Patent ID: 6571554
Filing Date: 2003-06-03
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 variable displacement fluid pump including a plurality of parallel axially oriented pistons, 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, said variable displacement fluid pump including a swash plate assembly engaging said axially oriented pistons; a block on which said pump is mounted and having a cylindrical surface, said block provided with at least one fluid passage, fluid which flows from said pump to said motor being flowed through said passage, said block provided with at least one fluid bleed hole extending from said fluid passage to said cylindrical surface of said block; a fluid sump external to said block; and an annular element disposed about and in sliding contact with said cylindrical block surface, said annular 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 fluid bleed hole, and a second position in which said void is substantially out of fluid communication with said fluid passage; and wherein said fluid passage and said sump are in fluid communication through said bleed hole and said void when said pump is operating at its said first displacement rate and said annular element is in its said first position, and said fluid bleed hole and said sump are substantially out of fluid communication when said pump is operating at its said second displacement rate and said annular element is in its said second position.