GB2090667A - Camera shutter - Google Patents

Abstract

An electrical shutter for a camera includes a prime mover spring 6 which is charged by rotation of a charging member 3 during a film winding operation and serves upon shutter release to rotatably drive a shutter drive disc 5 through a single revolution during which it opens then closes shutter blades 33, 34; the shutter drive discs 5 being maintained stationary at its start position by first detent means 10 displaceable by a first electromagnet Mg 1 to open the shutter 33, 34 and at a shutter open position by second detent means 24, 40 displaceable by a second electromagnet Mg 2 to close the shutter; and the first detent means 10 having a bevelled surface 10b (see Fig. 6) for engagement with the shutter drive disc to provide a smooth shutter release. Preferably the second detent means is a double lever 24, 40 of which one 24 can be retracted by the second electromagnet and the other 40 also has a bevelled surface. <IMAGE>

Description

1

SPECIFICATION

Improvements in or relating to electrical shutters of the electromagnetic release type for cameras The present invention relates to electrical shutters of the electromagnetic release type for cameras, and is more particularly concerned with electrical shutters in which shutter blades are operated for opening and closing by the force of a prime mover spring which is disposed on a single shaft.

An electrical shutter of the electromagnetic release type is already known in which a prime mover spring disposed on a single shaft is charged in response to a film winding operation and is released in response to an electromagnetic release to drive a shutter drive member for rotation in order to operate shutter blades and wherein the rotation of the drive member is controlled by a detent member which is con- strained by an electromagnet or the like in order to determine an exposure period. Such electrical shutter is simple in construction and provides an automatic stop of the film winding for each picture frame. Additionally it is constructed so as to prevent a dou- ble exposure.

With such a shutter mechanism the shutter drive member is maintained at rest in its start position by an arm thereof being engaged by a first detent member which is in the form of a plate-like lever which can be displaced in a vertical plane and has a broad side against which one side of the arm of the shutter drive member is engaged in face- to-face contact; consequently, upon shutter release, this causes a twisting action to occur between the arm of the shutter drive member and the detent member, and this results in an unstable release operation. Since the arm of the shutter drive member is strongly urged to rotate by the prime mover spring, it abuts against the detent member with a force sufficiently large to present a large resistance to sliding movement between the arm of the shutter drive member and the detent member, and this also results in the twisting action when a release operation should take place.

For a high speed shutter operation it is desirable that the shutter drive member should be able to be rotated through substantially one revolution at its maximum speed without any hindrance or engagement. However, in such a shutter mechanism, the arm of the shutter drive member is engaged by a second detent member when it is in the region of its position corresponding to the shutter blades being fully open, and this makes high speed shutter operation difficult and tends to cause the shutter blades to bounce.

According to the present invention an electrical shutter of the electromagnetic release type for a camera comprises a charging member, a prime mover spring and a shutter drive member adapted to be rotated about a single shaft, the charging member being adapted to be rotated in response to a film winding operation and arranged to charge the prime mover spring for driving the shutter drive member which is arranged to open and close shutter blades by being rotated through substantially one GB 2 090 667 A 1 revolution by the prime mover spring in response to an electromagnetic release operation, a first detent member adapted to engage the shutter drive member to maintain it stationary at its starting position before a shutter release is operated to effect said electromagnetic release operation, a second detent member for determining an exposure period and adapted to engage the shutter drive memberto maintain it temporarily at an intermediate position at which the shutter blades are in an open position and to be subsequently disengaged therefrom, means for moving the first detent member and the second detent member into their respective shutter drive member engaging positions prior to rotation of the charging member in response to a film winding operation to charge the prime mover spring, and the first detent member having a bevelled surface for abutment against the shutter drive member when at its starting position to provide a linear contact therewith whereby to facilitate disengagement of the first detent member from the shutter drive member under rotating force of the shutter drive member when the shutter drive member is to be released.

In a preferred embodiment of the invention, the detent member which maintains the shutter drive member in its starting position has a bevelled surface for engagement with the latter to provide a linear contact therebetween, thus substantially reducing the frictional resistance as compared with the face-to-face contact in the conventional arrangement and assuring a smooth disengagement. The other detent member which is associated with the determination of an exposure period comprises a double lever, one of which is retracted and the other of which has a bevelled surface that is expelled by the drive member during a high speed shutter operation, thus assuring the achievement of a reduced exposure period. During normal shutter operations, the drive member bears against said other detent member in a resilient manner so as to avoid a bouncing of shutter blades.

Various accessories can be selectively rendered operative when their associated normally open switch is turned on. A failure in the operation of such switch or its associated accessory circuit does not influence the operation of the electrical shutter circuit itself, whereby an automatic exposure photographing operation is always assured. The circuit arrangement is simplified since the individual acces- sory circuit is connected with a common bus of the shutter circuitthrough a respective normally open switch.

The invention will be further described by way of example with reference to Figs. 4 to 13 of the accompanying drawings, of which Figs. 1 to 3 illustrate prior art, and in which:-

Fig. 1 is a perspective view of a shutter drive mechanism used in a conventional electrical shutter of the electromagnetic release type, Figs. 2A and 2B are circuit diagrams illustrating conventional switching means associated with various accessory circuits, Fig. 3 is a circuit diagram illustrating conventional electrical connections between an X contact switch and an electronic flash unit and a data entry unit, 2 GB 2 090 667 A 2 Fig. 4 is a frontviewof an electrical shutterof electromagnetic release type constructed according to one embodiment of the invention, Fig. 5 is a plan view of the shutter drive mechan- ism shown in Fig. 4, Fig. 6 is a fragmentary perspective view of the mechanism shown in Figs. 4 and 5, Fig. 7 is a perspective view of the hook used in the mechanism of Figs. 4 and 5, Fig. 8 is a front view of the shutter drive mechanism shown in Fig. 4 in its operative position, Figs. 9 and 10 are plan views illustrating two operative positions of the shutter drive mechanism shown in Fig. 5, Fig. 11 is a circuit diagram of an electrical shutter circuit of the invention, Fig. 12 is a plan view showing the detailed con etruction of switch SW3, and Fig. 13 is a circuit diagram of another example of a circuit which prevents the discharge of capacitor C5. 85 Reference will first be made to Figs. 1 to 3 illustrat ing conventional prior art arrangements.

A shutter mechanism of a single shaft rotating type is usually constructed as shown in Fig. 1. Refer- ring to this Figure, shutter drive member 201 in the 90 form of a disc is fixedly mounted on a single rotat able shaft whose axis is indicated at 202 and around which a prime mover spring 203 is disposed. One end 203a of spring 203 is secured to the drive member 201 while its other end 203b is fixedly con- 95 nected with a charging member 210 which rotates in association with a film winding operation. The spring 203 is charged in response to a film winding operation, whereby the drive member 201 is urged to rotate counter-clockwise, as indicated by an arrow. Before the shutter release is operated, rota tion of the drive member 201 is blocked by an arm 201a extending from the drive member 201 abutting against a detent member 205 which is rockably mounted on a stud (not shown) having an axis 204.

In this manner, the drive member 201 is maintained at rest in its start position for shutter operation.

Another detent member 206 has its one arm 206a located in the path of rotation of the arm 201a. The detent member 206 is pivotally mounted on a stud (not shown) having an axis 207 and is urged by spring 208 to rotate counter-clockwise about stud axis 207. An armature piece 206b is formed on the end of the other arm and is held in abutment against an electromagnet 209.

In operation, when detent member 205 is moved out of abutting engagement with the arm 201a in response to a shutter release, the drive member 201 rotates counter-clockwise underthe resilience of spring 203 to open the shutter. In the fully open posi- 120 tion of the shutter, arm 201a comes into abutment against arm 206a of the other detent member 206, thus temporarily maintaining 1he shutter fully open.

At this time, electromagnet 209 holds detent member 206 attracted thereto. When a proper exposure has been given, the electromagnet 209 is de-energized to permit the drive member 201 to rock the detent member 206 and to rotate past it, thus undergoing a remaining one-half revolution about the shaft axis 202 until it returns to its start position,130 thus closing the shutter.

With a shutter mechanism of the single shaft rotating type as described above, the shutter drive member 201 is maintained at rest in its start position by the arm 201a being engaged by the detent member 205. The detent member 205 is in the form of a plate-like ieverwhich is oscillatable in a vertical plane, and has a broad side against which one side of the arm 201a engages in face-to-face contact.

Consequently, upon shutter release, this causes a twisting action to occur between the arm 201a and detent member205, resulting in an unstable release operation. Specifically, since arm 201a is strongly urged to rotate counter-clockwise by the spring 203, 8() it abuts against detent member 205 with a force of suff icient strength to present a large resistance to a sliding movement between the members 201 and 205, resulting in the twisting action when the release operation should take place.

To achieve a high speed shutter operation it is desirable that drive member 201 be capable of rotating through one revolution at its maximum speed without experiencing any constraint or engagement. However, with the conventional mechanism illustrated in Fig. 1, it is once engaged by the detent member 206 adjacent to the fully open shutter position, making it difficult to achieve high speed shutter operation and causing bouncing of the shutter blades.

The above described disadvantages in a conventional arrangement of the single shaft rotating type may be overcome by providing bevelled edges on detent members 205,206 so as to facilitate the disengagement of arm 201a therefrom. However, it will be appreciated that as spring 203 is charged in response to a film winding operation, the resilience stored therein which urges arm 201a against bevelled edge increases progressively. This means that the retention of drive member 201 at its start posi- tion by means of locating member 205 may be unstable during the charging operation.

It will be noted that a camera incorporating an electrical shutter usually includes a variety of electrical accessory circuits including a fixed exposure period selection circuit which permits synchro-flash photography, an exposure factor modification circuit which may be utilized during a photographing operation under rear light illumination, a battery check circuit, an electrical self-timer circuit orthe like, all of which are connected in circuitwith the electrical shutter circuit. These accessory circuits are connected with the shutter circuit by using a changeover switch. By way of example, Fig. 2A shows a fixed exposure period selection circuit which may be connected with the shutter circuit. Specifically, shutter circuit includes capacitor 301 which forms part of a photometric circuit which is used to provide a fixed exposure period and which is connected with the movable contact of changeover switch 302 having fixed contacts which are in turn connected with a photometric light receiving element 303 and with resistor 304. During flash photography, the switch 302 is thown to the fixed contact associated with resistor 304 to form a time constant circuit with capacitor 301 and resistor 304, thus establishing a 1 3 fixed exposure period for operating a comparator 305. Fig. 213 shows an automatic exposure control circuit 306 and a battery check circuit 307 which are selectively connected across a battery through changeover switch 308.

Itwill ' be appreciated that such additional means which are connected through changeover switches cannot operate properly if the switch fails. In addi tion, the failure of such switch may prevent a proper functioning of the shutter circuit.

On the other hand, when an electric flash unit and/or date entry unit is mounted on a camera which incorporates an electrical shutter, a signal which actuates a selected unit is derived from X contact switch which is provided on part of the camera.

Referring to Fig. 3, an illumination initate signal to an electric flash unit 150 or an entry initiate signal to data entry unit 151 is provided by X contact switch SW1 5 which is closed when the shutter is in the fully open position. Electronic flash unit 150 includes a power source 152 across which a main capacitor 153 and a flash discharge tube 154 as well as a series circuit including resistor 155 and an illumination test switch SW14 are connected in parallel. The switch SW14 is shunted by a series circuit including a trig ger capacitor 156 and a trigger transformer 157. The X contact switch SW15 is connected in parallel with switch SW14. Consequently, when X contact switch SW1 5 is closed, the trigger circuit is driven to pro vide an electronic flash illumination in synchronized relationship with the fully open condition of the shut ter, thereby permitting flash photography. When it is desired to testthe electronic flash unit 150, a test button (not shown) is depressed to close switch SW14to see if the electronic flash unit 150 operates 100 properly. It will also be noted that data entry unit 151 is also connected with switch SW15, the closure of which achieves a data entry.

However, when switch SW1 5 is connected in common with electric flash and data entry units 150, 105 151 as shown, the closure of test switch SW14 not only initiates an illumination by electronic flash unit 150, but also achieves a data entry by unit 151.

Therefore, if a picture is taken under flash-light illumination subsequent to such illumination test, data entry unit 151 will be operated for the second time to provide a double data entry, causing a blur ring of data and an overexposure.

A first embodiment of the present invention is illustrated in Figs. 4to 13 of the accompanying draw ings and will now be described.

Referring to Fig. 4 a gear 2 is integrally formed on the lower end of a charging member 3 which is in the form of a hollow shaft and has a journal 3a which is rotatably received in a basepl ate 1. A shaft 4 is rotat ably received in the charging member 3 and has a disc-shaped shutter drive member 5 secured to the top end thereof. A prime mover spring 6 is disposed on the member 3, and has its lower end 6a (see Fig.

5) engaged with one end of a stop arm 3b which is formed on the upper end face of the journal 3a and extending in a direction perpendicular to the plane of Fig. 5. Spring 6 has its upper end 6b (see Fig. 5) engaged in a notch 5a formed in the periphery of shutter drive member 5. In this manner, the spring 6130 GB 2 090 667 A 3 provides an operative connection between charging member 3 and shutter drive member 5.

Gear 2 is operatively connected with a film winding mechanism, not shown, which may have a known arrangement, and is adapted to rotate in a direction indicated by an arrowa shown in Fig. 5 in response to a film winding operation. Gear 2 is engaged by ratchet pawl 9 which is mounted on stud 7 and urged by coiled spring 8 into engagement with the gear, thus preventing rotation of gear 2 in the opposite direction from that shown by the arrowa.

As shown in Fig. 5, shutter drive member 5 is peripherally formed with an arm 5b, against which a detent arm 10a abuts, the arm 10a being formed as one arm of detent member 10 which defines the start position of the shutter drive member. As shown in Figs. 4 and 5, detent member 10 is in the form of a lever which is pivotally mounted on pin or screw 11. In Figs. 4 and 6, the detent arm 10a has an edge 1 Ob which represents a bevelled surface extending in an oblique direction downwardly and to the left as seen in Fig. 4, thus providing a linear contact against one lateral edge of the arm 5b. The detent member 10 has another arm 1 Oc which extends in the opposite direction from detent arm 10a and which has an armature piece 14 secured to its free end by means of pin 2, the armature piece 14 being adapted to be held attracted to shutter release electromagnet Mgl. The arm 10c is engaged by coiled tension spring 13, which normally urges detent member 10to rotate clockwise about pin 11. As a consequence, the edge 1 Ob of the detent arm 10a is brought into abutment against arm 5b while armature piece 14 is in abutment against the mating surface of electromagnet Mg11.

In the present embodiment, the electromagnet Mgl comprises a combination of a permanent magnet 15 and a coil 16, and thus forms a release electromagnet. Specifically, permanent magnet 15 is held between a pair of core limbs 17a, 17b, and coil 16 is disposed on limb 17a. Usually, the magnetic force from permanent magnet 15 holds the armature piece 14 attracted to the ends of the limbs, thus constraining it. However, when coil 16 is energized to magnetize the electromagnet comprising the core limbs in a direction to counteract the magnetic force from permanent magnet 15, the armature piece 14 is released from its constraint. The exciting current may be a current pulse.

Located in the path of rotation of arm 5b of the drive member 5 is controller 24b formed on one arm 24a of another detent member 24 and which is engaged by arm 5b when shutter blades 33,34, to be described later, assume their fully open positions.

The detent member 24 is in the form of a leverwhich is pivotally mounted on a pin or screw 25 secured to the baseplate 1. Controller 24b is in the form of an upstanding piece formed at the free end of arm 24a. The detent member 24 has another arm 24c which extends in the opposite direction from the arm 24a and which has an armature piece 27 secured to its free end by means of pin 26, the armature piece 27 being held attracted to an electromagnet Mg2 which controls the shutter closing operation. Electromagnet Mg2 comprises a channel-shaped core 28 and an 4 exciting coil 39. When the coil 39 is energized, the armature piece 27 is held attracted to the core 28 whereby to constrain it, but it is freed when the coil is de-energized.

The arm 24c is engaged by helical tension spring 19, which normally urges the detent member 24 to rotate counter-clockwise about pin 25. As a conse quence, the controller 24b is located in the path of movement of the arm 5b and the armature piece 27 is held in abutment againstthe mating surface of electromagnet Mg2. Pin 25 is fixedly mounted on the upper surface of detent member 24 and pivotally mounts an engagement control member 40, which is formed with a projecting edge 40a which is located adjacentthe controller 24b on the side thereof which is advanced, as viewed in the counter-clockwise rotation of the arm 5b, and which extends into the path of rotation of the arm 5b. On its side remote from the controller 24b, the edge 40a has a bevelled surface 40b, the arrangement being such that as the arm 5b rotates counter-clockwise, it initially bears againstthe bevelled surface 40b and causes clock wise rotation of the control member 40 about pin or screw 25, and then engages the controller 24b. Con troi member 40 and detent member 24 are opera tively connected together by means of spring 41 so as to form a double lever. Specifically, spring 41 comprises a torsion spring disposed on pin or screw and has its one end engaged with an upstanding piece 24d formed along one lateral edge of the arm 24c, and has its other end engaged with extension 40c projecting in a direction at right angles to the edge 40a. Consequently, control member 40 is urged to rotate counterclockwise about pin or screw 25, but the resulting rotation is blocked normally bythe 100 abutment of extension 40c against upstanding piece 24d to maintain the projecting edge 40a in the path of rotation of arm 5b.

As shown in Fig. 5, the charging member 3 is formed with notch 3c which can be engaged by a film locking hook 42, at a position outwardly of stop arm 3b which is engaged by the lower end 6a of the spring 6. Hook 42 is pivotally mounted on stationary pivot stud 43 and is urged to rotate counter clockwise about stud 43 by a helical tension spring 44 which engages the rear end thereof. As shown in Fig. 7, hook 42 has an inverted L-configuration extending from the pivoted end, and has a hook end 42a which is adapted to engage notch 3c. An upright piece 42d extends vertically upward from the lateral edge of the hook located nearerthe charging member 3 intermediate its length, and is formed with a release arm 42b which is bent from its upper end to extend toward the path of rotation of arm 5b. Release arm 42b is formed with bevelled edge 42c which extends nearerthe charging member 3 as viewed in the direction of rotation of arm 5b. Thus arm 5b is cap able of engaging bevelled edge 42c to rotate the hook 42 clockwise about pivot stud 43, thus moving the hook end 42a out of notch 3c. However, the resilience of spring 44 normally urges hook 42 to rotate counter-clockwise about pivot stud 43, as shown in Fig. 5, whereby hook end 42a engages notch 3c to prevent rotation of charging member 3 and thereby perform a film locking function. Under GB 2 090 667 A 4 this condition, the bevelled edge 42c is located in the path of rotation of arm 5b.

As shown in Figs. 4 and 5, a normally open switch SW2 comprising resilient blades 45a, 45b is dis- posed adjacent to but outwardly of upright piece 42d. The purpose of switch SW2 is to disconnect the shutter circuit from a power source upon termination of a film winding operation. The switch is closed by upright piece 42d when hook 42 rotates clockwise about pivot stud 43, and is opened upon termination of a film winding operation when hook 42 rotates counter-clockwise about pivot stud 43 and hook end 42a engages notch 3c.

Fig. 4 shows shutter release member 18 which is a vertically elongate member having a pair of vertically spaced elongate slots 18b, 18c formed therein, which are fitted over stationary pins 20, 21, thus enabling a sliding movement thereof in the vertical direction. Release member 18 is pulled upwardly by helical spring 22, and the extent of such movement is defined by the ends of slot 18c engaging the stationary pin 21. Shutter release button 23 is fixedly attached to the top end of release member 18.

A drive pin 29 is fixedly mounted on the upper end face of shutter drive member 5 adjacent to the periphery in the upper- right-hand region thereof, as viewed in Fig. 5. Pin 29 fits in an elongate opening 30b defined by a horizontally extending U-shaped portion 30a formed at the lower end of connecting link30, as shown in Fig. 4. It isto be understood that only the lower portion of connecting link 30 is shown in Fig. 5.

As indicated in Fig. 4, connecting link 30 is pivotally mounted on a stud 31, and fixedly carries on its upper end a pin 32 which fits simultaneously in elongate slots 33a, 34a, which are formed in one end of shutter blades 33,34 respectively. These shutter blades 33,34 are pivotally mounted on separate studs 35,36 and close a photographing optical path 37 under the conditions shown in Fig. 4. Shutter blades 33,34 constitute together a so-called vario type shutter, and open or close the optical path 37 in accordance with the oscillating motion of connecting link 30 about stud 31 as the shutter drive member 5 rotates under the resilience of spring 6 to move drive pin 29.

As shown in Fig. 4, the shutter release member 18 is formedMith a step 18d adjacent its top end and on the left-hand side thereof, and a normally open shut- ter release switch SW1 comprising resilient blades 38a, 38b is disposed below step 18d. The switch SW1 remains open under the conditions shown in Fig. 4.

Fig. 11 shows an electrical shutter circuit which automatically controls the described shutter mechanism. Referring to Fig. 11, a pair of positive and negative lines El, E2 are connected across the positive and negative terminals of power source E. Connected across these lines are a series circuit including the shutter release switch SW1 and resis- tors R1, R2; another series circuit including transistor Q4, resistor R5 and starting transistor Q1; and a further series circuit including a power supply connection transistor Q2 in the form of a controlled semiconductor rectifier resistor R6 and resistor R7.

Transistor Q2 has its anode connected with line E1 i 1:

GB 2 090 667 A 5 and its cathode connected with resistor R6 while its gate is connected with the collector of transistor Q4. Connected across the gate and line El is a parallel combination of resistor R4 and switch SW2. Resistor R3 is connected between the base of transistor Q4 and line El.

Capacitor C5 is connected across lines El, E2 through a discharge preventing transistor Q1 0 in the form of afield effect transistor FET. Capacitor C5 is normally charged from the source E, and discharges in a pulse manner through electromagnet Mg11 when shutter release button 23 (see Fig. 4) is depressed to close switch SW1, provided the source voltage is at or above a given value, thus demagnetizing magnet Mg11 to start the shutter mechanism.

A common line E3 is connected with line E2 through switching transistor Q3. Connected across lines E3 and El are a shutter control circuit as well as electrical circuits of accessories such as a self-timer circuit and battery check circuit. Transistor Q3 has its collector connected to line E3, its emitter connected to line E2 and its base connected to the junction between resistors R6, R7, thus connecting the line E3 with line E2 when transistor Q3 is rendered conductive. As a consequence transistor 03 essentially constitutes a power switch.

A source voltage decision circuit is connected across lines E3 and El, and includes a regulator circuit Al which forms a constant voltage source, a voltage divider including resistors R8, R9, a comparator A2 which essentially forms a decision circuit, and resistor RV1 which establishes a given source voltage level. Resistor R10 is connected between the output of comparator A2 and line El, and a source disconnection circuit including a series circuit of a resistor Rl 1 and a diode D3 is connected between the output terminal of the comparator A2 and the base of transistor G4. The decision circuit is followed by a series circuit including normally open switch SW5 which is closed during flash photography, and resistors R13,R14 as well as a series circuit including resistor R1 5 and transistor Q7 and which provides a long exposure period. Then follows a series circuit including time constant capacitor Cl, light receiving element P1 which may comprise a photoelectric transducer element such as CdS or the like, and semi-fixed resistor RV2; a voltage divider including semi-fixed resistor RV3 and resistor R19; and a photometric circuit which includes comparator A3.

The junction between capacitor Cl and element P1 is 115 connected through resistor Rl 6 to one input of comparator A3 while the junction between resistors RV3 and Rl 9 of the voltage divider is connected to the other input of comparator A3. Diode D1 is connected across the junction between capacitor Cl and element P1 and the line E3. Connected between the same junction and the line El is transistor Q5, which forms a trigger switch,in parallel relationship with the capacitor Cl. Resistor Rl 8 is connected between the base of transistor G5 and line El, and the base is connected to resistor R19 through which an operating signal from comparator A6, to be described later, is applied. An exposure correction circuit formed by a series combination of switch SW4 and capacitor C2 is connected across capacitor Cl, and switch SW4 is closed whenever it is desired to change the exposure factor. Magnet Mg2 is connected between the output of comparator A3 and line El. A disconnection circuit formed by a series combination of resistor R20 and diode D4 is connected between the comparator A3 and the base of transistor Q4. The disconnection circuit serves to turn off transistor Q2 through transistor Q4 in response to a signal from comparator A3 whenever magnet Mg2 is de-energized. The light input to element Pl is supplied through a diaphragm Gl.

The photometric circuit is followed in turn by a voltage divider including series resistors 13211,1322; another series circuit including comparatorA4, light emitting element P2 formed by light emitting diode, resistor R24 and transistors 08, Q9; a time constant circuit including capacitor C3 and resistor R27; and a self-timer circuit formed by diode D2. The junction between resistors R21 and R22 is connected to one input of comparator A4 while capacitor C4 is connected to the other input of comparator A4 and to line El. Resistor R23 is connected between the other input of comparator A4 and the outputthereof, and the outputterminal is also connected to the base of transistor 09. Transistor Q8 has its base connected with the final stage comparator A6, which will be described later, so as to be turned off in response to a signal from comparator A6 when magnet Mgl is energized. The purpose of the time constant circuit formed by capacitor C3 and resistor R27 is to establish a delay time for the self-timer, and it is connected between the fixed contact SW3c of changeover switch SW3 and line E3. The junction between capacitor C3 and resistor R27 is connected through resistor R28 to one input of comparator A6.

The self-timer circuit is followed by a battery check circuit, which comprises comparator A5 which determines the source voltage, and a voltage divider formed by resistors R25,R26. These series resistors are connected between the fixed contact SW3d of switch SW3 and line E2, and the junction between these resistors is connected with an input of comparator A5. An operating voltage for comparator A5 is supplied through the contact SW3d and line E2, and its outputterminal is connected to the junction between the collector of transistor Q8 and resistor R24.

The final stage is formed by an electromagnet drive circuit which activates shutter release electromagnet Mgl. It comprises a voltage divider formed by resistors R29,R30, comparator A6, electromagnet Mgl, and transistor Q6. The junction between resistors R29, R30 is connected to the other input of comparator A6 while electromagnet Mgl is connected to the output terminal of comparator A6 as shown. Transistor Q6 has its emitter connected to line El and its collector connected to the junction between capacitor C3 and resistor R27 while its base is connected through resistor Rl 2 to the output of comparator A2. It should be noted that the line El which is connected to the positive terminal of the source E is connected to ground.

The changeover switch SW3 comprises a rotary switch having a selection knob which is turned for enabling operation of the self-timer and for checking 6 the battery voltage. Specifically, it includes four fixed contacts, including battery check contact SW3d, automatic exposure contact SW3a, clear contact SW3b and self-timer contact SW3c, over which its movable contact SW30 can be moved in a rotary fashion. It will be noted that automatic exposure contact SW3a has no connection whatsoever,.jhile clear contact SW3b is connected to the gate of trans istor 02. The mechanical construction of the switch SW3 is shown in Fig. 12. Referring to this Figure, it includes an electrically insulating substrate 46 on which fixed contacts SW3c, SW3b, SVJ3d are formed as by conductive foil which are printed thereon. An insulating member 48 is used to fixedly mount the movable contact SW30 on a rotary shaft 47 which is rotatably mounted in the substrate 46. As shown, the movable contact SW30 is formed with three sliding contact pieces SW301, SW302, SW303, and fixed contacts SW3c, SW3b, SW3d are disposed on the paths of rotation of these sliding contact pieces.

It will be seen that sliding contact SW301 is located most close to the shaft 47 and is normally main tained in contact with an arcuate, common fixed con tact SW3e, which is connected to line El to supply an operating voltage to the other fixed contacts through 90 the movable contact SW30 when switch SW3 is selectively turned.

Fixed contact SW3c is located externally of the common contact SW3e and toward the left-hand side, as viewed in Fig. 12, for engagement with slid95 ing contact piece SW302. Fixed contact SW3d is located on the opposite side from contact SW3c or on the right-hand side, as viewed in Fig. 12, for engagement with sliding contact pieces SW302 and SW303. Fixed contact SW3b is located externally of 100 fixed contact SW3c, but more close to fixed contact SW3d, for engagement with sliding contact piece SW303. The automatic exposure contact may be considered as located intermediate the fixed con tacts SW3b and SW3d.

It will be noted that the right-hand end of the self timer contact SW3c has a circumferential overlap vOth the left-hand end of the clear contact SW3b over a length L When the movable contact is located in such overlap region, sliding contact piece SW302 engages fixed contact SW3c at the same time as slid ing contact piece SW303 engages fixed contact SW3b. The basic idea of this arrangement is that the shutter circuit of the invention is constructed such that an automatic exposure mode is established except during the battery check mode and the self timer mode. The purpose of such arrangement will be appreciated if one considers a situation in which the shutter release button is depressed after establ ishing the self-timer mode, but it is desired to stop the photographing operation by returning the change-over switch SW3. An automatic exposure mode will then be automatically established, thus causing an immediate shutter release operation. To preventthis, when switch SW3 is returned afterthe 125 self-timer mode has been once established, contact SW30 moves over clear contact SW3b when it moves through the overlap region/ where it engages both the self-timer contact SW3c and the clear con tact SW3b, thus disconnecting the circuit from the GB 2 090 667 A 6 sourceto resetthe shutter circuit to its initial condition. Consequently, a shutter release cannot occur unless the shutter release button is depressed once again. The shaft 47 extends above the top surface of the camera where selection knob 50 is secured thereto so as to be turned into alignment with indices A, B and S which represents the automatic photographing, battery check and self-timer mode, respectively.

The operation of electrical shutter will now be described. Figs. 4 and 5 show the shutter mechanism in its charged condition after the completion of a film winding operation. Spring 6 is charged to urge shutter drive member 5 to rotate counter-clockwise, but such movement is constrained by the abutment of arm 5b against the detent portion 10b of the detent member 10 which is constrained by shutter release electro-magnet Mgl. Thus, drive member 5 is maintained in its start position. The bevelled surface of the detent edge 10b is urged in the upward direction by the arm 5b under this condition.

When it is desired to take a picture in the automatic exposure mode, the selection knob 50 may be moved into alignment with the index A and the shutter release button 23 depressed. As shown in Fig. 12, when knob 50 is aligned with index A, the movable contact SW30 engages none of the fixed contacts. Also, the two shutter blades 33,34 are closed as shown in Fig. 4. The depression of shutter release button 23 causes release member 18 to move downward, with its step 18d closing release switch SW1. Then transistor Q1 is turned on in the electrical circuit shown in Fig. 11, and the conduction of this transistor bypasses the anode to gate path of transistor Q2 to turn it on, thus turning the next following transistor Q3 on. At this time, transistor 04 remains off. Since transistor Q2 comprises a controlled semiconductor rectifier as mentioned previously, it continues to conduct even if release switch SW1 is turned off after its conduction has been initiated, thus maintaining transistor Q3 on to maintain the circuit connected with the source E.

When transistor Q3 is turned on, the source voltage is applied across lines El, E3. Initially, the source voltage is checked by regulator circuit Al, comparator A2 or the like. If the detected value is lower than a preselected reference value, the final stage transistor contained in comparatorA2 conducts to draw a base current from transistor Q4 through diode D3 and resistor R1 1, thus turning it on to short-circuit the anode to gate path of transistor G2 to render it non-conductive. Thereupon, the base current ceases to be supplied to transistor 03, which is therefore turned off. This interrupts the connection of the lines E3, E1 with the source, so that the circuit is reset and cannot operate.

However, when the source voltage is found to be higher than the preselected reference value, the final stage of comparator A2 remains off, and hence transistor G4 is maintained off. Since transistor Q6 is off at this time, the voltage across resistor R27 is zero, whereby a negative input is applied to the negative or non-inverting input of comparator A6 which is of a higher potential than that applied to its positive or inverting input. Thus an NPN transistor 7 contained in the final stage of comparator A6 is turned on. Thereupon, the charge on capacitor C5 is discharged through the shutter release electromag net M91 in pulse-like manner, thus counteracting the attraction of the permanent magnet 15.

Upon demagnetization, the armature piece 14 which has been constrained by the electromagnet Mgl as shown in Fig. 4 is freed, so that arm 5b pushes out the detent edge 1 Ob under the force of spring 6to cause detent member 10to rotate counter-clockwise about the screw 11, thus starting the shutter drive member 5. When the detent is released, the bevelled surface of the detent edge 1 Ob presents a reduced frictional resistance with respect to arm 5b, thus assuring a facilitated disengagement thereof.

When drive member 5 rotates in the direction of arrow a shown in Fig. 5 and reaches its position shown in Fig. 9, drive pin 29 which is integral there with causes connecting link 30 to be rocked from its position shown in Fig. 4 towards its position shown in Fig. 8, whereby shutter blades 33,34 co-operate with each otherto begin opening. The photograph ing optical path 37 is completely opened as shown in Fig. 8, when arm 5b pushes away the projecting edge 40a of control member 40 and is locked by con trol ler 24b (see Fig. 9).

When arm 5b pushes away the projecting edge 40a, control member 40 rotates clockwise about the stud 25 against the resilience of the associated spring 41 whose ends are moved apart to facilitate movement of the detent member 24 away from the electromagnet M92. Since arm 5b abuts against the bevelled edge 40b before it is locked by controller 24b, it does not abut against the controller 24b with 100 an increased force, thus achieving a smooth locking action and assuring a full opening of shutter blades 33,34 without causing bouncing thereof.

Atthe same time that comparatorA6 supplies energizing curreritto electromagnet Mgl, an off signal is applied from comparator A6 to the trigger transistor Q5, shown in Fig. 11, through resistor R19.

This turns transistor Q5 off, initiating the operation of the photometric circuit. The circuit performs an integration of the amount of reflected light from an object being photographed by the time constant cir cuit including capacitor Cl, light receiving element P1 and resistor RV2. The integral is applied to corn paratorA3. The time constant circuit has a time con stant which is determined by Cl' x (RCdS + RV2') where RUs represents the resistance of element P1 which corresponds to the amount of light received, Cl'the capacitance of capacitor Cl and RV2'the resistance of semi-fixed resistor RV2. It will be seen that a proper exposure period for the object being photographed is determined by the time interval required for capacitor Cl to be charged to a level which is sufficient to provide an input to the negative or inverting input of comparator A3 which equals the potential at the junction between resistors RV3, Rl 9 125 which is applied to the positive or non-inverting input of the comparator A3, whereupon comparator A3 operates to de-energize electromagnet Mg2, thus closing the shutter. As described previously, when transistor Q3 was turned on, the magnet M92 was GB 2 090 667 A 7 immediately energized to constrain the armature piece 27, and thereby constrain the detent member 24. However, when it is de-energized, the constraint is removed, so that detent member 24 is free to rotate clockwise about stud 25 since its controller 24b is urged by arm 5b as shown in Fig. 9. Thus, controller 24b is retracted out of the path of rotation of arm 5b. When drive member 5 rotates counterclockwise from the position shown in Fig. 9 to the position shown in Fig. 10, it abuts against the lateral side of stop arm 3b where its rotation is interrupted. Shutter blades 33,34 begin to close the shutter opening when drive member 5 moves past the position shown in Fig. 9, and the optical path 37 is completely closed when drive member 5 reaches its stop position.

Where an object being photographed is under such a bright illumination as to energize control electromagnet Mg2 only fora brief period of time, detent member 24 can be angularly moved underthe resilience of spring 41 to permit rotation of arm 5b without it abutting against controller 24b since arm 5b initially pushes away the bevelled edge 40b to rotate control member 40 about stud 25 to move both ends of the spring 41 apart from one another, thus allowing its resilience to rotate detent member 24 clockwise about stud 25. Consequently, a high speed shutter operation is enabled without causing g reduction in the speed of rotation of drive member 5.

When electromagnet Mg2 is de-energized, comparator A3 draws a base current from transistor Q4 through resistor R20 and diode D4, thus shortcircuiting the anode to gate path of transistor 02 to render it non- conductive and turning transistor G3 off. This interrupts the connection of the electrical circuit with the source by rendering the transistor Q2 non-conducting.

Arm 5b pushes away the bevelled edge 42c of hook 42 immediately before it abuts against the stop arm 3b, and hence hook 42 is rotated clockwise about stud 43 to have its hood end 42a disengaged from notch 3c, as shown in Fig. 10. The angular movement of hook 42 enables its upstanding piece 42dto close switch SW2, which short-circuits the anode to gate path of transistor Q2 to turn it off, again interrupting the connection with the source.

It will be seen that the connection with the source which is achieved by transistor Q2 is interrupted at the end of the shutter operation by two separate means, namely transistor G4 and switch SW2, respectively. However, it will be seen that at least one means, for example, the provision of switch SW2, is sufficient. However, the short-circuiting action by transistor 04 is provided for added assur- ance. It is intended that switch SW2 be effective to interrupt the connection with the source until a film winding operation has been completely terminated. In other words, the depression of the shutter release button does not initiate a shutter operation unless this switch is so operated and released. The provision of transistor Q4 is obviously necessary forthe interruption of the source connection under a reduced source voltage condition.

When film winding takes place afterthe termina- tion of an automatic exposure with the electrical 8 GB 2 090 667 A 8 shutterof the invention, gear2 is rotated and its integral stop arm 3b angularly drives the lovier end 6a of spring 6, which in turn causes shutter drive member 5 to rotate until its arm 5b bears againstthe bevelled surface 10b of detent member 10. When such position is reached, drive member 5 is maintained stationary in its start position. Only gear2 continues to rotate to charge spring 6. When the rotation of charging member 3 brings notch 3c formed in the region of its journal 3a into alignment with the hook end 42a, book 42 rotates counterclockwise about stud 43 under the force of the associated spring 44, causing the hook end 42a to be engaged in notch 3c to lock the film, where charging member 3 ceases to rotate. In this manner, at the end 80 of the film winding operation, the various members return to their initial positions shown in Figs. 4 and 5 in preparation for a subsequent photographing operation.

It is to be noted that hook 42 has an important role 85 in the shutter arrangement of the invention. Towards the end of a film winding operation the hook 42 engages notch 3c to block the rotation of gear 2 immediately before stop arm 3b would engage the arm Eb. This means that arm 5b is normally only urged by the charged spring 6 to rotate and push out the detent edge 10b when it is in abutment against the latter. Otherwise the shutter mechanism might start to operate if the stop arm 3b were to apply an undue force upon arm 5b accidentally. This is prevented by the engagement of hook 42 with notch 3c immediately before stop arm 3b would abut against arm 5b, thereby interrupting the rotation of charging member 3 and gear 2 to charge the spring 6.

When it is desired to change an exposure factor which is used during the automatic exposure mode, exposure correction switch SW4 shown in Fig. 11 may be closed. When it is closed, capacitor C2 is connected in shuntwith capacitor Cl in the time constant circuit of the photometric circuit, and hence 105 the total capacitance increases to Cl + C2 or the exposure period is modified to (Cl + C2)/Cl times the original value.

A lengthened exposure period can be established during flash photography by closing switch SW5. The closure of this switch renders transistor C17 conductive, connecting resistor Rl 5 in shunt with the series circuit comprising light receiving element P1 and resistor RV2. Thus, while the photometric circuit will operate in response to the illumination level of natural light when the original series circuit is used, the connection of resistor R15 establishes an exposure period determined by the resistance of resistor R15, for example, 1130 sec..

When the use of the self-timer is desired, selection knob 50 (Fig. 12) maybe turned into alignment with the self-timer index S before shutter release. This changes swtich SW3 so that movable contact SW30 engages fixed contact SW3c. Referring to Fig. 11, the timer circuit or time constant circuit comprising capacitor C3 and resistor R27 is then connected across lines El and E3, so that the operation of comparator A6 is delayed by a time interval, of for example, 15 seconds, which is preset in the self-timer, commencing from the turning on of transistor Q3 in 130 response to the depression of the shutter release button 23. During the delay time, the electromagnet M91 is not energized, so that an on signal is applied from comparator A6 to transistor Q8 to render it conductive. When this transistor is turned on, a blocking oscillator is formed by comparator A4, capacitor C4, resistor R23 and transistor Q9, and produces an outputwhich causes flashing of a luminescent display comprising light emitting element P2 and resistor R24. During the time the element P2 flashes, it indicates that the self-timer is in operation. The period of flashing operation is determined by a time constant of capacitor C4 and resistor R23 as well as the ratio of resistors R21,R22. When the selftimer times out, comparator A6 and electromagnet Mg11 operate to achieve an automatic exposure operation as mentioned previously.

When it is desired to interrupt a photographing operation employing the self-timer before the selftimer has timed out, by turning selection knob 50 to the automatic exposure position, movable contact SW30 then engages fixed contact SW3c and clear contact SW3b simultaneously as switch SW3 is broughtto the automatic exposure position, whereby the connection of the electrical circuit with the source E is interrupted, returning the circuit to its initial condition. Though movable contact SW30 engages clear contact SW3b during its movement, it cannot be locked in that position, so that knol> 50 cannot remain in alignment with the clear index C.

When it is desired to check the source voltage, selection knob 50 may be turned into alignment with the battery check index B. Then, switch SW3 is changed, bringing movable contact SW30 into con- tact with fixed contact SW3d. At this time, the battery check circuit including comparator A5, resistors R25, R26, light emitting element P2 and resistor R24 is connected across the source E, independently of the remainder of the circuit. If the source voltage is equal to or above a given reference value, element P2 is illuminated, but does not do so if it is belowthe reference value. In this manner, an indication is provided whether or notthe battery is usable.

In the described arrangement, FET transistor Q1 0 is used and is turned off when the transistor Q3 is turned on in orderto avoid capacitor C5 being discharged when transistor Q3 is turned on. However, transistor G1 0 can be replaced by a series combination of a diode Do and resistor Ro as shown in Fig.

Claims (14)

13. This prevents the terminal voltage of capacitor C5 from being added to the source voltage during the battery check and assures a reliable battery check operation. CLAIMS

1. An electrical shutter of the electromagnetic release type fora camera, comprising a charging member, a prime mover spring and a shutter drive member adapted to be rotated about a single shaft, the charging member being adapted to be rotated in response to a film winding operation and arranged to charge the prime mover spring for driving the shutter drive member which is arranged to open and close shutter blades by being rotated through substantially one revolution by the prime mover spring in response to an electromagnetic release operation, X 1_ 1 al 1 9 a first detent member adapted to engage the shutter drive memberto maintain it stationary at its starting position before a shutter release is operated to effect said electromagnetic release operation, a second detent member for determining an exposure period and adapted to engage the shutter drive memberto maintain it temporarily at an intermedate position at which the shutter blades are in an open position and to be subsequently disengaged therefrom, means for moving the first detent member and the second detent member into their respective shutter drive member engaging positions prior to rotation of the charging member in response to a film winding operation to charge the prime mover spring, and the first detent member having a bevelled surface for abutment againstthe shutter drive member when at its starting position to provide a linear contact therewith whereby to facilitate disengagement of the first detent member from the shutter drive member under rotating force of the shutter drive member when the shutter drive member is to be released.

2. An electrical shutter as claimed in claim 1, in which said means for moving the first detent member and the second detent member into their respective shutter drive member engaging positions 90 comprise a first spring acting on the first detent member and a second spring acting on the second detent member.

3. An electrical shutter as claimed in claim 1 or2, in which the first detent member has a detent arm for engagement with the shutter drive member and a second arm arranged to be attracted by a first electromagnet to retain the detent arm in engagement with the shutter drive member to maintain it in its starting position, the first electromagnet being arranged to be effectively demagnetised in response to operation of said shutter release.

4. An electrical shutter as claimed in claim 3, in which the detent arm of the first detent member comprises a bevelled surface for engaging the shutter drive member at its starting position and to provide a linear contact therewith whereby to facilitate disengagement of the detent arm from the shutter drive member under rotating force of the shutter drive member when the shutter drive member is to be released.

5. An electrical shutter as claimed in claim 1, 2 or 3, in which the second detent member is retained in its shutter drive member engaging position by a second electromagnet which is arranged to be energised for a period of time determined by a photometric circuit responsive to light from a subject being photographed.

6. An electrical shutter as claimed in claim 5, in which the second detent member comprises a fourth rocking lever which has a first arm adapted to engage the shutter drive member, and a second arm carrying an armature piece arranged to be attracted by the second electromagnet, and a second control member mounted for pivotal movement relatively to the fourth rocking lever and having a bevelled surface to be engaged by the shutter drive member before the first arm is engaged thereby and resiliently urged relatively to the fourth rocking lever in a direction opposite that in which it is displaced by GB 2 090 667 A 9 engagement with the shutter drive member whereby to act as a shock absorber against impact of the shutter drive member on the first arm of the fourth rocking lever.

7. An electrical shutter as claimed in any of claims 1 to 6, in which the charging member comprises a sleeve formed by a hollow shaft and fixedly carries on its lower end a gear which is rotated in response to a film winding operation.

8. An electrical shutter as claimed in any preceding claim, in which the shutter drive member is in the form of a disc which is peripherally formed with a radially projecting arm, and in which the first detent member and the second detent member are arranged to engage the projecting arm of the shutter drive member.

9. An electrical shutter as claimed in claim 8, in which the shutter drive member disc carries on its upper surface a drive pin for engagement with a connecting link to drive the link in an oscillating motion to open and close the shutter blades as the shutter drive member is rotated.

10. An electrical shutter as claimed in claim 7,8 or 9, in which the prime mover spring is disposed around the hollow shaft sleeve of the charging member and is located axially between a disc portion of the charging member and the disc of the shutter drive member and radially between said sleeve and a stop arm extending axially from the disc por- tion of the charging member into the path of rotation of the projecting arm of the shutter drive member for engagement therewith at the completion of a shutter closing operation, and in which a film locking hook member having a hook end engageable in a notch in the periphery of the charging member has an arm extending into the path of the projecting arm of the shutter drive memberto be displaced by said projecting arm at the completion of a shutter closing operation to disengage its hook end from said notch to free the charging member for rotation in response to a film winding operation, rotation of the stop arm upon subsequent rotation of the charging member in response to a film winding operation permitting further rotation of the shutter drive memberto bring said projecting arm out of engagement with the arm of the film locking hook member and into engagement with the first detent member at its starting position, the hook end of the film locking hook member being resiliently urged into engagement in the notch of the charging member when a film winding operation has been completed.

11. An electrical shutter as claimed in claim 3 and in any of claims 2to 10, in which the firstelectromagnet contains a permanent magnet and has a coil adapted when energised to oppose the permanent magnet.

12. An electrical shutter as claimed in claim 11, including an electrical circuit including a shutter circuit comprising first and second electromagnets controlling respectively shutter opening and shutter closing operations and a photometric circuit for determining exposure periods, a common line for supplying an operating voltage to the shutter circuit, and connection means including normally open switch means for connecting to the common line accessory electrical circuits such as a fixed exposure period enable circuit, a circuitwhich modifies an exposure factorwhen taking a picture under very bright light, a battery check circuit, and an electronic 5 self-timer circuit.

13. An electrical shutter of,.he electromagnetic release type for a camera, constructed and arranged and adaptedto operate substantially as hereinbefore particularly described with reference to and as illus10 trated in Fig. 4 to 12 of the accompanying drawings.

14. An electrical shutter as claimed in claim 13, inciudingthe modification hereinbefore particularly described with reference to and as illustrated in Fig. 13 of the accompanying drawings.

Printed for Her Majesty's Stationary Office byTheTweeddate Press Ltd., Berwick-upon-Tweed, 1982. Published at the Patent Office, 25 Southampton Buildings, London, WC2A IlAY, from which copies may be obtained.

GB 2 090 667 A 10 1 A 1