Direct action fluid motor and injection pump

A fluid pressure operated motor for quietly reciprocating a fluid injection pump to inject predetermined quantities of a secondary fluid into a primary fluid stream, comprising:

• a housing having interior walls and an inlet and outlet for connection in fluid communication with pressurized primary fluid in an operating fluid line;
• a stepped piston mounted for reciprocation in the housing, said stepped piston having a larger diameter portion with a large face, and a smaller diameter portion with a smaller face in sliding sealed contact with said interior walls, said smaller face dividing the interior of the housing into a first variable chamber below the face and a second variable chamber above the face;
• a first passageway leading from the inlet to the first variable chamber and a second passageway leading from the second variable chamber to the outlet whereby operating fluid under pressure can traverse the housing by moving in a controlled path through the first and second chamber;
• a valve train carried by the piston comprising a valve positioner and a cooperating valve set operatively configured to axially shift together relative to the piston between alternate stable positions and an intermediate unstable position, the valve train including a holding mechanism which applies a holding force to the valve positioner which resists movement from an alternate stable position to the intermediate unstable position;
• said valve set comprising first valve means to open and close the smaller face of the piston and a second valve means to open and close the large face of the piston, said valve set being shiftable together with the valve positioner to alternately close one of said piston faces while opening the other of said piston faces at each of the alternate stable positions of the valve train;
• actuating means in the housing for applying a shifting force to the valve train, said shifting force being less than the force required to shift the valve train against the pressure force on the closed first or second valve means caused by the pressurized fluid in the housing;
• a first stop means positioned to stop the valve train as the piston is moving in one direction of reciprocation and second stop means positioned to stop the valve train as the piston is moving in the other direction of reciprocation, thereby preshifting the valve train to the intermediate unstable position and partially opening the closed face of the piston by unseating one of the first or second valve means until said shifting force exceeds the remaining pressure force on the unseated first or second valve means, whereupon the valve train immediately moves to an alternate stable position in response to the shifting force applied to the valve train by said actuating means, thereby closing the face of the piston that was open and fully opening the face of the piston that was partially open in response to unseating one of the first or second valve means;
• whereby the full force applied by the pressurized fluid to the closed face of the piston is used to preshift the valve train to reduce the pressure force on the closed valve means so that only a comparatively small shifting force is required to fully shift the valve positioner and valve set to reverse the direction of reciprocation.

A fluid pressure operated motor for reciprocating a fluid injection pump to inject predetermined quantities of a secondary fluid into a primary fluid stream, comprising:

• a housing having axially arranged internal cylinder walls for slidingly engaging the different diameters of a stepped piston having a large diameter face and a smaller diameter face;
• a stepped piston body in the housing having opposed large and smaller diameter step faces with at least one fluid opening in each face communicating through the piston body;
• an inlet passage in said housing for conducting primary fluid under pressure from an inlet to one of the step faces of the piston;
• an outlet passage in said housing for conducting primary fluid under pressure from the other one of the step faces of the piston to an outlet in the housing;
• stop members positioned in the housing above and below the stepped piston and biasing elements associated with the stop members;
• opposed valve means mounted for movement with the piston for closing said at least one fluid opening in one face of the stepped piston while opening said at least one fluid opening in the other of said faces;
• a valve positioner mounted for reciprocation with the piston and for movement relative to the piston between alternate stable positions and an intermediate unstable position, the valve positioner cooperating with said opposed valve means to alternately open one step face of the piston while simultaneously closing the other step face of the piston thereby changing the direction of reciprocation;
• a shifting force being applied alternately to the valve positioner by compression of one of said biasing elements as the piston approaches each end of its stroke, said shifting force being less than the force needed to shift the valve positioner from one of its alternate stable positions to said intermediate unstable position but greater than the force needed to shift the valve positioner from its unstable position to the next of said alternate stable positions;
• said opposed valve means comprising a second valve means mounted on the valve positioner and a first valve means mounted on one step face of the piston and extending therefrom toward a stop member, said first valve means and said valve positioner being aligned and configured to move as a unit in response to the valve positioner being stopped by a stop member near one end of the piston stroke or the first valve means being stopped by a stop member near the other end of the piston stroke, while the piston is moving in a given direction of reciprocation;
• the valve positioner being stopped alternately by a stop member or a stop member and the first valve means near each end of the piston stroke while the piston continues moving in a given direction, thereby causing relative movement between the valve positioner and the piston and moving the valve positioner from one alternate stable position to said intermediate unstable position and causing the closed face of the piston to partially open by substantially simultaneously unseating one of said first or second valve means as the intermediate unstable position is reached;
• whereupon the shifting force applied by the compression of a biasing element is sufficient to move the valve positioner to the next alternate stable position and shift the opposed valve means to reverse the reciprocating direction of the piston whereby the full power of the moving piston is available to positively change the position of the opposed valves without the necessity of accumulating and releasing a large amount of energy in a compressed spring to effectuate reversing the opposed valve means at the end of the stroke.

In a device for injecting predetermined quantifies of a secondary fluid into a primary fluid stream carried under pressure in a line, a motor housing connected in said line comprising a fluid motor having a stepped piston having stepped faces with a valve assembly and a valve shifting mechanism for shifting the valve assembly to apply line pressure alternately to the stepped faces of the piston thereby causing reciprocation of the piston in the housing, the housing having an inlet and an outlet for the primary fluid, a pump casing having an inlet for a secondary fluid mounted in sealed contact with the housing, the pump casing having a pump chamber and a pump mechanism therein connected to the stepped piston for reciprocation therewith, characterized in that:

• the pump mechanism comprises an elongated body having a back end connected to said piston and a front end disposed in the pump chamber, the elongated body being movable with the piston to an extended position at the bottom of the reciprocation and a retracted position at the top of the reciprocation, the elongated body displacing a volume of fluid in the pump chamber as it moves from the retracted to the extended position;
• a sliding valve member extending from the front of the elongated body which cooperates with a sealing surface at the inlet of the casing to open and close the pump chamber as said elongated body moves between the extended and retracted position;
• a selective adjustment mechanism associated with the elongated body which fixes the amount of maximum extension from the elongate body of the sliding valve member to establish the remaining volume in the pump chamber when the valve member seals the inlet as said elongated body moves toward the extended position to cause displacement of a selective amount secondary fluid from the pump chamber through a passage leading to the primary fluid line.

A method of operating a reciprocating fluid powered motor of the type having a housing installed in a pressurized primary fluid line, a stepped piston having a large and small face slidingly mounted for reciprocation in the housing, an upper valve means to close the large face, a lower valve means to close the small face, valve positioner shiftable with respect to the piston to operate the upper valve means and substantially simultaneously operate the lower valve means to change the direction of reciprocation of the piston in response to pressurized primary fluid applied to a closed face of the piston, the method comprising the steps of:

• providing lower valve means having a valve body which traverses the small face of the piston, having a closing surface without the piston and an opposite opening surface within the piston located to move with the valve positioner;
• providing stop means in the housing above and below the piston, placed to limit travel of the valve positioner on the upstroke of the piston and limit travel of the lower valve means on the downstroke of the piston;
• applying pressurized fluid to the closed small face of the piston causing the piston to move upwardly in the housing;
• closing the upper valve means and opening the lower valve means by bringing the valve positioner against a stop means while the piston is moving upwardly, to reverse direction of reciprocation;
• applying pressurized fluid to the close upper face of the piston causing the piston to move downwardly;
• stopping the lower valve means by contact of the closing surface of the lower valve means with the stop means below the piston while the piston is moving downwardly;
• shifting the valve positioner with the lower valve means to cause the upper valve means to open the large face of the piston while the stop means is closing the lower valve means to close the small face of the piston thereby reversing the direction of reciprocation.

A method of operating a reciprocating fluid powered motor which is installed in a pressurized primary fluid line to drive a reciprocating secondary fluid pump, the reciprocating motor having a housing with fluid inlet and outlet and a controlled path for fluid to pass from the inlet through a stepped piston to the outlet, a stepped piston slidingly mounted for reciprocation in the housing, the piston having a large diameter face and a smaller diameter face each being equipped with a valve set for opening one face and closing the other face at the end of the piston stroke, the method characterized by the following steps:

• (a) connecting the inlet and outlet of the housing in the primary fluid line to permit the pressurized primary fluid to follow the controlled path through the housing;
• (b) providing a valve shifting assembly including:
• an upper control surface in the housing above top dead center position of the piston and a lower control surface in the housing below bottom dead center position of the piston, the valve set of the smaller diameter face comprising valve bodies having an opposed opening and closing surface located on opposite sides of said face,
• a valve positioner carried by the piston, adapted to carry the valve set for the large diameter face and engage the opening surface of the valve set of the smaller diameter face, the valve positioner being shiftable relative to the piston a distance sufficient to open one of said valve sets and close the other of said valve sets;
• and
• a frictional holder for the valve positioner adapted to hold it in alternate stable positions comprising a first stable position corresponding to said valve sets closing the smaller and opening the larger face of the piston and a second stable position corresponding to said valve sets closing the larger and opening the smaller face of the piston and including an intermediate unstable position;
• (c) applying primary fluid pressure to the closed large face of the piston to cause the piston to move toward bottom dead center;
• (d) stopping the valve set located in the smaller diameter face of the piston and the valve positioner from further movement by bringing said closing surface against the lower control surface while the piston is still moving toward bottom dead center;
• (e) shifting the valve positioner relative to the piston from a stable position toward an alternate stable position as the piston continues to move toward bottom dead center;
• (f) closing the valve set of the smaller diameter face and substantially simultaneously opening the valve set of the large diameter face of the piston as the valve positioner moves to said alternate stable position to reciprocate the piston toward top dead center;
• (g) applying primary fluid pressure to the closed smaller diameter face of the piston to cause the piston to move toward top dead center;
• (h) stopping the valve positioner from further movement by bringing said valve positioner against the upper control surface while the piston is still moving toward top dead center;
• (i) shifting the valve positioner relative to the piston from said alternate stable position toward said stable position as the piston continues to move toward top dead center;
• (j) contacting the opening surface of the valve set of the smaller diameter face of the piston with the valve positioner as the piston continues to move toward top dead center while the valve positioner is being shifted;
• (k) closing by means of the valve positioner, the valve set located in the large diameter face while substantially simultaneously opening the valve set in the smaller diameter face of the piston as the valve positioner moves to said stable position, in order to reciprocate the piston toward bottom dead center;
• (l) repeating steps c-k to continue reciprocating the piston.