8/7/2019 design hammer pivoted to rotor

1/5

United States Patent [19]Hightower

[ 11] 39844,494[45] Oct. 29, 1974

[54] HAMMER MILL ROTOR ASSEMBLY[75] Inventor: William G. Hightower, Upland,

Calif.[73] Assignee: Ferromet, Inc., Etiwanda, Calif.[22] Filed: Feb. 1, 1973[21] Appl. No.: 328,841[52] U.S. CI... 241/197, 241/194[51] Int. CI. B02c 3/04, B02c 13/28[58] Field of Search 241/191,194,195,197,241/193[56] References Cited

UNITED STATES PATENTS845,1711,016,9792,268,8603,727,848Gardner. 241/194Williams 241/197Edens et al. 241/194 XFrancis 241/194

2/19072/19121/19424/1973

3,738,586 6/1973 Fabert... 241/195

Primary Examiner-Roy LakeAssistant Examiner-E. F. DesmondAttorney, Agent, or Firm-Christie, Parker & Hale[57] ABSTRACTIn a hammer mill having a rotatable shaft with out-wardly extending arms mounted to rotate with theshaft, swing hammers are pivotally secured to theouter ends of the arms and off the radial center line ofthe arms toward the direction of shaft rotation so thateach hammer leads the adjacent portion of its respec-tive arm to protect the arm from wear. A replaceablecap is disposed over the leading edge of the arm tofurther protect it from wear, and a replaceable head ismounted on each hammer so the head can be quicklyreplaced when worn to maintain hammer weight.

4 Claims, 2 Drawing Figures

\\

\

8/7/2019 design hammer pivoted to rotor

2/5

P A T E N T E D O C T 2 9 1 B 7 4 . .3.844,494

\42

14

\ z

8/7/2019 design hammer pivoted to rotor

3/5

3,844,494

DESCRIPTION OF THE PRIOR ART

2Machine efficiency is improved by replacing wornhammers, but in the prior art hammer mills, a hammeris replaced by withdrawing a retaining rod or pin whichextends through collinear holes in the set of arms on5 which the worn hammer is mounted. This requires the

removal and reinstallation of all hammers, whetherthey are worn or not. Consequently, worn hammers areoften left in operation beyond the optimum because ofthe extra work involved in handling hammers which10 may not be worn. This not only reduces the effective-ness of the machine, but also accelerates rotor arm

1HAMMER M ILL ROTOR ASSEM BLY

FIELD OF THE INVENTIONThis invention relates to hammer miIIsused to shred

or disintegrate solid materials, and is especially suitedto break up scrap automobiles, loose sheet metal,stoves, washing machines, and other appliances whichinclude a substantial amount of steel or sheet metal.

Rotary hammer mills have been used for a number of wear.years as disintegrators to crush and pulverize solid rna- This invention overcomes the disadvantages of theterials such as ore, coal, asphalt, bone, clam shells, and prior art hammer mills by using much larger hammers,the like. 15 and mounting them off the radial center line of the ro-More recently, hammer mills have been used to shred tors in the direction of shaft rotation. In operation, cen-scrap steel, particularly automobile bodies because trifugal force holds the large hammers extended out toshredded automobile scrap is superior to automobile a working position where they cover and protect thescrap prepared by other methods, such as, compressing 2 leading edges of the rotors. The greater mass of theor shearing. The shredded scrap is superior because 0 hammers increases the disintegrating power of theshredding produces smaller pieces and facilitates the equipment, and results in less swinging back of theseparation of the ferrous material from the non-ferrous, hammers. The larger hammers are secured to the rotorwhich accounts for about 20 percent of a typical arms so the hammers cannot swing freely. Instead, thescrapped automobile. U.S. Pat. No. 3,545,690 discloses 25 backface of a recoiling hammer strikes an adjacenta hammer mill installation for shredding automobile arm, and is not only prevented from rotating throughbodies. As disclosed in that patent, the automobile bod- more than about 120, but is immediately bouncedies slide down a chute into a rotary hammer mill which back into the working or disintegrating position. Thisincludes a heavy shaft rotated at a relatively high speed makes the machine more effective, and reduces wearby a powerful electric motor. Radially extending arms 30 of the rotor arms. A replaceable shoe is disposed overare secured to the shaft to rotate with it. The arms are the leading edge of each rotor arm to provide addi-usually arranged in two sets, the arms in one set being tional protection from random contact with disinte-parallel to each other and mounted on the shaft at lon- grated pieces within the hammer mill, and to protectgitudinally spaced locations to be perpendicular to the the arm when the hammer may be momentarily drivenarms in the second set. Arms in each set are located al- 35 away from the working position. When the shoe is suffi-ternately along the shaft. Swing hammers are pivotally ciently worn, it is quickly and easily replaced, thussecured to the outer ends of the rotor arms to travel at eliminating the more expensive hard facing processhigh speed around a circular path known as the "ham- previously used to rebuild a worn rotor arm.mer circle." Material fed into the mill enters the ham- This invention also provides a replaceable headmer circle where the fast moving hammers strike and 40 which can be removably secured to and removed fromdisintegrate the material. The hammers are free to the leading portion of a hammer body without havingswing through more than 360 so if they strike material to disturb any other hammer in the machine. This facil-which does not immediately disintegrate, they can itates quick replacement of only the worn hammer orswing back out of the way. The free swinging hammers hammers, so machine efficiency stays high and labor istend to continue to rotate about their respective pivot 45 minimized.points after striking a refractory piece of scrap. This The improved rotor assembly of this invention haswastes power, makes the machine less effective, and reduced operating, labor, and material costs by aboutsubjects the ends of the rotor arms carrying the ham- 62 percent compared to the hammer mill described inmers to excessive wear because the arms, instead of the U.S. Pat. No. 3,545,690. The location of the largerhammers, strike the material. 50 hammers to protect the leading edges of the rotor armsIn the prior art hammer mill, the hammers are rela- has increased the shredding machine rotor life by attively small and located on the center line of the rotor least 40 percent. The heavier hammers have also madearms, where they provide little or no protection for the the prior art shredding machine capable of producingarms, especially after the hammers lose weight by attri- about 25 percent more scrap in the same amount oftion and are more frequently knocked backward 55 time and using less electrical power than with thearound the pivot point where they are secured to the smaller hammers.arms. Thus, the more worn the hammers, the less effec- Thus, the improved rotor assembly of this inventiontive the machine, and the faster the wear of the rotor enables the production of more tons of scrap per poundarms. After an arm is sufficiently worn to threaten 60 of weight loss of hammers and rotor arms. These resultsstructural failure, the machine must be shut down, and are obtained because the larger hammers are muchthe arm rebuilt. This is often done by welding a "hard heavier and do not swing as freely away from the workfacing" material on the leading edge and outer end of load, therefore cutting more material in the same mo-the arm until the arm is substantially restored to its tion than the smaller hammers, and at the same timeoriginal dimension. The hard facing material is expen- 65 protecting the leading edge of the rotor arms. More-sive, and so is the labor required to apply it. The lost over, the larger hammers wear less because they soonproduction during the shutdown of the machine also become work hardened due tothe impact of the work.adds to the final cost of the product. Consequently, the larger hammers have a much longer

8/7/2019 design hammer pivoted to rotor

4/5

3,844,4943 4life than would be expected just from the increase inweight.

adjacent ends of the respective set of arms to which itis mounted.The hardened bushings in the rotor arms and thehammers extend the operating life of those componentsBriefly, this invention provides an improved rotor as- 5 because the bushings help prevent "spreading" of thesembly for a hammer mill which has a rotatable shaft. metal due to the force which is applied in substantiallyThe improvement includes an elongated rotor arm the same direction during the operation of the equip-mounted on the shaft to extend radially from the shaft ment. This is particularly true when manganese alloy isand rotate with it. The arm includes means for securing used for the hammers, because it tends to spread untila swing hammer to the arm to pivot about an axis sub- 10 it is sufficiently "work hardened."stantially parallel to the axis of shaft rotation. The pivot When the shaft is turned at a relatively high speed,axis of the hammer is located off the radial center line say 600 to 800 r.p.m., the hammers are held outwardlyof the arm towards the direction of shaft rotation. The in the solid line positions shown in FIG. 1with a stronghammer is secured to the arm to pivot about the pivot centrifugal force which ordinarily makes them performmeans, and be held by centrifugal force, when the shaft 15 as though they were rigidly secured to the arms in therotates, in a position where the hammer is ahead of the positions shown, and the tips of the hammers sweep atleading edge of the arm and thereby protects the arm high speed through a circular path known as the "ham-during operation of the mill. mer ~ircle." Material to be s~redded is fed down a ~on-Preferably, a replaceable shoe is mounted on the yentlOnal chute (not sh~wn) In~Othe path of the sWI~g-leading edge of the rotor arm at its outer end to provide 20 mg hammers. The typical pnor art .hammers weighadditional protection for the arm. The preferred form abou~ ~50 po~nds each, but by mounting the hammersof the invention also includes a replaceable head of this mvention ~omewhat back from the e~ds of themounted on the hammer so that when the head is worn rotor arms, the size of the hammers can be Increasedit can be removed and replaced with a new head with- to wh~re they weigh ~bout .380 pounds ea~h with?utout removing the hammer from its pivot point, and 25 ch~n~Ing the ~)Veralldimensions of c~nventlonal mll~s.without disturbing any other hammers in the mill. !hIS Inc~ease In hammer mass ~reatly Improve~ the dIS-integrating power of the machine. However, If one ofDESCRIPTION OF THE DRAWING the hammers strikes a portion of scrap which resists im-

FIG. 1 is a transverse sectional elevation taken per- mediate disintegration, the hammer is free to rotatependicular to the axis of shaft rotation of the preferred 30 backwards (counterclockwise about its pivot, asviewed in FIG. 1) approximately 100 about its pivotrotor assembly of this invention; andFIG. 2 is a fragmentary view taken on line 2-2 of point to the phantom line position 24' shown for thehammer on the right side of FIG. 1. The hammer doesFIG. 1. not swing back more than about 100 because its rearDESCRIPTION OF THE PREFERRED 35 face strikes the edge of the arm 12 sandwiched betweenEMBODIMENT the pair of arms 14 which carry the hammer. Thus, the

A hori I t bl h f 10 d . h hammer is bounded back immediately into the working. onzonta ro ata .e sat mounte In a a~mer position instead of ineffectively rotating in a counter-mill (~ot sho~n), which may be of the con~entlonal clockwise (as viewed in FIG. 1) direction around itstype dlscl?sed InU.S,.Pat. No. 3,545,690, carnes ~ first 40 pivot point. Moreover, the hammers in their respectiveset of ra~Iall~ extending arms 12 spaced at equal Inter- working positions are ahead of the forward and outervals 10ngltudIn.allyalong the shaft and secured ~y a key edges of the rotor arms so that those portions of the13 t~ rotate WIththe shaft. A second set of radially ex- rotor arms are protected from substantial direct or in i-tendl.ng arms 14 are ~ou~ted on the shaft so t~at each tial contact with the material fed into the mill. If the~rm In the secon~ set ISdisposed between. a pair of ad- 45 hammers were free to rotate freely about their pivotjacent rotor arms In the first set. The arms Inthe second points through 360, the rotor arms would be subjectedset are. secured by a key 16 to. the shaft so the arms ro- to substantial wear, which not only would result in inef-tate WIththe shaft. The arms !n each set are para.llel to ficient shredding, but would also subject the arms to ex-each other, and are perpendicular to the arms In the cessive wear requiring early replacement or repair ofother set. Each arm is a generally rectangular and rigid 50 the arms. 'plate with a hole 18 in its center making a c1~se fit Eventually, the leading and outer end portion of eacharound the shaft. The corners of the arms are shghtly hammer is worn away. The shape of a worn "one-rounded. piece" hammer is indicated by phantom line 26 for theAs viewed in FIG. 1, the shaft and rotor arms turn in hammer shown at the bottom of FIG. 1. The hammera clockwise direction. A se~arate ~ounti~g hole 19 ex- 55 can then be turned so that its previously trailing edge~ends th~ough each arm adJac.ent ItSlea~Ing edge, and becomes its leading edge. The hammer is then operatedISthus displaced from the radial center line of the arm until it has a shape indicated by the combined phantomtoward the direction of shaft rotation, and located lines 26 and 27. Once the hammer reaches this condi-about one-third of the arm radius in from the outer end 60 tion, it is relatively short and does not track the "ham-of the arm. The mounting holes in each set of arms are mer circle." The hammer is then secured to the rotorcollinear, lined with a hardened bushing 20, and re- by suitable rod or pin (not shown) passing through aceive a mounting rod or pin 21 which extends through hole 30 located on the radial center line of the rotormounting holes and through a hardened bushing 22 in arm. Since a securing pin (not shown) passing througha hole 23 in the inner end of a respective hammer 24 65 hole 30 would interfere with the partial rotation ofpivotally secured between adjacent arms in each set. hammers still mounted to pivot about holes 20, wornEach hammer is generally bell-shaped as viewed in hammers are not moved to the outer holes 30 until anFIG. 1, and extends a substantial distance beyond the entire set is available so that all hammers mounted on

SUMMARY OF THE INVENTION

8/7/2019 design hammer pivoted to rotor

5/5

3,844,4945 6the common ends on the arms in a set rotate about the is sufficiently worn to require replacement, the ma-same pivot axis. With the hammers mounted on the chine is stopped, and the hammer is rotated about itscenter line holes, the leading edges of the rotors are pivot in the direction of the shaft rotation to the posi-more exposed to impact with the material being shred- tion shown in phantom line for the hammer on the leftded, and are therefore each protected by a separate re- 5 side of FIG. 1 so that the pin 45 is no longer restrainedplaceable U-shaped shoe 32, which slips over the lead- from longitudinal movement. The pin is then removeding and outer edge of each rotor arm, which is cut away so the worn hammer head can be replaced by a newto the position shown by dotted line 34 in FIG. 1. This one without having to disturb any of the other ham-dotted line is also the bottom of the shoe, which ex- mers. This has the advantage of being faster and easiertends outwardly to make the leading portion of the arm 10 because only the hammer being replaced need be han-substantially symmetrical with respect to the trailing died, and the replacement part is substantially lighterportion. The shoe includes a pair of inwardly extending than the entire hammer. Moreover, the discarded wornside walls 36 which make a close sliding fit against op- hammer head is substantially smaller than the conven-posite faces of the arm, and which have collinear holes tional discarded whole hammer, and thus results in less38 to receive the hammer retaining pin 21. Thus, each 15 waste.shoe is held snugly in place to protect the rotor and it I claim:can be removed when necessary and replaced with a 1. In a hammer mill having a rotatable shaft, the im-new shoe. Such a replacement is considerably faster provement comprising an elongated rotor armand much less expensive than the previous practice of mounted on the shaft to extend radially from the shaftbuilding a worn rotor arm back up by welding on hard 20 and rotate with it, a hammer disposed adjacent thefacing material. The shoe protects not only the leading outer end of the arm, means for securing the hammeredge of the rotor arm, but also the sides of the arm, to the arm so the hammer projects beyond the outerwhich are sometimes subjected to abrasion from small end of the arm and ahead of the leading edge of the armpieces of hard material sifting in between the side of a when the shaft is rotated, the hammer including sepa-hammer and an adjacent face of the rotor arm. 25 rate head and body portions which overlap in the direc-When a hammer is to be replaced as described above, tion of shaft rotation and each have collinear holes ex-the retaining pin 21 passing through the collinear holes tending through them in the direction substantially par-in the set of arms to which the hammer is secured must allel to the axis of shaft rotation, and a retaining pin ex-be withdrawn to the point where the hammer is free to tending through the collinear holes in the overlappingbe removed. If the hammer is in the center of the set 30 portions of the hammer head and body to secure themof arms, it may be necessary to remove several of the together, the pin being positioned so that when thehammers to reach the one to be replaced. This is incon- shaft is rotated the pin is prevented from movementvenient and requires a great deal of work because the along its axis by the adjacent motor arms betweenhammers may weigh anywhere from 200 to 400 Ibs. which the hammer is secured, the location of the re-each. This problem isavoided by the preferred hammer 35 taining pin with respect to the pivot point for the ham-design of this invention as shown by the hammers on mer being such that when the shaft does not rotate andthe right and left sides of FIG. 1.The preferred hammer the hammer is rotated about its pivot point, the pinincludes an inner or body portion 40 secured to the moves clear of the rotor arms so it can be moved longi-rotor arm by the retaining pin 21 as previously de- tudinally to permit the hammer head to be removedscribed. The body is approximately one-half the mass 40 from the hammer body.of a conventional one-piece hammer, but includes a 2. A hammer mill having a rotatable shaft, an elon-forwardly extending boss 42 formed integrally with the gated rotor arm mounted on the shaft to extend radiallycentral and lower portion of the body to extend into a from the shaft and rotate with it, a hammer mounted onmatching cavity 43 in a hammer head 44 secured to the the outer end of the arm, and a replaceable shoe se-front face of the hammer body. The adjacent surfaces 45 cured over the leading edge of the rotor arm and itsof the body and head match in area and shape so the outer end.two pieces fit together to form what appears to be an 3. Apparatus according to claim 2 in which the armintegral weight. The two pieces are held together by a includes a hole extending in the same general directionpin 45 which extends through a pair of collinear holes as the shaft, and the shoe includes an inwardly extend-46 in the hammer head, and a bore 47 in the tongue of 50 ing portion with a hole collinear with the hole in thethe hammer body. The pin 45 is substantially parallel arm, and a retaining pin extending through the collin-to the axis of shaft rotation and is located so that when ear holes to secure the shoe to the arm.the shaft is rotated and the hammers are held in their 4. Apparatus according to claim 2 in which the shoeoperative positions, the pin 45 is prevented from mov- covers the leading edge and adjacent sides of the rotoring longitudinally by the adjacent rotor arms to which 55 arm at its outer end.the hammer is secured. After the head of the hammer * * * * *

60

65