GB2119142A - Inactivity alarm system - Google Patents

Abstract

Inactivity alarm apparatus for monitoring the well-being of a subject individual comprises a transmitting station carried in the shoe of the subject arranged to transmit a burst of r.f. radiation upon each step taken by the subject and a remote receiving station (Figure 2) to receive the transmitted bursts which each reset an interval timer (28). If inactivity persists for, say, a 2 minute interval without a resetting transmission an alarm (36) is sounded. The apparatus differs from similar inactivity alarm apparatus in that the transmitting station includes an electrical generator in the form of a piezoelectric element which is struck a percussive blow each time pressure is placed on the shoe and the electrical pulse generated is applied by way of spark gap element to a tuned circuit embedded in the heel of the shoe which radiates a burst of decaying oscillations for resetting the interval timer. The use of a self contained generator simplifies the construction and obviates the disadvantages associated with battery operated systems of remembering to switch the apparatus on and off and checking the charge status of the batteries to avoid false alarms. <IMAGE>

Description

SPECIFICATION Inactivity alarm system This invention relates to inactivity alarm apparatus, that is apparatus which monitors the well-being of a subject individual by detection of physical movements expected of the individual as part of normal activity.

Inactivity alarm apparatus is usually operated in connection with preset time intervals, a timercaus- ing an alarm to be sounded in a remote location if it is not reset within the preset time interval by some action on the part of the subject. The duration of the time interval may vary between a few minutes and a day depending upon the level of supervision required and the action required to reset the timer.

On the one hand, for a low level of supervision manual operation may suffice, the action requiring a subject to press a button once a day, for example, as described in U.K. Patent Specification No 1,318,891.

On the other hand, for a high level of supervision with a preset time interval of a few minutes automatic operation is desirable. To achieve such automation the subject may carry some form of automatic signalling means, such as an acceleration responsive switch, transmitter and battery power supply as described in U.K. Patent Specification No.

1,547,3654, No. 1,514,897 or in U.S. Patent Specification No. 3165856, to effect resetting of a timer.

A need exists in industry for monitoring the well-being of industrial personnel who may be required to work alone in enclosed areas in the presence of potentially hazardous chemicals and/or machinery. Clearly a high level of supervision is required and apparatus providing it must function automatically without distracting the subject from allotted tasks.

Known forms of inactivity monitoring apparatus employing self contained battery power supplies are liable in practice to suffer from failure to ensure the apparatus is switched on and/or off, in replacing batteries nearing the end of their life and the running down of the battery supply by an excessive number of resetting transmissions through normal activity time wasting false alarms. Thus what is intended as unobtrusive automatic activity monitoring can require a greater degree of attention on the part of user subjects than they may be prepared to comply with.

It is an object of the present invention to provide automatic activity monitoring apparatus which mitigates the requirement of frequent attention associated with known apparatus.

According to the present invention inactivity alarm apparatus comprises a transmitting station adapted to be carried by a subject including a tuned electronic circuit operable to radiate electromagnetic radiation in predetermined radio frequency range in responsive to the application of an electrical pulse thereto, and a receiving station including a receiver tuned to the frequency range of the transmitter to receive transmissions therefrom and timing means operable to cause an alarm indication to be given after a preset timing interval and repose to reception of a signal by the receiver within said timing interval to be reset to begin a new timing interval, the transmitter including electrical generating means operable by a predetermined physical activity of the subject to generate an electrical pulse for the tuned electronic circuit.

The use of electrical generating means to convert the physical activity directly into the electrical pulse applied to the tuned circuit eliminates all the routine inspection and maintenance associated with battery operation.

Preferably the electrical generating means comprises a piezo electric element.

The element may be carried in footwear of the subject the activity of applying body weight to the foot causing the generation of the electrical pulse.

The element preferably is caused to be struck percussively by a hammer as a result of such activity.

Such a percussive striking produces a high voltage pulse of short duration enabling electromagnetic radiation to be radiated directly by the tuned circuit in a radio frequency range permitting of local reception, such as by a loop aerial extending around an area in which inactivity of the subjects is to cause an alarm.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1(a) is plan view of an article of footwear showing disposition of a transmitting station of inactivity alarm apparatus included therein according to the present invention, Figure l fb) is a sectional elevation through the article of Figure 1(a) and Figure 2 is a schematic representation of the receiving station associated with the transmitting station of Figure 1.

Referring to Figures 1 (a) and (b) inactivity monitoring apparatus of the present invention comprises a transmitting station 10 contained within an article of footwear such as a shoe 11 or overshoe worn by a subject whose activity is to be monitored. The transmitting station may be conveniently housed in modular form in a cavity 12 in the heel portion 13 of the shoe.

The transmitting station comprises a tuned electronic circuit formed of a parallel combination of a capacitor 14, and a multiturn inductive coil 15 extending about the periphery of the cavity 12.

The heel portion 13 also contains electrical generating means 16 in the form of a piezoelectric element 17 adapted to be struck percussively by a hammer mechanism 18 when an actuator is depressed as the shoe is walked upon. The hammer mechanism 18 may be provided by a snap-action leaf spring arrangement biased normally against a flexible cavity closure 19 which forms not only the actuator but also the floor contacting or wearing surface of the heel portion.

The piezoelectric element is provided with electrodes 20 across which the voltage is developed and these are connected by leads, 21, and by way of a spark gap element 22 to the capacitor 14 of the tuned circuit.

Each time the heel is brought into contact with the ground during walking, or the feet repositioned in a standing or seated position, the piezo-electric element is struck percussively and an electrical pulse is generated which, when of a sufficient magnitude to break down the spark gap of element 22, is applied to the tuned circuit.

The inductance and capacitance values, are chosen to give a low-impedance high-Q circuit at a resonant frequency of a few tens of Kilo Hertz. When the voltage pulse is applied by breakdown of the spark gap the circuit is decoupled from the piezoelectric element and rings for several oscillations resulting in a burst of signal radiated at the resonant frequency of the circuit.

It will be seen that the transmitter comprises only a small number of inexpensive components arranged in a simple manner, requiring little, if any, maintenance and no attention i.e. switching a power suplly on/off on the part of the subject.

By arranging for the coil 15 to extend around the periphery of the heel portion 13 the radiating efficiency is maximised.

The apparatus is intended for use in an environment where a worker is required to undertake activities alone. Within an industriai environment this will in general be a relatively small area, e.g. an isolated room, and reception of signals from such an area is readily achieved by means of a simple loop aerial extending around the periphery of the area substantially in the same plane as the transmitting coil 15 and shown schematically at 23 in Figure 2.

The provision of such loop aerials is well known and will not be described further, but in this case the use of a floor-level transmitter it is convenient to mount the loop around the base of the wall or buried in the floor.

The aerial loop 23 with a parallel connected capacitor 24 forms a circuit tuned to a resonant frequency matching that of the tuned circuit of the transmitter.

Signals induced in the aerial circuit in the form of a burst of a few cycles for each transmission are applied to a detector 25. This may take any conventional form but usefully comprises a phase locked loop circuit such as a tone decoder device produced by Signetics Corporation designated type NE567.

The detector 25 tuned in accordance with the resonant frequencies of the transmitting and receiving circuits to respond to reception of several cycles of transmitted signal at the correct frequency, thereby distinguishing from ambient electromagnetic 'noise' to produce a logic level pulse at an output 26 which is connected to a reset input terminal 27 of a counter 28. The counter is arranged also to receive input pulses from a clock 29 and to count said pulses to a count limit, dependent upon the clock frequency, to correspond to an initial timing interval of two minutes. At the end of the initial timing interval, that is, when the count is completed. An output terminal 30 of the counter is connected to reminder means 31 in the form of a low intensity buzzer and to one input of a two-input AND gate 32.The other input of the gate 32 is connected to receive pulses from clock 29 such that when counter 28 has completed its count the gate is opened and clock pulses are applied to a second counter 33 whose count limit is set to give a secondary timing interval of ten seconds. This counter also has a reset terminal 34 connected to the output 26 of decoder 25.

The output of the second counter 33 is connected to trigger a driver 35 of a general alarm buzzer 36.

In operation, after a transmitted signal is received the counters 28 and 33 are reset. Counter 28 immediately commences to count clock pulses but is reset by the next transmitted signal which normally occurs within the two minute timing interval it defines. The gate 32 is normally closed.

If no transmitted signals is received to reset the counter 28 it eventually 'times out', opening gate 32 and causing the reminder means to warn the subject that a transmission has not been made. The gate 32 is opened and the second counter 33 is caused to commence counting.

If upon receipt of the reminder the subject applies pressure to the shoe to effect a signal transmission, the counters 28 and 33 are both reset.

If however the subject fails to respond to the reminder buzzer within the ten second period, the counter 33 produces an output signal and the general alarm is sounded after a total timing interval of two minutes ten seconds.

Clearly the use of reminder means and primary and secondary timing intervals to comprise the total.

timing interval enables the subject to remedy any inadvertent inactivity without the inevitable disruption of a general alarm, but does not seriously interfere with raising an alarm if the subject is unable to respond. The inclusion of this feature is however, optional, and the invention is fulfilled without its presence.

Similarly, the preceise form taken for subject reminder and/or general alarm is open to variation as is detailed construction of the timing elements and receiving means.

In some circumstances it may be that a subject is called upon to work in one of a complex of adjacent enclosed areas at different times so that it is preferred to extend the aerial loop about the periphery of the complex. In such circumstances the loop may be caused e.g. by multiplexing means (not shown), to be responsive to several different transmitters, each with a tuned circuit operative in a different frequency range, enabling a plurality of transmitters to be operated in different areas of the complex.

By incorporating the few components required in a single location the transmitting means may be conveniently formed as a module and housed in the heel during manufacture of the shoe or afterwards by modifying or replacing the heel.

It will also be appreciated that the transmitting means is not confined to incorporation in the heel of an article of footwear as described above. The inductive coil 15, may for instance be embedded in the sole of such a shoe. Alternatively the coil only may be mounted in the shoe, the transmitter may be carried in a housing worn on the body of the subject and the voltage-inducing movement against the piezo-electric element be caused by articulations between limbs or by disturbance of an inertial mass upon the predetermined activity.

It is preferred that the transmitting coil and receiving loop are coplanar and for normal activity this is satisfied by having both coils in a horizontal plane. It will be appreciated that the coils may be disposed in vertical planes if necessary although coplanar disposition will not normally be possible or may comprise a plurality of vertical aerial loops enabling the position of a subject to be determined by differential reception between them.

Furthermore it will be appreciated that the electrical generating means need not be restricted to a piezoelectric element. The generator may be of an electromagnetic nature would then benefit from the transmitter incorporating some form of voltage multiplication and/or amplification circuitry to effect efficient radiation.

Claims (10)

1. Inactivity alarm apparatus comprises a transmitting station adapted to be carried by a subject including a tuned electronic circuit operable to radiate electromagnetic radiation in a predetermined radio frequency range in response to the application of an electrical pulse thereto, and a receiving station including a receiver tuned to the frequency range of the transmitter to receive transmissions therefrom and timing means operable to cause an alarm indication be given after a preset timing interval and responsive to reception of a signal by the receiver within said timing interval to be reset to begin a new timing interval, the transmitter including electrical generating means operable by a predetermined physical activity of the subject to generate an electrical pulse for the tuned electronic circuit.

2. Inactivity alarm apparatus as claimed in claim 1 in which the electrical generating means is incorporated within an article of footwear and is responsive to the activity of a subject applying pressure to the ground by way of the footwear.

3. Inactivity alarm apparatus as claimed in claim 2 in which the whole transmitting station is incorporated in said article of footwear.

4. Inactivity alarm apparatus as claimed in any one of claims 1 to 3 in which the electrical generating means comprises a piezoelectric element.

5. Inactivity alarm apparatus as claimed in claim 4 in which the electrical generating means comprises hammer means responsive to pressure on the footwear to strike the piezoelectric element percussively.

6. Inactivity alarm apparatus as claimed in claim 5 in which the tuned circuit comprises a high-Q low impedance inductor-capacitor circuit connected to the piezo-electric element by way of a spark-gap element.

7. Inactivity alarm apparatus as claimed in claim 6 in which the receiver includes a phase locked loop element responsive to reception of a plurality of oscillations of the tuned electronic circuit of the transmitting station to verify said reception.

8. Inactivity alarm apparatus as claimed in any one of the preceding claims in which the receiver is tunable to different frequency ranges and the receiving means is able to respond to radiation in different predetermined frequency ranges from a plurality of transmitting stations.

9. Inactivity alarm apparatus as claimed in any one of the preceding claims including reminder means responsive prior to the end of the timing interval to alert the subject to the absence of a transmission before initiating the alarm.

10. Inactivity alarm apparatus as herein described with reference to and as shown in, the accompanying drawings.