US2792030A - Powder feeding machine - Google Patents

Description

ay 14, 1957 l E. A. WAHI. 2,792,030

POWDER FEEDING MACHINE 16 Sheets-Sheet l Filed March l. 1954 May mi 1957 E. A. WAHL.

` POWDER FEEDING MACHINE Filed March l, 1954 TO ELECTRO- MAGNEHC VIERBTORS AMPLIFIER 16 Sheets-Sheet 2 May 14, 1957 E. A. WAHL POWDER FEEDING MACHINE 16 Sheets-Sheet 3 Filed March l, 1954 May 14, 1957 E. A. WAH| 2,792,030

POWDER FEEDING MACHINE Filed March l, 1954 16 Sheets-Sheet 4 May 14, 1957 E. A. WAHL POWDER FEEDING MACHINE 16 Sheets-Sheet 5 Filed March l, 1954 f inw MM M 4,2/ j m IEE-i E. A. WAHL POWDER FEEDING MACHINE 16 Sheets-Sheet 6 May 14, 1957 Filed March A1, 1954 May 14, 1957 E. A. WAHL POWDER FEEDING MACHINE 16 Sheets-Sheet '7 Filed March 1, 1954 May 14, 1957 E. A. WAHI.

POWDER FEEDING MACHINE 16 Sheets-Sheet 8 Filed March l, 1954 May 14, 1957 E. A. WAHL 2592,03

POWDER FEEDING MACHINE .Filed March 1, 1954 1e sheets-sheet 9 E. A. WAHL POWDER FEEDING MACHINE May 14, 1957 Filed March l, 1954 ay M, 1957 EA A. WAHL 2,79230 POWDER FEEDING MACHINE Filed March 1, 1954 16 Sheets-Sheet 1l E. A. WAHL PCWDER FEEDING MACHINE May 14,I 1957v 16 Sheets-Sheet 12 Filed March l, 1954 /77 /40 Kif/621% Zdene :y MZZ May 14, 1957 E. A. WAHL. 2,792,030

l POWDER FEEDING MACHINE Filed March l, 1954 16 Sheets-Sheet 15 May 14, 1957 E. A. WAHL. 2,792,030

POWDER FEEDING MACHINE Filed March 1, 1954 16 Sheets-Sheet 14 JOE May 14, 1957 E. A. WAHL 2,792,030

POWDER FEEDING MACHINE Filed March l, 1954 16 Sheets-Sheet 15 @w54 ma jay/@22% May 14, 1957 E. A.WAHL 2,792,030

POWDER FEEDING MACHINE Filed -March l, 1954 16 Sheets-Sheet 16 United States Patent O POWDER FEEDING MACHINE Eugene A. Wahl, Glen Ridge, N. J.

Application March 1, 1954, Serial No. 413,108

35 Claims. (Cl. 141-145) This invention relates to automatic feeding apparatus and more particularly to a machine Iof novel con-struction for continuously feeding precisely measured quantities of a powdered material into a medium or into a container.

Various powder-feeding machines have been provided heretofore. However, such prior machines are of conrplex construction and, more importantly, are not adapted for uniform operation with powdered materials of widelydifferent ow characteristics as, for example, free-flowing granular dry powder and sticky amorphous powders. Nor are .such prior machines readily adjustable to compensate for the widely varying densities found in powders of the same composition. Still further, the constructions Vof existing machines are such that they are not adapted for convenient dismantling and reassembly, by unskilled help, for purposes of periodic sterilization 'as is required particularly in the pharmaceutical field.

An essential feature of my machine resides in a novel arrangement wherein powder from a storage hopper is fed at a predetermined and positive rate to Ia measuring and dispensing station from which precisely measured amounts of the powder are discharged at a controlled rate. The measured amounts of powder may -be discharged directly into a medium as, for example, liuoride salts into a stream of water for control of tooth decay. By provision of a suitable bottle-moving system the discharged powder from the measuring station may be fed directly int-o bottles at a high rate of Voperating speed and with a high degree of accuracy.

Machines which are designed to discharge measured or predetermined quantities of powder or granular material directly into a medium at a specified rate are known in the art as dry feeders whereas machines in which measured quantities of powder are fed directly into containers Iare known as filling machines.

With respect to feeders, those in general use fall into two categories; namely, the volumetric type and the gravimetric type. Present volumetric devices show measuring inaccuracies ranging from 3-15 percent, the prin cipal source of error being the inability of these devices to handle material with varying ilow characteristics ranging from free-flowing to sticky conditions often met under varying atmospheric and storage conditions. Also, some materials naturally resist gravitational ow by reason of the fact that such particular materials are sticky under most all conditions of use other than those subject Ato elaborate control. Consequently, such materials cannot generally be handled by present volumetric feeders. Gravimetric feeders, on the other hand, usually Vare'of more complicated construction and depend upon a weighing belt to control the ow-of powder from the supply hopper. Their high cost of construction and operation serve to restrict their use to such operations where greater accuracy is an absolute necessity. However,`gravimetric feeders Ialso reilect inaccuracies at times ranging from 2-5 percent. Aminherent source oferror in such feeders lies in the fact that the absolute dry weight of material fice measured out varies as the natural moisture content of the material uctuates. Such variations often exceed by far the mechanical inaccuracies of the weighing process. volumetric feeders are much less subject to this kind of error because the volume of moist materials does not change appreciably with moisture loss or pick-up and a given volume of material will more nearly reduce to the same weight or" dry material irrespective of moisture content. My novel feeder operates on the volumetric principle and includes numerous features which overcome the disadvantages of prior devices of this class.

A feeder constructed in accordance with my invention is also specically adapted for use as a powder-filling machine. A majority of machines heretofore employed for filling bottles with powder include either a rotating auger or operate on a differential air pressure system wherein the powder is drawn into a measuring chamber having a line-mesh screen bottom. In the former case a sticky powder will adhere to the auger and a granular, dry powder tends to overrun the auger when the latter is disposed in the customary vertical position. There occurs, therefore, a wide variation in the quantity of powder discharged from an auger rotating at constant speed. In the case of the differential air pressure machines the screens become progressively clogged with resultant serious volume variations. A powder-filling machine made in accordance with my invention is not subject to the mentioned influences and, therefore, operates at an accuracy far beyond that possible heretofore.

'In my co-pending United States patent application, Serial No. 388,543, riled October 27, 1953, I disclose a powder xbottle-lilling machine which includes a plurality of what may be termed reciprocating measuring chambers associated with a storage hopper. Such measuring chambers transfer precisely-measured quantities of powder from the hopper into the bottles and the machine has an operating accuracy and reliability factor far superior to the auger and pressure-diiferential machines. The present invention diiers from that disclosed in the referenced copending application in numerous respects. Primarily, my present invention comprises an arrangement wherein powder from the storage hopper is vibratorily moved along a trough, or chute, to a measuring station. At the measuring station, rotary measuring chambers are filled with powder 4at one position and at another position -such chambers discharge the volumetrically-measured quantities of powder either into a chute for directing the powder directly into a medium or into a funnel for directing the powder directly into a bottle or other container.

An object of this invention is the provision of a powderfeeding machine of simple, straight-forward design, rugged construction, of positive operation and having a high degree of operating accuracy.

An object of this invention is the provision of a powderfeeding machine operating o-n the volumetric metering principle having a high operating accuracy and adapted for use as a bottle-lling machine for pharmaceutical powders requiring sterile handling.

An object of this invention is the provision of a powder-feeding machine comprising a storage hopper for the powder, a vibratory trough having one end communicating with the hopper opening and the other end communicating with a measuring station, a rotary member at the measuring station and including a'plurality of discrete measuring chambers, means to lill the measuring chambers with powder at one position and means to discharge the powder from the measuring chambers at another position.

An object of this invention is the provision of a lower end of an inclined trough, a plurality of measuring chambers at the upper endl of the trough, means to vibrate the trough whereby powder discharged from thehopper moves up the trough and into the measuring chambers, automatic means to discharge the powder from the measuring chambers, and means to return an overilow of powder from the upper end4 of the trough backY to the lower end of the trough.

An object of this invention is the provision of a powder-feeding machine of the type wherein powder'is fed from a storage hopper into a plurality of measuring chambers for subsequent discharge therefrom at apredetermined Vrate and including means adjustable to vary the volumetric capacity of the measuring 4chambers and/or including means to direct the dischargey of the powder from the individual measuring chambers at two positions at a predetermined ratio.

An. object of this invention is theA provision of apowderfeeding machine comprising a storage hopper for thepowder, an. inclined trough having a lower end/ spaced from the hopper. opening, a rotatablemembendisposed at the upper endof the trough and including a pluralityof measuring chambers, means tovibratethe. trough so as to causev the powder discharged from the hopper opening to move up the trough and into. the measuring chambers, and` means, including vibration effective. uponrotation ofA the rotary member to, discharge. the powder from. the, measuring chamber.

An object of this invention is the provision of an. automatic machine for filling bottles with powder and; comprising a storage hopper fo r the powder, an inclined trough adapted to receive powder. from thehopper, means to vibrate the` trough so as to, move. the4 powder upwardly thereon, a plurality of measuring chambers movable into. positionI to beY filled by powder which hasv been moved u p the t rough,kr neans to vibrate said measuring chambers,

means to move a successionpof bottles into bottle-filling association with the measuring chambers, and means to discharge the powder from the measuring chambers into the bottles.

An object of this invention is the provision of an auto-V maticfmachinefon filling bottles with powder and comprising an inclined trough,l astorage hopper for powder disposed over the trough andv having an opening for discharging Vpowder into the lower endy of the trough, a rotatable member at the upper end of the trough and including a plurality of peripherally-spaced measuring chambers, means to vibrate the hopper and` rotatable member and the troughwhereby powderv discharged from the hopper moves up the trough and into the measuring chambers, means for rotating a plurality of bottles in 1 alinement with certain measuring chambers, means to discharge the powder from the filled measuring chambers into bottles aligned therewith, and means to move the filled bottles on to aconveyor belt. *i 'l M An object of this invention is the provision of a Inachine for filling bottles with powderand, comprising a,

vibratory trough adapted to receive powder atV one end,

a plurality of measuring chambers adapted to receivev powder at the other end of the trough, adjustable means to vary the capacity of the measuring chambers, means to feed a succession of bottles toward the measuring chambers, means mechanically coupled to the measuring chambers to aline the bottles into individual bottle-filling registry with the measuring chambers, means to discharge the powder from the measuring chambers into the alined bottles and means to remove the filled bottles from the bottle-filling registry position.

T hese and other objects and advantages will become apparent from the following description when taken with the accompanying drawings illustrating various modifications ofthe invention. It is to be understood that the In the drawings wherein like reference characters denote like parts in the several views:

Figure l is a side elevation of a powder-feeding machine made in accordance with one embodiment of my invention, certain parts being cut away and others being shown in section to facilitate an understanding of the construction;

Figure 2 is a top view of such machine with parts cut away;

Figure 3 is an enlarged, fragmentary side view of the front end of the feeder with parts drawn in section to show the measuring chamber arrangement;

Figure 4 is an enlarged, fragmentary, top view correspending to Figure 3;

Figure 5 is a fragmentary view showing one of the end plates having an arcuate side wall cooperating with the rotary wheel forming the measuring chambers;

Figure 6 is a similar view showing a modification of the other end plate which has an arcuate side wall cooperating with the rotary wheel to define the point at which the powderis discharged from the measuring chambers;

Figure 7 is a fragmentary, top view of the front end offfthe feeder and showing another form of the measuring chambers;

Figure 8 is a sectional view taken along the line J-I of Figure 7;

Figure 9 is similar to Figure 8 but showing an arrangement wherein powder discharged from the measuring chambers is directed into a bottle;

Figure l0 is a fragmentary, top view similar to Figure 7 and showing a modification wherein the rotary wheel includes two setsy of measuring chambers for feeding measured quantities of two powders into separate, directing troughs;

Figure 11 is la plan view-showing another modification of the multiple measuring chamber arrangement;

Figures l2 and 13 arefragmentary, plan views to illustrate the operation of the arrangement shown in Figure 11;

Figures 14-16 are fragmentary, vertical sections to further illustrate the operationV ofy the arrangement shown in Figure ll;

Figure 17 is, generally, similar to Figure 2 and includinga return trough for automatically returning the overflow of powder to the hopper end of the powder-feed trough;

Figure l8is a sectional view taken along the line A-A of Figure. 17;

Figure 19 is a-section'al view taken along line B-B of Figure 17;

Figure 20 is a side view, with parts in section, of the machine shown in Figure 17;

Figure2l isA similar to Figure 2O but taken from the opposite side;

Figure4 22 is `a fragmentary, perspective View of the return trough;

Figure 23is a fragmentary, top view showing a machine for filling bottles with powder as made in accordance with my invention;

Figure 24 is a side view, with parts in section, of such machine;

'Figure 25 is a fragmentary, side view, with parts in section, of the hopperend of the machine;

Figure 26 is essentially a front view of the machine, taken'alon'g the line C-C of Figure 24;

Figure 27 is a top view showing a safety switch controlled by' the bottles being fed to the filling station, said switch serving-to stop the operation ofthe machine in the event empty vbottles are not approaching the filling station;

Figure 28'- is an electrical circuit diagram ofthe bottlefilling-machine;

Figure 29 is a fragmentary side view, drawn to an enlarged scale, of the bottle-filling station with the bottle in-feed conveyor removed; p

Figure 30 is a horizontal section taken along the line D-D of Figure 29;

Figure 31 is a similar section taken along the line E-E of Figure 29;

Figure 32 is a similar section taken along the line F-F of Figure 29;

Figure 33 is'a similar section taken along the line G-G of Figure 29;

`Figure 34 is a top View of that portion of the machine shown in Figure 29; and

Figures 35 and 36 are plan views showing a dual, adjustable disc arrangement to condition the machine fo operation with bottles of a given diameter.

Reference is now made to Figures 1 and 2 which are, essentially, a side and top view, respectively, of the basic powder-feeding apparatus. All components of the apparatus are supported in operative relationship on ya platform provided with four bolts 11 and cooperating nuts 12 by means of which the platform can be adjusted to a level position on a at surface 13. A more-or-less rectangular trough, or chute 14, is rigidly secured to an electro-magnetic Vibrator 15 comprising a solenoid 16 including a soft-iron core spaced from the soft-iron frame, or yoke, 17. The vibrator frame 17 has its ends secured to a relatively heavy metal block 18 which, in turn, is supported on the sub-base 19 by suitable vibration-absorbing mountings 20, said sub-base being rigidly secured to the platform by fastening screws. The electro-magnetic vibrator is of conventional construction but I here wish to point out that the trough 14 effectively is supported solely by the vibrator frame 17, as will be explained in more detail hereinbelow with reference to Figure 3. Consequently, when the vibrator solenoid is energized by a pulsating current the resulting mechanical vibrations of the frame 17 are directly imparted to the trough for purposes explained in detail hereinbelow.

A storage hopper 22 for powder has its discharge opening positioned within, and at one end of, the trough, as shown, the trough cover 23 being provided with a suitable aperture for this purpose. The hopper is supported on the platform 1? by a rigid post 24, said hopper being secured to the post by a circular band 25 having its ends formed about the post and clamped thereto by a bolt 25 and cooperating nut 26. It will be apparent, therefore, that such arran-gement affords a ready means for adjusting the vertical position of the hopper relative to the trough to thereby space the discharge opening of the hopper a desired distance from the trough bottom. Such positional spacing of the hopper opening controls the rate of discharge of the powder 27 from the hopper into the trough. The hopper is provided with a cover 28 and the entire hopper may be removed by simply unscrewing the locking screw 29 that is threaded into the band 25 at a point opposite the supporting post 24. Secured to the outer wall of the hopper is a second electro-magnetic' vibrator 30 which, when energized, vibrates the hopper to assure a positive discharge of the powder therefrom.

As shown clearly in Figure l, the trough 14 has an inclined bottom terminating in a level portion directly beneath the discharge opening of the hopper. If, now, it be assumed the electromagnetic vibrators 1S and 30 are energized the powder will ilow from the hopper into the trough and will be moved up the inclined trough bottom by vibration. The character of the vibrations imparted to the hopper is not critical since any slight amount of vibration will assure a downward flow of powder into the trough. However, the vibrations imparted to the trough, by the vibrator 15, are such that the entire trough vibrates longitudinally in essentially a horizontal plane, as indicated by the solid arrows placed along the trough bottom. Such trough vibration is not solelyand strictly mono-planar but is somewhat elliptical by reason of the attachment of the vibrator frame ends t the relatively heavy block 18. Still further, the vibrational movement of the trough is substantially greater in one direction than the other. Specifically, the backward movement of the trough, that is, toward the post 24, has a velocity component exceeding that of the forward trough movement. Consequently, the powder carried by the lower end of the trough is caused to move up the inclined surface of the trough bottom. I have found that such upward movement of the powder is positive and continuous resulting in a uniform flow of powder from the left end to the right end of the trough and the rate of such powder ow is a functionof the frequency and amplitude of the trough vibrations.

.lf it be assumed that the discharge endof the trough (that is, the right hand end shown in Figure l) has an unobstructed discharge capacity equal to or exceeding the volumetric flow of the powder up the inclined surface of the trough, the stream of powder on such inclined surface will have a depth dependent upon the amplitude and frequency'of the trough vibrations, the size of the hopper discharge opening, the spacing of the hopper end from the trough bottom and the ow characteristics of the particular powder. In any event, the only mentioned variables which cannot be controlled positively are the characteristics of the particular powder. If now, we assume that the discharge end of the trough is partially blocked so that the quantity of powder actually owing out of the trough is somewhat less than that owing up the inclined surface, the depth of the powder stream will be increased. .I have found that in this case the depth of the powder reaches a maximum value since the'upper particles of powder actually flow back down along the inclined trough portion over the upwardly-moving particles proximate tothe trough surface. Such simultaneous, opposed movement of the powder is indicated by the dotted line arrows placed into the powder stream, Figure l. The excess powder, that is, the powder which flows back toward the lower end of the trough increases the depth of the powder around the discharge end of the hopper. Such build-up of the powder reduces the rate at which powder hows from the hopper into the trough. From this it will be seen that the upwardly-inclined vibratory trough arrangement results in what may be termed an automatic feed-back of excess powder and a concurrent control of the rate of discharge of powder from the hopper, highly desirable features in apparatus of this type.

While the arrangement just described is suitable for certain applications which do not require a high degree of precision with respect to the quantity per unit time of powder fed into a medium, I prefer to incorporate an arrangement for volumetrically-metering precise quantities of powder discharged from the trough. In order to relate such metering apparatus to that already described continued reference is made to Figures 1 and 2, although a detailed description thereof will follow with specific reference to Figures 3 and 4. The discharge end of the trough is provided with a downwardly-inclined chute 35 for directing the discharged powder either directly into a medium or into an intermediate trough or chute 36. It is here pointed out that at the front, or discharge, end of the vibratory trough 14, the bottom surface thereof is horizontal. Specifically, the trough bottom includes a horizontal lower portion at the hopper, an inclined center portion, and a horizontal upper portion at the discharge end. The passageway of the trough, at the discharge end, is, effectively, completely closed by a plate which has a horizontal portion 37 in smooth contact with the upper surface of a rotary disc 38 and an upwardly directed portion 39 terminating iiush with the upper end of the trough walls. The disc 38 has its lower surface in sliding contact with the trough bottom and is rotated by a motor 40 coupled to a reduction-gearing box 41 by the belt 42 and as will be described in more detail hereinbelow. AA pair of end plates 44, 45 having arcuate side walls conforming to the diameter of the.disc,38'close,off the'trough on either side ofthe disc. Thus; the powder from the trough can-pass to the discharge chute 35 only along1the chambers formed. by the peripheral recesses in thel disc 38 upon rotation ofthe latter, it being noted that a portion of the disc extends free and clear over the chute 35.

Inasmuch as Figures 3 and 4 are drawn on separate sheets, it is believed an understanding of the construction and operation-of the discharge portion of the trough will be facilitated if the description'is restricted to direct attention toonly one figure at a time, even though such procedure will entaill a certain..amountV of repetition. Attention, therefore, is first directedto Figure 4 which is a fragmentary view, drawn to an enlarged scale, of the corresponding discharge end of theapparatus shown in Figure 2. The disc 38is' secured to avertical shaft and when the motor. 40 senergizedl such disc rotates at a constant, predetermined speed' in-the direction indicated by thev arrowthereon. A major portion of the disc is covered by the horizontal section 37 of the plate which hasthe upturnedside walls 39,' such plate being held down and secured to the trough sidewalls by screws 48 and 49. The side plates 44, 45 have a thickness approximately 0.001 greater than that of the disc and each includes an arcuate sidewall corresponding to the maximum disc radius. The relatively short plate 44, see also Figure 5, is secured to the trough by screws 47 passing through the trough bottom, and the relatively long plate 45 is similarly secured by the other screws 47. The parts are so dimensionedfthat the outermost edges of the toothed disc 38 will be in smooth, sliding contact with the arcuate walls of the plates 44, 45 upon rotation of the disc. Inasmuch asthe lower surface of the disc is in smooth, sliding contact with the trough bottom and the upper disc surface is in smooth, sliding contact with the bottom of the plate portion37 it will be apparent that powder can pass from the troughy to the chute 35 only upon rotation of the disc, and the quantity of powder so passed depends upon the volume of the disc recesses and the speed of disc rotation. Thus, the individual recesses formed in the peripheral surface ofthe disc may be termed measuring chambers, each such chamber moving a precise quantity of powder. It should be particularly noted that a portion of the disc extends beyond, to the left of, the

offset portion of the vertical wall 39 and into contact with such powder as may be at this end of the trough, and an opposed disc portion extends over the inclined chute 35. The rate at which the powder is moved upwardly along the trough to the discharge end thereof is adjusted so P leave the chambers and, in the case of the Figure 4 art rangement, spread along the bottom of the trough to be vibrated into the chute 35. At this point attention is directed to Figure 6 which illustrates a longer side plate 45. Specifically, the right handV end of the plate 45 terminates at the point where the inclined chute 35 joins the main trough 14. it will be obvious that in such arrangement the powder will be discharged directly on to the chute 35 from the individual measuring chambers. Alternatively,` a similar discharge action will occur in the Figure 4 construction upon rotation of the toothed disc in a clockwise direction. ltv may be well to here again point out that thc the entire trough, including the toothed disc, is vibrated as alunit thereby assuring not only a positive. feed of the powder to the measuring chambers but' also the discharge of the powder from the measuring Upon further disc rochambersto. the directing chutey and from such;.chute to.

a desired point.

Referencec is now' made specificallyv tol Figure` 3' which is an enlarged, fragmentary view of theV front end' ofthe apparatus and, essentially, a.y sectionalfview taken along the line K-K of Figure 4. The output shaft 55', of the gear boxk 41, has attached thereto a universal' joint: 56 which, in turn, is coupled to a second universal joint 57 by the loose-fitting rod 58. The upper joint 57 is attached to a shaft 59 which passes through afiange bearingtl and is securely fastened tothe toothed disc 38 by any suitable means, the ange bearing 60. being secured to the bottom of the trough, as shown. It' will be noted that the universal joints are loosely coupled to the associated shafts by means of pins passing through elongated slots formed in the shaftszSS, S8 and159. Thus, the trough may be raised. or lowered somewhat relative to the platform 10 without effecting the drive shaftv arrangement between the shaft 55 and the disc 38. More importantly, the illustrated' drive shaft arrangementA does not impede the mechanical vibration ofthe trough and disc since the trough is' notA supportedl by the drive shaft.

Asralready explained, the vibration ofthe trough causes the powder to flow ina stream up the inclined portion of the trough bottom` and to pile up on the horizontal portion of the troughv bottom against the forward edge of the discv andthe vertical wallportion 39 of the plate 37. Hence, as the disc rotates, the powder completely fills the individualmeasuring chambers as they pass beyond, that is, to the left of the Wall' 39, one such chamber X being visible in the Figure 3`- view. Such filled chambers are closed off as they pass by the side plate 45, see Figure 4, and eventually are rotated clear of all obstructions over the inclined chute 35, as shown by thechamber X'. Since the disc rotates continuously and powder is fed to the disc at a rate exceeding the discharge rate of the measuring chambers, it will be apparent that individuallymeasured quantities of powder are discharged to the chute at a predetermined rate. In the case of a powderfeeder such measured quantities of powder can be directed by the chute directly Iinto a medium as, for example, fluoride fed into a stream of water.

A powder-feeding machine constructed as hereinabove described includes numerous structural and operational features. The machine is of simple, straight forward, rugged construction promoting long, trouble-free operation. Those parts coming into contact with the powder are readily dismantled for purposes of sterilization. Specifically, the hopper is removable simply by unscrewing the fastening screw 29, see Figure l. The entire trough is removable simply by removing the bolts which secure it to the vibrator frame 17. As will be clear from a study of Figure 3, by making the slot in the shaft 59 open-ended, the disc 3S and the trough may be uncoupled from the drive shaft arrangement by simply raising the trough. By providing an inclined bottom on the trough, between the hopper and the measuring chambers, I provide a positive, controllable flow of powder to the measuring chambers with an automatic feed-back flow of the excess powder. rI'he use of measuring chambers of equal and precise volume content, coupled with the mechanical vibration thereof, assures an exceptionally high degree of accuracy. A machine made as herein dcscribed has an operating accuracy of better than onehalf of one percent in any range from ounces per hour to tons per hour and such accuracy applies whether checked on a minute-to-rninute or hour-to-hour basis. Further, since the massi of the powder in the hopper is disassociated from the measuring function the accuracy of my machine obtains irrespective of the amount of powder in the hopper. Still further, the character of the powder, whether sticky or free-owing, and the moisture content thereof, do not adversely affect the operation of the machine since such` factors are effectively rendered in-

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