US3682401A

US3682401A - Hammermill hammer and assembly

Info

Publication number: US3682401A
Application number: US858683A
Authority: US
Inventors: Calvin L Jacobson; Robert E Morken; Norman C Silver
Original assignee: Individual
Current assignee: Individual
Priority date: 1969-09-17
Filing date: 1969-09-17
Publication date: 1972-08-08
Anticipated expiration: 1989-08-08

Abstract

An elongated hammermill hammer having an opening therethrough provided with a bearing wall portion disposed closest to one end of the hammer and of the shape of a portion of the curved surface of a cylinder for receiving a cylindrical hammermill attachment rod snugly thereagainst to provide a greater bearing surface to extend hammer life, the opening further having an access wall portion disposed closer to the other end of the hammer than the bearing wall portion, the access wall portion defining a part of the opening which is of larger area than that defined by the bearing wall portion for a more free reception of the access wall portion on the rod.

Description

United States Patent Jacobson et al.

[ 1 Aug. 8, 1972 [54} HAMMERMILL HAMMER AND ASSEMBLY [72] Inventors: Calvin L. Jacobson, 1421 Onyx Drive, Harlan, Iowa 51537; Robert E. Morken, 3818 Douglas Drive, Crystal, Minn. 55428; Norman C. Silver, 8212 So. Virginia Circle, St. Louis Park, Minn. 55426 [22] Filed: Sept. 17, 1969 [21] Appl. No.: 858,683

52 US. Cl ..241/195 [51] Int. Cl ..B02c 13/28 [58] Field of Search ..241/194, 193, 197, 196, 195

[56] References Cited UNITED STATES PATENTS FOREIGN PATENTS OR APPLICATIONS Larson 241/195 Austria ..'...241/194 277,595 9/1927 Great Britain ..24l/ 196 Primary Examiner-Andrew R. J uhasz Assistant Examiner-Michael Koczo, Jr.

Attorney-Hiram A. Sturges [5 7] ABSTRACT An elongated harnmermill hammer having an opening therethrough provided with a bearing wall portion disposed closest to one end of the hammer and of the shape of a portion of the curved surface of a cylinder for receiving a cylindrical harnmermill attachment rod snugly thereagainst to provide a greater bearing surface to extend hammer life, the opening further having an access wall portion disposed closer to the other end of the hammer than the bearing wall portion, the access wall portion defining a part of the opening which is of larger area than that defined by the bearing wall portion for a more free reception of the access wall portion on the rod.

5 Claims, 5 Drawing Figures PATENTEDA B 8 I97? 3.882.401

INVENTORS Fl G 4 CALVIN L. JACOBSON ROBERT E. MORKEN BY NORMAN c. SILVER HAMMERMILL HAMMER AND ASSEMBLY FIELD OF THE INVENTION This invention is in the field of hammermill installations for grinding grain and other products, and particularly in installations in which a rotor rotates at between 1, 200 and 3, 600 revolutions per minute.

DESCRIPTION of THE PRIOR ART Serious trouble has been experienced with the cracking off of the ends of hammermill hammer when the rotor revolutions per minute are as described, the most serious trouble occurring when the revolutions per minute are between 3, 000 and 3, 600.

In the past, the openings in hamrnerrnill hammers have commonly been punched or drilled of cylindrical shape. However, such openings have had diameters substantially greater than the diameter of the hammer attachment rod, as has been necessary to provide a looseness of fit enabling the hammer to be slid along a rod with ease to keep the labor time required for installation at a minimum.

As a result, the part of a prior art hammer opening wall surface which actually touches and bears against the rod is of very, very small area. This can be best understood when considering that in theory, two cylinders of different diameters can be tangent to one another only along a single thin line.

The pressure along this thin line is concentrated and is extremely great and even after a certain amount of wear in when the line has become a small thin area the force is very concentrated. The centrifugal force causes this pressure, at higher revolutions per minute of the rotor, to exceed the tensile strength of the hammer material, causing cracking.

This cracking spreads from the small thin area of bearing pressure outwardly until the end of the hammer has cracked away.

The seriousness of this cracking can be easily understood when one considers that the chips or pieces of metal coming from the hammer hit and damage other hammers.

Even one such broken away chip or piece can ruin an entire hammermill, including its fan, as is a most serious possibility.

High labor costs are involved in removing a hammer which is broken because, to reach .it, all hammers on the same end of a rod up to that hammer must be removed.

For this reason, the cost of replacement of a cracked hammer is a substantial part of the cost of hammermill operation. Also down-time for this maintenance results in lost production.

Furthermore replacing one hammer with a new one results in the mill being out of balance because the new hammer weighs more than worn hammers. This can lead to further maintenance problems.

Heretofore no solution to these problems has been found. 7

Since making our invention, we have become informed of an Austrian patent to Ole Rolfsen, Pat. No. 98012, issued Apr. 15, 1924, showing a special triangular hammer. We have never seen a triangularhammer. The millions of hammers sold each year are almost all of oblong rectangular shape.

The Rolfsen hammer patent teaches an opening formed by three lapping bores of equal diameter.

Before our invention, persons in the industry, Rolfsen himself included, have never conceived of forming a hammer with a two-section hole to solve the abovestated problems.

SUMMARY OF THE INVENTION An hammermill hammer having an opening therethrough provided with a bearing wall portion disposed closest to one end of the hammer and of the shape of a a portion of the curved surface of a cylinder for receiving a cylindrical hammermill attachment rod snugly thereagainst to provide a greater bearing surface to extend hammer life, the opening further having an access wall portion disposed closer to the other end of the hammer than the bearing wall portion, the access wall portion defining a part of the opening which is of larger area than that defined by the bearing wall portion for a more free reception of the access wall portion on the rod, all points on the access wall portion being spaced from respective points on the bearing wall portion, which latter are disposed directly across the opening from each bearing wall point by a spacing distance greater than the diameter of the curved surface of the bearing portion whereby the access wall portion defines a part of the opening which is of larger area as seen when looking therethrough than the portion bounded by the bearing wall portion for more free reception on the rod than is the case with the bearing portion itself.

The bearing wall portion being of a shape of not more than half of the curved surface of a cylinder for permitting the rod to pass into that part of the opening which is bounded partly by the bearing wall portion.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a fragmentary side elevational and part sectional view showing our improved hammer mounted on the rotor of a hammerrnill.

FIG. 2 is a frontal elevation of one of the thin sides of our hammer.

FIG. 3 is a side elevation of an end portion of our hammer.

FIG. 4 is a end view of our hammer.

FIG. 5 is a secu'onal view of FIG. 1 as taken along the line 5-5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The elongated hammer of this invention is generally indicated at 10 and is shown as mounted on a hammermill generally indicated at 12 and having a rotor generally indicated at 20 which rotates about an axis,

5 not shown, in a common manner within a cylindrical screen, a part of which is shown at 24.

The hammer 10, as well as other hammers, not shown, are attached to the rotor 20 by an attachment rod 30.

The rod 30 is always horizontally disposed and is of cylindrical shape.

In accordance with this invention, the hammer 10 is provided with a special opening 40 which extends transversely through the thickness of the hammer 10, the hammer 10 having a greater width than thickness.

The opening 40 has a wall 42 having a concave bearing wall portion 50 disposed closest to one end 54 of the hammer. The bearing wall portion 50 is for the purpose of snugly bearing against the cylindrical rod 30 which extends therethrough for securing the hammer to the rotor 20.

The bearing portion 50 is substantially of the shape of a portion of the curved surface of a as the outer surface of the rod 30 for closely fitting the rod 30.

The opening 40 further has an access wall portion 70 disposed closer to the other end 74 of the hammer than is the bearing wall portion 50.

All points on the access wall portion 70 are spaced from respective points on the bearing wall portion 50, which latter are disposed spaced directly across the opening 40 from each bearing wall point by a spacing distance greater than the diameter of the curved surface of the bearing wall portion 50, whereby the access wall portion 70 defines a part of the opening which is of larger area as seen when looking therethrough, as in FIG. 3, than the portion bounded by the bearing wall portion 50 for more free reception of the hammer on the rod than would be the case if the opening 40 were of the size of the bearing wall portion 50 itself.

The bearing wall portion 50 is of the shape of not more than half of the curved surface of a cylinder for permitting the rod to pass into that part of the opening 40 which is bounded partly by the bearing wall portion 50.

As best seen in FIG. 3, the access wall portion 70 can also be of the shape of the curved surface of a cylinder, although the diameter of the shape of the access wall portion 70 is greater than the diameter of the curvature of the bearing wall portion 50.

As best seen in FIG. 1, the hammer further has a second and identically definable opening 90 at the other end thereof and arranged so that the bearing surfaces of each opening are closest to the opposite ends of the hammer respectively, whereby in FIG. 2 the bearing surface of the opening 90 is at 94.

The ends of the bearing wall portion 50 are substantially equidistant from a line 100 extending through the center of gravity 102 of the hammer and through the center of the bearing wall portion 50.

The bearing wall portion 50 of the hammer should be of soft enough material to permit wear in to obtain good contact with the rod to compensate for manufacturing imperfection and it should be hard enough to give sufficient strength. We have found the hardness level of R 38-48 to be satisfactory. Where there is considerable manufacturing imperfection and an excessive hardness then there might be high concentrated stresses in small areas because of inadequate contact between the bearing surface and the rod give rise to premature failures.

It is to be realized however that wear in alone is not a substitute for striving to have the bearing surface substantialiy cylindrical because a tapered bearing side surface, for example, one which is substantially a portion of a frustro-conical configuration such as would be formed by punching the recess with a punch and with an identically sized die opening, would be much interiall'd.FIG.5h h odO t r ted tliiot l gh many lia ers lb as is a ri d done with high labor cost in the prior art whenever the rod-to-hammer-hole fit was snug, and as made easy by the enlarged hole 40 of this invention, accomplished with good rod-fit at bearing wall portion 50 of radius of arc-radius equal to the radius of the rod 30, which is cylindrical, for long hammer life and distributed pressure.

The reason high labor costs are involved with a snug or tight-fitting hammer hole is that sliding such hammers along a rod is difficult and there are so many hammers to put in place or remove.

We claim:

1. An elongated hammermill hammer of greater width than thickness and having an opening transversely through the thickness thereof, said opening having a wall having a concave bearing wall portion disposed closest to one end of said hammer, said bearing wall portion being for the purpose of snugly bearing against a cylindrical rod extended through said opening and securing said hammer to a harnmerrnill rotor, said bearing wall portion being substantially of the shape of a portion of the curved surface of the cylinder for closely fitting said rod, said opening wall further having an access wall portion disposed closer to the other end of said hammer than said bearing wall portion, all points on said access wall portion lying substantially on a cylindrical configuration and being spaced from respective points on said bearing wall portion which latter are disposed spaced directly across said opening from each bearing wall point by a spacing distance greater than the diameter of said curved surface of said bearing wall portion whereby said access wall portion defines a part of said opening which is of larger area as seen when looking therethrough than the portion bounded by said bearing wall portion for more free reception on said rod than said bearing wall portion.

2. The combination of claim 1 in which said hammer further has a second and identically definable opening at the other end thereof and arranged so that the bearing surfaces of each opening are closest to opposite ends of the said hammer respectively.

3. The hammer .of claim 1 in further combination with multiple similar hammers disposed alongside said first hammer, and in combination with said cylindrical rod extending through the respective ones of said openings of said multiple hammers.

4. The combination of claim 1 in which the ends of said bearing wall portion are substantially equidistant from a line extending through the center of gravity of the hammer and through the center of said bearing wall portion.

5. The combination of claim 1 in which said hammer is formed of plate material having large flat parallel sides and in which said bearing wall portion extends at a right angle to the large flat parallel sides of the hammer.

Claims

1. An elongated hammermill hammer of greater width than thickness and having an opening transversely through the thickness thereof, said opening having a wall having a concave bearing wall portion disposed closest to one end of said hammer, said bearing wall portion being for the purpose of snugly bearing against a cylindrical rod extended through said opening and securing said hammer to a hammermill rotor, said bearing wall portion being substantially of the shape of a portion of the curved surface of the cylinder for closely fitting said rod, said opening wall further having an access wall portion disposed closer to the other end of said hammer than said bearing wall portion, all points on said access wall portion lying substantially on a cylindrical configuration and being spaced from respective points on said bearing wall portion which latter are disposed spaced directly across said opening from each beAring wall point by a spacing distance greater than the diameter of said curved surface of said bearing wall portion whereby said access wall portion defines a part of said opening which is of larger area as seen when looking therethrough than the portion bounded by said bearing wall portion for more free reception on said rod than said bearing wall portion.

3. The hammer of claim 1 in further combination with multiple similar hammers disposed alongside said first hammer, and in combination with said cylindrical rod extending through the respective ones of said openings of said multiple hammers.