Method and apparatus for decorating objects by means of screen printing

Abstract

A screen printing method and an apparatus are provided for printing on objects (12) which can be rolled against a printing screen (34). The method and apparatus provide the possibility of printing on the region (13) of the object to be printed upon over the entire periphery thereof, that is over 360, even when the length of the final overall print image in the peripheral direction of the object is longer than the spacings between the individual objects passing through the printing station. For that purpose, the peripheral surface to which the final overall print image is to be applied is subdivided into at least two portions (13a, b) which are displaced relative to each other in the peripheral direction of the object (12). Each of those portions is provided with at least one individual print (53), wherein a plurality of individual prints applied to the same portion (13a, b) can supplement each other to afford a colored partial print image.

Claims

1. A screen printing method for printing on an object (12) after production of the object by a production machine, the method comprising: providing the object produced by the production machine directly to a printing machine (10), the object having a region (13) configured to receive a print image, the print image being comprised of at least two partial print images, the region (13) being comprised of at least two portions (13a, 13b) displaced relative to each other in a peripheral direction of the object; transporting the object (12) by a transport element (22) continuously through at least two printing stations (30) of the printing machine (10), each printing station (30) comprising: a printing screen (34) having a stencil (38) corresponding to at least one individual print (53) to be produced, at least one squeegee (46) which is moveable in a transport direction (28) along the stencil during a printing operation synchronously with the respective object to be decorated in the at least two printing stations (30), and holders (24, 26) which respectively carry the objects rotatably about their longitudinal axes (50), the holders being mounted to the transport element (22) and being arranged at a spacing (44) from each other in the transport direction (28), the spacing being smaller than a spacing that would be required for peripheral printing around 360 on the object in one working operation; and printing one of the at least two partial print images upon a respective one of each of the at least two portions (13a, 13b) separately during a transport by rolling the objects against the printing screen (34), the speed of the transport element (22) being predetermined by an output of the production machine.

2. The method as set forth in claim 1, wherein more than one individual print (53) is applied to at least one of the at least two portions (13a, 13b) and all individual prints on the at least one portion supplement each other to provide one of the at least two partial print images.

3. The method as set forth in claim 2, wherein the individual prints (53) on the at least one portion (13a, 13b) supplement each other to afford the print image.

4. The method as set forth in claim 1, wherein the object (12) while rolling against the printing screen (34) over a length (40) of a stencil (38) rotates not more than 180 about a longitudinal axis (50) of the object.

5. The method as set forth in claim 1, wherein the at least one individual print (53) is applied between two markings (62) extending on the object parallel to a longitudinal axis of the object, the markings being displaced relative to each other in the peripheral direction due to manufacture of the object.

6. The method as set forth in claim 1, further comprising subjecting the object (12) to a homogeneous UV beam array by a UV drying station (32) after printing the individual print (53).

7. An apparatus for decorating objects (12) by screen printing, the apparatus being configured to be arranged in a production line downstream of a machine for producing the objects (12), the apparatus comprising: at least two printing stations (30), each printing station (30) comprising: a printing screen (34) having a stencil (38) corresponding to a print to be produced, at least one squeegee (46) which is moveable in a transport direction (28) along the stencil during a printing operation synchronously with the respective object to be decorated in the at least two printing stations, and holders (24, 26) which respectively carry the objects rotatably about their longitudinal axes (50), the holders being mounted to a transport element (22) which transports the objects (12) continuously through the at least two printing stations (30) in which printing is effected during a transport by rolling the objects against the printing screen (34), the speed of the transport element (22) being predetermined by an output of the machine for producing the objects (12), wherein the holders (24, 26) for carrying the objects (12) are arranged at a spacing (44) from each other in the transport direction (28), the spacing being smaller than a spacing that would be required for peripheral printing around 360 on the object in one working operation, wherein the objects (12) have a region configured to receive a print image, the print image being comprised of at least two partial print images, the region being comprised of at least two portions (13a, 13b) displaced relative to each other in a peripheral direction of the objects, and wherein at least one of the at least two printing stations (30) is associated with each of the portions (13a, 13b) to apply one of the at least two partial print images to the associated portion.

8. The apparatus as set forth in claim 7, wherein more than two of the printing stations (30) are associated with at least one of the at least two portions (13a, 13b).

9. The apparatus as set forth in claim 7, wherein a length of an individual print (53) applied in one of the at least two printing stations (30) in the peripheral direction of the object is not more than 180.

10. The apparatus as set forth in claim 9, wherein the individual print (53) is applied between two markings (62) extending on the object (12) parallel to a longitudinal axis (50) of the object, the markings being displaced relative to each other through about 180.

11. The apparatus as set forth in claim 8, wherein at least two individual prints (53) applied to at least one of the portions (13a, 13b) supplement each other to afford a partial print image.

12. The apparatus as set forth in claim 11, wherein at least two of the partial print images supplement each other to afford an overall print image.

13. The apparatus as set forth in claim 7, further comprising a drying station (32) arranged downstream of each of the at least two printing stations (30) and having a UV lamp (56) producing a radiation field.

14. The apparatus as set forth in claim 13, wherein the UV lamp (56) produces a radiation field having a radiation intensity which is substantially uniform in the transport direction (28) of the object (12) to be printed upon.

15. The apparatus as set forth in claim 14, wherein a length of the radiation field in the transport direction (28) corresponds to a length of a partial print image in the peripheral direction of the object (12).

16. The apparatus as set forth in claim 13, wherein a common transport system is associated with the at least one printing station (30) and the drying station (32) associated therewith.

17. An apparatus for decorating objects (12) by screen printing, the apparatus being configured to be arranged in a production line downstream of a machine for producing the objects (12), the apparatus comprising: at least two printing stations (30), each printing station (30) comprising: a printing screen (34) having a stencil (38) corresponding to a print to be produced; at least one squeegee (46) which is moveable during a printing operation synchronously with the respective object to be decorated in the at least two printing stations, each object having a print region which is configured to receive a print image and which extends around a periphery of the object, the print image being comprised of at least two partial print images, the print region being comprised of a first portion which extends around a portion of the periphery of the object and a second portion which extends around another portion of the periphery of the object, the first and second portions being displaced relative to each other in a peripheral direction of the objects; and holders (24, 26) which respectively carry the objects rotatably about their longitudinal axes (50), the holders being mounted to a transport element (22) which transports the objects (12) continuously through the at least two printing stations (30) in which printing is effected during a transport by rolling the objects against the printing screen (34), the speed of the transport element (22) being predetermined by an output of the machine for producing the objects (12); wherein the holders (24, 26) for carrying the objects (12) are arranged at a spacing (44) from each other in a transport direction (28), the spacing being smaller than a spacing that would be required for peripheral printing around 360 on the object in one working operation, and wherein at least one of the at least two printing stations (30) is associated with each of the portions of the print region, to apply one of the at least two partial print images to the associated portion, such that the at least two partial print images together form the print image.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) The foregoing summary, as well as the following detailed description of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there are shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. An embodiment of the invention is illustrated in the drawing in which:

(2) FIG. 1 is a highly diagrammatic plan view of a printing machine according to an embodiment of the invention having a plurality of treatment stations arranged in succession in the transport direction of the objects;

(3) FIG. 2 is a simplified plan view of a screen printing station and a drying station arranged downstream thereof in the object transport direction of the printing machine of FIG. 1;

(4) FIG. 3 is a perspective view of a bottle disposed in the printing station of the printing machine and supported by a holder; and

(5) FIG. 4 is a diagrammatic simplified associated plan view of the bottle and printing station of FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

(6) The printing machine 10 shown in FIG. 1 is arranged as part of a production line downstream of an apparatus (not shown in the drawing) for the manufacture of glass bottles 12 (see FIG. 3). The bottles which come from the production apparatus and of which the region 13 to be printed upon is substantially cylindrical are fed by way of a transport screw 14 in a standing condition to a transport wheel 18 rotating continuously in the direction of the arrow 16. The transport wheel 18 is provided at its periphery with recesses 20, which each receive a respective bottle to feed the bottles at fixed spacings to a third circulating transport element 22 which, for example, can be in the form of a chain or otherwise of suitable configuration. That chain is provided with holders for the objects to be printed upon, that is the bottles 12. The holders generally comprise two components, namely a first holder portion 24 (see FIG. 3) which receives the bottom end portion of the bottle and which is matched to the bottom-end diameter of the bottle and is provided with a suitable receiving means, and a second holder portion 26. The latter usually has a conical extension which engages into the neck opening of the bottle so that the bottle is fixed between the two holder portions rotatably about its longitudinal axis.

(7) The two holder portions 24, 26 are arranged displaceably relative to each other in the usual way in the longitudinal direction of the bottle. When the respective bottle to be taken over from the transport wheel 18 is reached, the two holder portions are moved apart so that, in the course of the transfer from the transport wheel 18 to the third transport element 22, the bottle is moved between the two holder portions, whereupon, as soon as the bottle and the two holder portions are axially aligned with each other, the holder portions are moved relative to each other, with a reduction in their mutual spacing, so that they grip and support the bottle, as shown in FIG. 3.

(8) The spacings between the recesses 20, which are provided on the transport wheel 18 and which receive the bottles, correspond to the spacings 44 (FIG. 2) between the holders 24, 26 carried by the chain 22 or the like. Those spacings are determined by the output of the apparatus manufacturing the bottles, that is by the number of bottles produced per unit of time.

(9) The treatment stations, which involve in particular printing stations 30 and drying stations 32, are arranged along the third transport element 22 in the transport direction 28.

(10) Besides the printing and drying stations it is also possible to provide further stations, for example a station upstream of the first printing station 30a in the transport direction 28, being a station in which the bottles are aligned in the peripheral direction, that is brought into register relationship, in such a way that the print image is applied in a given region of the periphery on the bottle. Additional treatment and handling operations of that kind and the associated stations are known, so that they are not discussed in detail here.

(11) FIG. 2 of the drawing shows one of the printing stations 30 arranged along the third transport element 22 and a drying station 32 arranged downstream thereof in the transport direction 28. The printing screen 34, which is arranged in the printing station 30 and which is carried by a frame 36, has a stencil 38 corresponding to the print to be applied. The length 40 of that stencil in the transport direction 28 is of such a dimension that it approximately corresponds to half the periphery, preferably somewhat less, of the bottle 12 in the region 13 thereof. If the length 40 of the stencil corresponds to half the periphery of the bottle 12, then the latter performs a rotational movement through 180 about its longitudinal axis while passing through the travel path determined by the length 40.

(12) FIG. 2 shows that the printing screen 34 including the frame 36 is approximately of the maximum length for the spacings 44 between the individual objects, because, with a bottle 12a disposed on half the travel path 40 between the beginning and the end of the printing stencil 38, the object 12b printed upon in the preceding printing operation is just leaving the region of the printing screen. That is, it is at the end of the printing screen that is downstream in the transport direction 28, while the object 12c to be printed upon in the following printing operation has just reached the end of the printing screen 34, that is the leading end in the transport direction 28. That means that the print image in the transport direction 28 or in the peripheral direction of the object 12 may not be larger than approximately half the periphery of the object, as otherwise the preceding object 12b would still be in the region of the printing stencil 38 of the printing screen 34, and the following object 12c would already be in that region.

(13) The actual printing screen 34 has three portions disposed in succession in the transport direction 28, namely a first portion 34a upstream of the stencil 38 in the transport direction 28, the stencil 38 and a second portion 34b downstream of the stencil 38 in the transport direction 28. The two portion 34a, 34b do not serve directly for transfer of the printing ink from the printing screen 34 on to the object. Rather, it is in the portion 34a that the ink intended for the respectively following printing operation is applied. The ink which is put on to the printing screen in the portion 34a is then distributed by the squeegee 46, which is respectively associated with that printing operation, over the printing screen and the stencil therein. The ink is moved in the direction towards the end of the printing screen that is the rear end in the transport direction 28, in such a way that, in the region of the stencil, the printing ink is transferred through the open meshes of the screen on to the surface of the object, that is to be printed upon. After the conclusion of that ink transfer, that is after the squeegee 46 is downstream of the stencil 38 in the transport direction 28, the squeegee is lifted off the printing screen in the second portion 34b thereof. The excess of printing ink that possibly remains in the portion 34b after each printing operation can then be removed from the printing screen in the usual way and, for example, fed to a storage container.

(14) By virtue of the elasticity of the printing screen 34 it is pressed against the respective article by the squeegee 46 after it has been placed thereon in the portion 34a and is held in contact with the object during the synchronous movement of the squeegee 46 and the object 12 along the stencil 38, that is at least over the travel path 40 thereof. After the squeegee has been lifted off the printing screen 34 in the portion 34b thereof the printed article is no longer in contact with the printing screen 34 so that the printed article can be moved without any problems out of the region of the printing station in a direction towards the drying station 32 downstream thereof.

(15) A corresponding procedure applies for introduction of the respectively following object 12c into the printing station. FIG. 2 shows that the article 12c, which rotates about its longitudinal axis 50 in the direction of the arrow 48, is initially not in contact with the printing screen, as the squeegee 46a which is associated with that article and which causes the contact to occur between the article and the printing screen is applied to the stencil 38 only shortly before the end thereof, that is the leading end in the transport direction 28, and thereby forms the contact between the article and the printing screen. At that point in time the article 12a, which is shown in FIG. 2 approximately at the center of the stencil, is already in the region of the second portion 34b, in which case the associated squeegee 46b is already lifted off the printing screen and there is thus no longer any contact between same and the article.

(16) The squeegees are parts of a system having a plurality of squeegees, in the specific case here three squeegees, which circulate along an approximately elliptical path 52, as can also be seen from FIG. 2. Such a squeegee system is known, so that no further discussion thereof is required.

(17) When using printing ink which hardens under the effect of UV rays, a drying station 32 is arranged downstream of the printing station, wherein the objects provided with at least one individual print 53 are advanced into the drying station 32 by the third transport element 22 in order to dry the respective last applied individual print.

(18) The above-mentioned rotational movement of the individual bottles 12 is produced by a rack 54 (see FIGS. 3 and 4), which extends along the third endless transport element 22 and the guide wheels 64, 65 thereof. Each holder for the bottles is provided at its first holder portion 24 with a gear 55 in engagement with the rack 54 in such a way that, when the bottles are transported through the treatment stations, the above-mentioned rotational movement in the direction of the arrow 48 is transmitted to the gear and at least the first holder portion 24 connected thereto by way of a shaft 51. It is apparent that the peripheral speed of the bottle, caused by that rotational movement, in the bottle region to be printed upon, is so selected that, having regard to all parameters, for example bottle diameter, transport speed, a possible difference in the diameter of the gear 55 and the bottle region to be printed upon, the bottle is rolled against the printing screen or its stencil as much as possible without slip.

(19) The printing station 30 and the respectively associated drying station 32 are arranged along the transport path for the bottles relative to each other in such a way that, on the one hand, the distance between the printing station and the drying station is as short as possible while, on the other hand, the bottles are optimally oriented in the peripheral direction on passing through the drying station. The drying station 32 is provided with a UV radiating device 56 and a reflector 58. The latter is in the form of a scattering reflector, so that a homogeneous beam array with a substantially uniform beam intensity is present over the length in the transport direction of the UV drying section 60. The length of the drying section 60 approximately corresponds to the length of the individual print 53 or the partial print image, but at any event should not be shorter than same.

(20) In the illustrated embodiment the spacing between the printing station 30 and the drying station 32 is so selected that, after leaving the region of the printing screen 34, that includes the stencil 38, the bottle still performs one and a half revolutions about the longitudinal axis before it then passes into the UV drying section 60, in such a way that, in the course of the following rotation, the entire last-applied individual print of the partial printing image is exposed to the beam array. In that case, the partial print image is generally somewhat shorter than 180 in the peripheral direction, so that the individual printing of the partial print image can be applied in the region between the two markings 62 (see FIG. 4) caused by manufacture of the bottle, on the region 13 to be printed upon, without extending on to those markings, which are parallel to the longitudinal axis of the bottle.

(21) The printing machine shown in FIG. 1 of the drawing is provided with five printing stations 30a-e and five drying stations 32a-e, wherein a drying station is arranged downstream of each printing station in the transport direction 28. In the first printing station 30a the region 13 of the bottle, to which the printing is to be applied, as also shown in FIGS. 2 and 4, is provided on the first peripheral portion 13a, which extends between the two markings 62 that are displaced relative to each other through 180 in the peripheral direction, with a first individual print 53a of a partial print image. The partial print image comprises three individual prints, and approximately the first half is applied in the position of the parts shown in FIG. 4 relative to each other. In the course of the further transport movement and the rotation linked thereto about the longitudinal axis of the bottle, that individual print is completed on a peripheral length of about 180, as is the case with the bottle 12band the bottles preceding itin FIG. 2. The bottle printed upon in that way is then passed through the first drying station 32a, which is arranged downstream of the printing station 30a and in which the individual print 53a which has just been applied is dried.

(22) In the course of the further continuous transport movement in the direction of the arrow 28, the bottle passes into the second printing station 30b in which a second individual print is applied in another color in the region of the first individual print 53a, which had been applied in the station 30a. The second individual print in the other color is dried in the second drying station 32b. Those processes are repeated to apply a third individual print of a third color in the region of the individual prints already applied in the first two printing stations, in the third printing station 30c, followed by drying in the third drying station 32c. That means that the partial print image, which is to be applied in the portion 13a and which occupies almost one half of the bottle periphery, is finished.

(23) The third drying station 32c is disposed in the region of the second guide and/or drive wheel 65, around which the endless chain 22 is guided to form a second transport run 22b extending parallel to the first transport run 22a. Arranged at the latter are the three printing stations 30a-c and the two drying stations 32a, b. That way of guiding the transport chain 22 permits the printing station to be of a compact structure in spite of the presence of a larger number of treatment stations.

(24) In the fourth printing station 30d, associated with the second transport run 22b, a first individual print of a second partial print image can then be applied to the second portion 13b of the region 13 to be printed upon, that is in opposite relationship to the first peripheral portion 13a, and then dried in the following drying station 32d. Then, in the last printing station 30e, an individual print which, for example, is of a different color can then be applied in the region of the individual print produced in the printing station 30d. As a result thereof, there is a final overall print image comprising two three-colored or two-colored partial print images, which in turn are composed of a plurality of one-colored individual print images.

(25) In the above-described embodiment it is assumed that the partial print image, which can comprise a plurality of individual prints, extends continuously over the peripheral portion 13a. As a departure therefrom, however, it is also possible for at least one of the partial print images to be discontinuous in the sense that it comprises at least two portions which are arranged in succession in the peripheral direction of the bottle and/or in the direction of the longitudinal axis of the object.

(26) In regard to the printing machine, other combinations and associations from those described hereinbefore are also possible. Thus, there can be more or fewer printing stations and drying stations, always depending on the respective requirements involved, that is the nature of the respective final overall print image.

(27) The spacings between the individual treatment stations should be as small as possible in order also to keep the size of the printing machine as small as possible, although the dimensions thereof naturally depend on the number of printing and drying stations and the other treatment stations. In general, it will be desirable for the spacings between the individual stations to be so selected that they represent an optimum between achieving a minimum possible spacing between two successive stations and the length of the transport path required to ensure the respectively required positioning of the object in the peripheral direction for treatment in the next station, with a given object diameter. That includes, for example, the requirement that the individual prints of a respective partial print image should be respectively correctly oriented relative to each other.

(28) After leaving the last treatment station the bottles 12 provided with the final overall print image are transferred from the third transport element 22 to a second transport wheel 70 which, like the first transport wheel 18, is also provided with edge recesses 20 for receiving the bottles, wherein in the transfer station the two holder portions 24, 26 of the holder carrying the bottle during transport thereof through the third transport element 22 are moved apart to release the respective object. The second transport wheel 70 then passes the bottles to a next following transport means 72 which feeds the bottles to a further treatment or use.

(29) It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.