PROCESS AND RELATED APPARATUS FOR THE AUTOMATIC WASHING OF COMPONENTS OF PRINTING UNITS FOR ROTARY-DRUM PRINTING MACHINES

Abstract: Process for the automatic washing of the printing units of rotary-drum machines, kept in work position, consisting of the injection of pressurized water with preset intermittence unto the printing drum through the color feed tube, so as to force the water to mix with the residuals of color remaining within said color feed tube, within the drum and around the magnetic printing roller, then of the creation of a continuous depression inside the drum, so as to allow the continuous removal of the water-color mixture formed in said drum, the steps of intermittent injection of the washing water under pressure and of the start and end of the aspiration being controlled by an appropriately programmed microprocessor and provided with the printing machine rotating at a reduced speed with respect to the operating speed. Said process furthermore provides, to improve the effectiveness of the wash, the injection of pressurized air with preset intermittence so as to create alternate pressurized water/compressed air cycles such as to facilitate the elimination of all the residuals of color within the devices of the printing unit, said cycles of washing, air injection and aspiration being controlled by a microprocessor. Said process is produced by an automatic apparatus, constituted by a pump for the injection of pressurized water into the color feed tube, by a source of compressed air, and by an aspirating pump adapted to create a depression within the drum and to aspirate and draw out the mixture of water and residuals of color formed inside the drum, and by at least one tubular body connected to said aspirating pump, arranged inside the drum and having such holes so as to create a continuous depression inside said drum and thus allow, with the printing machine rotating at reduced speed and with the activation of the magnetic attraction field of the printing roller at the compressed air injection steps, the complete washing of all the components of the printing head, according to intervention steps programmed by means of a microprocessor.

Description: The present invention relates to a process for the automatic and simultaneous washing of all the components of the printing units used in rotary-drum fabric printing machines, keeping said components in their normal work position. The scope of the present invention furthermore includes an apparatus with automatic and programmed operating cycle, adapted to provide said washing process. As is known, rotary-drum printing machines for fabrics and the like, with one or more colors, use printing units each, whereof is substantially constituted by a screen drum, rotatable on the fabric guided on an endless conveyor belt or carpet, into which the color is introduced by means of a tubular collector-distributor; a roller in magnetizable metal, also arranged inside the drum, is pressed by magnetic attraction onto the fabric, so as to squeeze the color through the micro-holes of the drum, thus providing the printing of the fabric. Each printing unit is therefore constituted by a printing drum, by a color distribution tube and by a metallic roller. As is known, after each printing operation one must proceed to the washing of the components of the printing unit and of the carpet; currently the endless carpet is washed and cleaned by a wash unit supplied together with the machine itself, while the components of the various printing units are removed from the work table and are washed within adapted washing units placed proximate to the printing machine. In practice, the washing operations of the printing units consist of the disassembly of the drums, of the color distribution tubes and of the roller from their supports, in the placing thereof on adapted trolleys and then of their introduction into the washing units; at the end of the wash, the same components are either removed or repositioned on the printing table to allow the printing of another batch of fabric. Moreover, the cleaning cycle of the printing units also requires the cleaning of the color pump, which is washed automatically. All these operations, currently necessary for the washing of printing units, entail the use of personnel and require rather considerable times, as well as the consumption of considerable amounts of water, most of all for the washing of the color feed pump. Moreover, the operations of disassembly and reassembly of the screen drums, notoriously very delicate, may entail the damage and/or breakage of said screen, with obvious severe economic damage. Finally, the need to have washing units, transfer trolleys and various items of equipment entails considerable bulks proximate to the printing machine. Therefore,the main object of the present invention is to provide a process for the automatic and simultaneous washing of all the devices constituting the printing units of rotary-drum machines, without requiring their removal from their work position, as well as of the color feed pump, with obvious practical and economical advantages and with assurance of perfect cleaning of said components, including the micro-holes of the printing drums. Another object of the invention is to provide a process for the simultaneous washing of all the printing devices capable of being actuated even on printing units using spatular or flexible-blade doctoring devices, again with high reliability and with highly reduced running costs and washing times. The above objects,as well as other objects, which will become apparent hereinafter, are achieved by a process for the simultaneous and automatic washing of printing units, kept in work position on the machine, consisting, according to the present invention, of the injection, after the stopping of the printing and the removal of the printed fabric from the carpet, of pressurized water for preset successive times into the printing drum through the feed tubes and the color distribution tube, so as to force the water to mix with the residuals of color remaining within the color feed tube, within the drum, around the printing roller and in the color pump, then of the creation of a depression inside the printing drum simultaneously with, and preferably before, the injection of the washing water, so as to allow the aspiration and the removal of the water-color mixture from said printing drum, said steps of intermittent injection of pressurized water and of aspiration being controlled by an appropriately programmed microprocessor and provided with the printing machines rotating at a reduced speed with respect to the operating speed. More particularly, in order to improve the effectiveness of the washing of the various components of the printing unit and to reduce the washing times, the process according to the present invention provides the injection into said wash circuit of compressed air in an intermittent manner, so as to create alternate cycles of pressurized water and compressed air, such as to facilitate the removal of the residuals of color from the piping, from the color feed tube and from the drum, the magnetic attraction units of the printing roller being activated at each injection of compressed air, so as to allow said roller, pressed against the drum, to expel onto the underlying carpet the residuals of color present in the micro-holes of said drum, the residuals remaining on the carpet being then eliminated within the wash units of said carpet. The above described automatic washing process is in practice advantageously provided by means of an automatic-cycle apparatus, associable with the printing units of rotary-drum machines with one or more colors, comprising a screen drum, a color feed tube in its interior and a doctor in contact with the lower generatrix of said drum, substantially a roller with magnetic attraction, said apparatus providing, according to the present invention, quick-coupling means for the connection of the color feed tube, alternately, to the usual container of color and, by means of electric valves arranged upstream of said quick-coupling means, to a source of pressurized washing water and to a source of compressed air, with said color feed tube there being associated, inside the printing drum, at least one tubular body connected to a vacuum pump, substantially of the liquid-ring type, arranged in front of the printing roller, according to the direction of rotation of the screen drum, and downwardly provided with openings, such as to create a continuous depression inside said drum and thus aspirate and draw out the mixture formed by the washing water, sent into the drum through the color feed tube, and by the color remaining both in said color feed tube and in the drum, the complete washing cycle being controlled by a microprocessor previously programmed so as to send, at the end of the printing, pressurized washing water into the drum in an intermittent manner alternated with the injection of compressed air so as to create alternating cycles of water and air such as to perform the washing of all the components of the printing unit, with continuous elimination of the water-color mixture through said aspirating cylindrical body. More in particular, said operations of alternate injection of water and air are performed with the printing machine rotating at reduced speed and with the activation of the magnetic attraction unit of the printing roller only during the compressed air injection cycles. The invention is hereinafter described in further detail, according to a preferred embodiment, with reference to the accompanying drawings, given only by way of non-limitative example, wherein: figure 1 is a schematic view of a printing unit for machines with rotary drums and with magnetizable roller doctor, equipped with an automatic washing apparatus provided according to the present invention; figure 2 is an also schematic cross section view of figure 1, along the line II-II; and figure 3 is a schematic perspective view of an enlarged detail of the apparatus of figure 1. With reference to the above described figures, the apparatus for the automatic washing, directly in the machine, of the (one or more) printing unit(s) is provided and structured for specific use on printing machines with drums (or sweeps) rotating over a fabric-bearing carpet, closed in a loop. As shown in figure 1, the printing unit to be washed in place according to the invention is constituted by a screen drum 1, mounted rotating over an endless carpet 2 whereto is glued the fabric to be printed (not illustrated); the carpet is mounted taut between end rollers supported by a framework with two parallel shoulders 3. As is known, in these types of machine a color feed tube 4 is mounted inside the printing drum 2 coaxially or parallel to the longitudinal axis of said drum, and is closed at one end 4a and connected, at the opposite end 4b, to a color container 6 by means of tubes 5 and 5a. A pump 7 is interposed between the tubes 5-5a and sends the color from the container 6 inside the color feed tube 4; through a series of holes 8-8a etc. (figure 1-2), provided in the lower generatrix of the tube 4, the color enters the printing drum 1, guided during its fall by a wall 9 and by an inclined plane 10, 10a, so as to arrive in front of a printing roller 11 (figure 2), placed in contact with the lower generatrix of the drum 1 which is in turn in contact with the carpet 2. An electromagnet 12, placed under the carpet, exerting a constant attraction of the printing roller towards the carpet, forces the color to pass through the micro-holes of the printing drum thereby performing the printing of the fabric. In order to perform the automatic and simultaneous washing of all the components of the printing unit (that is to say, drum, color-carrying tube and printing roller) in a printing machine of this type, without their removal, a particular apparatus, as illustrated in the figures, is employed. This apparatus provides, according to the present invention, the installation of a pump 13, with related electric cutoff valve 15, adapted to inject pressurized water into the color feed tube 4 and thus inside the drum 1; said delivery tube 14 can be connected, by means of a mixing connection 16 inserted on said tube 14, to a source of compressed air (not illustrated) by means of an electric cutoff valve 17 and of a related one-way valve 18. The delivery tube 14 is connectable, by means of a quick coupling 19 or the like, to the tube 5a during the washing step, while during the printing operation said duct 5a is connected, in a known manner, to the color container 6. The apparatus furthermore provides a color feed tube 4 structured so as to perform the double function of distributor of the color inside the printing drum and, in the washing step, of conveyor of the washing water and of duct for the simultaneous expulsion from the drum of the mixture constituted by water and by the color remaining inside the tubes and in the drum itself. Said particular color feed tube is constituted by a tube 4, substantially of a known type, and by a tubular body 20, arranged parallel to the tube 4 so as to have its lower longitudinal side close to the lower inner surface of the printing drum 1. The tubular body 20 furthermore has its lower side in the shape of a corner, so as to have a cusp between the two angled sides 20a and 20b (figure 2) along the longitudinal extension whereof there being provided holes 21 (possibly distributed on two parallel and close rows, as indicated by 21a and 21b in figure 3), the function whereof is to allow the aspiration into said body 20 of the water-color mixture present in the drum 1, as will become apparent hereinafter. Said tubular body 20 is provided at the base of the wall 9, substantially vertical, and of the inclined wall 10-10a which constitutes its extension up to the height of the printing roller 11 and without contact therewith. In this manner, the aspirating body 20 is rigidly associated with the color feed tube 4 and is therefore supported by the same heads 22 which support the color feed tube. Moreover, the aspirating tube 20 is closed at its end 20c (figure 3), while at the opposite end it is connected, by means of a vertical duct 20d, to an external piping 23 which in turn is connected to an aspirating pump 24, of the liquid-ring type or the like. An electric cutoff valve 25 is interposed between the duct 23 and the pump 24. The aspirating pump 24 discharges the water-color mixture into a duct 26 from which it is drawn and sent to the water recovery devices. The operation of the water injection pump, of the air pump and of the aspirating pump is controlled, in a way known per se by a microprocessor 27 (figure 1) according to a program that will become apparent hereinafter. The washing apparatus described above operates in practice as described hereinafter. At the end of the printing operation, in order to perform the washing of the printing units which have been used, the machine is stopped and the fabric is removed from the carpet. The tube 5a, directed towards the color pump and towards the color feed tube 4, is diverted, by means of the quick-pitch coupling 19, onto the duct 14 connected to the pump 13 and to the electric valve 17. In this manner the delivery of color from the tank 6 to the printing drum is prevented. The printing machine is then started, making it rotate at reduced speed and with the magnetic attraction unit of the roller disabled; then the aspirating pump 24 and the pressurized water injection pump 13 are started substantially simultaneously. The water pump thus injects pressurized water into the circuit (color pump, color feed tube, drum and aspirating tube) intermittently and for preset durations of a few seconds (4-5 sec.). While the water flows in the circuit, mixing with the color remaining in the tubes and in the drum, the electric valve 17 is opened and injects air into the circuit at preset intervals, and the magnetic attraction unit of the printing roller is activated substantially simultaneously with each injection of compressed air. At each stopping of the compressed air, the magnetic attraction unit is also disabled, while the injection of pressurized water continues. These alternated cycles are repeated a few times for an overall time of 30-40 seconds. During said alternated cycles, the water mixes with the color remaining in the color pump, in the tubes, in the color feed tube, in the drum and around the printing roller, thus forming a mixture which is continuously aspirated and evacuated by the aspirating pump 24. The presence of the compressed air facilitates, by creating an emulsion with the washing water, the elimination of any residuals of color present in the discontinuities of the ducts, but most of all it contributes to the elimination from the micro-holes of the printing drum of the color retained therein, since the roller, pressed against the carpet during the compressed air injection cycles, expels the residual from the micro-holes directly onto the carpet which is then automatically washed in the washing units with which the printing machine is fitted. At the end of the above described alternated cycles, the washing of all the components of the printing head is completed and the printing of another batch of fabric can thus begin. Therefore, the apparatus according to the invention is capable of performing the thorough washing of the various devices which compose the printing head, in an automatic and simultaneous manner, by means of a single microprocessor appropriately programmed and without any intervention of the operator. Still according to the invention, the automatic and simultaneous washing of the printing devices as described above can be in practice be performed by intermittently injecting only pressurized water, possibly with non-foaming and non-corrosive detergent substances added, but in this case the washing times would be longer. In fact it has been observed that the provision of alternate cycles of pressurized water and compressed air allows to reduce the washing times and to make the cleaning action more effective. Moreover, the apparatus according to the invention can be adapted for the simultaneous washing of a plurality of printing units, for example three or four printing units, and can be provided so as to wash in the machine only those printing units which have been used or only those which are to be operated, cutting off any other units present in the machine. Finally, it is obvious that the invention as described above is in practice susceptible to structurally and functionally equivalent modifications and variations, without thereby abandoning the scope of the protection of the invention.

Claims: Process for the automatic and simultaneous washing of the printing units used on rotary-drum machines and kept in working position at the end of the printing, said process comprising the following steps: a) injection, after the stopping of the printing operations and the removal of the printed fabric from the carpet, of pressurized water for preset successive times into the printing drum through the feed piping and the color distribution tube, so as to force the water to mix with the residuals of color remaining within the color feed tube, inside the drum, around the printing roller and in the color pump; b) creation of a depression inside the printing drum simultaneously with, and preferably before, the sending of the washing water, so as to allow the aspiration and the removal of the water-color mixture from said printing drum. Process according to claim 1, characterized in that it furthermore comprises the following step: injection of compressed air, intermittently and alternately with respect to the injection of water, into said washing circuit. Apparatus for the automatic and simultaneous washing of the printing units of machines with rotating drums, kept in working position and constituted by a screen drum, a color feed tube in its interior and a magnetic-attraction roller doctor, said apparatus comprising quick-coupling means or the like for the coupling of the color feed tube, alternately, to the color container and, by means of electric valves, to a pressurized washing water injection pump and to a source of compressed air, with said color feed tube there being associated, inside the printing drum, at least one tubular body connected to a vacuum pump, substantially of the liquid-ring type, and arranged in front of the printing roller, according to the direction of rotation of the screen drum, and downwardly provided with openings, such as to create a continuous depression in said drum and thus aspirate and draw out the mixture of washing water, injected into the drum through the color feed tube, and of the color remaining both in said color feed tube and in the drum, the complete washing cycle being controlled by a microprocessor previously programmed so as to inject, at the end of the printing, pressurized washing water into the drum in an intermittent manner with respect to the injection of compressed air so as to create alternated water-air cycles such as to perform the washing of all the components of the printing unit, with continuous elimination of the water-color mixture through said cylindrical aspirating body. Apparatus according to claim 3, characterized in that it comprises means with automatic and programmed intervention adapted to cause the printing machine to rotate at reduced speed during the washing operation and to activate the magnetic attraction units of the printing roller only during the compressed air injection cycles. Apparatus according to claim 3, characterized in that an electric cutoff valve, alternately actuated by said microprocessor according to programmed intervention cycles, is interposed between said pressurized water injection pump, said aspirating pump and on the compressed air circuit. Apparatus according to claim 3, characterized in that said tubular body connected to said aspirating pump constitutes a monolithic structure with the color feed tube.

Inventors: FONTANA, FELICE
Applicants: REGGIANI MACCHINE S.P.A.
Application year: 1988
Main classification: B41F35
IPC codes: B41F35