Cryostat Having Separate Cooling Circuits for Cooling the Chamber and a Sample Holder

Abstract

According to an aspect of the present invention, a cryostat includes two separate cooling means, one for reducing the temperature in a cooling chamber ( 2 ) and the other arranged to cool a freezing plate ( 8 ). In one embodiment, there may be a single cooling circuit, with e.g. a single reservoir of refrigerant, but with a separate compressor provided for each of the cooling means i.e. one compressor to control the temperature within the cooling chamber (2) and a separate compressor for the cooling circuit associated with the freezing plate ( 8 ). In accordance with another aspect of the present invention, the freezing plate ( 8 ) includes means for retaining some liquid on the surface of the freezing plate. In an embodiment, these means are provided by a lip ( 12 ). In a further aspect a friction generating means provides resistance to the movement of the microtome head, for example by providing a spring loaded collar on rotatable shaft. In a further aspect a cryostat is provided with a touch screen display.

1 . A cryostat including a cooling chamber having cooling chamber fluid supply means for lowering the temperature in the cooling chamber and sample cooling means having sample cooling fluid supply means for lowering the temperature of the sample cooling means, wherein the sample cooling fluid supply means is separate from the cooling chamber fluid supply means.  
   
   
       2 . A cryostat according to  claim 1 , wherein the sample cooling means is located within the cooling chamber  
   
   
       3 . A cryostat according to  claim 1 , wherein sample cooling fluid supply means includes a first compressor and the cooling chamber fluid supply means includes a second compressor, separate from the first compressor  
   
   
       4 . A cryostat according to  claim 3 , wherein either or both of the cooling chamber fluid supply means and the sample fluid cooling supply means include two or more compressors.  
   
   
       5 . A cryostat according to  claim 1 , wherein the sample cooling fluid supply means is capable of cooling to a temperature in the range −300 C to −700 C.  
   
   
       6 . A cryostat according to  claim 5 , wherein the sample cooling fluid supply means is capable to cooling to a temperature in the range −45° C. to −65° C.  
   
   
       7 . A cryostat according to  claim 1 , wherein the sample cooling means is a freezing plate comprising a block of thermally conductive material in thermal contact with the sample cooling fluid supply means.  
   
   
       8 . A cryostat according to  claim 1 , wherein the cryostat is a cryostat microtome, and the cryostat microtome includes a sample mounting stage, sample mounting stage fluid supply means for cooling the sample mounting stage of the microtome, wherein the sample mounting stage fluid supply means is separate from the sample cooling fluid supply means and the cooling chamber fluid supply means.  
   
   
       9 . A cryostat according to  claim 1 , wherein the cryostat includes cooling chamber temperature regulation control means for controlling the temperature of the cooling chamber and sample cooling temperature regulation control means for controlling the temperature of the sample cooling means, wherein the temperature of the cooling chamber and the sample cooing means can be controlled separately.  
   
   
       10 . A method of operating a cryostat having a cooling chamber and sample cooling means, wherein the temperature of the cooling chamber and the temperature of the sample cooling means are controlled separately.  
   
   
       11 . A method according to  claim 10 , wherein the cryostat, includes a cooling chamber having cooling chamber fluid supply means for lowering the temperature in the cooling chamber and sample cooling means having sample cooling fluid supply means for lowering the temperature of the sample cooling means, wherein the sample cooling fluid supply means is separate from the cooling chamber fluid supply means  
   
   
       12 . A method of cooling a sample or sample holder using a sample cooling means having a sample cooling surface, wherein a low freezing point liquid is applied to the sample cooling surface to cover at least part of the sample cooling surface and the sample or sample holder is placed in thermal contact with the low freezing point liquid.  
   
   
       13 . A method according to  claim 12 , wherein the low freezing point liquid has a freezing point below about −200 C.  
   
   
       14 . A method according to  claim 13 , wherein the low freezing point liquid has a freezing point below about −400 C.  
   
   
       15 . A method according to  claim 14  wherein the low freezing point liquid has a freezing point below about −600 C.  
   
   
       16 . A method according to  claim 12 , wherein the low freezing point liquid is miscible with water.  
   
   
       17 . A method according to  claim 16 , wherein the low freezing point liquid will form mixtures with water at water concentrations up to about 10 wt %, at room temperature.  
   
   
       18 . A method according to  claim 12 , wherein the low freezing point i|quid includes as a major component a nontoxic organic compound.  
   
   
       19 . A method according to  claim 12 , wherein the low freezing point liquid is a low molecular weight organic compound.  
   
   
       20 . A method according to  claim 12 , wherein the low freezing point liquid is selected from alcohol, ether, ester ketone, aldeyde, carbocsilic acid and mixtures thereof.  
   
   
       21 . A sample cooling means having a sample cooling surface, wherein the sample cooling means includes liquid retaining means to retain a low freezing point liquid so that it covers at least part of the sample cooling surface.  
   
   
       22 . A sample cooling means according to  claim 21 , wherein the sample cooling means is a freezing plate.  
   
   
       23 . A sample cooling means according to  claim 22 , wherein the retaining means includes a raised lip.  
   
   
       24 . A sample cooling means according to  claim 23 , wherein the raised lip has a depth in the range of 0.5 to 5 mm.  
   
   
       25 . A sample cooling means according to  claim 24 , wherein the raised lip has a depth in the range 0.5 to 2 mm.  
   
   
       26 . A sample cooling means according to  claim 21 , wherein the retaining means include one or more recesses or blind holes in the sample cooling surface.  
   
   
       27 . A sample cooling means according to  claim 21 , wherein the sample cooling means includes sample cooling fluid supply means for lowering the temperature of the sample cooling means.  
   
   
       28 . A sample cooling means according to  claim 21 , wherein the sample cooling means is part of a cryostat.  
   
   
       29 . A sample cooling means according to  claim 28 , wherein the cryostat is a cryostat microtome.  
   
   
       30 . A microtome having a microtome head, a drive mechanism for moving the head, and a friction generating means for balancing the microtome head, the friction generating means being associated with a rotatable shaft of the drive mechanism, wherein the friction generating means is rotatable around the axis of the rotatable shaft when the shaft is rotated so as to move against a surface to provide resistance to rotation of the shaft.  
   
   
       31 . A microtome according to  claim 30 , wherein the friction generating means is connected to the shaft so that it rotates with the shaft.  
   
   
       32 . A microtome according to  claim 30 , wherein the friction generating means is connected to the shaft so that it is coaxial with the shaft.  
   
   
       33 . A microtome according to  claim 30 , wherein the friction generating means includes a collar located coaxially about the shaft.  
   
   
       34 . A microtome according to  claim 33 , wherein the collar is fixed to the shaft with fixing means selected from a pin and screw.  
   
   
       35 . A microtome according to  claim 30 , wherein the friction generating means includes a first member slidably axially connected to the shaft and a resilient means for urging the first member against the surface.  
   
   
       36 . A microtome according to  claim 35 , wherein the friction generating means includes a second member fixed to the shaft so that the resilient means s located between the first and second members.  
   
   
       37 . A microtome according to  claim 35 , wherein the resilient means is a spring.  
   
   
       38 . A microtome according to  claim 35 , wherein the first member is axially slidably connected to the shaft by a pin and corresponding slot.  
   
   
       39 . A microtome according to  claim 29 , wherein the friction generating means has a friction generating surface in contact with a friction generating surface of a member that does not rotate with the shaft.  
   
   
       40 . A microtome according to  claim 39 , wherein the member is fixed with respect to the microtome chassis.  
   
   
       41 . A microtome according to  claim 29 , wherein the surface against which the friction generating means moves is pat of the microtome chassis.  
   
   
       42 . A microtome according to  claim 41 , wherein the surface is the surface of a wall of the microtome chassis.  
   
   
       43 . A microtome according to  claim 30 , wherein the microtome is a cryostat microtome.  
   
   
       44 . A microtome according to  claim 30 , wherein the microtome does not include a spring-loaded roller and timing belt for generating friction to balance the microtome head.  
   
   
       45 . A method of modifying a microtome to provide a friction generating means being associated with a rotatable shaft of the drive mechanism of the microtome, wherein the friction generating means is rotatable about the axis of the rotatable shaft when the shaft is rotated so as to move against a surface to provide resistance to rotation of the shaft.  
   
   
       46 . A method according to  claim 45 , wherein the fiction generating means is for balancing the microtome head, the friction generating means being associated with a rotatable shaft of the drive mechanism.  
   
   
       47 . A cryostat having a control unit with input means by which a user may input control commands in order to control the cryostat, wherein the input means include a touch screen display which combines input functions with one or more display functions.  
   
   
       48 . A cryostat according to  claim 47 , wherein the input control commands which may be inputted via the touch screen display include one or more selected from measured temperature within one or more regions within the cryostat, sample cutting thickness, specimen temperature, freezing plate temperature and chamber temperature.  
   
   
       49 . A cryostat according to  claim 47  wherein the touch screen display is arranged to display different types of information at different times, in response to a user input.  
   
   
       50 . A cryostat according to  claim 47 , wherein the control unit includes security means which require the user to input a security code via the touch screen display in order to operate the cryostat.  
   
   
       51 . A cryostat according to  claim 47 , wherein the control unit configures the touch screen display to display different languages, in response to a user input.  
   
   
       52 . A cryostat according to  claim 47 , wherein the touch screen display provides a common set of buttons that can be used to adjust a plurality of different settings.  
   
   
       53 . A cryostat according to  claim 52 , wherein the common set of buttons includes an up arrow key and a down arrow key.  
   
   
       54 . A cryostat according to  claim 52 , wherein one or more of the size, shape and location of the common set of buttons changes when different information is displayed on the touch screen display.  
   
   
       55 . A cryostat according to  claim 47 , wherein the cryostat is a cryostat microtome.