Sheet feed mechanism and method of controlling the same in light beam scanning apparatus

A sheet feed mechanism in a light scanning apparatus includes two pairs of rollers for gripping and feeding a sheet-like medium such as a stimulable phosphor sheet or a photographic film in a subscanning direction. The two pairs of rollers are spaced a distance smaller than the length of the sheet-like medium in the subscanning direction. While the sheet-like medium is being fed by the sheet feed mechanism in the subscanning direction, the sheet-like medium is scanned by a light beam deflected in a main scanning direction substantially normal to the subscanning direction, for thereby two-dimensionally scanning the sheet-like medium.

BACKGROUND OF THE INVENTION 
The present invention relates to a sheet feed mechanism and a method of 
controlling the same in a light beam scanning apparatus, and more 
particularly to a sheet feed mechanism and a method of controlling the 
same for two-dimensionally scanning a sheet with a light beam, e.g., for 
applying stimulating light to a stimulable phosphor sheet with a radiation 
image recorded thereon to read the recorded image from the sheet, or for 
applying a light beam to a photographic photosensitive material in the 
form of a sheet film to record an image thereon. 
There has recently been developed and widely used a radiation image 
recording and reproducing system for producing the radiation-transmitted 
image of an object using a stimulable phosphor material capable of 
emitting light upon exposure to stimulating rays. When a stimulable 
phosphor is exposed to a radiation such as X-rays, .alpha.-rays, 
.beta.-rays, .gamma.-rays, cathode rays, or ultraviolet rays, the phosphor 
stores a part of the energy of the radiation. When the phosphor exposed to 
the radiation is subsequently exposed to stimulating rays such as visible 
light, the phosphor emits light in proportion to the stored energy of the 
radiation. 
In the radiation image recording and reproducing system employing such a 
stimulable phosphor, the radiation image information of an object such as 
a human body is stored in a sheet having a layer of stimulable phosphor 
(hereinafter referred to as a "stimulable phosphor sheet" or simply a 
"sheet"), and then the stimulable phosphor sheet is scanned with 
stimulating rays to cause the stimulable phosphor sheet to emit light 
representative of the radiation image. The emitted light is then 
photoelectrically detected to produce an image signal that is electrically 
processed for generating image information which is recorded on a 
recording medium such as a photographic photosensitive material or 
displayed as a visible image on a CRT or the like. 
The radiation image recording and reproducing system includes an image 
readout device for reading a radiation image from a stimulable phosphor 
sheet. More specifically, the stimulable phosphor sheet is 
two-dimensionally scanned by a laser beam, and light emitted from the 
sheet upon exposure to the laser beam is detected on a time-series basis 
by a light detector such as a photomultiplier which produces an image 
signal representative of the image information. The stimulable phosphor 
sheet is two-dimensionally scanned by the laser beam by deflecting the 
laser beam one-dimensionally over the sheet in a main scanning direction 
and simultaneously feeding the sheet mechanically with a feed mechanism 
such as an endless belt conveyor in a subscanning direction normal to the 
main scanning direction. 
The image information thus obtained from the stimulable phosphor sheet is 
then fed to an image recording device. The image recording device applies 
a laser beam modulated by the image information to a recording medium such 
as a photographic photosensitive material to record the image thereon. The 
image recorded on the photographic photosensitive material is thereafter 
developed, and the photographic photosensitive material is stored in a 
suitable location for use in medical diagnosis as required. 
The stimulable phosphor sheet fed by the belt conveyor in the image readout 
device must be positioned stably on the belt conveyor. If the stimulable 
phosphor sheet were displaced on the belt conveyor during the scanning 
thereof, the light beam applied to the sheet would be displaced out of a 
desired position. As a result, if the stimulable phosphor sheet displaced 
on the belt conveyor were continuously scanned by the laser beam, image 
information obtained from the sheet would be inaccurate. Stated otherwise, 
no accurate radiation image information could be produced from the 
stimulable phosphor sheet suffering from a positional error. When the 
imaged object is a patient, a diagnostic error would tend to result from 
such inaccurate image information. 
One conventional solution has been to use a suction box for holding a 
stimulable phosphor sheet being scanned stably on the belt conveyor 
without unwanted displacement. The suction box is positioned in a central 
space in the endless belt conveyor, and has a plurality of suction holes. 
When the stimulable phosphor sheet is delivered onto the belt conveyor, a 
vacuum generator coupled to the suction box is actuated to develope a 
vacuum in the suction box to attract the sheet under suction through the 
suction holes, thereby positioning the sheet stably on the belt conveyor. 
Therefore, the stimulable phosphor sheet is conveyed with the belt 
conveyor as it is moved in the subscanning direction. 
The suction box however makes the feed mechanism complex and large, and 
requires the vacuum generator to enable the suction box to attract the 
sheet and also a control system for controlling the vacuum generator. The 
sheet positioning and feeding means of this construction is considerably 
costly, and so is the radiation image recording and reproducing system. 
Another problem is that a feed path must be provided for feeding the 
stimulable phosphor sheet onto the belt conveyor in a direction parallel 
thereto in order to atract the sheet effectively on the belt conveyor. The 
radiation image recording and reproducing system with such a feed path is 
necessarily large in size. Where the system is installed in a hospital, 
for example, the size of the system makes it difficult to effectively 
utilize the space of a room in which it is located. 
In the image recording device, the photographic photosensitive material is 
scanned in a main scanning direction by the laser beam which is modulated 
by the image information and cyclically deflected. At same time, the 
photographic photosensitive material is gripped between a large-diameter 
drum coupled to a rotative drive source and a pair of rollers on the drum 
and is fed thereby in a subscanning direction substantially normal to the 
main scanning direction. 
The rotative drive source, such as a motor, for rotating the drum may be 
subjected to a load variation which leads to a failure of desired 
subscanning of the photographic photosensitive material. 
Heretofore, any variations in the load on the motor during the subscanning 
process have been minimized by support bases disposed in front of and 
behind the drum in the subscanning direction. Each of the support bases 
must be of a length at least equal to or greater than the length of the 
photographic photosensitive material in the subscanning direction. 
Therefore, the image recording device is considerably large in size. 
The drum has a width larger than the width of the photographic 
photosensitive material so as to be capable of stably feeding the 
material. Since the motor is disposed on one side of the drum in the 
direction of the width thereof, the image recording device is also of a 
large extent in the main scanning direction. For scanning the photographic 
photosensitive material highly accurately, it is necessary to control the 
motor highly precisely in order to convey the photographic photosensitive 
material at a constant speed in an accurate direction. Inasmuch as a motor 
capable of being controlled highly precisely is expensive, the cost of the 
image reading device is high. 
The roller pair on the drum is required to feed the photographic 
photosensitive material stably. The roller pair however presents an 
obstacle to the scanning of the photographic photosenitive material at its 
opposite ends in the subscanning direction, failing to meet the demand to 
surround the produced image with a black frame or edge. 
SUMMARY OF THE INVENTION 
In view of the drawbacks of the conventional sheet feed mechanisms, it is 
an object of the present invention to provide a sheet feed mechanism and a 
method of controlling the same in a light beam scanning apparatus, wherein 
two pairs of rollers for gripping and feeding a sheet-like medium being 
scanned, such as a stimulable phosphor sheet or a photographic 
photosensitive material, are disposed at a spacing smaller than the length 
of the sheet-like medium in the direction in which it is fed along, the 
roller pairs being synchronously rotatable, so that the sheet-like medium 
can be fed along accurately and smoothly in a subscanning direction by a 
simple and small feed structure for reading an image on or recording an 
image on the sheet-like medium. 
According to the present invention, the above object can be achieved by a 
sheet feed mechanism in a light scanning apparatus for scanning a 
sheet-like medium in a main scanning direction with a light beam which is 
deflected one-dimensionally and scanning the sheet-like medium in a 
subscanning direction by feeding the sheet-like medium in a direction 
substantially normal to the main scanning direction, for thereby 
two-dimensionally scanning the sheet-like medium, the sheet feed mechanism 
comprising two pairs of rollers for gripping and feeding the sheet-like 
medium, the two pairs of rollers being disposed at a spacing smaller than 
the length of the sheet-like medium in the direction in which the 
sheet-like medium is fed, the two pairs of rollers being synchronously 
rotatable for scanning the sheet-like medium in the subscanning direction, 
the light beam which is deflected being applicable to the sheet-like 
medium between the pairs of rollers for scanning the sheet-like medium in 
the main scanning direction. 
According to the present invention, there is also provided a sheet feed 
mechanism in a light scanning apparatus for scanning a sheet-like medium 
in a main scanning direction with a light beam which is deflected 
one-dimensionally and scanning the sheet-like medium in a subscanning 
direction by feeding the sheet-like medium in a direction substantially 
normal to the main scanning direction, for thereby two-dimensionally 
scanning the sheet-like medium, the sheet feed mechanism comprising two 
pairs of rollers for gripping and feeding the sheet-like medium, the two 
pairs of rollers being disposed at a spacing smaller than the length of 
the sheet-like medium in the direction in which the sheet-like medium is 
fed, an actuator for displacing one of the rollers of one of the pairs 
toward the other roller, and control means for controlling the actuator to 
displace said one roller at a prescribed speed. 
According to the present invention, there is also provided a sheet feed 
mechanism in a light scanning apparatus for scanning a sheet-like medium 
in a main scanning direction with a light beam which is deflected 
one-dimensionally and scanning the sheet-like medium in a subscanning 
direction by feeding the sheet-like medium in a direction substantially 
normal to the main scanning direction, for thereby two-dimensionally 
scanning the sheet-like medium, the sheet feed mechanism comprising two 
pairs of rollers for gripping and feeding the sheet-like medium, the two 
pairs of rollers being disposed at a spacing smaller than the length of 
the sheet-like medium in the direction in which the sheet-like medium is 
fed, a pair of resilient members engaging opposite ends, respectively, of 
a rotatable shaft of one of the rollers of at least one of the pairs, and 
an actuator for displacing said one roller toward the other roller through 
the resilient members. 
According to the present invention, there is also provided a sheet feed 
mechanism in a light scanning apparatus for scanning a sheet-like medium 
in a main scanning direction with a light beam which is deflected 
one-dimensionally and scanning the sheet-like medium in a subscanning 
direction by feeding the sheet-like medium in a direction substantially 
normal to the main scanning direction, for thereby two-dimensionally 
scanning the sheet-like medium, the sheet feed mechanism comprising a pair 
of rollers for gripping and feeding the sheet-like medium, the rollers 
being spaced from each other by a clearance smaller than the thickness of 
the sheet-like medium, displacing means for displacing one of the rollers 
to ihcrease the clearance, the rollers comprising a first roller and a 
second roller fitted in a guide hole for defining the clearance between 
the first and second rollers, a rotative drive source operatively coupled 
to the first roller for rotating the same, pressing means for pressing the 
second roller toward the first roller, the arrangement being such that the 
second roller can be displaced along the guide hole by the displacing 
means against the pressing force of the pressing means for thereby 
increasing the clearance between first and second rollers. 
According to the present invention, there is also provided a sheet feed 
mechanism in a light scanning apparatus for scanning a sheet-like medium 
in a main scanning direction with a light beam which is deflected 
one-dimensionally and scanning the sheet-like medium in a subscanning 
direction by feeding the sheet-like medium in a direction substantially 
normal to the main scanning direction, for thereby two-dimensionally 
scanning the sheet-like medium, the sheet feed mechanism comprising a pair 
of rollers for gripping and feeding sheet-like mediums of different sizes, 
a guide member for aligning the sheet-like mediums on one side thereof, 
and means for biasing the rollers to impose a greater pressure on said one 
side than on an opposite side of the sheet-like mediums. 
According to the present invention, there is provided a sheet feed 
mechanism in a light scanning apparatus for scanning a sheet-like medium 
in a main scanning direction with a light beam which is deflected 
one-dimensionally and scanning the sheet-like medium in a subscanning 
direction by feeding the sheet-like medium in a direction substantially 
normal to the main scanning direction, for thereby two-dimensionally 
scanning the sheet-like medium, the sheet feed mechanism comprising two 
pairs of rollers for gripping and feeding the sheet-like medium, the pairs 
of rollers being positioned upstream and downstream, respectively, of a 
scanning position in which the sheet-like medium is scanned, with respect 
to the direction of feed of the sheet-like medium, the pairs of rollers 
being disposed at a spacing larger than the length of the sheet-like 
medium in the subscanning direction, at least the downstream pair of 
rollers comprising a first roller and a second roller, a rotative drive 
source operatively coupled to the first roller for rotating the same, and 
an actuator engaging the second roller for displacing the same, the 
actuator having a damper mechanism, whereby the second roller can be 
displaced by the actuator toward the first roller to grip the sheet-like 
medium between the first and second rollers. 
According to the present present invention, there is also provided a sheet 
feed mechanism in a light scanning apparatus including two roller pairs 
each composed of a driver roller and a nip roller for gripping and feeding 
a sheet-like medium in a subscanning direction, the two pairs being 
disposed at a spacing smaller than the length of the sheet-like medium in 
the subscanning direction, and means for scanning the sheet-like medium 
between the two roller pairs in a main scanning direction with a light 
beam which is deflected substantially perpendicularly to the subscanning 
direction, for thereby two-dimensionally scanning the sheet-like medium, 
the nip roller of at least one roller pair disposed downstream in the 
subscanning direction being movable into and out of rolling contact with 
the driver roller of sad one roller pair, the nip roller being rotated in 
advance of movement thereof into rolling contact with the driver roller. 
According to the present invention, there is provided a sheet feed 
mechanism in a light scanning apparatus for scanning a sheet-like medium 
in a main scanning direction with a light beam which is deflected 
one-dimensionally and scanning the sheet-like medium in a subscanning 
direction by feeding the sheet-like medium in a direction substantially 
normal to the main scanning direction, for thereby two-dimensionally 
scanning the sheet-like medium, the sheet feed mechanism comprising two 
pairs of rollers for gripping and feeding the sheet-like medium, the pairs 
of rollers being positioned upstream and downstream, respectively, of a 
scanning position in which the sheet-like medium is scanned, with respect 
to the direction of feed of the sheet-like medium, the pairs of rollers 
being disposed at a spacing smaller than the length of the sheet-like 
medium in the subscanning direction, and a guide plate positioned between 
the two pairs of rollers and movable between a first position in which the 
guide plate projects into abutment against the sheet-like medium fed by 
the upstream roller pair to stop the sheet-like medium in the first 
position and a second position in which the guide plate lies in the 
subscanning direction to support the sheet-like medium for guiding the 
same in the subscanning direction. 
According to the present invention, there is also provided a sheet feed 
mechanism in a light scanning apparatus including two pairs of rollers for 
gripping and feeding a sheet-like medium in a subscanning direction, the 
two pairs being disposed at a spacing smaller than the length of the 
sheet-like medium in the subscanning direction, means for scanning the 
sheet-like medium between the two roller pairs in a main scanning 
direction with a light beam which is deflected substantially 
perpendicularly to the subscanning direction, for thereby 
two-dimensionally scanning the sheet-like medium, and means for releasing 
the sheet-like medium from gripping engagement with the pair of rollers 
which is disposed upstream in the subscanning direction when the leading 
end of the sheet-like medium is gripped by the pair of rollers which is 
disposed downstream in the subscanning direction. 
According to the present invention, there is also provided a method of 
controlling a sheet feed mechanism for gripping and feeding a sheet-like 
medium with two pairs of rollers in a subscanning direction while the 
sheet-like medium is being scanned with a light beam which is deflected in 
a main scanning direction substantially normal to the subscanning 
direction, the two pairs of rollers being disposed at a spacing smaller 
than the length of the sheet-like medium in the subscanning direction, the 
two pairs being disposed upstream and downstream in the subscanning 
direction, the method comprising the steps of detecting the sheet-like 
medium, gripping and feeding the sheet-like medium with the upstream pair 
of rollers, then gripping and feeding the sheet-like medium with the 
downstream pair of rollers upon elapse of a prescribed period of time, and 
simultaneously releasing the sheet-like medium from gripping engagement 
with the upstream pair of rollers. 
According to the present invention, there is also provided a method of 
controlling a sheet feed mechanism in a light scanning apparatus for 
scanning a sheet-like medium in a main scanning direction with a light 
beam which is deflected one-dimensionally and scanning the sheet-like 
medium in a subscanning direction by feeding the sheet-like medium in a 
direction substantially normal to the main scanning direction, for thereby 
two-dimensionally scanning the sheet-like medium, the sheet feed mechanism 
including two pairs of rollers for gripping and feeding the sheet-like 
medium, the two pairs of rollers being disposed at a spacing smaller than 
the length of the sheet-like medium in the subscanning direction, the 
method comprising the steps of gradually displacing one of the rollers of 
one of the pairs toward the other roller when the sheet-like medium is to 
be gripped and fed, and after said one roller has engaged the sheet-like 
medium, increasing a drive signal applied to means for displacing said one 
roller to quickly increase the force with which said one roller is pressed 
against the sheet-like medium for thereby gripping and feeding the 
sheet-like medium. 
The above and other objects, features and advantages of the present 
invention will become more apparent from the following description when 
taken in conjunction with the accompanying drawings in which preferred 
embodiments of the present invention are shown by way of illustrative 
example.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Like or corresponding parts are denoted by like or corresponding reference 
characters throughout this detailed description. 
FIG. 1 shows an image readout device, generally designated by the reference 
numeral 10, incorporating therein a sheet feed mechanism according to the 
present invention. The image readout device 10 has a chamber 12 housing a 
supply magazine 14 containing a stack of stimulable phosphor sheets A each 
recording a radiation image thereon. A sheet delivery mechanism including 
a suction cup 16 is also housed in the chamber 12 adjacent to the supply 
magazine 14. A first endless conveyor belt 18 for feeding the stimulable 
phosphor sheets A, one at a time, is disposed below the suction cup 16. 
The first conveyor belt 18 extends vertically downwardly and is bent into 
a horizontal direction at an inner corner of the image readout device 10. 
A plurality of rollers 20a through 20d are arranged at vertical intervals 
along one run of the conveyor belt 18. A large-diameter roller 22 is held 
against the bent portion of the first conveyor belt 18. The first conveyor 
belt 18 has a terminal end which is slightly spaced from a sheet feed 
mechanism 24 for feeding the sheet in a subscanning direction. 
As shown in FIGS. 1 and 2, the sheet feed mechanism 24 comprises first and 
second roller pairs 26, 28 disposed at a spacing smaller than the length 
of the stimulable phosphor sheet A in the direction in which it is fed. 
The first roller pair 26 comprises a roller 30 which is driven to rotate 
about its own axis and a roller 32 which is rotated by rolling contact 
with the roller 30. Similarly, the second roller pair 28 comprises a 
roller 34 which is driven to rotate about its own axis and a roller 36 
which is rotated by rolling contact with the roller 34, the roller 34 
being of a diameter equal to that of the roller 30. The rollers 30, 34 are 
rotated by a common rotative drive source through a belt, a chain, or the 
like (indicated by the broken lines in FIG. 2), so that the rollers 30, 34 
can be rotated in synchronism with each other. 
A guide member 38 is disposed between the first and second roller pairs 26, 
28 for supporting the lower surface of the stimulable phosphor sheet A. 
Above the guide member 38, there is disposed another guide member 40 
having a slit-like opening 42 defined therein and extending in a direction 
normal to the direction of travel of the stimulable phosphor sheet A 
through the sheet feed mechanism 24. 
An image readout unit 56 is disposed upwardly of the sheet feed mechanism 
24. The image readout unit 56 includes a laser beam source 58 for emitting 
a laser beam 60, a mirror 62 and a galvanometer mirror 64 for directing 
and deflecting the laser beam 60 to scan the stimulable phosphor sheet A 
through the opening 42 in the guide member 40. 
The image readout unit 56 also includes a light guide 68 having an entrance 
end 68a positioned in confronting relation to a scanning line on the sheet 
A and located within the opening 42. A photomultiplier 70 is mounted on 
the upper end (exit end) of the light guide 68. A light-collecting 
reflecting mirror 66 is disposed in opposite relation to the entrance end 
68a across the scanning line for efficiently guiding light emitted from 
the stimulable phosphor sheet A toward the entrance end 68a. 
As shown in FIG. 1, a second endless conveyor belt 44 is positioned in the 
vicinity of the second roller pair 28. The second conveyor belt 44 
includes a horizontal portion extending over a certain distance and a 
vertical portion extending upwardly from the end of the horizontal portion 
and having an upper end portion directed horizontally and then slightly 
downwardly. A large-diameter roller 46 is held against the lower bent 
portion of the second conveyor belt 44. A plurality of rollers 48a 
through 48e are disposed at spaced intervals along one run of the vertical 
portion of the second conveyor belt 44. A large-diameter roller 50 and 
rollers 52a, 52b are held against the upper bent portion of the second 
conveyor belt 44 for feeding the stimulable phosphor sheet A vertically 
downwardly along the downward upper end portion of the second conveyor 
belt 44. A receiver magazine 54 is disposed adjacent to the roller 52b for 
storing the stimulable phosphor sheets A from the second conveyor belt 44. 
An erase unit 72 is housed in the chamber 12 between the rollers 48b, 48c 
confronting the second conveyor belt 44. The erase unit 72 accommodates a 
plurality of erasure light sources (not shown) therein. 
Operation of the image readout device 10 with the sheet feed mechanism 24 
incorporated therein will be described below. 
First, the supply magazine 14 is loaded into the image readout device 10. 
The supply magazine 14 contains a stack of stimulable phosphor sheets A 
each recording a radiation image of an object such as a human body, for 
example. The stimulable phosphor sheets A are picked up, one by one, from 
the supply magazine 14 by the sheet delivery mechanism including the 
suction cup 16. The stimulable phosphor sheet A is then delivered to the 
sheet feed mechanism 24 through the first conveyor belt 18 below the 
suction cup 16 and the rollers 20a through 20d and 22 which coact with the 
first conveyor belt 18. 
The stimulable phosphor sheet A which has reached the sheet feed mechanism 
24 is gripped by the first roller pair 26, i.e., between the rollers 30, 
32, and fed thereby in the direction of the arrow B (FIG. 2). At this 
time, the image readout unit 56 is energized to emit the laser beam 60 
from the laser beam source 58. The laser beam 60 from the laser beam 
source 58 is reflected by the mirror 62 and then deflected by the 
galvanometer mirror 64 which is oscillating back and forth for thereby 
scanning the stimulable phosphor sheet A in the main scanning direction. 
Light emitted in all directions from the stimulable phosphor sheet A upon 
exposure to the laser beam 60 is directly applied to or reflected by the 
reflecting mirror 66 into the light guide 68. The light that has entered 
the light guide 68 is converted by the photomultiplier 70 to an electric 
signal, which is then supplied to an image recording device, for example. 
In this manner, the stimulable phosphor sheet A is two-dimensionally 
scanned by the laser beam 60. The stimulable phosphor sheet A is also 
gripped by the second roller pair 28 and transported thereby in the 
direction of the arrow B to pass through the image readout unit 56 so that 
all image signals can be read from the sheet A. Then, the stimulable 
phosphor sheet A is conveyed by the second conveyor belt 44 and the 
rollers 46, 48a, 48b to the erase unit 72. The non-illustrated erasure 
light source in the erase unit 72 is energized to apply erasing light to 
the stimulable phosphor sheet A to erase any remaining radiation image 
therefrom. 
Thereafter, the stimulable phosphor sheet A is fed upwardly by the second 
conveyor belt 44 and the rollers 48c through 48e into an upper portion of 
the image readout device 10, in which the sheet A is guided by the rollers 
50, 52a 52b to pass along the downward path into the receiver magazine 54. 
As described above, the distance between the roller pairs 26, 28 of the 
sheet feed mechanism 24 is smaller than the length of the stimulable 
phosphor sheet A in the direction in which it is fed, and the roller pairs 
26, 28 are rotated in synchronism with each other. Therefore, when the 
stimulable phosphor sheet A goes through the sheet feed mechanism 24, the 
sheet A is first gripped by the first roller pair 26 and fed thereby in 
the direction of the arrow B. Thereafter, while the trailing end of the 
sheet A is being gripped and pushed out by the first roller pair 26, the 
leading end of the sheet A is moved toward the second roller pair 28, so 
that the sheet A can be fed smoothly from the first roller pair 26 to the 
second roller pair 28. Since the stimulable phosphor sheet A is fed along 
by being always gripped by at least one of the first and second roller 
pairs 26, 28, the sheet A is prevented from being displaced out of the 
direction of feed thereof. 
As a consequence, the stimulable phosphor sheet A is fed accurately and 
smoothly without displacement after the leading end of the sheet A reaches 
the first roller pair 26 until the trailing end of the sheet A disengages 
from the second roller pair 28. The radiation image recorded on the 
stimulable phosphor sheet A can therefore be read highly accurately. The 
guide members 38, 40 between the roller pairs 26, 28 are effective in 
guiding the stimulable phosphor sheet A until the leading end thereof 
reaches the second roller pair 28. The laser beam 60 deflected by the 
galvanometer mirror 64 is applied to the stimulable phosphor sheet A 
through the slit-like opening 42 defined in the guide member 40. 
Therefore, when a stimulable phosphor sheet A is fed to the image readout 
unit 56 right after the radiation image of an object has been recorded on 
the sheet A, remaining light emitted from the sheet A upon exposure to the 
radiation is prevented by the guide member 40 from reaching the light 
guide 68. 
When the stimulable phosphor sheet A is exposed to the laser beam 60, the 
sheet A emits light commensurate with the radiation image recorded on the 
sheet A. It has been confirmed that such light is not emitted out 
instantaneously, but remains to be emitted from the sheet A for a certain 
period of time (see Japanese Patent Application No. 58(1983)-153691). 
Such remaining light emitted from the sheet A is also prevented by the 
guide member 40 from reaching the light guide 68. Inasmuch as light 
emitted from the sheet A upon exposure to the radiation and light emitted 
from the sheet A upon exposure to the laser beam 60 are prevented by the 
guide member 40 from entering the light guide 68, radiation image 
information obtained from the stimulable phosphor sheet A is clear and 
accurate. The stimulable phosphor sheet A is fed through the sheet feed 
mechanism 24 by being gripped by the roller pairs 26, 28. This arrangement 
allows the image readout device 10 to be as small in size as possible 
because those portions of the covneyor belts 18, 44 which are positioned 
near the roller pairs 26, 28, respectively, are not required to extend 
horizontally. 
A radiation image recording and reproducing system includes an image 
recording device for permanently recording radiation image information 
from a stimulable phosphor sheet on a recording material such as a 
photographic photosensitive material. The image is recorded on the 
photographic photosensitive material by applying a laser beam modulated by 
the radiation image information to the photographic photosensitive 
material. The sheet feed mechanism of the present invention can also be 
incorporated in such an image recording device for accurately and smoothly 
feeding the photographic photosensitive material to record a clear and 
accurate image thereon. 
Sheet feed mechanisms according to other embodiments of the present 
invention are shown in FIGS. 3 and 4. FIG. 3 illustrates a second 
embodiment in which a roller 80 of a sheet feed mechanism 24a is coupled 
to a rotative drive source (not shown), and an endless belt 84 is trained 
around the roller 30 and another roller 82 having the same diameter as 
that of the roller 80. The rollers 80, 82 are spaced from each other by a 
distance smaller than the length of the stimulable phosphor sheet A in the 
direction of travel thereof through the sheet feed mechanism 24a. A 
smaller-diameter roller 86 is disposed above the roller 80, and a 
smaller-diameter roller 88 is disposed above the roller 82. Therefore, 
when the non-illustrated rotative drive source is actuated to rotate the 
roller 80 in the direction of the arrow, the roller 82 is also rotated in 
synchronism through the belt 84. The stimulable phosphor sheet A, upon 
arrival at a position between the rollers 82, 88, is fed in the direction 
of the arrow by the belt 84 and the roller 88, and then the leading end of 
the sheet A is gripped between the belt 84 and the roller 86, which then 
feed the sheet A. At this time, the rollers 80, 82 are synchronously 
rotated to cause the stimulable phosphor sheet A to be fed smoothly 
through the sheet feed mechanism 24a. Between the rollers 88, 86, the 
stimulable phosphor sheet A is placed on the belt 84 which functions in 
the same manner as the guide member 38 in the first embodiment. 
According to a third embodiment shown in FIG. 4, a roller 90 of a sheet 
feed mechanism 24b is coupled to a rotative drive source (not shown), and 
a roller 92 equal in diameter to the roller 90 is operatively coupled to 
the roller 90 through a belt 94 for synchronous rotation. Two roller pairs 
96, 98 are disposed between the rollers 90, 92 in sandwiching relation to 
an upper run of the belt 94. The distance between the rollers 96, 98 is 
also smaller than the length of the stimulable phosphor sheet A in the 
direction of feed thereof. 
By rotating the roller 90, the roller 92 and the roller pairs 96, 98 are 
rotated through the belt 94. The stimulable phosphor sheet A as it reaches 
the sheet feed mechanism 24b is first gripped, at its leading end, by the 
roller pair 96, and fed with the belt 94 in the direction of the arrow by 
the roller pair 96. Then, with the leading end of the stimulable phosphor 
sheet A being gripped by the roller pair 96, the sheet A is gripped and 
fed by the roller pair 98 in the direction of the arrow. Since the roller 
pairs 96, 98 are rotated in synchronism with each other, the stimulable 
phosphor sheet A can smoothly and accurately be fed along. 
FIGS. 5 and 6 illustrate a sheet feed mechanism according to another 
embodiment of the present invention. In the embodiment shown in FIG. 2, 
the rollers 30, 34 are synchronously rotated by the belt trained around 
their pulleys. According to the embodiment shown in FIGS. 5 and 6, 
however, a larger-diameter idler pulley 100 is disposed between the 
rollers 30, 34 in rolling contact with the circumferential surfaces of the 
rollers 30, 34, the roller 34 being coupled to a rotative drive source 102 
comprising a motor. 
The idler pulley 100 may be of such dimensions as to be held in rolling 
contact with the rollers 30, 34 over their entire circumferential width, 
or may alternatively be held in rolling contact with pulleys mounted on 
axial ends of the rollers 30, 34. The nip roller 36 contacting the roller 
24 may be of the same material as that of the nip roller 32, e.g., 
synthetic rubber or the like having a large coefficient of friction. 
Preferably, the nip roller 36 comprises, as shown in FIG. 6, a cylindrical 
body 35b made of a foamed resilient material is fitted over a shaft 36a of 
metal on which the roller 36 is rotatably supported. 
When the rotative drive source 102 is energized, the roller 34 is rotated 
to rotate the roller 36 and the idler pulley 100, which then rotates the 
roller 30. Therefore, the nip roller 32 is also rotated in the same 
direction as that of rotation of the nip roller 36. At the moment the 
leading end of the stimulable phosphor sheet A is gripped by the roller 
pair 26, at the moment the leading end of the sheet A is gripped by the 
roller pair 28, at the moment the trailing end of the sheet A is released 
from the roller pair 26, or at the moment the sheet A is released from the 
roller pair 28, any of load variations imposed on the roller pair 26 or 28 
is transmitted to the motor 102, which can therefore be controlled in a 
feedback loop to enable the roller pairs 26, 28 to feed the sheet A 
smoothly in the direction of the arrow B irrespective of such load 
variations. Since the nip roller 36 of the roller pair 28 includes the 
cylindrical body 36b of a foamed resilient material, a load variation on 
the roller pair 28 at the time the leading end of the stimulable phosphor 
sheet A is gripped by the roller pair 28 can be absorbed by elastic 
deformation of the cylindrical body 36b. Therefore, such a load variation 
which is produced when the stimulable phosphor sheet A is gripped or 
released can be eliminated by elastic deformation of the cylindrical body 
36b, for thereby allowing the sheet A to be fed smoothly by the roller 
pairs 26, 28 in the direction of the arrow B, without causing changes in 
the rate of travel. 
In the illustrated embodiment, only the nip roller 36 of the downstream 
roller pair 28 is composed of a foamed resilient cylindrical body. 
However, the nip roller 32 of the roller pair 26 may also comprise such a 
foamed resilient cylindrical body for absorbing load variations produced 
at the moment the trailing end of the sheet A is released from the 
upstream roller pair 26. 
When the sheet A is fed along by a pair of rollers, a shock may be caused 
by a surface irregularity on the sheet A as it is gripped by the rollers, 
resulting in an image readout or recording irregularity. More 
specifically, a label bearing a bar code that represents identification 
data such as a sheet number is sometimes applied to the reverse side of a 
stimulable phosphor sheet which is opposite to the surface exposed to the 
stimulating laser beam. The bar code is optically read and recorded in a 
system controller in association with patient information or imaging 
information of the radiation image recorded on the sheet A. Since the 
label with the bar code thereon has a certain thickness, the reverse side 
of the sheet A has a step of different thickness where the label is 
applied. When the stimulable phosphor sheet is fed by the rollers in the 
subscanning direction, therefore, the step hits one of the rollers and 
imposes a shock thereon. The stimulable phosphor sheet is vibrated by such 
a shock, with the result that the stimulating laser beam is not applied 
properly to the sheet. 
The label is normally applied to the stimulable phosphor sheet closely to a 
side thereof. Therefore, the sheet has different thicknesses in the main 
scanning direction. Since the roller engages the sheet in an oblique 
fashion because of such different thicknesses, the sheet may not be fed 
accurately in the subscanning direction. As a result, the radiation image 
reproduced from the stimulable phosphor sheet may be unclear. 
FIG. 7 shows a sheet feed mechanism according to still another embodiment 
for eliminating the aforesaid drawback. As shown in FIG. 7, each of the 
rollers 30, 34 of the roller pairs 26, 28 comprises rollers 31a, 31b, 31c 
which are axially spaced from each other. Labels 33a, 33b bearing 
identification symbols are applied at a spaced interval by adhesive tapes 
35a, 35b, respectively, to one surface (lower surface in FIG. 7) of a 
stimulable phosphor sheet A. 
When the stimulable phosphor sheet A is fed into the image readout unit, 
the label 33a enters the gap between the rollers 31a, 31b, whereas the 
label 33b enters the gap between the rollers 31b, 31c. Therefore, the 
labels 33a, 33b do not hit the rollers 31a, 31b, 31c and hence do not 
impose shocks which would otherwise produce readout irregularities while 
the stimulable phosphor sheet A is being fed along. 
Various other structures are proposed according to the present invention 
for eliminating readout irregularities which would otherwise result from a 
nip roller engaging the stimulable phosphor sheet A at the time the image 
recorded on the sheet is read. 
An embodiment directed to one such structure is illustrated in FIGS. 8 
through 10. According to this embodiment, the downstream roller pair 28 is 
arranged as follows: As illustrated in FIG. 8, the roller 34 of the roller 
pair 28 is rotatably supported by a pair of support plates 150a, 150b 
erected in the image readout device 10, and has a shaft 34a coupled to the 
drive shaft of the rotative drive source 102. 
The nip roller 36 has opposite ends fitted in slots 152a, 152b, 
respectively, defined in the support plates 150a, 150b, and supported by 
stoppers 154a, 154b, respectively. As shown in FIG. 9, the stoppers 154a, 
154b have central openings 156a, 156b which open upwardly and have lower 
ends defined by semicircular edges. The stoppers 154a, 154b also have 
vertical slots 158a, 158b defined in opposite ends, respectively, thereof. 
The stoppers 154a, 154b are positioned on and secured to the support plates 
150a, 150b, respectively, by bolts 160a, 160b and bearings 162a, 162b 
mounted respectively on the opposite ends of the roller 36 are fitted 
respectively in the openings 156a, 156b. Pressing means 164a, 164b are 
mounted respectively on the support plates 150a, 150b. The pressing means 
164a, 164b include L-shaped brackets 166a, 166b, respectively, having 
first vertical plates 168a, 168b with a pair of vertical slots 170a, 170b 
defined therein. 
The L-shaped brackets 166a, 166b also include second horizontal plates 
172a, 172b to which rods 176a, 176b are secured, respectively, by 
retainers 174a, 174b. The rods 176a, 176b have on their lower ends flanges 
178a, 178b (FIG. 10), and are fitted in holes (not shown) defined in 
pressers 180a, 180b, respectively, which are retained by the flanges 178a, 
178b. The pressers 180a, 180b are of an L shape including vertical members 
with semicircular elongate openings 182a, 182b defined in the lower ends 
thereof. Compression coil springs 184a, 184b are disposed around the rods 
176a, 176b, respectively, between the pressers 180a, 180b and the brackets 
166a, 166b. 
The pressing means 164a, 164b are fixedly mounted on the support plates 
150a, 150b, respectively, by bolts 186a, 186b extending through the slots 
170a, 170b threadedly into threaded holes defined in the support plates 
150a, 150b. Bearings 188a, 188b mounted on the opposite ends of the roller 
36 are fitted respectively in the openings 182a, 182b of the pressing 
means 180a, 180b. 
The roller pair 28 is essentialy constructed as described above. Although 
not shown, the roller pair 26 may also be constructed in the same design. 
The roller pair 28 operates as follows: When the device is assembled, the 
distance H1 between the rollers 34, 36 of the roller pair 28 is adjusted 
to a preset distance. More specifically, the stoppers 154a, 154b are 
displaced through their slots 158a, 158b over the bolts 160a, 160b in the 
direction of the arrow C or D (FIG. 8) to adjust the distance H1 between 
the rollers 34, 36. Thereafter, the stoppers 154a, 154b are fixed to the 
support plates 150a, 150b by tightening the bolts 160a, 160b. In practice, 
the stimulable phosphor sheet A has a thickness H (FIG. 1) ranging from 
about 0.5 mm to 0.7 mm. It is preferable to select the distance H1 in the 
range of from about 0.3 to 0.4 mm. The distance H1 between the rollers 34, 
36 can easily be adjusted and hence the roller 36 can easily be positioned 
with respect to the roller 34 by using a clearance gage. 
Then, the pressing means 164a, 164b are positioned by displacing the 
brackets 166a, 166b in the direction of the arrow C or D to adjust the 
forces with which the roller 36 is pressed toward the roller 34 by the 
pressers 180a, 180b under the resiliency of the springs 184a, 184b, and 
then tightening the bolts 186a, 186b to secure the brackets 166a, 166b to 
the support plates 150a, 150b. 
The stimulable phosphor sheet A fed from the supply magazine 14 is gripped 
by the roller pair 26, i.e., the rollers 30, 32, and delivered thereby in 
the direction of the arrow B. At this time, the image readout unit 56 is 
energized to apply the laser beam to the sheet A, and light emitted from 
the sheet A is photoelectrically converted by the photomultiplier 70 into 
an electric signal for reading the recorded image, in the same manner as 
described above. 
While the recorded image is being thus read out, the stimulable phosphor 
sheet A starts to be gripped by the roller pair 28. Since the distance or 
clearance H1 of the roller pair 28 is smaller than the thickness H of the 
stimulable phosphor sheet A, the stimulable phosphor sheet A can smoothly 
be fed along through the image readout device. More specifically, the 
stimulable phosphor sheet A is first gripped by the roller pair 26, i.e., 
it is displaced in the direction of the arrow B to cause its leading end 
to be introduced into the roller pair 26. Inasmuch as the clearence H1 is 
defined between the rollers 34, 36, the stimulable phosphor sheet A can 
easily enter between the rollers 34, 36 through the clearance H1. With the 
clearance H1 slightly smaller than the thickness H of the simulable 
phosphor sheet A, the roller 36 is displaced in the direction of the arrow 
D (FIG. 10) against the resiliency of the springs 180a, 180b as the sheet 
A enters the roller pair 28. The roller 36 is pressed against the upper 
surface of the sheet A under the resiliency of the springs 184a, 184b, and 
the sheet A is gripped between the roller 36 and the roller 34 which is 
rotated by the motor 102, and fed by the rollers 36, 34 in the direction 
of the arrow B. 
The clearance H1 between the rollers 34, 36 allows the stimulable phosphor 
sheet A to be gripped by the rollers 34, 36 more smoothly and easily and 
with a less shock than would be if the roller 36 were displaced out of 
contact with the roller 34 by the sheet A. Accordingly, unwanted 
displacement or vibration of the laser beam on the sheet A due to such a 
shock can be avoided. For reading a radiation image from the stimulable 
phosphor sheet A over its entire surface in the image readout unit, the 
roller 26 may be of the same structure as that of the roller 28 to 
eliminate shocks when the stimulable phosphor sheet A enters the roller 
pair 26 and is released from the roller pair 28. Therefore, the radiation 
image recorded on the entire surface of the stimulable phosphor sheet A 
can smoothly and accurately be read out. 
The clearance H1 between the rollers of the roller pairs 26, 28 is also 
advantageous for the reason that where the rollers 32, 36 are made of a 
soft material such as polyurethane rubber to avoid scratches on the 
stimulable phosphor sheet A, they are prevented from being deformed since 
they are not pressed against each other. As a consequence, the roller 
pairs 26, 28 can feed the sheet A accurately in the subscanning direction. 
Because the stimulable phosphor sheet A is fed by being gripped by the 
roller pairs 26, 28, the portions of the conveyor belts 18, 44 which are 
close to the roller pairs 26, 28 are not required to extend horizontally, 
and hence the image readout device 10 can be reduced in size. 
In the embodiment shown in FIGS. 8 through 10, shocks produced when the 
stimulable phosphor sheet A enters or leaves the image readout unit are 
mechanically dampened. Such shocks can also be avoided by a combination of 
a mechanical arrangement and an electric control system. 
A sheet feed mechanism according to a still further embodiment shown in 
FIGS. 11 through 14 includes such an electromechanical arrangement for 
avoiding unwanted shocks from the stimulable phosphor sheet A. As shown in 
FIG. 11, the sheet feed mechanism 24 includes an upstream roller pair 26 
and a downstream roller pair 28 between which the guide members (not 
shown) for guiding the stimulable phosphor sheet A is disposed. A pair of 
sensors 200a, 200b is disposed just upstream of the roller pair 26 for 
detecting the stimulable phosphor sheet A as it is fed. 
Preferably, a light beam of such an wavelength or energy level which will 
not erase the image information recorded on the stimulable phosphor sheet 
A is emitted from one of the sensors 200a, 200b to the other sensor. The 
stimulable phosphor sheet A can therefore be detected when the light beam 
is cut off by the sheet A. The roller pairs 26, 28 are controlled by a 
control mechanism shown in FIG. 12. The opposite ends of the roller 30 are 
rotatably supported by the support plates 150a, 150b, respectively, 
erected in the image readout device 10, in the same manner as described 
with reference to the embodiment of FIG. 6. The roller 30 has a shaft 30a 
on which a pulley 202a is mounted. The roller 32 has a shaft 32a having an 
end fitted in a vertical slot 204a defined in the support plate 150a. The 
roller 32 is normally urged to move in a direction away from the roller 30 
by a coil spring 206a coupled to the shaft 32a. The other end of the 
roller shaft 32a is rotatably supported by the support plate 150b. An arm 
member 212a which is angularly movable by the rotatable shaft 210a of a 
rotary solenoid 208a is held in abutment against the shaft 32a. The rotary 
solenoid 208a is secured to the support plate 150a and can operate under 
the control of an electric control system or circuit (described later) for 
turning the arm member 212a against the resiliency of the coil spring 206a 
to displace the roller 32 toward the roller 30. 
The roller 34 of the roller pair 28 has a shaft 34a with a pulley 202b 
mounted thereon. The pulley 202b is operatively coupled to the pulley 202a 
by an endless belt 216 trained around the pulleys 202a, 202b. The control 
mechanism associated with the roller pair 28 is the same as the control 
mechanism associated with the roller pair 26, and its components are 
denoted by corresponding reference numerals with a suffix b and will not 
be described in detail. 
The rotary solenoids 208a, 208b are controlled by an electric control 
system or circuit as follows: As shown in FIG. 12, the control circuit 
includes first through fourth counters 220a, 220b, 220c, 220d for counting 
a clock signal .phi. up to T1, T2, T3, T4, respectively, from the time 
when a reset signal is applied, a driver 230a for energizing the rotary 
solenoid 208a in response to output signals from the first and second 
counters 220a, 220b, and a driver 230b for energizing the rotary solenoid 
208b in response to output signals from the third and fourth counters 
220c, 220d. The first and fourth counters 220a, 220d are supplied with a 
reset signal which is a sensor signal a from the sensors 200a, 200b, and 
the second and third counters 220b, 220c are supplied with a reset signal 
which is an inverted signal a of the sensor signal a applied from an 
inverter 240. 
Before the stimulable phosphor sheet A reaches the roller pair 26, the 
downstream rotary solenoid 208b remains de-energized. Therefore, the arm 
member 212b secured to the rotatable shaft 210b of the rotary solenoid 
208b does not press the shaft 36a of the nip roller 36 toward the roller 
34. The roller 36 remains displaced upwardly along the slot 204b under the 
force of the coil spring 206b, keeping a prescribed gap between the 
rollers 34, 36. The rotary solenoid 208a is energized before the 
stimulable phosphor sheet A reaches the roller pair 26. Thus, the arm 
member 212a is pressed by the rotary solenoid 208a against the shaft 32a 
against the resiliency of the coil spring 206a to position the roller 32 
closely to the roller 30. 
When the stimulable phosphor sheet A is conveyed by the belt conveyor 18 
until its leading end reaches a position between the sensors 200a, 200b l 
in front of the roller pair 26, the sensors 200a, 200b issue a sensor 
signal a which is applied as a reset signal to the first and fourth 
counters 220a, 220d, which are triggered by the positive-going edge of the 
reset signal to start counting the clock signal .phi.. Then, the leading 
end of the stimulable phosphor sheet A enters between the rollers 30, 32 
to feed the sheet A in the subscanning direction of the arrow B, whereupon 
the image recorded on the sheet A starts to be read out by the image 
readout unit 56 (FIG. 13(a)). 
When the fourth counter 220d counts the clock signal .phi. for a time 
period T4, it energizes the driver 230b to supply a driving current to the 
rotary solenoid 208b, the driving current increasing with time for an 
initial interval. The rotary solenoid 208b is now energized to cause the 
shaft 210b to rotate in the direction to turn the arm member 212b to press 
the roller shaft 36a toward the roller 34 against the resiliency of the 
coil spring 206b. As a result, the shaft 36a is moved downwardly along the 
slot 204b to displace the roller 36 gradually toward the roller 34 at a 
constant speed. The leading end of the stimulable phosphor sheet A has 
already been introduced over the roller 34, and is now smoothly gripped 
between the rollers 34, 36 to impose a stress on the sheet A (FIG. 13(b)). 
Therefore, the stimulable phosphor sheet A is gripped, without shocks, 
between the rollers 34, 36, and fed thereby in the direction of the arrow 
B. As the sheet A is thus fed along, the recorded image is read from the 
sheet A by the image readout unit 56. 
When the first counter 220a counts the clock signal .phi. for a time period 
T1 (T1&gt;T4) from the positive-going edge of the reset signal, the first 
counter 220a applies a stop signal to the driver 230a to stop supplying 
the driving current to the rotary solenoid 208a. Therefore, the arm member 
212a is angularly displaced away from the shaft 30a under the resiliency 
of the coil spring 206a to move the roller 32 away from the roller 30 
(FIG. 13(c)). Since, at this time, the leading end of the stimulable 
phosphor sheet A is firmly gripped by the rollers 34, 36, the sheet A is 
continuously fed in the subscanning direction without being shocked by the 
roller 2 as it is moved away from the roller 30. 
Thereafter, the trailing edge of the stimulable phosphor sheet A moves past 
the sensors 200a, 200b. An inverted sensor signal a from the inverter 240 
is now applied as a reset signal to the second and third counters 220b, 
220c, which then start counting the clock signal .phi. from the 
positive-going edge of the sensor signal a. 
When the second counter 220b counts the clock signal .phi. for a time 
period T2, it energizes the driver 230a to supply a driving current, 
increasing with time for an initial interval, to the rotary solenoid 208a. 
The rotary solenoid 208a is energized to angularly displace the arm member 
212a against the resiliency of the coil spring 206a for thereby moving the 
roller 32 toward the roller 30 at a constant rate. The stimulable phosphor 
sheet A is not gripped between the rollers 30, 32 as it has alreadly been 
moved past the rollers 30, 32 (FIG. 13(d)). 
When the third counter 220c counts the clock signal .phi. for a time period 
T3 (T3&gt;T2) from the positive-going edge of the reset signal a, the third 
counter 220c applies a stop signal to the driver 230b to stop supplying 
the driving current to the rotary solenoid 208b. The arm member 212b is 
now angularly moved away from the shaft 34a under the resiliency of the 
coil spring 206b to move the roller 36 from the roller 34. 
When the recorded image is read from the stimulable phosphor sheet A, the 
sheet A is firmly gripped by one of the roller pairs at all times. The 
recorded image can be read from the sheet A over its entire surface. This 
is advantageous in that as much image information as possible can be 
recorded on the sheet A. The count T2 of the second counter 220b may be 
the same as the count T3 of the third counter 220c. In this case, the 
roller pairs 26, 28 operate in a manner different from that shown in FIG. 
13(d), i.e., their rollers are moved toward and away from each other at 
the same time. 
FIGS. 15 through 17 illustrate a yet still further embodiment of the 
present invention. In this embodiment, after a nip roller has engaged a 
stimulable phopshor sheet, the roller is pressed against the sheet as 
quickly as possible to cause the sheet to be gripped under desired 
pressure conditions in a short period of time without imposing shocks to 
the sheet, so that the sheet can be fed along efficiently. 
According to this embodiment, each of the drivers 230a, 230b for the rotary 
solenoids 208a, 208b shown in FIG. 12 is arranged as follows: 
As shown in FIG. 15, a control circuit includes a switch controller 250 for 
actuating a polarity changing switch SW based on a sensor signal from the 
sensors 200a, 200b disposed near the roller pair 26, an integrator 254 for 
integrating a voltage applied from a positive terminal 252a or a negative 
terminal 252b of a power supply through the switch SW based on a 
prescribed time constant, and a driver 256 for converting the integrated 
voltage into a current to energize the rotary solenoid 208a. The current 
which energizes the rotary solenoid 208a is converted by a converter 258 
to a voltage, which is then applied to a comparator 260. 
The comparator 260 is also supplied with a reference voltage Vo. The 
comparator 260 compares the voltage applied by the converter 258 with the 
reference voltage Vo to control the time constant of the integrator 254. 
Another sensor pair identical to the sensors 200a, 200b may be provided in 
the vicinity of the roller pair 28 and coupled to another control circuit 
identical to that shown in FIG. 15, so that the roller pair 28 may be 
controlled in the same manner as that in which the roller pair 26 is 
controlled. 
In operation, the stimulable phosphor sheet A is fed in the direction of 
the arrow B (FIG. 11). When the leading end of the sheet A reaches the 
sensors 200a, 200b, they detect the arrival of the sheet A and apply a 
signal to the switch controller 250 to connect the switch SW to the 
positive terminal 252a of the power supply. The voltage applied from the 
power supply via the switch SW is integrated by the integrator 254, and a 
current corresponding to the integrated voltage is supplied from the 
driver 256 to the rotary solenoid 208a. The current supplied to the rotary 
solenoid 208a increases with time as shown in FIG. 16. As the current 
having a constant rate of increase is supplied to the rotary solenoid 
208a, the shaft 212a of the rotary solenoid 208a is turned at a prescribed 
speed against the resiliency of the coil spring 206a to cause the arm 
member 212a to push the roller shaft 32a downwardly. The shaft 32a 
descends along the slot 204a to move the roller 32 toward the roller 30. 
Since the leading end of the stimulable phosphor sheet A has already been 
introduced over the roller 30, the sheet A is smoothly gripped by the 
rollers 30, 32 and subjected to a gradual stress thereby. 
When the roller 32 is displaced toward the roller 30 at a rate determined 
by the current curve shown in FIG. 16, it takes a certain period of time 
for the stimulable phosphor sheet A to be gripped by the roller pair 26 
under a desired stress. This mode of operation may cause trouble if the 
sheet A is to be scanned at a high speed. 
Such a problem can be solved as follows: The current supplied to the rotary 
solenoid 208a is converted by the converter 258 to a voltage based on 
which the time constant of the integrator 254 is changed. In this manner, 
a current as shown in FIG. 17 can be supplied to the rotary solenoid 208a 
to enable the rollers to grip the stimulable phosphor sheet A quickly. 
More specifically, the voltage from the converter 258 is compared with the 
reference voltage Vo by the comparator 260. When the voltage reaches the 
reference voltage Vo, the comparator 260 applies a signal to change the 
time constant of the integrator 254. The reference voltage Vo is preset on 
the basis of the relationship between the driving current for the rotary 
solenoid 208a and the displacement of the roller 32. At the time the 
roller 32 engages the sheet A and hence has been displaced a certain 
interval, i.e., at a point P where the rate of increase of the current is 
varied, the time constant of the integrator 254 is changed to a greater 
value to supply a current with a larger rate of increase to the rotary 
solenoid 208a. 
Therefore, after the roller 32 has engaged the stimulable phosphor sheet A 
and been displaced a prescribed interval, the rotary solenoid 208a 
displaces the arm member 212a at a high speed to depress the roller 32 
rapidly toward the roller 30, whereupon the rollers 32, 30 grip the sheet 
A under a desired stress. As a consequence, the sheet A is gripped by the 
roller pair 26 within a short period of time and can hence be fed highly 
efficiently in the subscanning direction for high-speed scanning. 
The stimulable phosphor sheet A is gripped, without any appreciable shocks, 
between the rollers 30, 32, and can be fed in the direction of the arrow B 
quite smoothly and continuously. Accordingly, the image recorded on the 
sheet A can be read quite well by the image readout unit 56. 
The stimulable phosphor sheet A that has reached the sensors (not shown) at 
the second roller pair 28 can also be gripped quickly by the roller pair 
28 during the image readout operation. The gripping or nipping action on 
the sheet A by the roller pair 26 may be released at the time the trailing 
end of the sheet A passes the roller pair 26, so that no shock is imposed 
on the sheet A as it leaves the roller pair 26, thereby to allow a better 
image readout process. 
Instead of setting the point P with the reference voltage Vo applied to the 
comparator 260, the condition in which the roller 32 and the stimulable 
phosphor sheet A contact each other may be detected by a contact sensor or 
the like, and a signal from such a contact sensor may be applied to the 
integrator 254 for changing its time constant. FIG. 18 shows such a 
modified embodiment. As shown in FIG. 18, the sensors 200a, 200b detect 
the arrival of the leading end of the stimulable phosphor sheet A and 
apply a signal indicative of such arrival to a clock signal generator 270. 
In response to the sensor signal, the clock signal generator 270 supplies 
a clock signal to a frequency divider 272, which converts the supplied 
clock signal to a pulse signal of a prescribed period and supplies the 
pulse signal to a counter 274. The counter 274 issues an output signal 
which is converted by a D/A converter 276 to an analog signal that is 
supplied to the driver 256. The driver 256 then energizes the rotary 
solenoid 208a. The rotary solenoid 208a angularly moves the arm member 
212a based on a current that varies in a step-like pattern to move the 
roller 32 gradually toward the roller 30. 
The roller 32 has a contact sensor 278 which applies a contact signal to 
the frequency divider 272 when the roller 32 contacts the stimulable 
phosphor sheet A. The contact signal applied to the frequency divider 272 
changes the frequency-dividing ratio of the frequency divider 272 to 
reduce the period of the pulse signal issued by the frequency divider 272. 
As a result, the frequency of the signal applied to the counter 274 is 
increased to increase the rate at which the output voltage from the D/A 
converter 276 increases. Thus, the output current from the driver 256 is 
also increased more quickly. The rotary solenoid 208a now angularly moves 
the arm member 212a based on a current which varies at a higher rate than 
before the roller 32 contacts the stimulable phosphor sheet A, for thereby 
pressing the roller 32 against the roller 30. The sheet A is gripped by 
the rollers 30, 32 quickly without shocks and can smoothly be fed along 
thereby. 
A sheet feed mechanism according to another embodiment is illustrated in 
FIG. 19. An arm member 280 has one end fixed to the rotatable shaft 210a 
of the rotary solenoid 208a. A pin 282 has one end embedded in the other 
end of the arm member 280 and is held in abutment against one end of a 
link 284. The other end of the link 284 is angularly movably supported by 
a shaft 286 on the support plate 150a and attached to one end of a leaf 
spring 288 with its opposite end engaging the shaft 32a of the roller 32. 
A strain gage 290 is bonded to an intermediate portion of the leaf spring 
288. The rollers 30, 32, the sensors 200a, 200b, and the coil spring 206a 
are of the same construction as shown in FIG. 11, and will not be 
described in detail. 
A control system or circuit for the rotary solenoid 208a is shown in FIG. 
20. The control circuit includes a pressure sensor 294 composed of the 
strain gage 290 and an amplifier 292, an integrator 298 composed of an 
amplifier 296, a resistor R and a capacitor C which establish a time 
constant, and a driver 256 for converting a voltage to a current to 
energize the rotary solenoid 208a. When the sensors 200a, 200b disposed 
near the roller pair 26 detect the leading end of the stimulable phosphor 
sheet A, the sensors 200a, 200b apply a signal to the switch controller 
250. The switch controller 250 connects the polarity changing switch SW to 
the positive terminal 252a of the power supply to apply a predetermined 
voltage to the integrator 298. The integrator 298 then integrates the 
applied voltage based on the time constant determined by the resistor R 
and the capacitor C. An output signal from the integrator 298 is converted 
by the driver 108 to a current which is supplied to the rotary solenoid 
208a. The rotary solenoid 208a then rotates the shaft 210a to turn the 
arm member 280 and hence the pin 282 thereon for angularly moving the link 
284 about the shaft 286. Since one end of the leaf spring 288 is joined to 
the link 284, the roller shaft 32a engaging the other end of the leaf 
spring 288 is depressed by the rotary solenoid 208a against the resiliency 
of the coil spring 206a to move the roller 32 gradually toward the roller 
30. At this time, the strain gage 290 mounted centrally on the leaf spring 
288 detects the amount of distortion to which the leaf spring 288 is 
subjected. The detected distortion is converted by the amplifier 292 to a 
voltage, which is applied to the integrator 298. Therefore, the integrator 
298 is supplied with the constant voltage supplied from the power supply 
via the switch SW and also the voltage from the pressure sensor 294 which 
increases with the displacement of the roller 32. 
The output signal from the integrator 298 is supplied to the driver 256 and 
converted thereby to a current that is supplied to the rotary solenoid 
208a. As shown in FIG. 21, the current supplied to the rotary solenoid 
208a gradually increases with time. The roller 32 is displaced initially 
under a relatively small force toward the roller 30. Then, the force 
acting on the roller 32 to displace the same toward the roller 30 becomes 
increasingly greater to enable the rollers 32, 30 to grip the stimulable 
phosphor sheet A quickly under a prescribed stress. The roller pair 26 
therefore grips the stimulable phosphor sheet A quickly without any 
appreciable shocks thereon, and feeds the sheet A quickly in the direction 
of the arrow B. For moving the roller 32 away from the roller 30, the 
polarity changing switch SW is actuated by the switch controller 250 to 
supply the rotary solenoid 208a with a current having a characteristic 
curve in symmetric relation to the current curve shown in FIG. 21. The 
roller 32 is now displaced by the rotary solenoid 208a in a direction away 
from the roller 30 in a manner that is the reversal of the process 
described above. The roller pair 28 operates in the same way as described 
above with reference to the roller pair 26. 
With the above embodiment, after the roller has engaged the sheet, the rate 
at which the force on the sheet to depress the same varies is increased to 
enable the roller pair to grip the sheet within a short period of time. 
Thus, the sheet can quickly start being fed, and the cycle time for 
reading or recording an image can be reduced. 
FIGS. 22 and 23 show a sheet feed mechanism according to still another 
embodiment of the present invention. This embodiment differs from the 
embodiment of FIG. 19 primarily in that a shaft is rotatably supported 
between the support plates, and each leaf spring has one end fixed to this 
shaft with the other end engaging the shaft of the nip roller. More 
specifically, two leaf springs 300a, 300b have ends engaging the opposite 
ends of the shaft 32a of the roller 32 which is vertically movably 
supported by the support plates 150a, 150b. The other ends of the leaf 
springs 300a, 300b are fixed to the opposite ends of a rotatable shaft 302 
which is rotatably supported by the support shafts 150a, 150b and extends 
parallel to the roller 32. The rotatable shaft 302 is angularly movable by 
the rotary solenoid 208a supported on the support plate 150a. 
The rotatable shaft 210a of the rotary solenoid 208a is secured to one end 
of the arm member 280 which supports on the other end the pin 282 held in 
engagement with one end of the link 284 with its other end fixed to the 
rotatable shaft 302. The rotary solenoid 208a, when energized, causes the 
arm member 280 and the link 284 to turn the shaft 302 against 
theresiliency of the coil springs 206a, 206b for displacing the roller 32 
toward the roller 30. The downstream roller pair 28 is also associated 
with an identical structure. 
In operation, the rotary solenoid 208a is energized before the stimulable 
phosphor sheet A reaches the roller pair 26. The shaft 210a of the rotary 
solenoid 208a is turned to enable the arm member 280, the pin 282, and the 
link 284 to turn the shaft 302 about its own axis in the direction of the 
arrow (FIG. 23). Since the leaf springs 300a, 300b are fixed endwise to 
the shaft 302, the distal ends of the leaf springs 300a, 300b are caused 
by the turning movement of the shaft 302 to press the roller shaft 32a 
against the resilient forces of the coil springs 206a, 206b. As a result, 
the roller 32 is displaced along the slot 204a toward the roller 30. 
The stimulable phosphor sheet A is transferred by the conveyor belt to 
introduce its leading end between the rollers 30, 32 of the roller pair 
26. The leading end of the sheet A is gripped between the rollers 30, 32 
as the roller 32 is lowered. Then, the roller 30 is rotated to feed the 
sheet A in the direction of the arrow B toward the downstream roller pair 
28. The leaf springs 300a, 300b have substantially the same coefficients 
of elasticity, and are caused by the common rigid shaft 302 to press the 
roller 32 toward the roller 30. Therefore, the stimulable phosphor sheet A 
can be gripped under uniform forces at both marginal sides along the 
support plates 150a, 150b. The sheet A is thus prevented from being 
undulated due to different forces with which it is gripped, and can 
accurately be fed toward the roller pair 28, during which time the 
recorded image can well be read from the sheet A. The stimulable phosphor 
sheet A is also gripped and fed accurately by the roller pair 28 in the 
same manner as described above. 
Before the trailing end of the stimulable phosphor sheet A reaches the 
roller pair 26, the driving current supplied to the rotary solenoid 208a 
is cut off. The shaft 32 is now released from the depressing forces of the 
leaf springs 300a, 300b, and the roller 32 is allowed to ascend away from 
the roller 30 under the bias of the coil springs 206a, 206b. 
Since the nip rollers 32, 36 are pressed against the stimulable phosphor 
sheet A under uniform forces in a direction normal to the direction of 
feed of the sheet A, the sheet A is prevented from being undulated or wavy 
between the roller pairs, with the result that the recorded image 
information can be read well and efficiently from the sheet A. 
FIGS. 24 through 26 illustrate a sheet feed mechanism according to a still 
further embodiment of the present invention. As shown in FIGS. 24 and 25, 
the shaft 30a of the rlller 30 is rotatably supported by the support 
plates 150a, 150b extending vertically in the image readout device 10. The 
shaft 32a of the roller 32 is fitted at its opposite ends in the slots 
204a, 204b in the support plates 150a, 150b. When the roller 32 is in the 
lowermost position thereof, there is a gap or clearance H1 (FIG. 25) 
created between the rollers 32, 30, the clearance H1 being the same as the 
clearance H1 shown in FIG. 8. 
Presser members 350a, 350b are held in engagement with the roller shaft 32a 
at its opposite ends. As illustrated in FIG. 24, the presser member 350a 
is substantially C-shaped and includes an upper horizontal portion 352a 
with a groove 354a defined in a lower surface thereof, the shaft 32a being 
fitted in the groove 354a. The presser member 350a has a lower horizontal 
portion 356a engaging one end of a coil spring 358a. The other end of the 
coil spring 358a is fixed within the image readout device 10. The presser 
member 350a is thus normally biased by the coil spring 358a to move in a 
downward direction. The presser member 350b is of the same construction as 
that of the presser member 350a, and its components are denoted by 
identical reference numerals with a suffix b and will not be described in 
detail. 
The roller 32 is held in engagement with a displacing means 360 for moving 
the roller 32 vertically upowardly along the slots 204a, 204b. The 
displacing means 360 comprises the rotary solenoid 208a with its rotatable 
shaft 210a fixed to one end of an arm 362. The other end of the arm 362 
engages a bearing 366 on one end of an arm 364 near the support plate 
150a. A rotatable shaft 368 which is rotatably supported at its opposite 
ends by the support plates 150a, 150b is fitted substantially centrally in 
the arm 364 and secured thereto. The other end of the arm 364 has a 
stepped portion including an engaging tongue 364a on which one end of the 
shaft 32a of the roller 32 is placed. Similarly, an arm 370 is secured to 
the rotatable shaft 368 near the support plate 150b and has a stepped 
portion including an engaging tongue 370a on which the other end of the 
shaft 32a is placed. 
The stimulable phosphor sheet A is fed by the belt conveyor toward the 
image readout unit 56. The displacing means 360 is now actuated. More 
specifically, the rotary solenoid 208a is energized to rotate the shaft 
210a in the direction of the arrow E (FIG. 24). The arm 362 fixed to the 
shaft 210a is also angularly moved in the direction of the arrow E to push 
the bearing 366 also in the direction of the arrow E. When the bearing 366 
mounted on the arm 364 is pushed in the direction of the arrow E, the arm 
364 swings with the shaft 368 to cause the engaging tongue 364a to swing 
in the direction of the arrow G. The engaging tongue 370a of the arm 370 
on the shaft 368 is also swung in the direction of the arrow G. Therefore, 
the shaft 32a engaging the engaging tongues 364a, 370a is guided by the 
slots 204a, 204b so as to be displaced therealong in the upward direction 
against the resilient forces of the coil springs 358a, 358b. 
Thus, the roller 32 is moved away from the roller 30 by an amount larger 
than the thickness of the stimulable phosphor sheet A coming into the 
roller pair 26 (FIG. 26(a)). When the stimulable phosphor sheet A is 
introduced between the rollers 30, 32, the rotary solenoid 208a of the 
displacing means 360 is energized again. The shaft 210a of the rotary 
solenoid 208a is turned in the direction of the arrow F, opposite to the 
direction E, and so is the arm 362 fixed to the shaft 210a. Consequently, 
the shaft 32a is released from the lifting forces from the arms 364, 370 
and displaced downwardly by the presser members 350a, 350b biased by the 
coil springs 358a, 358b, respectively, to cause the roller pair 26 to grip 
the stimulable phosphor sheet A. Because the clearance H1 between the 
rollers 30, 32 is selected to be smaller than the thickness of the 
stimulable phosphor sheet A, when the stimulable phosphor sheet A is 
gripped by the rollers 30, 32, the shaft 32a is biased by the coil springs 
358a, 358b through the presser members 350a, 350b. As a consequence, the 
stimulable phosphor sheet A is appropriately gripped by the roller pair 26 
under the bias of the coil springs 358a, 358b. By energizing the 
non-illustrated rotative drive source to rotate the roller 30, the 
stimulable phosphor sheet A is fed toward the downstream roller pair 28. 
At the same time that the stimulable phosphor sheet A is fed in the 
subscanning direction, i.e., in the direction of the arrow B, the image 
readout unit 56 is energized for reading the recorded image from the sheet 
A. Then, the leading end of the sheet A reaches the roller pair 28 (FIG. 
26(b)). With the roller pair 28 being associated with the same structure 
as that shown in FIG. 24 for the roller pair 26, the stimulable phosphor 
sheet A as it is scanned in the image readout process can be smoothly 
gripped also by the roller pair 28 without imposing shocks on the roller 
pair 28. The image readout process can therefore be effected highly 
accurately and smoothly. 
Continued delivery of the stimulable phosphor sheet A causes the trailing 
end thereof to disengage from the roller pair 26. At this time, the 
displacing means 360 is actuated to displace the roller 32 upwardly away 
from the roller 30 to avoid undesired shocks which would otherwise be 
produced upon departure of the trailing end of the sheet A from the roller 
pair 26. The image readout process can thus be carried out accurately by 
the image readout unit 56 (FIG. 26(c)). 
In the above embodiment, the stimulable phosphor sheet A is released from 
gripping action of the roller pair 26 when the sheet A leaves the roller 
pair 26. However, the roller pair 26 may be actuated to release the sheet 
A when the leading end of the sheet A is gripped by the roller pair 28, 
and the sheet A may thereafter be fed only by the roller pair 28 in the 
subscanning direction. 
The sheet can accurately be fed in the subscanning direction by the roller 
pairs since the rollers are not subject to deformation because they are 
spaced from each other by a prescribed distance. Such accurate feeding 
operation allows an image to be read from or recorded on the sheet highly 
accurately. The rollers in a roller pair are relatively displaced a 
distance which is greater than the thickness of the sheet when the sheet 
enters or leaves the roller pair. Accordingly, no shock is applied to the 
sheet when it enters or leaves the roller pair, resulting in high accuracy 
for the image readout or recording process. 
As shown in FIG. 24, stimulable phosphor sheets of different sizes may 
successively be fed through the image readout unit. A stimulable phosphor 
sheet A of a considerably small size has one marginal edge guided by a 
register plate 380 to move between the rollers 30, 32 near the support 
plate 150b. As a result, the distance between the rollers 30, 32 becomes 
larger near the support plate 150b than near the support plate 150a. The 
roller 32 is now liable to be tilted about the side edge of the sheet A by 
the presser member 350a under the bias of the coil spring 358a as 
indicated by the dot-and-dash-lines in FIG. 25. 
Such a problem can easily be obviated by selecting the spring contact of 
the coil spring 358b coupled to the presser member 350b to be larger than 
the spring constant of the coil spring 358a coupled to the presser member 
350a. Even when a stimulable phosphor sheet A of a relatively small width 
is gripped by the roller pair 26 closely to one end thereof, as shown in 
FIG. 25, the roller 32 is not tilted on account of the greater resiliency 
of the coil spring 358b. The narrow stimulable phosphor sheet A can 
therefore be fed accurately in the direction of the arrow B (subscanning 
direction) by being gripped between the rollers 30, 32. The embodiment of 
FIGS. 24 and 25 is effective in accurately feeding stimulable phosphor 
sheets A of different sizes in the subscanning direction irrespective of 
such different sheet sizes. The recorded image on the sheet A can thus be 
read out highly accurately at all times by the image readout unit 56. 
Rather than selecting a larger spring constant for the coil spring 358b 
than for the coil spring 358a, the coil springs 358a, 358b may be of the 
same spring constant, and the length to which the coil spring 358b can be 
extended may be larger than the length to which coil spring 358a can be 
extended. 
FIGS. 27(a) and 27(b) show a sheet feed mechanism according to another 
embodiment of the present invention. In this embodiment, only the 
downstream roller pair 28 is selectively opened to grip the sheet A, 
without shocks, which is fed from the upstream roller pair 26. In FIGS. 
27(a) and 27(b), the roller 36 has its opposite ends rotatably supported 
on one end of a swing member 400 which is angularly movably mounted on a 
support bar 402 disposed at a substantially intermediate portion of the 
swing member 400. The swing member 400 has a slot 404 defined in the other 
end thereof and operatively coupled to an actuator 406 such as a solenoid 
406. More specifically, the solenoid 406 has a plunger 408 having on its 
distal end a pin 410 loosely fitted in the slot 404. When the solenoid 406 
is energized, the swing member 400 is angularly moved about the support 
bar 402 to swing the roller 36 in the direction of the arrow. The solenoid 
406 is energized under the control of a counter 412. When the image 
readout unit 56 is operated, the counter 412 starts counting a clock 
signal. The counter 412 generates a signal for energizing the solenoid 406 
upon elapse of a predetermined period of time. The time period for the 
counter 412 to produce such a signal is preferably selected such that when 
the leading end of the stimulable phosphor sheet A reaches a position over 
the roller 34, the roller 36 presses the upper surface of the stimulable 
phosphor sheet A. Preferably, the solenoid 406 is of the type having a 
damper mechanism (so-called a solenoid-operated actuator). The solenoid 
406 may however be replaced with a cylinder having a cushioning mechanism 
or a cam mechanism. 
Before the image readout unit 56 is operated, the roller 36 of the second 
roller pair 28 is normally positioned above the roller 34, as shown in 
FIG. 27(a). When the stimulable phosphor sheet A is fed by the first 
roller pair 26 into the image readout unit 56, the sheet A is detected by 
sensor (not shown) which then energizes the image readout unit 56 and 
enables the counter 412 to start its counting cycle. When the given period 
of time elapses, the solenoid 406 is energized to move the plunger 408 in 
the direction of the arrow D to cause the swing member 400 to swing the 
roller 36 downwardly in the direction of the arrow toward the roller 34. 
Therefore, upon arrival of the leading end of the stimulable phosphor 
sheet A at the roller 34, the roller 36 presses the upper surface of the 
sheet A, which is gripped between the rollers 34, 36 and fed in the 
direction of the arrow B. Prior to movement of the trailing end of the 
stimulable phosphor sheet A past the second roller pair 28, the solenoid 
406 is energized to retract the plunger 408 in the direction of the arrow 
C. The roller 36 is now swung upwardly away from the roller 34 to release 
the stimulable phosphor sheet A from the gripping action of the rollers 
34, 36. 
In this embodiment, when the stimulable phosphor sheet A fed toward the 
second roller pair 28 enters the space between the rollers 34, 36, the 
roller 36 is displaced toward the roller 34 by the solenoid 406 to cause 
the second roller pair 28 to grip the sheet A, which is then fed in the 
direction of the arrow B. Therefore, the stimulable phosphor sheet A can 
be fed smoothly from the first roller pair 26 to the second roller pair 
28. Since the solenoid 406 has a damper mechanism, the roller 36 is 
prevented thereby from abruptly hitting the upper surface of the sheet A 
and hence from imposing shocks on the sheet A. Because the stimulable 
phosphor sheet A is always gripped by one of the roller pairs 26, 28, 
there is no danger of the sheet A being displaced out of the proper 
direction of feed. The stimulable phosphor sheet A can therefore be fed 
smoothly and accurately through the image readout unit 56 without 
undesired positional displacement, so that the radiation image recorded on 
the sheet A can well be read by the image readout unit 56. 
According to still another embodiment illustrated in FIG. 28, a rotary 
actuator 420 is operatively associated with a presser member 430 normally 
urged downwardly by a coil spring 434 and a shock absorber 422. The shock 
absorber 422 is disposed closely to the roller 34 and has an upwardly 
extending rod 424 with a damper member 426 as of rubber mounted on the 
upper end thereof. The damper member 426 is disposed underneath a roller 
428 fixed coaxially to the roller 36. 
The rotary actuator 420 has an arm 429 normally pressed against the roller 
428 to displace the same upwardly. The presser member 430 is held in 
sliding contact with the upper surface of the roller 428. Specifically, 
the presser member 430 has a semicircular recess 430a in which the roller 
428 is partly fitted, the presser member 430 being mounted on the lower 
distal end of a rod 432. A coil spring 434 is disposed around the rod 432 
and has one end engaging a flange 346 on the upper end of the rod 432 and 
the other end pressed against the upper surface of the presser member 430. 
The rotary actuator 420 normally causes the arm 429 to be pressed against 
the roller 428 to displace the same upwardly, thus keeping the coil spring 
434 under compression. 
As the stimulable phosphor sheet A is guided by the guide member 38 and 
reaches a prescribed position, it is detected and a signal indicative of 
the arrival of the sheet A is applied to operate the rotary actuator 420 
to displace the arm 429 in the direction of the arrow away from the roller 
428. The coil spring 434 now resiliently presses the presser member 430 
downwardly. After the presser member 430 has been displaced a certain 
downward interval, the damper member 426 on the rod 424 engages the 
peripheral surface of the roller 428 thereby to dampen the resilient 
forces from the coil spring 434. 
When the stimulable phosphor sheet A has reached the prescribed position, 
therefore, the sheet A is gripped, without shocks, by the driver roller 34 
and the nip roller 36, and is then fed thereby in the direction of the 
arrow. 
A sheet feed mechanism according to a still further embodiment of the 
present invention is illustrated in FIG. 29. This embodiment differs from 
the preceding embodiment in that the rotary actuator 420 is replaced with 
a cam mechanism combined with an angle member for limiting vertical 
displacement of the nip roller 36. 
An eccentric cam 444 is attached to a rotatable shaft 422 projecting from a 
motor 440 through a gear train (not shown), and a second arm 448b of an 
angle member 448 pivotally mounted on a shaft 446 is held in sliding 
contact with the eccentric cam 444. The angle member 448 has a first arm 
448a held against the roller 428. 
The cam 444 is normally held in the illustrated position by the motor 440. 
With the second arm 448b slidingly contacting the cam 444, the first arm 
448a is held by the shaft 446 to maintain the roller 428 in the 
illustrated position. In this position, the rollers 34, 36 are spaced from 
each other. Since the roller 428 is now in the elevated position, the 
presser member 430 is depressed downwardly by the coil spring 434, but 
such downward displacement is limited by the first arm 448a. 
Upon arrival of the stimulable phosphor sheet A at a prescribed position on 
the guide member 38, a signal is applied to energize the motor 440 to 
cause the shaft 442 to rotate the cam 444, which allows the second arm 
448b to turn about the shaft 446 toward the motor 440. The first arm 448a 
is lowered to permit the coil spring 434 to displace the presser member 
430 resiliently downwardly until the roller 428 reaches the position 
indicated by the broken line in FIG. 29. The rollers 34, 36 thus jointly 
grip the stimulable phosphor sheet A therebetween and feed the sheet A in 
the subscanning direction. The driver roller 34 and the nip roller 36 can 
grip and feed the sheet A without imposing any appreciable shocks on the 
sheet A, as with the preceding embodiment. 
FIGS. 30(a) and 30(b) show a subscanning sheet feed mechanism according to 
a still further embodiment of the present invention. In this embodiment, a 
first pulley 450 is fixed coaxially to the nip roller 36, and a second 
pulley 452 coupled to a rotative drive source (not shown) is disposed 
below the driver roller 34. A belt 454 is vertically trained around the 
first and second pulleys 450, 452, and a roller 456 is held in rolling 
contact with the belt 450. The nip roller 36 is vertically movable. 
Before the stimulable phosphor sheet A reaches the guide member 38, the nip 
roller 36 and the driver roller 34 are spaced from each other as shown in 
FIG. 30(a). When the sheet A reaches a prescribed position on the guide 
member 38, a signal is applied to move the roller 456 in the direction of 
the arrow as shown in FIG. 30(b). This displacement of the roller 456 
shortens the vertical extent of the belt 454 to lower the pulley 450 and 
hence the nip roller 36 into contact with the sheet A, which is now 
gripped between the rollers 34, 36 and fed along in the direction of the 
arrow. According to this embodiment, the driver roller 34 and the nip 
roller 36 can grip and feed the stimulable phosphor sheet A without 
imposing shocks thereon. 
FIGS. 31 through 34 show a sheet feed mechanism according to another 
embodiment of the present invention, in which a downstream nip roller is 
displaceable and rotated in advance to grip and feed the sheet A without 
applying shocks. As shown in FIG. 31, a relatively short transmission 
roller 500 is held in frictional contact with the driver roller 34 of the 
roller pair 28. The transmission roller 500 has a shaft 502 on which a 
first pulley 504 is mounted. The shaft 502 has a distal end portion 
projecting out of the pulley 504 and serving as a smaller-diameter shaft 
506. A bent arm 508 which is angularly movably mounted at its center on 
one end of a shaft 510 has a lower end attached to the shaft 506 and an 
upper end attached to a shaft 512. The shaft 512 supports thereon a second 
pulley 514 and includes a larger-diameter shaft 516 extending beyond the 
second pulley 514 and supporting the nip roller 36 thereon. The arm 508 
thus extends upwardly from one side of the driver roller 34, and the nip 
roller 36 is positioned above the driver roller 34. A second arm 518 is 
angularly movably mounted on the shaft 510 on the axially opposite side of 
the nip roller 36 remote from the arm 508. 
The downstream driver roller 34 is coupled to the rotatable shaft of a 
motor 522. The rotative power of the motor 522 is also transmitted via a 
power transmission means (not shown) to the upstream driver roller 30. A 
swing rod 524 has one end coupled to the arm 508 at a position 
intermediate between the shafts 510, 512. Specifically, a pin 526 is 
embedded in one end of the swing rod 524 and pushes a coil spring 528 with 
one end thereof secured to the arm 508. The pressure imposed by the nip 
roller 36 on the stimulable phosphor sheet A is dampened by the arm 508 
under the resiliency of the coil spring 528. The other end of the swing 
rod 524 is pivotally coupled to a peripheral edge portion of a circular 
cam plate 534 supported on a rotatable shaft 532 of a motor 530. A belt 
536 is trained around the first and second pulleys 504, 514. 
The stimulable phosphor sheet A is fed while being guided by the guide 
members 38, 40 and reaches the driver roller 34. At this time, the shaft 
502 is rotated by the transmission roller 500 held in rolling contact with 
the driver roller 34 which is being driven by the motor 522, and therefore 
the pulley 504 is rotated by the shaft 502. The rotation of the pulley 504 
is transmitted via the belt 536 to the pulley 514, which then rotates the 
nip roller 36 in a direction opposite to the direction of rotation of the 
driver roller 34. Thus, when the driver roller 34 is rotated in one 
direction, the nip roller 36 is rotated in synchronism with the driver 
roller 34, but in the opposite direction. 
As the stimulable phosphor sheet A is delivered into the image readout unit 
56, i.e., when the leading end of the stimulable phosphor sheet A fed by 
the roller pair 26 reaches a prescribed position, it is detected by a 
sensor (not shown) which issues a signal to rotate the motor 530 at a slow 
speed. The rotation of the motor 530 is transmitted through the shaft 532 
to the cam plate 534 which is also rotated slowly in the direction of the 
arrow (FIG. 31). The swing rod 324 now lowers the arm 508 toward the 
driver roller 34 through angular movement about the shaft 510. When the 
leading end of the stimulable phosphor sheet A reaches the driver roller 
34, the nip roller 36 rotatably supported on the arm 508 catches the 
leading end of the sheet A while rotating at the same speed as the driver 
roller 34, and presses the sheet A against the upper surface of the driver 
roller 34 through damping action by the coil spring 528 (FIG. 34). Since 
the nip roller 36 and the driver roller 34 rotate at the same speed, no 
shock is applied to the stimulable phosphor sheet A when it is gripped by 
the rollers 36, 34, and the stimulable phosphor sheet is smoothly 
delivered to the erase unit 72. 
As described above, when the stimulable phosphor sheet A being fed by the 
roller pair 26 is delivered a prescribed distance, the arm 508 is 
displaced by the motor 530 to press the nip roller 36 against the leading 
end of the stimulable phosphor sheet A. Even while the stimulable phosphor 
sheet A is being scanned by a laser beam, the sheet A can thus be 
positioned and fed easily and reliably without being subjected to shocks. 
Due to the fact that the nip roller 36 is rotated in advance, the sheet A 
can be smoothly brought into the feed mode with any shocks reduced by the 
damping action of the coil spring 528 when the leading end of the sheet A 
engages the surface of the nip roller 36. The stimulable phosphor sheet A 
is prevented from abruptly hitting the downstream roller pair and hence 
from being shocked undesirably. The stimulable phosphor sheet A is fed 
while it is being firmly gripped at its leading and trailing ends by the 
roller pair 26 and the driver roller 34 and the nip roller 36, so that the 
sheet A is not displaced out of the direction of travel. The stimulable 
phosphor sheet A as it is not positionally displaced is scanned in both 
the main and subscanning directions for reading the recorded radiation 
image highly accurately from the sheet A in the image readout unit 56. 
FIGS. 35 and 36 show a sheet feed mechanism in accordance with another 
embodiment of the present invention. The sheet feed mechanism shown in 
FIGS. 35 and 36 is similar to the sheet feed mechanism of FIGS. 31 through 
34, except as follows: An arm 508 is of a Y-shaped configuration with a 
transmission roller 500a and the nip roller 36 rotatably mounted on the 
opposite ends of the arm 508. A larger-diameter transmission roller 550 is 
also rotatably mounted on the arm 508 between the rollers 36, 500a in 
rolling contact therewith. 
The rotative power of the transmission roller 500a held in rolling contact 
with the driver roller 34 is transmitted through the larger-diameter 
transmission roller 550 to the nip roller 36, which is therefore rotated 
at the same speed as the driver roller 34. The swing rod 526 is coupled 
through the coil spring 528 to the arm 508a. The swing rod 526 is 
angularly moved by the motor 530 to turn the arm 508a about the shaft 510, 
for thereby moving the nip roller 36 toward or away from the driver roller 
34. 
FIG. 37 shows a sheet feed mechanism according to still another embodiment 
of the present invention. A transmission roller 573 positioned directly 
above the nip roller 36 which is disposed directly above the driver roller 
34. A first pulley 560 is fixed coaxially to the driver roller 34, and a 
second pulley 562 is disposed in spaced relation to the first pulley 560. 
A first belt 564 is trained around the first and second pulleys 560, 562. 
A third pulley 566 is disposed upwardly of the second pulley 562, and a 
second belt 568 is trained around the second and third pulleys 562, 566. A 
third pulley 572 is trained around the third pulley 566 and a fourth 
pulley 570 fixed coaxially to the transmission roller 573. The nip roller 
36 is vertically movable between a position in which it is held in rolling 
contact with the transmission roller 573 and a position in which it is 
held in rolling contact with the driver roller 34. 
When the stimulable phosphor sheet A is fed by the roller pair 26 and 
reaches a prescribed position, a signal indicative of the position of the 
sheet A is applied to lower the nip roller 36 as it rotates into contact 
with the sheet A to feed the same continuously. More specifically, the 
driver roller 34 rotates the first pulley 560 which rotates the second 
pulley 562 through the first belt 564. The second pulley 562 then rotates 
the third pulley 566 through the second belt 568, and the third pulley 566 
rotates the transmission roller 573 in the direction of the arrow through 
the third belt 572. Therefore, the nip roller 50 held in rolling contact 
with the transmission roller 573 is rotated in the direction opposite to 
the direction in which the transmission roller 573 is rotated. 
Upon arrival of the stimulable phosphor sheet A at the prescribed position, 
as described above, the nip roller 36 is lowered out of rolling contact 
with the transmission roller 573 to the position shown by the broken line. 
At this time, the stimulable phosphor sheet A is caused by the roller pair 
26 to reach a position just above the driver roller 34. The sheet A is 
therefore gripped by the driver roller 34 and the nip roller 36 which 
rotates at the same speed as the speed of travel of the sheet A, and is 
continuously fed by the rollers 34, 36. 
With this embodiment, the rotative power of the driver roller 34 can 
reliably be transmitted to the nip roller 36 through a belt-and-pulley 
system which is simple in structure. 
A still further embodiment of the present invention is illustrated in FIGS. 
38 and 39(a) through 39(c). As shown in FIG. 38, a first pair of 
transmission pulleys 580 is disposed between the driver roller 30 of the 
upstream roller pair and the driver roller 34 of the downstream roller 
pair in rolling contact therewith, and similarly a second pair of 
transmission pulleys 582 is disposed between the nip roller 32 of the 
upstream roller pair and the nip roller 36 of the downstream roller pair 
in rolling contact therewith. The rotative power of the driver pulley 36 
coupled to the motor 522 is transmitted through the first transmission 
pulleys 580 to the driver roller 30. The nip roller 32 is positioned above 
the driver roller 30 and can be moved into rolling contact therewith. The 
nip roller 36 is positioned above the driver roller 34 and can be moved 
into rolling contact therewith. 
First, the driver roller 30 and the nip roller 32 of the upstream roller 
pair are brought into rolling contact with each other, and the driver 
roller 34 and the nip roller 36 of the downstream roller pair are spaced 
from each other. The motor 522 is energized to rotate the driver roller 
34, the transmission pulleys 580, and the driver roller 30. Since the 
driver roller 30 and the nip roller 32 are held in rolling contact with 
each other at this time, the nip roller 32 is also rotated. The rotation 
of the nip roller 32 is transmitted via the transmission pulleys 582 to 
the nip roller 36. When the stimulable phosphor sheet A reaches a position 
between the driver roller 30 and the nip roller 32, the sheet A is gripped 
between the driver roller 30 and the nip roller 32 as they are rotated and 
is fed in the subscanning direction (FIG. 39(a)). 
The stimulable phosphor sheet A is continuously fed along until its leading 
end reaches the downstream roller pair, whereupon the nip roller 36 is 
lowered against the sheet A. Therefore, the stimulable phosphor sheet A is 
gripped between the rollers 30, 32 and also between the rollers 34, 36 
(FIG. 36(b)). 
As the stimulable phosphor sheet A is gripped by the driver roller 34 and 
the nip roller 36 of the downstream roller pair, the nip roller 32 is 
lifted away from the driver roller 30 to release the stimulable phosphor 
sheet A, which is thereafter fed by the rollers 34, 36 (FIG. 36(c)). 
The rotative power of the motor 522 is transmitted through the driver 
roller 34, the transmission pulleys 580, the driver roller 30, the nip 
roller 32, and the transmission pulleys 582 to the nip roller 36. 
Therefore, the nip roller 36 is rotated before the sheet A is gripped by 
the nip roller 36 and the driver roller 34. As a result, the stimulable 
phosphor sheet A can smoothly be fed by the simple sheet feed mechanism. 
The sheet feed mechanisms according to the foregoing embodiments have been 
described as being incorporated in the image readout devices. A sheet feed 
mechanism according to the present invention can also be used in an image 
recording device for recording an image on a suitable recording medium 
such as a photographic photosensitive material. 
One such embodiment is illustrated in FIG. 40. As shown in FIG. 40, a guide 
plate 38a is relatively short, and a motor or a rotary solenoid 700 has 
its rotatable shaft engaging an end of the guide plate 38a. There is no 
other guide plate in confronting relation to the guide plate 38a. A laser 
beam source (not shown) is disposed directly above the guide plate 38a. A 
laser beam L emitted from the laser beam source is modulated by image 
information to be recorded and is deflected by a light deflector (not 
shown) in a main scanning direction. The other structural details are 
similar to those of the embodiment shown in FIG. 5. 
A photographic photosensitive material such as a film F is delivered by the 
belt conveyor 18. When the film F is detected by the sensors 200a, 200b, a 
signal is produced by the sensors to energize the rotary solenoid 700 for 
erecting the guide plate 38a between the roller pairs 26, 28. As a 
consequence, the film F is prevented by the guide plate 38a from being 
advanced, and hence is positioned by the guide plate 38a. After the film F 
has been positioned by the guide plate 38a, the rotary solenoid 700 is 
energized again to return the guide plate 38a to its original horizontal 
position. The time required for the film F to travel from the position 
established by the guide plate 38a toward the position in which the film F 
is to be scanned by the laser beam L can be determined in advance by the 
distance between those two positions and the speed at which the film F is 
fed by the first roller pair 26. Therefore, by applying the laser beam L 
to the film F upon when the predetermined time (referred to above) 
elapses, any desired image can be recorded from the leading end of the 
film F, namely, a black edge or frame may be produced on the leading end 
of the film F. The guide plate 38a may be positioned such that the 
position in which the film F is located by the guide plate 38a may be the 
same as the position in which the film F is scanned by the laser beam L. 
This allows the film F to be scanned immediately after the guide plate 38a 
is turned from the erected position to the horizontal position. It is also 
possible to start recording an image on the film F somewhere between its 
leading and trailing ends, leaving a blank margin of desired width on the 
leading end of the film F. Because the film F is supported in the scanning 
position by the guide plate 38a, the film F can stably be fed only by the 
roller pair 26. 
When the leading end of the film F reaches the roller pair 28 while the 
film F is being scanned by the laser beam L, the nip roller 36 of the 
roller pair 28 is lowered to grip the film F between the rollers 34, 36. 
Even after the trailing end of the film F has left the roller pair 26, the 
film F is supported on the guide plate 38a and fed reliably by the roller 
pair 28 until the image is recorded by the laser beam L on the film F down 
to the trailing end thereof. 
According to the previous embodiments, the stimulable phosphor sheet A or 
the film F is gripped and released, without shocks, by vertical movement 
of the nip rollers 32, 34. However, the stimulable phosphor sheet A or the 
film F may be gripped and released by vertically moving a roller below the 
sheet A or the film F. 
FIG. 41 shows a sheet feed mechanism according to such an embodiment. Nip 
rollers 804, 806 are held in rolling contact with driver rollers 800, 802, 
respectively. The driver rollers 800, 802 are rotated at the same speed 
and in the same direction by a suitable means such as a belt. The driver 
rollers 800, 802 are smaller in diameter than the nip rollers 804, 806. 
The nip roller 806 is rotatably supported on a fixed shaft 808 and pressed 
against the driver roller 802 under a constant force. The nip roller 804 
is rotatably supported by a pin 814 on an end of of a rod 812 which is 
pivotally mounted on a fixed pin 810. The rod 812 has a longitudinal slot 
816 defined in the opposite end thereof, with a slide pin 818 slidably 
disposed in the slot 816. The slide pin 818 is mounted eccentrically on a 
disc 822 fixed to the rotatable shaft (not shown) of a rotary solenoid 
820. 
In operation, the film F is fed by the rollers 800, 804 to reach the 
rollers 802, 806. When the film F has reached the rollers 802, 806, a 
signal indicative of arrival of the film F is applied to energize the 
rotary solenoid 820. More specifically, when the film F is gripped by the 
driver roller 802 and the nip roller 806, the rotary solenoid 802 is 
energized. As a result, the disc 822 is turned to angularly move the rod 
812 counterclockwise about the fixed pin 810, thus lowering the nip roller 
804 away from the driver roller 800. The film F is thus fed along only by 
the rollers 802, 806. The film F is always gripped by at least one of the 
roller pairs and hence is prevented from being displaced while it is being 
fed along. Accordingly, an image can be recorded highly accurately on the 
film F and can also be recorded over its entire surface. Since the driver 
rollers are of a small diameter and can be rotated at a high speed, the 
speed of feeding movement can be controlled through an inexpensive 
mechanism. 
According to the present invention, as described above, two pairs of 
rollers for gripping and feeding a sheet-like medium such as a stimulable 
phosphor sheet or a photosensitive film in a subscanning direction are 
spaced from each other by a distance smaller than the length of the 
sheet-like medium in the direction of feed thereof, and the two pairs of 
rollers are rotated in synchronism with each other. Therefore, the 
sheet-like medium is always gripped by at least one pair of rollers and 
fed accurately thereby, and can smoothly be brought into engagement with 
the other pair of rollers. When applying stimulating light to the 
stimulable phosphor sheet to read out recorded radiation image 
information, or when applying a laser beam to the photosensitive film to 
record a visible image thereon, clear image information can be read out or 
recorded. Since the sheet feed mechanism or subscanning mechanism is 
simple in construction, it can be manufactured inexpensively and small in 
size. Where the sheet feed mechanism is incorporated in a light beam 
scanning apparatus, the light beam scanning apparatus can also be small or 
compact and hence takes up only a small installation space. 
Although certain preferred embodiments have been shown and described, it 
should be understood that many changes and modifications may be made 
therein without departing from the scope of the appended claims.