Patent Grant
8561807
Magnetic drum separators are commonly used in recycling, municipal solid waste, wood waste, slag, incinerator bottom ash, foundry sand, and in mineral processing applications. Typically, these magnetic drum separators have a magnetic element that is used to sort material streams that comprise of both ferrous and non-ferrous scrap by extracting the ferrous scrap from the material stream. These magnetic drum separators are typically located immediately downstream of shredders and/or grinders that break up non-ferrous scrap that is not extracted into more manageable pieces for sorting and separating. What is presented is an improved magnetic drum separator for pulling ferrous scrap from a material stream.
A magnetic drum separator for the separation of ferrous and non-ferrous materials from a material stream comprising an outer shell that is rotatable around a central axis by a drive mechanism. The outer shell has a tubular length and a circular cross-section. The tubular length is parallel to the central axis and the circular cross-section is perpendicular to the central axis. A pickup magnet that is an electromagnet is positioned at a fixed location within the outer shell, extends along the tubular length, and has a cross-section that is perpendicular to the central axis in which a first end is closest to the inner circumference of the circular cross-section and a second end is located near the central axis. The pickup magnet comprises a core, at least one electrical wire wrapped around the core, and a backbar abutting the core at the second end. The core comprises a plurality of blocks, each block of different widths in a cross-section perpendicular to the central axis. The narrowest of the blocks is at the first end and the widest of the blocks abuts the backbar such that the core has a cross-section perpendicular to the central axis that is an incrementally stepped tapered shape. The pickup magnet is powerful enough to produce a magnetic field suitable for separating ferrous materials from non-ferrous material in the material stream.
Some embodiments of the magnetic drum separator have a carry magnet that is positioned at a fixed location within the outer shell, near the inner circumference of the circular cross-section and downstream of the pick-up magnet in the direction of rotation of the outer shell. Additionally, the magnetic drum separator can have each of the blocks wrapped by at least one electrical wire to form an independent circuit. The magnetic drum separator can also have an interpole magnet positioned at a fixed location between the pickup magnet and the carry magnet. The magnetic drum separator can also have a core that has a cross-section perpendicular to the central axis that is in three step increments. The magnetic drum separator can also have a pickup magnet that further comprises a nosepiece that abuts the core at the first end. The magnetic drum separator could have a core that further comprises a backbar with a cross-section perpendicular to the central axis that is in a stepped shape. The magnetic drum separator could have a core that comprises a single block that has a tapered cross-section perpendicular to the central axis that is narrowest at the first end and widest where the core abuts the backbar.
Other embodiments of the magnetic drum separator have a core that comprises a front block, a middle block, and a back block. Each block has a different width in a cross-section that is perpendicular to the central axis, such that the core has a cross-section perpendicular to the central axis that is an incrementally stepped tapered shape and each block is a different length in the cross-section parallel to the central axis. The front block is the narrowest of the blocks, located at said first end, and is longer than the back block. The back block is the widest of the blocks, abuts against the backbar, and is longer than the middle block.
This invention has been described with reference to several preferred embodiments. Many modifications and alterations will occur to others upon reading and understanding the preceding specification. It is intended that the invention be construed as including all such alterations and modifications in so far as they come within the scope of the appended claims or the equivalents of these claims.
For a more complete understanding and appreciation of this invention, and its many advantages, reference will be made to the following detailed description taken in conjunction with the accompanying drawings.
Referring to the drawings, some of the reference numerals are used to designate the same or corresponding parts through several of the embodiments and figures shown and described. Corresponding parts are denoted in different embodiments with the addition of lowercase letters. Variations of corresponding parts in form or function that are depicted in the figures are described. It will be understood that variations in the embodiments can generally be interchanged without deviating from the invention.
What is proposed is a new and improved magnetic drum separator for the separation of ferrous material and non-ferrous materials from a material stream where the internal components of the magnetic drum separator take up less space, weigh less, use less material to manufacture, and are generally more efficient.
Magnetic drum separator systems typically process several hundred tons of raw materials a day and even several hundred tons per hour depending on the size of the facility and the size of the equipment being used. As shown in
The material stream 20 to be sorted comprises a mixture of ferrous 22 and non-ferrous 24 materials. The material stream 20 is passed under the drum separator 10 using any appropriate first transfer system 26 such as conveyors, chutes, vibrators, etc. while the outer shell 12 rotates. As will be described later, the ferrous 22 material is magnetically attracted to the drum separator 10 and becomes magnetically attached to the surface of the outer shell 12. As the outer shell 12 rotates, the magnetically attached ferrous 22 material is rotated around the magnetic drum separator 10 until the ferrous 22 material passes out of the magnetic field generated within the magnetic drum separator 10 and falls off the outer shell 12 on the far side of the material stream 20 onto a second transfer system 28. The non-ferrous 24 material of the material stream 20 that is not attracted to the outer shell 12 falls off the first transfer system 26 into a chute 30 or other means for disposal or further processing.
The outer shell 12 of the magnetic drum separator 10 could comprise a series of cleats 32 that assist the movement of the ferrous 22 material on the outer shell 12 of the magnetic drum separator 10.
The internal workings of the magnetic drum separator 10 are at the heart of what makes the system work. Magnetic fields are generated by a series of magnets that are directed towards the first transfer system 26 to pull the ferrous 22 fraction from the material stream 20 and then to hold the ferrous 22 material onto the outer shell 12 as it rotates. The ferrous 22 material is carried around the outer shell 12 and deposited onto the second transfer system 28.
For purposes of illustration, the magnetic fields generated by the pickup magnet 34a and the carry magnets 36a are depicted as dashed lines emanating from the rotating outer shell 12a. The pickup magnet 34a is positioned and oriented such that the magnetic field 38a it generates is directed towards the material stream 22a on the first transfer system 26a. The carry magnets 36a are positioned above the pickup magnet 34a so that its magnetic field 40a continues to attract the ferrous 22a material to the outer shell 12a.
With some exceptions, the pickup magnets 34a are typically electromagnets which are normally created by wrapping an electrical wire 42a around a core 44a. The core 44a is typically made of some kind of ferrous material. Passing an electrical charge from a power supply (not shown) through the electrical wire 42a creates a magnetic field 38a as depicted by dotted lines in
There is a direct correlation between the number of times electrical wire is wound around a core and the strength of the magnetic field that is generated from an electromagnet. The number of windings versus the strength of the magnetic field can be represented by the following equation:
NI=B0·g·2.0195·(1+SF)
Where N is the number of windings of the electrical wire, I is the amperage flowing through the electrical wire (NI are measured in “ampere-turns” where turns refers to the number of windings of an electrical wire), B0 is the flux density of the air gap measured in gauss, g is the air gap measured in inches, and SF is the safety factor. The safety factor is generally added in at 5-10% to ensure a more accurate calculation. This equation is generally used for closed systems that are unlike the open loop systems found in magnetic drum separators. However, the effects of the magnetic fields generated by pickup magnets in magnetic drum separators begin to act like a closed loop system when the ferrous material of the core is magnetically saturated. As can be from the above equation, the flux density, B0, that is generated is directly related to the number of windings of the electrical wire in that the greater number of windings, the stronger the magnetic field.
An advantage of using electromagnets as pickup magnets 34a is that the magnetic field 38a can be manipulated by controlling the amount of current flowing through the electrical wire 42a. Moreover, the magnetic field 38a can be shut down altogether by turning off the current. This makes cleaning the outer shell 12a simpler and allows for safer routine maintenance when the magnetic drum separator 10a is not in use.
In the prior art embodiment shown in
In order to get the pickup magnet 34a as close to the inner circumference of the circular cross-section 18a as possible and within the confines of the outer shell 12a, the pickup magnet 34a is constructed so that fewer wrappings of electrical wire 42a are used around the first end 46a giving the electrical wire 42a a slightly tapered shape. This limitation means that there are fewer windings of the electrical wire 42a around the first end 46a of the core 40a which has a negative effect on the strength of the magnetic field 38a generated by the pickup magnet 34a. Moreover, because of the uneven number of windings across the length of the core 44a, it is common for the electrical wire 42a to unravel during construction when a pickup magnet 34a is inserted into the outer shell 12a.
Furthermore, the pickup magnet 34a has hardware that holds it in place within the magnetic drum separator 12a which takes up additional space. In the embodiment of the prior art shown in
The orientation of tapered electrical wire 42a in conjunction with the pivot point 52a means that, the pickup magnet 34a does not actually extend across the entire tubular length 16a of the magnetic drum separator 10a. This creates dead zones 54a where the magnetic field 38a generated by the pickup magnet 34a has limited to no effect and that ferrous 22a material within this area will not be attracted to the outer shell 12a. This means that any first transfer system 26a must be sized to fit within this limited magnetic field 42a and represents lost sorting capacity in the entire system.
The second set of magnets in the magnetic drum separator 10a are the carry magnets 36a that are positioned at a fixed location, near the inner circumference of the circular cross-section 18a, and downstream of the pickup magnets 34a in the direction of the rotation of the outer shell 12a. The primary purpose of the carry magnets 36a is to hold the already separated ferrous 22a materials onto the outer surface of the outer shell 12a and therefore they do not have to be as powerful as the pickup magnets 34a. As seen in
The carry magnets 36a are oriented so that the ferrous 22a material extracted from the material stream 20a is able to hold on to the outer shell 12a after the ferrous 22a material has rotated past the portion of the magnetic field 42a generated by the pickup magnet 34a. The location of the carry magnets 36a limits where the pickup magnet 34a can be positioned, forcing either: 1) the pickup magnet 34a being located such that the first end 46a is further away from the inner circumference of the outer shell 12a; or 2) reduce the number of windings of the electrical wire 42a around the core 44a. In either case, the strength of the magnetic field 38a generated by the pickup magnet 34a is hindered which reduces the effectiveness of the magnetic drum separator 10a. In order to reduce the space between the first end 46a and the inner circumference of the circular cross-section 18a, a nosepiece 56a is attached to the core 44a at the first end 46a. This nosepiece 56a pushes the magnetic field 38a strength of the pickup magnet 34a toward the inner circumference of the circular cross-section 18a, but adds to the weight and production costs of the magnetic drum separator 10a.
The space limitations which determine the location of the internal mechanisms of the magnetic drum separator 10a often means that the transition area between the pickup magnet's 34a magnetic field 38a and the carry magnet's 36a magnetic field 40a is somewhat weaker. Areas of weakened magnetic field strength 58a, similar to the one on magnetic drum separator 10a, are generally referred to as a “drop zones.” The magnetic field strength of the drop zone 58a is weak enough such that ferrous 22a material may continuously fall off the surface of the outer shell 12a and get caught again by the pickup magnet's 34a magnetic field 38a. This interaction will continue until the ferrous 20a material is either caught by the pick magnet's 36a magnetic field 40a or the ferrous 22a material falls off the drum separator 10a all together. Ultimately, the drop zone 58a keeps the drum separator 10a from reaching its full potential and leads to waste; costing time and resources; and reducing the overall lower quality drum separator.
As can be seen in
The limitations in the prior art magnetic drum separators are addressed in the preferred embodiment shown in
The pickup magnet 34c is an electromagnet that is positioned at a fixed location within the outer shell 12c. The pickup magnet 34c comprises a core 44c, at least one electrical wire 42c wrapped around the core 44c, and a backbar 50c, abutting the core 46c at the second end. The pickup magnet 34c extends along the tubular length 16c of the outer shell 12c and has a cross-section perpendicular to the central axis 14c in which a first end 46c is closest to the inner circumference of the circular cross-section 18c and a second end 56c is located near the central axis 14c. As shown in
Referring to
As seen in
Each block can be individually sized to maximize the available space within the rotating outer shell 12c. As can be seen in
As can be seen in
Each of the blocks, the front block 66c, the middle block 68c, and the back block 70c, of the core 44c are made from a metallic ferrous material, such as soft iron or mild steel. In most cases the core 44c will be made from mild steel as opposed to stainless steel because mild steel is more ferrous in content. However, one skilled in the art would see that any ferrous material will be adequate for the core 44c. It may also be feasible to construct the blocks of the core 44c using non-ferrous material or non-metal blocks so long as the pickup magnet 34c is powerful enough to produce a magnetic field 38c suitable for separating ferrous 22c materials from non-ferrous 24c materials in the material stream 20c.
A backbar 50c is located at the second end 48c of the pickup magnet 34c. The backbar 50c is typically made from the same ferrous material as the core 44c and provides an additional mass to support the entire pickup magnet 34c. The backbar 50c also creates a backstop for the back block 70c to push up against which supports the back block 70c in its respective location. The backbar 50c has a cross-section perpendicular to the central axis 14c that is in a stepped shape and abutting the core 44c at the second end 48c. This shape reduces the weight of the backbar 50c as well as the amount of material used in its construction. The backbar 50c also helps to drive the magnetic field 38c perpendicular to the backbar 50c to improve the operating efficiency of the magnetic drum separator 10c.
As can be seen by comparing
The stepped core 44c permits the entire pickup magnet 34c to be closer to the inner circumference of the circular cross-section 18c without interfering with the positioning of the other components. With the first end 46c of the pickup magnet 34c closer to the inner circumference of the circular cross-section 18c of the magnetic field 38c generated by the pickup magnet 34c is that much closer (and therefore that much stronger) to the material stream 20c which leads to more efficient separation of ferrous 22c materials from the material stream 20c.
The larger size and location of the back block 70c relative to the other blocks of the pickup magnet 34c requires that more electrical wire 42c be wound around the back block 70c than the other two blocks. These additional windings ensure that the back block 70c adequately contributes to the generation of the magnetic field 38c generated by the pickup magnet 34c. More windings also ensures that the back block 70c produces a magnetic field 38c strong enough to extend from the surface of the outer shell 12c around the locations that are perpendicular to the pickup magnet 34c. Being fundamentally closer to the inner circumference of the circular cross-section 18c, the middle block 68c requires fewer windings to contribute to the generation of an adequate magnetic field 38c. The front block 66c requires even fewer windings than the middle block 68c and the back block 70c.
As shown in
A different embodiment of the magnetic drum separator 10d is shown in
Another embodiment of the magnetic drum separator 10e is shown in
As seen in the embodiment of the magnetic drum separator 10f shown in
It will be understood that the actual number of blocks comprising the core of the pickup magnet need not be the three shown in the preferred embodiment. For example, in the embodiment shown in
Each of the blocks is an independent circuit that has electrical wire 42g wrapped around the block so that the electrical wire 42g only covers a single block and does not overlap any other block. The greater number of blocks creates more surface area for the wire to wrap around that further stabilizes the electrical wire 42g after it has been wrapped around the block and reduces the chances that the electrical wire 42g will come loose and unravel into the outer shell 12g. Thus, the electrical wire 42g used in this embodiment can have a much smaller diameter that may be too unstable for embodiments comprising fewer blocks.
This embodiment allows for the first end 46g of the pickup magnet 34g to be positioned even closer the inner circumference of the circular cross-section 18g than embodiments with fewer blocks. This allows the magnetic field 38g generated by the pickup magnet 34g (not shown) to extend further into the material stream 20g.
In another embodiment shown in
As with the embodiments described earlier, the core 44h is wrapped with an electrical wire 42h. However, unlike the previous embodiments with stepped cores, to construct this embodiment of the magnetic drum separator 10h, the slope of the core 44h demands that the electrical wire 42h must be a larger diameter than that used in the preferred embodiment because the larger diameter electrical wire 42h has more surface area causing friction to make the wire more stable and less likely to slip from position and unravel within the outer shell 12h. Using larger electrical wire 42h means that there can be fewer windings around the core 44h than the preferred embodiment, so the pickup magnet 34h will necessarily generate a weaker magnetic field 38h (not shown).
This invention has been described with reference to several preferred embodiments. Many modifications and alterations will occur to others upon reading and understanding the preceding specification. It is intended that the invention be construed as including all such alterations and modifications in so far as they come within the scope of the appended claims or the equivalents of these claims.
This application takes priority from U.S. Provisional Patent Application 61/568,991 filed on Dec. 9, 2011, which is incorporated herein by reference.
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