Abstract:
The invention relates to a device for spraying water, provided with a seal support ( 21 ) arranged between the body ( 1 ) and the perforated sheet ( 23 ) and in contact with the above. The seal support is mounted such as to be able to be removed from the body ( 1 ) with the joint ( 20 ). The above finds application in the production of non-woven materials.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a water jet spray device that is particularly useful in the hydroentanglement of fibres in nonwovens. Hydroentanglement involves sending a curtain of jets of water under pressure onto a web of fibres to entangle them and form them into a coherent web, without requiring the use of binders or resins. 
     2. Description of the Related Art 
     EP-0 725 175 discloses a water jet spray device comprising a pressure-resistant body defining an internal chamber. The oblong cylindrical internal chamber has one entrance, and preferably two entrances, one in each end face, and communicates, through an interposed perforated plate, with an outlet leading out of the body. The perforated plate is in contact with a seal. To facilitate replacement of the annular seal applied to the perforated plate, without the chore of removing screws and disassembling it, there is provided, all the way along the length and across the width of a groove containing the seal, a repair groove whose height is approximately the same as the thickness of the seal and a longitudinal metal sheet can be inserted into this repair groove, this longitudinal metal sheet having, on its lower face, a device for gripping the seal. To replace the seal which is removed as best one can, the metal sheet with a new seal is put into the repair groove and, with the aid of a tool, the new seal is rolled down where it must slide into the groove where it is to be housed. DE-A-199 21 694 improves on the device disclosed in EP 0 725 175 in order to simplify the fitting process. For this purpose it uses a seal holder of circular cross section that also carries the perforated plate. In the factory, the seals are placed in the seal holder and the seal holder is put into position in the body once for all, before installing the body. If the seal wears out, though it is emphasized that this rarely happens, it is easily replaced in the manner disclosed in EP-0 725 175. Experience has shown that performing these seal replacing operations is an operation that demands too much skill to be carried out in a short space of time, especially when it comes to very long seals measuring several meters. 
     U.S. Pat. No. 5,042,722 discloses a water jet spray device having a pull-out cassette in a body and comprising a perforated plate, a seal holder and a spacer. Just as in the previous documents, the cassette is large and therefore requires a large hole to be made in the body. This is undesirable from the point of view of pressure resistance, and replacing the perforated plate and/or the seal holder is a complicated task, since the spacer has to be unscrewed to allow access to the perforated plate. 
     SUMMARY OF THE INVENTION 
     The invention mitigates these problems in the form of a device in which seal replacement can be done reliably and in a short space of time, even by an inexperienced operator. Furthermore, the number of parts is reduced and the integrity of the body is less undermined. 
     The subject to the invention is a water jet spray device made up of basis components: a body, at least one clamp and a perforated plate, the clamp being fixed to the body in such a way as to keep the perforated plate, supported by a seal holder, held in position thereon and the device comprising means designed to spray water from the inside of the body out through the perforated plate and means for maintaining the shape of the seal holder, which device is characterized in that the maintaining means are formed by one of the basis components themselves. 
     To replace the seal, the seal holder containing the old seal is withdrawn and placed on the workbench, and the damaged old seal is removed perfectly easily without having to first remove a spacer. Then a new seal is put in its place, again perfectly easily because of the good access to the top of the seal holder which is placed flat on the workbench and there is not the difficulty of having to work in a confined space inside the body. These operations done, the seal holder with the seal in place is put back into the device with a simple sliding movement. 
     The perforated plate is preferably mounted in such a way that it can be withdrawn from the body independently of the seal holder. If only the perforated plate needs replacing, the seal holder can thus be left in place. 
     For better sealing, a first annular seal carried by the seal holder is in contact with the perforated plate, while a second annular seal carried by the seal holder is in contact with the body. The two seals extend one on each of the opposite faces of the seal holder. They are preferably rectangular seals with rounded vertices. 
     The seal holder is preferably in the form of a 2 to 10 mm-thick plate. Because this is not very thick, the jets do not lose much of their speed when they pass through the slit formed in the seal holder before passing out through the outlet. 
     In one very particularly preferred embodiment, the guide parts are so shaped as to allow the seal holder to slide in a direction parallel to the axis but with the possibility of movement in the two directions perpendicular to the perforated plate, the seal holder being in particular a U shaped bar, the web of the U carrying the seals, and the two arms of the U pointing towards the inner chamber fitting into respective grooves in the body designed to guide the seal holder and deeper than the height of the arms. The presence of these arms and grooves does not therefore make the clamp harder to screw onto the body during manufacture. The body has spacer parts for keeping the guide parts at the correct distance. This ensures that the seal holder maintains its geometry and its position, even when the jet spray device is at an angle to the vertical, which is frequently the case when it is fitted around a cylinder. The spacer parts may coincide with the indexing parts. 
     In another embodiment, the guide parts are ribs which are provided on only one of the end parts of the seal holder and which engage with grooves in the body acting as the indexing parts, and are formed along only a length corresponding approximately to that of the grooves. 
     The invention also relates to a method of replacing a seal of a device, characterized in that in succession, without unscrewing the clamp from the block of the device, the assembly consisting of the seal holder and the perforated plate is withdrawn from the device, the perforated plate is separated from the seal holder the worn seal is removed from the seal holder, a new seal is placed in the seal holder, the perforated plate is put back on the seal holder in such a way as to produce a new assembly, and the new assembly is put back exactly in position in the device by engaging the guide parts and indexing parts together. 
     In one embodiment, the guide parts are ribs which are formed on only one of the end parts of the seal holder and which fit into grooves in the body which are the indexing parts and are formed along a length approximately equal to that of the grooves and the new assembly is put back by inserting it via the said end part. 
     The invention also relates to an installation for entangling fibres in a nonwoven, comprising a cylinder, around the lateral face of which the fibres to be entangled are passed and a device according to the invention in which the jets are aimed at the lateral face of the cylinder. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the attached drawing, which is given purely by way of example: 
         FIG. 1  is a cross section through a preferred device according to the invention on a plane perpendicular to the axis of the inner chamber, 
         FIG. 2  is a cross section on the line marked II-II in  FIG. 1 , 
         FIG. 3  is a partial perspective view of the seal holder, 
         FIG. 4  is a cross section similar to  FIG. 1  through a variant. 
         FIG. 5  is a perspective view of the seal holder of the variant of  FIG. 4 , 
         FIGS. 6 to 8  are cross sections through three variants. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIGS. 1 to 3 , the jet spray device according to the invention comprises a fixed body  1  of parallelepipedal shape having two opposite large faces  2 ,  3 , two opposite small faces  4 ,  5 , and two opposite, end faces  6 . The body  1  is made of steel. An oblong chamber  7  of axis  8  is made in the body  1  from one end face  6  to the other. Both end faces  6  have connectors (not shown) forming an inlet communicating with a pressurized water source, which is not illustrated. The chamber  7  contains a cylindrical filter  9 , of the same shape as the chamber  7  but of smaller diameter. 
     The face  5  of the body consists of two clamps  10  screwed to the rest of the body  1  by screws  11 . 
     A channel  12  in the form of a slit extending along one generatrix or two adjacent generatrices of the chamber  7  leads from the chamber  7  to an opening  13  in the form of a slit formed in the face  5  and communicating with the exterior. 
     The clamps  10  define a cavity housing a seal holder  14  made of metal, plastic or a composite material, having a 5 mm thick web  15  and two side arms  16 ,  17  forming guide parts extending parallel to the axis  8 . The seal holder includes a longitudinal slit  18  aligned with the channel  12  and with the outlet  13 . On either side of the slit  18 , the seal holder  14  comprises a groove  19  which faces in towards the chamber  7  and which houses an annular seal  20 . On the opposite face, the seal holder  14  has an annular groove  21  like the groove  19  and housing a second annular seal  22 . The seal  20  is closer to the slit  18  than the seal  22 . Placed against the face containing the seal  20  is a perforated plate  23  with microperforations of diameter between 50 and 500 microns, and preferably between 100 and 200 microns, which is used to form jets or needles of water. These perforations are arranged in one or two rows parallel to the axis  8  in line with the slit  18 . 
     The arms  16 ,  17  fit into grooves  24  formed in the body  1  and this seal holder  24  can be removed from the device, after a plug  25  has been withdrawn. Likewise for the perforated plate  23 . The solid part of the body  1  between the grooves  24  acts as a spacer and thus maintains the shape of the seal holder  14  in spite of its thinness, preventing it from closing up when subject to the pressure forces. 
     To facilitate assembling the device, the free edges of the edge parts  16 ,  17  of the seal holder are at a distance from the bottom of the grooves  24 . When the clamps  10  are screwed onto the main part of the block  1 , the clearance between the edges  25  of the edge parts  16 ,  17  of the seal holder  14  and the block  1  ensures that there will be no blockage as the screws are driven in. 
     In the variant shown in  FIGS. 4 and 5 , the body  101  has two longitudinal bores  102  and  103 . The two bores  102  and  103  are separated from each other by an intermediate wall  104  in which through-holes  105  are made allowing communication between the bores  102  and  103 . In line with these through-holes, on the other side of the bore  103 , is a narrower slit  106  for the liquid outlet. The bore  102  is supplied with pressurized water by a source which is not presented. A perforated plate  107  is mounted in a cylindrical seal holder  108  whose outside diameter fits the diameter of the chamber  103  and which can slide along the chamber  103 . A filter  112  is mounted on top of the seal holder  108 . To install the perforated plate  107  with the aid of a part  115  which presses it against the seal holder  108 , the cylindrical seal holder  108  has a first longitudinal slit  109  that extends in the axial direction of the seal holder  108  and is about the same width as the perforated plate  107 . An annular seal  110  is housed in the bottom of the first longitudinal slit  109 . On one of the end faces of the cylindrical seal holder  108  there is, at least in the width of the seal-holding plate  107 , a slit  104 , more clearly visible in  FIG. 5 , so that the seal-holding plate  107  can be replaced without removing the seal holder  108 . However, another way is to remove the seal holder  108  from the water jet spray device by sliding it out. 
     Continuing on from the longitudinal slit  109 , on the other side of the seal holder  108 , is a second, narrower longitudinal slit  111 , via which the jets of liquid produced by the perforated plate  107  arrive in the slit  106  of the body  101 . 
     As shown in  FIG. 5 , the seal holder  108  comprises two ribs  116  which extend along only part of its length from the end containing the slit  104 . These ribs  116  act as guide parts and are complementary in shape with grooves formed in the body  101  acting as indexing parts. 
     To fit the seal holder  108  into the body  101 , it is engaged via the end  113  into the body  101  until the ribs  116  are in their grooves  120 . The seal holder  108  is thus fixed in position and cannot rotate. To change the seal, the seal holder  108  is withdrawn by sliding it out parallel to its axis in the same way as the perforated plate  107  slides, the worn seal is removed, a new seal is put in place—these two operations being performed perfectly easily on the workbench—and the seal holder  108  is reinserted into the body  101 . 
     Under pressure, the seal holder would tend to close in but is prevented from doing so by the body, with the result that the perforated plate experiences no mechanical stress from the seal holder. The perforated plate is not squeezed by the seal holder. The spacing feature allows the seal holder to be kept central when the injection device is under pressure. 
     In  FIG. 6  the maintaining means are represented by the fact that the seal holder  621  comprises in cross section two balls  622  which are guided in the body  605 . The shape of the seal holder  621  is thus maintained due to the fact that the balls  622  are engaged in complementary retaining cavities in the clamp  605 . 
     In  FIG. 7 , the clamp  705  contains two grooves  722  parallel to the axis of the device, with two ribs  723  projecting into them from the seal holder  721 . 
     Finally, in  FIG. 8 , it is the perforated plate  823  itself that acts as a spacer for the seal holder  821 . In this case, to replace the seal holder, the perforated plate  823  and the seal holder  821  are both removed together from the device. On the workbench, the perforated plate  823  is then removed, if necessary by prizing open the two edge parts of the seal holder  821 . This is the simplest embodiment, but in spite of that it not preferred because in the first place it is more complicated to replace the seal holder, and in the second place it imposes harmful stresses on the seal-holding plate.