Relief Valves For Tilt And Attachment Cylinders

TM-5-3805-258-24-1 Loader Scoop Type DED 4x4 Articulated Frame Steer 2 1/2 Cubic Yard Bucket (CCE) Airborne/Airmobile Manual
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TM 5-3805-258-24-1 H Y D R A U L I C S Y S T E M S Y S T E M S O P E R A T I O N If the pressure of the oil in the circuit through inlet opening (1) and in the chamber for spring (9) gets as high as the setting of the relief valve, the oil moves pilot valve (3) open. The oil in the spring chamber goes, through the open pilot valve and through pas- sage (8) to the tank. Now, with only the force of spring (9) on valve (2), the pressure of the oil in inlet opening (1) moves valve (2) far enough to let the oil in the inlet opening (and circuit) go through outlet openings (7) to the tank. When the oil in the circuit can go through inlet opening (1) and then through outlet openings (7), the pressure of the oil can not increase to a pressure higher than the setting of the relief valve. The pressure setting of the relief valve can be changed by either an increase or a decrease in the force of the spring that keeps pilot valve (3) closed. Remove plug (6) and turn plunger (5) clockwise for an increase or counterclockwise for a decrease in the pressure setting of the relief valve. Relief Valves For Tilt And Attachment Cylinders There is a relief valve in each of these circuits: head end of the tilt cylinder, rod end of the tilt cylinder, head end of attachment or third cylinders and rod end of attachment cylinders. These valves are the same in construction and operation. These valves are different in construction from the main relief valve, but their operation is similar. When either valve spool (tilt control or third con- trol) is in HOLD position, the relief valves in the head and rod ends limit the maximum amount of pressure in the cylinder lines. If an outside (external) force on the bucket or attachment becomes too high, the relief valve will permit movement of the cylinder piston. This prevents damage to the machine components. The relief valve for the rod end of the tilt cylinder also releases the rod end pressure when the lift arms are lifted with the bucket fully dumped and the tilt control valve spool is in HOLD position. BUCKET CONTROL GROUP The bucket control group gives a way to control the operation of bucket (3). This group is made up of two lift cylinders (4), one tilt cylinder (1), lift arm assembly (5), lever (2) and link (6). This type of linkage is known as Z-bar linkage because of the Z formed by the tilt cylinder, lever and link. Tilt cy- linder (1), lift cylinders (4) and lift arm assembly (5) are fastened to the loader frame by pins. B U C K E T C O N T R O L G R O UP 1. Tilt cylinder. 2. Lever. 3. Bucket. 4. Lift cylinders (in- side loader frame). 5. Lift arm assembly. 6. Link (between the lift arm assembly). When pressure oil is sent to the head end of the lift cylinders, lift arm assembly (5) is lifted. When pres- sure oil goes to the rod end of the lift cylinders (4), the lift arm assembly is lowered. The bucket will tilt back when pressure oil is sent to the head end of tilt cylinder (1). The bucket will dump when pressure oil goes to the rod end of the tilt cylinder. LIFT KICKOUT P A R T S T O A C T I V A T E T H E L I F T K I C K O U T 1. Magnet assembly. 2. Lift arm on left side. 3. Electric switch in the holder. 4. Holder for electrical switch. 3-109

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