Heart-shaped cam constant flow pump

Abstract

A constant flow pump and method of providing a constant fluid flow using such a pump, and more particularly a pump and method that maintain a constant flow by using a heart-shaped cam to directly reciprocate the pistons of the pump at a constant velocity are described. The pump operates by using heart-shaped cam to translate the rotational motion of a power source such as an engine or motor can into a constant speed linear motion.

1 . A constant flow positive displacement pump comprising:
 a power source;   at least one cam rotatably engaged to said power source through a drive shaft, said at least one cam having an approximately heart-shaped outer contour; and   at least two pistons slidingly engaged with the outer contour of said at least one cam, said pistons being engaged to points along the contour of said at least one cam that are rotated 180° relative to each other.   
   
   
       2 . The pump of  claim 1 , wherein a line of reflection can be defined through the center of said cam, and where each of the halves of the cam defined by said line of reflection is described by the equation r=kΘ. 
   
   
       3 . The pump of  claim 1 , wherein a line of reflection can be defined through the center of said cam, and where each of the halves of the cam defined by said line of reflection is an approximate 180° arc of an Archimedean spiral. 
   
   
       4 . The pump of  claim 3 , wherein the arcs of the cam are asymmetric. 
   
   
       5 . The pump of  claim 3 , wherein one half of the cam is an extending portion that serves to extend the piston and one half of the cam is a retracting portion that serves to retract the piston, and wherein the extending portion spans a larger angle arc than the retracting portion such that both pistons deliver fluid at the same time during the transition period. 
   
   
       6 . The pump of  claim 3 , wherein one half of the cam is an extending portion that serves to extend the piston and one half of the cam is a retracting portion that serves to retract the piston, and wherein the Archimedean spiral constant for the retracting portion is larger than the extending portion. 
   
   
       7 . The pump of  claim 5 , wherein the extending and retracting portions are designed such that the sum of the velocities of the accelerating and decelerating cams is constant. 
   
   
       8 . The pump of  claim 1 , further comprising at least two heart-shaped cams, wherein at least one of said at least two pistons is disposed on each of the at least two cams. 
   
   
       9 . The pump of  claim 8 , wherein the pistons are disposed in parallel relative to said cams and wherein said at least two cams are rotated 180° relative to each other on said shaft. 
   
   
       10 . The pump of  claim 8 , wherein the at least two cams are disposed adjacent and in parallel on said shaft, and wherein said pistons are rotated 180° relative to each other in relation to said shaft. 
   
   
       11 . The pump of  claim 1 , wherein the pump is a positive displacement pump. 
   
   
       12 . The pump of  claim 1 , wherein the pump is used for one of either concrete or fracture applications. 
   
   
       13 . A heart shaped cam for use in a constant flow pump, said heart-shaped cam having a line of reflection defined through the center of said cam, where the outer contour of each of the halves of the cam defined by said line of reflection is an approximate 180° arc of an Archimedean spiral. 
   
   
       14 . The cam of  claim 13 , wherein each of the halves of the cam defined by said line of reflection can be described by the equation r=kΘ. 
   
   
       15 . The pump of  claim 13 , wherein the arcs of the cam are asymmetric. 
   
   
       16 . The pump of  claim 13 , wherein one half of the cam is an extending portion that serves to extend a piston and one half of the cam is a retracting portion that serves to retract a piston, and wherein the extending portion spans a larger angle arc than the retracting portion. 
   
   
       17 . The pump of  claim 13 , wherein one half of the cam is an extending portion that serves to extend a piston and one half of the cam is a retracting portion that serves to retract a piston, and wherein the Archimedean spiral constant for the retracting portion is larger than the extending portion. 
   
   
       18 . The pump of  claim 16 , wherein the extending and retracting portions are designed such that the sum of the velocities of the accelerating and decelerating cams is constant. 
   
   
       19 . A method of providing a constant fluid flow comprising:
 providing at least one cam rotatably engaged to a power source through a drive shaft, said at least one cam having an approximately heart-shaped outer contour;   placing at least two pistons into slidingly engagement with the outer contour of said at least one cam, said pistons being engaged to points along the contour of said at least one cam that are rotated 180° relative to each other;   connecting said at least two pistons to a fluid delivery system; and   rotating said cam at a constant speed such that the pistons have a constant linear motion.   
   
   
       20 . The method of  claim 19 , wherein a line of reflection can be defined through the center of said cam, and where each of the halves of the cam defined by said line of reflection is described by the equation r=kΘ. 
   
   
       21 . The method of  claim 19 , wherein a line of reflection can be defined through the center of said cam, and where each of the halves of the cam defined by said line of reflection is an approximate 180° arc of an Archimedean spiral. 
   
   
       22 . The method of  claim 21 , wherein one half of the cam is an extending portion that serves to extend the piston and one half of the cam is a retracting portion that serves to retract the piston, and wherein the extending portion spans a larger angle arc than the retracting portion such that both pistons deliver fluid at the same time during the transition period. 
   
   
       23 . The method of  claim 21 , wherein one half of the cam is an extending portion that serves to extend the piston and one half of the cam is a retracting portion that serves to retract the piston, and wherein the Archimedean spiral constant for the retracting portion is larger than the extending portion. 
   
   
       24 . The method of  claim 22 , wherein the extending and retracting portions are designed such that the sum of the velocities of the accelerating and decelerating cams is constant. 
   
   
       25 . A method of performing an oilwell operation comprising:
 providing a constant flow positive displacement pump according to  claim 1  at the oilwell; and   operating the pump to inject a fluid at a constant flow into the oilwell.