System and method of injecting accurate quantities of foam into cavities without positive displacement flow meters or flow rate control apparatus

A method of filling a cavity with a foam-in-place insulation that is formed by a reaction of at least one precursor, the method comprising:

• (A) providing a foam dispensing system comprising:
• at least one precursor vessel, each of the at least one precursor vessel containing a current quantity of a corresponding one of the at least one precursor, each of the at least one precursor vessel further containing a gas located above the current quantity of the at least one precursor in the at least one precursor vessel, the gas having a gas pressure;
• and
• a precursor dispensing gun in liquid communication with the at least one precursor vessel, the precursor dispensing gun, when actuated by a user, being configured to concurrently dispense the at least one precursor from the at least one precursor vessel into the cavity, the at least one precursor being caused to react immediately before, during, or after dispensing thereof into the cavity;
• the foam dispensing system being self-contained, in that none of the at least one precursor vessel is in fluid communication with any positive displacement flow meter or flow control valve, nor with any external apparatus that would be capable of modifying the gas pressure in the at least one precursor vessel, or modulating a flow rate of the at least one precursor as it is dispensed from the at least one precursor vessel;
• the foam dispensing system being configured such that when the at least one precursor vessel comprises a plurality of precursor vessels, and when the gas pressures in the at least one precursor vessel are initialized to specified initial pressures that cause the at least one precursor to be dispensed in a specified ratio, the at least one precursor will continue to be dispensed in a specified ratio as the gas pressures within the at least one precursor vessel decrease due to the dispensing of the at least one precursor by the dispensing gun and the resulting quantity reductions of the at least one precursor in the at least one precursor vessel;
• (B) for each of the at least one precursor vessel, pre-calibrating a flow rate function characterizing a flow rate of the corresponding one of the at least one precursor from the at least one precursor vessel as a function of a system parameter;
• (C) pre-determining quantities of the at least one precursor to be dispensed in the specified ratio during each of a plurality of counts, each count comprising equal quantities of the at least one precursor to be dispensed;
• (D) measuring a current value of the system parameter for each of the at least one precursor vessel;
• (E) according to the flow rate function and the quantities of the at least one precursor to be dispensed in the specified ratio during each count, calculating a time duration of each count, referred to herein as a “count duration,” as a function of the system parameter;
• (F) determining a number of the plurality of counts, referred to herein as a “shot count,” that will cause a pre-determined required volume of the at least one precursor to be dispensed into the cavity during a shot;
• (G) actuating of an injection gun by a user, thereby initiating the shot;
• (H) announcing to the user a number of the plurality of counts that have elapsed since the injection gun was actuated by the user;
• and
• (I) instructing the user to cease actuation of the injection gun and to thereby end the shot, when the elapsed number of counts is equal to the shot count.