US2553394A - Photographic shutter mechanism - Google Patents

Description

y 15, 1951 F. P. WILLCOX 2,553,394

PHOTOGRAPHIC SHUTTER MECHANISM Filed June 17, 1947 E'eclerieii R VViIIc ox Patented May 15,- 1951 UNITED STATES PATENT OFFICE Frederick P. Willcox, Bethesda, Md., assignor to Graficx, Inc., Rochester, N. Y., a. corporation of New York Application June 17, 1947, Serial No. 755,049

2 Claims. 1

This invention relates to photographic apparatus, and particularly to improved shutter mechanisms for use in photographic cameras or re. lated equipment.

In conventional forms of pivoted blade shut.- tors, particularly of the multi-blade type, the driving of the blades between closed and open positions is accomplished by the movement of an operating member, usually a rotatably mounted ring surrounding the exposure aperture. Since the pivotal axis of the blades and of the are not concentric, some form of loose connection has always been utilized, most often a pin and slot connection, with a pin .on the driving ring operating in a straighter arcuateslot formed in the material of each shutter blade, .or conversely a pin on each shutter blade operating in a slot formed in the material of the driving ring.

Both of the above forms of driving connection are subject to certain disadvantages, which become increasingly important. as the speed of movement of the shutter blades is attempted to be increased. First, there is necessarily a certain amount of play between the pin and its slot, in order to ensure freedom of movement, which means that the position of the blade is not always under positive control from the driving member or ring. Thus the blade may be subject to flutter or erratic movements which reduce the efficiency of the shutter, and even multiple exposure where the blades are allowed to rebound after completion of one exposure.

In the second place, the impact force which occurs when the pin contacts the edge of the slot is localized along a line contact, and the stress applied to the slot may therefore be so large as to damage the slotted member or deform it in size and shape. This is particularly true where the slot is formed in the relatively thinmaterial of which the blades are manufactured, the pin being on the blade ring. It has been proposed to reenforce the edges of such a slot in order to strengthen the same against this impact force, but such a solution greatly increases the cost of the blades, as well as adding to their effective thickness and hence complicating the blade mounting and the arrangement oi associated parts. In the converse case where the blade carries the pin and the drive ring is slotted, the eccentricity of loading becomes objectionable.

In order to ensure unimpeded movement of the blades, and to eliminate friction, it has always been essential in these prior art constructions that the driving ring be spaced more or less from the blades themselves. Hence, the force applied to the pin by the end of the slot is not directed along the median plane of the blade, but is eccentric, and this eccentricity produces a couple tending to twist the blade out of its own plane. This tendency is objectionable both from the point of view of blade life and operating efficienc since the eccentric loading of the blade pivot increases friction between the blades and their guiding surfaces, wears the pivot bearing and increases the looseness of fit which in some measure exaggerates the lack of control of the blades by the driving member or ring.

It is a primary object of the present invention to provide a shutter blade driving connection which will overcome all of the above objections, and which is particularly adapted to shutters of a high speed type in which its advantages are most valuable. Specifically, the invention aims to obtain this object by utilizing a form of driving connection which, while compensating for the differences in movement paths of the shutter blades and the driving member, does so without introducing any undesired looseness or freedom of movement of the blades, hence reducing wear and increasing the possible speed of operation without danger of damage to the parts.

An additional object of the invention is to provide a shutter blade drive which will enable a large part of the effective mass of the mechanism to be brought up to a relatively high speed prior to any substantial movement of the shutter blades thereby, so that the actual dofling movement of the blades is performed in a shorter space of time than is required where all of the mechanism, including the blades, leaves its rest position at the same instant.

It is a further object of the invention to provide a shutter in which the chance of a rebound of the shutter blades, after completion of the donning or closing phase of their cycle, is rendered much less likely, and indeed substantially impossible, as compared with prior art constructions. Such a rebound, of course, is very objectionable, inasmuch as it permits a second exposure of the photographic film at some time after completion of the first exposure, and while the second exposure is quite small, in a welldesigned prior art shutter, there are conditions under which it is sufficient to ruin the image.

A still further object of the invention is to provide a shutter mechanism which permits the closing phase of the shutter blades to be accomplished in .a minimum of time for a given spring tension and clear aperture, and this feature, when coupled with the rapid opening speed of the blades mentioned above, provides a shutter whose optical efficiency is very materially increased. In other words, the time during which the shutter is in its fully open position is a very large percentage of the total time required from the commencement of the opening phase to the completion of the closing phase.

An ancillary object of the invention is to provide a construction having the above advantages with a minimum of complication of the parts, whereby the mechanism may be made rugged and reliable, and at a low cost.

The above and other objects and advantages of my invention will best be understood by reference to the following detailed specification of a preferred embodiment thereof, taken in connection with the accompanying drawings, in which:

Fig. l is a front elevational view of a typical form or muiti-blade shutter embodying the im proved construction, parts being broken away, and the blades being in closed position; and

Fig. 2 is a fragmentary view of a portion of the structure shown in Fig. l, but with the blades in their fully open position.

Speaking generally, I accomplish the objects of my invention by connecting the shutter blades to the operating member (usually an oscillatable ring) through a pivoted link, the point at which one end of the link is pivotally secured to the shutter blade being preferably so chosen that there is obtained a non-uniform transmission of the ring motion to the blade. More specifically, this point of connection to the shutter blade may be so selected that, during the initial portion of the movement of the ring in opening the blades, the transmission ratio is such that the shutter blades are moved only a short distance; as the ring movement progresses, the extent to which its motion is imparted to the blades is increased, reaching a maximum when the blades are fully open. During the retrograde or closing phase or" the cycle, the transmission ratio from ringto blades is decreased in a similar way until, when the blades are again fully closed, slight movements of the ring have little or no effect on the positions of the blades. As will more particularly be pointed out hereinafter, it is this latter feature which positively prevents any rebound of the ring itself from causing a secondary opening of the shutter blades from their closed positions.

Referring now to Fig. l of the drawings, I have illustrated the application of one form of my improved blade linkage to a shutter construction of a known type, comprising a shutter casing It provided with an upstanding outer flange [2 which supports a rotatable cover plate l4 adapted to control the shutter speed in a known manner, and here illustrated as provided with a serrated edge It and a shutter speed scale l8. Pivotally mounted in casing Hi, as by pivot pins 20, are a plurality (here five) of shutter blades 22, arranged for driving connection with an oscillatable ring 24. The manner in which ring 24 is oscillated through a forward and a reverse phase to accomplish the opening and closing movements will now be described, although this mechanism per se is well known in the art.

Pivotally mounted on a mechanism plate 25 is a Winding or cookin lever 28, normally biased to a counter-clockwise position by a power spring 30, one end of which engages a shoulder 32 on lever 28, the other being secured to a fixed part of the casing or plate 26. Pivoted to lever 28, as at 34, is a blade operating hook 36 receiving rithin its notched end 38 a lug 40 secured to ring 2-. and passing through plate 26 by means of a slot 42. A sprin 44 secured to plate 26 serves to maintain hook 35 in engagement with lug 40. When the parts are their Fig. 1 positions, hook 36 maintains ring 24 in its most counter-clockwise position, and hence the blades 22 are kept in closed position, it being understood that the windin lever 28 is latched in this position by the usual trip lever 44 and trigger 46. When trigger 46 is depressed in the direction of arrow at, a shoulder thereon engages and move trip lever 44 against the pressure of a spring 48, and the end of the trip lever is thereby disengaged from a shoulder 50 of lever 28, allowing the same to swing under the impetus of its spring 30, in the direction of arrow 22 to its dotted line position. During this movement, hook 35 causes lug 4! to move first to the right, swinging blade ring 24 clockwise to cause the shutter blades 22 to open the aperture in a known manner, and thereafter, hook 36 pulls lug 4U leftward, returning ring 24 to its counterclockwise position and closin the blades to complete the exposure.

The angular relation of lever 28 to hook 36, and of the latter to lug 40, are such as to prevent any opening of the blades 22 during the winding or cooking movement of lever 28 in preparation for the next exposure, in a manner well known in this art. Any known or convenient form of speed control mechanism may be incorporated in the shutter and connected for control by cover plate i l or otherwise, but as such mechanism forms no essential part of the present invention, it is not here described in detail.

In accordance with my invention, I provide between each of the blades 22 and the oscillating ring 24 a connection here shown as a link 52 pivoted at its respective ends to the blade and ring. As shown in Fig. 1, when the shutter is in closed position, these links 52 he nearly perpendicular to the ring 24, so that slight movements of the ring produce little or no movement of the blades. When, however, the ring has been oscillated counter-clockwise to its Fig. 2 position, the axis of each link 52 lies nearly tangential to the direction of ring 24, so that movements of the ring are transmitted practically directly to the blades.

The manner in which the above construction accomplishes the objects of the invention will now be clear. During the initial portion of the shutter opening movement of ring 24, the transmission ratio from ring to blades is practically zero, so that acceleration of the rin under the impetus of spring 35 and hook 35 is substantially unimpeded by the drag and inertia of the blades themselves. However, this transmission ratio gradually increases to such an extent that, as the blades begin to uncover the aperture, the kinetic energy of moving ring 24 readily overcomes their inertia and moves them very rapidly to the fully open position of Fig. 2, where it will be observed that motion of the ring 24 is being transmitted practically directly to the blades. In a similar manner, the initial closing movements of the blades are accomplished quite rapidly because of the high transmission ratio at this time. When however, the blades have again reached an overlapping or. closed relationship, the transmission ratio has again been reduced practically to zero, with the result that any over-running of the blade ring or associated driving parts is conveyed only slightly or not at all to the blades; in any event, insufficiently to permit the blades to reopen even slightly.

The particular arrangement of blade, link and operating ring illustrated in Figs. 1 and 2 has another advantageous aspect. It will be noted from these figures that the plane of link 52 lies between the planes of the blade and of the ring; in other words, the blade and ring are separated by the thickness of link 52. In prior art constructions, such as those utilizing a pin and slot connection of the type above mentioned, there is necessarily some space between the blades and the ring, as otherwise these parts would contact one another and exert a frictional drag on the blades. Also, such spacing is responsible for the eccentric forces above mentioned which apply an undesirable twisting force or couple to the blades. In the present construction, since the force applied by link 52 to blade 22 is applied practically in the plane of the blade, because there need be no separation between these parts except such as is necessary to ensure free movement of the parts, this twisting effort is almost if not entirely eliminated. It will be noticed, in comparing Figs. 1 and 2, that the direction of link 52 with respect to a line drawn between its point of attachment to the blade and the pivotal axis of the blade has hardly changed as between shutter open and shutter closed position; in both cases, the link axis is nearly perpendicular to such a line. This means that the link has rotated with respect to blade 22 very little during the blade movement, and hence that practically no energy has been dissipated in frictional movements between these parts; much less, obviously, than would be the case if blade 22 were in face contact with the underside of ring 24. Moreover, the area of contact between the upper surface of link 52 and the under surface of ring 24 is so small that here again there is only a trivial loss in friction. Thus, the object of reducing frictional loss and twisting forces has been accomplished in a very expeditious and efiicient manner.

Many changes and modifications may obviously be made in the constructions above described in detail, without departing from the scope of the invention as defined in the appended claims.

I claim:

1. A photographic shutter comprising a casing having an exposure aperture therein, a plurality of blades pivotally mounted in said casing at points spaced about said aperture for movement to cover and uncover said aperture, an operating rin surrounding said exposure aperture and mounted for rotation concentric with said aperture, said ring lying wholly outside the points of pivotal mounting of said blades, a plurality of links each having one of its ends pivotally connected to a corresponding one of said blades at a point spaced from the pivotal mounting of said blade, and its other end pivotally connected to said ring, the location of the last named pivotal connection being such that, when the blades are in their closed positions, each link lies perpendicular to the direction of movement of said ring, and when the blades are in open position, said links lie nearly parallel to the direction of movement of the ring.

2. A photographic shutter in accordance with claim 1, in which each of said blades lies in a plane spaced from the plane of said ring, and in which each of said links is disposed in a plane between the plane of its corresponding blade and the plane of said ring.

FREDERICK P. WILLCO-X.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,861,257 Barenyi May 31, 1932 2,168,893 Aiken Aug. 8, 1939 2,359,116 Johnson Sept. 26, 1944 2,398,567 Tranefors Apr. 16, 1946 FOREIGN PATENTS Number Country Date 155,213 Great Britain Mar. 10, 1922

Images