EP1726549A1

EP1726549A1 - Sheet stacking apparatus and sheet stacking method

Info

Publication number: EP1726549A1
Application number: EP06010676A
Authority: EP
Inventors: Hironari Fuji Photo Film Co. Ltd. Misu; Koichi Fuji Photo Film Co. Ltd. Tamai
Original assignee: Fujifilm Corp; Fuji Photo Film Co Ltd
Current assignee: Fujifilm Corp
Priority date: 2005-05-23
Filing date: 2006-05-23
Publication date: 2006-11-29
Anticipated expiration: 2026-05-23
Also published as: EP1726549B1; JP2006327713A; ATE517055T1

Abstract

The sheet stacking apparatus (100) provides a sheet stacking apparatus that positions sheets (P) that are sequentially supplied by a supplying device (200) in a predetermined stacking position, and stacks them in a pile, comprising a stacking platform (2) on which the sheets (P) supplied by the supplying device (200) are stacked, and a sheet holding device (10,4) that catches the sheet supplied by the supplying device above the stacking platform, and releases the sheet after catching so as to drop the sheet onto the stacking platform.

Description

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a sheet stacking apparatus and a sheet stacking method, and particularly, to a sheet stacking apparatus and a sheet stacking method by which a supplied sheet is effectively prevented from being rubbed against stacked sheets.

Description of the Related Art

A stacking apparatus in which planographic printing plates sequentially supplied from a conveying device are positioned in a predetermined stacking position and stacked in a pile, comprising a stacking face on which the planographic printing plates are stacked; a frame member which is provided on the outer periphery side of a planographic printing plate pile stacked on the stacking face so as to restrict the movement of the planographic printing plate along a face direction for positioning it in the stacking position; a cushioning material which is located between the frame member and the planographic printing plate pile stacked on the stacking face, and is elastically deformed by a load from the planographic printing plate pile; and a protection metal sheet located between the cushioning material and the planographic printing plate pile on the stacking face, and which is deformed together with the cushioning material at the time when the planographic printing plate hits thereon has been proposed in Japanese Patent Laid-Open Publication No. 2002-046924 .
The stacking apparatus comprises, as the frame member, a back stopper which catches the planographic printing plate supplied from the conveying device, such as a belt conveyor, or the such as; a front stopper which is provided so as to face the back stopper with the stacking face therebetween; and a pair of side stoppers provided along a pair of side edges of the stacking face extending along a planographic printing plate supplying direction.
The front stopper is provided with nozzle holes in the shape of a horizontal slit that blow out air toward the planographic printing plate supplied from the belt conveyor.
Therefore, it is considered that, by controlling the intensity and direction of the flow of the air blown out from the nozzle holes, the amount of lift of the supplied planographic printing plate can be controlled, and the possibility of contact of a newly supplied planographic printing plate with the planographic printing plates piled on the stacking face can be reduced.
However, in the stacking apparatus, the intensity and the direction of the air flow blown out from the nozzle holes are to be changed in accordance with the size, the grade, the amount of curl, and the such as, of the planographic printing plate that is to be supplied.
Particularly, with the planographic printing plate having no slip sheet on the surface thereof, such as a laser exposure type planographic printing plate, when a planographic printing plate having a different amount of curl is supplied, the back face of the supplied planographic printing plate touches a printing face of the planographic printing plate located at the top of the planographic printing plate pile stacked on the stacking face, and the printing face thereof is damaged.
The present invention has been made to solve the above-mentioned problems. The present invention is aimed at providing a sheet stacking apparatus and a sheet stacking method with which, whenever a planographic printing plate having a different size, grade, amount of curl, or the such as is supplied, rubbing of a newly supplied sheet such as a planographic printing plate against the sheets that are stacked and quality degradation of the sheets can be prevented from occurring without changing supplying and stacking conditions.

SUMMARY OF THE INVENTION

A first aspect of the present invention relates to a sheet stacking apparatus that positions sheets which are sequentially supplied by a supplying device in a predetermined stacking position, and stacks them in a pile, comprising: a stacking platform on which the sheets supplied by the supplying device are stacked, and a sheet holding device that catches a sheet that is supplied by the supplying device above the stacking platform, and after catching the sheet, releases the sheet so as to be dropped onto the stacking platform.
In the sheet stacking apparatus, the sheet supplied by the supplying device is caught by the sheet holding device before being dropped on the stacking platform, and thus, regardless of the size, the grade, the amount of curl, and the such as, the sheet is set on the stacking platform with a reduced velocity.
Therefore, the sheet can be stacked without the surface thereof being scratched or damaged, and there is no need for changing the supplying condition or the stacking condition whenever a sheet having a different size, grade, amount of curl, or the such as is supplied.
A second aspect of the present invention relates to the sheet stacking apparatus of the first aspect, wherein after the sheet caught by the sheet holding device comes to a standstill or is decelerated to a predetermined velocity or below, the sheet holding device releases the sheet so that the sheet drops onto the stacking platform.
In the sheet stacking apparatus, the sheet is caught by the sheet holding device, and at the time when the sheet caught by the sheet holding device comes to a standstill or is decelerated to a predetermined velocity or below, the sheet is dropped onto the stacking platform, whereby the sheet is dropped on the stacking platform with the velocity component in the supplying direction being substantially zero.
Therefore, rubbing between the face of the sheet newly supplied on the stacking platform and that of the sheet stacked on the stacking platform, which may result in damage to the face, can be effectively prevented.
A third aspect of the present invention relates to the sheet stacking apparatus of the first or the second aspect, wherein the sheet holding device comprises a sheet holding member which takes either a holding position at which the sheet holding member is located above the stacking platform so as to catch the sheet supplied by the supplying device from below, or a withdrawal position at which the sheet holding member is withdrawn from the stacking platform.
In the sheet stacking apparatus, the sheet supplied by the supplying device is caught by the sheet holding member which is in the holding position. The sheet holding member is withdrawn to the withdrawal position after catching the sheet. As a result, the sheet is dropped onto the stacking platform.
The fourth aspect of the present invention relates to the sheet stacking apparatus of the third aspect, wherein the sheet holding member is a sheet catching plate, and the sheet catching plate is held horizontally above the stacking platform in the holding position.
The sheet stacking apparatus comprises a sheet catching plate as the sheet holding member, and the sheet catching plate is held horizontally in the holding position. Therefore, the sheet supplied by the supplying device is held from below by the sheet catching plate which is horizontally held, whereby the sheet is stably held above the stacking platform.
Therefore, the process of halting the sheet to a standstill or decelerating the sheet and dropping the sheet onto the stacking platform is more reliably carried out.
A fifth aspect of the present invention relates to the sheet stacking apparatus of the fourth aspect, wherein the sheet catching plate moves horizontally from the holding position to the withdrawal position.
In the sheet stacking apparatus, the sheet catching plate moves horizontally above the stacking platform for shifting it from the holding position to the withdrawal position, and thus, when the sheet catching plate is shifted from the holding position to the withdrawal position, it will not interfere with a sheet aligning guide member described later.
A sixth aspect of the present invention relates to the sheet stacking apparatus of the fourth aspect, wherein the sheet catching plate is rotated horizontally or downwardly from the holding position to the withdrawal position.
In the sheet stacking apparatus, the sheet catching plate is rotated from the holding position to the withdrawal position, and thus, the mechanism for shifting the sheet catching plate from the holding position to the withdrawal position can be simplified.
A seventh aspect of the present invention relates to the sheet stacking apparatus of the first aspect, wherein the sheet stacking apparatus of claim 1, wherein the sheet holding member is a pair of sheet catching rotating members that are provided so that a sheet supplying path is located therebetween, and rotate or turn around a rotation axis thereof extending along the sheet supplying direction; the sheet catching rotating members comprising one or more sheet catching faces which extend along the rotation axis; wherein the sheet catching rotating members catch a supplied sheet from below the sheet by the sheet catching face, and then rotate or turn around the rotation axis so as to drop the sheet held by the sheet catching face onto the stacking platform.
In the sheet stacking apparatus, the supplied sheet is caught by the sheet catching rotating members, and then the sheet catching rotating members rotate or turn to drop the supplied sheet onto the stacking platform, and thus, no mechanism for shifting the sheet catching plate from the holding position to the withdrawal position is required. Therefore, the entire configuration of the sheet stacking apparatus is further simplified.
An eighth aspect of the present invention relates to the sheet stacking apparatus of any one of the first to the seventh aspects, wherein the sheet holding device blows air upward, and catches the sheet that is supplied by the supplying device in a levitating state.
In the sheet stacking apparatus, the supplied sheet is caught in a non-contact mode by the sheet holding device, and thus, the sheet stacking apparatus can be exemplarily used for stacking of sheets such as laser exposure type planographic printing plates having a surface that is susceptible to damage.
A ninth aspect of the present invention relates to the sheet stacking apparatus of any one of the first to the eighth aspects, wherein the sheet stacking apparatus of any one of claims 1 to 8, wherein the sheet holding device blows air to the sheet supplied by the supplying device in a direction substantially the same as the sheet supplying direction and substantially parallel with the sheet, and catches the sheet in a levitating state.
In the sheet stacking apparatus, the supplied sheet is also caught in a non-contact mode by the sheet holding device. In addition, the sheet holding device blows air to the sheet supplied by the supplying device in a direction substantially the same as the sheet supplying direction and substantially parallel with the sheet, and thus, the sheet is caught with an even smaller impact than that in the sheet stacking apparatus of the eighth aspect.
A tenth aspect of the present invention relates to the sheet stacking apparatus of any one of the first to the ninth aspects, further comprising a sheet aligning device for aligning the sheets dropped on the stacking platform by the sheet holding device.
When a sheet is released from the sheet holding device and is dropped onto the stacking platform, the edge of the sheet may not be aligned with those of the sheets already stacked on the stacking platform.
However, in the sheet stacking apparatus, the sheet dropped onto the stacking platform is aligned by the sheet aligning device, and thus, the sheet is stacked on the stacking platform with the edge being aligned.
An eleventh aspect of the present invention relates to the sheet stacking apparatus of the tenth aspect, wherein the sheet aligning device is a pair of sheet aligning guide members which are provided so that the sheets stacked on the sheet stacking platform are located therebetween.
In the sheet stacking apparatus, when the sheet supplied by the supplying device is released, the sheet is dropped toward the stacking platform, being guided by the sheet aligning guide members. As a result, the sheet is stacked on the stacking platform with the edge being aligned.
A twelfth aspect of the present invention relates to the sheet stacking apparatus of the eleventh aspect, wherein at least one of the sheet aligning guide members is driven so as to approach and separate from the sheets stacked on the stacking platform.
In the sheet stacking apparatus, even when the sheets are stacked on the stacking platform without the edges being perfectly aligned, the sheet aligning guide member approaches or separates from the sheets stacked on the stacking platform, whereby the edges of the sheets stacked on the stacking platform are perfectly aligned.
A thirteenth aspect of the present invention relates to the sheet stacking apparatus of any one of the first to the twelfth aspects, wherein the sheet is a planographic printing plate.
The sheet stacking apparatus is an application of the sheet stacking apparatus of the present invention to stacking of planographic printing plates.
As described above, in the sheet stacking apparatus of the present invention, planographic printing plates are stacked on the stacking platform with a velocity thereof in the supplying direction being substantially zero, and thus, even when the planographic printing plates are stacked with no slip sheet, printing faces thereof will not be damaged.
A fourteenth aspect of the present invention relates to a sheet stacking method for positioning sheets sequentially supplied by a supplying device in a predetermined stacking position, and stacking the sheets in a pile, comprising: holding a sheet supplied by the supplying device above the stacking platform by a sheet holding device; and when the sheet comes to a standstill or is decelerated to a predetermined velocity or below, releasing the sheet held by the sheet holding device so as to drop the sheet onto the stacking platform.
As in the sheet stacking apparatus of the first aspect, in the sheet stacking method, the sheet supplied by supplying device is caught by the sheet holding device before being dropped onto the stacking platform, and thus, the sheet is set on the stacking platform with the kinetic energy thereof being reduced.
Accordingly, the sheet can be stacked without the surface thereof being scratched or damaged, and there is no need for changing the supplying condition or the stacking condition every time the size, the grade, the amount of curl, or the such as, of the sheet supplied is changed.
A fifteenth aspect of the present invention relates to the sheet stacking method of the fourteenth aspect, wherein the sheet is a planographic printing plate.
As described above, according to the sheet stacking method of the present invention, planographic printing plates are stacked on the stacking platform with a velocity thereof in the supplying direction being substantially zero, and thus, even when the planographic printing plates are stacked with no slip sheet, the printing faces thereof will not be damaged.
As described above, according to the present invention, a sheet stacking apparatus and a sheet stacking method with which a sheet can be stacked without any damage being caused thereto, and yet in which there is no need for changing the supplying condition or the stacking condition every time the size, the grade, the amount of curl, or the such as, of the sheet supplied is changed is provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective side view illustrating the configuration of a stacking apparatus of a first embodiment;

FIG 2 is a side view of the stacking apparatus of the first embodiment with a planographic printing plate being supplied;
FIG. 3A and FIG. 3B are plan views illustrating the motion of planographic printing plate holding plates in the stacking apparatus of the first embodiment;
FIG 4 is a perspective side view illustrating the configuration of a stacking apparatus of a second embodiment;
FIG. 5A and FIG 5B are plan views illustrating the motion of planographic printing plate holding plates in the stacking apparatus of the second embodiment;
FIG 6A and FIG. 6B are front views illustrating the motion of the planographic printing plate holding plates in the stacking apparatus of the second embodiment;
FIG 7 is a perspective side view illustrating the configuration of a stacking apparatus of a third embodiment;
FIG 8A and FIG 8B are plan views illustrating the motion of planographic printing plate holding plates in the stacking apparatus of the third embodiment;
FIG 9A and FIG 9B are front views illustrating the motion of the planographic printing plate holding plates in the stacking apparatus of the third embodiment.
FIG. 10 is a perspective side view illustrating the configuration of a stacking apparatus of a fourth embodiment;
FIG 11 is a front view illustrating the configuration of the stacking apparatus of the fourth embodiment;
FIG 12 is an explanatory drawing illustrating the relationship between a planographic printing plate and a planographic printing plate catching rotating member in the stacking apparatus of the fourth embodiment;
FIG 13 is an explanatory drawing illustrating the relationship between the planographic printing plate and the planographic printing plate catching rotating member in the stacking apparatus of the fourth embodiment; and
FIG 14 is a front view illustrating a first modification of the stacking apparatus of the fourth embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

1. First embodiment
Hereinbelow, a stacking apparatus for planographic printing plates that is one example of the sheet stacking apparatus of the present invention will be described.
As shown in FIG 1, a stacking apparatus 100 of a first embodiment comprises a back stopper 4 which catches a planographic printing plate P supplied by a belt conveyor 200 at the leading end part therof; an elevatable stacking platform 2 which is provided at the rear of the back stopper 4 with respect to the direction of supplying the planographic printing plate P indicated by the arrow 'a', and on which the planographic printing plate P caught by the back stopper 4 is stacked; a front stopper 6 located on the side opposite to the back stopper 4 with respect to the stacking platform 2; a pair of side stoppers 8 provided along both side edges of the stacking platform 2, holding the planographic printing plates P stacked on the stacking platform 2 from both sides; two pairs of planographic printing plate holding plates 10 provided above the side stoppers 8, taking either a holding position as indicated by solid lines or a withdrawal position as indicated by long dashed and double short dashed lines; and a sensor 12 provided in the vicinity of a belt conveyor 200 and optically detecting the planographic printing plate P. The planographic printing plate P is an example of the sheet which is stacked by the sheet stacking apparatus of the present invention, and the planographic printing plate holding plate 10 and the side stopper 8 are examples of the sheet holding plate and the sheet aligning guide member of the sheet stacking apparatus of the present invention, respectively.
Each planographic printing plate holding plate 10 is pivotally supported by a rotation axis 11, and turns around the rotation axis 11 in a horizontal plane to be shifted from the holding position to the withdrawal position, or from the withdrawal position to the holding position.
In the front stopper 6, a plurality of nozzle holes 7 that are slits opening in a horizontal direction are provided over the entire width. From the nozzle holes 7, air is blown out obliquely upward against the planographic printing plate P supplied by the belt conveyor 200 as shown in FIG. 2.
Although the side stoppers 8 can be fixed to the stacking platform 2 as shown in FIG. 1, the side stoppers 8 can be provided so as to approach or separate from the stacking platform 2 for aligning the edges of the planographic printing plate P stacked on the stacking platform 2 thereby.
Hereinbelow, the function of the stacking apparatus 100 is described.
When the sensor 12 detects a planographic printing plate P, as shown in FIG. 3A, each planographic printing plate holding plate 10 turns around the rotation axis 11 to be shifted from the withdrawal position to the holding position.
The planographic printing plate P supplied by the belt conveyor 200 is lifted at the tail end and central parts thereof by the air flow blown from the nozzle holes 7 in the front stopper 6, and is simultaneously caught by the planographic printing plate holding plates 10 in the holding position from below, and by the back stopper 4.
When the planographic printing plate P is caught by the planographic printing plate holding plates 10 and the back stopper 4, the planographic printing plate holding plates 10 turn around the rotation axes 11 in the directions of the arrows 'b' as shown in FIG. 3A substantially simultaneously, and are withdrawn from a position above the stacking platform 2 and shifted to the withdrawal position as shown in FIG 3B. And thus, the planographic printing plate P held by the planographic printing plate holding plates 10 is dropped and stacked on the planographic printing plates P stacked on the stacking platform 2. At the same time, air can be blown from the nozzle holes 7 to levitate the planographic printing plate P.
In the stacking apparatus 100 of the first embodiment, there is a significant relative velocity between the planographic printing plate P supplied by the belt conveyor 200 and the planographic printing plates P stacked on the stacking platform 2.
However, in the stacking apparatus 100 of the first embodiment, the supplied planographic printing plate P is detected by the sensor 12 to move the planographic printing plate holding plates 10 to the holding position for catching the planographic printing plate P from below, and when the relative velocity between the newly supplied planographic printing plate P and the planographic printing plates P stacked on the stacking platform 2 is reduced substantially to zero, the planographic printing plate holding plates 10 are moved to the withdrawal position so as to drop the planographic printing plate P onto the top of the planographic printing plates P stacked on the stacking platform 2.
Consequently, damage to a printing layer of the planographic printing plate P caused by rubbing of the planographic printing plate P that is newly supplied with the planographic printing plates P stacked on the stacking platform 2 can be effectively prevented, and thus, the stacking apparatus 100 of the first embodiment can be exemplarily used for stacking planographic printing plates P such as laser exposure type planographic printing plates, which are particularly susceptible to friction, with no use of slip sheets.
2. Second embodiment
As shown in FIG. 4 to FIG 6, in a stacking apparatus 102 of a second embodiment, two pairs of, i.e. four in total, planographic printing plate holding plates 20 are provided above the side stoppers 8.
Each planographic printing plate holding plate 20 is pivotally supported in parallel with the side stopper 8 at the outside thereof by a rotation axis 21 provided along a longer edge of the periphery of the stacking apparatus 102. The planographic printing plate holding plate 20 turns upward or downward around the rotation axis 21, taking either the holding position as indicated by solid lines or the withdrawal position as indicated by long dashed and double short dashed lines in FIG 4. The planographic printing plate holding plate 20 is held horizontally in the holding position, and vertically in the withdrawal position. The side stopper 8 is provided in a location at which rotation of the planographic printing plate holding plate 20 is not interfered with, or cutouts are provided in the side stopper so as not to interfere rotation of the planographic printing plate holding plate 20.
The stacking apparatus 102 has the same configuration as that of the stacking apparatus 100 of the first embodiment, except for the above-mentioned features.
Hereinbelow, the function of the stacking apparatus 102 is described.
When the sensor 12 detects a planographic printing plate P, each of the planographic printing plate holding plates 20 turns around the rotation axis 21 to be shifted from the withdrawal position to the holding position as shown in FIG. 5A and FIG. 6A.
The planographic printing plate P supplied by the belt conveyor 200 is lifted by the flow of air blown from the nozzle holes 7 in the front stopper 6 at the rear part thereof, and is simultaneously caught by the planographic printing plate holding plates 20 in the holding position from below.
When the planographic printing plate P is caught by the planographic printing plate holding plates 20, each of the planographic printing plate holding plates 20 turns around the rotation axis 21 in the direction of the arrow 'c' as shown in FIG. 5A and FIG 6A, being withdrawn from a position above the stacking platform 2 to the withdrawal position as shown in FIG. 5B and FIG. 6B. As a result, the planographic printing plate P held by the planographic printing plate holding plates 20 is dropped and stacked on the planographic printing plates P stacked on the stacking platform 2.
In addition to the same merit as those of the stacking apparatus 100 of the first embodiment, the stacking apparatus 102 has a merit in that the space for the planographic printing plate holding plates 20 can be reduced because the planographic printing plate holding plates 20 are shifted from the holding position to the withdrawal position or from the withdrawal position to the holding position by rotating upward or downward.
3. Third embodiment
As shown in FIG. 7, FIG. 8A, FIG. 8B, FIG 9A, and FIG. 9B, in a stacking apparatus 104 of a third embodiment, two planographic printing plate holding plates 30 are provided above each respective side stopper 8 (thus, four planographic printing plate holding plates 30 are provided in total).
Each planographic printing plate holding plate 30 takes either a holding position at which the planographic printing plate holding plate 30 is located just above the stacking platform 2, or a withdrawal position at which the planographic printing plate holding plate 30 is located outside the stacking platform 2. In FIG.7, the planographic printing plate holding plate 30 in the holding position is indicated with solid lines, and the planographic printing plate holding plate 30 in the withdrawal position is indicated with long dashed, double short dashed lines. The planographic printing plate holding plate 30 is shifted from the holding position to the withdrawal position or from the withdrawal position to the holding position, by moving in a direction perpendicular to the supplying direction 'a' of the planographic printing plate P.
The stacking apparatus 104 has the same configuration as that of the stacking apparatus 100 of the first embodiment, except for the above-mentioned features.
Hereinbelow, the function of the stacking apparatus 104 is described.
When the sensor 12 detects a planographic printing plate P, each of the planographic printing plate holding plates 30 moves to the position above the stacking platform 2 to be shifted from the withdrawal position to the holding position as shown in FIG. 8A and FIG 9A.
The planographic printing plate P supplied by the belt conveyor 200 is lifted by the flow of air blown from the nozzle holes 7 in the front stopper 6 at the rear part, and is simultaneously caught by the planographic printing plate holding plates 30 in the holding position from below.
When the planographic printing plate P has been caught by the planographic printing plate holding plates 30 as shown in FIG. 8A and FIG. 9A, the planographic printing plate holding plates 30 move toward the outside so as to be shifted to the withdrawal position as shown in FIG. 8B and FIG 9B. As a result, the planographic printing plate P held by the planographic printing plate holding plates 30 is dropped and stacked on the planographic printing plates P stacked on the stacking platform 2.
The stacking apparatus 104 has the same merits as those of the stacking apparatus 100 of the first embodiment.
4. Fourth embodiment
As shown in FIG. 10 and FIG 11, in a stacking apparatus 106 of a fourth embodiment, a planographic printing plate catching rotating member 40 is provided above each of the stoppers 8 along the whole length thereof(thus, two planographic printing plate catching rotating members 40 are provided in total). The planographic printing plate catching rotating member 40 corresponds to the sheet catching rotating member in the sheet stacking apparatus of the present invention.
The planographic printing plate catching rotating member 40 is a bar-shaped rotating member rotating around a rotation axis 44 extending along the longitudinal direction, and four wedge-shaped planographic printing plate catching flanges 42 which continually extend along the longitudinal direction are protruded at equal intervals. The planographic printing plate catching flange 42 corresponds to the sheet catching face in the present invention. The planographic printing plate catching rotating members 40 are disposed such that the distance between the rotation axes 44 is larger than the width of the planographic printing plate P, and the distance between the tips of the planographic printing plate catching flanges 42 of each planographic printing plate catching rotating member 40, when the planographic printing plate catching flanges 42 are held horizontally pointing inward, is smaller than the width of the planographic printing plate P.
The planographic printing plate catching rotating member 40 can be provided with a rotation axis 44 that is hollow and connected to a blower 46 through a piping 45 so that the air supplied by the blower 46 is blown from the surface of the planographic printing plate catching flange 42, as shown in FIG. 14, which allows the planographic printing plate P to be caught in non-contact mode.
The stacking apparatus 106 has the same configuration as that of the stacking apparatus 100 of the first embodiment, except for the above-mentioned features.
Hereinbelow, the function of the stacking apparatus 106 is described.
When the sensor 12 detects a planographic printing plate P conveyed by the belt conveyor 200, each of the planographic printing plate catching rotating members 40 rotates around the rotation axis 44 so that one of the four planographic printing plate catching flanges 42 which is positioned inside is held horizontally as shown in FIG. 10 and FIG. 11. Hereinafter, the planographic printing plate catching flanges 42 positioned inside is referred to as a 'planographic printing plate catching flange 42A'.
Therefore, the planographic printing plate P supplied by the belt conveyor 200 is caught from below by the planographic printing plate catching flange 42A as indicated by long dashed and double short dashed lines in FIG 11.
When the planographic printing plate P is caught by the planographic printing plate catching flange 42A, the planographic printing plate catching rotating member 40 rotates by 90 degrees in an inward direction as indicated by the arrow 'd' in FIG 12 so that the planographic printing plate catching flange 42A is directed downward. And thus, the planographic printing plate P which is held from below by the planographic printing plate catching flanges 42A is dropped on the stacking platform 2 as shown in FIG 13.
The stacking apparatus 106 has the same features as those of the stacking apparatus 100. Further, planographic printing plate catching rotating member 40 which catches the planographic printing plate P can be provided along the side stopper 8, and thus, the stacking apparatus 106 can be configured compactly in both horizontal and vertical directions compared with a stacking apparatus having planographic printing plate catching plates.
The sheet stacking apparatus and the sheet stacking method of the present invention can be applied to stacking of planographic printing plates of photosensitive type, heat-sensitive type, and laser exposure type, and besides this, for stacking of metallic sheets, such as aluminum sheets, stainless steel sheets, plain steel sheets, high tensile strength steel sheets, and the such as; coated iron plates, various plastic sheets, and papers.
The foregoing description of the embodiments of the present invention has been provided for the purpose of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.

Claims

A sheet stacking apparatus that positions sheets which are sequentially supplied by a supplying device in a predetermined stacking position, and stacks them in a pile, comprising:
a stacking platform on which the sheets supplied by the supplying device are stacked, and

a sheet holding device that catches a sheet that is supplied by the supplying device above the stacking platform, and after catching the sheet, releases the sheet so as to be dropped onto the stacking platform.
The sheet stacking apparatus of claim 1, wherein after the sheet caught by the sheet holding device comes to a standstill or is decelerated to a predetermined velocity or below, the sheet holding device releases the sheet so that the sheet drops onto the stacking platform.
The sheet stacking apparatus of claim 1 or 2, wherein the sheet holding device comprises a sheet holding member which takes either a holding position at which the sheet holding member is located above the stacking platform so as to catch the sheet supplied by the supplying device from below, or a withdrawal position at which the sheet holding member is withdrawn from the stacking platform.
The sheet stacking apparatus of claim 3, wherein the sheet holding member is a sheet catching plate, and the sheet catching plate is held horizontally above the stacking platform in the holding position.
The sheet stacking apparatus of claim 4, wherein the sheet catching plate moves horizontally from the holding position to the withdrawal position.
The sheet stacking apparatus of claim 4, wherein the sheet catching plate is rotated horizontally or downwardly from the holding position to the withdrawal position.
The sheet stacking apparatus of claim 1, wherein the sheet holding member is a pair of sheet catching rotating members that are provided so that a sheet supplying path is located therebetween, and rotate or turn around a rotation axis thereof extending along the sheet supplying direction; the sheet catching rotating members comprising one or more sheet catching faces which extend along the rotation axis; wherein the sheet catching rotating members catch a supplied sheet from below the sheet by the sheet catching face, and then rotate or turn around the rotation axis so as to drop the sheet held by the sheet catching face onto the stacking platform.
The sheet stacking apparatus of any one of claims 1 to 7, wherein the sheet holding device blows air upward, and catches the sheet that is supplied by the supplying device in a levitating state.
The sheet stacking apparatus of any one of claims 1 to 8, wherein the sheet holding device blows air to the sheet supplied by the supplying device in a direction substantially the same as the sheet supplying direction and substantially parallel with the sheet, and catches the sheet in a levitating state.
The sheet stacking apparatus of any one of claims 1 to 9, further comprising a sheet aligning device for aligning the sheets dropped onto the stacking platform by the sheet holding device.
The sheet stacking apparatus of claim 10, wherein the sheet aligning device is a pair of sheet aligning guide members which are provided so that the sheets stacked on the sheet stacking platform are located therebetween.
The sheet stacking apparatus of claim 11, wherein at least one of the sheet aligning guide members is driven so as to approach and separate from the sheets stacked on the stacking platform.
The sheet stacking apparatus of any one of claims 1 to 12, wherein the sheet is a planographic printing plate.
A sheet stacking method for positioning sheets sequentially supplied by a supplying device in a predetermined stacking position, and stacking the sheets in a pile, comprising:
holding a sheet supplied by the supplying device above a stacking platform by a sheet holding device; and

when the sheet comes to a standstill or is decelerated to a predetermined velocity or below, releasing the sheet held by the sheet holding device so as to drop the sheet onto the stacking platform.
The sheet stacking method of claim 14, wherein the sheet is a planographic printing plate.