Pump

Abstract

A pump includes a drive assembly having a drive shaft rotatable about a drive axis, and an eccentric coupled to the drive shaft for rotation therewith. The eccentric includes a shaft portion defining an eccentric axis that is offset from the drive axis. The shaft portion includes a shaft end defining a first alignment feature. A piston is rotatably coupled to the shaft portion and defines a second alignment feature. A cylinder reciprocatingly receives the piston. Positioning the first alignment feature in a predetermined orientation with respect to the second alignment feature locates the piston in one of a top-dead-center position and a bottom-dead-center position with respect to the cylinder.

What is claimed is: 
     
         1 . A pump comprising:
 a drive assembly including a drive shaft rotatable about a drive axis;   an eccentric coupled to the drive shaft for rotation therewith, the eccentric including a shaft portion defining an eccentric axis, the eccentric axis offset from the drive axis, the shaft portion including a shaft end defining a first alignment feature;   a piston rotatably coupled to the shaft portion, the piston defining a second alignment feature; and   a cylinder reciprocatingly receiving the piston, wherein positioning the first alignment feature in a predetermined orientation with respect to the second alignment feature locates the piston in one of a top-dead-center position and a bottom-dead-center position with respect to the cylinder.   
     
     
         2 . The pump of  claim 1 , wherein the first alignment feature includes at least one of a projection extending from the shaft end and a recess formed in the shaft end. 
     
     
         3 . The pump of  claim 1 , wherein the second alignment feature includes two alignment features and a plane extending through the two alignment features of the second alignment feature. 
     
     
         4 . The pump of  claim 3 , wherein the first alignment feature includes at least one side, and wherein the predetermined orientation includes wherein the plane is substantially parallel with the at least one side. 
     
     
         5 . The pump of  claim 3 , wherein the predetermined orientation includes wherein the plane extends through the first alignment feature. 
     
     
         6 . The pump of  claim 3 , wherein the first alignment feature includes at least one side, and wherein the predetermined orientation includes wherein the plane is oriented at a predetermined angle with respect to the side. 
     
     
         7 . The pump of  claim 1 , wherein the second alignment feature includes at least one of an opening and a projection. 
     
     
         8 . The pump of  claim 1 , wherein the first alignment feature is a projection extending from the shaft end and including two parallel sides, wherein the second alignment feature is a pair of diametrically opposed openings formed in an end face of the piston and a plane extending through the diametrically opposed openings, and wherein when the plane is substantially parallel to the two parallel sides, the piston is in one of the top-dead-center position and the bottom-dead center position with respect to the cylinder. 
     
     
         9 . The pump of  claim 8 , wherein the projection is substantially rectangular and wherein the openings are substantially circular. 
     
     
         10 . The pump of  claim 1 , wherein the drive shaft includes a first end to which the eccentric is coupled, and a second end opposite the first end, the pump further comprising:
 a second eccentric coupled to the second end for rotation therewith, the second eccentric including a second shaft portion defining a second eccentric axis, the second eccentric axis offset from the drive axis, the second shaft portion including a second shaft end defining a third alignment feature;   a second piston rotatably coupled to the second shaft portion, the second piston defining a fourth alignment feature; and   a second cylinder reciprocatingly receiving the second piston, wherein positioning the third alignment feature in the predetermined orientation with respect to the fourth alignment feature locates the second piston in one of a top-dead-center position and a bottom-dead-center position with respect to the second cylinder.   
     
     
         11 . The pump of  claim 10 , wherein when the piston is in the top-dead-center position with respect to the cylinder, the second piston is in the bottom-dead-center position with respect to the second cylinder. 
     
     
         12 . The pump of  claim 1 , wherein the first alignment feature is non-circular. 
     
     
         13 . The pump of  claim 12 , wherein the first alignment feature has a shape including one of a cross, oval, rectangle, polygon, triangle, teardrop, and star. 
     
     
         14 . The pump of  claim 1 , wherein the first alignment feature is circular and is offset from the eccentric axis. 
     
     
         15 . A method for orienting a first piston and a second piston in a dual piston pump, the pump including a drive shaft having opposite ends, a first eccentric on one end of the drive shaft, and a second eccentric on an opposite end of the drive shaft, the first eccentric including a shaft portion having a first alignment feature, the first piston having a second alignment feature, the second eccentric including a shaft portion having a third alignment feature, and the second piston having a fourth alignment feature, the method comprising:
 mounting the first piston on the shaft portion of the first eccentric;   rotating the first eccentric to position the first alignment feature in a first predetermined orientation with respect to the second alignment feature, thereby locating the first piston in one of a top-dead-center position and a bottom-dead-center position;   mounting the second piston on the shaft portion of the second eccentric;   rotating the second eccentric to position the third alignment feature in a second predetermined orientation with respect to the fourth alignment feature, thereby locating the second piston in the other of the top-dead-center position and the bottom-dead-center position;   securing the first eccentric to the one end of the drive shaft to prevent relative rotation between the first eccentric and the drive shaft; and   securing the second eccentric to the opposite end of the drive shaft to prevent relative rotation between the second eccentric and the drive shaft.   
     
     
         16 . The method of  claim 15 , wherein rotating the first eccentric to position the first alignment feature in the first predetermined orientation includes engaging a first alignment tool with the first alignment feature and the second alignment feature. 
     
     
         17 . The method of  claim 16 , wherein the first alignment tool includes a first mating feature for mating with the first alignment feature, and a second mating feature for mating with the second alignment feature, and wherein engaging the first alignment tool includes mating the first mating feature with the first alignment feature and mating the second mating feature with the second alignment feature. 
     
     
         18 . The method of  claim 16 , wherein rotating the second eccentric to position the third alignment feature in the second predetermined orientation includes engaging a second alignment tool with the third alignment feature and the fourth alignment feature. 
     
     
         19 . The method of  claim 15 , wherein the second alignment feature includes two alignment features and a plane extending through the two alignment features of the second alignment feature, and wherein rotating the first eccentric to position the first alignment feature in the predetermined orientation with respect to the second alignment feature includes positioning the first alignment feature such that the plane extends through the first alignment feature. 
     
     
         20 . The method of  claim 15 , wherein the first alignment feature includes at least one side, wherein the second alignment feature includes two alignment features and a plane extending through the two alignment features of the second alignment feature, and wherein rotating the first eccentric to position the first alignment feature in the predetermined orientation with respect to the second alignment feature includes orienting the side to be substantially parallel to the plane. 
     
     
         21 . The method of  claim 15 , wherein the first alignment feature includes at least one side, wherein the second alignment feature includes two alignment features and a plane extending through the two alignment features of the second alignment feature, and wherein rotating the first eccentric to position the first alignment feature in the predetermined orientation with respect to the second alignment feature includes orienting the side at a predetermined angle with respect to the plane. 
     
     
         22 . A pump comprising:
 a motor including a motor housing having a first end and a second end;   a first crankcase coupled to the first end;   a second crankcase coupled to the second end;   a first cylinder coupled to the first crankcase;   a second cylinder coupled to the second crankcase;   a first valve body coupled to the first cylinder;   a second valve body formed separately from the first valve body and coupled to the second cylinder;   a first valve cover coupled to the first valve body;   a second valve cover formed separately from the first valve cover and coupled to the second valve body; and   a connecting tube formed separately from the first valve cover and the second valve cover and providing fluid communication between the first valve cover and the second valve cover.   
     
     
         23 . The pump of  claim 22 , wherein the motor includes a motor housing, a stator within the motor housing, and a rotor rotatably received within the stator, the rotor including a drive shaft having a first end extending into the first crankcase and a second end extending into the second crankcase, the drive shaft defining a drive axis. 
     
     
         24 . The pump of  claim 22 , further comprising a first eccentric coupled to the first end and a second eccentric coupled to the second end, each eccentric including a shaft portion defining an eccentric axis offset from the drive axis, and a counterweight portion positioned opposite the shaft portion with respect to the drive axis. 
     
     
         25 . The pump of  claim 24 , wherein the shaft portion of each eccentric includes a first alignment feature. 
     
     
         26 . The pump of  claim 25 , further comprising a first piston received by the first cylinder and rotatably coupled to the shaft portion of the first eccentric, and a second piston received by the second cylinder and rotatably coupled to the shaft portion of the second eccentric, each of the first piston and the second piston including a second alignment feature. 
     
     
         27 . The pump of  claim 26 , wherein when the first alignment feature of the first eccentric is in a predetermined orientation with respect to the second alignment feature of the first piston, the first piston is in one of a top-dead-center position and a bottom-dead-center position, and the second piston is in the other of the top-dead-center position and the bottom-dead-center position. 
     
     
         28 . The pump of  claim 27 , wherein when the first alignment feature of the first eccentric is in the predetermined orientation with respect to the second alignment feature of the first piston, the first alignment feature of the second eccentric is in substantially the same predetermined orientation with respect to the second alignment feature of the second piston.