EP1375921A1 - High pressure low volume piston pump - Google Patents

Abstract

A pump includes a seal (70) which comprises a c-shaped sealing element with a sealing lip. The surface of sealing lip is pressed against a piston (8) using a c-shaped spring provided on the opposing surface of the sealing lip contacting a displacement chamber (89). An incompressible filling element is inserted into the spring. Independent claims are also included for the following: (1) dead space adjustment method; and (2) high-pressure chromatography device.

Description

The present invention relates to pumps according to Preamble of claim 1. Furthermore, the Invention on adjustment methods and uses of such Pump.

Especially for HPLC ("High Performance Liquid Chromatography ") pumps are required, the smallest Liquids with minimal losses at high pressure, pulsation as low as possible and correspondingly exact promote certain flow. Nowadays, e.g. B. Flow rates up to approx. 5 ml / min (milliliters per minute) at an operating pressure of the chromatography column of z. b. 100 bar. The gradient suitability extends up to down to 100 µl / min (microliters per minute). Already however, pressures up to 700 bar are used today, and it there is also a tendency to use smaller amounts up to 1 µl / min and to use smaller rivers. In these applications are therefore losses of less than one microliter at least noticeable, if not inadmissible.

A common design has two positive displacement pump units which are arranged in series. The first unit is that Feed pump, the liquid under low pressure, e.g. B. Ambient pressure, sucked in and under operating pressure to the second Unit, the storage pump, promotes. The storage pump works essentially in opposition to the first unit. It ensures a fluid flow during the first Unit sucks, and absorbs the excess when the first unit the working medium under operating pressure ejects. This allows a steady flow with less Pulsation can be achieved.

Especially with high quality pumps for this application the pistons are made of hard material, in particular ceramic, which in stone bearings, i.e. bearings made of ruby, sapphire, synthetic Corundum or ceramic. The sealing takes place via piston seals that are open to the working volume. There so that the pressurized working medium has access to Has the outside of the sealing lip, it with the Working pressure pressed against the piston surface and ensures thus even for the sealing effect corresponding to the pressure. The parts that come into contact with the working medium are Made of high quality material, metal and Precious stones, executed to the required pressure resistance and to ensure chemical inertness. Common is z. B. the use of titanium. The pistons are driven via camshafts on the rear end of the pistons act in conjunction with resilient return elements.

Because of the high pressures and the required accuracy noticeable compressibility of the liquids in the However, such a pump usually only applies to a specific one Pressure to be adjusted to minimal compressibility, by the movements of the two pumping units be coordinated. To make matters worse, the known pumps of this type in relation to the delivery volume with gradient application of approx. 20-50 microliters per stroke have a relatively large dead volume, even larger than the funding volume is Main causes of the big one Dead volumes are the minimum distance of the piston from the Displacement chamber floor and the piston seal. The minimal one Distance must be provided in spite of manufacturing and Assembly tolerances to prevent the piston from operating hits the ground: Such a collision would damage the floor or other pump parts. In the Piston seal is noticeable that it Working medium open installation position, with the working medium is filled, for which relatively large quantities are required, z. B. roughly the same size as the funding volume. Dead volume such as the slightest leaks in the small amounts are not even visually recognizable, affect the delivery quality of the pump, in particular compliance with the set flow and the Pulsation.

The dead volume limits in particular the Gradient suitability, d. H. sets the minimum funding rate firmly, at which still without substantial mixing Working medium with changing composition of the Pump can be promoted. Contains a large dead volume correspondingly large amounts of working medium, which at Gradient operation also need to be replaced in order to avoid mixing.

The pumps are also subject to aging, which is their maintenance makes necessary. Because of the high demands, especially when Assembly is usually required to do this by a specialist.

Suitable pumps are e.g. B. known from DE-A-43 08 467. The pumps are characterized by the fact that they stand out disc-shaped function blocks is built up in a Clamping device can be clamped together. Because the transitions running from block to block, external ones are omitted Connection lines between the units.

A disadvantage of this arrangement, however, is that the Assemble the pump with the utmost care to achieve the required tightness, because the Add tolerances. Among other things are therefore two ruby guides in the pump blocks are necessary in order to guide the pistons precisely to reach the displacement chamber: direct contact of the Piston with the chamber wall is due to the resulting abrasion to avoid the u. a. falsify the result of the HPLC and can destroy the piston seal.

In addition, maintenance work is usually carried out by the entire arrangement must be dismantled. Finally points this pump has a considerable dead volume.

It is therefore an object of the present invention to to specify such a pump, which has less impact from design tolerances to the conveying quality.

Another task is to understand the influence of the Check and / or reduce dead volume.

Such pumps, at least one of the above Fulfill tasks are in the device claims specified. Procedure for operating the pumps and Uses are the subject of further claims.

A main aspect of the invention is therefore that Make dead volume adjustable and otherwise generally too reduce. One measure for this is a construction of the Displacement chamber and / or the piston, the adjustment on minimum dead volume allowed or to a dead volume that optimal behavior of the pump at the desired operating pressure results. On the one hand, the total length is suggested of the piston adjustable in that it in the actual piston and a piston rod is divided. The connection between the piston and piston rod is in the length is variable so that an adjustment at a minimal distance from the piston to the displacement chamber floor is possible. The distance can even be adjusted to zero when to avoid damage to the chamber floor is made by an insert that is under Operating pressure is sufficiently incompressible, but at Stop of the piston yields so far that no damage occurs. Another approach is one To provide an opposing piston, the front end of which is essentially represents the chamber floor. So that the chamber floor can be moved.

Novel designs of the Seals between the piston and displacement chamber, the one offer lower dead volume. The classic piston seal has a spiral spring that lies in the piston seal and runs around the sealing lip. Especially the interior the spiral spring results in a large dead volume.

In a first variant, a side open Spring element specified. Through the opening a Packing elements are inserted into the spring element, so that the Most of the cavity within the spring element is filled out. In the second variant, there is Spring element essentially from a band-shaped Sealing lip surrounding element. It is preferred a spiral made of a resilient material, especially metal. The flat shape of the spring element allows the inner wall of the displacement chamber in the Area of the seal with a small cross section perform and thus keep the dead volume small.

By reducing or adjusting the Dead volume is also the effect of manufacturing tolerances counteracted.

Another problem area of assembly tolerances is a slight misalignment or angular errors of the Connections that are on the inlets and outlets of the Pump units, i.e. the working medium access, attached Need to become. In the known version it is a so-called cartridge between the connection part and the access used as a connecting part. A cartridge can be in the essentially be a line piece (connecting sleeve) or z. B. contain a check valve ("valve cartridge"). According to a further aspect of the invention suggested the area pairs involved as one Combination of crowning (convex, spherical surface) and hollow cone surface. With an offset of Medium inlet and connecting part are easy tilted seat of the connecting cartridge. Through the mentioned training still results in a circular Contact line and an even pressure. The parties Area pairs can not only be between the named Parts, but also between the part and a sealing body (a capsule). Preferably located the cambered surface on the capsule.

Fig. 1:

Längsschnitt durch einen erfindungsgemässen Pumpkopf gemäss I-I in Fig. 2;

Fig. 2:

Schnitt gemäss II-II in Fig. 1;

Fig. 3:

Ausschnitt III in Fig. 1: Erste Ausführungsform einer Kolbendichtung (vergrössert);

Fig. 4:

Ausschnitt IV in Fig. 1: Zweite Ausführungsform einer Kolbendichtung (vergrössert; Schnitt);

Fig. 5:

Ausschnitt V in Fig. 1: Dichtung Anschlüsse (vergrössert; Schnitt);

Fig. 6:

Detailvergrösserung aus Fig. 7: schematische Darstellung eines Versatzes;

Fig. 7:

Ausschnittvergrösserung eines Übergangs Verdrängerkammer/Anschluss;

Fig. 8:

Variante einer Dichtung an einem Anschluss: Schnitt in starker Vergrösserung;

Fig. 9:

Ausbildung Dichtfläche: vergrösserter Teilausschnitt IX aus Fig. 7;

Fig. 10:

Variante der Dichtfläche gemäss Fig. 9;

Fig. 11:

Schnitt durch eine Dichtung für einen Gegenkolben;

Fig. 12:

Teilschnitt durch eine Variante der Anschlüsse;

Fig. 13:

Längsschnitt durch eine Verbindungsanordnung in gestrecktem Zustand.

The invention is further explained using an exemplary embodiment with reference to figures. Show it:

Fig. 1:

Longitudinal section through an inventive pump head according to II in Fig. 2;

Fig. 2:

Section according to II-II in Fig. 1;

Fig. 3:

Section III in Fig. 1: First embodiment of a piston seal (enlarged);

Fig. 4:

Section IV in Fig. 1: Second embodiment of a piston seal (enlarged; section);

Fig. 5:

Section V in Fig. 1: Seal connections (enlarged; section);

Fig. 6:

Detail enlargement from Fig. 7: schematic representation of an offset;

Fig. 7:

Enlargement of a transition from the displacement chamber / connection;

Fig. 8:

Variant of a seal on a connection: cut in large magnification;

Fig. 9:

Formation of sealing surface: enlarged partial section IX from FIG. 7;

Fig. 10:

Variant of the sealing surface according to FIG. 9;

Fig. 11:

Section through a seal for a counter-piston;

Fig. 12:

Partial section through a variant of the connections;

Fig. 13:

Longitudinal section through a connection arrangement in the stretched state.

Figg. 1 and 2 show a sectional view of a Head 1 of an HPLC pump designed according to the invention. The Parts not shown (drives with cam disks, etc.) are designed according to the state of the art. The Piston arrangements for feed pump device 3 (feed pump) and storage pump device 4 (storage pump) which the Replace known one-piece pistons, each consist of a piston 7, 8 and a piston rod 11, 12. Die Piston rods are in high quality linear guides in the Drive housing guided, especially in linear ball bearings (not shown). Such camps are in themselves Known specialist.

At the rear ends of the pistons 7, 8 is a sleeve 15, 16 on a hard material rod 19, 20 (e.g. made of ceramic) firmly attached. The sleeves 15, 16 are at the rear end closed. To the total length of the pistons 7, 8 (distance between the front end of the hard material rods 19, 20 and Rear ends 22, 23 of the sleeves 15, 16) during assembly a steel ball 25 is first to be defined precisely (z. B. hardened steel) in the holes 26 and then the respective hard material rod 19, 20 in the collar pressed. The balls 25 result in a defined one Support on the one hand in the center of the hard material rods and on the other other ring-shaped on the through the usual drill tips conical bottom of the holes 26.

The sleeves 15, 16 are seated in receiving bores 28 in the Ends of the piston rods 11, 12. In a smaller one Receiving hole 30 in the bottom of the receiving holes 28 is in the In the case of the piston 8 of the storage pump 4, a spring 32 used, the free end at the bottom 22, 23 of the sleeves 15, 16 is present. Outside is around the piston rods 11, 12 one collar 36 each. In each collar 36 is located in a thread 39 an adjusting screw 38, the end of a bore 40 in the piston rod 11, 12 on the sleeve 15, 16 is attachable. By screwing in the screw 38 the pistons 7, 8 can be locked in the respective piston rod. Through a recess 42 in the housing of the pump head 1 the screw 38 of the storage pump 4 accessible from the outside.

In the feed pump, however, is in the piston rod 11 Bore 31 provided with a thread in the Threaded pin 33 is screwed in, on the sleeve 15 is scheduled. By turning the threaded pin 33 can so that the length of the piston can be adjusted precisely. Against however, it is usually also an undesired change in length here necessary to provide a locking device, e.g. B. a Set ring 36 with set screw 38. The setting of the Dead volume in the assembled state can with this Execution by changing the displacement chamber, for which a solution is given below.

Both hard material rods 19, 20 protrude through one conventional piston seal 44, a stone guide 46 (z. B. from artificial gemstone such as ruby) and finally an inventive piston seal with reduced Dead volume in the actual displacement chamber 47. Die Chamber 47 consists of high strength and chemically inert Material, e.g. B. Titan.

Outlet 112 of the feed pump 3 is a conventional one flexible pipe 114 with a small internal volume with the Inlet 115 of the storage pump 4 connected. line 114 is close to the screw connections known per se Connections attached.

A first embodiment 48 is one on the delivery piston Piston seal according to the invention shown in Fig. 3rd is shown enlarged. It essentially consists of a sealing body 50 of substantially L-shaped Cross section, wherein one leg 52 is a sleeve-shaped Forms sealing lip through which the hard material rod 19, 20th a piston 7, 8 can be inserted. Around the sealing lip a spring 54 runs around such that the Wind spiral turns even around the sealing lip. As in Fig. 1, the inner wall 56 can thus be around the seal 48 are relatively narrow compared to the Training around the conventional piston seal 44, whereby the dead volume is significantly reduced. For clarification The following information is used for a pump version with an output volume of 23 microliters: dead volume a conventional piston seal itself: 18 microliters; Dead volume of the additional space in front of the piston seal inside the displacement chamber: 11 microliters; all in all Dead volume for a piston seal conventional: 29 Microliters. The described seal according to the invention allows a reduction to approx. 20%, i.e. approx. 6 microliters. The dead volume drops to a fraction of the Emissions volume.

The displacement chamber 47 of the feed pump 3 is open at the bottom executed and closed with a counter-piston 58, the front end the (movable) floor of the displacement chamber forms. The counter-piston 58 is also made of titanium. The Counter-piston passes through a sealing sleeve 60, which by a Clamping sleeve 62 in an extension 64 of Displacement chamber bore 57 is held. Is conceivable also, a screw connection of both the sleeve 62 in the Extension 64 and also the counter-piston 58 in the sleeve 62 to be provided by turning the counter piston Shift and thus a change in the volume of the To be able to effect displacement chamber.

Fig. 11 shows a known seal 64, which instead of Sealing sleeve 60 can be used and a small dead volume having. Because the counter piston 58 does not operate and is only rarely moved, these are Seal made significantly lower requirements. The Seal 64 has a sealing body 65 with a Sealing lip 66 on the counter piston 58 (not shown) is pressed. The proof is first of all embedded O-ring 67 applied and during operation of Internal pressure of the pump on the O-ring 67 and on the Sealing lip acts, reinforced. As material for the Sealing bodies come pressure-resistant and under the Operating conditions using chemically inert materials, such as PTFE in particular. There is a corresponding one for the O-ring Elastomer, e.g. B. KALREZ (DuPont) to choose. such Seals are known per se.

Another embodiment is 70 in the storage pump a piston seal according to the invention. A Figure shows an enlargement of the piston seal 70 used 4 and the special spring element Fig. 5. The sealing element 72nd the piston seal has a C-shaped cross section like also the spring element 74. At the end of the inner Sealing lip 73 is a thickening or crowning 75 educated. The spring element 74 is on the inner surface 76 and on the bend 77 several times through slots 79 separated. Depending on the desired stiffness, divide the Slits also the outer surface 81, the rigidity with the width of the remaining webs 82 decreases. The curvature 77 describes an angle that is slightly less than 180 °, so that the inner surface slopes slightly inwards. This means that when the spring element 74 is inserted into the sealing element 72 is inserted, a bias of the sealing lip 73 is achieved.

4, the spring element 74 is in the sealing element 72 arranged with parallel cross sections and in an annular filler 83 inserted. The packing consists of a material that chemically inert to the working medium and below that Working pressure is essentially incompressible. The Packing is dimensioned so that the interior of the Filled largely spring element, d. H. at least that Half, preferably at least 90% and more preferred at least 99%. Basically, it becomes as voluminous as possible chosen without, however, the spring action of To affect the spring element below the required size.

By filling the empty volume, the seal becomes generated dead volume significantly reduced and at the same time an installation dimension as for a conventional piston seal maintained.

The storage pump also has a precaution Adjustment of the dead volume on the adjustment device between piston 8 and piston rod 16 and an insert 87 in the displacement chamber 89. The material of the Insert 87 is chosen so that contact between the Hard material rod 20 and the insert 87 is possible without that damage occurs. In particular, a material chosen that inert to the working medium and under Operating pressure is practically incompressible, but from Hard material is still slightly deformable. It is also to take into account that the size of the front ends of the Hard material rods 19, 20 are rounded to them without damaging the seals and the guides in the To be able to introduce displacement chambers. The material of the Insert 87 can do something about this rounding nestle, which further reduces the dead volume becomes.

The displacement chambers 47, 89 are in bores in one Pump block 91 inserted. For the correct alignment with the laterally arranged access holes 92 have the Displacement chambers 47, 89 a groove 93 into which a pin 94 engages.

An extension ring follows the displacement chambers 47, 89 95, which in the block extension 96 by a threaded ring 97 is fixed. Block extension 96 is at block 91 screwed.

All parts exposed to the working medium consist of a material that is inert to the working medium. As far as they are also exposed to the operating pressure the pressure even without noticeable compression or deformation withstand. For housing parts, such as displacement chambers, Cartridges, connections, but also for metallic ones Sealing membranes, titanium has become a metal in particular proven. The hard material for the pistons is regarding Pressure resistance is usually not a problem. At most attention should be paid to the chemical inertness, but this in the Rule is also readily given. For parts that must have a certain elasticity (insert 87, Body of the piston seals, seals, etc.) is one Elastomer, preferably the plastic PTFE (Polytetrafluoroethylene), usable, especially one with Graphite fiber reinforced PTFE, which is an increased Wear resistance, pressure and temperature resistance having. PEEK is also particularly useful for seals (Polyether ether ketone) can be used.

Finally, it should be mentioned that feed pump and Storage pump can also be run identically. In particular, both can be the same Piston seals according to the invention of one or the other Be equipped.

The feed pump can be in a further preferred embodiment instead of a counter-piston, a closed displacement chamber have with an insert 87, so as that described Storage pump to be formed, and vice versa Storage pump like the feed pump described. So that can the dead volume of the feed pump to almost zero be set what is under practically all Operating conditions is optimal. By moving the Counter piston in the storage pump, it is then possible to To minimize pulsation, i.e. the pump to the working pressure and the compressibility properties of the working medium adjust.

Because the storage pump works under constant pressure and therefore has to meet lower requirements lower requirements for her also on measures in the Displacement chamber for reducing or adjusting the Dead volume can be dispensed with. In applications where the Quality particularly low demands are made, On the one hand, there can even be one in the storage chamber conventional piston seals are used and on the other hand to one or the other measure Reduction of the dead volume also in the feed pump to be dispensed with.

The setting of a certain dead volume to the bottom of the Displacement chamber, in extreme cases practically zero reduced dead volume, in any case takes place in that first the respective piston to top dead center is provided, d. H. the drive is positioned at which the piston reaches the maximum in the displacement chamber is inserted, the corresponding adjusting screw is solved. The version with an insert 87 now lies the hard material rod of the piston on the insert 87. The Set screw 38 is tightened, causing the dead volume the minimum is adjusted.

If there is a counter piston, the dead volume can then be determined by pulling the counter-piston back on desired size can be increased.

Another fundamental aspect for the quality of a Pump of this type is the tightness, being too take into account that even the slightest leakage that externally because of the small amounts of e.g. B. clearly less than 1 microliter and also in the nanoliter range the result is practically undetectable influence. Doing so seals the various Connections to the displacement chambers a first-rate Problem.

It is known that the connections via cartridges 101, 102 to be connected directly to the sealing surfaces of the displacement chambers. As usual, the cartridges can be both simple Represent passages (see Fig. 7: cartridge 101), but also z. B. Check valves 102 as in Fig. 1 and 2 at input 111 and output 112 of the feed pump.

However, the danger of a lateral one is unavoidable Offset 113 (FIG. 6) of the displacement chamber accesses 103 opposite the connections fastened to block 91 on the outside or their accesses 105. Such an offset leads to a slight tilting of the cartridge 101 (see FIG. 6). Both known designs with plan or conical Sealing surfaces at the entrances leads to a slight uneven pressure on the sealing line, because the Cartridge sealing surfaces and access at a small angle to stand by each other. At the present high pressures leads this leads to leaks and can even lead to a Push out the seal towards the opening of the Lead angle.

As shown in Figures 6-8, one Liaison to solve this problem one Sealing surface cambered, in particular convex spherical executed, each corresponding hollow cone-shaped. With such a sealing surface pairing also remains Inclination of the one sealing surface, d. H. the longitudinal axis of the channel arranged therein for the working medium compared to that of the channel of the adjacent part one circular contact line on which the Pressure is substantially constant. Unless the two Contact surfaces made of metal will be in between preferably a sealing membrane 117 made of metal, in particular because of contact with the working medium made of titanium, or from Plastic, especially PEEK, arranged.

In the example there are the round sealing surfaces the connections and the displacement combs, the conical on cartridges 102. However, the reverse is conceivable Execution. It is also conceivable, a sealing capsule 119, for. B. made of PEEK, with round sealing surfaces on both sides (see Fig. 8: transition between a connection 100 and a simple cartridge 101).

Leakages are also caused in the same way Angular error between the parts to be connected with the construction specified avoided.

In a more preferred training, everyone can Connection of 120 of the two sealing surfaces, conceivably but also in the case of two, especially metallic, Sealing surfaces with an intermediate membrane both Sealing surfaces, step-shaped 121 are formed (see Fig. 9). This results in a step-like sealing effect or a plurality of line contacts, creating the sealing effect is further improved.

Another proven way is to provide concentric grooves 123 (Fig. 10).

In Fig. 12 and 13 is another preferred one Embodiment of connections for connecting a Capillary line shown without additional function. Line 114 consists of titanium and is welded to an end piece 130. The connector 100 is a screw sleeve trained, which is displaceable on the capillary.

The implementation for line 114 through the Connector 100 is flared at inner end 132 to offer 134 space for the weld seam. The sealing surface 136 of end piece 130 is configured as described above To enable a perfect seal even when offset. In particular, the execution with sealing capsule or Version with a sealing membrane (see above). To the Attaching the cable is like the screw sleeve itself known screwed into the pump housing.

The contact surfaces 138 between end piece 130 and connection 100 are complementarily cambered, conical or the like. executed to an automatic centering at Screw the connection into the pump body cause. However, the contact surfaces 138 have none Sealing function. The connection 100 consists of PEEK or Steel.

Compared to the version described first join this solution two sealing surfaces less, and that Dead volume through the channel in the empty cartridge, the one has a relatively large diameter, and around additional screwed into the connections 100 Screw cuffs around are avoided.

13 shows a connecting line 114 at its ends the above connection arrangements are attached. In front the welding of the second of the end pieces 130 must two screw collars 100 on line 114 be postponed. Bending line 114 into the necessary form, e.g. B. U-shaped, can be done afterwards.

Each of the measures leads to an increase in quality the pump, but can also be used for maintenance to simplify, d. H. especially the skills of the To make maintenance personnel less demanding. In particular, it is possible that the maintenance on site can be carried out by the user without loss of quality to accept.

• Gradiententauglichkeit bis 30 µl/min und weniger, insbesondere wegen des verringerten Totvolumens (im praktischen Beispiel: 9,45 µl gegen 36 µl im Stand der Technik);
• Steigerung des Betriebsdrucks bis 1000 Bar;
• Möglichkeit, die Patronen 101, 102 mit anderen oder zusätzlichen Funktionen zu versehen, z.B. zur Durchflussoder Betriebszustandüberwachung;
• sichererer und einfacherer Zusammenbau, dadurch Erleichterung der Wartung; und/oder
• Verwendung für Hochdruckgradientensysteme, bei denen die Mischung der verschiedenen Komponenten im Hochdruckteil erfolgt.

Further achievable advantages emerge from the description of the preferred exemplary embodiment:

• Gradient suitability up to 30 µl / min and less, in particular because of the reduced dead volume (in practical example: 9.45 µl against 36 µl in the prior art);
• Increase in operating pressure up to 1000 bar;
• Possibility to provide the cartridges 101, 102 with other or additional functions, for example for flow rate or operating status monitoring;
• safer and easier to assemble, making maintenance easier; and or
• Use for high pressure gradient systems in which the various components are mixed in the high pressure part.

The exemplary embodiment described allows the person skilled in the art to to find obvious modifications and additions without to leave the scope of the invention by the Claims is defined. A number of such Variations have already been mentioned above. In addition, are conceivable also, for less demanding requirements none Possibility to adjust the length of the pistons or on the ball 25 for the exact positioning of the Hard material rods of the pistons in the sleeves 15, 16 dispense. Such simplifications are even more so conceivable with the storage pump because of the lower Influence on the properties of the pump. Is conceivable also, the inventive design of the sealing surfaces only to be provided where the working pressure prevails. Conceivable. is also a pump with only one pump unit, i.e. H. only the Feed pump, e.g. B. in applications where only an accurate Dosing small amounts of a flowable medium, especially a liquid (syringes or Dosing pumps).

The connections can also be flanged instead of screwed or otherwise attached to the pump body. Prefers however, they are removable for maintenance and repair work not to complicate.

Claims (23)

Pump (1) for conveying precisely determined small liquid flows, in particular flows up to a maximum of 5 ml / min, with at least one pump device (8) which comprises a piston (8) which can be moved in a displacement chamber (89), the piston at least one foremost , The piston has a first seal (70) sealing against the displacement chamber and the first seal has a sealing element (72) with a sealing lip surrounding the piston (73), the first surface of which by means of a spring-elastic element (74) which is on the opposite second surface is biased against the piston, the second surface being connected to the displacement chamber, characterized in that the sealing element (72) and the spring element have a substantially C-shaped cross section and therein a filling body which is essentially incompressible under the operating conditions of the pump device (83) is arranged around the dead volume originating from the seal men to reduce the pumping device. Pump according to claim 1, characterized in that the width of the slot of the C-profile is substantially equal to the height of the interior of the C, so that the filler (83) can be inserted axially into the spring element (74) and essentially the interior of the C at least for the most part, preferably almost completely. Pump, in particular according to one of claims 1 to 2, for delivering precisely determined small liquid flows, in particular flows up to a maximum of 5 ml / min, with at least one pump device (3) which comprises a piston (7) which can be moved in a displacement chamber (47) , wherein the piston has at least one foremost second seal (48) sealing the piston against the displacement chamber and the second seal has a sealing lip (52) surrounding the piston, the first surface of which by means of a resilient element (54) which is connected to the opposite second Surface rests against which the piston is biased, the second surface being connected to the displacement chamber, characterized in that the spring element essentially has the shape of a closed, spring-elastic band, the inside of which is on the second surface of the sealing lip abuts, and the inner wall of the displacement chamber with a low Abs Tand is designed to the outer surface of the spring element to reduce the dead volume of the pump device resulting from the seal. Pump (1) according to claim 3, characterized in that the band-like spring element (54) consists essentially of a spiral made of resilient material, the spiral windings running around the sealing lip (52). Pump (1), in particular according to one of claims 1 to 4, for conveying precisely determined small liquid flows, in particular flows up to a maximum of 5 ml / min, with at least one pump device (3; 4), which is located in a displacement chamber (47; 89 ) movable piston (7; 8), characterized in that the piston is operatively connected to the pump drive via a piston rod (11; 12), the piston via a piston adjusting device (15, 28, 31, 33, 36, 38; 16 , 28, 30, 32, 36, 38) is connected to the piston rod, and the piston adjusting device between the piston and the piston rod is designed to be adjustable in length by the total length of the arrangement of the piston and the piston rod to the distance between the drive and the displacement chamber floor and thus that To be able to set dead volume. Pump (1) according to claim 5, characterized in that the piston (7; 8) on the piston rod (11; 12) is arranged to be longitudinally movable. Pump according to one of claims 5 to 6, characterized in that the piston adjusting device (15, 28, 31, 33, 36, 38; 16, 28, 30, 32, 36, 38) is equipped with a clamping means (36, 38) in order to be able to fix the piston (7; 8) in a certain position in relation to the piston rod (11; 12). Pump (1) according to one of claims 5 to 7, characterized in that in the piston adjusting device (15, 28, 31, 33, 36, 38; 16, 28, 30, 32, 36, 38) a spring means (32) between Piston (7; 8) and piston rod (11; 12) is arranged so that the total length of the arrangement of piston and piston rod is shortened against the restoring force of the spring element. Pump (1) according to one of Claims 5 to 8, characterized in that a body (87) is present in the displacement chamber (89) as the displacement chamber base, which body is made of a material which is at most negligibly compressible under the operating pressure of the pump, but is sufficiently elastic than that There is a piston and completely fills the cross-section of the displacement chamber, so that the piston (8) can be adjusted to an arbitrarily small distance from the bottom of the displacement chamber at top dead center, in particular to a dead volume that is essentially no longer present, without the risk of damaging the piston if there is contact with the displacement chamber floor during the adjustment process or operation. Pump (1) according to one of claims 7 to 9, characterized in that the piston (7; 8) has a rod-shaped piston part (19; 20) made of a hard material, in particular of ceramic, crystalline or mineral material, the rear end of which in a Receptacle is held in a sleeve (15; 16) so that the clamping means (38, 39) can be placed on the sleeve essentially in a punctiform manner and can thus be fixed in the piston rod (11; 12) without the rod-shaped piston part being caused by the clamping means is damaged. Pump (1), in particular according to one of claims 1 to 10, for conveying precisely determined small liquid flows, in particular flows up to a maximum of 5 ml / min, with at least one pump device (3) which has a piston () which is movable in a displacement chamber (47) 7), characterized in that the bottom of the displacement chamber of at least one pump device is essentially formed from the front end of a counter-piston (58) which is displaceable in the displacement chamber, so that the dead volume of the pump device can be adjusted. Pump (1) according to claim 11, characterized in that the counter-piston (58) is provided with an adjusting device with position indicator device in order to be able to determine, in particular read off, the dead volume in the displacement chamber from the outside. Pump (1), in particular according to one of claims 1 to 12, to promote precisely certain smaller ones Liquid flows at high pressure, especially from Flow up to a maximum of 5 ml / min and / or when pressing at least 100 bar, with at least one pump device (3; 4), which can be moved in a displacement chamber (47; 89) Piston (7; 8), wherein at least one Working medium access the pumping device a detachable Connection arrangement (100, 101; 100, 102; 100, 130) available which has at least a pair of sealing surfaces which form a tight transition from the working medium, of which the one sealing surface is essentially spherical convex and the other substantially hollow cone-shaped is trained and at its center, especially at the highest and lowest points, one opening each of a channel for the working medium is available, so that even if the arrangement of the Channel openings form an annular contact line between the both sealing surfaces. Pump according to claim 13, characterized in that a seal (117) is arranged between the sealing surfaces of at least one pair of sealing surfaces, preferably all such pairs, in particular in the form of a membrane-like element made of metal or a high-pressure-resistant plastic, preferably made of PEEK. Pump (1) according to claim 13, characterized in that at least a first and a second pair of sealing surfaces are present and between the two pairs of sealing surfaces a sealing body (119) is arranged on which the respective inner sealing surface of the two pairs of sealing surfaces is formed and the consists of a dimensionally stable, high pressure-resistant plastic, preferably made of PEEK. Pump (1) according to one of claims 13 to 15, characterized in that at least a first and third pair of sealing surfaces are present, the two inner and the other pair facing sealing surfaces of the first and third pair on a connecting body (101, 102 ) are formed, which is arranged between the two other, outer sealing surfaces of the two pairs, so that the two sealing surface pairs each represent a tight transition to the connecting body. Pump according to one of claims 13 to 16, characterized in that in addition to a pair of sealing surfaces there is a pair (138) of a first and a second contact surface, the first and second contact surfaces abutting one another, the first contact surface and a sealing surface on one second connecting bodies (130) are formed in the connection arrangement (100, 130) and the second connecting body is held between the second contact surface and the other of the sealing surfaces and is firmly connected to a line (114) for the working medium, which opens into the channel, whose opening is in the sealing surface on the second connecting body. Pump according to claim 17, characterized in that the contact surfaces (138) are curved and complementary to each other in order to center the second connecting body (130) in the second contact surface. Pump according to one of claims 13 to 18, characterized in that at least in one of the first pairs of sealing surfaces, preferably in all first pairs of sealing surfaces, at least one of the sealing surfaces (120) has a concentrically stepped surface (121) in order to obtain a plurality of sealing lines. Pump with at least a first (7) and a second (8) Pump device consisting of displacement chamber (47; 89) and pistons (7; 8), those of the first pump arrangement downstream pump arrangement as a storage device of the Pulsation of the first pump device is operable and the Pump devices in each case according to one of claims 1 to 19 are formed. Method for setting the dead volume in a pump (1) according to one of claims 5 to 12 or according to one of claims 5 to 12 and one of claims 13 to 20, characterized in that the piston rod (11; 12) is set to the top dead center the piston (7; 8) is pushed into the displacement chamber up to the desired dead volume and the piston is locked in the piston rod by actuating a locking device (38) of the piston adjusting device. Use of the pump according to one of claims 1 to 20 and according to one of claims 11 to 12, characterized in that the counter-piston (58) is adjusted according to the intended operating pressure in order to achieve a low pulsation. High pressure chromatography device, especially for HPLC, with a pump according to one of claims 1 to 20 as a medium pump.

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