Adaptor for a film viewer

A moving film projector, viewer or an adaptor device therefor comprising a rotatable spindle to receive a let-off spool or reel of film, a rotatable take-up spool or reel and a guide to direct the film in its desired path from the let-off spool, when this is in position on the spindle therefor, past a viewing station at which the film can be viewed or projected, and over the edge of and down towards the center plane of, the take-up spool, the take-up spool having a substantially continuous peripheral side wall towards which the film strip is guided and against which the film is coiled during use.

This invention relates to viewers or projectors for cinematographic films 
and to devices for use therewith. 
In order to move a strip of film carrying a series of frames of "moving" 
pictures past an aperture through which the film can be viewed, or through 
which light may be directed to project the picture in the frame opposite 
the aperture, onto a screen or the like, it has hitherto been the practice 
to drive the let-off spool from which the film is unwound and/or the 
take-up spool onto which the film is wound. 
If the take-up spool is driven, a problem occurs in that if the speed of 
rotation of the spool is constant, the take-up speed of the film increases 
as the diameter of the roll of film wound on the spool, increases. 
Conversely, if the speed of the film is to remain constant, as it must in 
order to achieve correct timing of the movement of the picture frames past 
the aperture, then the speed of rotation of the take-up spool must 
constantly decrease during use. 
Furthermore the leading end of the film strip has to be securely engaged in 
the spindle of the driven take-up spool which can be a somewhat cumbersome 
task. 
These problems are to a large extent overcome by a "moving" film projector, 
viewer or an adaptor device therefor, in accordance with this invention 
comprising a rotatable spindle to receive a "let-off" spool or reel of 
film, a rotatable "take-up" spool or reel, a guide to direct the film in 
its desired path from the let-off spool when this is in position on the 
spindle therefor, past a viewing station at which the film can be viewed 
or projected and over the edge of and down towards the centre plane of, 
the take-up spool, the take-up spool having a substantially continuous 
peripheral side wall towards which the film strip is guided and against 
which the film is coiled during use. 
Thus during use the film strip is fed from the let-off spool or reel 
through the guide for viewing or protection and then it emerges from the 
guide to a position ready to engage the upstanding side wall of the 
take-up spool at an acute angle thereto. The strip then passes smoothly 
around the wall until the length of film in the engagement with the wall 
is sufficient for the frictional forces between the film and wall to turn 
the take-up reel or spool. Once the take-up spool is rotating further 
lengths of film strip are spirally wound inside the coils of film already 
present in the spool and it will be appreciated that since the take-up 
spool is being driven by the film it will rotate, at all times, at a speed 
which is correct to take up the film emerging from the guide. Thus as the 
diameter of the coil of film in the take-up spool diminishes during 
winding, the rotational speed of the spool will increase. 
Furthermore the leading end of the film does not have to be physically 
attached to the take-up spool. 
The base of the take-up spool including the upstanding peripheral wall is 
preferably rotatably mounted on a mounting plate and is provided with a 
removal cover containing a portion of the guide for the film, and having 
an aperture to allow film to enter the spool when the cover is in position 
thereon. 
The film strip may be driven in any convenient way. For example if the film 
strip is provided with a series of small apertures along one edge these 
apertures may be engaged, in turn, by a needle driven by a motor. The 
needle may be arranged to move transversely of the film strip to engage in 
a hole formed in the edge thereof, move in the longitudinal direction of 
the film for a distance equal to one frame and then retract and move back 
until it is positioned opposite the next aperture in the film. This drive 
is preferably the only one provided. 
As explained above, the invention can be used in a film projector it is 
particularly useful for use with a hand-held viewer, for example that 
described in the specification of co-pending U.S. patent application Ser. 
No. 846,456, filed Oct. 28, 1977 
When such a reciprocating drive is used the film is moved forward in a 
series of short steps or jerks causing the film to jerk and these jerks 
are transmitted to the let-off spool which, if free to rotate, is also 
driven in a series of jerks. Each jerk may in fact cause the spool to 
rotate to deliver more film than is required and the whole drive becomes 
erratic, loops of film being produced which may jam and stop operation of 
the device. 
This problem is solved in accordance with a further feature of this 
invention wherein the film guide is so arranged as to guide the film strip 
away from the direct line between the position in which it emerges from 
the let-off spool, when this is in position on its spindle, and its 
desired position prior to engagement by the drive motor or its passage 
past the viewing/projecting station. The path in fact is made such that 
there is a predetermined length of film between the end of the film guide 
and the position at which the film emerges from the let-off spool. The 
length, which may be determined by trial and error, is sufficient to allow 
the film to move up and down so as to form successive small loops which 
are subsequently taken up or smoothed out by the reciprocating film drive. 
Thus fluctuations in the film caused by the reciprocating drive are 
smoothed out by the fluctuating loop of film strip and a substantially 
constant speed of rotation of the letoff spool or reel can be achieved. 
This desirable effect may be enhanced by the provision of a pin or the like 
around which the film strip passes in its passage between the let-off 
spool and the beginning of the main film guide. The pin may be offset from 
the film path so as to cause the pin to be so positioned that the said 
pre-determined length of the film extends between the pin and the let-off 
spool. 
If a device in accordance with this invention is to be used with a 
hand-held viewer such as that described in the specification of co-pending 
U.S. patent application Ser. No. 846,456, filed Oct. 28, 1977, it will be 
in the form of an adaptor, which can be connected to the viewer thus 
enabling the viewer to be used not only with the endless film cassette 
described in the said specification but also with standard 15 meter 
("Super 8") film. In this case the film guide, the spindle, for the 
let-off spool and the take-up spool are all mounted on a base plate which 
is so dimensioned and arranged as to fit within the aperture in the viewer 
designed to receive an endless film cassette. The guide may then also have 
an aperture not only to permit the film to be viewed through the eye piece 
of the viewer but also to allow the needle of the reciprocating drive 
motor to engage the apertures in the edge of the film.

Referring to FIG. 1 of the drawings, the adaptor comprises a base or 
mounting plate generally indicated at 2, having a freely rotatable spindle 
4 onto which a standard let-off spool or reel 6, carrying for example 
standard 15 meter film, may be mounted. The base plate 2 has a freely 
rotatable spindle 7 carrying a take-up spool 8 formed with an upstanding 
peripheral wall 10 and a central core 12. 
The plate also carries an upstanding film guide 14 in which film, indicated 
at 16, is guided after leaving the let-off spool 6 and before being wound 
onto the take-up spool 8. The guide carries the film past a viewing 
station defined by an aperture 18 through which light passes to enable the 
frame of the film 16 positioned opposite the aperture, to be viewed by a 
person looking at the film through the aperture as is described hereafter 
with reference to FIG. 3. 
A drive motor 20 mounted within the viewer is provided with a needle member 
22 positioned to engage one of a series of apertures in the edge portion 
of the film strip 16. The needle is driven to move, as indicated by the 
arrows 24, forwardly to engage in an aperture as shown in FIG. 1, and then 
transversely in the direction of the film strip to move the film strip 
forward across the aperture by a distance equal to one frame, and then 
back again out from engagement with the film strip to a position opposite 
to the next successive aperture ready for its next drive stroke. Thus the 
film strip is moved successively frame by frame across the aperture by the 
motor 20 which acts also to pull the film from the let-off spool 6 and to 
feed it through the guide 14 towards the take-up spool 8. 
The take-up spool 8 is provided with a cover, as can clearly be seen in 
FIG. 2, which is provided with an aperture 26 through which the film strip 
passes on emerging from the guide 14 and is itself formed with a guide 28 
which extends over the peripheral wall 10 of the spool and then down 
within the spool to a position in the central plane of the spool. The 
outer wall 30 of the guide extends around the core and is bent so as to 
guide a film strip in contact therewith, into a position at which it 
engages the wall of the spool (or the inner coil of a coil of film being 
wound in the spool) approximately tangentially. The inner wall 32 of the 
guide 28 terminates adjacent the central core 12 of the spool. 
If the film strip 16 is fed from the guide 14 through the aperture 26 into 
engagement with guide 28 and the motor is then operated, the film strip is 
fed in a series of successive steps forwardly through the guides 14 and 28 
to a position at which the leading end engages the inner surface of the 
peripheral wall 10 of the take-up spool. The film strip then passes around 
the inner wall to a position in which the length of the film strip 
engaging the wall creates a sufficient frictional force so that further 
movement of the film strip 16 into the spool, causes the spool to rotate 
an its axis and the film strip to be wound up within the spool, from the 
outside wall towards the inner core. 
It will be appreciated that with such a construction the leading edge of 
the film strip need not be in any way connected to the core. Further, as 
the inner diameter of the coil being wound in the take-up spool diminishes 
during winding, the speed of rotation of the take-up spool will increase 
automatically due to the fact that the take-up spool is driven by the film 
strip itself. Hence the spool always rotates at the correct speed to take 
up the length of film moved forward for each step of the drive motor 20. 
As the drive motor 20 moves the film in a series of successive steps the 
film is in effect jerked which could cause a jerky rotation of the let-off 
spool 6 causing problems with film entanglement and an interrupted feed of 
the film past the viewing aperture. In order to avoid or diminish this 
jerky movement of the let-off spool it has been found desirable to feed 
the film strip 16 between the let-off spool 6 and the inlet to the film 
guide 14 around a guide pin 34 and beneath a pin 35 which upstand from the 
base plate 2. The pins are positioned at a sufficient distance from the 
let-off spool spindle to allow the length of film between the let-off 
spool and the pin to move up and down as illustrated by the arrows `a` so 
that in effect a series of successive small loose loops are formed, the 
loops then being taken up by the jerky feed of the film strip permitting 
the let-off spool 6 to rotate substantially smoothly. 
The correct position for the pins 34, 35 is determined by trial and error 
but it will be noticed that the pin is positioned to one side of the 
direct line between the let-off spool and the entrance to the film guide 
14 so that the film is, in effect, bent around the pin 34, the pin 35 
acting to restrain the movement. This somewhat tortuous path has been 
found to assist in obtaining the smooth rotation of the let-off spool. 
The film may be wound back onto the let-off spool 6 on rotation thereof for 
example by a handle connected to the spindle 4 and positioned on the 
underside of the mounting plate. The film will travel back to the spool 6 
either around the guide or pass directly from one spool to the other. 
When the adaptor device illustrated in FIGS. 1 to 3 is to be used with the 
viewer generally indicated in FIG. 3, its mounting plate is inserted in 
the opening 44 in the viewer and held therein with the viewing aperture 18 
aligned with the eye piece 46 of the viewer. The lens in the eye piece may 
be adjusted in a conventional manner by rotation of a knurled wheel 48. 
The pin or needle 22 of the drive motor 20 of the viewer engages in the 
apertures 18 in the film, the motor being powered by a battery on 
operation of a manual switch 50. The batteries for the motor 20 are held 
in a recess in the handle of the viewer, the recess having a removale 
cover 52. 
In use light passes through the aperture 18, through the film strip 16 so 
that a picture on the frame of the film opposite the aperture is seen by a 
user looking through the eye piece 46. 
It will be appreciated that the viewer can either be used to view standard 
15 meter film by using the adaptor device hereinbefore described or may be 
used with a film cassette of the type designed to hold endless coil of 
film and an example of which is described in detail in the specification 
of co-pending U.S. patent application Ser. No. 846,456, filed Oct. 28, 
1977. 
As an alternative the spindle for the let-off spool, the film guide and the 
take-up spool can form an integral part of a standard film projector, the 
main advantage being that only a drive for the film, and not a drive for 
the let-off or take-up spools, needs to be provided. Equally the invention 
can be used with a standard film viewer. 
The drive for the film could be continuous instead of step by step as 
described above.