| 摘要 |
<p>The invention concerns a freeze vale (2) for controlling the flow of small quantities of liquid in a conduit (1). Further objects of the invention are a network of conduits, a method of opening a freeze valve and a process for the separation of liquid fractions, which all involve the freeze valves (2) of the invention. The freeze valve (2) s defined by a tubular wall (3) integral with the conduit (1) and includes a thermal bridge (4) connecting the wall to a heat sink (5), to close the valve by freezing the liquid inside the wall, as well as a heating element (11) including a source of laser beam targeted at a wall, to open the valve by melting the frozen liquid (7). According to the invention the laser beam (13) is produced in the form of a transversally extended shroud and targeted at the wall (3) at a length extending to both sides of the point of connection (6) to the thermal bridge (4), so as to melt the block of frozen liquid (7) simultaneously along its entire length. The beam (13) can have the form of a divergent fan or flattened cone with across section corresponding to the elongate ice block (7) inside the wall and a radiation intensity higher in the center (15) of the beam and decreasing towards the beam edges (16). The beam can be obtained from a laser diode (11) and tailored and/or directed by optical means (12) as necessary. The network of conduits with freeze valves can be employed in analyzers for clinical chemistry, and the separation processes can be capillary electrophoresis or chromatography, where the freeze valves are used to immobilize the separated liquid samples.</p> |
