US3608463A

US3608463A - Camera shutter

Info

Publication number: US3608463A
Application number: US782047A
Authority: US
Inventors: Takeo Yamada
Original assignee: Nippon Kogaku KK
Current assignee: Nikon Corp
Priority date: 1967-12-08
Filing date: 1968-12-09
Publication date: 1971-09-28
Anticipated expiration: 1988-09-28
Also published as: GB1255500A; DE1813312B2; DE1813312A1; FR1594188A; DE1813312C3; CH487420A

Abstract

A high speed focal plane shutter employs two panels each having an exposure aperture. The panels are arranged in spaced parallel relationship. A pair of flexible curtains is disposed between the panels. Each curtain is U-shaped. One end of each curtain is fixed to one of the panels, or the first panel, and the other end of each curtain is connected to a mouthpiece movable between open and closed positions, that is, the positions where the exposure aperture is respectively uncovered and covered by the curtain. A pair of link mechanisms is provided for respectively moving the mouthpieces along the inner surface of the other or second panel to open and closed positions. Each link mechanism includes a driving lever and a driven lever pivotally connected to each other. One end of each driving lever is pivoted on the first panel and the other end is slidably connected to one end of a mouthpiece. One end of each driven lever is slidably connected to the first panel and the other end is pivoted to the opposite end of the mouthpiece.

Description

United States Patent [72] Inventor Takeo Ylmada Primary Examiner-Samuel S. Matthews Tokyo, Japan Assistant Examiner-Michael Harris [2|] Appl. No. 782,047 AttorneyHarry G. Shapiro [22] Filed Dec.9,1968 [45] Patented Sept. 28, 1971 [73] Assignee Nippon Kogaku K. K.

7 Tokyo, Japan ABSTRACT: A high speed focal plane shutter employs two [32] Priority Dee.'8, 1967, Dec- 8, 1967, Dec. 8, I967 panels each having an exposure aperture. The panels are ar- [33] Japan ranged in spaced parallel relationship. A pair of flexible cur- I] l/ 42/735145 and 2/78517 tains is disposed between the panels. Each curtain is U- shaped. One end of each curtain is fixed to one of the panels, [54] CAMERA SHUTTER or the first panel, and the other end of each curtaln is con scmmsy 15 Drawing Figs nected to a mouthpiece movable between open and closed positions, that IS, the positions where the exposure aperture IS [52] US. Cl 95/57 respectively uncovered and covered by the curtain A pair of l l 1 CI G03, 9/28 link mechanisms is provided for respectively moving the [50] Field of Search 95/57 4 mouthpieces along h inner Surface f he other or second anel to 0 en and closed ositions. Each link mechanism in- 156] References cued Eludes a dr i ving lever and a driven lever pivotally connected to UNITED STATES PATENTS each other. One end of each driving lever is pivoted on the 2,4l7,482 3/1947 Gacki 95/57 first panel and the other end is slidahly connected to one end 2,456,052 l2/l948 Doyle et al. 95/57 ofa mouthpiece. One end of each driven lever is slidably con 2,526,432 5 SVeHS-SOH 95/57 nected to the first panel and the other end is pivoted to the op- 3,006,263 l0/l96l Elliott et al. 95/57 posite end of the mouthpiece.

l I 2 6 A 5 I 8 L e l i I 1/y I711 I B- g [I lfiifi" m -B 5 l l r PATENTED scrzs I97! sma l or 6 FIG.5

mm EV PATENTE0s P2e|9n 3,608,463

SHEET 6 [1F 6 FIG. 13

( FC I ll 7 FIG. 14 4' 3 'l c T FC p 7 FIG. 15 3 \1 Ll mfilrmmmm 'l AC c I"* T FCI CAMERA suu'r'rsn -;The invention relates to an adjustable slit focal-plane shutter for a. photographic camera, and more particularly to an improved form of curtain shutter capable of making exposures at exceedingly high speeds.

Conventional focal-plane shutters are so constructed that exposure is initiated by winding up the first curtain covering the exposure window around the first cylinder by means of spring; and exposure is completed by winding up the string which is fitted to the second curtain in such a manner to render the second curtain to cover the exposure aperture, around the second cylinder by means of another spring; and

for preparation for the next exposure, the string fitted to the first curtain and the second curtain are restored to original positions by means of the third and fourth cylinders. Since each curtain is provided with a cylinder on each end, comparatively strong force is required as the spring force or brake force in order to accelerate or decelerate the inertia, in which is caused by the mass of curtains and strings and caused by the inertia efficiencies of the cylinders produced when opening or closing the curtains at a high speed. Moreover, since these forces work to tension the curtains and strings having cylinders on both ends, both the curtains and the strings must have strength enough to withstand the said forces. It is impossible, therefore, to use extremely light curtains and strings. Furthermore, since the tension strength is comparatively great and the variation of the tension strength during acceleration or deceleration is also large, the curtains are liable to start vibration and generate high and strong operation sound when the curtains are at nonrestraint position such as the exposure aperture.

It is an object of this invention to provide a focal plane shutter'not employing strings and cylinders but employing link mechanism instead which can have a small inertia efficiency compared with cylinders, and which does not give a large tension to the curtains and therefore makes it possible to construct a shutter with lightweight curtains which reduces the force or the amount of work required to open or close the curtains and at the same time minimizes the operation sound by damping the vibration generated when the curtains are positioned at the aperture section.

In this invention a pair of curtains is used as the flexible curtain for the camera shutter, as one end of the curtain is fixed, and the other end is moved to open or close the exposure aperture. When metallic materials are used for the curtain, the curtain has a tendency to roll into cylinder shape and, after assembly, the curtain is pressed against a guide plate by the stress generated within the curtain to prevent the buckling produced when one end of the curtain is moved to open or close the exposure aperture.

Another object of this invention is to provide a camera shutter employing a curtain with an element which functions to prevent the buckling of the curtain by inoving in constant contact with the innerside of the curved portion of the U- shaped curtain with the vibration absorbing element which moves to contact with the curtain within the exposure window when the curtain is at a position covering the exposure aperture and retreats with the certain retreats from the exposure aperture.

In this invention the driving device for the said camera shutter is so composed that a second pin' is installed on another end of a first lever fixed on one sid 'of the exposure aperture frame with a first pin, that a fourth pin is planted on an end of second lever having at another end a third pin which fits to a first groove provided on the other side of the exposure aperture frame, that the first and second levers are pivotably joined to each other by a fifth pin, that the second pin is fitted slidable into a second groove provided on one end of a mouthpiece secured to the movable end of the curtain, that the other end of the mouthpiece is pivotally connected to the end of the second lever by the fourth pin, that the first through fourth pins are positioned at apieces of a parallelogram through to each other and when their axes are projected on a plane perpendicular to the shafts of the pins, the axes of the first, fifth and second pins are on a straight line and the axes of the third, fifth and fourth pins are also on another straight line, that distances between first and fifth pins, fifth and second pins, third and fifth pins, and fifth and fourth pins are identical, and further, that the lengthway directions of the first and second grooves are parallel to the straight line connecting the first and third pins.

In this invention, the cylinders having a large inertia efficiency commonly used in conventional focal plane shutters are not employed and, instead the curtain stored in U-shape and a driving mechanism is provided for moving the free end of the curtain, the driving mechanism being positioned between the flat or ar rnportions of the U-shaped curtain Since this reduces the tension on the curtain considerably and enables a thinner curtain to be used, the weight of the curtain is reduced and, since the curtain is in U-shape and its free end is moved, the resistance caused by the inertia becomes small and, as afresult, the capacity of driving device becomes small "and consequently the inertia of the driving device itself also 5 caused by a small, drive force. This results in the lower operation sound. Moreover, since it is possible to effectively attenuate the vibration of the curtain, the operation sound can be made lower. It is highly'advantageous to be enabled to construct an exceedingly high-speed shutter which is relatively small in size, light in weight and silent for portable cameras.

This invention will be described with reference to the drawings, in which:

FIG. 1 is a plan view of a shutter made in accordance with the invention;

FIG. 2 Isa cross section showing the preexposure state of the shutter;

FIG. 3 is a cross section showing the state of the shutter during exposure;

FIG. 4 is a cross section showing the post-exposure state;

FIG. 5 is a plan view of the shutter, the front panel and the spacers or props being omitted for clarity in illustration;

FIG. 6 is a plan view of the leading curtain drive-link mechanism the curtains and mouthpiece being omitted from this view for clarity in illustration.

FIG. 7 is a vertical side view of FIG. 6;

FIG. 8 is a horizontal side view of FIG. 6;

FIG 9 is an perspective view of FIG. 6;

FIG. 10 is a plan of link device prior to exposure;

FIG. 11 is a plan of link device during exposure FIG. 12 is a plan of link device after completion of exposure; I

FIG. 13 is a stress-distribution diagram whenunformed material is used;

FIG. 14 is a stress-distribution diagram when formed material is used; and

FIG. 15 is a stress distribution diagram under accelerated state.

Referring to FIG. 1, 1 shows the front panel having an exposure aperture A and operates as a guide, 2 is a first or leading curtain covering A, and 4 is an element of a link mechanism driving the leading curtain 2. An element 4' is the element of a similar link mechanism driving a similar trailing curtain 21 stored at the left of the device shown in FIG. 1 and beyond the exposure aperture A. FIG. 2 shows the preexposure state wherein 2 and 2 are the leading and trailing curtains, respectively, 3 and 3' the mouthpicces fitted respectively to the leading curtain 2 and trailing curtain 2 by means of bonding etc., 4, 5, 4' and 5' are elements of link mechanisms used respectively to drive the leading curtain and trailing curtain 6 an 6 are vibration absorbing elements, such as sponges or brushes, which are fitted to the

members

5 and 5 to engage the leading curtain 2 and the trailing curtain 2'; 7 is a rear panel also operating as a guide, and has an aperture A almost as large as the aperture A and is fixed to the front panel 1 by a spacer or prop 8. The leading curtain 2 and trailing curtain 2' are folded in U I shape to provide curved portions B and B one of each is fixed to the rear panel 7 at positions C and C.

FIG. 3 shows the state during exposure wherein the leading curtain 2 and its mouth piece 3 move parallelwise fromthe original positions to the right in the direction perpendicular to the base of the curved portion B, and lets the light beam pass through the exposure operature A and aperture A. FIG. 4 shows the postexposure state wherein the trailing curtain 2' and mouth piece 3 move to cover the aperture A and the element 6' moves to the vicinity of the center of the aperture, keeping contact with the trailing curtain 2 In FIG. 5, D, D and E, E are the holds and oval grooves on the mouth pieces 3 and 3' respectively, and 10, 10 are the pins planted respectively on the elements of link mechanism driving the

mouthpieces

3 and 3. These pins are linked respectively to holds D, D and grooves E, E The straight lines connecting D, E and DEare respectively parallel to the base of the curved portion and lengthwise directions of E, E are also parallel to the base. A 1

FIGS. 6, 7, and 8 show the link mechanism used todrive the leading curtain 2. The state shown by dot-dash lines corresponds to FIG. 2 and the state shown by solid lines corresponds to FIG. 3; and 4, 5, 11 an 12 are levers. Lever 4 is pivotably connected to the rear panel 7 by means of the planted pin 13, one end of which is the arm section F for input,

and the other end is linked with the groove E of the mouth piece 3 by means of the planted pin 10. Level 11 is fitted to lever 4 together with lever free to rotate by means of a pin 14, its one end is linked with the hold D of the mouth piece 3 by means of the planted pin 9, and the other end is linked with the elongated groove G on the rear panel 7 by means of the planted pin 15. On the rear panel 7, the straight line connecting the pin 13 with the groove G is parallel to the base of the curved portion B of the leading curtain and the lengthwise direction of the groove G is also parallel to the base of the curved portion. On lever 4, the axes of the pins l3, l4 and onto the rear panel 7 are arranged in a straight line, the pin 14 being the middle point between the

pins

13 and 10. On lever 11, the axes of the

pins

15, 14 and 8 onto the rear panel 7 are arranged in a straight line, the pin 14 being the middle point between the

pins

15 and 9. The distance between the pins 15 and, when projected onto the rear panel 7, pins 17, '16, 14 and' 13 form a parallelogram. The element 6 made of such shockabsorbing material as sponge is bonded to the lever 5 at a place near the pin 14. The element 6 can be bonded either to the pin 14 or, when the lever 5 is omitted as described later, to lever 11 or lever 4.

Although omitted in FIG. 6, the link mechanism for driving the trailing curtain is similar to the above-mentioned link mechanism for driving the leading curtain 2, the former being symmetrical with respect to the latter. When the lever 4 is rotated, the straight line passing through projections of the

pins

9 and 10 onto the rear panel 7 is parallel to the straight line passing through the pin 13 and groove G and the pin 9 moves along a straight line passing through the pin 13 and perpendicular to the straight line passing through the pin 13 and groove G, and the mouthpiece 3 and the leading curtain 2 linked with the pin 9 open or close the apertures A and A. In this case, since the mouth piece 3 is suspended at both ends by

pins

9 and 10, deformation due to the load caused by inertia is reduced. The H section of lever,5 moves in parallel to the initial position and its right and left moving speed is equal to the half of the moving speed of

pins

9 and 10. Moreover, as is clear from FIG. 2, the moving speed of the mouthpiece 3 is identical with the moving speed of

pins

9 and 10 and the right and left moving speed of the phase of the canned portion B of the leading curtain 2 is equal to the half of the moving speed of I the mouthpiece 3. Consequently, the H portion of lever 5 moves always in contact with the inner side of the section B to prevent the buckling otherwise produced on the flexible leading curtain 2 when the leading curtain 2 and mouth piece 3 move in the direction making an aperture. Since the shock-absorbing element 6 is fitted to a position near the pin 14, its right and left moving speed is close to the half of the moving speed of the mouth piece 3 and, in a state that the leading curtain is covering the aperture, is in contact with the leading curtain 2 at the aperture section or near the center of the unrestrained portion in the direction of the thickness of the leading curtain 2, and is so positioned as to attenuate the vibration of the curtain near the loop point, In the state the leading curtain 2 is stored, the shock-absorbing element 6 is also retreats from the aperture section to be stored. During movement, the

thus serving always to attenuate the vibration of the leading curtain 2 effectively.

FIG. 9 is a perspective view representing the relationship of each element, and the state represented by solid lines in FIG. 6 and part of the leading curtain 2 and mouth piece 3 is shown. FIGS. 10, 11, and 12 show the states of the link mechanism before, during, andafter exposure respectively.

The theoretical basis of the inertia of the curtain will be explained in the following:

Referring to the inertia of the curtain that occupies a greater portion of the load on the drive device, when in general, making an aperture by moving a single curtain in the direction of longitudinal direction of the aperture at a predetermined acceleration of a, the following formulas are given, assuming the use of a curtain of minimum required area,

W,= l=a m bl where V m is the mass of the curtain per unit area;

I is the length of the aperture;

b is the width of the aperture; t

f is the force required to drive an unfolded curtain (either wound in a cylinder or plane); and

W, is the amount of work required for entire stroke.

On the other hand, when the same curtain is stored twicefolded, and assuming that F is the force required for driving the curtain; and W is the amount of work required for entire stroke; then F amb(Zs/2) =amb(l 9'l /4=) =3I4=ambl The formula (2) shows that in the present invention the amount of work required is small even when a curtain having the samemass of the formula (1). Moreover, since in this invention, no cylinders are used at both ends of the curtain, and the curtain itself forms the inertia load, the tension of the curtain is remarkably reduced and as a result, the curtain can be made of thin and light material, an the relationship shown by the formula (2) is further improved greatly.

Next, when such materials having comparatively high coefficient of elasticity and limit of elasticity and retaining the internal stress for a long period of time as metallic materials are i used to form the curtain, it is possible by performing the curtain over the entire length by winding in the same direction as the bending section and by assembling the shutter, to reduce the stress at the bending section than the stress produced by using the unformed material, and to change the distribution condition of the stress. This enables the curvature at the bending section to be taken larger and at the same time prevents the production of a concentrated pressure on the front panel 1 and rear panel 7 near the bending section of the curtain and retains the tension stress on the innerside of the flat portion of the curtain. FIGS. 13 and 14 show in model form the distribution. conditionof stress at each section and the distribution condition of pressures on the front panel 1 and rear panel 7 for each example of the case in which unformed material is used and the case in which formed material is used, respectively. In these drawings, P denotes pressure, P, the tension strength F the compression strength, and A the acceleration.

Furthermore, as illustrated in FIG. 15, a compression stress is produced on the portion moving to the right of the curtain due to the friction between the curtain 2 and front panel 1 and to the inertia of each section of the leading curtain 2 when accelerating the leading curtain 2 in the direction of making an aperture in other words in the direction of the bending section B by the mouthpiece 3. However, since the inner side of the flat portion of the curtain has been made previously to retain tension stress, the load is mainly supported by the outer portion of the cross section of the curtain and further since the action center of gravity caused by the reaction of friction is positioned to the left of the point shown in FIG. 13 and works to reduce the distance between the working points, the curtain which is thin compared with the length never produces a buckling. As has been stated so far, the

levers

5 and 12 used for preventing buckling can be omitted when metals or other materials are formed and used as the material of the curtain.

What is claimed is: l. A high-speed focal-plane shutter for a photographic camera comprising a first panel and a second panel each having an exposure aperture, the panels being arranged in spaced,

parallel relationship, a pair of flexible curtains disposed between the panels and symmetrically arranged with respect to each other, each curtain being U-shaped one end of each curtain being fixed to the first panel and the other end of each curtain being connected to a mouthpiece movable between open and closed positions, and a pair of link mechanisms for respectively moving the mouthpieces along the inner surface of the second panel to open and closed positions, the link mechanisms being symmetrical with respect to each other,

each link mechanism including a driving lever and a driven lever intersecting and pivotally connected to each other, one end of each driving lever being pivoted on the first panel and the other end being slidably connected to one end of a mouthpiece, one end of each driven lever being slidably connected to the first panel and the other end being pivoted to the opposite end of the mouthpiece, the levers being retractable into their respective U-shaped curtains when the mouthpiece is moved to open position. v

2. A high-speed focal-plane shutter according to claim 1; wherein the first panel has a pair of guide grooves extending parallel to the edge of the mouthpiece and are provided on the opposite side to the driving lever pivoted portion, the driving lever having a pin fitted into the guide groove.

3. A high-speed focal-plane shutter according to claim 2, wherein the mouthpiece has a groove at one end thereof, and the driving lever has a pin fitted into said groove.

4. A high-speed focal-plane shutter according to claim 3; wherein the driven lever is S-shaped, whereby the mouthpiece may pass over said guide groove and the pivoted portion of the driving lever. l

5. A high-speed focal-plane shutter according to claim I including vibration-absorbing elements provided near the pivotal connection to each other of the driving and driven levers in engagement with the inner surfaces of the curtains.

6. A high-speed focal-plane shutter according to claim I, in-

' cluding means for preventing buckling of the curtains, said cluding vibration-absorbing elements provided on said ivotable member m engagement w|th the inner surfaces of t e curtain.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Pa 3,603,463 Dated September 28, 1971 Inventor(s) eO Yamada It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 5, line 32, a comma should be inserted after "U-shaped";

Column 6, line 13, "driving" (second occurrence) should read driven Signed and sealed this 26th day of September 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents uscoMM-Dc 60376-P6D n U 5. GOVERNMENT PRINTING DFFICEI l9. O-'55"3l

Claims

1. A high-speed focal-plane shutter for a photographic camera comprising a first panel and a second panel each having an exposure aperture, the panels being arranged in spaced, parallel relationship, a pair of flexible curtains disposed between the panels and symmetrically arranged with respect to each other, each curtain being U-shaped, one end of each curtain being fixed to the first panel and the other end of each curtain being connected to a mouthpiece movable between open and closed positions, and a pair of link mechanisms for respectively moving the mouthpieces along the inner surface of the second panel to open and closed positions, the link mechanisms being symmetrical with respect to each other, each link mechanism including a driving lever and a driven lever intersecting and pivotally connected to each other, one end of each driving lever being pivoted on the first panel and the other end being slidably connected to one end of a mouthpiece, one end of each driven lever being slidably connected to the first panel and the other end being pivoted to the opposite end of the mouthpiece, the levers being retractable into their respective U-shaped curtains when the mouthpiece is moved to open position.

3. A high-speed focal-plane shutter according to claim 2; wherein the mouthpiece has a groove at one end thereof, and the driving lever has a pin fitted into said groove.

4. A high-speed focal-plane shutter according to claim 3; wherein the driven lever is S-shaped, whereby the mouthpiece may pass over said guide groove and the pivoted portion of the driving lever.

5. A high-speed focal-plane shutter according to claim 1, including vibration-absorbing elements provided near the pivotal connection to each other of the driving and driven levers in engagement with the inner surfaces of the curtains.

6. A high-speed focal-plane shutter according to claim 1, including means for preventing buckling of the curtains, said means including a pivotable member for each curtain, an end of each member being engageable with the inner surface of each U-shaped curtain at the curved base thereof.

7. A high-speed focal-plane shutter according to claim 6; wherein said pivotable member is T-shaped and acts as one link in a parallelogram for cooperation with said driving lever.

8. A high-speed focal-plane shutter according to claim 7, including vibration-absorbing elements provided on said pivotable member in engagement with the inner surfaces of the curtain.