Mechanism for preventing feeding of superposed copying paper sheets in an electrostatic copying apparatus

Abstract: A mechanism for preventing feeding of copying paper sheets in the superposed state. Said mechanism comprises a conveying roller (132) having a peripheral surface and mounted for rotation in a predetermined feeding direction; a frictional member (246) and pressing mechanism means for selectively moving said frictional member (246) between an operating state in which it acts on said peripheral surface of said conveying roller (132) and a non-operating state in which it is spaced from said peripheral surface of said conveying roller (132), said pressing mechanism including an oscillating arm (266) supporting said frictional member (246), said oscillating arm (266) being mounted for oscillating movement between a first position at which it maintains said frictional member (246) in said operating state and a second position at which it maintains said frictional member (246) in said non-operating state. Said pressing mechanism means further includes a supporting member (270) mounted on said oscillating arm (266) for movement relative thereto over a predetermined range toward and away from said conveying roller (132). Said frictional member (246) is mounted on said supporting member (270). A pressing spring member means (278) interposed between said oscillating arm (266) and said supporting member (270) for, when said frictional member (246) is in said operating state, elastically maintaining said frictional member (246) in pressing contact with said peripheral surface of said conveying roller (132)

Description: This invention relates to a mechanism for preventing feeding of copying paper sheets in a superposed state in an electrostatic copying apparatus of the kind referred to in the preamble portion of patent claim 1. Such a mechanism is known from US-A-4 113 245. As document copying has been diversified in recent years, an electrostatic copying apparatus of the type capable of forming a copied image on both surfaces of a copying paper sheet has been proposed and come into commercial acceptance. This type of electrostatic copying apparatus, as is well known to those skilled in the part, comprises a copying paper conveying passage, a copying paper feeding means for feeding copying paper to the copying paper conveying passage, a copying paper returning passage, and a copying paper re-sending means for receiving the copying paper sheet returned through the copying paper returning passage and re-sending the received copying paper sheet to the copying paper conveying passage, and is adapted to form a copied image on both surfaces of the copying paper sheet in the following manner. The copying paper sheet fed to the paper conveying passage from the paper feeding means is conveyed through the paper conveying passage and during this conveance, in an image is formed on one surface of the paper sheet. The paper sheet having the image formed on its one surface is then selectively introduced into the paper returning passage and sent to the paper re-sending means. The paper sheet thus received in the paper re-sending means is re-sent to the paper conveying passage by the action of the paper re-sending means. While it is again conveyed through the paper conveying passage, an image is formed on the other surface of the copying paper sheet. As a result, the desired images are formed on both surfaces of the copying paper sheet fed from the paper feeding means. The aforesaid type of electrostatic copying apparatus known in the art has the following inconveniencies or defects. In electrostatic copying apparatus not necessarily limited to the above-described type, a mechanism for preventing the conveying of copying paper sheets in superposed state is well known in order to accurately feed copying paper sheets one by one from the stack. This mechanism is composed of a combination of a conveying roller to be rotated in a predetermined direction and a frictional member to be in press contact with the peripheral surface of the conveying roller. This conventional preventing mechanism is of such a structure that the frictional member is always in press contact with the peripheral surface of the conveying roller. The frictional member is therefore worn within a relatively short period of time and the aforesaid preventing function of the preventing mechanism will be reduced. As a result, the copying paper sheets cannot be fed accurately one by one. JP-A-59-64 434 deals with the problem that the press contact of a frictional member changes with time and needs to be increased from time to time by adjusting the pressing force of a spring. UP-A-4 113 245 discloses a mechanism for preventing feeding of coyping paper sheets in the superposed state, said mechanism comprising a conveying roller having a peripheral surface and mounted for rotation in a predetermined feeding direction, a frictional member and pressing mechanism means for selectively moving said frictional member between an operating state in which it acts on said peripheral surface of said conveying roller and a non-operating state in which it is spaced from said peripheral surface of said conveying roller, said pressing mechanism including an oscillating arm supporting said frictional member, said oscillating arm being mounted for oscillating movement between a first position at which it maintains said frictional member in said operating state and a second position at which it maintains said frictional member in said non-operating state. It is the object of this invention to improve a mechanism for preventing feeding of copying paper sheets in the superposed state known, for example, from US-A-4 113 245 such that it exhibits an improved preventing function over a long period of time while inhibiting wearing of a frictional member. This object is accomplished with a mechanism as claimed in claim 1. Claim 2 is directed on an electrostatic copying apparatus including such a mechanism implemented as a preferred embodiment. To achieve the object, the present invention provides a mechanism for preventing feeding of copying paper sheets in the superposed state, comprising a conveying roller to be rotated in a predetermined direction, a frictional member and a pressing mechanism for moving the frictional member, said pressing mechanism being adapted to maintain the frictional member selectively in an operating state in which it acts on the peripheral surface of the conveying roller and in a non-operating state in which it moves away from the conveying roller. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a sectional view which shows in a simplified form the main constituent elements of an electrostatic copying apparatus improved in various respects in accordance with the present invention; Figure 2 is a sectional view showing a copying paper re-sending means and its vicinity in the electrostatic copying apparatus of Figure 1; Figure 3 is a top plan view showing the paper re-sending means of Figure 2 partly in section; Figure 4 is a sectional view taken along line IV-IV of Figure 3; Figure 5 is a perspective view, partly broken away, of the front portion of the paper re-sending means of Figure 3; Figure 6 is a side elevation of the front portion of the paper re-sending means of Figure 5 when viewed from ahead of the copying apparatus; Figure 7 is a perspective view for illustrating the actuation of one of electromagnetic solenoids of a copying paper re-sending means; Figure 8 is a side elevation of the state shown in Figure 7 as viewed from ahead of the copying apparatus; Figure 9 is a perspective view showing the actuation of the other electromagnetic solenoid of the paper re-sending means; Figure 10 is a side elevation of the state of Figure 9 as viewed from ahead of the copying apparatus; Figure 11 is a side elevation, partly in section, showing the state of means for preventing feeding of copying paper sheets in the superposed state when the aforesaid other electromagnetic solenoid of the paper re-sending means is inoperative; Figure 12 is a side elevation showing the state of the means for preventing feeding of copying paper sheets in the superposed state when the aforesaid electromagnetic solenoid of the copying paper re-sending means is in operation. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS The invention will now be described in detail with reference to the accompanying drawings. Outline of the General Structure and Operation of the Electrostatic Copying Apparatus First of all, the general structure of one embodiment of an electrostatic copying apparatus on which various improvements have been made in accordance with this invention will be described. 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 the arrow 10. A charging corona discharge device 22 is disposed in the charging zone, 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 50 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 56b 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 a copying paper conveying means, specifically 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 rollers 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 conveyer belt mechanism 84, a guide plate 86, a pair of heat-fixing rollers, a pair of guide plates 90 and a pair of conveying rollers 92 in the illustrated embodiment. 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 between them. 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 and at an elevated position shown by a two-dot chain line. Downstream of the conveyance controlling means 94 is provided a copying paper discharging passage 104 having a pair of discharge rollers 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 in a curved shape 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 reversing roller 114 adapted to be held selectively 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, and is defined by a copying paper returning means, specifically by a pair of guide plates 115, a pair of returning rollers 116, a pair of guide plates 117, a pair of returning rollers 118 and a guide plate 119 in the illustrated embodiment. 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 extending stand 122 for receiving copying paper, and a movement hampering means 124 for hampering the movement of the copying paper is provided at the front end (i.e., the right end in Figure 1) of the paper receiving stand 122. The movement hampering means 124 is adapted to be selectively held at a hampering position shown by a solid line and a receding 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 so that it can freely move upwardly from its illustrated position contacting the upper surface of the paper receiving stand 122. Normally, the roller 126 is forced downwardly by a biasing action attributed to its own weight (if required, by using a suitable spring means). 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 copying paper re-feeding means, specifically by a guide plate 130, a conveying roller 132 which also performs a paper separating action in cooperation with a frictional member to be described hereinafter, 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 the 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 shows 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 having an image formed 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 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 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. At this time, the under surface of the copying paper makes contact with one (102a) of the pair of discharge rollers 102. But since slippage is created between the discharge roller 102a and the copying paper, the copying paper can advance in the direction of arrow 138 in spite of the roller 102a being rotated in the direction of an arrow 140. When the trailing end of the copying paper has gone past the downstream end of the paper conveying passage 58, i.e. the nipping position of the pair of conveying rollers 92, the reversing roller 114 provided at the upstream end of the reversing passage 108 is held at the operating position shown by the two-dot chain line so that the copying paper is pushed against the discharge roller 102a. As a result, the trailing and leading ends of the copying paper are reversed by the action of the discharge roller 102a rotating in the direction of arrow 140, and the copying paper advances in the direction shown by an arrow 142. It is passed through one (92a) of the pair of conveying rollers 92 rotated in the direction of the arrow 140 and one (116a) of the pair of guide plates 116, and introduced into the paper returning passage 110 through which it advances. The reversing roller 114 in the paper reversing passage 108 is returned to the non-operating postion 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 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 122 to the right in Figure 1. The delivery roller 126 rotated in the direction shown by an arrow 144 acts on the copying paper to deliver it further to the right and thus cause the leading edge of the copying paper to abut against the movement hampering means 124 held at the hampering 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 the arrow 144, 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 movement hampering means 124 in the paper re-sending means 120 is held at the receding position shown by the two-dot chain line, and by the action of the delivery roller 126 rotating in the direction of the 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 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 paper re-sending means and its vicinity Now, the structure of the paper re-sending means 120 improved in accordance with this invention will be described. With reference to Figures 2 and 3 together with Figure 1, the paper re-sending means 120 in the illustrated embodiment includes the copying paper receiving stand 122 adapted to receive copying paper sheets returned through the paper returning passage 110, the delivery roller 126 (constituting delivery means) disposed above the paper receiving stand 122, and a width matching means 146 for matching the widthwise positions of the paper sheets received on the paper receiving stand 122. The illustrated electrostatic copying apparatus includes a vertical front base plate (not shown) and a vertical rear base plate 148 (Figures 3 and 4) arranged in spaced-apart relationship in the forward-backward direction (a direction perpendicular to the sheet surface in Figure 2; a vertical direction in Figure 3), and the paper receiving stand 122 is disposed between the vertical front base plate and the vertical rear base plate 148. The paper receiving stand 122 is composed of a plate-like member, and extends substantially horizontally between the vertical front base plate and the vertical rear base plate 148. The illustrated width matching means 146 includes a pair of spaced movable matching members 150 only one of which is shown in Figure 2). The pair of movable matching members 150 are set up so that they can move freely in the widthwise direction of the paper sheets received on the receiving stand,i.e., the aforesaid forward-backward direction in the illustrated embodiment. More specifically, the pair of movable matching members 150 can move between a receiving position at which they receive the copying paper and a matching position at which they match the positions of the paper sheets in the widthwise direction by the action of the actuating mechanism 152. The delivery roller 126 is held selectively in any one of a non-operating state (the state shown by a two-dot chain line in Figures 7 and 8), a first operating state (the state shown in Figures 1, 2, 3, 5 and 6 and by a solid line in Figures 7 and 8) and a second operating state (the state shown in Figures 9 and 10). The delivery roller 126 can be formed of a sponge, for example. Correspondingly to the delivery roller 126, a frictional member 154 formed of a woven cloth is disposed on the upper surface of the receiving stand 122 with which the delivery roller 126 comes into contact (see Figures 6 to 8 and 10). The paper re-sending means 120 also includes copying paper movement hampering means 124. The illustrated movement hampering means 124 is composed of a pair of plate-like pieces 156 spaced from each other in the widthwise direction of the paper sheets received on the receiving stand, i.e. in the forward-backward direction (Figures 3 and 5). The plate-like pieces 156 are held selectively at a hampering position (the position shown in Figures 2 to 6 and 11 and by a solid line in Figure 1) and a receding position (the position shown in Figures 9, 10 and 12 and by a two-dot chain line in Figure 1). In the illustrated embodiment, a supporting shaft 158 is rotatably mounted across the vertical front base plate (not shown) at the forward end of the receiving stand 122 and the vertical rear base plate 148. The two opposite end portions of the supporting shaft 158 (the parts supported by the vertical front base plate and the vertical rear base plate 148) are circular in cross section, and its intermediate portion (the part extending between the vertical front base plate and the vertical rear base plate 148) are rectangular in cross section. The plate-like piece 156 is fixed to one side surface of the intermediate portion by a screw 160 (see Figure 4). The paper re-sending means 120 further includes an actuating mechanism 152 for moving the delivery roller 126 and the pair of plate-like pieces 156. With reference to Figures 2 to 5, mainly to Figure 5, the illustrated actuating mechanism 152 has a first oscillating member 162, a second oscillating member 164 and a third oscillating member 166. The first oscillating member 162 includes a supporting side wall 168 and a side wall 170 spaced from each other in the forward-backward direction and an intermediate wall 172 connecting the supporting side wall 168 and the side wall 170, and the supporting side wall 168 and the side wall 170 are rotatably mounted on a rotating shaft 176 (on which the conveying roller 132 of a mechanism for preventing feeding of copying paper sheets in the superposed state is mounted) through a bearing member 174 (see Figures 3 and 5). The supporting side wall 168 of the first oscillating member 162 is positioned nearly centrally of the receiving stand in its width direction, and extends rearwardly (to the left in Figures 2 and 3) from the forward end side of the receiving stand 122. The aforesaid delivery roller 126 is mounted rotatably on the forward end portion of the supporting side wall 168 via a shaft member 180 (therefore, the delivery roller 126 acts on the central part in the widthwise direction of a copying paper sheet received on the receiving stand 122). The second oscillating member 164 has side walls 182 and 184 spaced from each other in the forward-backward direction and an intermediate wall 186 connecting the two side walls 182 and 184, and the side walls 182 and 184 are rotatably mounted on the rotating shaft 176. In the illustrated embodiment, the second oscillating member 164 is disposed rearwardly (upwardly in Figure 3, and to the right in Figure 4) of that site of the rotating shaft 176 on which the first oscillating member 162 is mounted, and a spring member 188 comprised of a coil spring, for example, is interposed between the first oscillating member 162 and the second oscillating member 164. A rearwardly extending projection 190 is provided in the upper end part of the side wall 170 of the first oscillating member 162, and a projection 192 extending in a direction away from the rotating shaft 176 is provided in the lower end part of the side wall 182 of the second oscillating member 164. The spring member 188 is engaged with the projection 190 of the first oscillating member 162 at one end and with the projection 192 of the second oscillating member at the other end. The spring member 188 acts to bias the second oscillating member 164 clockwise in Figures 5 and 6 relative to the first oscillating member 162. In the illustrated embodiment, a forwardly extending engaging projection 194 is further provided at the upper end part of the side wall 182 of the second oscillating member 164, and the engaging projection 194 is received in an arcuate elongate hole 196 formed in the side wall 170 of the first oscillating member 162. Accordingly, the first oscillating member 162 and the second oscillating member 164 can freely pivot relative to each other over a predetermined range. In other words, they can pivot relative to each other between a position at which the engaging projection 194 abuts against one end of the elongate hole 196 and a position at which the engaging projection 194 abuts against the other end of the elongate hole 196. The third oscillating member 166 is composed of an L-shaped member (see Figure 3) and fixed to the rear end portion of the supporting shaft 158. In relation to the third oscillating member 166, a pin member 200 (constituting an abutment portion) against which a part of the third oscillating member 166 can abut when the third oscillating member 166 pivots in the direction of an arrow 198 (Figures 9 and 10) is set firmly in the lower end portion of the side wall 184 of the second oscillating member 164. The illustrated actuating mechanism 152 further includes a first actuating means and a second actuating means composed of electromagnetic solenoids 202 and 204 respectively. A mounting member 206 is attached to the front surface of the vertical rear base plate 148, and the electromagnetic solenoid 202 constituting the first actuating means is mounted on the mounting member 206 (Figure 3). A short shaft 208 is set firmly in the front surface of the vertical rear base plate 148, and a revolving lever 210 is revolvably mounted on the forward end portion of the short shaft 208. One end portion 212a of the revolving lever 210 is connected to an output portion 216 of the electromagnetic solenoid 202 via a linking pin 214 (Figures 6, 8 and 10). A coil spring 218 (not shown in Figures 2, 3, 5, 7 and 9) is interposed between the electromagnetic solenoid 202 and the revolving lever 210 and covers the output portion 216. A projecting portion 222 having an abutting part 224 is provided in the revolving lever 210 (see Figures 6, 8 and 10). Hence, when the electromagnetic solenoid 202 is inoperative, the revolving lever 210 is held by the action of the coil spring 218 at an angular position at which the abutting part 224 of the projecting portion 222 abuts against the electromagnetic solenoid 202 (the position shown in Figures 2 to 6, 9 and 10, and the position shown by a two-dot chain line in Figures 7 and 8). In relation to the other end portion 212b of the revolving lever 210, a pin member 226 (constituting an abutment portion) against which the other end portion 212b of the revolving lever 210 can abut when the revolving lever 210 is pivoted in the direction shown by an arrow 225 (Figures 7 and 8) is set firmly in the forward end part of the side wall 170 of the first oscillating member 162. Accordingly, when the electromagnetic solenoid 202 is actuated, the revolving lever 210 is revolved in the direction shown by the arrow 225 (Figures 7 and 8) against the elastic biasing action of the coil spring 218, and the other end portion 212b of the revolving lever 210 abuts against, and thereby acts on, the pin member 226 provided in the first oscillating member 162. As a result, the first oscillating member 162 is pivoted about the rotating shaft 176 in a direction shown by an arrow 228 (Figures 7 and 8), namely clockwise in Figures 7 and 8. The electromagnetic solenoid 204 constituting the second actuating means is mounted on a plate-like mounting member 130 secured to the front surface of the vertical rear base plate 148 (Figure 3). One end portion of a linking member 234 is connected to the third oscillating member 166 through a pin member 232, and the other end portion of the linking member 234 is connected to an output portion 238 of the electromagnetic solenoid 204. A spring member 240 composed of, for example, a coil spring is interposed between the third oscillating member 166 and a part of the electrostatic copying apparatus. Accordingly, when the electromagnetic solenoid 204 is inoperative, the third oscillating member 166 is held at the position shown in Figures 2 to 6 and 11 by the action of the spring member 240. As will be understood from Figure 2, at this position, the pair of plate-like pieces 156 abut against the front end of the receiving stand 122 and thus the third oscillating member 166 is held at the aforesaid position. Furthermore, as can be understood from Figures 2, 4 and 5, the plate-like pieces 156 are held at an operating position at which they project upwardly from the upper surface of the receiving stand 122. On the other hand, when the electromagnetic solenoid 204 is actuated, the third oscillating member 166 is privoted in the direction shown by the arrow 198 (Figures 9 and 10) together with the supporting shaft 158 via the linking member 234 against the elastic biasing action of the spring member 240. As a result, a part of the third oscillating member 166 abuts against, and acts on, the pin member 200 provided in the second oscillating member 164, and the second oscillating member 164 is pivoted in the direction shown by an arrow 242 (Figure 10) about the rotating shaft 176 as a center. When the third oscillating member 166 is pivoted in the direction of the arrow 198, the supporting shaft 158 and the pair of plate-like pieces 156 mounted on it are likewise pivoted as a unit, and the plate-like pieces 156 are held at the receding position (the position shown in Figures 9, 10 and 12) at which they have receded, and thus are apart, from the upper surface of the receiving stand 122. In the illustrated electrostatic copying apparatus, a mechanism 178 for preventing feeding of copying paper sheets in the superposed state is provided in relation to the paper re-sending means 120 downstream of the re-sending means 120 as viewed in the paper conveying direction shown by an arrow 244 (Figures 2 and 3). With reference to Figures 2, 5 and 11, the preventing mechanism 178 includes a conveying roller 132 constituting a part of the paper re-feeding means, a frictional member 246 disposed correspondingly to the conveying roller 132, and a pressing mechanism 248 for moving the frictional member 246. The rotating shaft 176 is rotatably mounted through a bearing member 250 between the vertical front base plate (not shown) and the vertical rear base plate 148 (Figures 3 and 4) (in Figures 3 and 4, the rear end portion of the rotating shaft 176 is shown), and the conveyor roller 132 is mounted on the middle portion of the rotating shaft 176. Accordingly, the conveying roller 132 acts on the central part in the widthwise direction of the copying paper delivered from the receiving stand 122. The rear end portion of the rotating shaft 176 projects rearwardly through the vertical rear base plate 148, and a power transmission member 252 such as a gear is fixed to the rear end portion of the rotating shaft 176 (see Figure 4). The power transmission member 252 is drivingly connected to a main driving source of the electrostatic copying apparatus through a suitable power transmission means (not shown) such as a gear. A pulley portion 254 is provided at one end portion of the conveying roller 132, and a pulley portion 256 is provided at one end portion of the delivery roller 126. A power transmission member 258 such as a wire is wrapped about the two pulley portions 254 and 256. Hence, when the main driving source (not shown) is actuated, the conveying roller 132 is rotated in the direction shown by an arrow 260 (Figures 2 and 5) via the rotating shaft 176, and the delivery roller 126 is rotated in the direction shown by the arrow 144 (Figures 1, 2 and 5) via the power transmission member 258. The pressing mechanism 248 in the illustrated embodiment includes an oscillating arm 266 pivotably mounted on a projecting piece 264 (Figure 2) provided in the under surface of the receiving stand 122. With reference mainly to Figure 11, the illustrated oscillating arm 266 has a base portion 268a mounted pivotably on the projecting piece 264, an inclined portion 268b extending inclinedly from the base portion 268a, an abutting middle portion 268c extending nearly horizontally from the inclined portion 268b, an inclined portion 268d extending inclinedly from the abutting middle portion 268c, and a mounting portion 268e present at one end of the inclined portion 268d, i.e. the forward end of the oscillating arm 266. A supporting member 270 movable toward and away from the conveying roller 132 is mounted on the mounting portion 268e, and the frictional member 246 is mounted on the supporting member 270. In the illustrated embodiment, the supporting member 270 has a supporting portion 272a, a downwardly extending portion 272b extending from the supporting portion 272a, and an engaging portion 272c provided at the lower end of the downwardly extending portion 272b, and the frictional member 246 is fixed within a depressed portion formed on the upper surface of the supporting portion 272a. An elongate hole 274 is formed in the downwardly extending portion 272b of the supporting member 270. On the other hand, a projecting portion 276 is provided at the forward end of the oscillating arm 266 or more specifically at the forward end of its mounting portion 268e, and received in the elongate hole 274 of the supporting member 270. Hence, the supporting member 270 can move relative to the oscillating arm 266 between a position at which one end of the elongate hole 274 abuts against the projecting portion 276 and a position at which the other end of the elongate hole 274 abuts against the projecting portion 276. Incidentally, an engaging member 277 is mounted on the forward end portion of the projecting portion 276 to prevent detachment of the supporting member 270. A pressing spring member 278 composed of, for example, a coil spring is mounted between the forward end of the projecting portion 276 of the oscillating arm 266 and the engaging portion 272c of the supporting member 270. The pressing spring member 278 functions to bias the supporting member 270 relative to the oscillating arm 266 in a direction in which the supporting member 270 approaches the conveying roller 132, and therefore, the supporting member 270 is normally maintained in the state shown in Figure 11, namely in a state in which the lower end of the elongate hole 274 abuts against the projecting portion 276. In the illustrated embodiment, the oscillating arm 266 is adapted to pivot by the action of the electromagnetic solenoid 204 for pivoting the pair of plate-like pieces 156. With reference to Figures 5 and 11, the oscillating arm 266 of the pressing mechanism 248 is disposed above the middle portion of the supporting shaft 158 having the plate-like piece 156 mounted thereon. The oscillating arm 266 tends to pivot clockwise in Figure 11 owing to its own weight, and therefore, when the plate-like pieces 156 are held at the aforesaid hampering position (when the electromagnetic solenoid 204 is inoperative), the under surface of the abutting middle portion 268c of the oscillating arm 266 abuts against one side surface of the middle portion of the supporting shaft 158 (as stated above, the middle portion is rectangular in cross section) and the oscillating arm 266 is held at the second position shown in Figure 11. The frictional member 246 is maintained in the inoperative state in which it is apart from the conveying roller (see Figure 11). On the other hand, when the electromagnetic solenoid 204 is actuated to hold the pair of plate-like pieces 156 in the aforesaid receding position, one corner part of the plate-like pieces 156 acts on the under surface of the abutting middle portion 268c by the revolving of the supporting shaft 158. As a result, the oscillating arm 266 is slightly pivoted counterclockwise as shown by an arrow 280 (Figure 11) (the oscillating arm 266 is held at the first position shown in Figure 12), and the frictional member 246 is maintained in the operating state in which it is in press contact with the peripheral surface of the conveying roller 132 (see Figure 12). The conveying roller 132 can be formed of, for example, a synthetic rubber, and the frictional member 246 can be formed of, for example, a urethane rubber. In the illustrated embodiment, the oscillating arm 266 is pivoted by using the electromagnetic solenoid 204 adapted to move the plate-like pieces 156. If desired, an actuating means such as an electromagnetic solenoid may be used exclusively for pivoting the oscillating arm. In the illustrated electrostatic copying apparatus, a copying paper detecting mechanism constructed in accordance with this invention is also provided in relation to the paper re-sending means 120. With reference to Figures 3, 5 and 6, the illustrated paper detecting mechanism 282 includes a follower roller 284 and a detecting means 286 for detecting the revolving of the follower roller 284. The follower roller 284 is constructed of a disc-like member, and a plurality of circumferentially spaced rectangular openings 288 are formed on its side surface (Figure 6). The follower roller 284 is rotatably mounted on the forward end portion of a supporting side wall 168 of the first oscillating member 162 (which also acts as a supporting member for supporting the follower roller 284) via a short shaft 289. In the illustrated embodiment, the follower roller 284 is mounted on that surface of the supporting side wall 168 which is opposite to the surface on which the delivery roller 126 is mounted, as shown in Figure 3. Accordingly, the follower roller 284 is moved up and down together with the delivery roller 126 as the first oscillating member 162 makes a pivotal movement. It is important to construct the follower roller 284 such that when the peripheral surface of the delivery roller 126 acts on a copying paper sheet on the receiving stand 122, the peripheral surface of the follower roller 284 also acts in the same way. In the illustrated embodiment, the follower roller 284 is rotatably mounted on the first oscillating member 162 on which the delivery roller 126 is mounted. Instead of this construction, it is possible to provide a supporting member adapted to move up and down independently from the first oscillating member 162, and rotatably mount the follower roller 284 on this supporting member. The illustrated detecting means 286 is composed of a combination of a light emitting element 290 and a light receiving element 292. The light emitting element 290 is provided on one side (on the upper side in Figure 3) of the follower roller 284, and the light receiving element 292 is disposed on the other side (the lower side in Figure 3) of the follower roller 284. The light emitting element 290 and light receiving element 292 are mounted on a mounting block 294 in spaced-apart relationship in the forward-backward direction, and the mounting block 294 is fixed to the lower end of a downwardly extending member 296 provided within the electrostatic copying apparatus. The detecting means 286 may be mounted on the first oscillating member 162 mounted oscillably instead of mounting it on the main body of the copying apparatus. In this case, the positional relationship between the follower roller 284 and the detecting means 286 can be maintained constant irrespective of the number of copying paper sheets received in the stacked state on the receiving stand 122. Now, with reference mainly to Figures 2, 5 and 6, the operation and advantage of the paper re-sending means 120 described above will be described. In copying a document on both surfaces of a copying paper sheet, the electromagnetic solenoid 202 and 204 are maintained inoperative. Hence, the third oscillating member 166 is biased counterclockwise in Figures 5 and 6 by the action of the spring member 240, and by the abutting of the pair of plate-like pieces 156 against the forward end of the paper receiving stand 122, held at the angular position shown in Figures 2 to 6. In this state, the forward end portion of each of the plate-like pieces 156 projects upwardly from the upper surface of the receiving stand 122, and each plate-like piece 156 is exactly held at the hampering position (the position shown in Figure 1 by a solid line and also in Figures 2 to 6 and 12) by the action of the spring member 240. Furthermore, in the aforesaid state, the abutting middle portion 268c of the oscillating arm 266 abuts against one side surface of the middle portion of the supporting shaft 158, and the oscillating arm 266 is held at the second position (the position shown in Figure 11) spaced from the conveying roller 132. When the oscillating arm 266 is at the second position, the frictional member 246 is held in the non-operating state (the state shown in Figure 11) in which it is apart from the peripheral surface of the conveying roller 132 and does not act on the peripheral surface of the conveying roller 132. Furthermore, the revolving lever 210 is biased clockwise in Figures 5 and 6 by the action of the coil spring 218 and the abutting portion 224 provided in its projecting portion 222 abuts against a part of the main body of the electromagnetic solenoid 202 whereby the revolving lever 210 is held at the angular position shown in Figures 2 to 6 and by a solid line in Figures 7 and 8. It will be appreciated from the foregoing description taken in conjunction with Figures 5 and 6 that when the electromagnetic solenoids 202 and 204 are in the inoperative state, the first oscillating member 162 and the second oscillating member 164 are free to pivot over a predetermined range with respect to the rotating shaft 176, and therefore, the delivery roller 126 abuts against the upper surface of the receiving stand 122 by its own weight and is held at the first operating state (the state shown in Figures 2 to 6) in which it presses the upper surface of the receiving stand 122 relatively weakly (at this time, the follower roller 284 also abuts against the upper surface of the receiving stand as shown in Figure 6). At this time, the first oscillating member 162 is held at the angular position shown in Figures 2 to 6 as a result of the delivery roller 126 abutting against the upper surface of the receiving stand 122 (therefore, as shown in Figures 5 and 6, some space exists between the other end portion 212b of the revolving lever 210 and the pin member 226 provided in the side wall 170 of the first oscillating member 162). The second oscillating member 164 is biased clockwise in Figures 5 and 6 by the action of the spring member 188 interposed between the projection 192 of the side wall 182 and the projection 190 provided in the side wall 170 of the first oscillating member 162, and held at the angular position shown in Figures 2 to 6 and also by a solid line in Figures 7 and 8 at which its engaging projection 194 abuts against one end of the elongate hole 196 formed in the side wall 170 (the upper end of the elongate hole 196 in Figures 5 and 6). Hence, as shown in Figures 5 and 6, some space exists between the pin member 200 provided in the side wall 184 of the second oscillating member 164 and the third oscillating member 166. When a copying paper sheet having an image formed on one surface has been returned to the paper receiving stand 122 as described above, it is received on the receiving stand 122 and moved along the upper surface of the stand 122 in the direction of the arrow 244 (Figures 2 and 3). When the copying paper is conveyed to the delivery roller 126, the delivery roller 126 acts relatively weakly on the upper surface of the copying paper, and the copying paper is further moved downstream by the action of the delivery roller 126 rotating in the direction of the arrow 144 (Figures 1, 2, 5 and 6). When the copying paper is thus moved and its leading end arrives at the follower roller 284, the leading end portion of the copying paper being moved downstream by the action of the delivery roller 126 acts on the follower roller 284. The follower roller 284 thus undergoes the action of the copying paper and moves in the direction shown by an arrow 298 (Figure 6). As a result, the plurality of openings 288 formed in the follower roller 284 move in the desired required manner. When an opening 288 passes between the light emitting element 290 and the light receiving element 292, the light from the light emitting element 290 is projected onto the light receiving element 292 through the opening 288. Consequently, the detecting means 286 detects the arrival of the copying paper at the receiving stand 122. When the copying paper is further moved downstream, its leading edge abuts against the pair of plate-like pieces 156 held at the hampering position whereby the movement of the copying paper is hampered exactly. At this time, the delivery roller 126 is maintained in the first operating state and acts relatively weakly on the upper surface of the copying paper. Accordingly, when the movement of the copying paper is hampered, slippage occurs between the upper surface of the copying paper and the peripheral surface of the delivery roller 126 and the copying paper is exactly stopped without being bent or deflected by the action of the delivery roller 126. When the movement of the copying paper stops, the movement of the follower roller 284 also stops. The rolling of the follower roller 284 is continued from the arrival of the leading edge of the copying paper at the follower roller 284 until it touches the pair of the plate-like pieces 156. For easy detection of the arrival of the copying paper, therefore, it is desirable to set the distances between the openings 288 such that one of the openings 288 passes between the light emitting element 290 and the light receiving element 292 during the aforesaid rolling of the follower roller 284. If desired, however, the above distances may be set so that two or more openings 288 pass between the light emitting element 290 and the light receiving element 292 during the aforesaid rolling period. When the copying paper is thus received on the receiving stand 122, the electromagnetic solenoid 202 is then actuated, and then the pair of movable matching member 150 are moved in the desired manner. The actuation of the electromagnetic solenoid 202 causes the revolving lever 210 to revolve in the direction of the arrow 225 (Figures 7 and 8), and the other end portion 212b of the revolving lever 210 acts on the pin member 226 provided in the first oscillating member 162 to pivot the first oscillating member 162 in the direction of the arrow 228 (Figures 7 and 8) about the rotating shaft 176 as a center. As a result, the delivery roller 126 moves away from the copying paper on the receiving stand 122 and is positioned above the copying paper and thus maintained in the inoperative state shown by a two-dot chain line in Figures 7 and 8 (at this time, the following roller 284 is also positioned above the copying paper together with the delivery roller 126). It will be easily understood from Figure 6 that in the pivoting of the first oscillating member 162 in the direction of the arrow 225, the first oscillating member 162 and the second oscillating member 164 are pivoted together in the direction of the arrow 225 during the early stage of the pivoting movement, but when the second oscillating member 164 has been pivoted by a predetermined angle, the pin member 200 provided in its side wall 184 abuts against the third oscillating member 166; and therefore that after the pin member 200 has abutted against the third oscillating member 166, the pivoting movement of the second oscillating member 164 is restrained and only the first oscillating member 162 is pivoted in the direction of the arrow 225 against the biasing action of the spring member 188 (therefore, when the delivery rooler 126 is in the inoperative state owing to this, the engaging projection 194 provided in the second oscillating member 162 is located in the middle portion of the elongate hole 196 formed in the first oscillating member 162). Thus, when the electromagnetic solenoid 202 is actuated, the state shown in Figures 7 and 8 is created. It will be easily understood from the foregoing description that in this state, the pair of plate-like pieces 156 are held at the hampering position, the frictional member 246 is mainiained in the aforesaid inoperative state, and the delivery roller 126 is maintained in the aforesaid inoperative state. When the pair of movable matching members 150 are then moved in the desired manner in the forward-backward direction, namely in the widthwise direction of the copying paper received in the receiving stand 122, the inner surfaces of the movable matching members 150 act respectively on the two side edges of the copying paper in the receiving stand 122 to position the copying paper at a predetermined site on the receiving stand 122. Since the delivery roller 126 is held at the aforesaid inoperative position and does not act on the copying paper on the receiving stand, the positioning of the copying paper in the widthwise direction is exactly carried out as desired. When the copying paper has been positioned as stated above, the electromagnetic solenoid 202 is deenergized. As a result, the first oscillating member 162 is pivoted in a direction opposite to the direction of the arrow 228 (Figures 7 and 8) by the own weight of the delivery roller 126, etc., and the delivery roller 126, owing to its own weight, abuts against the upper surface of the copying paper received on the receiving stand 122 and presses it relatively weakly (therefore, it is again maintained in the first operating state). In relation to this, the revolving lever 210 and the second oscillating member 164 return to their original angular positions shown in Figures 2 to 6 and by a solid line in Figures 7 and 8. Hence, the follower roller 284 also abuts against the copying paper on the receiving stand 122. In the case of forming a copied image on both surfaces of one copying paper sheet, the copying paper sheet having an image formed on one surface is temporarily stored on the receiving stand 122. In the case of producing a plurality of copies on both surfaces, one copying paper is received on the receiving stand 122 as stated above, and then, the next copying paper is received on the first copying paper and moved on the upper surface of the first copying paper. When the next copying paper is conveyed to the follower roller 284 in the same way as above, the first copying paper acts on the follower roller 284, which again undergoes the action of the next copying paper moved and rolls in the direction shown by the arrow 298. As a result, by the rolling of the follower roller 284, the light from the light emitting element 290 is projected into the light receiving element 292 through the opening 288 formed in the follower roller 284, and the detecting means 286 detects the arrival of the next copying paper at the receiving stand 122. Accordingly, even when two or more copying paper sheets are received in the stacked state on the receiving stand 122, another copying paper sheet subsequently conveyed to the stack of copying paper sheets acts on the follower roller 284 to set it in motion, and therefore, the paper detecting means 282 can exactly detect the copying paper subsequently conveyed to the receiving stand 122. When the next copying paper has been moved downstream to the pair of plate-like pieces 156 as stated above, it abuts against the plate-like pieces 156 held at the hampering position and its further movement stops. Thereafter, the electromagnetic solenoid 202 is actuated to move the pair of movable matching members 150 as desired. As a result, the matching members 150 match the position of the next copying paper in the widthwise direction and it is put into proper coordination with the copying paper on the receiving stand. When this widthwise matching or the widthwise positioning is over, the electromagnetic solenoid 202 is again deenergized, and the delivery roller 126 is again maintained in the first operating state. In the production of a plurarity of copies on both surfaces, the above operation is repeated, and the copying papers having a copied image on one surface are received in the stacked state on the receiving stand 122 and matched, and temporatily stored before an image is formed on the other surface. It will be understood from the foregoing description that when the delivery roller 126 is in the first operating state, the first oscillating member 162 is pivoted slightly in the direction of the arrow 228 (Figures 7 and 8), and the delivery roller 126 and the follower roller 284 are slightly elevated, as the number of the copying paper sheets stacked on the receiving stand 122 increases. To re-feed the copying paper on the receiving stand 122 toward the paper conveying passage 58 through the paper re-feeding passage 128, the electromagnetic solenoid 204 is actuated. As a result, the third oscillating member 166 is pivoted through the linking member 234 in the direction of the arrow 198 (Figures 9 and 10) against the force of the spring member 240, and the supporting shaft 158 and the pair of plate-like pieces 156 are pivoted as a unit with the third oscillating member 166 whereby the plate-like pieces 156 are held at the receding positions (Figures 9 and 10) at which the have receded from the upper surface of the receiving stand 122. At the receding positions, the plate-like pieces 156 do not act on the copying paper sheets received on the receiving stand, and the copying paper is ready for feeding as will be described below. Furthermore, when the supporting shaft 158 is rotated as described above, its corner portion acts on the abutting middle portion 268c of the oscillating arm 266 to pivot the oscillating arm 266 slightly in the direction shown by the arrow 280 (Figure 11) and maintain the frictional member 246 in the operating state in which it is kept in press contact with the peripheral surface of the conveying roller 132 (the state shown in Figure 10). It will be readily appreciated by comparing Figure 11 with Figure 12 that in this operating state, owing to the press-contacting of the frictional member 246 with the peripheral surface of the conveying roller 132, the supporting member 270 is moved in a direction away from the conveying roller 132 relative to the mounting portion 268e of the oscillating arm 266 against the biasing force of the pressing spring member 278, and the frictional member 246 is elastically kept in press contact with the peripheral surface of the conveying roller 132 by the elastic recovering force of the pressing spring member 278 (therefore, at this time, the projecting portion 276 provided in the oscillating arm 266 is positioned in the middle portion of the elongate hole 274 formed in the supporting member 270). When the third oscillating member 166 is pivoted in the direction shown by the arrow 198, a part of it acts on the pin member 200 provided in the second oscillating member 164 to pivot the second oscillating member 164 in the direction of the arrow 242 (Figure 10) about the rotating shaft 176 as a center. Since at this time, the delivery roller 126 acts on the upper surface of the copying paper on the receiving stand 122, the second oscillating member 164 is pivoted relative to the first oscillating member 162 and the spring member 188 interposed between them is expanded. Consequently, the spring member 188 biases the first oscillating member 162 in the direction shown by the arrow 280 (Figure 10), namely counterclockwise in Figure 10, and the delivery roller 126 is pressed elastically against the copying paper on the receiving stand by the action of the spring member 188 and maintained in the second operating state in which it presses the copying paper relatively strongly (the state shown in Figures 9 and 10). At this time, the engaging projection 194 provided in the second oscillating member 164 is positioned in the middle portion of the elongate hole 196 formed in the first oscillating member 162. Thus, by the action of the delivery roller 126 being rotated in the direction of the arrow 144 (Figure 2), the copying paper on the receiving stand 122 is delivered in the direction of the arrow 244 (Figures 2 and 3) toward the preventing mechanism 178 for preventing feeding of copying papers in the superposed state which is present on the downstream side). Since the delivery roller 126 acts relatively strongly on the copying paper on the receiving stand 122 at the time of delivery, the paper is exactly delivered. When two or more copying paper sheets are received in the stacked state on the receiving stand 122, the delivery roller 126 acts relatively strongly on the upper surface of the uppermost copying paper of the stack and delivers the uppermost copying paper toward the preventing mechanism 178. When the number of the copying paper sheets on the receiving stand 122 decreases as a result of delivery, the first oscillating member 162 is pivoted in the direction of the arrow 280 (Figure 10) by the action of the spring member 188 in the aforesaid second operating state. Hence, the delivery roller 126 always presses the upper surface of the uppermost copying paper with a relatively strong pressure, and thereby exactly delivers it as desired, irrespective of the number of the copying paper sheets on the receiving stand 122. When the copying paper delivered from the receiving stand 122 is conveyed to the preventing mechanism 178, the conveying roller 132 rotating in the direction of the arrow 260 (Figures 2 and 5) acts on the upper surface of the copying paper, and the copying paper is again fed upstream of the paper conveying passage 58 by the action of the conveying roller 132. When, for example, two copying paper sheets are delivered in the superposed state from the receiving stand, the conveying roller 132 acts on the upper surface of the upper copying paper and the frictional member 246 acts on the undersurface of the lower copying paper whereby the movement of the lower paper alone is hampered by the frictional member 246. At this time, the papers undergo the separating action of the preventing mechanism 178, and only the upper copying paper is conveyed by the action of the conveying roller 132. The illustrated electrostatic copying paper is constructed such that when paper jamming occurs in the various passages through which the copying paper is conveyed (for example, the paper conveying passage 58, the paper returning passage 110 and the paper re-feeding passage 128), the power supply of the apparatus can be cut off at the time of removing the paper that has jammed (for example, the power supply can be cut off by opening the front cover not shown of the electrostatic copying apparatus). When the operator is removing the paper that has jammed near the preventing mechanism 178, for example, the power supply is off to make the electromagnetic solenoid 202 and 204 inoperative. When the electromagnetic solenoids 202 and 204 become inoperative, the paper re-sending means 120 assumes the state shown in Figures 2 to 6 and 11, and the frictional member 246 is rendered inoperative as stated above. As a result, the frictional member 246 moves away from the peripheral surface of the conveying roller 132, and as can be easily understood from Figure 11, the paper that has jammed near the preventing mechanism 178 can be removed easily. It is to be understood that the accompanying drawings show the absence of copying paper on the receiving stand 122. Since in the illustrated embodiment described above, the delivery roller 126 is maintained in the first operating state in which it acts on the paper relatively weakly when conducting the paper to the receiving stand 122, and in the second operating state in which it relatively strongly acts on the paper when delivering the paper from the receiving stand 122, this single roller can serve both as a conveyance assisting roller and a delivery roller conventionally provided above the paper receiving stand, and the structure of the paper re-sending means 120 can be relatively simplified. Furthermore, in the illustrated embodiment, actuations of the delivery roller 126 and the plate-like pieces 156 are controlled by two electromagnetic solenoids 202 and 204. Hence, the structure of the actuating mechanism 152 can be relatively simplified. Further, since in the illustrated embodiment, the frictional member 246 is maintained selectively in the inoperative state in which it is apart from the conveying roller 132 and in the operating state in which it is kept in press contact with the peripheral surface of the conveying roller, the wear of the frictional member 246 can be effectively inhibited so that its function to prevent feeding of paper sheets in the superposed state can be retained over an extended period of time. Moreover, in the illustrated embodiment, the frictional member 246 is maintained in the inoperative state and the operating state in relation to the movement of the plate-like pieces 156. It is not necessary therefore to provide a separate actuating source, and the desired effect can be achieved by a relatively simple structure. In the illustrated embodiment, the movement hampering means 124 is adapted to be held at the receding position by the action of the electromagnetic solenoid 204 for maintaining the delivery roller 126 in the second operating state. Alternatively, it is possible to provide an actuating means for exclusive use in moving the movement hampering means 124 in the required manner and hold the movement hampering means selectively at the hampering position and the receding position by this actuating means. In the illustrated embodiment, the movement hampering means 124 projects upwardly from the upper surface of the receiving stand 122 when it is at the hampering position, and recedes from the upper surface of the receiving stand 122 when it is at the receding position. In plate of this construction, it is possible to construct the movement hampering means 124 so as to be movable in the widthwise direction of the copying paper to be received on the receiving stand 122 and adapt it to act on the copying paper on the receiving stand 122 when it is at the hampering position, and moves in the widthwise direction of the copying paper away from the copying paper when it is at the receding position. While in the above embodiment, the paper detecting mechanism 282 is applied to the paper re-sending means 120, it is not limited to this feature, and can be used as a detecting mechanism for detecting a sheet material in electrostatic copying apparatuses of various types.

Claims: A mechanism for preventing feeding of copying paper sheets in the superposed state, said mechanism comprising: a conveying roller (132) having a peripheral surface and mounted for rotation in a predetermined feeding direction; a frictional member (246); and pressing mechanism means for selectively moving said frictional member (246) between an operating state in which it acts on said peripheral surface of said conveying roller (132) and a non-operating state in which it is spaced from said peripheral surface of said conveying roller (132), said pressing mechanism including an oscillating arm (266) supporting said frictional member (246), said oscillating arm (266) being mounted for oscillating movement between a first position at which it maintains said frictional member (246) in said operating state and a second position at which it maintains said frictional member (246) in said non-operating state; characterized in that said pressing mechanism means further includes a supporting member (270) mounted on said oscillating arm (266) for movement relative thereto over a predetermined range toward and away from said conveying roller (132), said frictional member (246) being mounted on said supporting member (270), and pressing spring member means (278) interposed between said oscillating arm (266) and said supporting member (270) for, when said frictional member (246) is in said operating state, elastically maintaining said frictional member (246) in pressing contact with said peripheral surface of said conveying roller (132). Electrostatic copying apparatus, including the mechanism of claim 1 wherein a copying paper re-sending means (120) for receiving a copying paper sheet having an image formed on one surface as a result of having been conveyed through a copying paper conveying passage (58) and again feeding the received paper sheet into the conveying passage (58) is provided upstream of the conveying roller (132) and the frictional member (246) in the paper conveying direction; the paper re-sending means (120) comprises a copying paper receiving stand (122) for receiving copying paper sheets in the stacked state, a delivery means disposed above the paper receiving stand and a movement hampering means (124) adapted to be movable between a hampering position at which it acts on a copying paper sheet received on the paper receiving stand (122) and a receding position at which it has receded from the paper sheet on the paper receiving stand (122); and the oscillating arm (266) is pivoted in relation to the movement of the movement hampering means (124), is held at the second position when the movement hampering means (124) is at the hampering position, and is held at the first position when the movement hampering means is at the receding position.

Inventors: KAJITA HIROSHI, UEHARA YOSHIYUKI, UJINO KOJI, KAJITA, HIROSHI, UEHARA, YOSHIYUKI NO. 309 CITY PARK IIYOTANYAMA, UJINO, KOJI
Applicants: MITA INDUSTRIAL CO LTD, MITA INDUSTRIAL CO. LTD.
Application year: 1985
Main classification: G03G15
IPC codes: G03G15, B65H3