1. Related Patents and Applications
This application is an improvement over applicant's U.S. Pat. No. 3,479,838 (1969) entitled "Cooling Material". It is also a continuation-in-part of applicant's pending application Ser. No. 383,004 entitled "Method and Apparatus for Monitoring and Diagnosing Peripheral Blood Flow" and Ser. No. 673,509 entitled "Blood Flow Monitoring Device" now Pat. No. 4,569,335 (1986).
2. Field of the Invention
This invention relates to fabric or garments for localized cooling of a person's skin or of another object.
3. Need For the Invention
Localized cooling is extremely useful in many applications of which the following examples are but a few. Industrial workers in high temperature environments such as foundries and agricultural workers in the desert are exposed to high temperatures. At high temperatures, workers fatigue more easily and productivity decreases. It is impractical to air condition an entire foundry; farm laborers also cannot work in air conditioned environments. Therefore, it is desirable to cool these workers' skin. Peak efficiency and comfort may still be maintained if only the trunk or trunk and head are cooled. The limbs, which have a large surface area to volume ratio, naturally radiate enough heat. As a matter of fact, amputees often find it difficult to radiate sufficient heat from their bodies even at low levels of activity in environments that would be relatively comfortable for persons with all of their limbs. Thus, cooling of the trunk of amputees is another application of the present invention.
Some persons are exposed to heat from one localized source. For example, a race car driver with a rear engine car is exposed to high heat quantities at his or her back. For racing efficiency, it is not practical to air condition the driver compartment, and added insulation adds undesirable weight to the vehicle. Moreover, race drivers usually wear protective clothing for fire and crash protection that tends to retain body heat. For them, localized cooling, which might concentrate on cooling the driver's back, would be most helpful.
Surgical patients, especially those undergoing open heart surgery, often must be cooled to lower metabolism and blood flow. This is normally done with ice, but the ice needs replenishing, and it is more difficult to control the actual temperature.
As another example, one can cool a small area only and give the user the perception of comfort. For example, a cool head band or cap worn during strenuous exercise may allow the user to feel comfortable even though the rest of the body is above normal temperature.
Localized applications of cooling are not confined to humans. Electronics components, for example, heat up. Although they may be ventilated with outside air, as more circuitry is confined to a smaller area, outside air may be insufficient or at too high a temperature to cool the components. It would be useful, therefore, to provide a small device that could be inserted into an electronic device merely for the purpose of cooling localized areas. There may also be certain chemical processes which would benefit from localized cooling.
Localized cooling can be obtained by refrigerated air conditioning, but in many of the applications just discussed, that type of air conditioning is not practical because of weight, power consumption, restrictions on mobility and/or other reasons.
4. Prior Art
Applicant's Pat. No. 3,479,838 teaches a cooling fabric primarily for use in space. The cooling fabric had several layers, and water is injected between some of the layers. In the vacuum of outer space, water boils at skin temperature, and heat from the skin causes the water to boil. Heat exchange during a change of phase is great, and the resultant boiling caused the skin to cool. The device does not work at or near standard temperatures (body or environment) and pressure.
There are garments with channels for carrying cooling water. Applicant's earlier patents suggest the use of additional cooling liquid to augment the cooling from the boiling water. That type of system is prohibitive for everyday use on the ground because of weight and power requirements. Recirculating water must be cooled somehow unless one has access to cooling water that can be expelled after use or refrigerated at the expense of energy. Also, if the garment uses cold water or other liquid, the liquid flows through tubes, which must have thick enough walls to avoid kinking. These tubes have poor surface area contact and poor heat transfer characteristics.
To cool the skin while taking advantage of boiling at atmospheric pressure, one needs a liquid with a boiling point at atmospheric pressure below normal ambient temperatures. Heat from the skin boils these liquids. These refrigerant liquids are known and are used in air conditioning systems. Various fluorinated hydrocarbon fluids, such as those sold under the trademark Freon and mixtures of Freons, are known refrigerant liquids, and the present invention uses them. For cooling skin, the boiling point at standard pressure should be above 0.degree. C. to prevent freezing of the skin. Liquids boiling below 0.degree. C. could be used for cooling other objects.
In applicant's pending applications, localized cooling is used to cool a very small area of skin for a medical application. The cooling is accomplished by means of vaporization of a refrigerant liquid. The resultant gas is expelled to the atmosphere. The gas is costly and considered by some to pollute, and some have an offensive odor; it may be objectionable to vent the gas to the atmosphere, but these factors are minor in the medical device because it vents relatively small amounts of refrigerant gas. In a whole-body cooling apparatus, a much greater volume of gas would be lost, which raises the cost of each application. Therefore, it is an object of the present invention to disclose and to provide a localized cooling material in which the vaporized gas is not vented to the atmosphere.
Recycling the gas creates a problem. One cannot allow the gas to stay in the cooling device or the device quickly becomes pressurized and boiling efficiency drops dramatically. It is impractical and inefficient to repressurize the relatively small amount of low pressure gas immediately and direct it back to the storage tank. It is an object of the present invention, therefore, to disclose and provide a system for holding interim storage of the spent gas and injecting it back into the storage tank as a liquid.
For maximum efficiency and control, the liquid should remain liquid until it is in a location where the skin temperature causes it to boil. Premature boiling in feed lines wastes the cooling potential of the liquid. Both of the pending applications attempt to cause the injection of the liquid to take place in the cooling chamber to conserve the cooling potential of the liquid so that it is not wasted in the lines. Also, by causing only liquid to be injected into the cooling chamber, control may be maintained. It is an object of the present invention, therefore, to disclose and provide valves or other controllers as close to the cooling location as possible. In the medical devices, very precise temperature controls to .+-.0.05.degree. F. (.+-.0.03.degree. C. [metric equivalents are approximate]), may be needed. A cooling fabric would not have to cool in such precise increments. A .+-.1.degree. or 2.degree. F. difference may be acceptable. Another object of this invention is to disclose and provide a relatively low-cost valve that can still be used to maintain the temperature control needed.
If the fabric covers wide areas of the body, it is desirable to be able to control those areas to effect different rates of cooling and different temperatures at localized sites. As a result, an additional object of the present invention is to design a valve that uses low power but is small and compact enough so that it can fit into the cooling fabric at one or several sites without being heavy, conspicuous and expensive.
Applicant's application Ser. No. 673,509 discloses (in somewhat schematic form) a cooling fabric which uses injectors disclosed in that application. It is an object of the present invention to improve on that system and utilize the fabric as a cooling chamber and to improve on the injectors themselves. These and other objects of the present invention will become evident from the following description of it.