WO2002017408A1 - Dispositifs rotatifs electroactifs - Google Patents

Dispositifs rotatifs electroactifs Download PDF

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Publication number
WO2002017408A1
WO2002017408A1 PCT/GB2001/003833 GB0103833W WO0217408A1 WO 2002017408 A1 WO2002017408 A1 WO 2002017408A1 GB 0103833 W GB0103833 W GB 0103833W WO 0217408 A1 WO0217408 A1 WO 0217408A1
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WO
WIPO (PCT)
Prior art keywords
electro
elements
active
rotary device
around
Prior art date
Application number
PCT/GB2001/003833
Other languages
English (en)
Inventor
Anthony Hooley
Ursula Ruth Lenel
Gareth Mckevitt
Mark Richard Shepherd
Richard John Topliss
Original Assignee
1... Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from GB0020944A external-priority patent/GB0020944D0/en
Priority claimed from GB0107694A external-priority patent/GB0107694D0/en
Application filed by 1... Limited filed Critical 1... Limited
Priority to AU2001282348A priority Critical patent/AU2001282348A1/en
Priority to GB0303992A priority patent/GB2383896B/en
Publication of WO2002017408A1 publication Critical patent/WO2002017408A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R17/00—Piezoelectric transducers; Electrostrictive transducers
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02N—ELECTRIC MACHINES NOT OTHERWISE PROVIDED FOR
    • H02N2/00—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction
    • H02N2/10—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction producing rotary motion, e.g. rotary motors
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/20—Piezoelectric or electrostrictive devices with electrical input and mechanical output, e.g. functioning as actuators or vibrators
    • H10N30/204—Piezoelectric or electrostrictive devices with electrical input and mechanical output, e.g. functioning as actuators or vibrators using bending displacement, e.g. unimorph, bimorph or multimorph cantilever or membrane benders
    • H10N30/2041—Beam type
    • H10N30/2042—Cantilevers, i.e. having one fixed end
    • H10N30/2044—Cantilevers, i.e. having one fixed end having multiple segments mechanically connected in series, e.g. zig-zag type
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R2217/00—Details of magnetostrictive, piezoelectric, or electrostrictive transducers covered by H04R15/00 or H04R17/00 but not provided for in any of their subgroups
    • H04R2217/01—Non-planar magnetostrictive, piezoelectric or electrostrictive benders

Definitions

  • the present invention relates to electro-active rotary devices. More particularly, the present invention concerns novel constructions for an electro-active device.
  • Electro-active devices are those which make use of components that display electro-active properties, that is those in which a component changes shape in response to a change of an appropriate electrical condition in which the component exists, or vice versa the component produces electrical signals in response to a shape change. In general such devices may be used in either mode.
  • the most developed type of electro-active device is a piezoelectric device. However, it will be understood that there are a number of other sorts of electro-active device including those that are electrostrictive or piezoresistive.
  • the devices of the present invention include those which show piezoelectric activity as well as other forms of electro- activity.
  • the present invention relates to a rotary device, that is one in which the application of an electrical signal generates a rotation, or vice versa.
  • rotary piezoelectric device helical and spiral benders.
  • Such devices are formed as an elongate multi-layer element having a bender construction. That is to say the element includes a first layer of active piezoelectric material. It also has at least one other layer which may be non-active (a unimorph construction) or a second piezoelectric layer poled oppositely to the first piezoelectric layer (a bimorph construction).
  • the element is formed with electrodes along opposite surfaces of one or more layers.
  • the electric field created between the electrodes causes the first piezoelectric layer to extend (or contract) longitudinally along the length of the element.
  • the non-active layer remains unaffected by the electric field.
  • the second piezoelectric layer contracts (or extends) longitudinally along the element, i.e. in an opposite sense to the first layer.
  • the differential expansion between the layers causes the element to bend perpendicularly to the layers.
  • the element is a tape wound into the shape of a helix or a spiral.
  • Activation of the bender causes a relative rotational displacement about the axis of the helix between the ends of the element, as the coils tighten or loosen.
  • the amount of rotation increases with the length of the helix, which in theory at least may be of any length. This results in quite significant rotations. For instance, in a helix having a diameter of about 1cm, an axial length of several cm and several helical turns of bender tape several millimetres wide, the relative rotation between the ends may be several degrees.
  • Helical and spiral rotary devices are advantageous in that a high degree of rotation can be achieved because each turn of the helix or spiral along which the device extends contributes to the net rotation between the ends of the device.
  • helical and spiral devices suffer from the problem that the device is not particularly easy to manufacture, because it is necessary either to curve a straight element into the desired shape or else to use a special technique in which the device is directly formed into the desired curved shape. Either of these manufacturing routes present a technical challenge.
  • a helical or spiral devices suffers from the problem that it si difficult to control the electrical and mechanical response of the device to the as desired for a particular application.
  • an electro-active rotary device comprising a plurality of electro-active elements, each element being arranged to bend, on activation, to generate relative rotation of its ends, the elements being connected together by their ends in series, with each element extending between its ends around a common axis to bend, on actuation, around the common axis, the elements being arranged to combine said rotation generated by each element to produce a net relative rotation around the common axis between the elements at the ends of the series on activation of all the elements.
  • the device of the invention is an electroactive rotary device comprising not one, but several, electro-active elements, connected together to produce rotation in an additive sense.
  • the net rotation between the ends of the device is high, because the relative rotation generated by each element is combined by the elements being connected together in series.
  • a device producing any desired net rotation may be reduced by selection of an appropriate number of elements.
  • devices in accordance with the present invention may be easily manufactured, as discussed in more detail below.
  • the device may be formed from a plurality of separate elements which may be connected together.
  • the elements may be straight or extend along a simple curve, so that the elements are simple to manufacture individually. It is then straight forward to manufacture the rotary device by connecting the elements together to build them into the desired structure.
  • devices in accordance to the present invention in which the electro-active elements and connecting portions are formed as a unitary member are easy to manufacture, as discussed in more detail below.
  • the electrical and mechanical properties of the device may be easily controlled.
  • the stiffener and force-to- voltage response of the device can be controlled by the mechanical design of the individual elements.
  • the electro-active device may be electrically activated or mechanically activated. Therefore, the device may be used as a rotary actuator by electrically activating the device, to produce a relative rotation between the ends, or may be used as a rotary sensor by mechanically activating the device by rotating the ends, to generate an electrical signal.
  • the device extends along the common axis with the elements arranged successively along the common axis. In such a device rotation of each elements adds incrementally along the axis, so that the structure of the device twists around the axis.
  • the electro-active elements may be separately formed and connected by separate connecting elements. This is particularly advantageous because it allows the mechanical response of the device to be controlled by appropriate selection of the form and material of the connecting elements. In contrast, in the known helical bender discussed above, the mechanical response derives entirely from the mechanical properties of the piezoelectric element. It is difficult to vary those properties of the piezoelectric material without harming its piezoelectric response.
  • the elements and possibly also connecting portions connecting the elements may be formed from a unitary elongate member.
  • the elements are curved around the common axis and nested together.
  • Such a device is compact as a result of the rotary elements being nested together.
  • the nested arrangement allows a large number of elements to be used generating a relatively large net rotation.
  • Such a device is most easy to manufacture if the elements are separate. In that case the individual elements are easy to manufacture and the device may be assembled simply by connecting the elements together.
  • the elements can have a number of different forms and configurations.
  • the elements may have non-circular geometry and may not be precisely co- axial, but preferably they extend around a common axis along arcs of concentric circles. To maximise the length and hence relative rotation of each element, the elements may each be cylindrical except for an axially-extending gap defining the ends of the element.
  • a helix may include plural turns each contributing to the relative rotation of the ends of the elements, such a helical form provides a relatively high rotation for an element of a given radius, as compared to an element which extends around the axis along an arc of a circle.
  • successive elements in the series extend in alternate senses around the common axis so that bending of the successive elements in alternate senses is concomitant with relative rotations of each element which combine together.
  • Fig. 1 is a cross-sectional view of a portion of an element used in the embodiments of the present invention
  • Fig. 2 is a view of a portion of a first embodiment of the present invention
  • Fig. 3 is a side view of a portion of a second embodiment of the present invention illustrating an alternative connection configuration
  • Fig. 4 is a side view of a third embodiment of the present invention having a different cross-section
  • FIGs. 5 to 7 illustrate three different forms of connecting element usable in the present invention
  • Fig. 8 illustrates a portion of a fourth embodiment of the present invention having curved electro-active portions and alternating connection positions
  • Figs. 9 to 11 illustrate successive steps in a method of manufacturing an electro-active device according to a fifth embodiment of the present invention.
  • Fig. 12 is a perspective view of a device which is a sixth embodiment of the present invention.
  • Fig. 13 is a cross-sectional view of the device of Fig. 12, the cross-section being taken in a radial plane of the device;
  • Fig. 14 is a cross-sectional view of the device of Fig. 12, similar to that of Fig. 13 but on activation of the device;
  • Fig. 15 is a perspective view of an element of a device which is a seventh embodiment of the present invention.
  • Fig. 16 is an axial end view of the device of Fig. 15;
  • Fig. 17 is a cross-sectional view of the device of Fig 15, the cross-section being taken axially along the line VII- VII in Fig. 16;
  • Fig. 18 is a perspective view of a device which is an eighth embodiment of the present invention.
  • Fig. 19 is a view of the device of Fig 18 during manufacture.
  • the embodiments of the present invention comprise electro active elements which have a bender construction so that they bend, on activation.
  • the elements may have a bimorph bender construction as illustrated in Fig. 1 which is a cross sectional view of a portion of an element 1 along the length L of the element 1.
  • the element 1 comprises two layers 2 of electro-active material coupled together with electrodes 3 extending parallel to the layers 2 of electro-active material on the surfaces of the layers 2.
  • the layers 2 are arranged to undergo a differential change in length between the ends of the element 1, that is in the direction along the length L of the element, for example with one layer 2 expanding and the other layer 2 contracting.
  • Such differential change in length causes the element 1 to bend perpendicular to the layers 2 as a result of the layers 2 being constrained where they are joined. Such bending on activation causes the ends of the element 1 to relatively rotate.
  • the electrodes 3 are electrically connected to a circuit 4.
  • the circuit 4 may apply voltages for electrical activation or may detect activation voltages developed by mechanical activation.
  • Alterative bender constructions for the elements are a unimorph construction consisting of a single electro-active layer and inactive layer, or a multi-morph bender construction consisting of more than two electro-active layers.
  • the structure may include non- active layers such as an inactive ceramic which affect the bending properties of the bender, as in a unimorph bender.
  • the non-active layer may enhance siiffhess and hence force capability, at the expense of displacement.
  • Low displacement devices may be used as drivers in actuators or positioning devices where a device is required to move a component of significant mass.
  • the inclusion of non-active layers also modifies the frequency response of the device and may be chosen to provide a damping effect.
  • a bender construction is preferred because it is simple and well understood, but in general the elements may have any construction which bends on activation.
  • the preferred type of electro-active material for use in the elements 1, for example as the layers 3 in the construction of Fig. 1, is a piezoelectric material. Any suitable piezoelectric material may be used. The piezoelectric material is poled across the layers 2 so that on activation a change in length is concomitant with a voltage between the electrodes 3.
  • the material may be piezoelectric ceramic such as lead zirconate titanate (PZT) or a polymer such as polyvinyl fluoride (PVDF). However, any other type of electro-active material may alternatively be used.
  • the electro-active material may be an electrostrictive material which contracts on the application of electric field, which field may again be applied through electrode layers.
  • the electro-active material may be a piezoresistive material in which the electrical resistance changes as the material is extended or contracted, ie. strained. In this piezoresistive case, the mechanical deformation may be measured as the change in resistance to an electrical current through this material. Consequently, such a device may be employed as a sensor. Piezoresistive material does not require face electrodes, but is connected at its ends to an external electrical circuit.
  • the stiffness and the force-to-voltage response of the elements and, hence of the device as a whole, can be controlled by the design of the elements, for example by selecting the length of the elements 1.
  • the elements are connected to extend around a common axis and are arranged to bend around that axis.
  • the axis is imaginary, but is useful for visualising and defining the structure.
  • bending of each given element around the axis relatively rotates the elements connected to the given element around the axis.
  • the elements are connected so that their relative rotations combine to produce a net rotation around the common axis between the elements at the ends series.
  • the device extends along the common axis with the elements arranged successively along the common axis.
  • the electro-active elements may be separately formed and connected together by connecting elements.
  • the electro-active elements and connecting portions may be formed together as a unitary member.
  • One way to connect the electro-active elements is with successive electro- active elements along the axis extending from the previous electro-active element in the same sense around the axis. Looking at this another way, successive connections are positioned at angles around the axis which progress in the same sense around the axis. As a result, the succession of connected elements form a structure which in effect extends in a helix around the axis. In this case, bending of the successive elements in the same sense around the axis produces the rotations which combine in the same sense.
  • FIG. 2 shows a first embodiment of the present invention.
  • This device 10 consists of rectangular electro-active elements 11 which are connected together in series at their ends to each extend around a common axis 13 by connecting elements 12 (described further below).
  • Each electro-active element 11 extends at 90° relative to the adjacent electro-active elements 11, so that the structure has a square cross-section when viewed along the axis 13.
  • the connecting elements 12 connect together the corners of successive elements 11.
  • the electro-active elements 11 bend perpendicular to their faces, hence relatively rotating connected elements 11 around the axis 13.
  • the rotations of structure add incrementally along the axis 13.
  • the structure of electro-active elements may take any form, so long as they extend around the axis.
  • the electro-active portions may be curved around the axis in their inactivated shape and/or may have shapes other than orientations or configurations, illustrated in Fig. 2.
  • the electro-active elements may be connected at different positions relative to each element.
  • Fig. 3 shows a device 20 which is a second embodiment having a structure of rectangular electro-active elements 21 which are connected by their end edges 22 which overlap at shifted positions relative to one another along the axis so that the structure as a whole progresses helically around the axis.
  • the electro-active elements may be connected at any angle relative to each other.
  • Fig. 4 illustrates a device 30 comprising rectangular electro- active elements 31 are connected at 60° relative to each other to form a triangular cross-section when viewed along the axis. Any other cross-section could be selected, either regular, such as hexagonal, or irregular.
  • the connecting elements may take any form provided they connect together the electro-active elements.
  • the connecting elements may be formed from a non- active material which is then fixed to the electro-active elements.
  • the connecting element may for example be made from polymer, ceramic, metal or composite material.
  • the connecting elements may be fixed to the electro-active elements in many ways, for example by an adhesive such as an epoxy or with a resilient fit. The connecting elements may even be simply an amount of adhesive.
  • Figs. 5 to 7 illustrate examples of connecting elements connecting to electro- active elements 41.
  • Figs. 5 and 6 illustrate respective connecting elements 42 and 43 in the form of blocks affixed to the electro-active elements 41 eg. by adhesive.
  • the block 42 illustrated in Fig. 5 is connected to the edges of the electro-active elements 41, whereas the connecting element 43 shown in Fig. 6 is connected to the faces of the electro-active elements 41.
  • Fig. 7 shows a connecting element 44 consisting of a resilient elongate member 44 having slots 45 into which the piezoelectric elements 41 are inserted and retained due to the resilience of the elongate member 45.
  • connection elements such as the connecting elements 42 to 44 shown in Figs. 5 to 7 allow the mechanical response of the electro-active structure to be controlled by a selection of materials having appropriate properties. This is a significant advantage. In contrast, the variation in the mechanical response of an electro-active element is comparatively restricted and different to control.
  • An alternative way to connect the electro-active elements is with successive electro-active elements along the axis extending from the previous electro-active element in alternate senses around the axis. Looking at this another way, successive connections are positioned at angles around the axis which progress in alternate senses around the axis. In this case, in use successive electro-active elements are activated to bend in alternate senses around the axis, so that they produce rotations which combine in the same sense.
  • the device 50 illustrated in Fig. 8 consists of curved electro- active elements 51, each extending around an arc of a circle about a common axis 53.
  • the electro-active elements 51 are connected by connecting portions 52 positioned at alternate ends of the electro-active elements 51.
  • the electro-active elements 51 extend around the axis 53 in alternate senses as one moves along that axis 53.
  • Alternate elements 51 are oppositely poled so that on activation they bend to produce rotation in opposite senses around the axis 53. Due to the alternate angular positions of the connecting elements 52, the net rotations combine.
  • the electro-active device may be manufactured from discrete electro-active elements. This is a particularly simple method of manufacture, because the discrete electro-active elements are simply connected together by the connecting elements gradually building up the structure into the desired form.
  • the individual electro-active elements may be manufactured using any known technique. A preferred method is simply to cut them from an elongate electro-active member.
  • Such an elongate electro-active member may itself be made by many known techniques such as extrusion or calendering. It may be made by co- extrusion of two or more layers of the chosen electro-active material, for instance a piezoelectric ceramic, such as lead zirconate titanate (PZT) ceramic. Alternatively, it may be made by co-calendering of the materials.
  • PZT lead zirconate titanate
  • such an elongate member may be made through lamination of thinner layers.
  • These thinner layers may themselves be made by any suitable route, such as high sheer mixing of a ceramic powder, polymer and solvent mixture, followed by extrusion and calendering.
  • Alternative routes such as tape casting or that referred to as the Solutech process, known in the field of ceramics, may be used.
  • the electrodes may be formed as an integral part of the techniques described above or may be printed or laminated onto the surface of the elongate member at a later stage.
  • the discrete electro-active elements may be formed together with connecting portions as a unitary member.
  • a structure may be manufactured by the following method described with reference to Figs. 9 to 11 which results in a device 60 which is a fifth embodiment
  • the method uses an elongate electro-active member which is formed as an elongate member having a multi-layer bender structure with electrodes using any known technique, for example as discussed above.
  • the elongate member 61 is cut by cuts 62 extending partially across the elongate member 61 from alternate sides as illustrated in Fig. 9.
  • the elongate member 61 is shaped into discrete electro-active elements 63 formed longitudinally between the cuts 62 and connecting portions 64 formed between the ends of the cuts 62 and the edges of the elongate member 61.
  • both the elongate member 61 and the electrodes formed thereon remain unitary.
  • alternate electro-active elements 63 are poled in opposite senses as indicated by the positive and negative signs on each discrete element 63 in Fig. 9.
  • the elongate member 61 is curved around axis 71 extending longitudinally along the elongate member 61 as shown in Fig. 10. Consequently, each electro-active element 63 extends circularly around the axis 71 and the connecting portions 64 progress in alternate senses around the axis 71 as one moves along the axis 71.
  • This curving of the elongate element 61 may be performed around a former (not shown).
  • the member may be set by heating to burn out the constituent polymers, typically at up to 600 °C. The material is then densified through sintering, typically at between 1000 ° C and 1200 ° C.
  • the curved elongate member 61 rotates around the axis 71.
  • the same voltage is applied in the same sense to each electro-active element 63 because the electrode formed on the elongate member 61 remains unitary across all the electro-active elements 63 through the connection portions 64.
  • the electro- active elements 63 are alternately poled, they bend in alternate senses around the axis 71. For example, along a section of the member 61 illustrated in Fig. 11, a first section 63 a bends outwardly and so rotates the first connecting portion 64a in a first sense A.
  • the second electro-active element 63b bends inwardly and so rotates the second connecting portion 64b in the same sense A as the first connecting portion 64a.
  • the third electro-active element 63c bends outwardly and so rotates the third connecting portion 64C in that same sense A. Therefore, actuation of the elements in alternate senses causes a relative rotation of the electro-active elements in the same sense, because the successive electro-active elements extend around the axis in alternate senses. In this way an incrementally adding rotation is generated along the length of the device.
  • Fig. 12 and 13 illustrates a device 101 which is a sixth embodiment of the present invention.
  • the device 101 comprises an assembly of separate electro-active rotary elements 102 nested together.
  • the element 102 is cylindrical except for an axially- extended gap 103.
  • the elements 2 are nested together concentrically about a common axis 4 and therefore have a compact arrangement.
  • the device 1 is illustrated as comprising four elements 2 for clarity, but it should be understood that any number of elements 2 may in fact be provided.
  • the gap 3 effectively defines ends 5 between which the elements 2 extend around the axis 4 along arcs of concentric circles centred on the axis 4.
  • the elements 2 have a construction which causes the ends 5 of each element to relatively rotate around the axis 4 on activation.
  • adjacent elements 102 are coupled together by coupling elements 106 to form an assembly of elements coupled together in series.
  • the coupling elements 106 may be adhesive or may be a separate coupling element.
  • the properties of the coupling elements 106 may be selected to control the overall stiffness, damping and/or mass of the device 101.
  • the coupling element 106 can also improve the robustness of the overall assembly of elements 102 in the device 101.
  • the coupling elements 106 extend along the entire axial length of the elements 102 to improve the strength of coupling.
  • the coupling elements 106 are positioned at the ends 105 of the element 102.
  • the coupling elements 10 6 are positioned at alternate ends 105 of the elements 102.
  • successive elements 102 in the series extend from the end 105 of which they are coupled to the previous element 102 in alternate senses around the common axis 104. Consequently, on activation, the relative rotation of the ends 105 of successive elements 102 in the series occurs in alternate senses. Concomitantly, the relative rotations of each element 102 combine together to produce a net overall rotation as a summation of the individual relative rotations of each element 102 in the series.
  • the element 102a is actuated in a first sense such that it bends so as to close the gap between its ends, causing the other end 122 of element 102a to rotate in a clockwise manner.
  • the end 122 is fixed through a coupling 106a to one end 123 of the element 102b, which end 123 therefore also rotates in a clockwise manner.
  • the element 102b is also actuated, with a sense of actuation opposite to that of element 102a, such that element 102b bends to open, rather than close, causing the end 124 of element 102b to rotate, again in a clockwise sense.
  • the elements 102c and 102d are arranged to cause additive clockwise rotation by alternating the sense of actuation from one layer to the next.
  • the free end 125 of the outermost element 102d rotates relative to the inner fixed end 121 of the innermost element 102a by a considerable clockwise amount.
  • anti-clockwise rotation is achieved.
  • Fig. 14 shows schematically the device 1 of Figs. 12 and 13 when activated as described above.
  • the position of the free end 125 of the outermost layer is shown by the solid line; its position is the inactivated state is shown by the dotted line 126.
  • the dashed lines 127, 128 demonstrate the degree of rotation in the sense of the arrow 129.
  • the individual elements 102 may be manufactured by any conventional technique.
  • the elements 102 may be manufactured as a cylinder which is cut to produce the gap 103.
  • the individual elements 102 may be initially formed as a flat plate which is subsequently bent into the curved shape.
  • the individual elements 102 must be sufficiently deformable, for example by including a plasticised material within the electro-active material which may be burnt out after bending the elements 102 into shape.
  • the individual elements 102 are then simply coupled together by the coupling element 6 to build the elements 102 up into the assembly of device 101.
  • the present invention may use elements 130 which extend around the common axis 131 in a helix as illustrated in Fig. 15.
  • Such a helical element 130 may be manufactured by bending a deformable tape or by initially forming the element 130 as a cylinder and making a helical cut so that the element extends helically between the turns of the cut. Otherwise the construction of the element 130 is the same as that of the element 102 of the first device 101. Accordingly, on actuation, relative rotation between the ends 132 of the elements 130 occurs around the axis 31 in the same way as the relative rotation of the elements 2.
  • the advantage of the helical element 30 is that it may comprise plural turns which each generate a rotation which sums along the length of the element 30, thereby producing a higher degree of rotation for an element 130 of given radius, as compared to an element 102 of the first device 101 of the same radius.
  • a device 133 which forms a seventh embodiment of the present invention comprises an assembly of the helical elements 130 as shown in Fig. 15 of different radii nested together concentrically around the axis 131.
  • the second device 133 is shown in end view in Fig. 16 and in axial cross-section in Fig. 17.
  • the helical elements 130 are coupled together in series by coupling elements 134, 135.
  • the coupling elements 134, 135 are arranged at alternate ends 132 of the helical elements 130 through the series of element 130. Consequently the operation of the device 133 is equivalent to that of the first device 101, as described above.
  • FIG. 18 An alternative configuration of nested helices is shown in Fig. 18, forming a device 181 which constitutes an eighth embodiment of the invention.
  • the device 133 of Figs. 16 and 17 above comprises a series of helices which although of different radii are wound in the same sense. To produce additive rotations, adjacent helices are activated with opposite polarities.
  • the alternative device 181 of Fig. 18 comprises a series of helical elements 182, 185 in which adjacent elements 182,
  • the outermost element 182 can be envisaged as being wound from a tape which winds clockwise from bottom 183 to top 184.
  • the adjacent helix i.e. the next to outermost helix 185, winds the opposite way, namely anti-clockwise from bottom
  • FIG. 18 An advantage of the configuration shown in Fig. 18 is that it allows a simplified manufacturing process in which the adjacent helices are formed from a single continuous element. This is possible because if the first helix winds, say, clockwise bottom to top, then the second winds clockwise top to bottom and can therefore be a continuation of the same winding, with further helices being made similarly.
  • the device is made by winding an element 190 having a zig-zag shape such as that illustrated in Fig. 19.
  • a mandrel 191 is rolled across the element 190 from right to left to produce nested helical elements of the desired sense each linear slope 194 of the element 190 forms one of the helical elements.
  • the mandrel 191 is shown near the beginning of winding with part of the first slope 194, which will become the inner element of 102 of the series.
  • manufacture such winding is carried out with a flexible plasticised element, which is then sintered as normal.
  • the electrodes may also be continuous along the length of the element.
  • the magnitude of the displacement of activation depends on the sizing and construction of the elements which can be freely selected during manufacture.
  • the total displacement achieved by the device may be controlled by selecting the number of elements in the device. As a typical example a single element of bimorph construction having a thickness of 1mm, a radius of 10mm and extending along an area of a circle subtending 340° has a displacement of about 4°.
  • the device 107 of Fig 12 has an outer radius of about 10mm then the total displacement of the device 101 will be about 10-12°.
  • a helical element creates more displacement due to the extra turns.
  • the element 30 of Fig. 15 having a 10mm outer radius has a displacement of about 7-8°, while the devices 133 and 181 of Figs 16 and 18, respectively, have displacements of around 15-20° and 25-30°, respectively.
  • Devices in accordance with the present invention have many uses, just as for known electro-active rotary devices.
  • the devices may be mechanically or electrically activated for use as a rotary sensor or a rotary actuator, respectively.
  • each element of the device is actuated in the appropriate sense by applying a voltage from the electrical circuit 4 to the electrodes 3 of the element 1 to cause relative rotation of the ends of the element 1 to combined in the same sense and, as a result, to produce a net relative rotation between the elements at the ends of the device.
  • the elements of the ends of the device may be coupled to further objects which are to be relatively rotated by the device.
  • Mechanical actuation is the converse process. Relative rotation between the elements at the ends of the series is induced.
  • the element at one end of the series may be fixed whilst the element at the other end is coupled to an object, the rotation of which is to be sensed.
  • relative rotation of the elements at the ends of the device causes a relative rotation of each individual element which generates a voltage across the electrodes 2 of that element 1.
  • the voltages thus generated are supplied to the electrical circuit 4 which protects the voltages as an electrical signal which indicates a degree of rotation.

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  • Signal Processing (AREA)
  • Micromachines (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

L'invention concerne un dispositif rotatif électroactif comprenant plusieurs éléments électroactifs, chacun étant disposé de manière à fléchir lorsqu'il est activé, afin de produire une rotation relative de ses extrémités, les éléments étant liés entre eux en série par leurs extrémités, avec chaque élément s'étendant entre ses extrémités autour d'un axe commun de manière à fléchir autour de l'axe commun. Les éléments sont arrangés de manière à combiner la rotation produite par chaque élément afin de produire une rotation relative nette autour de l'axe commun entre les éléments aux extrémités de la série lors de l'activation de tous les éléments. Dans un mode de réalisation, le dispositif s'étend le long de l'axe commun avec les éléments arrangés de manière successive le long de l'axe commun. Dans un autre mode de réalisation, les éléments sont incurvés autour de l'axe commun et emboîtés les uns dans les autres.
PCT/GB2001/003833 2000-08-24 2001-08-24 Dispositifs rotatifs electroactifs WO2002017408A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
AU2001282348A AU2001282348A1 (en) 2000-08-24 2001-08-24 Electro-active rotary devices
GB0303992A GB2383896B (en) 2000-08-24 2001-08-24 Electro-active rotary devices

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
GB0020944.5 2000-08-24
GB0020944A GB0020944D0 (en) 2000-08-24 2000-08-24 Electro-active rotary devices
GB0107694.2 2001-03-27
GB0107694A GB0107694D0 (en) 2001-03-27 2001-03-27 Electro-active rotary device

Publications (1)

Publication Number Publication Date
WO2002017408A1 true WO2002017408A1 (fr) 2002-02-28

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB2001/003833 WO2002017408A1 (fr) 2000-08-24 2001-08-24 Dispositifs rotatifs electroactifs

Country Status (3)

Country Link
AU (1) AU2001282348A1 (fr)
GB (1) GB2383896B (fr)
WO (1) WO2002017408A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2433174A (en) * 2005-12-07 2007-06-13 New Transducers Ltd Exciter for a bending wave distributed mode loudspeaker

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1945448A1 (de) * 1969-09-08 1971-03-11 Siemens Ag Piezoelektrisch anzutreibender Biegekoerper,insbesondere fuer Uhren und Relais
US3816774A (en) * 1972-01-28 1974-06-11 Victor Company Of Japan Curved piezoelectric elements
JPS5895710A (ja) * 1981-12-03 1983-06-07 Oki Electric Ind Co Ltd ミラ−偏向器
JPH0449876A (ja) * 1990-06-19 1992-02-19 Matsushita Electric Ind Co Ltd 角度調節装置
WO2001047041A2 (fr) * 1999-12-21 2001-06-28 1... Limited Dispositifs electro-actifs

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1945448A1 (de) * 1969-09-08 1971-03-11 Siemens Ag Piezoelektrisch anzutreibender Biegekoerper,insbesondere fuer Uhren und Relais
US3816774A (en) * 1972-01-28 1974-06-11 Victor Company Of Japan Curved piezoelectric elements
JPS5895710A (ja) * 1981-12-03 1983-06-07 Oki Electric Ind Co Ltd ミラ−偏向器
JPH0449876A (ja) * 1990-06-19 1992-02-19 Matsushita Electric Ind Co Ltd 角度調節装置
WO2001047041A2 (fr) * 1999-12-21 2001-06-28 1... Limited Dispositifs electro-actifs

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 007, no. 196 (P - 219) 26 August 1983 (1983-08-26) *
PATENT ABSTRACTS OF JAPAN vol. 016, no. 240 (E - 1211) 3 June 1992 (1992-06-03) *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2433174A (en) * 2005-12-07 2007-06-13 New Transducers Ltd Exciter for a bending wave distributed mode loudspeaker

Also Published As

Publication number Publication date
GB2383896B (en) 2004-02-25
GB2383896A (en) 2003-07-09
GB0303992D0 (en) 2003-03-26
AU2001282348A1 (en) 2002-03-04

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