Automatic printing device

Abstract: An automatic printing device according to this invention comprises a spray gun head (223) ejecting ink jets of e.g. three primitive colors and black, a CPU (1) processing image signals inputted from a television camera, (VM) a mechanism (fig. 4) for driving 3-dimensionally the spray gun head (223), etc., and can print automatically an enlarged color image consisting of a number of pixels directly on a wall surface, etc. by the fact that the mechanism drives the spray gun head (223) according to signals coming from this CPU (1).

Description: This invention relates to an automatic printing device capable of printing a color image directly on a wall surface, etc., while enlarging an original image. In one known type of device the image is adhered to the wall after having once printed on a sheet of paper. In this case, when a large image is divided into a number of small images, which are printed by means of a color pen device of ink jet system and since ejection of the ink is stopped for every small image, the small images gathered together are lacking in unity of tone. Such a color enlarging printing device, as indicated in Fig. 11 is developed as a device capable of color-printing a large image at once. In the Figure, A₁ is a printing and recording portion and A₂ is an image inputting and editing portion. The printing and recording portion A₁ consists of a rotating drum G, a motor H, a guide rail I, a micro-spray gun head J, etc., and the image inputting and editing portion A₂ consists of a camera A, a cylinder for original image B, an oscilloscope for monitoring C, a control panel D, etc. In the printing and recording portion A₁ the rotating drum G is supported rotatably by the motor H and the micro-spray-gun head J is disposed movably along the guide rail I in the direction of the length of the drum G. The spray gun head J is so constructed that compressed air is injected therein so as to eject ink and the amount of ejected ink and therefore the light and shade in the image are adjusted by regulating the flow rate of the air, which is in turn regulated by an actuator. The main scanning of the printed image is effected by the rotation of the drum G and the auxiliary scanning is effected by the movement of the spray gun head J. The spray gun is displaced from left to right by means of a belt, etc. by utilizing the rotation of the drum G by the motor H. On the drum G is disposed a rotary encoder and depth signals for each color are read out from a buffer memory in synchronism with signals read out from this encoder. The actuator is driven, responding to these depth signals, so as to control the flow rate of the air injected into the spray gun head J. On the other hand, in the image inputting and editing portion A₂ the cylinder B is mounted rotatably coaxially to the drum G and when an original image is mounted thereon and it is rotated, scanning of the original image with a narrow light beam begins, starting from a determined point on the original image. Light reflected by the original image changes without interruption due to the rotation thereof. The reflected light, whose intensity varies according to the original image with a high fidelity, is projected into the camera A, where it is decomposed into the three primary colors and electric signals corresponding to the respective colors are generated. These electric signals are given to the buffer memory stated above and in this way ink, whose amount varies according to the intensity of these signals, is projected to the sheet of paper mounted on the drum G by the spray gun head J so that a color image is printed in an enlarged scale of the original image. One of the most serious problematical points of the prior art enlarged image printing device described above is that the enlarged image can be printed only on a sheet of paper, but it is not possible to print it directly on a wall surface, etc., of a building. Further, since it uses a large rotating drum, which should be rotated with a high mechanical precision, and therefore the device for controlling the rotation of the large drum with a high precision is complicated, which makes it very expensive, practical usability thereof is bad and this it is not widely used. It is also known from US-A-4296317 and EP-A-0170137 to provide an automatic printing device comprising control signal means for generating 2- or 3-dimensional driving signals and ink ejection amount control signals for driving a spray gun unit, corresponding to the position and the color of each pixel in an original image, supporting means for supporting said spray gun unit 2- or 3-dimensionally movable with respect to an area, on which the image is to be printed, such as a wall surface, etc., and driving means for driving said spray gun unit and at the same time projecting an ink jet from said spray gun unit to said area in response to said control signals. A disadvantage of such devices is that in order to clean the spray gun unit to remove clogging by ink the unit must descend from the printing site to be accessed thereby interrupting the printing work. The spray gun head is driven successively to each position on the wall surface corresponding to each pixel in the original image and an amount of color ink corresponding to the color of each pixel and the depth thereof is projected so as to print directly a color image on the wall surface, enlarging the original image. According to the present invention said ink spray gun unit includes an air jet outlet along an outer circumference of an ink jet nozzle, an ink inlet in an ink chamber communicating with said ink jet nozzle and an air inlet in an air chamber communicating with said air jet outlet, and ink control means for controlling the quantity of ink supplied to said ink jet nozzle from said ink chamber and wherein a compressed air supply means and an ink solvent supply means are connected to said air inlet so as to be selectively operable through electromagnetic valve means operable to connect either one of the compressed air supply means and the ink solvent supply means with said air inlet. The nozzle can thereby be automatically and remotely cleaned by carrying out a cleaning operation in which the nozzle is washed with solvent. The nozzle cleaning operation thereby requires less labour and the printing work can be carried out more efficiently with less interruption. Preferred embodiments will now be described with reference to the drawings of which:- Fig. 1 is a block diagram illustrating the construction of an automatic printing device, which is an embodiment of this invention; Fig. 2 is a scheme illustrating the construction of the device indicated in Fig. 1; Fig. 3 is a perspective view of the device indicated in Fig. 1; Fig. 4 is a perspective view of a frame used for realizing this invention; Fig. 5 is an exploded perspective view of the frame indicated in Fig. 4; Fig. 6 is a side view of the frame indicated in Fig. 4; Fig. 7 is a plan view of an X - Y axis driving mechanism mounted on the frame indicated in Fig. 4; Fig. 8 is a perspective view of a part of the driving mechanism in an enlarged scale; Fig. 9 is a schematized side view of a Z axis driving mechanism; Fig. 10 is a plan view of a key board used for realizing this invention; Fig. 11 is a perspective view of a prior art color enlarged image printing device; Fig. 12 is a side view of another example of the Z axis driving mechanism for a spray gun unit; Fig. 13 is a perspective view of a part of the driving mechanism indicated in Fig. 12; Fig. 14 is a plan view of a part of the driving mechanism indicated in Fig. 12; Figs. 15 and 16 are schemes for explaining the operation of the driving mechanism indicated in Fig. 12; Fig. 17 is a perspective view of another example of the Y axis driving mechanism for the spray gun unit; Fig. 18 is a perspective view for explaining a method for supplying compressed air to the spray gun unit; Fig. 19 is a front view of a device for supplying compressed air thereto; Fig. 20 is a block diagram for explaining a method for controlling each spray gun in the spray gun unit; Fig. 21 is a side view of an ink spray gun device partially cut open; Fig. 22 is a cross-sectional view of the principal part of the gun in an enlarged scale; Fig. 23 is a side view of a mechanism portion for making the needle member in the gun go and come back; Fig. 24 is an exploded perspective view of a spray gun device, Fig. 25 is a perspective view of a ratchet mechanism portion partially cut open; Fig. 26 is a side view of a ball falling and emerging portion for the ratchet mechanism portion indicated in Fig. 25 in an enlarged scale; Fig. 27 is a perspective view of a spray gun device partially cut open; Figs. 28 to 30 are longitudinal cross-sectional views of alternative spray gun devices each of which is provided with a solenoid member; Fig. 31 is a plan view of the principal part of a spray gun device having a concentration type arrangement construction; Fig. 32 is a graph showing variations in the tone of color obtained by varying the amount of ejected ink with respect to the nozzle control time; Fig. 33 is a block diagram illustrating the construction of an ink ejection control device using a rotating type solenoid member; Fig. 34 is a side view of an ink spray gun device; Fig. 35 is a side view of an ink spray gun unit directed obliquely upward of the ink spray gun device indicated in Fig. 34; Fig. 36 is a scheme illustrating the construction of an ink spray gun device including longitudinal cross-sectional view of a spray gun used therefor; and Figs. 36A and 36B are cross-sectional views of the nozzle portion of the spray gun indicated in Fig. 36 in an enlarged scale. Hereinbelow this invention will be explained, referring to the preferred embodiments indicated in the drawings, in which Figs 1 to 3 show an embodiment of the automatic printing device according to this invention. In Fig. 1 reference numeral 1 is a CPU for processing image data; 2 is a mechanism for controlling the driving of a spray gun head and the amount of ejected color ink; 3 is a mechanism for controlling the mechanism stated above; 4 is a memory; 5 is a key board for the manual operation of the mechanism stated above; 6 is an LCD display device for displaying the operation by means of the key board stated above; 7, 8, 9 and 10 are an NTSC input terminal, an image scanner input terminal, a mouse input terminal and a first floppy disk input terminal, respectively. Further 11 is an A/D converter, 12 is a memory; 13 and 14 are an input and output portion; 15 is a frame memory; 16 is a D/A converter; 17 is a monitor output terminal; and 18 is a second floppy disk input terminal. The mechanism 2 described above consists of an X axis and a Y axis driving mechanism 20 and 21, respectively, driving the spray gun head in the directions of the X and the Y axes with respect to the wall surface, a Z axis driving mechanism 22, an ejected color ink amount controlling mechanism 23, etc. The input terminals 7 to 10 are so constructed that output signals coming from a video deck VD, video camera VM, an image scanner IM, a serial mouse SM and a first floppy disk FD₁ are inputted therethrough. These output signals, i.e. image data, are inputted in the image data processing CPU 1, by which signal processing such as edition of the image data, etc. is effected, so that the signals necessary for the imaging are given to the mechanism controlling CPU 3 through the input and output portion 14. Further the image data processing CPU 1 stores imaging signals obtained by editing imaging data taken-in from each of the input terminals in a second floppy disk FD₂ through the output terminal 18 so that they can be used, if necessary. The imaging signals stated above are outputted from the output terminal 17 through the frame memory 15 and the D/A converter 16 so as to be able to be monitored by the color monitor CM. The driving mechanisms for the spray gun head are disposed, opposite to a frame 30, e.g. as indicated in Fig. 4. The frame 30 is constructed by fastening an upper, a lower, a left and a right frame unit 31 to 34, a left and a right leg member 35 and 36 by means of screws, as indicated in Fig. 5, and fixed with a constant interval to the wall surface 37 so as to be parallel thereto at a job site, as indicated in Fig. 6. The X axis and Y axis driving mechanisms 20 and 21, respectively, are disposed, opposite to the frame 30, as indicated in Fig. 7. The X axis driving mechanism 20 consists of a fixing portion 40 mounted on the frame 30 and a driving portion 41 moving along it. The fixing portion 40 includes a rail 42 and a rack gear 43. On the other hand the driving portion 41 is provided with a linear roller 44, a pinion gear 45, a reduction gear 46, a motor 47, a rotary encoder 48 and a 2-axial driving mechanism supporting carriage 49. The linear roller 44 is engaged with the rail 42, slidably along it, and the pinion gear 43 is engaged with the rack gear 43. The motor 47 can move the Z axis driving mechanism supporting carriage 49 along the rail 42 in the direction of the X axis step by step of a predetermined distance by driving the pinion gear 45 through the reduction gear 46, responding to the X axis control signal coming from the CPU 3 stated above. The Y axis driving mechanism 21 consists of Y axis driving units 21a and 21b, as indicated in Fig. 7, each of which has a structure almost identical to that of the X axis driving mechanism. These units are arranged on the left and the right frame units 33 and 34 and support the two extremities of the X axis driving mechanism 20 so that they can move the X axis driving mechanism 20 in the direction of the Y axis ( up and downward ), responding to the Y axis controlling signal coming from the CPU 3. The Z axis driving mechanism 22 consists of a movable controller 221 mounted e.g. on a supporting carriage 49 for the X axis driving mechanism 20, a photosensor 222, a spray gun head 223, a spray gun supporting plate 224, etc., as indicated in Fig. 9. The movable controller 221 includes a roller 225 and a linear pulse motor 226 for controlling the position in the direction of the Z axis and controls the position of the spray gun head 223 so that the distance ℓ thereof from a wall surface 227 is constant, by using instruction pulses from the CPU 3, responding to signals coming from the photosensor 222 mounted at the lower extremity portion of the supporting plate 224. The Figs. 12, 13 and 14 show another example of the Z axis driving mechanism, which moves the spray gun unit ( head ) 108 forward and backward with respect to the wall surface R, on which the image is to be printed. The driving mechanism is composed of a carriage 125, which is mounted on a supporting plate 114 for a driving body 112 of the X axis driving mechanism stated above and on which the spray gun unit 108 is mounted, a roller 126, a linear pulse motor 127 and a photosensor 128 mounted on the carriage. The distance ℓ therefrom to the wall surface R is detected the photosensor 128 and the carriage 125 is moved through a linear pulse motor 127 by the signal thus detected, so that the position of the spray gun unit 108 from the wall surface R is kept to be constant. The photosensor 128 is so constructed that the position, where it is mounted, can be regulated in the forward and backward direction by using a slit 129 formed in the carriage 125 and a fixing screw 130 engaged with the sensor therethrough. The sensor stated above is not necessarily a photosensor, but an ultra-sonic sensor, an infrared ray sensor, etc. may be used therefor. By using the Z axis direction driving mechanism, in which the photosensor 125 is mounted on the carriage 125 stated above and for which the distance the spray gun unit and the wall surface is kept to be constant owing to the detection signal thereof, even if the wall surface is a slightly curved convex or concave surface, as indicated in Figs. 15 and 16, it is possible to move the spray gun unit, while keeping the distance thereof from the wall surface. S₅ and S₆ are limit switches for defining the displacement of the carriage 125. Fig. 17 shows another example of the Y axis direction driving mechanism. In the figure reference numeral 131 represents screw shafts mounted rotatably, standing at two positions with a necessary distance; 132 is a tapped body engaged with each of the screw shafts; 133 is a rail member connecting the two tapped bodies; 134 is a reversible motor; and 135 is a transmission gear mechanism transmitting the rotation of the motor to the screw shafts 131, a driving mechanism for the direction of the X axis similar to that described above being mounted on the rail member stated above. In the driving mechanism for the direction of the Y axis the rotation of the motor 134 is transmitted simultaneously to the left and the right screw shafts and the rail member 133, on which the driving mechanism for the direction of the X axis is mounted, is moved in the up and downward direction by the rotation of the screw shafts 131. By using this driving mechanism for the direction of the Y axis it is possible to move simultaneously the two extremities of the rail member, on which the driving mechanism for the direction of the X axis is mounted, in the up and downward direction with only one motor. Figs. 18, 19 and 20 show an example of the method for supplying compressed air to the spray gun unit and the method for controlling each of guns in the spray gun unit. In the figure a relay control box 322 is mounted on a frame unit 305 in a frame 301 for connecting a spray gun unit 308 and a driving portion 312 therefor with a compressed air supplying section and an electric control section. This relay control box 322 is provided with an air inlet portion 323 and an air outlet portion 324 for a compressor, an air pressure regulating portion 325, a power cable connector portion 326 and a sensor cable connector portion 327. A relaying air tube 328 and a cable 329 coming out from the relay control box 322 are connected with the spray gun unit 308 and the driving portion 312 therefor described above with a surplus length. 322 is a metal hanger for the air tube and the cable. The relay control box 322 is not necessarily mounted on the frame unit 305, but it may be mounted at any place on the frame. Fig. 20 is a scheme showing a control system for supplying compressed air from the air compressor 331 to the spray gun unit 308 through the relay control box 322 stated above. In the figure reference numeral 325 is the air pressure control portion, which cleans the compressed air ( removes oil and moisture contained therein ) and at the same time sets the input air pressure at a predetermined value ( 5 ∼ 10 kg/cm² ). 332 is a proportional electro-magnetic valve portion, which varies the air pressure applied to the spray gun nozzle according to a DC voltage controlled by the controlling CPU. 333 is a pressure sensor, which detects the output air pressure of the proportional electro-magnetic valve portion and sends it to the controlling CPU in the form of an electric signal. 334 is a ramifying section, which sends compressed air to spray guns 308a, 308b and 308c for the three primary colors and a spray gun 308d for black in the spray gun unit 308 while ramifying it. In the case where an image is printed on a wall surface by means of the automatic printing device having the structure described above, the frame 1 is installed at a position opposite to the wall surface. Then the compressed air supplying tube from the compressor is connected with the air input portion 323 in the relay control box 322 and the power cable connector portion 326 and the sensor cable connector portion 327 are connected with the controlling CPU by means of cables. Now an example of the key board 5 for operating the automatic printing device according to this invention is shown in Fig. 10, in which reference numeral 50 indicates ten keys representing numerals of 0 ∼ 9 and 51 to 64 are function keys having functions indicated in the figure, respectively. The function keys 54 to 57 are used for moving the spray gun head 223 in the directions indicated by arrows, respectively. For example, when one of them is pushed down within a predetermined period of time, the spray gun head can be moved in the corresponding direction by one pixel and when it is pushed down over the predetermined period of time, the spray gun head can be moved with a high speed, until it is released. The function key 51 is a key for executing a printing operation; the home position key 58 is one for moving the spray gun head 223 to the home position; the function key 60 is one for executing a mechanical test for the control mechanism 2; the function key 59 is one for instructing the spray gun head 223 to print a test pattern in order to check the ink ejection state thereof; the function key 52 is a temporary stop key for stopping temporarily an operation such as print, test print, mechanical check, home position, etc., when it is pushed down in the course of the execution thereof, and for beginning again the operation, when it is pushed down again; the function key 61 is a key for setting the air pressure for the spray gun head; the function key 62 is one for setting the operation starting position for the print; and the function key 63 is one for preventing plugging of the spray gun head 223 by ink. As far as this last key is pushed down, the head stated above can execute a spouting operation. The function key 64 is a key used for beginning the execution of the various operations indicated above or for inputting numerical data and the ten keys 50 are keys for inputting numerical values for setting the air pressure supplied to the spray gun head 223, etc. In the automatic printing device, when the image signals corresponding to the original image, which is to be printed, are inputted in either one of the input terminals 7 to 10, they are sent to the CPU 1, where they are dealt with, and the signals necessary for the print are given to the mechanism controlling CPU 3. The CUP 3 sends drive control signals to the mechanisms 20, 21 and 22, responding to the signals described above, and the spray gun head 223 is driven in the directions of the X and Y axes, while keeping the distance thereof from the wall surface constant. The spray gun head ejects ink for every pixel in the image, an enlarged image of which is to be printed and moved successively to the next pixel. In this case various kinds of manual setting and regulation of the spray gun head necessary for the print are possible by operating the key board described above. Further, since the image signals in the course of the print are outputted through the monitor output terminal 17, it is possible to monitor the image, which is in the course of the printing. Although, in the embodiment described above, the spray gun head is moved with respect to the wall surface by the driving mechanisms in the directions of the X, Y and Z axes supported by the frame, it is a matter of course that this invention is not limited to such a construction, but e.g. robot mechanisms can be used as well therefor. Furthermore various kinds of structures can be used as the frame. Figs. 21 to 23 show an embodiment of the spray gun device used in the automatic printing device described above. In the figure reference numeral 401 is a cylindrical main part of a spray gun. The cylindrical inner room thereof is divided coaxially by an inner cylinder 402 into two, i. e. an air room having an air inlet 403, which is on the outer side, and an ink room having an ink inlet, which is on the inner side. A needle member 405 is inserted in the center of the inner cylinder 402. The extremity of the inner cylinder and the tapered extremity portion of the needle member 405 are located coaxially at the extremity opening portion of the main part 401 so as to form an ink nozzle. A driving mechanism A for moving forward and backward the needle member 405 is coupled with a movable table 406 supporting the needle member 405 stated above. 407 is a mechanical housing for the driving mechanism A and 408 is a toothed wheel driven by a stepping motor. An extremity of a shaft 410 coupled with the needle member 405 through a joint 409 is contacted with the surface of teeth of this toothed wheel 408 through a steel ball 411 secured therewith, which is thrusted towards the surface of teeth by a spring 412. In the spray gun device thus constructed, ink is ejected continuously from the nozzle by connecting the ink inlet 404 with an ink supplying portion and the air inlet 403 with an air compressor and by rotating the toothed wheel 408 by means of the motor with a predetermined speed. That is, the needle member 405 is moved forward and backward by the rotation of the toothed wheel and the action of the return spring 412 and in this way the nozzle of the spray gun is opened and closed. The ink is ejected during a period of time, where the nozzle is opened. Fig. 32 indicates variations in the tone of color due to variations in the ejected amount of ink with respect to the nozzle control time t, in which t, indicates the rise time. T represents a period of time necessary for printing one dot and numerical signs 1 ○ ∼ indicate grades of the tone of color. As indicated in this diagram of the tone of color, when the tone is zero, time lapses, while the nozzle is in the state where it is closed. For example, for effecting an ink ejection of a tone indicated by , after a rise time of 2 m sec it falls down after 7 m sec. This control of the tone of color is effected only by controlling the rotation of the stepping motor under a constant air pressure without changing the air pressure for the spray gun. Figs 24 to 26 show another embodiment of the spray gun device according to this invention, in which reference numeral 413 is a stopper; 414 is a joint; 415 is a cylindrical shaft; 416 is a ratchet box; 417 is a movable ratchet plate; 418 is a fixed ratchet plate; 417a is receiving holes formed in the peripheral direction with a constant pitch on the surface of the ratchet plate 417; 418a is a ball disposed on the surface of the ratchet plate 418; 419 is a return spring; and 420 is a motor shaft. The movable ratchet plate 417 is moved forward and backward in the axial direction by the falling and emerging action of the ball 418 disposed on the ratchet plate 418a into and from the receiving holes 417a formed in the ratchet plate 417 due to the rotation of the cylindrical shaft 415 coupled with the motor shaft 420 and the action of the return spring 419. This forward and backward movement is transmitted to the needle member 405 so that the ink is ejected continuously. Fig. 27 shows still another embodiment of the spray gun device according to this invention, in which reference numeral 421 is a threaded shaft coupled with the needle member; 422 is a tapped cylinder engaged therewith; 423 is a rotating type solenoid body for moving forward and backward and rotating the tapped cylinder; 421a is a stopper for the threaded shaft; 422a is a lever serving as a stopper and protruding from the threaded cylinder; and 424 is a stopper. The needle member 405 is moved forward and backward by the helical movement of the tapped cylinder 422 and the threaded shaft 421 due to forward and backward rotation of the rotating type solenoid body 423 so that the ink is ejected continuously. Since the rotating type solenoid body 423 has characteristics that the response to the controlling power source is rapid, it is possible to eject from the nozzle an amount of ink corresponding to a digital value set with a high speed by detecting the rotational angle thereof by means of a potentiometer and by effecting a positional comparison. Fig. 33 is a block diagram showing an example of the method for controlling the ink ejection using the rotating type solenoid member. In the figure reference numeral 425 is an ejected amount instruction digital data section, in which data are given in the binary code of 4 bits so that the ejected amount can be varied in 16 grades ( tone of color ). When instruction data of the ejected amount is given by an operator, it is converted into an analogue value by a D/A converter 426, whose data are compared with the voltage in a potentiometer 428 by an adding circuit 427. The result of the comparison is inputted in the rotating type solenoid member 423 by a power amplifier 429. In this way the nozzle 430 of the spray gun is opened and closed and at the same time the potentiometer ( position sensor ) 428 is also driven so as to be rotated around the same axis. The rotational angle thereof is transformed into a voltage and outputted from the potentiometer 428. It is then compared with a reference value in the adding circuit 427. When it reaches a predetermined output voltage, this closed loop 427 - 429 - 423 - 428 is stabilized so that the spray gun is stopped there and the amount ejected by the nozzle is controlled. Figs. 28 to 30 show three different spray gun devices driven by solenoids, which are other embodiments of this invention. The device indicated in Fig. 28 is so constructed that a magnet 432, a yoke 433, a coil 434 and a vibrating plate 435 are mounted in a mechanical housing 431 disposed in the rear part of the principal part 401 of the spray gun and a needle member 405 is coupled with the vibrating plate 435 so that the displacement amount of the needle member can be controlled by varying the intensity of the current flowing through the coil. The device indicated in Fig. 29 is so constructed that the needle member 405 is moved forward and backward by a solenoid coil 437 and a spring 438 mounted in a mechanical housing 436. The device indicated in Fig. 30 is so constructed that a spring made of a non-magnetic material working together with a solenoid coil 439 is buried in the ink room together with the needle member 405. According to this structure, since the needle member is not in contact with packing for seal in the spring room, the resistance by friction is small and thus it is possible to control the needle member with a relatively small power. The device indicated in Fig. 31 is an embodiment of this invention, in which a plurality of principal parts of spray nozzle are combined. That is, four principal parts of spray nozzle 401, each of which is provided with a vibration generating mechanism A, are mounted on a movable plate 406 in such angular positions that their directions of ejection pass through a common point. According to this concentration type arrangement structure, since a desired color can be obtained by one ejection operation by mixing the three primitive colors, it can be expected to increase remarkably the printing operation efficiency with respect to the operation to mix the primitive colors by displacing separately the principal parts of spray nozzle of different colors. Although, in the above, various kinds of embodiments are described, apart from the method, by which the ink ejection time is controlled by opening the nozzle for one pixel, the control of the ejected amount of ink by moving forward and backward the needle member in order to obtain different tones of color can be effected also by a method, by which the number of openings and shuttings of the nozzle for one pixel by means of the needle member is controlled, or by another method, by which the ink ejection area is controlled on the basis of variations of the tapered extremity portion due to displacement of the needle member. These methods can be selected appropriately to be applied thereto. As explained above, since the spray gun device described above, in which ink is pulverized from the nozzle by the force of ejected air, is so constructed that the driving mechanism for moving forward and backward the needle member disposed in the nozzle of the spray gun is mounted within the spray gun, it is possible to control easily the ejected amount of ink necessary for obtaining a desired tone of color with a high precision under a constant air pressure. In the spray gun device described above, in order to prevent plugging by ink, a false ink spray is effected e.g. after the termination of printing of one line. Since in a prior art device this false ink spray was effected towards a part of the area, where an image was to be printed, there was a disadvantage that the area, where the image was printed, became narrower corresponding thereto. Figs. 34 and 35 show an embodiment of the the spray gun device according to this invention, which is so constructed that there exist no bubbles in the ink within the main part of the gun. In the figures A represents a cylindrical main part of the spray gun, which consists of an outer cylinder portion 610 and an inner cylinder portion 611, and the cylindrical inner room thereof is divided into an ink room 611, which is on the inner side, and an air room 613, which is on the outer side. The extremities of the two rooms form a coaxial nozzle. The ink room 612 is connected with an ink inlet 612a and the air room 613 is connected with an air inlet 613a. A needle member 614 for regulating the amount of ink ejected by the nozzle is inserted slidably in the ink room 612. The main part A of the spray gun described above is mounted on a work table 615 and the needle member 614 protruding outward from the rear portion of the main part A of the spray gun is linked with a driving mechanism B disposed on the work table 615. The work table 615 supporting a spray gun unit consisting of the main part A of the spray gun and the driving unit B described above is supported by a moving body 617, which can be moved arbitrarily in the horizontal direction along a rail 616 and by a hinge 618 so that the inclination can be varied freely. The moving body 617 displaces the spray gun unit in the horizontal direction ( X axis direction ) and if it is combined with means for displacing it in the vertical direction, it is possible to displace it also in the Y axis direction. For printing an image e.g. on a wall surface of a building by using the spray gun device constructed as described above, the main part A of the spray gun is positioned in a nearly horizontal posture in front of the wall surface R, as indicated in Fig. 34 , and ink is ejected from the nozzle of the main part A of the spray gun towards the wall surface. The tone of color of the ink on the wall surface is regulated by adjusting the ejected amount of ink corresponding to the nozzle control time by the forward and backward movement of the needle member 614. When an image is printed by using the main part A of the spray gun described above, the ink is poured and stored in the main part of the spray gun. When the ink is poured therein, the work table 615 is rotated around the hinge 618 so that the main part A of the spray gun is kept in a posture directed obliquely upward and the ink is poured in the ink room 612 through the ink inlet 612a in this posture. When the ink is poured in the main part A of the spray gun kept in the posture directed obliquely upward, bubbles of air admixed in the ink at the pour of the ink rise in the liquid ink. In this way, they are exhausted over the surface of the liquid and emerge to the outside through the nozzle so that the ink is stored, leaving no air bubbles therein. As described above, according to the construction of the spray gun device, since the ink spray gun for printing images is disposed on the work table mounted on the movable body so as to be able to vary the inclination, it is possible to keep the main part in a posture directed obliquely upward so that bubbles of air admixed in the ink rise easily to be discharged to the outside, when the ink is poured in the main part of the spray gun. Consequently, by using the ink spray gun according to this invention, since it is possible to prevent plugging of the nozzle produced by the fact that the ink is solidified by remaining air bubbles in the ink room in the main part of the ink spray gun, work for removing the plugging can be omitted, which contributes significantly to the improvement of the efficiency of the printing work. Fig. 36 shows the ink spray gun device according to this invention, in which ink plugging an air ejecting opening between a nozzle and a cap can be rapidly and surely eliminated. In the figure reference numeral 801 is a cylindrical main part of the spray gun; 802 is a nozzle; 803 is a cap; 804 is a needle member; 805 is an ink inlet; and 806 is an air inlet. A hose 807 connected with the air inlet 806 is ramified on the way. One branch hose 807a is connected with a compressed air supplying portion 810 such as an air compressor, etc. through an electro-magnetic valve 808 and a flow rate regulating valve 809 and the other branch hose 807b is connected with an ink solvent supplying portion 812 such as an alcohol tank through an electro-magnetic valve 811. Further the ink inlet 805 is connected with an ink supplying portion ( not shown in the figure ) through a hose, etc. In the ink spray gun device constructed as described above, at a printing operation, if the electro-magnetic valve 808 on the air supplying side is opened and the electro-magnetic valve 811 on the solvent supplying side is closed, the ink can be pulverized by the needle member 804. Then, in the case where ink is stuck at the neighborhood of the nozzle and the nozzle is in the plugged state, the electro-magnetic valve 808 on the air supplying side is once closed and the electro-magnetic valve 811 on the solvent supplying side is opened so that a suitable amount of solvent is sent out. Thereafter, when the electro-magnetic valve 808 is opened and the electro-magnetic valve 811 is closed, since the solvent is sent together with compressed air from the air room to the gap between the nozzle 802 and the cap 803 under pressure, the ink stuck at the neighborhood of the nozzle can be washed off. This cleaning operation is effected at a region, where the image is not printed. As described above, since the device stated above is so constructed that the compressed air supplying portion and the ink solvent supplying portion can be switched to be connected with the air inlet in the ink spray gun, when the nozzle is plugged by ink stuck at the neighborhood thereof, it is possible to wash off rapidly and surely the plugging ink by sending solvent together with compressed air to the gap between the nozzle and the cap and thus an ink spray gun device having a high usability can be obtained. As it is clear from the above explanation, according to this invention, it is possible to print automatically a desired color image directly on a surface such as a wall surface of a solid construction. Further, if a the driving mechanism for the spray gun head, which is supported by the frame described previously, an installation thereof at the site is easy and it can be easily moved. Other practical effects that it occupies no large floor space, that it is fairly cheaper than a prior art device, etc. are also remarkable.

Claims: An automatic printing device comprising: control signal means (1,3,14) for generating 2- or 3-dimensional driving signals and ink ejection amount control signals for driving a spray gun unit (223), corresponding to the position and the color of each pixel in an original image; supporting means (20,30,40) for supporting said spray gun unit 2- or 3-dimensionally movably with respect to an area, on which the image is to be printed, such as a wall surface, etc.; and driving means (2,20,21,22,23) for driving said spray gun unit and at the same time projecting an ink jet from said spray gun unit to said area in response to said control signals, characterised in that said ink spray gun unit includes an air jet outlet along an outer circumference of an ink jet nozzle (802), an ink inlet (805) in an ink chamber communicating with said ink jet nozzle and an air inlet (806) in an air chamber communicating with said air jet outlet, and ink control means (804) for controlling the quantity of ink supplied to said ink jet nozzle from said ink chamber and wherein a compressed air supply means (810) and an ink solvent supply means (812) are connected to said air inlet through electromagnetic valve means (808,811) operable to connect either one of the compressed air supply means and the ink solvent supply means with said air inlet. An automatic printing device according to claim 1, wherein said supporting means is provided with a frame (30), which can be installed at the neighborhood of said area, on which the image is to be printed, and said driving means includes an X and Y axis direction driving mechanism (20,21) for moving said spray gun unit at least in the X axis and the Y axis directions, said driving mechanism being disposed on a left and a right frame unit (33,34) of said frame. An automatic printing device according to claim 2, wherein said driving means comprises further a Z axis direction driving mechanism (22) for moving said spray gun unit so as to keep it at a predetermined distance from said area, on which the image is to be printed, said driving mechanism being disposed on said X axis direction driving mechanism. An automatic printing device as claimed in claim 1 wherein the supporting means comprises a frame, which can be installed arbitrarily with respect to the area, on which the image is to be printed; X axis direction supporting means (40) for supporting movably in the left and right direction the ink spray gun unit for printing an image on said area, on which the image is to be printed; Y axis direction supporting means (30) for supporting movably in the upward and downward direction said X axis direction supporting means; and Z axis direction supporting means (42) for supporting movably in the forward and backward direction said spray gun unit supported by said X axis direction supporting means; the driving means comprising means (20) for moving said spray gun unit supported by said X axis direction supporting means and said X axis direction supporting means according to control driving signals from the exterior; and means (22) for moving said spray gun unit supported by said Z axis direction supporting means according to detection signals obtained by at least one sensor detecting the distance thereof from said area, on which the image is to be printed. An automatic printing device as claimed in claim 1 wherein the supporting means comprises a frame (30) which can be installed arbitrarily with respect to the area, on which the image is to be printed; means (30,40,42) for supporting movably at least 2-dimensionally the ink spray gun unit; and means (20,21,22) for moving said spray gun unit according to control driving signals from the exterior; the control signal means comprising relaying control means (322) disposed on a part of said frame so as to be able to send control driving signals and compressed air for spraying ink to said spray gun unit. An automatic printing device according to claim 5, wherein said relaying control means is so constructed that a compressed air inlet portion (323), a compressed air outlet portion (324), a compressed air pressure regulating portion (325), a power cable connector portion (326), and a pressure sensor cable connector portion (327) are disposed in a relay box (322). An automatic printing device according to claim 1, 4 or 5, wherein said spray gun unit is constructed so as to eject ink from a nozzle by the force of ejected air and a driving mechanism (408) for moving forward and backward a needle member (405) disposed in said nozzle of the spray gun. An automatic printing device according to claim 7, wherein said driving mechanism for moving forward and backward said needle member is a mechanism, by which said needle member is engaged with a tooth surface of a toothed wheel (408) rotated by a stepping motor by pushing the former elastically towards the latter. An automatic printing device according to claim 7, wherein said driving mechanism for moving forward and backward said needle member is a mechanism, by which, when a movable ratchet plate (417), in which a number of receiving holes (417a) are formed with a constant pitch in the peripheral direction, is rotated by a motor, said movable ratchet plate working together with a fixed ratchet plate having balls (418a) freely falling in said receiving hole and emerging therefrom is moved forward and backward in the axial direction, this movement being transmitted to said needle member. An automatic printing device according to claim 7, wherein said driving mechanism for moving forward and backward said needle member is a mechanism, by which forward and backward rotational movement of a rotation type solenoid member is transformed into forward and backward axial movement by helical movement of a screw, which axial movement is transmitted to said needle member. An automatic printing device according to claim 7, wherein said driving mechanism, for moving forward and backward said needle member is a mechanism driven by a solenoid member (423). An automatic printing device according to claim 7, wherein a plurality of main parts (401) of spray guns are mounted on a movable table (406) provided with said driving mechanism for moving forward and backward said needle member and said spray guns are arranged at such angular positions that their ejection directions pass through a common point. An automatic printing device according to claim 1, 4 or 5, wherein said spray gun unit is so constructed that ink poured and stored therein is ejected from the nozzle by the force of ejected air and the ejected amount of ink is regulated by forward and backward movement of the needle member inserted in the nozzle, and said spray gun unit is disposed on a work table (615) mounted on a movable body (617) so that the inclination thereof can be varied. An automatic printing device according to claim 1, 4 or 5 wherein a needle member (804) is disposed movably forward and backward through the ink chamber and the ink jet nozzle, and either one of a compressed air supplying portion and an ink solvent supplying portion (812) is connected with said air inlet (806) by a switching operation. A method of operating an automatic printing device including the steps of operating a control signal means (1,3,14) generating 2- or 3-dimensional driving signals and ink ejection amount control signals for driving a spray gun unit (223), corresponding to the position and the color of each pixel in an original image; supporting said spray gun unit 2- or 3-dimensionally movably with respect to an area on which the image is to be printed such as a wall surface, etc.; and driving said spray gun unit and at the same time projecting an ink jet from said spray gun unit to said area in response to said control signals, characterised by the operation of the spray head being selectively switchable between a printing operation and a cleaning operation, the ink being sprayed from a nozzle (802) during the printing operation by action of an air jet emergent from an air outlet along an outer circumference of the ink jet nozzle while the quantity of ink is controlled by an ink control means (804) in response to the ink ejection control signals, the air jet being provided during the printing operation by supplying compressed air to an air inlet (806) communicating with the air outlet, and during the cleaning operation a supply of ink solvent (812) is connected to the air inlet in place of compressed air by a switching operation to facilitate cleaning of the nozzle.

Inventors: KAIBA TADASHI, MURAI SHUUSEI, KAIBA, TADASHI, MURAI, SHUUSEI
Applicants: LAC CORP, L. A. C. CORPORATION
Application year: 1988
Main classification: B41J2
IPC codes: B41J11, B41J2