Refrigeration – Using electrical or magnetic effect – Thermoelectric; e.g. – peltier effect
Patent
1995-03-21
1996-05-14
Sollecito, John M.
Refrigeration
Using electrical or magnetic effect
Thermoelectric; e.g., peltier effect
62 33, 62 36, 623241, F25B 2102
Patent
active
055156835
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND
1. Field of the Invention
The present invention relates to thermoelectric heating and cooling devices. More particularly, the invention pertains to apparatus for overcoming thermal limitations in heating and cooling devices that utilize arrangements of Peltier elements of higher and lower power levels.
2. Description of the Prior Art
It is known that refrigerators equipped with Peltier modules are capable of also operating in the opposite sense. That is, they can also provide a heat chamber, provided that they are surrounded by a housing. In comparison with compressor devices, such refrigerators possess the great advantage that they can be electronically controlled very accurately to attain a constancy of temperature that cannot be achieved by other refrigerating techniques. Peltier heating/cooling chambers of the prior art have a disadvantage in that the adjustable temperature range is very limited and/or the outlay for the power loss "to be pumped away" is too great. The plate-shaped Peltier elements, generally connected in a cascade arrangement, cannot then be adequately protected against overheating (in particular at the edge zones). This applies both to Peltier cascades in one plane (cf. British patent application GB-A-2 241 378) and, to a greater extent, to pyramidal arrangements of a plurality of Peltier cascades (cf. DD-A-0 049 626 and U.S. patent Ser. No. 4,833,889).
The solutions disclosed by the above-cited patent publications permit only limited heating operation of the cascade arrangement of Peltier elements. This is due to the fact that overheating of a portion of the Peltier elements can easily occur. Such overheating gives rise to other disadvantages. For one, as a result of a restricted heating operation, rapid temperature changes to an upper limit are neither permissible or possible. Secondly, greater electric power is required in heating operation. On the one hand rapid wear results from soiling of the semiconductor material and, on the other hand, material stresses result from greater expansions.
SUMMARY AND OBJECTS OF THE INVENTION
It is therefore an object of the invention to provide a thermoelectrically operated heating and cooling unit, in particular a heating and cooling chamber with corresponding heat insulation, that can be operated over a significantly greater temperature range.
Another object of the invention is to achieve the foregoing object with a device in which the outlay for power dissipation loss is not unacceptably large.
The present invention addresses the foregoing by providing an improvement in a thermoelectric device of the type that includes a plurality of Peltier elements in the region of a base area that are connected one behind the other in cascade arrangement and distributed in a heating and cooling area. Such device further includes a heat dissipating means located on an outer surface. The Peltier elements are subdivided into two groups of different power stages and arranged into two mutually parallel layers so that the Peltier elements of lower power form a first, inner heating and cooling area and the Peltier elements of higher power form a second, outer heating and cooling area. The Peltier elements of higher power are covered by the heat-dissipating means.
The improvement provided by the invention resides in the thermoelectric device being installed within a heating/cooling chamber with heat insulation. In addition, at least one of the Peltier elements of highest power is electrically bypassed by means of a bypass diode polarized so that, during heating operation, no electric current flows through a bypassed Peltier element.
The preceding and other features and advantages of the present invention will become further apparent from the detailed description that follows. Such written description is accompanied by a set of drawing figures. Numerals of the figures, corresponding to those of the written text, point to the features of the invention. Like numerals refer to like features throughout both the written description and the drawing figures
REFERENCES:
patent: 2978875 (1961-04-01), Lackey et al.
patent: 2998707 (1961-09-01), Meess et al.
patent: 3088288 (1963-05-01), Elfving
patent: 3091939 (1963-06-01), Baude
patent: 3125860 (1964-03-01), Reich
patent: 3195344 (1965-07-01), Francisco
patent: 3934758 (1976-01-01), Kipp
patent: 4671070 (1987-06-01), Rudick
patent: 4833889 (1989-05-01), Harwell et al.
Kramsky Elliott N.
Litef GmbH
Sollecito John M.
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