Hydraulically operated four wheel sweeper

A hydrostatic propulsion drive system for driving a vehicle having a pair of drive wheels and at least one steerable wheel supported on a support surface, comprising:

• an engine in said vehicle,
• means defining a variable displacement hydrostatic motor on said vehicle and connected in driving engagement to said drive wheels,
• means defining a variable displacement hydrostatic pump connected in driven engagement to said engine and in driving engagement to said motor,
• means defining an adjustable inching valve,
• shifting means for enabling an operator to shift said pump between a neutral position and reverse, low speed and high speed driving positions,
• accelerator means connected to said inching valve for enabling the operator to vary the capacity of fluid directed by said pump to said hydrostatic motor,
• a two-position valve means for selectively positioning the hydrostatic motor in a low speed position and in a high speed position, and
• means defining a metering control valve responsive to variations in reaction torque between the drive wheels and said support surface for varying the displacement and speed of said motor when said two position valve means is in the high speed position,
• said metering control valve means having a low speed driving position and a high speed driving position and being movably positioned into said high motor speed position in response to said two position valve means being positioned in its high speed position, said shifting means being in one of said driving positions, and said inching valve being at least partially closed.