Laboratory device for optional heating and cooling.

p0001In biochemical and biological or genetic laboratory, one is often faced with the task of bringing small quantities of materials to a certain temperature and to hold during a longer or shorter time. Equipment for this purpose are known and widely available commercially. Are generally known as thermostated liquid baths, especially water baths. They consist of a larger vessel, usually of a few liters, which is equipped with an electric heater, a stirrer and often also provided with a circulation pump. By a temperature sensor, the heater can be controlled so that the temperature of the moving or recirculating liquid can be maintained at a given, preset value. In certain cases, a cooling device is provided for such liquid baths that allows to keep the liquid temperature below the ambient temperature. That is, the liquid bath can be used in this case as a cryostat. As cooling devices for such cryostat conventional, operating according to the compression or adsorption refrigerating unit be used.

p0002Such liquid baths, which can be kept at a constant temperature by heating or cooling are suitable for many laboratory tasks and practical to handle. They are suitable both for the thermostating of samples in vessels that are placed directly into the liquid bath, a ls for the external heating or cooling of samples by liquid circulation.

p0003For heating larger or smaller samples, in particular fluid samples, and electric heating plates are often provided, which may also be equipped with a temperature probe and a thermostatting device. Also known are the commercially available laboratory hot plates, where in addition a motor-driven rotating permanent magnet is installed. Thus, a heating plate located on the liquid sample may be simultaneously or stirred by means of a submerged in the liquid magnetic bar.

p0004The laboratory thermostats described above respectively. -kryostaten with stirred or circulated liquid bath have the disadvantage that they are relatively heavy, lots of space and - in relation to the effective demand - also consume a lot of energy. The heating plates commercially available, with or without additional stirring apparatus, are naturally only for the case in which the target temperature of a sample is above the surrounding room temperature.

p0005Just for the biochemical, biological and genetic laboratory but is often required eg when working with living cells or cell components such as protoplasts or cell nuclei, and with living tissues, embryos and organs performing a temperature cycle which extends partially above and partially below room temperature. Compared to chemical or physical laboratory practice here are the temperatures to be maintained generally comparatively little above or below the room temperature. The typical temperature range for working in the biological or biochemical laboratory is approximately between -5 and +60^OC.

p0006The special conditions in the biological laboratory also in other respects special demands on the tools to be used: working vessels frequently used, such as the flat Petri dishes are bad for the use in liquid baths; the alcohol is often used as a refrigerant intermediaries in cryostat is due to the activity of its vapors in biological laboratory usually undesirable; restricted space conditions, as they are given as the aseptic work in clean air chapels, require the use of special space-saving devices. Of particular importance when working with organic, especially living material is often also the observance of sterility.

p0007The ice commonly used in biological laboratory for cooling has many drawbacks: it needs to be replaced frequently, and requires for its provision of a large and relatively expensive machine. It is also not have to keep sterile readily, and its handling is in many cases, for example, also impractical for cooling the flat petri dishes. Another disadvantage of ice as the coolant is by its constant temperature of 0^OC conditionally. Although lower temperatures can be achieved by the addition of salt, but also the programming in temperature changes due to the constant temperature of the coolant is difficult to carry out.

p0008Purpose of the present invention is to provide a handy device available, can be heated with low space and energy requirements and cooling or through predetermined temperature cycles with the material and fluid samples, and which meet the specific needs of the biological, biochemical and genetic is designed laboratory. In particular, the device is designed so that temperature cycles that move partly above and partly below room temperature, can be readily performed. The device also has a very small space and is easy to keep sterile. It can be equipped with the necessary means for stirring the sample or can be accommodated due to its low weight and small size, even on a conventional shaker. The separation of the device into a working part of a hand, and a power supply and control part on the other hand proves to be a particular advantage.

p0009The working part of the inventive apparatus consists essentially of a block (1) made of good heat conducting metal, preferably aluminum or stainless steel, which is heated electrically and can be cooled with a flat working surface (2), to which either directly a vessel with the sample or - can be mounted a likewise composed of highly thermally conductive metal work module (14) with one or preferably more matching recesses (15) for sample vessels - in another embodiment.

p0010In serving as a working part metal block (1) are, taken near the center, one or several Peltier elements (5), the thermally active pole surfaces (6) and (7) in thermal contact, on the one hand with the metal block (1), and on the other hand are connected to a heat exchanger (8). there is an insulating layer (9) between the metal block (1) and the heat exchanger. Likewise, the metal block along its border by a further insulating layer (10) is surrounded.

p0011The Peltier elements (5) consist of cuboid blocks, in which a large number of semiconductor pairs in parallel and electrically connected in series, is a compact summary. Such Peltier blocks warm up during the passage of a direct current on a surface and cool, respectively, to the opposite surface from. By reversing the current direction, the warming and the cooling down of surface can be interchanged with each other. The bieden a slowing respectively. warming surfaces are referred to as thermally pole faces.

p0012Now if the device are in heating mode, the current direction is selected such that the upper thermal pole surfaces (6) of the Peltier elements heat up and the counter surfaces (7) cool down. The heat released is transmitted to the metal block (1) on whose surface (2) to be heated samples respectively. the sample vessels receiving work modules are provided; the cooling of the lower surfaces (7) is transferred to the heat exchanger (8).

p0013To increase the cooling respectively. Heating effect may be used as needed a larger number of Peltier elements. If these, electrically connected in parallel, arranged in a single layer, so the thermal capacity multiplied according to the number of elements used; the attainable temperature difference between the pole surfaces which is essentially limited by the internal conductivity of the Peltier elements, thereby remains unaffected. However, it is also possible to arrange the Peltier elements in two or more vertically stacked layers, with the opposite pole surfaces of two superimposed thermal Peltier elements are in contact. This immediately superposed elements are thus thermally connected in series, and the achievable temperature difference between the respectively with the metal block. the heat exchanger in contact stationary outer pole faces can be increased. Of course, can also be used at the same time, when using a larger number of Peltier elements, parallel and series connection.

p0014In one embodiment, the heat exchanger consists of a metal block which is crossed by a system of channels through which a coolant is circulated as water. In another embodiment shown in Figures 1-3, the heat exchanger consists of a metal block, whose outer surface is held particularly great in the form of ribs. By means of a blowing by a fan (13) airflow generated a rapid heat exchange with the surrounding air can be achieved. The temperature difference between the hot and the cold surface of the Peltier elements is kept as small as possible, and the efficiency optimized.

p0015For cooling operation, the current direction is reversed, so that now cools the upper surface (6) of the Peltier elements and the bottom surface (7) is heated. The metal block (1) is thereby cooled; the at the lower surface (7) of the respectively. of the Peltier elements of heat given off is transferred to the heat exchanger (8) and is discharged from there to the surroundings.

p0016The heated and cooled working part with the metal block (1) is also through additional exchangeable work modules (14,17) in the form of metal blocks, with openings (15) for introducing a whole series of sample vessels, such as jars, vials, tubes or thin stalks , so-called. "Straws" supplements. Such block-shaped modules for different types of vessels are easy on the work surface (2) provided, or possibly screwed, being careful by accurate surface machining on a good thermal contact. The non with the work surface (2) of the metal block (1) in contact outer surfaces of the modules are thermally insulated.

p0017In another embodiment, the interchangeable work module of a rectangular open tray (33) having a laterally superior foot plate (34) serving for heat exchange with the working table (2). Tub and footplate can be made in one piece; the bottom surface of the latter has the purpose of good contact with the work table (2) to be processed as accurately as possible. The module can either be simply mounted or bolted to the table of the heating and cooling device.

p0018The trough of the power module can be filled with a liquid in which the sample vessels are inserted. To record the sample vessels to cover the pan with either a grid or a cover with matching holes for plugging the vessels. In another embodiment, the tub is filled with a solid in particulate form (40), for example in powder, grain or spherical shape. Suitable example is graphite powder or a filling of balls maximum diameter of about 5 mm made of metal or glass. Such solid filling can hold the sample containers in any position; a special pan cover with holder is therefore unnecessary. The voids between the solid particles can also be filled with a liquid, bringing the heat transfer can be further improved.

p0019In a further embodiment is the open trough for receiving replaceable inserts (43, 45) of metal, which in turn provided with openings (42, 44) are provided for receiving the sample containers. To facilitate the transfer of heat, the stakes must of course be fitted possible narrowly tolerance in the tub; the same applies for the fitting of the sample vessels in the designated openings. Grip screws (52) that can be screwed into the designated holes of the inserts are used for comfortable insertion and extraction of scarce seated inserts out of the tub.

p0020With all embodiments of the trough-shaped work module to use a heat-insulating lid (4), which may be for the purpose of good closure is also provided with a sealing ring (49) and screwed to the tub. Suitably the screws (47) for fixing the cover with the aforementioned grip screws for inserts are designed identical and interchangeable.

p0021Another embodiment of a module to be placed onto the working surface consists of a metal block (17), which is equipped with internal channels (18) through which a liquid is circulated by a pump. This liquid is either the sample itself, or, for example water or alcohol for use in an external heat exchange.

p0022A separate, with the working device via the socket (27) is connected supply and control part (32) provided for the supply and control of Peltier elements, in which one part is a switch mode power supply (20) for the supply of the feed-direct current and on the other hand one of a temperature sensor influenced control electronics (21) are incorporated, by means of which a preset temperature is sought. By installation or external connection by means of the socket (28) of a microcomputer also all temperature cycles can be programmed.

p0023Clocked power supply are used for the DC power supply of the Peltier elements chopped alternating current of the network at a high frequency and then transforms it to a low voltage. The low strained AC is finally rectified and smoothed and is then available as a feed stream for the Peltier elements (5) are available. This type of feed allows the construction of a small and lightweight device with optimum efficiency, which produces only a small proportion of unwanted heat.

p0024The controller also includes a display device (22) at which either the SET temperature, or the actual temperature of either the working block or, after switching by the switch (33), the sample can be read even. The signals to be supplied by corresponding temperature probes: one in the metal block (1) built-in probe for the temperature of the working surface and a via the socket (27) with the power supply and control part connected external probe (11) for the measurement of the sample temperature. On the device is a switch (24), by means of which can be switched to cooling or heating optional. If one uses the control unit includes a microcomputer programmed to perform temperature cycles, as is the function of this switch, ie the choice of heating or cooling mode automatically by the control unit based on the measured ACTUAL bezw.-SET temperature.

p0025The power supply of the unit is normally taken from the AC mains. However, it is also possible to feed the provided with a corresponding terminal (29) device with direct current, for example from a car battery of 12 V voltage. This is suitable in itself handy device especially for mobile working, eg in a car, in a train or even in an airplane or spacecraft.

p0026The separation of the working part of the supply and control part provides anywhere particular advantages where the heating and cooling unit must be housed in a confined space, or where developed at the power supply heat loss in samples close is undesirable.

p0027The construction of the device is shown in the following figures 1 to 8, without implying the possible embodiments are intended to be limited in any way:<ul><li><u>Fig. 1</u> shows a perspective view of the inventive device with the heatable and coolable metal block (1), the flat work surface (2), the ribbed heat exchanger (8), the fan (13) and the insulation layers (9) and (10).</li><li><u>FIG. 2</u> shows the device in cross-section, with the metal block (1), the user interface (2), a Peltier element (5) with the upper (6) and lower (7) thermally active surface, the built in the metal block internal temperature sensor (11), the finned heat exchanger (8) and the insulation layers (9) and (10).</li><li><u>Fig. 3</u> shows a view of the front face of the device with a fan (13).</li><li>The <u>FIGS. 4a and 4b</u> show the device with an additional module in the form of a parallelepiped-shaped metal block (14), the 0effnungen (15) for the reception of work vessels. The optionally removable insulating sheath (16) protects the module from the temperature equalization with the environment.</li><li>The <u>Fig. 5</u> shows a work module (17) is pumped through the one to be cooled or heated liquid with internal channels (18). The insulating jacket (19) protects the metal block of the module before the temperature equalization with the environment.</li><li>The <u>Fig. 6</u> shows a trough-shaped module with two different inserts in a perspective view. The open trough (33) with the foot plate (34) is enveloped by an insulation layer (35). The lid (36) with the sealing ring (49), by means respectively in the holes 37th 37 'inserted screws are screwed onto the working surface (2) of the heating and cooling unit. The insert (41) is for use with tube-shaped sample containers, the insert (43) with rectangular cells for use with optical cuvettes for spectroscopy. The grip screws (51) which can be screwed into the holes (46) serve for convenient manipulation of the inserts.</li><li>In the <u>Fig. 7</u> is a cross-section through that shown in Fig. 6 module taken along line A --- A is shown, wherein the tub (33) of the module Mi balls (40) is filled. The work table (39) of the metal block (2) is shown with its insulation (48) here; the screws (50) used to fasten the module to the metal block (2) of the heating and cooling unit.</li><li>In the <u>Fig. 8</u> the feed and control apparatus (32) ready, with the clocked power supply unit (20), the control electronics (21), the LCD display (22) for the temperature, an on-off switch for the power supply (23) and a switch (24) for selectively heating or cooling mode, as well as a push button (25) for selectively switching the temperature display on the set sET or aCTUAL temperature. With the push button (26) may be chosen to be achieved during the heating or cooling setpoint temperature. (27) the connection of the temperature probe for the sample temperature; an additional connection for the respectively in heatable. coolable working block (1) built-in temperature probe (11) is housed in the connection cable (30) containing the feed line for the Peltier elements. either the power cord (31) or the terminal (29) is used for a 12V battery for the power supply. With the switch (33) the temperature display (22) is selectively switched to the internal or external temperature probe. An external microcomputer for programming of temperature cycles can be connected to the socket (28).</li></ul>