Abstract:
A shield device includes: a main body having an opening portion; a cylindrical member that is movable in a direction substantially perpendicular to the opening portion; and a shield member, an outer edge of which is engaged to an inner edge of the opening portion, and an inner edge of which is fitted upon an outer surface of the cylindrical member so as to be slidable thereon and so as to shield a gap between the main body and the cylindrical member. And the cylindrical member is movable through the opening portion in a direction of a central axis of the cylindrical member; at least a portion of an outer circumferential surface of the cylindrical member has a shape different from another portion thereof along the direction of the central axis; and the shield member contacts along the outer circumferential surface having the different shape, as the cylindrical member moves in the direction of the central axis.

Description:
INCORPORATION BY REFERENCE 
     The disclosure of the following priority application is herein incorporated by reference: 
     Japanese Patent Application No. 2000-16684 filed Jan. 26, 2000. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a shield device which shields a gap between two members which relatively move with respect to one another, and more particularly relates to a shield device which intercepts light rays and prevent them from getting into the interior of an optical apparatus through a gap between the main body of the optical apparatus and a lens barrel comprised in the optical apparatus, and also relates to a camera. 
     2. Description of the Related Art 
     In the prior art, as a shield device which shields the gap between two members which move relative to one another (for example a main body and a cylindrical member), for example in Japanese Laid-Open Patent Publication No. H10-31146, it has been disclosed to provide a protuberance upon the sliding surface of the shield member which slides against the outer circumferential surface portion of the moving cylindrical member, and to increase the contact force of the shield member against the outer circumferential surface portion of the cylindrical member by the presence of this protuberance, so as to intercept the light rays. Further, in Japanese Laid-Open Patent Publications No. H8-146501 and No. H9-138334, it is disclosed to obtain increased shielding effectiveness by providing a plurality of protuberances upon the shield member which fit against the outer circumferential surface portion of a lens barrel. 
     However, if the movable cylindrical member is manufactured from a plastic material, depending upon the circumstances of the mold shape, a step or burr due to a parting line may be formed upon its outer circumferential surface. Even though this parting line step or burr typically is minute, it is unavoidable for it to cause a minute gap to be formed in the surface contact between the cylindrical member and the shield member. Furthermore, alternatively, if a minute particle of foreign matter should get caught between the cylindrical member and the shield member, this can also cause a minute gap of the same type to open up between them. 
     If a prior art type shield device is utilized with the intention of intercepting light from getting through the gap between the main body of the camera and the lens barrel, there has been the problem that light rays may get into the body of the camera through this minute gap and may expose the film, which is most undesirable. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to propose a shield device and a camera which can reliably and effectively intercept light rays, even if a minute gap is present in the fitting of the shield member upon the cylindrical member. 
     In order to attain the above object, a shield device according to the present invention comprises: a main body having an opening portion; a cylindrical member that is movable in a direction substantially perpendicular to the opening portion; and a shield member, an outer edge of which is engaged to an inner edge of the opening portion, and an inner edge of which is fitted upon an outer surface of the cylindrical member so as to be slidable thereon and so as to shield a gap between the main body and the cylindrical member, and: the cylindrical member is movable through the opening portion in a direction of a central axis of the cylindrical member; at least a portion of an outer circumferential surface of the cylindrical member has a shape different from another portion thereof along the direction of the central axis; and the shield member contacts along the outer circumferential surface having the different shape, as the cylindrical member moves in the direction of the central axis. 
     In this shield device, it is preferred that a diameter of the at least a portion of the cylindrical member is different from a diameter of the another portion of the cylindrical member. In this case, it is preferred that the at least a portion of the cylindrical member is an end portion of the cylindrical member. Furthermore, it is preferred that when the cylindrical member is retracted within the main body, the shield member contacts along a shape of the end portion of the cylindrical member. 
     Also, it is preferred that the shield member is ring shaped, and its inner peripheral portion is an elastic member which can contact along the outer circumferential surface having the different shape. 
     Also, it is preferred that at least a portion of a surface of the shield member contacting along the at least a portion of the outer circumferential surface having the different shape is not parallel to the central axis. 
     Also, it is preferred that a surface of the shield member contacting along the at least a portion of the outer circumferential surface having the different shape is bent in the direction of the central axis. 
     Also, it is preferred that: the cylindrical member has a groove provided in the outer circumferential surface, extending in a circumferential direction, as the different shape; and the shield member is ring shaped and has a protuberance, which roughly agrees in shape with the groove, upon a surface of an inner peripheral portion thereof which slides against the outer circumferential surface of the cylindrical member. 
     A camera according to the present invention, comprises: a body cover having an opening; a lens barrel which is movable in a direction substantially perpendicular to the opening of the cover; and a shield member, an outer edge of which is engaged to an inner edge of the opening, and an inner edge of which is fitted upon an outer circumferential surface of the lens barrel so as to be slidable thereon and so as to shield a gap between the body cover and the lens barrel, and: the lens barrel is movable through the opening along a direction of the optical axis of the lens barrel; the outer circumferential portion of the lens barrel has a ring shaped portion which is discontinuous in the direction of the optical axis of the lens barrel, at least at one place; and when the lens barrel is shifted to a predetermined position in the direction of the optical axis, the inner edge of the shield member contacts along the ring shaped portion which is discontinuous. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional view showing a camera which is equipped with a shield device according to a first embodiment of the present invention. 
     FIG. 2 is another sectional view showing this camera equipped with a shield device according to the first embodiment of the present invention. 
     FIG. 3A is an enlarged sectional view showing a portion of this camera equipped with a shield device according to the first embodiment of the present invention. 
     FIG. 3B is a view showing a front elevation of the camera in the FIG. 1 state. 
     FIG. 4 is a sectional view showing a shield device according to a second embodiment of the present invention. 
     FIG. 5 is a sectional view showing a shield device according to a third embodiment of the present invention. 
     FIG. 6 is a sectional view showing a shield device according to a fourth embodiment of the present invention. 
     FIG. 7 is a sectional view showing a shield device according to a fifth embodiment of the present invention. 
     FIG. 8 is a sectional view showing a shield device according to a sixth embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A first embodiment of the present invention will be explained with reference to FIGS. 1 through 3B. FIGS. 1 and 2 are sectional views of a retractable (or collapsible) type zoom camera which is equipped with a shield device (or a light intercepting device) according to this embodiment. This camera comprises a lens barrel  5  which can move relative to the camera body, and FIG. 1 shows the state with the lens barrel in the retracted (or collapsed) state (or, while FIG. 2 shows the state with the lens barrel projected in the telephoto state. A cover  1  which provides the external appearance of the camera encases a main body  2  to which various mechanisms not shown in the figures are fixed. A pressure plate  3  defines, against the main body  2 , a thin space through which passes a film not shown in the figures. A photographic optical system in the lens barrel is made up from a first lens group L 1  and a second lens group L 2 , and the focal distance is varied by shifting this first lens group L 1  and this second lens group L 2  individually along the optical axis I. 
     The lens barrel comprises the movable cylinder  5 , a cam cylinder  6 , and a lens holder  7 . A fixed cylinder  4  is fixed to the main body  2 , and a female helicoid  4   a  is formed on the inner surface of this fixed cylinder  4 . The movable cylinder  5  is screwingly engaged to the fixed cylinder  4  with a male helicoid  5   a  of the movable cylinder  5  and the female helicoid  4   a  of the fixed cylinder  4 , and is extended and retracted along the direction of the optical axis I by being rotated. The first lens group L 1  is mounted in an internal cylinder portion  5   b  of the movable cylinder  5 , while the second lens group L 2  is mounted within a lens holder  7 . The cam cylinder  6  is fixed in the inner surface of the movable cylinder  5 , and the second lens group L 2  is moved by this cam cylinder  6  rotating as one together with the movable cylinder  5 . These constructions for driving the movable cylinder  5  and the second lens group L 2  are per se known, and accordingly detailed explanation thereof will herein be curtailed. 
     Next, the shield member will be explained. This shield member is made up from an elastic member  8 , which can expand and contract and is made from a material which is endowed with elasticity such as silicon rubber or the like, and a ring shaped pad member  9  which is adhered to the elastic member  8  for ensuring the rigidity of the outer circumferential portion of this elastic member  8 . The outer circumferential portion of this ring shaped shield member is disposed between an end portion  4   b  of the fixed cylinder  4  and the inner surface of an opening portion  1   a  of the cover  1 , while, by taking advantage of the stretchability (elasticity) of the material of which this shield member is made, its inner circumferential portion is tightly but slidably engaged over the outer circumferential surface of the movable cylinder  5 . In other words, since in its unstressed state the inner diameter of the elastic member  8  is somewhat smaller than the outer diameter of the movable cylinder  5 , therefore when the elastic member  8  is fitted over the movable cylinder  5 , the internal circumferential portion of the elastic member  8  is closely contacted against (or along) the outer circumferential surface of the movable cylinder  5  while the shape being altered. The shield member is held at the end portion  4   b  of the fixed cylinder  4  while being rotatable around the optical axis, so that as the movable cylinder  5  rotates around the optical axis the shield member rotates along with it. This is in order to reduce the drag when driving the movable cylinder  5 . Due to this shield member (which may for example be blackened), light rays are intercepted and are prevented from getting into the inside of the camera through the gap between the opening portion  1   a  of the cover  1  and the outer circumferential surface of the movable cylinder  5 . It should be noted that it goes without saying that, even if the shield member were fixed by being adhered to the end portion  4   b  of the fixed cylinder  4  or the like, light rays would still be intercepted and be prevented from getting into the inside of the camera. 
     Now, the state of the shield member when the lens barrel is in the retracted position will be explained in detail, using FIG. 3A which consists of a magnified portion of FIG. 1. A tapered portion  5   c  is formed upon the end portion of the movable cylinder  5  (the outer end portion of the movable cylinder). In the state in which the elastic member  8  is not fitted over the movable cylinder  5 , it assumes the form shown by a two-dot chain line in the figure (and this undeformed state is shown in the same manner in FIGS. 4 through 7, to be described hereinafter); but, by fitting the movable cylinder  5  through the elastic member  8 , its inner circumferential edge portion  8   a  is somewhat deformed and is tightly but slidably pressed against the outer circumferential portion of the movable cylinder  5 . In the state in which the movable cylinder  5  is completely retracted, since the inner circumferential edge portion  8   a  is elastic, it deforms so as to lie against and to conform to the face of the tapered portion  5   c , thus covering it. In this configuration, it is possible more efficiently to intercept light rays coming from the direction of the arrow A shown in FIG. 3A, roughly parallel to the optical axis I. In other words, when the movable cylinder  5  is in the retracted state, at least a portion of the elastic member  8  which is in contact with the surface of the movable cylinder  5  does not lie in parallel to the direction of the arrow A. Accordingly, even if a slight gap is opened up between the movable cylinder  5  and the elastic member  8  due to a particle of foreign matter or the like, light rays coming in the direction of the arrow A are reliably shielded or blocked. Further, even if light rays get through the gap at the edge portion of the elastic member  8 , it is not possible for these light rays which have got in to proceed in straight lines, since they are diffracted by the surface where the elastic member  8  lies against the movable cylinder  5 , and therefore they are reliably shielded (or blocked or intercepted). 
     FIG. 3B is a figure showing the camera in the FIG. 1 state as seen from the front. The opening portion  1   a,  the elastic member  8 , the movable cylinder  5 , and the first lens group L 1  are visible. 
     FIG. 4 is a sectional view showing a shield device according to a second embodiment of the present invention, with the same principal portions shown magnified as in FIG.  3 A. Further, the basic construction of this shield device according to the second embodiment is the same as that of the first embodiment described above, and accordingly only the points of difference will be explained. 
     The end portion  45   c  of the movable cylinder  45  is formed as a smooth rounded chamfered edge. In the same manner as described above, with the movable cylinder  45  in the retracted state, the elastic member  8  is deformed so that its inner circumferential edge portion  8   a  wraps around this smooth rounded chamfered edge. 
     FIG. 5 is a sectional view showing a shield device according to a third embodiment of the present invention, with the same principal portions shown magnified as in FIG.  3 A. Further, the basic construction of this third embodiment is the same as that of the shield device according to the first embodiment described above, and accordingly only the points of difference will be explained. 
     At the portion of the inner edge of the elastic member  58  which contacts against the outer peripheral surface of the movable cylinder  55 , and particularly at its portion which covers over the tapered portion  55   c  of the movable cylinder  55 , there is provided a ring shaped protuberance  58   a . In the state in which the movable cylinder  55  is retracted, the protuberance  58   a  lies against and conforms to the face of the tapered portion  55   c , and thus this inner circumferential portion  58   a  of the elastic member  58  is made so as to cover the tapered portion  55   c.    
     FIG. 6 is a sectional view showing a shield device according to a fourth embodiment of the present invention, with the same principal portions shown magnified as in FIG.  3 A. Further, the basic construction of this fourth embodiment is the same as that of the shield device according to the first embodiment described above, and accordingly only the points of difference will be explained. 
     A step  65   c  is formed at the end portion of the movable cylinder  65 , and a protuberance  68   a  is formed upon the elastic member  68  which roughly coincides with the step shape of this step portion  65   c  of the movable cylinder  65 . In the state in which the movable cylinder  65  is retracted, the protuberance  68   a  is positioned over the step  65   c , and the end portion of the elastic member  68  (the inner circumferential portion  68   a ) is deformed so as to cover over the step  65   c.    
     It should be noted that, although with this fourth embodiment the protuberance  68   a  is formed upon the elastic member  68  and covers over the step  65   c  (contacts along the step  65   c ), the form of this protuberance  68   a  is not necessarily limited to the one shown in FIG. 6; for example, the same beneficial effect can also be obtained with the assembly of a movable cylinder  65  having a step  65   c  as shown in FIG.  6  and an elastic member  8  as shown in FIG.  3 A. 
     FIG. 7 is a sectional view showing a shield device according to a fifth embodiment of the present invention, with the same principal portions shown magnified as in FIG.  3 A. Further, the basic construction of this fifth embodiment is the same as that of the shield device according to the first embodiment described above, and accordingly only the points of difference will be explained. 
     A flange  75   c  is formed upon the end portion of the movable cylinder  75 . This flange  75   c  is made smaller, in the state in which the movable cylinder  75  is retracted, than the aperture in the cover  1 , in other words than the opening portion  1   a . And an elastic member  78  of the same form as the elastic member  8  of the first embodiment shown in FIG. 3A is fitted over the movable cylinder  75 , and, in the state in which the movable cylinder  75  is retracted, its end portion  78   a  is positioned behind the flange  75   c.    
     Now, normally, the time period over which the camera is exposed to light is overwhelmingly when the lens barrel is in the retracted state. As described above, if a minute gap is present in the engagement between the elastic member and the movable cylinder due to the influence of a step or burr shape of a parting line formed upon the outer circumferential surface when the movable cylinder is manufactured from plastic material, or if such a minute gap is present in the engagement of the elastic member and the movable cylinder due to a minute particle of foreign matter being caught between them, then light rays could pass through this minute gap and insinuate themselves into the interior of the camera, thus exposing the film, which is most undesirable. However, according to the embodiments described in FIGS. 3A through 7, light rays are effectively intercepted when the lens barrel is in the retracted state. When the lens barrel is not in the retracted state, in other words during the time period accompanying photography, there is no influence as compared to the time period in which the lens barrel is retracted, since this time period is by far the shorter, but in the retracted state which is the overwhelming time period over which the camera is exposed to light, the fact that it is possible for the light rays to be intercepted from getting into the interior of the camera is extremely effective. 
     Next, a shield device according to a sixth embodiment of the present invention will be explained with reference to FIG.  8 . 
     The camera to which the shield device according to this embodiment is provided is equipped with with a photographic optical system of a so called step zoom type. In other words, the lens barrel can be controlled so as to vary the focal distance of the photographic optical system in six steps, and the construction is arranged so that the lens barrel stops in positions in which it is extended to each of these focal distances. The other features of the construction are the same as in the camera shown in FIG. 1, and accordingly the same reference symbols will be appended to them, and their description will be curtailed. 
     At the end portion of the movable cylinder  85  there is formed a step  85   c  of almost the same form as the step  65   c  shown in FIG. 6, and furthermore six of ring shaped circumferential grooves  85   d  are formed around the outer circumferential surface of the movable cylinder  85 , spaced along the direction of the optical axis I. The number of these grooves  85   d  and their positions correspond to the number of zoom steps and their focal distances. Due to this, at each of the positions at which the lens barrel stops, the protruding portion  88   a  of the elastic member  88  engages into a corresponding one of the grooves  85   d . Because of this construction, light rays are effectively intercepted from getting into the interior of the camera, not only when the lens barrel is in the retracted position, but also in the same manner when it is in any one of its projected positions. 
     It should be noted that, although for the convenience of explanation in FIG. 8 the step  85   c  and the grooves  85   d  have been shown as enlarged, in practice it will be acceptable for them to be smaller, so as not to spoil the outward appearance of the camera, provided that they are of a size enough to be able to intercept light rays entering from the direction of the arrow A. Further, although in this sixth embodiment the protuberance  88   a  on the elastic member  88  was formed so as to contact against and cover over the step  85   c  and the grooves  85   d , it should be understood that the shape of the protuberance  88   a  is not limited to the one shown in FIG. 8; any shape which is capable of intercepting light rays entering from the direction of the arrow A in the figure will be acceptable. 
     Although in the above described embodiments a single movable cylinder which moved relative to the body of the camera was provided, it is hardly necessary to say that, even in a more complicated optical system with a lens barrel which needs to comprise two or three movable cylinders, it is possible to intercept the light rays by providing the same type of construction to each of the movable cylinders and between the movable cylinders. 
     Although in the above described embodiments the description has been made, by way of example, in terms of a camera which uses film, the present invention is not to be considered as limited to this application. It could also be applied to an apparatus other than a camera. Further, it could also be applied to a digital camera which uses internally an imaging element such as a CCD or the like. Yet further, it could also be applied to a video camera. In other words, the present invention can be applied to any apparatus which incorporates and employs a light sensitive element such as a film or a CCD or the like.