Abstract:
A personal alert safety system comprises a housing adapted to be worn by a user. An accelerometer is in the housing. An alarm device is operatively associated with the housing. A control in the housing is operatively connected to the accelerometer and the alarm device. The control is configured to operate the alarm device responsive to select acceleration movement of the housing sensed by the accelerometer.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not Applicable. 
     FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable. 
     MICROFICHE/COPYRIGHT REFERENCE 
     Not Applicable. 
     FIELD 
     This application relates to a personal alarm safety system device and, more particularly, to a new method to start an emergency alarm. 
     BACKGROUND 
     Statistics have shown that interventions in fire situations present important risks. In particular, firefighters suffer from heat and smoke caused by the fire and need to alert other fire fighting personnel for assistance. Personal alert safety system (PASS) devices are designed to assist firefighters during their mission. PASS devices provide audible alarms and/or visual indications responsive to various undue conditions. 
     Generally, PASS devices detect firefighter motion, surrounding temperature, air pressure of self contained breathing apparatus (SCBA) cylinders etc. If the PASS device detects the immobility of the firefighter, the PASS device generates a loud alarm to alert other personnel that a firefighter is in a hazardous situation. It helps to guide rescue personnel to the location of the incapacitated firefighter. 
     Known PASS devices may include controls to manually initiate an emergency alarm. If the firefighter is in a hazardous situation and wants to warn others, then the firefighter can manually initiate the alarm. Among the reasons for the firefighter to manually initiate an emergency alarm could be if the firefighter has any problem with the SCBA, if the firefighter is trapped somewhere, if the firefighter is under a collapsed structure and can&#39;t move, if the firefighter is injured or almost unconscious, or if the firefighter is surrounded by the fire. 
     Some known PASS devices provide for manual activation of the emergency alarm by the use of an electromechanical push button system. For example, the emergency alarm can be manually generated by pushing a button. The aim of this alarm is to alert others that a firefighter is in hazardous situation. It helps to guide rescue personnel to the location of the incapacitated firefighter. 
     One such PASS device uses a coupling between a sensor such as a reed switch and a magnet. The magnet is push by a plastic part (the button) to approach the reed switch. The reed switch is placed inside the device. The magnetic field of the magnet has enough power of attraction to close the reed switch. The reed switch is part of a non-contact position detector which connects directly to the interrupt input of a microcontroller. 
     Concerns may exist due to sensors being sensitive to electromagnetic fields or to antistatic plastic. Also, the buttons can wear out the button may be difficult to operate. 
     This application is directed to improvements in personal alert safety system devices. 
     SUMMARY 
     Broadly, there is disclosed a personal alert safety system device that senses acceleration movement of the device. 
     In accordance with one embodiment a personal alert safety system comprises a housing adapted to be worn by a user. An accelerometer is in the housing. An alarm device is operatively associated with the housing. A control in the housing is operatively connected to the accelerometer and the alarm device. The control is configured to operate the alarm device responsive to select acceleration movement of the housing sensed by the accelerometer. 
     It is a feature that the select acceleration movement comprises a single tap of the housing in any direction or a double tap of the housing in any direction. 
     It is another feature that the accelerometer sends an interrupt signal to the control. The control may comprise a microcontroller. 
     It is still another feature that the alarm device comprises a speaker. 
     It is a further feature that the housing is adapted to be mounted to a pressure hose of a self contained breathing apparatus and further comprising a pressure sensor operatively connected to the control for sensing pressure in the hose. A control is automatically activated responsive to sensed pressure. 
     It is an additional feature that the housing is adapted to receive an activation key operatively associated with the control. The control is activated responsive to removal of the activation key. 
     In accordance with another aspect, a method of generating an emergency alarm in a personal alert safety system comprises providing a housing adapted to be worn by a user, the housing including an accelerometer in the housing and an alarm device; and providing a control in the housing operatively associated with the accelerometer and the alarm device, the control operating the alarm device responsive to select acceleration movement of the housing sensed by the accelerometer. 
     Other features and advantages will be apparent from a review of the entire specification, including the appended claims and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a PASS used with an SCBA; 
         FIG. 2  is a perspective view of a PASS used as an independent device; 
         FIG. 3  is a block diagram of the PASS of  FIGS. 1 and 2 ; and 
         FIG. 4  is a timing diagram illustrating communication between the accelerometer of  FIG. 3  and the control. 
     
    
    
     DETAILED DESCRIPTION 
     Referring initially to  FIG. 1 , a personal alert safety system (PASS)  10  is shown in use with a self-contained breathing apparatus (SCBA)  12 . As described herein, the PASS  10  may be used with the SCBA  12  or independently, as necessary or desired. The SCBA  12  does not form part of the invention and is illustrated as an example of one form of an SCBA  12 . The PASS  10  may be operable to detect firefighter motion, surrounding temperature, air pressure of SCBA cylinders, or the like. This application is not directed to these features, but rather a new method to manually start an emergency alarm. 
     The SCBA  12  includes a high pressure air tank  14  providing breathable air in accordance with the EN12021 Standard. The SCBA  12  air is provided through a hose  16  to a mask  18 . The PASS  10  is operatively connected to a pressure hose  20  also connected to the tank  14 . 
     The PASS  10  includes a housing  22  of generally parallelepiped construction including opposite insets  24  and  26 . The first inset  24  has a sound hole  25 . The first inset  24  also receives an adaptor  28  through which the pressure hose  20  passes. The second inset  26  also has a sound hole (not shown) and receives an activation key  30 . The sound holes open into the housing  22  and connect an internal tunnel for passing the audio alarm. A lens  31  between the insets  24  and  26  overlies an LED  43 . As described below, the PASS  10  is activated, i.e., enabled for operation, responsive to the hose  20  being under pressure. In some instances, the PASS  10  may be used without the pressure hose  20  and adaptor  28 , as shown in  FIG. 2 . In these instances, the activation key  30  must be removed to activate circuitry in the device. 
     Referring to  FIG. 3 , a block diagram illustrates an electronic circuit  32  contained on a circuit board within the housing  22 . The control circuit  32  includes a control  34  for controlling operation of the PASS  10 . The control  34  may comprise a microcontroller including a processor and associated memory and operating in accordance with a control program for controlling operation of the PASS  10 . The circuit  32  includes an accelerometer  36  having an output at terminals INT  1  and INT  2  connected to an interrupt input of the control  34 . The control  34  is also connected to a strain gauge  38 , a key detector block  40 , a speaker  42  and the LED  43 . The speaker  42  may comprise, for example, a speaker and transducer functioning as a buzzer for generating an audio alarm that is dispersed through the sound holes  25 . 
     The accelerometer  36  as described herein comprises a type ADXL345 digital accelerometer. The accelerometer  36  is a low power device controlled by battery power from a power supply  44 . The accelerometer  36  measures dynamic acceleration resulting from pre-defined motion. Particularly, tap sensing functionality is able to detect single and double taps in any direction. Because the accelerometer  36  is fixedly mounted in the housing  22 , the accelerometer  36  is operable to sense tapping motion on the housing  22 . The accelerometer  36  is operated as illustrated in  FIG. 4  which compares acceleration to a threshold. The maximum tap duration time is defined by a value DUR. A tap latency time is a waiting period from the end of a first tap until the start of a time window when a second tap can be detected. An interval after the latency time is defined by a window register. Although a second tap must begin after a latency time has expired, the second tap does not have to finish before the end of the tap defined by the window register. The control circuit  32  can be used for either single tap operation or double tap operation although double tap is preferred to avoid inadvertent operation. A single tap interrupt is triggered when acceleration goes below the threshold as long as the duration DUR has not been exceeded. A double tap interrupt is triggered when a second tap is sensed within the time window for the second tap. 
     The control  34  is programmed to sense the interrupt from the accelerometer  36  and immediately initiate an alarm signal by providing a loud tone out the speaker  42 . A visual indication is provided by the LED  43 . Activation of the device and the alarm function are enabled by either the strain gauge  38  sensing a pressure condition from the high pressure hose  20 , in the configuration of  FIG. 1 , or by removal of the key  30 , in the configuration of  FIG. 2 , as sensed by the key detector block  40 . 
     As described herein, manual initiation of an emergency alarm may be based on a double tap made on a specific axis with predetermined frequency and strength, as determined by the settings made in the accelerometer  36 . As a result, the PASS  10  is easy to use with gloves and without sensitivity to how it is operated. The firefighter or other user need not search for a button in order to generate the alarm. Moreover, the accelerometer  36  is not sensitive to electromagnetic fields or anti-static plastic and the PASS  10  does not rely on buttons or the like which can wear out and require moving parts. In fact, there are fewer mechanical parts which can provide for faster assembly. This also results in lower manufacturing costs. 
     It will be appreciated by those skilled in the art that there are many possible modifications to be made to the specific forms of the features and components of the disclosed embodiments while keeping within the spirit of the concepts disclosed herein. Accordingly, no limitations to the specific forms of the embodiments disclosed herein should be read into the claims unless expressly recited in the claims. Although a few embodiments have been described in detail above, other modifications are possible. Other embodiments may be within the scope of the following claims.