Functionally stepped, resistive ceramic
AssigneePhilip Morris Incorporated
InventorsSeetharama C. Deevi, A. Clifton Lilly, Jr.
Life of this patent
Estimating the term…
Abstract
An electrically powered functionally graded ceramic composite heater and a functionally stepped ceramic composite heater useful for cigarette lighters. The electrical resistance heater includes discrete heating zones wherein each zone of the heater can be activated using an electric control module, and is capable of heating to a temperature in the range of 600.degree. C. to 900.degree. C. using portable energy devices. The ceramic heater can be made by pressing together layers of differing amounts of constituents of the ceramic precursor material followed by secondary processing steps to obtain discrete heating elements. The heater design can include a hub on one end to provide structural integrity, and function as a common for the heating zones.
Claims40
An electrically powered ceramic composite heater in an electric cigarette lighter, comprising a heating element of a functionally graded, monolithic, electrically resistance heating ceramic material, the ceramic material being functionally graded due to variation in composition of the ceramic material along the monolithic heating element, the electric lighter being operable to receive a cigarette and heat a portion thereof during a draw upon the cigarette, the heating element including a plurality of heating zones and at least one electrically conductive zone, the heating zones being of a sintered mixture comprising an insulator or semiconductive metal compound A and an electrically conductive metal compound B, the heating element including sequential first, second and third zones arranged next to each other, each of the zones having a different amount of compound A relative to compound B wherein compound A is Si.sub.3 Ni.sub.4 and compound B is MoSi.sub.2, the first zone including 35 to 45 vol. % MoSi.sub.2 and 65 to 55 vol. % Si.sub.3 Ni.sub.4, the second zone including 55 to 65 vol. % MoSi.sub.2 and 45 to 35 vol. % Si.sub.3 N.sub.4 and the third zone including 75 to 85 vol. % MoSi.sub.2 and 25 to 15 vol. % Si.sub.3 N.sub.4.
An electrically powered ceramic composite heater in an electric cigarette lighter, comprising a heating element of a functionally graded, monolithic, electrically resistance heating ceramic material, the ceramic material being functionally graded due to variation in composition of the ceramic material along the monolithic heating element, the electric lighter being operable to receive a cigarette and heat a portion thereof during a draw upon the cigarette, the heating element including a plurality of heating zones and at least one electrically conductive zone, the heating zones being of a sintered mixture comprising an insulator or semiconductive metal compound A and an electrically conductive metal compound B, the conductive zone including at least 70 vol. % MoSi.sub.2 and less than 30 vol. % Si.sub.3 N.sub.4 and the heating zones including at least 55 vol. % Si.sub.3 N.sub.4 and less than 45 vol. % MoSi.sub.2.
An electrically powered ceramic composite heater in an electric cigarette lighter, comprising a heating element of a functionally graded, monolithic, electrically resistance heating ceramic material, the ceramic material being functionally graded due to variation in composition of the ceramic material along the monolithic heating element, the electric lighter being operable to receive a cigarette and heat a portion thereof during a draw upon the cigarette, the heating element including an annular electrically conductive hub with a central axis and a plurality of electrically resistance heating conductive blades attached to the hub and extending from its perimeter in one direction parallel to the hub's central axis, the hub and the blades forming a hollow cylinder, the hub and blades comprising the functionally graded monolithic electrically resistance heating ceramic material, each of the blades having a resistance (R) of 0.05 to 7 ohms, a length (L), a width (W), and a thickness (T), and the ceramic material has a resistivity (.rho.), the blade dimensions being in accordance with the formula:
- R=.rho.(L/(W.times.T)).
- 4.
An electric cigarette lighter, comprising:
- a heating element of a functionally graded monolithic electrically resistance heating ceramic material, the ceramic material being functionally graded due to variation in composition of the ceramic material along the monolithic heating element, the heating element being operable to heat a portion of a cigarette supported by the lighter;
- and
- a cigarette disposed in proximity to the heating element so as to be heated by the heating element, the heating element including:
- an annular hub, the hub having a circumference and a central axis;
- and
- a plurality of electrically conductive blades, attached to the hub and extending from a perimeter of the hub in a first direction parallel to the hub's central axis, and defining between them spaces and together a cylinder with a blade portion circumference, the hub circumference exceeding the blade portion circumference, each of the blades having a free end remote from the hub functioning to electrically connect the blade to a power and control module of the cigarette lighter, the hub and blades comprising the functionally graded monolithic electrically resistance heating ceramic material;
- the cigarette lighter further including a metal cage comprising a hub and blades, the cage hub fitting against the heater hub and the cage blades extending between the heater blades with air gaps located between opposed edges of the cage blades and the heater blades.
An electric cigarette lighter, comprising:
- a heating element of a functionally graded monolithic electrically resistance heating ceramic material, the ceramic material being functionally graded due to variation in composition of the ceramic material along the monolithic heating element, the heating element being operable to heat a portion of a cigarette supported by the lighter;
- and
- a cigarette disposed in proximity to the heating element so as to be heated by the heating element, the ceramic material comprising a sintered mixture comprising an insulator metal compound A and an electrically conductive metal compound B, the heating element including a plurality of zones, each of the zones having a different amount of compound A relative to compound B.
An electric cigarette lighter, comprising:
- a heating element of a functionally graded monolithic electrically resistance heating ceramic material, the ceramic material being functionally graded due to variation in composition of the ceramic material along the monolithic heating element, the heating element being operable to heat a portion of a cigarette supported by the lighter;
- and
- a cigarette disposed in proximity to the heating element so as to be heated by the heating element;
- and
- a power and control module connected electrically to the heating element.
A method of making an electrically powered ceramic composite heater useful for devices such as electric cigarette lighters comprising steps of:
- forming a ceramic material into a heating element of a functionally graded monolithic electrically resistance heating ceramic material, the ceramic material being functionally graded due to variation in composition of the ceramic material along the monolithic heating element, said forming step including the step of shaping the functionally graded monolithic ceramic material into a form capable of receiving a cigarette, the shaping step including forming a compact by placing layers of varying compositions of the ceramic material in a container and pressing the layers together and machining the compact such that the heating elements are formed;
- and
- sintering the ceramic material, each of the consisting essentially of Si.sub.3 N.sub.4 and MoSi.sub.2, the Si.sub.3 N.sub.4 contents of the layers varying in composition such that the Si.sub.3 N.sub.4 content does not change by more than 20 vol. % from one of the layers to an adjacent one of the layers.
An electrically resistive element comprising:
- at least one conductive portion consisting essentially of a conductive ceramic component of MoSi.sub.2 or Mo.sub.5 Si.sub.3 ;
- at least one electrically resistive portion consisting essentially of said conductive ceramic component and an electrically insulating ceramic component;
- said electrically resistive element further comprising a transitional portion immediately between said conductive portion and said resistive portion, said transitional portion comprising said conductive ceramic component and said insulating component in mutual proportions such that said transitional portion has a resistivity of approximately 80 to 95% of a resistivity of said conductive portion, said insulating ceramic component constituting at least 15% by volume of said transitional portion, the electrically resistive element being tubular and including a hub and a plurality of blades extending from the hub, said at least one conductive portion including a first conductive portion at free ends of said blades and further including a second conductive portion at said hub, said electrically resistive portion located along said blades intermediate of said first and second conductive portions, said transitional portion including first and second transitional portions at locations along said blades immediately between said resistive portion and said first and second conductive portions, respectively.
Dependencies are inferred from the claim text.