Cooling of a Dewar vessel with ice free coolant and for short sample access

Abstract

The present invention relates to a pump (15) for pumping a coolant (9) within a Dewar vessel (1) and to a corresponding Dewar vessel (1) for storing samples in a coolant (9). The Dewar vessel (1) comprises a thermally insulated reservoir (3) for the coolant (9) and a sample vessel (11) provided separately and arranged in the thermally insulated reservoir (3). The reservoir (3) is connected to the sample vessel (11) in such a way that the level of coolant (9) is constant in the sample vessel (11). Pump (15) may help in keeping the level of coolant (9) in the sample vessel (11) constant. For this purpose the pump (15) comprises a chamber (17) with an inlet (19) and an outlet (21), a closing element (23) and a pressure increasing device (25). Therein, the inlet (19) is connectable to the reservoir (3) and the outlet (21) is connectable to a sample vessel (11) of the Dewar vessel (1). The chamber (17) is adapted to fill with coolant (9) through the inlet (19) by gravity and the closing element (23) is adapted to automatically close the chamber (17) when it is full of coolant (9). The pressure increasing device (25) is adapted to increase the pressure within the chamber (17), after the chamber (17) is closed, until the coolant (9) is released through the outlet (21).

Claims

1. Dewar vessel for storing samples in a coolant, the Dewar vessel comprising a pump for pumping the coolant within the Dewar vessel, the pump comprising: a chamber with an inlet and an outlet; a closing element; a pressure increasing device; wherein the inlet of the chamber is connected to a reservoir of the Dewar vessel; wherein the chamber is adapted to fill with coolant through the inlet such that the coolant flows downward by gravity into the chamber; wherein the closing element is adapted to automatically close the chamber by floating when chamber is filled by the coolant; wherein the pressure increasing device is adapted to increase a pressure within the chamber, after the chamber is filled with coolant, until the coolant is released through the outlet; a thermally insulated reservoir for the coolant; a sample vessel arranged in the thermally insulated reservoir; wherein the reservoir is provided separately from the sample vessel; wherein the reservoir is connected with the sample vessel in such a way that the level of coolant is constant in the sample vessel; wherein the pump is arranged in the reservoir; and wherein the pump is adapted to continuously, in a pulsed regime, convey coolant from the reservoir into the sample vessel.

2. Dewar vessel according to claim 1, further comprising an opening for accessing the sample vessel; wherein the sample vessel is arranged in the vicinity of the opening.

3. Dewar vessel according to claim 1, wherein the pump is immersed in the coolant in the reservoir; wherein the outlet of the pump is connected via a line to the sample vessel.

4. Dewar vessel according to claim 1, further comprising a particle filter for filtering ice; wherein the filter is arranged at the inlet of the pump.

5. Dewar vessel according to claim 1, further comprising an ice draining port; wherein the ice draining port is provided at a bottom of the sample vessel; wherein the ice draining port is adapted to release ice accumulated at the bottom of the sample vessel into the reservoir.

6. Dewar vessel according to claim 5, wherein a one way valve is arranged at the ice draining port; wherein the one way valve is adapted to open when a predetermined amount of ice is accumulated at the bottom of the sample vessel; and/or wherein the one way valve is adapted to open after a predetermined amount of time.

7. Method for producing a Dewar vessel, the method comprising the following steps: providing a thermally insulated reservoir for a coolant; providing a sample vessel separately from the thermally insulated reservoir; providing a pump for pumping the coolant within the Dewar vessel, the pump comprising: a chamber with an inlet and an outlet; a closing element; a pressure increasing device: wherein the inlet of the chamber is connectable to a reservoir of the Dewar vessel; wherein the chamber is adapted to fill with coolant through the inlet such that the coolant flows downward by gravity into the chamber; wherein the closing element is adapted to automatically close the chamber by floating when chamber is filled by the coolant; wherein the pressure increasing device is adapted to increase a pressure within the chamber, after the chamber is filled with coolant, until the coolant is released through the outlet: arranging the sample vessel within the thermally insulated reservoir; arranging the pump in the reservoir; connecting the reservoir with the sample vessel in such a way that the level of coolant is kept constant in the sample vessel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Exemplary embodiments of the invention will be described in the following with reference to the following drawings.

(2) FIG. 1 shows a cross section of a Dewar vessel according to an embodiment of the invention

(3) FIG. 2A to 2E show cross sections of a pump according to a further embodiment of the invention in different stages of a pump operation cycle

(4) FIG. 2F shows a cross section of a further embodiment of the pump

DETAILED DESCRIPTION OF EMBODIMENTS

(5) In FIG. 1 a Dewar vessel 1 is presented. The Dewar vessel 1 comprises a thermally insulated reservoir 3 for a coolant 9. The reservoir 3 is also denoted as buffer reservoir. A layer 7 of vacuum is provided between a casing 5 of the Dewar vessel 1 and the wall of the reservoir 3. The layer 7 of vacuum ensures that no heat is transferred between the environment around the Dewar vessel 1 and the reservoir 3. Thus, the reservoir 3 and in particular the coolant 9 within the reservoir 3 is thermally isolated.

(6) Furthermore, a sample vessel 11 is arranged within the reservoir 3. In other words the reservoir 3 houses the sample vessel 11. As shown in FIG. 1 the sample vessel 11 is arranged above the level of coolant 9 in the reservoir 3. However, it is also possible that the sample vessel 11 is at least partially immersed into the coolant 9. The sample vessel 11 is adapted to accommodate and cool e.g. frozen samples. To allow short access and a high sample turnover the sample vessel 11 is arranged in the vicinity of or directly at an opening 13 of the Dewar vessel 13. The opening 13 may be provided with a cover 51. However, it is also possible to keep the Dewar vessel 1 according to the invention permanently open without significantly affecting the quality of the coolant 9 or the cooling temperature.

(7) Moreover, the Dewar vessel 1 comprises a pump for automatically and continuously (in a pulsed regime) pumping coolant 9 from the reservoir 3 to the sample vessel 11. The pump 15 is preferably immersed into the coolant 9 in the reservoir 3 and comprises a chamber 17 with an inlet 19 and an outlet 21. The inlet 19 is connected to the volume of the reservoir 3 and the outlet 21 is connected via line 31 to the volume of the sample vessel 11. Furthermore, at the inlet 19 a particle filter 33 is provided. The filter 33 clears the coolant 9 which enters the pump 15 and subsequently the sample vessel 11 from ice which may come from new samples or from ambient air through the opening 13.

(8) The pump 15 continuously injects ice-free coolant 9, particularly liquid nitrogen, into the sample vessel 11 such that the level of coolant 9 is kept constant in the sample vessel 11. The functionality of the pump is described in greater detail below with reference to FIG. 2.

(9) At the upper edge of the sample vessel 11 an overflow 49 is provided. I.e. the pump 15 supplies more coolant 9 than necessary to fill the sample vessel 11. Thus, the excess coolant 9 flows over the edge of the sample vessel 11 back into the reservoir 3. For this purpose a pipe may be provided. The overflow 49 may also move ice which floats on the coolant 9 from the sample vessel 11 to the reservoir 3.

(10) Moreover, at least one ice draining port 43 is provided at the bottom 45 of the sample vessel 11. This is shown on the left side of the sample vessel 11 in FIG. 1. At the ice draining port 43 a one-way valve 47 may be provided. The one-way valve 47 may open only at certain time intervals or if a certain amount of ice is accumulated on top of the one-way valve 47.

(11) Additionally or alternatively, a pipe 50 for draining ice may be provided at the sample vessel 11. This is shown on the right side of the sample vessel 11 in FIG. 1. The pipe 50 comprises a first opening and a second opening. The bottom 45 of sample vessel 11 may be designed in a sloping manner, such that ice with a higher density than coolant 9 moves due to gravity to a first opening connected to the lowest point of the bottom 45. The second opening of the pipe 50 is arranged at the level of the edge of the sample vessel 11 such that high density ice may be drained out of the sample vessel 11 by overflow 52 at the second opening.

(12) The Dewar vessel 1 may be adapted for sample storage at an automated macromolecular X-ray crystallography beamline. The sample vessel 11 shown in FIG. 1 comprises a circular shape, for example an O-shape shown in cross section. The filter 33 and the pump 15 are arranged in the middle of the circular sample vessel 11. However, different shapes of the sample vessel 11 are possible. For example, several separate sample vessels 11 may be provided within the reservoir 3. Moreover, the pump 15 and the filter 33 may be arranged differently within the reservoir 3. For example, the pump 15 and the filter 33 may be arranged directly at the side wall of the reservoir 3.

(13) Due to the constant level of coolant 9 in the sample vessel 11 the Dewar vessel 1 according to the invention allows samples to be stored close to the surface near the opening 13. As the coolant 9 is stored deep within the Dewar vessel 1 below the sample vessel 3 the thermal losses in the reservoir 3 are kept at a minimum. Moreover, due to the filter 33, the overflow 49 and the ice draining port 43 the samples may stay in an ice free environment even when manipulated at a high rate. Furthermore, these components make it possible to remove ice from the Dewar vessel 1 without re-heating of the Dewar vessel 1, e.g. by exchanging the filter 33 in which the ice is accumulated. The Dewar vessel 1 may also advantageously remain permanently open without significantly affecting the quality of the coolant 9. Finally, the Dewar vessel 1, and particularly, the reservoir 3 may be refilled with coolant 9 without affecting the level of coolant 9 in the sample vessel 11.

(14) In FIG. 2A to 2E different states of operation of the pump 15 are shown. The pump 15 comprises a chamber 17 immersed in coolant 9. The chamber 17 fills by gravity and subsequently ejects the coolant 9 via line 31 into the sample vessel 11. The sample vessel is shown schematically in FIG. 2A. The pressure for ejecting the coolant 9 from the chamber 17 is created by evaporation of a part of the coolant 9 situated in the chamber 17 or alternatively by injecting a volume of gaseous coolant such as gaseous nitrogen with an external piston pump 29 as shown in FIG. 2F.

(15) As shown in FIG. 2A the pump 15 is designed as a static pump. I.e. the pump 15 has a simple design without complicated moving elements. The pump 15 comprises the chamber 17 with an inlet 19, also denoted as input port, and an outlet 21, also denoted as output port. In the embodiment shown, the inlet 19 is arranged at the top of the chamber 17 and the outlet 21 is arranged at the bottom of the chamber 17. The outlet 21 is closed by a non-return valve 39 as shown in FIG. 2A to 2E. Alternatively, as shown in FIG. 2F, the flow from the outlet 21 is restricted by a restrictor 41 such as a throttle valve.

(16) The pump 15 further comprises a closing element 23 which e.g. has a lower density than the coolant 9 and therefore floats on top of the coolant 9. In FIG. 2 the closing element 23 is shown as a floating element. However, the closing element 23 may also be designed as a large surface non-return valve possibly with a low force spring connected to the bottom of the chamber 17. The closing element 23 may be arranged at a guide or rail which guides the closing element 23 to the inlet 19. Moreover, a pressure increasing element 25 is provided which may increase the pressure within the chamber 17 and in this way to eject the coolant 9 into the sample vessel 11. In the embodiment shown in FIG. 2A to 2E the pressure increasing device 25 is designed as a resistor 27, in particular as a wire with a high resistance. The resistor 27 is arranged in the pump 15 in direct contact with the coolant 9 within the chamber 17. Alternatively, the pressure increasing device 25 is designed as a piston pump 29 as shown in FIG. 2F. The piston pump 29 may be arranged inside or outside the Dewar vessel 1 and may be connected to the chamber 17 via a tube for delivering gaseous coolant.

(17) Furthermore, a control device 35 connected to the pump is provided in the Dewar vessel 1. The control device 35 is shown only schematically in FIG. 2A. The control device 35 may be electrically or functionally connected by wires or wirelessly to components of the pump 15.

(18) For example, the control device 35 may be connected to the pressure increasing device 25 in order to activate or to actuate the pressure increasing device 25 at the right moment. Moreover, the control device 35 may be connected to the non-return valve 39 or to the restrictor 41 for opening the access to the sample vessel 11 at the right moment.

(19) Also, the control device 35 may be connected to a fill level sensor 37. The fill level sensor 37 may be optionally arranged within the chamber for determining a fill level of coolant 9 in the chamber 17. The fill level sensor 37 may be arranged at or in the vicinity of the inlet 19 as shown in FIG. 2A. Alternatively, the fill level sensor 37 may be included or integrated into the closing element 23 as shown in FIG. 2B. Furthermore, the control device 35 may comprise an energy source or be connected to an energy source. Moreover, the control device 35 may comprise a memory on which predefined values e.g. for necessary fill levels of the chamber 17 are stored.

(20) In the following the functionality or operation of the pump 15 is explained. As shown in FIG. 2A, chamber 17 automatically fills by gravity flow through the inlet 19. This happens during a thermal equilibrium time, i.e. while the pressure inside and outside the chamber 17 equilibrate.

(21) As shown in FIG. 2B the closing element 23 closes the inlet 19 as soon as the chamber 17 is full with coolant 9 or alternatively if a certain amount of coolant 9 is in the chamber 17. The control device 35 (not shown in FIG. 2B) determines or detects that that the chamber 17 is filled with coolant 9. This may for example take place by a fill level sensor or a contact sensor which transmits a corresponding signal to the control device 35. Alternatively, the control device 35 determines that the chamber 17 is filled based on a certain amount of time which passed since the last pumping cycle.

(22) FIG. 2C shows the next operational step of the pumping cycle. After the chamber 17 is filled with coolant 9 and closed by the closing element 23, the pressure increasing device 25 is activated by the control device 35. In the embodiment of FIG. 2C the pressure increasing device is a resistor 27 which is supplied with electric power via the control device 35. At the resistor 27 the electric power is partially transformed into heat and transferred to the coolant 9 within the closed chamber 17. This results in evaporating of a part of the coolant 9 in the chamber 17 which leads to an increase in pressure.

(23) FIG. 2F shows an alternative to the increase of pressure within the chamber 17. According to the embodiment in FIG. 2F the pressure is increased via a piston pump 29 which presses gaseous coolant 9 or any other gaseous substance into the chamber 17. Therein, the piston pump 29 may fill with gaseous coolant aspirated from the chamber 17 in an aspiration phase.

(24) When the pressure within the chamber 17 reaches a predetermined level the non-return valve 39 at the outlet 21 of the chamber 17 opens and the coolant 9 is expulsed via line 31 into the sample vessel 11. In the alternative embodiment shown in FIG. 2F the non-return valve 29 is replaced by a restrictor 41. In a further alternative line 31 may replace the functionality of a restrictor 41 by creating sufficient load. In the case of a restrictor 41 flow of coolant through the outlet 21 starts immediately when the pressure increases. However, the restrictor 41 limits the flow and makes possible the pressure increase in the chamber 17. After the pressure in the chamber 17 reaches the predetermined value, the coolant 9 flows fast through the restricted tubing shown in FIG. 2F. The pressure increase is fast enough for the inlet 19 to remain closed until most of the coolant 9 is ejected from the outlet 21. In particular, in the embodiment of FIG. 2C the heat may be provided in a flash.

(25) As shown in FIG. 2E, the equilibrium is reached after the emptying of the coolant 9 form the chamber 17 and the closing element 23 falls due to gravity as shown in FIG. 2A again. Thus, the inlet 19 is open and the chamber 17 fills again by gravity with coolant 9. In this way the next cycle of the operation starts. Therein, the pump 15 functions in a pseudo volumetric way. I.e. the amount of coolant 9 delivered in each cycle of operation to the sample vessel 11 is approximately the same and corresponds to the volume of the chamber 17. The volume expulsed can also be controlled by the amount of heat or volume of gas provided in the chamber. Furthermore, the pump 15 is advantageously simple and therefore does not require a lot of maintenance. Furthermore, the connection of the pump 15 to the external world is limited to a few electrical wires or to a pneumatic tube.

(26) It has to be noted that embodiments of the invention are described with reference to different subject matters. In particular, some embodiments are described with reference to method type claims whereas other embodiments are described with reference to the device or system type claims. However, a person skilled in the art will gather from the above and the following description that, unless otherwise notified, in addition to any combination of features belonging to one type of subject matter also any combination between features relating to different subject matters is considered to be disclosed with this application. However, all features can be combined providing synergetic effects that are more than the simple summation of the features.

(27) While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. The invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing a claimed invention, from a study of the drawings, the disclosure, and the dependent claims.

(28) Furthermore, the term comprising does not exclude other elements or steps, and the indefinite article a or an does not exclude a plurality. The mere fact that certain measures are re-cited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

LIST OF REFERENCE SIGNS

(29) 1 Dewar vessel

(30) 3 thermally insulated reservoir

(31) 5 casing

(32) 7 layer of vacuum

(33) 9 coolant (liquid nitrogen)

(34) 11 sample vessel

(35) 13 opening of the Dewar vessel

(36) 15 pump

(37) 17 chamber

(38) 19 inlet

(39) 21 outlet

(40) 23 closing element (e.g. floating element or non-return valve)

(41) 25 pressure increasing device

(42) 27 resistor

(43) 29 piston pump

(44) 31 line

(45) 33 particle filter

(46) 35 control device

(47) 37 fill level sensor

(48) 39 first non-return valve (of the pump)

(49) 41 restrictor (throttle valve)

(50) 43 ice draining port

(51) 45 bottom of sample vessel

(52) 47 second one-way valve (at the sample vessel)

(53) 49 overflow from sample vessel

(54) 50 pipe

(55) 51 cover

(56) 52 overflow from pipe