Claim of Priority

This application claims priority to US Patent Application 15/802,580 entitled "Loop-Band Devices Configured for Motion" filed on 11/03/2017 by Baoxiang Shan; US Serial No. 62/506,199 entitled "Looped Multistable System" filed on 05/15/2017 by Baoxiang Shan; to US Serial No. 62/506,828 entitled "Flexible Actuator and Sensor" filed on 05/16/2017 by Baoxiang Shan; to US Serial No. 62/507,300 entitled "Flexible Movement System" filed on 05/17/2017 by Baoxiang Shan; and to US Serial No.

62/509,102 entitled "Travelling Wave Pumps" filed on 05/20/2017 by Baoxiang Shan, the contents of all of which are hereby fully incorporated herein by reference.

Technical Field

The invention relates to a structure and a method for making loop-band devices configured for producing motion, and more particularly to loop-band devices configured to convert thermal, piezo-electric, electro-restrictive and magneto-restrictive stresses into mechanical motion, and vice-versa.

Background Art

The technical problems of converting thermal, piezo-electric, electro-restrictive and magneto-restrictive stresses into mechanical motion, and vice- versa, are inherent in the technical fields of motion generation and energy harvesting.

Possibly relevant art may include, but is not limited to, publications such as US Patent 6,392,331 and US Patent Application 20130082427. Disclosure of Invention

The present invention pertains to an inventive system and method of providing motion using a loop-band device.

In a preferred embodiment, the loop-band device may include a restraining loop that may retain a buckling loop such that the buckling loop assumes, or forms, a buckled mode having one or more buckles. Means may then be used to generate an activation force within the buckling loop. The activation force may, for instance, be any force that results in a change of stress in the buckling loop. Depending on the composition of the buckling loop, that stress may be generated via a means such as, but not limited to, heat, cold, light, an electric current or voltage, a magnetic field, or some combination thereof. The result of the stress may be a change in the configuration of the buckling loop such that there is a movement of the restraining loop and/or the loop-band device.

In a more preferred embodiment, the activation force may be applied at, or in, the vicinity of an inflection point of one or more of the buckles, as this may result in a more effective translation of activation force into loop-band device motion.

The restraining loop is preferably a continuous ribbon, having no end point, that may have a uniform thickness and a uniform width. The width of the restraining loop is preferably greater than its thickness, and, the restraining loop may be of homogenous composition.

The restraining loop may, for instance, be made of a relatively inextensible, but flexible material, such as, but not limited to, a fabric reinforced silicone, a fabric reinforced polyurethane, a Titanium alloy, a stainless steel alloy, a copper alloy or an aluminum alloy, or a combination thereof.

The buckling loop is preferably a continuous ribbon, having no end point, that may have a uniform thickness and a uniform width. The width of the buckling loop is preferably greater than the thickness of the buckling loop. While the buckling loop may be of homogenous composition, some embodiments may have multi-layer buckling loops, and/or buckling loops having a patterning of varying composition.

The buckling loop may, for instance, be made of a relatively flexible material that may develop stresses when subject to suitable activation forces. Such materials include, for instance, electroactive polymers. Other suitable buckling loop materials include, but are not limited to, metals, or metal alloys, having a suitable coefficient of linear, thermal expansion.

Both the restraining and the buckling loops are preferably of seamless

construction, though joints may be made if suitably constructed.

In a further preferred embodiment of the invention, the bucking loop may be a bilayer buckling loop having a substrate layer and an active material layer. The substrate layer and the active material layer may, for instance, be joined together. The substrate layer may be made of materials such as, or similar to, those of which the restraining loop may be made. Similarly, the active material layer may be made of materials such as, or similar to, those of which the buckling loop may be made.

In another embodiment of the invention, the restraining loop may include one or more engagement elements while the buckling loop may include one or more

complementary locating elements. Such an arrangement may, for instance, allow the buckling loop to assume more complex, higher eigenvalue modes that may have a greater number of buckles. The complementary engagement and locating elements may also, or instead, help transfer forces and/or motion between the restraining and buckling loops.

Further embodiments may include fixation points that may tie the restraining loop to the buckling loop at one or more points of fixation. Such fixation points may, for instance, be effective in allowing the loop-band device to be used to generate lateral motions that may, for instance, be useful in applications such as, but not limited to, robotic arm articulation.

In yet another embodiment of the invention, the buckling loop may be provided with one or more discrete force generating elements that may be individually activated, or activated in groups. These force generating elements may be materials such as, but not limited to, ceramic or polymer piezoelectric elements.

One of ordinary skill in the art will appreciate that while the loop-band devices are described herein primarily in terms of stresses being applied to the buckling loop to generate motion, many of the embodiments described may also be used in a further, or alternate, mode in which the loop-band device, or elements of it, are subject to motion and that the resultant motion related stresses applied to the loop-band device may generate electricity as its buckling loop, or elements thereof, alter shape or assume changed buckled modes. The loop-band devices of this invention may, therefore, also be useful in applications such as, but not limited to, energy harvesting from sources of motion such as, but not limited to, wind or wave motion, or a combination thereof.

Brief Description of Drawings

Fig. 1 shows a schematic cross-section of a loop-band device.

Fig. 2 shows a schematic cross-section of a loop-band device driven by a means for generating an activation force.

Fig. 3 shows a schematic cross-section of a single buckle loop-band device with point of fixation.

Fig. 4 shows a schematic cross-section of a two buckle loop-band device with engagement and location elements. Fig. 5 shows a schematic cross-section of a two buckle loop-band device with a point of fixation.

Fig. 6 shows a schematic, cross-section of a loop-band device with a bilayer buckling loop.

Fig. 7 shows a schematic, isometric view of a loop-band device with means for generating an activation force integrated into, or onto, the buckling loop.

Fig. 8 shows a schematic, cross-section of a loop-band device configured for rotary motion. Best Mode for Carrying Out the Invention

The best mode for carrying out the present invention will now be described with reference to the drawings. Identical elements in the various figures are identified with the same reference numerals.

Reference will now be made in detail to various embodiments of the present invention. Such embodiments are provided by way of explanation of the present invention, which is not intended to be limited thereto. In fact, those of ordinary skill in the art may appreciate upon reading the present specification and viewing the present drawings that various modifications and variations can be made thereto.

Figure 1 shows a schematic cross-section of a loop-band device of one

embodiment of the present invention.

The loop-band device 105 may include a restraining loop 110 and a buckling loop 115. The buckling loop may be constrained within the restraining loop in such a way that it assumes, or forms, a buckled shape, or buckled mode, having one or more buckles 120. Each of the buckles 120 may have a first and a second inflection point 135 and 136. A means for generating an activation force may introduce a stress into the buckling loop 115 that may cause it to change its shape, and in so doing result in a motion. The motion of the buckling loop changing shape may, for instance, result in a translation of the loop-band device 105 across a surface on which it may be resting.

Generating the activation force at, or in a vicinity of, one of the points of inflection of one of the buckles may be the most efficient method of translating an applied activation force into motion of the loop-band device. However, there may be advantages to applying the activating force at other sites. The activating force may, for instance, result in, or be a result of, a change in amplitude of a buckle, a bending moment, or change in angle of part of the buckling loop, or a change in curvature of a portion of the buckling loop. Applying such an activating force in a vicinity of where the buckling loop and the restraining loop begin to separate to form a buckle may, for instance, be a location at which the movement of the loop-band device may be most precisely controlled.

The restraining loop is preferably a continuous ribbon that has no end point and that may be of a uniform thickness and a uniform width. The width of the restraining loop is preferably 5-times greater than its thickness, and, the restraining loop is preferably of homogenous composition.

The activation force may, for instance, be any force that results in a change of stress in the buckling loop. Depending on the composition of the buckling loop that stress may be generated via a means for generating an activation force, such as, but not limited to, heat, light, an electric current or voltage, a magnetic field, or a combination thereof.

The result of the stress may be a change in the configuration of the buckling loop such that there is a movement of, or relative to, the restraining loop.

In a more preferred embodiment, activation force may be applied at, or in, the vicinity of an inflection point of one or more of the buckles, as this may result in an effective translation of activation force into loop-band device motion. The buckling loop is preferably a continuous ribbon, having no end point and which may have a uniform thickness and a uniform width. The width of the buckling loop is preferably 5-times greater than the thickness of the buckling loop. While the buckling loop may be of homogenous composition, some embodiments may have buckling loops having patternings of varying composition. For instance, the buckling loop may interpose strips, or bands, of activatable elements between more inert elements.

Both the restraining and the buckling loops are preferably of seamless

construction, though allowances for the manufacturing tolerances of joints may be made.

Figure 2 shows a schematic cross-section of a loop-band device driven by a means for generating an activation force.

The loop-band device driven shown in Figure 2 may, for instance, include a buckling loop 115 made of a suitably thin, relatively flexible, but springy material such as, but not limited to, a suitably thin metal, or metal alloy, that may have a suitably high coefficient of linear, thermal expansion. Although, theoretically, any material having a positive coefficient of linear expansion may be used, in a preferred embodiment of the invention, materials used may have a linear coefficient of expansion greater than 5 xlO ^"6 ml ml °C. In a more preferred embodiment, the materials may be required to have a linear coefficient of expansion greater than 15 xlO ⁶ ml mJ °C. Suitable metals and metal alloys include, but are not limited to Aluminum Bronze, Beryllium Copper, Manganese Bronze, Nickel-Base Ally, S31000 Stainless Steel or some combination thereof.

The means for generating an activation force associated with the loop-band device of Figure 2 may, for instance, be a source 151 of temperature change that may either be a heat source, or a refrigerating source. The loop-band device may also include a restraining loop 110 and a carrying platform 145 that may have support rollers 155. The carrying platform 145 may be situated within the buckling loop 115 and be carrying a means 131 for generating an activation force that may be a source 151 of temperature change. The source 151 of temperature change may be located such that a temperature change in the loop-band device may be generated at, or in a vicinity of, a first inflection point 135. The application of a source 151 of temperature change to the buckling loop 115 may cause local expansion or contraction, and therefore, stress, in a vicinity of the first inflection point 135. This stress may result in the buckling loop 115 deforming, and in doing so causing the loop-band device to move in a first lateral direction 160 along the substantially flat surface 165 on which the loop-band device may be resting.

The source 151 of temperature change may, for instance, be a source of heat that may be any suitable source of heat such as, but not limited to, a flame, an electrical resistance heater, a light bulb, an LED light source, or a focused light source, or some combination thereof.

The source 151 of temperature change may, for instance, be a source of cooling such as, but not limited to, a supply of a refrigerant, a liquid nitrogen spray, a Peltier device, or some combination thereof.

The restraining loop 110 may be made of any suitably thin, relatively inextensible yet flexible material such as, but not limited to, a fabric reinforced silicone, a fabric reinforced polyurethane, a Titanium alloy, a stainless steel alloy, a copper alloy or an aluminum alloy, or a combination thereof. Particularly suitable materials may include Titanium alloys such as, but not limited to, so called Beta titanium alloys, i.e., titanium alloyed in varying amounts with one or more of molybdenum, vanadium, niobium, tantalum, zirconium, manganese, iron, chromium, cobalt, nickel, and copper. This type of alloy may have a strength/modulus of elasticity ratios almost twice that of 18-8 austenitic stainless steel, allowing for larger elastic deflections in springs, and a reduced force per unit displacement. Suitable alloys may include, but are not limited to, "BETA III" (Ti- 11.5 Mo-6.5 Zr-4.6 Sn), Transage 129 (Ti-2Al-l l.5V-2Sn-ll.3Zr) or Ti-6A1-4V, or some combination thereof.

One of ordinary skill in the art will, however, appreciate that while Figure 2 shows a loop-band device driven by a source 151 of temperature change, the buckling loop 115 may instead be made of a suitable electroactive polymer (EAP), and the source of temperature change may then be replaced by a suitable electric current or voltage source, resulting in a loop-band device driven by an electro-magnetic source.

The source 151 of temperature change shown in Figure 2 may then, for instance, be replaced by an electrical current or voltage supplied by two separated conducting, contact rollers. Suitable materials for such an electroactive buckling loop may, for instance, be an electroactive polymer (EAP) or any electrostrictive materials having a piezoelectric voltage constant greater than lx 10 ^"3 V/ mN/ m ² . Particularly suitable polymers include, but are not limited to, polyvinylidene fluoride (PVDF) and Iodine doped polyacetylene

Similarly, the buckling loop may be replaced by one made of a suitably magnetostrictive material, and the heat source by a source of magnetic flux to produce a magnetically driven loop-band device. A suitable magnetorestictive material may be one have a magnetostrictive coefficient greater than 50 microstrains such as, but not limited to, Terfenol-D, or Galfenol. Terfenol-D stands for Ter for terbium, Fe for iron, NOL for Naval Ordnance Laboratory, and D for dysprosium. It is a material that may exhibits about 2,000 microstrains in a field of 2 kOe (160 kA/m) at room temperature. A suitable source of magnetic flux may be a magnet such as, but not limited to, a suitably strong rare-earth permanent magnet, or an electro-magnet or a combination thereof.

Figure 3 shows a schematic cross-section of a single buckle loop-band device with a point of fixation. The single buckle loop-band device with a point of fixation 180 shown in Figure 3 may include a restraining loop 110 and a buckling loop 115 held together at a point of fixation 170. The buckling loop 115 is shown having a buckle with a first inflection point 135. An activating stress may be generated at the first inflection point 135. This activating stress may result in the buckling loop deforming to take up the shape shown as the buckling loop after motion 190 in Figure 3. In assuming a change in shape because of the stress induced at the first inflection point 135, the entire loop-band device may be forced to move in an arc of motion 175 that may be centered on the point of fixation 170. The result of this motion may be the rotated loop-band device as represented by the buckling loop after motion 190 and the restraining loop after motion 185.

When the loop-band device is in the rotated position, as represented by the restraining loop after motion 185 and the buckling loop after motion 190 shown in Figure 3, a further activating stress may be generated to the second inflection point 136.

Application of this activating force, or stress, may result in the loop-band device being returned to its original orientation by rotation in an arc of motion 175 about the point of fixation 170.

Figure 4 shows a schematic cross-section of a two buckle loop-band device with engagement and location elements 220.

The restraining loop 110 may, for instance, have one or more engagement elements 205 that may correspond in position to one or more locating elements 195 of the buckling loop 115. The engagement element 205 may, for instance, be teeth, and the locating element 195 may be holes or spaces into which the teeth may engage. An advantage of having corresponding engagement and locating elements may be to allow the buckling loop 115 to assume and maintain buckling modes, or configurations, having two or more buckles. Such buckling modes with multiple buckles may be termed to be higher eigen- mode buckling configurations.

Figure 5 shows a schematic cross-section of a two buckle loop-band device 265 with a point of fixation.

As shown in Figure 5, the loop-band device may initially have a form shown by the restraining loop 110 and the buckling loop 115 that may be restrained to form a buckled mode with two buckles. The restraining loop 110 and the buckling loop 115 may also be fixed together at a point of fixation 170 that may lie outside the buckled regions of the buckling loop.

A means for generating an activation force may generate an activation force at, or in a vicinity of, a first inflection point 225 of a first buckle. Such an activation force may cause the buckling loop to change shape and in doing so cause the loop-band device to move in a first rotational direction 230 that may be an arc centered on the point of fixation. The result of the movement may be represented by the restraining loop 235 after motion in a first direction of rotation and the buckling loop 240 after motion in a first direction of rotation.

An activation force may instead have been generated at, or in a vicinity of, a first inflection point 260 of a second buckle. Such a force may cause the buckling loop to change shape and in doing so cause the loop-band device to move in a second rotational direction 245 that may be an arc centered on the point of fixation. The result of the movement may be represented by the restraining loop 250 after motion in a second direction of rotation and the buckling loop 255 after motion in a second direction of rotation.

Figure 6 shows a schematic, cross-sectional view of a loop-band device 305 with a bilayer buckling loop. The bilayer buckling loop 285 may be made up of a substrate layer 290 and an active material layer 295.

The bilayer buckling loop substrate layer may, for instance, be made of a material such as, but not limited to, a fabric reinforced silicone, a fabric reinforced polyurethane, a Titanium alloy, a stainless steel alloy, a copper alloy or an aluminum alloy, or a combination thereof.

The bilayer buckling loop active material layer may be made of a material such as, but not limited to, an electroactive polymer (EAP) selected from electrostrictive materials having a piezoelectric voltage constant greater than lxlO ³ Vm/ N, a magnetostrictive materials having a magnetostrictive coefficient greater than 50 microstrains, or a combination thereof; or a metal, or metal alloy, having a coefficient of linear, thermal expansion greater than 5 xlO ^"6 m/ m/ ⁰ C.

Figure 7 shows a schematic, isometric view of a loop-band device 280 with means 131 for generating an activation force integrated into, or onto, the buckling loop 115 force generating elements.

The means 131 for generating an activation force may, for instance, be force generating elements 270 disposed on either the inner or outer surface of the buckling loop 115, or incorporated into the body of the buckling loop. The force generating elements 270 may themselves be flexible, or they may be rigid, or semi-rigid tiles, thus allowing the use of, for instance, ceramic piezo-electric elements as the force generating elements. A change in shape of the buckling loop 115 may, therefore, be effected by activating one or more of the force generating elements 275 that may be located at, or in a vicinity of, an inflection point of the buckling loop 115. This change in shape of the buckling loop 115 may then result in relative motion of the bucking loop with respect to the restraining loop, and/or motion of the entire loop-band device with respect to a support surface. Suitable materials for the force generating elements 270 include electroactive polymers (EAP) such as, but not limited to, polyvinylidene fluoride (PVDF), and iodine doped polyacetylene, or some combination thereof. Ceramic electrostriction, known as relaxor ferroelectrics, such as, but not limited to, lead magnesium niobate (PMN), lead magnesium niobate-lead titanate (PMN-PT) and lead lanthanum zirconate titanate (PLZT), have extraordinarily high electrostrictive constants, and may, therefore, also be suitable as force generating elements 270.

For loop-band device with force generating elements 280 that may function by magnetostriction suitable materials include, but are not limited to, Terfenol-D™,

Galfenol™, Metglas™ or some combination thereof.

As force generating elements 270 may be solids, piezoelectric materials such as, but not limited to, quartz, Lead zirconate titanate (PZT), and Barium titanate may be used as well as polymers such as, but not limited to, Poly vinyl carbonate (PVC), Nylon 11, and polyvinylidene fluoride (PVDF).

Figure 8 shows a schematic, cross-section of a loop-band device 310 configured for rotary motion.

In the embodiment shown in Figure 8, the restraining loop may be configured to be an outer, circular, rigid support structure 320, as this may provide a well-defined axis of rotation for the buckling loop.

In a further embodiment, the loop-band device 310 configured for rotary motion may include an inner, circular, rigid support structure 315 having an axis of rotation 325 that is coincident with the axis of the outer, circular, rigid support structure 320. Such an arrangement may, for instance, be useful in providing higher eigenmode buckling of the buckling loop. In such a structure, application of an activation force 130 at, for instance, the first inflection point 135 of the buckling loop may result in a rotatory motion of the outer, circular, rigid support structure 320 relative to the inner, circular, rigid support structure 315 about the axis of rotation 325.

Although this invention has been described with a certain degree of particularity, it is to be understood that the present disclosure has been made only by way of illustration and that numerous changes in the details of construction and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention. Industrial Applicability

The present invention has applicability in providing controlled motion in, for instance, robotic mechanisms as used in, for instance, manufacturing industries. In addition, the present invention may have applicability in the harvesting of energy from sources of motion such as, but not limited to, wind or flowing water, as using in, for instance, electrical power generating industries.