Photography – Camera detail – Shutter
Reexamination Certificate
2003-08-25
2004-10-19
Fuller, Rodney (Department: 2851)
Photography
Camera detail
Shutter
C396S485000, C396S486000, C396S487000, C396S488000, C348S229100, C348S296000, C348S367000
Reexamination Certificate
active
06805500
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a focal-plane shutter for cameras which has one or two shutter blade groups, each including a plurality of arms, one end of each of which is pivotally mounted to a shutter base plate, and at least one blade pivotally supported by the arms.
2. Description of Related Art
In some focal-plane shutters used in recent years, two blade chambers are provided between three plate members, called a shutter base plate, an intermediate plate, and an auxiliary base plate, respectively, and two shutter blade groups, called a first blade (group) and a second blade (group), are separately placed in these blade chambers. Such focal-plane shutters are used in digital still cameras and silver salt film cameras as well. The focal-plane shutters used in the former cameras are known as ones in which a single shutter blade group is placed in a blade chamber provided between the shutter base plate and the auxiliary base plate.
In either type of the focal-plane shutters mentioned above, the fundamental structure of the shutter blade group is the same, and it is common practice that one or more (usually, a plurality of) blades are pivotally supported by two arms (the structure of three arms is also proposed), one end of each of which is pivotally mounted to the shutter base plate, and thereby a link mechanism of parallelogram is constructed. In the type that the two shutter blade groups are provided, a blade pivotally mounted at the foremost arm end of each shutter blade group is constructed as a slit-forming blade. The blades of the shutter blade groups relative to their respective arms have the same pivotal support structure, in which holes provided in the arms and blades are made to overlap and the tops of joint shanks which are rivet parts are inserted into the holes from the arm side and are secured to the blades by caulking work.
As a result, the joint shanks integrated with the blades and the arms are in a mutually rotatable state, but individual blades are pivotally supported by the two arms and thus only when the arms are actuated, relative rotation takes place at pivotal support portions. The caulking work mentioned above is such that each of caulking portions does not project from the sliding surface (a surface different from a surface opposite to the arm) of the blade by changing the shape of the blade, but the head of the joint shank projects from the arm. The structure of such a pivotal support portion is well known and is disclosed, for example, in Japanese Patent Kokai No. Hei 7-333684, but the auxiliary base plate is here referred to as a cover plate.
In the case of the focal-plane shutter which has two shutter blade groups, the sliding surface of each blade is directed toward the intermediate plate in the corresponding blade chamber, and thus the arms for one shutter blade group are placed on the shutter base plate side of the blades, while the arms for the other shutter blade group are placed on the auxiliary base plate side of the blades. Specifically, one shutter blade group causes all the heads of the joint shanks to project from the arms toward the shutter base plate side, while the other shutter blade group causes all the heads of the joint shanks to project from the arms toward the auxiliary base plate side.
Hence, where the shutter of this type is mounted in a camera, either one of the shutter blade groups causes the heads of the joint shanks to project toward the base plate located on the photographer side (namely the image sensor side or the film side) even though either the shutter base plate or the auxiliary base plate is located on the object side. On the other hand, in the focal-plane shutter which has only the single shutter blade group, the heads of the joint shanks can be located on the object side with respect to the camera, but a case occur in which they must be located on the photographer side because of space for incorporating the shutter in the camera.
In the shutter base plate, the intermediate plate, and the auxiliary base plate which constitute the blade chamber, apertures for exposure are provided at about their middle portions so that an exposure aperture of light from the object is determined by one or more of the apertures for exposure. Either of the focal-plane shutters described above is generally constructed so that since it is necessary to downsize the entire shutter unit, at least, the pivotal support portion at the foremost arm end is moved from the outside into the inside of the aperture and is removed from the inside to the outside of the aperture when each shutter blade group is actuated.
In the silver salt film camera as well as in the digital still camera, if dirt or dust particles adhere to the imaging surface of an image sensor or the photosensitive surface of a film, a favorable object image cannot be obtained. However, most of dirt or dust particles, usually produced in the camera, are so fine that it is difficult to see with the eye. Most of dust particles penetrating from the exterior into the camera are also fine, but sometimes contains large ones. In a conventional silver salt film camera, even when relatively large dust particles penetrate into the camera to adhere to the photosensitive surface of the film, only the frame of the film is affected, and thus little attention has been devoted to the dust particles. However, since the defect of the digital still camera to be described later has been known, special attention has frequently been devoted to this defect in recent years.
On the other hand, in the digital still camera, even though dirt or dust particles are extremely fine, attention is arrested. Specifically, when dirt or dust particles are fine, attention is not initially arrested, but they gather gradually on, and adhere to, the imaging surface and a filter placed in front thereof. In this way, the influence of the dust particles on the entire photographing image is gradually increased. Consequently, in the digital still camera, it is necessary to make some provision for any fine dirt or dust whatever. Thus, in the fabrication of the focal-plane shutter, as well as in the camera body itself, it is required to make provision for the structure as far as possible, and many proposals of such provisions have been offered.
Here, consider fine wear dust produced by the actuation of the focal-plane shutter. In the focal-plane shutter, it is generally known that extremely fine wear dust is produced from the sliding and abutting portions of the shutter in the actuation. However, it is very difficult to design the shutter so that the wear dust is not completely produced. The wear dust produced from the abutting portions is larger and more than that produced from the sliding portions. As such, it is necessary that the wear dust chiefly produced from the abutting portions is made to vanish completely or is reduced to a minimum. In this case also, it is advantageous that provision is first made with respect to a place where the wear dust is easy to reach the image sensor or the film. Therefore, it is most important to make provision in the proximity of the aperture of the base plate located on the photographer side, of the shutter base plate and the auxiliary base plate.
When the structure of the focal-plane shutter is seen from such a viewpoint, the focal-plane shutter is constructed so that the heads of the joint shanks used to pivotally support the blades with respect to the arms project from the arms toward the base plate on the photographer side in a state where the shutter is incorporated in the camera. Consequently, the most important problem is that the heads of the joint shanks moved inside the aperture during the actuation of the shutter blade group abut against the edge of the aperture of the base plate on the photographer side (the reason why this abutment is caused is well known and is also set forth in the prior art publication mentioned above) to produce the wear dust. Thus, it is conceivable that, as disclosed in Japanese Patent Kokai No. Hei 9-160
Blackman Rochelle
Fuller Rodney
Nidec Copal Corporation
Pillsbury & Winthrop LLP
LandOfFree
Focal-plane shutter for cameras does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Focal-plane shutter for cameras, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Focal-plane shutter for cameras will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3313886