FLEXIBLE STAMP APPARATUS FOR PRINTING THREE-DIMENSIONAL SPHERICAL OR CURVED OBJECTS

Abstract: Apparatus for printing three-dimensional objects, particularly objects having a substantially spherical shape, comprising a pad for printing by means of pad printing, wherein said pad has a silicon shape with a determined thickness, which is mounted on a hollow pad holder (1) made of an undeformable material which constitutes an isolated space together with said silicon shape (2), which is supplied with compressed air and which is connected to a pressure vessel by means of a main element (4) provided therefor through an opening (3), characterised in that the apparatus is arranged in open loop, wherein there is provided an additional separate aperture (8) for a separate inlet and outlet of air (3, resp. 8), with a pressure regulating unit (6) enabling to keep the pressure in the pad greater than or at a preset level P, wherein said pressure regulating unit (6) regulates the compressed air which enters the regulator through a supply main (7).

Description: Flexible stamp apparatus for printing three dimensional spherical or curved objects F ' ia of ftie invent fort This invention relates to a flexible stamp apparatus for printing three dimensional spherical and/or curved objects. ■Prior aft It is presentl known- to use .a hollow, half silicon spherical- shape for printing spherical objects, such as toy balls. This silicon shape has a thickness of about 2 cm and it is mounted on a hollow flexible stamp or pad holder. The silicon shape and the pad holder are designated hereafter as "the pad". The pad holder is made of ah undeformable material and has the shape of a drum. It forms- together with the siiicΘi* shape, an- ermetically osed space " having σnty one aperture as contact with the outside. At this sole aperture, a flexible tube having a sufficiently great diameter is connected to a pressure vessel. Said pressure vessel is not represented at scale. This pressure vessel heeds to have a volume which can contain 10 to 100 times the volume of the pad indeed. The pressure vessel is yet generally kept under a light over-pressure by means of a separate pressure regulator. This construction serves for keeping the pressure in the pad as constant as possible urin the-printing- cycle. Indeed, a pressure variation in the pa results in the dilatation or the retraction of the silicon part. Owing to this, the image on the silicon part becomes bigger or smaller with a bad printing quality on the printed spherical objects. The different times of the printing cycfe of the prior art show subsequently a rest position- wherein the pressure in the pad is eq ia. to the one in the pressure vessel. This pressure is designated hereafter with the reference P. ,- The pad " is moved from the rest positron to said object to be p ' ririted ϊri a relative movement according to arrow F and it bends over the object to he printed. The air in the pad is pressed to the pressure vessel through the flexible tube. However, despite the fact that the volume of the pressure vessel is several times greater than the content of the pad, this displacement of air volumes yet results in a slight increase of the pressure in the pad and vessel, which is designated hereafter by the reference P': After this, (he pad returns to its original state aocb ' rdThg td the direction of aπrow P, i.e. to the rest position. The air now moves back from the pressure vessel to the pad. The pressure in the system now becomes greater than P, which is referred to hereafter with P", but during this part of the cycle, the latter decreases again so as to become pressure P again. The above-mentioned known system is i dosed circuit wherein t aϊr, which is pressed out of the pad during the printing and inking stage; goes back to the pressure vessel. When the pad goes back to its original position, the air returns to the pad again from the pressure vessel. The great advantage of this system " consists in that despite the fact that the volume o the pressure vessel is sevefal times greater than the volume of the pad, there is still a small pressure variation, i.e. P, P\ P", which affects unfavourably the printing quality during the pad action on the objects to be printed. Alπϊ rif the irwentfnri This invention aims at remediating the above-mentioned drawback. Thus in this invention, a hollow pad as above is used, wherein instead of using a closed circuit, the pad is now incorporated in an open circuit according to the invention. Notwithstanding that the apparatus according to the invention has a lower air consumption, it yet- enables determining the pressure in the pad in a very accurate way at each time of the printing cycle. This is a very important parameter for printing at least partially spherical objects, particularly in connection with the printing quality thereof, the importance whereof increases as nowadays the requirements set for the printing quality are always becoming stronger: Further properties and j afticularities are defined in the appended claims. Some exemplary embodiments of the system according to the invention are described hereafter in the fight of the appended drawings. This invention also relate to a process for printing at least partially spherical and/or curved three dimensional objects. It is to be understood that a substantially differentiating element in this invention consists in that an open loop is used here and not a closed loop, wherein in addition the inlet side and the outlet . of the pad are clearly separated from each other. Thanks to this specific process according to the invention a remarkably higher printing quality is achieved. Brief descήDtioπ nf the drg lnafe Figure 1 is a schematic representation of a dosed pad system for printing spherical objects such as known from the prior art. Figures 2a to 2c are schematic representations of the various steps and states of the known system during a (complete) working cycle. Figure 3 is a schematic representation of an open system with a pad for printing spherical objects according to the invention. Figure 4 is the functional representation of the schematic view of the apparatus according " to the invention acc rdirig to Figure 3. Figures 4a to 4e represent in a schematic way the various steps and states of the apparatus according to the invention as represented in Figure 4 in its basic embodiment. Figure 5 is the representation 6f a first alternative of the apparatus with pad for printing spherieal objects according to the invention as represented schematically in a basic embodiment in figure 4. Figure 6 is the representation of a further alternative of the apparatus with pad for priritϊrig spHericSl objects acc rdirig to the invention. Figure 7 is the representation of a still further alternative of the apparatus with pad for printing spherical objects accordtng to the invention. πasmBH&h Figure 1- shews- an apparatus with a pad holder 1 and a so-called silicone shape 2 which are comparable to the present prior art. However, in this pad holder 1, there is provided in addition to a traditional aperture 3 an additional aperture 8, resulting in that the system presents separate apertures for tfϊe irifef 3 " o the air arid respectively the outlet 8 of the air through a conduit 4, resp. 4' provided therefor. A fast and accurate pressure regulating unit 6 which is incorporated in the inlet 4 causes the pressure in the pad 25 never to fall under a preset level established at pressure P. Therefor the pressure regulating unit " adjusts the compressed air which eRters the regulator 6 through a supply flexible tube 7 according to F. An accurate and fast over-pressure valve 9 is connected to the outlet - 8 of the pad holder 25 at the outlet hole 8. As soon as the pressure in the pad 25 becomes greater than the preset value of the pressure P, the όveϊ-pressure valve 9 win Sto off according to 6' to the outer air 40 through the outlet 10. Different embodiments are described hereinafter after the preliminary description of how the above described basic embodiment of the apparatus according to the invention works. Figure 4a shows the apparatus in rest position represented by A. There is a constant pressure P in the pad 25. Both the pressure regulating system 6 and the over-pressure valve 9 are in a closed position. Figure 4b shows how the pad 25 moves downwards according to arrow H arid how ii bends over the object 30 to be printed (state B). The atr in the pad 25 is pressed out of the pad according to G through the over-pressure valve 9 to the outside 40 according to the arrow direction G'. The pressure in the pad thus remains pressure P. Figure 4c shows the subsequent 'state C wherein the pad 25 goes upwardly a§iin according to— H, i-e to the rest position A. The over-pressure vafve 9 got closed and the pressure regulating unit 8 enters into action. The pressure regulating unit 6 will keep the pressure at pressure P by blowing the right quantities of air in the s pad 25. Despite the ffc that the system accbrdirig to the invention consumes more air, it enables determining very accurately the pressure in the pad 25 at each time of the printing cycle. This is a very important parameter for printing spherical objects 30, 0 particularly with respect to the printing quality thereof, the more that nowadays ever stronger printing quality requirements get imposed. Different embodiments and alternatives of the apparatus according to the invention are described hereinafter with Figures 6 to θ. The selection of a particular s embodiment depends on various factors, such as printing speed, cost of the system and desired accuracy of the printing. An alternative of the system with pad 25 with mechanical valves 6, 9 as described above brings a solution to the above-mentione requirement for finding accurate 0 and quick valves which are yet able to supply the required flow provided that an additional pilot valve 13 is incorporated in the system as shown on Figure 5. In this Figure, said " piTόt ' valve 13 ϊ§ connected directly dri the air supply rnarri T through a compressed air conduit 11. Further said pilot valve 13 is also directly 5 connected to the pad 25, particularly the pad holder 1, through a measuring tube 12. Said pilot valve is also directly connected to said pressure regulating unit 6 through a control pressure conduit 14. The latter alternative thu shows a pad 25 " with mechanical valves 6, 9 " arid a pilot 0 valve 13,- wherein this pHβt vafve- is fe through the compressed &ff conduit 11. Through the measuring tube 12 the pressure in the pad 25 is measured by the pilot vSfve 13 and the pressure regulating syste 6 is controlled through the control pressure conduit 14. Figure 6 srtows " a further alternative of the System which comprises a pad 25 with pressure sensors 19 and an electronical control unit 18. One or a plurality of pressure sensors 19 are incorporated in this alternative of the system at the pad 25, particularly the pad holder 1 , with a direct connection to an electronical control unit 18 through a conduit 17. S ' aJό electronical cbhtrol unit 18 is in turn iώrihected to an electronical valve 6 at the admission side on the one- and and with a over- pressure valve 9 of the same type as above on the other hand, in each case through a respective signal carrier 15 and 16. The electronical pressure sensor 19 measures continuously the right pressur of the pad 25, wherein this information is taken up in the sensor signal s that is delivered by said pressure sensor 19. This alternative of erribόdlrrieht shows at the input side between the pad 25 " arid the input 7 a simple pressure regulator 22 with a buffer vessel 20 streamdownwardly of the supplied compressed air, which is incorporated in the supply main 4, wherein a nonreturn valve 21 is provided at the inlet of the pad 25. At the output " . *'" of ssiid pad, there is provided the same outlet branch as in the above alternatives, i.e. with an over-pressure valve &. the sensor signal s Is transmitted to a electronic control Unit 18, such as, e.g. a P&, a micro-controller, a PG, an electrønicai regulator, and the- like... In case the measured pressure lies under the programmed value, an electronic valve 6 is opened by a signal Si along the conduit 15 in order to admit compressed air in the pad 25 through the supply main. In case the pressure in the pad 25 is greater than the value programmed in the control unit 18, another signal S 2 is sent to the electrical desaerating valve 9 through the conduit 16. Figure 8 shows a still further aitemtive of erhbodϊπϊeht which ' comprises a paid 25 with a- etrffer vessel and- a nonreturn valve. In this embodiment, the same- overpressure valve 9 is used as in the basic embodiment above as shown in Figures 5 and 3 to 4c. However, the inlet is supplied here through a simple pressure regulator 22 which builds up a preset pressure in said buffer vessel 20 in between the printing cycles. An nonreturn valve 21 prevents the air which is pressed out of the pad 25 during a printing stage from returning to the buffer vessel 20, since this would increase the pressure in the buffer vessel. The air pressed out of the pad leaves the system through the over-pressure valve 9 as above. The supply main 4 has a sufficient diameter so as to be able to supply the required air flow each time the pad goes up again away from the printed object 30 after an inking or printing cycle. (f is further yet possible to Use combinations ' of the embodiments described above, wherein it is to be understood that said combinations fall within the scope of protection of this application. The process for printing surfaces of ah object b means of the apparatus consists in first pressing the pad against an initially inked surface, in an open loop, whereupon the half spherical surface of the pad, which is in close contact with this inked surface, is flattened so that the figures to be printed are transferred όri the surface of the pad, in subsequently removing said pad from the original surface n order to enable the latter to recover its initial half spherical &ae again, and in subsequently pressing said pad against the three dimensional spherical and/or curved surface in such a way that said pad encompasses at least a spfiericaf or curved part of said object, arid in bringing the b ' ad Surface bearing the inked figure in contact with the surface of said object/thereby to transfer this inked figure on the desired spherical or curved part of the receiving object.

Claims: CLAIMS 1.- Apparatus for printing three dlrherisTόhal objects, particularly objects hSvlrig a substantially spherical shape, comprising a pad for printing by means of pad printing, wherein said pad has a silicon shape with a determined thickness, which iέ mounted on a hollow pad holder (1) rriade of an uhdθformabtέ material which constitutes an isolated space together with said silicon shape (2), which is supplied with compressed air and which is connected to a pressure vessel by means of a main element (4) provided therefor throug an opening (3), characterised in that the apparatus is arranged in open loop, wherein there is provided an additional separate aperture (8) for a separate inlet and outlet of air (3, resp. 8), with a pressure regulating Unit (6) enabling to keep the pressure in the pad greater than or at a preset level P, wherein said pressure regulating unit (6) regulates the compressed air which enters the regulator through a supply main (7). 2.- Apparatus according to the preceding claim, criaracterised in that there is provided an over-pressure valve (9) which is connected to the outlet (8) σf the pad holder (1) through a discharge conduit (4'). 3 Apparatus accordin to claim 1 or 2, characterised in that the pad is provided with a pilot valve (13) which is fed through a compressed air main (11), and with a measuring unit (12) for measuring the pressure in the pad and cbrifrolfihg the ' pressure regulating unit (6) through a control pressure cόridUft (14), which mutually connects the pilot valve (13) and the pressure regulating unit (6). 4.- Apparatus ' according to one of the preceding claims, cria acteriέed in that said pad (25) comprises pressure sensors (19) for measuring the pressure σf the pad (25), wherein the signal (s) delivered by said sensors (19) is transmitted to the electronical control unit (18). 5.- Apparatus according to brie of the preceding claimέ, characterised ift that said pad (25) comprises a buffer vessel (20) and a nonreturn valve (21), wherein the inlet is provided with a pressure regulator (22) which builds up a preset pressure between the printing cycles in said buffer vessel (20) aria wherein SSid nonreturn, valve (21) prevents the air which is pressed out of the pad from returning to the buffer vessel (20) during a printing stage, wherein subsequently the air pressed but from the pad leaves the apparatus through the over-pressure valve (9), and wherein the supply main (4) has a sufficient diameter for supplying the needed air flow each time the pad returns to its rest position (A) after an inking or prThtlrig cycle. 6.- Process " for printing sUrtaces of an object by means of an apparatus according to one of the preceding claims, characterised in that it consists in first pressing, the pad against an initially inked surface, in an open circuit, whereupon the half spherical surface of the pad which is in close contact with this inked surface, is flattened so that the figures to be printed are transferred on the surface of the-padϊ in- subsequently removing sai pad from the original surface in order to enable the latter to recover its initial half spherical άaae again, and in subsequently pressing said pad against the three dimensional spherical and/or curved surface in such a way that said pad encompasses at least a spherical or curved part of said object, and in bringing the pad surface bearing the inked figure into contact with the surface of said object (30) thereby to transfer this inked figure on the desired spherical or curved part of the receiving object.

Inventors: DE VOLDER LAURENT, DE VOLDER, LAURENT
Applicants: PRINTING INTERNATIONAL, VOLDER LAURENT DE, DE VOLDER, LAURENT
Application year: 2000
Main classification: B41F17
IPC codes: B41F17