System and method for dispensing hot melt adhesives

Abstract

A system for dispensing hot melt adhesives, comprising an adhesive dispenser including a fluid passage leading to an outlet. The system further comprises a supply conduit fluidly connected to the fluid passage and a feeding mechanism configured to feed an elongate, flexible element of solid adhesive into the supply conduit. The system further comprises a first heating element positioned along at least a portion of the supply conduit to melt a portion of the elongate, flexible element being fed into the supply conduit and thereby form a supply of liquid adhesive within the supply conduit.

What is claimed is: 
     
         1 . A method of dispensing hot melt adhesives using a system comprising a supply conduit fluidly connected to a hot melt adhesive dispenser, the hot melt adhesive dispenser comprising a fluid passage in fluid communication with an outlet, the method comprising:
 feeding a portion of an elongate, flexible element of solid hot melt adhesive into the supply conduit;
 heating at least a portion of the elongate, flexible element within the supply conduit to form a supply of liquid adhesive within the supply conduit; 
 advancing the elongate, flexible element relative to the supply conduit to direct at least a portion of the liquid adhesive from the supply conduit into the fluid passage of the adhesive dispenser; 
 closing the outlet with a valve member such that fluid pressure is built within the system; and 
 dispensing a portion of the liquid adhesive from the outlet. 
   
     
     
         2 . The method of  claim 1 , further comprising:
 sensing a pressure level of the liquid adhesive in the system; and   
       in response to the sensed pressure level, either advancing the elongate, flexible element relative to the supply conduit when the sensed pressure level in the fluid passage deviates from a predetermined pressure level, or maintaining a position of the elongate, flexible element relative to the supply conduit when the sensed pressure level is substantially equal to the predetermined pressure level. 
     
     
         3 . The method of  claim 1 , wherein feeding and advancing the elongate, flexible element further comprises:
 frictionally engaging the elongate, flexible element with at least one roller; and   operating a motor to rotate the at least one roller.   
     
     
         4 . The method of  claim 3 , further comprising:
 sensing a pressure level of the liquid adhesive in the system; and   when the sensed pressure level in the system is less than a predetermined pressure level, sending a signal to a controller to operate the motor; and   when the sensed pressure level in the system is approximately equal to the predetermined pressure level, sending a signal to the controller to cease operating the motor.   
     
     
         5 . The method of  claim 3 , further comprising:
 limiting a maximum amount of torque transferred to the at least one roller from the motor.   
     
     
         6 . The method of  claim 5 , wherein limiting a maximum amount of torque transferred to the at least one roller from the motor further comprises:
 limiting a maximum amount of torque transferred to the at least one roller from the motor with a clutch mechanism operably coupled to the at least one roller.   
     
     
         7 . The method of  claim 1 , wherein the system further comprises a heat exchange device between the supply conduit and the adhesive dispenser, and the method further comprises:
 directing at least a portion of the liquid adhesive through the heat exchange device, wherein the heat exchange device heats the liquid adhesive to an application temperature suitable for an adhesive bonding application.   
     
     
         8 . The method of  claim 7 , wherein the system further comprises a manifold fluidly connecting the heat exchange device and the adhesive dispenser, and the method further comprises:
 maintaining the liquid adhesive at the application temperature as it travels through the manifold to the adhesive dispenser.   
     
     
         9 . The method of  claim 1 , further comprising:
 sensing a pressure level of the liquid adhesive in the fluid passage; and in response to the sensed pressure level, either advancing the elongate, flexible element relative to the supply conduit when the sensed pressure level in the fluid passage deviates from a predetermined pressure level, or maintaining a position of the elongate, flexible element relative to the supply conduit when the sensed pressure level is substantially equal to the predetermined pressure level.   
     
     
         10 . The method of  claim 1 , further comprising:
 mounting the system in a position relative to a substrate that allows for non-contact application of the liquid adhesive onto the substrate.   
     
     
         11 . The method of  claim 10 , wherein the system further comprises a nozzle having an end portion defining the outlet, and mounting the system relative to the substrate further comprises:
 mounting the system relative to the substrate such that a distance between the end portion of the nozzle and the substrate is greater than a width of one bead of the liquid adhesive dispensed.   
     
     
         12 . The method of  claim 1 , wherein feeding and advancing the elongate, flexible element further comprises:
 engaging the elongate, flexible element with a feeding mechanism.   
     
     
         13 . The method of  claim 12 , wherein engaging the elongate, flexible element with a feeding mechanism and operating the feeding mechanism further comprises:
 engaging the elongate, flexible element with at least one set of rollers and operating at least one set of the rollers to advance the elongate, flexible element relative to the supply conduit.   
     
     
         14 . The method of  claim 1 , further comprising:
 determining a demand for an amount of liquid adhesive to be dispensed onto at least one substrate over a period of time; and   advancing the elongate, flexible element relative to the supply conduit at a rate sufficient to meet the demand.   
     
     
         15 . The method of  claim 14 , further comprising:
 reducing heat applied to the elongate, flexible element in response to detecting a reduced level of demand for an amount of liquid adhesive to be dispensed onto the substrate over a period of time.   
     
     
         16 . The method of  claim 14 , further comprising:
 increasing heat applied to the elongate, flexible element in response to detecting an increased level of demand for an amount of liquid adhesive to be dispensed onto the substrate over a period of time.   
     
     
         17 . The method of  claim 1 , further comprising forming an annular plug around a portion of the elongate, flexible element within at least a portion of the supply conduit. 
     
     
         18 . The method of  claim 17 , wherein forming an annular plug comprises solidifying a portion of the supply of liquid adhesive. 
     
     
         19 . The method of  claim 1 , further comprising:
 sensing an absence of the elongate, flexible element; and   sending a signal to a controller.   
     
     
         20 . The method of  claim 19 , wherein sending a signal to a controller comprises sending a signal to trigger an alarm. 
     
     
         21 . The method of  claim 19 , wherein sending a signal to a controller comprises sending a signal to cease operating a motor. 
     
     
         22 . The method of  claim 1 , wherein dispensing a portion of the liquid adhesive comprises opening the valve member such that the pressure outside of the system and the fluid pressure within the system may balance, so that the pressure required to dispense the liquid adhesive equals the pressure generated by a fixed speed delivery, thereby resulting in a metered dispensing. 
     
     
         23 . The method of  claim 1 , further comprising:
 limiting a force available to advance the flexible element such that the flexible element is prevented from advancing when the fluid pressure exceeds a predetermined value.   
     
     
         24 . A system for dispensing hot melt adhesives, comprising:
 an adhesive dispenser comprising a fluid passage leading to an outlet;   a supply conduit fluidly connected to the fluid passage;   a feeding mechanism configured to feed an elongate, flexible element of solid hot melt adhesive into the supply conduit;   a first heating element positioned along at least a portion of the supply conduit to melt a portion of the elongate, flexible element being fed into the supply conduit and thereby form a supply of liquid adhesive within the supply conduit; and   a pressure limiting mechanism for limiting fluid pressure within at least one portion of the system.   
     
     
         25 . The system of  claim 24 , wherein the pressure limiting mechanism comprises:
 a pressure sensor configured to sense a pressure of liquid adhesive in at least one portion of the system; and   a controller in communication with the pressure sensor, the controller configured to control the feeding mechanism.   
     
     
         26 . The system of  claim 24 , wherein:
 the feeding mechanism further comprises:
 at least one roller configured to frictionally engage the elongate, flexible element in order to feed and advance the elongate, flexible element; and 
 a motor operably coupled to the at least one roller; and 
  the pressure limiting mechanism comprises: 
 a torque limiting mechanism configured to selectively disengage the motor and the at least one roller when a pressure of liquid adhesive in the system is at a predetermined pressure level. 
   
     
     
         27 . The system of  claim 24 , wherein the pressure limiting mechanism is configured to maintain the pressure within the at least one portion of the system at or above a predetermined pressure. 
     
     
         28 . The system of  claim 27 , wherein the predetermined pressure is between 30 psi and 190 psi. 
     
     
         29 . The system of  claim 24 , further comprising a wiper element positioned upstream of the supply conduit. 
     
     
         30 . A method of dispensing hot melt adhesives using a system comprising a supply conduit fluidly connected to a hot melt adhesive dispenser, the hot melt adhesive dispenser comprising a fluid passage in fluid communication with an outlet, the method comprising:
 feeding a portion of an elongate, flexible element of solid hot melt adhesive into the supply conduit;
 heating at least a portion of the elongate, flexible element within the supply conduit to form a supply of liquid adhesive within the supply conduit; 
 advancing the elongate, flexible element relative to the supply conduit to direct at least a portion of the liquid adhesive from the supply conduit into the fluid passage of the adhesive dispenser; 
 controlling the rate of advancement of the elongate, flexible element to limit pressure within at least one portion of the system; and 
 dispensing a portion of the liquid adhesive from the outlet.