Tandem Pump Unit

Abstract

The present invention provides a tandem pump unit that includes: a first hydraulic pump and a second hydraulic pump respectively having a first pump shaft and a second pump shaft respectively having adjacent ends connected together so that the first and second pump shafts are coaxially aligned and non-rotatably connected in tandem; a common housing for accommodating the first hydraulic pump and the second hydraulic pump; and a first center section and a second center section that respectively support the first and second hydraulic pumps.

1 - 37 . (canceled) 
   
   
       38 . A pump unit for supplying oil to and suctioning the same from first and second hydraulic motors respectively connected to left and right drive wheels, comprising:
 first and second hydraulic pumps which are arranged in tandem to each other; and   a center section arranged between the first and second hydraulic pumps,   wherein the center section is provided with a first pair of inlet/outlet ports which serve as connection ports for fluidly connecting the first hydraulic pump with the first hydraulic motor, and a second pair of inlet/outlet ports which serve as connection ports for fluidly connecting the second hydraulic pump with the second hydraulic motor, and   wherein the first pair of inlet/outlet ports and the second pair of inlet/outlet ports are positioned at a same side surface of the center section.   
   
   
       39 . A pump unit according to  claim 38 , further comprising:
 a first bypass valve for selectively communicating or shutting off between a first pair of hydraulic lines which fluidly connect between the first hydraulic pump and the first hydraulic motor; and   a second bypass valve for selectively communicating or shutting off between a second pair of hydraulic lines which fluidly connect between the second hydraulic pump and the second hydraulic motor,   wherein the first and second bypass valves are arranged at a side surface of the center section on a side opposite to the side surface at which the first and second inlet/outlet ports are positioned.   
   
   
       40 . A pump unit according to  claim 38 , further comprising:
 a first housing which encloses the first hydraulic pump;   a second housing which encloses the second hydraulic pump;   a first control shaft for changing a supply/suction amount of the first hydraulic pump, the first control shaft being supported by the first housing; and   a second control shaft for changing a supply/suction amount of the second hydraulic pump, the second control shaft being supported by the second housing,   wherein the first control shaft is supported by a side surface of the first housing facing in a direction orthogonal to the side surface of the center section at which the first pair of inlet/outlet ports are positioned, and   wherein the second control shaft is supported by a side surface of the second housing facing in a direction opposite to the side surface of the first housing by which the first control shaft is supported.   
   
   
       41 . A pump unit according to  claim 39 , further comprising:
 a first housing which encloses the first hydraulic pump;   a second housing which encloses the second hydraulic pump;   a first control shaft for changing a supply/suction amount of the first hydraulic pump, the first control shaft being supported by the first housing; and   a second control shaft for changing a supply/suction amount of the second hydraulic pump, the second control shaft being supported by the second housing,   wherein the first control shaft is supported by a side surface of the first housing facing in a direction orthogonal to the side surface of the center section at which the first pair of inlet/outlet ports are positioned, and   wherein the second control shaft is supported by a side surface of the second housing facing in a direction opposite to the side surface of the first housing by which the first control shaft is supported.