Abstract:
A film trap and gate assembly for use on a motion picture projector. The film trap includes an image aperture and a first and second trap rail assembly. The film trap further includes a stripper plate having an angled stripper blade attached to an attachment flange. The stripper blade is attached to the attachment flange at an at least one degree angle, preferably biased towards the trap body. The film gate includes a projection aperture and a first and second gate rail assembly. A film tensioning assembly is attached to the gate body, the film tensioning device having a deformable body disposing at least two tensioning rollers, and an adjustable tensioning device. When assembled, the film trap and gate assembly forms a film movement channel to guide the film past an illumination source, while reducing the contact between the film strip and the film trap and gate assembly. Consequently, the number of showing of a motion picture film is substantially increased.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    In motion picture projectors, a succession of transparent or semi-transparent still images or frames are sequentially advanced before a suitable light source, thereby projecting an image onto a projection surface. The film is moved or advanced until a frame is in alignment with the projection aperture and then held stationary for a discrete period of time during which light is passed during two discrete time periods through the aperture, film frame, and then a focusing lens, resulting in an image being projected onto a screen. This is followed by movement of the film until the next frame is in alignment with the projection aperture. The rapid sequential advancement of the individual still frames, typically on the order of 24 frames per second, produces the illusion of motion. Typically, the film disposes at least one soundtrack synchronized with the picture projection. In this regard, recent advances in analog and digital sound recording technology have been rapidly incorporated in to modern films and film projector sound systems, more commonly referred to as “sound heads”.  
           [0002]    To effectuate sequential film advancement, motion picture projectors utilize toothed drive sprockets connected to a motor driven “star wheel” to sequentially pull a length of film before the light source. Such motion picture projectors further include tensioning shoes for maintaining the filmstrip in contact with the drive sprockets. The film disposes two drive tracks which are engaged by the toothed sprockets, thereby enabling frame advancement. Motion picture filmstrips generally include at least one soundtrack positioned near the edge of the film or within at least one film drive track.  
           [0003]    Commonly, motion picture projectors utilize a film trap and gate assembly to precisely align and position a filmstrip within an illumination plane. The film trap and gate assembly includes a pair of runners which provide controlled movement of the filmstrip past an illumination aperture. The edges of the filmstrip contact the runners, pressure bands, and tensioning shoes during operation. Consequently, over a period of time the edges of the filmstrip may become scratched or damaged due to the film remaining in constant contact with the runners, pressure bands, and tensioning shoes. Additionally, foreign materials such as dust, residues, and other impurities located on the runners, pressure bands, or tensioning shoes may be deposited on the film. The damage to the edges of the filmstrip or the foreign material deposited on the film may prevent the soundtracks from being clearly reproduced by the sound head.  
           [0004]    Additionally, motion picture projectors are designed primarily for forward film advancement, in that the drive sprockets pull the filmstrip past an illumination aperture. On occasion, a film trap will include a sharpen device called a stripper plate located near the drive sprocket, to strip film splices when the film is moved through the projector in reverse. Pushing a flexible portion of film material past the sharpened stripper plate and past the runners, pressure bands, and tensioning shoes is often impossible. Moreover, severe damage to a filmstrip could occur should the filmstrip contact the stripper plate. As such, reversing the direction of the film, particularly while viewing, often results in damage to the film.  
           [0005]    Thus, there is a need for a film trap and gate assembly for a motion picture projectors which reduces the amount of surface wear on the edges of the filmstrip, thereby increasing the lifetime of each film print. There is a further need for a film trap and gate assembly which enables the operator to reverse the direction of film travel without damaging the film.  
         BRIEF SUMMARY OF THE INVENTION  
         [0006]    The present invention solves the need for a film trap and gate assembly which reduces the damage to a filmstrip disposed therein, thereby extending the usable lifetime of the motion picture. The film trap and gate assembly disclosed herein has eliminated the need for maintaining constant contact between the film and the spring-loaded runners, pressure bands, and steel tensioning shoes thereby reducing or eliminating may damage to the filmstrip. Additionally, the present invention permits an operator to reverse the direction of film movement through the projector, while viewing or at higher speed, without damaging the film. The present invention may be utilized a an number of film projector systems with little or no modification required.  
           [0007]    The film trap and gate assembly of the present invention comprises a film movement channel, which defines a discreet area which the film strip may traverse. The film movement channel, which is formed by the film gate engaging the film trap, forms and orifice larger than the thickness of the film disposed therein. Similarly, the width of the film movement channel is greater than the width of the film positioned therein. Unlike prior art systems, which utilized spring-loaded pressure bands located on the film trap which remain in constant contact with the film and forcibly bias the film against the film gate, the film movement channel of the present invention permits a degree of film movement or float within the channel. As a result, damage to the film has been reduced or eliminated while the usable lifetime of the filmstrip has been increased.  
           [0008]    In an additional embodiment, the present invention discloses a film trap comprising a trap body having image aperture formed therein, and having a first and second trap rail assembly positioned thereon. The first trap rail assembly comprises a first trap rail in communication with a first trap guide. Similarly, the second trap rail assembly comprises a second trap rail in communication with a second trap guide. The film is positioned on the first and second trap rails. The amount of lateral displacement the film is limited by the first and second trap guides. Those skilled in the art will appreciate the present invention has eliminated the need for constant pressure applied by the spring-loaded pressure bands the film, thereby decreasing or eliminating damage to the film during operation.  
           [0009]    Additionally, the present invention discloses a film tensioning device which is attachable to a film gate. The film tensioning device comprises a deformable body having at least tensioning roller attached thereto, and a tensioning device in communication with tensioning rollers. The deformable body may further comprise a roller cradle which positions the tensioning rollers on the deformable body. Those skilled in the art will appreciate the tensioning rollers of the present invention may be comprised of non-abrasive materials, including, without limitation, elastomers, urethanes, and rubbers. In another embodiment, the tensioning device may be actuated to adjust the tensioning force applied by the tensioning rollers.  
           [0010]    In yet another embodiment of the present invention a film trap and gate system is disclosed herein. The film trap and gate system comprises a film trap capable of engaging a film gate. The film trap comprises a trap body having an image aperture formed thereon, and a first and second rail assembly attached thereto. The film trap further disposes a stripper plate comprising an angled stripper blade in communication with an attachment flange. The stripper plate is attached to the attachment flange at an at least one degree angle, thereby enabling the movement of the film to be reversed. The film gate comprises a gate body having a projection aperture formed therein, and a first and second rail assembly attached thereto. A film tensioning device is attached to the gate body. The tensioning device comprises a deformable body having an attachment orifice formed therein, an a roller cradle attached thereto. The attachment orifice preferably forms an attachment slot thereby enabling the user to adjust the length of the film tensioning device with respect to the gate body. At least tensioning rollers are in communication with the roller cradle. A tensioning device is in communication with the roller cradle such that the tensioning force applied by the tensioning device may be adjusted by the user.  
           [0011]    In an alternate embodiment, the present invention discloses a film gate stripper plate for use in motion picture projectors. The stripper plate comprises a stripper blade attached to an attachment flange. The stripper plate is angled, preferably towards the gate body, at least one degree. Those skilled in the art will appreciate the present invention permits the movement of the film to be reversed without the film contacting the stripper blade, thereby reducing the likelihood of damaging the film.  
           [0012]    In another embodiment, the present invention discloses a film trap and gate calibration device comprising a first member and a second member. The first member has a thickness greater than the thickness and width larger than motion picture film. The second member has a thickness and width smaller than the thickness of motion picture film. The operator may then position the trap and gate rails to be calibrated to be slightly larger or smaller than the motion picture film disposed thereon.  
           [0013]    The present invention discloses a method of advancing motion picture film through a motion picture projector. The advancement method comprises locating film within a film projector, using the a film trap and gate assembly to form a film movement channel within the projector, positioning the film within the film movement channel, attaching the film to a film drive system, and moving the film through the film advancing channel. Those skilled in the art will appreciate the present method results in the film intermittently contacting the film trap, film gate, or both, rather than utilizing constant pressure commonly used in prior art system.  
           [0014]    Other objects and further features of the present invention will become apparent from the following detailed description when read in conjunction with the attached drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    [0015]FIG. 1 is a schematic view of a film projector showing motion picture film threaded through the projector;  
         [0016]    [0016]FIG. 2 is an enlarged side view of motion picture film having multiple soundtracks disposed thereon;  
         [0017]    [0017]FIG. 3 is a perspective view of the film trap and gate assembly of the present invention having motion picture film disposed therein;  
         [0018]    [0018]FIG. 4 is a perspective view of the film trap of the present invention;  
         [0019]    [0019]FIG. 5 is a top view of the film trap of the present invention;  
         [0020]    [0020]FIG. 6 is an exploded view of the film trap of the present invention;  
         [0021]    [0021]FIG. 7 a  is a perspective view of an embodiment of the first trap rail assembly of the present invention;  
         [0022]    [0022]FIG. 7 b  is a perspective view of alternate embodiment of the first trap rail assembly of the present invention;  
         [0023]    [0023]FIG. 8 a  is a top view of the stripper plate used on the film trap of the present invention;  
         [0024]    [0024]FIG. 8 b  is a side view of the stripper plate used on the film trap of the present invention showing the angled stripper blade;  
         [0025]    [0025]FIG. 8 c  is a perspective view of the stripper plate used on the film trap of the present invention;  
         [0026]    [0026]FIG. 9 is a top view of the film trap of the present invention having motion picture film disposed thereon;  
         [0027]    [0027]FIG. 10 is a perspective view of the film gate of the present invention;  
         [0028]    [0028]FIG. 11 is a top view of the film gate of the present invention;  
         [0029]    [0029]FIG. 12 is an exploded view of the film gate of the present invention;  
         [0030]    [0030]FIG. 13 a  is a perspective view of the film tensioning assembly of the present invention;  
         [0031]    [0031]FIG. 13 b  is an exploded view of the film tensioning assembly of the present invention;  
         [0032]    [0032]FIG. 13 c  is a bottom view of the film tensioning assembly of the present invention;  
         [0033]    [0033]FIG. 14 a  is a side view of the film gate of the present invention having a depth set device disposed thereon;  
         [0034]    [0034]FIG. 14 b  is a bottom view of film trap and gate assembly of the present invention preparing to engage film;  
         [0035]    [0035]FIG. 14 c  is a bottom view of film trap and gate assembly of the present invention preparing to engaging film;  
         [0036]    [0036]FIG. 15 a  is a perspective view of an embodiment of the second gate rail assembly of the present invention;  
         [0037]    [0037]FIG. 15 b  is a perspective view of alternate embodiment of the second gate rail assembly of the present invention;  
         [0038]    [0038]FIG. 16 a  is a perspective view of the calibration device used to calibrate the film trap and gate assembly of the present invention;  
         [0039]    [0039]FIG. 16 b  is a side view of the calibration device being used to calibrate the film trap of the present invention; and  
         [0040]    [0040]FIG. 16 c  is a side view of the calibration device being used to calibrate the film gate of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0041]    Disclosed herein is a detailed description of various illustrated embodiments of the present invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention. The overall organization of the present detailed description is for the purpose of convenience only and is not intended to limit the present invention.  
         [0042]    Those skilled in the art will appreciate the present invention incorporating a continuous trap rail assembly and continuous gate rail assembly has eliminated the need for spring-loaded runners and pressure bands which remain in constant contact with film disposed thereon. In addition, the present invention incorporates non-abrasive tensioning rollers rather than steel tensioning shoes, which are commonly used on prior art devices. As such, damage to the film  14  caused by the constant contact between the film trap and gate assembly  24  is reduced or eliminated resulting in an increase in film print lifetime. Additionally, the present invention further comprises an angled stripper plate, which enables a user to operate a projector in reverse, either while viewing or at higher speed (in excess of 24 frames per second).  
         [0043]    A conventional motion picture projector for use with the present invention is shown in FIG. 1. The projector  10  has a compartment  12  which receives motion picture film  14  through an opening  16 . The film  14  engages a feed sprocket  18  and advances between the feed sprocket  18  and the feed roller  20 . The film then engages a roller  22  and is positions the film for entering the film trap and gate assembly  24 . The film trap and gate assembly  24  is comprised of a film trap  26  and a gate  28  which position the film  14  between an illumination source  30  and a projection assembly  32 . The film emerges from the film trap and gate assembly  24  and engages a receiving sprocket  34 . The film continues between a second feed sprocket  36  and a second roller  38 , and exits the projector  10 .  
         [0044]    With reference to FIG. 2, motion picture film  14  generally comprises an image area  40  positioned between a first drive track  42   a  and a second drive track  42   b . At least one soundtrack is positioned proximate the drive tracks  42   a  and  42   b . The film  14  shown in FIG. 2 comprises four soundtracks, enabling use of the film  14  with various projection systems or sound heads. As shown, the film comprises a SDDS digital soundtrack  44   a  and  44   b ; a SRD digital soundtrack  46 ; an analog soundtrack  46 ; and a DTS digital soundtrack.  
         [0045]    Referencing FIG. 3, the film trap and gate assembly  24  is shown engaging a portion of motion picture film  14 . The film trap and gate assembly  24  comprises a film trap  26  and a film gate  28 . During operation, the film  14  enters the first end  52  of the film trap and gate assembly  24  and an image is projected through the projection aperture  54 . The film  14  and exits the through the second end  56  of film trap and gate assembly  24 . Those skilled in the art will appreciate the present invention may be manufactured from a plurality of materials including, but not limited to, cast iron, steel, aluminum, reinforced plastic, urethane, rubber or any other useful material. Alternatively, the present invention may be manufactured from a plurality of materials. For example, the film trap  26  may utilize a relatively rigid material such as steel in one aspect, and a relatively flexible material such a urethane in another aspect.  
         [0046]    With reference to FIGS. 4 and 5, the film trap  26  of the present invention comprises a trap body  58  having two apertures  60  and  62 , respectively, formed therein, and having two trap rail assemblies  64   a  and  64   b  attached thereto. The first trap rail assembly  64   a  comprises a first trap rail  66   a  and a first trap guide  68   a , and further disposes a first movable guide roller  70   a . Similarly, the second rail assembly  64   b  comprises a second trap rail  66   b  and a second trap guide  68   b , and further disposes a second movable guide roller  70   b . A stripper plate  72  is attached to the trap body  58  and is positioned between the first and second trap rail assemblies  64   a  and  64   b . As shown in FIG. 5, the trap body  58  further comprises a trap attachment pin  74 , which attaches the film trap  26  to the projector  10  (not shown).  
         [0047]    [0047]FIG. 6 shows an exploded view of the film trap  24  of the present invention. As shown, the first guide roller  70   a  and second guide roller  70   b  are positioned on a guide roller shaft  76  which is positioned within the first aperture  60  of the film trap  26 . The plate spring  78  is attached to the film trap  26  such that the plate spring  78  is positioned within the second aperture  62 . A plate  80  having an aperture  82  and having screw receivers  84   a  and  84   b  formed therein attaches to the trap body  58  with screws  86   a  and  86   b , and is positioned over the first aperture  60  and partially occludes the second aperture  60 . As shown in FIG. 6, a first guide roller receiver  88   a  is formed in the first trap rail  66   a , and a first guide roller recess  90   a  is formed in the first trap guide  68   a . When assembled, the first rail assembly  64   a , comprised of the first trap rail  66   a  and first trap guide  68   a , is adapted to receive the first movable guide roller  70   a  through the first guide roller receiver  88   a  and recess  90   a . Similarly, a second guide roller receiver  88   b  is formed in the second trap rail  66   b , and a second guide roller recess  90   b  is formed in the second trap guide  68   b . When assembled, the second rail assembly  64   b , comprised of the second trap rail  66   b  and second trap guide  68   b , is adapted to receive the second movable guide roller  70   b  through the second guide roller receiver  88   b  and recess  90   b . The second aperture  62  is further occluded by the attachment flange  92  of the stripper plate  72 . The stripper plate comprises a stripping blade  94  integral to the attachment flange  92 , and an attachment orifice  96  formed in the attachment flange  92 . The stripper plate  72  is attached to the trap body  58  with a flange screw  98 .  
         [0048]    With reference to FIGS. 7 a  and  7   b , the present invention discloses several embodiments of rail assemblies which may be used with the film trap  26 . FIG. 7 a  shows a first rail assembly  64   a  comprised of a first film rail  66   a  and a separate first film guide  68   a . In an alternate embodiment, FIG. 7 b  shows a first rail assembly  64   a ′ having a first film rail  66   a ′ integral to the first film guide  68   a ′. Those skilled in the art will appreciate the continuous rail designs of the present invention eliminates the need for the spring-loaded runners found in present designs, thereby reducing wear and damage to the film.  
         [0049]    [0049]FIGS. 8 a - 8   c  show various views of the stripper plate of the present invention. The stripper plate  72  comprises an attachment flange  92  and a stripper blade  94  which is integral to the attachment flange  92 . As shown in FIG. 8 b , the stripper blade  94  is attached to the attachment flange  96  at an angle. The angled stripper blade  94  of the present invention reduces the likelihood the film  14  will contact the blade portion  94  of the stripper  52 , thereby enabling the user to operate the projector  10  in reverse.  
         [0050]    Referencing FIG. 9, a film trap  26  is shown having a portion of film  14  disposed thereon. As shown, the film drive tracks  42   a  and  42   b  are positioned on the trap rails  66   a  and  66   b  (not shown) between the trap guides  68   a  and  68   b  such that the film image area  40  is positioned over the first aperture  60  formed in the trap body  58 . The trap guides  68   a  and  68   b  restrict the amount of lateral displacement achievable by the film  14  during operation, thereby stabilizing the image projected on a screen (not shown).  
         [0051]    [0051]FIGS. 10 and 11 show the film gate  28  of the present invention. The film gate  28  comprises gate body  100  having a gate aperture  102  formed therein, and having two gate rail assemblies  104   a  and  104   b  attached thereto. The first gate assembly  104   a  comprises a first gate rail  106   a  attached to a first gate guide  108   a . Similarly, the second gate assembly  104   b  comprises a second gate rail  106   b  attached to a second gate guide  108   b . The film gate  28  further disposes a film tensioning assembly  110  comprising a deformable body  112  having an attachment slot  114  formed therein. An attachment screw  116 , positioned within the attachment slot  114 , is used to attach the tensioning assembly  110  to the gate body  100 . The deformable body  112  further comprises first tensioning rollers  118   a  and  118   b , and second tensioning rollers  120   a  and  120   b . As shown in FIG. 11, the film gate  28  further comprises a depth set orifice  142 , which will be discussed in detail below.  
         [0052]    Referencing FIG. 12, an exploded view of the film gate  28  of the present invention shown. As shown, the first rail springs  124   a  and  124   b  are positioned with the first rail spring receivers  126   a  and  126   b . Similarly, the second rail springs  128   a  and  128   b  are positioned within the second rail spring receivers  130   a  and  130   b . The first rail assembly  104   a , which comprises a first gate rail  106   a  and a first gate guide  108   a , is positioned on the gate body  100  covering the first rail spring  124   a  and second rail spring  128   a . Thereafter, the first rail assembly  104   a  is attached to the gate body  28  with the first and second assembly screws  132   a  and  136   a , respectively, positioned within first and second assembly orifices  134   a  and  138   a , respectively, formed in the first gate rail  108   a . Similarly, the second rail assembly  104   a , which comprises a second gate rail  106   b  and a second gate guide  108   b , is positioned on the gate body  100  covering the first rail spring  124   b  and second rail spring  128   b . Thereafter, the second rail assembly  104   b  is attached to the gate body  28  with the first and second assembly screws  132   b  and  136   b , respectively, positioned within first and second assembly orifices  134   b  and  138   b , respectively, formed in the second gate rail  108   b . A depth set device  140  is positioned within a depth set orifice  142  formed in the gate body  100 . The depth set device  140  permits an operator to precisely control the clearance between the trap  26  (not shown) and gate  28  when assembled. A depth set pin  144  may be used to set the depth. The gate body  100  further comprises a tensioning assembly receiver  146  having a mounting receiver  148  disposed therein. The deformable body  112  attaches to the gate body with screw  116  which is positioned within the attachment slot  114 . Those skilled in the art will appreciate the deformable body  112  enables the operator to precisely position the film tensioning member  110  in relation to the stripping plate  72 , thereby limiting the contact between the film  14  and the stripping plate  72  and tensioning rollers  118   a - b , and  120   a - b . The deformable body  112  may be manufactured from a plurality of materials including, without limitation, aluminum, steel, or other material. In an alternate embodiment, the deformable body  112  may be manufactured from a rigid material. The components of the film tensioning assembly  110  will be discussed in detail below.  
         [0053]    [0053]FIGS. 13 a - 13   c  show the film tensioning assembly  110  of the present invention. The film tensioning assembly  110  comprises a deformable body  112  having an attachment slot  114  formed therein, and having a tensioning screw receiver  152  disposed thereon. A roller cradle  156 , positioned over the tensioning screw receiver  152  and receiving a tensioning device  154  within a tensioning device receiver  158 , is attached to the deformable body  112  with a tensioning screw  150 . In use, the tensioning device  154  exerts an adjustable biasing force to the roller cradle  156 , thereby permitting the user to adjust the amount of force applied to the film  14  by the tensioning rollers  118   a - b  and  120   a - b . By actuating the tensioning screw  150 , the user increases the force applied by the tensioning device  154  to the roller cradle  156 , resulting in the tensioning rollers  118   a - b  and  120   a - b  applying more force. The first tensioning rollers  118   a  and  118   b , respectively, receive the first roller bearings  160   a  and  160   b , respectively, and are attached to the roller cradle  156  with first roller screws  162   a  and  162   b , respectively. Similarly, the second tensioning rollers  120   a  and  120   b , respectively, receive the second roller bearings  164   a  and  164   b , respectively, and are attached to the roller cradle  156  with first roller screws  166   a  and  166   b , respectively. FIG. 13 c  shows the film tensioning assembly  110  of the present invention attached to the film gate  28 . In contrast to prior art systems, which utilize a steel tensioning shoes which contact and damage film  14 , the film tensioning member  110  of the present invention incorporates non-abrasive materials. Those skilled in the art will appreciate the first tensioning rollers  118   a  and  118   b , and second tensioning rollers  120   a  and  120   b , may be manufactured from a plurality of materials, including, without limitation, elastomer, urethane, rubber, silicon, or other non-abrasive material. Alternatively, the film tensioning device may be incorporate friction reducing materials, such as Teflon.  
         [0054]    With reference to FIGS. 14 a - 14 , the gate  28  comprises a depth set device  140  positioned within a depth set orifice  142 . The depth set device permits the operator to ensure sufficient film clearance between the film trap  26  (not shown) and the film gate  28  is maintained, thereby forming a film movement channel. The operator advances the depth set device  140  such that when the film gate  28  is positioned on the film trap  26  the depth set device  140  contacts the trap body  58  wherein sufficient film clearance remains between the trap rails  66   a  and  66   b , and the gate rails  106   a  and  106   b . FIG. 14 b  shows the film  14  located on the first and second trap rails  66   a  and  66   b  of the film trap  26 . The film gate  28  is positioned thereabove. FIG. 14 c  shows the film gate  28  engaging the film trap  26 . FIG. 14 c  shows the film  14 , disposed within the film movement channel  168  formed by the trap rail assembly  64  and the gate rail assembly, non-biased and free to traverse the film movement channel  168 .  
         [0055]    [0055]FIGS. 15 a  and  15   b  show various embodiments of the rail assembly  104   b  of the present invention. As shown in FIG. 15 a , the present invention discloses a rail assembly  104   b  comprising a second gate rail  106   b  attached to a separate second rail guide  108   b . In an alternate embodiment, FIG. 15 b  shows a rail assembly  104   b ′ comprising a second rail portion  106   b ′ integral to a second gate guide  108   b ′. Similarly, the first rail assembly  104   a  may comprise either a separate second rail/guide assembly or an integral rail/guide assembly. The continuous gate rail assembly of the present invention cooperatively engages the continuous trap rail assembly thereby defining a discrete film pathway therebetween.  
         [0056]    The present invention further discloses a calibration device for use with the present film trap and gate assembly  24 . As shown in FIGS. 16 a - c , the calibration device  170  comprises a trap plate portion  172  and a gate plate portion  174  attached thereto. The trap plate portion  172  is manufactured with a width slightly, e.g. 0.005 inch, larger to the width of film  14 . To calibrate the trap  26 , the user positions the calibration device  170  on the film trap  26  such that the trap plate portion  172  is located between the trap rail assemblies  64   a  and  64   b  and in communication with the plate  80 . The trap rail attachment screws are then tightened. Similarly, the calibration device  170  may be used to calibrate the gate rail assembly  104   a  and  104   b . The gate plate portion  174  is placed on the gate  28  such that gate plate portion  174  is positioned between and in communication with the gate rail assemblies  104   a  and  104   b . The rail attachment screws  132   a - b  and  136   a - b  are then tightened. The gate plate portion  174  is manufactured with a width slightly, e.g. 0.005 inch, smaller than the width of the film  14 . Those skilled in the art will appreciate the present calibration device  170  permits the user to easily calibrate the film trap and gate assembly  24  without the plurality of sizing shims commonly required with present trap-gate systems.  
         [0057]    The present invention further discloses a method of using the film trap and gate assembly  24 . As shown in FIG. 1, the trap  26  and gate  28  are positioned within a film projector  10  such that the trap first aperture  60  and gate aperture  102  are positioned between the light source  30  and projection system  32 . Those skilled in the art will appreciate the present invention may replace existing film trap and gate assemblies for a plurality of film projection systems with little or no modification required. As shown in FIG. 3, with the film trap  26  and gate  28  are positioned within the film projector  10 , the film  14  is positioned on the first and second trap rails  66   a  and  66   b . The film  14  is then made to engage the drive system sprockets  18 ,  34 , and  36 , respectively. The film gate  28  is made to engage the film trap  26 , such that the first and second gate rails  106   a  and  106   b  are positioned proximate the film  14  disposed on the trap first and second rails  66   a  and  66   b . The depth set device  140 , positioned on the film gate  28 , may then be actuated to ensure sufficient clearance between to the trap rails  66   a  and  66   b , and gate rails  106   a  and  106   b  is present to permit free longitudinal movement of the film  14  positioned therebetween. The trap guides  68   a  and  68   b , and gate guides  108   a  and  108   b , assist in positioning and seating the trap  26  and gate  28 . Thereafter, the film projector drive system is activated and the film is advanced.  
         [0058]    Those skilled in the art will appreciate the present invention incorporating a continuous trap rail assembly  64   a  and  64   b , and continuous gate rail assembly  104   a  and  104   b  has eliminated the need for spring-loaded runners, pressure bands, and steel tensioning shoes which contact the film  14  disposed thereon. As such, damage to the film  14  caused by repeated contact with the film trap and gate assembly  24  is reduced or eliminated resulting in a decrease in film damage.  
         [0059]    In closing, it is noted that specific illustrative embodiments of the invention have been disclosed hereinabove. However, it is to be understood that the invention is not limited to these specific embodiments. Accordingly, the invention is not limited to the precise embodiments described in detail hereinabove. With respect to the claims, it is applicant&#39;s intention that the claims not be interpreted in accordance with the sixth paragraph of 35 U.S.C. § 112 unless the term “means” is used followed by a functional statement. Further, with respect to the claims, it should be understood that any of the claims described below may be combined for the purposes of the invention.