Pressure Reducing Folding System

BACKGROUND

Disclosed herein is a system and method for reducing the pressure applied to a stack of printed pages during a folding process.

An example of an application for a system for reducing the pressure applied to a stack of printed pages is a photocopier or printer that produces folded booklets.

In some booklet making systems, pressure is applied to the fold nip as the folded booklet is passed through. With warm solid inks, for example, "blocking" or image transfer can occur if the folded set is passed through a high pressure nip. This blocking or image transfer is undesirable.

<patcit id="pcit0001" dnum="US20080182740A1"><text>US 2008/0182740 A1</text></patcit> describes sheet feeding device and post-processing apparatus and image forming system comprising the same. A sheet folding device has a releasable clutch between a roll driving device and a pair of folding rolls for folding a sheet bunch so that when a folding blade inserts the sheet bunch to a nip position on the pair of folding rolls, the first and second folding rolls rotate following the inserted sheets. The sheet folding device includes a guide for holding the sheet bunch at a predetermined fold position. The first and second folding rolls arranged at the fold position are in pressure contact with each other. The folding blade inserts the sheet bunch supported on the guide to the nip position on the first and second folding rolls. The roll driving device rotationally drives the first and second folding rolls. The first and second folding rolls and the roll driving device are coupled together via the releasable clutch.

<patcit id="pcit0002" dnum="US20090200724A1"><text>US 2009/0200724 A1</text></patcit> describes sheet folding apparatus, image forming apparatus using the same, and sheet folding method. A sheet folding apparatus includes: a saddle-stitching unit configured to stitch a center of a sheet bundle; a folding unit configured to fold the sheet bundle at the center to form a fold; a loading base onto which the sheet bundle conveyed from the folding unit is loaded; a nipping plate configured to be pressed to and separated from the loading base in parallel to the loading base and to nip the sheet bundle loaded onto the loading base; and first and second rollers that move along a direction of the fold while nipping and pressing the fold of the sheet bundle nipped by the nipping plate to reinforce the fold. Here, a surface, which faces the loading base, of the nipping plate is provided with an elastic member.

<patcit id="pcit0003" dnum="US20080318752A1"><text>US 2008/0318752 A1</text></patcit> describes sheet folding apparatus, sheet folding unit and image forming apparatus. A sheet folding apparatus, including: a stacker configured to stack a plurality of sheets; a first folding roller configured to rotate around a first axis; a second folding roller configured to rotate around a second axis which is parallel with the first axis and biased to the first folding roller separably to make a nip together with the first folding roller therebetween; a blade unit configured to push a surface of the plurality of sheets, stacked by the stacker, into the nip; a stationary support configured to support the blade unit linearly movable to avoid deviating from a common tangential direction of the first folding roller and the second folding roller at the nip to a first folding roller side; and a movable support relatively movable against the blade unit, configured to bias the blade unit to the first folding roller side deviatably from the common tangential direction to a second folding roller side.

SUMMARY OF THE INVENTION

It is the object of the present invention to improve folding of a stack of printed pages. This object is achieved by providing a device for folding sheets of medium according to claim 1 and a method for folding sheets of a medium according to claim 9. Embodiments of the invention are set forth in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

<figref idref="f0001">FIG. 1</figref> is a diagram of an exemplary folding system in accordance with one possible embodiment of the disclosure;

<figref idref="f0002">FIG. 2</figref> is an exemplary diagram of a folding system in accordance with one possible embodiment of the disclosure at a first position;

<figref idref="f0003">FIG. 3</figref> is an exemplary diagram of a folding system in accordance with one possible embodiment of the disclosure at a second position;

<figref idref="f0004">FIG. 4</figref> is an exemplary diagram of a folding system in accordance with one possible embodiment of the disclosure at a third position;

<figref idref="f0005">FIG 5</figref>. is an exemplary diagram of a folding system in accordance with one possible embodiment of the disclosure;

<figref idref="f0006">FIG 6</figref>. is another view of the folding system shown in <figref idref="f0005">FIG. 5</figref>; and

<figref idref="f0007">FIG. 7</figref> is an exemplary schematic diagram of a printing device in accordance with one possible embodiment of the disclosure.

DETAILED DESCRIPTION

Aspects of the embodiments disclosed herein relate to a system and method for folding sheets of a printed medium. For example, a saddle stitching booklet maker system can use embodiments of the disclosure to produce booklets with little or no image transfer or blocking.

The disclosed embodiments may include a device for folding sheets of a medium. The device has a frame; a cam mechanism attached to the frame; a lever attached to the frame, the lever being actuated by the cam mechanism; a first scissor arm attached to the frame, the first scissor arm being actuated by the lever; a pair of first rolls, one of the first rolls being movable by the first scissor arm; a second scissor arm attached to the frame, the second scissor arm being actuated by the lever; a pair of second rolls, one of the second rolls being movable by the second scissor arm; and a crease blade for contacting the sheets to create a crease in the sheets. Rotation of the cam mechanism through a first period of rotation causes the crease blade to move in a contact direction to create the crease in the sheets by pushing the sheets between the first rolls. Rotation of the cam mechanism through a second period of rotation causes the crease blade to move in a retracting direction away from the sheets and causes the lever to move the first and second scissor arms such that the first pair of rolls is separated and the second pair of rolls is separated.

The disclosed embodiments may further include a printing device. The printing device has a medium storage area; a folding device for folding sheets of a medium being printed; and a controller that controls rotation of a cam mechanism. The folding device has a frame; a cam mechanism attached to the frame; a lever attached to the frame, the lever being actuated by the cam mechanism; a first scissor arm attached to the frame, the first scissor arm being actuated by the lever; a pair of first rolls, one of the first rolls being movable by the first scissor arm; a second scissor arm attached to the frame, the second scissor arm being actuated by the lever; a pair of second rolls, one of the second rolls being movable by the second scissor arm; and a crease blade for contacting the sheets to create a crease in the sheets. Rotation of the cam mechanism through a first period of rotation causes the crease blade to move in a contact direction to create the crease in the sheets by pushing the sheets between the first rolls. Rotation of the cam mechanism through a second period of rotation causes the crease blade to move in a retracting direction away from the sheets and causes the lever to move the first and second scissor arms such that the first pair of rolls is separated and the second pair of rolls is separated.

The disclosed embodiments may further include a method for folding sheets of a medium. The method includes rotating a cam mechanism through a first period of rotation to cause a crease blade to move in a contact direction to create a crease in the sheets by pushing the sheets between a pair of first rolls, and rotating the cam mechanism through a second period of rotation to cause the crease blade to move in a retracting direction away from the sheets and cause a lever to move first and second scissor arms such that the first pair of rolls is separated and a second pair of rolls is separated.

<figref idref="f0001 f0002 f0003 f0004">FIGS. 1-4</figref> show a first exemplary embodiment of a system in accordance with the disclosure. <figref idref="f0005">FIGS. 5</figref> and <figref idref="f0006">6</figref> show a second embodiment of a system in accordance with the disclosure.

<figref idref="f0001">FIG. 1</figref> is a partial view of an example of a system using an embodiment of the disclosure. <figref idref="f0001">FIG. 1</figref> shows an assembly 100 for producing a fold in a stack of printed pages. Assembly 100 has a crease blade 110 that creates a crease in the stack of printed pages. Crease blade 110 is moved toward a first pair of pressure rolls 120 to push the stack of printed pages into and between first pair of pressure rolls 120. A cam mechanism 150 actuates a lever 140 that, in turn, actuates a scissor arm that controls a gap between the first pair of pressure rolls 120. In this disclosure, a "cam" may be defined as a rotating or sliding piece in a mechanical linkage used to at least in part transform rotary motion into linear motion, for example. Lever 140 also actuates a scissor arm that controls a gap between a second pair of pressure rolls 130 (not shown in <figref idref="f0001">FIG. 1</figref>). In this disclosure, the term "scissor arm" may be defined as one of a pair of arms that are pivotably mounted relative to each other, for example. A drive motor 160 drives cam mechanism 150. A single motor 160 can be used to drive cam mechanism 150 and crease blade 110, or multiple motors can be used.

<figref idref="f0002 f0003 f0004">FIGS. 2-4</figref> show an example of the operation of Assembly 100.

<figref idref="f0002">FIG. 2</figref> shows assembly 100 with crease blade 110 in the back position while sheets 300 are moved into position for folding. <figref idref="f0002">FIG. 2</figref> shows second pair of pressure rolls 130 located downstream of first pair of pressure rolls 120. A first scissor arm 180 is attached to the upper roll of first pair of pressure rolls 120. A second scissor arm 190 is attached to the upper roll of second pair of pressure rolls 130. A pin 200 transfers motion from level 140 to scissor arms 180, 190. Springs 170 apply force to scissor arms 180, 190 that is in turn applied to pressure rolls 120, 130. As cam mechanism 150 rotates in the direction of arrow A, crease blade 110 moves toward sheets 300 to the position shown in <figref idref="f0003">FIG. 3</figref>.

<figref idref="f0003">FIG. 3</figref> shows crease blade 110 in the forward position pushing sheets 300 into the nip between first pair of pressure rolls 120. As cam mechanism 150 continues to rotate in direction A, lever 140 is moved such that downward force is applied to pin 200. As pin 200 is pushed downward in <figref idref="f0003">FIG. 3</figref>, first scissor arm 180 rotates to lift the upper roll of first pair of pressure rolls 120 and, as a result, decrease the pressure applied to sheets 300. Similarly, as pin 200 is pushed downward in <figref idref="f0003">FIG. 3</figref>, second scissor arm 190 rotates to lift the upper roll of second pair of pressure rolls 130 and, as a result, decrease the pressure applied to sheets 300 as they progress through second pair of pressure rolls 130. In one embodiment, the upper roll of first pair of pressure rolls 120 is lifted after crease blade 110 is inserted approximately 5 to 6 mm into the nip. By decreasing the pressure applied to sheets 300 by the pressure rolls, blocking can be reduced or eliminated. By allowing crease blade 110 to be inserted into the nip for a short distance before reducing the pressure applied by the pressure rolls, a satisfactory fold can be achieved with little or no blocking.

The timing of the pressure reduction at second pair of pressure rolls 130 relative to the pressure reduction at first pair of pressure rolls 120 can be dictated by the shapes of scissor arms 180, 190. In some embodiments, the pressure reduction at second pair of pressure rolls 130 is activated after the pressure reduction at first pair of pressure rolls 120. In other embodiments, the pressure reduction at both pairs of pressure rolls is simultaneous, or the pressure is reduced at second pair of pressure rolls 130 first.

As cam mechanism 150 continues to rotate, crease blade 110 is moved to the position shown in <figref idref="f0004">FIG. 4</figref>.

In <figref idref="f0004">FIG. 4</figref>, crease blade 110 is shown in the stop position where it does not contact sheets 300. Crease blade 110 is held in this position until sheets 300 are clear of the pressure rolls. After sheets 300 (in the form of a booklet) have cleared the pressure rolls, cam mechanism 150 begins to rotate to return to the position shown in <figref idref="f0002">FIG. 2</figref>, which releases lever 140 and permits full pressure to be restored at the pressure rolls.

<figref idref="f0005">FIGS. 5</figref> and <figref idref="f0006">6</figref> show partial views of an assembly in accordance with another embodiment of the disclosure. This embodiment operates similarly to the embodiment shown in <figref idref="f0002 f0003 f0004">FIGS. 2-4</figref>, but has fewer parts and uses a lever 140' that is shaped differently.

<figref idref="f0006">FIG. 6</figref> shows in closer detail how the movement of lever 140' pushing pin 200 downward causes first scissor arm 180 to lift the upper roll of first pair of pressure rolls 120 upward in direction B. Similarly, the movement of lever 140' pushing pin 200 downward causes second scissor arm 190 to lift the upper roll of second pair of pressure rolls 130 upward in direction B.

<figref idref="f0007">FIG. 7</figref> shows a printing device 400 including assembly 100, a medium storage area 410, and a controller 420. Controller 420 controls the operation of assembly 100. Sheets 300 are stored in medium storage area 410 prior to processing through assembly 100.

Particular ones of the exemplary embodiments described herein can be used in any machine that folds printed sheets. However, blocking is particularly problematic in machines that print in color.

It will be appreciated that variations of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications.