Fire alarm heat detector

Claim 2

An environmental heat detector comprising: a housing; electronics on a board within the housing for providing a rate of temperature rise output in response to a difference between first and second environmental temperature signals; a first temperature sensor exposed to the environment surrounding the housing to provide the first environmental temperature signal with a fast response to change in environmental temperature; a second temperature sensor positioned to provide the second environmental temperature signal with a response to change in environmental temperature which is slow relative to the fast response of the first temperature signal but which is fast relative to the temperature response of the electronics board to change in environmental temperature.

Claim 3

A heat detector as claimed in claim 1 wherein the second temperature sensor is positioned within a protuberance of the housing.

Claim 4

A heat detector as claimed in claim 1 where an alarm set point, at least equal to the temperature difference between the first and second temperature sensors after the heat detector is exposed to five minutes of a 12° F./minute rate of rise in environmental temperature, is reached in less than 20 seconds with an increase in temperature of about 50° in 20 seconds.

Claim 5

A heat detector as claimed in claim 1 wherein the electronics provide a rate of rise alarm indication from a single comparison of the first and second temperature signals and, in operation, the detector passes Underwriters Laboratories' UL521 fire test by responding to a rapid fire condition in less than 30 seconds and not indicating a fire condition at less than 130° F. where the rate of rise of environmental temperature is no faster than 12° F. per minute.

Claim 6

A heat detector as claimed in claim 4 which triggers an alarm in the fire test in less than 20 seconds.

Claim 7

A heat detector as claimed in claim 1 wherein the electronics further provide an alarm indication when the first temperature signal reaches a predetermined threshold.

Claim 8

A heat detector as claimed in claim 1 wherein the electronics comprises a single comparator for making a rate of rise comparison between the first and second temperature signals.

Claim 9

A heat detector as claimed in claim 1 wherein the temperature of the second temperature sensor is closer to the temperature of the first temperature sensor than it is to the temperature of the electronics board after the heat detector is exposed for five minutes to a 12° F./minute rate of environmental temperature rise.

Claim 10

An environmental heat detector comprising: a housing; electronics on a board within the housing for providing a rate of temperature rise output in response to a difference between first and second environmental temperature signals; a first temperature sensor exposed to the environment surrounding the housing to provide the first environmental temperature signal with a fast response to change in environmental temperature; a second temperature sensor positioned within a protuberance of the housing to provide the second environmental temperature signal with a response to change in environmental temperature which is closer to that of the first temperature sensor than to that of the electronics board after the heat detector is exposed for five minutes to a 12° F./minute rate of environmental temperature rise; wherein the electronics comprises: a first comparator for providing a rate of rise alarm indication from a comparison of the first and second temperature signals, the comparator having a set point, at least equal to the temperature difference between the first and second temperature sensors after the heat detector is exposed to five minutes of a 12° F./minute rate of rise in environmental temperature, which is reached in less than 20 seconds with an increase in temperature of about 50° in 20 seconds; and a second comparator for providing an alarm indication when the first temperature signal reaches a predetermined threshold.

Claim 11

An environmental heat detector comprising: a housing; electronics on a board within the housing for providing a rate of temperature rise output in response to a difference between first and second environmental temperature signals; a first temperature sensor exposed to the environment surrounding the housing to provide the first environmental temperature signal with a fast response to change in environmental temperature; a second temperature sensor positioned within a protuberance of the housing to provide the second environmental temperature signal with a response to change in environmental temperature which is closer to that of the first temperature sensor than to that of the electronics board after the heat detector is exposed for five minutes to a 12° F./minute rate of environmental temperature rise; wherein the electronics comprises: a first comparator for providing a rate of rise alarm indication from a comparison of the first and second temperature signals, the comparator having a set point, at least equal to the temperature difference between the first and second temperature sensors after the heat detector is exposed to five minutes of a 12° F./minute rate of rise in environmental temperature, which is reached in less than 20 seconds with an increase in temperature of about 50° in 20 seconds; and a second comparator for providing an alarm indication when the first temperature signal reaches a predetermined threshold.

Claim 14

A method as claimed in claim 10 wherein the second environmental temperature signal is obtained from a temperature sensor mounted within a protuberance of a detector housing.

Claim 15

A method as claimed in claim 10 where an alarm set point, at least equal to the temperature difference between the first and second temperature sensors after the housing is exposed to five minutes of a 12° F./minute rate of rise in environmental temperature, is reached in less than 20 seconds with an increase in temperature of about 50° in 20 seconds.

Claim 16

A method as claimed in claim 10 wherein the electronics are embodied in a heat detector, the rate of rise alarm indication is provided from a single comparison of the first and second temperature signals, and the heat detector in operation passes Underwriters Laboratories' UL521 fire test by responding to a rapid fire condition in less than 30 seconds and not indicating a fire condition at less than 130° F. where the rate of rise of environmental temperature is no faster than 12° F. per minute.

Claim 17

A method as claimed in claim 13 wherein the rate of rise alarm indication is provided in the fire test in less than 20 seconds.

Claim 18

A method as claimed in claim 10 further comprising providing an alarm indication when the first temperature signal reaches a predetermined threshold.

Claim 19

A method as claimed in claim 10 wherein the rate of rise alarm indication is provided from a single comparison between the first and second temperature signals.

Claim 20

A method as claimed in claim 10 wherein the second temperature signal is closer to the first temperature signal than it is to temperature of the at least one electronics board after the housing is exposed for five minutes to a 12° F./minute rate of environmental temperature rise.