FIELD OF THE INVENTION

The present invention relates to an apparatus for grinding fibrous material of vegetable or mineral origin, such as for example, peat, wood, asbestos, and the like..

BACKGROUND OF THE INVENTION

Known wood grinders which serve to remove cellulose fibres from wood stock for paper making are not suited for grinding peat moss and asbestos. The RAYMOND SCREEN pulverizer, which is a type of hammer mill, is often used for pulverizing asbestos. Unknown to applicants is a mill which is suited to grind not only wood but also peat material and asbestos, the grinding being effected in such a way as to form a material suitable for making pellets or granules (see for example Canadian patent application no. 2,076,598 which is publicly available).

OBJECTS OF THE INVENTION The object of the present invention is to provide a grinding apparatus which can process any type of fibrous materials of vegetable or mineral origin including wood, peat moss and asbestos.

SUMMARY OF THE INVENTION The present invention thus generally provides for a grinder for fibrous material of vegetable or mineral origin, comprising a generally cylindrical casing and a rotor rotatably disposed in said casing, said casing comprising a longitudinal axis, a cylindrical side wall, and a pair of opposed end walls, said cylindrical side wall comprising an inner face, an imperforate wall portion, a perforated wall portion and an inlet opening, said perforated portion

comprising a plurality of screen holes defining an outlet, said rotor extending, coaxially with said longitudinal axis, between and rotatably engaged in said end walls, said rotor having a two or more angularly spaced, radially extending, rigid imperforate blades, the blades each having a radially outer edge face, said blades, screen holes and said perforated portion being configured and disposed such that as said rotor rotates, the blades pass across the inner face of the perforated wall portion and the edge faces are separated from the perforated wall portion by a gap, said gap being sized such that as rotation of said rotor causes said blades to rotate fibrous material entering said casing through said inlet, fibrous material is able to be sheared at said holes and be ejected there through.

More particularly, a grinder of the present invention may comprise a generally cylindrical casing with a horizontal axis, a top inlet, vertical flat end walls, a partly cylindrical imperforate wall, a partly cylindrical screen forming the bottom of said casing, a rotor journalled in said end walls, extending across said casing and coaxial with said wall and said screen, said rotor having a number of angularly equally spaced, radial, rigid blades, each with a radially outer edge face defining a first uniform gap with the inner surface of said screen and across said screen, rotation of said rotor causing said blades to rotate the fibrous material entering said casing through said inlet and causing the separation and alignment of the fibres contained in said material by the shearing action of the blades moving past said screen and the ejection under centrifugal force of the thus treated fibrous material through the holes of said screen.

In accordance with the present invention the screen holes may each define a radial bore. The screen holes may be conical with their diametrically larger ends being located at the radially outer surface of the perforated wall portion or screen.

In accordance with the present invention the blade tips may form a flat transverse edge face which extends parallel to the generatrix of the perforated wall portion or screen.

In accordance with the present invention the grinder may have any suitable number of blades provided that the grinder is able to carry out its function, i.e. grind the desired material; depending on the overall size of the grinder relative to largest size of the material to be ground may have more or less blades. The grinder may have for example have two or

more blades, e.g 7 blades or less, e g 5 blades, e g up to 11 blades, e g 14 blades The blades may have the form of rectangular plates which project radially such that the plane defined thereby tangentially engages the inner face of the cylindrical sidewall

In accordance with the present invention the imperforate wall portion may define a face portion which may be essentially smooth, i e not provided with any interruptions in the form of openings or projections, or cutting edges or the like The perforated wall portion may also have a smooth surface (defining a portion of the inner face of the casing) but in this case the surface is interrupted by the screen holes or openings

In accordance with the present invention the interior of the casing may have an inner surface the periphery of which is defined by a relatively constant diameter Alternatively, the inner surface periphery may have a diameter for the screen part which is smaller than for the imperforate part.

Thus, in accordance with the present invention , the free edge face of the blades may make a second gap with the inner surface of the imperforate wall which is greater than the first named gap and wherein said imperforate wall is located downstream from said screen relative to the direction of rotation of said rotor Thus the rotor may include rigid radial blades with a free edge face defining a smaller gap with the inner surface of the screen and a greater gap with the inner surface of the imperforate wall This greater gap permits or facilitates unplugging of the fibrous material which might be caught between the blades and the imperforate wall In accordance with the present invention, a fibrous feeding funnel may be disposed over the inlet port and may include a downwardly inclined baffle

The grinder produces separation (and possibly alignment) of the fibres by the shearing action of the blades moving past the screen The ground material may depending on the rotational speed of the rotor be ejected under centrifugal force through the holes of the screen

BRIEF DESCRIPTION OF THE DRAWINGS

In the annexed drawings, like reference characters indicate like elements throughout Figure 1 is an cross-sectional view of an example embodiment of a grinder in

accordance with the present invention;

Figure 2 is a cross-sectional view at an enlarged scale, of part of the screen and blade tip of the grinder of Figure 1;

Figure 3 is a perspective view of the cylindrical portion of the grinder of figure 1, portions of the walls and ends being cut away, Figure 4 is a schematic illustration of a further example embodiment of a grinder in accordance with the present invention; and

.Figure 5 is a schematic illustration of a modified version of the example embodiment of figure 4.

DETAILED DESCRIPTION OF AN EXAMPLE EMBODIMENT The grinder of the invention comprises a housing 8 consisting of a downwardly, rearwardly inclined, rear wall 8a and a downwardly forwardly inclined front wall 8b joined by flat end walls 14b. A generally cylindrical casing 14 is formed within the housing 8,; a rotor is mounted within casing 14 and includes a hub 10 carried by a drive axle 12 which is joumalled within the end walls 14b and extends coaxially of casing 14. A suitable drive means (not shown) rotates axle 12 in clockwise direction.

Housing 8 is supported by ground engaging legs 18.

Casing 14 includes a partly cylindrical imperforate wall 20 and a partly cylindrical screen 20c. Casing 14 defines a cylindrical chamber 22 coaxial with the horizontally disposed axis of drive axle 12. The rotor further includes a plurality, preferably an odd number, of radial arms 24 secured to hub 10 and each reinforced by a trailing web 25. A radial flat rigid blade 26 is secured by a bolt 27 to the radial each arm 24. Each blade 26 is of generally rectangular shape and is provided with a slot through which bolt 27 extends, whereby the radial position of each blade can be adjusted. Each blade has a flat outer edge face 26a which is throughout and which is parallel to the generatrix of screen 20c and imperforate wall 20. The radial position of the blades 26 is selected so as to define a gap G, between the edge face 26a and the inner surface 20a of screen 20c.

Screen 20c has a plurality of holes 28 preferably of frusto-conical shape, the smaller end 28a of each hole being located at the inner surface 20a of screen 20 c and consequently,

the larger end 28b of each hole being located at the screen outer surface 20b The holes 28 are preferably disposed in transverse rows of pitch P between the rows.

As shown in Figure 2, the minimum diameter of holes 28 is indicated at D and the screen thickness at T.

Casing 14 has the top inlet port indicated at 30, which forms the lower end of a funnel 32. Funnel 32 is defined by the housing end walls 14b, a front flat vertical wall 33 and a back

-_, inclined wall 33b merging at 30 with the top end of partly cylindrical imperforate casing wall 20.

The lower end of front wall 33 is secured to a transverse bar 33a extending between and joining the end walls 14b. The screen 20c can be easily removed and replaced by another screen to suit the type of fibrous material being ground. Different screens may be provided with a different thickness T, with a different pitch P and/or with a different hole diameter D

The screen 20c is secured at its ends to the partially cylindrical shoulder strips 14a which are designed to flatly engage the end walls 14b. The two arcuate shoulder strips 14a are interconnected at their ends by a front transverse bar 33c and a back transverse bar 33f Bar 33c is removably secured to front bar 33a by bolt 33e while rear bar 33f is removably secured to the bottom edge of arcuate casing wall 20 by bolts 33g

Both ends of the screen 20c are extended by front extension sheet 33d and by back extension sheet 33e respectively which are secured to the front bar 33c and to the rear bar 33f respectively. The inner surface of casing wall 20 is at a greater distance from the axis of casing 14 than the inner surface 20a of screen 20c. It follows that the gap between the flat edge faces 26a of blades 26 and the inner surface casing wall 20 is greater than gap G of the blades with screen 20c relative to the direction of rotation of rotor 10, 24, 26. The screen 20c defines a transverse leading edge 20d. Figure 3 shows a perspective view of the cylindrical portion of the grinder with the surrounding environment (e.g. the surrounding wall structure, the legs, etc ) being removed The same reference numerals apply to the same elements The longitudinal (i.e horizontal) axis of the housing is designated by the reference numeral 50 The hub 10 is able to rotate about the axis 50 in the direction of the arrow 51 such that fibre material is able to be

compacted against the screen 20c, sheared and passed through the screen holes 28 As may be seen the hub 10 extends between the end walls 14b and is disposed coaxially with the axis 50. As may be seen the hub 10 and the blades 26 are imperforate and define the walls of a pocket in which fibre material may be rotated about the axis 50 In the illustrated embodiment there are 7 such pockets; other numbers of pockets could of course be used The grinder operates as follows fibrous material is fed to the funnel 32, dropping on baffle 32a and then inclined back wall 33b to enter casing 14 through top inlet 30 The fibrous material is engaged by the rotating blades 26 and is immediately subjected to a shearing action by edge face 26a of a blade 26 approaching the leading edge 20d of screen 20c. The shearing action is continued between the blade edges 26a and the screen 20c whereby the fibres contained in the fibrous material are separated from the remainder of the material (and possibly aligned), completion of this separation sometimes requiring several rotations of the rotor. Upon leaving the trailing edge of the screen, the shearing action on the fibrous material immediately decreases since the gap G immediately increases This allows easier return and recycling of fibrous material which, together with fresh material being fed through funnel 32, is again subjected to a shearing action between the blades and the screen

Finally, the ground material is sufficiently disintegrated so as to easily pass through the screen holes under the centrifugal force exerted thereon by the rotating blades

A large variety of fibrous material can be treated by the grinder of the invention, namely fibrous material of mineral or vegetal origin and in dry or wet state

Referring to figure 4, this figure illustrates an example embodiment of the invention wherein the inner peripheral surface of the casing has a uniform diameter as opposed to a two part diameter as shown in figure 1 ; apart from this the grinder is essentially the same as the grinder of figure 1. The grinder of this example embodiment of the invention comprises a generally cylindrical casing 114; a rotor is mounted within casing 114 and includes a hub 110 carried by a drive axle 112 which is joumalled within the end walls and extends coaxially of casing 114. A suitable drive means (not shown) rotates axle 1 12 in clockwise direct

Casing 114 includes a partly cylindrical imperforate wall 120 and a partly cylindrical screen 120c, the diameter of both is the same The screen is shown as being partially

detached from the rest of the grinder. Casing 1 14 defines a cylindrical chamber 122 coaxial with the horizontally disposed axis of drive axle 112.

The rotor further includes a plurality, preferably an odd number, of radial arms 124 secured to hub 110 and each reinforced by a trailing web 125. A radial flat rigid blade 126 is secured by a bolt 127 to the radial each arm 124. Each blade 126 is of generally rectangular shape and is provided with a slot through which bolt 127 extends, whereby the radial position of each blade can be adjusted. Each blade has a flat outer edge face 126a which is throughout and which is parallel to the generatrix of screen 120c and imperforate wall 120. The radial position of the blades 126 is selected so as to define a gap G, between the edge face 126a and the inner surface 120a of screen 120c. Screen 120c has a plurality of holes 128 preferably of frusto-conical shape, the smaller end of each hole being located at the inner surface 120a of screen 120 c and consequently, the larger end 128b of each hole being located at the screen outer surface 20b. The holes 128 are preferably disposed in transverse rows of pitch P between the rows.

Casing 1 14 has the top inlet port indicated at 130, which forms the lower end of a funnel 132. Funnel 132 is defined by the housing end walls, a front flat vertical wall 133 and a back inclined wall 133b merging at 130 with the top end of partly cylindrical imperforate casing wall 120.

The lower end of front wall 133 is secured to a transverse bar 133a extending between and joining the end walls. The screen 120c can be easily removed and replaced by another screen to suit the type of fibrous material being ground. Different screens may be provided with a different thickness T, with a different pitch P and/or with a different hole diameter D.

The screen 120c may be secured at its ends to the partially cylindrical shoulder strips which are designed to flatly engage the end walls. The two arcuate shoulder strips are interconnected at their ends by a front transverse bar and a back transverse bar. The front transverse bar is removably secured to a front bar by a bolt while back transverse bar is removably secured to the bottom edge of arcuate casing wall 120 by bolts.

Both ends of the screen 120c are extended by front extension sheet and by back extension sheet respectively which are secured to the front bar and to the rear bar respectively.

The inner surface of casing wall 120 is at the same distance from the axis of casing 114 than the inner surface 20a of screen 20c It follows that the gap between the flat edge faces of blades 126 and the inner surface casing wall 120 is the same as than gap G of the blades with screen 120c relative to the direction of rotation of the rotor

Figure 5 shows the same grinder of figure 4 but with a side (both) reinforcing annular plage 122a.