CA1183353A - Element and construction method for internal grinding surface - Google Patents

Abstract

ABSTRACT
There is provided a method of constructing a pulpstone with an internal grinding surface, unique grinding segments for use with the method, and the finished pulpstone. A plurality of grinding segments is placed around a form whose outside surface substantially corresponds to the desired internal grinding surface, and the segments are secured in place against the form. An envelope member which may be in the form of a steel sleeve is placed around the segments, and the segments are bonded to the envelope member. Thereafter, the form is removed from within the segments. Preferably, the segments are secured in place around the form by the use of steel bands or like elements.

Description

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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.

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
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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

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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.

Claims (18)

CLAIMS:

1. A method of constructing an internal grinding surface, comprising the steps.
placing a plurality of grinding segments around a form whose outside surface substantially corresponds to the desired internal grinding surface, and securing the segments in place against the form, surrounding the segments with an envelope member, bonding the segments to the envelope member, and removing the form from within the segments.

2. The method claimed in claim 1, in which the internal grinding surface and the said outside surface are surfaces of revolution.

3. The method claimed in claim 1, in which the securement of the segments is accomplished by wrapping a tension member around them.

4. The method claimed in claim 1 or claim 2, in which the segments are secured in place by using steel bands.

5. The method claimed in claim 1, claim 2 or claim 3, in which the bonding of the segments to the envelope member is accomplished by injecting a bonding material in plastic form through apertures in the envelope member.

6. The method claimed in claim 1, claim 2 ox claim 3, in which the surface of revolution is a cylinder.

7. The method claimed in claim 1, claim 2 or claim 3, in which the segments are hexagonal and having lateral recesses for accepting a steel band used to secure the segments in place against the form.

8. The method claimed in claim 2, in which the segments are hexagonal and have vertical recess means for registry with longitudinal ribs on the envelope member, the segments also having lateral recesses for accepting a steel band used to secure the segments in place against the form.

9. A grinding segment for use in constructing a pulpstone having an internal grinding surface, comprising:
a body of hexagonal outer configuration of six sides for interfitting with other like bodies, the body having first and second opposed faces, the body having a concave cylindrical grinding surface on the first face, and a channel like lateral recess means on the second face to receive a tension member.

10. The grinding segment claimed in claim 9, in which the recess means is a channel extending across the segment from the middle of one hexagonal side to the middle of the opposing hexagonal side, the segment further including additional recess means on said second face perpendicular to the first-mentioned recess means.

11. The grinding segment claimed in claim 10, in which the additional recess means is a further channel extending from one apex to the opposite apex of the hexagonal peripheral configuration.

12. The grinding segment claimed in claim 10, in which the additional recess means includes two semi-channels extending along the two hexagonal sides joined by the first-mentioned channel.

13. A pulpstone with an internal grinding surface, comprising:
a plurality of grinding segments, each being a body of hexagonal outer configuration of six sides for inter-fitting with other like bodies, the body having a concave cylindrical grinding internal face, tension means encircling the segments and lying in circumferential grooves in said segments, and an envelope member surrounding and bonded to the segments.

14. The pulpstone claimed in claim 13, in which the tension means includes a plurality of steel bands.

15. The pulpstone claimed in claim 13, in which the envelope member has internal rib means and each segment has channel means for registry with the rib means.

16. The pulpstone claimed in claim 13, in which the groove of each segment is constituted by a channel extending across the segment from the middle of one hexagonal side to the middle of the opposing hexagonal side, such segments further including additional recess means on the external faces perpendicular to the grooves.

17. The pulpstone claimed in claim 16, in which the additional recess means is a further channel extending from one apex to the opposite apex of the hexagonal peripheral configuration.

18. The pulpstone claimed in claim 16, in which the additional recess means includes two semi-channels extending along the two hexagonal sides joined by the first-mentioned channel.