Abstract:
A device for the topical dispensing of a powder, typically a powder medicament, comprises, or is adapted to be coupled to, a powder receptacle and a gasflow generator. The gasflow generator is adapted, in use, to cause gas to flow through the device, which further comprises an agitator by which the powder and/or the powder receptacle can be mechanically agitated. Actuation of the gasflow generator, which causes gas to flow through the device and to entrain powder from the powder receptacle, thereby to dispense powder from the device, is accompanied by actuation of the agitator, causing the powder receptacle to be mechanically agitated, thereby facilitating the release of powder from the powder receptacle.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from United Kingdom patent serial numbers UK 0822759.7 filed Dec. 15, 2008 and UK 0822770.4 filed Dec. 15, 2008, both of which are incorporated herein by reference in their entirety. 
     TECHNICAL FIELD 
     This invention relates to a device for the dispensing of a powder. The device is of particular utility in surgical procedures or other medical applications, for the topical delivery of a powder to an internal or external surface of the body. 
     BACKGROUND 
     Devices for the dispensing of powder onto a surface of the body, or for other purposes, are well known. Examples of such devices are disclosed in the following published documents: GB-A-472,355; GB-A-539,351; GB-A-572,015; GB-A-572,112; GB-A-607,237; GB-A-628,675; GB-A-649,506; GB-A-668,341; GB-A-808,273; GB-A-878,106; U.S. Pat. No. 1,929,154; U.S. Pat. No. 2,151,418; U.S. Pat. No. 2,501,279; U.S. Pat. No. 5,884,621; US-A-2005/0205087; FR-A-2 863 503. 
     There is an ongoing need for a device that can be used to deliver a powder to a surface of the body, whether an external surface or an internal surface, e.g. a surface exposed during a surgical procedure, in a controlled fashion. It may be necessary or desirable for the powder to be delivered to a highly localized site, i.e. with precision, and/or in a highly uniform manner. There is also an ongoing need for a powder delivery device that achieves these objectives, yet is simple and inexpensive to manufacture and to use. 
     SUMMARY 
     There has now been devised an improved form of powder delivery device that addresses these needs and/or overcomes or substantially mitigates disadvantages associated with the prior art. 
     Thus, according to a first aspect of the invention, there is provided a device for the dispensing of a powder, the device comprising, or being adapted to be coupled to, a powder receptacle and a gasflow generator adapted, in use, to cause gas to flow through the device, and the device further comprising an agitator by which the powder and/or the powder receptacle can be mechanically agitated, the gasflow generator and the agitator being operably linked such that actuation of the gasflow generator, which causes gas to flow through the device and to entrain powder from the powder receptacle, thereby to dispense powder from the device, is accompanied by actuation of the agitator, causing the powder receptacle to be mechanically agitated, thereby facilitating the release of powder from the powder receptacle. 
     In the device according to the invention, actuation of the gasflow generator, which results in dispensing of powder from the device, is accompanied by mechanical agitation of the powder receptacle. Such agitation facilitates the release of powder from the powder receptacle, and may also give a more uniform distribution of powder material dispensed from the device. 
     The powder receptacle may be an integral part of the device according to the invention, such that the device is supplied with a quantity of powder contained within the powder receptacle. In such a case, the device may be a disposable device, which is discarded after the desired quantity of powder has been dispensed from the powder receptacle. 
     Alternatively, the powder receptacle may be a separate component that is coupled to the device prior to use. In such a case, the powder receptacle, containing a quantity of powder, is typically supplied with a closure that is removed to enable the receptacle to be coupled to the device. The device and the receptacle may be formed with cooperating formations that enable them to be coupled together. For example, the device may be formed with an upstand or spigot that is received within or about a neck of the powder receptacle. 
     In currently preferred embodiments, the powder receptacle is supplied in the form of a sealed vial, e.g., of glass, that contains a quantity of powder. The vial has a neck that is sealed by a removable closure. When the closure is removed, a device according to the invention is engaged with the vial, by insertion into the neck of the vial of a tubular spigot that has an interference fit with the interior of the neck. When the vial, which is coupled to the device, is then inverted, powder in the vial falls into the spigot. In such an arrangement, loss of powder from the spigot is preferably inhibited or prevented by a perforated base member that extends across the interior of the spigot. Other embodiments of powder receptacle that may be used include cartridges, e.g., of plastics materials. Such receptacles may be supplied with closures that are removed prior to attachment of the cartridge to the device, or the device and the powder receptacle may be configured such that engagement of the powder receptacle with the device brings about opening of the powder receptacle. For instance, the powder receptacle may comprise a foil closure that is ruptured by appropriate formations on the device when the receptacle is engaged with the device. 
     The perforated base member retains the bulk of the powder within the powder receptacle prior to actuation of the gasflow generator, but permits powder to pass through the base member when the powder is entrained in the gasflow generated by actuation of the gasflow generator. The nature of the base member should therefore be such that the perforations in the base member are small enough that, when the powder rests upon the base member, its packing characteristics and angle of repose are such that the powder does not pass to any significant extent through the base member. On the other hand, the perforations should be such that, when the powder resting upon the base member is energized and entrained in the gasflow, it is able to pass through the perforations in the base member and be dispensed. 
     Conveniently, the base member takes the form of a perforated plate, which will typically be circular. Preferably, a substantial proportion, or the full extent, of the plate is perforated. The perforations in the base member may have any suitable shape, eg circular, square or hexagonal, and will typically be arranged in a regular array and/or uniformly across a substantial proportion, or even the full extent, of the base member. 
     Thus, according to another aspect of the invention, there is provided a device for the dispensing of a powder, the device comprising, or being adapted to be coupled to, a powder receptacle, the device further comprising, or being adapted to be coupled to, a gasflow generator adapted upon actuation to cause gas to flow into the powder receptacle, wherein the powder receptacle is oriented, in use, such that, prior to actuation of the gasflow generator, powder contained within the receptacle settles under gravity and is retained within the powder receptacle by, and rests upon, a perforated base member. 
     In such embodiments, the gasflow may enter the powder receptacle through the base member, thereby energizing powder resting upon the base member and causing said powder to be entrained in the gasflow and to pass through the base member into an outlet conduit, thereby to dispense said powder from the device. Gas is caused to flow through the perforated base member and this gasflow energizes the particles of powder resting upon the base member, in the sense of imparting kinetic energy to those particles and entraining them in the gasflow. In other embodiments, a channel or conduit is provided to conduct the gasflow to a point within the powder receptacle that is spaced from the perforated base member, so that the gasflow emerges into the powder bulk at a point that is above the powder particles resting on the base member. The energized particles are able to pass through the base member into an outlet conduit from which the powder particles entrained in the gasflow are dispensed. 
     In other embodiments, the gasflow is not directed at and through the perforated base member, but is caused to enter the outlet conduit in such a manner that powder is drawn from the powder receptacle and entrained in the gasflow. For instance, the gasflow may be directed into the outlet conduit through an appropriately shaped inlet, e.g., a slot, so that a jet of gas passes into the outlet conduit beneath the powder receptacle. The jet of gas may have a form that is dictated by the shape of the inlet and which is conducive to entrainment of powder material from the powder receptacle. For instance, the inlet may have the form of a slot that is disposed orthogonally to the plane of the perforated base member (i.e., in most configurations of the device, a vertical slot). In other embodiments, the inlet may have the form of a slot that is parallel to the plane of the perforated base member (i.e. usually a horizontal slot). Such a horizontal slot may conveniently be created as a clearance between components of the device that together define the outlet conduit (or at least that part of the outlet conduit that lies beneath the powder receptacle). In all such cases, a shaped jet of air is directed into the outlet conduit, beneath the powder receptacle. The relatively high velocity of that jet creates a venturi-type effect that draws air into it from the surroundings, thereby energizing powder at the base of the powder receptacle, drawing that powder from the powder receptacle, and entraining it in the gasflow. 
     Apart from retaining the powder material within the powder receptacle until energized by the gasflow, the perforated base member functions as a sieve, preventing large agglomerated particles passing through, and enhancing the uniformity of the powder material dispensed from the device. The high energy of the gasflow through the outlet conduit may also assist in deagglomerisation of the powder as it is dispensed from the device. 
     The gasflow generator may be either an integral part of the device according to the invention, or an external component to which the device is coupled. Where the gasflow generator is part of the device, it may take various forms. For instance, the gasflow generator may comprise a compressible bulb or bellows that can be manually compressed by the user. In such a case, the bulb or bellows is preferably resilient and may include a one-way valve or an opening that permits the ingress of air to permit the bulb or bellows to return to its expanded condition after pressure applied to it is released. In such embodiments, the gas is generally ambient air. 
     In other embodiments, the gasflow generator is a canister of a compressed gas or a liquefied propellant. Compressed gases include compressed air, and compressed hydrocarbons. Liquefied propellants include chlorofluorocarbons and hydrofluoroalkanes. In all such embodiments, the canister will generally be provided with a valve by which the gasflow can be controlled. 
     In yet further embodiments, the gasflow generator does not itself form part of the device according to the invention, but is an external gas source to which the device is coupled. In such embodiments the device may, for instance, be coupled to a compressed gas source by an appropriate conduit, e.g., a flexible tube. The gas line may be a compressed air line, though other compressed gases may be used, e.g., nitrogen or carbon dioxide. Again, the arrangement will generally include means by which the gasflow can be controlled. Typically, the device will include an actuator, e.g., of the push button type, by which the flow of gas can be controlled. 
     In the device according to the invention, actuation of the gasflow generator is effectively synchronized with actuation of the agitator. The arrangement may be such that actuation of the gasflow generator causes actuation of the agitator, or vice versa. 
     In certain embodiments of the invention, the agitator may be operably linked to the actuator by which the gasflow is controlled. For instance, the actuator may be coupled to a trigger mechanism that causes a striking element to impact upon the powder receptacle. 
     In other embodiments, the agitator may be driven by the gasflow, such that the agitator operates for as long as the gas flows and is disengaged when the flow of gas is halted. In presently preferred embodiments, the agitator includes a moveable element that is positioned within the gasflow path. Such a moveable element is preferably mounted such that its movement generates mechanical disturbances or vibrations within the device, leading to physical agitation of the powder contained within the powder receptacle. In particularly preferred embodiments, the path along which gas is caused to flow includes a loop within which an agitator element is driven. Conveniently, such a loop has the form of a circular track and the agitator element is a ball or the like that is driven around the track by the gas flow. The movement of the ball generates vibratory forces that are transmitted through the device to the powder receptacle. In other embodiments, agitation of the powder receptacle may be brought about by actuation of an electric motor or the like. 
     Powder is preferably discharged from the device according to the invention via a discharge tube or barrel. Such a discharge tube or barrel may be capable of a limited degree of orientational movement relative to the rest of the device, in order that the direction of flow of the discharged powder may be adjusted to suit the needs of the situation in which the device is used, e.g., to facilitate optimal delivery of the powder during a surgical procedure. 
     The device according to the invention will most commonly comprise components manufactured wholly or largely of plastics materials. Where appropriate, however, other materials such as metals, e.g., stainless steel, and glass, e.g., for the powder receptacle, may be employed. For medical applications, the materials used may be of suitable medical grade and sterilizable. For ease of use, the components of the device according to the invention may be incorporated into an outer housing that facilitates operation of the device. For instance, the device may be configured such that it can be readily held and operated in one hand. 
     The device according to the invention may be used to deliver a wide variety of powders to a surface of the body. Such powders include agents intended to have a therapeutic effect, either in terms of a pharmacological effect on the body or as disinfectants or the like useful in the prevention or treatment of infections. One particular field in which the device of the invention is useful, however, is for the delivery of haemostatic powder compositions to internal tissues exposed during surgical procedures or after traumatic injury. Such haemostatic compositions, which may also be described as tissue sealants, may for instance comprise dry powder mixtures of fibrinogen and thrombin. Such a mixture is essentially inert when formulated in the dry state, but once hydrated, e.g., upon application to a bleeding wound, the mixture leads to the production of fibrin which cross-links to form a blood clot. 
     Thus, according to a further aspect of the invention, there is provided a method of delivering a haemostatic composition to an internal tissue exposed during surgical procedures or after traumatic injury, which method comprises providing a device as described above, which device is charged with a quantity of a haemostatic composition in dry powder form, and dispensing said composition from said device onto said tissue. 
    
    
     
       DESCRIPTIONS OF THE DRAWINGS 
       Embodiments of the invention will now be described in greater detail, by way of illustration only, with reference to the accompanying drawings, in which: 
         FIG. 1  is a schematic side view of a first embodiment of a powder delivery device according to the invention, partly in section, and showing a trigger mechanism in a rest condition; 
         FIG. 2  is a view similar to  FIG. 1 , but from the other side of the device, and showing the trigger mechanism in an actuated condition; 
         FIG. 3  is a side view of a second embodiment of a powder delivery device according to the invention; 
         FIG. 4  is a perspective view of the device of  FIG. 3 ; 
         FIG. 5  is a partial exploded view of the device of  FIG. 3 ; 
         FIG. 6  is a schematic diagram illustrating the mechanism by which mechanical vibrations are generated during actuation of the device of  FIG. 3 ; 
         FIG. 7  is a cross-sectional view of a valve forming part of the device of  FIG. 3 ; 
         FIG. 8  is a perspective view of an alternative form of an intermediate component that forms part of a third powder delivery device according to the invention, that has a similar general form to that of  FIG. 3 ; 
         FIG. 9  is a cross-sectional view of the intermediate component of  FIG. 8 ; 
         FIG. 10  is a fragmentary perspective view of an upper housing component employed in conjunction with the intermediate component of  FIGS. 8 and 9 ; 
         FIG. 11  is a fragmentary underside view of the upper housing component of  FIG. 10 ; 
         FIG. 12  is a fragmentary sectional view of a fourth embodiment of a powder delivery device according to the invention; 
         FIG. 13  is a sectional side view of a powder delivery device that is similar in concept to that of  FIG. 1 , save that generation of a gasflow is not accompanied by agitation of the powder receptacle according to the invention; and 
         FIG. 14  is a fragmentary view, on an enlarged scale, of part of the device of  FIG. 13 , showing the flow of air into and out of a powder vial forming part of the device. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Referring first to  FIG. 1 , a first embodiment of a powder delivery device according to the invention is generally designated  1  and comprises a main body  3  to which is fitted an upstanding tubular spigot  5  and a bellows  7 . A glass vial  9  containing a quantity of the powder to be dispensed is engaged with the spigot  5 , as described below. 
     The main body  3  is injection molded in plastics material with the general shape of a pistol. A downwardly (as viewed in  FIG. 1 ) depending hollow limb  3   a  of the main body  3  is adapted to be held by a user, and has a socket  4  with which the bellows  7  is engaged. A horizontal (as viewed in  FIG. 1 ) limb of the main body  3  has an internal bore  3   c  and constitutes a barrel  3   b  along which powder is dispensed from the device  1 . 
     The spigot  5  is also molded in plastics material. The spigot  5  comprises an upwardly (as viewed) directed tubular connector  5   a  with a peripheral flange  5   b  at its lower extremity. The flange  5   b  is received within a correspondingly shaped recess in the upper surface of the main body  3 , the flange  5   b  and main body  3  being bonded together. 
     The internal bore of the spigot  5  is tapered such that it has a funnel-like form, the base of the bore being closed by a perforated plate  5   c  that is formed integrally with the rest of the spigot  5 . The bore  3   c  within the barrel  3   b  terminates beneath the perforated plate  5   c . The end of the bore  3   c  that lies beneath the plate  5   c  is upwardly open so as to be in communication with the perforations in the plate  5   c  and hence with the internal bore of the spigot  5  and the vial  9 . The bellows  7  comprises a concertina-type chamber, one end of which is fitted with a nozzle. The bellows  7  is formed in plastics material and has a certain degree of resilience, such that it can be manually compressed, but returns to the expanded configuration shown in  FIG. 1  when the pressure applied to it is released. The other end of the bellows  7  may be provided with a one-way valve, e.g., a flap valve (not visible in  FIG. 1 ) to permit the bellows  7  to fill with air when it expands back to the condition shown in  FIG. 1 . Alternatively, the end of the bellows  7  may simply be provided with an opening that is occluded, e.g., by the user&#39;s thumb, when the bellows is compressed and then exposed to permit the bellows  7  to expand back to the condition shown in  FIG. 1 . 
     The nozzle of the bellows  7  has an interference fit within the socket  4 . A conduit  3   d  connects the interior of the downwardly depending limb  3   a  and the spigot  5 . In particular, the conduit  3   d  provides for the passage of air expelled from the bellows  7  through a region of the perforated plate  5   c  adjacent to that part which overlies the end of the bore  3   c.    
     The vial  9  has a neck  9   a  that receives the tubular connector  5   a  with an interference fit. The vial  9  is supplied with a closure that seals the neck  9   a . With the vial  9  in an upright position, the closure is removed and the tubular connector  5   a  inserted into the neck  9   a . The assembly is then an inverted condition, relative to the orientation shown in  FIG. 1 . The assembly is turned through 180°, to the condition shown in  FIG. 1 , whereupon powder contained within the vial  9  falls under gravity and fills the internal bore of the tubular connector  5   a . The powder rests upon the perforated plate  5   c , little or no powder falling through the perforations in the plate  5   c.    
     A trigger  11  is pivotally mounted adjacent to the rear (i.e. the side distal to the barrel  3   b ) of the vial  9 . The trigger  11  carries a striker  13  that is mounted to an arcuate track  15 , such that the striker  13  is capable of a restricted range of movement relative to the trigger  11 . A tension spring  17  (see  FIG. 2 ) is mounted between the striker  13  and an upstand  18  on the main body  3 , close to the front of the vial  9 , so as to draw the striker  13  towards the vial  9 . 
     As can be seen in  FIG. 1 , the trigger  11  and the striker  13  are formed with cooperating detents  11   a , 13   a , such that when the trigger  11  is pressed down by a user (as described below), the striker  13  is drawn away from the surface of the vial  9 , against the action of the spring  17 . 
     The rear part of the main body  3  is formed with a ramp  19 . As the trigger  11  is depressed, the ramp  19  comes into contact with the striker  13 . Continued depression of the trigger  11  causes the ramp  19  to displace the striker  13  and to disengage the detents  11   a ,  13   a . When released from the trigger  11  by the ramp  19 , the striker  13  is drawn by the action of the spring  17  into contact with the vial  9 , thereby jarring the vial  9 . In practical embodiments of the device  1 , the trigger  11  is housed within a push button-type actuator (not shown), depression of which also results in compression of the bellows  7 . Thus, generation of an airflow is synchronized with mechanical jarring of the vial  9 , thereby facilitating entrainment of powder in the airflow and releasing powder from the vial  9 . 
     To dispense powder from the device  1 , the user holds the device  1  in a generally upright orientation, as shown in  FIG. 1 , and directs the barrel  3   b  at the intended site of application of the powder. The user then depresses the actuator, compressing the bellows  7  and depressing the trigger  11 . Appropriate formations (not shown) may be provided on the device  1  to facilitate gripping of it, e.g., so that the actuator can be depressed by the thumb. Compression of the bellows  7  causes a jet of air to be directed through the conduit  3   d . This jet of air passes through the perforated plate  5   c  and impacts upon the powder resting upon that plate  5   c . Simultaneously, the striker  13  is drawn away from the vial  9 , then released from the trigger  11  by the action of the ramp  19 , with the result that the striker  13  impacts upon the vial  9  as the jet of air impacts upon the powder. The energized powder is entrained in the flow of air that escapes from the device  1  by passing back through the perforated plate  5   c  and along the internal bore  3   c  of the barrel  3   b . The powder is blown out of the device  1  and deposited on the site of application. 
     When pressure is removed from the actuator, the bellows  7  relaxes to the condition shown in  FIG. 1 , air being drawn into the bellows through the one-way valve or opening in the free end of the bellows  7 . At the same time, the trigger  11  returns to its rest condition, as shown in  FIG. 1 , in which the detents  11   a ,  13   a  re-engage. Actuation may then be repeated as often as required. Powder may continue to be dispensed until the desired amount of powder has been dispensed, or until the vial  9  is exhausted, all the powder contained within it having been dispensed. Where the vial  9  becomes exhausted, it may be appropriate for it to be removed from the spigot  5  and replaced with a fresh vial, ie for the device to be reused with a fresh vial of powder. In other circumstances, the device may be used only once and then discarded. 
     Turning now to  FIGS. 3 to 7 , a second embodiment of a powder delivery device in accordance with the invention is generally designated  20 . This embodiment differs from the first embodiment 1 in that it is used in conjunction with an external source of compressed gas, and in that the mechanism by which the vial is agitated during dispensing of powder is different. 
     Referring first to  FIGS. 3 and 4 , the device  20  has a main body that comprises upper and lower housing components  23   a ,  23   b  that are formed in plastics material by injection molding. The main body has the general form of an elongate cylinder that is adapted to be held a user&#39;s hand, the underside of the lower component  23   b  being shaped to facilitate such grip. A push button-type actuator  27  is mounted in the top of the main body such that, when the device  20  is held by the user, the actuator  27  can be depressed by the thumb of the hand that holds the device  20 . 
     A flexible tube  25  extends from the rear end of the device  20  and is adapted to be connected to a gas source, e.g., a source of compressed air (not shown). A suitable connector (not shown) is provided at the distal end of the tube  25 . 
     The front end of the device  20  is provided with a tubular barrel  29 , through which powder is dispensed from the device  20 . A glass vial  31  is coupled to the device  20  in a similar manner to the way in which the vial  9  is coupled to the first embodiment of the device  1 . As can be seen in  FIG. 5 , the upper component  23   a  is formed with an upstanding spigot  33  that is received within the mouth of the vial  31 . A pair of clips  35  engages with a peripheral lip of the vial  31 , so as to hold it securely in place. As in the first embodiment, the interior of the spigot  33  is tapered such that it has a funnel-like form, the base of the spigot  33  being closed by a perforated plate  34 . 
     Referring again to  FIG. 5 , an intermediate component  41  is captivated between the upper and lower components  23   a ,  23   b  of the main body  23 . The intermediate component  41  is formed with a circular opening  61  near its rear, which receives a downwardly depending boss (not visible in  FIG. 5 ) formed integrally on the underside of the upper housing component  23   a . A circular track  43  is formed in the lower component  23   b , with air inlet  45  and outlet  46  channels. The intermediate component  41  cooperates with the lower component  23   b  to close the track  43 . A ball  50  (not shown in  FIG. 5 ) is held within the track  43  such that it can rotate freely around the circular track  43 . The tube  25  is connected to a valve  51  that is held within an upstanding boss  52  formed integrally with the lower component  23   b . The valve  51  is in turn connected to the intermediate component  41  by means of a short length of tubing  25   a  that is engaged with a tubular connector  47  formed integrally with that component and which, when the intermediate component  41  and lower component  23   b  are engaged, is in registration with the air inlet channel  45 . 
     The valve  51  is positioned beneath the actuator  27 , which is biased to the position shown in  FIG. 3 . The actuator  27  includes a cam (not visible in the drawings) which bears on the valve  51  to control the operation of the valve  51 . When the actuator is depressed, the valve  51  is opened to permit air to flow from the external source of compressed air through the device  20 , and when the actuator  27  is released the flow of air is halted. 
     The valve  51  is shown in cross-section in  FIG. 7 . It is of the type commonly referred to as a trumpet valve, and comprises a valve body  71  within which a valve stem  72  is capable of restricted reciprocating movement. The lower part of the valve stem  72  is of reduced dimensions, relative to the lower part of the valve body  71 , so that an annular space exists between those two components. A valve cap  73  is mounted about the upper part of the valve stem  72 . The range of movement of the valve stem  72  is restricted by engagement of an inwardly directed lip  74  at the base of the valve cap  73  with an outwardly directed flange  75  at the top of the valve stem body  71 . The valve stem  72  is biased to the position shown in  FIG. 7  by an arrangement of two compression springs  76  that act between the flange  75  and the underside of the top of the valve cap  73 . 
     A pair of spaced apart O-rings  77 , 78  provide for sealing engagement between the valve stem  72  and the internal walls of the valve body  71 . A valve inlet  79  receives the end of the tube  25 , and a similar valve outlet  80  is connected to the short tube  25   a  that leads to the intermediate component  41 . 
     In the position shown in  FIG. 7 , the valve  51  is closed. Passage of gas from the supply tube  25  to the valve outlet  80  is blocked. Depression of the valve stem  72 , for example by the user pressing on the actuator  27 , displaces the lower O-ring  78  to a position below the valve outlet  80 , thereby opening the valve  51  and enabling flow of gas through the annular space surrounding the valve stem  72  to the valve outlet  80 . 
     When the valve  51  is open, gas flows into the track  43  and drives the ball (not shown) around the track  43 . An air feed hole  48  is formed in the intermediate component  41 , above the rear portion of the track  43 . This creates a flow of a certain amount of air from the track  43 , that airflow being directed at the rear part of the perforated plate  34  and into a short feed pipe  49  that is formed integrally with the internal wall of the spigot  33  and terminates a short distance above the perforated plate  34 , within the powder that, as in the first embodiment, rests upon the perforated plate  34 . The feed hole  48  and feed pipe  49  direct a minor proportion of the airflow into the powder. The greater proportion of the airflow, however, is simply vented via the outlet channel  46 . Openings  59  at the rear of the device permit vented air to escape. The proportion of the airflow that is directed into the vial  31  can be adjusted to suit the intended application of the device (ie to suit the amount of powder to be delivered, the nature of the powder, and so on) by varying the sizes of the feed hole  48  and/or the outlet channel  46 . 
     The upper surface of the intermediate component  41  is formed, in the region beneath the perforated plate  34 , with a shallow well  53  with a forwardly-directed outlet  54 . The outlet  54  is connected, via a short tube  55 , to the barrel  29 . A nose  56  is formed integrally with the barrel  29  and is captivated between the forward ends of the upper and lower components  23   a ,  23   b . The nose  56  is generally hemispherical in shape, and is held within the end of the housing in the manner of a ball-and-socket joint, which permits a restricted range of orientational movement of the barrel  29  (as is most readily apparent from  FIG. 4 ). 
     To dispense powder from the device  20 , the user holds the device  20  in one hand, directs the barrel  29  at the intended site of application of the powder, and depresses the actuator  27  with the thumb. This opens the valve  51 , permitting air to flow through the device  20 . Air flows along the tubes  25  and  25   a  into the track  43 . The circulation of air within the track  43  causes the ball  50  to rotate rapidly around the track  43 . The movement of the ball  50  causes a degree of mechanical vibration that is transmitted to the intermediate component  41 , the upper component  23   a  and the vial  31 . 
     Most of the airflow is vented from the device  20  via the outlet  46  and openings  59 . However, a small proportion of air escapes from the track  43  via the feed hole  48 , from which it is directed at the underside of the perforated plate  34  and into the feed pipe  49 . This jet of air passes into the powder resting upon that plate  34 . The mechanical agitation of the device  20  caused by rotation of the ball  50  within the track  43  facilitates the release of the powder from the vial  31 . The powder is entrained in the flow of air that escapes from the device  20  by passing back through the perforated plate  34  into the well  53  and through the barrel  29 . The powder is blown out of the device  1  and deposited on the site of application. 
     Mechanical agitation of the device continues for as long as the actuator  27  is depressed. When the actuator  27  is released, the flow of air is halted and the ball  50  ceases its rotary motion within the track  43 . The device may be actuated for a continuous period, or intermittently. 
     As for the first embodiment 1, powder may continue to be dispensed until the desired amount of powder has been dispensed, or until the vial  31  is exhausted, all the powder contained within it having been dispensed. Where the vial  31  becomes exhausted, it may be removed from the spigot  33  and replaced with a fresh vial, or the device may be discarded, as appropriate. 
     Turning now to  FIGS. 8 to 11 , a third embodiment of a powder delivery device according to the invention is generally similar to that of  FIGS. 3 to 7 , but differs in the manner in which the gasflow entrains powder from the powder receptacle. Elements of the third embodiment that correspond to those of the second embodiment are identified by the same reference numbers, but with the prefix “1”. Thus, the intermediate component  143  corresponds to the intermediate component  43  of the second embodiment, the perforated base member  134  corresponds to the base member  34 , and so on. 
       FIGS. 8 and 9  show, in perspective and cross-sectional views respectively, an intermediate component  141  similar in general form to the intermediate component  41  of the embodiment of  FIGS. 3 to 7 .  FIGS. 10 and 11  show fragmentary views of the part of the upper housing component  123   a  that contains the perforated base plate  134 . In this embodiment, the lower housing component, barrel, valve and actuator (not shown) are identical to those of the second embodiment. The principal difference between the second and third embodiments lies in the manner in which air flows from the track  43  to the well  153  in the intermediate component  141  that is located beneath the perforated plate  134 . In the second embodiment ( FIG. 5 ), that air passes through feed hole  48  and feed pipe  49  to a position within the spigot  33  that is above the perforated plate  34 . In the third embodiment, on the other hand, there is no feed pipe. Instead, feed hole  148  terminates in a vertical slot  149 , the upper end of which is closed by an abutting part  158  of the undersurface of the upper housing component  123   a  (see  FIG. 11 ). 
     As can be seen in  FIG. 10 , the upper surface of the upper housing component  123   a  is similar to that of the second embodiment, in that it is formed with an upstanding spigot  133 , the base of which comprises the perforated plate  134 . However, the rear part of the interior of the spigot  133 , that in the second embodiment is occupied by the feed pipe  49 , is in this embodiment a simple ramp  163 . The interior side walls of the spigot  133  are also formed as ramps  164 , giving the interior of the spigot  133  a funnel-like form. The ramps  164  may be omitted, so that the perforated base plate  134  is generally circular, in which case the parallel ribs evident in  FIG. 11  may also be omitted. In fact, the presently most preferred embodiment of the device has such modifications. 
     As in the second embodiment, the intermediate component  141  is formed with a circular opening  161  that receives a corresponding downwardly-depending boss  162  formed on the underside of the upper housing component  123   a  (see  FIG. 11 ). 
     The device of the third embodiment is actuated in precisely the same manner as the second embodiment, i.e. the user depresses the actuator, thereby opening the valve and causing gas to flow into the track and to drive the ball around that track. Movement of the ball creates vibrations that are transmitted to the vial containing the powder that is to be dispensed. Some of the gasflow escapes from the track via the feed hole  148  and slot  149 . That gas is directed as a jet across the well  153  beneath the perforated plate  134 , towards the outlet  154 . The relatively high velocity jet of gas that traverses the well  153  creates a venturi-type effect that draws powder through the perforated plate  134  and entrains it in the gasflow. 
       FIG. 12  shows a sectional view of a fourth embodiment of a powder delivery device according to the invention. Again, elements of this embodiment that correspond to those of the embodiment of  FIGS. 3 to 7  are identified by corresponding reference numerals, but with the prefix “2”. Thus, the intermediate component  243  corresponds to the intermediate component  43  of the second embodiment, the perforated base member  234  corresponds to the base member  34 , and so on. 
     The fourth embodiment is again generally similar to the second and third embodiments just described. Thus, the fourth embodiment comprises upper and lower housing components  223   a ,  223   b  and an intermediate component  241 . The upper housing component  223   a  is formed with an upstanding spigot  233  about which the neck of a vial  231  is received. The base of the spigot  233  is formed as a perforated plate  234 . A well  253  is formed in the upper surface of the intermediate component  241  and is located beneath the perforated plate  234 . Cooperating parts of the intermediate component  241  and upper housing component  223   a  together form an outlet  253  that is connected to a tube  255 . The intermediate component  241  and lower housing component  223   b  together define a track  243  within which a ball (not shown) is driven, in use. 
     The fourth embodiment differs from the third in that the feed hole  248 , that leads from the track  243 , terminates not in a feed pipe ( FIG. 5 ) or a vertical slot ( FIG. 8 ), but in a planar horizontal gap  249  between the juxtaposed surfaces of the intermediate component  241  and the upper housing component  223   a  that surround the well  253 . 
     The effect of the gap  249  is to create a high velocity jet of gas in a plane parallel to the perforated plate  243 . As for the third embodiment, that jet of gas creates a venturi-type effect that draws powder through the perforated plate  243 . 
     Referring finally to  FIGS. 13 and 14 , a further embodiment of a powder delivery device is generally designated  91  and comprises a main body  93  to which is fitted an upstanding tubular spigot  95  and a bellows  97 . A glass vial  99  containing a quantity of the powder to be dispensed is engaged with the spigot  95 , as described below. 
     The main body  93  is injection molded in plastics material and the general shape of a pistol. A downwardly (as viewed in  FIG. 13 ) depending limb  93   a  of the main body  93  constitutes a tubular connector that receives the bellows  97 . A horizontal (as viewed in  FIG. 13 ) limb  93   b  of the main body  93  has an internal bore  93   c  and constitutes a barrel along which powder is dispensed from the device  91 . 
     The spigot  95  is also molded in plastics material. The spigot  95  comprises an upwardly (as viewed) directed tubular connector  95   a  with a peripheral flange  5   b  at its lower extremity. The flange  95   b  is received within a correspondingly shaped recess in the upper surface of the main body  93 , the flange  95   b  and main body  93  being bonded together. 
     The internal bore of the spigot  95  is tapered such that it has a funnel-like form, the base of the bore being closed by a perforated plate  95   c  that is formed integrally with the rest of the spigot  95 . The bore  93   c  within the horizontal limb  93   b  of the main body  93  terminates beneath the perforated plate  95   c . The end of the bore  93   c  that lies beneath the plate  95   c  is upwardly open so as to be in communication with the perforations in the plate  95   c  and hence with the internal bore of the spigot  95  and the vial  99 . 
     The bellows  97  comprises a concertina-type chamber  97   a , one end of which is fitted with a nozzle  97   b . The bellows  97  is formed in plastics material and has a certain degree of resilience, such that it can be manually compressed, but returns to the expanded configuration shown in  FIG. 13  when the pressure applied to it is released. The other end of the bellows  97  may be may be provided with a one-way valve, e.g., a flap valve (not visible in  FIG. 13 ) to permit the bellows  97  to fill with air when it expands back to the condition shown in  FIG. 13 . Alternatively, the end of the bellows  97  may simply be provided with an opening that is occluded, e.g., by the user&#39;s thumb, when the bellows is compressed and then exposed to permit the bellows  97  to expand back to the condition shown in  FIG. 13 . 
     The nozzle  97   b  has an interference fit within the downwardly depending limb  93   a  of the main body  93  such that the nozzle  97   b  is closely received within that limb  93   a , with the tip of the nozzle  7   b  directed at a conduit  3   d  that connects the interior of the downwardly depending limb  93   a  and the spigot  95 . In particular, the conduit  93   d  provides for the passage of air expelled from the bellows  97  through a region of the perforated plate  95   c  adjacent to that part which overlies the end of the bore  93   c.    
     The vial  99  has a neck  99   a  that receives the tubular connector  95   a . The vial  99  is supplied with a closure that seals the neck  99   a . With the vial  99  in an upright position, the closure is removed and the tubular connector  95   a  inserted into the neck  99   a . The assembly is then an inverted condition, relative to the orientation shown in  FIG. 13 . The assembly is turned through 180°, to the condition shown in  FIG. 13 , whereupon powder contained within the vial  99  falls under gravity and fills the internal bore of the tubular connector  95   a . The powder rests upon the perforated plate  95   c , little or no powder falling through the perforations in the plate  95   c.    
     To dispense powder from the device  91 , the user holds the device  91  in a generally upright orientation and directs the horizontal limb  93   b  of the main body  93  at the intended site of application of the powder. The user then compresses the bellows  97 . Appropriate formations (not shown) may be provided on the device  91  to facilitate gripping of it, e.g., between the thumb and first two fingers of one hand, and compression of the bellows  97 . Compression of the bellows  97  causes a jet of air to be directed at and through the conduit  93   d . This jet of air passes through the perforated plate  95   c  and energizes the powder resting upon that plate  95   c . The energized powder is entrained in the flow of air that escapes from the device  91  by passing back through the perforated plate  95   c  and along the internal bore  93   c  of the horizontal limb  93   b . The powder is blown out of the device  91  and deposited on the site of application. 
     The perforated plate  95   c  serves to retain the powder until it is energized and dispensed by the flow of air through the plate  95   c , and also facilitates deagglomeration and dispersion of the powder in the airflow. 
       FIG. 14  shows (by means of the arrow) the flow of air into the powder retained within the interior of the tubular connector  95   a  and the vial  99 , and the flow of air and entrained powder out of the device  91 . 
     When pressure is removed from the bellows  97 , it relaxes to the condition shown in  FIG. 13 , air being drawn into the bellows through the one-way valve or opening in the free end of the bellows  97 . Repeated compression of the bellows  97  causes repeated dispensing of powder from the device  91 . Powder may continue to be dispensed until the desired amount of powder has been dispensed, or until the vial  99  is exhausted, all the powder contained within it having been dispensed. Where the vial  99  becomes exhausted, it may be appropriate for it to be removed from the spigot  95  and replaced with a fresh vial, i.e. for the device to be reused with a fresh vial of powder. In other circumstances, the device may be used only once and then discarded. 
     While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiments but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as is permitted under the law.