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.

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 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 to the periphery of the core. 
BACKGROUND AND INFORMATION DISCLOSURE STATEMENT 
The following U.S. Patents are representative of the most relevant prior 
art known to the applicant at the time of the filing of this application. 
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U.S. Pat. Nos. 
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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. 
September 28, 1982 
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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 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 are assembled together with a concrete core by means of 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 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 supporting ring means. The grinding wheel of this disclosure 
utilizes the exposed ends of the segments 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 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 use in 
making wood pulp. Wagg and Minarik each show a bolting arrangement for 
attaching a 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 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 individual segments of a pulpstone to fasten the 
individual segments to the surface of a cylindrical cast iron drum. In 
this 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 
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 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 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 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. 1-5 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 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 particulars of 
the bolting system except as the bolt structures are modified to promote 
the circulation of water to the surface of the 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. 
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 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. 
In the practice of this invention, the plurality of segments that are to be 
carried on the periphery of the stone, are formed into an annular or a 
circular assembly of the segments that resembles a "chimney". This chimney 
is 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 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 are provided with a 
plurality of bolt holes extending from their grinding surfaces radially 
inwardly to receive bolt means. The shape of the seating means or bottom 
of the hole is of a special design; it is round, i.e. concave, or in the 
shape of a cone, i.e. non-flat. FIGS. 1 and 3 show the configuration of 
the bottom of the wide part of the hole as round. The bolt 18 in FIG. 1 
passes upwardly through the lower narrow section 20 of the hole and into 
the wider upper section 14. Each bolt 18 and hole is fitted with a 
hemispherical washer 32, a straight washer 30, both made of mild steel, 
and a compressible and resilient gasket 31 which is composed of a 
polymeric material such as polycarbonate, acrylonite-butadienestyrene, 
such as polytetrafluoroethylene, cork filled rubber, nylon, polyethylene 
polypropylene, or the like, located between the straight washer 30 and the 
hemispherical washer 32. Obviously if the bottom of the hole was cone 
shaped, then the washer 32 would also be cone shaped. The shank of the 
bolt extends radially inwardly so that the inner end of the bolt can be 
supported from the reinforcing rings. 
It is the aforedescribed combination of non-flat i.e. round or cone-shaped 
hole, hemi-spherical or cone-shaped washer, and compressible gasket, which 
results in the virtual elimination of segment loss. This novel hole shape 
and attachment means has the result that pocket pressures do not cause any 
compression in the attachment bolts and therefore do not create any stress 
concentrations. Pocket pressures actually reduce the amount of tension 
stress in the attachment bolt which improves the performance of the 
attachment. 
After the chimney has been built and the bolt and 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 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 
improve the firing process for the initial fabrication of the segments 
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 
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 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 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.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention is concerned with the mounting of a plurality of 
abrasive segments on the periphery of the more popular types of pulpstones 
having a concrete core generally similar to the structures shown in the 
above mentioned patents to Minarik and Schmoller et al., FIGS. 1-5. Such 
pulpstones are cylindrical in shape and may have a diameter falling within 
a range of from 50" 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 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 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 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 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 process and 
the heat will be distributed 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 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 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 the lower section 20 of the 
hole, which section has a smaller diameter than the upper section 14. As 
already described above, the seating means or bottom of the upper section 
14 of the hole cannot be flat and is preferably concave, filled with a 
washer 32 of matching configuration, a straight washer 30 and an 
intermediately located resilient gasket 31. In FIG. 3 the corresponding 
parts are matching shaped washer 48, straight washer 46, and resilient 
gasket 47. It should be understood that while only bolts with heads are 
shown in the drawing, a metal rod threaded on both ends could be used with 
two nuts. 
These segments are made to have the conventional shapes whereby to be 
assembled in the usual pattern in a 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 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 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 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 
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 
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 the segments. For this 
reason the reinforcing rings in the outer cage of the reinforcing 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 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 broken away portion of 
a segment that is shown in its 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 18 can be inserted in their respective holes in each of 
the segments from the outside of the annulus with a rigid washer 30 with a 
rigid straight washer, a compressible gasket 31, and a rigid 
hemi-spherical washer 32 under the head of the bolt. With the rigid 
straight washer, compressible (resilient) gasket, and rigid hemi-spherical 
washer shipped onto the bolt, each bolt is pushed through the several 
sections 14 and 20 of their respective holes so that the inner end of the 
bolt may be screwed into a cooperating nut means 34. The nut means shown 
in FIG. 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 facing saddle shaped wings 36 an 38. The 
wing 36 fits under and is adapted to engage the under side of ring 24 when 
the bolt is tightened and the wing 38 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 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 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 can then be poured 
and cured, whereupon the pulpstone is ready for finishing and ultimate use 
in a pulp grinding machine. 
FIGS. 1 and 2 show a custom made nut means for mounting the several 
segments 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 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 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 
disclosed bolting system utilized most of the standard techniques but 
simplifies the assembly operations by eliminating the necessity for 
preassembly of bolting studs in the threaded holes molded in the bottom 
sides of the conventionally used segments and the fixtures required for 
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 savings in 
the manufacturing procedures realized but there is a saving in the 
manufacturing equipment 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 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 the 
holes in the bottoms of the segments as used here-tofore 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 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 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 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.