Abstract:
The log washer with staggered paddles is a device for washing and separating aggregates, such as sand, gravel, ores, etc., from waste material. The log washer has a water tank or trough having one end inclined or raised relative to horizontal. A pair of shafts are mounted for rotation in bearings in the end walls of the tank, and connected to a driver by appropriate gearing so that the shafts rotate in opposite directions. Each shaft has a plurality of paddles mounted thereon, each paddle being mounted at an angle to the shaft to raise washed aggregates up the inclined trough to a discharge hopper or conveyor belt. Further, the paddles on each shaft are grouped in sections, the radial angle formed by adjacent sections with the shaft being staggered, the paddles on adjacent shafts being offset so that the aggregate material is ground between the paddles.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to apparatus for separating and washing clay, shale, and other contaminants from gravel, and particularly to a log washer having staggered paddles. 
     2. Description of the Related Art 
     Gravel is a commonly used material in the construction industry, being used in concrete, in paving, in landscaping, and as a component in other materials and the performance of other functions. Gravel may be obtained by strip mining techniques, from quarries, by dredging operations, and other methods. Typically gravel obtained by such methods will be mixed with clay mud balls or other soils, often containing grass, roots, and small wood or tree branch fragments, or with shale, sand, sandstone, limestone, or other earthen materials. In order to prepare gravel for market, it is necessary to separate the gravel from the earthen materials in which it is found, and to wash the gravel so that it is free from such contaminants. 
     Fine grades of gravel are usually separated and washed in devices which use a screw conveyor or auger, having a continuous, smooth, helical spiral blade about its circumference similar to the thread of a screw. Examples of such devices are shown in U.S. Pat. No. 1,695,021, issued Dec. 11, 1928 to Puryear (two parallel screws driven by planetary gears, with improved arrangement of water jets and valves for directing the flow of water in the tank), and in U.S. Pat. No. 2,025,841, issued Dec. 31, 1935 to Young (trough with screw conveyors and a novel de-shaling hopper for removing shale from gravel by water jets). Sometimes notches will be cut into the threads at regular intervals to break up clumped material, e.g., the cut-flight conveyor shown in FIG. 31 at page 1426 of Marks&#39; Mechanical Engineers&#39; Handbook (4th ed., 1941), U.S. Pat. No. 4,448,678, issued May 15, 1984 to Gentry (lignite separator with a single, hybrid shaft having a spiral lower end and a notched upper end). 
     Coarse gravel is usually separated and washed using log washers. Typical log washers have a water tank or trough mounted at an inclined angle relative to horizontal, with a pair of parallel shafts or logs mounted bearings in the end walls of the trough so that they are free to rotate. A motor is connected to one end of the shafts by appropriate gearing to drive the shafts to rotate in opposite directions. Each shaft has a plurality of paddles or blades mounted thereon, usually mounted to the shaft at an angle, the paddles on adjacent shafts being staggered so that mud balls and other clumps of material broken down by grinding between the blades of adjacent shafts, and so that the shafts carry solid rock and gravel material towards the raised end of the shaft, where the separated and washed gravel is discharged to an appropriate hopper or conveyor belt. Typically, in a conventional log washer, the paddles on a single shaft are mounted in long rows at equally spaced angular distances about the axis of the shaft, e.g., at 90° intervals. 
     Examples of conventional log washers with proposed improvements are disclosed in U.S. Pat. No. 1,609,652, issued Dec. 7, 1926 to McQueen (log washer with improved method of attaching the paddles to the shaft using keyways and aligned slots), and U.S. Pat. No. 3,807,558, issued Apr. 30, 1974 to Hamm (gravel separator using both sand screw and log washer where material introduced to trough lateral to screw or log washers into high velocity stream of water). U.S. Pat. No. 2,336,991, issued Dec. 14, 1943 to Leveke, shows a gravel washer with a single shaft having multiple sections of different diameters, one section being square in section, in which the sections are mounted eccentrically relative to the bearing to produce greater agitation in the trough. 
     The problem with conventional log washers is that the paddles on each shaft are mounted in straight rows. This configuration means that each time a row of paddles completes a revolution, the load in the tank of trough will be thrown or shifted laterally against the sidewalls of the tank. The lateral shifting of the load in the tank creates agitation and vibration along the entire length of the tank, at least four times per revolution in the case of log washers having four rows of paddles. The vibrations cause rocking in the tank supports, requiring that more time and effort be expended in preparing the foundation or supports for the tank or trough, and potentially result in greater wear and stress being placed on the bearings and/or the shaft. The present invention is directed towards a log washer shaft having staggered sections of paddles along each row, in order to reduce load shifting stresses, resulting in less strain and stress being placed upon the tank supports. 
     Other forms of separators are known for separating other mixtures of solids, having structures less related to the present invention, such as those described in the following patents: U.S. Pat. No. 1,972,195, issued Sep. 4, 1934 to Lacy, Jr. (ore washer with a chain and sprocket with buckets mounted on the chain to scoop material in a trough); U.S. Pat. No. 2,050,458, issued Aug. 11, 1936 to Ovestrud et al. (portable separator with a scrubber and a screen, but no log washers); U.S. Pat. No. 2,324,549, issued Jul. 20, 1943 to P. L. Wigton (separator with a spiral ribbon mounted on a shaft where the shaft is supported by a chain or belt); U.S. Pat. No. 2,489,161, issued Nov. 22, 1949 to Scholes (endless belt separator with improved seals); U.S. Pat. No. 4,234,415, issued Nov. 18, 1980 to de Tuya Casuso (ore separator with rotating drum); U.S. Pat. No. 5,868,256, issued Feb. 9, 1999 to Teppo (clay refiner with rotating drum); and International Patent No. WO 97/16253, published May 9, 1997 (rotating drum with inner and outer chambers). 
     None of the above inventions and patents, taken either singularly or in combination, is seen to describe the instant invention as claimed. Thus a log washer with staggered paddles solving the aforementioned problems is desired. 
     SUMMARY OF THE INVENTION 
     The log washer with staggered paddles is a device for washing and separating aggregates, such as sand, gravel, ores, etc., from clay, dirt, organic waste matter, and other impurities. The log washer has a water tank or trough having one end inclined or raised relative to horizontal. A pair of shafts are mounted for rotation in bearings in the end walls of the tank, and connected to a driver by appropriate gearing so that the shafts rotate in opposite directions. Each shaft has a plurality of paddles mounted thereon, each paddle being mounted at an angle to the shaft to raise washed aggregates up the inclined trough to a discharge hopper or conveyor belt. Further, the paddles on each shaft are grouped in sections, the radial angle formed by adjacent sections with the shaft being staggered, the paddles on adjacent shafts being offset so that the aggregate material is ground between the paddles. 
     The adjacent sections of paddles on each shaft are separated by transition zones characterized by an absence of paddles. The transition zones provide for enhanced scrubbing of the aggregate material. 
     Accordingly, it is a principal object of the invention to reduce the vibration in a log washer caused by shifting loads through staggering sections of paddles on the log washer shafts. 
     It is another object of the invention to relieve stress and strain on the supports of a log washer tank by staggering sections of paddles on the log washer shafts. 
     It is a further object of the invention to provide a log washer which separates aggregates from waste materials and washes the aggregate having smoother operation through staggering shifting loads in the log washer water tank. 
     Still another object of the invention is to reduce wear and tear on log washer tank supports, log washer shafts, and shaft bearings by offsetting sections of paddles in each row of log washer paddles. 
     It is an object of the invention to provide improved elements and arrangements thereof for the purposes described which is inexpensive, dependable and fully effective in accomplishing its intended purposes. 
     These and other objects of the present invention will become readily apparent upon further review of the following specification and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an environmental, perspective view of a log washer with staggered paddles according to the present invention. 
     FIG. 2 is a plan view of two adjacent log washer shaft with staggered paddles according to the present invention. 
     FIG. 3 is a section view along the lines  3 — 3  of FIG.  2 . 
     FIG. 4 is a section view along the lines  4 — 4  of FIG.  2 . 
     FIG. 5 is an end view of a log washer shaft with staggered paddles according to the present invention. 
     FIG. 6 is a plan view of a log washer shaft of the prior art. 
     FIG. 7 is an end view of a log washer shaft of the prior art. 
    
    
     Similar reference characters denote corresponding features consistently throughout the attached drawings. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention is a log washer with staggered paddles, designated generally as  10  in the drawings. Log washers (the device is called a log washer as they were originally made with timber logs, rather than steel shafts) are used in quarries, dredging operations, strip mining, cement mills, sand and gravel pits, and other industries where it is desired to separate and clean aggregate materials, such as gravel, sand, ores, insoluble clays, etc., which has become clumped together and/or mixed with organic waste materials and the like. FIG. 1 shows a diagrammatic view of a typical log washer installation. 
     The log washer  10  has an elongated, open top enclosure which is variously referred to as a box, trough, tank, tub, stockade, but will be referred to as a trough  12  herein. A pair of shafts  14  are mounted in parallel in the end walls of the trough  12 , each shaft  14  having a plurality of paddles  16  extending radially from the shaft  14 . The shafts  14  are hollow and made from steel. A motor  18  or other prime mover is mounted at one end of the trough  12 , the motor  18  driving a pulley  20  via an endless belt  24 , the pulley  20  being connected to the end of one of the shafts  12  via a coupling or stub shaft (not shown), causing the shaft  14  to rotate. The shafts  14  are typically coupled to each other by a gear train housed in a gear box  26 , the gear train being arranged to cause the two shafts  14  to rotate in opposite directions, i.e., one shaft  14  rotates in a clockwise direction while the other shaft  14  rotates in a counterclockwise direction. The ends of the shafts  14  opposite the motor  18  and gear box  26  are typically rotatably mounted in bearings (not shown) in the opposite end wall of the trough  12 . 
     The trough  12  is typically canted so that it slopes at an angle between 0° and about 12° relative to horizontal, preferably about 8°. Crude aggregate material  22  is introduced at the lower end of the trough  12  by a conveyor belt  28  or the like, the aggregate  22  being dropped between the shafts  14 . Water is introduced to the trough  12  in any of a variety of ways, such as with the aggregate, by means of an overhead sprayer  30 , or by introducing a current of water from the bottom of the trough  12 . The paddles  16  typically are mounted on the shaft  14  at an angle of about 25° and may be arcuate or cupped, so that the aggregate material  22  is scooped as the shafts  14  rotate and raised from the lower portion of the trough  12  to the upper portion of the trough  12  towards the gear box  26 , the aggregate material  22  being crushed and ground between the shafts  14  as the paddles  16  mesh. Soluble waste material exits the trough  12  through adjustable gates  32 , weirs or the like at the lower end of the trough  12 . Cleaned aggregate material  22  is discharged at the upper end of the trough  12  through a conveyor belt or discharge chute  34  to a collection bin  36 . 
     Frequently the log washer  10  must be installed with both ends elevated on scaffolding  38 , A-frames, or other structural supports. Log washer troughs  12  may vary in length from about eighteen to thirty-five feet, in width from four feet to nine feet, and a depth of between two and one-half to four and one-half feet. The log washer  10  may accommodate a flow of water between about twenty-five gallons per minute to seven hundred fifty gallons per minute, depending upon the capacity of the trough  12 . The weight of the log washer  10  may vary between about 9,000 pounds when unloaded to about 170,000 pounds when loaded, depending upon the size of the log washer. The shafts  14  may vary in length between about eighteen to thirty-five feet, and may have a diameter between six inches and forty-six inches. Each shaft  14  will typically have four rows of paddles  16 , with between twenty-five to thirty-five paddles  16  per row. (The span between the tip end of one paddle  16  and the tip end of the paddle  16  180° opposite may be between twenty-four and forty-six inches; log washers are frequently distinguished by the paddle span and length of the tub, e.g., 26″×18′). Each shaft  14  may rotate between about twenty-six to forty-eight revolutions per minute. 
     In a conventional log washer  10 , the four rows of paddles  16  will be spaced apart radially by about 90°, as shown in FIGS. 6 and 7. Consequently, the load, including water and aggregate material, is thrown laterally against the side walls of the trough  12  and against the bottom wall of the trough  12  four times per revolution, twenty-six to forty-eight times per minute, throughout the entire length of the shafts  14  and trough  12 . Such lateral shifting of the load sets up mechanical vibrations throughout the length of the trough  12 . These vibrations often require that additional bracing  40  be used to support the scaffolding  38 , with resulting increase in material costs and set-up time. Mechanical vibrations from shifting of the load may also result in increased torsional stresses on the shafts  14  and on the bearings supporting the shafts  14 , with consequent wear and maintenance and/or replacement costs. 
     Referring to FIGS. 2-5, the log washer  10  of the present invention reduces mechanical vibration and eliminates the need for additional bracing  40  by dividing each row of paddles  16  into sections and staggering the sections radially about the shaft  14 . By way of illustration, each row of paddles  16  on the shafts  14  shown in FIG. 2 are divided into three sections, including a first section  42 , a second section  44 , and a third section  46 . It will be noted that FIGS. 2-7 are diagrammatic, and not drawn to scale, the number of paddles  16  per shaft  14  and number of paddles  16  per section being reduced for purposes of illustration. 
     As shown in FIG. 3 the paddles  16  in the first section  42  are divided into four rows  42   a ,  42   b ,  42   c  and  42   d  which are spaced apart radially by 90°. This results in the paddles  16  of the first section  42  being spaced apart in rows centered at 0°, 90°, 180° an 270° radially about the shaft  14 . Paddles  16  in adjacent rows, e.g.,  42   a  and  42   b  are staggered axially on the shaft  14  due to the size of the paddles  16 . 
     As shown in FIG. 4, the paddles  16  in the second section  44  are also divided into four rows  44   a ,  44   b ,  44   c , and  44   d  which are spaced apart radially by 90°. However, unlike the conventional log washer shaft  14  shown in FIGS. 6 and 7, the row  44   a  is not linearly aligned with row  42   a , but is staggered radially by 120°, so that the rows in section  44  extend radially at 120°, 210°, 300°, and 30°, as shown by the dashed 0° and 120° reference lines. 
     As shown in FIG. 5, the paddles  16  in the third section  46  are also divided into four rows  46   a ,  46   b ,  46   c , and  46   d  which are spaced apart radially by 90°. The row  46   a  is not linearly aligned with the rows  42   a  or  44   a , but is staggered by 240° radially relative to the row  42   a , as shown by the dashed 0°, 120°, and 240° reference lines, so that the rows in section  46  extend radially at 240°, 330°, 60°, and 150°. Thus, rows a, b, c, and d are divided into sections  42 ,  44 , and  46 , respectively, which each of the sections  42 ,  44 , and  46  being staggered radially. 
     Consequently, the entire load in the trough  12  is not shifted simultaneously against the walls of the trough  12  four times per revolution. Rather, the load is thrown against the upper one-third of the length of the trough  12 , the middle one-third, and the lower one-third of the length of the trough  12  four times per revolution, but staggered in time by one-twelfth of a revolution. Hence the stresses generated by shifting the load are distributed over time throughout the length of the trough  12 , reducing mechanical vibration. 
     Another factor contributing to reduction in mechanical vibration are the transition zones  48  and  50  between the sections  42 ,  44 , and  46 . The transition zones  48  and  50  are regions of the shaft  14  characterized by an absence of paddles which separate the sections and have an axial length of about three inches greater than the separation between paddles  16 . The transition zones are required to maintain the spacing between paddles  16  of successive sections, and also contribute to damping of the trough vibrations. The load is raised from the lower end of the trough  12  to the higher end within the sections  42 ,  44 , and  46  by action of the paddles  16 , and is pushed through the transition zones  48  and  50  by accumulated aggregate  22  as the aggregate  22  clears each section. 
     It will be understood by those skilled in the art that the principles of the present invention have been illustrated by dividing the rows of paddles  16  on each shaft  14  into three sections  42 ,  44 , and  46 , but that the scope of the invention may extend to any embodiment which divides the rows into a plurality of sections and staggers the sections radially about the shaft  14 , optimally between two and five sections depending upon the length of the shaft  14 , three sections being preferable. It will further be understood that although the invention has been illustrated with successive sections being staggered by 120° radially, that the successive sections may be staggered by any other desired angular measure. 
     The paddles  16  (sometimes referred to as blades) may be unitary in construction, or they may be two piece in construction, having a stud or lug welded or bolted to the shaft and a cover bolted to the lug. The paddles  16  may have any desired shape, such as a fluted paddle for coarse aggregate or slurry paddles for washing clay. 
     It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.