US3923224A

US3923224A - Filament handling apparatus

Info

Publication number: US3923224A
Application number: US363317A
Authority: US
Inventors: James Brock
Original assignee: Imperial Chemical Industries Ltd
Current assignee: Imperial Chemical Industries Ltd
Priority date: 1972-05-26
Filing date: 1973-05-24
Publication date: 1975-12-02
Anticipated expiration: 1992-12-02
Also published as: NL7307329A; BE800153A; AU5621873A; ATA466573A; JPS4947673A; AT338961B; DE2327089C3; IT987977B; GB1436545A; CA1025614A; DE2327089B2; CH566412A5; DE2327089A1; FR2186850A5

Abstract

Improved filament separation without loss of the entrainment, tensioning or fluid consumption characteristics of a pneumatic spray gun are achieved by supplying a plurality of filament bundles containing preferably from 5 to 20 filaments. Apparatus is provided comprising a plurality of inlets communicating with a common chamber into which driving fluid is passed and a common exhaust passageway extending from the chamber to the outlet.

Description

Dec. 2, 1975 United States Patent [1 1 Brock 1 FILAMENT HANDLING APPARATUS FOREIGN PATENTS OR APPLICATIONS Cannon...

[75] Inventor: JameSBmCkPOMYPOOLEngland 3,754,694 8/1973 [22] Filed:

Primary Examiner-Richard A. Schacher [21 1 Appl Attorney, Agent, or Firm-Cushman, Darby &

Cushman [30] Foreign Application Priority Data May 26, 1972 United Kingdom..,............

[57] ABSTRACT Improved filament separation without loss of the entrainment, tensioning or fluid consumption characteristics of a pneumatic spray gun are achieved by sup- 72 93 67 21 2 W6 B m 1; G QML Um NH 55 plying a plurality of filament bundles containing preferably from 5 to 20 filaments. Apparatus is provided comprising a plurality of inlets communicating with a 3 w, QB 99 13 ,2 7; m II M m m2 m2 n M8 2 S f 0 d I e i F 8 5 References Cited common chamber into which driving fluid is passed UNITED STATES PATENTS and a common exhaust passageway extending from the chamber to the outlet. 6/1961 10/1965 226/7 16 Claims, 5 Drawing Figures Riseley.............. Lockshaw...............................

US. Patent Dec. 2, 1975 Sheet 1 of2 3,923,224

FIG]

US. Patent Dec. 2, 1975 Sheet 2 of2 3,923,224

FILAMENT HANDLING APPARATUS The invention relates to improved pneumatically powered apparatus for advancing filaments. Such apparatus is referred to hereinafter as a pneumatic spray gun. The invention also provides a method of improving the performance of such apparatus.

Pneumatic spray guns have been proposed for use in the manufacture of non-woven webs composed of continuous filaments. In essence, their operation is to accept a number of filaments 'at an inlet portion from a filament supply source, to act upon these filaments with a stream of fluid so as to tension and advance the said filaments, and to emit the filaments from an outlet portion.

When manufacturing continuous filament nonwoven webs the spray gun projects the filaments onto an advancing collector surface, and, in order that the non-woven web should be as uniform as possible, it is a generally accepted desideratum that the spray gun should separate as much as possible the filaments from each other'so that'bunching of filaments is minimised. The spray gun should be easy to string up and thus should possess entrainment properties at its inlet portion. The spray gun should also be capable of applying tension to the filament bundle upstream of the spray gun inlet portion at a level sufficient to overcome billowing and lick-back as the filament bundle leaves any roll or'pin'upstream of the spray gun and, to provide sufficient tension to orient the molecules of the filaments (ile., to draw synthetic filaments), where this is desired. These'functions should be carried out with a minimum consumption of the pneumatic fluid.

Many designs of spray guns have been proposed to achieve this aim and some perform adequately when acting on small numbers of filaments. However, it has been observed that even with spray guns which perform adequately at low throughputs, performance, in particular evenness of separation of the filaments, deteriorates rapidly as the throughput is increased. Clearly one solution to this problem is to employ more than one spray gun when high throughput processes are desired, but as it is extremely difficult to make two or more guns having exactly similar characteristics it becomes necessary to carefully and accurately adjust the spacing of the guns in order to produce a uniform non-woven web and in many cases the result is at best a compromise. An alternative approach has been to increase the dimensions of the spray gun to cope with increased throughput; however, this approach is not entirely satisfactory, since whilst good filament separation is maintained, the entrainment and tensioning characteristics deteriorate, and the consumption of pneumatic fluid is greatly increased.

We have now discovered a method in which the filament separation characteristics of a pneumatic spray gun advancinga bundle consisting of a large number of filaments can be greatly improved, without significantly affecting the entrainment or tensioning characteristics nor significantly increasing the air consumption.

Accordingly, in oneof its aspects, the invention provides a method of improving the filament separation characteristics of a pneumatic spray gun whereby a bundle consisting of a large number of filaments is accepted atan inlet portion, acted upon by a stream of fluid so as to tension and advance the said filaments and to emit. them from an outlet portion, wherein the bundle of filaments is separated into a plurality of small bundles each containing a few filaments and each of said small bundles are guided individually and independently into the said pneumatic spray gun. According to another aspect of the invention, we provide a pneumatic spray gun having inlet and outlet portions, a chamber within said spray gun with which an inlet passageway for a stream of fluid communicates and an exhaust passageway extending from the chamber to the outlet portion, and means associated with said inlet portion to guide a plurality of small bundles containing a few filaments individually and independently into the said chamber.

In yet another embodiment the invention provides a pneumatic spray gun capable of providing good fila- The number of small bundles of filaments into which the bundle of filaments is split, according to the invention, and the number of filaments in each small bundle,

will depend on a number of factors. We find that, even splitting a filament bundle into two small bundles reduces the amount of filament bunching in webs sprayed by the pneumatic spray gun. On the other hand splitting a filament bundle into, say, 8 small bundles maybe too time-consuming or tedious an operation to be economically viable. We prefer to split filament bundles into between 3 and 6 small bundles.

The number of filaments in each bundle is preferably between 5 and 20, and most preferably not more than 15, since with larger numbers of filaments the separation of the filaments begins to deteriorate.

The invention is applicable to a large variety of spray guns. For instance, the filament separation characteristics of a spray gun having a rectangular passageway extending therethrough may be enhanced by the provision of guide members arranged in the manner of a comb and situated in the vicinity of the inlet of the spray gun. The bundle of filaments upon which the spray gun acts is split up into a plurality of small bundles which are inserted between the teeth of the comb guide and thereby guided individually and independently into the spray gun inlet. Similarly with a,

spray gun having a passageway of circular or annular cross-section, guides may be mounted on the circumference of a circular support means situated in the vicinity of the inlet of the spray gun.

Since the invention provides a means of improving the separation of filaments emitted by a pneumatic spray gun, it is particularly suited to those spray guns which provide a spray pattern having a large area. (By spray pattern is meant the pattern occupied by filaments when collected in a plane situated at a distance below the outlet of the spray gun.) Thus, those designs of spray guns in which the cross-sectional area of the exhaust passageway is greater at the outlet of the spray gun than at the point in which it is adjacent to the chamber into which the stream of fluid is introduced, are particularly suited to perform the invention. These spray guns include those in which the exhaust passageway is a cone of circular, elliptical oreven rectilinear cross-section diverging towards its outlet end. Alternatively the exhaust passageway of such preferred spray guns is defined between two solids, for example, cones, of any cross-section, the two cones defining an annular passageway which has a greater cross-sectional area towards its open end. The rate of increase in cross-sectional area from chamber to open end of the passageway need not be a constant rate of increase, as for example in a trumpet-shaped passageway or a passageway defined between two solids of non-constant cross-section. However, those passageways which diverge towards their open ends are preferred in the preparation of non-woven webs since wide uniform spray patterns are thereby deposited onto a collector, which permits the manufacture of low weight (say gm nonwoven webs.

Whilst the spray pattern is largely determined by the geometry of the exhaust passageway, we find that owing to the improved separation between filaments provided by the invention, it is possible to modify the spray pattern of spray guns having its exhaust passagewy defined between two solids to some extent without affecting the good filament separation. We achieve this effect by extending the central solid portion beyond the end of the outer solid casing of the exhaust passageway, and so shaping it that the flow of exhausting fluid is either diverted outwardly or caused to flow inwardly, relative to the axis of the spray gun. By forming the extended portion to the required shape, a combination of these two effects can be achieved which causes the direction of travel of the entrained filaments to be altered and thereby the spray pattern to be modified. Further deflection of the exhaust fluid flow can be achieved by extending portions of the outer casing to act in conjunction with the extended central portion. For instance the extension of the central solid portion may consist of two diametrically opposite cusps, and two cooperating inwardly extending cusps may be formed on the outer casing and arranged to fit between the centre portion cusps. It is'possible by this means to modify a circular spray pattern into an elliptical spray pattern, whilst still retaining the overriding characteristic provided by the invention of excellent filament separation within the spray pattern.

We find that the internal surfaces of the spray gun, and especially of the exhaust passageway are preferably not of a polished finish and we prefer a satin finish. It is desirable to form those surfaces of the spray guns which are contacted by the filament bundles from an electrically conducting ceramic material, for example Conducting Faradex, supplied by Steatite and Porcelain Limited.

A preferred embodiment of the invention is a pneumatic spray gun for the manufacture of non-woven webs in which the outlet passageway is defined between two equiangular coaxially mounted cones.

The invention is further illustrated with reference to the accompanying drawing in which:

FIG. 1 is a longitudinal section through a pneumatic spray gun constricted in accordance with one embodiment of the invention,

FIG. 2 is a plan view of apparatus according to another embodiment of the invention,

FIGS is a section on the line 33 in FIG. 2,

FIG. 4 is a side elevation of the exhaust passageway of apparatus according to one embodiment of the invention provided with means to modify the spray pattern,

FIG. 5 is a section on line 5-5 in FIG. 4.

In FIG. 1 there is shown inlet tubes 2 which extend coaxially from passageways 3 defined within cap-piece 4. Passageways 3 enter chamber 5 which extends annularly around cone piece 6 and is defined between the base of cap-piece 4, the exterior of cone piece 6 and within the upper interior of base piece 7. An annular chamber 8, defined between the interior of body piece 9 and the upper exterior of base piece 7 communicates via a plurality of air inlet passageways 10 with an annular air inlet chamber 11 which in turn communicates via annular slot 12 with chamber 5. Defined between the exterior of cone piece 6 and the interior of base piece 7 and extending downwardly from chamber 5 is exhaust passage 13 which is annular in cross-section and increases in diameter further from chamber 5. The interior surface of base piece 7 and the exterior surface of cone piece 6 are machined parallel to each other.

FIGS. 2 and 3 show, in plan and section on line 33 respectively, an alternative arrangement, wherein a large bundle of filaments 20 are split into a number of small bundles 21 (four shown) by a guide 22 and bundles 21 are thereafter passed into an annular inlet passageway 23. Guide 22 is secured by arm 24 to anchorage 25 (not shown in FIG. 3) and is provided on its outer side with split eyelet guides 30 which receive bundles 21 and guide them individually and independently into inlet passageway 23. This arrangement may be strung up with greater ease than the embodiment shown in FIG. 1, in that the large bundle of filaments 20 may be introduced as a whole into the spray gun and thereafter split into the small bundles 21 with ease.

FIGS. 4 and 5 show an alternative embodiment of the gun in which cone piece 6 extends beyond the lower end of base piece 7 and is shaped to modify the spray pattern produced by the spray gun from an essentially circular pattern to an elliptical pattern. As shown, cone piece 6 has outwardly extending cusps 26 which deflect the air blast outwardly along their outer surfaces. In addition a partial vacuum is set up between and beneath the cusps 26, at 27, which pulls the air blast inwardly, as shown by arrows in FIGS. 4 and 5.

The spray guns of the invention produce extremely good filament separation even with a large total number of filaments. They are therefore capable of producing uniform non-woven webs having singularly low weights, by, for example, the technique described in our British Patent Specification No. L23 1 ,066. For example, the spray gun as described and illustrated in FIG. 1, having 4 inlet tubes, each receiving 10 filaments has been used to make a uniform web of weight 12 gm? The uniformity of the web was considered to be outstandingly good and the web could be used as a substrate for a flocked fabric, which by virtue of its low weight and cheapness was considered suitable in end uses, for example, surgical drapes, which demand a complete flock cover without pin-holes. By way of comparison, a non-woven web made with a spray gun having one inlet tube and with otherwise the same design as the spray gun described was poor in uniformity and the flocked fabric made from it showed a large number of pinholes.

What we claim is:

1. A pneumatic spray gun having a plurality of inlet passageways, each passageway being adapted to receive a plurality of filaments in the form of a small bundle, said inlet passageways communicating with a common chamber, a discharge passage extending from said chamber to an outlet, a driving air inlet passageway communicating with said chamber and arranged so that driving air enters said chamber via the driving air inlet and acts on the small bundles of filaments flowing from each of said inlet passageways to entrain the filaments in said discharge passage and to separate the filaments from each other and to discharge the separated filaments from said outlet.

2. A pneumatic spray gun as claimed in claim 1, wherein the cross-sectional area of the exhaust passageway is greater at the outlet portion than at the point where it is adjacent to the chamber.

3. A pneumatic spray gun as claimed in claim 2, wherein the exhaust passageway is shaped to have walls that are continuously diverging towards its outlet end.

4. A pneumatic spray gun as claimed in claim 2, wherein the exhaust passageway is an annular passageway defined between solid members.

5. A pneumatic spray gun as claimed in claim 4, wherein the rate of increase in the cross-sectional area of the exhaust passageway from the chamber to the outlet portion is a constant rate of increase.

6. A pneumatic spray gun as claimed in claim 4, wherein portions of the central solid member extends beyond the end of the surrounding solid member and are shaped so as to divert outwardly the flow of exhausting fluid.

7. A pneumatic spray gun as claimed in claim 6, including extending portions of the outer solid member which cooperate with the extending portions of the central solid member.

8. The pneumatic spray gun as claimed in claim 2 wherein the exhaust passageway is shaped as a cone of circular cross-section diverging towards its outlet end.

9. A pneumatic spray gun as claimed in claim 1, wherein the internal surfaces of the pneumatic spray gun are provided with a satin finish.

10. A pneumatic spray gun as claimed in claim 1, wherein the surfaces of the spray gun which are contacted by the filament bundles are formed from an electrically conducting ceramic material.

11. A pneumatic spray gun as claimed in claim 1 including means to guide between 3 and 6 bundles of filaments containing between 5 and 20 filaments individually and independently into the spray gun inlet portion.

12. In the method of separating a plurality of filaments one from another in a pneumatic spray gun by the action of a stream of fluid acting on the filaments in a passage within the gun so as to advance and tension the filaments by entrainment of the filaments and to emit them from an outlet portion of the gun, the improvement which comprises splitting a large bundle containing a large number of filaments into a plurality of small bundles each containing a few filaments and guiding each of the small bundles individually and independently into said passageway in the gun thereby achieving improved separation of the filaments being emitted from the gun while maintaining the entrainment and tension characteristics of the gun.

13. A method as in claim 12 wherein from 3 to 6 small bundles are guided into the passageway.

14. A method as in claim 12 wherein each small bundle contains from 5 to 20 filaments.

15. A pneumatic spray gun for separating a plurality of filaments for uniform distribution to a collection means, said gun having a filament inlet portion of circular cross section and a filament outlet portion, a chamber within said pneumatic spray gun with which a fluid inlet passageway for a stream of filament-entraining fluid communicates and an exhaust passageway extending from the said chamber to the said outlet portion through which said fluid and filaments issue, and means associated with said filament inlet portion to guide a plurality of small bundles each containing a few filaments individually and independently into the said chamber, said means including a plurality of guides mounted on the circumference of a support means, said support means being an arc of a circle and being situated in the vicinity of said inlet portion, the gun separating the small bundles into individual filaments and discharging them for deposition on the collecting means.

16. A pneumatic spray gun for separating a plurality of filaments for uniform distribution to a collection means, said gun having filament inlet portion of annular cross section and a filament outlet portion, a chamber within said pneumatic spray gun with which a fluid inlet passageway for a stream of filament-entraining fluid communicates and an exhaust passageway extending from the said chamber to the said outlet portion through which said fluid and filaments issue, and means associated with said filament inlet portion to guide a plurality of small bundles each containing a few filaments individually and independently into the said chamber, said means including a plurality of guides mounted on the circumference of a support means, said support means being an arc of a circle and being situated in the vicinity of said inlet portion, the gun separating the small bundles into individual filaments and discharging them for deposition on the collecting means.