Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
1999-06-09
2001-06-26
Le, Que T. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C250S231180
Reexamination Certificate
active
06252223
ABSTRACT:
The present disclosure relates to subject matter contained in Japanese Patent Application No. Hei-10-168354 filed on Jun. 16, 1998, which is expressly incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a rotary encoder.
2. Description of the Related Art
Rotary encoders are commonly used in a variety of applications. For example, many electronically-controlled cameras use a rotary encoder. An electronically-controlled camera uses electronics circuitry for controlling operations of the camera. When the user of the camera wishes to take a picture at his desired aperture or shutter speed, and/or with a certain correction to the exposure value, he/she has to enter corresponding parameter(s) into the electronics circuitry. The entry of parameters is often made using a dial supported on a rotary shaft, which is typically connected to a rotary encoder for converting angular positions of the dial into corresponding electrical signals.
A rotary encoder for use in a small-size electronic apparatus, such as an electronically-controlled camera as described above, is required to be compact among others requirements.
A typical rotary encoder for such purposes comprises a rotary shaft adapted to be supported for rotation about its axis, a disk fixedly secured to the rotary shaft and made of an insulating substrate with a conductive pattern formed on a side surface thereof, and a plurality of electrical contacts adapted for fixed mounting and so arranged as to be in contact with the conductive pattern depending on the angular position of the disk such that various combinations of the electrical contacts may be electrically interconnected one another depending on the angular position of the disk.
For a small-size rotary encoder having this arrangement, the reduction in volume of the structure for securing the disk to the rotary shaft is critical because the relative volume of this structure to the overall volume of the rotary encoder increases as the latter volume is decreased.
One typical structure for securing the disk to the rotary shaft includes mating portions formed on the disk and the rotary shaft and a single set screw for retaining the disk to the rotary shaft. The mating portions serve to define the relative angular position of the disk to the rotary shaft and prevent any angular displacement between them. The disk has a central hole formed therein and the rotary shaft has an axially-extending, central threaded hole formed therein. The set screw is passed through the hole in the disk and threadably engaged into the threaded hole in the rotary shaft.
However, since such a single set screw engaged into a central threaded hole in the rotary shaft is subject to unintentional loosening during use, a relatively large set screw is required for this purpose, resulting in a large volume of the structure for securing the disk to the rotary shaft and thus in a large overall size of the rotary encoder.
Use of two or more set screws located off-center with respect to the rotational center of the disk may be effective for preventing unintentional loosening and smaller set screws may be used in such arrangement. However, this arrangement may raise another problem that any set screws so located goes around the rotational center of the disk, which requires more space on the disk, still resulting in a large overall size of the rotary encoder.
SUMMARY OF THE INVENTION
In view of the foregoing, it is an object of the present invention to provide a rotary encoder comprising a rotary shaft and a disk fixedly secured to the rotary shaft, in which the overall size of the rotary encoder may be minimized while the disk may be safely secured to the rotary shaft with reduced possibility of loosening during use.
In accordance with one aspect of the present invention, there is provided a rotary encoder comprising a rotary shaft adapted to be supported for rotation about its axis and having at least one axially-extending, threaded hole formed therein at its one end. The rotary encoder further comprises a disk made of an insulating substrate with a conductive pattern formed on a side surface thereof. The disk is fixedly secured to the one end of the rotary shaft by means of at least one set screw threadably engaged into the at least one threaded hole formed in the rotary shaft such that the disk is rotatable about a rotational center defined by the axis of the rotary shaft. The rotary encoder further comprises a plurality of electrical contacts adapted for fixed mounting and so arranged as to be in contact with the conductive pattern depending on the angular position of the disk such that various combinations of the plurality of electrical contacts may be electrically interconnected one another depending on the angular position of the disk. The at least one threaded hole and the at least one set screw is located off-center with respect to the rotational center of the disk. The conductive pattern has a central portion covering the region of the rotational center of the disk. The plurality of electrical contacts include a centered electrical contact so arranged as to be in contact with the conductive pattern substantially at the rotational center of the disk.
In accordance with another aspect of the present invention, there is provided a rotary encoder comprising a rotary shaft adapted to be supported for rotation about its axis and having a plurality of axially-extending, threaded holes formed therein at its one end. The rotary encoder further comprises a disk made of an insulating substrate with a conductive pattern formed on a side surface thereof The disk is fixedly secured to the one end of the rotary shaft by means of a plurality of set screws threadably engaged into the plurality of threaded holes formed in the rotary shaft such that the disk is rotatable about a rotational center defined by the axis of the rotary shaft. The rotary encoder further comprises a plurality of electrical contacts adapted for fixed mounting and so arranged as to be in contact with the conductive pattern depending on the angular position of the disk such that various combinations of the plurality of electrical contacts may be electrically interconnected one another depending on the angular position of the disk. The plurality of threaded holes and the plurality of set screws are located off-center with respect to the rotational center of the disk and along a circle centered to the rotational center of the disk. The conductive pattern has a central portion covering the region of the rotational center of the disk. The plurality of electrical contacts include a centered electrical contact so arranged as to be in contact with the conductive pattern substantially at the rotational center of the disk.
The rotary encoder may be provided in an electronic apparatus having electronics circuitry defining a system ground, with the centered electrical contact being connected to the system ground.
REFERENCES:
patent: 5057684 (1991-10-01), Service
Asahi Kogaku Kogyo Kabushiki Kaisha
Greenblum & Bernstein P.L.C.
Le Que T.
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