Note: Descriptions are shown in the official language in which they were submitted.
3~
ELEM~NT ~ CONSTRUCTION M~T~I~D FO~ INTERNAL
GRINDING SURFACE
This invention relates generally to pulpwood
and wood chip grinding procedures, and has to do
particularly with a method for constructing an internal
grinding surface, an element for use in the method, and
the resulting internal yrinding structure.
BACKGROUND OF THIS INVENTION
Conventionally, two basic procedures have been
utilized for the grinding of pulpwood and wood chips.
The first, and still the most common, involves the
utilization of a rotating grinding stone having a
cylindrical outer grinding surface against which the
pulpwood or wood chips are urged. ~ater is normally
sprayed or o-therwise applied to the surface of the
grinding stone, and the grinding procedure results in an
aqueous slurry containing the ground wood. The slurry is
then removed for fuxther processing.
The second conventional grinding procedure
involves grinding discs rotating face-to-face at high
speeds, with the material to be ground Eeeding axially
into the space between the discs.
A recent invention, assigned to the same
company as the present case, has been filed as
Canadian patent Application Serial No. ~02r290
dated May 5, 19~2 invented by Allan ~. Wildey . In
this recent development, an internal grinding surface is
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provided, which is in the form of a surface of revolution
(preferably cylindrical), and pulpwood or wood chips are
carried around and against the internal grinding surface
by a rotor which also has means for applying or spraying
water against -the internal surface. The grinding surface
itself is s-tationary in a preferred embodiment, although
it is conceivable that the grinding surface could be
rotated in the opposite sense from the rotor in order to
increase linear grinding speeds.
GENERAL D~SCRIPTION OF THIS INVENTION
... . . _ .
It is an aspect of this invention to provide a
special grinding segment for use in constructing the
member which defines the internal grinding surface, a
method of construction for the internal grinding surface,
and the member which results and which defines the
surface.
Accordingly, this invention provides a method
of constructing an internal grinding surface which
includes a number!of steps. Firstly, a plurality of
20 grinding segments is placed around a form whose outside
surface substan-tially correspo~nds to the desired internal
grinding surface, and the segments are secured in place
against the form. Next, the segments are surrounded with
an envelope mel~er, and are bonded thereto. Finally, the
form is removed from within the segments.
There is further provided a grinding segment
for use in constructing a pulpstone having an internal
grinding surface. The grinding segment is a body having
a concave grinding surface on one face, and recess means
30 on the opposite face to receive a tension member. The
tension member is used to secure a plurality of the
segments against the form.
This invention also provides a pulps-tone with
an internal grinding surface, the pulpstone including a
35 plurality of grinding segments. Each grinding segment is
a body with a concave grinding internal face. Tension
means encircle the segments and an envelope member
surrounds and is bonded to -the segments.
353
GENERAL DESCRIPTION OF THE DRAWINGS
Three embodiments of grinding segment are
illustrated in the accompanying drawings, in which like
numerals denote like parts throughout the several views,
and in which:
Figure 1 is a perspective view of a first
e~bodiment of grinding segmen-t;
Figures 2 is a perspective view of a second
embodiment of grinding segment;
Figure 3 is an elevational view illustrating a
method of constructing a pulpstone using the first two
embodiments of grinding segment;
Figure 4 is a sectional view taken at the line
~-4 in E'igure 3;
Figure 5 is a sectional view taken at the line
5-5 in Figure 3;
Figure 6 is a perspective view showing a third
ernbodiment of grinding segment;
Figure 7 is an elevational view illustrating a
method of constructing a pulpstone utilizing the third
embodiment of grinding segment; and
Figure 8 is a sectional view taken at the line
8~8 in Figure 7.
DETAILED DESCRIPTION OF THE DRAWINGS
.
Attention is first directed to Figure 1, which
shows a grinding segment 10 which includes a body 12
having a concave grinding surface on the lower or inside
face 14, and various recess means on the opposite face
16. The recess means will be described in greater detail
below. The body 12 has a peripheral configuration
adapted to interfit with other like configurations. More
particularly, the body 12 has a hexagonal peripheral
configuration, which includes two longer sides of which
one is seen at 20 and which oppose each other, and four
shorter sides of which two can be seen at 23 and 24. It
will be noted that the obtuse angle be-tween sides 23 and
24 is larger than the obtuse angle be-tween sides 20 and
24. In view of this, and -the fact tha-t the sides are not
4 D ~ 35~
all of the same length, i-t will be unders-tood that the
hexagonal shape is not a "regular hexagon" ln the normal
meaning of that term. As can be seen in Fiyure 3, the
segments 10 are intended -to be orlented with their longer
sides (20) vertlcal.
Because the grinding segment lO is intended to
interfit with other like segmen-ts to surround and define
a cylindrical surface, it will be understood that the
longer side faces 20 and 21 are inclined with respect to
each o-ther, -the angle of inclination being the same as
that subtended at the hypothetical centre of the grinding
surface by the two faces 20 and 21. Conversely, the
other side faces (of which two are seen at 23 and 24 in
Figure 1) are not inclined in the direction from the
outside face 16 to the inside face 14.
The recess means on the outside face 16
includes a channel-like lateral recess 26 which extends
across the segment from the middle of the hexagonal side
face 20 to the middle of the opposing hexagonal side face
21. The broken line 28 identifies a mid-plane of
symmetry for the grinding segment 10, and the
channel like lateral recess 26 is located astride the
mid-plane identified by the line ~8. The grinding
segment 10 includes additional recess means, constituted
25 by two semi-channels 30 and 32 which extend along the two
hexagonal sides 20 and 21 which are joined by the
first-mentioned channel 26.
Attention is now directed to the grinding
segment 40 shown in Figure 2, which is very similar to
30 the grinding segment 10 shown in Figure 1, except that,
instead of two semi-channels 30 and 32, the grinding
segment 40 has a single channel 42 extending from one
apex 43 of the grinding segment 40 to -the opposite apex.
Thus, the channel 42 extends parallel to the longer side
35 faces 20a and 21a and is situated at right angles to a
channel 26a which bisects the two opposed longer side
faces 20a and 21a. Aside from the difference just
described, the two grlnding segments 10 and 40 may be
considered identical.
5 ~3~353
Attention is now directed to Figure 3, which
illustrates the method of construc-tion utiliz.ing the two
grinding element embodiments shown in Figures 1 and 2, in
combination with a plurali-ty of special grinding elements
shown at 45 in Figure 3, which are similar to the
grinding elements 10, except that they do not include -the
nearer portion in Figure 1 on the closer side of an
imaginary plane identified by the broken line 47. Thus,
the special grinding segment becomes a pentagonal
segment, having a flat lower side face (corresponding to
the plane identified by the numeral 47 in Figure 1),
parallel with the channel 26.
Turning again to Fi.gure 3, an apparatus for
constructing a pulpstone havi.ng an internal cylindrical
grinding surface includes a build-up table 48 from which
are upstanding a plurality of centering lugs 50 at spaced
intervals around the circumference of an imaginary circle
having a radius R. Centrally located on the table 48
with respect to the lugs 50 is a longitudinally split
cylindrical form 52 consisting of two substantially
semi~cylindrical portions 53 and 54. In Figure 3, the
portions 53 and 54 are viewed in the direction parallel
with the plane along which they are split. The portions
are adapted to move toward and away from each other
symmetrically about the mid-plane of -the form 52, which
is identified by the numeral 56 in Figure 3. The
portions 53 and 54 are shown in the position which they
assume during construction of the pulpstone, but can be
withdrawn toward each other for removal from the finished
30 pulpstone.
Durlng the method of manufacture for the
pulpstone, a first tier of special segments 45 is
arranged around and in contact with the form 52 in the
position shown in Figure 3, with sheet cor~ S9 or similar
35 material used between the mat:ing faces of adjacent stone
segments. Since all of the special segments 45 are
identical, it will be understood that the channels 26
will be aligned in a plane located in spaced relation
above the build-up table 4~, so that a steel band 56 can
3~
encircle the special segments 45, and -then be secured to
itself at 57 in order to -tightly maintain the special
segments 45 in place against the form 52. The element
~ identified by the numeral 57 is adapted to maintain the
steel band 56 in tension.
Next, a tier of gr:inding segments 40 is placed
above the special segments A5 wi-th sheet cork or -the like
between them, and a further steel band 60 is wrapped
around these segments within the channels 26, and secured
q in a tensioned condition by t:he element 62. Following
this, a next tier of grinding segments lO is positioned
above the grinding segments 40, and a further steel band
holds these latter segments in place~ It will be
understood that all adjacent stone segments are separated
by sheet cork or the like. The s-teel band is not
illustrated in F'igure 3, as this figure shows the tier of
grinding segmen-ts 10 only partially completed. It will
thus be unders-tood that, when the tier under discussion
is completed, the next-above tier will consist of the
grinding segments 40, then a tier of grinding segments
lO, and so forth until the uppermost -tier is put into
place. The uppermost tier will again consist of special
segments 45, but reversed in orientation from those at
the bottom of the pulpstone assembly shown in Figure 3.
When all of the grindirlg segments have been put
into position and secured in place against the form by
suitable steel bands under tension, an envelope member 63
in the form of a steel sleeve is lowered over and around
the assembled grinding segment:s and is bonded to themO
30 Externally, the envelope member 63 is cylindrical, but
has a portion 64 of increased diameter at its lower end.
~he other radius of the portion 64 is only slightly
greater than the radius R in Figure 3 r SO that the lugs
50 will centre the envelope member 63 about the segments
35 lO, 40 and 45. Internally, as shown in both Figuxes 4
and 5, the envelope men~er 63 includes a plurality of
longitudinal, inwardly direc-ted ribs 66, which are
adapted to register either with the full channels 42 in
the segments 40, as can be seen in Figure 4, or with the
33~i3
composite channels defined by the semi-channels 30 of the
grindlny segments 10, as can be seen in Figure 5.
In Figure 5, a steel band 67 for the grinding
segments 10 is illustrated.
Figure 5 shows a bore 70 through the envelope
rnember 63 centred at the rib 66 -to the left in the
figure. The bore 70 has an internal pipe thread 72 at
its outer end, so that it can receive a standard
pipe-thread plug.
The bore 70 constitutes an injection port for a
bonding agent such as bakelite or epoxy. Once the
bonding agent has been injected, a suitable plug is
placed in the injection port, and after the bonding agent
has set, the portions 53 and 54 of the form 52 can be
contracted so that the form itself can be removed from
the completed pulpstone.
Other ports -through the other ribs in Figures 4
and 5 have been been illustrated, but it is to be
understood that the ports would be staggered
longitudinally of all the ribs, so as to ensure a uniform
injection of the boncling agent.
Attention is now directed to Figure 6, which
shows the third embodiment of the grinding segment of
this invention. In general terms, the grinding segment
25 75 illustrated in Figure 6 is similar to the grinding
segment 10 shown in Figure 1, with the exception of the
shape of the semi-channels which are identified by the
numeral 76 in Figure 6 and which have an S-like profile,
and the height of the segment, which is greater than the
30 segment 10. The grinding segment 75 lncludes a body 78
which has an outside face 79, an inside face 80 which is
cylindrical in curvature, two longer, opposed side faces
82 and 83, and four additional side faces of which two
are seen at 85 and 86. The body 78 is thus hexagonal in
35 configuration although it does not constitute a regular
hexagon. It is, nonetheless, bi-laterally symmetrical
about a mid~plane identified by the broken line 88 in
Figure 6, in the manner similar -to tha-t of the grinding
segment shown in Figure 1. Across the body 78 of -the
~1&~3~
grinding segment 75 and straddling the mid-plane identified
by the broken line 88 is a channel 90 which ends at -the
semi-channels 76, but which, if extended, would bisect the
opposed longer side faces 82 and 83 of the body 78.
Because of the essential similarlty between -the
segment 75 and the segment 10 (aslde from -the points already
mentioned), further description of the specific configuration
of the grlnding segment 75 ls no-t necessary here.
Attentlon ls now dlrected to Figure 7, which
10 illustrates the method of cons-tructing a pulpstone utilizing
a plurallty of grlndlng segments 75 along wlth a number of
speclal grlnding segments whlch are ldentical -to the grindlng
segment 75, except for being truncated along a plane ldent-
ified by the broken line 91 in Figure 60 These special
15 segments are identified by the numeral 93 ln Flgure 7, in
which lt can be seen that they constl-tute the lowermost or
first tler of segments to be placed around the portions 53
and 54 of the form 52 which is centrally located on a build-up
table ~8 havlng a plurallty of lugs 95 slmilar to the lugs
20 50 in Figure 3, but spaced at a greater radius Rl than the
radius R shown in Figure 3.
The special segments 93 are secured around and
against -the form 52 by a steel band 95a having a connecting
element 96 which keeps the band 95a in tension. The second
25 tier of grlnding elements as consti-tuted by elements 75, and
likewise all additional tiers are constituted by elements 75
except for the uppermost tier, which would be constituted by
inverted special elements 93. All tiers are secured tightly
agains-t the form 52 by respective steel bands, of which one
30 is identified by the numeral 98.
After all of the grinding segments 75 and 93 have
been secured in place against the form 52, an envelope
member 100 (seen in Figure 8) in the form of a cylindrical
sleeve is fitted around the segments and is centred with
35 respec-t to the form 52 by the action of the lugs 95.
3~S3
The envelope member 100 has an expanded lower
portion similar to the portion 64 o-f the envelope member 63,
which interacts with the lugs 95 to facilitate centering.
The envelope member 100 has a larger internal
diameter than the envelope member 63 shown in Figure 3,
assuming the same diameter for the form 52, and Figure 8
explains why this addi-tional internal space is necessary.
In Figure 8, three grinding segments 75a, 75b and
75c are illustrated, and between each adjacent pair, the
semi-channels 76 define a complete channel into which a
radially inwardly directed reinforcing bar 105 projects.
Each reinforcing rod 105 is part of an l.-shaped item haviny
a further portion running parallel with the axis of the
envelope member 100, and welded there-to. Into the space
defined between the envelope member 100 and the plurality of
segment 75 injected concrete identified by the numeral 107.
The concrete thus enters the dovetail channels defined by
the two semi-channeis 76 and is reinforced by the reinforcing
bars 105, thus providing an interlocking connection between
the concrete and all of the grinding segments 75.
As with -the embodiment described in reference to
Figures 1-5, once the concrete has set, the portions 53 and
5~ of the form 52 are contracted and withdrawn, leaving the
completed pulpstone with the internal grinding surface
defined by the internal surfaces of the various grinding
segments 75 and 93.
The envelope member 100 constitutes a supporting
sleeve for the segments, as does the envelope member 63 for
the embodiment illustrated in Figure 3.
There are a number of advantages and features of
the design described herein which should be emphasized.
The plurality of individual stone grinding segments
are assembled together in an interloc~ing honeycomb pattern
surrounded by a reusable outermounting sleeve. The gap or
spacing between the sleeve and the grinding elements is
filled with a bonding or filler
~33~
material, or with concrete in the case of -the embodiment
shown in Figure 6.
The lateral mating faces be-tween adjacent
segments (i.e. between two adjacent segments in the sarne
tier) is such as to provide an "arch" effect, where a
wedging action pxeven-ts segment movemen-t in the radially
inward direction.
The constructlon herein disclosed allows for a
very slim wall, thus reducing the outside diameter of the
grinder and its static weigh-t. The cons-tructional method
shown in Figure 3 requires three unique stone segments,
whereas that of Figure 7 requires two stone segments.
The latter would thus have slightly lower tooling costs.
The assembly of the numerous segments around a build-up
form or cylinder matching the desired grinding surface
allows reduction of manufacturing time. Each segment
tier is banded in place to ensure proper location and to
prevent movement during the bonding procedure. By
comparison, the assembly of conventional external
grinding stones is accomplished through the use of a
fixture requiring three manually adjustable screw jacks
for each segment.
It will be appreciated that, by comparison with
conventional pulpstones, there is little or no internal
stress in the segments of this design due to the fact
that the pulpstone is stationary and does not rotate.
Thus the high internal stresses due to centrifugal forces
arising in conventional pulpstones are not encountered.
Also, in conventional rotating pulpstones, thermal
30 stresses are created by coolant as it is constantly
applied and centrifuged off. Such thermal stresses would
not be encountered in the design herein disclosed.
In general, the "thermal capacity", or the
ability of the stone to remove heat from the grinding
35 zone is considered a limiting factor in productivity.
The high centrifugal forces in the conven-tional rotating
stone keep the segments essentially dry, leaving the grit
matrix to absorb the bulk of the grinding zone heat. By
contrast, the grit matrix of the stationary pulpstone
3~53
defined herein will be satura~ed with water and will
assist grea-tly in the removal of heat. This increased
heat extraction allows higher .speeds and -thus higher
production. In general, the reduction of centrifugal and
thermal stresses will reduce the manufacturing cost and
extend the life of the stationary pulpstone.
In the conven-tional apparatus, the mounting of
a rotating pulpstone onto a shaft requires many expensive
components and time-consuming labour. In contrast, -the
stationary pulpstone of the present invention simply
bolts into position. Also, during the replacement of a
rotating conventional stone, the shaft -threads are
sometimes damaged, resulting in costly repair. No
comparable difficulty would arise with the pulpstone
disclosed herein, since no central shaft is required for
the stone.
In rotatiny pulpstone construction, it is
required that the stone be "trued" in a large lathe
apparatus prior to sale. However, the method of
constructing a pulpstone with an internal grinding
surface, as clisclosed herein, is expected to eliminate
this phase and reduce costs.
When a rotating stone has been reduced to a
specified diameter, the entire stone is discarded. By
contrast, the stationary pulpstone disclosed herein
would, after a certain amount of wear, be sent back to
the factory on an exchange basis so that new segments
could be installed within the outer sleeve or envelope
member. This is expected to reduce the cost of pulpstone
replacement.
While specific embodiments of this invention
have been disclosed herein and illustra-ted in the
accompanying drawings, it will be apparent -to those
skilled in the art that changes and modifications may be
made therein, without departing from the scope of this
invention as set forth in the appended claims.
