Ball mill for malleable material recovery

An apparatus for separating material includes a frame and a rotatable sleeve supported by the frame. The sleeve has a first end, a second end, and a wall with a plurality of apertures to permit material smaller than a first size to fall through the apertures. A source of forced air is arranged to force air through an interior of the sleeve.

BACKGROUND

Firing ranges or gun ranges are training or practice areas where firearms are fired at targets. When a weapon is fired, a projectile is propelled out of the weapon and lands down range near the target. Outdoor ranges are typically built with a dirt berm positioned behind the targets so that projectiles that miss the targets become embedded in the berm and do not strike unintended objects or persons. Projectiles can also become embedded in the ground beneath or around the target.

Some projectiles have been made and continue to be made with lead. As a result, the ground at firing ranges is often contaminated with lead.

SUMMARY

An apparatus for separating material includes a frame and a rotatable sleeve supported by the frame. The sleeve has a first end, a second end, and a wall with a plurality of apertures to permit material smaller than a first size to fall through the apertures. A source of forced air is arranged to force air through an interior of the sleeve.

A ball screen apparatus includes a rotatable sleeve having a material introduction opening and a side wall with a plurality of apertures forming a screen. The plurality of apertures are sized to permit material smaller than a first size to fall through the plurality of apertures. A plurality of balls is located within an interior of the rotatable sleeve. A source of forced air is arranged to force air through the interior of the rotatable sleeve.

A method of recovering material includes: placing material within a ball screen comprising sleeve having a plurality of apertures and a plurality of balls within an interior of the sleeve; rotating the ball screen to crush portions of the material to a size that allows the crushed material to pass through the plurality of apertures; and discharging material remaining in the ball screen from the ball screen.

In a further embodiment, an assembly is provided that includes a ball screen having a material introduction end and an opposing material exit end and having a screen surface between the material introduction end and the material exit end. The ball screen is configurable to crush some material between the material introduction end and the material exit end to produce crushed material that falls through the screen surface and to press other material without crushing the other material, which exits the material exit end.

DETAILED DESCRIPTION

Embodiments described below provide a system for separating malleable material, such as lead, from other materials found at a firing range such as paper wading, sticks, grass, rocks, and dirt. Once separated, the malleable material can be collected and recycled.

FIG. 1provides a perspective view andFIG. 2provides a side view of a system100, in accordance with one embodiment, for recovering lead from a firing range. In the embodiment ofFIGS. 1 and 2, system100is shown to be mounted on a trailer frame102having multiple wheels104. Trailer102is capable of being pulled by a semi-tractor or other vehicle (not shown) so that it can be moved onto the firing range. In other embodiments, the components of system100can be mounted within a building or exterior to a building, and dirt and soil from a firing range can be brought to the system for recovery of any lead contained in the material. By mounting the components of system100on trailer102, the material from the firing range does not need to be hauled over long distances.

Once system100has been positioned at the firing range, it is stabilized by using trailer dollies, such as trailer dolly106, and downriggers, such as downriggers108and110.

System100includes a number of hydraulic motors and pistons that are driven by hydraulic oil. A diesel engine112drives hydraulic pumps113to pressurize the hydraulic oil. A hydraulic oil reservoir114contains an extra supply of hydraulic oil, and a hydraulic oil cooler118cools the hydraulic oil. Valve bodies116, which are controlled by electronics in a control panel120, direct the hydraulic oil to the various motors and pistons to thereby control the speed at which the motors turn and to control the extent that the pistons are expanded or contracted. The speeds of the various motors may be controlled independently of each other and are set by control panel120to ensure a continuous flow of material through system100without material spilling from the components of system100.

Material from the firing range is dumped into hopper122using earth moving machinery such as a front-end loader or excavator. Hopper122includes an open bottom that is positioned over hopper conveyor124. Material placed in hopper122is carried upward by hopper conveyor124and over an end125where it pours into a crusher126. Crusher126includes a plurality of rotating, spaced teeth that crush rocks and other hard material into smaller pieces. These smaller pieces pass into trommel screen128, which includes a rotating sleeve having one or more screens. The sleeve rotates within an outer frame and is pitched at an angle that causes the material to move from an entrance127(FIG. 2) of trommel screen128to an exit129of trommel screen128. As the material passes from entrance127to exit129, fine material falls through the screens of the sleeve and onto smalls conveyor136, which extends below trommel screen128. A shoot or spout514(FIG. 5) at exit129of trommel screen128directs larger material onto a bigs conveyor130, which is a pivoting or oscillating conveyor. Conveyor130alternates between conveying material into a first ball screen132and conveying material into a second ball screen134by alternately positioning an end131of the conveyor in front of an entrance to ball screen132and an entrance to ball screen134. The system100may be configured to position end131automatically under the control of control panel120or so that the end131is moved manually by an operator of the system.

Ball screens132and134are connected to respective fans142and143by air conduits such as air conduit144. As described further below, each ball screen132/134includes an interior rotating sleeve formed of a screen or perforated material and containing freely moving, crushing objects such as a plurality of stainless steel balls. As the sleeve is rotated, the freely moving objects move up along the side of the sleeve and then fall down upon the material introduced into a material introduction end133. As the freely moving objects fall, the objects crush the material into smaller pieces. These smaller pieces fall through the screen material of the sleeve and onto smalls conveyor136, which runs below ball screens132and134. The material on smalls conveyor136is provided to a pivoting discharge conveyor138, which is pivoted from side-to-side while material discharges at an end139to provide a pile of cleaned material that can be returned to the firing range. Fans142and143blow air through the air conduits, such as air conduit144and into ball screens132and134. The airstream passes through the screen material of the sleeve and causes light material such as sticks, garbage, and paper wading to be blown out of the ball screens through the material introduction end133.

When all the light material has been blown out of material introduction end133and all of the crushable material has been crushed into fine-enough particles to fall through the screen of the sleeve, the only material remaining in ball screens132and134is malleable material that, instead of being crushed, is pressed or otherwise deformed by the freely moving objects. This malleable material is too large to pass through the apertures in the screens of the ball screens. To remove this material from the ball screens, gates at a material exit end135are opened to provide discharge openings that are larger than the openings in the screen but smaller than the smallest freely-moving object (e.g., steel ball) contained in the ball screen. As the sleeve rotates, the malleable material, such as lead, travels toward material end135and exits through the openings and onto a malleable material conveyor140. Malleable material conveyor140directs the malleable material to containers (not shown) at the sides of trailer102. Thus, the malleable material, such as lead, is separated from the crushable material and the light-weight material found on the firing range to thereby recover the lead material from the firing range and recover the lead for safe disposal or for reuse.

FIG. 3provides an expanded side view of hopper122and hopper conveyor124. Hopper122includes a hopper frame300that supports hopper walls302. As shown in the sectional view ofFIG. 4taken through lines4-4ofFIG. 1, hopper walls302include slanted sidewalls400and402and vertical back wall403. Hopper122also includes an open bottom410that opens onto hopper conveyor124. Slanted sidewalls400and402and vertical back wall403direct material dropped into hopper122onto hopper conveyor124.

Hopper conveyor124includes a conveyor belt304, which rolls over rollers, such as rollers308and310that are supported by a conveyor frame312. A hydraulic conveyor motor306drives conveyor belt304in a direction314. As shown inFIG. 4, the rollers include side rollers404and408, which are angled relative to a center roller such as center roller406. This construction forms a depression in conveyor belt304designed to maintain the material on the conveyor belt.

FIG. 5shows an enlarged side view of crusher126and trommel screen128andFIG. 6shows a sectional view of system100through lines6-6ofFIG. 1showing trommel screen128and crusher126. Trommel screen128is defined by a frame510that supports a set of dust covers, such as dust cover513, a funnel511, a motor mount506and crusher motor500of crusher126. Motor mount506supports trommel motor502. As shown inFIG. 6, trommel motor502rotates a rotating screen606. Trommel screen128and crusher126can be pivoted vertically about a point508in a pivot direction515by two hydraulic pistons507and509that are controlled by control panel120.

Crusher126includes a rotating cylinder601(FIG. 6) having protruding teeth such as teeth600and602. Rotating cylinder601is driven by crusher motor500and crushes material as it falls off of conveyor belt304ofFIG. 3. The crushed material enters rotating screen606and is transported from entrance end127to exit end129due to the force of gravity due to the angle of inclination formed by pivoting trommel screen128vertically in pivot direction515. At exit end129, frame510supports a partial wall512and spout514. An opening in partial wall512opens onto spout514thereby allowing material to exit trommel screen128in a controlled manner.

As the material moves through trommel screen128, material smaller than the apertures in rotating screen606fall through the screen and are directed by funnel511onto conveyor belt136. As a result, only material that is larger than the apertures in rotating screen606passes out exit end129through spout514.

FIG. 7provides a side view of ball screen134,FIG. 8provides a sectional view of ball screen134through lines8-8ofFIG. 1, andFIG. 9provides a perspective view of ball screen134with the dust covers over the top of the ball screen removed.FIGS. 10 and 11show rear views of ball screen134with rear gates opened and closed, respectively

As shown inFIGS. 7 and 9, ball screen134includes an outer frame700that supports a number of dust covers such as dust covers702,704,705and706. InFIG. 9, the dust covers other than dust covers705and706have been removed to show the interior of ball screen134. Frame700also supports a motor mount708that in turn supports a motor710. Roller wheels, such as roller wheels712,714,716,718,722and724are also supported on frame700. Roller wheels712,714,716and718support and engage with an entrance cylindrical support726which defines an opening731of a material introduction end or first end733of ball screen134. Roller wheels722and724support an exit cylindrical support728at a material exit end or second end729of ball screen134. Entrance cylindrical support726also includes a ring gear734that is engaged by a gear coupled to motor710to thereby allow motor710to rotate entrance cylindrical support726in a direction736. When entrance cylindrical support726rotates, roller wheels712,714,716and718also rotate as does exit cylindrical support728. Similarly, when exit cylindrical support728rotates, roller wheels722and724rotate.

A sleeve730extends between entrance cylindrical support726and exit cylindrical support728. Sleeve730comprises a sleeve surface or screen surface732and one or more sleeve supports such as sleeve supports735and737, shown inFIG. 9. Screen surface732has apertures that allow material smaller than the apertures to fall through sleeve730. In accordance with some embodiments, screen surface732is cylindrical, however, screen surface732can have any desired shape. In the embodiment ofFIG. 9, screen surface732is shown as a screen mesh or woven screen. In other embodiments, screen surface732is a sheet material that has been perforated to form the apertures. The apertures may have any shape and may be arranged in any suitable pattern. In accordance with one embodiment, the apertures are ¼ inch across. However, other sized apertures are used in other embodiments depending on the size of the malleable material to be recovered, for example. Also, the apertures may be distributed over the entire circumferential wall of sleeve730or may be limited to certain areas.

Within sleeve730, freely moving objects738, also referred to as crushing objects, are carried up screen surface732by the rotation736of sleeve730and friction between the sleeve and the objects. As the freely moving objects move up the sides of sleeve730, they eventually fall back toward to the bottom of sleeve730thereby crushing material as they fall. Freely moving objects738are constructed as metal balls in some embodiments, but may be constructed from any desirable material including rubber, flint pebbles or ceramic. Further, freely moving objects738may have any desired shape. In accordance with one embodiment, freely moving objects738are 1-3.5 inches in diameter. In other embodiments, freely moving objects738have other sizes. Freely moving objects738may all have the same size or have a plurality of different sizes. Freely moving objects738break some of the material introduced through the material introduction end into a plurality of smaller pieces while deforming other material introduced through the material introduction end without breaking the other material into a plurality of smaller pieces.

Ball screen134can be pivoted vertically along a pivot740using hydraulic pistons742and744that are attached near material introduction end733. Hydraulic pistons742and744act as adjustable supports attached to the outer frame such that an inclination angle between screen surface732of sleeve730from first end733to second end729and a horizontal plane can be changed by adjusting the adjustable supports742and744. As a result, material introduction end733may be moved in a vertical direction746relative to material exit end729thereby causing material introduced through material introduction end733to move toward material exit end729where it can be crushed by freely moving objects738. The degree to which material introduction end733is lifted relative to material exit end729is controlled through control panel120. The speed at which sleeve730is rotated is also controlled by control panel120through motor710.

Two air conduit ports748and750are provided in dust guards706and705, respectively, and are coupled to conduits such as air conduit144to channel air blown by fan143through screen surface732, into the interior of sleeve730, and out from opening731in an air flow direction751. Air flow direction751includes a vertical component designed to lift light-weight material and a lateral component designed to push the light-weight material toward opening731. The air flow through air conduit ports748and750is sufficient to blow light-weight material out of opening731.

Material exit end729, as best shown inFIGS. 10 and 11, includes a closed surface760having a plurality of openings such as openings762,764,766,768,770and772. Each opening can be opened and closed by a respective gate, such as gates774,776,778,780,782and784. Each gate forms part of a closure that includes a handle connected to the gate by multiple linkages and springs that maintain the gate in an open position when the gate is open and in a closed position when the gate is closed. For example, the closures can include handles, such as handles790,792,794and796. Each gate is supported on closed surface760by a set of guides such as guides800,802,804and806for gate780ofFIG. 10. InFIG. 10, the closures are shown in the closed position and inFIG. 11, the closures are shown in the open position with the handles pulled toward the center of material exit end729. When the handles are pulled radially toward the center, a center pivot point in the linkages is pulled upward thereby causing the last linkage to pull the respective gate radially inward toward the center. When the handle is pushed radially outward, the center pivot point drops thereby causing the gate to move radially outward through the action of the linkages.

When the gates are moved to the open position, the smallest dimension798of the openings is larger than the apertures in screen surface732. Thus, material that is too large to pass through screen surface732is permitted to pass through openings762,764,766,768,770and772. As a result, material that is not crushed by the freely moving objects738but instead is pressed due to its malleability, is allowed to exit through material exit end729via the openings. This malleable material can include, for example, lead. The largest dimension of the openings formed by the gates is slightly smaller than the smallest freely moving objects738in order to prevent these objects from passing through the openings.

FIG. 12provides a flow chart of a method of recovering malleable material from a site. In step1200, material from the site is dumped into hopper122. At step1202, the hopper conveyor124conveys the material to crusher126. At step1204, the crusher126breaks-up the material into smaller pieces and provides the smaller pieces to trommel screen128. At step1206, trommel screen128rotates to move the material through the trommel screen while allowing smaller material to fall through the trommel screen and onto smalls conveyor136.

At step1208, larger material that cannot fall through the trommel screen is dropped onto swivel conveyor130through spout514of trommel screen128. Swivel conveyor130provides the material to one of the two ball screens132and134in an alternating manner. In accordance with one embodiment, swivel conveyor alternately fills each ball screen132and134to a maximum capacity at which the ball screen can still operate. At step1210, ball screens132and134use motor710to rotate sleeve730thereby causing freely moving objects in the ball screen to crush non-malleable material into smaller pieces that fall through the screen surface732. At the same time, the freely moving objects press malleable pieces while blowing lighter material out of opening731using air conducted through air conduction ports748and750. When substantially all of the non-malleable material has been crushed and has exited through screen surface732and substantially all light-weight material has been blown out of opening731, gates774,776,778,780,782and784are moved to create openings762,764,766,768,770and772. Sleeve730is rotated while the gates are in the open position thereby causing the malleable material to exit through the openings and onto recovery conveyor140. Note that the openings are sized such that freely moving objects738cannot exit through the gate openings.

At step1214, the recovery conveyor drops the malleable material into a recovery container. At step1216, when the malleable material has exited through the openings, the gates are reclosed at step1216and the method returns to step1208where the swivel conveyor provides new material to the ball screen.

Thus, hopper122, crusher126, and trommel screen128operate in a continuous mode while ball screens132and134operate in alternating batch modes, for example. While one of ball screens132and134is being filled with material, the other of ball screens132and134is completing the crushing of its material and later is having its handles moved to create openings762,764,766,768,770and772so that malleable material exits the ball screen. The rate at which material is conveyed by conveyors124and130and by trommel screen128is controlled to maximize the throughput of ball screens132and134while not exceeding the material handling capacity of ball screens132and134when those ball screens are operated in batch mode.

The speed of rotation of trommel screen128and of sleeve730of ball screens132and134may be adjusted based on the material and on the size of the freely moving objects738to maintain a high rate of crushing in the ball screens and to allow a high flow rate of material through the screen surfaces.