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CROSS-REFERENCE TO RELATED APPLICATIONS
Reference is made to commonly assigned copending applications Ser. No.
07/320,440, entitled FILM CASSETTE, and filed Mar. 8, 1989 in the name of
John J. Niedospial, now U.S. Pat. No. 4,883,235, issued Nov. 28, 1989, and
Ser. No. 07/320,438, entitled FILM CASSETTE, and filed Mar. 8, 1989 in the
names of Christopher T. Mattson and John J. Niedospial.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to the field of photography, and
particularly 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' 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 2
1/3 inches long, commonly referred to as a "film leader", 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-light-tight 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 outside 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 respective flanges. However, severe transverse
bowing of the filmstrip in order to move its longitudinal edges under the
circumferential lips may damage the filmstrip.
Like the type of film cassette disclosed in U.S. Pat. No. 4,423,923,
commonly assigned U.S. Pats. No. 4,834,306, granted May 30, 1989, and U.S.
Pat. No. 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 outside 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 which prevent the outermost
convolution of the film roll, including its leading end, 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
annular lips. 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 annular lips to
an axial dimension exceeding the film width, in turn allowing the leading
end and successive sections of the film roll to be freed from the radial
confinement of the annular lips and to be advanced into and through a
light-tight film passageway to the outside of the cassette shell. A
stripper-guide is located adjacent an inner entrance to the film
passageway to divert the leading end of the film roll into the passageway.
To accomplish this, the stripper-guide must be received between the
leading end and the next-inward convolution of the film roll. If, however,
the film cassette is used during extremely high temperature and/or
humidity conditions, it might be possible that the leading end after being
freed from the radial confinement of the annular lips will retain a great
deal of inward curl. Consequently, the leading end will not have
sufficient clock-spring to separate sufficiently from the next-inward
convolution to move over the stripper-guide. Thus, when the spool is
rotated in the unwinding direction, the leading end may not be picked up
by the stripper-guide and guided into the film passageway. Another problem
is that the leading end may be slightly transversely bowed after being
freed from the annular lips. Thus, when the leading end is moved over the
stripper-guide, the leading end may stub at the inner entrance to the film
passageway.
The Cross-Referenced Applications
The cross-referenced applications each disclose a film cassette wherein a
film roll whose outermost convolution is a film leader is coiled about a
spool rotatable within the cassette shell, a pair of flexible flanges are
coaxially arranged on the spool to radially confine the film leader within
respective skirted peripheries of the flanges to prevent the leader from
substantially contacting an interior wall of the cassette shell, and a
film stripper-guide projecting from the interior wall is received between
a leading end of the film leader and the next-inward convolution of the
film roll to free the leader from the flanges and guide the leader through
a light-tight film passageway to the exterior of the cassette shell
responsive to rotation of the spool in a film unwinding direction.
Specifically, the stripper-guide frees the film leader from the flexible
flanges by inducing the leader to flex the flanges away from one another
at their skirted peripheries during unwinding rotation of the spool.
Moreover, the film leader and at least one of the flanges include mutual
engagement means for maintaining the leading end of the leader spaced at
least a minimum radial distance from the next-inward convolution of the
film roll sufficient to locate the leading end within range of the
stripper-guide, to ensure that the leading end will be advanced over the
stripper-guide responsive to rotation of the spool in the film unwinding
direction. This is in contrast to U.S. Pats. No. 4,834,306 and U.S. Pat.
No. 4,848,693 wherein the leading end of the film leader may not have
sufficient clock-spring to be picked up by the stripper-guide when the
spool is rotated in the unwinding direction.
SUMMARY OF THE INVENTION
According to the invention, a film cassette is provided wherein a spool is
rotatable within a cassette shell, a convoluted film roll whose outermost
convolution comprises a film leader is coiled about the spool, a pair of
flanges are coaxially arranged on the spool to radially confine the film
leader within respective skirted peripheries of the flange to prevent the
leader from substantially contacting an interior wall of the cassette
shell, and a film stripper projecting from the interior wall is received
between the film leader and the next-inward convolution of the film roll
to remove successive sections of the leader from the flanges responsive to
rotation of the spool in a film unwinding direction, to allow the leader
to enter an essentially non-curving light-tight passageway to the exterior
of the cassette shell, characterized in that:
film flattening means projects from the interior wall of the cassette shell
in the vicinity of the film stripper and the non-curving passageway for
supporting successive sections of the film leader substantially flat as
those sections are freed from the flanges, to facilitate initial and
subsequent movement of the leader into the non-curving passageway.
According to a further feature of the invention, the flanges are
sufficiently flexible to allow the film leader to flex the flanges away
from one another at their skirted peripheries, when the spool is rotated
in the film unwinding direction with the film stripper received between
the leader and the next-inward convolution of the film roll, to free
successive sections of the leader from the flanges.
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 end view partly in cross-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. 4, 5, 6 and 7 are end views similar to FIG. 3, 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; and
FIG. 12 is an exploded perspective view similar to FIG. 1, according to an
alternate embodiment of the invention.
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 and 2 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 end extensions 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 end
extensions 19 and 21 of the spool core 23 each include an annular groove
27 which mates with a corresponding edge 29 of the respective openings 15
and 17 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, not shown, of the film roll 33 is secured to the
spool core 23.
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, and 8. The two flanges 41 and 43 comprise respective integral
disks 45 and 47 and respective integral annular lips or skirts 49 and 51
which circumferentially extend from the disks. The two disks 45 and 47
cover opposite flat sides, not shown, 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, not shown, through which the spool core 23 axially extends to
permit rotation of the spool core relative to the flanges 41 and 43. See
FIG. 8. The annular lips 49 and 51 overlap the film leader (outermost
convolution) 35 of the film roll 33 radially outwardly of the respective
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 57 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' 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.
A film stripper-guide 67 projecting from the interior wall 57 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 film
spool 5 in the unwinding direction U. See FIGS. 1 and 4-7. The leading end
37 will be advanced over the stripper-guide 67 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 67 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 67 responsive to rotation of the film
spool 5 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 axially away from one another as shown in FIG. 11, first
to allow the notch 59 to separate from the lip section 51', and then to
allow successive longitudinal sections of the leader to exit from between
the flanges to the outside of the cassette shell 3. The local flexing of
the flanges 41 and 43 occurs because the film width W.sub.F between the
longitudinal film edges 53 and 55 is slightly greater than the axial
spacing A.sub.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 locally
flexed. A pair of flat curved bearing members 69 extend from the interior
wall 57 of the cassette shell 3 to lie flatly against successive arcuate
portions of the two disks 45 and 47 as the flanges 41 and 43 are locally
flexed axially away from one another, to thereby assure return of the
flexed portions of the flanges to their normal original non-flexed
condition. See FIGS. 1 and 2.
A film flattening member 71 projects from the interior wall 57 of the
cassette half 9 in the vicinity of the inner entrance to the film
passageway 25 and the stripper-guide 67 to support successive longitudinal
sections of the film leader 35, beginning with its leading end 37,
substantially flat as those sections are freed from the flanges 41 and 43,
to facilitate movement of the leading end into the passageway. See FIGS. 6
and 7. The light-trapping plush 31 within the film passageway 25 is
elevated along the passageway slightly beyond a longitudinal center line L
of the passageway. The film flattening member 71 as shown in FIG. 3
projects almost to the center line L in order to support successive
sections of the film leader 35 substantially flat at the center line. See
FIGS. 6 and 7. Preferably, a substantially planar film-supporting face 73
of the flattening member 71 is spaced 0.005"-0.030" short of the center
line L, and extends widthwise of the film passageway 25 as shown in FIG.
1.
A slot 75 is cut in the film leader 35 substantially proximate its leading
end 37. A tooth 77 fixed to the interior wall 57 of the cassette half 7
has a free pointed end 79 which is positioned to be received in the slot
75 to thus engage the film leader (outermost convolution) 35, when the
film spool 5 is rotated in the winding direction W as shown in FIG. 3, and
to exit the slot to thus disengage the leader, when the film spool is
rotated in the unwinding direction U as shown in FIG. 4. The engagement of
the film leader (outermost convolution) 35 and the tooth 77 responsive to
rotation of the film spool 5 in the winding direction W prevents the
leading end 37 of the leader from coming to rest between the
stripper-guide 67 and the next-inward convolution 39.
Operation
When the spool core 23 is initially rotated in the unwinding direction U,
the two flanges 41 and 43 momentarily may remain stationary and the film
roll 33, since its inner end is attached to the spool core, tends to
expand radially or clock-spring to ensure a firm non-slipping relation
between the film leader (outermost convolution) 35 and the annular lips 49
and 51 of the flanges. 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
stripper-guide 67, causing successive arcuate portions of the flanges 41
and 43 to be flexed axially away from one another as shown in FIG. 11.
This first allows the notch 59 to separate from the lip section 51', 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 67 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 might initially be supported along a narrow ridge 81
forming one end of the interior wall 57 of the cassette half 7. However,
the leading end 37 will tend to back away from the ridge 81 and move
against the film-supporting face 73 of the flattening member 71 as shown
in FIG. 6.
If the film spool 5 is rotated in the winding direction W before
substantially the entire length of the filmstrip is advanced to the
outside of the cassette shell 3, and it is desired to subsequently use the
remaining available portion of the filmstrip at a later time, the film
spool is rotated substantially until the slot 75 receives the free end 79
of the tooth 77 to thus engage the film leader (outermost convolution) 35
to the tooth. Thereafter, to use the remaining available portion of the
filmstrip, the film spool 5 is rotated in the unwinding direction U to
disengage the film leader (outermost convolution) 35 from the tooth 77 and
to re-advance the filmstrip to the outside of the cassette shell 3.
Alternate Embodiment
FIG. 12 shows an alternate embodiment of the film flattening member 71,
which is designated as 71. According to this embodiment, the film
flattening member 71' includes on its film-supporting face 73' a pair of
very slightly raised ribs 83 arranged to support successive longitudinal
sections of the film leader 35 proximate its longitudinal edges 53 and 55
to lessen the intimacy of contact between those sections and the
film-supporting face 73'. Preferably, the ribs 83 are raised 0.005"-0.010"
from the film-supporting face 73'.
The invention has been described with reference to a preferred alternate
embodiments. 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.
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