WO1990010198A1

WO1990010198A1 - Metering device and method of metering a flowable material

Info

Publication number: WO1990010198A1
Application number: PCT/GB1990/000288
Authority: WO
Inventors: Laurence Richard Penn; Steven Roger Anderson
Original assignee: Liquid Control International Company
Priority date: 1989-02-24
Filing date: 1990-02-23
Publication date: 1990-09-07
Also published as: JPH04503708A; EP0460046A1; GB8904305D0; AU5166190A

Abstract

A metering device for metering a flowable material comprises a housing having at least one inlet and at least one outlet for the material to be metered, means associated with the housing and defining at least one bore, the or each bore containing a sealing element substantially sealing the bore and movable axially of the bore. The device incorporates means which are movable between positions in which the respective ends of the bore are initially in communication with an inlet and an outlet and are subsequently in communication with an outlet and an inlet respectively.

Description

METERING DEVICE AND METHOD OF METERING A FLOWABLE MATERIAL

THE PRESENT INVENTION relates to a metering device and more particularly relates to a metering device adapted to met er and dispense a fluid such as a liquid, or in the form of a powder, pellets or other flowable powdery or particulate material. It is envisaged that embodiments of the invention may be utilised to meter materials of any type, provided that they can flow.

One primary field of application of the present invention, however, is the field of metering liquids. There are very many industrial processes which involve the dispensing and metering of liquids. For example, liquids have to be metered and dispensed in connection with the packaging of many products, ranging from pharmaceuticals to fizzy drinks, and from tomato ketchup to paint. Also liquids have to be dispensed and metered when creating high performance two component chemical adhesive syste Industry constantly seeks greater accuracy of metering, with reliability and simplicity. It is to be understood that in many cases the dispensing and metering of liquids is critical. For example, a metering error in creating a two- component adhesive used in the mass production of encapsulated components may cause thousands of manufactured components to be sub-standard. Also an undetected fault in the metering of a high performance adhesive may cause the failure of a product in the field, with disasterous results.

In many industries, metering is carried out with a rotary or reciprocating rod or piston pump. Rotary pumps have inherent slip, and are not suitable for use with liquids exhibiting abrasive qualities. Also such pumps have certain limitations as to the viscosity of the material that they can dispense, and the flow rate at which material can be dispensed, through cavitation problems, and such pumps are more applicable to continuous flow. Certain reciprocating pumps have a true "positive displacement" characteristic and may be used with materials within a wide viscosity range. However, cavitation may still give rise to difficulties, particularly with regard to flow rates.

It is to be appreciated that with reciprocating pumps, there is generally a relatively lengthy pause at the end of each stroke to enable the reciprocating pump to be reloaded, or to change over between reciprocating pumps which operate in tandem. It is also to be appreciated that through a "squeeze" effect, changes can occur to metered output when the output pressures are changed, due to the fact that the materials dispensed are mainly non-hydraulic liquids.

Both reciprocating and rotary metering pumps normally function as primary transfer pumps and also function as metering pumps. Wear may effect the metering accuracy or cause a failure to function. Both such faults may go undetected.

Metering of very small amounts, such as small fractions of a cubic centimetre, is usually achieved on a time/pressure basis because the miniaturisation of metering rod or piston pumps becomes impracticable. The liquid can move too little to allow the function of a check valve and the unit becomes progressively more sensitive, with reducing size, to particle or lump sizes, air bubbles and air bubble compression. For example, a bubble can alter or totally equal the volume to be dispensed.

Most reciprocating metering pumps have some form of inlet and outlet valving of either mechanical or pressure differential type. The efficiency of pressure differential valves tend to vary with changes in back pressure. Pressure differential valve seats are liable to clog and in particular inlet valves are the most sensitive to remaining clogged since, unlike outlet valves, they usually operate with low pressure differentials and low velocities. Mechanical valving is more effective with regards to efficiency of the valve seating but the likely constant time of the valve operation in relation to the cycle rate changes can effect metering efficiency. Often, metering pumps and their controlling mechanisms are sufficiently large that they have top be located at a position which is remote from the actual point of dispensing of the material being metered. Thus it is quite common to make a liquid flow several metres through a hose after the metering point to a production line dispensing point. Such arrangements give rise to problems with the metering, in that the materials are usually non-hydraulic causing compression and then decompression. Some hoses can expand and may entrap air which thus often leads to a very inaccurate metering condition at the hose end. Counter measures are usually necessary, such as pumping up the hoses to pressurise them and maintaining tight hydraulic conditions. Thus hose end shut-off valving may be used with resultant complications. It is then necessary to synchronise the meter pump and the shut-off valve. The present invention seeks to provide a metering device which can be utilised with a wide range of fluids or liquids to be dispensed, and which may be made to be relatively small in size (when compared with prior metering pumps), and which may thus be suitable to be located close to the point of dispensing. The invention also seeks to provide a metering device which does not have conventional valving, which has very low wear, and little if any effect of wear on metering accuracy, and which is fail-safe and which may be self-checking.

According to this invention there is provided a metering device for metering a flowable material, said device comprising a housing, defining at least one inlet for material to be metered and at least one outlet for that material, means associated with the housing and defining at least one bore, the or each bore containing a sealing element, substantially sealing the bore and movable axially of the bore, the device incorporating movable means which are movable between positions in which the respective ends of the bore are initially in communication with an inlet and outlet and are subsequently in communication with an outlet and inlet respectively.

Preferably said movable member is in the form of a rotatable member, or assembly, the or each bore being defined in or carried by the said rotatable member or assembly.

Conveniently the said bore comprises a bore extending substantially diametrically of said rotatable member. Advantageously the rotatable member has a conically tapering exterior form and the housing defines a bore of corresponding tapering shape which receives the rotatable member . Preferably said inlet and outlet are at diametrically opposed positions on said housing, the transverse bore in the rotatable member being off-set from the axis of the inlet and outlet, there being axially extending recesses providing communication between the inlet and outlet and the said bore.

Conveniently said axially extending recesses are formed in the rotatable member.

Preferably circumferentially extending recesses are provided associated with the opposed ends of the bore.

Advantageously said circumferentially extending recesses are formed in the rotatable member.

Alternatively the said bore extends substantially axially of said rotatable member or assembly. Alternatively the movable member is in the form of a member or assembly which is movable axially of the housing, the or each bore being defined in or carried by the said axially movable member or assembly. Preferably a plurality of axially extending bores are provided in the movable member.

Conveniently the housing defines at least one inlet port and at least one outlet port, the inlet and outlet ports extending radially relative to the axis of the movable member and being spaced apart relative to that axis.

Advantageously there are a plurality of inlet ports and plurality of outlet ports.

Preferably the ends of the or each axially extending bore are closed by means of threaded plugs.

Conveniently the or each axially extending bore receives, at each end, a stop element in the form of a sleeve mounted within the bore, the stop element having an internal diameter less than the diameter of said sealing element.

Alternatively the rotatable member comprises a member which defines said bore as a single axial bore, the bore being provided with radially opening apertures at each end, the housing defining inlet and outlet ports alignable with the said apertures. Alternatively again the or each bore is fixed in position and the movable means comprise movable valve elements, each valve element being in a three-port two-way valve . Preferably the or each said bore is provided, at each end thereof, with a stop which engages the sealing element to terminate movement thereof, the stop being adjustably positioned . Conveniently the stop is adjustably positioned by means of a screw-thread arrangement engaging the stop or engaging an element associated with the stop.

The metering device may be in combination with at least one proximity sensor, the proximity sensor being responsive to a sealing element reaching a terminal position within the or the respective bore.

Preferably the sealing element is in the form of a ball. Advantageously the sealing element is in the form of a diaphram.

The invention also relates to a method of metering a flowable material, said method comprising the steps of introducing the material through an inlet port of an apparatus as described above, moving the movable means until one end of the or a bore is in communication with the inlet port, causing the material to flow through the inlet port and into the bore, moving the sealing element to the end of the bore remote from the inlet, subsequently moving the movable means until the end of the bore at which the sealing element is located is in communication with the (or another) inlet and so that the other end of the bore is in communication with an outlet, and causing further material to flow into the bore through the (or said another) inlet, thus causing the sealing element to move to the end of the bore in communication with the outlet, thus discharging a substantially predetermined volume of material through the outlet.

The invention also relates to a material whenever metered by a method as described above. In order that the invention may be more readily understood, and so that further features thereof may be appreciated, the invention will now be described, by way of example, with reference to the accompanying drawings in which

FIGURE 1 is an exploded view of a housing and a rotor of a dispensing device in accordance with the invention,

FIGURE 2 is a cross-sectional view of the components of Figure 1 when assembled, FIGURE 3 is a perspective view of a rotor for use in an alternative embodiment of the invention,

FIGURE 4 is a cross-sectional view of the rotor of Figure 3 when located within a housing,

FIGURE 5 is an end elevational view of another embodiment of the invention, FIGURE 6 is a horizontal cross-sectional view of the embodiment shown in Figure 5.

FIGURE 7 is a cross-sectional view of another embodiment of the invention, and

FIGURE 8 is a cross-sectional view of yet another embodiment of the invention.

Referring initially to Figure 1 of the accompanying drawings a metering device in accordance with the invention comprises a fixed housing 1 and a rotor 2. The fixed housing 1 is of generally cylindrical form, and defines therethrough a bore 3 which is of tapering configuration. Provided on the exterior of the housing 1, at two diametrically opposed positions, are respective inlet and outlet spigots 4, only the inlet spigot being shown.

Inserted into the open end 5 of the bore 3 is the rotor 2, which comprises a generally cylindrical body 6 of slightly tapering form and a drive shaft 7 adapted to rotate the body 6. Formed in the body 6 is a diametrically extending bore 8 of uniform cross-section. At each end of the bore 8 there is an axially extending recess 9 formed in the outer surface of the rotor 2. The bore 8 receives a ball 10, as can be seen in Figure 2. The diameter of the ball 10 is slightly less than the diameter of the bore 8, so that the ball 10 is free to move along the bore 8.

The rotor 2 is so dimensioned that when the rotor is fully inserted into the housing 1 the rearward ends of the recesses 9 can be aligned with the inlet and outlet spigots 4.

The rotor 2 and the bore 3 each taper slightly, thus enabling an axial pressure applied by the drive shaft 7 to establish a seal.

In operation of the device, as described, the inlet spigot 4 is connected to a pressurised supply of a fluid to be dispensed. The rotor 2 is then rotated to such a position that the ends of the recesses 9 are aligned with the inlet and outlet spigots 4. It will be appreciated that with the rotor in this position fluid may flow through the inlet spigot 4, along the axially extending groove 9 formed on the exterior of the rotor 2 and into one end of the bore 8. The fluid will flow into the bore 8, pushing the ball 10 before it until the ball 10 reaches the other end of the transverse bore 8. The ball will then engage the side wall of the housing 1. No more fluid may then flow into the device.

If the rotor 2 is then rotated by 180°, the axial recess 9 associated with the end of the bore 8 at which the ball 10 is located will then be aligned with the inlet spigot 4. The recess 9 associated with the other end of the bore 8 will be aligned with the outlet spigot 4.

The fluid that is present in the bore 8 at the beginning of the rotation will, of course, rotate with the rotor and will still be present in the bore at the end of the rotation step. Fluid from the inlet spigot 4 may thus flow along the recess 9 aligned with the inlet spigot 4 and into the transverse bore 8 formed in the rotor 2. The l iquid will push the ball before it , and thus the ball will effectively push the charge of fluid that remained present within the transverse bore 8 through the recess 9 at the other end of the bore 8 and to the outlet spigot and thus this material will be dispensed through the outlet spigot. The ball 10 will travel along the bore 8 until it reaches the other end of the bore 8. It will then again engage the side wall of the housing 1, and then no more fluid will flow through the device. This cycle of operation may be repeated, with the rotor, together with a charge of material to be dispensed contained within the axial bore 8 extending across the rotor, being successively rotated, and on each rotation of the rotor a further charge of material will be dispensed through the outlet spigot.

It is to be appreciated that, as a consequence of the described design, the ball 10 cannot leave the bore 8. At the end of each cycle of operation the ball 10 engages the side wall of the bore 3 in the housing 1. The ball cannot escape from the bore 8. If the transverse bore 8 were actually aligned with the inlet spigot 4 and the outlet spigot, the ball might, if dimensions permitted it, pass through the spigot and escape from the bore 8. It is for this reason that the recesses 9 are provided.

Whilst the expedient of the axially extending recesses 9 has been provided to ensure that the ball 10 is retained within the transverse bore 8, it is to be appreciated that other expedients may be adopted such as, for example, making the bore passing through the inlet spigot 4 and the outlet spigot of a lesser diameter than the diameter of the transverse bore 8. It will be appreciated that material will be dispensed in successive "shots" each "shot" of material having a volume substantially equal to the difference between the volume of the transverse bore 8 extending across the rotor 2 and the volume of the ball 10. It has thus been found that on each rotation of the rotor a volume of material is dispensed, the volume dispensed on each occasion being substantially constant.

An embodiment of the invention as described may readily be fabricated to be of almost any size, and thus the volume metered by such a device may be from fractions of a cubic centimetre to tens or hundreds of litres.

It is to be appreciated that in operating the arrangement described in Figures 1 and 2, the device will operate in a very cyclical manner, with material being dispensed only when the transverse bore 8 is aligned with the axially extending recesses 9. Figures 3 and 4 illustrate a modified embodiment of the invention in which the parts which are the same as illustrated in Figures 1 and 2 carry the same reference numerals. It can be seen immediately that the ends of the transverse bore 8 formed in the rotor 2 is associated with recesses 11 formed in the outer surface of the rotor 2, the recesses 11 extending circumferentially, in contrast to the axially extending recesses of the first embodiment.

Stops 12 are provided located within the transverse bore 8 formed within the rotor 2, one stop 12 being located adjacent each end of the bore 8. Each stop is formed by a ring, the outer periphery of which is provided with threading, which engages threading provided at the open ends of the transverse bore 8. The rings each have a central aperture which is of a smaller diameter than the diameter of the ball 10.

The rings may be selectively adjusted, thus adjusting the quantity of material dispensed at each "shot". The rings may also define seats which sealingly engage the ball. This may be desirable if the ball is to make a fluid-tight seal when engaging the ring. This may be of benefit when dispensing fluids which have a low viscosity, or which have "penetrating" properties.

It is to be appreciated that the material to be metered will flow whenever any part of the recesses 11 formed in the rotor 2 are aligned with the inlet and outlet spigots 4 formed on the housing 1. Thus, as the rotor is rotated, there is a brief period during each 1δ0° rotation when there is no recess 11 aligned with the spigots 4, and during that period of time there is no flow of material being metered. However, as soon as any part of the recesses 11 are aligned with the spigots 4 the flow of material commences. The rate of rotation of the rotor can be selected, with regard to the viscosity and pressure of the fluid supplied to the inlet spigot, so that, during the period that the recesses 11 are aligned with the spigots 4 the ball will traverse the bore 8 formed in the rotor 2, so that the rotor can rotate at a uniform rate, whilst still dispensing material in the general manner as described above. The material will then be dispensed in discrete "shots" which follow each other in relatively rapid succession.

In the embodiments described with reference to Figures 1 to 5 the rotor 2 is of conically tapering form and is inserted into a conically tapering bore 3. An adequate seal between the rotor 2. and the bore 3 can be achieved merely by the application of an axially pressure to the rotary shaft 7. However, the design is such that the components can readily be separated for cleaning purposes. The spigots 4 are shown in Figure 4 as being internally threaded. However, the spigots may equally be externally threaded.

The components may be made of any desired size. For example, although the rotor 2 is shown as being larger than the drive shaft 7 , the rotor 2 could have the same diameter as the drive shaft 7. Thus the rotor 2 may have a diameter as small as, for example, 5 millimeters, which is approximately the diameter of a conventional pencil, or less. A device of this size would, of course, only meter very small quantities of material, but the material would be metered accurately. Alternatively the rotor may be very large, and the rotor may then dispense large quantities of material .

It is to be appreciated that if the diameter of the ball 10 is larger than the diameter of the bore through the inlet spigot 4 and the corresponding outlet spigot, the bore 8 may be aligned with the inlet and outlet spigots. If the housing 1 is then located with the inlet spigot vertically above the outlet spigot, it will be appreciated that the metering device may be utilised to meter a powdery or granular material which will flow, either under its own weight, or under the assistance of a pneumatic air-flow, through the device. Such granular material may be, for example, dehydrated soup, coffee, tea, washing powder or even materials such as breakfast cereals. It will be appreciated that all these materials have to be dispensed accurately during the packaging stage, and a metering arrangement in accordance with the invention may be used for such purposes. In such an embodiment the device may not have any recesses such as the recesses 9 or 11 in the rotor 2. Whilst the invention has been described with reference to embodiments in which a ball is provided in the transverse bore, the ball may be replaced by a slidable diaphragm or the like. The diaphragm should ideally form a seal against the wall of the transverse bore, but the nature of the seal actually required does depend on the nature of the material to be metered and dispensed.

The ball 10 need not have a diameter which is exactly the same as the diameter of the bore 8. There may be a certain amount of space between the ball 10 and the walls of the bore 8 without reducing the efficiency of the metering device to an unacceptable level, particularly if the material to be metered is thick or viscous.

It will be appreciated that the described embodiments of the invention may, however, be of particular value in metering low to very high viscosity liquids, especially where the metering device is to be situated close to the point of dispensing of the liquid. The described arrangements are unaffected by particles or lumps which may tend to clog prior art arrangements since the fluid is never caused to flow through a constriction, such as the constriction between a conventional valve and valve seat. Any lump will be able to flow through the inlet spigot and through the recess 9 or 11 into. the transverse bore 8. The lump is not caused to flow past the ball 10, but instead is retained within the bore 8 while the rotor 2 rotates. The lump is then discharged through the bore 8 and the corresponding recess 9 or 11 associated with the outlet. The apparatus described is not really subject to much wear, and there is little effect of wear on the accuracy of metering. The device has a high volumetric efficiency and accuracy. The device can be operated under a pressurised regime, and under such a regime the liquid to be dispensed may be substantially hydraulic, thus providing significant accuracy. The apparatus is capable of metering single shots, which may be very large, or which may be very small, at inlet pressures from zero up to several bar. The apparatus may dispense single shots or multiple shots. The apparatus may also provide substantially continuous flow, especially if the apparatus of Figures 3 and 4 is utilised.

It is to be appreciated that if two or more metering devices are utilised, which are either mechanically or electrically interconnected to provide desired relative metering, the devices may be utilised in proportioning chemical streams in multicomponent reactive systems such as epoxy resins. The apparatus as described may be fabricated from steel or other metal, plastic or ceramic materials, depending upon the nature of the fluid to be dispensed.

Figure 5 and 6 illustrate another embodiment of the invention. In this embodiment of the invention a housing 21 is provided which has an axial bore therethrough which receives a rotor 22. The housing 21 has a first inlet port 23 and a first outlet port 24, which are co-aligned and spaced axially of the housing. At a position diametrically opposed to the outlet port 24 there is a second inlet port 25 and at a position diametrically opposed to the inlet port 23 there is a second outlet port 26. The inlet and outlet ports are axially spaced along the housing. As can be seen more clearly from Figure 6 the rotor 22 is provided with a drive shaft 27 and is provided with a plurality of axially extending bores 28,29 which are adjacent the outer periphery of the rotor. The axially extending bores thus resemble the bores provided in a conventional revolver. Each bore is sealed, at each end, by means of a plug 30. Each plug has a screw-threaded exterior which engages with a screw threading provided at the end of the respective bore, and each plug is provided with a hexagonal recess 31 to receive a wrench to enable the plug to be inserted into position.

Within each end of each bore is provided a sleeve 32 formed of an appropriate material. The length of the sleeve may be selected, as required. The sleeve is provided with a side aperture 33 which is aligned with a corresponding side aperture 34 formed in the rotor 22. When the rotor 22 has been rotated to an appropriate indexed position the apertures 33 and 34 are aligned with an inlet or outlet spigot, 23 or 24. Provided in each bore 28, between the opposed inner facing ends of the sleeves 32 is a ball 35, the diameter of the ball being slightly less than the diameter of the bore 28. The ball can sealingly engage the ends of the sleeves 32.

It can be seen, from a consideration of Figure 6, that when the rotor 22 has been indexed to the position illustrated, the bore 28 shown to the right of Figure 6 will receive material through the inlet spigot 23, thus forcing the ball 35 to the position 35' illustrated in dotted lines, and it will be understood that when the metering device has been appropriately primed, this action will cause a shot of material of predetermined volume already located in the bore 28 to be dispensed through the outlet spigot 24. Simultaneously, the bore 29, provided to the left of Figure 6, will receive material through the inlet spigot 25, moving the ball 35 to the position 35 as shown in dotted lines, simultaneously ejecting a shot of material through the outlet spigot 26. When this process has been completed, the rotor may be indexed by 180°, and the process will then repeat. It is to be appreciated, however, that the rotor 22 is provided with three pairs of opposed bores, and thus the rotor will, at any instant, only be indexed by 60°. Of course further inlet and outlet ports may be provided at 60° off-set positions, thus providing a metering device with a very large through-put.

It is to be appreciated that this embodiment -of the invention readily lends itself to the provision of a proximity sensor 36 adapted to sense when the ball 35 has reached its terminal position 35'. If proximity sensors, such as the proximity sensor 36, are provided adjacent each outlet port, a control arrangement for the device may be provided which is such that the rotor 22 can only be indexed after all proximity sensors have sensed that the respective balls have reached their terminal positions.

Figure 7 illustrates another embodiment of the invention in which a housing 40 is a two-part housing which define two inlet spigots 41,42 and two outlet spigots 43,44.

Each inlet spigot 41,42 is aligned with a corresponding outlet spigot 43,44.

A rotatable shaft 45 is provided, which has opposed tapering ends 46,47. The part of the housing defining the inlet spigot 41 and the outlet spigot 43 is mounted on the tapered end 46 of the shaft 45, whereas that part of the housing defining inlet spigot 42 and the outlet spigot 44 is mounted on the other tapered end 47 of the shaft 45.

The shaft 45 is provided with an axial bore 48. The bore is formed by drilling in through the end 46 of the shaft, that end of the shaft subsequently being sealed by means of a screw-threaded plug 47. The bore 48 extends axially of the shaft 45 and is provided, adjacent each end, with a port 49,50 opening radially from the shaft. The port 49 is aligned with the inlet spigot 41 and outlet spigot 43, whereas the port 50 is aligned with the inlet spigot 42 and the outlet spigot 44. The portion of the bore 48 between the ports 49 and 50 is provided with two stop rings 51,52 which are located adjacent the ends of the bore. Each stop ring is in the form of a ring having a threaded exterior, the threading on the exterior of the ring engaging threading provided on the inner surface of the bore 48.

A ball 53, having a diameter slightly less than the diameter of the bore 48 is trapped between the stop rings. The ball 53 may sealingly engage the stop rings, which act as valve seats.

Two sensors 54,55 are illustrated associated with the housing 40. If the shaft is initially positioned as illustrated in Figure 7 fluid may flow, through the inlet spigot 41 and the port 49 which is aligned therewith, into the bore 48, thus forcing the ball 53 towards the right as shown in Figure 7. When the ball 53 reaches the stop ring 52, the ball will be sensed by the sensor 54.

If the shaft is then rotated through 180° the port 50 will be aligned with the inlet spigot 42. Fluid supplied through the inlet spigot 42 will then force the ball 53 to the left, as shown in Figure 7, simul taneously discharging through the port 49, which is then aligned with the outlet spigot 43, the material previously introduced to the bore 48. When the ball 53 has moved to the left it touches the stop ring 51 and the presence of the ball is sensed by the sensor 55. The shaft 45 may then again rotate through 180°, and then fluid will again be introduced through the inlet spigot 41 and the associated port 49, whilst fluid is discharged through the port 50 which is aligned with the outlet spigot 44. It is to be appreciated that in an embodiment of the invention as illustrated in Figure 7, circumferentially extending grooves, corresponding to the grooves 11 illustrated in Figure 3, may be provided on the exterior of the shaft 45 associated with the port 49 and associated with the port 50. Figure 8 illustrates another embodiment of the invention, in which the housing 60 comprises a tubular member 61 defining a bore 62 which is associated with two valve housings 63,64 provided at each end thereof. Each valve housing defines an inlet port 65,66 and an outlet port 67,68. Each valve housing contains a valve member 69,70 movable by means of a respective operating shaft 71. The valve members 69,70 are adapted to move in synchronism between two operative positions, one of which is illustrated in Figure 8. It can be seen, in Figure 8, that the valve member 69 serves to connect the inlet port 65 in the valve housing 63 with one end of the bore 62, whereas the other valve member 70 serves to connect the other end of the bore 62 to the outlet 68 in the valve housing 64. When the valve members are in their other operative position, the valve member 69 serves to connect said one end of the bore 62 to the outlet port 67 of the valve housing 63, whereas the other valve member 70 serves to connect the other end of the bore 62 to the inlet port 66 of the valve housing 64.

Contained within the bore 62 defined within the tube 61 is a ball 72 having a diameter which is slightly less than the internal diameter of the bore 62 defined by the tube 61, and adjacent the ends of the bore 62, stop rings 73,74 are provided. Each stop ring comprises a ring having a threaded exterior surface, that threaded exterior surface engaging corresponding threading provided on the interior of the tube 61. The aperture defined by each ring 73,74 is less than the diameter of the ball 72. Each stop ring thus comprises a valve seat that can sealingly engage the ball.

Proximity sensors 75,76 are provided in order to sense when the ball 72 has reached terminal positions in contact with the rings 73,74. It will be appreciated that when this embodiment of the invention is utilised, if fluid is supplied when the device is in the condition illustrated in Figure 8, the fluid will pass through the inlet port 65, through the valve member 69, into the left-hand end of the bore 62, and will drive the ball 72 towards the right until it touches the stop ring 74. The position of the ball will then be sensed by the sensor 76. The positions of the valve member 69 and 70 will then be reversed, and fluid will then enter the inlet port 66 in the valve housing 64, passing through the valve member 70 and into the right-hand end of the bore 62. The ball 72 will thus move to the right and a predetermined quantity of fluid will be discharged through the outlet port 67 of the valve housing 63. When the ball 72 engages the stop ring 73 the ball will be sensed by the sensor 75. The position of the valve members will again be reversed and the cycle of operation will be repeated.

It is to be understood that in the embodiments described which have sensors to sense the position of the ball, signals from the sensors can be utilised to control the operation of the described device and if a sensor does not sense a ball in a correct position at the end of a cycle of operation, operation of the described device can be terminated. In such a case, the device is self-checking, and the device stops operating if the device is not functioning correctly. Whilst the sensors have only been specifically described with reference to the embodiments illustrated in Figures 5 to 8 of the accompanying drawings it is to be appreciated that sensors may be incorporated in the emnbodiments illustrated in Figures 1 to 4, although the sensors will need to be incorporated in the rotor and, of course, appropriate slip rings, commutators or trailing wire systems will be needed to transfer signals from the sensors to appropriate machinery and devices adapted to control the described devices.

By way of example, a metering device in accordance with any of the embodiments described above may operate under the following conditions: liquid will be pumped at a pressure of between, say, 13 bar and 345 bar from a transfer pump into one of the metering devices. The liquid is then metered by the device which 'fires' pre-squeezed small shots of, say, 1cc per revolution. The device is operated so as to create a measured flow of liquid (for example 1 litre per minute) and/or to meter a predetermined total volume of liquid. It will be appreciated that as the speed of operation increases the small metered shots become indiscernible within what eventually becomes a stream flow.

Whilst the invention has been described with reference to embodiments in which a fixed housing is provided defining at least one inlet and at least one outlet, the housing containing a rotor which has a transverse bore containing a sealing member movable along the bore, it is to be appreciated that in alternative embodiments of the invention a fixed housing may be provided which receives a linearly or axially movable element which defines an appropriately configured bore, containing a sealing element movable axially of the bore.

Claims

1. A metering device for metering a flowable material, said device comprising a housing, defining at least one inlet for material to be metered and at least one outlet for that material, means associated with the housing and defining at least one bore, the or each bore containing a sealing element, substantially sealing the bore and movable axially of the bore, the device incorporating movable means which are movable between positions in which the respective ends of the bore are initially in communication with an inlet and outlet and are subsequently in communication with an outlet and inlet respectively.

2. A metering device according to Claim 1 wherein said movable means is in the form of a rotatable member or assembly, the or each bore being defined in or carried by the said rotatable member or assembly.

3. A metering device according to Claim 2 wherein the said bore comprises a bore extending substantially diametrically of said rotatable member.

4. A metering device according to Claim 3 wherein the rotatable member has a conically tapering exterior form and the housing defines a bore of corresponding tapering shape which receives the rotatable member.

5. A metering device according to Claim 3 or Claim 4 wherein the said inlet and outlet are at diametrically opposed positions on said housing, the transverse bore in the rotatable member being off-set from the axis of the inlet and outlet, there being axially extending recesses providing communication between the inlet and outlet and the said bore.

6. A metering arrangement according to Claim 5 wherein said axially extending recesses are formed in the rotatable member.

7. A metering device according to Claim 3 or Claim 4 wherein circumferentially extending recesses are provided associated with the opposed ends of the bore.

8. A metering device according to Claim 7 wherein said circumferentially extending recesses are formed in the rotatable member.

9. A metering device according to Claim 2 wherein the said bore extends substantially axially of a said rotatable member or assembly.

10. A metering device according to Claim 1 wherein the movable means is in the form of a member or assembly which is movable axially of the housing, the or each bore being defined in or carried by the said axially movable member or assembly.

11. A metering device according to Claim 9 or 10 wherein a plurality of axially extending bores are provided in the movable member.

12. A dispensing device according to Claim 9 or 10 or 11 wherein the housing defines at least one inlet port and at least one outlet port, the inlet and outlet ports extending radially relative to the axis of the movable member and being spaced apart relative to that axis.

13. A dispensing device according to any one of Claims 9 to 12 wherein there are a plurality of inlet ports and plurality of outlet ports.

14. A metering device according to any one of Claims 9 to

13 wherein the ends of the or each axially extending bore are closed by means of threaded plugs.

15- A metering device according to any one of Claims 9 to

14 wherein the or each axially extending bore receives, at each end, a stop element in the form of a sleeve mounted within the bore, the stop element having an internal diameter less than the diameter of said sealing element.

16. A metering device according to Claim 2 wherein the rotatable member comprises a member which defines said bore as a single axial bore, the bore being provided with radially opening apertures at each end, the housing defining inlet and outlet ports alignable with the said apertures.

17. A metering device according to Claim 1 wherein the or each bore is fixed in position and the movable means comprise movable valve elements, each valve element being in _a three-port two-way valve.

18. A metering device according to any one of the preceding Claims wherein the or each said bore is provided, at each end thereof, with a stop which engages the sealing element to terminate movement thereof, the stop being adjustably positioned.

19- A metering device according to Claim 18 wherein the stop is adjustably positioned by means of a screw-thread arrangement engaging the stop or engaging an element associated with the stop.

20. A metering device according to any one of the preceding

Claims in combination with at least one proximity sensor, the proximity sensor being responsive to a sealing element reaching a terminal position within the or the respective bore .

21. A metering device according to any one of the preceding Claims wherein the sealing element is in the form of a ball.

22. A metering device according to any one of Claims 1 to 14 wherein the sealing element is in the form of a diaphram.

23. A metering device substantially as herein described with reference to and as shown in Figures 1 and 2 of the accompanying drawings.

24. A metering device substantially as herein described with reference to and as shown in Figures 3 and 4 of the accompanying drawings.

25. A metering device substantially as herein described with reference to and as shown in Figure 5 and 6 of the accompanying drawings.

26. A metering device substantially as herein described with reference to and as shown in Figure 7 of the accompanying drawings.

27. A metering device substantially as herein described with reference to and as shown in Figure 8 of the accompanying drawings.

28. A method of metering a flowable material, said method comprising the steps of introducing the material through an inlet port of an apparatus according to any one of Claims 1 to 27, moving the movable means until one end of the or a bore is in communication with the inlet port, causing the material to flow through the inlet port and into the bore, moving the sealing element to the end of the bore remote from the inlet, subsequently moving the movable means until the end of the bore at which the sealing element is located is in communication with the (or another) inlet and so that the other end of the bore is in communication with an outlet, and causing further material to flow into the bore through the (or said another) inlet, thus causing the sealing element to move to the end of the bore in communication with the outlet, thus discharging a substantially predetermined volume of material through the outlet.

29. A material whenever metered by a method in accordance with Claim 28.