|Title of Invention||
IMPACT PAD FOR A TUNDISH
|Abstract||A tundish impact pad formed from refractory material, the impact pad (1) comprising a base (3) having an impact surface (5) which in use faces upwardly to receive molten metal poured onto the impact pad, and a wall (7) extending upwardly from the base around at least part of the periphery of the impact surface, the wall including an overhang (9) projecting over a peripheral region (11) of the impact surface (5), the overhang (9) including a plurality of protrusions (13) which project further over the impact surface (5) than the remainder of the overhang (5).|
|Full Text||FORM 2
THE PATENTS ACT 1970
[39 OF 1970]
THE PATENTS RULES, 2003
[See Section 10; rule 13]
"DEVICE FOR OPENING AND DISTRIBUTING A BUNDLE OF FILAMENTS WHEN PRODUCING A NONWOVEN TEXTILE WEB"
RIETER PERFOJET [Fonnerly ICBT PERFOJET], of ZA Pre Millet, 38330 Montbonnot, France,
The following specification particularly describes the invention and the manner in which it is to be performed:
The invention relates to an improvement made to The installations for making a nonwoven textile web, which is commonly referred to by the generic name of apunbond and which is formed by continuous synthetic filaments.
It concerns more particularly an improvement made to the means for distributing the extruded filaments, after drawing, over a movable transporting belt, over which they are randomly distributed aa as to form a regular web, with a weight and thickness which can be adjusted according to the. applications.
The production of nonwoven webs of. the apunbond type
goes back decades and consist, generally speaking:
in extruding a melted organic polymer through a spinneret perforated with holes, so as to form a bundle or curtain of filaments? then, in orienting; the extruded filaments by drawing by means of one or more fluid-jee, in particular compressed"air, devices, and finally, in receiving: the bundle of filaments in. the form of a web on a movable transporting belt, which is generally subjected to a suction source and the speed of which is adjusted according to the characteristics of tha web, in particular thickness, which it is desired to achieve.
After production, tha web is consolidated, for example by performing a sizing or calendering, preferably hot calendering, so that che elementary filaments are joined to one another.
Other coneolidation treatments may be performed, where appropriate, such as for example a needling treatment (conventional or by fluid jeta), and/or the deposition of a bonding substance on. the surface or in the interior of the web.
Generally speaking, the installations used to produce such products comprise
at least one extruder for a melted organic polymer feeding a spinneret for producing a curtain of filamenta
a cooling zone for bringing about at least surface solidification off the said extruded filaments;
a suction device in the form of a narrow chamber of rectangular cross-section, inside which the curtain -of filaments is subjected to the action of high-speed air streams causing the filaments to be drawn, which assembly will, be referred to hereinbalow by the term "drawing slot" and; a means for deflacting and slowing down the air flow at the outlet of the drawing slot and for distributing the filaments randomly over a receiving belt.
In such installations, the filaments emerge at the outlet of the drawing slot in the form of a bundle of filaments grouped together in the mid-plane of the said slot--
Thesa filaments are ejected at very high speed from the said drawing slor, a speed which can reach 3000 m/min or more depending on -he state.
In order to obtain a nonwoven web as homogeneous as possible on the receiving belt onto which the filaments leaving the drawing lot are projected* it is necessary not
only to separate the said filaments front one another, but also to slow down their speed before their impact with the said belt, in order to limit the uncontrollable rabound phenomena which generate a heterogeneous formation of the sheet.
To ensure such a break-up and distribution of the curtain of extruded filaments, various techniques have been proposed to date.
The oldest technique which emerges in particular from ths patent GB-A-932 482, and from the patent US-A-3 967 118, consists in electrostatically charging the filamentsr which tends to push them away from one another (corona effect).
This technology makes it possible Co improve the formation of the sheet when the- filaments are ejected at relatively low speed front the drawing slot and, consequently, what are called the grouping-together phenomena of ths filaments are dominant over those of the rebounding- of the filaments on the belt.
This is the case in particular when the sheet consists of relatively coarse filaments, that is to say with a count greater than or equal to 2.2 dtex per filament, which filaments are generally produced with speeds at the drawingr-slot outlet of less than 3000 m/min.
In order to reduce tha speed without adding an additional element, it is necessary in this caser ear the end of the drawing slot on which the electrostatic device is fixed to be situated at a relatively large distance front the receiving belt, of the order of 500 mm- or more, in order that the friesianal forces of the filaments in the air alow down their speed, thereby limiting the rebound phenomena and thus improving- the formation of the sheet.
This device is not entirely satisfactory, since no control of the- speed ie possible and the filaments" are also subjected, to alL the outside air currents, thereby disrupting the sheet and creating defects.
Finally, the simple friction of the filaments in the air over such a short distance does not: permit sufficient slowing-down of their speed which would enable the rebound phenomena of the filaments on the belt to be attenuated sufficiently.
Consequently, it has been proposed, as emerges from the patent US 3 285 896, to fit to the end of the drawing slot (see Figures 7 and 8) a deflecting system to ensure a better distribution and opening of the bundles of filaments produced.
However, since this solution, does not give complete satisfaction, it has been proposed, as emerges from the patent US-A-3 325 906, to associate with the divergent nozzle at the drawing-slot outlet an assembly for insufflating air on each, aide of thie divergent nozzle, which creates a negative pressure in the vicinity of the walls, thus attracting the fibres towards the walla, thereby tending to open the bundle of filaments and also alow down the speed thereof.
Such a device, which is satisfactory in theory, nevertheless has a limited effectiveness, since it is mainly the fibres situated on each side of the bundle which, are thua "spread", those grouped together at the centre of the said bundle baing extremely difficult to separata from one another.
Summary of the invention
Now, it has been found, and chia forms the subject of the invention, that it was possible to achieve not only a
perfect opening of the bundle of extruded filaments at the outlets of the drawing slot but also a very homogeneous distribution over the receiving belt, on the one hand by separating the assembly for opening the bundle of filaments from the actual drawing slot, and on the other hand and above all, by designing this opening assembly such that it combines both the advantages of the techniques of electrostatically charging the filaments and the techniques of opening the bundle by slowing down the air speed at the drawing-slot outlet and thus the speed of the.filaments before reception on the receiving belt.
Generally speaking, the invention thus relates to a device for opening and distributing a bundle of filaments during the production of a nonwoven textile web, according to the technique which consists:
in extruding a melted organic polymer through a
spinneret perforated with holes, so as to form a
bundle or curtain, of filaments;
then, in orienting the extruded filaments by
drawing by means of one or more fluid-jet
and finally in receiving the bundle of filaments
in the form of a web on movable transporting
belt below which is arranged a auction source.
The device for opening and distributing the bundle of filaments according to the invention consists of an assembly arranged downstream of the outlet of the drawing assembly and separated therefrom, this assembly comprising, arranged closed to the outlet of the drawing slot, a diffuser comprising an inlet zone in the form of a convergent nozzle extending over the entire width of the installation opposite the outlet of the drawing slot for producing the web, extended by a divergent nozzle, the said assembly being assocotion with a rail electrostatically
charging the filaments before they are received on the receiving belt.
According to one embodiment, the divergent zone of the diffuser comprises two walls and two lateral aloes situated at the top of the said diffuser, on each aide thereof, and permitting either an indraught of air front outside owing to the venturi effect, or, where appropriate, an injection of air under a pressure less than one bar and advantageously between 0.4 and O.a bar, bringing about an air flow against the walls of the said diffuser.
The above diffuser makes it possible to precisely adjust the width of the bundle of fibres and also the impact speed o£ the filaments orr the receiving belt, the electrostatic charging assembly being able to be situated where appropriate, downstream of. the diffuser assembly, but preferably being integrated inside the latter, thereby accentuating the opening of the bundle of filaments.
Advantageously and in practice
the diffuser comprises an inlet zone in the form of a convergent nozzle connected to the two walls of the divergent zone by a rectilinear slot, the rail electrostatically charging the filaments being mounted at the level of the rectilinear slot immediately upstream of the divergent zona; the distance of the diffuser from the receiving belt is adjustable, in order to minimise the influence of the outside air currents on the bundle of fibres;
the pressure of the air which flows in the diffuser against the walls thereof and the adjustment of the voltage applied in the electrostatic rail makes it possible to adapt very precisely the conditions of the formation of the aheac according to the speed of the filaments
at the drawing-slot outlet thereby making particularly such a device suitable for the formation of a sheet consisting of low-denier filaments, and also for production installations working at high speed;
finally, the separation of the actual drawing system and that for distributing the curtain of filaments allows a possibility of adjusting the count of the said filaments without changing the appearance of the sheet and vice versa.
Brief description of the drawings
The invention and the advantages which result from it will be better understood thanks to the concrete exemplary embodiment which is given by way of guidance but without limitation, and which is illustrated by the attached diagramsr in which:
Figure 1 is a general view off an installation for producing a nonwoven web of the spunbond type; Figure 2 is a detail view showing schematically the structure and functioning of an assembly for the opening of the bundle of filaments which is formed and its deposition on the. receiving belt; Figure 3 illustrates a variant embodiment according to the invention in which the electrostatic charging of the filaments is obtained by way of a rail integrated inside Che diffuser it being possible for the flow of air inside the latter against the walls to be produced either by natural indraught of the outside air. or by a. system of injection under low pressure leas than one bar.
Way of carrving out the invention.
Referring to the attached figures the device according to the invention is thus intended for usa on a
line for producing a nonwoven textile web consisting of continuous synthetic filaments.
Generally speaking, as can be seen from Figure 1, such an inscallation is thus composed- essentially of at least one extruder, designated by the general reference (l), which feeds synthetic polymer, such as polyamide, polyethylene, polyester, etc to a spinneret (2) for the formation ofa curtain of filaments (3)
Prom a practical point of view, by way-of guidance, the spinneret consists of a plate each containing a multitude of holes, for example 5000 per metre of width and. having a diameter depending on the extruded filaments, for example of 0.5 mm. These holes axe distributed over a plurality of parallel rows, for example over eighteen rows and over a width at the spinneret outlet of 140 mm.
At the outlet of this spinneret is arranged the cooling assembly (4) for adjusting the temperature of the filaments depending on the polymers and composed for example of a plurality of successive zones (4a,4b,4c) for subjecting the curtain of filaments (3) to traversing air flows, the speed and temperature of which may be adjusted.
By way of guidance, the length of this cooling zone is of the order off 1200 mm and the temperature and speed of each-of the zones decreases from the first zone (4a) to the third zone (4e).
Downstream of this cooling 2one is arranged the actual drawing assembly (5) , which is in the form of a closed enclosure having a slot (P) into which air is injected under pressure, far example o£ the order of 0.5 bar.
Such a drawing system makes it possible to bring about the auction of the curtain of filament and its entrainment by high-speed air streams for affecting the drawing.
At the outlet of the drawing assembly (5), the bundle of filaments (3) is projected onto the receiving belt (7) by way of aa assembly ($), which assembly forms the subject of the invention and the two embodiments of which can be seen in Figures 2 and 3, and which causes the air flow leaving the slot (S) to deviate and slow down, thus bringing about the opening of the bundle of filaments.
In the first embodiment illustrated in Figure 2, such an assembly comprises, close to the outlet of the drawing slot (P) of the assembly (5), on the one hand, a diffuser, designated by the general reference (10), consisting essentially of a divergent nozzle which extends over the entire width the production of the web and on the other hand, downstream of this opening assembly, a rail (11) for electrostatically charging the filaments at the outlet of the assembly (10), bringing about art opening at the heart of the said bundle of filaments before they are deposited on the receiving belt (7).
In this embodiment, the diffuser assembly (10) ia composed essentially of a chamber (12) having an inner slot (13) in the form of a convergent/divergent nozzle extending over the. entire width of the installation opposite the outlet of the drawing slot (F) of the assembly (5) .
Opening; into this slot (13), close to the lower part of the divergent zone are two laterally arranged symmetrical alota (14) . These symmetrical slots (14) may be either connected to a source of compressed air injected under a pressure leas than l bar and advantageously of the order of 0.4 bar, or be simply open to the outside air.
The divergent zone, is, in this; embodiment extended by-two walls (15) which are likewise divergent.
Arranged immediately downstream, of this diffuser assembly, or where appropriate- integrated inside the latter* is a conventional rail (11) for electrostatically charging the filaments, thus making it possible to intensify the opening of the bundle. Such a rail (l) is a conventional rail for example of the type described in US-A-3 967 118
Figura 3 illustrates a second embodiment of an assembly for opening and distributing- a bundle of filaments in the form of a web produced in. accordance with the invention.
In this variant, using the same references as those employed to describe the example illustrated by Figure 2, the device for opening and distributing; the bundle of filaments (6) is, aa before, separated from the drawing assembly (S).
This embodiment also comprises an inlet zone (13) in Che form of a convergent nozzle extending opposite the outlet of the drawing slot (F). This inlet zone (13) in the form of a convergent nozzle is connected to the two walls (15) of the divergent zone by a rectilinear slot (20).
The rail (11) for electrostatically charging the filaments is, in. this embodiment integrated inside the diffuserv at the end of the rectilinear slot (20) immediately upstream of the divergent zone (15).
An indraught of air coming from outside owing to the venturi effect is produced through the two adjacent lateral slots formed by the lower face of the drawing assembly (5)
and the upper face of the opening and distributing- assembly (6).
An air flow thus arises along the walls (20,3.5) over the opening and distributing assembly.
Where appropriate, as in the embodiment described in conjunction with Figure 2, an injection of air under low pressure, less than 1 bar, could be produced at the two lateral slots formed between the drawing assembly (5) and the opening and distributing assembly (6).
It was found that with such. a. device not only was a perfect opening of the bundle of filaments obtained, but that, furthermore, the reception on the belt (7) was very regular and led to a very homogeneous nonwoven web being obtained.
Of course the invention is not limited to such an embodiment, but covers any variant* thereof realised in the same spirit.
WE CLAIM :
1. Device for opening and. distributing a bundle of filaments during" the production of a. nonwoven textile web, according to the technique which consists:
in extruding a melted organic polymer through a spinneret perforated with holes, so as to form a bundle or curtain of filaments;
then, in orienting the extruded filaments by drawing by means of on or more fluid-jet devices (5);
and finally, in receiving the bundle of filaments in the form of a web on movable receiving belt below which is arranged a suction source,
characterized in that it consists of art assembly (6) arranged downstream of the outlet of the drawing assembly (5) and separated therefrom, the said assembly comprising, arranged close to the outlet of the drawing slot (F) a diffuser (10) comprising an inlet zone (13) in the form of a convergent nozzle extending over the entire width of the installation opposite the outlet of the drawing slot (F) for producing the web, extended by a divergent nozzle (15), the said assembly being associated with a rail (11) electrostatically charging the filaments before they are received on the receiving belt (7).
2. Device as claimed in claim 1, wherein the diffuser (10) comprises an inlet zone (13) in the form of a convergent nozzle connected to the two walls (15) of the divergent zone by a rectilinear slot (20), the rail (11) electrostatically charging the filaments being mounted at the level of the rectilinear slot immediately upstream of the divergent zone (15).
3. Device as claimed in claim 1, wherein an injection of air under the pressure less than 1 bar is produced between the faces opposite the outlet of the drawing slot (5) and the inlet of the diffuser assembly.
Dated this 19th day of October, 2001.
|Indian Patent Application Number||IN/PCT/2001/01389/MUM|
|PG Journal Number||04/2008|
|Date of Filing||09-Nov-2001|
|Name of Patentee||FOSECO INTERNATIONAL LIMITED|
|Applicant Address||BURMAH CASTROL HOUSE, PIPERS WAY, SWINDON, WILTSHIRE SN3 1RE, ENGLAND|
|PCT International Classification Number||B22D 41/00|
|PCT International Application Number||PCT/GB00/02070|
|PCT International Filing date||2000-06-07|