However, as is seen graphically in the accompanying Drawings (discussed further hereinafter), the elongate body: need not be straight, like a tape, but can be curved; need not be parallel-sided, like a tape, but can (for instance) be triangular; and need not be long and thin, like a tape, but can be disk-like (though a disk-shaped body could, for the purposes of this invention, be considered as a number of triangular “radial” segments fixed side by side round in a circle). In operation the device of the invention, which has portions in groups that are spatially separated across the notional median plane, bends as the result of any dimension change of the piezoelectric-layer portions in the group on one side. If, as shown, the applied activation field alternates between adjacent electrode pairs, so each is in the opposite sense of that of its immediate neighbours either side, then all the corrugations on one side of the sheet 11 (and thus on one side of the median plane MP) will suffer the same effect-expansion or contraction, depending on the field direction-while all the corrugations on the other side of the sheet 11 (and on the other side of the median plane MP) will suffer the opposite effect.
- Algunos de los defibriladores y marcapasos cardíacos más antiguos
- Aplicación de fuerzas G positivas
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- Arotor=Swept Area of the Rotor
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If, with such a corrugated body, all the peak portions (in the top group) were caused to expand, the body’s dimensions (and particularly its length) on its upper side would increase, and it would bend down, normal to the median plane, away from that side-it would become convex, with that upper side on the outside. In each case, because of the spatial separation of the device’s two layers either side of the joint face (the median plane) the composite is caused to bend (in the case of an elongate beam device one end moves up or down, or back or forth, relative to the other)-and this bending can provide movement and force so as to actuate some suitably-connected machinery. And in each case, the simple, single layer acts as though it were a bimorph-if elongate and beam-like, bending along its length, one end moving up/down, or back/forth, relative to the other-but without any need for the middle, internal, electrode.
In this way a single sheet of piezoelectric material behaves just like a unimorph or bimorph, yet without the need for two layers, and without the concomitant need for, and the problem of, a central electrode. More specifically, the invention proposes that an equivalent to the spatial separation either side of a nominal median plane that is inherent in a bimorph (with one piezoelectric layer on one side, and the second on the other side of the plane) be attained by structurally shaping the cross-section of a simple, single piezoelectric layer such that it has a multiplicity of piezoelectric portions arranged in two generally-planar groups one either side of a median plane, so that any dimension change undergone by a portion on one side of that plane will tend to bend the whole device in the opposite direction to the same sense dimension change undergone by a portion on the other side of that plane.
The number of piezoelectric portions in each group is not that important, provided there are sufficient (and here the term “multiplicity” is to be construed as meaning at least three, so that there are at least two portions in one group and one in the other, as noted above for both the V- and U-shaped devices). It will be understood, therefore, that the direction/nature of a “bend”-a dimension change-of each piezoelectric-layer portion in a device of the invention depends both on how that portion was poled and on the direction of the activation field. Thus, the invention provides a piezoelectric device that is a simple, single-layer elongate body physically shaped in a direction across the length of the elongate body so as to have separate, distinct piezoelectric-portion groups extending along the body and on each side of a nominal median plane through the whole body, which groups are thus spatially separated by and face each other across that median plane, with the result that any piezoelectric portion dimension change in the group on one side of the median plane will tend to bend the whole device normal to the median plane and along its length in the opposite direction to the same sense piezoelectric portion dimension change in the group on the other side of that median plane.
Dolor Espalda Y Abdomen
If, alternatively, all the peak portions (top group) were caused to contract, the body’s dimensions on its upper side would reduce, and it would bend up, towards that side-it would become concave, with that upper side on the inside. So if, say, all the upper (as viewed) corrugations contract, then all the lower corrugations expand, and because the upper and lower corrugations are spaced across the median plane it necessarily follows that the sheet as a whole bends normal to that plane as dictated by these contractions and expansions-namely up, as shown by the dotted lines in FIG. The sheet has a notional median plane MP shown dashed, and has seven clearly distinct piezoelectric portions, three on one side (the upper half, as shown) and four on the other (the lower half). In a beam-shaped corrugated device, then, there might be seven portions, three on one side and four on the other; in a disc-shaped device there might be 24 portions, 12 on each side; in a curved strip device (of the sort described further in connection with the drawings) there might be as many as, or even more than, 40 (20 and 20). It is generally preferable for the corrugations to be disposed evenly and symmetrically about a centre line normal to the median plane, rather than for there to be more, or greater, corrugations adjacent one edge than the other.
Indeed, in some such devices (tape-form devices, as discussed further hereinafter with reference to the accompanying Drawings) the pitch of the corrugations should be several times smaller than the width of the tape, to ensure the corrugations appear as unidirectional benders on the scale of the device. Examples of known benders and actuators are described in U.S. Dolor de espalda lado izquierdo medio . Pat. No. 4,284,921 and U.S. Pat. No. 4,028,566; U.S. Pat. No. Dolor lumbar caminar . 3,816,774, in which various, mostly bimorph-type, structures are described.
Dolor Neuropatico Curso
The manner in which such structures works is complex, and not easy to appreciate. FIELD OF THE INVENTION This invention is concerned with novel piezoelectric structures that exhibit “bender” effects, and relates in particular to the construction of benders that are a single, active layer rather than, as is usual, a double layer of the unimorph or bimorph type. The invention’s device may take any convenient shape, though as noted one preferred such is an elongate body-by which it is meant that, rather like a tape or rule, its length is considerably greater than its width (as, indeed, is so with most bimorph benders). For shape-changing piezoelectric devices which, like these, utilise a single piece, or layer, of piezoelectric material the range of shape changing is usually extremely small-possibly no more than 0.01 mm (10 micrometre). During manufacture, such devices are poled-that is, the layers are subjected to a very high electric field.
Dolor Espalda Pecho
For example, it may be formed by extruding (through a suitably-shaped orifice) a supply of plastic piezoelectric material (such as PZT paste), or by pressing (into a mould) a sheet of such material. The device is little more than an elongate sheet 11 of piezoelectric material that has been pressed (or folded) into a simple corrugated shape with the semi-circular corrugations 12 running the length of the sheet.
Dolores Musculares Piernas
One of the main manufacturing issues associated with corrugated structure devices of the invention is the need for a number of different electrical connections to be made to the device, since there are different regions that must deform differently. Examples of these possibilities are shown in the accompanying Drawings; it is worth noting here that the different forms have different deformations when activated. BACKGROUND OF THE INVENTION Many natural crystalline materials-quartz is an example-exhibit piezoelectric properties-that is, when a piece is squeezed it develops a significant electric potential across the relevant opposite faces. These corrugations are straight, and the strip 81 is otherwise flat; in FIG. The FIG. 4 is a rectangularly-sectioned corrugated device. Either corrugated form can be utilised to achieve this type of shape change. This is quite useful for making complex corrugated shapes which are subsequently fired/sintered. In low volumes, this approach will also reduce the manufacturing cost, since the costs of custom tooling will be reduced.
14. Together these make effective pairs of electrodes, and in each such pair’s case a small electric field applied using that pair will cause the piezoelectric material in the corrugation to expand or contract, depending on the direction of the field relative to the poling direction. 2B it is the electric fields 26 which are in the same direction and the poling 25 that alternates.