This invention relates to metering valves particularly, but not exclusively to such valves intended for metering viscous, or viscoelastic materials such as pastes, doughs, rubbers and plastics. Such valves may be used for delivering charges of plastics material for moulding, or foodstuffs such as bread dough for making loaves or rolls, and may be adapted to deliver charges of controlled volume and well-defined shape.

Problems are experienced in the design of valves to deliver charges with sufficiently precisely controlled volume and which are nevertheless of inexpensive and easily maintained construction and which are simple to operate.

The present invention provides valves that meet these requirements.

The invention comprises a metering valve comprising a valve body having a metering cavity, a material inlet to said metering cavity and an outlet for metered material, and comprising an operating member reciprocable relative to the valve body comprising a plug closure for said outlet and having a material delivery action by which the contents of the metering cavity are delivered from the outlet, the outlet having a reduced cross section as compared to the metering cavity and the operating member being extendable out of the metering cavity away from the reduced cross section outlet to open the outlet to deliver the contents of the metering cavity.

The closure may have a trimming action in which it oscillates relatively to

the outlet.

The closure may have such a fit in the outlet that a film of material to be metered can occupy the gap between closure and outlet and act as lubrication.

The operating member may close off connection between the material inlet and the metering cavity with its material delivering action. The material inlet may open into a wall of the metering cavity along which a part of the operating member slides to cover and uncover the inlet.

The closure may be displaceable relative to the outlet, without opening the outlet, over an initial distance in which the connection between the inlet and the metering cavity remains open, such displacement causing flow of material from the cavity back into the inlet before the connection is closed off. The valve may have an adjustment for said initial distance.

The metering cavity may be cylindrical and the outlet cylindrical with a smaller cross-section and the outlet and plug closure may be so constructed and arranged that they can constitute a flush end face of the valve. The metering cavity may be circular cylindrical and the outlet circular cylindrical and coaxial with the metering cavity. The outlet, however, may be rectangular and the closure and the outlet have cooperating straight edges.

The valve may comprise multiple metering cavities and operating members, all operated together.

The valve may comprise actuating means effecting relative reciprocation of the valve body and the operating member.

The valve may be used in combination with a delivery surface and so constructed and arranged that the delivery action leaves the operating member and its closure substantially stationary above said surface and retracts the valve body away from said surface.

The material inlet in the valve body may connect with a material feed duct in the operating member when the operating member is in a position relative to the valve body in which the material can be fed into the cavity, the operating member feed duct being adapted for connection to a supply of material.

Embodiments of metering valves according to the invention will now be described with reference to the accompanying drawings, in which :

Figure 1 is an axial section through one embodiment,

Figure 2 is a section on the line II-II of Figure 1,

Figure 3 is a section like Figure 1 of a detail showing the valve in a first, cavity charging position,

Figure 4 is a section like Figure 3 showing the valve in a second position in an operating cycle.

Figure 5 is section like Figure 3 showing the valve in a third, material delivering position,

Figure 6 is a section like Figure 3, showing the valve in a trimming mode,

Figure 7 is a section like Figure 3, showing the valve in a purge condition,

Figure 8 is a section like Figure 1 of another embodiment,.

Figure 9 is a section on the line IX-IX of Figure 8,

Figure 10 is a section like Figure 1 of yet another embodiment,

Figure 11 is a section on the line XI-XI of Figure 10,

Figure 12 is a section on the line XII-XII of Figure 11,

Figure 13 is a section like Figure 2 of a further embodiment,

Figure 14 is a section on the line XTV-XIV of Figure 13,

Figure 15 is a section like Figure 13 showing the valve in closed, material charging position,

Figure 16 is a section like Figure 15, showing the valve in delivery mode, and

Figure 17 is a section like Figure 15 showing the valve in trimming mode.

The drawings illustrate metering valves 11 comprising a valve body 12 having a metering cavity 13, a material inlet 14 and an outlet 15 for metered material, and comprising an operating member 16 reciprocable (in the direction of double arrow "A" in the axial sections) relative to the valve body 12. The operating member 16 comprises a plug closure 17 for said outlet 15 and has a material delivery action by which the contents of the metering cavity 13 are delivered from the outlet 15. The outlet 15 has a reduced cross-section as compared to the metering cavity 13 and the operating member 16 is extendable out of the metering cavity 13 away from the reduced cross section outlet 15 to open the outlet to deliver the contents of the metering cavity 13.

The metering valve illustrated in the drawings is suitable for metering precisely defined or controlled quantities of fluid material which is viscous or viscoelastic such, for example, as paste or dough material such as bread or biscuit dough and rubber and plastics materials dispensed for moulding or the like. In addition to delivering or dispensing a precisely metered volume of material it is often required that the material be delivered or dispensed in a predetermined shape, and the metering valves as illustrated in the drawings are designed to dispense a variety of shapes and different designs could be developed for other shapes as required.

For such materials, the closure 17 has a trimming action in which it oscillates relatively to the outlet 15, and the closure 17 has such a fit in the outlet 15 that a film of material to be metered can occupy the gap between closure 17 and outlet 15 and act as lubrication.

Figures 3 to 6 illustrate various important stages in an operating cycle of the valve shown in Figures 1 and 2 which, from these two Figures, will be seen to be of circular cylindrical construction. The valve body 12 has a circular cylindrical inner wall portion 18 connected by a conical portion 19 to the outlet 15 which has a circular cylindrical face 21. The operating member 16 has a first circular cylindrical face 22 which is a sliding fit in the wall portion 18 joined by a conical portion 23 to a reduced diameter cylindrical section 24 which joined by a conical section 25 to a cylindrical section 26 which slides - with lubrication clearance as noted above - in the face 21 of the outlet 15. A typical clearance between faces 21 and 26 is 0.05mm.

A typical diameter for the outlet 15 is 200mm, but of course much larger and much smaller sizes are possible.

The valve of Figures 1 and 2 will, of course, deliver an annular charge of material. The valve is shown in Figures 1 to 7 to have the plug closure 17 and outlet 15 so constructed and arranged that they can form a flush end face 27 of the valve as seen in Figure 1.

The end face 27 is located over a delivery surface 28 and it is arranged that the operating member 16 is held stationary above the surface 28 while the valve body 12 reciprocates under the control of a fluid pressure ram or an electric motor driven activator

29 shown diagrammatically in Figure 1.

Figure 3 shows the valve 11 in the first position of its operating cycle in which the plug closure 17 closes off the outlet 15 and material is admitted from the inlet 14 into the cavity 13 formed between the portions 18, 19, 23, 24 and 25. Because, in this embodiment, the operating member 16 is stationary it is convenient to arrange for material feed ducts 31 to be incorporated in the member 16 so that the inlets 14 - of which there are eight distributed around the annular metering cavity 13 - are fed from the ducts 31 which can be connected to a source of the material to be dispensed which is held under pressure.

Air present in the metering chamber 13 during filling will of course escape via the gap between the faces 21 and 26 and material will eventually seal the gap the width of which, typically, as noted, 0.05mm, is so selected in relation to the viscosity of the material to be metered that the pressure of the material in the metering cavity 13 is insufficient to force the material through the gap.

Once the metering cavity 13 is full, the delivery or dispense stage can begin with the valve body 12 being raised by the actuator 29 as seen in Figure 4. It will be noted that the raising of the valve body 12 before the face 21 has cleared the face 26 will effectively reduce the volume of the metering cavity 13 and if the cavity is full of relatively incompressible material this will lead to high forces. In fact, material can escape against the feed pressure back into the inlets 14 and ducts 31. As the face 21 clears the face 26, however, the inlet 14 is closed off from the cavity 13 so that no further material can enter the cavity 13. Continued upward displacement of the valve body 12

to the position shown in Figure 5 ejects the material in an annulus from the cavity 13 on to the surface 28.

A viscous, viscoelastic or tacky material will, however, not necessarily separate cleanly from the valve 11. The closure 17 however, now has a trimming action in which the valve body 12 is lowered and oscillated with the surface 21 passing repeatedly over the surface 26 to trim off the material with a shearing action.

The initial position of the operating member 16 relative to the valve body 12 can be pre-set using the actuator 29 to suit the physical properties - viscosity, elasticity - of the material to be metered. If the cavity 13 is filled with the valve body 12 at its upper trim position - T2, Figure 6 - the volume of material to be pushed back into the inlets 14 and ducts 13 is reduced as compared to when the valve body 12 starts off from a lower position.

This "upper trim" position at fill may be inappropriate for low-viscosity materials, of course, which could leak under pressure through the gap between surfaces 21 and 26.

The amount of material that is dispensed will of course depend upon the extent to which the valve body 12 is raised relative to the operating member 16. Figure 5 shows the maximum elevation of valve body 12 giving maximum material delivery - the actuator 29 can be controlled, as by a microprocessor, suitably programmed, perhaps to give any volume of dispense up to the maximum by adjusting the stroke of the valve body 12.

A control arrangement such as a microprocessor may also be adapted to control other aspects of the metering operation. For example in some cases it may be found advantageous to control the feed pressure, and in particular to relax that pressure during the delivery stage of the metering cycle.

Figure 7 illustrates a "purge" position of the valve 11 in which the valve body 12 is lowered slightly relative to the operating member 17 so that the inlet 14 is open to the metering cavity 13 - and the duct 31 is open to the inlet 14 - while the outlet 16 is open. The valve 11 may then be flushed through to clear it of material. This purge position could also be utilised within the metering cycle to allow some escape of material after filling the cavity 13 to avoid a build up of pressure as the cavity volumes is initially reduced on the upward stroke of the valve body 12.

The valve 11 illustrated in Figures 1 to 7 is thus a positive displacement metering valve which can be adapted and controlled to give precise - and adjustable, if required - metering and dispensing of viscous, viscoelastic and tacky materials, Where a valve is dedicated, of course, to dealing with one type of material and adjustable delivery is not required, the construction and control arrangement can be simplified.

Figures 8 and 9 illustrate a valve like that of Figures 1 to 7, but adapted to dispense pellets instead of an annular shape. The valve body 12 is identical to that of the valve 11 of Figures 1 to 7, while the operating member 16 is divided into eight compartments 61 by webs 62.

Figures 10 to 12 show a valve 11 which delivers a strip of material, the

valve body 12 having a rectangular cross-section in plan view (Figure 11) with a rectangular through way 17 accommodating the operating member 16. This design can be modified to produce a line of pellets instead of a strip in similar fashion to the modification to the design of the embodiment of Figures 1 to 7 which is illustrated in Figures 8 and 9, namely by dividing the elongate metering cavity 13 up into compartments.

Figures 13 to 17 illustrate a further embodiment of metering valve according to the invention which is not, however, a positive displacement metering valve but which depends on the material feed pressure to effect delivery of the material.

The valve, which is illustrated generally in Figures 13 and 14, has its valve body 12 stationary and having a plurality - four in this case, but only one being shown - of operating members 16 gauged for simultaneous operation by being secured in a plate 121 which is raised and lowered by the actuator 29 shown diagrammatically.

The metering cavities 13 are fed from ducts 122 in the valve body 12 supplied from a central feed duct. The operating member 16 can be a simple circular cylindrical plunger which is seen in Figure 13 closing off the outlet 15 which has a reduced cross section as compared to the metering cavity 13.

Figure 16 shows the operating member 16 withdrawn into the metering cavity 13 in the delivery or dispensing position in which material flows out from the outlet 15 under the feed pressure at a rate determined by that pressure, the characteristics of the material and the extent to which the operating member 16 is raised up from the

outlet 15. Delivery is terminated by the plunger plugging the outlet 15 again and trimming is effected by oscillation of the operating member 16 in the outlet 15 as seen in Figure 17, the positions Tl and T2 indicating lower and upper trim positions.

In this design it is important, with a multiple valve arrangement, to have the ducts 122 the same length and cross section if all the individual valves 11 in the assembly are to deliver the like quantities - this is not so important in the system described with reference to Figures 1 to 12, where the positive displacement action ensures regular delivery despite irregularities in the feed channels.

All the embodiments described, however, can be readily constructed and arranged for precise and convenient delivery or dispensing of viscous, viscoelastic and tacky substances as well as less viscous substances and can be readily configured for dedicated operation or as multi-purpose metering valves.