SHEET FEED DEVICE

Abstract

A sheet feed device is provided which can feed sheets with good accuracy even if the sheets are formed with a crease near the front or rear end of the sheet. A plurality of roller units 3 each having an upper feed roller 1 and a lower feed roller 2 are arranged perpendicularly to the sheet feed direction with spaces left therebetween, and adjacent ones of the roller units 3 are offset with respect to the sheet feed direction. Upper feed roller driving means for rotating the upper feed rollers 1 of the roller units simultaneously and lower feed roller driving means for rotating the lower feed rollers 2 of the roller units simultaneously are provided to feed sheets 5 with each sheet 5 clamped between the upper feed rollers 1 and the lower feed rollers 2 which are rotating.

Description

TECHNICAL FIELD

This invention relates to a sheet feed device for feeding sheets such as corrugated sheets.

BACKGROUND ART

With a printing press for printing on corrugated sheets, the sheets are fed to a plate cylinder by a sheet feed device provided with a pair of feed rollers. One problem is that if the corrugated sheets are marked with a crease running perpendicularly to the sheet feed direction, the nip pressure under which the feed rollers clamp the sheets can be too low at the crease to feed the sheets stably, thus causing poor registration in printing.

In order to prevent such a poor registration, a sheet feed device has been proposed which as shown in FIG. 7(a), has two pairs of upper and lower feed rollers, each pair being spaced from the other pair in the sheet feed direction to feed corrugated sheets 31 supplied from a sheet delivery unit 30 between a plate cylinder 32 and a pressure cylinder 33 of a printing press with each sheet 31 clamped between the upper and lower feed rollers. With this sheet feed device, even if the surface of the corrugated sheet 31 is off one of the two pairs of feed rollers 34, 35 at a crease 31a, the other pair of feed rollers 36, 37 clamp the sheet 31, so that the sheets can be fed with good accuracy.

But, if as shown in FIG. 7(b) the crease 31a is formed near the front end of the corrugated sheet 31, the sheet comes to a position where the crease 31a is between the feed rollers 34, 35 on the upstream side before the feed rollers 36, 37 on the downstream side clamp the front end of the sheet 31, resulting in unstable feed of the sheet. Similarly, if the sheet 31 is formed with a crease near the rear end of the sheet, the crease 31a comes between the feed rollers 36, 37 on the downstream side after the sheet 31 has left the feed rollers 34, 35 on the upstream side, thus resulting in unstable feed of the sheet.

This problem can be solved by reducing the diameter of the feed rollers and thus the distance between the upstream feed rollers and the downstream feed rollers. But, if the roller diameter is small, the feed rollers tend to deflect and resonate. Therefore, the roller diameter cannot be reduced excessively.

Therefore, with a conventional sheet feeder, as shown in FIGS. 7(a) and 7(b), the feed rollers 34, 35 on the upstream side are arranged so as to laterally overlap with the downstream feed rollers 36, 37, thereby reducing the distance between the upstream feed rollers 34, 35 and the downstream feed rollers 36, 37. But this distance can be decreased only to such a degree that the upstream feed rollers 34, 35 do not interfere with the downstream feed rollers 36, 37. Thus, such a conventional sheet feeder cannot feed the sheets 31 with good accuracy if the sheets are formed with a crease 31a near their front or rear end.

DISCLOSURE OF INVENTION

Problems to be Solved

The problem is to provide a sheet feeder which can feed sheets with good accuracy even if the sheets are formed with a crease near their front or rear end.

Means for Solving the Problems

To solve the problem, according to the invention, a sheet feed device is provided which comprises a plurality of roller units each having an upper feed roller and a lower feed roller and arranged in a perpendicular direction to the sheet feed direction with spaces left therebetween, adjacent ones of the roller units being offset from each other with respect to the sheet feed direction, upper feed roller driving means for rotating the upper feed rollers of the roller units simultaneously, and lower feed roller driving means for rotating the lower feed rollers of the roller units simultaneously, thereby feeding sheets with each sheet clamped between the upper feed rollers and the lower feed rollers which are rotating.

With the sheet feed device of this arrangement, because the roller units arranged perpendicularly to the sheet feed direction are separated from each other, the amount of offset between the adjacent roller units in the sheet feed direction can be freely set. Therefore, even if the sheets are formed with a crease near their front or rear end, the amount of offset between the adjacent roller units in the sheet feed direction can be set to be smaller than the distance from the front or rear end of the sheet to the crease, so that the sheets can be fed with good accuracy.

Preferably, the upper feed roller driving means comprises an upper driving shaft provided parallel to the upper feed rollers and a torque transmitting means for transmitting the rotation of the upper driving shaft to the upper feed rollers. By doing so, because the upper feed rollers can be driven by a common upper driving shaft, the rotation speeds of the individual upper feed rollers are made uniform, so that the sheet can be fed with better accuracy.

It is preferable that the plurality of roller units are arranged in a staggered fashion with alternate ones of the roller units offset in the sheet feed direction and the upper driving shaft is arranged over an intermediate point between the upper feed rollers on the upstream side and the upper feed rollers on the downstream side. Because with this arrangement, the feed rollers and the upper driving shaft are arranged in a vertical direction, the mounting space in the sheet feed direction can be saved. This makes it easier to mount such a device in a printing press unit such as a flexo folder gluer.

Similarly, it is preferable that the lower feed roller driving means comprises a lower driving shaft provided parallel to the lower feed rollers and a torque transmitting means for transmitting the rotation of the lower driving shaft to the lower feed rollers. Also, it is preferable that the plurality of roller units are arranged in a staggered fashion with alternate ones of the roller units offset in the sheet feed direction and the lower driving shaft is arranged under an intermediate point between the lower feed rollers on the upstream side and the lower feed rollers on the downstream side.

Effects of Invention

With the sheet feed device of this invention, the amount of offset in the sheet feed direction between the roller units arranged perpendicularly to the sheet feed direction can be set freely. This makes it possible to feed the sheets with high accuracy even if the sheets are formed with a crease near the front or rear end of the sheets.

BRIEF DESCRIPTION OF THE DRAWINGS

[FIG. 1] Side view of the roller unit of the sheet feed device according to this invention

FIG. 2 Perspective view of the roller unit of FIG. 1

FIG. 3 Side view showing how a corrugated sheet is off the upstream side feed roller of FIG. 1 at a crease

FIG. 4 Front sectional view of the roller unit of FIG. 1

FIG. 5a Sectional view taken along line A-A of FIG. 4

FIG. 5b Sectional view taken along line B-B of FIG. 4

FIG. 6 Sectional view taken along line C-C of FIG. 4

FIG. 7 Side view of a conventional sheet feed device

DESCRIPTION OF THE REFERENCE NUMBERS

• 1 Upper feed roller
• 2 Lower feed roller
• 3 Roller unit
• 5 Corrugated sheet
• 9, 11, 15, 17 Gears
• 10 Upper driving shaft
• 16 Lower driving shaft

BEST MODE FOR EMBODYING THE INVENTION

FIG. 1 shows an embodiment of the sheet feed device of the present invention. It includes a plurality of roller units 3 each having a pair of feed rollers 1, 2. The roller units 3 clamp corrugated sheets 5 fed from a sheet delivery unit 4 and feed them between a plate cylinder 6 and a pressure cylinder 7 of a printing press.

As shown in FIG. 2, the roller units 3 are arranged with spaces therebetween in a perpendicular direction to the sheet feed direction. Any adjacent roller units 3 are offset or displaced from each other in the sheet feed direction. The amount of offset in the sheet feed direction is set to be smaller than the shortest one of the distances from the front or trailing ends of the respective corrugated sheets to their creases 5a. Therefore, with any sheet 5, as shown in FIG. 3, when the crease 5a faces the feed rollers 1 and 2 on the upstream side, the sheet 5 is clamped by the feed rollers 1 and 2 on the downstream side. When the crease 5a faces the feed rollers 1 and 2 on the downstream side, the sheet is clamped by the feed rollers 1 and 2 on the downstream side. This assures stable feed of the corrugated sheets.

The upper feed rollers 1 are rotatably supported by an upper stay 8 as shown in FIG. 4. A gear 9 is provided at one end of each feed roller 1. An upper driving shaft 10 is rotatably provided on the upper stay 8 in parallel with the upper feed rollers 1. Gears 11 are mounted on the upper driving shaft 10 so as to mesh with the gears 9 for the upper feed rollers 1. The upper driving shaft 10 is driven and rotated by a driving unit (not shown). When the upper driving shaft 10 rotates, its rotation is transmitted through the gears 11 and 9 to the upper feed rollers 1 to rotate them simultaneously. Thus, all the upper feed rollers 1 rotate at the same speed, so that the corrugated sheets 5 can be fed with high accuracy.

Also, since the upper feed rollers 1 are supported individually by the upper stay 8, they are less likely to deflect. This minimizes resonance of the upper feed rollers 1 and assures high feed accuracy when the corrugated sheets 5 are fed at high speed.

The upper stay 8 is mounted to a frame 12 so as to be movable in a vertical direction. On the frame 12, adjusting cams 13 are rotatably mounted in contact with the upper stay 8 as shown in FIG. 5. When the adjusting cams 13 are rotated by a driving unit (not shown), the adjusting cams 13 push the upper stay 8 up or down. Because the upper feed rollers 1 move together with the upper stay 8, the gaps between the upper feed rollers 1 and the lower feed rollers 2 change. Thus, it is possible to change and adjust the gaps between the upper feed rollers 1 and the lower feed rollers 2 according to the thickness and the degree of warp of the sheets 5, and thereby feed the corrugated sheets 5 with better accuracy.

The upper driving shaft 10 is supported by the upper stay 8. Thus, when the adjusting cams 13 are turned to move the upper feed rollers 1 up or down, the upper driving shaft 10 move together, so that the gears 11 and 9 remain meshed with each other.

As shown in FIG. 4, the lower feed rollers 2, too, are rotatably supported individually by a lower stay 14 and a gear 15 is provided at one end of each lower feed roller 2. The gears 15 are meshed with gears 17 mounted on a lower driving shaft 16 provided parallel to the lower feed rollers 2. With this arrangement, when the lower driving unit 16 is driven by a driving unit (not shown), the lower feed rollers 2 rotate simultaneously. The lower stay 14 has both ends thereof fixed to the frame 12.

Because the lower feed rollers 2 are supported individually by the lower stay 14, they are less likely to deflect. This minimizes the resonance of the lower feed rollers 2 and the corrugated sheets 5 can be fed with good accuracy even if they are fed at high speed.

Preferably, as shown in FIG. 6, the roller units 3 are arranged in a staggered fashion with any adjacent ones offset from each other in the sheet feed direction. Also, as shown in FIG. 5, it is preferable to arrange the upper driving shaft 10 over an intermediate point between the feed rollers 1 on the upstream side and the feed rollers 1 on the downstream side. With this arrangement, the feed rollers 1 and the upper driving shaft 10 are arranged one over the other. This saves the mounting space of the sheet feed device in the sheet feed direction and makes it easier to mount such a device in a printing press unit such as a flexo folder gluer. Also, because the distances between the axes of the respective upper feed rollers 1 and the axis of the upper driving shaft 10 are made uniform, it is possible to use common gears as gears for coupling the upper driving shaft 10 with the respective upper feed rollers 1. This improves ease of maintenance and economy.

Similarly, it is preferable to arrange the lower driving shaft 16 under an intermediate point between the feed rollers 2 of the roller units 3, which are arranged in a staggered fashion.

Although the roller units 3 are arranged in a staggered fashion in the embodiment, they may be arranged in any other way so long as the adjacent roller units 3, which are arranged perpendicularly to the sheet feed direction, are offset from one another in the sheet feed direction. For example, the roller units 3 may be arranged in a V shape such that each roller unit is located downstream of the adjacent roller unit that is located nearer to the center of the device.

The torque transmitting means for transmitting the rotation of the upper driving shaft 10 to the upper feed rollers 1 is not limited to gears. It may be chains, timing belts, V-belts, etc. The same is true for the torque transmitting means for transmitting the rotation of the lower driving shaft 16 to the lower feed rollers 2.

Although in the embodiment, the upper feed rollers 1 are coupled to the upper driving shaft 10 through gears to rotate the upper feed rollers 1 simultaneously, this may be done by providing a driving unit such as a motor for each feed roller and starting the driving units simultaneously. With this arrangement, it is possible to selectively drive the feed rollers 1 according to the size of the corrugated sheet 5 and minimize the wear of the parts. The same is true for the driving of the lower feed rollers 2.

Also, although in the embodiment, corrugated sheets are cited as sheets to be fed, other sheets such as resin sheets formed with grooves may be fed instead.

Claims

1. (canceled)

2. The sheet feed device as claimed in claim 6 wherein said upper feed roller driving means comprises an upper driving shaft provided parallel to said upper feed rollers and a torque transmitting means for transmitting the rotation of said upper driving shaft to said upper feed rollers.

3. The sheet feed device as claimed in claim 2 wherein said plurality of roller units are arranged in a staggered fashion with alternate ones of said roller units offset in the sheet feed direction and said upper driving shaft is arranged over an intermediate point between said upper feed rollers on the upstream side and said upper feed rollers on the downstream side.

4. The sheet feed device as claimed in claim 6 wherein said lower feed roller driving means comprises a lower driving shaft provided parallel to said lower feed rollers and a torque transmitting means for transmitting the rotation of said lower driving shaft to said lower feed rollers.

5. The sheet feed device as claimed in claim 4 wherein said plurality of roller units are arranged in a staggered fashion with alternate ones of said roller units offset in the sheet feed direction and said lower driving shaft is arranged under an intermediate point between said lower feed rollers on the upstream side and said lower feed rollers on the downstream side.

6. A sheet feed device comprising a plurality of roller units each having an upper feed roller and a lower feed roller and arranged in a perpendicular direction to the sheet feed direction with spaces left therebetween, adjacent ones of said roller units being offset from each other with respect to the sheet feed direction, upper feed roller driving means for rotating said upper feed rollers of said plurality of roller units simultaneously, lower feed roller driving means for rotating said lower feed rollers of said plurality of roller units simultaneously, and an upper stay vertically movably provided for supporting said upper feed rollers and said upper roller driving means together, said upper stay being vertically movable to adjust the gap between said upper feed rollers and said lower feed rollers, thereby feeding the sheets with each sheet clamped between said upper feed rollers and said lower feed rollers which are rotating.

7. The sheet feed device as claimed in claim 2 wherein said lower feed roller driving means comprises a lower driving shaft provided parallel to said lower feed rollers and a torque transmitting means for transmitting the rotation of said lower driving shaft to said lower feed rollers.

8. The sheet feed device as claimed in claim 3 wherein said lower feed roller driving means comprises a lower driving shaft provided parallel to said lower feed rollers and a torque transmitting means for transmitting the rotation of said lower driving shaft to said lower feed rollers.