Abstract:
In a finder apparatus, a diopter adjusting knob for driving an eyepiece back and forth is supported by a shaft portion of a main body. A plurality of V-shaped ratcheting grooves are disposed in a direction orthogonal to a parting line caused by molding under the shaft portion of the main body. The diopter adjusting knob is ratchetingly adjusted when a ball supported on a diopter adjusting knob slides in contact with the V-shaped grooves. The main body can be molded using simple dies without slides because the V-shaped grooves are orthogonal to the parting line.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a ratcheting device and more particularly to a diopter adjustment device. 
     2. Related Art Statement 
     A diopter adjusting mechanism incorporating a ratchet device for locating the position of a diopter adjusting dial has been disclosed in Japanese unexamined patent publication No. H1-291227. This diopter adjusting mechanism has a rotatable cylindrical cam ring integral with an adjusting dial for diopter adjustment. A series of grooves are provided on the outer circumference of the cam ring, and a ratchet ball is disposed in such a manner that it always contacts and slides on the groove like a pawl. When the adjusting dial is rotated, the position of the dial can be located with the ratchet device. 
     However, the ratchet device incorporated in the above-described diopter adjusting mechanism makes it difficult to configure an apparatus like a camera with a small size because the ratchet grooves provided on the cylindrical cam ring increase the space occupied by the device. 
     Other conventional ratchet devices constituted by a rotary member occupying a ball space and having simple structures include ratchet devices having a ratchet ball provided on a rotary member such that it moves to draw an arcuate locus on a plane and having ratchet grooves provided on a fixed member on which the ball slides. The grooves of such a ratchet device are disposed in a radial configuration on a plane of the fixed member. 
     In the case of the above-described ratchet device, however, the area of the fixed member where the grooves are formed must be released from the molding die in which it is formed in a direction orthogonal to the plane of the grooves because the grooves are disposed in a radial configuration. This makes it necessary to use a slide die and can reduce productivity. 
     SUMMARY OF THE INVENTION 
     The present invention has been conceived to solve the above-described problem, and it is an object of the invention to provide a ratchet device which has a simple structure, whose components can be easily manufactured and which can be made compact. 
     According to an aspect of the invention, there is provided a ratchet device having a rotary member rotated about a rotary shaft, a base member for rotatably supporting the rotary member, a contact member provided between the rotary member and base member and an urging member. The base member has a plurality of linear ratcheting grooves which are provided on a surface orthogonal to the rotary shaft and which extend in parallel with each other. 
     In the ratchet device, the rotary member is in contact with the contact member which is in contact with the grooves for ratcheting movement. When the rotary member is rotated, the contact member moves over the grooves resulting in a ratcheting operation. 
     According to another aspect of the invention, there is provided a ratchet device having a rotary member rotated about a rotary shaft, a base member for rotatably supporting the rotary member, a contact member provided between the rotary member and base member and an urging member. The base member is formed using injection molding, such that the parting line forced during the injection molding process passes through the center of the rotary shaft. The base member has ratcheting grooves forming part of the ratchet mechanism. The grooves are parallel linear grooves which are provided on a surface orthogonal to the rotary shaft so as to be orthogonal to the parting line. The urging member urges the rotary member into contact with the contact member which is in turn urged into contact with the ratchet grooves. 
     In the ratchet device, when the rotary member is rotated, the contact member moves over the ratchet grooves, resulting in a ratcheting operation. 
     According to still another aspect of the invention, there is provided a ratcheting device for a camera having a manually operated operating member, a molded ratcheting member having ratcheting grooves and a contact member sliding in contact with the ratcheting grooves as the operating member is rotated. The ratcheting grooves on the ratcheting member are provided on a surface extending perpendicular to a parting line on the ratcheting member which is created during the molding operation. 
     In the ratchet device for a camera, when the operating member is rotated, the contact member moves across the grooves, resulting in a ratcheting operation. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view of a finder apparatus incorporating a ratchet device which is a first embodiment of the invention. 
     FIG. 2 is a sectional view taken along the line A—A in FIG.  1  and showing a section in the region of a diopter adjusting knob. 
     FIG. 3 is a sectional view taken along the line B—B in FIG.  2  and showing disposal of V-shaped grooves provided on the main body. 
     FIG. 4 is a sectional view taken along the line C—C in FIG.  3  and showing a sectional configuration of the V-shaped grooves. 
     FIG. 5 is an exploded perspective view of a major part in the region of a diopter adjusting knob of a finger apparatus incorporating a ratchet device which is a second embodiment of the invention. 
     FIG. 6 is a sectional view taken along the line D—D in FIG.  5  and showing a vertical section in part of the region of the diopter adjusting knob. 
     FIG. 7 is a sectional view taken along the line F—F in FIG.  6  and showing disposal of a ball groove provided on the main body. 
     FIG. 8 is a view taken in the direction of the arrow E in FIG.  5  and showing a configuration of the diopter adjusting knob. 
     FIG. 9 is a sectional view taken along the line G—G in FIG.  8  and showing a sectional configuration of the V-shaped grooves. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Preferred embodiments of the invention will now be described with reference to the drawings. 
     FIG. 1 is an exploded perspective view of a view finder apparatus incorporating a ratchet device which is a first embodiment of the invention. FIG. 2 is a sectional view taken along the line A—A in FIG. 1 showing a section in part of a ratchet device in the finder apparatus. FIG. 3 is a sectional view taken along the line B—B in FIG. 2, and FIG. 4 is a section taken along the line C—C in FIG. 3, each of them showing a configuration of ratchet grooves forming part of the ratchet device. 
     The finder apparatus of the present embodiment is formed by a screen portion  1 , a Dachkant prism portion  2  and a finder eyepiece portion  3 . The ratchet device is incorporate in the finder eyepiece portion  3 . 
     The finder eyepiece portion  3  is formed by a main body  11  which is a base member (frame member), an eyepiece  12  having a finder optical axis  100 , a diopter adjusting knob  13  which is a rotary member (operating member), an urging spring  14  for urging the eyepiece  12  and a spherical ball  15  which is a contact member attached to the adjusting knob  13 . 
     On the main body  11 , there is provided a lens hole  11   a  into which the eyepiece is inserted, a guide groove  11   b  and a semi-cylindrical projection  11   c  facing each other and extending in parallel in the direction of the optical axis  100 , a shaft portion  11   d  having a flange  11   e  located under the projection  11   c  and a plurality of V-shaped grooves  11   f  located under the shaft portion  11   d.    
     After the main body  11  is molded, the die is released in the vertical direction D shown in FIGS. 2 and 3, and a mold parting line  11   g  in the vicinity of the shaft portion  11   d  is formed which runs orthogonal to the direction D. 
     The plurality of linear V-shaped grooves  11   f  having a V-shaped section at parallel unequal intervals (FIG. 3) are provided on a surface orthogonal to the shaft portion  11   d  and are orthogonal to the parting line  11   g . As detailed later, the ball  15  of the diopter adjusting knob  13  slides across the plurality of V-shaped grooves  11   f , in contact therewith, along a ball locus S in the form of an arc about the shaft portion  11   d.    
     Pitches P 1  through P 3  (pitches in the direction of the parting line) of the plurality of the V-shaped grooves  11   f  are defined such that divided central angles of the ball  15  describes as the ball  15  travels along the ball locus S for the pitches are equal to each other. The diopter adjusting knob  13  clicks (ratchets) at equal angular intervals, and the pitches P 2  and P 3  are set smaller than the V-groove pitch P 1  located directly under the shaft portion  11   d  according to their increasing distances from the shaft position. 
     Provided integrally with the eyepiece  12  (FIG. 1) are a guide pin  12   a , a U-shaped groove  12   b  provided opposite to the guide pin in a direction parallel with the optical axis  100  and a pin slide groove  12   c  which is provided on the side of the U-shaped groove and which extends in the vertical direction perpendicularly to the optical axis  100 . 
     The diopter adjusting knob  13  is formed with knurl portion  13   a  on an outer circumferential surface thereof, a fitting hole  13   b  having an opening portion  13   c  smaller than the mating hole, a cylindrical projecting  13   d  and support hole  13   f  holding the ball  15  in a predetermined position. 
     Referring to the assembly of the finder eyepiece portion  3 , the eyepiece  12  is first inserted into the lens hole  11   a  of the main body  11 . At the same time, the guide pin  12   a  and the U-shaped groove  12   b  of the eyepiece are slidably inserted in the guide groove  11   b  and the projection  11   c  of the main body, respectively. 
     The ball  15  is inserted in the support hole  13   f , and the diopter adjusting knob  13  with the urging spring  14  attached to the projection  13   d  mounted by fitting the shaft portion  11   d  of the main body into the fitting hole  13  while expanding the opening portion  13   c  with a pressure and by inserting the projection  13   d  into the pin slide groove  12   c  of the eyepiece simultaneously such that it can slide in the groove. 
     When the diopter adjusting knob  13  is rotated in the above-described mounted state, the ball  15  slides along the V-shaped grooves in contact therewith and is held by a predetermined biasing force when located in the valley of each of the V-shaped grooves. 
     In such a ratcheting operation, the ball  15  must be displaced relative to the peaks and valleys of the V-shaped grooves  11   f  in the urging direction. While the displacement can be also achieved as a result of slight elastic deformation of the diopter adjusting knob  13 , the wall of the main body  11  and the like in the direction in which the ball contacts them, the ball  15  is pre-loaded by the urging spring  14  through the diopter adjusting knob  13  and can be displaced when the diopter adjusting knob  13  is slightly inclined relative to the shaft portion  11   d.    
     Since the eyepiece  12  is urged by the urging spring  14  to be held with the U-shaped groove  12   b  in contact with the projection  11   c , no shake, inclination or the like occurs on it even when it is moved back and forth in the direction of the optical axis  100 . 
     When the diopter adjusting knob  13  of the finder apparatus of the present embodiment having the above-described configuration is rotated, the eyepiece  12  is moved back and forth in the direction of the optical axis  100  to allow diopter adjustment of the eyepiece  12 . The ball  15  moves in contact with the V-shaped grooves  11   f  of the main body  11 , and the diopter adjusting knob  13  is ratcheted into discrete positions of rotation where the ball  15  fits in the valleys of the V-shaped grooves. 
     In the above-described finder apparatus according to the present embodiment, the ratchet device for ratcheting the diopter adjusting knob  13  has a simple structure, and the V-shaped grooves  11   f  on which the ball  15  of the ratchet device slides in contact therewith has a configuration extending in the direction in which the main body  11  is released from the die (configuration orthogonal to the parting line). This makes it possible to use a simple die having no sliding part or the like and to improve productivity. 
     A description will now be made on a finder apparatus for a camera incorporating a ratchet device according to a second embodiment of the invention. 
     FIG. 5 is an exploded perspective view of the region of a diopter adjusting knob of the finder apparatus for a camera according to the present embodiment. FIG. 6 is a sectional view taken along the line D—D in FIG. 5 showing a vertical section in part of the region of the diopter adjusting knob. FIG. 7 is a sectional view taken along the line F—F in FIG.  6 . FIG. 8 is a view taken in the direction of the arrow E in FIG.  5 . FIG. 9 is a sectional view taken along the line G—G in FIG.  8 . 
     The finder apparatus of the present embodiment has substantially the same configuration as that of the finder apparatus of the first embodiment. Specifically, it is formed by a screen portion  1  as shown in FIG. 1, a Dachkant prism portion  2  and a finder eyepiece portion  3 ′, and a ratchet device is incorporated in the finder eyepiece portion  3 ′. 
     The finder apparatus of the present embodiment is different from the finder apparatus of the first embodiment in the configuration of the ratchet device in the finder eyepiece portion  3 ′. Specifically, the finder eyepiece portion  3 ′ has a main body  11 ′ as a base member and a diopter adjusting knob  13 ′ as shown in FIG. 5 in addition to an eyepiece  12 . The description will be made only on the difference from the finder apparatus of the first embodiment. 
     No V-shaped groove is disposed on the main body  11 ′ and, instead, a ball groove  11   h  in which a ball  15  (as a contact member) can fit in contact therewith is provided in a direction orthogonal to a parting line  11   g  and orthogonal to a shaft portion  11   d  (see FIGS.  6  and  7 ). The structure is otherwise the same as that of the main body  11 . 
     The support hole  13   f  for holding the ball  15  is not provided on the diopter adjusting knob  13 ′ and, instead, a plurality of V-shaped grooves  13   g  are provided under a fitting hole  13   b  (FIG. 6) in which the shaft portion  11   d  is fitted. 
     As shown in FIGS. 8 and 9, the plurality of linearly extending, parallel V-shaped grooves  13   g  are formed at unequal intervals. The ball  15  of the diopter adjusting knob  13 ′ slides across the V-shaped grooves  13   g  in contact therewith along a ball locus S in the form of an arc about the shaft portion  11   d.    
     The pitches W 1  through W 3  (pitches in a direction orthogonal to the V-shaped grooves) of the plurality of the V-shaped grooves  13   g  are defined such that divided central angles of the ball locus S for the pitches are equal to each other. Therefore, the diopter adjusting knob  13 ′ ratchets at equal angular intervals, and the pitches W 2  and W 3  are set smaller than the V-groove pitch W 1  of the V-shaped grooves  13   g  located directly under the shaft portion  11   d  (fitting hole  13   b ) according to their increasing distances from the region passing through the center of the shaft portion. 
     In the ratchet device incorporated in the finder apparatus of the present embodiment having the above-described configuration, when the diopter adjusting knob  13 ′ is rotated, the ball  15  slides across the V-shaped grooves  13   g  in contact therewith and is held by a predetermined ratcheting force when located in the valley of each of the V-shaped grooves. 
     In such a ratcheting operation, the ball  15  must be displaced relative to the peaks and valleys of the V-shaped grooves  13   g  in the urging direction. An urging force is applied to by an urging spring  14  through the diopter adjusting knob  13 ′ and can be displaced when the diopter adjusting knob  13 ′ is slightly inclined relative to the shaft portion  11   d  as a result of deflection of the urging spring  14 . 
     In the above-described finder apparatus according to the present embodiment, the ratchet device for ratcheting the diopter adjusting knob  13 ′, like the first embodiment, has a simple structure, and the ball groove  11   h  in which the ball  15  of the ratchet device fits in contact therewith can be formed in a configuration extending in the direction in which the main body  11 ′ is released from the die (configuration orthogonal to the mold parting line). This makes it possible to use a simple die having no sliding part or the like as the die for molding the main body  11 ′ and to improve productivity. 
     In the first and second embodiments the plurality of V-shaped grooves  11   f  and  13   g  are formed as recesses on the surface  11   h  of the main body  11  or the surface  13   h  of the diopter adjusting knob  13 ′ as shown in the sectional view in FIG. 4 or  9 . The invention is not limited thereto, and the grooves may be provided by forming a plurality of peak portions or projections which rise on the main body surface  11   h  or knob surface  13   h , which provides the same effect. 
     Although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is preferred, therefore, that the present invention be limited not by the specific disclosure herein, but only by the appended claims.