JPS61134714A - Zoom lens driving device for tv camera - Google Patents

Abstract

PURPOSE:To decrease the required operating power for turning in the stage of a manual operation by interposing a centrifugal clutch mechanism which connects a driving motor and a drive transmission system when the rotating speed of the driving motor attains a specified value. CONSTITUTION:Electricity is conducted to the driving motor 40 to drive an output shaft 41 in the stage of an electrical driving operation. The output shaft 41 and a clutch drum 36 are then integrally rotated by the friction force acting between a clutch plate 42 and a clutch face 38 upon attainment of the rotating speed at which the centrifugal force acting on the plate 42 overcomes a compression spring 52. On the other hand, the plate 42 and the clutch face 38 are held in the non-contact state, i.e., the clutch is held disengaged during the non-driving of the motor 40. The rotation of a zooming ring 11 is simply transmitted up to the drum 36 and is not transmitted to the shaft 41 of the motor 40 when the ring 11 is manually turned. The rotation of the ring 11 with the light force is thus made possible.

Description

TECHNICAL FIELD The present invention relates to a drive device for a TV left camera zoom lens that rotates a focusing ring and/or a zooming ring both manually and electrically.

"Prior Art and its Problems" FIG. 4 shows a conventional example of a drive device for a zooming ring 11. The zooming ring 11 is rotatably supported by a fixed lens barrel 12, and fixed by a well-known interlocking mechanism. Lens barrel 12
It rotates together with the cam ring 13 inside. The fixed lens barrel 12 includes a lens movable along the guide rod 14 in the optical axis direction.
A variator (variable magnification) lens frame 15 and a compensator (compensation) lens frame 16 are supported, and interlocking bins 17 and 18 provided integrally with the variator lens frame 15 and the compensator lens frame 16 are connected to a cam groove 19 formed in the cam ring 13. .20
I'm stuck in it. Therefore, when the cam ring 13 is rotated by the zooming ring 11, the variator lens frame 15 and the compensator lens frame 16 move in the optical axis direction according to the relationship between the cam grooves 19 and 20, and the focal length of the entire lens system changes. Reference numeral 21 designates a focusing lens frame that is movably provided at the tip of the fixed lens barrel 12, and reference numeral 22 designates a focusing ring that allows the focusing lens frame 21 to move forward and backward in the optical axis direction. Further, a master lens frame 23 is fixed to the rear end of the fixed lens barrel 12.

A zoom gear 25 is supported at the rear end of the zooming ring 11 via a clutch spring 24 made of wire. Due to the frictional action of the clutch spring 24, the zoom gear 25 and the zooming ring 11 rotate together when the rotational force acting between them is below a certain value, and slips when this exceeds a certain value. The zoom gear 25 meshes with a pinion 28 provided on an output shaft 27 of a reduction gear mechanism 26, and the reduction gear mechanism 26 is driven by a drive motor 29.

Therefore, in this conventional device, when the drive motor 29 is driven, the zooming ring 11 rotates via the reduction gear mechanism 26, the output shaft 27, the pinion 28, and the zoom gear 25.
Therefore, zooming is performed as shown in the following. Further, by applying a rotational force to the zooming ring 11 that is sufficient to cause slippage between the zooming ring 11 and the zoom gear 25, the zooming ring 11 can be rotated manually.

However, this manual rotation operation of the zooming ring 11
Since it is necessary to apply rotational torque to the zooming ring 11 that is sufficient to overcome the spring force of the clutch spring 24, a large operating force is required. Furthermore, the required rotational torque of the zooming ring 11 during zooming is
5, the full weight of the compensator lens frame 16, and the cam ring 13
Since it depends on the shape of the cam grooves 19, 20, the friction of each sliding surface, etc., the brighter the lens and the higher the magnification, the higher the necessary rotational torque of the zooming ring 11 is required.

Therefore, in order to drive this with the drive motor 29, the spring force of the clutch spring 24 is necessarily set strong. In other words, in this conventional device, the brighter the lens and the higher the magnification, the greater the rotational torque that must be applied to the zooming ring 11 during manual operation, making the operation more difficult.

``Object of the Invention'' The present invention solves the problems of the conventional device and provides a zoom lens for a TV camera that can be operated both manually and electrically. The object of the present invention is to obtain a drive device that is easy to operate and has good operability.

``Summary of the Invention'' The present invention was made based on the idea of using a centrifugal clutch mechanism as a clutch mechanism, as a result of research into a mechanism that does not cause rotational resistance on the drive motor side during manual operation. In other words, the present invention provides an arrangement between an output shaft rotated by a drive motor and a drive transmission system linked to a focusing ring or a zooming ring, when the rotational speed of the drive motor reaches a certain value. It is characterized by the interposition of a centrifugal clutch mechanism that connects the transmission system.

"Embodiments of the Invention" The present invention will be described below with reference to illustrated embodiments. FIGS. 1 and 2 show a first embodiment of the present invention, and some of the same parts as the conventional device shown in FIG. 4 are omitted, and the same parts are given the same reference numerals. .

A zoom gear 30 is cut at the rear of the zooming ring 11, and a binion 33 fixed to an output shaft 32 of a reduction gear mechanism 31 meshes with the zoom gear 30. A pulley 35 is fixed to the input shaft 34 of the reduction gear mechanism 31, and the belt 37 connects the pulley 35 and the clutch drum 36, which is rotatably supported by the output shaft 41 of the drive motor 40.
It is linked with The drive system from the second zoom gear 30 to the clutch drum 36 is a drive transmission system interlocked with the zooming ring 11.

On the other hand, as shown in FIG. 2, the output shaft 41 of the drive motor 40 supports a clutch plate 42 that makes up the centrifugal clutch mechanism 100 by coming into contact with and separating from the clutch surface 38 on the inner surface of the clutch drum 36. . A fixed plate 43 and a movable plate 44 are supported on the output shaft 41 . Both the fixed plate 43 and the movable plate 44 rotate together with the output shaft 41, and the movable plate 44 is prevented from being removed by an E-ring 45 and a washer 46. One end of a pair of links 49.50 is pivotally connected to the fixed plate 43 and the movable plate 44 by pins 47.48, and the other end of this link 49.50 is connected to the bin 51.
A clutch plate 42 is pivotally mounted. Therefore, when the fixed plate 43 and the movable plate 44 rotate together with the output shaft 41, the centrifugal force acting on the clutch plate 42 causes the movable plate 44 to move in the direction of arrow C in the figure, while moving the clutch surface of the clutch drum 36. 38. A compression spring 52 is provided between the fixed plate 43 and the movable plate 44.
is inserted, and the movable plate 44 is normally separated from the fixed plate 43. Reference numerals 53 and 54 designate a washer and an E-ring for removing the clutch drum 36 from the output shaft 41.

Accordingly, in this device having the configuration described above, during electric operation, the drive motor 40 is energized to drive the output shaft 41, and when the number of rotations thereof reaches a certain value or more, the clutch plate 42 engages the clutch surface of the clutch drum 36. Contact with 38. That is, when the rotation speed reaches such a point that the centrifugal force acting on the clutch plate 42 overcomes the compression spring 52, the frictional force acting between the clutch plate 42 and the clutch surface 38 causes the output shaft 41 and the clutch drum 3 to
6 will now rotate together. Therefore, the drive motor 40
If the force of the compression spring 52 is set so that the clutch plate 42 has sufficient contact pressure with the clutch surface 38 at the rated rotation speed of , when the drive motor 40 is driven, the clutch drum 3
6. Bell)・37. The zooming ring 11 is rotationally driven via the input shaft 34, output shaft 32, pinion 33, and zoom gear 30 of the reduction gear mechanism 31.

On the other hand, when the drive motor 40 is not driven, the compression spring 5
Due to the force of 2, the clutch plate 42 and the clutch surface 38 are in a non-contact state, that is, the clutch is in a disengaged state. Therefore, when the zooming ring 11 is manually rotated, the rotation of the zooming ring 11 is only transmitted to the clutch drum 36 and not to the output shaft 41 of the drive motor 40. Therefore, first, the zooming ring 11 can be rotated by the eaves force.

FIG. 3 shows another embodiment of the present invention, in which a gear 55 that meshes with the zoom gear 30 of the zoom ring 11 is formed directly on the outer periphery of the clutch drum 36. The other parts are the same as those of the apparatus shown in FIGS. 1 and 2, and the same parts are given the same reference numerals and the explanation thereof will be omitted. According to this embodiment, the clutch drum 36 is the only drive transmission system interlocked with the zoom gear 30 of the zooming ring 11, so that the torque required to manually rotate the zooming ring 11 is further reduced. Note that the output shaft 41 may be the output shaft of the drive motor 40 or the output shaft of a reduction gear mechanism driven by the drive motor 40.

In the above embodiment, the present invention is applied to the drive mechanism of the zooming ring 11, but the present invention can be similarly applied to the drive mechanism of the focusing ring 22.

"Effects of the Invention" As described in (2) below, according to the TV camera zoom lens drive device of the present invention, the output shaft rotationally driven by the drive motor and the drive transmission system interlocked with the focusing ring or the zooming ring. With a simple configuration in which a centrifugal clutch mechanism is interposed between the two, the rotational operating force during manual operation can be significantly reduced. Therefore, even a bright, high-magnification zoom lens that requires a large rotational operating force can be operated manually with a light operating force.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the main parts showing an embodiment of the drive device for a zoom lens for a TV camera according to the present invention, FIG. 2 is a cross-sectional view of the centrifugal clutch mechanism, and FIG. 3 is a cross-sectional view of another embodiment of the present invention. FIG. 4 is a sectional view showing an example of a conventional drive device of this type. 11... Zooming ring, 12... Fixed lens barrel, 13...
...Cam ring, 15...Variator lens frame, 16...
・Convencator lens i, 2-toe focusing lens frame, 22... Focusing ring, 30... Zoom gear, 31... Reduction gear mechanism, 36... Clutch drum, 38... Clutch surface, 40... ... Drive motor, 41... Output shaft, 42... Clutch plate, 100...
...Centrifugal clutch mechanism.

Claims (1)

[Claims] (1) A TV in which at least one of the focusing ring and zooming ring of a zoom lens for a TV camera can be rotated by both manual operation and electric operation using a drive motor.
In a camera zoom lens drive device, when the rotational speed of the drive motor reaches a certain value between the output shaft rotated by the drive motor and the drive transmission system linked to the focusing ring or zooming ring, A drive device for a zoom lens for a TV camera, characterized in that a centrifugal clutch mechanism is interposed to connect the drive motor and the drive transmission system.