This application claims priority of Austrian patent application number A 1762/2011 filed Nov. 29, 2011, the entire disclosure of which is incorporated by reference herein.
The invention relates to the processing of samples under cooled conditions. The invention further relates to a system for cooling a sample for processing of the sample in a processing device.
Processing apparatuses of the kind recited are manufactured for the preparation of samples in particular for producing microtome sections. For this, for example, tissue samples to be investigated are embedded in synthetic resin and these samples are processed by means of a milling cutter into the shape of truncated pyramids (so-called “trimming”). The samples trimmed in this fashion are then sectioned in a microtome, with the result that tissue sections having a thickness in the micrometer or nanometer range are obtained, which can then be investigated.
The Applicant has developed a unit suitable for such purposes, which is described in EP 1 923 686 A2=US 2008-0115640 A1 and is already on the market in an implementation under the designation “Leica EM TXP.”
Cover 101 serves as an accidental contact protector during sample processing. The lower part of cover 101 can moreover be used as a collection pan for polishing agent or other liquids that are directed onto the sample. The upper part of cover 101 is transparent and removable; it is equipped with a switching element that interrupts rotation of the tool is the cover is removed.
Apparatus 100 comprises an observation device 103, for example a stereomicroscope, that serves for viewing of the sample. If applicable, a measurement device that enables monitoring and/or measurement of the sample can be provided in the observation device. In a preferred variant of the invention, for example, a measuring eyepiece is used in the stereomicroscope; with this the sample itself, but also the progress of the processing action, can be accurately measured. Other systems, such as e.g. video cameras and the like, can also be utilized as observation device 103.
To allow the sample to be cooled or lubricated during processing, unit 101 can be equipped with a pump 106; via an inflow 107a, a cooling or lubricating agent is delivered (from a reservoir container, not depicted) to pump 106 and is conveyed via an outflow 107b from pump 106 to the sample.
Sample mount 104 is held in an arm 102 that is pivotable around a horizontal axis S that extends perpendicular to the viewing direction of observation device 103. The pivoting of sample mount 104 by means of the arm allows the sample to be brought into different working positions, for example a measurement position, a processing position, and a monitoring position.
In the processing position (which is not shown in
This known unit of the Applicant is, however, like other conventional units of this kind, designed principally for processing hard samples or at least dimensionally stable samples, and not for processing samples that are soft at room temperature.
Processing of samples at low temperatures is described, for example, in the Applicant's DE 40 28 806 C2=U.S. Pat. No. 5,299,481, which discloses a microtome having a cooling chamber accessible from above. Cooling of the sample and of other cooled parts in the cooling chamber occurs here exclusively by way of the gaseous cryogen with which the chamber is charged. This prevents the deposition of moisture from the environment onto the sample as ice (as a result of displacement by the gas), as well as direct contact by the sample with cooling liquid; but it does considerably complicate reliable setting of the sample temperature, and limits the achievable cooling performance.
It is therefore an object of the invention to make possible the processing of samples while the samples are cooled to a desired settable temperature, while at the same time condensation of cooling liquid and/or moisture/ice on the sample and the sample environment is to remain precluded.
The stated object is achieved by a system for cooling a sample of the kind mentioned earlier, in that according to the present invention, the holding device can be cooled to a settable temperature by means of a fluid coolant, the holding device comprising a coolant conduit through which the coolant can flow and which for that purpose is furnished with the coolant at the input end and opens into the cooling chamber at the output end; in addition, there is provided in the cooling chamber a window through which a tool receptacle (of the sample processing apparatus), which serves to receive a tool for processing the sample, is positionable in a manner projecting into the cooling chamber, and in that context usefully is arranged without contact with the chamber.
The stated object is likewise achieved according to the present invention, in the context of the processing of samples under cooled conditions, by a method having the steps of:
This approach allows the stated object to be achieved in surprisingly efficient fashion. Cooling of the sample occurs not as a result of contact with coolant, but by heat transfer via the holding device. The interior of the chamber is filled only with coolant gas, which serves less for cooling than for the displacement of (as a rule, moist) ambient air, which avoids undesired condensation of moisture as ice. The tool as such is not cooled (only indirectly via the coolant gas inside the chamber); cooling of the tool is dispensable, and results in a simplification of the configuration of the apparatus.
According to an aspect of the invention it is advantageous, as already indicated, if the cooling chamber is designed to hold in its interior a gas atmosphere that is constituted by the coolant and surrounds at least the sample. For this, after cooling the holding device the coolant can flow into the cooling chamber, and can create therein a cold gas atmosphere. Outflow of the gas can be enabled by the fact that the cooling chamber comprises, in addition to a window, an opening that is arranged on the upper side of the cooling chamber, although the cooling chamber is otherwise (i.e. aside from the aforesaid window and the opening) substantially closed off from the environment of the apparatus. “Substantially closed off” means here that the chamber comprises no openings that, when the processing system is in the operating state, permit an inflow of ambient air or the like, although minor gaps, e.g. between movable parts, can be permitted if, for example, coolant gas can penetrate through them to a sufficient extent and thereby suppress any inflow of gases from outside. The cooling chamber can thus contain a gas atmosphere that is constituted by the coolant and surrounds at least the sample.
In order to allow reliable setting of the temperature of the sample on the holding device, a temperature control system can be provided which is designed to guide a liquid cryogen, in particular liquid nitrogen, in the coolant conduit and evaporate it, and to allow only gaseous cryogen to travel into the cooling chamber. A temperature sensor associated with the temperature control system, which sensor is arranged at the output end of the coolant conduit in order to monitor the passage of liquid cryogen, is suitable for preventing the cryogen from traveling in a liquid state into the cooling chamber.
For provision of the coolant, the coolant conduit can comprise at the input end a coolant connector that is designed for connection of a coolant line of an external coolant vessel.
In a particularly advantageous refinement of the invention, the holding device is arranged on a pivot arm that enables pivoting of the sample around a pivot axis with respect to the tool receptacle. The pivot arm can be arranged outside the cooling chamber, such that a base of the holding device and/or the sample holder projects through an opening into the cooling chamber. This opening can furthermore be closed off by a shield that is pivotable together with the holding device or the sample holder. The previously mentioned coolant connector can moreover be oriented coaxially with the pivot axis. In a favorable embodiment, the arrangement of the coolant connector and pivot arm can be such that the pivot arm is held by a joint located to the side of the cooling chamber, and the coolant connector is arranged on that side of the cooling chamber which is located opposite the joint.
According to a further aspect of the invention, the system for sample cooling is removable, so that the cooling chamber together with the holding device and pivot arm is embodied in a sample cooling arrangement that is removable from the sample processing apparatus. In the context of a removable system, the cooling chamber can have a connection interface by way of which it is detachably mountable on the aforementioned apparatus for processing samples; the aforesaid window, through which a tool receptacle projects in the state mounted on the apparatus, is provided in this context inside the connection interface.
A further aspect of the invention relates to an apparatus for processing samples of the kind recited earlier, in which apparatus the holding device together with a cooling chamber is embodied in accordance with the above-described system according to the present invention.
The invention, along with further details and advantages, will be explained below with reference to an exemplifying embodiment, namely a sample processing apparatus having an arrangement for sample cooling that is removable as an add-on unit, which arrangement is shown in the appended drawings. In the individual drawings, in schematic form:
The exemplifying embodiment described below represents a further development of the unit discussed earlier with reference to
Referring to
Apparatus 10 further comprises, as already mentioned earlier, an observation device 13 (e.g. stereomicroscope) as well as a pump 14 with which the sample can be supplied with a liquid during processing; for processing with grinding discs, for example, a low-temperature-compatible liquid can be introduced as a grinding agent for wet grinding. Tube 15 can be guided, on the upper side of the cooling chamber, through a separate opening in order to bring the liquid to position P of the sample. The lower part of chamber 12 can in turn serve as a collection pan for said liquid. It is significant in this context that in the processing position, the sample and the tool are held in substantially horizontal axes, since this allows excess grinding liquid to flow off quickly and decreases undesired deposition of solids.
Arrangement 11 for sample cooling is shown in
Arrangement 11 thus integrates the components of the system according to the present invention for sample cooling into a system that advantageously is removable as a unit.
Arrangement 11 is mounted on apparatus 10 by means of a connection interface 17 that is embodied on chamber 12 and that surrounds a window 47. Upon mounting onto apparatus 10, the chamber is positioned like a cap over tool receptacle 16, so that the tool receptacle projects through window 47 into the interior of chamber 12 but without touching components of the chamber. A tool mounted on tool receptacle 16 can thus move freely inside window 47 to the extent necessary for processing the sample.
Arrangement 11 can be brought with the aid of pivot arm 21 into a variety of working positions, e.g. a processing position (
The sample is positioned at a predefined position P with respect to tool W or tool receptacle 16 with the aid of a sample holder 20. The sample is symbolized here by its position P. Sample holder 20 is embodied preferably as a separate detachable component, and is fastened in a holding device 22 so that a sample present on sample holder 20 is entirely located in the interior of cooling chamber 12. Holding device 22 is held by pivot arm 21 at a distance from pivot axis S and comprises a base 25, oriented with respect to the pivot axis, which projects through a passthrough opening 42 into chamber 12 and whose inwardly directed end is set up for fastening and cooling of sample holder 20 together with the sample.
Referring again to
Connector 31 is preferably embodied coaxially with pivot axis S, by the fact that is located rotationally symmetrically with its axis in pivot axis S, and permits a rotation with respect to base part 32, attached to the chamber, of connector piece 30. The result is that the hose connector remains stationary even in the context of rotation of the sample mount; the rotation in connector piece 30 occurs between base part 32 and the attached part (
The liquid nitrogen flows along conduit 24 through holding device 22 in a cooling block 26, evaporates there, and travels as a cold gas through base 25 into cooling chamber 12. The pump for conveying liquid nitrogen (not shown) is regulated, with the aid of temperature sensors and using a heating device (see below with reference to
Referring to
Nitrogen delivery via coolant pump 51 is controlled as a function of the setpoint temperature T. The rotation speed ranges of pump 51 are defined in the software of temperature control system 50 in such a way that for each settable value of the setpoint temperature, the liquid nitrogen becomes gaseous within the meanders of conduit 24. The resulting nitrogen gas is guided through openings 41 into chamber 12 and acts as a protective gas against ice deposits on the cold surfaces in the interior of the chamber. Heating system 35 is operated at only low output, and serves to increase the control accuracy and temperature consistency; without a heating system, the temperature would be several K below the setpoint temperature.
A second temperature sensor 36, preferably arranged close to exit openings 41, for example in a separate orifice 46, can be provided in order to prevent liquid nitrogen from getting into the cooling chamber, said sensor. If the temperature at temperature sensor 36 drops below the temperature of liquid nitrogen, or more precisely to a limit value just thereabove, the nitrogen is converted into the gas phase by additional heating.
The chamber and other external surfaces can additionally be heated in order to prevent the condensation of water.
Consistent with pivotability, a geometry of passthrough opening 42 for the sample holder as an elongated or slot-shaped opening is useful. A shield 29 that is prolonged in wing-like fashion along the pivoting direction on both sides is provided on base 25 in order to close off opening 42 in the various working positions. Passthrough opening 42 is closed off by shield 29 in every pivot position, and undesired emergence of cold gas at this point is suppressed. Provided at the attachment of shield 29 are wave spring washers 39 that counteract lifting of the shield away from the edge of opening 42.
With the aid of the invention it is possible to process samples that are too soft for processing at room temperature, by cooling them to a temperature at which said processing is possible, for example below an associated glass transition temperature. A typical temperature range for processing is, for example, −120° C. to 170° C. Examples of sample materials for which the invention enables processing are, for example, polymer- or rubber-based samples (e.g. structures made of wire or the like embedded in rubber material), as well as biological samples.
The invention is not to be limited to the specific embodiments disclosed, and modifications and other embodiments are intended to be included within the scope of the invention.
10 Apparatus for sample processing
11 Sample cooling arrangement
12 Cooling chamber
13 Observation device/stereomicroscope
14 Pump
15 Tube
16 Tool receptacle
17 Interface
20 Sample holder
21 Pivot arm
22 Holding device
23 Joint
24 Conduit for coolant
25 Base (cooling block)
26 Cooling block
27 Body (of cooling block)
28 Side part (of cooling block)
29 Shield
30 Connector piece
31 Coolant connector
32 Base of connector piece
33 Hose part
34 Heating system/heating cartridge
35 First temperature sensor
36 Second temperature sensor
37 Reservoir
38 Cover plate of reservoir
39 Wave spring washers
41 Exit opening
42 Passthrough opening
43 Observation opening
44, 45, 46 Orifices
47 Window
50 Temperature control system
51 Coolant pump
52 Membrane pump
53 Membrane
54 Eccentric motor
55 Eccentric axis
56 Pump tube
57 Pump head
58 Pump headspace
59 Riser tube
60 Inlet opening
61 Inlet valve
62 Delivery valve
63 Connector for coolant hose
S Pivot axis
P Position of sample
W Tool
T Setpoint temperature
100 Apparatus (existing art)
101 Cover
102 Arm (pivot arm)
103 Observation device/stereomicroscope
104 Sample receptacle
108 Rotary knob for sample mount
105 Opening (in cover)
106 Pump
107
a,
107
b Inflow and outflow of pump
108 Rotary knob for sample mount
Number | Date | Country | Kind |
---|---|---|---|
A1762/2011 | Nov 2011 | AT | national |