IMAGING DEVICE

Abstract: In an imaging device for forming a visible image on a recording medium by pressurizing the recording medium, provided are means for detecting a certain position of the recording medium to be pressurized before the recording medium is pressurized, and means for controlling timing of beginning and stopping to pressurize the recording medium based upon a result of the detecting poeration. Thus, the recording medium is accurately begun to pressurize at the leading end and stopped to pressurize at the trailing end regardless of a variation of a travelling speed for the recording medium.

Description: This invention relates to an imaging device employing a so-called transfer type pressure-sensitive recording medium consisting of a sheet having microcapsules (pressure-sensitized medium) and a developing sheet. An imaging device employing a pressure-sensitive recording medium consisting of a microcapsule sheet and a developing sheet will be described below as an example of known devices. The microcapsule sheet forms a roll with a leading end to be pulled out in operation. The developing sheet is in cut form. Such an imaging device generates through exposure, a latent image, corresponding to the actual image on the microcapsule sheet. The developing sheet is then laid on the side carrying the latent image of the microcapsule sheet and both are pressurized between a pair of opposed pressure rollers. This pressure operation develops the latent image formed on the microcapsule sheet into a visible image which is transferred to the developing sheet. The pair of pressure rollers are normally in a standby open position, while moving to a closed position then a sensor, for instance, detects the developing paper passing a certain position upstream of the pair of the pressure rollers. The pressure rollers resume their open position when they are rotated through a certain angle after closure thereof. However, there are some cases in which adjusting the degree of exposure of the pressure-sensitized recording medium or enlarging or reducing the image size is effected by varying the travelling speed of the pressure-sensitive recording medium. As the travelling speed thus varies, there is some irregularity in the feed quantity of the developing medium and the pressure-sensitized recording medium into the space between the pressure rollers when the opposing pressure rollers of the pressure developing unit are completely brought to their closing position. This makes the pressure-developing operation on the developing sheet start at varying start positions, resulting in difficulty in providing an exact reproduction of the image. Also, when employing a pressure-sensitive recording medium consisting of a microcapsule sheet and developing sheet, a problem has been encountered that, if a microcapsule sheet with no developing sheet laid on it is put under pressure, the content of the microcapsules is deposited on the rollers, staining the back of the developing sheet at the time of the following development. Furthermore, a thickened layer of capsule content laid upon the roller surface makes pressure distribution over the pair of pressure rollers less uniform, so that the developed image suffers uneven color quality. EP-A2-0263609 discloses a copier of the above type in accordance with the pre-characterising portion of claim 1 and in which the pressure developing rollers are set to close by detection of the leading edge of a developing sheet and to open on detection of the trailing edge. In an alternative device the length of the sheet is detected in the sheet storage tray and the rollers are set to open and close in accordance with that length. According to this invention there is provided an imaging device employing a continuous-form recording sheet coated with a plurality of photo and pressure sensitive microcapsules and a cut-sheet type developing sheet to be superposed on said recording sheet to develop a visible image thereon, said imaging device comprising: exposing means for exposing an original to provide a latent image on said recording sheet; a pair of pressure-developing rollers adapted to be brought into and out of contact with each other, for pressurizing said recording sheet and said developing sheet to develop a visible image on said developing sheet; feed means for feeding said recording sheet and said developing sheet in close contact with each other toward said pair of rollers; and control means including a detector for detecting at least a passing of a leading end of said developing sheet before said developing sheet is pressurized, a drive power source for driving said pair of pressure rollers into and out of contact with each other; magnification setting means connected to said interface unit for setting a magnification factor of a latent image formed on said continuous-form recording sheet ; and a motor connected to said interface unit for feeding said continuous-form recording sheet characterized in that the feeding speed of the recording sheet is variable in accordance with the magnification factor, and by an interface unit connected to said detector and a central processing unit in the control means connected to said interface unit for controlling said drive power source to bring pair of rollers into contact at a time after the detection of the developing sheet selected in accordance with the feeding speed of the developing sheet as or after the leading end of said developing sheet is fed into a space between said pair of rollers. The invention will be better understood from the following description which is given byway of example only with reference to the accompanying drawings in which: Fig. 1 is a view showing the configuration of the control unit for controlling the pair of pressure rollers of the imaging device according to the invention; Fig. 2 is a view showing the configuration of the imaging device according to the invention; and Fig. 3 is a view showing a one embodiment of a pressure developing unit incorporated in the imaging device according to the invention. Fig. 2 is a schematic sectional view of a photo- and pressure-sensitive copying machine capable of full-color copying. Sensitized sheets for use in such copying (consisting of paper coated with microcapsules and developing paper) have been proposed in Japanese Patent Provisional Publication Sho58-88739. The photo- and pressure-sensitive duplicating machine 40 includes, as shown, a glass original tray 2 whose top panel is reciprocally movable rightward and leftward and an original tray cover 1. A desired original can be placed on the glass original tray 2 up side down. Secured to the upper right portion of the machine 40 is a light source unit consisting of a halogen lamp 3 extending perpendicularly to the direction of reciprocal movement of the glass original tray 2 and a semi-cylindrical reflection mirror 4 located to surround the lamp 3, so that it illuminates the glass original tray 2 with linear beams of light. As the glass original tray 2 is reciprocated, the light beams emitted from the halogen lamp 3 are thus allowed to shine on the entire surface of the glass panel from its left end to right. The light beams emitted from the light source are passed through the glass original tray 2 and reflected on the original placed on it. In order to confine the reflection light to the area of the original, the original tray cover 1 is provided over the top surface of the glass original tray 2. Furthermore, in order to use the light emitted from the halogen lamp 3 for illuminating the original with a higher efficiency, there is a reflector 5 located to the left of the light source so that the light beams that have not reached the original are again reflected there to shine on the original. A fan 6 and a louver 7 are provided to the right of the halogen lamp 3 to intake air from outside. This allows the glass original tray 2 to be ventilated. The light beams emitted from the halogen lamp 3 and reflected from the original placed on the glass original tray 2 are passed through a filter 8 to a lens 9. The filter 8 is provided to change the light transmitting characteristics in dependence on the sensitivity of the micro-capsule sheet 37 so as to adjust the tonality of the duplicated image. The lens 9 is mounted on the lens mount plate 10 with a possibility of fine angle adjustment with respect to the optical path. Furthermore, the lens 9 is vertically movable so that it is moved up and down by means of a lens moving unit 51 shown in Fig. 1. The light beams converged by the lens 9 are turned through an angle of 180 degrees by means of two reflection mirrors 11, 11 and form an image on the microcapsule sheet 37 in close contact with the down side of an exposure tray 19. The two reflection mirrors 11, 11 are fixedly mounted on a mirror mount plate 12 so that adjustment of the length of optical path and focusing takes place by fine adjustment of the mounting position of the mirror mount plate 12. The microcapsule sheet 37, in continuous form, is wrapped around a cartridge shaft 14 which is housed in a detachable cartridge 13 located under the glass original tray 2. One end of the sheet 37 reaches a take-up shaft 25 by way of multiple rollers and a pressure-developing unit 20. The microcapsule sheet 37 coming from the underside of the cartridge 13 is guided along the under face of the exposure tray 19 by means of feed rollers 15 and a guide roller 17 and fed to the pressure-developing unit 20. The microcapsule sheet 37 passed through the pressure-developing unit 20 is then sent to a separation roller 23 and a winding run adjustment roller 24 and is taken up onto the take-up shaft 25. The unexposed microcapsule sheet 37 leaving the cartridge 13 is protected against light by means of a shield cover 16. The travelling speed of microcapsule sheet 37 is controlled by sheet feed rollers 22, 22 connected to a motor 52 shown in Fig. 1 and is varied in dependence on the reciprocal speed of the glass original tray 2 and the magnification factor. Accordingly, the latent image of certain lines on the text are built one by one on the microcapsule sheet 37 while it is passed through the exposure tray 19. Below the pressure-developing unit 20 is a developing sheet cassette 32 accommodating developing sheet 38 in cut form. The developing sheet 38 is picked out one by one by means of a semi-cylindrical roller 33 and is at its end registered by means of developing sheet rollers 34 and a registration gate 35 to be brought to the paper inlet of the pressure-developing unit 20. Consequently, the microcapsule sheet 37 and the developing sheet 38 in close contact with each other are together sent to the pressure-developing unit 20. The pressure-developing unit 20 consists of a first pressure roller 21 and a second pressure roller 31. The two sheets of paper are thus pinched and pressed between the first pressure roller 21 and the second pressure roller 31, with the inside surface of the microcapsule sheet 37 on which the latent image is created in contact with the inside surface of the developing sheet 38 which is coated with a developing material. With this pressure, the microcapsules remaining unexposed are crushed to develop an image on the developing sheet 38, because they have not been hardened by exposure to light. The microcapsule sheet 37 and the developing sheet 38 leaving the pressure-developing unit 20 are then conveyed by means of the capsule sheet feed rollers 22. The microcapsule sheet 37 and the developing sheet 38 are then separated from each other by the separation roller 23, the former going upwardly and the latter forward. On the developing sheet 38, colors are developed by means of a heat setting unit eventually forming a visible image. The paper is then discharged to a paper outlet tray 27 with the image-carrying side facing up. The heat setting unit consists of a hollow heat roller 29 accommodating a heater 30 and a developing sheet feed rollers 28, 28. The microcapsule sheet 37 separated is now taken up around the take-up shaft 25 by way of the winding run adjustment roller 24. The arrangement as described above is operated as to be described below. When the start button (not shown) is pressed down after opening the original tray cover 1 and placing an original on the glass original tray 2, the latter is moved rightward of Fig. 2 and is brought to a stop at a position where the left end of the glass original tray 2 is placed opposite to the light source. Thereafter, the text tray 2 is moved to left, with the halogen lamp 3 kept illuminated. The light emitted from the halogen lamp 3 is reflected on the original and further on the filter 8, lens 9 and two reflection mirrors 11, 11 and forms an image on the microcapsule sheet 37 placed under the exposure tray 19. At this time, the microcapsule sheet 37 is moved to left on the exposure tray 19 at the same speed as the reciprocation speed of the glass original tray 2, so that a latent image of the picture on the original is formed on the microcapsule sheet 37. With the leftward movement of the glass original tray 2, the developing sheet 38 is picked up by the semi-cylindrical roller 33 from the developing sheet cassette 32 and is laid upon the exposed microcapsule sheet 37 to be together fed to the pressure-developing unit 20. The developing sheet 38 is then thermally set by the heat setting unit and is discharged from the duplicating machine 40. On the other hand, the microcapsule sheet 37 passed through the pressure-developing unit 20 is continuously taken up onto the take-up shaft 25. When the glass original tray 2 is brought to a position in which its right end opposes to the light source, duplication of the original text is completed to turn off the halogen lamp 3. The pressure developing unit 20 as mentioned above will be described below. Fig. 3 is a sectional view showing a pressure developing unit There are the first pressure roller 21 and the second pressure roller 31 placed in opposition to each other, between which the microcapsule sheet 37 and the developing sheet 38 laid upon each other are passed. The first pressure roller 21 is movably mounted on a first frame 42 together with a first backup roller 41. The second pressure roller 31 is likewise movably mounted on a second frame 44 together with a second backup roller 43. The second frame 44 itself is configured to be movable relative to the first frame 42. Referring to its mechanism, a cam shaft 46 of eccentric shape for a frame lift roller 45 is driven by a drive power source 53 shown in Fig. 1, so that the frame lift roller 45 is rotated along the cam contour. As the cam shaft 46 is rotated, the cam lobe reaches the position for contact with the frame lift roller 45, whereupon the second frame 44 and therefore the second pressure roller 31 are moved toward the first frame 42. Since the first pressure roller 21 is here loaded by a pressure spring 47 via the first backup roller 41, the first pressure roller 21 and the second pressure roller 31 are in pressure contact with each other under the pressure force of the pressure spring 47. When, on the other hand, the lowered portion of the cam comes into contact with the frame lift roller 45, the second frame 44 is moved apart from the first frame 42, whereby the second pressure roller 31 comes out of pressure contact with the first pressure roller 21 generating a space to receive the developing sheet 38. Now described below is a drive power source 53 for rotating the cam shaft 46 and a control unit 50 for it. The drive power source 53 is electrically cconnected to a well-known CPU (Central Processing Unit) 55 via an interface circuit 54, which is in turn connected to a sensor 56. The sensor 56 is located at a position before the first pressure roller 21 and the second roller 31 and detects paper when the leading or trailing end of the developing sheet 38 passes the position at which the sensor 56 is located. The sensor 56 is usually a reflection type photo sensor monitoring a reflection factor of the travelled sheet, and detecting a leading or trailing end of the developing sheet 38 by sensing a difference of the reflection facotrs of the microcapsule sheet 37 and the developing sheet 38. The interface circuit 54 is further connected with a lens moving unit 51 and a motor 52. The CPU 55 controls the lens moving unit 51 and the motor 52 to effect exposure with a desired magnification. The CPU 55 has further connected therewith a RAM (Random Access Memeory) 57 as work area of the CPU 55 and a ROM (Read Only Memory) 58 describing the procedure of the CPU 55. Explanation is now given to the timing of opening and closing the first and second pressure rollers 21 and 31 of the pressure developing unit 20 configured as described above. When exposure is finished, the microcapsule sheet 37 and the developing sheet 38 laid upon each other are fed together. The travelling speed of them is determined by the CPU 55 in dependence on a magnification given by a position of the lens 9. The CPU 55 then controls tie motor 52 in response to the travelling speed given, to thereby rotate the sheet feed rollers 22, 22. When the sensor 56 provided in the feed path detects the leading end of the developing sheet 38 passing the sensor 56, the drive power source 53 is controlled to rotate the cam shaft 46 by half a turn, after the time Ts given by the following equation elapses, thus closing the first and second rollers 21 and 31 Ts ≧ (ℓ/ v) - Ti where, 1 : distance between the sensor 56 and a contact point between the first and second rollers 21 and 31, v : travelling speed, Ti: the time required for the pair of rollers to be brought into contact with each other. With this arrangement, and with the equality in the equation, the first and second pressure roller 21 and 31 are brought into pressure contact with each other, as the leading end of the developing paper 38 reaches the pressure contact point. When the trailing end of the developing 38 now passes the sensor, the CPU causes the drive power source to rotate by half a turn after the time To given by the following equation elapses from that timepoint, to thereby open the first and second pressure rollers 21 and 31. To ≦ ℓ / v With this arrangement, and with the equality in the equation, the first and second pressure rollers 21, 31 are brought to an open position simultaneously as the trailing end of the developing sheet 38 reaches the pressure contact point. While in this embodiment, Ts and To are calculated after development, there will be no need of occasional calculation if the values of Ts and To calculated with respect to every possible travelling speed "v" are stored in the ROM 58 in advance. Also, the first and second rollers 21 and 31 can be brought to a closed position in the following manner. Assuming that the travelling speed is "v" as mentioned above, the CPU 55 controls the drive power source 53 simultaneously as the sheet passes the sensor 56, to thereby rotate the cam shaft 46 at an angular velocity defined by the following equation. ψ ≦ (180°) · v /ℓ (deg/sec) or π · v/ℓ (rad/sec) With this arrangement, and with the equality in the equation pressure development starts simultaneously as the leading end of the developing sheet 38 reaches the pressure contact point as in the embodiment described. On passing of the trailing edge the cam may be rotated at a speed of ψ ≧ vπ/ℓ (rad/sec) . It is obvious that many other modifications can be made to the present invention.

Claims: An imaging device employing a continuous-form recording sheet (37) coated with a plurality of photo and pressure sensitive microcapsules and a cut-sheet type developing sheet (38) to be superposed on said recording sheet (37) to develop a visible image thereon, said imaging device comprising: exposing means (3-11) for exposing an original to provide a latent image on said recording sheet (37); a pair of pressure-developing rollers (21, 31), adapted to be brought into and out of contact with each other, for pressurizing said recording sheet (37) and said developing sheet (38) to develop a visible image on said developing sheet (38); feed means (22) for feeding said recording sheet (37) and said developing sheet (38) in close contact with each other toward said pair of rollers (21, 31); and control means (50) including a detector (56) for detecting at least a passing of a leading end of said developing sheet (38) before said developing sheet (38) is pressurized, a drive power source (53) for driving said pair of pressure rollers (21, 31) into and out of contact with each other; magnification setting means (51,52) connected to said interface unit (54) for setting a magnification factor of a latent image formed on said continuous-form recording sheet (37); and a motor (52) connected to said interface unit (54) for feeding said continuous-form recording sheet (37) characterized in that the feeding speed of the recording sheet (37) is variable in accordance with the magnification factor, and by an interface unit (54) connected to said detector (56) and a central processing unit (55) in the control means connected to said interface unit (54) for controlling said drive power source (53) to bring pair of rollers (21, 31) into contact at a time after the detection of the developing sheet (38) selected in accordance with the feeding speed of the developing sheet (38) as or after the leading end of said developing sheet (38) is fed into a space between said pair of rollers (21, 31). The imaging device according to claim 1 wherein said control means (50) controls said pair of rollers (21, 31) so as to bring them into contact when the time period Ts defined by the following equation elapses after the passing of the leading end of the developing sheet (38) is detected by said detector (52), Ts ≧ (l/v) - ti (sec.) where, v : travelling speed of the developing sheet (38) in per second, l : distance from the detected point to the space between the pair of rollers (21, 31), and ti : the time required for the pair of rollers (21, 31) to be brought into contact with each other. The imaging device according to claim 1 or 2 wherein one of said pair of rollers (21) is mechanically connected to a cam shaft member (44) having an eccentric cam (46), said pair of rollers (21,31) being adapted to be brought into contact when the one of said pair of rollers (31) is connected to the portion corresponding to a large radius portion of said cam (46) while being adapted to be brought out of contact when the one of said of rollers (31) is connected to the portion corresponding to a small radius portion of said cam (46), and wherein said control means (50) controls said cam (46) so as to begin to rotate at an angular velocity defined by the following equation when the passing of the leading end of the developing sheet (38) is detected by said detector (56), ψ ≦ vπ/ℓ (rad. /sec.) where, ψ : angular velocity of the cam (46) to be rotated. v : feeding speed of the developing sheet (38) in per second, and ℓ : distance from the detected point to the space between the pair of rollers (21,31). The imaging device according to claim 1, 2 or 3 wherein said detector (56) further detects a passing of a trailing end of the developing sheet (38) and control means (50) further controls said pair of rollers (21, 31) to be brought out of contact as or before the trailing end of the developing sheet (38) is pressurized by said pair of rollers (21, 31). The imaging device according to claim 4 wherein said control means (50) controls the rollers (21, 31) to bring them out of contact when the time of period To defined by the following equation elapses after the passing of the trailing end is detected, To ≦ l/v (sec.) where, v : feeding speed of the developing sheet (38) in per second, and l : distance from the detected point to the contact point of said pair of rollers (21,31). The imaging device according to claim 3 wherein said detector (56) further detects passing of a trailing end of the developing sheet (38) and wherein said control means (50) controls said cam (46) so as to be begun to rotate in an angular velocity defined by the following equation when the passing of the trailing end of the developing sheet (38) is detected by said detector (56), ψ ≧ vπ/ℓ (rad. /sec.) where, ψ : angular velocity of the cam (46) to be rotated, v : feeding speed of the developing sheet (38) in per second, and ℓ : distance from the detected point to the contact point of said pair of rollers (21,31). The imaging device according to any preceding claim wherein said detector (56) is a reflection type photo sensor capable of detecting the difference between the reflection factor of the recording sheet (37) and the developing sheet (38). A copier including any imaging device according to any preceding claim.

Inventors: AKAO, MICHITOSHI BROTHER KOGYO K. K., KATOH, TOKUNORI BROTHER KOGYO K. K., SAKAKIBARA, KENJI BROTHER KOGYO K. K., SAWAKI, YUKICHI BROTHER KOGYO K. K., SONODA, TAKAKUNI BROTHER KOGYO K. K.
Applicants: BROTHER KOGYO KABUSHIKI KAISHA
Application year: 1989
Main classification: G03F7
IPC codes: G03D13, G03G15, G03F7