Note: Descriptions are shown in the official language in which they were submitted.
~Z~326
This invention relates to conveyor systems and
particularly conveyor systems wherein a carrier is moved
by a power device along a track to a work station.
Background and Summary
of the Invention
In certain types of conveyor systems, it is customary
to provide a motor power unit that is movable along a track
for moving load carriers along the track. In a typical arran~e--
ment, the track is mounted overhead and the carrier supports
loads and is moved by a tractor. With the advent of automatic
devices and machines including robotic type machines, it has
become essential to be able to stop the load carrier in a precise
position or location at a work station for the performance of
work on the load. Heretofore controls for the motor power units
have been unable to provide accurate positioning in a precise
manner, for example, on the oraer of plus or minus one milli-
meter.
Accordingly, among the objectives of the present
invention are to provide a conveyor system which will effectively
move a load carrier into a station and position the load carrier
in a precise position at the work station; which system is rel-
atively simple and economical to rnanufacture, install and
maintain.
In accordance with the invention, an extendible-
retractible coupling is provided between the motor power unit
and the carrier such that when the carrier is stopped at a
station, the coupling can be actuated to precisely locate
the carrier at the station.
'121~326
Description of the Drawings
FIG. 1 is a fragmentary side elevational view of a
conveyor system embodying the invention.
FIGo 2 is a diagram showing the manner in which the
carrier is positioned.
FIG. 3 is a diagram showing the manner in which the
extendible-retractible coupline functions.
FIG. 4 is an electrical schematic view o~ the c~r
circuit.
12~326
Description
Referring to FIG. 1, the invention is shown as
applied to a monorail tractor conveyor which comprises a
rnonorail 10 defining a track, a carrier 11 having wheels 12
engaging the track 10 and a motor power unit in the form of
a tractor 13 that includes an electrie motor-brake that rotates
a drive wheel 14 whieh frietionally engages the underside of
the traek 10 and move the power unit along the track 10. 'rhe
earrier 11 is adapted to earry a load and also carries a power
unit 15 having controls for sensors as presently described.
Sueh an arrangement is known in the art.
In accordance with the invention, a retractible-
extendible coupling 16 is provided on the carrier 11 between
the motor power unit 13 and carrier 11 and comprises an electrie
motor 17 that reeiprocates a shaft 18 through a gear box 19.
The end of the shaft 18 is pivotally connected to the motor
power unit 13.
The carrier 11 supports a photocell #1 and photocell
#2 which projeet beams of radiant energy sueh as visible light
horizontally toward reflectors positioned alongside the path of
the carrier at a station.
In normal station-to-station transport the coupling
is fully retracted. As the traetor 13 and earrier 11 approach
a work station, a signal from photocell #l causes the tractor
13 to reduce its speed from fast to slow and to stop.
Referring to FIG. 2, the signal to stop always places
the centre position of the stop station between the centre posi-
3.
121832t~
tion of the carrier and the tractor drive in the area represented
by band A. When the tractor has completely stopped a signal is
given to extend shaft 18 of the coupling 16 pushing the carrier
towards its final required stopping position. As the centre line
of the load reaches the required centre line of the stop position
of the station, a signal from highly sensitive photocell #2
causes the coupling 16 to cease motion. This distance of possible
movement of the carrier is represented by the band B. The centre
line of the load is now located accurately within plus/minus
1 mm. of the predestinated point along the track. On start-up
to exit the station, the coupling 16 is retracted to its minimum
length in readiness in the next station.
The length of stroke to the coupling is related to the
required stopping distance after receipt of the final signal to
stop. The speed of the stroke of the coupler has a relationship
to the accuracy of final positioning. However, with additional
contro]s, the speed of the coupler can be changed for the last
several millimeters of travel by inserting additional detectors
and controls.
Referring to FIG. 4, the schematic of the control
circuit, as the tractor 13 with the carrier 11 enters the work
station to which it has been programmed to stop, photocell ~PC-l)
is energized causing a time relay (TD-l) to be energized which
causes the tractor motor to stop. Due to the coasting of the
tractor, time delay TD-l is sealed in by its own contact since
the tractor will move beyone the reflective signal causin~
photocell PC-l to be energized. Time relay TD-l provides a
~Z~3326
time delay to allow for stopping and/or reduction in load sway.
After the time delay, the coupling 16 is energized (MFL)
causing the load carrier to be moved in a direction toward the
center line of station. At the center line of the station,
second photocell (PC-2) is energized causing the load carrier
to accuately stop (PC-2 energizes CR-2). Once the tractor is
ready to depart the station, a relay (CR) causes CR-2 to drop
out and other controls will cause the tractor motor to be
energized. Once the tractor motor is energized the coupling 16
is reversed, causing the load carrier to move to a home position
in readiness for next station entry. Should a malfunction
occur and the second photocell (PC-2) is not energized, the
coupling 16 extenas to its extreme position, tripping LS-2.
This stops the forward motion of the coupling 16 as well as
energizes a relay (CR-l) which will prevent the tractor from
moving and also sound an alarm.
As shown in FIG. 3, limit switches LS-l and LS-2 are
associated with the coupling 16 to limit the extent of movement
of the shaft 18.
Although the invention has been described as preferably
being applied to an overhead tractor ana carrier system, it
can also be applied to other motor power unit and carrier systems
such as driverless vehicles and carriers.
It can thus be seen that there has been provided a
conveyor system wherein a load carrier driven by a motor power
unit can be positioned at a station in a precise position.
