Counter device for sheet photo film pack

A sheet photo film pack includes a pack housing for containing a stack of eight sheet photo film units. The counter device is used with the sheet photo film pack. A counter chamber is formed in the pack housing. A counter disk is contained in the counter chamber rotatably, and has first and second faces. A train of counter numerals are arranged on the first face in an arc-shaped manner at a predetermined pitch. Plural stepping claws are disposed on the first face to project in a thickness direction of the counter disk, arranged in an arc-shaped manner at the predetermined pitch, and rotationally shifted by an external mechanical shift signal. The shift signal is associated with each one of the sheet photo film units to be counted, and adapted to setting the counter numerals in a counter indicator window.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a counter device for a sheet photo film 
pack. More particularly, the present invention relates to a counter device 
for a sheet photo film pack capable of properly indicating a counted 
number of exposures taken in combination with a camera and a pack holder. 
2. Description Related to the Prior Art 
A sheet photo film pack has a pack housing, which contains a stack of 
plural sheet photo film units. A pack holder is loaded with the sheet 
photo film pack. The pack holder is used in combination with a 
large-format camera of a frame size of 4.times.5 inches (102.times.127 
mm). The pack housing has a slidable lid. The use of the pack holder makes 
it easy to take photographs in the large-format camera one after another, 
because the slidable lid is only slid back and forth before each of the 
sheet photo film units can be readily positioned at an exposure aperture 
in place of a preceding exposed one of the sheet photo film units. Each of 
the sheet photo film units is constituted of a sheet photo film having a 
size of 4.times.5 inches, and a plastic sheath for containing the sheet 
photo film for the purpose of protection. 
U.S. Pat. No. 5,710,952 (corresponding to JP-A 8-110568) discloses a sheet 
photo film pack, in which a counter chamber is formed in the pack housing 
in a box shape. The counter chamber contains a rotatable counter disk, 
which is rotated and stepped up by a counter advance spring plate or lever 
of the pack holder. One face of the counter disk, where a train of counter 
numerals are arranged, is provided with stepping claws of a gear shape. 
The counter advance spring plate of the pack holder is engaged with the 
stepping claws, and rotates and steps the counter disk in one direction in 
cooperation with the stepping claws. 
The counter advance spring plate or lever is produced by cutting an end of 
a metal thin arm obliquely, and is bent vertically. The bent end of the 
arm is provided with a shape of a right-angled triangle. Each time that 
one exposure is taken, the counter advance spring plate is rotated from 
its initial position, causes the counter disk to make stepwise rotation by 
one step, and is rotated back to its initial position to be stand by for 
next stepping operation. In the returning operation, the counter advance 
spring plate forcibly comes back to the tip of one of the stepping claws 
next to the present one of them, and moves past it. 
Also the counter disk has plural ratchet claws for anti-reversal operation. 
The ratchet claws are located on a disk face reverse to that having the 
counter numerals. The ratchet claws are combined with a push plate to 
constitute a ratchet mechanism. There is a spring portion formed 
integrally with the push plate, which is vertically pressed against the 
counter disk by the bias force of the spring portion. 
However failure related to the counter advance spring plate or lever is 
likely to cause erroneous operation of the counter disk. Examples of the 
failure include burrs created with the claw drive end with low precision 
at the time of cutting out the counter advance spring plate, failure in 
precisely bending the counter advance spring plate, and failure in 
precisely positioning the counter advance spring plate. In the returning 
movement, it is likely that the counter advance spring plate does not move 
past one of the stepping claws next to one of them engaged with the 
counter advance spring plate. Backward push of the counter advance spring 
plate occurs to the one stepping claw. For example, the counter disk 
rotates in reverse by half a step. In the next stepping operation of the 
counter device, the counter advance spring plate pushes again the same one 
of the stepping claws. Accordingly there occurs a difference between an 
indicated counter numeral and the number of the actually exposed sheet 
photo film units. When all the sheet photo film units are exposed finally, 
the pack is erroneously enabled to take another exposure. The first 
exposed one of the sheet photo film units is exposed again as a double 
exposure. 
It is also likely that the counter disk does not make enough rotation of a 
predetermined angle for various causes, including insufficiency in the 
swinging angle of the counter advance spring plate or lever due to failure 
in assembly of the counter advance spring plate, and errors in molding the 
pack housing. At this time of the insufficient rotation, the push plate 
remains in contact with the tip of the ratchet claws, and does not operate 
for preventing the reverse rotation. This is included in the causes of the 
above-described half-step reversal in rotation of the counter disk. 
In the above-described push plate, the bias force of the spring portion is 
lowered with time, for example after preservation for a long time. There 
occurs failure in correct stepping in the counter device. If the sheet 
photo film pack is dropped forcibly or shocked considerably in any manner, 
the indicated counter numeral is likely to change as the counter disk may 
come to an unwanted position. 
There is an adequate clearance between a slidable tray and the inside of 
the pack housing for the purpose of convenience in loading the pack 
housing. A problem lies in that the stepping of the counter device is 
unstable because the clearance involves a changeable relation in the 
distance between the counter disk and the counter advance spring plate or 
lever. Should the distance be too great, the counter advance spring plate 
is likely not to be engaged with the counter disk. The counter advance 
spring plate may swing without driving the counter disk, so that the 
counter device may not be stepped properly. Should the distance be too 
small, the counter advance spring plate may come to too deep a position 
between the stepping claws of the counter disk. In the return operation of 
the counter advance spring plate, the counter advance spring plate may be 
caught by the stepping claws, and may rotate back the counter disk in the 
manner of "back-stepping" of the counter device. 
SUMMARY OF THE INVENTION 
In view of the foregoing problems, an object of the present invention is to 
provide a counter device for a sheet photo film pack, capable of being 
stepped even in occurrence of various kinds of failure related to the 
counter advance spring plate or lever. 
Another object of the present invention is to provide a counter device for 
a sheet photo film pack, capable of being stepped properly even after a 
long time, and free from influence of external shock in relation to the 
counter stepped position. 
Still another object of the present invention is to provide a counter 
device for a sheet photo film pack, in which play between the inside of 
the pack housing and the slidable tray of the pack holder can be reduced, 
to stabilize the counter operation. 
In order to achieve the above and other objects and advantages of this 
invention, a counter device is used in a sheet photo film pack, which 
includes a pack housing for containing a stack of plural sheet photo film 
units. The counter device includes a counter chamber formed in the pack 
housing. A counter disk is contained in the counter chamber in a rotatable 
manner, and has first and second faces. A train of counter numerals are 
arranged on the first face in an arc-shaped manner at a predetermined 
pitch. Plural stepping claws are disposed on the first face to project in 
a thickness direction of the counter disk, arranged in an arc-shaped 
manner at the predetermined pitch, and rotationally shifted by an external 
mechanical shift signal in a predetermined stepping direction, the shift 
signal being associated with each one of the sheet photo film units to be 
counted, and adapted to setting the counter numerals in a predetermined 
index position. 
A guide inclined surface is formed on each one of the stepping claws, 
positioned thereon in the stepping direction, and inclined with reference 
to the thickness direction of the counter disk. 
An erect surface is formed on each one of the stepping claws, positioned 
thereon backwards to the stepping direction, erect in the thickness 
direction of the counter disk, and pushed in the stepping direction by an 
external counter advance mechanism, for receiving the shift signal. The 
guide inclined surface allows the counter advance mechanism to slip from 
the stepping claws in reverse to the stepping direction. 
The sheet photo film pack is used with a pack holder, and the pack holder 
includes a holder housing for containing the sheet photo film pack. Also 
the pack holder includes the counter advance mechanism, disposed in the 
holder housing, engageable with the stepping claws by confrontation 
therewith in the thickness direction of the counter disk, and actuated in 
response to an operation associated with use of each one of the sheet 
photo film units, for generating the shift signal. 
Consequently the counter device is capable of being stepped even in 
occurrence of various kinds of failure related to the counter advance 
spring plate or lever. 
A ratchet mechanism prevents the counter disk from rotating in reverse to 
the stepping direction when the counter numerals are set in the index 
position. 
The ratchet mechanism includes plural ratchet claws, disposed on the second 
face to project from the counter disk, and arranged in an arc-shaped 
manner at the predetermined pitch. A push plate is disposed in the counter 
chamber in a movable manner, confronted with the second face, for blocking 
rotation of the ratchet claws in reverse to the stepping direction. 
An additional inclined surface is formed on each one of the stepping claws, 
and inclined to decrease a radius of the stepping claws in the stepping 
direction, the radius being defined with reference to a center of the 
counter disk. 
In a preferred embodiment, the sheet photo film pack further includes an 
engaging portion, disposed on the pack housing, and shaped in an 
asymmetrical manner with respect to a center line of the pack housing. The 
pack holder includes a slidable tray, disposed in a manner slidable into 
and out of the holder housing, for containing the sheet photo film pack. A 
receiving portion is disposed in the slidable tray, engaged with the 
engaging portion, for positioning the sheet photo film pack in the 
slidable tray, to tighten engagement between the counter disk and the 
counter advance mechanism. 
Consequently the play between the inside of the pack housing and the 
slidable tray of the pack holder can be reduced, to stabilize the counter 
operation. 
In the counter device, an access opening is formed through a bottom wall of 
the counter chamber confronted with the first face, and adapted to 
engagement between the stepping claws and the counter advance mechanism 
therethrough. 
The pack holder further includes a slidable tray, mounted in the holder 
housing, for the sheet photo film pack, the slidable tray being slid in a 
first direction to come out of the holder housing, and slid in a second 
direction to come into the holder housing. An exposure opening is formed 
in the holder housing, for receiving an exposure surface of a first one of 
the plural sheet photo film units, the exposure opening being adapted to 
exposure of the first sheet photo film unit. A shifter mechanism shifts 
the first sheet photo film unit away from the exposure opening in response 
to a slide of the slidable tray and the sheet photo film pack in the first 
direction after the exposure, then the slidable tray and the sheet photo 
film pack being slid in the second direction, the exposure opening 
receiving a second one of the plural sheet photo film units next to the 
first sheet photo film unit. The counter advance mechanism applies the 
shift signal to the counter disk in the sheet photo film pack in response 
to a back-and-forth slide of the slidable tray and the sheet photo film 
pack. 
In still another preferred embodiment, a ratchet erect surface is formed on 
each one of the ratchet claws, positioned thereon backwards to the 
stepping direction, erect in the thickness direction of the counter disk. 
An auxiliary inclined surface is formed on each one of the ratchet claws 
by chamfering an edge of the ratchet erect surface, for guiding movement 
of the push plate toward the ratchet erect surface during rotation of the 
counter disk in the stepping direction. 
An inclined surface is formed on each one of the ratchet claws, positioned 
thereon in the stepping direction, inclined with reference to the 
thickness direction of the counter disk, for slipping from the push plate 
while rotated in the stepping direction. 
In a further preferred embodiment, a metal spring presses the push plate 
against the second face. 
Consequently the counter device is capable of being stepped properly even 
after a long time, and free from influence of external shock in relation 
to the counter stepped position. 
In still another preferred embodiment, a ring-shaped groove is formed in a 
bottom wall of the counter chamber confronted with the first face, for 
receiving the stepping claws. 
A numeral indication portion is disposed on the first face, and having the 
counter numerals arranged thereon. A peripheral portion is disposed about 
the numeral indication portion on the first face, formed to retreat from 
the numeral indication portion in the thickness direction, and having the 
stepping claws arranged thereon. The stepping claws have a top point erect 
in the thickness direction, and the top point projects over the numeral 
indication portion. 
Consequently the tightness in engagement of the counter disk claws with the 
advance spring plate or lever is increased.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE PRESENT INVENTION 
In FIG. 1, a sheet photo film pack 1 incorporates a counter mechanism of 
the present invention. The sheet photo film pack 1 is constituted of a 
pack housing 3 and a slidable lid 5. The pack housing 3 has a box shape. A 
cap 2 is fitted on an end of the pack housing 3 in a removable manner. A 
stack of eight sheet photo film units 4 are contained in the pack housing 
3. The slidable lid 5 is mounted on the pack housing 3 in a manner 
slidable to open/close an opening 3a in the pack housing 3. The slidable 
lid 5 includes a grip 5a. Each of the sheet photo film units 4 is 
constituted of a sheet photo film 6 having a size of 4.times.5 inches 
(102.times.127 mm), and a plastic sheath 7 for containing the sheet photo 
film 6. 
The slidable lid 5 has a size larger than the sheet photo film units 4, and 
slider when pushed or pulled by a user's hand holding the grip 5a. The 
slidable lid 5 is slidable in a direction of grooves 8a and 9a in guide 
rails 8 and 9 formed in edges of the pack housing 3. In FIG. 2, the sheet 
photo film pack 1 before being loaded in a pack holder 10 is depicted. 
Retainer holes 5c and 5d formed in an advancing edge 5b of the slidable 
lid 5 are engaged with claws 12a and 12b, which are formed with a fastener 
12 of the cap 2. A ridge 5e is disposed near to the grip 5a, and contacts 
an end of the pack housing 3 to keep it in a position of closing the 
opening 3a. 
A pressure plate spring 15 is disposed on a bottom of a photo film chamber 
3b where the sheet photo film units 4 are contained in the stacked manner. 
The pressure plate spring 15 biases the sheet photo film units 4 toward 
the opening 3a. A groove 16 is formed in a V-shape as viewed in section, 
and extends vertically to the sliding direction of the slidable lid 5 on 
the pack housing 3 near to the photo film chamber 3b. Light-trap fabric 17 
is fixed in the groove 16. There is a box-shaped counter chamber 18 in the 
pack housing 3 near to the grip 5a, and contains a counter disk 19. The 
counter disk 19 is rotatable in the counter chamber 18 about a shaft 18b, 
which is formed integrally with a bottom wall 18a. 
In FIG. 3, a push plate 22 included in a ratchet mechanism is inserted in a 
guide groove 18f in the counter chamber 18, and covers the counter disk 
19. The push plate 22 includes a spring portion 22a constituting a bias 
mechanism. Then a cover plate 24 is fitted to close an open face 18g of 
the counter chamber 18 to cover the push plate 22. The cover plate 24 has 
three projections 24a, 24b and 24c at its corners. The projections 24a, 
24b and 24c are received by holes formed in a bottom wall of the counter 
chamber 18 at its corners, to secure the cover plate 24 to the counter 
chamber 18 fixedly. 
As a bias end 22b of the push plate 22 is regulated by the inside of the 
cover plate 24, a bottom end 22d of the push plate 22 is kept in contact 
with a second face 19a of the counter disk 19. See FIG. 4. The push plate 
22 constitutes the ratchet mechanism in combination with seven ratchet 
claws 25 or anti-reversal teeth and a ratchet claw 26 or tooth. The 
ratchet claw 26 has a greater height and a greater length than that of the 
ratchet claws 25. The combination of the counter disk 19 and the push 
plate 22 constitutes the counter device. There is a sleeve 19b, which is 
formed on the second face 19a, and receives insertion of the shaft 18b. 
In FIG. 5, one of the ratchet claws 25 is viewed from the periphery of the 
counter disk 19. The ratchet claws 25 include an inclined surface 25a with 
a small inclination, a ratchet erect surface 25b and an auxiliary inclined 
surface 25c. The inclined surface 25a is rotationally positioned in the 
stepping direction P of the counter disk 19 indicated by the arrow. The 
inclined surface 25a has the inclination ready to move to the bottom of 
the bottom end 22d of the push plate 22. The ratchet erect surface 25b and 
the auxiliary inclined surface 25c are positioned back with reference to 
the stepping direction P. The ratchet erect surface 25b operates for 
preventing rotation in reverse. The auxiliary inclined surface 25c is 
chambered, and guides the push plate 22 to a drop position between the 
ratchet claws 25. The auxiliary inclined surface 25c makes it possible to 
guide the push plate 22 to a predetermined drop position readily even when 
a counter advance spring plate or lever is insufficiently swung. A 
rotational angle of the counter disk 19 can be kept regular. See FIG. 9. 
Note that a flat top 25d is formed between the ratchet inclined surface 
25a and the auxiliary inclined surface 25c. 
If the height h1 of the ratchet erect surface 25b is great, the reversal 
preventing effect is increased. However the stop position of the push 
plate 22 is instable. If in turn the height h1 of the ratchet erect 
surface 25b is small, the stop position of the push plate 22 is stable. 
But the reversal preventing effected is decreased. Experiments were 
conducted in these respects, to obtain the results of TABLE 1. In the 
table, a sign A represents "Excellent", B represents "Good", C represents 
"Usable", D represents "Unreliable and requiring a change" and E 
represents "Unusable". 
TABLE 1 
______________________________________ 
Height h1 Reversal Precision 
of erect preventing 
in stop 
surface 25b effect positions 
______________________________________ 
0.0 mm E A 
0.05 mm D A 
0.1 mm C A 
0.2 mm B B 
0.3 mm B B 
0.4 mm B B 
0.5 mm A C 
0.55 mm A D 
0.6 mm A E 
______________________________________ 
In conclusion of observing the results of TABLE 1, the height h1 of the 
ratchet erect surface 25b is in a preferable range of 0.1-0.5 mm, and in a 
desirable range of 0.2-0.4 mm. In the present embodiment, h1=0.3 mm. A 
whole height h2 of the ratchet claws 25 is 0.6 mm. An inclination angle 
.theta. of the auxiliary inclined surface 25c is 50 degrees. 
In FIG. 6, a first face 19c of the counter disk 19 has counter numerals 1, 
2, 3, . . . , 8 to indicate the number of the exposed sheet photo film 
units. The first face 19c also has an end sign E to indicate the finish of 
all exposures. Around the counter disk 19 are formed eleven stepping claws 
28 or teeth. The stepping claws 28 are engageable with a counter advance 
spring plate or lever 27 of the pack holder 10 having a claw. 
The stepping claws 28 include an erect surface 28a and a guide inclined 
surface 28b. The erect surface 28a is pressed by the counter advance 
spring plate or lever 27. The guide inclined surface 28b is inclined with 
respect to the thickness direction of the counter disk 19. The guide 
inclined surface 28b has a level lowered in the stepping direction P. The 
counter advance spring plate 27 is produced by cutting an end of an arm 
obliquely, and is bent vertically. A claw end 27a with the claw has a 
shape of a right-angled triangle. Each time that the slidable lid 5 is 
moved back and forth after taking an exposure, the counter advance spring 
plate 27 of the pack holder 10 is swung. The claw end 27a pushes the erect 
surface 28 a to step up the counter disk 19 by one step. In FIG. 7, an 
inclined end of the claw end 27a moves along the guide inclined surface 
28b and past the stepping claws 28 easily in the course of the return of 
the counter advance spring plate 27 to its initial position. Delay in the 
counting operation and double exposure are avoided, because the counter 
advance spring plate 27 does not push the stepping claws 28 in reverse to 
the stepping direction. 
In FIG. 8, a counter indicator window 18c is formed in the bottom wall 18a 
of the counter chamber 18 close to the grip 5a for indicating the counter 
numerals and the end sign E. Also an access opening 18d is formed in the 
bottom wall 18a to receive the counter advance spring plate or lever 27. 
When the push plate 22 is positioned between adjacent two of the ratchet 
claws 25 or between the ratchet claw 26 and the ratchet claws 25, one of 
the counter numerals 1-8 is indicated in the counter indicator window 18c. 
See FIG. 9. When the push plate 22 comes to the top of the ratchet claw 26 
and contacts a projection 26a, the end sign E is indicated in the counter 
indicator window 18c. 
The pack holder 10 for use with the sheet photo film pack 1 is depicted in 
FIG. 1. The pack holder 10 is constituted by a holder housing 10a, a 
housing cover 51 and a slidable tray 52 or carriage frame. The housing 
cover 51 is pivotally mounted on the holder housing 10a. The slidable tray 
52 is slidable into or out of the holder housing 10a. There is an exposure 
opening 53 formed in the housing cover 51. The exposure opening 53 has a 
size smaller than the sheet photo film units 4. 
The rear of the housing cover 51 has a receiving face 54, which receives 
the top face of the sheet photo film unit 4 to set the sheet photo film 
unit 4 fixedly on an exposure position. A pair of slots 54a are formed in 
the receiving face 54 and extend in its longitudinal direction. There are 
shifter springs 56 of which one end is secured to the inside of the slots 
54a. Each of the slots 54a is associated with two of the shifter springs 
56. The shifter springs 56 push the pack housing 3 in the downward 
direction when the housing cover 51 is closed after the pack holder 10 is 
loaded with the sheet photo film pack 1. Also the shifter springs 56 push 
the first one of the sheet photo film units 4 positioned in the exposure 
station. 
A ridge 57 is located on the housing cover 51 near to its hinge, and 
engageable with a groove 2a in the cap 2 when the sheet photo film pack 1 
is loaded, to retain the cap 2 to the inside of the holder housing 10a. 
Also projections 58a and 58b are disposed on the housing cover 51, and 
adapted to push down projections 12c and 12d of the fastener 12 to 
separate the claws 12a and 12b from the retainer holes 5c and 5d in the 
slidable lid 5. For the projections 12c and 12d, see FIG. 2. Light-trap 
fabric 59 is fixedly secured to the inside of the housing cover 51 and 
near to a shorter side of the exposure opening 53, and prevents ambient 
light from entry through a gap between the inside of the housing cover 51 
and the slidable lid 5. A knob 61 or tab is disposed slidably on the 
upside of the housing cover 51, and operable to remove the sheet photo 
film pack 1 from the holder housing 10a. 
Box-shaped chambers 62 and 63 are disposed on corners of the slidable tray 
52, and incorporate mechanisms, including one for controlling a slide of 
the slidable tray 52 on the holder housing 10a, and another for stepping 
the counter disk 19. There are claws 64 and 65 protruded over upper walls 
of the chambers 62 and 63 through openings in them. The claws 64 and 65, 
when the opening 3a is fully opened, are engaged with the retainer holes 
5c and 5d, to limit a range within which the slidable lid 5 is drawable. 
Referring to FIG. 9A, the counter advance spring plate or lever 27 is moved 
from an initial position to a ready position in response to a slide of the 
slidable tray 52 and the sheet photo film pack 1 in a first direction, and 
is moved from the ready position to the initial position to output a 
mechanical shift signal in response to a slide of the slidable tray 52 and 
the sheet photo film pack 1 in a second direction. To be precise, the 
counter advance spring plate 27 is associated with a pin 40, disposed in 
the holder housing 10a, for moving in response to the slide of the 
slidable tray 52 and the sheet photo film pack 1 in the second direction. 
The counter advance spring plate 27 has a driven end 27b and the claw end 
27a. The driven end 27b is engaged with the pin 40. The claw end 27a is 
engaged with the stepping claws 28. The counter advance spring plate 27 
rotates in response to movement of the pin 40, so that the claw end 27a 
outputs the shift signal. This mechanical structure is similar to that 
disclosed in U.S. Pat. No. 5,448,324. 
In FIG. 10, the top of the housing cover 51 includes ridges 73 and 74, 
which fixedly set the pack holder 10 on an exposure aperture 72 of a 
large-format camera 71. There is a light-trap fabric 75, which avoids 
entry of ambient light through a gap between an inner wall of the holder 
housing 10a and a sliding surface of the slidable tray 52. 
When the housing cover 51 is closed after inserting the sheet photo film 
pack 1 into the holder housing 10a of the pack holder 10, the ridge 57 
becomes engaged with the groove 2a of the cap 2, to hold the cap 2 in the 
holder housing 10a. The projections 58a and 58b contact the projections 
12c and 12d to push down the fastener 12. The claws 12a and 12b are 
disengaged from the retainer holes 5c and 5d of the slidable lid 5, to 
unlock the slidable lid 5. 
After the pack holder 10 is mounted on the exposure aperture 72 of the 
large-format camera 71, the grip 5a is manually grasped to pull the 
slidable lid 5 to the position of FIG. 11. The slidable lid 5 in this 
state is kept by the claws 64 and 65 from being pulled further. The 
opening 3a of the pack housing 3 is entirely opened. A first sheet photo 
film unit 4a is passed through the opening 3a by the bias force of the 
pressure plate spring 15, contacts the receiving face 54, and is set in 
the exposure position. A latch mechanism incorporated in the chamber 62 
retains the slidable tray 52 in the holder housing 10a. The slidable tray 
52 is not slid even when the slidable lid 5 is pulled out. 
Then the slidable lid 5 is slid back to the initial position. In FIG. 12, 
the slidable lid 5 is moved to a position between the first sheet photo 
film unit 4a and a second sheet photo film unit 4b, so that the slidable 
lid 5 keeps the first sheet photo film unit 4a flat on the exposure 
station. The latch mechanism inside the chamber 62 retains the slidable 
lid 5 on the slidable tray 52. The slidable tray 52 is disengaged from the 
holder housing 10a. Also an indication of the ready state for an exposure 
appears in an arc-shaped projection 78 observable to a user. See FIG. 1. A 
shutter device of the large-format camera 71 is operated to take an 
exposure to the first sheet photo film unit 4a. 
After taking one exposure, the grip 5a is grasped and pulled. In FIG. 13, 
the slidable tray 52 and the sheet photo film pack 1 are slid together out 
of the holder housing 10a. Only the cap 2 remains in its innermost 
position in the holder housing 10a. An edge 54b of the receiving face 54 
keeps the first sheet photo film unit 4 a positioned. The first sheet 
photo film unit 4a is therefore removed from the pack housing 3 by 
relative movement between the receiving face 54 and the upside of the 
slidable lid 5. 
The first sheet photo film unit 4a removed from the pack housing 3 is 
pushed by the shifter springs 56 toward the bottom surface of the holder 
housing 10a. A mechanism (not shown) for regulating the slidable tray 
operates to prevent the slidable tray 52 from being further drawn. As the 
slidable lid 5 is closing the opening 3a of the pack housing 3, no ambient 
light impinges on the sheet photo film unit 4 in the pack housing 3 even 
while the sheet photo film pack 1 is pulled out of the pack holder 10. 
In the course of insertion of the sheet photo film pack 1 and the slidable 
tray 52 into the holder housing 10a, the first sheet photo film unit 4a 
enters the pack housing 3 by movement through a reinsertion mouth 35, 
which is a gap defined between a partition plate 33 and an advancing edge 
3e of the pack housing 3. The rear end of the first sheet photo film unit 
4a is being regulated by a ridge 31a of a sheath receiver 31. Then the 
first sheet photo film unit 4a comes to overlie on the pressure plate 
spring 15, and to a position under the lowest one of the sheet photo film 
units 4 which are still unexposed. 
Upon the finish of the insertion of the sheet photo film pack 1 with the 
slidable tray 52, the counter advance spring plate or lever 27 
incorporated in the chamber 62 pushes the erect surface 28a of the 
stepping claws 28 on the counter disk 19 through the access opening 18d, 
to step up the counter disk 19 rotationally. Then the counter numeral "2" 
comes to appear in the counter indicator window 18c instead of "1". Then 
the counter advance spring plate 27 is moved back to its initial position. 
In the returning movement, the claw end 27a of the counter advance spring 
plate or lever 27 moves in contact with the guide inclined surface 28b. 
Consequently the counter advance spring plate 27 can easily move past the 
stepping claws 28. There is no accidental operation of backward push of 
the counter advance spring plate 27 to a preceding one of the stepping 
claws 28. The counter disk 19 is not rotated in reverse by half a step. It 
is likely that there occur plural kinds of failure, including burrs 
created with the claw end 27a at the time of cutting out the counter 
advance spring plate 27 with insufficient precision, failure in precisely 
bending the counter advance spring plate 27, and failure in precisely 
positioning the counter advance spring plate 27. However there is no 
backward rotation of the counter disk 19 even despite any of those kinds 
of failure. 
When the counter disk 19 is stepped rotationally by the counter advance 
spring plate or lever 27, the bottom end 22d of the push plate 22 is moved 
up along the inclined surface 25a of the ratchet claws 25, then moved in 
contact with the flat top, and guided by the auxiliary inclined surface 
25c before dropping in next intermediate position between adjacent two of 
the ratchet claws 25. See FIG. 9. By the virtue of the auxiliary inclined 
surface 25c, the stepping angle of the counter disk 19 is kept unchanged 
irrespective of minute differences in the swing amount of the counter 
advance spring plate 27. 
The sheet photo film pack 1 now has the same state as that of FIG. 10 
except for the second sheet photo film unit 4b positioned directly under 
the slidable lid 5. Exposures are taken by repeating the same operation. 
After the eighth one of the sheet photo film units 4 is exposed, the sheet 
photo film pack 1 is pulled out and pushed in. The pack housing 3 contains 
the sheet photo film units 4 all exposed and overlaid as a stack in the 
order of exposures. The opening 3a is covered by the slidable lid 5. See 
FIG. 10. 
After all the sheet photo film units 4 in the sheet photo film pack 1 are 
exposed, the push plate 22 comes to the top of the ratchet claw 26 and 
contacts the projection 26a. The counter disk 19, therefore, is inhibited 
from being rotated any more. The end sign E is indicated in the counter 
indicator window 18c to give information of unavailability of unexposed 
photo film unit. A top end 22c of the push plate 22 is engaged with a 
retainer hole 5f of the slidable lid 5 through an opening 24d, to retain 
the slidable lid 5 to the pack housing 3. The housing cover 51 is 
unlocked. The housing cover 51 is opened by operation of the knob 61. 
The housing cover 51 being swung, the projections 12c and 12d are released 
from being pressed by the projections 58a and 58b. The fastener 12 is 
moved up to engage the claws 12a and 12b with the retainer holes 5c and 
5d, to connect the cap 2 with the slidable lid 5. As the ridge 5e of the 
slidable lid 5 is engaged with the end of the pack housing 3, the cap 2 is 
retained on the pack housing 3. The cap 2 is released from being pressed 
by the ridge 57. The sheet photo film pack 1 being used can be removed 
from the pack holder 10. 
In the above embodiment, the outer surface of the stepping claws 28 is 
inclined with reference to the circumferential surface of the counter disk 
19. The stepping claws 28 has a gear shape as viewed from the first face 
19c of the counter disk 19. Alternatively a construction of FIG. 14 can be 
used, in which a counter disk 91 includes stepping claws 92 or teeth, of 
which an outer portion 92b outside a guide inclined surface 92a is 
included in a circumferential surface 91a of the counter disk 91 in a 
manner of a "crown gear". 
In the above embodiment, the spring portion 22a is included in the single 
piece of the push plate 22. The piece is formed from thermoplastic resin. 
This is advantageous in small cost for raw material and manufacturing 
operation. However the spring portion 22a is likely to be degraded in its 
bias force with time, for example after preservation for a long time. In 
view of this, another preferred embodiment is described, in which a metal 
coil spring is used which is unlikely to be degraded with time. 
In FIG. 15, a push plate 101 of a ratchet mechanism has a flat support 
portion 101a, which projects vertically to the moving direction of the 
push plate 101. The flat support portion 101a receives a metal spring 100. 
A retainer projection 102 is formed integrally with the top of the flat 
support portion 101a in such a shape that the metal spring 100 is lightly 
pushed to the retainer projection 102 to be retained thereto. The retainer 
projection 102 has a cross shape including four segments, each of which 
has a subsidiary projection 102a of a small size. When an end of the metal 
spring 100 is pushed to the retainer projection 102, one turn of the metal 
spring 100 is captured by the subsidiary projection 102a to secure the 
metal spring 100 to the retainer projection 102. 
In combination with the push plate 101 having the coil spring, a 
ring-shaped ridge 105 is formed on the rear of the cover plate 24 at its 
center. The ring-shaped ridge 105 has a sector shape of 270 degrees 
without a range of the remaining 90 degrees, for the purpose of keeping a 
vertically moving path of the push plate 101. A shape 105a of the 
ring-shaped ridge 105 viewed in cross section is triangular, and has a 
thick foot and a thin end. Consequently the shape 105a makes it possible 
to guide the top of the metal spring 100 to the center of the ring-shaped 
ridge 105 even when the engagement between the metal spring 100 and the 
retainer projection 102 becomes less tight due to irregularities in the 
size of molding the push plate 101. The orientation of the metal spring 
100 is corrected even if an inclination occurs in the metal spring 100 
with reference to the top face of the flat support portion 101a. 
Note that a U-shaped spring may be used instead of the metal spring 100. 
Also the retainer projection 102 for retaining the metal spring 100 may be 
formed on the rear of the cover plate 24. 
The bias force applied by the metal spring 100 to the push plate 101 to 
push the counter disk 19 while the number of the exposures is indicated is 
in a range of 20-400 gf on the condition of the metal spring 100 having 
the compressed length of 6 mm in an ordinary state of the use. When the 
sheet photo film pack is handled roughly or subjected to a considerable 
shock, the stop position of the counter disk 19, and thus the indicated 
numeral, is offset if the metal spring 100 is not strong. This is because 
the inertia in the rotation of the counter disk 19 operates beyond the 
force of the metal spring 100. Should the force of the metal spring 100 be 
too great, there occurs great resistance specially during the rotating 
operation to the end sign E. Accordingly it is concluded that bias force 
of the metal spring 100 is in a preferable range of 120-350 gf, and in a 
desirable range of 150-300 gf. 
To stabilize the stepping operation of the counter disk, it is important to 
keep the distance between the counter disk claws and the advance spring 
plate or lever within a suitable range. In FIGS. 16 and 17, ridges 107 and 
108 are formed on an outer wall of the counter chamber 18 near to the 
access opening 18d. The ridges 107 and 108 extend vertically to the bottom 
wall 18a. Engaging portions 111 and 112 are disposed respectively under 
the guide rails 8 and 9, and in an asymmetric manner with respect to a 
center line L1 of the pack housing 3 crosswise to a shorter side of the 
pack housing 3. In the present embodiment, the engaging portions 111 and 
112 lie on a center line L2 of the pack housing 3 crosswise to a longer 
side of the pack housing 3, but are offset in the longitudinal direction 
of the pack housing 3. See FIG. 17. Edges of the slidable tray 52 have 
receiving portions 114 and 115, which correspond to the engaging portions 
111 and 112. 
The receiving portion 115 has an inclined edge located closer to the 
chamber 62. The receiving portion 115, when receiving the engaging portion 
112, operates to shift the pack housing 3 in the arrow direction .alpha. 
which is away from the chamber 62. The receiving portion 114 has an 
inclined edge located opposite to that of the receiving portion 115. The 
receiving portion 114, when receiving the engaging portion 111, operates 
to shift the pack housing 3 in a direction opposite to the arrow direction 
.alpha.. The engaging portions 111 and 112 are asymmetrical to each other 
with respect to the center line L1. When the pack housing 3 is inserted in 
the slidable tray 52, the pack housing 3 is rotated in the arrow 
directions .beta.1 and .beta.2 of FIG. 17. The ridges 107 and 108 are 
pressed against the chamber 62. Even if there is a play between the pack 
housing 3 and the slidable tray 52, the distance from the counter disk 19 
to the counter advance spring plate or lever 27 is kept constant. In the 
present embodiment, the pack housing is provided with the projections. The 
slidable tray is provided with the recesses. Alternatively the pack 
housing may be provided with recesses, and the slidable tray may be 
provided with projections. 
In FIG. 18 depicting the end of the counter advance spring plate or lever 
27 in enlargement, let be an inclination angle of the counter advance 
spring plate 27 with reference to a line S perpendicular to a lateral face 
62a of the chamber 62. Let D be a claw projecting length with which the 
counter advance spring plate 27 projects over the lateral face 62a in the 
direction of the line S while is 2.57 degrees. Experiments were conducted 
to find relationships between the claw projection length D, the counter 
stepping and the counter back-stepping, as indicated in TABLE 2. 
The term "counter back-stepping" is used to mean a state in which the claw 
end 27a of the counter advance spring plate or lever 27 when moved back to 
its initial position is contacted by one of the stepping claws to cause 
erroneous rotation in reverse to the normal stepping direction. In TABLE 
2, the Shape I is related to stepping claws 150 or teeth of a comparative 
example as illustrated in FIG. 27. The Shape II is related to the stepping 
claws 28 of FIG. 6. The Shape III is related to the stepping claws 92 of 
FIG. 14. The signs A, B, C, D and E respectively represent "Excellent", 
"Good", "Usable", "Unreliable and requiring a change" and "Unusable". For 
the counter back-stepping, a higher one of the grades is provided 
according to the smallness of the counter back-stepping. For example, the 
sign E means inevitable occurrence of the counter back-stepping. 
TABLE 2 
______________________________________ 
Shape I of claws 150 
Shapes II & III of 
Claw pro- 
(Comparative ex.) 
claws 28 & 92 
jecting 
Counter Counter back- 
Counter 
Counter back- 
length D 
stepping stepping stepping 
stepping 
______________________________________ 
4.60 mm 
E A E A 
4.70 mm 
D A D A 
4.80 mm 
C A C A 
4.90 mm 
B B B B 
5.00 mm 
B B B B 
5.10 mm 
B B B B 
5.20 mm 
B B B B 
5.30 mm 
B C B B 
5.40 mm 
A D A B 
5.50 mm 
A E A C 
5.60 mm 
A E A D 
5.70 mm 
A E A E 
______________________________________ 
As is observed in TABLE 2, the claw projecting length D for the shape I is 
preferably in a range of 4.8-5.3 mm, more preferably in a range of 4.9-5.2 
mm, and desirably in a range of 5.0-5.1 mm. The shapes II and III with the 
improvements can have a larger tolerable range of the claw projection 
length D. It is possible to set the length D in a preferable range of 
4.8-5.5 mm, in a more preferable range of 4.9-5.4 mm, and in a desirable 
range of 5.0-5.3 mm. In a preferred aspect of the present invention, the 
stepping claws of the shape III can be used. The claw projecting length D 
can be 5.1-5.3 mm. The central value of the claw projecting length D can 
be determined 5.2 mm in the course of assembly operation. 
In the above embodiments, the counter indicator window 18c is used for 
indication. However a greater opening may be used for appearance of a part 
of the disk, in combination with which a pointer indicia or index indicia 
may be used. 
In the above embodiment, the eleven stepping claws 28 are used. 
Alternatively another number of stepping claws may be used, and can be 
nine or more. Of course the rotational pitch of the stepping claws 28 is 
equal to that of the counter numerals 1-8 and E and that of the ratchet 
claws 25. 
In one aspect of the present invention, the ratchet claws 25 have the 
auxiliary inclined surface 25c. It is possible in the present invention 
that a counter disk having the stepping claws 150 of FIG. 27 is provided 
with the ratchet claws 25 having the auxiliary inclined surface 25c in the 
face opposite to the stepping claws 150. 
In another aspect of the present invention, the metal spring 100 of FIG. 15 
is used. It is possible in the present invention that a counter disk 
having the stepping claws 150 of FIG. 27 is combined with the push plate 
101 and the metal spring 100. 
Referring to FIGS. 19-26, still another preferred embodiment is described, 
in which the tightness in engagement of the counter disk claws with the 
advance spring plate or lever is increased. A counter disk 119 of FIGS. 19 
and 20 is contained in a counter chamber 118 of FIG. 21. There are holes 
118h, 118i and 118j respectively at corners of the counter chamber 118. A 
cover plate has three projections which are formed with its corners, and 
received in the holes 118h, 118i and 118j, to secure the cover plate to an 
open face 118g of the counter chamber 118. 
Each of stepping claws 128 or teeth is provided with an erect surface 128a 
and a guide inclined surface 128b. The erect surface 128a is pushed by a 
counter advance spring plate or lever 127 having a claw. The guide 
inclined surface 128b is inclined with respect to the thickness direction 
of the counter disk 119, and has a level coming lower in the stepping 
direction P. A claw top 128c of the stepping claws 128 protrudes over a 
level of a first face 119c in the thickness direction. In FIGS. 21, 22 and 
23, a bottom wall 118a of the counter chamber 118 is provided with a 
ring-shaped groove 118k, which is concentric with a shaft 118b, and 
receives the claw top 128c of the stepping claws 128. 
It is possible to keep the engaging amount sufficient between a claw end 
127a having the claw of the counter advance spring plate or lever 127 and 
the erect surface 128a of the stepping claws 128. Even if there is 
smallness in precision in the manufacture of the counter advance spring 
plate 127 or failure in assembly of the counter advance spring plate 127, 
the claw end 127a of the counter advance spring plate 127 can be engaged 
with the erect surface 128a reliably each time when the counter advance 
spring plate 127 of the pack holder swings upon sliding the slidable lid 
after taking an exposure. The counter disk 119 therefore is stepped up 
accurately by one step. 
In FIG. 21, let D1 be a length of the counter chamber 118 in the lid 
sliding direction inclusive of a width of a groove 118n, which is formed 
on the periphery of the open face 118g for receiving the cover plate. D1 
is determined as 24.7 mm. Let D2 be a distance between centers of the 
holes 118i and 118j. D2 is determined as 19.7 mm. Let D3 be a distance 
between centers of the hole 118i and the shaft 118b in the width direction 
of the slidable lid. Let D4 be a distance between centers of the hole 118h 
and the shaft 118b in the width direction of the slidable lid. In the 
present embodiment, D3=9.95 mm and D4=11 mm. Let D5 be a distance from the 
center of the shaft 118b to a first corner of the counter chamber 118 
inclusive of the width of the groove 118n in the lid width direction. Let 
D6 be a distance from the center of the shaft 118b to a second corner of 
the counter chamber 118 inclusive of the width of the groove 118n in the 
lid width direction. In the present embodiment, D5=12.3 mm and D6=13.2 mm. 
Let a be an inner diameter of the ring-shaped groove 118k. Let .beta. be 
an outer diameter of the ring-shaped groove 118k. In the present 
embodiment, .alpha.=18.2 mm and .beta.=23.6 mm. 
In FIG. 23, the bottom wall 118 a has an indicia projection 120, with which 
each of the counter numerals 1, 2, 3, . . . , 8 and the end sign E is 
formed. There is a washer-shaped projection 118p, formed close to the 
shaft 118b of the counter chamber 118, for preventing the indicia 
projection 120 from being rubbed on the bottom wall 118a. Let a be a 
height of the washer-shaped projection 118p. a is determined as 0.2 mm. 
Let h be a projecting amount at which the claw top 128c of the stepping 
claws 128 projects over the first face 119c. Should the projecting amount 
h be set great, the engaging amount with the counter advance spring plate 
or lever 127 is increased to enable the counter disk 119 to be stepped 
stably. However a groove depth d of the ring-shaped groove 118k is the 
greater. The thickness of the bottom wall 118a is the smaller, so that 
flow of resin becomes the less smooth in the course of molding the pack 
housing. There occurs a problem of insufficient moldability. If in turn 
the projecting amount h should be set small, then there occurs a problem 
of failure in stepping operation of the counter disk 119. Experiments were 
conducted with changes in the groove depth d and the projecting amount h, 
to find results of the steppability of the counter disk 119 and the 
moldability, as indicated in TABLE 3. Note that a distance b between the 
claw top 128c of the stepping claws 128 and the bottom of the ring-shaped 
groove 118k was determined 0.1 mm in an unchanged manner. In TABLE 3, the 
signs A, B, C, D and E respectively represent "Excellent", "Good", 
"Usable", "Unreliable and requiring a change" and "Unusable". 
TABLE 3 
______________________________________ 
Projecting length 
Depth d of 
h of claw 128 
groove 118k 
Steppability 
Moldability 
______________________________________ 
0.00 mm 0.00 mm E A 
0.10 mm 0.00 mm D A 
0.15 mm 0.05 mm C A 
0.20 mm 0.10 mm B B 
0.25 mm 0.15 mm B B 
0.30 mm 0.20 mm B B 
0.35 mm 0.25 mm B B 
0.40 mm 0.30 mm B B 
0.45 mm 0.35 mm A C 
0.50 mm 0.40 mm A D 
0.60 mm 0.50 mm A E 
______________________________________ 
In conclusion of observing the results of TABLE 3, the height h of the 
stepping claws 128 is in a preferable range of 0.15-0.45 mm, in a more 
preferable range of 0.20-0.40 mm, and in a desirable range of 0.25-0.35 
mm. In the present embodiment, h is determined as 0.30 mm. A depth d of 
the ring-shaped groove 118k is determined as 0.30 mm. 
In operation, the claw end 127a of the counter advance spring plate or 
lever 127 is engaged with the erect surface 128a of the stepping claws 128 
with high reliability even occurrence of low precision in manufacturing 
the counter advance spring plate 127 or assembly of the same. The claw top 
128c of the stepping claws 128 effectively has the level projecting over 
the first face 119c. 
Reference numeral 118 c designates a counter indicator window. Also the 
counter chamber 118 includes an access opening 118d and a guide groove 
118f. The counter disk 119 includes a second face 119a and a sleeve 119b. 
A push plate 122 as ratchet mechanism includes a spring portion 122a, a 
bias end 122b, a top end 122c and a bottom end 122d. Ratchet claws 125 or 
anti-reversal teeth include an inclined surface 125a and an auxiliary 
inclined surface 125c. A ratchet claw 126 or tooth has a projection 126a. 
In FIG. 24, a further preferred embodiment is illustrated, in which an 
additional inclined surface 132 is formed between adjacent two of the 
stepping claws 128 of the counter disk 119 for the purpose of guiding the 
advance spring plate or lever. The additional inclined surface 132 
communicates with the guide inclined surface 128b only at a point. There 
is no step between the guide inclined surface 128b and the additional 
inclined surface 132. The additional inclined surface 132 being formed, 
the claw end 127a of the counter advance spring plate 127 is prevented 
from being captured in contact with the circumferential portion between 
the stepping claws 128 in the course of return of the counter advance 
spring plate 127 to its initial position even when the position of the 
counter advance spring plate 127 is offset in the longitudinal direction 
of the counter advance spring plate 127. 
In FIG. 25, let D7 be an interval between a center of the counter disk 119 
and the stepping claws 128. Let D8 be the maximum of a width of the 
additional inclined surface 132. In the present embodiment, D7=9.42 mm and 
D8=0.5 mm. In FIG. 26, let be a diameter of the counter disk 119. Let H 
be a height of the stepping claws 128 over the first face 119c. In the 
present embodiment, =23 +0.1 mm, and H=0.3 mm. 
As described above, the shape of the counter disk 119 has numerous 
projections or recesses, including the claw top 128c protruding at 0.3 mm 
over the first face 119c. Extremely high precision is required for molding 
the counter disk 119. In molding of resin, deformation called "molding 
strain" is likely to occur due to differences in the shrinkability between 
portions with different thicknesses in the course of drop of temperature. 
It is therefore preferable to subject the counter disk 119 as a resin 
product to the annealing process in which the product after being molded 
is cooled at an extremely low speed. 
Also residual strain may occur in the molded product after being molded. To 
remove the residual strain quickly, it is also possible to utilize a 
technique in which the molded product is heated again, for example at 
80.degree. C. for 1-2 hours, and then cooled gradually down to the room 
temperature. In the sheet photo film pack of the present embodiment, this 
technique is used in the cap, the fastener, and the push plate 122. 
Although the present invention has been fully described by way of the 
preferred embodiments thereof with reference to the accompanying drawings, 
various changes and modifications will be apparent to those having skill 
in this field. Therefore, unless otherwise these changes and modifications 
depart from the scope of the present invention, they should be construed 
as included therein.