The present invention relates, in general terms, to a device for use in the feeding of material of any given type, and more especially paniculate material, such as powders and the like. More particularly, but not exclusively, the invention relates to an improved form of gear box for use in an apparatus intended for such usage or purpose, although it should be understood that the arrangement in accordance with the present invention is not to be considered to be limited to use in such a context. Indeed, the apparatus in accordance with the present invention lends itself to usage in a variety of different contexts, for the feeding, blending and/or mixing of materials, whether such materials be in the form of powders or liquids. In accordance with the known art various forms of apparatus are provided for the feeding and/or mixing and for blending, of for example, dry bulk materials, such as for example powders, at substantially accurately controlled flow rates. Such known apparatus or devices suffer from the disadvantage, however, that during the course of feeding it is difficult, if not actually impossible, to ensure a constant bulk density of the material being fed. There are a variety of reasons for this. One reason, for example, is because of the tendency of powders to "bridge" within a hopper or the like. Once such a "bridge" forms, the result will be inconsistency in feed of the material. Eventually, however, the sheer bulk (weight) of material supported by such a "bridge" will result in the destruction thereof, in turn leading to a sudden and dramatic increase in material to be fed. Such inconsistent feeding gives rise to an unsatisfactory result.

Variations in the bulk density of material being fed can in turn give rise, for example, to variations in the volume of material being fed or discharged per unit of time and, in practical terms and for purposes of proportioning in the preparation of so-called admixtures, such can have serious practical and economic

consequences. In that regard it should be noted that the process known as proportioning, the purpose of the different speeds is to provide the minimum movement of product - and thereby degradation of product - that will effectively 'condition' the product to a uniform bulk density.

The present invention seeks to overcome the problems and disadvantages associated with the prior art by providing an improved form of apparatus for use in the feeding and/or mixing and/or blending of materials, more especially dry bulk materials. In general terms the apparatus in accordance with the invention includes at least two concentrically mounted output shafts, with the inner of those shafts preferably being driven at a greater speed when compared with the outer shaft, in other words with there being a relative speed difference in terms of rotation of the respective inner and outer shafts. In an especially preferred embodiment the concentrically mounted shafts may be rotating in the same direction at different speeds, but it would be equally possible to have such shafts rotating in opposite directions at different speeds.

In accordance with one aspect of the present invention, therefore, there is provided a speed reduction drive apparatus including a single input shaft and at least two output shafts, said output shafts operating at different speeds, said input shaft being in drive connection via an intermediate gear train.

In accordance with a further aspect of the invention there is provided an apparatus for the controlled feeding and/or mixing and/or blending of material, preferably particulate material, including a speed reduction drive apparatus of the aforementioned type.

In accordance with yet another aspect of the present invention there is provided a method for controlled feeding and/or mixing and/or blending of a material, preferably particulate material, especially a powdered material, employing a reduction drive apparatus of the aforementioned type, wherein one of said at least two output shafts has associated therewith means for conditioning

the material being fed, thereby to ensure substantially constant bulk density thereof.

Drawings

In order that the invention may be more clearly understood and put into practical effect there shall now be described in detail a preferred embodiment of a gear box or drive train arrangement in accordance with the invention. The ensuing description is given by way of non-limitative example only and is with reference to the accompanying drawings, wherein: FIG. 1 is a sectional view of a combined single and double speed reduction unit in accordance with the present invention; and FIG. 2 is a view taken along the line 2-2 in FIG. 1 . Description of Preferred Embodiment The arrangement in accordance with the invention incorporates what is to be termed a primary speed reduction unit which, in the preferred embodiment illustrated, includes a worm wheel 1 and worm shaft 2 driven by any suitable means, as for example an electric motor 3. Suitable bearing means 4 of any given type are included to ensure correct mounting and operation of the worm wheel 1 /worm shaft 2. It should be realised that the actual means for driving such worm wheel 1 and worm shaft 2 is not of the essence of the invention. In an especially preferred embodiment the worm wheel 1 can run at a typical speed of 1 20 revolutions per minute with an input speed of 1 500 RPM. It should be realised, however, that input speed as such is generally variable - as could be achieved, for example, using an electric motor with a variable speed controller.

In the preferred embodiment illustrated the worm wheel 1 is in drive connection with the first of two concentrically mounted shafts 5 and 6, more particularly the inner shaft 5 of said two concentrically mounted shafts 5 and 6. In an alternative embodiment, not illustrated, more than two such concentrically

mounted shafts may be employed. That worm wheel 1 is also in drive connection with the sun gear or central gear 7 of a compound epicyclic gear speed reduction train of any given type. In the preferred embodiment illustrated a planetary gear set 8, comprising three or more planet wheels or gears and constituting part of the aforementioned epicyclic gear train, arranged so as to revolve around the aforementioned sun or central gear 7 and within a stationary gear 9, is then in drive connection with the outer shaft 6 of the two concentrically mounted output shafts 5 and 6. In that regard of course the said outer shaft 6 is hollow. In an especially preferred embodiment the outer shaft 5 is driven at a speed of the order of 1 2 RPM, but in practice this will vary with desired or existing input speed. An adaptor plate and seal housing, generally designated 1 0, is employed to assist in correct location and operation of the output shafts 5 and 6. In that regard the adaptor plate 10 has associated therewith a seal cap, generally designated 1 1 , with the interposition of a spring means 1 2 of any given type (preferably spring steel) and suitable packing material, as for example braided teflon packing 1 3.

One application for the gear box or gear train or drive means in accordance with the present invention is, as stated earlier, in the controlled feeding and/or mixing and/or blending of dry bulk materials, as for example powders. Such controlled feeding is desired in a number of different situations and, no matter what the situation involved, accuracy of feeding rate is imperative, not only in terms of efficiency but also in terms of cost. To be more specific, such accuracy/constancy of feeding rate is imperative in terms of, for example, consistency of the final product, or alternatively the dependability of any uniform chemical reaction desired between the product being fed and the base or receiving product. In that regard it should be understood that the arrangement in accordance with the present invention also has application in processes such as or involving the mixing and/or blending of dry bulk materials or liquids, in particular viscous liquids. In such an application the plurality of

concentrically mounted shafts may rotate in opposite directions.

With an especially preferred embodiment of the present applicant's arrangement, as illustrated, the inner shaft 5 of the two concentrically mounted shafts 5 and 6, in other words the shaft 5 operating at a higher speed, can in turn drive a feed means, typically an auger or the like 14 disposed and operating in what might be termed the feed chamber 15 of a hopper or the like apparatus 16, thereby constituting what is commonly known in the relevant art as a dry materials feeder. The outer shaft 6 of the two concentrically mounted shafts 5 and 6, running at a lower speed than the inner shaft 5, can then be used to drive a means 17 which serves to condition the bulk material being fed. In that regard the expression "condition" is intended to mean ensuring that the material being fed exhibits constant bulk density or consistent bulk density whereby to maintain accuracy of feeding rate. In the especially preferred embodiment illustrated the conditioning means driven by 17 can take the form of a further auger or the like means, which functions to keep the bulk material in the vicinity of and in contact with feed auger 14 in motion and hence at a constant or substantially constant bulk density.

In the embodiment illustrated the so-called feed auger 14 and the device driven by 17 used for conditioning the bulk material rotate concentrically within the feed chamber 15, with the inner feed auger 14 being extended through that feed chamber 15 - and into a feed tube (not shown) from which the product or bulk material is to be delivered for subsequent processing of any given type.

For ease of explanation reference has been made in detail herein to an arrangement including two concentrically mounted output shafts. In a practical sense, however, more than two shafts may be employed, and under no circumstances is the invention to be considered to be restricted only to the preferred embodiment described and illustrated. In an alternative embodiment, not illustrated, the two output shafts could be arranged side by side, with

the distance or spacing therebetween being variable.

The arrangement in accordance with the present invention is especially, although not exclusively, suited for usage in the food and related industries, where cleanliness is essential. Prior art arrangements used in this context, which utilized for example a combination of spur gears, have been found to be somewhat unsatisfactory in that it was possible, and more often than not was the case, that dirt and/or dust, or other unwanted material, could intrude into or invade the gearbox, gear train or the like. The present applicant's arrangement overcomes this problem principally by virtue of the fact that the drive system/gear train or the like is completely sealed. The ramifications of such an arrangement, in terms of overall cleanliness and hygiene, long term availability, efficiency of operation, etc. should be evident. The present applicant's arrangement is an extremely well- designed assembly of components, which lends itself to ready installation, operation and maintenance, without the need even for the use of skilled labour and specialized equipment. The various components are so constructed as to fit together in one way and one way only - giving rise to obvious savings in terms of labour costs, etc.

It should also be understood that the present applicant's arrangement, by virtue of its simplicity, is responsible for a number of other practical advantages when compared with the prior art, including:

(i) overall compactness - important in terms of locale of use; (ii) more efficient mixing and/or blending capability, this being no more evident than in an especially preferred embodiment wherein, for example, one shaft will function to direct material in a "downwards" direction whilst the other shaft functions to direct material in the reverse or "upwards" direction; and

(iii) the case of operation etc in fact allows for the apparatus to be mounted in a variety of different positions relative to a hopper or the like, dependent on the intended usage, the nature of the material being fed, spatial limitations and requirements.

It should be understood that the aforegoing description refers merely to preferred embodiments of the invention and that variations and modifications will be possible thereto without departing from the spirit and scope of the invention, the ambit of which is to be determined from the following claims.