DOOR POSITION SENSOR FOR AN ELECTROMAGNETIC DOOR LOCK

Abstract

A door position sensor of an electromagnetic door lock. The electromagnetic lock also includes an electromagnet and a strike plate. The electromagnet is secured to the door frame and the strike plate is movably mounted to the door so that a controlled amount of door movement in the opening direction is permitted while the strike plate remains in contact with an energized electromagnet. The door position sensor may comprise a sensor in or on the electromagnet and a permanent magnet mounted to the door and disposed in proximity to the sensor when the door is in a closed position. The sensor may be a reed switch or a Hall Effect sensor. The permanent magnet and strike plate may be mounted to the door by a mounting tray. The mounting tray may include indicia to aid in providing a proper alignment of the strike plate to the door and electromagnet.

Claims

1. A door position sensor for use in conjunction with an electromagnetic door lock for securing a door to a door frame, wherein the electromagnetic door lock includes a strike plate assembly and an electromagnet and wherein a strike plate of said strike plate assembly is magnetically held in contact with said electromagnet when said electromagnet is energized to secure said door to said door frame, said door position sensor comprising: a) a sensor connectable to said door frame; and b) a permanent magnet fixably connectable to said door, wherein movement of said door away from said door frame is detected by said door position sensor while said strike plate is held in contact with said electromagnet.

2. The door position sensor of claim 1 wherein said sensor is a Hall Effect sensor or a reed switch.

3. The door position sensor of claim 1 wherein said movement of said door away from said door frame is less than about ¾ inches.

4. The door position sensor of claim 1 wherein said movement of said door away from said door frame is within the first ⅛ inches of door movement away from said door frame.

5. The door position sensor of claim 1 wherein said sensor is on or in said electromagnet.

6. The door position sensor of claim 1 wherein a second permanent magnet is fixably connected to said door, a second sensor is connectable to said door frame to form a second door position sensor, and wherein movement of said door away from said door frame is detected by at least one of said door position sensors while said strike plate is held in contact with said electromagnet.

7. The door position sensor of claim 1 further including a strike tray having a cavity defined by said strike tray and fixably connectable to said door, wherein said permanent magnet is integrally mounted to said strike tray and wherein said cavity is proportioned to receive said strike plate.

8. The door position sensor of claim 7 wherein a second permanent magnet is integrally mounted to said strike tray and a second sensor is connectable to said door frame to form a second door position sensor, and wherein movement of said door away from said door frame is detected by at least one of said door position sensors while said strike plate is held in contact with said electromagnet.

9. The door position sensor of claim 7 wherein said strike tray includes indicia to aid in the proper positioning of the strike plate relative to the electromagnet.

10. The door position sensor of claim 7 wherein said strike tray includes a wall and wherein when said strike plate is received in said cavity, said strike plate abuts said wall to align said strike plate with the electromagnet.

11. The door position sensor of claim 10 wherein said cavity is defined by at least one wall or at least one edge for receiving said strike plate.

12. An electromagnetic door lock for selectively locking and unlocking a door to a door frame, the door being pivotally coupled to the door frame, the electromagnetic lock comprising: a. an electromagnet mountable to the door frame; b. a strike plate configured to be mounted to the door; c. a door position sensor comprising a permanent magnet fixably connectable to said door and a sensor on or in said electromagnet, wherein movement of said door away from said door frame is detected by said door position sensor while said strike plate is held in contact with said electromagnet when energized.

13. The electromagnetic door lock of claim 12 wherein said sensor is a Hall Effect sensor or a reed switch.

14. The electromagnetic door lock of claim 12 wherein said movement of said door away from said door frame is less than about ¾ inches.

15. The electromagnetic door lock of claim 12 wherein said movement of said door away from said door frame is within the first ½ inches of door movement away from said door frame.

16. The door position sensor of claim 12 wherein a second permanent magnet is fixably connected to said door, a second sensor is on or in said electromagnet to form a second door position sensor, and wherein movement of said door away from said door frame is detected by at least one of said door position sensors while said strike plate is held in contact with said electromagnet.

17. The door position sensor of claim 12 further including a strike tray having a cavity defined by said strike tray and fixably connectable to said door, wherein said permanent magnet is integrally mounted to said strike tray and wherein said cavity is proportioned to receive said strike plate.

18. The door position sensor of claim 17 wherein a second permanent magnet is integrally mounted to said strike tray and a second sensor is connectable to said door frame to form a second door position sensor, and wherein movement of said door away from said door frame is detected by at least one of said door position sensors while said strike plate is held in contact with said electromagnet.

19. The door position sensor of claim 17 wherein said strike tray includes indicia to aid in the proper positioning of the strike plate relative to the electromagnet.

20. The door position sensor of claim 17 wherein said strike tray includes a wall and wherein when said strike plate is received in said cavity, said strike plate abuts said wall to align said strike plate with the electromagnet.

21. The door position sensor of claim 20 wherein said cavity is defined by at least one wall or at least one edge for receiving said strike plate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG. 1 shows a typical electromagnetic door lock installation;

[0027] FIG. 2 is a plan view of an electromagnetic door lock, including a strike plate and permanent magnets connected to sides of the strike plate as in the prior art;

[0028] FIG. 3 is a plan view of a mounting bracket for the electromagnet and a template used in mounting the strike plate to a door as in the prior art;

[0029] FIG. 4 is an exploded perspective view of the strike plate with the at least one permanent magnet connected to the strike plate and the strike plate mounting bolt assembly used to movably mount the strike plate to the door;

[0030] FIG. 5 is an exploded perspective view of the strike plate in accordance with the invention with one of the associated permanent magnets separately mountable/mounted to the door;

[0031] FIG. 5A is a schematic drawing of an electromagnetic door lock in a door-closed position in accordance with the invention;

[0032] FIG. 5B is a schematic drawing of the electromagnetic door lock shown in FIG. 5A with the door opened a first distance without separation of the armature from the electromagnet in accordance with the invention; and

[0033] FIGS. 6 and 6A are exploded perspective views of a strike plate and tray assembly in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0034] FIG. 1 shows a typical electronic door lock installation. In a typical installation, an electromagnet 12 is secured to a door frame 14. A ferromagnetic armature or strike plate 16 is mounted on front face 33 of door 18. When door 18 is closed and electromagnet 12 is energized, electromagnet 12 exerts a magnetic force against strike plate 16 to hold door 18 in a closed and magnetically locked position.

[0035] FIGS. 2 through 4 show electromagnetic lock 20 comprised generally of an electromagnet 12 and strike assembly 22 which includes strike plate 16 and permanent magnets 62 connected to ends of strike plate 16. A prior art door position sensor 32 as shown as shown in FIG. 2 includes permanent magnet 62 connected to strike plate 16 and sensor 65 on or in electromagnet 12 wherein magnet 62 is disposed in proximity to sensor 65 when the door is closed. With reference to FIG. 3, as disclosed in commonly owned U.S. Patent Publication No. 2013/0127260, electromagnet 12 may be mounted onto a door frame 14 via electromagnet mounting bracket 26 or other mounting means. A template 28 may be mounted to door 18 and keyed to reference mounting bracket 26 so as to indicate proper placement and hole sizes and depths for drilling pilot holes 30 used in mounting strike plate. Permanent magnet 62 is used to sense the proximity of strike plate 16 to electromagnet 12 and, in conjunction with sensor 65 in or on the electromagnet, form door position sensor 32. Note that, since the permanent magnet 62 is connected directly to the strike plate, door position sensor 32 of the prior art detects only the movement of magnet 62, and therefore strike plate 16, away from electromagnet 12. Sensor 32 does not sense initial movement of the door away from the door frame while the strike plate remains in contact with an energized electromagnet.

[0036] Turning further to FIG. 4, an exploded view of the device described in reference to FIG. 2 is shown. Included in FIG. 4 is strike assembly 22, including strike plate 16 and permanent magnets 62 connected to ends of strike plate 16. FIG. 4 also depicts an exploded view of strike plate strike plate mounting bolt assembly for movably mounting the strike plate to the door, as disclosed in commonly owned U.S. Provisional Application Ser. No. 62/322,344, hereby incorporated by reference. Strike assembly 22 including strike plate 16 and one or more permanent magnets 62, is movably mounted to door 18 via strike plate mounting bolt assembly 34. One or more flexible washers 36 may be included to allow strike plate 16 to move, to a degree, so that strike plate 16 can abut the electromagnet in full contact for maximum hold force when door 18 is shut and the electromagnet is energized. Guide pins 38 are mounted in holes 31 in the door whereby pins 38 may slideably mate with corresponding holes in the strike plate (not shown) so as to keep the strike plate in proper alignment with the door through the strike plate's movement relative to the door. Strike plate mounting bolt assembly 34 may include a bolt (see e.g., bolt 40 in FIG. 6A), post 42 and a resilient member 44. In one aspect of the invention, resilient member 44 is a Belleville washer assembly composed of at least one Belleville washer. As seen in FIG. 6A, bolt 40 may include a flange or head 46 which abuts the rear face 48 of door 18 (see FIG. 1), and a shaft 50. Through bore 30′, formed in door 18, is sized to receive an outer diameter of shaft 50. Head 46 of bolt 40 may be configured to be tamper-resistant from its exposed end.

[0037] Returning to FIG. 4, post 42 includes head end 52 and shaft end 54 wherein the head end is larger in diameter than the shaft end. Male threads formed in shaft end 54 are configured for engagement with female threads in bolt 40. Strike plate 16 includes first bore 56 and second bore 58 larger in diameter than first bore 56. First bore 56 is sized to loosely receive shaft end 54 of post 42. Second bore 58 forms a cavity for receiving resilient member 44 which may be comprised of one more individual Belleville washers. Each Belleville washer may be dimensioned to have an outer diameter smaller than a diameter of second bore 58 and a center hole larger in diameter than the outer diameter of shaft end 54 of post 42.

[0038] To complete the assembly of the strike plate to the door, bolt 40 is inserted into through bore 30′ defined within door 18. After inserting the shaft end 54 of post 42 through each bore of the at least one Belleville washers, shaft end 54 is inserted through first and second bores 56, 58 of strike plate 16. Male threads on shaft end 54 are then threaded into female threads within bolt 40. Post 42 is then tightened into bolt 40 until opposing surfaces of the at least one Belleville washer are in contact with second bore surface 58 and the underside of head end 52 of post 42 and, preferable, until post head end 52 is flush or below the outer surface of the strike plate 16.

[0039] As described in commonly owned U.S. Provisional Application Ser. No. 62/322,344, selective stacking of two or more Belleville washers (Belleville washer assembly 44) may be utilized to tune the force/deflection characteristics needed for the particular application. As is known in the art, a single Belleville washer is generally conical in cross-section and exhibits certain load/deflection characteristics based upon its thickness, material, shape, etc. When two washers are stacked so that their convex surfaces are facing in the same direction, the force (load) doubles with no increase in deflection. When two washers are stacked so that their convex surfaces are facing in opposite directions, deflection is doubled with no increase in force (load). Thus, by selecting the number of washers and the relative orientations of the selected washers, the force/deflection characteristic of the collection of Belleville washers can be varied to suit the application.

[0040] With reference to FIGS. 5, 5A and 5B, and in accordance with the invention, one or more permanent magnets 62′ is fixedly mounted directly to door 18 by fasteners 63 inserted into holes 67. (In reference to FIG. 5, one magnet (left side) is shown for mounting to the door and the right side magnet is already mounted to door 18). Each one or more magnets 62′ is positioned so as to correspond to and magnetically engage with a respective sensor 65 housed within electromagnet 12 when door 18 is in the fully closed position, thereby forming a door position sensor. By way of example, electromagnet 12 may include one or more reed switches 65a as sensors, in or on the electromagnet, in the vicinity shown as X in FIG. 2, and excited by a respective permanent magnet 62′. The one or more sensors may have a first operating condition (i.e. open or closed contacts in the exemplar reed switch) when door 18 is fully closed as shown in FIG. 5A. As the door is opened while strike plate 116 remains in contact with the electromagnet (FIG. 5B), one or more magnets 62′ no longer bear upon the sensor causing the sensor to toggle to the opposing second operating condition (i.e. the open contacts are now closed or vice versa). The operating condition status of the sensor may be monitored by software operating in conjunction with electromagnetic lock 20, or by software provided by the user in the field, so as to sense the position of door 18 relative to door frame 14. It should be noted that, because one or more magnets 62′ are fixedly mounted to door 18, door 18 may be opened a first distance—shown as D.sub.1 minus D in FIGS. 5A and 5B (such as less than about ¾ inches)—due to initial compression of Belleville washer assembly 44 before strike assembly 22 begins to move away from electromagnet 12. The initial movement causes sensor 65, such as reed switch 65a, to toggle and to cause the software to sense an opened door state while the strike plate remains in contact with the energized electromagnet. Thus, a door-opening signal is triggered much earlier than if triggered by initial movement of the strike plate away from the electromagnet.

[0041] In the case of an electromagnetic door lock having the De-Mag design feature, compression of Belleville washer assembly 44 allows door 18 to move away from door frame 14 to thereby allow the delay function of the lock to operate. In the case of an electromagnetic door lock having an Eco-Mag design feature, compression of the Belleville washer assembly 44 allows the lock circuitry time to sense an initial unauthorized movement of the door away from the door frame (i.e., movement of the door without receipt of proper credentials) and to then provide full power to the electromagnet to keep the door in its locked state.

[0042] The one or more reed switches 65a discussed above may be replaced with one or more Hall Effect sensors 65b to provide greater sensitivity for detecting initial door movement away from the door frame in an opening direction which may be required by the Eco-Mag design feature. With greater sensitivity, a Hall Effect sensor may be capable of detecting initial door movement away from the door frame of as little as about ⅛ inch, as measured between the face of the electromagnet and the associated permanent magnet. Thus, in the case of an electromagnetic door lock having an Eco-Mag design feature, within the first ⅛ inch of door movement in the opening direction, if an unauthorized attempt to open the door is detected (the door is moved in an opening direction without proper credentials) the circuitry of the electromagnetic door lock will receive a signal from the Hall Effect sensor and provide full power to the electromagnet to prevent the door from being opened further.

[0043] Turning now to FIGS. 6 and 6A, in accordance with a further aspect of the invention, exploded views of a strike assembly 122 are shown. Again, a complementary electromagnet (such as electromagnet 12 shown in FIG. 2), with suitable sensor 65, 65a, 65b as described above, is mounted to door frame 14 as known in the art. Strike assembly 122 is generally comprised of a strike plate 116, strike tray 124 and at least one permanent magnet 162 integrally connected to tray 124. Strike tray 124 has a back panel 125 and walls 126, 127. Opposing side edges 128, 129 abut permanent magnets 162, respectively. Walls 126, 127 and side edges 128, 129 define a cavity 131 which is proportioned to receive strike plate 116. Strike tray 124 includes a plurality of holes 130 configured to receive fasteners 132 for fixedly mounted strike tray 124 to front face 32 of door 18. As shown in FIG. 6, to properly position and orient strike tray 124, and to provide the location for pilots holes 130′ within door 18 which correspond to mounting holes 130 on strike tray 124, back panel 125 of strike tray 124 may include template indicia 133 keyed to reference mounting hole locations of bracket 26.

[0044] Strike plate 116 may be movably mounted to door 18 and within strike tray 124 via strike plate mounting bolt assembly 34, as described above. It should be noted that guide pins 38 (see FIG. 4) and corresponding holes in the strike plate and door are no longer necessary. In accordance with the invention, strike plate 116 slideably resides within cavity 128 where at one or more of walls 126, 127 and side edges 128, 129 have a sufficient thickness to abut a side surface 150 of strike plate 116 such that strike plate 116 may remain within cavity 131 and in proper alignment with the door through the strike plate's movement relative to the door. This allows the body of the face plate to be unimpeded, without any holes needed to receive the guide pins. Therefore, with the greater mass due to the absence of guide pin holes, the holding force exerted on the ferromagnetic strike plate by the energized electromagnet is enhanced.

[0045] As described above, strike plate mounting bolt assembly 34 may include bolt 40, post 42 and a Belleville washer assembly 44 composed of at least one Belleville washer as described above. As seen in FIG. 6A, bolt 40 may include a flange or head 46 which abuts the rear face 48 of door 18 (see FIG. 1), and a shaft 50. Through bore 130″ formed in door 18 and hole 134 in tray 124 are sized to receive an outer diameter of shaft 50. Head 46 of bolt 40 may be configured to be tamper-resistant from its exposed end.

[0046] As described above, post 42 includes head end 52 and shaft end 54 wherein the head end is larger in diameter than the shaft end. Male threads formed in shaft end 54 are configured for engagement with female threads in bolt 40. Strike plate 116 includes first bore 156 and second bore 158 larger in diameter than first bore 156. First bore 156 is sized to loosely receive shaft end 54 of post 42. Second bore 158 forms a cavity for receiving Belleville washer assembly 44 which may be comprised of one more individual Belleville washers. Each Belleville washer may be dimensioned to have an outer diameter smaller than a diameter of second bore 58 and a center hole larger in diameter than the outer diameter of shaft end 54 of post 42.

[0047] To complete the assembly of strike assembly 122 to door 18, strike tray 124 (with attached permanent magnet(s)) is first aligned with and secured to door 18. Then, bolt 40 is inserted into through bore 130″ defined within door 18 and hole 134 in strike tray 124. After inserting the shaft end 54 of post 42 through each bore of the at least one Belleville washers, shaft end 54 is inserted through first and second bores 56, 58 of strike plate 116. Male threads on shaft end 54 are then threaded into female threads within bolt 40. Post 42 is then tightened into bolt 40 until opposing surfaces of the at least one Belleville washer are in contact with second bore surface 58 and the underside of head end 52 of post 42 and, preferable, until post head end 52 is flush or below the outer surface of the strike plate 116.

[0048] Strike tray 124 may include at least one permanent magnet 162 fixedly mounted thereon, as described above. Sensor 65 may include a Hall Effect sensor 65b positioned to be excited by magnet 162 when door 18 is in the fully closed position. Complementary electromagnet may alternatively include a reed switch 65a to be excited by the at least one permanent magnet 162. In the case where a permanent magnet is disposed adjacent each side wall 128, 129 of strike tray 124, any combination of reed switches/Hall Effect sensors may be incorporated in the complementary electromagnet, making the strike assembly 122 flexibly adaptable to a multitude of electromagnetic lock assemblies found in the field. For example, a first permanent magnet may be used in cooperation with a Hall Effect sensor to operate an Eco-Mag design feature while a second permanent magnet may be used in conjunction with a reed switch to operate a De-Mag design feature or to work in conjunction with another type of field-selected circuitry in need of sensing the initial movement of a door.

[0049] In FIGS. 5, 5A, 5B and 6, the “one or more” permanent magnets 62′ are shown as two permanent magnets, both being fixably connectable to the door. It is understood that the invention disclosed herein also comprehends one permanent magnet being fixably connectable to the door and a second permanent magnet being fixably connectable to an end of the strike plate.

[0050] Although the present invention has thus been described in detail with regard to the preferred embodiments and drawings thereof, it should be apparent to those skilled in the art that various adaptations and modifications of the present invention may be accomplished without departing from the spirit and the scope of the invention. Accordingly, it is to be understood that the detailed description and the accompanying drawings as set forth hereinabove are not intended to limit the breadth of the present invention, which should be inferred only from the following claims and their appropriately construed legal equivalents.