Proximity switch insensitive to interference fields
First Claim
1. A proximity switch for detecting the position of a machine element comprising:
- at least one sensor providing a first signal having a total signal comprising a detection field signal component caused by a machine element in proximity with said at least one sensor and in interference field signal component caused by an interference field;
circuit means, responsive to said first signal for providing an output signal as a function of the detection field signal component, said circuit means including;
means for providing a sequence of scanning pulses in response to a time dependence of said interference field;
means for scanning said first signal with said scanning pulses; and
means for providing a threshold signal in response to the scanning pulses indicating that said machine element is in a position to be detected, wherein the value of the threshold signal is preselectable to a minimum value with which a minimum field strength required for response of said proximity switch is established.
1 Assignment
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Accused Products
Abstract
In order to improve a proximity switch insensitive to interference fields r detecting the position of a machine element with at least one sensor which generates in the proximity of a machine element standing in a position to be detected a total signal having a detection field signal component caused by the machine element and an interference field signal component caused by the interference field and transmits it to a circuit which converts the total signal into an output signal, such that both the gradients of the detection field generated by the machine element and the gradients of the interference field do not affect response of the proximity switch, it is suggested that the conversion of the total signal into the output signal be carried out by the time dependence of the interference field being determined, by a corresponding sequence of scanning pulses being obtained therefrom and the first signal being scanned with these, and by a value which is determined thereby resulting in an output signal indicating that the machine element is in its position to be detected if this value exceeds a preselectable minimum value with which a minimum field strength required for response of the proximity switch is preselectable.
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Citations
49 Claims
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1. A proximity switch for detecting the position of a machine element comprising:
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at least one sensor providing a first signal having a total signal comprising a detection field signal component caused by a machine element in proximity with said at least one sensor and in interference field signal component caused by an interference field; circuit means, responsive to said first signal for providing an output signal as a function of the detection field signal component, said circuit means including; means for providing a sequence of scanning pulses in response to a time dependence of said interference field; means for scanning said first signal with said scanning pulses; and means for providing a threshold signal in response to the scanning pulses indicating that said machine element is in a position to be detected, wherein the value of the threshold signal is preselectable to a minimum value with which a minimum field strength required for response of said proximity switch is established. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31)
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18. Proximity switch as defined in claim 7, characterized in that an output of said element ascertaining pulse coincidence is followed by a holding element.
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19. Proximity switch as defined in claim 18, characterized in that said holding element holds an output signal of said element ascertaining pulse coincidences over at least a half period of said interference field.
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20. Proximity switch as defined in claim 4, characterized in that said first sensor is arranged at a minimum distance from a source of said interference field which corresponds to the equation ##EQU2## wherein r=minimum distance of said first sensor from a source of said interference field;
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d=sensor spacing; and k=ratio of width of first pulse to width of second pulse.
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21. Proximity switch as defined in claim 6, characterized in that said first and second sensors have a preferred direction of sensitivity and are arranged such that said preferred directions of sensitivity stand parallel to each other.
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22. Proximity switch as defined in claim 21, characterized in that said first and second sensors are magnetic field sensors.
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23. Proximity switch as defined in claim 22, characterized in that a permanent magnet whose magnetic field causes flux through said first sensor in its preferred direction of sensitivity is associated with said first sensor.
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24. Proximity switch as defined in claim 23, characterized in that said permanent magnet is arranged with a north or a south pole facing said first sensor.
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25. Proximity switch as defined in claim 23, characterized in that said first reference value corresponds to a first signal in the absence of said interference field and in the absence of said machine element from its position to be detected.
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26. Proximity switch as defined in claim 23, characterized in that said first and second sensors are arranged such that their preferred directions of sensitivity point in the direction of a line between said first and second sensors, and that said permanent magnet is arranged on a side of said first sensor that faces away from said machine element in its position to be detected.
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27. Proximity switch as defined in claim 23, characterized in that said first and second sensors are arranged such that their preferred directions of sensitivity stand approximately perpendicularly on a line between said sensors.
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28. Proximity switch as defined in claim 1, characterized in that said at least one sensors are Hall sensors.
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29. Proximity switch as defined in claim 1, characterized in that said at least one sensors are magnetoresistive sensors.
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30. Proximity switch as defined in claim 29, characterized in that said at least one sensors are Permalloy sensors.
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31. Proximity switch as defined in claim 1, characterized in that a material with a susceptibility μ
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1 is arranged on an active surface of at least one of said at least one sensors.
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32. A proximity switch for detecting the position of a machine element comprising:
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at least one sensor providing a first signal having a total signal comprising a detection signal component caused by a machine element in proximity with said at least one sensor and an interference field signal component caused by an interference field; circuit means responsive to said first signal for providing an output signal as a function of the detection field signal component, said circuit means including; means for generating an indication signal according to the time-dependent appearance of the interference field, means for coincident selection comprising a signal input and receiving said first signal at said input, a clock input and receiving said indication signal at said input, and a signal output, at which an output signal appears; said means for coincident selection being designed for changing said output signal in accordance with said first signal at said signal input as long as no indication signal appears at said clock input and for maintaining said output signal in accordance with said input signal applied before the appearance of said indication signal at said clock input during application of said indication signal. - View Dependent Claims (33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49)
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40. Proximity switch as defined in claim 32, characterized by first and second sensors, each having a preferred direction of sensitivity and arranged such that said preferred directions of sensitivity stand parallel to each other.
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41. Proximity switch as defined in claim 40, characterized in that said first and second sensors are magnetic field sensors.
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42. Proximity switch as defined in claim 41, characterized in that a permanent magnet whose magnetic field causes flux through said first sensor in its preferred direction of sensitivity is associated with said first sensor.
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43. Proximity switch as defined in claim 42, characterized in that said permanent magnet is arranged with a north or a south pole facing said first sensor.
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44. Proximity switch as defined in claim 42, characterized in that said first and second sensors are arranged such that their preferred directions of sensitivity point in the direction of a line between said first and second sensors, and that said permanent magnet is arranged on a side of said first sensor that faces away from said machine element in its position to be detected.
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45. Proximity switch as defined in claim 42, characterized in that said first and second sensors are arranged such that their preferred directions of sensitivity stand approximately perpendicularly on a line between said first and second sensors.
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46. Proximity switch as defined in claim 32, characterized in that said at least one sensors are Hall sensors.
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47. Proximity switch as defined in claim 32, characterized in that said at least one sensors are magnetoresistive sensors.
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48. Proximity switch as defined in claim 47, characterized in that said at least one sensors are Permalloy sensors.
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49. Proximity switch as defined in claim 32, characterized in that a material with a susceptibility μ
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1 is arranged on an active surface of at least one of said at least one sensors.
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Specification