Hammer Mill With Replaceable Spider Arm Tips

Abstract

A hammer mill in which the outer end portions of the spider arms between which the free swinging hammers are mounted, are protected against deleterious wear by replaceable caps or tips which are held in place by the insertion of a part thereof into a socket in the spider arm.

Description

This invention relates to hammer mills and especially to heavy duty hammer mills such as those employed to break up discarded automobile bodies.

Hammer mills of this type are large enough to receive an entire automobile body and sufficiently powerful to reduce it to small fragments in a very short time. Examples of such hammer mills will be found in the Williams U.S. Pat. Nos. 3,283,698 and 3,335,967.

One of the main parts of a hammer mill is its rotary hammer assembly which comprises a series of axially adjacent spiders mounted on a shaft which has its end portions journalled in bearings in the opposite side walls of the mill. Between and mounted on the outer end portions of the spider arms are freely swinging hammers that coact with stationary comb teeth and grate bars spaced circumferentially around part of the orbit of the hammers to fragmentize whatever is fed into the mill.

To be effective, the orbit of the hammers must be quite close to the comb teeth and grate bars, and for this to be possible the extremities of the spider arms are inevitably involved in the fragmentizing action. As a result, the outer end portions of the spider arms are subjected to severe wear. Unless the worn surfaces of the spider arms are replaced, the mill loses effectiveness and the connections between the spider arms and the hammers is dangerously weakened. The swinging hammers, too, become worn and must be replaced, but their replacement does not present as serious a problem as the restoration of the worn spider arms. Heretofore this restoration was accomplished by sputtering steel onto the worn surfaces. Building up the worn spider arm tips in this manner was a time-consuming and laborious job which had to be done every day if the mill was used to its full capacity. And, of course, during the time required for the restoration job, the mill had to be shut down.

With a view to eliminating the costly rebuilding of the worn spider arms by sputtering molten metal thereon, this invention has as its object to provide readily replaceable protective tips for the outer end portions of the spider arms, and a way of attaching the tips to the arms that is secure and yet leaves the tips readily removable.

While the broad concept of providing protective tips or caps for the spider arms is not new, where they have been used in the past the manner of their attachment entailed objectionable structural modifications of the rotary hammer assembly -- as, for example, increasing the distance between adjacent spiders and thereby requiring broader hammers in order to span the increased distance between the spiders. Broad hammers require more power to drive the hammer assembly. For best results, the hammers should not be significantly wider than the spider arms between which they are located.

The present invention does not affect the width of the hammers. Instead it provides a protective tip that has a shroud portion no wider than the spider arm, shaped to fit the extremity of the arm and its adjacent leading edge portion (with reference to the direction of rotation of the hammer assembly during operation of the mill). This protective tip is detachably secured to the spider arm in a manner which to some extent resembles a mortise and tension joint, with the tenon in the form of a web projecting from the inner surface of the shroud and entering a socket (the mortise) in the spider arm through the mouth of the socket which opens the leading edge of the arm. Interengaging abutments on this web and the contiguous inner faces of the socket securely support the tip against the thrust of centrifugal force incident to the rapid rotation of the hammer assembly during operation of the mill, and thus hold the tip on the arm without need for any extraneous securing means.

Another feature of the invention is the use of the same means that mounts the swinging hammers between the end portions of the spider arms to also prevent unintentional displacement of the protective tips from the spider arms, so that whenever the hammers are replaced, the protective tips can likewise be replaced, if needed, without entailing additional time to do so.

With these observations and objectives in mind, the manner in which the invention achieves its purpose will be appreciated from the following description and the accompanying drawings, which exemplify the invention, it being understood that changes may be made in the specific apparatus disclosed herein without departing from the essentials of the invention set forth in the appended claims.

The accompanying drawings illustrate one complete example of the embodiment of the invention constructed according to the best mode so far devised for the practical application of the principles thereof, and in which:

FIG. 1 is a vertical sectional view through a hammer mill embodying this invention;

FIG. 2 is a perspective view of a portion of the hammer assembly of the mill;

FIG. 3 is an enlarged view of an end portion of one of the spider arms, with the protective tip of this invention applied thereto;

FIG. 4 is a sectional view through FIG. 3 on the plane of the line 4--4; and

FIG. 5 is a perspective view of the end portion of a spider arm and a protective tip therefor, showing the same disassembled.

Referring to the accompanying drawings, the numeral 8 designates generally the fragmentizing chamber of a hammer mill which, as is customary, has a rotary hammer assembly 9 mounted therein.

The hammer assembly 9 comprises a series of four-armed spiders 10 mounted on and keyed to a shaft 11 which is journalled in bearings (not shown) that are structurally supported in the side walls of the mill. As best seen in FIG. 2, the two pairs of diametrically opposite arms 12 of each spider are axially offset from one another, and the spiders are all similarly mounted on the shaft. Hence, the circumferentially adjacent arms of the entire series of spiders are axially offset, as are also the spaces between their outer end portions.

In the spaces between the outer end portions of the spider arms, hammers 13 are freely swingingly mounted on shafts 14 that extend through aligned holes in the spider arms. The hammers coact with the teeth of a rigidly mounted cutting comb 15 that extends lengthwise of the hammer assembly and with grate bars 16 that are circumferentially spaced around part of the orbit of the hammers, to break up any material entering the mill through its inlet chute 17. The pieces or fragments into which the mill brakes the incoming material fall through the spaces between the grate bars and onto a delivery conveyor 18 which carries them out of the mill. Since the invention is not concerned with the structure of the mill generally, there is no need to illustrate or describe the same beyond the extent shown in FIG. 1, which can be taken as exemplary of specifically different mill designs to which this invention is applicable.

As noted hereinbefore, the purpose of this invention is to eliminate the need for repairing the worn spider arms of the rotary hammer assembly by sputtering molten steel onto the worn surfaces, by providing replaceable caps of tips 19 for the spider arms, and attaching them to the arms in a manner which requires no change in the design of the hammer assembly beyond providing the outer end portion of its spider arms with sockets 20. To achieve this purpose, the caps or replaceable tips 19 -- which are all alike and preferably castings -- have a crescent-shaped shroud portion 21 shaped to fit the outer extremity of any spider arm and its adjacent leading edge portion, with reference to the direction of rotation of the hammer assembly during operation of the mill.

Attachment of the replaceable tips to the spider arms is effected in each instance, by inserting a web 22 that projects from the inner surface of the crescent-shaped shroud portion, into the socket 20 of the spider arm to which the tip is to be attached. Both the socket and the web are symmetrically located with respect to the thickness of the spider arms and the width of the tips, and since the width of the shroud portion of the tips is the same as the thickness of the spider arms, the side edges of the shroud portion are flush with the axially opposite faces of the spider arms, as seen in FIG. 4.

The mouths 23 of the sockets 20 not only open to the leading edge 24 of the spider arms, but also to the extremities thereof so that the web 22 can be integrally joined to the shroud portion along the entire length thereof. To support the replaceable tips against being thrown from the spider arms by the centrifugal force incident to rotation of the hammer assembly during operation of the mill, there are coacting abutments on the opposing inner faces of the side walls 25 of the sockets and on the opposite faces of the web 22. These abutments interengage as the web is inserted into the socket through that portion of its mouth which opens to the leading edge 24 of the spider arms.

The abutments on the spider arms are provided by opposite sides 26 and 27 of a boss or pad 28 rising from the inner face of each socket side wall 25 around a hole 29 therein, and the coacting abutments on the web 22 are formed by shoulders 30 and 31 that result from having the medial portion 32 of the web reduced in thickness. This medial portion of the web has a hole 33 therein which is of the same size as the hole 29 in the side walls of the socket, and so located that upon complete insertion of the web into the socket the holes 29 and 33 align with one another.

Attention is directed to the fact that the abutments 27 and 31 extend along straight lines transversely of the spider arms and are substantially bisected by a plane -- represented by the line L--L' in FIG. 3 -- containing the axes of the rotary hammer assembly and the aligned holes 29 and 33. Accordingly, the interengagement of these abutments carries the thrust imposed upon the cap or tip by centrifugal force. Also, as seen in FIG. 3, the straight lines on which all surfaces of the interengaging abutments 27 and 31 lie are so inclined with respect to the aforesaid plane that centrifugal force acting on the cap or tip tends to draw its web into the socket. Displacement of the caps or tips from the spider arms on which they are located by centrifugal force is thus most dependably and securely prevented.

Accidental or unintentional removal of the caps or tips from the spider arms is prevented by having the shafts 14 by which the hammers are swingingly connected with the spider arms, pass through the aligned holes 29 and 33. Each of these shafts preferably consists of two end-to-end sections or lengths that are assembled with the rotary hammer assembly from the opposite ends thereof through appropriately located holes in the side walls of the mill. Thus when replacement of hammers is required it is only necessary to withdraw the shaft section on which they are mounted, and when that is done, any worn cap or tip held by the withdrawn shaft section can be readily removed and replaced with a new one.

Those skilled in the art will appreciate that the invention can be embodied in forms other than as herein disclosed for purposes of illustration.

The invention is defined by the following claims.

Claims

I claim:

1. In a hammer mill having a rotary hammer assembly which coacts with a cutting comb and circumferentially spaced cage bars to break up material fed into the mill, the hammer assembly including a plurality of axially spaced spiders and freely swinging hammers between and connected with the outer end portions of the spider arms, and the extremities of the spider arms traveling in an orbit sufficiently close to the cutting comb and the cage bars to be subjected to severe wear during operation of the mill, the improvement by which the spider arm extremities and adjacent surfaces of the arms are protected against such wear, and which comprises:

A. a replaceable protective tip on each spider arm, each replaceable protective tip having

1. a generally crescent-shaped shroud portion which in the operative position of the protective tip embraces the extremity of the spider arm and an adjacent edge portion thereof, and

2. a web portion projecting from the inner face of the generally crescent-shaped shroud portion and having its opposite faces spaced inwardly from the side edges of the shroud portion;

B. a socket in the outer end portion of each spider arm into which the web portion of a replaceable protective tip fits, to thereby hold the tip in its operative position, the socket having spaced side walls, the opposing inner faces of which are contiguous to the opposite faces of the web portion in the socket;

C. mating abutments on at least one of the opposite faces of the web portion and on the contiguous side of the socket that interengage when the web portion of the replaceable protective tip is inserted into the socket and, by such interengagement, support the tip against the thrust of the centrifugal force incident to rotation of the hammer assembly; and

D. detachable means to hold the web portion of the replaceable tip in the socket.

2. In a hammer mill, the improvement set forth in claim 1, further characterized in that the mouth of the socket in the outer end portion of each spider arm opens to the leading edge of the arm with reference to the direction of rotation of the hammer assembly during operation of the mill.

3. In a hammer mill, the improvement set forth in claim 2, further characterized in that the abutment on the side of the socket faces towards the axis of the hammer assembly.

4. The hammer mill of claim 3, wherein said detachable means by which the web portion of the replaceable tip is held in the socket comprises a shaft passing through aligned holes in the web portion of the tip and the side walls of the socket.

5. The hammer mill of claim 4, wherein said shaft that holds the web portion of the replaceable tip in the socket passes through more than one of the axially spaced spider arms and also provides a support for the hammers located between the spider arms,

so that withdrawal of the shaft enables replacement of both protective tips on the axially spaced spider arms and the swinging hammers therebetween.

6. The hammer mill of claim 4, wherein at least one of the side walls of the socket has a boss rising therefrom and encircling the hole therein,

a portion of said boss providing said abutment on the socket wall.

7. The hammer mill of claim 6, wherein said abutment-forming portion of the boss extends transversely across a plane containing the axes of said hole and the axis of the rotary hammer assembly.

8. The hammer mill of claim 1, wherein both of the opposite faces of the web portion of each protective tip and the contiguous sides of the socket in which it is received have said mating abutments.

9. The hammer mill of claim 8, wherein each of said replaceable protective tips is symmetrical to a plane bisecting the web portion thereof and parallel to its opposite faces.

10. The hammer mill of claim 9, wherein all of the replaceable protective tips are identical and fit all of the spider arms of the hammer assembly.