US 3764780 A
A portable apparatus for use in hospitals for the collection and preparation of blood samples under controlled conditions comprising a culture-tube holder in a heavily insulated heat sink provided with thermostatic controlled heater for connection to public service power during the heat-up time in the laboratory; and the heat sink enhanced in effectiveness by the use of a fusible material such as paraffin for the purpose of maintaining a constant temperature environment for the culture tubes while the apparatus is being transported to the hospital rooms, where the blood samples are taken, and then back to the laboratory for incubation. The paraffin, of a pure form, characteristically has a sharp melting point and absorbs heat during the melting period which is returned at constant temperature as the material freezes.
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Description (OCR text may contain errors)
Unite States Patent [191 Ellis 1 BLOOD CULTURE APPARATUS Charles A. Ellis, 501 Point Rd., Marion, Mass. 02738  Inventor:
 U.S. Cl 219/430, 165/104, 219/433,
219/436, 219/439, 219/441, 219/521, 219/530  Int. Cl. F27d 11/02  Field of Search 219/209, 210, 430,
[451 Oct. 9, 1973 2,932,718 4/1960 Marsters 219/521 2,993,979 7/1961 Hornsby 219/212 FOREIGN PATENTS OR APPLICATIONS 169,295 10/1934 Switzerland 219/439 Primary Examiner-Velodymyr Y. Mayewsky Attorney-Char1es A. Ellis  ABSTRACT A portable apparatus for use in hospitals for the collection and preparation of blood samples under controlled conditions comprising a culture-tube holder in a heavily insulated heat sink provided with thermostatic controlled heater for connection to public service power during the heat-up time in the laboratory; and the heat sink enhanced in effectiveness by the use of a fusible material such as paraffin for the purpose of maintaining a constant temperature environment for the culture tubes while the apparatus is being transported to the hospital rooms, where the blood samples are taken, and then back to the laboratory for incubation. The paraffin, of a pure form, characteristically has a sharp melting point and absorbs heat during the melting period which is returned at constant temperature as the material freezes.
4 Claims, 5 Drawing Figures  References Cited UNITED STATES PATENTS 3,110,633 11/1963 Bachmann 136/161 2,897,334 7/1959 McFarlane et a1 219/436 3,264,448 8/1966 Lehner 219/210 2,431,582 11/1947 Page 219/442 1,946,220 2/1934 Lotz 219/440 2,907,861 10/1959 Melton 1 219/433 X 3,310,652 3/1967 Williams 219/530 X 2,052,014 8/1936 Chamberlain... 165/104 X 1,455,909 5/1923 Ditton 219/430 2,313,015 3/1943 Hesse 219/540 X I IS r I 3 t :x '1 1 z O V r A r r I A it t 5 I v w d 1 :1 /E w v t s 2 I ,2 w y I V PATENTED UB7 9 I973 SHEET 10F 2 TIME PATENTED BET 91975 SHEET 2 BF 2 BLOOD CULTURE APPARATUS BACKGROUND OF THE INVENTION This invention is broadly a heat storage device of a form that is readily transportable and characterized by a fusible heat storage medium whereby a substantial quantity of the stored heat may be returned at constant temperature.
The immediate application for this device is for an apparatus for the collection of blood samples for culturing under controlled conditions in a hospital laboratory. It has been the custom to take blood samples at bedside, in collection tubes, and carry these back to the laboratory under ambient conditions and to prepare the cultures in the laboratory. However, in many instances the blood had clotted by the time it reached the laboratory and in so doing introduced biological as well as mechanical changes to the blood character thus introducing the possibility of erroneous samples. Under the system for which the subject apparatus was developed the culture medium is prepared in the laboratory and carried to bedside at constant temperature in the apparatus. There a sample of fresh blood is taken and immediately placed in a tube of the culture medium and mixed by shaking. The tube is then replaced in the apparatus, still at constant temperature, for transport back to the laboratory where the culture is processed.
One of the principal objects of this invention is to provide a portable constant-temperature container for culture tubes.
Another object is to provide an apparatus for maintaining a constant temperature for a significant period of time in excess of one hour in the absence of power.
A further object is to provide apparatus whereby freshly taken samples of blood for laboratory culturing may be conveniently introduced into the culture medium with minimum loss of time and change of biological state.
Yet another object is to provide an apparatus for the temporary storage of culture medium at a constant temperature provided by the latent heat of fusion of the material of the primary heat sink.
Another object is to provide a simple equipment of the character described that will be economical to manufacture and involve a minimum of maintainence.
Other objects and advantages will be apparent from the description which follows:
Referring to the drawings:
FIG. 1 is a perspective view of the apparatus as viewed from slightly above;
FIG. 2 is a vertical diametral section showing details of construction and location of the culture tubes;
FIG. 3 is a graph showing the relation between time and temperature as measured in a typical culture tube.
FIG. 4 is a diagram of one modification of this apparatus.
FIG. 5 is a partial vertical diametral section relating to FIG. 4 showing immersed thermostatic switch.
Referring now in greater detail to the drawings where like numerals indicate the same object in the various views:
FIG. 1 illustrates one embodiment of this invention.
The apparatus comprises two major elements; a body the bottom through an insulating bushing, 22, and terminates in a male plug, 5, which serves to connect the heater to electric power. On the opposite side a tell-tale light, 6, is shown; its purpose being to indicate when power is being supplied to the heating coil. A handle, 7, for lifting the cover is centrally located on the top surface thereof.
In the sectional view of FIG. 2 the body, 1, is seen to consist of an outer protective shell member, 8, of metal; an inner vessel, 9, also of metal and having an outwardly flared upper rim, 10. This rim receives the circumferential portion, 40, of the top of a metal cul ture tube holder generally indicated at 11 and the lower outwardly flanged edge, 12, of the liner generally indicated at 13. These parts are cement bonded or otherwise fastened together at this point. The vessel, 9, is preferably of a highly heat conductive metal such as copper and carries wrapped upon its vertical walls a helically wound heating cable, 14. The heating cable is connected in series with a thermostatic control switch, 15, to the power cord 4. The tell-tale light, 6, is connected by conventional means in parallel with the heating so that it will be lighted only when power is being supplied to the heater. The thermostatic switch is cemented to or held in firm heat conductive contact with the bottom surface of the vessel, 9, and has a downwardly projecting adjustment screw, 16, extending in alignment with a hole, 17, in the bottom surface of the shell, 8, through which it may be reached for temperature adjustment. The vessel, 9, is supported within the shell, 8, by three insulating posts, 18, cemented to the innner bottom surface of the shell, these being of cork or balsa to minimize heat loss to the shell.
The liner, 13, is preferably made of an insulating material such as a styrene or styrene acrylonitrile copolymer also to minimize heat loss to the shell. Its vertical cylindrical wall, 19, is evenly spaced from the inner shell surface by an outwardly flared upper rim, 20. Glass fiber, 21, is used as an insulating heat barrier between the walls of the shell, 8, and the liner, 13, and vessel, 9. Electrical insulation of the line cord from the shell is provided by the bushing 22.
The culture tube holder, 11, is of copper for maximum heat conductivity and consists of a flat header section, 23, in which are secured a number of cavities or culture tube holding jackets, 24, having closed bottoms as indicated at 26. The vessel, 9, contains a quantity of fusible material, 27, such as paraffin, and this in turn surrounds and contacts the various tube holding jackets. A small vent hole, 28, is provided in header 23 through which air may pass during the heating and cooling cycles. This is necessitated by the expansion and contraction of the paraffin and trapped air in the otherwise sealed vessel. Culture tubes, 29, containing a culture medium, when placed in the tube holding jackets, 24, are effectively immersed in the heated paraffin, 27, without being in actual contact with it, because of the high conductivity of the copper material.
The cover, 2, is comprised of an outer metallic shell,
\ 30, which receives a liner, 31, in telescoping relation,
these parts being held together by a through screw, 32, having its head socketed in the center of liner 31 passing through shell 30, and is threadedly received by the handle 7. A low heat conductive material such as a styrene or styrene-acrylonitrile plastic is preferred for the liner 31. The space between shell 30 and liner 31 is filled with glass fiber heat insulation material, 33.
Referring now to FIG. 3, a chart is shown representative of the temperature-time relationship that might be measured in a typical culture tube in this apparatus starting from room temperature RT at time zero when the power to the heating coil is turned on. Heat is supplied from time zero until point 34 is reached when the thermostatic switch acts to cut off power. Temperature continues to rise to a maximum at point 35 because of the loose coupling between the thermostat and the heater. From point 35 on the temperature drops at a rate determined by the heat loss through the walls of the apparatus. If only solid materials were used to store the heat energy the temperature would drop through point 36 to point 39 and onward at a slightly decreasing rate. However, when the melted paraffin material reaches its congealing temperature at 36 the temperature within the equipment remains at a constant temperature while the heat used in melting is given off. After a time at this temperature point 37 is reached when the paraffin has congealed and from 37 to 38 the temperature falls again at a rate determined by the heat losses through the walls of the apparatus. The rate of decrease of temperature from 37 to 38 is exactly the same as it would have been had there been no fusible material and the path 36 39 been followed. It is to be understood that the degree to which the ideal of zero temperature change from 36 to 37 is reached is determined by the choice of material. A pure n-Tetracosane with melting point at l.l C will exhibit such a constant temperature characteristic. In contrast, commercial paraffin has been found to have a less definite melting point but still is capable of the exchange of a large quantity of heat in a 2 C range which translated into a temperature loss of less than 34 C for a three hour period in a'sample device containing two pounds of paraffin and holding a dozen culture tubes, which is adequate for many purposes.
In FIG. 4 the heating cable, 14, is shown connected in parallel with tell-tale light, 6, both supplied through thermostatic control switch, 15, with power from lines 40 and 41. The timing motor generally indicated at 42 is electrically connected at one side to line 40 and at the other side through the thermostatic control switch, 15, to the second line, 41. The movable contact of the thermal control rests when cold upon contact 43 to supply power to the heating cable and when control temperature is reached, transfers to contact 44 to energize the coil 48 and start the timing motor. Mechanically driven by the timing motor is a cam, 45, having high and low segments. A switch member, 46, is biased to hold toward the surface of cam 45 and is connected at one end to power source 41. When on the low segment of the cam the contact rests upon contact 47 thus completing the power circuit to the heater. When on the high portion of the cam the power to the heater is denied. The dwell periods on high and low segments are proportioned to permit the supply of power for a period sufficient to store a high percentage, say 80 percent of the latent heat of fusion and to allow time for the return of this amount of the latent heat to supply heat losses before reconnecting the supply of power.
In use this equipment is first connected to power and allowed to store heat until the pilot light indicates that the shut-off temperature has been reached. It is then removed from the power line and culture tubes at 50 C placed in the holders and the whole allowed to equilibrate. The apparatus use period is that time between the points 36 and 37 of FIG. 3. During this period the apparatus can be freely transported for sample collection and the culture medium will remain at known substantially constant temperature except for the short period for introduction of the blood sample and shaking to mix the sample.
This apparatus takes advantage of the physical change of state of a material. The change of state from solid to liquid or from liquid to vapor is brought about by the addition of heat. In chemically pure substances this change takes place at a specific temperature and the heat required to bring about the change is known as the latent heat. More specifically the latent heat absorbed during melting is called the heat of fusion and that absorbed during change from liquid to vapor is the heat of vaporization. If the material is not chemically pure or is a mixture of chemically pure substances the transitions generally take place at lower temperature and over a range of temperature. This phenomenon of absorbtion is a two-way proposition and the heat thus put in in melting and vaporizing is given off again as the material congeals or condenses.
Where portability is not required by constancy of temperature is a prime consideration the device may be modified to produce constant temperature for a continuous period by using the fusible material as a heat energy flywhee1." In this case a timer would be arranged to turn power ON just before the point 37 was reached on the time-temperature curve. The timer would be arranged to be turned to OFF just before remelting was complete so that heat would be added always at the fusion point. For complete effectiveness the control element in this case should be as closely coupled to the fusible material as possible as by immersion in it, as shown in FIG. 5, and means should be provided within the fusible material to aid in the even distribution of the heat energy rapidly because of the low heat conductivity. High heat conductive members extending from the heating element or even a mechanical stirrer would satisfy the latter requirement.
A convenient table of the normal saturated hydrocarbons that form the series of higher homologs of methane is shown on page 33 of Organic Chemistry, by Feiser & Feiser, second edition, D C. Heath & Co., Boston.
It is apparent that all of the objects and advantages have been accomplished. It will also be apparent, however, that changes may be made in the details of construction and arrangement of parts shown and described above without departing from the spirit of the invention as expressed in the accompanying claims. Therefore, it is to be understood that all matter set forth or shown in accompanying drawings is to be interpreted as illustrative and not in a limiting sense.
1. A heated test tube holding apparatus for maintaining the tubes at a substantially constant temperature while tubes and contents are in transit between bedside and hospital laboratory comprising in combination: an insulated container; a second container within said insulated container; a test tube receiving body within said second container having spaced test tube holding cells; a quantity of fusible material selected from the normal saturated hydrocarbon series that are higher homologs of methane and having a melting point at the desired temperature of operation, and the said material within said second container and in contact with a major portion of the length of the said tube holding cells; a resistance wire heating element wound upon the outer surface of said second container adapted, when connected to a power source, to supply heat for melting the said fusible material; an indicator lamp in parallel with the heating element adapted to indicate the energized condition of the heating element; and a thermostatic current interrupting switch in good heat conductive relationship with the said fusible material adapted to shut off power to the heating element as soon as the temperature of the fusible material exceeds its melting point, whereby, upon disconnection from the power source, heat stored as latent heat of fusion within the fusible material may be used to maintain the temperature of the test tubes and contents at the melting temperature of the fusible material for an extended period during transport as it changes from the liquid to the solid state.
2. The article of claim 1 wherein the fusible material comprises a mixture of the higher homologs of methane selected and compounded to have a melting point intermediate of those available in the single pure substances.
3. A heated test tube holding apparatus for maintaining the tubes and contents at substantially constant temperature for extended periods of time comprising in combination: an insulated container; a second container within said insulated container; a test tube receiving body within said second container having spaced test tube holding cells; a quantity of fusible material selected from the normal saturated hydrocarbon series that are higher homologs of methane and having a melting point at the desired temperature of operation, and the said material within the said second container and in contact with a major portion of the length of the said tube holding cells; a resistance wire heating element wound upon the outer surface of said second container adapted, when connected to a power source, to supply heat for melting the said fusible material; an indicator lamp in parallel with the heating element adapted to indicate the energized condition of the heating element; and a thermostatic current interrupting switch within said second container and immersed in the said fusible material adapted to shut off power as soon as the fusible material reaches its melting temperature; together with cyclical time controlled switching means initiated by the said thermostatic device adapted to first supply energy to the heating element for a period sufficient to permit storage of the major portion of the latent heat of fusion of the fusible material, and second, to interrupt the supply of energy for a further period sufficient to permit the fusible material to supply heat losses of the apparatus from a major portion of the latent heat thus stored, and further adapted to repeat these two operations in a continuous cyclical manner whereby the treatment chamber will remain at substantially constant temperature for any desired period.
4. The article of claim 3 wherein the fusible material comprises a mixture of the higher homologs of methane selected and compounded to have a melting point intermediate of those available in the single pure substances.