Field of the invention
[0001] The present invention relates to a preseparator means for a dust collector and more
particularly preseparator means having two separation units operating intermittently
to enable continuous operation of the preseparator means.
State of the art
[0002] Dust collectors are previously known devices employed to separate dust particles
from a gas flow. For example they may be used when grinding and polishing floors,
as described in
EP 1 580 801. Typically, a dust collector incorporates or is connected to a preseparator collecting
a greater part of the particles and a filter unit collecting the remainder of the
particles when functioning properly.
[0003] Filters are disposable units and need maintenance, such as cleaning, for prolonged
life. However, the filter maintenance should be kept at a minimum since it is time
consuming, and changing filters involves a cost. On the other hand, the preseparator
is often a cyclone, which only needs emptying from time to time. When the cyclone
unit begins to fill up, the efficiency decreases. When the cyclone is contains a small
amount of dust, it can typically remove 95 % of the particles, but it is usually not
emptied until efficiency has decreased to 70 %. This is because the gas flow has to
be shut off in order to empty the cyclone resulting in an undesired down period.
[0004] It would be an advantage to provide a preseparator means capable of continuous operation,
such that the dust collection and the associated grinding or polishing operation need
not be interrupted. Also, a preseparator capable of 95 % efficiency would mean savings
relative to filter maintenance and exchange.
Summary of the invention
[0005] An object of the invention is to provide a preseparator means capable of continuous
operation. Another object of the invention is to provide a preseparator means having
separation units working in unison such that one separation unit may be emptied while
the other is in operation.
[0006] The invention provides a preseparator means for a dust collector, comprising: at
least two dust separation units, each adapted to receive a gas flow carrying dust
particles at an inlet, separating and collecting at least a part of the dust particles
from the gas, and emitting the gas thus treated at an outlet;
switching means adapted to switch the operation between said separation units, so
that each separation unit is shut off from the gas flow intermittently, in order to
allow removal of collected dust particles from the shut off separation unit, while
the other separation units are in operation.
[0007] Preferably, the switching means comprises a rotary valve assembly connecting a main
inlet of the preseparator means to inlets of respective separation units, and connecting
outlets of respective separation units to a main outlet of the preseparator means.
[0008] Each separation unit may comprise a cyclone.
Brief description of the drawings
[0009] The invention will be described in detail below with reference to the accompanying
drawings, in which:
fig. 1 is a perspective view of a preseparator means with a valve assembly,
fig. 2 is a perspective view from below of a part of the preseparator means,
fig. 3 is a cutaway side view of the valve assembly with all valves open,
fig. 4 is a view similar to fig. 3 with valves opened to a first separation unit and
closed to a second separation unit,
fig. 5 is a view similar to fig. 3 with valves opened to the second separation unit
and closed to a first separation unit, and
fig. 6 is a side view of a rotary valve plate according to one embodiment of the invention.
Detailed description of preferred embodiments
[0010] The preseparator means of the present invention is intended to be connected to a
further dust collection unit, typically a filter unit. The invention has been developed
in connection with grinding floors and similar operations, but the invention is also
applicable in other contexts. The invention is not restricted to any particular form
of dust, neither with respect to material nor particles size.
[0011] Fig. 1 shows one embodiment of a preseparator means according to the invention. Generally,
it comprises separation units 2A and 2B with respective inlets 3A (on the rear side)
and 3B, respectively, and outlets 4A and 4B, respectively. A main inlet 5 is connected
to a gas intake, typically a casing of a finishing machine having a tool producing
dust released into the gas (air). A main outlet 6 of the preseparation devices connected
through an interposed filter unit to a suction source, typically an industrial vacuum
cleaner.
[0012] During operation, the suction source draws gas carrying dust particles through the
separation units 2A and 2B. As will be explained more in detail below, a cycle of
the operation of the preseparator means involves operation of one separation unit
2A, while the other separation unit 2B is shut off and emptied, and vice versa, and
preferably also a period when both separation units 2A and 2B are operating.
[0013] Fig. 2 shows the underside of the separation units 2A and 2B. Each separation unit
comprises a shutter 7A, 7B, adapted to close an opening at the bottom of the separation
unit where dust will settle by force of gravity. When gas is flowing through a separation
unit, the shutter is sucked upwards closing the opening in the bottom. When the gas
flow through a separation unit is shut off, the shutter is pulled down by gravity,
allowing the collected dust to fall out. Conveniently, a wide tube, or sack, is connected
at the lower end of the cycle for removing the dust.
[0014] In one embodiment, each separation unit comprises a cyclone. The cyclone comprises
an outer cylinder wall with an inlet at the top, such as inlet 3B, where gas carrying
dust particles enters. Inside the cyclone is an inner cylinder, extending down from
the top of the cyclone approximately one third of its height. The gas flow enters
the inlet in a peripheral direction and spirals down between the outer cylinder and
inner cylinder. Dust particles collide with the wall reducing their speed, and fall
down to settle on the bottom of the cyclone. The gas turns at the bottom and rises
upwards through the inner cylinder and through an outlet at the top, such as outlet
4B. An example of a cyclone may also be seen from
US Patent No. 6,195,835.
[0015] The operation cycle is controlled by switching means 8. In one embodiment the switching
means comprises a rotary valve assembly, comprising stationary plates 9 with holes
10A, 10B, 10C, 10D, connected to the main inlet 5, the inlets and outlets 4A, 4B of
the separation units 2A, 2B and the main outlet 6. The connections are made by means
of tubes and manifolds which are not shown. A rotary valve control plate 11 is interposed
between the stationary plates 9 to open and close the holes 10A, 10B, 10C, 10D, in
a predetermined cycle.
[0016] The main inlet 5 is connected to the lower holes 10C and 10D by means of a manifold,
part of which is seen in fig. 2, to the left side of the valve assembly 8. The main
outlet 6 is similarly connected to the top holes 10A and 10B at the right side by
means of another manifold. The inlet 3A of the separation unit 2A is connected to
the right side of the hole 10C, while the outlet 4A of the separation unit 2A is connected
to the left side of the hole 10B. The inlet 3B of the separation unit 2B is connected
to the right side of the hole 10D, while the outlet 4B of the separation unit 2B is
connected to the left side of the hole 10A.
[0017] Fig. 3 shows the valve assembly 8 with the rotary plate 11 (Fig. 6) in a middle position.
The position of the rotary plate is controlled by a motor 13 connected by means of
a rod 15 to crank 14 in turn connected to the rotary plate. When the motor is rotating,
the rotary valve plate 11 is reciprocating between the end positions of figs. 4 and
5, while fig. 3 shows the middle position.
[0018] An embodiment of the rotary valve plate 11 is shown in fig. 6. It is provided with
four holes 12A, 12B, 12C, 12D, which are elongated in the peripheral direction. There
are two vent holes 19A and 19B. A center hole 17 is connected by means of a shaft
to the crank 14.
[0019] In the middle position shown in fig. 3, the holes 12A through 12D coincide with the
holes 10A through 10D, respectively. In this position, all holes 10A, 10B, 10C, 10D
are open, allowing gas flow. Thus, both separation units 2A and 2B are in operation.
[0020] In fig. 4, the rotary plate has been rotated counterclockwise to a first end position.
Now the hole 12A coincides with the hole 10C, and the hole 12D coincides with the
hole 10B, while solid areas of the rotary plate block the holes 10A and 10D. Thus,
all the gas flow is drawn through the separation unit 2A, while the separation unit
2B is shut off. As the separation unit 2B is shut off from the gas flow, the shutter
7B is opened and collected dust is emptied from the unit 2B. At the same time, the
vent hole 19B is connected by means of a separate tube (not shown) to the separation
unit 2B admitting air under atmospheric pressure to the unit. The vent hole facilitates
the opening of the shutter and emptying of dust.
[0021] In fig. 5 the rotary valve plate has been rotated clockwise to the other end position.
Now the hole 12C coincides with the hole 10A and the hole 12B coincides with the hole
10D, while solid areas of the rotary plate block the holes 10C and 10B. In this position
the whole gas flow is drawn through the separation unit 2B, while the separation unit
2A is shut off, resulting in emptying of dust from this unit similarly to what is
described above.
[0022] With this arrangement, both separation units are in operation one half of the cycle,
while only one or the other of the separation units 2A and 2B are shut off during
the other half of the cycle. The time of the shut off period is not very critical
and is dependent on the type of dust and particle size etc. However, a separation
unit should never be allowed to be too full, as the separation efficiency will decrease
when the separation unit starts to fill up. On the other hand, frequent release of
dust is no disadvantage.
[0023] Typically, the shut off period is greater than 20 seconds, preferably in the range
of 30 - 90 seconds. In an exemplary embodiment a whole cycle is two minutes, i.e.
30 seconds with both units operating, 30 seconds with separation unit A operating,
30 seconds with both units operating and finally 30 seconds with separation unit B
operating.
[0024] The relative time period of overlap, when both units are operating, relative to the
time period when only one unit is operating is dependent on the peripheral extension
of the elongated holes 12A through 12D. Also, this extension controls the time period
when there is full flow through the respective separation units.
[0025] It will be appreciated that the switching between the separation units may be performed
by other alternative means, such as sliding shutters or individual valves. With individual
valves, the switching of operation between the separation units may be dependent of
the amount of dust collected in each unit.
[0026] Also, the described embodiment comprises two separation units, while it is possible
to add even further separation units working in unison to allow at least one separation
unit to be shut off intermittently. Also, the separation units need not be the type
of cyclone specifically described here.
[0027] The invention enables continuous operation as the individual separation units are
emptied alternatively. Thus, the down period of the prior art has been eliminated.
Since dust is not allowed to accumulate, each separation unit will also retain its
high efficiency during operation. As mentioned in the introduction, as much as 95
% of the dust may be collected in the preseparator means relieving the subsequent
filter units. This results in less filter maintenance and exchange costs.
[0028] The scope of the invention is only limited by the claims below.
1. A preseparator means for a dust collector, comprising:
at least two dust separation units, each adapted to receive a gas flow carrying dust
particles at an inlet, separating and collecting at least a part of the dust particles
from the gas, and emitting the gas thus treated at an outlet; switching means adapted
to switch the operation between said separation units, so that each separation unit
is shut off from the gas flow intermittently, in order to allow removal of collected
dust particles from the shut off separation unit, while the other separation units
are in operation.
2. A preseparator means according to claim 1, wherein a shut off period for one separation
unit during one operation cycle of the preseparator means is greater than 20 seconds.
3. A preseparator means according to claim 1, wherein a shut off period for one separation
unit during one operation cycle of the preseparator means is greater than 30 seconds
and less than 90 seconds.
4. A preseparator means according to claim 1, 2, or 3, wherein some separation units
are operating simultaneously during one operation cycle of the preseparator means.
5. A preseparator means according to claim 4, wherein two separation units are operating
simultaneously during a half cycle, and a first and a second separation unit are operating
alternately during a half cycle.
6. A preseparator means according to any one of the preceding claims, wherein the switching
means comprises a rotary valve assembly connecting a main inlet of the preseparator
means to inlets of respective separation units, and connecting outlets of respective
separation units to a main outlet of the preseparator means.
7. A preseparator means according to claim 6, wherein the valve assembly comprises two
stationary plates with through holes connecting the main outlet and inlet with the
inlet and outlets of the separation units, and a rotary valve plate having holes that
may be brought to coincide with the holes of the stationary plates, and the rotary
valve plate having areas that may be brought to close the holes of the stationary
plates.
8. A preseparator means according to claim 7, wherein the holes of the rotary valve plate
are elongated in a peripheral direction.
9. A preseparator means according to any one of the preceding claims, wherein the each
separation unit comprises a cyclone.
10. A preseparator means according to claim 9, wherein each cyclone comprises a shutter
at the bottom, the shutter being adapted to be closed by gas flow and opened by gravity
in the absence of gas flow.