Positive Displacement Injection Pump

Abstract

A reciprocating drive mechanism having a housing with upper and lower internal chambers with a spool slidably positioned inside the upper internal chamber. There is at least one fluid inlet and fluid exhaust communicating with the upper internal chamber and at least one slide valve positioned within the upper internal chamber and traveling with the spool. A piston positioned in the lower internal chamber divides the lower internal chamber into an upper and lower cylinder space. There is at least one fluid conduit communicating between the upper internal chamber and the upper cylinder space and at least one fluid conduit communicating between the upper internal chamber and the lower cylinder space. A valve stem is connected to the piston and includes a bore communicating with the upper internal chamber and an exhaust passage is positioned between the upper and lower internal chambers. A first side passage is formed on the valve stem and connects to the bore in the valve stem and a second side passage formed in the valve stem below the first passage and shaped to bridge a seal positioned between the exhaust passage and the upper internal chamber.

1 - 30 . (canceled) 
     
     
         31 . A reciprocating drive mechanism comprising:
 a. a housing including upper and lower internal chambers and housing sidewalls;   b. a spool slidably positioned inside said upper internal chamber;   c. at least one fluid inlet and fluid exhaust communicating with said upper internal chamber;   d. at least one slide valve positioned within said upper internal chamber and traveling with said spool;   e. a piston positioned in said lower internal chamber and dividing said lower internal chamber into an upper and lower cylinder space;   f. at least one upper chamber conduit communicating between said upper internal chamber and said upper cylinder space;   g. at least one lower chamber conduit communicating between said upper internal chamber and said lower cylinder space;   h. wherein at least three of said fluid inlet, said fluid exhaust, said upper chamber conduit, and said lower chamber conduit are angularly offset from one another; and   i. wherein an entire length of said upper chamber conduit and said lower chamber conduit are formed in said housing sidewalls.   
     
     
         32 . The reciprocating drive mechanism according to  claim 31 , further comprising two upper chamber conduits and two lower chamber conduits. 
     
     
         33 . The reciprocating drive mechanism according to  claim 31 , wherein said housing forming said upper and lower internal chambers is a unitary section of material. 
     
     
         34 . The reciprocating drive mechanism according to  claim 33 , wherein said section of material includes an upper solid cylinder of one diameter and a lower solid cylinder of a second, larger diameter. 
     
     
         35 - 41 . (canceled) 
     
     
         42 . The reciprocating drive mechanism according to  claim 32 , wherein all or the two upper chamber conduits and the two lower chamber conduits are angularly offset from one another. 
     
     
         43 . The reciprocating drive mechanism according to  claim 42 , wherein all conduits of the drive mechanism are formed within the housing sidewalls. 
     
     
         44 . The reciprocating drive mechanism according to  claim 31 , further comprising a valve stem connected to the piston and comprising an internal bore, said valve stem having sufficient length for the bore to communicate with the upper internal chamber. 
     
     
         45 . The reciprocating drive mechanism according to  claim 45 , further comprising first and second side passages formed in the valve stem.