US3077310A - Pulpwood grinding apparatus - Google Patents

Description

1963 HORNBOSTEL 3,

PULPWQOD GRINDING APPARATUS Filed Dec. 51. 1959 Z/ya/ f/arn basis! United States Patent M 3,077,310 PULPWOOD GRINDHNG APPARATUS Lloyd Hornbostel, Eeloit, Wia, assignor to ltleloit iron llorirs, Beloit, Wis, a corporation of Wisconsin Filed Dec. 31, 1959, iscr. No. 863,295 2 Claims. (Cl. 241-280) The present invention relates broadly to the art of pulp production, and is more particularly concerned with novel method and apparatus for grinding pulpwood featuringmovement of a pulp stone and pocket relative to one another, whereby there is obtained'pulp of consistently uniform quality at substantial power economies.

Since the advent of the early pulpwood grinders using j-ackscrews and a car jack for maintaining pressure and down to the modern high production magazine grinders and continuous grinders of the ring or chain feed types, it has been found difficu'lt to produce consistently uniform pulp. One explanation for this is the great number of variables in the pulping process, and among those of considerable importance are the sharpness of the pulp stone, the moisture content of the pulp wood and the pulpwood density.

To explain, an accepted control used in the manufacture of pulp is freeness or measurement of the drainage characteristics. Since all pulp is at one time in a suspended form, in order to make a sheet of paper the water must be removed, and'theease or lack of ease with which this mixture, or slurry, will drain is referred to as free ness or slowness. A free stock is usually composed of relatively long, coarse fibers, or is a stock from which the fines or flours (gelatinous bits of fractured fibers) have been removed; while a :slow stock generally consists of short, fine, well-fibrillated fibers intermixed with fines. Now, in pulp grinding, freeness changes markedly from the time of sharpening the pulp stone until sharpening is again required. The sharp stone tends to cut the fibers and decreasethefines, whereas asthe stone becomes worn, the extent of cutting decreases and the rubbing and refining action has the efiect of producing more fines and greater fibrillation;

The variable of pulpwood moisture content bears importantly on the efiiciency of the pulping operation, since when the wood is relatively wet the fibers separate more easily, their strength'is greater and the power consumption is lower. While eitorts are made by soaking or like procedures to have at least 30% moisture content, it is apparent that this condition cannot always be attained and a uniform moisture content for a particular load of pulpwood cannot be efliciently accomplished, even when pre-soaking is used.

Accordingly, to compensate for moisture content and density variations, while striving for consistently uniform pulp quality, the grinding pressure or unit loading is adjusted or varied. The pulpwood pocket, however, of the prior art presents a relatively large contact area both arcuately and axially, and the power requirements to vary the loading are therefore substantial. As is known, the efiiciency of the pulping process is expressed in terms of horsepower per daily ton of fiber, and it can therefore be seen that when wide variations in grinding pressure or load required to obtain optimum unit loading for consistent pulp quality are necessary, the pulping efficiency is substantially diminished.

It is accordingly an important aim of the present invention to provide method and apparatus for pulpwood grinding productive of uniformly consistent pulp quality at minimum power requirements.

Another object of this invention lies in the provision of improved structures and procedures for producing pulp, wherein the pulp stone and pocket are moved relative to one another to vary the contact area of said stone artists Patented Feb. 12, i953 in abrasive engagement with pulpwood supported by said pocket, producing as among the advantages reduced stone wear.

Another object of the instant invention is to provide apparatus for grinding pulpwood to obtain pulp there from, comprising a rotatable grinding member, a housing for pulpwood positioned adjacent said grinding member, force applying means for advancing said pulpwood into grinding contact with said grinding member, and means for effecting relative movement between said grinding member and housing to vary the contact area of said member in abrasive engagement with said pulpwood, whereby frequency of sharpening of said grinding member and the magnitude of grinding pressure variations to attain quality control are reduced.

A further object of the invention lies in the provision of a method of grinding pulpwood, which comprises advancing a plurality of pulpwood sticks into abrasive engagement with a rotatable grind member.

Other objects and advantages of the invention will become more apparent during the course of the following description, particularly when taken in connection with the accompanying drawings.

In the drawings, wherein like numerals designate like parts throughout the same:

FIGURE 1 is a top plan view of the apparatus effective to practice the instant method, and incorporating a conical grinding member and a pulpwood pocket which is moved laterally with respect thereto;

FIGURE 2 is a fragmentary end View to illustrate the grinding action on a pulpwood stick at the relatively larger radius of the conical pulp stone of FIGURE 1; and

FIGURE 3 is a view similar to FIGURE 2 and showing the grinding action at the relatively smaller radius of the conical grinder stone.

As earlier stated, it has been difficult in the past to obtain consistently uniform pulp quality at reasonable power expenditures, due to the greater number of variables involved in the pulpwood grinding process. The freeness or measurement of pulp drainage characteristics changes substantially from the time of stone sharpening until it again becomes necessary to sharpen said stone, since it is now known that a sharp stone tends to cut thefibers and decrease the fines, whereas as the stone becomes Worn, the amount of cutting decreases and the rubbing and refining action tends to increase, producing more fines and greater fibrillation. On the other hand, the variations in pulpwood moisture content and density require that the grinding pressure or unit loading be varied, and by reason of the relatively great contact area of the conventional grinder pocket, wide pressure variations or large changes in loading are necessary. This markedly increases the total power requirements for the grinding process, and a point is approached at which mechanical pulp grinding loses some of its economical attractiveness.

It has now been discovered that uniformly consistent pulp quality at minimum power expenditures is obtained by varying the contact area of the pulp stone and pulpwood relative to one another, so that pulp stone Wear is reduced and the stone remains in relatively sharp condition for a longer period, and thereby continues to out rather than rub the fibers.

The relative movement described can be accomplished by moving the grinder pocket laterally with respect to a generally conical grinder stone, or in other Ways which will become immediately apparent to those skilled in the art upon a consideration of the instant disclosure.

The apparatus is illustrated in FIGURE 1 and is clos ignated therein generally by the numeral ill. As shown,

there is provided a pulp stone or grinding member 71 of generally frusto-conical onfiguration supported for rotation at opposite ends by shaft means 72a journaled in bearing means 7373a, respecdvely, said pulp stone 71 being driven in rotation by motor means or the like '7 having shaft means '75 coupled at 7'6 to shaft means 77 received in the bearing means 730.

To vary the grinding contact area, a grinder pocket or housing 73 is provided with guide means 79 received in track means disposed generally parallel to the grinding surface of the conical grinder 71. The pocket 78 is laterally reciprocable along the track and suitable motive means for this purpose may take the form of a double acting cylinder having ports and 33 admit- \Lw ting pressurized fluid to opposite sides of a piston 8 having a rod portion connected either directly to the grinder pocket 78 or to the guide means '79 thereon. Pulpwood (not shown) in the pocket it? is urged into abrasive engagement with the conical grinder 71 by means shown in FIGURE 1 as comprising a cylinder 35 provided with ports 3% and S7 to reciprocate a piston ti? with arm portion connected to plate means 8% bearing against the pulpwood sticlzs.

Buring lateral movement of the grinder pocket 78 along the track 89, the pulpwood sticks in the pocket 73 are continuously subjected to a changing stone radius, in the manner indicated in FEGURES 2 and 3. The pulp stone 71 has a relatively large radius end 71:; and a relatively smaller radius end 7122 between which the pulpwood sticks continuously travel under action of the motive means 81 for the grinder pocket 78. By reason of the continuously changing grinding surface in abrasive engagement with the pulwood, no single area or band along the pulp stone is subjected to greater Wear, and the stone 71 accordingly longer retains a good tooth and the fibers from the pulpwood are cut, rather than rubbed, so that a minimum amount of fines are produced. it may be observed upon reference to FEGURE 1 that a relatively small pocket 78 is utilized, presenting to the changing grinding radius a relatively smaller contact area than has heretofore been employed with the result that not only is the sharpening eriod prolonged, but the power requirements to maintain the optimum unit loading or grinding pressure at the nip is markedly less than has previously been the practice.

It is apparent from the foregoing description that simultaneous movement of the grinder member and pulpwood sticlrs relative to one another can be accomplished in numerous ways utilizing various structures. The ground pulp is of course collected in any convenient manner, and thereafter subjected to conventional processing steps. The apparatus disclosed functions effectively on all known wood employed for mechanical pulping, and customary pre-treatrnent may be utilized as desired. in substitution for generally fiat grinding suriaces lying parallel with the pocket and sticks being abraded, convoluted pulp stories may of course be employed and in this case the motion of the pocket can be relatively slower and the power requirements would of course be reduced. This and other variations and modifications, including tie use of more than a single grinder pocket for each pulp stone, may of course be practiced without departing from the novel concepts of the present invention.

1 claim as my invention:

1. Apparatus for grinding pulpwood to obtain pulp therefrom, comprising a generally frusto-conical grinding member, means for rotating said grinding member, a housing for pulpwood positioned adjacent said grinding member, force applying means connected to said housing for advancing said pulpwood into grinding contact with said grinding member, track means disposed generally parallel to the surface of said grinding member and receiving said housing for movement .therealong, and motive means reciprocating said housing along the track means and laterally with respect to said grinding member to vary the location of grinding contact of said member with said pulpwood, whereby frequency of sharpening of said grinding member and the power require ments to effect grinding are reduced.

2. A pulpwood grinding mechanism comprising in combination a grinding rotor having a generally frusto-conical grinding surface, rotating driving means for driving the rotor in rotation about its axis, a support for pulp wood adjacent said grinding surface for holding pulpwood in grinding contact with a portion of the length of said surface, means operatively associated with said support for moving said pulpwood support toward the surface to hold the pulpwood in grinding contact, and linear drive means operatively associated with said support relatively moving the support in a general axial direction parallel to the grinding surf-ace to progressively change the axial location of grinding contact between the pulpwood and grinding surface whereby the pulpwood progressively engages areas of the grinding surface of changing diameter.

References Cited in the file of this patent UNITED STATES PATENTS 87,139 Burghardt Feb. 23, 1869 491,971 Schmidt Apr. 23, 1889 492,425 Eilers, Jr Apr. 30, 1889 571,019. Roberts Nov. 10, 1896 1,476,032 Aicher Dec. 4, 1923 FGREEGN PATENTS 20,141 Germany Nov. 22, 1882 41,073 Norway Mar. 9, 1925 49,672 ermany Nov. 25, 1889 629,394 Germany May 6, 1936 682,946 France Feb. 24, 1929

Claims (1)

1. APPARATUS FOR GRINDING PULPWOOD TO OBTAIN PULP THEREFROM, COMPRISING A GENERALLY FRUSTO-CONICAL GRINDING MEMBER, MEANS FOR ROTATING SAID GRINDING MEMBER, A HOUSING FOR PULPWOOD POSITIONED ADJACENT SAID GRINDING MEMBER, FORCE APPLYING MEAN CONNECTED TO SAID HOUSING FOR ADVANCING SAID PULPWOOD INTO GRINDING CONTACT WITH SAID GRINDING MEMBER, TRACK MEANS DISPOSED GENERALLY PARALLEL TO THE SURFACE OF SAID GRINDING MEMBER AND RECEIVING SAID HOUSING FOR MOVEMENT THEREALONG, AND MOTIVE MEANS RECIPROCATING SAID HOUSING ALONG THE TRACK MEANS AND LATERALLY WITH RESPECT TO SAID GRINDING MEMBER TO VARY THE LOCATION OF GRINDING CONTACT OF SAID MEMBER WITH SAID PULPWOOD, WHEREBY FREQUENCY OF SHARPENING OF SAID GRINDING MEMBER AND THE POWER REQUIREMENTS TO EFFECT GRINDING ARE REDUCED.

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