The present invention is directed to a vibratory conveying apparatus that is adapted to be driven by a plurality of pairs of rotatable eccentric weights, wherein the vibratory conveying apparatus includes sub-resonant tuned drive springs and the plurality of pairs of rotatable weights are accumulatively phased during rotation.
In the vibratory industry, vibratory conveying apparatus such as vibrating feeders, vibrating conveyors, vibrating screens, vibrating heat transferring fluidized beds, attrition mills, and the like, were all powered by a well-known and popular driving method called the “Single Input” or “Brute Force” type of drive. A single pair of rotating eccentric weights is the sole source of the input power in this kind of drive. Being installed directly across from one another, a single pair of eccentric weights rotating in opposite directions, as shown in FIG. 1, would vibrate the vibratory conveying apparatus with a linear or “back and forth”, straight line motion. As the load carrying capability of the conveying apparatus increased over the years, the weight of the rotating eccentric weights also necessarily increased in size. So did the horsepower demand of the electric motor utilized to rotate the eccentric weights. Examples of this practical situation are seen in U.S. Pat. No. 4,180,458 and U.S. Pat. No. 4,826,017. In both of those patents, only one pair of rotating eccentric weights is utilized. U.S. Pat. No. 4,180,458 utilizes a “vee-belt” type of connection between the jack shaft which is rotating the eccentric weights and the driving motor. In U.S. Pat. No. 4,826,017, vibratory motors could be utilized, or eccentric weights mounted on a jackshaft that are rotated by a vee-belt or chain type of motor drive could be utilized.
To achieve a circular conveying motion, a pair of rotating eccentric weights are mounted diametrically opposite to one another. Then, by rotating the eccentric weights in the same direction, a “twist” type of vibratory action or circular conveying could be achieved. An example is U.S. Pat. No. 3,254,879. As shown therein two electric motors are directly coupled to eccentric weights mounted on a jack shaft. The result is a helical stroke that conveys the contained material in a circular direction. Another example of this situation is illustrated in Dumbaugh U.S. Pat. No. 3,178,068 and in FIGS. 5A and 5B.
For many years, it has been well known that a single pair of rotating eccentric weights can be combined for use with a vibratory conveying apparatus to produce either a “linear” or “twist” kind of stroke action. By mentally “stopping” and picturing the position of the eccentric weights 20 in four 90° increments of one 360° rotation, one complete revolution is diagramed in each of FIGS. 2A and 2B. When both of the eccentric weights 20 rotate in opposite directions relative to one another as diagramed in FIG. 2A, a “linear” type of stroke output is achieved. By making the pair of rotating eccentric weights 20 rotate in the same direction relative to one another, as depicted in FIG. 2B, the stroke output develops a “twist” from the resulting force-couple.
A pair of rotating eccentric weights will properly “phase” to produce either a “linear” or “twist” kind of vibratory force and resulting stroke output because they inherently seek their lowest level of energy output. Said differently, the vibratory motors which rotate the eccentric weights try to do as little work as possible. Consequently, the eccentric weights “balance” or cancel the force output for two-quarter portions of the rotational cycle at 0° and 180°. In so doing, the two eccentric weights are necessarily prompted to combine their force outputs for the remaining two-quarter portions, or the other half, of their rotational cycle at 90° and 270°. When that happens, the two motors involved accumulatively add their power capability. For example, if two 1.5 horsepower (HP) motors are used, the total power capability of the pair of motors would be 3 HP.
The pair of rotatable eccentric weights can be mounted on a jackshaft with two bearings and driven by a motor through an appropriate “vee” belt combination. Two jackshafts, one for each eccentric weight, would be required. Any other type of suitable transmission such as a chain, gears, or the like could also be used. Another alternative is to utilize a vibratory motor 11 as provided by Kinergy Corporation, as shown in FIG. 3. Such a vibratory motor has a double extended shaft. Eccentric weights 20 can be installed on both ends of the shaft, but are cumulatively considered as a single rotatable eccentric weight. Vibratory motors equipped with shaft mounted eccentric weights will be emphasized herein, but other jackshaft driven combinations can also be used such as vee-belts and the like. In either instance, the pair of rotatable eccentric weights are installed on and become an integral part of the conveying trough assembly.
When more input power is needed to move heavier loads along the length of the conveying trough, more rotating eccentric weight force and horsepower are needed. Consequently, the rotatable eccentric weights become larger and heavier and have a greater force output. Likewise, the electrical windings in the vibratory motor increase in size to produce more horsepower. This increase in eccentric weight force output and the respective vibratory motor horsepower has approached the point that the vibratory motors are presently as large as practical to manufacture or to utilize on a vibratory conveying type of apparatus. Therefore, if some method of combining a plurality of pairs of vibratory motors and rotatable eccentric weights could be found, it would enable two or more pairs of vibratory motors and eccentric weights to be used in combination instead of only one pair of motors that are essentially two times as large or more.
Over the years, many attempts have been made to combine more than one pair of vibratory motors and eccentric weights to increase the total force output and the horsepower capability. Unfortunately, when more than one pair of rotating eccentric weights were utilized, they would always tend to “cancel” their respective force outputs. The resulting stroke action on the vibratory machine would actually become less or might even be reduced to virtually no displacement or zero stroke. An example of this unwanted situation is illustrated in FIG. 4. In FIG. 4, a second pair of rotating eccentric weights is being utilized. After the rotating eccentric weights are started up and are turning at their appropriate speed, each of the four eccentric weights will move to a place in its rotation so that all the output forces cancel one another. Consequently, the net force output is essentially zero and the motors involved are developing virtually no horsepower. This also happens when the motors are changed to rotate in opposite directions. Instead of adding their respective force outputs from each pair of eccentric weights, they cancel one another. This is the reason any combination of free-wheeling eccentric weights utilized on a vibratory conveying apparatus has always previously been limited to one pair.
The desired accumulative phasing of a plurality of pairs of rotating eccentric weights has never been successfully achieved with free-wheeling rotating eccentric weights that are not physically or mechanically rotationally linked or coupled to one another. Therefore, for many years, there has been an unanswered need for the ability to use more than one pair of rotating eccentric weights to enable the total vibratory force output capability to be increased and the related total amount of horsepower increased.