An assembly of lifting equipment has been devised to enable the safe removal of water filters used in electrical-discharge machining (EDM). As explained below, this equipment prevents injuries of a type formerly associated with changing the filters.

In the particular machine shop in which the equipment is used, there are seven EDM machines, each equipped with filters located in a water tank at about knee level. The filters must be changed at intervals of operating time that range from 10 to 200 hours, depending on the material being cut. A filter to be removed is full of water and weighs about 50 lb (≈23 kg). The filter must be held in place while the water drains out before completing its removal. Previously, the filters were changed by hand, without the help of any equipment. Some workers suffered back injuries from bending over, lifting the water-laden filter elements, and holding them while the water drained out.

The present lifting equipment prevents these injuries by changing the nature of the lifting operation. The equipment includes a special-purpose tool on one end of a cable, the other end of which is wound on a ratcheting hand crank. The tool includes a part that is mounted on the inner diameter of a filter element on an outlet shaft. The tool also includes lifting arms that are lowered and attached to the outside diameter of the filter. Once the tool has been attached to the filter, the hand crank is actuated to raise the filter partly out of the tank. Once the water has drained out of the filter element, a worker can safely lift the filter element and the tool out of the tank. The filter is then disconnected from the tool and discarded.

This work was done by Timothy G. Schilens of Microcraft Inc. for Glenn Research Center.

Inquiries concerning rights for the commercial use of this invention should be addressed to

NASA Glenn Research Center
Commercial Technology Office
Attn: Steve Fedor
Mail Stop 4-8
21000 Brookpark Road
Ohio 44135

Refer to LEW-16795.