FLUID PUMP HAVING A PISTON AND A SUPPORTING BODY BEARING THE PISTON FOR SEALING

Abstract

A fluid pump for pumping fluid in a sample separation device includes a pump body device, a piston arranged for conveying fluid in a reciprocable manner in the pump body device, a seal arranged fluid-sealingly in contact with and between the pump body device and the piston, and a supporting body, which is coupled to the seal for supporting the latter. The supporting body is arranged at the pump body device, thereby forming a bearing for the piston.

Claims

1. A fluid pump for pumping fluid in a sample separation device, the fluid pump comprising: a pump body device; a piston arranged for conveying fluid in a reciprocable manner in the pump body device; a seal arranged in contact with, and fluid-sealingly between, the pump body device and the piston; and a supporting body coupled to and supporting the seal; wherein the supporting body is arranged at the pump body device, thereby forming a stationary bearing for the piston, and wherein the supporting body comprises a coating selected from the group consisting of: diamond; polycrystalline diamond; and smoothed polycrystalline diamond.

2. The fluid pump according to claim 1, wherein the supporting body and the piston are arranged such that the supporting body and the piston are, in operation of the fluid pump, at least temporarily in touching contact with each other.

3. The fluid pump according to claim 1, wherein the seal is formed to be arranged, in operation of the fluid pump, at least temporarily and/or at least partially, in a gap between the supporting body and the piston.

4. The fluid pump according to claim 1, wherein at least a first surface section of the piston, which is, in operation of the fluid pump, at least temporarily in touching contact with the supporting body, comprises a hardening coating.

5. The fluid pump according to claim 4, wherein at least a first surface section of the supporting body, which is, in operation of the fluid pump, at least temporarily in touching contact with the piston, comprises the coating, and the hardening coating of the at least first surface section of the piston is the same material as the coating of the at least first surface section of the supporting body.

6. (canceled)

7. The fluid pump according to claim 4, wherein at least a second surface section of the piston, which is, in operation of the fluid pump, at least partially in touching contact with the seal, is thermally highly conductive, in particular has a thermal conductivity of at least 200 W/mK.

8. The fluid pump according to claim 5, wherein at least a second surface section of the supporting body, which is, in operation of the fluid pump, at least temporarily in touching contact with the seal, is thermally highly conductive, in particular has a thermal conductivity of at least 200 W/mK.

9. The fluid pump according to claim 7, wherein the first surface section of the piston and the second surface section of the piston are formed by the hardening coating.

10. The fluid pump according to claim 8, wherein the hardened first surface section of the supporting body and the thermally highly conductive second surface section of the supporting body are formed by the coating.

11. The fluid pump according to claim 1, wherein the seal surrounds the piston annularly with an annular sealing flange that adjoins the supporting body and with an annular lip area that adjoins the piston and the pump body device.

12. The fluid pump according to claim 11, comprising an elastic assembly part arranged at least partially in a hollow space between an inner sealing lip and an outer sealing lip of the lip area, wherein the inner sealing lip and the outer sealing lip are arranged opposite to each other.

13. The fluid pump according to claim 1, wherein the supporting body is formed as a supporting ring that surrounds the piston annularly.

14. The fluid pump according to claim 1, wherein the supporting body and the piston are arranged such that they have a maximum distance in a range between 10 m and 200 m.

15. The fluid pump according to claim 1, wherein the pump body device comprises a first housing part having a fluid conveying space in fluid connection with a fluid intake and a fluid outlet, and a second housing part for receiving the supporting body, wherein the first housing part and the second housing part are formed with a sealing arranged therebetween to be connectable with each other pressure-resistantly and fluid-resistantly.

16. The fluid pump according to claim 1, comprising at least one of the following features: wherein the seal comprises a polymer; wherein the supporting body comprises a material selected from the group consisting of: a ceramic; a metal; a hard metal; a hard plastic material; polyaryletherketone; polyetheretherketone; polyetherketone; polyetherketoneketone; polyetherketoneetherketoneketone; wherein the piston comprises at least one material selected from the group consisting of: zirconium oxide; sapphire; hard metal; and silicon carbide; wherein at least one of the supporting body or the piston has a coating of diamond on a hard metal body.

17. The fluid pump according to claim 1, wherein the fluid pump is formed as a high-pressure pump for pumping a mobile phase as a fluid to a separation device of the sample separation device for separating different fractions of a fluidic sample being in the mobile phase.

18. The fluid pump according to claim 1, wherein the bearing is a radial bearing.

19. The fluid pump according to claim 1, wherein the supporting body is configured as a radial bearing, which holds a gap between the supporting body and a piston surface and enables a piston surface of the piston to get in a permanent or at least temporarily physical contact with an opposite surface of the supporting body according to existing radial bearing forces.

20. A sample separation device for separating in fractions a fluidic sample in a mobile phase, the sample separation device comprising: the fluid pump according to claim 1, configured for driving the mobile phase and the fluidic sample through the sample separation device; and a separation device downstream of the fluid pump for separating the different fractions of the fluidic sample in the mobile phase.

21. (canceled)

22. A method for manufacturing a fluid pump for pumping fluid in a sample separation device, the method comprising: arranging a piston in a reciprocable manner for conveying fluid in a pump body device; arranging a seal in contact with, and fluid-sealingly between, the pump body device and the piston; providing a supporting body, which is coupled to and supports the seal; and arranging the supporting body at the pump body device, such that the supporting body forms a stationary bearing for the piston, wherein the supporting body comprises a coating selected from the group consisting of: diamond; polycrystalline diamond; and, smoothed polycrystalline diamond.

23.-25. (canceled)

Description

SHORT DESCRIPTION OF THE DRAWINGS

[0043] Other objects and many of the accompanying advantages of embodiment examples of the present invention will become easily perceivable and better understandable with reference to the following detailed description of embodiment examples in relation with the appended drawings. Features, which are substantially or functionally the same or similar, are provided with the same reference numerals.

[0044] FIG. 1 shows a HPLC system according to an exemplary embodiment example of the invention.

[0045] FIG. 2 shows a cross-sectional view of an inner pump housing of a sample separation device according to an exemplary embodiment example of the invention.

[0046] FIG. 3 shows a side view of an annular supporting body of the fluid pump according to FIG. 2.

[0047] FIG. 4 to FIG. 6 show details of the fluid pump according to FIG. 2.

[0048] The depiction in the drawings is schematic.

[0049] Before exemplary embodiment examples are described with reference to the figures, some basic considerations shall be summarized, based on which exemplary embodiment examples of the invention have been derived.

[0050] According to an exemplary embodiment example of the invention, in a pump seal of a fluid pump, mutually opposing surfaces of a piston and a supporting body, which is embodied, for example, as a bearing, are highly thermally conducting and scratch-resistant (which can be achieved simultaneously by a diamond coating). Thereby, it is possible to keep a gap between the piston and a supporting ring that surrounds the piston circumferentially as narrow as possible, and to predefine piecewisely even a touch (or contact) between the piston and the supporting ring and/or the bearing. Even for an at least temporary contact between the piston and the supporting body, there must not be much fear of an undesired scratch formation due to the diamond layer. Furthermore, even for a small dimension of the gap, a heat dissipation effected by thermal conduction of the seal material, which is extruded into the narrow gap and/or squeezed therein, is ensured, whereby in turn a melting or a further softening of the seal material, and in result a further undesired extruding of the seal material, can be impeded. Demonstratively, according to an exemplary embodiment example, a heat-distributing narrow gap is thus provided for a pump seal of a HPLC with simultaneous abrasion protection.

[0051] Many HPLC pumps, which are configured for a continuous transport of liquid, follow the principle of a longitudinal, bi-directional piston movement in the interior of a pump body device, which is connected with valves. If an inlet path and an outlet path of this pump body device open and close by switching the valves, a pressure increase, which goes along therewith, along the piston is held by a seal. A PTFE-based seal is usable up to pressures of about 600 bar. At pressures above 600 bar, for example 1200 bar and more, only very few polymer composites are suitable to satisfy the necessary chemical inertness and the load-carrying capacity under highest pressure conditions. In such an area of applications, polymeric seals of polyethylene material having an ultra-high molecular weight and specific additives can be formed advantageously. In order to withstand the axial pressure load, such polymer seals can be supported additionally by a rigid supporting ring at the rear side of the seal, in order to impede a penetration (or intrusion) of material of the seal in the direction of the pressure drop. Only a small gap close to the piston surface remains, if the inner diameter of this supporting ring is configured to adapt itself (or fit itself) as close as possible to the surface of the piston, however also at a sufficient distance in order to prevent a direct contact with the piston surface while the piston is moving. Conventionally, the supporting ring must be kept away reliably from the piston surface, in order to avoid deposition or scratches on the piston surface. Conventionally, the sleeve-shaped (or jacket-shaped) gap between the supporting ring and the piston surface defines substantially concentric thin walls, wherein sealing material is extruded into the gap at least partially under the system pressure and the piston movement.

[0052] In contrast to conventional approaches, exemplary embodiment examples of the invention avoid undesired depositions or scratches on the piston surface. Furthermore, it is possible with exemplary embodiment examples of the invention to loose significantly less sealing material due to pressure-induced extrusion of sealing material into the gap between the supporting ring on the one hand and the piston surface on the other hand. An undesired melting of sealing material and a subsequent deposition of the same on the piston surface can be strongly reduced (for example, at least by a factor of ten), or avoided totally by exemplary embodiment examples of the invention. In this manner, according to exemplary embodiment examples of the invention, for HPLC pumps, which are advantageously provided with a seal of polyethylene having an ultra-high molecular weight or the like, the limit of the possible system pressure, the maximum achievable piston velocity, and the service life can be increased significantly.

[0053] According to an exemplary embodiment example, this can be realized with an outstanding performance by the combination of a specific design and a specific heat distribution material on a contact surface for the seal.

[0054] Firstly, the specific design is described. As has been explained above, in a conventional implementation, the supporting ring only supports the seal and must not have a contact at all or only temporarily little contact to the piston itself. A shaft of the seal conventionally serves as a radial bearing and keeps the supporting ring away from the piston surface at the very most and without large contact forces, however, causes an unfavourable gap between the sealing ring and the piston surface. In contrast to this, according to an exemplary embodiment example of the invention, the supporting ring can be configured as a radial bearing, which keeps the gap between the supporting ring and the piston surface as narrow as possible and allows the piston surface to get in permanent or at least temporary physical contact with the opposing surface of the supporting ring according to the existing radial bearing forces. For this purpose, it is advantageous that the materials of the piston and the supporting ring, which get in contact with each other, are very resistant (or hard-wearing) in respect of wearing, such that a formation of scratches on the piston surface is not arrived at. This can be combined advantageously with a low-friction behaviour in the contact area of the supporting ring and the piston surface. For example, a smoothed, polycrystalline diamond coating both on the piston surface and also on the opposing surface of the supporting ring can satisfy all these requirements in an excellent manner. Such a coating can be formed on the piston and the supporting ring with a CVD coating method and a subsequent smoothing (or grading). Also, since polycrystalline diamond has the maximum achievable hardness among all known materials, no scratches can generated on the piston surface. Depending on the implementation of the polycrystalline diamond layer, a subsequent smoothing method may also be dispensed with.

[0055] In the following, the specific heat distribution material is described. In a conventional implementation (or formation) of the material of the plastic ring at the rear side of the seal, this material has a moderate thermal conductivity of, for example, only approximately 1 W/mK. Conventionally, frictional heat, which is accumulated in a high-pressure operation, at the seal thus cannot be effectively dissipated. Experimental results show that conventionally, due to the limited operational temperature for sealing materials and the high frictional temperature within the unfavourable gap between the supporting ring and the piston surface, the sealing material, which is squeezed therein, melts onto the piston surface at least in the form of small points (or dots) and may result in a very fast wearing of the seal. These disadvantages can be overcome or at least mitigated with exemplary embodiment examples of the invention. An exemplary embodiment example of the invention provides a very thin heat distribution gap on both sides of the sealing material, which extrudes into the gap between the supporting ring and the piston surface due highest system pressures above 1000 bar or the like. If both walls of the narrow, sleeve-shaped gap are manufactured from polycrystalline diamond having a thermal conductivity of approximately 2000 W/mK or are covered therewith, undesired excessive heat can be dissipated from a polyethylene seal having an ultra-high molecular weight or the like, and the service life of the seal can be increased dramatically, even if very high piston velocities and very high system pressures are implemented.

[0056] FIG. 1 shows the basic setup of a HPLC system as an example for a sample separation device 10, such as it is used, for example, for liquid chromatography. A fluid pump 20 as a fluid drive device, which is supplied with solvents from a supply unit 25, drives (or conveys) a mobile phase through a separation device 30 (such as, for example, a chromatographic column), which contains a stationary phase. A degasser 27 may degas the solvents before these are supplied to the fluid pump 20. A sample application unit 40 is arranged between the fluid pump 20 and the separation device 30, in order to introduce a sample liquid into the fluidic separation path. The stationary phase of the separation device 30 is provided in order to separate the components of the sample. A detector, see the flow cell 50, detects separated components of the sample, and a fractioning device can be provided in order to output separated components of the sample in containers provided therefore. Liquids that are no longer required can be output into a discharge container (or outlet container) 60.

[0057] A control unit 70 controls the individual components 20, 25, 27, 30, 40, 50, 60 of the sample separation device 10.

[0058] FIG. 2 shows a cross-sectional view of an inner pump housing of a fluid pump 20 according to an exemplary embodiment example of the invention. FIG. 3 shows a sectional view of an annular supporting body 206 of the fluid pump 20 according to FIG. 2. FIG. 4 to FIG. 6 show details of the fluid pump 20 according to FIG. 2: FIG. 4 shows, in a magnified representation, a border area between the piston 202, the seal 204 and the supporting body 206, and FIG. 5 and FIG. 6 show further perspective views of the seal 204 in this border area in different operational states.

[0059] In FIG. 2, the cross-section of the fluid pump 20 for pumping fluid (in particular a solvent or a solvent composition, for example water and acetonitrile) in a sample separation device 10, which is configured as a HPLC, is shown. The fluid pump 20 has a pump body device 200, which is herein formed and/or defined by a plurality of housing components. Stated more precisely, the pump body device 200 is formed of a first housing part 260 having a fluid conveying space 222 in fluid communication with a fluid inlet 224 (which is arranged, for example, downstream of a fluid valve (not shown)) and a fluid outlet 220 (which is arranged, for example, upstream of a further fluid valve (not shown)) as well as of a second housing part 262 for receiving (or accommodating) a supporting body 206. Alternatively, the second housing part 262 and the supporting body 206 can also be formed in one piece and/or as a common component part. The first housing part 260 (which may be manufactured, for example, from steel or ceramics) and the second housing part 262 (which may be manufactured, for example, also of steel or ceramics) with a seal 204 arranged therebetween are high-pressure-resistant (in particular at least high-pressure-resistant up to 1200 bar) and fluid-resistant (i.e. such that no appreciable leakage of the pumped fluid occurs) connected to each other (for example, screwed together to each other). The two housing parts 260, 262 can be implemented mechanically sufficiently robust so as to withstand highest pressures of up to 1200 bar and more. The first housing part 260 forms part of a pump head, whereas the second housing part 262 represents a pump head covering. The second housing part 262 cares, in a state mounted to the first housing part 260, for a firm termination of the fluid pump 20, and, demonstratively, sets itself rigidly against the pressure in operation. Fluid, which is supplied at the fluid inlet 224, is moved by a piston 202, which is movable back and forth in horizontal direction according to FIG. 2 (see double arrow 290) in the operating volume or fluid conveying space 222 (which is at a system pressure of, for example, 1200 bar) and is pumped to the fluid outlet 220 under high pressure. The fluid inlet 224 and/or the fluid outlet 220 may be connected operatively to one or plural valves, which are not shown in the figure. Thus, the piston 202 is arranged in the pump body device 200 in a reciprocable manner (or in a manner capable to move back and forth) for conveying fluid. A core of the piston 202 may, for example, be formed of thermally well conducting silicon carbide, which is at least in part functionally coated, as is described in more detail below.

[0060] Furthermore, the fluid pump 20 has the flexible or elastic, thus deformable for effecting a sealing effect, seal 204, which is arranged fluid-tight in contact with the pump body device 200 and the piston 202, and which is located between the pump body device 200 and the piston 202. The seal 204 is formed as a seal 204, which annularly (or circumferentially) surrounds the piston 202, and which has a sealing flange 270 that adjoins to the supporting body 206 and the second housing part 262, a central annular sealing shaft 208, and an annular lip area 210 formed onto the sealing shaft 208. The sealing shaft 208, which may be considered as a solid part of the visco-plastic seal 204, behaves, under system pressure, as a viscous hydraulic medium, which flows into cracks (or scars). The lip area 210 having an inner sealing lip 254 and an outer sealing lip 256 effects the sealing between the piston 202 and the first housing part 260. The sealing flange 270 lies form-fittingly on an annular contact face of the second housing part 262 and keeps the seal 204 in place. In the shown embodiment example, the seal 204, which is made of one material (or is of a one-material design), is formed of polyethylene having an ultra-high molecular weight. Due to its mechanically resilient material, the seal 204 is formed to be located, in operation of the fluid pump 20, at least temporarily and at least partially in a gap (see border area 230) between the supporting body 206 and the piston 202. Furthermore, an elastic component part 250 in the form of a spiral spring is arranged in an annular hollow space 252, which is only partially filled by the component part 250, between the mutually opposing inner and outer sealing lips 254, 256 of the lip area 210. At low pressures of some bar, an elastic force of the elastic component part 250 predominantly effects the sealing effect. By contrast, at high pressures of some hundred bar, a hydraulic force predominantly effects the sealing effect, which results from fluid, which is pressed into the hollow space 252 and which pushes the two sealing inner and outer sealing lips 254, 256 inwardly against the piston 202 and/or outwardly against the pump body device 200.

[0061] The rigid supporting body 206, which is represented magnified in FIG. 3 and which is formed as a PEEK ring, ceramic ring, hard metal ring or metal ring in the shown embodiment example, is coupled to the seal 204 and supports the latter. The supporting body 206 serves as an intermediate element, which prevents that heated-up and deformed material of the seal 204 extrudes, under the prevailing pressure, through a gap between the piston 202 and the second housing part 262. Furthermore, the supporting body 206 provides support to the seal 204. The supporting body 206 and the piston 202 are arranged such that they are, in operation of the fluid pump 20, at least temporarily, in particular permanently, in touching contact with each other. The supporting body 206 is arranged at the pump body device 200, thereby forming a stationary bearing for the piston 202. For this purpose, the annular supporting body 206 is accommodated in a front-side annular recess of the second housing part 262 (also referred to as chamber cap). In the border area 230 between the supporting body 206 on the one hand and the piston 202 on the other hand, there prevails ambient pressure or at least approximately ambient pressure.

[0062] In the detailed view of the inner pump housing according to FIG. 4, it is shown which conditions (or proportions) arise in the border area 230 between the piston 202, the pump body device 200, the seal 204 and the supporting body 206 in the presence of a high system pressure of, for example, 1200 bar. As is indicated with the reference numeral 302, material of the seal 202 is, under high pressure, pushed into an at least temporarily formed gap between the supporting body 206 on the one hand and the piston 202 on the other hand, and/or additionally pulled thereinto during the stroke of the piston 202 out of the fluid conveying space 222. As is indicated by the reference numeral 304, a very narrow, sleeve-shaped, heat-distributing gap forms at least temporarily between the supporting body 206 on the one hand and the seal 202 on the other hand.

[0063] According to FIG. 4, see reference numeral 300, the surface of the piston 202 is provided with a smoothed (or graded, or abraded) ultra-hard and thermally highly conductive coating, for example, a polycrystalline diamond layer, which is deposited by CVD and smoothed. In a corresponding manner, the surface of the supporting body 206 is provided with a smoothed ultra-hard and thermally highly conductive coating, for example polycrystalline diamond deposited by CVD and smoothed. Preferably, the two coatings on the piston 202 and on the supporting body 206 are identical. This has advantages: In the area corresponding to the reference numeral 304, in which no sealing material is present and a direct contact between the piston 202 and the supporting body 204 can arise, the both-sided, identical and ultra-hard as well as smoothed coating effects a low-friction contact of the mutually opposing contact faces of the piston 202 and the supporting body 206 and prevents the formation of scratches due to the identical hard contact faces. In the area corresponding to the reference numeral 302, in which material of the seal 204 is extruded into the narrow gap between the piston 202 and the supporting body 206 in the form of a thin film (or pellicle), the both-sided, thermally highly conductive coating effects a double-sided heat dissipation from the heated-up seal 204, and prevents that the latter softens undesirably under high-pressure conditions or is even liquefied. A damage of the seal 204 can thereby be obviated efficiently. In an area represented by the reference numeral 400, there prevails approximately system pressure (for example 1200 bar), whereas in an area represented by the reference numeral 402, there prevails ambient pressure (for example 1 bar). Due to this pressure gradient and/or pressure drop, there is effected an extruding of sealing material with formation of the film (or pellicle). The highly heat conductive hardening coating on the piston 202 and the supporting body 206 thus acts also synergistically as a scratch protection and a highly effective heat conductor, and thus as a heat sink for a seal section, which is in addition intensified by an enabled narrowed gap between the piston 202 and the supporting body 206, which in turn impedes additionally an undesired extruding and melting of sealing material. The result is a very low-wear fluid pump 20.

[0064] FIG. 5 shows a detail of the seal 204 in a viewing direction from the low pressure side (see reference numeral 402 in FIG. 4), and relates to the situation of the presence of a clearance or interstice (or gap) of circumferentially constant thickness d, in result of which there is presently no contact between the piston 202 on the one hand and the supporting body 206 on the other hand. There arises concentrically extruded material of the seal 204 due to the concentric gap between the supporting body 206 and the surface of the piston 202. FIG. 5 thus shows a concentric position.

[0065] FIG. 6 shows again a detail of the seal 204 in a viewing direction from the low pressure side, and relates to the situation, in which the piston 202 on the one hand and the supporting body 206 on the other hand are in touching contact with each other. There arises eccentrically extruded material of the seal 204 due to an eccentric gap between the supporting body 206 and the surface of the piston 202. In an area 600 there is no extruded sealing film at all due to a direct contact between the supporting body 206 and the piston 202, whereas a maximum thickness D of the sealing pellicle in a circumferentially opposite area may amount to, for example, 15 m. In the area 600, the seal 204 is virtually transparent, i.e. there is presently, in the operational state shown, approximately no sealing material.

[0066] With the embodiment according to FIG. 2 to FIG. 6, it is possible to allow (or tolerate) an extremely small gap (which may become at least piecewise and/or at least temporarily zero and then may allow a touching contact) between the piston 202 and the supporting body 206. By this small or even dissappearing gap, an undesired extruding and subsequent melting of material of the seal 204 in this gap can be prevented or even eliminated. This increases the service life of the seal 204, because its material wears less quickly and/or detaches from the seal 204, and increases the service life of the piston 202, because less material of the seal 204 deposits in an undesired manner on the surface of the piston 202. The reduced and/or even disappearing gap acts synergistically together with the thermally highly conductive hardening coating (see reference numeral 300) of the corresponding sliding and/or touching surfaces of the piston 202 as well as the supporting body 206, because this hardening coating 300 ensures simultaneously a low-wear sliding of the sliding and/or touching surfaces on each other as well as an efficient heat dissipation of the thin, sealing film, which is extruded and formed by pinching, in a remaining narrow gap. This is possible particularly well with an extremely heat conductive and an extremely hard polycrystalline diamond layer as the hardening coating 300. The hardening coating is shown here by way of example only on the minimum necessary surface, may however also comprise the total surface of the supporting ring and/or the piston.

[0067] It should be noted that the term having (or comprising) does not exclude other elements, and that a or an does not exclude a plurality. Also, elements, which are described in relation to different embodiment examples, can be combined. It should also be noted that reference numerals in the claims are not to be construed as limiting the scope of protection of the claims.