Abstract This invention pertains to breath warming devices and particularly of the self contained type wherein heat and moisture from the exhaled breath is utilized to warm and humidify the ensuing inhaled breath. Under arctic conditions air of temperature as low as minus 50 degrees F. may be inhaled. Under such conditions approximately 44 percent of the total heat generated within the body is lost through breathing. Previous attempts to develop self contained breath warming devices have met with discouragement because at low ambient temperatures ice and frost formation tends to block the air flow and render the device inoperable. The subject invention discloses a design which is free of such difficulty. The design employed in the device incorporates an automatic valve which opens responsive to increasing air friction within the device when frost or ice begin to obstruct the air flow therethrough. The valve operates only to bypass a portion of inhalation air while leaving the flow and volume of exhaled air unaffected. The amount of heat recovered from exhalation thus remains constant whereas the demand for heat to warm inhaled air is decreased when ice begins to form in the unit. Due to this change in heat balance further ice does not form, and the device remains operative despite very low ambient temperature. Also shown are additional features of novel nature particularly related to improvement of means for effecting efficient and comfortable mounting and fit of the device relative to the face of the wearer.
In a breath warming device of the self contained type wherein heat and moisture from an exhaled breath is used to warm and humidify the ensuing inhaled breath, said device having a heat sink-exchanger pack through which exhaled air is caused to pass to impart heat thereto and to deposit moisture therein and through which in opposite direction the subsequent breath of inhaled air is caused to pass to absorb heat and moisture therefrom, said device including an oral-nasal housing having walls and at least partially open ends and being adaptable to the passage of air therethrough, said housing having mounted therein and adjacent one end thereof said heat sink-exchanger pack and having the opposite end thereof constructed as a plenum chamber adapted to provide respiratory association with the oral-nasal area of the human face, that improvement which comprises an inhalation by-pass aperature adaptable to allow movement of ambient air into said plenum chamber, said aperature being selectively closed by a moveable inhalation by-pass valve arranged in manner such that said valve will open responsive to differential air pressure to admit ambient air direct to said plenum chamber when and only when the air pressure within said chamber decreases to a pre-determined value below ambient air pressure, such decrease in pressure being caused during inhalation cycle by increase in resistance to air flow through said heat sink-exchanger pack due to cause such aS accumulation of frozen water vapor adjacent the inlet area of said pack.
Claim 2
Dependent Claim
245 words
In a breath warming device of the self contained type wherein heat and moisture from an exhaled breath is used to warm and humidify the ensuing inhaled breath, said device having a heat sink-exchanger pack through which exhaled air is caused to pass to impart heat thereto and to deposit moisture therein and through which in opposite direction the subsequent breath of inhaled air is caused to pass to absorb heat and moisture therefrom, said device including an oral-nasal housing having walls and at least partially open ends and being adaptable to the passage of air therethrough, said housing having mounted therein and adjacent one end thereof said heat sink-exchanger pack and having the opposite end thereof constructed as a plenum chamber adapted to provide respiratory association with the oral-nasal area of the human face, that improvement which comprises an inhalation by-pass aperature adaptable to allow movement of ambient air into said plenum chamber, said aperature being selectively closed by a moveable inhalation by-pass valve arranged in manner such that said valve will open responsive to differential air pressure to admit ambient air direct to said plenum chamber when and only when the air pressure within said chamber decreases to a pre-determined value below ambient air pressure, such decrease in pressure being caused during inhalation cycle by increase in resistance to air flow through said heat sink-exchanger pack due to cause such aS accumulation of frozen water vapor adjacent the inlet area of said pack.
Claim 3
Dependent Claim
52 words
A breath warming device as per claim 1 wherein the surface area of material within said heat sink-exchanger pack is substantially three hundred square inches and wherein the porosity of said material is such to offer approximately one sixteenth inch of water differential resistance to air flow therethrough during normal respiration rates.