PRODUCTS INCORPORATING PIEZOELECTRIC MATERIAL

Abstract: A product, in particular a shoe (10), a ball or a fishing lure, incorporates an impact sensing element (18) made from polymeric piezoelectric material. In response to impact, the material provides an electrical trigger signal to a battery-powered light- or sound-emitting unit which is at least partly moulded into the product, thus causing a monostable circuit (20) in the unit to energise the light- (26) or sound-emitting device from the battery (22). In some embodiments involving light-emitting devices (26) such as LEDs, the light is conducted to an outside surface of the product via one or more optical fibres.

Description: PRODUCTS INCORPORATING PIEZOELECTRIC MATERIAL This invention relates to products incorporating piezoelectric material, and is more particularly but not exclusively concerned with such products in the form of sports shoes and balls. It has already been proposed, for example in US Patent No. 4 478 366, to provide dancing shoes and a child's ball each incorporating a layer of piezoelectric material and a light source. The piezoelectrical material and the light source are directly electrically connected together so that the electrical energy produced by piezoelectric effect upon impact of the shoe or ball against, eg the ground, directly energises the light source. However, the amount of electrical energy normally produced in response to a typical impact is insufficient to produce readily visible energisation of the light source, ie energisation of the light source which is clearly visible in daylight and/ or of significant duration. It is therefore an object of the present invention to alleviate this problem. According to one aspect of the present invention, there is provided a product adapted to emit light or sound energy in response to impact, the product comprising or consisting of a moulded part having a battery-powered light- or sound-emitting unit at least partially moulded therein, said unit comprising an impact-sensing element made from polymeric piezoelectric material, a battery, a light- or sound- emitting device and a circuit connected to said piezoelectric material and responsive to electrical energy produced thereby in response to impact to energise said device from said battery. Thus the electrical energy resulting from each impact can be used merely as a trigger to operate the light- or sound-emitting unit via the circuit incorporated therein, and the amount and/or duration of the light or sound emission can be independently determined/controlled by appropriate design of the circuit. The circuit preferably comprises a monostable circuit whose time constant determines the duration of energisation of the light- or sound-emitting device and may advantageously be adjustable, for example by means of a variable resistance. Where the product includes a light-emitting device, the device may be a light-emitting diode or a gas discharge lamp such as a neon lamp. Additionally, the light-emitting device may be disposed within the product, and the product may further include optical fibre means arranged to conduct light emitted by said light-emitting device to an outside surface of the product. Thus the product may be a fishing lure, and the optical fibre means may comprise a bundle of optical fibres, each fibre conducting said emitted light to a different point in the outside surface of the lure, preferably in the fins and/or the tail where the lure is shaped like a fish. Where the product is a ball, at least its radially outer region is preferably moulded in a translucent polymeric material, and it preferably includes two light-emitting devices both arranged to be energised by the circuit, for example simultaneously, the devices being arranged to emit light in generally opposite directions. SUββTTTUTE SHEET Where the product is a shoe, particularly a running shoe or a jogging shoe, the moulded part is preferably a unitary sole-and-heel structure, with at least the battery, the circuit and the light-emitting device disposed in or moulded into the heel part of the structure, and with the light-emitting device being arranged to emit light rearwardly from said heel part. However, the polymeric piezoelectric material may be moulded into the sole part of the structure, preferably in the region of maximum stress. Another embodiment of a shoe may include a plurality of light-emitting devices, either positioned at a plurality of points over the outside upper surface of the shoe or connected to said plurality of points via respective optical fibres, said devices being selectively energisable in a predetermined sequence, for example in response to each successive group of a predetermined number of impacts sensed by the impact-sensing element. This embodiment is particularly suitable for use as an exercise shoe in performing sequences of different exercises, since different light-emitting devices, perhaps differently coloured, can be energised for each different exercise. Alternatively, the shoe with a plurality of light-emitting devices can also incorporate a plurality of impact-sensing elements distributed throughout the sole of the shoe, the circuit being arranged to energise the light-emitting devices in dependence upon the relative stress sensed by each impact-sensing element so as to provide an indication of the weight distribution over the sole of the shoe. This embodiment is particularly suitable for use as an athletic, gymnastic or dancing training SUBSTITUTESHEET shoe, since it can provide useful information on the style or angle of foot-ground contact of an athlete, gymnast or dancer wearing it. According to another aspect of the present invention, there is provided a shoe containing an impact-sensing element made from polymeric piezoelectric material, a battery, a light-emitting device, a circuit connected to said impact-sensing element and responsive to electrical energy produced thereby in response to impact to energise said light-emitting device from said battery, and optical fibre means arranged to conduct light emitted by said light-emitting device to an outside surface of the shoe, preferably an upper surface (ie a surface visible when the sole of the shoe is flat on the ground) . Thus the optical fibre means may comprise a single optical fibre at least a part of which runs around said outside upper surface of the shoe, said part having a plurality of notches therein so as to emit light at each notch. The notches may be coloured, eg with different coloured translucent inks or dyes, so that the emitted light is correspondingly coloured. Alternatively, the optical fibre means may comprise a bundle of optical fibres, each fibre conducting said emitted light to a different point in the outside upper surface of the shoe: for example, where the shoe has a tongue, at least some of the fibres may terminate in the free end of the tongue. Said points may form an abstract or geometrical pattern, or a logo or one or more alphanumeric characters constituting, for example, a trade mark of the manufacturer of the shoe. The ends of the fibres SUBSTITUTESHEET at said points may be coloured, eg with different coloured translucent inks or dyes. The invention will now be described, by way of non-limitative example only, with reference to the accompanying drawings, of which: Figure 1 shows, somewhat schematically, a running- or jogging-shoe in accordance with the present invention; Figure 2 shows, again somewhat schematically, a ball in accordance with the present invention; Figure 3 shows a simplified circuit for incorporation in the shoe of Figure 1 or the ball of Figure 2; Figures 4 to 8 show further embodiments of shoes in accordance with the present invention; and Figure 9 shows a fishing lure in accordance with the present invention. The shoe of Figure l is indicated generally at 10, and comprises a unitary sole-and-heel structure 12 moulded to an upper 14. The moulded sole-and-heel structure 12 may be moulded using a method generally along the lines of that iescribed in my United Kingdom Patent Application No. 8915923, filed on 12 July 1989. Moulded within the sole part 16 of the sole-and-heel structure 12, adjacent the point of maximum stress (ie near the part corresponding to the ball of the wearer's foot) is a thin rectangular sheet or layer 18 of polymeric piezoelectric material, preferably of polyvinylidene fluoride (PVDF) , which has been stretch oriented and electrically polarised to enhance its piezoelectric properties. The sheet 18 is electrically connected to a battery-powered circuit 20 which together with its lithium battery pack 22 is moulded into the heel part 24 of the SUBSTITUTESHEET sole-and-heel structure 12. The circuit 20, which basically comprises a monostable circuit and will be described in more detail hereinafter, is connected to energise a light-emitting diode (LED) 26, which is moulded into the heel part 24 so as to face rearwardly therefrom. In use, as the wearer of the shoe 10 runs or jogs, the layer 18 of piezoelectric material produces a pulse of electrical energy each time the sole part 16 of the structure 12 impacts the ground, ie at each step 'or stride of the wearer, by virtue of the piezoelectric effect. Each pulse of electrical energy triggers the monostable circuit within the circuit 20, which in turn energises the light-emitting diode 26 from the battery pack 22. A bright flash of light is therefore emitted rearwardly from the heel of the shoe 10. Thus the wearer of a pair of the shoes 10 is clearly visible from behind by virtue of the flashes of light emitted rearwardly with each stride, which has considerable advantages from a safety point of view for runners and joggers on public roads, particularly in low light conditions. The ball illustrated in Figure 2 is indicated at 30, and is moulded in a translucent synthetic rubber material around a central cavity 32 containing a battery-powered light emitting unit 34. The unit 34 comprises a sheet 36 of PVDF similar to the sheet 18 of Figure 1, the sheet 36 being electrically connected to a circuit 38 similar to the circuit 20 of Figure 1. The circuit 38 is powered by a battery pack 40 similar to the battery pack 22 of Figure 1, and is connected to energise two LEDs 42 both similar to the LED 26 of Figure 1. The LEDs 42 face out of the cavity 32 in generally opposite directions. SUBSTITUTESHEET The sheet 36 of PVDF may be arranged to line as much of the cavity 32 as is conveniently possible, although this is not essential. In operation, each time the ball 30 impacts a hard surface, eg each time it is bounced, the sheet 36 of PVDF is stressed, and so produces a pulse of electrical energy which causes the circuit 38 to energise both LEDs 42. Since the LEDs 42 face in generally opposite directions, one or other of them tends to be visible regardless of the direction from which the ball 30 is viewed. The fact that the ball 30 is moulded in a translucent (as opposed to a fully transparent) material means that the emitted light tends to be diffused, and the components making up the unit 34 (ie the PVDF sheet 36, the circuit 38, the battery pack 40 and the LEDs 42) are not clearly and individually visible as separate components. Figure 3 shows the circuit 20 in a little more detail. Thus the circuit 20 comprises a pair of inputs 52 connected externally to the sheet 18 of PVDF, and internally to the control input 54 of a monostable circuit 56. The monostable circuit 56 has a timing circuit constituted by a resistor 58 and a capacitor 60, power supply inputs connected to the battery pack 22, and outputs 62 connected to the LED 26. Adjustment or selection of the value of the resistor 58 determines the duration of the time period for which the monostable circuit 56 energises the LED 26 in response to each impact to which sheet 18 of PVDF is subjected. Many modifications can be made to the described embodiments of the invention. In particular, the PVDF sheet 18, the circuit 20, the SUBSTITUTESHEET battery pack 22 and the LED 26 of the shoe 10 of Figure 1 can be formed as a single encapsulated unit which fits removably into the heel part 24 of the shoe. The LED 26 of this unit is arranged to align with an optical fibre bundle or other light guiding medium (eg a layer of suitable translucent plastics material) moulded into the heel part 24, so as to guide the light emitted by the LED to an external surface of the shoe, eg to a point exit facing rearwardly from the heel part 24 as before, or to one or more ribs or spines extending vertically up and down the heel part. This enables the encapsulated unit simply to be replaced when the battery pack 22 is exhausted, or when it is desired to change a unit with an LED of one colour for a unit with an LED of another colour. Alternatively, just the battery pack 22 can be arranged to be replaceable. Additionally the LEDs 26, 42 can if desired be replaced by sound-emitting devices, and the output of the circuit 20 in the shoe 10 can be arranged to operate other devices, eg an electronic pedometer. In embodiments of the shoe 10 where the LED 26 is used in conjunction with an optical fibre bundle, the individual fibres can be arranged to conduct the light from the LED to respective points on the outside surface of the shoe, eg distributed in an abstract or a geometric pattern over the upper part of the front of the shoe, or distributed to form a logo or one or more alphanumeric characters constituting a trade mark of the manufacturer of the shoe, or disposed throughout the free end of the tongue of the shoe: such an embodiment is illustrated in Figure 4, with the optical fibre bundle, the individual fibres and the points on the outside surface of the shoe SUBSTITUTE SHEET being indicated at 70, 72 and 74 respectively. Alternatively, and as shown in Figures 5 and 6, at least a part of the optical fibre bundle can be replaced by a single optical fibre 76 which runs around the upper part of the front of the shoe and which has a plurality of notches 78 distributed along its length from each of which light from the LED 26 is emitted. These notches 78, as well as the ends 74 of the individual fibres 72 of the optical fibre bundle 70, can be coloured, for example with different coloured translucent inks or dyes, to create a variety of multi-coloured effects. The shoe 10 can also be provided with a plurality of LEDs like the LED 26, either distributed over the outside upper surface of the shoe as shown at 80 in Figure 7, or disposed within the shoe as shown at 82 in Figure 8 and coupled to a plurality of points in the outside upper surface of the shoe via respective optical fibres 82. In this case, the circuit 20 can include a counter and gating circuit arranged to count successive impacts sensed by a single PVDF sheet 18 and to sequentially energise successive ones of the LEDs, say ten or twenty times each. This arrangement is particularly useful in an exercise shoe, since it can be used to assist and/or indicate the timing of a sequence of different exercises, with perhaps a different colour emitted for each different exercise. In addition to a plurality of LEDs, the shoe 10 can also incorporate a plurality of individual PVDF sheets 18 distributed throughout the sole of the shoe, as also shown in Figure 7. In this case, the circuit 20 is arranged to energise respective ones of the LEDs in dependence upon the relative stress sensed by SUBSTITUTESHEET respective ones of the PVDF sheets, so as to provide an indication of the weight distribution over the sole of the shoe. This forms an excellent training aid for athletes, particularly runners, as well as for gymnasts and dancers, more especially if the athlete, gymnast or dancer is filmed in action with a video camera and the film is then played back in slow motion. In embodiments of the shoe 10 involving optical fibre bundles, the LEDs 26, 42 can if desired be omitted altogether, their effect being achieved simply by use of ambient light. Thus the fibre bundles act as light gatherers, so if their input ends are disposed say all over the front of the shoe facing generally forwardly and upwardly, while their output ends are disposed in the heel, facing rearwardly and distributed to form, for example, a logo or alphanumeric character constituting a trade mark as mentioned earlier, ambient light will in many circumstances be sufficient to make the output ends of the fibre appear to light up. Again, multicoloured effects can be created if desired, as described earlier. Finally, and as shown in Figure 9, a unit consisting of the PVDF sheet 18, the circuit 20, the battery pack 22 and the LED 26 can be moulded into a flexible plastics fishing lure 86 shaped like a fish having fins 88 and a tail 90, with optical fibres 92 conducting light from the LED 26 to, eg, the fins and/or tail (or even eyes) of the fish-shape of the lure. SUBSTITUTESHEET

Claims: CLAIMS 1. A product adapted to emit light or sound energy in response to impact, the product comprising or consisting of a moulded part having a battery-powered light- or sound-emitting unit at least partially moulded therein, said unit comprising an impact- sens ing element made from polymeric piezoelectric material, a battery, a light- or sound- emitting device and a circuit connected to said piezoelectric material and responsive to electrical energy produced thereby in response to impact to energise said device from said battery. 2. A product as claimed in claim 1, wherein the circuit comprises a monostable circuit whose time constant determines the duration of energisation of the light- or sound-emitting device. 3. A product as claimed in claim 2, including means for adjusting the time constant of the monostable circuit. 4. A product as claimed in claim 3 , wherein the adjusting means comprises a variable resistance 5. A product as claimed in any preceding claim, including a light-emitting diode as said light-emitting device. 6. A product as claimed in any preceding claim, comprising a light-emitting device disposed inside the product, and further comprising optical fibre means arranged to conduct light emitted by said light-emitting device to an outside surface of the product . 7. A product as claimed in any preceding claim, said product being a fishing lure. SUBSTITUTE SHEET 8. A product as claimed in claim 6, said product being a fishing lure shaped like a fish and having fins and a tail, wherein said optical fibre means comprises a bundle of optical fibres at least some of which conduct said emitted light to said fins and tail. 9. A product as claimed in any one of claims 1 to 5, said product being a ball. 10. A product as claimed in claim 9, having a radially outer region moulded in a translucent polymeric material. 11. A product as claimed in claim 10, including two light-emitting devices both arranged to be energised by the circuit and arranged to emit light in generally opposite directions. 12. A product as claimed in any one of claims 1 to 5, said product being a shoe. 13. A product as claimed in claim 12, wherein said moulded part is a unitary sole-and-heel structure, with at least the battery, the circuit and a light-emitting device disposed in the heel part of the structure. 14. A product as claimed in claim 13, wherein said light-emitting device is arranged to emit light rearwardly from said heel part. 15. A product as claimed in claim 13 or claim 14, wherein said polymeric piezoelectric material is moulded into the sole part of the structure. 16. A product as claimed in claim 12, including a plurality of light-emitting devices positioned at a plurality of points over the outside upper surface of the shoe. SUBSTITUTESHEET 17. A product as claimed in claim 12, including a plurality of light-emitting devices coupled to a plurality of points over the outside upper surface of the shoe via respective optical fibres. 18. A product as claimed in claim 16 or claim 17, wherein' said devices are energised in a predetermined sequence in response to successive impacts or groups of impacts sensed by the impact-sensing element. 19. A product as claimed in claim 16 or claim 17, comprising a plurality of impact-sensing elements distributed throughout the sole of the shoe, the circuit being arranged to energise the light-emitting devices in dependence upon the relative stress sensed by each impact-sensing element so as to provide an indication of the weight distribution over the sole of the shoe. 20. A shoe containing an impact-sensing element made from polymeric piezoelectric material, a battery, a light-emitting device, a circuit connected to said impact-sensing element and responsive to electrical energy produced thereby in response to impact to energise said light-emitting device from said battery, and optical fibre means arranged to conduct light emitted by said light-emitting device to an outside surface of the shoe. 21. A shoe as claimed in claim 20, wherein the optical fibre means comprises a single optical fibre at least a part of which runs around the outside upper surface of the shoe, said part having a plurality of notches therein so as to emit light at each notch. 22. A shoe as claimed in claim 21, wherein the notches are coloured with coloured translucent inks or dyes, so that the emitted light is correspondingly coloured. SUBSTITUTESHEET 23. A shoe as claimed in claim 20, wherein the optical fibre means comprises a bundle of optical fibres, said fibres conducting said emitted light to a plurality of points over the outside upper surface of the shoe. 24. A shoe as claimed in claim 23, said shoe including a tongue and at least some of the fibres terminating in the free end of the tongue. 25. A shoe as claimed in any one of claims 16, 17 and 23, wherein said points are arranged to form an abstract or geometric pattern, a logo or one or more alphanumeric characters. 26. A shoe as claimed in claim 25, wherein the ends of the fibres at said points are coloured with coloured translucent inks or dyes. SUBSTITUTESHEET

Inventors: MOTT JONATHAN CHRISTOPHER, MOTT, JONATHAN, CHRISTOPHER
Applicants: MOTT JONATHAN CHRISTOPHER, MOTT, JONATHAN, CHRISTOPHER
Application year: 1991
Main classification: F21V23
IPC codes: A01K85, A43B3, A43B5, A43B13, A43B23, A61B5, A63B43, F21L13, F21V8, F21V23