CA2023282C - Pulpstone - Google Patents

Abstract

ABSTRACT
A segmental grinding stone, particularly a pulpstone, wherein the segments are assembled to a ring or central support portion through a bolt which passes through a recessed hole in the face of the segment and screws into a nut means.

Description

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Docket BV-2399 PULPSTONE

DAN D. BACIC
32 Goldcrest Drive Stoney Creek, Ontario L8G 4T9 Canada TECHNICAL FIELD
This invention relates to an improved pulpstone or grinding wheel having an abrasive periphery that is filled with a concrete core and the method of making the 5 pulpstone. More particularly it is concerned with a novel structure for holding the abrasive segments of a pulpstone together whereupon they are then used as a form for molding the concrete core that is poured into the assembled annulus of segments for completing the attachment of the segments 10 to the periphery of the core.
Background and Information Disclosure Statement The following U.S. Patents arP representative of the most relevant prior art known to the applicant at the time of the filing of this application.
U.S. Patents 933,603 Wagg September 7, 1909 2,369,639 Ball et al. February 20, 1945 2,453,748 Fisher et al, November 16, 1948 2,887,276 Minarik May 19, 1959 4,351,486 Schmoller et al. ~eptember 28, 1982 The conventional pulpstone is usually made by assembling a plurality of abrasive segments that are then filled with a concrete core whereby to form an abrasive periphery integral with a central core made of concrete, or 25 in some instances it has been proposed to assemble such segments on the periphery of another form of a rigid body like a cylindrical metal annulus. The segments are frequently provided with integral studs extending radially inwardly toward the center of the pulpstone, which segments 30 are assemblecl together with a concrete core by means of ~32~

these studs being bolted to the reinforcing cage of the concrete core, the studs subsequently becoming permanently bonded and sealed within the center core.
The patent to Fisher et al. is of general 5 interest only in showing an abrasive grinding wheel for the surface finishing of glass plates wherein the grinding wheel means is constructed with abrasive segments bolted to a circular supportin~ ring means. The grinding wheel of this disclosure utilizes the exposed ends of the segments 10 for grinding the glass sheet being polished as distinguished from the periphery of the wheel as with a pulpstone used for grinding logs to make a wood pulp. As the segments of the glass plate grinding means wear down, the successive rings that support the segments may be 15 removed to provide a continuing support for the remaining portions of the abrasive segments forming the wheel.
The remaining patents cited above all show grinding wheels for usP in making wood pulp. Wagg and ~inarik each show a bolting arrangement for attaching a 20 plurality of abrasive elements to a centrally disposed metal cylinder or ring. The Wagg patent teaches the use of a molten filler flowed into place between the segments and the mounting means therefore to preclude any movement of the segments relative to it's metal support ring when the 25 wheel is in use. The Minarik disclosure uses an eye-bolt with each segment, the eye-bolt being carried on a crossrod that passes through the center of each of the indi~idual segments of a pulpstone to fasten the individual segments to the surface of a cylindrical cast iron drum. In this 30 construction the individual segments are mounted on the drum with spaces between all sides of the individual segments to make passages available for the circulation of a fluid from the cylinder through the spaces to the grinding surface of the stone to assist in the grinding 35 process.
Ball et al. provides a wheel wherein a unitary solid annulus constitutes the grinding element of a pulpstone, as distinguished from a pulpstone fabricated 2~2~2~2 with a plurality of individual segments assembled together on the periphery of the grinding stone to form the grinding surface of the pulpstone structure. This Ball et al.
disclosure provides for the attachment of the annulus to a 5 metal ring positioned concentrically within the annulus and threaded spokes that have one end integrally attached to the respective side walls of the annulus that are used to tension the annulus around the metal ring to prestress the abrasive ring against the stresses produced by the grinding 10 process. The central opening in the Ball et al. annulus is filled with concrete after the annulus has been mounted on the metal ring and the nuts 11 by which the tension in each of the respective spokes is adjusted then become permanently sealed within the concrete core.
Schmoller et al. disclose several systems for mounting abrasive segments on the periphery of pulpstones.
In Figs. 1-~ a very general disclosure sets forth a bolting arrangement for supporting such segments on a concrete core and in Figs. 6-11 the segments are shown mounted on a steel 20 ring or cylinder. In each instance the segments are each provided with nut means situated within the segments that are simply threaded onto bolts extending outwardly from a support cylinder to hold the several segments onto their support means, there being no detailed discussion of the 25 particulars of the bolting system except as the bolt structures are modified to promote the circulation of water to the surface of th~ pulpstones through the segments which are made somewhat porous or are spaced apart to permit the water to flow outwardly to the surface of the pulpstone.
30 Brief Description of This Invention - An improved bolting arrangement and method of completing the assembly of a pulpstone is shown herein for mounting a plurality of abrasive segments on the periphery of a pulpstone. The invention is concerned with the 35 mounting of the individual segments on the concrete core of an otherwise conventional type of such pulpstones and makes use of the internal reinforcing means of the core for supporting the segments.

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In the practice of this invention, the plurality of segments that are to be carried on the periphery o* the stone, are f~rmed into an annular or a circular assembly of the segments that resembles a "chimney". This chimney is 5 constructed by first using a number of appropriately shaped abrasive segments to form a ring or circular assembly and then another circular assembly of the segments is built up on the first ring and so forth to finally assemble all of the segments into the cylindrical chimney of a desired 10 height. Then certain of the reinforcing rings for the concrete core that is to be subsequently poured into the chimney and cured to form the support core for the segments, are fitted concentrically within the chimney.
Each one of the several segments in the chimney 15 are provided with a plurality of bolt holes extending from their grinding surfaces radially inwardly to receive bolt means. Suitable seating means are provided in each hole and either the head of the bolt or the nut means for the bolt is engaged on the seat with a somewhat plastic or 20 deformable washer fitted between the seat and the engaged element. The shank of the bolt extends radially inwardly so that the inner end of the bolt can be supported from the reinforcing rings.
After the chimney has been built and the bolt and 25 nut means have been assembled together with the reinforcing rings and drawn up to the proper tension, the remaining reinforcing structure is built up within the center of the chimney and the concrete is poured into the mold thus formed. When the concrete is cured the wheel structure may 30 be finished.
The preliminary molding of the green segments with the holes for the bolts for securing the segments to the reinforcing rings makes it possible to improvs the firing process for the initial fabrication of the segments 35 themselves. The production of a finished segment with such bolt holes also simplifies the assembly process for completing the wheel structure. Since the green molded segments are processed with a plurality of bolt holes 2 ~ ~ 3 .d ~ 2~
extending entirely through the mass of the segment, when the abrasive grains and the bond mixture for the segments is fired to produce the ultimate abrasive segment, the burn can be completed in a shorter time and with the expectation 5 that a better quality of product will result since the heat to cure the segment can blow more rapidly and evenly throughout the mass being fired. As will be made more fully evident from the discussion below, these fired segments can be more easily and quickly assembled together 10 with the reinforcing rings of the core means as compared with the procedure heretofore required to complete the assembly of conventional pulpstones and with a saving in time needed for the production of the known product.
In the Drawings Figure 1 is a vertical sectional view partly broken away,-~showing one of the several bolt means and reinforcing ring assemblies used for mounting an abrasive segment on the periphery of a pulpstone, included in the showing is the broken away segment mounted on a cured 20 concrete core;
Figure 2 is a detailed vertical side view taken at 90 with re ~ ct to the view in Fig. 1 showing a side view of the nut means for cooperating with the bolt as shown in Fig. l; and Figure 3 is a vertical sectional view like Fig. 1 showing an alternate form of bolt and nut arrangement.
Description of the Preferred Embodiments The present invention is concerned with the mounting of a plurality of abrasivs segments on the 30 periphery of the more popular types of pulpstones having a concrete core generally similar to the structurPs shown in the above mentioned patents to Minarik and Schmoller et al., Figs. 1-5. Such plupstones are cylindrical in shape and may have a diameter falling within a range of from 50"
35 to 75" or more and a length of from 27" to 90" or more.
The present invention makes use of a poured center core of reinforced concrete and the abrasive blocks are supported in part from certain of the reinforcing rings centered in , -`-" 2 ~

the core to hold the segments on the periphery of the core to produce a pulpstone adapted to be rotatably driven in the known type of pulp grinding machine to convert logs into a pulp for the manufacture of paper products and the 5 like.
The abrasive segments can be of any known shape having side edges that can be interfitted to completely cover the peripheral surface and usually the edges of the individual segments are angularly related to produce the 10 best grinding relationship between the ultimate abrasive surface of the pulpstone and the wood being ground. The preferred segments used on this pulpstone are roughly 7" by 12" and are about 5" thick. None of these dimensions, however, are critical.
The segments used in this invention are formed of a known abrasive mix and ceramic bond that is first molded in the usual manner. The specified mix is pressed into the proper shape and is provided with a plurality of holes for the bolts as will be explained more fully below, said holes 20 extending radially inwardly from the grinding face of the segment. The molded segment having a plurality of holes therein extending through the body of the segment is then fired and because the plurality of holes extend entirely through the body it may be fired in the conventional 25 process and the heat will be distri~uted more rapidly and evenly throughout the body of the mass being fired. This makes for a more uniform and faster firing process.
Referring to the drawings, a segment 10 that is shown partly broken away is provided, which segment 30 preferably has two or more spaced apart holes to receive bolts as will appear more fully below, one of which holes is shown in Fig. 1. The hole is perpendicular to the grinding surface 12 and is disposed to extend radially inwardly from that surface. The hole has an upper section 35 with a larger diameter 14 at its top end referring to Fig.
1 that is provided for the purpose of receiving the head 16 of a bolt that has a shank portion 18 that fits neatly into - 2~3~
the lower section 20 of the hole, which section has a smaller diameter than the upper section 14.
These segments are made to have the conventional shapes whereby to be assembled in the usual pattern in a 5 chimney for making a pulpstone and thus a plurality of these segments may be fitted together by forming a ring of the end segments in a fixture for holding the segments in a precise position and spaced apart with a conventional rubber-cork gasket or similar compressible material between 10 all the adjacent sides of the abutting segments. When the first ring has been assembled, a second ring of segments is laid precisely on top of the completed ring and the gasket material is put in place between all of the abutting side faces of the segments in that ring. Succeeding rings are 15 similarly precisely aligned with the other segments with the usual gaskets between the segments until the desired pulpstone wheel length has been assembled. This precision assembly of segments may then be fired or baked or otherwise treated to cure the gasket material, to complete 20 the chimney that is then ready for further processing.
When the chimney-like assembly has been baked or otherwise solidified, the outer reinforcing rings for the concrete center that is to be subsequently poured into the center of the chimney, are assembled within the annulus 25 formed by the segments. The outer cage of these reinforcing rings is supported on suitable straps, fixtures or other known means (not shown), two of which rings 24 and 26 are shown spaced on the opposite sides of the nut means and the bolt hole shown in Fig. 1. These rings are held 30 concentrically spaced within the annulus of the assembly of segments and the reinforcing rings are positioned to cooperate with the bolts that are fitted into the plurality of holes in each of thP segments. For this reason the reinforcing rings in the outer cage of the reinforcing 35 rings are mounted on their supporting means in closely spaced pairs such as 24 and 26, with the two rings of each of the respective pairs spaced closely to but on the 2~3.~
opposite sides of each of the vertical center lines that extend through the centers of all of the holes 14-20.
The view shown in Fig. 1 shows a detailed view of a bro~en away portion of a segment that is shown in its 5 assembled relationship on the periphery of the concrete center core that has been poured and cured within the annulus of abrasive segments. But before the concrete is poured, and after the rings forming the outer cage of the reinforcing have been set in position, the several bolts 1 10 can be inserted in their respective holes in each of the segments from the outside of the annulus with a rigid washer 30 and a deformable or compressible washer 32 under the head of the bolt. Each bolt is pushed through the several sections 14 and 20 of their respective holes so 15 that the inner end of the bolt may be screwed into a cooperating nut means 34. The nut means shown in ~ig. 1 is a custom made shape having a central threaded body portion to coact with the threaded bolt means and the body of the nut means each of which has a pair of oppositely 20 facing saddle shaped wings 36 an 38. The wing 36 fits under and is adapted to enga~e the under side of ring 24 when the bolt is tightened and the wing 3~ cooperates with the ring 26 in a similar manner. The bolt shown in Fig. 1 is a cap screw type and may be hand tightened with an Allen 25 wrench that fits into the head of the bolt.
When all of the segments and their respective bolt and nut means have thus been preliminarily assembled together with the outer cage members 24 and 26 of the reinforcing, the bolts can all be carefully torque 30 tightened to the same tension, preferably about 35 foot pounds to produce a tensile stress of 3000 pounds in each bolt. The remaining more centrally disposed reinforcing elements can then be placed in their normal positions and the wet concrete to complete the basic pulpstone structure 35 can then be poured and cured, whereupon the pulpstone is ready for finishing and ultimate use in a pulp grinding machine.

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Figs. 1 and 2 show a custom made nut means for mounting thé several segme*ts on the reinforcing rings 24 and 26 but Fig. 3 shows a simpler assembly of bolt means, washers, and conventional nut means. In this disclosure, a 5 standard bolt having a hex head 40 is shown. The bolt engages a washer 42 that seats under the rings 24 and 26 of the outer reinforcing cage. A nut means 44 cooperates with this bolt, there being a washer 46 and a compressible or deformable washer 48 between the nut and the seat in the 10 hole.
When either the nut and bolt means of Figs. 1 and 2 or the means shown in Fig. 3 is used, a much simpler method of manufacturing a pulpstone is shown as compared with the assembly procedure used heretofore. The herein 15 disclosed bolting system utilized most of the standard techniques but simplifies the assembly operations by eliminating the necessity for preassembly of bolting ~tuds in the threaded holes molded in the bottom sides of the conventionally used segments and the fixtures required for 20 the precision mounting of the studs in the segments, as well as the curing of the cement used for bonding the threaded ends of the studs in the threaded holes of the segments and the necessity for the manufacture of the custom made stud structures themselves. Not only are these 25 savings in the manufacturing procedures realized but there is a saving in the manufacturing e~uipment needed, and the custom manufacture of the studs. Furthermore, the herein disclosed mounting means for the abrasive segments makes it possible to correct the torque specifications in the wheel 30 on each segment after the concrete is cured, to assure the correct compression stressing of the segments before the pulpstone is put into use and even after it has been in use. It is to be especially noted, that because the threaded engagement of the studs in the molded threads of 35 the holes in the bottoms of the segments as used here-to-fore has been entirely eliminated, a stronger attachment of the segments of this invention to the core is achieved.
Also cracked or broken segments can be more easily replaced ~328~
than is possible in pulpstones with concrete cores used today.
This method of building a pulpstone permits compression forces to be built up in the chimney structure 5 or core assembly by the torquing of the bolts before the concrete is poured whereby a more precise adjustment of the stresses in the rim of the wheel can be made. As mentioned above, the proper prestressing of all of the abrasive segments can be assured from time to time while the 10 pulpstone is in use.
While the above describes the preferred form of this invention it is suggested that modifications thereof may occur to those skilled in the art that will fall within the scope of the following claims.

Claims (6)

1. A pulpstone, comprising:
a) an abrasive peripheral surface comprising a plurality of spaced abrasive segments, each segment having a grinding surface and a predetermined thickness, b) a poured concrete center core comprising a plurality of reinforcement rings concentrically placed within the core, and c) a plurality of mechanical attachments adapted for securing the abrasive segments to the center core under compressive force;
characterized in that each mechanical attachment is seated within an unthreaded hole extending radially inwardly from the grinding surface of each abrasive segment through the thickness of the abrasive segment, the hole having a upper section diameter at the grinding surface, an upper section bottom having a non-planar shape, and a lower section diameter, all within the abrasive segment, the upper section diameter being larger than the lower section diameter; and wherein the mechanical attachment is seated against at least one washer placed on the upper section bottom, the washer having a diameter larger than the diameter of the lower section diameter.

2. The pulpstone of claim 1, wherein the mechanical attachments are supported by the reinforcement rings within the center core.

3. The pulpstone of claim 1, wherein the mechanical attachments are selected from bolts having a cap and a connecting nut and metal rods having at least two connecting nuts.

4. The pulpstone of claim 1, wherein the washer is a deformable washer.

5. The pulpstone of claim 4, wherein a second gasket is disposed between the deformable washer and the mechanical attachment.

6. The pulpstone of claim 1, wherein each mechanical attachment is tightened to a tension of 3,000 pounds.