Photography – Camera detail – Shutter
Reexamination Certificate
2002-05-07
2004-04-27
Rutledge, D. (Department: 2851)
Photography
Camera detail
Shutter
C396S487000, C396S488000, C396S493000
Reexamination Certificate
active
06726381
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a focal-plane shutter for cameras.
2. Description of Related Art
Shutters for cameras are roughly divided into two classes, focal-plane shutters and lens shutters. Focal-plane shutters used in recent years are mainly provided with two shutter blades (a first blade (group) and a second blade (group)), which are separately placed in two blade chambers constructed with three plate members, called a shutter base plate, an intermediate plate, and an auxiliary base plate, respectively. The shutters of this type are used in film cameras and digital cameras as well, and the two shutter blade groups are actuated in turn at a preset interval of time in photography so that an exposure operation is continuously performed, through a slit provided by the shutter blade groups, from one side of a rectangular imaging surface toward its opposite side.
Some of focal-plane shutters used only in digital cameras have a single shutter blade group. In this case, of the three plate members, the intermediate plate is not provided and the shutter base plate and the auxiliary base plate constitute a single blade chamber. In the shutters of this type, the imaging surface is usually exposed to light from an object, and only when photographing is completed, the imaging surface is temporarily covered.
In both types mentioned above, however, the shutter blade groups have the same structure, each with a mechanism in which one or more strip-shaped blades are supported to be rotatable with respect to a plurality of arms whose ends are pivotally mounted to the shutter base plate and thereby a link mechanism of parallelogram is applied. This pivotally supporting structure with the arms and the blades is such that holes provided in the arm and the blades are superposed and the tops of joint shanks which are rivet parts are inserted into the holes from the arm side and are caulked to the blades. The shutter is designed so that each of caulking portions does not project from the sliding surface of the blade in accordance with the shape of the blade, but the head of the joint shank, situated on the shutter base plate side or the auxiliary base plate side, projects from the arm.
The lens shutters, on the other hand, are of two types: a lens shutter located between two photographic lenses and a lens shutter located behind them. Most of such lens shutters are such that an exposure aperture is opened and closed at about the middle thereof. In either type, the lens shutters can be used in both film cameras and digital cameras. When they are used in the digital cameras, the imaging surface is usually exposed to light from the object, and only when photographing is completed, the imaging surface is temporarily closed.
Moreover, some of the lens shutters have an aperture restriction as in a stop mechanism. In this case, when they are used in the film cameras, a closing operation is performed from a preset position of the aperture restriction before a circular exposure aperture is fully opened in photography, while when used in the digital cameras, the aperture is opened at a preset position of the aperture restriction before photography, and the closing operation is temporarily performed only when photographing is completed. Even in such lens shutters, blades and members actuating the blades are connected by fitting structures that the joint shanks inserted into the holes can be rotated.
The shutter mechanism constructed as mentioned above is operated at fairly high speed, and thus the shutter appears to work and stop without any problem. In practice, however, the shutter is operated with complicated movement, as the case may be, and experiences a serious shock when stopped, so that, for example, the blades are temporarily deformed. Consequently, extremely fine wear dust is produced by sliding and abutment due to movements of individual members. Such wear dust may be produced even where one surface slides over another surface as in the blades or the blade and the base plate, but most often where the shank slides along the hole as in a portion connecting the blade to another member.
A typical example of the above description in the focal-plane shutter will be explained below. An ordinary shutter blade group, as mentioned above, is constructed with the arms, blades, and joint shanks. As such, in the operation of the shutter blade group, the fitting portion in which the joint shank is inserted into the hole of the arm is relatively brought into a sliding and contacting state. The impact force exerted by the stop of the shutter considerably influences this fitting portion. Moreover, in the operation of the shutter blade group, the heads of the joint shanks slide over the surface of the base plate. In this operation, not only is the shutter blade group normally actuated, but it is irregularly moved. In particular, since the arms and the blades are deformed at a stop, the phenomenon occurs such that the heads of the joint shanks are struck against the surface of the shutter base plate or the auxiliary base plate. Furthermore, in most cases, the pivotally supported portion of a slit-forming blade is constructed to enter and leave the exposure aperture in the operation of the shutter blade group, and thus when it leaves the exposure aperture, the heads of the joint shanks abut on the edge of the aperture of the shutter base plate or the auxiliary base plate.
This will be explained with reference to a conventional example shown in FIG.
1
. In this figure, an aperture Aa is provided at about the middle of a shutter base plate A. Although this conventional example is actually provided with two shutter blade groups, only the second blade group is shown in FIG.
1
. Thus, in the conventional example, an intermediate plate B is placed on the back side of the shutter base plate A, and an auxiliary base plate C is also placed on the back side thereof, so that the second blade group is situated in a blade chamber provided between the intermediate plate B and the auxiliary base plate C. Apertures Ba and Ca, similar in shape to the aperture Aa, are provided in the intermediate plate B and the auxiliary base plate C, respectively, and the shape of the exposure aperture (an image frame) is restricted by at least one of these apertures.
The second blade group is constructed with two arms D and E and four blades F, G, H, and I. The arms D and E are rotatably mounted to the shutter base plate A at their left ends, and the blades F, G, H, and I are pivotally supported with respect to the arms D and E through the joint shanks (rivet parts). The pivotally supporting structures of individual blades are the same, and hence only the pivotally supporting structure of the blade I will be described here. A joint shank J is inserted into the holes of the arm D and the blade I from the side of the auxiliary base plate C, and the end of the inserted shank is caulked to the blade I. A joint shank K is also inserted into the holes of the arm E and the blade I from the side of the auxiliary base plate C, and the end of the inserted shank is caulked to the blade I. Consequently, the heads of the joint shanks J and K are situated on the side of the auxiliary base plate C, and the arms D and E and the joint shanks J and K are not fixed. The caulking portions of the joint shanks J and K, not shown in the figure, are such that they do not project into the surface side of the blade I (this side of the paper of
FIG. 1
) by partially deforming the blade I.
In the structure mentioned above, when the second blade group is actuated, the joint shanks J and K follow arcuate working paths indicated by chain lines in the figure. Since the remaining six joint shanks are also operated at the same angle, their working paths likewise become arcuate. In this operation, the blades F, G, H, and I, in which a mutually overlapping relation is changed, slide along adjacent blades. The blades F, G, H, and I also slide along the intermediate plate B and the auxiliary base plate C. On the other hand, individua
Takahashi Shigemi
Usuda Yuichirou
Nidec Copal Corporation
Pillsbury & Winthrop LLP
Rutledge D.
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