Working principle of non-leakage sucker pump is shown in figure 2, during the upstroke, the traveling valve is closed and the fixed valve on the bottom of the pump barrel is open, the pressure of plunger inner cavity is high, the pressure of pump barrel under the plunger is low, the outer of plunger is connected to pump barrel cavity, because of the pressure difference between inside and outside of the plunger, the elastic sealing body deforms and then swells outwards to the inside wall of pump barrel, forming good seal and making the leakage almost zero.
During the downstroke, the traveling valve opens, while the fixed valve at the bottom of the pump barrel closes, the pressures of plunger inner and outer cavity tend to be equal, the elastic sealing body gradually restitutes, causing clearance between pump barrel and plunger, making the downstroke resistance to be zero, and guaranteeing liquid lubrication to prolong the life of pump.
The traveling valve will remain closed at the start of the downstroke until pump pressure rises above tubing discharge pressure.
The path from point C to point D transition consists of the plunger moving downward with gas compressed as pressure within the pump increases on the fluid until is rises above tubing discharge pressure, at which point the traveling valve will open.
At point D, the traveling valve opens allowing fluid to flow upward