WO1999067492A1

WO1999067492A1 - Pet door

Info

Publication number: WO1999067492A1
Application number: PCT/US1999/014175
Authority: WO
Inventors: Beth A. Marcus; Richard R. Fontana; Christopher J. Corcoran
Original assignee: Glow Dog, Inc.
Priority date: 1998-06-22
Filing date: 1999-06-21
Publication date: 1999-12-29
Also published as: WO1999067492A9; AU4709199A

Abstract

An pet door security system which includes a locking device (26) coupled to one or more sensors (28, 30, 32, 34) for detecting a change in the local magnetic field caused by one or more magnets (54) located on a pet's collar (52), or a change in the impedance in a reference circuit caused by a resonant circuit located on a pet's collar, or a specified color on the pet's collar.

Description

PET DOOR

The present invention relates generally to pet doors, and more particularly to an improved pet door security system which prevents ingress by unauthorized pets or persons.

Unattended care of intelligent pets is an issue of increasing importance to busy people. Pet doors are generally known in the prior art for allowing ingress and egress of pets, such as cats or dogs, to/from dwellings without the necessity of human intervention. Such pet doors provide the pet with freedom to come and go at will. These pet doors are usually installed in outside doors used by people for ingress and egress to the dwelling. Use of these prior art pet doors, however, introduces other annoying problems. One such problem concerns unwanted access to the dwelling by other animals, such as other cats. Once a neighbor's cat, or a stray cat, observes the owner's cat using the pet door, that unwanted cat can "learn" how to enter and leave the subject dwelling via the pet door. Another associated problem with prior art pet doors concerns the security of the dwelling with respect to entry by unauthorized persons. Because pet doors are generally installed in an outside door, a person can reach through the pet door and unlock the outside door from the inside thereby gaining access to the dwelling. U.S. Pat. No. 4,216,743 to Robert E. Cohen discloses a magnetically unlocked pet door. U.S. Pat. No. 4,991 ,350 to Christopher P. Kirk discloses an electromagnetically controlled cat flap. The inventions disclosed in both the '743 and the '350 patents, however, have certain deficiencies. Both inventions detect the presence of a magnetic field generated by a magnet disposed on a pet's collar. Both inventions unlock their respective pet doors upon detecting the presence of a magnetic field. One embodiment of Applicant's invention also detects the presence of a magnetic field generated by a permanent magnet disposed on a pet's collar. In sharp contrast to the '743 and '350 inventions, however, this embodiment of Applicant's invention unlatches the pet door only in response to a change in the detected magnetic field. Therefore, Applicant's invention is more robust to magnetic noise in the environment and to baseline drifts in the circuitry associated with the detection and latching mechanisms. In addition, both the '743 and the '350 inventions lock in one direction only. While such a mechanism might disallow entry by an unwanted pet, these pet doors are not secure with respect to unwanted entry by persons. Applicants' invention comprises a number of embodiments. For example in a first embodiment, sensors detect the presence of a magnetic field generated by a permanent magnet disposed on a pet's collar. The mere presence of such a magnetic field, however, is not sufficient to unlock the pet door. Rather, if Applicant's pet door further detects an appropriate change in the observed magnetic field, then the pet door unlocks and allows access to the authorized pet. In a second embodiment, a passive loop antenna coupled to a resonant circuit is integrated into the authorized pet's collar. The perimeter of the pet door frame houses a loop antenna and an excitation circuit. When such an authorized pet approaches a suitably equipped pet door, the mutual inductance of the tuned collar and the door- mounted antenna produces an impedance change in the excitation circuit which causes the pet door to unlatch. In a third embodiment, a specially colored pet collar is used in combination with one or more optical sensors integrated into the frame of the pet door. The optical sensor(s) is/are wavelength specific, and unlock the pet door's latching mechanism only if a certain pre-determined color is detected. For most pets, a colored collar will be visible to the optical sensors. For pets having thick fur covering the collar and thereby masking the "key" for the pet door, a colored tag may be disposed on the pet's collar for enhance visibility. This embodiment optionally includes an illumination system for nighttime use. The invention will be better understood from a reading of the following detailed description taken in conjunction with the drawings in which like reference numerals are used depict like elements, and in which: FIG. 1 is an isometric view of a pet door according to the present invention; FIG. 2 depicts a first embodiment of the sensors used in the instant invention; FIG. 3 is a first cross sectional view of a first embodiment of the locking means used in the invention; FIG. 4 is a second cross sectional view of the first embodiment of the locking means used in the invention ; FIG. 5 illustrates a second embodiment of the sensors used in the instant invention; FIG. 6 illustrates a third embodiment of the sensors used in the instant invention; FIG. 7 is a first front perspective of a second embodiment of the locking means used in the invention; FIG. 8 is a second front perspective of the second embodiment of the locking means used in the invention; FIG. 9 is a first perspective view of the second embodiment of the locking means used in the invention; and FIG. 10 is a second perspective view of the second embodiment of the locking means used in the invention. With reference first to FIG. 1 , there is shown a pet door 10 according to Applicant's invention. Pet door 10 is disposed in door panel 12 and comprises a frame formed from top member 14, bottom member 16, first side member 18, and second side member 20. Alternatively, pet door 10 may be disposed in a wall. This frame defines an aperture through which a pet may pass in order to gain ingress/egress to a dwelling. Top member 14, bottom member 16, and side members 18 and 20 are formed from conventional materials such as wood, metal, or plastic. Flap 22 is pivotally attached to first and second side members 18 and 20 near top member 14 by rod 24. In the alternative, flap 22 is connected to top member 14 using a hinge such as a piano hinge. Flap 22 can be formed from conventional materials such as wood, metal or plastic materials. For example, flap 22 can be formed by extruding and/or injection molding polyethylene, polypropylene, polystyrene, polyethylene terephthalate. and the like. When at rest, flap 22 obstructs passage through the aperture described above. Flap 22 can be secured in place by locking means 26 disposed on bottom member 12. Locking means 26 has two positions, namely a locked position and an unlocked position. When locking means 26 is in the unlocked position, flap 22 may pivot around rod 24 and thereby allow ingress/egress. When locking means 26 is in the locked position, however, flap 22 is secured in the rest position and cannot be pivoted in either direction. Locking means 26 is normally in the locked position. Side members 18 and 20 have proximal edges located near flap 22 and opposite distal edges. Sensors 28 and 30 are located near the distal edge of side member 18. Similarly, sensors 32 and 34 are located near the distal edge of side member 20. Communication link 40 connects sensors 28 and 30 to control circuit 36. Communication link 44 connects sensors 32 and 34 to control circuit 36. Communication link 38 connects control circuit 36 to locking means 26. An external source of power, not shown in FIG. 1, is connected to locking means 26, sensors 28, 30, 32, 34 and to control circuit 36. This external source provides sufficient power, i.e. voltage and amperage, to these devices such that they are always in an operating mode. Alternatively, this external power source also includes an "on-off ' switch. When that switch is in the off position, pet door 10 is locked, and sensors 28, 30, 32, 34 as well as control circuit 36 are inoperable, and thereby incapable of causing locking means 26 to move to the unlocked position. Alternatively, an always-open switch may be employed. In a first embodiment of Applicant's novel invention, permanent magnets attached to a pet's collar causes the pet door to unlock and thereby allow ingress/egress. In this embodiment, sensors 28, 30, 32, and 34 can detect perturbations in the local magnetic field existing within the above-defined aperture. This local magnetic field comprises a vector having a certain direction and magnitude. Sensors 28, 30, 32, and 34 comprise multi-turn coils of wire. These coils can detect a change in the local magnetic field. The voltage (N) induced in the sense coils is proportional to the rate of change of magnetic filed per unit time (dB/dt) multiplied by the number of turns (Ν) in the coil according to the formula: V « Ν x dB/dt One key advantage of this design is the fact that the sensors only respond to changes in the local magnetic field. This makes the activation of the locking means robust to noise in the system and baseline drifts. In the event one or more of sensors 28, 30, 32, and 34 detect a pre-determined perturbation in the local magnetic field, i.e. a specific change to the local magnetic field vector, which exists for a pre-determined period of time, a signal is sent to control circuit 36 which in turn causes locking means 26 to move from the locked position to the open position. In contrast to prior art devices which unlock when any change in the local magnetic field is detected, Applicant's invention only responds to, i.e. unlocks, when a defined change in the local magnetic field vector is detected. This defined change includes perturbations to the direction and magnitude of the local field as well as a temporal component, i.e. the detected perturbations must exist for a defined period of time. Turning to FIG. 2, pet dog 50 is shown approaching flap 22 moving in a direction from the distal edges of side members 18 and 20 toward the proximal edges of those members, i.e. from left to right. Pet dog 50 is wearing collar 52 upon which is disposed permanent magnet 54. Although only a single magnet 54 is shown, collar 52 can include a plurality of such magnets each having a desired magnetic field, and each arranged in such a fashion such that the plurality of magnets creates a desired resultant magnetic field vector. Because the magnetic field produced by the magnet(s) 54 disposed on collar 52 are vectors, sensors 28, 30, 32, and 34 can determine the direction of travel of pet 50 wearing collar 52 as the animal approaches the pet door of this invention. Referring once again to FIG. 1 , sensors 28, 30, 32, and 34, in concert with control circuit 36, can cause locking means 26 to selectively allow movement of flap 22 in one direction only based upon the determined direction of travel of the pet. This being the case, in the absence of a perturbation in the local magnetic field caused by the approach of a pet wearing the necessary collar to activate the system, flap 22 can be securely locked such that it cannot be moved in either direction. Referring to FIG. 3, a first embodiment of locking means 26 is shown. The lower aspect of flap 20 is shown, with flap 20 being in the rest position. Rod 68 is attached to the bottom aspect of flap 20. Electric motor 76 is attached to bottom member 16, and includes external rotating shaft 62. The distal end of external rotating shaft 62 is attached to cam 60. Lip 72 comprises the distal aspect of cam 60. Motor 76 is designed such that external shaft 62 can only rotate 90 degrees in either direction. Similarly, electric motor 78 is attached to bottom member 16, and includes external rotating shaft 66. The distal end of external rotating shaft 66 is attached to cam 64. Lip 74 comprises the distal aspect of cam 64. Motor 78 is designed such that external shaft 66 can only rotate 90 degrees in either direction. Motors 76 and 78 are disposed on bottom member 16 such that when cams 60 and 64 are in the vertical position as shown in FIG. 3, gap 70 formed between the end of lip 72 and the end of lip 74 is larger than the thickness of flap 20 but smaller than the diameter of rod 68. Thus, when cams 60 and 64 are both in the vertical position, flap 20 cannot be pivoted in either direction, and cannot be removed from the locking cams in the upward direction. Referring to FIG. 4, cam 60 is shown having been rotated clockwise 90 degrees to a horizontal position. With cam 60 in this horizontal position, flap 20 can be pivoted counter-clockwise thereby allowing passage through the pet door from left to right as depicted in FIG. 4. If sensors 28, 30, 32, and 34 (FIGS. 1 and 2) detect a pet wearing an appropriate collar approaching flap 20 from the left side, control circuit 36 will actuate motor 76 (FIG. 4) thereby rotating cam 60 from the horizontal position to the vertical position and allowing passage through the pet door security system. FIG. 5 shows another embodiment of the instant invention. Loop antenna 80 is located on the inner, distal surfaces of top member 14, bottom member 16, and side members 18 and 20. Loop antenna 80 is connected by communication link 84 to excitation circuit 82 located on side member 20. As shown in FIG. 5, the pet passing through the pet door is wearing collar 88. Loop antenna 90 is located on the outer surface of collar 88, and is connected to resonant circuit 92 also located on the outer surface of collar 88. Resonant circuit 92 comprises an inductor having inductance L in parallel with a capacitor having capacitance C. (A series arrangement also is possible). The resonant frequency of that resonant circuit is determined by the equation: f_R = l/[2π(L*C)^1/2] The resonant frequency of resonant circuit 92 can be varied by changing either the inductance or the capacitance of that circuit. When a pet wearing collar 90 approaches the pet door of the instant invention, the mutual inductance of the tuned collar 90 and loop antenna 80 produces an impedance change which is sensed by excitation circuit 82. Upon detecting such an impedance change, excitation circuit 82 signals locking means 26 (FIG. 1) by communication link 86 to release flap 22. Excitation circuit 82 can determine the direction of travel of the pet wearing collar 90 by the magnitude of, and the rate of change of, the impedance change detected by loop antenna 80. This being the case, this embodiment of Applicant's invention can utilize the dual cam/dual motor locking means depicted in FIGs. 3 and 4, and described above. In a third embodiment of Applicant' s novel invention, color is used as the "key" for unlatching the pet door. Referring to FIG. 6, the pet dog is shown wearing collar 96. Substantially all of the outer surface of collar 96 bears a certain color. Sensors 90, 92, 94, and 96 are optical detectors having detection elements which are highly wavelength specific such that those sensors can detect the presence of certain specified colors. Sensors 90, 92, 94, and 96 are connected to control circuit 36 which in turn is connected to locking means 26 disposed on bottom member 12. As shown in FIG. 6, as a pet wearing colored collar 96 approaches the pet door of this embodiment through the aperture defined by bottom member 12, top member 14 and side members 18 and 20, and past sensors 90, 92, 94, and 96, one or more of those sensors detects the color "key" comprising the color disposed on collar 96 and signals control circuit 36. Control circuit then actuates locking mean 26 to unlatch flap 22 and allow passage through the pet door. For most pets, the colored collar will be visible to one or more of optical sensors 90, 92, 94, and/or 96. For pets having thick fur covering the collar, however, a tag bearing the appropriate color can be attached to the pet's collar. Referring again to FIG. 6, colored tag 98 is shown attached to collar 96. Such an attached colored tag can be affixed to either the pet's regular collar or to a colored collar which itself bears the appropriate "color key." To facilitate nighttime use, this embodiment also optionally includes an illumination system comprising motion detector 100 disposed on the inner surface of top member 14, and lights 102 and 104 located on the interior surfaces of the two side members. Motion sensor 100 and lights 102 and 104 are connected to and powered by an external source of electric power not shown in FIG. 6. In the event motion sensor 100 detects motion in near vicinity to the pet door, motion sensor 100 signals lights 102 and 104 to turn on thereby illuminating colored pet collar 96 and/or colored tag 98. Because this embodiment can only detect the approach of a pet from a single direction, passage through the pet door is only controlled in a single direction. This being the case, a different locking means is employed. Referring to FIG. 7, first front member 116 is attached to first side member 18, top member 14 and bottom member 16. Second front member 118 is attached to second side member 20, top member 14, and bottom member 16. Flap 132 is pivotally attached to first and second front members 116 and 118 near top member 14. When at rest, flap 132 obstructs passage through the pet door. Flap 132 can be secured in place unidirectionally by locking cams 120 and 122 disposed on the inside surfaces of first front member 116 and second front member 118, respectively. Cams 120 and 122 have two positions, namely a locked position and an unlocked position. Cams 120 and 122 are shown in the locked position in FIG. 7. Referring to FIG. 8, cams 120 and 122 have been rotated 90 degrees, are shown in the unlocked position. Referring now to FIG. 9, with cams 120 and 122 in the locked position, flap 132 can rotate in one direction only, i.e. clockwise. Thus when cams 120 and 122 are in the locked position, flap 132 can only be pivoted away from the pet door thereby only allowing egress. With cams 120 and 122 rotated into the unlocked position as shown in FIG. 10, flap 132 can pivot either clockwise or counterclockwise. Thus, when cams 120 and 122 are in the unlocked position, flap 132 can pivot in either direction thereby allowing either ingress or egress. Referring again to FIG. 7, the rotation of cams 120 and 122 between the locked and unlocked positions, and vice versa, is effectuated by electric motors. Electric motor 128 is attached to the inside surface of first front member 116, and includes external rotating shaft 124. The distal end of external rotating shaft 124 is attached to cam 120. Motor 128 is designed such that external shaft 124, and thereby cam 120, can only rotate 90 degrees in either direction. Similarly, electric motor 130 is attached to the inside surface of second front member 118, and includes external rotating shaft 126. The distal end of external rotating shaft 126 is attached to cam 122. Motor 130 is designed such that external shaft 126, and thereby cam 122, can only rotate 90 degrees in either direction. The invention is susceptible to modification. For example, the control unit may be programmed to restrict ingress and egress to prescribed times. Also, the collar and sensors may be keyed or coded so as to permit the sensor system to differentiate key configurations and thus permit ingress and egress of a specific pet. And, other sensor types such as magneto resistive, flux gate, magneto inductive, Hall effect, and the like, also may advantageously be employed in the present invention.

Claims

What is claimed is: 1. A pet door security system, comprising: a frame 14, 16, 18, 20, an aperture defined by the frame, the frame being adapted to be mounted in a generally upright attitude to control passage of a small animal through the aperture and whereby the frame has upper and lower members joined by a first side member and a second side member; a closure for said aperture, defined by a flap 22, the flap being pivotally mounted in said frame near said upper member so as to close said aperture when hanging in a rest position by intersecting with said bottom member and being pivotable from said rest position to permit passage of said animal through said aperture; an electrically operated locking device 26 disposed on said lower member of said frame, wherein said locking device is movable between a first position obstructing movement of said flap and a second position permitting said movement of said flap, and wherein said locking device is normally in said first position; a source of electrical energy; a circuit 36 interconnecting said source and said electrically operated locking device; and at least one sensor 28, 30, 32, 34 mounted on said frame and included in said circuit such that detection of first information by said at least one sensor will cause actuation of said electrically operable locking device such that said locking device is moved from said first position to said second position thereby allowing movement of said flap 22.

2. The pet door security system of claim 1 , wherein said at least one sensor 28, 30, 32, 34 communicates second information to said electrically operable locking device 26 upon cessation of reception of said first information, whereby said electrically operable locking device causes said locking device to move from said second position to said first position upon receiving said second information.

3. The pet door security system of claim 2, further comprising a pet collar 52, wherein said pet collar comprises at least one permanent magnet 54 disposed thereon.

4. The pet door security system of claim 3, wherein said first information comprises a changing magnetic field.

5. The pet door security system of claim 4, wherein said at least one sensor 28, 30, 32, 34 comprises multi-turn coils of wire.

6. The pet door security system of claim 5, further comprising a rod 24 disposed along the top edge of said flap, and wherein said electrically operable locking device comprises a first electric motor 76 connected to said power source and disposed on said bottom member anterior to said intersection of said flap with said bottom member, wherein said first motor has a first external shaft 62 that can be rotated 90 degrees in either direction, and a second electric motor 78 connected to said power source and disposed on said bottom member posterior to the intersection of said flap with said bottom member, wherein said second electric motor has a second external shaft 66 that can be rotated 90 degrees in either direction; and wherein said locking device comprises a first cam 60 attached to said first external shaft, such that said first cam can be rotated between a vertical position and a horizontal position, wherein said first cam has a first lip 72 disposed on its distal end, such that when said first cam is in said vertical position said first lip is superior to said rod and said first lip points toward but does not touch said flap, a second cam 64 attached to said second external shaft, such that said second cam can be rotated between a vertical position and a horizontal position, wherein said second cam has a second lip 74 disposed on its distal end, such that when said second cam is in said vertical position said second lip is superior to said rod and said second lip points toward but does not touch said flap.

7. The pet door security system of claim 6, further comprising a plurality of first cams 60 and a plurality of second cams 64.

8. The pet door security system of claim 7, wherein the width of said first cam 60 equals the length of said rod, and wherein the width of said second cam 64 equals the length of said rod.

9. The pet door security system of claim 2, further comprising a pet collar, wherein said pet collar 90 comprises: a resonant circuit 92 having a capacitor and an inductor in parallel; a passive loop antenna 80 connected to said resonant circuit; wherein said at least one sensor comprises a loop antenna connected to an excitation circuit 82, and wherein said first information comprises an impedance change in said excitation circuit.

10. The pet door security system of claim 1, wherein said electrically operable locking device is adapted to automatically revert from said second position to said first position after a specified period of time.

11. The pet door security system of claim 10, wherein said specified period of time is adjustable.

12. The pet door security system of claim 10, further comprising a pet collar, wherein said collar 96 comprises a color, and wherein said color comprises said first information.

13. The pet door security system of claim 12, further comprising a metal or plastic member 98 disposed on said pet collar 96, wherein said member comprises said color.

14. The pet door security system of claim 12, further comprising: an illumination system including at least one light bulb 102, 104 mounted on said frame and connected to said source, and wherein said illumination system has a first state and a second state, wherein said at least one light bulb is turned off when said illumination system is in said first state, and is turned on when said illumination system is in said second state, and wherein said illumination system is normally in said first state; a motion detector 100 connected to said source and connected to said illumination system such that upon detecting motion in near proximity to said frame said motion detector causes said illumination system to switch from said first state to said second state, and wherein said motion detector causes said illumination system to revert from said second state to said first state after cessation of said motion.

15. The pet door security system of claim 12, further comprising a first front member 116 attached to said first side member, to said top member, and to said bottom member, and a second front member 118 attached to said second side member, to said bottom member, and to said top member, such that said first front member and said second front member narrow the width of said aperture, and wherein said electrically operable means comprises a first electric motor connected to said power source and disposed on said first front member, wherein said first motor has a first external shaft that can be rotated 90 degrees in either direction, and a second electric motor connected to said power source and disposed on said second front member, wherein said second electric motor has a second external shaft that can be rotated 90 degrees in either direction; and wherein said locking device comprises a first cam 120 attached to said first external shaft, such that said first cam can be rotated between a first position which restricts the movement of said flap in one direction and a second position which does not restrict the movement of said flap, and a second cam 122 attached to said second external shaft, such that said second cam can be rotated between a first position which restricts the movement of said flap in one direction and a second position which does not restrict the movement of said flap.

16. The pet security system of claim 1 , wherein said sensor comprises a magnetic field sensor.

17. The pet security system of claim 16, wherein said magnetic field sensor is selected from the group consisting of a magneto resistive sensor, a flux gate sensor, a magneto inductive sensor and a Hall effect sensor.

18. The pet security system of claim 1 , wherein said sensor is key coded.

19. The pet security system of claim 1 , wherein said sensor is programmed to predetermined entry/exit schedule.