Foam generating system with a substantially constant foam delivery rate

Abstract

A foam generating system utilizes a positive displacement pump to deliver liquid at a substantially constant liquid delivery rate to a foam generator. The liquid delivery rate is independent the pressure of air supplied by a pressurized air source to the foam generator, the back pressure of the foam generator itself, the volume of liquid in a supply tank, and the pressure drop of the connection line from the foam generator to a user appliance. The foam generator delivers foam at a constant foam delivery rate (expressed as weight of foam per unit time) to the user appliance. The liquid supply tank is vented to atmosphere.

What is claimed is:  
     
         1 . A foam generating system for delivering foam for use in a user appliance, the foam generating system comprising: 
 a foam generator having an inlet port and an outlet port, the introduction of pressurized air and a liquid at the inlet port of the foam generator resulting in the delivery of foam at the outlet port thereof, during operation the foam generator having a predetermined back pressure associated therewith, the outlet port of the foam generator being connectable to a user appliance through a connection line having a predetermined pressure drop;    a source for supplying pressurized air at a predetermined air pressure to the inlet port of the foam generator; and    a supply tank for carrying a liquid; the improvement comprising:    a vent through which the supply tank is vented to atmosphere; and    a positive displacement pump operable at a constant liquid delivery rate for pumping liquid from the liquid supply tank to the inlet port of the foam generator, the liquid delivery rate from the pump to the inlet port of the foam generator being independent of the pressure of the air supplied by the pressurized air source, the back pressure of the foam generator, the volume of liquid in the supply tank, and the pressure drop of the connection line,    whereby the delivery rate of foam from the outlet port of the foam generator for delivery to the user appliance (expressed as weight of foam per unit time) is substantially constant.    
     
     
         2 . A carpet cleaning apparatus comprising: 
 a frame with a carpet cleaning assembly mounted thereon; and    a foam generating system for delivering foam to the carpet cleaning assembly, the foam generating system comprising: 
 a foam generator having an inlet port and an outlet port, the outlet port of the foam generator being connected to the carpet cleaning assembly through a connection line having a predetermined pressure drop;  
 the introduction of pressurized air and a liquid cleaning agent at the inlet port of the foam generator resulting in the delivery of foam at the outlet port thereof, during operation the foam generator having a predetermined back pressure associated therewith,  
 a source for supplying pressurized air at a predetermined air pressure to the inlet port of the foam generator; and  
 a supply tank for carrying a liquid cleaning agent;  
 the improvement comprising:  
   a vent through which the supply tank is vented to atmosphere; and    a positive displacement pump operable at a constant liquid delivery rate for pumping liquid cleaning agent from the supply tank to the inlet port of the foam generator, the liquid cleaning agent delivery rate from the pump being independent of the pressure of the air supplied by the pressurized air source, the back pressure of the foam generator, the volume of liquid cleaning agent in the supply tank, and the pressure drop of the connection line,    whereby the delivery rate of foam from the outlet port of the foam generator for delivery to the carpet cleaning assembly (expressed as weight of foam per unit time) is substantially constant.