Electronically controlled rotational control apparatus

An apparatus (10) is disclosed including a friction clutch (12) and an overload apparatus (14) connected in parallel between an input (16) and an output (18). Encoders (20, 22) are provided for separately detecting the rotational positions of the input (16) and the output (18). A microcomputer controller (580) controls actuation of the friction clutch (12) and the overload apparatus (14) in response to the rotational positions detected by the encoders (20, 22) allowing the clutch (12) to bring the output (18) to be generally aligned with a select rotational position of the input (16) at which time the overload apparatus (14) can be actuated to rotatably relate the input (16) and the output (18) at the select rotational position and actuation of the clutch (12) can be removed. The microcomputer controller (580) also removes actuation of the overload apparatus (14) when the encoders (20, 22) detect rotation of the input (16) relative to the output (18) from the select rotational position. In the most preferred form, the encoders (20, 22) include codewheels (500, 501) rotatable with the input (16) and the output (18), respectively, and relative to slotted optical switches (502-505), with the codewheels (500, 501) including 64 evenly spaced slots which rotate past the slotted optical switches (502-505).

BACKGROUND 
The present invention generally relates to rotational control apparatus, 
particularly to rotational control apparatus for informationally relating 
and, at times connecting with particular position registration an output 
to an input, at least one of which is rotating, and in the preferred form 
shown, with a single position registration between the input and output, 
and specifically to rotational control apparatus for connecting an output 
to an input, at least one of which is continuously rotating, and also for 
allowing overload protection. 
U.S. Pat. No. 4,770,281 discloses an overload apparatus of the ball-detent 
type which has achieved considerable commercial success and which provides 
crisp, repeatable disengagement at a preset torque level which is a linear 
function of the applied air pressure. After a disengagement, however, the 
input to the overload apparatus must be completely stopped and the 
overload apparatus manually engaged before the driven machinery can be 
restarted. This presently requires time and human intervention in addition 
to requiring the machine to be shut down. Serious difficulties can arise 
from shutting down a machine. For example, the output to be connected will 
typically have significant inertia and must again be accelerated to 
"linespeed" in such a way that avoids damage to either the output load, 
the drive power source, or the specific torque overload apparatus being 
used. Although it would be possible (as is often done) to accelerate the 
output load to proper speed with an auxiliary drive, the problem of 
locating correct relative angular position remains and also the overload 
apparatus cannot be engaged without damage until such registry is located. 
Furthermore, locating the necessary relative rotational position can be 
time consuming since typical inertial values may require differential 
speeds on the order of one RPM or less so as to avoid interface damage at 
engagement of the overload apparatus. Hunting for registry at one relative 
RPM or less can obviously take 60 seconds or more with the potentiality of 
a miss, after which the apparatus would again be subjected to an 
additional 60 seconds or more of seek/search time. 
Thus, a need exists for apparatus having the ability to connect or 
disconnect a load to or from a source of rotational power which is 
rotating at a speed, now preferably in the range of 15 to 3,600 RPM, while 
at the same time providing position registration and/or information, and 
in the most preferred form which provides position registration at a 
single rotational position. Additionally, a need exists for such an 
apparatus which can provide overload protection of the output. 
SUMMARY 
The present invention solves these needs and other problems in the field of 
rotation control by providing, in the preferred form, apparatus and method 
for connecting an output to an input at select rotational positions while 
the input continues to rotate without stopping. Particularly, the input 
and output are initially rotatably related by a first rotational control 
apparatus independent of the relative rotational positions of the input 
and output such as by a friction clutch. The rotational positions of the 
input and output are separately detected such as by the use of encoders 
each including a codewheel having peripheral, evenly spaced slots which 
rotate past first and second slotted optical switches. In response to the 
relative rotational positions of the input and output, a second rotational 
control apparatus is actuated by a controller when the input and the 
output are aligned in the select rotational position. 
In other aspects of the present invention, overload protection is provided 
by the second rotational control apparatus, with actuation of the first 
rotational control apparatus being removed when the second rotational 
control apparatus is actuated and actuation of the second rotational 
control apparatus being removed when relative rotation of the input and 
output is detected from the select rotational position. 
In preferred aspects of the present invention, actuation of the rotational 
control apparatus is by fluid pressure, with the controller electronically 
controlling valves for the fluid pressure. 
The present invention will become clearer in light of the following 
detailed description of an illustrative embodiment of this invention 
described in connection with the drawings.

All figures are drawn for ease of explanation of the basic teachings of the 
present invention only; the extensions of the Figures with respect to 
number, position, relationship, and dimensions of the parts to form the 
preferred embodiment will be explained or will be within the skill of the 
art after the following teachings of the present invention have been read 
and understood. Further, the exact dimensions and dimensional proportions 
to conform to specific force, weight, strength, and similar requirements 
will likewise be within the skill of the art after the following teachings 
of the present invention have been read and understood. 
Where used in the various figures of the drawings, the same numerals 
designate the same or similar parts. Furthermore, when the terms "first", 
"second", "end", "side", "radial", "circumferential", "clockwise", 
"counter-clockwise", and similar terms are used herein, it should be 
understood that these terms have reference only to the structure shown in 
the drawings as it would appear to a person viewing the drawings and are 
utilized only to facilitate describing the invention. 
DESCRIPTION 
Device or apparatus for connecting and disconnecting an output load to or 
from an input source, at least one or both of which are continuously 
rotating, while at the same time providing position registration and/or 
information and also overload protection according to the preferred 
teachings of the present invention is shown in the drawings and generally 
designated 10. Device 10, in a preferred embodiment, generally includes a 
friction clutch 12 of any conventional design such as the type shown and 
described in U.S. Pat. No. 3,497,046. Device 10, in a preferred 
embodiment, further includes an overload apparatus 14 of any conventional 
design such as the type shown and described in U.S. Pat. No. 4,770,281. In 
the most preferred form, apparatus 14 provides rotational position 
registration, such as a single position registration. Clutch 12 and 
apparatus 14 are connected in parallel as diagrammatically shown in FIG. 
1, in a preferred embodiment, such that either or both may transmit 
rotational power from a source or input 16 to a load or output 18. One 
arrangement of clutch 12 and overload apparatus 14 is shown in FIG. 2 
wherein clutch 12 and overload apparatus 14 are mounted on a through shaft 
which comprises output 18. The output sides of clutch 12 and overload 
apparatus 14 are then rotatably related and rotate with the through shaft 
comprising output 18 whereas the input sides of clutch 12 and overload 
apparatus 14 which are connected together are rotatably mounted relative 
to the through shaft comprising output 18. The input sides of clutch 12 
and overload apparatus 14 are then rotated by a timing belt drive or other 
positive displacement power transmission device such as but not limited to 
a chain drive which comprises input 16. However, it can be appreciated 
that the through shaft could comprise input 16 and the belt or other drive 
comprises output 18, if desired. 
It can then be appreciated that clutch 12 is able to selectively rotatably 
relate input 16 to output 18 independent of the relative rotational 
positions and speeds of input 16 and output 18 at engagement or actuation 
whereas overload apparatus 14 can only selectively rotatably relate input 
16 to output 18 only when input 16 and output 18 are rotating at 
relatively the same speeds and only at select rotational positions of 
input 16 relative to output 18 such as at a single rotational position of 
engagement or actuation which in conventional use is when input 16 and 
output 18 are both stopped. 
Device 10 further includes provisions 20, in a preferred embodiment, such 
as an optical shaft encoder for detecting the angular position of input 16 
and also provisions 22, in a preferred embodiment, for detecting the 
angular position of output 18. Device 10, in a preferred embodiment, 
further includes valves 24 and 26 which are electrically controlled for 
supplying compressed fluid such as air to clutch 12 and also to overload 
apparatus 14, respectively, at pressures which can be adjusted by the 
operator. 
Device 10, in a preferred embodiment, further includes a 
microcomputer-based electronic controller 580 which receives digital 
signals from each of encoders 20 and 22 and receives input commands from 
the operator or another control system, and sends commands to valves 24 
and 26. 
Each encoder 20 and 22, in a preferred embodiment, consists of first 
slotted optical switches 502 and 504, and second slotted optical switches 
503 and 505 and a codewheel 500 and 501, respectively. Codewheels 500 and 
501 are manufactured parts and may be of plastic, metal, etc., in the 
preferred embodiment, and in the most preferred form described include 64 
evenly spaced slots at their optical circumference. Slotted optical 
switches 502-505 are mounted appropriately with respect to each codewheel 
500 and 501. Slotted switches 502-505 used in the preferred embodiment are 
manufactured by Optek Technology and are type OPB930W55. 
Each encoder 20 and 22 translates rotary motion into a two-channel digital 
output. Slotted optical switches 502-505 are aligned with codewheels 500 
and 501 such that, when rotating clockwise, a point on codewheel 500 or 
501 first passes the slotted optical switch 502 or 504 and then slotted 
optical switch 503 or 505, respectively. Furthermore, in a preferred 
embodiment, the digital output of switch 502 or 504 is in quadrature with 
switch 503 or 505 (90 electrical degrees out of phase) as shown in FIG. 3. 
The quadrature output is necessary, in a preferred embodiment, if 
microcomputer controller 580 is to determine the direction of rotation of 
the individual codewheels 500 and 501 of encoders 20 and 22. For examples 
as shown in FIGS. 3 and 5 for clockwise (positive) rotation, switch 502 or 
504 leads switch 503 or 505 by 90 electrical degrees. Similarly as shown 
in FIGS. 3 and 5 for counter-clockwise (negative) rotation, switch 503 or 
505 leads switch 502 or 504. In the preferred form, slotted optical 
switches 502-505 are of the non-inverting type--that is, they output a 
logical 1 when a slot of codewheel 500 or 501 passes through the aperture 
and also have a built-in Schmitt trigger circuit to provide hysteresis for 
stability and low-level noise rejection. 
Quadrature decoding of the signals coming from slotted optical switches 
502-505 of encoders 20 and 22 is performed entirely by microcomputer 
controller 580. The decoding approach multiplies the resolution of the 
input signals by a factor of four, thus providing 256 counts per 
revolution from codewheel 500 or 501 having 64 slots. One count 
corresponds to an angular displacement of approximately 1.4.degree., which 
is presently sufficient resolution for device 10 according to the 
preferred teachings of the present invention. Of course, higher or lower 
resolution is within the skill of the art once the teachings of the 
present invention have been read and understood. However, the ability to 
represent angular position with a single byte (8 bits) has obvious 
computational advantages. 
Optical switches 502-505 are connected by their respective output wires, 
designated 512, 517, 522, and 527 in FIG. 5 to the remaining logic of the 
diagrammatic/schematic of FIG. 5. For example, optical switches 502-505 
are connected to logic gates 534, 535, 536, and 537, each of which form 
one-quarter of a logic gate designated MM74HC266A as manufactured by 
National Semiconductor. 
Encoders 502-505 are configured so that a slot in output codewheels 500 and 
501 is a logical one. Optical switches 502-505 and gates 534-537 are 
further interconnected with microcomputer controller 580. Microcomputer 
controller 580, in the preferred embodiment, is a single-chip 
microcomputer and in the preferred form an Intel 87C51. 
Microcomputer controller 580 is further interconnected with further logic 
gates 600, 601, 602, 603, 604, and 605 which function as lamp drivers for 
indicator lamps 620, 621, 622, 623, 624, and 626, respectively. Logic 
gates 600-605 each form one-sixth of MM74HC14 manufactured by National 
Semiconductor. 
Logic gates 600-605 are further connected through one kilohm resistors 611, 
612, 613, 614, and 615 to indicator lamps 620, 621, 622, 623, 624, and 
626. 
Indicator 620 indicates the condition of overload apparatus 14, with the 
lamp on indicating engagement. Indicator 621, when lit, indicates that a 
disengagement of overload apparatus 14 has occurred as the result of an 
overload condition. Indicator 622 signifies an input encoder fault. 
Indicator 623 signifies an output encoder fault. Indicator 624 signifies a 
drag fault on overload apparatus 14. Indicator 626 signifies a 
clutch-engage time-out condition. 
Further connected to microcomputer controller 580 are switches 625 and 630. 
Switch 625 is a momentary, normally off switch. Switch 625 is pushed once 
every time the electronics are energized to provide information to the 
system as to the zero location, as will be further explained. Switch 630 
is a toggle switch which may be thrown to engage clutch 12 of the 
preferred embodiment of the present invention. Of course, switches 625 and 
630, among other parts, may be replaced by logical inputs to the system of 
the present invention. 
Optional hexadecimal display 650 is also provided as an output to 
microcomputer controller 580. Hexadecimal display 650 is an HDSP-0762 
manufactured by Hewlett Packard. Display 650 can display the position of 
the balls of overload apparatus 14 with respect to its detents. Also 
connected to microcomputer controller 580 are two further logic gates 680 
and 681 which further connect to indicators 685 and 686 through one kilohm 
resistors 689 and 690, respectively. Indicator 685 is configured to 
provide a "clutch on" representation. Indicator 686 is configured to 
provide an "overload apparatus on" representation. 
Further interconnected with microcomputer controller 580 is driver 710. 
Driver 710 is a type DS3669 as manufactured by National Semiconductor. 
Driver 710 is interconnected with a further indicator 712 through a 150 
ohm resistor 714 to provide an indication that clutch 12 is in a "ready" 
condition. 
All indicators are type HLMP-K150 as manufactured by Hewlett Packard except 
for "ready" indicator 712 which is green, not red, and is Hewlett Packard 
HLMP-1523. 
Various electrical connections are provided to appropriate power, including 
510, 511, 515, 520, 521, and 525. Various electrical connections are also 
provided between parts, including 513, 516, 523, and 526. Also, various 
electrical connections are provided to electrical ground, including 514, 
518, 519, 524, 528, and 529. 
The signals from slotted optical switches 502-505 enter microcomputer 
controller 580 in the preferred form of Intel 87C51 single-chip 
microcomputer by means of the Port 1 pins and the external interrupt pins 
NOT INT0 and NOT INT1. The present states of slotted optical switches 
502-505 are read by pins P1.0, P1.2, P1.4, and P1.6. The past states of 
slotted optical switches 502-505 are output by pins P1.1, P1.3, P1.5, and 
P1.7. Each input signal along with its corresponding past value is fed to 
the two inputs of one of exclusive-NOR gates 534-537. Exclusive-NOR gates 
534-537 act as equality detectors and output a logical 1 only when the two 
inputs are at the same logic level--in other words, as long as the present 
state of the appropriate slotted optical switch 502-505 is equal to its 
past state. Exclusive-NOR gates 534-537 in the preferred form of 
MM74HC266A made by National Semiconductor have open drain outputs which 
cannot source current; they can only sink current. By connecting the 
outputs of exclusive-NOR gates 534-535 together and 536-537 together and 
adding 10K pullup resistors 538 and 539, a wire-0R function is achieved. 
In this manner, the signals from exclusive-NOR gates 534 and 535 for input 
codewheel 500 are combined and connected to external interrupt NOT INT0, 
while the signals from exclusive-NOR gates 536 and 537 for output 
codewheel 501 are combined and connected to external interrupt NOT INT1. 
The external interrupts are programmed to be edge-sensitive; that is, an 
interrupt is generated when a 1-to-0 transition (a falling edge) is 
detected at one of the external interrupt pins. There are two interrupt 
service routines in the system that process external interrupts. One 
routine decodes signals from the input encoder (NOT INT0), and the other 
decodes signals from the output encoder (NOT INT1). These interrupt 
service routines increment (add 1 to) or decrement (subtract 1 from) an 
8-bit position counter read by display 650 (called THETA in microcomputer 
controller 580) that keeps track of the position of the balls with respect 
to the detents of overload apparatus 14. The interrupt service routines 
also control the pins that output the past states of slotted optical 
switches 502-505. Initially, the past state of each slotted optical switch 
502-505 is set equal to its present state. In this condition, the NOT INT0 
and NOT INT1 pins are both held at a logic 1 and no external interrupts 
are generated. Now, if any of the slotted optical switches 502-505 change 
logic states, an interrupt will be generated. When the appropriate 
interrupt service routine is vectored to, it examines the Port 1 data to 
determine which channel made the transition, whether it was a rising edge 
or a falling edge, and what logic state the remaining channel is in. If 
the state transition is valid, position counter 650 is either incremented 
or decremented, depending on the Port 1 data. In addition, the past state 
of the appropriate slotted optical switch 502-505 is set equal to its 
present state, thereby returning the appropriate interrupt pin to a logic 
1. 
To maintain the integrity of position counter 650, short duration noise 
spikes are rejected and illegal state transitions are detected and flagged 
as encoder faults. When input codewheel 500 rotates clockwise one count, 
position counter 650 is incremented. When the input codewheel 500 rotates 
counter-clockwise one count, position counter 650 is decremented. When 
output codewheel 501 rotates clockwise one count, position counter 650 is 
decremented. When output codewheel 501 rotates counter-clockwise one 
count, position counter 650 is incremented. All of these events happen 
quite rapidly. For example, when the engaged overload apparatus 14 is 
rotating at 1,800 RPM, microcomputer controller 580 must process 15,360 
interrupts per second. 
The method of position sensing just described is an incremental system. 
Without additional information, it cannot measure absolute position, only 
changes in absolute position. At some point microcomputer controller 580 
needs to be told where home position is. After that, it will always know 
the position of the balls with respect to the detents of overload 
apparatus 14 as long as the electronics, including slotted optical 
switches 502-505, remain powered up. To do this, the operator must 
manually engage overload apparatus 14 and then press zero switch 625. 
Notice that device 10 does not need to know the absolute position of the 
input and output codewheels 500 and 501, only their position relative to 
each other. 
when device 10 receives an engage command, as from switch 630, it must 
first debounce the signal and make sure that it is a valid command and not 
just noise. To do this, microcomputer controller 580 waits approximately 
1/15 second to make sure that the command is still active. During this 
time, it also computes the differential speed and the direction of 
rotation. If the differential speed is less than 14.3 RPM, microcomputer 
controller 580 assumes that overload apparatus 14 is essentially at rest 
and applies air pressure to it without engaging clutch 12. Overload 
apparatus 14 may then be manually engaged so that the home-position can be 
set by pressing zero switch 625. zero switch 625 only needs to be pressed 
when the electronics of device 10 are first powered up or when the home 
position has been lost because of an encoder fault. If the differential 
speed is greater than 14.3 RPM and the home position has been set, 
microcomputer controller 580 applies air pressure to clutch 12 and enters 
a digital control loop. If the home position has not been set or has been 
lost, the engage command is ignored. 
The digital control loop operates as follows. Every time position counter 
650 advances one count (increments if the balls of overload apparatus 14 
are moving clockwise with respect to the detents, decrements if the balls 
of overload apparatus 14 are moving counter-clockwise with respect to the 
detents), microcomputer controller 580 compares the actual angular 
velocity of the balls with respect to the detents to the desired angular 
velocity from a velocity profile stored in a look-up table in program 
memory. The velocity profile represents the desired angular velocity, as a 
function of angular position, for the final revolution of clutch slipping. 
If the actual velocity is greater than the desired velocity, microcomputer 
controller 580 opens valve 24 of clutch 12. If the actual velocity is less 
than the desired velocity, microcomputer controller 580 closes valve 24 of 
clutch 12. Angular velocity is expressed in terms of the time interval, in 
microseconds, between successive transitions of position counter 650. The 
desired velocity profile is based on a constant angular acceleration of -1 
rev/sec.sup.2 until the velocity drops to 1/16 rev/sec (3.75 RPM) at an 
angular position 16 counts (1/16 rev) from the home position. The velocity 
is then held constant at 3.75 RPM until 2 counts before reaching the home 
position. At this point, if the actual velocity does not exceed 14.3 RPM, 
valve 26 of overload apparatus 14 is opened and valve 24 of clutch 12 is 
closed. After a 0.25 second delay to allow the balls to settle in the 
detents of overload apparatus 14, overload apparatus 14 should be engaged 
and microcomputer controller 580 begins looking for an overload. 
Microcomputer controller 580 does this by constantly monitoring position 
counter 650 to make sure it does not fall outside an error band centered 
on the home position. If it does, microcomputer controller 580 exhausts 
the air from overload apparatus 14 and turns on overload indicator 621. 
To operate device 10 of the present invention, certain procedures are of 
course desirable. For example, it has been explained that switch 625 of 
FIG. 5 is pushed once to set the zero position of overload apparatus 14. 
Similarly, toggle switch 630 of FIG. 5 is moved from an "on" position for 
engagement to a "off" position for disengagement. When an "off" to "on" 
transition is detected by microcomputer controller 580, it waits 
approximately 1/15 second to debounce the signal and compute the magnitude 
and direction of the differential speed. If the differential speed is less 
than 14.3 RPM, in the preferred form microcomputer controller 580 will 
apply air pressure through the controlling valve 26 for overload apparatus 
14 without engaging clutch 12. Overload apparatus 14 may then be manually 
engaged. If the differential speed is greater than 14.3 RPM, microcomputer 
controller 580 opens clutch valve 24 and then pulse width modulates the 
clutch pressure during the final revolution of clutch slipping so as to 
control the relative velocity of the balls of overload apparatus 14 as 
they approach the detents, i.e. home position. At 1/128 revolution before 
reaching the home position, microcomputer controller 580 applies air 
pressure to overload apparatus 14 through valve 26 and the air pressure is 
exhausted from clutch 12. At this point, overload apparatus 14 should be 
engaged properly. The engagement sequence may be aborted at any time by 
moving toggle switch 630 to the "off" position. 
Next, the zero command may be actuated. This command tells microcomputer 
controller 580 that overload apparatus 14 is engaged. It is used to set 
the home position after device 10 has been powered-up, and it is activated 
by the operator or logic device only after overload apparatus 14 has been 
properly engaged. The zero command is given by pressing switch 625. As 
long as device 10 is powered-up, microcomputer controller 580 will know 
the position of the balls of overload apparatus 14 with respect to the 
detents. During normal operation (differential speed greater than 14.3 RPM 
in the preferred form), the zero command as provided by switch 625 may be 
ignored. 
Next, overload sensitivity may be set by engaging or disengaging switch 631 
shown in FIG. 5. When pin P0.2 on microcomputer controller 580 is grounded 
with a jumper wire, the low sensitivity setting is selected. When the 
jumper wire is removed, the high sensitivity setting is selected. Use of 
the high sensitivity setting is desirable unless nuisance trip-outs occur. 
Next, the ready indicator light, indicator light 712 on FIG. 5, must be on 
before device 10 is ready to receive an engage command from switch 630. In 
order for the ready indicator lamp 712 to be lit, the following must be 
true. First, no fault lamps may be lit. Fault lamps are such as 621, 622, 
623, and 624. Next, toggle switch 630 must be in the disengage position. 
Last, the home position must be set, as previously described. When these 
three conditions exist, the ready indicator light 712 will indicate green. 
Next, overload apparatus 14 status indicator 620 should be investigated. 
Indicator lamp 620 is lit whenever overload apparatus 14 is engaged. This 
means that the balls are seated in the detents, not just that air pressure 
is being applied to overload apparatus 14. 
Lamp 621 is lit whenever there has been a disengagement of overload 
apparatus 14 as the result of an overload condition. The overload 
condition is cleared by moving toggle switch 630 to the disengage position 
and re-engaging toggle switch 630. 
Indicator 685 is lit whenever valve 24 associated with clutch 12 is turned 
on. During the final revolution of clutch slipping, indicator 685 will 
flash on and off as the pulse width of microcomputer controller 580 
modulates the clutch pressure. 
Overload apparatus 14 limiter valve indicator 686 is lit whenever valve 26 
associated with overload apparatus 14 is turned on. Indicator 686 being 
lit does not necessarily mean that overload apparatus 14 is engaged. 
Indicator 622 is lit when microcomputer controller 580 detects an illegal 
state transition in the quadrature signals coming from codewheels 500 and 
501 of slotted optical switches 502-505. This fault indicates a serious 
hardware problem, such as a damaged or misaligned slotted optical switch, 
dirt or other obstruction in the gap of a slotted optical switch 502-505, 
a damaged codewheel 500 or 501, or a faulty electrical connection between 
slotted optical switches 502-505 and microcomputer controller 580. 
Unfortunately, it is impossible for microcomputer controller 580 to detect 
every type of encoder error that could possibly occur, and certain encoder 
errors may be interpreted as an overload by microcomputer controller 580. 
The encoders have, however, been found to be very reliable. If an encoder 
fault does occur, it cannot be cleared simply by moving toggle switch 630 
to the disengage position because the home position may have been lost. 
The operator must stop device 10, manually engage overload apparatus 14, 
set the home position again by pressing switch 625, and restart device 10. 
Output encoder fault indicator 623 is lit when microcomputer controller 580 
detects an illegal state transition in the quadrature signals coming from 
output codewheel slotted optical switches 504 and 505. 
Drag fault indicator 624 is lit when, in the manual engagement mode with 
air pressure applied to overload apparatus 14, the differential speed in 
either direction of rotation exceeds 14.3 RPM in the preferred form. This 
feature protects overload apparatus 14 from ratcheting and provides 
overload protection even if overload apparatus 14 is disengaged and the 
home position has not been set. This fault is cleared by moving toggle 
switch 630 to the disengage position and re-engaging. 
Clutch engagement time-out fault indicator 625 is lit if overload apparatus 
14 has failed to engage after 16.7 seconds of clutch slipping in the 
preferred form. This feature protects clutch 12 from overheating as a 
result of excessive slipping caused by malfunction, a leak in the air line 
to clutch 12, or the pressure regulator of valve 24 for clutch 12 being 
set too low for the load. This fault is cleared by moving toggle switch 
630 from the engage to the disengage position and re-engaging. 
If any of the above faults occur, microcomputer controller 580 will 
immediately disconnect output 18 from input 16 by exhausting the air from 
both of valves 24 and 26 for clutch 12 and overload apparatus 14. This 
exhausting of air will occur even if toggle switch 630 is still in the 
engage position. 
One preferred method of operating device 10 of the present invention may 
now be explained. First, after insuring that all is wired properly 
according to the Figures, it is recommended that the DC power be applied 
to device 10 which will light all of the indicator lamps except for lamps 
685 and 686. Display 650 will display FF. If a valid reset has occurred, 
all of the indicator lamps will then turn off and the display will show 
00. 
The next step is to set the home position. To do this, first set overload 
apparatus 14 regulator to an appropriate pressure so overload apparatus 14 
can be rotated by hand while air is applied. Then toggle switch 630 may be 
moved to the engage position. Overload status indicator lamp 620 should 
light, and you should hear a loud click as overload apparatus 14 valve 26 
opens and air enters overload apparatus 14. Now, with air pressure applied 
to overload apparatus 14, slowly rotate input 16 with respect to output 18 
until the balls drop into the detents. If you rotate too fast, you will 
trigger an overload drag fault, indicator 624 will become lit, and the air 
will be exhausted from overload apparatus 14. If this happens, move toggle 
switch 630 to the disengage position and back to the engage position, then 
resume the search for the home position. Once you have found the home 
position, and with toggle switch 630 still in the engage position, press 
switch 625, the zero position button. At this point, indicator 626 will 
light. If toggle switch 630 is then moved to the disengage position, 
overload status indicator 620 and overload valve indicator 686 will both 
turn off, and green ready indicator 712 will light. If toggle switch 630 
is then moved to the disengage position, overload apparatus 14 status 
indicator 620 and overload valve indicator 686 will both turn off and 
green ready indicator 712 will turn on. With overload apparatus 14 
engaged, it should be possible to rotate output 18 one full revolution in 
either direction without triggering an overload. If this test fails, it is 
best to reset the home position by again manually engaging overload 
apparatus 14 and pressing momentary switch 625. When the test is passed, 
device 10 is ready for operation and will require no further adjustments 
as long as power is maintained. 
The reason the home position must sometimes be reset during installation is 
as follows. Inside microcomputer controller 580 there is an 8-bit register 
used as a position counter and read by display 650. This register keeps 
track of the angular position of the balls with respect to the detents 
with a resolution of 1 part in 256. In theory, the position counter should 
always be equal to zero as long as overload apparatus 14 is engaged. 
However, for this to be true, both codewheels 500 and 501 would have to be 
perfect. Since these requirements are difficult if not impossible to 
achieve, it has been found that position counter 650 is equal to zero plus 
or minus one count as engaged overload apparatus 14 is rotated. Now, when 
overload apparatus 14 is engaged and the home position has been set, 
microcomputer controller 580 constantly monitors position counter 650 to 
make sure it is always equal to zero plus or minus some tolerances. For 
high sensitivity settings, this tolerance is equal to plus or minus one 
count; for low sensitivity settings, this tolerance is equal to plus or 
minus two counts; for the high sensitivity setting, position counter 650 
must always be equal to 255, 0, or 1 (the error band) because, if it is 
not, microcomputer controller 580 thinks the balls are starting to roll 
out of the detents and interrupts the sequence as an overload condition. 
Position counter 650 must be at the midpoint of the error band at the 
moment zero set switch 625 is pressed. This may be explained as follows. 
Suppose that when zero set switch 625 is pressed, codewheels 500 and 501 
just happen to be oriented so that position counter 650 is not at the 
center of the error band. When engaged overload apparatus 14 is then 
rotated, position counter 650 is going to read either 0 plus 2 counts or 0 
minus 2 counts, depending on which end of the error band exists when zero 
set switch 625 was pressed. To microcomputer controller 580, this will 
appear to be an overload condition. Clearly, for proper operation, 
position counter 650 must be at the midpoint of the error band at the 
moment zero set switch 625 is pressed. The better the encoder, the more 
likely this is to occur. 
In FIG. 6 a block diagram of the overall approach of the electronics 
according to the present invention may be explained. In this Figure, 
initialization block 100 assures that device 10 is in a preset state 
before beginning. With respect to the previous figures, initialization 
block 100 assures that valve 24 of clutch 12 causes clutch 12 to be 
disengaged; and valve 26 of overload apparatus 14 assures that overload 
apparatus 14 is disengaged. In the preferred embodiment, device 10 assures 
that there is no air applied to clutch 12 or overload apparatus 14. 
Further, the initialization stage clears the home status position flag in 
the electronics to clearly indicate that the home position is not yet 
known. 
The initialization stage also turns off all of the indicator lamps, in the 
preferred embodiment. 
The initialization stage also configures all timers and establishes the 
interrupt priorities. The initialization stage then configures the 
interrupts and enables the interrupts. 
The initialization stage also sets the past states of slotted optical 
switches 502-505 equal to their present states. 
After that, the initialization stage waits for the disengage command, and 
will not proceed until a disengage command is received. The disengage 
command is received from switch 630 or its logical equivalent. This "wait" 
stage is a safety feature which prevents device 10 from starting up 
unexpectedly if, for example, a live shaft exists at input 16 when the 
electronics is powered-up. With this safety feature, device 10 will not 
engage either clutch 12 or overload apparatus 14 until the operator or 
other control device has gone to a disengage position and then to an 
engage position. The event that triggers start-up of device 10 is a 
transition from the disengage state to the engage state, a conscious, 
purposeful action. 
After the system is initialized, the states of clutch 12 and overload 
apparatus 14 are detected by detection block 102. Detection block 102 
constantly monitors the position of the balls of overload apparatus 14 
with respect to its detents. Detection block 102 accomplishes this through 
the codewheels 500 and 501 in connection with their associated 
electronics, as previously explained. Detection block 102 monitors device 
10, as previously explained in connection with the explanation of how to 
operate device 10. 
Detection block 102 then provides a signal to engagement block 104 to 
engage overload apparatus 14 and clutch 12 of the preferred embodiment of 
the present invention in a manner also previously described. 
Detection block 102 also provides a signal to feedback block 106 which also 
interrelates with engagement block 104 to engage or disengage overload 
apparatus 14 and/or clutch 12 in a manner hereinbefore explained. 
Of course, operator/logic control block 108 is in control of the entire 
operation and may contain as little as switch 630 of FIG. 5. 
FIG. 6 is exemplary of the overall operation of the system of the present 
invention and its most basic, block diagram form to merely illustrate the 
functional blocks associated with the explanation previously given. 
Lastly, object code for microcomputer controller 580 follows and those 
skilled in the art will be aware of the use of this object code listing. 
______________________________________ 
LOC OBJ 
______________________________________ 
0000 011D 
0003 4191 
000B 
000B 6155 
0013 
0013 41F3 
001B 
001B 6190 
001D C200 
001F 758007 
0022 75B00F 
0025 75829B 
0028 75F004 
002B 752380 
002E 752402 
0031 75254B 
0034 752600 
0037 758912 
003A 75B805 
003D E590 
003F 23 
0040 F590 
0042 758815 
0045 75A887 
0048 3080FD 
004B D2B0 
004D D2B1 
004F C283 
0051 C284 
0053 C285 
0055 300008 
0058 E5B0 
005A 54F0 
005C 7002 
005E D283 
0060 758107 
0063 C2AB 
0065 C28E 
0067 E4 
0068 F58B 
006A F58D 
006C D28E 
006E 308FFD 
0071 C28F 
0073 C28E 
0075 2080FD 
0078 C283 
007A 200010 
007D C2AF 
007F 7590FF 
0082 E590 
0084 23 
0085 F590 
0087 758815 
008A 75A887 
008D 852122 
0090 758BC0 
0093 758DE0 
0096 D28E 
0098 308FFD 
009B C28F 
009D C3 
009E E521 
00A0 9522 
00A2 C201 
00A4 30E704 
00A7 D201 
00A9 F4 
00AA 04 
00AB 54FC 
00AD 6016 
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00B2 C28F 
00B4 C28E 
00B6 200005 
00B9 3080FD 
00BC 014B 
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00C1 218D 
00C3 21E4 
00C5 C28E 
00C7 852122 
00CA E4 
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00CD F58D 
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00D1 308FFD 
00D4 C28F 
00D6 C28E 
00D8 C3 
00D9 E521 
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00E2 D201 
00E4 F4 
00E5 04 
00E6 54FC 
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00F2 2001CE 
00F5 218D 
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00FA 014B 
00FC C2B1 
00FE 852122 
0101 E4 
0102 F58B 
0104 F58D 
0106 D28E 
0108 20810F 
010B C2AF 
010D 752100 
0110 C2B4 
0112 C2B5 
0114 D200 
0116 D2AF 
0118 802C 
011A 300010 
011D E521 
011F B4FF02 
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0124 7002 
0126 801E 
0128 B40102 
012B 8019 
012D 30BFD8 
0130 C28F 
0132 C28E 
0134 C3 
0135 E521 
0137 9522 
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013D 04 
013E 54FC 
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0152 D28E 
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015F 208103 
0162 752100 
0165 E521 
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0173 80EA 
0175 20820A 
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017D B40202 
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0186 D2B1 
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0194 308002 
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01A4 D28E 
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01A7 E8 
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01B4 758D00 
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01C4 CB 
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01C6 93 
01C7 99 
01C8 EB 
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01CF 4006 
01D1 7C00 
01D3 7D00 
01D5 80CF 
01D7 EA 
01D8 2C 
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01DB 3D 
01DC FD 
01DD B8FEC6 
01E0 60C4 
01E2 413B 
01E4 E4 
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01E7 F58D 
01E9 FC 
01EA FD 
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01EE 014B 
01F0 C2B0 
01F2 D2AB 
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01F6 14 
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0202 C28E 
0204 A98B 
0206 AA8D 
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020B 758D00 
020E D28E 
0210 F4 
0211 04 
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021D CB 
021E 04 
021F 93 
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0221 EB 
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0223 92B0 
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0226 24FA 
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022A 7C00 
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0230 EA 
0231 2C 
0232 FC 
0233 E4 
0234 3D 
0235 FD 
0236 B802C4 
0239 60C2 
023B C2B1 
023D D2B0 
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0248 758D2F 
024B D28E 
024D 7E04 
024F 308FFD 
0252 C28F 
0254 DEF9 
0256 C28E 
0258 E521 
025A B4FF02 
025D 80F9 
025F 7002 
0261 80F5 
0263 B40102 
0266 80F0 
0268 20820A 
026B B4FE02 
026E 80E8 
0270 B40202 
0273 80E3 
0275 C284 
0277 D285 
0279 D2B1 
027B 3080FD 
027E 014B 
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0282 C285 
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0286 D2B1 
0288 3080FD 
028B C2B6 
028D C2B7 
028F 014B 
0291 20932A 
0294 209214 
0297 209109 
029A 209001 
029D 32 
029E D291 
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02A2 32 
02A3 209004 
02A6 C291 
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02AB 209108 
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02B1 D293 
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02BD 32 
02BE 209213 
02C1 209108 
02C4 209021 
02C7 C293 
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02CB 32 
02CC 309019 
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02D3 32 
02D4 209109 
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02DB D291 
02DD 1521 
02DF 32 
02E0 209004 
02E3 C291 
02E5 0521 
02E7 32 
02E8 C2A8 
02EA C200 
02EC D2B4 
02EE C023 
02F0 C024 
02F2 32 
02F3 20972A 
02F6 209614 
02F9 209509 
02FC 209401 
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0300 D295 
0302 1521 
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0305 209404 
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030A 0521 
030C 32 
030D 209508 
0310 209437 
0313 D297 
0315 0521 
0317 32 
0318 30942F 
031B D297 
031D 1521 
031F 32 
0320 209613 
0323 209508 
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032B 1521 
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032E 309419 
0331 C297 
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0336 209509 
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033C 32 
033D D295 
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034E D2B5 
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0352 C024 
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03D1 0BD4 
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0501 161A 
0503 1649 
0505 167A 
0507 16AB 
0509 16DE 
050B 1712 
050D 1747 
050F 177E 
0511 17B7 
0513 17F1 
0515 182C 
0517 186A 
0519 18A9 
051B 18EB 
051D 192E 
051F 1974 
0521 19BC 
0523 1A07 
0525 1A54 
0527 1AA3 
0529 1AF6 
052B 1B4C 
052D 1BA5 
052F 1C01 
0531 1C61 
0533 1CC6 
0535 1D2E 
0537 1D9B 
0539 1E0D 
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053D 1F02 
053F 1F85 
0541 200F 
0543 20A0 
0545 2139 
0547 21DB 
0549 2287 
054B 233D 
054D 23FF 
054F 24CE 
0551 25AC 
0553 269A 
0555 279B 
0557 28B1 
0559 29DF 
055B 2B29 
055D 2C93 
055F 2E23 
0561 2FE1 
0563 31D6 
0565 340D 
0567 3697 
0569 398B 
056B 3D09 
056D 4140 
056F 467A 
0571 4D34 
0573 5651 
0575 63AC 
0577 7A12 
0579 ACA2 
057B F424 
057D F424 
057F F424 
0581 F424 
0583 F424 
0585 F424 
0587 F424 
0589 F424 
058B F424 
058D F424 
058F F424 
0591 F424 
0593 F424 
0595 F424 
0597 F424 
0599 F424 
______________________________________ 
Thus since the invention disclosed herein may be embodied in other specific 
forms without departing from the spirit or general characteristics 
thereof, some of which forms have been indicated, the embodiments 
described herein are to be considered in all respects illustrative and not 
restrictive. The scope of the invention is to be indicated by the appended 
claims, rather than by the foregoing description, and all changes which 
come within the meaning and range of equivalency of the claims are 
intended to be embraced therein.