JPS6125140B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a malfunction prevention circuit for a camera, particularly for a camera equipped with a magnet for driving a shutter rear curtain.

In the case of the above-mentioned camera, for example, dirt may be attached to the attracting surface of the magnet, foreign matter may be mixed in, mechanical failure such as deformation or breakage of the attracting member of the magnet, disconnection of the magnet drive circuit, or poor soldering may occur. If there is an electrical failure such as this, the rear shutter curtain cannot be held in the position where the shutter is opened, and the shutter rear curtain also travels (travels) as the shutter front curtain moves due to the release operation, resulting in exposure. Unable to perform action.

Therefore, if such a magnet abnormality is not detected and subsequent shooting operations are not prohibited, the photographer will think that the camera is working properly and will continue shooting, resulting in unnecessary film wastage. There is a risk of consumption.

A conceivable method for detecting abnormality in the magnet is to use a switch that performs a switch operation in conjunction with the magnet to determine whether or not the power supply to the magnet is cut off after the release operation.

However, even if the magnet is operating normally, the power to the magnet is cut off after the shutter seconds have elapsed, so simply detecting whether or not the power to the magnet has been cut off will cause the magnet to malfunction. A problem arises in that it is impossible to determine whether the power supply to the magnet has been cut off or whether the power supply to the magnet has been cut off as a result of shutter time control during normal operation.

The present invention has been made in view of the above-mentioned matters, and has a structure in which electricity is applied before the start of the camera start-up operation, and when the electricity is applied, the movement of the shutter rear curtain is locked, and when the electricity is released, the shutter rear curtain is locked. A first electromagnetic magnet (corresponding to 34 in Fig. 2) that releases the shutter shutter and moves the shutter rear curtain, and a first electromagnetic magnet (corresponding to 34 in Fig. 2) that is activated by the release operation and changes the output from the first state to the second state after counting a predetermined time. A first timer circuit (corresponding to the one in FIG. 2) that causes the transition, and detects the energization state of the first electromagnetic magnet after the start of the camera start-up operation, and detects the energization state of the first electromagnetic magnet after the start of the camera start-up operation. a detection circuit (corresponding to SW4 in FIG. 2) that outputs a first signal when the magnet is not energized and outputs a second signal when the magnet is energized; and the first timer. In response to the circuit output and the detection circuit output, the first
a prohibition signal forming circuit (corresponding to G3 in FIG. 2) that outputs a prohibition signal when the timer circuit output of is in the first state and the detection circuit output is outputting the first signal; A release signal forming circuit (G in Fig. 2) that forms a release signal simultaneously with activation of the first timer circuit by the release operation.
Corresponds to 2. ), a second electromagnetic magnet (corresponding to the one in FIG. 2) that starts the camera starting operation by the release mechanism in response to the release signal, and a second electromagnetic magnet (corresponding to the one shown in FIG. 2) that measures the shutter seconds after the camera starting operation. and a shutter time control timer circuit (corresponding to the one in FIG. 2) that prohibits energization of the first electromagnet, and prohibits the release signal forming circuit from responding to the release operation by the prohibition signal. Further, the first timer is configured such that the time when the shutter timer circuit for controlling the shutter timer circuit prohibits energization is delayed from the time when the output becomes the second state after the time measurement time of the first timer circuit. The above-mentioned problem is attempted to be solved by setting the clock time of the circuit.

An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 shows the internal mechanism of the camera. Reference numeral 1 denotes a release electromagnet equipped with a permanent magnet 1a, and the armature 1b of this electromagnet 1 is always attracted by the magnetic force of the permanent magnet 1a. Reference numeral 2 denotes a holding lever of the armature 1b, and this holding lever 2 is urged to rotate counterclockwise by a spring 3. Such an electromagnet is cased by a frame 4 made of a non-magnetic material, and a shielding member 5 is provided on the lower surface of the frame 4 for shielding magnetic influences. The shaft 2a of the holding lever 2 protrudes from the frame 4 and has a start lever 6 attached thereto.
A pin 6a that engages with one end of the release lever 7 is installed at one end, and a pin 6b that engages with the charge plate 8a of the armature is installed at the other end of the start lever 6.
has been planted. Reference numeral 9 denotes an automatic aperture lever rotated counterclockwise by a spring 9a, and this automatic aperture lever 9 engages with a pin installed in an aperture drive ring that narrows down the aperture of a photographic lens (not shown). The automatic throttle lever 9 has an automatic throttle accumulating lever 10 pivoted coaxially therewith and biased to rotate clockwise by a spring 10a. A common lever 11 is pivotally supported at the center of the automatic throttling energy storage lever 10 via a spring 11a. Further, the automatic aperture accumulating lever 10 is locked to a locking lever 12, and this locking lever 12 is engaged with the other end of the release lever 7. The release lever 7 is rotated counterclockwise by a spring 7a, and when the release lever 7 is rotated clockwise against the spring 7a, the locking lever 12 and the automatic throttle storage lever 10 are engaged. The suspension is now being lifted. The joint lever 11
is the falling part 9 of the automatic aperture lever 9 at its end.
b, and the common lever 11 has a pin 11 that engages with one end of the automatic aperture return signal lever 13.
It has c. Reference numeral 14 denotes a stopper pin that restricts the rotation range of the automatic throttle accumulating lever 10. 15 is a charge lever, and this charge lever 15 is connected to one end 10 of the automatic throttle storage lever 10.
The charge lever 15 has a pin 15a that can be engaged with the charge plate 8a, and the charge lever 15 can be rotated clockwise by a pin 16b installed in the intermediate lever 16 provided with the charge plate 8a. A hoisting force of a hoisting lever (not shown) is transmitted to the intermediate lever 16 via a hoisting shaft 17, a hoisting cam 18, a roller 19, and a pin 20a of a transmission lever 20 to which the roller 19 is attached. It's summery.

The other end 10b of the automatic aperture accumulating lever 10 is engaged with a mirror drive lever 21 which is urged to rotate counterclockwise by a spring 21a. A mirror flip-up lever 22 is coaxially connected to the mirror drive lever 21.
is pivotally mounted, and the mirror flip-up lever 22
is engaged with a hook portion 23a of a flip-up locking pawl 23 pivotally attached to the me drive lever 21. This locking pawl 23 is urged to rotate clockwise by a spring 23b. The mirror flip-up lever 22 is engaged with a pin 24a implanted in one end of the intermediate lever 24, and the other end of this intermediate lever 24 is engaged with a pin 25a implanted in the mirror receiving plate 25. . 2
Reference numeral 6 indicates a rotation axis of the mirror receiving plate 25 provided with the mirror 27. Further, the mirror drive lever 21 is provided with a protrusion 21b that engages with one end of the leading curtain locking lever 28, and the other end of this leading curtain locking lever 28 locks the bent piece of the leading curtain release lever 29. There is. spring 2
Front curtain release lever 2 rotationally energized by 9a
The tip of 9 is engaged with a front curtain tensioning lever 30 for starting the shutter front curtain of the shutter mechanism.
Reference numeral 31 denotes a trailing curtain signal lever coaxially and independently pivotally connected to the leading curtain locking lever 28;
1 has one end engaged with a signal lever 32 which is activated by a shutter trailing curtain operation end signal of the shutter mechanism, and the other end engaged with one end of a mirror return signal lever 33. A pin 33a planted in the center of the mirror return signal lever 33 engages with the other end of the flip-up locking pawl 23, and the other end of the mirror return signal lever 33 is connected to the automatic aperture return signal lever 1.
It is engaged with the other end of 3. Reference numeral 34 denotes a trailing curtain control electromagnet, and the armature 34a of this electromagnet 34 is attached to a trailing curtain tensioning lever 35.
is energized to move away from the electromagnet 34. Reference numeral 37 denotes a cam for tightening the rear curtain of the shutter; this cam 31 is engaged with a protrusion 35a of a tension lever 35, and this engagement is released when the tension lever 35 is rotated by a spring 36. It is becoming more and more common.
This tension lever 35 has the mirror drive lever 2
An armature set lever 39 is attached to which the tip of the armature set lever 39 can be brought into contact. SW4 is an abnormality detection switch that is opened and closed in conjunction with the rotation of the tension lever 35.

Here, FIG. 2 shows the exposure control circuit of the camera shown in FIG. 1, and 1, 2, and 6 are the release electromagnet, armature holding lever, and start lever shown in FIG. 1, and 21, 34, 35 are and
SW4 is a mirror drive lever, a trailing curtain control electromagnet, a trailing curtain tensioning lever, and a switch shown in FIG.

In FIG. 2, E is a power battery, SW1 is a power switch that is closed by the first operation of a release button (not shown), and the power battery E is connected to a voltage detection circuit, a delay circuit, and a trailing curtain control via switch SW1. The circuits are connected in parallel. The voltage detection circuit is formed from the following: R ₁ and R ₂ are voltage dividing resistors, VC is a constant voltage circuit, CP ₁ is a comparator, and the voltage dividing point of resistors R ₁ and R ₂ is connected to the first input terminal of this comparator CP ₁ , and the second input A constant voltage circuit VC is connected to the end. The output of the comparator CP ₁ is applied to the first input terminal of the NOR gate G ₁ as the output of the voltage detection circuit. The second input terminal of this NOR gate _G1 is connected to the connection point between the release switch SW2, which is closed by the second-stage operation of the release button, and the resistor _R3 connected in series with the switch SW2.
The third input terminal of _G1 is connected to a connection point between a switch SW3, which is closed in conjunction with the completion of winding, and a resistor _R4 connected in series with the switch SW3. The output of the NOR gate _G1 is applied to the first input terminal of the comparator _CP2 via the buffer amplifier _B1 within the delay circuit. Further, the first input terminal of the comparator CP ₂ is connected to the connection point between the variable resistor RV ₁ and the capacitor C ₁ forming a time constant circuit, and the second input terminal of the comparator CP ₂ is connected to the connection point between the voltage dividing resistor R ₅ and the capacitor C 1. Connected to the connection point with ₆ . The time determined by the variable resistor RV ₁ and the capacitor C ₁ is determined by the switch when the trailing curtain control electromagnet 34 operates normally.
It is set to be shorter than the time the switch SW ₄ is turned on from off and longer than the time the switch SW ₄ is turned on from off when the electromagnet 34 does not operate normally.
The output of the comparator CP ₂ is applied to the first input of the NAND gate G ₂ as the output of the delay circuit. The second input terminal of this NAND gate _G2 is connected to the NAND gate G2.
The output of _G1 is applied, and the third input terminal of NAND gate _G2 is connected to switch _SW4.
A low level signal is input when the is closed. When the rear curtain control electromagnet 34 normally holds the tension lever 35, the switch SW ₄ is turned from off to on after a shutter time has elapsed after the release electromagnet 1 is activated. nand gate
The output of G ₂ is connected to the buffer amplifier B ₂ and the resistor R ₇ and capacitor via the coil 1C of the release electromagnet 1.
Connected to the connection point with C ₂ and also NAND gate G ₂
The output of is connected to the first input terminal of NOR gate _G3 . The second input terminal of this NOR gate _G3 is a resistor
R ₈ and the switch connected in series with the resistor R ₈
Connected to the connection point with SW ₄ . The output of this NOR gate _G3 is applied to the first latch relay _L1 via an inverter. This first latching relay _L1 closes the relay contacts when energized. SW6 is a reset switch that is closed in conjunction with the pressing operation of a sprocket release button (not shown), and this switch SW6 forms a series circuit with the second latch relay _L2 to connect the power supply
It is directly connected to _E1 without going through the power switch SW1. This second latch relay _L2 opens the relay contacts when energized. The relay contact connects a resistor ^R9 and a light emitting diode LED in series, and a connection point between the resistor _R9 and the relay contact is connected to the third input terminal of the NAND gate _G2 . Therefore, when the relay contact is closed, the light emitting diode LED is turned on and a low level output is applied to the third input terminal of the NAND gate _G2 . In the rear curtain control circuit, R _T and C _T are variable resistors and capacitors that constitute a time constant circuit for controlling exposure time, and the capacitor C _T is connected to a count switch SW5 that is opened when the shutter front curtain moves. are connected in parallel. CP ₃ is a comparator, and the first input terminal of this comparator CP ₃ is connected to the connection point of the variable resistor R _T and the capacitor C _T , and the second input terminal is connected to the voltage dividing resistors R ₁₀ and R ₁₁
The dividing points of are connected. Comparator like this
Coil ₃ of trailing curtain control electromagnet 34 is connected to the output end of CP 3.
4b is connected and the output of the comparator CP ₃ changes from low level to high level, the trailing curtain control electromagnet 34
is in a de-energized state.

Next, the operation of the above configuration will be explained, but first, a case where the camera operates normally will be explained. When the release button is pressed in the winding completed state, the first stage operation closes the power switch SW1 and applies power voltage to each circuit. At this time, the output of the comparator circuit CP ₃ becomes low level, and the coil 34b is energized and the rear curtain control electromagnet 34 is turned on.
is in the excited state. Therefore, the armature 34a is held by suction and is in the illustrated state. In the voltage detection circuit, the power supply voltage is higher than the specified value, so the resistance
The divided voltage of R ₁ and R ₂ is higher than the constant voltage of the constant voltage circuit VC, and the output of the comparator CP ₁ becomes low level. When the release switch SW ₂ is closed by further pressing the release button, the output of the Noah gate G ₁ becomes high level because the switch SW ₃ is closed in the winding completed state. Therefore, the output of buffer amplifier B ₁ becomes high level, the short circuit of capacitor C ₁ is released, capacitor C ₁ is charged through resistor RV ₁ , and after a time determined by capacitor C ₁ and resistor RV ₁ , the output of comparator CP ₂ is reversed from high level to low level. When the output of this comparator CP ₂ is at high level,
The third input terminal of NAND gate _G2 is at a high level because the relay contact is open. Therefore, all inputs to NAND gate _G2 are at high level. Therefore, since the output of comparator CP ₂ is at a high level before a predetermined time has elapsed since the release operation, the switch is not activated during the release operation.
When SW ₂ is turned on, the output of NAND gate G ₂ becomes low level, so the coil 1c of the release electromagnet 1 becomes excited via the buffer amplifier B ₂ , and the magnetic flux of the coil 1c and the magnetic flux of the permanent magnet 1a are combined. are offset and the suction of the armature 1b is cut off, so the holding lever 2 is rotated by the spring 3. Since the start lever 6 also rotates together with this, the release lever 7 rotates clockwise against the spring 7a, and the locking lever 12 and the automatic aperture storage lever 10 are unlocked. For this reason, the automatic throttle storage lever 10
is rotated clockwise by the spring 10a, and the automatic aperture lever 9 is rotated clockwise via the shared lever 11. This narrows down the photographic lens. Further, since the other end 10b of the automatic aperture accumulating lever 10 rotates in a direction away from the mirror drive lever 21, the mirror drive lever 21 is rotated counterclockwise by the spring 21a. Therefore, the tip of the mirror drive lever 21 releases the armature set lever 39 from being pressed. Further, a mirror flip-up lever 22 coaxial with the mirror drive lever 21 is locked to a hook portion 23a of a locking pawl 23, so that they rotate together. As a result, the intermediate lever 24 rotates counterclockwise, and the mirror receiving plate 25 is flipped upward about the shaft 26. Furthermore, the counterclockwise rotation of the mirror drive lever 21 causes the front curtain locking lever 28 to rotate clockwise and disengage from the bent piece of the front curtain release lever 29. For this reason, the first curtain release lever 2
9 is rotated clockwise by a spring 29a to rotate the front curtain tensioning lever 30 in the direction of arrow A, so that the shutter front curtain of the shutter mechanism runs. As the leading shutter curtain runs, the count switch SW5 is opened, so that the capacitor _C2 is charged through the variable resistor _T.sub.T , and after a time determined by the values of the variable resistor _R.sub.T and the capacitor _C.sub.T , the output of the comparator _CP3 becomes low level. The level is reversed from 1 to 1, and the electricity to the rear curtain control electromagnet 34 is cut off. Therefore, the trailing curtain tensioning lever 35 to which the armature 34a is attached is rotated counterclockwise by the spring 36, so that it is disengaged from the trailing curtain tensioning cam 37, and the shutter trailing curtain is allowed to travel. At this point, switch SW ₄ will turn on from off, but
The timer time determined by the resistors RW ₁ and C ₁ is determined by the electromagnet 3 after the shortest shutter time has elapsed.
4 is activated and switch SW ₄ is turned on, the output of comparator CP ₂ is already at low level at this point, so the output of NOR gate G ₃ is It remains at a low level and does not make the first latch relay _L1 conductive. The signal lever 32 is rotated in the direction of arrow B in response to a shutter operation end signal upon completion of travel of the shutter trailing curtain, and the trailing curtain signal lever 31 is rotated counterclockwise. Therefore, the mirror return signal lever 33 rotates clockwise, and the locking pawl 23 rotates counterclockwise to release the engagement with the mirror flip-up locking lever 22. As a result, the mirror receiving plate 25 is released from the raised state and returned to the lowered position by a spring (not shown). Also, the mirror return signal lever 33
rotates the automatic aperture return signal lever 13 counterclockwise at the other end, so the shared lever 11 rotates counterclockwise and disengages from the automatic aperture lever 9. Therefore, the automatic aperture lever 9 is rotated counterclockwise by the spring 9a and returned to its original position, and the aperture of the photographic lens is opened to complete the photographing.

To wind the film after shooting, when the winding lever is raised, the winding shaft 17 and charge cam 18 are rotated in the direction of arrow C, and the shutter mechanism is charged in a known manner to wind the film. . At this time, the rotation of the charge cam 18 is transmitted to the intermediate lever 16 via the roller 19 and the pin 20a of the transmission lever 20. As a result, the intermediate lever 16 is rotated clockwise, the pin 6b is pressed by the charge plate 8a, the start lever 6 is rotated, and the armature 1b of the holding lever 2 is attracted to the release electromagnet 1. At this time, armature 1b
is attracted to the release electromagnet 1 by the magnetic flux of the permanent magnet 1a. Further, since the rotation of the start lever 6 releases the locking of the release lever 7 by the pin 6a, the release lever 7 is rotated counterclockwise by the spring 7a. Said intermediate lever 1
Since the clockwise rotation of 6 rotates the charge lever 15 clockwise, the automatic throttling energy storage lever 10 is rotated counterclockwise against the spring 10a. The rotation of this automatic throttle storage lever 10 is controlled by a locking lever 12.
is in the locked state and the mirror drive lever 21 is
is rotated clockwise against the spring 21a. This rotation of the mirror drive lever 21 locks the mirror flip-up lever 22 with the locking pawl 22 and locks the front curtain release lever 29 with the front curtain locking lever 28. The rotation of the mirror drive lever 21 presses and holds the armature set lever 39, and the protrusion 35a of the trailing curtain tensioning lever 35 engages with the shutter trailing curtain tensioning cam 37, and the armature 34a is attracted to the electromagnet 34. This will return you to the same state you were in.

Next, a case where the power supply voltage is less than or equal to a predetermined value will be described.

First, when you press the release button, the first
In stage operation, the power switch SW1 is closed and the power supply voltage is applied to each circuit, but at this time, the divided voltage of the resistors _R1 and _R2 is lower than the constant voltage of the constant voltage circuit _Vc , The output of comparator _CP1 becomes high level. Therefore, even if the release button is further pressed and the release switch SW2 is closed, the output of the NOR gate _G1 does not become high level but remains low level. Therefore, the output of the NAND gate G ₂ continues to maintain a high level, and the output of the buffer amplifier B ₂ continues to send out a high level, so the start lever 6 cannot operate without the coil 1c of the release electromagnet 1 being energized. Since there is no camera, pressing the release button will not activate the camera.

Next, the power supply voltage is sufficient and the release electromagnet 1
The following describes a case where the system operates, but there is a failure in other electrical circuits or mechanical elements. This electrical circuit failure is when a signal is not output from the trailing curtain control circuit due to damage to an element in the trailing curtain control circuit, poor soldering, etc., or faulty soldering or disconnection of the terminal of the trailing curtain control electromagnet 34. It's time to be.
Mechanical failures include dirt on the suction surface of the trailing curtain control electromagnet 34, contamination of foreign matter, and the armature 34a.
Insufficient set amount, electromagnet 34 and armature 34
This is a case where the armature 34 is not attracted to the electromagnet 34 because the spring pressure of the spring 36 that biases the trailing curtain tensioning lever 35 is greater than the attraction force of the electromagnet 34 due to deformation or damage of the armature a.

First, when the release button is pressed, the first stage operation closes the power switch _SW1 , and each circuit,
, the power supply voltage is applied to. At this time, resistance
The divided voltage of R ₁ and R ₂ is higher than the constant voltage of the constant voltage circuit _VC , and the output of the comparator CP ₁ becomes low level. When the release button is further pressed and release switch SW ₂ is closed,
Since the switch SW ₃ is closed in the winding completed state, the output of the NOR gate G ₁ becomes high level. Therefore, the output of buffer amplifier B ₁ becomes high level, so capacitor C ₁ is charged through resistor RV ₁ , and after a time determined by capacitor C ₁ and resistor RV ₁ , the output of comparator CP ₂ changes from high level to low level. Invert. When the output of the comparator CP ₂ is at a high level, the third input terminal of the NAND gate G ₂ is at a high level because the relay contact is open. Therefore, all inputs to NAND gate _G2 are at high level. Therefore, the output of NAND gate _G2 becomes low level, so the coil 1c of the release electromagnet 1 becomes a buffer amplifier.
The holding lever ₂ is rotated by the spring 3 because the magnetic flux of the coil 1c and the magnetic flux of the permanent magnet 1a cancel each other out through B2, and the attraction of the armature 1b is cut off. Since the start lever 6 also rotates together with this, the release lever 7 rotates clockwise against the spring 7a, and the locking lever 12 and the automatic aperture storage lever 10 are unlocked. Therefore, the automatic throttle accumulating lever 10 is rotated clockwise by the spring 10a, and the automatic throttle accumulating lever 9 is rotated clockwise via the common lever 11. This narrows down the photographic lens. Also, since the other end 10b of the automatic aperture storage lever 10 rotates in a direction away from the mirror drive lever 21, the mirror drive lever 21
1 starts rotating counterclockwise by the spring 21a, and the tip of the lever 21 releases the armature set lever 39 from being pressed. At this time, due to the above-mentioned electrical failure or mechanical failure, the armature 34
a is not attracted to the electromagnet 34, the rear curtain tensioning lever 35 is rotated by the spring 36, and the switch SW4 is rotated.
Close. Also, the timer time determined by the resistor RV ₁ and the capacitor C ₁ is set when the switch is activated after the shortest shutter time has elapsed since the release, as described above.
It is set to a shorter time than the time it takes for SW ₄ to turn on, and it is also set to a longer time than the time from the release operation until switch SW ₄ closes in the above operation when the electromagnet is not activated. Therefore, when switch SW ₄ is closed as described above, the comparator is closed.
The output of CP ₂ is still at high level and the switch
When SW ₄ is closed, the output of Noah gate G ₃ changes from low level to high level, and this Noah gate
Since the output of _G3 is applied to the first latch relay _L1 through the inverter, the first latch relay _L1 is energized and closes the relay contact, and thereafter the relay contact continues to maintain the closed state. Therefore, the light emitting diode LED is energized and lights up to warn the photographer that an electrical or mechanical failure has occurred in the trailing curtain control circuit.
At the same time, a low level signal is applied to the third input terminal of NAND gate G ₂ , so the output of NAND gate G ₂ will not become low level unless reset switch SW ₆ is closed. 1 is not excited and never activates. Further, since the mirror drive lever 21 rotates the coaxial mirror flip-up lever 22 integrally, the intermediate lever 24 rotates counterclockwise to flip the mirror receiving plate 25 upward about the shaft 26. Furthermore, the counterclockwise rotation of the mirror drive lever 21 causes the leading curtain locking lever 28 to rotate clockwise and disengage from the bent piece of the leading shutter release lever 29. For this reason, the front curtain release lever 29 has a spring 29
Rotate clockwise with a to release the leading curtain tensioning lever 30.
is rotated in the direction of arrow A, so that the leading shutter curtain of the shutter mechanism travels.

However, since the rear shutter curtain is not locked by the tension lever 35, it runs at the same time as the front shutter curtain, and the shutter is not opened and the film is not exposed.

Even though the light emitting diode LED lights up to warn you that a malfunction has occurred, if you wind the camera as described above and press the release button again, the power switch will turn off in the first step. SW1 is closed and power supply voltage is applied to each circuit. At this time, the divided voltage of the resistors _R1 and _R2 is higher than the constant voltage of the constant voltage circuit _Vc , and the output of the comparator _CP1 becomes low level. When release switch SW2 is closed by further pressing the release button, the switch
Since SW3 is closed with winding completed, the output of NAND gate G ₁ becomes high level and is applied to the first input terminal of NAND gate G ₂ , but the relay contact at the third input terminal of NAND gate G ₂ is closed. It remains at a low level. Therefore, the output of NAND gate G ₂ continues to maintain a high level, and since the output of buffer amplifier B ₂ is at a high level, that is, in an off state, the release electromagnet 1
Since the coil 1c is not excited and the start lever 6 does not operate, the camera will not start even if the release button is pressed.

Furthermore, when the light emitting diode LED lights up to warn that a malfunction has occurred, a reset operation member is used to return the device to its original state. If the multiple exposure mechanism is utilized, it is effective without wasting a single frame of film. When a sprocket release button (not shown) is used as the reset operation member, when the sprocket release button (not shown) is pressed, the film winding mechanism is deactivated, the reset switch SW6 is closed, and the second latch relay is activated.
_L2 becomes conductive and changes the relay contact from the closed state to the open state. Then, when the hoisting lever is hoisted up, the sprocket release button returns to its original position due to the predetermined amount of hoisting. As a result, the reset switch SW6 also becomes open, so that the second latch relay _L2 becomes non-conductive, but the relay contacts continue to maintain the open state. Further, the winding operation of the winding lever is performed in the same manner as the other above-mentioned winding operations in which the film winding mechanism does not operate. At this time, if the cause of the camera failure is a simple and temporary mechanical failure such as insufficient armature setting, the camera can operate normally and take pictures by pressing the release button afterwards.

As described above, in the present invention, when the shutter rear curtain moves in the specified manner, the next photographing is prohibited, so that the user does not notice the incorrect movement of the shutter rear curtain.
This prevents the film from being wasted by repeating subsequent photo shoots.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a camera malfunction detection device according to an embodiment of the present invention, and FIG. 2 is an electrical control circuit diagram of the device shown in FIG. 1... Release electromagnet, 6... Start lever,
21... Mirror drive lever, 34... Rear curtain control electromagnet, 35... Rear curtain tension lever,... Voltage detection circuit,
... trailing curtain control circuit, SW4 ... abnormality detection switch, L ₁ and L ₂ ... first and second latch relays,
…Relay contact, LED…Light emitting diode, G ₂ …
Nand gate, SW6...reset switch.

Claims (1)

[Scope of Claims] 1. Electricity is applied before the start of the camera start-up operation, and when the electricity is applied, the movement of the shutter rear curtain is locked, and when the electricity is turned off, the lock of the shutter rear curtain is released and the shutter rear curtain is made to run. a first electromagnetic magnet; a first timer circuit that is activated by a release operation and causes the output to shift from the first state to the second state after a predetermined time has been counted; and a camera. detects the energization state of the first electromagnetic magnet after the start of the camera start-up operation, outputs a first signal when the magnet is not energized after the start of the camera start-up operation, and energizes the magnet. a detection circuit that outputs a second signal when the first timer circuit output is in the first state and the detection circuit output is in the first state in response to the first timer circuit output and the detection circuit output; a prohibition signal formation circuit that outputs a prohibition signal when the first timer circuit is outputting the first signal; a release signal formation circuit that generates a release signal simultaneously with activation of the first timer circuit by a release operation; a second electromagnetic magnet that responds to start the camera start-up operation by the release mechanism; and a shutter time control that measures the shutter second time after the camera start-up operation and prohibits energization of the first electromagnetic magnet after the time measurement. a timer circuit for inhibiting the response of the release signal forming circuit to the release operation by the inhibiting signal, and further comprising: a timer circuit for inhibiting the response of the release signal forming circuit to the release operation by the inhibiting signal; A malfunction prevention circuit for a camera, characterized in that the time measured by the first timer circuit is set so that the time at which energization is prohibited in the shutter time control timer circuit is delayed.