JPS6235065Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a shutter brake mechanism for a camera.

The shutter brake mechanism of a camera needs to exert a large braking force with a small amount of actuation due to the internal space, and various mechanisms have been proposed in the past. One example is one in which a swinging member to which a braking force is applied by a spring or the like collides with a member that is linked to a reciprocally rotating shutter (such as Publication of Utility Model Publication No. 31-3037, Publication No. 43533 of 1982). Yes, the above-mentioned swinging member needs to be returned to the operating position before the next time the shutter is operated.
Generally, this is done in a winding operation, but since the winding force becomes heavy at the end of winding due to the shutter curtain spring charge, etc., it is restored at the beginning of winding. However, the swinging member restored by the winding (forward movement) of the shutter will return to some extent due to its hysteresis, and there is a risk of interference with the member interlocking with the shutter at the end of the travel (backward movement) of the shutter. As a result, the exposure at the end of the shutter travel (return motion) was unstable.

The present invention was devised in view of the above points, and aims to maintain the balance of the winding force of the shutter, prevent the above-mentioned interference, and stabilize exposure.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of a shutter mechanism incorporating a brake mechanism according to the present invention, in which 1 is a front curtain, one end of which is fixed to a front curtain spring drum 2, and the other end has a front slit. A forming member 3 is attached, and each other end of a leading ribbon 5, one end of which is fixed to a leading ribbon winding shaft 4, is fixed to the upper and lower ends of the forming member 3, and is stretched in front of the film.

Further, reference numeral 6 denotes a trailing curtain, one end of which is fixed to the trailing curtain drum 7, a trailing slit forming member 8 is attached to the other end, and trailing ribbons 10 each having one end attached to a trailing curtain spring drum 9 are attached to its lower end. The other ends of the film are fixed and stretched just in front of the film.

The leading spring drum 2 and the trailing spring drum 9 each have built-in springs (not shown) for rotationally driving each drum.
Each spring is charged in conjunction with the winding of the film, and with the release, the transmission gear 11 is released and rotated, and the front pinion 1 engaged with the transmission gear 11 is rotated.
2 also rotates, leading curtain 1 runs in front of the film,
After the preset shutter time has elapsed, the transmission gear 13 is released and rotated to rotate the rear pinion 14 and run the rear curtain 6, exposing the film through the slit formed by the front curtain 1 and the rear curtain 6. I am learning to give.

15 is a brake disc provided coaxially with the shaft 11a of the transmission gear 11, and the brake disc 15 is
It rotates back and forth around the shaft 11a in conjunction with the winding of the shutter (forward motion) and the running of the shutter (backward motion).

Reference numeral 16 denotes a swinging lever pivotably supported near the brake disc 15, and the swinging lever 1
6 is a spring 1 disposed on the shaft of the swing lever 16;
The frictional force of 6a acts, and the rocking is normally kept stationary.

Further, on the periphery of the brake disc 15, there is a protrusion 15a for colliding with the swinging lever 16 at the end of the shutter travel to stop the shutter travel, and a protrusion 15a for stopping the travel of the shutter at the end of the shutter travel.
A restoring protrusion 15b is provided for regulating the bounce of the brake disc 15. Furthermore, an auxiliary protrusion 15c is formed on the periphery of the brake disk 15, and the auxiliary protrusion 15c comes into contact with the swinging lever 16 at the end of winding. 15c has a diameter Rc from the center of rotation larger than the diameter Rb of the restoring projection 15b by the return amount due to hysteresis of the swing lever 16, which will be described below.

That is, before winding up, the brake disc 15 and the swing lever 16 are in the state shown in FIG. 2, but when the winding operation starts, the brake disc 15 rotates clockwise as shown in FIG. 3, and the restoring protrusion 15b is the swing lever 16
is swung against the static force caused by the friction of the spring 16a, but when the restoring protrusion 15b passes, the tip of the swing lever 16 returns somewhat due to hysteresis Δ, and as shown in FIG. It will come to the position of '. Furthermore, at the final stage of winding, the swing lever 16 moves to the auxiliary protrusion 15c as shown in FIG.
and swings to the position of the diameter Rc of the auxiliary protrusion 15c. Next, when the shutter is operated, the brake disc 15 is unlocked and rotates counterclockwise, but at this time, the swing lever 16
Since the contact with the auxiliary protrusion 15c is broken, it will return by the amount of hysteresis again (that is, return to the point with the radius Rc' from the center of rotation), but the radius Rc from the center of rotation of the auxiliary protrusion 15c should be determined by taking into account the amount of return described above. If Rc>Rb is set, the restoring protrusion 15b is
There will be no interference that would cause collision with 6 and make running unstable.

Further, since the movement of the swinging lever 16 by the auxiliary protrusion 15c is only a small amount, the increase in torque at the final stage of winding, when winding becomes heavy, is also small.

As described above, according to the present invention, a brake mechanism with a simple structure, no interference that would disrupt the exposure time, and a well-balanced distribution of winding forces can be obtained.

[Brief explanation of the drawing]

Figure 1 is a perspective view of the shutter mechanism, Figure 2 is a plan view of the shutter brake mechanism before winding and at the end of travel, Figure 3 is a plan view of the shutter brake mechanism at the beginning of winding, and Figure 4 is at the middle stage of winding. FIG. 5 is a plan view of the shutter brake mechanism at the time of completion of winding, and FIG. 6 is a plan view of the shutter brake mechanism at the end of the shutter run. 15: Brake disc, 15a: Projection, 15b: Restoration projection, 15c: Auxiliary projection, 16: Swing lever.

Claims (1)

[Scope of Claim for Utility Model Registration] In a brake mechanism that stops the movement of the shutter due to a collision between a brake disc that rotates back and forth in conjunction with the shutter and a swinging member that applies braking force through friction, In addition to the restoring protrusion that initially swings the swinging member, an auxiliary protrusion that swings the swinging member at the end of winding is provided, and the diameter of the auxiliary protrusion from the center of rotation corresponds to the hysteresis of the swinging member. A shutter brake mechanism for a camera, characterized in that the diameter of the restoring protrusion is made larger by an amount that takes into account the return due to