GB2310063A

GB2310063A - Personal alarm

Info

Publication number: GB2310063A
Application number: GB9602399A
Authority: GB
Inventors: Helen Louise Allen
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-02-06
Filing date: 1996-02-06
Publication date: 1997-08-13
Anticipated expiration: 2016-02-06
Also published as: GB9602399D0; GB2310063B

Abstract

The present invention relates to a personal alarm 1 that can be worn next to the body eg. on a person's chest 22. The alarm comprises a casing 3 with a front face 2 and a rear face 4, the rear face having means 5,7 for suspending the alarm on the chest and a pressure activated switch 11 for activating an audible sounder within the casing. The sounder is activated by pressing on the front face of the casing with a force to compress the switch against the chest. The sounder may then be deactivated by pressing on the switch again. The alarm may take the form of a brooch, pendant, bracelet or buckle.

Description

Personal Alarm The present invention relates to a personal alarm, and in particular to an alarm that can be worn on the body and activated by pressing on the alarm.

Known personal security alarms include devices that emit sound in order to deter or terminate an attack on a person.

One type consists of a pressurised gas canister that is activated by pressing on a nozzle to release the gas through an orifice designed to produce a loud noise. This type of personal alarm is effective in producing a loud sound, but suffers from several disadvantages. For example, in order to store enough gas, the gas canister is relatively bulky, and will normally be carried in a pocket, purse or stored in a compartment, so it will not normally be readily to hand when it is needed. It may not, therefore, be activated in time to deter an attack. Another problem is that these canister alarms are not designed to be rechargeable with gas, and so once the alarm has been used, it must be discarded. One significant limitation is that the nozzle must be pressed continuously, and if for any reason it is not pressed, the alarm will immediately stop.Since the canister alarm also has be held by hand, this hand will be disabled from defending against an attack.

According to the invention there is provided a personal alarm that may be worn on a person's chest, comprising a casing with a front face and a rear face, the rear face having means for suspending the alarm on the chest and a pressure activated switch for activating an audible sounder within the casing, in which the sounder may be activated by pressing on the front face of the casing with a force to compress the switch against the chest.

Also according to the invention there is provided an item of personal jewellery that may be worn on a person's chest, comprising a personal alarm having a casing with a front face and a rear face, the rear face having means for suspending the alarm on the chest and a pressure activated switch for activating an audible sounder within the casing, in which the sounder may be activated by pressing on the front face of the casing with a force to compress the switch against the chest.

The force required to activate the sounder should be more than may inadvertently be applied to the front face of the casing, and is therefore no less than 1.5 N and preferably between 3 N and 5 N. The force required to activate the should also not be so high as to make the alarm difficult to activate. The force should therefore not be more than approximately 10 N.

The sounder, once activated, preferably remains activated when the force on the front of the casing is released.

The alarm may have deactivating means for deactivating the sounder once the sounder has been activated. The deactivation means may be operated by the switch, for example, by pressing the switch continuously for at least five seconds.

The switch may protrude from the rear face of the casing and be push activated. Alternatively, the switch may be flush with the casing, for example being operated by a static pressure sensitive area on the rear face of the casing.

Preferably, the suspension means protrudes from the rear face of the casing more than the switch protrudes from the rear face of the casing, the switch and the suspension means being separated so that when the front of the casing is pressed, the suspension means is pressed against the chest to pivot the casing about the suspension means until the switch is compressed with sufficient force to activate the sounder. The force applied to the front face of the casing will then compress both the switch and the suspension means against the chest, so dividing the applied force between the switch and suspension means. This provides a convenient way, when the switch itself may be activated at a relatively low force, to increase the required force on the front face to activate the alarm.

Since the alarm will normally be suspended from a person's chest, and will therefore be suspended substantially vertically, the suspension means may advantageously suspend the alarm from above the alarm's centre of gravity, in order to help prevent the alarm from pulling forwards or becoming inverted. Similarly, the switch is preferably below the suspension means, so that the switch does not become widely separated from the chest as the personal alarm is being worn.

The suspension means will generally comprise fittings fixed to the rear face of the casing, for example eyelets, chains, clasps, safety pins or other such means. This would permit the personal alarm to be worn in a prominent location, such as about the neck or at the centre of the chest, for easy and quick access in the event of an emergency. The alarm could then be activated by pressure before any potential attacker could prevent its activation.

At least a part of the casing, and preferably the rear face of the casing may be provided with one or more holes for transmitting sound from the sounder.

The sounder itself may be electrically powered from a battery within the casing. In order to allow the personal alarm to be reusable, the battery should be a replaceable or rechargeable battery.

In the case of a rechargeable battery the casing may have electrical contacts which allow the battery to be recharged without removing the battery from the casing. Then, to recharge the battery, the personal alarm, or at least part of the casing, could be inserted into a battery recharger unit that has a matching socket and matching contacts to supply a recharging current to the battery.

In order to deter or terminate an attack, or to draw attention to oneself, the alarm when worn and with the sounder activated should produce a noise of at least 90 dB, and preferably 110 dB, at a distance of greater than 300 mm from the casing. A suitable alarm noise will also generally be a high-pitched tone or tone, at between 1 kHz and 5 kHz.

A low frequency amplitude modulation may be applied to the high frequency tone.

In order to provide the maximum volume within a casing of a given total surface area, yet still allow the casing to be conveniently worn and press-activated, it is preferred if the casing is substantially cylindrical in shape with circular rear and front faces.

Other shapes with somewhat less volumetric efficiency may alternatively be employed, for example a casing with generally square or rectangular faces. Whatever the shape, the switch may be near a lower edge of the rear face.

It is particularly advantageous if the personal alarm is made to look unobtrusive and disguised so that it does not appear to be an alarm. For example, at least the front face of the casing may be disguised to appear to be an item of personal jewellery.

The invention will now be described further by way of example with reference to the accompanying drawings in which: Figure 1 is a view of a personal alarm according to the invention, showing decoration applied to a front face of a casing of the alarm; Figure 2 is a view of a rear face of the casing of Figure 1; Figure 3 is a side view of the personal alarm of Figure 2, taken along the line III-III; Figure 4 is a view of the rear of the alarm with the rear face removed and with internal components exposed; Figure 5 is a cross section view of the personal alarm of Figure 2, taken along the line V-V; Figure 6 is a side view of the alarm, showing a finger pressing on the front face of the alarm to activate the alarm; Figure 7 is a diagram of power supply circuitry in the alarm; and Figure 8 is a diagram of alarm sounder circuitry in the alarm.

Figure 1 shows a personal alarm 1 which has a cylindrical shape and a decorated front face 2, and a plain side face 3 which is integral with the front face. The front face 2 is decorated with a simple surface relief pattern to disguise the alarm as jewellery.

Figures 2 and 3 show, respectively a rear a side view of the alarm 1. A rear face 4 has mounted on its surface near a top edge 6 an eyelet 5 through which a chain (not shown) may pass. Below the eyelet, but in the upper half of the rear face is a safety pin 7, the ends of which are held by a pivot 8 and a clasp 9. Both the eyelet and safety pin may be used to suspend the alarm 1 above its centre of gravity, which in this example is near the middle of the alarm.

The rear face 4, front face 2 and side 3 of the alarm define a casing which, in this example, is made from press-moulded 0.5 mm brass sheet, lacquered to prevent corrosion.

The rear face 4 of the casing connects to the other part of the casing formed by the front 2 and side 3 surfaces by a single screw 12 accessible at the rear face.

Referring now also to Figures 4 and 5, which show some of the internal components of the alarm 1, a button 11 for activating and deactivating the alarm is provided near a bottom edge 10 of the rear face 4. The button projects 2 mm above the surface of the rear face through a hole 20 in the rear face 4.

Above the button 11 are two apertures 13 in the rear face aligned with an internal sounder 14. The apertures increase the transmission of an alarm sound generated by the sounder.

The sounder 14 and button 11 are mounted on a doubled sided printed circuit board (PCB) 15. Other electronic components, described in detail below, are also mounted on the PCB, but not shown in the drawing for the sake of clarity.

The circuit board 15 is substantially disc shaped to fit snugly within the side wall 3 of the alarm. A rectangular recess 16 is cut through the board 15. In part of the recess 16 stands a stud 30 with a threaded bore for receiving the screw 12.

The ends of the recess have electrical contacts 17,18 to hold and make electrical contact with a battery 19, which powers the sounder 14 and all other circuity in the alarm.

In use, the alarm 1 may be worn on the chest area. Figure 6 shows the alarm pinned to some clothing 21 near the middle of a person's chest 22 about the sternum. The area near the sternum is a preferred location because it is centrally located with respect to the arms, easily reached by hand and not a part of the body likely to be accidentally bumped.

Importantly, the sternum also provides a relatively solid base so that when the front face 2 of the alarm is pressed by a finger 23, the force 24 imparted by the finger is transmitted to the chest 22 mainly by the eyelet 5, safety pin 7 and switch 11. The chest therefore provides restoring forces 25,26,27 through the eyelet, pin and switch, and it is the restoring force 27 through the switch which activates the alarm.

If the alarm were pressed against a part of the body with softer tissue underneath, then the rear face 4 would itself make significant contact with the body, and so reduce the restoring force 27 transmitted through the switch. This would result in the need to apply a greater force 24 when pressing the front face 2 of the alarm, making the alarm more difficult to operate. Alternatively, a switch with a lower operating force could be selected, but this would make it more difficult to avoid accidentally activating the alarm, say when putting it on or taking it off.

It has been found that the present arrangement gives satisfactory performance, being readily operated but not easily accidentally activated, with a button switch which is activated on its own by a pressure of about 1.6 N. When worn and activated as illustrated by pressing near the centre of the front face, the alarm with this switch may be activated with a pressure of approximately at least 4 N.

Figures 7 and 8 show circuit diagrams for the personal alarm described above, showing respectively a power control circuit 70 and a sounder circuit 80. The power control circuit 70 has Darlington transistors Q2 and Q4 which operate as a latching switch. In the quiescent off state, all transistors are switched off, and the circuit 70 draws no power, apart from a leakage current of about 0.05 yA.

Momentarily pressing switch SW1 to close the switch allows a current to flow from a 12 V battery B1, type MN21, through diode D1 to the base of transistor Q2, thereby switching transistor Q2 on.

This action pulls the base of transistor Q4 low so that transistor Q4 is also switched on. Current then flows from the collector of transistor Q4, supplying power to the sounder circuit 80, and also keeping both transistors Q2 and Q4 switched on.

When the power is supplied to the sounder circuit 80, a 4069 inverter chip is used to create two square wave oscillators, one with a frequency of about 6 Hz and the other with a frequency of about 3.5 kHz. The outputs from these oscillators are combined together to give a single waveform, and amplified using transistor Q1 and autotransformer T1, giving a peak voltage of approximately 50 V to drive a thin film piezo diaphragm X1.

Diode D1 stops capacitor C6 from being charged up while the alarm is sounding.

It has been found that a low frequency modulation of about 6 Hz applied to a 3.5 kHz signal produces an audible alarm which is, subjectively, much more piercing than a continuous 3.5 kHz tone with the same rating in decibels.

Pressing and holding switch SW1 will start to charge up capacitor C6 through resistor R10. When the voltage across capacitor C6 reaches 0.9 V, transistor Q3 will switch on and its collector will be pulled down to 0.2 V. After about five seconds, this will cause both transistors Q2 and Q3 to be switched off, and the circuit will return to its quiescent off state. Capacitor C6 will discharge through resistor Rll without affecting the rest of the circuit.

Resistor R14 discharges any capacitative elements in the sounder circuit to stop the circuit from reactivating after it has been switched off.

Diode D2 stops capacitor C6 from re-activating the circuit after a switch-off. Diode D3 stops the circuit 80 from being powered through switch SW1 and diode D1 during switchoff.

The circuits 70,80 draw about 120 mA at peak operation of the sounder X1. Although the MN21 battery B1 has a life of about 28 mAH, such a high current consumption gives an effective life of about five minutes.

The casing can be formed from a corrosion resistant metal, for example copper or brass, which may then be gold or silver plated to help give the appearance of precious jewellery. The casing may also be formed from sterling or brittania silver or, alternatively any of the usual carats and colours of gold. The front face 2 of the casing may also be enamelled, gem set, or otherwise sculpted or decorated to give the personal alarm a pleasing appearance, and in particular to disguise its function.

The front face 2 could also be perforated. This could enhance the aesthetic quality of the surface design, as well as the magnitude of the sound output. However, the thickness of the casing should be kept to a minimum so as not to impede the sound output from the audible alarm.

The diameter and thickness the casing portions should be small enough to be visually unobtrusive, but also large enough so that the battery B1 and audible generator X1 may be comfortably housed. For the personal alarm described above, it was found that a reasonable compromise balancing the required loudness with a reasonable size resulted in a diameter of 42 mm, and a thickness of about 10 mm.

A personal alarm as described herein may be worn at any time, and in particular may be worn by ladies as an item of jewellery. It is convenient and quick to activate, and may be used more than once before it becomes necessary to change the battery. Such a personal alarm and will provide a degree of protection and confidence whenever it is worn.

Although it is preferred that the embodiment illustrated be worn on the chest, a similar alarm may be adapted to be worn elsewhere about the body as a pendant, broach, bracelet or belt buckle.

Claims

1. A personal alarm that may be worn on a person's chest, comprising a casing with a front face and a rear face, the rear face having means for suspending the alarm on the chest and a pressure activated switch for activating an audible sounder within the casing, in which the sounder may be activated by pressing on the front face of the casing with a force to compress the switch against the chest.

2. A personal alarm as claimed in Claim 1, in which the force is at least 1.5 N.

3. A personal alarm as claimed in Claim 1 or Claim 2, in which the force is between 3 N and 10 N.

4. A personal alarm as claimed in any preceding claim, in which the sounder, once activated, remains activated when the force on the front of the casing is released.

5. A personal alarm as claimed in any preceding claim, in which the alarm has deactivating means for deactivating the sounder once the sounder has been activated.

6. A personal alarm as claimed in Claim 5, in which the deactivation means is operated by the switch.

7. A personal alarm as claimed in any preceding claim, in which the switch protrudes from the rear face of the casing.

8. A personal alarm as claimed in Claim 7, in which the suspension means protrudes from the rear face of the casing more than the switch protrudes from the rear face of the casing, the switch and the suspension means being separated so that when the front of the casing is pressed, the suspension means is pressed against the chest to pivot the casing about the suspension means until the switch is compressed with sufficient force to activate the sounder.

9. A personal alarm as claimed in any preceding claim, in which the suspension means suspends the alarm from above the alarm's centre of gravity.

10. A personal alarm as claimed in any preceding claim, in which the switch is below the suspension means.

11. A personal alarm as claimed in any preceding claim, in which the suspension means is a chain fixed to the rear face of the casing so that the alarm may be worn about the neck.

12. A personal alarm as claimed in any of Claims 1 to 10, in which the suspension means is a safety pin for pinning the alarm to clothing.

13. A personal alarm as claimed in any preceding claim, in which the rear face of the casing is provided with one or more holes for transmitting sound from the sounder.

14. A personal alarm as claimed in any preceding claim, in which the sounder is electrically powered and the alarm has a battery within the casing for powering the sounder.

15. A personal alarm as claimed in Claim 14, in which the battery is a rechargeable battery.

16. A personal alarm as claimed in Claim 15, in which the casing has electrical contacts which allow the battery to be recharged without removing the battery from the casing.

17. A personal alarm as claimed in any preceding claim, in which the alarm when worn and with the sounder activated produces a noise of at least 90 dB at a distance of greater than 300 mm from the casing.

18. A personal alarm as claimed in any preceding claim, in which the casing is substantially cylindrical in shape with circular rear and front faces.

19. A personal alarm as claimed in any preceding claim, in which the switch is near a lower edge of the rear face.

20. A personal alarm as claimed in any preceding claim, in which at least the front face of the casing is disguised to appear to be an item of personal jewellery.

21. An item of personal jewellery that may be worn on a person's chest comprising a personal alarm, in which the personal alarm is as claimed in any one of Claims 1 to 19.

22. A personal alarm substantially as herein described with reference to and as shown in the accompanying drawings.

23. A item of personal jewellery substantially as herein described with reference to and as shown in the accompanying drawings.