Note: Descriptions are shown in the official language in which they were submitted.
The present invention relates to apparatus for comminuting
bulky commodities, especially for comminuting large pieces of
industrial and/or domestic waste materials.
Canadian patent No. 911,398 discloses an apparatus which
is used to comminute bulky pieces of sheet metal, synthetic plastic
substances, glass, wood, textile materials and the like. The
apparatus comprises two shafts which are driven to rotate at the
same speed but in opposite directions and carry cooperating cu-tting
or comminuting elements. Each comminuting element on one of the
shafts cooperates and comminutes oncoming pieces of waste material
with the adjacent comminuting element on the other shaft. Also,
each comminuting element has a flat end face, which is normal to
the axis of rotation of the respective shaft, and several peripheral
projections or lobes which alternate with recesses. The cooperating
comminuting elements on the two shafts are positioned in such a
way that the marginal portions of their end faces (which are bounded
by sharp cutting edges~ partially overlap each other. When the
apparatus is in use, successive lobes and recesses of a comminuting
element on one of the shafts overlie successive recesses and lobes
of the cooperating comminuting element on -the other shaft whereby
the material is comminuted by the aforementioned sharp cutting
edges which surround the flat end faces of the comminuting elements.
It has been found that the marginal portions of end faces
of the comminuting elements in the apparatus of the Canadian
publication undergo very pronounced wear, i.e., the wear on such
marginal portions is much more pronounced than the wear on the
inner portions of the comminuting elements. Consequently, the
comminuting action of the apparatus becomes less satisfactory with
progressing wear upon the marginal portions, and the apparatus
ceasesto comminute the introduced material after a certain period
of use. Compensation for such wear by shifting the comminuting
elements axially of the respective shafts or by shifting one of
the shafts relative to the other shaft can be resorted to but only
to a certain degree. In fact, such axial adjustment can result in
further deterioration of the comminuting action because the
originally sharp cutting edges which surround the flat end faces
of comminuting elements on one of the shafts rub against and are
dulled by the adjacent surfaces of cooperating comminuting elements
on the other shaft. As a rule, the comminuting elements must be
ground after a certain period of use or they must be replaced by
fresh comminuting elements. All this contributes to the maintenance
cost of the apparatus and results in long intervals of idleness.
The invention is embodied in an apparatus for comminuting
bulky pieces of waste material or the like. The apparatus comprises
first and second rotary comminuting elements or knives having
adjacent end faces which are bounded by cutting edges and include
raised marginal zones which partially overlap each other, and means
for rotating the knives in opposite directions, preferably at the
same speed, about parallel axes to thereby move successive increments
~o of the marginal zones into ovexlapping positions. Thus, as the
knives rotate in opposite directions, their margina] zones travel
with respect to each other but a portion of one raised marginal
zone always overlaps a portion of the other raised marginal zone.
The locus of overlap is located between the two axes. The knives
preferably comprise peripheral projections or lobes which alternate
with recesses, and the angular positions of the kni~es are such
that, in the region where successive increments of the two raised
marginal zones overlap each other, a projection of one of the
knives moves along a recess of the other knife and vice versa in
each angular position of the knives.
The raised marginal zones are preferably obtained by
providing the end faces of the knives with shallow grooves or
depressions which are surrounded by the respective marginal zones
and which preferably constitute endless grooves. A portion of the
cutting edge of one of the knives preferably extends all the way to
the outer boundary of the nearest portion of the groove in the end
face of the other knife and vice versa. This insures uniform wear
upon the entire marginal zones of both knives.
The novel features which are considered as characteristic
of the invention are set forth in particular in the appended claims.
The improved comminuting apparatus itself, however, both as to its
construction and its mode of operation, together with additional
features and advantages of its comminuting elements, will be best
understood upon perusal of the following detailed description of
certain specific embodiments with reference to the accompanying
drawing.
FIG. 1 is a fragmentary schematic transverse sectional
view of a portion of a comminuting apparatus which embodies the
invention; and
FIG. 2 is a sectional view of a set of cooperating
comminuting elements as seen in the direction of arrows from the
line II-II of FIG. 1.
The comminutlng apparatus of FIG. 1 comprises two parallel
shafts 5 (only one shown) which respectively support and rotate
two groups of comminuting elements A and B. One of the comminut:ing
elemen-ts A is shown in full detail in each of FIGS. 1 and 2. A
- portion of one of the co-~ninuting elements B is shown in FIG. 2.
The comminuting element A (hereinafter called knife for short)
comprises three equally spaced peripheral projec-tions or lobes 1
which alternate with recesses 2. The end face 3 of the knife A
has a shallow depression 4 which is a circumferentially complete
groove of triangular outline. Each of the three apices of the
groove 4 extends into a different lobe 1. The outer boundary 41
of the groove 4 is closely adjacent to and follows, to a certain
degree, the outline of the peripheral surface of that portion of
- the knife A which is adjacent to the end face 3. Successive
- increments of the raised marginal zone 141 around the outer boundary
41 of the groove 4 are contacted by successive increments of the
similar raised marginal zone of the knife B when the appara-tus is
LQ in use and the knives A and B rotate with respect to each other
in opposite directions. The speed of the shaft 5 for the knife A
equals the speed of the shaft for the knife B. The shaft 5 extends
through a central bore 105 of the knife A and is connected thereto
by a key 5a.
The inner boundary 42 of the groove 4 has a pronounced
triangular shape (i.e., it is a polygon with n sides wherein _
equals the number of lobes 1 or recesses 2) and is spaced apart
from the shaft 5.
The end face 3 of the knife A has three equidistant blind
bores or socke-ts 7 for coupling pins (one indicated at 7a by
phantom lines) which connect the knife A to the adjacent knife on
the same shaft 5. The other end face 103 of the knife A has three
equidistant socke-ts 6 for coupling pins (one indicated by phantom
lines, as at 6a) which connect the knife A to another knife on the
same shaft 5. The sockets 6 and 7 are angularly offset relative
to each other~ as considered in the circumferential direction of
the shaft 5, to an extent which corresponds to angular spacing of
two neighboring knives on the same shaft. The centers of all
sockets 6 and 7 are located on a circle whose center is located on
the a~is of the shaft 5. The angular distance between two
neighboring sockets 6, 7 is between 8 and 10 degrees. It will be
noted that the sockets 7 are disposed between the inner boundary
42 of the groove 4 and the bore 105.
The configuration of the knife B is ldentical to that of
the knife A.
The sharp cutting edge 241 of the knife A surrounds the
raised marginal zone 141 and cooperates with the cutting edge of
the knife B to sever a piece of waste material which penetrates
between the knives A and B when the knives rotate in opposite
directions. The comminuted material thereupon advances into the
range of the next set of cooperating knives (adjacent to the knives
A and B) to undergo further comminuting action, and so forth until
the finely comminuted fragments reach the outlet of the apparatus.
When the raised marginal zones 141 undergo a certain
amount of wear, the knife A and/or B is shifted axially of the
respective shaft to move the marginal zones nearer to each other.
The same procedure is repeated again, when necessary, at least
until the zones 141 wear away to such an extent that their exposed
surfaces are flush with the bottom surfaces of the respective
recesses 4~ i.e., until the recesses disappear. Thus, the knife
A and/or B can be adjusted at least once without any danger that
the cutting edge 241 of the knife A would penetrate into the end
face 3' of the knife B or vice versa. It has been found that the
useful life of improved knives is a multiple of the useful life of
conventional knives without raised marginal zones.
In order to insure uniform wear upon the entire raised
marginal zones 141, a portion of the cutting edge 241 of the knife
A preferably extends all the way to the nearest portion of the
outer boundary 41 of the groove in the knife B and vice versa.
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