Solid material comminution or disintegration – Apparatus – With separation or classification of material
Reexamination Certificate
1999-08-16
2001-10-23
Husar, John M. (Department: 3725)
Solid material comminution or disintegration
Apparatus
With separation or classification of material
C241S243000, C241S280000
Reexamination Certificate
active
06305623
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a rotary grinder with an improved ram and screen. Rotary grinders of the present invention are, for example, used to grind plastic or wood to reduce the size of the material to a desired size. Material to be ground is placed inside a hopper and a ram is used to force the material toward the rotor having a plurality of cutters thereon. The ram does not have to ride in horizontal channels on the sides of the hopper so material does not interfere with or jam the ram. Further, a grooved screen may be employed wherein the screen has a plurality of V-shaped grooves therein in which the cutters travel. This permits the cutters to “clean” the screen so that ground material, for example, plastic, does not block the openings in the screen.
2. Discussion of the Prior Art
Rotary grinders with forced horizontal feed are known, such as, for example, the ReTech Model RG-52 Rotary Grinder, wherein the ram compartment lower portion of the hopper of the grinder contains a pair of horizontal channels or grooves on the opposed sides of the hopper. A ram, typically horizontally driven by a hydraulic piston system, has its top plate or deck slidably received in the two opposed grooves, which are lined with a plastic bearing material, to reduce friction and prevent metal to metal contact. If a heavy load is dropped on top the ram during its travel, the large bearing surface of the grooves stabilize against the impact. A disadvantage of these grooves is that they are exposed on the inside of the hopper compartment and, as a result, can be jammed with small material which is to be ground. This can cause wear or failure of the plastic guide rails and can jam the ram and prevent horizontal movement of the ram. The long channels can also affect the strength of the hopper, as the channels traverse along most of the horizontal length of both sides of the hopper.
This channel system provides little or no stabilization in the vertical plane and result in rollers being added to the back side of the ram to improve this stability. However, because of the manufacture, additional clearance is provided between the periphery of the ram and the ram compartment and, therefore, the necessity of an elaborate seal system to close the gap.
In grinders such as the ReTech Model RG-52 Rotary Grinder, an arced screen is spaced from the rotor containing a plurality of cutters attached thereto. One grinder may have a plurality of screens, each with a different size openings therethrough. A screen with desired size openings is selected and positioned after the rotor. Only material which has been ground down to a sufficient size to pass through the screen openings will exit the grinder onto a conveyor or container. Ground material which is too large to pass through the screen openings will be reground to a smaller size. When grinding certain plastic, it has been found that the plastic will not pass completely through the screen openings but, instead, hangs up in the openings and results in a blockage of the screen openings and requires shutting down of the grinder to clear the plastic material from the screen openings.
German patent reference no. 3,932,345 teaches a typical rotor and cutters. U.S. Pat. No. 4,844,363 teaches a non-horizontal moving hopper ram wherein the ram is guided by a pair of grooved tracks
49
. U.S. Pat. Nos. 5,509,613 and 5,344,088 teach material grinders having a ram driven by a pair of pistons
24
from hydraulic cylinders
23
. U.S. Pat. No. 5,645,234 teaches another grinder having a ram head
50
.
SUMMARY OF THE INVENTION
The present invention is for a rotary grinder with an improved ram and screen. Rotary grinders of the present invention are, for example, used to grind plastic or wood to reduce the size of the material to a desired size. Material to be ground is placed inside a hopper and a ram is used to force the material toward the rotor having a plurality of cutters thereon. The ram does not have to ride in horizontal channels on the sides of the hopper so material does not interfere with or jam the ram. Further, a grooved screen may be employed wherein the screen has a plurality of V-shaped grooves therein in which the cutters travel. This permits the cutters to “clean” the screen so that ground material, for example, plastic, does not block the openings in the screen.
The grinder of the present invention eliminates the horizontal channels which guide the ram. The ram system of the present invention employs a linear bearing system which is mounted remotely under the ram compartment. The linear bearing system is connected to the ram assembly with U-shaped brackets which allows the ram to operate above the linear bearing system with the floor of the ram compartment in between. While still driven by an hydraulic piston and cylinder system, the ram is guided in the horizontal direction by a center horizontal shaft member of circular cross-section.
The ram guide system of the instant invention has several advantages over other known rams. First, the ram guide system employs a reasonably frictionless dry slide bearing system impervious to product grit and particles since it is mounted remotely, since it uses no lubrication, and since it employs a hardened and ground bearing path combined with low friction bearing material. Second, it provides close tolerance stability in both the vertical and horizontal planes as the ram moves horizontally, resulting in smaller clearance requirements between the periphery of the front ram plates and the ram compartment. This results in less sophisticated product sealing system between the ram and compartment walls. Third, there are no exposed guide grooves in the ram compartment, so there can be no jamming of the ram in its horizontal movement due to product. Fourth, the quick wearing plastic bearing channels or grooves are replaced with a longer life sealed dry slide hardened race bearing system. Fifth, the need for numerous rollers to stabilize the ram in the vertical plane is eliminated. Sixth, there is less friction during ram horizontal travel, so less energy is required. Seventh, by connecting the linear bearing system with U-shaped brackets permits the bearing system to extend under the a compartment floor as opposed to having to extend from the rear of the grinder, thereby resulting in a more dimensionally compact grinder.
REFERENCES:
patent: 3891152 (1975-06-01), Guggenheimer
patent: 4844363 (1989-07-01), Garnier et al.
patent: 5005614 (1991-04-01), Rossler
patent: 5062575 (1991-11-01), Barnabie et al.
patent: 5344088 (1994-09-01), Page
patent: 5509613 (1996-04-01), Page
patent: 5628467 (1997-05-01), Graveman
patent: 5645234 (1997-07-01), Zotto
King Kenneth W.
Sotsky George R.
Eaves, Jr. James C.
Greenebaum Doll & McDonald PLLC
Husar John M.
Republic Welding Company
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