In one embodiment a pressure regulator for an ink pen includes: a diaphragm between a lower pressure region and a higher pressure region, the diaphragm movable toward the lower pressure region in response to an increase in a pressure difference across the diaphragm; a valve operative between an open position in which ink may flow into the lower pressure region and a closed position in which ink may not flow into the lower pressure region; a first lever rotatable on a first fulcrum in response to movement of the diaphragm toward the lower pressure region; and a second lever connected to the valve, the second lever rotatable on a second fulcrum in response to rotation of the first lever to move the valve from the closed position to an open position.