Patent Grant
7347419
The present invention relates to a sheet supplying device for sequentially separating sheets on a stacker and feeding a sheet to a processing platen for reading or printing an image, and a method of detecting overlapping of a plurality of sheets while the sheets are being fed.
A sheet supplying device sequentially supplies sheets stacked on a stacker to a processing platen of a device such as a printer, a copier, or a scanner. An image reading apparatus such as a scanner feeds documents on a stacker to a platen one by one, so that a photoelectric converting device reads an image on the document.
When such a device separates sheets on a stacker one by one and supplies the sheet to the processing platen, if a plurality of sheets (documents) is overlapped and fed (double feed), an erroneous processing may be executed at the processing platen. Accordingly, it is necessary to accurately separate the sheets into a single sheet and detect the double feed of the sheets before the sheet reaches the processing platen, so that the processing is stopped or processing data such as reading information is discarded not to be sent to a processing device such as a printer.
A conventional method of detecting the double feed of the sheets includes an ultrasonic sensor or a photo-sensor for detecting attenuation in an ultrasonic wave or an intensity of light passing through the sheet, thereby determining whether there is a single sheet.
Japanese Patent Publication (Kokai) No. 10-257595 discloses an ultrasonic sensor for detecting a sheet. The ultrasonic sensor includes a piezoelectric oscillation plate such as piezoelectric ceramic at a wave transmission side. A pulse voltage with a predetermined frequency is applied to the piezoelectric oscillation plate to generate oscillation, thereby transmitting ultrasonic waves. A similar oscillation plate is provided at a wave reception side for receiving the ultrasonic waves and converting to an electrical signal. Electric energy is compared with a reference value, thereby determining a single sheet or several sheets.
Japanese Utility Model Publication (Kokai) No. 06-49567 proposes a structure in which a wave transmission element and a wave reception element are arranged opposite to each other between a downstream roller and an upstream roller arranged with a predetermined distance in between, thereby making it possible to detect the double feed while the sheet is in a stable condition. More specifically, with such a structure, the double feed is detected while the downstream and upstream rollers nip the sheet in a straight position during transportation. Accordingly, it is possible to accurately detect the double feed since a leading edge or a trailing edge of the sheet is not curved or does not flip vertically.
When the ultrasonic sensor or optical sensor is used to detect the overlapping of the sheets, if the sheets have different quality, a thickness, or a size, it is difficult to accurately determine whether one or more sheets are being fed at a time. That is, when several sheets contact tightly with one another due to humidity or other environmental factors, it is difficult to determine between a single sheet having a large thickness and overlapped several sheets. When sheets with various sizes are overlapped and shifted in a longitudinal direction, it is difficult to determine between a single sheet having a large size and several sheets overlapped in the longitudinal direction. Moreover, when the sheets are flapped in a vertical direction at a position of the sensor, a transmitted quantity of sound wave or light varies, thereby making it difficult to accurately determine the double feed.
Japanese Utility Model Publication (Kokai) No. 6-49567 has proposed that the overlapping of the sheets is detected while the pair of the rollers supports the sheets. However, it is still difficult to detect the double feed when the sheets tightly contact with one another. Further, when the double feed is detected over a predetermined length to determine that the sheets are shifted in the longitudinal direction, the trailing edge of the sheets flaps upon leaving from the roller, thereby causing a misdetection.
In view of the problems described above, an object of the present invention is to provide a sheet supplying device that can accurately detect the overlapping of sheets even when the sheets tightly contact with one another or are shifted in the longitudinal direction thereof.
Another object of the present invention is to provide an image reading apparatus and a method of accurately detecting the overlapping of original documents while the sheets are fed from a stacker to a reading platen.
Further objects and advantages of the invention will be apparent from the following description of the invention.
To accomplish the objects described above, according to the present invention, a sheet supplying device comprises a stacker for placing documents (sheets) toward a processing position such as an image reading platen, and a sheet conveying guide for guiding the sheet from the stacker to the processing position. The stacker is provided with a delivery device for separating the sheet from others and feeding the sheet. The delivery device is formed of, for example, a sheet feeding roller contacting the uppermost sheet on the stacker to convey the sheet toward the processing position, and a friction pad contacting the roller with pressure. A register device such as a pair of pressure contact rollers is placed in the sheet conveying guide for temporarily holding the sheets fed by the delivery device. A sheet sensor is disposed at an upstream side of the register device for detecting the sheets. An overlap sensor is disposed at a downstream side of the register device for detecting overlapping of the sheets. The delivery device and the register device are controlled so that the delivery device feeds the sheet to the register roller and forms a loop at a leading edge of the sheet. A control circuit, for example, a CPU and a driver circuit, controls a driving device such as a motor connected to the delivery device and the register device in accordance with a signal from the sheet sensor for detecting the leading edge of the sheet, so that the delivery device feeds the sheet by a controlled amount.
An overlap determining device determines the overlapping of the sheets on the basis of a detection signal from the overlap sensor and a detection signal from the sheet sensor. When the CPU or the like receives an overlap signal and the sheet sensor detects the sheets, the overlap determining device determines that the overlap signal is valid. When the CPU or the like receives an overlap signal, and within a predetermined period of time after the sheet sensor detects the trailing edge of the sheet, the overlap determining device determines that the overlap signal is valid. A clocking device such as a timer sets a period of time from the sensor to immediately before the trailing edge of the sheet passes (leaves) the register device as the predetermined time.
The overlap sensor detects the sheets that are bent and loosened by the register device. When the overlapping sheets are bent, the sheets are released from a tight contact state, so that the overlapping is surely detected from an air layer between the sheets. The overlap determining device determines that the overlap signal from the sheet sensor is valid when the register device nips the trailing edge of the sheet. Accordingly, the overlap determining device does not determine the overlapping from the detection signal while the trailing edge of the sheet leaves the register device and is flapping.
According to the present invention, the conveyance control device may be provided with a first clocking device for forming the loop (hereinafter referred to as a register loop) in the sheet after the sheet sensor detects the leading edge of the sheet, and a second clocking device to be activated when the register device starts feeding the sheet to a platen. The second clocking device sets a time equal to or longer than that of the first clocking device. The overlap determining device is configured to determine the overlapping of the sheets on the basis of an output signal from the overlap sensor after the time set for the second clocking device. Accordingly, the register loop is removed, thereby making it possible to accurately determine the overlapping while the documents extend along a conveying path.
According to the present invention, the sheet conveying guide may include a bent guide member. The overlap sensor is disposed in a bent area of the guide member, so that the overlapping sheets are detected after being bent and loosened, thereby improving detection accuracy.
According to the present invention, a method of detecting overlapping sheets (documents) comprises a sheet delivering step of separating each sheet from others on a stacker and delivering the sheet; a loop forming step of abutting the document against a conveying roller to bend the document in a loop form; a document feeding step of extending the document bent by the conveying roller and feeding the extended document to the platen; a conveyance status detecting step of detecting the document on an upstream side of the conveying roller and detecting the overlapping on a downstream side of the conveying roller during the document feeding step; and an overlap determining step of determining the overlapping on the basis of an output signal indicating the overlapping and an output signal indicating the document obtained in the conveyance status detecting step.
In the present invention, the register device bends the sheets delivered from the stacker in a loop form, and the downstream overlap sensor detects the overlapping of the sheets, thereby accurately detecting the overlapping. In particular, when an ultrasonic wave sensor is used as an overlap sensor, tightly contacting sheets are bent so as to form air layers between the sheets. Accordingly, it is possible to easily determine whether a thick sheet or several overlapping sheets. Further, the sheet sensor disposed between the stacker and the register device detects the leading edge of the sheet to regulate the loop of the sheet. The sheet sensor also detects the trailing edge of the sheet to determine whether an output signal from the overlap sensor indicates that the register device is holding the sheet or that the sheet leaves the register device and is flapping, thereby making it possible to accurately detect the overlapping.
Accordingly, it is possible to accurately determine the overlapping of the sheets regardless of whether the sheets tightly contacts with each other or are overlapped and shifted in the longitudinal direction. In particular, for an image reading apparatus, it is possible to handle various types of sheets having different quality, thickness, size, or the like.
a) to 5(e) are views showing a process of delivering a sheet in the sheet supplying device shown in
a) to 6(e) are charts showing waveforms of the ultrasonic sensor shown in
a) and 9(b) are views showing driving mechanisms of the image forming apparatus shown in
a) to 11(e) are views showing an operation of supplying a sheet in the image forming apparatus shown in
Hereunder, embodiments of the present invention will be described with reference to the accompanying drawings.
As shown in
A sheet sensor 7 is provided between the separating device 4 and the register device 5. The sheet sensor 7 has a light emitting element 7a and a light receiving element 7b formed of light emitting diodes or the like and arranged opposite each other with the sheet in between. The sensor 7 is not limited to a photo sensor, and may be formed of a combination of a micro switch and a lever contacting the sheet. An overlap sensor 6 (described later) is placed at a downstream side of the register device 5.
The separating device 4 and the register device 5 are connected to a driving device M and rotate in a sheet conveying direction. The driving device M is a stepping motor that can rotate forward and backward. The driving device M is connected to a motor driving circuit 16. The driving device M is supplied with power from a power source 18 via a pulse generator 17. A one-directional transmission clutch such as a one-way clutch is provided for transmitting an opposite rotating force to the separating device 4 and the register device 5. When the separating device 4 rotates to deliver the sheet from the stacker 1, the leading edge of the sheet abuts against the register device 5, so that the sheet is bent in a loop form. When the register device 5 is actuated to feed the sheet to the platen 2, the separating device 4 is stopped not to deliver a subsequent sheet.
An image reading mechanism is placed in the platen at a position where the sheet is to be processed. The image reading mechanism is formed of a light source 27 for irradiating the sheet on the platen 2; a lens for focusing light reflected from the light source 27; and a photoelectric converting device 38 such as a CCD (Charge Coupled Device) for electrically converting light from the lens 29. Reference numeral 28 in the figure denotes a polarizing mirror. The sheet conveying guide 3 is formed of guide members 3a and 3b arranged with a small space in between as a path for passing the sheets. The sheet conveying guide 3 forms a generally U-shaped conveying path 20 connected to the platen 2.
A pressing member 19 formed of an elastic film is provided on one of the guide members 3a at a downstream side immediately after the ultrasonic sensor 6 for deflecting the sheet toward the other of the guide members 3b. Accordingly, the sheet is pressed against the guide member 3b and stabilized, thereby preventing vertical flapping of the sheet and a misdetection. A feeding roller 24, an unloading roller 25, and a sheet discharging roller 26 are arranged on the conveying path 20. The feeding roller 24 is placed at an upstream side of the platen 2 and formed of a pair of rollers for supplying the sheet to the platen. Each of the unloading roller 25 and the sheet discharging roller 26 is formed of a roller pair for conveying the sheet from the platen to the sheet discharging tray 15.
The overlap sensor will be described with reference to
When high-frequency power is supplied through the lead 13 in the wave transmitting element 6a, the piezoelectric vibrator 11 and the housing case 10 contacting the piezoelectric vibrator 11 vibrate at a predetermined frequency. An ultrasonic wave is emitted from the wave transmitting surface 10a. In the wave receiving element 6b, a wave receiving surface 10b and the piezoelectric vibrator 11 integrated with the wave receiving surface 10b are resonated with the ultrasonic wave. Accordingly, electricity is generated in the piezoelectric vibrator 11 and output to an external apparatus via the lead 13.
The ultrasonic sensor 6 described above is placed on the conveying path 20. The ultrasonic sensor 6 is connected to an oscillation circuit and an oscillation receiving circuit 23 as shown in
When power is supplied to the high-frequency oscillation circuit 22a, the ultrasonic wave of a particular frequency is excited in the piezoelectric vibrator 11 of the wave transmitting element 6a. The vibrator 11 emits the ultrasonic wave with a high frequency and specific amplitude (output level LV1) as shown in
The amplification circuit 23a and the smoothing circuit 23b process electric energy output with waveforms shown in
d) shows the level LV2 obtained when one sheet is conveyed. A part A indicates that the leading edge of the sheet from the register rollers 5a and 5b reaches the sensor 6 and a detected value is disturbed. This is because the sheet is bent in a loop form when delivered by the register roller 5, and the leading edge of the sheet flaps. A part B indicates that the sheet is nipped by the register roller 5 so as to extend along the sheet conveying guide 3 and a detected value is stable. A part C indicates that the trailing edge of the sheet leaves the register rollers 5a and 5b (passed through the rollers) and a detected value is disturbed.
When a reference value is set at a level LVO shown by a hidden line, in the case of one sheet shown in
When the reference value is determined, first, conditions such as a thickness, quality of the sheets, and a sheet conveying speed are determined according to an environment in which the device is used. Then, under these conditions, boundary values of the output levels of the wave receiving sensor in the cases of one sheet and two sheets are experimentally determined to be set as the reference value.
As described above, the reference values are determined in the cases of one sheet and two sheets. A plurality of reference values may be set for cases of one sheet, two sheets, and more sheets. Accordingly, when the output signals are compared with the reference values, it is possible to detect the number of the overlapping sheets. The high-frequency oscillation circuit 22a instantaneously applies a high-frequency voltage to the wave transmitting element 6a to generate a burst wave, or consecutively applies a high-frequency voltage to the wave transmitting element 6a to generate a standing wave. In this case, the output signal from the wave receiving element 6b may become unstable (vary depending on environmental conditions) due to the overlapping of the sheets. Accordingly, it is preferable that the burst wave is detected consecutively and repeatedly a number of times.
The wave transmitting element 6a and the wave receiving element 6b are arranged as described below.
(1) The wave transmitting element 6a and the wave receiving element 6b are arranged opposite each other so as to incline at a predetermined angle relative to a sheet traveling along the conveying guide 3. As shown in
(2) In the direction of gravity, the wave transmitting element is placed below the conveying guide 3, and the wave receiving element is placed above the conveying guide 3. As previously described, the intensity (LV1) of vibration on the wave transmitting surface of the wave transmitting element 6a is greater that that of the wave receiving element 6b. Further, to determine a difference in the level of resonance (intensity of vibration) on the wave receiving surface between the case of one sheet and the case of two sheets, it is necessary to reduce an external effect on the wave receiving surface. The wave transmitting element 6a is disposed at a lower position and the wave receiving element 6b is disposed at an upper position in the direction of gravity, so that an adverse effect of paper dusts falling from the sheet conveying guide on the detection accuracy is reduced.
(3) The wave transmitting surface 10a of the wave transmitting element 6a located at a lower position is inclined at a predetermined angle (β) relative to the horizontal direction. The angle β is selected such that dusts fall from the surface naturally or in corporation with the ultrasonic vibration. In the figure, the angle β is set at 30 degrees, and is preferably closer to 90 degrees.
a) to 5(e) are views showing a process of delivering the sheet in the sheet supplying device shown in
The sheet feeding stacker 1 is provided with an empty sensor 21 that detects the sheets placed on the stacker. When the device is powered on, a control CPU 31 uses the empty sensor 21 to detect the sheets are on the stacker 1. The driving motor M rotates in a forward direction (
Upon detecting the leading edge of the sheet in the state shown in
When a main body processing apparatus such as an image reading apparatus sends a sheet feed instruction signal S04, the driving motor M is driven backward to rotate the register roller 5a to feed the sheet to the platen 2. At the same time, in response to the sheet feed instruction signal S04, the control circuit 31b activates a timer T2 that is the second clocking device and turns on the oscillation circuit 22 of the ultrasonic sensor 6 (
The clocking device (T2) is formed of a delay circuit for counting, for example, a reference clock of the control CPU 31. The control circuit 31b receives a signal indicating that the empty sheet sensor 21 detects the sheets, and supplies power to the oscillation circuit. The wave transmitting element 6a of the ultrasonic sensor 6 generates the ultrasonic wave with a predetermined frequency. The wave receiving element 6b receives the ultrasonic wave passing through the sheet. The wave receiving element 6b then provides an output corresponding to a condition of the sheet. The comparison circuit 13c then compares the reference value with the output processed at the amplification circuit 13a and the smoothing circuit 23b. A result of the comparison is stored in a buffer memory 31c and transferred to a determining circuit 31a.
The reverse rotation of the driving motor rotates the register roller 5a clockwise to feed the sheet to the processing platen 2. At this time, the separating roller 4a remains stopped. The loop in the leading edge of the sheet is removed, and the sheet is supported by the separating roller 4a and the register roller 5a. The timer T2 provides an overlap detection start signal (S05). Each of the timers T1 and T2 is formed of a delay circuit that uses a counter to count the reference clock in the control circuit 31.
In the overlap detection carried out by the determining circuit of the control CPU, an output signal from the wave receiving element 6b is divided into pieces corresponding to a predetermined time, for example, 1 millisecond. The divided signal is then compared with the reference value, and the buffer memory 23 sends a result of the comparison to the determining circuit (see
When the output level of the comparison data from the comparison circuit 23c is smaller than that of the reference value, that is, when the output level of the wave receiving element 6b is smaller than that of the reference value, the determining circuit 31a of the control CPU determines the overlapping in accordance with the following step (1) as ST6 shown in
(1) When the comparison data indicates the overlapping, the determining circuit 31a determines the comparison data to be valid and executes overlap processing when a status signal from the sheet sensor 7 indicates presence of the sheets (
(2) When the comparison data indicates that the overlapping does not occur, the determining circuit 31a executes the sheet processing or continues the sheet processing being executed when the status signal from the sheet sensor 7 indicates absence of the sheets. In the case of the presence of the sheets, while the sheet processing is executed or the sheet processing is continued, the determining circuit 31a loads the next comparison data to monitor the data overlapping (
The status signal from the sheet sensor 7 may determine the presence of the sheets based on whether a predetermined time elapses since the trailing edge of the sheet passes the sensor 7. In other words, the timer may be started in response to a change in the status signal from the sensor 7 from the presence to the absence of the sheets. Then, whether the process is to shift to step ST06 or ST08 may be determined on the basis of whether an expected time elapses for the trailing edge of the sheet to pass through (leave) the register rollers 5a and 5b. The comparison data indicating the overlapping is determined to be valid depending on whether the register roller nips and supports the trailing edge of the sheets, thereby determining whether to shift to the overlap processing or sheet processing.
A method of detecting the overlapping will be explained according to an embodiment of the present invention.
[Sheet Delivering Step]
A step of separating the sheet from others on the stacker and delivering the sheet includes placing a series of sheets on the sheet feeding tray, separating each sheet from the others, and delivering the sheet. In the above device, the conveyance control circuit 31b uses the separating roller 4a and the friction pad 4b to separate each sheet from the others on the sheet feeding tray and feed it, and is formed of a program of the control CPU.
[Loop Forming Step]
The register device constitutes a loop forming step of abutting the document delivered in the above step against the conveying roller to bend the document in a loop form. The above device controls the separating roller 4a and the register rollers 5a and 5b, so that the separating roller 4a delivers the sheet to the register rollers 5a and 5b to bend the leading edge of the sheet.
[Document Feeding Step]
In a document feeding step of using the conveying roller formed of the register roller to extend the bent document sheet and then feed it to the platen, the driving motor rotates the register rollers 5a and 5b.
[Conveyance Status Detecting Step]
In a conveyance status detecting step, the sheets are detected on an upstream side of the conveying roller means, and the overlapping status is detected on a downstream side of the conveying roller during the document feeding step of feeding the sheet to the platen. In the above device, the photo sensor is provided at an upstream side of the register roller 5a to detect the sheets. The ultrasonic sensor is placed at a downstream side of the register roller to detect the overlapping status.
[Overlap Determining Step]
In an overlap determining step, the overlapping is determined on the basis of the results of detection of the document overlapping status and the sheets carried out in the conveyance status detecting step. The above device determines the overlapping on the basis of the overlap sensing signal from the ultrasonic sensor and the sheet presence signal from the sheet sensor.
An image reading apparatus according to an embodiment of the present invention will be explained next.
The image forming apparatus B is widely known as a printer and formed of a sheet feeding section, a printing section, and a discharged sheet housing section. The functional parts are not limited to those described above, and may have various functions such as ink jet printing and silk screen printing. The print head 103 is electrically connected to a storage device 109 such as a hard disk for storing image data and a data management control circuit 122 for sequentially transferring the image data to the print head. The image reading device A is mounted on an upper part of the image forming apparatus B as a unit.
In the image reading apparatus A, a platen 112 is mounted in the casing 110. An optical mechanism 114 and a photoelectric converting element 113 are arranged in the casing 110 to read a document sheet via the platen. A CCD or the like is widely known as the photoelectric converting element 113.
A sheet supplying device C shown in
A separating roller 119 and a fixed roller 120 are arranged at an upstream side of the sheet feeding stacker 115, and the fixed roller 120 pressingly contacts the separating roller 119. A kick roller 118 is attached to a bracket 119b mounted to a rotating shaft 119a of the separating roller 119. When the rotating shaft 119a rotates clockwise, the kick roller 118 lowers onto the sheet feeding stacker 115. When the rotating shaft 119a rotates counterclockwise, the kick roller 118 elevates to a state shown in the figure (described in detail with reference to
An overlap sensor 124 is placed at a downstream side of the register roller 125 and formed of a pair of ultrasonic sensors. In each ultrasonic sensor, a wave transmitting element and a wave receiving element are arranged and configured as described above (see
A driving mechanism of the conveying rollers will be described next.
A bracket 119b is supported on a rotating shaft of the separating roller 119 via a spring clutch 144. A belt B3 is used to transmit a driving force to the kick roller 118 attached to the bracket 119b. The sheet feed driving motor 140 rotates forward to drive the separating roller 119 and the kick roller 118. A spring of the spring clutch 144 is loosened to release the bracket 119b. The bracket 119b thus lowers from a withdrawn position where the bracket 119b is elevated. Consequently, the kick rocker 118 contacts the sheet on the stacker. The sheet feed driving motor 140 rotates backward to transmit a driving force to the register roller 125. The spring clutch 144 is contracted to elevate and return the bracket 119b to the withdrawn position in
A conveying section driving motor 141 is connected to the feeding roller 127, unloading roller 129, and sheet discharging roller 130 as shown in
A sensor is placed on the conveying path 134 to detect the leading edge of the sheet. The sensor will be described below together with an operation thereof. A plurality of sensors (not shown) is arranged on the sheet feeding stacker 115 for detecting a specific size of the sheet. These sensors detect the size of the sheet to control the conveyance of the sheets. The empty sensor 117 is provided at a tip portion of the sheet feeding stacker 115 to detect the sheets on the stacker. The empty sensor 117 detects that the final sheet is fed to provide a signal to a processing apparatus such as the image reading apparatus A. An ultrasonic sensor 123 and a sheet end detecting sensor 124 are provided at a downstream side of the separating roller 119.
A lead sensor 126 is provided before the feeding roller 127 for notifying the image reading apparatus that the leading edge of the sheet arrives. The lead sensor 126 further determines a line on the sheet where reading or printing is to be started. When no sheet is detected even after a predetermined time since the feeding instruction signal is sent to the register roller 125, the lead sensor 126 determines that a jam occurs. The lead sensor 126 stops the driving motor and sends a warning signal. A sheet discharge sensor 145 is placed at a downstream side of the unloading roller 129 for detecting the leading and trailing edges of the sheet. The sheet discharge sensor 145 thus determines whether a jam occurs.
An operation of the above apparatus will be described.
As shown in
As shown in
The disclosure to Japanese Patent Application No. 2003-428192, filed on Dec. 24, 2003, is incorporated in the application.
While the invention has been explained with reference to the specific embodiments of the invention, the explanation is illustrative and the invention is limited only by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-428192 | Dec 2003 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 5222724 | Hirano et al. | Jun 1993 | A |
| 5362041 | Ryuzaki et al. | Nov 1994 | A |
| 6040923 | Takashimizu et al. | Mar 2000 | A |
| 6565079 | Kakegawa et al. | May 2003 | B1 |
| 20010042956 | Minoru et al. | Nov 2001 | A1 |
| Number | Date | Country |
|---|---|---|
| 6-49567 | Dec 1994 | JP |
| 10-257595 | Sep 1998 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20050140087 A1 | Jun 2005 | US |
