GB2084341A - Film threading a motorised camera - Google Patents

Abstract

Film 14 is threaded automatically to a film capturing post 108 of a take- up spool 110 by means of a roller 54 having a flat (60, Fig. 2) which frees the film before and after the film- threading operation. Take-up spool 110 rotates at a slightly faster rate than roller 54. Roller 54 may be of polyurethane, have a plurality of protuberances which engage the film sprocket holes, and be slightly sloped to urge the film against a guide 26. When the camera back 28 is closed (a) door latch lever 68 enters slot 69 and closes a motor drive switch to commence rotation of take-up spool 110 and of a clutch gear (104) which is engageable with a partial index gear (52) attached to roller 54 (b) a post 36 frees a spring-biased pawl wheel (48) from a spring-biased pawl 40, allowing engagement of the partial index gear with the clutch gear and enabling one complete revolution of roller 54, whereupon the pawl wheel is engaged by pawl 40 once again. <IMAGE>

Description

SPECIFICATION Film threading apparatus The present invention relates to film threading apparatus for photographic cameras. In particular the invention relates to apparatus for threading roll film from a film cassette onto a camera takeup spool.

Roll film for 35mm cameras is normally supplied in a film cassette and has a film leader extending through a light-tight slot. To load the film in the camera the operator must (1) insert the film cassette into a film supply chamber, (2) pull the film leader along film guides defining a film passageway extending between the supply chamber and a take-up chamber, (3) attach the end of the film leader to a film take-up spool rotatably mounted in the take-up chamber, (4) turn the film advance lever to wind the film around the take-up spool, making sure that the sprocket holes in the film are engaged by the teeth of a film transport sprocket, (5) close the camera back cover and (6) turn the film rewind crank to take up any film slack. If the film is not properly loaded, the operator must open the back cover and repeat the film loading procedure from the start.Many amateur photographers find 35mm film loading to be tedious, difficult and of uncertain result. As a result, simple and reliable film loading of 35mm cameras has long been a desired objective of the photographic industry.

According to the present invention there is provided a camera, for use with a film cassette having an elongate film leader extening therefrom, the camera comprising a film supply chamber for receiving the film cassette; a film take-up chamber including means for capturing the film leader; a film guide for receiving the film leader and defining an edge of a passageway extending between the supply chamber and the take-up chamber; a film transport mechanism for transporting the film leader through the passageway and into the take-up chamber; a rotatable film-threading roller having an outer surface comprising a generally cylindrical portion and a generally flat portion; roller drive means; and control means for actuating the drive means to sequentially (1) locate the roller in an initial position in which the flat portion aligns with the passageway, (2) drive the roller through an integral number of rotations in which the cylindrical portion extends into the passageway for frictionally engaging and transporting the film leader into the take-up chamber and to the capturing means and (3) terminate rotation of the roller with the roller again located at the initial position.

There is further provided a camera comprising a housing having a film take-up chamber arranged to accommodate a film capturing member, a film guide for guiding the film, and defining an edge of a passageway leading to the take-up chamber, a rotatable film threading roller having an outer surface comprising a film engaging portion and a non-film engaging portion, roller drive means, and control means for actuating the drive means to locate the roller at an initial position in which the non-film engaging portion is aligned with the passageway to drive the roller through an integral number of rotations in which the film engaging portion extends into the passageway for frictionally engaging and transporting the film to the film capturing means and to terminate rotation of the roller with the roller again located in the intitial position.

The present invention will now be described, by way of example, with reference to the accompanying drawings in which: Fig. 1 is a perspective view of a photographic camera incorporating one embodiment of film threading apparatus according to the present invention; Fig. 2 is an explodedview of some details of the film threading apparatus shown in Fig. 1; Figs. 3A-3D are schematic side views illustrating the various positions of the film threading apparatus and a film leader during the film loading procedure; Fig. 4 is a perspective view of a photographic camera incorporating a second embodiment of film threading apparatus according to the present invention; Fig. 5 is an exploded view of some details of the film threading apparatus shown in Fig. 4;; and Fig. 6 is a bottom view of a camera with portions cut away to expose the drive actuation mechanism of the film threading apparatus shown in Fig. 5.

Because photographic cameras and film cassettes are well known, the present description will be directed in particular to elements forming part of, or cooperating more directly with, apparatus in accordance with the present invention. It is to be understood that camera elements and cassette elements not specifically shown or described may take various forms well known to those having skill in the art.

Referring to Figure 1, a film cassette 10, containing a roll of film coiled upon a spool 12 and having an elongate film leader 14 extending through a light-tight slot 16, is shown in position for insertion into a camera 18. The camera 18 includes a body portion 20 having a film supply chamber 22 and a film take-up chamber 24 arranged with a pair of film guides 26 and 27 extending therebetween, and a camera door 28 hinged to the camera body 20. The guides 26 and 27 define a film passageway 30 extending between the supply and take-up chambers 22, 24 and, in conjunction with a spring biased pressure plate 32 mounted on the interior of the camera door 28, maintain the film in a flat, properly orientated position in the focal plane of a camera objective lens 34.

To load the camera 18, the film cassette 10 is inserted into the film supply chamber 22 with the film leader 14 lying along the guides 26 and 27.

The door 28 is then closed.

In a fully automatic embodiment of the present invention, as best shown in Figs. 2 and 3B, a pin 36 mounted on the interior of the door 28 engages a cam surface 38 of a pivotable pawl 40 as the door 28 closes and moves the pawl 40 in a counterclockwise direction against the bias of a spring 42. The counterclockwise movement of the pawl 40 withdraws a pawl arm 44 from a tooth 46 of a pawl wheel 48 fixed on a shaft 50. A film threading roller 54 and a partial index gear 52, having a gear segment 56 and a relieved portion 55, are also fixed on the shaft 50.In the initial latched position of the pawl wheel 48, the gear 52 and the roller 54 are held shown in Fig. 3A with the relieved portion 55 of gear 52 aligned with and spaced from a drive transmission mechanism 58 and the roller 54 positioned in a film guide rail slot 61 with a generally flat roller surface 60 aligned with and spaced from the lower surface of the film leader 14. The withdrawal of the pawl arm 44 from the tooth 46 allows a spring 62 to rotate the pawl wheel 48, the index gear 52 and the threading roller 54 about the shaft 50 in a clockwise direction.As shown in Fig. 3B, the clockwise rotation of the shaft 50 under the urging of the spring 62 advances:-- the gear 52 so that the leading edge 56a of the gear segment 56 is brought into engagement with the transmission mechanism 58; the threading roller 54 so that the leading edge 64a of a generally cylindrical roller surface 64 is brought into frictional engagement with the film leader 14; and the pawl wheel 48 so that when the pin 36 moves past the cam surface 38 and into a notch 63, the pawl arm 44 pivots in a clockwise direction, engages and rides upon a generally cylindrical cam surface 66.

When the door 28 reaches its closed position a door latch lever 68, enters a slot 69 and closes a motor drive switch (not shown). Closing the motor drive switch energizes a motor 92 whose output shaft 94 is connected to the transmission mechanism 58 via a gear 96. The transmission mechanism 58, which is comprised of drive train gears 98, 100, 102, and 104 and a friction clutch 106 interposed between the gears 102 and 104, transmits the drive of the motor 92 to the gear segment 56 of the index gear 52. A shown in Figs.

3C and 3D, the coupling of the drive power from the motor 92 to the gear segment 56 causes the index gear 52, the pawl wheel 48 and the threading roller 54 to rotate through one revolution.

During the rotation of the roller 54 by the motor 92, the frictional engagement between the roller's generally cylindrical outer surface portion 64 and the lower surface of the film leader 14 advances the film past a film guide member 93, into the take-up chamber 24 and into engaging relationship with one of a plurality of film capturing posts 1 08. The film capturing posts 108 are positioned at equally spaced intervals about the periphery of a film take-up spool 110 rotatably mounted within the take-up chamber 24.As shown in Fig. 3D, when the index gear 52 completes one revolution, the gear segment 56 disengages from the drive train gear 104, the pawl arm 44 re-engages the pawl tooth 46, and the threading roller 54 is held stationary with the generally flat surface portion 60 again positioned aligned with and spaced from the lower surface of the film leader 14.

To assist in the advancement of the film leader 14, the threading roll,er 54 is made of a soft, high friction material such as polyurethane and is provided at equally spaced positions around its cylindrical outer surface portion 64 with a plurality of protuberances 112 which enter into the film leader sprocket holes 114. Film advancement is thus achieved by a combination of (1) friction between the roller surface portion 64 and the lower surface of the film leader 14 and (2) the engagement of the leading edge of the protuberances 112 with the leading edge of the sprocket holes 114. The film threading roller 54 is also canted at a slight angle, preferably about 5 degrees, with respect to the film guide 26 and urges the film leader 14 against the side of the guide 26, thereby assuing lateral alignment of the film leader 14 and the film capturing posts 108.

The transmission mechanism 58 also transmits the drive of the motor 92 to the take-up spool 110 via the drive train gear 100 which is fixed to the take-up spool 11 0. The gear tooth ratio between the gear segment 56 and the take-up spool gear 100 and the effective diameters of the threading roller 54 and the take-up spool 110 are selected so that the film advancing velocity imparted to the film capturing post 108 is greater than the film advancing velocity imparted to the film leader 14.

This film advancing velocity difference enables a film capturing post 108 to firmly secure the film leader 14 to the take-up spool 110 by entering an aperture 11 6 provided near the leading edge of the film leader 14 and then tensioning the film leader 14 between the capturing post 108 and the threading roller 54. When the film leader 14 is properly tensioned, the clutch 106 allows slippage between the drive gears 102 and 104 during the time required for the gear segment 56 to complete its engagement with the gear 104 of the drive transmission mechanism 58. The trailing edges of the protuberances 11 2 on the cylindrical roller surface portions 64 are slanted to permit the film leader 14 to disengage from the protuberances 112 and to slide in overrunning fashion between the roller surface portion 64 and the pressure plate 32.

From the foregoing it can be seen that each time the camera door 28 is closed, the threading roller 54 is enabled for one revolution and advances the film leader 14 to the camera take-up spool 110 where the film leader 1 4 is captured by a film capturing post 1 08. The threading roller 54 is then held stationary in a non-film engaging position during further film advancement by the motor 92 for exposure purposes and during the rewinding of the film by means (not shown) back into the film cassette 1 0. To remove the film from the camera 18, the operator depresses a release button 114 which disengages the door latch 68 permitting the cover 28 to be swung to its open position.

Figs. 4 to 6 show a second embodiment of the invention in which the drive power for initiating the rotation of the threading roller 54 to advance the film leader 14 into the take-up chamber 24 is provided by a manually operated door latch lever 1 60. In this second embodiment of the invention, parts identical to those in the first embodiment are identified by the same reference numerals.

In the second embodiment the door 28, upon reaching its closed position, engages a finger 1 70 of a clock lever 1 72 and rotates the lever counterclockwise about pivot 1 73 against the bias of a spring 174, thereby withdrawing an ear 1 76 from a slot 178 in the door latch lever 1 60. When the ear 1 76 is withdrawn from the slot 178, a spring 1 82 rotates the latch lever 1 60 about a shaft 181 in a counterclockwise direction from an unlatched position shown in the drawings to a latched position in which an abutment surface 1 84 rests against a stop 1 86.

During the movement of the latch lever 1 60 from its unlatched to its latched position, a turned up lip 189 on the lever 1 60 slides over a door latch 1 88 and locks the door 28 and camera body in a light-tight manner.

As shown in Fig. 5, the door latch lever 160 is coupled to the threading roller 54 via a gear 190, fixed on the shaft 181 and meshing with a gear 1 92 fixed on the shaft 50. The counterclockwise rotation imprated to the latch lever 1 60 by the spring 1 82 causes the gear 1 90 to rotate through approximately 1 200 of rotation, and the gear 1 92 and the threading roller 54 to rotate through one complete revolution. The single revolution of the roller 54 transports the film leader 14 to the takeup chamber 24 and into engagement with one of the film capturing posts 108 in the manner previously described.

Further film advancement for exposure purposes is then achieved, while the threading roller 54 is held stationary in its non-film engaging position, by means of a conventional film winding mechanism 1 94 which is coupled to the take-up spool 110 via a shaft 195 and a slip clutch 196.

To remove the film from the camera, the film is first rewound by means (not shown) back into the film cassette 10. The camera operator then rotates the latch lever 1 60 in a clockwise direction against the bias of spring 182 until the ear 176 of the lock lever 1 72 enters slot 1 78. During this clockwise rotation, the latch lever lip 1 89 disengages from the door latch 1 88 permitting the door 28 to be swung to its open position.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the scope of the appended claims. For example, by providing appropriate gearing between the threading roller 54 and its drive gears, any integral number of threading roller revolutions could be provided. Where space is a consideration, increasing the number of threading roller revolutions is advantageous because it allows the size of the threading roller 54 to be reduced.

Claims (9)

1. A camera for use with a film cassette having an elongate film leader extending therefrom, the camera comprising a film supply chamber for receiving the film cassette; a film take-up chamber including means for capturing the film leader; a film guide for receiving the film leader and defining an edge of a passageway extending between the supply chamber and the take-up chamber; a film transport mechanism for transporting the film leader through the passageway and into the take-up chamber; a rotatable film-threading roller having an outer surface comprising a generally cylindrical portion and a generally flat portion; roller drive means; and control means for actuating the drive means to sequentially (1) locate the roller in an initial position in which the flat portion aligns with the passageway, (2) drive the roller through an integral number of rotations in which the cylindrical portion extends into the passageway for frictionally engaging and transporting the film leader into the take-up chamber and to the capturing means and (3) terminate rotation of the roller with the roller again located at the initial position.

2. A camera according to Claim 1 comprising a door movable to (1) an open position providing access to the passageway and the supply and take-up chambers and (2) a closed position, wherein the drive means includes a rotatable, partial gear connected to the threading roller; a drive-transmission engageable with the partial gear; means for biasing the partial gear for engagement with the drive-transmission; a pivotable pawl movable between a first position latching the partial gear at a position out of engagement with the drive transmission means and a second position releasing the partial gear for movement into engagement with the drivetransmission; and release means responsive to the movement of the door from its open to its closed position for moving the pawl from its first to its second position.

3. A camera according to Claim 2 wherein the pawl is moved to its first position when the biasing means and the drive-transmission have rotated the partial gear through one complete revolution.

4. A camera according to Claim 2 or 3 wherein the control means comprises a door latch lever movable between an unlatched position and a latched position, a motor coupled to the drive transmission means and a switch responsive to the movement of the door latch lever from its unlatched to its latched position for energizing the motor.

5. A camera according to any preceding Claim wherein the threading roller is canted with respect to the film guides.

6. A camera according to Claim 5 wherein the threading roller is canted at an angle of approximately 5 .

7. A camera according to Claim 2, or any Claim appendent thereto, wherein the drive-transmission is coupled to the film-capturing means, the drivetransmission tending to impart a faster film advancing velocity to the film capturing means than the film advancing velocity imparted to the film leader by the threading roller, whereby the film leader is secured to the film capturing means by tensioning the film leader between the film capturing means and the threading roller.

8. A camera comprising a housing having a film take-up chamber arranged to accommodate a film capturing member, a film guide for guiding the film and defining an edge of a passageway leading to the take-up chamber, a rotatable film threading roller having an outer surface comprising a film engaging portion and a non-film engaging portion, roller drive means, and control means for actuating the drive means to locate the roller at an initial position in which the non-film engaging portion is aligned with the passageway, to drive the roller through an integral number of rotations in which the film engaging portion extends into the passageway for frictionally engaging and transporting the film to the film capturing means and to terminate rotation of the roller with the roller again located in the initial position.

9. A camera substantially as hereinbefore described with reference to and as illustrated in Figs. 1,2, and 3A to 3D, or Figs. 4,5 and 6 of the accompanying drawings.