Theory of Operation
Boom, bucket and arm cylinders have a cushion (N) in
The boom, arm, and bucket cylinders are similar in
front of the piston to provide cushioning action in
design. The bucket cylinder (R) is illustrated. The rod
cylinder extension. As the cylinder nears the end of
guide (Q) is fastened to the cylinder barrel with cap
stroke the cushion enters a bore in the rod guide. The
screws and is fitted with a wear guide (F) held in place
remaining return oil ahead of piston must flow through
by a snap ring (G). A buffer ring (E), U-cup seal (D),
a small clearance between the cushion and rod guide.
backup ring (C), and wiper seal (B) are used in the rod
Only the arm cylinder is cushioned in retraction. The
guide. A snap ring (A) is used to help hold wiper seal
end of the rod enters a bore in the head end of the
in place. The U-cup seal (D) is protected against high
cylinder. The remaining return oil ahead of the piston
pressure by the buffer ring (E) and stops the small
and nut must flow through this small clearance as the
amount of oil which may pass by the buffer ring.
cylinder bottoms out in this direction.
The piston (H) is a slip fit on the cylinder rod (P) and is
retained with a nut (M). A set screw (L) prevents
loosening of the nut. The piston is fitted with a cap
seal (K), wear rings (J), and buffer rings (I).