Electrically coupled multiple shaft drive system for vibrating equipment

The control system of the present invention is particularly usable with extended vibration conveyors and permits the installation of a multiple of drive vibratory drive units comprised of one or more vibratroy modules. Each module comprises a motor, one or more shafts mounting eccentric weights, and a shaft encoder device monitoring the "relative position" of each shaft with respect for each shaft. One shaft, a master shaft, is driven continuously driven at a predetermined speed from which the actual relative positions are compared. A control device is programmed with the predetermined relative shaft positions and receives signals from the various encoder devices indicative of the actual relative positions of the shafts, compares the signals to a position of the master shaft and causes one or more motor control devices to alter the speed of each motor having a shaft whose actual relative position has varied from the predetermine relative position until the actual relative position essentially matches the programmed relative position.

BACKGROUND OF THE INVENTION 
This invention is related to a control system for vibratory conveyors and, 
more particularly, to a control system adaptable for use with vibratory 
systems having vibrating housings or surfaces of extended length for the 
conveying and/or treatment of articles in which the vibratory force is 
controlled over the entire length of the housing or surface. 
There are a number of systems in which the vibratory motion providing 
direction and/or speed to material being conveyed by the conveyor is 
controlled. An example of such a system is set forth in U.S. Pat. No. 
5,615,763 assigned to the same assignee of the present invention. As 
described therein with respect to one embodiment thereof, a pair of spaced 
shafts rotating in opposite directions are operatively coupled to a 
conveyor trough mounted on a stationary base through a plurality of 
isolating springs. The shafts have eccentrically mounted weights that are 
oriented such that the resultant force acting on the conveyor due to the 
rotation of the shafts and thus their associated weights goes through a 
maximum and minimum in a sinusoidal manner. The direction of the maximum 
resultant force is dependent upon the "relative phase angle" between the 
position of the rotating weights and a data plane. By varying the phase 
angle between the shafts, the direction or angle of attack of the 
resultant force can be changed so that the conveying rate and even the 
direction of the material on the conveyor can be changed. The invention in 
the aforementioned Patent addresses the problem of maintaining a 
predetermined phase angle for providing the desired angle of attack 
throughout an operating cycle of the conveyor through use of a control 
system. Such control system continuously measures the actual relative 
positioning of the weights, compares this to a programmed and 
predetermined positioning of the weights, and adjusts the speed of the 
motor driving one of the shafts until the actual positioning of the 
weights corresponds to the programmed positioning. Through the use of such 
a control system, the attack angle is maintained constant throughout the 
operating cycle of the conveyor. 
While the above described system functions admirably for conveyors of 
standard and short lengths, many industries require extended treatment 
lengths of the material during processing. For example, long vibratory 
conveyors are frequently desired for heat transfer processing. When it is 
required to move material over such extended lengths such as, for example, 
spans exceeding about 30 feet, the use of a single unitary vibratory 
conveyor has heretofore been largely impractical. Extended length 
conveyors become unwieldy due, in part, to strength necessary to withstand 
the significant stress imposed on the frame of the conveyor by the 
vibratory system along its length. The size of the frame and concomitant 
cost become prohibitive. To address this problem, the manufacturers of 
vibratory equipment have found it necessary to employ two or more separate 
vibratory conveyors mounted end to end or having some technique of moving 
the material between the separated conveyors. 
It is therefore a primary object of this present invention to provide a 
control system for a vibratory conveyor that permits the construction of a 
single unitary conveyor of extended length. It is still another important 
object of the present invention to provide for a control system for a 
vibratory conveyor that permits the tandem arrangement of a plurality of 
rotating shafts and eccentric weights to provide for a single angle of 
attack over the entire length of an extended unitary conveyor. It is still 
a further object of the present invention to provide for a control system 
for tumbling vibratory conveyors of extended lengths. 
SUMMARY OF THE INVENTION 
The objects of the invention set forth above are generally addressed by a 
vibratory control system in accordance with the present invention. Such a 
system generates a periodic resultant vibratory force from a plurality of 
separated driving "modules" to a unitary conveying surface and is capable 
of maintaining or changing the resultant vibratory force during operation 
thereof . For purposes of the description, vibratory "modules" are 
vibratory components typically comprised of a motor, one or more shafts 
driven by the motor, the eccentric weight(s) mounted on the shaft(s), and 
any shaft position monitoring devices that may be associated with the 
shafts. In some instances, two modules are combined to form a "linear 
force output drive unit" that is used to provide a periodic resultant 
force to the conveyor. The system generally includes a stationary frame 
connected by a plurality of spring members to a unitary conveying surface 
and a plurality of separated drive units operatively connected to the 
conveying surface and spaced along the length thereof with each of the 
drive units comprising two modules having respective spaced first and 
second shafts driven by respective first and second motors. Eccentric 
weights are mounted on each of the shafts. One of the modules is a master 
module with the first motor driving the first shaft at a programmed 
predetermined speed. A shaft position encoder device is associated with 
the end of each shaft and continuously generates a shaft position feed 
back signal indicative of the position of the eccentric weight on that 
associated shaft. A motion controller receives each of the shaft position 
feed back signals, compares each of the shaft positions with a 
predetermined relative phase angles or positions of the shafts, and 
generates a control signal for each of the shafts whose position has 
varied from the predetermined position. A motor speed controller 
responsive to the control signal for adjusting the speed of each of the 
motors associated with the shafts whose actual relative position has 
varied until the actual relative position matches the predetermined 
relative position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Reference is first made to FIGS. 1 and 2 depicting a conveyor system 
generally noted by the character numeral 10. System 10 comprises a 
vibratory conveying surface or trough 12 mounted to a stationary base 14 
by a plurality of springs 16. A break in the length of the trough 12 is 
shown to connote its extended length. The base 14 is rendered motionless 
and is typically fixed to the floor of the area in which the apparatus 10 
is used. Springs 16 serve solely to isolate trough 12 from the base 14 and 
do not directly function to provide vibratory motion to the trough 12. 
Frames 18 and 20, may be secured to the under carriage of the trough 12 as 
shown or connected to the trough through plenum walls (not shown). Each 
frame 18 and 20 houses a vibratory drive unit that includes the motors, 
shafts, eccentric weights, and gearing that impart a linear force 
vibratory output to the trough 12. Each drive unit is comprised of a pair 
of modules as defined above. It is contemplated that the number of drive 
units could be replicated and used in larger numbers than the two shown 
for extremely long conveyors. 
Referring now to the drive units within frame 18, it may be seen that three 
shafts 22, 24, and 26 are mounted for rotational movement within the frame 
18. A pulley 28 is mounted on one end of shaft 22 and driven via belt 30 
by pulley 32 of motor 34. A second pulley 36 is mounted on the other end 
of shaft 22 and is coupled by belt 38 to a pulley 40 mounted on one end of 
shaft 28. Thus, motor 30 drives both shafts 22 and 26 collectively with 
the aforementioned shafts and weights and form a first module. A second 
motor 42 has a pulley 44 coupled by belt 46 to a pulley 48 of shaft 26. 
Again, motor 24 along with pulley 44 and shaft 26 with weights form a 
second module within frame 18. Motors 34 and 42 are preferably secured to 
the under carriage of the trough 12. As best illustrated in FIG. 2, shafts 
22 and 26 have eccentrically mounted weights 50 and 52 mounted 
intermediate the ends thereof. Although not required in all situations, 
the weights preferably have the same mass and angular orientation with 
respect to their associated shafts. A pair of eccentric weights 54 and 56 
are mounted in a spaced apart relationship on shaft 24. When a linear 
stroke is required, it is preferable that the total mass of the weights 54 
and 56 are approximately twice those of the individual masses of weights 
50 and 52. However, it should be understood that a different weight 
structure may be employed to provide a different stroke distribution such 
as elliptical if desired. 
The various elements of the modules of frame 20 generally have the same 
functional relationships as the elements described above in frame 18. For 
clarity, such elements of frame 20 are denoted by the same numerals 
followed by the letter "a". It is preferred that the eccentric weights in 
frame 20 have the same angular orientation and mass as the counter part 
weights of frame 18. The theory of operation of an eccentric weight 
vibratory conveyor is explicitly described in U.S. Pat. No. 5,064,053 
incorporated by way of reference herein for its explanation of the theory. 
Briefly, however, the system set forth in FIGS. 1 and 2 operates upon the 
principal of altering the direction of the maximum resultant force acting 
on the conveyor due to the centrifugal forces imparted by the rotating 
eccentric weights. The maximum of the resultant force goes between a 
maximum and minimum in sinusoidal manner. The direction of the maximum 
resultant force is dependent upon the relative phase angle between the 
position of the rotating weights. For example, as seen in FIG. 1, shafts 
22 and 26, with respective weights 50 and 52, have an angle A measured 
between an outwardly directed radial line from the center of the 
respective rotating shafts through the midpoint of the weights (or some 
other selected reference point on the shaft) and a data plane, e.g., a 
horizontal plane passing through the respective shafts. At the same point 
in time, each of the weights 54 and 56 mounted on shaft 24 has an angle B 
similarly measured. The centrifugal force generated by each of the 
rotating weights will be outwardly directed along the respective radial 
lines. The direction and magnitude of the movement imparted to the 
conveyor at a point in time is determined primarily by the resultant of 
the centrifugal forces of the rotating weights which in turn depends upon 
the relative position of the rotating eccentric weights with respect to 
each other. For example, if at a first point in time, angles A and B both 
have the same value, e.g., 135.degree. in quadrant II, the magnitude of 
the resultant force would be at a maximum in that direction. Upon rotation 
of 90.degree., angle A is now 225.degree. while angle B is 45.degree., 
thus the forces are pointing in the opposite directions and the resultant 
force is at a minimum. With an additional rotation of 90.degree., the 
forces are again pointing in the same direction, i.e., at 315.degree. in 
quadrant IV, and the resultant force is at a maximum. A further rotation 
of 90.degree. takes the resultant force back at the minimum. Thus, in any 
360.degree. rotation, the resultant force goes to the minimum and maximum 
values twice. By varying the relative positioning or relative phase angle 
between the shafts, the direction or angle of attack of the resultant 
forces can be changed so that the conveying rate (and even the direction 
of movement) of the material on the conveyor trough can be changed. 
In the invention as illustrated in the environment of FIGS. 1 and 2, it is 
essential that each drive unit module provide the same angle of attack and 
the same magnitude of resultant forces. Thus, it is preferred that the 
counterpart shafts within frame 20 have eccentric weights of the same mass 
and angular orientation as those within frame 18. A control system for 
assuring the maintenance of the proper phase angles among the various 
rotating shafts is shown generally in FIG. 1 in which sensing or shaft 
encoder devices 58 are positioned adjacent each shaft 22, 24 and 22a, 24a. 
It should be recalled that shafts 26 and 26a are driven respectively by 
shafts 22 and 22a through a pulley and belt arrangement and thus always 
rotate at the same speed and thus have the same actual relative positions 
at all times. Such encoder devices 58 are well known in the prior art and 
are readily available, for example, from Danaher Controls of Gurnee, Ill., 
as indicated in the Table of Parts below. Each encoder device 58 senses a 
particular point on an associated rotating shaft and provides a continuous 
signal indicative of the relative position of the associated shaft. This 
information is fed to a controller 60 which compares the received signals 
to predetermined values for relative positions programmed into the 
controller. Controller 60 may be, for example, a programmable computer 
with a program to drive the motors and/or change the phase angles of the 
eccentric weights. When the controller 60 detects a deviation from the 
predetermined values, it causes one or more of the variable frequency 
drive units 62, as required, to adjust the speeds of an associated motor 
and relative phase angles of the associated shaft to match the 
predetermined value(s) for the relative positions. 
______________________________________ 
TABLE OF TS 
COMPONENT 
DESCRIPTION COMPANY T NUMBER 
______________________________________ 
Encoder (58) 
Shaft Position 
Danaher Controls 
HS 35025083442 
Gurnee, ILator Device 
Controller (60) 
Computer with 
Galil Motion 
DMC-1530 
Control Inc.to Gear 
Mountain View,s 
CA 
Variable Variable Speed 
Mitsubishi 
Freqrol A200 
Frequency 
Motor Control 
Electric 
Drive (62) 
Vernon Hills, IL 
Display (64) 
User Interface 
Eason Eason 800 
Technology 
Healdsburg, CA 
______________________________________ 
Reference is now made to FIGS. 3 and 4 to better describe the operation of 
the present invention. For clarity, shafts 24 and 24a and their associated 
weights, pulleys, and belts are not shown in FIG. 3. Initially, the user 
programs the controller 60 as represented by input arrow 62 with a desired 
angle of attack as represented by the relative phase angles or positions 
for the various shafts into controller 60. Additionally the master shaft 
is provided a predetermined rotational speed. Thus, the controller 60 
calculates the appropriate relative phase angle or the predetermined 
relative position for each shaft 26 and 22a and 26a. It should be noted 
that the predetermined relative position of shaft 22a will ordinarily be 
programmed to be the same as that of shaft 22 although in some situations 
this may not be true. In a perfect system, the actual relative positions 
of the various shafts would be completely matched to the predetermined 
positions and maintained at all times during operation. However, shafts 
speeds will vary from time to time due to many external influences. These 
minor changes can over a period of time greatly vary the actual relative 
positions and thus influence the angle of attack to the detriment of the 
proper operation of the conveyor system. The encoder devices 58, however, 
are continuously monitoring the rotating shafts and provide a "shaft 
position feed back" signals 66 to the motion controller 68 of controller 
60. The motion controller then reads the signals 66 at READ 69, compares 
the actual relative position of the shafts using the predetermined speed 
of the master shaft, and determines at comparison routine 70 if the shaft 
position of the shaft associated with a particular signal 66 has the 
predetermined relative phase angle or position inputted into controller 
60. If YES, meaning the real relative phase angle matches the relative 
phase angle, then a continuous loop occurs. If NO, then an angular 
correction is required in the positioning of the "slave" shaft, e.g. 
shafts 26, 22a or 26a, to match the predetermine relative phase angle 
between the "master" shaft 22 and the slave shaft. To make this 
correction, a determination is made at calculation 72 of the change of 
speed needed for the slave shaft to bring it back to the proper relative 
phase angle. A variable frequency drive 62 adjusts the speed of 
appropriate slave motor, e.g. motor 42, 34a, or 42a, to cause the 
associated shaft to rotate relative to the master shaft to reach the 
proper relative phase angle and thereafter maintained at the same speed as 
the master shaft. 
The foregoing illustrates that the present invention may incorporate a 
multiplicity of drive units each comprised of one or more vibratory 
modules. Unitary conveyors of considerable length may be constructed 
employing a number of vibratory drive units as dictated by the conveyor 
length. This provides a solution to the problem posed by need to have 
systems that convey and/or treat materials over long lengths of vibratory 
surfaces. 
Still another use for the present invention is with vibratory systems of 
the tumbling type, primarily used to clean work pieces, separate the work 
pieces from coatings, or otherwise treat the work pieces through the 
vigorous tumbling action of the work pieces against each other and/or 
media having certain treatment characteristics such as abrasiveness, for 
example, in a vibrating housing of the system. Such systems are well known 
in the prior art. One system is described in U.S. Pat. No. 5,109,633 to 
Durnil assigned to the same assignee as the present invention in which the 
system causes the loci of points on the tumbler housing surface to have an 
elliptical motion path thereby providing an inward tumbling movement of 
the work pieces and media contained by the housing. Heretofore, such 
tumbling apparatus were limited in size due to mechanical constraints 
imposed by the components used in vibrating the work piece containing 
housings and the structure of the apparatus itself. Typically, a single 
vibrating drive unit with a pair of modules was used to provide the 
particular vibration characteristics necessary to effect appropriate and 
desired tumbling within the housing. Any additional vibrating drive unit, 
if employable, was mechanically coupled together with the first drive unit 
to ensure that drive units provided the same vibration characteristics to 
the housing. 
FIGS. 5, 6, and 7 are illustrative of a control system in accordance with 
the present invention that provides a superior tumbling apparatus when 
used particularly in combination with the tumbling type of system 
described in the above mentioned patent. As best seen in the blended 
schematic of FIG. 5, a cylindrically shaped housing 74 is isolated from a 
base 76 through a plurality of springs 78. The housing 74, while 
illustrated as cylindrical, could have any arcuate configuration, 
particularly with respect to the bottom half, that is conducive to 
appropriate tumbling action. Vibration is provided by a plurality of 
vibratory drive units illustrated by the dashed lines as modules A, B, and 
C. It should be understood that the number of drive units that should be 
employed is largely a function of the length of the housing 74 and the 
materials comprising the housing and supporting infrastructure. Each drive 
unit A, B, C as shown is comprised of two modules each having a motor, a 
pair of shafts driven by each motor with the distal ends of each shaft 
mounting an eccentric weight. For convenience, the motors, shafts, and the 
associated weights of the drive units A, B, C are distinguished from each 
other with consistent letter subscripts matching the character letter 
designation of the drive unit in which the motors, shafts, and weights are 
positioned. For example, motors 80a, 82a are in unit A while motors 80b, 
82b, and motors 80c, 82c are in units B and C, respectively. Each motor of 
the units A, B, and C is mounted between a pair of brackets 88 extending 
outwardly from the wall of housing 74. The left and right shafts 81a-c, 
83a-c of each motor 80a-c, 82a-c respectively mount eccentric weights 
84a-c, 86a-c that provide the centrifugal force when rotated. The axes of 
shafts 81a-c and 83a-c lie in planes that are substantially parallel to 
the longitudinal axis 110 of the housing 74 (as best seen in FIG. 7). 
Thus, the eccentric weights 84a-c and 86a-c rotate in planes that are 
substantially perpendicular to the longitudinal axis 110. While not 
required in all situations, the eccentric weights in the various units 
preferably have the same mass. 
FIG. 7 shows an expanded drive A and illustrates that the eccentric weights 
84a and 86a on the left side of their motors respective rotate co-planarly 
as do the eccentric weights 84a and 86a on the right side of their 
respective motors. The same co-planar relationship is involved between the 
left and right weights 84b, 86b and 84c, 86c. Moreover, each drive unit is 
tilted with respect to the vertical and inclined an angle 90 shown between 
the brackets 88 and the axis toward one end of the housing 74 for reasons 
set forth below. Finally, as best seen in the side section of FIG. 6, the 
weights 84a and 86a, while rotating in the same plane, also rotate in 
opposite directions depicted by arrows 94 and 96. Again, the same counter 
rotating relationship holds true for weights 84b, 86b and 84c, 86c. 
The theory of operation of the vibrating system illustrated in FIGS. 5, 6 
and 7 is set forth in detail in the aforementioned U.S. Pat. No. 5,109,633 
(with particular reference to FIGS. 30 and 31 thereof) in which a single 
module comprising the drive unit has a motor driving a pair of spaced and 
counter rotating shafts each have eccentric weights of the same mass 
mounted to rotate co-planarly. The shafts illustrated in U.S. Pat. No. 
5,109,633 are mechanically coupled so that the shafts rotate at the same 
speed and thus maintain the same relative position as dictated by the 
single motor. The discussion of the theory of operation as set forth in 
U.S. Pat. No. 5,109,633 is identical to the present invention set forth in 
FIGS. 5, 6, and 7 and is incorporated by way of reference herein. 
Basically, however, the effect of the counter rotating and spaced apart 
eccentric weights rotating in the same plane is to cause points on the 
internal surface of housing 74 to follow an elliptical path. The media 
contained by the housing 74 is caused to move or flow circumferentially 
across and climb upwardly of the bottom portion of the housing 74 and is 
thrown inwardly of the housing along with the work pieces being treated. 
The inclination of the weights as discussed above tends to cause the media 
and work pieces to move slowly in the direction of the inclination. 
Alternatively, while not shown here, the housing 74 could be inclined in 
the opposite direction so as to cause the enclosed material to move in the 
direction of housing inclination with the inclination of the weights 
acting to retard this movement. 
To address the problem of treatment environments in which the articles are 
preferably treated over long treatment lengths where it would be desirable 
to utilize an extended vibrating and tumbling housing, those in the prior 
art have resorted to a partial solution in which a first pair of counter 
rotating weights are coupled mechanically to a second pair of counter 
rotating eccentric weights. This partial solution maybe seen in FIG. 29 of 
the aforementioned U.S. Pat. No. 5,109,633. This structure, however, is 
quite limited in its application, providing a much greater opportunity for 
mechanical failure and adding considerably to the complexity of the 
machinery. Applicant, however, has determined that a control system in 
accordance with the present invention may easily be combined with the 
desired vibratory system for tumbling that addresses the problem of 
extended vibratory housings. From the view of FIG. 5, it may be seen that 
the extended length of housing 74 is again connoted by a break in the 
length thereof. Each of the shafts 81a-c and 83a-c are monitored by 
encoder devices 100 that provide continuous inputs representing the actual 
relative position of the monitored shafts to a controller 98 that 
incorporates variable frequency drives (as described above) to control the 
speed of motors 80a-c and 82a-c. As discussed previously with respect to 
FIGS. 3 and 4, the controller 98 compares this information to a 
predetermined relative position programmed into the controller 98 by user 
input device 102. One motor, for example, motor 80a, making up one module 
(the "master" module) may be considered the master motor that is 
continuously driven at a predetermined speed. When one or more of the 
other motors called the "slave motors", e.g., 80b-c or 82a-c, making up 
the respective other modules (the "slave" modules), drifts away from the 
programmed relative position as monitored by the respective shaft encoders 
100 of the various slave modules, the controller 98 increases or decreases 
the speed of rotation of the identified slave motor(s) and associated 
shafts to make the shafts match the programmed relative positions for the 
identified shafts. From this it may be seen that mechanical coupling is 
completely eliminated while the proper speed of all motors/shafts are 
maintained at the programmed speed so that the characteristic of the force 
applied to the housing is consistent along the entire length of the 
housing. This permits the use of a unitary tumbling housing of 
considerably greater length than was heretofore possible without the 
concomitant increase in the mechanical complexity and structural strength 
of the conveyor necessary with mechanically coupled vibratory devices. 
From the above discussion, it may be seen that the vibratory control system 
in accordance with the present invention addresses the significant 
problems of the prior art systems, particular where it is necessary to 
utilize a vibrating surface or housing of considerable length to treat or 
convey articles. Modifications of the control system will become readily 
apparent to those with ordinary skilled in the art without departing from 
the scope of the invention as set forth in the appended claims.