COMPOSITE COUNTERWEIGHT AND METHOD OF MAKING SAME
Background of the Invention
Cross-Reference to Related Application
[0001] This application claims the benefit of U.S. utility patent application Serial No.
11/735,059, filed April 13, 2007, which is incorporated herein in its entirety.
Field of the Invention
[0002] In one aspect, the invention relates to a counterweight. In another aspect, the
invention relates to a counterweight fabricated of high density particulate waste materials.
Description of the Related Art
[0003] It is often necessary to counterbalance an off-centered load associated with a
piece of machinery, a vehicle, or a piece of furniture. Counterweights are utilized for this
purpose. Typically, such counterweights are incorporated into the item. Due to aesthetic
and size constraints, it is frequently necessary to minimize the dimensions of the counter
weight. Thus, a material having a high density is utilized.
[0004] High-density counterweight material typically consists of steel, iron, and
similar high-density metals. However, such materials are costly.
[0005] It is increasingly desirable to find alternative uses for manufacturing
byproducts and other waste materials that are generally disposed of in a landfill or
offshore. Material that is a byproduct of smelting, steelmaking, and other foundry
operations frequently has a relatively high density. It is readily available, and economical
compared to the cost of high-density metals. However, such material is typically
generated in a loose, granular condition, which can complicate its use as a counterweight.
Summary of the Invention
[0006] In a first embodiment of the invention, a composite material comprises a
particulate material generated as a waste by-product of an industrial process, and a binder
for binding the particulate material into a uniform mass. The particulate material and
binder are combined in preselected proportions and compressed to form a counterweight
having a preselected density and a fixed configuration.
[0007] In a second embodiment of the invention, a method of manufacturing a
counterweight comprises the steps of selecting a first proportion of a particulate material
generated as a waste by-product of an industrial process, selecting a second proportion of
a binder for binding the particulate material into a uniform mass, combining the first
proportion of the particulate material with the second proportion of the binder into a
uniform mass, forming the counterweight from the uniform mass, and incorporating the
counterweight into a finished product.
Brief Description of the Drawings
[0008] In the drawings:
[0009] Figure 1 is a schematic view of a first embodiment of a process for fabricating
a counterweight from a particulate waste material and a thermoplastic or thermoset binder
according to the invention.
[0010] Figure 2 is a schematic view of a second embodiment of a process for
fabricating a counterweight from a particulate waste material and a thermoplastic or
thermoset binder according to the invention.
[0011] Figure 3 is a schematic view of a third embodiment of a process for
fabricating a counterweight from a particulate waste material and a thermoplastic or
thermoset binder according to the invention.
Description of an Embodiment of the Invention
[0012] An embodiment of the invention is described herein as comprising a
composite mixture of granular or particulate waste material and a thermoplastic or
thermoset binder, which are combined in selected proportions and compacted into a
generally homogeneous material having a selected density. The compacted material can
be fabricated in selected sizes and utilized as inexpensive counterweights for a variety of
applications. A preferred application is a counterweight for filing cabinets.
[0013] The counterweights can be prepared from a variety of waste materials such as
mill scale, oxygen furnace clarifier grit, taconite mine tailings, and the like. The principal
factor in determining the suitability of a material is the density of the material. Other
factors include uniformity of particle size and the proportions of constituents comprising
the waste material.
[0014] Mill scale is a byproduct of steel production. Molten steel is used to produce
slabs, which are worked by rollers during the cooling process to produce slabs of a
selected thickness. As a slab passes through a succession of rollers, a thin layer of
oxidized iron is created on the surface of the slab. High pressure water is directed onto
the surface of the slab to remove the oxidation, referred to as "scale." The resulting
mixture of scale and water is collected and filtered to separate the scale from the water.
The scale is disposed of as a non-hazardous waste material.
[0015] The scale is typically a uniform, flaky or granular material containing greater
than 70% by weight of iron oxide. Other constituents, such as manganese, carbon,
silicon, aluminum, chromium, lead, zinc, and other metals, are present in proportions of
generally less than 1%. It is a normally stable, inert material, with a specific gravity of
greater than 5.0.
[0016] Oxygen furnace clarifier grit is a waste product generated by steel mill off gas
scrubbers used with basic oxygen furnaces. The grit is typically a uniform granular or
particulate material generally containing greater than 76% iron oxide, and lesser
proportions of calcium oxide, carbon, manganese, zinc, chromium, lead, and other
constituents. It is generally stable and inert, and has a specific gravity of about 7.0.
[0017] Scrubbers typically utilize a closed loop water system to accumulate and
remove particulates from the oxygen furnace off gas. The grit may be generated in the
form of a sludge when mixed with water as part of the scrubber process. Large particles
and heavy fractions are mechanically removed from the water-based sludge, with finer
particles collected in clarifiers and dewatered using a filter press. The accumulated grit
and fine particles are typically disposed of as a non-hazardous waste material.
[0018] Taconite mining waste is generated in one of two forms. The waste comprises
either bedrock that does not contain sufficient ore for processing and must be disposed, or
unwanted minerals which are an intrinsic part of the ore-containing rock and must be
removed during processing. This material is referred to as "tailings." Taconite tailings
contain primarily quartz in the proportion of 55-60% by weight, followed by hematite at
8-12%, and iron-bearing carbonates, silicates, and magnetite, in proportions of less than
10%). Trace concentrations of heavy metals are also frequently found in tailings.
[0019] Each of these waste products can be utilized as a counterweight material. Mill
scale has been found to be particularly well-suited for counterweight production because
of its ready availability, its high proportion of high density constituents, and its generally
uniform particle size distribution.
[0020] The production of counterweights according to the invention will now be
described with respect to the use of mill scale. However, the process is generally the
same for other waste materials such as oxygen furnace clarifier grit and taconite tailings.
The basic process involves mixing a binder with the mill scale in selected proportions to
provide a counterweight having an optimum density. It has been found that a preferred
binder comprises a thermoplastic or thermoset material.
[0021] The thermoplastic or thermoset binder can comprise a polyolefin such as high
density polyethylene or polypropylene, a phenolic, methylene diphenyl diisocyanate, and
the like. The binder can comprise virgin material, or a recycled material such as recycled
powder coating or other commonly-recycled thermoplastics or thermoset materials.
Other suitable binders can include a non-polymeric material such as sodium silicate, also
known as "waterglass," or a mixture of molasses and lime. It may be necessary to pre-
process the thermoplastic material into a selected particle size, or to remove impurities or
contaminants, particularly if waste materials are used as the binder.
[0022] Referring to Figure 1, the mill scale 12 is obtained from a suitable generator
10, such as a steel mill. An optional first step in the production of counter weights is to
dry the mill scale in a dryer 16 to drive off excess moisture that may be present. The
moisture content of the mill scale 18 after drying should be no more than 12% by weight.
A preferred moisture content is 2% by weight. Drying can be accomplished prior to
mixing the mill scale with the binder, as illustrated in Figure 1. Alternatively, the mill
scale can be dried during the process of mixing the mill scale with the binder in a mixing
apparatus or a combination mixing and extruding apparatus, as hereinafter described.
Drying may not be necessary, but is preferred in order to more accurately control the
fabrication of the end product, and its resultant density.
[0023] The mill scale 18 can be combined with oversize material 26 that has been
further processed and ground to produce a mixture 28 that is delivered to a screening
apparatus 24. The mill scale 22 is screened to remove particles 26 which are too large for
incorporation into the selected end product, or which fall outside a preselected size
distribution. The particle size distribution can range from 0.1 mm to 12.5 mm. A
preferred particle size is between 0.5 mm and 6.25 mm.
[0024] The screened material 27 is delivered to a storage reservoir 29, while the
oversized material 26 is delivered to a grinder 20 for further processing into the selected
size distribution. Grinding may be accompanied by additional screening and grinding as
necessary to generate a material falling within the selected size distribution. The particle
size distribution of the mill scale as it comes from the source may allow the screening and
grinding steps to be eliminated. The ground and screened mill scale 27 is then sent to the
storage reservoir 29.
[0025] The thermoplastic or thermoset binder 14 is also processed as necessary,
particularly if the binder 14 is a recycled material, to remove unwanted constituents or
contaminants, or to generate a preselected particle size distribution. The binder 14 is
stored in a binder reservoir 30, then combined with the mill scale from the storage
reservoir 29 in a combination mixer/extruder 50, or a mixing station 32 (Figures 2 and 3).
[0026] The mill scale 27 and/or the binder 14 may be heated prior to the introduction
of the two components into the mixer/extruder 50 or mixing station 32. Thermoplastics
typically will not require preheating, as the mixing and working of the binder and mill
scale in the mixer/extruder 50 or mixing station 32 will generate sufficient heat to place
the binder in a desired workable state. It has been found that a temperature of about
180°F can be generated in this way for a high-density polyethylene. Thermosets will
typically require a higher temperature, which will necessitate the use of an external heat
source. Thermoset materials will typically be heated to a temperature of between 325°F
and 500°F. This heating can occur in the mixer/extruder 50 or mixing station 32. The
temperature of the binder is selected primarily on the basis of the specific thermoplastic
or thermoset binder utilized and the workability desired for the composite material in
order to facilitate the mixing of the materials and the homogeneity of the resulting
mixture.
[0027] Several alternative heating methods can be employed for heating and mixing
the mill scale with the binder. In one process, the mill scale and binder are heated
separately and then combined. In another process, room temperature mill scale is mixed
with heated binder. In another process, the mill scale and binder are mixed at room
temperature, followed by heating of the entire mixture in the mixing apparatus. In yet
another process, the mill scale and binder are combined at room temperature and heated
through the shearing action of the mixing machine on the mixture. This generally is only
effective for thermoplastic binders, since the temperature generated through the mixing
action will be insufficient for thermoset binders.
[0028] Referring to Figure 1, after processing the mill scale and binder, the materials
can be delivered from the reservoirs 29, 30 to a combination mixing and extruding
apparatus 50. A suitable combination mixing/extruding apparatus is a single or twin-
screw extruder manufactured by CDL Technology Inc. of Addison, Illinois. The mixing
process in the mixing/extruding apparatus 50 may be sufficient to heat a thermoplastic
binder to a desired degree of workability. The mixing/extruding apparatus 50 combines
the mill scale and binder into a composite product 38 having a selected density and
dimensions.
[0029] The composite material is then passed through a cooling chamber 40 and
cooled using either air or water, followed by machining of the material into the final
product in a machining apparatus 42. Machining can be completed when the material has
completely cooled and hardened, or while the mixture is still somewhat warm and
pliable. The finished product 44 can then be utilized in the further manufacture of items
requiring a counterweight, such as a file cabinet 46.
[0030] An alternate process for combining the mill scale and binder and forming the
composite product is illustrated in Figure 2. In this embodiment, the mill scale and
binder are processed as previously described, and stored in the reservoirs 29, 30.
Material from the reservoirs 29, 30 is delivered to a suitable mixer 32 for combining the
mill scale and binder into the composite material 34, such as a Banbury® internal batch
mixer manufactured by Farrel Corporation of Ansonia, Connecticut. As with the
combination mixing/extruding apparatus 50, the mixing process in the mixer 32 may be
sufficient to heat a thermoplastic binder to a desired degree of workability. After mixing,
the composite material 34 is delivered to a die 54 configured to provide a product having
selected finished product dimensions. The material 34 is compressed in the die 54 by a
suitable press apparatus 52 to a selected density. It is anticipated that compression would
be done after the mixture has cooled somewhat in order to facilitate the compression
process. The material is then removed from the die 54, cooled, and machined, as
described above.
[0031] A third process for combining the mill scale and binder and forming the
composite product is illustrated in Figure 3. In this embodiment, the mill scale and
binder are processed as previously described, and stored in the reservoirs 29, 30.
Material from the reservoirs 29, 30 is combined in the mixer 32. After heating and
mixing, the mixture 34 is extruded in an extrusion apparatus 36 into a composite product
38 having a selected density and dimensions. The extrusion process and apparatus can be
adapted to provide a product having a selected size and density.
[0032] The relative proportions of mill scale and binder will be dependent upon such
factors as the unit weight of the mill scale, the type of thermoplastic or thermoset binder
utilized, and the target density of the end product. Preferred proportions of mill scale and
binder are 95% by weight mill scale and 5% by weight binder. However, proportions of
80-98% by weight mill scale and 2-20% by weight binder have been found to be suitable.
A target density for a counterweight for use in a file cabinet is 51% of the density of
steel, or approximately 250 pounds per cubic foot. However, achievable densities can
range from 170 pcf to 340 pcf.
[0033] Steel scrap, such as scrap from the manufacture of nails, screws, and the like,
can be added at the time of heating and mixing the mill scale and binder in order to
provide a product having an increased density.
[0034] While the invention has been specifically described in connection with certain
specific embodiments thereof, it is to be understood that this is by way of illustration and
not of limitation. Reasonable variation and modification are possible within the scope of
the forgoing disclosure and drawings without departing from the spirit of the invention
which is defined in the appended claims.
CLAIMS
What is claimed is:
1. A composite material (34) comprising:
a particulate material (12)generated as a waste by-product of an industrial process
(10); and
a binder (14) for binding the particulate material (12) into a uniform mass;
wherein the particulate material (12) and binder (14) are combined in preselected
proportions and compressed to form a counterweight (44) having a preselected density
and a fixed configuration.
2. A composite material according to claim 1, wherein the particulate material (12)
is one of mill scale, basic oxygen furnace clarifier grit, and taconite mine tailings.
3. A composite material according to claim 1, wherein the particulate material (12)
comprises iron oxide.
4. A composite material according to claim 1, wherein the binder (14) is one of a
polyolefin, polyethylene, polypropylene, a phenolic, methylene diphenyl diisocyanate,
sodium silicate, a thermoset plastic, and a mixture of molasses and lime.
5. A composite material according to claim 1, wherein the proportion of particulate
material (12) ranges from 80% to 98%, and the proportion of binder (14) ranges from
20% to 2%.
6. A composite material according to claim 5, wherein the proportion of particulate
material (12) is 95%, and the proportion of binder (14) is 5%.
7. A composite material according to claim 1, wherein the density of the
counterweight (38) ranges from 70 pcf to 340 pcf.
8. A composite material according to claim 7, wherein the density of the
counterweight (38) is 250 pcf.
9. A method of manufacturing a counterweight comprising the steps of:
selecting a first proportion (29) of a particulate material (12) generated as a waste
by-product of an industrial process (10);
selecting a second proportion (30) of a binder (14) for binding the particulate
material into a uniform mass;
combining the first proportion of the particulate material (12) with the second
proportion of the binder (14) into a uniform mass (38);
forming the counterweight from the uniform mass (40,42); and
incorporating the counterweight into a finished product (46).
10. A method of manufacturing a counterweight according to claim 9 and further
comprising the step of drying (16) the particulate material (12) to a moisture content of
no more than 12% by weight.
11. A method of manufacturing a counterweight according to claim 10 and further
comprising the step of drying (16) the particulate material (12) to a moisture content of
2% by weight.
12. A method of manufacturing a counterweight according to claim 9 and further
comprising the step of heating the binder (14) to a temperature of between 325°F and
500°F.
13. A method of manufacturing a counterweight according to claim 9 and further
comprising the step of combining the first proportion of the particulate material (12) with
the second proportion of the binder (14) in a mixing apparatus (32).
14. A method of manufacturing a counterweight according to claim 13 and further
comprising the step of mixing the first proportion of the particulate material (12) with the
second proportion of the binder (14) so that the temperature of the mixture (36) is
approximately 180°F.
15. A method of manufacturing a counterweight according to claim 13 and further
comprising the step of extruding (36) the mixture (34) into a counterweight (38) having a
preselected density.
16. A method of manufacturing a counterweight according to claim 15 and further
comprising the step of machining (42) the counterweight (38) into a fixed configuration.
17. A method of manufacturing a counterweight according to claim 9 and further
comprising the step of processing the particulate material into a particle size range of
between 0.1 mm and 12.5 mm.
18. A method of manufacturing a counterweight according to claim 17 and further
comprising the step of processing the particulate material (12) into a particle size range of
between 0.5 mm and 6.25 mm.
19. A method of manufacturing a counterweight according to claim 9, wherein the
first proportion of the particulate material (12) ranges from 80% to 98% by weight, and
the second proportion of the binder (14) ranges from 20% to 2% by weight.
20. A method of manufacturing a counterweight according to claim 19, wherein the
first proportion of the particulate material (12) is 95% by weight, and the second
proportion of the binder (14) is 5% by weight.
21. A method of manufacturing a counterweight according to claim 9 and further
comprising the step of forming the counterweight (38) to have a density of between 170
pcf and 340 pcf.
22. A method of manufacturing a counterweight (38) according to claim 9 and further
comprising the step of forming the counterweight to have a density of 250 pcf.

A composite material comprises a particulate material generated as a waste by-product of an industrial process, and
a binder for binding the particulate material into a uniform mass. The particulate material and binder are combined in preselected
proportions and compressed to form a counterweight having a preselected density and a fixed configuration. A counterweight is
manufactured by selecting a first proportion of a particulate material generated as a waste by-product of an industrial process, se-
lecting a second proportion of a binder for binding the particulate material into a uniform mass, combining the first proportion of
the particulate material with the second proportion of the binder into a uniform mass, forming the counterweight from the uniform
mass, and incorporating the counterweight into a finished product