Title:
Sheet feeding device
United States Patent 3871641
Abstract:
A device for feeding individual sheets of a stack to apparatus in which these sheets are to be processed further, which comprises a sheet transporting element having a plane underside of non-slippery material which may be brought into contact with the uppermost sheet of the stack, said sheet transporting element being provided with means for moving it backwards and forwards in the direction of transportation of the sheets.
US Patent References:
Paper feeding device
Roque - July 1937 - 2086138
Sheet handling units
Manthey - April 1959 - 2883190
Paper dispenser with pusher feet
Harter - August 1966 - 3269590
Apparatus and structure for handling copy paper
Eisner et al. - February 1967 - 3306491
VACUUM OPERATED DOCUMENT FEEDER SYSTEM
Staples - January 1969 - 3421753
Paper feeding device
Roque - July 1937 - 2086138
Sheet handling units
Manthey - April 1959 - 2883190
Paper dispenser with pusher feet
Harter - August 1966 - 3269590
Apparatus and structure for handling copy paper
Eisner et al. - February 1967 - 3306491
VACUUM OPERATED DOCUMENT FEEDER SYSTEM
Staples - January 1969 - 3421753
Inventors:
Marx, Gerhard (Taunusstein, DT)
Kramer, Gunter (Wiesbaden, DT)
Kramer, Gunter (Wiesbaden, DT)
Application Number:
05/324234
Publication Date:
03/18/1975
Filing Date:
01/16/1973
View Patent Images:
Export Citation:
Assignee:
Kalle Aktiengesellschaft (Wiesbaden-Biebrich, DT)
Primary Class:
Other Classes:
271/167, 221/276, 271/208, 221/210
International Classes:
B65H1/04; B65H3/02; B65H3/02; B65H3/52
Field of Search:
271/42,145,167,169,208,104,121,137 221/228,244,210,268,276
US Patent References:
| 3640524 | SHEET-SEPARATING APPARATUS | February 1972 | Fredrickson |
Primary Examiner:
Blunk, Evon C.
Assistant Examiner:
Miller, James W.
Attorney, Agent or Firm:
Stevens, Davis Miller & Mosher
Claims:
What is claimed is
1. An apparatus for feeding individual sheets of a stack to a device on which said sheets are further worked comprising a reciprocating conveyor element for the displacement of the top sheet of the stack and a reciprocating telescopic rod comprising a rod and sheath, said conveyor element having a flat bottom of gripping foam which contacts the top sheet of the stack, said telescopic rod being arranged to extend obliquely downwardly and rearwardly with respect to the sheet-conveying direction and having its sheath fastened to the conveyor element.
2. A device as claimed in claim 1, wherein the angle between the telescopic rod system and the normal to the paper is between 5° and 20°.
3. A device as claimed in claim 2, wherein the angle is about 13°.
4. A device as claimed in claim 1, including a lid positioned above the stack, and provided with a slit in which a slider is displaceably mounted in the slit, one end of the telescopic rod being angularly attached to the sider.
5. The device as claimed in claim 1, including a box having a front wall transverse to the sheet transporting direction, facing towards the direction to which the sheets are to be transported and sloping outwardly from the bottom of the box.
6. The device as claimed in claim 5, wherein said box has a rear wall transverse to the sheet transporting direction a portion of which is parallelly sloped to the front transverse wall.
7. The device as claimed in claim 5, wherein the front transverse wall is provided with at least one strip having a rough surface, running in the sheet transporting direction.
8. The device as claimed in claim 7, wherein the strip of rough material on the front sloping transverse wall tapers such that it is broader at the bottom than at the top.
9. The device as claimed in claim 7, wherein the strip comprises a glued-on fabric strip.
10. The device as claimed in claim 1, including an insulated housing defining an outlet edge for said sheets which is electrically conducting and so disposed that each sheet comes in contact therewith as it leaves the housing.
11. The device as claimed in claim 10, wherein the electrically conducting outlet edge comprises the upper edge of the sloping front transverse wall.
12. The device as claimed in claim 4, including a spring interconnecting the slider and housing such that said spring is tensioned when transporting a sheet and then retracts the transporting element to its starting position.
13. The device as claimed in claim 1, including a microswitch which can be operated by the displacement of the sheet transporting element, said microswitch being connectable to apparatus in which further processing of the sheets is to occur such as to actuate this further processing apparatus when the displacement of the sheet transporting element occurs.
14. The device as claimed in claim 13, wherein the apparatus in which further processing is to occur comprises an electrophotographic apparatus.
15. The device as claimed in claim 1, wherein the sheet transporting element comprises a foam block to the top of which is fixed a metal plate, the telescopic rod being fixed at an angle onto this metal plate, and the metal plate being bored and connected to the extending end of the sheath of the telescopic rod.
16. The device as claimed in claim 15, wherein the outer sheath of the telescopic rod is located in an approximately shaped bore of the foam block.
17. The device as claimed in claim 1 for transporting sheets comprising four telescopic rods arranged transversely to the sheet transporting direction and equidistant from one another.
1. An apparatus for feeding individual sheets of a stack to a device on which said sheets are further worked comprising a reciprocating conveyor element for the displacement of the top sheet of the stack and a reciprocating telescopic rod comprising a rod and sheath, said conveyor element having a flat bottom of gripping foam which contacts the top sheet of the stack, said telescopic rod being arranged to extend obliquely downwardly and rearwardly with respect to the sheet-conveying direction and having its sheath fastened to the conveyor element.
2. A device as claimed in claim 1, wherein the angle between the telescopic rod system and the normal to the paper is between 5° and 20°.
3. A device as claimed in claim 2, wherein the angle is about 13°.
4. A device as claimed in claim 1, including a lid positioned above the stack, and provided with a slit in which a slider is displaceably mounted in the slit, one end of the telescopic rod being angularly attached to the sider.
5. The device as claimed in claim 1, including a box having a front wall transverse to the sheet transporting direction, facing towards the direction to which the sheets are to be transported and sloping outwardly from the bottom of the box.
6. The device as claimed in claim 5, wherein said box has a rear wall transverse to the sheet transporting direction a portion of which is parallelly sloped to the front transverse wall.
7. The device as claimed in claim 5, wherein the front transverse wall is provided with at least one strip having a rough surface, running in the sheet transporting direction.
8. The device as claimed in claim 7, wherein the strip of rough material on the front sloping transverse wall tapers such that it is broader at the bottom than at the top.
9. The device as claimed in claim 7, wherein the strip comprises a glued-on fabric strip.
10. The device as claimed in claim 1, including an insulated housing defining an outlet edge for said sheets which is electrically conducting and so disposed that each sheet comes in contact therewith as it leaves the housing.
11. The device as claimed in claim 10, wherein the electrically conducting outlet edge comprises the upper edge of the sloping front transverse wall.
12. The device as claimed in claim 4, including a spring interconnecting the slider and housing such that said spring is tensioned when transporting a sheet and then retracts the transporting element to its starting position.
13. The device as claimed in claim 1, including a microswitch which can be operated by the displacement of the sheet transporting element, said microswitch being connectable to apparatus in which further processing of the sheets is to occur such as to actuate this further processing apparatus when the displacement of the sheet transporting element occurs.
14. The device as claimed in claim 13, wherein the apparatus in which further processing is to occur comprises an electrophotographic apparatus.
15. The device as claimed in claim 1, wherein the sheet transporting element comprises a foam block to the top of which is fixed a metal plate, the telescopic rod being fixed at an angle onto this metal plate, and the metal plate being bored and connected to the extending end of the sheath of the telescopic rod.
16. The device as claimed in claim 15, wherein the outer sheath of the telescopic rod is located in an approximately shaped bore of the foam block.
17. The device as claimed in claim 1 for transporting sheets comprising four telescopic rods arranged transversely to the sheet transporting direction and equidistant from one another.
Description:
The present invention relates to a device for feeding individual sheets of a stack to an apparatus in which the sheets are processed further, for example a copying apparatus.
The feeding of individual sheets from a stack to a copying apparatus represents a problem which has hitherto not been satisfactorily solved in the art. Numerous attempts have been made in this field. There are feeding devices with circulating chains, devices with friction rollers and needle gripping devices. However, these devices are either extremely involved in construction and therefore unusable for simple apparatus, or do not operate with sufficient reliability. Feeding sheets from a stack proves particularly difficult where precoated sheets are concerned, especially electrophotographic recording material, for example zinc oxide paper.
There is therefore a need for a sheet feeding apparatus which is simple in construction and cheap to manufacture and may also be used with small manual copying apparatures. The apparatus should have a high degree of reliability that several sheets will not be fed simultaneously, and should at the same time be rapidly and reliably utilisable.
The present invention accordingly provides a device for feeding individual sheets of a stack to apparatus in which these sheets are to be processed further, especially an electrophotographic copying machine, which comprises a sheet transporting element having a plane underside of non-slippery material, preferably non-slippery foam material, which may be brought into contact with the uppermost sheet of the stack, said sheet transporting element being provided with means, preferably comprising at least one telescopic rod system for moving it backwards and forwards in the direction of the transportation of the sheets.
The means for moving the sheet transporting element preferably comprises at least one telescopic rod system running downwards at an angle and backwards through the sheet transporting element, relative to the sheet transporting direction.
The present invention also provides a process for supplying individual sheets from a stack to apparatus in which the sheets are to be further processed, especially an electrophotographic copying machine, using the device of the invention. On displacing the telescopic rod system in the sheet transporting direction, the telescopic rod system is self-locking to prevent telescoping, and hence the uppermost sheet is shifted relative to the stack, whilst during the return movement the telescopic rod system is slightly telescoped and, as a result of the inclined position, as in the case of a sloping plane, the non-slippery transporting element is lifted off the uppermost sheet of the stack of sheets and hence the paper is not buckled but remains lying flat. This device is of extremely simple construction and permits rapid and reliable feeding, especially of zinc oxide copying papers to an electrophotographic reproduction apparatus.
The angle between the telescopic rod system and the normal to the paper should preferably be in the range of from 5° to 20°; an angle of about 13° between the telescopic rod system and the normal to the paper (or of 77° between the telescopic rod system and the paper surface) has proved particularly satisfactory.
The transporting element can be arranged particularly simply to be displaceable in the device by providing, in the lid above the stack, a slit in which a slider is displaceably mounted, the end of the telescopic rod system being fixed thereto. The slope of the telescopic rod system is of decisive importance and is always kept constant whilst the complete stack is being fed, since the telescopic rod system is not arranged so that it can be tilted. As the stack becomes smaller, the transporting element nevertheless remains in engagement with the sheet of the copying stack which is uppermost at any time, since the telescopic rod system is automatically extended as the stack height decreases.
The device of the invention preferably comprises a box to hold the stack of sheets, wherein the front transverse wall, that is the wall transverse to the sheet transporting direction towards which the sheets are to be transported, slopes outwards from the bottom of the box. The front transverse wall thus acts as a ramp for the sheets to be transported. Preferably the rear transverse wall is also sloped and parallel to the front transverse wall. The two sloping transverse defining walls also always cause a little fanning of the papers on insertion into the sheet stacking device. This permits air to penetrate between the individual sheets and thereby enables them to be drawn off more readily.
Further reliability in ensuring that several sheets are not fed simultaneously is achieved if the front sloping transverse wall possesses at least one strip, having a rough surface, running in the sheet transporting direction. The front edge of the sheet flicks along this strip and a further sheet which may have been fed with it is retained by the roughness. Here, it is particularly advantageous if the rough strip on the front transverse defining wall is somewhat broader at the bottom than at the top, that is to say if it tapers conically. This permits very reliable feeding of single sheets particularly also for the bottom sheets of a stack of sheets. The strip having a rough surface can be formed particularly simply by a glued-on fabric strip of not excessively rough structure.
For electrophotographic apparatuses in which photo-conducting sheet material is to be fed to the apparatus it has proved particularly advantageous if the sheet stack is located in an insulated housing and the outlet edge of this housing, that is to say, for example, the upper edge of the front sloping transverse defining wall, is electrically conducting and exposed so that it comes into contact with the fed sheet and thus prevents the charge emanating from the corona from being conducted into the stack of sheets.
The process is further facilitated if a return spring is provided in the device, between the housing and the transporting element displaceable therein, this spring being tensioned when transporting the sheet and being capable of retracting the transporting element thereafter to its starting position. At the same time it is preferred to locate a micro-switch in the device in such a way that on displacing the transporting element from the starting position the switching of the micro-switch causes the various subsequent stations of an apparatus in which further processing of the sheets is to occur, for example an electrophotographic apparatus, to be switched on.
The transporting element may suitably comprise a foam block to the top of which is fixed a metal plate, the telescopic rod system being fixed at an angle on to this metal plate. This construction is particularly space-saving if the outer sheath of the telescopic rod system is located in an appropriately shaped sloping bore of the foam block, the metal plate is bored and is connected to the extending end of the sheath. The inner rod of the telescopic rod system can then be drawn out but the requisite height of the construction is kept low due to the fact that the length of the telescoped telescopic rod system and the thickness of the foam block are not additive.
The invention is described in further detail, by way of example only, with reference to the accompanying drawings, in which:
FIG. 1 represents an enlarged vertical section along the line I-- I of FIG. 2,
FIG. 2 represents a plan view of a device according to the invention, with the lid 12 omitted, and
FIG. 3 represents a detail of the device shown in FIG. 1, taken along the line III-- III of FIG. 1.
An angled metal sheet 2 is located in a housing 1. This sheet 2 has a bottom section 2a and two sloping sections 2b and 2c which are parallel to one another. The two sloping sections 2b and 2c of the sheet 2 represent the sloping transverse defining walls for a stack of sheets 17 consisting of sheets of zinc oxide paper. Furthermore, a removable cover plate 12 and a guide sheet 3 are provided. The guide sheet 3 causes the paper sheet which has been pushed forward to be moved in the direction of guiding elements which are not shown, for example transporting belts of an electrophotographic copying apparatus.
Laterally, the stack of sheets 17 is held by two guide sheets 4 and 5 which are internally lined with felt-like or velvet-like fabric 4B and 5B. At the same time, one guide sheet 5 is lightly pressed against the stack 17 by means of a spring 13 or a foam slab.
A foam block 6 of soft porous foam rests on the uppermost sheet of the stack of sheets 17. A block of "Moltopren" (Trade Mark, product of Beiersdorf A.G., Hamburg, Germany) or similar material has proved very successful. A metal plate 18 is fixed to this block. Furthermore, the block 6 possesses a sloping bore in which is located the outer sheath of a telescopic rod system 7. This sheath is soldered to the plate 18 in the desired sloping position, as is indicated schematically by the soldering point 19.
The extensible rod of the telescopic rod system 7 is connected at its end to an angled metal sheet 8, which in turn is connected to a handle 10. The handle 10 with the metal sheet 8 located below it and the telescopic rod system fixed thereto, as well as the Moltopren block 6, can be pushed to and fro in a slit in the lid 12. The paper transporting direction is here indicated by the arrow 20. On moving the unit 6, 7, 8, 10 in the direction of the arrow 20, a normal force N 1 is produced between the two components of the telescopic rod system 7, which acts at right angles to the direction in which the telescopic rod is guided. As can be seen from the left-hand triangle of forces shown in FIG. 1, this normal force N 1 is substantially directed towards the lower left-hand corner. It may be split into a downwardly directed vertical force V 1 corresponding to the weight of the foam block 6 and that of the plate 18, and a horizontal frictional force R 1 . The vertical component V 1 effects the necessary pressure of the foam block 6 and thus causes the uppermost sheet to be pushed forward. If the handle 10 and the unit 6, 7, 8 connected thereto are then moved to the right, a normal force N 2 is produced which is directed toward the right top corner, as shown in the right-hand triangle of forces. This normal force is composed of a frictional force R 2 and a vertical force V 2 . Due to this vertical component V 2 , the foam block has a tendency to climb along the telescopic rod 7, and the top sheet of the stack of sheets is thus relieved. This relief is only effective as long as there is at least a slight contact (friction) between the foam block 6 and the uppermost sheet of the stack. It is also possible, and comes within the scope of the present invention, for the foam block 6 to be in lateral contact with the felt-or velvet-covered guides 4B and 5B, in which case it could be completely lifted from the stack of sheets. The first-mentioned embodiment is preferred, however, since it is not necessarily desirable that the foam block 6 is completely lifted, because a residual friction, which may even cause a slight displacement of the following sheet, facilitates the separation of the next sheet from the stack.
A return spring 14 is mounted between the edge of the lid 12 and the angled metal sheet 8. When the handle 10 is moved in the direction of the arrow 20, this spring is tensioned and automatically pulls the foam block 6 back to its starting position when the top sheet has been pushed forward.
A micro switch 11 is located in the device in such a way that the movement of the handle 10 switches on, for example, the corona discharge device and the further transport devices of an electrophotographic apparatus.
Particularly good and reliable separation into individual sheets is achieved by the measure described below. Two narrow fabric strips 15 are glued onto the base 2a and the front sloping transverse defining wall 2b. These fabric strips, consisting of a fabric which is not excessively coarse (the self-adhesive "Leukoplast" tape manufactured for medical purposes by Messrs. Beiersdorf A.G., Hamburg, has proved successful) terminate just before the upper edge 3A of the sloping transverse defining wall 2b. Furthermore, the base sheet of metal 2 is electrically insulated from the paper stack by means of thin insulating strips 16 (about 20 μ thick). On displacing a double sheet by means of the block 6 against the "ramp" 2b, the edges of the sheet jump over the unevennesses of the fabric surface of the strips 15. As a result, the double sheets are separated from one another especially in the particularly strongly adhering initial region. Air enters between sheets and the inadvertent simultaneous transporting of two or more sheets is reliably prevented.
The exposed electrically conducting edge 3A, past which the zinc oxide paper is pushed, prevents charge from flowing back from the immediately following corona discharge device via the transported sheet into the stack of paper.
In the embodiment shown, a stack of paper of size DIN A4 was transversely used. Four telescopic rod systems 7 were provided on the angled metal sheet 8. The extension length of the telescopic rod systems 7 depends on the number of sheets which are supposed to be in the stack. The process was successfully carried out with a stack of 250 sheets. It was found, surprisingly, that no traces of the sheet feed mechanism were to be found on the otherwise very sensitive zinc oxide paper. After having been used to transport several thousand sheets, no wear effect was as yet detectable on the Moltopren block 6.
As a result of the sloping arrangement of the transverse defining walls 2b and 2c, the stack of paper to be inserted in this lower section must be fanned. Hence air enters between the individual sheets. Furthermore, the adhesion of the cut edges, which results on cutting the sheets to size, is broken. In this way, pushing off the sheets one by one is facilitated.
Using the device described it was possible substantially to increase the output of an electrophotographic copying apparatus working with ZnO paper. The possibility is provided, for the first time, to work, in a cheap manual apparatus, not with pre-exposed papers but with papers which can be fed in from the dark. This substantially improves the copy quality and the working speed.
The feeding of individual sheets from a stack to a copying apparatus represents a problem which has hitherto not been satisfactorily solved in the art. Numerous attempts have been made in this field. There are feeding devices with circulating chains, devices with friction rollers and needle gripping devices. However, these devices are either extremely involved in construction and therefore unusable for simple apparatus, or do not operate with sufficient reliability. Feeding sheets from a stack proves particularly difficult where precoated sheets are concerned, especially electrophotographic recording material, for example zinc oxide paper.
There is therefore a need for a sheet feeding apparatus which is simple in construction and cheap to manufacture and may also be used with small manual copying apparatures. The apparatus should have a high degree of reliability that several sheets will not be fed simultaneously, and should at the same time be rapidly and reliably utilisable.
The present invention accordingly provides a device for feeding individual sheets of a stack to apparatus in which these sheets are to be processed further, especially an electrophotographic copying machine, which comprises a sheet transporting element having a plane underside of non-slippery material, preferably non-slippery foam material, which may be brought into contact with the uppermost sheet of the stack, said sheet transporting element being provided with means, preferably comprising at least one telescopic rod system for moving it backwards and forwards in the direction of the transportation of the sheets.
The means for moving the sheet transporting element preferably comprises at least one telescopic rod system running downwards at an angle and backwards through the sheet transporting element, relative to the sheet transporting direction.
The present invention also provides a process for supplying individual sheets from a stack to apparatus in which the sheets are to be further processed, especially an electrophotographic copying machine, using the device of the invention. On displacing the telescopic rod system in the sheet transporting direction, the telescopic rod system is self-locking to prevent telescoping, and hence the uppermost sheet is shifted relative to the stack, whilst during the return movement the telescopic rod system is slightly telescoped and, as a result of the inclined position, as in the case of a sloping plane, the non-slippery transporting element is lifted off the uppermost sheet of the stack of sheets and hence the paper is not buckled but remains lying flat. This device is of extremely simple construction and permits rapid and reliable feeding, especially of zinc oxide copying papers to an electrophotographic reproduction apparatus.
The angle between the telescopic rod system and the normal to the paper should preferably be in the range of from 5° to 20°; an angle of about 13° between the telescopic rod system and the normal to the paper (or of 77° between the telescopic rod system and the paper surface) has proved particularly satisfactory.
The transporting element can be arranged particularly simply to be displaceable in the device by providing, in the lid above the stack, a slit in which a slider is displaceably mounted, the end of the telescopic rod system being fixed thereto. The slope of the telescopic rod system is of decisive importance and is always kept constant whilst the complete stack is being fed, since the telescopic rod system is not arranged so that it can be tilted. As the stack becomes smaller, the transporting element nevertheless remains in engagement with the sheet of the copying stack which is uppermost at any time, since the telescopic rod system is automatically extended as the stack height decreases.
The device of the invention preferably comprises a box to hold the stack of sheets, wherein the front transverse wall, that is the wall transverse to the sheet transporting direction towards which the sheets are to be transported, slopes outwards from the bottom of the box. The front transverse wall thus acts as a ramp for the sheets to be transported. Preferably the rear transverse wall is also sloped and parallel to the front transverse wall. The two sloping transverse defining walls also always cause a little fanning of the papers on insertion into the sheet stacking device. This permits air to penetrate between the individual sheets and thereby enables them to be drawn off more readily.
Further reliability in ensuring that several sheets are not fed simultaneously is achieved if the front sloping transverse wall possesses at least one strip, having a rough surface, running in the sheet transporting direction. The front edge of the sheet flicks along this strip and a further sheet which may have been fed with it is retained by the roughness. Here, it is particularly advantageous if the rough strip on the front transverse defining wall is somewhat broader at the bottom than at the top, that is to say if it tapers conically. This permits very reliable feeding of single sheets particularly also for the bottom sheets of a stack of sheets. The strip having a rough surface can be formed particularly simply by a glued-on fabric strip of not excessively rough structure.
For electrophotographic apparatuses in which photo-conducting sheet material is to be fed to the apparatus it has proved particularly advantageous if the sheet stack is located in an insulated housing and the outlet edge of this housing, that is to say, for example, the upper edge of the front sloping transverse defining wall, is electrically conducting and exposed so that it comes into contact with the fed sheet and thus prevents the charge emanating from the corona from being conducted into the stack of sheets.
The process is further facilitated if a return spring is provided in the device, between the housing and the transporting element displaceable therein, this spring being tensioned when transporting the sheet and being capable of retracting the transporting element thereafter to its starting position. At the same time it is preferred to locate a micro-switch in the device in such a way that on displacing the transporting element from the starting position the switching of the micro-switch causes the various subsequent stations of an apparatus in which further processing of the sheets is to occur, for example an electrophotographic apparatus, to be switched on.
The transporting element may suitably comprise a foam block to the top of which is fixed a metal plate, the telescopic rod system being fixed at an angle on to this metal plate. This construction is particularly space-saving if the outer sheath of the telescopic rod system is located in an appropriately shaped sloping bore of the foam block, the metal plate is bored and is connected to the extending end of the sheath. The inner rod of the telescopic rod system can then be drawn out but the requisite height of the construction is kept low due to the fact that the length of the telescoped telescopic rod system and the thickness of the foam block are not additive.
The invention is described in further detail, by way of example only, with reference to the accompanying drawings, in which:
FIG. 1 represents an enlarged vertical section along the line I-- I of FIG. 2,
FIG. 2 represents a plan view of a device according to the invention, with the lid 12 omitted, and
FIG. 3 represents a detail of the device shown in FIG. 1, taken along the line III-- III of FIG. 1.
An angled metal sheet 2 is located in a housing 1. This sheet 2 has a bottom section 2a and two sloping sections 2b and 2c which are parallel to one another. The two sloping sections 2b and 2c of the sheet 2 represent the sloping transverse defining walls for a stack of sheets 17 consisting of sheets of zinc oxide paper. Furthermore, a removable cover plate 12 and a guide sheet 3 are provided. The guide sheet 3 causes the paper sheet which has been pushed forward to be moved in the direction of guiding elements which are not shown, for example transporting belts of an electrophotographic copying apparatus.
Laterally, the stack of sheets 17 is held by two guide sheets 4 and 5 which are internally lined with felt-like or velvet-like fabric 4B and 5B. At the same time, one guide sheet 5 is lightly pressed against the stack 17 by means of a spring 13 or a foam slab.
A foam block 6 of soft porous foam rests on the uppermost sheet of the stack of sheets 17. A block of "Moltopren" (Trade Mark, product of Beiersdorf A.G., Hamburg, Germany) or similar material has proved very successful. A metal plate 18 is fixed to this block. Furthermore, the block 6 possesses a sloping bore in which is located the outer sheath of a telescopic rod system 7. This sheath is soldered to the plate 18 in the desired sloping position, as is indicated schematically by the soldering point 19.
The extensible rod of the telescopic rod system 7 is connected at its end to an angled metal sheet 8, which in turn is connected to a handle 10. The handle 10 with the metal sheet 8 located below it and the telescopic rod system fixed thereto, as well as the Moltopren block 6, can be pushed to and fro in a slit in the lid 12. The paper transporting direction is here indicated by the arrow 20. On moving the unit 6, 7, 8, 10 in the direction of the arrow 20, a normal force N 1 is produced between the two components of the telescopic rod system 7, which acts at right angles to the direction in which the telescopic rod is guided. As can be seen from the left-hand triangle of forces shown in FIG. 1, this normal force N 1 is substantially directed towards the lower left-hand corner. It may be split into a downwardly directed vertical force V 1 corresponding to the weight of the foam block 6 and that of the plate 18, and a horizontal frictional force R 1 . The vertical component V 1 effects the necessary pressure of the foam block 6 and thus causes the uppermost sheet to be pushed forward. If the handle 10 and the unit 6, 7, 8 connected thereto are then moved to the right, a normal force N 2 is produced which is directed toward the right top corner, as shown in the right-hand triangle of forces. This normal force is composed of a frictional force R 2 and a vertical force V 2 . Due to this vertical component V 2 , the foam block has a tendency to climb along the telescopic rod 7, and the top sheet of the stack of sheets is thus relieved. This relief is only effective as long as there is at least a slight contact (friction) between the foam block 6 and the uppermost sheet of the stack. It is also possible, and comes within the scope of the present invention, for the foam block 6 to be in lateral contact with the felt-or velvet-covered guides 4B and 5B, in which case it could be completely lifted from the stack of sheets. The first-mentioned embodiment is preferred, however, since it is not necessarily desirable that the foam block 6 is completely lifted, because a residual friction, which may even cause a slight displacement of the following sheet, facilitates the separation of the next sheet from the stack.
A return spring 14 is mounted between the edge of the lid 12 and the angled metal sheet 8. When the handle 10 is moved in the direction of the arrow 20, this spring is tensioned and automatically pulls the foam block 6 back to its starting position when the top sheet has been pushed forward.
A micro switch 11 is located in the device in such a way that the movement of the handle 10 switches on, for example, the corona discharge device and the further transport devices of an electrophotographic apparatus.
Particularly good and reliable separation into individual sheets is achieved by the measure described below. Two narrow fabric strips 15 are glued onto the base 2a and the front sloping transverse defining wall 2b. These fabric strips, consisting of a fabric which is not excessively coarse (the self-adhesive "Leukoplast" tape manufactured for medical purposes by Messrs. Beiersdorf A.G., Hamburg, has proved successful) terminate just before the upper edge 3A of the sloping transverse defining wall 2b. Furthermore, the base sheet of metal 2 is electrically insulated from the paper stack by means of thin insulating strips 16 (about 20 μ thick). On displacing a double sheet by means of the block 6 against the "ramp" 2b, the edges of the sheet jump over the unevennesses of the fabric surface of the strips 15. As a result, the double sheets are separated from one another especially in the particularly strongly adhering initial region. Air enters between sheets and the inadvertent simultaneous transporting of two or more sheets is reliably prevented.
The exposed electrically conducting edge 3A, past which the zinc oxide paper is pushed, prevents charge from flowing back from the immediately following corona discharge device via the transported sheet into the stack of paper.
In the embodiment shown, a stack of paper of size DIN A4 was transversely used. Four telescopic rod systems 7 were provided on the angled metal sheet 8. The extension length of the telescopic rod systems 7 depends on the number of sheets which are supposed to be in the stack. The process was successfully carried out with a stack of 250 sheets. It was found, surprisingly, that no traces of the sheet feed mechanism were to be found on the otherwise very sensitive zinc oxide paper. After having been used to transport several thousand sheets, no wear effect was as yet detectable on the Moltopren block 6.
As a result of the sloping arrangement of the transverse defining walls 2b and 2c, the stack of paper to be inserted in this lower section must be fanned. Hence air enters between the individual sheets. Furthermore, the adhesion of the cut edges, which results on cutting the sheets to size, is broken. In this way, pushing off the sheets one by one is facilitated.
Using the device described it was possible substantially to increase the output of an electrophotographic copying apparatus working with ZnO paper. The possibility is provided, for the first time, to work, in a cheap manual apparatus, not with pre-exposed papers but with papers which can be fed in from the dark. This substantially improves the copy quality and the working speed.