Developing device for copying apparatus of the diazo type
United States Patent 1191 Yamashita et a].  
 [451 Apr. 1, 1975 DEVELOPING DEVICE FOR COPYING APPARATUS OF THE DIAZO TYPE [75] Inventors: Tadashi Yamashita, Yokohama;  
 Yasuhiro Takahashi, Tokyo, both of Japan [73] Assignee: Ricoh Co., Ltd., Tokyo, Japan [22] Filed: June 26, 1973 21 Appl. No.: 373,892  
 [30] Foreign Application Priority Data July 15, 1972 Japan 47-71090 [52] Cl 354/318, 118/203, 118/249, 118/262, 355/10 [51] Int. Cl. G03d 5/00 [58] Field of Search 95/89 R, 89 A, 89 G;  
 [56] References Cited UNITED STATES PATENTS 2.605.684 8/1952 Nagels et a1]. 95/89 A 2,676,563 4/1954 Montgomery et al. 95/89 R UX 2,887,029 5/1959 Druce 95/89 R SOL 3,580,158 5/1971 Scholle et a1. 95/89 G 3,687,049 8/1972 Koch et al 95/89 R FOREIGN PATENTS OR APPLICATIONS 302,567 10/1968 Sweden 355/10 Primary ExaminerFred L. Braun Attorney, Agent, or Firm-Cooper, Dunham, Clark, Griffin &amp; Moran [57] ABSTRACT A device comprising a developing liquid quantity control member operatively associated with a developing liquid supply roller for adjusting to an optimum level the quantity of a nonvolatile, concentrated developing liquid supplied to a developing position between a developing liquid applicator roller anda pressure applying roller so as to apply an essential minimum of the developing liquid to an exposed photosensitive sheet of the diazo type fed to the developing position. There is also provided a developing liquid removal member disposed posteri&#39;orly to the developing position for removing from the periphery of the developing liquid applicator roller any excess developing liquid which might otherwise remain thereon.  
 12 Claims, 11 Drawing Figures i 1 iii-R 1 m5 SHEET 1 0F 5 IIIIIIIIIIIIIIIIII/ I I I I I I I I I I I I I I I I 0 a PERIPFERAL VELOCITY OF SUPPLY ROLLER TEI-I&#39;IEIIIII I I975 I 8755.581  
  QUANTITY OF DEVELOPING LIQUID APPLIED fifiRLHRQEEXFEiQ? fiE T0 PHOTOSENSITIVE SHEET OF A4 SIZE SLZT 2 0F 5 mg FIG. 5  
  0 6 I00 e/ &#34;r 0 I00 200 300 400 500 600 &#34;1 PERIPHERAL vEL0cITY OF APPLIcAToR ROLLER 9 PERIPHERAL VELOCITY OF APPLICATOR ROLLER sczmms Cl g PIC-3.7 E 80- E0 6 3g 60- EE F c c 3 J- PERIPHERAL VELOCITY OF suPPLY RoLLER mg g L PIC-3.8 3 0 h o 5 I60 9g 0 E ma; o -cL O 320- RE g O L I l l I I l PERIPHERAL VELOCITY OF SUPPLY ROLLER BACKGROUND OF THE INVENTION This invention relates to developing devices for copying apparatus of the diazo type, andmore particularly it is concerned with a developing device of the type described whereby a diazo photosensitive sheet of the binary system exposed to an optical image of an original is developed by applying a very small quantity of a developing agent consisting of an organic amine and other elements.  
  In addition to a dry developing agent and liquid developing agent, a developing liquid consisting of an organic amine and other elements and usually in the form ofa nonvolatile, concentrated developing liquid is used to develop optical images of originals formed by exposure on diazo photosensitive sheets. The use ofthis type of developing liquid is advantageous in that the optical images can be developed by applying a very small quantity of the developing liquid so that the photosensitive sheets are dry when the images thereon are developed in spite of the fact that the developing liquid is used. A developing system using this type of developing liquid is described, for example, in Japanese Pat. Pub. No. Sho 44-24998.  
  The quantity of the developing liquid required in this developing system for developing optical images formed on diazo photosensitive sheets is only 60 to I50 mg., when the sheets are of a particular size, which is about one tenth the quantity of the developing liquid required in conventional developing systems using a liquid developing agent. The paucity of the developing liquid required for performing this developing operation permits the photosensitive sheets to be in a dry state after developing as if a dry developing agent were used.  
  In carrying out development by this developing system, it is essential that the very small quantity of the developing liquid used be uniformly applied to the photosensitive surface of the photosensitive sheet in order to achieve satisfactory result. If the developing liquid is not evenly applied to the photosensitive surface of the photosensitive sheet, the photosensitive sheet may show a change in color with time. Since the developing liquid is applied to the photosensitive surface only, if the quantity of the developing agent applied to the photosensitive surface is larger than is necessary, the photosensitive sheet may curl up with the photosensitive surface facing inwardly when developed, so that the photosensitive sheet may not be of any practical value.  
  Difficulty has hitherto been experienced in this developing system in applying a very small quantity of the developing liquid evenly on a photosensitive sheet to form a layer of the developing liquid of a uniform thickness. It has hitherto been customary to form a layer of the developing liquid of a uniform thickness on an applicator roller by some meansand to bring the exposed photosensitive surface of a diazo photosensitive sheet into pressing engagementtherewijtli so as to develop the image on the photosensitive surface.  
  In forming a layer of the developing liquid on an applicator roller, it has hitherto been customary to use a roller for adjusting the thickness of the layer to any level as desired or to usea doctor blade for forming a layer of a uniform thickness. Thefuse of the roller or doctor blade has problems which are hard to obviate.  
 More specifically, the use ofthe roller has the problem of how to preclude deflection of the roller or to improve the degree of precision with which the roller is made. The peripheral velocity of the roller is also a factor influencing the quantity of the developing liquid applied to the applicator roller. The method of using a doctor blade for forming a coat of the developingagent of a uniform thickness makes it necessary to fabricate the front end of the doctor blade with a considerably high degree of precision. Besides, the manner of application of the doctor blade to the applicator roller and the degree of coarseness of the surface of the applicator roller tend to affect the adjusments of the quantity of developing liquid applied to the applicator roller. Frictional dragging of the doctor blade on the applicator roller tends to cause wear and damage thereto, sometimes resulting in the applicator roller oscillating in small amplitude. By and large, the use of a doctor blade for adjusting the quantity ofthe developing liquid on the applicator roller is more advantageous than the use of a roller for forming a layer of the developing liquid of a uniform thickness on the applicator roller in that the operation is less affected by speed and can be performed by using a lower pressure at which it is maintained in engagement with the applicator roller.  
 SUMMARY OF THE INVENTION This invention has as its object the provision of a developing device for copying apparatus of the diazo type using a developing liquid of high efficiency consisting of an organic amine and other elements which device comprises a developing liquid quantity control member operatively associated with a developing liquid supply roller having a relatively coarse peripheral surface for adjusting the quantity of the developing liquid supplied to a developing liquid applicator roller maintained in pressing contact with the developing liquid supply roller to an optimum level so as to form on the periphery of the latter a layer of the developing liquid of a uniform thickness which is insusceptible to changes in the peripheral velocity of the developing liquid applicator roller.  
  According to the invention, there is provided a developing device for copying apparatus of the diazo type comprising a developing liquid quantity control member operatively associated with a developing liquid supply roller for adjusting to an optimum level the quantity of a nonvolatile, concentrated developing liquid supplied to a developing position between a developing liquid applicator roller and a pressure applying roller so as to apply an essential minimum of the developing liquid to an exposed photosensitive sheet of the diazo type fed to the developing position. There is also provided a developing liquid removal member disposed posterior to the developing position for removing from the periphery of the developing liquid applicator roller any excess developing liquid which might otherwise remain thereon. The invention is effective to form on the periphery of the developing liquid applicator roller a layer of the developing liquid of a uniform thickness at all times so that the features of the nonvolatile, concentrated developing liquid can be brought into full play.  
 BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of the developing device for copying apparatus of the diazo type comprising one embodiment of the present invention;  
  FIG. 2 and FIG 3 are sectional views of the developing device for copying apparatus of the diazo type comprising second and third embodiments of the invention respectively;  
  FIG. 4 is a diagram showing curves representing the quantities of the developing liquid applied to the photosensitive sheets as a body function of supply roller speed using different embodiments of developing device;  
  FIG. 5 to FIG. 8 are diagrams showning curves representing the quantities of the developing liquid applied to the photosensitive sheets as a function of applicator roller speed; and  
  FIG. 9 to FIG. 11 are sectional side views of different types of mechanism in concrete form for operating the device according to the invention.  
 DESCRIPTION OF PREFERRED EMBODIMENTS FIG. 1 shows one embodiment of the developing device according to the invention. A liquid supply roller 1, which is adapted to be rotated in the direction of an arrow a by a drive (not shown), is made of a nonporous material or rubber of 40to 60 of hardness and an average surface coarseness of 3 to 5 [.LRZI. The developing liquid supply roller 1 has a lower portion of its periphery immersed in a nonvolatile, concentrated developing liquid 3 contained in a developing pan 2 and is maintained at an upper portion of its periphery in pressing engagement with a developing liquid applicator roller 4 adapted to rotate in the direction of an arrow h.  
  A developing liquid quantity control member 5 or a first doctor blade is maintained in engagement with the periphery of the developing liquid supply roller 1 in a position which is disposed anterior to or leftwardly in FIG. I of the position in which the developing liquid applicator roller 4 is maintained in pressing engagement with the supply roller 1. The developing liquid quantity control member 5 is constructed such that the angle at which it is disposed with respect to the periphcry of the developing liquid supply roller 1 and the degree at which it is maintained in pressing engagement with the periphery of the supply roller 1 can be varied so as to thereby adjust to an optimum level the quantity of the developing liquid scooped up by the supply roller 1 and supplied to the applicator roller 4. Thus the quantity control member 5 is disposed above the liquid level in the developing liquid pan 2.  
  The developing liquid supply roller 1 is shown and described as having the lower portion of its periphery being immersed in the developing liquid 3 in this embodiment. This is not essential, however, and the developing liquid can be supplied to the supply roller either by spraying or other means.  
  The developing liquid scooped up by the supply roller 1 is supplied to a developing position 7 disposed between a pressing roller 6 and the applicator roller 4 maintained in pressing engagement with each other. The pressing roller 6 is in the form of a metallic roller made as of stainless steel in this embodiment and rotates in the direction of an arrow 0. Preferably, a series of peripheral grooves or a spiral groove disposed peripherally of the roller is formed in the roller 4 so as to prevent the developing liquid from being collected between the two rollers and 4. In the developing position 7, the pressing roller 6 is maintained in line or surface engagement with the applicator roller 4, and an exposed photosensitive sheet 8 is fed to the developing position 7 from right to left in FIG. 1.  
  A developing liquid removal member 9 or a second doctor blade is disposed posterior to the developing position 7 in which the pressing roller 6 is in engagement with the applicator roller 4. It is maintained at its forward end in pressing engagement with the periphery of the applicator roller 4 so as to remove therefrom any excess developing liquid which might otherwise remain thereon. Like the quantity control member 5, the developing liquid removal member 9 is constructed such that the angle at which it is disposed with respect to the periphery of the applicator roller 4 and the degree at which it is maintained in pressing engagement with the periphery of the applicator roller 4 can be varied as desired.  
  The developing liquid removal member 9 and the quantity control member 5 each have a length which is slightly greater that the width of the periphery of the supply roller 1 and the applicator roller 4. The reason why the developing liquid removal member 9 is disposed posterior to the developing position 7 is because the layer of the developing liquid on the portion of the periphery of the applicator roller 4 disposed anterior to the developing position 7 has an optimum thickness by virtue of the presence of the quantity control member 5. It is to be understood that the position in which the removal member 9 is disposed may be nearer to the developing position 7 than is shown in FIG. 1. However, the position in which the removal member 9 is shown as being disposed in FIG. 1 is a most convenient one from the point of view of removing the developing liquid when the length of the member 9, means for adjustably fixing the same and the peripheral velocity of the applicator roller 4 are taken into consideration.  
  The developing device constructed as aforementioned is advantageous in supplying the developing liquid from the supply roller 1 to the applicator roller 4. The physical properties of the developing liquid will show variations due to changes in the peripheral velocity of the rollers and the environmental conditions including temperature. That is, the viscosity of the developing liquid will vary depending on temperature, and the quantity of the developing liquid scooped up by the supply roller will vary depending on a change in the peripheral velocity of the roller. This is clearly shown by the results of tests. More specifically, curves shown in the diagram in FIG. 4 represent the quantities of the developing liquid applied to the photosensitive sheets obtained by plotting the quantities of the developing liquid as the ordinates against the peripheral velocities of the supply roller as the abscissae. The broken line A represents the quantity of the developing liquid which is adjusted only by using a doctor blade as a developing liquid quantity control member and transferring the developing liquid directly from the supply roller to the photosensitive sheet. It will be seen that the quantity increases substantially in proportion to the peripheral velocity of the supply roller. The dash-and-dot line B represents the quantity of the developing liquid which is adjusted only by transferring the developing liquid from the supply roller to the applicator roller without the use of a doctor blade. It will be seen that in this case the quantity is reduced because the time during which the developing liquid is transferred to the applicator roller becomes shorter as the peripheral velocity of the supply roller increases. Thus, by suitably combining the aforementioned two control methods with each other, it will be possible to supply the developing liquid in uniform quantity as shown by the solid line C irrespective of changes in the peripheral velocity of the supply roller. This invention is based on the aforementioned concept. 7  
  Generally, an increase in the peripheral velocity of the developing liquid supply roller 1 results in an increase in the quantity of the developing liquid supplied from the supply roller 1 after being adjusted by the control member 5. Therefore, if the photosensitive sheet 8 is moved between the rollers l and 4 in a position disposed immediately posterior to the position in which the control member 5 is maintained in engagement with the supply roller 1, the developing liquid will be applied in a large quantity to the photosensitive sheet. However, if the photosensitive sheet 8 is brought into contact with the applicator roller 4 after the developing liquid is transferred from the supply roller 1 to the applicator roller 4 after being adjusted by the control member 5, the quantity of the developing liquid applied to the photosensitive sheet will be reduced when the peripheral velocity of the supply roller increases because the quantity transferred to the applicator roller 4 is reduced and will be increased when the peripheral velocity of the supply roller decreases because the quantity transferred to the applicator roller is increased.  
  Because of this, it is possible to apply the developing liquid in a substantially uniform quantity to the photosensitive sheet 8 by causing the latter to move through the developing position 7 between the applicator roller 4 and the pressing member 6 irrespective of changes in the peripheral velocity of the supply roller 1.  
  By varying the pressure at which the rollers l and 4 are maintained in pressing engagement with each 7 other, it is possible to control to a certain extent the quantity of the developing liquid transferred from the supply roller 1 to the applicator roller 4. It is thus possible to form on the periphery of the applicator roller 4 a layer of the developing liquid of a substantially uniform thickness at all times. Preferably, the applicator roller 4 is made of a non-porous material which suits photosensitive sheets. The material used for making the applicator roller 4 in this embodiment is rubber having a hardness in a range from 40 to 70 (preferably from 40 to 50) and a mean surface coarseness of less than 3 uRa (preferably between 1 and 1.5 ,uRa). When the periphery of the applicator roller 4 has a mean coarseness of above 3 p.Ra, the coarseness of the roller unfavorably affects the photosensitive sheets and lowers the quality of the duplicates produced.  
  The developing liquid on the applicator roller 4 can be applied by pressure transfer in a quantity which is an essential minimum to the photosensitive sheet fed to the developing position 7 in which the pressing roller 6 is maintained in line or surface engagement with the applicator roller 4.  
  When no photosensitive sheet is fed to the developing position, any excess developing liquid on the applicator roller 4 is removed therefrom by the removal member 9. Thus, when thedeveloping device is set in motion, the developing liquid is continuously supplied from the supply roller 1 to the applicator roller 4. If no removal member 9 were provided, the developing liquid supplied and retained on the applicator roller 4 would become so great in quantity that it would satu-.  
 rate the periphery of the applicator roller 4 and no more developing liquid would be supplied from the supply roller 1 to the applicator roller 4. If a photosensitive sheet were fed to the developing position 7 at this time, more developing liquid than is necessary would be applied to the photosensitive sheet by the applicator roller 4, so that the duplicate produced would be degraded in quality. In order to avoid such phenomenon, the removal member 9 is essential to remove excess developing liquid from the applicator roller 4 and return it to the developing pan 2. The removal member 9 and adjusting member 5 are preferably made of a resilient material and covered with a material of low coefficient of friction, such as Teflon, for example.  
  The supply roller 1 may be rotated at the same peripheral velocity as the applicator roller 4. The developing liquid can be supplied satisfactorily to the applicator roller 4 to form a layer of developing liquid of a uniform thickness thereon even if the peripheral velocity of the supply roller 1 is slightly lower than that of the applicator roller 4.  
  FIG. 2 and FIG. 3 shown modified forms of the developing device according to the invention. In the embodiment shown in FIG. 2, the developing liquid quantity control member 5 is in the form of a squeeze roller 5a, with the rollers 1, 5a, 4 and 6 being maintained in pressing engagement with one another. The developing liquid scooped up by the supply roller 1 is transferred to the squeeze roller 5a where the quantity of the developing liquid is adjusted to an optimum level before being transferred to the applicator roller 4. The transfer of the developing liquid from roller to roller is carried out continuously while the rollers rotate. For practical purposes, the squeeze roller 5a is required to be fabricated with a considerably high degree of precision. The developing position is disposed between the applicator roller 4 and the pressing roller 6 in this embodiment too. In the embodiment shown in FIG. 3, a roller 9a is substituted for the doctor blade 9 of FIG. 1 as a developing liquid removal member 9.  
  FIG. 5 to FIG. 8 show the results of experiments carried out on the quantity of the developing liquid applied to the photosensitive sheet 8 by the applicator roller 4 as a function of the peripheral velocity of the applicator roller. A line D in FIG. 5 represents the weight of developing liquid transferred to an overlying sheet of two photosensitive sheets superposed one on the other and fed between the rollers 1 and 4. A line E in FIG. 6 represents the quantity of the developing liquid remaining on the applicator roller 4. A line F in FIG. 7 shows the rate of transfer of the developing liquid from the supply roller 1 to the applicator roller 4. A line G in FIG. 8 represents the quantity of the developing liquid on the supply roller 1.  
  From the data shown in the figures, it will be seen that changes in the quantity of the developing liquid are very small and the transfer of the developing liquid from the supply roller 1 to the applicator roller 4 can achieve satisfactory results in forming a layer of the developing liquid of a uniform thickness on the latter, although no definitive relation is established between the peripheral velocity of the supply roller and the quantity of the developing liquid applied to the photosensitive sheet because of the fact that the efficiency of the doctor blade 5 is higher than expected.  
  In order to prevent deformation of the supply roller 1 and the applicator roller 4, the control member 5 and the removal member 9 are preferably released from engagement with the rollers l and 4 respectively or maintained in light engagement therewith when the developing device out of service. The rollers 6. 5a and l are preferably released from pressing engagement with one another when the developing device is out of service. The pressure at which the removal member 9 is in engagement with the applicator roller 4 is preferably the same as or higher than the pressure at which the control member 5 is in engagement with supply roller 1.  
  Accordingly, the developing device according to the invention is operated by a mechanism which comprises a solenoid adapted to be energized when a start switch (not shown) is turned on so that the rollers may be brought into pressing engagement with one another and the control and removal members may be brought into pressing engagement at their front ends with the respective rollers. Such mechanism will now be described with reference to embodiments shown in FIG. 9 to FIG. 11.  
  The embodiment shown in FIG. 9 utilizes a togglejoint and is constructed such that upon energization of the solenoid SOL a link 11 is pivoted counter clockwise at one end about an immovably pin 12 and the other link 13 is guided by another immovable pin 14 received in a slot 13a formed in the link 13, so that a pressure applying arm 15 is moved upwardly.  
  More specifically, the solenoid SOL has connected thereto an actuator SOLo which is pulled by the solenoid SOL upon energization thereof and which has a pin 16 riding in a transverse slot 16a therein and supporting the link 11 at the end opposite that which is pivotally supported by the immovable pin 12 as aforementioned. The pin 16 also supports the link 13 at one end which is symmetrically arranged with respect to the link 1]. the link 13 being formed at the other end portion with the slot 13a for receiving therein the immovable pin 14 as aforementioned.  
  By the aforementioned arrangement, the link 11 will pivot counter clockwise in FIG. 9 about the pin 12 when the actuator SOLo is pulled toward the solenoid SOL, so that the pin 16 will move along an are leftwardly in FIG. 9 and the link 13 will move upwardly as guided by the pin 14 received in the slot 13a. The link 13 moves by its upper end the pressure applying arm 15 upwardly. The pressure applying arm 15 is pivotally supported by a pressure applying roller shaft 17 and includes a free end portion 15:! extending above the upper end of the link 13 and moved downwardly about shaft 17 by the biasing force of a spring 18, so that a bent portion 15b formed on the free end portion 15a is maintained in contact with the upper end of the link 13. The pressure applying arm 15 has firmly secured to an end portion thereof which is disposed at the opposite end from the free end portion 15: a pressure applying roller supporting member 19 supporting a pressure applying roller 20. The pressure applying roller 20 is adapted to bear against the pressing roller 6 so as to bring the roller 6 into pressing engagement with the applicator roller 4 and to bring the roller 4 into pressing engagement with the supply roller lfwhen the link 13 moves the pressure applying arm 15 upwardly.  
  On the other hand, a bar 21 extending toward the rollers is connected at one end 21a to thefreeend portion 15a of the pressure applying arm 15 through a pin 22 and supports at the other end 21h oneend of connector 23 through a pin 24, the connector 23 being firmly secured at the other end to a rotary shaft 25. The rotary shaft 25 has secured thereto a segmental gear 26 which in turn has secured thereto a blade mounting member 27. The developing liquid removal member 9 in the form of a doctor blade is secured at its base to the mounting member 27 and has a forward end which is disposed near the periphery of the applicator roller 4 and which is adapted to be brought into pressing engagement with the periphery of the applicator roller 4 when the segmental gear 26 pivots counterclockwise about the shaft 25 which angularly rotates in the same direction as the segmental gear 26.  
  The segmental gear 26 is maintained in meshing engagement with another segmental gear 28 pivotally supported by a shaft 29 and has a mounting member 30 secured thereto. The developing liquid quantity control member 5 in the form of a doctor blade is secured at its base to the mounting member 30 and has a forward end which is disposed near the periphery of the supply roller 1 and which is adapted to be brought into pressing engagement with the periphery of the supply roller 1 when the segmental gear 28 pivots clockwise about the shaft 29.  
  Operation of the embodiment constructed as aforementioned will now be described. Upon energization of the solenoid SOL the actuator SOLo is pulled toward the solenoid SOL and moves leftwardly in FIG. 9, so that the link 11 pivots counterclockwise about the pin 12 under the action of pin 16. This causes the pin 16 to move in an arc leftwardly and push the link 13 so that the latter moves upwardly while being guided by the pin 14 received in the slot 13d. This causes the front end edge of the link 13 to push and move the bent portion 15b of the pressure applying arm 15, so that the arm 15 pivots clockwise about the pressure applying roller shaft 17. This causes the pressure applying roller 20 to push the pressing member 6 downwardly, so that the pressing member 6 bears against the applicator roller 4 and the applicator roller 4 bears against the supply roller 1.  
  On the other hand, clockwise pivoting of the pressure applying arm 15 also causes, through the bar 21, the connector 23 to pivot counterclockwise about the shaft 25 which angularly rotates about its own axis. Counterclockwise pivoting of the connector 23 causes the segmental gear 26 to pivot counterclockwise about the shaft 25 which angularly moves in the same direction the segmental gear 26. so that the front end of the removal member 9 is brought into pressing engagement with the periphery of the applicator roller 4. Counter clockwise pivoting of the segmental gear 26 causes the segmental gear 28 in meshing engagement with the segmental gear 26 to pivot clockwise about the shaft 29 so as to bring the front end of the control member 5 into pressing engagement with the periphery of the supply roller 1.  
  The embodiment shown in FIG. 10 employs a hydraulic pressure cylinder and piston arrangement in place of the toggle-joint for causing the pressure applying arm 15 to pivot. More specifically, the actuator connected to and pulled by the solenoid SOL is in the form of an arm 31 which is supported at a base 31a by an immovable member 32 through a pin 33 and connected at its front end&#39;3&#39;1b to the solenoid SOL. Connected to the arm 31 between the opposite ends thereof is a piston rod supporting at its end a piston 34 received in a cylinder 35 for compressing the fluid contained therein. Another cylinder 37 is disposed below the bent portion 15b of the pressure applying arm 15 which is adapted to be pushed and moved upwardly by a piston rod supporting at its end a piston 36 received in the cylinder 37 for compressing the fluid contained therein. The cylinders 35 and 37 are maintained in communication with each other through a pipe 38&#39;. Other parts of the mechanism are substantially similar to the corresponding parts of the mechanism shown in FIG. 9 except for the arrangement in which the connector 23 and the pressure applying arm 15 are connected to each other by a compression spring 39 and the pin 24 planted on the connector 23 is adapted to be pushed and moved by an arm 15c projecting from the lower edge of the pressure applying arm 15.  
  Upon energization of the solenoid SOL the front end 31b of the arm 31 is pulled toward the solenoid SOL and the arm 31 pivots clockwise about the pin 33, so  
 that the piston 34 moves rightwardly in FIG. and compresses the fluid in the pipe 38. This pushes and moves the piston 36in the cylinder 37 upwardly, so that the pressure applying arm pivots clockwise in FIG. 10 about the pressure applying roller shaft 17. Operation of the mechanism thereafter is substantially similar to operation of the mechanism shown in FIG. 9, so that the description thereof will be omitted, although the parts similar in function to the parts shown in FIG. 9 are designated by like reference characters.  
  FIG. ll shows another embodiment of the mechanism in which the segmental gears 26 and 28 employed in the two embodiments shown in FIG. 9 and FIG. 10 are replaced by a linkage. More specifically, the segmental gears 26 and 28 are replaced by links 40 and 41 and the blade mounting member 27 is directly fixed to the link 40 while the blade mounting member is directly fixed to the link 4], with the control member 5 and the removal member 9 being supported by the blade mounting members 27 and 30 respectively.  
  The link has a free end portion 4011 which is connected by a connector 42 to one arm portion 151: of the pressure applying arm 15. More specifically, the free end portion 40a is supported by the pin 24 planted at one end of the connector 42 which is supported at the other end by a pin 43 planted on one arm portion 15a of the pressure applying arm 15. The link 41 has a free end portion 41a which is connected by a connector 44 to the other arm portion 15b. More specifically, the free end portion 411: is supported by a pin 45 planted at one end of the connector 44 which is supported atthe other end by a pin 46 planted on the other arm portion 15d.  
  In operation, clockwise pivoting of the pressure applying arm 15 about the pressure applying roller shaft 17 causes, through the connector 42, the link 40 to pivot counter clockwise about the shaft 25, so that the front end of the removal member 9 is brought into pressing engagement with the periphery of the applicator roller 4. Clockwise pivoting of the arm 15 about the shaft 17 simultaneously causes, through theconnector 44, the link 41 to pivot clockwise about the shaft 29, so that the front end of the control member Sis brought into pressing engagement with the periphery of the supply roller 1.  
  From the foregoing description, it will be understood that the rollers 6, 4 and 1 are released from pressing engagement with one another and the members 5 and 9 are brought out of pressing engagements with the peripheries of the rollers l and 4 respectively when the developing device is rendered inoperative, so that deformation of the rollers can be precluded.  
 What is claimed is:  
  l. A developing device for copying apparatus of the diazo type comprising:  
 a. an rotating applicator roller having a peripheral surface for applying a nonvolatile concentrated developing liquid to a diazo photosensitive sheet exposed to an optical image of an original to be duplicated:  
 b. a supply roller having a peripheral surface maintained in pressing engagement with said peripheral surface of the applicator roller to form thcrebetween an engaging position and rotating at approximately the same peripheral velocity as said applicator roller for supplying the developing liquid to the applicator roller;  
 0. a control member maintained in pressing engagement with said peripheral surface of the supply roller in a position disposed anterior to the engaging position of said surfaces of the applicator and supply rollers along their paths of rotation for adjusting the quantity of the developing liquid supplied to the applicator roller;  
 d. a pressing member maintained in pressing engagement with said applicator roller to form therebetween a developing position through which a diazo photosensitive sheet passes to be developed; and  
 e. a removal member maintained in pressing engagement with said peripheral surface of the applicator roller in a position disposed posterior to the developing position along its path of rotation so as to remove any excess developing liquid from the applicator roller after a developing operation is performed and before any further developing liquid is supplied thereto.  
  2. A device according to claim 1 wherein said control member and said removal member are both doctor blades.  
  3. A device according to claim 1 wherein said control member is a squeeze roller, and said removal member is a doctor blade.  
  4., A device according to claim 1 wherein said control member is a doctor blade, and said removal member is a roller.  
  5. A device according to claim 1 wherein said applicator roller is of a rubber material having a hardness in a range from 40 to and a mean surface coarseness of less than 3p.Ra.  
  6. A device according to claim 1 wherein said supply roller is of rubber material having a hardness in a range form 40 to 60 and the average surface coarseness is in a range between 3 and 4p.Ra.  
  7. A device according to claim 1 further comprising operating means for releasing said pressing member, said applicator roller and said supply roller from pressing engagement with one another and releasing said control member and said removal member from pressing engagement with said supply roller and said applicator roller respectively when the developing device is rendered inoperative, and for bringing said pressing member, said applicator roller and said supply roller into pressing engagement with one another said control member and said removal member into pressing engagement with said supply roller and said applicator 8. A device according to claim 7 wherein said pressing member comprises a pressing roller whose axis lies on a line with the axes of said applicator roller and said supply roller, and said operating means comprises a lever means having a pressure rolleron one end for engaging&#39;s&#39;aid pressing&#39;roller, and pivotable for pressing said pressure roller against said pressing roller to bring &#39;mental gears for rotating said gears and operatively coupled at the other end to said lever means for transmitting the pivoting of said lever means into rotation of said two segmental gears, and actuation means for pivoting said lever means whereby said pressing roller,  
 said applicator roller, and said supply roller are brought into pressing engagement with one another and said &#39;control&#39;memher and said removal member are brought &#39;into pressing engagement with said supply roller and said applicator roller respectively.  
  9. A device according to claim 8 wherein said actuation means comprises a solenoid having an actuator,  
 and toggle-linkage means connected to said actuator for pivoting said lever means upon the actuation of said solenoid.  
  10. A device according to claim 8 wherein said actuation means comprises a solenoid having an actuator, and an hydraulic transmission means for pivoting said lever means upon the actuation of said solenoid.  
  11. A device according to claim 8 wherein said crank means comprises two links pivotally connected at one end to each other and each connected at its other end respectively to-said lever means and one of said two segmental gears.  
  12. A device according to claim 8 wherein said crank means comprises two links each connected at one end to said lever means and at the other end respectively to one of said two segmental gears.