Back to results
US 4,543,474 AGranted
Layered self-regulating heating article
AssigneeRaychem Corporation
InventorsDavid A. Horsma, Bernard J. Lyons, Robert Smith-Johannsen
Life of this patent
Estimating the term…
Abstract
A self-regulating heating article comprising a layer of material exhibiting a positive temperature coefficient of resistance (PTC) and said PTC layer having at least partially contiguous therewith at least one layer of constant wattage output material. The article operates such that when connected to an electric power source, the current flows through at least a portion of the thickness of the PTC layer and of the constant wattage layer. In a preferred embodiment, upon heating the article, a change in dimensions as well as activation of an adhesive occurs.
Claims47
A self-regulating electrical device which comprises
- (a) at least one PTC layer composed of a PTC material which exhibit PTC behavior with an anomaly temperature T.sub.s ;
- (b) at least one CW layer composed of a CW material which exhibits substantially CW behavior at T.sub.s and below, at least a part of a surface of the CW layer being in direct electrical and physical contact with at least a part of a surface of the PTC layer;
- and
- (c) at least two electrodes which can be connected to a source of electrical power to cause electrical current to flow through the device;
- said device, when said electrodes are connected at ambient temperature to a suitable source of electrical power, undergoing conversion from an ambient temperature state to a high temperature equilibrium state in which (a) the device generates heat by resistive heating at the same rate as it dissipates heat to its surroundings and (b) the PTC element is in a high temperature high resistance state;
- the electrical current flowing across the interface between the PTC layer and the CW layer at least at some stage during said conversion and more than 50% of the heat output of the device being generated in said at least one CW layer when the device is connected to a source of electrical power at ambient temperature;
- subject to the proviso that if there are electrodes of opposite polarity which are in direct physical and electrical contact with the same PTC layer, the electrodes are embedded in and surrounded by the PTC layer, and the CW layer substantially surrounds the PTC layer.
4 more elements
A self-regulating electrical device which comrises
- (a) at least one PTC layer composed of a PTC material which has a resistivity at 75.degree. F. of e.sub.1 ohm.cm and which exhibits PTC behavior with an anomaly temperature T.sub.s ;
- (b) at least one CW layer composed of a CW material which has a resistivity at 75.degree. F. of e.sub.2 ohm.cm, where e.sub.1 /e.sub.2 is from 0.1 to 20, and which exhibits substantially CW behavior at T.sub.s and below, at least part of a surface of the CW layer being in direct electrical and physical contact with at least a part of a surface of the PTC layer;
- and
- (c) at least two electrodes which can be connected to a source of electrical power to cause electrical current to flow through the device;
- said device, when said electrodes are connected at ambient temperature to a suitable source of electrical power, undergoing conversion from an ambient temperature state to a high temperature equilibrium state in which (a) the device generates heat by resistive heating at the same rate as it dissipates heat to its surroundings and (b) the PTC element is in a high temperature high resistance state;
- the electrical current flowing across the interface between the PTC layer and the CW layer at least at some stage during said conversion;
- subject to the proviso that if there are electrodes of opposite polarity which are in direct physical and electrical contact with the same PTC layer, the electrodes are embedded in and surrounded by the PTC layer, and the CW layer substantially surrounds the PTC layer.
4 more elements
A self-regulating electrical device which comprises
- (a) at least one PTC layer composed of a PTC material which exhibits PTC behavior with an anomaly temperature T.sub.s ;
- (b) at least one CW layer composed of a CW material which has a resistivity at 25.degree. C. of more than 1 ohm.cm and which exhibits CW behavior at T.sub.s and below, at least a part of a surface of the CW layer being in direct electrical and physical contact with at least a part of a surface of the PTC layer;
- and
- (c) at least two electrodes which can be connected to a source of electrical power to cause electrical current to flow through the device;
- said device, when said electrodes are connected at ambient temperature to a suitable source of electrical power, undergoing conversion from an ambient temperature state to a high temperature equilibrium state in which (a) the device generates heat by resistive heating at the same rate as it dissipates heat to its surroundings and (b) the PTC element is in a high temperature high resistance state;
- the electrical current flowing across the interface between the PTC layer and the CW layer at least at some stage during said conversion;
- subject to the proviso that if there are electrodes of opposite polarity which are in direct physical and electrical contact with the same PTC layer, the electrodes are embedded in and surrounded by the PTC layer, and the CW layer substantially surrounds the PTC layer.
4 more elements
A self-regulating electrical device which comprises
- (a) a laminar PTC layer composed of a PTC material which exhibits PTC behavior with an anomaly temperature T.sub.s ;
- (b) a first laminar CW layer composed of a CW material which exhibits CW behavior at T.sub.s and below;
- (c) a first electrode in physical and electrical contact with the first CW layer;
- (d) a second laminar CW layer composed of a CW material which exhibits CW behavior at T.sub.s and below;
- and
- (e) a second electrode in physical and electrical contact with the second CW layer;
- each of said CW layers being in direct physical and electrical contact with said PTC layer;
- said electrodes being connectable to a source of electrical power to cause electrical current to flow through the device;
- and at least one of the electrodes physically extending over a part only of the CW layer which it contacts, whereby, when said device is connected at ambient temperature to a suitable source of electrical power, it undergoes conversion from an ambient temperature state to a high temperature equilibrium state in which (a) the device generates heat by resistive heating at the same rate as it dissipates heat to its surroundings and (b) the PTC element is in its high temperature high resistance state;
- the electrical current flowing across the interfaces between the PTC layer and the CW layers at least at some stage during said conversion;
- and at least at some stage in said conversion, current flows along at least one of the CW layers in the thickness thereof.
8 more elements
Dependencies are inferred from the claim text.