GB2157198A

GB2157198A - Particle separator

Info

Publication number: GB2157198A
Application number: GB08403487A
Authority: GB
Inventors: Arthur Roger Shipley
Original assignee: Magnavac Air Systems Ltd
Current assignee: Magnavac Air Systems Ltd
Priority date: 1984-02-10
Filing date: 1984-02-10
Publication date: 1985-10-23
Also published as: DE3502137A1; GB2157198B; FR2559403A1; GB8403487D0

Abstract

A particle separator is provided for separating composite materials which have generally similar characteristics within an air stream such as density and/or shape. The separator comprises an input fan (3) and an output fan (7), between which is connected a duct (6) within which is disposed a set of helical vanes (19). The duct is also provided within an exhaust vent (14) and an inlet vent (15) and is surrounded in the region of these vents by a hood (10). In operation, the input and output fans provide a flow of air along the duct and when composite material is introduced into the duct the helical vanes impart a spiral motion which tends to throw the relatively dense constituents of the composite material outwardly. As the material passes the exhaust vent (14) in the duct, the relatively dense constituents are able to exit and fall from the separator under gravity. However, in order to provide a balanced flow of air within the separator, the inlet vent (15) allows air to be re-introduced into the duct, along with any relatively lightweight constituents of the composite material which may have exited from the exhaust vent with the relatively dense constituents. <IMAGE>

Description

SPECIFICATION Particle separator This invention relates to a particle separator of the type in which composite material can be separated into its constituents by introducing it into a spiral air stream.

Known particle separators of the type referred to above are usually referred to as cyclone separators and these utilise the principle whereby heavier particles of the composite material which cannot be supported by the air stream are extracted by allowing such particles to fall out of the spinning air stream, leaving a residue of lighter particles. However, a conventional cyclone separator is unsuitable for separating composite materials in which the constituent particles have similar characteristics within the air stream such as density and/or shape. In such circumstances, the composite material will be simply borne by the air stream and will exit from the separator without being separated into its constituents.This drawback applies particularly where the composite material is generally of a light fibrous nature such that the constituents thereof would ordinarilly be easily transported by an air flow, even if separated.

A particular example of such composite material occurs during the manufacture of disposable childrens' nappies in which the finished nappy usually comprises a layer of plastics material, a fibrous absorbent material, a lining which usually lies against the baby's skin and elastomeric leg bands which prevent leakage from the nappy. When such nappies are manufactured in high volume faults can occur which, if not identified immediately, can mean that large batches of faulty nappies are produced. In such circumstances, although it is desirableto re-cycle the absorbent layer in the nappies, it is impractical to individually open each faulty nappy in order to separate the absorbent layer from the remaining parts.Similarly, it has not been found practicable to cut the nappies into small pieces and separate the constituent materials using a cyclone separator since none of the unwanted constituents has sufficient mass to fall out of the spinning air stream under the force of gravity and against the force of the air stream.

It is an object of the present invention to provide means whereby substantially lightweight composite materials having similar characteristics when introduced into an air flow can nevertheless be separated into constituent parts.

According to the invention there is provided a particle separator comprising input and output means adapted to transport composite material in an air stream up a generally vertical duct between the input and output means, means to impart spiral motion to the air stream in the duct such that centrifugal force is imparted to composite material therewithin which thereby induces separation of the constituents of the composite material whereby relatively dense constituents thereof are generally displaced outwardly, an exhaust vent in the duct adapted to permit the outflow of outwardly displaced material from the duct whilst permitting the remaining constituents of the composite material to be borne up the duct by the air stream, a hood surrounding the duct having an open end adjacent the exhaust vent and a closed end adjacent the duct at a position beyond the exhaust vent, the open end of the hood permitting relatively dense constituents of the outwardly displaced material to fall under gravity therefrom whilst permitting the inflow of air towards the closed end thereof, an inlet vent in the duct between the exhaust vent and the closed end of the hood adapted to permit the inflow of air into the duct from the open end of the hood and the inflow of any remaining constituents of the outwardly displaced material which have not fallen from the hood under gravity, the input and output means being balanced to provide a flow of air in the duct beyond the inlet vent which is substantially equal to the flow of air in the duct before it reaches the exhaust vent.

Conveniently, the input and output means comprise rotary fans which force air and the composite material along the duct.

The means to impart spiral motion to the air stream may conveniently comprise helical vanes set within the duct at a position between the input means and the exhaust vent.

The exhaust vent may comprise one or more slots set within the duct. The or each slot may extend around the whole of the circumference of the duct such that the duct is discontinuous.

The inlet vent may comprise one or more slots set within the duct. The or each slot may extend around the the whole of the circumference of the duct such that the duct is discontinuous.

The hood may conveniently be of conical-shape which tapers inwardly, having an open end which lies concentric with the exhaust vent and a closed end which lies adjacent the duct at a position beyond the inlet vent. The hood may be provided with adjustment means whereby it is slidable along the length of the duct such that the position of the hood can be adjusted with respect to the exhaust and inlet vents.

The width of the exhaust and/or inlet vent may be adjustable such that the separator can be "tuned" to perform satisfactorily with various composite materials. If the dimension of the exhaust and/or inlet vents is adjustable, such adjustment may be achieved by providing the duct in the region between the exhaust vent and the inlet vent with interlocking duct segments which permit telescoping of the duct such that the width of one or both vents may be altered.

In order to achieve a high proportion of separation of the composite material into its constituent parts, the particle separator may be connected in series to one or more particle separators such that progressively greater proportions of separation can be achieved. In such an arrangement the output means of the first separator also acts as the input means of the second separator, and so on.

According to a further aspect of the invention there is provided a method of separating substantially lightweight composite material including the steps of transporting the composite material within a spirally moving air stream up a generally vertical duct such that centrifugal force is imparted to the composite material which thereby induces separation within the air stream of the constituents of the composite material whereby relatively dense constituents are generally displaced outwardly, providing an exhaust vent in the duct adapted to permit the outflow of outwardly displaced material from the duct whilst permitting the remaining material to be borne up the duct by the air stream therewithin, providing a hood surrounding the duct which has an open end adjacent the exhaust vent and adapted to permit relatively dense constituents of the outwardly displaced material to fall under gravity, providing means whereby air may be drawn into the duct through the open end of the hood such that relatively lightweight constituents of the outwardly displaced material which have not fallen under gravity can be reintroduced into the air stream within the duct, and providing means whereby the flow of air within the duct beyond the closed end of the hood is substantially equal to the flow of air in the duct before it reaches the exhaust vent.

The invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a front view of a particle separator according to the invention, and Figure 2 is a schematic part-sectional view similar to that of Figure 1 Referring firstly to Figure 1 of the drawings there is shown a particle separator which comprises a hollow inlet hopper 1 fixed to a horizontally disposed tubular inlet duct 2 which is itself connected to an electrically activated rotary fan 3 having a base support 4 which extends upwardly from a rectilinear base plate 5 fixed to the floor by bolts (not shown).

Extending upwardly from rotary fan 3 is an elongate tubular duct 6, the top end of which is connected to a second rotaryfan 7. Rotary fan 3 defines the input means and rotary fan 7 defines the output means according to this aspect of the invention. Extending horizontally from the fan 7 is a generally "L" shaped outlet duct 8, the free end 9 of which extends vertically downwardly. Concentric with the duct 6 is a frusto-conical hood 10 having an open end 11 and a closed end 12 having a collar 13 concentric with the duct 6. The hood 10 is slidable along the duct 6 and can be releasably secured thereto by adjustable bolts (not shown) which extend through the collar 13.

Ducts 2,6 and 8 define a path through which air can flow.

Referring now to Figure 2, there is shown a view similarto that of Figure 1 but in which for clarity the hood 10 is shown in vertical cross-section, along the lines x-x of Figure 1. Within the hood 10 it will be seen that the duct 6 is discontinuous in that there exists a small circumferential vent 14 adjacent the open end 11 of hood 10. Similarly, above the vent 14 there is a further circumferential event 15 near the closed end 12 of the hood 10. The vent 14 defines the exhaust vent and the vent 15 defines the inlet vent of the particle separator according to this aspect of the invention.Between the vents 14, 15 the duct 6 is comprised of a tubular inner sleeve 16 atthe lower end of which is slidably attached a concentric outer sleeve 17 and to the upper end of which is similarly attached a correspondingly shaped slidable outer sleeve 18. The duct 6 between the vents 14, 15 can thus be telescoped to vary the width of either or both vents 14, 15. The width of vent 14 may also be varied by slidable movement of the hood 10 along the upper end of duct 6.

Within the duct 6 between the exhaust vent 14 and rotary fan 3 are disposed helical vanes 19 (shown in dotted outline) which induce spiral motion to air passing upwardly through the duct 6..

The operation of the particle separator will now be described with reference to Figure 2 and in which the composite material requiring separation comprises faulty disposable nappies which have previously been cut up into small segments containing a mixture of plastics material, elastomeric material, absorbent material and lining material. As an initial step, the electrical supply to the fans 3, 7 is activated to provide a balanced flow of air through ducts 2, 6 and 8. The composite material is then fed into the hopper 1 and drawn along the inlet duct 2 in the direction of the arrow marked "A". The mixture is thereafter transported vertically up duct 6 and and the helical vanes 19 impart a spiral motion to the air stream and composite such that, in turn, centrifugal force is imparted to the composite material.As a result of this centrifugal force, relatively dense constituents of the composite are thrown outwardly such that when the air stream passes the exhaust vent 14, some or all of the relatively dense constituents of the composite material are able to exit from the duct 6 in the direction of the arrows marked "B" whereafter they fall downwardly out of the open end 11 of the hood 10 under the force of gravity, to be collected in a suitable container (not shown). The remaining composite material in the duct is then transported upwardly.

The total air flow output of the second rotary fan 7 is substantially balanced with the total airflow output of the first rotary fan 3 and because of this, air from the open end 11 of the hood 10 is able to re-enter the duct 6 through the in let vent 15, as shown bythe arrows marked "C". If any relatively lightweight constituents of the composite material have exited from the exhaust vent 14 with the relatively dense material they can thus be drawn back into the duct 6 through the inlet vent 15. Since the total air flow output of each of the fans 3,7 is substantially balanced, a constant air flow can be maintained throughout the separator by which the required constituents of the original composite material can be transported and eventually ejected through the outlet duct 8 into a suitable container (not shown).

It will be appreciated that, depending upon the characteristics of the constituents of the original composite material, adjustment of the width of the vents 14, 15 and even the diameter of the ducts 2, 6, 8 may be necessary. In order to accomodate adjustment of the vents 14, 15, the outer sleeves 17, 18 are able to telescope about the inner sleeve 16 and in a similar manner the hood 10 is able to slide along the upper part of the duct 6 at the collar 13. Adjustment of the hood 10 around the exhaust vent 14 can also serve to "tune" the separator such that relatively dense constituents of composite material may be extracted whilst nevertheless permitting inflow of air which prevents relatively lightweight constituents of the composite material from falling under gravity.

Similarly, the output of each rotary fan 3,7 can be adjusted to provide a balanced air flow through the separator by e.g. variation of the rotational speed of each fan and hence the velocity of air which exists therefrom.

Claims

1. A particle separator comprising input and output means adapted to transport composite material in an air stream up a generally vertical duct between the input and output means, means to impart spiral motion to the air stream in the duct such that centrifugal force is imparted to composite material therewithin which thereby induces separation of the constituents of the composite material whereby relatively dense constituents thereof are generally displaced outwardly, an exhaust vent in the duct adapted to permit the outflow of outwardly displaced material from the duct whilst permitting the remaining constituents of the composite material to be borne up the duct by the air stream, a hood surrounding the duct having an open end adjacent the exhaust vent and a closed end adjacent the duct at a position beyond the exhaust vent, the open end of the hood permitting relatively dense constituents of the outwardly displaced material to fall under gravity therefrom whilst permitting the inflow of air towards the closed end thereof, an inlet vent in the duct between the exhaust vent and the closed end of the hood adapted to permit the inflow of air into the duct from the open end of the hood and the inflow of any remaining constituents of the outwardly displaced material which have not fallen from the hood under gravity, the input and output means being balanced to provide a flow of air in the duct beyond the inlet vent which is substantially equal to the flow of air in the duct before it reaches the exhaust vent.

2. A separator according to Claim 1 in which the input and output means comprise rotary fans which force air and the composite material along the duct.

3. A separator according to Claim 1 or Claim 2 in which the means to impart spiral motion to the air stream comprises helical vanes set within the duct between the input means and the exhaust vent.

4. A separator according to any preceding Claim in which the exhaust vent comprises one or more slots set within the duct.

5. A separator according to Claim 4 in which the or each slot extends around the whole of the circumference of the duct such that the duct is discontinuous.

6. A separator according to any preceding Claim in which the inlet vent comprises one or more slots set within the duct.

7. A separator according to Claim 6 in which the or each slot extends around the whole of the circumference of the duct such that the duct is discontinuous.

8. A separator according to any preceding Claim in which the hood is of conical-shape which tapers inwardly, having an open end which lies concentric with the exhaust vent and a closed end which lies adjacent the duct at a position beyond th inlet vent.

9. A separator according to any preceding Claim in which the hood has adjustment means whereby it is slidable along the length of the duct such that the position of the hood can be adjusted with respect to the exhaust and inlet vents.

10. A separator according to any preceding Claim in which the width of the exhaust and/or inle vent is adjustable such that the separator can be "tuned" to perform satisfactorilly with various composite materials.

11. A separator according to Claim 10 in which the adjustment is achieved by providing the duct in the region between the exhaust and inlet vent with interlocking duct segments which permit telescoping of the duct such that the width of the exhaust and/or inlet vent can be altered.

12. A particle separator substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

13. A series of one or more particle separators according to any preceding Claim in which the output means of the first separator in the series also acts as the input means of the second separator in the series, and so on such that progressively greater proportions of separation can be achieved.

14. A method of separating substantially lightweight composite material including the steps of transporting the composite material within a spirally moving air stream up a generally vertical duct such that centrifugal force is imparted to the composite material which thereby induces separation within the air stream of the constituents of the composite material whereby the relatively dense consitituents thereof are generally displaced outwardly, providing an exhaust vent in the duct adapted to permit the outflow of outwardly displaced material from the duct whilst permitting the remaining material to be borne up the duct by the air stream therewithin, providing a hood surrounding the duct which has an open end adjacent the exhaust vent adapted to permit relatively dense constituents of the outwardly displaced material to fall under gravity, providing means whereby air may be drawn into the duct through the open end of the hood such that relatively lightweight constituents of the outwardly displaced material which have not fallen under gravity can be re-introduced into the air stream within the duct, and providing means whereby the flow of air within the duct beyond the closed end of the hood is substantially equal to the flow of air in the duct before it reaches the exhaust vent.

15. A method of separating composite material substantially as hereinbefore described.