Apparatus for dispensing cryogenic liquids

Abstract: A liquid dispenser for dispensing liquid cryogen comprises a vessel (10) and a valve/actuator arrangement (16, 18) said valve being positioned within the vessel and operable to obturate or uncover an outlet orifice (14). Said actuator (18) being positioned wholly outside the vessel but being able to generate a magnetic force with the vessel for moving a magnet or magnetic portion (24, 26) on the valve so as to move the valve between open and closed positions.

Description: The present invention relates to apparatus for dispensing droplets of liquid and relates particularly, but not exclusively, to apparatus for dispensing droplets of chosen or suitable volume of a cryogenic liquid, for example, liquid nitrogen. Liquid gases are typically used in industry in bulk quantities and can thus be metered by conventional methods. On some occasions, however, a need arises for only a small quantity, for example, up to a few millilitres of liquified gas to be delivered. Such a need may arise when bottling a beverage. It is often desirable for the neck of each bottle to contain an atmosphere consisting essentially of a gas such as nitrogen that does not adversely affect the quality of the beverage. Moreover, even if nitrogen is not required for this reason, it has been found that in a closed plastic bottle containing a beverage, a partial vacuum can be created in its neck as a result of a reduction in temperature, which partial vacuum can cause a wall of the bottle to be sucked inwards, and accordingly filling the neckspace with a small volume of nitrogen (or other suitable gas) before fitting a closure to the bottle will guard against the creation of such a partial vacuum. Previous attempts to solve the problem of delivering or dispensing droplets of liquid nitrogen (or other liquified gas) include that described in GB2092552 in which an insulated tank of liquid nitrogen is provided with a valve on its inside bottom surface and an actuator on an outer upper surface thereof. The actuator is linked to the valve via a long rod such that, in operation, the valve is actuated whenever the rod is moved up and down. This arrangement whilst providing a perfectly adequate method of dispensing droplets does suffer from problems associated with the use of a slender rod connector. The mass of the rod must be as low as possible in order to minimise its inertia and facilitate high speed operation. Unfortunately, there is a point beyond which it is not possible to reduce the diameter (and hence the mass) of the rod without adversely affecting the strength of the rod. Additionally, the higher the rod mass the higher the valve wear rate and hence the higher the leakage potential. Consequently, this arrangement does not lend itself to use at relatively high frequencies. An alternative arrangement is illustrated in GB2251296 in which an insulated vessel is provided with a valve and actuator arrangement both of which are located wholly within the vessel. The valve comprises a tapered member which is biased downwardly by a spring and which is connected to a permanent magnet disposed in a coil which forms part of the actuator. The tapered member can be driven upwardly or downwardly according to the sense in which a direct current is applied to the coil. This arrangement whilst overcoming the problems associated with an actuator positioned outside the cryogenic vessel does not lend itself to easy maintenance, the vessel having to be drained and the entire valve/actuator assembly having to be dismantled just to service the actuator. Additional problems present themselves when routing electric wires through the walls of an insulated container. It is an object of the present invention to provide a liquid dispensing apparatus which reduces and possibly eliminates the problems associated with the above two dispensers. Accordingly, the present invention provides a dispenser for dispensing drops of cryogenic liquid comprising a vessel for holding cryogenic liquid and having an outlet orifce for allowing liquid cryogen to drain from said vessel, a valve associated with said outlet orifice and operable, in use, to allow or inhibit the flow of cryogenic liquid from said vessel and an actuator comprising a magnetic device and operable, in use, to cause said valve to be opened and closed characterised in that the valve is arranged completely inside the vessel, in that said magnetic device is positioned immediately adjacent the valve and wholly or mainly outside said vessel, the magnetic device comprising a coil arranged completely outside the vessel, in that all the moving parts of the valve and the actuator are arranged completely inside the vessel, and in that the magnetic device, in operation, is adapted to generate a magnetic force within the vessel capable of causing said valve to move between open and closed positions. Advantageously, the actuator comprises an electromagnet having a core with a proximal and a distal end and a coil positioned around said core, said proximal end of said core extending into a base portion of said vessel, said coil being arranged to receive, in operation, a current for generating said magnetic field within said vessel. In one embodiment the core terminates flush with or beyond an inner surface of the base. Alternatively, the core terminates short of an inner surface of said base and a portion of the base covers the proximal end of said core thereby to protect said core from the contents of the vessel. In one arrangement, the actuator comprises two core portions, each core portion being linked at its distal end to the other core portion via a bridging member and being provided with a coil portion around each core portion. Preferably, when an actuator having just one core is used, the valve includes a magnet of opposite polarity to the polarity of the magnetic field generated by the magnetic device. Preferably, when an actuator having two core portions is used, the coils around said core portions are wound so as to produce a magnetic field of different polarity at each proximal end and said valve includes a magnetic portion which, in operation, forms a bridge between the poles thereby to complete a magnetic loop. Advantageously, the dispenser includes a spring for biasing said valve towards or away from said closed position. Conveniently, said valve comprises a rod having a rounded end for engagement with a tapered portion of said outlet orifice thereby to obturate said outlet when said valve is in said closed position. The dispenser may include guide means for guiding the valve between its opened and its closed positions. The present invention will now be more particularly described by way of example only with reference to the accompanying drawings in which: Figure 1 is a cross sectional view of a cryogenic liquid vessel incorporating a dispenser according to the present invention, some features of which are omitted for reasons of clarity; Figure 2 is a detailed view of the dispenser of the present invention taken in the direction of arrow A in Figure 1; Figure 3 is a detailed view of the dispenser of the present invention taken in the direction of arrow B in Figure 2; Figures 4 and 5 illustrate alternative forms of the dispenser shown in Figure 1; and Figure 6 is a schematic drawing illustrating part of a bottle or canning line fitted with apparatus similar to that shown in Figures 1 to 4. Referring now to the drawings in general but particularly to Figure 1 a cryogenic vessel 10 includes a base portion 12 having an outlet orifice 14 for allowing liquid cryogen to drain from the vessel 10. A valve 16 associated with the outlet orifice and operable, in use, to allow or inhibit the flow of cryogenic liquid from the vessel 10 is positioned immediately above the base portion 12. The valve includes a low mass (approximately 1.5g) rod 16a made from, for example, aluminium and having a rounded end 16b for engagement in a tapered portion 14a of orifice 14. A magnetic device such as, for example, an electromagnetic device 18 is positioned wholly outside the vessel 10 but acts to generate a magnetic force within the vessel 10 capable of causing said valve 16 to move between open and closed positions. The actuator 18 may comprise any one of a number of well known magnetic field generators but most conveniently comprises a single or multiple coil and core arrangement similar to that shown in Figures 1 to 5. If a single coil arrangement is used, (best seen in Figure 4), then the core 20 and coil 22 is matched with a magnet portion 24 provided on the valve such that, in operation, the polarity of the core end 20a proximal to the magnet portion 24 is such as to drive the valve in a desired direction so as to open or close the valve. In the embodiment having a single core 20 arranged beneath the valve, it may be most convenient to arrange the polarities such as to cause the valve 16 to be drawn downwardly thereby to obturate the outlet on orifice 14 whenever the coil is energised. Alternative arrangements will however present themselves to the reader knowledgeable in the art of electromagnetic actuators. The double core arrangements, (best seen in Figures 1, 3 and 5) comprise two cores 20 each having a proximal end 20a positioned sufficiently close to the valve portion so as to enable any magnetic field generated thereat to act upon a magnetic portion 26 of valve 16. The distal ends 20b of the rods 20 are connected via a simple magnetic ring 21 having a hole 21a through which, in operation, drops of liquid cryogen pass. Conveniently, the two coils 22, 28 may be wound in opposite directions so as to produce differing polarities at their proximal ends. In such an arrangement, the magnetic portion 26 need have no magnetism of its own and may simply comprise a steel portion. The magnetic portion 26 simply acting to bridge the gap G between the core ends 20a so as to complete the magnetic circuit whenever the coils are energised. A spring 30 and guide arrangement 32, best seen in Figure 2, is provided so as to bias the valve towards an opened position and guide the valve when in operation. Conveniently, the guide 32 and spring 30 are mounted on a frame 34 comprising a pair of uprights 36 having the guide 32 and an anchor point 38 for the spring mounted thereon. a pin 40 acts to limit valve travel. Figures 1 and 3 to 5 illustrate various core proximal end positions. In Figure 1 the proximal ends 20a are arranged to extend into and through base plate 12 such that they terminate just inside the vessel 10 and, in operation, are surrounded by cryogenic liquid. This arrangement has the advantage of ensuring the magnet or magnetic portion 24, 26 of the valve remains well clear of the bottom of the vessel thereby ensuring valve operation is not compromised by the presence of any particulate matter which might collect on the bottom of the vessel 10. Alternatively, one could employ the arrangements shown in Figures 3 and 4 in which the proximal ends 20a are flush with the inner surface 12a of base plate 12. The arrangement shown in Figure 5 in which the proximal ends 20a terminate just short of the inner surface 12a of base plate 12 and are protected by a thin layer 50 of base plate material, may be employed whenever it is desired to protect the core 20 from the liquid to be contained within the vessel. This arrangement has the additional advantage of avoiding problems associated with sealing the core within the base plate so as to prevent leakage of liquid. In the Figure 5 arrangement, the base plate may be selected from a range of suitable non-magnetic materials and the thickness T of layer 50 is chosen so as to ensure an adequate magnetic force can be transmitted therethrough. Stainless steel lends itself to use as a base 12 in any of the illustrations in Figures 1 to 5, such steel generally being non-magnetic. Operation of the dispenser is achieved by applying a D.C. current to coils 22, 24 so as to generate a magnetic field adjacent the proximal end(s) of core(s) 20. The magnetic field acts to attract (or repel in appropriate arrangements) the magnet 24 or magnetic portion 26 of valve 16 thereby drawing the rounded end of rod portion towards a closed position in it acts to obturate the tapered portion 14a of outlet orifice 14. As soon as the current is turned off, spring 30 acts to retract the rod 16 and allow liquid cryogen to pass through orifice 14. By simply turning the current on and off, it is possible to initiate control over the valve so as to allow or inhibit the flow of cryogen from the vessel 10. The faster the rate of switching the higher the number of drops of cryogen per minute. Operation at over 1000 cycles per minute and possibly 1800 cycles per minute is possible. Clearly, one could use an A.C. current so as to electromagnetically drive the valve between open and closed positions. In such an arrangement one need only vary the frequency of the current in order to control the speed of the valve operation. Turning now briefly to Figure 6, it will be seen that vessel 10 is positioned above a bottle or canning line 60 such that, in operation, droplets 62 of dispensed cryogen (eg nitrogen) may be dispensed directly into the opening 63 in a bottle or can 64 positioned thereunder. An optical or mechanical sensor 66 acts to detect the presence of a can or bottle and sends a signal to control panel 68 which initiates operation of actuator 18 as and when desired. A bulk source of liquid cryogen 70 is provided for ensuring an adequate liquid level is maintained in vessel 10. It will be appreciated that the present invention has a number of advantages over the prior art dispensers. Firstly, by providing the actuator mechanism 18 wholly outside the vessel 10 it is possible to eliminate the requirement to route electrical wires into the interior of the vessel, thereby eliminating the sealing problems associated with such wiring. Additionally, the actuator is not exposed to the sometimes hostile environment inside the vessel. Maintenance is also simplified as the actuator can be serviced and possibly even replaced without first draining the vessel 10 and without disturbing the somewhat delicate valve assembly. By placing the actuator immediately adjacent the valve it is possible to eliminate the long actuator rod assembly as described in GB2092552 and the problems associated therewith. The relatively low mass and hence inertia of the rod lends itself to high speed operation.

Claims: A dispenser for dispensing drops (62) of cryogenic liquid comprising a vessel (10) for holding cryogenic liquid and having an outlet orifice (14) for allowing liquid cryogen to drain from said vessel (10), a valve (16) associated with said outlet orifice (14) and operable, in use, to allow or inhibit the flow of cryogenic liquid from said vessel (10) and an actuator (18) comprising a magnetic device and operable, in use, to cause said valve to be opened and closed characterised in that the valve (16) is arranged completely inside the vessel (10), in that said magnetic device is positioned immediately adjacent the valve (16) and wholly or mainly outside said vessel (10), the magnetic device comprising a coil (22, 28) arranged completely outside the vessel (10), in that all the moving parts of the valve (16) and the actuator (18) are arranged completely inside the vessel (10), and in that the magnetic device, in operation, is adapted to generate a magnetic force within the vessel (10) capable of causing said valve to move between open and closed positions. A dispenser as claimed in Claim 1 characterised in that said actuator (18) comprises an electromagnet having a core (20) with a proximal (20a) and a distal end (20b) and a coil (22) positioned around said core (20), said proximal end (20a) of said core (20) extending into a base portion (12) of said vessel, said coil (22) being arranged to receive, in operation, a current for generating said magnetic field within said vessel. A dispenser as claimed in Claim 1 or Claim 2 characterised in that said core (20) terminates flush with or beyond an inner surface (12a) of said base. A dispenser as claimed in Claim 2 characterised in that said core (20) terminates short of an inner surface (12a) of said base and in which a portion of the base covers the proximal end of said core (22) thereby to protect said core from the contents of the vessel (10). A dispenser as claimed in any one of the previous claims characterised in that said actuator (18) comprises two core portions (20), each core portion (20) being linked at its distal end (20b) to the other core portion via a bridging member (21) and being provided with a coil portion (22) around each core portion (20). A dispenser as claimed in any one of Claims 1 to 4 characterised in that said valve (16) includes a magnet (24) of opposite polarity to the polarity of the magnetic field generated by the magnetic device (18). A dispenser as claimed in Claim 5 characterised in that the coils (22, 28) around said core portions are wound so as to produce a magnetic field of different polarity at each proximal end (22a) and said valve includes a magnetic portion (26) which, in operation, forms a bridge between the poles thereby to complete a magnetic loop. A dispenser as claimed in any one of the previous claims characterised by a spring (30) for biasing said valve (16) towards or away from said closed position. A dispenser as claimed in any one of the previous claims characterised in that said valve (16) comprises a rod (16a) having a rounded end (16b) for engagement with a tapered portion (14a) of said outlet orifice (14) thereby to obturate said outlet (14) when said valve (16) is in said closed position. A dispenser as claimed in any one of the previous claims characterised by guide means (32) for guiding said valve (16) between its opened and its closed positions.

Inventors: WARDLE DAVID GRANT, WARDLE, DAVID GRANT
Applicants: BOC GROUP PLC, THE BOC GROUP PLC
Application year: 1995
Main classification: B65B31
IPC codes: B65D50, F17C9, B65B31, B65D49