Importance

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Abstract

A portable punching machine is disclosed which has a hydraulic, single acting, spring return cylinder for linearly moving a punch toward and away from a die. The cylinder is driven in turn by a hydraulic pump disposed in a fluid chamber built into the machine. The pump fluid chamber is in constant communication with a fluid control chamber accommodating an elastic air bag capable of contraction and expansion for keeping constant the amount of hydraulic oil in the pump fluid chamber. Characteristically, a spacer of polyurethane foam or like elastic material is loosely inserted in the air bag in order to prevent the mutual contact of the inside surface of the bag, such contact being undesirable because the inside surface of the bag is customarily covered with a sticky parting agent that has been used in molding the bag from rubber.

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First Claim