Information
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Patent Grant
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6603378
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Patent Number
6,603,378
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Date Filed
Thursday, September 19, 200222 years ago
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Date Issued
Tuesday, August 5, 200321 years ago
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Inventors
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Original Assignees
-
Examiners
Agents
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CPC
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US Classifications
Field of Search
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International Classifications
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Abstract
An improved magnetic switch (10) is provided which is designed for use in an alarm circuit (52) in order to detect relative movement between first and second members such as a door (14) and frame (12), so as to signal unauthorized opening of the door (14). The switch (10) includes a switch assembly (20) for mounting in frame (12) and having first and second switch elements (40, 42), an electrically conductive shiftable body (44) adjacent the elements (40, 42), and a first attractive component (45). Additionally, the switch (10) has a second attractive component (22) for mounting to the door (14). In use when door (14) is closed and circuit (52) is armed, the magnetic attraction between body (44) and component (22) shifts the body (44) to a switch position where the body (44) is out of simultaneous contact with the switch elements (40, 42). If the door (14) is opened, the magnetic attraction between body (44) and component (45) moves the body to another switch position establishing simultaneous contact with the switch elements (40, 42).
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is broadly concerned with magnetic switches of the type used as a part of alarm systems for detective relative movement between first and second structural members such as a door and door frame or a window and window frame. More particularly, the invention is concerned with such switches which are especially designed to defeat attempted unauthorized external magnetic manipulation thereof. The magnetic switches of the invention include first and second spaced apart electrically conductive switch elements typically within an enclosed housing and including an electrically conductive body adjacent the contacts which can be shifted by virtue of magnetic attractions between a first position where the body simultaneously contacts both of the switch elements, and a second position where the body is out of simultaneous contact with the switch elements.
2. Description of the Prior Art
Prior art security alarm systems often make use of magnetic switches attached to doors and windows and integrated with the system for detecting unauthorized openings. One common type of magnetic switch used in these situations is a so-called reed switch. It has been found that reed switches are subject to unauthorized manipulation through use of an external magnet. Specifically, an intruder can hold a relatively strong magnet adjacent the reed switch which will then be operated (to either open or close depending on the control scheme). With this accomplished, an intruder can open the door or window without triggering the alarm system.
A number of magnetic switches have been proposed in the past to overcome the inherent deficiencies of reed switches. U.S. Pat. Nos. 5,997,873, 5,530,428, 5,332,992, 5,673,021, 5,880,659, and pending U.S. patent application Ser. No. 09/909,216 filed Jul. 19, 2001 describe switches of this type. These switches typically include a pair of spaced apart switch elements with a shiftable body (e.g., a spherical ball) movable between a first position where the ball is in simultaneous contact with both elements and a second position out of such simultaneous contact. An alarm circuit is operatively coupled with the switch elements so as to detect movement of the body. These switches represent a very significant advance in the art.
SUMMARY OF THE INVENTION
The present invention is directed to improved magnetic switches for detecting relative movement between first and second members such as doors/door frames or windows/window frames, and normally are used to detect when one of the members is moved from a first position in close adjacency with the second member, to a second position where the one member is moved to a separated open position. Broadly speaking, the magnetic switches of the invention include a switch assembly for mounting to the first member and having first and second switch elements in spaced relationship to each other, an electrically conductive body shiftable between a first body position where the body is in simultaneous contact with both of the switch elements, and a second body position where the body is out of contact with both of the switch elements. The switch assembly also includes a first magnetically attractive component adjacent the contacts in the first structural member and a second magnetically attractive component for mounting to the second member. The first and second attractive components are selected and located so that, when the first and second structural members are in the first, adjacent position, the body will be shifted to a position out of simultaneous contact with said first and second switch elements by virtue of a magnetic attraction between the body and the second attractive component; moreover, when the first and second members are in the second, separated position, the body will be shifted to a position into simultaneous contact with both of said switch elements by virtue of a magnetic attraction between the body and the first attractive component.
In preferred forms, the shiftable switch body is permanently magnetized and the first and second attractive components may be complementary magnets or formed of steel or other magnetically susceptible material. Alternately, the first and second attractive components may be permanently magnetic whereas the shiftable body is formed of steel or other material which is magnetically attractive to the components.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
illustrates a preferred magnetic switch in accordance with the invention, depicted in use for protecting a door;
FIG. 2
is a vertical sectional view depicting the construction and operation of the preferred magnetic switch when the door is closed;
FIG. 3
is a vertical sectional view similar to that of
FIG. 2
, but illustrating the operation of the preferred magnetic switch when the door is open; and
FIG. 4
is a schematic depiction of a preferred alarm system using the preferred magnetic switch device of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Turning now to the drawing,
FIG. 1
illustrates a magnetic switch
10
(dashed lines) shown in use with a door frame
12
and door
14
. Appropriate electrical leads
16
,
18
are operatively coupled with the switch
10
as will be described below in more detail.
The switch
10
includes a switch assembly
20
designed to be secured to frame
12
, as well as a second attractive component
22
which is mounted to door
14
. The switch assembly
20
in preferred forms includes a housing
24
having a circumscribing annular sidewall
26
, an integral concavo-convex bottom wall
28
and a top cover
30
. Preferably, the integral sidewall and bottom wall
26
,
28
presents a circumscribing flange
32
and is formed of a suitable electrically conductive stainless steel such as
304
. The top cover
30
includes an outboard flange
34
adapted to mate with flange
32
, and a central glass or ceramic nonconductive plug
38
. The flange
34
is preferably formed of stainless steel.
The assembly
20
also includes an elongated, depending, substantially upright first switch element
40
which as shown extends downwardly through plug
38
to a point spaced above bottom wall
28
, the latter having an annular contact surface
42
which serves as the second switch element.
A shiftable body
44
is located within housing
24
and is formed of electrically conductive material. Preferred configurations of body
44
include substantially spherical balls as well as cylinders.
The overall assembly
20
further includes a first attractive component
45
associated with housing
24
. In the illustrated embodiment, the component
45
is situated slightly below and exteriorly of housing
24
and is laterally offset rightwardly relative to the central axis of the housing.
The top cover
30
is welded to sidewall
26
at the facing contact between the flanges
32
and
34
, thereby creating a hermetically sealed internal chamber
46
. It is preferred that the chamber
46
be filled with an inert gas such as argon.
As illustrated, the housing
24
and first attractive component
45
may be located within a mounting box
48
positioned within an appropriately sized recess in frame
12
. However, such a mounting arrangement is not essential.
The second attractive component
22
is mounted to door
14
, preferably along a vertical edge thereof near the top of the door. When the door
14
is closed relative to frame
12
, it will be seen that the component
22
is directly in juxtaposition to housing
24
. Obviously, when the door
14
is opened, the component
22
is shifted away from the housing
24
.
The materials used in fabricating the first and second attractive components
45
,
22
and body
44
can be varied, so long as the operational principles of the switch
10
are maintained. For example, and in preferred forms, the body
44
may be formed of a permanently magnetized material. Suitable materials include an appropriate samarium-cobalt alloy with a thin (usually about 0.001-0.002″) outer coating of nickel for wear purposes or neodynium iron boron. In such an instance, the attractive components
45
and
22
may be formed of steel (e.g., partially annealed steel) or of complementary magnetized material relative to the body
44
. Alternately, the first and second components
45
,
22
may be formed of permanently magnetized material while the body
44
is formed of any material which is magnetically attracted to the first and second components. As explained in more detail hereafter, the goal in selecting the materials for the components
45
and
22
and body
44
is to assure that the body
44
may be appropriately magnetically shifted when the door
14
is moved between the closed and open positions thereof.
Specifically, and referring to
FIG. 2
, it will be seen that, when the door
14
is closed relative to frame
12
, the body
44
is shifted laterally by virtue of a magnetic attraction between the second attractive component
22
and the body
44
, so as to hold the body
44
in the
FIG. 2
position out of simultaneous contact with the switch elements
40
,
42
. Of course, in this orientation, the magnetic attraction between component
22
and body
44
is greater than and overcomes the magnetic attraction between body
44
and first attractive component
45
. The offset position of the component
45
augments this differential attraction relative to body
44
.
When the door
14
is open so that second attractive component
22
is remote from the switch assembly
20
, the body
44
is magnetically shifted to the
FIG. 3
position thereof, i.e., in simultaneous contact with the switch elements
40
,
42
. As will be readily understood, this shifting is effected because of the magnetic attraction between the body
44
and first attractive component
45
.
FIG. 4
illustrates a conventional hookup of switch
10
within an alarm circuit
52
. In particular, the housing
24
is electrically coupled with a conventional alarm control
54
, that is lead
16
is operatively coupled with first switch element
40
and lead
18
is coupled with the second switch element
42
, with both leads connected to control
54
. The alarm circuit
52
in the illustrated embodiment is configured so that when door
14
is closed, the body
44
is in the
FIG. 2
position, and no alarm signal is generated. However, when the door
14
is opened and the body
44
is shifted to the
FIG. 3
position, such a signal is generated. An alarm bell
56
or similar output device is typically connected with control
54
.
It will thus be appreciated that if an intruder uses an external magnet (not shown) in an attempt to defeat switch
10
while door
14
is closed, the body
44
is moved because of the magnetic attraction between such external magnet to the
FIG. 3
position. Specifically, a magnet placed adjacent frame
12
in proximity to switch assembly
20
when door
14
is closed will have the effect of shifting body
44
to the first position thereof in simultaneous contact with switch elements
40
,
42
. Consequently, any such attempt to defeat the switch
10
will immediately set off the alarm.
As explained above, the relative magnetic strengths or susceptibilities of the first and second components
45
,
22
relative to body
44
must be considered in the design of switch
10
. That is, the magnetic attraction generated between the body
44
and component
22
when the door
14
is closed must be significantly stronger than the countervailing magnetic attraction between the body
44
and the first component
45
.
Claims
- 1. A magnetic switch for detecting relative movement between first and second members, said switch comprising:a switch assembly for mounting to the first member, including a first switch element, a second switch element in spaced relationship to the first element, an electrically conductive substantially spherical ball, and a first attractive component, said ball shiftable between a first position where the ball is in simultaneous contact with said first and second switch elements, and a second position where the ball is out of said simultaneous contact with both of the switch elements; and a second attractive component for mounting to said second member, said first and second attractive components being selected and located so that, when the first and second members are in an initial relative orientation wherein the second attractive component is proximal to said switch assembly, said ball will be shifted to said second position thereof by virtue of a magnetic attraction between said ball and said second attractive component, and so that, when the first and second members are in a different relative orientation wherein the second attractive component is remote from the switch assembly, said ball is shifted to said first position thereof by virtue of a magnetic attraction between the ball and said first attractive component.
- 2. The switch of claim 1, said first attractive component formed of partially annealed steel.
- 3. The switch of claim 2, said switch assembly including a closed housing, said first attractive component being associated with said housing.
- 4. The switch of claim 3, said first attractive component being formed separately of said housing and proximal thereto.
- 5. The switch of claim 3, said housing including a cover formed of non-conductive material.
- 6. The switch of claim 1, said second attractive component comprising a ferromagnetic component.
- 7. The switch of claim 6, said ferromagnetic component being a permanent magnet.
- 8. The switch of claim 1, said ball being formed of a permanently magnetized material.
- 9. The switch of claim 8, said ball formed of a material selected from the group consisting of samarium-cobalt alloy and neodynium iron boron.
- 10. The switch of claim 1, said first and second attractive components being formed of permanently magnetized material, said ball being formed of a material which is magnetically attracted to the first and second attractive components.
- 11. The switch of claim 1, said first switch element presenting an elongated, rod-like configuration which is oriented in a substantially upright manner, said second switch element being substantially disc-like with the second switch element disposed below the first switch element and generally transverse to the longitudinal axis of the first switch element.
- 12. The switch of claim 11, said second switch element presenting a concave surface adjacent said first switch element.
- 13. A magnetic switch for detecting relative movement between first and second members when the members are moved from a first, substantially adjacent position to a second position where the members are separated, said switch comprising:a switch assembly for mounting to the first member, including a housing presenting a chamber with a circumscribing sidewall, a concavo-convex bottom wall, and a top cover, said top cover including a relatively weak first attractive component, said bottom wall having a contact surface; an elongated, electrically conductive element extending downwardly through said top cover and into said chamber, said elongated element and said contact surface defining first and second switch elements, respectively; and a shiftable body within said chamber, said body shiftable between a first position where the body is in simultaneous contact with said first and second switch elements, and a second position where the body is out of said simultaneous contact with both of the switch elements; and a second attractive component for coupling to said second member, said first and second attractive components being selected and located so that, when the first and second members are in an initial relative orientation wherein the second attractive component is proximal to said switch assembly, said body will be shifted to said second position thereof by virtue of a magnetic attraction between said body and said second attractive component, and so that, when the first and second members are in a different relative orientation wherein the second attractive component is remote from the switch assembly, said body is shifted to said first position thereof by virtue of a magnetic attraction between the body and said first attractive component.
- 14. The switch of claim 13 said first attractive component formed of partially annealed steel.
- 15. The switch of claim 14, said first attractive component being associated with said housing.
- 16. The switch of claim 15, said first attractive component being formed separately of said housing and proximal thereto.
- 17. The switch of claim 15, said housing including a cover formed of non-conductive material.
- 18. The switch of claim 13, said second attractive component comprising a ferromagnetic component.
- 19. The switch of claim 18, said ferromagnetic component being a permanent magnet.
- 20. The switch of claim 13, said body comprising a substantially spherical ball.
- 21. The switch of claim 13, said body being formed of a permanently magnetized material.
- 22. The switch of claim 21, said body formed of a material selected from the group consisting of samarium-cobalt alloy and neodynium iron boron.
- 23. The switch of claim 13, said first and second attractive components being formed of permanently magnetized material, said body being formed of a material which is magnetically attracted to the first and second attractive components.
- 24. The switch of claim 13, said first switch element presenting an elongated, rod-like configuration which is oriented in a substantially upright manner, said second switch element being substantially disc-like with the second switch element disposed below the first switch element and generally transverse to the longitudinal axis of the first switch element.
- 25. The switch of claim 24, said second switch element presenting a concave surface adjacent said first switch element.
- 26. A magnetic switch for detecting relative movement between first and second members, said switch comprising:a switch assembly for mounting to the first member, including a first switch element, a second switch element in spaced relationship to the first element, an electrically conductive body and a first attractive component, said body shiftable between a first position where the body is in simultaneous contact with said first and second switch elements, and a second position where the body is out of said simultaneous contact with both of the switch elements; and a second attractive component for mounting to said second member, said first and second attractive components being selected and located so that, when the first and second members are in an initial relative orientation wherein the second attractive component is proximal to said switch assembly, said body will be shifted to said second position thereof by virtue of a magnetic attraction between said body and said second attractive component, and so that, when the first and second members are in a different relative orientation wherein the second attractive component is remote from the switch assembly, said body is shifted to said first position thereof by virtue of a magnetic attraction between the body and said first attractive component, said first switch element presenting an elongated, rod-like configuration which is oriented in a substantially upright manner, said second switch element disposed below the first switch element and generally transverse to the longitudinal axis of the first switch element.
- 27. The switch of claim 26, said second switch element comprising a substantially disc-like portion.
- 28. The switch of claim 26, said first attractive component formed of partially annealed steel.
- 29. The switch of claim 28, said switch assembly including a closed housing, said first attractive component being associated with said housing.
- 30. The switch of claim 29, said first attractive component being formed separately of said housing and proximal thereto.
- 31. The switch of claim 29, said housing including a cover formed of non-conductive material.
- 32. The switch of claim 26, said second attractive component comprising a ferromagnetic component.
- 33. The switch of claim 32, said ferromagnetic component being a permanent magnet.
- 34. The switch of claim 26, said body comprising a substantially spherical ball.
- 35. The switch of claim 26, said body being formed of a permanently magnetized material.
- 36. The switch of claim 35, said body formed of a material selected from the group consisting of samarium-cobalt alloy and neodynium iron boron.
- 37. The switch of claim 26, said first and second attractive components being formed of permanently magnetized material, said body being formed of a material which is magnetically attracted to the first and second attractive components.
US Referenced Citations (4)