VIBRATION SOURCE

Abstract

An actuator comprises a magnetostrictive element operably connected to a solenoid coil, preloaded to a default length, having an expanded length greater than the default length, and having a compressed length less than the default length. The compressed length of the magnetostrictive element is not less than a length at which permanent mechanical degradation of the magnetostrictive element occurs. An output element is disposed proximate to a terminal end of the actuator and movable between an original position and an actuated position. The coil can be energized or deenergized between a lower level and a higher level for part or all of an expansion or compression of the magnetostrictive element anywhere within the range between the compressed length and the expanded length. The magnetostrictive element can comprise a terbium alloy.

Claims

1. An actuator comprising: a magnetostrictive element: operably connected to a solenoid coil; preloaded to a default length; having an expanded length greater than the default length; having a compressed length less than the default length, wherein the compressed length of the magnetostrictive element is not less than a length at which permanent mechanical degradation of the magnetostrictive element occurs; an output element disposed proximate to a terminal end of the actuator and movable between an original position and an actuated position; wherein the solenoid coil is energized from a lower level to a higher level during expansion or contraction of the magnetostrictive element.

2. The actuator of claim 1 further comprising a biasing element operably connected to an output element and configured to bias the magnetostrictive element in its default length position.

3. The actuator of claim 1 wherein the magnetostrictive element comprises terbium, dysprosium, and iron.

4. The actuator of claim 1 wherein the magnetostrictive element is subject to a magnetic field from not less than one permanent magnet secured proximate to the magnetostrictive element.

5. The actuator of claim 1 wherein a length of the magnetostrictive element is selectively variable between the expanded length and compressed length to selectively displace the output element by the expansion or compression of the magnetostrictive element.

6. The actuator of claim 1 wherein the solenoid coil comprises one or more windings of conductive wire and further wherein the one or more windings of conductive wire are wound around a bobbin.

7. The actuator of claim 1 further comprising a magnetic flux return path comprising at least a fixed end cap at an end of the actuator opposite the terminal end.

8. The actuator of claim 1 wherein the magnetic flux return path further comprises a movable end cap at the terminal end.

9. The actuator of claim 1 wherein the magnetic flux return path further comprises a cylinder and a plurality of disks fabricated of ferromagnetic material.

10. A method for creating vibration comprising the steps of: providing an actuator having a magnetostrictive element electromagnetically connected to a solenoid coil, a biasing element, and an output element; energizing the solenoid coil from a lower magnitude to a higher magnitude to cause expansion of the magnetostrictive element or de-energizing the solenoid coil from a higher magnitude to a lower magnitude to cause compression of the magnetostrictive element; and displacing the output element by the expansion or the compression of the magnetostrictive element.

11. The method of claim 10 wherein the solenoid coil is energized and de-energized in periods that at least nearly coincide with the harmonic mechanical resonant frequency of the combined actuator and load.

12. The method of claim 11 wherein energizing the solenoid coil causes the output element to be displaced in a direction away from a terminal end of the actuator.

13. The method of claim 10 wherein the applied electrical input begins with zero slope.

14. The method of claim 13 wherein the applied electrical input begins near zero.

15. The method of claim 10 wherein the applied electrical input ends with zero slope.

16. The method of claim 15 wherein the applied electrical input ends near zero.

17. The method of claim 10 further comprising winding the solenoid coil around a bobbin.

18. The method of claim 10 further comprising returning magnetic flux along a path defined in part by a movable end cap, a fixed end cap, a cylinder, and a plurality of disks.

19. A system comprising: a control signal; a source of energy for the control signal; the actuator of claim 1; and a mechanism configured to be mechanically moved when the actuator receives the control signal.

20. An actuator comprising: a piezoelectric element: preloaded to a default length; having an expanded length greater than the default length; having a compressed length less than the default length, wherein the compressed length of the piezoelectric element is not less than a length at which permanent mechanical degradation of the piezoelectric element occurs; an output element disposed proximate to a terminal end of the actuator and movable between an original position and an actuated position; wherein the piezoelectric element is energized from a lower level to a higher level during expansion or contraction of the piezoelectric element.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] FIG. 1 shows an external view of a magnetostrictive actuator, according to some aspects of the present disclosure.

[0038] FIG. 2 shows a cross-sectional view of the magnetostrictive actuator of FIG. 1, according to some aspects of the present disclosure.

[0039] FIG. 3 graphs displacement with respect to time for a periodic energization, according to some aspects of the present disclosure.

[0040] FIG. 4 graphs displacement with respect to time for non-periodic energization, according to some aspects of the present disclosure.

[0041] Several embodiments in which the present invention may be practiced are illustrated and described in detail, wherein like reference characters represent like components throughout the several views. The drawings are presented for exemplary purposes and may not be to scale, unless otherwise indicated, and thus proportions of features in the drawings shall not be construed as evidence of actual proportions.

DETAILED DESCRIPTION OF THE INVENTION

DefinitionsIntroductory Matters

[0042] The following definitions and introductory matters are provided to facilitate an understanding of the present invention. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which embodiments of the present invention pertain.

[0043] The terms a, an, and the include both singular and plural referents.

[0044] The term or is synonymous with and/or and means any one member or combination of members of a particular list.

[0045] The terms invention or present invention as used herein are not intended to refer to any single embodiment of the particular invention but encompass all possible embodiments as described in the specification and the claims.

[0046] The term about as used herein refers to slight variations in numerical quantities with respect to any quantifiable variable. One of ordinary skill in the art will recognize inadvertent error can occur, for example, through use of typical measuring techniques or equipment or from differences in the manufacture, source, or purity of components. The claims include equivalents to the quantities whether or not modified by the term about.

[0047] The term configured describes an apparatus, system, or other structure that is constructed to perform or capable of performing a particular task or to adopt a particular configuration. The term configured can be used interchangeably with other similar phrases such as constructed, arranged, adapted, manufactured, and the like.

[0048] Terms characterizing a sequential order (e.g., first, second, etc.), a position (e.g., top, bottom, lateral, medial, forward, aft, etc.), and/or an orientation (e.g., width, length, depth, thickness, vertical, horizontal, etc.) are referenced according to the views presented. Unless context indicates otherwise, these terms are not limiting. The physical configuration of an object or combination of objects may change without departing from the scope of the present invention.

[0049] As would be apparent to one of ordinary skill in the art, mechanical, procedural, or other changes may be made without departing from the spirit and scope of the invention. The scope of the invention is defined only by the appended claims, along with the full scope of equivalents to which such claims are entitled.

Overview

[0050] FIGS. 1 and 2 show an actuator 100 in accordance with an illustrative embodiment of the present disclosure.

[0051] Magnetostrictive element 110 can comprise an alloy including one or more rare earth and/or transition elements. More specifically, the alloy can be formed of grain-oriented polycrystalline rare earth and/or transition metal materials of the formula Tb.sub.xDy.sub.x-1Fe.sub.2-w, wherein 0.20x1.00 and 0w0.20. The grains of the material have their common principal axes substantially along the growth axis of the material. As the alloy has its grain oriented in the axial direction, the favored direction of magnetostrictive response of magnetostrictive element 110 is formed into a shape with ends that are substantially parallel to each other and substantially perpendicular to the favored direction of magnetostrictive response. Magnetostrictive element 110 can have a transverse dimension perpendicular to the direction of magnetostrictive response substantially smaller than one-quarter wavelength at the electromechanical resonant frequency of the apparatus. Magnetostrictive element 110 can have a length in the direction of magnetostrictive response of no greater than one-quarter wavelength at the electromechanical resonant frequency of the apparatus. Magnetostrictive element 110 has a default length and is configured to expand to an expanded length and/or is selectively expandable to any length between the default length and the expanded length to selectively control its displacement output.

[0052] In an exemplary embodiment, magnetostrictive element 110 is elongated or rod-shaped. In a preferred embodiment, magnetostrictive element 110 is cylindrical, but the present disclosure contemplates the shape can be an ellipsoid, parallelepiped, prismatic, or other similar or suitable shapes. To guard against fracture of magnetostrictive element 110, a fixed end cap 111 can be secured to the immobile end or end cap 111 of magnetostrictive element 110 and a moving end cap 112 can be secured to the mobile end of magnetostrictive element 110. In a preferred embodiment, end caps 111 and 112 are made of a hardened material. End caps 111 and 112 distribute the load across each face of magnetostrictive element 110 through the compliant epoxy used for bonding.

[0053] Actuator 100 includes a preloading element 120. Preloading element 120 compresses magnetostrictive element 110 from its free length to its default length.

[0054] Actuator 100 includes a solenoid coil 130. Solenoid coil 130 can include one or more windings of conductive wire. In the exemplary embodiment illustrated in FIG. 2, solenoid coil 130 has two layers of windings. Solenoid coil 130 can be wound about a bobbin 131 comprised of non-conductive material. Thus, bobbin 131 is coaxially disposed between the solenoid coil 130 and the magnetostrictive element 110.

[0055] A magnetic flux return path is provided to guide the lines of magnetic force around the outside of the solenoid coil 130 from one end of magnetostrictive element 110 to the other. In addition to end caps 111 and 112, the magnetic flux return path consists of cylinder 140, disk 141, and disk 142, preferably fabricated of ferromagnetic material.

[0056] Some aspects of the technical operation of magnetostrictive element 110 are described in co-pending, co-owned U.S. patent application Ser. No. 14/174,560, filed on Feb. 6, 2014, and Ser. No. 14/577,240, filed on Dec. 14, 2014, both of which are incorporated herein by reference in their entireties. In short, a voltage waveform of one polarity is applied, inducing a current waveform of matching polarity to flow through solenoid coil 130. The current within solenoid coil 130 establishes a magnetic field of matching polarity. This magnetic field generates magnetic lines of force that cross into magnetostrictive element 110 with corresponding magnetic flux density of matching polarity. Lines of magnetic flux close back on themselves through flux return path 140, 141, and 142 which, together with magnetostrictive element 110, forms a complete magnetic circuit. The magnetic flux waveform within magnetostrictive element 110, regardless of polarity, causes a corresponding axial expansion. Continuous control of current into solenoid coil 130 continuously controls the axial expansion or contraction of magnetostrictive element 110. The rate at which current increases or decreases and its maximum magnitude are both converted by magnetostrictive element 110 into corresponding mechanical displacement. As used herein, contract or contraction refer to the shortening of magnetostrictive element 110 from a length greater than the default length.

[0057] To achieve the advantages of magnetostrictive actuation of a vibrator, the expansion and contraction of magnetostrictive element 110 must be translated into a corresponding output that provides for precise and variable control over vibration.

[0058] The biasing element 120 is operably connected to output element 150 and configured to bias the output element 150 to the default, unenergized position. The biasing element 120 can include a compression spring and/or shim. In the illustrated embodiment of FIG. 2, the biasing element 120 is disposed between the output element 150 and moving end cap 112.

[0059] In operation, as solenoid 130 is energized and magnetostrictive element 110 expands, end cap 112 moves output element 150 in the direction of arrow 160.

[0060] After completion of an expansion event, solenoid 130 is deenergized and magnetostrictive element 110 contracts from its the expanded length. Due to the contraction of magnetostrictive element 110, magnetostrictive element 110 no longer forces output element 150 to push on its load (not shown). Rather, the forces on the end of output element 150 from the load, together with biasing element 120, overcome the forces associated with the motion of the load. As a result, output element 150 returns from the expanded position to the de-energized position.

[0061] Output element 150, which remains adjacent to and/or in direct contact with end cap 120 of magnetostrictive element 110, further provides a constant compressive force on magnetostrictive element 110. This advantageous feature results in a compressive preload on magnetostrictive element 110 and prevents tensile failure during operation. Further, magnetostrictive element 110 has a default length and is configured to expand to an expanded length, and/or selectively expandable to any length between the default length and the expanded length to selectively control displacement. Selectively controlling the expansion or contraction of magnetostrictive element 110 variably controls the magnitude of displacement, thereby selectively controlling the magnitude of vibration.

[0062] FIG. 3 illustrates a particular mode of operation enabled by this disclosure. Two normalized traces are shown with respect to time. The lower trace is electrical current, the cause of actuator expansion. From zero current, three separate input pulses of identical magnitude are shown. The three pulses are separated in time by identical amounts. More pulses can be added as desired.

[0063] The first current pulse, shown starting and stopping at zero with zero slopes, results in an initial actuator expansion from its default, preloaded, and unenergized position. The current has returned to zero at the moment that expansion has reached its maximum. With zero current and with biasing element 120 having been deflected, the balance of forces causes the load to compress magnetostrictive element 110 further than its default position.

[0064] By superposition, the two additional current pulses of the same magnitude increase the magnitude of the vibrational output of the actuator. The limits of vibration amplitude described above are included.

[0065] FIG. 4 illustrates a second particular mode of operation enabled by this disclosure. Two normalized traces are shown with respect to time. The lower trace is electrical current, the cause of actuator expansion. Each current pulse can be independent with respect to pulse width and magnitude and with respect to the amount of delay between it and the next pulse. Delay can be arbitrary down to zero. Each current pulse starts and stops at zero with zero slopes. This results in an actuator expansion starting and stopping at the default length with zero slopes.

[0066] In the mode shown in FIG. 4, the nature of the terbium alloy is readily apparent. That is, the expansion of magnetostrictive element 110 is a nearly linear scale of current. Further, the time rate of the expansion of magnetostrictive element 110 is a nearly linear scale of the time rate of change of current. Thus, shaping the current to start and stop at zero with zero slopes yields an expansion that starts and stops at the default length with zero slopes. Any number of such pulses of any magnitude and any delay down to zero delay between pulses can be strung together as desired.

[0067] The disclosure is not to be limited to the particular embodiments described herein. In particular, the disclosure contemplates numerous variations in which an appropriate sensor and feedback loop can translate an input force from a magnetostrictive actuator into an output response to provide precise control over vibration creation.

[0068] The terbium alloy offers high mechanical output and is therefore the preferred embodiment of this disclosure. However, it is not the only magnetostrictive material nor do magnetostrictive materials only expand under the influence of a magnetic field. For example, the word magnetostriction was coined to describe the constriction of iron under the influence of a magnetic field. Magnetostriction is exhibited by, for example, various combinations of other rare earth elements, iron, nickel, cobalt, aluminum, and gallium.

[0069] Similarly, piezoelectric materials that can operate for sufficient time near their destructive limit or limits are compatible with the present invention.

[0070] From the foregoing, it can be seen that the present invention accomplishes at least all of the stated objectives.

EXAMPLES

[0071] Many applications will benefit from durable, precise, and continuously controllable high output magnetostrictive actuator technology. To illustrate the breadth of possibilities, the following examples are listed.

[0072] For a first example, some manufacturing processes require transfer of particles or powders or the like through equipment where they may stick to or otherwise clog the equipment. Vibration is a known remedy. Vibration of continuously variable force, displacement, and frequency will enhance certain of these processes.

[0073] For a second example, some higher-powered sources of vibration rotate an offset weight, limiting force and frequency while imposing maintenance requirements.

[0074] For a third example, a single pulse of expansion and contraction can be selected, the pulse having a magnitude and duration that are each separately and continuously selectable within the design range of a particular actuator embodiment. Not only can the pulse be single, but that mechanical output pulse can be shaped to start at zero expansion with zero slope and end at zero expansion with zero slope by appropriately shaping the electrical input pulse. That is, what has been colloquially termed soft-start can be implementedthe pulse can be shaped to avoid undesirable ringing and harmonics. Naturally, it follows that any number of pulses can be excited, here termed a pulse train. Given the actuator's continuous controllability, the pulse train can be formed from any number of individual pulses of any size within the same pulse train, the pulses being separated by any delay or delays down to zero delay.

[0075] A fourth example is identical to the third example above, except expansion can be selected to be different than contraction. Not only can expansion and contraction be different, they can be separated by any time delay and one or both can feature the soft start characteristic as desired.

[0076] For a fifth example, pulses superposed at resonance to generate high mechanical force and displacement from relatively smaller electrical input pulses can be used for industrial processes such as friction welding.

LIST OF REFERENCE CHARACTERS

[0077] The following reference characters and descriptors are not exhaustive, nor limiting, and include reasonable equivalents. If possible, elements identified by a reference character may replace or supplement any element identified by another reference character. [0078] 100 actuator [0079] 110 magnetostrictive element [0080] 111 fixed end cap [0081] 112 moving end cap [0082] 120 preloading element [0083] 130 solenoid coil [0084] 131 bobbin [0085] 140 cylinder [0086] 141 first disk [0087] 142 second disk [0088] 150 output element [0089] 160 direction of expansion

[0090] The present disclosure is not to be limited to the particular embodiments described herein. The following claims set forth a number of the embodiments of the present disclosure with greater particularity.