Patent Application
20170328600
The present invention relates to thermal baths for heating biological samples in a laboratory. More specifically, the present invention relates to a system and method of precisely controlling the temperature and thermal uniformity of a thermal bead bath to heat, or in some cases cool biological samples more efficiently, precisely and with more temperature uniformity. The present invention provides a thermal airflow system to uniformly maintain the control temperature desired in thermal bead bath.
Thermal bead baths have been used by laboratories engaged in biological and/or biomedical research to heat biological samples, and are currently used in such laboratories. In previous embodiments of thermal bead baths, aluminum beads were placed in standard laboratory water bath, and the water bath provided heat to the beads. However, problems have arisen in the use of these bead baths to heat biological samples. Specifically, aluminum beads typically used in such baths are inefficient conductors of heat, and the heating source only supplies heat from the perimeter of the bath. Thus, aluminum bead baths typically suffer from slow warm up times and the inability to achieve thermal uniformity. The heating of the aluminum beads also creates hotspots within the bath, which furthers the problem of thermal discrepancy within the baths. Some have attempted to overcome these challenges by designing baths and control systems specifically for the aluminum beads to eliminate hot spots. However, these baths still experience slow warm up or ramp up times, poor thermal uniformity, poor control and slow response to changes in control temperatures.
The fundamental problem with the thermal bead bath approach is that it is created and operated on the concept of thermal conductivity. Thus, there is a dependency upon thermal conductivity from bath to bead, bead to bead, and then bead to sample. The more the heat is conducted through the elements of the system, temperature variance and heat loss occur. It is therefore desirable to design a system for achieving a desired temperature of a biological sample wherein the temperature throughout the system is controlled with precision and maintained substantially uniformly. It is further desirable for this system to utilize non-liquid, non-fluidized bead baths yielding high thermal efficiency and consistency with suppressed contamination of the beads.
The present invention overcomes the issues of prior thermal bead baths by providing a recirculating thermal air supply to heat the bulk bead volume contained in the bath. The system transfers thermal energy through the laboratory bead bath and provides improved warm-up speed, thermal uniformity, thermal recovery and overall temperature control. The present invention also is more energy efficient and produces fewer temperature gradients, enabling end-users to thaw reagents or samples more quickly.
The present invention achieves these advantages by supplying heated air to the bulk bead volume, which is the combination of the volume of the beads and the volume of the void space between adjacent beads. Thus, the need for thermal conductivity between adjacent beads is greatly reduced. The present invention provides a closed thermal air recirculation system comprising an insulated outer shell, an inner shell for receiving a mesh basket holding the beads, at least one air injection port, at least one thermal sensor, at least one thermal element, at least one air extraction port, a fan aerodynamically positioned to draw air out of the air extraction port, and a cover. A “fan” of the system of the present invention is meant to encompass, include and mean a fan, a centrifuge blower, an air pump or any other device for circulating air or drawing air.
The outer shell is insulated between its outer wall and the inner air shield. There is an inner shell with its top edge adjacent a top inner edge of the outer shell. The outer shell is generally cylindrically shaped and defines a cavity within the outer shell. The inner shell is disposed within the cavity and is adjacently attached along a top surface to a top surface of the outer shell. The inner shell comprises a side wall and a bottom surface, defining cavity. The inner shell is partially conically shaped. The inner shell recesses in diameter as it extends downward into the cavity of the outer shell such that it is spaced from the inner air shield to define a space between the inner air shield and the inner shell. The space between the inner air shield and the inner shell provides a recirculation pathway for recirculation of air.
The bottom surface of the inner shell comprises an air extraction port. A fan is disposed at an aerodynamic position to draw air through the air extraction port. In one embodiment, the fan is disposed on a bottom surface of the outer shell and in close proximity to the air extraction port, and is oriented in an upward direction. However, the fan may be located anywhere in the system where it can draw air through the air extraction port. In one embodiment, an air filter is provided over the air extraction port to trap bacteria and microbial agents. However, in another embodiment, no air filter is used. The sidewall of the inner shell comprises a plurality of air injection ports which are disposed partially above and partially below a desired fill line of thermal beads. Each air injection port is substantially equally spaced from adjacent air injection ports. Disposed along the inner air shield is a plurality of thermal elements which are connected to a controller (not shown). Any thermal element known in the art of thermal baths may be used.
The thermal elements and the controller are connected to an electrical power distribution block within the outer shell. The thermal elements are connected to the controller and the controller controls operation of the fan and the thermal elements. The fan resides within a diverter plate. The diverter plate comprises a plurality of air distribution ports (not shown) around its periphery. The fan is connected through the diverter plate to a motor within the outer shell which runs the fan. The motor is also connected to the electrical power distribution block, which is connected to a power source (not shown). In another embodiment, the outer shell has an extended periphery, and a recessed cavity within the extended periphery, defining an outer cavity. In this embodiment, the fan is connected to the motor through the bottom of the outer shell. The motor and electrical power distribution block are attached to the outside of the outer shell within the outer cavity. In one embodiment the motor is a variable speed motor that is connected to the controller (not shown) to control the speed of the fan. However, in another embodiment, the motor is a one speed motor operated by the controller.
At least one thermal sensor is disposed within the recirculation pathway in close proximity to one of the air injection ports, and is attached to the inner air shield. In the preferred embodiment, only one thermal sensor is used. However, in an alternative embodiment, more than one of the plurality of air injection ports has a thermal sensor disposed on the inner air shield and extending into the recirculation pathway in close proximity to its corresponding air injection port. In another alternative embodiment, a thermal sensor is placed, alone or in addition to the other one or more thermal sensors, between the fan and the air extraction port. In yet another embodiment, a thermal sensor is placed, alone or in addition to the other one or more thermal sensors within or above the beads in the inner shell. A cover is removably disposed above the outer shell and inner shell and completely covers the inner shell. In one embodiment, a gasket is disposed along the periphery of the cover to engage an indentation along the periphery of the outer shell to form a substantially air-tight engagement between the cover and the outer shell.
In one embodiment, a mesh basket is removably disposed within the inner shell. The mesh basket holds the thermal beads and the biological samples. The thermal beads fill the mesh basket to a desired level. In an alternative embodiment, there is no mesh basket, but rather a wire mesh cover over the injection port. In this embodiment, the thermal beads and biological samples are placed directly in the inner shell to a desired level.
Once the thermal beads are placed in the inner shell, either directly or in the mesh basket, the user secures the cover over the inner shell. A user sets the controller to a desired control temperature, which activates the heating elements to provide heat. The fan is operated by the controller. The fan rotates within the diverter plate and creates a negative atmosphere to draw air out of the bulk bead volume. The air moves through the air distribution ports (not shown) of the diverter plate into the recirculation pathway and upward across the thermal elements to the air injection ports.
Once at the air injection ports, the air is at atmosphere and is injected into the internal shell and through the bulk bead volume where it is drawn back to and through the air extraction port. In the preferred embodiment, the thermal sensor is connected to the controller and sends the temperature information to the controller. In the alternative embodiments where more than one thermal sensor is used, the plurality of thermal sensors, whether along the plurality of injection ports, within the inner shell, or between the fan and the air extraction port, are connected to the controller and each sends its respective temperature information to the controller.
Referring to
Referring to
Along an upper portion of sidewall 27, a plurality of air injection ports 22 are disposed through sidewall 27 and extend into recirculation pathway 24. Bottom 29 of inner shell 20 comprises an air extraction port 28 extending through bottom 29 and into recirculation pathway 24. Air extraction port 28 is shown as being substantially circular. However, air extraction port 28 may be of any other shape. In one embodiment of the present invention, a filter 36 may be disposed along bottom 29, extending over air extraction port 28. Filter 36 is an anti-microbial filter to filter bacterial or other microbial agents out of the air as it flows through the system of the present invention 10. In another embodiment a mesh wire overlay 42 is placed over air extraction port 28. In another embodiment of the invention, filter 36 may be placed over mesh wire overlay 42.
Referring to
Fan 30 is disposed within, and rotates within a diverter plate 34. Diverter plate 34 comprises a plurality of substantially equally spaced air distribution ports (not shown) below fan 30 for distributing air into the recirculation pathway. Fan 30 extends through diverter plate 34 and is connected to motor 32. Motor 32 is connected to an electrical power distribution block 50 which is connected to an electrical source (not shown).
In one embodiment, motor 32 and electrical power distribution block 50 are attached to an interior surface of a bottom 17 of outer shell 12. However, as shown in
Referring again to
Referring to
Although the present invention 10 can work well with any thermally conductive or thermally non-conductive beads in the art, referring to
This design of beads 100 provides optimal void space between adjacent beads 100 to moderate airflow restriction, and eases insertion of containers of various shapes and sizes containing samples 50. As force is applied during sample insertion into the system of the present invention 10, the aspherical design of beads 100 allows the beads 100 to rotate in place, thus reducing the linear dimension of the beads 100 along the axis of the force (not shown). This rotation results in an increase of localized bead bed density and less bead 100 movement, which reduces the insertion force into the system of the present invention 10. In one embodiment, beads 100 are made of a polymer such as polypropylene, and are minimally thermally conductive. However, in other embodiments, beads 100 may be made of any suitable thermally conductive material out of which other thermally conductive beads are made.
Referring to
Fan 30 is oriented within recirculation pathway 24 and diverter plate 34 such that air is drawn out of inner shell 20, as indicated by airflow directional arrows A in
As shown and described, airflow A through the bulk bead volume is vertical from top to bottom through inner shell 20. However, it should be understood that other airflow patterns may be used depending on the size and/or shape of the system of the present invention 10. Other airflow configurations include, but are not limited to vertical bottom to top, laterally side to side, radial, or any combination thereof. Moreover, the system of the present invention can operate with thermally non-conductive beads or thermally conductive beads effectively, due to the fact that the system of the present invention 10 is heated by heating recirculating air instead of requiring the walls to provide heat to the system, which require heat transfer through the medium, as is done with all other baths of the prior art.
The system of the present invention 10 is further illustrated by the following Examples, which should not be construed in a limiting sense.
The system of the present invention 10 was compared against a standard, universally accepted laboratory water bath (not shown), and a standard bead bath using thermally conductive aluminum beads (not shown). Two variations of the system of the present invention 10 were tested. First, a system of the present invention 10 wherein thermally conductive aluminum beads (not shown) was tested. Second, a system of the present invention 10 wherein thermally non-conductive polymer beads (not shown) was tested. “Thermally non-conductive polymer beads” means, for purposes of this disclosure, beads having a thermal conductivity value low enough so as not to be a significant contributor to the thermal conductivity of the system of the present invention 10. All baths were tested with each bath's respective factory installed digital controllers with 0.1° C. digital readouts. All samples were tested with digital controllers with 0.1° C. digital readouts, and connected to 0.1° C. thermal digital probes. The following Table 1 shows the results of the tests of the four baths:
Temperatures were monitored, and the amount of time in minutes to achieve a control temperature were recorded in Table 1. First, the amount of time in minutes was recorded for the bath type to achieve 38° C. was recorded. Recording of time was taken from room temperature of each bath type to 38° C. Standard water bath achieved 38° C. in thirty six minutes. The system of the present invention 10 using thermally conductive aluminum beads (“Thermal Air Recirculation—Aluminum” in Table 1) achieved 38° C. in twelve minutes. The system of the present invention 10 using thermally non-conductive polymer beads (“Thermal Air Recirculation—Polymer” in Table 1) achieved 38° C. in five minutes. Standard aluminum bead bath achieved 38° C. in ninety minutes.
Next, volumes of samples were inserted into containers and into each bath type. Distilled water was used as the sample. Containers for the 10 ml and 50 ml samples were conical test tubes, and the container for the 500 ml sample was a standard laboratory bottle. Distilled water in the amounts indicated in Table 1 were inserted into the containers at a temperature of 7° C., and the time in minutes taken by each bath type for the sample to achieve 35° C. was recorded. The results are found in Table 1 for each bath type and each sample. Both the Thermal Air Recirculation—Aluminum and Thermal Air Recirculation—Polymer achieved the desired temperatures of the samples substantially quicker than the standard aluminum bead bath.
Next, volumes of samples were inserted into containers and frozen to −20° C. Distilled water was used as the sample. Containers for the 10 ml and 50 ml samples were conical test tubes, and the container for the 500 ml sample was a standard laboratory bottle. Distilled water in the amounts indicated in Table 1 were inserted into the containers and frozen to at a temperature of −20° C., and the time in minutes taken by each bath type for the sample to achieve 35° C. was recorded. The results are found in Table 2 herein below for each bath type and each sample. Both the Thermal Air Recirculation—Aluminum and Thermal Air Recirculation—Polymer achieved the desired temperatures of the samples substantially quicker than the standard aluminum bead bath.
In this example, a standard rectangular bead bath (not shown) was filled with aluminum beads (not shown). A digital controller with 0.1° C. digital readouts was connected to four 0.1° C. thermal digital probes. Two of the probes were inserted in diagonally opposite corners of the bath from one another; with one being closest to the temperature sensor, and both being inserted one half the depth of the aluminum bead media depth. A third thermal probe was inserted in the center of the aluminum bead media, approximately one inch from the top thereof. A fourth thermal probe was inserted in the center of the media approximately one inch from the bottom of the bath.
Temperatures were measured and recorded for each thermal probe in one minute increments for over one thousand minutes.
In this example, a system of the present invention 10 was tested to determine thermal uniformity at different locations within the polymer bead media. A digital controller with 0.1° C. digital readouts was connected to six 0.1° C. thermal digital probes (not shown). Three of the probes were placed along the center vertical axis of the bead media: a first probe one inch from the top of the bead media, a second probe one inch from the bottom of the bead media, and a third probe substantially equally distant between the first and second probes. A fourth probe and a fifth probe opposed one another on lateral sides of the bead media and approximately half way down in depth. A sixth probe was disposed above the bead media near an air injection port 22.
Temperatures were measured and recorded for each thermal probe in six second, or 1/10 of a minute increments.
Second ramp up of the system of the present invention was from 45° C. to 50° C. Again, substantial thermal uniformity was observed, with thermal variance being observed to be no greater than a few tenths of a degree. During plateau at 50° C., the time to reach useful stability was observed well under ten minutes from ramp up, and variance was generally observed to be no more than one tenth of a degree.
Although the invention has been described with reference to specific embodiments and working Examples herein, this description is not meant to be construed in a limited sense. Various modifications of the disclosed embodiments and Examples, as well as alternative embodiments of the invention will become apparent to persons skilled in the art upon the reference to the description of the invention and the Examples. Such embodiments include, but are not limited to embodiments of the system of the present invention 10 wherein the outer shell 12 and inner shell 20 are of different shapes and configurations, including but not limited to rectangular embodiments. Moreover, thermally conductive beads, thermally non-conductive polymer beads, or other known alternatives to aluminum thermally conductive beads may be used as the medium within mesh basket 44. It is therefore contemplated that the appended claims will cover such modifications that fall within the scope of the invention.
The present application is a Divisional of U.S. application Ser. No. 13/793,863, filed Mar. 11, 2013.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 13793863 | Mar 2013 | US |
| Child | 15668495 | US |
