ELECTROSTATIC COPYING APPARATUS

Abstract: An electrostatic copying apparatus which can form an image on both surface of a copying paper as required. The apparatus includes a copying paper conveying passage (58), copying paper feeding means (48) for feeding a copy­ ing paper sheet to the paper conveying passage (58), con­ veyance controlling means (94) disposed adjacent to the downstream end of the paper conveyancing passage, a copying paper discharging passage (104) extending from its up­ stream end adjacent to the downstream end of the convey­ ance controlling means, a copying paper reversing passage (108) extending from its upstream end adjacent to the down­ stream end of the conveyance controlling means (94), a co­ pying paper returning passage (110) extending from its up­ stream end adjacent to the upstream end of the conveyance controlling means, copying paper re-feeding passage (118), and copying paper resending means (120) for re-sending a copying paper returned through the paper returning pas­ sage (110) to the paper conveying passage (58) through the paper re-feeding passage (118).

Description: This invention relates to an electrostatic copying apparatus of the kind referred to in the preamble portion of patent claim 1. Such an electrostatic copying apparatus is known for example from JP-A-59-211 055. It is frequently desired to form an image on both surfaces of a copying paper sheet for saving copying papers and reduce the number of documents to be preserved. This desire has been achieved in recent years by the development of an electrostatic copying apparatus of the type adapted for forming an image on both surfaces of a copying paper sheet as required. A typical example of such an electrostatic copying apparatus includes a copying paper conveying passage, a copying paper feeding means for feeding a copying paper sheet to the paper conveying passage, a conveyance controlling means disposed adjacent to the downstream end of the paper conveying passage, a copying paper discharging passage extending from its upstream end adjacent to the downstream end of the conveyance controlling means, a copying paper reversing passage extending from its upstream end adjacent to the downstream end of the conveyance controlling means, a copying paper returning passage extending from its upstream end adjacent to the upstream end of the conveyance controlling means, a copying paper re-feeding passage, and a copying paper re-sending means for re-sending a copying paper returned through the paper returning passage to the paper conveying passage through the paper re-feeding passage. The conveyance controlling means comprises a lower movable guide member and an upper movable guide member defining a paper moving passage therebetween. The lower and upper movable guide members are adapted to be selectively held at a first position at which the downstream end of the paper conveying passage communicates with the upstream end of the paper discharging passage and a second position at which the downstream end of the paper conveying passage communicates with the upstream end of the paper reversing passage and the upstream end of the paper reversing passage communicates with the upstream end of the paper returning passage. In this type of electrostatic copying apparatus, an image is formed on one surface of a copying paper sheet while it is conveyed through the paper conveying passage after being fed thereto from the paper feeding means. When it is desired to form an image only on one surface of the sheet, the sheet having one image formed on it is introduced into the paper discharging passage through the paper moving passage defined between the lower and upper movable guide members held at the first position, and then discharged through the paper discharging passage. On the other hand, when it is desired to form an image on both surfaces of an image, the aforesaid copying paper bearing an image on one surface is then introduced into the paper reversing passage through the paper moving passage defined between the lower and upper movable guide members held at the second position. After the trailing end of the paper sheet has passed the downstream end of the paper conveying passage, the moving direction of the paper sheet is reversed, and the sheet is introduced into the paper returning passage. The paper sheet is returned to the paper re-sending means through the paper returning passage. The sheet is re-fed to the paper conveying passage through the paper re-feeding passage from the paper re-sending means. During re-conveyance of the sheet through the paper conveying passage, an image is formed on the other surface of the paper. The sheet bearing an image on both surfaces is then introduced into the paper discharging passage through the paper moving passage between the lower and upper movable guide members held at the first position, and discharged through the paper discharging passage. The aforesaid type of conventional electrostatic copying apparatus has not proved to be entirely satisfactory, and has various problems to be solved, for example with regard to the operation of removing copying paper that jams up in various passages, the structure of the apparatus on the upstream side of the conveyance controlling means (and therefore on the downstream end of the paper conveying passage and the upstream end of the paper returning passage), the structure of the apparatus on the downstream side of the conveyance controlling means (and therefore the upstream end of the paper discharging passage and the upstream end of the paper reversing passage), and the structure of the paper returning passage. JP-A-59 211 055 discloses an electrostatic copying apparatus comprising a lower supporting frame, an upper supporting frame mounted on the lower supporting frame for free pivotal movement between an operating position and a non-operating position, a copying paper conveying passage, a copying paper feeding means for feeding a copying paper sheet to the paper conveying passage and a copying paper returning passage, and being adapted to form an image on one surface of the copying paper sheet while it is conveyed through the paper conveying passage after being fed to the conveying passage from the feeding means, to introduce the paper sheet bearing an image on one sur face selectively into the paper returning passage, to return it through the returning passage, to re-feed it into the paper conveying passage and to form an image on the other surface of the paper sheet while it is reconveyed through the paper conveying passage, at least a greater portion of the paper conveying passage being defined between the lower supporting frame and the upper supporting frame when the upper supporting frame is held at the operating position and being opened when the upper supporting frame is held at the non-operating position, and at least a greater portion of the paper returning passage being provided inside the lower supporting frame. It is the object of the present invention to provide an electrostatic copying apparatus with an improved possibility to remove jammed sheets of paper from the paper feeding passage. This object is accomplished with an electrostatic copying apparatus as claimed in claim 1. Dependent claims are directed on features of preferred embodiments of the invention. Various specific advantages of the invention in various aspects will become apparent from the following detailed description taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a sectional view showing in a simplified form the principal structural elements of the electrostatic copying apparatus constructed in accordance with this invention; Figure 2 is a sectional view, similar to Figure 1, showing an upper supporting frame in the electrostatic copying apparatus of Figure 1 as it is held at a non-operating position; Figure 3 is a simplified perspective view showing a supporting frame structure in the electrostatic copying apparatus in Figure 1 as its upper supporting frame is held at the non-operating position; Figure 4 is a partial front view showing a part of a lower front base plate of a lower supporting frame in the electrostatic copying apparatus of Figure 1; Figure 5 is a partial perspective view showing a locking means and a detecting means in the electrostatic copying apparatus of Figure 1; Figure 6 is a partial sectional view showing a conveyance controlling means in the electrostatic copying apparatus of Figure 1; Figure 7 is a partial sectional view, similar to Figure 6, showing the conveyance controlling means in the electrostatic copying apparatus of Figure 1 as the upper supporting frame has been moved to some extent toward the non-operating position from its operating position; Figure 8 is a partial perspective view showing the conveyance controlling means in the electrostatic copying apparatus of Figure 1. The invention will now be described in detail with reference to the accompanying drawings. With reference to Figure 1, the illustrated electrostatic copying apparatus includes a nearly rectangular housing 2. A stationary transparent plate 4 on which to place a document (not shown) to be copied and an openable document holding member 6 for covering the transparent plate 4 and the document to be placed on it are disposed on the top surface of the housing 2. A rotating drum 8 having an electrostatographic material on its peripheral surface is rotatably mounted nearly centrally within the housing 2. Around the rotating drum 8 to be rotated in the direction shown by an arrow 10 are defined a charging zone 12, an exposing zone 14, a developing zone 16, a transferring zone 18 and a cleaning zone 20 defined in this order in the direction of arrow 10. A charging corona discharge device 22 is disposed in the charging zone 12, and a developing device 24 is disposed in the developing zone 16. A transferring corona discharge device 26 and a peeling corona discharge device 28 are provided in the transferring zone 18. In the cleaning zone 20, a charge eliminating lamp 30 and a residual toner removing blade 32 are set up. An optical system shown generally at 34 is provided above the rotating drum 8. The optical system 34 comprises a movable document illuminating lamp 36, a first movable reflecting mirror 38, a second movable reflecting mirror 40, a third movable reflecting mirror 42, a stationary lens assembly 44 and a stationary reflecting mirror 46. During scanning exposure, the movable document illuminating lamp 36 and the first movable reflecting mirror 38 are moved at a predetermined speed V from a start-of-scan position shown by a solid line to a desired position (for example, a maximum end-of-scan position shown by a two-dot chain line) substantially horizontally. The second movable reflecting mirror 40 and the third movable reflecting mirror 42 are moved at a speed half of the above predetermined speed (V/2) from a start-of-scan position shown by a solid line to a desired position (for example, a maximum end-of-scan position shown by a two-dot chain line) substantially horizontally. During this action, the document placed on the transparent plate 4 is illuminated by the document illuminating lamp 36, and the light reflected from the document is reflected successively by the first, second and third reflecting mirrors 38, 40 and 42 and reaches the lens assembly 44. Then, it is reflected by the stationary reflecting mirror 46 and projected onto the electrostatographic material in the exposing zone 14. When the scanning exposure is over, the movable document illuminating lamp 36 and the first, second and third reflecting mirrors 38, 40 and 42 are returned to the start-of-scan positions shown by the solid lines. In one end portion (the right end portion in Figure 1) of the housing 2, a copying paper feeding means shown generally at 48 is provided. The paper feeding means 48 includes a lower cassette receiving section 50a, an intermediate cassette receiving section 50b and an upper cassette receiving section 50c for selectively and detachably receiving several types of copying paper cassettes 52 containing copying paper sheets of different sizes. Delivery rollers 54a, 54b and 54c for delivering the copying paper sheets one by one from the paper cassettes 52 are provided respectively in the lower, intermediate and upper cassette receiving sections 50a, 50b and 50c. The copying paper delivered from the paper cassette 52 mounted on the lower cassette receiving section 50a is introduced into a copying paper conveying passage generally shown at 58 through a copying paper delivery passage 56a. The copying paper delivered from the paper cassette 52 mounted on the intermediate cassette receiving section 50b is introduced into the paper conveying passage 58 through the paper delivery passages 56a and 56a. The copying paper delivered from the paper cassette 52 mounted on the upper cassette receiving section 50c is introduced into the paper conveying passage 58 through a copying paper delivery passage 56c and the paper delivery passages 56b and 56a. The paper delivery passage 56a is defined by the upstream portion of a guide plate 60 and a part of a guide plate 62. The paper delivery passage 56b is defined by a pair of guide plates 64. The paper delivery passage 56c is defined by a pair of guide plates 66. A pair of delivery rollers 68 are disposed between the upstream end of the paper delivery passage 56a and the downstream end of the paper delivery passage 56b, and a pair of delivery rollers 69, between the upstream end of the paper delivery passage 56b and the downstream end of the paper feed passage 56c. The paper conveying passage 58 extends nearly horizontally from right to left in Figure 1 from its upstream end 70 to its downstream end 72, and is defined by the downstream portion of the guide plate 60, the downstream portion of the guide plate 74, a pair of conveying rollers 76, a pair of guide plates 78, a pair of conveying roller 80, a guide plate 82, the transferring zone 18 (an area between the rotating drum 8 and the transferring corona discharge device 26 and the peeling corona discharge device 28), a conveyor belt mechanism 84, a guide plate 86, pair of heat-fixing rollers 88, a pair of guide plates 90, and a pair of conveying rollers 93 in a first multifunctional conveying means generally shown at 92 (the first multifunctional conveying means will be described in detail hereinafter). A conveyance controlling means 94 is disposed adjacent to the downstream end 72 of the paper conveying passage 58. The conveyance controlling means 94 includes a lower movable guide member 98 and an upper movable guide member 100 defining a copying paper moving passage 96 therebetween. The lower movable guide member 98 and the upper movable guide member 100 are selectively held at a lowered position shown by a solid line (a first position) and at an elevated position shown by a two-dot chain line (a second position). The conveyance controlling means 94 will be described in detail hereinafter. Downstream of the conveyance controlling means 94 is provided a copying paper discharging passage 104. At the upstream end of the paper discharging passage 104 are disposed a pair of conveying rollers 103 in a second multifunctional conveying means shown generally at 102. A receiving tray 106 is mounted detachably at the other end (i.e., the left end portion in Figure 1) of the housing 2. In relation to the conveyance controlling means 94, a copying paper reversing passage shown generally at 108 and a copying paper returning passage shown generally at 110 are provided. The paper reversing passage 108 is defined by a pair of guide plates 112 and extends curvilinearly from its upstream end adjacent to the downstream end of the conveyance controlling means 94. At the upstream end of the paper reversing passage 108 is disposed a pressing member 114 in the second multifunctional conveying means 102. The pressing means 114 may be constructed of a rotatable roller, and is adapted to be selectively held at a non-operating position shown by a solid line and an operating position shown by a two-dot chain line. The paper returning passage 110 extends inclinedly somewhat in a downward direction from left to right in Figure 1 from its upstream end adjacent to the upstream end of the conveyance controlling means 94. At the upstream end of the paper returning passage 110 is disposed a guide plate 116 in the first multifunctional conveying means 92, and a guide plate 117 is provided above the downstream portion of the guide plate 116. A returning mechanism shown generally at 118 is provided downstream of the guide plates 116 and 117. The returning mechanism 118 will be described in detail hereinafter. It will be readily understood from Figure 1 that when the lower movable guide member 98 and the upper movable guide member 100 of the conveyance controlling means 94 are held at the lowered positions shown by solid lines, the paper conveying passage 58 and the paper discharge passage 104 are brought into communication with each other through the paper moving passage 96 in the conveyance controlling means 94. On the other hand, when the lower and upper movable guide members 98 and 100 are held at the elevated positions shown by two-dot chain lines, the paper conveying passage 58 and the paper reversing passage 108 are brought into communication with each other through the paper moving passage 96 of the controlling means 94 and at the same time, the paper reversing passage 108 and the paper returning passage 110 are brought into communication with each other through the moving passage 96 of the controlling means 94. The illustrated electrostatic copying apparatus further includes a copying paper re-sending means shown generally at 120 below the paper returning passage 110. The paper re-sending means 120 includes a substantially horizontally exetending stand 122 for receiving copying paper, and a stopping means 124 is provided at the front end (i.e., the right end in Figure 1) of the paper receiving stand 122. The stopping means 124 is adapted to be selectively held at an operating position shown by a solid line and a non-operating position shown by a two-dot chain line. A delivery roller 126 is provided on the front end portion of the receiving stand 122. The delivery roller 126 is mounted such that it can freely move upwardly from its illustrated position contacting the upper surface of the paper receiving stand 122, and can be elastically biased downwardly by a suitable press controlling means (not shown). A copying paper re-feeding passage shown generally at 128 is provided which extends from the front end of the paper re-sending means 120 to the upstream end 70 of the paper conveying passage 58. The paper re-feeding passage 128 is defined by a guide plate 130, a re-feeding roller 132, a pair of re-feeding rollers 134, a pair of guide plates, 136 and the upstream portion of the guide plate 74. The outline of the operation of the electrostatic copying apparatus described hereinabove is now described. The rotating drum 8 is rotated in the direction of arrow 10. In the charging zone 12, the surface of the electrostatographic material on the rotating drum 8 is charged to a specific polarity by the charging corona discharge device 26, and in the exposing zone 14, the image of a document placed on the transparent plate 4 is scanned, exposed and projected onto the electrostatographic material by the optical system 34 to form a latent electrostatic image on the electrostatographic material. In the developing zone 16, a toner is applied to the latent electrostatic image on the electrostatographic material by the developing device 24 to develop the latent electrostatic image to a toner image. In the transferring zone 18, a copying paper sheet conveyed through the transferring zone 18 (the conveying of copying paper will be further described hereinbelow) is brought into contact with the surface of the electrostatographic material, and by the action of the transferring corona discharge device 26, the toner image on the electrostatographic material is transferred to the copying paper sheet. Thereafter, the copying paper is peeled from the electrostatographic material by the action of the peeling corona discharge device 28. The peeled copying paper is conveyed to the pair of heat-fixing rollers 88, and during passage between the rollers 88, the toner image is fixed to the copying paper. In the meantime, in the cleaning zone 20, light from the charge eliminating lamp 30 is illuminated onto the electrostatographic material to erase the residual charge on it. The residual toner is removed from the surface of the electrostatographic material by the action of a residual toner blade 32. The conveying of copying paper will now be described. First, with reference to the formation of an image only on one surface of a copying paper, the lower and upper movable guide members 98 and 100 of the conveyance controlling means 94 are held at the lowered positions shown by solid lines. A copying paper sheet introduced into the paper conveying passage 58 from the paper cassette 52 loaded into the lower cassette receiving section 50a, the intermediate cassette receiving section 50b or the upper cassette receiving section 50c is conveyed through the conveying passage 58. During this time, a toner image is transferred to the upper surface of the copying paper in the transferring zone 18, and the toner image is fixed to that surface of the copying paper by the action of the pair of heat-fixing rollers 88. As a result, an image is formed on one surface of the copying paper. The copying paper bearing an image on one surface is then introduced into the paper discharge passage 104 through the paper moving passage 96 in the conveyance controlling means 94, and discharged into the receiving tray 106 through the paper discharge passage 104. Thus, a copy having an image formed on one its one surface is obtained. When an image is to be formed on both surfaces of copying paper, the lower and upper movable guide members 98 and 100 of the conveyance controlling means 94 are first held at the elevated positions shown by the two-dot chain lines. When the copying process is started, a copying paper introduced into the paper conveying passage 58 from the paper cassette 52 loaded into the lower cassette receiving section 50a, the intermediate cassette-receiving section 50b or the upper cassette receiving section 50c is conveyed through the paper conveying passage 58. During this time, a toner image is transferred to one surface (the upper surface) of the copying paper in the transfering zone 18, and fixed onto one surface of the copying paper by the action of the heat-fixing rollers 88 to form an image on one surface of the copying paper. The copying paper from the paper conveying passage 58 is introduced into the paper reversing passage 108 through the paper moving passage 96 in the conveyance controlling means 94, and advances in the direction shown by an arrow 138 through the paper reversing passage 108. When the trailing end of the copying paper has passed the downstream end of the paper conveying passage 58, i.e. the nipping site of the conveying rollers 92, the pressing means 114 in the second multifunctional conveying means 102 is held at the operating position shown by the two-dot chain line. As a result, the trailing end and the leading end of the copying paper are reversed and the copying paper is moved in the direction shown by an arrow 142. By being guided by the guide plate 116 of the first multifunctional conveying means 92, the copying paper is introduced into the paper returning passage 110. The reversing roller 114 in the paper reversing passage 108 is returned to the non-operating position shown by the solid line at a suitable time after the copying paper has been introduced into the paper returning passage 110. The copying paper which has advanced through the paper returning passage 110 is conducted to the paper receiving stand 122 of the paper re-sending means 120 and advances on the receiving stand to the right in Figure 1. The delivery roller 126 rotated in the direction shown by arrow 144 acts on the copying paper to deliver it further to the right and thus cause its the leading edge to abut against the stopping means 124 held at the operating position shown by the solid line. This hampers the advancing of the copying paper, and the copying paper is stopped at a desired position on the paper re-sending means 120. Even when the delivery roller 126 is rotated in the direction of arrow 144 at this time, slippage is created between the delivery roller 126 and the copying paper, and there is no further advancing of the copying paper. When a predetermined number of copying paper sheets have been returned to the paper re-sending means 120, the lower and upper movable guide members 98 and 100 of the conveyance controlling means 94 are returned to the lowered positions shown by the solid lines. The stopping means 124 in the paper re-sending means 120 is held at the non-operating position shown by the two-dot chain line, and by the action of the delivery roller 126 rotating in the direction of arrow 144, the copying paper is delivered from the paper re-sending means 120 to the paper re-feeding passage 128. The copying paper sheets delivered to the paper re-feeding passage 128 are caused to advance one by one through the paper re-feeding passage 128 and again fed to the copying paper conveying passage 58. As can be easily understood from Figure 1, the copying paper is reversed as a result of passing through the nearly semicircular paper re-feeding passage 128 and fed to the paper conveying passage 58 with its image-bearing surface down. It is then conveyed through the paper conveying passage 58. At this time, a toner image is transferred to the other surface of the copying paper (i.e., the upper surface) in the transferring zone 18, and fixed to the copying paper by the action of the pair of heat-fixing rollers 88. As a result, an image is formed on the other surface of the copying paper. Thereafter, the copying paper is introduced from the paper conveying passage 58 into the paper discharging passage 104 through the paper moving passage 96 in the conveyance controlling means 94, and discharged onto the receiving tray 106 through the paper discharge passage 104. Thus, a copy having an image formed on both surfaces is obtained. The structure and operation described above of the illustrated electrostatic copying apparatus do not constitute novel features improved in accordance with the present invention, but merely illustrate one example of electrostatic copying apparatus to which the present invention is applicable. Hence, a detailed description of these will be omitted in the present specification. Structure of the supporting frame With reference to Figures 1 and 2, the housing 2 is comprised of a lower supporting frame 146 and an upper supporting frame 148. The upper supporting frame 148 is pivotably mounted on the lower supporting frame 146 via a supporting shaft 150, and pivots between an operating position (closed position) shown in Figure 1 and a non-operating position (open position) shown in Figure 2. The method of mounting the upper supporting frame 148 on the lower supporting frame 146 may be that disclosed, for example, in Japanese Laid-Open Patent Publication No. 100459/1984, 152458/1984 or 188670/1984. With reference to Figure 3, the lower supporting frame 146 is nearly in the shape of a box having an open top, and the upper supporting frame 148 is nearly in the shape of a box having an open bottom. The lower supporting frame 146 has a lower front base plate 152 and a lower rear base plate 154 disposed therein substantially vertically with a space therebetween in the forward-backward direction (a direction perpendicular to the sheet surface in Figures 1 and 2). Likewise, the upper supporting frame 148 has an upper front base plate 156 and an upper rear base plate 158 (Figures 1 and 2) disposed therein substantially vertically with a space therebetween in the forward-backward direction. Those of the various constituent elements described with reference to Figure 1 which are disposed below a one-dot chain line 160 in Figure 1 are mounted between the lower front base plate 152 and the lower rear base plate 154, and those constituent elements disposed above the one-dot chain line 160 in Figure 1, between the upper front base plate 156 and the upper rear base plate 158. It will be understood therefore by reference to Figures 1 and 2 that in the illustrated embodiment, when the entire paper feeding passages 56a, 56b and 56c, a greater part of the paper conveying passage 58 (more specifically that portion of the passage 58 excluding the portion defined by the pair of heat-fixing rollers 88), and the paper discharge passage 104 are defined between the lower supporting frame 146 and the upper supporting frame 148 when the upper supporting frame 148 is held at the operating position shown in Figure 1, and are set free when the upper supporting frame 148 is held at the non-operating position shown in Figure 2. In the illustrated embodiment, an upper roller 88a of the pair of heat-fixing rollers 88 and means for supporting it are mounted for free pivotal movement between an operating position (closed position) shown in Figure 1 and a non-operating position shown in Figure 2 about a supporting shaft 162 as a center. Accordingly, when the upper supporting frame 148 is held at the non-operating position shown in Figure 2 and when the upper roller 88a and the supporting means therefor are held at the non-operating position shown in Figure 2, the paper conveying passage 58 is opened entirely. The paper reversing passage 108 is provided within the upper supporting frame 148, more specifically between the upper front base plate 156 and the upper rear base plate 158, and the paper returning passage 110, the paper re-sending means 120 and the paper re-feeding passage 128 are provided inside the lower supporting frame 146, more specifically between the lower front base plate 152 and the lower rear base plate 154. With reference to Figures 1 and 2 taken in conjunction with Figure 4, a relatively large single continuous opening 164 is formed in the lower front base plate 152 of the lower supporting frame 146. The opening 164 continuously extends along a greater part of the paper returning passage 110, more specifically, over an area where a portion defined by the returning mechanism 118 exists, and an area where nearly entire copying paper re-sending means 120 exists. The right edge of the opening 164 in Figures 1 and 4 adjoins the paper re-feeding passage 128. Hence, when paper jamming occurs in the paper returning passage 110, paper re-sending means 120 and paper re-feeding passage 128, the paper which has jammed up can be easily removed by hand through the opening 164. The returning mechanism 118 in the paper returning passage 110 has a movable frame 166. The movable frame 166 is mounted on the lower rear base plate 154 (Figure 3) such that it can pivot between an operating position shown by a solid line in Figure 4 and a non-operating position shown by a two-dot chain line in Figure 4 about a pivot axis extending along its rear edge as a center. As is clearly seen from Figure 4, the opening 164 extends not only in an area where the movable frame 166 exists when held at the operating position but also in an area where the movable frame 166 exists when held at the non-operating position. The upper elements in the returning mechanism 118 (i.e., the elements defining the upper portion of the paper returning passage 110) are directly mounted on the lower front base plate 152 and the lower rear base plate 154 of the lower supporting frame 146, but the lower elements of the returning mechanism 118 (i.e., the elements defining the lower portion of the copying paper returning passage 110) are mounted on the movable frame 166. Hence, when paper jamming occurs in the returning mechanism 118, the operator can easily get access to the copying paper that has jammed up by holding a gripping portion 168 formed at the front end of the movable frame 166 and moving the movable frame 166 from the operating position shown by the solid line to the non-operating position shown by the two-dot chain line thereby to open the paper returning passage 110 in the returning mechanism 118. Thus, he can easily remove that paper from the returning passage. With reference to Figure 3, the front wall of the lower supporting frame 146 is defined by a lower front cover member 170 that can be freely opened and closed. The lower front cover member 170 is mounted by a suitable mounting mechanism (not shown) so that it can pivot freely between a closed position (the position shown by a two-dot chain line in Figure 3) at which it covers nearly the entire front surface of the lower supporting frame 146 and an open position (the position shown by a solid line in Figure 3) at which the nearly entire front surface of the lower supporting frame 146 is exposed to view about a pivot axis 172 extending along its lower edge as a center. Likewise, that part of the front wall of the upper supporting frame 148 which is other than the upper end portion is defined by an upper front cover member 174 that can be freely opened and closed. The upper front cover member 174 is mounted on a suitable mounting mechanism (not shown) so that it can freely pivot between a closed position (the position shown by a two-dot chain line in Figure 3) at which it covers the front surface of the upper supporting frame 148 excepting the upper end portion and an open position (the position shown by a solid line in Figure 3) at which the front surface of the upper supporting frame 148 excepting the upper end portion is exposed to view about a pivot axis 176 extending along its lower edge. Locking means and detecting means With reference to Figure 5 as well as Figure 3, a supporting plate 178 extending forwardly from the upper front base plate 156 in the upper supporting frame 148 is fixed to the upper front base plate 156. A first detecting element 180 is fixed to one surface of the supporting plate 178, and a second detecting element 182, to the other surface. The first detecting element 180 may be a limit switch having a detecting arm 184, and likewise, the second detecting element 182 may be a limit switch having a detecting arm 186. To the upper front base plate 156 in the upper supporting frame 148 is further fixed a restraining member 188 composed of a plate-like member extending forwardly from the upper front base plate 156 below the supporting plate 178. An opening 190 located beneath the forward end portion of the detecting arm 184 of the first detecting element 180 is formed in the forward end portion of the restraining member 188. A piece 192 is fixed to the back surface of the lower front cover member 170 in the lower supporting frame 146. As is clearly shown in Figure 3, the free end of the piece 192 projects beyond the upper end of the lower front cover member 170 via a cut 193 formed in the upper wall portion of the lower front cover member 170. The piece 192 functions not only as a restrained member constituting a locking means in cooperation with the restraining member 188 but also as a detected element constituting a first detecting means in cooperation with the first detecting element 180. A piece 194, on the other hand, is fixed to the back surface of the upper front cover member 174 in the upper supporting frame 148. As will be clear from a description to be given hereinafter, the piece 194 functions as a detected element constituting a second detecting means in cooperation with the second detecting element 182. It will be appreciated with reference to Figures 3 and 5 that when the lower front cover member 170 in the lower supporting frame 146 is held at the closed position shown by the two-dot chain line and then the upper supporting frame 148 is held at the operating position (Figure 1), the front end portion of the piece 192 is received in the opening 190 of the restraining member 188. As a result, the forward movement of the piece 192 is restrained by the restraining member 188, and therefore, the lower front cover member 170 is locked at the closed position shown by the two-dot chain line in Figure 3. In other words, in the illustrated electrostatic copying apparatus, when the upper supporting frame 148 is at the operating position (Figure 1), the lower front cover member 170 is locked at the closed position by the cooperative action of the restraining member 188 and the piece 192, and the lower front cover member 170 cannot be moved to the opened position shown by the solid line in Figure 3. When the upper supporting frame 148 is held at the non-operating position shown in Figure 3, the restraining member 188 is disengaged from the piece 192 and the lower front cover member 170 can be moved to the opened position shown by the solid line in Figure 3. When the lower front cover member 170 in the lower supporting frame 146 is held at the closed position shown by the two-dot chain line in Figure 3 and then the upper supporting frame 148 is held at the operating position (Figure 1), the forward end portion of the piece 192 is received in the opening 190 of the restraining member 188 and the lower front cover member 170 is locked at the closed position. In addition, as can be understood from Figure 5, the forward end of the piece 192 presses the detecting arm 184 of the first detecting element 180 whereby the first detecting element 180 is turned on. When the upper front cover member 174 in the upper supporting frame 148 is held at the closed position shown by the two-dot chain line in Figure 3, the forward end of the piece 194 presses the detecting arm 186 of the second detecting element 182 whereby the second detecting element 182 is turned on. The first detecting element 180 and the second detecting element 182 function as safety switches, and the electrostatic copying apparatus can be operated when both the first detecting element 180 and the second detecting element 182 are on. If desired, the restrained member and the detected element may be constructed of separate pieces. It is also possible to fix the piece 192 to the upper front base plate 156 of the upper supporting frame 148 and the first detecting element 180 and the restraining member 188, to the lower front cover member 170 of the lower supporting frame 146. Furthermore, it is possible to fix the piece 194 to the upper front base plate 156 of the upper supporting frame 148 and the second detecting element 182, to the upper front cover member 174 of the upper supporting frame 148. Procedure of dealing with paper jamming With reference to Figures 1, 2 and 3, when paper jamming occurs in the paper feeding passage 56a, 56b or 56c, the paper conveying passage 58 or the paper discharging passage 104 during its operation in a mode of forming an image only on one surface of a copying paper and the operation of the copying apparatus is stopped, the operator first brings the upper supporting frame 148 to the non-operating position shown in Figures 2 and 3. As a result, the entire paper feeding passage 56a, 56b or 56c, a greater portion of the paper conveying passage 58 (excepting a portion defined by the pair of heat-fixing rollers 88) and the entire paper discharging passage 104 are open. As required, the operator keeps the upper roller 88a of the heat-fixing rollers 88 and the supporting means therefor at the non-operating position shown in Figure 2 and thus opens the entire paper conveying passage 58. The operator can then get access to the copying paper and remove it from the paper feeding passage 56a, 56b or 56c, the paper conveying passage 58 or the paper discharging passage 104. Now, let us assume that paper jamming occurs during the operation of the electrostatic copying apparatus in a mode of forming an image on both surfaces of a copying paper, and the operation of the electrostatic copying apparatus is stopped. In this case, the following fact should be noted. In the case of obtaining a plurality of copies from the same document, when paper jamming occurs in the paper returning passage 110 or the paper re-sending means 120, successive copying paper sheets exist in the paper feeding passage 56a, 56b or 56c, the paper conveying passage 58 or the paper reversing passage 108 unless the paper that has jammed up is for the last copy to be obtained. Hence, these paper sheets should also be removed. In the illustrated electrostatic copying apparatus, it is first necessary to hold the upper supporting frame 148 at the non-operating position shown in Figures 2 and 3 prior to opening movement of the lower front cover member 170 in order to remove paper sheets existing in the paper returning passage 110, the paper re-sending means 120 or the paper re-feeding passage 128 disposed within the lower supporting fame 146. So long as the upper supporting frame 148 is kept at the operating position shown in Figure 1, the opening movement of the lower front cover member 170 is hampered by the action of the locking means (the restraining member 188 and the piece 192) described above. Thereafter, as required, the upper roller 88a of the heat-fixing rollers 88 and the supporting member therefor are held at the non-operating position shown in Figure 2, and then the paper sheets existing in the paper feeding passage 56a, 56b or 56c, the paper conveying passage 58 or the paper reversing passage 108 are removed. The copying paper existing in the paper reversing passage 108 can be easily removed by hand from the open bottom surface of the upper supporting frame 148. Thereafter, the lower front cover member 170 is held at the open position shown by the solid line in Figure 3. Then, as required, the movable frame 166 of the returning mechanism 118 is held at the non-operating position shown by the two-dot chain line in Figure 4. When the lower front cover member 170 is held at the open position, the opening 164 formed on the lower front base plate 152 is exposed to view. The copying paper existing in the paper returning passage 110, the paper re-sending means 120 or the paper re-feeding passage 128 can be easily removed by hand through the opening 164. When, for example, a copying paper is removed only from the paper returning passage 110 or the paper re-sending means 120 and a copying paper to be removed is carelessly left in the paper feeding passage 56a, 56b or 56c, the paper conveying passage 58 or the paper reversing passage 108, various inconveniences will occur upon resumption of the operation of the electrostatic copying apparatus. In the electrostatic copying apparatus shown in the drawings, the occurrence of such inconveniences can be fully and accurately prevented. Conveyance controlling means With reference to Figures 6 to 8, the structure of the conveyance controlling means 94 will be described in detail. As stated above, the conveyance controlling means 94 includes the lower movable guide member 98 and the upper movable guide member 100. As most clearly shown in Figure 8, the lower movable guide member 98 has a supporting shaft 196, and a plurality of axially spaced lower guide pieces 198 of a nearly triangular shape are formed integrally with the supporting shaft 196. The opposite end portions of the supporting shaft 196 are pivotably mounted on the lower front base plate 152 and the lower rear base plate 154 in the lower supporting frame 146. Consequently, the lower movable guide member 98 is pivotably mounted at a predetermined position of the lower supporting frame 146 (see Figure 3, also). A linking piece 200 (Figures 6 and 7) is also formed integrally with the supporting shaft 196. An actuating means which may be an electromagnetic solenoid 202 is connected to the linking piece 200. More specifically, the main body of the electromagnetic solenoid 202 is fixed to a predetermined position of the lower supporting frame 146 (Figure 7), and its iron core 204 is connected pivotably to the linking piece 200 by means of a linking pin 206. When the electromagnetic solenoid 202 is deenergized, the lower movable guide member 98 is held at the position shown by the solid line in Figure 6, i.e. at the lowered position. When the electromagnetic solenoid 202 is energized, the lower movable guide member 98 is pivoted to the position shown by a two-dot chain line in Figure 6, i.e. the elevated position. The lower movable guide member 98 has also formed integrally therewith projections 208 extending outwardly from the outside surfaces of those lower guide pieces 198 which are located outermost on both sides. Such projections 208 constitute an abutting means acting on the upper movable guide member 100 as will be apparent from a statement given hereinafter. The upper movable guide member 100 has an elongate plate-like member 212 having formed integrally therewith a plurality of longitudinally spaced upper guide pieces 210 of a nearly triangular shape. The upper guide pieces 210 are located such that they correspond respectively to the lower guide pieces 198 in the lower movable guide member 98. Nearly rectangular pieces 214 are formed integrally on both ends of the plate-like member 212, and outwardly extending short shafts 216 are formed integrally on the outside surfaces of the pieces 214. The pieces 214 constitute an abutment means which cooperates with the projections in the lower movable guide member 98, i.e. the abutting means 208. The short shafts 216 are respectively mounted pivotably on the upper front base plate 156 (Figure 3) and the upper rear base plate 158 (Figure 7) in the upper supporting frame 148. Pins 218 are formed integrally on the outside surfaces of the rear end portions of those upper guide pieces 210 which are located outermost on both sides in the upper movable guide member 100. Pins 220 are correspondingly formed also on the inner surfaces of the upper front base plate 156 (Figure 3) and the upper rear base plate 158 in the upper supporting frame 148. An elastic means which may be a tension spring 222 is disposed between each pin 218 and each pin 220. The tension spring 222 elastically biases the upper movable guide member 100 counterclockwise in Figure 6. If desired, the upper movable guide member 100 can be biased counterclockwise in Figure 6 by the own weight of the upper movable guide member 100. Furthermore, in the illustrated embodiment, a restriction means 224 constructed of a plate-like member is fixed to a predetermined position of the upper supporting frame 148. When in the conveyance controlling means 94 described above, the upper supporting frame 148 is held at the operating position shown in Figure 1 and the electromagnetic solenoid is in the deenergized state, the lower movable guide member 98 is held at the lowered position shown by the solid line in Figure 6. The upper movable guide member 100 elastically biased counterclockwise in Figure 6 by the tension spring 222 is held at the lowered position shown by the solid line in Figure 6 as a result of its abutment means 214 being brought into abutment against the abutting means 208 of the lower movable guide member 98. With reference to Figures 1 and 6, when the lower movable guide member 98 and the upper movable guide member 100 are held at the lowered positions shown by the solid lines, the paper moving passage 96 defined between the upper edge of the lower guide member 198 in the lower movable guide member 98 and the lower edge of the upper guide member 210 in the upper movable guide member 100 permits communication between the paper conveying passage 58 and the paper discharging passage 104. On the other hand, when the electromagnetic solenoid 202 is energized, the lower movable guide member 98 is pivoted clockwise in Figure 6 and held at the elevated position shown by the two-dot chain line in Figure 6. As a result, the upper movable guide member 100 is also pivoted clockwise in Figure 6 against the elestic biasing action of the tension spring 222 by means of the abutting means 208 in the lower movable guide member 98 and the abutment means 214 in the upper movable guide member 100, and held at the elevated position shown by the two-dot chain line in Figure 6. With reference to Figure 1 as well as Figure 6, when the lower movable guide member 98 and the upper movable guide member 100 are held at the elevated positions shown by the two-dot chain line, the paper moving passage 96 defined between the upper edge of the lower guide piece 198 in the lower movable guide member 98 and the lower edge of the upper guide piece 210 in the upper movable guide member 100 permits communication between the paper conveying passage 58 and the paper reversing passage 108 and between the paper reversing passage 108 and the paper returning passage 110. The lower movable guide member 98 is mounted on the lower supporting frame 146 (Figure 7), whereas the upper movable guide member 100, on the upper supporting frame 148 (Figure 7). Accordingly, as shown in Figure 7, when the upper supporting frame 148 is moved from the operating position shown in Figure 1 toward the non-operating position shown in Figures 2 and 3, the upper movable guide member 100 moves upwardly away from the lower movable guide member 98 and the paper moving passage 96 (Figure 6) defined between them is open. When the upper movable guide member 100 is moved upwardly away from the lower movable guide member 98, the abutment means 214 in the upper movable guide member 100 is disengaged from the abutment means 208 in the lower movable guide member 98. Hence, by the elastic biasing action of the tension spring 222, the upper movable guide member 100 tends to be pivoted counterclockwise in Figure 7. When, however, the upper movable guide member 100 is pivoted slightly in the counterclockwise direction, the upper edge of the rear end portion of at least one of the upper guide pieces 210 in the upper movable guide member 100 abuts against the restriction means 224 fixed to the upper supporting frame 148 to hamper further counterclockwise pivoting of the upper movable guide member 100 in Figure 7. If desired, there may be an alternative embodiment in which in a state where the upper supporting frame 148 is held at the operating position and the electromagnetic solenoid 202 is in the deenergized state, the upper edge of the rear end portion of the upper guide piece 210 in the upper movable guide member 100 abuts against the restriction means 224 thereby to hold the upper movable guide member 100 at the lowered position shown by the solid line in Figure 6, and at this time, there is some space between the abutting means 208 in the lower movable guide member 98 and the abutment means 214 in the upper movable guide member 100. In still another embodiment, the upper movable guide member 100 is held at the lowered position by the action of the abutting means and the abutment means when the upper movable guide member 100 is biased to the elevated position and the lower movable guide member 98 is held at the lowered position. Alternatively, contrary to the illustrated embodiment, it is possible to annex an actuating means such as an electromagnetic solenoid to the upper movable guide member 100 so that when the upper movable guide member 100 is moved to the lowered position (or the elevated position) from the elevated position (or the lowered position), the lower movable guide member 98 biased to the elevated position (or the lowered position) is brought to the lowered position (or the elevated position) by the action of the abutting means and the abutment means. In the illustrated conveyance controlling means 94, the abutting means 208 and the abutment means 214 are Provided respectively in the lower movable guide member 98 and the upper movable guide member 100 in order to enable both the lower movable guide member 98 and the upper movable guide member 100 to be positioned by a single actuating means (the electromagnetic solenoid 202). If desired, it is possible to connect the lower movable guide member 98 and the upper movable guide member 100 integrally at their both side portions thereby enabling both the lower movable guide member 98 and the upper movable guide member 100 to be positioned by the single actuating means (electromagnetic solenoid 202). However, if such a structure is taken, the upper movable guide member 100 cannot be mounted on the upper supporting frame 148, and it is necessary to mount both the lower movable guide member 98 and the upper movable guide member 100 connected integrally to each other on the lower supporting frame 146. Alternatively, it is necessary to mount both the lower and upper movable guide members 98 and 100 connected integrally to each other on the upper supporting frame 148. Consequently, even when the upper supporting frame 148 is moved to the non-operating position shown in Figures 2 and 3, the paper moving passage 96 defined between the lower movable guide member 98 and the upper movable guide member 100 is not open, and therefore, in the case of dealing with paper jamming, it is somewhat troublesome to remove a copying paper existing at least partly in the paper moving passage 96.

Claims: An electrostatic copying apparatus comprising a lower supporting frame (146), an upper supporting frame (148) mounted on the lower supporting frame for free pivotal movement between an operating position and a non-operating position, a copying paper conveying passage (58), a copying paper feeding means (48) for feeding a copying paper sheet to the paper conveying passage and a copying paper returning passage (110), and being adapted to form an image on one surface of the copying paper sheet while it is conveyed through the paper conveying passage after being fed to the conveying passage from the feeding means, to introduce the paper sheet bearing an image on one surface selectively into the paper returning passage, to return it through the returning passage, to re-feed it into the paper conveying passage and to form an image on the other surface of the paper sheet while it is re-conveyed through the paper conveying passage, at least a greater portion of the paper conveying passage (58) being defined between the lower supporting frame and the upper supporting frame when the upper supporting frame is held at the operating position and being opened when the upper supporting frame is held at the non-operating position, and at least a greater portion of the paper returning passage (110) being provided inside the lower supporting frame (146); characterized in that a lower front cover member (170) is mounted on the lower supporting frame (146) so that it is free to move between a closed position at which it covers at least a greater part of the front surface of the lower supporting frame and an open position at which said front surface is open to permit removal of copying paper which has jammed up in the paper returning passage (110), and that a locking means (192, 188) for the lower front cover member is provided which prevents the lower front cover member from being moved to the open position from the closed position when the upper supporting frame (148) is at the operating position, and which permits the lower front cover member to be moved to the open position from the closed position when the upper supporting frame is pivoted to the non-operating position from the operating position. The apparatus of claim 1 wherein said locking means is comprised of a restraining member (188) provided in one of the upper supporting frame and the lower front cover member and a restrained member (192) provided in the other of the upper supporting frame and the lower front cover member; and wherein when the lower front cover member (170) is at the closed position and the upper supporting frame is at the operating position, the restraining member restrains the restrained member whereby the lower front cover member is prevented from being moved to the open position from the closed position, and when the upper supporting frame (148) is pivoted to the non-operating position from the operating position, the restraining member and the restrained member are moved away from each other. The apparatus of claim 1, wherein the lower front cover member (170) is free to pivot between the closed position and the open position about a pivot axis (172) extending along its lower edge as a center. The apparatus of claim 1 wherein an upper front cover member (174) is mounted on the upper supporting frame (148) such that it is free to move between a closed position at which it covers at least a greater portion of the front surface of the upper supporting frame and an open position at which said front surface is open. The apparatus of claim 4 wherein the upper front cover member (174) is free to pivot between the closed position and the open position about a pivot axis (176) extending along its lower edge as a center. The apparatus of claim 1 which further comprises a detecting means (180) for detecting the fact that the lower front cover member is at the closed position and the upper supporting frame is at the operating position. The apparatus of claim 6 wherein the detecting means (180) is comprised of a detecting element provided in one of the upper supporting frame and the lower front cover member and a detected element (192) provided in the other of the upper supporing frame and the lower front cover member, and when the upper supporting frame is at the operating position and the lower front cover member is at the closed position, the detecting element detects the detected element. The apparatus of claim 7 wherein said locking means is comprised of a restraining member (188) provided in one of the upper supporting frame (148) and the lower front cover member (170) and a restrained member (192) provided in the other of the upper supporting frame and the lower front cover member, and when the lower front cover member is at the closed position and the upper supporting frame is at the operating position, the restraining member restrains the restrained member whereby the lower front cover member is prevented from being moved to the open position from the closed position; when the upper supporting frame is pivoted to the non-operating position from the operating position, the restraining member and the restrained member are moved away from each other; and the restrained member of the locking means and the detected member of the detecting means are comprised of a common member. The apparatus of claim 1 which further comprises a copying paper re-feeding passage (128) and a copying paper re-sending means (120) for receiving a copying paper sheet returned via the paper returning passage (110) and re-feeding the received copying paper sheet to the paper conveying passage (58) through the paper re-feeding passage, and in which at least a greater portion of the paper re-feeding passage and the paper re-sending means are provided inside the lower supporting frame, and the lower front cover member (170) should be held at the open position to remove a copying paper that has jammed up in the paper re-feeding passage and a copying paper that has jammed up in the paper re-sending means. The apparatus of claim 9 wherein the lower supporting frame (146) includes a lower front base plate (152) and a lower rear base plate (154) spaced from each other in the forward-backward direction, at least a greater part of the paper returning passage (110), at least a greater part of the paper re-feeding passage (128), and the paper re-sending means (120) are provided between the lower front base plate (152) and the lower rear base plate (154), and a single opening (164) is formed in the lower front base plate which extends at least over a region where at least a greater part of the paper returning passage (110) and the paper re-sending means (120) exist. The apparatus of claim 10 wherein at least a greater part of the paper returning passage (110) is defined between a plurality of upper elements and a plurality of lower elements, the plurality of upper elements are mounted between the lower front base plate (152) and the lower rear base plate (154), a movable frame (166, Figure 4) is mounted on the lower rear base plate for free movement between an operating position and a non-operating position, the plurality of lower elements are mounted on the movable frame, and at least a greater part of the paper returning passage is defined when the movable frame is at the operating position, and at least a greater part of the paper returning passage is opened when the movable frame is held at the non-operating position, and the opening (164) formed in the lower front base plate extends not only to the operating position of the movable frame but also to its non-operating position. The apparatus of claim 11 wherein the movable frame (166) is mounted on the lower rear base plate (154) for free pivotal movement between the operating position and the non-operating position about a pivot axis extending along its rear edge as a center.

Inventors: FUJIOKA, TADASHI, KAJITA, HIROSHI, SUMIDA, YASUJI
Applicants: MITA INDUSTRIAL CO. LTD.
Application year: 1985
Main classification: G03G15
IPC codes: G03G15, G03G21