EP1808234A1

EP1808234A1 - Separator means for dust collector

Info

Publication number: EP1808234A1
Application number: EP06100366A
Authority: EP
Inventors: Karl Thysell; Johan Sunesson
Original assignee: HTC Sweden AB
Current assignee: HTC Sweden AB
Priority date: 2006-01-16
Filing date: 2006-01-16
Publication date: 2007-07-18
Anticipated expiration: 2026-01-16
Also published as: DE602006005133D1; ATE422392T1; EP1808234B1

Abstract

The invention relates to a preseparator means for a dust collector. The preseparator means comprises: at least two dust separation units (2A, 2B), each adapted to receive a gas flow carrying dust particles at an inlet (3A, 3B), separating and collecting at least a part of the dust particles from the gas, and emitting the gas thus treated at an outlet (4A, 4B); switching means (8) adapted to switch the operation between said separation units (2A, 2B), 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 unit is in operation. The invention enables continuous operation of the preseparator means.

Description

Field of the invention

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

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.
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.
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

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.
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.

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.
Each separation unit may comprise a cyclone.

Brief description of the drawings

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

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.
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.
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.
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.
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 .
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
The scope of the invention is only limited by the claims below.

Claims

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.
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.
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.
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.
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.
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.
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.
A preseparator means according to claim 7, wherein the holes of the rotary valve plate are elongated in a peripheral direction.
A preseparator means according to any one of the preceding claims, wherein the each separation unit comprises a cyclone.
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.