Hammermill Hammers

Abstract

A hammermill hammer design to increase the life of the hammer due to the placement of more of the hard facing material on the working edge. The hammer has a steel body with end surfaces having a centrally raised portion on which surfaces hard facing material is applied to a depth at least equal to the height of the raised portion. The hammer corners are beveled to permit more facing material at the corners. Mounting pin holes are provided adjacent each end of the hammer such that it may be reversed when worn.

Description

This invention relates to hammermill hammers having a hard facing applied to an edge thereof in a manner to increase life of the hammers.

In a hammermill, large numbers of hammers are pivotally suspended about and along a rotating shaft on suitable arms by an opening near one end of the hammer. In use the hammers are subjected to severe abrasive and shock forces directed transversely of the hammers and longitudinally of the working end of the hammer. As the hammers wear where one leading edge is no longer effective the hammers are turned to present a different corner in working position. For this reason the hammers are generally symmetrical to provide four working corners. After the hammers are turned to wear all four corners the hammers are replaced.

Hammermill hammers of this type are conventionally stamped from steel bar stock about one-eighth to one-half inch thick and 11/2 to 3 inches wide. The hammer bodies, so formed, are then provided with a coating of hard facing material at each end to increase the abrasion resistance of the working edges of the hammers.

The life of the hammer is dependent on amount or degree of hard facing on the hammer and how well the facing material is fused to the steel hammer body. U.S. Pat. No. 3,045,934, issued to H. F. Eilers, discloses a commercially available hammer with a hard facing. This hammer however has no more than one-eighth to one-fourth inch of hard facing at the corners, and wear of the working edge begins relatively soon after placed in operation.

The present invention provides a hammer with more hard facing material at the corners and less material in the center of the body ends where it will afford no worthwhile function. The hammer design of the present invention is also effective to resist spalling or breaking away of the hard facing when subjected to the transverse forces at the ends of the hammer.

The method of manufacturing the hammers according to the present invention comprises the steps of placing two rows of hammer bodies in abutting relationship in a fixture with the hammers in each row in face-to-face contiguous position, passing a hard facing applicator longitudinally of the rows above the inner half of each row to apply molten hard facing material to one-half of each hammer body in each row, allowing the material to cool, separating the rows by splitting the hard facing material, transposing the rows and placing them in abutting relationship, passing a hard facing applicator longitudinally of the rows above the inner half of each row to apply molten hard facing material thereto, allowing the hard facing material to cool, separating the rows of hammers, and separating the individual hammers in each row.

The above and additional novel features and advantages of the present invention will be more apparent after reading the following description which refers the accompanying drawing wherein:

FIG. 1 is an elevational view of a pair of hammers formed according to the present invention as removed from a production fixture after one step in the process;

FIG. 2 is a fragmentary perspective view of a fixture and hammers therein diagrammatically illustrating one step in the method of making the hammers;

FIG. 3 is a fragmentary view of the hammer bodies placed in the fixture prior to another step in the manufacture; and

FIG. 4 is a fragmentary perspective view of one end of a completed hammer.

Referring now to the drawing, FIG. 1 illustrates two hammer bodies 5 and 6, each of identical shape as formed by stamping the same from a strip of steel bar stock having a width and thickness equal to that of each hammer. Each hammer has an opening 8 adjacent each end, of a size and spaced to meet various hammermill requirements. The ends of the hammers are contoured to have a raised rib 9 at each end positioned symmetrically along the longitudinal center line of the hammer and with flat or planar portions 10 leading to the corners which are preferably rounded or beveled as illustrated at 11. The ribs 9 extend between one-sixteenth inch to one-fourth inch above the flat portions 10 and are rounded to expose the entire end surface to the hard facing applicator for preheating and receiving molten hard facing material generally designated 12, whether cooled or molten. The operation and control of the applicator is such that a good thermal bond is formed between the hard facing material and the bar stock.

The end of the hammers of my invention will retain a maximum thickness of the hard coating at the corners. The beveled corners place the hard facing not only on the ends of the hammers and at the corners but down the edge approximately one-eighth inch. This provides a longer hard wear surface where the greatest forces which strike the end portions longitudinally thereof are directed during use in the mills.

The hammers of the present invention are formed by placing two rows of stamped hammer bodies in abutting parallel relationship with the hammers of each row placed in face-to-face contiguous position in a fixture 15, a portion of which is shown in FIG. 2. This fixture 15 has a central rectangular opening to receive about 8 dozen one-half inch thick hammer bodies. The bodies are clamped in the fixture and brought into a close fitting relationship. A hard facing applicator including a pair of oxygen-acetylene flame heads is then moved down the middle of the fixture above one-half of each row of hammer bodies. A first head 17 supplied with fuel through tube 18 and having a very high heat flame preheats the inner one-half of the end surfaces of the hammers of each row to a temperature to wet those portions of the end surface of the hammer bodies. A second head 20, supplied with a gaseous fuel through a tube 21, moves along the hammer bodies immediately behind head 17, and with head 17 melts rods 22 of the hard facing material fed down between the heads. The rods 22 are guided downward between the heads by suitable brackets. The rods 22 supply the molten hard surfacing alloy or compound 12, and when molten the material fills the cavity defined between the ribs 9 of the two rows of hammers as shown in FIGS. 1 and 2. After allowing time for cooling the hard facing material, the two rows of hammers are removed from the fixture 15 and the two rows of hammers are separated. This can be accomplished by a sharp chisel blow along the abutting line at the opposite ends of the hammers. The rows are then transposed and returned to the fixture 15 in a position as illustrated from one end in FIG. 3. Again the heads 17 and 20 are moved down the middle of the rows, filling the center cavity with molten hard facing material. When the material cools the hammers are removed from the fixture and the rows are separated at the center. Next, the individual hammers in each row are split apart by a chisel blow delivered between the uncoated contacting faces of the hammers to separate the hammers and fracture the coating material along a plane coextensive with the hammer faces.

When both ends of the bodies are to be hard coated the hammers are then placed in the same pattern as they were before being fractured into individual hammers with the fractured edges in mating position, and are inserted in the fixture 15 with the opposite uncoated ends upward or exposed and horizontally positioned. After movement of the heads 17 and 20 of the hard facing applicator along the rows as then exposed to fill the cavity between the rows, the rows are again removed and split apart, as described above and transposed. Again the cavities are filled. Thereafter the hammers are removed, the rows split and individual hammers in each row separated affording finished hammers with each end hard faced as illustrated in FIG. 4.

The hard facing material may be any suitable material known in the art to provide a facing having a hardness high on the Rockwell scale. Examples of such materials are tungsten carbide, or iron alloys of chromium, molybdenum, cobalt and carbon.

The improved hammer of my invention provides a hammer with the hard facing having a maximum depth at the corners and along the work engaging side to increase the life of the hammer. The method of forming the hammers in at least two rows in side-by-side relation permits the molten material to form the hard faced ends and not result in the loss of any substantial amount of material during the process.

Claims

I claim:

1. A hammermill hammer comprising a steel body comprising an end portion with a longitudinal dimension greater than the width dimension, said end portion having generally planar surface portions separated by a raised central portion, and hard facing material applied across said generally planar surface portions of the end portion to a depth thereon at least equal to the height of said raised central portion.

2. A hammermill hammer as claimed in claim 1 wherein said end portion has a width of between one-eighth to one-half inch and is straight in the widthwise direction and in the longitudinal direction except for said raised central portion which joins a portion of said generally planar surface portions on each side by smooth contours, and wherein the end portion is beveled at the corners to shorten the edges of the body to permit more hard facing at the corners.

3. A hammermill hammer as claimed in claim 2 wherein the beveled corners of said end portion extend down the edges of the bodies approximately one-eighth inch.

4. A hammermill hammer as claimed in claim 2 wherein the hammer is symmetrical at each end and the hard facing material on each end affords a rectangular profile for the ends of the hammer.

5. A hammermill hammer having opposed planar faces and generally similar end portions, said end portions each comprising planar surface portions separated by a smoothly contoured central rib portion extending in a widthwise direction across said end portion between said planar faces, and hard facing material joined to said end portions by a thermal bond, said hard facing material having a depth on said planar surface portions at least equal to the height of said rib portion defining on said hammer as a uniform hard wear resistant coating along said planar surface portions to said central rib portion.