JPS6120842B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a zoom lens barrel, and more particularly to a zooming operation member and a cam portion that contributes to extending the lens. Furthermore, the present invention relates to the arrangement position of the cam portion and the structure of its driven means. Conventionally, most of the cam barrels used in zoom lens barrels are made of cylindrical metal materials, which are NC-machined to form highly accurate cams with complex shapes.
The cam barrel is constructed separately from the zooming operation member, and the cam follower (hereinafter referred to as cam follower) is pressed into contact with the cam barrel to move the movable lens integrally combined with the cam follower along the cam in the optical axis direction. The lens was then moved to obtain a predetermined focal length. When operating the zoom ring, if there is a slight scratch on the cam, the torque will fluctuate slightly, making it impossible to obtain a good zoom operation feeling, and also having a negative effect on optical performance. Therefore, in order to achieve a smooth and highly accurate finish on the surface of the cam part that the cam follower presses against, a large number of steps are required during machining, which inevitably increases the cost of the cam barrel. Further, in the case of a grooved cam, since a groove is formed in the cylinder from the outer periphery to the inner periphery, deformation occurs, which limits the rotation angle of the cam. In addition, there was a space problem because the thickness and length of the cam cylinder had to be increased to prevent deformation. In response, a proposal has been made to integrally mold the cam cylinder. Kimiaki Sane
Taking 52-4924 as an example, although it has a large cost advantage, the large cylindrical notch causes deformation during molding, the zoom rotation angle is limited, and the zoom movement is difficult due to the two points of action. The drawback is that the movement of the ring is difficult. Also, Jitsukō 52-36571
For example, although this has great cost advantages, it also has some difficulties in terms of deformation, cam surface accuracy, cam wall thickness, etc.

The present invention has been made in view of the above points, and includes providing a cam with two cam surfaces, forming a straight groove intersecting with the cam surface in a fixed cylinder, and fitting a key member into the straight groove. A cam follower in contact with one cam surface of the cam is fixed to the member, a groove is formed in the key member, a protrusion in contact with the other cam surface of the cam is engaged with the groove, and the cam follower and the protrusion are is tensioned by a spring tensioned in a groove of the key member, thereby biasing the cam follower and the projecting piece against each cam surface of the cam.

This embodiment will be described below with reference to the figures.

FIG. 1 is a schematic cross-sectional view of a main part of a zoom lens barrel according to the present invention. The upper half shows the wide-angle part, the lower half shows the telephoto side, and in both cases, the distance ring shows the infinity side. Note that only the cam portion and cam follower portion of the front group are shown, and details of the throttle portion or mound portion and interlocking levers are omitted.
In the figure, 1 is a distance ring, 2 is a front group, 3 is a front group holding frame, 3a is a focusing helicoid, 4 is an index ring, 5a is a cam follower for the front group, 5 is a key member, 6 is a zooming operation member, 6a is a cam portion for the front group, 6b is a cam surface of the cam portion, 7 is a protrusion for the front group, 8
is the rear group holding frame, 9 is the rear group, 10 is the aperture ring, 1
1 is a fixed barrel, 11a is a linear elongated hole, 12 is a lens mount part, 13 is an aperture part, 14 is a spring,
15 is a dovetail. The distance ring 1 and the front group 2 are integrally connected, and are screwed to the front group holding frame 3 via a focusing helicoid 3a.
A cam follower 5a, a key member 5, and a projection piece 7 are integrally implanted in the front group holding frame 3, and the key member 5
is fitted into the linear guide groove 11a of the fixed cylinder 11, and its rotation is restricted. Therefore, by rotating the distance ring 1, the front group 2 is rotated and moved back and forth in the optical axis direction to perform focusing. When the zooming operation member 6 is rotated, the holding frame 3 is rotated along the cam surface 6a of the zooming operation member 6 in the optical axis direction by the action of the cam follower 5a, key member 5, and protrusion 7 that are integrally connected. Go straight back and forth. On the other hand, the rear group, like the front group, moves straight back and forth in the optical axis direction along a rear group cam surface (not shown) to obtain a predetermined focal length. FIG. 2 is a cross-sectional perspective view of a zoom cam according to the present invention. As can be seen from the figure, there is a continuous convex protrusion 6a on the inner peripheral surface of the zooming operation member 6, and both side surfaces 6b of the protrusion 6a form a zoom cam surface. The cam portion and the zoom portion are integrally molded from a synthetic resin material. This protrusion (cam portion 6a) is sandwiched between a cam follower 5a and a driven means consisting of a protrusion 7 to regulate the position of the movable lens. FIG. 3 is an enlarged perspective view of the cam follower portion. Explaining FIGS. 4 and 5 together, the cam follower 5a is integrally connected to the key member 5 (see FIG. 6), and the projecting piece 7 is inserted into the dovetail groove 15 provided at one end of the key member 5.
(see FIG. 7) is connected to the key so that it can move freely in the longitudinal direction of the key, and the other end of the spring 14 extended from one end of the cam follower 5a is connected to the protruding piece 7, so that the protruding piece 7 is connected to the key. It is guided by the groove of the member and is always urged in the direction of the cam follower 5a. Since the cam protrusion 6a exists between the two, the position of the moving lens coupled to the cam follower is regulated without causing play in the optical axis direction.
That is, the position of the lens by the cam is determined by the cam follower 5a, and the protrusion 7 is configured to prevent backlash, so that there is no backlash and it does not affect the zoom rotation torque.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a lens barrel showing an embodiment of the present invention. FIG. 2 is a cross-sectional perspective view showing main parts of a zooming operation member and a cam portion according to the present invention. FIG. 3 is a perspective view of a main part of the driven means of the zoom lens barrel of the present invention. FIG. 4 is a sectional view taken along line A-A' in FIG. FIG. 5 is a sectional view taken along the line B-B' in FIG. 6th
The figure is a perspective view of the cam follower 5a. Figure 7 shows
FIG. 7 is a perspective view of the projecting piece 7; 6...zooming operation member, 6a...cam part,
5...Following means (cam follower).

Claims (1)

[Scope of Claims] 1. A lens that performs a focusing action or a zooming action, a holding frame that holds the lens, a fixed cylinder that fits the holding frame, an operating member that moves the lens, and In the lens barrel having a cam that rotates around the optical axis by operation of the operating member, the cam is provided with two cam surfaces, the fixed barrel is formed with a rectilinear groove that intersects with the cam surface, and the A key member fixed to the holding frame is fitted into the straight groove, a cam follower in contact with one cam surface of the cam is fixed to the key member, a groove is formed in the key member, and the other cam of the cam is fitted into the groove. At the same time as engaging the protruding piece in contact with the surface,
A lens barrel characterized in that the cam follower and the protruding piece are tensioned by a spring stretched in a groove of the key member to bias the cam follower and the protruding piece against each cam surface of the cam. .