초록 ▼

A method and apparatus for controlling the gas content of dispensed hot melt thermoplastic adhesive foam. Air or another relatively inert gas is mixed with molten thermoplastic adhesive, and the mixture is pressurized to form a gas and molten adhesive “solution”. When the molten adhesive and gas “so

A method and apparatus for controlling the gas content of dispensed hot melt thermoplastic adhesive foam. Air or another relatively inert gas is mixed with molten thermoplastic adhesive, and the mixture is pressurized to form a gas and molten adhesive “solution”. When the molten adhesive and gas “solution”is dispensed at atmospheric pressure, the gas is released from “solution”and becomes entrapped in the adhesive in order to form a homogeneous closed cellular adhesive foam. In order to control the gas content of the dispensed adhesive and gas “solution”, in accordance with one preferred embodiment, the pressure drop across a restriction in the flow path of the solution is sensed, and a control circuit controls the addition of gas to the adhesive to maintain the sensed pressure drop at a desired level. Other sensing techniques can be used to measure a parameter of the dissolved gas/molten adhesive single phase liquid solution which is correlated to the dissolved gas content of the solution and substantially independent of the molten adhesive content thereof, such as measuring the transmittance of infrared radiation through the gas/adhesive single phase solution at a wavelength relatively heavily absorbed by the gas and unabsorbed by the adhesive.

대표청구항 ▼

Apparatus for controlling the gas content of dispensed hot melt thermoplastic adhesive foam comprising: means for supplying heated thermoplastic adhesive material in a molten state at an outlet; means for supplying gas at an outlet; means, coupled to the adhesive material supplying means outlet and

Apparatus for controlling the gas content of dispensed hot melt thermoplastic adhesive foam comprising: means for supplying heated thermoplastic adhesive material in a molten state at an outlet; means for supplying gas at an outlet; means, coupled to the adhesive material supplying means outlet and to the gas supplying means outlet, for agitating and pressurizing the molten adhesive material in the presence of the gas to force the gas into solution with the molten adhesive material to form a substantially single phase liquid of unfoamed molten adhesive and gas in solution at an outlet, whereby a dispenser may be coupled to the outlet of the agitating and pressurizing means for dispensing the molten adhesive and gas solution at a reduced pressure so that the gas is released from solution and forms a dispensed adhesive foam; means for sensing a parameter of said substantially single phase liquid of molten adhesive and gas in solution while said solution is in said substantially single liquid phase, unfoamed state, said parameter being correlated to the dissolved gas content of said substantially single phase liquid solution for producing an output dependent upon said sensed parameter; and means, coupled to the parameter sensing means and to the gas supplying means, for controlling the flow of gas from the gas supplying means to the agitating and pressurizing means dependent upon said parameter sensing means output.