Abstract:
In a film cassette, a film spool comprises a spool core supported for rotation in an unwinding direction to thrust a leader section of a film roll coiled about the spool core to the exterior of the cassette, a pair of flanges radially confining the film roll and loosely coupled coaxially with the spool core normally to permit the spool core to be rotated relative to the flanges in the unwinding direction, and engagement means rotatably fixed to the spool core for rotation with the spool core relative to the flanges in the unwinding direction to move into engagement with one of the flanges to make the one flange rotate in unity with the spool core in the unwinding direction. According to the invention, the one flange is resiliently flexible, and biasing means distorts the one flange for urging the one flange firmly against the engagement means to ensure the engagement means will engage the one flange when the spool core is rotated relative to the flanges in the unwinding direction.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     Reference is made to commonly assigned copending application Ser. No. 07/464,264 entitled FILM CASSETTE, and filed Jan. 12, 1990 in the names of Edward H. Dowling et al. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates generally to the field of photography, and in particular to a film cassette containing roll film. More specifically, the invention relates to a film cassette that is capable of automatically advancing a non-protruding film leader to the exterior of the cassette shell responsive to unwinding rotation of a film spool within the shell. 
     2. Description of the Prior Art 
     In conventional 35 mm film manufacturers&#39; cassettes, such as manufactured by Eastman Kodak Co. and Fuji Photo Film Co. Ltd., the filmstrip is wound on a flanged spool which is rotatably supported within a cylindrical shell. A leading or forward-most section of the filmstrip approximately 21/3 inches long, commonly referred to as a &#34;film leader&#34;, normally protrudes from a light-trapped slit or mouth of the cassette shell. One end of the spool has a short axial extension which projects from the shell, enabling the spool to be turned by hand. If the spool is initially rotated in an unwinding direction, the film roll inside the shell will tend to expand radially since the inner end of the filmstrip is attached to the spool, and the fogged leader section protruding from the slit will remain stationary. The film roll can expand radially until a firm non-slipping relation is established between its outermost convolution and the inner curved wall of the shell. Once this non-slipping relation exists, there is a binding effect between the film roll and the shell which prevents further rotation of the spool in the unwinding direction. Thus, rotation of the spool in the unwinding direction cannot serve to advance the filmstrip out of the shell, and it is necessary in the typical 35 mm camera to engage the protruding leader section to draw the filmstrip out of the shell. 
     A 35 mm film cassette has been proposed which, unlike conventional film cassettes, can be operated to automatically advance a film leader out of the cassette shell by rotating the film spool in the unwinding direction. The film leader originally is located entirely inside the cassette shell. Specifically, in U.S. Pat. No. 4,423,943, granted Jan. 3, 1984, there is disclosed a film cassette wherein the outermost convolution of the film roll wound on the film spool is radially constrained by respective circumferential lips of two axially spaced flanges of the spool to prevent the outermost convolution from contacting an inner curved wall of the cassette shell. The trailing end of the filmstrip is secured to the film spool, and the forward or leading end of the filmstrip is slightly tapered purportedly to allow it to freely extend from between the circumferential lips and rest against the shell wall at a location inwardly of a non-lighttight film passageway to the outside of the cassette shell. During initial unwinding rotation of the film spool, the leading end of the filmstrip is advanced along the shell wall until it reaches an inner entrance to the film passageway. Then, it is advanced into and through the film passageway to the exterior of the cassette shell. The passageway has a width that is less than the width of the filmstrip, thus resulting in the filmstrip being transversely bowed as it is uncoiled from the film spool, and thereby facilitating movement of the film edges under the circumferential lips of the flanges. However, severe transverse bowing of the filmstrip in order to move its longitudinal edges under the circumferential lips of the flanges may damage the filmstrip. 
     Like the type of film cassette disclosed in U.S. Pat. No. 4,423,923, commonly assigned U.S. Pat. Nos. 4,834,306 granted May 30, 1989, and 4,848,693, granted Jul. 18, 1989, each disclose a film cassette that is capable of automatically advancing a non-protruding film leader to the exterior of the cassette shell in response to rotation of the film spool in the unwinding direction. Specifically, there is disclosed a film cassette wherein a film roll is wound on a spool between a pair of coaxially spaced, independently rotatable flanges. The two flanges have respective circumferential annular lips or skirted peripheries which prevent the outermost convolution of the film roll from clock-springing into contact with the interior wall of the cassette shell. When the spool is initially rotated in the unwinding direction, the flanges may momentarily remain stationary and the film roll, since its inner end is secured to the spool, tends to expand radially to ensure a firm non-slipping relation between the outermost convolution and the skirted Peripheries. Once the non-slipping relation exists, continued rotation of the spool will similarly rotate the flanges. This allows stationary internal spreaders to deflect successive portions of the skirted peripheries to an axial dimension exceeding the film width, in turn allowing the leading end of the film roll to be freed from the radial confinement of the annular lips and to be advanced into and through a lighttight film passageway to the exterior of the cassette shell. A stripper-guide located adjacent an inner entrance to the film passageway diverts the leading end of the film roll into the passageway by being received between the leading end and the next-inward convolution of the film roll responsive to unwinding rotation of the spool. 
     THE CROSS-REFERENCED APPLICATION 
     It has been found that by fixing at least one of the flanges to the film spool during unwinding rotation of the spool, as contrasted with allowing each of the flanges to remain rotatable independently of the spool as in commonly assigned U.S. Pat. Nos. 4,834,306 and 4,848,693, there is immediately effected a frictional relationship between the outermost convolution of the film roll and the skirted periphery of the fixed flange which improves the ability of the spool to thrust the film leader through the lighttight passageway to the exterior of the cassette shell. In particular, the frictional relationship increases the pushing force the spool will apply to the film leader to propel the leader out of the cassette shell. Moreover, it has been found that by allowing both of the flanges to be rotated independently of the spool during winding rotation of the spool, as in commonly assigned U.S. Pat. Nos. 4,834,306 and 4,848,693, it is substantially ensured that the leader can be rewound within the skirted peripheries of the flanges without being obstructed by the skirted peripheries. 
     The cross-referenced application discloses a film cassette wherein a film spool comprises a spool core supported for rotation in an unwinding direction to thrust a leader section of a film roll coiled about the spool core to the exterior of the cassette and in a winding direction to return the leader to the interior of the cassette, and a pair of flanges positioned along the spool core to overlie opposite sides of the film roll to radially confine the film roll within skirted peripheries of the flanges. The flanges have respective central openings through which the spool core coaxially extends to normally permit the flanges and the spool core to be independently rotated in the two directions. According to the invention, engagement hooks are rotatably fixed to the spool core for initial rotation with the spool core relative to the flanges in the unwinding direction, for movement into engagement with at least one of the flanges to make the flange rotate in unity with the spool core when the spool core is rotated further in the unwinding direction, to improve the ability of the film spool to thrust the leader from the cassette, and in the film winding direction, for movement out of engagement with the flange to permit the flange to be independently rotated when the spool core is rotated further in the winding direction, to substantially ensure the leader can be rewound within the skirted periphery of the flange. 
     SUMMARY OF THE INVENTION 
     According to the invention, there is provided a film cassette wherein a film spool comprises (a) a spool supported for rotation in an unwinding direction to thrust a leader section of a film roll coiled about the spool core to the exterior of the cassette, (b) a pair of flanges radially confining the film roll and loosely coupled coaxially with the spool core normally to permit the spool core to be rotated relative to the flanges in the unwinding direction, and (c) engagement means rotatably fixed to the spool core for rotation with the spool core relative to the flanges in the unwinding direction to move into engagement with one of the flanges to make the one flange rotate in unity with the spool core in the unwinding direction, and which is characterized in that: 
     said one flange is resiliently flexible; and 
     biasing means is positioned to distort the one flange for urging the one flange firmly against the engagement means to ensure the engagement means will engage the one flange when the spool core is rotated relative to the flanges in the unwinding direction. 
     More particularly, the one flange has a plurality of concentric arcuate slots cut in it which longitudinally extend in the unwinding direction and are spaced from one another to include respective flat areas of the one flange between the slots. The engagement means includes respective hook-like members sized to move fully into the slots to engage the one flange. And the biasing means includes integral means for distorting the one flange when the hook-like members are out of the slots, to urge the flat areas firmly against the hook-like members to ensure the hook-like members will move fully into the slots when the spool core is rotated relative to the flanges in the unwinding direction. 
     Conversely, in the cassette design disclosed in the cross-referenced application, it has been found that when the spool core is initially rotated relative to the flanges in the unwinding direction, the hook-like members, should they not be in the respective slots in the flanges, may not enter the slots to engage the flanges. The invention solves this possible problem by distorting the flanges to urge their flat areas between their slots against the hook-like members to ensure the hook-like members will be received in the slots when the spool core is initially rotated relative to the flanges in the unwinding direction. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view of a film cassette according to a preferred embodiment of the invention; 
     FIG. 2 is an elevation view of the film cassette, illustrating the cassette shell open to reveal a film roll coiled about a film spool; 
     FIG. 3 is an elevation view similar to FIG. 2, through in section; 
     FIG. 4 is an end view partly in section of the cassette shell, the film roll and the film spool, illustrating the manner in which the film roll is originally stored on the film spool; 
     FIGS. 5, 6, and 7 are end views similar to FIG. 4, illustrating the manner in which the film roll is unwound from the film spool; 
     FIGS. 8 and 9 are elevation views of the film roll and the film spool, illustrating the manner in which the film roll is originally stored on the film spool; 
     FIGS. 10 and 11 are elevation views similar to FIGS. 8 and 9, illustrating the manner in which the film roll is unwound from the film spool; 
     FIG. 12 is an exploded perspective view of the film spool without the film roll; 
     FIG. 13 is an elevation view partly in section of the film roll and the film spool, illustrating the manner in which a pair of film confining flanges of the spool may be fixed via respective engagement hooks to the spool for concurrent rotation with the spool; 
     FIG. 14 is a blow-up of a Particular portion of FIG. 13, illustrating one of the engagement hooks engaging one of the film confining flanges; and 
     FIG. 15 is a blow-up similar to FIG. 14, illustrating the engagement hook not engaging the film confining flange. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The invention is disclosed as being embodied preferably in a 35 mm film cassette. Because the features of this type of film cassette are generally well known, the description which follows is directed in particular to elements forming part of or cooperating directly with the disclosed embodiment. It is to be understood, however, that other elements not specifically shown or described may take various forms known to persons of ordinary skill in the art. 
     Referring now to the drawings, FIGS. 1, 2 and 12 depict an improved 35 mm film cassette 1 comprising a light-tight cassette shell 3 and a film spool 5 which is rotatable about an axis X in film unwinding and winding directions U and W within the cassette shell. The cassette shell 3 consists of two shell halves 7 and 9 which are mated along respective grooved and stepped edge portions 11 and 13. The mated halves 7 and 9 define upper and lower aligned circular openings 15 and 17 for relatively shorter and longer opposite open-end pieces 19 and 21 of a spool core or hub 23, and they define a narrow relatively-straight film passageway 25 to the exterior of the cassette shell 3. The longer and shorter open-end pieces 19 and 21 of the spool core 23 each include an annular peripheral groove 27 which mates with a corresponding edge portion 29 of the respective openings 15 and 17 in the cassette shell 3 to rotatably support the film spool 5 for rotation about the axis X in the film unwinding and winding directions U and W. A known black velvet or plush material 31 lines the interior of the film passageway 25 to prevent ambient light from entering the film passageway. 
     A roll 33 of 35 mm filmstrip F is coiled about the spool core 23 to form successive film convolutions. As shown in FIG. 3, the film roll 33 includes an outermost convolution which comprises a film leader 35 having a leading or forward end 37, and it includes a next-inward convolution 39 coiled behind the outermost convolution. The inner or trailing end of an innermost convolution 40 of the film roll 33 is secured to the spool core 23 using known attachment means, not shown. See FIG. 13. 
     A pair of upper and lower identical, very thin, flexible film constraining flanges 41 and 43 are coaxially spaced along the spool core 23 as shown in FIGS. 1, 2, 8, 12 and 13. The two flanges and 43 comprise respective integral disks 45 and and respective integral annular lips or skirts 49 and 51 which circumferentially extend from the disks. The two disks 45 and 47 cover opposite substantially flat sides of the film roll 33 which are defined by corresponding opposite longitudinal edges 53 and 55 of each successive convolution of the film roll, and they have respective central holes 56 through which the spool core 23 coaxially extends to permit rotation of the spool core relative to the flanges 41 and 43. Biasing means in the form of pairs of supports 57, 57 and 57, 57 are fixed to the spool core 23 to support the flanges 41 and 43 at their disks 45 and 47. See FIGS. 13 and 14. The two pairs of from one another along the spool core 23 to maintain respective inner faces 45&#39; and 47&#39; of the disks 45 and 47 spaced from the longitudinal edges 53 and 55 of each successive convolution of the film roll 33. See FIG. 13. The annular lips 49 and 51 overlap the film leader (outermost convolution) 35 of the film roll 33 radially outwardly of the longitudinal edges 53 and 55 of the leader to radially confine the leader to thus prevent it from radially expanding or clock-springing into substantial contact with an interior curved wall 58 of the cassette shell 3. A lip-receiving notch 59 is cut in the film leader (outermost convolution) 35 along its longitudinal edge 55, relatively close to its leading end 37, to receive a peripheral section 51&#39; of the annular lip 51. This allows a relatively short edge-section 61 of the film leader (outermost convolution) 35 connecting the leading end 37 and the notch 59 to overlap the annular lip 51 radially outwardly to thus maintain the leading end spaced a radial distance D from the next-inward convolution 39 of the film roll 33. See FIGS. 4 and 9. The leading end 37 has a forward edge 63 inclined from the longitudinal edge 53 of the film leader (outermost convolution) 35 to the other longitudinal edge 55 of the leader to form a forward-most tip or tab 65 of the leader which, like the edge-section 61, overlaps the annular lip 51 radially outwardly. See FIGS. 1, 2, 8 and 9. 
     The two flanges 41 and 43 have a plurality of concentric arcuate slots 66 cut in their respective disks 45 and 47 to longitudinally extend in the film unwinding and film winding directions U and W. Engagement means in the form of respective hook-like members 67, located on the short and longer open-end pieces 19 and 21 of the spool core 23, are normally located in the concentric slots 66 for movement along the slots into engagement with the flanges 41 and 43 responsive to rotation of the spool core relative to the flanges in the unwinding direction U and for movement along the slots out of engagement with the flanges responsive to rotation of the spool core relative to the flanges in the winding direction W. See FIGS. 12-15. Preferably, each of the hook-like members 67 has an end face 67&#39; that is beveled to ease the hook-like member out of one of the concentric slots 66 responsive to rotation of the spool core 23 relative to the flanges 41 and 43 in the winding direction W, in the possible event the spool core is rotated relative to the flanges far enough in the winding direction to back the hook-like member out of the slot. 
     The two pairs of supports 57, 57 and 57, 57 are positioned to distort the flanges 41 and 43 at their disks 45 and 47 when the hook-like members 67 are not in the slots 66. See FIG. 15. More specifically, in this instance, the two pairs of supports 57, 57 and 57, 57 distort the flanges 45 and 47 in a manner such that respective flat areas 66&#39; of the disks located between the slots 66 are urged firmly against the hook-like members 67. This will ensure that the hook-like members 67 are received in the slots 66 when the spool core 23 is rotated relative to the flanges 45 and 47 in the unwinding direction U and thus will engage the flanges. See FIG. 14. 
     A film stripper-guide 68 projecting from the interior wall 58 of the cassette half 7 is Positioned immediately inward of the inner entrance to the film passageway 25 to be received between the leading end 37 of the film leader (outermost convolution) 35 and the next-inward convolution 39, close to the forward-most tip 65 of the leader, to pick up the leading end and guide it into the film passageway responsive to rotation of the spool core 23 in the unwinding direction U. See FIGS. 1 and 4-7. The leading end 37 will be advanced over the stripper-guide 68 and into the film passageway 25, rather than between the stripper-guide and the next-inward convolution 39, because it is spaced the radial distance D from the latter convolution. Thus, as shown in FIG. 4, the leading end 37 will be located within range of the stripper-guide 68 due to such spacing D from the next-inward convolution 39. 
     When the leading end 37 of the film leader (outermost convolution) 35 is advanced over the stripper-guide 68 responsive to rotation of the spool core 23 in the unwinding direction U, the longitudinal edges 53 and 55 of the leader start to gently flex respective arcuate portions of the two flanges 41 and 43 away from one another, i e. farther apart, first to allow the notch 59 to separate from the lip section 51&#39;, and then to allow successive longitudinal sections of the leader to uncoil from between the flanges and exit to the outside of the cassette shell 3. See FIGS. 10 and 11. The flexing of the flanges 41 and 43 occurs because the film width W F  between the longitudinal film edges 53 and 55 is slightly greater than the axial spacing A S  between the annular lips 49 and 51. Moreover, successive convolutions of the film roll 33 have a resistance to transverse bowing that is greater than the resistance of the flanges 41 and 43 to be flexed. Two pairs of flat curved bearing members 69 project from the interior walls 58 of the respective shell halves 7 and 9 to lie flatly against successive arcuate portions of the two disks 45 and 47 as the flanges 41 and 43 are flexed away from one another, to only allow those flange portions separated from the bearing members to be flexed farther apart. See FIGS. 1, 2 and 4. The bearing members 69 are positioned relatively remote from the film passageway 25. Thus, the leader 35 is only allowed to uncoil from between the flanges 41 and 43 relatively close to the passageway 25. See FIG. 7. 
     A film flattening rib 71 projects from the interior wall 58 of the cassette half 9 in the vicinity of the inner entrance to the film passageway 25 and the stripper-guide 68 to support successive longitudinal sections of the film leader 35, beginning with its leading end 37, substantially flat widthwise as those sections are freed from the flanges 41 and 43, to facilitate movement of the leading end into the passageway. See FIG. 7. The light-trapping plush 31 within the film passageway is elevated along the passageway slightly beyond a longitudinal center line L of the Passageway. The film flattening rib 71 as shown in FIG. 4 projects almost to the center line L in order to support successive sections of the film leader 35 substantially flat at the center line. Preferably, the film-supporting tip or longitudinal edge of the flattening rib 71 is spaced 0.005&#34;-0.030&#34; short of the center line L. 
     Two substantially parallel curved film supporting ribs 75 and 76 project from the interior wall 58 of the cassette half 7 to longitudinally extend from the film flattening rib 71 to part-way between the pair of bearing members 69 which project from the same wall. See FIGS. 1, 3, and 4. The film supporting ribs 75 and 76 longitudinally extend the entire location at which the film leader (outermost convolution) 35 can escape the confinement of the flanges 41 and 43, when the leader axially flexes the flanges away from one another. The film supporting ribs 75 and 76 as shown in FIG. 3 are positioned to be slightly spaced from the film leader 35, when the leader is confined within the annular lips 49 and 51. Another film supporting rib 77 projects from the interior wall 58 of the cassette half 7, opposite the stripper-guide 68. The other rib 77 is substantially parallel to and shorter than the first-two ribs 75 and 76. All three of the ribs 75-77 longitudinally extend perpendicular to and adjoin the flattening rib 71. See FIG. 1. 
     Operation 
     When the spool core 23 is initially rotated in the film unwinding direction U, the two flanges 41 and 43 momentarily tend to remain stationary and the film roll 33, since its inner end is attached to the spool core, will expand radially or clock-spring to force the film leader (outermost convolution) 35 firmly against the annular lips 49 and 51 of the flanges. Generally however, before the film roll 33 can be expanded radially to the extent a non-slipping relation would be created between the film leader (outermost convolution) 35 and the annular lips 49 and 51, the hook-like members 67 will have moved along the respective slots 66 (or from the flat areas 66&#39; into the slots 66, and then) into engagement with the two flanges 41 and 43 to fix the flanges to the spool core. Then, further rotation of the spool core 23 will similarly rotate the flanges 41 and 43. As a result, the leading end 37 of the film leader (outermost convolution) 35 will be advanced over the shorter rib 77 and the stripper-guide 68, causing successive arcuate portions of the flanges 41 and 43 to be flexed away from one another as shown in FIG. 11. This first allows the notch 59 to separate from the lip section 51&#39;, and then it allows successive longitudinal sections of the film leader 35 to exit from between the flanges to the outside of the cassette shell 3. Since the stripper-guide 68 initially picks up the leading end 37 of the film leader 35 close to its forward-most tip 65, the forward edge 63 of the leading end will move against the film flattening rib 71 as shown in FIG. 6. 
     When the film leader 35 is thrust through the film passageway 25 to the outside of the cassette shell 3, the passageway due to the plush material 31 presents some resistance to outward movement of the leader. This resistance causes the leader 35 to further flex the flanges 41 and 43 away from one another to, in turn, allow more of the leader to uncoil from between the flanges If the two ribs 75 and 76 were omitted from the shell half 9, the leader 35 would uncoil against the interior wall 58 of the shell half. As a result, increased torque would be required to rotate the spool core 23 in the film unwinding direction U. However, the two ribs 75 and 76 serve to severely limit the extent to which the leader 35 can uncoil from between the flanges 41 and 43. 
     If the spool core 23 is rotated in the film winding direction W after some length of the filmstrip F has been advanced from the cassette shell 3, the spool core is free to rotate relative to the two flanges 41 and 43 because the hook-like members 67 can move along the respective slots 66 out of engagement with the flanges. This permits the flanges 41 and 43 to be independently rotated in the winding direction W, though at a slower speed than the spool core 23 is rotated in that direction. Each of the hook-like members 67 may back out of one of the slots 66 and into the next slot during continued rotation of the spool core 23 in the winding direction W. At the same time, the filmstrip F will be rewound onto the spool core 23 between the flanges 41 and 43. 
     The invention has been described with reference to a preferred embodiment. However, it will be appreciated that variations and modifications can be effected within the ordinary skill in the art without departing from the scope of the invention.