Field Of The Invention

THIS INVENTION relates, broadly, to both apparatus and an associated method for dosing an additive into a metered flow of material. More particularly, but not exclusively, the invention has application to liquid and paste additives, and to liquid, powder and granular materials.

It is stressed that this invention concerns itself with metered flows of material - as opposed the dosing of additives into a batch of material within a vessel. Background To The Invention

The art of mixing additives (notably: colourants) into a mixture or solution is well-known. Naturaily, depending on the nature of the particular additive, and the nature of the particular material to which it is added, different techniques have been developed over time, in order to make the process more efficient. in this specification, the concept of viscosity is particularly important and it is measure here in centipoise (cP) which, as will be appreciated by the person skilled in the art is well-defined as follows:

Traditionally in the prior art, it is common to encounter additives demonstrating a viscosity within the range of ~3,000 cP - 30,000 cP. (This range covers, broadly: oil-based, water-based and silicone-based additives).

Regrettably, the detail disciosed in the present state of the art is plagued by a number of disadvantages and shortcomings. For example: a commonly employed method of dosing liquid or paste additives into plastics materials involves the use of a reservoir-pump system - such as the type that is illustrated schematically in Figure 1. Specifically, in that system, the solution comprise a dosing controller (to control a stepper motor), a reservoir (for storing the liquid or paste additive), and a positive displacement pump to dose the additive into a plastic injection or extrusion moulding application. That system is unnecessarily complicated, in that it requires pneumatic or hydraulic piping and associated fittings and couplings in order to connect the reservoir to the pump, and the pump to the injection or extrusion moulding machine. A number of problems are associated with this. For example: the reservoirs will, necessarily, need to be replaced or refilled whenever the supply of additive is depleted - typically, this is a disruptive, messy process, especially given the large number of mechanical parts involved, and, as a result, an appreciable amount of additive tends to be wasted on refilling: this is highly undesirable. all the more so when dealing with caustic or volatile additives, as this also poses a health and safety risk. Furthermore, it will be appreciated that the continual re-filling of the reservoir adds to the wear and of the machinery involved. Another problem associated with the prior art is that positive displacement pumps tend to be increasingly inaccurate in maintaining required rates of dosing when pumping additives of relatively high viscosities (for present purposes: viscosities greater than 30,000 cP are regarded as high). A necessary consequence of this is that the rates of dispersion achievable of pigments or dyes in liquid or paste additives quickly reaches an upper limit. This, in turn, places significant restrictions on the concentration levels and dosage rates that one is capable to achieve in the additives. It will be appreciated that high concentration levels of additives is regarded as being significantly desirable in this industry, and that the limitations on efficiency and performance in the prior art pose a major drawback to desired levels of efficiency.

Yet another problem associated with the prior art is that the (relatively) low viscosity liquid or paste additives that are used (owing to the problem described above) tend to demonstrate inferior shelf life and pigment- separation properties, both of which are regarded as undesirable.

Object Of The Invention ft is an object of the present invention to provide both apparatus and also an associated method of mixing an additive to a materiai. that will overcome, at least partially, the disadvantages described above.

Summary Of The Invention

According to a first aspect of the invention, there is provided an apparatus for dosing an additive into a metered flow of materiai, the apparatus comprising:

· a frame, for maintaining the structural rigidity of the apparatus;

• a receiving formation, located within the frame, for receiving a cartridge filled with a predetermined amount of the additive; and

• a throat formation, through which the material is directed to flow into a dosing zone,

the apparatus being connectable to a displacement regulator for regulating selectively the dispersal of additive into the dosing zone.

The displacement regulator may comprise:

• a motor, coupled to an actuator; and

· a push rod being dimensioned and configured to abut the cartridge and. on actuation, to force the additive from the cartridge at a predetermined rate

Preferably, the cartridge includes a piston formation, alternatively a plug formation, that is dimensioned and configured complimentari!y to the push rod, to facilitate discharge of the additive from the cartridge on actuation.

The actuator may be selected from the group consisting of: a lead screw, a hall screw, a linear guide, a linear actuator, a belt-pulley system, and a mechanical device that converts rotational motion into linear motion.

The cartridge may further comprise a nozzle, the nozzle being dimensioned and configured to dispense additive at an optimal rate, alternatively in an optimal direction, into the dosing zone.

According to a second aspect of the invention, there is provided a method for dosing an additive into a metered flow of material, the method comprising:

· providing a predetermined voiume of additive, of a predetermined concentration, in a sealed cartridge;

• loading the cartridge into a dosing apparatus;

• directing the movement of the flow of material, at a predetermined rate, into a dosing zone within the apparatus; and

· actuating dispensed flow of the additive from the cartridge into the dosing zone, at a predetermined rate.

The additive may be a water-based liquid, alternatively a paste, having a viscosity in the range of 1 cP - 2,000,000 cP. The additive may be an oil-based liquid, alternatively a paste, having a viscosity in the range of 1 cP - 2,000,000 cP.

Brief Description Of The Drawings

!n order to describe the invention, embodiments thereof are described hereunder, purely as examples, without limiting the scope of the invention, wherein: Figure 1 is a schematic representation of a typical liquid / paste dosing system that is disclosed in the prior art;

Figure 2 is an isometric view from above of the dosing apparatus according to a first aspect of the invention;

Figure 3 is a plan view, from above, of the dosing apparatus, also depicting a reservoir of material, in use;

Figure 4 is a right side view of the dosing apparatus depicted in Figure 2;

Figure 5 is a transverse section of dosing apparatus depicted in Figure 4, along the line A-A; and is a front view depicting a series of cartridges that are envisaged for use within the apparatus, and in the method according to a second aspect of the invention.

Detailed Description Of The Drawings

Referring to the figures, which depict a preferred embodiment of the invention, apparatus in accordance with the invention is provided, and is referred to generally by numeral (10). The guide (10) includes a frame 20, and within it. a slot 30, which acts as a receiving formation for the cartridge 40. that is described in further detail below. The apparatus (10) also includes a throat formation 50, and it is through this formation (50) that the feed of materials wi!i be fed during the dosing process, into a zone described as the "dosing zone" 90. The apparatus (10) also comprises a motor 70, the purpose of which is to turn actuator (60) - in the accompanying Figures, actuator (50) takes the form of a lead screw. This action, in turn, causes push rod (80) to move in the direction of cartridge (40). The operation of these components of the apparatus (10), in use. is described in further detail beiow. Before describing the invention in further detail, it is instructive to elaborate on the prior art solution that is depicted in Figure 1. It depicts a reservoir (140) containing a liquid additive (100), which is pumped freely into the fiow of materia! (110), via operation of positive displacement pump (150). It will be immediately apparent to the person skilled In the art how the disadvantages of the prior are (described above) arise in such a system. It is convenient to describe aspects of the apparatus (10) simultaneously with steps in the corresponding method for dosing an additive (100) into a metered flow of material (110) (the method is not depicted in the Figures, although the steps in that method are described sequentially and in detail here). In the first step in the method, a cartridge (40) is pre-packaged with a desired additive (100), having a predetermined concentration. The cartridge (40) is sealed hermetically at that point. This, alone, shows a distinct advantage of the invention, namely that any desired concentration and any desired volume of apparatus (10) may be achieved - this is a significant improvement over the prior art.

It will be noted - most predominantly in Figure 6 - that the cartridge (40) has a peculiarly shaped nozzle (120). This is quite intentional: it will be appreciated that the shape and configuration of the nozzle (120) is designed to achieve particular rates of dispersal of the additive (100) from the cartridge (40). The cartridge (40) also includes a plug formation (130), that is dimensioned and configured complimentarily to the push rod (80).

This leads to the second step in the method, in which the cartridge (40) is loaded into the slot (30). It will be noted that the slot (30) orients the cartridge (40) such that its nozzle (120) is directed to open in the direction of the dosing zone (90). The next step in the method occurs in use. Specifically, a batch of material (110) is placed in a reservoir (140) (see, in particular: Figure 3). The material (110) is fed, at a predetermined rate and under gravity, to fail through the throat formation (50). and thence into the dosing zone. In the example illustrated in the Figures, reservoir (140) has a hopper (not depicted) and is set-up to ensure that the release hatch of the hopper opens into an injection moulding machine (as seen, in part, in Figure 5). It is also conceivable, in other embodiments of the invention, that the hopper opens into an extrusion moulding machine (not depicted). The operation of the release hatch is controlled electronically via conventional software program that is hard-coded into the hopper. In this fashion, the feed-rate of the materia! (110) is controlled. When the feed commences, the next step of the method entails the actuation of the actuator (60), which is turned by operation of the motor (70), causing it (the actuator (60)) to compel the push rod (80) toward the cartridge (40). It has already been described above how the operative end of the push rod (80) is dimensioned and configured complimentarily to the cartridge (40) (and - more specifically - to the plug formation (130) in the cartridge (40)). This causes the additive (110) to be forced towards and then dispersed from the nozzle (120), and into the dosing zone to meet the material (110) that is also being fed through that zone simultaneously. The rate of dispersal of the apparatus (10), of course, is proportional to the speed of the push rod (80) on actuation. In simitar fashion to the operation of the hopper, the speed of the push rod (80) is also controlled through the use of a conventional software program that, in this example, is hard-coded into the controller (75), which controls motor (70). It will be appreciated by the expert in the field that the invention results in the full volume of additive (100) being dispensed into the dosing zone 90. with none being spilled beyond that region. On completion of that step, the operator of the apparatus (10) need only remove the (now emptied) cartridge (40) from the slot (30), and replace it with another full cartridge (40), in order to commence the next dosing batch. This advantage overcomes a number of the disadvantages of the prior art that has been described above. The motor (70) depicted jn the Figures is a traditional stepper motor, the operation of which turns actuator (60) which in turn compels the push rod (80) to move in the direction of the cartridge (40). However, it is equally feasible that other forms of actuator (60) might be used including: a bail screw, a linear guide, a linear actuator, a belt-pulley system, and in fact. any other mechanical device that converts rotational motion into linear motion (none of these alternative embodiments is depicted here). In ail cases, the actuator (60) would be placed in mechanical contact with pushrod (80).

It has been found that optimal dosing conditions occur within particular temperature ranges. More specifically: when the metered flow of material (110) is maintained at a temperature in the range: 15°C - 190°C. It is also preferable thai the temperature is maintained at a rate of 15"C -45*C. where the material (110) is a liquid, alternatively at a rate of 15 ^e C - 190°C, where the material (110) is a powder, further alternatively at a rate of 15°C - 190*C, where the material (110) is in granulated form. Further, still, it has also been found to be preferable that the temperature of the cartridge (40) in use is maintained at a temperature in the range: 10 ^* C - 50*C.

Some worked examples are now described, in particular, seven separate trials in the field of application of granular flow, and one trial in the field of power flow, have been conducted. In each case, cartridges (40) of the following specifications were used:

Material Polypropylene

Results:

By visual inspection, there was no colour variation of the article, therefore dosing was determined to be consistent. Replacement of an empty cartridge (40) with that of a new full cartridge (40) was completed within a minute, without any spills or contamination.

Trial 2 of 8: Granular Flow

The critical aspects of the trial may be summarised as follows:

By visual inspection, there was no colour variation of the article, therefore dosing was determined to be consistent. Replacement of an empty cartridge (40) with that of a new full cartridge (40) was completed within a minute without any spills or contamination.

Trial 3 of 8: Granular Flow

The critical aspects of the trial may be summarised as follows:

33.35% castor oil

3% wetting agent

3% UV absorber

Results:

By visual inspection, there was no colour variation of the article, therefore closing was determined to be consistent. Replacement of an empty cartridge (40) with that of a new full cartridge (40) was completed within a minute without any spills or contamination.

Trial 4 of 8: Granular Flow

The critical aspects of the trial may be summarised as follows:

By visual inspection, there was no colour variation of the article, therefore dosing was determined to be consistent. Replacement of an empty cartridge (40) with that of a new full cartridge {40) was completed within a minute without any spills or contamination.

Trial 5 of 8: Granular Flow

The critical aspects of the trial may be summarised as follows:

By visual inspection, there was no colour variation of the article, therefore dosing was determined to be consistent. Replacement of an empty cartridge (40) with that of a new fuii cartridge (40) was completed within a minute without any spiiis or contamination.

Trial G of 8: Granular Flow

The critical aspects of the trial may be summarised as follows:

Results:

By visual inspection, there was no colour variation of the article, therefore dosing was determined to be consistent. Replacement of an empty cartridge (40) with that of a new full cartridge (40) was completed within a minute without any spills or contamination.

Trial 7 of 8: Granular Ftow

The critical aspects of the trial may be summarised as follows:

Results:

By visual inspection, there was no colour variation of the article, therefore dosing was determined to be consistent. Replacement of an empty cartridge (40) with that of a new full cartridge (40) was completed within a minute without any spills or contamination.

Trial 8 of 8; Powder Ftow

The critical aspects of the trial may be summarised as follows:

Results-.

By visuai inspection, there was no colour variation of the article, therefore dosing was determined to be consistent. Replacement of an empty cartridge (40) with that of a new full cartridge (40) was completed within a minute without any spills or contamination.

It will be appreciated that the advantages achieved through the use and exercise of this invention overcomes, to at least some degree, each one of the disadvantages described above. It will be appreciated, further, that numerous embodiments of the invention could be performed without departing from the scope of the invention as defined in the consistory statements above.