Patent Publication Number: US-2002005350-A1

Title: Double line electrode unit for electro-coagulation printer and method of making it

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] This invention generally relates to electro-coagulation printers in which electrodes are selectively electrified to coagulate liquid ink to form images, which are transferred onto papers. Particularly, this invention relates to double line electrode units that contain double lines of electrodes, which are selectively electrified to coagulate liquid ink to form images on papers. In addition, this invention also relates to methods of making the double line electrode units.  
       [0003] 2. Description of the Related Art  
       [0004] Conventionally, there are provided electro-coagulation printers, each of which contains a rotation drum and a number of electrodes. An example of the electro-coagulation printer is disclosed by Japanese Patent No. 2,764,065. Herein, the circumferential surface of the rotation drum functions as a positive electrode against the negative electrodes, which are linearly arranged with prescribed intervals of distance therebetween along an axial direction of the rotation drum. The electrodes are aligned above the surface of the rotation drum and are spaced apart from the surface of the rotation drum by a prescribed gap. From an input side of the rotation drum, liquid ink is sprayed into the gap between the negative electrodes and the circumferential surface of the rotation drum, so that the gap is being filled with the liquid ink. Applying negative voltage to the negative electrodes which are adequately selected, the ink is partially coagulated and temporarily adhered to the circumferential surface of the rotation drum, so that a desired image is formed on the circumferential surface of the rotation drum. At an output side of the gap, remained non-coagulated ink is removed from the circumferential surface of the rotation drum. Thus, the image formed on the circumferential surface of the rotation drum is to be transferred onto a paper.  
       [0005] Due to the electricity being applied to the negative electrodes in the aforementioned electro-coagulation printer, coagulated ink is sometimes stuck to the negative electrodes and peripheries. If the negative electrodes are partially or entirely covered with the coagulated ink, there occurs electrification failure (or print failure) in the electro-coagulation printer. To solve the problem due to the electrification failure, engineers propose double line arrangement of electrodes, which is disclosed by U.S. Pat. No. 6,045,674, for example. That is, there are arranged two lines of negative electrodes, which are spaced apart from each other by a predetermined interval of distance in the rotating direction of the rotation drum. Herein, the two lines of negative electrodes are alternately electrified by certain intervals of time, so that each line is intermittently rested in electrification. Such double line arrangement of the electrodes is advantageous because ink almost stuck to the electrodes and peripheries by electrification can be washed away by newly supplied liquid ink during rest periods of the electrification. Thus, it is possible to continuously perform print operations for a long time without failures. However, if positional deviations exist in arrangement of the double lines of the electrodes in the axial direction and rotating direction of the rotation drum, there occurs unwanted non-uniformity in printing densities, which may deteriorate quality of prints. Therefore, it is necessary for the manufacturer to carefully arrange the electrodes in lines with a very high accuracy.  
       SUMMARY OF THE INVENTION  
       [0006] It is an object of the invention to provide a double line electrode unit for use in an electro-coagulation printer, which facilitates double line arrangement of electrodes with a high accuracy.  
       [0007] It is another object of the invention to provide a manufacturing method of the double line electrode unit in which units of electrodes are inspected to exclude failure units so that remained units of electrodes are arranged to adjoin with each other in formation of electrodes plates.  
       [0008] A double line electrode unit for use in an electro-coagulation printer contains a pair of electrode plates, negative electrodes and a prepreg (or an insulating layer). The negative electrodes are linearly arranged with prescribed intervals of distance (L) therebetween on surfaces of the electrode plates respectively and are embedded in insulating resin materials being solidified. The insulating resin materials contain fillers that are selected from among prescribed materials of boron nitride, aluminum nitride, alumina and silica. In addition, connectors are arranged on other surfaces of the electrode plates in connection with the negative electrodes respectively. The electrode plates are jointed together under heating and pressurized conditions by way of the prepreg such that the negative electrodes respectively arranged on the surfaces of the electrode plates face with each other by intervention of the prepreg, which has a prescribed thickness and is made by fabric material such as cloth made of glass fibers impregnated with unhardened resin.  
       [0009] In a manufacturing process of the double line electrode unit, after filling and solidifying the insulating resin materials on the negative electrodes of the electrode plates, inspection is performed such that electrification is made with respect to each of basic units of negative electrodes to locate an electrification failure area. Then, the complete electrode plate is made by jointing together a prescribed number of the basic units of negative electrodes excluding a basic unit of negative electrodes corresponding to the electrification failure area, which is cut and removed. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0010] These and other objects, aspects and embodiment of the present invention will be described in more detail with reference to the following drawing figures, of which:  
     [0011]FIG. 1 is a side view partly in section diagrammatically showing selected parts of an electro-coagulation printer that contains a double line electrode unit in accordance with a preferred embodiment of the invention;  
     [0012]FIG. 2 is an enlarged sectional view showing an internal construction of the double line electrode unit;  
     [0013]FIG. 3 is a cross sectional view taken along a line  3 - 3  in FIG. 2;  
     [0014]FIG. 4 is an enlarged view showing supply of liquid ink into a gap between a print head and a circumferential surface of a rotation drum in the electro-coagulation printer shown in FIG. 1;  
     [0015]FIG. 5 is a side view partly in section showing an electrode formation step in a manufacturing process of the double line electrode unit;  
     [0016]FIG. 6 is a side view partly in section showing a resin filling step in the manufacturing process of the double line electrode unit;  
     [0017]FIG. 7 diagrammatically shows a linear arrangement of negative electrodes on a substrate to locate an electrification failure area in an inspection step of the manufacturing process of the double line electrode unit;  
     [0018]FIG. 8 diagrammatically shows an arrangement of the negative electrodes from which a basic unit of electrodes corresponding to the electrification failure area is excluded by a cut and removal step of the manufacturing process of the double line electrode unit;  
     [0019]FIG. 9 is a cross sectional view showing an arrangement of the negative electrodes on a surface plate;  
     [0020]FIG. 10 is a cross sectional view showing the negative electrodes that are unified together in a unification step of the manufacturing process of the double line electrode unit;  
     [0021]FIG. 11 is a view partly in section showing an electrode plate having negative electrodes and connected with connectors in a connector connection step of the manufacturing process of the double line electrode unit; and  
     [0022]FIG. 12 is a view partly in section showing electrode plates both having negative electrodes and connectors which are jointed together in a joint step of the manufacturing process of the double line electrode unit. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
     [0023] This invention will be described in further detail by way of examples with reference to the accompanying drawings.  
     [0024]FIG. 1 diagrammatically shows construction of selected parts of an electro-coagulation printer, which contains a rotation drum  10 , a print head  20 , a coating device  30 , an ink spray device  40 , an electrolytic solution supply device  50 , a removal device  60 , a transfer device  70  and a cleaning device  80 .  
     [0025] The rotation drum  10  has a circumferential surface, which is grounded to secure a function as an positive electrode  11 . The rotation drum  10  is supported by a frame (not shown) and is driven by a drive device (not shown) to rotate in a counterclockwise direction in FIG. 1. The print head  20  is elongated in a width direction along an axial direction of the rotation drum  10 . That is, the print head  20  is arranged opposite to the circumferential surface of the rotation drum  10  and contains a double line electrode unit  21  and its holder  22 .  
     [0026]FIGS. 2 and 3 diagrammatically show detailed construction of the double line electrode unit  21 , which contains a pair of electrode plates  211 ,  212 , a prepreg  213  and a pair of fixed frames  214 ,  215  which are made by the FRP material. Herein, the prepreg  213  functions as a joint member between the electrode plates  211  and  212 . The electrode plates  211 ,  212  contain substrates  211   a,    212   a,  negative electrodes  211   b,    212   b  and connectors  211   c,    212   c  respectively. Herein, the negative electrodes are arranged on one side of the substrate with predetermined intervals of distance ‘L’ therebetween. Each of the negative electrodes has approximately a square shape whose side is approximately 30 μm, so that the interval of distance L is set to approximately 60 μm to realize 400 dpi in printing. In addition, the connectors are arranged on another side of the substrate in connection with the negative electrodes. Spaces formed between the negative electrodes  211   b,    212   b  are filled with insulating resin materials  211   d,    212   d,  which contain fillers and are solidified. As the filler, it is necessary to select from among the prescribed materials that improve corrosion resistance and thermal conductivity. For example, it is preferable to select from among the materials of boron nitride, aluminum nitride, alumina and silica.  
     [0027] The holder  22  is made by insulating resin material and has a lengthy shape that extends along the axial direction of the rotation drum  10 . In addition, the holder  22  is assembled together with the frame (not shown) and is connected with a printed circuit board (not show). Circuit components such as a data processing circuit and a drive circuit are fabricated on the printed circuit board. Herein, the data processing circuit processes print data representing print images output from an external print data output device  23 , thus producing negative voltage pulse string signals in response to the print data. Based on the negative voltage pulse string signals, the drive circuit drives the negative electrodes  211   b,    212   b  of the double line electrode unit  21 . Further, the printed circuit board also contains a connector (or connectors, not shown) that is electrically connected with the connectors  211   c,    212   c  of the double line electrode unit  21  via a flat cable or flexible printed wiring.  
     [0028] The coating device  30  is arranged in an input side of the ink spray device  40  on the rotation drum  10 . The coating device  30  coats the circumferential surface of the rotation drum  10  with olefin materials containing metallic oxide, films of which are continuously formed on the circumferential surface of the rotation drum  10 . FIG. 4 diagrammatically shows supply of liquid ink A on the circumferential surface of the rotation drum  10  from its input side. That is, the ink spray device  40  sprays the liquid ink A into the gap between tip edges of the negative electrodes  211   b,    212   b  and the circumferential surface of the rotation drum  10 . Thus, the gap is entirely filled with the liquid ink A.  
     [0029] The electrolytic solution supply device  50  has an outlet opening  51 , which is directed to the circumferential surface of the rotation drum  10 . The outlet opening  51  of the electrolytic solution supply device  50  is carefully placed at a prescribed position in proximity to the double line electrode unit  21  and in connection with the ink spray device  40 , wherein it is spaced apart from the double line electrode unit  21  by a prescribed short distance. The outlet opening  51  outputs electrolytic solution C to avoid sticking of the ink on tip edges of the negative electrodes  211   b,    212   b,  wherein the electrolytic solution C do not substantially contain coagulating components due to electrification. The electrolytic solution C is stored in a tank  52  and is pumped up using a pump  53 , so that the electrolytic solution C is supplied to the outlet opening  51 . One end of a communication pipe (or communication path)  54  communicates with the outlet opening  51 , while another end is connected with the tank  52  by way of a control valve  55 , which controls a flow of the electrolytic solution C to be supplied to the outlet opening  51 . That is, the communication pipe  54  returns an excessive amount of the electrolytic solution C to the tank  52 .  
     [0030] The removal device  60  is arranged apart from the print head  20  along the circumferential surface of the rotation drum  10  in its output side. The removal device  60  has a flexible rubber spatula  61  that removes remained non-coagulated ink from the circumferential surface of the rotation drum  10 . The removed ink can be reused for next cycles of printing. The transfer device  70  is arranged apart from the removal device  60  along the circumferential surface of the rotation drum  10  in its output side. The transfer device  70  transfers desired images of coagulated ink, which is adhered to the circumferential surface of the rotation drum  10 , to a paper (or print material) B. That is, the transfer device  70  has a pressure roller  71  that rotates in a clockwise direction in FIG. 1 and presses the paper B against the circumferential surface of the rotation drum  10 . The cleaning device  80  is further arranged apart from the transfer device  70  along the circumferential surface of the rotation drum  10 . The cleaning device  80  continuously cleans the circumferential surface of the rotation drum  10 .  
     [0031] In the aforementioned electro-coagulation printer shown in FIG. 1, the coating device  30  coats the circumferential surface of the rotation drum  10 , which rotates in the counterclockwise direction, with the olefin material containing metallic oxide. In addition, the ink spray device  40  sprays liquid ink A into the gap between the print head  20  and the circumferential surface of the rotation drum  10 , so that the gap is filled with the liquid ink A. Under the aforementioned condition, negative voltage pulses are applied to the negative electrodes  211   b,    212   b  in response to print data output from the print data output device  23 , so that coagulated ink Al (see FIG. 4) is formed in response to the negative voltage pulses on the circumferential surface of the circumferential surface of the rotation drum  10 , which functions as the positive electrode  11  against the negative electrodes due to electrification. Accurately speaking, the coagulated ink A 1  is formed on the film of the olefin material containing metallic oxide, which is formed on the circumferential surface of the rotation drum  10  by the coating device  30 . In this case, the tip edges of the negative electrodes  211   b,    212   b  are entirely covered with the electrolytic solution C supplied from the electrolytic solution supply device  50 . Hence, there is substantially no possibility in that the liquid ink A is coagulated on the tip edges of the negative electrodes  211   b,    212   b.    
     [0032] The removal device  60  removes the non-coagulated ink A, excluding the coagulated ink A 1 , from the circumferential surface of the rotation drum  10 . Then, the transfer device  70  transfers desired images, which are formed by coagulation of the ink in response to the print data, from the circumferential surface of the rotation drum  10  to the paper B. Thereafter, the cleaning device  80  cleans the circumferential surface of the rotation drum  10 . Thus, the aforementioned operations are repeated on the cleaned circumferential surface of the rotation drum  10 . As a result, it is possible to print images successively on the papers.  
     [0033] In printing, the present embodiment alternately uses double lines of the negative electrodes  211   b,    212   b,  which are changed over by prescribed units of printing. That is, applying negative voltage pulses (or electrification) is changed over between the negative electrodes  211   b  and  212   b  by a prescribed number of times of printing, e.g., one-hundred times or two-hundred times. Namely, the double lines of the negative electrodes  211   b,    212   b  are alternately rested in electrification during printing. During electrification rest periods, it is possible to wash away ink that is almost adhered to the negative electrodes and peripheries due to electrification. As compared with printing using a single line of electrodes, it is possible to double the period for washing the electrodes. This brings reduction of frequency of works for removing the coagulated ink on the negative electrodes and peripheries by removal tools such as rotation brushes. Hence, it is possible to perform long-time printing or repetition of printing. In short, it is possible to improve printing efficiencies of the electro-coagulation printers by using double line electrode units.  
     [0034] Next, a description will be given with respect to the manufacturing process of the double line electrode unit  21  shown in FIGS. 2 and 3 with reference to FIGS.  5  to  12 . Namely, FIG. 5 shows an electrode formation step, FIG. 6 shows a resin filling step, FIG. 7 shows an inspection step, FIG. 8 shows a cut and removal step, FIGS. 9 and 10 show a unification step, FIG. 11 shows a connector connection step, and FIG. 12 shows a joint step.  
     [0035] In the electrode formation step of FIG. 5, a number of negative electrodes  211   b  (or  212   b ) are formed on one surface of the substrate  211   a  (or  212   a ) and are arranged apart from each other by the prescribed intervals of distance L therebetween. This step is implemented by the photolithography technique and plating method, which are used in the super fine structure processing technology such as the semiconductor manufacturing technology. In the resin filling step of FIG. 6 that is performed after the electrode formation step of FIG. 5, spaces between the negative electrodes  211   b  (or  212   b ) are filled with the insulating resin materials  211   d  (or  212   d ), which are solidified. If the resin is supplied and solidified on the negative electrodes  211   b  (or  212   b ) as well, it is necessary to produce a satisfactory precision by controlling thickness of the resin.  
     [0036] In the inspection step of FIG. 7, electrification is performed on the negative electrodes  211   b  (or  212   b ) by basic units of inspection respectively. Through the electrification, each of the negative electrodes  211   b  (or  212   b ) is examined whether it is in a conducting state or a short-circuited state. Thus, it is possible to detect electrification failure with respect to each of the basic units of the negative electrodes. That is, an electrification failure area (see x mark in FIG. 7) is detected on a certain basic unit of the negative electrodes by the inspection step of FIG. 7. Then, the cut and removal step of FIG. 8 is effected to cut and remove the detected basic unit of the negative electrodes containing the electrification failure area. For example, the inspection step locates the basic unit of the negative electrodes containing the electrification failure location as an area whose width S is greater than L and which is sandwiched between dashed lines in FIG. 7. That is, the inspection step locates the basic unit of the negative electrodes corresponding to all electrodes connected with one connector  211   c  (or  212   c ), which are cut and removed by the cut and removal step of FIG. 8. In addition, approximately halves of the insulating resin materials  211   d  (or  212   d ) on the left and right sides of the basic unit of negative electrodes, which are cut and removed, are also removed together with their corresponding portions of the substrate  211   a  (or  212   a ).  
     [0037] In the unification step of FIGS. 9 and 10, the negative electrodes  211   b  (or  212   b ) are arranged using a fixed frame  214  (or  215 ) on a surface plate  100 . Herein, a prescribed number of basic units of the negative electrodes are aligned and jointed together on the surface plate  100 , so that an electrode plate  211  (or  212 ) is formed to realize linear arrangement of the negative electrodes whose overall length reaches seventeen inches, for example. Actually, eight to ten sheets of electrode plate elements (see FIG. 7) are linearly aligned and jointed together on the surface plate  100 . In this case, alignment and joint operation are performed by confirming that an interval of distance between two negative electrodes  211   b  (or  212   b ), which correspond to a joint area encompassed by a circle in FIG. 9, is accurately adjusted to the prescribed interval of distance L.  
     [0038] In the connector connection step of FIG. 11, the connectors  211   c  (or  212   c ) for transmitting negative voltage pulses to the negative electrodes  211   b  (or  212   b ) are fabricated on another surface of the substrate  211   a  (or  212   a ). The connector connection step of FIG. 11 can be performed after the resin filling step of FIG. 6. In the joint step of FIG. 12, a pair of the electrode plates  211 ,  212  are jointed together by way of the prepreg  213  by heating and pressurizing adhesion such that the double lines of the electrodes  211   b ,  212   b  are arranged opposite to each other. Herein, the prepreg  213  is made by cloth material of glass fibers that is impregnated with unhardened resin. To increase rigidity of the prepreg, it is possible to use other base materials that are impregnated with unhardened resin. The joint step securely determines the prescribed interval of distance between the double lines of the negative electrodes  211   b ,  212   b  which are arranged opposite to each other.  
     [0039] As described above, the double line electrode unit  21  is manufactured such that the electrode plates  211 ,  212 , in which the negative electrodes  211   b ,  212   b  are linearly arranged opposite to each other on one sides of the substrates  211   a,    212   a,  are jointed together by using the prepreg  213 . Thus, it is possible to consolidate the electrode plates  211 ,  212  via the prepreg  213 . In the electrode plate  211  (or  212 ), the negative electrodes  211   b  (or  212   b ), which are linearly arranged apart from each other by the prescribed intervals of distance L therebetween, are enclosed in the insulating resin material  211   d  (or  212   d ) being solidified in advance. Due to solidified enclosure, it is possible to accurately retain the prescribed intervals of distance between the negative electrodes  211   b  (or  212   b ) in their alignment direction within the insulating resin material  211   d  (or  212   d ). In addition, it is possible to increase compressive rigidity of the negative electrodes  211   b  (or  212   b ) due to enclosure of the insulating resin material  211   d  (or  212   d ) in a thickness direction of the electrode plate  211  (or  212 ). In other words, it is possible to secure sufficient strength of the negative electrodes against the external force. Hence, even if pressure is applied in the thickness direction to the electrode plates  211 ,  212  that are jointed together via the prepreg  213 , it is possible to accurately retain the prescribed intervals of distance between the negative electrodes  211   b ,  212   b  in their alignment directions. In addition, the negative electrodes  211   b ,  212   b  would not be damaged in the operation for cutting and removing the electrification failure area(s) as well as in the alignment and joint operations. As a result, it is possible to manufacture without troubles, the double line electrode unit  21  in which double lines of the negative electrodes  211   b ,  212   b  are arranged opposite to each other with a high accuracy.  
     [0040] The manufacturing process of the double line electrode unit  21  is characterized by provision of the electrode formation step and resin filling step. Under the heating and pressurized conditions in the joint step, the unhardened resin of the prepreg  213  is softened and may be deformed, however, the base material of the prepreg  213  has a relatively high compressive rigidity. Applying pressure whose value is above a prescribed value, it is possible to control the shape of the prepreg  213  that has the prescribed thickness. In the electrode plates  211 ,  212 , the negative electrodes  211   b ,  212   b  are embedded in the insulating resin materials  211   d,    212   d  are embedded in the insulating resin materials  211   d,    212   d  being solidified, so it is possible to accurately retain the prescribed intervals of distance among the negative electrodes  211   b ,  212   b  in their alignment directions. By appropriately controlling prescribed parameters such as the thickness of the base material of the prepreg  213 , resin characteristics, pressurizing timing and heating temperature, it is possible to manufacture the double line electrode unit  21  such that prescribed intervals of distance are accurately retained in linear arrangement of the negative electrodes and the prescribed interval of distance (or gap) is accurately retained between the negative electrodes  211  and  212 .  
     [0041] The manufacturing process of the double line electrode unit  21  is characterized by providing the inspection step, cut and removal step and unification step between the aforementioned resin filling step and joint step. As compared with the post-manufacture inspection in which after the joint step (or after completion of manufacture), the negative electrodes are examined by electrification to remove defective ones, it is possible to reduce a waste of resources, and it is possible to reduce wastefull operations in manufacture of the double line electrode units. As a result, it is possible to reduce manufacturing cost of products. During the inspection step, cut and removal step and the unification step, the negative electrodes are enclosed in the insulating resin materials being solidified. Hence, there are no troubles due to damaging of the negative electrodes.  
     [0042] The present embodiment describes such that the double line electrode unit  21  is applied to the print head  20  used in the electro-coagulation printer having the electrolytic solution supply device  50 . Of course, it is possible to apply the double line electrode unit to the print head used in the electro-coagulation printer that does not have the electrolytic solution supply device.  
     [0043] The present embodiment describes the double line electrode unit  21  such that the substrates  211   a ,  212   a  respectively have the connectors  211   c,    212   c.  So, it is necessary to perform electrification by switching the connectors or by alternately changing over the connectors. Instead, it is possible to introduce a signal switch device that switches over signals, being supplied to the connectors, by predetermined periods of time. In this case, the signal switch device is incorporated as a part of the double line electrode unit.  
     [0044] As this invention may be embodied in several forms without departing from the spirit of essential characteristics thereof, the present embodiment is therefore illustrative and not restrictive, since the scope of the invention is defined by the appended claims rather than by the description preceding them, and all changes that fall within metes and bounds of the claims, or equivalence of such metes and bounds are therefore intended to be embraced by the claims.