JPH0542423Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a braking mechanism for a focal plane shutter, and particularly to a braking mechanism that converts and absorbs the kinetic energy of the shutter blade at the end of its travel into thermal energy due to friction, etc. It is something.

[Prior Art] In recent years, there has been a demand for faster exposure times that are synchronized with strobe lights, but to achieve this, it is necessary to increase the traveling speed of the shutter blade group. Therefore, it has become necessary for a braking mechanism, such as the mechanism disclosed in Japanese Utility Model Application Publication No. 60-68523, to brake with a relatively weak frictional force at the start of braking, and to brake with a relatively strong frictional force immediately before stopping. However, such a mechanism requires two brake levers and has the problem of increasing the load when resetting the brake.

[Purpose] This invention was made in view of these problems,
The purpose is to provide a braking mechanism for a focal plane shutter with a simple structure that can apply a relatively weak braking force at the beginning of braking and a relatively strong braking force to the shutter blade drive lever at the end of braking. It's about doing.

[Means for Achieving the Object] That is, according to the present invention, the shutter blade is driven, and a first contact portion for being braked and a second contact portion located at a far radial position from the first contact portion are provided. a blade drive lever that is biased in one direction and rotates about a shaft fulcrum; a first contact part that contacts a first contact part of the blade drive lever; a brake lever that has a second contact portion that contacts the second contact portion of the blade drive lever at a near radial position and rotates about a pivot point, the blade drive lever and the brake lever; is arranged such that after the first contact portion contacts the first contact portion at the end of rotation of the blade drive lever, the second contact portion contacts the second contact portion. The above object is achieved by the braking mechanism of the focal plane shutter as described above, and also because the first contact portion of the blade drive lever or the first contact portion of the brake lever has flexibility.

[Example] The details of the present invention will be explained below based on the illustrated example.

FIG. 1 is a plan view showing the apparatus according to the present invention in a state immediately before exposure. In the figure, reference numeral 2 denotes a leading blade drive lever, which is rotatably supported by a shaft 1, has a drive pin 3 upright, has bent portions 2a, 2b, and 2c, and has an iron piece 4 pivotally attached thereto. The drive pin 3 is an arm (not shown) of an open blade group that opens and closes by operating a known parallel link mechanism.
to transmit driving force. The leading blade drive lever 2 is dextrorotatory by the spring 5 and levorotatory by the spring 12, but in this state, since the force of the spring 5 is strong, a dextrorotatory driving force is applied.

A leading blade set gear 10 is rotatably supported by the shaft 1, has a pin 11 planted thereon, has a gear portion 10a, and is provided with dextrorotation by a spring 12. 16 is a brake lever for the leading blade, which includes cam parts 16a, 16b and a bent part 1.
6c and is pivotally supported by the shaft 15, and the cam portion 1
6a has entered the operating locus of the drive pin 3.
The leading blade brake lever 16 uses a known means in which frictional force from a friction plate acts. 17
is fixed around the pin 18 with cushioning rubber, and is provided so that the arm portion 16d comes into contact with it.

Reference numeral 22 denotes an iron core for the leading blade, which is fitted into an eccentric pin 23 set up on a substrate 24 and guided and supported by the coil 21. By rotating the eccentric pin 23, the iron core 22 is moved, and the start position of the leading blade drive lever, which is held by attraction thereto, is changed, and the exposure time and exposure unevenness can be adjusted.

27 is a set lever that is pivotally supported by the shaft 26, and pins 28 and 29 are installed to connect the gear parts 27a and 27.
7b. 25 is a contact piece for the x contact, which is connected to a printed circuit board (not shown).

Reference numeral 32 denotes a rear blade drive lever, which is supported by a shaft puller and has drive pins 33 and 39 erected, and the bending portion 32
a and 32b, and an iron piece 34 is pivotally connected thereto. The drive pin 33 fits into an arm (not shown) of the closing blade group to transmit the drive force. 38 is a cushioning rubber that is fixed around the pin 39. Like the leading blade drive lever, the trailing blade drive lever is dextrorotatory by the spring 35 and levorotatory by the spring 42, but because the force of the spring 35 is strong, the dextrorotatory driving force is applied. . Reference numeral 40 denotes a rear blade set gear, which is rotatably supported by the shaft 31, has a pin 41 planted thereon, has a gear portion 40a, and is provided with dextrorotation by a spring 42. Reference numeral 46 denotes a rear blade brake lever, which is rotatably supported by a shaft 45 and has cam portions 46a, 46b, and 46c.
Also, like the leading blade brake lever, frictional force is obtained by a friction plate (not shown). Reference numeral 47 is a cushioning rubber that is fixed around the pin 48, and is provided so that the cam portion 46c of the brake lever 46 comes into contact with it. Reference numeral 52 denotes an iron core for the rear blade, which is fitted into a pin 53 erected on the substrate 24 in the same way as for the leading blade, and is guided and supported by the coil 51.

Next, the operation of the above configuration will be explained.

First, when the power to the coil 21 is cut off, the iron core 2
The magnetic force of 2 disappears, and the leading blade drive lever 2 is moved by the spring 5.
Due to the difference between the forces of the spring 12 and the force of the spring 12, the leading blade group rotates to the right, and in conjunction with this, the leading blade group operates to a position where an aperture (not shown) is opened. At this time, the drive pin 3 contacts the brake lever cam portion 16a and rotates the brake lever 16 to the left against the frictional force. Therefore, a braking force is applied to the leading blade drive lever 2 to slow it down. Thereafter, the brake lever 16 comes into contact with the cushioning rubber, thereby stopping the leading blade drive lever 2. The brake lever 16 also serves as an x-contact lever, and when it comes into contact with the x-contact piece 25 in its operation end region, it becomes possible to emit a strobe light.

Then, after a predetermined exposure time has elapsed, the current to the coil 51 is cut off, the magnetic force of the iron core 52 disappears, and the rear blade drive lever turns clockwise due to the difference in force between the springs 35 and 42, and the rear blade group It is displaced from a stopped state to a position covering the aperture. At that time, as shown in FIG. 2, first, the buffer rubber 38 comes into contact with the cam part 46a of the rear blade brake lever 46, and when the rear blade drive lever 32 further rotates to the right, the drive pin 33 contacts the cam part 46a. Then, as shown in FIG. 3, the brake lever 46 comes into contact with the cushioning rubber, so that the trailing blade drive lever 32 stops, completing one exposure.

Next, the braking force that acts to slow down the rear blade drive lever 32 will be described.

If the brake torque that the brake lever 46 receives from the friction plate is M, the acting force F ₁ at point P in FIG. 2 is F ₁ =M/l ₁ Therefore, the brake torque T ₁ to the rear blade drive lever 32 is: T ₁ = F ₁ · L ₁ = M · L ₁ / l ₁ Similarly, the acting force F ₂ at point Q in Fig. 3 is F ₂ = M / l ₂ Therefore, the brake torque T ₂ is, T ₂ = F ₂・L ₂ =M・L ₂ /l ₂ , and the ratio of the initial and final brake torques is T ₂ /T ₁ = (l ₁ /l ₂ )×(L ₂ /L ₁ ).

For example, if l ₁ /l ₂ = 1.9 and L ₁ /L ₂ = 1.3,
The brake torque ratio is T ₂ /T ₁ = 2.47. In other words, it is possible to obtain an effect as if two brake levers act as shown in Japanese Utility Model Application No. 60-68523. Also, first the cushioning rubber 38
As the effect of contacting the brake lever 46, the frictional force applied to the brake lever 46 at the moment of contact is static friction, so a large braking force is applied, and an impact force is exerted on the blade group, which can be alleviated. .

Next, we will discuss the set operation.

As mentioned above, when one exposure operation is completed,
A set member on the camera side (not shown) pushes the set lever pin 28 to rotate the set lever 27 to the right. The leading blade set gear 10 and the trailing blade set gear 40 have gear portions 10a and 40a meshed with the set lever gear portions 27a and 27b, respectively, so they rotate to the left as the set lever 27 rotates to the right. At this time, the leading blade set gear pin 11 pushes the drive spring 5 to rotate to the left, so the force acting on the leading blade drive lever 2 is the same as that of the spring 12.
Therefore, the leading blade drive lever 2 rotates left.
Similarly, the rear blade drive lever 32 is rotated right by the spring 42 because the rear blade set gear pin 41 rotates the rear blade drive spring 35 left. When it further rotates left, the iron piece 4 abuts against the iron core 22 and the leading blade drive lever 2 stops rotating left. Since the set lever 27 is overset by the camera side set member, the leading blade set gear further rotates left and stops and is held in the state shown in Fig. 4. This is achieved by locking the camera side set member (not shown) to a locking member (not shown).
Furthermore, the left rotation of the set gear 10 causes the pin 11 to push the brake lever cam portion 16b, returning the brake lever 16. The same applies to the trailing blade drive lever 32, so a description thereof will be omitted.

Next, when the release button is pressed, the coils 21, 51
When energization is started and the iron pieces 4 and 34 are excited, the iron pieces 4 and 34 are attracted and held by the iron cores 22 and 52. At this moment, the camera-side set member is unlocked and in conjunction with the returning operation, the set lever 27 also starts returning, and the leading blade set gear and trailing blade set gear that engage with this also start returning. At this time of return, the drive springs 5, 35 come into contact with the leading blade drive lever 2 and the trailing blade drive lever 32, and apply an impact force in the direction of separating the iron pieces 4, 34 from the iron cores 22, 52. It is known that the impact force is proportional to the mass of the moving body, but in the present invention, since the moving body is only a spring, the impact force can be made extremely small.

FIG. 5 shows a modification of the set gear spring in an overset state. The numbers in the figures with 100 added to those in the first embodiment indicate the same members as in the first embodiment. The difference from the first embodiment is that the leading blade set gear spring 112 acts on the leading blade drive lever 102 only when setting. The set lever 127 and the leading blade set gear 110 are returned by the return spring 100. In the returned state, the leading blade set gear spring 112 is a so-called neutral spring that sandwiches the pin 111 with each other.

In addition, in the above-described configuration, since the set lever and the set gear are connected by gears, unevenness in the set torque is less likely to occur, and it is possible to increase the winding speed of the camera and extend the battery life.

[Effect] As described above, in the present invention, the near radius part of the vane drive lever and the far radius part of the brake lever come into contact during the early stage of braking, and the far radius part of the vane drive lever and the near radius part of the brake lever come into contact during the latter half of braking. Since the shutter blades are configured so that they are in contact with each other, a weak braking force can be applied to the blade drive lever in the early stages of braking, and a strong braking force can be applied to the blade drive lever in the latter stages of braking, which has the effect of safely and reliably stopping the shutter blades even when running at high speed.

[Brief explanation of drawings]

Figure 1 is a plan view of an embodiment according to the present invention, Figure 2 is a plan view of an embodiment of the present invention;
3, and 4 are plan views showing operating states of the main parts of FIG. 1, and FIG. 5 is a plan view showing a modification of FIG. 4. 2... Leading blade drive lever, 10... Leading blade set gear, 16... Leading blade brake lever, 27
... Set lever, 32 ... Rear blade drive lever,
40... Rear blade set gear, 46... Rear blade brake lever, 21, 51... Coil.

Claims (1)

[Claims for Utility Model Registration] (1) A shutter blade is driven and has a first contact portion for being braked and a second contact portion located at a far radius position from the first contact portion. , a blade drive lever that is biased in one direction and rotates around a shaft fulcrum, a first contact portion that contacts a first contact portion of the blade drive lever, and a radius closer to the first contact portion. a brake lever that has a second contact portion that contacts a second contact portion of the blade drive lever at the position and rotates about a pivot point, and the blade drive lever and the brake lever After the first contact portion contacts the first contact portion at the end of rotation of the blade drive lever, the second contact portion is arranged to contact the second contact portion. A focal plane shutter braking mechanism characterized by: (2) Utility model registration Claim 1 of the focal plane shutter characterized in that the first contact portion of the blade drive lever or the first contact portion of the brake lever is flexible. Braking mechanism.