Proximity switch with magnetic field-sensitive sensor
First Claim
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1. A proximity switch, comprising:
- a U-shaped permanent magnet with a vertical direction of magnetization, said permanent magnet defining a magnetic flux-free region formed by three like mutually repelling poles and positioned between limbs of the U-shaped magnet;
a magnetic field-sensitive sensor positioned in said magnetic flux-free region between said limbs and inwardly of terminating ends of said limbs, said flux-free region having a longitudinal extent substantially perpendicular to a magnetic pole axis of each of said limbs;
a flat ferromagnetic triggering part positionable closely above said limbs of the U-shaped magnet in a plane parallel to a base of the U-shaped magnet; and
a switching signal triggered from the sensor by at least partial cancellation of the magnetic flux-free region when the triggering part is brought close to poles of said limbs of the U-shaped magnet, the switching signal being capable of evaluation to indicate activation of the proximity switch.
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Abstract
A proximity switch with a magnetic field-sensitive sensor is formed of limbs of a U-shaped permanent magnet with a vertical direction of magnetization. A magnetic flux-free region, in which the sensor is fitted, is formed by three like poles. When a flat ferromagnetic triggering part is brought close to the two poles of the limbs of the U in a plane parallel to the base of the U, a switching signal which is triggered from the sensor by the cancellation of the magnetic flux-free region can be evaluated.
127 Citations
8 Claims
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1. A proximity switch, comprising:
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a U-shaped permanent magnet with a vertical direction of magnetization, said permanent magnet defining a magnetic flux-free region formed by three like mutually repelling poles and positioned between limbs of the U-shaped magnet; a magnetic field-sensitive sensor positioned in said magnetic flux-free region between said limbs and inwardly of terminating ends of said limbs, said flux-free region having a longitudinal extent substantially perpendicular to a magnetic pole axis of each of said limbs; a flat ferromagnetic triggering part positionable closely above said limbs of the U-shaped magnet in a plane parallel to a base of the U-shaped magnet; and a switching signal triggered from the sensor by at least partial cancellation of the magnetic flux-free region when the triggering part is brought close to poles of said limbs of the U-shaped magnet, the switching signal being capable of evaluation to indicate activation of the proximity switch. - View Dependent Claims (2, 3)
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4. A method for constructing a proximity switch, comprising the steps of:
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forming a U-shaped permanent magnet with a vertical direction of magnetization with a plastic-bonded permanent magnet powder, the U-shaped permanent magnet having a magnetic flux-free region between limbs of the U-shaped magnet caused by three like mutually repelling poles of the U-shaped permanent magnet, said flux-free region having a longitudinal extent substantially perpendicular to a magnetic pole axis of each of said limbs; providing a magnetic field-sensitive sensor and positioning said magnetic field-sensitive sensor in said magnetic flux-free region between said limbs and inwardly of terminating ends of said limbs by encapsulating the U-shaped permanent magnet and the magnetic field-sensitive sensor in a housing; and dimensioning said housing such that a flat ferromagnetic triggering part can be brought close above said limbs of the U-shaped magnet in a plane parallel to a base of the U-shaped magnet so that a switching signal is triggered from the sensor by cancellation of the magnetic flux-free region when the triggering part is brought close to poles of said limbs of the U-shaped magnet, the switching signal being capable of evaluation to indicate activation of the proximity switch. - View Dependent Claims (5, 6, 7)
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8. A proximity switch system, comprising:
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a U-shaped permanent magnet with a vertical direction of magnetization, said permanent magnet defining a magnetic flux-free region formed by three like mutually repelling poles and positioned between limbs of the U-shaped magnet, a first of the like poles being in a base of the U-shaped magnet between the limbs and second and third ones of the like poles being at ends of said limbs, said flux-free region having a longitudinal extent substantially perpendicular to a magnetic pole axis of each of said limbs; a magnetic field-sensitive sensor positioned in said magnetic flux-free region between said limbs and inwardly of terminating ends of said limbs; a housing encapsulating the permanent magnet and the sensor and positioning the sensor relative to the magnet; a flat ferromagnetic triggering part positionable closely above said limbs of the U-shaped magnet in a plane parallel to the base of the U-shaped magnet; and a switching signal triggered from the sensor by cancellation of the magnetic flux-free region when the triggering part is brought close to poles of said limbs of the U-shaped magnet, the switching signal being capable of evaluation to indicate activation of the proximity switch.
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Specification