Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
2000-09-25
2001-06-19
Lee, Benjamin C. (Department: 2632)
Communications: electrical
Condition responsive indicating system
Specific condition
C340S545100, C340S547000, C340S693600, C340S686300, C200S061930
Reexamination Certificate
active
06249224
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to alarm switches used with security systems, and more particularly to an electromagnetic alarm switch that is substantially tamper-resistant.
BACKGROUND OF THE INVENTION
FIG. 1
shows a prior art electromagnetic alarm switch assembly
1
. The assembly generally includes a magnetic switch
2
and a magnet
3
that are separate components and are mounted in close proximity to each other on a closed door
4
and door frame
5
(or window and window frame). In operation, as the door
4
is opened and the switch
2
and magnet
3
move apart, at a predetermined distance the effect of the magnetic field of the magnet is no longer imposed on the switch, the switch reacts, and the alarm sounds. Typically, the switch
2
is normally “open,” meaning that the alarm is on. However, when the door
4
is closed and the magnet
3
is in close proximity, the magnet
3
holds the switch
2
in a closed (alarm off) position. As the door
4
is opened and the magnet
3
moves away from the switch
2
, the switch
2
reverts to the normally open position, thus sounding the alarm. These types of switches can be easily circumvented simply by holding a magnet in close proximity to the switch
2
while the door is opened, thereby maintaining the switch
2
in the closed position.
FIG. 2
shows another prior art electro-magnetic alarm switch assembly
6
. The assembly
6
includes a housing
7
having a first
8
and second
9
portion. The first portion
8
includes a switch and the second portion
9
includes a magnet. The assembly
6
is designed to function with a slidable door latch
10
, such as is often used on a raisable overhead door. The closed door latch
1
0
lies at rest through the open mid-portion
11
of the “U”. The switch is normally “closed” (alarm off). When the slidable latch
10
is in the closed door position, as shown, interaction between the magnet and the switch is blocked by the latch
10
(as shown by arrows A). When the slidable latch is withdrawn, as to open the door, the magnet causes the switch to open, thereby sounding the alarm. A drawback to this design is that the assembly
6
can easily be “tampered with” by inserting into open mid-portion
11
a metal “dummy” latch before withdrawing the latch
10
, thereby maintaining the block between the magnet and the switch and allowing the door to be opened while preventing activation of the alarm.
Other prior art alarm switches are known, however many of these are not provided for use with a slidable door latch. Examples of prior art alarm switches can be found in U.S. Pat. Nos. 5,673,021 to Woods and 5,668,533 to Jackson et al.
A long felt need exists for an alarm switch assembly that is provided for use with a slidable door latch and is substantially tamper-resistant.
SUMMARY OF THE PREFERRED EMBODIMENTS
In accordance with one embodiment of the present invention there is provided an alarm switch assembly that includes a housing having first and second surfaces and an opening defined therein that extends from one surface toward the other surface. The opening is further defined by at least four inner surfaces. A magnetic field generating device is disposed adjacent the opening and between the first and second surfaces, and a switch is disposed adjacent the opening and is opposed to the magnetic field generating device.
In a preferred embodiment, the opening is rectangular and preferably includes a pair of projections that extend inwardly from opposed inner surfaces that define the opening. In a particular embodiment, the switch is disposed in a switch opening that is at least partially defined in one projection and the magnet is disposed in a magnet opening that is at least partially defined in the other projection.
In another preferred embodiment, the opening includes a convergent section and a divergent section.
In accordance with another aspect of the present invention there is provided a latch system that includes the alarm switch assembly described above and a latch received in the opening. A clearance not exceeding about 0.020″ is defined between the latch and at least one of the inner surfaces of the housing.
In accordance with yet another aspect of the present invention there is provided an alarm system that includes the latch system described above and an alarm. The lead wires electrically connect the switch to the alarm.
In accordance with another aspect of the present invention there is provided a door assembly that includes a door, the latch slidably affixed to the door, a door frame having an opening defined therein at least partially surrounding the door, and the alarm system described above affixed to the door frame. The opening in the door frame and the opening in the housing cooperate to define a latch opening; the latch is received in the latch opening; and a clearance not exceeding about 0.020″ is defined between the latch and at least one of the inner surfaces of the housing.
In accordance with another aspect of the present invention there is provided a method of activating an alarm. The method includes the steps of providing the door assembly described above and detecting withdrawal of the latch from the latch opening.
In accordance with yet another aspect of the present invention there is provided an alarm switch assembly that includes a housing having first, second and third portions that cooperate to define an opening. The housing also includes at least one blocking portion that extends inwardly from the first or the third portion. A magnetic field generating device is disposed adjacent the opening and between the first and second surfaces, and a switch is disposed adjacent the opening and opposed to the magnetic field generating device.
It will be understood that the device is not limited to activation by a magnetic field generating device. Any field, beam or the like that is blocked by the latch and can be sensed when the latch is removed is within the scope of the present invention. For example, a light beam emitting device and appropriate receptor can be used. A jet of air emitting device and appropriate receptor can be used. Sound waves, such as ultrasonic waves produced by a magnetostrictive element can be used.
Other objects, features and advantages of the present invention will become apparent to those skilled in the art from the following detailed description. It is to be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are given by way of illustration and not limitation. Many changes and modifications within the scope of the present invention may be made without departing from the spirit thereof, and the invention includes all such modifications.
REFERENCES:
patent: 912454 (1909-02-01), Fesenbeck
patent: 1044099 (1912-11-01), Spring
patent: 2436470 (1948-02-01), Fleming
patent: 2588080 (1952-03-01), Boodakian
patent: 2818475 (1957-12-01), Harry
patent: 2924682 (1960-02-01), Winterburn
patent: 3196293 (1965-07-01), Howard
patent: 3284593 (1966-11-01), Hawkins
patent: 3410245 (1968-11-01), Kashden et al.
patent: 3569645 (1971-03-01), Lea
patent: 3704460 (1972-11-01), Frank
patent: 3793565 (1974-02-01), Smith
patent: 3932718 (1976-01-01), Porat
patent: 4100419 (1978-07-01), Pedroso
patent: 4196422 (1980-04-01), Swigert et al.
patent: 4211990 (1980-07-01), Gwozdz
patent: 4232309 (1980-11-01), Dillitzer
patent: 4283718 (1981-08-01), Butler et al.
patent: 4536754 (1985-08-01), Holce et al.
patent: 4671549 (1987-06-01), Marotto et al.
patent: 4845471 (1989-07-01), Chu
patent: 4866426 (1989-09-01), Evans et al.
patent: 4903010 (1990-02-01), Greene
patent: 4990898 (1991-02-01), Greene
patent: 5484177 (1996-01-01), Fortune et al.
patent: 5493278 (1996-02-01), MacKenzie et al.
patent: 5656982 (1997-08-01), Kurahara
patent: 5668533 (1997-09-01), Jackson et al.
patent: 5673021 (1997-09-01), Woods
patent: 5878606 (1999-03-01), Chaput et al.
patent: 5925861 (1999-07-01), Fromberg
patent: 6124792 (2000-09-01), Shoen et al.
Hayden William A.
Shoen Edward J.
Berman, Esq. Rod S.
Jeffer Mangels Butler & Marmaro LLP
Lee Benjamin C.
U-Haul International Inc.
LandOfFree
Latch integrated, tamper resistant, electro-magnetic alarm... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Latch integrated, tamper resistant, electro-magnetic alarm..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Latch integrated, tamper resistant, electro-magnetic alarm... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2510247