Solid material comminution or disintegration – Apparatus – Rotary striking member or hammer
Reexamination Certificate
2000-02-25
2002-07-23
Rosenbaum, Mark (Department: 3725)
Solid material comminution or disintegration
Apparatus
Rotary striking member or hammer
C241S294000
Reexamination Certificate
active
06422495
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to rotary grinders used for grinding things such as waste materials. More particularly, the present invention relates to rotary grinders having rotating arrangements of hammers.
BACKGROUND OF THE INVENTION
Tub grinders for grinding waste material such as trees, brush, stumps, pallets, railroad ties, peat moss, paper, wet organic materials and the like are well known. An example of such prior art tub grinders is shown in commonly assigned U.S. Pat. No. 5,507,441 dated Apr. 16, 1996. Another example is shown in U.S. Pat. No. 5,419,502 dated May 30, 1995.
Tub grinders typically include a rotary grinding device such as a hammermill that is mounted on a frame for rotation about a horizontal axis. A rotating tub surrounds the grinding device. The tub rotates about a generally vertical axis. Debris is deposited in the rotating tub and the grinding device grinds the debris.
FIG. 1
illustrates one type of prior art hammermill
20
commonly used with conventional tub grinders. The hammermill
20
includes a plurality of hammers
22
secured to a plurality of rotor plates
24
. The rotor plates
24
are rotatably driven about a generally horizontal axis of rotation
26
. Cutters
25
(e.g., cutter blocks, cutter teeth, etc.) are mounted on the hammers
22
(e.g., with nuts
30
and bolts
28
). The hammers
22
are secured between the rotor plates
24
by shafts or rods
31
aligned generally parallel to the horizontal axis of rotation
26
. For example, each hammer defines two holes
32
and
34
each positioned to receive a different shaft
31
(only one shown). Shims
36
are mounted between the hammers
22
and the rotor plates
24
. When the rotor plates
24
are rotated about the axis of rotation
26
, the hammers
22
are carried by the rotor plates
24
in a generally circular path. Material desired to be ground is fed into the circular path such that the material is impacted and reduced in size by the cutters
25
of the hammers
22
.
A conventional tub grinder also typically includes a sizing screen (not shown) that curves along a lower half of the hammermill. A grinding chamber is formed between the screen and the hammermill. The screen performs a sizing function and defines a plurality of openings having a predetermined size. In use, material desired to be ground is repeatedly impacted by the hammers
22
against the screen causing the material to be reduced in size. When the material is reduced to a size smaller than the predetermined size of the openings defined by the screen, the material moves radially through the screen. Upon passing through the screen, the reduced material commonly falls by gravity to a discharge system located beneath the hammermill
20
.
Hammer wear is a significant concern relating to hammermills. For example, hammer wear results in loss of hammer integrity, out-of-balance conditions, reductions in grinding efficiency, and increases in maintenance and service costs. With a conventional hammermill, it is difficult to replace the hammers because the hammermill must be disassembled. Disassembling a hammermill can be particularly labor intensive and time consuming because the rods used to connect the hammers to the hammermill are quite heavy. There are typically several rods per hammermill and frequently two rods must be removed to replace a single hammer. Furthermore, rods can be corroded in place or deformed thereby making it even more time consuming and costly to disassemble a hammermill.
SUMMARY OF THE INVENTION
One aspect of the present invention relates to a rotary grinder having a cylindrical drum rotatable about its axis. The cylindrical drum has a cylindrical wall, a first end and a second end. The cylindrical wall defines a first receiving hole and a second receiving hole for receiving opposite ends of a through-member. The first end of the through-member extends to the outside of the cylindrical wall by passing through the first receiving hole such that the first end of the through-member comprises a first grinding portion (e.g., a hammer, cutter, blade, tooth, etc.) when the cylindrical drum is rotated. Likewise, the second end of the through-member extends to the outside of the cylindrical wall by passing through the second receiving hole such that the second end of the through-member comprises a second grinding portion (e.g., a hammer, cutter, blade, tooth, etc.) when the cylindrical drum is rotated. Thus, the through-member forms a duplex grinding member (e.g., a duplex hammer).
Another aspect of the present invention relates to a grinding device having a plurality of grinding members secured to a drum by a single retaining member that extends longitudinally through the drum.
In accordance with another aspect of the invention, a method for replacing a drum in a rotary grinder is presented. The rotary grinder includes a rotatable drum having a first end and a second end and a cylindrical surface. The rotary grinder also includes a plurality of hammers attached to the cylindrical surface and a first end cap attached to the first end of the drum and a second end cap attached to the second end of the drum. The method comprises the steps of removing the first end cap from the rotatable drum; removing the second end cap from the rotatable drum; replacing the rotatable drum with a second rotatable drum; attaching the first end cap to the first end of the second rotatable drum; and attaching the second end cap to the second end of the second rotatable drum.
A variety of advantages of the invention will be set forth in part in the description that follows, and in part will be apparent from the description, or may be learned by practicing the invention. It is to be understood that both the foregoing general description and the following detailed description are explanatory only and are not restrictive of the invention as claimed.
REFERENCES:
patent: 20282 (1858-05-01), Mackerley
patent: 380245 (1888-03-01), Creager
patent: 750329 (1904-01-01), Windingstad
patent: 939776 (1909-11-01), Williams
patent: 939777 (1909-11-01), Williams
patent: 1344832 (1920-06-01), Stubbs
patent: 1565842 (1925-12-01), Aram
patent: 2221002 (1940-11-01), Mankoff
patent: 3380672 (1968-04-01), Weispfenning
patent: 3650484 (1972-03-01), Kimble et al.
patent: 3758035 (1973-09-01), Ushiku et al.
patent: 4056232 (1977-11-01), Linnerz et al.
patent: 4076177 (1978-02-01), Hirayama et al.
patent: 4114817 (1978-09-01), Harris
patent: 5967436 (1999-10-01), Balvanz
patent: 6042035 (2000-03-01), Grobler et al.
patent: 3211648 (1983-10-01), None
Figure entitled “FIG. 1 (Prior Art)” from patent application Serial No. 09/513,011, 1 pg. (Feb. 25, 2000).
De Boef Duane R.
Roozeboom Keith
Verhoef Gary
Merchant & Gould P.C.
Rosenbaum Mark
Vermeer Manufacturing Company
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