EP0259689A1
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EP
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Apparatus for controlling the gas content of dispensed hot melt thermoplastic adhesive foam
Assignee: Nordson Corp
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Filing: 1987-08-25
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Granted: —
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Expires: 2007-08-25
Abstract
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 indepen dent 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.
Inventors
- 👤 Richard G. Klein
- 👤 James W. Schmitkons
- 👤 Laurence B. Saidman
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-08 20:48
CPC Classifications
G; G05; G05D; G05D11/00; G05D11/02; G05D11/13; G05D11/135; G05D11/136; B; B05; B05B; B05B12/00; B05B12/08; B05B12/085; B05B7/00; B05B7/24; B05B7/26; B05B7/262; B29; B29B; B29B7/00; B29B7/30; B29B7/58; B29B7/72; B29C; B29C44/00; B29C44/34; B29C44/60; Y; Y10; Y10T; Y10T137/00; Y10T137/0318; Y10T137/0324; Y10T137/0329; Y10T137/0335; Y10T137/2496; Y10T137/2499
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
253 words
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; gas sensing means for sensing the gas content of the unfoamed molten adhesive and gas solution comprising 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 unfoamed molten adhesive and gas solution and said detecting means sensing said radiation emerging from said substantially single phase unfoamed molten adhesive and gas solution; and means, coupled to the gas 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 gas sensing means output.
Claim 2
Dependent Claim
253 words
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; gas sensing means for sensing the gas content of the unfoamed molten adhesive and gas solution comprising 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 unfoamed molten adhesive and gas solution and said detecting means sensing said radiation emerging from said substantially single phase unfoamed molten adhesive and gas solution; and means, coupled to the gas 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 gas sensing means output.
Claim 3
Dependent Claim
164 words
The apparatus of Claim 1 wherein said gas means further includes sampling means defining a sample flow path for processing a sample of said substantially single phase unfoamed molten adhesive and gas solution between said infrared radiation source and said detecting means, said sampling means comprising: a body having inlet and outlet ports between which is connected an intermediate sample flow region, said intermediate sample flow region having a cross-sectional flow area defined by a width and by a height which is substantially smaller than said width to minimize the pressure drop across said intermediate sample flow region, said inlet and outlet ports and said intermediate sample flow region collectively comprising said sample flow path, said infrared radiation source passing infrared radiation along a radiation path through said intermediate sample flow path to said detecting means in a direction approximately parallel to said height thereof to maximize transmission of infrared radiation from said source through said intermediate sample flow region to said detecting means.
Claim 4
Dependent Claim
67 words
The apparatus of Claim 2 wherein said radiation path through said intermediate sample flow region has a width measured parallel to said width of said intermediate sample flow region cross-sectional area which is substantially less than, and approximately centered relative to, said width of said intermediate sample flow region cross-sectional area to minimize sampling errors due to effects at the edges of said intermediate sample flow region.
Claim 5
Dependent Claim
97 words
The apparatus of Claim 2 wherein said sampling means further comprises: a heater for heating said body to a temperature approximating the temperature of said molten adhesive material output from said adhesive supply means, and first and second windows of solid state material transmissive to said infrared radiation located within said body along said radiation path on opposite sides of, and adjacent to, said intermediate sample flow region, said body having substantial thermal mass to avoid rapid temperature changes adjacent said first and second radiation windows to minimize the risk of subjecting said windows to thermal shock.
Claim 6
Dependent Claim
76 words
The apparatus of Claim 4 wherein said windows and said body have significantly different coefficients of thermal expansion, said apparatus further comprising: a layer of resilient sealant mounting said windows within said body to resiliently mount said windows in sealed relation to said body to accommodate thermally-induced dimensional changes between said body and windows and seal said windows relative to said body to prevent the flow therebetween of said solution from said intermediate sample flow region.
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