Photographic film cassette and lens-fitted photographic film unit using the same

A lens-fitted photographic film unit has a film supply chamber preloaded with unexposed photographic film. A cassette-containing chamber contains a film cassette. The film after exposure is wound on a spool of the cassette. The film unit is provided with a mechanism for exposing the film in a succession of frames. An axial hole is formed in an upper end of the spool. Knurled inner teeth are formed inside the axial hole. A wind-up wheel is mounted on the film unit over the cassette-containing chamber to be externally operable for rotation. A drive shaft on the wind-up wheel protrudes into the cassette-containing chamber, and is received in the axial hole. Knurled outer teeth about the drive shaft mesh with the inner teeth on the spool. The drive shaft and spool will thus mesh with each other in any relatively rotated position thereof, which avoids loss of usable film.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a photographic film cassette, and to a 
lens-fitted photographic film unit using the same. More particularly, the 
present invention relates to a photographic film cassette which is 
improved as to its use with a lens-fitted photographic film unit, and to 
the lens-fitted photographic film unit using the same. 
2. Description of the Prior Art 
Lens-fitted photographic film units (hereinafter referred to simply as film 
units) are now on the market, e.g. under the trademark "Fujicolor Quick 
Snap" (manufactured by Fuji Photo Film Co., Ltd.). Such known film units 
are a single-use camera preloaded with photographic film strip 
(hereinafter referred to as film). The film unit has a main body provided 
with a film supply chamber and a cassette-containing chamber formed on 
opposite horizontal sides of a taking lens. The unexposed film is wound in 
a roll in the film supply chamber. An externally rotatable wind-up wheel 
is coupled with a spool in the cassette contained in the 
cassette-containing chamber. A user who has purchased the film unit winds 
the film frame by frame back into the cassette after each exposure. The 
film unit in its entirety is then forwarded to a photo laboratory after 
exposure of the film. An operator at the laboratory unloads the film, and 
subjects it to development and printing. The user receives finished 
photographs and a negative film but does not receive the film housing of 
the film unit. 
A 135-type photographic film as defined by the International Organization 
for Standardization (ISO) has a standard number of photographable frames 
and a length sufficient for such imaging these frames. The prevailing 
standard provides an allowance of film beyond the length sufficient for 
the nominal number of exposures, to such an extent that a conventional 
camera can take with standard film one or two exposures in addition to the 
standard number of exposures ascribed to the film. To make greatest use of 
such allowance in the available length of the film, improved film units 
are now on the market, e.g. under the trademark "Fujicolor Quick Snap 
Econoshot" (manufactured by Fuji Photo Film Co., Ltd.), with which a user 
can take a greater number of photographs than the stated number of 
photographable frames of the strip of film contained therein, e.g. 27 
photographs on a 24-exposure film. 
To take good photographs greater in number than the stated number of 
exposures on the film, it is necessary to position the film initially 
relative to the exposure aperture of the film unit, so as to keep 
unchanged the interval between the first frame on the film and the film 
end attached to the spool in the cassette. This is because, should the 
interval between the first frame and the film end be too long, it may 
happen that a predetermined greater number of photographs, e.g. 27, cannot 
all be taken. 
To insert the film cassette into the cassette-containing chamber, it is 
necessary to engage the spool of the cassette with a drive shaft formed on 
the wind-up wheel of the film unit. The conventional spool is provided 
with a key structure formed at an upper end of the spool and shaped in 
rotational symmetry about 180 degrees or half a rotation. The conventional 
drive shaft on the wind-up wheel is provided with a fork structure shaped 
in rotational symmetry about 180 degrees. It may happen that either of the 
spool and the drive shaft must be rotated relatively through as much as 
180 degrees before the spool can be engaged with the drive shaft. 
When the film is inserted and positioned in the exposure aperture, the 
shutter mechanism is set to have a predetermined orientation. This is 
because even operations in factory associated with assembly, e.g. testing 
of the shutter mechanism, never consume any extra portion of the film. 
When the film is wound up back into the cassette, it rotates a driven 
sprocket wheel which engages perforations in the film, and this causes a 
wind-up stop mechanism to prevent the wind-up wheel from rotating further 
than is necessary to rewind the film by one frame. When the shutter 
mechanism is kept oriented in consideration of positioning of the film, 
correspondingly the sprocket wheel is kept positioned rotationally. In 
further correspondence with this, the wind-up stop mechanism, and the 
wind-up wheel are kept positioned rotationally. Because of the key 
structure of the spool, it is impossible when positioning the film to 
adjust the rotational position of the wind-up wheel as preferred. 
Accordingly the direction of the key structure of the spool requires 
adjustment in view of the rotational position of the wind-up wheel. 
Prior to inserting the film into the film housing in the course of 
manufacturing the film unit, nearly all the strip of the film is drawn out 
of the cassette. Drawing out of the film is terminated before tension 
along the film increases excessively between the roll and the cassette. 
This is because, should the tension become excessive while the film is 
fully drawn out of the cassette, this tension would pull and stretch the 
film, or curl the film in the direction along the film width, thereby to 
cause difficulties in positioning the film inside the film unit. 
However, reduced tension of the film in the course of insertion frequently 
causes some deviation in the rotational positions of the spools in the 
mass production of the film units. As it may happen that the conventional 
spool must be rotated at 180 degrees relative to the drive shaft before 
the spool can be engaged with the drive shaft, it frequently happens that 
a rotational position of the spool is such that the key structure of the 
spool cannot be engaged with the fork of the wind-up wheel. If the spool 
is rotated through an angle up to 180 degrees for adjustment according to 
the fork, the precision of positioning of the film initially relative to 
the exposure aperture is reduced. The interval between the first frame and 
the film end will vary. As a result, a predetermined number of 
photographs, greater than the stated number of exposures on the film, 
cannot be taken completely. 
OBJECT OF THE INVENTION 
In view of the foregoing problems, an object of the present invention is to 
provide a photographic film cassette having a spool such that, when 
associated photographic film is initially positioned inside a lens-fitted 
photographic film unit, precision in positioning is ensured. 
It is also an object of the invention to provide a lens-fitted photographic 
film unit for use therewith. 
SUMMARY OF THE INVENTION 
In order to achieve the above and other objects and advantages of this 
invention, an axial hole is formed in a distal end of a spool in a 
photographic film cassette, which is specially adapted to receive a rotary 
drive shaft when a camera is loaded with the film cassette. Knurled inner 
teeth are formed on the inside of the axial hole in the end of the spool 
that receives the drive shaft, thereby to rotate the spool upon rotation 
of the drive shaft. 
A wind-up wheel is mounted over the cassette-containing chamber of the 
camera, to be rotated by the user. The drive shaft is formed on the 
wind-up wheel to protrude into the cassette-containing chamber and to be 
inserted in the axial hole in the cassette spool. Knurled outer teeth are 
formed around the drive shaft to mesh with the inner teeth of the axial 
hole. 
The interval between the first frame and the film end is thus prevented 
from varying. A predetermined number of photographs, greater than the 
stated number of exposures on the film, can thus be taken without fail.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In FIG. 1 illustrating a photographic film cassette having a novel spool, a 
cassette shell 2 formed of thin metal plate is constituted of a body plate 
4 rolled cylindrically, caps 5 fitted on both ends thereof, and 
light-shielding member or plush attached to a passage port 6 for 
photographic film. As is illustrated in FIG. 2 in detail, a spool 7 is 
rotatably contained in the cassette shell 2. Photographic film 9 is wound 
on the spool 7 between a pair of spool flanges 8. 
One distal end of the spool 7 is provided with an axial hole 3 which 
receives a drive shaft, as shown for example in FIGS. 8 and 9, 
incorporated in a camera or a lens-fitted film unit, for winding up the 
film 9. A pair of diametrically opposed engageable keys 10 are formed in 
the bottom of the axial hole 3. The keys 10 have tops whose level is D 
deep from the distal end of the spool 7. D is preferably 3.5 mm in the 
present embodiment, but can be from 2 to 4.2 mm. The keys 10 are 
symmetrical so they have the same orientation upon each half rotation of 
the spool 7. 
The keys 10 are accessible to a fork-shaped drive shaft 41 (see FIG. 10) 
having a fork 40 formed in a rotationally symmetrical shape with respect 
to half a revolution. When the drive shaft 41 rotates, rotation is 
transmitted via the engaged keys 10 to the spool 7 to rotate it. In a 
spool end opposite to the axial hole 3, there is formed an axial hole (not 
shown) and engageable keys, in the manner of a conventional standardized 
spool. 
On the inside of the axial hole 3, there is formed an inner gear with a 
depth D. The inner gear is constituted of a plurality, for example thirty, 
of inner teeth 12 of roulette or knurled arrangement, which are arranged 
at a predetermined pitch, namely at the angular pitch .theta.1 being equal 
to 12 degrees. The tip angle .theta.2 of the inner teeth 12 is 90 degrees. 
The height of the teeth 12 is 0.55 mm. The interval W between adjacent 
tips of the inner teeth 12 is 0.96 mm. Those values are changeable with 
the circumstances. It is preferable that .theta.2 is in the range from 60 
to 100 degrees. 
In FIG. 4, reference numerals 12a and 12b respectively represent tips of 
the inner teeth 12 and bottoms between the inner teeth 12. A distal end of 
the inner teeth 12 is provided with sloping faces 14 spaced apart by 
cylindrical faces 7a inside the spool 7. When a drive shaft 28 (see FIG. 
8) is inserted in the axial hole 3, the sloping faces 14 guide the drive 
shaft 28. The sloping faces 14, as is illustrated in FIG. 4, are curved in 
arcuate fashion at a radius of curvature of about 0.75 mm, and slope on an 
arc lying on a circle whose axis extends radially of the spool 7. Such a 
slope is also useful for preventing wind-up wheel 27 from rotating in the 
clockwise direction X as viewed in FIG. 7, namely in the reverse direction 
to that for winding up the film, when the drive shaft 28 formed integrally 
with the wind-up wheel 27 is pressed into the axial hole 3. 
The wind-up wheel 27 is provided with peripheral teeth 27a of roulette or 
knurled arrangement. A main body 20 of the film unit is provided with a 
preventive claw 20a (FIG. 7) for contact with the peripheral teeth 27a in 
order to prevent the wind-up wheel 27 from rotating reversely, namely, in 
the clockwise direction. Should the spool 7 lack the sloped faces 14, the 
drive shaft 28 could be pressed into the axial hole 3 so as to apply 
reverse rotational force to the wind-up wheel 27 for slight rotation. The 
reverse rotational force applied to the wind-up wheel 27 would press the 
peripheral teeth 27a against the preventive claw 20a, which would hinder 
the axial hole 3 from receiving the drive shaft 28. Even if the axial hole 
3 should fully receive the drive shaft 28, a manufacturing step of 
ultrasonic welding following the cassette-loading step would weld the 
preventive claw 20a to wind-up wheel 27 while there is pressure of the 
peripheral teeth 12 on the preventive claw 20a. But this problem is solved 
by the construction having the sloped faces 14. 
FIGS. 5 and 6 illustrate other preferred sloped faces 34 and 44, 
respectively. The planar sloped faces 34 in FIG. 5 are radially inwardly 
directed relative to the axis of spool 37. The planar sloped faces 44 in 
FIG. 6 are triangular. Shown at 32 and 42 are inner teeth, on which 32a 
and 42a are tooth tips, and 32b and 42b are tooth bottoms. 37a and 47a are 
cylindrical faces inside the spools 37 and 47. Those planar sloped faces 
34 and 44 are advantageous as well as a tooth-tip angle .theta.2 of 90 
degrees, because it is then easy to prepare molds for forming the spools 
37 and 47. 
FIG. 7 illustrates the relationship between the parts of the lens-fitted 
film unit to be assembled together. A film housing of the film unit is 
constituted of the main body 20, a front cover 21 and a rear cover 22, 
each molded from plastics. The main body 20 is provided with a 
cassette-containing chamber 24 and a film supply chamber 25. The film 
cassette 2 is contained in the cassette-containing chamber 24. The 
unexposed film 9 drawn out of the cassette 2 in a roll is inserted into 
the film supply chamber 25 through the bottom of the main body in the 
axial direction. 
The main body 20, as is well known in the art, is provided with a 
photograph-taking mechanism PM comprising a shutter and other conventional 
parts to effect photography by exposing the film. On the main body 20, the 
wind-up wheel 27 is mounted rotatably. As is illustrated in FIG. 8, the 
drive shaft 28 on the bottom of the wind-up wheel 27 is inserted through 
the top wall of the cassette-containing chamber 24 and projects into the 
cassette-containing chamber 24. The drive shaft 28 is provided with outer 
teeth 30 of rouletted or knurled arrangement. When the film cassette 2 is 
inserted into the cassette-containing chamber 24, the drive shaft 28 is 
inserted into the axial hole 3 to engage the outer teeth 30 on shaft 28 
with the inner teeth 12 in spool 7. The outer teeth 30 are formed to have 
an angular pitch of 12 degrees, a tip angle of 79.79 degrees, and a tooth 
height of 0.58 mm. The bottom end of the drive shaft 28 is provided with a 
conical surface slanted at about 30 degrees, so as to facilitate insertion 
of the drive shaft 28 into the axial hole 3. 
The operation of the above construction will now be described. In the 
course of manufacturing the lens-fitted film unit, the film housing is 
assembled together. To load the main body 20 with the film cassette 2 
within the cassette-containing chamber 24 as illustrated in FIG. 9, the 
film 9 is drawn out of the film cassette 2 by the maximum withdrawable 
amount. The film 9 formed in a roll is inserted into the film supply 
chamber 25. Note that the film 9 is omitted from FIG. 9 for clarity of 
illustration. The assembling operation takes care to avoid applying too 
much tension to the film 9 when the film is fully withdrawn. Were it not 
for the teeth 12 and 30, the rotational position of the spool 7, when the 
cassette-containing chamber 24 is loaded with the cassette 2, would not be 
constant. 
In the novel spool 7, the inner teeth 12 in the axial hole 3 cooperate with 
the outer teeth 30 formed on the drive shaft 28. The coupling of the spool 
7 to the wind-up wheel 27 is effected irrespective of the position of the 
engageable keys 10 and dependent only on the engagement of the outer teeth 
30 with the inner teeth 12. At the beginning of insertion of the drive 
shaft 28 into the axial hole 3, the outer teeth 30 can momentarily fail to 
engage with, but rather can abut on, the inner teeth 12. If this happens, 
the spool 7 can be rotated to a small extent in order to couple the drive 
shaft 28 engagedly with the axial hole 3, i.e. by one angular pitch or 
half the angular pitch of the inner teeth 12, namely 6 or 12 degrees. Such 
small rotation of the spool 7 rewinds the film 9 only to the extent of 
about 0.5 mm, which is small enough to have no influence to the position 
of the first frame to be exposed in the film unit. It is therefore 
possible for the film supply chamber 25 to contain the greatest possible 
amount of film 7. To be precise, the film 7 of a length for 24 exposures 
in a conventional use can be contained in the novel film unit in a form 
capable of providing 27 exposures, while being positioned with exactitude, 
thanks to the interengaging teeth 12 and 30. 
Such a lens-fitted film unit is manufactured on the assumption that it will 
be put to only a single use, so that the film housing lacks adaptation to 
repeated use. But there are some users who use such single-use 
photographic film units repeatedly, by repeatedly loading unexposed film, 
as in a conventional camera. In the film unit adapted to make 27 exposures 
on a 24-exposure film, there is a frame counter for counting 27 frames. 
Adaptation of the 24-exposure film to use for 27 exposures requires 
factory-loading of the film unit with film precisely positioned. It is 
very difficult for users manually to reload the film unit with unexposed 
film, because manual handling can position with only low precision a film 
portion to be first exposed inside the film unit. It can cause an 
erroneous condition wherein the shutter is operated 27 times to use only 
24 or 25 frames on the film, with consequent overlapping of two or three 
exposures. 
The above failure is caused by use of a film cassette having a conventional 
spool. In accordance with the present invention, however, such a failure 
is prevented. When it is intended to reload film in the film unit having 
the wind-up wheel 27, a conventional film cassette having a spool without 
inner teeth is inserted, but its conventional spool will not couple with 
the drive shaft 28 of the wind-up wheel 27. This lack of engagement 
operates to warn the user that 27 exposures could not be effected even 
though the counter is adapted to count 27 frames. This avoids use wherein 
fewer frames are created on the film than the times of operating the 
shutter. 
Notice from FIG. 10 that the novel spool 7 with its inner teeth 12 is 
usable with a conventional drive shaft 41 which has been in use so far in 
lens-fitted film units and cameras. The axial hole 3 in the spool 7 and 
the engageable keys 10 are formed following the definition standardized by 
ISO. The engageable keys 10 are adapted to engage firmly with the 
conventional fork 40 on the conventional drive shaft 41. It is easy for 
users manually to reload a conventional camera or film unit with unexposed 
film, because a film portion to be first exposed is manually positioned 
inside the camera, without need for particularly high precision. No fewer 
imaging frames will ever be created on the film than the times of 
operating the shutter. The compatibility of the novel spool and drive 
shaft with the conventional spool and drive shaft is shown in the 
following table: 
______________________________________ 
Conventional 
Novel Drive 
Drive Shaft 
Shaft 
______________________________________ 
Conventional Spool 
Usable Unusable 
Novel Spool Usable Usable 
______________________________________ 
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 being included therein.