GB2495961A - Rotating powder dispenser - Google Patents

Abstract

Dispensing a particulate product (e.g. powder 4 or granulated materials, beads, etc) from a vessel 1 through an outlet 2 therein by rotating the vessel about a pivot (e.g. shaft 3) so that the outlet rotates towards and away from a downward-facing position. The vessel may be rotated to and fro between two downward orientations and may accelerate away from and decelerate towards each. It may periodically be rotated to an upward orientation e.g. decelerating towards the upward orientation and/or rotating to and fro between two upward orientations - so as to agitate the powder whilst the outlet is facing upward, thus breaking any powder bridges. The powder may be collected in a receptacle (102, Fig.2) on balance (103, Fig.2) to measure the amount or rate of dispensed powder and control the rotation accordingly so as to dispense a target amount of powder. The rotation generates less interference to the balance than electro-magnetic or pneumatic tapping actuators.

Description

Apparatus and Method for Dispensing Powder The present invention is directed to apparatus and a method for dispensing a powder.

0S2009/014003, US200601 1653, US2007006942, LJS2O1O/0051648, EP1752744 and W02006003379 disclose examples of prior art powder dispensers.

US2009 140003 relates to powder metering apparatus having a reservoir with a metering head having a flow control element which can be a screw or a shutter valve element. These moving parts can damage the powder and produce micro particulates.

In US2007006942. the container holding the powder has an outlet with a valve in the form of a plate. The valve is caused to open and close by oscillating the container and plate in a vertical direction into and away from a housing. These moving parts can damage the powder and produce micro particulates. It is also difficult to clean and refill with powder.

US2007601 1653 comprises a container for powder having an adjustable opening in the form of a value which is operated by a tool. The container holds a stirrer to iS agitate the powder. This complicates the device as additional componentiy is required to drive the stirrer. The container may also be tapped or vibrated.

EP1752744 relates to a dispenser comprising a hopper having a mesh at its base.

When a dispensing powder is placed in the hopper, the powder will initially pass through the mesh, however, shortly thereafter, the powder forms bridges over the holes of the mesh and the flow of powder ceases. The dispenser further comprises an electro-mechanical actuator to tap the hopper. Each tap causes the powder bridges to temporarily break, allowing a small portion of the powder to pass through the mesh and out of the hopper before the bridges reform. By repeatedly tapping the hopper. it is possible to accurately dispense a required amount of powder. The hopper is held at S.)-the end of a cantilevered arm. The arm can rotate in a horizontal plane to move the hopper above or away from the receptacle. The taps are produced by lateral impulses along the length of the cantilevcrcd arm.

W02006003379 discloses a similar tapping machine in which the hopper is supported by pawis on an annular ratchet surface. This allows the dispense head to rotate as a side effect of the tapping action so reducing the effect of powder climbing the sides of the hopper. These dispensers arc effective at dispensing precise amounts of powder.

There are, however, a number of disadvantages of this technique.

Problems with EP 1752744 and W02006003379 include: II is difficult to remove the powder from the dispenser tiller a dispensing action, without powder spilling from the vessel.

There is a tendency to spill powder through tile mesh when the head is first filled before bridges form, Attempting to load a pre-fihled dispense head is liable to disrupt the bridges and also cause spillage.

The maximum frequency of tapping, and hence maximum rate of dispense for any mesh size, is limited by the resonance of the dispense head support system (flexures), the resonance of the plunger/solenoid, and the power density and consequent heating of the solenoid. A square law effect applies so thai doubling the fiequency of tapping requires doubling of tapper speed which results in 4 times tile energy being imparted at each tap.

The vibrations generated from the tapping mechanism often interfere with the balance used to weigh the dispensed powder. Tapping also creates airborne energy that can cause the balance pan or mechanism to ring or resonate even though this resonance is not necessarily the same as the tapping repeat frequency.

The head space above the dispensing mesh must remain open to atmosphere, since enclosing the powder hopper may result in a pressure drop as powder is dispensed that could inhibit further dispensing.

Multiple dispense heads are typically supplied with a dispenser, each with a different mesh. Meshes with a range of different sized apertures are required depending upon the type of powder to be dispensed. For example, a fine free flowing powder requires a small aperture size, whereas a light cohesive powder needs a larger aperture size.

Furthermore, to cater for ranges of dispensed amounts within a reasonable dispense time (e.g. less than about 15 seconds), there must be alternative mesh areas, i.e. different number of apertures, available for a given aperture size.

The number of apertures in the mesh, as well as the size and shape of the individual apertures in the mesh, affects the amount of powder which will be dispensed with each tap. Where a large amount of powder is to be dispensed, it is usually necessary to use a mesh with a Large number of apertures in order that the powder can be dispensed in period of time deemed acceptable to the operator, however, because more powder is dispensed per tap, the weight of powder dispensed cannot be controlled with as great an accuracy.

The appropriate mesh needs to be selected by the operator before a dispensing action, depending on the type and quantity of powder to be dispensed. This complicates the use of the device for an operator.

The dispense bead must be moved away from the receptacle at the end of a dispense operation to ensure that the final weight can be correctly recorded. Tins horizontal movement can cause unwanted spillage and adds to the time taken to perform the overall dispense operation as well as additional mechanics to provide this movement.

The present invention aims to provide a low cost dispensing device which ameliorates some or all of the above mentioned problems.

The invention provides a method for dispensing a particulate product comprising: placing the powder in a vessel having an outlet, and agitating the vessel so that a portion of the powder is dispensed through the outlct; dharacterised in that agitation is achieved by rotating the vessel about a pivot so that thc outlet rotates towards and away from a downward facing direction.

By employing the invention, the agitation required to temporarily break the bridges and allow a portion of the powder to pass through the outlet under gravity, can be achieved using a relatively small number of components, thus obviating the need to provide the complex actuating mechanisms used in the prior art.

Although the invention is described below with reference to dispensing powders, it will be understood that it may be equally suitable for dispensing other forms of particulate product such as granulated materials, beads and other finely divided solid materials.

In addition, the rotary mechanism of the invention generates less interference to the balance as compared with electro-magnetic or pneumatic tapping actuators. The masses of the dispensing vessel and its support can be distributed about the axis of rotation so that there is minimal if any imbalance, and hence far less vibration that may be transmitted to and interfere with the balance. This allows powder to be dispensed more quickly as less down-lime is required between dispensing actions to ensure the balance reading has stabilised. The rotaiy mechanism is also much quieter and so there is less airborne energy that might cause acoustic disturbance to the balance or a nuisance to staff in a laboratory environment.

Rotation of the vessel may be perfomed by an electric motor, optionally having a feed back system. This allows the movement of the vessel to be controlled more precisely than the prior art lapping mechanisms. This provides a number of advantages which will become apparent.

The accelerations, displacement and hence frequency of the motion that this motor can impart to the vessel can be higher than any of the prior art forms and hence provide a wider range of dispense rates from a given vessel. This single actuator provides a convenient way of employing various modes of dispensing that can be selected or combined as required.

It is preferable that the outlet comprises a plurality of closely spaced openings, for example the outlet may comprise an orifice plate, with a pattern of apertures. The size of the openings is chosen depending on the nature of the powder used and therefore there maybe a number of different orifice plates defining different sized openings for use with different powders types. The number of apertures and their layout may also be varied for a given aperture size to increase or decrease the amount of powder dispensed per actuation. Alternatives to an orifice plate include a mesh or other shaped component comprising orifices.

S

In order to prevent unwanted spillage of the powder during rotation of the vessel, particularly when the vessel is rotated through large angles, it is preferable that the nature of the rotation (e.g. at least one of: the angle through which the vessel rotates, the speed of rotation and angular aecelerationIde-aeceleration) is controllable. The nature of the rotation may also be varied depending upon the type of powder being dispensed in order to maximise the dispensing rate and reduce the propensity for the powder to compress or clog the outlet.

The dispenser will generally be required to dispense a powder into a receptacle placed below the vessel. It is therefore favourable that the powder is only dispensed when the vessel is in a dispensing position, i.e. when the outlet is facing downwardly over the receptacle so that all dispensed powder falls into the receptacle.

To inhibit or prevent the spilling of powder when the vessel is being rotated away from a dispense position, the vessel may be accelerated at a rate and to a rotational specd sufficient to maintain the powder bridges and prevent the powder from spilling through the outlet There are a number of modes of rotation which may be employed to dispense the powder contained within the vessel.

The vessel can be caused to rapidly decelerate when substantially at or towards a dispensing position. The deceleration rate is sufficient to cause movement of the powder relative to the vessel, so that the powder bridges temporarily break allowing a small portion of powder to fall through the outlet under gravityc The vessel may be caused to rotate and episodically stop with the outlet in a downward facing direction. The vessel may also be caused to episodically stop with the outlet in a non-downward facing direction, preferably an upward Thcing direction, between downward ftcing stops. This allows the powder to be safely contained within the vessel without spillage, for example whilst a balance forming part of the dispensing system records the weight of the dispensed powder.

Rotating from a downward facing dispensing orientation to a non-downward orientation can be used 10 de-compact the powder, and/or allow air back into the vessel to overcome any drop in pressure that has occurred during dispensing, and/or to unblock the outlet. Therefore rotation to an upward position may be caused to occur periodically, e.g. after a to and fro rotation between Iwo downward directions (see below). This obviates the need for the dispenser 10 incorporate a stirrer which could damage ihe powder and/or produce particulates that may contaminate it.

Initial experimentation indicates that it is preferable that deceleration from a downward dispensing orientation into a non-downward orientation should not, depending on the powder used, be greater than 5 rps2 (revolutions per second per second) and preferably equal or less than 2 rps2 in order to prevent powder from being unintentionally ejected flani the upward facing oullet.

The vessel may be initially mounted and held by the dispensing apparatus in an upright orientation. This ensures that no powder is spilt before the dispensing operation. The vessel can then be rotated into a downward dispensing position once dispensing operation commences.

Rotation of the vessel may be in single direction, or where the vessel is caused to rotate between alternate orientational positions, the vessel maybe caused to rotate back and forth. Controlled rotation of the vessel back and forth rapidly between two dowiiward orientation positions separated by a small angular displacement, with the outlet remaining directly above the inlet of the receptacle, is able to provide high powder dispense rates.

The rate of dispensing increases with the frequency of to and fro movements, and the angular acceleration and deceleration. Generally, the smaller the angular displacement the better, since a smaller displacement permits a higher frequency, and therefore a higher rate of dispense for a given acceleration. Nevertheless, there will be a lower limit which is governed by the displacement required to ensure the powder has sufficient inertia to move relative to the vessel and break the bridges during the acceleration or deceleration movement.

When more accurate dispensing is required, the magnitude of the acceleration andior deceleration of the rotational movements may be decreased so as to decrease the rate of dispensing. Additionally or alternatively, the size of the rotation angle may be increased, or a pause of the vessel at at least one dispensing position may be introduced so that there is more time to react to feedback from the balance, or other sensing device, to control the total weight or volume dispensed.

Where very precise dispensing is required, the vessel may be caused to rotate into a non-downward orientation between each dispensing action. This provides time to allow powder dispensed from the vessel in each dispensing action, to fall into the collector and its weight to be registered by the balance. Rotation of the vessel through a large angle to the dispensing orientation may result in a relatively large amount of powder being dispensed per action, it may therefore be preferable to minimise the rotational angle provided that the vessel is rotated to the dispensing oricirtation from a non-upward orientation where the outlet is not directly above the inlet of the receptacle.

These above methods can be used in conjunction effectively where it is required to measure out an amount of powder accurately and quickly.

For example, for a light cohesive powder, the vessel can be rotated between a downward orientation and a non-downward orientation to provide a series of discrete dispense actions to measure out a bulk of the required powder quickly, then as the target amount is approached, rapid rotation back and forth between two downward orientations can be used as described above, during which the dispensed weight can be accurately monitored to ensure that the target weight is not exceeded, and the dispense rate may be controlled, e.g. by varying the acceleration rate.

For a free-flowing powder, rapid rotation back and forth between two downward orientations can be used to dispense the majority of the powder, during which the dispensed weight can be accurately monitored to ensure that the target weight is not exceeded, and the dispense rate may be controlled, e.g. by varying the acceleration rate. As the final dispense weight is approached, the vessel can be rotated away from a dispensing orientation to an orientation in which the outlet is not directly above the inlet of the receptacle for the purpose of confirming the dispensed amount, allowing the vessel to then either rotate to an upward orientation if the dispense has completed or be returned to a downward dispensing orientation if further dispensing is required.

Other combinations of these modes may be employed.

in general the dispense rate may be ramped up at the beginning of the dispensing operation, and1or, as the target amount is approached the dispense rate may be slowed, until the target amount is dose enough to use the second method. -9-.

By varying the rotation it is possible to provide a wider range of dispensing rates with a single outlet size/aperture pattern than compared with pilot tapping methods. This reduccs the need for as many different aperture patterns and sizes as required in the prior art. Additionally a small outlet can be used to dispense a relatively large volume of powder in a given time without the loss in accuracy that would occur if using a larger outlet, e.g. in the form of an orifice plate with larger apertures.

Once the required quan of powder has been dispensed, the vessel may be rotated to an up-ward facing orientation, preferably a substantially upright position, without spilling further powder. This allows the vessel to be safely removed from the dispenser without the risk of further powder falling into the vessel, and advantageously removes the need to provide a separate moving mechanism as required in the prior ait The vessel containing any remaining powder can be then stored until that powder is needed to be dispensed again. To seal the vessel during storage, a capping system may be provided. The top of the vessel may be threaded or suitably formed so as to allow a removable cap to be applied over the outlet, and optionally over the orifice plate or mesh, preventing the powder from exposure to the environment.

Prior to removing the vessel from the dispenser, the vessel may be rotationally oscillated through a small angle a number of times with the outlet remaining in an up-ward facing orientation during the oscillation (in a similar manner to when in the downward dispense mode), to cause any powder that has passed through the apertures but not left the vessel, (e.g. held within the guide nozzle) to pass back inside so removing risk of spillage or exposure of powder when stored.

The invention was originally conceived to provide an improved laboratory dispenser to measure out relatively small amounts of powder in the order at most of a few lOs of grams, but usually less than 1g. Nevertheless, it is envisaged that the invention may be applied to larger scale dispensem (e.g measuring in the order of Kilo's). It may be also used in automated processes, which for example may include the use of autoloaders to load and unload vesseLs and receptacles from dispcns lag apparatus. -to-

The invention may be used for weighing particulate products for any purpose, examples include measuring of medicinal powders, e.g. into capsules or caplets, for the manufacture of tablets, or for use in inhalers. Non-medicinal uses include measuring powders used as/in food, paints, and ehemica.l reactants.

The invention may also be expressed in terms of apparatus, and thus according to the invention there is also provided apparatus for dispensing a powder comprising a vessel to hold a powder to be dispensed, means to agitated the vessel so that portion of the powder held therein is dispensed through an outlet of the vessel, characterised in means to rotate the vessel about a pivot so titan an outlet of the vessel is rotated towards and away from a position in which the outlet faces downwardly.

To minimise spillage it is preferred that the vessel, holding the powder, is introduced and mounted to the means to agitate the vessel such that the outlet is orientated upwardly. The means to agitate the vessel can then rotate the vessel towards a dispensing orientation once it is desired to dispense the powder. Preferably the vessel is secured to the means to agitate the vessel by a simple mechanical fitting, such as a push fit as this simplifies and quickens operation for the user.

The vessel, which in a preferred embodiment is a vial, may comprise a fitting which defines the outlet and may also define a guide means e.g. a nozzle. In one example the fitting acts to hold an orifice plate or mesh. In another example the orifice plate is an integral part of the fitting. The fitting which may take the form of a cap may be secured to the vessel, e.g. through a push or screw fit so that it can be easily mounted and removed from the vessel.

So that powder can continue to be stored in the vessel once removed from the dispensing apparatus, means may be provided to seal the outlet so that the powder does not spoil or becomes contaminated.

A number of advantages of the invention may instead be provided by agitating the vessel with a linear actuator in a precisely controlled manner. As such, according to a second aspect of the invention them is provided a powder dispenser comprising a vessel to hold a powder and means to agitate the vessel so that a portion of the powder is dispensed through the outlet, the means to agitate the vessel comprising an electric motor and a control unit programmable to control and vary the output of the electric motor so as to control the profllc of the agitation.

For example, the vessel may be mounted to a rig which is driven repeatedly back and forth in a linear motion between two positions by the electric motor. The control unit is used to control the rotational direction, speed, acceleration and deceleration of the motor output in order to control the profile of the agitation. Use of the electric motor, particularly when used with a fiedback system, allows very precise control of the movement profile of the vessel between the two positions. Additionally the profile may be changed during a dispensing operation in order to vary the rate at which powder is dispensed fitnn the vesseLThe invention will now be described by way of example with reference to the following figures in which: Figure 1 is a schematic illustration of a simple powder dispenser; Figure 2 is a perspective view of a powder dispenser arranged to dispense powder held within a vial; Figure us an exploded perspective close-up of the bead assembly of the dispenser of Figure 2; Figure 4 is a perspective view of the head assembly sbown in cross section; FigureS is a perspective close up illustrating an alternative nozzle assembly having a rotary orifice plate selector; and Figure 6 is a schematic cross section of a variant powder dispenser, adapted with a powder feeder.

Figure 1 illustrates schematically a dispenser comprising a cylindrical vessel 1 which S is closed other than for an outlet 2 formed in a side wall of the vessel 1. The vessel 1 is mounted at an end lace IA of the vessel ito a shaft 3. Within the vessel 1 there is placed a powder 4 to be dispensed.

The outlet 2 comprises one or more apertures each large enough to allow the powder to pass through, but sufficiently small that the powder 4 readily bridges over the aperture(s) when the powder 4 or vessel 1 is not agitated.

Todispcnsethcpowdcr4,thcveelliscausedtorotatconthcshaft3aboutaxisx between one or more dispensing orientations in which the outlet faces a downward direction, usually directly above a receptacle to collect and bold the dispensed powder.

There are various modes of rotation which can be employed to dispense the powder.

A basic mode the vessel is caused to rotate through a sufficient angle and at an angular velocity slow enough to allow the powder to till away front and towards the outlet under the influence of gravity. Generally howeveç the angular acceleration or deceleration is employed to create a differential motion of the powder relative to the vessel in order to temporarily break the powder bridges and allow powder to Ml through the outlet In an example of this latter mode the vessel is continuously ntaS in a single direction, the vessel being rapidly decelerated towards a downward pointing -I] -dispensing orientation so that a portion of powder is released into the collecting receptacle.

The deceleration is chosen to be sufficient to cause the powder to move relative to the vessel, temporarily breaking the powder bridge over the outlet to cause a small portion of the powder to fall through the outlet(s) under gravity. When the vessel is accelerated away from the dispensing orientation, the rate is chosen to be insufficient to cause a similar breakdown but sufficient that centrifugal forces hold the bridges in place as the vessel rotates away from the dispense position.

When in an upward orientation, the powder is safely contained within the vessel and cannot spill out. The vessel may be caused to decelerate into an upwards orientation so that the powder is caused to fall away from an area proximate to the outlet under gravity. This can be used to dc-compact the powder and/or unblock the outlet.

Initial experimentation by the invcntors has indicated that where deceleration towards an upright orientation is employed, the rate of deceleration should preferably be controlled as excessive deceleration can cause powder to be ejected from the outlet.

Spillage of this type can be reduced or prevented by using decelerating rates of about S rn (revolutions per second per second) or less, depending upon the powder used, but no spillage appears to occur when the vessel is decelerated at a rate of about 2 rps or less.

Rather than employing a continuous rotation, the vessel may be brought to rest at one or more downward dispensing orientations or upward orientations.

The vessel may be caused to change direction between rest orientations. For example the vessel may be rotated back and forth between an upright orientation and a downward dispensing orientation. -14-

Rotating the vessel through large angles provides lower powder dispense rates, as & large portion of the operating time is spent rotating the vessel towards and away from a dispensing orientation during which no powder is being dispensed from thc outlet As such the rotation angle may be increased when it is wished to slow the rate that powder is dispensed.

When a fast dispense rate is required the vessel can be repeatedly rotated back and forth between two downward orientations separated by a small angular displacement Both orientations arc selected to be directly both above the collector to ensure the powder dispensed is not spilt.

In an example of this later method the vessel is caused to hunt between two downward orientations displaced from the vertical by 0.7 degrees such that the rotation angle is 1.4 degrees.

The vessel starts at rest at a first orientation, accelerates at a known rate towards a true vertical orientation, decelerates from the vertical orientation towards a second orientation; accelerates at a known rate from the second orientation towards the vertical and decelerates from vertical back to the first orientation.

Depending on the angular span and acceleration it may be useful to introduce a constant angular velocity portion of each motion, after acceleration to the defined speed and before deceleration to a halt.

Increasing the frequency of the rotation movements is found to increase the rate at which powder is dispensed. This can be achieved by increasing the acceleration rate away from the first and second orientations.

The dispense rate has also been found to increase when the rate of deceleration is less than the acceleration rate, initial experimentation has indicated that a deceleration rate which is about 25% of the acceleration rate provides the greatest dispense rate for any given acceleration.

-Is -The above methods can be used in conjunction to allow a relatively large amount of powder to be dispensed accurately. For example, in a possible dispensing operation, the dispenser starting in an upright position, is rotated into a downward orientation over a collector. The bulk of the powder is dispensed using the fast dispense rate method by rapidly rotating the vessel back and forth between two downward orientations separated by a small angular displacement and high accelerations/decelera.tions. Once the target weight of powder is approached, the frequency of the rotation is slowed down (which may be achieved by slowing the acceleration/deceleration rate from each downward position). When the target weight is close (e.g. the difference between the target weight and the dispensed weight is a few times larger than the expect amount dispensed in a single dispense action) the vessel may optionally be caused to rotate between a downward dispensing orientation and an orientation in which the outlet is not directly over the collector and if necessary waiting in the latter position to check the dispensed weight in case the target weight has been reached. The latter mode ensures sufficient time is provided for the dispensed powder from each action to fall and be registered by the balance before more powder is dispensed whilst preventing any powder that may be spilt from falling into the collector and being registered by the balance. Once the target weight is achieved the vessel can be rotated to an upward pointing orientation.

Control of the rotation of the vessel to provide the above operations can be provided by an electronic control system which is arranged to receive signals fiom a balance sensing the weight of dispensed powder, and in response to the received signals to control an actuator e.g. an electric motor, used to rotate the vessel.

To provide an effective means to dc-compact powder and/or, unblock the outlet, the vessel may be caused to rotate rapidly between multiple upward orientational positions (between which the vessel maintains an upward orientation). This niay be perfoirned periodically during a dispensing operation, and/or may be also performed as a precursor before a dispensing operation, and/or following a dispensing operation.

Alternatively or in addition, a control system can trigger these dc-compaction or de- -16-clogging movements automatically during a dispensing operation by detecting a reduced rate of dispensing.

The size of the one or more apertures each need to be large enough to allow the powder to pass through, but sufficiently small that the powder 4 readily bridges over the aperture(s) when the powder 4 or vessel I is not agitated. The tendency for the powder to bridge varies depending upon the powder type. Powders which are fine and free flowing such as Avicel® 102, generally need smaller apertures, whereas powders which are likely to conglomerate such as lactose monohydrate, require larger apertures.

The rotation speed and acceleration of the vessel may also be tailored to the type of powder being dispensed in order to maximisc dispensing rates or reduce spillage. For example a fine free flowing powder may require a faster acceleration rate from a dispensing position to ensure no powder is spilled. Powders which tend to conglomerate may require a lower overall rotation rate to prevent or amehorate the extent of compaction. These parameters may be selected by the user or left as defaults when setting up a dispensing operation. Alternatively, a control unit associated with the dispenser may be programmed to adjust the parameters from one dispense to another or duing a dispense operation by analysing feedback signal from the balance or other measuring device.

Provided that the mass of the rotated components are reasonably balanced about the axis of rotation to avoid vibrations of the components or interfere with the balance, the shape of the vessel is not of great importance so long as it will allow powder to freely reach the outlet. To ensure this occurs, the part of a vessel nearest the oufict, may be provided with a taper, in addition the vessel may be provided with a nozzle to guide powder into the collector.

Figure 2 illusflates a laboratory dispenser system using the rotary mechanism to dispense powder. -I?-

The dispenser apparatus 100 comprises a head assembly 10! to dispense a powder into a receptacc 102 which sits on a balance 103 having a user interface 104 associated also with control unit 120. The head assembly 101 and receptacle 102 sit within a draft shield 105 shown with the front wall and a side wall removed.

The head assembly 101 is arranged to be rotated by a drive unit 106A, typically a servomechanism including an electric motor, which sits within a drive housing 106 outside the draft shield 105. Power from the drive unit is transferred through a cantilcvcred arm 107, onto which the head assembly 101 is supported. The arm 107 extends through a slot IOSA in the draft shield 105.

The drive housing 106, drive unit, arm 107 and head assemble 101 are adjustably mounted upon a pillar 108 so that the distance between the head assembly 101 and the balance 103 can be varied. The pillar 108 and balance 103 are supported onto a base plate 109 having levelling feet 109A, of which only two are shown, and an integrated spirit level 1093.

The apparatus 100 further comprises a control unit 120 connected to the balance 103 the user interface 104 and the drive unit bOA.

As illustrated in Fig 3, the head assembly 101 shown in an upright orientation comprises a holding clamp 111 arranged to be supported to the free end of arm 107.

The holding clamp Ill comprises a resiliently flexible portion ill A curved to fonn an annulus 111 C. A nozzle member 1 12 functions to retain the vial 113 and to direct powder dispensed from the vial 113 though a nozzic portion I l2A so that it can be more reliably poured into receptacle 102 (shown in figure 2).

As can be seen in Fig4 the inner surface of the nozzle member 112 defines a ciivwntbrentiat step 1128, and a circumferential recess 112C into which is heLd an 0-ring 114. Interposed and held between the step 112B and the 0-ring 114 is aplate 115 defining a pattern of holes upon which powder 117 in the vial 113 can bridge across and 611 through. The nozzle member 112 kther comprises a second circumferential recess 11 2D housing a second 0-ring 116 which protmdes out of the recess I 12D into the main cavity of the nozzle member 112.

To assemble, the vial 113 holding a powder ill is held with its opening 113A upwards so that assembly can take place without risk of spillage of powder. The vial 113 and nozzle member 112 arc brought together so that the nozzle member 112 is mounted over the opening 1 13A of the vial 113. Insertion of the vial 113 into the nozzle member 112 causes compression of the 0-ring 116 which retains the vial 113 by an interfrrence fit.

The vial 113 and nozzle member 112 are then lowered through annulus L1IC. The diameter of an outer wall portion ll2E of nozzle member 112 being slightly larger than the inner diameter of the ring ii IC, causes the resiliently flexible portion LI IA toflexandtosecurethenonlentemberll2 andvial 113 totheholdingclamp lii by an interference fit.

Thepowder 117 within thevial 113 is thenreadyto be dispensedoutthrougb the nozzle member 112 by rotating the head assembly 101.

Rotation of the bead assembly 101 is controlled by the control unit 120. The control unit 120 is provided, through user interlace 104, with a target weight of powder to be dispensct The control unit 120 then operates the drive unit 106A so that ihc vial 113 is rotated using one or more of the methods described above until the target amount has been sensed by the balance 103. Once the target weight has been sensed, the control unit 120 causes the vial 11310 be rotated and held in an upright position unit the vial 113 is removed from the apparatus 100. -19-

The control unit 120 may be provided with functionality to detect that the powder within the vessel 113 has compacted or blocked the outlet, and can cause the vessel 113 to rotate to an upward orientation in order to uncompact the powder/unblock the outlet 115.

The control unit 120 may be provided with further information such as the powder type 117 and/or characteristics of the orifice plate 115, e.g. size of apertures, number of apertures. This can bc used to estimate an expected dispensing rate or dispensing weight for each dispensing action. Alternatively, the control unit 120 may be programmed to record the rate powder 117 is dispensed during a dispensing operation and to use that as the expected rate.

The control unit 120 is programmed to compare the expected rate with the actual rate dispensed as determined from measurements from balance 103. If the actual amount is found to fall below the expected rate, the control unit 120 can operate the drive unit to: optionally increase the frequency of acceleration deceleration movements, and should that fail to increase the dispense rate, cause the vial 113 to be rotated to an upright position to dc-compact the powder 117 without risk of spillage. Once the powder 117 is dc-compacted, dispensing can then continue.

It is expected that the above apparatus 100 will include a number of nozzle members 112 housing plates 115 with different sized apertures. The nozzle member 112 with the plate 115 appropriate to the powder type 117 is selected by the operator before use.

As shown in Figure 4 the nozzle member 112 may be provide with a capping member 1 l2F to seal the outlet 1120 of the nozzle member 112 when not in use. This allows the no1e member 112 and vial 113 to be removed and stored away from the apparatus 100 containing unused powder 117.

In an alternative embodiment, the orifice plate 115 may be integrally formed as a cap with a thread which engages with a corresponding thread on the outer sutface of the vial 113.

A thrther alternative illustrated in Figure 5 comprises a nozzle member 212 supporting a vial 213. The nozzle member 213 defines a slot 212A which extends in a lateral direction partially through the nozzle member 212. Partially housed within the slot 212A is a rotor 218 housing three plates 215. Each plate 215 defines a pattern of apertures 215A of a different number and or size of apertures. The rotor 218 is mounted to the nozzle member 212 about a pivot 219 so that the rotor 218 can be turned relative to thc nozzle member 212 to bring any one of the plates 215 in line with the outlet of the vial 213.

Additionally, the plate 215 may be positioned so as to only expose a portion of the pattern 21 SA so that, this allows the effective area of the plate 215 to be adjusted.

Referring now to Figure 6 there is shown in cross section dispensing apparatus similar to that of Figure 1 provided with means to feed powder into the vesseE during a dispensing operation. The vessel 301 is provided with an inlet 305 foined in an end wall 301B preferably opposing end wall 301A. A conduit 306 provides a communication means for the flow of powder from a reservoir not shown, to the vessel 301 through inlet 305. The conduit 306 and vessel 301 are preferably arranged to allow the vessel to rotate about axis X relative to the conduit. A seal 307 may be provided to ensure powder 304 in the vessel 301 does not escape through inlet 305.

The inner surface 308 of the vessel 301 is shaped to retain powder withm the vessel 301 as it rotates and to guide powder 304 towards the outlet(s) 302A, 3028. When shown in cross section through a plane parallel and passing through axis X the inner surface 308 defines a conical surface about axis X. -21 -The vessel 301 of Figure 6 is optionally provided with a further outlet 302B, though it maybe possible for the vessel 301 to have 2,3,401 more outlets spaced at different positions about the vessel's surface 30 IC. For example the vessel may have two outlets spaced 90 or 180 degrees apart or 3 outlets each spaced by 90 degrees. The vessel may be rotated to cause powder to fall through each outlet in turn.

Each outlet may comprise different apertures patterns and/or apertures of different sizes. The required outlet and may be selected depending upon the dispensing operations. Alternatively multiple outlets may be used in a single dispense operation, e.g. using a larger or greater number of apertures for a faster dispense rate before swapping to an outlet with smaller or fewer aperwres to ensure accurate weighing to the target amount The spatial orientation of the outlets relative to each other is preferably chosen so that the vessel 301 can be rotated into an orientation in which no outlet is in a dispensing position, otherwise it may be necessary to provide means to temporariLy close off one or more of the outlets when loading the vessel 301 to prevent spillage.

Vessels having multiple outlets may be used without powder feeding apparatus.

Although it is expected that the dispensed powder xviii be weighed, it is possible that other methods may be used to measure the dispensed powder such as measuring volume or recording the height of the dispensed powder.

in a variation to the above examples. the rotational actuating mechanism may be used to tip a vessel to dispense powder over an edge of the outlet in the maimer similar to a vibratory feeder. The vessel (which may lake a form similar to a scoop or tray) is rotated about a pivot to move the edge from the upward pointing orientation downwards until powder flows and can agitate (rotate back and forth) gradually steepening the mean orientation to maintain flow. This may be particularly suitable for free flowing powders where large volumes are to be dispensed aecurat&y.

-22 -The frequency and acecicration of movement can be more accurately controlled compared with existing vibratory feeders and automatically adjwtcd to dispense to a targct weight. Additionally thc vcsscl can be rotated away from the dispense orientation to avoid spillage, permit dc-compaction, and facilitate refilling.