Fluid handling – Systems – With selective motion for plural valve actuator
Reexamination Certificate
2000-05-23
2001-06-19
Hail, III, Joseph J. (Department: 3723)
Fluid handling
Systems
With selective motion for plural valve actuator
C137S596200, C137S625300, C251S127000, C254S00800R
Reexamination Certificate
active
06247498
ABSTRACT:
FIELD OF THE INVENTION
The field of the invention is hydraulic valves. More particularly, the invention relates to hydraulic valves used in camera dollies, to raise and lower a camera.
Camera dollies are used in the television and motion picture industries to support and maneuver a camera. Typically, the-camera dolly is on wheels and has an arm to raise and lower the camera. The camera dolly is generally moved by dolly operators or “grips”, to properly position the camera, to follow the film or video sequence.
Various designs have been used to raise and lower a camera on a camera dolly. For example, U.S. Pat. No. 4,360,187 describes a two piece arm design for use in a camera dolly. The arm is raised and lowered via a hydraulic actuator and a control valve. Other camera dollies use a straight single piece beam arm or a telescoping pedestal lifted by a hydraulic or pneumatic actuator, such as described in U.S. Pat. No. 5,516,070.
The valves used to control a hydraulically driven camera dolly arm should meet certain design objectives. For example, the opening and closing characteristics of the valve should allow the camera dolly operator to accurately and easily control the speed and direction of the arm movement. The valve should also allow the arm to be accurately stopped at a selected elevation. In addition, the valve should operate silently, so as not to interfere with the sound track being recorded for the motion picture or video sequence.
U.S. Pat. Nos. 4,747,424 and 4,109,678, incorporated herein by reference, describe hydraulic valves which have been successfully used in camera cranes and dollies for many years. However, the valve described in U.S. Pat. No. 4,109,678 will occasionally generate fluid rushing or whistling sounds, especially on the “down” side, as hydraulic fluid rapidly flows through the valve, when the camera dolly arm is quickly lowered. In addition, controlling this valve to begin movement of the camera dolly arm at a precise time can require a level of skill and experience, as the control handle must be turned by a certain amount before the camera dolly arm actually begins to move. The delay between control handle movement and arm movement results because the swash plate in the valve must turn sufficiently, before the valve cracks open. This characteristic can make precise control of the movement of the camera dolly arm more difficult. As split second timing is often needed to position a camera, the delay in arm movement can be a disadvantage. The delay may also induce less experienced grips to over-compensate by turning the control handle too far. This results in arm movement that is too fast, or that overshoots the desired camera lens height.
Accordingly, there remains a need for an improved hydraulic valve to control movement of a hydraulically actuated camera dolly arm.
SUMMARY OF THE INVENTION
To these ends, in a first aspect of the invention, an improved hydraulic valve has a head bushing positioned around the head of the valve pin on the down side of the valve.
In a second aspect of the invention, a shaft bushing is located around the shaft of the pin on the down side of the valve.
In a third aspect of the invention, a detent provides for instant down movement, closed, and instant up movement positions for the valve control.
In another separate aspect of the invention, the ratio of movement between the valve control and the valve is selected to provide desensitized control of the valve, and therefore of the camera dolly arm, thereby making the arm easier to precisely control. Accordingly, it is an object of the invention to provide an improved hydraulic valve for a camera dolly.
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Technical Manual -“The Super Peewee”, Chapman/Leonard Studio Equipment, 1992, 5 pages.
Chapman/Leonard Studio Equipment
Hail III Joseph J.
Lyon & Lyon LLP
Wilson Lee
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