US2042678A - Process for impregnating fibrous conduits - Google Patents

Description

June 2, 1936. s. P. MILLER PROCESS FOR IMPREGNATING FIBROUS QONDUITS Filed Dec. 16, 1935 2 Sheets-Sheet 1 5 27 0 Q6) (3Q) (D (D TOR Mf/ler l'TORN EY June 2, 5 IL ER PROCESS FOR IMPREGNATING FIBROUS CONDUITS Filed .Dec. 16, 1953 2 Sheets-Sheet 2 ATTORNEY Patented June 2, 1936.

PATENT OFFICE PROCESS FOR IMPREGNATING FIBROUS COND UITS Stuart larmelee Miller, Scarsdale, N. Y., assignor to The Barrett Company, New York, N. Y., a corporation of New Jersey Application December 16, 1933, Serial No. 702,750

17 Claims.

This invention is directed to the saturation of absorbent articles, and particularly, the continuous staturation and impregnation of fibrous conduits employed to conduct and protect under-' derstood that it may be employed to saturate.

fibrous or other absorbent articles requiring im- 15 pregnation, such as spools, fibrous boards, molded fibrous articles, etc.

The articles to be saturated may, of course, be

prepared in any known manner. In the case of fibrous bases for conduits, newsprint and paper the usual paper heaters and the resultant stock screened and then pumped to paper cylinder machines and there formed into wet felts or paper. The wet paper may be wound about a cylindrical or other shaped tube or mandrel vto produce a wet conduit of proper thickness. This conduit may be dried in kilns to remove the major portion of its moisture content; i. e., so that the dried conduits contain from 5 to 8 per cent of moisture. The fibrous base may, of course, be prepared in other known manner, as, for example, a fibrous sheet may be spirally wound on a mandrel to form the conduit base. Fibrous conduits are made in several sizes, commonly varying from.2 inches to 6 inches or largerin internal diameter, having an average wall thickness of approximately of an inch and being produced in 5, 6, and 8 foot lengths. The wall thickness of the conduits may, of course, be greater or less than of an inch and other dimensions may vary. As they come from the drying kilns, they usually contain from 5 to 8 per cent moisture, although considerably more than 8 per cent moisture may, on occasion, be found present.

The porosity or absorptive characteristics of ,the walls of fibrous conduits may vary within wide limits from a very dense wall of a density corresponding to hard wood and exceedingly difficult to saturate with low carbon water gas tar pitch or even with other waterproofing material, such as asphalt, to a porous open wall similar in 1 density to that, of roofing felt, which will readily absorb bituminous saturants. Samples of prescnt commercial fibrous conduits have been tested and found to vary from substantially less than pulp or other fibrous material may be beaten in 1 c. c. of voids per gram of tube wall to 2.8 or

more 0. c. of voids per gram of tube wall. To

determine the cubic centimeters of voids per gram of tube wall, a small sample of tube wall (say 2"x 5") is dried for one hour at 100 C.,

cooled, dessicated, and thereafter weighed. It is then immersed in kerosene, maintained at a temperature of 25 C., for eighteen hours. Thereafter, the sample is removed from the kerosene,

drained in vertical position for thirty seconds,

and again weighed. The difference in weight represents'the kerosene absorbed. This difference in weight in grams, divided by the specific gravity of the kerosene, corresponds to the cubic centimeters of kerosene absorbed. volume 15 in cubic centimeters, divided by the original weight in grams, gives the voids in cubic centimeters per gram. v

The fibrous conduits have heretofore commonly been impregnated with water gas tar pitch by immersing batches of a large number of conduits in tanks of molten pitch maintained at atmospheric pressure or pressure above atmospheric and at a temperature of 275 F. to 300 F.

or upwards.- Such batches might comprise sev- 5 eral hundred conduits. When conduits were to be saturated under superatmospheric pressure, they have in many cases been allowed to soak" in the molten pitch for several hours to expel moisture, then subjected to pressure treatment, withdrawn, and permitted to drain to remove excess .saturant therefrom. Heretofore, in general, in order to prevent excessive foaming of the conduits during the saturation thereof, it was considered necessary to dry "the conduits thoroughly before saturation, as for example by soaking them in hot saturant for several hours or heating them in a drying oven, in order to remove water as steam, and hence prevent foaming in the saturator.

This process of saturating fibrous conduits, it will be noted, requires the soaking of the conduits or drying in an oven for long periods of time to obtain, first, satisfactory drying, and second, sat- 45 isfactory penetration of the saturant throughout the walls of the conduit. In the practice of the process, numerous diflicultiesare encountered, among the mostimportant of which may be mentioned- 7 0 (1) Loss of volatile oils from the saturant due 5 to prolonged heating in inadequately covered apy,

' maintained at a temperature of approximately 77 F. for 48 hours, then ascertain the percently described above, show an absorption of mois- I of the pitch due to the prolonged maintenance of large bodies of pitch in which the conduits are immersed under heat, resulting in decomposition tar industry to indicate material contained in the bituminous saturant which is insoluble in benzol or carbon bisulfide. It is commonly determined as described by Weiss (Journal of Industrial and Engineering Chemistry, vol. 10, 1918, pages 736 and 820, Test D) It comprises high-molecular carbon compounds of low solubility, carbon, and other insoluble material;

(3) Unsatisfactory saturation of the conduits due to the fibrous walls not absorbing suflicient saturant to render them substantially waterproof.- Conduits which are not adequately saturated do not attain maximum strength and resistance to deflection or deformation;

(4? In the case of saturation of conduits under substantially atmospheric pressure, or under higher pressures, a substantial fire hazard may exist. This is especially the case where increased pressure is produced by air pressure on the saturant, and where incompletely covered and prov 'tected saturating tanks are used; and

(5) Owing to long time immersion of the organic or fibrous bases in hot saturant, deterioration of the organic material of the bases frequently takes place, due to its continued exposure to high temperatures.

In order to satisfactorily protect cables and other electrical conductors, it is important that the fibrous conduit be substantially waterproof, resistant to abrasion and soil pressures, and capable of withstanding underground conditions and notfpunctured or broken by the soil and debris surrounding it. One of the tests to which conduits are subjected to determine their waterproofness is'to immerse them in distilled water,

age increase in the weight of the conduit and thus arrive at the .amount of water absorbed thereby. Present conduits, saturated with water gas tar pitch, havebeen tested in this manner and maywhave been found to absorb in the neigh-' waterproofed conduit. A conduit absorbing not more than 4 per cent moisture under these conditions is regarded as eminently satisfactory. It should be noted that as. indicated hereinabove, many of the saturated fibrous conduits now made, when subjecteito the waterproofness test briefvid; a processor saturating porous or absorbent fibrous conduits in a simple and continuous manher, and without subjecting the conduits to a This may even result in charring of the base material.

prolonged preliminary soaking or other prolonged heat treatment to remove moisture prior to actual saturation. The process of this inven-.

tion is of high capacity, low in equipment and operating costs, capable of automatic regulation, requires a minimum of saturant for its practice, materially reduces saturation costs, and results in uniformly saturated conduits of improved waterproofness and resistance to corrosion, abrasion, and soil pressures. Furthermore, the saturation of conduits inaccordance with this invention requires a relatively short time of'contact between the saturant and the conduits. Hence, tendencies toward charring or-burning of the fibrous bases are substantially reduced if .not completely eliminated. Further, the process of this invention is flexible and can readily be adapted to eihlciently saturate conduits varying widely in their porosity, e. g., dense or porous conduits with different saturants.

In accordance with a preferred embodiment of this invention, the conduits individually or in groups placed in baskets or other holders are introduced directly into a bath of saturant, i. e., without preliminary soaking. and while they still have a substantial moisture content. The conduits are moved gradually through the bath or column of saturant so that the pressure there-, on is slowly and gradually reduced. This prevents sudden ebullition and minimizes foam formation due to the passage of steam formed by the heating of the moisture in the conduit walls through the bituminous or ther saturant employed. Furthermore, since the conduits or other absorbent materials to be saturated are introduced into the saturant only a. few at a time,

only a relatively few wet conduits are present in the. system at one time. The evolution of steam at any given time is, therefore, limited to the steam from these conduits. The foaming tendency is correspondingly lessened. The saturant may be continuously withdrawn from the column ,of saturant and sprayed onto the surface thereof, thus tending to break up any foam layer'which, might form. The column of saturant is main tained under vacuum. The conduits after passage through the saturant may be moved into an evacuated space above the column of saturant and there subjected to vacuum while out of contact with the main body of saturant and then again passed through the saturating bath or they may be kept continuously immersed until removed from the apparatus. While in contact with the saturant, the conduit may be subjected to increased pressures. The conduits are preferably withdrawn from the saturating bath at a rateequal to the feed of iiicoming conduits into the bath.

' The term continuous is used in the specification. and claims in a broad sense and is intended to differentiate the process of this invention from batch'processes involving the drying of conduits in suitable apparatus, followed by the saturation of the dried conduits, the apparatus throughout the period required for-drying andsaturation being employed to dry and saturate one and the same batch of conduits. By the term continuousfi as used herein, it is intended to include the passage of conduits or other articles to be saturated'intermittently, i. e., stepby-step, through the drying and/or saturation zone, the material remaining at rest for prede-. termined periods of time in its'passage therethrough, as well as the non-stop passage of the uum of 28 to 29 inches of mercury) may be maintained in the upper portion of the saturatingtank. The higher the vacuum maintained, the more effective is the removal of air and water from the voids and the more complete is the absorption of saturant. The tank is preferably made of such height that a considerable evacuated space is provided above the maximum level of saturant.

A conveyor carrying baskets or other holders may be loaded with tubes or conduits. The baskets enter the pitch or other saturant, travel down through the pitch under the sealing edge of the saturating tank, and then pass upwardly through the saturant. The conduits on entering the hot saturant give up part of their contained air and water. metric column of saturant, more and more of the air and water will escape as the pressure on the conduit walls decreases, ,due to the decreasing head of pitch thereon. Pitch or other maintained in the top portion of the saturating saturant will flow into the voids in the conduit walls. The conduits leave the upper surface of the pitch and are then exposed to the vacuum in the evacuated space above the pitch. This results in the withdrawal of residual air and moisture in the conduit walls. The conduits then reenter the pitch or other saturant, passing downwardly therethrough, the saturant entering the voids evacuated as a result of exposure of the conduits to the maximum vacuum tank. Thereafter the conduits are passed under the sealed edge of the saturating tank and withdrawn, drained, and cooled. The time required for the passage of the conduits through the cycle briefly described above can be varied by regulating the speed of the conveyor carrying the conduits or adjusting the depth of the saturant through which the conduits are passed or'by operating the conveyor as a periodically interrupted mechanism.

The time of treatment of the conduits may vary from one-half hour for passage through the barometric column of saturant in the case of open wall conduits, which are relatively thin,

to six or more hours for dense conduits having relatively thick walls; 1. e., the conduit will slowly be moved up through the barometric column of saturant so that in the case of the one-half hour treatment, it takes approximately fifteen minutes for the conduit to enter the saturant,

pass up through the column of saturant, and.

reach its midpoint of travel, and fifteen minutes for the conduit to be moved down through the saturant to the point 'of discharge therefrom. The thinner the conduit and the more open its fibrous structure, the less will be the time re- .quired to completely saturate it. Conversely, the

thicker the conduit and the closer its wall texture, the greater the time required for satisfactory saturation thereof. spirally wrapped conduits will ordinarily require more time for satu- As they rise in the baroration than conduits made by molding the fibrous material about a mandrel.

During the final downward passage of the conduits through the column of saturant, increase of the pressure head of the pitch as the conduit o passes downwardly forces additional amounts of saturant into the vaporand air-tree voids effecting substantiallycomplete saturation. 'Slow change of pressure head of pitch on the conduit walls during bothv the upward and downward l) passage through the barometric column of saturant has the advantage of permitting satisfactory saturation with saturants containing fine suspended or colloidal matter, like the free'carbon of coal tar pitch. Slow increase in pressure, as is well known in the filtering art, tends to eliminate the building up of impenetrable layers of such suspended matter, e. g., free carbon, on the surface of the fibrous conduit and the avoidance of such impenetrable layers insures greater penetration and improved saturation. The withdrawal of the conduits from the saturant into the vacuum space above the satu-.

rant not only is efiective in withdrawing residual gases and water vapor from the conduit voids but is also effective in loosening and in part removing any more or less impenetrabl layers of free carbon or similar material which may have accumulated on .the conduit surfaces during the upward passage through the saturant. On the subsequent downward passage, the saturant readily passes through the loosened layers of free carbon and fills the exhausted pores orvoids.

As the saturant for the conduits, coal tar pitch, water gas tar pitch, asphalt, cutback pitches, blended pitches, or other waterproofing material may be used. A' coal tar'pitch having a melting point of from 140 to 180 F. is particularly suitable for saturation of fibrous conduits. 40 Pitch of a melting point as high as 225 F. may be used in special cases, e. g., where conduits are to be exposed to temperatures which would soften the lower melting point pitches. Pre; ferred pitches having melting points of from 140 to 180 F. or higher will have a free carbon content of from 5 to 9 per cent, but pitches of higher free carbon? content up to from 15 to 25 per cent, or even higher may be used to give commercially satisfactory saturation under fa- I vorableconditions, e. g., in saturating articles having comparatively open wall structure.

Preferably coal tar pitch made by a vacuum distillation process, such for example as disclosed in Patent No. 1,759,816, granted May 20, 1930, or other processes minimizing decomposition of the tar undergoing distillation, is employed as the saturant; Pitches made by a low temperature vacuum; distillation process are characterized by low free carbon content as compared with pitches'made by higher temperature processes from the same tar, and I have found that such pitches are particularly suitable as the saturant for fibrous conduits. For example, such pitch of 149 F. melting point (cube in water) when tested 6 had a free carbon content of from 5 to 9 per cent; such pitch of 156 F. melting point when tested (cube in. water) had a free carbon content of from 5 to 9 per cent; suchpitch of 226 F. melting point (cube in air) had a free carbon content of from 11 to 15 per cent; and such pitch of 291 F. melting point when tested (cube in air) had a free carben content of from 16 to 1 per cent. Pitchesproduced by distilling tar not under vacuum but by continuously heating the tar and then passing the heatedtar into a flash box where the vapors separate from the carbon" content of from 11 to 13 per cent; a

pitch of 158'F. melting point (cube in water) ,had a free carbon content of from-10 to 14 per cent; a pitch of 226 F. (cube. in air) had a free carbon content of from 19 to 23 percent; and a pitch of 291 F. melting point had a free carbon content of from 33 to 37 per cent. The free carbon content will depend largely on the temperature treatment during distillation as well as on the melting point of the pitch and the free carbon content of thetar used to make the pitch.- Coke oven tar generally will not run much above 5 per cent free carbon; 1 per cent free carbon content is relatively low for such tars.

The use of a pitch made by a vacuum distillation process for saturation has a two-fold advantage; (1) In its manufacture, this pitch is distilled under vacuum and consequently at' aflower temperature than would be needed to produce a pitch of the same melting point by the usual methods of distillation.- This low temperature causes mini- .mum decomposition and hence free carbon formation in the pitch. Low free carbon content is an aid in effecting complete penetration and saturation of porous material.

(2) In its manufacture, the pitch has been subjected to temperatureand vacuum conditions such as'to insure the substantially complete removal of oils which would be volatile under the conditions maintained in thesaturating operation of my invention. Such pitches will be substantially free from oils volatile under the temperature and vacuum conditions encountered in the saturating operation, and consequently, will suffer minimum or at least only nominal losses from volatilization during saturation. Owing to low volatilization losses, concentration of free carbon resulting from oil losses as well as increases in melting point during saturation will b reduced to a minimum.

, Other methods of manufacture, such as steamor inert-gas-distillation, which effect distillation at relatively low temperatures, will yield desirable pitches for my process for the reasons outlined above.

After final saturation, the conduits are drained. Heretofore, they have'been drained in vertical position so that frequently the surface of the lower end contained more saturant than the surface of the upper end. To avoid this objection, in accordance with my invention, the conduits may be rotated about their longitudinal axes while still hot so that drainage longitudinally of the axis of the .conduits is retarded. and due to centrifugal force exerted on the conduit, the pitch is maintained in position onthe "conduit walls while setting. Rotation of the conduits has a tendency to cause concentration of the saturant at the outer periphery, leaving the inner walls .extent in the top or tank 2. The base of tank 2 is open and extends below the level of saturant verted position. By regulating the rate of temperature drop in the draining zone and the rate of cooling, a uniformly saturated conduit will be obtained. Still another form of draining is to squeegee the tube walls as they leave the saturat- 5 ing bath and then chill rapidly, preferably while rotating the tubes.

As a modification of the procedure hereinabove described, instead of maintaining a. barometric column of saturant, a column of saturant of any 10 desired height may be provided in a tank that is mechanically sealed so thata column of any desired height may be maintained under vacuum thereon. The tank may be relatively small and not of a height necessary to accommodate a bar- 15 ometric level. Conduits may be continuously fed to the tank while pitch is circulated under pressure therethrough and the conduits thus effectively saturated as more fully pointed out hereinafter.

In the drawings, in which like reference numerals designate like parts- .chanically sealed type apparatus for saturating conduits in accordance with the process of this invention, 1. e., the saturating tank of Fig. 5 is sealed at its base sothat any desired height of bogy of saturant maybe maintained therein; an Fig. 6 is a vertical section, partly in elevation, taken in a plane passing through the line 6'-6 of Fig. 5. I

In the drawings, referring to Fig. 1, reference numeral I indicates a, container for the saturant 45 required in the saturating process. Disposed within the container iis the tank 2 of a height sufiicient to accommodate a-barometric column of saturant and-leave a. space 3 of substantial in container I so that a liquid seal is provided in. the base of the saturating tank. A partition I may be provided extending from the base of tank I up through the tank 2, dividing this tank into two equal portions. Preferably, this partition terminates at the level of the column of saturantin tank 2. If desired, the partition may be omitted. A valve-controlled pipe 4 leads from the top of saturating tank 2 through a condenser 5 into a separator 6. Condenser 5 condenses any oil vapors coming oil? from the saturant and reduces the volume of gas and water vapor handled by vacuum pump 1' communicating by means of pipe 8 with a trap or separator 6.

A pipe 9 connects trap 6 with the saturating tank 2 to return, if desired, distillate oil'in the separator or trap 6 to the tank 2. Valve II in pipe 9 controls flow therethrough. Valve-controlled pipe I! communicates with pipe 9, for withdrawing oil from the separator 6 when it is not, desired to return the oil to the tank 2.

.A valve-controlled pipe I 3 of a length suflicient to accommodate a barometric column of water,

leads from separator 6 to a suitable point.

Fresh saturant may be added continuously to replace the saturant absorbed by the conduits so that the volume of saturant within the system is maintained substantially constant. The

amountof saturant fed to the'tank must be such that the level of saturantin container I is maintained at a height above the base of tank 2 so that the liquid seal at the base of this tank I is not broken. A pump I4 in line I5 con-' necting container I with a spray header I6 disposed in the top of tank 2 may be employed to circulate the pitch saturant within the system and thus maintain it at substantially uniform viscosity and free carbon content throughout the tank I and container 2. The spraying of the saturant onto the top of the body of saturant in tank 2 has the further function of hindering th formation and causing the destruction of a film or layer of foam, if any, formed over the surface of the body of saturant in tank 2. Container I may be provided with a valve-controlled drawofi I1 and an overflowpipe I8 communicating with a storage tank (not shown);

Container I and tank 2 may be equipped with suitable heating elements, such as steam jackets or coils, and regulators of any well known type for maintaining and controlling the temperature and vacuum. The apparatus may be suitably heat-insulated to reduce heat losses. For the sake of clearness, .insulation, heating elements, andregulators have been omitted from the drawings.

One type of apparatus for moving the fibrous conduits through the container I and saturating tank 2 is shown in Figs. 1 to 4 of the drawings. As appears from Fig. 2, the conveyor for moving the conduits through the saturant involves two chains 2I, 22, arranged in spaced relation and disposed to pass over pairs of spaced sprockets. Two such sprockets 23, 24 are shown in the topof Fig. 2. These sprockets are rotatably mount-v ed on stub shafts 25 extending through suitable stufling boxes in the walls of tank 2 and rotatably mounted in suitable bearings 26. One pair. of stub shafts carrying the sprockets may be suitably driven from a source of power such as an electric motor (not shown) and the conveyor thus actuated. The chains 2|, 22 may be composed of usual links employed in chain conveyors.

The holder of Fig. 2 comprises a strap or rod 28 formed at one end with a hook 29 and weighted at the other end. The lower .end is provided with a perforated plate 3| on which the lower end of the conduit 32 rests. The upper end of the conduit may be engaged by a perforated plate 33, the conduit being securely held by the plates 3| and 33. Any other type of holder for the conduits may, of course, be employed.

Instead of employing an individual holder for each fibrous conduit, a basket 35 made of foraminous material and adapted to contain a plurality of conduits, as shown in Fig. 3, maybe suspended as indicated at 36 fromthe pin 21. When saturating tubes of different internal diameters,

tubes of smaller diameter may be nested withi the larger tubes and the assembly of nested tubes placed within a basket such as 35, Figs."

3 and 4. The basket may-be provided with a removable cover having a hook 36 arranged to engage pin 21 of the conveyor. Detents or other the moving conveyor.

At corresponding spaced intervals both chains have special links for carrying a, pin 21,

Suspended from this pin, as shown on Figs. 1 and 2, are suitable holders for a fibrous conduit.

fasteners (not shown) which may be spring-actuated, are provided on the sides of the baskets securely locking the perforated or foraminous cover thereon. As in the case of the individual conduit holders of Figs. 1 and 2, the basket of conduits may be suspended from the pins extending across the space between the conveyor chains and may be maintained with the same end lowermost throughout the passage of the conduits through the up and down passes through the saturant.

The baskets may be fixedto the conveyor or detachably secured thereon. In the former case, the conduits or fibrous tubes may be inserted in the baskets prior to the passage thereof into the saturant, as for example, at the loading point A, Fig. 1. For this purpose, the conveyor may be momentarily stopped or the conveyor may be system, the conveyor being, if desired, momentarily stopped to permit the removal of the baskets from and attachment to the conveyor or the baskets may be'detached from and attached to For this purpose, automatic pick-up and drop mechanism for conveyor baskets of any well known type may be employed.

The baskets may be formed with projections or other members for spacing the fibrous conduits therein so that they do not touch one an,- other thus insuring improved saturation. Also, quick-opening basket doors may be provided, permitting prompt loading and discharging of the conduits into and from the baskets. The conveyor may be of any suitable type. e. g., chain, cable, belt, apron, .etc.

In the operation of the apparatus of Fig. 1, the pitch saturant is maintained in tank 2 and container I in fluid condition. saturating, fibrous conduits having approximately 1.66 c. c. of voids per gram of tube wall with coal tar pitch of specific gravity of 1.2 and a melting point of about F., the pitch may be maintained at a temperature of from 300 to 350 F., preferably at about 320- F., while a vacuum of from 2'7 to 29 inches of mercury is maintained in the evacuated space 3 above the surface of the column of pitch. The height of the tank 2 above the atmospheric level of pitch in container I with such pitch should be approximately 38 feet, providing for an evacuated space of approximately 10 feet above the maximum barometriccolumn of pitch. To accommodate variations in atmospheric conditions, different specific gravity pitches, etc., a

minimum.- olearance of two feet between the upper level of pitch in tank 2 and the bottom of the conduit or basket of conduits when disposed in the evacuated space 3 completely out I of contact with the body of saturant should be The basket then gradually move upwardly through the 001- 75 'plete removal of air and other from the tube walls.

umn of saturant. Hence, the tubes are first subjected to saturant at atmospheric pressure, then to saturant at somewhat above atmospheric pressure as they are moved downwardly into the saturant in the container I and then gradually rise in the column, the head of saturant on theconduit walls being gradually reduced. Consequently, as the conduits pass through the initial steps of the saturating process, more and more moisture and gas are removed from the tube walls and more and more pitch flows into the voids in the walls. The gradual reduction of the pressure on the walls of the conduit results in a relatively uniform evolution of steam from the conduit walls and lessens the tendency towards foam formation due to sudden evolution of steam. As compared with processes in which a large batch, sayseveral hundred tubes, are treated at once, the process herein for the same output per unit of time, distributes the moisture evolution throughout the period of saturation and does not concentrate it in the initial portion of the operation. In other words, this process provides a high throughput with the presence of but relatively few conduits in the saturant at a time. The evolution of steam, and consequently the tendency to foam, is far less at any given time because of the presence of relatively few wet tubes at one time in the saturant. Finally, the tubes leave the pitch and are subjected to the vacuumin space 3. This effects withdrawal of maximum amounts of residual air and water possible under equilibrium conditions existing in the evacuated space 3. It will be noted that these conditions are favorable to substantially comgas and vapor While the conduits are in the evacuated space 3 and and during the movement thereof through the body of saturant in tank 2, saturant is continuously sprayed over the conduit and onto the surface of the body of saturant in tank 2. This showering of recirculated saturant on the surface of the body of saturant in tank 2 tends to break up any foam layer thatmight form thereon. Furthermore, the subjection of the conduits to vacuum out of contact with the saturant in space 3 and the showering of the conduits with the pitch saturant in this space loosens and removes deposits of free carbon on the walls of the conduits. From the evacuated space 3, the conduits reenter the saturant and move downwardly therethrough being subjected to gradually increasing pressure heads of pitch as they move downwardly. -Uponreentry of the conduits into the pitch, the voids-evacuatedas a result of exposure to vacuum in space 3 are filled. The gradual pressure increase on the conduit walls due to downward movement through the column of saturant results in maximum amounts of saturant entering the conduits. For example, I have found that it is possible to saturate fibrous conduits containing between 8 and 10 per cent moisture by this process without difficulty from foaming. Felt base tubes weighing approximately ten pounds each and containing 9 per cent by weight of moisture were introduced as described into a barometric column of molten pitch having a cross-section of about 110 square inches. The. tubes were passed upwardly through the molten pitch into an evacuated space where they were flushed with a shower of pitch recirculated fromthe bottom of the apparatus. In the particular apparatus used, the tubes were then carried downwardly through another barometric column of pitch, adjacent to and of the same cross-section as the first column, and removed from the apparatus. The complete cycle of treatment required thirty minutes. The tubes were satisfactorily saturated and no trouble was encountered due to their moisture content.

From the bottom of the column of saturant, the

conveyor carries the saturatedconduits out of p the saturating bath to the withdrawal point B.

in a tank sealed against the atmosphere. Hence a column of saturant of any desired height may be maintained in this tank and the tank need not be of a height sufllcient to accommodate a maximum barometric leg of saturant, in the case of coal tar pitch of specific gravity of 1.2 at least 28 feet high since the device'of Fig. 5 is sealed mechanically and with fluid against the ingress of air.

Referring to Fig. 5, tank 4| is shown in which any desired-level of coal tar pitch or other saturant may be maintained constant by a floatcontrolled valve 42 regulating the discharge of saturant from the tank 4| through pipe-43 which connects with the valve-controlled drawoff 44 at the base of the tank. Disposed within this tank is an endless conveyor 45 passing over sprockets 46 suitably mounted in the tank. Conveyor 45 is shown provided with clamps 41 at spaced intervals therealong and at opposite sides thereof arranged to support and feed the fibrous conduits through the saturant in tank 4i. The clamps 45 are arranged to be opened by a cam 41' on the shaft carrying the lower sprocket 46 and are provided with springs or other means to cause the fingers to close and grip the conduit when the clamps are moved so that the extensions 48 thereof are no longer in engagement with cam 41.

Other means than the clamps 41 shown for holding the fibrous conduits may be employed. I

A rotary feed device 50 delivers the fibrous conduits from the entry chute 49 to the clamps 41 carried by the conveyor 45. This feed device comprises a casing ii in which a rotor 52 having pockets 53 is rotatably mounted. Only a small clearance is provided between the rotor 52 and the casing I. This clearance is maintained sealed by the continuous feed of pitch or other saturant through the valve-controlled pipe 54. The conprovided with a sleeve 59 extending through a suitable bearing ii formed on the side of the housing 5|. Sleeve 59 may have suitably secured, thereto a gear or pulley 62 arranged to be driven from a suitable source of power to rotate the rotor as will be understood.

Movement of conveyor 45 may be continuous or intermittent and synchronized with the move ment of rotor 52 so that as clamp 41 is brought into position, the plungers 55 effect the discharge of a fibrous conduit thereinto. The conveyor elevates the conduits through the column of saturant in tank 4| into the evacuated space 3 in the top of this tank. From the evacuated space 3, the conveyor 'moves the conduits down through the column of saturant in tank 4|. Upon the conveyor leaving the position indicated by the reference character 63, cam 41 or other mechanism causes the clamps to disengage the conduits and permit their discharge into the pockets '84 of a rotor 65 rotatably mounted in much the same manner as hereinabove described in ,connection with the rotor'52 in a casing 66. A guide plate 61 disposedbetween clamps 41 holding the opposite ends of each conduit aids. the discharge of'the conduit; Rotor 65, like 52, has but a small clearance between its end and side walls and casing 66 which is maintained sealed by liquid saturant leaving tank 4|. Movement of rotor 65 brings the pockets 64 into registry with the clamps discharging the saturated conduits.

As hereinabove described in connection with the apparatus of Fig. 1, a pump I4 is disposed in line l5 connecting the base portion of tank 4| with a spray head l6 disposed in the evacuated space 3 of this tank. The'top of tank 4| communicates by means of a valve-controlled pipe 69 with a foam chamber 11. This chamber may be filled with suitable packing, the passage of the foam through which causes destruction of the foam. Foam chamber II is provided with a valve controlled liquid drawofl l2 and a baflle plate 13 extending downwardly from the top thereof dividing the chamber into two passes. The discharge base 14 of this chamber has leading therefrom a passage I5 which passes through condenser 16 into a trap or separator l'l. A vacuum pump 18 is connected with the separator 11 by means of a pipe 19. The separator 11 may be provided with a valve-controlled oil drawoflt' pipe 8| which may lead into the tank 4| for return of oil removed in this separator or to any suitable disposal point. A second valve-controlled drawoff pipe 82 leads from the separator TI to permit the discharge of water collected in the separator.

Approximately the same amount of saturant is fed to tank 4| through the feed line 54 as will be absorbed by the conduits and discharged by the rotor 55. If by chance more pitch is introduced than the conduits will absorb and the rotor discharge, the level of the saturant may be held constant by withdrawing pitch through float-controlled valve 42.

The conduits are discharged into a casing 81 located in a horizontal direction'with the feed rotor at either the top or bottom and the discharge rotor at either the bottom or top, respectively. The fibrous conduits may be fed in either horizontal or vertical position. In lieu of arotary typefeeder and discharger, reciprocating plunger or caison lock type feeders and dischargers sealed against ingress of air may be employed.

As shown in Fig. 6, one side of casing 5| may be provided with an inlet pipe 83 for saturant and the other side with an exit pipe 84. Side walls 5 of the rotor 52 are provided with apertures 85, 86 registering with the pockets in the rotor. As the apertures 85, 86 come into registry with the inlet pipe 83 and the exit pipe 84, a stream of pitch saturant may be forced axially through the conduit and about the outer walls thereof washingthe same. This insures that a relatively clean fibrous conduit is delivered to the body of saturant maintained in tank 4 I.

The operation of the apparatus of Fig. 5 will be understood from the above detailed description thereof and in general is similar to that hereinabove described in connection with the apparatus of Fig. 1; fibrous conduits containing their original moisture content being fed by rotor 52 to the conveyor 4| carried thereby through the body of saturant into the evacuated space 3 being sprayed in this space with recirculated saturant from the spray head l6 and the conduits being carried downwardly through the body of saturant delivered to the rotor 65 and discharged by this rotor into the discharge conduit 81.

Itwill be noted that the process of this invention is continuous, of high capacity, does not require initial soaking of the conduits to remove moisture, is capable of automatic regulation, requires a, minimum of saturant for its practice, and results in uniformly saturated conduits of improved 'waterproo-fness.

It is to-be understood that this invention is not restricted to the present disclosure other than defined by the appended claims.

I claim:

1. The process of saturating fibrous conduits containing substantial amounts of moisture, 40 which comprises, introducing said conduits without subjecting them to a preliminary drying step into a body of hot saturant and gradually moving .said conduits through said body of saturant so that the pressure of the saturant thereon is gradually reduced and moisture removed therefrom, and thereafter completing the saturation of said I conduits.

2. The process of saturating fibrous conduits containing not less than 8 per cent moisture,

which comprises, introducing said conduits containing not less than 8 per cent moisture into a body of coal tar pitch and gradually moving said conduits through said body of pitch so that the pressure of pitch-thereon is gradually reduced and moisture removed therefrom, and thereafter substantially completely filling the voids of said conduits with coal tar pitch.

3. The process of saturating absorbent articles containing not less than about 8 per cent moisture, which comprises, introducing said articles into a body of hot saturant and gradually moving them through said body of saturant until the of hot saturant maintained with an evacuated space thereabove and gradually moving said articles through said body of saturant so that the pressure of the saturant thereon is gradually reduced, the moisture being substantially complete- 1y removed therefrom, moving said articlesinto said evacuated space and subjecting them to vacuum-conditions out of contact with the body of saturant, .and thereafter moving the articles through the body of saturant and withdrawing t that the pressure of the saturant thereon is gradually reduced and moisture removed therefrom, moving said conduits into said evacuated space and subjecting them to vacuum conditions out of contact with the body of saturant and thereafter moving the conduits through the body of saturant and withdrawing them therefrom.

6. The process of saturating fibrous conduits containing from 8 to 10 percent moisture, which comprises, introducing said conduits into a body of hot saturant maintained with an evacuated space thereabove, gradually moving said conduits through said body of saturant so that the pressure of the saturant'thereon is gradually re-) duced and moisture substantially completely removed therefrom whiie spraying saturant on the surface of said body of saturant to prevent the formation of a layer of foam on said surface, moving said conduits into the evacuated space and subjecting them to vacuum outof contact with said body of saturant, and thereafter moving said conduits through said body of saturant and withdrawing them therefrom.

7. The process of saturating absorbent articles containing not less than about 8 per cent moisture, which comprises, introducing said moist articles into 'a body of hot coal tar pitch maintained with an evacuated space thereabove and gradually moving said articles through said body of coal tar pitch so that the pressure of the coal tar pitch thereonis gradually reduced and moisture removed therefrom, moving said articles into said evacuated space and subjecting them to vacuum conditions out of contact with the body of coal tar pitch, and thereafter moving the articles through the body of coal tar pitch and withdrawing them therefrom.

8. The process of saturating fibrous conduits containing substantial amounts of moisture, which comprises, introducing said conduits without subjecting them to a preliminary drying step into a body of hot coal tar pitch maintained with an evacuated space thereabove, gradually 'moving said conduits through said body of coal tar pitch so that the pressure of the waiter pitch thereon is gradually reduced-and moisture removed'therefrom while spraying coal tar pitch on the surface of said body of coal tar pitch to prevent the formation [of a layer of foam on said surface, moving said conduits into the evacuated space and subjecting them to vacuum out of contact with said body of coal tar pitch, and thereafter moving said conduits through said body of coal tar pitch and withdrawing them therefrom. 9. The process of saturating absorbent articles containing substantial amounts of moisture, which comprises. introducing said articles containing substantial amounts of moisture into hot saturant having an evacuated space thereabove, gradually reducing the pressure of the saturant on said articles until the moisture is substantially completely removed therefrom, and then saturating said articles with saturant.

body of pitch and withdrawing them therefrom;

11. The process of saturating absorbent articles' containing substantial amounts of moisture, which comprises, introducing said articles containing moisture into a barometric column of hot saturant having an evacuated space thereabove and gradually moving said articles through said saturant so that the pressure of the pitch thereon is gradually reduced and moisture removed therefrom, moving said articles into the evacuated space above said body of pitch and subjecting-them to vacuum conditions out of contact with the body of pitch while spraying pitch on the surface of said body of pitch, and thereafter moving said articles through the body of pitch and withdrawing them therefrom.

12. The process of saturating fibrous conduits containing substantial amounts of moisture, which comprises, introducing said conduits without subjecting them to a preliminary drying step into a body of hot saturant, continuously recirculating saturant from the base of said body of saturant and spraying the same onto the surface of said body of saturant, gradually moving said conduits through said body of saturant so that the pressure of saturant thereon is gradually reduced and moisture removed therefrom, and thereafter completing the saturation. of said conduits.

13. The process of saturating fibrous conduits containing substantial amounts of moisture, which comprises, introducing said conduits without subjecting them to a preliminary drying step into a body of hot coal tar pitch, gradually moving said conduits through said body of pitch so that the pressure of pitch thereon isgradually reduced and moisture removed therefrom, continuously withdrawing pitch from said body and spraying the same onto the surface of said body of pitch and completing the saturation of said conduits by passing them through said body of pitch.

14, The process of saturating fibrous conduits containing substantial amounts of moisture, which comprisesestablishing a barometric leg of saturant with an evacuated space thereabove, passing the conduit containing moisture through the barometric leg of saturant into the evacuated space while withdrawing from said evacuated conduits due to contact thereof with the bituminous saturant, spraying the conduits with bituminous saturant while in said space, passing the sprayed conduits down through the leg of bituminous saturant, and withdrawing the saturated conduits from the saturant.

16. The process of saturating fibrous conduits containing substantial amounts of moisture, which comprises, introducing said conduits without subjecting them to-a preliminary drying step into a column of saturant with an evacuated space thereabove, passing said conduits through said column of saturant while spraying saturant onto the surface of said column of saturant to decompose and prevent the formation of a layer of foam thereon and withdrawing the saturated conduits from said column of saturant.

17. The process 0! saturating fibrous conduits containing substantial amounts of moisture, which comprises, introducing said conduits containing moisture without subjecting them to a preliminary drying step into a column of coal tar pitch with an evacuated space thereabove, passing said conduits through said column of pitch into said evacuated space while continuously recirculating pitch from the base of said column of pitch and spraying the recirculated pitch onto the surface of said column of pitch, passing the conduits from said evacuated space into and through the column of pitch and withdrawing the saturated conduits from the column of pitch.

STUART P. MILLER.

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