A hydraulic manifold is a device used to direct the flow of hydraulic fluid and pressure to different areas of the hydraulic system. Typically manufactured of billet steel or aluminum, the hydraulic manifold is fitted with actuators that are either manually operated through the use of levers or switches, or manipulated by electronic actuators that can be triggered by a computer or a switch somewhere on the machinery. The actuators on a hydraulic manifold act to control or modulate hydraulic valves that open and close to create the desired flow path of the hydraulic fluid.
Some hydraulic systems, such as the types used on a backhoe tractor, are systems of hydraulic cylinders operating on pressurized hydraulic fluid. The fluid is pressurized by a hydraulic pump feeding the fluid through a series of hydraulic lines. The hydraulic manifold directs the fluid to individual hydraulic cylinders by closing valves in one area of the manifold and opening others. This movement of hydraulic fluid is controlled by an operator who pulls and pushes control levers affixed to the hydraulic manifold. Each valve in the hydraulic manifold works on both a pushing and pulling motion, with the hydraulic fluid being pressurized and released by the manipulation of a control lever.
On any given hydraulic system, there may be more than one hydraulic manifold. In the case of a typical backhoe tractor, there are commonly two manifolds — one controlling the front-mounted bucket and the other controlling the rear-mounted backhoe attachment. The front manifold is usually comprised of a two-lever manifold or a single joystick-type controller. In either case, the manifold is commonly fitted with four actions: raise the bucket, lower the bucket, roll the bucket back and roll the bucket forward. Moving a control one way completes one operation, such as raising the bucket, and moving the control the other way completes the opposite reaction, such as lowering the bucket.
Each valve in the manifold is made up of a cylinder, a spring and a rubber diaphragm. As the valve is manipulated by the control lever, the cylinder is directed toward one fluid path or another, with each directing a particular action. The spring located within the valve maintains the valve in a neutral position and prevents fluid from neither entering or exiting the valve and the manifold. There is often an adjustment on the hydraulic manifold that increases or decreases the amount of hydraulic pressure entering the manifold, thus speeding or slowing the reaction to moving a control lever.