Title:
ALARM
United States Patent 3623063


Abstract:
An alarm device in which an oscillator controls the condition of actuating means for a signalling device which provides an alarm signal when the frequency of the oscillator is changed, the device including a conductive suspending handle electrically connected to the oscillator for (a) suspending the device from a conductive doorknob of a door and (b) electrically connecting the oscillator to the doorknob, and a balancer plate for the oscillator to capacitively couple a reference portion of the oscillator to the door when the device is suspended from the doorknob by the handle, whereby touching of the doorknob changes the frequency of the oscillator to actuate the signalling device.



Inventors:
FONTAINE JOHN V
Application Number:
04/868424
Publication Date:
11/23/1971
Filing Date:
10/22/1969
Assignee:
JOHN V. FONTAINE
Primary Class:
Other Classes:
340/562
International Classes:
G08B13/26; (IPC1-7): G08B13/26
Field of Search:
340/258C,283,274
View Patent Images:
US Patent References:
3508239BURGLAR ALARM1970-04-21Fontaine
3465325SELF-CONTAINED CONTACT ALARM DEVICE1969-09-02Goldfarb et al.
3254313Touch responsive oscillator and control circuits1966-05-31Atkins et al.



Primary Examiner:
Caldwell, John W.
Assistant Examiner:
Slobasky, Michael
Claims:
Having thus described my invention, I claim

1. In a battery-operated alarm device having a radiofrequency oscillator controlling the condition of actuating means for a signalling device which provides an alarm signal when the frequency of the oscillator is changed, the combination therewith of a conductive suspending handle electrically connected to the oscillator for (1) suspending said device from a conductive doorknob of a door and (2) electrically connecting the oscillator to the doorknob, and conductive balancer plate means connected to the oscillator to capacitively couple a reference portion of said oscillator to the door when said device is suspended from the doorknob by said handle, so that the door serves as external ground for the oscillator and touching of the doorknob, even with gloves on, changes the frequency of the oscillator to actuate the signalling device.

2. In an alarm device having a battery-powered oscillator controlling the condition of actuating means for signalling means which produces an alarm signal when the frequency of the oscillator is changed, the oscillator having a tuned circuit controlling the frequency thereof, the combination therewith of a hooking conductor connected to said oscillator for hookingly attaching said device to a doorknob of a door and electrically connecting said oscillator to the doorknob, and a planar balancer conductor capacitively coupling a reference portion of said oscillator to the door when the hooking conductor is attached to the doorknob with the plane of the balancer conductor close to and parallel with the door, so that when the doorknob is touched, the frequency of the oscillator is changed to actuate the signalling means.

3. An alarm device comprising a battery supply, signalling means, actuating means for said signalling means, an oscillator controlling the condition of said actuating means to in turn cause said signalling means to produce an alarm signal when the frequency of said oscillator is changed, a conductive suspending handle electrically connected to said oscillator means and mechanically connected to a housing for the device for (a) suspending said device from a conductive doorknob of a door and (b) electrically connecting the oscillator to the doorknob, and conductive balancer plate means connected to said oscillator to capacitively couple a reference portion of said oscillator to the door when said device is suspended from the doorknob by said handle with said balancer plate means close to and parallel with the door, whereby touching of the doorknob, even with gloves on, changes the frequency of the oscillator to actuate the signalling means.

4. An alarm device having a housing and comprising,

5. attaching said device to a doorknob of a door,

6. connecting the oscillator to the doorknob, and

7. positioning said planar balancing conductor close to and parallel to the door to capacitively couple the planar conductor to the door, whereby in the operation of said device, a person touching the doorknob, even with gloves on, changes the frequency of said oscillator to change the conductive condition of said switch and thereby actuate said signalling device.

8. The alarm device as claimed in claim 4 in which said attaching means comprises a hooking handle which telescopes into and out of said housing.

9. The alarm device as claimed in claim 4 in which said signalling means comprises a transmitter.

10. The alarm device as claimed in claim 4 in which said signalling means comprises a horn or buzzer.

11. The alarm device as claimed in claim 7 in which said signalling means has a volume control.

12. THe alarm device as claimed in claim 5 in which said hooking handle has a sharp point engageable with the doorknob to pierce a film thereon and establish good electrical contact with the doorknob.

13. A portable, battery-operated alarm device comprising:

Description:
BACKGROUND OF THE INVENTION

Although many types of burglar alarms and other alarm devices have been proposed, there remains a need for a portable, battery-powered compact alarm device that a person before retiring, or at other times, can place at a door to be protected and which will sound an alarm in the event the doorknob is touched, even with gloves, before entry is gained. Some known devices have not been portable, others have required relatively large pieces of equipment, and others have required that external connections be made from the device, for example to ground the device. It would be desirable if the alarm device could hang on the doorknob of a door, but a problem is encountered in making electrical contact to the doorknob, particularly with aluminum doorknobs which often have an oxide coating which usually is nonconductive.

OBJECTS OF THE INVENTION

It is an object of the present invention to provide a portable, long battery life, self-contained, compact unit that a householder before retiring, or at other times, can simply hang on the doorknob from the inside of the residence, that will sound an alarm in the event the doorknob is touched, even with gloves, before entry is gained.

A further object of the invention is to provide one oscillator that alone will produce a variation in voltage through a change of frequency thereby reducing the number of components required to accomplish the desired results, unlike other capacity reactors which require an oscillator as well as an additional tuned circuit.

Still another object of the invention is to provide a portable alarm system as herein described with a balancer plate incorporated as an integral part thereof, thereby resulting in a workable, compact unit which requires no ground or other wires extending therefrom, resulting in increasing its desirability and usage.

A further object of the invention is to provide means whereby when the unit is hung on a doorknob the anodized or other coating which usually is nonconductive will be pierced thereby assuring contact at all times.

Then still another object of the invention is to provide means whereby the hook can be extended, positioning the unit beyond doorknob plates, found in a number of homes, which tend to interfere with its performance when in alignment with the balancer plate, while on the other hand permitting the unit to be portable by retracting the hook and be carried in a briefcase or other luggage while traveling.

While yet another object of the invention is to provide a volume control on the face of the unit whereby the user, when confined to small quarters such as a hotel room, or bedroom, can alter the volume to a suitable intensity.

Still one last object of the invention is the incorporation therein of a miniature transmitter that when the doorknob is touched before entry is gained a silent signal is transmitted to a remote receiver to in turn activate any number of apparatus.

Other objects of this invention will appear from the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

ON THE DRAWINGS

FIG. 1 is an elevational view of a portable alarm device in accordance with one embodiment of the invention showing the device hanging on a doorknob of a door;

FIG. 2 is an elevational view of the device of FIG. 1 also hanging on a doorknob, but with the handle of the device extended to position the device below a doorknob plate on the door;

FIG. 3 is a perspective view of a telescoping handle of the alarm device; and

FIG. 4 is a schematic diagram of a circuit for this embodiment of the alarm device.

Before explaining the present invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also, it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

AS SHOWN ON THE DRAWINGS

FIG. 1 shows a portable alarm device 10 suspended by a handle 12 from a conductive doorknob 14 of a door 16. The device 10 has a plastic or other nonconductive housing 18 with a grill 20 through which an audible alarm signal sounds when the doorknob 14 is touched either from the outside or the inside of the door. It is to be understood that the doorknob 14 has a like knob on the opposite side of the door 16, the two knobs being conductively connected together in the usual manner, and it is intended that if the outside knob is touched, even with gloves, the device 10 will sound an alarm. The device 10 has an on-off switch 22, a sensitivity control 25 and a volume control 24.

FIG. 2 shows the device 10 suspended by the handle 12 from a doorknob 14 having a doorplate 15 which might tend to interfere with proper operation of the device. For this reason, the handle 12 of the device is extended to position the housing 18 of the device below the door plate 15.

FIG. 3 shows an example of a telescoping handle for the device 10. The handle 12 is an arm having a hook 26 at its upper end, the handle being made of conductive material such as metal. On the lower side of the hook there is sharp point 28 which contacts the doorknob 14 when the device is suspended, and this point 28 will break through any oxide film or other similar film on the metal of the doorknob to establish good continuous electrical contact with the doorknob. Such oxide films are usually nonconductive, and they are often found on aluminum doorknobs particularly. The handle 12 extends through a bracket 30 having a flange 32 which may be attached to the housing 18 of the device through apertures 34 as with rivets. The bracket 30 is hollow, and has an opening 36 in which a contact spring 38 is mounted. The spring curves downwardly as viewed in FIG. 3 and engages the handle 12 frictionally under bias to hold the handle at any position where it is set, but to allow extension of the handle in the manner shown in FIG. 2 and retraction of the handle in the manner shown in FIG. 1. Thus, the handle telescopes relative to the housing 18 of the device to permit the handle to be extended for suspending the device below a doorplate 15 in the manner shown in FIG. 2, and also to permit the handle to be retracted either for hanging the device on a doorknob as shown in FIG. 1 or to make the device more readily portable so that it can easily be packed in luggage or the like. The handle 12 has a shoulder 40 which catches on the bracket 30 as the handle is retracted into the case and forms a stop for limiting inward movement of the handle. The handle 12 is electrically connected to an oscillator inside the case as will be described further in connection with FIG. 4.

FIG. 4 shows the circuit diagram for one embodiment of the invention. In this diagram, the handle 12 is represented by a sensor which is intended to be the electrical equivalent of the handle. A line 42 is the positive voltage supply line of the circuit. The reference or negative supply line 44 of the circuit is actually a metallic conductor plate which acts as a balancing means for the circuit. A plate 44 is shown at the left side of the circuit diagram to illustrate the fact that this is a planar conductor serving as an internal reference conductor for the circuit. The balancer plate 44 also acts to couple the oscillator of the circuit to the door when the device 10 is suspended from the handle of the door, as will be described further.

Connected between lines 42 and balancer plate 44 is a battery 46 in series with an on-off switch 48. The battery 46 may, for example, have a value of about 3 volts, and it supplies operating potential to the rest of the circuit. Also connected between line 42 and balancer plate 44 are a signalling device 50 and a semiconductor switch 52. The semiconductor switch 52 is the actuating means for actuating the signalling device 50 to sound an alarm when the frequency of the oscillator of the circuit is changed. The semiconductor switch may be a semiconductor controlled rectifier as shown, a suitable rectifier being a GE C106Y2 SCR. The signalling device 50 may be a horn or buzzer, the type of device not being critical, but a suitable horn will provide a loud alarm when it is actuated by conduction of the semiconductor switch 52. The semiconductor switch 52 is connected with its anode-cathode portion in series with the signalling device 50 with this series combination being connected between line 42 and the balancer plate 44.

Also connected between line 42 and balancer plate 44 is a third series circuit which includes the oscillator 54 of the circuit. The oscillator 54 includes a transistor 56 having an emitter 58 and its collector 60 connected in a series circuit path 62. A first tuned circuit 64 is connected between the collector 60 of transistor 56 and line 42, and a second tuned circuit 66 is connected to the emitter 58 of transistor 56. A resistor 68 is connected between tuned circuit 86 and balancer plate 44. The base 70 of transistor 56 is connected by a capacitor 72 and a resistor 71 to the balancer plate 44 and is connected by a resistor 74 to the positive supply line 42. Handle 12 is connected to base 70.

Tuned circuit 64 includes a coil 76 and a capacitor 78 in parallel, and tuned circuit 66 includes a coil 80 and a capacitor 82 in parallel. In a particular embodiment, the two coils 76 and 80 each have a resonance value of 262 kilocycles, capacitor 78 has a value of 180 pf. and capacitor 82 has a value of 39 pf. The capacitors 78 and 82 slightly modify the resonance values of the coils. Coil 76 is variable by knob 25 for sensitivity control. Knob 24 is part of the signalling device 50. In the particular embodiment being described, resistor 71 has a value of 18 kiloohms, capacitor 72 has a value of 700 pf., resistor 74 has a value of 68 kiloohms, and resistor 68 has a value of 680 ohms. In this same embodiment, the transistor 56 is an NPN-type designated 2N2924. Values are given for these components by way of example, but it is not intended that the invention should be limited in any way to these values.

It is apparent that the oscillator 54 has tuned emitter and tuned collector circuits for the transistor 56, and this tuning causes the transistor to sustain oscillations when operating potential is supplied thereto by closing the switch 48. Operating potential is applied to the base 70 of transistor 56 through the resistor 74. The oscillator 54 oscillates at the resonance frequency of the two tuned circuits 64 and 66 in this quiescent condition of the alarm device. The sensor 12, which is the handle as previously explained, electrically connects the oscillator 54, and particularly the tuned circuit 64, to the conductive doorknob 14 of the door. The balancer plate 44 is mounted on the inside of the back cover plate of the housing 18, and therefore it is positioned close to and parallel to the door 16 when the device 10 is suspended from the doorknob 14 by the handle 12. Thus, the balancer plate 44 capacitively couples the reference point of the oscillator 54 to the door 16 so that the door provide an external reference potential for the oscillator. This capacitive coupling is indicated in FIG. 4 by a dashed-line capacitor 84 which is really a distributed capacitance.

By means of this capacitive coupling, the door becomes a part of the oscillator circuit in the same sense as the relationship of one side of a capacitor has with the other. The balancing plate is, in effect, one side of the capacitor and the door is the other side of the capacitor. It should be noted that the door, if made of wood and not a conductor of electricity, is nevertheless a conductor of radiofrequency signals and has adequate mass to constitute ground for a small oscillator. The relationship of the balancing plate and the door allows the oscillator to have the necessary grounding that is essential for operation. Without this balancing plate and the capacitive coupling it provides to the door, the alarm itself becomes capacity sensitive rather than the doorknob.

When a person touches the handle 12, either on the inside of the door or on the outside of the door, even with gloves on, this places additional capacitance in parallel with the bias circuit of the transistor which changes its operating frequency. The additional capacitance is effectively amplified. The semiconductor switch 52 is normally off since the power supplied by resistor 68 is insufficient to turn the switch on. However, when the frequency of the oscillator changes, current is drawn through the gate 86 of the semiconductor switch, and this current turns on the anode-cathode portion of the switch to produce a relatively large current through the signalling device 50, causing the alarm to sound. The device 50 can be a miniature transmitter which sends an RF signal to a remote receiver having an audible alarm.

Thus, the alarm device includes an oscillator that alone will produce a variation in voltage applied to the actuating means 52 of the circuit through a change in frequency in the oscillator, and no additional tuned circuits are required other than those included in the oscillator itself. The oscillator is a simple emitter and collector tuned circuit requiring very few components. The alarm device is a portable, compact unit which can simply hang on the doorknob of a door and that will sound an alarm in the event that the doorknob is touched by a person. No ground wires or other wires need extend from the alarm device since a balancer plate is incorporated into the unit and couples the oscillator of the circuit to the door itself so that the door provides an external reference potential for the oscillator. The handle of the device is retractable and extendable, the extended position being desirable to accommodate doorknob plates found on some doors, and the retracted position being desired for other installations and also for packing of the device. The handle has a sharp point on the hooking portion thereof which assures that the handle or sensor of the device makes good electrical contact with the doorknob so that the doorknob itself acts as a sensor.