US 4,779,762 A · Method and apparatus for controlling the gas content of dispensed hot melt thermoplastic adhesive foam

Abstract

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.

Claims48

Dependent claims

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.

3 more elements

Apparatus for dispensing hot melt thermoplastic adhesive foam having a controlled gas content comprising:

a heated thermoplastic adhesive material supply container providing molten adhesive material at an outlet;
means for supplying gas at an outlet;
means, coupled to the outlet of the adhesive material supply and to the outlet of the gas supply, for agitating and pressurizing the molten adhesive material in the presence of the gas to force the gas into solution with molten adhesive material to form substantially single phase liquid of unfoamed molten adhesive and gas in solution at an outlet;
means, coupled to the outlet of the agitating and pressurizing means, for dispensing the molten adhesive and gas solution at a reduced pressure whereby 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 parameters;
and
means, coupled to the parameter sensing means and coupled between the gas supply outlet and the agitating and pressurizing means, for controlling the flow of gas which is coupled to the agitating and pressurizing means dependent upon said parameter sensing means output.

4 more elements

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 unfoamed molten adhesive and gas 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 differential pressure across a restrictor along a flow path of the substantially single phase unfoamed molten adhesive and gas solution and for producing an output dependent upon said sensed differential pressure;
and
means, coupled to the differential pressure 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 differential pressure sensing means output.

3 more elements

Apparatus for controlling the gas content of dispensed thermosplastic 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 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, for comparing the parameter sensing means output with a desired parameter input to produce a comparison signal;
and
means, coupled to the comparing 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 comparison signal.

5 more elements

An 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 in an outlet;
means for supplying gas at an outlet;
a positive displacement pump having a first inlet coupled to the adhesive material supplying means outlet and having a second inlet coupled 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 a pump outlet, whereby a dispenser may be coupled to the pump outlet for dispensing the molten adhesive and gas solution at a reduces pressure, so that the gas is released from solution and forms a dispensed adhesive foam;
means for recirculating the molten adhesive and gas solution from the pump outlet to the first pump inlet;
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 second inlet of the pump dependent upon said parameter sensing means output.

4 more elements

Apparatus for controlling the gas content of dispensed 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 substantially single phase liquid of unfoamedd 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 unfoamed molten adhesive and gas in solution which is correlated to the dissolved gas content of said substantially single phase liquid solution and for producing an output dependent upon said sensed parameter, said parameter sensing means comprising differential pressure sensing means including (a) a movable slug having an orifice therethrough positioned in a flow path of said substantially single phase liquid of molten adhesive and gas in solution and (b) means for producing a differential pressure sensing means output dependent upon the position of the slug in the flow path;
means, coupled to the parameter sensing means, for comparing the parameter sensing output with a desired parameter input to produce a comparison signal;
and
means, coupled to the comparing 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 comparison signal.

4 more elements

Apparatus for controlling the gas content of dispensed 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 pressuring 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 unfoamed molten adhesive and gas in solution which is correlated to the dissolved gas content of said substantially single phase liquid solution for producing an output dependent upon said sensed parameter, said sensing means including a source of infrared radiation having a specified wavelength substantially absorbed by said gas and substantially unabsorbed by said adhesive material, and detecting means for sensing radiation at said specified wavelength, said source directing said radiation into said substantially single phase liquid of unfoamed molten adhesive and gas in solution and said detecting means sensing said radiation emerging from said substantially single phase liquid of unfoamed molten adhesive and gas in solution;
means, coupled to the parameter sensing means, for comparing the parameter sensing means output with a desired parameter input to produce a comparison signal;
and
means, coupled to the comparing 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 comparison signal.

4 more elements

An 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 in an outlet;
means for supplying gas at an outlet;
a positive displacement pump having a first inlet coupled to the adhesive material supplying means outlet and having a second inlet coupled 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 a pump outlet, whereby a dispenser may be coupled to the pump outlet 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 recirculating the molten adhesive and gas solution from the pump outlet to the first pump inlet;
means for sensing a parameter of said substantially single phase liquid of unfoamed molten adhesive and gas in solution which is correlated to the dissolved gas content of said substantially single phase liquid solution for producing an output dependent upon said sensed parameter, said sensing means including a source of infrared radiation having a specified wavelength substantially absorbed by said gas and substantially unabsorbed by said adhesive material, and detecting means for sensing radiation at said specified wavelength, said source directing said radiation into said substantially single phase liquid of unfoamed molten adhesive and gas in solution and said detecting means sensing said radiation emerging from said substantially single phase liquid of unfoamed molten adhesive and gas in solution;
and
means, coupled to the parameter sensing means and to the gas supplying means, for controlliing the flow of gas from the gas supplying means to the second inlet of the pump dependent upon said parameter sensing means output.

4 more elements

Dependencies are inferred from the claim text.

Method and apparatus for controlling the gas content of dispensed hot melt thermoplastic adhesive foam

Life of this patent

Method and apparatus for controlling the gas content of dispensed hot melt thermoplastic adhesive foam

Life of this patent

Abstract

Claims48