Patent ID: 8176734
Filing Date: 2012-05-15
Classification: F16H

Abstract:
1. A hydrostatic transmission comprising; a hydraulic pump that moves between a minimum displacement and a maximum displacement fluidly connected to a hydraulic motor that operates a fan; a control circuit including a cartridge valve fluidly connected to a pressure control valve having first and second stages and fluidly connected to the hydraulic pump; wherein the pressure control valve modulates between the first stage that causes the hydraulic pump to move toward minimum displacement and the second stage that causes the hydraulic pump to move toward maximum displacement; wherein a pilot pressure applied by the cartridge valve to a spring chamber of the pressure control valve determines the modulation of the pressure control valve between the first and second stages and an outlet pressure of the hydraulic pump; and wherein the hydraulic pump communicates through a hydrostatic transmission charge circuit to the hydraulic motor.