Piezofilm impact detector with pyro effect elimination
First Claim
1. Impact detector comprising first and second piezofilm sheets arranged to define a bimorph, the first sheet being defined by a plurality N of positively and negatively poled segments each for producing electrical signals of opposite polarity in response to impact thereon or changes in temperature thereof, each segment having an area, the total area of the positively poled segments being substantially equal to the total area of the negatively poled segments, the magnitude of the signal produced by each segment as a result of a change in temperature being dependent upon the area of that segment, whereby substantially uniform changes in temperature of the first sheet result in substantially no net signal output thereof as a result of production of signals having opposite polarities that tend to cancel one another, the second sheet being of single polarity, whereby the second sheet produces a signal output when the temperature thereof changes.
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Accused Products
Abstract
A structure for a piezo film impact detector eliminates or minimizes false outputs due to pyroelectric effects. The detector structure has particular application to outdoor and underground use.
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Citations
62 Claims
- 1. Impact detector comprising first and second piezofilm sheets arranged to define a bimorph, the first sheet being defined by a plurality N of positively and negatively poled segments each for producing electrical signals of opposite polarity in response to impact thereon or changes in temperature thereof, each segment having an area, the total area of the positively poled segments being substantially equal to the total area of the negatively poled segments, the magnitude of the signal produced by each segment as a result of a change in temperature being dependent upon the area of that segment, whereby substantially uniform changes in temperature of the first sheet result in substantially no net signal output thereof as a result of production of signals having opposite polarities that tend to cancel one another, the second sheet being of single polarity, whereby the second sheet produces a signal output when the temperature thereof changes.
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8. Impact detector comprising first and second piezofilm sheets arranged to define a bimorph, the first and second sheets each being defined by pluralities N and M, respectively, of positively and negatively poled segments each for producing electrical signals of opposite polarity in response to impact thereon or changes in temperature thereof, each segment having an area, the total area of the positively poled segments in each sheet being substantially equal to the total area of the negatively poled segments in that sheet, and wherein the segments of the first and second sheets define parallel lines of demarcation on each sheet and wherein there is no substantial parallel overlap of the parallel lines of demarcation of the first sheet and those of the second sheet.
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9. Impact detector comprising:
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a) first and second piezo film sheets arranged to define a bimorph, the first and second sheets being separated by an intermediate layer of substantially thermally nonconductive material for interposing a delay to propagation of thermal energy from the first sheet to the second sheet, both the first and second sheets producing output signals substantially simultaneously in response to an impact upon the detector, but, in the absence of an impact and in response to a change of temperature at the detector, the first sheet producing an output signal and the second sheet providing no substantial output signal until thermal energy has propagated through the intermediate layer to the second sheet wherein production of any signal by the second sheet is delayed with respect to production of an output signal by the first sheet; and
,b) circuit means coupled to receive output signals produced by the first and second sheets for providing an indication, based upon the signals, that an output from the detector is due to an impact and not to thermal energy, the circuit means comprising means for summing the output signals produced by the first and second sheets and for multiplying the result thereof by a constant having a value related to a characteristic of the intermediate layer. - View Dependent Claims (10, 11, 12, 13)
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- 14. Impact detector comprising a piezo film bimorph having first and second piezo film layers, the second layer being defined by a plurality of mechanically decoupled but electrically coupled fingers of piezo film, the overall area of piezo film of the first and second layers being substantially equal, the first and second layers providing electrical signals of substantially equal magnitude in response to a substantially uniform change in temperature of the first and second layers, the first and second layers providing electrical signals in response to an impact upon a portion of the detector but the magnitude of the electrical signal provided by the first layer in response to an impact being greater than the magnitude of the electrical signal provided by the second layer in response to an impact.
- 29. Impact detector comprising first and second coplanar piezo film sheets, the overall area of piezo film of the first and second sheets being substantially equal, both sheets having a stretch direction, the stretch direction of the first sheet being substantially transverse to the stretch direction of the second sheet, the first and second sheets providing electrical signals of substantially equal magnitude in response to a substantially uniform change in temperature of the first and second sheets, the first and second sheets providing electrical signals in response to an impact upon a portion of the detector but the magnitude of the electrical signal provided by the first sheet in response to an impact being greater than the magnitude of the electrical signal provided by the second sheet in response to an impact.
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37. Pyroelectric compensated impact detector comprising first and second piezofilm sheets arranged to define a bimorph, the first sheet being defined by a plurality N of positively and negatively poled segments each for producing electrical signals of opposite polarity in response to impact thereon or changes in temperature thereof, each segment having an area, the total area of the positively poled segments being substantially equal to the total area of the negatively poled segments, the magnitude of the signal produced by each segment as a result of a change in temperature being dependent upon the area of that segment, the second sheet being of single polarity;
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wherein substantially uniform changes in temperature of the first sheet results in substantially no net signal output thereof as a result of production of signals having opposite polarities that tend to cancel one another, and the second sheet produces a signal output when the temperature thereof changes, the substantially simultaneous occurrence of substantially no net signal output from the first sheet an a signal output from the second sheet being indicative that there has been a temperature change of the detector but no impact upon the impact upon the detector, and, wherein the first and second sheets both produce a signal output in response to impact upon a portion of the detector, and the substantial simultaneous occurrence of a signal from both the first and second sheets is indicative of an impact upon the detector. - View Dependent Claims (38, 39)
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40. Pyroelectric compensated impact detector comprising:
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a) first and second piezo film sheets arranged to define a bimorph, the first and second sheets being separated by an intermediate layer of substantially thermally nonconductive material for interposing a delay to propagation of thermal energy from the first sheet to the second sheet, both the first and second sheets producing output signals substantially simultaneously in response to an impact upon the detector, but, in the absence of an impact and in response to a change of temperature at the detector, the first sheet producing an output signal and the second sheet providing no substantial output signal until thermal energy has propagated through the intermediate layer to the second sheet wherein production of any signal by the second sheet being delayed with respect to production of an output signal by the first sheet; and
,b) circuit means coupled to receive output signals produced by the first and second sheets for summing the output signals produced by the first and second sheets and for multiplying the result thereof by a constant having a value related to thermal insulation characteristic of the intermediate layer, the circuit means providing an indication that an output from the detector is due to an impact and not to thermal energy. - View Dependent Claims (41, 42)
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43. Pyroelectric compensated impact detector comprising:
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a) a piezo film bimorph having first and second piezo film layers, the second layer being defined by a plurality of mechanically decoupled but electrically coupled fingers of piezo film, the second layer having a uniaxial stretch direction, the fingers extending in a direction substantially transversely of the stretch direction, the overall area of piezo film of the first and second layers being substantially equal, the first and second layers providing electrical signals of substantially equal magnitude in response to a substantially uniform change in temperature of the first and second layers, the first and second layers providing electrical signals in response to an impact upon a portion of the detector but the magnitude of the electrical signal provided by the first layer in response to an impact being greater than the magnitude of the electrical signal provided by the second layer in response to an impact; and
,b) circuit means for receiving the signals produced by the first and second layers for providing an output signal indicative that electrical signals from the first and second layers are the result of an impact and not the result of a change in temperature at the detector. - View Dependent Claims (44, 45, 46, 47, 48)
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49. Pyroelectric compensated impact detector comprising:
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a) first and second coplanar piezo film sheets, the overall area of piezo film of the first and second sheets being substantially equal, both sheets having a stretch direction, the stretch direction of the first sheet being substantially transverse to the stretch direction of the second sheet, the first and second sheets providing electrical signals of substantially equal magnitude in response to a substantially uniform change in temperature of the first and second sheets, the first and second sheets providing electrical signals in response to an impact upon a portion of the detector but the magnitude of the electrical signal provided by the first sheet in response to an impact being greater than the magnitude of the electrical signal provided by the second sheet in response to an impact; and
,b) circuit means coupled to receive as inputs the signals produced by the first and second sheets for detecting whether the inputs are substantially different in magnitude and for providing an output signal indicative that electrical signals from the first and second layers are the result of an impact and not the result of a change in temperature at the detector. - View Dependent Claims (50, 51, 52, 53)
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- 54. Impact detector comprising first and second piezo film sheets, the first sheet overlaying the second sheet and the two sheets being affixed to each other by an adhesive to define a bimorph, the bimorph comprising a plurality of fingers, the overall area of the piezo film of the first and second sheets being substantially equal, both sheets having a stretch direction, the stretch direction of the first sheet being substantially transverse to the stretch direction of the second sheet, the first and second sheets providing electrical signals of substantially equal magnitude in response to a substantially uniform change in temperature of the first and second sheets, the first and second sheets providing electrical signals in response to an impact upon a portion of the detector but the magnitude of the electrical signal provided by the first sheet in response to an impact being greater than the magnitude of the electrical signal provided by the second sheet in response to an impact.
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60. Pyroelectric compensated impact detector comprising:
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(a) first and second piezo film sheets, the first sheet overlaying the second sheet and the two sheets being affixed to each other by an adhesive to define a bimorph, the bimorph comprising a plurality of fingers defined by a plurality of substantially aligned slits extending through both the first and second sheets, the overall area of piezo film of the first and second sheets being substantially equal, both sheets having a stretch direction, the stretch direction of the first sheet being substantially traverse to the stretch direction of the second sheet, the slits being substantially perpendicular to the stretch direction of one of the first and second sheets, the first and second sheets providing electrical signals of substantially equal magnitude in response to a substantially uniform change in temperature of the first and second sheets, the first and second sheets providing electrical signals in response to an impact upon a portion of the detector but the magnitude of the electrical signal provided by the first sheet in response to an impact being greater than the magnitude of the electrical signal provided by the second sheet in response to an impact; and
,(b) circuit means coupled to receive as inputs the signals produced by the first and second sheets for detecting whether the inputs are substantially different in magnitude and for providing an output signal indicative that electrical signals from the first and second layers are the result of an impact and not the result of a change in temperature at the detector. - View Dependent Claims (61, 62)
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Specification