Patent Application
20110036759
This invention relates to screening machines of the type used to separate or classify mixtures of solid particles of different sizes. The invention also relates to screening machines of the type used for liquid/solid separations, i.e., for separating solid particles of specific sizes from a liquid in which they are carried. More particularly, the invention relates to an improved screen panel for use within the screening machine.
In screening machines of the type described, a screen (which may be woven, an aperture plate or another design) is mounted in what is often called a “screen frame” or “screen deck” which includes a supporting peripheral frame around the perimeter of the screen. Some screens are tensioned when they are installed in the screening machine and other screens are pre-tensioned in a frame prior to being installed in the machine. Typically associated with the screen deck are other material handling elements which are moved with the screen and form walls or partitions above or below the screen for containing the liquid and/or particulate materials adjacent to the screen and directing them to appropriate outlets. These elements may comprise a top cover and a pan beneath the screen deck. In the case of screening machines with multiple screens or deck units, spacer pans or frames are provided between the multiple screens.
The screens are often removed from the screening machines for cleaning, replacement, readjustment or installation of a screen of a different mesh size or the like. The screen is releasably mounted to a carrier, table or box to which vibratory motion is imparted, typically by one or more eccentric motors or other means of excitation. The carrier, table or box is referred to herein as a “vibratory carrier”. The vibratory carrier may be moved in oscillatory, vibratory, gyratory, gyratory reciprocating, fully gyratory, rotary or another type of motion or combinations thereof, all of which are herein collectively referred to as “vibratory” motion or variations of that term.
In large commercial screening machines, the weight of the various components including the screen assembly carried by the vibratory carrier, and the weight of the material being processed on the screen assembly may total several hundred pounds or more. Screening machines which tension the screen, as opposed to those utilizing pre-tensioned screens, include the added weight associated with the screen tensioning mechanism and related components. This presents a very substantial inertial mass which resists the changes of motion applied thereto by the vibratory drive acting through the vibratory carrier. As a result of these inertial forces, a relative motion may exist between the vibratory carrier and the screen assembly. Typically, the screen assembly and vibratory carrier are each constructed of metal which could result in significant noise, wear and damage due to the relative motion or rubbing action there between. The resulting impact forces between the screen assembly and vibratory carrier significantly increase the stresses on the components and reduce their useful life.
Reducing the metal-to-metal contact minimizes the wear on the various metal components and the noise associated with the operation of the screening machine. Currently, certain screen assembly designs may not be sealed or secured relative to the remainder of the screening machine, particularly in larger screening machines. This results in the above-described metal-to-metal contact between the screen assembly and the remainder of the screening machine and prevents the screening of very fine material, such as sand or the like. The screens in larger screening machines are typically inserted and/or removed from the machine in a generally horizontal, longitudinal direction typically through an opening or slot at the head or foot end of the machine. This method of installation and removal of the screen is detrimental to known sealing arrangements because a seal which would engage the screen assembly could be torn or damaged during the installation/removal of the screen. In other screening machines, the screen is inserted vertically, typically from the top of the machine. Access to the screens from the top of the machine or the longitudinal ends is often very inconvenient and difficult.
The above-described and other problems with prior art screening machines and associated screen panels have been resolved by this invention. Screening machines according to one embodiment of this invention utilize one or more pre-tensioned screens mounted in a perimeter frame for separating various granular and particulate material. One aspect of this invention is the profile or contour of opposite ends of the perimeter frame for the screen. The mesh screen is mounted to a rigid perimeter frame. The screen is pre-tensioned in the frame as opposed to screens which are stretched or tensioned during the screening machine set up. The frame is slid into the side of the machine in a direction parallel with two opposing contoured profile ends of the frame. In one embodiment, the profile of the frame along each end includes a downwardly directed bevel relative to the plane of the screen. The profile or contour of these ends align with and mate in the screening machine with a complementary channel such that when the screen is raised into sealing contact in the screening machine, the bevel ends of the screen panel frame align the screen panel in the machine through a comparably dimensioned and configured channel on the screening machine. Likewise, the bevels on the screen panel frame provide a positive sealing surface for contact with the adjacent portions of the channel to prevent product from escaping off of the screen during use.
Therefore, according to this invention, the screening operation is much more efficient and more easily accomplished while offering significant advantages in screen service life, installation and removal.
The objectives and features of the invention will become more readily apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
Referring to
The screening machine 10 includes an inlet port 12 near an inlet section 14 proximate a head end 16 of the machine 10. The screening machine 10 may also include a top cover 18 in any one of a variety of forms. Particulate or other material to be screened is fed into the inlet port 12 from a hopper (not shown) for screening and processing by the machine 10.
The screening machine 10 is supported structurally by a base frame 20 including beams 22 connected together by laterally oriented struts 24 on each end of the screening machine 10. The screening machine 10 includes an electric motor 26 coupled to a drive weight (not shown) to impart an oscillatory, vibratory, gyratory, gyratory reciprocating, fully gyratory, other motion or combinations thereof (herein collectively referred to as “vibratory” motion or variations of that term) to at least the head end 16.
Within a screening chamber of the screening machine 10, one or more screen panels 28 are each mounted in combination to form one or more screen decks 30 to receive the material being screened from the feed chute 12 at the head end 16 of the machine 10. The screen panels 28, are mounted on slightly sloping planes (approximately 4°) with the head end thereof being slightly elevated relative to a foot end so that during the screening process the material advances, in part by gravity, over the screen panels 28 toward the foot or discharge end 32 of the machine 10. Even though the screen panels 28 of the screening machine 10 may be on a slightly sloping plane, to provide a reference for the purposes of clarity herein, these components will be considered to be generally horizontal and the direction perpendicular or orthogonal to the screen panels 28 will generally be referred to as a vertical orientation, direction or attitude. The direction of travel of the material being screened from the head end to the foot end across the screen panels 28 is referred to as the longitudinal direction and the perpendicular orientation extending from side to side on the screen panels is a lateral direction.
In the embodiment of the screening machine 10 shown in
The unacceptably sized particles remain atop the first upper screen deck 30 and fall off the terminal edge thereof into a collection basin for discharge through the outlet section 36. Material that passes through the upper screen deck 30 and remains atop the lower screen deck 30 falls off the terminal edge thereof and into the collection basin for discharge through a reject port (not shown). The discharge and reject ports are separated by a baffle (not shown) to keep the classified particles separate from one another.
Referring to
As shown generally in
Referring to
The panel 28 may be manufactured by a variety of processes, one of which utilizes a bare metal frame which is dipped into an epoxy and allowed to air dry. The epoxy is hard to the touch but has not cured. The frame 54 with dry epoxy is then placed on a table with mesh screen material 34 on top. This stack-up is then bonded together with a heat press for a few minutes. The edges are then cleaned up with a hand grinder, if necessary.
A further benefit of this aspect of the invention is that the process leaves the panel 28 feeling tensioned although no time or fixture is required to pull (tension) the screen material 34 prior to bonding it to the frame 54 or when installing the screen frame panel into the screening machine 10. The new panel 28 design incorporates this approach such that open area is maximized but the tension level is comparable to known tension techniques, such as spring clips.
The leading side edge 56 of the screen panel frame 54 is typically inserted laterally into the screening machine 10 while a user or operator grasps the trailing side edge 58 for manipulation. In particular, a downwardly turned elongate handle 60 is formed on the trailing side edge 58 of the screen panel 28. In one embodiment, the handle 60 is oriented approximately 90° relative to the plane of the screen panel 28 and provides a convenient and easy access for the user or technician to grasp or manipulate the screen panel 28. Additionally, the handle 60 or adjacent surfaces of the screen panel frame 54 provide a convenient location for identifying indicia and labels indicating various service parameters, design characteristics and other aspects of the screen panel 28.
One or more tabs 62 each located proximate a head end 64 or a tail end 66 of the screen frame 54 are located along the trailing side edge 58 of the frame. The tabs 62 are each oriented approximately 90° relative to the plane of the screen panel 28 and along with the handle 60 provide a convenient location for the user or technician to grasp and manipulate the screen panel frame. Likewise, upon insertion of the screen panel 28 into the screening machine 10, the tabs 62 and handle 60 provide a detent when juxtaposed against the vibratory carrier 44 for proper orientation and location of the screen panel 28 in the screening machine 10.
Another aspect of the screen panel 28 and associated frame 54 according to this invention are beveled edges or lips 68 along the longitudinal head end 64 and/or foot end 66 of the screen panel frame 54. Each bevel 68 is oriented approximately 45° relative to the upper surface or plane of the screen panel 28 and extends substantially the entire width of the frame 54. While the bevel 68 are shown along both the longitudinal head and foot ends 64, 66 of the screen panel frame 54, one of ordinary skill in the art will readily appreciate that the bevel edge 68 may be provided at either or both of the head and foot ends 64, 66 within the scope of this invention.
Referring to
The screening machine 10 includes a bracket 76 in which a rotational cam 78 is seated to support the carrier 44. The rotation of the cam 78 is accomplished by an actuator 80 accessible to the operator or technician when the door 38 of the screening machine 10 is open. One known mechanism suitable for use with this invention to raise/lower the carrier 44 and screen panel 28 is disclosed in Rotex' U.S. Pat. No. 6,070,736 which is incorporated by reference herein. The screening machine 10 also includes a downwardly depending channel 82 initially spaced from the bevel lip 68 of the screen frame 54 as shown in
Upon rotation in the direction of arrow A of the actuator 80, the cam 78 is rotated thereby raising the carrier 44 and screen panel 28 supported thereon upwardly to sealing engagement with an upper portion 84 of the screen deck 30 as shown in
The bevel edges 68 on two opposite ends in conjunction with the lift system described in U.S. Pat. No. 6,070,736 permits insertion and proper location, alignment, sealing, and securing of the screen panel 28 to the screening machine 10 while maintaining a smooth transition (no bumps or wear points). This invention offers a screen panel 28 that is pre-tensioned, ready to use, lightweight, standardized in size to lower cost, simple design, mass producible, easy to handle, nestable for storage and shipping. The bevel lip 68 also acts as a seal holder for reusable seal strips 72.
Referring to
From the above disclosure of the general principles of the present invention and the preceding detailed description of at least one preferred embodiment, those skilled in the art will readily comprehend the various modifications to which this invention is susceptible. Therefore, I desire to be limited only by the scope of the following claims and equivalents thereof.
