Self-advancing film cassette including an auxiliary rotation transmittance structure

A self-advancing film cassette is provided with an auxiliary rotation transmittance structure for reliably transmitting rotation of a spool to the inner turns of a roll of film in order to prevent reverse rotation of the film caused by loosening of the inner turns of the roll of film or inferior bending rigidity. According to one preferred embodiment, a step portion for pushing the bending line of a film trailer is formed on a slit, permitting the end of the film trailer to be inserted therein. In another preferred embodiment, a spool is provided with a resilient member or flap member for urging the inner turns of the roll of film toward its outer turns. The film trailer has increased bending rigidity by having an embossing treatment, applied thereto, or by attaching a skirt thereto.

BACKGROUND OF THE INVENTION 
This invention relates to a self-advancing film cassette for advancing the 
leader of a photographic film strip through a film passage mouth of the 
cassette in accordance with rotation of a spool. 
Presently, a photographic film cassette containing a roll of photographic 
film strip of 135 type (35 mm in width) is most widely used. This 
photographic film cassette is constituted by a light tight cylindrical 
cassette housing provided with a film passage mouth, a spool rotatably 
contained in the cassette housing, and a roll of film coiled on the spool. 
The leader of the film protrudes outside through the film passage mouth. 
When loading the film cassette in a camera, the film leader is brought 
into engagement with a threading member of the camera. By driving the 
threading member, the film is pulled out from the cassette housing and is 
fed to a film take-up chamber so as to be wound on a take-up spool in this 
chamber. 
In recent years, in order to make the photographic film cassette compact 
and easy to handle, a self-advancing film cassette has been proposed in 
which the entire film is contained in the cassette housing, and the film 
leader is advanced from the film passage mouth in accordance with rotation 
of the spool. In order to advance the film leader reliably, it is 
necessary for this kind of film cassette to rotate the spool integrally 
with the roll of film, thereby to transmit the rotation of the spool to 
the film leader reliably. For example, in Japanese Patent Laid-open 
Publication No. Sho 53-13918, a self-advancing film cassette is described, 
in which both sides of a film trailer and a spool shaft are provided with 
teeth. By meshing with these teeth, the spool and the roll of film are 
rotated integrally. On the other hand, in Japanese Utility Model Laid-open 
Publication No. Sho 62-164343, another self-advancing film cassette is 
described, in which a spool is provided on its outer surface with a 
substance having a shock absorbing property and resilience in order to 
increase friction between the spool and the film. 
If the roll of film is partially loosened, a part of the film is reversed 
and is bent in a generally U-shape. In U.S. Pat. No. 4,832,275, a 
self-advancing film cassette is described, in which a pair of rings are 
disposed around both ends of a roll of film wound on a spool. Further, in 
U.S. Pat. No(s). 4,834,306 and 4,848,693 a self-advancing film cassette is 
described, in which a rim is provided on flanges of a spool in order to 
press both sides of the outermost turn of a roll of film with the rim. In 
U.S. Pat. No. 4,846,418, a construction is described in which a spool is 
formed of a pair of spool halves which are slidable in an axial direction, 
and both sides of a roll of film are clamped by the pair of spool halves. 
However, when both sides of the film trailer and the spool shaft are 
provided with teeth there arises a problem in that the configurations of 
the film and the spool become complicated, and manufacturing costs become 
high. Although all the other self-advancing film cassettes mentioned above 
have such an advantage that the loosening of the peripheral portion of the 
roll of film can be prevented, a space is likely to be formed in the 
vicinity of a shaft of the spool because of loosening of the roll of film. 
If this space is formed, the film is likely to be reversed in a U-shape 
when the spool rotates in the unwinding direction. This causes the film to 
jam and makes it impossible to advance the film leader. 
SUMMARY OF THE INVENTION 
Therefore, it is an object of the present invention to provide a 
self-advancing film cassette in which rotation of a spool is transmitted 
to a film leader reliably. 
Another object of the invention is to provide a self-advancing film 
cassette which is simple in construction and yet is able to prevent 
reverse rotation of the film. 
To achieve the above and other objects, the present invention includes an 
auxiliary rotation transmittance structure for transmitting force of 
rotation of a spool to the innermost turn of a roll of film when the spool 
rotates in the unwinding direction. In a preferred embodiment, proper 
treatment is applied to a film trailer so that the film trailer will not 
be reversed when the film advances. The auxiliary rotation transmittance 
structure, formed on the outer periphery of the spool, is constituted by a 
step portion extending in the axial direction, and a slit formed in the 
step portion and adapted to permit a trailer end of the bent film to be 
inserted therein, the bent portion of the film being pushed by the step 
portion when the spool rotates in the unwinding direction. 
In another embodiment of the present invention, an auxiliary rotation 
transmittance structure is mounted on a spool and is adapted to urge the 
inner turns of a roll of film toward the outer turns. This auxiliary 
rotation transmittance structure includes a flap member which is swung to 
urge the innermost turn of the roll of film toward the outermost turn when 
the spool rotates in the unwinding direction. In still another embodiment, 
the auxiliary rotation transmittance structure is formed of a coiled 
resilient member, disposed in the inner side of the innermost turn of a 
roll of film, and adapted to urge the innermost turn of the roll of film 
toward the outermost turn of the roll of film. The resilient member may be 
disposed between the innermost and second innermost turns in such a manner 
as to cover up the innermost turn. 
Since the inventive auxiliary rotation transmittance structure urges the 
innermost turn of the roll of film toward the outermost turn of the roll 
of film, or pushes the film trailer or increases the bending rigidity of 
the film trailer, reverse rotation of the roll of film can be prevented at 
its inner turns. As a result, force of rotation of the spool can be 
transmitted reliably to the film leader.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In FIG. 1, the self-advancing film cassette 2 is constituted by a roll of 
film 4 and a cassette 3 for containing the roll of film 4 in light tight 
manner. The cassette 3 in turn is constituted by a cylindrical cassette 
housing 5, a pair of end caps 6 and 7 engageable with the cassette housing 
5 in a light tight manner, and a spool 8. These component members 
preferably are formed of plastics. The cassette housing 5 is provided with 
a film passage mouth 11 extending in the axial direction thereof. In order 
to prevent light from entering the cassette housing 5 through the film 
passage mouth 11, the film passage mouth 11 is provided with a plush, 
having a light trapping function, attached thereto. The cassette housing 5 
is provided on its inner wall, in the vicinity of both ends thereof, with 
a pair of annular ridges 12 for contacting the outermost turn of the roll 
of film 4 in order to prevent the roll of film 4 from being loosened and 
to reduce friction with the film. 
The roll of film 4 is constituted by a 135 type film (35 mm in width) wound 
on the spool 8 with its back surface facing outwardly. Before or after the 
roll of film 4 is loaded in a camera (not shown), a film leader 16 is 
drawn in the cassette housing 5. The pair of end caps 6 and 7 are provided 
with openings 6a and 7a for rotatably holding a spool shaft 13 of the 
spool 8. One of the end caps 6a and 7a may be integrated with the cassette 
housing 5. Furthermore, it may be designed such that the end caps are 
attached to the cassette housing 5, and such that in the foregoing state, 
the cassette housing 5 integrated with the end caps is divided into two 
equal halves, each cassette half being molded integrally from plastic 
material 
In FIG. 2, the spool 8 is constituted by the spool shaft 13 and a pair of 
flanges 14 and 15. The spool shaft 13 has a slit formed thereon. An end 
17a of a film trailer 17 is inserted into the slit so as not to escape 
therefrom. The trailer end 17a may be secured in the slit by an adhesive 
agent. A pair of rings 20 and 21, constituting the auxiliary rotation 
transmittance structure are supported rotatably on the spool shaft 13. As 
shown in FIG. 2, these rings 20 and 21 include flap portions 20a and 21a 
defined by channel-like cuts 22 and 23 formed in a part of the 
corresponding rings 20 and 21. The flap portions 20a and 21a are swung by 
a projection 13a (FIGS. 3A and 3B) formed on the spool shaft 13 when the 
spool 8 rotates in the unwinding direction. The rings 20 and 21 are 
provided with means for enlarging the coefficient of friction such as, for 
example, minute rough spots formed on the peripheral surfaces of the rings 
20 and 21, so that the film will not slip. Flap members, formed separately 
from the rings 20 and 21, may be attached swingably to the rings 20 and 
21. In an actual construction, each of the rings 20 and 21 consists of two 
ring halves, which are mounted first on the spool shaft 13, and then are 
integrated by adhering or fitting them to each other. 
Operation of the above embodiment now will be described. The self-advancing 
film cassette 2, as shown in FIG. 3A has the film leader 16 fully drawn 
into the cassette 3. When this self-advancing film cassette 2 is loaded in 
a film supply chamber, a driving shaft (not shown) is coupled with the 
spool shaft 13. When the spool shaft 13 is rotated in the unwinding 
direction by the driving shaft, the projection 13a pushes the flap 
portions 20a and 21a outwardly. Since these flap portions 20a and 21a, as 
shown in FIG. 3B, are swung to urge the innermost turn of the roll of film 
4 toward the outermost turn thereof, the loosening at the inner turns of 
the roll of film 4 can be obviated an frictional force between the turns 
can be increased. As a result since the force of rotation of the spool 
shaft 13 is transmitted reliably to the roll of film 4, the film trailer 
17 is reversed to prevent occurrence of jamming, and the spool 8 is 
rotated integrally with the roll of film 4. While the roll of film 4 is 
being rotated together with the spool 8, the film leader end 16a is 
separated by a separation claw 25. The film leader end 16a is protruded 
outside through the film passage mouth 11 and advances toward the film 
take-up chamber. 
FIGS. 4 and 5 show one embodiment in which the loosening of the roll of 
film is prevented by a resilient member. Members similar to those of the 
above-mentioned embodiment are denoted by like reference numerals in this 
embodiment. The spool shaft 13 is provided with a substantially 
cylindrical resilient member 30 having a spring property for spreading 
outwardly. The resilient member 30 is disposed in such a manner as to 
cover up the spool shaft 13 with one end 30a thereof inserted into the 
spool shaft in a substantially perpendicular direction and fixed thereto. 
The resilient member 30 preferably is a thin metallic plate, but also may 
be molded from plastic material. A surface treatment is applied to the 
surface of the periphery of the resilient member 30 in order to enlarge 
its coefficient of friction, thereby to prevent the film from slipping. 
As shown in FIG. 5, the film trailer end 17a is fixed to the spool shaft 13 
at the side of a fixed end 30a of the resilient member 30. The film 
trailer 17 is wound on the resilient member 30 in such a manner as to 
enclose the fixed end 30a. In this embodiment, as the resilient member 30 
pushes the innermost turn of the roll of film 4 toward the outermost turn 
because of its resilience the loosening of the inner turns of the roll of 
film 4 can be prevented. In order to prevent the take-in action caused by 
reverse rotation of the film, it is preferable that the film trailer end 
17a and the fixed end 30a of the resilient member 30 be as close as 
possible. 
In the embodiment shown in FIG. 6, the fixed end 31a of the resilient 
member 31 is disposed at an outer side of the film trailer end 17a so as 
to enclose the innermost turn of the roll of film 4. When the bending 
portion 31b of the resilient member 31 abuts against the bending portion 
of the film trailer 17 to rotate the spool 8 in the unwinding direction, 
it pushes the bending portion of the film from the backward direction. In 
this embodiment, the resilient member 31 urges the roll of film 4 from its 
inner side to enlarge force of friction between the turns, and in addition 
the resilient member 31 pushes the film trailer 17. As a result, the force 
of rotation of the spool 8 is transmitted reliably to the roll of film 4. 
FIGS. 7 and 8 show an embodiment in which the bending line of the film 
trailer is pushed by a part of the spool shaft. In this embodiment a slit 
35 is formed on the spool shaft 13 so as to extend toward the center of 
the spool shaft 13. The slit 35 has a wedge shape, and is narrower in a 
deeper position thereof. The radius at an edge 35a of one wall of the slit 
35 is larger than that at an edge 35b of the other wall. Owing to the 
foregoing arrangement a step having a length H, larger than the thickness 
of the film, is formed between the edges 35a and 35b. Instead of forming 
the inner wall of a coil core 26 high as mentioned above, a thin plate may 
be inserted into the slit 35 together with the film trailer end 17a. 
The film trailer end 17a is inserted into the slit 35 in such a manner as 
not to escape therefrom, and is bent by substantially 90.degree. along a 
sharp bending line 17b so that the film trailer 17 can contact the edge 
35b. The film trailer 17 may be bent naturally by rotating the spool 16 
after the film trailer end 17a has been inserted into the slit 35a, but it 
is more preferable that the film trailer 17 be bent beforehand by heat 
pressing or mechanical means. Otherwise, an adhesive agent may be charged 
into the slit 35. 
In this embodiment, when the spool 8 is rotated in the unwinding direction, 
the edge 35a abuts and pushes the bending line 17b of the film trailer 17. 
As a result, rotation of the spool 8 is reliably transmitted to the film 
leader end 16a. By this, the film leader end 16a can be advanced through 
the film passage mouth 11. 
FIG. 9 shows another embodiment in which rotation of the spool 8 can be 
transmitted reliably to the roll of film 4 by applying no extra mechanical 
improvement to the cassette body or the spool and by increasing bending 
rigidity of the film trailer. That is, in a film 40 shown in FIG. 9, by 
forming embossing 42 on the film trailer 41 fixed to the spool shaft, the 
bending rigidity of the film trailer 41 is increased. With the foregoing 
construction, when the spool 8 is rotated in the unwinding direction, the 
film trailer 41 is not taken in by being bent, and rotation of the spool 8 
is transmitted reliably to the roll of film 4. The embossing 42 can be 
formed by applying, for example, the film 40 to a heat-embossing roller 
under pressure. 
In the embodiment shown in FIG. 10, one end of a skirt 45 having a high 
bending rigidity is attached to the film trailer 44 and the other end of 
the skirt 45 is fixed to the spool shaft 13. This skirt 45 is made from 
material having higher rigidity than the film 40, such as polyester, 
polyimide, polyphenylene sulfite and polyether imide. The thickness of the 
skirt 45 preferably is approximately 100 to 200 microns. The embodiment 
shown in FIGS. 9 and 10 also may be used in combination with any of the 
above-mentioned embodiments. 
While the invention has been described in detail above with reference to a 
preferred embodiment, various modifications within the scope and spirit of 
the invention will be apparent to people of working skill in this 
technological field. Thus the invention should be considered as limited 
only by the scope of the appended claims.