US 3502456 A
Description (OCR text may contain errors)
6 R W W 5 T mm M a m w .31 N Mm E m m CB March 24, 1970 c. B. FETNER METHOD AND APPARATUS FOR HEAT CLEANING GLASS FIBER FABRIC Filed Sept. 6, 1968 T s w m m G? w. 0 9 0 3 o 4 2 1 M A 6 P N" 6 4 4. Wu 0 4, 4 4 2 n .S M m 2. 4M M. Z Z 4 4. v 4 \r 4 2 u a o s 4 a a M a a 7 u z 3 v u z z mw a m FUEL SUPPLY United States Patent Oflice 3,502,456 Patented Mar. 24, 1970 3,502,456 METHOD AND APPARATUS FOR HEAT CLEANING GLASS FIBER FABRIC Campbell B. Fetner, Charlotte, N .C., assignor to Gas Heat Engineering Corporation, Charlotte, NC, a corporation of North Carolina Filed Sept. 6, 1%8, Ser. No. 758,079 Int. Cl. C031: 25/00 US. Cl. 65--32 6 Claims ABSTRACT OF THE DISCLOSURE A process and apparatus for heat cleaning glass fiber fabric to free it of size. The sized fabric is moved continuously through a cleaning chamber. The heat cleaning is accomplished by subjecting the fabric, within the cleaning chamber, to flameless size-volatilizing heat by an impinging convection action of inert combustion gas generated in and ejected from a plurality of burners installed in the side Walls of the cleaning chamber in spaced relation along the path of fabric travel. Each burner has a combustion chamber which terminates in a nozzle opening into the cleaning chamber. There is a mixing valve for pressure feeding a regulated air-fuel mixture to each burner, and each burner has a felt layer for finely dispersing the mixture within the combustion chamber. The cleaning chamber is thus pressurized, by the ejection of the inert combustion gases, against infiltration of air at the entrance and exit ports of the chamber. Bafiles are provided at these ports for restricting them sufficiently so that the openings serve to maintain pressurization of the chamber. Suction plenums are further provided adjacent the ports but exterior to the chamber for disposing of the volatilization products.
BACKGROUND OF THE INVENTION It is established practice to size glass fiber for the purpose of conditioning it for fabric formation. The sizing used is characteristically organic in nature and is formulated to serve as a lubricant and binding agent for protecting the fiber against the abrasive influences encountered during weaving and improving in general the behavior of the fiber as it is formed into fabric.
Such fiber sizing, however, must be removed from the fabric prior to finishing it for ultimate use, and it is also established practice to effect such removal by heating the fabric sufiiciently to volatilize the organic size constituents. A commonly employed size removal tech- I nique involves passing the fabric through a radiant oven maintained at a temperature causing the heat-generated volatiles to burn as an open flame at the surface of the fabric. US. Patent No. 2,845,364 describes a heat cleaning technique of this sort.
While such burning of the size is still a widely used heat cleaning technique, it leaves a good deal to be desired. In the first place, it subjects the fabric to a rather drastic thermal treatment that materially reduces tensile strength. Additionally, it presents the continual possibility of leaving objectionable carbon deposits on the fabric, and it is generally difficult to control.
The prior art has sought to improve this situation by arranging in various Ways to eliminate the open flame burning of the volatilized size. US Patent No. 3,008,846, for example, proposes a flameless heat cleaning method based on conditioning the oven atmosphere so that it will not support combustion. A nitrogen-fed atmosphere is disclosed as preferred for this purpose, while other conditioning fluids, such as helium, carbon dioxide, water and the like, are indicated to be usable.
A further variation is disclosed by US. Patent No.
3,012,845 in which the oven heating is done progressively with a first stage of modulated heating for removing a predominant portion of the size and a second higher temperature stage to complete the size removal and obtain the so-called weave setting effect, while diffusing the oven atmosphere during both stages by air additions sufficient to prevent ignition and burning of the volatilized size. A comparable proposal is found in US. Patent No. 3,253,897 in which preheated air is circulated for the size-volatilizing heating at a throughput sufficient to maintain the oven atmosphere lean enough to avoid combustion.
These prior proposals for flameless heat cleaning, however, have all involved the use of special auxiliary means for diffusing the oven atmosphere sufficiently to preclude ignition, with the attendant disadvantage of either complicating the oven arrangement undesirably or of adding the burden of providing and handling a special diffusing medium. The present invention makes it possible to heat clean flamelessly with an exceedingly simple oven ar r-angement and without any need to provide for diffusion of the oven atmosphere.
SUMMARY OF THE INVENTION Briefly described, the present invention is characterized by the application of size-volatilizing heat to the glass fiber fabric by the convection action of gases generated by complete combustion of a pressure-fed fuel. An appropriate fuel is a hydrocarbon gas, such as natural gas, and the combustion gases are applied to the fabric as it is caused to travel through an oven chamber under conditions that produce flameless size-volatilizing convection heating, and that pressurize the oven chamber against infiltration of air from the surrounding atmosphere. The pressurized condition of the oven chamber during operation also serves to expel the organic volatiles generated by the heat cleaning for disposal.
DESCRIPTION OF THE DRAWING The single drawing figure is a diagrammatic illustration of an oven arrangement adapted for heat cleaning in accordance with the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT The oven arrangement of the embodiment illustrated in the drawing is designated generally by the reference numeral 10, and a traveling glass fiber fabric Web W is indicated as being trained therethrough, under the direction of guide rolls 12 and 14, for heating cleaning. It will be understood that the web W has a width (perpendicular to the plane of the drawing illustration) corresponding to that produced by the loom on which it Was formed, and that the guide rolls 12 and 14 and the oven arrangement 10 have a lateral extent proportioned to accommodate the web Width.
Before passing over the guide roll 12 to enter the oven arrangement 10, the web W may be drawn directly from any usual preparatory equipment, such as washing (or scouring) and drying means, and upon leaving past the guide roll 14 it may be forwarded directly for finishing in the usual manner, as the oven arrangement 10 is readily operable for heat cleaning at whatever rate is required by the web travel speed dictated or desired for effective operation of such related equipment.
The oven arrangement 10 preferably has a vertical disposition forming a heat cleaning zone in relation to a vertical reach of the traveling web W between the guide rolls 12 and 14, both for the purpose of minimizing floor space requirements and for facilitating effiuence of the volatiles produced by the heat cleaning. The heat cleaning zone of the oven 10 is formed between closely spaced side walls 16 arranged parallel to the path of the traveling web W and extending widthwise thereof, with end walls, as at 18, closing the zone in relation to the web selvages.
Application of heat to the traveling web W Within this heat cleaning zone is effected by a plurality of fuel burners 20 installed in the side walls 16 in spaced relation along the path of fabric travel. The burners 20 employed for this purpose are of the type disclosed by U.S. Patent No. 3,390,944, which burn a pressure-fed hydrocarbon fuel gas to produce a high temperature, high volume, high velocity, fiameless stream of combustion gases.
Pressure-feeding of the hydrocarbon fuel, such as natural gas, is accomplished from a mixing valve 22 at which the fuel is supplied through a conventional gas train (not shown) for proportioning with air also supplied thereat from a blower or other pressure source (not shown). The mixing valve 22 is adjusted to produce a gas-air mixture proportioned for combustion, but with the admixed air-modulated for virtually complete oxygen consumption during combustion, so that the resulting combustion gases are composed predominantly of nitrogen and carbon dioxide, together with a small amount of Water vapor. Any air surviving the combustion may be readily maintained at such a minimal amount as to lack significance in the essentially inert composition of the combustion gases.
Distribution of the combustible gas-air mixture from the mixing valve 22 to the respective burners 20 is effected through feed lines 24 that branch as at 26 to each burner 20. The branch lines 26 are connected to feed the gas-air mixture to a manifold 28 of each burner 20, that is assembled with ceramic chamber-forming blocks 30 to enclose a mounting plate 32 for a series of burner subassemblies 34 to which the pressure-fed gas mixture is admitted from the manifold 28 through access openings 36 spaced along the mounting plate 32 in relation to each burner sub-assembly 34. The manifold 28, ceramic chamber-forming blocks 30, and mounting plate 32 extend for substantially the full width of the oven side walls 16, with the series of burner sub-assemblies 34 arranged therewith in a number suflicient to occupy this full extent.
Each burner sub-assembly 34, as described in detail by the previously noted U.S. Patent No. 3,390,944, comprises a refractory fibrous felt layer supported by overlying screen means so that the pressure-fed gas-air mixture admitted thereto through the registering access opening 36 is distributed in a uniform manner through the felt layer to emerge in finely dispersed form at the opposite face. Ignition of the finely dispersed gas-air mixture, by any suitable ignition means (not shown), results in combustion at this opposite felt layer face in a manner that can be controlled readily for completeness to produce the essentially inert combustion gases referred to above.
The inert combustion gases thus produced collect at high temperature and high volume within the space defined by the chamber-forming blocks 30 and related chamber-forming configurations provided in the oven side walls 16. This collection space is defined by diverging inner walls 38 of the chamber-forming blocks 30, and related converging chamber walls 30 formed in the oven side walls 16, that terminate in a restricted nozzle passage 42 opening through the side walls 16 to the heat cleaning zone. In the region of the combustion chamber walls 30 and nozzle passages 42, the side Walls 16, like the chamber-forming blocks 30, are formed of ceramic for refractory purposes. The drawing illustration indicates a complete ceramic construction of the side Walls 16, although except for portions corresponding in complementary fashion to the chamber-forming block 30, the side walls 16 might alternatively be formed as well of stainless steel panels fitted with a suitable insulation backing.
The result of the foregoing combustion chamber arrangement is a high velocity and flameless ejection of the inert combustion gases through the nozzle passages 42 for impingement upon and convection heating of the glass fiber fabric web W as it passes through the heat cleaning zone. The convection heating output can be regulated simply by setting the pressure-fed gas-air mixture input at the level ineeded for the desired output, and the temperatures needed for heat cleaning are readily obtained in this manner.
The embodiment illustrated in the drawing indicates three pairs of burners 20 provided for heat application to the Web W as it passes through the heat cleaning zone, but more or fewer burners may be provided as a matter of choice in balancing the heating application to given or desired operating conditions. Also, it should be noted that gradient heating of the web W is easily provided for, by arranging separate mixing valves 22 to control the pressure-feeding of the gas-air mixture to each pair of burners 20 and regulating the respective valves 22 proportionately to produce the desired pattern of gradient heating.
The pressure-feeding of the burners 20 that generates the inert combustion gases and produces the flameless convection heating of the web W, also serves the purpose of pressurizing the heat cleaning zone against infiltration of air at the oven chamber openings that must be provide to allow the web W to enter and leave. For this purpose, the illustrated oven arrangement includes bafile elements 44 to define restricted entrance and exit ports vertically aligned at the respective ends of the heat cleaning zone, so that the area of the entrance and exit openings is sufficiently less in aggregate than that of the nozzles 42 to maintain the heat cleaning zone pressurized by the throttling effect that results, while allowing the generated volatiles to escape in a regular manner. Beyond these baffie elements 44, suction plenums 46 are then provided to capture the effiuent volatilization products of the heat cleaning and carry them off through suction lines 48 under the influence of a suction extractor 50 for disposal.
The oven arrangement thus provided for heat cleaning glass fiber fabric is quite apparently a very simple one structurally, and one that avoids all necessity for troubling with recirculation facilities, or with any supplemental diffusion medium, in maintaining an inert and flameless heat cleaning atmosphere, and that applies an effective convection heating that is readily operated and controlled for heat cleaning at excellent advantage.
The present invention has been described in detail above for purposes of illustration only and is not intended to be limited by this description or otherwise to exclude any variation or equivalent arrangement that would be apparent from, or reasonably suggested by, the foregoing disclosure to the skill of the art.
What is claimed is:
1. The process of heat cleaning glass fiber fabric to free it of size which comprises:
(a) moving the sized fabric continuously through a cleaning chamber defined by side and end walls and having entrance and exit ports for the fabric;
(b) applying fiameless size-volatilizing heat to the fabric moving within said cleaning chamber by an impinging convection action of inert combustion gases generated in, and ejected from fuel burners installed in the side walls of the cleanng chamber in spaced relation along the path of the moving fabric and supplied with pressure-fed fuel;
(c) maintaining the pressure-feeding of the supplied fuel at a level sufficient to pressurize said cleaning chamber against infiltration of air at said entrance and exit ports; and
(d) disposing of the volatilization products of said heating entirely in exterior relation to said cleaning chamber adjacent said entrance and exit ports.
2. The process defined in claim 1 in which said supplied fuel is a hydrocarbon gas.
3. The process defined in claims 1 or 2 in which the pressure-feeding of said supplied fuel is carried out in combustible admixture with air, and in which the quantity of admixed air is modulated for virtually complete oxygen consumption during said combustion.
4. Apparatus for heat cleaning glas fiber fabric to free it of size comprizing:
(a) a cleaning chamber defined by side and end walls and having entrance and exit ports for said fabric;
(b) means for traning said fabric to travel through said cleaning chamber While respectively entering at and leaving through said ports;
(c) a plurality of pressure-fed burners installed in the side walls of said cleaning chamber in spaced relation along the path of fabric travel therethrough, with each burner including a combustion chamber terminating in a nozzle opening into said cleaning chamber and means for finely dispersing a pressure: fed air-fuel mixture within said combustion chamber for ignition;
(d) means for pressure-feeding a regulated air-fuel mixutre to each of said burners,
(i) to generate inert combustion gases within each of said combustion chambers by maintaining conditions of essentially complete combustion therein,
(ii) to produce flameless size-volatilizing convection heating of said fabric by ejection of said inert combustion gases through each of said combustion chamber nozzles for impingement upon said fabric within said cleaning chamber, and
(iii) to pressurize said chamber by said ejection of the inert combustion gases against infiltration of air at said entrance and exit ports; and
(e) means adjacent said entrance and exit ports for disposing of the volatilizing products of said heating entirely in exterior relation to said cleaning chamber.
5. Apparatus as defined in claim 4 in which said clean ing chamber is arranged Withsaid entrance and exit ports aligned vertically, and in which said training means is disposed to provide a vertical path of fabric travel through said cleaning chamber.
6. Apparatus as defined in claims 4 or 5 in which means are provided at said entrance and exit ports for restricting the same sufiiciently so that the aggregate area of the openings provided thereat for fabric travel through said cleaning chamber serve to throttle and thereby maintain said cleaning chamber pressurized, While also allowing escape of the volatilization products therethrough to said disposal means.
References Cited UNITED STATES PATENTS 7/1968 Flynn 263- XR 11/1961 Caroselli 117-54 S. LEON BASHORE, Primary Examiner SAUL R. FRIEDMAN, Assistant Examiner