Permanent magnet holding system
Patent 3978441 Issued on August 31, 1976. Estimated Expiration Date: 
August 31, 1993. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
August 31, 1993. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent References 3089064 3428867 3732550 3740683 3824516 InventorsAssigneeApplicationNo. 05/503508 filed on 09/05/1974US Classes:335/284, For magnetizing or demagnetizing335/289Electromagnet type (e.g., electromagnetic chuck)ExaminersPrimary: Broome, HaroldAttorney, Agent or FirmInternational ClassesH01F 7/20 (20060101)H01F 7/02 (20060101) B23Q 3/15 (20060101) B23Q 3/154 (20060101) Foreign Application Priority Data1973-09-13 DTAbstractA permanent magnet holding system, e.g. adapted to handle ferromagnetic material, of which the cancellation of the magnetic holding force is effected with a minimum expenditure of energy, and wherein the external magnetism may reliably be cancelled out, comprises two or more permanent magnets fitted with polepieces so disposed that the external holding force can be controllably varied to total disappearance by a polarity reversal of permanent magnets by means of an electromagnetic coil; wherein the permanent magnet or magnets which the coil is intended to repolarize is/are made of a low coercivity permanent magnet material, and the other permanent magnet(s) is/are made of a relatively high coercivity material. | |
