Abstract:
A vibratory conveying feeder, which includes a power control circuit for locally providing an adjusted drive signal to the vibratory drive. Inclusion of a power control circuit into one or more vibratory conveying feeders within a system including multiple vibratory conveying feeders, enable the feeders to share a common power supply bus. By enabling multiple feeders to share a common power supply bus, the wiring associated with providing power connections to the multiple vibratory conveying feeders is correspondingly reduced. Consequently, initial system installation or system reconfiguration is greatly simplified.

Description:
FIELD OF THE INVENTION 
     The present invention relates to vibratory feeders and particularly to a vibratory feeder for conveying materials, which has a self-contained power control circuit. 
     BACKGROUND OF THE INVENTION 
     Vibratory feeders have been widely used in controlling the bulk delivery of various types of product including materials for use in feeding, mixing, grinding and packaging. Generally, the vibratory feeders are comprised of two elements, commonly referred to as two masses, which are vibrated with respect to one another. The first element is generally referred to as a base, and the second element is generally referred to as a trough. Located between the two elements is a vibratory drive, which vibrates the trough with respect to the base. As the trough is vibrated with respect to the base, the material located in the trough is conveyed or thrown forward at a predetermined rate, the rate being determined by the frequency, the force, and the angle of the vibrations. 
     The trough, is generally disposed above the base and is connected to the base by a system of springs. The springs are connected to the trough and base on an angle. A vibratory drive is mounted to the base and operatively coupled to the trough, so as to impart vibrations to the trough with respect to the base. At least one example of a vibratory drive includes an armature of an electromagnet, which is connected to one of the base or trough, usually the trough, and an electromagnet core and coil, which is connected to the other. 
     The feeder as a whole, generally rests upon a support structure. The base of the feeder, while resting upon the support structure, is generally vibrationally isolated from the support structure by one or more coil springs, or elastomer springs to minimize unwanted forces from being transmitted into the support, and surrounding structures. 
     When an electric current is caused to flow through the magnet, the armature and magnet pole faces are mutually attracted to each other, causing the springs to deflect, and the trough to be displaced with respect to the base, and relative to their rest positions. When the current is removed, the magnet releases the armature and the energy stored in the spring system causes the trough to move back toward its rest position. The movement of the trough generally continues through the rest position to a deflected position in the opposite direction, where the movement of the trough with respect to the base once again changes direction, back toward the rest position. As current is reapplied and removed, the process is repeated. If the current is turned on and off at a uniform rate, the trough and base will generally vibrate with respect to one another at a similar rate, or frequency. 
     In at least one type of vibratory feeder, the vibratory feeders are operated at a frequency determined by the power line frequency, or at twice the power line frequency where a diode rectifier is used, or a permanent magnet is used as part of the electromagnetic vibratory drive system. Examples of such feeders are manufactured by FMC Corporation of Homer City, Pa., under the trade name SYNTRON. In such feeders, the frequency is fixed at 120 Hz or 60 Hz in North America, and 100 Hz or 50 Hz (usually 50 Hz) in most other countries of Europe or Asia. Since the frequency at which these feeders operate is generally fixed, only the stroke and stroke angle can typically be adjusted to optimize the feed rate. The stroke angle is largely dependent upon the construction and the orientation of the parts with respect to one another. Once the specific construction of the vibratory feeder has been determined, the stroke angle for that particular model becomes relatively fixed. Consequently, only the stroke magnitude remains as a parameter, which can be adjusted for adjusting the feeder&#39;s performance. Even still, the stroke magnitude of these feeders is constrained by the amount of magnetic force available to deflect the spring system, and ultimately by the stress limitations of the spring system and the other structural elements of the feeder. 
     The vibrational feeders generally attempt to take advantage of the natural amplification of the stroke due to resonance, by adjusting the natural frequency of the mass/spring system to be close to that of the operating frequency. This assures that there will be sufficient power available to operate the feeder with a reasonably sized electromagnetic. A typical maximum stroke value for feeders, of the above mentioned type, operating between 50 and 60 Hz. is between approximately 0.0625 inches and approximately 0.144 inches. Generally the lower the frequency the greater the possible maximum value of the stroke. A more detailed discussion of stroke angle and stroke magnitude is discussed in connection with Patterson et al., U.S. Pat. No. 5,967,294, entitled “High Stroke, Highly Damped Spring System for Use with Vibratory Feeders, the disclosure of which is incorporated herein by reference. 
     As the vibratory drive is actuated, and the trough is accelerated, the material resting on the surface of the trough is accelerated with the trough. As the trough reaches its maximum point of deflection, the trough begins to slow down and move back. If the material located in the trough has been accelerated sufficiently for the material to take flight, the material will continue to move forward as the trough reaches its maximum deflection, changes direction and moves back toward its rest position. Eventually, the material will fall back toward the surface of the trough, generally displaced at some distance forward from where the material originally took flight. During subsequent applied vibrations, the material is progressively moved even further forward. In this way, the material located in the trough can be conveyed in the desired direction by the vibratory feeder. 
     Generally, the magnitude and the frequency of the vibrational force applied to the trough is controlled by the characteristics of the power signal supplied to the vibratory drive of the vibratory feeder. In current vibratory feeders the power signal supplied to the vibratory feeder is generally controlled by an external controller. The external controller generates a conditioned power signal having the specific magnitude and frequency necessary to convey the material located in the trough at the desired rate and in the appropriate direction. The conditioned power signal is then conveyed over power lines specific to the corresponding vibratory feeder. Often times the external controller has one or more controls for adjusting the characteristics of the power that is supplied to the vibratory feeder. 
     Individual control of the specific power characteristics supplied to each vibratory conveyor is important, because each vibratory feeder will have its own unique material conveyance characteristics including its own resonant frequency. The material conveyance characteristics will vary between different vibratory feeders, due to inherent differences, which can result from known tolerances during their manufacture and/or dissimilar wear during their subsequent use. Where multiple vibratory feeders are used within the same system for a particular process it will likely be necessary to separately adjust each of the individual vibratory feeders in order to correctly manage material flow. As a result, each feeder will have a different power requirement, regardless of whether or not the material conveyance rates are the same or different for the different vibratory feeders. Consequently, prior systems have traditionally run separate power lines to each vibratory feeder, even where the multiple vibratory feeders are controlled through a common external controller. 
     As noted previously, vibratory feeders are commonly used in controlling the bulk delivery of product. One such noted example includes the use of vibratory feeders in product packaging. In many such instances multiple vibratory feeders are needed to provide accurate weights and corresponding processing rates demanded by the packaging process. Often times the multiple vibratory feeders are aligned either linearly or peripherally about a processing head for access by a packaging machine. Because each vibratory feeder has its own power requirements, each vibratory feeder will have its own corresponding power lines. Unfortunately, the physical routing requirements for running separate wiring for each vibratory feeder in a system where multiple vibratory feeders are used can be quite burdensome. Furthermore, because the power signals being supplied to vibratory feeders generally have a signal amplitude of a hundred volts or more, electrical cross-talk and interference between different sets of power control lines can be a problem, especially where the vibratory feeders and the separate corresponding sets of power lines are located proximate to one another. 
     Consequently, it would be desirable to provide a vibratory feeder, which is capable of locally providing for any required power adjustments, thereby enabling multiple vibratory feeders to receive power from a shared set of power lines. 
     These and other objects, features, and advantages of this invention are evident from the following description of a preferred embodiment of this invention, with reference to the accompanying drawings. 
     SUMMARY OF THE INVENTION 
     The present invention provides for a vibratory conveyor which includes a base and a trough. The vibratory driver is mounted to said base and is operatively connected to the trough to impart vibrations thereto. An integrated power control circuit is connected to the vibratory drive and a common supply bus for generating a locally adjusted drive signal. the locally adjusted drive signal is then supplied to the vibratory drive. In a preferred embodiment the power control circuit includes an output rate adjustment, which controls at least one of a frequency and an amplitude of the adjusted drive signal. 
     By incorporating a power control circuit as part of each vibratory conveyor, the one or more vibratory conveyors can receive power from a common or shared set of power lines. Any required adjustment of the power signal is provided locally by the power control circuit integrated as part of the vibratory conveyor. In this way it is no longer necessary to run separate power signals along separate power lines to each vibratory conveyor. The specific power adjustment (i.e. power shaping) for each vibratory conveyor is performed locally. This allows for specific power adjustments to similarly follow the vibratory conveyor, if the vibratory conveyor is subsequently moved. As a result initial setup or subsequent reconfiguration of the vibratory conveyors can be accomplished without requiring the routing or reconfiguration of separate power lines. 
     To the extent that it may be desirable to continue to route specific control signals to a vibratory conveyor, this can be accomplished using control signals having lower and safer voltage levels. Furthermore the signals could be digitally encoded and/or superimposed upon the power signals being routed along the common supply bus. 
     Other features and advantages of the present invention will be apparent from the following detailed description, the accompanying drawings, and the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic wiring diagram for a prior art system including multiple vibratory feeders including separate power supply lines for each vibratory feeder; 
     FIG. 2 is a schematic wiring diagram for a system including multiple vibratory feeders, in accordance with the present invention; 
     FIG. 3 is a block diagram of a vibratory feeder for use in the system shown in FIG. 2; 
     FIG. 4 is a side view of one example of a vibratory feeder in accordance with the block diagram shown in FIG. 3; 
     FIG. 5 is a circuit schematic of a power control circuit and a vibratory drive for use in the vibratory feeder shown in FIG. 3; 
     FIGS. 6A-6C are examples of voltage waveforms which are produced within the power control circuit shown in FIG. 5; and 
     FIG. 7 is a block diagram of an alternative power control circuit and vibratory drive for use in the vibratory feeder shown in FIG.  3 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     While the present invention is susceptible of embodiment in various forms, there is shown in the drawings and will hereinafter be described presently preferred embodiments with the understanding that the present disclosure is to be considered an exemplification of the invention and is not intended to limit the invention to the specific embodiments illustrated. 
     FIG. 1 illustrates a schematic wiring diagram for a prior art system  10  including multiple vibratory feeders  12 , where separate power supply lines are provided for each of the vibratory feeders. In addition to the multiple vibratory feeders  12 , the system includes a central feeder control  14 . The central feeder control  14  provides power to each of the individual feeders  12 . In the prior art system  10 , a separate set of power signals meeting the specific power requirements for each of the vibratory feeders  12  is produced in the central feeder control  14 . The separate power signals are then relayed to the corresponding vibratory feeders  12  via separate sets of power lines  16 . Generally, the central feeder control  14  controls the amplitude and/or the frequency of the power signal produced for each of the vibratory feeders  12 . In this way the rate at which the material is conveyed by the vibratory feeders  12  is controlled. Typically, each vibratory feeder  12  will have unique power requirements, due to planned or intended differences in the rates at which the vibratory feeders  12  will convey material, as well as unplanned inherent differences in the specific contruction of each of the vibratory feeders  12 . In addition to supplying power to each of the vibratory feeders  12 , the central feeder control  14  potentially transmits and/or receives additional control signals  18  for monitoring system status or controlling various functions throughout the system. 
     As noted previously, routing separate power lines  16  to each vibratory feeder  12  can be very time consuming and burdensome, especially when the system  10  is initially set up, or if the system is ever reconfigured. Furthermore, the separate power lines, which carry relatively high voltage power signals, have the added disadvantage of producing unwanted cross-talk and interference with respect to one another, thereby potentially negatively affecting their individual performance. 
     FIG. 2 illustrates a schematic wiring diagram for a system  20  including multiple vibratory feeders  22 , in accordance with the present invention. Whereas the prior art system  10 , illustrated in FIG. 1, provides separate power lines for carrying separately conditioned supply power to each of the vibratory feeders  12 , the present system  20  provides for a shared common supply bus  24 , which can be supplied by the central feeder control  26  or can be supplied directly from the main central utility power line, and which can be shared by one or more vibratory feeders  22 . The separate power requirements for each of the vibratory feeders  22  is produced by separate power control circuits  28 , which are integrated as part of the vibratory feeders  22 . The power control circuits  28  locally provide for separate power conditioning including adjustments to amplitude and/or frequency for producing and maintaining the desired material throughput. By incorporating a power control circuit in each of the vibratory feeders  22 , not only is the wiring of power lines greatly simplified but any power adjustments specific to a particular vibratory feeder  22  will be incorporated as part of the specific vibratory feeder  22 . If a particular vibratory feeder  22  is subsequently moved, the adjustments specific to the feeder  22  are moved with it. Similar to the prior art system  10  of FIG. 1, system  20  as illustrated in FIG. 2 is also capable of receiving and/or transmitting other control signals  30 . While the exemplary system is shown having five vibratory feeders  22 , one skilled in the art will readily recognize that the use of any number of vibratory feeders  22  is possible without departing from the teachings of the present invention. 
     FIG. 3 illustrates an example of a block diagram for a vibratory feeders  22  for use in the system  20  shown in FIG.  2 . The vibratory feeder  22  includes a base  32  and a trough  34 . The trough  34  is generally a pan like structure, which conveys material received therein. The trough  34  is coupled to the base  32  via a vibratory drive  36 , which vibrates the trough  34  with respect to the base  32 . The vibratory drive  36  is coupled to a shared common supply bus  26  via a power control circuit  28 , which receives power for driving the vibratory drive  36 . The power control circuit  28  provides for any specific power conditioning including any adjustments to amplitude and/or frequency required for conveying material at the appropriate rate. 
     FIG. 4 illustrates a side view of one example of a vibratory feeder  22 , which embodies the present invention. The vibratory feeder  22  includes a base  32  and a trough  34 . The trough  34  is generally located above the base  32  and is coupled to the base  32  via a pair of springs  38 . In the illustrated embodiment, the springs  38  are mounted at an angle, with at least one spring being located in the front and one or more additional springs being located in the back. The angle of the springs  38  define, at least in part, the direction of movement of the trough and correspondingly the material located in the trough including the amount of vertical movement and the amount of horizontal movement as the trough  34  moves with respect to the base  32 . 
     The movement of the trough  34  with respect to the base  32  is effected by a vibratory drive  36 , which is mounted to the base  32 , and is operatively coupled to the trough  34 . In the illustrated embodiment, the motion is achieved through an electromagnetic attraction. The vibratory drive  36  includes an electromagnetic core and coil  40 , which is coupled to the base  32 , and an armature  42 , which is coupled to the trough  34 . As power is supplied to the electromagnetic core and coil  40  and current is caused to flow within the coil, a magnetic force is induced in the electromagnetic core and coil  40 . The armature  42  is correspondingly attracted to the electromagnetic core and coil  40  by the magnetic force induced in the core and the coil  40 . This causes the trough  34  to move with respect to the base  32  as well as any material located in the trough  34 . As the trough  34  moves relative to the base  32 , the springs  38  are caused to deflect resulting in energy being stored within the springs  38 . When the current is removed, the electromagnetic force causing the trough  34  to be deflected disappears, and the energy stored within the springs is released. The trough  34  then reverses direction and begins to move back to its non-deflected position away from the base  32 . 
     However, whereas the motion of the trough  34  is restricted by the springs, the material located in the trough  34  is not similarly restricted. As the trough begins to reach its maximum deflection point and begins to decelerate, the momentum of the material located in the trough  34  causes the material to separate from the trough  34  and continue to move forward for a short distance before the material eventually loses its momentum and falls back to the trough  34  having traveled a distance along the length of the trough  34 . By repeating this relative motion between the base  32  and the trough  34 , material located in the trough  34  can be moved progressively forward. 
     While the described embodiment provides for a vibratory drive  36  which includes an electromagnetic core and coil, and a corresponding armature, one skilled in the art will readily appreciate that alternative types of vibratory drives could alternatively be used, without departing from the intended scope of the present invention. Examples of alternative vibratory drives include vibratory drives, which use permanent magnets or linear actuators. 
     The magnitude and the frequency of the vibrations are controlled by the frequency and the amplitude of an AC power signal applied to the electromagnetic core and coil  40 . In accordance with the present invention the AC power signal applied to the electromagnetic core and coil  40  is adjusted and controlled by a power control circuit  28  integrated as part of the vibratory feeder  22 . In the preferred embodiment, the power control circuit  28  is potted within the end of the electromagnetic core and coil  40  (as shown in FIG.  4 ). Alternatively, the power control circuit  28  can be positioned in a cutout located in the base  32 . Other locations for the power control circuit  28  within the vibratory feeder  22  are similarly possible. 
     One example of a specific power control circuit  50  for locally adjusting a drive signal supplied to a vibratory drive  36  is illustrated in FIG.  5 . In the illustrated example, circuit  50  is coupled to one of three power terminals corresponding to a shared common supply bus  26 . The first power terminal  52  provides a supply voltage connection. The second power terminal  54  provides a neutral connection. The third power terminal  56  provides a signal ground connection. 
     The first power terminal  52  is coupled to a switch  58 , which can be actuated for selectively supplying power to the vibratory feeder  22  and the corresponding power control circuit  50 . The switch  58  is additionally coupled in series with a fuse  60 , which prevents the current being supplied to the vibratory feeder  22  from exceeding a specified limit. The fuse in turn is coupled to a gating circuit  62 , which selectively applies the supply voltage received via the first power terminal  52  to the coil of an electromagnet  64  of the vibratory drive  36 . The other end of the coil of the electromagnet  64  is coupled to the neutral connection via the second power terminal  54 . The third terminal  56  is coupled to the exposed metal case of the vibratory drive  36  as well as other portions of the vibratory feeder  22  having exposed metal, thereby generally providing for exposed metal surfaces which are grounded. 
     The gating circuit  62  includes a silicon controlled rectifier (SCR)  66 , which once activated will conduct current so long as positive current is flowing through the SCR  66 . When the current through the SCR  66  reaches zero or drops below zero, the SCR  66  will stop conducting and will no longer pass even positive current unless or until the SCR  66  is reactivated. The SCR  66  is activated by a voltage being applied to the gate of the SCR  66 , which exceeds the turn-on threshold voltage of the SCR  66 . The gate of the SCR  66  is coupled to the cathode of diode  68 . 
     The timing for turning on the SCR  66  is affected by a capacitor  70  coupled between the anode of diode  68  and the cathode of SCR  66 . Effectively, capacitor  70  limits the rate at which the gate voltage of SCR  66  can be charged up to the threshold voltage, after a positive voltage from the first power terminal  52  is first applied. The rate is further limited by a pair of resistances  72  and  74 , which are coupled in series between the first power terminal  52  and the gate of the SCR  66 . 
     The first resistance is a resistor  72  having a predetermined fixed resistance, which effectively limits the maximum charge rate, and correspondingly the minimum turn-on delay of the SCR  66 . The second resistance is a potentiometer  74  having a variable resistance, whose value can be adjusted to further affect the charge rate, and the corresponding time for the SCR  66  to turn on. By altering the charge rate and the turn-on time of the gating circuit  62 , the amplitude of the power signal and the magnitude of the current supplied to the vibratory drive  36  can be adjusted. Further details are provided in connection with the subsequent discussion of FIGS. 6A-6C. 
     The power control circuit  50  further includes a diode  76  coupled in parallel with the potentiometer  74 , which enables the charge stored in capacitor  70  to bypass potentiometer  74  and discharge through diode  76 , during the negative half cycles of the supply voltage received via the first power terminal  52 . The power control circuit further includes a switch  78  coupled in series between the resistor  72  and fuse  60 . The switch  78  enables the gating circuit  62  to be separately disabled by preventing the charging of the gate voltage of the SCR  66  without removing power from the rest of the vibratory feeder  22 . 
     The power circuit  50  additionally includes a pair of varistors  80  and  82 , which provide overvoltage protection. The first varistor  80  is coupled in parallel with the gating circuit  62 . The second varistor  82  is coupled in parallel with diode  76  and potentiometer  74 . 
     FIGS. 6A-6C illustrate various signals received or generated in connection with the power control circuit  50  illustrated in FIG.  5 . FIG. 6A illustrates a waveform of voltage versus time of the supply voltage provided by the first power terminal  52  at the input Vin of the gating circuit  62 . The supply voltage supplied across the series combination of resistances  72  and  74 , and capacitor  70  produces a voltage Vg at the gate of SCR  66 , represented by the waveform illustrated in FIG.  6 B. The waveform Vg is a sinusoidal signal, similar to the supply voltage Vin. More specifically waveform Vg has a frequency that is equivalent to the frequency of Vin. The waveform Vg has a phase difference θ, which lags behind the phase of Vin. The specific phase difference is largely dependent upon the component values of resistances  72  and  74 , and capacitor  70 . The SCR  66  will begin to conduct, when the voltage of waveform Vg exceeds the turn-on threshold voltage Vth for the SCR  66 . 
     FIG. 6C represents the voltage waveform Vout which is seen at the output of the SCR  66 . When the SCR  66  is conducting the voltage waveform Vout is nearly equivalent to the voltage waveform of the supply voltage Vin seen at the first power terminal  52 . Regardless of the gate voltage being applied to SCR  66 , when the voltage across the SCR  66  falls below zero or becomes negative the SCR  66  will shut off and/or stop conducting. Because of the delay associated with turning on the SCR  66 , an adjustable portion of the first part of the input signal Vin is not correspondingly reproduced at the output Vout of the gating circuit  62 . 
     By altering the values of capacitor  70  or resistances  72 ,  74  the delay before the SCR is turned on can be shortened or lengthened. This will result in more or less of the the beginning portion of the positive half cycle of the voltage supplied by the first power terminal  52  being clipped or not being transmitted by the gating circuit  62 . In this way the magnitude of the power signal supplied to the vibratory drive  36  can be correspondingly adjusted. 
     While the power control circuit  50 , illustrated in FIG. 5, represents one example of a suitable circuit for locally adjusting the power supplied to the vibratory drive  36 , other circuits which similarly adjust signal amplitude could also be used. Alternatively, circuits which adjust frequency, or both frequency and amplitude could similarly be used. 
     FIG. 7 illustrates an alternative embodiment of a power control circuit  100 , which provides for adjustment of both amplitude and frequency of a received power signal. In addition to providing for a locally adjusted control, the power control circuit is also capable of receiving additional control signals via the shared common supply bus or alternatively via separately wired control signals. More specifically, FIG. 7 provides for a power control circuit  100 , which includes a power conditioning circuit  102  that is coupled to the shared common supply bus  26 . 
     In addition to providing a locally adjusted control  104 , which is analogous to the potentiometer  74  provided for in the power control circuit  50  illustrated in FIG. 5, the power control circuit  100  provides for a control signal decode circuit  106  coupled to the shared common supply bus  26  for decoding control signals received from either a central source (i.e. the central feeder control  26 ) or a distributed source (i.e. other vibratory feeders  22 ). 
     In at least one embodiment the control signals received from the central feeder control  26  are digitally encoded, and can be received by all of the vibratory feeders  22  coupled to the shared common supply bus  26 . Each control signal is encoded with an address or an identifying sequence, which identifies which vibratory feeder  22  is to receive the corresponding control signals. The digitally encoded signals are generally superimposed upon the general power supply voltage using a carrier frequency that does not interfere with the power signal, and which can be readily discerned from the power supply voltage. 
     The power conditioning circuit  102  includes both an amplitude control circuit  108  and a frequency control circuit  110 . In this way both the amplitude and the frequency of the power signal supplied to the vibratory drive  36  can be adjusted. Both the amplitude control circuit  108  and the frequency control circuit  110  can each be coupled to the control signal decode circuit  106  and/or the locally adjusted control  104  for receiving control signals for receiving the adjustments to be made to either the amplitude and/or the frequency of the power signal, if any. 
     In at least one embodiment, the amplitude control circuit  108  includes a variable gain amplifier, and the frequency control  110  circuit includes a variable frequency oscillator. In a further embodiment the variable frequency oscillator includes a digital-to-analog convertor coupled to a microcontroller, which is adapted for generating an output signal having the desired frequency. The power conditioning circuit  102  further includes a power output circuit  112 , which electrically isolates the amplitude control circuit  108  and the frequency control circuit  110  from the vibratory drive  36 , and also produces a conditioned power output signal having a sufficient power level for driving the vibratory drive  36 . 
     From the foregoing, it will be observed that numerous modifications and variations can be effected without departing from the true spirit and scope of the novel concept of the present invention. It is to be understood that no limitation with respect to the specific embodiments disclosed herein is intended or should be inferred. The disclosure is intended to cover by the appended claims all such modifications as fall within the scope of the claims.