Title: Electronic industrial motor operator control system
Abstract: This invention discloses an electronic control system for an Industrial Motor Operator that uses standard steady state logic to improve reliability in rough service wet and dirty environments. It includes means of providing electronic snow limit to close limit sensing removing the need for two switches and radically improving its accuracy. A low voltage switch reverses the high voltage motor wires and at the same time reverses the open limit, close limit, and snow limit sensors mechanical positions. It discloses a system using lamps to indicate that the power wiring is connecting to three-phase motors in the correct sequence or that single-phase motors have their windings correctly phased.
Patent Number: 6,943,511 Issued on 09/13/2005 to Beckerman
| Inventors:
|
Beckerman; Howard (Red Bank, NJ)
|
| Assignee:
|
Mechanical Ingenuity Corp (Shrewsbury, NJ)
|
| Appl. No.:
|
773291 |
| Filed:
|
February 9, 2004 |
| Current U.S. Class: |
318/286; 49/28; 318/266; 318/283; 318/285; 318/467 |
| Intern'l Class: |
H02P 001/22 |
| Field of Search: |
318/285-286,468,282,283,256,466,467,480,465,265,266
388/815,833,903
49/28
|
References Cited [Referenced By]
U.S. Patent Documents
| 3855509 | Dec., 1974 | Wright.
| |
| 4035702 | Jul., 1977 | Pettersen et al.
| |
| 4119896 | Oct., 1978 | Estes et al.
| |
| 4234833 | Nov., 1980 | Barrett.
| |
| 4263536 | Apr., 1981 | Lee et al.
| |
| 4338553 | Jul., 1982 | Scott, Jr.
| |
| 4357564 | Nov., 1982 | Deming et al.
| |
| 4360801 | Nov., 1982 | Duhame.
| |
| 4369399 | Jan., 1983 | Lee et al.
| |
| 4385296 | May., 1983 | Tsubaki et al.
| |
| 4405923 | Sep., 1983 | Matsuoka et al.
| |
| 4408146 | Oct., 1983 | Beckerman.
| |
| 4433274 | Feb., 1984 | Duhame.
| |
| 4464651 | Aug., 1984 | Duhame.
| |
| 4491774 | Jan., 1985 | Schmitz.
| |
| 4701684 | Oct., 1987 | Seidel et al.
| |
| 5218282 | Jun., 1993 | Duhame.
| |
| 5247232 | Sep., 1993 | Lin.
| |
| 5357183 | Oct., 1994 | Lin.
| |
| 6020703 | Feb., 2000 | Telmet.
| |
| 6064165 | May., 2000 | Boisvert et al.
| |
| 6181095 | Jan., 2001 | Telmet.
| |
Primary Examiner: Ip; Paul
Claims
1. A motorized door/gate operator the improvement comprising;
a logical means connected such that at least one input produces an open-output-signal
and all other inputs disables the open-output-signal;
a logical means connected such that at least one input produces a close-output-signal
and all other inputs disables the close-output-signal;
said open-output-signal connects to inverting means that disables the close logical
means, thereby disabling the close-output-signal;
an open-to-close delay circuit, arranged such that it delays the close-output-signal
only after receiving the open-output-signal, otherwise, no significant open-output-signal
delay is present;
a close-to-open delay circuit, arranged such that it delays the open-output-signal
only after receiving the close-output-signal, otherwise, no significant open-output-signal
delay is present;
a first switching means that reacts to the open-to-close delay output signal
to supply power line voltage to a motor causing it to rotate in one direction; and
a second switching means that reacts to the close-to-open delay output signal
to apply power line voltage to the motor causing it to rotate in the opposite direction.
2. The motorized door/gate operator according to claim 1 further comprising:
the open limit and the virtual-close-limit signal connect into a logical means
producing a new either-limit-signal;
the either-limit-signal couples to a one-shot circuit, producing one short duration
pulse each time it is activated; and
the short duration pulse connects to stop the motor operator whenever the either-limit-signal activates.
3. The motorized door/gate operator according to claim 1 further comprising:
an open switch signal and a close switch signal, connects to a first logical
means producing at its output an either-switch-signal;
signal indicating that a low voltage exists and signal of the activation of a
stop pushbutton switch connecting to a second logical means to produce an All-Stop
Signal, such All-stop signal connects to stop the opening and closing of the motor operator;
the either-switch signal and the All-Stop signal connects to a logical means
producing at its output a third signal, such third output signal indicates pressing
either pushbutton at the same time as a low voltage is present, or while a stop
pushbutton is pressed; and
feeding back the third signal into the logical means producing an All-Stop signal
thereby latching the All-Stop signal until removal of the either-switch-signal.
4. The motorized door/gate operator according to claim 1 further comprising:
a close pushbutton switch connects such as to produce a close-switch-signal;
the close-switch-signal couples to a one-shot-circuit, producing a short duration
pulse with each press of the close pushbutton switch;
the short duration pulse connects to stop the opening cycle of the motor operator; and
the close-switch-signal also connects to start rotation of the motor in the close direction.
5. A motorized door/gate operator the improvement comprising:
a close limit of travel sensing means connecting to change the logical operation
of obstruction sensing from opening a motor if obstructed to stopping the motor
if obstructed;
the close limit of travel sensing means also connects to a delay circuit, arranged
such that it delays the close limit signal forming a virtual-close-limit signal;
the virtual-close-limit signal connects to stop rotation of the motor in the
close direction; and
an open limit sensing means connects to stop rotation of the motor in the open direction.
6. The motorized door/gate operator according to claim 5 further comprising:
switching means to reverse the limit sensing signals such that the close limit
of travel becomes the open limit of travel and conversely the open limit becomes
the close limit.
7. The motorized door/gate operator according to claim 6 further comprising:
light means indicating which particular limit sensor is active;
placing the light means next to said limit-sensors such that, when the motor
produces the correct rotation a moving mechanical position indicator moves toward
the illuminated light means; and
conversely, when the motor produces the incorrect rotation the moving mechanical
position indicator moves away from the illuminated light.
8. The motorized door/gate operator according to claim 5 further comprising:
first relay means to rotate an electric motor shaft in one direction and a second
relay means to rotate the motor shaft in an opposite direction;
a first signal represents an opening command and a second signal represents a
closing command;
a switch selects one of two rotational directions;
means configures to reverse the first signal and the second signal in response
to the position of the switch; and
means to energize the relays based on reversing the first and second signals.
Description
BACKGROUND OF THE INVENTION
Industrial door/gate motor operators distinguish themselves from residential
garage door operators by using three pushbuttons, open, close, and stop. Called
a three-button station their operation would seem to be obvious but there are variations.
Automatic operation, termed "momentary", requires just a momentary press of the
open or close button to move the motor operator to its limit of travel. Momentary
operation requires a safety device such as a safety edge or photo-eye so as not
to crush something in the opening. Non-Automatic operation, termed "constant",
requires constant pressure on a pushbutton to move the motor operator to its limit
of travel. Constant operation requires that all three-button stations be next to
the entryway and that releasing the pushbutton will immediately stop the operator.
Further distinction between residential and industrial motor operators is that
of output torque, industrial operators are those that exceed 100-lbs of force,
and such distinctions are in U.L. Specification 325.
Single button operation is a rarely used option but available for industrial
motor operators. If the entry is fully open, pushing this button will close it.
If the entry is fully closed, pushing this button will open it. If the entry is
actively closing, pushing this button will cause it to stop for a moment and then
re-open. This is termed, an "Auto" function and is different from residential door
operators. Residential motor operators have only a single button that delivers
the sequence,
opening-stop-closing-stop and the cycle repeats.
A quick glance at the sequence shows that whenever the door, stops between the
limits, either opening or closing will follow with equal certainty. If the person
standing at the button walks away, the next person attempting to enter a partially
open door may press the button and get an unexpected closing, followed by an unexpected
stop. Rapidly pressing the pushbutton during an emergency gives a revolving roulette
wheel of commands and three out of four are wrong. Industrial motor operators command
hundreds or even thousands of pounds of force and uncertainty about their direction
of movement is bad. Therefore, the single button auto function in industrial motor
operators should not include the ability to stop the operator in a partially open position.
There usually are numerous pushbuttons, radio controls and pull cords in operation
on one motor operator at one time and conflicts occur regularly. If one person
is pressing a close button on one side of an entryway, while at the same time another
person is pressing an open button on the other side of the entryway, the motor
operator must prefer the open command. The occupant entering has priority over
those leaving an entrance. In addition, the closing function is to some extent
more hazardous than the opening function. Pressing a stop button, even for a moment,
overrides the continuous pressing of either an open or a close button. A shorted
button, stuck radio control, blocked photo-eye can issue a continuous command to
the motor operator to move in a direction. A continuous command to move might force
a person to stand at the stop button, holding it, to prevent movement. This does
not allow a responding person to give aid to potential victims. Trapped at the
pushbutton station he can only call for someone to turn off power. Therefore, the
stop function should latch until all buttons are released everywhere in the system.
In general, the person standing at the entryway will always be able to interpret
a safety hazard better than any safety sensor or computer controlled motor operator.
The person responding to an emergency will not be skilled in motorized operators.
Assuredly, they will not have time to read the manual, safety stickers, or interpret
alarms and flashing lights. They are likely to be just a passerby rushing to the
aid of someone in trouble at the door or gate. Therefore, the Open Close and Stop
buttons must always perform as stated and not change their functions.
Motor operators must have a fully open and a fully closed position setting
most commonly implemented by two limit switches and a rotating threaded shaft with
non-rotating threaded nuts. The threaded shaft rotates as the door/gate moves by
a mechanical linkage driving the threaded nuts linearly. Thereby every position
of the door/gate has an exact proportional position of the nut on this shaft. At
the limit of travel, the nut presses against a limit switch that signals the motor
operator to stop moving in that direction. Limit switches are commonly of the,
"normally closed" type, which open their contacts when the threaded nut presses
on their lever. This configuration allows that if contact is lost, the motor will
not even begin to operate in that direction, indicating a defective or disconnected
switch. This is an important safety feature when commanding thousands of pounds
of force.
The safest method of obstruction detection is the sensing edge that attaches
to and travels with the edge of the moving load. Other fixed, non-moving means
of detection such as photo-eye beams, ultrasonic detectors, infrared or motion
detectors all have dead zones and blind spots. Motor operator torque detectors
using speed, current, chain tension, etc. all depend on a smooth running load because
a torque dip follows a torque spike and during the dip, obstruction-sensing force
is huge. Force applied along a sensing edge is independent of motor load and there
are no dead zones. A sensing edge makes an electrical contact by touching an object
signaling the motor operator to immediately stop and then open. Using such devices
requires a new operator positional limit in addition to the standard "close limit"
and "open limit", called the "snow Limit". Historically named, because a buildup
of snow activated the sensing edge too early; before actually reaching the motor
operators close limit. In fact, even when there is no snow, it is impossible to
close an entryway so that it will seal tightly without first pressing its sensing
edge. Therefore, at or past the snow limit, the sensing edge signal no longer reverses
the motor operator, but just stops it.
The snow-limit distance, as stipulated in standards, is 2-inches before the fully
closed position. During the final 2-inches of travel, the sensing edge will just
stop the operator thereby trapping anything it stops on and pressing on it with
considerable force. Even so, the two-inch standard seems to be reasonable in that
even if a child were to press the close button and then lie down in the doorway
to see what develops he will project more than 2-inches. Any other living thing
less than 2-inches in height are not likely to be able to complain about the experience.
Nevertheless, if this snow limit were to drift to 4-inches a serious safety hazard
would exist. The operator could stop trapping a person under it with the full force
of both the door and the motor operator pushing on him. It is therefore important
that the snow limit never exceed 4-inches from the fully closed position.
Installers typically test the operation of each sensing edge by using
a tool called a "two by four" placed between the sensing edge and the fully closed
position. The motor operator optimally causes the sensing edge to stop on the 1½-inch
side and then in a second test, stop and open on the 3½-inch side. Passing
this test means that the motor operator's snow-limit engages 2½ inches from
the floor with a tolerance of (+/-) 1-inch to allow for drift or wear. Mechanically
the tolerance from the snow-limit switch to the close-limit switch is hard to adjust
and critical to safety. The threaded limit shafts length, typically 5-inches, proportions
to a 20-foot door/gate, or a ratio of 5:240 inches, such that 1-inch at the entryway
equals 0.020-inches on the threaded shaft. Therefore, the snow-limit switch lever
must be located 0.050-inches before the close-limit switch lever at a tolerance
of +/-0.020-inches. In practice this is hard to achieve and harder to maintain
over time as the various mechanical components wear.
Reversing the direction of a motor operator while, it is still rotating
places a strain on its bearings, windings and metal components that is hundreds
of times greater than its normal static load. Some single-phase motors will not
reverse direction at all unless they come to a complete stop and continue to run
in the original direction at full torque. Therefore, it is desirable to allow the
motor operator to come to a complete stop before reversing direction. A simple
timer set for one or two seconds whenever reversing direction can allow the motor
to coast to a stop before reversing. Unbalanced loads can cause longer coast to
stop times by back feeding from the output shaft through the gearbox to the motor.
In these instances manufacturers use electrically actuated brakes or special gearboxes
to prevent such excessive coasting.
Most industrial motor operators will drive their connected load at velocities
less than 6-inches per second. If the moving edge contacts an obstruction, it has
more than enough force to move it 6-inches in a second; for example, pressing the
top of a persons head even with their shoulder blades. It is critical that any
obstruction sensors such as sensing edges, photo-eyes, ultrasonic, or other devices
are working prior to using a motor operator. Many but not all obstruction sensors
are "monitored", "fail-safe", or "supervised" such that if they are not operating
correctly, or are disconnected they signal a continuous obstruction and the motor
operator will not run. Monitored sensors have two circuits, the monitoring circuit
and the sensing circuit. The sensing part is mounted somewhere in the entryway
to sense an obstruction while the monitoring part is mounted inside or on the motor
operator. If the monitoring part detects the loss of the sensing part it closes
a contact, signaling the motor operator to stop operating in one direction.
Industrial motor operators have a rotating output shaft that couples to
its load using roller chain and is relatively universal. It can drive its connected
load from the right hand side, left hand side, from the front, back, top or bottom
and thereby may require differing rotational direction with different installations.
For example, opening an entryway could require a clockwise shaft rotation with
the motor operator mounted inside the room and counterclockwise rotation if mounted
outside the room. Reversing the output shafts rotation involves reversing motor
wires and reversing the open-limit, close-limit, and snow-limit switches location
on the threaded shaft. If a motor operator manufacturer makes two models for the
different rotations, he still must deal with three-phase motors and power lines
connecting out of sequence. The installer knows he has the wrong power line sequence
or the wrong rotation if he presses the open pushbutton and the connected load closes.
It is critical to know that when the motor is driving the load open, the threaded
shaft nuts are traveling toward the open limit switch. Conversely, when closing,
the nuts must travel toward the close-limit and snow-limit switches. Incorrect
rotation has the entry opening when the threaded shaft nuts are traveling toward
the snow and close-limit switches. This is a serious safety hazard as the motor
operator will run past the incorrect limit and apply its full torque to the stalled
load or the structure holding it. Motor operators thereby should function such
that pressing either limit switch, or specifically the wrong limit switch, stops
its rotation. This solves one problem but creates another; it becomes possible
to have an entryway that opens when pressing the open button but inside the motor
operator, it is actually stopping at the close limit switch. The snow-limit function
is then missing from the closing cycle and has moved to the opening cycle. Thereby,
a closed entryway opens by pressing on the sensing edge or blocking a photo-eye,
and the entryway is no longer secure. The installer must insure that the threaded
shaft nut is traveling toward the correct limit switch.
The installer usually adjusts the limit switches or threaded shaft nuts while
the motor operator has power, and while standing on a 25-foot ladder. Seemingly,
no amount of coaxing will get them to stop doing this. During this adjustment,
the limit switch will make and brake numerous times until deemed, just right. It
is therefore safer if the limits electrically latch such that releasing the limit
switches lever does not cause the motor to run.
Connections from pushbuttons to the motor operator use long lengths of
low voltage, multi-conductor, unshielded thermostat wire. Nearly every motor operator
manufactured uses thermostat type 24-volt controls and wires. It is common that
a complete switch wire run totals 1,000-feet. Electronic motor operators do not
draw significant current through their switches and therefore do not have wire
length limitations but must deal with 1,000-feet of unshielded wire picking up
every electrical blip produced by an industrial environment.
It is common wiring practice to disconnect low voltage power from the operator
if the motor overheats or when using a manual pull chain. Most stop switches or
lock switches simply disconnect 24-volt control power to the operator. Thereby,
motorized operators must identify the loss of power as a stop switch signal.
This background description incorporates technical data from the author's knowledge,
Underwriters Laboratories specification UL-325, and DASMA, (Door & Access Systems
Manuf. Assoc., www.dasma.com) documents. It is a condensed representation of the
field of industrial motor operators, is comprised of well-known facts, and well-known
functions to those experienced in this subject matter.
DESCRIPTION OF PRIOR ART
Pertinent patent office art utilizing three button stations in any motor
operator or prior art on industrial types of motor operators seem to be lacking.
Thereby, mitigating this applications long and extensive Background Description.
Prior patent office art primarily addresses residential garage doors with single
pushbutton operation. Indicative art includes my U.S. Pat. No. 4,408,146, October-1983
and U.S. Pat. No. 4,369,399, Lee et al, January-1983 both utilizing single button
operation and flip-flop controlled hard wired logic circuitry. U.S. Pat. No. 5,218,282,
Duhame, June 1993 also utilizes single button operation but avoids hard wire logic
by using a microprocessor control.
Most industrial operators manufactured today use relay-logic with individual
connected wires. They typically miss many of the primary safety functions described
in the background of the invention but are popular due to their simplicity. Other
industrial operator manufacturers use microprocessors to master some of the complex
functions described in the background of the invention. Microprocessors have some
reliability disadvantages in a simple control system, most notably a high frequency
clock, and stored software programming requiring some kind of non-volatile memory.
Low voltage DC logic generally performs well in the presence of heat or moisture
and a typical example is 12-volt automobile engines that operate reliably with
open soaking wet connectors and wires. The exception is low voltages at high frequencies
wherein moisture conducts the oscillating signal over to adjacent lines causing
corrosion and wreaking all kinds of logic mayhem. A clock signal is susceptible
to having its transitions deformed by moisture, electrical noise and double or
missing clocks occur. Coating the circuitry removes the moisture but adds dielectric
capacitance to adjacent paths and spacing becomes important. Automobile designers
place microprocessors inside a watertight enclosure and that is part of its associated
overhead cost. These problems, common with microprocessors, are not a factor with
simple steady state hardwired logic.
Flip-flop logic relies upon the storage of one-bit of electronic memory
and a fast rising clock signal. The fast rising clock has the aforementioned moisture
and noise susceptibility. Losing one-bit of flip-flop storage during a power outage
can mean that the direction of travel is uncertain. Battery backup solves this
problem but adds significant cost and once the battery wears out, a dangerous situation
develops. Industrial motor operators command hundreds or even thousands of pounds
of force and uncertainty about their direction of movement is bad.
Microprocessors use software but also require substantial hardwired
logic to interconnect external support items such as power supplies, memory, data
busses, noise filters and power components such as relays. The hardwired logic
portion requires a printed circuit board its printed pattern establishing a secondary
type of programming, because different connections produce diverse logical results.
In contrast, simple wired logic uses various logic elements connecting with a printed
circuit pattern to produce a specific logical result, but does not require the
additional step of software programming. In a simple system, Microprocessors are
more expensive than individual logic elements but make up for this by requiring
less labor due to a lower number of components. However, the recent arrival of
automatic insertion equipment capable of placing microscopically small components
at a 300-per-minute rate makes such labor advantages moot. The objective of this
invention is to provide all the functions of an industrial operator without using
microprocessors or flip-flop logic thereby lowering overall costs and improving reliability.
BRIEF SUMMARY OF THE INVENTION
This invention discloses an electronic control system for an Industrial Motor
Operator that uses standard steady state logic to improve reliability in rough
service wet and dirty environments. It includes means of providing electronic snow
limit to close limit sensing removing the need for two switches and radically improving
its accuracy. A low voltage switch reverses the high voltage motor wires and at
the same time reverses the open limit, close limit, and snow limit sensors mechanical
positions. It discloses a system using lamps to indicate that the power wiring
is connecting to three-phase motors in the correct sequence or that single-phase
motors have their windings correctly phased.
It discloses a system allowing the close pushbutton to close the entryway even
when it is actively opening or partially open and still have open button priority
over the close button. It eliminates stuck auto, stuck radio control and stuck
close switch problems. The new stop function discloses latching a stop command
and gives it priority over all opening or closing commands. Thereby the Open Close
and Stop buttons always perform as stated and do not change their functions based
on some complicated control scheme.
Dozens of auxiliary functions are possible by using a parallel data-buss system.
The motor operator stops even if the wrong limit switch activates preventing over
traveling of the limit problems.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of the inventions control logic.
DETAILED DESCRIPTION OF THE INVENTION
The Open-Button gate
10, of FIG. 1, reacts to Open-Pushbutton
2
or any other open signal (logical OR) by driving resistor
11 to input
12
of the Open-Gate
30. The output of Open-Gate
30 connects to slide
switch
29, feeding back into the Open-Button gate
10 thereby latching
both gates. Once latched, both gates remain latched even after releasing Open-Pushbutton
2. Removing any other input signal from Open-Gate
30, such as, stop
signal
13, or limit switch signal
14, or the I-shot signal
15
will disable gate
30 and unlatch its output. Open-Gate
30 remains
off and disabled until the return of all its input signals (logical AND). Disconnecting
slide switch
29, removes the abovementioned feedback latching command such
that constant pressing of Open-Pushbutton
2 is required to maintain an output
signal from Open-Gate
30. A constant open command at
12 cannot produce
an output signal from Open-Gate
30 unless signals
13,
14,
and
15 are continuously present. In this manner, slide switch
29
is able to select between "constant" or "momentary" operation of the open function.
The Close-Button gate
26, of FIG. 1, reacts to Close-Pushbutton
7
or any other close input signal (logical OR) by driving resistor
27 to input
28 of the Close-Gate
32. The output of Close-Gate
32 connects
to slide switch
33, feeding back the signal into the Close-Button gate
26
thereby latching both gates. Once latched, both gates remain latched even after
releasing Close-Pushbutton
7. Removing any other input signal from Close-Gate
32, such as, stop signal
13, or limit switch signal
22, or
safety edge signal
35, or un-open signal
34, will disable Gate
32
and unlatch its output. Close-Gate
32 remains off and disabled until the
return of all its input signals (logical AND). Disconnecting slide switch
33,
removes the abovementioned feedback latching command such that constant pressing
of Close-Pushbutton
7 is required to maintain an output signal from Close-Gate
32. Furthermore, a constant close command at
28 cannot produce an
output signal from Close-Gate
32 unless signals
13,
22,
34,
and
35 are continuously present. In this manner, slide switch
33
is able to select between "constant" or "momentary" operation of the close function.
Inverter
31 disables Close-Gate
32 when the Open-Gate
30
output signal is present thereby preventing both opening and closing at the same
time. This is not an instantaneous occurrence as Open-Gate
30 signal is
there moments before Close-Gate
32 signal releases, such that for several
microseconds Open-Gate
30 and Close Gate
32 both have output signals.
The output delays
36 and
37 solve both this ripple effect problem
and an instant reversing problem. Normally
36 and
37 produce no discernable
delay, the Open-Gate
30 output passes instantly through delay
36
and Close-Gate
32 output passes instantly through delay
37. The Close-Gate
32 output signal enables a 1-2 second delay into
36 producing a close
to open signal delay and conversely, the Open-Gate
30 output signal enables
a 1-2 second delay into
37 producing a open to close signal delay. This
allows the motor to coast to a stop before reversing direction and prevents any
ripple problems in the logic circuitry but allows for instant action while no actual
reversing is occurring.
A signal from Delay
36 drives resistor
38 through reversing switch
40 energizing relays and lamps depending on the position of the reversing
switch. For example, in the position indicated it drives CW-Lamp
43, CW-Relay
44 and Com-Relay
45. Conversely, a signal from Delay
37 drives
resistor
42 through reversing switch
40 energizing relays and lamps
depending on the position of the reversing switch. For example, in the position
indicated it drives CCW-Lamp
47, CCW-Relay
46 and Com-Relay
45.
Relays
44 and
46 are reversing relays that cross connect the power
line voltage to the motor in order to drive it in different directions. Relay
45
is common to either direction of rotation and is handy for actuating electric brakes,
lamps, or any item that must operate in either direction. On three-phase motors,
relays
44 and
46 reverse two of the power line phases while relay
45 simply connects the third phase directly. On single-phase motors, relays
44 and
46 reverse the polarity of the start winding while relay
45
simply connects the motors run winding. In this manner one relay arrangement, handles
three-phase or single-phase motors.
The Snow limit switch and the close limit switch described in the background
statement are, per this invention, one actual switch for example switch
6
followed by a filter and a short interval electronic timer
20. There is
always some doubt over the accuracy of any timing means that measures a distance
because as the load varies the motor speed varies and therefore the distance changes.
In reality, once an AC motor reaches its full speed it synchronizes closely to
the power line frequency such that for short distances time is an extremely accurate
indication of position.
The difference between a fully loaded motor, drawing full load amperage, and
an unloaded motor is about 30-rpm, using 1800-rpm motors. Fully loaded the motor
spins at 1,750-rpm, while unloaded it spins at 1,780-rpm. Thereby, there is only
a 1.7% speed variation from full to no load (30-rpm/1800). If a snow limit switch
is set such that it activates 2-inches from the fully closed position and starts
a timer the deviation of the snow limit to close limit due to motor loading will
be, 2-inches multiplied by 1.7% or 0.034-inches in the entryway.
Since the threaded shaft inside the motor operator is 5-inches long and the
entryway is 20-feet long, a ratio of 5:240-inches exists. The 0.034-inch accuracy
at the entryway divided by 240 then equates to a threaded shaft accuracy of +/-0.00015-inches.
Therefore, the timer method of determining snow limit to close limit position is
several orders of magnitude above that obtainable by a field mechanic.
This methodology only works well over short distances and only after the motor
reaches synchronous speed. For example, a 1.7% variation due to motor load on the
entire 20-foot entryway yields 4-inch accuracy (1.7%×240"). The difference
between an entryway being closed, sealed, and secure verses being open too much
is just a ¼-inch gap. The 4-inch variation is 16-times this and is the reason
motor operators avoid using time as a position indicator. Reversing the calculation
to determine the maximum distance for ¼-inch accuracy, yields 60-inches (¼×240")
and therefore the 2-inch snow to close limit distance is well below this maximum.
Prior to this disclosure, the closing limit of travel produced two signals,
close and snow signals, therefore were substantively different from the open limit.
Eliminating the mechanical close-limit and replacing it with an electronic timer
makes the open limit of travel and close limit of travel essentially appositionally
interchangeable. Switch
5, of FIG. 1, is 2PDT connecting with its outside
poles cross wired such that it can electrically exchange position detectors
4
and
6. A limit becomes the open-limit whenever it connects to the resistor
16 and becomes the snow/close-limit if it connects to the Snow-To-Close-Timer
20. The benefit of Timer
20 is that the limits need not move mechanically
to reverse them, and the benefit of switch
5 is that the wires need not move.
The limits
4 and
6 are of the normally closed type such that at
either limit of travel a signal is lost. The loss of an Open-Limit signal travels
through a noise filter removing the drive from resistor
16, input
14
and disabling the Open-Gate
30 thereby stopping the open cycle. Loss of
the Close-Limit signal travels through a noise filter to Delay
20 and after
a short delay removes drive voltage from resistor
21, input
22 and
disables Close-Gate
32. This stops the closing cycle. A broken wire to either
limit also causes a loss of signal and the operator will not move in that direction.
Once the limit signal is lost, Open-Gate
30 or Close-Gate
32 de-latches
and restoration of the signal cannot move the operator until a pushbutton command
occurs. In this manner, the adjustment of the limits is safer during installation.
Switch
5 and switch
40 are actually one 4PDT switch in this
embodiment that reverses both the motors direction of rotation and the limit switches
at the same time. This effectively allows the motor operator to open with either
clockwise or counter clockwise shaft rotation. Each switch cross connects such
that in one position CW limit switch
4 connects through switch
5
a filter and resistor
16 to open limit input
14. In its other position
CW limit switch
4 connects through switch
5 a filter and snow to
close limit delay and resistor
21 to close limit input
22. In this
manner, the installer only flips a switch to reverse the operators' rotational
direction and need not reverse the motors wires and limit switches positions depending
on his mounting location.
Follow the signal from CW-Limit
4 through switch
5, in its drawn
position, to resistor
16, then input
14 of Open-Gate
30, Delay
36, resistor
38, and through switch
40, in its drawn position,
to CW-Lamp
43. CW-Limit
4 controls CW-Lamp
43 and placing
the CW-Lamp mechanically next to the CW-Limit indicates it is the active limit.
In this switch position, the
Open-Button rotates the motor
operator CW (clockwise).
When switch
5 and
40 slide together to the left the CW-Limit
4
connects now to
23, through Delay
20, resistor
21, Close-Gate
32, Delay
37, resistor
42, switch
40, and finally once
again back to CW-Lamp
23. The CW-Limit
4 and CW-Lamp
43 remain,
linked together. In this switch position, now the
Close-Button
rotates the motor CW (clockwise).
Mechanically placing CW-Lamp
43 next to CW-Limit
4 and
CCW-Lamp
47 next to CCW-Limit
6 informs the installer which specific
limit is active. If the electric motor is driving the limit indicator, for example
moving threaded nuts towards the illuminated limit-switch, then the motors power
line wires have the correct phase. Conversely, if it drives the threaded nuts towards
the unlit limit-switch, the motors power line wires need reversing. In this manner,
the system aids in the correct wiring of the operator.
Pressing the close-switch
7 sends a signal through a filter to an
input of the Close-Button-Gate
26 causing a signal on its output. This output
signal drives resistor
27 to the Close-Gate input at
28 to start
the closing cycle but also to
17 a one shot that disables the Open-Gate
30 at its input
15. A fully open entryway disables the Open-Gate
30 in advance due to its open-limit input
14 such that the close-one-shot
circuit has no visible effect once fully open. On an actively opening entryway,
the close-one-shot pulse from
17 disables the Open-Gate
30 allowing
inverter
31 to enable the Close-Gate
32 and the closing cycle begins.
Thereby, pressing the close button during the opening cycle stops the operator
for 1-2 seconds and begins a closing cycle. The close-one-shot duration is less
than 0.1-second such that pressing both open and close buttons always has the open
button winning because the close signal disappears rapidly. Also holding the close
button or a shorted close button cannot stop the open cycle and allows the freeing
of an obstruction.
Pressing the sensing edge switch
8 sends a signal through a filter
to disable an input
35 of the Close-Gate
32, thus immediately stopping
the closing cycle. The sensing edge also connects to an Edge-Opens gate
25
(logical AND) that enables/disables based on the snow-limit at its input pin
23.
The Edge-Opens
25 output pin
24 connects to an Open-Button
10
input such that it signals an open command when not at the snow-limit and disables
the open command when at the snow-limit. Thus, the sensing edge always stops the
closing cycle on sensing an obstruction but reverses the operator to the opening
cycle before reaching the snow-limit. Continuous sensing edge signals permanently
disable the close cycle and the operator can then only open. A fully closed entryway
will usually press on the sensing edge and a continuous signal generates, but the
operator will still open.
Pressing the Auto-Switch
1 sends a signal through a filter to enable
an auto-one-shot circuit
9 that produces a very short 0.1-second pulse signal
with each press of the switch. The auto-one-shot signal enables the Open-Button
gate
10 and an Auto-Fully-Open gate
19. The Auto-Fully-Open gate
19 (logical AND) enables only at the fully open position as its input
18
connects to the open limit signal. Thus, the Auto-Switch always tries to enable
the Open-Button gate
10 but enables the Close-Button gate
26 only
at the fully open position. The brief one-shot pulse insures that the auto signal
is gone far before the motor operator can rotate off the open limit thereby changing
signal
18. It also prevents the auto signal or a stuck auto signal from
interfering with the three-button station.
The stop function generates whenever pressing the stop pushbutton
53,
or if there is low line voltage
50, or upon reaching either limit of travel
54. These various stop signals connect to the All-Stop gate
57 (logical
OR) that in turn un-drives resistor
59 to pin
13 disabling both the
Open-Gate
30 and the Close Gate
32. The signal from the All-Stop
gate
57 is in reality a go, or all is well signal, while removal or lack
of the signal is a stop command. This go signal is initially absent upon the application
of power until the supply achieves enough voltage to operate all the various logic
gates correctly.
If a stop command occurs during an open or a close command the stop system must
latch until resolution of the conflict or the removal of the open or close commands.
The Stop-Button gate
58 (logical AND) performs this function by feeding
back its signal to the All-Stop gate
57 thereby latching it when it receives
both the stop and either button signal. Such latching continues until the removal
of the either button signal. Either-Button gate
56, (logical OR) interprets
pressing of the open or the close pushbutton. Its input
28 connects to the
Close-Button
26 output, and input
12 connects to the Open-Button
gate
10 output. It then generates a signal indicative that either button
is active.
It is common wiring practice to disconnect low voltage power from the circuitry
if the motor overheats or when a pull chain is in use and many stop switches or
lock switches simply disconnect power. The Low-Volts comparator
50 compares
a reference voltage on pin
51 to the low voltage supply on pin
52
thereby removing the go signal at its output until the power supply on
52
rises above the reference voltage on pin
51. A transformer external to the
circuitry supplies the low voltage and its output is radiometric to the power line
voltage. Thereby, Low-Volts comparator
50 also detects low primary side
power line voltages as well as low secondary side voltages.
Either-Limit gate
54 and One-Shot
55 stops the motor operator
when the wrong limit activates. Gate
54 produces an output if the open limit
at
14 or the close limit at
28 activates (logical OR). Its output
triggers one-shot
55 which produces a momentary pulse at its output. The
one-shot pulse connects to an input of All-Stop gate
57 and stops the motor
operator until the release of all pushbuttons due to the Stop-Button gate
58.
It can be seen that if the one-shot were not present that the activation of either
limit could cause the operator to stop permanently and never move again.
A data-Buss connector allows bi-directional remote access to the logic circuitry
and all of its functions. The input/output pin
12 signals and accepts an
open-button command and pin
14 signals and accepts an open-limit. The input/output
pin
22 signals or accepts a close-limit command and pin
28 a close-button
signal. The input/output pin
43 signals an opening command while accepting
a signal to force the operator to open regardless of limits or stop signals. The
input/output pin
45 signals a closing command while accepting a signal to
force the operator to close regardless of limits or stop signals. The input/output
pin
3 signals and accepts an Auto-button command and pin
35 signals
and accepts a sensing edge signal. The input/output pin
8 signals and accepts
a stop command. With these pins, external circuitry can analyze the functions and
perform test procedures. They also provide functional inputs and outputs for auxiliary
functions such as a Timer-To-Close function or automation controls.
Accordingly, there has been disclosed an improved industrial motor operator.
While disclosing typical embodiments of this invention, various modifications to
the disclosed embodiments are possible, and it is intended that this invention
be limited only by the scope of the appended claims.
*
