US3462089A - Mechanical defibering means - Google Patents

Description

Aug. .19, 1969 s. D. WHITLOW 3,462,089

MEcH-AmcM. DEPIBERING MEANS Filed Dec. 21, 1966 2 Sheets-Sheet 1 32 FIG. 4

INVENTOR BAILEY D. WHITLOW V mam Q) ATTORNEY Aug. 19, 1969 B. D. WHITLOW MECHANICAL DEFIBERINGMEANS 2 Sheds-Sheet? Filed Dec. 21. 1966 I FIG. 6

INVENTOR BAILEY D. WHITLOW ATTORNEY United States Patent 3,462,089 MECHANICAL DEFIBERING MEANS Bailey Duane Whitlow, Richardson, Tex., assignor to Texas Instruments Incorporated, Dallas, Tex., a corporation of Delaware Filed Dec. 21, 1966, Ser. No. 603,481 Int. Cl. B02c 1/10, 7/12, 7/00 US. Cl. 241-296 6 Claims ABSTRACT OF THE DISCLOSURE A face plate for a pulp slurry refiner disk. The plate comprises a metal substrate provided with upstanding, sharp edged teeth and a relatively thin, dense, hard, wear and corrosion resistant, vapor deposited coating over at least that portion of the face plate conventionally exposed to the pulp slurry, the coating having a Mohs scale hardness of about 8 to 9 and preferably being a titanium carbide coating having a ductile metal dispersed therein. 1

BACKGROUND OF THE INVENTION Field of the invention This invention relates to paper making and fiber liberation, and particularly to mechanical refining means utilized in the paper making process.

Description of the prior art into a wet sheet on an endless bronze screen, stainless steel screen, or the like where water begins to drain off. This wet web of paper is then carried through press rolls and over steam-heated cylindrical dryers to complete the drying. While being dried it may be given a variety of different treatments to adapt it to various end uses.

In the refining step, to which this invention is directed, the pulp slurry, after digestion, is introduced proximate the center of and between two confronting and proximately abutting refiner disks. The refiner disks, one of which is usually fixed and the other of which is mounted for rotation, are provided with removable face plates having a plurality of sharp teeth which refine the pulp slurry as it passes radially outwardly between the plates due to fluid pressure behind the slurry and the centrifugal force created by the rotating disk upon which one of the plates is mounted. The pulp slurry contains various abrasive items, such as grit and metal shavings which over a period of time will wear the normally sharp edges of the teeth provided on the plate. When the teeth begin to wear, the plate becomes less efiective and eventually must be replaced. Also, as the teeth wear, the consistency of the refined pulp slurry is changed, altering the quality of the eventual paper product.

The face plate of a refiner disk, depending upon the particular mill in which it is employed and the type of pulp circulated through the refiner, will usually require replacement at least once or twice a year, and in some instances as often as once a month. Replacement of the plates can require shutdown of the entire mill, or in the 3,462,089. Patented Aug. 19, 1969 ice alternative, circulation of the pulp stream to other refiners. The loss of a refiner can reduce the amount of slurry being processed, thus reducing the amount of paper produced.

The installation of new face plates requires the time and eflorts of a maintenance crew, increasing the expense of producing paper. Sometimes, due to the urgency of placing the refiner back on stream, the maintenance crews work overtime further'increasing costs. After removal of a worn face plate, its condition permitting, the plate is sometimes machined to sharpen the teeth, and the more frequently the plate has to be replaced, the more time and effort will be expended in sharpening worn plates.

Face plates for refiner disks are commercially available in metals ranging from cast iron to various grades of stainless steel. While stainless steel disks will have a greater life than cast iron disks, the expense is also greater.

Summary of the invention This invention may be generally described as a face plate for a pulp slurry refiner disk having a metal substrate provided with upstanding, sharp edged teeth, and a relatively thin, dense, hard, wear and corrosion resistant, vapor deposited coating over at least that portion of the disk which conventionally is exposed to the pulp slurry. The coating has a Mohs scale hardness of about '8 to 9 and preferably is a titanium carbide coating having a ductile material dispersed therein. The invention permits the use of a relatively inexpensively formed metal substrate which is then provided with an extremely hard and dense vapor deposited coating that greatly extends the life of the face plate requiring fewer shutdowns of the paper mill and thus lowering the expense of the process.

Brief description of the drawings FIGURE 1 is a front elevational view of a pair of refiner disks which embody the present invention;

FIGURE 2 is a side elevational view, partially broken away, of the refiner disks illustrated in FIGURE 1;

FIGURE 3 is a side elevational view of one segment of a face plate illustrated in FIGURE 2;

FIGURE 4 is a section taken along line 44 of FIG- URE 3;

FIGURE 5 is an elevational view in section of an apparatus suitable for vapor depositing a coating on a face plate; and

FIGURE 6 is an enlarged view of the receptacle used in the FIGURE 5 apparatus.

Description ofthe preferred embodiment With reference to FIGURE 1, a pulp slurry 10 is refined 'by introducing it through a conduit 11 which discharges proximate the center of and between confronting refiner disks 12 and 13. Conduit 11 is fixed to the backplate 14 of stationary disk 12 by any suitable means, such as weldment 15 and discharges the pulp slurry 10 through port 16 (illustrated in FIGURE 2) in stationary disk 12. Refiner disk 13 is mounted by weldment 17 to a cylindrical shaft 18 driven by a suitable primer mover 19. To the backplate 21 of rotatable refiner disk 13 is bolted a face plate 22 comprised of a plurality of arcuate segments 23, such as illustrated in FIGURE 3. Segments 23 include a plurality of upstanding, relatively radially short teeth 24 between which are disposed a plurality of upstanding, relatively radially long teeth 25. Both teeth 24 and 25 are provided with sharp edges, the purpose of which is to eifect refining of the fibers in the pulp slurry introduced through conduit 11. Segments 23 are secured to backplate 21, as by bolts 26, illustrated in FIGURE 2,

which pass through apertures 27 in segments 23 for engagement with threaded mating recesses in backplate 21 (not illustrated). Segments 23 when assembled to backplate 21 form a continuous face plate 22, as illustrated in FIGURE 2. Stationary disk 12 is also provided with a backplate 14, as described before, which like backplate 21 of disk 13, receives a plurality of identical segments 23 which are secured thereto in the same manner as segments 23 are secured to backplate 21. Pulp slurry charged to the refiner will pass through conduit 11 and be centrally discharged between refiner disks 12 and 13 where fluid pressure on pulp slurry and the centrifugal force generated by rotation of refiner disk 13 will combine to discharge the pulp slurry radially outwardly between refiner disk 12 and 13 causing an engagement of the pulp particles with the teeth 24 and 25 of face plates 22 and 29 which further defibrates the slurry resulting in the discharge at the outer periphery of disks 12 and 13 of a refined slurry generally indicated by the reference numeral 28.

As explained before, after a certain operating period, it becomes necessary to replace the face plate 22 on disk 13 and the face plate 29 on disk 12 due to wear on teeth 24 and 25. In order to extend the life of face plates 22 and 29, each of the segments 23, which when assembled comprise face plates 22 and 29, are coated with a relatively thin, hard, dense, wear and corrosion resistant, vapor deposited coating 31, such as illustrated in FIGURE 4. The coating is deposited upon a metal substrate 32 which conforms in configuration and has substantially the same dimensions as the segments illustrated in FIGURE 3. Coating preferably applied to the metal substrate is a titanium carbide coating having a ductile metal such as cobalt dispersed in the titanium carbide phase. Vapor deposited pure titanium carbide is quite brittle and lacks toughness, with the result that it exhibits inadequate resistance to shear forces, and is therefore not preferred. To impart toughness to the titanium carbide coating, a suitable ductile metal such as cobalt or nickle is simultaneously deposited with the titanium carbide upon the substrate. The dispersion that is formed is of the type in which titanium carbide is continuous phase and the ductile metal is the dispersed phase. In this type of dispersion, the ultra-hard characteristics of the pure titanium carbide are retained. Moreover, the dispersed particles of the ductile metal absorb energy, prevent high energy buildup from reaching the threshold energy density for fracture propagation and thereby function to stop the propagation of cracks which may originate in the titanium carbide matrix. Moreover, because of its greater coherence, such a dispersion strengthened material has considerably more impact resistance than ordinary titanium carbide. Metal substrates having the form of segments 23 may be coated in an apparatus such as identified in FIGURES 5 and 6.

FIGURE 5 illustrates a reactor comprising a cylindrical body 33 surrounded by a heating coil 34 and having two fitted end caps 35 and 36. End cap 35 has exhaust outlet 37 and a hollow cylindrical portion 38 which extends upwardly into a portion of the tubular reactor 30. The cylindrical portion 38 extending into the reactor has a fiat surface 39 upon which the substrate 32 is positioned. End cap 36 mounted on top of the cylindrical body 33 has a reaction tube 41 formed therein which extends into the central portion of the body 33. Reaction tube 41 has a flared portion 42 at its lower end which extends over the recessed cylindrical portion 38 of the bottom end cap 35, thus enclosing the substrate 32 within the lower end of reaction tube 41. The flared portion 42 extends down from the substrate carrier surface 39 of end cap 35 and acts as a guide to direct gasses passing over the substrate 32 downwardly between the walls of the flared portion 42 and the upwardly extending recessed portion 38 of end cap 35. The zone at which deposition occurs generally is identified in FIGURE 5 by the reference numeral 43.

Body 33 and tube 41 effectively divide the reactor into two separate chambers, namely the deposition chamber zone 43, previously described, and a flush chamber 44, defined between reaction tube 41 and cylindrical vessel 33.

Reaction tube 41 is appropriately fitted with a cap 45 which carries a tube 46 extending therethrough and annularly down into the central portion of tube 41 to within one inch or so of the substrate 32. A receptacle 47 containing metal halide granules, cobalt chloride, for example, is suspended within the tube 46 (shown in greater detail in FIGURE 6) at a point near the upper zone of the heating coils 34 surrounding the outside of cylinder 33. The heating coils controllably maintain the interior of the reactor 30 within a temperature gradient of about 600 C. in the receptacle zone and about 1,000 C. in the deposition zone 43, as shown. Heating coils 34 may be either RF induction heaters, resistance heaters or any other suitable heating means for controllably maintaining the desired temperature in the zone of the receptacle 47 and the substrate zone 43.

A carrier gas stream of argon or helium gas is passed through the tube 46, carrying the metal halide vapor toward the surface of the substrate 32, as shown in FIG- URE 6. Cap 45 is further provided with an inlet 48 through which titanium tetrachloride and carbon tetrachloride and a stream of hydrogen are introduced into tube 41 and passed downward outside the walls of the metal chloride tube 46. Upon reaching the deposition site 43, the metal chloride, titanium tetrachloride, carbon tetrachloride, hydrogen and cobalt chloride gasses mix and react to form a deposit of ductile metal in titanium carbide upon the substrate 32.

The reactions may be represented as:

Tlclq Co], an TiO snot C0011 Hz CO 81101 End cap 36 is fitted with a flush inlet 49, through which a flush gas (argon, for example) is passed through the flush chamber 44. The flush gas entering inlet 49 passes through chamber 44 between the walls of the cylinder 33 and the reaction tube 41 and downwardly over guide 42 to exit through exhaust 37 provided in the lower end cap 35. The flush gas is used primarily to prevent contamination of the deposition chamber 43 by back-drafts passing upwardly between the guide 42 and the walls of the recessed portion 38 of end cap 35.

In operation, purified helium or argon is first flushed through inlets 48, 49 and 51 to purge atmospheric gasses from the reactor in preparation for the deposition. When the reactor has been sufficiently purged, the flow of argon through tube 48 is stopped. Argon is introduced through tube 49 at the rate of approximately 35 cc./ min. The flow rate of argon (or helium) to tube 51 is varied according to the deposition rate of ductile metal desired. The chamber is then rapidly brought up to operating temperature within the gradient previously given. Titanium tetrachloride and carbon tetrachloride are admitted to the reactor through feed tube 48, entrained in a carrier of hydrogen gas. This feed gas is prepared by bubbling hydrogen through bubbler bottles (not shown) containing the liquid titanium tetrachloride (TiCl and carbon tetrachloride (CCl at room temperature. The gas thus admitted through feed tube 48 is hydrogen saturated with TiCL; and CCl Upon reaching deposition zone 43, the hydrogen. titanium tetrachloride, and carbon tetrachloride from tube 48 and the metal halide vapors from tube 46 mix and are simultaneously reduced by the hydrogen gas into a mixture of titanium carbide and ductible metal which is deposited upon the substrate 32. The spent gas is passed outwardly between the guide 42 and the recessed portion 38 of end cap 35 to exit through exhaust outlet 37. A coating of from /2 to 1 mil in thickness is suitable for a face plate, such as used on refiner disks, and only the surface of the segments 23 which conventionally contact the pulp slurry need be coated, as principal wear occurs on this surface.

With the apparatus illustrated in FIGURE 5, the face of the segment 23 which conventionally contacts pulp slurry will be coated, as will the sides of the substrate 32, but the bottom of substrate 32 will not be coated as it is isolated from the deposition vapors by the supporting piece 39. The time required to deposit a desired thickness of titanium carbide having cobalt dispersed therein will vary with the size of the substrate 32 and the flow rates of the reactants. With a specimen metal substrate, and the following flow rates:

Millimoles/min.:

TiCL, 1.342 CCl, 1.342 H 122.000 CoCl 0.029

the deposition rate was found to be .13 mil per hour. The titanium carbide coating having cobalt dispersed therein has a Mohs scale hardness of between about 8 and 9, which is the preferred hardness. While cobalt is a desired ductile metal to be dispersed in the titanium carbide coat-' ing, it is to be understood that other ductile metals, such as nickel, for example, may be dispersed in titanium carbide by selection of the appropriate reactants, flow rates and temperatures. Moreover, it will be clear to one skilled in the art, after reading the above, that halides other than chlorides may be employed.

Indeed, various designs and types of reactors may be employed, it only being necessary to provide an apparatus capable of depositing a dense, hard, wear and corrosion resistant coating on the metal substrate, though a titanium chloride carbide coating having cobalt dispersed therein is preferred.

It is also possible to use flame spray techniques to apply a coating such as chromium oxide to the metal substrate, but such a technique is not preferred since the coating will not be as hard as the vapor deposited coating.

A titanium carbide coating having a ductile metal deposited therein, such as described above, may also be applied to the blades of a Jordan, a refiner usually employed downstream from the refiner described above and utilized to further reduce the size of fibers in the pulp slurry. Such a coated blade will also have the advantages described in connection with the refiner disk face plates.

Because of the greater life of apparatus embodying the present invention, a desired consistency of the refined pulp slurry can be maintained for longer periods resulting in a finished product having more uniform quality.

While rather specific terms have been used in describing one embodiment of the present invention, they are not intended, nor should be construed, as a limitation upon the invention as defined in the following claims.

I claim:

1. A pulp slurry refining member having sharp edges for engagement of wood particles in the pulp slurry and comprising:

a metal substrate provided with sharp upstanding teeth;

and

a relatively thin, dense, hard, wearand corrosionresistant, vapor deposited, continuous titanium carbide coating containing a ductile metal dispersed therein over at least that portion of said member conventionally exposed to the pulp slurry, said coating having a hardness from about 8 to about 9 on the Mohs scale.

2. The article of claim 1, in which:

the ductile metal dispersed in said titanium carbide is cobalt.

3. The article of claim 2, in which:

said coining has a thickness of between about /2 and 4. The article of claim 1, wherein said pulp slurry refining member comprises a face plate for a disk adapted to be positioning in proximate confronting abutment with another disk mounted for rotation relative thereto.

5. The article of claim 4, in which: the ductible metal dispersed in said titanium carbide is cobalt. 6. The article of claim 5, in which: said coating has a thickness of between about /2 and 1 mil.

References Cited UNITED STATES PATENTS 1,017,914 2/1912 Richardson 148-31.5 1,248,814 12/1917 Craig 241296 1,424,615 8/ 1922 Buckley 241-296 2,293,422 8/1942 Brown 241296 2,729,146 1/1956 Wandel 241--296 X 2,756,166 7/ 1956 Alexander. 3,064,349 11/1962 Fiitterer 30350 X 3,240,437 3/1966 Horstman 241296 X ROBERT C. RIORDON, Primary Examiner D. G. KELLY, Assistant Examiner

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