Dispenser, system and method for taking up and dispensing fluid volumes

Abstract

A dispenser for taking up and discharging fluid volumes which has an exchangeable piston-cylinder unit. The dispenser has a housing and a device for incremental distance measurement that, when there is relative movement between the piston and the cylinder, the distance traveled by the piston relative to the housing can be determined incrementally. The dispenser has a piston actuation member which can be releasably connected to the piston moving the piston in order to take up and/or discharge fluid volumes. The dispenser has a position determining device which has a first position element and a second position element. The first position element is fixed in or on the housing of the dispenser. The second position element is coupled so as to be able to move with the piston actuation member. The position determining device is for continuously sensing the position of the second position element.

Claims

1. A dispenser for taking up and dispensing fluid volumes, comprising: a housing, an exchangeable piston-cylinder unit having a piston and a cylinder and being releasably attached to the housing, a piston actuator which is moveable in the housing and is releasably connected to said piston in such a manner that said piston is moved translationally by the piston actuator for taking up and dispensing fluid volumes, an incremental distance measuring device in the housing and configured to incrementally determine a distance axially traveled by said piston of said piston-cylinder unit relative to said housing, and a position determining device which has a first position element and a second position element, wherein the first position element is arranged rigidly fixed in or on said housing and the second position element is coupled to axially move with the piston actuator, and wherein the position determining device determines the axial position of the second position element.

2. The dispenser as claimed in claim 1, wherein the first position element is a position sensor and the second position element is a position marker, and wherein the position sensor is operative to determine the position of the position marker.

3. The dispenser as claimed in claim 2, wherein the position sensor comprises a printed circuit board.

4. The dispenser as claimed in claim 2, wherein the position marker comprises an electrical resonator.

5. The dispenser as claimed in claim 4, wherein the electrical resonator comprises at least one of a coil or a capacitor.

6. The dispenser as claimed in claim 1, wherein the first position element is a position indicator and the second position element is a position sensor, and wherein the position sensor is constructed to determine the position at which the position sensor is located using the position indicator.

7. The dispenser as claimed in claim 1, wherein the position determining device is constructed without electrical contact between the first position element and the second position element.

8. The dispenser as claimed in claim 1, further comprising a motor coupled to the piston actuator and configured to perform revolutions to drive the piston actuator and wherein the incremental distance measuring device comprises a rotary measuring device for determining the number of revolutions of the motor and thus for incrementally determining the distance traveled by the piston during displacement by the piston actuator.

9. The dispenser as claimed in claim 1, wherein the position determining device is constructed to determine the distance traveled by the piston relative to at least one of the first position element or to said housing during a relative movement between the piston and the cylinder of said piston-cylinder unit.

10. The dispenser as claimed in claim 2, further comprising an acquisition element in the housing, wherein the acquisition element is insertable into a recess in an end face of the piston, and wherein the second position element or the position marker is coupled to move with the acquisition element, and wherein a depth of the recess is determinable by the position determining device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic perspective view of a preferred embodiment of a dispenser according to the invention,

(2) FIG. 2 is a simplified schematic perspective view of a preferred embodiment of a system according to the invention with the dispenser of FIG. 1 and a piston-cylinder unit inserted into the dispenser, leaving out parts of the dispenser, and

(3) FIG. 3 is a perspective view of a longitudinal section through the system of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

(4) FIG. 1 shows a schematic representation of a perspective view of a preferred embodiment of a dispenser 1 according to the invention for taking up and dispensing fluid volumes. The dispenser 1 has a housing 2 with an opening 23 and a fixing device 24 for the piston-cylinder unit 3 which is arranged behind the opening 23 inside the housing 2.

(5) FIG. 2 shows a schematic representation of a perspective view of the dispenser 1 from FIG. 1 and of a piston-cylinder unit 3, which is inserted into the dispenser 1 and held by the fixing device 24, as parts of a preferred embodiment of a system 4 according to the invention for taking up and dispensing fluid volumes. In this case, the dispenser 1 is only shown in part. FIG. 2 is restricted to showing the components which are necessary to explaining the present invention.

(6) FIG. 3 shows a schematic representation of a perspective view of a longitudinal section through the system 4 of FIG. 2.

(7) The dispenser 1 and the piston-cylinder unit 3 have an axial direction A shown in FIG. 2 and a radial direction R which extends perpendicularly to the axial direction A and through the longitudinal axis of the dispenser 1 or of the piston-cylinder unit 3.

(8) The piston-cylinder unit 3 is an exchangeable part. It can be realized in the form of a syringe and can be present in various sizes with different volumetric capacities. It comprises a sealed piston 5 which is movable in a cylinder 6 of the piston-cylinder unit 3 for the purpose of taking up or drawing in and dispensing or ejecting a liquid which is to be pipetted or dosed. The piston 5 can only be seen in FIG. 3.

(9) With the piston-cylinder unit 3 in the inserted state, the cylinder 6 abuts against a rocker (not shown) of the dispenser 1. Hereby and with the aid of the fixing device 24, the cylinder 6 is fixed on the dispenser 1 or on the system 4 so that, with regard to the piston-cylinder unit 3, only the piston 5 is movable in the cylinder 6 for taking up or drawing in or dispensing or ejecting liquid.

(10) The dispenser 1 has an incremental distance measuring device 7 which is constructed such that, in the case of a relative movement between the piston 5 and the cylinder 6, the distance traveled by the piston 5 relative to the housing 2 of the dispenser 1 can be incrementally determined.

(11) The dispenser 1 or the system 4 comprises a piston actuator 8 which is releasably connectable to the piston 5 of the piston-cylinder unit 3 in such a manner that the piston 5 is movable by means of the piston actuator 8 to take up and/or dispense fluid volumes.

(12) The dispenser 1 or the system 4 comprises a position determining device 9 which has a first position element 10 and a second position element 11. The first position element 10 is arranged rigidly in or on the housing 2 of the dispenser 1. The second position element 11 is motionally coupled with the piston actuator 8, by the second position element 11 being arranged on the piston actuator 8. The position determining device 9 is constructed to determine the position of the second position element 11.

(13) In the case of the embodiment that is shown and preferred, the dispenser 1 can provide the respective position of the second position element 11 immediately after the power supply is switched on. The respective position is continuously determined and can be called up at any time by further electronics of the dispenser 1.

(14) In the case of the embodiment that is shown and preferred, the first position element 10 is a position sensor and the second position element 11 a position marker. The position sensor 10 is constructed to determine the position of the position marker 11.

(15) The position determining device 9 is constructed here to determine the position of the position marker 11 in a resonantly inductive manner. There is no mechanical and electrical contact between the position sensor 10 and the position marker 11.

(16) The position sensor 10 here comprises a printed circuit board. The position marker 11 has an electrical resonator with multiple coils and a capacitor. In this case, one of the coils is used to provide the resonator with power. The coils are arranged such that a sine/cosine variation in the coupling factor is generated when the position marker 11 is moved. The calculation of the respective position of the position marker 11 corresponds to the calculation of a phase angle and is carried out by way of an inverse four quadrant tangent.

(17) The position determining device 9 enables the position of the position marker 11 to be determined in a simple, sturdy and cost-efficient manner.

(18) In the case of the embodiment that is shown and preferred, the piston actuator 8 is driven by a motor 12 via a gear unit 25 which is disclosed in the prior art. The incremental distance measuring device 7 comprises a rotary measuring device by means of which the revolutions of the motor 12 of the dispenser 1 can be determined. The distance traveled by the piston 5 when the piston actuator 8 is displaced can be determined incrementally based on the revolutions determined and on a conversion factor of the gear unit 25.

(19) In the case of the embodiment that is shown and preferred, the position determining device 9 is constructed to determine the distance traveled by the piston 5 relative to the position sensor 10 and to the housing 2 in the case of a relative movement between the piston 5 and the cylinder 6. In particular, the position determining device 9 is constructed to subtract two determined position values. Consequently, the position determining device 9 can perform an absolute distance measurement. In this case, the incremental distance measuring device 7 has a smaller resolution with regard to the distance measurement than the position determining device 9.

(20) In the case of the embodiment that is shown and preferred, the dispenser 1 is constructed to determine a variable reversal stroke based on a subtraction between measured values of the incremental distance measuring device 7 and of the position determining device 9. In addition, the dispenser 1 is constructed to determine a starting point which is defined after a variable reversal stroke based on a measured value of the position determining device 9. A fluid volume previously taken up can be dispensed from the starting point determined in this way or the incremental distance measurement of the piston actuator 8 is commenced in each case when a fluid volume is taken up.

(21) In the case of the embodiment that is shown and preferred, the piston actuator 8 can be moved toward the piston 5 for determining a piston-side reference point until a stop 13 of the piston actuator 8 abuts against an end face of the piston 5. The absolute position of said piston-side reference point can be determined by means of the position determining device 9 and/or by means of the incremental distance measuring device 7.

(22) In the case of the embodiment that is shown and preferred, the dispenser 1 comprises an acquisition element 14 which is insertable in the axial direction A at least in part into an axially aligned recess 15 in an end face of the piston 5. The position marker 11 is motionally coupled with the acquisition element 14. The depth of the recess 15 can be determined by means of the position determining device 9. Based on the depth of the recess 15 determined in this manner, it is possible to identify at least in part the type of the piston-cylinder unit 3 with its individual dimensions and requirements when used with the dispenser 1.

(23) The previously determined piston-side reference point marks the starting point of determining the depth of the recess 15.

(24) The acquisition element 14 is prestressed elastically here in opposition to the insertion direction of the piston-cylinder unit 3 by means of a spring 16. The dispenser 1 comprises a locking element 17, by way of which the acquisition element 14 can be moved into a release position and be held there. The locking element 17 holds the acquisition element 14 in the release position by an entrainment means 18 of the locking element 17 counteracting the force of the spring 16 at a continuation 19 of the acquisition element 14 and blocking a movement of the acquisition element 14 in the direction of the spring force (that is to say in the axial direction A toward the piston-cylinder unit 3).

(25) The locking element 17 can be displaced in the axial direction A in the dispenser 1 and relative to the housing 2 and to the piston actuator 8. As a result of displacing the locking element 17 in the direction of the piston-cylinder unit 3, movement of the acquisition element 14 is no longer blocked so that the acquisition element 14 is pressed by the spring 16 toward the piston 5 and then into the axially aligned recess 15 until the acquisition element 14 contacts the end of the recess 15 and is blocked there.

(26) The axially aligned recess 15 is upwardly open here in the axial direction A, open to the left, therefore, in FIG. 3. The recess 15 is realized here in the form of a groove. It is therefore not a bore which is surrounded in the radial direction R. The recess is, in fact, outwardly open in part in the radial direction R, along the entire depth of the recess 15. As an alternative to this, the axially aligned recess 15 can be realized as a blind hole.

(27) In the case of the embodiment that is shown and preferred, the depth of the axially aligned recess 15 can assume one of multiple discrete values, for example one of eight possible depth values. The discrete depth values comprise a minimum distance, preferably approximately 2 mm. If a depth is 0 mm, it is not a recess in the sense of the present invention.

(28) In the case of the embodiment that is shown and preferred, the piston 5, in particular a piston head 20 of the piston 5, has an information carrier portion 21 which specifies in part the type of the piston-cylinder unit 3 and is aligned radially. In this case, the radially aligned information carrier portion 21 is formed by a recess 21 on the piston head 20, which recess extends in the radial direction R and extends in the circumferential direction of the piston-cylinder unit 3. It can be seen in FIG. 3 that the radially aligned recess 21 is formed as a result of the piston head 20 having a smaller diameter in said portion.

(29) In the case of the embodiment that is shown and preferred, the depth of the axially aligned recess 15 and the depth of the radially aligned recess 21 specify the type of the piston-cylinder unit 3.

(30) In the case of the embodiment that is shown and preferred, the dispenser 1 has a sensor device for detecting the attachment of the piston-cylinder unit 3 to the dispenser 1. A light barrier 22 is provided here as a sensor device. Once successful attachment of a piston-cylinder unit 3 has been detected, fluids can be taken up into the cylinder 6 or dispensed from the cylinder 6.

(31) The dispenser 1 has further devices which are not shown, among others an electronic control device, a gear unit, power supply equipment, a coupling device for connecting the piston 5 to the piston actuator 8, a display device and an input device.

(32) A preferred sequence of a method for picking up and dispensing fluid volumes is depicted below.

(33) First of all, the piston-cylinder unit 3 is inserted releasably into the dispenser 1 by means of a movement which extends at least substantially in the axial direction A. The cylinder 6 of the piston-cylinder unit 3 is fixed.

(34) Once the piston-cylinder unit 3 has been inserted successfully into the dispenser 1, this is detected by means of the sensor device, here the light barrier 22.

(35) The piston-side reference point is then determined by generating a relative movement between the piston 5 and the piston actuator 8. In this case, the piston actuator 8 is moved toward the piston 5 until the stop 13 of the piston actuator 8 abuts against an end face of the piston 5 (blocked movement). The length of the relative movement is determined by means of the incremental distance measuring device 7 or the position determining device 9.

(36) The piston-side reference point is then determined as absolute travel position by means of the position determining device 9, which is motionally coupled with the piston actuator 8. The reference point provides, as it were, a distance calibration which makes the method at least largely independent of differences in the dimensional tolerances of the parts of the piston-cylinder unit 3. For the determining of the reference point enables a starting point to be established for reading-out the information of the recesses 15, 21.

(37) In the case of the preferred embodiment of the method, after the blocked movement, the acquisition element 14 of the dispensers 1 is inserted in the axial direction A at least in part into the axially aligned recess 15 and the depth of said recess 15 is determined by way of determined positions of the position marker 11. The determined depth value is used to identify in part the type of the piston-cylinder unit 3.

(38) Thereafter, at the same time or prior to this, the piston head 20 of the piston-cylinder unit 3 is connected releasably to the piston actuator 8 of the dispenser 1. A coupling between the piston actuator 8 and the piston 5 is achieved in this way.

(39) A relative movement between the piston 5 and the cylinder 6 is then generated by the piston actuator 8 moving the piston 5, in particular displacing it in a linear manner. In this case, the piston actuator 8 is driven by the motor 12. The distance traveled by the piston actuator 8 in the case of said relative movement corresponds to the distance traveled in this case by the piston 5.

(40) The distance traveled by the piston 5 in the case of said relative movement relative to the housing 2 of the dispenser 1 is determined incrementally by means of the incremental distance measuring device 7. In this case, the revolutions of the motor 12 which drives the piston actuator 8 are determined.

(41) In addition, the absolute travel position of the position marker 11 of the dispenser 1 is determined continuously by means of the position determining device 9. Absolute distances are calculated as a result of subtracting two absolute travel positions.

(42) If a reversal of direction takes place, for example, when changing from taking up to dispensing a fluid volume or the other way around, during the relative movement between the piston 5 and the cylinder 6, said reversal of direction is determined immediately at the piston actuator 8 and at the piston 5 coupled therewith by way of the continuous determining of the absolute travel positions of the position marker 11. The stroke of the driving motor 12 when the direction is reversed, without the piston actuator 8 being moved and a relative movement being generated between the piston 5 and cylinder 6, is variable as a result of different driving forces, mechanical play and wear. Both the reversal stroke and the relative movement can be independently determined. In addition, a starting point is determined for determining a further relative movement after the direction has been reversed. From the starting point determined in this way, the distance traveled by the piston 5 relative to the housing 2 is determined incrementally by means of the incremental distance measuring device 7.

(43) In the case of the preferred embodiment of the method according to the invention, the values of incremental distance measurements are related to determined positions of the position marker 11, in particular absolute distance measurements by way of the determined positions of the position marker 11. The distance measurement and the position determination are adjusted on this basis. In addition, the related values are compared to one another and any deviations are used for adjustment. In this way, plausibility checks are also carried out with regard to the determined distances and to the determined positions. Non-plausible values, for example, can be rejected.