SBS140 188-4210 PISTON SHOE 9 PCS FOR CAT 324D 325D 328D 329D 325C HYD PUMP

SBS140 188-4210 PISTON SHOE 9 PCS FOR CAT 324D 325D 328D 329D 325C HYD PUMP

Force transmission and spherical self‑adaptation (spherical hinge pair) The inner spherical socket of the piston shoe embraces the piston ball head to form a universal spherical hinge. The thrust generated by reciprocating motion of the piston is transmitted to the swash plate via the piston shoe. As the pump rotates, the piston shoe can swing freely and maintain constant contact with the plane of the swash plate to prevent seizure.

Hydrostatic oil film lubrication (most critical) High‑pressure oil flows through the central hole of the piston, passes through the orifice of the piston shoe and enters the oil chamber on the bottom face of the piston shoe. A 0.01~0.03 mm high‑pressure hydrostatic oil film forms between the piston shoe and swash plate, avoiding direct metal contact. It significantly reduces friction and wear, and prevents swash plate burning and piston shoe scoring.

Enlarge bearing area and reduce contact stress The piston ball head cannot push directly against the swash plate (extremely high stress from point contact causes instant wear). The flat bottom of the piston shoe expands the contact area to distribute heavy high‑pressure loads and protect the swash plate and piston assembly.

Cooperate with retainer plate to forcibly reset pistons The retainer plate presses against the back of piston shoes. When the cylinder block rotates, the retainer plate pulls the piston shoes and drives the pistons to retract into the cylinder block to complete the suction stroke.

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