ALARM SYSTEMS

Abstract: A problem with alarm systems using an aerosol-driven siren is that the propellant may squirt out not as a gas but as a liquid. The invention seeks to deal with this by feeding the propellant (6) not directly to the siren mechanism proper (1, 2) but instead to an expansion chamber (16), conveniently in the cap (3) around the siren mechanism, which communicates (17) with the siren mechanism so that the fully volatilised propellant therein is driven out to the siren to activate the latter. If this does not solve the problem, then the invention suggests a second solution, which is to fill the container itself with a material - for example, an open-celled foam (66) - that allows the propellant to leave the container but with a significantly reduced, restricted flow, so that (in theory) at no time can the flow of liquid be so high as to result in liquid leaving the container faster than it can volatilise. The present invention also relates to alarm systems, particularly those button tag systems employed in shops as part of an Electronic Article Surveillance system, using a propellant-powered siren. To reduce the possibility of the tag button being unlawfully removed without some indication, the invention proposes the use, as the head of the stem (58) securing the tag button (501) to the article, of a miniature aerosol-driven siren alarm device triggered into operation by attempts to remove the button by pulling the stem. Finally, in connection with this latter idea, which requires a small siren alarm actuated by pulling the stem, the invention proposes propellant-driven device support means by using which the pulling force applied to the stem (58) of the button securing means is delivered to one side of a see-saw-pivoted lever (57) the other side of which provides a corresponding pushing force which can be applied to the aerosol propellant container/siren mechanism combination (50) in such a way to release some propellant and cause the operation of the siren.

Description: Alarm systems This invention relates to alarm systems, and concerns in particular improvements in or modifications to propellant-powered arrangements for sirens suitable for use in alarm systems, and to the utilisation of such alarm systems in electronic article surveillance alarms. Alarm systems invariably need some mechanism for alerting the system User to the fact that the alarm has been activated, and one such mechanism involves a siren triggered by the system to sound. Although many sirens are electrically powered, a fan. driving a stream of air through an orifice in short, high-frequency pulses (it is this chopping of the airflow that gives the siren its characteristic sound), some are gas powered - that is, they have a source of compressed gas that is expelled through the orifice vi a a vibratable diaphragm (and the vibrations of the diaphragm induced by turbulence and vortex-formation in the stream of gas produce the required "siren" pulses). For large installations a cylinder of compressed gas is satisfactory, but such cylinders are usually rather heavy and bulky, and for a small alarm, particularly one that is to be man-portable, and even hand-held (as is the sort of personal alarm nowadays commonly carried by women), something much smaller is required. The solution is to employ not a gas but an extremely volatile liquid - such as those found and used in aerosol dispensers - which may be a liquid gas (some gases, such as carbon dioxide, can easily be compressed into liquid form even at room temperature) or an actual - ? but nevertheless very volatile liquid such as one of the several halogenated hydrocarbons (bearing in mind, of course, the desirability of the device being ecologically safe, and not having any significantly deleterious effect on, for example, the ozone layer). Such volatile liquids useful for energising a siren are for convenience referred to hereinafter as "aerosol propellants" because they are the sort generally found in aerosol devices. A problem experienced with the use of aerosol propellants in cases where they are required to exit the device in completely gaseous form, as is so when they are employed to drive a siren, is that their volatility is not always as high as might be wished, and depending on the method of feeding them to the siren mechanism, and also on the size of the container they are in, they may squirt out not as a gas but as a liquid. Not only is this extremely wasteful of the limited supply of available propellant, but in a siren mechanism relying on a vibratory diaphragm the issue of liquid rather than gaseous propellant to and past the diaphragm may prevent it vibrating, or may even not cause it to vibrate at all, so defeating the whole object of the exercise. The egress of liquid rather than gaseous propellant is particularly likely where the propellant container is used the wrong way up (commonly the feed to the orifice is a tube that extends down to near the bottom of the container, and the container should be used upside down so that the tube's free end projects into the gas space that is now above the liquid propellant level). It is even more likely if for good reasons the container is very small - say, no more than lOcc in volume - and there is little or no room for any gas space. The present invention seeks to deal with this problem of liquid propel lants issue in one (or both) of two different ways. It is common, in the design of the siren mechanism for an alarm powered by an aerosol propellant, for the actual siren part to be made as a two-piece device (usually moulded out of some suitable plastic) in which an outer part is in effect the cap of the mechanism while an inner part is the siren mechanism proper, fed with a "gas" supply from the propel lant ' container to which it is affixed and outputting that gas (and the noise generated) through a nozzle to the outside world through an aperture in the cap part. The way the outer (cap) and inner (nozzle) part are shaped there is a considerable enclosed empty space between the two, and it is the first proposal of the invention that this "inbetween" space should be used as an expansion chamber for the aerosol propellant issuing from the container thereof. In other words, the propellant egressing from the container should be fed not directly to the siren mechanism proper but instead to a chamber - this "inbetween" space - where it has a substantially improved chance of vaporising completely, and that the chamber - the inbetween space - should communicate with the siren mechanism so that the volatilised propellant therein is driven out to the siren to activate the latter. In one aspect, therefore, the invention provides the combination of a gas-driven device, such as a siren, together with a container for an aerosol propellant usable to drive the device, which combination incorporates an expansion chamber to be fed with propellant from the container and from which in turn is to be fed the actual mechanism of the device driven by the propellant, in which chamber that propellant is able fully, or at least substantiall , to volatilise before it exits therefrom to the mechanism it is to drive. While the expansion chamber could take many forms, such as the space between the aerosol container and a jacket sealingly mounted around the container, or an intermediate container disposed between the propellant container and the aerosol-driven device mounted thereon, it most conveniently has the form of what is in effect a jacket-defined space around the driven device itself. More specifically, where the device is a siren and the siren is a two-piece construction having an outer part, which is in effect a cap for the container, sealed to and around an inner part, which is the siren mechanism proper and which incorporates the siren nozzle aligned with an aperture in the cap -part, then the outer (cap) and inner (nozzle) part are so shaped that there is a considerable empty space between the two, and it is this space that defines the expansion chamber. In this particularly preferred embodiment, the two-part siren construction is itself novel, and therefore the invention provides it per se - that is, a siren for use with an aerosol propellant container, which siren is a two-piece construction having an outer part, which is in effect a cap for the container, sealed to and around an inner part, which is the siren mechanism proper and which incorporates the siren nozzle aligned with an aperture in the cap part, and wherein-. the outer (cap) and inner (nozzle) part are so shaped and sized that there is a considerable empty space between the two, this space defining an expansion chamber; and there is a passageway into this expansion chamber that is connectabie to the container's propellant egress means, and there is a passageway out of the expansion chamber that operatively communicates with the siren mechanism in the nozzle part so that in use the volatilised propellant fed into that space is driven out to the siren to activate the latter. The gas-driven device of the invention, such as a siren, is for use with an aerosol propellant container. The latter is essentially conventional (although it may be on the small side, for the main purpose of this aspect of the invention is to permit the use of small containers while reducing or even eliminating the chance of squirting out liquid propellant), and no more need be said about it here. The invention's siren is a two-piece construction having an outer and an inner part. The outer part is in effect a cap - that is to say, when the device is used on a propellant container the outer part looks as though it is the cap. This part is sealed to and around the inner part, which is the siren mechanism proper - that is, which incorporates the siren nozzle with the vibratory diaphragm at its input end and has its output end aligned with a corresponding aperture in the cap part. The shapes of the outer (cap) and inner (nozzle) parts are such that when the one fits onto and around the other there is a considerable empty space between the two. Thus far, the two parts are essentially conventional, and look almost identical to the same parts as used in a present-day siren device. However, the combination differs in that the siren mechanism proper receives the aerosol propellant egressing from the container not direct ly but ( via an exit passageway) from the "inbetween" space, and it is this latter that receives it ( vi a an input passageway) directly from the container. Thus, the propellant egressing from the container is fed into the inbetween space, which space defines an expansion chamber in which any liquid propellant has a much greater chance to volatilise completely, and from the chamber the now-gaseous propellant is delivered to the siren mechanism in the nozzle part along an exit passageway operatively connecting the chamber to the diaphragm and hence to the nozzle and out. This exit passageway may operatively connect the chamber and the nozzle part wherever is appropriate; preferably, though,, the chamber end of the passageway is effectively well spaced from the point where the propellant is input from the container into the chamber, so as to reduce further the likelihood of liquid propellant reaching the nozzle and being squirted out thereof (and is typically in that surface of the nozzle part furthest opposed to the chamber input point ) . Use of the cap/nozzle inbetween space as an expansion chamber will normally solve the problem of the system squirting out unvola i 1 ised liquid aerosol propellant in most ordinary situations. However, it may not always work, especially where the available space is very small, and so in a preferred embodiment - aspects of which are novel and inventive per se . and so are described and claimed separately hereinafter - the expansion chamber space is filled with a material that allows the propellant to leave the container through the expansion chamber but with a significantly reduced, restricted flow, so that (in theory) at no time can the flow of liquid be so high as to result in liquid leaving the chamber faster than it can volatilise. More particularly, the expan ion chamber space is filled with a suitable open-celled cellular material (physically and chemically stable under the ambient conditions, and of the right cell structure) that acts as a slight but- significant barrier to the progress of propellant liquid therethrough. The open-celled cellular material is suitable - that is, it is able not only to withstand the physical and chemical effects of the propellant liquid but also to be of a cell size and structure, and of a density, such that propellant transport therethrough is hindered to the point where full volatilisation occurs but not significantly beyond that point (and thus not to where the propellant transport is so slowed that it fails to act properly as a propel lant ) . The "chemical" nature of the cellular material can be any appropriate, and the material can be, for example, a sintered powder (typically a sintered metal or ceramic). Most preferably, however, the cellular material is a foam, conveniently a synthetic resin foam, and typical stable such foams are polyether foams with 35-45 cells per linear inch (about 14-18 per cm), a density of 20kg/m 3 and a hardness of 120-150 N (according to BS 4443 pt 2, method 7A, 1988). The foam has to be sufficiently elastic to pass through the restricted opening of the canister, after which it must fully recover dimensional ly so as to fill the can's internal volume without cell collapse (it should have a compression set of less than 10% (BS 4443 pt 1, method 6A, 1988). Use of the cap/nozzle inbetween space as an expansion chamber, especially when the chamber is filled with an open-celled cellular material retarding propellant flow, will normally solve the problem of the system squirting out unvol t i 1 ised 1 iquid aerosol propellant in most ordinary situations. However, even this may not always work, especially where the expansion space and the propellant container are very small, and so the invention suggests a second solution to the problem, which is to fill the container itself with a material that allows the propellant to leave the container but with a significantly reduced, restricted flow, so that (in theory) at no time can the flow of liquid be so high as to result in liquid leaving the container faster than it can volatilise. More specifically, the invention proposes that the container should have internally thereof a "filling" of an open-celled cellular material (physically and chemically stable under the ambient conditions, and of the right cell structure) that acts as a slight but significant barrier to the progress of propellant liquid through and out of the container. In a second aspect, therefore, the invention provides a container for aerosol propellant liquid, which container has been modified so as in use to prevent the squirting out of unvolati 1 ised liquid aerosol propellant therefrom, the modification comprising a "filling" of a suitable open-celled cellular material that acts as a slight but significant barrier to the progress of propellant liquid through and out of the container. The container employed in this aspect, of the invention may be any conventional container, although this use of a cellular material filling is especially suited to very small containers, and no more need be said about it here. The container modi ficat i n forming this aspect of the invention is a "filling" of a cellular material . The material need not totally fill the container - though for small containers it preferably does - and may merely be a thin plug appropriately disposed within the container (for example, as a co-axial cylinder fully extending from side to side of the container and located so as to "block" the space leading to the container's exit tube). Where the cellular material actually fills the container then it is convenient if it have an axial passageway into which the exit tube loosely fits. The modification requires the use of a suitable open-celled cellular material*, and basically this material can be any one of those proposed above for filling the expansion chamber space. Thus, it nan be, sintered powder (typically a sintered metal or ceramic), but preferably it is a foam, conveniently a synthetic resin foam, and typical stable such foams are of those types already mentioned hereinbefore. The present invention relates to alarm systems, and as so far described concerns in particular improvements in or modifications to propel lant-powered sirens. These sirens can be utilised in a number of ways - for example, as personal alarms (to be activated manually by someone if they are attacked) or as anti-theft alarms (such as those attached to a bag and activated if the bag is snatched away from the wearer) - but * one particularly interesting possibility is in connection with electronic article surveillance alarms. Electronic Article Surveillance - EAS - i s an anti-shoplifting alarm system finding increasing use in stores and shops of the "department" arid/or "self-service" (all too literally) variety. In brief, it is an alarm system wherein each, or some suitable selection, of the articles on display in the shop has "permanently" attached to i a small button-like aerial tag device, and wherein at the exit to the shop there is a corresponding loop aerial, and signal generating and detection equipment, that transmits a signal to any button aerial that passes through the loop, this causing the receiving tag's button aerial to transmit an "echo" back which the equipment picks up and utilises to trigger an alarm. The idea is that articles honestly purchased have the tag button removed by the shop Staff (in theory, only they have the necessary means for detaching the button), and so do not trigger the alarm when taken out of the shop, whereas those removed unlawfully - those "shop-lifted" - still carry the tag button, and so do trigger the alarm (so that the miscreant may be apprehended). Unfortunately, it has not taken the potential thieves long to discover the means whereby the tag button can be removed and the whole system circumvented (it is said that at the end of a Saturday the floors of the changing rooms of the well-known Department Stores are littered with unlawfully-removed tag buttons). The tag button is held in place by a headed stem, rather like a drawing pin' but with a longer shank, that pierces the fabric of the article and is held by a releasable clamp inside the tag button (the button itself is solidly opaque, and this clamp mechanism cannot be seen or physically tampered with, to release the stem, without the correct tool); regrettably, however, there is usually some very slight space between the button and - l i ¬ the stem head, and it is possible to pull and twist the tag/head combination sufficient ly to enable the insertion into this space of a suitable cut t i ng implement, and the simply to cut the head off - at which point the button falls away, and the article is no longer tagged! Of course, cutting off the button can be made more difficult, by using a headed stem made of, for example, hardened steel, and this would certainly be advantageous. However, a solution which would have a greater long term dissuading effect - by, for instance, actually drawing attention to, and so identifying, the putative thief - would be one in which any attempt to remove the button would itself set off an alarm. It is here that the present invention has a proposal. It would undoubtedly be possible to furnish each tag button with some form of electronic alarm-triggering device that would respond to attempts to remove the button, and with modern solid state electronics and the economies of scale - several tens of millions of tag buttons are presently in use - it would be reasonably inexpensive so to do. However, there is a simpler - and cheaper - solution, as suggested by the present invention, which is to use as the head of the stem securing the tag button to the article a miniature aerosol-driven siren alarm device triggered into operation by attempts to remove the button. More specifically, it is suggested that there could be employed a siren-headed securing stem wherein the ^ siren alarm is operated by pulling the stem (as would be the case were an attempt made to pull the tag button and the stem head apart sufficiently to insert therebetween a stem cutting implement). In a third aspect, therefore, the invention provides a tag button and securing means for an electronic article survei llance system, wherein the securing means, by which the tag button is to be secured to the article to be under surveillance, comprises a headed stem wherein the head is a propel lant-operated siren alarm actuated by pulling the stem. In general, the tag button and securing means combination of the invention is little more than a conventional electronic article surveillance system tag button and a stemmed, headed securing means wherein the head is a propel lant-operated siren alarm. However, to manufacture such a siren alarm that is not only small enough to be utilised as the head of the securing means stem but is also actuated by pul l ing the stem (aerosol propellant devices are conventionally operated by pushing the top of the siren portion down onto the propellant container so as to open the spring-loaded exit valve therein) has involved some interesting re-design of a propel lant-driven device, to make a siren apparatus that is inventive per se , as is now discussed in more detai 1. The aerosol propellant containers generally employed to power an aerosol-propel lant-actuated device have an exit tube in the top which not only leads down into the container but is attached to the spring-loaded valve mechanism sealing the container. To open the valve the tube is simply pushed down "into" the container, the valve opens, and propellant spews forth. Accordingly, it is usual to construct whatever device fits onto the tube (to take the propellant issuing therefrom, and be actuated thereby), in the present invention a siren mechanism, so that it is activated - ) ' - simply by pushing the device down onto the container - by squeezing the containe /device combina ion. To operate such a propel 1 ant -powered device by pulling rather than pushing therefore necessitates that the applied pulling force be converted into a pushing one. No doubt there are a number of ways in which this can be achieved, but for the purposes of the invention it is very convenient to employ the "see-saw" lever principle, where a down force on one side of the see-saw's pivot causes an upwards reaction on the other .side. Thus, in the present invention there is proposed support means by using which the pulling force applied to the stem of the button securing means is delivered to one side of a see-saw-pivoted lever the other side of which provides a corresponding pushing force which can be applied to the aerosol propellant container/siren mechanism combination in such a way to release some propellant and cause the operation of the siren. More specifically, the invention provides support means for an aerosol-propel lant-powered device, which support means comprises: an outer casing, having both side and end walls, for enclosing and firmly holding between its two end walls the combination of the propellant container and the device powered thereby, the side wall(s) being apertured to permi the escape of expended propellant and device output, and one end wall having therein an aperture; and a see-saw member pivotal ly mounted internally of the casing adjacent the apertured end wall , and having secured to one of its ends an elongate shank extending out of the casing via the end wall aperture; _ j 4 _ so that in operation, with a propellant container/device combination mounted in the casing between the two end walls and inboard of the see-saw member, pulling the projecting stem (as though to pull it out of the casing) will cause the see-saw's other end to push the container/device combination towards the other end wall, and so squeeze the combination to actuate the container valve and so operate the device. The support means of the invention is for an aerosol-propellant-powered device - typically a propel lant-operated siren alarm suitable for use, as described herein, as the headed stem for the tag button of an electronic article surveillance system. Such a device will be the combination of a small container of aerosol propellant together with the mechanism - uch as a siren - to be operated thereby. The support means includes an outer casing, having both side and end walls. The casing is conveniently tubular, and shaped to hold the chosen combination of the (miniature) propellant container and the (siren) device powered thereby. The casing's side walls are apertured to permit the escape of expended propellant and device output (in the case of a siren its noise). The aperture(s) is/are advantageously barred, and most preferably covered with a finer mesh, to resist or prevent the operation of the device being too easily interfered with (as by blocking a siren's exit orifice with some muffling substance such as chewing gum or cotton wool ) . One end wall of the casing has therein an aperture, and this is conveniently located centrally of the wall (and thus aligned axially of the casing). It is through this aperture that there can project t e elongate shank secured to one end of the see-saw member * . When the support means i used as the I mj but Ion of an electronic article surveillance system, this shank is the button's stem. Pivotally mounted internally of the casing adjacent the apertured end wall is a see-saw member whose purpose is to convert a pulling force acting on one of its ends to a pushing force delivered by its other end (so that this other end can push a propellant container/device combination up against the other end wall of the casing and so cause the device to operate). Although a single such see-saw member could be employed, it is more effective to have four see-saw members, arranged as the four arms of a cross, and all operatively joined together in the middle so that by pulling down on this middle joint the free ends of all four members pivot up together. It is then very convenient to arrange that the propellant container/device combination to be actuated is located wi th one end up against the see-saw member cross, the free ends of each arm being symmetrically arranged around the periphery of, and pushing against, that one end of the combination. The (or each) see-saw member is pivotally mounted in the casing. The pivot means is itself conveniently located between the member and the inside surface of the relevant end wall, and is most preferably a low ridge upstanding from that inner surface and against which the see-saw member is disposed. With the preferred arrangement of four see-saw members in a cross, this ridge is advantageously an elongate ridge extending around the surface in a circle positioned roughly halfway between the side wall and the centre of the end wal 1. As the or 'each see-saw member is pivoted, to push against the container/device combination, so there is a slight tendency for the free end to be drawn towards the pivot. Accordingly, to enhance the pushing effect of the free ends, each is preferably provided with a small upper wedge-shaped portion the ramped surface of which acts to squeeze the combination further in the desired direction. Moreover, each end is also preferably given a small lower wedge-shaped portion the ramped surface of which slides across either the pivot means or some other upstanding surface, and so acts to squeeze even further the container/device combination in the desired direction . Secured to one of the or each see-saw member's ends is an elongate shank extending out of the casing via the end wall aperture (to form, in the preferred case, the stem of the tag button/headed stem combination). Where there are four see-saw members arranged in a cross with a common centre, then there is a single shank secured to that common centre. The invention's aerosol-propel Iant-powered device support means is intended primarily to hold a propel lant-operated siren alarm, and to be used, as described, as the headed stem for the tag button of an electronic article surveillance system. In operation, with its outer casing holding a miniature propellant container and siren powered thereby, pulling the projecting stem (as though to pull it out of the casing) in an attempt to pull apart the tag and the button, will cause the container/siren combination to be squeeze by the see-saw member(s) actuate the container valve and so operate the siren. An embodiment of the invention is now described, though by way of illustra ion only, wi h reference to the accompanying diagrammatic Drawings in which: Figures IA & B show sectional views through an anti-theft "bag snatcher" alarm employing an aerosol-propel lant- driven siren with an expansion chamber according to the invention; Figure 2 shows a sectional view through another anti-theft siren alarm, similar to that of Figure 1; Figures 3A & B show details of one form of actuating mechanism for a siren alarm of the invention like that of Figure 1 ; Figures 4A & B show details of another form of actuating mechanism for an alarm of the invention like that of Figure 1 ; Figures 5_A_- .. _F show an exploded perspective view of an alarm device of the invention suitable for use with an electronic article surveillance system; Figures 6A - F show in section the parts of the alarm device of Figure 5; and F . i_g . ures_7A & B show in sectional view an assembled alarm device of Figure 5 (Figure 7B shows it activated). - 1 8 - Figures 1 and 2 illustrate an aerosol -propel 1ant- powered siren alarm of the invention, intended for use as a personal alarm, wherein I he propellant is delivered not directly to the siren but instead indirectly, via an expansion chamber. The alarm comprises a siren device, or actuator head (generally 1), carried at the blind end of a closed tubular housing (3) mounted on and around a tubular aerosol propellant container (5) and driven by the release and volatilisation of the liquid propellant (6) therein. The actuator head 1 is essentially a conical volume with a vibratory diaphragm (2) at the narrow end and its larger mouth opening to the outside through an aperture (4) in the housing 3. The propellant container 5 is held in the housing 3 by an end cap (7) sealingly mounted to the housing by way of a sealing ring (8) so that the space above (as viewed) the ring - the combination of those individual spaces (16) within the housing 3 around the actuator 1 - is sealed off from the outside, and forms the required expansion chamber. Into this chamber is fed vi a the feed tube (14) the propellant from the container 5 when the valve (above spring 15); the gas formed as the liquid volatilises escapes from the chamber 16 vi a a passageway (17) that feeds it to the actuator's diaphragm 2 and thence out through the cone. Beneath, and supporting, the container 5 is a multi-spoked springy ring (10: this is similar to the comparable item in Figures 5 and 6, discussed hereinafter) with a centrally-attached plug and pull ring (9) on its underside that projects out of the container through an aperture (11a: Figure IB) in the cap 7. The plug 9 "plugs" the aperture; the shoulder 11 provides a firm seat to prevent the plug accidentally being pushed in to cause device operation by mistake. As can be seen from Figure IB, when the plug 9 is pulled out (by pulling the cord or chain 13 attached to the ring) the centre of the spoked ring 10 is pulled down (as shown) and the spokes pivot on the edge of the aperture 11a so that their other ends are caused to rise up. These ends contact the underside of the propellant container 5, and push i t up towards the top end of the housing 3 (where it is held, to keep propellant flowing and the siren sounding, even though the pull on the cord 13 may stop, by inwardly projecting and container- gripping fingers 12) . As a result, the container and the actuator are "squeezed" together, and the valve 15 is caused to open, allowing egress of propellant 6 therefrom via the input tube 14 into the expansion chamber 16 and thence, after volatili ation, vi a the exit passageway 17 to the diaphragm 2 and on out of the system. A simple variant of the housing - and expansion chamber - sealing arrangement is shown in Figure 2, where the seal (18) . instead of being between the housing 3 and the end cap 7, is between the housing 3 and the top edge of the propellant container. In Figure 1 the propellant container 5 is pushed up, to open the valve 15, by springy spokes 10. Figures 3 and 4 show two other ways to achieve the same end. Thus, in Figures 3A and B respectively there is shown the valve-closed and valve-open positions attained not with springy spokes but with a similar set of "hinged" radial arms (19) attached at their outer ends to the housing inner wall (they are shown "trapped" between the cap 7 and the housing 3) . And in Figures 4A and B there is shown the use of a springy dished plate, or dome (20), that can fi i to the bot om of the container 5 but be pulled by the shaped plug (21) so as to "snap" into the reverse configuration and so push the bottom of the container up and away. Figures 5 and 6 show the components of an alarm device of the invention suitable for use with an electronic article surveillance system - and, more specifically, as the "head" on the end of the headed stem used with a tag button surveillance system. The assembled device is shown in Figure 7 (7A shows it unactivated, while 7B shows it after activation). Briefly, what is shown here is: support means (generally 70) for a miniature aerosol-propel lant- powered siren (generally 50), which support means comprises an outer casing (51), having both side (52) and end (53,54) walls, the side wall(s) being apertured (as 55) near casing's the upper (as viewed) end 53, and one end wall 54 having a central aperture (56); and four see-saw members (as 57) arranged in a cross and pivotally mounted internally of the casing adjacent the apertured end wall 54, there being secured to the cross's centre an elongate shank (58) extending out of the casing via the end wall aperture 56. The casing 51 has a tubular body portion (61) topped with an apertured frustoconical top portion (62) the apertures in which are "protected" by bar-like flanges (as 63) and a finer inner mesh (64). The body's bottom edge is swaged round to hold the separately- formed bottom end wall 54 in place (see Figure 7). Fitting fairly tightly inside the casing 51 is the propellant container/siren combination 50. made up of a container (65) on which i fil l d a iren mechanism and cap (65a: much like those items in Figures 1 and 2, but very much smaller). In this particular case, the propellant container 65 has within it a coarse open- celled foam plug (66) that restricts the flow of propellant to the exit tube 14 and so increases the chance that all the liquid propellant will in fact fully volatilise before it actually reaches the siren's diaphragm. At the bottom of the casing 51, located between the end wall 54 and the bottom of the propellant container 65, are four see-saw members 57 (separated by four corresponding stub arms 57a; see below) arranged into a cross with a common centre (67) where they are all joined together; to this centre is attached the elongate shank 58 which projects out of the casing through the aperture 56 (partially plugged with movable plug 56a) in the bottom end wall 54. On the inside surface of the end wall 54 there is a circular ridge (68) that constitutes the pivot for the see-saw members 57, and somewhat further out from that ridge 68 is a second upstanding ridge (68a) . On the upper surface at the free end of each see-saw member is a wedge/inclined plane surface (as 69) , while on the opposed lower surface there is another wedge/inclined plane surface (as 69a). It will be evident that as the shank 57 is pulled downwards so the free ends of the see-saw members 57 rise up and, their action enhanced by the two ramp surfaces 69/69a (the latter acting on the outer upstanding ring ridge 68A), push the propellant container 65 away from the casing's bottom, so "squeezing" the contai er/siren combinal ion to cause the container's valve 15 to open, thus operating the siren. Tt will also be evident that the movable plug 56a is pulled down to the outside end of the aperture 56, indicating that the combination has been activated even though the siren may have stopped (having run out of propellant). This is now jammed in place - preventing it being pushed back to make it look like the device had not been activated - by the four small arms 57a (shown in Figures 5D and 7B but for clarity left out of Figure 7A) being pulled into the aperture 56 and past the inwardly-directed lip (56b) at the inside end thereof . Figures 7 and 7A also show, positioned beneath but (here) separate from the headed stem, the actual tag button device (71) used to "alarm" the goods. Though, for security reasons, the details are not shown, the tag button has a central aperture into which the stem 58 fits, and locks, until released by a special (external) releasing mechanism.

Claims: CLAIMS 1. Support means for an aerosol-propel lant-powered device, which support means is characterised in that it comprises: an outer casing, having both side and end walls, for enclosing and firmly holding between its two end walls the combination of the propellant container and the device powered thereby, the side wall(s) being apertured to permit the escape of expended propellant and device output, and one end wall having therein an aperture; and a see-saw member pivotally mounted internally of the casing adjacent the apertured end wall, and having secured to one of its ends an elongate shank extending out of the casing via the end wall aperture; so that in operation, with a propellant container/device combination mounted in the casing between the two end walls and inboard of the see-saw member, pulling the projecting stem (as though to pull it out of the casing) will cause the see-saw's other end to push the container/device combination towards the other end wall, and so squeeze the combination to actuate the container valve and so operate the device. 2. A support means as claimed in Claim 1, wherein the outer casing is tubular, and shaped to hold the chosen combination of the propellant container and the device powered thereby. 3. A support means as claimed in either of the preceding Claims, wherein the apertures in the casing's side walls are barred, and covered with a finer mesh, to resist or prevent the operation of the device being too easily interfered with. 4. A support means as claimed in any of the preceding Claims, wherein the aperture in the one end wall of the casing is located centrally of the wall (and thus aligned axially of the casing). 5. A support means as claimed in any of the preceding Claims, wherein there are four see-saw members, arranged as the four arms of a cross, and all operatively joined together in the middle so that by pulling down on this middle joint the free ends of all four members pivot up together. 6. A support means as claimed in any of the preceding Claims, wherein the pivot means by which the (or each) see-saw member is pivotally moun.ted in the casing is located between the member and the inside surface of the relevant end wall. 7. A support means as claimed in Claim 6, wherein the pivot means is a low ridge upstanding from that inner surface and against which the see-saw member is disposed. 8. A support means as claimed in Claim 7, wherein, with the preferred arrangement of four see-saw members in a cross, this ridge is an elongate ridge extending around the surface in a circle positioned roughly halfway between the side wall and the centre of the end wal 1. 9. A support means as claimed in any of the preceding Claims, wherein to enhance the pushing effect of the (or each) see-saw member's free end, each is provided with a small upper wedge-shaped portion the ramped surface of which acts to squeeze the combination further in the desired direction. 10. A support means as claimed in Claim 9, wherein each free end is also given a small lower wedge-shaped portion the ramped surface of which slides across either the pivot means or some other upstanding surface, and so acts to squeeze even further the container/device combination in the desired direction. 11. A support means as claimed in any of the preceding Claims, wherein where there are four see-saw members arranged in a cross with a common centre, then there is a single shank secured to that common centre. 12. The combination of a gas-driven device, such as a siren, together with a container for an aerosol propellant usable to drive the device, which combination is characterised in that it incorporates an expansion chamber to be fed with propellant from the container and from which in turn is to be fed the actual mechanism of the device driven by the propellant, in which chamber that propellant is able fully, or at least substantially, to volatilise before it exits therefrom to the mechanism it is to drive. 13. A device/container combination as claimed in Claim 12, wherein the expansion chamber which has the form of a jacket-defined space around the driven device itself. 14. A device/container combination as claimed in Claim 13, wherein the device is a siren and the siren is a two-piece construction having an outer part, which is in effect a cap for the container, sealed to and around an inner part, which is the siren mechanism proper and which incorporates the siren nozzle aligned with an aperture in the cap part, and wherein the outer (cap) _ 2 fi _ and inner (nozzle) part are so shaped that there is a considerable empty space between the two, this space defining the expansion chamber. 15. A siren for use with an aerosol propellant container, which siren is a two-piece construction having an outer part, which is in effect a cap for the container, sealed to and around an inner part, which is the siren mechanism proper and which incorporates the siren nozzle aligned with an aperture in the cap part, and wherein the construction is characterised in that: the outer (cap) and inner (nozzle) part are so shaped and sized that there is a considerable empty space between the two, this space defining an expansion chamber; and there is a passageway into this expansion chamber that is connectabie to the container's propellant egress means, and there is a passageway out of the expansion chamber that operatively communicates with the siren mechanism in the nozzle part so that in use the volatilised propellant fed into that space is driven out to the siren to activate the latter. 16. A propel lant-driven siren as claimed in Claim 15, wherein the passageway operatively connecting the chamber and the nozzle part is so positioned that the chamber end of the passageway is effectively well spaced from the point where the propellant is input from the container into the chamber. 17. A propellant-driven siren as claimed in either of Claims 15 and 16, wherein the expansion chamber space is filled with a material that allows the propellant to leave the container through the expansion chamber but with a significan ly reduced, restricted flow, so that (in theory) at no time can the flow of liquid be so high as to result, in liquid leaving the chamber faster than it can volatilise. 18. A propellant-driven siren as claimed in Claim 17, wherein the material is a suitable open-celled cellular material . 19. A propel lant-driven siren as claimed in Claim 18, wherein the open-celled cellular material is a synthetic resin foam. 20. A container for aerosol propellant liquid, which container has been modified so as in use to prevent the squirting out of unvolati 1 ised liquid aerosol propellant therefrom, the modification being characterised by comprising a "filling" of a suitable open-celled cellular material that acts as a slight but significant barrier to the progress of propellant liquid through and out of the container. 21. A container as claimed in Claim 20, wherein the cellular material is a thin plug appropriately disposed within the container. 22. A container as claimed in either of Claims 20 and 21, wherein the cellular material is a co-axial cylinder fully extending from side to side of the container and located so as to "block" the space leading to the container's exit tube, with an axial passageway into which the exit tube loosely fits. 23. A container as claimed in any of Claims 20 to 22, wherein the open-celled cellular material is a synthetic resin foam. — a — 24. A tag button and securing means for an electronic article surveillance system, characterised in that the securing means, by which the tag button is to be secured to the article to be under surveillance, comprises a headed stem wherein the head is a propellant-operated siren alarm actuated by pulling the stem. 25. A tag button and securing means as claimed in Claim 24, whenever employing a support means as claimed in any of Claims 1 to 11.

Inventors: WORTHINGTON JOHN ALFRED, WORTHINGTON, JOHN, ALFRED
Applicants: WORTHINGTON JOHN ALFRED, WORTHINGTON, JOHN, ALFRED
Application year: 1993
Main classification: G10K9
IPC codes: G08B3, G10K9