Currently, film projectors employ various types of film looping between input and take-up reels when film is being conveyed intermittently through film gates. Film gates are known also as light gates but will be referred to as film gates for consistency in this document. Film loops in conventional systems compensate for rapid changes of un-reeled length of film above and below a film gate as a result of timed stops of the film at the film gates between evenly synchronized input and take-up of the film by the respective reels. Traditional film projection systems have only a bottom film-transport wheel, called a bottom intermittent sprocket, which pulls the film through a film gate. Unfortunately, such traditional systems require high friction at the film gates to prevent the film from over shooting the film trap.

A variety of prior-art means and methods have been employed to control but not to eliminate film looping between top and bottom sprockets while also eliminating detrimental flutter, wear, noise, damage and danger from operation of a projection machine as taught by this invention.

Examples of different but related projection systems and methods are described in the following patent documents. U. S. Patent Number 3,303,981, issued to Wiese, described top and bottom film sprockets that were rotated simultaneously in order to drive film through a film gate in the most nearly similar manner in relation to some aspects of this invention that is known. It was limited, however, to a fixed frame 11 that functioned in relation to a moveable

frame 12 with a complex indexing means that generated and controlled a relatively small loop that was, nevertheless, a"film-gate loop"between top and bottom film sprockets 13 and 14. Instead of eliminating the film-gate loop with better means and methods, it attempted to minimize the problem in ways that perpetuated its basically detrimental features and taught against a thorough solution that is made possible by this invention.

Two U. S. patents, Numbers 4,022,525 and 4,253,749, issued to Boudouris, also perpetuated means and methods for forming a film-gate loop between top and bottom film-conveyance sprockets. The'749 Boudouris patent provided for forming a looped film at a distance from a surface of a film gate.

This"distance looping"was a prior-art continuation of the film-loop problem that apparently was recognized and attempted to be solved by an indexing system that was similar in principle to the above Wiese patent. The'525 Boudouris patent had larger film-loop problems that were diminished but not eliminated by the latter'749 Boudouris patent.

Other known projection systems are further yet different but pertinent to understanding the significance of this invention. U. S. Patent Number 4,537,482, issued to Weiner, taught a barrel cam for intermittent transfer of film-gate sections of film between top and bottom film loops. German Application Number DE 3324-911-A, by Thiele, taught a controlled-motorization means between top <BR> <BR> and bottom film loops. U. S. Patent Number 4,150,886, issued to Merkel, et al., taught a double-sided gear-belt drive of film-gate sections of film between film loops that were regulated loosely by top and bottom capstan gearing. U. S. Patent Number 3,937,378, issued to Kopernicky, described detent control of film loop.

U. S. Patent Number 3,494,524, issued to Jones, taught a circumferential loop- control mechanism.

Contrary to the prior art, the present invention provides precision film placement in the film gate by using two synchronized film sprockets that accelerate and decelerate simultaneously. Thus, each frame of film is accurately placed in the same position as the previous frame.

On the other hand, prior art projection systems use pressure friction and registration pins or loops through the film gate assembly to perform this task.

Such friction must be overcome to pull the next frame into position. Although the latter friction use may work satisfactorily with 35 millimeter film, it does not work well with larger film stocks and frame sizes, as the friction which is used and must be overcome increases logarithmically. The increased film mass and surface friction requires large film movements and results in increased mechanical failure and film wear.

The present invention eliminates the need to use friction by having a deceleration sprocket before the film gate which also eliminates any slack in the film so the film cannot flutter or jump.

Summary of the Invention In light of need for improvement of film projectors, objects of this invention are to provide a motion-picture-projection system which: Eliminates film-gate loop of film between top feed sprockets and the intermittent sprockets; Prevents the overshooting of film through the film gate by controlled deceleration of the film without using friction or registration pins; Eliminates significant flutter, movement noise, heat generated"breathing" and wear of film from conveyance when the film is decelerated and thus stopped in the film gate;

Avoids damage and danger associated with malfunctioning of projection equipment; Allows use of a wider range of film speeds without picture distortion or film damage due to either accelerated or decelerated rates of film conveyance either forwards or backwards through film gates; and Allows use of wider film that requires rates of picture-frame cycling equal to smaller film for similar motion-picture effects and, therefore, requires higher film-travel speeds that are made possible by this invention.

This invention accomplishes these and other objectives with a motion- picture-projection system having a film-gate-inlet sprocket and a film-gate-outlet sprocket that are rotated intermittently in unison by mechanical and/or electrical means for conveyance of film through a film gate without formation of intermediate loops of film between the film-gate-inlet sprocket and the film-gate outlet sprocket. Absence of intermediate loops allows absolute control of film in order to avoid film flutter, inaccurate positioning of picture frames and other problems associated with conventional film looping. To compensate for differences of length of unreeled film due to its cyclic advance and film-frame stoppage, compensatory loops are formed prior to instead of after a film-gate- inlet sprocket and after instead of before a film-gate outlet sprocket. Projection intensity of light at the film gate can be directed by a mirror through a dichroic infrared heat filter to prevent transmission of infrared heat energy from a light source to a projection mechanism at the film gate. A film-contact surface of the film gate can be arcuate and covered at least at film edges with non-abrasive and suitably pliable material to minimize film wear. Compressed air can be directed onto the film for cooling and for preventing distortion resulting from heat absorption that is related to film"breathing". Electronic monitoring of film

speed, frame-dwell time, heat, light, film noise, film flutter, film condition, compensatory-loop conditions, equipment functioning, equipment condition and other projection aspects with automatic warnings and operational adjustments can be provided.

The above and other objects, features and advantages of the present invention should become even more readily apparent to those skilled in the art upon a reading of the following detailed description in conjunction with the drawings wherein there is shown and described illustrative embodiments of the invention.

Brief Description of Drawings This invention is described by appended claims in relation to description of a preferred embodiment with reference to the following drawings which are referred to as FIGS. in this document and described briefly as follows: FIG. 1 is a partially cutaway side elevation view of a film projector of the invention; FIG. 2 is a side elevation view of a sequentially controlled dual-sprocket intermittent with shaft-geared rotation of a film-gate-inlet sprocket and a film- gate-outlet sprocket using a Geneva dual drive movement; FIG. 3 is a side elevation view of a sequentially controlled dual-sprocket intermittent with gear-belt rotation of a film-gate-inlet sprocket and a film-gate- outlet sprocket; FIG. 4 is a side elevation view of a first of two sequentially controlled motors of a dual-sprocket intermittent with gear-belt rotation of a film-gate-inlet sprocket;

FIG. 5 is a side elevation view of a second of two sequentially controlled motors of a dual-sprocket rotator with gear-belt rotation of a film-gate-outlet sprocket; FIG. 6 is a front elevation view of a film-gate lens having a film-steadying surface; and FIG. 7 is a cross-sectional view of the FIG. 6 illustration through section line 7-7'of FIG. 6.

Description of Preferred Embodiment Terms used to describe features of this invention are listed below with numbering in the order of their initial use with reference to the drawings. These terms and numbers assigned to them designate the same features wherever used throughout this description.

1. Top intermittent sprocket 21. First dual motor 2. Film-gate inlet 22. First-motor gear belt 3. Film 23. Second dual motor 4. Film gate 24. Second-motor gear belt 5. Motion-picture projector 25. Film-contact surface 6. Bottom intermittent sprocket 26. Projection portion 7. Film-gate outlet 27. Film trap 8. Sequentially controlled 28. Projection light electrical motor 29. Projection lens 9. Gear drivetrain 30. Standard shutter 10. Sprocket teeth 31. Infrared heat filter 11. Film-input reel 32. Sprocket spring 12. Film-output reel 33. Sprocket base 13. Feed sprocket 34. Frame base 14. Hold-back sprocket 35. Upper optical encoder 15. Input-loop controller 36. Lower optical encoder 16. Input loop 37. Detectors 17. Output-loop controller 38. Communication lines 18. Output loop 39. Power-source switch 19. First gear belt 40. Encoder sprockets 20. Second gear belt

Reference is made to the drawing figures. A top intermittent sprocket 1 is positioned proximate a film-gate inlet 2 of film 3 to a film gate 4 of a motion- picture projector 5. Oppositely disposed, a bottom intermittent sprocket 6 is positioned proximate a film-gate outlet 7 of the film 3 from the film gate 4. A dual-sprocket intermittent rotator, such as a sequentially controlled electrical motor 8 with a gear drivetrain 9 to both the top intermittent sprocket 1 and the bottom intermittent sprocket 6, has rotational actuation with intermittent stoppage of the top intermittent sprocket 1 simultaneously with rotational actuation with intermittent stoppage of the bottom intermittent sprocket 6.

Sprocket teeth 10 are extended radially from ends of a circumferential periphery of the top intermittent sprocket 1 to engage sprocket-drive apertures in film 3 being unwound from a film-input reel 11. Similarly, sprocket teeth 10 are extended radially from ends of a circumferential periphery of the bottom intermittent sprocket 6 to engage sprocket-drive apertures in film 3 being wound onto a film-take-up reel 12.

The dual-sprocket rotator, such as sequentially controlled electrical motor 8, has film-advancement rotation cyclically alternate from frame-projection stoppage of the film 3 in the film gate 4 for a select time of frame-projection stoppage in proportion to film-advancement rotation of the film 3 frame-by- frame. A feed sprocket 13 is positioned intermediate the film-input reel 11 and the top intermittent sprocket 1, the feed sprocket 13 being actuated to unwind film 3 from the film-input reel 11 at a select rate prior to cyclically rotational actuation of the film 3 with the top intermittent sprocket 1. In opposite working relationship, a hold-back sprocket 14 is positioned intermediate the bottom intermittent sprocket 6 and the film-take-up reel 12, the hold-back sprocket 14 being actuated to wind film 3 at a select rate after cyclically rotational actuation

of the film 3 with the bottom intermittent sprocket 6. Other film transport systems may be used in place of reels.

Intermediate the feed sprocket 13 and the top intermittent sprocket 1 is an input-loop controller 15 which confines an input loop 16 in a V-route with noise- suppressant material that has solid viscosity in relationship to sliding contact of the film 3. Intermediate the hold-back sprocket 14 and the bottom intermittent sprocket 6 is an output-loop controller 17 which confines an output loop 18 in a V-route with noise-suppressant material that has solid viscosity in relationship to sliding contact of the film 3.

Instead of minimally controlled film looping at both sides of a film gate 4 between top and bottom"intermittents"as in conventional practice, there is no film looping between a top intermittent sprocket 1 and a bottom intermittent sprocket 6 that replace the conventional intermittents at opposite sides of the film gate 4. Rather, to compensate for rapid changes of film length between the film- input reel 11 and the film-take-up reel 12 resulting from intermittent or cyclical stoppage and advancement of film 3, there is controlled and noise-suppressed film looping that is isolated from the film gate 4. There is no uncontrolled movement of film 3 at opposite sides of the film gate 4 where it now affects quality of motion-picture projection adversely in conventional practice.

Dual-sprocket rotation can be achieved with a selection of dual-sprocket rotators. FIG. 2 illustrates a Geneva dual-sprocket intermittent rotator that is the sequentially controlled electrical motor 8 with a gear drivetrain 9 in rotative communication with a top intermittent sprocket 1 and a bottom intermittent sprocket 6, in Geneva intermittent movements.

FIG. 3 depicts a dual-sprocket rotator that is the sequentially controlled electrical motor 8 with a first gear belt 19 driving a top intermittent sprocket 1 and a second gear belt 20 driving a bottom intermittent sprocket 6.

FIGS. 4-5 depict a dual-sprocket rotator that is a first dual motor 21 that is sequentially controlled and has a first-motor gear belt 22 which drives a top intermittent sprocket 1 and a second dual motor 23 that also is sequentially controlled and has a second-motor gear belt 24 which drives a bottom intermittent sprocket 6.

Mechanical gearing for the dual-sprocket rotator includes metal gearing, gear-belt gearing and direct drive from a sequentially controlled electrical motor 8 or other source of rotative power. A sequentially controlled electrical motor 8 can be referred to also as a step motor of a particular variety that provides precisely controlled stopping and starting. Cyclic stopping and starting of rotation by a dual-sprocket rotator can be provided also by select mechanical means in working relationship with continuous rotation of an electrical motor or other rotational power source.

Referring to FIGS. 6-7 and referring further to FIG. 1 also, the film gate 4 has a light side that is arcuate or curved with a film-contact surface 25. The film-contact surface 25 borders a projection portion 26 and has solid-lubricant viscosity to sliding contact of the film 3. The projection portion 26 is optimized for picture projection and the film-contact portion 25 is optimized for sliding contact of film 3 and for standardization.

Aiding further in stabilizing film 3 at the film gate 4 is a film trap 27 into which air is directed from an externally positioned conventional air pump against a light side of film 3 intermediate a projection light 28 and the film gate 4. The

air cools the film gate 4, the film 3 and a projection lens 29 to aid picture projection in addition to stabilizing the film 3 against the film gate 4.

The projection light 28 is directed intermittently through a standard shutter 30, through the film 3, through a dichroic infrared heat filter 31, to the projection lens 29 and onto a screen.

Motors 8,21, and 23 provided to rotate the top intermittent film-gate-inlet- sprocket 1, the bottom intermittent film-gate-inlet sprocket 6, the feed sprocket 13 and the hold-back sprocket 14 respectively with associated mechanical means are reversible in direction of rotation and variable selectively in speed of rotation.

Referring further to FIG. 3, an alternative for aiding stabilization of film 3 is tightening it against the film gate 4 with sprocket springs 32 between a sprocket base 33 and a frame base 34 to spring-pressure the top intermittent sprocket 1 and the bottom intermittent sprocket 6 apart with relatively light pressure. This can be accomplished for either type of sprocket mounting or dual- sprocket rotator.

An electronic monitor has electrical-shutdown communication with the motion-picture-projection system in response to select signals and predetermined conditions. The electronic monitor has an upper optical encoder 35 and a lower optical encoder 36 through which select physical conditions related to operation are detected by optimally positioned detectors 37 and communicated through communication lines 38 to a power-source switch 39 for electrical shutdown in accordance with predetermined factors at an input side and at an output side of the projection system. The detectors 37 and the communication line 38 are representative of electrical, fibre-optical and/or radio-wave communication selectively. Encoder sprockets 40 are employed to aid electronic monitoring.

A new and useful motion-picture-projection system having been described, all such foreseeable modifications, adaptations, substitutions of equivalents, mathematical possibilities of combinations of parts, pluralities of parts, applications and forms thereof as described by the following claims and not precluded by prior art are included in this invention.