JPH0341811B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a camera take-up spool reversal mechanism.

Conventionally, the take-up spool has a structure in which the take-up spool is rotated at a constant torque by the rotational force transmitted from the take-up system via a friction mechanism installed between the take-up spool and the take-up system. Even at the beginning of film winding, the amount of film taken up by the take-up spool is slightly larger than the amount of film fed by the sprocket.

Therefore, a slip occurs between the take-up spool and the wind-up gear every time the film is wound, and the slip torque applies winding tension to the film. This tension is
Since the slip torque is constant, it is inversely proportional to the winding diameter of the film wound around the take-up spool, and is at its maximum at the beginning of winding. In the case of ordinary film that takes 36 shots, the ratio of the diameter at the beginning of winding and the diameter when 36 films have been wound is approximately 1:2, and the tension will be the same at the time when 36 films have been wound. This will be about 1/2 of the start of winding. This tension remains in the film even after each shot is completed. In ordinary films, this residual tension is
Film that has a base thickness thinner than regular film that has come into use recently (hereinafter referred to as thin film), although it is not possible to move the film from a stationary state during shooting with a shot such as a shutter.
In this case, the rigidity of the film is smaller than that of ordinary film, and the thickness of the film is small relative to the amount of tunneling at the pressure plate, so it is quite possible for the film to move due to residual tension triggered by the shock of a shutter during shooting. .

SUMMARY OF THE INVENTION An object of the present invention is to solve these drawbacks and to provide a camera take-up spool reversing mechanism which prevents the film from being moved by a shutter such as a shutter during shooting even when using thin film.

In order to clarify the features of the present invention, an example of a conventional take-up spool will first be explained using FIG.
The take-up spool 1 is located at a portion 2, which is the wall of the take-up spool chamber and also serves as a take-up spool receiver.
2'. The slip spring 3 transfers the rotational force from the winding system to the winding spool 1.
The face plate 4 is pressed against the spool 1 so as to convey this. A spool gear 5 for rotating the face plate 4 receives rotational force from the winding system via transmission gears 6 and 7. These have the drawbacks mentioned above. Therefore, the embodiments of the invention shown in FIGS. 2 to 5 are applied to eliminate this drawback.

In FIGS. 2 to 5, parts common to those in FIG. 1 are designated by the same reference numerals.

A clutch 8 is provided between the face plate 4 and the spool gear 5 to disconnect the two from each other when the film winding is completed. In part 2',
An annular free disk 10 whose movement is made heavy by a corrugated washer 9 is attached. A pin 11 is fixedly mounted on the free disc 10, and this pin 11 fits into a groove 1a in the outer circumference of the spool 1, which is clearly shown in FIG.

Next, the operation of this embodiment will be explained. When winding a film, the rotation of the winding system is transmitted to the gear 5 and further transmitted to the face plate 4 via the clutch 8. The take-up spool 1 is a spool 1 by a slip spring 3.
Rotation (counterclockwise in FIG. 3) is effected by frictional connection between the and face plate 4, and the film is wound up. At this time, the free disk 10 is attached to the pin 1 as shown in the fourth figure.
1 and groove 1a, they rotate together. Since the amount of film taken up by the spool 1 is greater than the amount of film fed by the sprocket, the spool 1 rotates while slipping in accordance with this difference during winding.

However, when winding is completed, a clutch 8 (for example, a spring 3
A friction clutch (having a greater sliding force than the friction clutch consisting of the face plate 4 and the face plate 4) is provided to allow the spool 1 to be reversed due to residual film tension and curling forces. Therefore, at this time, the spool 1 rotates in the unwinding direction due to the remaining film tension, and the remaining film tension is removed. At this time, if the spool 1 is completely free from rotation, the spool 1 will continue to rotate in the opposite direction until the film becomes loose due to the curling force of the film, but the free disk 10
A reverse rotation restricting member consisting of a corrugated washer 9 prevents such reverse rotation until the film becomes loose. That is, immediately after the winding operation is completed, the positional relationship between the groove 1a of the spool 1 and the pin 11 is in the state shown in FIG. 4, and from this state, as shown in FIG. The spool 1 is allowed to reverse clockwise until it reaches the state shown in FIG.
However, since the movement of the free disk 10 is made heavy or the load of the free disk 10 is applied to the spool 1, the reverse rotation of the spool 1 due to the curling force of the film is stopped in the state shown in FIG.

It goes without saying that the relationship between the pin 11 and the groove 1a may be reversed as long as the same function is performed.

The final winding completion state is the state shown in FIG. 5, and in this state the next winding is awaited. The next winding is carried out by rotating the spool 1 counterclockwise from FIG. 5 to FIG.

In the embodiment shown in FIG. 2, the friction clutch consisting of the spring 3 and the face plate 4 is removed, the face plate 4 and the spool 1 are integrated, and the clutch 8 has the same amount of sliding force as the friction clutches 3 and 4. As a clutch,
A similar effect can be obtained by disengaging the engagement upon completion of winding.

As described above, according to the present invention, not only is there an advantage that the film does not move due to the residual tension of the film due to a shock such as a shutter, especially when shooting with thin film, but also when shooting with ordinary film. Movement of the film inside can be completely prevented, resulting in images with high resolution.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a conventional device, Fig. 2 is a cross-sectional view of a device according to the present invention, Fig. 3 is a partial perspective view of Fig. 2, and Fig. 4 is a sectional view taken along line A-A in Fig. 2. The location of the pins on the take-up spool and free disk is shown when completed. FIG. 5 is a sectional view taken along the line A-A in FIG. 2, and shows the state in which the take-up spool reverses from the completion of winding until it is restricted by the pin on the free disc. [Description of symbols of main parts], 1... Take-up spool, 1a... Groove, 8... First member, 10...
Second member, 11...pin.

Claims (1)

[Scope of Claims] 1. A first device which transmits the winding force to the winding system during winding to rotate the winding spool in the forward direction, and when winding is completed, the winding spool is freely rotatable in the opposite direction to the winding direction by the winding system. and a second member that restricts rotation of the spool in the opposite direction to a predetermined amount, and when winding is completed, the spool is reversed by the residual tension and curling force of the film to remove the residual tension of the film. A camera take-up spool reversing mechanism characterized by: 2. The first member is a friction clutch, and the second member is a free disk whose movement is weighted to restrict the movement of the spool due to the cooperative action of pins and grooves between the first member and the spool. The mechanism according to claim 1, characterized in that: