Electromagnetic chuck with magnetizing/demagnetizing circuit
First Claim
1. An improved electromagnetic chuck comprising:
- a main body defining a plurality of recesses therein and forming a cover, said cover having a plurality of magnetically conductive portions and non-magnetically conductive portions alternately arranged;
a plurality of magnetic units arranged within said plurality of recesses and corresponding to said plurality of magnetically conductive portions, each magnetic unit having a permanent-magnetic material and a coil around said permanent-magnetic material, said coils of each magnetic unit being serially connected; and
a magnetizing/demagnetizing circuit electrically connected with said coils for magnetizing/demagnetizing said plurality of magnetic units, said circuit comprising;
a magnetizing circuit for generating a direct current signal;
a demagnetizing circuit for generating a pair of positive and negative phase pulse signals with a gradually increased frequency, said demagnetizing circuit comprising;
a linear voltage oscillation generator for generating a series of pulse signals with a gradually increased frequency, said linear voltage oscillation generator being comprised of a sawtooth wave generator and a voltage controlled oscillator; and
a frequency divider for dividing the frequency of said pair of positive and negative phase signals; and
a time delay circuit for respectively adding an appropriate time delay on said pair of positive and negative phase signals from said frequency divider, said time delay circuit being comprised of two sets of resistor and capacitor circuits; and
an output circuit electrically connected with said magnetizing circuit and said demagnetizing circuit for outputting said direct current signal or said pair of positive and negative phase pulse signals to said coils of said plurality of magnetic units so as to magnetize or demagnetize said plurality of magnetic units;
wherein a magnetizing current generated by the magnetizing/demagnetizing circuit is cut off upon magnetization of said plurality of magnetic units, whereby said plurality of magnetic units maintain their magnetism without being continuously supplied with a direct current.
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Accused Products
Abstract
An improved electromagnetic chuck which does not require a continuous direct current supply while being magnetized, including a main body defining a plurality of recesses and forming a cover, which includes a plurality of magnetically conductive portions and non-magnetically conductive portions alternately arranged, a plurality of magnetic units arranged within said plurality of recesses, and a magnetizing/demagnetizing circuit for magnetizing/demagnetizing said plurality of magnetic units, is provided. The magnetizing/demagnetizing circuit includes a magnetizing circuit, a demagnetizing circuit and an output circuit, by which a direct current is generated to magnetize the electromagnetic chuck, or a pair of positive and negative phase pulses with a gradually increased frequency is generated to quickly demagnetize the electromagnetic chuck.
15 Citations
18 Claims
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1. An improved electromagnetic chuck comprising:
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a main body defining a plurality of recesses therein and forming a cover, said cover having a plurality of magnetically conductive portions and non-magnetically conductive portions alternately arranged; a plurality of magnetic units arranged within said plurality of recesses and corresponding to said plurality of magnetically conductive portions, each magnetic unit having a permanent-magnetic material and a coil around said permanent-magnetic material, said coils of each magnetic unit being serially connected; and a magnetizing/demagnetizing circuit electrically connected with said coils for magnetizing/demagnetizing said plurality of magnetic units, said circuit comprising; a magnetizing circuit for generating a direct current signal; a demagnetizing circuit for generating a pair of positive and negative phase pulse signals with a gradually increased frequency, said demagnetizing circuit comprising; a linear voltage oscillation generator for generating a series of pulse signals with a gradually increased frequency, said linear voltage oscillation generator being comprised of a sawtooth wave generator and a voltage controlled oscillator; and a frequency divider for dividing the frequency of said pair of positive and negative phase signals; and a time delay circuit for respectively adding an appropriate time delay on said pair of positive and negative phase signals from said frequency divider, said time delay circuit being comprised of two sets of resistor and capacitor circuits; and an output circuit electrically connected with said magnetizing circuit and said demagnetizing circuit for outputting said direct current signal or said pair of positive and negative phase pulse signals to said coils of said plurality of magnetic units so as to magnetize or demagnetize said plurality of magnetic units; wherein a magnetizing current generated by the magnetizing/demagnetizing circuit is cut off upon magnetization of said plurality of magnetic units, whereby said plurality of magnetic units maintain their magnetism without being continuously supplied with a direct current. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A circuit used for an electromagnetic chuck including a plurality of magnetic units, each said magnetic unit being comprised of a permanent-magnetic material and a coil around said permanent-magnetic material, the circuit comprising:
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a magnetizing circuit for generating a direct current signal; a demagnetizing circuit for generating a pair of positive and negative phase pulse signals with a gradually increased frequency, said demagnetizing circuit comprising; a linear voltage oscillation generator for generating a series of pulse signals with a gradually increased frequency said linear voltage oscillation generator being comprised of a sawtooth wave generator and a voltage controlled oscillator; and a frequency divider for dividing the frequency of said pair of positive and negative phase signals; and a time delay circuit for respectively adding an appropriate time delay on said pair of positive and negative phase signals from said frequency divider, said time delay circuit being comprised of two sets of resistor and capacitor circuits; and an output circuit electrically connected with said magnetizing circuit and said demagnetizing circuit for outputting said direct current signal or said pair of positive and negative phase pulse signals to said coils of said plurality of magnetic units so as to magnetize or demagnetize said plurality of magnetic units. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17)
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18. A circuit used for an electromagnetic chuck including a plurality of magnetic units, each said magnetic unit being comprised of a permanent-magnetic material and a coil around said permanent-magnetic material, the circuit comprising:
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a magnetizing circuit for generating a direct current signal; a demagnetizing circuit for generating a pair of positive and negative phase pulse signals with a gradually increased frequency, said demagnetizing circuit comprising; a linear voltage oscillation generator for generating a series of pulse signals with a gradually increased frequency, said linear voltage oscillation generator being comprised of a sawtooth wave generator and a voltage controlled oscillator; and a frequency divider for dividing the frequency of said pair of positive and negative phase signals; and an output circuit electrically connected with said magnetizing circuit and said demagnetizing circuit for outputting said direct current signal or said pair of positive and negative phase pulse signals to said coils of said plurality of magnetic units so as to magnetize or demagnetize said plurality of magnetic units.
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Specification