GB2044631A - Conical refiners - Google Patents

Abstract

A conical rotor or stator is made by welding blades to a body, the blades, body and welds being of corrosive resistant material, e.g. stainless steel, upon wearing the blades may be removed by machining and new blades re-welded onto the body. <IMAGE>

Description

SPECIFICATION Pulp refining cone This invention relates to refining cones e.g. for use in the pulp and paper industry and to a method of making such cones.

Refining cones are used in conical assemblages usually consisting of a rotor and a stator e.g. for the comminution and refinement of cellulose pulp and other similar materials employed in the pulp and paper industry. The rotor and stator each consists of a conical body from whose surfaces project an array of blades. The rotor and stator are mounted with their bladed surfaces opposing one another and the rotor is rotated relative to the stator. A slurry consisting of pulp fibres and water is fed into the annular space between the rotor and stator and these fibers are pulverized and refined to a state where they are useful in the manufacture of paper.

Traditionally refining cones have been monoblock parts cast of stainless steel or other corrosion resistance material. In other words, the conical body and the blades were cast as an integral piece using conventional foundry procedures. However, cones made in accordance with that traditional technique have not been entirely satisfactory. The cast blades which are on the order of 3 mm high tend to break after the cone has been in use for only a relatively short time because of their porosity and lack of flexibility. This is particularly so if the cones are used to refine hardwood fibers such as eucalyptus wood.

Also when casting refining cones, due to the foundry process, the blades have to be spaced relatively far apart in order to remove the piece from the mold.

Therefore, when the cones are in operation, it takes longer to achieve fine comminution of the pulp fibers.

Most importantly because of their aforesaid porosity, the cast blades become worn quite quickly and lose their edge. Consequently the cones have a relatively short operating life. Moreover, as the blades wear down, the clearance between the rotor and stator must be reduced in order to adequately pulverizethe pulp. That, in turn, necessitates using a higher specific pressure in order to force the pulp through the refiner, which higher pressure results in the consumption of more energy.

We are also aware of a refining cone composed of a carbon steel sheet which is rolled into a cone and welded along the abutting edges to provide a plane conical body. Then stainless steel blades are welded to the surface of the body. Following that, all of the spaces between the blades are covered with stainless steel electroded material so that only stainless steel surfaces are exposed to the pulp. Cones made in accordance with that technique are longer lived than the cast variety. However, they are quite costly and time consuming to fabricate because of the necessity of covering up the spaces between the blades with noncorrosive material.

According to the present invention, a pulp refining cone comprises a conical body of corrosion-resistant metal, an array of spaced-apart blades of a corrosion-resistant metai, and welds securing the base of each blade to the body, said welds being formed of a corrosion-resistant metal.

Preferably, the metal of the body, the blades and the welds is the same.

Conveniently, the corrosion-resistant material is stainless steel.

Conveniently, the body is plane, Conveniently, the body is cast.

Conveniently, the blades are forged or relaminated.

Conveniently, the welds are continuous uninterrupted or interrupted welds.

Conveniently, the welds are at opposite sides of each blade.

Conveniently, at least some of the blades are of different lengths.

The invention also includes a method for the preparation and recuperation of refining cones comprising the steps of casting a conical body of stainless steel, said body having a hollow interior, forming a multiplicity of blades of relaminated or forged stainless steel, positioning the blades in an array on the surface of the body so as to produce refining areas for fibers, securing the blades at their bases to said surface by uninterrupted or interrupted stainless steel welds, there being welds on both sides of each blade, and machining and balancing the bladed body to its finished form.

The invention further includes a conical refining assemblage comprising a rotor cone according to the present invention or as manufactured by the method of the present invention in combination with a stator cone according to the present invention or as manufactured by the method of the present invention.

Refining cone according to the present invention may therefore comprise a forged plane conical body cast of stainless steel or other corrcjsive-resistant material which faithfully reproduces the part known as the refiner rotor or the stationary part known as the stator. The surfaces of the conical part may be made smooth and be prepared for receiving the refining blades. These blades produce the refining areas whose shapes and sizes depend upon the refinement desired for the pulp fibers being processed.

As already discussed above, the blades themselves may be made of relaminated or forged stainless steel and be affixed to the conical body by means of continuous welding either uninterrupted or interrupted (e.g. spot welding). If the cone is to be used as a rotor, the blades are affixed to the outside surface of the body. If the cone is designed to be a stator, the blades are welded to the inside surface of the conical body. Thus two conical bladed bodies are required for a complete refining assemblage. The bladed cones are then finished machined and balanced whereupon they are ready for use.

The forged blades may be designed in a variety of shapes and sizes and oriented in a variety of ways on the conical bodies depending upon the particular application. When the blades are made of forged stainless steel which is extremely strong and rugged, the blades typically have an operating life of three to four times that of the prior art cones and their edges tend to remain sharp and without burrs during that operating life. Consequently, there is little or no necessity to lessen the clearance between the rotor and stator because of excessive blade wear. As a result, the pulp fibers flow relatively easily through the refiner so that pulp pulverization is achieved using a reduced amount of energy.

Because the entire cone is constructed of stainless steel e.g. stainless steel body, stainless steel blades and stainless steel welds, or other corrosion resistant metal, there is no problem of corrosion and there is no need to apply e.g. a stainless steel covering in the spaces between the blades to mask or cover the underlying corrosion prone cone body as was necessary in the case of some of the prior art cones. Therefore, the aforesaid longevity may be achieved without materially increasing the overall cost of the finished cone.

When the blades on the cones ultimately do wear down through prolonged usage, the conical body can simply be machined to remove or to resmoothen its surface and eliminate traces of the worn blades.

Whereupon new sharp blades can be welded to the body in exactly the same way so that the body e.g. of stainless steel, which constitutes the largest and most expensive component of the cone can be used and reused many times to achieve the same superior results over many years.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure lisa perspective view of a refining cone rotor made in accordance with this invention; Figure 2 is a similar view of a stator cone component; Figure 3 is a smaller view showing a conical body for the Figure 1 rotor; Figure 4 is a similar view showing a conical body for the Figure 2 stator; and Figure 5 is a perspective view showing a plurality of blades used to form the rotor and stator of Figures 1 and 2.

Referring first to Figures 3 and 4 of the drawings, hollow forged conical plane bodies 1 and 2 are cast of stainless steel, body 1 for the refining rotor and body 2 for the stator The shapes of these two bodies should of course correspond so at the rotor can fit inside the stator with their sidewalls uniformly spaced apart around the circumferences of the two bodies.

A plurality of forged stainless steel blades 3 are secured to the outside surface of body 1 (Figure 1) and to the inside surface of body 2 (Figure 2). The dimensions of the blades as well as their oreintations-on the conical bodies may vary depending upon the particular application. Figure 5 illustrates rotor blades in the upper half of the Figure and stator blades in the lower half. These blades comprise relatively long rectangular blades 3a and shorter rectangular blades 3b. In this specific embodiment, the blades are arranged parallel to the generatrix of the conical bodies. They could, of course, be longer or shorter than shown and be arranged in various criss-crossing patterns as is common with such refining disks and cones.

In any event, each blade 3 is secured to the appropriate body surface by continuous stainless steel welds 6 at each side of the blade at the base thereof.

These welds may be uninterrupted in the form of beads orspotwelding may be employed to securely anchorthe blades to the bodies. By virtue of thins mode of formation of the blades on the bodies, the blades can be spaced very closely together so that the cones perform their refining functions very efficiently.

Further, since the conical bodies 1 and 2, the blades 3 and the welds 6 are all made of noncorrosive stainless steel, there is no necessity to coat the spaces between the blades with some form of noncorrosive coating as was necessary heretofore with the prior art systems. Typically, the blades are forged of 304 stainless steel (AISI). Each blade may be on the order of 10 to 40 mm high and 3 to 12 mm thick. The spacing between the blades may vary from, say, 3 mm to 18 mm and they may be inclined relative to the cone axis of symmetry from 0 to 45".

Because the blades 3 are forged of rugged stainless steel material, they maintain their edges without burrs for a prolonged period of time even though the cones are used to refine very hard pulp fibers. Consequentlythe refining assemblages can be operated for a prolonged period at the same set spacing so that the pulp fibers pass relatively easily between the rotor and stator units. Thus a refiner employing these cones can be operated with a minimum amount of energy.

When the blades 3 ultimately become worn, the conical bodies 1 and 2 can simply be machined to remove the blade residuums and new sharp blades attached in the same way to the new refurbished bodies 1 and 2. Thus the relatively expensive stainless steel bodies can be recycled time after time resulting in a considerable cost savings over the years.

Thus when compared with prior art systems, pulp refining cones according to the present invention tend to have the following advantages. An especially long useful life; teeth which maintain their edges for a prolonged period; a main body which can be reused a plurality of times; and blades which can be positioned closely together for maximum refining effectiveness.

In addition pulp refining cones according to the present invention tend to be relatively easy and inexpensive to manufacture and they offer the possibility of providing conical refining assemblages which promote energy conservation when used in a refiner.

Claims (13)

1. A pulp refining cone comprising a conical body of corrosion-resistant metal, an array of spaced-apart blades of a corrosion-resistant metal, and welds securing the base of each blade to the body, said welds being formed of a corrosion resistant metal.

2. A cone as claimed in Claim 1 in which the metal of the body, the blades and the welds is the same.

3. A cone as claimed in Claim 2 wherein said corrosion-resistant material is stainless steel.

4. A cone as claimed in any of Claims 1 to 3 in which the body is plane.

5. A cone as claimed in any of Claims 1 to 4 in which the body is cast.

6. A cone as claimed in any of Claims 1 to 5 in which the blades are forged or relaminated.

7. A cone as claimed in any of Claims 1 to 6 in which said welds are continuous.

8. A cone as claimed in any of Claims 1 to 7 in which said welds are at opposite sides of each blade.

9. A cone as claimed in any preceding Claim in which at least some of said blades are of different lengths.

10. A cone substantially as hereinbefore described with reference to, and as illustrated in, Figures 1,3 and 5 of the accompanying drawing.

11. A cone substantially as hereinbefore described with reference to, and as illustrated in, Figures 2,4 and 5 of the accompanying drawing.

12. A method for the preparation and recuperation of refining cones comprising the steps of casting a conical body of stainless steel, said body having a hollow interior, forming a multiplicity of blades of relaminated or forged stainless steel, positioning the blades in an array on the surface of the body so as to produce refining areas for fibers, securing the blades at their bases to said surface by uninterrupted or interrupted stainless steel welds, there being welds on both sides of each blade, and machining and balancing the bladed body to its finished form.

13. A conical refining assemblage comprising a rotor cone as claimed in any of Claims 1 to 9 or Claim 100rays manufactured in accordance with the method of Claim 12 in combination with a stator cone as claimed in any of Claims 1 to 9 or Claim 11 or as manufactured in accordance with the method of Claim 12.