System for controlling motor speed

Claim 1

An apparatus for controlling the rotation speed of a shaft driven by a motor, said apparatus comprising: a nonmagnetic disk carried on said shaft and having an outer periphery; a regularly undulated ferromagnetic ring carried on said outer periphery and forming a plurality of magnetically detectable and angularly equispaced regions thereon; a detector head fixed adjacent said ring and having a magnetic coil, whereby rotation of said shaft displaces said regions past said head and causes said coil to generate a generally sinusoidal signal having a frequency corresponding to the rotation speed of said shaft; means connected to said head and including a diode for clipping said sinusoidal signal and thereby forming a succession of pulses of like amplitude; amplifier means connected to the clipping means and including a transistor, a zener diode connected across said transistor, and a capacitor connected between said transistor and said coil increasing the amplitude of said succession of pulses; filter means including a resonant circuit connected to said amplifier means and receiving the amplified clipped pulses for producing a sinusoidal output only when the frequency of said amplified clipped pulses lies within a predetermined range; detector means including a capacitor and a diode connected to said filter means for converting said sinusoidal output into a direct-current voltage signal; and switch means connected between said detector means and said motor operable by said voltage signal when same exceeds a predetermined threshold value to alter the rotation speed of said motor, said switch means including a Schmitt trigger and a relay connected thereto.

Claim 2

An apparatus for controlling the rotation speed of a shaft driven by a motor, said apparatus comprising: a nonmagnetic disk carried on said shaft and having an outer periphery; a regularly undulated ferromagnetic ring carried on said outer periphery and forming a plurality of magnetically detectable and angularly equispaced regions thereon; a detector head fixed adjacent said ring and having a magnetic coil, whereby rotation of said shaft displaces said regions past said head and causes said coil to generate a generally sinusoidal signal having a frequency corresponding to the rotation speed of said shaft; means connected to said head and including a diode for clipping said sinusoidal signal and thereby forming a succession of pulses of like amplitude; amplifier means connected to the clipping means and including a transistor, a zener diode connected across said transistor, and a capacitor connected between said transistor and said coil increasing the amplitude of said succession of pulses; filter means including a resonant circuit connected to said amplifier means and receiving the amplified clipped pulses for producing a sinusoidal output only when the frequency of said amplified clipped pulses lies within a predetermined range; detector means including a capacitor and a diode connected to said filter means for converting said sinusoidal output into a direct-current voltage signal; and switch means connected between said detector means and said motor operable by said voltage signal when same exceeds a predetermined threshold value to alter the rotation speed of said motor, said switch means including a Schmitt trigger and a relay connected thereto.

Claim 4

An apparatus for controlling the rotation speed of a shaft driven by a motor, said apparatus comprising: a nonmagnetic disk carried on said shaft and having an outer periphery; a regularly undulated ferromagnetic ring carried on said outer periphery and forming a plurality of magnetically detectable and angularly equispaced regions thereon; a detector head fixed adjacent said ring and having a magnetic coil, whereby rotation of said shaft displaces said regions past said head and causes said coil to generate a generally sinusoidal signal having a frequency corresponding to the rotation speed of said shaft; means connected to said head and including a diode for clipping said sinusoidal signal and thereby forming a succession of pulses of like amplitude; amplifier means connected to the clipping means and including a transistor, a zener diode connected across said transistor, and a capacitor connected between said transistor and said coil increasing the amplitude of said succession of pulses; filter means including a resonant circuit connected to said amplifier means and receiving the amplified clipped pulses for producing a sinusoidal output only when the frequency of said amplified clipped pulses lies within a predetermined range; detector means including a capacitor and a diode connected to said filter means for converting said sinusoidal output into a direct-current voltage signal; switch means connected between said detector means and said motor operable by said voltage signal when same exceeds a predetermined threshold value to alter the rotation speed of said motor; and means for biasing said transistor of said amplifier means so that the clipped sinusoidal signal saturates said transistor.

Claim 5

An apparatus for controlling the rotation speed of a shaft driven by a motor, said apparatus comprising: a nonmagnetic disk carried on said shaft and having an outer periphery; a regularly undulated ferromagnetic ring carried on said outer periphery and forming a plurality of magnetically detectable and angularly equispaced regions thereon; a detector head fixed adjacent said ring and having a magnetic coil, whereby rotation of said shaft displaces said regions past said head and causes said coil to generate a generally sinusoidal signal having a frequency corresponding to the rotation speed of said shaft; means connected to said head and including a diode for clipping said sinusoidal signal and thereby forming a succession of pulses of like amplitude; amplifier means connected to the clipping means and including a transistor, a zener diode connected across said transistor, and a capacitor connected between said transistor and said coil increasing the amplitude of said succession of pulses; filter means including a resonant circuit connected to said amplifier means and receiving the amplified clipped pulses for producing a sinusoidal output only when the frequency of said amplified clipped pulses lies within a predetermined range; detector means including a capacitor and a diode connected to said filter means for converting said sinusoidal output into a direct-current voltage signal; switch means connected between said detector means and said motor operable by said voltage signal when same exceeds a predetermined threshold value to alter the rotation speed of said motor; and means for biasing said transistor of said amplifier means so that the clipped sinusoidal signal saturates said transistor.

Claim 7

An apparatus for controlling the rotation speed of a shaft driven by a motor, said apparatus comprising: a plurality of angularly equispaced magnetically detectable elements carried on said shaft, generator means including a coil and magnet fixed adjacent said shaft near said elements for generating a sinusoidal signal having a frequency corresponding to the rotation speed of said shaft, threshold-amplifier means for clipping said sinusoidal signal and thereby forming a succession of pulses of like amplitude and for increasing the amplitude of the clipped pulses, detector means including a resonant circuit connected to said amplifier means for generating an output only when said succession of pulses has a frequency within a predetermined range, and switch means connected between said detector means and said motor for altering said motor speed when said detector means stops generating said output, said switch means including a Schmitt trigger which changes state only on said output of said detector means exceeding a predetermined threshold level.

Claim 8

An apparatus for controlling the rotation speed of a shaft driven by a motor, said apparatus comprising: a plurality of angularly equispaced magnetically detectable elements carried on said shaft, generator means including a coil and magnet fixed adjacent said shaft near said elements for generating a sinusoidal signal having a frequency corresponding to the rotation speed of said shaft, threshold-amplifier means for clipping said sinusoidal signal and thereby forming a succession of pulses of like amplitude and for increasing the amplitude of the clipped pulses, detector means including a resonant circuit connected to said amplifier means for generating an output only when said succession of pulses has a frequency within a predetermined range, and switch means connected between said detector means and said motor for altering said motor speed when said detector means stops generating said output, said switch means including a Schmitt trigger which changes state only on said output of said detector means exceeding a predetermined threshold level.