Note: Descriptions are shown in the official language in which they were submitted.
35~36
The present invention relates to mineral
sizing in partlcular to mineral sizer and a tooth
construction~
According to one aspect of the present
invention, there is provided a mineral breaker including
a pair of side by side breaker drums each having breaker
teeth projecting radially therefrom, the teeth being
arranged so as to define a series of discrete
circumferentially spaced helical formations extending
along the drum, and wherein the teeth on each drum are
arranged in circumferentially extending groups of teeth,
the groups of teeth on one drum being located between
adjacent groups of teeth on the other drum, the teeth on
at least one of said pair of drums being arranged to
define said helical formations.
According to another aspect of the present
invention, there is provided a tooth for a mineral
hreaker comprising a main support body covered by a
sheath, the tooth sheath including a hollow tooth forma-
tion having a pocket which is seated on the support body
and fully envelopes said support body, the shape of said
body and pocket being complementary so that loadings
applied to the tooth sheath are transmitted onto the
main body.
Advantageously, when assembling a drum composed
oE a series of annuli, the annuli may be either
independently keyed or splined to the common shaft or they
may be rings being fixedly secured to one another to form
said drum. The former is presently preferred as it
enables the drum to be disassembled. Alternatively the
assembly of annuli and shaft may be cast integrally to
provide a support for the tooth sheaths.
Preferably, the tooth sheaths when in position
on all projections serve to completely cover the support
or drum to thereby protect it from abrasive wear caused
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~ ~35~36
by breakage of mineral,
According to another aspect of ~he present
invention there is provided a mineral sizer having at
least one rotatable drum assembly ~ncluding a tooth
S construction as defined above~
Various aspects of the present invention will
now be descrlbed with reference to the accompanying
drawings, in which:-
Figure 1 ls a part perspective view of a mineral10 sizer according to one aspect of the present invention;
Figure 2 is an end view, partly ln section, of
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shown in Figure l;
Figure 3 is a side view of the sizer shown in Figure l;
Figure 4 is a longitudinal section through the sizer
shown in Figures 1 to 3 wherein the sizer teeth are arranged
in lines parallel to the axis of rotation of the drums;
Figure 5 is an exploded perspective view of a tooth
sheath and support according ~o another aspect of the present
invention;
Figure 6 is a diagrammatic end view of the sizer drums
shown in Figure 2;
Figure 7 is a diagra~natic view of the sizer drums shown
in Figure 2;
Figure 8 is a similar view to Figure 4 showing an
alternative embodiment according to the present invention;
Figure 9 shows a support ring for forming part of a
breaker drum in a mineral si~er according to another
em~c~liment of the present invention;
Figure 10 shows a sec-tion along line X-X in Figure 9;
Figure 11 shows a support ring similar to the support
ring shown in Figure 9 but of reduced diameter;
F`igure 12 is a front view of a tooth cap for fitting
onto the support rings o~ Figures 9 to 11;
Figure 13 is a side view of tooth cap of Figure 12;
Figure 14 is a plan view of the tooth cap of Fiqure 12;
Figure .15 is a section along line VII-VIf in Figure 14;
Figure 16 is a section along line VIII-VIII in Figure
14;
Figure 17 is a side view of a further tooth sheath
construction according to the present invention;
Figure 18 is a section along line A-A in Figure 17;
Figure 19 is an end view as seen in the direction of
arrow B in Figure 17;
Figure 20 is a side view oE a further tooth sheath
construction accordinq to the present invention;
Figure 21 is a pl~n view taken along arrow C in Figure
20;
Figure 22 is a section view taken along line BB-BB in
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F'igure 21 and showing the sheath seated on a corresponding
support ring; and
Figure 23 isa part perspective view of a mineral sizer
including drum assemblies made up of tooth sheaths and
support rir.gs illustrated in Figures 20 - 22.
Referring initially to Figures 1 to ~ and 7 the sizer 10
includes a housing 11 having sides 12 and end walls 14. The
housing 11 is conveniently fabricated from steel plate panels
which are bolted and welded together.
Rotatably mounted to extend between the end walls 14 are
a pair of breaker drum assemblies 15 each of which is ~eared
at one end to the other so that they are driven from a common
drive 18 to be rotated in opposite directions. In the
embodiment illustrated in Figure 1 the drums are rotated so
as to direct material between them. The gear connection
between the drums also serves to set the rotary positions of
the drums relative to one another.
Each drum assembly 15 is provided with circumferentially
extending groups 19 of breaker teeth 20, the groups 19 being
spaced axially along the drum assembly 15. The axial spacing
of groups 19 on one drum assembly is staggered to that on the
other drum assembly so the teeth 20 in a group 19 on one drum
assembly pass between an adjacent pair of groups 19 on the
other drum assembly.
As seen by reference to Figures 1 and 7, the teeth 20
are also preferably arranged to define a series of discrete
helical formations 21 which are spaced circumferentially
about each drum assembly 15. The helical formations 21 as
shown in Figures 1 and 7 extend along the axes of each drum
in a different sense, i.e. for the left hand drum as seen in
Figure 1 the helical format:ions 21 extend away from the
nearest end wall 1~ in an anti-clockwise sense and for the
right hand drum the helical formations 21 extend in a
clockwise sense. Preferably each helical formation 21 in
extending along its respective drum passes through an arc of
about 90.
rrhe shape of teeth 20 and their relative positions and
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size are such that during use, two types of breaking action
are present, viz a primary breaking action on larger pieces
of mineral whereat the mineral is gripped betw~en opposing
leading faces 46 of teeth on opposite drums and a secondary
breaking action wherein mineral is trapped between the rear
edges 47 of teeth and the leading face 46 o~ another tooth.
Preferably the arc through which end helical formation passes
is such as to ensure that a secondary breaking action occurs.
Additionally the spacing between the drums is chosen to
that when the tips of teeth on one drum sweep passed the
trough defined between groups 19 of teeth on the other drum
there is sufficient clearance so that compaction of material
is avoided. Accordingly by a suitable choice of spacing it
is possible for fine material to quickly pass through the
sizer without compaction, thus leaving the sizer to break
down larger pieces of material either by the primary and/or
secondary breaking action.
The shape of teeth 20 are designed bearing in mind the
hardness and tensile strength of the mineral to be broken.
Preferably the teeth are designed to provide as much bite as
possible for the primary type of breaking action for the
diameter of the drum assembly so as to positively grip large
pieces of material. Accordingly the ratio of height of teeth
relative to drum diameter is normally large. For example,
the tooth height to diameter of drum ratio can be 1 : 4. In
this respect, the cross-sectional extent of a bite region 70
for primary breaking is illustrated in Figure 6, the depth of
the region 70 is defined by the trailing edge 47 of one tooth
and the leading edge 46 of a succeeding tooth; and the length
of the region 70 is defined between the leading face 46 of
one tooth and the leading face 46' of an opposed tooth on the
opposite drum. In the embodiment of Figure 6, the trailing
edge 47 which is slightly curved, but which may be straight
if desired, is chosen to be approximately tangential to the
drum diameter and the leading face 46 is chosen to be
approximately located radially relative to the drum. The
grip region between teeth on the same qroup may be varied to
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alter the size of the grip region by either altering the size
of tooth or by altering the number of teeth in each group l9,
the maximum grip region being achieved when the point of
intersection of face 46 is on or behind (in the direction of
rotation of the drum) the location whereat the trailing edge
of the preceding tooth merges into the periphery of the drum.
~ hen the teeth are arranged to form helical formations
21 as shown in Figures l and 7 the grip reqion varies in
width longitudinally of the drums as illustrated in Figure 7.
Accordingly a large piece of material 80 (shown in broken
lines) undergoes a succession of primary breaking actions and
due to the helical formations 21 the large piece of material
~0 is exposed to twisting forces and is urged to move axially
along the drums. These actions on a large piece of material
result in the piece being successively exposed to positive
primary breaking actions and cause it to dance on the drums
and do not allow it to settle on them. A similar action is
imposed during secondary breaking. Thus problems associated
with pieces of mineral settling on the drums and becoming
grooved by the rotating teeth are avoided.
A further advantage resulting from the actions imposed
on a large piece of material by the helical formations is
that the large piece is positively moved along the axes of
the drums thereby permitting smaller pieces to pass
downwardly thereby and pass through the mineral breaker.
Accordingly the mineral breaker is able to handle an in fill
of mineral which contains a large variation in size such as
mineral obtained in open-cast quarrying which contains small
particulate material as well as large lumps of mineral.
It will be appreciated that the teeth impose tensile
breaking forces onto the mineral and so positively breaks the
material with minimal production of fines. Additionally
since each tooth passes between groups of teeth on the
opposite clrum positive sizing of mineral occurs since the
maximum size of mineral passing through the sizer is
determined by the space between the trailing ec!ge 47 of one
tooth and the leading face ~6 of a succeeding tooth and the
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distance between adjacent groups 19 of teeth. Therefore if
the in-fill material contains only large pieces of mineral
the mineral on leaving the sizer will contain no pieces over
a predetermined size and will contain a small quantity of
fines.
It is also envisaged that the breaker drums may be
inclined to the horizontal and arranyed so that large pieces
of mineral are made to climb up the incline by the helical
formations. Cue to the agitation of the large piece of
mineral it is likely to fall down the incline and is
accordingly repeatedly moved along the drums until it has
been broken down sufEiciently to be broken by the secondary
breaking action.
As shown schematically in Figure 7, the mineral sizer
according to the present invention is normally located above
a takeaway conveyor TC so that the axes of the drums are
generally parallel to the direction of travel of the conveyor
TC. By setting the sizer so that the spacing between the
drums is generally located above the longitudinal axis of the
conveyor material being deposited by the sizer onto the
conveyor TC is arranged centrally thereon. This is
advantageous as it minimises spillage.
Referring now to the speclfic construction of the
mineral si~er shown in Figure 1, each drum assembly 15 is
shown in lonyitudinal section in Figure 4 and includes a
stepped shaft 25 on which is keyed a support sleeve 26 made
up of three support sleeve portions 26a, b and c. The centre
sleeve 26b is of larger internal diameter so that it can be
easily slid over most of the shaft 25 during assembly and
disassembly. The sleeve portions 26a, b and c are fixedly
secured to one another by weld lines 26d so as to form an
integral sleeve 26 running the majority of the length of the
shat 25.
A series of annular support rings 28 are mounted on each
sleeve 26 and are secured to one another and also to sleeve
26 by weld lines 30. Each riny 28 has a series of teeth
support projections 34 integrally formed therewith which are
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spaced circumferentially about its periphery. Each ring 28
is conveniently formed from a cast metal.
Accordingly, the rotational position of each ring 28 may
be easily set during assembly to align or stagger the teeth
support projections 34 of adjacent rings 28 by rotating the
rings 28 on sleeve 26 and then fixedly securinq them in that
position. In Figure 4, the projections 34 on adjacent rings
28 have been set so that the projections form lonyitudinally
extending rows which are substantially parallel to the axis
of rotation of the drum assembly 15 in contrast to the
arrangement in Figure 1 wherein adjacent rings 2B have been
set so that the projections 34 form the longitudinally
extending helical formations 21.
In Figure 8 an alternative construction is illustrated
wherein the annular support rings 28 are each keyed or
splined directly onto the shaft 25. Each ring 28 is
therefore only in abutment with its neighbour and the
assembly of rings 28 are prevented from axial movement by
virtue of a shoulder 25_ and a removable collar 25z.
Accordingly should the shaft or a ring become damaged during
use, the shaft and ring assembly may be disassembled for
replacement of the damaged component. It will be appreciated
that each ring may be easily angularly offset to its
neighbour to provide the desired helical formation 21, the
amount of offsetting being determined in steps dictated by
the pitch of the splines.
A further alternative is to cast the series of annular
support rings and shaft integrally with one another.
A tooth sheath 40 is secured to each projection 34 via a
bolt 41, or other similar means such as a sprung spigot,
which is located in pockets 42 in the sheath and are thus
protected Erom damage during use. When all sheaths are in
position they collectively form a cover over adjacent rings
23 so that the rings are protected from wear by mineral being
sized.
Each sheath 40 has an annular base portion 43 which
follows the contour of ring 2~ and a hollow tooth portion 45
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integrally connected to the base portion 43. The tooth
portion ~5 has an internal pocket which is of a complementary
shape to a projection 34 so when the tooth portion is seated
upon a projection, loads imparted onto the tooth portion 45
5 during use are transmitted onto the projection 34.
In this respect, during use each tooth is exposed to two
main sources of loadings; firstly a loading on its leading
face 46 resulting from a primary or secondary breaking action
and secondly a loading on its trailing edge 47 resulting from
a secondary breaking action. The shape of projection 34 and
that of tooth portion 45 is chosen so that when the tooth is
exposed to the first type of loading the face 46 transmits
the loading onto the leading face 150 of projection 34 and is
encouraged to move in a generally radially inward direction
so that the sheath 40 is pressed onto the projection 34 and
peripheral surface of ring 28. The shape of the trailing
edge 47 and of the complementary surface 53 of projection 34
are chosen to provide a wedge effect to restrain movement of
the sheath 40 in a generally circumferential direction about
ring 28, the wedge effect serving also to transmit loadings
on the trailing edye 47 onto the complementary surEace 53.
Accordingly loadings arising from breakage of mineral are
transmitted on to the rings 28 and so bolts 41 are not
exposed to loadings and merely act to retain its associated
sheath on a projection 34.
As seen in ~igure 2 a rebate 60 is preferably provided
at the base of each face 46 to receive a marginal end portion
of the annular base portion 43 of the pereceding sheath 40.
If desired the base of each tooth and the base portion 43 of
each preceding sheath 40 may be joined together by welding to
thereby form a more rigid annular cover for each ring 28.
It will be apapreciated that during use, portions o:E
each sheath 40 will wear away and that eventually the sheaths
40 will have to be replaced. This is easily and quickly done
with the present sizer by removal of bolts 41 (and, if
appropriate removal of weld) and so refurnishment of the
sizer teeth may be quickly achieved on site by personnel
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without the need of heavy lifting gear~ Additionally, the
inner surfaces of the side walls and end walls may be lined
with steel plate which act as wear plates 50, 51 respectively
to protect the side and end walls from abrasive wear. The
wear plates are removably secured in position so that they
can be replaced periodically after excessive wear has
occurred.
A row of teeth 62 are provided to extend longitudinally
along each side wall to intermesh with teeth 20 to prevent
material passing between the side wall and adjacent drum
assembly. The teeth 62 are conveniently secured to wear
plates 50 by welding.
An alternative ring and tooth construction is
illustrated with reference to Figures 9 - 16 wherein similar
parts are designated by similar refere~ce numerals.
In Figures 9 and 11 there are shown two alternative
support rings 28 which are intended to be keyed directly to a
shaft as in the Figure 8 embodiment and which are of
different external diameter but are intended to receive the
same dimensioned tooth sheath 130.
Each support ring 28 shown in Figures 9 and 11 is
provided with a series of teeth support projections 34 which
are integrally cast with the support ring.
The tooth cap 130 illustrated in Figures 12 to 16 is
cast from a suitable wear resistant material and its external
shape is designed so as to be symmetrical about section lines
VII-VII and VIII-VIII respectively. The terminal end of
each cap 130 terminates in the form of a ridge 136 which
extends in the direction of rotation of the drum. By varying
the length o~ the ridge 136 the strength of the tip of the
tooth can be adjusted. The cap 130 has an internal pocket or
recess 131 Eor receiving a projection 34, the recess 131
having a shape complementary to the shape of projection 34 so
that loadings are transmitted onto the projection 34.
~s seen in Figures 9 to 11 each projection lS has a pair
of recesses 118 (only one of which is visible in Figures 9
and 11) and the internal recess 131 of each cap 130 has
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inwardly projecting flanges 132 of complementary shapes to
recesses 118 so that the flanges 132 and recesses 118
co-operate to positively key the tooth caps 130 in position.
The caps 130 and projections 34 each have co-operating bores
134 passing therethrough to enable a bolt to be passed
through for preventir.g removal of the cap from an associated
projection.
By altering the diameter of the support rings but
retaining the same shape of projection 34 it is possible to
use the same size of caps 130 for different diameters of
breaker drums. This is il ustrated by comparison between
Figures 9 and 11 wherein the bottom edge of each tooth cap
130 is of the same radius of curvature as the diameter of
ring 28 in Figure 11 whereas in Figure 9 the radius of
curvature of the ring 28 is greateer. Accordingly, in order
to accommodate caps 130 on ring 28 shown in F`igure 9,
complementary curved support surfaces 139 are provided
separated by ridges 138.
A further alternative of a tooth sheath is illustrated
in Fi~ures 17, 18 and 19 wherein the tooth sheaths 40 on a
given support ring 28,in addition to being connected to a
respective projection 34 by a bolt 41, the tooth sheaths are
also connected to one another by a connection formation 200
which is itself preferably tooth shaped. ~ccordingly, at one
circumEerential end of each sheath 40 is provided first part
201 of the formation 200 and at the other circumferential end
with a second part 202 of the formation 200. The first part
201 is generally tooth shaped having a leading face 203 and
trailing face 204. The first part 201 is provided with a
centrally located recess 206 into which the second part 202
of a preceding sheath 40 projects. Both the first part 201
and second part 202 are provided with through bores 208 which
align when adjacent sheaths are positioned on a ring 28 and
through which a bolt (not shown) is passed in order to secure
co-opera~ing parts 201, 202 together. The provision of
connection ~ormations 200 stabilises the annulus of connected
sheaths ~0 extending about a given ring 28 and serves to
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reduce chatter between ~he sheaths 40 and ring 28 during use.
In view of the stabilising effect it has been found possible
to provide the teeth 20 with a leading face 46 which has a
positive rake as is clearly illustrated in Figure 17.
A further alternative shape of tooth 20 and
corresponding projection 34 is illustrated in Figures 20 to
23 wherein the tooth 20 is in the form of a pick having a
generally cylindrical body. In this embodiment the sheaths
40 are secured onto a given ring 28 by being connected to one
lO another by connection formations 200 only.
It is to be appreciated that drums assembled from any of
the tooth sheath constructions described above are preferably
arranged so that the teeth form helical formations 20. By
way of further example reference is made to Figure 23 which
is a view similar to Pigure 1 and in which each drum includes
a series of sheaths as shown in Figures 20 ~ 22 arranged to
define helical formations 21. It is however also possible
in certain applications for the teeth 20 to be arranged in
rows extending generally parallel to the axis of the drum.
It is also envisaged that the helical formations 21 on both
drums may extend about their respective axes in the same
sense. In such a situation large pieces of mineral deposited
on the drums will be acted upon by the helical formations on
one drum to move in one axial direction and be acted upon by
the helical formations on the opposite drum to be moved in
the opposite axial direction. Such movement results in an
agitation of the large pieces of mineral deposited on the
drums and so assist gripping of the mineral by the teeth. A
further alternative is Eor one drum to have a helical
formation and the other drum to have teeth aligned in rows
arranged parallel to the axis of the drum.
It is also envisaged that the drums may be rotated in
opposite directions so that material deposited thereon is
moved toward the side walls of the sizer for breaking.
Additionally it is also envisaged that a sizer having a
single breaker drum may be provided in which the teeth on the
drum co-operates with a side wall of the sizer housing and/or
static teeth mounted thereon for breakage of mineral.
