Patent ID: 6578819
Filing Date: 2003-06-17
Classification: B66F,F15B,Y10T

Abstract:
A camera dolly comprising:an arm for supporting a camera; a hydraulic actuator attached to the arm; and a hydraulic valve for controlling flow of hydraulic fluid to and from the hydraulic actuator, with the hydraulic valve comprising: a housing: a pressure port connecting into a first bore in the housing; an exhaust port connecting into a second bore in the housing; a passageway connecting the first bore and the second bore; an actuator port connecting into the passageway, between the first bore and the second bore; a first seat at the first bore; a first pin engageable against the first seat, to seal the first bore from the passageway, and movable away from the first seat, to allow fluid flow between the first bore and the passageway; a first spring urging the first pin into engagement against the first seat; a second seat at the second bore; a second pin engageable against the second seat, to seal the second bore from the passageway, and movable away from the second seat, to allow fluid flow between the second bore and the passageway; and a second spring urging the second pin into engagement against the second seat, with the second pin having a head and a solid extension therefrom extending through an opening in the housing and through a second pin seal surrounding the opening, the extension reducing the area of the head that is exposed to hydraulic force.