Abstract:
A balanced vibrating conveyor apparatus is provided by using a torsion bar spring and rocker arm for conveyor trough and balancing weight. The design provides synchronized 180° out of phase vibrations of trough and balancing weight as well as balance at variations in stroke lengths. With a torsion bar spring at the rocker arm node point, dynamic forces are minimized in the conveyor frame, as well as the building support structure.

Description:
REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims the benefits, under 35 U.S.C. §119(e), of U.S. Provisional Application Ser. No. 61/075,397 filed Jun. 25, 2008 entitled “Vibratory Conveyor” which is incorporated herein by this reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates to the field of vibratory conveyors, feeders and vibrating screens. 
       BACKGROUND 
       [0003]    Vibratory conveyors are widely used for material handling applications such as conveying, feeding or screening particulate materials. According to existing designs, a longitudinally-extending material-conveying deck, tray or trough is supported on leaf or coil springs mounted on a base which itself is fixed or may be spring-mounted. A motor-driven eccentric drive device or other source of vibration imparts vibratory movement to the deck or tray, which vibration is maintained by the leaf or coil springs connected to the base. The vibratory movement of the deck or tray conveys the particulate material on the deck surface. 
         [0004]    A problem with the existing designs is that balancing vibrating conveyors which use coil springs is costly and unbalanced systems can cause heavy vibrations and noise in support structures which must be heavy and carefully designed. 
         [0005]    The foregoing examples of the related art and limitations related thereto are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings. 
       SUMMARY 
       [0006]    The following embodiments and aspects thereof are described and illustrated in conjunction with systems, tools and methods which are meant to be exemplary and illustrative, not limiting in scope. In various embodiments, one or more of the above-described problems have been reduced or eliminated, while other embodiments are directed to other improvements. 
         [0007]    The present invention provides a simple economical design to achieve a balanced vibrating conveyor or similar apparatus by using a common spring and rocker arm for conveyor trough and balancing weight. The design provides synchronized 180° out of phase vibrations of trough and balancing weight at all frequencies as well as balance at variable stroke lengths. With a torsion bar spring at the rocker arm node points, dynamic forces are minimized in the conveyor frame, as well as the building support structure. 
         [0008]    The present invention provides a vibratory conveyor comprising a frame, and a source of vibratory force for providing vibratory movement to a conveying surface, the conveying surface being pivotally attached to a counterweight element by a plurality of rocker arms, each rocker arm being mounted on the frame for pivoting motion about the central axis of one end of a torsion spring element to which it is fixed, the second end of the torsion spring element being fixed to the frame. Preferably the rocker arms are arranged in opposed pairs, with a first rocker arm in the pair being mounted on a first side of the frame for pivoting motion about the central axis of one end of a first torsion spring element to which it is fixed, the second end of the torsion spring element being fixed to the opposite side of the frame, and a second rocker arm in the pair being mounted on the opposite side of the frame for pivoting motion about the central axis of one end of a second torsion spring element to which it is fixed, the second end of the torsion spring element being fixed to the first side of the frame. Alternatively other combinations and arrangements of rocker arms and torsion spring elements can be used. Torsion bars or torsional bushings may be provided as the torsion spring element. 
         [0009]    The present invention further provides a method of conveying material comprising i) providing a vibratory conveyor comprising a frame, and a source of vibratory force for providing vibratory movement to a conveying surface, the conveying surface being pivotally attached to a counterweight element by a plurality of rocker arms, each rocker arm being mounted on the frame for pivoting motion about the central axis of one end of a torsion spring element to which it is fixed, the second end of the torsion spring element being fixed to the frame; ii) applying vibratory movement to the conveying surface and thereby applying corresponding vibratory movement to the counterweight element until a steady state oscillation is reached; and iii) either before or after step ii) transferring the material to or placing the material on the conveying surface. 
         [0010]    In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the drawings and by study of the following detailed descriptions. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0011]    Exemplary embodiments are illustrated in referenced figures of the drawings. It is intended that the embodiments and figures disclosed herein are to be considered illustrative rather than restrictive 
           [0012]      FIG. 1  is an elevation view of the vibratory conveyor according to the invention. 
           [0013]      FIG. 2  is a plan view of the vibratory conveyor shown in  FIG. 1 . 
           [0014]      FIG. 3  is a detail of the vibratory drive shown in  FIG. 1 . 
           [0015]      FIG. 4  is a cross-section taken along lines  4 - 4  of  FIG. 1 . 
           [0016]      FIG. 5  is a detail elevation view of the rocker arm and torsion bar spring assembly shown in  FIG. 1 . 
           [0017]      FIG. 6  is a detail perspective view of the rocker arm and torsion bar spring assembly shown in  FIG. 5 . 
           [0018]      FIG. 7  is a detail elevation view of a second embodiment of the invention using rocker arm and torsion bushings. 
           [0019]      FIG. 8  is a detail perspective view of the rocker arm and torsion bushing assembly shown in  FIG. 7 . 
           [0020]      FIG. 9  is a detail elevation view of a third embodiment of the invention in which the torsion bar spring assembly is located below the lower trough. 
           [0021]      FIG. 10  is a cross-section view of the assembly shown in  FIG. 9  taken along lines  10 - 10 . 
           [0022]      FIG. 11  is an elevation view of a fourth embodiment of the invention having uneven rocker bars to reduce the overall height. 
           [0023]      FIG. 12  is a cross-section view of the assembly shown in  FIG. 11  taken along lines  12 - 12 . 
           [0024]      FIG. 13  is a plan view of a screen for use in the invention. 
           [0025]      FIG. 14  is a cross-section view of the screen shown in  FIG. 13  taken along lines  14 - 14 . 
           [0026]      FIG. 15  is a cross-section view of the screen shown in  FIG. 13  taken along lines  15 - 15 . 
           [0027]      FIG. 16  is a plan view of a second embodiment of the vibratory drive. 
           [0028]      FIG. 17  is a side view of the vibratory drive shown in  FIG. 16 . 
           [0029]      FIG. 18  is a rear view of the vibratory drive shown in  FIG. 16 . 
           [0030]      FIG. 19  is a perspective view of the vibratory drive shown in  FIG. 16 . 
       
    
    
     DESCRIPTION 
       [0031]    Throughout the following description specific details are set forth in order to provide a more thorough understanding to persons skilled in the art. However, well known elements may not have been shown or described in detail to avoid unnecessarily obscuring the disclosure. Accordingly, the description and drawings are to be regarded in an illustrative, rather than a restrictive, sense. 
         [0032]    With reference to  FIG. 1 , a vibratory conveyor  10  having a flow direction as shown has a conveying trough  12 , connected to base  14  and pivoting counterweight  16  by rocker arms  18  arranged in pairs on each side of trough  12 . Motor  20  drives drive wheel  22  through drive belt  24 . As shown in  FIG. 3  in which drive wheel  22  is removed for illustration, drive wheel  22  has an eccentric axle  26  which transmits a vibratory motion to trough  12  through connecting arm  28  and coil spring  30  which is connected to trough  12  through flange  31 . Other forms of a flexible connection could be used instead of coil spring  30 , such as a rubber connector. Base  14  is raised off a supporting surface  33  by a number of legs  32 . A lower trough  34  connected to counterweight  16  may also be used as an additional counterweight while forming a lower conveyor used to convey materials. Trough  12  has an inner surface  13  which may be perforated, as further described below in reference to  FIG. 13-15 , to screen particles which fall through to trough  34  to act as a lower conveyor to convey the screened material. 
         [0033]    As shown in  FIGS. 4 ,  5  and  6 , each rocker arm  18  is pivotally connected at its upper end to trough  12  on axle  36  which is journaled in rocker arm  18  in bushing  38 . Axle  36  is fixed to trough  12  by bolt  40 . Rocker arm  18  is pivotally connected at its lower end on axle  42  which is journaled in rocker arm  18  in bushing  44 . Axle  42  is fixed to counterweight  16  by bolt  45 . Weights  46  may be placed in counterweight pan  47  to match or fine tune the weight of the counterweight  16  to that of the trough  12 . The center of rocker arm  18  is provided with a circular opening  52  for receiving the end of torsion bar  50 . The end of torsion bar  50  is secured fixedly in aperture  52  by a keyless shaft-hub friction connector  54  such as a B-LOC™ keyless shaft-hub friction connector. The other end of torsion bar  50  is secured fixedly in aperture  56  of flange  58  also by a keyless shaft/hub friction connector  60  or by other suitable means. Flange  58  is secured to base  14  by bolts, welding or the like. Horizontal torsion bar  50  pivots in bushing  64  mounted in aperture  66  of flange  68  which is secured to base  14  by bolts, welding or the like. Transverse members  62  join the parallel longitudinal members  70  of base  14 .  FIG. 6  illustrates a preferred configuration in which a pair of torsion bars  50 ,  50 ′ is mounted in each set of flanges  58 ,  68 , each connected to a rocker arm  18 , slightly offset to permit installation. 
         [0034]    Horizontal torsion bars  50  may be made of any suitable fatigue-resistant material and will vary depending on the application. A preferred form of torsion bars comprises spring steel cylindrical bars, and more preferably precision ground rounds such as C1045 or 4140HTSR, high carbon 5160H heat treated bars. Bars  50  should be free of any nicks or marks. Other suitable cylindrical bars of metal or other material may be used. In the embodiment shown in  FIG. 1-6 , horizontal torsion bars  50  are mounted half-way between the points of rotation of axles  36  and  42 . By balancing the weight of the counterweight  16  to that of the loaded trough  12  this results in balancing of the vibratory forces transmitted through the base  14  to the supporting structure. The angle of attack A ( FIG. 5 ) is the angle of the rocker arms  18  from vertical. It can be varied to vary the speed of conveying by rotating the rocker arms around their node or stationary pivot point (which in  FIG. 5  is the central axis of torsion bars  50 ) thereby changing their inclination. Suitable angles of attack have been found to be 30 degrees plus or minus 15 degrees. The direction of transport can be changed by rotating the rocker arms to the other side of a vertical line through their node or stationary pivot point. Angle B in  FIG. 5  is the total angle through which the end of torsion bar  50  which is fixed in rocker arm  18  twists. A typical setup will see a displacement or twist of the end of torsion bar  50  of a few degrees from the rest position, for a total twist in a cycle of twice that angle. The stroke of the conveyor, namely the horizontal displacement of the trough with each vibration at the steady state forced vibration frequency of torsion bars  50 , is a function of the length of the rocker arm, the weight of the trough  12  and counterweight  16 , the frequency of the vibration, the number and length and diameter of the torsion bars  50  and the modulus of elasticity of the torsion bars  50 . In the configuration described, the rocker arms also provide a vertical component of vibratory movement which in combination with the horizontal component causes the particulate material to be conveyed when in operation. 
         [0035]    For different size conveyors having differing widths, torsion bars  50  having different diameters will be advisable, since the spring force of the bars  50  is a function of the diameter and length of the bars. Torsion bars having a variable or progressive spring rate can also be provided by varying the diameter of the torsion bar along the length of the bar. 
         [0036]    In operation, motor  20  is started and oscillatory motion is transmitted through flange  31  to trough  12 . Such oscillatory motion causes rocker arms  18  to start to pivot about the central axes of torsion bars  50  at increasing angles of displacement until a steady state oscillation is reached at a smooth operational state, referred to herein as the “natural frequency” of torsion bars  50 . The stationary pivot point about which the rocker arms pivot at their natural frequency is referred to as their “node”. Particulate material placed on surface  13  of trough  12  is then conveyed due to the vertical component of vibration accompanying the horizontal component of vibration. If desired, the lower trough  34  can be used as a second vibratory conveyor to transport material from another source or screened from the conveyor trough  12  above. 
         [0037]    The conveying speed may be varied by varying the frequency of vibration. This can be accomplished by varying the speed of motor  20 . This can be done simply by use of a variable frequency drive to vary the frequency of the electric power provided to the motor  20 . For example motor  20  may run at 1800 rpm with a 60 hertz frequency of the electric power provided. Using a variable frequency drive the speed of the motor can be increased or decreased by varying the electrical power above or below 60 hertz by varying the frequency drive. In turn this will vary the conveying speed. The frequency of the drive may alternatively be varied by the use of variable pitch belt sheaves or other variable-RPM arrangement. 
         [0038]      FIGS. 7 and 8  illustrate an alternate embodiment in which torsion bars  50  are replaced with torsion bushings  80 . The torsion bushing  80  has an outer cylindrical metal surface  88  which is welded to the rocker arm  18  and an inner cylindrical bushing surface  86  which is secured to flange  84  by bolt  82 . The material  81  between surfaces  88  and  86  has a suitable degree of flexibility that it functions in the same way as the torsion bars  50 . A suitable material for example is TDI polyester based polyurethane. Suitable torsion bushings are manufactured by Redwood Plastics. Alternatively inner cylindrical bushing surface  86  of the torsion bushing  80  can be welded to the rocker arm  18  and the outer cylindrical metal surface  88  secured to flange  84 . Similar torsion bushings can be provided at any one, or two or all of the pivot axes  83 ,  85 ,  87  of rocker arms  118 . 
         [0039]      FIGS. 9 and 10  illustrate an alternate embodiment of the conveyor  100  having two conveying troughs  104 ,  106  wherein the torsion bar  102  is located beneath the lower trough  106  in order to clear the space above the lower trough  106 . In this case the central axis  108  of rocker arms  18  pivots freely on central beam  114  which is fixed on legs  115  to base  116 . The lower pivot point  110  of rocker arms  18  is fixed on one end of torsion bar  102  in the manner described above while the other end  111  of torsion bar  102  is fixed in flange  112 , which in turn is connected to trough  106  by plate  107 . Torsion bar  102  rotates in flange  113  which is secured to trough  106  by plate  109 . Otherwise this embodiment functions as in the first embodiment. Motor  20  can be mounted centrally of the conveyor lengthwise with springs  30  straddling either side of trough  106 . Motor  20  can also be mounted towards either end of the conveyor. Similarly the torsion bars  102  can be located above trough  104  or at any one, or two or all of the pivot axes of rocker arms  18 . 
         [0040]      FIGS. 11 and 12  illustrate an alternate embodiment of the conveyor  120  having a low profile to reduce the overall height of the machine. A single conveying trough  122  is provided and the torsion bar  124  is located beneath the conveying trough. To achieve a lower height the rocker arms have uneven lengths about the central pivot point  128 . That is, the length C of the arm from the lower axis  126  to the central axis  128  is greater than the length D of the arm from the upper axis  130  to the central axis  128 . The upper end of rocker arms  118  are pivotally connected to parallel longitudinal balance beams  132  by bolts  138  as described above. Balance beams  132  provide the upper counterweight during the oscillatory motion. They may be stiffened to move in unison by providing connector bars  134  which are connected by beams  136  extending beneath the torsion bars  124 . The center  128  of rocker arms  118  is connected to parallel central beams  142  by bolts  140  as described above. Beams  142  are secured to legs  135 . Motor  20  can be mounted in the center of the conveyor lengthwise with springs  30  straddling either side of trough  122 . Motor  20  can also be mounted towards either end of the conveyor. 
         [0041]      FIGS. 13 to 15  illustrate a design for the conveyor trough  150  with a slotted profiled screen horizontal support surface  152 , in the case of a conveyor moving particles in the direction from right to left in  FIG. 13 . This is an alternative to the inner surface  13  described above in respect of  FIG. 2  which may be perforated to screen particles. A series of parallel transverse slotted apertures  154  is formed by transverse plates  158 . A series of diverting bars  156  are secured to plates  158 , the lower leading edge of bars  156  being welded to the upper surface of plates  158  and the upper trailing edge of bars  156  being welded to the lower surface of plates  158 . Bars  156  are angled from the vertical on either side of the longitudinal center line of the trough at progressively greater angles as the distance from the center increases in order to fan out the material to prevent plugging. The larger conveyed pieces continue over plates  158  from right to left while the smaller screened pieces drop down through apertures  154 . The diverting bars  156  therefore tend to spread the screened materials away from the center of the conveyor as it passes through apertures  154 . 
         [0042]      FIGS. 16 through 19  illustrate a second embodiment of the vibratory drive which is springless. Motor  20  as in  FIG. 1  drives sheave  216  through drive belt  24 . Sheave  216  is mounted on an eccentric shaft  214  which rotates in bearing  223  and transmits a vibratory motion to rocker arms  18  through drive arms  226 ,  227  as described below. The ends of rocker arms  18  are pivotally connected to the conveyor troughs on bushings  210  as previously described. A balancing weight  213  is attached to shaft  214  by a hub  212  and lock assembly  234  in order to assist in balancing the drive system by countering the offset of eccentric shaft  214 . Drive arms  226 ,  227  are journaled at one end on shaft  214  for rotation on bearings  222  and pivotally connected at the other end  219  to torsion arms  215 . In the configuration shown one of the drive arms  226  is shorter than the other  227 . Torsion arms  215  are locked at their upper end on torsion bars  50  by lock assembly  235  adjacent the flanges  228  in which the end of torsion bar  50  is free to rotate in bushing  227 . The other end of torsion bar  50  is locked in the central axis of rocker arm  18  by lock assembly  236 . In this way the drive provides a vibratory motion directly to torsion bars  50  which is communicated to the rocker arms  18  and thence to the conveyor. 
         [0043]    The vibrating conveyor systems described above can be applied generally to vibratory feeders as well as to vibrating screens whereby the angle of attack of the rocker arms can be selected to reduce the amount of conveying movement. 
         [0044]    The present invention therefore provides a vibratory conveyor comprising a frame, and a source of vibratory force mounted on a suitable location for providing vibratory movement to a conveying surface, the conveying surface being pivotally attached to a counterweight element by a plurality of rocker arms, each rocker arm being mounted on the frame for pivoting motion about the central axis of one end of a torsion spring element to which it is fixed, the second end of the torsion spring element being fixed to the frame. Preferably the rocker arms are arranged in opposed pairs, with a first rocker arm in the pair being mounted on a first side of the frame for pivoting motion about the central axis of one end of a first torsion spring element to which it is fixed, the second end of the torsion spring element being fixed to the opposite side of the frame, and a second rocker arm in the pair being mounted on the opposite side of the frame for pivoting motion about the central axis of one end of a second torsion spring element to which it is fixed, the second end of the torsion spring element being fixed to the first side of the frame. Alternatively other arrangements of torsion spring element configurations can be used. 
         [0045]    The present invention further provides a method of conveying material comprising i) providing a vibratory conveyor comprising a frame, and a source of vibratory force mounted on the frame for providing vibratory movement to a conveying surface, the conveying surface being pivotally attached to a counterweight element by a plurality of rocker arms, each rocker arm being mounted on the frame for pivoting motion about the central axis of one end of a torsion spring element to which it is fixed, the second end of the torsion spring element being fixed to the frame; ii) applying vibratory movement to the conveying surface and thereby applying corresponding vibratory movement to the counterweight element until a steady state oscillation is reached at or near a natural frequency of the torsion elements; and iii) either before or after step ii) transferring the material to or placing the material on the conveying surface. Material can also be conveyed on the counterweight element where the counterweight element also provides a conveying surface. 
         [0046]    While a number of exemplary aspects and embodiments have been discussed above, those of skill in the art will recognize certain modifications, permutations, additions and sub-combinations thereof. It is therefore intended that the invention be interpreted to include all such modifications, permutations, additions and sub-combinations as are within their true spirit and scope. 
         [0047]    While a number of exemplary aspects and embodiments have been discussed above, those of skill in the art will recognize certain modifications, permutations, additions and sub-combinations thereof. It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions and sub-combinations as are within their true spirit and scope.