Liquid flow rate detector

An injection system adapted to be coupled to a conduit adapted to carry flowing liquid;

• injection means adapted for injecting a substance at a predetermined rate into the conduit;
• means for switching said injection means to an activated state at which the substance will be injected into the conduit in response to a first control signal, and for switching said injection means to a deactivated state at which the substance will not be injected into the conduit in response to a second control signal;
• first and second thermally conductive liquid contact members;
• means for supporting said liquid contact members on the conduit with said liquid contact members in contact with liquid within the conduit;
• means coupled to said first liquid contact member for detecting the ambient temperature of the liquid in contact with the first liquid contact member;
• means including an electric heater for supplying a limited amount of heat in an attempt to heat a portion of said second liquid contact member to a threshold temperature at least a predetermined number of degrees above the ambient temperature determined by said means coupled to said first liquid contact member;
• means for detecting the temperature of said portion of said second liquid contact member;
• means for generating said first control signal when the temperature of said portion of said second liquid contact member is at least at said threshold temperature to detect a liquid flow rate below the predetermined liquid flow rate at which the liquid is not capable of cooling said portion of said second liquid contact member below said threshold temperature;
• and
• means for generating a second signal when the temperature of said portion of said second liquid contact member is maintained below said threshold temperature to detect a liquid flow rate above the predetermined liquid flow rate at which the flowing liquid is capable of cooling said portion of said second liquid contact member below said threshold temperature.

A foam concentrate injection system comprising:

• an injection conduit portion adapted to be coupled between inlet and outlet conduit portions adapted to carry flowing water used to fight a fire;
• injection means adapted for injecting foam concentrate at a metered rate into said injection conduit portion so that a foam can result from the water and concentrate mixture that will much more efficiently extinguish the fire than water alone;
• means for switching said injection means to an activated state at which concentrate will be injected into said injection conduit portion in response to a first control signal, and for switching said injection means to a deactivated state at which the concentrate will not be injected into said injection conduit portion in response to a second control signal;
• first and second thermally conductive liquid contact members;
• means for supporting said liquid contact members on said injection conduit portion with said liquid contact members in contact with water within the injection conduit portion;
• means coupled to said first liquid contact member for detecting the ambient temperature of water with which the first liquid contact member is in contact;
• and
• an electric circuit comprising:
• first detecting means including an electric heater for supplying a limited amount of heat in an attempt to heat a portion of said second liquid contact member to a threshold temperature at least a predetermined number of degrees above the ambient temperature determined by said first detection means;
• second detection means for detecting the temperature of said portion of said second liquid contact member;
• means for generating said first control signal when the temperature of said portion of said second liquid contact member is at least at said threshold temperature to detect a water flow rate below the predetermined water flow rate at which the water is not capable of cooling said portion of said second liquid contact member below said threshold temperature;
• and
• means for generating a second signal when the temperature of said portion of said second liquid contact member is maintained below said threshold temperature to detect a water flow rate above the predetermined water flow rate at which the flowing water is capable of cooling said portion of said second liquid contact member below said threshold temperature.