Methods and apparatus for human motion controlled wearable refrigeration

A wearable, portable, self-contained refrigeration/cooling garment may effectively convert the energy of human movement into heat flux. The heat flux can then used to actively control the temperature of the human body or of part of it. In one example of the present disclosure, the garment is a type of footwear powered by the wearer's ambulation.

FIELD OF THE DISCLOSURE

The present description relates generally to a refrigeration device and more particularly to a human motion controlled wearable refrigeration device.

BACKGROUND OF RELATED ART

U.S. Pat. No. 8,561,399 describes a compressed air energy storage system utilizing two phase flow to facilitate heat exchange. More particularly, the patent describes a compressed-air energy storage system comprising a reversible mechanism to compress and expand air, one or more compressed air storage tanks, a control system, one or more heat exchangers, and a motor-generator. The reversible air compressor-expander uses mechanical power to compress air (when it is acting as a compressor) and converts the energy stored in compressed air to mechanical power (when it is acting as an expander). A suitable valve allows air to enter and leave the pressure cell and cylinder device, if present, under electronic control.

U.S. Pat. No. 8,531,291 generally describes a wearable personal emergency response (PER) system including one or more sensors mounted on a mobile patient. A wireless transceiver communicates with a remote station, and a processor coupled to the sensor and the wireless transceiver requests assistance if the processor detects a fall by the mobile patient.

U.S. Pat. No. 8,487,456 describes a methods and apparatus for harvesting energy from motion of one or more joints. The described energy harvester includes a generator for converting mechanical energy into corresponding electrical energy, one or more sensors for sensing one or more corresponding characteristics associated with motion of the one or more joints, and control circuitry connected to receive the one or more sensed characteristics and configured to assess, based at least in part on the one or more sensed characteristics, whether motion of the one or more joints is associated with mutualistic conditions or non-mutualistic conditions. If conditions are determined to be mutualistic, energy harvesting is engaged. If conditions are determined to be non-mutualistic, energy harvesting is disengaged.

U.S. Pat. No. 7,956,476 describes a system for harvesting footwear energy. The energy may be in a form of footwear movement which involves a compression and decompression of chambers situated in the footwear. There may be a back chamber in the heel area and a front chamber in the toe area of the footwear. The chambers may be filled with gas which moves in and out upon compression and decompression of the chambers at the heel and toe areas upon the ambulatory motion of a person wearing the footwear. The moving gas may go through a pneumatic rectifier that provides a unidirectional stream of gas to spin a micro-turbine which turns an electrical generator, or operate a pneumatic device.

U.S. Pat. No. 7,977,807 describes the use of a hydraulic or pneumatic passageway to create a wearable, portable, washable, and relatively unobtrusive device for converting movement of a relatively large portion of the human body into electricity. The described device includes a flowable substance, passageways through which the flowable substance flows that are worn over the exterior of the human body, and energy-converting members that convert the energy of the flow of the flowable substance into electricity.

U.S. Pat. No. 7,107,706 describes a medical therapy system that includes surfaces provided with adjustable contour, transient force damping and temperature. The described theory system can be applied to footwear, seating surfaces and cryotherapy devices. The cooling and cryotherapy system employs an evaporator in close proximity to skin, and therefore employs methods to reduce the risk of frostbite.

Despite the forgoing, there is a recognized need for a human motion controlled wearable refrigeration device as disclosed herein.

DETAILED DESCRIPTION

The following description of example methods and apparatus is not intended to limit the scope of the description to the precise form or forms detailed herein. Instead the following description is intended to be illustrative so that others may follow its teachings.

The present disclosure generally describes a wearable, portable, self-contained refrigeration/cooling garment. In one example, the garment may effectively convert the energy of human movement into heat flux. The heat flux can then be used to actively control the temperature of the human body or of part of it. In one example of the present disclosure, the garment is a type of footwear powered by the wearer's ambulation.

Referring now toFIGS. 1A-1E, an example of a refrigerating footwear device, such as a shoe10is illustrated. In this example, the shoe10includes a footbed12comprising an integrated refrigeration device14. As illustrated, the footbed12generally includes a midsole portion16and an insole portion18at least partially defining a space20at least partially containing the refrigeration device14. In the illustrated example, the refrigeration device14includes a plurality of distributed chambers30extending between the midsole16and the insole18, wherein the chambers30are operatively, fluidly coupled via at least one channel32. As will be described in greater detail below, the chambers30may be divided into at least two groupings (chamber group30aand30b, respectively) and the groups30a,30b, may be operatively coupled to a regenerator37disposed between the two chamber groups. In the present example, the regenerator may be any suitable thermal inertia element including, for example, a porous metal sponge as illustrated inFIG. 1E. In addition, in this example, the chambers30and the channels32are each filled with air, although it will be appreciated by one of ordinary skill in the art that the fluid may be any suitable gas, liquid, or otherwise. Furthermore, the chemical makeup of the fluid may be any suitable combination.

It will be further understood that the chamber30and the channels32may be separately or integrally formed with the shoe10, and more particularly with the insole18and midsole16as desired. Furthermore, it will be appreciated by one of ordinary skill in the art that the location of the components of the refrigeration device14(e.g, the chambers30, the channels32, and the regenerator37) may be located at any suitable location within the shoe10. Still further, the refrigeration device14can be suitable coupled to any garment and/or article worn or otherwise handled by a wearer as long as the general operating principles of the device14are suitably achieved.

The physical principle exploited in this disclosure relies on the Stirling cycle which allows obtaining a temperature difference (and a corresponding heat flux) by converting an external mechanical input. This principle may be illustrated in the device300illustrated inFIG. 3A. In the disclosed example device300, a basic Stirling refrigerator can be built out of a pair of flexible structures, such as a flexible chamber310a, and a flexible chamber310b, operatively coupled to, and separated by a porous material defining a regenerator312. By properly miniaturizing this device300into the refrigeration device14(e.g. shoes), the device14is able to harvest the energy from human motion and converting it into usable heat flux.

As illustrated inFIG. 3B, a plot320of experimental data shows the time evolution (non-dimensional time scale τ) of the temperature difference between the two chambers.

The human body performance and recovery from intense efforts are drastically affected by the ability to rapidly cool the body's core temperature back to normal values. It is fairly well known that by refrigerating specific parts of the body, such as the hands' palms, the core body's temperature can be quickly reduced to normal values after intense physical activity. This result is possible due to the high concentration in certain parts of the body (e.g. hands, feet, face etc.) of a specific vein type that is responsible for the thermal regulation of the body. These specialized veins, known as AVA (Arteriovenous Anastomoses), are mainly devoted to temperature control. Experimental results have shown that proper refrigeration of these veins is extremely effective in increasing the exercise recovery and performance, and can ultimately affect the endurance of the human body during prolonged physical efforts.

Although initially investigated for its possible impact on athletes' performance, this effect can have critical implications on the performance and endurance of other wearers in various situations, such as for instance, soldiers on the battle field, particularly when operating in a high temperature environment. In fact, it can be realistically envisioned that gloves, shoes or even suits able to maintain or rapidly cool down the body temperature at normal values can be used to enhance the performance and resilience of soldiers to prolonged physical efforts. Despite the discovery and experimental validation of this very promising biomedical effect, current known technologies do not allow for the implementation of portable and wearable refrigerating devices. To-date, refrigerating gloves have been developed only for laboratory testing. These gloves use cold water injected in the glove liner in order to control the temperature and requires bulky equipment to pump and maintain the temperature of the working fluid. It follows that this device is not suitable for practical implementation out of a laboratory or a medical facility environment.

Accordingly, the present device, such as the shoe10enables the fabrication of wearable items with fully embedded and autonomous refrigerating capabilities. In particular, the present disclosure includes the device (e.g., refrigeration device14) that can be fully integrated into the shoe10, and that can harvest the mechanical work produced by the motion of the human body and convert it into heat. This heat flux is then used to cool down selected parts of the human body. It will be appreciated by one of ordinary skill in the art that this device14can be used in at least two different modalities: (1) as a main “refrigeration pump” connected to a specially designed suit with an internal liner in order to achieve full body temperature control, or (2) to control the temperature of AVAs in the lower limbs for improved recovery and performance.

The shoe10is generally based on the physical principle of a Stirling refrigerator. In conventional Stirling devices (see for exampleFIG. 2) two pistons200,202are driven by an external mechanical input (not shown) forcing a working fluid (e.g. air) to flow cyclically between two chambers (210,212) connected by a thermal inertia element, called regenerator214. The periodic motion of the pistons200,202and the corresponding periodic flow of air in the regenerator214result in a temperature gradient between the two chambers210,212and in a net heat flux. Due to this temperature gradient one chamber increases its temperature while the other reduces it over time. Realistically the system can be used as either a heat pump or a refrigerator depending on what chamber is utilized for temperature control.

Based on the operating cycle of a Stirling refrigerator the example refrigeration device14is embedded in the midsole16is able to convert the work produced by the human body during ambulation into heat flux. As described above, to achieve this goal the device14comprises two or more flexible chambers32and the regenerator37. In this example, the flexible chambers32replace the pistons200,202in the conventional Stirling machine design. During ambulation, the flexible chambers32are periodically compressed by the force exerted by the human body therefore forcing the working fluid (e.g. air) to flow through the regenerator37and into the adjacent chamber32. The result of this process is a temperature gradient between the two chambers32.

Preliminary numerical and experimental studies have included a detailed one dimensional mathematical nonlinear model of a conventional Alpha Stirling refrigerator able to capture the effects of different input and design parameters on the performance of the device10. This model provided detailed insight into the operating conditions of the Stirling device as well as a very effective modeling tool to evaluate the impact of different design parameters on the generation of heat flux. As an example, this model provided insight on the effect of the relative phase between the pistons showing that this parameter is one of the main contributor determining amplitude and direction of the heat flux. Additionally, the example device300was utilized in order to show the feasibility of the concept and acquire preliminary data to characterize the performance of the shoe10including the device14. In the device300the regenerator312was implemented by a dense distribution of copper rods in a hollow plastic (HDPE) cylinder.

Although further experimental testing is currently ongoing, preliminary results demonstrate the feasibility of the design and the ability to get a net heat flux. For instanceFIG. 3Bshows the time history of the temperature difference between the two chambers310a,310bof the Stirling device300given an input at the different frequencies of 1 Hz (plot324) and 2 Hz (plot322). As is illustrated, it can be seen that the temperature difference is higher at lower frequency (1 Hz; plot324) than at the higher frequency (2 Hz; plot322). This different may be exploited to extract more energy during regular (low-pace) walking cycles. It is noted that in order to mimic a normal human cadence, the test also utilized a non-perfectly periodic input (results not shown), which are more representative of a realistic walking cycle. Due to the nonlinear character of the system dynamics, this input results in noise-like oscillations produced by the heat flux at nonlinear harmonics. These oscillations are also visible in the periodic 1 Hz and 2 Hz cases but are dramatically amplified by non-periodic inputs. We highlight that, despite these nonlinear effects, a net temperature difference is always attainable. It is also observed that the design of the Stirling device300inFIG. 3Awas not optimized, therefore the measured temperature differences are not indicative of the maximum achievable performance.

Thus, it can be understood that the example Stirling based refrigerating shoe10is able to harvest the mechanical energy produced by human ambulation and convert it into heat flux. The heat flux can then be used to actively control the temperature of feet, lower limbs or even the entire body (if connected to a properly design suit, not shown).

Referring again to the shoe10ofFIG. 1, during a normal the walking cycle, bellows (e.g., the chambers30) on separate paths (30a,30b) compress or expand differently therefore controlling the phase and the amount of working fluid traversing through the regenerator37. As noted previously, the example regenerator37comprises a metallic porous materials (FIG. 1E), although other materials may be suitable as desired. Specifically, it will be understood that the density and porosity can be adjusted to tune the performance of the device14. The heat transfer from the chambers30to the interior of the shoe10may be designed in different ways, for example, using a liner for the circulation of the refrigerating fluid or by designing a system generating advective heat flux.

Referring toFIGS. 4A and 4B, there is illustrated a second example of the shoe10ofFIG. 1. In this example, the shoe10includes a first air chamber400located near the heel of the shoe10, and a second air chamber410located near the toe of the shoe10. In this example, the second air chamber410is illustrated as being approximately two thirds of the way towards the toe, but it will be appreciated by one of ordinary skill in the art that the location of the chambers400,412, may vary as desired, and further, the number and size of the chambers may vary as desired. Also in this example, the first air chamber400is larger in size, i.e., has a greater chamber volume, than the second air chamber410. It will be understood, however, that the chamber may be similar in size or the second air chamber410may be larger than the first air chamber400as desired. Furthermore, in this example, the chamber400and410are mechanically independent of any neighboring chamber and are free to be independently compressed.

As shown, the example shoe10includes a silicon tube420coupled between the first chamber400and the second chamber410. The silicon tube comprises a set of twisted copper wires (hidden from view). As a consequence, the silicon tube420serves as a regenerator422. It will be understood be one of ordinary skill in the art that any suitable device may be utilized as a regenerator.

Still further, in this example arrangement, the shoe10includes an optional pair of K-type thermocouples430,432, operably coupled to a respective one of the two chambers400,412. For instance, in this example, the thermocouples430,432are inserted into the chambers400,412. Still further, the example thermocouples430,432are configured in a differential mode such that the temperature difference between the two chambers430,432will produce a measurable voltage. It will be understood that the shoe10can, if utilized, employ any suitable device for measuring the temperatures of the chambers400,412, and the chosen device may employ any suitable method of measuring the temperature.

As noted, in this example, the thermocouples430,432produce a voltage that is measurable, by way of example, by an external multimeter. As configured in this example, the thermocouples are configured such that 40 microvolts is equivalent to one degree Celsius (1° C.). In addition, as will be appreciated by one of ordinary skill in the art, in this configuration, the initial reading of the thermocouple, i.e., the offset reading before any compression, may be subtracted out such that the only measurable change in the voltage is due to the temperature change.

In the illustrated example, the shoe10includes a pair of wedges450,452, adhered to the bottom chamber400,410, which are included merely for experimental purposes (i.e., to make compression of the chambers410,412easier) and are not necessary for normal operation.

The example shoe10ofFIGS. 4A, 4Bwas then subjected to a dynamic test of approximately 120 steps. In this instance, each step comprised the compression of one chamber, releasing the chamber, and then compressing the other chamber to mimic a normal walking motion. The temperature difference measured by the thermocouples430,432changed with respect to time until it reached a steady value. In this dynamic test, compression of the chamber400made the chamber hotter and the voltage reading was negative. Compression of the chamber410, meanwhile, made that chamber hotter and thus the measured reading was positive. Thus, the sign of the voltage measurement was an indication as to which chamber was getting hotter (e.g., a negative measurement meant the chamber400while a positive measurement meant the chamber410). Compression of both chambers at the same time had no effect on the temperature difference between the two chambers.

To observe the efficiencies in the shoe10, eighteen dynamic tests were conducted with approximately five hours rest between the tests. During the rest period, the temperature differences normalized to zero. The results of the dynamic tests indicated an average temperature change of 1.4° C. (plus or minus 0.5° C.) after 119 steps (plus or minus 27.8 steps). In this setup, the chamber400typically was hotter than the chamber410. This phenomena is likely due to the asymmetry of the two chambers400,410, where the two chambers differ in volume. As such in this instance, the chamber410was more difficult to compress than the chamber400. Accordingly, it was experimentally clear that a significant temperature difference was achieved after about 150 steps.

As demonstrated by the dynamic tests, the shoe10illustrates that a self-refrigerated footwear may be powered by the mechanical energy produced by the human body during ambulation. In addition, the footwear may be connected to an external device, such as for instance a refrigeration suit, etc. to serve as the “main engine” to refrigerate the external device. Still further, it will be appreciated that the cooling/heating capacity of the shoe10, or any device utilizing the disclosed mechanism can be reversible and can be used both for heating or refrigeration purposes as desired.