Refrigeration – With indicator or tester – Operatively correlated with automatic control
Reexamination Certificate
1999-10-06
2001-05-08
Tanner, Harry B. (Department: 3744)
Refrigeration
With indicator or tester
Operatively correlated with automatic control
C062S052100, C236S051000, C606S022000
Reexamination Certificate
active
06226996
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device for uniformly cooling a surface, such as human skin, to a specified temperature using a cold mist of a cryogenic fluid and a non-contact temperature sensor.
2. Description of Related Art
The use of liquified gas coolants to cool and freeze tissue has long been known. For example, dichlorotetrafluoroethane (also known as Frigiderm® or Freon 114) has been used extensively in cosmetic surgery to cool and stiffen skin properly before mechanical dermabrasion with a rotating abrasive wheel.
The hardness of the skin freeze has been shown to be critical in controlling the depth of dermabrasion and classified as either superficial (0.2-0.5 mm), moderate (0.5-1.0 mm), or deep (1.5-2.0 mm) according to Ayres {Ayres S III: Superficial chemosurgery, including combined technique, using dermabrasion, in Epstein E, Epstein E Jr, editors: Skin surgery. Springfield, Ill., 1982, Charles C Thomas, Publisher.} The skin temperatures achieved and thus the hardness of the skin is dependent upon the type of freezing agent, skin temperature prior to treatment, operating room temperature, distance of spray, pressure of spray, density of spray, angle of spray and time of spray, among other variables.
The advantage of dichlorotetrafluoroethane is that under normal conditions its maximum skin cooling temperatures is −40° C., even though its boiling point is +3.8° C. Ethyl chloride was an efficient skin refrigerant but had the undesirable qualities of being explosive when mixed with air, toxic to the liver, as well as capable of causing general anesthesia upon inhalation by the patient or doctor.
It has been proven that colder cryorefrigerants (ie Cryosthesia −60° C. also known as dichlorodifluoromethane or Freon 12, boiling point −29.8° C.) can produce maximum skin cooling temperatures of −66° C. causing unwanted tissue damage and resulting in serious complications (scarring, depigmentation, infection).
Unfortunately, all of these chlorofluorocarbon refrigerants have been shown to damage the ozone layer and their use is now strictly controlled if not outright banned in many countries.
Dry ice or frozen carbon dioxide has also been used to cool the skin. However, applying dry ice to the skin's surface can quickly produce temperatures of close to −78° C. “Dry ice” application has been shown to be destructive to the epithelium layer and is now more commonly used to improve the penetration of skin peeling chemicals by removing the epidermis just prior to peel-acid application. Because temperatures of −78° C. are rapidly approached with little room for manual control, direct solid state, “dry ice” contact is not a viable option for controlled cooling of skin prior to or during dermabrasion if the surgeon is to minimize thermal damage. Surgeons have reported that solid carbon dioxide contact produced scarring because it was applied under pressure that occluded the, otherwise warming, local blood supply.
Cryogenic fluids such as liquid nitrogen, which pose little risk to the environment, have also been used extensively to cool surfaces. However, when sprayed on surfaces liquid nitrogen can quickly produce surface temperatures as low as −196° C. Unfortunately, for many applications and in particular cosmetic surgery this low temperature can seriously damage and kill human tissue.
Given the disadvantages of current human skin cooling techniques, a need exists for a device that provides a safe and economical alternative. The present invention uses a cryogenic mist and non-contact temperature sensor to cool a surface to a desired temperature. By using a cryogenic mist, the cooling can be maintained at safe levels that allow the user to either electronically or manually control the cooling process.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a device that can uniformly cool a surface to a specified temperature using a cold gas or mist. The device comprises a reservoir for a cryogenic fluid, a valve for controllably releasing the fluid through an atomizing nozzle, a non-contact temperature sensor, and an electronic control unit to display the temperature values and optionally control the valve. It is further an object of this invention to provide a tool for safely cooling skin for performing dermabration without using chlorofluorocarbon gas.
In one embodiment of the present invention, the user sets the desired temperature on the electronic control unit using a touch pad or other user interface. The device is then directed at the target surface, and the valve is opened manually or electronically by pressing a button, switch, or lever. The cryogenic fluid in the reservoir flows through the valve and exits an atomizing nozzle, where the liquid is turned into a gas or mist of small droplets (aerosol) that can evaporate as they propagate towards the target surface. The cryogenic fluid can be any low temperature liquid or gas, for example, nitrogen, helium, xenon, carbon dioxide, chlorofluorocarbon (CFC) refrigerants or the many low temperature alternatives to CFC's.
The surface temperature of the area being exposed to the cold mist is measured with a non-contact temperature sensor, and the value is displayed on the control unit, such as on a liquid crystal display. The control unit may be programmed to produce an audible or optical alarm or signal when the measured temperature reaches the desired (pre-set) temperature. At this point, the user manually closes the valve, thereby stopping the fluid flow and cooling. Alternatively, the control unit may be programmed to automatically close an electronic valve when the desired temperature is reached, thereby eliminating the need for the user to manually operate the valve and providing a safety mechanism.
The cryogenic reservoir can be any one of a variety of reservoirs that are commercially available or known in the art (e.g., U.S. Pat. No. 4,116,199). The cryogenic reservoir operating pressure and atomizing nozzle are selected to produce a fine mist that uniformly cools the surface over a desired area. The device uses a non-contact temperature sensor to avoid perturbing the surface. The preferred non-contact temperature sensor is an infrared temperature sensor, but could include other sensors such as fluorescence temperature sensors. Since most non-contact temperature sensors average the temperature over a specified field, it is important that the cooled area overlaps the area sampled by the temperature sensor. To that end, a properly aligned optical source that generates an optical beam or pattern may be added to identify a spot or area where the temperature is measured.
The present invention is useful for cooling human or animal skin for dermatological applications, such as dermabrasion. Other applications include cooling metal surfaces for assembly or surface conditioning. The foregoing and other objects, features and advantages of the present invention will become apparent from the following description and accompanying drawings.
REFERENCES:
patent: 3534739 (1970-10-01), Bryne
patent: 3651813 (1972-03-01), Bryne
patent: 4043341 (1977-08-01), Tromovitch
patent: 4116199 (1978-09-01), Bryne
patent: 4348873 (1982-09-01), Yamauchi et al.
patent: 5098428 (1992-03-01), Sandlin et al.
patent: 5814040 (1998-09-01), Nelson et al.
Bader Robert S.
Da Silva Luiz B.
Weber Paul J.
Tanner Harry B.
Wooldridge John P.
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