Patent ID: 6739128
Filing Date: 2004-05-25
Classification: B60K,B60Y,F16H

Abstract:
A hydrostatic transmission comprising:a fluid motor; a variable displacement fluid pump in fluid communication with said fluid motor, said pump having first fluid displacement rate and a second fluid displacement rate, said second fluid displacement rate being much greater than said first displacement rate; a block on which said pump is mounted and having an outer surface, said block provided with at least one fluid passage, fluid which flows from said pump to said motor flowing through said passage; a fluid sump external to said block; a cylindrical bore disposed within said block, said bore having at least two apertures located diametrically opposite each other; said block having at least one first fluid bleed hole extending from said fluid passage to one of said apertures in said cylindrical bore and at least one second fluid bleed hole extending from the other of said apertures in said bore to said outer surface of said block; a sliding element disposed within said cylindrical bore, said sliding element provided with at least one void and having a first position in which said void is in fluid communication with said fluid passage through said first fluid bleed hole and said void is in fluid communication with said sump through said second fluid bleed hole, and a second position in which said void is substantially out of fluid communication with said fluid passage and said sump; and wherein said fluid passage and said sump are in fluid communication through said first bleed hole, said void, and said second fluid bleed hole when said pump is operating at its said first displacement rate and said sliding element is in its said first position, and said fluid passage and said sump are substantially out of fluid communication when said pump is operating at its said second displacement rate and said sliding element is in its said second position.