US3918399A

US3918399A - Spreading of particulate matter

Info

Publication number: US3918399A
Application number: US283289A
Authority: US
Inventors: John Cuthbert Fox; Martin Richard Winterbottom; Michael Frank Culpin
Original assignee: Imperial Chemical Industries Ltd
Current assignee: Imperial Chemical Industries Ltd
Priority date: 1971-08-25
Filing date: 1972-08-24
Publication date: 1975-11-11
Anticipated expiration: 1992-11-11
Also published as: CA997925A; NL7211621A; AU4600272A; GB1409241A; FR2151408A5; IT964273B; DE2241959A1; JPS4828770A; AU468192B2

Abstract

A process and apparatus for continuous uniform distribution of particulate matter onto a substrate. The apparatus comprises a hollow cylinder having a slot extending along its effective length, and a rotatable member located coaxially within the cylinder, the member having a plurality of vanes, each as long at least as the slot, the outer edges of the vanes being adjacent but not touching the inner wall of the cylinder and the vanes having a radially measured dimension less than the radius of the cylinder to define a central channel within the member. When particulate matter is supplied and suspended in a turbulent stream of gaseous fluid to the central channel, and the member is rotated, the particulate matter issues from the slot in a uniform distribution.

Description

United States Patent 1191 Fox et a1.

1 1 Nov. 11, 1975 1 SPREADING OF PARTICULATE MATTER [75] Inventors: John Cuthbert Fox; Martin Richard Winterbottom; Michael Frank Culpin, all of Pontypool, England 221 Filed: Aug. 24, 1972 211 App]. No.: 283,289

[30] Foreign Application Priority Data Wilhelm 1 18/308 3.230.105 1/1966 Spraul et a1 1124/3014 3.299.853 1/1967 Whitaere 118/312 3,426,729 2/1969 Hawkins 118/312 3.678.894 7/1972 Walsh 118/308 Primur E.\'un1t'm'/'Mervin Stein Assistant Iitaminer-D0uglas Salser Attorney, Agent, or Fir/21-Cushman. Darby & Cushman [57] ABSTRACT A process and apparatus for continuous uniform distribution of particulate matter onto a substrate.

The apparatus comprises a hollow cylinder having a slot extending along its effective length, and a rotatable member -located coaxially within the cylinder, the member having a plurality of vanes, each as long at least as the slot, the outer edges of the vanes being adjacent but not touching the inner wall of the cylinder and the vanes having a radially measured dimension less than the radius of the cylinder to define a central channel Within the member. When particulate matter is supplied and suspended in a turbulent stream of gaseous fluid to the central channel, and the member is rotated, the particulate matter issues from the slot in a uniform distribution.

13 Claims, 4 Drawing Figures US. Patent Nov. 11, 1975 Sheet 1 of2 3,918,399

US. Patent Nov.11, 1975 Sheet20f2 3,918,399

SPREADING OF PARTI C ULATE MATTER The invention relates to improvements in spreading small particles of material in a uniform manner onto a surface. More particularly the invention relates to a method, and apparatus, for spreading flock fibres uniformly onto a. substrate.

lt has previously been proposed to apply flock fibres onto a substrate to which adhesive has been applied by spreading an excess of said flock fibres onto the substrate and thereafter removing the excess flock fibres which have not adhered to the substrate, by a vacuuming technique. lt has also been proposed to direct flock fibres onto a substrate by means of an electrostatic field. The former method requires an initial substantially uniform distribution of flock fibres followed by costly vacuuming and, optionally, recirculation devices for coping with the excess flock applied to the substrate. The final weight of flock adhered to the substrate using this method is determined by the quantity and distribution of adhesive. The second method requires the generation and maintenance of a uniform electrostatic field and produces a product in which the flock fibres are aligned with their long axes at least substantially perpendicular to the plane of the substrate. When the object of flocking is principally to increase the opacity of the substrate, then such an arrangement of flock fibres is neither necessary nor desirable.

' We have now invented an improved method and apparatusfor distributing flock fibres in a uniform manner onto a substrate which requires neither the use of an excess quantity of flock, nor the use of an electrostatic field.

Accordingly the invention provides in one of its aspects a process for the continuous uniform distribution of particulate matter onto a substrate advancing at a constant rate, comprising continuously forming a suspension of said particulate matter in a turbulent stream of gaseous fluid, and directing said suspension whilst maintaining turbulence in the gaseous fluid onto the said substrate at a constant mass flow rate.

Generally the gaseous fluid will be air.

The apparatus for performing the above process comprises a hollow cylinder provided with a slot extending along its effective length and a member located coaxially within the cylinder and rotatable about its lengthwise axis comprising support means'extendin'g beyond the ends of said hollow cylinder and having mounted therebetween a plurality of vanes disposedwithin the said hollow cylinder, each vane extending along the entire effective length at least of said hollow cylinder, the outer edges of said vanes being adjacent but not touching the inner wall of said cylinder and said vanes having radially measured dimensions less than the internal radius of the hollow cylinder to define a central, cylindrical channel within the said member means for supplying particulate matter suspended in a turbulent stream of gaseous fluid at a constant rate to the said channel defined within said member, means for axially rotating said member at a uniform rate and means for advancing a substrate perpendicular to said slot in said hollow cylinder.

The apparatus is capable of uniformly distributing small quantities of particulate material over a large area. For example, we have distributed as little as 0.5 g of a-cellulos'e flock fibres uniformly over 1 square metre. The apparatus is equally capable, however, of metering and distributing uniformly much larger quantities of particulate matter at high rates.

By effective length" of the first member we mean the width over which it is desired to deposit particulate matter. Thus the slot need not extend across the whole width of the first member. However, it is desirable that the length of the vanes should be at least as long as the slot.

It is only necessary that the vanes of the second member be mounted to support means at their desirable although frequently it will prove disirable to provide a number of strengthening and bracing means at spaced intervals along the length of the vanes. The bracing means connect adjacent vanes and thereby serve to stiffen up the second member. Care must be taken, however, to ensure that the presence of the bracing means does not interfere with the uniform deposition of particulate matter and, therefore, we prefer to use the minimum of bracing means necessary to maintain the second member stable.

Advantage may lie in avoiding positioning the bracing means in planes perpendicular to the axis of the apparatus, since the presence of the bracing means may produce irregular distribution of the particulate matter on the substrate material which will be apparent as longitudinally extending stripes. Alternatively We find that a uniform distribution may be obtained if a large number of bracing means positioned perpendicularly to the axis of the apparatus are employed, for example, if the bracing means are spaced at intervals of between 2and 8 cm apart along the length of the second member. The latter arrangement is preferred for reasons of ease of manufacture. The clearance between the ends of the vanes of the second member and the inner walls of the enclosing first member should be as small as is practicable. The number of vanes is an important factor in achieving uniform flock deposition and should not be less than 6, preferably not less than 16. Preferably the vanes are symmetrically disposed around the axis.

If desired the stability of the second member can be further increased by means of an axially situated shaft with the hollow channel, which shaft serves to link the vane support means.

We have observed that} the distribution of flock fibres onto a substrate improves as the number of vanes passing the slot increases. S-uch improvement can obviously be achieved either by using a second member with a relatively large number of vanes, at a relatively low speed of revolution or, alternatively, a small number of vanes at high speeds of revolution.

The actual design of the vanes may take a number of forms. For example the vanes may be of plane rectanvshaped, with, for example, the thickness of the crosssection greater at the vane tip than towards the centre of the vane assembly. Again, the vanes may be curved in the planes perpendicular and/or parallel to the axis of the apparatus.

The vanes may be made of any material capable of resisting dimensional distortion under the loads experienced in operation and which are further safe in operation. Thus mild steel and fibrereinforced plastics are suitable materials.

With reference to the process aspects of the invention, we find that the particulate matter is preferably supplied at as high a concentration in as small a quantity of air as is feasible for this reason a turboblower is preferred to a centrifugal fan as the fluid supply means.

Fluid, for example air, supplied at presures of up to 0.35 Kgcm" are preferred, more preferably pressures between 0.05 and 0.2 Kg.cm and fluid flow rates of about 0.02 to 0.05 m. s are preferable.

The fluid should be supplied in a turbulent state, as opposed to a streamlined flow. Whilst there will be inequalities in the degree of turbulence, for example towards the edge of the ducting, it is an essential feature of our invention that turbulent conditions are maintained so that the particulate matter remains suspended in the stream of fluid. This is particularly important just before the suspended particles are deposited on the substrate.

A substantially uniform supply of particulate matter should be fed into the stream of turbulent fluid. We find with flock fibres of a -cellulose that a conventional vibro-screw feeder is a convenient and satisfactory means of ensuring a uniform supply to the turboblower, the rate of supply being readily adjustable by adjustment of the speed of rotation of the screw. The uniformity of supply of particulate matter may be improved by placing a vibrated gauze between the screw feed and the point at which the particulate matter enters the stream of gaseous fluid.

By rotating the second member within the first member there is maintained a turbulency in the suspension of flock in air which prevents any localised concentration of particulate matter and the sweeping action of the vanes prevents any deposition of particulate matter on the inner walls of the first member.

We find that when the suspension of particulate matter in gaseous fluid is supplied to one end only of the hollow shaft of the second member, the apparatus of the invention is capable of uniform distribution across widths of up to about 2 metres. For greater widths it is preferable to supply the shaft with a suspension of particulate matter in gaseous fluid from both ends in which case it is desirable that the opposing streams are directed by baffles or otherwise, so that the one stream passes over or alongside the other, so that a direct meeting of the opposing streams to the centre of the second member is avoided. The nature of the particulate matter and the substrate will obviously depend upon the type of product it is desired to make.

The invention is further illustrated in the following drawing in which FIG. 1 shows the construction of the first and second member in perspective from below, the second member being partly withdrawn from the first member,

FIG. 2 is a cross-section through the assembled first and second member,

FIG. 3 is a schematic side view of the apparatus of the invention, and,

FIG. 4 illustrates the use of the invention in the manufacture of a non-woven fabric.

Referring to FIGS. 1 and 2, reference number 1 indicates the first member and reference number 2 the second member. First member 1 consists of a hollow tubular casing 3 having a longitudinally extending narrow slot 4. Second member 2 comprises vanes 7 which are supported at their ends by support means (not shown in FIGS. 1 and 2 for clarity), said support means being linked by means of axial shaft 5. Bracing members 6 link adjacent vanes 7, to further support vanes 7 and thereby to improve the stability second member 2. Vanes 7 extend outwardly radially and are arranged so 4 that a small clearance exists between the tips of vanes 7 and the inner wall of easing 3 (shown in FIG. 2);

Vanes 7 and bracing means 6 define a central channel 20 (shown in FIG. 2) which extends the length of second member 2. Means (not shown) to supply particulate matter suspended in gaseous fluid to channel 20 are incorporated in at least one of the support means.

The support means (not shown) are provided with rotatable bearings (not shown) and drive means (not shown) whereby second member 2 may be rotated.

As shown in FIG. 2 the assembled first and

second members

1, 2 are supported by rigid stands 10 shown in the vicinity of advancing substrate 11.

FIG. 3 shows schematically first member 1, stands 10, support means 8 of the second member, means 9 whereby particulate matter is supplied to the apparatus and thence to substrate 11. Reference numeral 12 indicates a turbo-blower, which is connected by vibroscrew feed 13 to storage hopper 14. If the length of the apparatus of the invention is long, supply means 9, turbo-blower l2, vibro-screw feed 13 and hopper 14 may be duplicated at the other end of the apparatus as indicated in dotted lines. Alternatively a single screw feed 13 may feed both ends of the apparatus.

In operation, particulate material stored in hopper 14 is metered by vibro-screw feed 13 to turbo-blower 12 and thence into central channel 20 of second member 2 by way of supply means 9. Second member 2 is rotated by, for instance, an electric motor and drive means (not shown). The air-borne particulate matter passes from channel 20 into the volumes between vanes 7 and the inner surface of casing 3, and thence via slot 4 onto advancing substrate 11.

The invention is further illustrated by the following example with reference to FIG. 4, in which one application of the invention is described.

EXAMPLE A non-woven web having a weight of 12 gm and composed of continuous bicomponent filaments having an extensibility to break of about and a count of about 5 denier per filament, the components being a core of nylon 6.6 with a sheath of nylon 6 (the core weighing about 65% of the total filament weight) was manufactured by forwarding the freshly spun filaments onto a collecting surface by means of a traversing pneumatic forwarding device. The web so produced, which had a width of 1.0 m, was wound up on a roll, interleaved with tissue paper, and the roll was subsequently passed through an atmosphere of steam at 1.75 Kg.cm at a speed giving a residence time of some 5 secs, which treatment bonded the filaments of the web together by softening the nylon 6 sheath. The bonded web was rewound as a roll, the interleaving tissue paper being discarded. This roll of web was used as the feed stock for the apparatus illustrated in FIG. 4, reference numeral 20 indicating the roll of web, and reference numeral 21 the passage of the web as it was unwound from roll 20.

Base web 21 was passed between nip rolls 22, 23 at a speed of about 5 m. min roll 22 being a gravure roll contacting adhesive 25 contained in bath 26. Doctor blade 24 ensures even distribution of adhesive along the length of roll 22 and hence across the width of web 21. The adhesive employed was a self-linking acrylic copolymer, designated Primal HA8, supplied by Lennig Chemicals Limited, emulsified in water to give about 50% solids. The amount of solids applied to the web 21 by roll 22 was adjusted to about 2 g. m by further diluting the emulsion with water.

The base web coated with adhesive (designated 27) was advanced to a flocking station 28, comprising the apparatus of the present invention situated above (29) and below (30) web 27. Flock fibres of a-cellulose having a nominal length of 0.3 cm were advanced from storage hoppers (not shown) via vibro-screw feeds 31, 31' into a stream of air at venturi 32, 32, said stream of air being supplied by turbo-blowers 33, 33 at a rate of 50 ft /min. The air-borne flock fibres, which were supplied at a rate of 100 g. min were passed via pipe 9, 9' (shown schematically) to barrel 5,5 and was distributed uniformly by rotating vanes 7, 7' onto the adhesive coated base web 27 via slot 4, 4'. Slot 4 was offset from slot 4'. The apparatus 29 and 30 comprised a cylindrical first member of length 110 cm and diameter 15.5 cm having a slot of width 0.65 cm. The second 7 member in each case comprised 18 equispaced vanes mounted radially with respect to the axis. The vanes were manufactured from mild steel sheet of 1.50 mm thickness and were supported by mild steel sheet bracing means spaced apart at 2.5 cm intervals. The second member was rotated at 385 rpm. The clearance between the vanes and the inner wall of the second member was nominally 0.6 cm. The apparatus 29, 30 was enclosed within extraction hood 35, 35 and mild suction was applied to remove any surplus flock fibres which failed to contact the adhesive. The flock fibres were thereby applied to the base web at a rate which gave 20 cm flock fibres on the web. Subsequently, flocked web was passed through a hot dry zone 41 in which the adhesive was cured. The zone 41 may be a hot air blower, radiant heaters or a hot air oven. The residence time was about 2 minutes at a temperature of 140C. Finally web 40 is passed via idler and spreading rollers 45, 46 to wind-up means 50.

The physical properties of the product were found to be as follows:

Weight: Tear strength:

Machine direction: 1.95 Kg Cross-machine direction: 2.l0 Kg Machine direction: 42.0% Cross-machine direction: 430 g.cm

Machine direction: 1.40 Kg Cross-machine direction: l.27 Kg Extension:

Burst strength: Breaking load:

The product was a lightweight drapeable fabric having good tear strength, burst strength and breaking load. It had excellent drape, stretch properties and crease resistance. It could be dyed, printed, cut without fraying,v sewn, glued and sterilised by conventional 1. Apparatus for the uniform distribution of particulate matter on to a substrate advancing at a uniform rate, comprising an elongated hollow cylinder provided with a slot extending along its effective length; a member located coaxially within the cylinder and rotatable about its lengthwise axis, said member comprising support means extending beyond the ends of said hollow cylinder and having mounted therebetween a plurality of vanes disposed within said hollow cylinder, each of said vanes extending along the entire effective length of said hollow cylinder, the outer edges of said vanes being adjacent but not touching the inner wall of said cylinder, said vanes having radially measured dimensions less than the internal radius of the hollow cylinder to define a central, cylindrical channel within said member; means for supplying particulate matter suspended in a turbulent stream of gaseous fluid at a constant rate to said channel defined within said member; means for axially rotating said member at a uniform rate; and means for advancing a substrate perpendicular to said slot in said hollow cylinder, the slot in said hollow cylinder and said rotatable member each having a length sufficient to enable uniform distribution of particulate matter onto a substrate having a width in the range of 1 meter and above.

2. Apparatus according to claim 1, wherein bracing means extending between adjacent vanes are provided at intervals along the length of the said member.

3. Apparatus according to claim 2, wherein said bracing means are set at angles to planes perpendicular to the lengthwise axis of said member.

4. Apparatus according to claim 2, wherein said bracing means are set perpendicularly to the lengthwise axis of said second member and at intervals of between 2 and 8 cm.

5. Apparatus according to claim 1, wherein there are at least 6 vanes preferably not less than 16 vanes in said member.

6. Apparatus according to claim 1, wherein an axial shaft is situated within central channel of said second member links the vane support means thereof.

7. Apparatus according to claim 1, wherein the crosssection of the vanes is wedge-shaped.

8. Apparatus according to claim 1, wherein the vanes are manufactured of mild steel.

9. Apparatus according to claim 1, wherein the vanes are manufactured of a fibre-reinforced plastic material.

10. Apparatus according to claim 1, wherein the means for supplying particulate matter comprises a hopper and a vibrated screw feed.

1 1. Apparatus according to claim 1, wherein the gaseous fluid is supplied by means of a turbo-blower.

Claims

1. Apparatus for the uniform distribution of particulate matter on to a substrate advancing at a uniform rate, comprising an elongated hollow cylinder provided with a slot extending along its effective length; a member located coaxially within the cylinder and rotatable about its lengthwise axis, said member comprising support means extending beyond the ends of said hollow cylinder and having mounted therebetween a plurality of vanes disposed within said hollow cylinder, each of said vanes extending along the entire effective length of said hollow cylinder, the outer edges of said vanes being adjacent but not touching the inner wall of said cylinder, said vanes having radially measured dimensions less than the internal radius of the hollow cylinder to define a central, cylindrical channel within said member; means for supplying particulate matter suspended in a turbulent stream of gaseous fluid at a constant rate to said channel defined within said member; means for axially rotating said member at a uniform rate; and means for advancing a substrate perpendicular to said slot in said hollow cylinder, the slot in said hollow cylinder and said rotatable member each having a length sufficient to enable uniform distributioN of particulate matter onto a substrate having a width in the range of 1 meter and above.

7. Apparatus according to claim 1, wherein the cross-section of the vanes is wedge-shaped.

11. Apparatus according to claim 1, wherein the gaseous fluid is supplied by means of a turbo-blower.

12. Apparatus according to claim 10, wherein a vibrated gauze is interposed between the screw feed and the point at which the particulate matter enters the stream of gaseous fluid.

13. Apparatus according to claim 1, wherein the suspension of particulate matter is directed into the central chamber within the said second member from both ends thereof.