| 摘要 |
An apparatus adapted for attachment to the frame of a truck, usually within a bed of a conventional pickup truck. A generally planar base is rigidly attached to the truck frame with bolts. A platform is rotatably connected to the base with a pair of four-bar linkages, one on the right side of the platform and one on the left. The platform has a low position close to the base, and a high position that is typically 15 or 20 inches higher. A double-acting hydraulic cylinder is anchored at one end to the base and connected at its other end to the platform. Pressurizing the cylinder one way causes the platform to be raised and translated backwardly with respect to the base. Pressurizing the cylinder the other way causes the platform to be moved toward the base in a relatively slow and deliberate manner. To improve the angles through which the hydraulic cylinder acts when the platform is being raised and lowered-especially when the platform is relatively close to the base, a bell crank mechanism is provided between the base and the barrel end of the hydraulic cylinder. As the hydraulic cylinder is pressurized for upward movement, the bell crank rotates and causes the platform to be lifted for a few inches. A low-friction device like a roller pushes against a lower surface of the platform, moving the platform upward until the pushing angle of the hydraulic cylinder is sufficient to cause more efficient lifting of the platform.
|
