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United States Patent | 3,579,037 |
Hackman , et al. | May 18, 1971 |
An electric motor-driven portable tool for use underwater. The tool and motor are insensitive to water depth and corrosion because of the tool design and choice of materials. To minimize the danger of electrical shock to the human operator, the tool isused in combination with a safety trip circuit which is effective to cut off all power to the tool in less than 30 milliseconds in the event of a short circuit or even a minimal current leak in either the tool or cable supplying current to the tool. Additionally, the tool motor is insulated from the housing, the tool housing is grounded by a third ground or neutral wire in the power cable and thecable has a metal sheath which is also grounded at or near the power source.
Inventors: | Hackman; Donald J. (Columbus, OH), Legue; Ronald L. (Columbus, OH), Harris; Jeremy M. (Worthington, OH), Roop; Donald E. (Worthington, OH) |
Assignee: | Oceanautic Manufacturing and Research Company (Cincinnati, OH) |
Appl. No.: | 04/774,622 |
Filed: | November 12, 1968 |
Current U.S.Class: | 361/46 ; 310/87; 318/753; 361/31 |
Current International Class: | H01H 9/02 (20060101); H01H 9/06 (20060101); H02H 3/32 (20060101); H02K 7/14 (20060101); H02K 5/128 (20060101); H02H 3/33 (20060101); H02K 17/30 (20060101); H02K 5/12 (20060101); H02K 17/02 (20060101); H02h 003/28 (); H02h 007/26 () |
Field of Search: | 310/51,90,47,50,83,87 318/207,220,221 317/18,27,45 |
ReferencesCited [Referenced By]
U.S. Patent Documents
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2568548 | September 1951 | Howard et al. |
2944297 | July 1960 | Maynard |
2964660 | December 1960 | Herrick et al. |
3048756 | August 1962 | Voepe |
3171062 | February 1965 | Rowe |
3267868 | August 1966 | Page |
3483407 | December 1969 | Frohmuller et al. |
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Primary Examiner: Trammell; James D.
Parent Case TextThis application is a continuation-in-part of application Ser. No. 754,783, filed Aug. 23, 1968.
1. In combination, a portable electric tool for use underwater by a human operator, and an electrical control circuit for actuating said tool, said combination providing minimal danger of harmful electrical shock to said human operator,
said tool comprising a housing,an electrical drive motor having a stator and a rotor, and an output shaft, said stator being fixedly mounted within sad housing, said rotor being operatively connected to said output shaft, said housing having passages therein to permit the flow of water between said stator and rotor,
said electrical control circuit being operatively connected to windings of said stator so as to supplyelectrical current to said windings, said control circuit including a current leakage responsive trip circuit operative to cut off current to said stator in the event of a leakage current of a magnitude potentially harmful to said human operator when underwater, said trip circuit having a response time less than the cycle time required for current to build to a level harmful to said human operator inthe event of said current leakage.
2. The combination of claim 1 wherein said trip circuit is responsive in less than 30 milliseconds to cut off current flow completely in the event of current leakage as small as 5 milliamps.
3. The combination of claim 1 wherein said trip circuit includes a differential transformer to detect said current leakage.
4. The combination of claim 1 whereinsaid trip circuit comprises a differential transformer connected in series with windings of said stator, said transformer being operative to control a relay, said relay having contacts in the circuit to said stator windings, said contacts being so connected to said control circuit that a current leakage through said portable tool is operative to deenergize said relay, open said relay contacts,...