As grease passes IN, each piston balances at the position as Diagram 1.

The grease continuously pushes the left side of No.3 piston hole and pushes piston 3-7 rightward to discharge grease in No.6 outlet.

The inclined right-sided holes of the closed No.3 piston hole and No.4 piston hole connect, and the inclined left-sided hole of No.4 piston hole connects the No.3 outlet.

The grease continuously pushes the right side of No.4 piston hole and pushes piston 4-8 leftward to discharge grease in No.3 outlet.

The inclined left-sided holes of the closed No.4 piston hole and No.1 piston hole connect, and the inclined right-sided hole of No.1 piston hole connects the No.8 outlet.

The grease continuously pushes the left side of No.1 piston hole and pushes piston 1-5 rightward to discharge grease in No.8 outlet.

The inclined left-sided holes of the closed No.1 piston hole and No.2 piston hole connect, and the inclined left-sided hole of No.2 piston hole connects the No.1 outlet.

The grease continuously pushes the right side of No.2-6 piston hole and pushes piston leftward to discharge grease in No.1 outlet.

The first half of the discharging completes, and the final position is as Diagram 2. The second half cycle is almost the same.