EP0889784A1

EP0889784A1 - Doctor blade for a screen printing machine

Info

Publication number: EP0889784A1
Application number: EP97916420A
Authority: EP
Inventors: Dominique Giard
Original assignee: Fimor SA
Current assignee: Fimor SA
Priority date: 1996-03-29
Filing date: 1997-04-01
Publication date: 1999-01-13
Anticipated expiration: 2017-04-01
Also published as: DE69708070T2; FR2746704A1; AU2507697A; JP2000507514A; ATE208267T1; US6109174A; FR2746704B1; EP0889784B1; WO1997036747A1; DE69708070D1

Abstract

PCT No. PCT/EP97/01628 Sec. 371 Date Apr. 15, 1999 Sec. 102(e) Date Apr. 15, 1999 PCT Filed Apr. 1, 1997 PCT Pub. No. WO97/36747 PCT Pub. Date Oct. 9, 1997A doctor blade for use in screen printing includes a head, a base in the form of a lip and at least one elastically deformable member connecting the head and the base. The elastically deformable member is structurally discontinuous on at least one location in the longitudinal direction of the doctor blade extending along a plurality of spaced spring layers. The elastically deformable member is realized from a plurality of elastically deformable wires which are arranged in spirals or in undulations or from a cut-out sheet so as to form a double comb the stiffness of which is controlled by the transverse dimension of the windings, undulations, or cut-outs, or the characteristics of the constituent material, and the spacing between the teeth of the comb.

Description

Squeegee for a screen printing machine

The invention relates to a doctor blade intended to be part of a screen printing machine, or to be handled by an operator, for printing or transferring fluids or pastes, or other applications.

There are already known scraper heads of the type comprising a scraper holder and a deformable scraper blade, extending longitudinally and rigidly associated with one another. Such known scraper heads are the subject of numerous variant embodiments. They are fixed to support means of the machine by means of screws, stirrups or other clamping or fixing members.

The downward pressure must both:

- cancel what is known in the art as "off contact", that is to say the distance of 2 to 5 millimeters existing between the screen and the support to be printed, this function essentially falling to the ends of the scraper blade ;

- compensate for the differences in thickness of the stencil, support for the coated image on or under the sieve;

- compensate for the unevenness of the print media, the thickness of which can vary by plus or minus 6% for cardboard, for example, depending on the seams and hems for textile prints, etc .; - expel an adequate and constant part of the ink through the sieve to carry out the printing by releasing an energy depending on the thixotropy of the ink;

- push the wave of ink which accumulates in front of the scraper blade as it advances.

Before each scraping, a metal counter scraper or according to the terminology of the "flood bar" profession grazes the sieve to re-coat it with ink that was pushed to an edge of the screen by the previous print.

The scraper blade is traditionally made of rubber and typically has the shape of a rectangular parallelepiped, it is continuous, both longitudinally and transversely. It can also present, in its part in contact with the sieve, different profiles deemed more favorable for certain works.

The scraper blade must simultaneously have characteristics which seem contradictory.

It must be sufficiently rigid (nervous) to: - cancel the "off contact";

- expel an adequate and constant part of the ink through the sieve to carry out the printing,

The scraper blade must also be flexible enough to:

- compensate for the unevenness of the image support coated on, or under, the sieve; - compensate for the unevenness of the print media;

- compensate for surface unevenness of the printing tables.

According to alternative embodiments, the doctor blades are incorporated into machines. We can thus refer in particular to documents US-A-4,854,230, EP-A-140,165, EP-A-460,267. Whether the doctor blade is intended for manual operation as it results from documents GB-A-2.175.850, US-A-4.102.266, FR-A-2.302.199, US-A-4.989.511 or that either incorporated into a machine, there is the problem of having a scraper blade having both the rigidity and the flexibility required, as explained above. Document US-A-5,345,862 provides in one embodiment that the scraper blade has two outer layers and a more rigid inner layer.

We can also refer to documents EP-A-29894 and DE-B-38 12 826.

Document EP-A-167,906 provides a support bar made of a hard elastic material inserted in the doctor blade holder, to which a profiled blade made of a flexible material is connected.

Whatever the variant embodiments envisaged for the scraper blade, a certain number of problems arise which, to date, have not found a satisfactory solution.

The scraping support inevitably has uneven surfaces. During the scraping, the passage of the scraper blade causes vibrations due to these surface inequalities which both affect the quality of the printing and contribute to the fatigue of the machine including the scrapes.

The surface unevenness, in addition to the vibrations, affects the printing since the operating conditions, in particular the application pressure of the scraper blade, its angle of inclination, and even its contact with the support to be printed are variable. from one place to another of the surface to be printed.

When the scraping speed is high, the accumulation of ink in front of the scraping blade can cause an "inkplaning" phenomenon (neologism analogous to aquaplaning and signifying lifting of the scraping blade by an ink film) which also affects the quality of the print. The known scraper blades cannot be conveniently adjusted as regards their stiffness, whether over time or locally in such or such zone of their length.

It is certainly known to provide a doctor blade to its end portions of reducers, screens as is described in particular in document US-A-5,345,862. It has also been proposed to give the scraper blades a curved profile. However, these achievements are complex, often imprecise, of limited scope and, ultimately, of unsatisfactory efficiency compared to current requirements of quality and productivity.

The invention therefore aims to remedy the drawbacks or limitations of the current scraper heads.

More specifically, the invention aims to solve the problems inherent in surface unevenness of the scraping supports.

To this end, the invention relates to a doctor blade intended to be part of a screen printing machine, or to be handled by an operator, for printing or transferring fluids or pastes, or other applications, comprising a head, a base in the shape of a lip and at least one elastically deformable member connecting the head and the base, the flexibility of the doctor blade, at each point independent of its length, resulting from the combination of the inherent flexibility of the lip and the elasticity of the elastically deformable member, characterized in that the elastically deformable member is structurally discontinuous in at least one place in the longitudinal direction of the doctor blade and extends along several layers of springs spaced from one another.

The elastically deformable organ is located on all, substantially all or only part of the Ion- scraper. The doctor blade comprises one or more elastically deformable members.

Preferably, the respective elasticities of the lip and of the elastically deformable member are different from each other.

In one embodiment, the body of the elastically deformable member is produced from either one or more elastically deformable wires, in particular metallic wires, arranged in spirals or in undulations, or from a cut sheet, to form a simple comb or double whose stiffness is adjustable by the transverse dimension of the turns, undulations, cuts, or by the characteristics of the constituent material, or by the spacing existing between the teeth of the comb.

The teeth of the comb formed by the elastically deformable member individually exert pressure on each of the longitudinal sectors of the lip, thus made independent.

In one embodiment, the independent distribution of the pressure by the teeth of the comb of the member is completed by a sliding of the head in a doctor blade and the ac¬ tion of an inflatable sleeve.

The elastically deformable member comprises several functional parts as regards the elasticity, situated along the longitudinal direction of the doctor blade, these functional parts being substantially independent of each other so as to be able to take account of the surface unevenness of the support. to be printed.

Where appropriate, some flexible interdependence is provided between the turns or undulations in question towards the scraping lip, this being due to a certain overlapping of the turns or undulations and / or to a connecting member of the turns or undulations such as a wire or cable extending parallel to the length of the doctor blade.

According to another possible embodiment, the body of the elastically deformable member comprises at least one and in particular two wires arranged in spirals or in undulations, defined with the head and the base a deformable quadrilateral according to the pressure exerted by the doctor blade. on the print media.

This deformable quadrilateral is either a deformable parallelogram so that the angle of inclination of the lip on the support to be printed is constant whatever the pressure of the doctor blade on the support to be printed, or a trapezium whose large base is situated towards the head and conversely the small base situated towards the base of the elastically deformable member, the angle of inclination then being deliberately modified with the pressure of the doctor blade on the support to be printed.

According to one embodiment, the body of the elastically deformable member, the head and the base are either electrically conductive or associated flush, so as to ensure a certain electrical continuity between the lip and the doctor blade via the elastically deformable member so as to evacuate static electricity.

The elastically deformable member can be made of plastic or metal, metal alloy, or in combination of plastic, metal, metal alloy. This matter is armed or not.

The scraping lip itself is in the form of a strip in one or more layers, possibly profiled. Its main constituent material is chosen from the group comprising elastomers, rubbers, plastics or other equivalent materials, and in particular polyurethanes. This lip, about 10 to 30 mm high and fixed resiliently to the elastically deformable member, is produced by casting, extrusion, machining or the like. If necessary, it conducts electricity so as to evacuate the static electricity developed during the scraping.

According to one embodiment, the scraper lip comprises two parts, namely a core permanently fixed to the base of the elastically deformable member and an outer scraper part, preferably of low linear mass, fixed to the core. This attachment is removable, by clipping or otherwise.

A doctor blade as just described may further include two screen lowerers at its two ends.

The elastically deformable member can be sealed or closed, but preferably, it comprises at least over part of the length of the doctor blade a plurality of openings or bores above the lip allowing the passage of excess ink printing.

The scraper lip of the doctor blade described may have a reduced transverse height, in particular of the order of a centimeter. This low height then allows the passage, over, of excess printing ink, in order to be able to use the doctor blade in both directions. For some appli¬ cations, this height can even be reduced to a simple steel wire with disappearance of the elastomer part.

In one embodiment, the elastically deformable member is in the general form either of a strip of substantially constant width, or of a sheet or strip comprising one or more cutouts or protrusions extending transversely, or of a comb or a spiral or wavy piece having projections extending in particular vertically. These protuberances or projections extend either over the same distance along the doctor blade, or over different distances depending in particular on the flexibility / hardness desired.

Neighboring functional parts which are functionally sub¬ stantially independent of one another forming part of the elastically deformable member, in particular the protuberances or projections adjoin or adjoin each other sub-stantially or, on the contrary are spaced along the longitudinal direction of the doctor blade . If necessary, this spacing is variable depending on the flexibility / hardness desired.

Typically, a ply along which an elastically deformable member extends is located between or outside but in the vicinity of the two planes externally limiting the scraper blade.

In one embodiment, an elastically deformable member is interposed between the head and the lip. In particular, the elastically deformable member forms the single member or the main member by which the lip is carried by the head.

The head in general is relatively hard, about 60 ° Shore D and more, intended to be fixed in the manual or machine doctor blade and is about 10 to 30 mm high, preferably 12 to 18 mm. The upper parts of the elastically deformable members are rigidly fixed in or on the surface of the head.

According to one embodiment, the doctor blade head slides freely in the doctor blade holder, an inflatable sleeve ensures a pressure equal to each point of the lip whatever the unevenness of the printing medium. The elastically deformable member and the scraping lip are placed substantially in extension of one another.

In one embodiment, the elastically deformable member is, at least in part, in the form of a part of the doctor blade head having a certain capacity for elastic deformation.

The elastically deformable member has a different linear mass from that of the scraper blade proper, so as to have a very different vibration period than that of the lip, the combination of the lip and the elastically deformable member (s) does not not being likely to enter into resonance under normal conditions of implementation, during the scraping of a support having surface inequalities.

The elastically deformable member is rigidly fixed to the head on the one hand and elastically to the lip on the other hand, by crimping, bonding, overmolding or the like. This association is carried out either with immobilization, or with a certain possibility of relative pivoting around an axis extending parallel to the length of the doctor blade.

In a specific embodiment, the elastically deformable member is functionally and / or structurally composite and comprises a rigid or substantially rigid head intended to be associated with the doctor blade holder, a semi-rigid base intended to be associated with a removable lip and, between the head and the base, a body essentially forming the elastically deformable member. The head and / or the base and / or the body are associated detachably or not.

According to one embodiment, the body of the elastically deformable member is associated with the head and / or the lip in a removable manner by force or by means of fixing members such as clips. The head and base have a contoured shape. The scraping lip is associated or forms with the head and / or the base of the elastically deformable member an angle relative to the longitudinal axis of the doctor blade.

Preferably, the head has a profile allowing the installation on a doctor blade holder with several angles of inclination relative to the longitudinal axis of the doctor blade.

The doctor blade which has just been described has many advantages:

The flexibility / hardness of the doctor blade can be adapted in all directions, in particular from top to bottom. One can also produce doctor blades whose stiffness is slightly increased in the center and strongly at the ends.

The doctor blade avoids "encplaning" at high speed, the edge of the lip no longer pitching the screen and the excess ink possibly being able, if it is sufficiently fluid, to be discharged over the upper edge of the lip.

It may, under certain conditions, be no longer essential to have recourse to a counter-doctor blade, the printing may be faster, in particular back and forth.

Such a doctor blade makes it possible to optimize the ink flow and to control the hydraulic pressure and the quantity of ink deposited, independently of the speed of scraping.

The doctor blade makes it possible to control the angle of attack of the doctor blade regardless of the vertical bearing pressure exerted on the doctor lip. As required, with two substantially parallel plies of springs, this angle remains constant or, on the contrary, is modified positively as a function of the pressure exerted. A doctor blade according to the invention makes it possible to take advantage of the fact that the material constituting the elastically deformable member does not retain residual deformation, unlike the rubbers of conventional doctor blades.

This generates a flap or flip-flap effect for certain printing machines. This effect allows the scraper blade to return to its position at each end of its sliding stroke without the need for expensive systems for rapid tilting of the scraper blade or without the need for a double scraper blade or a flood bar.

The doctor blade according to the invention allows the lip to conform exactly to the support to be printed, even if the latter has surface irregularities. The spacing variations can be adapted.

A doctor blade according to the invention also makes it possible to transfer the pressure to the screen outside the printing area, which has the effect of extending the life of the constituent elements of the machine as well as of the screen used for printing. .

The resonance effects resulting from surface imperfections of the print medium are eliminated or attenuated. The same is true of the vibrations arising from these surface imperfections.

A doctor blade as described has also reduced the total weight compared to a conventional doctor blade. This reduction in weight results in lower inertia which is favorable to the operation of the doctor blade.

The other characteristics of the invention will result from the description which follows with reference to the appended drawings in which: - Figure l is a side view of a known doctor blade, while

- Figures 2 to 13 are views of different embodiments of the invention.

In FIG. 1, a doctor blade 2 is fixed to the doctor blade holder 1 by a screw 10. It can be seen that during bending, the angle a on the sieve 7, initially established around 75 °, rapidly decreases towards an angle β of 40 °. This occurs whether the doctor blade 2 has one or more layers.

In FIG. 2A representing a doctor blade 2 according to the invention, seen in profile, it can be seen that, by the effect of the deformable parallelobgram 4.1 and 4.2, the angle β formed by the lip 5 in work is equal to the initial angle at .

FIG. 2B is a front view of different types of spring 4a, 4b and 4c which can constitute the double elastically deformable member 4.

Figures 3A, B, C and D illustrate alternative springs. FIG. 3A represents an overlap of the turns of the spring 4 creating a flexible interdependence in the lip 5. FIG. 3C illustrates a mode of hardening of the doctor blade 2 by bringing the turns 6 together.

Figures 3E to H are sectional views of the different arrangements of the elastically deformable member. FIG. 3E illustrates an adjustable angle doctor blade intended for old machines which do not have this adjustment.

FIGS. 4A, B and C illustrate the variations in point hardness of a doctor blade 2 due to the variations in the spacing of the U-shaped pins constituting the elastic member. FIG. 4D represents the profile view of the same doctor blade. We notice the trapezoid shape. FIG. 5 illustrates the case where the elastically deformable member 4 is an extension of the head 3, in the present case a plastic profile. Sectors 4a, 4b and 4c illustrate the hardness setting by digging more or less deep slots 16.

FIG. 6 represents a doctor blade 2, the deformable elastic member 4 of which is constituted either by a strip folded in a U 13 ′ or by two strips 13. A plastic profile constitutes the head 3 of the doctor blade 2, it is included in the U or pinched by the doctor blade 1 between the two strips. The front views illustrate two types of teeth, hollow or solid, of the elastically deformable member 4.

FIG. 7A illustrates the passage of an ink 8 of low thixotropy in the openings 16 between the teeth of the comb constituting the elastically deformable member 4.

In FIG. 7B, the openings 16 are closed with an adhesive 17 to facilitate cleaning without weighing down the apparatus.

FIG. 8 illustrates a doctor blade where the springs are molded over a large part of their height by a thin layer of rubber constituting the lip 5. The space 14 between the two plies of springs is either empty or filled with foam 15. The front view 8C illustrates, in exploded view, the different layers constituting the elastically deformable member 4 in the case of foam filling.

Figure 9 illustrates a rectangular single-wire spiral construction, entirely included in the material constituting the lip 5. This assembly is suitable for doctor blades of small sections.

FIGS. 10A, 10B, 11A and 11B are two pairs of diagrams illustrating the structure of a doctor blade whose elastically deformable member forms a quadrilateral and this in different possible embodiments, the pressure being greater in the case of FIGS. 10B and 11B than in the case of FIGS. 10A, and 11A; in Figure 11B the trapezoidal shape positively corrects the angle under vertical pressure.

FIG. 12 also illustrates a variant embodiment of the doctor blade in which the doctor lip is in two parts, one of which is easily removable by clipping.

FIGS. 13A, B and C illustrate a doctor blade whose head 3, which accepts longitudinal flexions, can slide vertically in the doctor blade holder 1, an inflatable sleeve 19 exerts a constant linear pressure downwards. The lower part 5 consists of a fixed core 23 and a removable lip 24.

In the embodiments shown in more detail in the figures, the doctor blade 2 is functionally and structurally composite and comprises a head 3, a lip 5 and an elastically deformable member 4.

The head 3 is rigid or substantially rigid, it is intended functionally to be associated with the doctor blade 1. The member 4 is placed between the head 3 and the lip 5. The head 3 and the lip 5 have a profiled shape. The member 4 is also profiled, solid or perforated.

Such a profiled shape allows the lip 5 to be associated or to form with the head 3 a certain angle α, β relative to the longitudinal plane of the doctor blade 2.

The elastically deformable member 4 is, according to the embodiments considered, in the general form of either a strip, of substantially constant width, the profile of which, transversely can be more or less developed, or in the form of a strip comprising one or more slits or protrusions extending transversely, either under the shape of a comb or of a spiral or wavy piece, also having protrusions. These protrusions extend in particular transversely. According to other embodiments, they can be extended differently.

These protuberances or protrusions extend over the same distance, along the doctor blade or, on the contrary, over different distances, depending in particular on the flexibility / hardness desired.

These outgrowths / protrusions form in particular parts which are functionally substantially independent of each other which have been mentioned above.

Such so-called functional parts, in particular the protuberances or protrusions, either adjoin or substantially adjoin, or overlap, or are separated from the neighboring functional parts along the longitudinal direction of the doctor blade.

This spacing is either constant or variable, depending in particular on the flexibility / hardness desired locally.

In Figure 2, we see the doctor blade 2 rigidly removably associated with the doctor blade holder 1. The doctor blade 2 being in contact with the screen 7 has a head 3, a lip-shaped base 5 and at least one elastically deformable member 4 connecting the head 3 and the base 5. The assembly extends longitudinally along an axis. In operation, this axis is placed horizontally or substantially horizontally. The doctor blade holder 1 has a high overall rigidity and constitutes the carrier element of the doctor blade 2. The doctor blade 2 has on the contrary a certain deformability.

The head 3 and the lip 5 of the doctor blade 2 are in the form of a strip in one or more layers of polyurethane than elastomer, each before 12 to 18 mm high, approx. ron, but different elasticities, with the head 3 being more rigid and the lip more flexible.

The elastically deformable member 4 according to FIGS. 2 to 4 is produced from one or more elastically deformable wires arranged in undulation to form a single or double comb whose stiffness is adjustable by the transverse dimen¬ sion of the undulations 6, or by the characteristics of the constituent material, or by the spacing existing between the corrugations 6. A wire or cable 20 extends parallel to the length of the doctor blade 2 to create a certain flexible interdependence in the corrugations 6 towards the lip 5.

The elastically deformable member 4 is structurally discontinuous in the longitudinal direction of the doctor blade 2 at at least one location, because of the succession of the wire forming the corrugations 6 and the space between the corrugations 6.

By structurally discontinuous is meant the fact that the elastically deformable member 4 is produced in such a way that a material or mechanical discontinuity is ensured along the doctor blade 2. The structural parts 6 constituting the elastically deformable member 4 are then or separated from each other.

The doctor blade 2 comprises at least one elastically deformable member 4 located in at least one location of its length.

The elastically deformable member 4 acts on the lip 5 so that the flexibility of the doctor blade 2 in the location where the member 4 is located results in combination from the inherent softness of the lip 5 and the elasticity of the elastically deformable member 4. The respective elasticities are different. According to the embodiments, the elastically deformable member 4 is located over the entire length of the doctor blade or over all of this length or over a portion only of this length. For example, the elastically deformable member 4 is placed at the end parts of the doctor blade or, on the contrary, in its middle part.

Where appropriate, one or more elastically deformable members 4 may be provided located in combination over all or substantially the length of the doctor blade 2 or over only a part of it. The doctor blade 2 comprises either a single elastically deformable member, or several.

The elastically deformable member 4 comprises, in the embodiment more particularly shown in FIG. 2B, several functional parts, having regard to the elasticity.

These functional parts are located along the longitudinal direc¬ tion of the doctor blade 2. These functional parts are functionally substantially independent of each other. This means that a functional part of the elastically deformable member 4 can react to a stress due in particular to the unevenness of the surface to be printed without substantially affecting the functional part adjacent to the elastically deformable member 4.

Furthermore, the elastically deformable member 4 has passages, openings, perforations, spacings, slots or the like piercings 16 above the lip 5 allowing the passage of excess printing ink. Thus, the doctor blade 2 and devoid of a counter doctor blade and simpler than in the known art.

The elastically deformable member (s) 4 have a different linear mass from that of the lip 5. It follows that the elastically deformable member 4 has a vibra¬ tion period which is very different from that of the lip 5. The com ¬ pairing of the lip 5 and of the elastic member (s) deformable 4 is therefore not likely to resonate at least substantially, and under the normal conditions of use of the doctor blade 2. In particular, this resonance is prevented or attenuated during the scraping of a support having the surface inequalities conventionally encountered.

According to the variants considered, the elastically deformable member 4 is either separate from the head 3 and / or the lip 5, so as to be attached to the head 3, or it is an integral part of the head 3 and / or lip 5.

In the embodiments shown, the elastically deformable member 4 is associated with the head 3 and the lip 5 by being interposed between them. More precisely, the elastically deformable member 4 forms the single member or the main member by which the lip 5 is carried by the head 3.

In these embodiments, the elastically deformable member 4 is located transversely at least partially in extension of the head 3 and the lip 5.

By transverse direction is meant here a direction generally orthogonal to the longitudinal axis of doctor blade 2.

According to the embodiment of FIG. 2, the head 3 of the doctor blade 2 is rigidly fixed by the screw 10 in the vice constituted by jaws 9 of the doctor blade holder 1. Here, the elastically deformable member 4 is formed by two struts or sheets struc¬ turally discontinuous in at least one place in the longitudinal direc¬ tion of the doctor blade 2 and constituting two combs which • extend along two sheets of springs spaced from one another. We see the elastic deformations which make it possible to adjust or fix the angle of inclination of the lip 5, and therefore the angle of attack a of the doctor blade 2 on the screen 7 or on the support to be printed. Such a ply is, generally, located between or outside but in the vicinity of the planes externally limiting the doctor blade 2. For example, a ply, along which extends the elastically deformable member 4 , is located substantially either in the middle zone between the two planes, or in the vicinity of at least one of the planes externally limiting the doctor blade 2.

In FIGS. 3 to 6, the elastically deformable members 4 also extend along several layers of springs spaced from one another, (visible in the profile views 3E to H).

In the case of FIG. 3A, the turns or undulations of the member 4 are of triangular shape and come overlapping in the lip 5 to ensure flexible interdependence while they are an extension of the head 3.

According to a preferred aspect, demonstrated in FIGS. 10 A / B and 11 A / B, a double elastically deformable member 4 comprises pivoting elements 12, for example in the form of two wires arranged in a spiral or in undulation, which define with head 3 and lip 5 a deformable quadrilateral. This quadrilateral has four vertices, namely two vertices 21a, 21b in the head 3 and two vertices 22a, 22b in the lip 5. The vertices 21a and 22a are located on one side of the elastically deformable double member 4 and belong to the one of the wires, while the vertices 21b and 22b on the opposite opposite side belong to the other wire. At each end of the doctor blade 2, a spring 11 connects the pivoting elements 12 diagonally.

With such a structure, the angle of inclination of the lip 5 is maintained whatever the pressure of the doctor blade on the screen or support to be printed. This situation is clearly visible by comparing Figures 10A and 10B. It follows that whatever the pressure of the doctor blade on the sieve or support to be printed, the lip 5 has the same angle α.

In the case of FIG. 11A, the vertices 21a, 21b, 22a, 22b form a trapezium whose large base is located on the side of the head 3, and the small base on the side of the lip 18. When pressure is exerted on the head 3, there is a gain in the angle of the lip 5.

In the alternative embodiment of FIG. 12, the scraper lip comprises two parts, namely a core 23 fixed permanently to the base of the elastically deformable member 4, and an outer scraper part 24 of low linear mass, fixed to the core 23. This attachment is in this case of the removable type and by clipping.

Claims

claims

1. Squeegee intended to be part of a screen printing machine, or to be handled by an operator, for printing or transferring fluids or pastes, or other applicati¬ ons, comprising a head (3) , a lip-shaped base (5) and at least one elastically deformable member (4) connecting the head (3) and the base (5), the flexibility of the doctor blade (2), at each point independent of its length, resulting from the combination of the inherent flexibility of the lip (5) and the elasticity of the elastically deformable member (4), characterized in that the elastically deformable member (4) is structurally discontinuous in at least one place in the longitudinal direction of the doctor blade (2) and extends along several layers of springs spaced from one another.

2. Squeegee according to claim 1, characterized in that the body of the elastically deformable member (4) is produced from either one or more elastically deformable wires arranged in a spiral or in undulation, or of a cut sheet, to form a single or double comb whose stiffness is adjustable by the transverse dimension of the turns, undulations, cuts, or by the characteristics of the constituent material, or by the spacing existing between the teeth of the comb.

3. Squeegee according to claims 1 or 2, characterized in that the teeth of the comb formed by the member (4) individually exert pressure on each of the longitudinal sectors of the lip (5), thus made independent.

4. Squeegee according to claims 1 to 3, characterized in that the independent distribution of the pressure by the teeth of the comb of the organ (4) is completed by a sliding of the head (3) in a doctor blade holder (1) and the action of an inflatable sleeve (19).

5. Squeegee according to one of claims 1 to 4, characterized in that the body of the elastically deformable member (4) defines with the head (3) and the base (5) a deformable quadrilateral according to the pressure exerted by the doctor blade on the support to be printed.

6. Squeegee according to claim 5, characterized in that the deformable quadrilateral is either a deformable parallelogram, so that the angle of inclination of the lip (5) on the support to be printed is constant whatever the pressure of the doctor blade on the support to be printed, that is a trapezium whose large base is towards the head (3) and the small base towards the base (5), the angle of inclination being modified positively under pressure.

7. Squeegee according to one of claims 1 to 6, characterized in that the body of the elastically deformable member (4), the head (3) and the base (5) are either conductors of elec¬ tricity , or associated flush, so as to ensure electrical continuity between the lip (5) and the doctor blade holder (1) via the elastically deformable member (4) so as to evacuate static electricity.

8. Squeegee according to one of claims 1 to 7, characterized in that the lip-shaped base (5; 18) is in the form of a strip in one or more layers.

9. Squeegee according to one of claims 1 to 8, characterized in that the elastically deformable member (4) comprises at least over part of the length of the doctor blade a plurality of openings or bores above the lip (5) permitting passage of the excess printing ink.

10. Squeegee according to one of claims 1 to 9, characterized in that the elastically deformable member (4) is fixed to the head (3) and / or to the lip (5) by crimping, bonding, overmolding or equivalent , either with immobilization, or with a certain possibility of relative pivoting about an axis extending parallel to the length of the doctor blade (2).

11. Squeegee according to one of claims 1 to 10, characterized in that the head (3) and / or the base (5) and / or the elastically deformable member (4) are detachably associated.

12. Squeegee according to one of claims 1 to 11, characterized in that the head (3) and / or the base (5) form with the elastically deformable member (4) an angle relative to the axis longitudinal of the doctor blade (2).

13. Squeegee according to one of claims 1 to 12, characterized in that the head (3) has a profile allowing the installation on the doctor blade holder (1) with several angles of inclination relative to the 'longitudinal axis of the doctor blade (2).