Patent ID: 7712555
Filing Date: 2010-05-11
Classification: B62D,E02F,F15B,F16H

Abstract:
1. A vehicle comprising: a prime mover; first and second hydraulic pumps driven under the influence of the prime mover, such that each of the first and second pumps creates a flow of hydraulic fluid at a basic flow rate; first and second motors operating in response to the flow of hydraulic fluid from the first and second pumps; first and second travel mechanisms driven in response to operation of the first and second motors, respectively; and a valve system for selectively placing the first and second motors in series and parallel relationship, wherein in series relationship at least one of the first and second motors operates using combined flow of hydraulic fluid from the first and second pumps, and wherein in parallel relationship each of the first and second motors operates using flow of hydraulic fluid only from a respective one of the first and second pumps such that no combined flow of hydraulic fluid from both of the first and second pumps is provided to either of the first and second motors; wherein the valve system selectively provides hydraulic fluid to the first and second motors at the basic flow rate and at a combined flow rate that is twice the basic flow rate; wherein the valve system is configurable to selectively provide hydraulic fluid at the combined flow rate to both of the first and second motors to cause the motors to operate in series at high speed; and wherein the valve system is also configurable to provide hydraulic fluid to one of the first and second motors at the combined flow rate to cause that motor to operate at high speed, and to provide hydraulic fluid to the other of the first and second motors at the basic flow rate to cause that motor to operate at low speed, to effect steering of the vehicle while maintaining the first and second motors in series relationship.