Method for threading a string through HVAC ducts

Abstract

The invention is a method for threading a thin string through an HVAC duct system from a vent to the HVAC equipment supply plenum where the vent is connected to a small supply duct which in turn is connected to a large supply trunk connected to the plenum. The method uses a high speed blower at the vent to propel a small resistance object connected to the string through the small duct until it reaches the trunk. Then a capture mechanism is used from the HVAC plenum to capture the object and pull the string to the plenum. In an example of the method, the resistant object includes a packed parachute that is released after it travels a predetermined distance.

1 . In a forced air HVAC system having a network of air ducts connecting a central supply plenum to a plurality of air vents, a method for threading a string from at least one of said air vents to said plenum, comprising:
 a. providing a light weight resistance object that easily fits inside the duct connected to said one of air vents, said duct being in said network;   b. connecting said object to a string;   c. providing a blower at one of said vents;   d. using said blower to propel said object from one of said vents through said duct to where said duct connects to a large duct of said network;   e. providing at said plenum a capture means for pushing into said network and capturing said object;   f. pushing said capture means into said plenum and said network toward said object;   g. capturing said object;   h. pulling said object and said string back to said plenum;   
       thereby threading said string from one of said vents to said plenum. 
     
     
         2 . The method of  claim 1  where said object approximates the shape of a sphere. 
     
     
         3 . The method of  claim 1  where said object approximates the shape of a sphere and is composed of foam plastic. 
     
     
         4 . The method of  claim 1  where said capture means is a semi flexible element suitable for pushing with a snag tool attached to one end of said element. 
     
     
         5 . The method of  claim 1  where said capture means is a semi flexible hose suitable for pushing, said hose attached to a source of vacuum airflow. 
     
     
         6 . The method of  claim 1  where capture means is an apparatus for cleaning ducts. 
     
     
         7 . In a forced air HVAC system having a network of air ducts connecting a central supply plenum to a plurality of air vents, a method for threading a string from at least one of said air vents to said plenum, comprising:
 a. providing a light weight object with two resistance states that easily fits inside the duct connected to said one of air vents, said duct being in said network;   b. connecting said object to a string;   c. providing a blower at one of said vents;   d. using said blower to propel said object in low resistance state from one of said vents through said duct to where said duct connects to a large duct of said network;   e. providing at said plenum a vacuum blower;   f. connecting said vacuum blower to said plenum and creating an airflow toward said plenum;   g. providing a means for said object to transition to high resistance state;   h. allowing said object and said string to be pulled back to said plenum by said airflow;   
       thereby threading said string from one of said vents to said plenum. 
     
     
         8 . The method of  claim 7  where said object includes a packed parachute with a means for controlling unpacking of said parachute. 
     
     
         9 . The method of  claim 7  where said object is a packed parachute with a mechanism that unpacks said parachute after a predetermined distance traveled in said duct. 
     
     
         10 . The method of  claim 7  where said object is a combination of a parachute and a spool suitable for winding said parachute and a length of string into a shape suitable for rolling, said length of string being longer than the length of said duct. 
     
     
         11 . In a forced air HVAC system having a network of air ducts connecting a central supply plenum to a plurality of air vents, a method for threading a string from at least one of said air vents to said plenum, comprising:
 a. providing a light weight resistance object that easily fits inside the duct connected to said one of air vents;   b. winding a length of string onto said object;   c. providing a means for generating an airflow from one of said vents to said plenum;   d. using said airflow to propel said object from one of said vents through said network and unwinding said length of string in said network as said object is propelled;   e. recovering said object at said plenum;   
       thereby threading said string from one of said vents to said plenum. 
     
     
         12 . The method of  claim 11  where said airflow is generated by a combination of a blower at one of said vents and a blower at said plenum. 
     
     
         13 . The method of  claim 11  where said resistance object approximates the shape of a sphere. 
     
     
         14 . The method of  claim 11  where said object approximates the shape of a sphere composed of foam plastic. 
     
     
         15 . The method of  claim 11  where said object has a low air resistance state and a high air resistance state. 
     
     
         16 . The method of  claim 11  where said object has a low air resistance state and a high air resistance state, and is in said low resistance state when at said one of vents, and transitions to said high resistance state after being propelled a predetermined distance in said network.