Photographic Film Cassette

1. Field of the Invention

The present invention relates to a photographic film cassette, more particularly to a self-advancing photographic film cassette in which rotation of a spool causes photographic film to advance to the outside of a cassette shell.

2. Description Relative to the Prior Art

A known film cassette includes photographic film positioned so that the film leader does not protrude from the cassette shell prior to loading the cassette in a camera. Such a film cassette is easily loaded into a camera. Simple feeding mechanisms are used with the latter type of film cassette and include a construction which rotates the spool to unwind the film, thereby causing the leads to move through a film passageway and exit the cassette. A film cassette disclosed in U.S. Pat. No. 4,834,306 has a spool provided with rotatable flanges on both lateral sides of the film wound in a roll. Each flange consists of a disk and a circumferential lip. Lips are formed on the periphery of the disks to project in the direction along the length of the cassette. Spreading projections are formed on the inside of the cassette shell in positions where the film is directed to the film passageway for deforming the flanges outwardly to widen the interval between the flanges. The spreading projections continuously spread the flanges in the positions close to the film passageway so as to release the outermost turn of the film from contact with the lips. Therefore, the film leader is advanced to exit the cassette through the film passageway by rotating the spool in the direction to unwind the film.

However, the film cassette described in the above U.S. Pat. has a disadvantage in that the flanges cannot recover their initial shape, because the continuous deformation of the flanges by means of the spreading projections gives rise with time to a creep of the flanges, though the deforming load is considerably small. If the flanges become permanently deformed, the lips of the flanges might not cover the edges of the outermost turns of the film, and this may cause the film to be so loosened that film leader will not advance when the spool is rotated. There is also a problem of a large friction between the contact surfaces of the spreading projections and the flanges spread by the spreading projections. A large load applied to the spool causes necessity of a camera having a film feeding mechanism capable of providing a large torque for rotating the spool, of which the manufacturing cost might be enlarged.

It is therefore an object of the present invention to provide a film cassette capable of preventing the film in a roll from loosening without irrecoverable deformation of the flanges on the spool supporting the film.

It is another object of the present invention to provide a film cassette moving a spool which can be rotated by applying a small rotary torque thereto.

In order to achieve the above and other objects and advantages of this invention, a photographic film cassette comprises: a cassette shell provided with a film passageway through which the film is passed; a spool disposed in the cassette shell for winding the film in a roll; a pair of flanges rotatably provided on the spool in positions close to both ends of the spool for defining positions of both lateral edges of the film; each flange consisting of a disk and a circumferential lip; a pair of lips formed on the disks along peripheries thereof to project face to face with each other for contact with edges of an outermost turn of the film so as to prevent the film from loosening; and means for pressing partly the flanges against the film in order to clamp partly both side faces of the film in a state with the flanges out of the vertical relative to the spool. Both lateral sides of the leading end portion are cut off so as to determine an interval between the lateral edges of the film to be smaller than an interval between circumferential edges of the lips opposing in a state where the flanges are in contact with the side faces of the film. The film is prevented from loosening without irrecoverable deformation of the flanges.

In accordance with a preferred embodiment, a pair of spreading projections are formed on an inside of the cassette shell in positions close to the film passageway for projecting to be in contact with circumferential edges of the lips. The spreading projections and a pair of ridges constituting pressing means keep the flanges out of the vertical relative to the spool. Contact surfaces of the pair of ridges and the flanges in contact with each other and contact surfaces of the spreading projections and the lips in contact with each other are previously processed with embossing. The spool can be rotated even by applying a small rotary torque thereto.

The above objects and advantages of the present invention will become more apparent from the following detailed description when read in connection with the accompanying drawings, in which:

FIG. 1 is a section view illustrating a film cassette in accordance with a preferred embodiment of the present invention;

FIG. 2 is a section view illustrating the film illustrated in FIG. 1, taken along line II--II of FIG. 1;

FIG. 3 is a section view illustrating a film cassette in accordance with another preferred embodiment of the present invention; and

FIG. 4 is a section view illustrating the film cassette illustrated in FIG. 3, taken along line IV--IV of FIG. 3.

In FIGS. 1 and 2 illustrating a photographic film cassette 1 according to the present invention, the film cassette 1 consists of a spool 10, a pair of flanges 11, and a cassette shell 12 for containing them in a light-tight fashion. The cassette shell 12 is constituted by upper and lower shell halves 13 and 14 separated along a juncture indicated as line II-II in FIG. 1, which shell halves are molded from plastics each integrally, and joined together in a light-tight fashion by use of an ultrasonic welding or the like. A positioning tool or jig is used for holding the two shell halves 13 and 14 in a joined state for welding. The outsides of the two shell halves 13 and 14 are provided with respectively two positioning ridges 15 for positioning the two shell halves 13 and 15 on the positioning tool. The ends of the spool 10 do not project from the cassette shell 12, but are included in the outline of the cassette shell 12 underneath so as to prevent a user from rotating the spool 10 only with his fingers.

A trailing end portion of the film 16 is fixedly inserted in a groove 17 of the spool 10, about which the film 16 is wound. A leading end portion 16a of the film 16 has a width smaller than that of the film 16. A stepped portion thus formed by changing the width of the film constitutes curved edges 16b of a smooth curve at a radius of 5 mm or more. A separation claw 19 is provided on the film passageway 18 in order to separate the leading end portion 16a from the outermost turn of the film 16, which is wound in a roll on spool 10. For the time of separation, the front end of the leading end portion 16a is cut in an oblique fashion so as to prevent jamming of the leading end portion 16a.

The flanges 11 are formed in a manner separate from the spool 10, around which spacings are defined in the openings of the flanges 11. Openings for rotatably supporting the spool 10 on the cassette shell 12 require a construction which will shield light. Collars 20 formed on both ends of the spool 10 are inserted in annular grooves 21 on each of the two shell halves 13 and 14. Each flange consists of a disk and a circumferential lip. The flanges 11 are disposed between the collars 20. Lips 22 are formed on the periphery of the disks of the flanges 11 to project in directions facing each other, and serve to prevent the outermost turn of the film 16 from loosening.

Two ridges 23 formed on the inside of the cassette shell 12 contact the flanges 11 causing the flanges to deviate from a vertical position relative to a horizontal position of spool 10. The ridges project on inner lateral walls around the openings having the annular grooves 21 toward the flanges 11, and define a straight line intersecting vertically the juncture indicated by line II--II in FIG. 1. The ridges 23 are in contact with the surfaces of the flanges 11 that are opposite the lips 22, and press the flanges 11 toward a position to clamp the outermost turn of the film 16 wound on the spool. The circumferential edges of the lips 22 in the state with the flanges 11 pressed by the ridges 23 are spaced at a distance slightly larger than the width of the leading end portion 16a, which is therefore free from the lips 22 and separated from the outermost turns of the wound film 16 by the separation claw 19 at the time of advancing the film 16.

A pair of ridges 24 are formed in the vicinity of the film passageway 18 and project from the inner lateral walls of the two shell halves 13 and 14 in the direction toward the flanges 11 in a manner similar to the ridges 23. The projecting height of the ridges 24 is set to be smaller than that of the ridges 23. The ridges 24 restrict the spreading between the flanges 11 in the vicinity of the film passageway 18 so as to prevent an excessive loosening of the wound film 16. When the outer surfaces of the flanges 11 are in contact with the ridges 24, the interval between the circumferential edges of the lips 22 are larger than the width of the film 16, so that the film 16 is allowed to be separate in the vicinity of the film passageway 18 and not be covered by the lips 22, whereas the flanges 11 are movably disposed out of the vertical relative to the spool 10.

As used herein the phrase "out of the vertical", and the like, when used to describe the orientation of the flanges 11, means that the flanges do not form right angles with the axis of the spool or wound film. The phrase is used as a convenient description with reference to a horizontally positioned spool or wound film.

The inside horizontal surfaces of the film passageway 18 as illustrated in FIG. 2 are provided with passage ridges 25 projecting from the upper and lower surfaces. The passage ridges 25 extend in the direction of passing the film 16 and are positioned in correspondence with the disposition of perforations 26 of the film 16. When the film 16 passes through the film passageway 18, it is in contact with the passage ridges 25 in the position of the perforation 26 to protect image frames in exposure. A conventional plush material 27 is provided with the film passageway 18 for trapping light entering the film passageway 18.

The operation of the embodiment as constructed above is now described. To advance the leading end portion 16a of the film 16 to the outside of the cassette shell 12, the spool 10 is rotated leftward in FIG. 1. The leading end portion 16a is separated by the separation claw 19 and is directed to the film passageway 18. Further rotation of the spool 10 brings the curved edges 16b of the film 16 in contact with the circumferential edges of the lips 22, which are pushed outward to spread the interval between the flanges 11 until their outer surfaces come near to the ridges 24. The distance between the circumferential edges of the lips 22 becomes greater than the width of the film 16, which is released from the restriction of the lips 22 and is advanced to the outside of the cassette shell 12 through the film passageway 18.

To wind up the film 16 drawn out of the cassette shell 12, the spool 10 is rotated rightward. The film 16 is wound up in contact with the passage ridges 25 coming in contact with the perforations 26, whereby the image frames on the film 16 will not be scratched or damaged.

When the wound film 16 is loosened during advance or wind-up, the outermost turn of the film 16 presses the inner side of the lips 22 so that the friction between the film 16 and the lips 22 causes the flanges 11 to rotate. The loosening of the outermost turn of the film 16 therefore causes the flanges 11 to rotate, making it possible to advance/wind up the film 16.

It is noted that the ridges 23 and 24 are formed in a disposition of lines vertical to the juncture between the two shell halves 13 and 14, so that each of the shell halves 13 and 14 can be molded in a manner integral with the ridges 23 and 24. Moreover, the precision is improved in forming the plane surfaces of the inner lateral walls of the cassette shell 12.

The present embodiment is provided with the collars 20 formed in both inner lateral walls of the cassette shell 12 in the vicinity of both ends of the spool 10. Such a light shielding construction may be alternatively that in which gaps defined in the openings of the cassette shell 12 around the spool 10 are bent in the direction vertical to the spool 16.

The spool 10, the flanges 11 and the cassette shell 12 are formed from different kinds of material, because they might be welded together by a frictional heat generated by their sliding movement at the time of ultrasonic sealing if they were formed from one material. It is possible to use or reuse the spool 10 and the flanges 11 for a long time. The cost for manufacturing the cassette 1 is reduced.

A film cassette 30 according to another preferred embodiment of the present invention is described referring to FIGS. 3 and 4. A cassette shell 31 of the film cassette 30 is provided with ridges 32 and spreading projections 33, so that the flanges 11 are supported out of the vertical relative to the spool 10 in order to let out a leading end portion 34a of photographic film 34 through a film passageway 35. The ridges 32 are similar to the above ridges 23, project from the inner lateral walls of upper and lower shell halves 36 and 37 toward the flanges 11 in order to press the flanges 11 toward a position to clamp the outermost turn of the would film 34, and define straight lines intersecting vertically the juncture indicated by line IV--IV in FIG. 3.

The two spreading projections 33 are formed in the positions where the film 34 comes near to the film passageway 35, and where they are in contact with the lips 22 of the flanges 11 so as to keep the separation between the circumferential edges of the lips 22 greater than the width of the film 34. The film 34 is prevented from loosening by the lips 22 and is released by the spreading projections 33 in a position close to the film passageway 35. The flanges 11 are still rotatably supported out of the vertical relative the spool 10. It is preferable in order to reduce friction that a processing of embossing, or forming irregularities of a size approximately from 10 to 30 um is effected on the whole contact surfaces between the ridges 32 and the flanges 11 and those between the spreading projections 33 and the lips 22.

In the film cassette 30 as constructed above, the leftward rotation of the spool 10 causes separation claws 38 to separate the leading end portion 34a of the film 34 to feed it to the outside of the cassette shell 31 through the film passageway 35. It is noted that the interval defined between the interior circumferential surface of the cassette shell 31 and the periphery of the flanges 11 is determined to be approximately 0.2 mm, so that the leading end portion 34a of the film 34 can be rotated while the leading end portion 34a is separate from the lips 22 of the flanges 11.

An experiment was conducted to measure a rotary torque to rotate the spool 10 for advancing the leading end portion 34a of the film 34 from the cassette shell 31 containing the film 34. The measured torque was 220 g.multidot.cm, which is a value considerably smaller than 350 g.multidot.cm, a value measured by applying the conventional film cassette described as a prior art.

Another experiment was conducted with respect to this cassette subjected to a processing of embossing. A measured value 170 g.multidot.cm was obtained. A torque which is half as large as that required for the conventional cassette is sufficient to rotate the spool 10, so that the cost for manufacturing a film feeding mechanism of a camera can be highly reduced.

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.