US 2467878 A
Abstract available in
Claims available in
Description (OCR text may contain errors)
A ril 19 1949- H. W- BETH PULPSTONE Filed 1946' Patented Apr. 19, 1949 PULPSTONE Hugo W. H. Beth, Worcester, Mass, assignor to Norton Company, Worcester,.Mass., a corporation of Massachusetts Application August 1, 1946, Serial No. 687,583
The invention relates to segmental block type grinding wheels, and with regard to its more specific Efeatures to pulpstones.
:One object of the invention is to provide a stronger pulpstone. Another object is to provide a pulpstone in which cracking at the ends caused by heat difierential is eliminated. Another object is to provide a pulpstone with extra expansion joints at its ends to allow its abrasive blocks more chance to expand and contract and thus eliminate cracking caused by internal strains and heat differential. Another object is to prevent cracking due to heat differential at areas on the grinding surface which are partly covered by logs and partly by water. Another object is .to improve the pulpstone described in prior patent to Thure Larsson No. 2,141,608.
The invention accordingly consists in the tea tures of construction, combinations of elements and arrangements of parts as will be exemplified in the structure to be hereinafter described, and the scope of the application of which will be indicated in the following claims.
In the accompanying drawing illustrating one of many possible embodiments of the mechanical features of .this invention:
Figure 1 is a longitudinal sectional View of one half of .a pulpstone constructed in accordance with the invention and mounted upon a shaft.
Figure 2.is'a fragmentary end view of the pulpstone, partly broken away to show the anchor bolts.
Figure "3 is a development of the cylindrical surface of the pulpstone showing the shape of .the segmental blocks and the relative size of the small and large blocks.
' The improved construction may be embodied in many difierent types of pulpstone but is particularly applicable to that of the patent hereinb'efore mentioned. The present invention is herein shown as embodied in the type of pulpstone construction disclosed in said patent.
described in Patent No. 2,141,608, 1 provide a number of segmental blocks Iii of bonded abrasive material having the projected shape shown in Figure '3 which is an irregular hexagon formed by two trapezoids whose bases are coter- :minous. .I also provide a number of segmental dilocks Ialla of bonded abrasive material having the proiectedshape shown in .lifigure 3 which is an irregular pentagon formed by two traperzoids whose bases are .coterminous. The blocks Illa are of the shape and size of the blocks it cut in halves, as will be more fully explained.
Z filaims. (Cl. 51-206.4.)
a washer =23.
Each block Ill and ma of bonded abrasive material is composed of any desired type of abrasive such as-quartz, silicon carbide or fused alumina, the latter being preferred, bonded together with suitable bond material, preferably vitrified ceramic bond. Each block Ill and Illa is therefore formed of a mixture. of clay or frit with abrasive, suitably plasticized as by the provision of a suitable amount of plastic clay and the addition of water, then molded in a suitable mold and pressed under high pressure to cause the block to have sufiicient green strength for handling. After each block Ill and Illa comes from the mold, it has an outer cylindrical surface Ii bounded by radial surfaces I2 and, as shown in Figures 1 and 3, fiat surfaces 93, and, as shown in Figure 2, a. plane inner surface I4. While the blocks ii) and Ilia are in a green state, I bore holes I5 therein, four holes It in block It and two holes I5 in block Ida; each hole I-5 having grooves IS in its side walls. I then form reentrant grooves I! in the inside corners where the radial faces I2 join the-segmental face It. Each-groove II is adjacent to a corresponding groove I! in the adjacent block.
The blocks I0 and Ida are then iired in a kiln and the shape thus becomes permanent and the material is thereby converted to vitrified -bonded abrasivematerial. I provide a quantity of bolts 2% having heads 2i with grooves 22. I further provide an equal quantity of nuts 23, washers 24 and sleeves- 25. I place the sleeves 25 on the bolts 20 abutting the heads 21. I then place the washers 2 5 against the ends of the sleeve-25, place the nuts 23 upon the outer threaded ends 23 of the bolts 2:0 and tighten the nuts 23. Thereby the bolts 20 are placed under initial tension. I then place in each hole I5 a head 21 of a bolt 29 and fill the space with a suitable self setting cementfifi such as a mixture of Portland cement and iron filings. This has em'ellerit holding power. Each block it thus has four bolt-sit projecting therefrom and *each block Ifia "has two 'boltsazt projecting therefrom, each bolt t'll being encased by a sleeve 25 and having attached to it Each bolt 2i! is under initial ten.- sion such that a considerable force is needed to move the 'head '21 away from the washer 24 by even/a very slight distance. Each bolt 23' is securely lockedxto its block I 0 and Ifla by reason of the fact that the cement 3t interlocks with the grooves 16 in the block and also interlocks with the grooves 22 in the head 21'.
I provide a pair of center metal moldpieces (not shown), join them end to end and set them up upon an end mold piece of metal shaped to make the ends of the pulpstone as shown in the drawings. I arrange the blocks Illa and it upon the end mold piece and concentrically about the center mold pieces in circular courses to form a cylindrical wall, with a suitable filler material 36 such as described in patent to Larsson No. 2,054,171 between blocks. I lay the first or end course with blocks ma. I then lay courses with blocks until all but the top course which forms the other end of the pulpstone have been laid. The top or opposite end course I again lay with blocks Illa. I locate a plurality of steel reinforcing hoops 3'! suitably wired together and forming in effect a cage within the cylindrical space bonded by the blocks iii and Illa and the outside of the central mold pieces. The cage formed of the hoops 37 can be placed in position around the mold pieces, then the blocks built up around them with pairs of bolts 28 between successive levels of hoops 37. I use any temporary holding members such as clamps to hold the blocks i ll and l 0a closely together during construction of the pulpstone.
I form the blocks Ill with a hexagonal shape and blocks i 0a with a pentagonal shape to fit together about the periphery of the pulpstone, as well illustrated in Figure 3, which breaks the joints in obtuse angles between the blocks around the surface of the stone in order to provide continuous grinding at every iven point when work is held against the stone. By forming these angular end joints between the abrasive blocks I provide continuous zigzag joints in the direction of rotation of the wheel so that a continuous abrasive surface will be presented to work touching all points along the length of the pulpstone. In this manner I avoid non-abrasive tracks which would be formed by continuous or interrupted plane circular joints about the surface of the wheel were I to use abrasive blocks with square ends, or any part of whose edges lay in planes normal to the axis of the pulpstone.
When I have completed the hollow cylindrical wall of blocks It and la and installed the reinforcing member 3?, as described, I place the entire assembly in a vulcanizing oven at a suitable temperature to vulcanize the filler material 36. Preferably I have erected the abrasive structure and reinforcing members about the central mold pieces and upon the end mold piece upon a carriage or car so that the whole structure may be easily wheeled into the vulcanizing oven.
When the cylinder of abrasive blocks l0 and Illa has sufficiently cooled I pour concrete 40 in position between the central mold pieces and the blocks in and Illa and allow it to set. Before it hardens I shape the upper end of the stone the same as the shape of the lower end. I then strip the central and bottom mold pieces from the pulpstone.
The stone is now substantially complete except for features of construction of the mounting which need not be described herein.
In the grinding of logs for pulp, the logs are pressed against the stone at high pressure by hydraulic rams throughout the length of the stone except for a short distance at each end of the stone amounting to about six inches.
This tends to generate great heat in and throughout the segmental blocks where the logs touch. To counteract this, water is played upon the surface of the stone. However heat is still generated in the blocks where the logs touch them. At either end of the pulpstone, the blocks are rendered much cooler by the water. This creates a sharp heat differential about the periphery of the pulpstone at both ends.
In pulpstones heretofore constructed substantially by the method described in which the blocks 19 were of full size throughout the length of the grinding surface, this heat differential tended to cause cracking of the full length end segmental blocks due to the great internal strains. According to this invention I place small segmental blocks Illa at each end of the pulpstone so that there is a low heat differential from end to end of the pulpstone. The small dimension of the end blocks results in less dimensional change of the blocks and reduces internal strain. An extra expansion joint around the pulpstone at each end resulting from the use of the small end blocks allows the blocks more chance to breathe or expand and contract due to heating and cooling.
The construction herein described has in addition all of the advantages described in Patent No. 2,141,608.
It will thus be seen that there has been provided by this invention an article in which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved.
As many possible embodiments may be made of the above invention and as many changes might be made in the embodiment above set forth, it is to be understood that all matter hereinbefore set forth (or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.
1. In a pulpstone, a plurality of blocks of bonded abrasive material, said blocks being arranged in courses to form a hollow cylinder of revolution, a hollow concrete core inside of said cylinder of revolution, means attaching said blocks to said hollow concrete core, each of the blocks in the courses of said blocks at the ends of said pulpstone being appreciably shorter than each of the remaining blocks included between said courses measured in a direction parallel to the axis of the said pulpstone.
2. In a pulpstone, a plurality of blocks of bonded abrasive material, said blocks being arranged to form a hollow cylinder of revolution, a hollow concrete core inside of said cylinder of revolution, means attaching said blocks to said hollow concrete core, each of the blocks in the end courses of said blocks being of a length of each of the order of one half the length of the blocks included between said end courses measured in a direction parallel to the axis of said pulpstone.
HUGO W. H. BETH.
REFERENCES CITED The following references are of record in the Larsson Dec. 27, 1938