Silk-screen printing machine for the printing of cylindrical objects

Abstract

 Rotary machine for the silk-screen printing of substantially cylindrical objects (1), comprising a vertical axis of rotation (20), at least one arm (12) supporting at least one printing frame (210,211) and at least one doctor blade (230), means (50,51) for supporting the object (1), rotatable about their longitudinal axis, means (40,41) for rotational actuation, about the vertical axis (20), of the said means (50) for supporting the container (1), in which said support arm (12) is movable translationwise, parallel to the vertical axis of rotation (20), towards/away from the object (1) to be printed.

Description

[0001] The present invention relates to a rotary machine for the silk-screen printing of substantially cylindrical objects, comprising a vertical axis of rotation, at least one arm supporting at least one printing frame and at least one doctor blade, in which said support arm is movable translationwise parallel to the vertical axis of rotation towards/away from the object to be printed.

[0002] In the art of printing images on objects with a substantially cylindrical shape, rotary-operation silk-screen printing machines with a plurality of printing stations to which the part for successive printing of the images/colours on the side surface thereof is fed are known.

[0003] It is also known that these machines comprise, for each printing station, a corresponding apparatus formed by a frame/screen/doctor blade which must be lowered towards the container and then made to move during the simultaneous and synchronized rotation of the latter.

[0004] Although functional, these machines of the known type have a few drawbacks which limit their performance; more particularly, each frame supporting the screen and the associated doctor blade are constrained to an arm which is in turn hinged on a special fixed upright which is arranged on the peripheral edge of the rotary machine in the region of each printing station.

[0005] This arm is therefore made to rotate about the fixed hinge so as to cause the raising/lowering of the frame and the doctor blade away from/towards the container to be printed; since the doctor blade is arranged at a distance from the hinge different from that of the screen, the latter performs a rotation through a circumferential arc which is different from that of the doctor blade which therefore is unable to maintain its constant distance from the screen during raising/lowering, resulting in the risk of breakage of the said screen, in particular during raising thereof.

[0006] The doctor blade must therefore be provided with an autonomous device for effecting translation towards/away from the screen, which moves it away from the latter during the rotational raising movement of both of them by the rotating arm.

[0007] The presence of the auxiliary device for operating the doctor blade in turn gives rise to other drawbacks due to the need for costly actuating and control devices, the increase in the overall dimensions and also the fact that, during the downwards movement towards the screen and towards the container, the doctor blade inevitably strikes the latter which, being supported in a projecting manner, tends to be displaced from its correct axial alignment, increasing the number of rejects due to printing errors.

[0008] In addition to the above, the known machines have a device for locating the zero generatrix of the container based on the engagement of bevel gears or the like which, being present on each printing station of the rotary machine, result in the need for the relative adjustment and synchronization, thereby complicating considerably re-tooling of the machine when there is a change in size, thereby making the machine unsuitable for the production of small batches and/or frequent changing of the images to be printed.

[0009] The technical problem which is posed, therefore, is that of providing a rotary machine for the silk-screen printing of substantially cylindrical containers, which solves the abovementioned drawbacks of the known art. Within the context of this problem a further requirement is that the machine should be provided with loading/unloading devices comprising safety means designed to prevent damage to the machine following abnormal interruption in the working stroke, due for example to breakage of the container or accidental interference by the operator during loading/unloading.

[0010] These technical problems are solved according to the present invention by a rotary machine for the silk-screen printing of substantially cylindrical objects, comprising a vertical axis of rotation, at least one arm supporting at least printing frame and at least one doctor blade, means for supporting the object, rotatable about their longitudinal axis, means for rotational actuation, about the vertical axis, of the said means for supporting the container, in which said support arm is movable translationwise parallel to the vertical axis of rotation towards/away from the object to be printed.

[0011] Further details may be obtained from the following description of a non-limiting example of embodiment of the invention provided with reference to the accompanying drawings, in which:

• Figure 1 shows a schematic top plan view of the machine according to the invention;
• Figure 2 shows a top plan view of a detail of a printing station;
• Figure 3 shows a cross-section along the line indicated by III-III in Fig. 2;
• Figure 4 shows a partially sectioned view of a detail of the means for angular synchronization of the container;
• Figure 5a shows a cross-section along the plane indicated by Va-Va in Fig. 4, illustrating the synchronization device in the zero position during printing;
• Figure 5b shows a cross-section along the plane indicated by Vb-Vb in Fig. 4, illustrating the synchronization device during location of the zero point during rotation of the container from one printing station to the next one;
• Figs. 6a,b,c are schematic views of the cycle for transportation of the container from one printing station to the next one;
• Figs. 7a,b,c are schematic views of the container printing cycle;
• Figure 8 is a side view of the assembly for actuating the loading/unloading device with associated safety means in the normal operating condition;
• Figure 9 shows a cross-section along the plane indicated by IX-IX in Fig. 8 and;
• Figure 10 shows a side view of the assembly for actuating the loading/unloading device with associated safety means in the release condition.

[0012] As illustrated in Fig. 1, the machine according to the invention has a substantially circular base along the circumference of which the loading station 100, the printing stations 200 and the unloading station 300 are arranged, being all oriented in radial directions and at a relative angular distance determined in relation to the number of colours to be printed.

[0013] The structure 10 of the machine supports a central fixed pillar 20 on which a sleeve 11 is coaxially mounted, said sleeve being designed to move translationwise on the pillar 20 from a high position to a lower position, but not to rotate on the said pillar.

[0014] The said sleeve 11 has, constrained to it, the arms 12 supporting the frame 210 which carries the printing screen 211 and the doctor blade 230 of each printing station 200 located in radial directions.

[0015] In greater detail the frame 210 carrying the printing screen 211 is mounted on an upright 212 which is slidable in a radial direction on the arm 12 and can be locked in position on the latter by means of associated screw means 212a.

[0016] The same is applicable to the doctor blade 230 which is mounted on an upright 232 which is slidable in a radial direction on the arm 12 and can be locked in position on the latter by means of associated screw means 232a.

[0017] The bottom part of the upright 212 has, mounted on it, opposing rollers 212b for guiding the frame 210 which is supported on the opposite side by means 241 integral with a carriage 240 movable (Figs. 2,3) in the tangential direction of the machine upon actuation of means known per se and not illustrated nor described in detail.

[0018] The bottom surface of one of the two tangential sides of the frame 210 also has, constrained to it, a rack 213 which is designed to mesh with a corresponding pinion 214 integral with the shaft 52 (described below) for rotationally actuating the container 1 so that the translation, in a tangential direction, of the frame 210 and hence the printing frame 211 and the rack 213 causes the rotation of the pinion 214 and therefore the container 1, as will be explained more clearly below.

[0019] The sleeve 11 of the central pillar 20 also has, coaxially mounted on it, a first circular plate 30 which is in turn fixed rotationally, but movable translationwise with the sleeve 11 from a first lowered position (Fig. 7c) to a second raised position (Fig. 3) where it makes contact with means for rotating the container, described further below.

[0020] The circular plate 30 is also provided underneath with a second circular plate 40 which has a larger diameter and is fixed translationwise with respect to the pillar 20, but is rotationally movable with respect thereto upon actuation of an associated rotating table 41 (Fig. 3).

[0021] The underlying plate 40 carries the devices 50 for supporting and rotating the container 1, which are arranged in a radial direction and, from the external circumference towards the axis of rotation, comprise (Fig. 4):

• a buffer member 51 with a suitable diameter, which is designed to engage with the mouth of the container 1 and is connected to means designed to produce a vacuum inside the said container for stable holding thereof;
• the said pinion 214 meshing with the rack 213 of the screen-carrying frame 210;
• a transmission shaft 52, the free end of which opposite the container is inserted in:
• means 60 for automatically locating the zero position of the container 1, described in detail below;
• a cylinder 53 made of friction material such as rubber or the like, which is designed to come into contact with the upper surface 30a of the said plate 30 during the angular rotation of the plate 40 so as to cause the rotational actuation, about its axis, of the shaft 52 and therefore the entire support assembly, as well as the container 1.

[0022] Said cylinder 53 is mounted on the threaded end-piece 54a of a rubber buffer member 54 which in turn is in abutment against a wheel 61 of the said means 60; the threaded end-piece 54a also has, mounted on it, resilient means 55, the reaction force of which may be adjusted by means of a locking nut 56.

[0023] Said means 60 for automatically locating the zero position of the container 1 consist (Figs. 4,5a,5b) of a wheel 61 which is coaxially mounted on the shaft 52 and is provided with a radial notch 62 which is designed to engage with a tooth 63a forming the free end of a lever 63, the other end of which is pivotably mounted on a support 64 fixed to the plate 40, between the plate 40 and the lever 63 there being arranged a spring 65 which pushes the lever in anti-clockwise direction and hence the tooth 63a into the notch 62 of the wheel 61.

[0024] The cyclical operation of the machine may be divided into two separate steps which are synchronized with each other;

a) the step of transporting the container 1 from the loading station 100 to the first printing station 200 or from a printing station 200 to the next station; and

b) the actual printing step with the container stationary in the corresponding station 200.

[0025] At the start of each cycle:

• the support 51 for the container 1 is free, opposite the loading station 100;
• the first overlying plate 30 is lowered and then disengaged from the cylinder 53 actuating the device for synchronization of the container 1;
• once the container has been loaded and the vacuum produced for retention thereof on the buffer element 51;
• the plate 30 is raised so as to come into contact with the cylinder 53;
• the step involving rotation of the plate 40 is started so as to move each support assembly 50 by the predefined angular amount;
• during this step, the cylinder 53, which has come into contact with the plate 30 which is in the axially raised position, starts rotating causing rotation also of the shaft 52 which starts rotation of the wheel 61 which, rotating, keeps lowered, as a result of interference, the lever 63 against the thrusting action of the spring 65 until the notch 62 is located opposite the tooth 63a which, pushed by the spring 65, enters into the notch 62, locking the wheel 61 and thus producing the angular zero position of the container 1;
• once the angular displacement of the container 1 has terminated, the latter is securely in the correct angular position relative to its longitudinal axis and therefore angularly synchronized with the image position of the screen 211 and may commence the printing step, for actuation of which:
• the arm 12 is moved downwards translationwise, conveying with it the printing frame 210 together with the associated screen 211 and the doctor blade 230 which therefore keeps constant the relative distance from the said screen;
• the support 240 is moved in a tangential direction, causing the parallel displacement of the frame 210 and therefore the rack 213 integral therewith, the rack 213 being meshed with the pinion 214;
• the shaft 52 is rotated so as to cause the simultaneous rotation of the container 1 which, having been previously been synchronized angularly, then undegoes printing in the correct position envisaged for that printing station;
• successive raising of the plate 30 and successive rotation of the plate 40 which follows loading of a further container produces a further angular feeding movement of the container from one printing station to the next station for the application of a further image/colour.

[0026] During this feeding rotation, the angular zero position of the container 1 is restored by means of the device 60 so that the subsequent printing occurs in the correct angular side surface portion of the container 1.

[0027] In the loading stations 100 and unloading stations 200, automatic gripper means for inserting/removing the container 1 onto/from the buffer member 51 may also be provided, said gripper means being known per se and not described in detail; these gripper means are actuated by an associated device 70 (Fig. 8) comprising a rod 71, the top end of which is connected to a connecting rod 71a integral with a pin 72 for actuating the gripper towards/away from the support for the container 1 and the bottom end of which is connected by means of a safety device 80 to an actuating cam 73 in turn operated by a transmission of the main motor of the machine (not shown).

[0028] Said safety device 80 consists of a substantially U-shaped fork, in which the ends of the parallel arms 81a of the "U" have a seat 82 with rounded edges 82a into which a pin 74 connected to the ends of the said rod 71 is inserted.

[0029] In this way any obstacle, such as for example an accidental interruption in the working stroke due to breakage of the glass or an incorrect manoeuvre on the part of the operator which opposes the normal outward and return stroke of the rod 71, would cause the pin 74 to be pushed out of its seat 82, preventing the gripper from moving against the obstacle so as to avoid damage to the machine or physical damage to the operator.

[0030] Since the pin 74 is retained in the seat by the recall action of a pair of springs 84, with the next cycle of the cam 73, the said pin 74 is recalled into its seat and, if the obstacle has been removed, it is possible to resume the normal operating cycle, whereas, if the obstacle is still present, the pin is pushed out again.

[0031] It is therefore obvious how the machine according to the invention is able to solve the problems of the known art owing to the translatory movement of the screen support frame and doctor blade which, moving together, allow adjustment of their relative position during tooling-up of the machine, without the need for relative movements during operation of the said machine.

[0032] This results in a general simplification of the machine as a whole, speeding up considerably tooling-up thereof, making the machine suitable also for the production of small batches of containers.

[0033] Although, during the course of the description, reference has been made to hollow containers such as glasses and the like for which the support device is of the vacuum type, it is envisaged that the machine is also suitable for containers which do not have an open side, such as, for example, cans or full objects for which the holding means will be of the gripper type or the like.

Claims

1. Rotary machine for the silk-screen printing of substantially cylindrical objects (1), comprising a vertical axis of rotation (20), at least one arm (12) supporting at least one printing frame (210,211) and at least one doctor blade (230), means (50,51) for supporting the object (1), rotatable about their longitudinal axis, means (40,41) for rotational actuation, about the vertical axis (20), of the said means (50) for supporting the container (1), characterized in that said support arm (12) is movable translationwise, parallel to the vertical axis of rotation (20), towards/away from the object (1) to be printed.

2. Machine according to Claim 1, characterized in that said axis of rotation consists of a central fixed pillar (20) on which a sleeve (11) is coaxially mounted, said sleeve being designed to move translationwise on the said pillar from a higher position to a lower position.

3. Machine according to Claims 1 and 2, characterized in that said arms (12) supporting the printing frame and the doctor blade are integral with said sleeve (11).

4. Machine according to Claim 1, characterized in that said printing frame (210) is connected to means (240) for translation thereof in a direction tangential to the machine.

5. Machine according to Claim 1, characterized in that said at least one of the tangential sides of said frame (210) is provided with a rack (213).

6. Machine according to Claim 1, characterized in that said means (51) for supporting the object (1) are mounted on a shaft (52) arranged in a substantially radial direction with respect to the axis of rotation (20).

7. Machine according to Claim 6, characterized in that said support shaft (52) is provided with first means (53) and second means (213) for rotational actuation of the said shaft (52).

8. Machine according to Claim 6, characterized in that said shaft (52) is provided with means (60) for angular synchronization of the object (1) with respect to its longitudinal axis for locating the angular zero position of the said container.

9. Machine according to Claim 7, characterized in that said first means for rotational actuation of the shaft (52) consist of a substantially cylindrical element (53) made of friction material such as rubber or the like, designed to come into contact with the upper surface (30a) of a plate (30) stationary during the angular rotation of the support (51), produced by the associated operating means (40,41).

10. Machine according to Claim 9, characterized in that said cylindrical element (53) is associated with coaxial resilient friction elements (55), the reaction force of which may be adjusted by associated means (56).

11. Machine according to Claim 8, characterized in that said means (60) for automatically locating the zero position of the container 1 consist of a wheel (61) which is coaxially mounted on the shaft (52) and provided with a radial notch (62) designed to engage with a corresponding projection (63a) forming the free end of a lever (63), the other end of which is pivotably mounted on a support (64) fixed to the means (40,41) for rotational actuation of the support assembly about the vertical axis.

12. Machine according to Claim 11, characterized in that resilient means (65) which act so as to insert the tooth (63a) into the notch (62) of the wheel (61) are located between said actuating means (40) and the lever (63).

13. Machine according to Claim 7, characterized in that said second means (214) for rotational actuation of the support for the object (1) consist of a pinion (214) designed to engage with the rack (213) of the printing frame (210) during tangential translation of the latter.

14. Machine according to Claim 1, characterized in that it comprises devices (80) for ensuring safe control of the means for loading/unloading the object (1) to be printed.

15. Machine according to Claim 14, characterized in that said safety devices (80) consist of a substantially U-shaped fork, the ends of the parallel arms (81a) of which have a seat (82) with rounded edges (82a), into which a pin (74) is inserted, said pin being retained in the seat by the recall action of a pair of springs (84) and connected to the actuating rod (71) of said loading/unloading means.

Drawing