Solid material comminution or disintegration – Apparatus – Cooperating comminuting surfaces
Patent
1980-03-05
1982-09-14
Rosenbaum, Mark
Solid material comminution or disintegration
Apparatus
Cooperating comminuting surfaces
241294, B02C 408
Patent
active
043491596
DESCRIPTION:
BRIEF SUMMARY
The invention relates to cutters for a rotary shredding machine, and to rotary shredding machines of the kind (hereinafter referred to as a "machine of the kind hereinbefore specified") having a comminuting chamber, a pair of parallel cutter shafts arranged for simultaneous contra-rotation in the comminuting chamber, and a plurality of said cutters carried by the shafts, at least one of the shafts having more than one said cutter secured thereon and the cutters of one shaft being interleaved with the cutter or cutters of the other, so as to co-operate in comminuting material fed into the chamber. The cutters to which the invention relates are of the kind comprising a generally disc-like body having at least one radially-projecting peripheral tooth provided with a cutting edge, along a leading edge thereof, and the body defining a coaxial shaft aperture therethrough to accommodate a said shaft and defining a cutter axis. Such a cutter will be called a "cutter of the kind hereinbefore specified".
Although machines of the above kind are normally referred to as shredding machines or shredders, their comminuting action takes a form or forms which depend largely on the nature of the material being comminuted, and on the design of the cutters. The latter may in practice perform very little cutting as such; for example, glass will tend to be crushed into small pieces, whilst other common materials, such as thin metal, will tend to be torn and/or deformed by crushing. The material to be comminuted is most usually scrap or waste material, though shredders can be used to break up solid materials as part of, or in preparation for, industrial processes of various kinds.
Various types of shredding machine of the kind hereinbefore specified are in commercial use or have been proposed. For example, such patent specifications as those of British Pat. Nos. 1315347, 1310057 and 1491611 variously teach the use of cutter shafts of cylindrical or hexagonal cross-section, with various means for securing the cutters to the shafts. Hexagonal shafts, by virtue of their shape, have an advantage in that if the cutter has a hexagonal hole fitting the shaft, the former cannot slip around the latter. On the other hand, a circular shaft is very much easier to make and probably cheaper, but may require additional expedients such as splining, keying or the use of suitable adhesives, to ensure that the cutter will not rotate with respect to the shaft.
According to the present invention, in a first aspect, in a machine of the kind hereinbefore specified, each cutter shaft is of substantially square cross-section, a shape which is both simple to machine and enables the shaft aperture of each cutter to be made with a minimum number of stress raisers without the disadvantages attendant on a cylindrical shaft.
In a second aspect, the invention provides a cutter for mounting on such a cylindrical cutter shaft in a machine according to the invention, wherein the shaft aperture of the cutter is itself substantially square, the cutting edge of the or each tooth being intersected by a radial plane inclined at an angle in the range 0.degree. to 60.degree. with respect to a diametral plane bisecting one side of the square shaft aperture, said angle being defined forward of the cutting edge in the direction of intended rotation of the cutter. The value of this angle is preferably chosen so that the optimum strain pattern is set up in the cutter body members when the cutting edge of the tooth is subjected to a tangentially applied force, i.e. the most even stress distribution throughout the cutter consistent with the greatest local strain at any one point in the cutter being at an acceptable level. Tests for one design of cutter according to the invention have established on this basis an optimum value of 50.degree. for this angle.
A cutter having a square shaft aperture, according to the invention, is preferably of split form having two or more cutter body members held together by releasable fastening means, with a tooth carried, integrally or as a sepa
REFERENCES:
patent: 779625 (1905-01-01), Scheetz
patent: 3840187 (1974-10-01), Brewer
Hardwick John P.
Pezet Michael J.
Sarvestany Asadollah A.
Satharasinghe Dayananda
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