GB2101001A - Metering and mixing apparatus - Google Patents

Abstract

Apparatus for supplying, mixing and apportioning-out specific quantities of two-component media, is adapted to be coupled to a volumetric dosing device and comprises a variable volume supply and mixing chamber (2) which communicates with an outlet valve (18), via a conduit (17) disposed between the supply mixing chamber (2) and the outlet valve (18). A displaceable apportioning needle (14) which determines the quantity dispensed, is movable within the conduit (17) to regulate the supply of the media to the outlet valve 18. A rotary agitator 4 is situated in the mixing chamber and is actuated by motor 6. <IMAGE>

Description

SPECIFICATION Metering and mixing apparatus This invention relates to apparatus for dosing, mixing and apportioning-out specific quantities of two-component media.

In apportioning mixers use is normally made of rotary dosing pumps which are supplied with the media from a pressure tank. This is performed stepwise to conduct the media to a mixer. When using a method ofthis kind for small and very small quantities, as is known, sources of error are engendered, attributable in particular to the fact that rotary dosing pumps of this nature must have some clearance so that they can at any rate turn. This clearance means leakage and such leakage, referred to in technical language as slip, can be ofvariable amount depending on viscosity, counter-pressure and the like. Thus it must be appreciated that a 50 fluctuation in temperature can produce a notable variation in viscosity so that when using this method considerable deviations from prescribed tolerances are to be expected.

This effect becomes more marked the more viscous the media. These difficulties are encountered even in the case of water-thin media.

An object of the present invention is to provide apparatus in which small and very small quantities of two-component media of a viscosity varying from light fluid to prime setting mastic can be processed with great accuracy.

This object is met in the present invention by apparatus comprising a volumetric dosing device, a housing connected to this device and containing an expansible supply and mixing chamber communicating through a conduit with an outlet valve, a spring-urged mixing piston in said mixing chamber and a displaceable apportioning needle in said conduit between the supply and mixing chamber and the outlet valve.

Further advantageous features of the invention are set out below.

The apportioning valve can be dispensed with for small quantities and the outlet valve can be associated directly with the mixing and supply chamber.

The invention affords the substantial advantage that small and minimal portions can be dispensed with major accuracy from two-component media mixed in a corresponding ratio, it being possible to obtain portion sizes of say 1 to 200 mm3 of infinite variation. The tolerance of the dosing in the present invention will be much greater, as will be illustrated by the ensuing example. With a ratio of for example 4:1 and a portion size of 4 mm3 the permissible tolerance for the hardening component would be + 0,0002 grams. The invention can attain accuracies of this nature. The advantage of the invention is above all shown by the fact that the dosing quantity is considerably increased so that variation will fall within tolerable limits and then these larger quantities can be divided up into appropriately smaller and minimum quantities.Variations in viscosity do not have any effect.

The invention will be further explained in the following description in reference to examples of embodiment illustrated in the accompanying drawings, in which Figure lisa section through a first embodiment of apparatus ofthis nature which operates dynami caliy, and Figure 2 a further embodiment of this apparatus in section with a static mixing tube and an outlet valve disposed directly at the mixing and supply chamber.

Figure 1 illustrates a dynamically-operating apparatus for mixing and apportioning twocomponent media which will be built on to a normal commercial volumetric dosing device. It has a housing 1 provided with a longitudinal cylindrical mixing chamber 2. Opening into this mixing chamber through a hole 3 is a conduit through which the two media are supplied in the chosen ratio. Inside this chamber 2 is a beater 4 rotated from a driving motor 6through a shaft 5.

The drawing is divided by a central axis 7. Left of this axis the component parts are shown in the position which they assume when the dosing media flows into the mixing chamber 2 with the beater 4 and the shaft 5 pressed downwards, whilst at the righthand side the beater 4 is shown in its situation when the apportioned medium is shot in.

The shaft 5 is mounted with a running fit in a bush 8 in housing 1 through the agency of ball bearings 9.

The shaft 5 and the driving motor 6 are mounted at the lower part in a housing portion 10 which in turn is displaceable on axial bearing races 11. Arranged in the housing portion 10 are compression springs 12 which are pressed together during the retraction of the beater 4 (lefthand half of the illustration).

Disposed transversely in the housing 1 at the end ofthe mixing chamber 2 is a channel 13 guided in which is an apportioning needle 14 moved with an appropriate ram action by a driving device 15.

Secured to the housing 1 in the direction of travel of the needle 14 is a part 16 having a second channel 17 representing an extension of channel 13 and an outlet valve 18 attached to this part 16 and carrying a plunger arrangement 19. The discharge conduit of valve 18 is indicated by the reference numeral 20.

The components of the medium flowing under pressure through the hole 3 press the beater 4 back against the compression springs 12, for example pneumatic springs, the outlet valve 18 being at this time closed. Mixing is performed by the rotating beater 4, this being pressed upwards (righthand side ofthe drawing) and the conduit 17 being completely filled with the medium up to the outlet valve 18. This outlet valve 18 is then opened and the apportioning needle 14 pushes the required quantity out with its adjustable thrust and at a variable speed.

The construction of the beater 4 may vary. First of all of course it has to produce a deal of friction and turbulence to mix the individual components together. It may for example be a spiral drill, a cylindrical part grooved around its periphery, or it may have individual pins distributed around the periphery. The chosen form of the beater is primarily dependent on the reaction period and the reaction capability of the components to be mixed. Further the form may be determined by the viscosity of the media and the ratio of the mixture. The beater may even be conical so that its speed will vary during retraction.

To prevent leakage losses a sealing liquid chamber 21 is installed between the mixing chamber 2 and the bearings 9, 11, this chamber 21 providing seals at the two sides ofthe shaft 5. This chamber 21 has externally open holes through which the leaking liquid can be removed by a neutral carrier liquid.

The embodiment illustrated in Figure 2 has a static mixing tube 23 instead of a dynamic mixer, this mixing tube having blades and the like to mix the media together. This system will be used more particularly in the case of readily-miscible media.

The static mixing tube 23 is in this example held by a retaining bush 24 in the portion 10 of the housing, the material inflow 25 taking place into this bush 24.

A ring 26 is in this example provided to retain the parts ofthe sealing liquid chamber 21.

A further variant is shown in Figure 2 namely where the outlet valve 18 is arranged directly above the supply chamber 2. The quantity issuing out is determined by a timing member which operates the needle 19 so as to allow the outflow of the appropriate media by opening the valve 18 for a greater or lessertime. Thus in addition to dispensing small quantities of media, it can deal with even minute amounts.

Claims (10)

1. Apparatus for dosing, mixing and apportioning-out specific quantities of twocomponent media, comprising a volumetric dosing device, a housing connected to this device and containing an expansible supply and mixing chamber communicating through a conduit with an outlet valve, a spring-urged mixing piston in said mixing chamber, and a displaceable apportioning needle in said conduit between the supply and mixing chamber and the outlet valve.

2. Apparatus according to Claim 1, in which a static mixing tube is arranged in the said chamber and is displaceable axially in this chamber.

3. Apparatus according to Claim 1, in which a dynamic mixer in the form of an axially displaceable and rotatable beater is provided in the chamber.

4. Apparatus according to Claim 2 or 3, in which the mixing tube or the dynamic mixer can be pressed against mechanical, pneumatic or hydraulic compression spring means.

5. Apparatus according to Claims 3 and 4, in which the housing is provided with a portion which accommodates the compression spring means and the said beater has an operating shaft mounted on a fixed bush and held against said housing portion.

6. Apparatus according to Claim 5, in which a sealing liquid chamber is provided between bearings of said shaft and said beater.

7. Apparatus according to any of Claims 1 to 6, in which the apportioning needle is arranged in front of an opening between the supply and mixing chamber and said conduit.

8. Apparatus according to any of Claims 1 to 7, in which the stroke of the apportioning needle is infinitely variable.

9. Apparatus according to any of Claims 1 to 8, comprising a sub-unit containing said outlet valve and connected to the said housing directly above the supply and mixing chamber, and comprising a timing member controlled by said needle for adjusting the quantity of discharge through said valve.

10. Apparatus for dosing, mixing and apportioning-out specific quantities oftwocomponent media, substantially as herein described and as shown in Figure 1 or Figure 2 of the accompanying drawings.