Abstract:
The present invention relates to a mechanical vibrating drive system for supplying a consistent, elliptical driving force to a conveyor trough. In a preferred embodiment of the invention, the vibrating conveyor has a set of vertical leaf springs connecting the conveyor trough to a vibratory frame, and a set of horizontal leaf springs connecting the vibratory frame to a stationary frame. The leaf springs amplify the motion initiated by a reversible motor, and the net result is a force output from the drive module that produces a uniform elliptical vibratory motion throughout the length of the conveyor trough. By reversing the motor, a symmetric elliptical motion for moving product in the opposite direction is generated without any further adjustments to the leaf springs.

Description:
BACKGROUND OF THE INVENTION 
     This invention is related to a mechanical vibrating drive system for a vibratory conveyor apparatus and, more particularly, to a vibratory conveyor apparatus utilizing the natural frequencies of two spring sets to impart a resultant vibratory drive force to the conveyor apparatus. 
     There are various vibrating drive systems for controlling the direction and/or speed of product being carried by a vibratory conveyor. The vibrating conveyor apparatus typically includes a trough mounted for vibratory motion, such as provided by a plurality of springs. In general, product is moved along the conveyor trough by a force applied to the trough. The product can be moved along a linear path or along an elliptical path, the path being determined by the force applied to the conveyor trough. 
     One type of vibrating drive system is a mechanical system utilizing fixed eccentric rotating weights and a phase angle adjustment means. A system of this type is described in detail in U.S. Pat. No. 5,064,053, assigned to the same assignee as the present invention. In the system of the &#39;053 patent, a single rotating shaft bearing an eccentric weight is in a parallel relationship with and positioned between paired additional rotating shafts bearing eccentric weights. The centered single shaft rotates in one direction while the paired shafts rotate in the opposite direction but at the same number of revolutions per minute. When the shafts rotate, the weights impart a force to the conveyor trough which, in turn, causes the product to move along the conveyor. Because the force to move the product is supplied by the eccentric weights, the force generated in insensitive to the product load on the conveyor. Thus, there is a consistent force generated by the drive system regardless of the type or quantity of product that is conveyed. The user can reverse the direction in which the material is being conveyed, but to ensure that product moves along the desired path requires physically changing the positioning of one or more of the eccentric weights and its associated shaft by repositioning the phase angle adjustment means. This change-over requires considerable down time, which is highly undesirable when time is a critical factor in the application. 
     A second type of vibrating drive system is a mechanical system that uses a reversible motor and dynamic balancers to produce the driving forces. A system of this type is described in U.S. Pat. No. 5,713,457, assigned to General Kinematics Corporation. In the system of the &#39;457 patent, a reversible motor with a rotary output shaft and eccentric weight is mounted near the center of gravity on a conveyor apparatus, and a dynamic balancer is positioned at each end of the conveyor trough. The dynamic balancers are spring and weight systems designed to move the product in an elliptical path as it travels along the conveyor trough. For optimum performance, the dynamic balancers (or absorbers) must be selected such that their natural frequency is just greater than the operational frequency of the system as determined by the frequency of the motor. Maintaining a consistent driving force can be difficult with this type of system because the dynamic balancers are very highly tuned, so small changes in product load or motor speed may affect the performance of the equipment. In particular, the user must be cautious of producing overstrokes that can permanently damage the conveying equipment. As with the eccentric weight systems, the user can reverse the direction of product flow in the system of the &#39;457 patent by reversing the motor. However, because the dynamic balancers are set only for one speed, to make any changes in the system other than reversing the direction of product flow requires that the system be completely modified, which can result in considerable down time. 
     Eccentric weight systems that include electronic drive capabilities, such as described in U.S. Pat. No. 5,615,763, assigned to the same assignee as the present invention, allow for a rapid change of direction of the product flow. However, such systems are expensive relative to the cost of mechanical systems. 
     Thus, there is a paramount need for an inexpensive mechanical vibrating drive system that will allow the user to easily and frequently change the direction of flow of the conveyed product without incurring the down time of the system heretofore necessary with prior art mechanical vibrating drive systems. In addition, there is a need for an inexpensive conveying system that will allow the user to convey product along a reversible, symmetric, elliptical path as it travels along the conveyor trough. Further, there is a need for a natural frequency conveyor that will allow product to be conveyed long distances as compared to the prior art feeders which arc limited in length, and for a natural frequency conveyor that preferably will incur relatively low maintenance costs for the user. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a mechanical vibrating drive system for supplying a consistent, elliptical driving force to a conveyor trough. The mechanism for supplying the force to vibrate the trough includes a set of essentially vertical springs which connect the conveyor trough to a vibrating frame and provides a horizontal vibratory motion to the trough, and a set of essentially horizontal springs which connect the vibrating frame to a stationary frame and provides a vertical vibratory motion to the vibrating frame. The vibrating frame holds a rotating eccentric crank arm drive, having a shaft with a plurality of eccentric cuts, and associated crank arms. A crank arm from the drive is indirectly connected to the conveyor trough causing the trough to vibrate as the shaft rotates. A second crank arm in indirectly connected to the vibrating frame causing the frame to vibrate. The amplitude of vibration in the vertical and horizontal directions is determined by the drive shaft eccentrics selected. A standard reversing type motor is used to drive the shaft in either a forward or a reverse direction. 
     In a preferred embodiment of the invention, vertical and horizontal leaf springs provide the vibratory motion to the trough, and the drive shaft eccentrics are selected so that the magnitude of the major (horizontal) axis is approximately four times the magnitude of the minor (vertical) axis. The net result is a force output from the drive module that produces a uniform elliptical vibratory motion throughout the length of the conveyor trough. By reversing the motor, a symmetric elliptical motion for moving product in the opposite direction is generated without any further adjustments to the leaf springs or shafts. 
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic of an embodiment of the present invention showing a side view of a natural frequency vibratory conveyor apparatus having leaf spring systems to impart a vibratory motion to the conveying trough; 
     FIG. 2 is top view of the vibratory apparatus of FIG. 1; 
     FIG. 2A is a side view of the eccentric bearing shaft of the apparatus of FIG. 1; 
     FIG. 2B is a side view of the eccentric bearing shaft of the FIG. 2A fitted with two base bearings and two drive arm bearings; 
     FIG. 3 is cross-sectional view of the vibratory apparatus of FIG. 1 taken along line  3 — 3  showing the respective location of the vertical leaf springs and the coil springs; 
     FIG. 4 is a cross-sectional view of the vibratory apparatus of FIG. 1 taken along line  4 — 4  showing the respective location of the eccentric cuts on the shaft, and the second crank arm shaft; 
     FIG. 5 is a schematic of an alternative embodiment of the present invention showing a side view of a natural frequency vibratory conveyor apparatus having leaf spring systems to impart a vibratory motion to the conveying trough; and 
     FIG. 6 is cross-sectional of the vibratory apparatus of FIG. 5 taken along line  6 — 6  showing the respective location of the vertical leaf springs and the coil springs. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The conveyor system depicted in the various Figures is a multiple spring set system driven by a single motor and is selected solely for the purposes of illustrating the invention. Other and different eccentric shaft conveyor systems may utilize the inventive features described herein as well. Further, a plurality of systems can be utilized in a series along a single long conveyor. 
     Reference is first made to FIGS. 1-4 in which the two-way vibratory conveyor system constructed in accordance with the present invention is generally noted by the character numeral  10 . The system of  10  has as major components a vibrating trough or pan  12 ; a vibrating frame  20 ; a stationary frame  30 ; a pair of vertical leaf spring sets  40 ; a set of horizontal leaf springs  50 ; and a rotating eccentric crank arm drive system  70 . The stationary frame  30  rests on a stationary support  32 , such as a floor, and can be affixed to the support  32  by any suitable means, such as by using bolts or anchors. The vibrating frame  20  is connected to the stationary frame  30  with the horizontal leaf springs  50 , which run essentially parallel to the vibrating frame  20 , and are mounted toward the ends  21 ,  23  of the frame  20 . The vibrating pan  12  runs essentially parallel to the vibrating frame  20  and is connected to the vibrating frame  20  by the vertical leaf spring sets  40 , which are essentially perpendicular to the pan  12 . The rotating eccentric crank arm drive system  70  is attached to the vibrating frame  20  between the vertical leaf spring sets  40 . Alternatively, the vertical leaf springs  40  may be replaced with vertical coil springs, or the horizontal leaf springs  50  may be replaced by horizontal coil springs, or both sets of leaf springs  40 ,  50  may be replaced by coil springs (not shown). 
     As shown in FIGS. 1-3, the rotating eccentric crank arm drive system  70  includes a single reversible motor  100  that is connected to an eccentric bearing shaft  72  via a belt  74  attached to a belt sheave  90 . As shown in FIGS. 2A and 2B, cut into the shaft  72  are two eccentric cuts  71 ,  73 , each of which hold a drive arm bearing  71 A,  73 A, respectively; and the shaft  72  is mounted on the vibrating frame  20  by a pair of base bearings  92 ,  94 . One of the drive arm bearings  71 A is connected via a crank arm  76  to a steel arm with a rubber bushing  78  which imparts motion, through a pan drive connection  84 , to the vibrating pan  12 ; and the other bearing  73 A is connected via a second crank arm  80  to a steel arm bushing and drive clip  82  connected to the vibrating frame  20 . Optionally, other drive springs may be used in place of the bushings  78 ,  82 , and additional cuts and drive arms may be added to the shaft  72  if so warranted by the width and length of the conveyor trough  12 . As the motor  100  rotates, the belt  74  drives the eccentric bearing shaft  72  which in turn drives the crank arms  76 ,  80 , and thereby the bushings  78 ,  82 , causing the vibrating pan  12  and the vibrating frame  20  to move. The vertical leaf springs  40  and the horizontal leaf springs  50  then amplify the motion initiated by the motor  100 , with the vertical leaf springs  40  causing the vibrating pan  12  to move horizontally and the horizontal leaf springs  50  causing the vibrating frame  20  to move vertically. 
     The eccentric bearing shaft  72  creates a driving force having a vertical and a horizontal component, directed toward the vibrating pan  12 . These force components are then amplified by the spring sets  40 ,  50 . The net driving force, then, is the summation of the individual force components, and this net driving force is transferred to the pan  12  which, in turn, transfers the force to the product on the pan  12  causing the product to move. When the net driving forces are essentially 90° out of phase—i.e. when the horizontal vibration is at its peak the vertical vibration is at it neutral point, and vice versa—the vibrating pan  12  has an elliptical motion thereby moving the product along the pan  12  with a shuffling linear motion. The proper combination of the elliptical stroke with conveying speed produces an extremely rapid conveying action which is gentle to the product, thus minimizing product degradation, and is relatively quiet. When the net driving forces are in phase, the product moves in the vibrating pan  12  by following a linear motion. In the preferred embodiment, the bearing shaft  72  and the spring sets  40 ,  50  are selected such that net driving forces are out of phase, and the eccentric magnitude of the major axis is approximately four times the minor axis. 
     The product can be moved in the opposite or reverse direction on the pan  12  by simply reversing the motor  100 , without any further adjustments to the spring sets  40 ,  50 , or to the eccentric bearing shaft  72 . When the motor  100  is reversed, the pan  12  is moved along an essentially identical elliptical path as when the motor  100  operates in the forward direction, except the product moves in the opposite direction. That is, if as the motor  100  operates in the forward direction, the pan  12  moves counterclockwise about the elliptical path, then as the motor  100  operates in the reverse direction, the pan  12  moves clockwise about the elliptical path. By reversing the rotational direction of the motor  100 , the product effectively moves in the opposite direction along the conveyor pan  12 . 
     FIGS. 5 and 6 show an alternative embodiment  110  of the two-way vibratory conveyor system. The system of  110  has as major components a vibrating pan  112 ; a vibrating frame  120 ; a stationary frame  130 ; a plurality of vertical leaf spring sets  140 ; a horizontal leaf spring set  150 ; a pair of vertical coil spring sets  160 ; and a rotating eccentric crank arm drive system  170 , including a drive shaft  172  with eccentric cuts. Similar to the embodiment  10  of FIG. 1, the stationary frame  130  rests on a stationary support  132 , such as a floor, and can be affixed to the support  132  by any suitable means, such as by using bolts or anchors. The vibrating frame  120  is connected to the stationary frame  130  by the horizontal leaf springs  150 , which are essentially parallel to the support  132  and which are mounted essentially perpendicular to the length of the vibrating frame  120 , and with the vertical coil spring sets  160 . The vibrating pan  112  is connected to the vibrating frame  120  by the vertical leaf spring sets  140 , which are essentially perpendicular to the pan  112 . The rotating eccentric crank arm drive system  170  is attached to the vibrating frame  120  between the vertical leaf spring sets  140 . Alternatively, either vertical or horizontal coil springs may be used in place of the respective leaf springs  140 ,  150  (not shown), or both the vertical and horizontal leaf springs  140 ,  150  may be replaced by coil springs. 
     As shown in FIG. 5, the rotating eccentric crank arm drive system  170  is essentially identical to the eccentric crank arm drive system  70  of FIG. 1, and functions to impart motion to the vibrating pan  112  as described previously herein. Similar to the embodiment of FIG. 1, the vertical leaf springs  140  and the horizontal leaf springs  150  then amplify the motion initiated by the motor  200  of the rotating eccentric crank arm drive system  170 , with the vertical leaf springs  140  amplifying the horizontal motion of the vibrating pan  112 , and the horizontal leaf springs  150  amplifying the vertical motion. In the preferred embodiment, the eccentric bearing drive shaft  172  and the spring sets  140 ,  150  are selected and oriented on the shaft  172  such that net driving forces are out of phase, and the magnitude of the major axis is approximately four times the minor axis; and the product can be moved in the opposite or reverse direction on the pan  112  by simply reversing the motor  200 , without any further adjustments to the system  110 . 
     It is understood that, in light of a reading of the foregoing description and drawings, those with ordinary skill in the art will be able to make changes and modifications to the present invention without departing from the spirit or scope of the invention, as defined herein.