JPH0233204Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a zoom lens in which a lens frame is moved to a predetermined zooming position by rotation of a cam barrel.

Conventionally, in lens barrels that move the movable frame using this type of cam control, such as zoom lens barrels, a cam follower that fits into the cam groove of the cam barrel and the guide groove of the fixed barrel is implanted in the movable frame. However, the movement of the moving frame was controlled by rotating the cam cylinder. or,
In recent years, improvements in plastic molding technology have made lens barrels lighter and cheaper.
Parts such as lens barrels and moving frames are molded. When using a plastic molded moving frame with a cam follower, conventionally the cam follower was fixed to the moving frame of the plastic mold using screws, etc., but in order to tighten the screws, the moving frame required a wall thickness greater than that of metal parts. This was an obstacle to making the lens barrel more compact and smaller in diameter. In addition, when the movable frame and cam follower are made of a single plastic molded part, it is necessary to elastically deform the cam follower part of the movable frame in order to fit the movable frame into the fixed cylinder, but if the lens barrel receives an impact, the cam follower will deform. It has the disadvantage that it separates from the cam groove and movement control becomes impossible.

FIG. 1 shows such a conventional two-group zoom lens barrel. That is, the third lens _L3 is held in the mount 1 having the attachment part 1a to the camera body, and the fixed cylinder 2 fixed to the mount 1 with screws etc. has the first lens group on its inner diameter.
First moving frame 3 and second lens group L ₂ for L ₁
A second movable frame 4 is fitted so as to be slidable in the optical axis direction, and a cam follower 3a implanted in the first movable frame 3 and a cam follower portion 4a integrally provided in the second movable frame 4 are slidably fitted in the optical axis direction. They fit into linear guide grooves 2a and 2b provided in the fixed barrel 2, respectively, and also into cam grooves 5a and 5b provided in a cam barrel 5 rotatably fitted to the outer diameter portion of the fixed barrel 2, respectively. ing. The first movable frame 3 has a first
The first movable frame 6 holding the lens group _L1 is connected by a helicoid 3b, and the inner circumference of the focus tube 7 is screwed to the outer circumference of the second fixed tube 8 fixed to the tip of the fixed tube 2 in the optical axis direction. A protrusion 6 formed on the first holding frame 6 in the straight guide groove 7a formed in the
A is inserted. Further, a zoom ring 9 is fixed to the outer periphery of the cam cylinder 5.

With such a configuration, when the focusing tube 7 is rotated, the first holding frame 6 is also rotated, and it moves back and forth in the optical axis direction according to the lead of the helicoid 3b to perform focusing, and when the zoom ring 9 is rotated, the cam Tube 5
The first movable frame 3 and the first holding frame 6 are guided by the cam groove 5a and the linear guide groove 2a of the fixed barrel 2, and the second movable frame 4 is guided by the cam groove 5b and the linear guide groove 2b. Both move along the optical axis direction to perform zooming.

However, when an impact force is applied to the lens barrel in the optical axis direction, the cam follower 4a, which is integrally provided in the second moving frame 4, deforms in the radial direction of the cam cylinder and disengages from the cam groove 5b. have.

The present invention aims to eliminate the drawbacks of the conventional example described above and to provide a zoom lens having a simple structure and impact resistance.

Embodiments of the present invention will be described below based on the drawings. FIG. 2 is a sectional view on the optical axis of an embodiment of the zoom lens barrel according to the present invention, and FIG. 3 is an exploded perspective view of the main parts thereof.

However, the same components as those of the conventional example shown in FIG. 1 are given the same reference numerals, and the explanation thereof will be omitted, and particularly the different structures will be explained.

Particularly different is the second moving frame 4, in which a jaw 4c having a tapered part _4c1 is integrally molded at the tip of a cam follower 4a provided in front of the extension part 4b, and the outer circumference of the cam groove 5b of the cam cylinder. A chamfered portion 5c (tapered surface) corresponding to the tapered portion _4c1 of the jaw 4c is provided on the portion. Further, an opening 2c larger than the jaw 4c is provided at the extension of the linear guide groove 2b of the fixed barrel 2 which is outside the normal range of magnification, and an opening 5d is also provided at the extension of the cam barrel.

In order to fit the second movable frame 4 into the fixed cylinder 2, the elasticity of the extension part 4b made of resin material is used to fit the cam follower 4a into the opening 2c of the fixed cylinder 2, and the cam cylinder 5.
into the opening 5d. In the movable barrel 4 assembled in this way, the cam follower 4a never faces the openings 5d, 2c in the normal range of magnification, but always moves in the inner radial direction due to the relationship between the jaws 4c and the chamfered portions 5c. The separation of the cam follower 4a is restricted.

In order to operate this zoom lens barrel, when the focus tube 7 is rotated, the first holding frame 6 is also rotated, and it moves back and forth in the optical axis direction according to the lead of the helicoid 3b to perform focusing, and the zoom ring 9 is rotated. When the movement is performed, the first movable frame 3 and the first holding frame 6 are guided by the cam groove 5a of the cam cylinder 5 and the linear guide groove 2a of the fixed cylinder 2, and the first moving frame 3 and the first holding frame 6 are guided by the cam groove 5b and the linear guide groove 2b. Then, the second movable frame 4 moves along the optical axis direction to perform rezooming.

By the way, when an impact force in the optical axis direction is applied to the lens barrel, the cam follower 4a, which is integrally provided in the second moving frame 4, deforms in the radial direction of the cam cylinder, and the cam follower tries to separate from the cam groove of the cam cylinder. However, the tip jaw portion 4c of the cam follower comes into contact with the cam groove chamfered portion 5c of the cam cylinder, thereby preventing the cam follower from coming off.

Although the above-mentioned embodiment is used in a zoom system, it can also be applied to other lens drives or movable light-shielding tube drives as long as the structure is driven by a cam. Furthermore, in the embodiment, the cam cylinder is externally mounted on the fixed cylinder, but it is also possible to apply the reverse pattern.

As explained above, the present invention enables elastic movement in the radial direction by forming the cam follower, which is inserted into the cam groove of the cam tube, into an extension part extending from the main body of the lens frame. Furthermore, the cam follower is formed with a tapered part whose width is in the outer radial direction, and the cam groove into which this cam follower is inserted is also formed with a similar taper part, thereby making it easier for the lens frame or cam cylinder to To provide a zoom lens capable of preventing a cam follower from coming off a cam groove when an impact force is applied.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of a conventional zoom lens barrel, FIG. 2 is a vertical cross-sectional view of an embodiment of the zoom lens barrel according to the present invention, and FIG. 3 is an exploded perspective view of essential parts thereof. _L1 ...first lens group, _L2 ...second lens group,
L ₃ ...Third lens group, 1...Mount, 2...
Fixed barrel, 5...cam barrel, 2b...straight guide groove,
2c...opening, 5b...cam groove, 5c...chamfer, 5d...opening, 4...movable cylinder, 4b...
Extension part, 4a...cam follower, 4c...jaw part.

Claims (1)

[Claims for Utility Model Registration] (1) A fixed cylinder having a first groove, a cam cylinder having a second groove and rotated by a zooming operation, and the intersection of the first and second grooves. a lens frame having a cam follower inserted at a position, and the first and second grooves are set so that the lens frame is moved to a predetermined zooming position by rotation of the cam barrel. In the zoom lens, the cam follower is formed in an extension part extending from the main body part of the lens frame.
While enabling elastic movement in the radial direction,
At a position corresponding to the first or second groove,
A first tapered portion is formed that is wide in the outer diameter direction, and a second tapered portion that contacts the tapered portion is formed in the first or second groove corresponding to the first tapered portion. A zoom lens characterized by: (2) The cam follower and the extension part are integrally molded with the lens frame, and an opening larger than the cam follower including the first tapered part is provided at the ends of the first and second grooves. A zoom lens according to claim 1 of the utility model registration claim.