Gear Pump

Abstract

A gear pump includes a drive shaft, a rotatable pump element mounted on the drive shaft, a side wall member disposed on one side of the pump element, and formed with a shaft hole through which the drive shaft extends, and a side plate disposed on the other side of the pump element. The gear pump further includes a connecting section connecting the drive shaft with the pump element in a manner to prevent relative rotation and to allow relative axial movement between the drive shaft and the pump element. The connecting section includes a drive recess formed in the pump element, and a drive projection projecting radially outwards from the drive shaft, and engaging in the drive recess to prevent the relative rotation. The drive projection is arranged to limit the axial movement of the drive shaft relative to the pump element with one of the side wall member and the side plate.

1 . A gear pump comprising:
 a drive shaft adapted to be connected with a drive source;   a first gear driven by the drive shaft and arranged to form a first pump;   a second gear driven by the drive shaft and arranged to form a second pump;   a seal member disposed between the first and second gears, and formed with a shaft hole extending through the seal member and receiving the drive shaft, the seal member being arranged to seal one of side surfaces of the first gear and one of side surfaces of the second gear;   a first side plate arranged to seal the other of the side surfaces of the first gear;   a second side plate arranged to seal the other of the side surfaces of the second gear; and   a connecting section connecting the drive shaft with the first and second gears in a manner to prevent relative rotation and to allow relative axial movement, the connecting section including first and second drive recesses formed, respectively, in the first and second gears, and first and second drive projections projecting radially outwards from the drive shaft, engaging in the first and second drive recesses, respectively, and determining a relative axial position of the drive shaft relative to the first and second gears, together with at least one of the seal member and first and second side plates.   
   
   
       2 . The gear pump as claimed in  claim 1 , wherein the seal member is arranged to determine the relative axial position of the drive shaft relative to the first and second gears, with the first and second drive projections. 
   
   
       3 . The gear pump as claimed in  claim 2 , wherein the gear pump further comprises a stopper member which is made of a material harder than a material of the seal member, and which is disposed between one of the drive projections and the seal member so that the relative axial position of the drive shaft is determined through the stopper member. 
   
   
       4 . The gear pump as claimed in  claim 3 , wherein the stopper member is an annular member, and a radial dimension from a center axis of the drive shaft to an outer end of the drive projection adjacent to the stopper member is smaller than a radius of the stopper member. 
   
   
       5 . The gear pump as claimed in  claim 1 , wherein the gear pump further comprises a stopper member disposed axially between an adjacent projection which is one of the drive projections and an adjacent side wall member which is one of the seal member and the first and second side plates, and the stopper member is fit in a recessed portion which is formed in the adjacent side wall member, and which has a depth substantially equal to a thickness of the stopper member. 
   
   
       6 . The gear pump as claimed in  claim 1 , wherein the first drive projection is arranged to determine the relative axial position of the driver shaft on one side, and the second drive projection is arranged to determine the relative axial position on the other side. 
   
   
       7 . The gear pump as claimed in  claim 6 , wherein the first and second drive projections are arranged to determine the relative axial position of the drive shaft, with the seal member. 
   
   
       8 . The gear pump as claimed in  claim 7 , wherein the gear pump further comprises a stopper member which is made of a material harder than a material of the seal member, and which is disposed between one of the drive projections and the seal member so that the relative axial position of the drive shaft is determined through the stopper member. 
   
   
       9 . The gear pump as claimed in  claim 8 , wherein the stopper member is an annular member, and a radial dimension from a center axis of the drive shaft to an outer end of the drive projection adjacent to the stopper member is smaller than a radius of the stopper member. 
   
   
       10 . The gear pump as claimed in  claim 1 , wherein the seal member includes a seal receiving portion opening toward one of the first and second gears, and the gear pump further comprises a shaft sealing element arranged to seal a clearance between an outer circumference of the drive shaft and the through hole of the seal member and received in the seal receiving portion of the seal member, and a stopper member closing the seal receiving portion, the seal member and one of the drive projections being arranged to determine the relative axial position of the drive shaft through the stopper member. 
   
   
       11 . The gear pump as claimed in  claim 1 , wherein an axial width of the first drive projection is smaller than a thickness of the first gear, and the axial width of the second drive projection is smaller than the thickness of the second gear. 
   
   
       12 . A gear pump comprising:
 a drive shaft adapted to be connected with a drive source;   a first gear driven by the drive shaft and arranged to form a first pump;   a first pump chamber in which the first gear is received;   a second gear driven by the drive shaft and arranged to form a second pump;   a second pump chamber in which the second gear is received;   a partition member arranged to separate the first and second pump chambers, formed with a shaft hole extending through the partition member and receiving the drive shaft, and disposed axially between one of side surfaces of the first gear and one of side surfaces of the second gear;   a first side plate arranged to confront the other of the side surfaces of the first gear;   a second side plate arranged to confront the other of the side surfaces of the second gear; and   a connecting section connecting the drive shaft with the first and second gears in a manner to prevent relative rotation and to allow relative axial movement, the connecting section including a drive pin which is provided in the drive shaft and which extends radially outwards from the drive shaft, and a recess which is formed in one of the first and second gears, and which is engaged with the drive pin, the drive pin forming a limiting means for limiting the axial movement of the drive shaft, together with one of the partition member and the side plates.   
   
   
       13 . The gear pump as claimed in  claim 12 , wherein the limiting means is provided between the drive pin and the partition member. 
   
   
       14 . The gear pump as claimed in  claim 13 , wherein the gear pump further comprises a stopper member which is made of a material harder than a material of the partition member, and which is disposed between the drive pin and the partition member. 
   
   
       15 . The gear pump as claimed in  claim 14 , wherein the stopper member is an annular member, and a radial dimension from a center axis of the drive shaft to an outer end of the drive pin is smaller than a radius of the stopper member. 
   
   
       16 . The gear pump as claimed in  claim 15 , wherein the partition member is formed with a recessed portion receiving the stopper member and having a depth substantially equal to a thickness of the stopper member. 
   
   
       17 . The gear pump as claimed in  claim 12 , wherein the drive pin includes a first drive pin to drive the first gear and a second drive pin to drive the second gear, the first drive pin is arranged to limit the relative axial movement of the drive shaft in a second direction, and the second drive pin is arranged to limit the relative axial movement of the drive shaft in a first direction opposite to the second direction. 
   
   
       18 . The gear pump as claimed in  claim 17 , wherein the limiting means is formed by the first and second drive pins and the partition member. 
   
   
       19 . The gear pump as claimed in  claim 18 , wherein the gear pump further comprises a stopper member which is made of a material harder than a material of the partition member, and which is disposed between one of the drive pins and the partition member. 
   
   
       20 . The gear pump as claimed in  claim 19 , wherein a radial dimension from a center axis of the drive shaft to an outer end of the drive pin is smaller than a radius of the stopper member. 
   
   
       21 . The gear pump as claimed in  claim 12 , wherein the partition member includes a seal receiving portion opening toward one of the first and second gears, and the gear pump further comprises a shaft sealing element arranged to seal a clearance between an outer circumference of the drive shaft and the through hole of the partition member and received in the seal receiving portion of the partition member, and a stopper member closing the seal receiving portion, the partition member and the drive pin being arranged to determine the relative axial position of the drive shaft through the stopper member. 
   
   
       22 . A gear pump comprising:
 a drive shaft adapted to be connected with a drive source;   a first gear driven by the drive shaft and arranged to form a first pump;   a first pump chamber in which the first gear is received;   a second gear driven by the drive shaft and arranged to form a second pump;   a second pump chamber in which the second gear is received;   a partition member arranged to separate the first and second pump chambers, and disposed axially between one of side surfaces of the first gear and one of side surfaces of the second gear;   a first side plate arranged to confront the other of the side surfaces of the first gear;   a second side plate arranged to confront the other of the side surfaces of the second gear; and   first and second drive pins projecting radially outwards from the drive shaft and engaging, respectively, in a first drive recess formed in the first gear and a second drive recess formed in the second gear so that the first and second gears are driven, respectively, through the first and second drive pins in a manner allowing relative axial movement,   the first drive pin being arranged to limit axial movement of the drive shaft in a second direction, with the first side plate or the partition member, and the second drive pin being arranged to limit the axial movement of the drive shaft in a first direction opposite to the second direction, with the second side plate or the partition member.   
   
   
       23 . A gear pump comprising:
 a drive shaft;   a gear driven by the drive shaft;   a side wall member disposed on one side of the gear;   a side plate disposed on the other side of the gear, so that the gear is interposed, and sealed so as to restrain leakage of an operating fluid, between the side wall member and the side plate; and   a connecting section connecting the drive shaft with the gear in a manner to prevent relative rotation and to allow relative axial movement between the drive shaft and the gear, the connecting section including a drive projection which is provided in the drive shaft and which projects radially outwards from the drive shaft and a drive recess which is formed in the gear and which is engaged with the drive projection, an axial dimension of the drive projection being smaller than or equal to a width of the gear, the drive projection being arranged to limit the axial movement of the drive shaft relative to the gear, with one of the side wall member and the side plate.