SHEET HEAPING NIP ROLLS

Abstract: A pair of sheet heaping nip rolls are installed near and above an end portion of an approximately horizontal tray for loading sheet members into the tray. The nip rolls are positioned so that the angle between the plane in which the rotation axes of the nip rolls lie and a surface of the tray on which the sheet members are heaped up on the downstream side of the nip rolls in the sheet feeding direction is obtuse. The sheet members are delivered upwardly from the nip rolls and prevented from being scratched due to friction with a sheet member previously loaded into the tray.

Description: BACKGROUND OF THE INVENTION Field of the Invention This invention relates to sheet heaping nip rolls for loading sheet members one by one into trays for storing therein a stack of sheet members. This invention particularly relates to sheet heaping nip rolls for handling the sheet members used repeatedly, such as stimulable phosphor sheets. Description of the Prior Art When certain kinds of phosphors are exposed to a radiation such as X-rays, a-rays, trays, y-rays or ultraviolet rays, they store a part of the energy of the radiation. Then, when the phosphor which has been exposed to the radiation is exposed to stimulating rays such as visible light, light is emitted from the phosphor in proportion to the stored energy of the radiation. A phosphor exhibiting such properties is referred to as a stimulable phosphor. As disclosed in U.S. Patent No. 4,258,264 and Japanese Unexamined Patent Publication No. 56(1981)-11395, it has been proposed to use a stimulable phosphor in a radiation image recording and reproducing system. Specifically, a sheet provided with a layer of the stimulable phosphor (hereinafter referred to as a stimulable phosphor sheet or simply as a sheet) is first exposed to a radiation passing through an object to have a radiation image stored therein, and is then scanned with stimulating rays such as a laser beam which cause it to emit light in the pattern of the stored image. The light emitted from the stimulable phosphor sheet upon stimulation thereof is photoelectrically detected and converted to an electric image signal, which is processed as desired to reproduce a visible image on a recording medium such as a photographic light-sensitive material or on a display device such as a cathode ray tube (CRT). This radiation image recording and reproducing system using the stimulable phosphor sheet is advantageous over conventional---radiography--using a silver halide photographic material in that the image can be recorded over a very wide range (latitude) of radiation exposure and further in that -the electric s-ignslased for#reproducing the visible image can be freely processed to improve the image quality for viewing, particularly for diagnostic purposes. In more detail, since the amount of light emitted upon stimulation after the radiation energy is stored in the phosphor varies over a very wide range in proportion to the amount of energy stored therein, it is possible to obtain an image having desired density regardless of the amount of exposure of the phosphor to the radiation by reading out the emitted light with an appropriate read-out gain and converting it to an electric signal to reproduce a visible image on a recording medium or a display device. The electric signal may further be processed as desired to obtain a radiation image suitable for viewing, particularly for diagnostic purposes. This is very advantageous in practical use. The stimulable phosphor sheets used in the aforesaid radiation image recording and reproducing system are handled in the form housed in a cassette for containing a single stimulable phosphor sheet or in a magazine for containing many stimulable phosphor sheets. After radiation images are stored in the stimulable phosphor sheets, the cassettes or the magazine containing the stimulable phosphor sheets carrying the radiation images stored therein is loaded into a sheet feeding apparatus, i.e. a cassette feeder or a magazine feeder, from which the stimulable phosphor sheets are fed one by one to a radiation image read-out apparatus. After the radiation images stored in the stimulable phosphor sheets are read out in the read-out apparatus, the radiation energy remaining in the stimulable phosphor sheets is erased in an image erasing apparatus, and the stimulable phosphor sheets are reused for recording of radiation images. In the aforesaid radiation image recording and reproducing system, trays for storing a stack of the stimulable phosphor sheets are usually used, for example, for collecting the sheets ejected from the image erasing apparatus or for temporarily storing the sheets conveyed in the radiation image read-out apparatus. -Specifically, the stimulable phosphor sheets of various sizes are used according to the area of the portion of the object to be recorded. These stimulable phosphor sheets are fed at random to the radiation image recording and reproducing system, and thereafter put together according to the sheet size in several kinds of trays. In order to install many trays in the same position and thereby to minimize the space for installing the trays, it is desired to horizontally position the respective trays. Normally, the stimulable phosphor sheets are loaded into each tray by use of a pair of nip rolls exactly vertically positioned one upon the other near and above an end portion of the horizontal tray. However, when the stimulable phosphor sheet is loaded into the tray by the nip rolls of this type, the sheet rubs against and scratches a sheet already loaded into the tray. Scratches of the sheet present a serious problem particularly when the sheet should be used repeatedly. Figure 1 is a sectional side view showing the conventional sheet heaping nip rolls. In Figure 1, a pair of rolls 1A and 1B are exactly vertically positioned one upon the other so that the plane in which the rotation axes of the rolls 1A and 1B lie is normal to the bottom surface of a tray 4. Therefore, approximately the whole weight of a sheet 3 delivered from the rolls 1A and 1B is exerted on a sheet 3' already loaded into the tray 4 via a front end portion of the sheet 3. In this case, since the front end portion of the sheet 3 exerts a large surface pressure on the upper surface of the sheet 3', the lower surface of the sheet 3 and the upper surface of the sheet 3' are readily scratched by friction therebetween. SUMMARY OF THE INVENTION The primary object of the present invention is to provide sheet heaping nip rolls which prevent sheet members from being scratched by friction therebetween when the sheet members are delivered from the nip rolls and heaped up in a tray. Another object of the present invention is to provide sheet heaping nip rolls which has a very simple construction and is advantageous for preventing the surfaces of stimulable phosphor sheets used repeatedly for image recording from being scratched by friction between the surfaces of the sheets when the sheets are delivered from the nip rolls and heaped up in a tray. The sheet heaping nip rolls in accordance with the present invention are characterized by being positioned so that the angle between the plane in which the rotation axes of the nip rolls lie and a surface of a tray on which the sheets are heaped up on the downstream side of the nip rolls in the sheet feeding direction is obtuse. In the present invention, since a pair of nip rolls are positioned as described above, each sheet is delivered upwardly from the nip rolls, and the portion of the sheet delivered from the rolls extends in the arch-like form by the action of rigidity of the sheet while the remaining portion of the sheet is supported between the rolls. Accordingly, when the front end portion of the sheet comes into contact with a sheet previously loaded into the tray, the weight of the sheet being delivered from the rolls is shared between the front end portion of the sheet and the rolls. As a result, the surface pressure exerted to the sheet previously loaded into the tray by the front end portion of the sheet being delivered from the rolls is decreased. Further, since the front end portion of the sheet being delivered from the rolls comes into contact with the sheet in the tray at a position far from the rolls, the area over which the sheets rub against each other is minimized. Thus the sheet heaping nip rolls in accordance with the present invention have a very simple construction and are advant2gçus dor-p;reventing the -surfa#es of sheet members, particularly the surfaces of stimulable phosphor sheets used repeatedly for image recording, from being scratched by friction between the surfaces when the sheet members are delivered from the nip rolls and heaped up in a tray. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a sectional side view showing the conventional sheet heaping nip rolls, Figure-2 is a schematic view showing a radiation image read-out system in which an embodiment of the sheet heaping nip rolls in accordance with the present invention is employed, and Figure 3 is a detailed sectional side view showing the embodiment of the sheet heaping nip rolls shown in Figure 2. DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will hereinbelow be described in further detail with reference to the accompanying drawings. Figure 2 shows a radiation image read-out system in which an embodiment of the sheet heaping nip rolls in accordance with the present invention is employed. A cassette 13 housing a stimulable phosphor sheet 12 carrying a radiation image stored therein is loaded into a cassette loading section 11 of a cassette feeder 10. Then, the sheet 12 is sucked by a suction arm 14 and taken out of the cassette 13. The suction arm 14 is moved to introduce the front end of the sheet 12 (i.e. the lower end thereof in the drawing) to the section between a pair of endless belts 15, and then air suction of the suction arm 14 is stopped. The sheet 12 is sent by the endless belts 15 to an outlet 17 via a pair of nip rolls 16, and ejected from the outlet 17. At the outside of the outlet 17 is positioned a sheet inlet 21 of a radiation image read-out apparatus 20. The sheet 12 ejected from the outlet 17 of the cassette feeder 10 is introduced from the sheet inlet 21 into the radiation image read-out apparatus 20, and placed on a horizontal conveying belt 22 in the apparatus 20. Above the horizontal conveying belt 22 is positioned an image read-out system 23 for scanning the sheet 22 with stimulating rays such as laser beams which cause the sheet 12 to emit light in proportion to the radiation energy stored therein, and photoelectrically reading out the emitted light. While the sheet 12 is conveyed by the horizontal conveying belt 22, the radiation image stored in the sheet 12 is read out by the image read-out system 23. After the radiation image read-out is finished, the sheet 12 is ejected from a sheet outlet 24 and introduced into an image erasing apparatus 30 via a sheet inlet 31. While the sheet 12 is conveyed by a horizontal conveying belt 32 in the image erasing apparatus 30, the sheet 12 is exposed to erasing light emitted from an erasing light source 33 positioned above the horizontal conveying belt 32, and the radiation energy remaining in the sheet 12 is thereby erased. The erasing light source 33 emits light having a wavelength distribution within the stimulation-wa-v#elength range of the stimulable phosphor of the sheet 12, thereby to release the radiation energy remaining in the stimulable phosphor of the sheet 12. The erasing light source 33 may, for example, be a tungsten-filament lamp, a halogen lamp, an infrared lamp, or a laser beam source, as disclosed in Japanese Unexamined Patent Publication No. 56(1981)-11392. Since the radiation energy stored in the stimulable phosphor can be released also by heating the stimulable phosphor as described in Japanese Unexamined Patent Publication No. 56(198I)-l2599, the erasing light source 33 may be replaced by a heating means. After the radiation energy remaining in the sheet 12 is erased, the sheet 12 is ejected from the image erasing apparatus 30 via an outlet 34 and introduced into a sheet heaping apparatus 40 via a sheet inlet 41. In the sheet heaping apparatus 40, the sheet 12 is conveyed by an elevator 42 to the position of a tray 47, 48, 49 or 50, for example, according to the size of the sheet 12. The trays 47, 48, 49 and 50 are respectively provided with sheet heaping nip rolls 43, 44, 45 and 46. The condition of the sheet 12 heaped up in the tray by the sheet heaping nip rolls will be described in detail below with reference to Figure 3. The sheet heaping nip rolls 43 comprise a pair of nip rolls 43A and 43B positioned near and above the front end portion of the tray 47 which is positioned approximately horizontally. (When the tray is positioned horizontally, it becomes possible to install many trays in the sheet heaping apparatus 40.) The nip rolls 43A and 43B are rotated by a drive unit (not shown) in the directions of the arrows indicated at the nip rolls 43A and 43B in Figure 3 to load the sheet 12 into the tray 47. The pair of nip rolls 43A and 43B are positioned so that an angle t between a plane P, in which a rotation axis 0 of the roll 43A and the rotation axis 0' of the roll 43B lie, and a bottom surface 47a of the tray 47 on the downstream side of the nip rolls 43A and 43B in the sheet feeding direction is obtuse (i.e. t > 90 ). Accordingly, the sheet 12 is delivered upwardly from the nip rolls 43A and 43B. When the length of the portion of the sheet 12 delivered from the nip rolls 43A and 43B becomes long, the delivered portion of the sheet 12 is bent by the weight thereof, and the front end portion of the sheet 12 comes into contact with an uppermost sheet 12' among the sheets previously loaded into the tray 47. That is, the sheet 12 is bent in the arch-like form while the front end portion thereof is supported by the sheet 12' and the rear end portion is supported by the nip rolls 43A and 43B. This condition of the sheet 12 is maintained until the sheet 12 is completely delivered from the nip rolls 43A and 43B and the rear end portion of the sheet 12 falls onto the sheet 12'. While the sheet 12 is delivered in the archlike form from the nip rolls 43A and 43B, the front end portion of the sheet 12 slides on the sheet 12' from the left side to the right side in Figure 3. However, since the weight of the sheet 12 is shared between the front end portion of the sheet 12 and the pair of the nip rolls 43A and 43B, the force of the front end portion of the sheet 12 pressing the upper surface of the sheet 12' is not so large. Therefore, the lower surface of the sheet 12 and/or the upper surface of the sheet 12' are not scratched due to friction therebetween. Further, since the front end portion of the sheet 12 bent in the arch-like form comes into contact with the sheet 12' at a position farther from the nip rolls 43A and 43B than in the case where the conventional apparatus as shown in Figure 1 is used, the area over which the sheets 12 and 12' rub against each other becomes smaller than in the case of the conventional apparatus. This also contributes to the prevention of scratching of the sheets 12 and 12'. In the embodiment as described above, good results were obtained when stimulable phosphor sheets having a size of 356mm x 432mm (thickness: about 500p, weight: about 200g, deflection when the sheet is supported at one end with a 200mm length portion thereof being overhung: about 100mm) were used, the tray 47 was 440mm long and 360mm wide, the distance from the bottom surface 47a of the tray 47 to the nip point between the nip rolls 43A and 43B was 50mm, the angle t was within the range of 950 to 1200 so that the sheet 12 was delivered upwardly at an angle within the range of 5 to 300 with respect to the tray bottom surface 47a from the nip rolls 43A and 43B. In the above-described embodiment, the present invention is applied to the sheet feeding nip rolls for heaping the.stimulable phosphor sheets in the trays 47, 48, 49 and 50 after the radiation images stored in the sheets are erased. However, the present invention can be applied to the sheet heaping nip rolls for any other trays on which the stimulable phosphor sheets are heaped, such as the trays for temporarily storing some sheets conveyed in the radiation image read-out apparatus for the purpose of preferentially processing other sheets.

Claims: CLAIMS 1. A pair of sheet heaping nip rolls for loading sheet members into a tray positioned approximately horizontally, wherein the improvement comprises positioning said nip rolls so that the angle between the plane in which the rotation axes of said nip rolls lie and a surface of said tray on which said sheet members are heaped up on the downstream side of said nip rolls in the sheet feeding direction is obtuse. 2.. A pair of sheet heaping nip rolls as defined in Claim 1 wherein said nip rolls are positioned near and above an end portion of said tray. 3. A pair of sheet heaping nip rolls as defined in Claim 1 wherein said angle is within the range of 950 to 1200. 4. A pair of sheet heaping nip rolls as defined in Claim 1 wherein said sheet members are stimulable phosphor sheets used in a radiation image recording and reproducing system.

Inventors: KOHKETSU, KAZO C/O FUJI PHOTO FILM CO., LTD.
Applicants: FUJI PHOTO FILM CO., LTD.
Application year: 1983
Main classification: B65H29
IPC codes: G03G15, B65H29