GB2415949A

GB2415949A - Dispensing apparatus with variable flow rate

Info

Publication number: GB2415949A
Application number: GB0415252A
Authority: GB
Inventors: Laurence Richard Penn; Philip Kenneth Thompson
Original assignee: Failsafe Metering International Ltd
Current assignee: Failsafe Metering International Ltd
Priority date: 2004-07-07
Filing date: 2004-07-07
Publication date: 2006-01-11
Also published as: GB0415252D0

Abstract

A dispensing apparatus for dispensing e.g. an adhesive is provided with means to vary the flow rate of the adhesive from an outlet nozzle. An irregular bead 52 of adhesive may therefore be formed as the dispenser is moved along a surface, the irregular bead comprising spots 53 with thin traces 54 in between. This form of bead has been found to give good sealing properties whilst using the minimum of adhesive. Alternatively, discrete unlinked spots of adhesive may be formed, or a wave-shaped bead (figures 8 and 9, not shown). The dispenser may comprise a moveable shuttle configured to supply two components of the adhesive to a mixer, which is connected prior to the outlet.

Description

241 5949 PATENTS ACT 1977 Pi 8719GB - NHF/ns

DESCRIPTION OF INVENTION

"IMPROVEMENTS IN OR RELATING TO A DISPENSING APPARATUS" THE PRESENT INVENTION relates to a dispensing apparatus and more particularly relates to a dispensing apparatus to dispense a single component liquid or liquid formed from two separate components.

Various types of apparatus have been proposed before to dispense a liquid formed from one component or from two separate components. A typical example is where a two component adhesive or a two component sealant is to be dispensed. It has been proposed, for example, to provide the two liquid components of the adhesive or sealant within a cartridge, and to connect a static mixer to the cartridge. Operation of a pair of pistons within the cartridge forces the two components through the static mixer where the components are mixed.

The components are preferably to be mixed to be substantially homogenous and, in many cases, are dispensed as a uniform cross-section bead.

In most cases it is critical that the components of the two component adhesive or sealant are mixed together in a precisely predetermined ratio, so that the sealant or adhesive will have the desired properties. In order to achieve this end it has been proposed to utilise metering devices to dispense each 1 1 component, the metering devices being operatively interconnected so that if one metering device should fail, the other metering device will stop so that no adhesive is dispensed which is incorrectly mixed.

A typical metering device proposed for use in this situation is a metering device of the type which includes a shuttle which is moveable within a chamber, the shuttle acting as a piston to seal the two ends of the chamber from each other. A valving arrangement is provided which, in one position, can supply liquid under pressure to one end of the chamber, whilst opening a flow path from the other end of the chamber to an appropriate outlet. Consequently the piston moves along the chamber pushing liquid located between the piston and the outlet out of the chamber forming a "shot" of liquid. When the piston completes it stroke, the position of the valve is changed so that the liquid supply is then connected to the end of the chamber adjacent the piston and the other end of the chamber is connected to the outlet. The piston then moves back along the chamber driving the liquid that was introduced during the first described stroke towards the outlet, thus forming another "shot" of liquid.

Each "shot" of liquid is of a precisely predetermined volume.

It has been proposed to utilise two devices of this type, with the valve of each device being actuated in response to a signal from the other device confirming that the other device has successfully completed a stroke and thus delivered a "shot" of liquid to its outlet. Thus the devices work in anti-phase delivering successive shots of respective liquids to the respective outlets of the devices.

The liquids are directed towards a mixer, the mixer receiving a "shot" of the first liquid followed by a "shot" of the second liquid. The liquids are mixed on passing through the mixer, and because the "shots" of liquid follow in succession, again a very uniform and homogenous mix may be achieved and a uniform bead may be produced. Any fluctuations in pressure may be absorbed by the slight amount of "give" that will exist in a practical apparatus, caused by slight resilience of the material forming any pipes or conduits through which the mixed liquids may flow and also due possibly to the presence of small amounts of air within the mixed liquids.

Thus, in past years attention has been given to making a uniform mix provided at a substantially uniform speed thus providing a uniform bead.

A uniform bead of this type may be ideal for use when securing two elements or components together. The bead must have a sufficient diameter that when the components are compressed together the bead will "spread" appropriatly to provide a sufficient area in contact with each of the components being adhered together that a bond of adequate strength is formed.

Of course, various devices have been proposed previously to dispense a single component fluid, such as an air or moisture cooling adhesive. Again, in the prior proposed apparatus, the primary requirement has been for an apparatus that will produce a substantially uniform bead.

The present invention seeks to provide an improved dispensing apparatus, and also relates to a method of producing a bead.

According to one aspect of this invention there is provided a dispensing apparatus for dispensing a liquid comprising at least one component, the apparatus comprising a dispensing arrangement to be connected to a source of the said at least one liquid and being connected to an outlet element having an exit port through which liquid is to be dispensed, the dispensing device being configured to supply the liquid to be dispensed to the outlet with a flow rate which fluctuates with time.

Preferably the apparatus is an apparatus for dispensing a mixture of two liquids, wherein the dispensing arrangement comprises two metering devices, each metering device being configured to provide a plurality of sequential "shots" of liquid, each metering device generating an output signal when a "shot" of liquid has been dispensed, the metering devices being connected to a controller, the controller controlling the metering devices so that the metering devices can only generate a succeeding "shot" when both of the metering devices have provided an output signal confirming production of the preceding "shot", the controller being configured to deliver the control signals simultaneously to the metering devices so that the metering devices produce the next "shot" simultaneously, the outputs of the metering devices being connected to a mixer comprising the outlet from which the mixed liquids are dispensed.

Preferably an outlet control valve is provided at the exit port of the outlet, the outlet control valve being controlled by the controller to control the flow rate.

Advantageously the outlet control valve is controlled to be open when "shots" are being produced by the metering devices, but to be substantially closed at other times.

Conveniently the metering device incorporates an elongate chamber, there being a shuttle contained within the chamber, the shuttle having a portion which is a substantially sealing sliding fit within the chamber, the shuttle being moveable axially between an initial position and a second position within the chamber, each end of the chamber being provided with a liquid flow duct through which pressured liquid may enter and leave the chamber, there being valve arrangement to control the flow of liquid to and from the chamber such that, during successive cycles of operation of the metering device, liquid is supplied to one end of the chamber causing the shuttle to move from the initial position at said one end of the chamber to the second position at the other end of the chamber, thus ejecting a pre-determined volume of liquid from the other end of the chamber, and subsequently liquid is supplied to said other end of the chamber causing the shuttle to move back from the second position to the initial position, ejecting a pre-determined quantity of liquid from the said one end of the chamber, the valving means comprising a rotary valve rod contained within a valve bore, and a mechanism to rotate the valve rod, the liquid flow ducts from the chamber extending to the valve bore, at least one liquid inlet extending to the valve bore and at least one liquid outlet extending from the valve bore, the valve rod, in combination with the valve bore, defining liquid flow passages which, in one orientation of the valve rod, serve to interconnect a liquid flow inlet and the liquid flow duct extending to one end of the chamber whilst interconnecting the liquid flow duct extending to the other end of the chamber with an outlet and, in an alternate orientation, serving to interconnect the liquid flow inlet with the liquid flow duct extending to the other end of the bore whilst connecting the liquid flow duct extending to the said one end of the bore with an outlet.

Advantageously the shuttle is provided with two rods, each rod extending beyond the chamber, there being a contact of proximity sensor located adjacent each rod to generate a signal when the shuttle reaches the initial position and the second position.

The invention also relates to a method of producing a bead from a liquid having at least one component, the method comprising the steps of supplying the liquid to an outlet at a flow rate which fluctuates with time, whilst moving the outlet relative a substrate, thus creating a nonuniform bead.

Preferably the bead is provided with a plurality of spaced apart "spots" of the said liquids.

Conveniently adjacent spots of liquid are interconnected by a relatively thin strand.

Advantageously the spots form part of wave-sectioned segments of bead which merge into one another.

Preferably the bead is a one component liquid in the form of a curable adhesive curing in response to oxygen or moisture or heat on light.

Conveniently the liquid is a two component liquid.

Preferably the method comprises the steps of metering the first liquid with a metering device that produces successive "shots" of liquid and metering the second liquid with a metering device which produces successive "shots" of liquid, mixing the "shots" of liquid ejected from the two metering devices to form a bead, wherein the metering devices are controlled so that the metering devices produce said "shots" simultaneously, thus causing an uneven flow of liquid from the metering devices to an outlet, thus producing the non-uniform bead.

The method may include the step of controlling the flow of liquid from an exit port with an outlet control valve.

The invention also relates to a bead produced by the 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 a partly cut-away view of one metering device for use in accordance with the invention; FIGURE 2 is a view of the rotary valve rod of the metering device of Figure l; FIGURE 3 is a diagrammatic sectional view illustrating one phase of operation of the device of Figures 1 and 2; FIGURE 4 is a view corresponding to Figure 3 illustrating another phase of operation of the device of Figures 1 and 2; FIGURE 5 is a diagrammatic view of a dispensing apparatus in accordance with the invention which incorporates two metering devices of the type shown in Figures 1 to 4; FIGURE 6 is a graphical figure illustrating controlling pulse signals and liquid flow rates; FIGURE 7 is a perspective view of a bead formed using an apparatus in accordance with the invention; FIGIURE 8 is a view of another bead formed using an apparatus in accordance with the invention; and FIGURE 9 is a view of a plurality of separate units of dispensed adhesive.

A metering device for use in one form of apparatus in accordance with the invention will initially be described with reference to Figures 1 to 4. The metering device incorporates a shuttle and, in operation, produces a plurality of discrete "shots" of liquid. In contrast to earlier arrangements where two metering devices of this general type have been used, in the described embodiment of the invention the "shots" from two metering devices are produced simultaneously thus providing, over a period of time, an uneven flow of dispensed liquid, leading to the creation of a bead of non-uniform cross section or even a plurality of separate "spots" of dispensed mixed liquid.

Referring initially to Figure 1 of the accompanying drawings, a metering device for use in an embodiment in accordance with the invention comprises a housing 1 which defines a cylindrical chamber 2. Contained within the chamber 2 is a shuttle 3. The shuttle 3 is a unit or assembly which has a central cylindrical portion 4 which is a sliding sealing fit with the chamber 2. The shuttle incorporates two rods 5,6 which extend axially from opposite sides of the cylindrical portion 4 and which pass, as a sliding sealing fit through apertures formed in the end walls of the chamber 2, the rods 5,6 thus projecting beyond the housing. Mounted on the projecting portions of the rods 5,6 are adjustable collars 7,8, the position of which may be adjusted to alter the "spoke" of the metering device as will become clear from the following description. Located adjacent the ends of the rods 5,6 are sensors 9,10 which are responsive to the rods 5,6 each reaching a pre-determined position. The sensors may, ideally, be responsive to physical contact of the end of the rod with the sensor.

The central cylindrical portion 4 of the shuttle effectively divides the chamber 2 into two separate parts, one at the left-hand end of the chamber and the other at the right-hand end of the chamber. Respective liquid flow ducts 11,12 connect these end parts of the chamber 2 to spaced-apart points of a cylindrical valve bore 13 defined within the housing 1. Outlet and inlet ducting also communicate with the bore 13. Thus the housing defines a first outlet flow duct 14 offset from the flow duct 11 and second outlet flow duct 15 offset from the flow duct 12. The outlet flow ducts 14 and 15 are off-set axially from the flow ducts 11 and 12, being closer to the ends of the valve bore 13, but are diametrically opposed to the flow ducts 11,12. A liquid inlet flow duct 16 is also defined located at a position between the two liquid flow ducts 11,12.

Contained within the cylindrical valve bore 13 is a rotary valve rod 17 which is driven rotationally by a stepping motor M in response to signals from the sensors 9, 10.

The rotary valve rod 17 has parts thereof cut away in the form of a channel or recess in the periphery of the rod and passages or bores through the rod so that the rotary valve rod 17, in the cylindrical valve bore 13, may define liquid flow paths. The rotary valve rod 17 is provided with a first through bore 18 which is inclined to the axis of the valve rod 17 and which, in one rotational position of the valve rod 17, when the valve rod 17 is present in the bore, serves to interconnect the liquid flow duct 11 and the first outlet flow duct 14. A second corresponding bore 19 is provided, parallel with the first bore 18, the second bore 19, as will be understood from Figure 2, in an alternate rotational position of the valve rod 17, serves to interconnect the liquid flow duct 12 and the second outlet flow duct 15. Between the two bores 18,19 there is an annular groove 20 formed in the exterior surface of the rotating valve rod 17 which is in alignment with the inlet flow duct 16. The groove 20 is provided with two diametrically opposed axial extensions 21,22, which extend in opposite axial directions. It is to be appreciated that in one rotational position of the rotary valve rod 17 the axial extension 21 will extend to the end of the flow duct 12 thus forming a flow path from the inlet 16 to the right-hand end of the chamber 2, and in an alternate position of the rotary valve rod 17 axial groove 22 will establish communication with the flow duct 11.

Looking now at Figure 3, the shuttle 3 is shown in a right-hand most position with the end of the projecting shuttle rod 6 engaging the sensor 10. As the shuttle rod 6 contacts the sensor 10, so the stepping motor M rotates the valve rod 17 by 180 , thus moving the valve rod 17 to the position as shown in Figure 4.

When the rotary valve rod 17 is in the orientation or the position as shown in Figure 4 the groove 20 and the axial extension 21 serve to connect the inlet 16 to the liquid flow duct 12 which communicates with the right-hand end of the chamber 2, whereas the bore 18 serves to interconnect the liquid flow duct 11 (which, in turn, communicates with the left-hand end of the chamber 2), and the outlet flow duct 14. Pressured liquid may thus flow from the inlet flow duct 16 through the annular groove 20 and the axial extension 21, through the liquid flow duct 12 into the right-hand end of the chamber 2 thus serving to move the shuttle 3 towards the left. As the shuttle 3 moves towards the left, so liquid in the right-hand end of the chamber is discharged through the liquid flow duct 11, and the bore 18 and through the outlet 14. The shuttle 3 thus continues to move towards the left until the shuttle rod 5 contacts sensor 9.

When the sensor 9 is contacted, the shuttle 3 has completed its stroke and a pre- determined quantity of liquid in the form of a metered "shot" of liquid has been ejected through the outlet flow duct 14.

In response to a signal generated by the sensor 9 when touched by the shuttle rod 5, the stepping motor M again rotates the valve rod 17 by 180 , thus returning the valve rod 17 to the position or orientation shown in Figure 3.

With the valve rod 17 in the position shown in Figure 3 liquid will flow from the inlet through the annular groove 20, the axial extension 22, and through the liquid flow duct 11 to the left-hand end of the chamber 2. The bore 19 in the valve rod 17 interconnects the liquid flow duct 12 and the outlet 15, allowing liquid from the right-hand end of the chamber to flow to the outlet 15. Thus the shuttle 3 will move towards the right until the shuttle rod 6 establishes contact with the sensor 10. As the shuttle makes the movement to the right a pre determined quantity of liquid, in the form of a metered "shot" of liquid, is ejected from the right-hand part of the chamber 6 through the outlet 15. When the shuttle rod 6 contacts the sensor 10 the motor M is actuated again. The cycle of operation may then repeat.

Since the stepping motor M only rotates the valve rod 17 on receipt of a signal from the sensor 9, or the sensor 10, if the shuttle 3 is not able to complete its stroke, for example due to a lack of liquid, or insufficient liquid pressure, no signal will be given and the metering unit will cease operation. In this way it can be ensured that for each cycle of operation the metering unit delivers an appropriate quantity of liquid, in the form of a correctly metered "shot", which can be of crucial importance if two liquids, which are components of, for example, a two-part adhesive or the like, are to be metered by two separate metering units and mixed in a precisely pre-determined ratio, relative to each other.

It is to be appreciated that the position of the collars 7,8 on rods 5,6 may be adjusted and the position of the sensors 9,10 may be adjusted to increase or decrease the stroke of the shuttle, thus increasing or decreasing the quantity of liquid ejected on each stroke of the shuttle.

As shown in Figures 3 and 4 the chamber 2 may be provided on either side of the cylindrical portion 4 of the shuttle 3, with air bleeds 23, 24. These may be opened to permit air to be discharged from the chamber 2, especially when the described metering device is first filled with the liquid to be metered, to ensure that hydraulic integrity can be established with no compressible air remaining in the chamber 2.

In the described embodiment, the valve is a rotary valve rod, which facilitates manufacture and maintenance of the valve. In use, the valve rod may rotate almost uniformly, avoiding sudden changes of momentum as maybe experienced with a reciprocating valve.

Of course, the metering device as described may be "reversed", with pressurised liquid being supplied to the 'outlets" 14,15, and with the "inlet" 16 actually acting as an outlet.

Whilst, in above description of the metering device, reference has been made to contact sensors 9, 10 responsive to contact with the shuttle rods, proximity sensors which respond to the shuttle rods reaching predetermined positions may be used. Also in another alternative embodiment the sensors 9,10 may be annular, with the rods 5 and 6 passing through the sensors, with the sensors 9,10 providing an output signal when contacted by the collars 7 and 8.

Turning now to Figure 5 a dispensing apparatus 30 is shown schematically. The apparatus, as illustrated, includes a source 31 of a first liquid under pressure and a source 32 of a second liquid under pressure. The two liquids may be the two components of, for example, a two component adhesive which have to be mixed together in precisely predetermined relative quantities if the adhesive is to is to have the desired skrength and stability.

The source of the first liquid 31 is connected to a metering device 33 of the type described above with reference to Figures 1 to 4. Similarly the source of the second liquid 32 is connected to an equivalent metering device 34. The metering device 33 has outlet 35 which extends to a mixer arrangement 36.

Similarly the second metering device 34 has an outlet 37 which extends to the mixer 36. The mixer 36 may be a rotary mixer or may be a mixer which incorporates, as in the illustrated embodiment, a static mixer 38 of the type disclosed in EP 0105181. The end of the static mixer may be provided with a controllable valve 39 to control the flow of liquid from the mixer, but this is an optional feature. The mixer is an outlet element having an exit port through which the mixed liquids are ejected to form a bead.

A controller 40 is provided. The controller 40 is connected to receive signals from each of the metering devices 33,34 to indicate when the shuttles of the two devices have reached the two respective end positions. Thus two leads 41,42 are shown extending from the metering device 33 to the controller 40 and similarly two leads 43,44 are shown extending from the metering device 34 to the controller 40. The two signals, from each metering device, indicative of the two terminal positions of the respective shuttle, are passed to the controller along the respective leads. The controller 40 is also connected, by means of a lead 45 to the motor associated with the first metering device 33 and a further lead 46 connected to the motor associated with the second metering device 34.

It is to be understood that, in operation of the device, liquid under pressure is supplied to each of the metering devices 33,34, and the motors of the metering devices are controlled by the controller 40 to advance the valves at appropriate times so that the shuttles within the metering devices will reciprocate, with each metering device thus delivering sequential "shots" of liquid to the respective outlets 35,37. The shots of liquid are mixed within the mixer 36,38 and flow towards the control valve 39.

As can be seen from Figure 6, the control signals issued by the controller 40 on the line 45, as indicated by the graphical representation 47 in Figure 6, and also the signals passed by the controller 40 on the line 46, as indicated by the graphical representation 48 in Figure 6, comprises a series of control "spikes" which are issued, by the controller at precisely the same instant, that is to say in synchronization. Thus, when the two metering devices 33,34 receive the control signals, the motor of each metering device is actuated and the valve is turned to cause the shuttle to move axially along the chamber simultaneously, thus dispensing two separate shots of liquid at the same instant.

As can be seen, again from Figure 6, the rate of liquid flow along the line 35, as indicated by graphical representation 49 and the rate of flow along connection line 37, as indicated by graphical representation 50, comprise sequential pulses of flow following each control signal from the controller. The controller will not generate a successive control signal until the controller has received a signal from each of the metering devices confirming that the shuttle of the metering device has fully completed its intended stroke. If the controller does not receive a signal from either one of the metering devices the entire operation of the dispensing unit is terminated.

The valve 39 provided at the mixer may also be controlled by the controller 40 and may be provided with a control signal as illustrated graphically at 51 in Figure 6. It is thus to be observed that the exit port to the mixer is open for the period of time in which liquid is flowing from the metering device 33 and the metering device 34, but is closed when liquid is no longer flowing. It helps to ensure that the hydraulic integrity of the system is maintained, with the liquid between the two metering devices 33,34 and the outlet control valve 39 remaining under a slight pressure and thus in a "hydraulic" condition.

Figure 7 illustrates a typical bead that may be made using the described apparatus. The bead 52 is a bead of an adhesive material, and the bead may be applied to one component, such as a supporting frame or the like, to which a second component, such as a panel, is to be adhered. The bead 52 is of elongate form and is caused by drawing the outlet of the outlet valve 39 across part of the support frame at a uniform speed.

Because the bead 52 is formed from a mixed adhesive material which is not emerging from the mix in a uniform manner, but instead is emerging from the mixer at a relatively fast flow rate while the dispensing devices are i dispensing their "shots" and with, effectively, a very low flow rate during the; intervening periods of time, the bead is of a non- uniform form. The bead is formed at separate "spots" or small 'piles" of adhesive, generated when the "shots" are being ejected from the metering devices, interconnected by a small relatively thin "strand" formed during the intervening periods of time.

It is to be understood that in producing the bead of Figure 7, the control valve 39 is not totally closed, when it is in the non-open position, and thus the bead consists of a plurality of relatively large spots 53 of adhesive, with adjacent spots being interconnected by a relatively thin strand 54. A bead of this type will use much less material than a single bead having a diameter equivalent to the diameter of the spots 53. However, the spots 53 may be sufficient to provide an adequate bond strength between the panel and the support frame, as in the manner of spot welding. It is to be appreciated that whilst the spots 53 may provide the strength, the relatively strand 54 ensures that an effective "seal" is provided between the two components that are being secured together, as the bead is unbroken from beginning to end, even though of non-uniform form.

Figure 8 illustrates an alternative form of bead, where the bead comprises a plurality of wave-sectioned segments 55 which merge into one another. Each wave segment has a first head or end portion which is relatively large which tapers towards a smaller tail. The tail of one wave-sectioned segment merges with the head of the next segment. Again a bead of this type may be used with adhesive, utilising a lesser quantity of adhesive then if the bead had been uniform.

Figure 9 illustrates a further form of "bead" which consists of a plurality of totally discrete and separate "spots" 56 of adhesive. These spots will act in the manner of"spot" welding.

It is to be appreciated that in the described embodiment, the metering devices are arranged so that they can be operated in synchronism, with the end result that the liquid dispensed is supplied to the outlet with a pressure which fluctuated with time.

It is to be appreciated that beads of a similar form may be created using any sort of pumping or dispensing arrangement which provides an equivalent fluctuation of pressure or flow rate with time. It is envisaged, for example, that a single component fluid may be dispensed in this way, with the single component fluid being, for example, an adhesive that may set or cure when exposed to moisture or when exposed to oxygen, or when exposed to hear, or even when exposed to light.

It is believed that a bead having the form shown in Figure 7 or Figure 8 may be of a special benefit in that the parts of the bead which arerelatively voluminous, such as the "spots" 53 of the bead shown in Figure 7, will, when compressed between two items that are to be secured together, provide a flattened adhesive "patch" of substantial area, thus providing sufficient bonding strength to secure the items together, as in the manner of a "spot weld".

However, the then strand, such as the strand 54, interconnecting the spots will, when two elements are adhered together, form a substantially gas tight seal.

Thus, by using a bead of the type shown in Figures 7 and 8, it is possible to achieve a very satisfactory degree of adherence between two items, whilst also providing a substantially gas tight seal, whilst using a minimum quantity of adhesive.

When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

CLAIMS: 1. A dispensing apparatus for dispensing a liquid comprising at

least one component, the apparatus comprising a dispensing arrangement to be connected to a source of the said at least one liquid and being connected to an outlet element having an exit port through which liquid is to be dispensed, the dispensing device being configured to supply the liquid to be dispensed to the outlet with a flow rate which fluctuates with time.
2. A dispensing apparatus according to Claim 1 for dispensing a mixture of two liquids, wherein the dispensing arrangement comprises two metering devices, each metering device being configured to provide a plurality of sequential "shots" of liquid, each metering device generating an output signal when a "shot" of liquid has been dispensed, the metering devices being connected to a controller, the controller controlling the metering devices so that the metering devices can only generate a succeeding "shot" when both of the metering devices have provided an output signal confirming production of the preceding "shot", the controller being configured to deliver the control signals simultaneously to the metering devices so that the metering devices produce the next "shot" simultaneously, the outputs of the metering devices being connected to a mixer comprising the outlet from which the mixed liquids are dispensed.
3. A dispensing apparatus according to Claim 1 or 2 wherein an outlet control valve is provided at the exit port of the outlet, the outlet control valve being controlled by the controller to control the flow rate. r
4. A dispensing apparatus according to Claim 3 as dependent on Claim 2 wherein the outlet control valve is controlled to be open when "shots" are being produced by the metering devices, but to be substantially closed at other times.
5. A dispensing apparatus according to Claim 2 or any Claim dependent on Claim 2 wherein the metering device incorporates an elongate chamber, there being a shuttle contained within the chamber, the shuttle having a portion which is a substantially sealing sliding fit within the chamber, the shuttle being moveable axially between an initial position and a second position within the chamber, each end of the chamber being provided with a liquid flow duct through which pressured liquid may enter and leave the chamber, there being valve arrangement to control the flow of liquid to and from the chamber such that, during successive cycles of operation of the metering device, liquid is supplied to one end of the chamber causing the shuttle to move from the initial position at said one end of the chamber to the second position at the other end of the chamber, thus ejecting a pre-determined volume of liquid from the other end of the chamber, and subsequently liquid is supplied to said other end of the chamber causing the shuttle to move back from the second position to the initial position, ejecting a pre-deterrnined quantity of liquid from the said one end of the chamber, the valving means comprising a rotary valve rod contained within a valve bore, and a mechanism to rotate the valve rod, the liquid flow ducts from the chamber extending to the valve bore, at least one liquid inlet extending to the valve bore and at least one liquid outlet extending from the valve bore, the valve rod, in combination with the valve bore, deeming liquid flow passages which, in one orientation of the valve rod, serve to interconnect a liquid flow inlet and the liquid flow duct extending to one end of the chamber whilst interconnecting the liquid flow duct extending to the other end of the chamber with an outlet and, in an alternate orientation, serving to interconnect the liquid flow inlet with the liquid flow duct extending to the other end of the bore whilst connecting the liquid flow duct extending to the said one end of the bore with an outlet.
6. A dispensing apparatus of Claim 5 wherein the shuttle is provided with two rods, each rod extending beyond the chamber, there being a contact of proximity sensor located adjacent each rod to generate a signal when the shuttle reaches the initial position and the second position.
7. A method of producing a bead from a liquid having at least one component, the method comprising the steps of supplying the liquid to an outlet at a flow rate which fluctuates with time, whilst moving the outlet relative a substrate, thus creating a non-uniform bead.
8. A method according to Claim 7 wherein the bead is provided with a plurality of spaced apart "spots" of the said liquids.
9. A method according to Claim 8 wherein adjacent spots of liquid are interconnected by a relatively thin strand.
10. A method according to Claim 8 wherein the spots form part of wavesectioned segments of bead which merge into one another.
11. A method according to any one of Claims 7 to 10 wherein the bead is a one component liquid in the form of a curable adhesive curing in response to oxygen or moisture or heat on light.
12. A method according to any one of Claims 7 to 10 wherein the liquid is a two component liquid.
13. A method according to Claim 1 wherein the method comprises the steps of metering the first liquid with a metering device that produces successive "shots" of liquid and metering the second liquid with a metering device which produces successive "shots" of liquid, mixing the "shots" of liquid ejected from the two metering devices to form a bead, wherein the metering devices are controlled so that the metering devices produce said "shots" simultaneously, thus causing an uneven flow of liquid from the metering devices to an outlet, thus producing the non-uniform bead.
14. A method according to any one of Claims 7 to 13 including the step of controlling the flow of liquid from an exit port with an outlet control valve.
15. A bead produced by the method of any one of Claims 7 to 14.
16. A dispensing apparatus substantially as herein described with reference to and as shown in the accompanying drawings.
17. A method of dispensing liquid substantially as herein described with reference to and as shown in the accompanying drawings.
18. A bead substantially as herein described with reference to and as shown in Figure 7 of the accompanying drawings.
19. A bead substantially as herein described with reference to and as shown in Figure 8 of the accompanying drawings.
20. A bead substantially as herein described with reference to and as shown in Figure 9 of the accompanying drawings.
21. Any novel feature or combination of features disclosed herein.