Abstract:
Disclosed is a vibrating material sorting screen with a substantially variable tilt angle and a tilt angle measuring device where the screen has a gear box which is horizontal when the screen is horizontal and inclined when the screen is inclined and further where the gear box has a plurality of oil level sensors or indicators therein which are sized, placed and configured to provide proper oil volume while the screen is oriented horizontally or at various inclines.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of the filing date of co-pending provisional patent application entitled “VARIABLE SLOPE 3-SHAFT VIBRATING MECHANISM”, having Ser. No. 61/088,987, which was filed on Aug. 14, 2008, by Edwin J. Sauser, which provisional patent application is incorporated herein in its entirety by this reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention generally relates to vibrating screens used in mining or road building material handling and processing. 
       BACKGROUND OF THE INVENTION 
       [0003]    In the past, vibrating screen machines are normally made of a box-like structure mounted on flexible springs and contain one or multiple layers of screen mesh to sort granular materials. The different sized openings in the mesh allow sizing of materials according to the size of these openings. The box structure usually contains an eccentric weighted shaft that shakes the box and its screen mesh to agitate and separate the granular materials fed into the top of the machine. 
         [0004]    Vibrating screens can be categorized in many ways. Horizontal (see  FIG. 1 ) and sloped screens (see  FIG. 2 ) are common ways to categorize these screens. 
         [0005]    The two designs are used in different applications. The sloped screen decks are desirable in applications where there is a high percentage of “oversize” material that is larger than the openings in the screen cloth. The opening size is determined by the size of the material desired to remove from the feed material. When too much material is riding on the deck, the material is too deep to efficiently allow fine material to sift through the bed of material and get to the screen cloth for separation. The horizontal screens are more effective when there are difficult conditions requiring more retention time on the screen decks; for example, a high amount of “near size” material. Also, applying water to clean the material is more desirable on horizontal decks, since the sloped decks will wash material down and off the end before it can drop through the screen cloth. 
         [0006]    There are many types of triple shaft screens. One could gather a group of prior art sloped screens, each of which has a different single set angle at which the decks are sloped. One thing in common with these sloped machines is that they still utilize a horizontal constructed gear case (See  FIG. 2 ). 
         [0007]    Typically, the 3-shaft vibrating mechanism consists of three eccentrically weighted shafts geared together, so that the center or second shaft rotates counter of the adjacent first and third shafts. This mechanism utilizes a common gear case with common oil splash lubrication for all gears and bearings. All three shafts are geared together on a common horizontal plane to maintain uniform splash lubrication on all three shaft/bearing assemblies. 
         [0008]    The counter rotating center eccentric adds or subtracts from the total vibrator thrust, depending on phase with the outer two eccentrics to create the unique oval motion on the vibrating screen box. It is well known that an oval stroke is preferred and that the manner for producing an oval stroke is also well known. 
         [0009]    It is well known that a sloped gear case will, at least when the screen is not operating, let lubrication oil pool to the low end, thus increasing the oil depth on the low end. It is also widely believed that since the oil flows to the lower end, there is a danger of starving the bearings toward the high end of oil. It is also believed that simply increasing the amount of oil in the gear case, and thereby increasing the overall oil depth, would create more splash in the upper end, but would flood the lower bearings, causing excessive heat. 
         [0010]    It is also widely believed that if a user desires the ability to utilize triple shaft screening over a wide range of angles, that a collection of several sloped screens, each with a single fixed slope angle, be available. However, this can be extremely expensive and difficult to exchange on the machine in which the screen is operating. 
         [0011]    Requiring a horizontal mounting plane of the shaft housings for the multiple shaft style screen which is operating on a sloped orientation requires greater distance between the decks directly above and below the shaft housings since all the housings are not aligned along the upper deck. 
         [0012]    Consequently, there is a need for a relatively inexpensive way to provide a triple shaft screen to operate over a wide range of screen slope angles and not require different screens built on different slopes for different applications. 
       SUMMARY OF THE INVENTION 
       [0013]    It is an object of the present invention to provide a vibrating screen machine with geared counter rotating shafts which can be operated with the counter rotating shafts aligned along the slope of the screen surface, whether horizontally or on a sloped plane, without modifying the oil level or lubrication system when the screen is operated at various sloped angles. 
         [0014]    It is a possible feature of the present invention to provide a mechanical means configured to assist in raising and lowering a 3-shaft vibrating screen over a wide range of angles. 
         [0015]    It is another possible feature of the present invention to provide a means and instructions for measuring the slope angle of a screen over a wide range of angles. 
         [0016]    It is another possible feature of the present invention to include a system for or perform the step of determining an amount of airborne and otherwise displaced oil in an operating vibrating screen with an inclined 3-shaft gear case. 
         [0017]    It is an advantage of the present invention to provide for the ability of deploying a single 3-shaft vibrating screen over a wide range of angles. 
         [0018]    It is also an advantage of the present invention to provide maximum clearance under the shaft housings running through the screen to the screening surface directly below the shaft housings. 
         [0019]    The present invention is an apparatus and method for screening material which is designed to satisfy the aforementioned needs, provide the previously stated objects, include the above-listed features, and achieve the already articulated advantages. For some screening operations, the present invention is carried out in an “oil-starved bearing-less system” in a sense that the oil-starved bearings believed to result from excessive incline of the screen during operation have been eliminated. 
         [0020]    Accordingly, the present invention is a system and method for operating 3-shaft screening operations over a wide range of screen slope angles. 
         [0021]    The present invention is a system for screening material comprising: 
         [0022]    a vibrating screen having a material receiving surface; 
         [0023]    means for continuously varying a continuously variable slope angle of said material receiving surface with respect to a ground reference over an extended range of angles which is substantially greater than 3 degrees; 
         [0024]    means for measuring said continuously variable slope angle; 
         [0025]    means for housing a plurality of gears each coupled to one of a plurality of eccentric shafts; 
         [0026]    means for measuring an oil level at a downhill end of said means for housing when said plurality of eccentric shafts are not rotating; 
         [0027]    means for detecting varying reductions in said oil level when said plurality of eccentric shafts are rotated at variable rotation rates; and 
         [0028]    means for regulating rotation rates of said plurality of eccentric shafts so as to maximize a reduction in said oil level from said oil level when said plurality of eccentric shafts are not rotating. 
         [0029]    The present invention is also a method of screen material comprising the steps of: 
         [0030]    providing a vibrating screen having a material receiving surface; 
         [0031]    providing a means for continuously varying a continuously variable slope angle of said material receiving surface with respect to a ground reference over an extended range of angles which is substantially greater than 3 degrees; 
         [0032]    providing a means for measuring said continuously variable slope angle; 
         [0033]    providing a means for housing a plurality of gears each coupled to one of a plurality of eccentric shafts; 
         [0034]    providing a means for measuring an oil level at a downhill end of said means for housing when said plurality of eccentric shafts are not rotating; 
         [0035]    detecting varying reductions in said oil level when said plurality of eccentric shafts are rotated at variable rotation rates; and 
         [0036]    regulating rotation rates of said plurality of eccentric shafts so as to maximize a reduction in said oil level from said oil level when said plurality of eccentric shafts are not rotating. 
         [0037]    This invention is further a material sorting screen comprising: 
         [0038]    a material sorting screen comprising: 
         [0039]    a housing structure, comprising a base having a base longitudinal axis; 
         [0040]    a screen at least indirectly coupled to said housing structure, said screen comprising a plurality of openings of a predetermined size; 
         [0041]    a gear case, at least indirectly coupled to said housing structure; and having a gear case longitudinal axis which is oriented so as to be substantially parallel with said base longitudinal axis; 
         [0042]    a plurality of unbalanced shafts coupled to a plurality of gears in said gear case; said plurality of unbalanced shafts, when rotated, are configured to create vibration in said screen; 
         [0043]    said housing structure is installed at an operational location such that said base longitudinal axis is at an angle of inclination substantially greater than 3 degrees with respect to a horizontal reference line. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0044]    The invention may be more fully understood by reading the following description of the preferred embodiments of the invention, in conjunction with the appended drawings wherein: 
           [0045]      FIG. 1  is an elevation view of a vibrating screen of the prior art, shown in a horizontal configuration. 
           [0046]      FIG. 2  is an elevation view of a vibrating screen of the prior art, shown in an inclined operating configuration. 
           [0047]      FIG. 3  is a side view of a partially dismantled 3-shaft gear box of the present invention. 
           [0048]      FIG. 4  is a view of the 3-shaft gear box of  FIG. 3  in an inclined orientation and in a non-operating state. 
           [0049]      FIG. 5  is a view of the gear box of  FIGS. 3-4  shown in a horizontal orientation and in a non-operating state. 
           [0050]      FIG. 6  is a view of the gear box of  FIG. 4  in an operating state. 
           [0051]      FIG. 7  is a view of the gear box of  FIG. 5  in an operating state. 
           [0052]      FIG. 8  is a side view of the system of the present invention in a horizontal orientation. 
           [0053]      FIG. 9  is a side view of the system of the present invention in an inclined orientation. 
       
    
    
     DETAILED DESCRIPTION 
       [0054]    Now referring to the drawings wherein like numerals refer to like matter throughout, and more particularly to  FIG. 1 , there is shown a vibrating screen system  100  of the prior art. Vibrating screen system  100  is a horizontal system which is configured to be used in a level or horizontal orientation, with respect to a ground level  101  which is parallel with and adjacent to system bottom line  104 , which is parallel with top screen  105 . It should be noted that the gear case  102  is shown in a totally non-skewed level orientation as well; i.e., the gear box  102  is parallel with the top screen  105  and with the ground line  101 . 
         [0055]    Now referring to  FIG. 2 , there is shown the vibrating screen system  200  of the prior art which shows a gear box  202  which is skewed with respect to a bottom line  204  of system  200  and with respect to top screen  205 , but is level or non-skewed with respect to the ground line  101 . The angle between ground line  101  and bottom line  204  is theta θ and is herein referred to as the slope or the slope angle. In  FIG. 1 , θ is 0 and is not shown. 
         [0056]    Now referring to  FIG. 3 , there is shown a side view of the 3-shaft gear box  300  of the present invention, which has a cover removed to expose the internal components. Gear box  300  may employ many well-known prior art structures, including, but not limited to, the system described in U.S. Pat. No. 6,161,650 entitled “Lubricating System for a Vibratory Apparatus”, issued on Dec. 19, 2000. 3-shaft gear box  300  includes left gear  302 , center gear  304 , and right gear  306 , all disposed between left gear box side  312  and right gear box side  316  and between gear box bottom  320  and gear box top  330 . 3-shaft gear box  300  is shown having a means for measuring the oil level and oil pool orientation within the 3-shaft gear box  300 . The means for measuring oil level includes left side vertical oil height sensor array  340 , which can be sensors extending vertically at the left side. These sensors can be contact sensors which sense contact with the oil or may be optical sensors paired with opposing optical transmitters on the opposing side of the 3-shaft gear box  300 . Electrical and mechanical sensors and any other type of sensor could be substituted as well. Bottom oil height sensor array  350  is shown extending across the bottom of the 3-shaft gear box  300 . This could be a single line of sensors or multiple lines of sensors. Right side vertical oil height sensor array  360  can be similar to left side vertical oil height sensor array  340 . Any suitable means for measuring the oil pool level at varying depths and locations could be substituted. In some embodiments of the present invention, it might be desirable to utilize a simpler oil level or oil volume indicator, such as including multiple oil level plugs or a clear sight glass or clear hose, which would permit visual inspection of the oil level and oil volume. If multiple oil level plugs are used, each oil level plug could be associated with a predetermined inclination angle or range of inclination angles. 
         [0057]    Now referring to  FIG. 4 , there is shown the 3-shaft gear box  300  of  FIG. 3  except that it has been inclined with a slope angle of θ, and non-operating oil pool  402  is also shown. The non-operating oil pool  402  is shown at the downhill end of 3-shaft gear box  300 , as would be expected. 
         [0058]    Now referring to  FIG. 5 , there is shown the 3-shaft gear box  300  of  FIG. 3  except that it has been inclined with a slope angle of θ, where θ is 0, and non-operating oil pool  402  is also shown. The non-operating oil pool  402  is shown evenly distributed across the 3-shaft gear box  300 , as would be expected. 
         [0059]    Now referring to  FIG. 6 , there is shown the 3-shaft gear box  300  of  FIG. 5  except that it has been inclined with a slope angle of θ, where θ is 0, and operating oil pool left dead zone  602  is also shown. Operating oil pool right dead zone  604  is also shown. If the oil level determination means determines that no oil is in the bottom right end of the gear box  300 , it can be deduced that a large portion of the remainder of the oil is either airborne in a mist, on the gears or in dead zone. If the oil is in either the operating oil pool left dead zone  602  or the operating oil pool right dead zone  604 , it will be in contact with each gear and will be providing the desired lubrication. Since many factors can affect the size of the dead zones, such as the temperature, the speed of the gears, the pressure within the gear box, the amount of oil in the gear box, and the slope angle θ, it may be necessary to regulate one or more of these variables (except slope angle θ) to assure that proper dead zones are being maintained for each chosen slope angle θ. The present invention provides all of the information if a thermometer, a pressure sensor and some means for determining oil level are included in the 3-shaft gear box  300 . The first slope angle determination device  810  can be an electronic sensor coupled with a system for processing data from the other sensors so as to provide information to an i/o device  850 , which could be a touch screen display or any suitable substitute. The electronic control system could be used to control at least some of the parameters being monitored so as to regulate the dead zone size. 
         [0060]    The “dead” zones in the gear case are believed to allow oil to be pushed into them, preventing excess turbulence and heat buildup from over-churning the oil. The turbulence and air currents are believed to create these dead zones whether the gear case is mounted horizontally or at some angle θ. With the existence of turbulence and the creation of the dead zones, the gear case is able to provide adequate lubrication at any normal screening slope. A screen with a fixed gear case construction will be able to operate horizontally or at an extended range of slope angles, thus increasing the capabilities and applications a single screen machine can operate in. The term “extended range” is used herein to extend from 0 degrees up to 10-15 degrees or more. A range of 0-3 degrees would not be considered an “extended range”. “Extended range” should be interpreted to cover various ranges and could include a range from 3-15 degrees or any ranges contained within this range. 
         [0061]      FIG. 7  shows the 3-shaft gear box  300  of  FIG. 6 , but inclined at slope angle θ. 
         [0062]      FIG. 8  shows the variable angle screen  800  of the present invention disposed at a slope angle θ of 0, which can includes various additional structural features, such as outer hydraulic cylinder  802 , inner hydraulic cylinder  804  and foot pad  806 , all shown in a configuration where no lifting forces are being applied to the variable angle screen  800  to create a slope angle θ greater than 0. 
         [0063]    Also shown are first slope angle determination device  810  and air bubble  812 , which assumes a simple level mechanism is used. It should be understood that other more or less sophisticated angle determination devices could be used, including electronic and other mechanisms. 
         [0064]    Also shown is tether  822  which could be attached to the top of variable angle screen  800  and hang downward to nearly the bottom of variable angle screen  800  at level termination point  826  and acts like a plumb bob. The location of the free end of tether  822  is adjacent the gauge  824 , which provides for measurement of slope angle. The location of the tether attached to the vibrating screen section is shown primarily for illustrative purposes and is not preferred. It may be preferred to deploy a similar system on the base or frame section which would not be vibrating as much as the upper sections of the screen. Also shown is computer/communication electronics module  850  which can provide communication and control for any electronic components on variable angle screen  800 . Similarly, the electronics module  850  is shown for illustrative purposes, but it may be preferred to mount it at a lower portion on the screen system which vibrates less. 
         [0065]      FIG. 9  shows a view of the variable angle screen  800  disposed at a non-zero slope angle. Inner hydraulic cylinder  804  is shown exposed, and tether  822  is shown hanging down to inclined termination point  928 , which indicates the slope angle when read against the gauge  824 . 
         [0066]    It should be understood that while the description is focused on 3-shaft gear cases, the present invention is intended to include any multiple-shaft gear case from 2 shafts, three shafts, 4 shafts or more. 
         [0067]    It is thought that the method and apparatus of the present invention will be understood from the foregoing description and that it will be apparent that various changes may be made in the form, construct steps, and arrangement of the parts and steps thereof, without departing from the spirit and scope of the invention or sacrificing all of their material advantages. The form herein described is merely a preferred exemplary embodiment thereof.