Heat exchanger

Aug. 17, 1965

G. S. BIRD, JR

HEAT EXCHANGER

3,200,601

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FIG.2

INVENTOR

GORDON S. BIRD JR.

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ATTORNEY

Aug. 17, 1965

G. S. BIRD, JR

HEAT EXCHANGER

3,200,601

Sheets-Sheet 2

Filed Oct. 25, 1962

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FIG. 5

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FIG.4

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FIG.6

INVENTOR.

GORDON S. BIRD JR.

BY

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ATTORNEY

United States Patent Office Patented Aug. 17, 1965 ing out of the invention, such disclosed means illustrating, however, but one of the various ways in which the principle in the invention may be employed.

In the drawings:

FIG. 1 is a view in perspective of the apparatus embodying the feature of this invention;

FIG. 2 is a top plan view, partly broken away of the power supply of the apparatus;

FIG. 3 is a view in section of the operational head of the apparatus;

FIG. 4 is a top plan view partly in section of the operational head of the apparatus;

FIG. 5 is an end view of the operational head and cooling duct of this invention; and

FIG. 6 is an electrical schematic of this invention.

Reference is now to be had to the drawings wherein an illustrative embodiment of the medical instrument, a construction made in accordance with the present invention and designated by the reference numeral 10 is shown.

The medical instrument consists primarily of a cabinet 12 having outlet ports 14 and 16 on the front and rear sides 18 and 20. A carrying handle 22 is positioned on the upper surface 24 to permit transporting the apparatus to various locations.

As illustrated in FIGS. 1 and 2 the front panel 18 of the cabinet 12 contains an on-off switch 26 and an indicator light 28. The rear surface 20 of the cabinet 12 contains a variable rheostat at 30 for a purpose to be more fully described hereinafter.

Certain operating components of the invention are positioned within the cabinet as shown in FIG. 2 and included therein is a fan motor 32 secured to the base 34 of the cabinet 12 by a transversely extending bracket 36. Attached to the shaft 38 of the fan motor 32 and extending 35 in the direction of one end 40 of the cabinet 12 is a rotary impeller 42. A partition 44 extends transversely across the interior of the cabinet 12 having a port 46 formed therein so as to be in alignment with the intake of the impeller 42. Extending laterally away from the partition 44 40 and contiguous with the edges of the port is a circular flange 47 having an external diameter less than the diameter of a flexible duct 48 which is inserted thereover. Located within the cabinet 12 is a conventional direct current power supply 50 having the capability of providing 45 10 amperes and either 142 or 184 volts. A plurality of thermal dissipating heat sinks 52 are mounted on a panel 53 adjacent the other end 54 of the cabinet 12.

As illustrated in FIGS. 3-5 the operational head 56 which is positioned at a point remote from the cabinet 12 is disposed adjacent the free end 58 of the flexible duct 48. As shown in FIG. 3 the operational head includes N and P types of thermoelectric couples 60 which are composed of a quaternary alloy of Bismuth Teluride. The thermoelectric couples 60 are arranged alternately ⁵⁵ and spaced from each other by a fibrous glass wool insulation 62. The couples 60 are connected by a copper strip 64 to effectuate the flow of electric current therethrough and an aluminum plate 66 acts as the freezing plate and is secured to the upper surface 68 of the con60 necting copper strip 64. The exterior of the thermocouples 60 are surrounded by a poly-urethane foam 79 to insulate the sides from a chrome plated outer housing 72. The leads 74 coming from the power supply 50 are directly connected to the lower copper strip 64 as il65 lustrated in FIGS. 3 and 5.

The operational head 56 is bonded by an epoxy resin to the upper surface 78 of an air cooled heat sink 80.

The heat sink 80 comprises a hollow rectangular box having a plurality of heat conducting folded metal fins g2 positioned therein adapted to conduct heat away from the operational head 56 and conventionally carried away from the area through the flexible duct 48. A mounting

3,200,601 HEAT EXCHANGER

Gordon S. Bird, Jr., Brighton, Mass., assignor, by mesne assignments, to Sanbern Mortgage and Finance Co., Boston, Mass.

Filed Oct. 25,1962, Ser. No. 233,074 1 Claim. (CI. 62—3)

This invention relates generally to medical instruments and in particular to a thermoelectric device for use as a heat exchanger in the preparation of histological specimens prior to microtomic operations.

In the preparation of organic tissues for microscopic examination, it is essential that sections of an extremely thin nature are sliced from the original sample. Since the tissue sample is normally at room temperature, a method must be provided to maintain the tissue sample in a rigid state for the proper operation of a microtome.

Heretofore in medical technology two methods are in use to maintain a sample in a rigid state. One method involves the employment of hot paraffin to permeate the sample, allowing the paraffin to cool to present an inflexible paraffin tissue structure. There are several disadvantages with this method, the major one being that tissue slices in the magnitude of six microns or less are virtually impossible to obtain and secondly it is a time consuming operation. The other method utilizes carbon dioxide gas applied directly to tissue samples from a cylinder in such a manner as to freeze the sample and change it to a rigid state. However, cylinders of carbon dioxide gas are extremely bulky and are more or less in a fixed position within the laboratory thus requiring all preparation of slides to be made in a predetermined location.

Furthermore in both the paraffin and carbon dioxide methods of preparing tissues, special jigs must be provided to hold the sample during the operation of the microtome.

Therefore it is an object of this invention to provide a thermoelectric medical instrument which will quickly freeze tissue samples into a rigid state.

Another object of this invention is to provide a portable, compact and light-weight thermoelectric medical instrument adapted to prepare organic tissues for sectioning by a microtome.

It is another object of this invention to provide a medical instrument for the preparation of organic tissues for sectioning which will quickly accomplish its ultimate purpose and which has relatively few moving parts.

A further object of the invention is to provide a universal tissue preparing instrument which can be readily used 50 with existing microtomes without the use of special adapters.

Another object of this invention is to provide a medical instrument in which the degrees of freezing of tissue specimens may be varied.

Other objects of the invention will, in part, be obvious and will, in part, appear hereinafter.

Broadly stated one feature of this invention is to provide a medical instrument which is capable of lowering the temperature of an organic tissue sample to —32° C. in three minutes and maintaining this temperature so that slices having a thickness in the magnitude of six microns may be taken with a microtome. Since time is an important factor in biopsy examinations, on smaller specimens the temperature can be reduced to zero degrees centigrade in 25-30 seconds enabling a report to be returned to the surgeon during the actual operation.

To the accomplishment of this and the foregoing related ends, the present invention then consists of the means hereinafter fully described and particularly pointed out in the claim, the annexed drawings and the following description setting forth in detail certain means in the carry3,200,601

.. . ³ jig 83 is secured to the under surface of the heat sink 80 for a purpose to be set forth hereinafter.

In FIG. 6 there is illustrated an electrical schematic having the line voltage connected by a conventional plug (not shown) at 84 with the όη-off switch 26 positioned in the line. The remainder of the circuit includes a fuse port 86, indicator light 28, fan motor 32, rheostat 38 and a transformer 88. The secondary of the transformers is adapted to deliver 10 amperes at either .42 or .84 volt to the rectifiers 90 which in turn passes through a choke 92 across a capacitor 94 to the leads 74 which convey the D.C. current to the thermo-couples 6®.

In operation the mounting jig 83 is inserted in the microtome holder in an upright position and an organic sample placed on the aluminum plate 66. The on-off switch energizes the power supply 50 and simultaneously the fan motor 32. Due to the action of the thermocouples 60 heat is drawn from the sample and radiated over the metal fins 82 and due to the action of the induction fan drawn in the direction of the cabinet 12 through the flexible duct 48. Under optimum operating conditions i.e., where the room temperature is at approximately 25° C., the following time and temperature relationships have been established:

Time: Temperature, ° C.

25-30 seconds 0 minute—10

1½ minutes___ —15 minutes —20 minutes —25 minutes —32

When the temperature is reduced sufficiently for the proper operation of the microtome, the jig may be rotated in the clamp so as to present the specimen for slicing without the necessity of removing the sample from the operating head.

With smaller samples of tissue the variable rheostat 30 may be adjusted to regulate the power supply and vary the time required to freeze the sample.

Furthermore it will be seen that utilizing an induction type air flow through the heat sink 80 provision is made to cool off the components disposed within the cabinet with particular emphasis on the rectifiers 80 as to maintain the temperature there within a 50-55° C. range.

While there have been described herein what are at present considered preferred embodiments of the invention, it will be obvious to those skilled in the art that modifications and changes may be made therein without departing from the essence of the invention. It is therefore to be understood that the exemplary embodiments are illustrative and not restrictive of the invention, the scope of which is defined in the appended claim, and that all modifications that come within the meaning and range of equivalency of the claim is intended to be included therein.