Screw driven piston pump

Abstract

A fluid pump comprises an electric motor configured to provide a unidirectional rotational output. The fluid pump further comprises a screw drive coupled to the electric motor. The screw drive is configured to convert the unidirectional rotational output of the electric motor into reciprocating motion. The screw drive comprises a piston rod, a nut, and a connection assembly configured to couple the piston rod to the nut such that the piston rod is linearly reciprocated with the nut.

What is claimed is: 
     
         1 . A fluid spraying system comprising: 
 a unidirectional electric motor configured to generate a unidirectional rotational output;    a screw drive coupled to the unidirectional electric motor, the screw drive configured to convert the unidirectional rotational output of the unidirectional electric motor into reciprocating motion, wherein the screw drive comprises: 
 a self-reversing screw configured to be rotatably driven by the unidirectional rotational output of the unidirectional electric motor; and  
 a nut configured to move reciprocally along the self-reversing screw by rotation of the self-reversing screw;  
 a fluid pump comprising a piston rod coupled to the nut and configured to be reciprocally driven by reciprocation of the nut; and  
 a connection assembly configured to couple the piston rod to the nut such that the piston rod is linearly reciprocated with the nut.  
   
     
     
         2 . The fluid spraying system of  claim 1 , wherein the nut includes at least one aperture, wherein the piston rod comprises a flange, and wherein the connection assembly includes at least one fastener configured to fixedly couple the flange of the piston rod to the at least one aperture of the nut.  
     
     
         3 . The fluid spraying system of  claim 1 , wherein the self-reversing screw includes a double helix raceway comprising a first thread and a second thread, and wherein the first thread is of a different handedness than the second thread. 
     
     
         4 . The fluid spraying system of  claim 1 , wherein the self-reversing screw is in operative communication with the piston rod via a piston guide configured to maintain alignment of the piston rod during reciprocation. 
     
     
         5 . The fluid spraying system of  claim 4 , wherein the piston rod includes a cavity configured to receive the piston guide. 
     
     
         6 . The fluid spraying system of  claim 1 , wherein a portion of the piston rod is disposed within a fluid cylinder, and wherein the piston rod is configured to draw fluid into the fluid cylinder, pressurize the fluid, and output a flow of pressurized fluid through a fluid outlet. 
     
     
         7 . The fluid spraying system of  claim 6 , and further comprising:  
       a hose having a first end and a second end, wherein the first end is coupled to the fluid outlet and is configured to receive the flow of pressurized fluid, and wherein the second end is coupled to a handheld fluid applicator and is configured to provide the pressurized fluid to the handheld fluid applicator.  
     
     
         8 . The fluid spraying system of  claim 1 , and further comprising:  
       a second fluid pump, wherein the fluid pump is configured to communicate with the second fluid pump; and 
       a controller configured to control the fluid pump and the second fluid pump.  
     
     
         9 . A fluid pump comprising:  
       a screw drive configured to receive unidirectional rotational output and convert the unidirectional rotational output into reciprocating motion, wherein the screw drive comprises: 
 a self-reversing screw configured to be rotatably driven by the unidirectional rotational output; and  
 a nut configured to move reciprocally along the self-reversing screw by rotation of the self-reversing screw;  
 a piston rod coupled to the nut and configured to be reciprocally driven by reciprocation of the nut; and  
 a connection assembly configured to couple the piston rod to the nut such that the piston rod is linearly reciprocated with the nut. 
 
     
     
         10 . The fluid pump of  claim 9 , wherein the screw drive is coupled to an electric motor, and wherein the electric motor provides the unidirectional rotational output.  
     
     
         11 . The fluid pump of  claim 9 , wherein the nut includes at least one aperture, wherein the piston rod comprises a flange, and wherein the connection assembly includes at least one fastener configured to fixedly couple the flange of the piston rod to the at least one aperture of the nut.  
     
     
         12 . The fluid pump of  claim 9 , and further comprising: 
 a piston guide coupled to an end of the self-reversing screw and configured to maintain concentric alignment of the piston rod during reciprocation, wherein the piston guide is received by a cavity of the piston rod.    
     
     
         13 . The fluid pump of  claim 9 , wherein the fluid pump includes a housing, and wherein the piston rod is reciprocally driven through the housing. 
     
     
         14 . The fluid pump of  claim 13 , wherein a wiper seal element is disposed between the piston rod and the housing, and wherein the wiper seal element is configured to prevent fluid from entering the housing.  
     
     
         15 . The fluid pump of  claim 9 , and further comprising: 
 a wear ring positioned around an outer diameter of the piston rod.    
     
     
         16 . The fluid pump of  claim 9 , and further comprising: 
 a bearing assembly having one or more bearings configured to assist rotation of the self-reversing screw   
     
     
         17 . A fluid spraying system comprising: 
 a unidirectional electric motor configured to generate a unidirectional rotational output;    a screw drive coupled to the unidirectional electric motor and configured to convert the unidirectional rotational output of the unidirectional electric motor into reciprocating motion, wherein the screw drive comprises: 
 a self-reversing screw configured to be rotatably driven by the unidirectional rotational output of the unidirectional electric motor; and  
 a nut configured to move reciprocally along the self-reversing screw by rotation of the self-reversing screw;  
 a fluid pump comprising a piston rod coupled to the nut and configured to be reciprocally driven by reciprocation of the nut, wherein the piston rod includes a flange; and  
 a connection assembly configured to couple the flange of the piston rod to the nut, wherein the connection assembly includes at least one fastener configured to fixedly couple to at least one aperture to couple the flange of the piston rod to the nut.  
   
     
     
         18 . The fluid spraying system of  claim 17 , wherein the at least one aperture comprises one or more of: 
 an aperture of the flange of the piston rod; and    an aperture of the nut.    
     
     
         19 . The fluid spraying system of  claim 17 , and further comprising:  
       a first wear ring, wherein the first wear ring is positioned on an outer diameter of the nut; and  
       a second wear ring, wherein the second wear ring is positioned on an outer diameter of the piston rod.  
     
     
         20 . The fluid spraying system of  claim 17 , wherein the self-reversing screw includes threads defining a path along the self-reversing screw, and wherein the nut includes roller elements configured to engage the threads and travel along the path defined by the threads.