Flow indicator for positive displacement pump

Abstract

A flow indicator for a positive displacement pump is connected to a liquid supply reservoir below the liquid level in the reservoir. The indicator has a first passage through which liquid is supplied from the reservoir to the inlet of the pump. The first passage has an inlet below the liquid level in the reservoir and an outlet coupled to a supply conduit in turn coupled to the pump inlet. A restrictor is positioned in the first passage adjacent the inlet to partially restrict fluid flow through the passage. A secondary passage is coupled in fluid communication with the first passage downstream from the restrictor. A transparent tube is coupled to the secondary passage and extends upwardly alongside the reservoir to a location above the liquid level in the reservoir. A float is slidably positioned in the transparent tube. When the pump is not operating or is functioning on a return stroke, as opposed to a suction stroke, the liquid level in the tube seeks the same as the liquid level in the reservoir, thereby positioning the float adjacent the liquid level in the reservoir. When the pump draws liquid from the reservoir through the flow indicator, the restrictor is sized so that only a portion of the liquid is drawn from the reservoir, while the remaining liquid is drawn through the secondary passage from the transparent tube. As liquid is drawn from the reservoir and the transparent tube, the liquid level in the tube lowers, causing the float to visibly drop within the tube. The restrictor is sized so that during the return stroke of the pump liquid flows from the reservoir into the transparent tube, returning the liquid level in the tube and thus the float to the same level as the reservoir liquid level.