referring to fig1 to 4 , the dispensing canister of the invention 10 includes an upright reservoir 11 having oppositely disposed sidewalls 12 , 13 and oppositely disposed terminal walls , respectively a front wall 14 and a rear wall 15 . the sidewalls and terminal walls are interconnected to one another and preferably are injection molded from a polymeric plastic material integral with a bottom wall 16 . the terminal walls 14 , 15 may preferably comprise a substantially vertical portion followed by progressively downward tapered portions . within the reservoir 11 , there is provided a volumetric dosing means 20 . the volumetric dosing means advantageously comprises a spring auger 21 as shown or , alternatively , a screw auger . the volumetric dosing means 20 extends for substantially the entire length of the reservoir at the lower end thereof adjacent the bottom wall 16 . the rear end of the auger 21 is rotatably supported by an aperture of the rear wall 15 and terminates by a connector 22 . the connector 22 is intended to be linked to a shaft of a conventional electrical actuating system such as a dc motor of the dispensing device ( not shown ). at the opposite end of the auger , i . e ., the front end , the terminal wall 14 is provided with an opening 16 to which is mounted a chute 17 . the chute 17 is secured to the front wall in any convenient manner such as by tight fitting engagement , screwing , riveting , adhesion and combinations thereof . the chute 17 channels the powder from the auger to a discharge port 18 arranged in a selected direction , usually for guiding the powder toward a mixing bowl or a dispensing line . according to an important aspect of the invention , a main agitating wheel 40 and a secondary agitating wheel 41 are both provided within the reservoir 11 and supported by the sidewalls 12 , 13 along respective transversal rotation axles or hubs 42 , 43 on each side that engage bearings of the sidewalls . when properly installed , the wheels are substantially parallel and equally spaced from the sidewalls 12 , 13 . the main agitating wheel 40 is geared to the dosing means , more specifically to the auger , so that as the auger rotates to move power forward in direction a , the agitating wheel rotates in rotational direction b . as generally known , a gear configuration of wheel and auger can be constructed at the periphery of the wheel , by a plurality of teeth 44 circumferentially and evenly disposed therearound . the main agitating wheel must be of a size sufficient to provide an effective agitation along the height of the reservoir while still being able to properly engage the auger . the secondary agitating wheel or satellite wheel 41 is provided to be driven by the main agitating wheel so that it rotates in a reverse direction c . both first and second wheels 40 , 41 are therefore arranged within the reservoir in a manner that promotes downward motion of the powder in the region adjacent the terminal walls 14 , 15 . for that , the axis of the wheels are vertically offset and the main wheel is preferably positioned closer to the rear wall 15 whereas the secondary wheel is positioned closer to the front wall 14 . the wheels may not necessarily be horizontally aligned along their axis . in a preferred aspect , the axis of the secondary wheel may be positioned within an arc portion θ of between 270 degrees and 350 degrees , and more preferably between 280 and 310 degrees . the dimensions of the wheels may preferably be determined to provide an optimized occupation of the internal volume of the reservoir while not physically abutting against the terminal walls . the size of the secondary wheel 41 is not critical but may encompass a wide range of diameters depending upon the length of the vertical portions and the specific tapered geometry of the canister . typically , the diameter of the secondary wheel may be of from about 0 . 05 to 1 . 0 time , preferably 0 . 1 to 0 . 6 time , the diameter of the main wheel . in another embodiment , more than one secondary wheel of smaller size may be provided , horizontally offset from one another with each one directly geared onto the main wheel . one result of this multi - wheel configuration is that there is less a tendency for local accumulation , cliffing or bridging along the terminal ends of the canister since the powder is constantly pushed down toward the longitudinally oriented dosing device . in an even more preferred aspect of the invention , the multi - wheel configuration is combined with a dosing device that comprises an auger arranged to transport a volume of powder that varies as a function of the longitudinal position along the dosing means . depending on the type of powder used , the modifications to the auger may be such that the volume of powder transported or delivered at the outlet is reduced or , alternatively , such that the volume of powder transported at the rear of the canister is reduced . more specifically , in a first embodiment shown in fig5 the auger is arranged to comprise a transport volume for the powder that is lower in the rear portion of the auger than in the front portion of the auger . the volume can increase on a progressive or stepped basis . in case the auger is an helicoidal spring , a solid insert 23 may , for example , be located within the screw in a rear portion 24 of the auger . hence , the solid insert creates a reduction of the capacity of the auger to transport powder in this area as compared to the front area . it has surprisingly been found that such a configuration is primarily effective for improving the dosing consistency of powder of average cohesiveness such as for agglomerated milk powder and the like . one reason for this is due to the powder moving downward more uniformly . the state of the powder , especially its compaction and the effective bulk density at the point where it feeds into the auger , becomes more consistent for cohesive powders . hence , the powder density in the exit opening varies less and the volume based dosing leads to a more consistent mass . in a second embodiment shown in fig6 in particular for very cohesive powder types such as non agglomerated milk powder , mix or dehydrated fat based culinary products , superior results have surprisingly been obtained when the auger is arranged with a volume of transport for the powder that is lower in the front portion of the auger than in the rear portion of the auger . for instance , for a spring type auger , a solid insert 25 may be located within the screw in a front portion 26 of the auger . the insert does not need to longer than a few centimeters , and in general is about 10 to 30 % of the auger length . the front portion of the auger can be considered as a portion situated in the vicinity of the outlet . the lower volume left in the front of the dosing device tends to compact the powder near the outlet , thus eliminating the presence of holes and maintaining the powder mass sufficiently dense in this area . as a result , very cohesive powders can be uniformly dispensed in that the dose - to - dose variation for such powders can be effectively reduced . in a third embodiment as shown in fig7 the auger may be an endless screw 27 made of a longitudinal pipe and an helicoidal thread mounted around the pipe . in one embodiment , the volume of transport may be made constant . in a variant , the volume of transport may be made variable by different means such as by a variation of the diameter of the pipe as a function of its length or by a variation of the pitch of the thread or a combination thereof . for example , if the powder has a high level of cohesiveness , the screw will preferably have a greater diameter in the front than in the rear . on the contrary , if the powder has a lower cohesiveness , it will be preferable to have a screw with a higher diameter in the rear than in the front . as common to all embodiments , it is preferred to include at least one breaking extension that can extend radially from the main wheel and at least one breaking extension that can extend radially from the secondary wheel . as shown in fig5 those breaking extensions may , for instance , be formed of pairs of long wire springs 50 - 55 that scrape onto the inner surfaces of the terminal walls upon rotation of the wheels downwards . the springs can be attached to each side of the wheels to protrusions 47 as best shown in fig4 . the helicoidal springs may be replaced by any equivalent breaking elements such as a resilient plastic or rubber tube , whisker or wire . the action of the breaking extensions on the wheels also contributes to increase the powder density by compacting on the downstroke in direction to the dosing system , thus , reducing the areas of lower density and improving the dosing consistency . drawing fig8 - 11 illustrate the gram throw performance of various canisters according to the prior art and the invention . fig8 displays the gram - throw performance of a traditional canister (“ rhea lioness ” like canister ) with a single wheel using a cappuccino dry mix and an exit area of about 300 mm 2 . the total evacuation of the reservoir is of only 51 % by weight and the standard deviation is of about 4 . 2 % by weight . the standard deviation is a measure of total measurement deviation from the average . it can also be defined as an estimate of average uncertainty of the measurements and is expressed in this case in percentage average . as it can be observed from the graph , the gram - throw ( in grams ) gradually decreases to an unacceptable level after about less than 17 throws , so as the canister empties , the product prepared from the machine becomes more and more diluted and less desirable to consumers . fig9 displays the gram - throw performance a canister according to the invention that includes a main wheel and a satellite wheel for the specific embodiment of fig5 ( rear insert within spring auger ). the total evacuation is of about 76 % by weight and the standard deviation of about 3 . 4 % by weight . there is no gradual decline in gram - throw at the end of the test so that products made near the depletion of the canister are of the same quality as those made when the canister is full . also , the dosing time is about 40 % longer than that of the traditional canister . fig1 displays for the gram - throw performance for the embodiment of fig6 ( front insert within spring auger ). the total evacuation is about 82 % by weight and the standard deviation is only about 1 . 3 %. there is a gradual decline of gram - throw at the end of the evacuation cycle , but this occurs only after about 30 throws , an increase of over 75 % compared to that of the traditional canister . furthermore , the dosing time is about 120 % longer than that of the traditional canister . fig1 displays the gram - throw performance for the embodiment of the invention that is shown in fig7 . the auger is an helicoidal screw of constant feed rate . the evacuation is of about 73 % by weight and the standard deviation is only about 1 . 3 %. the dosing time has been improved by about 20 % compared to the traditional canister . while illustrative embodiments of the invention are disclosed herein , it will be appreciated that numerous modifications and other embodiments may be devised by those skilled in the art . for example , the wheels may be of various other types , shapes or constructions that may also be appropriate for the intended result provided they are capable of gearing on the auger or to one another .
the invention relates to a dispensing canister that improves dosing consistency and powder evacuation , particularly when dry powdered beverage - forming or food - forming material having poor intrinsic flowing properties are to be dispensed . the canister includes a reservoir having two terminal walls and two side walls , a rotatable volumetric dosing device longitudinally extending in the reservoir , and a main agitating wheel arranged to gear on the rotatable volumetric dosing device to rotate in the reservoir upon actuation of the rotatable dosing device . the secondary agitating wheel is arranged to gear on the main agitating wheel and the two wheels are vertically offset so that the main wheel is arranged to act in a downward rotation closer to a first terminal wall whereas the secondary wheel is arranged to act in a downward rotation closer to the second terminal wall .