US2276940A - Combined grinding and bagging mill - Google Patents

Description

March 1942- P. c. DELLINGER ET AL I 2,276,940

COMBINED GRINDING AND BAGGING' MILL 2 Sheets-Sheet 1 Filed Oct. 19, 1939 nvesfi; MILES LSENSENIG,

March 17, 1942. P, c. DELLINGER ET AL 2,276,940

.COMBINED GRINDING AND BAGGING MILL ,F'iled oct. 19, 1939 2 Sheets-Sheet 2 mu col-2110 MIlES Lssmssws;

Patented Mar. 17, 1942 COIWBINED GRINDING AND BAGGING MILL Paul C. Dellinger and Miles L. Sensenig, Lancaster, Pa., assignor to Dellinger Manufacturing Company, Lancaster, Pa., a corporation of Pennsylvania Application October 19, 1939, Serial No. 300,264

6 Claims.

This invention relates to combined hammerv hammer rotor, an evacuating or discharging fan either blowing or sucking the ground meal from the lower part of the hammer mill casing and discharging it through a collar or other suitable fitting into the lower end of a discharge tube or pipe leading to the upper part of a conventional dust collector or cyclone separator at a considerable distance above the top of the hammer mill grinding case, the air passing out of the upper part of the dust collector or cyclone separator and the meal dropping down into the lower part of the separator, which was provided at its lower end usually with two diverging discharge bagging legs or ports, the discharge through which was controlled by a swingable flap or valve, whereby although the discharge from the dust collector might be continuous it was alternate through the two legs.

While the above mentioned prior known operative unit could be operated by one man to feed the material to be ground into the mill and to bag the ground material as discharged from the bagger, it made a rather awkward unit, it required special bracing to support the dust collector or cyclone separator and such supports often constituted obstructions preventing quick and easy access for the removal or interchangeability of different size or mesh screens or of other parts.

Also such operative unit, as above referred to,

are to so modify and combine the hammer mill casing, the feed hopper, the grinding hammer mill rotor, and the discharge chamber as to eliminate the evacuating fan and all other separate driven discharge means distinct from the grinding hammer mill rotor, all piping, and the dust collector as heretofore known, simply providing a twolegged or divergingly two-legged flap controlled bagging means on the lower end of the discharge chamber, which forms a part of the hammer mill casing and directly bagging the meal as it comes I from the discharge chamber; to provide a single casing combined grinding and bagging unit which will afford the greatest possibleaccess to the feeding hopper and to the bagging attachment and the means for attaching the bags thereto, and which may be operated with the greatest ease and facility by a single man or operator from a single fioor level or ground level; to provide a combined grinding and bagging unit wherein the path of travel of the material operated on from the point of its introduction into the feed hopper to the point of its discharge through the discharge chamber may be said to be generally in a horizontal direction between horizontal planes lying slightly above and slightly below respectively the highest and lowest points of travel defined by the hammers of the hammer rotor, it being recognized that the material will move downward on an incline at an angle to the lower plane as it enters the casing and will be whirled by the rotor in the processof grindingand that some of it as discharged from the grinding chamber into the discharge chamber will probably be discharged at an angle slanting up towards the upper plane of said zone defined by said upper and lower planes, but nevertheless thegeneral direction of movement from point of feed to point of discharge will be horizontal; to provide a combined hammer mill grinding and meal bagging unit having a single casing provided with a feeding hopper andwith a discharging bagging port or means and into the feeding hopper of which material to be operated upon may be placed'by a man of average size and height without any stretching or 'efiort and to the bagging attachment of which bags may be attached or applied by said average size and height man without necessity for stooping to an uncomfortable degree, or doing more than bending at the waist.

Other objects are to provide a construction whereby the usual grinding and discharge screen may be easily and quickly inserted into or removed from place by a direct straight line movement; to provide means carried by and moving with the discharge chamber and bagging means as the same is swung about its hinge point, which means serve to engage and clamp the grinding and discharge screen in place when the discharge and bagging casing is'in operative or lapped closed position; to provide a special grinding plate cooperating with the hammer rotor; to provide a special eccentric relationship 'of said grinding plate with relation to the axis of rotation of said hammer mill whereby a special grinding throat tapering in the direction of travel of the material being ground is provided; to avoid the expense of providing, in addition to the common or grinding rotor and its casing, an evacuating fan, a cyclone separator or dust collector, and

. piping means for conveying and discharging ground material evacuated by the fan to the dust collector, while at the same time providing a hammer mill unit and bagging means as a single unit, and whereby all of the functions served by the eliminated elements are served and whereby the ultimate object of grinding the raw material into granular form and bagging it are achieved and so as to avoid the expenditure of energy necessary to drive an evacuating fan without loss of efiiciency as compared with the prior practice units used to accomplish the same result and in relatively the same time unit per bag of ground material or other unit of Volume.

Only the preferred exemplification of the present invention is shown in the present application, as by law required. It is recognized however that the invention is capable of other and different embodiments and that the various details thereof may be modified in numerous ways all Without departing from the spirit of the in vention and therefore the drawings and description herein are to be understood as merely illustrative and not as exclusive.

In the accompanying drawings:

Figure l representsa view partly in side elevation broken away and partly in central section of a combined hammer mill and ground material bagger embodying my invention;

Figure 2, a sectional View on the line 22 of Figure 1, looking in the direction of the arrows; Figure 3, a sectional View on the line 3-3 of Figure 1, looking in the direction of the arrows; Figure 4, a sectional View on the line 45 of Figure 1, looking in the direction of the arrows; Figure 5, a sectional view on the line 55 of Figure 1, looking in the direction of the arrows;

Figure 6, a view on line 66 of Figure 1, looking in the direction of the arrows;

Figure 7, a sectional view on the line '|'I of Figure 6, looking in the direction of the arrows; and I Figure 8, a top plan fragmentary View of the grinding plate I5.

Referring now in detail to the drawings, A represents the ground or floor level or floor to which the mill base B is preferably firmly and rigidly secured, as by means of bolts C.

The side plates I and 2 respectively of the mill casing are firmly and rigidly connected or secured to the upper portion of the base B at the respective sides thereof in any suitable manner, as by means of the bolts D or by welding or in any other usual manner.

The base B will preferably be formed of fairly heavy sheet metal stock and will be preferably of such form and construction as will make it substantially rigid, or in other words it will be of such construction as to constitute a firm substantially rigid non-weaving base or foot for the mill. By non-weaving we mean not appreciably weaving and not having a relative move-,

ment between its parts within itself beyond such relative movement within itself as is inherent in all sheet metal parts or articles.

The respective side sheets I and 2 of the main casing are formed with registering round narrow U-shaped slots E extending slanting-wise down from the upper rear portions thereof to substantially certainly beyond the center of the grinding chamber to permit the bodily insertion and removal of the rotor H as assembled and mounted on its shaft G and having end portions protruding beyond the slots E and are supported by suitable usual or conventional bearings K which may be of any usual well known type now in use and which will be secured to their respective side plates I and 2 by any usual means or in any usual manner, as by bolts or bolts and nuts L.

Suitable breast guards or cover plates F may be secured over the portions of the respective slots E not occupied by the shaft G to prevent the escape of ground or partially ground material or dust from the interior of the grinding chamber through said slots and said cover plates or guards will be secured in position in any convenient usable removable manner, as by bolts or screws M.

In practice the rotor or hammer mill grinder rotor H will rotate in the direction indicated by the arrow in Figure l and will carry a plurality of hammers I freely pivotally mounted therein, as by pivot pins J so as to have a freely swinging flail action.

The hammer mill rotor may be constructed as shown in Dellinger Patent No. 1,757,452, grant- ,ed May 6, 1930, and the hammers may be constructed as there shown and may be mounted as there shown and described.

Of course the rest of the rotor is to turn with the shaft G at high speed and will be driven or rotated in any usual well known manner, as for instance by means of a drive belt, not shown, passing over a pulley, not shown, keyed or otherwise mounted on the haft G to turn therewith and said drive belt will be driven by any suitable internal combustion engine or other convenient and usual source of power, not shown.

The main casing housing the rotor and defining the grinding chamber consists of the two side plates I and 2, an upper front plate 4 angular in shape and extending in a horizontal direction forwardly from a point slightly in front of the axis of the shaft G to a point beyond the circle described by the outer ends of the hammers I in rotating, and extends down vertically to a point slightly above the axis of the shaft G and has its lower marginal edge portion bent slightly inward to lie against the upper face of the upper plate 9 of the mouth or intake chute, while still lying with its extreme end edge located beyond the path of travel of the free ends of the hammers I; together with the inclined upper plate 9 and lower plate 3 of the mouth, the lower plate 5 of the grinding chamber, and the grinding and discharge screen I6.

The marginal side edge portions of the plate 4, the plates 9 and 3, and the plate 5 will be secured to or against the opposed inner face portions of the respective side plates I and 2 in any usual and well known manner, as by, for instance, welding or by being flanged marginally and clamped to or against the respective side plates by means of short bolts passing through the respective edge flanges of the respective plates A, 9, 3 and 5, and the respective side plates I and 2, and drawn tight by means of nuts, not shown, in accordance with usual well known practices, or any other known usual manner.

A feeding chute or hopper l with an inclined bottom, shown broken away in Figure 1, will be secured in the feeding mouth by means of rivets II respectively passing through the respective sheets I and 2 and the respective sides of the chute 1, or in any other known and convenient manner. This chute or hopper I may be of any convenient or preferred known construction, with its top edge preferably flush with the upper outer face of the mouth plate 9 and with its inclined bottom tight against the lower mouth plate 3 to make a preferably dust tight joint with the outer edge of said plate 3 and with the upper face of its inclined bottom preferably just a little above the upper face of the inclined upper face of plate 3 so as to guard against the reverse relationship of these surfaces, whereby the material being fed might lodge and stick.

The front portion of lower plate has its upper corner of its front edge substantially in abutment with the lower rear edge of the plate 3 or the upper marginal portion of its front edge very slightly lapping the lower marginal portion of the rear edge of the plate 3 and preferably in tight engagement therewith and preferably welded thereto to make a dust tight joint, which construction results in an abrupt step or recess to accommodate the thickness of the front end portion of the grinding plate I5.

The grinding plate I5 extends from the rear edge of plate 3 on a curve eccentric to the axis of rotor H and from a point roughly corresponding to the furthermost point of travel of the free ends of said hammers I rearwardly to a point substantially beyond the axis of said rotor H and above the lowest point of the path of travel of said hammers I. As thus located and arranged the upper face of grinding plate I5 extends flush with the upper face of plate 3 and as an uninterrupted continuation thereof rearwardly to define with the moving free ends ofsaid hammers I a grinding throat which tapers in a radial direction from its forward end toward its rear end until it reaches its portion of narrowest crosssection or its closest approach to the extreme rear portion of the grinding plate I5, which also marks its closest approach to the grinding and discharge screen I6.

Grinding plate I5 preferably is welded to the upper face of plate 5 and stops a little in front of the rear edge of said bottom plate 5 which extends rearward and slightly upward roughly half an inch or slightly less beyond the rear edge of grinding plate I5 and angle irons II respectively Welded to the inner faces of the respective side plates I and 2 with their lower faces adjacent the opposed adjacent side marginal portions of the grinding plate I5 and screen It and extending rearwardly preferably as far as the rear edge of the bottom plate 5 or slightly to the rear thereof cooperate with said extension of plate 5 and the rear edge of plate I5 to support, center and hold the lower portion of screen IS in proper position.

Similarly a stop bar or metal strap I ,8 preferably welded to the top of plate 4 and extending roughtly half an inch or slightly less beyond the rear edge of plate 4 cooperates with the rear edge of plate 4 and L-shaped flange clips or plates I8 to support, center and hold the upper portion of screen IS in proper position. Said plates I8 respectively are preferably welded to the inner faces of the respective plates l and 2 and extend rearwardly beyond the rear edge of plate 4.

The grinding plate I 5 is preferably of the same material, construction and thickness as screen I6, except that it is bent on a curvature eccentric to the axis of shaft G, whereas screen I6 is preferably concentric to shaft G. Accordingly grinding plate I5 is formed with a plurality of round perforations extending completely through it. It is found that by using such a perforated plate I5 in opposition to the flail action hammers I or freely swinging hammers I of the rotor H the material operated upon is ground in less time and with the expenditure of less energy and to a smaller size for a given size or diameter of discharge holes in the grinding and discharge screen I6. It is not essential that the perforations or holes in the grinding plate I5 shall correspond in diameter or size to the perforations in the grinding or discharge screen I6, and as a matter of fact they may be either larger or smaller than the perforations in the plate I 6.

The angular or upward and forward top plate 4 of the casing, being of angular form defines an emergency space or overload chamber I3 in the interior upper forward part of the grinding chamber to take care of excess material fed into the grinding chambershould the single operator shove an extra or excessive amount of material into the hopper to besure to give it sufficient material for the grinder to handle while he goes around to the rear toremove a filled bag and to replace the same by an empty bag, so that the operator need have no fear of lost time in operation due to the feeding or bagging activities on his part.

.The discharge casing 6 is hingedly connected at its lower end portion, or preferably at its lower end portion to swing open to the dotted line position shown in Figure 1 or to substantially such a position to provide a wide opening to give free access for the insertion or removal of parts, and

such hinge mounting of the casing 6 may 'be'pro- I vided for in any of a number of different ways and by any of a number of different constructions. In the embodiment illustrated, hinge straps or plates or preferably bars of thick preferably sheet metal are respectively welded or otherwise secured to the sides of the casing 6- to 1 i lie against the outer faces of the'respective side plates I and 2 and the hinge pin I0 passing through aligned openings in said plates or bars 8 and in the intervening respective side plates I and 2 serve to pivotally connect the casing 6 to the plates I and 2 to swing about theaxis of pin 8, as illustrated in Figure 1.

The inner face of this discharge casing 6 defines a discharge chamber I 4 which is of relatively small cross-sectional area at its extreme upper portion approximately above the axis of the shaft G and increasing in cross-sectional area rearwardly and downwardly of the chamber I4, the radially outer wall of the casing 6 being eccentric to the axis of the shaft G.

A diverging leg or two-bag bagging element or unit 2|, which may be-referred to as a bagging collar or unit, is connected by a dust-tight joint to the lower end of the casing 6, as by being riveted thereto by rivets 2'2, andhas two diverging discharge legs or chutes 23 and 24 through which the ground material is ultimately discharged, such ultimate discharge being controlled by the position of a flap valve or plate 25 mounted upon and to turn with the pin 26 extending from rear to front through the bagging unit or collar 2I at a point centrally between the sides thereof and at the juncture of the legs 23 and 24, said pin 26 having a crank handle 21 to facilitate the movement of the plate or flap 25.

Hooks 28 mounted on the external faces of the legs 23 and 24 serve to hold the upper portions of the bags applied to the respective legs and of course if desired cords or bands may be applied about the upper ends of the bags to hold them tightly against the outer faces of the respective legs.

A clamping plate 32 formed with a slot 33 is welded or otherwise permanently rigidly connected to the upper end portion of the casing 6 and a clamping bolt or pin 36 having its free swinging end screw-threaded to receive a nut 34 has anchored end bent and tied through a perforation in a tab or car or lug 26 welded or otherwise secured to the upper face of plate 4 and a cotter pin 3I passing through a hole in said anchored end of the pin 30 serves to freely swingably permanently connect said pin 30 to the tab or lug 29.

Normally when the discharge casing 6 is in its normal closed position it will be held in such position by means of the nut 34 turned up tight on the stem or bolt 30 and bearing with its forward face against the rear face of the portions of the lug or plate 32 adjacent the respective walls of the slot 33 through which the bolt 36 extends.

In order to make a dust-tight or substantially dust tight closure of the casing 6 the marginal side portions of the casing 6 will make a snug tight rubbing contact by their inner faces respectively with the respective outer faces of the respective side plates I and 2 and will slightly overlap the adjacent marginal rear portions of said plates I and 2 and the lower plate 5 will be provided at or adjacent its rear end with a radially outwardly extending sealing flange 5 extending transversely from the plate 2 to the plate I, and the upper portion of the inclined front wall of the bagging unit or collar 2I will be provided with packing or sealing means 2| which in the closed position of the casing 6 will be pressed upwardly with its rear upper face against the lower forward face of the sealing flange 5' to make a dust-tight closure at this point. Similarly, the upper free swinging end of the casing 6 will be provided with a resilient metal or other suitable material packing strip 5 extending from the inner face of side plate I tothe opposed face of side plate 2 and in closed position of casing 6 bearing tightly against the upper face of plate 4 and so making a dust tight closure at this point.

The grinding and discharge screen I6 extends downward and forward very slightly beyond the rear end of the lower plate 5, which thereby provides a slight ledge or toe-hold to help position screen I6, while permitting the same torock, swing or fulcrum on its lower end during its insertion into position or removal from position and without bending, twisting, straining or deforming said screen, and also serves to prevent the lower portion of screen It from being outwardly deformed or blown out by granular particles propelled by the hammers I.

Upper clamping lugs I9 and lower clamping lugs I9 are respectively secured in any usual manner, as by welding, to the inner faces of the respective sides of the discharge chamber 6 in such position that in the operative closed position of chamber 6, as illustrated in solid lines in Figure 1, their free inner ends will engage the the operative closed position of discharge chamber 6 that its forward edge is substantially in contact with the opposed rear face portion of the screen I6 preferably substantially for the full width thereof.

When the discharge casing 6 is in operative closed position and is held in such position by the nut 34 and cooperating parts, the lugs I9 and I9 clamp the screen I6 in proper position with its lower edge portion extending forwardly above and contacting or adapted to contact the upper face of the rearwardly extending lip or extension of the lower plate 5, and with its upper and forward edge portion below and contacting or adapted to contact the lower face of the stop bar or strap I8.

As thus clamped in position the screen I6 will have its respective lower and upper edge portions properly supported and positioned by the rear edge face of grinding plate I5 and its adjacent cooperating angle cleats or plates I1 and by the rear edge face of the plates 4 and its adjacent cooperating angle cleats or plate I8.

During operation the top bar I8 keeps the upper end of the screen I5 from being displaced or blown from operative screening position by material thrown against it by the hammers I, and the rearwardly extending lip or extension of lower plate 5 serves a similar function with re tent as not to be engaged by the lugs IS and I9.

From the foregoing it will be seen that the screen 56 is positively clamped and held in position when the casing 6 is clamped closed, and that when the casing 6 is opened the screen I6 is simply loosely resting in position and may be lifted in a direct straight line from position, simply swinging or turning on its lower end so that a finger may be passed under or about its edge so as to grip it in order to lift it out of position and likewisei'n order to insert it in position it is simply necessary to move or fit it in position with a straightforward movement without any need for any arcuate or curvilinear movement or any other special class of movement.

The bagging unit or collar 2| is located approximately 31 inches from the ground or floor level to afford sufficient room for the bags to be filled and, keeping this distance in mind in relation to the. other parts of the machine, it will be evident that the material may be fed into the hopper without any excessive stretching or straining, but on the contrary with the utmost comfort of movement without any necessity for bending or straining, and likewise that the bagging operation may be performed without any need for tiring squatting or excessive stooping and that in fact the unit has been devised and designed with the purpose of making it practical for a single operator to perform the duties necessary to accomplishment of the ultimate object with the least fatigue possible, with an appreciable saving of energy, and with the same efficiency as to time as was possible by heretofore employed apparatus and without the necessity for as large an investment in equipment as was heretofore necessary.

In actual practice it is found that the operation of the hammers I in rotating or swinging about the axis of shaft G at a high rate of rotation serves to eject or discharge the material or meal after it has been ground to size through the apertures or perforations in the grinding and discharge screen l6 into the discharge chamber l4 either by knocking the same through by physical contact or by a slight blowing action or both, without the necessity of using any evacuating fan or fan attachment on the rotor H and without forcing an objectionable amount of air into the discharge chamber I4 of discharge casing 6 and that in fact in operation the amount of air that passes into chamber l4 and down through the same into the bags is not of such extent as to be objectionable or raise difliculty or blow meal or dust through the bags or result in other real difiiculties.

Of course any means for pressing against the outer face of the screen [6 to hold or clamp it in operative position and which will not obstruct an appreciable area of the screen nor result in piling up or bridging of the ground material on the upper rear face of the screen l6 may be used in place of the lugs l9 and I9 and rod or bar 20.

Also, if preferred the rod or bar 20 may be omitted entirely and the resilient metal screen [6 made of thicker material to reduce the risk of buckling, or some presser means adapted to engage the outer face of the screen l6 at one or more points in case pressure be exerted against the face presented to the rotor I-I may be employed to in general serve the same function.

Preferably an anti-buckling means such as rod or bar 25] is not employed between the clamping lugs l9 inasmuch as it is found by experience that the ground material would pile up in front of a bar located at this point or bridge and clog the holes in the upper portion of the screen It against discharge therethrough of the ground material.

We claim:

1. A combined grinding mill and bagger consisting of a main casing defining a grinding chamber, a grinding hammer rotor assembly mounted for rotation in said chamber, a feed hopper for discharging material to be ground into said grinding chamber on one side of the axis of said grinding rotor, a screen removably disposed in the wall of said main casing on the other side of the axis of said grinding rotor, and support means carried by said main casing to engage marginal portions of said screen, in combination with a discharge casing mounted on said main casing to cover said screen, hinge means for connecting said discharge casing to said main casing, means for holding said discharge casing in operative closed position with its marginal portions in substantially dust-tight contact with opposed portions of the main casing beyond and at all points about the marginal portions of said screen which constitutes a perforated wall common to said casings, special lugs and a transverse bar carried by said discharge casing and engaging, in the closed operative position of the latter, the radially outer face of the screen to press the latter against said support means, and a bagging attachment secured to the lower portion of said discharge casing and in communication with the lower portion of the discharge chamber therein.

2. A combined grinding mill and bagger consisting of a main casing defining a grinding chamber, a grinding hammer rotor assembly mounted for rotation in said chamber, a feed hopper for discharging material to be ground into said grinding chamber on one side of the axis of said grinding rotor, a screen removably disposed in the 'wall of said main casing on the other side of the axis of said grinding rotor, and supportmeans carried by said main casing to engage marginal portions of said screen, incombination with a discharge casing mounted on said at all points about the marginal portions of said screen which constitutes a perforated wall common to said casings, spaced lugs carried by saiddischarge casing engaging, in the closed operative position of the latter, the radially outer face of the screen to press the latter against said support means, and a bagging attachment secured to the lower portion of said discharge casing and in communication with the lower portion of the discharge chamber therein.

3. A combined grinding mill and bagger consisting of a main casing defining a grinding chamber, a grinding hammer rotor assembly mounted for rotation in said chamber, a feed hopper for discharging material to be ground into said grinding chamber on one side of the axis of said grinding rotor, a screen removably disposed in the wall of saidmain casing on the other side of the aXis of said grinding rotor, and support means carried by said main casing to engage the marginal portions of said screen, in combination with a discharge casing mounted on said main casing to cover said screen, hinge means for connecting said discharge casing to said main casing, means for holding said discharge casing in operative closed position with its marginal portions in substantially dust-tight contact with opposed portions of the main casing beyond and at all points about the marginal portions of said screen which constitutes a perforated wall common to said casings, means carried by said discharge casing and in the closed operative position of the latter engaging the marginal Side portions of the radially outer face of the screen to press the latter against said support means, and a bagging attachment secured to the lower portion of said discharge casing and in communication with the lower portion of the discharge chamber therein.

4. A combined grinding mill and bagger concisting of a main casing defining a grinding chamber, a grinding hammer rotor assembly mounted for rotation in said chamber, a feed hopper for discharging material to be ground into said grinding chamber on one side of the axis of said grinding rotor, a screen removably disposed in the wall of said main casing on the other side of the axis of said grinding rotor, and support means carried by said main casing to engage the marginal portions of said screen, in combination with a discharge casing mounted on said main casing to cover said screen, hinge means for connecting said discharge casing to said main casing, means for. holding said discharge casing in operative closed position with its marginal portions in substantially dust-tight contact with opposed portions of the main casing beyond and at all points about the marginal portions of said screen which constitutes a perforated wall common to said casings, means carried by said discharge casing engaging, in the closed operative position of the latter, the radially outer face of the screen to press the latter against said support means, and a bagging attachment secured to the lower portion of said discharge casing and in communication with the lower portion of the discharge chamber therein.

5. A combined grinding mill and bagger comprising a main casing consisting of longitudinally extending walls and vertical side plates respectively disposed to define a grinding chamber, said walls being formed with an aperture extending for the length of the casing, and said side plates being respectively formed with slots extending from the edges thereof at points within the width of said aperture to the medial portions of said plates, and a grinding hammer rotor assembly mounted for rotation in said chamber on a shaft disposed through the slots of said side plates, in combination with a screen removably disposed over said aperture in marginal engagement with said main casing, a discharge casing hingedly mounted on said main casing to in closed position cover said screen, and means carried by said discharge casing to, in the closed position of the latter, press against and maintain said screen in position on said main casing, whereby swinging said discharge casing to open position away from said screen will permit removal of said screen and subsequent removal of said rotor assembly as a unit through said aperture and said slots.

6. A grinding mill comprising a main casing consisting of longitudinally extending walls and vertically disposed side plates respectively disposed to define a grinding chamber, said walls being formed with an aperture extending for the length of the casing, and said plates being respectively formed with slots extending from the edges thereof at points within the width of said aperture to th medial portions thereof, and a grinding hammer rotor assembly mounted for rotation in said chamber on a shaft disposed through the slots of said side plates, in combination with a screen removably disposed over said aperture, whereby removal of said screen will permit removal of said rotor assembly as a unit through said aperture and said slots.

PAUL C. DELLINGER. MILES L. SENSENIG.

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