Liquid metering pump, and device for detecting the variation in pressure for such a pump

1. A liquid metering pump comprising:

a suction nozzle ( 2 ) fitted with an intake valve ( 3 ) communicating with a working chamber ( 4 ) in which a piston ( 5 ) can be moved in a reciprocating movement; and

a pressure-variation detection device (D) that detects variations in pressure in the working chamber ( 4 ), the pressure-variation detection device (D) comprising a duct ( 10 , 10 ′) located between the intake valve ( 3 ) and the working chamber ( 4 ), the duct ( 10 , 10 ′) comprising a wall with an internal surface and an external surface, a first end of the duct connected to one end of the working chamber ( 4 ) and a second end of the duct equipped with the intake valve ( 3 ),

wherein, when the piston ( 5 ) moves away from the suction nozzle ( 2 ), a suction is produced, with opening of the intake valve ( 3 ), and a liquid entering through the suction nozzle ( 2 ) is delivered to the working chamber ( 4 ) via the duct ( 10 , 10 ′),

wherein, when the piston moves closer to the suction nozzle ( 2 ), with closure of the intake valve ( 3 ), the liquid delivered to the working chamber ( 4 ) via the duct ( 10 , 10 ′) leaves the working chamber ( 4 ) through an outlet valve ( 6 ), and

wherein, the pressure-variation detection device (D) further comprises

i) a membrane ( 13 ) installed fluidtight against an end wall ( 14 ) of a cavity provided in the external surface of the wall of the duct ( 10 , 10 ′), the membrane ( 13 ) being subjected to the pressure emanating from the working chamber ( 4 ) via an orifice ( 16 ) extending from the internal surface of the wall to the external surface of the wall of the duct, the membrane being held in place by a cap ( 17 ) and constituting a deformable partition of a chamber ( 15 ) provided in the wall of the duct, and

ii) a detection means ( 18 , 19 , 20 ; 18 ′, 20 ′) detecting movements of the membrane resulting from variations in pressure within the working chamber ( 4 ), including detecting displacement of the membrane,

wherein the detection means is a mechanical means comprising an optical sensor ( 20 ), a rotary lever ( 19 ) with a first end ( 19 c ) that moves to cross an optical beam of the optical sensor and thereby trigger an electrical signal, and a finger ( 18 ) with a first end that passes through the cap ( 17 ) and an opposite second end that is connected to the membrane, wherein the first end of the finger is connected to a second end of the rotary lever ( 19 ) by an articulation such that movement of the membrane moves the first end of the finger to actuate the optical sensor by causing rotary movement of the rotary lever, the rotary movement of the rotary lever triggers the optical sensor by causing the first end ( 19 c ) of the rotary lever to cross the optical beam of the optical sensor and thereby trigger the electrical signal.

2. The pump as claimed in claim 1 , wherein the pressure-variation detection device (D) is connected dissociably to the working chamber ( 4 ).

3. The pump as claimed in claim 1 , wherein the duct ( 10 , 10 ′) is connected dissociably to one end of the working chamber ( 4 ) of the pump and is fitted at another end with the intake valve ( 3 ), and wherein the membrane is mounted on the wall of the duct ( 10 , 10 ′).

4. The pump as claimed in claim 1 , wherein the pressure-variation detection device is connected to an electronic computer for exploiting the pressure variations detected in order to analyze an operation of the pump.

5. The pump as claimed in claim 4 , wherein the electronic computer ( 12 ) is programmed to determine operating parameters from the group consisting of

i) calculation of dosage in real time,

ii) calculation of a time for which the metering device has been in use,

iii) calculation of consumption of chemical product, and

iv) calculation of a number of breakdowns.

6. A liquid metering pump comprising:

a suction nozzle fitted with an intake valve communicating with a working chamber in which a piston can be moved in a reciprocating movement, i) a suction being produced, with opening of the intake valve, when the piston moves away from the suction nozzle, and ii) a delivery being produced, with closure of the intake valve and discharge of a liquid in the working chamber through an outlet valve, when the piston moves closer to the suction nozzle, and

a pressure-variation detection device (D) that detects variations in pressure in the working chamber, the pressure-variation detection device (D) being located between the intake valve and the working chamber, the pressure variation detection device (D) comprising:

i) a duct comprising a wall with an internal surface, a first end of the duct connected to one end of the working chamber and a second end of the duct equipped with the intake valve, and

ii) a means sensitive to the pressure of the fluid in the duct, the means sensitive to the pressure of the liquid in the duct being mounted on the wall of the duct,

wherein the means ( 11 ) sensitive to the pressure of the liquid in the duct comprises a membrane ( 13 ′) installed on an exterior portion of the wall of the duct ( 10 ′) that defines a chamber ( 15 ), and subjected to the pressure emanating from the working chamber ( 4 ), the membrane being leaktight held in place by a cap ( 17 ′), and a detection means detecting movements of the membrane resulting from variations in the pressure in the working chamber ( 4 ), including detecting displacement of the membrane, and

wherein the detection means is a mechanical means comprising an inductive displacement sensor ( 20 ′) having a feeler, and a finger ( 18 ′) with a first end ( 18 ′) that passes through the cap ( 17 ′) and an opposite second end ( 18 ′ a ) that is connected to the membrane and partially engages in an orifice ( 16 ) of the wall of the duct when the membrane is pressed against the cap ( 17 ′), and during an intake phase, the membrane ( 13 ′) moves away from the cap ( 17 ′) and is pressed against a wall of the chamber ( 15 ), and

wherein the first end of the finger is connected to the feeler of the inductive displacement sensor such that the feeler is actuated by movement of the membrane causing movement of the finger, and the movement of the feeler triggers the inductive displacement sensor.

7. The pump as claimed in claim 6 , wherein the detection means detecting movements of the membrane comprises a Hall-effect sensor.