US1828143A - Feed grinder - Google Patents

Description

Oct. 20, 1931. v E. R. HOBBS ET AL 1 1,828,143

FEED GRINDER Filed Jan. 14, 1928 3 Sheets-Sheet 1 Oct. 20, 1931. R HOBBS ET AL 1,828,143

FEED GRINDER Filed Jan. 14. 1928 s Sheets-Sheet 2 Oct. 20, 1931. I E. R. HOBBS ET AL 1,828,143

FEED GRINDER Filed Jan. 14. 1928 3 Sheets-Sheet 5 wuemtoz attozmm Patented Oct. 20, 1931 STATES 1 PATENT OFFICE.

ELBERT B. HOBBS, 0F CASTLEIEORD, IDAHO, AND ARCH V. STOMIBAUGH OI! HOLBROOK;

NEBRASKA.

FEED GRINDER Application filed January 14, 1928. Serial No. 246,874.

Our invention relates to the art of grinding, and especially of grinding feed for stock, and it has for its object the production of an improved method of grinding and crushing materials such as feed, and improved apparatus for the practice of said method.

@ur invention is based on the use of a hammer principle as distinguished from the oldfashioned burr or contact grinding principle. /Ve find that a hammer typeof mill, in which the grain is not crushed between two rough surfaces but is merely struck by hammers moving at high speed, and is ground by impact alone, has certain advantages, viz: lit uses less power, it does better work, it does not heat the grain, its capacity is greater than that of the burr mill, and any foreign substances, such as loose nuts, bolts, etc. ac cumulating in the mill do not injure the same.

in follbwing this method of grinding, our

general plan of operation is to allow the grain to fall to the bottom of the grinding chamber, where it is struck by fast moving parts and crushed by impact, the fine ground grain being gradually worked down and then drawn away by suction, to a point where the meal is separated and allowed to fall into a sacker. In order to obtain the best results, the following must be observed:

First, the grain should not be fed in at the top of the mill, to be hammered around promiscuously and struck by all parts of the fan and other moving elements. To break the grain by impact a high minimum velocity is required, and in practice this required velocity may be obtained in the greatest degree from the periphery of the fan or other moving member and any rain struck by slower moving parts of the fan is not broken proportionately, while grain struck bythe slowly moving parts near the center of the mill is not broken at all, but merely carried or hammered around and around. Nevertheless, all this operation consumes power. In practice we find that a minimum velocity of 2000 R. P. M. is required to grind successfully with this type of mill, and a speed of 1000 R. P. M. will hardly grind at all, while on the other hand as the speed rises above 2000 R. P. M. the grinding capacity increases much-more rapidly than the increase in speed. Thus it is apparent that to obtain the highest efiiciency the grain should be struck by the periphery only of the moving member and in order to attain this, we feed material into the mill from the bottom up.

Second, it is apparent that the impact of the blades of the mill will be more efi'ective if a pile of grain is struck instead of scattered grain suspended momentarily in the air, or lying on the floor of the chamber. A fan of less than 20 inches in diameter rotating at a velocity of 2000 R. P. M. and a maximum peripheral velocity of less than 10,000 feet per second would have little effect upon a single grain, but will pulverize a large percentage of the grain instantly if collected in a compact pile. Consequently we arrange so as to collect our grain in a compact pile to be struck.

Third, in order to attain maximum efficiency in grinding, the grain when struck must be promptly removed,i-f sufliciently reduced in fineness, and any particles not reduced to the desired fineness must be returned for further treatment. We attain these requirements by providing a casing with perforations of the desired fineness, and we have found that it increases eficienoy to place these perforations around the periphery of the easing, that is to say, around the periphery of the grinding wheel. The casing is then circular with a fiat head, against which the grinding wheel turns, and the grain after being struck is drawn or forced through the openings in the side or periphery of the easing by a suitable blast. For reasons that will be stated we employ grinding blades to strike the grain, and wehang these blades in air passages in the wheel, admitting air near the center and forcing it to go through these pas sages to the periphery around the grinding blades and out through the screen, thus assisting in forcing the ground grain through the screen or casing. We have found however that a continuous blast through the air passages is too much for convenience in handling the ground grain, as it tends to blow it too far from the mill and requires too large a collector to et it into the sacker.

We there ore employ an intermittent blast, whereby we also conserve power. The

5 method of producing intermittent blast is simple, comprising ports or openings to register with openings in the air passages at certain points in their rotation, when the blast is required. In practice the air is admitted through these 'orts a little before the grind ing blades reac the screen or perforated portions of the casing, so that the actual blast through the air passages will be at its maximum when needed. In order to still further strengthen the blast, making it a maximum at the instant of application, we use an auxiliary fan or fans to compress the air and force it into the air passages under initial pressure. As described hereinafter, the means for producin this pressure blast is a closed chamber outsi e the flat face of the casing, and the fans compress air in this chamber so that when the ports are opened into the air passages, the air rushes into the passages and instantaneously builds up pressure. The rotation of the parts, the admission of such pressure, and the stroke of the blades on the grain are so timed that when the grinder reaches the screen the blast for discharge is in full force. In addition to the ordinary openings or ports which admit the blast intermittent y to the air passages in the mill, we provide means to roduce a heavy continuous last when neede to elevate the ground material to a required height, or the like. These means comprise adjustable openings in the mill wall and registering openings in the wheel or fan body, with peripheral discharge for same. When all these parts are open, the grinding body or fan becomes in effect a centrifugal blower with continuous discharge through the perforated side of the casing. With this design built into the mill any desired blast can be obtained by merely regulating the adjustable opening in the side wall.

Fourth, for a general utility mill it is usually necessary to have a cob crusher in connection, and in the usual type of high speed mills such a device as a crusher is attached to and driven by a separate shaft. We have found it possible however to incorporate the crushing feature into our principal method, and to combine the apparatus so that our cob crusher is driven by the main shaft of the grinding r'nill. We have found that a crusher operating at a speed of2000 rpm. will act efliciently with only two fingers one upon each side of the crusher; but such a device requires special features to prevent certain disadvantages. For example, if the discharge feed should be shut off, a two finger crusher would fill the crushe'r chamber and then throw off cobs on the upward movement and so bury itself, causing a loss of power and tending to choke the machine. We remedy this by having separate fingers secured on the shaft movably so that when the crusher is not rotating the fingers can fall into pockets, being controlled by weights whose inertia tends to cause the fingers to stand out straight when the crusher body is in motion. These weights have so much inertia that crushing a cob will not deflect the fingers to any extent. The weight is so proportioned that at a speed of 2000 r m. it requires two revolutions, more or less, or a finger to leave its pocket and stand out straight. If the cob crushing chamber becomes gorged and choked pressure on the fingers through an entire revolution is sufficient to cause them to lie flat until the choke is relieved. We also rovide a speed actuated governor for regu ating the feed opening from the cob crusher, and fixed means for closing the same when grinding small grain that needs no crushing, but which can be removed when grinding ear corn. A special governor is required for these purposes, because the usual speed governor merely varies the speed in proportion to the work done. and would not control a source of power sufficientto prevent variation of speed. We have devised a combination speed and torque governor by which the feed will be automatically regulated with any kind of motor, either one powerful enough to maintain an invariable speed under all loads, or one just sufiicient to operate the mill under normal loads. 'We have also provided an auxiliary governor that is regulated by the work done by the cob crusher so that if the crusher is doing heavy work then this regulator automatically opens the feed opening, and when the draft upon the cob crusher is reduced then the feed opening is automatically reduced in size. This makes a triple combination governor all mounted upon a single shaft. By means of it, ear corn can be ground and a coarse combination of cobs, etc. can be fed more readily than if grain were shoveled in, or ear corn were substituted.

Fifth, to insure the smooth running of the whole machine we mount the journals in elastic spring seats.

Sixth, we present certain details of construction including a method of formation of the perforated screen, in which the said screen or casing for the grinding wheel is drilled and then stamped with corrugations, having two or more rows of holes in the same corrugations. We have also devised a detachable knife which we have bolted to the cob crusher fingers and used for cutting hay and grinding it, with good results. e have also designed a special form of grinding blade which has its body perforated and the edge preferably solid, so that it will wear longer and the blade will retain its shape better. We have also devised a form of corrugated screen with teeth milled or stamped upon its grinding surface to help cut the grain, and still another form in which the holes are staggered and drilled through obliquely behind 2 is a section on the line 2-2 of Fig. 1.

Fig. 3 is a plan View, and Fig. dis a side view of one grinding blade, with connected parts broken away.

Figs. 5, 6, 7 aresections taken on the lines 5, 6, '7 respectively ofFig. 1 looking in the direction of the arrows.

Fig. 8 is a view of a portion of the screen or casing made after the fashion of a ras with holes drilled behind the teeth to permit the egress of the ground material.

Fig. 9 is an inner face view of the part shown in section in Fig. 8.

Referring to the drawings, Fig. 1 shows the full assemblage of our feed grinder with the casing and enclosing walls in section and the principal operating parts in side elevation. l is a frame carrying journal hearings 2-3 which may he of any desired or suitable type and may be multiplied and their location changed without departing from the invention. Supported on the frame 1 is a casing 4 the upper portion of which is closed in by one wall of a hopper 5 which const1tutes the general intake feed hopper of the machine. Material to be ground is dumped in the hopper 5, WOIliS dOWIl through the cob crusher 6 into the lower part of the casmg 4:, piles up at 7 beneath the grinding blade 8 and when struck i) said blade (see Fig. 2), is driven by the lo ast of air through the air passage 9 into and through the screen or perforated casing 19 and thence through the discharge passage 11 to the sacking platform or elsewhere according to design. This general statement of function will enable the connection and operation of the difi'erentv parts to be grasped without lengthy description. The main drive shaft is marked 12 and is journaled in the two bearings 2-3, extendin through the machine from one to the ot er, and preferably mounted as shown, on elastic spring seats. Upon this shaft a sleeve 13 is secured within the box 14 for the pur pose of governing the position of the closure or outlet plug 15 of the cob crusher 6. The sleeve 13- carries cams 16-17 which work in slots opposite projecting fingers 31- 32 of the cylindrical member 15, while the latter slides back and forth in a flanged orifice 18 in the side of the hopper 6 and also turns therein with the drive pulley 29 and the box 14. The working of these cams, both of which turn concentrically with the sleeve 13 around the pulley 29, is by means of pinions 19-20 meshing with a. gear wheel 21 which is mounted on the sleeve. Each of the pinions 19-20 carries a tubular sleeve 22 or 23 and on these two tubular sleeves are mounted two weights 24-25, which constitute a governor responsive to concentrifugal force, which is to say speed of the shaft increases and the balls 24-25 are thrown more and more outwardly, they turn the sleeve 13 so as to pull back the cylindrical stopper 15 and open up more and more the discharge opening 26 ofthe hopper 6. Thus far, the governor uses only the speed principle which is common to others, and if the mill is retarded in its'speed then the feed is reduced. However, our regulator not only regulates the speed by the responsive to speed of the shaft 12. As the I feed, but also by the torque on the main shaft,

so that if there is an excessive torque upon the said main shaft the feed is reduced even though the speed of the mill remains the same. This is accomplished as follows: The belt wheel by which the shaft 12 is driven, is marked 29 in the drawings, and it does not fasten directly to the shaft, but is loose thereon and rocks back and forth upon it. The pulley 29 is secured to the casing of box 14,

which carries pinions 1919a, and 20-20a, the first two of which as already stated mesh with the gear 21 and through this turn the main shaft. Gear 21 through the sleeve 13 is rigidly connected with the cams ill-17 and therefore any rocking back and forth of the gear 21 also rocks the cams 161Z. The fingers 3132 of the sliding regulator or stopper 15 project through openings in the head 33 of the box 14, hence the stopper 15 turns with the box and with the drive wheel 29. It will be obvious that if the casing or box 14 and the spiral cams 16-17 do not remain in the same relation to each other the spiral cams will cause the regulator 15 to slide one way or the other and thus regulate the feed. Also, if the cob crusher, 2827 is retarded inits movement, then gear 34 will be effected, as that gear is integral with the part 39 that holds the fingers 27-28. 34 meshes with gear 35 which has attached to it a pinion 36 meshing into the gear 20a, which in turn through gear 20 is meshed with the main shaft gear 21 so that retardation of the cob crusher also results in changing the angular relations between the shaft and the drive pulley 29, and hence by moving the spiral cams 16-17 adjusts the sliding regulator 15. The net result of all naled in opposite hearings in a cylindrical body 39 which in turn is carried loosely on the main shaft 12 and is rotated by 34 through sleeve 39a. The outer ends of these shafts 37-38 are journaled in bearings in a cross head 143 loose on the shaft 12 and held in position thereon by fixed collar 143a, as shown in Fig. 1, and the body 39 is so constructed that the shafts 37-38 may be drawn out by removing said collar and cross head and may be thereby detached from the body. In normal position as shown in Fig. 1, the fingers 2728 stand vertical, with their two shafts 37-38, which carry two governor weights 4142 (see Figs. 6-7). These gov-- ernor weights at normal speeds keep the fingers 27-28 perpendicular to the shaft 12, so that as the shaft rotates in the direction of the arrow of Fig. 7, they will break and grind up any cobs or similar matter which are deposited in the casing 6 through the hopper 5. As shown in Fig. 6, if the casing 6 becomes jammed, or if the device is rendered inoperative for any other reason, as by clogging, the fingers 2728 will lie down in their recesses 40 (see Fig. 7) and the body 39 will turn idly under low power and with no torque resistance, until the condition is remedied. At the same time, the regulator will be automatically moved to give relief.

This brings us to the feed grinder, proper, shown at the left hand end of Fig. 1, and in a side view and section in Fig. 2. This consists essentially of a wheel or fan 43 bolted to the main shaft 12 and including as elements two side plates 4445 secured together by a plurality of intermediate partitions 46, 47, 48, 49, and intermediate fan blades 50, 51, 52. These blades 50, 51, 52, etc. in the order named, are made shorter in succession, the idea being that the piles of grain in building up do not touch these blades but only the main grinding blades. Of course in case the mill be fed beyond its capacity, then the small blades will each strike some from the top of the pile but in ordinary operation this is not intended.

The bottom of the casing 4 beneath the grinding wheel is bent down to form a cup or channel as shown at 7 in Figs. 1 and 2. As also in Fig. 2, this cup as one side of the peripheral casing slopes up at 53 to form a shoulder against which the grain impinges beneath the grinding blade 8. The blades 8 are pivoted at 54 in the air passages 9, and each blade is formed as shown in Figs. 3 and 4, being provided on its back with a link 55 slotted to receive a fixed pin, 56, set in the wall of the wheel, and serving as a limiting stop for the movement of the blade 8. In body contour, each blade is curved or cupped like the palm of a hand, with the outer edge 57 solid, where it strikes thegrain, but with the body 58 filled with perforations. The forward part of this blade at 54 passes over the grain pile in the cup 7, and the rearward portion of the blade 57 strikes the grain pile, whereupon the grain is thrown forward and upward the major portion thereof being thrown at an approximate angle of 40 degrees from the horizontal. The rain striking the concave surface and being efiected forward, in its forward movement bears against the forward portion of the concave surface whereby the grain itself serves as part of the general medium for transmitting power, and helps carry the blades and the wheel around. In this way some of the force of impact which might otherwise be lost is restored to the wheel.

After the grain has left the forward part of the blade 8, upon which it has exhausted a part of its force, the struck grain is thrown further forward and out toward the screen 106, where the screen further assists in grinding, making it what may be called a triple duty blade. It should be noted that the rear of the blade is so shaped that it fits the pile in its normal shape as nearly as possible, thus making impact upon the whole pile at once which greatly increases the efficiency of each blow, and we believe this to be original with ourselves. Also it should be noted that each inding blade is shown with straight sides tting the cheek plates 44 of the wheel, which in the passages 9 form side plates for the blades 8, to confine the material being ground between said plates and underneath each blade. These side blades may be formed on the blades themselves, if desired, but as the principle remains the same, it is not deemed necessary to illustrate this modification.

The reason for perforatingthe grinding blades 8 and for also perforating other blades such as 50, 51, 52, 47, etc., if desired, is because a perforated blade is more eflicient for our purpose for two reasons First, because it is rough, and second, because it allows the air to pass through it and does not permit the formation of a cushion of air beneath it or between it and the grain.

The screen, through which the ground meal passes, impelled by the air blast, is a matter of some importance in the design of our machine and the preferred form is illustrated in Fig. 2 extending from 53 to 59 forming the inner wall of the passage 11, leading to the sacker or other outlet. It will be understood that the grain when struck and reangle portion, we place perforations of an appropriate size to pass the meal and it will be observed that as the blast through the space 62 is tangential, all the crushed grain will be blown out tangentially through the perforations 107) in the screen portion 100.. The discharge through theseperforations is in straight lines tangential to the blades of the rotating wheels and maximum movement 19 is obtained for a minimum amount of power expended. In order to augment the blast up through exit 11 for higher elevating of the ground material, a slide is provided with openings that can be made to register with 5 openings leading from'the air pressure chamber 64, thus completing a continuous passage up through 11a and 11, and this in turn tends to augment the blast through perforations 106 by means of the principle of adhesion of gases to gases. We present this as a modification of the main design, the motion of the slide 10 being at right angles to the plan of the drawing in Fig. 2, andjthe handle of the same projecting through the side of the casing toward the observer.

The openings 61 in the cheek plate 45 of th grinding wheel normally rotate idly without passing any air, next to the inner wall 63 of the air chamber at of the casing 65. This casing may be continuous with the part 4, to which reference has heretofore been made,

' and in any case is secured to the latter, and completely encloses the grinding wheel, as shown in Fig. 2, including in part of its periphery the screen just described and extended on the inner face of the grinding wheel in a drop-sheet 66 which entirely closes that side of the casing toward the feed hopper, except for the opening 67 at the bottom where the grain enters. The outside casing 65 at the left hand end of Fig. 1 is provided with a pair of connected parallel face plates 6869, having central openings 7 0-71, to which are fitted the fan casings 72 and 73. The fans in these casings'are fastened to the main shaft 12, and serve as hereinbefore mentioned, to produce initial air pressure in the chamber 64, which normally passes through the open ports 7 4 (Figs. 1 and 2) into the air chambers 9 and so on as already described. When a general blast is wanted, an annular valve 75 which contains ports 74 and 76 is turned so as to open all the ports, which admits air not only to the air passages in Fig.2, but also through the openings 61 in Fig. 2 so that the entire fan becomes one centrifugal blower and the grain thrown u into passage 62 is violently beaten about hack and forth between the blades and the faces 10al0b of the screen as well as other parts of the casing until it is reduced to a fine enough meal to go through the openings at 105. In Fig. 1 the valve 75 is indicated with all the openings open. it may be rotated so as to close the 65 ports 76 which open into the ports 61 of Fig.

this case the inner surface of the screen bears 2, while still leaving the central ports 74 open for ordinary operation. In any case we have found it important to have tandem fans at points -71, in order to produce a high and steady pressure in the chamber 64. Que fan "5' does not give the same result, even though it have suficient power.

lln Figs. 8 and 9 we have shown a modified structure that may be employed in place of the stepped screen at 10a --10b in Fig. 2. In

teeth 77 similar to the teeth on a rasp, and beneath each tooth an opening 78 is drilled through, these openings being inclined at such angles that when the entire arc of the screen is in place, the opening 78 will all be tangential, or substantially so, to the advancing blades of the fans. It is to be understood that Figs. 8 and 9 show only a small part of the arc, which extends from point 59 to point 79 in Fig. 2. For those portions of the rain which strike and are thrown backwar without passing through the orifices 78, this form of screen shown in Figs. 8 and 9 we have found ver eflicient, or in other words it facilitates t e driven grinding, which is supplemental to the im-: pact grinding produced by the blades 8.

The practice of our method, and the 0 ,r-

ation or the apparatus hereinbefore descrl ed will now be understood. Grain, fine or coarse, husks and cobs, and even hay may be fed into the hopper 5, thence passing into the container 6 in which the fin ers 2728 are rotating at a high speed, whic we have specified for example at 2000 R. P. M. Here the larger and coarser portions of the charge are reduced and broken, and by means of the geared relation between the driving pulley 29 and the shaft 12, the size of the feed'opening 26 is regulated automatically according to the nature and condition of the material being thus treated. Passing out of the orifice 26 the grain and other material slides down the inner side of the casing 4 to the point-7 beneath the grinding wheel, where it piles up as best shown in Fig. 2 and forms a mass or pile large enough to be efiicientl broken and ground by impact of the grin ing blades 8 in their rotation. As the grindin wheel 43 is also mounted on the same sha 12, it is also rotated at the same high speed, which we have suggested as 2000 R. P. M. or higher. Normally, the grinding blades 8 are held out in the position shown in Fig. 2, due to centrifugal force, and when one of them comes to the pile of grain, to which it substantially conforms in shape, the entire pile is subjected to a violent blow, by which a considerable percentage of it is reduced to meal at once, and the balance is thrown up in violent motion, to be carried around by the wheel and beaten back and forth in the passageway 62 until it works back and runs down into the pocket 7 to ice retreated. As the wheel 43 rotates the ports 74 are opened and closed in succession by the rotatlon of the cheek plate 45 and each time a blow is delivered, or just in advance of the blow, pressure from the wind chamber 64 is admitted throu h the port 74 to the air passage 9 and at t einstant the blow is delivered to the pile of rain the blast is in full force, ready to proect the meal in straight tangentlal lines through the screen at 10b into the passageway 11 where it is carried off as indicated by the arrow to any desired oint such as the sacking platform. Meanw ile, the portions of rain which are not yet reduced to meal, an which rebound from the inner surface of the screen 10a 10b, are prevented from passing into the interior of the wheel by the blades 51, 52, etc. around the periphery which tend to throw out all the unbroken aim and keep it in the passageway 62, where it may be carried all the way around within the casing 65 until it again comes to the point 7, or art of it may simply drop'through the in uence of gravlty within the face plate 66 (see Fig. 1.)

The operation of the cob crusher and the adjustment of its fingers 27-28 by the automatic means shown in Figs 6 and 7 has been described, as also has the automatic 0 eration of the gears and cams within the poo ets 14, whereby constant speed is maintained reardless of variations in resistance or load in the machine.

We shall claim herein various novel features of the apparatus presented but we wish it distinctly understood that this apparatus may be modified and non-essential details may be changed without departure from the invention, and without efiecting the method. We find that by means of the simplified method of operation which we have devised, we save power, achieve a better result, and fully attain all the objects set forth in the beginning of this specification.

It is understood that any desired curvature or sha e of hammers 8 may be used that best suits t e needs of any particular machine; also that the slide 10 and accompanying chamber wall may be varied in size or omitted altogether, and the screens 10a and 10b may be varied in size to suit any special requirements, and may be extended over any part or the whole of the periphery of the casing.

What we claim is:

1. The method of reducing materials such as grain and feed, which consists in accumulating the same in a compact mass or pile, at a low point in a circle, intermittently discharging into said pile sufficient energy to reduce the same, and thereafter causing the reduced portion of the grain to be blown out of the periphery of the circle, and the unreduced portion to be returned to the lower portion of the circle for retreatment.

of contact with the material to be reduced,

said body consisting of a rotating wheel and a movable grinding blade carried thereon and means for accumulating a pile or mass of said material comprising a casing terminating in a suitable chamber beneath the grindin wheel, over which the grinding blade on said wheel passes in its rotation and becoming operated by impact discharges a sufficient amount of energy from said rotating wheel into said pile or mass of material to reduce the same to meal.

4. A grinding machine comprising a body with means to drive it at high velocity out of contact with the material to be reduced, said body comprising a rotating wheel and grinding blades carried thereon and having substantially closed radial air passages leading from the center of the wheel to said blades, means to accumulate a pile or mass of the material to be ground in such relation to the wheel that said blades will become operative by impact to discharge a sufficient amount of energy from said moving body into said mass of material to reduce the same to meal, means to introduce an air blast at the center of the Wheel and through said air passages at the approximate moment of im act of the grinding blades with the material to be ground, and discharge means for the meal, whereby the meal will be blown out from around the grinding blades at the moment when it is produced.

5. A machine for grinding feed and the like comprising a casing having a chamber at its bottom, a rotary'grinder carrying impact means in said casing, means for introducing the material to be ground beneath said rotary grinder in said bottom chamber, and means for removing the ground meal peripherally of the grinder.

6. In a machine of the class described, a circular casing, a rotary impact grinder therein, oppositely acting grinding or impact blades oppositely pivoted at the periphery of the rotary grinder, means for feeding material to be ground to a point beneath the rotary grinder but in the path of travel of said impact blades, the feeding means for feeding the material to the point of impact being composed in part of the circular casing, and the latter being formed with a shoulder against which the material impinges, together with a screen containing openings interposed in the casing beyond said wheel of the grinder, whereby the impact blades may strike the pile of material, and the latter will be reduced to meal by the impact, the parts being so shaped and arranged that the reduced or ground material will be changed to and passed out through said screen, the path of travel of said material intersecting the path of travel of said impact blades so as to impinge thereon in passing out.

7. 'An impact grinder comprising a rotary grinding wheel carrying impact blades, a

1 casing surrounding said rotary grinder and having means for feeding material to be ground therein to a point beneath the grinder, means for producing an air blast at substantially the moment of impact, and a perforated screen forming part of the peripheral casing of the grinder following the point of impact in the direction or" travel thereof, said screen containingtangential openings with an inner roughened surface.

8. An impact grinder comprising a rotary grinding wheel carrying impact blades, a casing surrounding said rotary grinder and having means for feeding material to be ground therein to a point beneath the grinder,

means for producing an air blast at substantially the moment of impact, and a perforated screen forming part of the peripheral casing of the grinder following the point of impact in the direction of travel thereof, said screen containing tangential openings with an inner roughened surface, and a supplemental slide containing openings which may be opened at will to permit additional venting at a point nearer the point of impact, where= by high pressure on the discharged meal may be relieved,

9. A grinding machine of the class described, comprising a casing, a rotary impact grinder with means to drive the same at. high speed in said casing, a pair of impact blades movably secured on said grinder, a pair of air passages with ports and means for discharging a blast of air through said passages and 'around said impact blades at substantially the moment of impact, with means to open supplemental air passages through said grinder when desired to produce a general blast through the body of the grinder and around the periphery of the entire casing, whereby the material to be ground is exposed not only to impact, but also to continued high speed travel and collision with moving parts.

of the grinder and parts of the casing.

10. The grinding machine claimed in claim 9 having as additional elements a pressure chamber, outside the side face of the casing of the grinder, means for continuously producing air pressure therein, and a valve controlling ports between said chamber and the interior of the casing, through the side wall oi the grinder.

the same and the interior of the grinder casing for producing an air blast therein and therethrough, an auxiliary inlet chamber for said pressure chamber, an outer opening in said auxiliary chamber and a pressure blower applied thereto adapted to maintain an intermediate pressure in said auxiliary chamber, with a tandem blower between said auxiliary chamber and the main pressure chamber, to raise the said pressure to the maximum required. whereby a steady and unbroken pressure for blast purposes, with continuous volume of delivery, is maintained.

12. In a grinding machine of the class described, means for preventing stalling and choking of the machine comprising a governor, working means secured on one side to said governor and a driving element secured on the other side of said governor, together with means whereby any change in torque or resistance in the working means onone side, will cause a readjustment of the relation between the driving means and the working means.

13. In an impact grinder, a rotatiiig body,

a concave hammer hinged thereto at one end with its concavity outward from the center of the rotating body, the opposite end being maintained in operating position by centrifuga-l force, and a stop to limit the outward v movement.

14 In an impact grinder, a moving body a perforated body, with its concavity down-' ward.

16. In an impact grinder, a hammer adapted to impinge against the material to be ground, and means moving with said hammer and extending into the path of said material on either side and in the rear of the hammer, to prevent scattering of said material.

17. In an impact grinder, a sloping sup port, along which the unground material slides, an obstruction in the path of said material to impede its movement and cause it to collect into a pile, and a moving part adapted to strike said pile.

18. In an impact grinder, a revolving grinding member, means to cause the uni ground material to slide downward and under said revolving grinding member, and

thereafter to be forced along by a movement of air accompanying said member to a predetermined point, an obstruction in its path at said point causing it to collect into a pile in the path of a portion of the grinding A member, and adapted to be struck thereby.

19. In an impact grinder of the type described, means to collect the material to be ground into a compact mass, and a hammer ooncaved to fit over said mass in delivering its blow.

20. In an impact grinder, a movable hammer adapted to impinge upon the material to be ground, a casing surrounding said hammer, and deflecting means in the path of material struck by said hammer and adapted to guide the same onward and outward towards said casing.

21. In an impact grinder, primary hammers to impinge against material to be ground when collected at a predetermined place, a casing surrounding the grinding members, and auxiliary hammers interposed between said primary hammers, each auxiliary hammer substantially shorter than the one preceding it.

22. An impact grinder comprising grinding means and a casin having a chamber in its bottom projectingI neath and across the grinding means, wit means to feed the ma terial into said chamber and to feed the grinder from the chamber upward.

23. A grinder having a grinding member mounted on a shaft, a fan mounted on the same shaft, a casing around the grinding member and; around the fan, and means to feed the ground materiai from the grinding member into the blast from said fan, to be carried away thereby.

24;. In an impact grinder, a grinding member consisting of a revolving body built up of discs with partitions interposed between said discs constituting in effect a centrifugal blower, generating a blast of air, perforated casing members in proximity to said revolving discs, and openings in said discs operating in connection with said openings in the casin member for the purpose of controlling t e centrifugal. blast of air from said grinding member.

25. In an impact grinder, pivoted traveling hammers therefor, a casin surrounding the grinder, a rotating body 1ournalled in said casing carrying said hammers, means to support grain to be pulverized in the path of said hammers, and rigid means on said body traveling with said hammers in the path of material deflected from the casing after being struck by the hammers.

In testimony whereof I hereunto aflix my signature.

ELBERT R. HOBBS.

In testimony whereof I hereunto afiix my signature.

. ARCH V. STOMBAUGH.

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