JPH0655140U - Lens accessory attachment / detachment mechanism - Google Patents

Abstract

(57) [Summary] [Purpose] In an attaching / detaching mechanism that allows accessories such as a lens hood to be attached to and detached from the tip of the lens barrel by using a bayonet mechanism, the sliding portion of the tip of the lens barrel is unlikely to be scratched, (EN) Provided is a lens accessory attaching / detaching mechanism which is less likely to change the attaching / detaching torque due to temperature changes and has excellent cost performance. A structure for attaching / detaching a tubular portion of an accessory to / from a tubular portion at a tip of a lens barrel, wherein the tubular portion at a tip of the lens barrel is formed to project on an outer periphery thereof at equal angular intervals. A plurality of bayonet claws are provided, and the tubular portion of the accessory has a width on its inner periphery that can enter between adjacent bayonet claws, and is formed at equal angular intervals that can engage with the bayonet claws. A plurality of engaging pieces are provided, and the engaging pieces are alternately provided with a pair of symmetrical shapes with respect to the circumferential direction in which the bayonet claws are formed. A lens accessory attaching / detaching mechanism that elastically engages the back surface and the other engaging piece elastically engages the front surface of another bayonet claw when the one engaging piece elastically engages the back surface of the bayonet claw. .

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an attachment / detachment mechanism for attaching / detaching an accessory such as a lens hood to a tip portion of a lens barrel.

[0002]

[Prior art and its problems]

 In some lens barrels, accessories such as a lens hood for preventing harmful rays from other than the angle of view of the lens can be attached to the tip of the lens barrel. In the case where the bayonet mechanism is used as a means for attaching and detaching accessories such as a lens hood to the lens barrel, a metal spring member is provided on the lens barrel side or the accessory side, and the weight of the bayonet claws of each other is provided by this spring member. It is common to press the open part in the front-back direction or in the radial direction of the lens barrel and fix it by the frictional force between the two claws. This conventional structure has a drawback that the sliding member that slides on the metal spring is easily scratched. Since the tip of the lens barrel is a portion that is particularly easily noticed, it is not preferable for the appearance to be scratched.

Further, the accessory body is formed of an elastically deformable material such as synthetic resin, and the accessory body is radially deformed by a plurality of claw portions provided on the accessory side, and the reaction force causes the lens mirror to be deformed. It is known that it is fixed to the cylinder side. In this conventional structure, the accessory body expands or contracts due to temperature changes, and therefore, there is a drawback that the attachment / detachment torque fluctuates greatly when the accessory is attached / detached. The attachment / detachment torque is used to prevent the accessory from falling off, to prevent rattling in the mounted state, and to give a feeling of attachment / detachment during rotation attachment / detachment and rotation attachment / detachment. Also, it refers to a constant torque generated by sliding friction between the predetermined members of the lens barrel and the accessory during rotational attachment / detachment.

[0004]

[The purpose of the device]

 The present invention has been made in view of the above-described conventional problems, and an accessory mechanism such as a lens hood in which the accessory such as a lens hood can be attached and detached using a bayonet mechanism is provided in the lens barrel. It is an object of the present invention to provide a lens accessory attachment / detachment mechanism that is less likely to be scratched on the sliding part of the tip portion, has little fluctuation in attachment / detachment torque due to temperature changes, and has excellent cost performance.

[0005]

[Outline of the device]

 The accessory attachment / detachment mechanism of the lens according to the present invention is a mechanism for attaching / detaching the tubular portion of the accessory to the tubular portion at the tip of the lens barrel, and the tubular portion at the tip of the lens barrel is attached to the outer periphery thereof. Equipped with a plurality of bayonet claws protruding at equal angular intervals, the tubular part of the accessory has a width on its inner circumference that allows it to enter between adjacent bayonet claws, and engages with this bayonet claw. A plurality of engaging pieces formed at equal angular intervals are provided. The engaging pieces are alternately provided with a pair of symmetrical shapes in the circumferential direction in which the bayonet claws are formed. One engaging piece is elastically engaged with the back surface of the bayonet claw, and the other engaging piece is the front surface of the other bayonet claw when the one engaging piece is elastically engaged with the back surface of the bayonet claw. It is characterized by elastically engaging with.

[0006]

【Example】

 The present invention will be described below with reference to illustrated embodiments. 1 to 9 show a first embodiment of an attaching / detaching mechanism according to the present invention. 1 and 2 respectively show a lens barrel 10 to which an attachment / detachment mechanism according to the present invention is applied, and a lens hood 20 which can be attached to and detached from a front end portion of the lens barrel 10. The lens barrel 10 is a lens barrel of an interchangeable lens used in, for example, a single-lens reflex camera, and has a taking lens L inside the front (on the left side in FIG. 1) thereof. The outer ring 11 that constitutes the exterior of the lens barrel 10 is made of a rigid synthetic resin material or a metal material, and the outer ring 11 that is located in front of the outer ring 11 has four outer circumferential surfaces 12a at equal angular intervals. However, it is provided with a bayonet claw 13 that is formed to project radially outward.

On the other hand, the lens hood 20 shown in FIG. 2 is made of an elastically deformable synthetic resin material, and has a tubular portion to be fitted to the front end portion of the lens barrel 10 including the tubular portion 12. It is equipped with 21. The tubular portion 21 is integrally provided with four engaging pieces 22 having a predetermined shape and formed inwardly in the radial direction at four locations on the inner peripheral surface 21a thereof at equal angular intervals. When the lens hood 20 is mounted on the lens barrel 10, the engaging pieces 22 are engaged with the bayonet claws 13.

FIG. 3 is a development view of the outer peripheral surface 12a showing the positions of the bayonet claws 13 on the outer peripheral surface 12a. Each bayonet claw 13 is located in a plane perpendicular to the optical axis X of the lens barrel 10 along the virtual line T indicated by a dashed-dotted line extending in the circumferential direction. Lines are provided on the outer peripheral surface 12a at equal angular intervals at four positions, that is, at intervals of 90 degrees. The bayonet claw 13 has sliding surfaces 13a and 13b at the front and rear in the optical axis X direction, and has end surfaces 13c at both ends in the circumferential direction. The widths of all the bayonet claws 13 in the direction of the optical axis X are the same, and in this embodiment, the dimension A is set as shown in the drawing. The bayonet claws 13 have the same length in the circumferential direction, and the length in the circumferential direction is set as the dimension Q. Further, the length from the optical axis X to the upper end surface of the bayonet claw 13 is set to be slightly shorter than the length from the central axis C of the lens hood 20 to the inner peripheral surface 21a.

FIG. 4 is a development view of the inner peripheral surface 21 a showing the position of each engagement piece 22 on the inner peripheral surface 21 a of the lens hood 20. The engagement piece 22 has a substantially convex shape that is symmetrical with respect to an imaginary line W extending in the circumferential direction and shown by a dashed-dotted line, which is located in a plane perpendicular to the central axis C of the lens hood 20. One pair is provided alternately at equal angular intervals at four positions, that is, at 90 ° intervals. Each of the engagement pieces 22 has a sliding surface 22a that should be in sliding contact with the sliding surface 13a or 13b of the bayonet claw 12 when the lens hood 20 is mounted on the lens barrel 10. The surface 22a opposes and is parallel to the imaginary line W at a predetermined distance (B 2/2). Therefore, the distance in the central axis C direction between the sliding surface 22a of an arbitrary engaging piece 22 and the sliding surface 22a of the engaging piece 22 adjacent to the engaging piece 22 is B shown in FIG. It This distance B is set to be slightly shorter than the width A of the bayonet claw 13. Further, the distance S between the respective engaging pieces 22 in the circumferential direction along the imaginary line W is set so that the bayonet claws 13 can enter between the two adjacent engaging pieces 22. Is set to be equal to or more than Q. In this embodiment, the distance Q is set to be slightly shorter than the distance S. Further, the engagement piece 22 is provided with a locking projection 22b extending from the central portion of the sliding surface 22a in the direction of the central axis C, and at both ends of the sliding surface 22a in the circumferential direction from the imaginary line W. It is provided with an inclined sliding surface 22c that is inclined in a direction away from it.

The functions of various members related to the present invention will be described below in accordance with the procedure for mounting the lens hood 20. FIG. 5 shows a state immediately before the engagement piece 22 is engaged with the bayonet claw 13 in a state where the tubular portion 21 of the lens hood 20 and the tubular portion 12 of the lens barrel 10 are fitted. Is. When the lens hood 20 is attached to the lens barrel 10, first, as shown in the figure, the cylindrical portion 21 of the lens hood 20 is arranged so that the engaging pieces 22 are positioned between the bayonet claws 13. Is fitted into the tubular portion 12 of the lens barrel 10. From the state shown in the figure, the lens hood 20 is rotated to the left or right with respect to the lens barrel 10. Then, one of the slanting sliding surfaces 22c of the engaging pieces 22 starts to slide with the end surface 13c of the adjacent bayonet claw 13 and the sliding surface 22a connected to the slanting sliding surface 22c is the bayonet claw 13. The sliding projections 22b come into contact with the end surface 13c of the bayonet claw 13 after sliding contact with the sliding surface 13a or 13b on the side. As a result, the rotation of the lens hood 20 is restricted, and the lens hood 20 reaches the mounting completion state shown in FIG. The relationship between the bayonet claw 13 and the engagement piece 22 in the completed mounting state is enlarged in FIGS. 7 and 8.

FIG. 7 is a view for explaining the relationship between the bayonet claw 13 and the engaging piece 22 on the assumption that the lens hood 20 made of an elastically deformable material does not elastically deform after the mounting is completed. is there. As described with reference to FIGS. 3 and 4, the width of the bayonet claw 13 in the optical axis X direction is A, and the distance between the sliding surfaces 22a of the adjacent engaging pieces 22 in the central axis C direction is B and the distance B is set to be shorter than the width A by a predetermined amount. Therefore, when the mounting is completed, that is, when the bayonet claw 13 and the engaging piece 22 are engaged, the engaging piece 22 and the engaging piece 2 are The sliding surface 13a or 13b and the sliding surface 22a of the bayonet claw 13 to be engaged with 2 move in the optical axis X direction (central axis C direction). This movement amount is (A−B) / (A−B) when the virtual line W on the lens hood 20 side and the virtual line T on the lens barrel 10 side shown in FIG. 7 are aligned in the optical axis X direction (central axis C direction). It becomes 2. In practice, since the lens hood 20 is made of an elastically deformable material, one engagement piece 22 is (AB) / 2 in the forward direction of the optical axis X 2 and the engagement piece 22 is The lens hood 20 is deformed so that the adjacent engaging pieces 22 move backward by the same amount of (AB) / 2. FIG. 8 shows the relationship between the bayonet 13 and the engaging piece 22 when the lens hood 20 is actually elastically deformed.

In FIG. 8, the adjacent engaging pieces 22 move by (AB) / 2 each in the front-rear direction in the optical axis X direction, which is a distance of AB in total, that is, the lens hood 20 side is deformed. Is shown. Due to this deformation, a stress corresponding to the distance A-B is generated, and a force F that presses the sliding surface 22a of the engagement piece 22 toward the sliding surface 13a or 13b of the bayonet claw 13 is generated. Here, if the distance from the optical axis X (central axis C) to the engagement piece 22 is R, the number of engagement pieces 22 is N, and the friction coefficient between the sliding surfaces 13a and 22a is μ, A detachment torque T of T = FμRN is generated. Therefore, the engaging pieces 22 mesh with the four bayonet claws 13 alternately in the optical axis X direction, and the presence of the attachment / detachment torque T ensures that the lens hood 20 is held in the lens barrel 10. . The lens hood 20 may be attached and detached by rotating the lens hood 20 with respect to the lens barrel 10 in a direction opposite to the direction in which the lens hood 20 was rotated when it was attached.

Note that the relationship between the width A of the bayonet claw 13 in the optical axis X direction and the distance B in the central axis C direction between the sliding surfaces 22a of the adjacent engaging pieces 22 is AB> 0. Yes, the larger the value of AB is set, the larger the attachment / detachment torque T becomes. Therefore, the magnitude of the attachment / detachment torque T can be adjusted by changing the value of AB.

10 through 13 show a second embodiment of the present invention. In this embodiment, the lens barrel is a lens barrel 10 'in which the stopper portion 15 or 16 is formed on the lens barrel 10 in the first embodiment. Other configurations are similar to those of the first embodiment. The lens barrel 10 ′ is provided with a stopper portion on the sliding surface 13 b side of either one of the bayonet claws 13 in the circumferential direction.

FIG. 11 is a development view of the outer peripheral surface 12a of the lens barrel 10 '. FIG. 12 shows a state immediately before engaging the engaging piece 22 with the bayonet claw 13 in a state where the tubular portion 21 of the lens hood 20 and the tubular portion 12 of the lens barrel 10 ′ are fitted. FIG. 13 is a diagram showing a state where the lens hood 20 is completely attached. Due to the presence of the stopper portion 15 or 16, the rotation direction when the lens hood 20 is attached to the lens barrel 10 can be limited. That is, when the stopper portion 15 is provided, the lens hood 20 rotates only rightward toward the lens barrel 10 'side, and when the stopper portion 16 shown by the broken line in the figure is provided, the lens hood 20 rotates leftward. Will only be. Thereby, when the lens hood 20 is attached to or detached from the lens barrel 10, the attachment / detachment position of the lens hood 20 with respect to the lens barrel 10 can be made clear.

By the way, FIG. 14 shows a conventional example of an accessory in which the main body 31 is elastically deformed in the radial direction by the plurality of claw portions 32 and is fixed to the lens barrel by the reaction force thereof. Since the main body 31 is fixed to the cylindrical portion at the tip of the lens barrel by changing the dimension A in the direction, the main body 31 expands and contracts constantly in the circumferential direction due to temperature changes, so that the dimension A The fluctuation is large. Therefore, the attachment / detachment torque at the time of attaching / detaching the accessory is greatly changed by the temperature change. On the other hand, in the first and second embodiments of the present invention, the lens hood 20 is moved to the lens barrel by changing the slight distance B (FIG. 4) in the front-back direction of the tubular portion 21. Since it is configured to be mounted on No. 10, the distance B does not change so much due to temperature changes, and therefore the variation of the attachment / detachment torque due to temperature changes is significantly smaller than in the conventional case.

In both of the above-described embodiments, since the engagement pieces 22 of the lens hood 20 are formed line-symmetrically with respect to the imaginary line W, the front and the rear of the lens hood 20 are reversed to form the lens barrel 10 or 10 ′. It can be attached to. Therefore, the lens hood 20 can be attached to the lens barrel 20 even when the lens hood 20 is not used, which is advantageous when carrying or storing.

In this embodiment, the accessory attached to the tip of the lens barrel has been described with respect to the lens hood, but the present invention is not limited thereto. The mounting mechanism is not limited to the lens hood, and may be any mounting mechanism that allows the tip of the lens barrel to be attached to and detached from other barrel-shaped or ring-shaped accessories. Further, it goes without saying that the lens barrel is not limited to a lens barrel for photographing, and may be various lens barrels such as a telescope.

[0019]

[Effect of device]

 As described above, according to the present invention, the engaging pieces formed on the accessory side are provided with a pair of symmetric shapes that are symmetrical with respect to the circumferential direction in which the bayonet claws on the lens barrel side are formed. One of the engaging pieces elastically engages the back surface of the bayonet claw, and the other engaging piece of the other bayonet claw when the one engaging piece elastically engages the back surface of the bayonet claw. Since the front surface is elastically engaged, since no metallic spring member or the like is used on either the lens barrel side or the accessory side, it is possible to prevent the occurrence of scratches on the sliding portion.

Further, in the accessory according to the present invention, the adjacent engaging pieces are elastically deformed in the front-rear direction and are attached to the lens barrel by the reaction force thereof, so that a plurality of claw portions provided on the accessory side are provided. As a result, the accessory body is deformed in the radial direction and the reaction force reduces the fluctuation of the attachment / detachment torque due to the temperature change compared with the conventional one in which it is fixed to the lens barrel.

Further, the accessory according to the present invention elastically deforms the accessory main body in the front-rear direction with a long span in the circumferential direction between the adjacent engaging pieces, so that the accessory main body is provided by the plurality of claw portions provided on the accessory. In comparison with the conventional one in which the claws are locally deformed and the reaction force fixes them to the lens barrel, both maximum strain and maximum stress can be reduced when similar detaching torque is obtained. It is possible to set the attachment / detachment torque.

Furthermore, since the accessory can be integrally molded, the number of parts can be small and the cost performance is excellent.

[Brief description of drawings]

FIG. 1 is a perspective external view showing a lens barrel according to a first embodiment of the present invention.

FIG. 2 is a perspective external view showing a lens hood according to the present invention.

FIG. 3 is a development view of an outer peripheral surface of the lens barrel shown in FIG.

FIG. 4 is a development view of an inner peripheral surface of the lens hood shown in FIG.

FIG. 5 is a perspective development view of the outer peripheral surface of the lens barrel and the inner peripheral surface of the lens hood, showing a state in which the engagement piece and the bayonet claw are being mounted in the first embodiment.

FIG. 6 is a perspective development of the outer peripheral surface of the lens barrel and the inner peripheral surface of the lens hood as seen from the outside of the lens barrel, showing the state when the engagement piece and the bayonet claw have been mounted in the first embodiment. It is a figure.

FIG. 7 is an enlarged view showing a portion Z surrounded by a chain double-dashed line in FIG. 6 on the assumption that the lens hood is not deformed.

8 is an enlarged view showing a portion Z surrounded by a two-dot chain line in FIG.

FIG. 9 is an optical axis X taken along a line IX-IX in FIG.
It is sectional drawing which shows only an upper part.

FIG. 10 is a perspective external view showing a lens barrel according to a second embodiment of the present invention.

11 is a development view of the outer peripheral surface of the lens barrel shown in FIG.

FIG. 12 is a perspective development view of the outer peripheral surface of the lens barrel and the inner peripheral surface of the lens hood, showing a state in which the engagement piece and the bayonet claw are being mounted in the second embodiment.

FIG. 13 is a perspective development view of the outer peripheral surface of the lens barrel and the inner peripheral surface of the lens hood, showing the state when the engagement piece and the bayonet claw are completely mounted in the second embodiment.

FIG. 14 is a schematic front view of the accessory seen from the lens barrel side, showing a conventional example of a lens accessory attaching / detaching mechanism.

[Explanation of symbols]

 10, 10 'Lens barrel 11 Outer ring 12 Cylindrical portion 12a Outer peripheral surface 13 Bayonet claws 13a, 13b Sliding surface 13c End surface 15, 16 Stopper portion 20 Lens hood (accessory) 21 Cylindrical portion 21a Inner peripheral surface 22 Engagement Piece 22a Sliding surface 22b Locking protrusion (stopper) 22c Inclined sliding surface C Center line T, W Virtual line X Optical axis

Claims (4)

[Scope of utility model registration request] 1. A mechanism for attaching / detaching a tubular portion of an accessory to / from a tubular portion at the tip of a lens barrel, wherein the tubular portion at the tip of the lens barrel is formed to project at an equal angular interval on the outer periphery thereof. A plurality of bayonet claws, and the tubular portion of the accessory has a width on its inner periphery that allows entry between adjacent bayonet claws and is formed at equal angular intervals that can engage with the bayonet claws. A plurality of engaging pieces, which are symmetrically arranged with respect to the circumferential direction in which the bayonet claws are formed.
One of the engaging pieces is elastically engaged with the back surface of the bayonet claw, and the other engaging piece is of the other bayonet claw when the one engaging piece is elastically engaged with the back surface of the bayonet claw. A lens accessory attaching / detaching mechanism characterized by elastically engaging the front surface. 2. The lens accessory attachment / detachment according to claim 1, wherein each of the one and the other engagement pieces is provided with a stopper portion at its center position for engaging with a bayonet claw to regulate a relative rotation position. mechanism. 3. The cylindrical portion at the front end of the lens barrel according to claim 1 or 2, when the cylindrical portion of the accessory is rotated in a non-engaging direction from the engaged state of the bayonet claw and the engaging piece. An accessory attachment / detachment mechanism for a lens, which is formed with a stopper portion that abuts on an end portion of an engagement piece adjacent to the engagement piece that has been engaged up to and controls the relative rotation position of the bayonet claw. 4. A lens accessory attaching / detaching mechanism according to claim 1, wherein the tubular portion of the accessory is made of a synthetic resin material.