Note: Descriptions are shown in the official language in which they were submitted.
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The invention relates to a blasting wheel to provide a granular
material stream, designed particularly for sho~ blasting machines used in
foundries, paint shops, enamel shops, or galvanizing plants, or for surface
hardening and superfinishing machines, Eor thickening sand mix by slinging,
or for plaster floating etc.
Airless hot blasting machines, which are well known, have
rotatable throwing wheels with blades. The wheel consists of a distributing
impeller, a regulating sleeve and a blade wheel mounted on a common axis.
In such ~Iheels shot passes between the blades o-f the dlstributi~e impeller
and from there flows through an opening in the stationar~ regulating
sleeve between the blades of the work wheel, and thence to the edges of the
blades. The blades throw the shot in a direction substantially perpendicular
to their work surfaces.
The basic disadvantage of known wheels is that of rapid wear of the
blades of the work wheel, and of the elements of the distributing impeller
and regulating sleeve. In spite of being made of highly abrasion resistant
materials they must be replaced very often. Uneven wear of the wheel parts
and in particular of its blades causes unbalance of the wheel that increases
considerably the load on the wheel bearings and the nolse of its operation.
2~ German Patent specification number 834341 discloses a wheel to
provide a stream of granular material, which consists of two basic subassem-
blies, namel~ a rotating disk with spiral channels therein, in which blades
are mounted at the outlets of the channels, and of a pan shaped element rota-
ting with the disk. The axis of rotation of the pan in relation to the axis
of the disk is set at an angle. The granular material is supplied through
the hub, in the circumferential walls of which are radial openings connected
with the spiral channels in the disk. The material flows under centri-
fugal force from spiral channels onto the blades where it is accelerated to
throw speed. In the areas outside the radial sector of the throw the disk
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blades are shielded by the edge of the pan rotating with the throw. ~ut the
outlet openings of the spiral channels are not closed. Therefore in the area
outside the radial throw sector the material can also flow out which in
practice can cause throwing of material by the wheel in undesirable directions.
United States Patent specification number 2,275,434 discloses a
centrifugal abrasive blasting machine operable to throw a concentrated stream
of abrasive over a predetermined limited arc. This machine includes a rotor
having a plurality of equally spaced radial abrasive discharge passages extend-
ing inwardly to a central space, a rotatably mounted control runner positioned
within said space and having its axis of rotation in alignment with the axis of
rotation of the rotor. The control runner has a plurality of equally spaced
abrasive discharge passages differing in number from the number of discharge
passages of the rotor. The driving means are operable to rotate the rotor and
runner at speeds, which are in inverse ratio to the number of discharge passages
in the rotor and runner respectively so as to move the successive passages in
the runner into discharging alignment with the successive passages in the rotor
at a predetermined angular position during rotation.
During operation the rotor and control runner are exhibited to
abrasive wear over the entire width of the rotor's central space, the runner
and their discharge passages.
It is an object of the invention to eliminate rapid wearing of the
component parts of the blasting wheel and to design such a wheel in which the
degree to which the material rubs against the component parts of the wheel as
it is accelerated to throw speed is reduced.
The invention provides apparatus for generating a stream of granular
material over an angular throw sector, said apparatus comprising: a throwing
element formed by a bladeless rotatable drum having an interior which defines
a rotating chamber for the granular material, said container having at least
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one peripheral outlet opening, means for supplying granular material into said
chamber, drive means for rotating the drum to discharge granular material
through each said outlet opening, and means for blocking each said outlet open-
ing when outside said angular throw sector, whereby material is discharged there-
from only within said angular throw sector, wherein said means for blocking
comprising a ring rotatable with the drum on an axis at a pre-set angle to that
of the drum and enclosing part of the drum circumference, the non-enclosed
remainder of the drum circumference defining said throw sector, including means
for adjusting the orientation of the ring axis around the axis of the drum
thereby to selectively vary the location of said throw sector.
In operation, the chamber of the rotating drum is fed with material
through an axial inlet opening. The material accumulates in form of a layer
mainly at the circumference of the chamber, resulting in self balancing of the
rotating system. During each full revolution of the drum each of outlet open-
ings is uncovered in a certain angular sector. Outside that sector the outlet
openings remain closed.
Preferably, the width of the drum chamber is greater than the width
of its outlet opening. Such design enables setting the granular material inside
the rotating drum not only on a circumferential wall but also along side walls.
Thus the whole area of inside walls of the drum has a covering layer of material.
The material introduced through inlet opening at the axis hits the layer of the
rotating material. Therefore the drum chamber inside walls are exposed to very
much less wear.
` It is favourable if the hub of the rotating ring is set on a body,
which in turn is rotatably mounted in relation to the drum axis and is provided
with a lock to set its position. Such a bearin& system of the ring hub enables
adjustment of the direction in which a stream of grain material is thrown out of
the drum.
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Particularly low erosion of the outlet openings is achieved when they
are inclined in relation to the radius of the drum in a direction reverse to
the direction of revolution. Because of this design, the material that is
accelerated to the throw speed inside the drum does not touch the walls of the
outlet openings, or its pressure on the inside walls of the outlet openings is
minute. That protects the walls of the outlet openings against erosion and
contributes to a considerable lengthening of the service life. Preferably,
outlet openings have changeable inserts made of abrasion resistant materials,
such as sintered carbides. The inserts are mounted in the wheel body. To
facilitate periodical change of the inserts it is preferred to mount them in
frames removably fixed on the drum body.
It is also advantageous if the rotating drum shaft as well as the
rotating ring have their bearing systems located at one side of the drum and
the inlet opening at the other. The infeed opening then does not require a
cylindrical sleeve, and the end of the infeed hopper can be inserted directly
into the drum chamber. Such design in practice eliminates the possibility of
hopper clogging.
The rotational speeds of the rotating drum and the rotating ring
can be the same or different. In the last case more uniform wear of the work
periphery of the ring is achieved over the whole circumferen~e. To achieve the
required speed ratio between drum and ring these two elements are movably con-
nected. This movable connection can be done with constant speed universal joints
- or flexible joints, or claw or friction clutches or transmissions, in particular
gear ones. In the latter case the required transmission ratio between the drum
revolutions and ring revolutions can be easily achieved.
The present invention will now be described by way of example with
reference to the attached drawings in which:
Figure 1 shows the wheel in vertical axial section;
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Figure 2 shows a further wheel construction in vertical axial section;
Figure 3 shows the wheel drum in cross-section on the line A - A in
Figure 2;
Figure 4 shows the structural detail of an outlet opening sleeve in
the drum body in a cross-section on the line A - A in Figure 2, to an enlarged
scale; and
Figure 5 shows another design of sleeve mounting of the outlet open-
ing in the drum body.
In Figure 1 the drum 1 is fixedly mounted on the sleeve 2 carried in
two roller bearings 3. A pul]ey wheel 4 is attached to the sleeve. An infeed
hopper 5 extends into the opening of the sleeve 2. Outlet openings 6 are
regularly spaced around the circumferential wall of the drum 1. The circum-
ferential wall of the drum 1 is enclosed within a ring 7 mounted on a disk 8
connected to a shaft 9. The shaft 9 is set in rol~er bearings 10 and is provided; with a belt pulley 11. The axis of the shaft 9 and ring 7 is inclined at an
angle ~ to the axis of the drum 1 and sleeve 2. Because of this angular setting,the ring 7 blocks some of the openings 6 of the drum 1 (the upper openings in
the drawing) while others of them remain uncovered (the lower openings in the
drawing).
The wheel operates as follows: the drum 1 and the ring 7 are rotated
by a driving unit (not shown in the drawing). The speeds of rotation of the
drum 1 and of the ring 7 are the same. Granular material is introduced into
the cylinder drum chamber through the hopper 5. The drum 1 rotates about its
axis and the ring 7 rotates synchronously around the axis inclined at an angle
to the drum 1 axis, so that during such rotation the ring 7 uncovers success-
ively these outlet openings 6 that are instantaneously directed in the set throwdirection. Due to centrifugal force, the granular material in the drum distri-
butes itself on the inside wall of the drum forming a layer thereon. Material
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introduced from the hopper 5 inside the rotating drum 1 does not strike the
walls of the drum but impacts the adherent layer of granular material, so that
the drum wall is to a great extent protected against wear. The material is
thrown out only through such outlet openings 6, that are at a given moment
uncovered by the ring 7 (the lower openings in the drawing). The sector through-out which the openings 6 are opened can be adjusted by changing the angle
between drum 1 and ring 7 axes.
The wheel of Figures 2 and 3 is similar to the one shown in Figure 1,
but has more favourable structure.
In Figure 2 the drum 21 is fixed on the shaft 22 mounted in two roller
bearings 23. In the end wall of the drum 1 opposite to the shaft 22 is an axial
opening 24 through which the end of the hopper 25 is introduced. In the circum-
ferential wall oE the drum 21 are regularly spaced outlet openings 26. Around
the circumferential wall of the drum 1 there is a ring 27, having an integral
hub 28. In the end wall between the ring 27 and the hub 28 are openings 29.
The hub 28 is carried on two roller bearings 30, that are mounted on the body
31, and inside which the drum-shaft 22 extends. The axis of the bearing system
of the drum 21 forms the angle d with the axis of the bearing system of the hub
- 28. The body 31 is rotatably mounted on the bearing system base 32. The body
31 can be turned in relation to that base by any angle around the axis of the
shaft 22 and can be locked in a desired position by a clamp 36. Between the
hub 28 and the drum 21 is a bevel gear transmission 33 in which two changing
gears have unequal number of teeth.
As it has been shown in Figures 3 and 4 the outlet openings 26 are
inclined by angle ~ to the radius of the drum opposite to the direction of
rotation marked with B arrow. The most favourable magnitude of r angle inclina-
tion is determined from the equation:
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360 ~R2 2 i ~ /
= arc tg 2 r R
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R cos / r - arc sin ~R - r2 / - r
2 r R
where: R means radius from the drum axis to the outside end of the outlet open-
ing 26, r means the radius from the drum axis to the inside end edge of the out-
let opening 26.
To facilitate changing of outlet channels that wear out during opera-
tion the following design was applied (see Figures 3 and 4).
In the circumferential wall of the drum 21 removable frames 34 are
installed, that can be slipped off the drum parallel to its axis. In each
of the frames 34 there is a square opening of a narrowing diameter in direction
of the circumference of the drum 21. The walls of this opening are lined by the
inserts 35 shaped as plates made of nonabrasive material. The inserts 35 are
locked in the frames by plates 37 screwed to the frames 34. It is obvious that
instead of square openings, openings of triangular or any other suitable shape
can be used in the frames 34.
In the design of Figure 5 the inserts 351 have the shape of tapered
sleeves and are mounted by pressing them into taper seats made in the frames 34,
This facilitates easy changing of the inserts.
The wheel of Figures 2 and 3 operates as follows: Before start up
granular material is poured into the drum through the infeed hopper 25, so that
it fills the inside of the drum chamber up to the level of the infeed opening
24 The drum 21 and the ring 27 are then caused to rotate by a motor (not shown
in the drawing) which is connected with a belt pulley 38, without interrupting
infeed of the material into the drum chamber. Grains that reach the vicinity
of outlet openings 26 are accelerated to throw speed. The grains are thrown
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outside only through those openings 26 that are at the moment uncovered by the
ring 27. Because of the inclination of the outlet openings 26 to the radius of
the drum 21 in the direction opposite to the direction of drum rotation, grains
passing through outlet openings 26 do not in practice undergo any acceleration
and therefore the friction of the material on the outlet openings walls is very
small, and consequently the erosion of the outlet openings walls is minimal.
The direction in which the stream of material is thrown can be
adjusted with turning the body 31 with respect to the base 32 after loosening
the clamp 36.
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