GB2272532A

GB2272532A - Electromagnetic shutter apparatus

Info

Publication number: GB2272532A
Application number: GB9300765A
Authority: GB
Inventors: Jaekyeong Seo; Deogho Choi; Seonho Lee
Original assignee: Samsung Aerospace Industries Ltd
Current assignee: Hanwha Aerospace Co Ltd
Priority date: 1992-11-10
Filing date: 1993-01-15
Publication date: 1994-05-18
Anticipated expiration: 2013-01-15
Also published as: FR2697924B1; DE4302389C2; KR970011200B1; FR2697924A1; RU2103709C1; KR940012035A; CN1090395A; GB2272532B; JP2868965B2; GB9300765D0; DE4302389A1; JPH06324378A

Description

2272532 ELECTROMAGNETIC SHUTTER APPARATUS The present invention relates to

an electromagnetic shutter apparatus, more particularly to an electromagnetic shutter apparatus of which ' ' a electromagnetically.

shutter blade is operated open and closed functions of a shutter blade is carried out by controlling a direction and a time of an electrical current which flows through an electromagnet in an electromagnetic shutter apparatus. Such the electromagnetic shutter apparatus has a simple construction compared with a mechanical shutter which uses an electrical force of a spring.

U.S. - Pat. No. 4,881,093 by David R. Dowe discloses an electromagnetically operated shutter assembly for a camera which includes permanent magnets which are affixed to shutter blades.

An electromagnetic field is generated by a number of armatures

1 which interacts with the permanent magnets to cause the shutter I$ blades to move between open and closed positions. The configurations of the permanent magnets and armatures permit the blades to be held in the open and closed positions without the further application of current to the armatures. Also, the permanent magnets are levitated by the electromagnetic field in order to facilitate movement of the shutter blades between the opening and closing positions. However, the shutter in accordance with the present invention cannot be applied to an automatic focusing and exposure camera.

Unlike this, in Japanese Pat. Publication No. 90-33130, there is described an electromagnetically operated shutter mechanism in which a first moving coil member for moving a shutter blade and an second moving coil member for deciding an open degree of the shutter blade are positioned between an affixed permanent magnet and an yoke at an opposing position of the permanent magnet, and an operation of both moving coil members is carried out at a predetermined time differ@nce, so 2 that the automatic exposure is embodied. However, since the 7 shutter in this manner does not have the automatic focusing function, it is applied only to a simple fixed focus cam era and it cannot be applied to a zoom camera commonly used in recent days.

The object of the present invention is to provide an electromagnetic shutter apparatus which has a compact construction and can be applied to an automatic focus and exposure control camera to overcome disadvantages of the prior art described above.

To accomplish the above-mentioned object, the present invention comprises:

a lens mount including a flange fixed on a cylindrical 1 portion and a floor of the cylindrical portion; two sheets of shutter blades installed to be rotated on an opposite side against the side thereon the cylindrical portion of the flange placed and substantially being linearly opposite 3 each other; 7 an exposure adjustment ring 8 including an exposure adjustment cam, a jug and a release cam formed one by one in accordance with a predetermined rotation direction, and rotated by a linear pulse motor; a focus adjustment ring 10 including a front arm, a lens interlocking means and a rear arm formed one by one in accordance with the predetermined rotation direction; a return means for driving the focus adjustment ring to the opposite direction against the rotation direction; a locking means for locking, releasing and holding in release state the rotation operation of the focus adjustment ring in accordance with the operation of the release cam; an open means for opening and closing, with an open degree of the shutter blades being controlled in accordance with the operation of the exposure adjustment cam; a contact switch to generate an electronic signal in accordance with the operation of the rear arm; and 4 a central processing unit including the function to control 7 the rotation of the linear pulse motor in accordance with the signal inputted from a light measuring circuit and a distance measuring circuit:

wherein.,the exposure adjustment ring and the focus adjustment ring are installed around the cylindrical portion to be rotated.

1 These and other embodiments and features of the present invention will become more readily apparent upon reading the following detailed description in conjunction with the attached drawings, in which:

FIG. 1 is an exploded perspective view schematically illustrating a construction of an preferred embodiment 'of an electromagnetic shutter apparatus in accordance with the embodiment of the present invention; FIG. 2 is an enlarged perspective view illustrating a ratchet operation mechanism shown in FIG. 1 in accordance with the embodiment of the present invention; FIG. 3 is an imaginary schematic diagram illustrating a ring-shaped rotor and a stator placed around the rotor in case of exploding linearly the ring-shaped rotor and a stator placed around the roto,r shown in the embodiment of FIG. 1 in accordance with the embodiment of the present invention; FIG. 4 is a schematic diagram illustrating a motion of a rotor shown in FIG. 3 in accordance with the embodiment of the present invention; FIG. 5 is an imaginary schematic diagram of a stator and a rotor in case that the stator and the rotor different from those shown in FIG. 3 are exploded on a plane in accordance with the embodiment of the present invention; FIG. 6 is a plane and side view of the rotor shown in FIG.

in accordance with the embodiment of the present invention; FIG. 7 is a perspective view illustrating one field of a pair of fields forming the stator shown in FIG. 5 in accordance with the embodiment of the present invention; 6 FIG. 8 is a timing chart showing illustrating that electric current flows to each armature of the stator shown in FIG. 5 in accordance with the embodiment of the present invention; FIG. 9 is an exploded diagram illustrating the operation of the shutter blade shown in FIG. 1 in accordance with the embodiment of the present invention; FIG. 10 is a diagram illustrating open and closed state of the shutter blade shown in FIG. 9 in accordance with the embodiment of the present invention; FIG. 11 is a front view schematically illustrating that an electromagnetic shutter apparatus shown in FIG. 1 is assembled in accordance with the embodiment of the present invention; FIG. 12 is a side view schematically illustrating that an electromagnetic shutter apparatus shown in FIG. 1 is assembled 4 in accordance with the embodiment of the present invention; FIG. 13 is a block diagram of a circuit used in an electromagnetic shutter apparatus in accordance with the embodiment of the present invention; 7 FIG. 14 is a schematic diagram illustrating that a focus 1 adjustment ring is released shown in FIG. 11 in accordance with the embodiment of the present invention; FIG. 15 is a schematic diagram illustrating that a focus is controlled by---the rotation of the focus adjustment ring shown in FIG. 14 in accordance; with the embodiment of the present invention; FIG. 16 is a schematic diagram illustrating that a shutter is opened by the rotation of an exposure adjustment ring shown in FIG. 14 in accordance with the embodiment of the present invention.

Referring to FIG. 1, a lens mount 2 comprises a cylindrical portion 4 and a flange 6 fixed on the floor of the cylindrical portion 4.

An exposure adjustment ring 8, a focus adjustment ring 10 and a rotor are installed to be able to rotate one by one in an outer circumference of the cylindrical portion 4.

a 1 An exposure adjustment cam 14 for adjusting an open amount of the shutter blades, a jug 18 and a release cam 16 are formed in the outer circumference of the exposure adjustment ring 8 one by one in a counterclockwise direction.

in accordance with the counterclockwise rotation of the exposure ajustment ring 8, the release cam 16 moves a ratchet fixed to be able to rotate on a flange 6 of the lens mount 2.

As shown in FIG. 2, the ratchet has a stopper 22 and a pin 26.

This ratchet 20 is pressed by a torsion spring 24 in a predetermined direction. If the exposure adjustment ring 8 is rotated in the counterclockwise direction, the pin 26 fixed on the stopper 22 by the release cam 16 is pushed, and the ratchet is rotated in the counterclockwise direction.

The pin 26 of the ratchet 20 is in gear with a notch 30 formed in an engaging member 28 made of magnetic material. The engaging member is slidably placed on the flange 6 at a predetermined spacing f rom an electromagnet 32 placed on the flange 6 of the lens mount 2, and the engaging member is adsorbed 9 v to the electromagnet 32 if the electromagnet is excited.

Referring to FIG. 1, a front arm 34, a rear arm 36, a lens interlocking arm 38 and a spring fixed projection 40 are formed in the outer circumference of a focus adjustment ring 10. A ratchet gear 42-engaged with the stopper 22 of the ratchet 20 is formed in the predetermined portion of the outer circumference of the focus adjustment ring 10. As shown in FIG. 1, it is preferable that the lens interlocking arm 38 is formed in a fork shape, and the lens interlocking arm 38 forms a lens interlocking means together with a lever 90 (See to FIG. 12) that will be describe later.

The above ratchet 20, the ratchet gear 42, the torsion spring 24, the engaging member 28 and the electromagnet 32 forms a locking means, and the rotation movement of the above-focus adjustment ring 10 is locked, released and is held released by the locking means.

When the focus adjustment ring 10 is mounted to the outer circumference of the cylindrical portion 4, the front arm 34 :L 0 meets the counterclockwise side of the engaging member 18 of the v exposure adjustment ring 8.

The spring fixed projection 40 is connected to one end of a tension spring 43 with the other end thereof on the flange 6 of the lens mount 2. The tension spring 43 is a return means to return the'focus adjustment ring 10 to an early position.

A rotor 12 forms a linear pulse motor together with a stator 48 that will be described later. If the rotor 12 is installed to the outer circumference of the cylindrical portion 4, the rotor 12 and the exposure adjustment ring 8 are rotated in one body since a rod 44 extended axially around the outer circumference is inserted in a fixing hole 45 of the rotor 12 and connected to the fixing hole 45. The number of the rod 44 and the fixing hole can be more than one.

The rotor 12 is a kind of permanent magnet, and a plurality of poles 46 projected externally from a radius direction substantially at the same interval in the predetermined area of the outer circumference of the rotor 12 are formed. These north 1 X pole and south pole of the poles 46 are placed by turns at the predetermined space between them.

The stator 48 is placed on the outer circumference of the rotor 12, with being away at the predetermined distance from the rotor 12. Actually, the stator 48 is fixed and attached to a camera body separately from the lens mount 2. The stator 48 is formed in a pair of fields 50 and 52 having an "E" letter shape.

Each field 50 and 52 has two armatures 54, 56 and 58, 60 respectively. If needed, the permanent magnet 61 is placed between both fields 50 and 52, so that a magnetic field formed by the armatures 54, 56, 58 and 60 can be reinforced.

AS shown in FIG. 3, to explain the movement of the rotor 12 with respect to the stator 48, these armatures are imaginarily exploded on the plane for ease of illustration. Actually, of course, the armatures 54, 56, 58 and 60 are circularly placed around the rotor 12 as shown in FIG. 1.

Referring to FIG. 3, each armature 54, 56, 58 and 60 has the same coil winding direction. Current is separately supplied to :L 2 a the armatures 54 and 56 of the field 50 and to the armatures 58

Y and 60 of the field 52.

The interval between two armatures 54 and 56 of said each field 50 can be set to allow the armatures 54 and 56 to be opposite again.st the poles of said rotor having different polarities respectively. Namely, if the pole 46 of the rotor 12 being opposite to the armature 54 is the south pole, the pole 46 of the rotor 12 being opposite to the armature 54 is the north pole. It is also true of the distance between the armatures 58 and 60 of the field 52.

On the other hand, when the armatures 54 and 56 of the f ield are opposite to the pole 46 respectively, the armatures 58 and of the field 52 are opposite to the interval between each - pole

46 of the rotor 12.

FIG. -4 illustrates the operation of the rotor shown in FIG.

3 in four steps. In FIG. 4, imaginarily, it is shown that the coil of each armature is wound to the direction shown in FIG. 3.

In a first step, the current flows from an E4 termi.nal only 3-3 to an E3 terminal. Accordingly, end portions of the armatures 58 7 and 60 turn to the south pole and the north pole respectively, and since the south pole of the rotor 12 being adjacent thereto, so that the rotor 12 is moved to the left of the figure by a quarter pitch In a second step, the current flows from an E2 terminal of the field 50 only to an E, terminal. In a third step, the current flows from the E3 terminal of the field 52 only to the E4 terminal. And in a fourth step, the current flows from the E, terminal of the field 50 only to the E2 terminal. In the second, the third and the fourth step, the end portion polarity of each armature corresponds to that shown in each corresponding figure, and since the end portion polarity of each armature pulls the adjacent opposite polarity of the rotor 12 like in the -first step, the. rotor 12 is moved to the left of the figure by a quarter pitch at each step.

If one cycle from the first step to the fourth step is finished, the rotor 12 is moved to the left of the figure by one 3L 4 pitch. (Accordingly, the rotor 12 is rotated in the 11 counterclockwise by one pitch.) The rotor 12 can be rotated in the reverse direction by altering the order and direction of the current flow described in the above.

FIG. 5 or FIG. 7 shows a preferred embodiment of a construction be diferent from that of the rotor 12 and the stator 48 shown in FIG. 3.

Referring to FIG. 6 first, the predetermined space of the outer circumference of the rotor 12 is divided by an upper part and a lower part in the preferred embodiment. A plurality of north pole 46a in the upper part and a plurality of south pol 46b are respectively formed at the regular interval substantially being projected externally from the radius direction. FIG. 5 shows the poles imaginarily exploded on the plane in a strip shape, and the north pole is indicated by a numeral 46a and the south pole is indicated by the numeral 46b in this figure.

FIG. 7 shows one of a pair of fields 50 and 52 forming the stator 48 in the preferred embodiment according to the. present invention. The end portions of the armatures 54, 56 or 58, 60 are 7 also divided by the upper and lower parts,corresponding to the poles 46 of the rotor 12 divided by the upper and lower parts, and a plurality of projecting portions (Two in FIG. 2) substantially extended internally from the radius direction are formed at te regular interval in each part. The projecting portions in the upper and lower parts are placed to be cross with one another.

FIG. 3A shows that the fields 50 and 52 actually placed around the rotor 12 are exploded on the plane imaginarily. In FIG. 3A, the upper part of the armatures 54, 56, 58 and 60 shown under the south pole 46b of the rotor 12. Actually, the upper and lower parts of the armatures 54, 56, 58 and 60 are not the separate from each other, but is one body.

Referring to FIG. 5, the projecting portions of the upper part of the'armature 54 are opposite against the north poles 46a of the rotor 12, and the projecting portions of the lower part of the armature 54 are apposite against the intervals between the JL 6 south poles 46b of the rotor 12. Also, the projecting portions of the upper part of the armature 56 are opposite against the intervals between the north poles 46a of the rotor 12, and the projecting portions of the lower part of the armature 56 are opposite gainst the south poles 46b of the rotor 12.

The projecting portions of the upper part of the armature 58 are opposite against the north poles 46a of the rotor 12, with being overlapped by a quarter pitch to the left of the north poles 46a, and the projecting portions of the lower part of the armature 58 are opposite against the south poles 46b of the rotor 12, with being overlapped by a quarter pitch to the right of the south poles 46b. Also, the projecting portions of the upper part of the armature 60 are opposite against the north poles 46a of the rotor 12, with being overlapped by a quarter pitch to the right of the north poles 46a, and the projecting portions of the lower part 'of the armature 60 are opposite against the south poles 46b of the rotor 12, with being overlapped by a quarter pitch of to the left of the south poles 46b.

:17 The current f lows as shown in a timing chart of FIG. 8 according to the preferred embodiment of the present invention.

In the first step, the current flows from the E, terminal to the E2 terminal, and f rom the E3 terminal to the E4 terminal. At this point, the projecting portions of the armatures 54 and 58 turn to the north poles, and the projecting portions of the armatures 56 and 60 turn to the south poles. Accordingly, a repulsion is generated between the projecting portions of the upper part of the armature 58 and the north poles 46a of the upper part of the rotor 12 opposite against the projecting portions with being partially overlapped, and an attraction is generated between the projecting portions of the lower part of the armature 58 and the south poles 46b of the lower part of the rotor 12 opposite against the projecting portions with 'being partially-overlapped. Also, the attraction is generated between the projecting portions of the upper part of the armature 60 and the north poles 46a of the upper part of the rotor 12 opposite against the projecting portions with being partially ove.rlapped, ]L 8 1 and the repulsion is generated between the projecting portions of the lower part of the armature 60 and the south poles 46b of the lower part of the rotor 12 opposite against the projecting portions with being partially overlapped. Accordingly, as a whole, the rotor 12 is moved to the right by a quarter pitch relatively to he stator 48.

AS shown in FIG. 8, the pulse of the current f rom the E, terminal to the E2 terminal does not reach to all the sections in a first step to prevent an overrunning of the rotor 12. The same may be said of next second and fourth steps.

In a second step, the current flows from the E, terminal to the E2 terminal, and from the E3 terminal to the E4 terminal. At this time, the projecting portions of the armatures 54 and 60 turn to the north poles, and the projecting portions of the armatures 56 and 58 turn to the south poles. Accordingly, the repulsion is generated between the projecting portions of the upper part of the armature 54 and the north poles 46a of the upper part of the rotor 12 opposite against the pr.ojecting 2-9 portions with being partially overlapped, and the attraction is generated between the projecting portions of the lower part of the armature 54 and the south poles 46b of the lower part of the rotor 12 opposite against the projecting portions with being partially overlapped. A1SO, the attraction is generated between the projecting portions 'of the upper part of the armature 56 and the north poles 46a of a the upper part of the rotor opposite against the projecting portions with being partially overlapped, and the repulsion is generated between the projecting portions of the lower part of the armature 56 and the south poles 46b of the lower part of the rotor 12 opposite against the projecting portions with being partially overlapped. As a result, as a whole, the rotor 12 is moved again to the right by a quarter pitch relatively to the stator 48.

In a third step, the current flows from the E2 terminal to the E, terminal, and from the E4 terminal to the E3 terminal. In a fourth step, the current flows from the E2 terminal to the E3 terminal. The detailed description about the operation in the cl third and fourth steps is omitted, but substantially the operation principle thereof is the same as that in the first and second steps.

Since the rotor 12 is moved to the right by a quarter pitch at each step relatively to the stator 48, the rotor 12 is moved to the right by one pitch during one cycle of passing the first step or the fourth step. (Actually, the rotor 12 is rotated to a clockwise by one pitch.) The rotor 12 can be rotated in the reverse direction by altering the order and direction of the current flow described in the above.

Referring again to FIG. 1, a circular slot 62 is formed on the flange 6 of the lens mount 2 approximately to the radius direction of the cylindrical portion 4.

Two sheets of the shutter blades 64 and 66 substantially linearly opposite each other are supported to be rotated on a reverse side of the side thereon the cylindrical portion 4 of the flange 6 is set up. The configurations of these shutter blades are well shown in FIG. 9 and FIG. 10.

21 A guide slot 78 and an aperture 74 are formed in the blade 7 66, and a guide slot 76 and an aperture 72 are formed in the blade 64 linearly opposite against the guide slot 78 and the aperture 74 in the blade 66.

The blades 64, 66 are rotatably supported on support pins 68, 70 secured in the flange 6 via each aperture 72, 74, respectively.

The support pin 68 passes through the aperture 72 of the blade 64, and also supports a guide arm 82 to be rotated.

A guide pin 80 slidably mounted within the circular slot 62 is fixed in the guide arm 82. The guide arm 82 is always biased in the clockwise direction by a torsion portion 84 having one end portion abutting a pin 83 (see FIG. 9) projecting from the flange 6 and the other end portion engaged with one side of the,guide arm 82. The guide pin 80 passes through guide slots 76, 78 of the shutter blades 64, 66, through the circular slot 62 of the flange 6 and contacts the side of an exposure adjustment cam 14 in the exposure adjustment ring 8.

22 1 The circular slot 62, guide arm 82, torsion spring 84 and 1 guide slots 76, 78 form an opening means which open and close the shutter blades 64, 66 in accordance with the operation of the exposure adjustment cam 14.

In FIGs. 9 and 10 illustrates the open and closed states of the shutter blades 64, 66, respectively. if the exposure adjustment ring 8 rotates in a clockwise direction, the guide pin is pushed by the exposure adjustment cam 14 along the slot 62 outwardly in a radial direction of the flange 6. Accordingly, as shown in FIG. 10, the shutter blades 64, 66 are respectively rotated outwardly of each other, rotating around the support pins 68, 70, and opened.

At this time, the movement distance of the guide pin 80 can be controlled by a rotation angle of the exposure adjustment cam 14, and an open degree of the shutter blades 64 and 66 can be controlled."

Referring to FIG. 11, the rotor 12 installed on the outer circumference of the cylindrical portion 4 can be rotated by the armatures 54, 56, 58 and 60. Since the rotor 12 and the exposure adjustment ring 8 are connected each other by the rod 44, the exposure adjustment ring 8 is rotated together with the rotor 12.

if the exposure adjustment ring 8 is rotated in a counterclockwise direction, since the front arm 34 of the focus adjustment ring 10 is pushed by the lug '18 of the exposure adjustment ring 10, the focus adjustment ring 10 is also rotated in the counterclockwise direction. At the same time, since the release cam 16 of the focus adjustment ring 8 pushes the pin 26, the ratchet 20 is rotated in a counterclockwise direction. Also, a rear arm 36 of the focus adjustment ring 10 turns OFF a contact switch 86 arranged on the flange 6 of the lens mount 2, and thereby an electric signal is generated. This electric signal is applied to a central processing unit which will be described later.

As shown in FIG. 12, a lens barrel 88 is installed in front of the lens mount 2.

A lever 90 is placed in a movable lens part of the lens 24 Y barrel 88, and the lever 90 is connected to the interlocking arm 38 of the focus adjustment ring 10. As shown in FIG. 1, the end portion of the arm 38 is formed in a fork shape to connect the interlocking arm 38 and the lever 90.

The electromagnetic shutter apparatus is controlled by an ordinary electronic control system as shown in FIG. 13.

Referring to FIG. 13, current flows to the stator 48 by the operation of a CPU 92 in accordance with the signal inputted from a light measuring circuit 94 and a distance measuring circuit 96.

FIG. 11 shows an early operation state of the shutter. If the shutter button (not shown) is pressed to a first stage, namely, a preposition in the early state, current flows to the stator 48 in accordance with the control signal from the CPU 92.

AS shown in FIG. 14, the rotor 12 is rotated counterclockwise and the ratchet 20 is rotated to the release position by the release cam 16 of the exposure adjustment ring 8. At this time, the focus adjustment ring 10 is also rotated by being pushed by the lug 18 of the exposure adjustment ring 8 and thereby the contact switch 86 is turned OFF. In accordance with this operation, the operation start signal is inputted to the CPU 92.

The CPU 92 which received the operation start signal excites the electromagnet 32 and thereby the engaging member 28 is pulled to the electromagnet so that the ratchet 20 is held in the release position. Concurrently, the CPU 92 outputs an inverting signal corresponding to a distance value measured by the measuring distance circuit 96 to the stator 48. As a result, the rotor 12 is rotated at the corresponding angle and moves into the state as shown in FIG. 15. At this point, the focus adjustment ring 10 is also rotated by the torsion spring 43 clockwise.

If the rotation operation of the rotor 12 stops, the CPU 92 demagnetizes the electromagnet 32. Thus, the ratchet 20 is biased by the torsion spring 24, and the stopper is engaged with a ratchet gear 42 of the focus adjustment ring 10.

While the focus adjustment ring 10 is rotated by a return spring 43 clockwise till the front arm 34 of the focus adjustment ring 8 contacts the lug 18, the lever 90 rotating together with 2-6 p the lens interlocking arm 38 rotates the movable part of the lens barrel 88, and thereby the focus control is carried out.

If the shutter button is pressed to a second stage, namely, to a photographing position, in accordance with the control of the CPU 92, current flows to the stator 48 for the rotor 12 to be further rotated clockwise by an angle corresponding to the measured value from the light measuring circuit 94.

Accordingly, as shown in FIG. 16, the exposure adjustment cam 14 of the exposure adjustment ring 8 pushes the guide pin 80 and opens the shutter blades 64, 66.

As described above, the open degree of the shutter blades 64, 66 is decided by the movement distance of the guide pin 80 being rotated by the exposure adjustment cam 14. Also, an open period is decided by the time until the focus adjustment ring 8 is rotated counterclockwise by a noninverting signal of the CPU 92 and thus'the guide pin 80 returns to the initial position. If the focus adjustment ring 8 is rotated counterclockwise in accordance with the noninverting signal and returns to the state shown in FIG. 11, one cycle of the shutter is completed.

In summary, the operation of the electromagnetic shutter apparatus can be exemplified in six steps.

In a first step; if the shutter button is pressed to a first stage, the linear pulse motor is rotated in a rotation direction in accordance with the control signal from theCPU, the locking means is released by the release cam 16, the focus adjustment ring 10 is also rotated in the rotation direction (counterclockwise as viewed in FIG. 11) since the front arm 38 is pushed by the lug 18, and a predetermined electronic startsignal is inputted to the CPU by the contact switch 86 operated in accordance with the rear arm 36.

In a second step; the locking means is held in the release position in accordance with the control signal from the CPU, and the CPU outputs an inverting signal corresponding to a distance value measured by the measuring distance circuit to the linear pulse motor.

In a third step; the linear pulse motor is rotated in the 28 opposite direction by an angle corresponding to the distance value, and the focus adjustment ring 10 is also rotated in the opposite direction (clockwise) by the return means 43.

In a fourth step; the rotation operation if the pulse motor stops, the focus adjustment ring 10 is locked by the locking means in accordance with the control signal from the CPU.

In a fifth step; if the shutter button is pressed to a second stage, the linear pulse motor is further rotated in the opposite direction by the corresponding angle to the measured value from the light measuring circuit in accordance with the control signal of the CPU. Thus, the exposure adjustment cam of the exposure adjustment ring operates the opening means, and thereby the shutter blades 64, 66 are opened.

In a sixth step; the exposure adjustment ring 8 is rotated in the rotation direction (counterclockwise) in accordance with a predetermined inverting signal from the CPU 92. Thus, the shutter blades 64, 66 return to the initial closed position via the opening means.

:2 9 The invention thus provides an electromagnetic shutter apparatus of simple construction. In particular, since the electromagnetic shutter apparatus can be applied to a camera having an automatic exposure control function and-an automatic focus control function, the electromagnetic shutter apparatus can be applied to a so-called auto zoom camera in which a focus distance has to be automatically focused.

7

Claims

1 1. An electromagnetic shutter apparatus comprising a lens mount including a cylindrical portion and a flange fixed on said cylindrical portion; two shut.ter blades rotatably mounted on said flange on a side opposite said cylindrical portion; an exposure adjustment ring rotatably mounted on said cylindrical portion and including an exposure adjustment cam, a lug and a release cam formed sequentially in accordance with a predetermined rotation direction; a linear pulse motor for rotating said ring; a focus adjustment ring rotatably mounted on said cylindrical portion and including a front arm, a lens interlocking means and a rear arm formed sequentially in accordance with said predetermined rotation direction; a return means for driving said focus adjustment ring in the opposite direction to said rotation direction; a locking means for selectively locking said focus 3 X adjustment ring; opening means for opening and closing said shutter blades in accordance with the operation of said exposure adjustment cam; a contact switch to generate an electronic start signal in accordance with the operation of said rear arm; and a central processing unit to control the rotation of said linear pulse motor in accordance with a signal inputted from a light measuring circuit and a distance measuring circuit.

2. An electromagnetic shutter apparatus as set forth in claim 1 wherein said lug from an outer periphery of said exposure adjustment ring.

3. An electromagnetic shutter apparatus as set forth in claim 1 wherein said linear pulse motor comprises a circular rotor rotatably mounted on said cylindrical portion and a ttator placed around said rotor.

4. An 'electromagnetic shutter apparatus as set forth in claim 3 wherein said rotor has a plurality of north poles and south poles projecting radially outwardly in an alternating 1 equally spaced manner and said stator has two fields, each said field having two armatures with an interval between two armatures of one field set to position the armatures opposite the poles of said rotor having different polarities respectively, and the armatures of the other field set opposite the interval between the poles of each rotor.

5. An electromagnetic shutter apparatus as set forth in claim 4 which further comprises a permanent magnet between said fields.

6. An electromagnetic shutter apparatus as set forth in claim 3 wherein a predetermined space of an outer circumference of said rotor is divided into an upper part with a plurality of north poles and a lower part with a plurality of south poles formed at regular intervals; and said- stator includes two fields, each field having two armatures,With each armature having each portions divided into the upper and lower parts with projecting portions corresponding to said poles of said rotor, and said projecting portions in said upper and lower parts being staggered relative to one another overlapped by a quarter pitch to one side of the south poles of said rotor.

An electromagnetic shutter apparatus as set forth in claim 6 which further comprises a permanent magnet between said f ields.

8. An electromagnetic shutter apparatus as set forth in claim 1 which further comprises at least one pin secured to said exposure adjustment ring and passing into a movable part of said linear pulse motor.

9. An electromagnetic shutter apparatus as set forth in claim 1 wherein said lens interlocking means is a projecting portion having a fork shape for engaging with a movable lent of a lens barrel.

10. An electromagnetic shutter apparatus as set forth in claim 1 wherein said return means is a torsion spring placed between said focus adjustment ring and said flange.

11. An electromagnetic shutter apparatus as set gorth in 34 v claim wherein said locking means comprises a ratchet gear formed on said focus adjustment ring; a ratchet rotatably mounted on said f lange and having a stopper and a pin; a torsion spring biasing said ratchet in an opposite direction against the direction of force imposed by said release cam; and an engaging member with a notch engaged with said pin of said ratchet and an electromagnet to attract said engaging member wherein engagement of said stopper and said ratchet is released if said release cam pushes said pin of said ratchet and wherein said pin of said ratchet is constrained by said notch of said engaging member if said electromagnet is excited and said release state is held.

12. An electromagnetic shutter apparatus as set forth in claim 1, wherein said open means comprises:

a circular slot in said flange; a guide arm rotatably mounted on said flange and having a guide pin passing through said slot; a torsion spring biasing said guide arm to close said shutter blades; and guide slots formed in said shutter blades - in crossing relation to each other with said guide pin passing therethrough:

and wherein said guide pin rotates along said circular slot if said exposure adjustment cam pushes said guide pin and said shutter blades rotate in opposite directions to each other.

13. An electromagnetic shutter apparatus comprising a lens mount including a hollow cylindrical portion defining an opening and a flange fixed on said cylindrical portion; at least two shutter blades rotatably mounted on said flange on a side opposite said cylindrical portion to cover over said opening; an exposure adjustment ring rotatably mounted on said cylindrical portion and including an exposure adjustment cam; a linear pulse motor for rotating said ring; 3 6 I 1 opening means for opening and closing said shutter blades in accordance with the operation of said exposure adjustment cam; a contact switch to generate an electromagnetic start signal; and a central.processing unit to control the rotation of said linear pulse motor in accordance with said start signal.

14. An electromagnetic shutter apparatus as set forth in claim 13 wherein said exposure adjustment ring includes a lug and which further comprises a focus adjustment ring rotatably mounted on said cylindrical portion and including a front arm for abutting said lug of said exposure adjustment ring, a lens interlocking means and a rear arm for abutting said contact switch to generate said start signal; a return means for biasing said focus adjustment ring towards an initial position to abut said front arm against said lug; and a locking means for selectively locking said focus adjustment ring against rotation.

15. An electromagnetic shutter apparatus as set forth in claim 14 wherein said lug projects from an outer periphery of 37 said exposure adjustment ring.

16. An electromagnetic shutter apparatus as set forth in claim 14 wherein said lens interlocking means is a- projecting portion having a fork shape for engaging with a movable lens of a lens barrel.

17. An electromagnetic shutter apparatus is set forth in claim 14 wherein said return means is a torsion spring placed between said focus adjustment ring and said flange.

18. An electromagnetic shutter apparatus as set forth in claim 13 wherein said linear pulse motor comprises a circular rotor rotatably mounted on said cylindrical portion and a stator placed around said rotor.

19. An electromagnetic shutter apparatus as set forth in claim 18 wherein said rotor has a plurality of north poles and south poles projecting radially outwardly in an alternating equally spaced manner and said stator has two fields, each said field having two armatures with an interval between two armatures of one f ield set to position the armatures opposite the poles of 3 8 1 said rotor having different polarities, respectively, and the armatures of the other field set opposite the interval between the poles of each rotor.

20. An electromagnetic shutter apparatus as set forth in claim 18 which further comprises at least one pin secured to said exposure adjustment ring and passing into said rotor of said ii near pulse motor.

21. An electromagnetic shutter apparatus substantially as herein described with reference to the accompanying drawings.

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