GB1571725A

GB1571725A - Method and apparatus for separating air from a transporting duct

Info

Publication number: GB1571725A
Application number: GB733777A
Authority: GB
Original assignee: Maschinenfabrik Rieter AG
Current assignee: Maschinenfabrik Rieter AG
Priority date: 1976-02-27
Filing date: 1977-02-22
Publication date: 1980-07-16
Also published as: CH595469A5; JPS52106167A; AR211288A1; BE851140A; DE2649344A1; DE2649344B2; FR2342230A1; IT1077824B

Description

(54) METHOD AND APPARATUS FOR SEPARATING AIR FROM A TRANSPORTING DUCT (71) We, MACHINENFABRIK RIETER A.G. a body corporate organised under the laws of Switzerland, of Winterthur, Switzerland, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a method of, and apparatus for, separating air from a transporting duct carrying an air-stream transporting fibre flocks to a spinning preparatory machine.

In spinning, the separation of an airstream carrying fibre flock into fibre flocks and air is a known operation in which the fibres are transferred to a storage room or to a spinning preparatory machine, and the transporting air is drained off as exhaust air.

There is a known device for cleaning the exhaust air drained from the spinning plant in which fibres contained in the exhaust air are recovered. In this known device, the exhaust air is divided in a pre-separator into a pre-cleaned air-stream containing fibres and into an air-stream containing impurities.

Nowadays a spinning preparatory machine cannot sufficiently take up the airstream carrying the fibres, particularly where two or more ducts are combined into a single transporting duct. The capacity of the subsequent fibre processing machine is then too small, and the situation can only be remedied by using an over-sized air separating plant.

An object of the present invention is to avoid these disadvantages and to provide a method and an apparatus which enable the quantity of transporting air to be adapted to the capacity of the subsequent spinning preparatory machine without impairing the fibre transport.

In the method according to the invention there is provided a method of separating air from a transporting duct in which a fibreflock-transporting air stream flows to a spinning preparatory machine, wherein the air stream is passed into a duct portion having a flow passage extending between a flow inlet and a flow outlet, said flow passing being of reducing cross section in the flow direction and being at least partially defined by an air permeable wall so that the air stream is divided by said portion into a fibre-carrying transporting air stream leaving said flow passage at said flow outlet and fibre-free exhaust air stream leaving said flow passage via said air permeable wall.

The invention will now be described with reference to the accompanying drawings in which: Fig. 1 is a schematic cross-section of an apparatus, according to this invention, Fig. 2 is a schematic illustration of the air speed and air quantity conditions in an intermediate section of the apparatus, and Fig. 3 is a vectorial diagram of the air speeds in an exhaust air-stream.

An input section 1 of a transporting air duct merges into a closed housing 2 in which the input section 1 is connected with a tapered tube 3. The tube 3 is provided with small circular air escape openings 4, the diameters of which are smaller than 3 mm and therefore considerably smaller than the fibre length, these openings being regularly distributed over the whole surface. The distance between centres of neighbouring openings is preferably 2.5 mm if the diameter of the openings is 1.5 mm. The other end of the tapered tube 3 is connected to an output section 5 of the transporting duct which continues outside the housing 2.

The length of the tube 3 can be chosen freely but preferably it should not be less than 0.3 m and should not exceed 2.5 m. If the diameter (A) of the input section 1 is 300 mm and the diameter (B) of the output section 5 is 180 mm the length of the tapered tube 3 should for example, be, 1 m.

Preferably, the input diameter and the output diameter respectively of the tapered tube 3 coincide with the diameter A and B respectively. An exhaust air duct 6, the diameter of which is preferably about the same as diameter A, is connected to the housing 2. An adjustable baffle 7 can be arranged at the entrance of the exhaust air duct 6 or of the output section 5 and a dampening plate 8 can be arranged at the housing inside wall. The function of these is hereinafter described.

The apparatus now functions as follows: The air-stream 10 transporting fibre flocks 9 passes through the input section 1 of the transporting duct into the tube 3 in the housing 2 and on into the output section 5 of the transporting duct. In the tapered tube 3, part of the transporting air now escapes through the small openings 4 to the inside of the housing 2. Thus, the fibre flocks 9 are transported by the air-stream 11 remaining within the tube 3 through the output section 5 of the transporting duct to the subsequent spinning preparatory machine (not shown in the Figures). The air 12 which is separated into the housing 2 can be transferred through the exhaust air duct 6 to a central air conditioning plant (not shown) or can be transferred via a filter (not shown) back into the room.

The transporting air carrying fibre flocks can be pushed through the transporting air duct by an above-atmospheric pressure prevailing in the transporting duct as well as sucked through the transporting duct if a vacuum prevails.

It has been found that under steady conditions the following relations prevail (Figs. 2 and 3): M, F, I) = M2 F2 2) V,=V2=VA where: M,=total transporting air quantity supplied per time unit through section 1.

M2=transporting air quantity transferred further via the transporting duct section 5 per time unit.

M3=M 1-M2=air quantity exhausted through the openings in the perforated tapered tube per time unit.

F,=cross-section area of the input end of the perforated tapered tube.

F2=cross-section area of the output end of the perforated tapered tube.

V1, V2, V3 air speeds.

a=angle of taper of the tapered zone.

In Fig. 3 the resulting speed V3 of the exhaust air is shown split into an axial component VA and a radial component VR. If only a part of the tapered tube is perforated, the cross-section area F, and F2 refer to the perforated portion of the tapered tube, in which case the relation 2) no longer is valid.

By choosing a ratio of the input cross section area to the output cross-section area of the perforated tapered tube, the ratio of the air quantity transporting further to the air quantity exhausted can be determined.

As the axial speed component is the same for all air part quantities, the speed of the input air-stream is of no great consequence.

At a diameter A=300 mm of the input cross section area and a diameter B=180 mm of the output cross-section area of the perforated tapered tube, the quantity of air transporting the flocks further is, for example, about one third of the total quantity of input air whereas about two thirds are separated as exhaust air. If, for example, in this apparatus, 1.2 m3/s of air are introduced at a speed of 17 m/s, then 0.4 m3/sec transport the fibre flocks further at a speed of 17 m/s, whereas 0.8 m3/s air is exhausted, the axial speed component of the exhaust air also being 17 m/s.As with the diameters mentioned of A=300 mm and B=180 mm and with a length of 1 m of the tapered tube the angle of taper a is very small, it is between 3 and 4", the radial component is also very small and the axial component is therefore the major part of the exhaust air speed. As a stationary pressure should prevail within the housing 2, it is advantageous to arrange an adjustable baffle at the exit of the exhaust air duct or at the exit of the output section of the transporting duct, so that pressure irregularities caused by the housing 2, for example by air vortex formation, can be levelled out and that an equilibrium condition can be set.

There is the danger of the perforation openings being clogged up by fibres inside the tapered tube. However, it has been proved that this danger diminishes the smaller the diameter of the perforations and eventually vanishes completely. Diameters of the opening of less than 3 mm have proved particularly advantageous.

Furthermore, the zone of transition from the perforation openings to the surface of the tapered tube is an even greater source of danger of fibre accumulation due to the nicks and burrs created by the stamping process. Only a very smooth transition zone prevents the accumulation of fibres. Such a smooth transition zone can be obtained by the so-called electrolytical polishing process. In this process the microscopically small surface points protruding in the tube are removed electro-chemically. As this process is optimally effective only with stainless steel, the perforated tapered tube is preferably made from such material.

The tapered tube may produce a whistling sound under certain air conditions. It has now been proved that this whistling sound can be eliminated if the regularly arranged perforation openings are of different diameters. Another remedy can be an irregular arrangement of the openings.

However. the whistling sound can also be eliminated, in a particularly simple manner, if a dampening plate made of any sound deadening material is arranged on the inside wall of the housing. The best position for the dampening plate can be determined simply by trial.

The present invention is not limited to the tapered tube provided with openings over its full length hereinbefore described. The shape of the intermediate section may be varied, in which case the same good results achieved using the tapered tube are not usually quite reached but the result can still be satisfactory.

The intermediate section can be a tapered tube which is provided with openings only over part of its length. Furthermore an intermediate section with a rectangular or square cross-section can be used in such an arrangement all the side walls or only some of them can be provided with openings.

Finally, the housing itself may be dispensed with, which arrangement however has the disadvantage, that the exhaust air is drained into the room without being cleaned. In addition to numerous possible solutions not herein mentioned, a direct connection of the exhaust air duct to the transporting duct is also possible, a perforated plate being inserted at the connection point.

The intermediate section may be made from a material other than steel. For example, it may be of aluminium, but nonmetallic materials such as fabrics or plastics material may also be suitable. However, a fabric, would have to have openings which are large enough to permit the passage of dust, i.e. the distance between the threads would have to exceed 0.1 mm. In a sieve-type plastic material, the openings would have to be of the same order of diameter magnitude as in an intermediate section made of steel.

WHAT WE CLAIM IS: 1. A method of separating air from a transporting duct in which a fibre-flocktransporting air stream flows to a spinning preparatory machine, wherein the air stream is passed into a duct portion having a flow passage extending between a flow inlet and a flow outlet, said flow passage being of reducing cross section in the flow direction and being at least partially defined by an air permeable wall so that the air stream is divided by said portion into a fibre-carrying transporting air stream leaving said flow passage at said flow outlet and a fibre-free exhaust air stream leaving said flow passage via said air permeable wall.

2. A method according to claim 1, wherein the flow passage is frusto-conical.

3. A method according to either preceding claim, wherein, downstream of said portion the exhaust air-stream passes through a filter for cleaning.

4. A method according to any preceding claim, wherein the fibre flock-transporting air-stream is pushed through the transporting duct by an above-atmospheric pressure prevailing in the duct.

5. A method according to any one of claims 1--3, wherein the fibre-flocktransporting air-stream is sucked through the transporting duct by sub-atmospheric pressure.

6. A method according to any preceding claim, wherein the ratio of the air quantity carrying the flocks at the flow outlet to the air quantity carrying the flocks at the flow inlet is determined by the ratio of the crosssection area of the flow passage at the upstream end of the air permeable wall to the cross-section area of the flow passage at the downstream end of the air permeable wall.

7. A method of separating air from a transporting duct in which a fibre flock transporting air steam flows to a spinning preparatory machine substantially as described with reference to the accompanying drawings.

8. An apparatus for carrying out the method according to claim 1, comprising a transporting air duct arranged to supply a fibre-flock-transporting air stream to a spinning preparatory machine and including a duct portion having a flow passage arranged to receive said air stream, said flow passage extending between a flow inlet and a flow outlet, being of reducing crosssection in the flow direction and being at least partially defined by an air permeable wall so that, in use, the air stream is divided by said portion into a fibre-carrying transporting air stream leaving said flow passage at said flow outlet and a fibre free exhaust air stream leaving said flow passage via said air permeable wall.

9. An apparatus according to claim 8, wherein the duct portion is a tapered tube providing said wall and containing openings over its whole length.

10. An apparatus as claimed in claim 9 wherein the transporting duct comprises an input section and an output section formed separately from but connected to said duct portion the input end diameter of which portion corresponds to the diameter of the input section of the transporting duct and the output end diameter of which portion corresponds to the diameter of the output section of the transporting duct.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. sound under certain air conditions. It has now been proved that this whistling sound can be eliminated if the regularly arranged perforation openings are of different diameters. Another remedy can be an irregular arrangement of the openings. However. the whistling sound can also be eliminated, in a particularly simple manner, if a dampening plate made of any sound deadening material is arranged on the inside wall of the housing. The best position for the dampening plate can be determined simply by trial. The present invention is not limited to the tapered tube provided with openings over its full length hereinbefore described. The shape of the intermediate section may be varied, in which case the same good results achieved using the tapered tube are not usually quite reached but the result can still be satisfactory. The intermediate section can be a tapered tube which is provided with openings only over part of its length. Furthermore an intermediate section with a rectangular or square cross-section can be used in such an arrangement all the side walls or only some of them can be provided with openings. Finally, the housing itself may be dispensed with, which arrangement however has the disadvantage, that the exhaust air is drained into the room without being cleaned. In addition to numerous possible solutions not herein mentioned, a direct connection of the exhaust air duct to the transporting duct is also possible, a perforated plate being inserted at the connection point. The intermediate section may be made from a material other than steel. For example, it may be of aluminium, but nonmetallic materials such as fabrics or plastics material may also be suitable. However, a fabric, would have to have openings which are large enough to permit the passage of dust, i.e. the distance between the threads would have to exceed 0.1 mm. In a sieve-type plastic material, the openings would have to be of the same order of diameter magnitude as in an intermediate section made of steel. WHAT WE CLAIM IS:

1. A method of separating air from a transporting duct in which a fibre-flocktransporting air stream flows to a spinning preparatory machine, wherein the air stream is passed into a duct portion having a flow passage extending between a flow inlet and a flow outlet, said flow passage being of reducing cross section in the flow direction and being at least partially defined by an air permeable wall so that the air stream is divided by said portion into a fibre-carrying transporting air stream leaving said flow passage at said flow outlet and a fibre-free exhaust air stream leaving said flow passage via said air permeable wall.

2. A method according to claim 1, wherein the flow passage is frusto-conical.

I 1. An apparatus as claimed in any of

claims 8 to 10 wherein said portion is arranged within a housing connected to an exhaust duct.

12. An apparatus according to any of claims 8 to 11 wherein the duct portion is made of stainless steel.

13. An apparatus according to any of claims 8 to 12 in which said wall is made air permeable by providing it with circular openings.

14. An apparatus according to claim 13, wherein the diameter of the openings is smaller than 3 mm.

15. An apparatus according to claim 13 wherein the circular openings are arranged in a regularly spaced arrangement and are of the same diameter.

16. An apparatus according to claim 13, wherein the distance between neighbouring circular openings is 2.5 mm, the hole diameter being 1.5 mm.

17. An apparatus according to claim 13, wherein the circular openings are of different diameters.

18. An apparatus according to claim 13, wherein the arrangement of the circular openings is irregular.

19. An apparatus according to any one of claims 8 to 18 wherein the duct portion is electrolytically polished.

20. An apparatus according to claim 9, wherein, for exhausting about two thirds of the transporting air quantity, the diameter of the tapered tube is about 300 mm at the input and about 180 mm at the output end.

21. An apparatus according to claim 10 wherein an adjustable baffle is provided at the output section of the transporting duct.

22. An apparatus according to claim 11 wherein an adjustable baffle is provided at the exhaust duct.

23. An apparatus according to any one of claims 8 to 20 wherein the length of the air permeable wall is in the range from 0.3 m to 2.5 m.

24. An apparatus according to claim 11 in which a dampening plate is arranged at the inside wall of the housing.

25. An apparatus according to claim 8, wherein the air permeable wall is made of a fabric.

26. An apparatus according to claim 8, wherein the air permeable wall is of a sievelike plastics material.

27. An apparatus for separating air from a transporting duct in which a fibre flock transporting air stream flows to a spinning preparatory machine substantially as described with reference to the accompanying drawings.