GB2242369A - Metering system for flowable components - Google Patents

Abstract

A metering system for a two-component composition, eg. a two-component adhesive composition, comprises two supply lines (736, 724) along which each component can be supplied from a source to a delivery point (392). In each supply line is a branch line (754, 772) leading to a collapsible container, preferably in the form of a bellows unit (756, 774). The bellows units are caused to increase or decrease in volume at a controlled rate, such that the component flow rate therefrom is constant throughout their operation, by means of a control device including a pivotal lever to which each bellows unit is connected by an articulated linkage (760, 778). In this way the two components may be fed to the delivery point in the desired quantities for mixing and immediate application to, e.g., shoes. <IMAGE>

Description

METERING SYSTEM This invention is concerned with a metering system for two or more flowable components, e.g. which may when mixed constitute an adhesive composition.

Two-component compositions are well known; for example two-component adhesive compositions are available, usually comprising a first component which is referred to as the "hardener" and a second component which is usually referred to as the "adhesive". Two-part adhesive compositions of this kind are for example polyurethane compositions, neoprene compositions and indeed rubber solutions.

In many instances it may be merely a question of ensuring that the correct quantities of each component are supplied to a mixing chamber, whereafter mixing can take place and the thus mixed composition is then supplied to a point of application. In some circumstances, however, it is desirable for mixing to take place progressively according to need, bearing in mind that in the case of two-component compositions of this kind, once mixed they tend to "cure" relatively rapidly so that there is available only a relatively short time between mixing and application.Thus, for example, where it is a question of applying the adhesive composition progressively to marginal portions of a shoe bottom, e.g. for the subsequent attachment of an outsole thereto, and thus relatively small quantities are being applied, such as would not justify the pre-mixing of a relatively large batch of such composition, it is desirable that mixing takes place in an appropriate quantity and not at too early a time in relation to its application.

In handling components which make up e.g. polyurethane or neoprene compositions, attention has to be given also to the dangers involved, especially in the case of the hardener, which may be toxic. Thus it is desirable that a closed, leak-proof, system be utilised for the supply of such components In this regard, for example, it may be considered that a piston-and-cylinder arrangement, which relies upon seals (piston rings) to prevent leakage, would not be adequate, even though from the point of view of metering the provision of such arrangements for each component may be considered otherwise attractive.

It is thus the object of the present invention to provide an improved metering system for two or more flowable components, wherein no sliding or rotating seals are utilised, but nevertheless satisfactory control of the flow rate of each component, sufficient to facilitate a progressive application of the mixture, can be achieved.

The invention thus provides a metering system for two or more flowable components e.g. which may when mixed constitute an adhesive composition, comprising for each component a collapsible container which, except for an inlet/outlet, is otherwise closed, wherein control means is provided effective, when expelling components from their containers, to control the rate of decrease of the volume of each container, and thus the flow rate at which the quantity of each component is expelled from its container, such that the ratio between the flow rates from the containers is maintained constant.

It will thus be appreciated that by using a collapsible container which, except for an inlet/outlet, is otherwise closed, no reliance need be placed upon sliding or rotating seals and thus the risk of leakage of either of the components is mitigated. Moreover, by maintaining constant the ratio between the flow rates from the containers, properly metered quantities of each component may thus be supplied to a delivery point at a controlled rate sufficient for progressive mixing and application to a workpiece surface.

Conveniently the control means is also effective, prior to such expulsion, to cause a quantity of each component to be supplied to its container, the quantities thus supplied being in the same ratio as the ratio between their flow rates from the containers. In this way, the metering system always remains in an equilibrium state where at any given time the available volume of each component is in the correct ratio.

In a preferred embodiment of the metering system the control means comprises a single motor acting through a linkage including a pivotal lever to which each container is connected for collapsing it. More particularly, the pivotal lever is mounted for pivotal movement about a pivot point and the ratio of the flow rates from each container is determined according to the distance of the connection for each container from the pivot point as well as the actual volume of each container (or, in the case of a cylindrical container, the cross-sectional area thereof).

It may of course be desirable, for different twocomponent compositions, to vary the ratio between the flow rates and to this end conveniently in accordance with the invention the position of the pivot pin about which the pivotal lever can pivot can be adjusted in a direction along the length of the lever.

The collapsible containers used in the metering system in accordance with the invention may be in the form of e.g. expansible bag members which have a plastic memory but preferably, and in accordance with the present invention, each collapsible container is constituted by a bellows unit. (Bellows units are formed either by the hydraulic deformation of a tube over a mould or form, or by electro-deposition onto such a mould or form, and are thus unitary, except for welding end closure members onto the thus formed tubular portions.Provided that the welding of the ends is complete, a closed chamber is thus provided.) The use of collapsible containers as aforesaid enables the relative quantities of the two components to be predetermined so that the ratio between the two quantities can readily be set, e.g. in the case of a curable adhesive composition, to achieve adequate cure of the adhesive composition without excessive use of the hardener; the generally accepted optimum quantity of hardener to be used is in the region of 3%of 5% of the total volume of the composition.

In a preferred embodiment of the metering system in accordance with the invention first and second supply lines are provided, extending from sources of the two components respectively to a common delivery point, whereafter the two components may be mixed together, a first branch line from the first supply line being connected to a first container for one of the components, and a second branch line from the second supply line being connected to a second container for the second component. For preventing backward flow along either of the supply lines because of the pressure created therein hy the expulsion of the components from their containers, furthermore a restrictor valve arrangement is provided in each supply line, "upstream" of the branch line therein, serving te direct the component flow in a direction towards the delivery point.

There is preferably arranged at said delivery point furthermore a shut-off valve for preventing component flow from the system when it is in a rest condition. Moreover, the pressure applied to the component in the second supply line is greater than that applied in the first. The pressurising of the second component in this way is thus also effective to maintain the first component under the same pressure in the first supply line. In order, however, to avoid any risk of the pressure applied by the second component to the first component causing the second component to be driven into the first supply line, a further restrictor valve arrangement is provided in the first supply line, "downstream" of the first branch line, and adacent the delivery point. In this way, component flow in the first supply line in a direction away from the delivery point is prevented.

The metering system in accordance with the invention preferably comprises sequence control means whereby the expulsion of components from their containers is initiated prior to the opening of the shut-off valve. In this way, the whole system is pressurised to the pressure required for the expulsion of the two components from their containers prior to the opening of the shut-off valve.

Moreover, preferably the shut-off valve comprises a ball valve arrangement which is opened by the ball valve being pressed against the workpiece surface to which the adhesive composition is to be applied.

There now follows a detailed description, to be read with reference to the accompanying drawings, of a metering system in accordance with the invention. It will be appreciated that this metering system has been selected for description merely by way of exemplification of the invention and not by way of limitation thereof.

In the accompanying drawings: Figs. 1 and 2 are side and end views respectively of control means and associated parts of the metering system in accordance with the invention; and Fig. 3 is a schematic diagram showing the layout of the metering system in accordance with the invention.

The metering system in accordance with the present invention now to be described is for metering quantities of two components which when mixed will form an adhesive composition, said components being supplied to an applicator device 380 along supply tubes 382, 726 which are arranged one inside the other within the applicator device. The applicator device also comprises a shut-off valve in the form of a ball valve arrangement including a ball 392 captively accommodated within a housing 384, the arrangement being such that, in the rest condition of the system, the ball 392 is urged by a spring (not shown) into sealing engagement with an annular rim forming part of the housing 384, but is retracted from such position when the ball 392 is-pressed against a workpiece surface to which adhesive composition is to be applied.

The metering system in accordance with the invention comprises a frame 742 for metering quantities of two components which when mixed will form an adhesive composition, said components being supplied to the applicator device 380 along the supply tubes 382, 726.

The metering device comprises a frame 742 supporting first and second manifold blocks 744, 746. The manifold block 744, which is arranged for the supply of hardener (constituting a first component of the adhesive composition) comprises an inlet port 748 and internal passageway 750 extending through the block 744 and opening at an outlet port 752 to which the pipe 724 is connected. Non-return (restrictor) valve arrangements RV1, RV2 are associated respectively with the inlet and outlet ports 744, 752 whereby the flow of hardener in a direction from the outlet to the inlet port is prevented.

A branch line 754 opening into the passageway 750, between the two valve arrangements RV1, RV2, said branch line leading to a collapsible container in the form of a bellows unit 756 secured to the underside of the block 744. The bellows unit 756 is a unitary collapsible element, being closed except for the inlet/outlet by which it is connected to the branch line 754. The lower end cap 758 of the unit 756 is connected by an articulated linkage 760 to a lever 762, which is mounted for pivotal movement on a block 764 secured to the frame 742, as will be discussed in detail later.

The manifold block 746 also has an inlet port 766 for the supply of adhesive and an internal passageway 768 extending through the block 746 and opening at an outlet 770 to which the pipe 382 is connected. Non-return (restrictor) valve arrangements RV3, RV4 are associated respectively with the inlet and outlet ports 766, 770, preventing the flow of adhesive in a direction from the outlet to the inlet port. A branch line 772 opens into the passageway 768 between the two valve arrangements RV3, RV4, said branch line leading to a further collapsible container in the form of a bellows unit 774.

This unit is substantially larger than the bellows unit 756, since the amount of hardener in the adhesive composition is expected to be in the order of 3% to 5% of the volume of the composition as a whole. The unit 774 has an end cap 776 which is connected by an articulated linkage 778 to the lever 762, at its end remote from its pivot point.

Also connected to the lever 762, at the same point as the articulated linkage 778 is one end of a piston rod 780 of a piston-and-cylinder arrangement PC1. Actuation of the arrangement PC1 is thus effective to pivot the lever 762 about its pivot and thus, through the linkages 760, 778, to increase or decrease the volume of each of the bellows units 756, 774. Moreover, by reason of the particular arrangement ust described, it will be appreciated, the rate of flow of the components from each of the two bellows units will remain at a constant ratio throughout the decrease in the volume of each container (and indeed the rate of drawing components into the containers will also be similarly controlled) by reason of the arrangement of the lever 762.

For adjusting the ratio between the two flow rates the block 764 is provided with a plurality of (in the particular case four) holes in any one of which a pivot pin 782 can be accommodated, an equivalent number of holes also being provided in the lever 762, such that they coincide with the holes in the block 764 when the lever is in a horizontal condition, i.e. in its rest position. By selecting one or other of the four holes for the pivot pin 782, the geometry of the pivotal action of the lever 762 in response to actuation of the pistonand-cylinder arrangement PC1 is varied, and thus the ratio of the flow rates of components from the two containers 756, 774 is adjusted.

From Fig. 3 is will be seen that the hardener is contained in a tank T and is fed under gravity through an on/off control valve CV1 to the input port of the manifold block 744. To this end, it will further be noticed, regulator valve RV1 is not provided with a spring but rather allows free flow of the hardener under the gravity feed. The regulator valve RV2 on the other hand is provided with a spring and serves to prevent continuous flow of the hardener through the system except when fed past regulator valve RV2 under pressure from the bellows unit 756. The manifold block 744 has a further branch line 786 to which is connected a venting valve arrangement EV1, again manually operable, for allowing air to vent from the bore 750 and branch line 754 through a return line 788 which connects to the tank T. It will be appreciated that, because of the gravity feed arrangement involved, when the valve arrangement EV1 is open the fluid in the return pipe 788 will seek the same level as the fluid in the tank T, thereby eliminating air from that portion of the system which includes the branch line 754, bellows unit 756 and manifold block 744. As the volume of the bellows unit 756 increases hardener is drawn thereinto, without pressure. When the volume is decreased, under the action of piston-and-cylinder arrangement PC1, the hardener is expelled from the bellows unit 756 in a direction towards the applicator 380, regulator valve RV2 yielding to such pressure. Also arranged in the line 736 is a further non-return (restrictor) valve arrangement RV5 which also allows the passage of the hardener to the ball 392 of the applicator head 380.The valve arrangement RV5 does however prevent backs low of adhesive and hardener when the system is pressurised and the ball 392 is in its sealing position.

The supply system for the second component (i.e. the adhesive itself) is pressurised, and indeed comprises a pressurised pot arrangement consisting e.g. of a reservoir R and pump P, by which fluid under pressure is supplied to the input port of the manifold block 746.

The pressure under which the adhesive is maintained by this system in fact pressurises the whole of the adhesive supply system but is less than the pressure which is applied by the decrease in volume of the bellows units 756, 774. The operation of the bellows unit 774 is the same as for the unit 756 and serves to cause a metered quantity of adhesive to be supplied to the ball 392 as above described.

At the end of a working day it is desirable that no mixture of adhesive and hardener remain in the system; otherwise that will cure overnight leading to a problem of blockage at the start of the next shift. In order to avoid this problem, therefore, while at the same time preventing any risk of drooling from the applicator head between shifts, an on/off flow control valve EV2 is provided in the line 724. At the end of the working day the valve EV2 is switched to an "off" position and an end piece (not shown) is attached to the applicator head which holds the ball 392 out of its sealing position. In this situation the valve EV2 is then once more opened and the pressure from the pressurised pot arrangement urges adhesive through the line 724, flushing out any hardener remaining in the vicinity of the ball 392.It is to be noted that hardener may remain in the tube 726 "downstream" of valve RV5 without problem; the problem would be if any hardener remains in the applicator head beyond the end of the pipe 726. After a relatively small amount of adhesive has been thus flushed through, valve EV2 is again closed and the attachment to the applicator head removed. The ball 392 thus moves back to its sealing position and the valve arrangement EV2 remains closed until the start of the next working shift.

The metering system in accordance with the invention may advantageously be incorporated in a machine for performing a progressive adhesive-applying operation, e.g.

a machine for applying adhesive progressively to marginal portions of shoe bottoms. Such a machine is described e.g. in EP-A0353881. This machine is provided with a rotary brush element (not shown) which is mounted on the outside of the applicator head 380 and, during the application of adhesive, is caused to rotate, thus providing a rotary annular operating surface portion for spreading the adhesive on the workpiece surface. Where a metering system in accordance with the invention is incorporated in such a machine, it will be appreciated that because the adhesive and hardener are maintained separate until they reach the vicinity of the ball, they tend to be applied to the workpiece surface separately, but in the desired ratio.The action of the rotary brush element is then effective not only to "scrub" the adhesive composition into the surface of the workpiece, but also to ensure that proper mixing of the two components takes place. In the operation of the machine, furthermore, the adhesive composition is applied progressively around the margin of the shoe bottom and, in order to ensure delivery of adhesive at a rate which is commensurate with the speed of traverse of the tool along the shoe bottom, the operation of piston-andcylinder arrangement PC1 is controlled accordingly.

Moreover, in order to ensure that adhesive is ready for delivery as soon as the ball 392 is moved out of its sealing position by engagement with the shoe bottom, a control signal is provided, at the time when the machine signals the tool supporting means to advance towards the workpiece, to supply fluid under pressure to said piston-and-cylinder arrangement PV1 and thus pressurise the system by initiating the decrease in volume of the two bellows units 756, 774.

In practice, it has been found desirable, in order to prevent over-flexing of the two bellows units 756, 774, to utilise a relatively short stroke of the piston-andcylinder arrangement PV1; this has also the benefit that, where more adhesive is required, the stroke can be lengthened without recourse to two or more strokes of the unit four a single workpiece application.

Claims (10)

Claims:

1. A metering system for two or more flowable components e.g. which may when mixed constitute an adhesive composition, comprising for each component a collapsible container which, except for an inlet/outlet, is otherwise closed, wherein control means is provided effective, when expelling components from their containers, to control the rate of decrease of the volume of each container, and thus the flow rate at which each component is expelled from its container, such that the ratio between the flow rates from the containers is maintained constant.

2. A system according to Claim 1 wherein the control means is also effective, prior to such expulsion, to cause a quantity of each component to be supplied to its container, the quantities thus supplied being in the same ratio as the ratio between their flow rates from the containers.

3. A system according to Claim 1 or Claim 2 wherein the control means comprises a single motor acting through a linkage including a pivotal lever to which each container is connected for collapsing it.

4. A system according to Claim 3 wherein the pivot pin about which the pivotal lever can pivot can be adjusted in a direction along the length of the lever thus to adjust the ratio between the flow rates from the containers.

5. A system according to any one of the preceding Claims wherein each collapsible container is constituted by a bellows unit.

6. A system according to any one of the preceding Claims wherein first and second supply lines are provided, extending from sources of the two components respectively to a common delivery point, whereafter the two components may be mixed together, a first branch line from the first supply line being connected to a first container for one of the components, and a second branch line from the second supply line being connected to a second container for the second component, and wherein a restrictor valve arrangement is provided in each supply line, "upstream" of the branch line therein, to direct the flow from the container, as the component is expelled therefrom, in a direction towards the delivery point.

7. A system according to Claim 6 wherein a shut-off valve is provided for preventing component flow from the system when it is in a rest condition, and wherein the pressure applied to the component in the second supply line is greater than that applied in the first.

8. A system according to Claim 7 wherein a further restrictor valve arrangement is provided in the first supply line, "downstream" of the first branch line, and adjacent the delivery point.

9. A system according to any one of Claims 6 to 8 wherein sequence control means is provided whereby the expulsion of components from their containers is initiated prior to the opening of the shut-off valve.

10. A system according to Claim 9 wherein the shut-off valve comprises a ball valve arrangement which is opened by the ball valve being pressed against the workpiece surface to which the adhesive composition is to be applied.