike, and controlled operation of the piston is required regardless of the direction of travel of the piston.

In recent years, linear motors have been considered as piston drives in percussion hammers/drills. The linear motor includes a stator and a translator capable of linearly moving in a longitudinal direction of the stator. The translator and the stator are provided with magnetically operated means for converting electrical energy into linear motion.

WO2020/058565A1 discloses a linear motor for driving a piston of a hammer device. In the disclosed solution, the mover of the linear motor is configured to operate as a piston in the hammer device. The mover includes permanent magnets disposed one after another in a longitudinal direction of the mover. The disclosed apparatus provides for reciprocating movement of a piston in a hammer device.

WO2019/068958A1 discloses a hammer apparatus comprising a linear motor for linearly moving an actuator member. The mover includes a central rod surrounded by a plurality of ring-shaped elements, which are arranged in a stacked structure one after another in the longitudinal direction of the mover.

However, when a joint element or magnet is provided in the movable part of the linear machine, the joint element or magnet is subjected to high impact and high energy acceleration/deceleration at each hammer strike. The joint element or magnet is also exposed to a large amount of heat and vibration. Thus, the linear machine will operate in a challenging environment, which will affect the fixtures between the joint elements and between the magnets and the mover, i.e. the fixtures between each element or each magnet and the mover, thereby subjecting the fixtures to wear and fatigue. The magnets are also typically sintered and may fracture due to mechanical shock waves generated by repeated hammer strikes. Furthermore, magnets are sensitive to heat and vibration, which may damage the magnetization of the permanent magnets. Faults in the element or even in the fixing of the single magnet may cause serious damage to the hammer device, for example partially obstructing the movement of the piston; when operating a hammer device comprising a linear machine, damage to the magnetization of the permanent magnets may reduce the ability to achieve the desired impact.

Disclosure of Invention

While solutions in the art are known, it is desirable to develop a hammer apparatus and a piston drive that overcome or alleviate at least some of the above-mentioned disadvantages of the presently known solutions.

It is therefore an object of the present disclosure to provide a hammer apparatus and a piston drive device that is less susceptible to wear and consumption caused by the high impacts and high energy acceleration/deceleration experienced during operation of the hammer apparatus.

This and other objects are achieved by means of a hammer device and a piston drive as defined in the appended claims.

According to a first aspect of the present disclosure, this object is achieved by a hammer apparatus comprising a hammer body, a hammer piston and an electrically operated piston drive. The piston drive comprises a stator, for example a tubular stator, fixedly positioned within the hammer body and at least partially surrounding a translator configured to act on the hammer piston. The stator includes a plurality of circumferential windings embedded in an inner surface of the stator, e.g., in stator slots, and the stator is configured to cause reciprocating linear motion of the translator. The translator includes an elongate rod surrounded by peripheral, outwardly extending, e.g., circumferential, teeth integrally formed in the elongate rod along a longitudinal extension of the translator. The elongate rod has a material with a relative permeability >10 at a magnetic flux density of 0.2 tesla.

The advantage of the proposed hammer device is that it alleviates the problem of achieving an impact-resistant fixation of the magnet on the translator and the problem of achieving an impact-resistant structure of the translator, while maintaining electrical properties that enable a sufficient impact to be achieved, when operating the hammer device.

In some examples, the hammer piston is an integral extension of the elongate rod.

The combination of the elongated rod and the hammer piston further reduces wear and consumption problems due to high energy impact exposure on the movable parts in the hammer device.

In some examples, the teeth include a plurality of annular protrusions, e.g., uniformly shaped annular protrusions, extending from the elongate rod.

Thus, a synchronous reluctance piston drive is achieved which has salient poles and uniform magnetic flux directions, thereby having a positive effect on eddy current generation within the translator.

In some examples, two adjacent projections, such as annular projections, define an intermediate U-shaped or semi-circular cavity having side walls extending marginless from the elongate rod.

Thus, a translator with improved wear/fatigue resistance is achieved, eliminating the presence of joints and internal corners within the translator.

In some examples, two adjacent projections, e.g., annular projections, have a mutual distance L and are separated by a gap having a width of 0.6L to 0.8L, preferably 0.65L to 0.75L, as measured at the peripheral top surface of the projections.

In some examples, a subset of the annular protrusions have a tapered shape and a peripheral surface width that is less than a width proximate the cylindrical stem, wherein the subset may each include an annular protrusion.

In some examples, the hammer body includes an open end portion configured to allow the hammer piston to reciprocate in a back and forth direction of the hammer body and a closed end portion including a gas-filled chamber configured to receive the first end portion of the translator and apply a return motion to the translator to accelerate the hammer piston in the direction of the open end portion of the hammer body.

According to a second aspect of the present disclosure, this object is achieved by an electrically operated piston drive for a hammer device. The piston drive includes a stator fixedly positioned within the hammer body and at least partially surrounding a translator configured to act on the hammer piston. The stator includes a plurality of circumferential windings embedded in an inner surface of the stator, e.g., in stator slots, and the stator is configured to cause reciprocating linear motion of the translator. The translator comprises an elongated rod surrounded by circumferential, outwardly extending teeth, e.g. circumferential, integrally formed in a cylindrical rod along a longitudinal extension of the translator, and the elongated rod has a material with a relative permeability >10 at a flux density of 0.2 tesla.

Improvements in the design of the hammer apparatus, piston drive, and more particularly the translator allow for reduced maintenance and downtime of the hammer apparatus due to failure of the piston operation. Furthermore, the wear performance and fatigue performance of the hammer device are improved. The combination of the translator and the hammer piston reduces the complexity of the hammer apparatus as a whole and in particular of the piston drive.

Drawings

The foregoing will be apparent from the following more particular description of exemplary embodiments, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating exemplary embodiments.

Fig. 1 schematically discloses a hammer device according to an example;

fig. 2a to 2b schematically disclose a piston drive according to an example;

fig. 3 discloses schematically a part of the hammer body.

Detailed Description

In order to obtain a robust and simple solution for an electrically driven impact unit, a hammer device and a piston drive according to the present disclosure have been developed. The proposed solution can be applied to various types of hammer devices, such as rock drills, crushers, drills or impact hammers, which comprise stand-alone devices, attachment means on a carrier vehicle and are comprised in a drilling machine or a down-the-hole device.

Aspects of the present disclosure will be described more fully hereinafter with reference to the accompanying drawings. The apparatus and methods disclosed herein may, however, be embodied in many different forms and should not be construed as limited to the aspects set forth herein. Like reference numerals refer to like elements throughout the drawings.

The terminology used herein is for the purpose of describing particular aspects of the disclosure only and is not intended to limit the scope of the disclosure. It should be emphasized that the term "comprises/comprising" when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

Embodiments of the present disclosure will be described and illustrated more fully hereinafter with reference to the accompanying drawings. The solutions disclosed herein may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

Fig. 1 schematically discloses an example hammer device 10 according to a non-limiting embodiment. The hammer device 10 is configured to be included in a rock drill that may be attached to a carrier vehicle, such as a drilling rig or an excavator. The hammer apparatus includes a hammer body 11, a hammer piston 12, and an electrically operated piston drive device 13. The piston drive 13 comprises a hollow, for example tubular, stator 14 fixedly positioned within the hammer body 11. In some examples, the stator 14 is fixedly positioned within the hammer body 11 by means of a suspension device comprising an impact absorbing material such as a polymer or rubber. The stator 14 encloses the translator 15 at least partially along a longitudinal extension of the stator 14. Translator 15 is configured to act on hammer piston 12 to move hammer piston 12 in a linear direction to transfer reciprocating motion to hammer piston 12. The hammer piston 12 is configured to act on the shank adapter 12a, which shank adapter 12a in turn may act on a hammer tool, such as a tool including a drill bit or chisel, at the outward end of the shank adapter 12 a. The rotary drive motor of the rock drill may be configured to: during operation, for example when a reciprocating motion is induced in the hammer piston 12, the shank adapter 12a of the hammer piston 12 is rotated. In some examples, the stator 14 may include a central cavity having a non-circular cross-section, such as a polygonal cross-section, i.e., an octagonal or square cross-section. In some examples, the stator 14 may be configured as a double sided stator 14 with a flat translator 15. The hammer piston 12 may be operatively connected to the translator 15, e.g., mechanically connected to the translator 15 or integral with the translator 15, as disclosed in fig. 1. As shown in fig. 1, the piston drive 13 may be centered along the longitudinal centerline of the hammer body 11.

The stator 14 includes a plurality of circumferential windings, such as copper windings, disposed in stator slots formed in an inner surface of the stator 14. Thus, the circumferential windings may be embedded in the inner surface of the stator 14, for example in the stator slots. The stator slots may be equally spaced over at least a portion of the longitudinal extension of the stator 14. In some examples, non-equidistant placement of the stator slots is also conceivable, e.g. the stator slots are arranged such that the distance between adjacent stator slots may vary along the longitudinal extension of the stator. This arrangement of stator slots may provide improvements when seeking to reduce cogging. In some examples, stator 14 is configured to include 20 to 80 windings, preferably 30 to 60 windings, and more preferably 35 to 45 windings. Fewer windings are typically used for longer pole lengths. A long pole length may mean a simplified manufacturing process with fewer and thicker windings, but may require a greater material thickness at the translator 15, which may have the disadvantage of reducing the force per translator mass ratio of the machine and thereby reducing the maximum acceleration of the piston. The windings may be configured as conductor coils, i.e. phase windings, arranged in internal stator slots within the stator 14, i.e. in the inner surface of the stator 14. The windings may be implemented such that each slot comprises only one conductor coil, or a plurality of conductor coils. Thus, the windings may be implemented in a centralized fashion with only one conductor coil/phase winding in each slot, or in a distributed fashion with more than one conductor coil/phase winding in each slot. Having multiple phases in the stator 14 provides benefits in that it provides improvements in terms of force fluctuations experienced, e.g., reduces the effects of force fluctuations. For three or more phases it is possible to achieve a constant force and the sum of the currents is zero, which eliminates the need for a return conductor. The stator slots may have an internal distance D, each two slots being separated by the following wall sections: the width of the wall section corresponds to 30% to 70% of the inner distance D, preferably 40% to 60% of D, and more preferably 45% to 55% of D. A protective layer, for example a polymer layer, may be provided on the inner surface of the stator 14 as a sealing layer on top of the windings, thereby protecting the windings from mechanical effects of the reciprocating linear movement of the translator 15 and reducing the risk of short-circuit isolation faults occurring in the stator.

Typically, the windings are arranged to form a multi-phase winding structure, such as a three-phase winding structure. The windings may be configured as single-phase, two-phase or three-phase windings, which may be wound in opposite directions in adjacent stator slots. However, it is also possible that each stator slot contains, for example, two conductor coils, which may belong to different phases of the winding or to the same phase of the winding. In some examples, the windings are arranged in an equidistant configuration. When connected to the grid or another power source, such as a battery, for example by means of a control system and a power converter, the position of the translator 15 and the desired acceleration direction are used to control the electrical phase angles of the different phases, so that a suitable magnetic force is achieved. The position of the translator can be estimated from the electrical signal using sensorless control or by determining the position by means of a sensor. When the estimation or measurement of the translator position is given in electrical angle, a start-up procedure may be used, wherein the translator 15 is first moved towards one of the end positions. From this known absolute position, the control system can then track the absolute position during operation by using the position in electrical angle. By using such a control method, the alternating current feed in the stator windings causes a reciprocating linear movement of the translator 15, i.e. a movement of the translator 15 in a direction parallel to the longitudinal centre line of the stator 14.

In some examples, the longitudinal length of the translator 15 is greater than the longitudinal length of the stator 14 such that at least the first end portion 15a of the translator 15 extends beyond the longitudinal extension of the stator 14. The second end portion 15b of the translator may also extend beyond the longitudinal extension of the stator 14. The second end portion 15b is operatively connected to the hammer piston, for example by forming the hammer piston as an integral extension of the second end portion 15 b. Thus, the hammer piston 12 may be formed as an integral extension of the translator.

Turning to fig. 2a and 2b, a piston drive is illustrated. The translator 15 comprises an elongated rod 16, for example a cylindrical rod/core structure or an equilateral rod, the rod 16 being surrounded by teeth 17 integrally formed in the translator rod. The translator 15 is made of a magnetic material, i.e. of a high permeability material with a relative permeability >10 at a flux density of 0.2 tesla. Examples of materials that may be used for the translator include hardened steel, including ferromagnetic steel and martensitic steel. The rod 16 is surrounded by peripheral, outwardly extending, for example circumferential, teeth 17, which teeth 17 are integrally formed in the translator along its longitudinal extension, i.e. parallel to its longitudinal centre line. Thus, in the example configuration disclosed, the translator has a geometry comprising a plurality of different, integral, identically shaped projections 17a, also known as ridges, the projections 17a projecting from the stem 16, preferably having a disk-shaped geometry in the radially outwardly directed portions of the projections.

In some examples, adjacent projections 17a1, 17a2, for example, each two adjacent projections define an intermediate U-shaped or semi-circular cavity having side walls extending marginless from the elongate rod. In some examples, two adjacent protrusions have a mutual distance L; the distance is determined relative to a corresponding measurement point on each protrusion and corresponds to the pole length. In some examples, the width W of the cavity defined by two adjacent protrusions is 0.6L to 0.8L, preferably 0.65L to 0.75L, as measured at the peripheral surface of the protrusion.

When the piston drive 13 is powered, electrodes are formed on each tab and the adjacent cavity. Magnetic flux is induced in a closed loop extending over the pole length L, i.e. over the translator protrusion/cavity pair and over the corresponding section of the stator 14 comprising one or more conductor coils, as shown in fig. 2 b. When the piston drive 13 is configured with a short pole length, a high magnetic force can be generated with a lightweight translator, for example a translator 15 with a hollow rod 16. The wall thickness L-W of the protrusion, i.e. the difference between the pole length and the cavity width, is selected based on the electromagnetic angle. Thus, the wall thickness (protrusion width) is selected to be thick enough to transfer magnetic flux from one protrusion to another without saturating the material in the translator rod. The shorter the pole length, the less flux needs to be delivered by the translator rod. Since the magnetic shear stress in the air gap can be maintained with shorter poles, a larger magnetic force per unit mass of translator can be obtained, since more air gap surface can be fitted per unit mass of translator. However, a short pole length has the disadvantage of increasing manufacturing difficulties. In the present disclosure, example pole lengths of 8mm to 50mm, preferably 12mm to 35mm, and more preferably 15mm to 25mm may be applied.

As previously disclosed, two adjacent projections 17a1, 17a2, for example annular projections, may define an intermediate U-shaped or semicircular cavity having side walls extending marginless from the elongate bar. Two adjacent projections may be spaced apart by a distance L; the distance may correspond to a pole length. The diameter of the semi-circular cavity may correspond to the outer width of the cavity. In some examples, the U-shaped cavity is delimited by two symmetrically shaped curved corners having a respective inner radius greater than 2.5%, and preferably greater than 10%, of the distance between two adjacent protrusions. In some examples, an inner radius greater than 20%, and more preferably greater than 30% of the distance between two adjacent protrusions may be selected to provide a smooth, rimless cavity that provides benefits in withstanding fatigue due to repeated impacts.

In the most outwardly directed portion, the plurality of protrusions may have outwardly directed outer surfaces of the same diameter along the longitudinal direction of the protrusions, e.g. surfaces orthogonal to the longitudinal extension of the translator. Thus, each protrusion may have an outwardly facing cylindrical surface, and the outer surfaces of the plurality of protrusions define a cylindrical shape. In some examples, a subset of the annular protrusions may have a tapered shape and a peripheral surface width that is less than a width proximate the elongate stem. In some examples, all of the annular protrusions may have the same shape, which may be a tapered shape. The outermost diameter of the translator, i.e. the outermost diameter of the protrusions and the intermediate air gap formed between the opposite sides of the translator and the stator 14 corresponds to the inner diameter of the stator 14. At the outermost portion of the protrusion, the air gap G to the inner surface of the stator 14 may be in the range of 0.25mm to 1mm, preferably 0.25mm to 0.5 mm. At the bottom of the cavity formed between each two protrusions, the air gap to the stator 14 may be 1mm to 15mm, preferably 2mm to 8mm, more preferably 3mm to 7mm, and most preferably 3mm to 5mm. The translator material is configured to undergo a high degree of magnetization when operated in the piston drive 13.

In some examples, translator 15 may be at least partially hollow, such as a cylindrical hollow rod/core structure implemented in a uniform material. In other examples, the elongate rod 16 may include two or more materials, such as a low density inner core material and a high strength outer core material; that is, the outer core portion includes an integral tooth portion. In some examples, translator 15 is made of a uniform material, providing a constant modulus of elasticity and density throughout the translator. In some examples, translator 15 may have a transverse cross-section of the same size along the longitudinal extension of the translator. In some examples, translator 15 has a cross-section designed to produce a stress wave of progressively increasing force, for example having a cross-section that progressively increases or decreases along the longitudinal direction.

When the translator and the hammer piston 12 are configured as a single integral unit, i.e. by combining the cylindrical rod and the piston, the high permeability material for the integral unit can be hardened in the piston portion of the unit to ensure adequate wear/fatigue resistance at the piston portion configured to act on the hammer tool.

The tooth 17 comprises a plurality of shaped teeth, i.e. a plurality of projections extending from the bar. Each protrusion 17a is magnetic, preferably having uniform magnetic properties. When powering the piston drive 13, the magnetic flux may travel in a closed loop extending over one or more pole lengths, i.e. over one or more translator protrusions and corresponding sections of the stator 14 comprising one or more conductor coils/phase windings. The pole length L of the translator 15 may be matched to the corresponding periodicity on the stator 14, i.e. to the periodicity of the stator windings 14a, such that an equal stator magnetic circuit is experienced along each pole of the translator. The configuration of the stator windings 14a is selected to maximize the average force generated. In some examples, the periodicity of the translator teeth 17 and stator windings 14a will be configured to have a slight mismatch; this provides the benefit of significantly reducing force fluctuations and voltage/current fluctuations. There are various ways to implement this configuration. In some examples, translator 15 is arranged with teeth 17 such that teeth 17 provide a slight increase or decrease in pole length. In some examples, the translator protrusions are arranged at varying distances, i.e., meaning that the respective pole distances are varied along the direction of movement of the translator, to form a suitable pattern that can be optimized to create and optimize a balance between average force and force/voltage/current fluctuations.

Fig. 2a and 2b show more details of the piston drive as illustrated in the description of fig. 1. The piston drive 13 comprises a hollow, e.g. tubular, stator 14 fixedly positioned within the hammer body 11, and a translator configured to act on the hammer piston 12. The stator 14 includes a plurality of circumferential windings 14a embedded in an inner surface of the stator 14, i.e., within stator slots 14b, and the stator 14 is configured to cause reciprocating linear motion of the translator. Thus, the piston driving means 13 is a linear motor. The translator comprises an elongated rod 16, the elongated rod 16 being surrounded by peripheral, outwardly extending teeth 17 integrally formed in the translator 15 along the longitudinal extension of the translator. The translator is made of a material having magnetic properties, i.e. a material with a relative permeability >10 at a magnetic flux density of 0.2 tesla. In some examples, the translator includes hardened steel including ferritic steel and martensitic steel. In other examples, the translator may include two or more materials, such as a low density inner core material and a high strength material at least partially used in the teeth. The electromagnetic excitation portions of the translator and stator 14 are preferably rotationally symmetric with respect to the line of symmetry. Fig. 2a and 2b show a three-phase configuration of the piston drive 13; wherein the translator protrusions/teeth are spaced apart from each other in the longitudinal direction by a distance L corresponding to a distance comprising 2 to 4, preferably 2.5 to 3.5, and most preferably 2.8 to 3.2 windings 14a provided on the stator 14. Thus, in a three-phase configuration, three phases are supported, each with 2 winding directions, with the stator 14 configured as six current variables for 60 degree electrical separation. In some unpublished examples, a two-phase configuration may be employed, as well as a single-phase configuration. In a two-phase configuration, the distance L between two adjacent translator teeth/projections will correspond to the distance comprising two adjacent windings provided on the stator. For a single phase configuration, the distance L between two adjacent translator teeth/projections will correspond to the distance comprising a single winding on the stator. However, it is noted that an implementation with multiple phases does not necessarily need to have two different winding directions in the stator slot 14 b. Any of the mentioned phase configurations of the phase pairs can be realized with half the number of slots and windings per electrical cycle and twice the electrical angle between each stator slot 14 b. Then, for one distance between the protrusions on the translator, there is also only half a slot in the stator 14. This arrangement has the advantage that fewer slots and windings are required, which makes manufacture simpler, but on the other hand, this arrangement increases the force variation, which produces more vibrations. The piston drive can of course also be implemented with more than three phases and the more phases that are used the more even the forces will be, but the more complicated the manufacture and assembly of the machine will be.

Turning to fig. 2b, details of the translator teeth are disclosed. In some examples, the teeth include a plurality of uniformly shaped protrusions, such as teeth, extending from the stem and having a base width at a base portion joined to the stem and spaced apart from one another by a gap distance. In some examples, the width of the translator tooth is set to 30% of the distance L between two adjacent projections, i.e. 30% of the pole length. The protrusion may have a tapered shape and a peripheral surface width smaller than the base width, for example, a root width representing 30% to 50% of the pole width. The tapered width of the translator teeth provides the following advantages: i.e. the magnetic saturation effect is reduced and thereby the reluctance in the innermost part of the tooth, i.e. the part integral with the elongated bar. Furthermore, the tapered width of the protrusion reduces mechanical stress in the innermost portion. In some examples, the rod of the translator has a cylindrical shape with a diameter d, and the teeth are integrally formed in the translator. The diameter of the elongate rod will vary with the size of the hammer apparatus.

Fig. 2b also discloses a part of the stator 14 and a plurality of circumferential windings 14a of the stator 14, e.g. copper windings, which are arranged in stator slots 14b in the inner surface of the stator 14. In some examples, stator 14 is configured to include 20 to 80 windings, preferably 30 to 70 windings, and more preferably 35 to 65 windings. The windings may be configured as conductor coils disposed in internal stator slots 14b within the stator 14. The stator slots may have an average internal distance D, each two slots being separated by the following wall sections: the width of the wall section corresponds to 30% to 70% of the inner distance D, preferably 40% to 60% of D, and more preferably 45% to 55% of D. In some examples, each winding 14a arranged in the stator 14 has at least one tooth, i.e. the number of circumferential windings embedded in the inner surface of the stator 14 corresponds to a multiple of the number of teeth included in the teeth, e.g. circumferential, extending outwards of the circumference of the translator. In a three-phase configuration, the number of windings arranged along the stator 14 may correspond to 2 to 4 times, preferably 2.5 to 3.5 times, and most preferably 2.8 to 3.2 times the number of teeth provided along the corresponding longitudinal extension of the translator. Another option is to provide half the number of windings and only use windings wound in the same direction.

Turning to fig. 1, an open end 11a and a closed end 11b of a hammer body 11 are disclosed. The hammer body 11 includes an open end portion 11a and a closed end portion 11b, the open end portion 11a being configured to allow the hammer piston 12 to reciprocate in a back and forth direction of the hammer body 11, the closed end portion 11b including a gas-filled chamber, which will be described in more detail in fig. 3. The gas-filled chamber is configured to receive the first end portion 15a of the translator and to exert a return action on the translator to accelerate the hammer piston 12 in the direction of the open end portion 11a of the hammer body 11. The toothed portion of translator 15 may be longer than stator 14 such that during reciprocal linear motion, at least some of the teeth move into and out of the interior of stator 14. In some examples, the toothed portion of translator 15 may also be arranged shorter than stator 14, which may mean a disadvantage in that the motor becomes heavier and less efficient, but this maximizes the force per unit translator mass, since all translator teeth are excited during the entire movement. As shown in fig. 2b, the outer diameter of the toothed portion of the translator 15 corresponds substantially to the inner diameter of the stator 14, leaving an air gap G. The air gap may be less than <1mm, preferably <0.5mm, and more preferably <0.35mm. As the air gap becomes smaller, the electromagnetic performance of the machine increases, but the smaller the air gap, the more difficult it becomes to construct and manufacture the hammer device, and finer manufacturing tolerances of the machine components are required.

Turning again to the disclosure in fig. 2 a-2 b, the hammer body 11 may comprise a bearing 18, the bearing 18 being positioned, for example, to support the translator 15 at said open end 11a and closed end 11b of the hammer body. The diameter of the support 18 corresponds to the diameter of the translator. In some examples, the inner diameter of the support disposed near the first open end portion 11a of the hammer body 11 corresponds to the outer diameter of the teeth 17 of the translator 15. In some examples, the outer diameter of the support arranged near the closed end portion 11b corresponds to a cavity in the second portion of the rod of the translator, or the inner diameter of the support corresponds to the outer diameter of the tooth. The support 18 will be arranged to bear on the translator, thereby supporting the movement of the translator within the stator 14. In some examples, the support 18 is made of a low friction material, such as brass or plastic. This provides the advantage that the electromagnetic properties are independent of the electrical conductivity and magnetic permeability of the support material, which would be a problem when using translators with permanent magnets.

In some examples, the cavity between each two protrusions 17a1, 17a2 of the translator may be filled with a non-magnetic and non-conductive material, e.g. a non-magnetic material with an elastic modulus >1GPa, whereas the translator may have an elastic modulus of 180GPa to 220GPa, preferably 190GPa to 210 GPa. To alleviate the known wear and fatigue problems, a protective layer, such as a polymer layer, may be provided as a sealing layer on the surface of the translator; this protects the non-magnetic filler from the mechanical influence of the reciprocating linear motion of the translator.

To alleviate the known wear and fatigue problems, a protective layer, such as a polymer layer, may be provided as a sealing layer on the surface of the translator; this protects the non-magnetic filler from the mechanical influence of the reciprocating linear motion of the translator.

Furthermore, the translator may experience eddy currents caused by the time-varying magnetic flux in the translator. In some examples, a longitudinal cut is provided in the translator teeth and/or the rod along the longitudinal extension of the translator, i.e. in the direction of movement. This provides the benefit of reducing eddy currents in the teeth and in part in the rod, and thereby improving the efficiency of the motor.

Fig. 3 discloses a part of an exemplary hammer body 11 comprising a piston drive 13 as described above. The translator 15 is configured such that at least a first end portion 15a of the translator 15 extends outside the enclosed stator 14 throughout the reciprocation of the translator 15. The hammer body 11 further includes a chamber 19, the chamber 19 being configured to receive and accelerate the translator at the turning position of the reciprocating motion.

In the disclosed example, the translator 15 is at least partially hollow and is configured to receive a cylindrically shaped piston 20, the piston 20 extending from the upper closed end portion 11b of the hammer body 11 into a corresponding cylindrical cavity formed in the translator 15. Thus, the cylindrical cavity of the translator may be configured to represent another gas-filled chamber that aids in the acceleration of the translator stroke when reaching the turning point in the reciprocating motion of the translator. This alternative configuration of the upper closed end portion 11b of the hammer body 11 provides radial support during the reciprocal movement of the translator and facilitates the acceleration of the stroke of the translator from the return position of the translator 15. Thus, a higher gas pressure can be obtained, so that when the chamber is used as a gas spring, the force of the spring will be greater, the travel will be shorter, and the bounce time will be significantly shorter.

In some examples, the outer diameter of the bearing 18 disposed on the barrel piston 20 corresponds to the inner diameter of the bore of the translator. The support 18 is arranged to be supported on the translator so as to support the movement of the translator in the longitudinal direction of the piston drive 13 in the radial direction. As mentioned, the space formed between the cylindrical piston and the translator represents a further gas-filled chamber 19a, the gas-filled chamber 19a being able to exert a return action on the translator. In some examples, the support is made of a low friction material, such as brass or plastic.

In general, all terms used herein are to be interpreted according to their ordinary meaning in the relevant art, unless explicitly given a different meaning and/or implied by the context in which the terms are used.

Various embodiments have been referenced herein. However, a person skilled in the art will recognize numerous variations to the described embodiments that would still fall within the scope of the claims.

Any feature of any of the embodiments disclosed herein may be applied to any other embodiment as appropriate. Likewise, any advantages of any of these embodiments may be applied to any other embodiment, and vice versa.

In the drawings and specification, exemplary aspects of the disclosure have been disclosed. However, many variations and modifications may be made to these aspects without substantially departing from the principles of the present disclosure. Accordingly, the present disclosure is to be considered as illustrative and not restrictive, and not limited to the particular aspects discussed above. Accordingly, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation.

Therefore, it should be understood that the details of the described embodiments are presented by way of example only for illustrative purposes, and that all variations falling within the scope of the claims are intended to be included herein.

Claims (9)

1. Hammer apparatus (10) comprising a hammer body (11), a hammer piston (12) and an electrically operated piston drive (13), wherein the piston drive (13) comprises a stator (14), the stator (14) being fixedly positioned within the hammer body (11) and at least partially surrounding a translator (15), the translator (15) being configured to act on the hammer piston (12), wherein the stator (14) comprises a plurality of circumferential stator windings (14 a) embedded in an inner surface of the stator (14), and the stator (14) is configured to cause a reciprocating linear movement of the translator (15),

-the translator (15) comprises an elongated rod (16), the elongated rod (16) being surrounded by peripheral, outwardly extending teeth (17) integrally formed in the elongated rod along a longitudinal extension of the translator (15), and

-the translator (15) comprises a material with a relative permeability >10 at a magnetic flux density of 0.2 tesla.

2. The hammer apparatus (10) according to claim 1, wherein the hammer piston (12) is operatively connected to the translator (15).

3. The hammer apparatus (10) according to claim 1, wherein the hammer piston (12) is an integral extension of the translator (15).

4. A hammer apparatus (10) according to any one of claims 1-3, wherein the teeth (17) include a plurality of annular protrusions (17 a) extending from the elongate rod (16).

5. The hammer apparatus (10) according to claim 4, wherein adjacent annular projections (17 a1, 17a 2) define an intermediate U-shaped or semicircular cavity having side walls extending marginless from the elongate rod (16).

6. Hammer device (10) according to claim 4 or 5, adjacent annular protrusions (17 a1, 17a 2) have a mutual distance L, and the defined cavity has a width of 0.6L to 0.8L, preferably 0.65L to 0.75L, as measured at the peripheral surface of the protrusions.

7. The hammer apparatus (10) according to any one of claims 4-6, wherein the subset of annular protrusions (17 a) has a tapered shape and a peripheral surface width smaller than a width proximate the elongated rod (16).

8. The hammer apparatus (10) according to any one of the preceding claims, wherein the hammer body (11) comprises an open end portion (11 a) and a closed end portion (11 b), the open end portion (11 a) being configured to allow the hammer piston (12) to reciprocate in a back and forth direction of the hammer body (11), the closed end portion (11 b) comprising a gas filled chamber (19, 19 a), the gas filled chamber (19, 19 a) being configured to apply a return action to the translator (15) to accelerate the hammer piston (12) in a direction of the open end portion (11 a) of the hammer body (11).

9. An electrically operated piston drive (13) for a hammer device (10), the piston drive (13) comprising a stator (14), the stator (14) being fixedly positioned within a hammer body (11) and at least partially surrounding a translator (15), the translator (15) being configured to act on a hammer piston (12), wherein the stator (14) comprises a plurality of peripheral windings (14 a) embedded in an inner surface of the stator (14), and the stator (14) is configured to cause a reciprocating linear motion of the translator, characterized in that,

-the translator (15) comprises an elongated rod (16), the elongated rod (16) being surrounded by peripheral, outwardly extending teeth (17) integrally formed in the elongated rod (16) along a longitudinal extension of the translator (15), and

-the translator (15) comprises a material with a relative permeability >10 at a flux density of 0.2 tesla.