US 3406624 A
Description (OCR text may contain errors)
Oct. 22, 1968 Q H KUTCHERA ET AL 3,406,624
WOOD CHIP CRUSHER Filed Nov. 10, 1966 2 Sheets-Sheet 1 United States Patent 3,406,624 WOOD CHIP CRUSHER Don H. Kutchera, Oshkosh, Wis., and Donald A. Payant,
Child ersburg, Ala., assignors to Kimberly-Clark Corporatlon, Neenah, Wis., a corporation of Delaware Filed Nov. 10, 1966, Ser. No. 593,406 10 Claims. (Cl. 100-176) This invention relates to a mechanism for the crushing of wood chips.
Roll devices currently available for the crushing of wood chips suffer from a number of drawbacks. Chief among these are that it is difiicult to feed the crushing equipment at constant and high input rates. This we find to be for the reason that the chips fed to the roll system are not adequately gripped and carried by the mechanism. Also, wear on available crushing equipment is high requiring frequent down time, this being particularly a factor with rolls which are knurled and the like. The knurling, as might be expected, aids gripping of chips but is subject to the excessive wear and also to causing excessive fines in the crushed or cracked product.
A primary object of this invention is to provide a wood chip crusher mechanism of the roll type which is operable at chip input rates more than adequate for commercial operation and which is not subject to excessive wear or excessive production of fines in the operation of the equipment.
The invention will be more fully understood with respect to the following detailed description and accompanying drawings wherein:
FIG. 1 is a diagrammatic view illustrating mechanism for chip handling including a wood chip crusher roll device in accordance with the invention;
FIG. 2 is a view illustrating one embodiment of the chip crusher roll device for use in a system such as is illustrated in FIG. 1;
FIG. 3 is an end view of the rolls of FIG. 2 illustrating the action of the roll arrangement in chip crushing;
FIG. 4 is an enlarged and fragmentary view of a portion of a surface of one of the rolls of FIGS. 2 and 3; and
FIG. 5 illustrates a further embodiment of the chip crusher roll device in accordance with the invention.
Referring to FIG. 1, a hopper designated at 1 is arranged for feeding wood chips to a roll device 2 having a pair of cooperating cylindrical rolls indicated at 3, 4. The rolls are spaced slightly apart, about 0.005 inch to form a nip 5. In operation rolls 3, 4 rotate in the directions indicated by the arrows, and chips 6 fed from the hopper to the rolls are pressed and cracked in the nip. Such action does not break the chips into smaller fragments but simply opens them along natural lines of cleavage of the wood. The cracked chips pass to a suitable receiving zone 7 which may be an inclined screen; in such instance any small fines or small foreign material in the chips will pass to the reject box 8. Such fines may be recovered for other purposes. To avoid material accidentally being carried around by the rolls in their rotation, air blasts or wipers 9, 10 may be provided as indicated to maintain the rolls clear. The rolls themselves may be each driven by any suitable means (not shown) and the rolls may be movably mounted to adjust nip spacing 5.
The embodiment of the crushing device shown in FIG. 2 includes one ribbed roll 3 and one smooth roll 4. The ribs 11 of roll 3 are shown as relatively narrow and uniformly circumferentially spaced and spiraled. These ribs also project a uniform height above the roll surface; the roll surface, in accordance with the description herein and the claims, will be understood to be the surface 12 at the base of the ribs.
The ribs 11 (FIGS. 3 and 4) project to a very limited 3,406,624 Patented Oct. 22, 1968 ice height above the roll surface. We have found that this height should be not more than about 0.020 inch in instances where one roll of the set is ribbed (FIGS. 2-4). Such projection should also be at least 0.010 inch where one roll of the set is ribbed but may be less if the second roll has a rib height greater than 0.010 inch. In instances where both rolls are ribbed, the sum of the rib heights on both rolls we find should not exceed about 0.020 inch.
As illustrated in FIG. 3, the chip 6 entering the nip 5 tends to orient itself so that the smallest chip dimension is presented between the rolls. This factor plus the provision of the narrow ribs uniformly spaced about the circumference resulting in a considerable multiplicity of ribs leads (FIG. 3) to both a gripping and a supporting action by the rolls on chips in the nip. Such actions is in the nature of a feed pocket action with the spacings between ribs serving as the pockets.
Not only are the pockets designated for convenience by the numeral 13 shallow but, suitably also, the walls 14 of the ribs are angularly disposed (FIG. 4) to the roll surface. The angle 0 (FIG. 4) is preferably large but less than 90, suitably about to to prevent holding or snagging of the chips and to inhibit against the collection of material in the pockets.
The rolls 3, 4 are suitably of hardened steel. The ribs 11, it has been found, may be very suitably provided on the rolls by an engraving process. In this procedure a die conforming to the pattern to be formed on the roll is first made up. The steel roll itself is provided with a coating of wax. The die and wax-covered roll are then run together to open up waxed areas for the necessary attack by the acid in the etching process. The waxed areas opened up are those corresponding to the pockets. The operation, including the acid etch, is repeated a multiple of times for the purpose of adequately providing the very narrow rib areas and the relatively wide base areas. Referring again to FIG. 4, the roll surface width between ribs may suitably vary from about inch to 1% inches. The rib surface or land width is suitably about 0.12 inch to 0.20 inch and preferably about 0.18 inch. In effect, the roll has a continuous series of very shallow pockets which extend across the width of the roll angularly to the roll axis.
As illustrated in FIG. 5, the rolls 3a, 4a constituting the chip crusher may each be spirally ribbed and the ribs may be counteracting, that is, of opposite hand. The provision of ribs on each roll of the set is considered particularly desirable where the chips may be of such a nature that they tend to slip readily. Frozen chips are subject to slippage and are most suitably fed by a device having two ribbed rolls. Roll sets such as illustrated in FIG. 5 wherein the rib heights are 0.007 and 0.013 have been found very effective. Apparently it is not desirable that the rib height ratio of two rolls should exceed about 4: 1. For example, one roll may be 0.016 and the other 0.004 in rib height.
The pitch of the ribs does not appear critical. With rolls of about '24 inches diameter and a 36 inch face a pitch of inch per foot of face width up to 12 inches per foot of face width is apparently satisfactory. Rolls have been successfully operated having a 24 inch diameter and between 45 and ribs. Utilizing different pitches on the two rolls (FIG. 5) has been found a most suitable approach to the cracking.
It will be understood that this invention is susceptible to modification in order to adapt to different usages and conditions and, accordingly, it is desired to comprehend such modifications within the invention as may fall within the scope of the appended claims.
What is claimed is:
1. In a chip crusher for wood chips, a pair of cylindrical cooperating rolls defining a crushing nip and adapted for crushing wood chips, spiraled relatively narrow ribs unitormly spaced circumferentially on at least one of the rolls and projecting'to a uniform height above the roll from between about 0.010 inch to about 0.020 inch and designed to grip and roll chips passing in said nip to exert a compressive force on chips in the nip, said ribs having a uniform face width which is materially less than the roll surface distance between adjacent ribs.
2. A wood chip crusher according to claim 1 wherein the ratio of the roll surface distance between adjacent ribs to the uniform face width of a rib is at least 2:1.
3. A wood chip crusher according to claim 2 wherein the second of the rolls is also ribbed and the sum of the heights of a rib of each roll above the roll surface does not exceed about 0.020 inch and is at least 0.010 inch.
4. A wood chip crusher according to claim 2 wherein the second of the rolls is a smooth cylinder.
5. A wood chip crusher according to claim 2 wherein the ribs of a roll are engraved.
6. A wood chip crusher according to claim 3 wherein the height of the ribs of each roll above the roll surface is about 0.010 inch.
7. A wood chip crusher according to claim 3 wherein the height of the ribs of one roll above the roll surface is greater than 0.010 inch, the height of the ribsof theother roll above that roll surface is less than about 0.010 inch and the sum of the mentioned heights is not greater than 0.020 inch.
8. A wood chip crusher according to claim 3 wherein the height of the ribs of one roll. above the surface of that roll is not more than four timesthe height of the ribs of the other rollabove its surface.
9. A wood chip crusher accordingto claim 3 wherein the cylindrical cooperating rolls have a clearance of about 0.020 inch.
10. A Wood chip crusher according to claim 3 wherein the two ribbed rolls have opposite pitches.
References Cited 7 UNITED STATES PATENTS 292,577 1/1884 Penfield 241'-235 X 2,306,427 12/ 1942 Christman et a1. 24l-'235 X ANDREW R. JUHASZ, Primary Examiner.