Pre-stack Mechanism

This machine uses two methods to pre-stack paper.

The former method is the same as that employed in Booklet Finisher SR5060 and Finisher SR5050.

New Method Adopted with These Machines

The former method stacked sheets in the stapling tray with their leading edges not completely aligned, but the new method greatly improves the accuracy of stack alignment in the stapling tray with the addition of a 3rd pre-stack roller and timing adjustments to align the leading edges of the standby sheet and next sheet before they are sent to the stapling tray.

Here is a description of both methods.

Former Method

1) Small-size Paper (A4 and smaller)

The first sheet (red line in the drawing above) is directed in the pre-stack paper path by the staple junction gate. The sheet brushes past the spring loaded pre-stack junction gate. The weight of the paper allows it to push past the junction gate and then the spring attached to the gate pulls it closed.

The pre-stack paper sensor detects each sheet of paper that enters the pre-stack paper path. The sensor switches on the pre-stack motor that rotates the 1st and 2nd pre-stack rollers to feed the leading edge of the paper the prescribed distance (a).

The motor stops, reverses, and the rollers feed the paper under the pre-stacker junction gate and into the shunt of the pre-stacker unit where the leading edge of the paper stops at the nip of the 1st pre-stack rollers (b).

Next, the 2nd sheet (blue line in the drawing above) feeds (c). When it reaches the 1st pre-stack rollers, the pre-stack roller motor switches on and the 1st and 2nd sheets feed together (d). The pre-stack motor reverses again and both sheets are fed up into the shunt. This cycle can repeat up to 5 times until finally, after one additional sheet feeds, all 6 of the sheets are fed together to the corner stapling tray.

• Up to 4 sheets are held in the pre-stack unit for stapling at one corner.
• Up to 5 sheets are held in the pre-stack unit for stapling at two places on the edge of the stack.

2) Large-size Paper (B4 and larger)

The sequence of events in the pre-stacker unit for large paper sizes is the same as that for A4 and smaller sizes with one important exception.

• Before large paper sizes are fed in staple mode, the pre-stack release motor switches on and pulls the drive roller of the 1st pre-stack roller pair away from its idle roller (a).
• The forward and reverse feeding is performed by the pre-stack motor driving the 2nd pre-stack rollers and feeding the paper only as far as the nip of the 2nd pre-stack rollers.
• The nip of the 1st pre-stack rollers remains open.
• Reverse feeding the leading edges as far as the 2nd pre-stack rollers saves time. (Reverse and forward feeding the leading edges as far as the 1st pre-stack rollers would require more time.)

New Method: Small-size Paper (A4 and smaller)

The old method of feeding, stacking, and stapling has been improved to come up with a new method that improves the efficiency of jogging the sides of a stack for booklet stapling.

This has been done with the addition of a third pre-stack roller in the path where the sheets are pre-stacked.

• At [A] the junction gate transport rollers feed the 1st sheet which brushes past the pre-stack junction gate and into the nip of the 1st pre-stack rollers.
• When the trailing edge of sheet passes the junction gate at [B], the pre-stack motor reverses and the 1st pre-stack roller and 3rd pre-stack roller feed the sheet into the standby path. Next, just before the leading edge of sheet passes the 1st pre-stack roller, the pre-stack motor stops with sheet in the nip of the 1st pre-stack roller and pauses (standby), and then waits for the next sheet to feed.
• Next, at [C] just before the leading edge of sheet passes the 1st pre-stack roller, the pre-stack motor starts to rotate forward to drive the 1st pre-stack roller and 3rd pre-stack roller that feed sheet at standby and stacks it onto sheet.
• The leading edge of sheet that was at standby and the leading edge of sheet that was just fed are aligned [D], and then the sheets are fed together to the stapling tray.
• Thereafter, it is possible to stack several sheets through repetition of this operation (pre-stacking). One or the other mode is employed, depending on the paper size, stapling mode, and the number of sheets to be pre-stacked.

New Method: Large-size Paper (B4 and larger)

The 2nd pre-stack roller at the rear and 3rd pre-stack roller are used to align the leading edges of the paper and send them to the stapling tray in the same way that the 1st pre-stack roller is used in the older method to perform the same task.

Control of Both Methods

The size of the paper, specifically the length of the paper, is used to select automatically the method of control as shown in the table below. (The paper sizes are fixed and cannot be switched with SP codes or by other means.)

The paper length, measured in the sub scan direction (direction of paper feed), can adversely affect paper feed and productivity of the new method. The older method is used for such paper.

However, the number of sheets that are pre-stacked can be selected with SP codes.