Dosing pump

Abstract

A dosing pump comprises an inlet for a solvent, an injection device for an additive, a reciprocating main piston for mixing the solvent with the additive during a suction stroke and for discharging the mixture from an outlet in an evacuation stroke. A divider substantially perpendicular to a rod connected to the main piston separates a main piston housing from a switching device for controlling a main piston stroke direction. The switching device comprises two inlet rotary valve assemblies that are disposed externally to a corresponding inlet aperture bored in the divider when in an opened state and are rotatable about an axis substantially perpendicular to the axis of the main piston. Each of the valve assemblies alternately opens and occludes a corresponding inlet aperture so that solvent flowing through a first inlet aperture performs a suction stroke and solvent flowing through a second inlet aperture performs an evacuation stroke.

1 . A dosing pump, comprising:
 a. an inlet for a solvent;   b. an injection device for an additive;   c. a reciprocating main piston and longitudinally disposed rod connected thereto, for mixing said solvent with said additive during a suction stroke and for discharging said mixture from an outlet in an evacuation stroke;   d. a switching device for controlling a main piston stroke direction; and   e. a divider substantially perpendicular to said rod, for separating a main piston housing from said switching device, wherein two inlet apertures for directing the flow of solvent are bored in said divider,   
       wherein said switching device comprises two inlet rotary valve assemblies rotatable about an axis substantially perpendicular to the axis of said main piston, each of said valve assemblies adapted to alternately open and occlude a corresponding inlet aperture and being disposed externally to an inlet aperture in an opened state, solvent flowing through a first inlet aperture adapted to perform said suction stroke and solvent flowing through a second inlet aperture adapted to perform said evacuation stroke. 
     
     
         2 . The dosing pump according to  claim 1 , wherein the switching device further comprises two outlet rotary valve assemblies rotatable about an axis substantially collinear with the axis about which the inlet valve assemblies rotate, each of said outlet valve assemblies adapted to alternately open and occlude a corresponding outlet aperture bored in the divider and being disposed externally to an outlet aperture in an opened state, fluid being discharged from each of said outlet apertures to a dosing pump outlet. 
     
     
         3 . The dosing pump according to  claim 1 , wherein the rod interconnects the main piston and an injection device piston. 
     
     
         4 . The dosing pump according to  claim 2 , wherein the main piston housing comprises a cylindrical wall substantially perpendicular to the divider and defining an annular chamber between the piston housing and a pump housing outer wall, said annular chamber being in fluid communication with a distal variable volume chamber between the main piston and a pump housing terminal surface. 
     
     
         5 . The dosing pump according to  claim 4 , wherein a first inlet aperture and a first outlet aperture are in communication with the annular chamber and a second inlet aperture and a second outlet aperture are in communication with a proximal variable chamber between the main piston and the divider, solvent admitted to said first inlet aperture adapted to initiate an evacuation stroke while fluid located within said proximal chamber being discharged through said second outlet aperture, and solvent admitted to said second inlet aperture adapted to initiate a suction stroke while solvent located within the distal chamber overflows into the annular chamber and is discharged through said first outlet aperture. 
     
     
         6 . The dosing pump according to  claim 5 , wherein the inlet valve assemblies are located within an inlet flow chamber in communication with the dosing pump inlet and with the first and second inlet apertures, and the outlet valve assemblies are located within an outlet flow chamber in communication with the closing pump outlet and with the first and second outlet apertures, said inlet and outlet flow chambers being provided with mutually parallel planar walls defining therebetween an additive discharge chamber in communication with the proximal chamber to which additive is discharged from the injection device. 
     
     
         7 . The dosing pump according to  claim 6 , wherein the switching device further comprises mutually longitudinally disposed, parallel and similarly shaped inlet and outlet toggle plates rotatably mounted in the planar wall of the inlet and outlet flow chambers, respectively, said inlet and outlet toggle plates being connected to the inlet and outlet valve assemblies, respectively, and adapted to rotate a predetermined angular distance and in a first rotational direction, so that the first inlet aperture and the second outlet aperture are in an opened state while the second inlet aperture and the first outlet aperture are in an occluded state, or in a second rotational direction so that the second inlet aperture and the first outlet aperture are in an opened state while the first inlet aperture and the second outlet aperture are in an occluded state. 
     
     
         8 . The dosing pump according to  claim 7 , wherein the switching device further comprises a connector for connecting the inlet and outlet toggle plates such that said plates will retain a mutually parallel disposition, a longitudinally displaceable toggle frame, and a dual coiled spring assembly attached to said toggle frame and to each of the toggle plates or to said connector, a change in longitudinal displacement of said toggle plate inducing a corresponding change in a spring caused moment acting on an axis about which the toggle plates rotate. 
     
     
         9 . The dosing pump according to  claim 8 , wherein the axis about which the toggle plates rotate is substantially collinear with the axis about which the valve assemblies rotate. 
     
     
         10 . The dosing pump according to  claim 9 , wherein a tubular carrier support is perpendicularly attached to a corresponding toggle plate and two arms carrying two valve assemblies, respectively, radially extend from said support, said two valve assemblies being angularly spaced by a predetermined value suitable for alternately closing and occluding two apertures, respectively, bored in the divider. 
     
     
         11 . The dosing pump according to  claim 8 , wherein the spring assembly comprises an a U-shaped head element received in a cavity formed in the toggle frame, two coiled springs, and an element by which each of said springs is attached to a corresponding toggle plate or to the connector. 
     
     
         12 . The dosing pump according to  claim 8 , wherein the toggle frame comprises a head portion and a leg portion substantially perpendicular to said head portion, a first through hole being bored in said leg portion through which the main piston rod interconnected with an injection device piston passes and at least one second through hole being bored in said head portion, said at least one second through hole adapted to receive therein a corresponding longitudinally oriented post, whereby to urge the toggle frame when displaced to maintain a solely longitudinal displacement path. 
     
     
         13 . The dosing pump according to  claim 12 , wherein the main piston rod is configured with an enlarged portion located proximally to the injection device piston, said enlarged portion adapted to contact a wall of the first through hole during a suction stroke, whereby to cause the toggle frame to be proximally displaced. 
     
     
         14 . The dosing pump according to  claim 13 , wherein a longitudinally oriented post extends proximally from the leg portion of the toggle frame, the toggle frame post adapted to be contacted by the main piston during an evacuation stroke, whereby to cause the toggle frame to be distally displaced. 
     
     
         15 . The dosing pump according to  claim 14 , wherein the spring caused moment changes direction during longitudinal displacement of the toggle plate when a spring caused force vector coincides with the toggle plate axis and a corresponding moment arm changes direction. 
     
     
         16 . The dosing pump according to  claim 15 , wherein the toggle plates are provided with means for repressing a change in their rotational direction. 
     
     
         17 . The dosing pump according to  claim 16 , wherein the rotational change repressing means comprises first and second straight edges provided at the toggle frame facing end of the toggle plates for producing a moment counteracting the spring caused moment, a sidewall of the toggle frame head portion adapted to slide along said first edge, following rotation in the first rotational direction of a corresponding toggle plate along the predetermined angular distance, during proximal displacement of the toggle frame and to slide along said second edge, following rotation in the second rotational direction of the corresponding toggle plate along the predetermined angular distance, during distal displacement of the toggle frame. 
     
     
         18 . The dosing pump according to  claim 4 , wherein the divider comprises a distal level and a proximal level, and the cylindrical wall of the main piston housing is configured with an undercut arranged such that a proximal end of the cylindrical wall is separated from said proximal level and an element radially extends from the cylindrical wall to a transitional wall extending between said distal and proximal levels. 
     
     
         19 . The dosing pump according to  claim 8 , further comprising a deactivation switch protrudable from the pump housing outer wall and adapted to prevent operation of the switching device, said deactivation switch being a terminal end of a unitary assembly which comprises first and second cylindrical extension elements having a substantially equal diameter, and a cylindrical connecting element interposed between said first and second extension elements and having a smaller diameter than that of said first and second extension elements, said unitary assembly being axially displaceable upon depression of said deactivation switch to such a distance that an abutment element protruding from the connector will contact said first extension element when the toggle plates are at a predetermined angular disposition at which the first and second inlet apertures and the first and second outlet apertures are in a neutral state.