US Patent 9574666 Mechanical face seal with a reverse trapezoidal face pattern

An improved mechanical face seal is provided which includes a pair of relatively rotatable seal rings having opposing seal faces. At least one of the seal faces includes a reverse trapezoidal face pattern having a sine wave depth profile wherein individual face features are circumferentially spaced over the seal face. The reverse trapezoidal face pattern serves to generate a hydrodynamic lift which provides a stable separation of the seal faces that permits formation of a fluid film between the seal faces. The individual trapezoidal grooves have a sinusoidal or similarly shaped depth profile wherein the trapezoid shape is arranged with the narrower edge communicating with the high pressure side of the seal, and the wider edge forms a circumferential dam region towards the low pressure side of the seal. Alternatively, the reverse trapezoidal face pattern may also be provided as a primary face pattern on a dry gas seal in combination with a secondary face pattern wherein the faces operate with a controlled gap under normal pressure conditions as well as when the pressure direction across the seal face is reversed.