Patent Grant
7370858
This application claims the priority of Korean Patent Application No. 2002-49210, filed on Aug. 20, 2002, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a printer, and more particularly, to an apparatus for and method of preventing paper double feeding in a paper feeding unit of a printer.
2. Description of the Related Art
In general, a printer or a copier includes a paper feeding unit which receives a plurality of sheets of paper and sequentially feeds the received sheets of paper.
Referring to
The apparatus for preventing the paper double feeding is provided in the paper feeding unit of the printer having the above structure. As shown in
Referring to
A paper feeding force Fp that acts on the first sheet of paper P1 due to the friction force between the pickup roller 30 and the first sheet of paper P1 may be obtained by Equation 1.
Fp=μroll×N (1)
Here, μroll represents a friction coefficient between the pickup roller 30 and the first sheet of paper P1, and N represents a vertical force that acts on the first paper P1 from the pickup roller 30.
Also, a second paper feeding force FD that acts on the second sheet of paper P2 due to another friction force between the first sheet of paper P1 and the second sheet of paper P2 may be obtained by Equation 2.
FD=μpaper×N (2)
Here, μpaper represents another friction coefficient between the sheets of paper P. Meanwhile, a paper feeding resistance force FN that disturbs feeding of the paper P is generated by the friction force between the paper P and a resistance generated by the stripper 52, and the paper feeding resistance force FN may be obtained by Equation 3.
FN=μpaper×N+Fstripper (3)
Here, Fstripper represents the resistance that acts on the paper P due to the stripper 52. The resistance Fstripper generated by the stripper 52 is proportional to the tilt angle θ of the stripper 52.
Likewise, the above-mentioned three forces are generated when the paper P is picked-up by the pickup roller 30 and is transferred into the printer. In order to prevent double feeding and non-picking up of the paper P, the three forces should satisfy the following conditions of Equation 4.
Fp>FN>FD (4)
More specifically, the paper feeding force Fp that acts on the first sheet of paper P1 should be larger than the paper feeding resistance FN, so that the first sheet of paper P1 is picked-up and is transferred into the printer. Accordingly, in order to satisfy the above conditions, the tilt angle θ of the stripper 52 should be properly set. If the tilt angle θ of the stripper 52 is too large, the paper feeding resistance force FN becomes larger than the paper feeding force Fp such that the first sheet of paper P1 is not picked-up.
Also, in order to prevent double feeding of the second sheet of paper P2 together with the first sheet of paper P1, the paper feeding resistance force FN should be larger than the paper feeding force FD that acts on the second sheet of paper P2. Thus, in order to satisfy the above conditions, the tilt angle θ of the stripper 52 is appropriately set.
That is, the stripper 52 as the conventional apparatus for preventing the paper double feeding has the tilt angle θ of about 70 degrees, large enough to satisfy the above-mentioned two conditions.
However, when an adhesive force is generated between the first sheet of paper P1 and the second sheet of paper P2 due to static electricity generated therebetween or an alien substance interposed therebetween, the paper feeding force FD that acts on the second sheet of paper P2 may be larger than the paper feeding resistance force FN. This is because since the paper feeding resistance force FN that acts on the second sheet of paper P2 is defined by the friction force between the second sheet of paper P2 and a third sheet of paper P3 and by the resistance Fstripper generated by the stripper 52, the paper feeding resistance force FN remains constant, whereas the adhesive force between the first sheet of paper P1 and the second sheet of paper P2 is added to the paper feeding force FD that acts on the second sheet of paper P2. In this case, a double feeding phenomenon occurs when the second sheet of paper P2 is transferred into the printer together with the first sheet of paper P1. The double feeding phenomenon may occur in a case of the third paper P3 or another paper thereunder. In this case, three or more sheets of paper are transferred into the printing unit of the printer.
As described above, the friction force or the adhesive force between the sheets of paper P is not always uniform. Thus, in order to prevent the paper double feeding, the tilt angle θ of the stripper 52 should be large. In this case, the paper feeding resistance force FN may be larger than the paper feeding force FP, so that the first sheet of paper P1 is not picked-up. Thus, the pickup roller 30 is rotated with a larger torque by using the driving motor 42 having a large capacity or controlling a deceleration ratio, so that the paper feeding force FP increases. In this case, a load on other elements of the paper feeding unit, such as the gear group 46, increases. Thus, these elements wear or break rapidly, and a life span of the elements is reduced.
The present invention provides an apparatus for and method of preventing paper double feeding in a printer, which can prevent sheets of paper from not being picked-up and double feeding of the sheets of the paper by intermittently applying a friction force to a rear side of paper, which is picked-up by a pickup roller and transferred into the printer.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
According to one aspect of the present invention, an apparatus for preventing paper double feeding in a paper feeding unit of a printer includes a pickup roller which picks up a sheet of paper stacked on a paper cassette and transfers the paper into the printer, and a plurality of paper guides which are installed on a front portion of the paper cassette and guide the paper transferred by the pickup roller. The apparatus includes a stripper which is installed to be inclined at a predetermined angle with respect to the paper and attached to at least one front side of the paper guides, a lever which is installed at a rear side of the stripper and has a contact surface contacting the paper transferred by the pickup roller, and a lever shaking unit which shakes the lever to intermittently contact a rear (lower) side of the paper transferred by the pickup roller. A friction force is intermittently applied to the rear side of the paper such that double feeding of the paper is prevented.
It is possible that the apparatus further includes a lever shaft which is placed at the rear side of the stripper and rotatably installed in a frame of the printer, and the lever is fixed on the lever shaft, and the lever shaking unit shakes the lever shaft so that the lever is shaken.
It is also possible that an opening groove is formed in an upper portion of the stripper such that the contact surface of the lever contacts the rear side of the paper through the opening groove.
It is also possible that a friction pad is attached to the contact surface of the lever, and the friction pad is formed of rubber.
It is also possible that the lever shaking unit includes a shaking plate fixed on the lever shaft, a cam gear which contacts one side of the shaking plate, rotates, and periodically shakes the shaking plate so that the lever coupled with the lever shaft is shaken, a spring which is installed between the other side of the shaking plate and the frame and applies an elastic force to the shaking plate so that the shaking plate is closely attached to the cam gear, and a driving motor which rotates and drives the cam gear.
It is also possible that at least one cam protrusion is formed on a cam surface to contact the shaking plate. It is possible that three cam protrusions are formed at the same intervals along a circumference of the cam surface to contact the shaking plate.
According to another aspect to the present invention, the lever shaking unit includes a shaking plate fixed on the lever shaft, and a solenoid which is coupled with the shaking plate and periodically shakes the shaking plate so that the lever coupled with the lever shaft is shaken.
According to another aspect of the present invention, a method of preventing paper double feeding is employed in a paper feeding unit of a printer when sheets of paper stacked on a paper cassette are picked-up and are transferred into the printer one by one. The method includes applying a first paper feeding resistance force to the sheet(s) of paper which is picked-up by a pickup roller and transferred into the printer, and intermittently applying a second paper feeding resistance force to a rear side of the sheet(s) of paper. Here, it is possible that the first paper feeding resistance force includes a resistance force generated by a stripper which is installed to be inclined at a predetermined angle on a paper path, wherein the resistance force is smaller than a first paper feeding force applied to a first sheet of paper by the pickup roller, and is larger than a second paper feeding force applied to a second sheet of paper due to a friction force between the sheets of paper.
It is also possible that the second paper feeding resistance force includes a second friction force intermittently applied to the rear side of the sheet(s) of paper by a lever which is installed to be shaken on the paper path, wherein the second friction force and is larger than the first paper feeding resistance.
According to the present invention, the second friction force is intermittently applied to the rear side of paper by the lever such that double feeding and non-picking-up of the paper are prevented.
According to another aspect of the present invention, an apparatus for preventing paper double feeding in a paper feeding unit of a printer includes a frame, a pickup roller which picks up paper stacked on a paper cassette and transfers the paper into the printer, and a plurality of paper guides which are installed at a portion of the paper cassette and guide the paper transferred by the pickup roller in a paper feeding path. The apparatus further includes a stripper disposed on the paper feeding path, fixedly installed on the frame to be inclined at a predetermined angle with respect to the paper stacked on the paper cassette, and contacting the paper transferred by the pickup roller to apply a first paper feeding resistance force to the paper, and a lever disposed on the paper feeding path, movably installed on the frame, and having a contact surface contacting the paper transferred by the pickup roller to apply a second paper feeding resistance force to the paper.
These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the preferred embodiments, taken in conjunction with the accompanying drawing; of which:
Reference will now be made in detail to the present preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present invention by referring to the figures.
Hereinafter, the present invention will be described in detail by describing preferred embodiments of the invention with reference to the accompanying drawings.
Referring to
The apparatus 160 for preventing paper double feeding is employed in the paper feeding unit of the printer and prevents two or more sheets of the paper P from being picked up to overlap on the paper feeding unit and being simultaneously transferred into the printer. The apparatus 160 for preventing paper double feeding includes a stripper 152 attached to at least one front side of the paper guides 150, one or more levers 162 installed to be shaken on a rear side of the stripper 152, and a lever shaking unit 161 which shakes the levers 162 to intermittently contact a rear (lower) side of the paper P transferred by the pickup roller 130.
The stripper 152 is attached to the at least one front side of the paper guides 150, that is, to a surface of the paper guide 150 facing the paper P. It is possible that the stripper 152 may be attached to each of the paper guides 150. The stripper 152 is formed of stainless plates or a synthetic material such as TEFLON, and is installed on the surface of the paper guide 150 at a predetermined angle θ from a horizontal plane, to prevent double feeding of the paper P. As described above, the stripper 152 generates a resistance force Fstripper that disturbs a transfer of the paper P. The resistance force Fstripper and a friction force between the sheets of paper P form a paper feeding resistance force FN that disturbs paper feeding as shown by Equation 3. In the present invention, the tilt angle θ of the stripper 152 is less than about 70 degrees to prevent the paper P from not being picked-up by the excessive resistance force Fstripper generated from the stripper 152. The tile angle θ of the stripper 152 may be smaller than 70 degrees.
The levers 162 are installed at the rear side of the stripper 152 and are periodically shaken by the lever shaking unit 161. The levers 162 having the same number as the number of the strippers 152 may be installed. However, as shown in
As described above, the levers 162 are periodically shaken by the lever shaking unit 161 such that the friction pad 163 intermittently contacts the rear side of the paper P transferred into the printer by the pickup roller 130 through the opening groove 154. Thus, another friction force is intermittently applied to the paper P by the friction pad 163 of the levers 162 such that the paper feeding resistance force FN that acts on the paper P periodically increases. That is, when the levers 162 are shaken with respect to the paper P, and the friction pad 163 contacts the paper P, the paper feeding resistance force FN that acts on the paper P may be expressed by Equation 5.
FN=μpaper×N+Fstripper+FL (5)
Here, FL represents another friction force that acts on the paper P due to the levers 162. In comparison with the paper feeding resistance force given in Equation 3 for a conventional apparatus for preventing paper double feeding, the paper feeding resistance force FN according to an embodiment of the present invention periodically increases by as much as another friction force FL that acts on the paper P due to the levers 162. Effects thereof will be described in detail later.
Meanwhile, the apparatus 160 for preventing paper double feeding further includes a lever shaft 164, which is arranged on the rear side of the stripper 152 and is rotatably installed on the frame 110 of the printer. In this case, the levers 162 are fixed on the lever shaft 164, and the lever shaking unit 161 shakes the lever shaft 164 so that the levers 162 are shaken. The lever shaking unit 161 may directly shake the lever 162. However, when two or more levers 162 are installed, two or more lever shaking units should be installed. When the lever shaft 164 is provided as described above, only one lever shaking unit can simultaneously shake the levers 162.
The lever shaking unit 161 serves to shake the lever 162 so that the friction pad 163 intermittently contacts the rear side of the paper P transferred by the pickup roller 130. For this purpose, the lever shaking unit 161 includes a shaking plate 166, and a shaker. In this embodiment, the shaker includes a cam gear 170, a compression coil spring 168, and a lever driving motor 172.
The shaking plate 166 is fixed at one side of the lever shaft 164 and extends in a direction perpendicular to a longitudinal direction of the lever shaft 164.
The cam gear 170 is installed to contact a first side of the shaking plate 166, i.e., a bottom surface of the shaking plate 166. A cam surface 170a that contacts the shaking plate 166, and a gear portion 170b engaged with a driving gear 174 of the lever driving motor 172 are formed on an outer surface of the cam gear 170. The cam gear 170 is rotated by the lever driving motor 172, interferes the shaking plate 166 and periodically shakes the shaking plate 166. As such, the levers 162 fixed on the lever shaft 164 is also shaken. For this purpose, at least one cam protrusion 170c is formed on the cam surface 170a. The number of the cam protrusions 170c may be properly set by considering a shaking period of the levers 162 and a deceleration ratio of the lever driving motor 172. That is, when the deceleration ratio of the lever driving motor 172 is reduced by increasing a diameter of the driving gear 174 of the lever driving motor 172, a rotation speed of the cam gear 170 becomes larger, and thus the levers 162 can be shaken at a first period even though only one cam protrusion 170c is formed on the cam surface 170a. Meanwhile, when the deceleration ratio of the lever driving motor 172 is increased by reducing the diameter of the driving gear 174, the rotation speed of the cam gear 170 becomes smaller, but a plurality of the cam protrusions 170c are formed such that the levers 162 are shaken at a second period. In the latter case, the cam gear 170 generates a sufficient torque even though the lever driving motor 172 having a smaller capacity is used. Thus, three cam protrusions 170c are formed at the same intervals along an circumference of the cam surface 170a as shown in
The compression coil spring 168 is installed at a second side of the shaking plate 166, i.e., on an upper portion of the shaking plate 166, thereby applying an elastic force to the shaking plate 166 so that the shaking plate 166 is closely attached to the cam surface 170a of the cam gear 170. The shaking plate 166 is always closely attached to the cam surface 170a of the cam gear 170 by the compression coil spring 168 and thus shakes by the rotation of the cam gear 170. Meanwhile, the compression coil spring 168 may be replaced with a leaf spring which can perform the same function as the compression coil spring 168. The lever driving motor 172 serves to rotate and drive the cam gear 170 as described above.
Meanwhile, the lever shaking unit 161 may include a solenoid (not shown) instead of the compression coil spring 168, the cam gear 170, and the lever driving motor 172. Thus, in this embodiment, the shaker includes the solenoid. The solenoid is coupled with the shaking plate 166 and periodically and directly shakes the shaking plate 166 so that the levers 162 coupled with the lever shaft 164 are shaken.
The apparatus 260 for preventing paper double feeding shown in
Meanwhile, reference numerals 143 and 276 denote a driving gear and an intermediate gear which connects the driving gear 143 to the cam gear 270, respectively.
Hereinafter, an operation of the apparatus 161, 260 for preventing paper double feeding having the above structure will be described.
Referring to
Thus, the paper feeding resistance force FN that acts on the first paper P1 is smaller than the paper feeding force FP that acts on the first paper P1 until the front end of the first sheet of paper P1 contacts the friction pad 163 of the levers 162 such that the first paper P1 is prevented from not being picked up.
Meanwhile, as shown in Equations 2 and 3, the paper feeding force FP that acts on a second sheet of paper P2 is generally smaller than the paper feeding resistance force FN such that traveling of the second sheet of paper P2 is disturbed by the levers 162.
However, when an adhesive force occurs between the first sheet of paper P1 and the second paper P2 by static electricity generated between the first sheet of paper P1 and the second sheet of paper P2 or an a foreign substance interposed there between, a second paper feeding force FD that acts on the second sheet of paper P2 may be larger than the paper feeding resistance force FN. In this case, the second sheet of paper P2 is simultaneously transferred with the first sheet of paper P1.
Referring to
Meanwhile, a second friction force or the adhesive force between the plurality of sheets of paper P is not uniform, and the second paper feeding force FD that acts on the second sheet of paper P2 may be almost the same as the first paper feeding force FP that acts on the first sheet of paper P1. Accordingly, in order to prevent paper double feeding, as shown in
However, the another friction force FL generated by the levers 162 also acts on the first sheet of paper P1 when the first sheet of paper P1 is picked-up and transferred. However, the another friction force FL intermittently acts on the first sheet of paper P1 for a short time, whereas the paper feeding force FP generated by the pickup roller 130 continuously acts on the first sheet of paper P1 such that the traveling of the first sheet of paper P1 is not disturbed by the levers 162.
Thus, according to the present invention, when the sheets of paper P are simultaneously fed, the traveling of the second sheet of paper P2 can be effectively disturbed by the lever, and when only one sheet of the paper P is fed, the traveling of the first sheet of paper P1 is not disturbed by the lever.
As described above, in the apparatus for and method of preventing paper double feeding in the printer according to the present invention, the another friction force is intermittently applied to the rear side of the paper double fed (simultaneously fed) by shaking the levers such that the paper double feeding is prevented. In addition, the another friction force generated by the levers is not applied to the picked-up paper when the paper is initially picked-up such that a problem that the paper is not picked-up is prevented. In addition, the another friction force generated by the lever is intermittently applied to the rear side of the paper such that the paper is picked-up by the pickup roller and traveling of the paper transferred into the printer is not disturbed by the levers.
While this invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2002-0049210 | Aug 2002 | KR | national |
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| Number | Date | Country | |
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| 20040065992 A1 | Apr 2004 | US |
