ALTERNATING PISTON DOSING PUMP.

Abstract

L'addition concerne le mécanisme de distribution d'un fluide sous haute pression, adaptable à la pompe doseuse du brevet principal. Le distributeur comprend un manchon (56) avec les orifices d'admission (78) et refoulement (77) du fluide. Un piston (62) est ajusté glissant dans la chambre (79) alésée au diamètre (y) du manchon (56). Le piston (62) a une chambre (66) qui communique par un canal (74) dans la chambre (79). Un ressort (64) taré appuie la couronne de frottement (75) du piston (62) sur la céramique (18). Un joint d'étanchéité (63) de type "haute pression" isole la chambre de compression (79) de la chambre d'admission (68). Le piston (62) est immobilisé en rotation par une goupille (73). Le diamètre (y) de la chambre (79) est supérieur au diamètre (x) de la chambre (66). Application de ce distributeur de fluide notamment à la chromatographie liquide haute performance.

Description

The main patent relates to a reciprocating piston pump comprising a pump body, a cylinder block located within the pump body rotating about an axis A, and in which at least one cylinder is provided, at least one piston housed within the cylinder and moving in a reciprocating translation relative to the cylinder block, this piston defining a chamber with the cylinder, a distributor block located in contact with a friction surface of the cylinder block, this friction surface being perpendicular to the axis A, the distributor block delimiting with the friction surface an intake chamber and a compression chamber for a fluid, a communication channel being provided in the cylinder block between the piston chamber and the friction surface, the end of this communication channel which opens onto the friction surface passing alternately from the intake chamber to the compression chamber during the relative rotational movement of the cylinder block with respect to the distributor block, said compression chamber having a circular section whose center is offset with respect to axis A, said intake chamber entirely surrounding the compression chamber. This addition relates to a distribution mechanism designed to improve the reciprocating piston pump of the main patent, so as to allow this pump to operate under high fluid pressure. The characteristics of the reciprocating piston metering pump of the Main Patent are already known, but the performance of this pump is limited to pressures of a few tens of bars. Indeed, its distribution mechanism has a pressure limiter consisting of a spring set to a value that defines the maximum fluid pressure tolerated by the pump. Due to space constraints and wear on the friction part which ensures the fluid seal between the compression chamber and the intake chamber, it is not possible to incorporate a spring capable of resisting pressures of several hundred bars. The purpose of this addition to the Patent is to enable the metering pump to work under high pressure by incorporating a fluid distributor capable of withstanding pressures of several hundred bars without premature wear of the sealing gasket, at all fluid pressures. This refers more particularly to a pump according to claim 1 of the main patent, characterized in that the piston is fitted sliding in an internal chamber to a sleeve of said distributor block which communicates with the compression chamber of said piston by a central channel thereof. The pump also advantageously possesses at least one of the following characteristics - the diameter of the sleeve chamber is larger than the diameter of the piston chamber. - the piston has a friction ring which presses on a ceramic and which ensures the seal between the compression chamber and the intake chamber. - the diameter of the sleeve chamber is approximately equal to the outside diameter of the piston friction ring. - the axis of the sleeve chamber is eccentric with respect to the axis of rotation of the ceramic. - the piston is prevented from rotating in the associated chamber by a locking means. - A compression spring bears on one side against the bottom of the sleeve chamber and, on the other side, against a flange of the piston. This spring is calibrated to allow the piston's friction ring to isolate, under low fluid pressure, the intake chamber from the compression chamber of said piston. - a "high pressure" type sealing gasket rests on a collar of the piston so as to allow the chamber of the sleeve to be isolated from the intake chamber under high fluid pressure. - the sleeve has laterally a channel parallel to the axis of said sleeve which allows the aspiration of the fluid into the intake chamber as well as a longitudinal channel centered with respect to the axis of the piston which allows the discharge of the fluid under pressure and the connection of a resistive element connected to the outlet of said pump. The invention, which is the subject of this addition, will now be described in more detail with reference to the single attached figure. The attached figure is a cross-sectional view illustrating the structure and operation of the high-pressure fluid distribution block. The distributor block includes a stainless steel sleeve 56 having axis A as its general axis of axial symmetry. The sleeve 56 has a bore of diameter y with axis B eccentric with respect to axis A by a distance 52. The sleeve 56 is fixed securely to the pump cover, a longitudinal channel 78 opens into the fluid inlet chamber 68 which is hermetically sealed by a seal 65. Parallel to and centered on B, a longitudinal channel 77 allows the fluid to be discharged. The bore of diameter y machined in the sleeve 56 forming a chamber 79 guides in translation a piston 62 permanently applied against the ceramic 18 by a compression spring 64 bearing on a collar of the piston 62 by means of a washer 80. A "high pressure" type sealing gasket 63 bears against a second flange of the piston 62. An angular positioning pin 73, tightly fitted onto the outer circumference of the piston 62, is held radially by a notch 76 machined in the sleeve 56. The interior of the piston 62 forms a chamber 66 of diameter x. A longitudinal channel 74 centered on B passes through the center of the piston 62. The friction surface 75 of the piston 62 on the ceramic 18 is crown-shaped. The piston 62 is machined from a material similar to Arlon. The ceramic 18 rotates about axis A. The diameter y of chamber 79 of sleeve 56 is greater than the diameter x of chamber 66 of piston 62. The diameter y of chamber 79 is approximately equal to the outer diameter of the friction ring 75 of piston 62. The operation of this high-pressure distributor can now be described We already know, from the main patent, how the fluid passes from the intake chamber 68 to the compression chamber 66 of the piston 62. The spring 64 constantly presses the piston 62 on the ceramic 18 with the force necessary to isolate, under low fluid pressure, the compression chamber 66 of the piston 62 with the intake chamber 68 of the sleeve 56. During the discharge of the fluid by the pistons, it passes successively into chambers 66 and 79 through channel 74 which passes axially through piston 62. The high-pressure type seal 63 prevents the passage of fluid from the compression chamber 79 to the intake chamber 68. The fluid pressure then increases simultaneously in chambers 66 and 79 to a value relative to the flow rate of the pump and the resistance of the element connected to the outlet of the channel 77 of the sleeve 56. By virtue of the law which defines pressure as the quotient of the force exerted by a fluid on a surface by the value of that surface, and given that the pressure of the liquid is exerted on a larger surface of the piston in chamber 79 than in chamber 66, for the same fluid pressure, the resultant of the opposing forces acting on the piston 62 tends to press it more strongly on the ceramic 18. This resultant force increases proportionally to the fluid pressure demanded of the pump by the resisting element. This resultant force is added to the calibrated force of the compression spring 64, thus increasing the seal of the friction ring 75 of the piston 62 on the ceramic 18. This self-compression distributor allows the pump to deliver high pressures of liquid. The friction ring 75 of the piston 62 is protected from excessive wear by acting on the difference in surfaces that constitute the chambers 66 and 79. This distributor, which has just been described, is particularly efficient because it allows the pump to work in a wide range of fluid pressure with moderate wear of the friction ring 75 of the piston 62 on the ceramic 18. This constitutes a very important advantage for the distributor, because, in the absence of this improvement, it would require an excessively powerful compression spring to push back high fluid pressures, resulting in premature wear of the friction ring 75, particularly in the range of low fluid pressures, where the opposing force of the chamber 66 vis-à-vis the spring 64 is weak.

Claims

DEMANDS 1- Reciprocating piston pump comprising a pump body, a cylinder block located in the pump body rotating about an axis (A), and in which is provided at least one cylinder, at least one piston housed in the cylinder and moving in an alternating translation relative to the cylinder block, this piston defining a chamber with the cylinder, a distributor block located in contact with a friction surface of the cylinder block, this friction surface being perpendicular to the axis (A), the distributor block delimiting with the friction surface an inlet chamber and a compression chamber for a fluid, a communication channel being provided in the cylinder block between the piston chamber and the friction surface,the end of this communication channel which opens onto the friction surface passing alternately from the intake chamber to the compression chamber during the relative rotational movement of the cylinder block with respect to the distributor block, said compression chamber having a circular cross-section whose center is offset with respect to the axis (A), said intake chamber entirely surrounding the compression chamber, according to claim 1 of the main patent, characterized in that the distributor has a piston (fitted) sliding in a chamber (79) internal to a sleeve ( of said distribution block) and which communicates with the compression chamber ( of said piston by a central channel (74) thereof. 2 - Pump according to claim 1, characterized in that the distributor has a sleeve (56) whose chamber (79) has a diameter (y) of dimension greater than the diameter (x) of the chamber w of the piston (tu2). 3 - Pump according to claim 1 or 2, characterized in that the distributor has a piston (62) whose support on the ceramic (18) determines a friction ring (75) which isolates the compression chamber (66) from the intake chamber (68) with a watertight seal. 4 - Pump according to any one of claims J a 3 > characterized in that the distributor has a sleeve (56) whose chamber (79) has a diameter (y) substantially equal to the outside diameter of the friction ring (75) of the piston (62).. 5 - Pump according to any one of claims 1 to 4, characterized in that the distributor has a sleeve (56) whose chamber (79) has an axis (B) eccentric by a value (e) with respect to the axis (A) of rotation of the ceramic (18). 5 - Pump according to any one of claims 1 to 5, characterized in that the distributor has a piston (62) immobilized in rotation by a pin (73) carried by said piston and engaged in a notch (76) machined in the sleeve (56). 7 - Pump according to any one of claims 1 and 6, characterized in that the distributor has a compression spring (64) which bears against the bottom of the chamber (79) of the sleeve (56) and against a washer (80) placed on a collar of the piston (62) and a sealing gasket (63) which bears against another collar of said piston. 8 - Pump according to claim 7, characterized in that the distributor has a compression spring (64) calibrated so as to allow the friction ring (75) of the piston ( to isolate, under low fluid pressure, the inlet chamber (68) from the compression chamber (66) of said piston. 9 - Pump according to claim 7, characterized in that the distributor has a "high pressure" type sealing seal (63), which prevents the high pressure fluid from exiting the compression chamber (79) into the inlet chamber (68). 10 - Pump according to any one of claims 9, characterized in that the distributor has a sleeve (56) laterally traversed by a channel (78), parallel to the axis (8) of said sleeve, which allows the aspiration of the fluid into the inlet chamber (68), as well as a longitudinal channel (77) centered on the axis (8) which allows the discharge of the fluid under pressure and the connection of a resistive element connected at the outlet of said pump.