Abstract: The disclosed supply utilizes the capability of two-way power flow, from a DC source to the load and from the load to a DC source, so as to be able to track a desired output wave form while running reactive loads. This method of operation requires minimum filtering for loads of various power factors and transient characteristics. Two equal and opposite DC sources, such as batteries, furnish and accept current, through switches, to and from an inductor-capacitor filter to which the load is connected. A feed-back circuit compares the voltage furnished to the load with a reference of the desired output wave shape, so as to control the switches in such manner as to force the output voltage to follow that wave form.

Abstract: An expansion bolt assembly of the type used in supporting mine roofs including an expansible shell having a tapered plug movable axially therein to force the outer surface of the shell into engagement with the interior of a drilled opening in the mine roof. The plug is moved by rotation in a threaded opening thereof of an axially fixed bolt, the plug being rotationally fixed with respect to the shell. The invention resides in the structure maintaining the bolt, plug and shell in assembled relationship during insertion into the drilled opening which comprises a circular metal stamping having a central opening through which the bolt is threaded and means for frictionally engaging the sides of the shell.