Magnetic switch assembly

Information

  • Patent Grant
  • 6603378
  • Patent Number
    6,603,378
  • Date Filed
    Thursday, September 19, 2002
    22 years ago
  • Date Issued
    Tuesday, August 5, 2003
    21 years ago
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)
Number Name Date Kind
5877664 Jackson, Jr. Mar 1999 A
5880659 Woods Mar 1999 A
5929731 Jackson, Jr. Jul 1999 A
5977873 Woods Nov 1999 A