 |
Description  |
|
|
BACKGROUND OF THE INVENTION
Motion picture projectors, with or without accompanying sound, have been
used for many years; such projectors have used two exposed hubs, often
with both hubs actually located external to projector body. In some cases,
non-sealed cassette has been disposed outside the projected body and an
exposed take-up hub located within the non-sealed projector body. In
either case, the exposed film must be threaded through the optical
projecting system and the leading end affixed to the take-up hub.
In certain applications, it is desirable to provide a miniaturized, rugged
projection system which not only is simple to operate, but also capable of
operation, storage and transport in almost any climatic condition to be
encountered throughout the world. These objectives can be met by using a
completely sealed film cassette which can be inserted rapidly into, or
removed readily from, the projector and by mounting the cassette within
the projector in such a manner that the film is moved within the sealed
cassette by drive means within the projector which is external to the film
cassette.
The projector has a relatively narrow hinged and latchable cassette cover
which can be opened to provide a narrow access opening in which to insert
the sealed film cassette. The cassette can be readily, simply, and
accurately positioned with the projector by placing its alignment key into
an alignment key slot in the projector. The keyed cassette cover then is
pressed against the partially inserted cassette until the cover latch
engages a latch on the projector body. There are driven connectors in the
projector which interface mechanically with the cassette film control
driving means for the film rewind and take-up hubs, and with the
intermittent and continuous film drive sprocket wheels. This interface is
accomplished by rotatable connectors which extend through seals in the
periphery of the film cassette and are biased in engagement with the
driven connectors in the projector by the latching of the hinged cover of
the projector to the projector body, in conjunction with the pressure
exerted on the aforesaid engaging connectors by leaf springs in the cover
along one edge of the aforesaid access opening.
In prior film projectors, the optical projecting beam(s) which is directed
through the film normally passes between the two film hubs with the axis
of the beam(s) lying substantially in a plane passing through the two
hubs. With such an arrangement, it can be shown that the overall space
required to receive the film reels on two such hubs must be four times the
radius R of a fully wound reel of film. In addition, a considerable space
of width must be provided between the points of maximum excursion of film
on each film reel to permit uninterrupted passage, at all times, of the
optical projection and optical sound extraction beams through the reels of
film. In summary, a minimum width of 4R+ d would be required. It is
important that the space occupied by the reels of film and the optical
projection equipment be kept to a minimum. In accordance with the
invention, the film is twisted through ninety degrees in the region of the
two optical projection beams in order to obviate the need for projecting
the optical beams between the reels of film. Also, in accordance with the
invention, the film after being removed from the rewind hub onto the
take-up hub, subsequently can be driven in the reverse direction back onto
the rewind hub. In this manner, the maximum spacing between the two hubs
is substantially equal to the radius R of a completely full reel of film,
as contrasted with a spacing= 2R+d for the conventional projector. Since
the maximum excursion of periphery of the full reels of film from the
empty hub is equal to the radius of a full reel of film, it is obvious
that the minimum cassette width needed to just accommodate the film in the
projection system of the invention is approximately 3R, as contrasted with
4R+ d for the usual film projection systems of the prior art. If one were,
for the sake of argument only, to attempt to operate the projector system
of the invention without the aforesaid ninety degree twist in the film, it
would be essential to introduce a group of mirrors within the sealed
cassette; this would complicate construction of the film cassette and
alignment of the cassette within the projector and would require undue
enlargement of the cassette in order to accommodate the mirrors.
Certain other advantages of the projection system design of the invention
can be summarized as follows:
The film remains completely enclosed in the sealed film cassette during
transport, presentation, and storage, and is never directly exposed to
harmful environmental conditions such as dirt, dust, moisture and the
like. The projector mechanism does not physically contact the film at any
time. Because of this fact, and because the operator cannot accidentally
touch, jar, jam, scratch, or otherwise mutilate the film, film image
quality and film sound quality can be maintained reliably at a high level
for a long time. The usable life or the film also can be increased because
special lubricants can be sealed along with the film in the cassette under
controlled conditions in the manufacturer's plant or in the laboratory.
The projector is extremely simple to operate since the operator does not
come into direct contact with the film. Moreover, no delicate film
threading or film-gate or aperture cleaning operations are required.
The projector design permits the film cassette to be changed rapidly-- in
less than 10 seconds. The projection cassette design inherently permits
fast forward and reverse winding of the film, in addition to offering the
capability of operating at all standard film projection speeds.
Since each film cassette inherently contains its own film take-up and
rewind hubs, immediate rewinding of the film need not be done in the case
of a multi-reel presentation, but can be done at the conclusion thereof;
this is an important factor where multi-reel presentations are required
and only a single projection device is available.
An intermittent film advance movement is needed to move the motion picture
film through the film projector gate of the projector. Each film image
frame must be moved rapidly into the projection gate position and then
held steadily for projection in that position for a discrete time
interval. The cycle then is repeated by rapidly advancing the next film
image into position. Current intermittent film advance mechanisms used in
projection equipment normally use either a mechanical claw or a "Maltese
cross" type of movement. All of these movements are essentially mechanical
cam and pin systems which require a minimum of two moving parts with
considerable dynamic mechanical contact and interaction therebetween. High
speed intermittent movement, as now used on projectors, would cause damage
to the film by placing reverse stress in the film perforations and would
rip the film stock. Moreover, mechanical wear of such conventional
intermittent movements at high speed would be excessive. In accordance
with the invention, the desired film advance intermittent movement is
obtained by simple electronic control of a stepping motor. Each
incremental stepwise rotation is accomplished by applying an electronic
pulse to said motor. In the case of sound film, the film must be driven in
continuous fashion at relatively constant speed past the sound extraction
beam location of the projector. The use of low voltage stepper motors
provide incremental rotary response to thousands of pulses per second. The
stepping motor can be advanced by a symmetrical train of such electronic
pulses to provide relatively high speed continuous film movement. A full
range of pulse rates can be obtained readily by miniaturized electronic
circuitry to provide any number of desired continuous operating speeds.
The stepping motor allows for both intermittent and continuous motion in
the forward or reverse direction and allows for safe, high speed movement
of the film through the projector. In this way, rapid access to any
portion of a lengthy film reel can be had. The overall reliability of the
projector is increased by use of the stepping motor, since no dynamic
interaction of mechanical parts is required, as in the case of
conventional pin and cam type projector movements. A reduction of parts,
as well as spare parts inventory for projectors is possible, since one
type of stepping motor can be used to provide the film advance function
and the rewind function. Moreover, the electrically controlled stepping
motor can operate from low voltage battery supplies.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a general pictorial view of a film projector with a hinged and
latched cover for a film cassette;
FIG. 2 is a schematic view showing the relationship between the two
projector optical beams and between the projector optics and the film
cassette;
FIG. 3 is a view, partially in section, illustrating details of the film
cassette cover and showing the way in which the film cassette is inserted
into and held in proper alignment within the projector;
FIG. 4 is a view showing the aperture in the projector within which the
film cassette is inserted, together with certain drive means and
connections;
FIG. 5 is a traverse view of a film cassette, showing the manner in which
the film is transported across the projection locations and twisted on
either side of said locations;
FIG. 6 is a pictorial view of the film cassette illustrating pertinent
interior construction;
FIG. 7 is a detail view showing the relationship between the driving means
in the projector and a driven film hub in the film cassette;
FIGS. 8 & 9 are detail views showing the construction of the two film
twisting means in the film cassette;
FIG. 10 is an electrical diagram of a projector drive system illustrating
the manner in which the various projector drive motors are coupled to the
driven means of the film cassette for various operating modes;
FIG. 11 is a diagram illustrating typical pulse waveforms suitable for
application for stepping drive motors; and
FIG. 12 is a diagram illustrating mechanical details of a modification of
the drive system of FIG. 10 wherein some of the drive motors are replaced
by electromagnetic clutches.
DETAILED DESCRIPTION OF INVENTION
The projector 10 and the details thereof are illustrated in FIGS. 1 to 4. A
film cassette 100, which is illustrated in varying detail in FIGS. 5 to 9
and described in detail subsequently, is held in position within the
projector body 12 by a projector cassette cover 25. The latter is secured
in the closed position by the cover latch 27 which includes engaging
members 27a and 27b affixed, respectively, to the cassette cover 25 and to
the projector body 12. As indicated more clearly in FIG. 3, the cassette
cover 25 may be unlatched and pivoted about the hinge 28 to a position
allowing either for insertion of the sealed cassette 100 into the
projector body 12, or removal of the sealed cassette from the projector
body, as desired. As indicated schematically in FIG. 2, the projector body
12 houses the light and sound optical systems, including the projection
optics 29, a portion of which also appears in FIG. 1. The projector main
optical system includes a projection lamp 31 with accompanying reflector
32, a condensing lens system 33, a shutter 34, and the projection optics
29. The film image projector beam is indicated by the long-dashed arrow
35. Interposed between the condensing lens system 33 and the projection
optics 29 is the film cassette 100 which fits within an appropriate recess
in the projector body 12, as will be shown later. The optical sound system
includes an exciter lamp 36, focusing lens 37 and a detector 38 which
receives the light beam, indicated by the dot-dashed arrow 40 in FIG. 2,
that passes through the film and converts the light energy into an
electrical signal corresponding to the film scene; this electrical signal
can be supplied by amplifier 41 and supplied to a speaker 42. The plane of
the film in the region penetrated by the two light beams is indicated by
the short-dashed line 43 in FIG. 2. The projector body 12 further contains
the various film drive means and controls to be described in detail later.
The manner of positioning the sealed film cassette 100 into the projector
10 is best shown in FIG. 3, which, for the sake of clarity, shows only
half of the projector cassette cover 25. The film cassette 100 contains
alignment keys 102 and 103 which engage, respectively, the alignment slot
46 in cassette cover 25 and alignment slot 47 in the wall 48 of the
projector body 12. The bottom surface of cassette 100 rests on the step
portions 51 and 52 of the projector body. The projector cassette cover 25
has a doubly curved interior surface 53 with a central projecting portion
54 adapted to fit within a corresponding central slot 152 in the doubly
curved periphery 153 of cassette 100. A first pair of leaf springs 55a and
55b, a portion of which are visible in FIG. 3, serve to maintain the
mechanical coupling elements 105 and 106 of the film cassette 100 in close
contact, respectively, with the intermittent film drive connector 57 and
the continuous film drive connector 58. The drive connectors 57 and 58 are
rotatably mounted in bearings 59 affixed to the wall 48. The drive
connectors 57 and 58, in turn, are mechanically coupled to the respective
film drive motors 61 and 62. These motors may be disposed in recesses
found within the back wall 48 of the projector body 12, or encapsulated
within the back wall 48. The exposed face of film drive connectors 57 and
58 can be roughened, as indicated in FIGS. 3 and 4, to increase the
frictional coupling between the film drive connectors and the mating
mechanical connectors 105 and 106 which are connected to sprocket wheels
in the film cassette 100.
A second pair of leaf springs 60a and 60b, visible in FIG. 4, maintain the
mechanical coupling elements of the film cassette 100 in film contact with
the drive connectors 63 and 64 for the respective film drive motors 65 and
66. One of the coupling elements, viz., element 107 is visible in FIGS. 6
and 7; the coupling element associated with the take-up hub 112 and
meshing the coupling element 64 in projector 10 is not visible in the
drawings. The drive connectors 63 and 64 are rotatably mounted in bearings
67 in the supporting medium 68 of the projector body 12, as shown in FIGS.
4 and 7; the drive motors 65 and 66 are mounted to, or encapsulated
within, the supporting medium 48 which forms a portion of the projector
body 12 lying outside the two optical beam paths shown in FIGS. 2 and 5.
Further details of the sealed film cassette 100 for film 110 is shown in
FIGS. 5 to 9. The cassette 100 comprises a cassette body 101 and a cover
plate 102; the latter is secured to the peripheral wall 103 of the main
body 101 by screws 104. A gasket seal may be used between the cover plate
102 and the cassette body 101 when screws are used, or the cover plate 102
may be fused to the peripheral wall 103 once the film has been inserted. A
film take-up hub 112 provides capability to take up the projected film and
includes a film leader 113 which is permanently affixed to hub 112, as by
insertion of the leader within a slot in hub (see FIG. 6) and by initially
driving a wedge pin 114 into the aperture within the tubular hub 112. The
film received hub 116 includes a wedge 117 for permanently affixing the
film trailer 118 to film rewind hub 116. The two hubs 112 and 116 rotate
on bearings 119 in the base plate 120, and are separately driven by
respective drive motors 65 and 66 through a corresponding mechanical
clutch including two engaging clutch plates. The clutch plate 107 is
attached to the hub 116 as shown in FIGS. 6 and 7 and engages the clutch
plate 63 attached to drive motor 65. See FIG. 7. Similarly, a clutch
plate, not visible in FIGS. 6 and 7, but connected to take-up hub 112
engages the clutch plate 64 connected to drive motor 66. See FIG. 7. The
bearing areas of the two hubs are appropriately sealed to prevent entrance
into the cassette 100 of moisture, dust and other foreign substances.
Further details of operation of the various driving motors will be given
subsequently after explaining certain structural means along which the
film is transported.
The film 110 must be oriented so that, as it passes the projected film
frame location (film projection gate) and sound take-off location (optical
sound projection gate), the plane of the film is normal to the film
projector light beam and sound exciter light beam. The orientation of the
film will be referred to as the projection orientation of the film. The
projection orientation of the film is shown schematically in FIG. 2. The
film 110, a portion of which is shown in both FIGS. 5 and 6, travels from
left to right and emerges from the film rewind hub 117 with the film plane
oriented 90 degrees with respect to said projection orientation. Film 110,
after passing around film guide post 127, undergoes a 90 degree twist,
accomplished by feeding the film through the molded film trough 130,
visible in FIG. 6 and shown in detail in FIG. 8. One end of the twisted
film trough 130 either is formed integral with, or very closely spaced
from the film guide post 127. The other end of twisted trough 130 lies in
a plane perpendicular to both of the aforesaid optical axes 35 and 40. The
trough 130 can be molded as an integral extension of the peripheral wall
103 of the cassette body 101, or, as shown in FIG. 8, it may be a separate
trough sealed on the base plate 120 of the cassette base section
contiguous with the aforesaid wall 103. As indicated in FIG. 8, the trough
130 can have a recess 131 formed therein to prevent scratching or other
damage to the film as it passes along the trough. The film 100, after
emerging from the rewind hub 116 and being routed around guide post 127,
is twisted gradually through 90 degrees and, upon emerging from the trough
130, attains the desired projection orientation. The film then passes
between a pair of film guide posts 133 and 134. These guide posts, like
the guide posts 127, 135, 136, 137, 138 and 139, may be fixed or roller
type guide posts. The guide posts 133 to 138, for example, may fit into
aligned receiving apertures, not visible in FIG. 6, in the peripheral
cassette wall 103 and the interior wall 132, in a manner similar to that
in which spring-loaded wrist-watch strop pins fit into a wrist-watch case.
The film, after passing through guide posts 133 and 134, passes around
guide post 135 and over the intermittent drive film advance sprocket wheel
140. The sprocket wheel 140 is driven intermittently through clutch plates
105 and 57 by drive motor 61 located in the projector 10 past the
projection frame aperture 142 formed within the lip portion 143 of flange
144; the latter can be either integral with the cassette body 101, as
indicated in FIG. 5, or a separate element attached to the base plate 120.
The film 110 then passes under guide post 136, over a continuous drive
film advance sprocket wheel 145, thence past the optical sound system
detection aperture 147 (see FIG. 6) formed within a solid flange 148
which, as in the case of flange 144, may be integral with the cassette
body 101 or a separate element secured to base plate 120. In practice, the
flanges 144 and 148 may be part of a complete molded cassette body 101.
The film next passes between film guide posts 137 and 138 and passes over
a molded trough 150 which is shown in detail in FIG. 9. The comments made
in connection with the trough 130 are equally applicable to trough 150,
except, of course, that the direction of the 90 degree twist in trough
150, and hence, of the film traversing it, is opposite to that for the
trough 130. The plane of the film, after emerging from trough 150, is
oriented in the same plane as when entering the trough 130. After emerging
from trough 150, the film passes around film guide 139 and is wound onto
the take-up hub 112 which is driven by motor 66 located in projector 10.
At the projected frame aperture location, a glass window 161 is mounted
within an aperture cover plate 102 and a glass window 162 similarly
mounted at the sound take-off aperture in the base plate 120. At the
optical sound exciter location, a glass window 164 is mounted within an
aperture in cover plate 102 and a glass window 166 is mounted in alignment
with window 164 within an aperture in base plate 120. The windows 160 to
164, are appropriately sealed to prevent entrance of dust, moisture and
the like into the interior of cassette 100. As indicated in FIG. 5, the
projection frame light beam 35 (see also FIG. 2) passes through the
aligned window 161, aperture 142 and window 162; similarly, the sound
take-off optical beam 40 passes through aligned window 163, aperture and
window 164.
Intermittent frame advance motion is provided by the intermittent drive
sprocket wheel 140 which is located close to the frame gate (projection
aperture) to insure accurate film movement and maintenance of the film
flate in a plane normal to the direction of the optical beams 35 and 40.
Each film image frame must be rapidly moved into the projection gate
position and held fixed in that position for a discrete time interval. The
single frame change must occur in the time increment when the shutter 34
is blocking light from the projection lamp 31 (see FIG. 2). For
conventional sound projection operation, the film frames are advanced at
24 frames per second and a two-blade shutter is used to block the
projection lamp twice during each frame interval--once for frame position
charge, and again to increase the flicker rate of the projected image. As
the off-on shutter intervals are equal in time, the interval available for
frame change is one quarter of the 1/24 second frame duration, or 1/96
second. The film must be advanced one frame (one incremental step) in 1/96
second, then held fixed for 3/96=1/32 second for projection of the frame
before advancing to the next frame.
In order to provide intermittent film advance past the film projection
gate, the intermittent drive sprocket wheel 140 is driven intermittently
by projector motor 61. This motor may be a stepping motor to which an
electronic pulse can be applied to perform each incremental angular
stepped rotation. The relationship between the stepping increment angle
.theta., the arc length S along the periphery of a sprocket wheel of
diameter D and having 24 sprockets is
##EQU1##
where .theta. is expressed in radians and D and S in inches. Assuming a
desired stepping increment angle .theta. of 15 degrees for moving the film
by one frame (the value of .theta. considered to be most favorable in
minimizing mechanical motion required by the motor for each frame advance)
a sprocket arc length S=0.166 inches (corresponding to the perforation
pitch for Super 8 film), the diameter D of a 24 sprocket wheel necessary
to provide for an advancement of exactly one frame of Super 8 film for
each incremental 15 degree step of the motor would be 2 (0.166)/0.262=1.27
inches.
Summarizing, the operation sequence of a projection device using the
stepping motor film advance mechanism, as the shutter blocks light from
entering the film image projector gate, the steppig motor 61 is
electronically pulsed causing it to rotate the film advance sprocket wheel
140 one increment, and thereby the film by one frame, the shutter opens
permitting the next frame--which is now in the projection frame gate--to
be projected, and finally, the shutter is used to block (chop) the light
through this projected film image frame either once or twice, as explained
above. This sequence is repeated for subsequent frames.
As each frame of the film is advanced, the film passes into a film loop
region lying roughly between the flange 144 and the film guide post 136.
Some portion of the film always remains in this region prior to being
advanced by the continuously driven sprocket wheel 145 at constant speed
past the optical sound detection gate location. It is necessary, of
course, to move the film past this optical sound readout location at a
constant speed in order to achieve accurate sound reproduction. The motor
62 used to continuously drive sprocket wheel 145 can be a low voltage
stepper motor which can be advanced by a symmetrical series of electronic
pulses to provide smooth and continuous high speed movement of the film
past the optical sound detection location without damage to the film
perforations, which would be inherent in a high speed intermittent
movement used on current film projection equipment. Safe, high speed film
movement, attainable with the stepping motor, permits rapid access to any
portion of a film reel presentation in either the forward or reverse
direction. Complete rewind of the film back onto the rewind hub 116 at the
end of the film presentation can be accomplished without any film handling
or any mechanical changes on the part of the operator.
In the device shown in FIGS. 3 to 6, separate motors 65 and 66 are used for
driving the rewind hub 116 and take-up hub 112, respectively, about which
the film is wound. With this arrangement, the motors 65 and 66 would be
driven continuously at a speed equal to that of motor 62.
Alternatively, the hubs 112 and 116 could be driven from motor 62 by belts
or other drive means, not shown. With such an arrangement, the motors 65
and 66 would be dispensed with.
The diagram of FIG. 10 and the accompanying caplanatory waveforms of FIG.
11 illustrate three modes of film drive operation, while FIG. 12
illustrates a modification of the film drive system of FIG. 10. In FIGS.
10 and 12, the elements of the system which correspond to those shown in
prior figures are indicated by the same reference numerals. A pulse
generator 78 produces a train A of equally spaced pulses (see FIG. 11a)
during each time interval t. When such a train of pulses is applied to a
steppig motor, the latter is driven smoothly and continuously and at
comparatively fast speed, each pulse of duration n being responsible for
one incremental stepwise motion. Because of the symmetry of the pulse
waveform, the rotation essentially is continuous in nature. In FIG. 11a
the pulses are exemplified as having an amplitude range of 0 to +v. By
using a polarity reversing circuit 79 in a series with the pulse generator
78, the polarity of the pulses of train A is reversed and a pulse train B
(see FIG. 11b) of individual pulse duration t/n and amplitude range 0 to
-v is obtained. If such a pulse train is applied to a stepping motor, the
latter is driven substantially continuously in a direction opposite to
that obtained when the motor receives pulse train A.
By supplying the pulses from pulse generator 78 to a counter circuit 80, a
symmetrical pulse waveform C (as indicated in FIG. 11c) is provided at the
output thereof, which, when applied to a stepping motor, will cause it to
rotate continuously in the forward direction at a speed slower than would
be obtained were the pulse train A to be applied.
Finally, if the pulse train A from pulse generator 78 is supplied to a
counter 81 which provides one narrow pulse during time interval t (the
waveform D (see FIG. 11d) is provided. The waveform D, when applied to a
steppig motor, will cause it to rotate intermittently, in a manner
mentioned previously.
During normal projection the ganged switch arms of all of the wafer
switches 71, 72, 73 and 74 are in the left hand position. In this
position, the motor 61-- used to drive the intermittent drive sprocket
wheel 140-- is supplied with pulse waveform D, whereupon sprocket wheel
140 is driven in stepped fashion through a desired angular increment for
each time interval t. Concurrently, the switches 72 and 74 are in the left
hand position, whereupon, the drive motors 62 and 66 are receptive of wave
train C; the continuous drive sprocket wheel 145 and take-up hub 112 are
driven at normal speed, and, consequently, the film is driven continuously
at normal speed past the optical sound system location. A slip clutch 76,
which may be of the permanent magnet type, which is always engaged, but
subject to slippage is provided between the take-up drive motor 66 and the
clutch plates 64 and 108 associated with take-up hub 112. This slip clutch
is needed, as in all film drive systems, to take into account changes in
load on motor 66 as the amount of film collected on take-up hub 112
changes during the forward film drive modes. A similar slip clutch 77 is
provided between the rewind hub drive motor 65 and the clutch plates 63
and 107 associated with rewind hub 116 to allow slippage as the amount to
film accumulated on rewind hub 116 changes during the reverse film drive
mode. The clutches 76 and 77 can be keyed directly to the shafts
interconnecting the clutch plates 64, 108 and 63, 107 to hubs 112 and 116,
all respectively. During normal projection, the drive motor associated
with rewind hub 116 is disabled; movement of rewind hub 116 is retarded by
virtue of the frictional contact of the juxtaposed clutch plates 62 and
107 and the film is withdrawn from the rewind hub 116 because of rotation
of drive motor 61.
When it becomes desirable to move the film rapidly to examine some advance
film frame, the switch arms of all of these switches 71 to 74 are placed
in the middle position. In this mode of operation, the pulse train A is
applied to all drive motors, except for motor 65, which is disabled. Now,
the drive motor 61, which normally is driven intermittently, the drive
motor 62 associated with sprocket wheel 145, and the drive motor 66
coupled to take-up hub 112, are driven at relatively high speed until
projection of the desired film frame to be examined occurs. At this point,
the drive motors 61, 62, and 66 can be disabled by opening a mechanical
switch 82 if detailed examination of the frame is desired. The arms of
switches 71 to 74 are returned to the NORMAL (left hand) position when
normal projection is to be resumed.
When it is desirable to reverse the film rapidly to examine some previously
projected frame, reverse rewind of the film onto the rewind hub 116 can be
attained by placing the switch arms of switches 71 to 74 in the right hand
(FAST REVERSE) position. How, the drive motors 61, 62 and 65 are energized
by the pulse train B, and consequently, the sprocket wheels 140 and 145
and the rewind hub 116 are rotated rapidly in the reverse direction;
movement of the take-up hub 116 occurs rapidly in the reverse direction;
movement of the take-up hub 112 is retarded by frictional contact of the
engaging hub plates 64 and 108. The film thus is rapidly removed from
take-up hub 112 and driven through the cassette 100 onto the rewind hub
116. As in the rapid forward mode of operation, the film may be stopped
when the proper film frame to be inspected is reached by operating switch
83. The switch 83, of course, is left closed whenever the usual rapid
rewind of the entire film onto rewind hub 116 is desired.
In some applications, it may be desirable to eliminate the drive motors 65
and 66 and to use drive motor 62 as a prime mover for the hubs 112 and
116. Such a modification of the system of FIG. 10 is shown in FIG. 12
wherein the motors 65 and 66, in effect, are replaced by electromagnetic
clutches 85 and 86. The driven system modification of FIG. 12, of course,
represents but one of may possible embodiments.
The shaft of drive motor 62 in addition to carrying the clutch plate 58,
also carries a pulley 89. A bevel gear 90 is rotated by means of a belt 91
which engages both pulley 89 and a pulley 92 mounted on the gear shaft 93.
The bevel gear 90 translates the rotation of shaft 93 into rotation of
shaft 94 about on axis normal to the axis of rotation of shaft 93. Shaft
94 carries a pulley 95 and electromagnetic clutch 85. The electromagnetic
clutch 86 is mounted on a shaft 96 which also carries a pulley 97.
Rotation of shaft 96 in the same direction as shaft 94 is accomplished be
means of a belt 98 which passes around pulleys 95 and 97. The
electromagnetic clutch 85 is coupled mechanically to clutch plate 63 which
is spring biased against the clutch plate 107 in cassette 100. Similarly,
the electromagnetic clutch 86 is coupled mechanically to clutch plate 64
contacting clutch plate 108 in the cassette. When an electrical input
(shown in FIG. 12 as a direct current voltage) is supplied to clutch 85,
the latter engages and the rotation of shaft 95 (driven from motor 62) is
imparted to the rewind hub 116. The same type of electrical input supplied
to clutch 86 causes engagement of the latter and the rotation of shaft 96
is imparted to the take-up hub 112. As already pointed out, the drive
motor 65 for rewind hub 116 is disabled except during fast reverse
operation, during which it is driven in the same manner as motor 62.
Consequently the clutch 85, which replaces motor 65, should be engaged
during the fast reverse mode of operation so as to effect rapid reverse
rotation of the rewind hub 116 in response to rapid reverse rotation of
motor 62. As shown in FIG. 12, de-energization of electromagnetic clucth
85 occurs only when the arm of switch 73 is in the right hand (FAST
REVERSE) position. It has also been shown that the drive motor 66 for
take-up hub 112 is disabled during the frst reverse mode of operation, but
engaged in the same manner as motor 62 during the other two modes of
operation. Consequently, clutch 86, which replaces motor 66, should be
engaged during the first two modes of operation only, so that clutch 86
effects rotation of the take-up hub 112 in response to either the normal
continuous forwarded or fast continuous forward rotation of motor 62. This
is accomplished, as shown in FIG. 12, by supplying a direct current
voltage to the clutch 86 through switch 74 when the arm thereof is in the
normal or fast forward position. On the other hand, the clutch receives no
direct current voltage input by way of switch 74 during the FAST REVERSE
mode and, hence, is disengaged so that take-up hub is not rotated in
response to rotation of motor 62 in the fast reverse mode.
It will be noted that the sli | | |
