HK1018816B - Method and film projector movement for transporting film through a motion picture projector - Google Patents

Description

Film projection mechanism and method for feeding film in a film projector

Technical Field

The present invention relates to a film transport apparatus for a film projector, and more particularly, to a film projection mechanism and method for transporting a film print which is converted between different frame sizes having different numbers of perforations per frame without interrupting the projection during the conversion.

Background

Existing 35mm motion picture projectors use motor driven sprocket wheels to intermittently pull film through the film gate at a standard rate of 24 frames per second. During the film movement cycle, a rotary shutter driven by a constant speed motor interrupts the screen to prevent blurring. The viewer is unaware of these dark moments due to the phenomenon called "persistence of vision". The film is supplied to and from the film gate and intermittent feed gear by a constant speed feed gear on each side. The film on both sides of the intermittent film feeding gear is kept in a sagging state by the two constant speed film feeding gears, so that the film is smoothly moved periodically at the film gate.

Existing projectors are almost without exception of the mechanical type. Generally, a single synchronous motor drives a drive shaft having a plurality of drive gears thereon, which drive the shutter and the plate transfer gears, respectively, at appropriate speeds. The intermittent sprocket is driven by a device known as a geneva mechanism which converts one full revolution of the drive shaft into a 90 ° rotation of the intermittent sprocket and a subsequent stationary projection cycle. This 90 rotation of a 16-tooth film gear results in a change in the frame of 4 holes (i.e. a "grab film"). The 4-piece aperture frame standard for a 1.33: 1 aspect ratio has been established at the end of the 19 th century and is used to date. Thus, a 35mm projector uses 4-hole catch sheets.

Although almost all 35mm projectors are mechanical, there are several professional projectors on the market that use electronic grab sheets. These designs use a highly responsive servo motor rather than a geneva mechanism to feed and position the film at the film gate.

The "1.85" screen specification was developed at the end of the 50 s of the 20 th century in order to enable viewers to view "half-width screen" movies without relying on an anamorphic camera and projection lens for a truly wide screen, which can compress a 2.35: 1 aspect ratio to a 1.33: 1 aspect ratio for 4-hole frames. Almost 85% of the movies that are now released use the 1.85: 1 specification. To achieve this aspect ratio, only one mask has to be inserted into the film window of the film door. The mask covers the top and bottom areas of the frame, thereby increasing the aspect ratio of the motion picture. Thus, the images in these covered areas are not visible.

This is clearly seen in fig. 1. The diagonal area 64 is the area that can be wasted in the 1.85: 1 format of 4 perforation height film using film. The area indicated by reference numeral 66 is the optical vocal cord. One solution to the film waste problem is to change to another frame height standard that provides the same projection area as fig. 1 but no waste area at the top and bottom. One such frame standard is the 3-hole frame shown in figure 2. Since most of the area originally wasted by the mask is eliminated, the same projection area can be obtained with a 3-perforation picture instead of a 4-perforation picture. Thus, the elimination of this "wasted" area can reduce the footage of film prints, and thus the cost, by about 25%.

Although the 3-perforation format steps one step in the right direction, it is not the end result in terms of film savings since there are still some wasted areas at the top and bottom that must be hidden from view. FIG. 3 shows the final frame height of the 1.85: 1 format with no wasted area of film. The 1.85 standard image width is limited by the space on the left side of the film for the optical soundtrack. This limited frame width plus a 1.85: 1 aspect ratio results in a frame height of no less than 0.446 inches. This height is exactly equal to the length of the film of 2.5 perforations, since there must be a space of a few thousandths of an inch between every two frames. The 2.5 perforation grab format saves about 37.5% compared to the standard 4 perforation format and is therefore now used as another industry standard for motion picture prints.

It will be apparent from the above that it is preferable to use these several new frame sizes for a variety of reasons, but the problem is that they are not compatible with existing projection apparatus. To successfully introduce new frame sizes into a movie, a movie theater must be equipped with a projector that can project all of these sizes. Importantly, these projection devices retain the ability to project 4 perforation gauge film in addition to the new gauge, since the full 4 perforation frame is required for the anamorphic wide screen. In addition, there are always some "classic" movies and other features (e.g., trailers and bulletins) that use the original 4-hole format.

To switch between the 3/4 perforation specifications in existing projectors, several configurations have been proposed. However, these arrangements have the problem that the plate gears must be manually switched when changing the specification in both the forward and reverse directions. This makes these structures impractical due to time and labor. The invention provides a full-automatic convertible film-grabbing projection device. The device can continuously display films of various specifications by using the same projector, and does not need a projector to carefully watch the films and does not need to interrupt the films during the displaying. Thus, the present invention solves the problems of existing projectors and has other advantages.

Disclosure of Invention

The present invention provides a convertible film-capturing projection apparatus including a film transport for transporting film in a projector. The film transport apparatus, also known as a motion picture projection mechanism or "head", includes a plurality of film transport gears having teeth thereon for engaging perforations in the film and a power element for rotating the film transport gears to advance the film through a window in the projector one by one. In accordance with the present invention, the power member is controlled by a controller to maintain or change the speed and position of the sprocket according to the film gauge depending on the number of perforations per frame, and the controller also controls the output of the power member to re-center (i.e., reposition) the frame relative to the perforations each time the film gauge changes. Thus, the film feeding device can feed various films of different specifications on the same projector without any technical problems and without interruption or delay in the operation of the projector.

In one embodiment of the invention, the film feeding device includes a pair of film feeding gears one on each side of a film gate and an intermittent film feeding gear between the pair of film feeding gears for advancing the film through a film window of the film gate one by one. The speed of rotation of the pair of sprockets is determined by a variable speed motor, and the speed and positioning of the intermittent sprocket is determined by another motor, such as a high response servo motor. In this embodiment, the two motors constitute the power elements of the device. But a single motor or three (or more) motors may be used as the power element if desired.

The controller, which coordinates the outputs of the variable speed motor and the servo motor, includes a switch that operates in accordance with a trigger signal indicative of the film format. For example, the trigger signal may be a message encoded on the film strip that is read by a sensor. The change-over switch changes the output of the variable speed motor according to the type of the received trigger signal, thereby changing the rotational speed of the pair of plate gears.

The variable speed motor also drives a plurality of synchronized discs, each disc having a series of apertures equally spaced about the circumference of the disc. An independent light source and a photocell are arranged on both sides of each synchronization disc. In operation, the light beam emitted by the light source passes through the apertures as the disk rotates. Each synchronization disc and its photocell are used to control the operation of the apparatus under different film specifications.

The output of the synchronous disc controls the starting of the servo motor, so that the film is grabbed. Each time the light beam passes through a small hole of a selected synchronization disc, it is detected by a corresponding photocell. The photocell then emits a pulse signal which is transmitted by the controller to the servomotor to start the film advance for one frame. A series of positioning disks rotated by servomotors each cooperate with its other pair of light source/photocell sets to communicate film position information to the controller so that the film intermittently stops in position, ensuring accurate alignment of each frame with the film gate. Redundant light source/photocell sets may be provided on each synchronization disc and positioning disc, if desired.

The trigger signal is designed to indicate when the film gauge changes, e.g., the film changes from 4 perforations per frame to 3 perforations per frame. Of course, the trigger signal may indicate a change between many different formats, typically indicating a change in film format in the projector from one format with a certain number of perforations to another format with a certain number of perforations.

The trigger signal indicating a change in film gauge can be generated in a number of ways. In one embodiment, the trigger signal is generated by a sensor electronic device connected to a transfer switch. The sensor can read information encoded on the film entering the projector indicating a change in film gauge. The information may be encoded on a sheet or magnetic strip, an optically read bar code, or using mechanical means. Alternatively, the projectionist may manually generate the trigger signal based on visual inspection of the film. Other suitable means of generating the trigger signal are known and the invention is not limited to generating the trigger signal by manual or electronic means.

Regardless of the manner in which the trigger signal is generated, an important feature of the present invention is that the film transport apparatus can be changed between different film formats without interrupting or stopping the projection of the projector. So that there is no delay in switching between different film formats and therefore films of different formats can be spliced on the same film tape. In addition, no special skill is required to switch between different film formats, as the device is simple, reliable to operate, and requires no special training. Moreover, the film transport apparatus can be retrofitted into existing 35mm projectors, thereby reducing the cost of replacing the entire projection apparatus, including the light box, spot lights, mother board assembly and other components.

Other features and advantages of the present invention will become apparent from the following description of the invention, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention.

Drawings

The figures illustrate the invention. In the drawings:

FIG. 1 shows a segment of film of 4 perforation size per frame;

FIG. 2 shows a segment of film of 3 perforation size per frame;

FIG. 3 shows a segment of film of 2.5 perforation size per frame;

FIG. 4 is a perspective view of all components of the film transport apparatus of the present invention, including control components, with other portions of the projector not shown for clarity;

FIG. 5 shows a film strip including multiple gauges that can be used in the film transport;

FIG. 6 is a side view of a sheet transport gear and a plurality of timing disks driven by a variable speed motor;

FIG. 7 is a front view of one of the timing disks of FIG. 6;

FIG. 8 is a side view of a servo motor driving an intermittent sprocket and a plurality of positioning discs;

FIG. 9 is a front view of one of the positioning disks of FIG. 8; and

fig. 10a-10d illustrate another embodiment of the invention similar to the embodiment of fig. 6-9, with an increase in film gauge and therefore a corresponding increase in synchronization and registration discs.

Detailed Description

A film transport apparatus 10 embodying the principles of the present invention transports film 12 in a projector. As shown in FIG. 4, the film feeding device 10 includes two constant speed film feeding gears, one for the film feeding gear 22 and the other for the film winding gear 24, which are arranged on both sides of a door 26. An intermittent sprocket 28 is provided directly below the gate 26 between the two constant speed sprockets 22 and 24 to intermittently feed the film 12 frame by frame through the gate as is conventional. Thus, the intermittent sprocket 28 precisely aligns frames of the film 12 with the film gate 26 at a U.S. standard rate of 24 frames per second. The film gate 26 also includes a film window 29 for screening the film and a light source (not shown). The film 12 is looped between the film supply and transport gears 22 and 26 and between the intermittent transport gear 28 and the film take-up and transport gear 24 to prevent film breakage.

The film feeding device 10 further includes a power unit including a variable speed motor 30 and a servo motor 32. The variable speed motor 30 in this embodiment is a two speed motor, such as a crystal controlled motor. However, as described below, the variable speed motor 30 may be a three-speed motor or a desired multi-speed motor. The servomotor 32 is preferably a high response servomotor. Alternatively, the power unit may include only one motor, and mechanical and other means are used to drive and change the speed and position of the sprockets 22, 24 and 28.

The variable speed motor 30 rotates an output shaft 34 extending from both ends of the motor. One end of output shaft 34 is connected to rotate film winding plate transmission gear 24. The shaft 34 also rotates a drive pulley 36 on which is mounted a timing belt 38 which is also mounted on a second pulley 40. The second wheel 40 is connected to a shaft 42 that rotates the film supply sprocket 22. Thus, the supply and take-up sprockets 22 and 24 are coupled together by the timing belt 38 to be synchronously rotated at a constant speed by the variable speed motor 30.

The shaft 34 of the variable speed motor 30 also has a plurality of timing discs. In this embodiment, there are two such synchronization discs 44 and 46. Thus, the rotation speeds of the supply and take-up sprockets 22, 24 and the timing discs 44 and 46 connected to the shaft 34 are the same.

The servomotor 32 also rotates an output shaft 48 extending from both ends thereof. One end of the shaft 48 is connected to rotate the intermittent sprocket 28 and the other end of the shaft 48 has a plurality of positioning disks. In this embodiment of the invention, there are two positioning disks 50 and 52. The servomotor 32 also rotates a tachometer 54 located at the outermost end of the shaft 48.

Figure 5 shows a length of film 12 having perforations 56 on both sides. Between the perforations 56 are panels 58, which are separated by vertical lines 60 for illustrative purposes. The length of 35mm standard film is of various sizes along its length. The film 12 has two panels 58 of 4 perforations 56 gauge and a middle panel 58 of 3 perforations 56 gauge. The transition between these two gauges has a trigger spring 62, the function of which is described in detail below. The foregoing figures 1 and 2 show two film formats in detail.

Figures 6 and 7 show the timing discs 44 and 46 in detail. A plurality of small holes 68 are equally spaced around the circumference of each synchronization disc 44 and 46. The first synchronization disc 44 on the shaft 34, which is located outside the second synchronization disc 46, has 6 equally spaced apertures 68, while the second synchronization disc 46 at the inner end of the shaft 34 has 8 apertures 68.

A light source 72 is mounted on a support 70 adjacent the timing discs 44 and 46 to direct a beam of light toward each of the timing discs. The beam is aligned with the aperture 68 on each synchronization disk 44 and 46 so that the beam passes through the apertures as the two synchronization disks rotate. The frame has a pair of photocells 74 and 76 located on the side of the synchronization discs 44 and 46 opposite their light sources 72. Thus, each time a small aperture passes between the light source and a selected photocell while the light source 72 is emitting light, the selected photocell 74 or 76 receives the light beam.

Fig. 8 and 9 show the positioning disks 50 and 52 in detail. As with the synchronization discs 44 and 46, a plurality of apertures 78 are equally spaced about the circumference of each positioning disc 50 and 52. The first positioning disk 50 on the shaft 48 outside the second positioning disk 52 has 6 equally spaced apertures 78 and the second positioning disk 52 on the inner end of the shaft 48 has 8 apertures 78. Also located on the periphery of each positioning disk 50 and 52 are a plurality of equally spaced vanes 80. The first positioning disk 50 has 6 vanes 80 and the second positioning disk 52 has 8 vanes 80.

A support 82 mounted adjacent the positioning disks 50 and 52 has two light sources 84 and 86, one mounted inside the other, for emitting light beams toward the positioning disks 50 and 52, respectively. The light beam from the inner light source 84 is aligned with the apertures 78 in the two positioning disks 50 and 52 so that the light beam passes through each aperture as the two positioning disks rotate. Similarly, the light beam from the outer light source 86 is directed through the space 87 between the vanes 80 to the other side of the positioning disks 50 and 52.

The other side of the positioning disks 50 and 52 also has two photocells 88 and 90 aligned with the two light sources 84 and 86, respectively. Thus, when the light sources 84 and 86 are illuminated, a selected pair of photocells 88 or 90 receive a light beam that passes through the space 87 between the aperture 78 and the blade 80.

The operation of the film feeding device 10 will be described with reference to fig. 4. For the sake of illustration, it is assumed that the film transport apparatus 10 initially transports 4-perforation format films per frame and then switches to 3-perforation format films per frame, which are spliced to the same film tape. For convenience, these two specifications will be referred to hereinafter as "4-hole specification" and "3-hole specification", respectively.

Initially, the variable speed motor 30 is energized and commanded to rotate its output shaft 34 at the appropriate speed corresponding to the 4-perforation format of 35mm film. This causes the film supply and take-up sprocket 22 and 24 to rotate in the feeding direction so that the film 12 is supplied and taken up equally on either side of the film gate 26 and intermittent feed sprocket 28. At the same time, the variable speed motor 30 also rotates the timing disks 44 and 46.

The light source 72 emits a beam of light to both synchronization discs 44 and 46, but since the device operates at a 4-hole format, only the photocell 74 of the first synchronization disc 44 is on. Each time the photocell 74 receives a light beam passing through one of the apertures 68, it emits a pulse signal 92. Since the first synchronization disc 44 has 6 holes, it sends out 6 pulse signals 92 per revolution.

A pulse signal 92 from the energized photocell 74 of the first synchronization disc 44 is sent to an electronic controller 94 which controls the operation of the energized servo motor 32. The intermittent sprocket 28 is driven by a signal 96 transmitted from the controller 94 to the servo motor 32. These signals 96 are generated by the controller 94 based on the pulse signal 92 received from the photocell 74 and triggered by the first synchronization disc 44. Thus, the signal 96 initiates rotation of the intermittent sprocket 28.

As the intermittent sprocket 28 is driven, the film 12 passes through the film gate 26 at a rate of one frame per output pulse signal 92 of the photocell 74. Thus, for each revolution of the first synchronization disc 44, the film has 6 frames of "catch", which corresponds to 6 steps per revolution of the 24-tooth intermittent film transfer gear 28, with 4 teeth per step, which matches the 4-perforation specification. In this process, the electronic controller 94 ensures that each film frame is precisely aligned with the film gate 26. This precise alignment is achieved as follows.

When the intermittent sprocket 28 rolls the film frame 58 into position on the film gate 26, the first positioning disk 50 detects the position of the intermittent sprocket, and thus the film frame, by the aperture 78 and the vane 80 which allow the light beams from the light sources 84 and 86 to be received by the corresponding photocell group 88 of the first positioning disk 50. At the same time, a tachometer 54 mounted at the outermost end of the shaft 48 of the servo motor 32 detects the rotational speed of the intermittent sprocket 28. The electronic controller 94 constantly monitors this information through a set of feedback signals 98 and 100, and the electronic controller 94 then uses this information to shape the voltage waveform as needed to accelerate, decelerate, or stop rotation of the servo motor 32. Thereby allowing the film frame 58 to quickly enter into precise alignment with the film gate 26. Such a feedback system can be seen in U.S. Pat. No.3,819,258, which is incorporated by reference herein.

As the film 12 continues to travel in the apparatus 10, a sensor 102 above the film gate 26 reads one of the trigger springs 62 on the film. In one embodiment, the trigger bar 62 has magnetic, optical, or other information encoded thereon. The trigger spring 62 is preferably located at the splice between the two film formats. The information read by the sensor 102 at this time indicates, for example, that the film gauge has changed from 4-perforation gauge to 3-perforation gauge, and the sensor 102 emits a pulse signal 104 corresponding to this change in gauge. The pulse signal 104 is amplified in an amplifier (not shown) and received by switching electronics 106 forming part of the overall film transport control system. (the switching electronics 106 also turn on the light sources 72, 84, and 86 with signals 107 and 109.)

The pulse signal 104 from the sensor 102 causes the switching electronics 106 to send a signal 108 to the variable speed motor 30 to adjust its speed to fit the 3 hole specification. During this transition, the photocell 76 of the second synchronization disc 46 is switched on and the photocell 74 of the first synchronization disc 44, which was switched on, is switched off. Thus, the photocell 76 of the second synchronization disc 46 receives the light beam 8 times for each revolution of the second synchronization disc, thereby generating a corresponding number of pulse signals 92 to the electronic controller 94.

It should be noted that one revolution of the second synchronizing disk 46 corresponds to one revolution of the 24-tooth intermittent wafer transfer gear 28. Since each pulse signal generated by the photocell 76 of the second synchronization disc 46 is transmitted to the servomotor 32 via the electronic controller 94, which causes the intermittent drive gear to rotate forward once, thereby completing one slice-grabbing, the second synchronization disc 46 grabs 8 slices per rotation, 3 teeth each, which is consistent with the 3-hole specification.

In the 3-hole format shown in FIG. 2, the centerline from left to right of each frame passes through the center of one of the holes 56. But in the 4-perforation specification shown in fig. 1, the centerline of each frame bisects the space between two perforations 56, which are separated by half a perforation. Thus, the first centerline-to-centerline step between the 4-hole gauge and the 3-hole gauge is 3.5 holes. Thereafter, the centerline-to-centerline spacing was kept constant for 3 holes per frame. Therefore, the film feeding device 10 must be designed to reposition the intermittent film feeding gear 28 to eliminate this misalignment. To this end, the angular position of the second positioning disk 52 (with 8 apertures 78 and vanes 80 corresponding to the 3-hole format operation) is set 7.5 ° behind the first positioning disk 50 (with 6 apertures 78 and vanes 80 corresponding to the 4-hole format operation), which corresponds to half a hole on a 24-tooth film gear. Thus, the intermittent sprocket 28 is repositioned while the spacing between frames is maintained at 3 holes to maintain the correct image frame in the 3 hole format.

The transfer of control from the first synchronizing disk 44 to the second synchronizing disk 46 takes place during the idle period of the intermittent sprocket. However, since the angular position of the leading edge of the blade 80 and the aperture 78 on the second positioning disk 52 lags behind the first positioning disk 50 by one-half of a perforation, during the first movement after a period of inactivity, the second positioning disk 52 rotates only 7.5 (one-half of a perforation) before the blade and aperture cause the newly energized photocell 90 to emit the pulse signal 98. The electronic controller 94 must be programmed to ignore these initial transition pulse signals and wait for the next set of pulse signals to occur so that the film 12 advances 3.5 perforations at first.

Since the sensor 102 must be positioned before the film gate 26, the trigger spring 62 passes the sensor slightly before the film reaches the correct switch position. Therefore, the conversion electronics 106 must provide a time delay in this process. This time delay is determined by the constant distance between the sensor 102 and the chip gate 26 and the current mode of operation of the device 10 as determined by the information encoded on the trigger bar 62. This delay is slightly longer because the film 12 moves more slowly at the 3-perforation specification. Another way to compensate for the positional deviation of the sensor 102 is to offset (i.e., retard) the position of the trigger spring on the film print by an amount equal to the deviation between the sensor and the film gate.

When the sensor 102 reads another trigger spring 62 on the film 12, another pulse signal 104 is transmitted to the switching electronics 106, which then instructs all components of the device 10 to revert to the 4-hole mode of operation described above.

As is apparent from the above, the present film transport apparatus 10 can switch back and forth between different film formats on the same film strip 12 without interrupting or stopping the projection of the projector 14. This is a great boon for film makers, film distributors, and exhibitors who are now free to splice two (or more) different film formats onto the same film tape. Film distribution and projection costs and workload are greatly reduced. Moreover, the conversion between film formats requires no skill or training and the theater hires a regular person to show the movie using the device.

The convertible take-up motion picture projection apparatus allows a film distributor to make film prints with new specifications that eliminate waste. So that the material cost is reduced without the image quality being degraded. The advantage of this method is not only a reduction in material costs. The copy becomes shorter and lighter as waste is eliminated. Their transportation costs are reduced and even entire copies can be shipped in a mother board for screening.

Currently, a film 100 minutes long is 9,000 feet long and, due to its weight, requires 2000 foot film reels to ship. These film reels must be connected together on the particular projector used to project them. This process is called "lens grouping". This must be done by a technician such as a projectionist. When the theatre manager decides to transfer the copy to another screen, it is difficult to transfer from one projector to another on a mother board because the copy is too heavy, and therefore must be "disassembled" and "reassembled". However, the present invention allows prints to be made shorter and lighter, with a film strip that is also 100 minutes long being only 6,750 feet (using a 3-perforation specification) or 5,625 feet (using a 2.5-perforation specification). Due to the reduced length and weight, films can be transported in individual reels from one projector to another without the need for "disassembly" and "reassembly".

It should be understood, of course, that when a new reel of film 12 of constant gauge is first loaded into the projector, the trigger strip 62 can be placed at the beginning of the film strip or it may be necessary to command the projector to operate properly with the manual switch 130. Thus, upon reading the trigger bar 62 or depressing the manual switch 130, the necessary adjustments can be made by the switching electronics 106 to properly operate the film transport 10 to transport a particular format of film 12 in the projector.

It should also be appreciated that the film transport apparatus 10 can switch between any other number of different film formats as well as between two film formats as described above. Thus, by way of further example, the film transport apparatus 10 can be configured to use the film format shown in fig. 3, i.e., 2.5 perforations per frame 58 of film 12. To be able to switch from a 4-hole or 3-hole format to a 2.5-hole format, the number of apertures 68 in the timing disks 44 and 46 and the number of apertures 78 and vanes 80 in the positioning disks 50 and 52 must be changed. Alternatively, if a switch is to be made between all three film formats, three synchronization disks 44, 46 and 110 and three positioning disks 50, 52 and 112 are used as shown in FIGS. 10a-10 d. Switching between three film formats requires three different speeds of the variable speed motor 30. The number of teeth on the intermittent drive sprocket has also been changed to be evenly divisible by 2.5, 3.0 and 4.0, in this case 60 teeth.

Thus, the first synchronization disc 44, corresponding to the 4-hole format, has 15 equally spaced holes 68. The second synchronization disc 46, which corresponds to a 3-hole format, has 20 equally spaced holes 68. A third synchronization disc 110 corresponding to the 2.5 hole size is also added. The third synchronization disc 110 has 24 apertures 68 and its light source 114 and photocell 116 to generate the required pulse signals to control the operation of the servo motor 32. The first and second pucks 50 and 52 and the added third puck 112, which corresponds to a 2.5 hole gauge, have a corresponding number of apertures 78 and vanes 80. The third puck 112 also has its light source 118 and photocell group 120.

It can be seen from the above that film of different or more sizes can be fed in the film feeding device by simply reconfiguring the apertures, spaces and vanes of the synchronizing and positioning disks. Thus, although not all of the timing and positioning disks are shown in the drawings, it will be apparent to those skilled in the art from the foregoing description in conjunction with FIGS. 7, 9, 10b and 10d how to construct the orifices, spaces and vanes in accordance with different or more specifications of the sheet transport apparatus.

In addition, each synchronization disk 44, 46, and 110 and the positioning disks 50, 52, and 120 may be provided with redundant light source and photovoltaic cell sets 122 and 126 and 124 and 128. These redundant light sources and photovoltaic cell sets 122 and 126 and 124 and 128 are shown in figures 10a and 10 c. These redundant light sources and photocells ensure trouble-free operation in the event of failure of one of the combinations of light sources 72, 84 or 86 and photocells 74, 76, 88 or 90. The embodiment of figure 4 may also be provided with redundant light sources and photovoltaic cells.

When the film transport apparatus 10 is switched from 4 hole size to 2.5 hole size, the first step must move 3.25 holes. The third synchronization disc 110 must therefore lag behind the first synchronization disc by 4.5. Thus, the first step causes the intermittent sprocket 28 travel to add 0.75 perforations to the 2.5 perforations commanded by the electronic controller 94.

As with the conversion from the 4 hole format to the 3 hole format described above, the 4.5 ° offset of the second puck 52 causes the newly turned on photocell 90 to prematurely issue the pulse signal 98. The electronic controller 94 must be programmed to ignore these pulse signals and wait for the next pair of pulse signals to appear.

Likewise, the conversion from a 3-hole gauge to a 2.5-hole gauge requires a first step of moving 2.75 holes. However, this is automatically solved by the half-hole offset already existing between the second synchronization disc 46 and the first synchronization disc 44.

Although fig. 4 shows a separate sensor 102 at the film gate 26, the apparatus 10 may also use sensors that are already present in the projector. These existing sensors are typically used to dim lights, pull curtains open, and perform other tasks. The trigger spring 62 may also be a thin strip of material that cannot be demagnetized, an optically read bar code, a mechanical trigger (e.g., scoring, punching or embossing the film), or other suitable device. Further, if desired, the sensor 102 may be replaced with a manual switch 130 on the projector 14 for specification switching by the projectionist upon visual inspection of the film 12.

Another advantage of the film transport apparatus 10 of the present invention is that the entire film in the film transport apparatus 10 can be automatically rewound back into the film mother apparatus that supplies the film to the film transport apparatus 10. In existing motherboard assemblies, the exhibitor must return the entire film to the motherboard assembly before the film can be shown again. However, the conventional film feeding apparatus uses a mechanical device, and thus the film cannot be rewound at high speed. However, the sheet feeding device 10 of the present invention does not use these mechanical devices, but is of an all-electronic design, so that the intermittent sheet feeding gear does not perform intermittent motion during the rewinding process, and therefore, the rewinding is smooth and high-speed. The film transport 10 can be commanded to rewind at high speed by providing a trigger spring 62 at the end of the film 12 to command the motors 30 and 32 to rewind at high speed as described above.

While a particular form of the invention has been shown and described, it will be obvious that various modifications may be made within the spirit and scope of the invention. Accordingly, the invention is not to be restricted except in light of the attached claims.

Claims (21)

1. A motion picture projection mechanism for transporting film in a motion picture projector wherein the film includes a series of frames and a plurality of perforations on opposite sides of the film, the motion picture projection mechanism comprising:

a plurality of sprocket wheels having teeth for engaging the perforations for transporting the film in the projector;

a power member that rotates the film transport gears to cause the film to pass through a window in the projector frame by frame; and

a controller controlling the power member to maintain or change the speed and position of the sprocket according to film specifications determined by the number of perforations per frame, the controller also controlling the output of the power member to re-center the frame relative to the perforations each time the film specifications change.

2. The motion picture projection mechanism of claim 1, wherein the plurality of film transport gears comprises:

a pair of constant speed film feed gears arranged on opposite sides of the film window and having teeth for engaging the film perforations for feeding film in the film projector;

an intermittent feed gear having teeth for engaging the perforations for advancing the film frame by frame through the film window.

3. The motion picture projection mechanism of claim 2, wherein the power element comprises:

a first motor having a rotational output for rotating the pair of constant speed film transfer gears; and

a second motor having a rotational output for rotating the intermittent drive sprocket.

4. The motion picture projection mechanism of claim 3, wherein the first motor is a variable speed motor and the second motor is a servo motor.

5. The motion picture projection mechanism of claim 3, wherein the controller controls and coordinates the first and second motors, including a switch responsive to a trigger signal to vary the output of the first and second motors and thereby vary the speed of rotation of the pair of sprockets and the positioning of the intermittent sprocket; the trigger signal indicates when the film in the projector changes from a first predetermined number of perforations to a second predetermined number of perforations.

6. The motion picture projection mechanism of claim 5, wherein the trigger signal is determined by a number of perforations in each frame of the film.

7. The motion picture projection mechanism of claim 6, wherein the trigger signal is automatically generated during projection by the projector using electrical, magnetic, optical, or mechanical means.

8. The motion picture projection mechanism of claim 6, wherein the trigger signal is generated manually.

9. The motion picture projection mechanism of claim 1, wherein said plurality of film transport gears includes an intermittent film transport gear having teeth for engaging the film perforations for moving film frame by frame through a window in the projector and a pair of constant speed film transport gears spaced on opposite sides of the window and the intermittent film transport gear having teeth for engaging the film perforations for transporting film in the projector in cooperation with the intermittent film transport gear; said power element including a first motor having a rotational output for rotating said pair of constant speed drive sprocket wheels and a second motor having a rotational output for rotating said intermittent drive sprocket wheels; the controller is a controller for controlling and coordinating the rotational outputs of the first and second motors, wherein the controller includes a switch for changing the rotational outputs of the first and second motors without interrupting the projection of the projector, thereby changing the rotational speed of the pair of constant speed film transport gears and the positioning of the intermittent film transport gears as the film in the projector changes from a first film format with a first number of perforations per frame to a second film format with a second number of perforations per frame, and controlling the output of the motors to re-center the frame relative to the perforations each time the film format changes.

10. The motion picture projection mechanism of claim 9, wherein the switch is controlled by information indicating when film in the projector changes from a first film format to a second film format.

11. The motion picture projection mechanism of claim 10, wherein the film carries information that is sensed by a sensor to indicate when the film gauge in the projector has changed.

12. The motion picture projection mechanism of claim 10, wherein the switch controls the rotational output of the first motor based on a trigger signal from the sensor.

13. The motion picture projection mechanism of claim 12, wherein the trigger signal is determined by film specifications.

14. The motion picture projection mechanism of claim 1, wherein the motive member is a motor for rotating the film transport gears at a selected speed and intermittently positioning the film frame by frame at a window in the projector.

15. The motion picture projection mechanism of claim 14, wherein the controller reverses the film at high speed by the motor changing the speed and direction of rotation of the sprocket.

16. A method of transporting film in a projector including a motive member for rotating a plurality of film transport gears to move the film through a film window frame by frame, the method comprising: determining a film specification dependent upon the number of perforations per frame on the film; generating a trigger signal according to the film specification during the projection process to control the output of the power member and the rotational movement of the film transport gear; controlling the output of the power part by using the trigger signal so as to keep or change the rotating speed and the positioning of the film transmission gear according to the specification of the film; and controlling the rotational movement of the power member and the film transport gear using the trigger signal to re-center the frame relative to the perforation each time a film gauge change occurs.

17. A method of transporting film in a projector including an intermittent sprocket and a pair of constant speed sprockets which engage perforations in the film to cause the film to pass frame by frame through a window in the projector, wherein the rotational output of a first motor rotates the constant speed sprocket and the rotational output of a second motor rotates and positions the intermittent sprocket, the method comprising:

determining a film specification dependent upon the number of perforations per frame on the film;

controlling the rotation output of the first motor and the rotation speed of the constant speed film transmission gear according to the film specification;

controlling the rotational output of the second motor and the positioning of the intermittent film-conveying gear according to the film specification;

generating a trigger signal in response to a change in film gauge to vary the rotational output of the first and second motors and the rotational speed of a pair of constant speed sprocket gears and the positioning of the intermittent sprocket gears;

the frame is re-centered with respect to the perforation each time the film gauge changes.

18. The method of claim 17, further comprising: generating a trigger signal for controlling the rotational output of the first motor and the rotational speed of the constant speed sprocket, wherein the trigger signal is dependent upon the film gauge.

19. The method of claim 18, further comprising: information indicating the film specification is encoded on the film and detected to generate the trigger signal.

20. The method of claim 19, further comprising: the trigger signal is transmitted to a switch which generates a second signal for controlling the rotational output of the first motor in response to the trigger signal.

21. The method of claim 19, further comprising: a plurality of trigger springs are provided on the film at positions corresponding to changes in the specification of the film; encoding information indicative of a change in film gauge on the trigger springs; and detecting the information to generate a trigger signal.