EP0039142A2
Expired / Lapsed
EP
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Alarm system
Assignee: Individual
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Filing: 1981-03-30
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Granted: —
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Expires: 2001-03-30
Abstract
Abstract An alarm system comprises a blower (10) driven by an electric motor (12), the blower being fitted to the premises to be protected and serving to blow air into the premises. With all doors (OD) and windows (W) shutthe blower (10) supplies a steady flow of air, the flow rate depending on the nature of the blower and how fast air can leak out of the premises around doors and windows, through air vents etc. The current drawn by the motor (12) is constant in these circumstances and is monitored. When entry is made to the premises, by opening a door (OD) or window (W), the airflow rate increases and the load on the motor changes. This is reflected in a change in the current drawn by the motor. The change or rate of change of current is detected by detecting means, which activates an alarm in the event of unauthorised opening of door or window. The blower can blow air from the premises, air entering around doors and windows etc.
Inventors
- 👤 Alexander Thompson Mckinley
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-28 03:30
CPC Classifications
G; G08; G08B; G08B13/00; G08B13/20; G08B13/02; G08B13/08
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
76 words
An alarm system for indicating that entry has been made into closed premises comprising a blower and an electric motor for driving the blower, the system being characterized by means (26,54) for monitoring the current being drawn by the motor (12), means (32,56) for detecting the change or rate of change in motor current which occurs upon there being a change in the load on the motor, and an alarm (16,70) activated by the detecting means.
Claim 2
Dependent Claim
76 words
An alarm system for indicating that entry has been made into closed premises comprising a blower and an electric motor for driving the blower, the system being characterized by means (26,54) for monitoring the current being drawn by the motor (12), means (32,56) for detecting the change or rate of change in motor current which occurs upon there being a change in the load on the motor, and an alarm (16,70) activated by the detecting means.
Claim 3
Dependent Claim
40 words
An alarm system according to claim 1, characterized in that said monitoring means (26)generates an electric field, and the detecting means detects the change in the strength of the field which occurs upon there being a change in motor current.
Claim 4
Dependent Claim
59 words
An alarm system according to claim 1, characterized in that said monitoring means (54) includes means for generating a voltage proportional to the current being drawn by the motor, and said detecting means (56) includes means for generating two reference voltages and comparator means for determining if said proportional voltage lies within the limits represented by said reference voltages.
Claim 5
Dependent Claim
33 words
An alarm system according to claim 1 or 2, and characterized by timing means (38) for delaying activation of said alarm for a predetermined period after a change in motor current is detected.
Claim 6
Dependent Claim
41 words
An alarm system according to any preceding claim and characterized by means (18,66) operable by the user to arm the system, and timing means (34,64) for delaying arming of the system for a predetermined time after operation of the arming means.
Claim 7
Dependent Claim
76 words
An alarm system according to claim 5, characterized by means (68) for activating the alarm (70) in response to a change in the condition of the arming means to the disarmed condition, timing means C641 for delaying activation of the alarm for a predetermined period after such change in the condition of the arming means to the disarmed condition, and manually operable means (78) for operation during the delay period for preventing the alarm being activated.
Claim 8
Dependent Claim
30 words
An alarm system according to claims 1,4,5 and 6, characterized by a battery (48) and a rectifier (46) for supplying current to power said motor and maintain the battery charged.
Claim 9
Dependent Claim
39 words
An alarm system according to claim 7, characterized in that said motor (12) is a D.C. motor and there is a voltage regulator (52) between said motor on the one hand and the battery and rectifier on the other.
Claim 10
Dependent Claim
37 words
An alarm system according to claim 7, characterized in that said motor is an A.C. motor and there is an inverter (52) between the motor on the one hand and the battery and rectifier on the other.
Claim 11
Independent Claim
89 words
A method of protecting closed premises which comprises creating a flow of air through a bounding wall of the premises by means of a blower (10) driven by an electric motor (12), monitoring the current being drawn by the motor, detecting the change or rate of change in motor current which occurs upon there being a change in load on the motor stemming from a change in the pneumatic resistance imposed on said blower when the premises are opened, and activating an alarm (16,70) upon such change being detected.
Claim 12
Independent Claim
89 words
A method of protecting closed premises which comprises creating a flow of air through a bounding wall of the premises by means of a blower (10) driven by an electric motor (12), monitoring the current being drawn by the motor, detecting the change or rate of change in motor current which occurs upon there being a change in load on the motor stemming from a change in the pneumatic resistance imposed on said blower when the premises are opened, and activating an alarm (16,70) upon such change being detected.
References Cited (Backward Citations)
No citation records indexed.
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