Abstract:
A portable alarm device ( 100 ) for guarding a car ( 200 ) or another mobile object having a lockable compartment against theft or burglary, comprising: a housing ( 1 ) having at least one opening ( 2 ) and a microphone ( 4 ) therein for detecting infrasound; electrical circuitry ( 5 ) within housing ( 1 ) for processing signals and for transmitting an alarm signal on the detection of a forced entry; and a built-in power supply ( 7 ), i.e. batteries. The housing ( 1 ) is provided with steering features ( 2,9,11 ) for ensuring the existence of an unobstructed air path to opening(s) ( 2 ) regardless of the orientation and position assumed by the alarm device ( 100 ) being put rapidly into the coupe of the car by a staff member. The steering features may be legs ( 9 ) proximate to opening ( 2 ), a grating ( 10 ) surrounding opening ( 2 ), or alternatively surrounding the entire housing ( 1 ), or may be comprised of a number of openings in housing ( 1 ), spaced around the housing.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to an alarm device for protecting a car against burglary and theft. The invention is particularly useful in connection with cars being temporarily located in certain parking areas, such as auto dealer/repair shops, short- and long-term car parks, company car parking areas of larger companies, etc. 
         [0002]    The alarm device of the present invention may also be used for securing e.g. containers/workmen&#39;s huts, etc. being temporarily disposed/parked in connection with either freight or storage. Similarly, airplanes, choppers, and boats being temporarily located at suitable sites (airport areas, hangars, marinas, ports) may also be secured using the alarm device of the invention. 
       BACKGROUND OF THE INVENTION 
       [0003]    There is a need for being able to temporarily provide an individual car with reliable warning/protection equipment communicating by way of a radio connection with a nearby alarm central. Typically, this is of interest in a scenario in which a number of cars, for example, have arrived during the day, while in the same period perhaps roughly the same number of cars have been removed. The object then is to distribute and place an alarm device onto or into each individual car in a simple manner that minimizes the effort for an employee at the site. If each alarm unit needs to be positioned accurately and configured correctly for the alarm to function properly, a lot of time will be spent in carrying out this task, hence making the use of the alarm systems prohibitively time-consuming. 
         [0004]    Alarm devices for the temporary protection of cars as indicated above are previously known, for example, from U.S. Pat. No. 3,864,675, U.S. Pat. No. 4,155,067, U.S. Pat. No. 4,187,497, and U.S. Pat. No. 5,463,371. In U.S. Pat. No. 3,864,675, an alarm device is disclosed that needs to be hanged inside the car in a vertical position and that responds to movements/vibration of the car body. U.S. Pat. No. 4,155,067, U.S. Pat. No. 4,187,497, and U.S. Pat. No. 5,463,371 also disclose alarm devices responding to movements/vibration, which are carefully positioned using a hanger means suspended from the top of one of the windows of the car. 
         [0005]    Thus, it appears that the site personnel have to spend a lot of time positioning and adjusting the alarm device appropriately for each individual car so that it will be able to cooperate properly with the monitoring central. This is a consequence, inter alia, of the type of detection principle being used. 
         [0006]    Ideally, an employee should only have to open a car door, then put or even toss the alarm device into the car seat without any concern for its position or orientation, and thereafter just close and lock the door. Alternatively, the employee could hide the alarm device under the seat or in the trunk, for example. The object of the present invention is to provide an alarm device that following such a simple deployment is still able to function 100% reliably. 
         [0007]    Hence, an important part of the present invention is that the detection principle being used works omnidirectionally, meaning that the detector receives external signals from all directions. Another important part is to avoid blocking of the path for the external signal towards the detector, regardless of how the alarm device is positioned within the car. 
         [0008]    Thus, according to the present invention, a portable alarm device for protecting a car against theft or burglary is provided, the alarm device comprising
       a housing having at least one opening through at least one of the housing walls for providing an air flow path to a microphone located within the housing, the microphone being adapted for detecting infrasound signals within the frequency range of 0.1-15 Hz,   electrical circuitry within the housing for processing signals received from the microphone and transmitting an alarm signal on the automatic determination that a detected event is abnormal, and   a power supply embedded in the housing.       
 
         [0012]    In particular, the alarm device according to the invention is characterized in that the housing is provided with steering features for ensuring the existence of an unobstructed air flow path to the at least one opening regardless of the orientation assumed by the alarm device when put in by the employee to rest on one of the available support surfaces within the coupé of the car, e.g. a seat, floor, or trunk. 
         [0013]    According to a first embodiment, said steering features are comprised of at least one projection or leg on the housing in the vicinity of the microphone opening. 
         [0014]    According to an alternative embodiment, the steering features may consist of a netting or grating secured to the housing and spaced at a certain distance from the housing surrounding the opening. In this case, the netting may enclose the entire housing like a ball or an egg, and the netting/grating may be secured to the housing at the housing corners, or be secured to the housing by way of short struts. Preferably, the struts are flexible in order to provide a shock dampening function. Moreover, it would be advantageous if the netting/grating were split through a hinge and locking arrangement to provide easy access to the housing. The netting/grating is preferably made of a strong plastic material. 
         [0015]    According to a further embodiment, the steering features may be comprised of a number of openings in the form of perforations in the housing wall(s) formed in the housing wall(s) in areas ensuring that at least one of the perforations points upwards/outwards regardless of the orientation of the alarm device. The perforations may advantageously be distributed throughout the entire outer surface of the housing. 
         [0016]    In some embodiments it will be advantageous to have a soft outer casing surrounding the housing, preferably of a soft rubber material, for mechanical shock absorption. 
         [0017]    Also, it is advantageous if the at least one opening in the housing wall is covered by a membrane preventing the intrusion of dust while allowing infrasound signals to pass. 
         [0018]    In an embodiment wherein the electrical circuitry is connected to an acoustic alarm signaller, the alarm signal emitted may be an audio signal. 
         [0019]    In another embodiment, the electrical circuitry is connected to a radio antenna for transmitting a radio signal to an external alarm central. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    In the following, the invention will be illustrated in greater detail in connection with a few preferred embodiments, and with reference to the accompanying drawings, in which: 
           [0021]      FIG. 1  shows a first preferred embodiment of an alarm device according to the present invention, 
           [0022]      FIG. 2  shows the alarm device of  FIG. 1 , but in a bottom view, 
           [0023]      FIG. 3  shows a second preferred embodiment of the alarm device according to the invention, 
           [0024]      FIG. 4  is similar to  FIG. 3 , but viewed from a different angle, 
           [0025]      FIG. 5  shows a third preferred embodiment of the alarm device according to the invention, 
           [0026]      FIG. 6  schematically shows a forth preferred embodiment of the alarm device according to the invention, 
           [0027]      FIG. 7  shows a variant of the embodiment of  FIG. 6 , 
           [0028]      FIG. 8  shows an additional advantageous detail of the embodiments of  FIGS. 6 and 7 , 
           [0029]      FIGS. 9 and 10  show the deployment of the alarm device according to the invention into a vehicle, and 
           [0030]      FIG. 11  illustrates the transmission of a radio signal from the alarm device according to the invention to an external alarm central. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0031]    As mentioned introductorily, the object of the present invention is to provide an alarm device that may be deployed with great ease anywhere within the coupé of a car (the use of the term car is also meant to include a bus, van, trailer, truck, tractor, recreational vehicle, caravan, construction machine, as well as any other vehicle having a lockable coupé. Moreover, as stated above, the alarm device may also be used for temporarily parked containers and workmen&#39;s huts). It is assumed that an employee at a site at which a number of cars are parked may carry with him a necessary number of such alarm devices, unlock the door of a given car, and relatively quickly and recklessly put or even toss the alarm device into a seat of the car, a floor of the car, the car trunk, or in the rear compartment in the case of a station wagon, for example. Such an operation may then be completed within a few seconds, of which most of the time is actually spent on unlocking the car door and subsequently locking it. (If desired, the alarm device may be placed in such a manner that it cannot be seen from the outside.) 
         [0032]    In order for such a rather reckless deployment of the alarm device to still result in an adequate detection function, a detection principle is chosen that is based on the detection of infrasound waves (also sometimes referred to as “volumetric signals” by those skilled in the art). Such very low frequency pressure waves propagate through the air and are typically initiated by the movement of an air mass induced by a moving object. Exemplary moving objects are windows and doors that are opened/closed, windows that are crushed, or even a bending wall, floor, or roof. Thus, infrasound contains a lot of information regarding relevant events associated with human activity such as burglary and the low frequency signals tend to spread out in the surroundings in a uniform manner. Hence, an infrasound detector will, in principle, be omnidirectional, i.e. it will detect signals from all directions. 
         [0033]    The present invention is not directed to the processing of the detected signals. For a description of such processing, it is referred to the previous Norwegian Patent Application no. 2005 2403, submitted May 18, 2005, of which the inventor of the present invention is listed is a co-inventor. Thus, in the preferred embodiment of the invention, signal processing means are used that operates according to the principles disclosed in the above referenced patent application to automatically make decisions as to whether or not a burglary is in progress. 
         [0034]    The present invention, however, is related to the physical design of the alarm device, particularly designed for random handling on deployment in the coupé of a car, as indicated above. The goal is that the alarm device shall function equally well regardless of how it ends up in the coupé of the car, with respect to both position and orientation. 
         [0035]    It is therefore important that there exists, at all times, an air path into a microphone embedded in the alarm device of the invention. Unless certain measures are taken, an alarm device that is not designed in accordance with the present invention may easily end up in a position in which there does not exist any unobstructed air path into the sensor/microphone that is supposed to receive the signals, and, additionally, an unfavourable position within the car coupé, e.g. on a floor far down in the coupé, will result in a weak reception of common sound frequencies. Said infrasound frequencies, however, may work well anywhere in the car&#39;s coupé. 
         [0036]    Accordingly, the invention is based on two important principles, namely the use of infrasound/volumetric signals rendering the position within the car unessential (the term coupé is meant to include both the coupé and trunk of a car) and special so-called steering features on the alarm device itself, ensuring the existence of an unobstructed air path towards the microphone for the reception of infrasound at all times. 
         [0037]    Reference is now made to  FIG. 1 , which schematically shows an alarm device generally referred to as  100 . The alarm device comprises an outer casing in the form of a housing  1 , which in this particular example is a parallelepiped box. As such, there are no limitations on the geometric shape of the box. The box could also have curved walls, or a larger number of walls/sides/corners. However, some kind of opening  2  has to exist that provides an unobstructed air path into an important element, namely a sound/vibration sensor, or microphone,  4 , as shown schematically in the figure. Microphone  4  is connected to signal processing circuitry  5 , which will not be discussed in more detail in the present invention. The signal processing circuitry is capable of deciding whether or not an abnormal situation exist, i.e. a burglary, in a given case, and if so a radio signal, for example, may be emitted by way of an associated antenna  20 , which is also shown schematically on the outside of housing  1 . 
         [0038]    For the invention, the important element of  FIG. 1  is the projections or legs  9 , which ensure that there will always exist an unobstructed air space into opening  2 , even if opening  2  has ended up facing down against a car seat or against a floor in the coupé of the car. In the absence of such legs  9 , opening  2  could very well end up against some supporting surface, so that no free air path would exist into opening  2  and thus microphone  4 . 
         [0039]      FIG. 2  shows the alarm device of  FIG. 1 , but in a bottom view. In the embodiment shown, it can be seen that alarm device  100  is provided with three legs  9 , even though only two such legs would suffice in practice. Actually, with a proper length leg, one leg  9  would be sufficient, that is, assuming that it is located in the vicinity of the opening  2 . The alarm device would then assume a “tilted” position, but still provide an unobstructed air path into opening  2  and microphone  4 . 
         [0040]      FIG. 3  shows an alternative solution that will also ensure the existence of an unobstructed air path into opening  2 . In principle, the alarm device  100  is similar to the one shown in  FIGS. 1 and 2 , with the exception that legs  9  are now replaced with a grating  10 , which in the example shown is hemispherical in shape and surrounds opening  2 . This represents another way of ensuring the existence of the required free air path into opening  2 . The remaining elements appearing in  FIG. 3 , as well as in  FIG. 4  showing the same device as  FIG. 3 , are the same as those shown in  FIGS. 1 and 2 . It is understood that such a grating, which could also have a different shape from that shown, will ensure that there will always exist an unobstructed air path into opening  2  and microphone  4 . 
         [0041]      FIG. 3  also shows an acoustic alarm signal transmitter  18  for an embodiment emitting an audio signal in the case of a burglary. An alarm device may very well include both such an acoustic signal transmitter as well as a radio signal antenna as shown above. It will be possible to selectively configure such functions. 
         [0042]    It can be noted that should the alarm device  100  end up upside-down as compared to the position shown in  FIGS. 4 and 1 , i.e. with the radio antenna located on the “underside”, this is not a big problem as the radio signal being emitted is only to propagate a relatively short distance from the car to a nearby alarm central. It is no problem to provide sufficient signal power for the radio signal to easily reach a few hundred meters away from the car triggering the alarm, even with a downwardly facing antenna and with the alarm device located at the bottom of the car. In other words, the propagation of a radio signal will not present any problems in this respect. 
         [0043]      FIG. 5  also shows a parallelepiped box, i.e. a housing  1 , containing the other necessary elements. However,  FIG. 5  features a third embodiment of the above-mentioned “steering features” provided for ensuring the existence of an unobstructed air path regardless of the position and orientation of the alarm device in operation. In this case multiple openings  2  are provided through walls  3  of housing  1 , as opposed to a single opening as in the above embodiments. Consequently, we use the term “perforations”, and, again, note that several holes are provided in the walls  3 , so that regardless of the orientation of the alarm device on a seat or floor within the coupé of the car, a number of holes will be facing outwardly or upwardly. In the embodiment shown, holes are provided in four of the side faces  3  of the parallelepiped box, even though additional holes could also be provided in the remaining two, largest, faces. 
         [0044]    Further details set out in this drawing are a microphone  4 , signal processing circuitry  5 , power supply  7  (preferably constituted by electrical batteries), internally or externally mounted transmitter/antenna  20 , as well as an outlined membrane  16  covering each opening/perforation  2 . The purpose of membrane  16  is to prevent dust from entering into the alarm device while infrasound/volumetric signals are let through without being dampened. In the example shown, one such membrane may be provided for each opening, or a band extending across the entire inner circumference may be used. Such a membrane  16  may advantageously be made of an elastic material like rubber or a similar material, but this is not a requirement. 
         [0045]    The main point is that the membrane prevents the intrusion of dust while transmitting movement/vibration of the air mass. 
         [0046]    In  FIGS. 6 ,  7 , and  8 , another embodiment is shown that will ensure the existence of an unobstructed air path into an opening  2  in a housing  1  of the type shown in  FIGS. 1 and 2 , for example, but having no projections or legs. In this case the entire housing  1  is accommodated within a grating shaped like a ball or an egg, and the housing, which could equally well be of another shape than a parallelepiped box, is fixed to the grating ball either by struts  13 , or in such a manner that the housing corners are connected directly to the grating. The first variant is shown in  FIG. 6 , whereas the variant in which the corners  12  are fixed to the grating is shown in  FIG. 7 . The reference number  11  refers to the totally enclosing grating/netting of  FIGS. 6 ,  7 , and  8 .  FIG. 8  shows an essential detail, namely an opening and closing mechanism constituted by a hinge  14  and locking means  15  to allow access intothe inside housing  1 . 
         [0047]    Moreover, it is also possible to provide means reducing the effect of any mechanical shock to which the alarm device might be subject being put rather quickly or even tossed into a car. Such a provision is shown in  FIG. 6  in the form of a flexible suspension comprising spring struts  13 . 
         [0048]    Another way of providing shock absorption is to provide a soft outer casing surrounding the entire housing, with such an outer casing  17  being indicated by dashed lines in  FIG. 1 . Such casing preferably comprises a soft rubber material, foam rubber, or the like. Obviously, the soft material  17  must not cover opening  2 . 
         [0049]      FIGS. 9 and 10  schematically outline the placement of the alarm device of the invention in a car. The alarm device  100 , being of an embodiment corresponding to the one shown in  FIG. 1 , is to be deployed into a car  200 . As appears from  FIG. 10 , any supporting surface within the car may be used, i.e. the alarm may be put in a front or rear seat, on any floor, or alternatively in a rear compartment of the coupé or in the trunk. When positioned in the trunk, the alarm device will still cover the coupé, assuming that there is no physical seal between the coupé and trunk comprised of a non-transmitting material. 
         [0050]      FIG. 11  outlines a parking area for cars  200  at which each car has been fitted with an individual alarm device  100 . A radio signal may be emitted from one of the alarm devices into the surroundings, intended to reach an antenna connected to an external alarm central  6  at the site, e.g. in a guard building  300  (or in the case of “smaller” scenarios, to an alarm central in a nearby apartment/house). The use of an embedded cellular transmitter calling a target receiver by way of a public network is contemplated. 
         [0051]    Preferably, microphone  4 , which is used for the reception of the ultra low frequency sound signals, is of the Silicon Machined Diaphragm (SMD) or Back Electret Condenser (ECM) type. In the case of emitting radio signals from a housing located within a grating ball or egg, the grating should not be made of metal, as metal may impair the radio signals. A strong plastic material is preferred for the grating. 
         [0052]    The use of a membrane  16  (see  FIG. 5 ) to prevent the ingression of dust may also be adopted in the other embodiments, c.f.  FIGS. 1-4  and  FIGS. 6-8 . 
         [0053]    In the embodiment shown in  FIGS. 7 and 8 , i.e. wherein a housing is attached to the outer grating at its corners, advantageously mounting brackets fixed to the grating may be used, into which the housing is fitted. 
         [0054]    Opening  2  into housing  1  may be constituted by an aperture or gap between two (or more) parts composing the housing. Frequently it will be practical to create a housing of multiple parts that is assembled together, in which case such a solution may be convenient. 
         [0055]    Thus, through an alarm device according to the present invention, the following advantages are attained: Firstly, the alarm device detects incoming signals from all directions, i.e. provides omnidirectional detection. Further, no installation process needs to be carried out for each car. Furthermore, the alarm device may be moved from one car to another without any kind of adjustment or reconfiguration. Also, such an alarm device may be used as a sensor being part of some larger system. The alarm device contains its own batteries for power supply and is hence totally self-sufficient. The alarm device may be provided with dust protection as well as with mechanical shock absorption means. The alarm device may be put anywhere in the coupé or trunk of the car, with the above limitations, regardless of its final orientation. Irrespective of its location the alarm device will guard the entire coupé against burglary. 
         [0056]    A further possible embodiment is based on the cardanic suspension of an inner housing inside a grating, for example, in order to ensure that a microphone opening will always face upwardly regardless of the final orientation of the alarm device as positioned in the coupé of the car. However, such a floating suspension (gimbal mount) within a cage will be an excessively complicated solution as the cage itself will provide a sufficient “steering feature”, as set out in the embodiment of  FIGS. 6 ,  7 , and  8 .