US2282887A - Wood grinding machine - Google Patents

Description

May 12, 1942. F. w. ROBERTS woon GRINDING MACHINE 4 Sheets-Sheet 1 Filed Dec. 30, 1938 JP'Eeo WORM ei-Dace? 40 H K Ira-PUMP May 1942' F. w. ROBERTS WOOD GRINDING MACHINE 4 Sheet s-Sheet 2 Filed Dec. 30, 1938 /N I/EN 70K ,4 TTOENEY.

May 12, 1942; F. w. ROBERTS WOOD GRINDING MACHINE 4 Sheets-Sheet 4 Filed Dec. 30, 1958 I INVENTOIF. 3am 77- Patented May 12, 1942 STATES WOOD GRINDING MACHINE Frederick W. Roberts, Lockport, N. Y.

' Application December 30, 1938, Serial No. 248,468

25 Claims.

' object of this invention is to provide a machine of this kind with means for varying the surface area of the grindstone which is operating on the wood. Another object is to provide, in a machine of this kind, an adjustable shield forvarying the surface area of the stone which is effective in grinding the wood.

Another object of this invention is to provide a machine of this kind with a feed ring of im; 1

proved construction for feeding the wood into operative relation to the grindstone. It is also an object of this invention to provide a machine of this kind with means for releasing and discharging the ground pulp immediately after the grinding of the same to prevent regrinding thereof.

Another object of this invention is to provide a machine of this kind with means for grinding the shims or thin remnants of wood, to produce wood pulp.

A further object is to provide a machine of this kind in which the freeness or particle size of the pulp may be controlled as desired.

Still another object of this invention is to provide a machine of this kind capable of using the maximum power available for driving a machine with a continuous high degree of efficiency, re-

gardless of the size or, freeness of the pulp. It is also an object of this invention to provideimproved means for controlling the rate of feed 'of the wood to the stone by means of the feed ring.

Another object of this invention is to provide in a machine of this kind adequate means for supplying water or other liquid to the wood which is being ground, for proper lubrication of the same. Another object is to provide in a machine of this kind a grindstone provided with means for passing water or other lubricant through the stone itself to the wood to be ground.

It is also an object of this invention to provide means for grinding an excess quantity of the wood into a very fine grade of pulp.

Other objects of this invention will appear from the following description and claims.

In the accompanying drawings:

Fig. l is aside elevation, partly in section, showing a grinding machine embodying this invention.

Fig. 2 is a longitudinal central sectional view thereof, on an enlarged scale, on line 2-2, Fig. .4.

Fig. 3 is a top plan view showing the wood hopper of the machine removed therefrom.

Fig. 4 is a sectional plan view thereof, on line 44., Fig'. 2.

Fig. 5 is a fragmentary sectional view of the shim grinding device of the machine, the section being taken on the line 55, Fig. 2.

Fig. 6 is'a similar sectional view of a modified form of shim removing device, the section being taken on line 6--6, Fig. 11.

Fig. 7 isa fragmentary sectional view of a spike or prong used in connection with the mechanism shown in Fig. 6.

Fig. 8 is an end view of the grinding machine shown in Fig. 1.

Fig. 9 is a transverse sectional elevation thereof, on line 9-9, Fig. 2.

Fig. 10 is a longitudinal sectional elevation thereof, on line Ill-Hi, Fig. 4.

Fig. 11 is a longitudinal sectional elevation of a grinding machine of slightly modified construction.

A represents a grindstone, which may be of any usual or suitable construction, and which is arranged eccentrically within a feed ring B, both the grindstone and the feed ringrotating in the same direction as indicated by the arrows in Fig. 2. The inner surface of the ring is formed in any suitable manner, for example, with teeth or projections I 6 which engage the wood and feed it toward the grindstone as the feed ring rotates. The periphery of the grindstone extends into close proximity to the inner periphery of the feed ring B so that by rotation of the feed ring about its axis the Wood to be ground is fed and wedged into the space between the feed ring and the grindstone so that the necessary pressure of the wood against the stone is produced. The stone is mounted upon'a suitable shaft H, which 4 is journalled in bearing pedestals I8 of any usual or suitable construction, which are preferably mounted upon a fixed foundation or base l9, see particularly Figs. 1 and 8. The shaft I! may be rotated by means of any suitable power device, such for example as an electric motor,

a water turbine, an engine, or the like.

The lower part of the grinding machine preferably extends into a trough or pit 2| formed in the supporting base I9. In the bottom of this I trough or pit, there is preferably arranged a base plate 22 which supports the'feed, ring B. The outer periphery of this feed ring preferably has a plurality of cylindrical surfaces or bearing faces 24, see for example Figs. 4, 8 and 9, which cooperate with suitable hearings on which the feed ring is rotatably supported. These bearings, of course, may be of any suitable or desired form and in the construction shown, a pair of bearing blocks 25 are employed having suitable bearing surfaces 26' of any bearing material capable of operating in water. The bearing blocks 25 are preferably pivotally mounted on adjustable base blocks 21, of any suitable construction. As illustrated, the base blocks, see particularly Fig. 8, are arranged in pairs, the two blocks of a pair being suitably connected by means of an integral connecting part 28 so that the supporting base blocks at each end of the machine may be simultaneously adjusted. The base blocks are guided for correct movement lengthwise of the machine by any suitable guide means or tracks, such as flanges 29, Fig. 8.

Any suitable means may be provided for adjusting the base blocks 21, and in the construction illustrated, adjusting screws 30 are employed which cooperate with upright flanges 31 which are securely arranged in flxed relation to the base 21 may be adjusted. 32, Fig. 1, represents lock or jamb nuts on the screws 30 for holding the base blocks in adjusted positions. If the bearings are of a kind which operate with water as a lubricant, they may be kept wet in any suitable manner, for example, by means of sprays discharged from spray pipes or nozzles 34, Fig. 2.

By means of the adjusting screws 30, the base blocks 21 may be adjusted relatively to each other to raise or lower the feed ring B to a limited extent, and also the base blocks may be adjusted in such a manner as to compensate for the wearing away of the grindstone, so that as the diam-- eter of the grindstone decreases, the feed ring-B may be moved to the right in Fig. 2, so that the feed ring B will remain in close proximity to the surface of the'grindstone. Any other means for adjusting the feed ring and grindstone relatively to each other may be employed, if desired.

The grindstone and feed ring are preferably confined within a fixed housing or casing, which, for sake of convenience, may be made in two parts, a lower part 35 being arranged to rest upon the bottom plate 22 in the pit 2|, and the upper part 36 being arranged to rest upon the upper edge of the lower part of the housing. These two parts may be suitably secured together in any usual manner, such for example, as by means of bolts 31 shown in Fig. 9, which extend through flanges of the upper and lower housing parts. The housing is provided with suitable means for rotating the feed ring and, in the particular construction shown, a worm 40 is provided which is arranged on the top wall of the upper portion 36 of the housing and extends through ahole in the top wall into engagement with teeth 4!. formed on the outer peripheral portion of the feed ring B.

The stationary housing, as is clearly shown in Figs. 4, 8 and 9, extends beyond the opposite sides of the grindstone and feed ring and the portions of the housing beyond the grindstone and feed ring serve to carry away the ground .wood. The upper housing part 36 is provided with an opening 43 through which the wood to be ground may be passed into the space between the feed ring B of the grindstone 8, and if des ed, this opening may be closed by a door 44 when no wood is being fed to the machine. I prefer to employ a suitable magazine or wood hopper in a portion of the space between the grindstone and the feed ring, so that the feeding of wood into the desired relation to the feed ring and grindstone is facilitated." This wood hopper includes a curved or slanting supporting wall 45 upon which the wood may be deposited and alongwhich it moves by gravity into correct relation to the lower portion of the grindstone. Opposite side walls 46 extend from thesupporting wall 45 into proximity to the inner surface of the feed ring B. These side walls are so positioned relatively to the opposite plate 22 and relatively to which the base blocks ends of the grindstone as to guide the wood into correct relation to the grindstone, so that none of the wood extends beyond the ends of the grinding surface of the stone. It will be noted that the inner surface of the feed ring B forms the fourth wall of the wood hopper. The wood hopper is suitably supported on the stationary housing of the machine and is provided at the upper portion thereof with a lateral extension 41 terminating at the feed-opening 43 in a side wall of the upper housing part 36. The wood to be ground may be fed through the feed opening 43 upon the projection 41 and to the upper surface of the wood supporting wall 45 of the wood hopper. The wood'will move down the inclined wall 45 into the wedge-shaped pocket formed between the grindstone and the feed ring B. The wood supporting wall 45 is also provided with an upright wall 49 at its upper end, which ensures the proper feeding of the wood from the feed opening 43 into correct relation to the grindstone and feed ring. By means of this construction, wood may be fed to the hopper through the opening 43 by means of a conveyor belt or other feed means and the hopper .also has sufficient capacity to contain a considerable supply of wood, so that constant attention to the feeding of wood to the machine is not necessary.

The wood hopper has the advantage that it maintains only the desired quantity of wood in engagement with the stone, any excess wood fed to the grinding machine being held out of contact with the stone. Consequently, the-machine will operate to maintain a substantially uniform area of grinding surface and a substantially uniform pressure per unit area of wood against the stone, and this results in a uniform grade of pulp, without requiring skill and care in feeding wood to the machine.

The wood hopper is preferably provided with laterally extending portions or flanges 50 extending outwardly from the side guard walls 46 into positions in whichtheir edges may be secured in any suitable or desired manner to the side members of the top portion 36 of the outer casing. For reasons hereinafter more fully explained, these flanges 50 terminate some distance above the bottom portion of the feed ring B and a number of spaced rods or bars 5|, Fig.

10, extends from the side walls 46 outwardly to the side walls of the housing for reinforcing the lower ends of the side walls 46 of the hopper and for ensuring their accurate positioning relatively to the grindstone. The lower portions of the side walls 46 are provided with holes or openings 52 through which the pulp may be discharged from the machine. The wood hopper may, of course, be of any other suitable construction, and while formed separately from the side walls of the housing in the construction shown, it is obvious that the hopper could be entirely or gravity and by the toothed or roughened inner surface of the feed wheel B. In order to avoid binding of the wood in this hopper, the wood supporting wall or shield 45 diverges slightly from the inner surface of the feed wheel B from the upper to the lower portion of the shield.

In order to control the area of the periphery of the grindstone with which the wood contacts, I provide means for adjusting the relationship of the hopper relatively to the grindstone. This may be accomplished in any suitable manner, and in the construction illustrated, I provide at the lower portion of the hopper an adjustable gate or extension of the lower end of the wall 45 of the hopper. This extension may be of any suitable or desired form, and in the construction 11- lustrated, an adjustable shield 55 is provided which forms substantially a continuation of the wall 45. This shield is of arc shape and may be guided for movement in any suitable or desired manner, for example, on the portions of the side walls 46 which extend below the lower end of the wood supporting wall 45 of the hopper. Guide flanges or projections are preferably provided on the side walls 46 with which the edges of the adjustable shield may slide, see Figs. 2 and 4. In the construction shown, the outer surface of the arc-shaped adjustable shield 55 engages or operates in close proximity to the inner surface of the hopper wall 45 so as to form substantially an extension thereof.

Any suitable or desired means may be employed for adjusting the shield 55 and for holding the same in adjusted position. In the construction shown for this purpose, the adjustable shield 55 is provided near the opposite sides thereof with internal gear teeth 51 with which pinions 58 mounted on a shaft 59 mesh. The shaft 59 extends transversely of the machine and through the side walls of the outer housing and is provided at each outer end' with suitable means for turning the shaft, such, for example, as a hand wheel 60. The shaft may have suitable bearings on any desired part of the machine, for example,

area. of the grindstone A, whichis exposed for grinding wood, is restricted to the maximum extent. As the shield 55 is raised, more of the surface of the grindstone is exposed for contact with the wood. This construction, consequently,

makes it possible to readily vary the grinding area of the wood, and thus the pressure of the wood against the grindstone per unit of area may be varied through a wide range. Thismakes possible an accurate control of the quality of the pulp with the minimum dressing of the stone. Other means for varying the grinding area of the stone may be employed, if desired.

In addition to controlling the surface area of the stone which acts on the wood, it is also desirable in connection with this apparatus to provide means for maintaining the desired pressure of the wood against the stone, and this can, of course, be readily controlled by controlling the rate of rotationof the feed ring B. This in turn can be accomplished by controlling the torque applied to the shaft to which the worm 40 is secured and many ways of applying torque in'this manner are known. I have, therefore, not illustrated in detail any mechanism for accomplishing known in the art, one being shown, for example,

in Hele-Shaw Patent No. 1,250,170 of December 18, 1917. These pumps commonly have their controls operating against a spring so that when a predetermined pressure is reached, the controls are shifted against the action of the spring into a neutral or non-delivery position, or just sufficiently on stroke to maintain the pressure and compensate for leakage. By adjusting the initial stress on the spring, the pressure which must be built up in order to set the pump'to no delivery position may be varied. One example of such controls is illustrated in Patent No. 2,072,141 of March 2, 1937. The coupling of a rotary hydraulic pump to a driven part and the operation of such a pump by liquid from a variable delivery pump which is driven by a motor is shown by way of example in Fig. 1 of Patent No. 1,243,223 of October 16, 1917. Any other means for supplying fluid at a constant pressure to the hydraulic motor and for setting this pressure as may be desired, may be employed. This pump is shown in Fig. 1 as supplying fluid to a hydraulic motor 61 which drives the worm 40 through the means for adjusting the delivery pressure of the hydraulic pump 66', and in this manner, the pressure of the wood against the grindstone "can be varied. If, for example, it is desirable because'of the nature of the wood or the condition 'of the surface of the grindstone to move the adjustable shield 55 into another position in which a greater or less surface area of the stone is used for grinding, it may be desirable to increase or decrease the pressure of the wood against the stone so that the grinding machine will consume the full power available for driving it and will produce pulp of the desired fineness Consequently, by varying the area of the stone exposed for grindingby adjusting the shield 55 and by varying the pressure with which the feed ring B presses the wood against this area, an accurate.

control of the grinding and'of the nature of the pulp produced, is provided and furthermore, the

,. mechanism operates automatically to keep the machine running at the desired load.

The feed ring B may be of any suitable or desired construction, but preferably this ring is made in such a manner that the ground wood can readily pass through the ring-for discharge from the machine without regrinding the fibers and thus reducing them to smaller size. For this purpose, the feed ring B comprises a pair of concentric and spaced apart annular walls 10 and It I thus forming a space between the two walls and H which are, nevertheless, rigidly connected with each other by means of the connecting ribs or posts 12, which may, if desired, be formed integral with the two walls. 'I'heinner ring 10 is also provided throughout its periphery with a relatively large number of discharge holes or openings 13 through which water carrying wood pulp may pass into the space between the Walls 10 and ii. This space between these rings, as clearly shown, for example, in Figs. 4 and 9, is open at opposite sides of the ring B so that water carrying ground wood pulp can pass from the sides of the feed ring into passages formed adjacent to the outer side walls of the lower part 35 of the housing.

The pulp receiving and discharging portion of the machine may be of any suitable or desired construction, and in order to keep the pulp out of contact with the grinding portion of the machine to prevent regrinding of the same, one or more pulp troughs may be .provided, which receive water and ground wood from the feed ring. Two such troughs are shown in the construction illustrated, and are arranged at opposite sides of the machine. If desired, one wall of each trough may be formed by the adjacent side wall of the outer housing of the machine. Each of these side troughs includes a curved peripheral transverse wall 11 extending inwardly from the adjacent side wall of the housing and joining at its inner edge with an upright wall 18, one edge of which conforms closely to the periphery of the feed ring B. Preferably suitable packing I9 is employed between this edge of the upright wall 18 and the feed ring B to form a substantially water tight joint between the feed ring and each of the pulp troughs. Since the outer wall of the feed ring B is imperforate, all of the water and wood pulp will be discharged through the opposite sides of the space between the inner and outer walls of the feed ringB, and will, consequently, find.

its way into one or other of the pulp troughs. Thesetrough's extend around approximately the lower half of the opposite sides of the feed ring, and as clearly shown in Figs. 1 and 2, the trough ment of the gate shown in that figure and shows that a part of the lower portion of the stone is submerged.

This arrangement of the troughs with the feed ring has the further advantage that any desired portion of the wood to be ground may be im-' peratures, since by means of the construction.

described, a relatively small quantity of water is confined in the troughs and in the'lower portion of the feed ring, so that this relatively small body tion of the feed hopper will be pressed into engagement with the surface of the stone, the extent of the pressure depending upon the force exerted upon the feed ring B. This in turn is increases in depth from the left of Figs. 1 and 2 to the right, so that the walls I8 increase in height accordingly.

The pulp troughs are provided with discharge passages or ducts 80 which extend outwardly through an end wall of the outer housing of the machineand through which water carrying the pulp is discharged from the machine. In the particular construction shown, these discharge passages are of rectangular cross section, and suitable means are preferably provided to con trol the level of the liquid in the discharge passages. A gate of any suitable or desired construction may, for example, be arranged at each discharge passage, and this gate may be of any suitable or desired construction. For example, a vertically movable plate 8| of this gate may be adjustable vertically by means of a handle 82 secured thereto. This plate may slide up and down relatively to the lower plate (not shown) and is guided between suitable guide rails 83 formed on the sides of the'discharge passage 80. If it is desirable, for example, to operate the machine with all or most of the grinding surface of the stone immersed in water, it is only necessary to raise the gate 8| to the desired extent, whereupon the water level will rise until it. flows over the top edge of the plate 8|. 84 in Fig. 2 represents the water level for the particular adjustcontrolled by the pressure for which the hydraulic pump 66 is set to operate. The wood which is pressed against the grindstone is accordingly ground and the wood pulp thus removed from the stone is washed away from the grinding area of the stone by water supplied by the usual sprays (not shown), or in any other manner. This water and the ground wood passes laterally toward either side through the openings 52' in the side walls 46 of the wood hopper or through the holes 13 of the inner wall 10 of the feed ring B. The ground wood passing through the holes 52 in the side walls enters directly into one or other of the pulp troughs. Other portions of the ground wood pass through the holes 13 in the inner wall of the feed ring B and pass toward opposite'sides of ,this ring into the pulp troughs. By thus providing ample passages through which water and wood pulp can flow away from the grinding surface, regrinding of the pulp is avoided to the maximum extent.

Means may also be provided, if found necessary, to prevent the formation of too much finely ground wood pulp in the portion of the machine at which the stone and feed ring approach closest to each other. Inthis portion of the machine, a comparativelyjarge rotary movement of the feed ring B results in a comparatively small component of movement toward the grinding surface, so that in this portion of the machine the wood is fed toward the stone more slowly than at other portions of grinding surface of the stone, where the stone and feed ring are spaced farther apart,- and this results in the formation of finer wood pulp, too much of which may be objectionable. This difliculty can readily be remedied H feed ring, so that wood fed by the feed ring will move into engagement with the face "and will,

consequently, be moved toward the grindstone much more rapidly than if it were allowed to continueto pass toward the surface of the grindstone,,as in the case of Fi 11. The face 01 of the wood guide member 86 may, of course, be inclined at different angles, depending upon the desired rate of feed of wood toward the grindstone.

The feed ring B is provided at intervals on its inner face with shallow grooves or'recesses 90 which are free from projections or wood gripping parts, and the wood deflecting member 86 is provided with forwardly projecting parts which extend into the grooves 90 soas to enter underneath the logs or pieces of wood and thus move them out of engagement with the prongs or projections on the inner wall of the feed ring B during rotation of this ring.

Any suitable means may be provided for lubricating the grinding surface of the stone to pre-' vent charring of the .wood. The usual shower or spray pipes (not shown) may, of course, be em- -ployed for this purpose, or the grinding surface of the stone may be entirely or partly submerged in water, by raising the gate 8! to the necessary level, as has been described. I prefer, however, to supply at least a part of the lubrication through the stone itself and this may be done in any suitable or desired manner. In the construction shown for this purpose, the shaft I l which drum the segments 95 of abrasive materialare mounted. Fluid from the passages 94 passes to the segments of the stone, and due to the porosity of these segments will find its way outwardly to the peripheral surface of the grind stone. Steam may be passed through the stone,

if it isdesired to heat the wood which is being operated upon, as well as to lubricate the surface of the stone, or water may be employed, and in either case, the flow of fluid directly out of the surface-of the stone moves the ground particles away from the grinding surface. Consequently, byproviding holes 52 in the side walls 66 and holessl't in the inner wall of the feed ring, the ground :wood can be more effectively moved away from the grinding surface, if fluid flows outwardly' from this surface. This prevents regrinding of the pulp, and thus produces longer fibered pulp, which inturn produces stronger paper.-

The lubrication of the surface-of the stone by means of fluid passed through the stone itself is particularly important in connection with a machine of the kind described, for the reason that in this machine, a large and continuous area of the stone is subjected to the grinding action of wood. Consequently, it is much more difflcult with a machine of this type to lubricate this entire grinding surface than in the case of the usual pocket type grinder, in which the pockets containing the wood are spaced apart so that shower pipes may be placed between pockets. In machines of the type herein described, the grinding area is continuous and no shower pipes can be introduced at intervals at this area, sothat wood at the trailing end of this area may be improperly lubricated, if shower pipes are depended upon. 'By forcing lubricant through the stone itself, all portions of the grind* ing surface are equally well lubricated and by submerging the wood in water, equally effective lubrication can be obtained.

The wood as it passes through the grinding area will be reduced to fairly thin pieces or shims which adhere to the roughened portion of the inner wall 10 of the feedring. These shims will pass-beyond thegrindstone to the portion of the machine at which the feed ring moves away from the grinding surface. Means are preferably provided for again subjecting these shims to the grinding action of the stone, and in order to accomplish this result, one type of shim grinding device is shown in Figs. 2, 4, 5 and 10. In this device, a wedge-shaped block or member I00 is arranged between the stone and the feed ring B at a portion thereof at which these parts diverge. The wedge-shaped' block I00 extends across the full width of the stone and feed ring I B and preferably has extensions IOI, see Fig. 5,

which are secured to the opposite side walls of. the housing. This wedge-shaped block also has at the thinner portion thereof extensions I02, which project into the groov'es of the feed ring B so as'to remove the shims from the feed ring in the same manner as the wood deflecting device 86 removes the wood out of engagement with the feed ring. These shims, consequently,

accumulate in the space between the wedgeshaped block I00 and the grindstone A.

A plate I06 extends across the top of the shim through holes in the brackets for adjustably securing the plate to the brackets. By releasing the bolts, the plate I04 may be adjusted toward and from the surface of the grindstone so that, as the space between the shim block I00 and the surface of the grinds tone becomes filled with these shims, they are forced into the space between the stone and the plate I04 because of the movement of the stone and the feed ring. Ad-

justment of the plate will, of course, only be necessary when the position of the feed ring B is adjusted and to compensate for wear of the stone.

In the construction shown in Figs. 6 and 11,

shown in Figs. 6 and 11, a transversely extending rod or bar H0, the ends of which may extend through the side walls 66 of the wood hopper and through the side walls of the machine housing and may be securely clamped in placeon theside walls by means of nuts I I I engaging threaded ends of the rod or bar. At suitable intervals along the rod or bar, wedge-shape scrapers II2 are provided which are rigidly secured to the rod or bar H0 and extendinto the grooves 90 on' the inner wall of the feed ring B. These wedgeshaped scrapers H2, consequently, remove the shims or slabs of unground wood from the feed ring and permit them to drop into the woodhoppen In order to ensure the carrying of the shims by the feed ring B to the upper portion thereof, spikes or prongs are preferably provided on the inner surface of the feed ring. These spikes or prongs may be of any suitable or desired construction. For example, as illustrated in Fig. 7, spikes HQ are formed on the ends of short threaded studs H which are suitably secured in threaded holes on the inner wall of the feed ring. The outer ends of the studs may be provided with suitable heads by means of which they can be secured in place in the threaded holes. Consequently, the studs can be readily removed and replaced by others in case the spikes or prongs H S become broken or damaged. The sharp prongs or projections H4 are so formed as to pierce into the wood and retain the shims on the feed ring until released by the wedge members H2. When these prongs or projections are employed, they will generally extend inwardly from the inner wall of the feed ring to a greater extent than the teeth or projections l6 heretofore referred to, and consequently, when these spikes are used, the feed ring B is spaced farther from the grindstone A. When this arrangement for grinding shims is employed, a wood deflecting member such as shown at 88 is ordinarily not used. Any other means for grinding shims or slabs of wood which have passed between the feed wheel and the grindstone may be employed, if desired.

The grindstone may, of course, be dressed by means of any usual or suitable dressing rig and no means for dressing the stone are shown in the drawings. There is, however, provided in the outer housing of the machine a door H6, Fig. 1, through which access may be had to the interior ofthe housing for operation of a stone dressing rig, or for other purposes.

In addition to the advantages already referred to which result from the grinding machine herein described,'further advantages result from the particular construction illustrated. For example, the formation of the feed ring B with an outer cylindrical imperforate wall and an inner perforate wall spaced therefrom results in several advantages.

pulp or ground wood can be readily floated away gear are in no way interfered with by the water or wood pulp. Furthermore, the feed ring maybe adjusted relatively to the grindstone without interrupting the operation of the machine, since the adjusting means are accessible'at all times.

The machine described has the further advantage that it is very adaptable to produce various grades or finenesses of wood pulp without varying the amount of power consumed by the machine. This can be accomplished by varying the pressure applied to the feed ring, in conjunction with variations in the position of the shield 55. For example in Fig. 2, the: shield 55 is shown in its lowest position, and consequently, the machine will operate at its maximumcapacity only when the wood is pressed against the stone with the maximum pressure. If less pressure is de- In the first place, the wood sired, this can, of course, be accomplished by reducing the pressure at which liquid is delivered to the hydraulic motor 671 but this results in less power consumption, and the grinding machine will then not operate at its maximum capacity. If, however, the shield is raised to expose a larger surface of the stone, the pressure per unit area on the wood may be decreased without decreasing the pressure of the fluid delivered to the motor 61 and the-machine will. consequently, continue to operate at its full capacity and at a reduced pressure per unit of grinding surface. By varying the pressure exerted on the feed ring by the motor 61 and by adjusting the shield 55, many variations of pressure and total grinding surface may be made, and consequently, the quality as well as quantity of wood pulp produced may be varied and the machine can be kept in operation at its maximum capacity under the various operating conditions. This adjustability of the machine is particularly desirable in cases where power is purchased by the paper mill on a peak load basis,.in which case, the automatic control mechanism including the hydraulic pump 66 and motor 61 serve at all times to prevent the machine from consuming more power than its intended peak load, and in combination with the adjustable shield, it is also possible to produce the desired grade of wood pulp without decreasing the load consumption by the machine.

I claim as my invention:

1. A wood grinding machine including a rotary grindstone, a feed ring arranged eccentrically about said grindstone with a portion of its inner surface in close proximity tothe outer surfaceof said grindstone, and rotatable to feed wood against the surface of said grindstone, and .a wood magazine located within said feed ring for conducting wood to the portion of the machine at which said stone and said ring converge and having a wood supporting wall spaced from said feed ring, said wall and said feed ring diverging to form a magazine of gradually increasing space between said wall and ring in the direction of movement of the wood.

2. In a. wood grinding machine of'. the type having a rotary abrasive grindstone mounted for,

closely to the periphery of the stone to form a wedge-shaped space between said ring and said stone, into which wood is forced by said ring to press against the grindstone, the combination of an arcuate wood retaining wall extending from above to below the axis of the, feed ring in a direction substantially parallel to the axes of said grindstone and feed ring and extending into a portion of said wedge-shaped space, said wall, when wood to be ground is placed into the space between said wall and said feed ring, permitting wood to fill only a portion of said wedge-shaped space, to provide a substantially constant pressure area in which wood is pressed into contact with the stone. I

3. A wood grinding machine including a rotary grindstone, a rotatable feed ring arranged eccentrically about said stone with a portion thereof approaching closely to the periphery of said stone, said-stone and said ring being rotatable about substantially horizontal axes, a relatively stationary wall arranged in and spaced from said ring and forming therewith a magazine for receiving wood at the upper portion thereof and for discharging woodat the lower part thereof ly rotatable and positively driven feed ring arranged eccentrically about said stone with a portion thereof approaching closely to but out of contact with the periphery of said stone, said grindstone and ring being rotatable about substantially horizontal axes, the combination of a wood magazine in said ring for receiving wood at the upper portion thereof and for discharging wood at the lower part thereof to said approaching portions of said ring and stone, the location of the lower end of said magazine with relation to said grindstone determining the area of the stone exposed to grinding, the interior dimensions of said magazine in a direction radially of said ring increasing in the direction of movement' of the wood in said magazine to prevent binding of the wood in said magazine.

5. In a wood grinding machine including a rapidly rotatable abrasive grindstone and a slowly rotatable and positively driven feed ring arranged eccentrically about said stone with a portion thereof approaching closely to the periphery of said stone at the lower portion thereof, said grindstone and ring being rotatable about substantially horizontal axes, the combination of a wood magazine without said ring for receiving wood at the upper portion thereof and for-discharging wood at the lower part thereof and including a rigid wall extending substantially parallel to said axes for keeping wood in said magazine out of engagement with the stone, and a shield forming substantially a continuation of the lower portion of said wall and adjustable relatively to said wall and said stone in a direction for exposing a greater or less area of said stone to act on the wood.

6. In a wood grinding machine'of the type including a cylindrical grindstone and a revolvable substantially imperforate open-ended feed ring arranged eccentrically about said grindstone for pressing wood tobe ground against the surface of said grindstone, means for supplying water to the portion of the stone against which wood is pressed, and a housing in which said grinddrical grindstone mounted for rapid rotation, a slowly revolvable feed ring arranged eccentrically about said grindstone and having inner and outer annular walls spaced apart and secured to each other to form a space between said walls, the inner wall of said feed rin'g serving to press wood into grinding engagement with said stoneand being provided with perforations to permit water carrying ground wood to flow into the space between said walls, and said outer wall being imperforate, and .means for discharging water carrying ground wood from said space at an end'of said outer wall of said ring.

stone and feed ring are arranged, the ends of said feed ring and said grindstone being spaced from the adjacent walls of said housing, the combination of a pair of separated troughs arranged in the lower portion of said housing beyond the ends of said feed ring and into which wood pulp is discharged withwater by gravity from the ends of said feed ring for discharge out of said housing, said troughs being spaced apart to keep wood pulp and water out of contact with the middle portion of the exterior of said feed ring.

7.- A wood grinding machine including a c'ylindrical grindstone, a revolvable feed ring arranged eccentrically about said grindstone for feeding wood into engagement with said grindstone and having a substantially imperforate outer cylindrical face, stationary troughs arranged at the ends of said feed ring and intowhich water and ground wood is discharged from the ends of said feed ring, and bearing surfaces on the exterior of said feed ring and which pass between 7 said troughs during the revolution of said feed ring.

9. A wood grinding machine including a cy lindrical grindstone mounted for rapid rotation,

a slowly revolvable feed ring arranged eccentrically about said grindstone and having inner and outer annular walls. spaced apart and secured to each other to form a space between said walls, the inner face of the inner wall of the feed ring being provided with projections adapted to engage the wood for pressing the same into grinding engagement with the stone and being provided with perforations through which .water carrying ground wood may flow into the space between said walls, the outer of said walls being substantially imperforate and the space between said walls being open at opposite ends of said walls for the discharge of water and ground wood from said space.- a

10. In a wood grindingmachine including a cylindrical grindstone, mounted for rapid rota-' tion about a substantially horizontal axis, and a slowly revolvable feedring arranged eccentrically about said grindstone with the lower portion thereof approaching into close proximity to but out of contact with said grindstone, said feed ring having the inner face thereof roughened to press wood into engagement with the lower face of said grindstone and having a substantially imperforate outer surface, the combination of a stationary trough into which water and ground wood is discharged from said feed ring and having a substantially water-tight connection with said outer surface of said feed ring to maintain a portion of the outer surface of said feed ring out'of contact with water and wood pulp, and adjustable means for maintaining water at the desired level in said trough and within said feed ring for submerging wood in said feed ring adjacent to the grindstone.

11. In a wood grinding machine including a rotary grindstone mounted for rapid rotation about a substantially horizontal axis, and a slowsaid ring and arranged substantially parallel to the axis of said stone for limiting the surface area of the stone against which wood is pressed by said ring, and means for adjusting said shield to vary said area. l

12. In a wood grinding machine including a rotary grindstone mounted for rapid rotation about a substantially horizontal axis and a slowly rotatable positively driven feed ring arranged eccentrically about said stone with a portion thereof approaching closely to but out of contact with the periphery of said stone at the lower portion thereof at a pressure depending upon the rate of rotation of said feed ring, said feed ring forcing wood' to be ground into engagement with said stone, the combination of an adjustable shield extending into the space between said 6 stone and said ring and arranged substantially parallel to the axis of said stone for varying the area of the stone against which wood is pressed bysaid ring, and means for applying a variable force to said feed ring in a direction to rotate 10 the same, whereby the grade of pulp produced may be varied as desired while the machine is operating near maximum capacity.

13. A method of grinding wood to produce a wood pulp on a wood grinding machine, while operating the machine at substantially constant load, said method including pressing wood to be ground against a portion of the peripheral surface of a grindstonavarying the pressure at which the wood is pressed against said stone to produce different grades of pulp, and varying the area of the portion of said surface against which the wood is pressed by increasing the area when said pressure is decreased and decreasing the area when said pressure is increased, to maintain a substantially constarit load on the grinding machine.

14. In a wood'grinding machine including a rapidly rotatable grindstone and a slowly rotatable feed ring arranged eccentrically about said stone with a portion thereof approaching closely to the periphery of said stone for urging wood into contact with said grindstone, the combination of means for automatically maintaining a substantially constant pressure of the wood against the grindstone, including a hydraulic variable speed motor for imparting rotation to said feed ring, means for supplying fluid at different predetermined constant pressures to said motor, and means for varying the areaof that portion of the surface of the grindstone against which wood to be ground-is pressed by said feed ring, whereby different grades of pulp may be produced while the machine is operating approximately at its maximum capacity. 45

15. In a wood grinding machine including a rapidly rotatable grindstone and a slowly rotatable feed ring arranged eccentrically about said stone with a portion thereof approaching closely to the periphery of said stone, to form a wedge-shaped pocket between said ring and said stone in which wood is forced by said ring into engagement with said stone, the combination of a stationary deflector arranged in said wedgeshaped portion near the part thereof of smallest dimension and-which deflects some of the wood from said feed ring toward the stone and forces said wood under pressure against said grindstone at a greater rate of speed than said feed ring. 0

16. A wood grinding machine, including a-rapidly rotatable grindstone, a slowly rotatable feed ring arranged eccentrically about said stone with a portion thereof approaching closely to the periphery of said stone, said feed ring by its rotation forcing wood into engagement with said stone, and stationary deflecting means arranged in the space between said stone and ring slightly in advance of the portions thereof extending closest to each other and having an inclined face which deflects wood from said ring to said stone at an inclination to the inner periphery of said ring and which forces said wood to said grindstone at a greater speed than said feed ring.

17. A wood grinding machine including a rapidly rotatable grindstone, a slowly rotatable feed ring arranged eccentrically about said stone with a portion thereof approaching closely to the periphery of said stone and having a roughened inner surface for feeding wood into contact with said grindstone in the portion of the machine in which said ring and the surface of said stone converge, means for removing from said ring wood which has passed the converging portion of said ring and stone, and means for again subjecting said wood to the grinding action of said stone, said first means comprising a wedgeshaped block having the leading end thereof shaped to removed wood from said ring at the portion of the machine at which said ring and stone diverge, said second means including an adjustable plate at the opposite end of said wedge block which is adjustable toward and from said stone and between which and said stone the wood removed from said ring by said wedge must pass.

18. A wood grinding machine including a rapidly rotatable grindstone, a slowly rotatable feed ring arranged eccentrically about said stone with a portion thereof approaching closely to the periphery of said stone, said ring feeding wood into engagement with said stone at the portion of the machine at which said stone and ring converge, a wood magazine within said ring having an open upper portion for receiving wood and a lower portion for discharging wood into said converging part, said ring having the inner face H thereof provided with projections for engaging the wood, and means arranged above said open upper portion of said magazine for removing from said ring wood which has passed through the space between said ring and stone, to permit said wood to drop into said magazine.

19. A wood grinding machine including a rapidly rotatable grindstone, a slowly rotatable feed ring arranged eccentrically about said stone with a portion thereof approaching'closely to the periphery of said stone, said ring feeding wood into engagement with said stone at the portion of the machine at which said stone and ring converge, a wood magazine within said ring having an open upper portion for receiving wood and a lower portion which discharges wood into said converging part, said ring having the inner face v thereof provided with projections for engaging the wood, means arranged above said open upper portion of said magazine for removing from said ring wood which has passed through the space between said ring and stone, to permit said wood to drop into said magazine, said ring having annular portions free from said projections, and wedge-shaped portions projecting from said wood removing means into engagement with said annular portions for wedging the wood out of engagement with said projections.

20. A wood grinding machine including a rapidly rotatable grindstone, a slowly rotatable feed ring arranged eccentrically about said stone with a portion thereof approaching closely to the periphery of said stone, said ring moving wood to be ground into engagement with said stone at v the portion of the machine at which said stone and said ring converge, said ring having openings therein through which fluid and wood pulp may pass away from the grinding surface of said stone, and means for supplying-lubricant to the surface of said stone from the interior of said stone, for carrying ground wood from said stone to said openings in said ring.

21. A wood grinding machine including a cylindrical grindstone, a revolvable feed ring arat the desired level, whereby wood in the lower portion of said 'feed ring may be submerged in water. e

22. In a wood grinding machine including a rapidly driven rotary abrasive grindstone and a slowly rotatable positively driven feed-ring arranged eccentrically about said stone with a portion thereof approaching closely to the periphery of said stone to form a wedge-shaped space between said ring and said stone, the combination of a wood magazine in said ring for receiving wood at the upper portion thereof and having the lower part thereof extending into said space and having a lower open end for discharging and including a wall arranged between said stone and said ring and holding the wood in said magrapidly rotatable grindstone, a slowly rotatable wood to said approaching portions of said ring and stone, said magazine including a part spaced from and diverging downwardly from the adjacent portion of said feed ring and terminating adjacent to said grindstone, to keep wood in said magazine out of contact with said stone, to maintain a substantially uniform pressure area of said stone in engagement with wood to be ground.

23. In a wood grinding machine including a rapidly driven rotary grindstone and a slowly rotatable positively driven feed ring arranged eccentrically about said stone with a portion thereof approaching closely to the periphery of said stone to form a wedge-shaped space between said ring and said stone, the combination of a wood magazine formed in part by said ring azine out of contact with said stone, the rotation of said ring feeding wood through said magazine and compacting the wood below said magazine into a substantially unitary mass, and pressing said mass against the portion of saidstone arranged below said wall, and means for varying the position of the lower end of said wall relatively to said stone to vary the area of said stone contacting with the wood.

24. A wood grinding machine, including a feed ring arranged eccentrically about said stone with a portion thereof approaching closely to th periphery of said stone, said feed ring by its rotation forcing wood into engagement with said stone, said feed ring having a roughened internal surface and having annular grooves formed on the inner face thereof, a wood deflecting member arranged in the portion of the machine at which the stone and ring during their rotation approach closely'to each other and having an inclined face for deflecting wood from said ring and pressing said wood toward said stone at a greater speed than said feed ring, said deflector also having projections forming continuations of said inclined face and extending into said grooves.

25. A method of grinding wood to produce wood pulp of different desired qualities at substantially the maximum capacity of the grinding machine, which includes varying both the area of that portion of the surface of the stoneon which the'wood is pressed, and the pressure with which the wood is pressed against the stone, in such manner that when the pressure is increased, the area is decreased and when the pressure is decreased, the area is increased. to place the desired-load on the grindstone.

. FREDERICK W. ROBERTS.

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