Patent Application
20190083988
This invention relates generally to a processing plant for crushing, screening and separating aggregate materials. More particularly, the invention relates to a method of using such a processing plant in two alternative modes of operation in order to maximize efficiency.
The construction of roadways, parking lots and driveways requires much aggregate material in the nature of crushed stone having various particle sizes. Some of this stone is used for base material and some is combined with asphalt cement to produce asphalt concrete. Still other crushed stone is combined with Portland cement and water for use in constructing concrete pavement and in building construction. Consequently, there is a great demand for crushed stone for use as aggregate materials in paving and building products.
Crushed stone used as aggregate material has three principal functions. It provides a relatively low-cost filler for cement-based products and asphalt concrete. It also provides a mass of particles that will resist the action of applied loads, abrasion, and the percolation of moisture and water. Finally, it minimizes volume changes in the pavement or building product resulting from the setting and hardening process and from moisture and temperature changes. The performance of these functions by the aggregate material depends on the mineral character of the aggregate as related to strength, elasticity and durability, and on the surface characteristics and gradation of the aggregate particles, particularly as related to workability and bonding within a hardened mass, and the density of the product.
Much of the crushed stone used as aggregate materials for roadway and building construction is blasted from quarry walls and processed into various aggregate sizes. Some quarries have permanent processing plants, and others employ portable processing plants for crushing, screening and separating the aggregate materials into various size fractions. In the operation of an open-pit quarry, it is common for holes to be drilled adjacent a wall or face of the quarry pit and for explosive charges to be placed in these holes. The explosives are detonated in order to loosen and remove stone for further processing. A large loader is employed to load off-road trucks with the stone for transport to the processing plant. The stone placed in these off-road trucks will include many large pieces that must be crushed, but it will also include stone that has been reduced to small particulate by the blasting process.
Frequently, an aggregate processing plant will include one or more items of reducing equipment such as jaw crushers, gyratory crushers, cone crushers, vertical shaft impact crushers or horizontal shaft impact crushers. Typically, an aggregate processing plant will also include one or more vibratory and/or grizzly screens to separate the aggregate materials into fractions of varying particle sizes. In addition, an aggregate processing plant will usually include one or more conveyors to transfer aggregate material for processing or to stockpile processed aggregates. Some aggregate processing plants are fixed installations. Others comprise portable processing plants that are mounted on trailers, or on a self-propelled chassis driven by wheeled or track drive systems. Portable processing plants are typically more compact than those comprising fixed installations.
One type of portable processing plant includes a crusher and a crusher feed conveyor to feed material to the crusher. It also includes a crusher collection conveyor under the crusher that delivers crushed material to a vibratory screen assembly, a transfer conveyor for conveying material too large to pass through the vibratory screen assembly to the crusher, and a plurality of discharge conveyors for separating material passing through the screens of the screen assembly. Such a processing plant is typically moved to a suitable location in the quarry for processing of the stone that is delivered by the off-road trucks. However, when the processing plant is loaded with stone obtained from a blasting process, all of the aggregate material, including portions that have already been reduced in particle size, is loaded into the crusher. This causes unnecessary wear on the crusher and reduces the speed at which material is processed. Furthermore, when all of the material is processed through the crusher, the screen assembly must be sized to process material having a top size that is dictated by the top size setting of the crusher.
One conventional way to avoid the unnecessary wear on the crusher incurred when all of the material to be processed is loaded into the crusher is to add a pre-screen component to remove the smaller sized aggregate material that does not need to be processed through the crusher.
It would be desirable, however, if the conventional processing equipment could be altered in such a way that it could be operated without processing all of the aggregate material through the crusher and without the addition of a separate pre-screen component.
The use of the terms “a”, “an”, “the” and similar terms in the context of describing the invention are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising”, “having”, “including” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. The terms “substantially”, “generally” and other words of degree are relative modifiers intended to indicate permissible variation from the characteristic so modified. The use of such terms in describing a physical or functional characteristic of the invention is not intended to limit such characteristic to the absolute value which the term modifies, but rather to provide an approximation of the value of such physical or functional characteristic.
Terms concerning attachments, coupling and the like, such as “connected” and “interconnected”, refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both moveable and rigid attachments or relationships, unless specified herein or clearly indicated by context. The term “operatively connected” is such an attachment, coupling or connection that allows the pertinent structures to operate as intended by virtue of that relationship.
The use of any and all examples or exemplary language (e.g., “such as” and “preferably”) herein is intended merely to better illuminate the invention and the preferred embodiment thereof, and not to place a limitation on the scope of the invention. Nothing in the specification should be construed as indicating any element as essential to the practice of the invention unless so stated with specificity.
The invention comprises an aggregate processing plant and a method of operation of an aggregate processing plant according to two alternative modes of operation. The preferred aggregate processing plant comprises a crusher feed conveyor, a crusher, a crusher collection conveyor under the crusher that delivers crushed material to a vibratory screen assembly, a transfer conveyor for conveying material too large to pass through the vibratory screen assembly to the crusher, and a plurality of discharge conveyors for separating material passing through the screens of the screen assembly. Preferably, the screen assembly is modified, as compared to a typical conventional screen assembly, to provide a larger screen feedbox or screen infeed section. These modifications also require changing the location of the impulse mechanism of the screen assembly to achieve a weight balance that facilitates a proper vibratory amplitude to be obtained throughout the length of the screen decks. It may also be necessary to increase the space between the top deck of the screen assembly and the crusher collection conveyor in order to account for the additional bounce or projectile height from the larger material being processed by the screen assembly. It may also be necessary to increase the spacing between the screen decks to allow for handling larger sized material. It may also be necessary to provide more screen decks than in a conventional screen assembly. Furthermore, it may be necessary to modify the transfer conveyor and the crusher return conveyor to allow for the handling of larger material. Such material will flow differently than smaller material, because it will have a different angle of repose and a different surcharge angle. It may also be necessary to provide more spacing between the conveyors and other components to allow for handling larger sized material. In some embodiments of the invention, oversized wire mesh, or grizzly bars or a punch plate may be added to protect the screen assembly and conveyors from damage due to the handling of larger sized material. A tramp iron component can be added to the transfer conveyor for conveying material too large to pass through the vibratory screen assembly to the crusher. Such tramp iron component will include a sensor to detect the presence of tramp iron in the material and a diverter to divert such material onto the ground before it enters the crusher.
In another embodiment of the invention, the operating speed of the crusher collection conveyor is varied to control the rate of placement of the crushed material onto the vibratory screen assembly. When loading aggregate material into the crusher feed conveyor according to this embodiment, the crusher collection conveyor is operated at full speed to discharge the crushed aggregate material near the upper end of the screen assembly to get maximum efficiency. When loading aggregate material onto the screen assembly, instead of the crusher feed conveyor, the crusher collection conveyor is operated at a slower speed to discharge crushed aggregate material lower on the screen assembly to relieve the load on and improve the performance of the screen assembly.
In order to facilitate an understanding of the invention, the preferred embodiments of the invention, as well as the best mode known by the inventor for carrying out the invention, are illustrated in the drawings, and a detailed description thereof follows. It is not intended, however, that the invention be limited to the particular embodiments described or to use in connection with the apparatus illustrated herein. Therefore, the scope of the invention contemplated by the inventor includes all equivalents of the subject matter described herein, as well as various modifications and alternative embodiments such as would ordinarily occur to one skilled in the art to which the invention relates. The inventor expects skilled artisans to employ such variations as seem to them appropriate, including the practice of the invention otherwise than as specifically described herein. In addition, any combination of the elements and components of the invention described herein in any possible variation is encompassed by the invention, unless otherwise indicated herein or clearly excluded by context.
The presently preferred embodiments of the invention are illustrated in the accompanying drawings, in which like reference numerals represent like parts throughout, and in which:
This description of the preferred embodiments of the invention is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description of this invention. The drawings are not necessarily to scale, and certain features of the invention may be shown exaggerated in scale or in somewhat schematic form in the interest of clarity and conciseness.
As shown in the drawings, conventional portable processing plant 10 comprises frame 12 which is supported by left and right track drive assemblies, one of which, left track drive assembly 14 is shown in
A crusher, such as cone crusher 16, is mounted on frame 12 above the drive assemblies. Crusher feed conveyor 18 and feed chute 20 are provided to feed material to be processed into the top of crusher 16. Cone crusher 16 operates to reduce the size of aggregate material introduced through feed conveyor 18 and includes a conventional housing that contains in its upper section a moveable cone (not shown) and a concave or bowl liner (also not shown). The cone is mounted on a crusher shaft (also not shown), and the concave or bowl liner is fixed to the upper part of the crusher housing. Aggregate material to be crushed is fed via feed chute 20 to crusher feed conveyor 18, which drops it into the gap between the cone and the concave or bowl liner of cone crusher 16. This gap is adjustable in width in order to control the top size of material passing through the crusher. The crushing force is produced by an eccentric component, which drives the crushing cone towards the crushing concave or bowl liner in a circular oscillating movement. Due to the friction of the material to be crushed against the cone and concave or bowl liner, the crushing cone moves slowly around the concave in the direction opposite to that of the driving rotation.
Aggregate material that passes through crusher 16 falls onto crusher collection conveyor 22 that delivers crushed material to vibratory screen assembly 24. Vibratory screen assembly 24 is comprised of upper screen deck 26 and lower screen deck 28 (shown in
The invention comprises a method of operation of aggregate processing plant 10 according to two alternative modes of operation. According to the invention, the operating speed of crusher collection conveyor 22 is varied, between a first speed and a second speed which is less than the first speed, to control the rate of placement of the crushed material onto vibratory screen assembly 24. When loading aggregate material only into crusher feed conveyor 18, as shown in
The invention thus provides a method of operation of an aggregate processing plant according to two alternative modes of operation, which does not require processing all of the aggregate material through the crusher of the processing plant or the addition of a pre-screen component.
Although this description contains many specifics, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments thereof, as well as the best mode contemplated by the inventor of carrying out the invention. The invention, as described and claimed herein, is susceptible to various modifications and adaptations as would be appreciated by those having ordinary skill in the art to which the invention relates.
This application claims the benefit of U.S. Provisional Patent Application No. 62/560,833, filed on Sep. 20, 2017 and entitled METHOD OF USE OF PORTABLE CRUSHING/SCREENING EQUIPMENT, which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62560833 | Sep 2017 | US |
