Foam pump system for firefighting apparatus

Abstract

A foam pump system for injecting chemical foamant into a firefighting stream includes a water pump, a foam pump, and an optional air compressor which are all connected to a common transmission. The transmission includes an input shaft which may be connected to a single power source (such as an engine of a fire truck) for driving the water pump, foam pump, and air compressor. The water pump, foam pump, and air compressor are preferably mounted (directly or indirectly) on the transmission to provide a compact unit that may be sold in modular form for ready incorporation into a firefighting apparatus such as a fire truck. The system also advantageously includes a hydrostatic transmission for selectively and accurately driving and controlling the speed of the foam pump and the resultant proportion of chemical foamant that is injected into the fire fighting stream. The hydrostatic transmission preferably includes a hydraulic motor for driving the foam pump and a variable displacement hydraulic pump for driving the hydraulic motor. By varying the displacement of the hydraulic pump, the speed of the foam pump can be selectively and accurately controlled. The displacement of the hydraulic pump is controlled with an ellectrically operated actuator, such as a hydraulic actuator, a pneumatic actuator, or an electrical solenoid. The system also includes a flow control system for measuring the flow rates of the foam and fire stream and for selectively controlling the proportion of chemical foamant introduced into the fire stream by adjusting the speed of the foam pump with the actuator and hydrostatic transmission.

Dependencies are inferred from the claim text.