JP2755261B2 - Camera film presser - Google Patents

Description

The present invention relates to a film holding mechanism for guiding a film from a roll container to a take-up spool in a camera using a roll film such as a 35 mm film.

[Conventional technology]

In general, a camera performs a series of operations of moving a film drawn from a patrone to an aperture screen as shown in FIG. 2 to take a picture, and winding the film around a spool 4 via a sprocket 3. It has been frequently used to provide a guide member such as a roller on a camera body or a back cover to ensure operation.

For example, as shown in FIG. 2, rollers 9 and 10 are provided on both sides of the sprocket 3 to secure the engagement ratio of the sprocket 3, or the lever 12 is turned counterclockwise so that the film is securely wound around the spool 4. In general, a roller 11 is provided at the leading end to prevent the leading end of the film from being lifted.

These rollers 9 and 10 (especially roller 10)
Are provided on both sides of the sprocket 3 in order to secure a constant engagement ratio of the sprocket 3, and the film is wound around the spool as shown in FIG. Even if the diameter increases, C
By slightly warping the film with the roller 10 in the section, the winding angle of the film around the sprocket 3 is kept constant, and the film is properly engaged with the sprocket teeth.

[Problems to be solved by the invention]

On the other hand, when the roll film is pulled out from a container such as a patrone, in the natural state, the roll film has both the winding in the roll direction (X direction in the figure) and the winding in the vertical direction (Y direction) as shown in FIG. Therefore, bending the film in the direction opposite to the direction in which it is curled is not originally desirable for the film, and the film loses flexibility, especially under low temperature and low humidity, becomes hard and brittle, When bent in the direction, the film is easily broken.

Especially in the case of a roller, the diameter cannot be made too large due to the compactness of the camera, etc., so if the film is guided using a roller, the curvature in the X direction of the film will change rapidly, and the film will be damaged in the vertical direction There is a fear that it will be done. The degree of these damages varies depending on the temperature / humidity, the type of film, and the lot, and cannot be unconditionally determined, but is as follows.

FIG. 8 shows the film base broken,
-A is the worst case and shows that the film is completely broken. Next, although the portion 8-b did not break, the crack ran vertically and was about to break. Next, the portion 8-c has a crack or a crack formed outside the perforation hole. In any of the sections 8-a, 8-b and 8-c, such severe damage to the film must be avoided because the winding and rewinding operations may not be possible.

FIG. 9 shows that the base of the film is not damaged at all, but the emulsion surface applied to the base is partially peeled off by bending and appears as a vertical wrinkle, and the portion 9-a extends over the entire width of the film. The vertical wrinkles generated over the portion 9-b are slightly lighter and are generated only outside the perforations. These vertical wrinkles must also be avoided because they become flawed after development and remain on the photographing screen. (In practice, the above various types of damage often occur in combination.) When the film is bent using a roller in the opposite direction to the winding direction, the bending angle is as close as possible to 180 ° It is necessary to make the radius of curvature of the bend large enough, but in reality there is no choice but to bend the film in this way due to the internal structure of the camera. Was causing the decrease.

[Means to solve the problem]

In order to solve the above-mentioned problem, the present invention adopts a drum-shaped shape in which the diameter of the roller gradually becomes smaller toward both ends, instead of a simple cylindrical shape.

(Operation)

FIG. 6 is a perspective view of the case where the film with the curl as shown in FIG. 7 is warped in the direction opposite to the curl direction using the roller according to the present invention. A pulling force acts for winding in the direction of the arrow in the figure. 8th
As described with reference to FIG. 9 and FIG. 9, the perforation holes are juxtaposed on both sides of the film, so that stress concentration tends to occur from the center, and cracks in the film base and cracks on the emulsion surface also occur near the perforation holes. easy.

In the present invention, focusing on the above phenomenon, the diameter of the roller 10 is formed to be thinner from the center 10c to both ends 10b, and the bending in the vicinity of the perforations at both ends of the film is reduced, and the longitudinal direction of the film is reduced. By increasing the degree of freedom and preventing the concentration of stress, it has become possible to provide a roller in which the film is less likely to break.

〔Example〕

 FIG. 1 is a perspective view showing an embodiment of the present invention.

The camera body is omitted. 3 is a sprocket on the camera body side, and B is a film. On the back cover 5, a pressure plate 6, a pressure plate spring 7 for urging the pressure plate 6, a substrate 8 for holding rollers, film guide rollers 9 and 10 for pressing the film from both sides of the sprocket 3, and a spool of the film. An easy road roller 11 whose tip is securely wound around, a lever 12 for applying a rotational biasing force to the roller 11 in a counterclockwise direction, and a torsion spring 13 are provided.

The rollers 9 'and 10' in FIG. 1 show the relative positional relationship with the sprocket 3 when the back lids of the film guide rollers 9 and 10 are closed.

The film drawn from the patrone (not shown) (to the right of the film B) is substantially flat at the aperture part 1c as shown in FIG. Is curved in a direction approaching the pressure plate 6, enters a tunnel formed by the pressure plate 6, the pressure plate spring 7, and the inner rail 1a and the outer rail 1b on the camera body side, and has a flatness that does not hinder photographing. Is secured.

At this time, the cross section of the film is almost flat or slightly curved as shown in the portion (a) of the film B in FIG. Such a cross-sectional shape of the film continues to the position of the roller 9 '(the imaginary line of the roller 9).

Next, near the roller 10 '(the imaginary line of the roller 10), it is bent along the cross-sectional shape of the roller 10', that is, the radius of the roller, in the X direction (see FIG. 7) in the direction opposite to the original winding. In the Y direction, the film is bent along the longitudinal cross-sectional shape of the roller 10 ', that is, the drum-shaped bulge. Fig. 5 shows this state in a longitudinal section. The film is strongly bent in the vicinity of the center of the width due to the drum-shaped bulge of the roller 10 ', but the film is near the perforation holes at both ends. Because the diameter is small, the degree of reverse warpage is weakened, while maintaining engagement with the sprocket teeth 3a, a gap is secured between the sprocket step 3b and the roller 10 'in the case of a simple cylindrical shape. In comparison, the degree of freedom at both ends of the film is secured.

Next, when the film is wound around a spool (not shown), the film becomes almost flat again as shown in the state (C) of the film B in FIG.

The section between the roller 10 'and the roller 9' and the section between the spool and the roller 10 'are regions where the sectional shape gradually changes.

In this way, the roller 10 for warping the film in the direction opposite to the original winding direction is formed in a drum shape by decreasing its diameter from the center portion 10c to both end portions 10b, thereby forming a drum shape. By reducing the bending force near the perforations, weakening the bending force where stress concentration is likely to occur, and increasing the bending force where stress concentration is less likely to occur in the center, ensuring the necessary and sufficient engagement ratio It balances protection against film breakage.

Although it is not preferable to make the roller 10 'drum-shaped and to warp the film in the Y direction (see FIG. 7) in the direction opposite to the original winding direction at the roller 10' contact portion of the film, Since the radius of curvature of the drum shape of the roller 10 'is very large and has a gentle curvature, it can be said that there is no adverse effect on the film in this direction.

Therefore, it can be said that a drum-shaped roller that can uniformly support the force required for bending by the width of the film and gradually reduce the stress toward both ends of the film having the perforation hole is most effective.

Further, it is not necessary to provide a gentle curvature over the entire width of the roller 101 as shown in FIG.
As shown in the central portion a of 102, even if some linear portion is provided in the large diameter portion of the roller in consideration of the processing convenience of the roller, the effect does not change and it can be insignificant.

Another reason for making the roller 10 'drum-shaped in the present invention is that if the diameter is gradually reduced toward both ends, the film bends along its curvature as shown in FIG.
There is an effect of preventing stress from being concentrated at one place on the film without causing discontinuous portions in the bending state of the film. For example, a step may be provided as shown in FIG.
Although some effects are obtained even when the tapered portion is provided as shown in the figure, stress concentration occurs in the film at the place where the step portion or the taper starts, that is, in the figure b, as shown in FIG. Cracks may be formed on the surface of the emulsion when stress is concentrated.

〔The invention's effect〕

As described above, according to the present invention, the force applied to both ends of the film pressed by the rollers on the sprocket and the spool can be reduced, and breakage at both ends of the film can be prevented.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing an embodiment of a film holding mechanism according to the present invention. FIG. 2 is a cross-sectional view showing a conventional example. FIG. 3 is a cross-sectional view showing a conventional example (showing a state in which a film is wound around a spool). FIG. 4 is a longitudinal sectional view showing a conventionally known tunnel structure. FIG. 5 is a longitudinal sectional view showing a film holding mechanism according to the present invention. FIG. 6 is a perspective view showing the principle of the film holding mechanism according to the present invention. FIG. 7 is a perspective view showing the original winding of the film when the film is normally pulled out from the patrone. 8 to 10 are plan views showing examples of various types of breakage of the film under bad conditions. 11 to 14 are explanatory views showing various shapes of rollers used in the film holding mechanism according to the present invention. [Explanation of Signs of Main Parts] 1 Camera body 11 Easy road roller 2 Lens 12 Easy road lever 3 Sprocket A Patrone 4 Spool B Film 5 … Back cover, 7… press plate spring, 9… roller 6… press plate, 8… roller board, 10… roller

Claims (1)

(57) [Claims] 1. A film holding apparatus for a camera using a roll film, comprising: a spool for winding the roll film; a sprocket rotatably provided; a sprocket between the sprocket and the spool; A roller disposed on the opposite side to the sprocket and pressing the roll film against the sprocket and the spool, wherein the diameter of both ends of the roller is smaller than the diameter of the central part. A film holding device for a camera.