AU680580B2 - Screen material made of wire, method and device for the production thereof, and a sleeve made of such screen material - Google Patents

Description

WO 017306 WO 95)17306PTINUM4"131S 0 Screen mterial made of wire, method and device for the production thereof# and a alcoeve made of ouch screen material.

The present invention relates in the first place to a screen material made of wire, inltenlded in particular for screen printing.

Such a material in known and is generally made by 6 weaving, braiding, knitting or the like of a wire-type material.

The final screen printing material is obtained by pattern-wise masking of the holes, for example mocking the holes with a light-sensitive lacquer or the like, and then pattern-wine exposure of the lacquer, following which the exposed or non-exposed parts (depending on the type of lacquer) are removed. The holes can also be masked with a lacquer and, after it has cured, the lacquer in burnt away pattern-wise by means of a los~er or the like.

is During screen printing a printing medium, such as ink, is forced by means of a squeegee through the holes of such a screen onto a substrate to be printed.

The printing quality with these woven, knitted or braided screen materials is unsatisfactory for many applications, since the surface in relatively uneven and channels can form between the screen wires and the substrate to be printed, which gives rise to loss of contour sharpness, due to undesirable running of the printing medium over the substrate.

Screen printing screens which do not have the abovementioned disadvantages are thin-walled flat metal plates or seamless thin-walled metal cylinders provided with holes. This material can be made by providing a thin metal plate or a thin-walled metal cylinder with a lightsensitive lacquer coating, which is exposed according to the desired hole pattern and developed, following which an etching operation is carried out in order to obtain the holes. This screen material can also be grown by electroplating on a conducting substrate which has been provided Guitably pattexawa witi. an inoulating lacuer. For tiao latter cperatzen a rolle to which lacqer so appled locally, or a rollor vv~ided in a pateo-rwnoo anneor with amall holeo in which the lacquer io apphed, o uoned.

However, the abve techn'queoo are fairly complex, eonvironmentally unfriendly and expoesve, The object of preferred ebodim ent of the present invention in to provide a coreen material made of wire which hao the advantageouo printing propertien f the lfantmentioned metal ocreeno, but which can be made simply and cheaply and from a multiplicity of materialo.

According to a first asoect of the present invention, there io provided a screen material made of wire, suitable for ocreen printing wherein the holeo are bounded in ouch a way by wire 15 pieces, which are joined to each other locally, that an at least virtually flat non-woven screen surface io obtained.

The screen material according to preferred embodiments of the invention can be produced cheaply from a very wide variety of types of wire, and both the dimenoons and the shape of the holeo can be net, while an at least virtually flat screen Ourface is always obtained. As discussed earlier, this is desirable in particular in the case of screen printing. The method for producing the screen material in environmentally friendly, since no etching or electroforming is required.

In WO-91/17006, a mesh material for security windows and doors has been proposed, made of preformed steel bars, which are joined to form a planar assembly. This material is not meant to be used as, nor is it suited for, screen materials for screen printing as it comprises relatively large mesh holes. It in designed to be an obstacle against infringing forces.

V n4 -a Tie G&2'c(Pr7~Lrtl to the :et o ncoA toi ncenpit P 3oL1~~ that it U-11 t o tuu~e can alo eA ui ~ably cr, for f 1 wiho Ut the Geripen mara I2cfl3 oaFected i iniA WshP e jj chiclttorccvac in tho.e ane of woven, braidedI or wmilav 'Ef* t W '3it 0 i a I The OCren Material acci7Cii to the invention ,o alo suitable for tine an hea-recitant filtern, 1or emrnple for flue gao filtration, an wire skeletons for catalyst cem itiono, for uine anein equipment and for all other purposne for which acreen wmaterxal can be uced. The screen materi.al itself can aloe be applied to a oupport, followIng which the holes are filled wtI lacquer and a screen material n be trcwn by meana of technique,,) on the careen *9g* material taordig to the invention, in ozer to prduc-e the *00 9 0 Of 09 *Get*: 0 .9 9* .9.

9.

IVO ON17306 WO 'WI 7304M TNL41003 abovementioned thin-walled metal producto provided with holes.

The wire used in the screen material according to the invention is not rarticularly restricted# and can be of 9 round, oval, square, rectangular, triangular or other desired cro55-section, and it could even be approximdaly strip-like.

In the present description, joining wires to each other "locally" should be understood as meaning both pointwise and over some distance, since as will be explained later a very wide variety of screen types can be obtained through selection of a pattern of joining points# i.e.

points set up at a distance from each other, or groups of points set up adjacent to each other, or continuous joining 1S over a fairly great distance.

Adjacent wire sections, each comprising two or more wire pieces, preferably extend uncrossed in substantially the same direction.

Wire pieces should be understood as those wire parts extending between two joining points. wire sections comprise a plurality of wire pieces.

making adjacent wire sections run uncrossed gives rise to a non-woven, at least virtually flat screen surface which has advantageous printing properties.

When a part of the screen material of the abovementioned embodiment according to the invention is examined more closely, wire sections running substantially parallel to each other and joined locally to each other are clearly visible.

The screen holes can be formed in many ways, but the screen material is advantageously made of zigzag wire sections which are joined to each other locally at the tips. such a material can be produced in a simple and reproducible manner, as will be discussed below. Zigzag should be understood as being a sawtooth shape, a sinusoidal shape, a flattened sawtooth shape, or an form of these.

According to another *sP~ot~of the invention the material comprises at least two groups of wire sections, the wire nectiono i.i each group running ouvtant.all.y parallel, and crossing those of another group at one nide, while the wire nectiono are joined in ouch a way to each other at the crossing points through fusion and/or merging S that an at leant virtually flat screen surf ace in obta'ined.

in the cane of thin embodiment a non-woven material in which each group of wires extending in a particular direction lien at one aide of another group of wires in obtained. Thin embodiment again provides a flat screen surface, an in denirable in the cane of screen printing in FR-A-2188501 to produce non-woven ncreen materialn, comrprining several layers of wiren which extend parallelly. These layers of wire are not joined by welding/merging, but by electroplating. Further said material, therefore, consists of more layers and is not flat.

in particular, the wires are linear in thin embodiment, no that the number of holes per linear cm of screen material, and thus the dimensions of the holes, can be regulated in a nimple manner. it will be clear that nquare openingn are obtained with two groups of linear wires, while with three groups of wires triangular and even pentagonal and hexagonal openings can also be obtained.

The wire material used for the screen material according to the present invention is not particularly restricted, but this material and the method of joinin5 of the wire pieces to each other are preferably selected in such a way that the screen material finally obtained is dimensionally stable. This ensures that, for example, a rotary ncreen printing cylinder made from the abovementioned screen material, or a screen plate, does not deform in an undesirable and irregular manner, thus becoming unusable or producing uneven printing results.

The wire of the screen material is advantageously made of a weldable material, and is particularly advantageously made of an electrically conducting material.

Metal wire is preferred, because of its electrical conductivity and durability, since screen material made of Ia t metal wire can acoily te additionally reinforced by electroplating, preferential or otherwioe, or it can be coated with a ca rroionreooitant metal or provided with a coating for another purpooe.

S The ocreen material according to the invention preferably hao at leaot 1S holc per linear cm, and more AMENDED

SHEET

v preferably h.Aas at least so holeo per linear cm. Such screen materials are particularly ouitoble for screen prnting.

The invention also prov:.des a cylinder made of screen material, intended for rotary screen printing, which cylinder is characterized in that the screen material is a screen material according to the invention.

The invention further provides a method for the production of a screen material according to the invention, which method is cha. u'.erized in that wire sections are laid next to one ano.Ier, the wire sections are joined to each other locally, and the screen holes are then formed through deformation of the wire sections. Depending on the way in which the wires are joined, the wires are laid at a short distance from each other or against each other. For example, where soldering techniques are used, in the case of which material is fed in at the position of the joint, a certain distance between the wire parta.will not present a problem, while if laser welding is used, the wire sections preferably rest against each other.

in another embodiment the method for the production of a screen material according to the invention is characterized in that wire sections are preformed and then joined pointwise locally to optionally preformed wire sections.

Both methods provide a screen material made of wire sections which extend uncrossed and essentially in the same direction.

The wire sections are preferably joined to each other on a support, it being particularly preferable for the support used to be a roller. A cylindrical screen material can be obtained in this way, For this purpose, one or more optionally preformed wires are wound around the roller, the number of wires, the cross-sectional dimension of the wires in question and the winding method determining 3S the pitch. Unclosed ring-shaped wire sections can also be laid on the roller and then joined locally, and the screen holes are finally formed.

in particular, the wire sections are joined to each other locally through laser weldSiag, in which case the 74h -i ~AMENDEDSEr WO 9S17306 PCT/NL94/00315 6 laser can operate continuously or intermittently (in a pulsed manner). Apart from welding, all kinds of other joining techniques such as soldering, gluing, merging etc.

may be mentioned.

The invention also provides a method for the production of a screen material according to the invention, which method is characterized in that groups of wire sections are laid in succession on a support at an angle relative to each other, the wires being laid in such a way per group that they run substantially parallel to each other at some distance from each other, following which the wire sections are joined to each other at the crossing points through fusion and/or merging.

Here again, for the production of a seamless cylinder made of screen material it is preferable to wind wires onto a roller, in which case the distance between the wires of each group, and thus the number of holes per linear cm of the screen material finally produced, can be set by setting the pitch of wires to be wound. Fusion and/or merging can be carried out under the influence of temperature increase and/or pressure increase or the like.

In the case of this method it is preferable to subject the screen material to a flattening operation, for example, planing, polishing or gauging, after production.

In order to simplify the abovementioned fusion and/or merging, the wire sections of at least one group are preferably made of plastic. If desired, after completion of the screen material, such plastic wire parts can be provided with a metal layer in a manner known to those skilled in the art.

In order to give additional strength to the screen material according to the invention, or to coat it for another purpose, it is preferable to carry this out by electroplating techniques which are known to those skilled in the art. A technique suitable for this purpose is preferential growth of a metal layer.

The wire material used in the method according to the invention is preferably a hardenable or curable material. Examples are metals which can be hardened by, for iM WO 95/17306 PCT/NL94/00315 7 example, nitriding, or curable plastics. The above is particularly advantageous if the wire has to be wound, for example, prior to joining, so that some flexibility of the wire is desirable. The ability to be hardened or cured makes it possible to give the final product the required strength, dimensional stability, hardness or wear resistance.

The invention also provides a screen material which is obtained by subjecting a screen material according to the invention to electrolysis in an electrolysis bath, which bath contains at least one organic compound with at least one unsaturated bond which does not belong to a I I =C-S=0

I

group, and has the properties of a class-two brightener, the openings in the final screen material essentially corresponding to the openings in the starting screen material. In this connection reference is made to Applicant's EP-B-0 038 104, which discloses a method for preferential growing of a metal on a screen skeleton in an electrolytic bath. With this method the growth cin take place essentially at right angles to the plane of a screen.

The invention further provides a wire material, comprising essentially linear wire sections which are joined to each other locally, which material is intended for use in the production of a screen material according to the invention. In the case of this wire material the screen holes have not yet been formed through deformation of the wire sections, but all wire sections lie essentially next to each other.

The invention finally provides a device for the continuous production of wire material according to the invention, at least comprising a frame with a wire support, wire feed means for feeding wire sections to the wire support, and joining means for joining the wire sections to each other locally. Such a device according to the invention can be designed in different ways.

Preferably the wire support is designed as a rotatable roller, driving means being present to rotate WO 95/17306 PCT/NL9400315 8 said roller, so that wire can be wound onto said roller.

More preferably said roller is supported at one end only and a circumferential stop is present near said supported end.

Advantageously the wire feed means comprise at least one wire reel feeding wire continuously.

Thus, wire can be wound onto the roller in such a manner, that the wire is wound onto the roller between the wire already present on the roller surface, and the -ircumferential stop near the supported end. Thereby, the wire present on the roller is pushed to the unsupported end. Before leaving the roller, the wire sections are joined to each other locally, e.g. by welding or the like.

It will be clear, that the shape of the roller is not critical, and depends on the final application of the material produced. In the case of cilindrical screens for rotary screen printing a roller with a circular cross section is preferred, although other cross section are also feasible for other purposes.

In another aspect of the device according to the invention, th wire support is designed as at least two rotatable support wheels with radially extending projections, and with a common axis, driving means being present to rotate said wheels. In this case advantageously the wire feed means comprise at least one wire reel feeding wire continuously, and whereby reciprocating means are present to guide the wire from one wheel to another, and around the projections.

The wheels are provided with radially extending projections, being spikes, pins or the like, such that the wire can be carried between the wheels in a zig-zag winding around the respective projections on the wheels.

That is, the wire is guided to a wheel, bent around a projection of said wheel, guided to the other wheel and bent around a projection of the respective wheel back to the first wheel again etc. The means which guide the wire from one wheel to another need to reciprocate, whereas the wheels rotate, which movements together position the wire in a zig-zag condition between the wheels. This will be

Q

i V t IC) N y mu,3 ot 1-c corec cia Gere Thi ca01 idageG,101Y c- evecI by a dov~ce for o2 i ocreel; 0oeoi 4 yM~cr~.~il oc of wi.re mt-evia accorcin3 the f~B at leodt aODOf3( 12ro,-f-,O r-00aoenio -PnIn eMn OOM~rI~ing a coni cal Lboro, and moveacble vw~n~~I rreano for puJje t cylindical preiwut through, the t~r ,P the %-44~o whfL Wch the ci letr of the borve (.(,lreaseo, in which the conical tore and the insunting meano arc ieoigned in ouch a way, that at Icaot a portion f the cylindrical prlc can rotate re'lat tote 0re~oe a. eg* Ew odirento ofthe laont~ventie"n will nwLe do ited, Ily way of oxamrple only, with reference to ut, e acc.T ny In g Jiiwinqo i.n whi.ch: 0* Fig. 1 ohowo an embcdimomn. of jereen miaterial according to the i.nvention, S Piq 2 ohowo the acreen mtaterial according to Fig I which hao Ieon aubjeoteci to additional deeta i n the horiLjontal iiits'jtion: F 3 0110wo an other omp 1oimnt ot the neoreen, material acording to the invention; Fig. 4 ohcwg yet another embcorlittent of t~io ocreen material according to the invention with zigzag wireo and linear wireon; iFig. S ohowo yet another emtciment of the ncreen, material ,4 ,A t,4 11, 41 Pi.? ahco a a~aeview of Ac:I (a e(Nt, cOntacting wito Llectiono with -u.ciOao~ectiom which ar'e weldel to each @ther; S Fig. 8 OhGVIO ai Ce~tion of Fig. 7 along the line VIII-VIIZ; Fig. 9 ohowo acr'eein mateial according to the invention, oL~bammec1 byj foirnmicj the heleo of the we-Iled- 0000 00 00 a 0 000 *0 00 0 0#06 WO 95117306 WO 95117306PCt/NL94031S material according to Fig* 7; Fig. 10 shows a diagrammatic vidiw of wire sections with oval cross-section which have been welded to each other locally; Fig. 11 shows a section of Fig. 10 along the line

XI-XI;

Fig. 12 shown screen material according to tha invention which has been obtained by forming the holes of the welded material according to Fig. Fig. 13 shows an embodiment of screen material according to the invention with crossing wires; Fig. 14 shows a section of Fig. 13 along the line

XIV-XXV;

Fig. 15 shows a section of Fig. 13 along the line

XV-XV;

Fig. 16 shows a diagrammatic view of a device for producing a sinusoidal wire; Fig. 17 shows a diagrammatic view of a device for winding wire around a roller and joining adjacent wires locally; Fig. 1S shows a diagrammatic view of the winding of a plurality of wires; Fig. 19a shows a diagrammatic view of a continuously operating device for the production of screen material according to the invention prior to the formation of the holes; Fig. 19b shows a section of the bearing arm with wound and welded cylindrical material; Fig. 19c shows a section of another embodiment of the bearing arm, from Fig. 19a; Fig. 20 shows a diagrammatic view of a device for forming screen holes; and Fig. 21 shows a diagrammatic view of a continu~ously operating device for the production of flat screen material according to the invention prior to the formation of the holes.

Fig. 1 shows a first embodiment of a screen material according to the invention made of iron wire, with wir. pieces and junction points 2. A wire section 3 is W095/17306 WO 95)17306 'CTMN9fO31 11 indicated by hatching. In the case of this embodiment of the screen material, wire sections 3 comprising several wire pieces I are joined to each other by welding at Junction points 2. This embodiment can be produced by placing linear wire sections 3 next to one another, then joining them point-wise in a suitable manner, for example by laser welding, and subjecting the material thus formed to a tensile force essentially at right angles to the wire sections, in order to form the screen holes 4. Wire sections 3 which have been provided beforehand with a zigzag shape can also be welded to each other at the tips/ with the result that the formation of the holes is not necessary.

Fig. 2 shows the material according to Fig. 1 with the formation of the holes being continued through drawing in the horizontal direction in the figure, so that the screen holes 4 have become lozenge-shaped.

Fig. 3 shows an embodiment of the screen material according to the invention in which the wire sections 5 are sinusoidal and are made of wire pieces 6 which bound screen holes 7. The sinusoidal wire sections 5 are joined to each other at the tips at 8.

Fig. 4 shows another embodimuent of the screen material according to the invention, comprising wire sections 9 and 10 with respective wire pieces 11 and 12.

The wire sections 9 are linear, and the wire sections are sinusoidal. It will be clear that this embodiment cannot be produced by placing wire sections next to each other, joining them point-wise, and then forming the screen holes, but that th~a wire sections 10 must be provided with the abovementioned sinusoidal shape prior to being joined to the wire sections 11.

Fig. S shows an embodiment corresponding to Fig. 1 with wire sections 14, which comprise two types of wire pieces 15 and 16 respectively of differing lengths which hound rectangular screen holes 17. This embodiment can be obtained by laying wire sections next to one another and joininig them point-wise in a suitable pattern.

In the light of the above, i.t will be clear that WO 95/17306 WPTNIN34100315 12 the shape and dimensions of the screen holes can be varied in a very wide variety of ways through selection of the wire thickness, the wire material, the position of the junction points, the aperture of the screen holes etc.

The wire shape used in the screen material according to the invention is not very restricted. Figs.

6a-e show a round, square, triangular, "ectangular and oval wire cross-section, all of which are suitable for use in the invention. The triangular and oval cross-sections are preferable, the latter being most preferable. Use of a triangular wire cross-section will produce a screen with an approximately conical hole shape at one side, which during use of the screen easily releases material to be screened and does not become blocked when material is supplied to the flat side, something which is also an advantage during use for screen printing. Use of an oval cross-section produces a screen material which is very similar to the screen materials obtained by electroplating and discussed in the introductory section of the description, which screen materials have particularly good printing properties.

Fig. 7 shows metal wire sections 18 placed next to one another and having weld points 19, a section of which is shown along the line VIII-VIII in Fig. 8. If the interconnected wire sections 18 from Fig. 7 are deformed in the direction indicated by the arrows, the structure indicated diagrammatically in Fig. 9 is obtained, with screen holes 20. It will be clear that the shape of the holes can be suitably varied, as was discussed earlier.

Fig. 10 shows diagrammatically wire sections 21 situated adjacent to each other and interconnected over some length at 22.

Fig. 11 shows a sectional view along the line XI-XI in Fig. 10, in which it can be seen clearly that the wire sections have an oval cross-section.

Fig. 12 shows a preferred embodiment of screen material according to the invention, which is obtained by subjecting the wire material according to Fig. 10 to a tensile force in the direction of the arrows, so that the

II

Wo 9SI17306 WO 911736 FMINL94100315 13 screen holes are formed, These hexagonal screen holes, in particular in combination with an oval, wire cross-section, have very advantageous characteristics for screen printing, since hexagonal holes approach the traditional shape of screen printing stencils, and optimum distribution of screen holes is also obtained over the surface, with additional strength compared with differently shaped holes.

The wire pieces 21' are joined to each other over a short length by weld points. It will be clear that a smaller number of weld points situated further apart or a continuous weld can also be used. A wire piece 21' comprises a wire section going out from the centre of a weld to the centre of an adjoining weld in the same wire section 21. if the hexagonal structure from Fig. 12 is stretched (opened) further, an essentially rectangular hole shape will be obtained, the holes being arranged in a staggered manner (brickwork structure).

For the joining of netal wires, a soldering medium such as tin, lead, lead-tin, brass, silver or the like can also be fed in during the welding, with or without a flux.

Of course, a corresponding technique can also be used for joining wires made of other materials.

Fig. 13 shows another embodiment of screen material according to the invention, showing two groups of wire sections 24 and 25 which are joined to each other at the crossing points through fusion and/or merging, through which screen holes 26 are formed.

Figs. 14 and 15 show the sectional view along the line XIV-XIV and taie line XV-XV. As is clear, a screen material with an esentially flat screen surface is also obtained in the case of this embodiment.

The joining of such crossing wires can be carried out by techniques which are known to those skilled in the art. For example, the wires can merge with each other at the crossing points through welding or the like, or through the application of pressure locally at raised temperature or otherwise, i.e. by setting up the groups of wire seictione, 24 and 25 so that they cross each other and then compressing themt between heated or unheated pressure plates WO 9./17306 0PCTINL94l 31S 14 or the like. A quartz lamp can also be used for forming connections at the crossing points through fusion and/or merging.

The material of the wire used for the screen material according to the invention is not very limited, but in particular for the production of screen printing material it is preferable to use metal wire, since the latter is easily joined locally by welding by means of, for example, a laser, and any curves made in advance in metal wire are dimensionally stable. Examples of suitable metals are: iron, steel, copper, nickel, chromium etc.

In the embodiment shown in Fig. 13 it is preferable for at least one of the groups to be made of plastic, so that the compound is simplified through merging at the position of the crossing points.

The screen material according to the invention can be subjected to additional coating steps after its production, for example in order to strengthen it. For instance, after its surface has been made conducting if desired, in the case of plastic wire, the screen material can be plated with a suitable metal in a known manner.

After production and before possible metallization, the material can also be subjected to a flattening operation, in order to remove uneven points. Extlmples are planing, polishing, gauging etc.

Fig. 16 shows diagrammatically a device with two gear wheels 27 &nd 28, between which a wjre 29 is conveyed by way of guide rollers 30 and 31. A zigzag-shaped wire is obtained by driving the abovementioned gear wheels 27, 28 in the direction indicated. If the wire is a metal wire, it may if desired be subjected to a heat treatment after the deformation operation, in order to give the wire dimensional stability, as a result of the hardening properties of the chosen material.

Fig. 17 shows diagrammatically a device for the production of screen material according to the invention, in which a wire 33 is wound around a roller 32. The roller is rotated in the direction of the arrow, and the wire 33 is drawn off a reel 34. During the winding, the reel 34 can WO 95/17306 P'CT/NL94100315 15 be moved parallel to the roller 32 in the direction of winding. Reference number 35 indicates a moving laser device which locally welds the wire 33 wound around the roller 32. The laser device advantageously comprises positioning means which can comprise a tracer for determining the mutual position of the weld points in relation to the wire sections, on the basis of which the position of the laser can be set by means of suitable laser movement means. After the roller 32 has been provided with wire 33 over its full length and local welding has been carried out, the material thus produced is removed from the roller 32 and subjected to a tensile force in the lengthwise direction, as a result oi. ,wiich the length of the cylinder increases, the diameter decreases, and the screen holes are formed. It will be clear that the reduction in diameter or the increase in length of the screen cylinder and the hole shape and hole size depend on the mutual position and dimensions of the junctions, the wire diameter and the degree of deformation.

If the wire 33 is conveyed through the device of Fig. 16 prior to winding, the final material need not be subjected to a deformation treatment. The mutual positioning of the tips of the already wound wire relative to the wire yet to be wound can be regulated by regulating the wire tension in a suitable manner in the inlet during winding.

Fig. 18 shows the same roller 32, winding here taking place simultaneously with a plurality of wires 33, of the same or different type and shape, as a result of which the surface of the roller can be covered with wire more quickly at the same speed of rotation. During winding involving a plurality of wires in this way, the winding pitch will increase for each individual wire.

The result of this is that when the screen holes are formed in the screen material removed from the roller 32 after welding, by a tensile force in the lengthwise direction, the material will have an inherent twist. This means that during drawing at the ends of the screen cylinder, at least one of the attachment components must be WO 95/17306 PC1NL94100315 16 set up in a rotatable manner.

Fig. 19a shows diagrammatically a device for the continuous production of screen material according to the invention. It contains a reel 34 from which wire 33 is unreeled. Although one reel is shown, it is, of course, possible, as discussed earlier, for a plurality of wires to be wound simultaneously.

Reference number 35 shows a drive mechanism of a mandrel 36, onto which the wire 33 is wound. The wire 33 is guided through a wire feed control unit 37 to the mandrel 36. The wire 33 is guided between a stationary stop 38 and the already wound material, with the result that during the winding the already wound material is forced to the left in the figure. During the abovementioned movement, the wire is welded locally by means of a laser 40 set up in a fixed position. Many types of lasers are suitable for this purpose. Depending on the wire pitch, the winding speed, the type of weld and the weld pattern, the laser can operate continuously or intermittently.

The mandrel 36 used is preferably interchangeable, so that cylinders 39 of different diameters, witn the same number of standard measurements (pattern repeat measurements) and cross-section shapes, can be produced.

Different cross-section shapes should be understood as meaning oval, triangular, square etc. cross-sections.

Reference number 41 indicates a movable trestle, which by means of a bearing arm 42 serves to support the material 39 moving from the roller 36.

The bearing arm 42 of the trestle 41 is preferably in the form of a freely rotating roller, and more preferably the bearing arm is designed in such a way that it has several freely rotatable rollers disposed around the inner periphery of the cylinder produced, so that the cylinder material produced can be supported at several points. Fig. 19b shows a section of the bearing arm 42 from Fig. 19a with cylindrical material 39 which has been produced. Fig. 19c shows a preferred embodiment of the bearing arm 42 in section, which has four supporting rollers 44 for supporting the material 39. The mutual WO 95117306 PCTVNL94/00315 17 position of the rollers advantageously is adjustable.

With the device according to the invention the pitch can be regulated by, for example, placing a ringshaped stop with an oval cross-section at a suitable angle around the mandrel.

Reference number 43 indicates diagrammatically a cutting device which also moves along and serves to cut off a certain length of material after it has formed. After cutting, said cylindrical material can be moved by means of the trestle 41. Thereafter, the arm of another trestle can be placed in the material 39 moving off the roller 36. The supporting arm 42 on the trestle 41 can be suitably adjusted in height, for example by means of a screw spindle or the like.

Lengths of the cylindrical material to be obtained can also be separated from each other in another way. For example, if the laser is interrupted for some time after a certain period of operation of the device, a number of windings of wire are not welded. This number can be selected in such a way that at a suitable moment the cylindrical material already produced can be removed from the mandrel, in which case the wound wire material not welded is drawn as a coil and can be severed. The advantage of this is that only one wire need be cut through, as against the complete severing of a cylinder.

Fig. 20 shows diagrammatically a device for forming screen holes, comprising a forcing device 46 as a screenhole-opening element. With this device 46 the material 39 in which screen holes are not yet formed is forced, as shown diagrammatically at 47, in the direction of the arrow, as a result of which the screen holes are formed in the material 39, as indicated at 48. It will be clear that the drawing section (not shown) by means of which the material 39 is moved through the forcing device or the forcing device itself must be set up in a rotatable manner, since a certain degree of rotation, depending on the method of winding the wire (or wires), will occur during the formation of the screen holes. It may be advantageous during the formation of the holes by means of the forcing WO 95/17306 PCT/NL94/00315 18 device 46 to set up a support element in the product, in order to be able to carry out this operation in a reproducible manner.

If in a production process large numbers of wire cylinders whose holes have not yet been formed are being produced, in successive wire cylinders the screen holes can be formed to a gradually increasing extent, which means that successively cylinders with slightly decreasing diameter are produced and can be pushed into one another.

The transportation and storage thereof is thus greatly simplified. The screen holes in the desired final form can then be made in these cylinders at a desired time. The same applies for wire material wound in the lengthwise direction of a roller, where the diameter increases and the length decreases during formation of the screen holes.

In the case of cylindrical screen material the wire can also be wound in the lengthwise direction of a roller, in which case projections, for example, such as pins, can be present around the periphery at the ends of the roller, so that the wire can be wound to and fro in the lengthwise direction. For winding in the lengthwise direction, the wire can also be wound so as to cross over the end faces of the roller. When such a cylinder made of wire material is welded locally, during formation of the screen holes a diameter increase and a length reduction of the cylinder %ill be the result, contrasting with what has been described above. For this operation it is possible to use, for example, an expandable core, or the wound wire material can be moved in the opposite direction over the forcing device 46 from Fig. 20, in order to form the screen holes.

For the production of the embodiment of the screen material according to Fig. 13 in cylindrical form, a wire can be wound at such a pitch in one direction around a support, as shown, for example, in Fig. 17 or 18, that wire sections disposed at a distance from each other are obtained, following which the same wire may if desired be wound over the first group of wire sections in the opposite direction with corresponding desired pitch. Furthermore, several groups of wires can be wound, following which the WO 5117306 PCTINL94/00315 19 wires are joined to each other at the crossing points by means of suitable techniques known to those skilled in the art, such as welding or pressing at elevated temperature through fusion and/or merging.

By means of the method described above, screen material according to the invention can be produced with a very wide range of numbers of holes per linear cm and of hole shapes, while flat screens can also be produced in a corresponding manner. These can be produced directly or by cutting open cylinders according to the invention in the lengthwise direction.

It is also pointed out that although essentially symmetrical screen materials are described above, the invention is not limited thereto, since any desired deformed wires can be joined to each other in any desired way, so that flat screen material is obtained with any desired shape of holes and any desired dimensions, which can be advantageous for certain applications. The so-called moir6 effects in particular are suppressed in this case.

Screen material can also be produced in flat form by laying wire sections which may consist of one and the same wire next to each other on a flat support, then joining them locally, and subsequently forming the screen holes.

Finally fig. 21 shows a diagrammatic view of a continuously operating device for the production of flat screen material according to the invention, prior to the formation of the holes. Said device comprises at least two rotatable support wheels 50, 51 with a common axis 52 and radially extending projections designed as pins 53. These pins 53 are shown in an enlarged view A in fig. 21.

The wheels support endless belts 55 and 56 provided with openings 57 into which the pins 53 fit. It will be clear that the belts are endless belts and guided over an additional pair of driving wheels (not shown), also comprising pins or the like.

A guide bar 58 is present forming the reciprocating means to guide a wire 60 from wheel 51 to wheel 50 and back, around the respective pins 53. Thus, a zig-zag movement of the wire is provided. The driving means of said WO 95/17306 PCTNL94iO0315 20 guide pin are not shown for clarity reasons.

The wire 60 is unreeled from a reel 61 provided with a slip-coupling 62 to provide the necessary wire tension.

65 schematically shows a laser welding device which is moveable along a slit 66 in guide means 67. In the laser welding device a laser beam 68 is passed through a focussing optic 69 and impacts on the zig-zag wire material at a focal point 70. Very close to said focal point 70 a wedge 71 is present, which is shown in the enlarged crosssection B. Said wedge 71 can be moved in the direction of the arrow 72 to move the wire section 73 against the wire material 74 ?.lr'-dy locally welded in the direction of arrow 78. Said wedge 71 is provided with drive means (not shown) to follow the movement of the focal point of the laser welding device, assuring that at the focal -oint the wires are positioned against each other for accurate welding.

The wire material 75 being locally welded is supported by the driving belts 55 and 56 and further by an additional conveyor belt 76 driven by a drive roller 77 and another corresponding drive roller, nit shown.

For the purpose of clarity only the important details are shown in fig. 21 and of course many modifications can be made.

The drive belts 55 and 56 do not only drive the wheels 50 and 51, and support the wire material 75, but also assure that the welded wire material 75 is removed from the pins 53.

Preferably means are present between the guide bar and the reel 61 to compensate for differences in length of the wire 60 fed to the pins of the wheels, due to the reciprocating movement of the guide bar 58. This can be achieved by moving the reel 61 together with the guide bar 58, or by spring loaded wheels or the like.

After manufacture of the wire material 75 the screen holes can be opened by suitable deformation of the material as discussed with reference to earlier figures.

Claims (15)

1. A screen material made of wire, suitable for screen printing wherein the holes are boundel in ouch a way by wire pieces, which are joined to each other locally, that an at least virtually flat non-woven screen surface is obtained.

2. A screen material according to claim 1, wherei.n adjacent wire sections each having two or more wire pieces extend uncrossed in substantially the same direction.

3. A screen material according to claim 1 or 2, wherein the screen material is made of zigzag wire sections which are joined locally to each other at the tips. ise

4. A screen erial according to claim 1, wherein the material comprises at least two groups of wire sections, the wire sections in each group running substantially parallel, and -ossing those of another group at one side, and in that the wire sections are joined in such a way to each other at the crossing points through fusion and/or merging that an at least virtually flat screen nurface is obtained. @00S. A screen material according to claim 4, wherein the wires are substantially linear.

6. A screen material according to any preceding claim, wherein the wire material and the method of joining are selected in such a way that the screen material is dimensionally stable. v on" Q 01' 141 t I f 'V A oreen material a"rL oay p ceLn ln wh~erein f i w I e of th0c.,@@n ?-,or1'a 17' mL f"A e a wda1Ao I nv ter a I. A A Goreen rnleriC-1 aCCr-dir<I to Clair,7 wi eroe th wire of Ilte ncieen .40al± a."e o all oecot rially czcutn Doreen M-terial according to claim 8, wherein the wire of tho~ oe-reen material zo trad1e of mottal. A cereon m-iterial accord~ing to one or more of the preceding laimoj, wherein the mterial haa at~ leaot 15j hol es per linea I~11. A oe-een mterial according to Claim 10, wherein the atez'ial hao at leaat 50 holeto per linear on.. *12. A Cylinder made Of Dereon material intended for rotary ocrgen printing, wherein the acreen material in a Doreen inaterial according to any preceding claim. A mnetholt Pnr the production of a ore-en material acce dinri **to any onki of olaitmo 1-3f 6-11, wherein Wire 0eotiOnO are laid nexKt to one an,-ther, the wire Geotiono are Joined to each other locally, and the scoen holen are then f ormed through deformation of the wire aectiona.

14. A method for the production of a ncreen material according to any one of claimo 1-41 6-11, Wherein Wire GectionO are preformed and theni joined point-wice to optionally preformed *21 wire oectlino. A t'h()i aeclcdang t elaim 13 or 14, wherein the wire cectiono are joined to each other on a oujp -ort

26. A neft eL ac@odJng to Olaim 15, wherein a roller is used as 17 A method according to claim 16, wherein one or more optionally preformed wires are wound around the roller. 18. A eth©d according to any one of claims l3°17, wherein the wire ooset©o are joined to each other locally through laser 0 welding. ise 06•* 19. A method for the production of a ocreen material according to claim 4 or 5, wherein groups of wire sections are laid i" a succession on a oupport at an angle relative to each other, the wires being laid in ouch a way per group that they run subostantially parallel to each other at some distance from each t. other, following which the wire sections are joined to each other at crossing pointso through fusion and/or merging. a. S. 20. A method according to claim 19, wherein the wire sections o£ at leaost one group are made of plastic. S. S a. 21. A methed aecording to any one of claims 13-20, wherein the a screen material is subjected to a flattening operation after production. 11 am VPO(LW.Z1113 "li IT"1f -24. 22. A method according to any one of claims 13-21, wherein the screen material is plated. 23. A screen material which is obtained by subjecting a screen material according to any one of claims 1-11 to electrolysis in an electrolysis bath, which bath contains at least one organic compound with at least one unsaturated bond which does not belong to a group, and has the properties of a class-two brightener, the openings in the final screen material essentially corresponding the openings in the starting material. is 00060* 24. A wire material comprising essentially linear wire sections which are joined to each other locally, for use in the production of a screen material according to any one of claima 1-3, 6-li. A device for the continuous production of wire material according to claim 24, at least comprising a frame with a wire support, wire feed means for feeding wire sections to the wire support, and joining means for joining the wire sections to each other locally. 26. A device according to claim 25, wherein the wire support is designed as a rotatable roller, driving means being present to rotate said roller, so that wire can be wound onto said roller. P Mu1 R. UVIN14 "MI 1

27. A device according to claim 263, wherein said roller is supported at one end only and that a circumferential stop is present near said supported end.

28. A device according to any one of ClaimO 25-27, wherein the wire feed means comprise at least one wire reel feeding wire contin.fuously.

29. A device according to claim 25, wherein the wire support is designed as at least two rotatable support wheels with radiall.y extending projections and with a common axis, and that driving means are present to rotate said wheels.

30. A device according to claim 29, wherein the wire feed means comprise at least one wire reel feeding wire continuously, and that reciprocating means are present to guide the wire from one wheel to another and around the projections.

31. A device according to any one of claims 2S-30, wherein the joining means are designed as a moveable laser welding device.

32. A device for forming screen holes in a cylindrical product made of wire material according to any one of claims 1-12, at Sleast comprising a frame with a a creen- hole -opening -elemenlt 215 comprising a conical bore, and moveable mounting means for pulling the cylindrical product through the conical bore in the **toodirection in which the diameter of the bore decreases, in which the conical bore and the mountig means are designed in such a way, that at least a portion of the cylindrical product can rotate relative to the screen-hole-opening-element. P Iffl'J :wVI:I.O 91 H$ WIl

33. A screen or a wire material substantially as hereinbefore described with reference to the accompanying drawings.

34. A method for the production of a screen material substantially as hereinbefore described with reference to the accompanying drawings. A device for t-it continuous production of a wire material substantially as hereinbefore described with reference to the accompanying drawings. DATED this 6th day of May 1997 Stork Screens B.V. DAVIES COLLISON CAVE Patent Attorneys for the Applicants ,bb I