Abstract:
In a film cassette, a light blocking device is supported for movement to a light blocking position for preventing ambient light from entering a cassette shell and to a non-blocking position, and a separate cassette element such as a film spool is supported for movement to use the film cassette. According to the invention, locking apparatus for normally engaging the cassette element to prevent movement of the cassette element is coupled with the light blocking device for movement, when the light blocking device is moved to its non-blocking position, to a non-locking position disengaged from the cassette element to allow movement of the cassette element. Thus, the film cassette cannot be used unless the light blocking device is in its non-blocking position.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Reference is made to commonly assigned copending applications Ser. No. 07/787,802 entitled FILM CASSETTE WITH UNITARY FILM STRIPPER AND LIGHT BLOCKING DEVICE and filed Nov. 14, 1991 in the name of Dennis R. Zander, and Ser. No. 07/787,803 entitled FILM CASSETTE WITH FLANGED FILM SPOOL and filed Nov. 4, 1991, in the name of Dennis R. Zander. 
     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. 
     2. Description of the Prior Art 
     German Offenlegungsschrift DE 4002778 Al, published Aug. 2, 1990, discloses a film cassette wherein a light blocking valve is supported for movement to a closed position for preventing ambient light from entering a cassette shell and an opened position for allowing a filmstrip to be advanced out of the shell. The filmstrip is advanced out of the shell when a spool on which the filmstrip is wound is rotated in an unwinding direction and a film engaging sprocket located between the spool and the light valve is similarly rotated. The spool can be rotated in the unwinding direction even though the light blocking valve is closed. Consequently, the filmstrip may be unwound from the spool and jammed inside the shell. 
     SUMMARY OF THE INVENTION 
     The invention solves the problem occurring with the film cassette disclosed in German Offenlegungsschrift DE 4002778 Al. 
     According to the invention, there is provided an improved film cassette wherein light blocking means is supported for movement to a light blocking position for preventing ambient light from entering a cassette shell and to a non-blocking position, and a separate cassette element such as a film spool is supported for movement to use the film cassette, and wherein the improvement comprises: 
     locking means for normally engaging the cassette element to prevent movement of the cassette element is coupled with the light blocking means for movement, when the light blocking means is moved to its non-blocking position, to a non-locking position disengaged from the cassette element to allow movement of the cassette element, whereby the film cassette cannot be used unless the light blocking means is in its non-blocking position. 
     Preferably, the light blocking means and the locking means are united to form a single part. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view of a film cassette according to a preferred embodiment of the invention, showing two halves of the cassette shell opened and the various cassette components removed from the shell halves; 
     FIG. 2 is a perspective view of the film cassette, showing the two shelf halves opened with the various cassette components in place; 
     FIG. 3 is a perspective of the film cassette partly cut away; 
     FIG. 4 is an elevation view in cross-section of the film cassette; 
     FIG. 5 is a plan view in cross-section of a flange to spool core engagement in the film cassette; and 
     FIGS. 6-14 are either plan views in cross-section or end views of the film cassette, showing operation of a unified light valve, film stripper and spool lock. 
    
    
     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 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. 
     The Film Cassette--General 
     Referring now to the drawings, FIGS. 1 and 2 show a 35 mm film cassette 1 comprising a cassette shell 3 and a film spool 5. The film spool 5 is rotatable about an axis X in film unwinding and film winding directions U and W inside the cassette shell 3. The cassette shell 3 consists of two shell halves 7 and 9 which are connected by a pair of spaced, integrally formed hinges 11 and 13 and otherwise are secured together by known means. 
     A roll 15 of 35 mm filmstrip F is coiled about a core or hub 17 of the film spool 5 to form successive convolutions of the filmstrip. As shown in FIGS. 4 and 8, the film roll 15 includes an outermost convolution which is a film leader 19 having a leading or forward inclined end 21, and it includes a next inward convolution 23 coiled beneath the outermost convolution. An inner or trailing end of an innermost convolution 24 of the film roll 15 is secured to the spool core 17 by appropriate means such as a hook or tape, not shown. 
     Adjacent one end 25 of the spool core 17, a pair of parallel inner and outer rigid disks 27 and 29 are integrally formed with the spool core. Both of the disks 27 and 29 are arranged perpendicular to the axis X. See FIGS. 1-4. Adjacent another end 31 of the spool core 17, a rigid flange 33 is supported inclined to the axis X by four disk guides 35, 37 and 39, only three shown, projecting from an inner wall 41 of the shell half 7. Other disk guides, not shown, project from an inner wall 42 of the shell half 9. The flange 33 has a central opening 43 through which the spool core 17 extends to allow rotation of the spool core independently of the flange, and it includes an annular lip or skirt 45 which circumferentially extends from the flange. As shown in FIGS. 1-4, the inner disk 29 and the flange&#39;s annular lip 45 are spaced from each other a distance that is less than the width W of the filmstrip F for an approximately 270° arc that is remote from a film egress/ingress passageway 47 to outside the cassette shell 3, to radially confine the film leader 19 to the film roll 15 along that arc in order to substantially prevent clock-springing of the film roll against the respective inner walls 41, 42 of the shell halves 7, 9. Conversely, the inner disk 29 and the flange&#39;s annular lip 45 are spaced from each other a distance that is greater than the width W of the filmstrip F for an approximately 90° arc that is close to the passageway 47, to allow the film leader 19 beginning with its leading end 21 to escape the radial confinement of the flange&#39;s annular lip along that arc in order to enter the passageway. A functionally similar arrangement is disclosed in commonly assigned U.S. Pat. No. 4,832,275, issued May 23, 1989. 
     Flange To Spool Core Engagement 
     The flange 33 includes an integrally formed resilient cantilever 48 bordered by a pair of longitudinal slits or openings 49 and 50 cut in the flange to interconnect at a common opening 51 to the central opening 43 of the flange. See FIG. 5. The cantilever 48 has a free end portion at the common opening 51 which defines a locking pawl 52 that is inherently biased against the periphery of the spool core 17 at a location within the central opening 43, to drop into either one of two identical notches or detents 53 and 54 cut in the periphery of the spool core. When the locking pawl 52 rests against the periphery of the spool core 17, the cantilever 48 occupies the longitudinal slit 49. When the locking pawl 52 is in one of the detents 53, 54, it is removed from the longitudinal slit 49. The locking pawl 52 and the detents 53, 54 are complementarily shaped to locking engage the pawl and one of the detents when the spool core 17 is rotated relative to the flange 33 in the unwinding direction U. Once the locking pawl 52 and one of the detents 53, 54 are lockingly engaged, the flange 33 must rotate with the spool core 17 in the unwinding direction. Conversely, the locking pawl 52 and the detents 53, 54 are complementarily shaped to disengage the pawl and one of the detents and force the pawl onto the periphery of the spool core 17 when the spool core is rotated relative to the flange 33 in the winding direction W. Other details of the locking pawl 52 and the detents 53, 54 are disclosed in cross-referenced application Ser. No. 07/787,803. Another type of flange to spool core engagement arrangement is disclosed in commonly assigned U.S. Pat. No. 5,031,852, issued Jul. 16, 1991. 
     Unitary Film Stripper, Spool Lock and Light Valve 
     A control shaft 55 has an integrally formed light valve 57, film stripper 59 and spool lock 61. See FIGS. 1-4. The stripper 59 comprises the free end of a resilient cantilever 63 extending from the control shaft 55. 
     The control shaft 55 is rotatably supported within the cassette shell 3 by the shell halves 7 and 9. See FIGS. 1-3. Opposite ends 64 and 65 of the control shaft 55 are accessible at the exterior of the cassette shell 3 for engagement to rotate the control shaft. 
     As shown in FIG. 6, when the control shaft 55 is rotationally oriented with the light valve 57 in a light blocking or closed position extending across the film egress/ingress passageway 47 to prevent ambient light from entering the cassette shell 3 through the passageway, the film stripper 59 is in a non-stripping position removed from the film roll 15. Conversely, as shown in FIG. 8, when the control shaft 55 is rotationally oriented with the light valve in a nonblocking or opened position to allow movement of the filmstrip F through the passageway 47, the stripper 59 is in a stripping position to be received between the leading end 21 of the film leader 19 and the next-inward convolution 23 of the film roll 15 responsive to rotation of the film spool 5 in the unwinding direction U. Other details of the stripper 59 are disclosed in cross-referenced application Serial No. 07/787,802. If the film spool 5 is rotated in the unwinding direction U with the stripper 59 in its stripping position, the film leader 19 beginning with the leading end 21 will be guided by the stripper from between the flange&#39;s annular lip 33 and the inner disk 29 into the passageway 47. A protuberance 67 may be provided on the underside of the film leader 19 at a location proximate the leading film end 21 to normally lie against the outerside of the next-inward film convolution 23, to maintain a slight space between the leading film end and the next-inward film convolution for receipt of the stripper 59. See FIG. 8. 
     As shown in FIGS. 2 and 8, when the control shaft 55 is rotationally oriented with the light valve 57 in its non-blocking position, the spool lock 61 is in a non-locking position removed from the inner disk 29. Conversely, as shown in FIG. 6, when the control shaft 55 is rotationally oriented with the light valve 57 in its light blocking position, the spool lock 61 is in a locking position protruding into any one of four notches or detents 69, 71, 73 and 75 cut in the periphery of the inner disk 29, to prevent substantial rotation of the film spool 5 in the unwinding and winding directions U and W. When the spool lock 61 protrudes into the detent 69, the film spool 5 is rotationally arrested with a film exposure status indicator 77 completely filling a window 79 in one end 81 of the shell half 7, to visibly indicate the filmstrip F is unexposed (fresh). See FIGS. 6 and 7. Moreover, a beveled edge portion 83 of the outer disk 27 is present at two windows 85 and 87 in the end 89 of the shell half 9, to disable a cassette load prevention mechanism in a camera or other apparatus adapted to receive the film cassette 1. See FIG. 7. An example of the cassette load prevention mechanism is disclosed in commonly assigned U.S. Pat. Nos. 5,032,861, issued Jul. 16, 1991, and U.S. Pat. No. 5,047,794, issued Sep. 10, 1991. When the spool lock 61 protrudes into the detent 71, the film spool 5 is rotationally arrested with the exposure status indicator 77 only partly filling the window 79 to visibly indicate the filmstrip F is partly exposed. See FIGS. 9 and 10. Moreover, the beveled edge portion 83 is only present at the window 85. A cut-out edge portion 91 of the outer disk 27 is present at the window 87. See FIG. 10. Consequently, the cassette load prevention mechanism would be disabled at the window 87 but not at the window 85. This permits the film cassette 1 to be used with two different types of cameras, one that can receive the film cassette with the filmstrip F either partly exposed or unexposed and the other that can receive the film cassette only with the filmstrip unexposed. When the spool lock 61 protrudes into the detent 73, the film spool 5 is rotationally arrested with the exposure status indicator 77 completely removed from the window 79 to visibly indicate the filmstrip F is fully exposed. See FIGS. 11 and 12. Moreover, the cut-out edge portion 91 is present at the windows 85 and 87. See FIG. 12. Consequently, the cassette load prevention mechanism would be disabled at the windows 85 and 87. This is in order to prevent any type camera from receiving the film cassette 1 with the filmstrip F fully exposed. When the spool lock 61 protrudes into the detent 75, the film spool 5 is rotationally arrested with the exposure status indicator 77 completely removed from the window 79. However, another indicator, not shown, may be provided on the outer disk 27 to be present at the window 79 to visibly indicate the filmstrip F has been processed to develop any latent images. See FIGS. 13 and 14. Moreover, the cut-out edge portion 91 is present at the window 85 and the beveled edge portion 83 is present at the window 87. See FIG. 14. Consequently, the cassette load prevention mechanism would be disabled at the window 85 but not the window 87. This is in order to allow the film cassette 1 only to be received in apparatus other than a camera, such as an image display device, which would make use of the filmstrip F when it is processed. 
     Operation 
     Initially, the control shaft 55 must be rotated to move the light valve 57 from its light blocking position to its non-blocking position, to move the spool lock 61 from its locking position to its non-locking position, and to move the film stripper 59 from its non-stripping position to its stripping position. See FIGS. 6 and 7. 
     Then, the spool core 17 is rotated relative to the flange 33 in the unwinding direction U until the two pieces are lockingly engaged by means of the locking pawl 52 and one of the detents 53, 54. See FIG. 5. Continued rotation of the spool core 17 in the same direction will similarly rotate the flange 33 to allow successive longitudinally sections of the filmstrip F beginning with its leading end 21 to exit from between the flange&#39;s annular lip 45 and the inner disc 29 along the 90° arc close to the film egress/ingress passageway 47 where the lip and the disc are spaced from each other a distance that is greater than the width W of the filmstrip F. Simultaneously, the film stripper 59 will direct successive longitudinal sections of the filmstrip F beginning with its leading end 21 into the passageway 47 for advancement outside the cassette shell 3. 
     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.