Device for fixing a flat screen printing frame to a supporting structure of an apparatus for manufacturing the screen or for flat screen printing

Abstract

 A fabric supporting frame (2) of a screen for flat screen printing comprises a substantially right-angled quadrangular perimetric element, with which it is possible to rigidly associate the perimetric edge (3) of a flat screen printing screen fabric and which comprises a portion (7) which can be associated detachably with a supporting structure (4) of an apparatus or machine for manufacturing the screen or for screen printing substantially flat elements, and at least one element (9) for fixing and centering with respect to the supporting structure (4) which is formed in the portion (7).

Description

[0001] The present invention relates to a device for fixing a fabric supporting frame of a screen for flat screen printing to a supporting surface, particularly of an apparatus or machine for manufacturing the screen or for screen printing substantially flat elements.

[0002] Particularly but not exclusively with reference to the ceramics sector, the technique of flat screen printing, used to apply a decorative pattern to the exposed surface of substantially flat elements, such as for example tiles, is known.

[0003] This technique uses printing screens which are constituted substantially by a frame with a right-angled quadrangular perimetric element, on which a panel of a fabric having a grid-like weave, more commonly known as screen fabric, is stretched and fixed, for example by adhesive bonding. The stencil is applied to the screen fabric, for example by means of the known technique of photoengraving; the open meshes of the screen fabric reproduce the image to be printed.

[0004] Printing occurs by arranging the screen on the exposed surface of a flat element to be decorated, so that the screen fabric is substantially parallel to it and spaced from it, by spreading a printing fluid, such as for example a glaze or paste, on the upper surface of the screen fabric and, with the aid of a spatula, forcing the fluid thus distributed to pass through the open meshes of the screen fabric in order to reproduce the pattern of the stencil on the exposed surface of the underlying flat element.

[0005] Moreover, apparatuses for manual flat screen printing are known which are used in particular for laboratory tests and are constituted substantially by a supporting surface for a flat element, for example a tile, to be subjected to a print test and on which a reference square for positioning said element is movably associated.

[0006] A supporting structure is articulated to one side of the supporting surface, by means of a cylindrical hinge with an axis which is substantially parallel thereto, and the supporting frame of a screen fabric is anchored detachably to said structure.

[0007] The supporting structure is constituted for example by a profiled element or bracket which has a C-shaped cross-section, runs parallel to the articulation axis of the hinge, and in which it is possible to insert with play an edge of the frame, the remainder of which protrudes in a cantilever fashion from it. In the active configuration, i.e., the printing configuration, the supporting structure is arranged so that the two parallel portions of the C-shape are substantially parallel to the supporting surface, and feet for support at an adjustable height are fixed detachably to the opposite edge of the frame.

[0008] The frame is fixed to the supporting structure by way of threaded stems, which are inserted in corresponding threaded holes formed through the side of the C-shape which, in the active configuration, is directed away from the supporting surface. The end of each threaded stem which is directed toward the outside of the supporting structure is provided with an actuation knob or handwheel, and their opposite end is instead adapted to rest against the edge of the frame inserted in said structure; fixing is produced by the friction generated as a consequence of the pressure applied by the stem to the edge of the frame.

[0009] Fixing means fully similar to the one described above are used to fix the screen fabric supporting frames to the supporting structure of automated machines for continuous flat screen printing, which are conventionally known and used in glazing lines, and of known apparatuses and/or machines for manufacturing meshes, such as for example apparatuses for the adhesive bonding of the stretched screen fabric on the frame and/or machines for the photoengraving of the screen fabric already bonded by adhesive on a frame.

[0010] These known types of fixing means are not free from drawbacks, including the fact that they do not allow to center the frame with respect to the supporting structures of the apparatuses or machines for manufacturing printing screens and of the apparatuses or machines for screen printing substantially flat elements. The arrangement of the frame with respect to the supporting structure is in fact controlled and adjusted visually and manually by the assigned operators and is therefore inaccurate and inconstant, since it depends on their manual skills, experience and precision. During screen production, this accordingly entails errors in the centering of the stencil on the screen fabric, while during printing it entails errors in the centering of the stencil of the screen fabric with respect to the flat element to be screen printed, causing in both cases a significant waste of time and a disadvantageous manufacture of rejects.

[0011] Another drawback of known fixing means is that they do not ensure a fixing which is safe and stable over time, with the consequent possibility of movement of the frame during the steps for the production of the screen or during printing steps for laboratory tests and for line production.

[0012] The aim of the present invention is to eliminate the above-mentioned drawbacks of known types of fixing means for fabric supporting frames of screens for flat screen printing by providing a device for fixing a fabric supporting frame of a screen for flat screen printing to a supporting structure, particularly of an apparatus or machine for manufacturing the screen or for screen printing substantially flat elements, which allows to fix the fabric supporting frame of a screen for flat screen printing correctly, precisely and consistently to the supporting structure of an apparatus or machine for manufacturing screen printing screens or for flat screen printing, so as to eliminate, during the production of the screens, errors in the positioning of the stencil with respect to the screen fabric and, during printing, errors in positioning the stencil of the screen fabric with respect to the flat element to be screen printed, reducing production times and eliminating the production of rejects.

[0013] An object of the present invention is to provide a fixing device which ensures a fixing of the frame which is stable and safe over time, eliminating the possibility of being affected by unwanted movements during the steps for production of the screens or during printing steps for laboratory tests or for line productions.

[0014] Another object of the present invention is to provide a fixing device which can be applied simply and cheaply to known frames and to frame supporting structures of known apparatuses and machines without requiring particular work.

[0015] Within this aim, another object of the present invention is to provide a structure which is simple, relatively easy to provide in practice, safe in use, effective in operation, and has a relatively low cost.

[0016] This aim and these and other obj ects that will become better apparent hereinafter are achieved by the present fabric supporting frame of a screen for flat screen printing, which comprises a substantially right-angled quadrangular perimetric element, with which it is possible to rigidly associate the perimetric edge of a flat screen printing screen fabric and which comprises a portion which can be associated detachably with a supporting structure of an apparatus or machine for manufacturing said screen or for screen printing substantially flat elements, and is characterized in that it comprises at least one element for fixing and centering with respect to the supporting structure which is formed in said portion.

[0017] This aim and these objects are also achieved by the present element for fixing a fabric supporting frame of a screen for flat screen printing to a supporting structure, particularly of an apparatus or machine for manufacturing the screen or for screen printing substantially flat elements, characterized in that it comprises a stem which can be associated with said supporting structure so that said stem can slide axially with a reciprocating rectilinear motion substantially at right angles to the plane of arrangement of the frame in a configuration supported by the supporting structure, and in that its end directed toward said plane of arrangement is provided with a pin for fixing and centering the frame and the opposite end is associated with motion actuation means.

[0018] This aim and these objects are also achieved by a device for fixing a screen fabric supporting frame of a screen for flat screen printing to a supporting structure, particularly of an apparatus or machine for manufacturing the screen or for screen printing substantially flat elements, which is characterized in that it comprises a frame according to the present invention and at least one fixing element according to the present invention, said pin being suitable to cooperate with the at least one fixing and centering element.

[0019] Further characteristics and advantages of the present invention will become better apparent from the following detailed description of a preferred but not exclusive embodiment of a device for fixing a screen fabric supporting frame of a screen for flat screen printing to a supporting structure, particularly of an apparatus or machine for manufacturing the screen or for screen printing substantially flat elements, illustrated by way of non-limiting example in the accompanying drawings, wherein:

Figure 1 is a schematic perspective view of a laboratory apparatus for manual screen printing of substantially flat elements, with the fixing device according to the invention applied thereto, during the fixing of a frame;

Figure 2 is a schematic perspective view of the apparatus of Figure 1, with the frame fixed;

Figure 3 is a schematic sectional view, taken along the line III-III of Figure 2, of the device according to the invention during the fixing of the frame;

Figure 4 is a schematic sectional view, taken along the line III-III of Figure 2, of the device according to the invention with the frame fixed;

Figure 5 is an enlarged-scale view of a detail of the frame of the device according to the invention.

[0020] With reference to the figures, the reference numeral 1 generally designates a device for fixing a frame 2 for supporting a fabric 3 of a screen for flat screen printing to a supporting structure 4, particularly of an apparatus or machine for manufacturing the screen or for screen printing substantially flat elements.

[0021] The present description and the accompanying drawings refer particularly but not exclusively to a device 1 which is applied to an apparatus 5 for a manual print test performed in a laboratory, without this constituting a limitation of the present invention, the device 1 being also applicable to machines for the continuous flat screen printing of substantially flat elements or to apparatuses or machines for manufacturing printing screens, such as for example apparatuses for the adhesive bonding of the stretched screen fabric on the frame and/or machines for the photoengraving of the screen fabric already adhesive-bonded to a frame, as can be easily understood by a person skilled in the art.

[0022] The frame 2 comprises a substantially right-angled quadrangular perimetric element, with one face of which it is possible to rigidly associate, for example by adhesive bonding, the perimetric edge of the screen fabric 3, which is appropriately stretched. A rectangular region 6 is formed on the screen fabric 3 and its dimensions correspond to those of the flat element to be printed, for example a tile, in which the stencil which reproduces the image to be applied by screen printing to the exposed surface of said flat element is provided for example by means of the photoengraving technique.

[0023] The assembly constituted by the frame 2 and by the screen fabric 3 fixed thereto accordingly forms a screen for flat screen printing.

[0024] A portion 7 of the perimetric element of the frame 2 is detachably associable with the supporting structure 4.

[0025] The supporting structure 4 is constituted for example by a profiled element or bracket 8, the cross-section of which is substantially C-shaped or similarly shaped, and inside which it is possible to insert with play the portion 7.

[0026] The device 1 comprises one or more elements 9 for fixing and centering the frame 2 with respect to the supporting structure 4, which are formed in the portion 7; each of said elements can be constituted for example by a corresponding hole 10.

[0027] The device 1 further comprises one or more elements 11 for fixing the frame 2 to the supporting structure 4; said elements can be associated with the supporting structure 4 and are equal in number to the fixing and centering elements 9 with which they cooperate. In particular, the fixing elements 11 are associated with the side of the bracket 8 which, in the printing configuration, is directed away from the flat element to be printed.

[0028] In a preferred embodiment, the device 1 comprises two fixing and centering elements 9, which are formed in the portion 7 and are mutually spaced and aligned along a direction 12 which is substantially parallel thereto, and a corresponding pair of fixing elements 11, which are mutually spaced and aligned along a direction 13 which is substantially parallel to the longitudinal extension of the supporting structure 4, i.e., of the bracket 8.

[0029] Each hole 10 lies substantially at right angles to the plane formed by the perimetric element of the frame 2 and is substantially shaped like a frustum which diverges from said plane.

[0030] In a preferred embodiment, each fixing and centering element 9 comprises a bush 14, provided with the corresponding hole 10 and rigidly associable with the portion 7, in which a corresponding receptacle 15 is conveniently provided. Each bush 14 is therefore recessed within the portion 7 and is rigidly coupled thereto, for example, by welding, and it is possible to use alternative systems for completely fixing the bush 14 to the portion 7 of a conventionally known type.

[0031] Each fixing element 11 comprises a stem 16, which can be associated with the supporting structure 4; each stem 16 can slide axially with a reciprocating rectilinear motion along a direction 17 which is substantially perpendicular to the plane of arrangement of the frame 2 when it is in the configuration in which it is supported by the supporting structure 4. The end of the stem 16 which is directed toward said plane of arrangement is provided with a pin 18 for fixing and centering the frame 2, which is adapted to cooperate with the corresponding fixing and centering element 9, while the end which lies opposite thereto is associated with means 19 for actuating the reciprocating rectilinear motion of the stem 16.

[0032] The pin 18 is shaped substantially like a frustum which converges toward the plane of arrangement of the frame 2 in the configuration in which it is supported by the supporting structure 4, and it can be inserted substantially snugly in the hole 10 of the corresponding fixing and centering element 9.

[0033] The pin 18 protrudes from a cylindrical collar 18', while the hole 10 extends from an annular surface 10'.

[0034] Conveniently, each fixing element 11 comprises a body 20 for supporting the stem 16 and the corresponding actuation means 19; said body can be associated, for example detachably by way of threaded fixing elements 21 or other complete fixing systems of a known type, with the supporting structure 4, particularly with the upper face of the side of the bracket 8 to which they are anchored. A through hole 8' is formed on this last side of the bracket 8, i.e., of the supporting structure 4, at each fixing element 11, for the passage of the stem 16 through it from a retracted configuration to an extended configuration, in which the pin 18 is respectively disengaged and engaged with respect to the hole 10 of the corresponding fixing and centering element 9, and vice versa (Figures 3 and 4).

[0035] The actuation means 19 can be advantageously of the automated type and can be of the linear type and pneumatic, hydraulic, mechanical, electrical or electromechanical. In a preferred embodiment, the actuation means 19 are constituted by a pneumatic linear actuator, such as a double-acting cylinder.

[0036] With particular reference to Figures 1 and 2, the apparatus 5 comprises a supporting surface 22 for a substantially flat element to be screen printed, such as for example a tile; a reference square 23 for the positioning of said flat element can move on the supporting surface 22. A pivot 24 is fitted to one side of the supporting surface 22, is substantially parallel thereto, and its opposite ends are fixed to corresponding sliders 25, which are supported slidingly on corresponding straight guides 26 and are actuated so as to slide along said guides by a respective actuation screw 27.

[0037] The supporting structure 4, i.e. the bracket 8, is rotationally associated with the pivot 24 by way of articulation bushes 28 and runs parallel to said pivot.

[0038] Two fixing elements 11 are rigidly associated with the supporting structure 4 and are adapted to cooperate with a corresponding pair of fixing and centering elements 9, i.e., of holes 10, which are formed in the portion 7 of the frame 2 which is suitable to be inserted in the bracket 8.

[0039] The apparatus 5 further comprises one or more feet 29 for resting on the supporting surface 22, which have an adjustable height and can be associated detachably with the frame 2 and in particular with the portion 30 thereof which lies opposite the portion 7; the supporting feet 29 are adapted to support the frame 2 in a position which is substantially raised and parallel with respect to the exposed surface of the underlying flat element to be printed.

[0040] As mentioned, the device 1 can be applied not only to fix the frame 2 to a supporting structure 4 of an apparatus for manual screen printing tests in a laboratory, such as the apparatus 5, but also of a machine for automated continuous flat screen printing or of apparatuses or machines for manufacturing screens for flat screen printing. In other words, the device 1 can be applied to all apparatuses or machines, whether manual, semiautomated or automated, in which it is necessary to fix the supporting frame of screen fabric for flat screen printing to the supporting structure of said apparatus or machine.

[0041] The operation of the invention is as follows.

[0042] The frame 2 is fitted to the supporting structure 4 by inserting the portion 7 of its perimetric element in the supporting structure 4, i.e., in the bracket 8, so that the holes 10 are arranged substantially at the fixing elements 11, the stems 16 of which are retracted or raised with respect to the side of the supporting structure 4 with which they are associated.

[0043] By way of the actuation means 19, the stems 16 are made to slide along the direction 17 in order to pass from the retracted position to the extended and lowered position with respect to the side of the supporting structure 4 with which they are associated; in this extended configuration, the pins 18, after passing through the through holes 8', are inserted snugly in the corresponding holes 10, fixing and centering the frame 2 with respect to the supporting structure 4.

[0044] In order to disassemble the frame 2, it is sufficient to act on the actuation means 19 in order to move the stems 16 from their extended position to the retracted position and extract the frame 2 from the supporting structure 4.

[0045] In practice it has been found that the described invention achieves the intended aim and objects.

[0046] The fixing device according to the invention, by way of the cooperation between the fixing and centering elements formed on the frame and the fixing elements associated with the supporting structure, particularly by way of the conical coupling between the holes formed in the frame and the pins of the fixing elements and by way of the pressure applied by the actuation means of the latter, allows to fix and center precisely, consistently and stably the screen fabric supporting frame of a screen for flat screen printing to the supporting structure of an apparatus or machine for manufacturing the screen or for screen printing substantially flat elements. In particular, the fixing and centering of the frame are independent of the precision, manual skill and experience of the assigned operators.

[0047] The device according to the invention allows to fix and center the frame with respect to the supporting structure simply and rapidly and ensures a stable fitting of said frame, eliminating the risk of any movement thereof in any step of work.

[0048] The device according to the invention therefore allows to eliminate, during the production of screens for screen printing, the errors in centering the stencil with respect to the screen fabric and, during printing, the centering errors of the stencil with respect to the element to be screen printed, consequently eliminating production rejects.

[0049] The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims.

[0050] All the details may further be replaced with other technically equivalent ones.

[0051] In practice, the materials used, as well as the shapes and the dimensions, may be any according to requirements without thereby abandoning the scope of the protection of the appended claims.

[0052] The disclosures in Italian Patent Application No. MO2005A000071 from which this application claims priority are incorporated herein by reference.

[0053] Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims

1. A fabric supporting frame of a screen for flat screen printing, comprising a substantially right-angled quadrangular perimetric element, with which it is possible to associate rigidly the perimetric edge of a flat screen printing screen fabric and which comprises a portion which can be associated detachably with a supporting structure of an apparatus or machine for manufacturing said screen or for screen printing substantially flat elements, characterized in that it comprises at least one element for fixing and centering with respect to said supporting structure which is formed in said portion.

2. The frame according to claim 1, characterized in that it comprises two of said fixing and centering elements, which are formed in said portion and are mutually spaced and aligned along a direction which is substantially parallel to said portion.

3. The frame according to one or more of the preceding claims, characterized in that each one of said fixing and centering elements comprises a hole.

4. The frame according to one or more of the preceding claims, characterized in that said hole lies substantially at right angles to the plane formed by said perimetric element.

5. The frame according to one or more of the preceding claims, characterized in that said hole is substantially shaped like a frustum which diverges from said plane formed by said perimetric element.

6. The frame according to one or more of the preceding claims, characterized in that each one of said fixing and centering elements comprises an annular surface from which said hole extends.

7. The frame according to one or more of the preceding claims, characterized in that each one of said fixing and centering elements comprises a bush in which the corresponding hole is formed and which is rigidly associable with said portion.

8. The frame according to one or more of the preceding claims, characterized in that said portion comprises at least one receptacle for accommodating one of said bushes.

9. An element for fixing a screen fabric supporting frame of a screen for flat screen printing to a supporting structure, particularly of an apparatus or machine for manufacturing the screen or for screen printing substantially flat elements, characterized in that it comprises a stem which can be associated with said supporting structure so that said stem can slide axially with a reciprocating rectilinear motion substantially at right angles to the plane of arrangement of the frame in the configuration supported by said supporting structure, the end of said stem which is directed toward said plane of arrangement being provided with a pin for fixing and centering said frame, the opposite end being associated with means for actuating said motion.

10. The element according to claim 9, characterized in that said pin is shaped substantially like a frustum which converges toward said plane of arrangement.

11. The element according to claim 9 or 10, characterized in that said pin protrudes from a substantially cylindrical collar.

12. The element according to one or more of claims 9 to 11, characterized in that it comprises a body for supporting said stem which can be associated with said supporting structure.

13. The supporting element according to one or more of claims 9 to 12, characterized in that said actuation means are of the automated type.

14. The element according to one or more of claims 9 to 13, characterized in that said actuation means are of the linear type and are pneumatic, hydraulic, mechanical, electrical or electromechanical.

15. A device for fixing a screen fabric supporting frame of a screen for flat screen printing to a supporting structure, particularly of an apparatus or machine for manufacturing the screen or for screen printing substantially flat elements, characterized in that it comprises a frame according to one or more of claims 1 to 8 and at least one fixing element according to one or more of claims 9 to 14, said pin being suitable to co-operate with said at least one fixing and centering element.

16. The device according to claim 15, characterized in that said pin can be inserted substantially snugly in the hole of the corresponding fixing and centering element.

17. The device according to claim 15 or 16, characterized in that it comprises two of said fixing elements, which cooperate with a corresponding pair of said fixing and centering elements.

18. The device according to one or more of claims 15 to 17, characterized in that it comprises at least one through hole, which is formed in said structure for the passage of said stem from a retracted configuration to an extended configuration, in which said pin is respectively disengaged and engaged with respect to the corresponding fixing and centering element, and vice versa.

Drawing