SCOPE OF THE INVENTION

The present invention relates to an apparatus for use in the pulping of cellulose fibres, and more preferably a pulping apparatus for use in the pulping or re-pulping and hydration of virgin cellulose or recycled paper and cardboard fibres.

BACKGROUND OF THE INVENTION

The use of pulpers in paper manufacturing processes to form virgin or recycled pulp is well known. Conventionally, pulpers are constructed with large vertically elongated mixing tanks or vats in which raw cellulose material, water and pulping chemicals are mixed. The vats typically have a diameter of between about 3 and 5 metres and may exceed 3 metres in height. A large rotor or mixing blade positioned at the bottom of the vat is used to break up the cellulose material into small fibres in the formation of pulp. In operation, bales of virgin or recycled cellulose such as paper or cardboard, are fed into the vat and mixed with the water/chemical pulping fluid by the agitation of the moving rotor, to defibre and pulp the mixture for further use.

Conventional pulpers and re-pulpers (hereinafter generally referred to as pulping apparatus) suffer a disadvantage in that because of the large size and vertical orientation of the pulping vat, high horsepower electric motors of 500 horsepower or more, are required to drive the mixing rotor. The use of high horsepower motors dramatically increases energy use and the operation in costs of entire system. As a result, the use of conventional pulpers is frequently cost prohibitive in re-pulping recycled cellulose fibres such as paper and cardboard waste.

Another disadvantage exists with conventional pulpers in that as the mixing rotors are often constructed in a form of an oversized agitator mounted to the bottom floor of the mixing vat with a diameter and/or height of up to two metres. In addition to the requirement to provide adequate rotary seals, the drive assemblies used to couple the rotors to the motor require complex and expensive gearing and transmissions which are susceptible to fatigue and failure. Conventional pulping apparatus suffer a further disadvantage in that if the mixing rotor or blade is damaged, it is necessary to first completely drain and empty the mixing vat to permit maintenance access to the damaged blade. This may involve the added expense and inconvenience of having to manually remove any unpulped cellulose through the bottom of the vat.

SUMMARY OF THE INVENTION

To at least partially overcome at least some of the difficulties associated with prior art devices, the present invention provides for a pulping apparatus which includes a hollow mixing cylinder which is journaled for rotation about a generally horizontal cylinder axis. The mixing cylinder includes a generally solid side wall which extends radially about the central axis from a proximal inlet end to an outlet end distal therefrom. The interior of the mixing cylinder is divided into two or more discrete chambers which are configured to break-up and/or hydrate input cellulose fibres to form a desired pulp as the cylinder rotates. A drive is provided to rotate the mixing cylinder about its central axis, while cellulose and pulping fluid is fed therein.

Accordingly, one object of the present invention is to provide a pulper or re- pulper which may be operated more cost effectively using a drive which includes a low horsepower motor having a horsepower less than about 1 OObhp, preferably less than about 50bhp, and most preferably between about 20 and 30bhp.

Another object of the invention is to provide a pulping apparatus for use in the hydration and pulping of either virgin, or more preferably recycled cellulose fibres, and which is provided with one or more horizontally extending cylindrical mixing chambers adapted for rotation about a generally horizontal (+ 20°) axis, as part of a substantially continuous pulping operation.

Another object of the invention is to provide a pulping apparatus which is adapted to permit the rapid and simplified replacement and/or repair of damaged pulper mixing blades or vanes, without requiring the complete emptying of mixing tank or chamber. A further object of the invention is to provide a pulping apparatus which is adapted for use as part of a continuous production line, and which provides the enhanced defϊbring of recycled paper and cardboard materials, while minimizing fibre damage.

Yet another object of the invention is to provide a pulping apparatus which incorporates a horizontally elongated mixing cylinder which is rotatable about a central cylinder axis by way of a conventional direct chain drive, without the requirement of complex gearing and/or transmission assemblies.

To at least partially achieve at least some of the foregoing objects, the present invention provides for a pulping apparatus which includes a hollow mixing cylinder, a drive assembly, and a feed hopper assembly operable to supply cellulose material to an interior of the cylinder. The mixing cylinder has size selected to receive and retain therein a selected volume of pulping fluid and cellulose fibres. The mixing cylinder includes a cylinder sidewall which extends radially about a central cylinder axis, a proximal inlet end to an outlet end spaced in a longitudinal direction distally therefrom. The mixing cylinder is journaled for rotation about its central axis, with the axis oriented at + 20° from horizontal, preferably + 10°, and most preferably at about + 3° from horizontal.

The drive assembly includes a motor selectively actuable to rotate the mixing cylinder during pulping operations. Preferably, the motor is a low horsepower electric motor having a horsepower of less than about lOOhp, preferably less than about 50hp, and most preferably between 20 and 30 hp. Other types and sizes of motors may however, also be used. The feed hopper assembly is adapted for supplying virgin or recycled cellulose fibres and preferably pulping fluid into an inlet end portion of the mixing cylinder, as part of either a batch or continuous process.

In a preferred construction, the mixing cylinder is provided with a solid cylinder sidewall and is divided internally into at least two, and preferably three or more discrete mixing chambers. The mixing chambers are each configured to maintain a minimum pulp/fluid level therein, while facilitating the outward flow of defibred pulp from the cylinder infeed end to and outwardly from the outlet end. The first mixing chamber is characterized by a series of mixing and cutting vanes, blades, flutes, or plow bars (hereinafter generally referred to as cutting blades) mounted to the interior cylindrical wall of the mixing chamber. The cutting blades are configured to facilitate the mixing, breakdown and defibring of the cellulose material in the pulping fluid as the mixing cylinder is rotated about its central axis. The first mixing chamber is delineated longitudinally at a proximal most first end by an end cover or sealing member, and at its second distalmost end, by a first divider provided laterally across the interior of the cylinder a distance spaced distally from the end cover. The end cover is configured to substantially close the inlet end of the cylinder to prevent the reverse flow of pulping fluid and/or cellulose therefrom. In one simplified construction, the hopper assembly includes a feed pipe configured to convey cellulose fibres and/or pulping fluid through an inlet opening formed in the end cover and into the mixing cylinder interior.

The next immediately adjacent downstream mixing chamber is delineated longitudinally by the distalmost first divider of the first mixing chamber, and by a second further downstream divider extending across the cylinder interior spaced longitudinally therefrom. The second mixing chamber may furthermore include cutting vanes or blades or internal ribs, but most preferably is characterized by a generally smooth chamber sidewall.

Each of the dividers are provided with one or more flow passages or through- openings formed therethrough. The through-openings of each divider are configured to regulate the flow of pulp and any or partially pulped material and pulping fluids longitudinally along the mixing cylinder and outwardly therefrom through the outlet end. The cylinder dividers preferably act as weirs to maintain minimum cellulose/fluid levels in each mixing chamber as the cylinder is rotated. Preferably, the second divider is configured to maintain a minimum fluid level in the second mixing chamber selected less than the minimum level of fluid maintained in the first.

In a simplified construction, each through opening is formed as a generally circular opening which is substantially centered on the cylinder axis. The diameter of the through-opening formed through the second divider is selected larger than the diameter of the through-opening which is formed in the first divider, maintaining a lower minimum fluid level in the second mixing chamber. Optionally, the end cover may also be provided with a circular outlet opening having a diameter which is greater than that of the second through-opening to maintain a minimum fluid level between the end cover and second divider plate, which is lower than the level maintained between the first and second dividers.

In an alternate construction, all or part of the through-openings which extend through the divider may be positioned in an asymmetrical arrangement relative to the central axis, so as to move eccentrically relative to the central axis as the mixing cylinder is rotated. Although not essential, most preferably the flow through-passages are spaced from the cylinder sidewall to restrict the movement of larger fibre particles from moving outwardly therefrom. More preferably, the eccentrically moving portion of the flow through-openings formed through the second downstream divider has a greater total area than the eccentrically moving portion of the flow through-openings formed through the first divider, with the maximum fluid/pulp flow from the first mixing chamber being less than that from the second chamber. Further as the mixing cylinder rotates, the eccentric rotation of the through-openings provides for the variable fluid flow past each divider during use of the apparatus.

As such, with the present invention after an initial period of residence time in the first mixing chamber, fluid and pulp will thereafter tend to flow into and be retained in the second mixing chamber for a period of time, prior to flowing outwardly therefrom.

Accordingly, in one aspect the present invention resides in a pulping apparatus for the hydration of recycled cellulose fibres comprising a hollow mixing cylinder having a cylinder wall which extends radially about a central axis oriented at approximately + 10° from horizontal, the cylinder being mounted for rotation about the axis and extending longitudinally therealong from a proximal inlet end to a distal outlet end, and including an end cover partially closing said inlet end, the end cover including an inlet opening spaced inwardly from said cylinder wall towards said axis; a first divider extending laterally across an interior of said cylinder, the first divider being distally spaced from said end cover to define a first mixing chamber therebetween, a first flow passage formed through said first divider, the first flow passage having a first diameter; a second divider extending laterally across an interior of the cylinder, the second divider being distally spaced from the first divider plate to define a second mixing chamber therebetween, a second flow passage formed through said second divider; a hopper assembly for conveying said cellulose fibres into said cylinder through said inlet opening; a drive assembly selectively actuable to rotate said cylinder about said axis.

In another aspect, the present invention resides in a pulping apparatus for cellulose fibres comprising a hollow mixing cylinder having a cylinder wall which extends radially about a central axis oriented at approximately + 10° from horizontal, the cylinder being journaled for rotation about the axis and extending longitudinally therealong from a proximal inlet end to a distal outlet end; an end cover partially closing said inlet end and including an inlet opening; an infeed hopper assembly for conveying said cellulose fibres into said cylinder through said inlet opening; a fluid supply for supplying a pulping fluid into said cylinder for admixture with said cellulose fibres; a first divider plate disposed in said cylinder, the first divider plate being longitudinally spaced from said end cover to define a fist mixing chamber therebetween, a first flow passage formed through said first divider plate, the first flow passage configured to maintain a first minimum fluid level in the first mixing chamber as said cylinder is rotated about said axis; a second divider plate disposed in said cylinder, the second divider plate being remote from said end cover and longitudinally spaced from said first divider plate to define a second mixing chamber therebetween, a second flow passage formed through said second divider plate, the second flow passage configured to maintain a second minimum fluid level in the second mixing chamber as said cylinder is rotated about said axis, the second fluid level being less than the first fluid level; a drive assembly selectively actuable to rotate said cylinder about said axis.

In a further aspect, the present invention resides in a hollow mixing cylinder having a generally solid cylinder wall which extends radially about a central axis oriented at approximately + 3° from horizontal, the cylinder being mounted for rotation about the axis and extending longitudinally therealong from a proximal inlet end to a distal outlet end and including; an end cover partially closing said inlet end, the end cover including an inlet opening; a first divider disposed in said cylinder, the first divider being distally spaced from said end cover and generally sealing with said cylinder wall to define a first mixing chamber therebetween, a first flow passage formed through said first divider, the first flow passage having a first diameter; a second divider being disposed in the cylinder, the second divider being distally spaced from the first divider and sealing with said cylinder wall to define a second mixing chamber therebetween, a second flow passage formed through said second divider; an end cover distally spaced from the second divider and defining a third mixing chamber therebetween, an outlet flow opening formed through said end cover, the outlet flow opening having a third diameter selected greater than the second diameter; an infeed hopper assembly for conveying a slurry of said recycled paper and cardboard fibres and a fluid into said cylinder through said inlet opening; a drive assembly selectively actuable to rotate said cylinder about said axis.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference may now be had to the following detailed description, taken together with the accompanying drawings in which:

Figure 1 shows a perspective view of a pulping apparatus in accordance with a preferred embodiment of the invention;

Figure 2 shows a partially cut away side view of the apparatus shown in Figure 1 , illustrating the positioning of cutting blades in a first mixing chamber;

Figure 3 shows a cut away perspective view of the pulping apparatus of Figure 1, showing the positioning of longitudinally spaced mixing chambers within the mixing cylinder;

Figure 4 shows a cross-sectional view of the pulping cylinder shown in Figure 2 taken along line 4-4, illustrating the relative positioning of divider flow through- openings relative to the cylinder axis, in accordance with a first embodiment of the invention;

Figure 5 shows a cross-sectional view of the pulping cylinder as shown in Figure 5, illustrating the positioning of the divider flow through-openings in maintaining minimum pulp/fluid levels in the cylinder mixing chambers;

Figure 6 shows a cross-sectional view of the pulping cylinder shown in Figure 2 taken along line 4-4 illustrating the relative positioning of divider flow through openings relative to the cylinder axis, in accordance with a second embodiment of the invention; and Figure 7 shows a cross-sectional view of the pulping cylinder showing the relative positioning of the divider flow through-openings in accordance with a further embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference is first made to Figure 1 which shows best a pulping apparatus 10 for use in the re-pulping of recycled cardboard and paper waste in accordance with a preferred embodiment of the invention. The pulping apparatus 10 includes a mixing cylinder 12, a drive assembly 14 and a hopper assembly 16 which are mounted on a support frame 18. As well described, the hopper assembly 16 is used to supply a slurry mixture 8 (Figure 2) of pulping fluid and recycled paper and cardboard fibres into the interior of the mixing cylinder 12 for re-pulping and formation of a defibred pulp 8", which for example, is suitable for use in subsequent paper processing applications.

The mixing cylinder 12 is shown best in Figures 2 and 3 as having a generally solid stainless steel sidewall 22 which extends radially about a central cylinder axis Ai- A ₁ . As shown best in Figure 2, the mixing cylinder sidewall 22 is rotatably supported towards each end of the cylinder 22 by opposing pairs of roller wheels 28a, 28b which are secured to the support frame 18. The cylinder 12 is extends longitudinally along the axis Ai-Ai, from an inlet end 24 which is positioned proximal-most to the hopper assembly 16, to an outlet end 26 spaced distally therefrom. As will be described, the mixing cylinder 12 is positioned on the rollers 28a, 28b with the axis A]-Ai in a generally horizontal orientation (+ 3°), so as to be selectively rotatable thereabout by the activation of the drive assembly 14.

In a preferred construction, the mixing cylinder 12 is provided with an overall longitudinal length selected at between about 3 and 6 metres, and a lateral diameter of between about 1 and 3 metres, and most preferably about 2 metres. Mixing cylinders 12 having larger or smaller diameters and/or lengths may however, also be used depending on the type and volume of material to be pulped.

Figure 3 shows best the mixing cylinder 12 as being divided internally into three separate mixing chambers 30, 32, 34 which are each delineated radially by the cylinder sidewall 22. The first proximal-most mixing chamber 30 adjacent to the inlet end 24, is delineated in a longitudinal direction by a cylinder end cover 36 at a proximal end, and by a first divider plate 38 at a downstream end 1.5 to 2.5 metres distal therefrom. The end cover 36 is preferably formed as a stainless steel plate which is bolted or welded over the inlet end 24 of the cylinder 12 to substantially prevent the outflow of the pulping fluid/cellulose fibre slurry mixture 8 outwardly therepast. An axially aligned circular end opening 40 is formed through the end cover 36. As will be described, the end opening 40 is configured for cooperation with an infeed pipe 76 of the hopper assembly 16, to permit the substantially continuous input flow of the raw slurry mixture 8 therethrough, and into the mixing chamber 30 during pulping operations.

The downstream divider plate 38 is formed as a circular stainless steel plate which extends laterally across the interior of the mixing cylinder 12 in an orientation substantially transverse to the axis Ai-Aj. Although not essential, most preferably the divider plate 38 is mounted in a substantially sealing arrangement with the cylinder sidewall 22, to prevent the movement of cellulose fibres and/or pulp therebetween.

As shown best in Figures 2 and 3, a number of longitudinally spaced cutting blades or vanes 40a, 40b, are fixedly secured to the cylinder sidewall 22, radially about the mixing chamber 30. The cutting vanes 40a, 40b are shown as being formed as rigid curved bars, and have a length and configuration selected to facilitate the defibering and breakdown of the raw cellulose material 8 as it moves therethrough in the chamber 30, as the mixing cylinder 12 is rotated. Other cutting vane configurations are however, possible.

Figures 3 and 4 illustrate best the divider plate 38 as having a through-opening 42 foπned therethrough. Although not essential, most preferably the through-opening 42 is formed as a circular opening having a diameter di selected at between about 20 and 50 cm. The through-opening 42 is furthermore formed through the divider plate in an asymmetrical position relative to the central axis Aj-Ai, whereby the radial centre Ci (Figure 4) of the through-opening 42 is offset from the axis Ai-Ai by a distance of between about 10 and 25 cm. It is to be appreciated that with this configuration, the rotation of the mixing cylinder 12 about the central axis Ai-Ai in the direction of arrows 100 (Figure 5), moves the through-opening 42 eccentrically relative to the cylinder axis

A ₁ -A ₁ .

Figure 3 shows best the second mixing chamber 32 as immediately adjacent to and downstream from the chamber 30. The mixing chamber 32 has a substantially smooth radial surface, and is delineated in the longitudinal direction by the first divider plate 38 at its proximal end, and at its second distalmost end by a second divider plate 48. Most preferably, the second divider plate 48 is spaced a distance of between about 1.5 and 2.5 metres from the divider plate 38. The divider plate 48 is provided in a substantially sealing arrangement with the sidewall 22 and includes a generally circular through-opening 52 formed therethrough.

As shown best in Figure 4, the through-opening 52 is provided with a diameter d ₂ which is selected greater than the diameter di, and which preferably is selected at between about 30 and 60 cm. The radial centre C ₂ of the through-opening 52 is laterally offset from the axis Ai-Ai to provide for the eccentric movement of the through-opening 52 relative thereto, as the mixing cylinder 12 is rotated. Although not essential, preferably centre C ₂ of the through-opening 52 is spaced from the axis Aj-Ai a greater distance, and in the same radial direction as the centre Ci of through-opening 42.

The downstream-most mixing chamber 34 is likewise provided with a generally smooth sidewall and is delineated longitudinally by the second divider plate 48 at its proximalmost inner end, and an outlet cap plate 54 at its distalmost outer end. The cap plate 54 is formed provided as a stainless steel plate 54 which partially closes the distal end of the mixing cylinder 12. An outlet flow passage or opening 62 formed through the cap plate 54 permits the outflow of the re-pulped fibres 8" from the mixing cylinder 12 for further processing and/or manufacturing applications. The outflow opening 62 is likewise provided for eccentric movement relative to the axis A ₁ -A ₁ . In this regard, the opening 62 is formed as a circular opening having a diameter d ₃ (Figure 4) which is selected larger than the diameter d ₂ of the through-opening 52. Most preferably, the diameter d ₃ is selected at between about 80 and 120 cm, and most preferably about 100 cm. The centre C ₃ of the outlet flow opening 62 is shown best in Figure 4 as being spaced radially from the axis A ₁ -A ₁ , in substantially the same direction as centres Ci and C ₂ , and preferably, with the centre C ₃ is located radially outwardly from the centre C2 of through-opening 52.

Although not essential, in a most preferred construction the minimum radial distances between each of the openings 42, 52 and 62 and the axis A ₁ -A ₁ are approximately equal. The eccentric movement of the openings 42, 52 and 62 relative to the axis Ai-A ₁ , results in the cross-sectional area of the through-opening 52 which is moved eccentrically being greater than the area eccentrically moved portion of the through-opening 42. Similarly, the portion of the outlet flow opening 62 which moves eccentrically about the axis A ₁ -A ₁ , has a greater cross-sectional area than the eccentrically moved portion of the second through-opening 52. As such, as the cylinder 12 rotates, the first divider plate 38 acts as a weir to maintain a greater minimum level Li of raw slurry 8 in the first mixing chamber 30. This increases the residence time of the slurry 8 in the end chamber 30, allowing for maximum mechanical defibration by the rotating cutting vanes 40a, 40b. Because of its larger diameter, d ₂ a greater area of the through-opening 52 moves eccentrically relative to the axis A ₁ -A ₁ , than that of the first flow passage 42. As a result, the through-opening 52 results in a greater outward flow of slurry 8' from the chamber 32 than that from the mixing chamber 30. The divider plate 48 thus maintains a lower minimum level L ₂ of pre-treated slurry 8' in the chamber 32 less than the level Li This ensures the downstream fluid flow from the first mixing chamber 30, into the second mixing chamber 32 when the opening centres Ci, C ₂ are moved downwardly directly below (+ 120°) the axis Aj-Ai.

Similarly, the larger diameter d ₃ of the outlet flow opening 62 allows for a greater outward flow of treated pulp 8" therethrough, then flows through the through-opening 52. This results in the end cover plate 54 maintaining a minimum fluid/slurry 8" mixture level L ₃ in the mixing chamber 34 which is less than the level L ₂ . This again ensures the continued downstream flow of pulp 8" from chamber 32 into and then from chamber 34.

In this configuration, the slurry 8' flows along the mixing cylinder 12 sequentially from the first mixing chamber 30, to the second mixing chamber 32, and thereafter from the second mixing chamber 32 into the third mixing chamber 34, prior to moving outwardly therefrom via the outlet flow opening 62. The eccentric positioning of the through-openings 42, 52 and outlet flow opening 62 further provide a variable slurry 8 flow therethrough. Most preferably, the openings 42, 52 and 62 are provided to restrict or substantially prevent fluid flow from the mixing chambers 30, 32, 34, respectively as the mixing cylinder 12 is rotated through between about 70° and 120° of movement when for example the centres Ci, C ₂ , C ₃ are moved to a position above the axis Ai-Aj. The variable flow advantageously eliminates the formation laminar flow across the top of the slurry volume 8, 8' and 8" in each chamber 30, 32, 34, respectively. In addition, variable flow increases the residence time of the pulp fibres in each of the mixing chambers 30, 32, 34, to maximize the time period for rehydration, agitation and mechanical working by the cutting vanes 40.

Figures 1 and 2 show best the drive assembly 14 as including an electric motor 64 which is coupled in a direct drive manner to a drive chain 66. Optionally a shroud box 70 (Figure 1) may be secured in place over the chain drive 66 and output motor shaft 64 for enhanced safety. The drive chain 66 frictionally engages a rack 68 formed on the end cover 36 and which extends radially about the axis Ai-Aj. The applicant has appreciated that by coupling the motor 64 to the cylinder 12 directly by way of a simple drive chain 66 allows for the use of low horsepower motors. In particular, motors having horsepower selected at less than about 50hp, and preferably about 20 to 30hp may be used to drive the cylinder 12 in rotation about the axis A ₁ -A ₁ . This construction advantageously enables the more economical operation of the pulping apparatus 10, lowering operational costs and thereby increasing the operational efficiency of the apparatus 10 as contrasted with conventional pulpers.

Figure 3 shows best the hopper assembly 16 as including a hopper box 74, infeed pipe 76 and pulping fluid conduits 78. The hopper box 74 opens along its lower most centre into an upper most portion of the feed pipe 76. The feed pipe 76 extends in a generally downwardly sloping configuration through the end cover opening 40 to provide fluid communication with the first mixing chamber 30. Most preferably, an electric feed auger 80 is disposed within the feed pipe 76. The auger 80 is operable to assist in the movement of the fluid cellulose fibre/slurry 8 from the hopper box 74 and into and along the feed pipe 76 and into the cylinder 12. It is to be appreciated that fluid conduit pipes 78 provide fluid communication between a water and pulping chemical sources (not shown) and an upper portion of the hopper box 74. The conduit pipes 78 most preferably supply water and pulping fluid into the upper portion of hopper box 74 to assist in the flow of slurry 8 into mixing cylinder 12 via the feed pipe 76. It is to be appreciated that other constructions for supplying pulping fluid into the cylinder 12 may also be used.

In use of the apparatus of Figure 1, the electric motor 64 is initially actuated to rotate the mixing cylinder 12 about the axis Ai-Ai. Partially shredded recycled paper and cardboard cellulose fibres are fed in a continuous manner into the open hopper box 74. Concurrently, water and pulping fluid is supplied to the hopper box 74 via the conduit pipes 78, with the electric feed auger 80 is activated to provide a substantially constant supply of the raw slurry 8 into the first mixing chamber 30.

As the input raw slurry 8 moves into the first mixing chamber 30, the rotation of the cylinder wall 22 moves the cutting vanes 40 through the slurry 8 to assist in breaking up the cellulose fibres a first stage process. Because of the smaller diameter di and eccentric movement of the through-opening 42, as the mixing cylinder 12 rotates, the partially processed slurry 8 mixture will move from the first mixing chamber 30, through the divider plate 38 and into the second mixing chamber 32 at a variable rate, with an increased flow occurring as the through-opening 42 travels along a downwardly extending arc, and with a reduced flow rate as to the centre of the opening 42 moves upwardly relative to the axis Ai-Ai.

As the partially processed slurry 8' moves into the second mixing chamber 32, the smooth sidewall of the second mixing chamber results in the settling of heavier unhydrated cellulose fibres towards the chamber bottom 12. As the residence time of the heavier cellulose fibres increases, the fibres tend to more fully hydrate. The rotation of the mixing cylinder 12 in turn results in the buoyancy of the more hydrated cellulose fibres towards the top portion of the slurry 8'. The hydrated fibres tend to move by way of variable flow through the opening 52 and into the third mixing chamber 34, as the flow volume from the mixing chamber 32 increases with the eccentric movement of the through-opening 52 along the downwardmost path of movement. In the third mixing chamber 34, any remaining heavier unhydrated or partially hydrated fibres 8" tend to settle towards the bottom of the chamber 34. The partially hydrated fibres thus are similarly retained in the mixing chamber 34 resulting in more complete hydration, prior to movement through outlet flow passage 62, the eccentric path of the opening 62 providing variable flow therefrom.

Although the preferred embodiment shown in Figure 3 illustrates the mixing cylinder 12 as including a number of cutting vanes 40 within the mixing chamber 30, the invention is not so limited. It is to be appreciated that in an alternate construction, cutting or mixing blades, vanes, ploughs or other equivalent structures could be included in one or more of each of the mixing chambers 30, 32, 34, without departing the spirit and scope of the invention.

While Figure 3 shows the cylinder 12 as having three separate mixing chambers 30, 32, 34, it is to be appreciated that in an alternate configuration, the mixing cylinder 12 could include either additional or fewer mixing chambers without departing from the spirit and scope of the invention.

Although Figure 4 illustrates the centres C ₁ , C ₂ , C ₃ of the through-openings 42, 52 and outlet flow opening 62 as being spaced radially in the same direction away from the axis A ₁ -A ₁ , the invention is not so limited.

Figure 6 illustrates an alternate possible through-opening configuration, wherein like reference numerals are used to identify like components. In Figure 6, each of the through-openings 42, 52, 62, is formed as a cylindrical opening which are arranged in a concentric position centered on the axis Ai-Aj. Through-opening 42 is provided with a diameter di which is preferably selected at between about 30 and 60 cm. Through- opening 52, is provided with a diameter d ₂ which is greater than the diameter di, and most preferably which is selected at between about 50 and 100 cm. The outlet flow opening 62 is foπned with a diameter d ₃ , which is selected greater than d ₂ , and is preferably sized between about 100 and 150 cm. It is to be appreciated that larger or smaller diameter openings 42, 52, 62 could equally be provided. From the construction shown, it is to be appreciated that the smaller diameter of the through-opening 42 acts as a weir to maintain a higher level Li of pulp 8 in the mixing chamber 30, than the level L ₂ maintained in mixing chamber 32. Similarly, because of the larger diameter d ₃ of the outlet opening 62, the level of pulp 8" (Figure 2) is maintained in the mixing chamber 34 at a lower level L ₃ which is less than the level L ₂ .

The greater volume of fluids maintained in the mixing chamber 30 acts to increase the residence time of the pulp therein as the cylinder 12 rotates about the axis

A ₁ -A ₁ .

Figure 7 illustrates yet a further alternate possible through-opening configuration, wherein like reference numerals are used to identify like components. In the construction shown in Figure 7, the through-opening 52 of the second divider plate 48 is positioned for eccentric movement in a radially opposite manner as the path of movement for the through-opening 42, and outlet flow passage 62. It is to be appreciated that the construction of Figure 7 advantageously allows for the backflow of slurry 8 within the cylinder 12 as it rotates. Other opening positions and/or configurations are also possible and will now become apparent.

Similarly, although Figures 4, 6 and 7 illustrate the through-openings 42, 52 and outlet flow opening 62 as each having axially overlapping circular shapes, the invention is not so limited. It is to be appreciated that the through-openings could be provided a variety of shapes, including without restriction, either a polygonal or non-geometric profile. Alternately, the divider plates 38, 48 and/or end cap plate 54 could be provided with multiple openings as fluid flow passages adapted to permit variable fluid flow therethrough, while maintaining the desired minimum fluid levels in each of the mixing chambers 30, 32, 34.

Although Figure 3 illustrates the second and third mixing chambers 32, 34 as having a substantially smooth solid radial sidewall, the invention is not so limited. If desired, the mixing chambers 32, 34 could equally include vanes, mixing members, or agitators without departing from the spirit and scope of the invention. Although the detailed description describes and illustrates the pulping apparatus 10 as being used in the re-pulping of waste cardboard and paper, the invention is not so limited. In an alternate use, the apparatus is equally suitable for use as a pulper in the processing and defibration of virgin cellulose material.

While the detailed description describes the pulping apparatus 10 as incorporating a low voltage electric motor 64 and drive chain 66, the invention is not so limited. It is to be appreciated that in a less preferred construction, higher horsepower motors and/or geared drive linkages and/or transmission could alternately be employed to effect rotational movement of the mixing cylinder 12, without departing from the spirit and scope of the invention.

Although the detailed description describes and illustrates as preferred aspects, the invention is not so limited. Many modifications and variations will now occur to persons skilled in the art. For a definition of the invention, reference may be had to the appended claims.