Top sheet feeding apparatus

Abstract: The apparatus (38) comprises a laying plate (149) on which sheets (P) are stacked up; feeding means (220) disposed above the sheets (P) for vacuum attracting, partly deforming in the widthwise direction and feeding the top sheet (P1); and air flow forming means (168) for injecting an air flow (D) toward the deformed parts of said top sheet (P1).

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a top sheet feeding apparatus in accordance with the precharacterising part of the independent claim 1. Such a top sheet feeding apparatus is known from EP-A-0222588. 2. Description of the Prior Art In a copying machine equipped with a recirculating document handler (RDH) for stacking up documents of single form in a plurality, separating and feeding the documents one by one from the top side or bottom side, and returning to the stacked position after reading the documents in the bottom side or top side, a sheet feeder is used, such as the feeding apparatus of documents and the feeding apparatus of separating and feeding the stacked recording sheets one by one. In printing apparatus and photographic printing device, too, an apparatus for separating and feeding stacked recording papers is employed. In such paper feeding device, it is necessary to separate the stacked sheets one by one, and various separating methods are known, such as the air flow separating method, separating claw method, and method for separating sheets by using a roller rotating in a reverse direction of sheet feeding direction. As an example of the prior art of separating sheets by using air flow, "the sheet feeding apparatus" is disclosed in the Japanese Laid-open Patent No. 58-78932, and a similar structure is found in the United States Patent No. 3,198,514 or the Japanese Patent Publication No. 55-19859. The structure is shown in Fig. 1, a side view, and in Fig. 2, a plan view. This composition is, for example in a copying machine of RDH method, a paper feeding 1 for feeding by separating the stacked recording papers one by one. The paper feeder 1 is provided with a support tray 3 on which recording papers 2 are stacked up. At the downstream side of the feeding direction A1 of the recording paper 2 and near the middle of the widthwise direction of the support tray 3 intersecting with the feeding direction A1, a notch 4 is formed, and a feed belt 7 stretched on a pair of rotating rollers 5, 6 disposed beneath the support tray 3 and having many penetration holes formed is exposed at this notch 4. Between the rotating rollers 5, 6 is arranged an air intake duct 8 opposite to the notch 4 across the feed belt 7, and the recording paper 2 on the support tray 3 is attracted by vacuum to the feed belt 7, and is fed in the feeding direction A1 by running and driving of the feed belt 7. On the other hand, since there is a possibility that plural recording papers 2 on the support tray 3 be attracted and fed together by the feed belt 7, an air injection duct 9 is disposed above the downstream side of the feeding direction A1 from the support tray 3, and nozzles 10b to 10e parallel to the feeding direction A1, and plural nozzles 10a, 10f directed toward the middle of the widthwise direction are communicated. On the other hand, the support tray 3 has a base part 15 in an extended shape from the downstream side to the upstream side of the feeding direction A1, and a side wing parts 15, 16 formed obliquely upward from the both sides of the widthwise direction of the base part 14, as shown in Fig. 3. The air injection duct 9 and support tray 3 in this prior art are arranged as shown in Fig. 1, and the air stream in a flat shape is concentrated near the middle position in the widthwise direction of the support tray 3 by the nozzles 10a to 10f. This state of distribution of air stream by the air injection duct 9 is indicated in the shaded area in Fig. 4. This prior art is capable of separating the recording papers 2 favorable as far as the size of the recording papers 2 is relatively small or the weight is relatively large. However, in the case of recording paper of relatively large size or small weight, or therefore in the case of recording paper of weak consistency, favorable separation may not be always possible. That is, in this prior art, by concentrating the air stream near the middle position of the widthwise direction of the support tray 3, the air stream is inflated in the vertical direction near the middle position to realize the action of separating the recording papers. On the other hand, in the recording paper of large size or small weight, not only the lowermost recording paper but also plural recording papers are deformed with a relatively large deflection, in a recess 19 formed by the base part 15 and side wing parts 15, 16 of the support tray 3, in a shape corresponding to the pattern of the recess, and the gap for entry of air stream is hardly formed among the recording papers, and separation of recording papers may be sometimes unsuccessful. Or among the recording papers indicated in the shaded area in Fig. 4, the area of separation region 17 mutually separated by entry of air from the air injection duct 9 becomes relatively smaller than the area of the non-separating region 18 where the recording papers adhere with each other, and therefore when the lowermost recording paper is attracted in vacuum by the conveying belt 7 and conveyed, duplicate feed may occur due to the frictional force in the non-separating region 18. At this time, in order to extend the separating region 17, when nozzles 10g, 10h indicated by double point chain line in Fig. 2 are disposed further outward in the widthwise direction of the nozzles 10a, 10f in the air injection duct 9 so as to be directed outward in the widthwise direction, in the case of recording paper 2 of which width W1 is smaller than the interval L11 shown in Fig. 2 between the nozzles 10g, 10h, the air stream from the nozzles 10g, 10h collides against the both ends 2a, 2b in the widthwise direction of the recording paper, and these end parts 2a, 2b come to flap. In this case, the stacked state of the recording papers 2 piled up in the paper feeder 1 is disturbed, and duplicate feed or defective feed may take place. Or when the recording paper 2 is relatively small in size, the separation capacity due to the air stream concentrated by the nozzles 10a to 10f is excessive, and the recording papers of small size may scatter about in the paper feeder 1. Such problem in the prior art occurs also in the constitution of so-called top feeding type in which the stacked-up sheets are fed by separating one by one from the top sheet. In the prior art, therefore, although the separating capacity is relatively favorable as far as the recording paper is limited in type, separation failure or feeding failure may occur from the viewpoint of versatility of separating recording papers in a wide variety of sizes effectively, and it is not sufficient in versatility, and the sheet feeding apparatus with versatility having the favorable separating capacity in a wide range of size and weight of recording paper is desired. The top sheet feeder as known from EP-A-0222588 and corresponding to the precharacterising part of claim 1 comprises one centrally located projection, named corrugation rail which is attached or molded to the underside of the vacuum attraction box or plenum and causes sheets acquired by the vacuum attraction box to bend during the corrugation so that if a second sheet is still sticking to the sheet having been acquired by the vacuum plenum, the corrugation will cause the second sheet to fall back into the paper tray. Further, EP-A-0446889 is a Prior Art Document according to Article 54 (3) and (4) EPC however, the features of the characterising part of the present independent claim 1 are not described in the Japanese Priority Document JP6220590 having the filing date of 13 March, 1990. The latter priority document of EP-A0446889 discloses protrusions 306 such as shown in the Figs. 52, 53 and 55 of EP-A0446889 provided in feeding means disposed below the stacked sheets. SUMMARY OF THE INVENTION It is hence a primary object of the invention to present an improved top sheet feeding apparatus possessing a favorable separating and feeding capability of sheets in a wide variety of sizes, in an apparatus for feeding stacked-up sheets by separating one by one from the top sheet, by solving the above-discussed technical problems. The above object is, according to the invention solved by a top sheet feeding apparatus specified by the features of the independent claim 1. Depending claims 2 to 9 are respectively specifying advantageous developments thereof. The feeding means is disposed above the sheets stacked up on the laying plate, and this feeding means deforms the top sheet of the stacked-up sheets to be fed, at least at the end part of the feeding direction downstream side of the top sheet, that is, at the front end part, at plural positions in the widthwise direction, partly upward by a negative pressure in, for example, a corrugated form, and feeds the top sheet in such deformed state by attracting in vacuum to the feeding surface, while air flows are injected by the air flow forming means toward the deformed parts from the feeding direction downstream side. The top sheet is deformed as stated above, while the other sheets are nearly flat, not attracted in vacuum to the feeding surface. Therefore, a gap is produced between the deformed part of the top sheet and the second and remaining sheets, and an air flow is blown into this gap. Hence, the top sheet and the other sheets are separated securely, and only the top sheet can be fed, thereby preventing simultaneous feed of plural sheets. The air flow is blown into the part partly deformed upward of the top sheet by negative pressure, and this air flow is synthesized, for example, by the outward air in the widthwise direction and the parallel air in the feeding direction, or formed by only the outward air in the widthwise direction or only the parallel air In the feeding direction, thereby blowing air flow into the gap between the stop sheet and the second and subsequent sheets, and therefore not only sheets of small size, that is, light weight may be fed one by one, but also sheets of large size, that is, heavy weight may be also separated vertically and fed one by one securely, so that sheets in a wide variety of sizes can be securely fed one by one. The feeding means has plural feeding stretch belts disposed at mutual intervals in the widthwise direction, and these belts possess multiple air passage holes, and the top sheet is attracted in vacuum to the feeding surface which is a nearly horizontal lower stretching part of each belt. The belt is rotated and driven by driving means, and the top sheet attracted in vacuum to the lower stretching part is fed from the feeding direction upstream side toward the downstream side, and a vacuum attraction box is disposed immediately above this lower stretching part, and hence air is taken in from the mutual gaps of the adjacent belts as well as the multiple air passage holes in the belts, so that the sheet is attracted In vacuum to the lower stretching part. Between belts, as being attracted by negative pressure through the vacuum attraction box, the sheet is deformed in an upward deflection with roundness upward between the mutual interval of belts. The remaining sheets are nearly flat. Therefore, an air flow may be blown into the space formed between the top sheet and the remaining sheets, and the top sheet may be securely separated from the other sheets. The protrusions projecting downward from the feeding surface are disposed at the fixed position at plural interval positions between mutual lower stretching parts of adjacent belts, and air flows are injected obliquely toward the protrusions. Therefore, the top sheet attracted in vacuum to the lower stretching part of the belt which is the feeding surface of the feeding means is largely deformed along the protrusions, while the remaining sheets are almost flat. Hence, by injecting and blowing air flow into the space between the top sheet and the remaining sheets, the sheets may be separated easily. Since the air flow is injected obliquely toward the protrusions, the top sheet is pressed against the protrusions, and the space from the remaining sheets is increased, so that the air flow easily gets into the space. This air flow is oriented to be directed outward in the widthwise direction from the central side in the widthwise direction to each protrusion, or oriented to be parallel to the feeding direction, or the air directed outward in the widthwise direction and the air directed parallel to the feeding direction may be combined to form one air flow. Still more, the air blown in between the top sheet and the remaining sheet is, so to speak, shielded by the protrusions, and the air hardly runs through outward. In particular, the air directed outward in the widthwise direction is shielded by protrusion. Therefore, the sheets may be separated more securely. Using such protrusions, particularly broad sheets may be securely fed one by one. The protrusions may have a slender shape extending in the feeding direction, and the space between the top sheet and the remaining sheets may be set slender in the feeding direction, and the air flow may be blown in a relatively long distance to the upstream side of the feeding direction, and the vertical separation of the top sheet and the remaining sheets may be done more securely. Moreover, the laying plate is composed symmetrically on right and left sides of the symmetrical surface passing the central position in the widthwise direction, and the air flow forming means injects air flows from the symmetrical positions to the symmetrical surface, so that the air is blown in over the widthwise direction of the sheets, so that the upper and lower sheets may be separated securely. By forming such symmetrical laying plate and injecting air flows from mirror-symmetrical positions, each air flow is injected from the nozzle member possessing first nozzle hole and second nozzle hole, and the first nozzle hole injects air in the direction of the outward side in the widthwise direction as going upstream in the feeding direction toward the deformed part of the bottom sheet from the central side in the widthwise direction, that is, in the direction of diffusing to the outer side, and the air from such nozzle hole is restricted more or less in the diffusion by the air nearly parallel to the feeding direction from the second nozzle hole, and the air flows from the first and second nozzle holes are converged. Therefore, the air getting into the space between the top sheet and the remaining sheets is concentrated to spread in the vertical direction, so that the sheets may be separated securely in the vertical direction. The protrusions project within mutual intervals of the lower stretching parts of the belts to form a negative pressure deforming space against the side edge of one lower stretching part, and an air flow is injected from the negative pressure deforming space side toward the projection, and the top sheet may be pressed against the protrusion by the air flow, and the top sheet being pressed is curved and deformed upward in the negative pressure deforming space, so that the partial deformation of the top sheet may be increased. Therefore, particularly wide and heavy sheets may be separated vertically air the air and fed one by one securely. When the protrusions are arranged symmetrically and disposed at one side in the widthwise direction within mutual intervals of the lower stretching parts of the belts, a negative pressure deforming space is formed against the side edge of one lower stretching part forming the gap, and the air flow is injected to the negative pressure deforming space side toward the protrusion, then the top sheet is pressed against the protrusion by the air flow, and the top sheet is attracted in negative pressure to the negative pressure deforming space, so that the top sheet is partly deformed largely upward. Therefore, a wide space is formed between the top sheet and the remaining sheets, and a large air flow may be blown into the large space. Accordingly, even very broad sheets may be separated securely. When feeding the top sheet of the plural sheets stacked up on the laying plate by attracting in vacuum by the feeding means, this feeding means deforms the top sheet at least at the end part of the feeding direction downstream side, that is, at least at the front end part, at plural positions in the widthwise direction, vertically by negative pressure to attract in vacuum to the feeding surface, while the second and other sheets on the laying plate remain almost flat, and a space is produced between the deformed part of the top sheet and the remaining sheets. Toward the space in this deformed area, that is, between the sheets, an air flow is injected by the air flow forming means, and therefore the top sheet and the remaining sheets may be separated vertically and very easily, and only the top sheet may be fed. Other and further objects, features, and advantages of the invention will be more explicit from the following detailed description taken with reference to the drawings wherein: Fig. 1 is a side view of a typical conventional paper feeder, Fig. 2 is a sectional view for explaining the layout of an air injection duct 9 and nozzle 10 used in the paper feeder 1, Fig. 3 is a perspective view of a support tray used in the paper feeder 1, Fig. 4 is a plan view for explaining the state of air stream in the prior art, Fig. 5 is a sectional view of a copying machine 22, Fig. 6 is a side view showing the composition of the paper feeder 38, Fig. 7 is a plan view near a belt 157 stretched for feeding paper in the paper feeder 38, Fig. 8 is an exploded perspective view of the composition shown in Fig. 7, Fig. 9 is a plan view for explaining a paper width detecting mechanism 135 in the paper feeder 38, Fig. 10 is a front view of a main body 169 of a draft duct 168, Fig. 11 is a plan view of the main body 169, Fig. 12 is a rear view of the main body 169, Fig. 13 through Fig. 16 are sectional views seen from sectional lines A-A, B-B, C-C, D-D in Fig. 12, Fig. 17 is a front view of a cover main body 170, Fig. 18 is a block diagram for explaining a lifting mechanism of the laying plate 149 in the paper feeder 38, Fig. 19 is a perspective view for explaining the action of air streams in the embodiment, Fig. 20 is a sectional view for explaining the action of the embodiment, Fig. 21 is a sectional view for explaining other constitution of the embodiment, DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Now referring to the drawing, preferred embodiments of the invention are described below. Fig. 5 is a sectional view of a copying machine 22. The copying machine 22 comprises a recirculating document handler unit (hereinafter called RDH unit) 23, and a main body 24. The RDH unit 23 has a document feeder 25 of so-called bottom-take top-return system, and the taken document is exposed in an exposure region 28 by a light source 27 while being conveyed through a conveying route 26, and is returned to the document feeder 25. The document feeder 25 comprises a document laying plate 29, paper feeder 30, and air injection unit 31. The main body 24 has the light source 27 in its inside, and an exposure region 28 of the RDH unit 23 by the light source 27 and an exposure region 32 of the main body 24 are set. The document reflected light beams from the exposure regions 28, 32 are focused on a photosensitive drum 34 through an optical system 33. Around the photosensitive drum 34 are arranged a charger 35, a developer 36, and a transfer unit 37, and recording papers of various sizes are supplied from three paper feeders 38, 39, 40 to the transfer region 41 between the transfer unit 37 and the photosensitive drum 34, and the document images by the document reflected light are recorded. The recording papers after transfer are fixed in a fixing unit 42, and filed in every specified number of pieces in a bundling unit 43, and stored in a discharge tray 44. In the paper feeder 21, the copied recording papers are carried in the direction of arrow A1, and fed along the direction of arrow A2. Fig. 6 is a side view showing a section of a paper feeder 38 in a copying machine 22, Fig. 7 is a plan view of Fig. 6, Fig. 8 is an exploded perspective view of the paper feeder 38, and Fig. 9 is a simplified plan view of the paper feeder 38. Referring now to these drawings, the constitution of the paper feeder 38 is explained below. The other paper feeders 39, 40 are composed alike. Meanwhile, the constituent elements of the paper feeder in this embodiment are similar to the constituent elements in the paper feeder 21 in the foregoing embodiments, except that this embodiments relates to the top-taking structure while the paper feeder 21 is of so-called bottom-taking top-returning structure. The paper feeder 38 comprises a frame body 148 in which recording papers are stacked and stored, and a feeding unit 220 for separating and feeding one by one the recording papers stacked and stored in the frame body 148, and the frame body 148 incorporates a laying plate 149 being driven vertically by a lifting mechanism mentioned below on which recording papers P are stacked up. The laying plate 149 has a slot 150 extending in the feeding direction A2, and a guide rail 151 extending along the feeding direction A2 is formed beneath the laying plate 149. This guide rail 151 is provided with a mounting part 153 of a rear end defining member 152, slidably in the longitudinal direction, through plural insertion holes 154 in the mounting part 153. The rear end defining member 152 is provided with a defining part 155 extending above the laying plate 149 through the slots 150 of the laying plate 149 disposed in the mounting part 153. At a predetermined position of the defining part 155, an upper limit sensor 156 such as limit switch is provided, and when an excessive recording paper P is put on the laying plate 149, it is detected. At a position predetermined with respect to the laying plate 149 of the machine body of the copying machine 22, an upper limit switch 185 realized, for example, by a limit switch is provided, and it is detected that the top recording paper P1 of the recording papers P stacked up on the laying plate 149 has a predetermined gap of H4 to the feeding stretch belt 157. That is, when the top recording paper P1 approaches abnormally, exceeding the distance of H4 to the feeding stretch belt 157, the upper limit sensor 185 is actuated to stop elevation of the recording paper. The paper feeder 38 is provided with, for example, four feeding stretch belts 157a to 157d at predetermined positions with respect to the frame body 148. These feeding stretch belts 157a to 157d are stretched respectively on the rollers 160a to 160d; 161a to 161d fixed on the rotary shafts 158, 159. Between the rollers 160 and 161, a vacuum attracting box 162 is stored, which comprises a main body 164 forming attracting ports 163a to 163d opposite to the feeding stretch belts 157a to 157d, and a cover body 165 covering the main body 164. A damper 166 is contained in the vacuum attracting box 162, and a vacuum source (not shown) to which the vacuum attracting box 162 and the vacuum attracting box 162 are communicated/shut off. The attracting box 162 is supported by a support member 260 fixed on the frame body 148. Between attracting ports 163a, 163b and the attracting ports 163c, 163d of the main body 164, protrusions 167a, 167b extending along the feeding direction A2 and projecting downward are formed, and they project downward from between the feeding stretch belts 157a, 157b, and feeding stretch belts 157c, 157d. At the downstream side of the feeding direction A2 of the frame body 148 and beneath the feeding stretch belt 157, a nozzle member 168 is provided. The nozzle member 168 contains the main body 169 and cover body 170, and a damper 171 is included in an internal air passage 216, thereby communicating/shutting off the blower (not shown) and the nozzle member 168. The laying plate 149 in the frame body 148 is provided with slots 209, 210 along the widthwise direction, and lateral end defining plates 195, 196 are inserted from top to bottom of the laying plate 149. Near the rear end side of the laying plate 149 of the lateral end defining plates 195, 196, one longitudinal end of the driving members 197, 198 extending along the widthwise direction is fixed. At the mutually confronting end parts along the feeding direction A2 of the driving members 197, 198, racks 199, 200 are formed, and these racks 199, 200 are engaged mutually from the opposite sides with a pinion 201 rotatably disposed on a support plate 149 disposed between the driving members 197, 198. Regarding the lateral end defining plate 195, a widthwise displacement position is detected, for example, by three positions sensors S1, S2, S3 which are disposed from outward to Inward in the widthwise direction. The lateral end defining plates 195, 196 cooperate with each other by means of the racks 199, 200 and pinion 201, and by aligning the distance of the lateral end defining plates 195 in the widthwise length of the stored recording papers P, the widthwise length of the stored recording papers can be detected on the basis of the output from the position sensors S1 to S3. Fig. 10 is a front view of the main body 169, Fig. 11 is a plan view of the main body 169, Fig. 12 is a back view of the main body 169, and Figs. 13 to 17 are sectional views seen from the sectional lines A-A, B-B, C-C, D-D in Fig. 34. Referring together to these drawings, the composition of the nozzle member 168 is described in detail below. The main body 169 comprises a flat plate 172 extending in the widthwise direction, and slopes 173, 174 consecutive to the vertical direction thereof and Inclined by an angle 3 (e.g. 20 degrees) to the main body 148 side. At the downstream side of the feeding direction A2 of the slopes 173, 174, plural guide pieces 175 are formed, and when the cover body 170 is put on the main body 169, nozzle holes 176a to 176f forming the same jet flows D1 to D3 as the jet flows C1 to C3 by the nozzle 96 in the foregoing embodiment are formed by the adjacent guide pieces 175, and the nozzle is composed of the nozzle holes 176a to 176f and the adjacent guide pieces 175. The nozzle holes 176a, 176f form a jet flow of arrow D1 toward the feeding stretch belt 157, in the vertical plane parallel to the feeding direction A2. The nozzle holes 176b, 176f have an angle of α11 (e.g. 30 degrees) to the feeding direction A2 in a plan view, and form a jet flow expressed by arrow D2 directed to the feeding stretch belt 157. The nozzle holes 176c, 176d form a jet flow and an air flow parallel to the arrow D2 and indicated by arrow D3. The jet flows D1, D2 are converged and synthesized on the central line 11 to form an air flow D11. In the lower stretched part 215 of the feeding stretch belt 157, the flow is injected to the position remote to the downstream side by the predetermined distance L5 from the downstream side end part of the feeding direction of the recording paper attracted so as to cover the attracting region 108 defined by the attracting vacuum box 162 and the range exceeding to the downstream side of the feeding direction A2. The reflected air flow from the feeding stretch belt 157 is blown and injected between the top recording paper P1 and the second recording paper P2. The injected air flow is inflated in the vertical direction, thereby separating the recording papers P1, P2. Further outward of the nozzle holes 176a, 176f of the main body 169, there are formed nozzle holes 177a, 177b having the sectional shapes as shown in Figs. 14 and 15. The nozzle holes 177a, 177b are composed at an inclination outward in the widthwise direction as going upstream in the feeding direction at an angle of α12 (e.g. 40 degrees) with respect to the widthwise direction as shown in Fig. 12 outward in the widthwise direction, and are composed at an inclination to the upstream side of the feeding direction A2 as going from downward topward by an angle of α13 (e.g. 65.7 degrees) from the vertical direction as shown in Fig. 14. That is, to the upstream side of the feeding direction A2 than the jet flow of the nozzle holes 176a to 176f, the jet flow and air flow are injected as indicated by arrow D4. Further outward in the widthwise direction from the nozzle holes 177a, 177b of the main body 169, grooves 178a, 178b parallel to the feeding direction A2 are formed as the sectional shape is shown in Fig. 16. The grooves 178a, 178b are covered with the cover body 170 as shown in Fig. 16, and form a jet flow and an air flow parallel to the feeding direction A2 (indicated by arrow D5). The cover body 170 shown in Fig. 13 is put on thus composed main body 169. At both sides of the cover body 170 in the widthwise direction, fitting projections 251a and 251b having a pair of upper and lower nozzle holes 252a and 252b are formed. These projections 251a and 251b are projected in the feeding direction A2, and the nozzle holes 252a and 252b are composed by the holes 250a, 178a; 250b and 178b in the state of being fitted to the grooves 178a and 178b of the main body 169. From these nozzle holes 252a and 252b, a jet flow may be formed in the direction of arrow D5 as shown in Fig. 16. A pair of upper and lower ribs 254 and 255 are integrally formed on the end plate 253 of such cover body 170, and by these ribs 254 and 255, the nozzle holes 176a to 176e are defined in the state of communicating in the direction of jet flows D1 to D3. Fig. 18 is a perspective view showing the composition of elevating the laying plate 149 in the paper feeder 38. In the frame body 148, plural pulleys 180a to 180f are disposed as shown in the drawing at a predetermined height H5 from the bottom of the frame body 148, and pulleys 180g to 180j are disposed at a position of a predetermined height H6 from the bottom. A wire 181 is applied on these pulleys 180a to 180j, and the both ends of the wire 181 are wound around a driving roller 183 rotated by a pulse motor 182. In the portions stretching vertically at four corners of the frame body 148 of this wire 181, support pieces 184a to 184d from mounting the four corners of the laying plate 149 are fixed. That is, when the driving roller 183 is rotated in the direction of arrow E1 by the pulse motor 182, the laying plate 149 is elevated, while the laying plate 149 is lowered. Thus, as shown in Fig. 28, the highest recording paper P1 in the vertical direction of the recording papers P put on the laying plate 149 is maintained at a position remote by a predetermined distance of H4 from the feeding stretch belts 157a to 157d. Consequently, a favorable vacuum attracting action of the top recording paper P by the feeding stretch belts 157a to 157d may be realized. Fig. 19 is a perspective view for explaining the basic function of each air flow indicated by arrows D1 to D5 and D11 from the nozzle holes 176a to 176f; 177a, 177b; 178a and 178b. The jet flows of arrows D1 and D2 are concentrated as an air flow D11 in the widthwise direction of the recording paper P, and it is blown in and injected in the gap formed as shown below between the top recording paper P1 and the second recording paper P2, and is inflated in the vertical direction to separate the recording papers P1 and P2. The air flow indicated by arrow D3 also separates the recording papers P1 and P2 as mentioned below. The air flow D5 from the nozzle holes 178a and 178b is an air stream injected parallel to the feeding direction A2 in the relatively upward portion of the stacked recording papers P, and it maintains a plurality of recording papers P near the upper part always in a lifted state. On the other hand, the air flow indicated by arrow D4 from the nozzle holes 177a and 177b pushes up the uppermost recording paper P1 of the plurality of recording papers P lifted by the air flow of arrow D5 to the feeding stretch belt 157 side, and the recording paper P1 is attracted in vacuum to the feeding stretch belt 157 by the negative pressure by the vacuum attracting box 162. At this time, in order that the plural recording papers P may not be attracted at the same time, the recording papers P are separated by the air flows indicated by arrows D11 and D3. Fig. 20 is a sectional view explaining the separating action of the recording papers P in the paper feeder 38. For the sake of simplicity of explanation, the structure is shown in a simplified form in Fig. 20. Hereinafter, the nozzle holes 176a to 176f and the guide pieces 175 for defining them are collectively called a handling nozzle and indicated by same reference number. Besides, the nozzle holes 177a, 177b; 179a and 179b and guide pieces 175 for defining them are called pushing nozzle and lifting nozzle, respectively, and indicated by same reference numbers. As shown in Fig. 6 and Fig. 19, when the air flow indicated by arrow D5 is injected from the lifting nozzle 179 of the nozzle member 168 to the recording papers P stacked up on the laying plate 149, the relatively upper recording papers of the stacked recording papers P are lifted within the frame body 148. At this time, when a negative pressure is generated in the vacuum attracting box 162, the floating recording papers P are attracted vacuum to the lower stretching part 215 of the feeding stretch belt 157. The top recording paper P1 at this time is attracted In vacuum to the lower stretching part 215 of the feeding stretch belt 157 while being lifted by the protrusions 167a, 167b projecting downward from within the feeding stretch belt 157, being formed in the vacuum attracting box 162. The second recording paper P2 is prevented from being attracted to the feeding stretch belt 157 because almost entire portion of the lower stretched part 215 of the feeding stretch belt 157 is covered by the recording paper P1. If attracted, it is only relatively weakly attracted. Accordingly, as shown in Fig. 20, a gap 186 is produced between the recording papers P1 and P2, near the protrusions 167a and 167b. The air flow D from the handling nozzles 176a to 176f collides against the portion not opposing the attracting port 163, once at the feeding stretch belt 157, as mentioned above, and its reflected flow is injected between the recording papers P1 and P2. Therefore, the air flow injected downward in the gap 186 is inflated in the vertical direction, and the recording papers P1 and P2 are separated by this positive pressure. The air flow in the direction of arrow D3 from the handling nozzles 176c and 176d is attracted into the gap 186, and realizes the same separating action. The pushing nozzles 177a and 177b are to lift one or plural recording papers P of the uppermost area of the floating recording papers P to the feeding stretch belt 157 side. In this embodiment, too, air flows C11 and C3 inflating in the vertical direction are formed at symmetrical positions about the widthwise central position CNT of the recording paper, and a satisfactory separating action is realized whether the recording papers P being used are relatively large or small in size. What is more, the air flow from the nozzle member 168 is concentrated in the widthwise plural positions to the recording papers P, and if the recording papers are relatively small in size or weight, scattering of the recording papers P by the air flow from the handling nozzles 176a to 176f without being attracted to the feeding stretch belt 157 may be avoided. Besides, although the air flow from the handling nozzle 176e is directed from inward to the outward side in the widthwise direction, this air flow is blocked by the air flow from the handling nozzles 176a and 176f, and leakage from both ends of the widthwise direction of the recording papers P may be prevented. Hence, it is possible to avoid flapping of the both ends in the widthwise direction of the recording papers P, disturbance of stacked state, or generation of noise. Fig. 21 is a sectional view showing other constitutional example of the feeding unit 220 of the paper feeder 38. This embodiment is similar to the foregoing embodiments, and corresponding parts are identified with same reference numbers. What is of note in this embodiment is that the protrusion 167 formed in the vacuum attracting box 162 is determined so as to be positioned in the widthwise central position CNT between the feeding stretch belts 157b and 157c, and that attracting ports 163e and 163f are disposed in the vacuum attracting box 162 between the feeding stretch belts 157a and 157b, and between the feeding stretch belts 157c and 157d. Employing such constitution, as explained by reference to Figs. 6 and 19, the recording paper P on the laying plate 149 is lifted by the lifting nozzles 179a and 179b, and the lifted recording paper P is pushed up by the pushing nozzles 177a and 177b to the feeding stretch belt 157 side. When the vacuum attracting box 162 generates a negative pressure, the top recording paper P1 is attracted to the feeding stretch belt 157, but the range opposing the attracting ports 163e and 163f is the gap of the feeding stretch belt 157, and therefore the recording paper p1 is attracted and dented to the vacuum attracting box 162 side as shown in Fig. 17. It is the same with the recording paper P1 opposing the attracting port 163f. Furthermore, the recording paper P1 is lifted in the direction of going away from the vacuum attracting box 162 by the protrusion 167 formed in the central position CNT. Therefore, between the recording papers P1 and P2, a gap 186 is formed at the position corresponding to the attracting ports 163e, 163f and protrusion 167. Therefore, the air flows C11, C3 due to handling nozzles 176a to 176f are injected into the gap 186, and inflated in the vertical direction as mentioned above to separate the recording papers P1 and P2. In such embodiment, too, the same effect as mentioned in the foregoing embodiments is achieved. Meanwhile, the protrusions 167a, 167b are not limited to the shape continuous on a straight line, but may be formed in a shape of single projection of circular head, for example, and a plurality of such protrusions may be composed along the feeding direction A2. In the preceding embodiments, it is composed so that the recording paper may be attracted to the feeding stretch belts 46a to 46c, 157a to 157d and 208, in a range exceeding the attracting region 108, and that the air flow for separation is once injected to a remote position preliminarily to the downstream side in the feeding direction from the downstream side end part of the feeding direction A2 of the recording paper as mentioned above, thereby the reflected flow acts to separate the recording papers. As other example of the invention, for example, when the recording paper is relatively small in size, it may be also designed that the recording paper may be exposed, not covered, near the downstream side end portion of the attracting region 108. In such a case, the air flow for separating is attracted into the attracting region 108, and the flow rate is suppressed. Therefore, scatter of the small-sized recording paper by the air flow of large flow rate may be avoided. In the case of recording papers of relatively large size or large weight, it is enough to suck as in the preceding embodiment. In other embodiment of the invention, the ends of one side in the widthwise direction of sheets may be stacked up on the laying plate, and the papers may be fed in this end aligned state. Furthermore, in a different embodiment of the invention, the rear end defining members 58 and 152 may be designed to detect the size of the sheets (that is, width or length) or the pile of the stack by detecting means, thereby driving to displace forward or backward in the feeding direction. The invention may be applied in a wide range, not only for feeding the recording papers of copying machine, but for feeding the recording papers of a printer, or feeding other sheets than recording papers.

Claims: A top sheet feeding apparatus comprising: a laying plate (149) on which plural sheets (P) are stacked up, feeding means (220) disposed above the sheets (P) on the laying plate (149) at plural positions in its widthwise direction for attracting the top sheet (P1) by applying vacuum to the feeding surface and feeding by partly deforming upward by applying negative pressure to the top sheet (P1) at least at its end part at the downstream side in the feeding direction (A2) at plural position in its widthwise direction, said feeding means comprising: plural feeding stretch belts (157) possessing multiple air passage holes (103) being disposed at mutual intervals (103) in the widthwise direction, driving means (160, 161) for rotating and driving the belts (157) to feed the sheets (P) and a vacuum attraction box (162) opened downward, being disposed immediately above the nearly horizontal lower stretching part (215) of the belts (157), and air flow forming means (168) disposed at the downstream side of the feeding direction (A2) from the laying plate (149) for injecting and forming an air flow (D, D1-D5) toward the deformed parts of the top sheet (P1), said top sheet being attracted by the applied vacuum to the feeding surface, characterised in that protrusions (167) are disposed at fixed positions between attraction parts (163) of the open lower part (164) of the vacuum attraction box (162), said protrusions (167) being provided at plural intervals of the respective lower stretching parts of the feeding stretch belts extending along the feeding direction and projecting downward from the feeding surface of said lower stretching parts of the feeding stretch belts, and said air flow forming means (168) are arranged to inject air flows (D) toward the vicinity of the protrusions (167). The top sheet feeding apparatus of claim 1, wherein the air flow (D) in the deformed parts of the top sheet (P1) is composed of air flows (D2), (D3) directed outward in the widthwise direction and air flows (D1) parallel to the feeding direction (A2). The top sheet feeding apparatus of claim 1, wherein the air flows (D2, D3) to individual protrusions (167) are directed outward in the widthwise direction. The top sheet feeding apparatus of claim 1, wherein the air flows (D1) for individual protrusions (167) are parallel to the feeding direction (A2). The top sheet feeding apparatus of claim 1, wherein the air flows (D) for individual protrusions (167) are a combination of air flows directed outward in the widthwise direction and air flows directed parallel to the feeding direction (A2). The top sheet feeding apparatus of claim 1, wherein the protrusions (167) are in slender shape extending along the feeding direction. The top sheet feeding apparatus of claim 1, wherein the laying plate (149) is composed symmetrically on right and left sides of the symmetrical surface passing the central position in the widthwise direction, and the air flow forming means (168) injects air flows from symmetrical positions on the right and left side of the symmetrical surface. The top sheet feeding apparatus of claim 1, wherein the air flow forming means (168) comprises: a nozzle member (168) possessing a first nozzle hole (176B), (176C), (176D), (176e) and a second nozzle hole (179) for forming the air flows (D) and the first nozzle hole (176b), (176c), (176d), (176e) injects air flows, (D2, D3) outward in the widthwise direction as going upstream in the feeding direction (A2) toward the deformed part of the bottom sheet from the central side of the widthwise direction, and one second nozzle (176a), (176b) injects air flows toward the upstream side nearly parallel to the feeding direction (12) toward the deformed part. The top sheet apparatus of claim 8, wherein the protrusions (167) are arranged as being shifted to one side in the widthwise direction, within mutual intervals of the lower stretching parts (215) of belts (157), and a negative pressure deforming space is formed against the lateral edge of one lower stretching part (215), and the air flow is injected from the negative pressure deforming space side toward the protrusion (167).

Inventors: NAMBA TOYOAKI, OKADA KENJI, TAKATA SOUICHI, WAKUDA OSAMU, NAMBA, TOYOAKI, OKADA, KENJI, TAKATA, SOUICHI, WAKUDA, OSAMU
Applicants: SHARP KK, SHARP KABUSHIKI KAISHA
Application year: 1991
Main classification: B65H3
IPC codes: B65H83, G03G15, B65H3