Claims
- 1. A sheet transport apparatus in which a sheet to be transported along a sheet transport path is put to a stand-by position so that the transport is resumed at a predetermined timing, said apparatus comprising:
- a gate member for opening and closing said sheet transport path to intercept the front end of the sheet to cause the sheet to form a loop on the upstream side of said gate member in the direction of the transport; and
- means for initiating a downward force on the loop of the sheet at a point on the loop that is closer to the upstream side of the loop in the direction of the transport than the top of the loop simultaneously with the opening action of said gate member in order to enable the looped sheet to move forward in the direction of transport due to the stiffness of the sheet itself when depressed from above;
- wherein said means for initiating a downward force moves from a first position to a lower second position relative to said transport path.
- 2. A sheet transport apparatus as claimed in claim 1, wherein said gate member is pivotably provided between a point where said sheet transport path is closed and a point where said sheet transport path is opened.
- 3. A sheet transport apparatus as claimed in claim 2, wherein said pressing means takes the form of a plate which is so moved as to depress the looped sheet from above.
- 4. A sheet transport apparatus as claimed in claim 3, wherein said pressing means comprises a link mechanism connected with said gate member so that said pressing means depresses the sheet simultaneously with the opening action of said gate member.
- 5. A sheet transport apparatus in which a sheet to be transported along a sheet transport path is once put to a stand-by position so that the transport is resumed at a predetermined timing, said apparatus comprising:
- a gate member for opening and closing said sheet transport path to intercept the front end of the sheet;
- a transport roller located upstream of said gate member in the direction of the transport for transporting the sheet towards said gate member;
- controlling means for enabling said transport roller to continue the transport of the sheet for a predetermined period of time after the movement of the front end of the sheet is stopped by the closing action of said gate member to cause the sheet to form a loop between said gate member and said transport roller;
- sheet guide means located between said gate member and said transport roller and capable of moving between a first position which enables said sheet to form a loop of a first size and a second position wherein the sheet guide means contacts the loop at a location closer to the upstream side of the loop of the sheet, in the direction of the transport, than the top of the loop, at which second position the size of the loop of the sheet is smaller than the first size; and
- means for initiating a downward force on the sheet guide means to move said sheet guide means to said second position when said sheet transport path is opened by said gate member.
- 6. A sheet transport apparatus as claimed in claim 5, wherein said gate member is pivotably provided between a point where said sheet transport path is closed and a point where said sheet transport path is opened.
- 7. A sheet transport apparatus as claimed in claim 6, wherein said sheet guide means takes the form of a plate which is so moved as to depress the looped sheet from above.
- 8. A sheet transport apparatus as claimed in claim 7, wherein said enabling comprises a link mechanism connected with said gate member so that said sheet guide means depresses the sheet simultaneously with the opening action of said gate member.
- 9. A sheet transport apparatus in which a sheet to be transported along a sheet transport path is once put to a stand-by position so that the transport is resumed at a predetermined timing represented by a synchronizing signal, said apparatus comprising:
- a gate member for opening and closing said sheet transport path to intercept the front end of the sheet;
- a transport roller located upstream of said gate member in the direction of the transport for transporting the sheet towards said gate member;
- first controlling means for enabling said transport roller to continue the transport of the sheet for a predetermined period of time after the movement of the front end of the sheet is stopped by the closing action of said gate member to cause the sheet to form a loop between said gate member and said transport roller;
- a pair of register rollers located downstream of said gate member in the direction of the transport;
- sheet guide means located between said gate member and said transport roller and capable of moving between a first position which enables said sheet to form a loop of a first size and a second position wherein the sheet guide means contacts the loop of the sheet so as to depress the loop;
- second controlling means for opening said gate member and for moving said sheet guide means from the first position to said second position after the formation of the sheet loop by said first controlling means, so that the front end of the sheet comes into contact with the nipping portion of said pair of register rollers while said pair of register rollers is at rest; and
- third controlling means for rotating said pair of register rollers in response to the synchronizing signal.
- 10. A sheet transport apparatus as claimed ian claim 9, further comprising means for detecting the sheet upstream of said gate member in the direction of the transport.
- 11. A sheet transport apparatus as claimed in claim 10, wherein said first controlling means stops the rotation of said transport roller after a predetermined period of time from the time when the front end of the sheet is detected by said detecting means.
- 12. A sheet transport apparatus as claimed in claim 10, wherein said second controlling means enables said gate member to open said sheet transport path and said sheet guide means to move to said second point after a predetermined period of time from the time when the front end of the sheet is detected by said detecting means.
- 13. A sheet transport apparatus as claimed in claim 10, further comprising fourth controlling means for stopping the rotation of said transport roller when the rear end of the sheet is detected by said detecting means, for stopping the rotation of said pair of register rollers, for letting said gate member to return to the position where said sheet transport path is closed and for enabling said sheet guide means to return to said first point after a predetermined period of time from the time of the detection of the rear end of the sheet by said detecting means.
Priority Claims (1)
| Number |
Date |
Country |
Kind |
| 62-53763 |
Mar 1987 |
JPX |
|
BACKGROUND OF THE INVENTION
This application is a continuation, of application Ser. No. 07/164,893, filed Mar. 7, 1988, now abandoned.
1. Field of the Invention
The present invention relates to a sheet transport apparatus particularly one capable of starting the transport of the sheet from stand-by position, on which the sheet sent out from a sheet stocker is temporarily stopped at a predetermined and synchronized timing.
2. Description of Related Art
In general, the transfer type copying machine has a sheet transport system wherein a copying sheet, which is sent out one by one from a sheet stocker and put to a stand-by position once by a register device, is transported to the copying unit in response to the synchronizing signal for synchronizing the transport of the sheet with the formation of the toner image on the photosensitive drum. Such sheet transport system is required to comprise the register device which permits the sheet to be transported to the copying unit accurately at the synchronized timing and also required to have the function to correct the skewing of the sheet.
For the prior art, the gate register system comprising a plate-form gate serving as a register member and installed so as to be able to open and close the sheet transport path is known publicly as described in Japanese Patent Laid Open Publication No. 59-50936.
In said gate register system, however, the front end of the sheet in contact with the gate is apt to slip to cause the delay of synchronization timing in spite of its excellent skew-corrective function, and the higher the operating speed (sheet transport speed) of the system or the smaller the stiffness of the sheet, the greater the delay of synchronization timing. More specifically, when the gate is opened in response to the synchronizing signal, the sheet is made to move forward due to the force of the loop of the sheet formed on the upstream side of the gate in the direction of the transport, but, if the stiffness of the sheet is not large enough, the forward movement of the sheet is not able to follow the speed of the sheet transport system.
Accordingly, it is an object of the present invention to provide a sheet transport apparatus which is not only capable of surely correcting the skewing of the sheet and enabling the front end of the sheet to acquire an increased force for the forward movement when the sheet transport path of the gate member is opened, regardless of whether the stiffness of the sheet is relatively small or the transport speed is relatively high, but also capable of accurately making the synchronization of the timing when resuming the transport of the sheet after the stop.
To realize the above object, a sheet transport apparatus according to the present invention in which a sheet to be transported along a sheet transport path is once put to a stand-by position so that the transport is resumed at a predetermined timing, the apparatus comprises a gate member for opening and closing the sheet transport path to stop the movement of the front end of the sheet once to cause the sheet to form a loop on the upstream side of the gate member in the direction of the transport and means for pressing down the loop of the sheet simultaneously with the opening action of the gate member in order to enable the looped sheet to move forward in the direction of transport due to the stiffness of the sheet itself when depressed from above.
Further, a sheet transport apparatus according to the present invention in which a sheet to be transported along a sheet transport path is once put to a stand-by position so that the transport is resumed at a predetermined timing, the apparatus comprises a gate member for opening and closing the sheet transport path to stop the movement of the front end of the sheet once, a transport roller located on the upstream side of the gate member in the direction of the transport for transporting the sheet towards the gate member, controlling means for enabling the transport roller to continue the transport of the sheet for a predetermined period of time even when the movement of the front end of the sheet is stopped by the closing action of the gate member to cause the sheet to form a loop between the gate member and the transport roller, sheet guide means located between the gate member and the transport roller and capable of moving between a first point where the form of the sheet loop is limited when the sheet forms the loop and a second point where the loop of the sheet is depressed and means for enabling the sheet guide means to move to the second point when the sheet transport path is opened by the gate member.
According to the present invention, the front end of the transported sheet first comes into contact with the gate member to form a loop on the upstream side of the gate member in the direction of the transport, whereby the skew of the sheet is corrected. Then, when the sheet transport path is opened by the gate member, the sheet guide means depresses the loop towards the direction of the transport to cause the front end of the sheet to move forward aided by the stiffness of the sheet itself, whereby the follow-up speed of the sheet can be increased.
US Referenced Citations (6)
Foreign Referenced Citations (1)
| Number |
Date |
Country |
| 59-50936 |
Apr 1984 |
JPX |
Continuations (1)
|
Number |
Date |
Country |
| Parent |
164893 |
Mar 1988 |
|
Patent Grant
4936567
