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(11) | EP 1 040 920 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | A silk-screen decorating machine |
| (57) The silk screen decorating machine comprises: a belt-shaped flexible silk screen
(1) ring-wound and stretched between two parallel-axis rotors (2, 3) by at least one
of which the screen (1) is drawn; means for spreading a decorating fluid and causing
the fluid to pass through the screen (1). The parallel-axis rotors (2, 3) are arranged
projectingly above a mobile plane (21) for conveying tiles (22) and are constituted
by pairs of wheels (4, 5), on which the screen (1) partially windingly couples. The
wheels (4, 5) are mounted on respective shafts (6, 7), which shafts (6, 7) are each
constituted by a first segment (8) and a second segment (9) which are coaxial, solid
in rotation and axially displaceable one with respect to another. The wheels of each
pair of wheels are mounted solidly, one of each pair on a first segment (8) and one
of each pair on a second segment (9). Also provided are means for interacting on command
with free ends of the shafts (6 and 7) so as to position the shafts (6 and 7) at a
predetermined reciprocal distance. |
[0001] Specifically, though not exclusively, the machine is usefully applied in decorating ceramic tiles in production lines.
[0002] The prior art has for a long time taught silk screen machines which use a silk screen in the form of a thin rotary circular cylinder which is brought into contact with underlying tiles being transferred on a conveyor with the same peripheral speed as the cylinder in such a way that there is no dragging between the two.
[0003] Inside the cylindrical screen a doctor spreads the fluid (glaze) so as to fill the perforations in the screen and transfer the thus-loaded quantity of glaze on to the surface of the underlying tile. These decorating machines, though having many plus-points, also have some drawbacks which are in a large part attributable to the fact that the operation of glaze-laying on the tiles is done by rolling a cylinder on a flat surface.
[0004] Italian patent 01287622 describes a silk-screen decorating machine which comprises a flexible band-type silk screen, ring-wound and stretched between two parallel-axis rotors. The screen is drawn by at least one of these rotors, which are arranged projectingly above a mobile plane for tile conveying and are constituted by couples of wheels, on which the silk screen partially winds. The two coaxial wheels of each couple are solidly mounted on a shaft; the first wheel on a first segment of the shaft and the second on a second segment of the shaft, which second segment can be moved in an axial direction with respect to the first segment, while being solid in rotation with said first segment.
[0005] A doctor spreads and forces the glaze through the perforations in the screen, which is stretched between the two couples of wheels.
[0006] A serious drawback of the above-described invention is connected with the fact that the necessary stretching of the screen in a longitudinal direction produces a considerable flexion of the shafts supporting the screen on which the screen winds.
[0007] Since the shafts are typically projecting, the elastic deformation is considerably greater in the region of the external wheels, i.e. those wheels located at the free ends of the shafts with respect to the internal wheels. The two lateral edges of the screen therefore are never subject to exactly the same longitudinal stretching force. The edge coupled on the two external wheels is always less stretched than the edge coupled on the two internal wheels. The result is an incorrect functioning which causes a not inconsiderable number of drawbacks. The present invention obviates the above-mentioned drawbacks and limitations in the prior art.
[0009] A further advantage of the invention is that it gives rise to a structure which in no way limits the mounting, dismounting, substitution and regulation operations on the screen.
[0010] These aims and advantages and more besides are all attained by the present invention, as it is characterised in the claims that follow.
[0011] Further characteristics and advantages of the present invention will better emerge from the detail description that follows, of a preferred embodiment of the invention illustrated purely by way of non-limiting example in the accompanying figures of the drawings, in which:
figure 1 shows a schematic frontal view in vertical elevation;
figure 2 is a schematic plan view from above of figure 1;
figure 3 is a partially-sectioned schematic lateral view from the left of figure 1;
figure 4 is an enlarged-scale view of detail X of figure 3;
figure 5 schematically shows a detail of figure 2 in a different configuration.
[0012] With reference to the above-mentioned figures, 1 denotes a belt-type silk screen, flexible and ring-wound and stretched between two parallel-axis and horizontal rotors 2 and 3.
[0013] The two parallel-axis rotors 2 and 3 are projectingly arranged above a mobile plane 21 for conveying tiles 22, in such a way that the lower branch of the screen stretched between the two rotors is more or less horizontal and located at a short distance from the mobile plane 21.
[0014] The two rotors 2 and 3 are constituted by pairs of wheels 4 and 5, around which the screen 1 is partially wound. The pairs of wheels 4 and 5 are mounted on respective shafts 6 and 7.
[0015] Each of the shafts 6 and 7 is constituted by a first segment 8 and a second segment 9 which are coaxial, solid in rotation and reciprocally axially displaceable.
[0016] A wheel 4 is solidly mounted on each first segment 8, while another wheel 5 is mounted on each second segment 9. In particular, the first segment 8 of the shaft 6 is rotatably supported on a frame 19 of the machine and is connected through a normal mechanical gear transmission 23 to a motor 24 which on command draws the shaft 6 in rotation.
[0017] The rotor 3 and especially the first segment 8 of the shaft 7 are mounted on a support 18 which is constrained to the frame 19 translatably in a perpendicular direction to the rotation axis of the shaft 7 itself. A pneumatic cylinder 20 on command translates the support 18 in two directions with respect to the frame 19. Thus, by activating the cylinder 20 it is possible to near or distance shaft 7 from shaft 6 so as to stretch the screen mounted on the wheels 4 and 5.
[0018] The coupling of the screen 1 on the pairs of wheels 4 and 5 is realised in such a way as to enable the screen to be drawn without any sliding and also for the wheels to grip on the screen itself so as to realise a good transversal stretching. For this purpose the silk screen I exhibits, solidly constrained to its edges, two ring-wound longitudinal elements, or belts 11, which are elastically flexible and mechanically sturdy and which are provided with two transversal coggings 12, predisposed to enable enmeshing with corresponding transversal cogs provided on the wheels 4 and 5.
[0019] The belts 1 also bear at least one trapezoid-section longitudinal rib 13, predisposed to couple in a corresponding hollow seating or gullet 28 afforded on each of the wheels 4 and 5.
[0020] The coupling of the longitudinal ribs 13 with the gullets 28 of the wheels 4 and 5 is mainly for transversally anchoring the lateral edges of the screen 1 to the wheels 4 and 5 so as to enable the screen 1 to be transversally stretched simply by coaxially distancing wheel 5 from wheel 4 in each of the wheel pairs 4, 5 mounted respectively on shafts 6 and 7.
[0021] The axial displacement of wheels 5 with respect to wheels 4 is obtained by axially sliding the second segments 9 (by means of pneumatic cylinders 14) with respect to the first segments 8.
[0022] The free ends of the second segments 9 of both shafts 6 and 7 are rotatably coupled with two supports 10.
[0024] Both of the con rods 16 have other ends which are symmetrically hinged to a single central element 15 by means of pivots 25 so as to give rise to a mechanism, denoted in its entirety by 26, which connects the free ends of the two shafts 6 and 7.
[0025] The essential characteristic of the mechanism 26 consists in the proportioning and relative arrangement of the various elements so that the sum of the lengths of the two con rods 16 with the distance between the axes of the two pivots 25 is definitely greater than the distance between the axes of the two shafts 6 and 7 in an undeformed configuration, meaning a non-stressed configuration.
[0026] This enables the mechanism 26 to be used to locate the two free ends of the shafts 6 and 7 at a predetermined distance one from the other. In particular the two free ends can be positioned so that the inter-axes between the shafts 6 and 7, measurable at the keying section portions of the wheels 4 and 5, are equal. The mechanism 26 can be activated to the desired extent simply by producing a displacement of the central element 15 with respect to the shafts 6 and 7 which exhibits at least one component which is parallel to the axes of the shafts themselves. The entity of the transversal displacement is geometrically determined according to the desired transversal displacement of the two free ends of the shafts 6 and 7.
[0027] The desired transversal displacement of the two free ends of the shafts 6 and 7 is obtained by producing a predetermined axial translation by means of the pneumatic cylinders 14 of the two second segments 9 with respect to the relative segments 8 after the central element 15 has interacted with an external fixed striker 17 which in the example is solidly connected to the frame of the machine 19.
[0028] In this way, after having mounted the screen 1 on the wheels 4 and 5 and having stretched the screen longitudinally by distancing shaft 7 from shaft 6 (by means of the cylinder 20), by operating the other cylinder 14 the two second segments 9 can be moved with respect to the first segments 8 up until the central element 15 interacts with the external striker element 17.
[0029] When the central element 15 contacts the external striker 17 the continuation of movement of the segments 9 causes the free ends of the shafts 6 and 7 to separate. This separation can continue up until the inter-axes between the shafts 6 and 7, measurable at the keying sections of the wheels 4 and 5, are equal to each other. At this point the two belts 11 laterally delimiting the screen 1 are equally stretched.
[0031] In a further embodiment the mechanism 26 can be made differently, for example with the two con rods 16 exhibiting their first ends reciprocally hinged with no interpositioning of the central element 15. Obviously, in this case it would be the sum of the lengths of the two con rods 16 which would have to satisfy the condition of being greater than the distance between the axes of the two shafts 6 and 7 in the undeformed configuration (i.e. with no stress).
1. A silk-screen decorating machine, comprising:
a belt-shaped flexible silk screen (1) ring-wound and stretched between two parallel-axis rotors (2, 3) by at least one of which the screen (1) is drawn;
means for spreading a decorating fluid and causing said fluid to pass through the screen (1); the parallel-axis rotors (2, 3) being arranged projectingly above a mobile plane (21) for conveying tiles (22) and being constituted by pairs of wheels (4, 5), on which said screen (1) partially windingly couples, which pairs of wheels (4, 5) are mounted on respective shafts (6, 7); said shafts being each constituted by a first segment (8) and a second segment (9) which are coaxial, solid in rotation and axially displaceable one with respect to another; each said first segment (8) bearing a first wheel (4) of the pair of wheels (4, 5) solidly mounted thereto, each said second segment (9) bearing a second wheel (5) of ht epair of wheels (5) solidly mounted thereto; characterised in that it comprises means for interacting on command with free ends of the shafts (6 and 7) so as to position skid shafts (6 and 7) at a predetermined reciprocal distance.
a belt-shaped flexible silk screen (1) ring-wound and stretched between two parallel-axis rotors (2, 3) by at least one of which the screen (1) is drawn;
means for spreading a decorating fluid and causing said fluid to pass through the screen (1); the parallel-axis rotors (2, 3) being arranged projectingly above a mobile plane (21) for conveying tiles (22) and being constituted by pairs of wheels (4, 5), on which said screen (1) partially windingly couples, which pairs of wheels (4, 5) are mounted on respective shafts (6, 7); said shafts being each constituted by a first segment (8) and a second segment (9) which are coaxial, solid in rotation and axially displaceable one with respect to another; each said first segment (8) bearing a first wheel (4) of the pair of wheels (4, 5) solidly mounted thereto, each said second segment (9) bearing a second wheel (5) of ht epair of wheels (5) solidly mounted thereto; characterised in that it comprises means for interacting on command with free ends of the shafts (6 and 7) so as to position skid shafts (6 and 7) at a predetermined reciprocal distance.
2. The machine of claim 1, characterised in that said means for interacting comprise:
a central element (15) to which first ends of two con rods (16) are symmetrically
hinged; second ends of the con rods (16) being hinged to supports (10), in which supports
(10) free ends of the shafts (6, 7) are rotatably coupled; at least one external striker
(17) for interacting with the central element (15) by effect of relative displacements
having at least one component which is parallel to axes of the shafts (6, 7).
3. The machine of claim 2, characterised in that the silk screen (1) exhibits, solidly
constrained to edges thereof, two ring-wound closed longitudinal belts (11) which
are elastically flexible and mechanically resistant and which are destined to couple
with the pairs of wheels (4 and 5).
4. The machine of claim 3, characterised in that the belts (11) exhibit a transversal
cogging (12) for enmeshing with a corresponding cogging on the pairs of wheels (4,
5), and in that they also exhibit at least one longitudinal ribbing (13) for coupling
with a corresponding gullet (28) afforded on the pairs of wheels (4, 5); a coupling
of said longitudinal ribbing (13) with the corresponding gullet (28) in the pairs
of wheels (4, 5) being predisposed for realising a transversal stretching of the screen
(1).
5. The machine of claim 4, characterised in that each said second segment (9) solidly
bearing a second wheel (5) is axially displaceable with respect to a relative first
segment (8) bearing a first wheel (4), on receiving a command from an operator.
6. The machine of claim 5, characterised in that the rotor (3) is mounted on a support
(18) which is constrained, with ability to translate in a normal direction to a rotation
axis of the rotor (3), to the frame (19) to which the rotor (2) is rotatably supported;
a pneumatic cylinder (20) being provided to induce translation displacements, on command
and in both directions, of the support (18) with respect to the frame (19).
7. The machine of claim 6, characterised in that the external striker (17) is fixed to
the frame (19).