Water-resistant structure of a lens barrel

A water-resistant structure of a lens barrel includes a sealing member that seals an annular gap between inner and outer annular members, wherein the sealing member is positioned in a vicinity of an open end of the outer annular member and is fixed to one of the inner and outer annular members to be slidable on the other of the inner and outer annular members, and a drain groove formed on the inner annular member and positioned alongside the sealing member at a position closer to the open end of the outer annular member than the sealing member. Furthermore, a frictional resistance of a first sealing member produced between a secondary annular member and a manually-rotatable annular members is greater than a frictional resistance of the second sealing member that urges one of two of the manually-rotatable annular members to follow a rotation of the other thereof when rotated.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a water-resistant structure provided between concentrically-arranged annular members of a lens barrel.

Lens barrels (e.g., photographic lenses) are generally provided with a plurality of annular members which are concentrically arranged and relatively movable along an optical axis or rotatable about an optical axis. In the case where one of the plurality of annular members is provided as a manually-operated ring (i.e., a zoom ring or a focusing ring) and where another annular ring is configured to move forward/rearward along the optical axis by manually rotating the manually-operated ring, the lens barrel has been conventionally constructed so that the user can feel a moderate resistance in the manually-operated ring when manually rotating the manually-operated ring by intentionally generating a frictional resistance between adjacent (radially overlaid) annular members.

As an example of a device for generating such a frictional resistance, frictional resistance has been generated by fixing one side of an annular synthetic leather, having fine hair implanted on the other side thereof, onto an outer or inner peripheral surface of an annular member while the other side (hair-implanted surface) of the annular synthetic leather is in slidable contact with an inner or outer peripheral surface of an adjacent annular member.

However, in the case of using an annular synthetic leather in such a manner, the user can feel a moderate resistance in the manually-operated ring (zoom ring or focus ring) when manually rotating it, but it becomes difficult to prevent drops of water, dust, and the like, from entering inside the lens barrel through the gap between adjacent ring members (i.e., it is difficult for the lens barrel to exhibit a water-resistant effect).

Lens barrels disclosed in Japanese Unexamined Patent Publication 2000-227534 and Japanese Unexamined Patent Publication 2003-202481 are known in the art as examples of lens barrels which are constructed to allow the user to feel a resistance in a manually-operated ring (zoom ring or focus ring) when the user manually rotates the manually-operated ring while the lens barrel exhibits a water-resistant effect.

In the lens barrel disclosed in Japanese Unexamined Patent Publication 2000-227534, an annular washer made of a plastic or vinyl chloride sheet is inserted in between the rear end of the outer peripheral surface of a front exterior ring and the front end of the inner peripheral surface of a manual ring which is positioned immediately behind the front exterior ring and capable of rotating about an optical axis relative to the front exterior ring (incapable of moving in the optical axis direction relative to the front exterior ring), and another annular washer made of a plastic or vinyl chloride sheet is inserted in between the outer peripheral surface of the rear end of the manual ring and the front end of the inner peripheral surface of a rear exterior ring positioned immediately behind the manual ring. In addition, a water-repellent material is filled in between the rear end of the outer peripheral surface of the front exterior ring and the front end of the inner peripheral surface of the manual ring to be positioned immediately behind the annular washer, while a water-repellent material is also filled in between the rear end of the outer peripheral surface of the manual ring and the front end of the inner peripheral surface of the rear exterior ring to be positioned immediately in front of the annular washer.

In the lens barrel disclosed in Japanese Unexamined Patent Publication 2000-227534 having the above described structure, drops of water and dust on the outside of the lens barrel can be prevented from entering the lens barrel since the annular washers and the front and rear water-repellent materials exhibit water-resistant effects. In addition, since a washer is held between the front exterior ring and the manual ring and also since another washer is held between the manual ring and the rear exterior ring, the user can feel a resistance in the manual ring when manually rotating the manual ring.

In the lens barrel disclosed in Japanese Unexamined Patent Publication 2003-202481, a manually-operated focus ring is provided, on an end surface thereof in an optical axis direction, with a circular groove concentric with the optical axis in which a viscous water repellent or grease is filled, and an exterior ring is provided, on an end surface thereof which faces the focus ring in the optical axis direction, with a circular projection concentric with the optical axis which is loosely engaged in the concentric circular groove.

With such a structure, the gap between the outer exterior ring and the focus ring is sealed by grease so that drops of water, dust, and the like, can be prevented from entering the lens barrel from the outside thereof through the gap, and the operational torque (resistance) of the focus ring can be changed by selecting from among different types of greases having different viscosities.

However, in the lens barrel disclosed in Japanese Unexamined Patent Publication 2000-227534, an annular washer is formed using a plastic sheet or a vinyl chloride sheet that is a relatively hard material, and accordingly, it is difficult to create a resistance like that created when a synthetic leather is used. In particular, in the case where an annular member rotates about an optical axis while sliding in the optical axis direction, it is even more difficult to create a resistance like that created when a synthetic leather is used as compared with the case where an annular member solely slides in an optical axis direction or solely rotates about an optical axis. In addition, if minute projections and depressions exist on the surface of the washer, there is a possibility of the manual rotation operation of the manual ring becoming unsmooth due to the effects of such projections and depressions since each washer is made of a plastic or vinyl chloride sheet. In this manner, each washer needs to be precisely formed according to a designated shape; however, it is difficult to make each washer out of a plastic or vinyl chloride sheet with such precision.

In the lens barrel disclosed in Japanese Unexamined Patent Publication 2003-202481, since the gap between the focus ring and the exterior ring is made watertight by the circular projection that is formed on an end surface of the exterior ring in the optical axis direction and the grease filled in the aforementioned circular groove that is formed on an end surface of the focus ring in the optical axis direction, this type of watertight structure using a circular projection, a circular groove and grease cannot be adopted if the diameters of the exterior ring and the focus ring are not substantially the same.

Additionally, such a structure, since the resistance (operational torque) varies while the water-resistant effect varies according to the strength of the pressure for holding a light shielding member between two barrels, the water-resistant effect becomes too small if the pressure is weakened to reduce the resistance, or the resistance becomes too great if the pressure is conversely increased to enhance the water-resistant effect, so that there a problem exists in which it is difficult to adjust the water-resistant performance and the sense of resistance.

SUMMARY OF THE INVENTION

The present invention provides a water-resistant structure of a lens barrel which can exhibit a water-resistant effect while enabling the user to feel a moderate resistance in an annular member of the lens barrel when the user manually rotates the annular member, and which can even be produced in an easy manner.

In addition, the present invention provides a water-resistant structure of a lens barrel which enables the user to feel a moderate resistance when manually operating one of a plurality of manually-rotatable annular members, which are independently and relatively rotatable, while preventing the other manually-rotatable annular members from following the rotation of the manually-operated annular member, and which can even be produced in an easy manner.

According to an aspect of the present invention, a water-resistant structure of a lens barrel is provided, having at least two annular members which are concentrically arranged and relatively rotatable, the water-resistant structure including a sealing member that seals an annular gap between an inner annular member and an outer annular member of the annular members, wherein the sealing member is positioned in a vicinity of an open end of the outer annular member and is fixed to one of the inner and outer annular members to be slidable on the other of the inner and outer annular members; and at least one drain groove formed on the inner annular member and positioned alongside the sealing member at a position closer to the open end of the outer annular member than the sealing member.

It is desirable for a plurality of the drain grooves to be provided at different positions, and for the depth of at least one of the plurality of drain grooves to be different from the depth of another of the plurality of drain grooves.

It is desirable for the drain groove to be defined between a plurality of flanges which project from an outer peripheral surface of the inner annular member.

It is desirable for the outer annular member to include an overhang which overhangs the drain groove.

It is desirable for a surface of the overhang which faces the drain groove to be inclined to widen a gap between the surface of the overhang and the bottom of the drain groove in a direction toward an end of the overhang.

It is desirable for the drain groove to be formed so that an upper portion of the drain groove is smaller in depth than a lower portion of the driven groove when the lens barrel is in a normal position.

It is desirable for the sealing member to be fixed to an outer peripheral surface of the inner annular member so as to be in slidable contact with an inner peripheral surface of the outer annular member.

It is desirable for the sealing member to be an annular sealing member.

The sealing member can be a flocked cloth material or a water-repellent material.

It is desirable for the outer annular member to be one of a zoom ring and a focus ring.

It is desirable for the plurality of annular members include a plurality of manually-rotatable annular members which are independently relatively rotatable; and at least one secondary annular member to which the plurality of manually-rotatable annular members are relatively rotatable. The water-resistant structure includes a first sealing member which seals a gap defined between two of the plurality of manually-rotatable annular members, one of which is fitted on an outer side of the other, the first sealing member being positioned in a vicinity of an open end of the outer of the two manually-rotatable annular members; and a second sealing member which seals a gap defined between one of the plurality of manually-rotatable annular members and the secondary annular member, the second sealing member being positioned in a vicinity of an open end of the outer of the one of the plurality of manually-rotatable annular members and the secondary annular member. A frictional resistance of the second sealing member which is produced between the secondary annular member and the one of the plurality of manually-rotatable annular members is greater than a frictional resistance of the first sealing member that urges one of the two manually-rotatable annular members to follow a rotation of the other of the two manually-rotatable annular members when the other of the two manually-rotatable annular members is rotated.

In an embodiment, a water-resistant structure of a lens barrel is provided, having a plurality of annular members which are concentrically arranged, wherein the plurality of annular members include a plurality of manually-rotatable annular members which are independently relatively rotatable, and at least one secondary annular member to which the plurality of manually-rotatable annular members are relatively rotatable. The water-resistant structure includes a first sealing member which seals a gap defined between two of the plurality of manually-rotatable annular members, one of which is fitted on an outer side of the other, the first sealing member being positioned in a vicinity of an open end of the outer of the two manually-rotatable annular members; and a second sealing member which seals a gap defined between one of the plurality of manually-rotatable annular members and the secondary annular member, the second sealing member being positioned in a vicinity of an open end of the outer of the one of the plurality of manually-rotatable annular members and the secondary annular member. A frictional resistance of the second sealing member which is produced between the secondary annular member and the one of the plurality of manually-rotatable annular members is greater than a frictional resistance of the first sealing member that urges one of the two manually-rotatable annular members to follow a rotation of the other of the two manually-rotatable annular members when the other of the two manually-rotatable annular members is rotated.

It is desirable for the first sealing member to be positioned between the two of the plurality of manually-rotatable annular members, which are independently relatively rotatable, and for the second sealing member to include at least two sealing members positioned between the secondary annular member and the plurality of manually-rotatable annular members. A frictional resistance of the first sealing member that is produced between the two of the plurality of manually-rotatable annular members is smaller than a frictional resistance of the second sealing member that is produced between the secondary annular member and the plurality of manually-rotatable annular members.

It is desirable for at least one drain groove to be formed on an inner manually-rotatable annular member of the two of the plurality of manually-rotatable annular members, and for the drain groove to be positioned alongside the first sealing member at a position closer to the outside of the inner manually-rotatable annular member than the first sealing member in an axial direction of the inner annular member.

It is desirable for the drain groove to be formed between two flanges which project from an outer peripheral surface of the inner manually-rotatable annular member.

It is desirable for an outer manually-rotatable annular member of the two of the plurality of manually-rotatable annular members to include an overhang which overhangs the drain groove.

According to the present invention, drops of water on the lens barrel enter the drain groove, thus being difficult to reach the sealing member through the inner annular member, so that a high water-resistant effect is achieved. In addition, the resistance caused by the sealing member that the user can feel can be easily set (adjusted) as desired because the degree of dependence on the water-resistant effect by the sealing member is low.

Furthermore, according to the present invention, a water-resistant structure of a lens barrel can be achieved in which, when the user manually rotates one of a plurality of manually-rotatable annular members which are independently relatively rotatable, no other manually-rotatable annular members follow the rotation of the manually-operated manually-rotatable annular member. Since the degree of dependence on the water-resistant effect by the sealing member is low, adjustment of the rotational resistance caused by the sealing member becomes easy, and the ease of rotation and the independency of the plurality of manually-rotatable annular members are facilitated.

The present disclosure relates to subject matter contained in Japanese Patent Applications Nos. 2009-39074 and 2009-39075 (both filed on Feb. 23, 2009) which are expressly incorporated herein by reference in their entireties.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1is a longitudinal sectional view of a zoom lens barrel (zoom lens)10to which an embodiment of a water-resistant structure according to the present invention is applied, taken along a plane passing through an optical axis O.

The lens barrel10is an interchangeable type of zoom lens barrel having two lens groups L1and L2. The lens barrel10is provided, at the rear end of a first stationary barrel (secondary annular member)11having a cylindrical shape about the optical axis O of each lens group L1and L2, with a lens mount12which is detachably attached to the body mount of a camera body (not shown). The lens barrel10is further provided inside the first stationary barrel11with a second stationary barrel13having a cylindrical shape concentric with the first stationary barrel11. The rear end of the second stationary barrel13is fixed to a front surface of a rear wall of the first stationary barrel11.

The lens barrel10is provided on the front end of the first stationary barrel11with a manually-operated zoom ring (rear zoom ring)15having a cylindrical shape concentric with the first stationary barrel11and the second stationary barrel13, and the zoom ring15is mounted to the front end of the first stationary barrel11to be rotatable about the optical axis O (but non-slidable in the optical axis direction). The lens barrel10is provided immediately in front of the zoom ring15with a manually-operated zoom ring (front zoom ring)17which is coupled to the front end of the zoom ring15so as to rotate integrally therewith. In other words, a zoom ring30is divided into two components: the front zoom ring17and the rear zoom ring15that are coupled to each other so as to rotate as a single zoom ring about the optical axis O. A grip ring16is fixed onto the outer peripheral surfaces of the front zoom ring17and the rear zoom ring15(zoom ring30). The zoom ring30constitutes a manually-rotatable annular member of a plurality of manually-rotatable annular members of the lens barrel10. The first stationary barrel11constitutes a single annular member to which the manually-rotatable annular member (zoom ring30) relatively rotates.

The lens barrel10is provided with a manually-operated focus ring19having a cylindrical shape concentric with the first stationary barrel11. A non-slip ring20is fitted onto the periphery of the manually-operated focus ring19. The rear end of the focus ring19is fitted on the front end of the outer peripheral surface of the first stationary barrel11to be rotatable about the optical axis O while being prevented from moving in the optical axis direction relative to the first stationary barrel11. The rear end of the focus ring19is positioned radially inside the zoom rings15and17. The focus ring19is provided on an inner peripheral surface of the rear end thereof with a circumferential gear (not shown) which is engaged with an output gear (not shown) which is rotatably supported in the vicinity of the front end of the outer peripheral surface of the second stationary barrel13. Upon the lens barrel10being attached to a camera body, this output gear is connected to a focusing motor incorporated in the camera body via a gear mechanism provided in the camera body. The focus ring19constitutes one of the plurality of the manually-rotatable annular members, and also serves as an inner manually-rotatable annular member that is positioned radially inside the zoom rings15and17.

The lens barrel10is provided radially outside the second stationary barrel13with a cam ring21having a cylindrical shape concentric with the second stationary barrel13. The cam ring21is supported by the second stationary barrel13to be freely rotatable about the optical axis O without moving in the optical axis direction relative to the second stationary barrel13. In addition, the cam ring21is connected with the zoom ring15via a zoom linkage lever18. Therefore, a rotation of the zoom ring15causes the cam ring21to rotate about the optical axis O without moving in the optical axis direction.

The second stationary barrel13supports a second lens group support frame23positioned radially inside the cam ring21. The second lens group support frame23is a member which supports the second lens group L2that serves as a variator lens group. The second lens group support frame23is guided linearly in the optical axis direction by linear guide grooves (not shown) formed on the second stationary barrel13and is engaged with cam grooves formed on an inner peripheral surface of the cam ring21. Therefore, rotating the cam ring21via the zoom ring15causes the second lens group support frame23to move forward/rearward along the optical axis O without rotating about the optical axis O at a speed determined according to the lead of the cam grooves of the cam ring21.

The lens barrel10is provided on the outer peripheral surface of the front end of the cam ring21with a linearly movable ring25having a cylindrical shape concentric with the cam ring21. Although not discussed in detail, the linearly movable ring25is supported by the second stationary barrel13to be freely movable forwardly and rearwardly along the optical axis O without rotating, and is connected with the cam ring21so that a rotation of the cam ring21causes the linearly movable ring25to move forward/rearward along the optical axis O without rotating via a cam mechanism provided between the linearly movable ring25and the cam ring21.

The lens barrel10is provided between the linearly movable ring25and the focus ring19with a rotatable advancing ring (secondary annular member)27having a cylindrical shape concentric with the linearly movable ring25and the focus ring19. Although not discussed in detail, the rotatable advancing ring27is connected with the linearly movable ring25via a helicoid mechanism, and is connected with the focus ring19to be freely movable forwardly rearwardly along the optical axis O relative to the focus ring19and to be rotatable with the focus ring19about the optical axis O. Therefore, a rotation of the cam ring21causes the rotatable advancing ring27to move forward/rearward with the linearly movable ring25, which moves forward/rearward along the optical axis O via the aforementioned cam mechanism provided between the linearly movable ring25and the cam ring21, along the optical axis O without rotating. On the other hand, a rotation of the focus ring19causes the rotatable advancing ring27to move forward/rearward along the optical axis O via the helicoid mechanism provided between the rotatable advancing ring27and the linearly movable ring25while rotating with the focus ring19. The rotatable advancing ring27constitutes an annular member to which the aforementioned manually-rotatable annular members rotate relatively.

The lens barrel10is provided immediately inside the rotatable advancing ring27with a first lens group support frame29having a cylindrical shape which supports the first lens group L1. The rear end of the first lens group support frame29is connected into the front end of the second stationary barrel13in a manner to be freely movable forward/rearward linearly in the optical axis direction without rotating relative to the second stationary barrel13. The first lens group L1serves as a compensator lens and a focusing lens. The outer periphery of the front end of the first lens group support frame29is connected to the rotatable advancing ring27in a manner to be freely rotatable about the optical axis O relative to the rotatable advancing ring27and to be movable with the rotatable advancing ring27in the optical axis direction. Therefore, manually rotating the focus ring19causes the rotatable advancing ring27to move forward/rearward in the optical axis direction while rotating, and this forward/rearward movement causes the first lens group support frame29that supports the first lens group L1to move forward/rearward along the optical axis O without rotating. On the other hand, manually rotating the zoom ring15causes the first lens group support frame29, which is prevented from rotating, to move forward/rearward in the optical axis direction relative to the second stationary barrel13and the focus ring19by the linearly movable ring25and the rotatable advancing ring27.FIG. 2shows a state where the rotatable advancing ring27, the first lens group support frame29and the first lens group L1have been fully advanced via rotation of the focus ring19.

Therefore, the rotatable advancing ring27moves forward/rearward without rotating when the linearly movable ring25moves linearly in the optical axis direction by a rotation of the cam ring21, and the rotatable advancing ring27moves forward/rearward while rotating when the focus ring19rotates.

A rotation of the cam ring21causes the second lens group support frame23that supports the second lens group L2to move forward/rearward in the optical axis direction without rotating along the aforementioned linear guide grooves (not shown) formed on the second stationary barrel13due to the lead of a cam mechanism provided between the cam ring21and the second lens group support frame23, and also causes the first lens group support frame29that holds the first lens group L1to move forward/rearward without rotating to thereby carry out a zooming operation due to the aforementioned cam mechanism provided between the linearly movable ring25and the cam ring21(seeFIG. 3).

Water-resistant structures provided between the rotatable advancing ring27and the first lens group support frame29, between the front zoom ring17and the focus ring19, and between the rear zoom ring15and the first stationary barrel11will be hereinafter discussed with reference further toFIGS. 4 through 7.

FIG. 4is a longitudinal sectional view of a portion of the lens barrel10, showing the water-resistant structure provided between the rotatable advancing ring27and the first lens group support frame29in an enlarged view. A flocked cloth31serving as a sealing member is installed in a gap (annular gap) defined between an inner peripheral surface of a front part of the rotatable advancing ring27and an outer peripheral surface of the first lens group support frame29. The flocked cloth31is shaped into a ring, and the inner peripheral surface (adhesive surface) of the flocked cloth31is bonded to an outer peripheral surface of the first lens group support frame29, while the outer peripheral surface (flocked surface) of the flocked cloth31is in contact with the rotatable advancing ring27to be freely slidable thereon. However, the flocked cloth31can be installed between the first lens group support frame29and the rotatable advancing ring27in a reversed fashion. Namely, it is possible that the outer peripheral surface of the flocked cloth31be bonded to the rotatable advancing ring27while the inner peripheral surface of the flocked cloth31be in contact with an outer peripheral surface of the first lens group support frame29to be freely slidable thereon. In addition, the sealing member is not limited solely to a flocked cloth and can be any other ring-shaped sealing member such as synthetic leather having a flocked surface over one side thereof. Furthermore, a water-repellent material or a surface having a water-repellent finish can be used as a sealing member.

The first lens group support frame29is provided, on an outer peripheral surface thereof at a position closer to the outside (left side with respect toFIG. 4) of the lens barrel10than the flocked cloth31(more specifically, at a position slightly away from the position of the front end surface of the flocked cloth31in the optical axis direction), with a drain groove29adefined by a front flange29band a rear flange29ctherebetween. The front flange29band the rear flange29care formed circumferentially around the first lens group support frame29, i.e., the drain groove29ais formed circumferentially around the first lens group support frame29. The front flange29bis greater in radial height than the rear flange29c.

The rotatable advancing ring27is provided at the front end thereof with an overhang (ring-shaped overhang)27awhich covers the drain groove29a. The overhang27aextends forward to cover the drain groove29abeyond the outer peripheral surface of the rear flange29c, to a position where a slight gap remains between the front end of the overhang27aand the front flange29b. In addition, the overhang27ais provided on a surface thereof facing the drain groove29awith a tapered portion27a1which tapers rearwardly so that the distance between the tapered portion27a1and the bottom of the drain groove29aincreases in the forward direction, toward the front end of the overhang27a.

Since the drain groove29awith the overhang27ais provided alongside (left side with respect toFIG. 4) the flocked cloth31, drops of water splashed onto the lens barrel10enter into the drain groove29athrough the gap formed between the overhang27aand the front flange29b; however, such drops of water run downwardly in the direction of gravity along the drain groove29ato drain out of the drain groove29athrough the gap formed between the overhang27aand the front flange29b. Namely, when drops of water are splashed onto the lens barrel10with the camera body held normally (horizontally), some of the drops of water drain down and out of the lens barrel10via the drain groove29a. In addition, in the present embodiment of the water-resistant structure, the tapered portion27a1of the overhang27ais inclined downwardly in the direction toward the gap formed between the tapered portion27a1and the front flange29b, which enhances the drainage performance.

Even if drops of water from the drain groove29awere to enter through the gap between the outer peripheral surface of the rear flange29cand the overhang27aand enter into the groove between the rear flange29cand the flocked cloth31, such drops of water would run down this groove in the direction of gravity and drain out at the lower end through the gap formed between the rear flange29cand the overhang27a.FIG. 5is a longitudinal sectional view of a portion of the lens barrel10, showing the water-resistant structure between the front zoom ring17and the focus ring19in an enlarged view. A flocked cloth33serving as a sealing member is installed in a gap (annular gap) defined between the inner peripheral surface of a portion of the front zoom ring17in the vicinity of the front end thereof and an outer peripheral surface of the focus ring19. Although the inner peripheral surface (adhesive surface) of the flocked cloth33is bonded to an outer peripheral surface of the focus ring19, while the outer peripheral surface (flocked surface) of the flocked cloth33is in contact with an inner peripheral surface of the front zoom ring17to be freely slidable thereon, the flocked cloth33can be installed between the front zoom ring17and the focus ring19in a reversed fashion. Namely, it is possible that the outer peripheral surface of the flocked cloth33be bonded to an inner peripheral surface of the front zoom ring17while the inner peripheral surface of the flocked cloth33be in contact with the focus ring19to be freely slidable thereon.

The focus ring19is provided on an outer peripheral surface thereof in front of the flocked cloth33at a position closer to the outside (left side with respect toFIG. 5) of the lens barrel (zoom lens)10than the flocked cloth33(more specifically, at a position slightly away from the position of the front end surface of the flocked cloth33in the optical axis direction), with a drain groove19adefined by a front flange19band a rear flange19ctherebetween. The front flange19band the rear flange19care formed circumferentially around the focus ring19, i.e., the drain groove19ais formed circumferentially around the focus ring19. The front flange19bis greater in radial height than the rear flange19c.

The front zoom ring17is provided at the front end thereof with an overhang (ring-shaped overhang)17awhich covers the drain groove19a. The overhang17aextends forward to cover the drain groove19abeyond the outer peripheral surface of the rear flange19c, to a position where a slight gap remains between the front end of the overhang17aand the outer peripheral surface of the front flange19b.

Since the drain groove19awith the overhang17ais provided alongside (left side with respect toFIG. 5) the flocked cloth33, drops of water splashed onto the lens barrel10enter into the drain groove19athrough the gap formed between the overhang17aand the front flange19b; however, such drops of water run downwardly in the direction of gravity along the drain groove19ato drain down and out of the drain groove19athrough the gap formed between the overhang17aand the front flange19b. Namely, when drops of water are splashed onto the lens barrel10with the camera body held normally, some of the drops of water drain and out of the lens barrel10via the drain groove19a.

Furthermore, even if drops of water from the drain groove19awere to enter through the gap between the outer peripheral surface of the rear flange19cand the inner peripheral surface of the front zoom ring17and enter into the groove between the rear flange19cand the flocked cloth33, such drops of water would run down this groove in the direction of gravity and drain out at the lower end through the gap formed between the rear flange19cand the front zoom ring17.

The gap (annular gap) defined between the front end of the focus ring19and the rotatable advancing ring27is water-sealed by a flocked cloth37serving as a sealing member (seeFIG. 4). The outer peripheral surface of the flocked cloth37is bonded to an inner peripheral surface of the focus ring19, while the inner peripheral surface of the flocked cloth37is in contact with the rotatable advancing ring27to be freely slidable thereon.

FIG. 6is a longitudinal sectional view of a portion of the lens barrel10, showing the water-resistant structure provided between the rear zoom ring15and the first stationary barrel11in an enlarged view. A flocked cloth35serving as a sealing member is installed in a gap (annular gap) defined between an inner peripheral surface of the rear end of the rear zoom ring15and an outer peripheral surface of the first stationary barrel11. The inner peripheral surface (adhesive surface) of the flocked cloth35is bonded to an outer peripheral surface of the first stationary barrel11, while the outer peripheral surface (flocked surface) of the flocked cloth35is in contact with an inner peripheral surface of the rear zoom ring15to be freely slidable thereon. However, the flocked cloth35can be installed between the first stationary barrel11and the rear zoom ring15in a reversed fashion. Namely, it is possible that the inner peripheral surface of the flocked cloth35be in contact with an outer peripheral surface of the first stationary barrel11to be freely slidable thereon, while the outer peripheral surface of the flocked cloth35be bonded to an inner peripheral surface of the rear zoom ring15.

The first stationary barrel11is provided on an outer peripheral surface thereof behind the flocked cloth35at a position closer to the outside (right side with respect toFIG. 6) of the lens barrel (zoom lens)10than the flocked cloth35(more specifically, at a position slightly away from the position of the rear end surface of the flocked cloth35in the optical axis direction), with a drain groove11adefined by a front flange11band a rear flange11ctherebetween. The front flange11band the rear flange11care formed circumferentially around the first stationary barrel11, i.e., the drain groove11ais formed circumferentially around the first stationary barrel11. The front flange11bis greater in radial height than the rear flange11c.

The rear zoom ring15is provided at the rear end thereof with an overhang (ring-shaped overhang)15awhich covers the drain groove11a. The overhang15aextends rearward to cover the drain groove11abeyond the outer peripheral surface of the front flange11b, to a position where a slight gap remains between the rear end of the overhang15aand the rear flange11c. In addition, the overhang15ais provided on a surface thereof facing the drain groove11awith a tapered portion15a1which tapers forwardly so that the distance between the tapered portion15a1and the bottom of the drain groove11aincreases in the rearward direction, toward the rear end of the overhang15a.

Since the drain groove11ahaving the overhang15ais provided alongside (right side with respect toFIG. 6) the flocked cloth35, drops of water splashed onto the lens barrel10enter into the drain groove11athrough the gap formed between the overhang15aand the rear flange11c; however, such drops of water run downwardly in the direction of gravity along the drain groove11ato drain down and out of the drain groove11athrough the gap formed between the overhang15aand the rear flange11c. Namely, when drops of water are splashed onto the lens barrel10with the camera body held normally, some of the drops of water drain down and out of the lens barrel10via the drain groove11a. In addition, the drain groove11ais formed to decrease in depth in the downward direction as shown inFIG. 7, and the tapered portion15a1of the overhang15ais inclined in a direction to drain the drops of water in the drain groove11aout of the drain groove11a(in a direction to increase the gap between the tapered portion15a1and the bottom of the drain groove11ain the rearward direction), which makes the drops of water in the drain groove11aeasy to flow out of the drain groove11aalong the tapered portion15a1and thus enhances the drainage performance.

In addition, the drain groove11ais formed to increase in depth in the upward direction and to decrease in depth in the downward direction (seeFIG. 7). Due to this groove structure in which the depth of the drain groove11avaries in such a manner, water splashed onto the lens barrel10, with the camera body held normally, enter into the an upper part of the drain groove11aand thereafter easily drain down and out of the lens barrel10through a lower part of the drain groove11a.

Furthermore, even if drops of water from the drain groove11awere to enter through the gap between the outer peripheral surface of the rear flange11band the overhang15aand enter into the groove between the rear flange11band the flocked cloth35, such drops of water would run down this groove in the direction of gravity and drain out at the lower end through the gap formed between the rear flange11band the overhang15a.

As described above, according to the present embodiment of the water-resistant structure, since the drain grooves29a,19aand11aare formed at positions closer to the outside of the lens barrel10than the flocked cloths31,33and35, respectively, the drops of water on the lens barrel10which enter into the drain grooves29a,19aand11aflow to the outside of the drain groove11aalong the drain grooves29a,19aand11afrom the lowermost parts thereof, respectively, so that the water resistant effect is higher than the case using only sealing members.

According to the water-resistant structure provided with the overhangs27a,17aand15athat cover the drain grooves29a,19aand11a, respectively, drops of water are obstructed by the overhangs27a,17aand15a, thus making it difficult for water to enter the drain grooves29a,19aand11a, respectively, and also drops of water flow down to the outside of the lens barrel10via the outer surfaces of the overhangs27a,17aand15a, which further improves the water resistant effect.

Each of the overhangs27a,17aand15acan be shaped so as to either fully cover the associated drain groove (e.g., shaped like the overhang17a) or partly cover the associated drain groove (e.g., shaped like the overhang27aor15a).

Although the tapered portions27a1and15a1are formed on the overhangs27aand15a, respectively, in the above described embodiment of the water-resistant structure, a similar tapered portion can also be formed on the overhang17a.

As shown inFIG. 6, according to the above described structure of the drain groove19ain which the depth thereof increases and decreases in the upward direction and the downward direction, respectively, with respect to when the camera body is held normally (horizontally), the drops of water having fallen into the drain groove19aand flown down through the drain groove19aeasily overflow from the drain groove19aand drop therefrom out of the lens barrel10, which further improves the water resistant effect.

In another embodiment of the water-resistant structure, the depths of drain grooves129a,119aand111awhich correspond to the drain grooves29a.19aand11aare formed mutually different in depth.FIGS. 8A,8B and8C that respectively correspond toFIGS. 4,5and6show longitudinal sectional views of this embodiment of the water-resistant structure, in which the drain groove on the object side (front end side of the lens barrel) and the drain groove on the camera body side (the lens mount side) are different in depth from each other. Elements of the lens barrel shown inFIGS. 4,5and6which are similar to those shown inFIGS. 8A,8B and8C are designated by the same reference numerals. In this embodiment, the depths of the drain grooves129a,119aand111aare determined so that the drain groove closer to the object side (front end side of the lens barrel) is greater in depth, i.e., the drain groove closer to the camera body side (the lens mount side) is smaller in depth. Specifically, the depth of the drain groove129ais the greatest while the depth of the drain groove111ais the smallest. The closer the drain groove to the front end of the lens barrel10, the easier for drops of water to flow into the drain groove, and accordingly, the water-resistant effect is enhanced by forming the drain grooves129a,119aand111aso that the depths thereof increase in the direction toward the front end of the lens barrel.

In another embodiment of the water-resistant structure, at least one drain groove formed on the lens barrel10includes of more than one drain groove.FIG. 9shows an embodiment of the water-resistant structure in which the drain groove (which corresponds to the drain groove29ashown inFIG. 4) formed in the vicinity of the front end of the first lens group support frame29includes of two drain grooves29a1and29a2. In this embodiment, the first lens group support frame29is provided between the flanges29band29cwith a third (middle) flange29dwhich projects radially outwards from the outer peripheral surface of the first lens group support frame29between the flanges29band29cto form the two drain grooves29a1and29a2. The formation of the plurality of drain grooves29a1and29a2enhances the water-resistant effect. Each drain groove (e.g., the drain groove29a,19aor11a) can be made of more than two drain grooves.

Although the water-resistant structure according to the present invention has been described with reference to the above illustrated embodiments, in which the water-resistant structure according to the present invention has been applied to the zoom lens having two lens groups, the present invention is not limited solely to these particular embodiments and can be applied to any other type of lens barrel.

Operations of the (zoom) lens barrel10when the zoom ring (zoom rings15and17)30is manually operated and operations of the (zoom) lens barrel10when the focus ring19is manually operated will be hereinafter discussed with reference toFIGS. 2 and 3.

Upon the focus ring19being rotated, this rotation is transmitted to the rotatable advancing ring27, thus causing the rotatable advancing ring27to rotate. The rotatable advancing ring27moves forward/rearward while rotating due to being connected with the linearly movable ring25(that is guided linearly in the optical axis direction) via a helicoid mechanism. Forward and rearward movements of the rotatable advancing ring27cause the first lens group support frame29to integrally move with the first lens group L1forward and rearward along the optical axis O without rotating (seeFIG. 2).

The gap between the focus ring19and the front zoom ring17is water-sealed by the flocked cloth33. Therefore, the torque of the focus ring19acts on the zoom rings15and17(zoom ring30) so as to rotate the zoom rings15and17via a frictional resistance caused between the front zoom ring17and the flocked cloth33(i.e., so as to generate rotational torque causing the zoom rings15and17to rotate). For this reason, in the present embodiment of the water-resistant structure, the frictional resistance (maximum amount of static friction/rotational torque produced by sliding friction) caused between the rear zoom ring15and the flocked cloth35that is bonded to the first stationary barrel11is set to be greater than the frictional resistance (maximum amount of static friction/rotational torque produced by sliding friction) caused between the front zoom ring17and the flocked cloth33that is bonded to the focus ring19. Due to the difference between these frictional resistances (rotational torques), neither the rear zoom ring15nor the front zoom ring17follows the rotation of the focus ring19even if the focus ring19rotates.

Upon the zoom rings15and17, which are coupled together to integrally rotate as the single zoom ring30, being rotated, i.e., upon the grip ring16being rotated, this rotation is transmitted to the cam ring21, thus causing the cam ring21to rotate. This rotation of the cam ring21causes the linearly movable ring25, which is connected with the cam ring21via a cam mechanism, to move forward/rearward without rotating. The rotatable advancing ring27, which is connected with the linearly movable ring25via a helicoid mechanism, moves forward/rearward with the linearly movable ring25without rotating. Therefore, the first lens group support frame29and the first lens group L1move forward/rearward with the rotatable advancing ring27.

The gap between the front zoom ring17and the focus ring19is water-sealed by the flocked cloth33. Therefore, the torque of the front zoom ring17acts on the focus ring19so as to rotate the focus ring19via a frictional resistance caused between the front zoom ring17and the flocked cloth33. For this reason, in the present embodiment of the water-resistant structure, the frictional resistance (maximum amount of static friction/rotational torque produced by sliding friction) caused between the rotatable advancing ring27and the flocked cloth37that is bonded to the focus ring19is set to be greater than the frictional resistance (maximum amount of static friction/rotational torque produced by sliding friction) caused between the rear zoom ring15and the flocked cloth33that is bonded to the focus ring19. Due to the difference between these frictional resistances (rotational torques), the focus ring19does not follow the rotation of either the zoom ring30even if the zoom ring30rotates.

According to the above described embodiment of the zoom lens barrel, the frictional resistance caused by the flocked cloth33that seals the gap between the focus ring19and the zoom lens ring30(the front zoom ring17), which are manually independently rotated relative to each other, in a watertight fashion is set to be smaller than each of the frictional resistance caused by the flocked cloth37between the focus ring19and the rotatable advancing ring27and the frictional resistance caused by the flocked cloth35between the first stationary barrel11and the zoom lens ring30(the rear zoom ring15). Accordingly, even if one of the focus ring19and the zoom ring30is manually rotated, the other does not follow this rotation.

In addition, in the present embodiment of the zoom lens barrel, the frictional resistance caused by the flocked cloth33can be easily adjusted to be small because the drain groove19a, the flanges19band19cand the overhang17aare provided, in addition to the flocked cloth33, as elements of a water-resistant structure for watertight seal between the front zoom ring17and the focus ring19. Even if the contact pressure of the flocked cloth33with the front zoom ring17is adjusted to be small to thereby reduce the frictional resistance caused by the flocked cloth33, a sufficient water-resistant effect is maintained by the drain groove19a, the flanges19band19cand the overhang17a.

In addition, in the present embodiment of the zoom lens barrel, the drain grooves11a,19aand29acan be formed to be mutually different in depth. Since the water-resistant performance can be varied by making the depths of the drain grooves11a,19aand29adifferent from one another, a torque adjustment, e.g., an adjustment for reducing the frictional resistance of a sealing member by enhancing the water-resistant performance becomes possible. A similar effect can be obtained even by changing the number of the drain grooves.