GB2161217A - Air blowing unit - Google Patents

Abstract

The unit incorporates a low pressure air blower pump 1 having at least one outlet tube 13 arranged and adapted to serve as an absorptive and/or reactive silencing chamber; and wherein the outlet tube is at least partially located below the unit and serves as a base support structure therefor. The unit may have a motor 5 mounted therewith compartmented separately from the pump and provided with entry and exhaust for cooling air separate from the air supply to the pump. The outlet tube is internally lined with rockwall (15, Fig. 3) surrounding a pair of perforated tubes (16, 18), separated by a liner (17). <IMAGE>

Description

SPECIFICATION Improvements in or Relating to Air Blowing This invention relates to air blowing, and more particularly although not exclusively to the transportation of powdered or granulated rock or coal material by means of an air blowing system.

It has been proposed to use a totally enclosed low pressure air blower (usually of the type commonly referred to as the "Rootes" type of air blower) in mining and civil engineering for transporting powdered or granular material such as coal or rock considerable distances.

A typical Rootes type positive displacement air blower pump would be driven by an electric motor rated at 112 kw or more having two twin lobe impellers rotating at, say, 1470 rpm and of dimensions such as to provide large volumes of low pressure air at high velocity. Such an arrangement can be used for example for conveying sized or graded coal or stone through a pipeline.

A Rootes type machine of typical specification would be provided with twin-lobe type impellers such as to provide compressed air for a pneumatic conveyor at excess pressures of up to 1 atmosphere.

With this kind of machine air passes into the partial vacuum created by the impellers at the inlet of the blower from atmosphere.

As the impellers rotate air is compressed and djscharged into a pipeline through silencer tubes.

It is common for initial noise levels on an unclad blower of this kind to be in excess of 110 Dba. Such noise level is reduced to an acceptable level by silencing tubes and/or cladding with insulating materials. Problems arise with such air blowers in the conflict between practical requirements of being capable of location in confined spaces underground, whilst being moveable from one site to another as mining or similar operations progress, and at the same time have sufficient operating power to provide an efficient materials moving service.

It is an object of the present invention to overcome or at least substantially reduce the above mentioned problems.

In accordance with the invention there is provided an air blowing unit incorporating a low pressure air blower pump, the pump incorporating at least one outlet tube arranged and adapted to serve as an absorptive and/or reactive silencing chambers; and wherein the outlet tube is at least partially located below the unit and serves as a base support structure therefore.

The outlet from the pump may be bifurcated so as to provide two outlet tubes (preferably parallel) for silencing and support of the pump assembly. The two outlet tubes may converge into a single discharge tube connectable to a main free air pipeline spooi pressure relief valve assembly. In a preferred embodiment of the invention the outlet tubes are so disposed and located along and below the unit as to act as skids for enabling the pump to be moved over the ground in a sledge like manner.

This is particularly efficacious where twin parallel outlet tubes are provided. In such an arrangement the tubes preferably extend one each side of the structure along the full length of the unit.

Longitudinal protective shoes may be secured to the lower surfaces of the outlet tubes to prevent damage thereto by abrasion with the ground for example and provide further mechanical rigidity to the base in the event that the blower Linit is suspended as in a mono-rail installation.

The blower pump is preferably arranged with an upper inlet and a lower outlet.

A unit in accordance with the invention meets the frequent practical requirement of providing a mobile installation for use in underground roadways in mines of restricted room, that require a unit of minimum overall dimensions and weight.

In order that the invention may be more fully understood one embodiment thereof will now be described by way of example with reference to the accompanying drawings in which: Figure lisa sectional side elevation of an air blower unit according to the invention; Figure 2 is an end elevation of the blower unit of Figure 1; Figure 3 is a section on the line Ill-Ill of Figure 1; Figure 4 is a scrap view showing the disposition of the twin lobe impellers of the pump unit; Figure 5 is an under plan view of the silencer base configuration including the discharge spool; and Figure 6 is a diagrammatic representation showing an application of the blower unit of the previous Figures.

Referring now to Figures 1 to 5 of the drawings, it will be seen that a Rootes type air blower of usual configuration having twin impellers 2 and 3 disposed in side by side arrangement, is mounted on a rigid base plate 4. Axially related to the air blower pump lisa motor 5, the pump and the motor being located within separate acoustically clad casings or compartments 6 and 7. As can be seen air enters the blower pump via an upper inlet 8 after passing into the casing 6 via a filter and acoustic baffles 10 and exits via a lower outlet 11.

The outlet 11 from the blower pump is directed via a bifurcated elliptical feeder tube 12 into twin exhaust/ silencing tubes 13 and 14 located one along each side of the unit. It is to be observed that the twin tubes 13 and 14 support the total unit and serve as the base support structure. Each silencer tube is dimensioned and arranged to act both as an absorptive and a reactive silencing system. The tubes join together into a common discharge pipe 33 at the motor end of the blower unit. In a particular example the tubes are of steel and are of approximately 9.27 mm thickness. They have an internal rock wall filling 15 which is 50 mm thick at approximately 45 kgs per cu.m. Each is provided with an internal perforated steel non-galvanised tube 16 which is approximately 3.2 mm thick having an overall open area of 40%.Surroundung this is a 19 micron thick layer of melinex liner 17 and then an intermediate steel perforated tube 18 having an open area of 62.7%. It has been found that a pair of silencing tubes of this structure are effective both for reactive silencing and for acoustic absorption silencing through the lining, reducing noise levels to 85 measured 1 m from the blower unit.

Protection and support for the twin silencing tubes is provided by an elongate steel shoe 19 extending the full length of each so that the tubes can act as skids whereby the total unit can be towed along the ground for usage in different locations.

As has been noted above, the electric motor 5 is in a separate compartment 7 from the blower pump 1 and is provided with separate acoustic splitter air entry 20 for cooling the motor and a separate acoustic splitter silencer 21 to exhaust the heated air from the motor compartment.

This arrangement assists the desired condition of reducing the temperature of air leaving from the pump 1, since heated air passing over the electric motor 5 is not passed into the inlet of the blower pump (as is often the case with blower units of the kind to which the invention relates). In addition the separation of the motor from the blower pump aids silencing of both of them, since each is provided with its own acoustically clad compartment adapted for the different frequency of noise emitted from the pump and motor respectively.

Dimensions of a unit as herein described would, typically be 1 m wide, 1.02 m high and 3.4 m long to facilitate transport to site underground or surface, without dismantling. By the invention the gross weight can be reduced by approximately 35% compared with known existing units used for mine work.

With reference to Figure 6 it will be seen that the unit is capable of convenient location within an underground mine roadway 22 supported by arches 32.

In the embodiment iliustrated the blower unit 23 is providing a high velocity high throughput airflow through an air pipe 24 leading underneath a rotary air lock at which granular coal or rock is supplied from a chain conveyor through a slotted pan arrangement 26. The air now carrying the granular material passes through a conveying pipe 27 to a flexible tube end 29 where it is blown at high velocity into the packing are via a pipe bend 28, packing in beds adjacent the underground roadway.

This can be immediately behind a working area 30 of the mine, so that infil is rapidly and easily discharged into a pack area 31 to support the roof behind the working area. The rotary valve or venturi box can be sited in line with the pack area as required. The arrangement of the unit, and its sledge like mounting, ensures that it can easily and rapidly be advanced forward as the pack area 31 is filled when the face moves forward exposing a subsequent pack area for filling behind roadway arches 32.

The invention as described above is arranged for use in relation to a particular range of applications of the blower unit in relation to mining and like needs. Thus, the blower can be used in association with a rotary air lock feeder where a feeding machine for granular coal or rock has pocketed paddle type wheels rotated at low speed to convey the material from atmospheric pressure into a pipeline disposed therebelow of pressurised high velocity air for conveying the material elsewhere.

Again air from the blower can pick up material by venturi effect from a venturi type receiving box. Yet again the air from the blower can be used with a "blowpot" arrangement whereat powdered material is fluidised and allowed to flow through differential pressure into a pressurised pipeline disposed therebelow.

It isto be appreciated however that the invention provides a blower unit which can be used in many installations and situations requiring the provision of a large volume of air at low pressure with compact dimensions and manoeuvrability and movability.

Claims (8)

1. An air blowing unit incorporating a low pressure air blower pump, the pump incorporating at least one outlet tube arranged and adapted to serve as an absorptive and/or reactive silencing chamber; and wherein the outlet tube is at least partially located below the unit and serves as a basf support structure therefor.

2. A unit according to Claim 1 incorporating a motor mounted integrally therewith on the base structure, wherein the motor is compartmented separately from the pump and is provided with entry and exhaust for cooling air separate from the air supply to the pump.

3. A unit according to Claim 1 or 2 wherein the blower pump is arranged with an upper inlet and a lower outlet.

4. A unit according to any one of the preceding claims wherein the outlet from the pump is bifurcated so as to provide two outlet tubes for silencing and support of the unit.

5. A unit according to Claim 4 wherein the two outlettubes converge into a single discharge tube.

6. A unit according to Claim 4 or 5 wherein the outlet tubes are generally parallel and are so disposed and located along and below the unit as t act as skids for the unit.

7. A unit according to Claim 6 wherein longitudinal protective shows are secured to the lower surfaces of the outlet tubes.

8. An air blowing unit substantially as shown in and as hereinbefore described with reference to th accompanying drawings.