U.S. patent number 3,677,421 [Application Number 04/851,666] was granted by the patent office on 1972-07-18 for storage courier boundary control system.
This patent grant is currently assigned to Cutler-Hammer, Inc.. Invention is credited to Paul M. Kintner.
United States Patent |
3,677,421 |
Kintner |
July 18, 1972 |
STORAGE COURIER BOUNDARY CONTROL SYSTEM
Abstract
In a warehouse having horizontal rows and vertical columns of
bins in which packages are stored by a positive address code
controlled courier (stacker crane), different size bins vary in
height and are divided into zones of small, medium and large size
bins. This system is arranged to check the size of the package.
Subtraction of the read code from zone boundary codes provides
information indicative of the zone of arrival. And comparison of
the sizing information with the zone information will either allow
the action to proceed or will return the package. Shelf error is
handled by providing a code for each hoist address that defines the
validity of the address for the several zones of different size
bins. The integrated circuits send the package back to the pickup
station if the validity code indicates that there is no shelf at
the hoist address. In the event of a power failure, upon
restoration, the integrated circuits automatically program for a
large package sizing indication.
Inventors: |
Kintner; Paul M. (Bayside,
WI) |
Assignee: |
Cutler-Hammer, Inc. (Milwaukee,
WI)
|
Family
ID: |
25311344 |
Appl.
No.: |
04/851,666 |
Filed: |
August 20, 1969 |
Current U.S.
Class: |
414/275 |
Current CPC
Class: |
B65G
1/0421 (20130101) |
Current International
Class: |
B65G
1/04 (20060101); B65g 001/06 () |
Field of
Search: |
;214/16.4,16.42 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
1,163,584 |
|
Feb 1969 |
|
DT |
|
158,669 |
|
Apr 1964 |
|
SU |
|
Primary Examiner: Forlenza; Gerald M.
Assistant Examiner: Johnson; Raymond B.
Claims
I claim:
1. In a courier control system for an automatic warehouse having a
rack providing a multiplicity of storage bins arranged in a
plurality of zones with each zone having the same size bins and the
bins in adjacent zones being of different size, and adjacent zones
having the bin shelves at the same or different levels, and an
article handling courier provided with an article supporting
extendable table, and a pickup station from which the courier picks
up an article by extending and lifting and retracting its table,
digital codes mounted along the horizontal and vertical paths of
movement and digital address code controlled means including means
for connecting power thereto and being operable in accordance with
pickup and store and retrieve operating programs for moving the
courier to the pickup station or in front of a selected bin in one
of the zones and for extending the table to reach into the bin and
lower and retract the table to store an article therein or to reach
into the bin and lift and retract the table to retrieve an article
therefrom, the digital address code controlled means including
means providing input digital codes indicative of the coordinate
horizontal and vertical positions of desired bins, horizontal and
vertical reader means for reading actual position digital codes
along the coordinate paths of movement of the courier, and means
for comparing the input codes with the actual position codes to
control movement of the courier to its selected final horizontal
and vertical destination, the improvement comprising:
bin selection error program means for preventing initiation of the
table extension operation in the event of address error in bringing
the courier to the selected bin comprising:
additional digital address comparing means having registered
therein a digital boundary code indicative of the boundary between
adjacent zones;
said additional digital address comparing means comprising means
for comparing at least one of the actual position digital code that
is read when the courier reaches its destination with said digital
boundary code to provide a first zone signal if the actual position
digital code is smaller than the boundary code indicating that the
courier has arrived in a first zone and to provide a second zone
signal if the actual position digital code is larger than the
boundary code indicating that the courier has arrived in the next
zone;
means for sizing the article and for registering a classification
signal indicative of its size category;
means for comparing the zone signal with said size classification
signal to provide an error signal if the article is too large for
the bin in the arrived-at zone;
and means operable by said error signal for returning the courier
to its pickup station.
2. The invention defined in claim 1, wherein said digital boundary
code comprises:
a binary code corresponding to the code of the first row of bins at
the leading edge of the zone immediately following the boundary
between adjacent zones;
and said actual position digital codes comprise binary codes
whereby a subtraction produces a carry for said first zone signal
corresponding to a first binary symbol value of voltage when said
actual position binary code is smaller than said boundary binary
code, and said subtraction produces a carry for said second zone
signal corresponding to the other binary symbol value of voltage
when said actual position binary code is equal to or larger than
said boundary binary code.
3. The invention defined in claim 1, wherein said bin selection
error program means comprises:
means for providing a shelf validity signal when the courier
arrives at the selected bin indicative of whether there is a bin
shelf for the size of bin required by the size of the article
destined therefor;
and means responsive to such shelf validity signal indicating the
absence of a bin shelf at the arrived-at address for preventing
extension of the table.
4. The invention defined in claim 3, wherein said means for
providing a shelf validity signal comprises:
a shelf validity code added to the vertical movement control
code;
and means for reading said shelf validity code at the same time as
the vertical code is read when the article arrives at its
destination.
5. The invention defined in claim 2, wherein said sizing means
comprises:
means for scanning the article as the extendable table is being
retracted to detect the largest dimension thereof;
a size indicating flip-flop circuit for registering sizing
information;
and means responsive to said scanning means for setting said
flip-flop circuit.
6. The invention defined in claim 5, together with means for
resetting said flip-flop circuit on a predetermined step in the
operation program.
7. The invention defined in claim 5, together with:
means responsive to reconnection of power to the system following
interruption thereof when there is an article on the table for
forcing said size indicating flip-flop circuit to large article
indication to prevent attempted insertion of an article into a bin
too small to receive it regardless of its original pre-programmed
destined bin or zone.
8. The invention defined in claim 6, together with:
permissive means for allowing setting of said size indicating
flip-flop circuit during the program step that retraction of the
table occurs and allowing resetting thereof during the program step
that extension of the table occurs.
9. The invention defined in claim 1, wherein said means for
comparing said actual position digital code with said zone boundary
digital code comprises:
integrated circuit adder means and means for applying said actual
position digital code thereto in inverted form so that it will
perform a subtraction to indicate on which side of said boundary
the article has arrived.
10. The invention defined in claim 9, wherein said digital boundary
comprises code comparing means:
an integrated circuit board bucket into which said integrated
circuit adder means is inserted to connect it to the system;
and jumper wire means connecting voltage to certain of the bucket
terminals to wire in said digital boundary code.
11. The invention defined in claim 1, wherein said means for
comparing the zone signal with said size classification signals
comprises:
integrated circuit AND/OR inversion logic circuit means for
providing said error signal to shift the program from store mode to
pickup mode thereby to return the article back to the pickup
station.
Description
BACKGROUND OF THE INVENTION
Automatic stacker crane control systems have been known heretofore.
Such systems have used either a counting system or a positive
address, binary code system for controlling movements of and
stopping of the article carrier in front of the bin. In a counting
system, numbers proportional to the distances to be traveled are
put into the system and each number or count is counted out as the
crane moves from column to column or from bin to bin and stops at a
zero count. In the positive address, binary code system, as for
example, that disclosed in R. K. Cotton et al. copending
application Ser. No. 498,326, filed Oct. 20, 1965, now U.S. Pat.
No. 3,504,245, dated Mar. 31, 1970, a horizontal-vertical code
representing the destination bin is put into the system and a
magnetic code is read and subtracted therefrom at each column and
bin to obtain difference codes indicative of the remaining
distances and polarity codes indicative of the directions of
travel-forward, reverse, up or down. Neither of these systems
provides for variable bin size self error detection or automatic
programming for a large bin following power failure, nor does the
positive address system take into account any error that might
occur in sending an article to a wrong size bin.
SUMMARY OF THE INVENTION
This invention relates to improvements over prior automatic stacker
crane positive address control systems whereby provision is made
for a plurality of different size bins to accommodate different
sizes of articles.
An object of the invention is to provide a courier control system
with improved means for sizing an article and for activating error
detection and control apparatus if an article is sent to a wrong
size bin.
A more specific object of the invention is to provide positive
address courier control system with improved means for storing
package sizing data and for operating error control apparatus when
a package is sent to a too small bin.
Another specific object of the invention is to provide a stacker
crane control system with error control apparatus that programs the
crane for return to the point of origin in response to detection of
bin size or wrong shelf error.
Another specific object of the invention is to provide such system
with improved means for sizing a package during retraction of the
article supporting table and for storing the sizing data in
integrated circuit means for later use when the package arrives in
front of the bin.
Another object of the invention is to provide a courier control
system with improved means for sizing an article and for activating
error detection and control apparatus if the courier is sent to the
wrong shelf in a zone of given bin size.
A more specific object of the invention is to provide a stacker
crane control system with zones of variable size bins and a code
for each hoist address that defines the validity of the address for
each zone.
Another object of the invention is to provide such system with
improved means for resetting the package sizing data storing means
prior to the program step during which retraction of the table
takes place.
Another object of the invention is to provide such system with
improved means effective upon power restoration following power
failure when an article is on the table for automatically
programming the sizing data storing integrated circuits to large
package indication to prevent any erroneous attempt to put a
package already on the table into a bin too small for it.
Other objects and advantages of the invention will hereinafter
appear.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a rack of bins and a stacker crane
(courier) mounted for movement past the front of the the bins for
storing articles therein;
FIG. 2 is a front elevational view of storage bins arranged in
three zones of small, medium and large size bins, respectively, and
indicating at the left by short horizontal lines the required hoist
code addresses and showing at the right horizontal alignment
therewith the shelf validity codes;
FIG. 3 is a schematic side view of the article supporting table, an
irregular shaped article thereon and the article sizing
photocells;
FIGS. 4a-b show a flow diagram depicting the operating modes and
program steps for each such operating mode of the courier control
system; and
FIGS. 5a-j show an integrated circuit logic system for controlling
package sizing and variable bin size and shelf error detection and
control of the courier.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1, there is shown a rack structure including a
plurality of bins in which articles such as pallet supported boxes
or packages may be stored. This rack structure is made from steel
members such as angle members, channel members and the like, and
includes horizontal members 2, vertical members 4 and lateral
support members 6. These support members may have flanges
projecting into the bin from opposite sides thereof in known manner
onto which a load may be deposited after it has been extended
between the horizontal and vertical members.
While only a right rack is shown, it will be apparent that there is
a similar left rack on the other side of the aisle in which the
courier travels.
The courier shown in FIG. 1 comprises a frame 8 (or mast) that runs
on horizontal tracks 10 along the aisle, driven by an electric
motor, and guided by rails 11. This horizontal movement is
controlled by a code reader mounted on the top or bottom of the
frame. This code reader reads a series of sets of horizontal code
bars 12, there being one set of magnetic code bars for each
vertical column of bins. While the code bars 12 are shown at the
top, they could as well be at the bottom near the floor of the
warehouse.
This courier also comprises a hoist 14 mounted on the frame for
vertical movement. The hoist is driven by an electric motor up and
down along the frame. Vertical code bars 16 are mounted along the
frame. These vertical code bars are magnetic code bars that are
arranged to be read by a code reader to control vertical movement
of the hoist to the selected bin in a selected column.
A control cabinet 18 is also mounted on the frame and houses
electronic controls and supports a control panel 18a whereby the
input codes may be put into the system when the courier is at a
pickup station at an end of the aisle.
The hoist 14 comprises a table 20 that supports a load or package
22 and can be driven in opposite directions to reach into the right
or left bins on opposite sides of the aisle. This table is driven
by an electric motor from either of two vertical positions at each
bin. When it is extended from a lower position it will be raised
within the bin to pick up the load and then retracted to retrieve
the load as indicated by program steps 3-6 of the retrieve mode in
FIG. 4b. When it is extended from the upper position, it will be
lowered within the bin to deposit the load and then retracted to
store the load in the bin as indicated by program steps 3-6 of the
store mode in FIG. 4a. A similar retrieve operation is performed at
the pickup station as indicated by program steps 3-6 of the pickup
mode in FIG. 4a. A similar store operation is performed at the
delivery station as indicated by program steps 3-6 of the deliver
mode in FIG. 4b.
The integrated circuit logic system shown in FIGS. 5a-j will be
primarily concerned with sizing of the packages and detection of
bin size and shelf errors and return of the courier to the pickup
station when such error is detected.
The zones of variable bin sizes, their boundary codes and shelf
validity codes with which the logic circuits operate are shown in
FIG. 2. As shown in FIG. 2, the bins are arranged in zones of
small, medium and large bins. For exemplary purposes, the small bin
zone extends from zero through the horizontal binary code
equivalent to decimal number 30. The medium bin zone extends from
horizontal binary code 31 through 126. And the large bin zone
extends from horizontal binary code 127 through 255.
The boundaries between the zones are indicated in FIG. 2 as
boundary A and boundary B. The code of boundary A is 31 since any
horizontal code less than this is in the small bin zone and any
code equal to or larger than this is in the medium or large zones.
The code of boundary B is 127 since any code less than this is in
the small or medium bin zones and any code equal to or larger than
this is in the large bin zone.
These boundary codes provide a simple and convenient way of
determining what zone the courier arrives at. These boundary codes
are wired into adders A and B shown in FIG. 5d. By subtracting (by
inversion and adding) the "read" code at the destination bin from
the boundary codes, the "carry" accompanying the difference codes
indicates the zone as hereinafter more fully described.
FIG. 2 also shows at the right the shelf validity codes hereinafter
more fully described. Briefly, a "1" bit in the left or S bit
position indicates that this hoist address is valid for the small
bin zone. A "1" bit in the middle or M bit position indicates that
this hoist address is valid for the medium bin zone. And a "1" bit
in the right or L bit position indicates that this hoist address is
valid for the large bin zone. A "0" bit indicates lack of validity.
This shelf validity code is read by the magnetic code reader along
with the hoist code and operates the error control integrated
circuits as hereinafter described.
FIG. 3 shows the means provided for sizing the package while the
table is being retracted at the pickup station and at the bin when
a load is being retrieved. As shown therein, a package PK rests on
table 20. Scanning means is provided for detecting a large load
when the table is retracted. This means comprises a left large load
photocell LLP and a right large load photocell RLP, one at each
side of the table so that a large load even if it is irregular in
shape will interrupt the light beam thereto. Photocell LLP will
function when a large load is retracted from the left bin or pickup
station and photocell RLP will function when a large load is
retracted from the right bin or pickup station.
Similar scanning means is provided for detecting a medium load when
the table is retracted. This means comprises a left medium load
photocell LMP mounted at the left side of the table below photocell
LLP and a right medium load photocell RMP mounted at the right side
of the table below photocell RLP for detecting a medium size load
or package PK that may be irregular in shape as shown by the broken
line in FIG. 3.
Light beams from suitable lamps (not shown) impinge on these
photocells and interruption of one of these beams by a load causes
a signal to be provided as hereinafter described in connection with
FIGS. 5b-c.
No interruption of a light beam is indicative of a small load.
The overall system operation or program is shown in the flow
diagram in FIGS. 4a and 4b. The rectangles represent program steps
and are arranged in four vertical columns according to the four
modes of operation. These modes are the pickup mode M-O, the store
mode M-1, the retrieve mode M-2, and the delivery mode M-3. These
modes are selected by setting M program flip-flops into different
operating states in a manner shown in the following mode program
table to provide the mode signals hereinafter described.
Each mode has a plurality of program steps. The numbers in the
upper left corner of the rectangles in FIGS. 4a-b indicate the
program steps. These steps are selected by setting flip-flops into
different operating states, that is, P and Q program flip-flops, as
hereinafter more fully described. To this end, two P program
flip-flops and two Q program flip-flops, each having two states,
will give 16 steps in accordance with 16 possible combinations of
the flip-flop states as shown in the following step program table.
All of these steps are not used in each mode as will be apparent in
FIG. 4a-b. The legends within the rectangles describe generally the
functions performed at the respective steps and these will be
referred to later on in connection with the specific operations
described hereinafter.
VARIABLE BIN SIZE
The normal warehouse arrangement is for all the bins to have the
same size. Sometimes, however, the material being stored can be
classified into general groups of different size packages and it is
then advantageous to have different size bins, small bins for small
packages, medium size bins for medium packages and large bins for
large packages. This will enable use of the available space most
efficiently.
There are a number of ways of doing this, one of which is to divide
the warehouse into three zones, characterized as small, medium and
large zones. FIG. 2 shows how this is done. While the variation in
bin size is in the vertical direction, and the horizontal
dimensions or widths are the same for all bins, other variations
could readily be used. The zones are arranged in order as shown in
FIG. 2 with the small zone at the left, the medium zone at the
middle and the large zone at the right. The small zone corresponds
to the small numbered travel addresses with increasing travel
address proceeding to the right through the medium and large zones
in the forward direction of horizontal travel.
The main effect of variable bin size as shown in FIG. is to
increase the number of possible hoist or vertical movement stopping
positions. For example, there would be only eight hoist positions
if the warehouse consisted of only small bins. However, the
variable bin arrangement requires establishment of 16 stopping
positions with the arrangement shown in FIG. 2 where the medium and
large bin heights are not multiples of small bin heights.
The integrated circuit logic system for variable bin size error
control is shown in FIG. 5d whereas FIGS. 5a-c and 5e-j show
portions thereof to depict the various operations thereof generally
entitled as follows.
Fig. 5a --Sizing small package.
Fig. 5b --Sizing medium package.
Fig. 5c --Sizing large package.
Fig. 5d --Bin selection error-store medium package in small
bin.
Fig. 5e --Bin selection error-store large package in not large
bin.
Fig. 5f --Bin selection error-small zone and not small bin
shelf.
Fig. 5g --Bin selection error-medium zone and not medium bin
shelf.
Fig. 5h --Bin selection error-large zone and not large bin
shelf.
Fig. 5i --Reset package sizing flip-flops.
Fig. 5j --Force package sizing flip-flops to large indication in
response to power-on.
THE AND/OR LOGIC SYMBOLS
The logic operations generated by the circuits, or more precisely,
the logic operations that the circuits are being asked to perform,
are shown in FIGS. 5a-j by shapes. The symbols prefixed AND and OR
therein show the two shapes that correspond to the inverting AND
and OR (NAND and NOR) logic operations, respectively. The symbol
prefixed INV performs an inversion or NOT logic operation. These
are the shapes that are in prevalent use for switching circuits
based on integrated circuits.
The next task of the symbol is to show what signal value, or signal
values, are significant. The symbols in FIGS. 5a-j show this also.
A "high" value is significant if there is no circle (small circle
at the inputs or outputs) and a "low" value is significant if there
is a circle. The high value of signal is a positive voltage and the
low value of signal is at or near ground potential.
The symbols in FIGS. 5a-j show what to look for. If the circuit is
supposed to behave as an AND circuit, one looks for high on all
inputs and low on the output. If the circuit is supposed to behave
as an OR circuit, one looks for low on one or more inputs and high
on the output.
If the proper signals are in place for a given operation, that
operation is activated. Actually this can be given in terms of only
the output. The circuit is an activated AND when the output is low.
It is an activated OR when the output is high. It is therefore
evident that if the circuit is an activated AND, it is an
inactivated OR and vice versa.
The logic diagrams may be understood by tracing down through the
active portions thereof. For this purpose, the active parts are
shown in FIGS. 5a- j as follows. An active line that has a high
signal is shown as a heavy dark line superimposed on the usual
interconnecting line. An active line that has a low signal is shown
as a heavy dashed line superimposed on the connecting line. The
lines that are not active are assumed to be inactive.
If one of the inputs to the logic circuit is allowed to float or is
connected to a plus five volt supply, the circuit becomes an
inverter as far as the output is concerned. That is, the output
signal value is the opposite of the input signal value. The symbol
for the inverter is prefixed by INV. The significance circles are
customarily placed on the inverter symbol in order to match the
circles of an element connected to the inverter as shown in FIGS.
5a- j.
BIN SELECTION ERROR PROGRAM
One of the options that is available in the courier control system
is rack adjustability whereby the warehouse can be divided into
three zones where the bin heights vary as shown in FIG. 2.
This rack adjustability increases the possibilities of errors and
these must be prevented. One of these errors is attempting to store
a package in a zone where the bins are too small for it. For
example, a large package cannot be stored in either the medium or
small bin zones. A medium size package cannot be stored in the
small bin zone. Another error is directing the courier to the wrong
zone (in the horizontal direction) for a given shelf position
(vertical direction). This is a shelf selection error.
All of these error prevention controls are combined into one error
program, the bin selection error program. Bin selection errors can
occur only in the Store Mode or in the Retrieve Mode where the
courier is operating in the rack structure. The program exits
directly from these modes to the Pickup Mode that brings the
courier directly back to the home station as shown in the flow
diagram in FIGS. 4a-b.
The integrated circuit shown in FIG. 5d is mounted on a single
board. This is an option board that may be plugged into its slot
when it is desired to have bins of different sizes and to control
the storage of proper size articles therein. The receptacle wiring
is in place whether this option is used or not. If this option
board is removed, the terminal to which error output terminal 36
normally connects will be floating voltagewise which is the same as
a high signal indicative of no bin selection error.
The main function of the integrated circuit on this board is to
detect bin select errors. For example, the bin to which a package
is set must be of a size, small, medium or large, capable of
receiving the package.
The bins are divided into small, medium and large bin zones. Each
zone has a distinctive address. Once the zone is known, this must
be compared with the actual package size to see if the bins in that
zone are capable of receiving the package, that is, to insure that
a small, medium or large package is addressed to a small, medium or
large bin, respectively.
The integrated circuit shown in FIGS. 5a-d also contains the logic
and memory elements for the sizing of packages. For this purpose,
classification is based on a set of photocells at two levels. One
level corresponds to the boundary between small and medium packages
and the other level corresponds to the boundary between medium and
large packages as shown in FIG. 3.
It might be thought that two such photocells could be placed in the
center of the table and load size determined in that manner.
However, this would only determine the size of the center of the
load and would not detect an outsize dimension because of load
irregularity.
To determine the maximum size of the load regardless of its
irregularity requires scanning the load. This is done by mounting
photocells displaced from the center of the table toward the side
by the amount of the widest load to be carried. The actual sizing
operation is then carried out as the load is retracted. Any
protrusion on the load placing it into a particular size
classification will then trip a corresponding photocell as the load
moves past it.
As shown in FIG. 3, two sets of photocells are provided, one at the
left extremity of the centered load and another at the right
extremity of the centered load. When the large load is retracted
from its left-hand position toward the right to its center
position, the large photocell at the left will trip although such a
cell if it had been located at the center of the table would not
have detected the large dimension.
The classification of the package as based on the tripping of
photocells (breaking of light beams) is performed by the integrated
circuit logic in FIGS. 5a-d. It is apparent that the actions of the
photocells must be remembered because they might trip only
momentarily during the scanning action. Therefore, two flip-flops
FF1 and FF2 are provided as shown at the bottom portion of FIG.
5d.
These flip-flops are reset to "0" condition sometime before the
scanning takes place and are set to "1" condition in the following
combinations by photocell trip signals (low value) during retract
movement.
Medium Package Large Package Package Size Flip-Flop Flip-Flop
Indication
__________________________________________________________________________
0 0 Small 1 0 Medium 1 1 Large
__________________________________________________________________________
SMALL PACKAGE
Referring to FIG. 5a, it will be seen that when the package is a
small one, a low signal will appear on left-hand terminal 13
designed MEDIUM PACKAGE PHOTOCELL Land a low signal will appear on
left-hand terminal 19 designated LARGE PACKAGE PHOTOCELL. These low
signals are applied to inputs of logics AND-1 and AND-2,
respectively. As a result, these AND logics apply high signals to
the set to "1" inputs of flip-flops FF1 and FF2, keeping these
flip-flops in their "0" states. That is, these flip-flops require
low signals on their set to "1" inputs to flip to their "1" states.
Consequently, under present conditions they will remain in their
"0" states.
From the foregoing, it will be seen that determination of the size
of a small package is one of no action since there is no change in
the state of the flip-flops.
Under these conditions, as shown in FIG. 5a flip-flop FF1 applies a
low signal to the upper input of logic AND-3. Flip-flop FF2 applies
a high signal to logic INV-1 and the lower input of logic AND-3.
This causes logic INV-1 to provide a low signal to terminal 34
designated LARGE PACKAGE RELAY, this low signal indicating that the
package is not a large package.
With high and low signals at the two inputs, logic AND-3 provides a
high signal that is inverted in logic INV-2 to a low signal. This
low signal is applied to terminal 31 designated MEDIUM PACKAGE
RELAY to indicate that the package is not a medium size
package.
MEDIUM SIZE PACKAGE
When a medium size package is on the table, the medium package
photocell is actuated during retraction of the table. This is done
by the package interrupting the light beam. As a result, a high
signal is applied to left-hand terminal 13, designated MEDIUM
PACKAGE PHOTOCELL in FIG. 5b. This high signal goes to the upper
input of logic AND-1.
Left-hand terminals 21, 23 and 24 in FIG. 5b have high signals
during the package scanning operation for the following reasons.
This scanning takes place during the table retract operation. It
will be seen from the flow diagram in FIG. 4 that the retract
operation occurs on step 6 of the program in each of the four
modes, pickup, store, retrieve and deliver. This step 6 is the step
program corresponding to P-1 and Q-1, meaning that the P and Q
flip-flops are in their "1" state as shown below.
STEP PROGRAM
Flip-Flops P & Q Step Position Outputs P Q P Q A B C D
__________________________________________________________________________
0 0 0 0 0 0 0 1 1 0 1 0 0 0 2 2 0 1 1 0 0 3 3 0 0 1 0 0 4 3 1 0 1 1
0 5 2 1 1 1 1 0 6 1 1 1 0 1 0 7 0 1 0 0 1 0 8 0 2 0 0 1 1 9 1 2 1 0
1 1 10 2 2 1 1 1 1 11 3 2 0 1 1 1 12 3 3 0 1 0 1 13 2 3 1 1 0 1 14
1 3 1 0 0 1 15 0 3 0 0 0 1
__________________________________________________________________________
MODE PROGRAM
Mode Flip-Flop M Position Outputs M E F
__________________________________________________________________________
Pick-up 0 0 0 Store 1 1 0 Retrieve 2 1 1 Deliver 3 0 1
__________________________________________________________________________
Consequently, the P and Q program flip-flops will apply high
signals to terminals 23 and 21, marked P-1 and Q-1, respectively,
in FIG. 5b. These high signals go to two inputs of a three-input
logic AND-4.
The third input of logic AND-4 receives a high signal under the
following alternative permissive conditions. The power must be
turned on and the system must be either in the pickup or retrieve
mode. Under either of these two conditions, a high signal is
applied to terminal 24 designated LIFT-UP ACTION and goes to the
third input of logic AND-4 to activate this logic.
This high signal is preferably developed in the following manner. A
power-on signal and a pickup mode (M-0) signal are applied through
a two-input AND logic to one of two inputs of an OR logic. This
power-on signal and retrieve mode (M-2) signal are applied through
a two-input AND logic to the other input of the OR logic. The
output of the OR logic is applied to terminal 24 in FIG. 5b. In
this manner either pair of conditions will supply a high signal to
terminal 24.
All three inputs of logic AND-4 now having high signals, a low
signal is applied to logic INV-3 and inverted therein to a high
signal. This high signal is applied to the lower input of logic
AND-1.
Both inputs now having high signals, logic AND-1 applies a low
signal to the set to "1" input of flip-flop FF1. As a result, this
flip-flop goes to its "1" state and applies a high signal to the
upper input of logic AND-3 and the lower input of logic AND-5 as
shown in FIGS. 5b and 5d.
Both inputs now having high signals, logic AND-3 applies a low
signal that is inverted in logic INV-2 to a high signal and applied
to terminal 31 marked MEDIUM PACKAGE RELAY. The high signal to
logic AND-5 constitutes a registration or remembering of the fact
that the package is of medium size. This information will be used
later to prevent erroneously placing it in a different size bin as
hereinafter described.
The medium package relay will set up a limit switch circuit that
will stop the hoist to prevent a medium package from hitting the
ceiling if sent to a small bin at the top of the column.
During the time that the medium size package photocell signal is
received, terminal 19 of FIG. 5b has a low signal since the large
package photocell has not been activated. This low signal is
applied to one input of logic AND-2 to maintain its output at a
high signal value. This high signal is applied to the set to "1"
input of flip-flop FF2 to maintain it in its "0" state. Also,
terminal 11 marked P-3 has a low signal, meaning that the program
is not in step (P program step 3 in position 3 in accordance with
above step program). This prevents sensing the load size during the
time that the table is being extended. This low signal is applied
to one input of logic AND-6 whereby a high signal is applied from
its output to the set to "0" inputs of flip-flops FF1 and FF2. This
conditions these flip-flops for setting to their "1" state.
LARGE PACKAGE
When a large package is on the table, the large package photocell
is activated during retraction of the table in the pickup or
retrieve modes of operation. This is done by the package
interrupting the light beam as before. As a result, a high signal
is applied to left-hand terminal 19 marked LARGE PACKAGE PHOTOCELL
in FIG. 5c. This high signal goes to the lower input of logic
AND-2.
Terminals 21, 23 and 24 have high signals and terminal 11 has a low
signal as described in connection with medium size package
scanning. And since a large package will also trip the medium
package photocell, terminal 13 will have a high signal.
As a result of this, logics AND-1 and AND-2 will have high signals
on both inputs to provide low signal outputs. Logic AND-6 will
provide a high signal output to the set to "0" inputs of the
flip-flops to allow operation thereof. The low signals from logics
AND-1 and AND-2 are applied to the set to "1" inputs of flip-flops
FF1 and FF2, respectively, to change both of them to their "1"
states.
This gives a large package indication only although both medium and
large package photocells are tripped. A high signal is applied from
flip-flop FF1 to the upper input of logic AND-3. A high signal is
applied from flip-flop FF2 to logic AND-7. A low signal is applied
from flip-flop FF2 to the lower input of logic AND-3 and to logic
INV-1. As a result, logic INV-1 provides a high signal to terminal
34 marked LARGE PACKAGE RELAY. The high and low inputs to logic
AND-3 cause it to provide a high signal that is inverted in logic
INV-2 to a low signal at terminal 31 marked MEDIUM PACKAGE RELAY.
Thus, only a large package indication has been registered. For this
purpose, the high signal to logic AND-7 constitutes a registration
or remembering of the fact that the package is large size. The
large package relay will set up a limit switch circuit that will
stop the hoist before it reaches the end of hoist movement to
prevent the large package from hitting the ceiling if sent to a
small or medium size bin at the top of the column.
BIN SELECTION ERROR
When the code reader stops the courier in front of a bin during the
store or retrieve modes of operation, a check is made for variable
bin selection error. This is done by comparing the package size
signal (as registered during the table retraction operation
hereinbefore described) with a resultant "arrived position" signal
obtained by subtracting the address read by the code reader from
the zones boundary addresses wired into the logic system of FIG. 5d
as hereinafter more fully described. This subtracting is done by
the two adders in FIG. 5d marked ADDER A ZONE ADDRESS =31 and ADDER
B ZONE ADDRESS =127.
For this purpose, it may be assumed that the bin zones have been
selected as follows with respect to the code addresses of the bins
in the horizontal travel direction.
Small zone -- addresses 1 through 30
Medium zone -- addresses 31 through 126
Large zone -- addresses 127 through 255
As will be apparent, there are two boundaries between these three
zones, one between the small and medium zones and another between
the medium and large zones. The first boundary is designated the A
zone boundary and the second boundary is designated the B zone
boundary. The A zone boundary address that is 31 is wired into the
A ZONE ADDRESS ADDER by jumper wires connecting pins 27, 30 and 28
to ground as represented in FIG. 5d. These pins are actually in the
receptacle into which the integrated circuit board is inserted.
This leaves the remaining five pins having binary values of 1, 2,
4, 8 and 16 unconnected which puts in the binary value equivalent
to decimal value 31.
In a similar manner, the B zone boundary address that is 127 is
wired into the B ZONE ADDRESS ADDER by a jumper wire connecting pin
42 to ground. These pins are actually in the receptacle into which
the integrated circuit board is inserted. This leaves the remaining
seven pins having binary values of 1, 2, 4, 8, 16, 32 and 64
unconnected which puts in the binary value equivalent to decimal
value 127.
As a result of the above, the two adders have the following values
at first inputs thereof:
(128) (64) (32) (16) (8) (4) (2) (1) A ZONE 0 0 0 1 11 11 - 31 B
ZONE 0 1 1 1 11 11 - 127
it is now possible to determine where the courier has stopped by
determining if the code read by the reader is larger or smaller
than the numbers wired into the adder. If the read address is
smaller than both A and B zone addresses, the courier is in the
small zone. If the read address is equal to or larger than the A
zone address and smaller than the B zone address, the courier is in
the medium zone. And if the read address is larger than the A zone
address and equal to or larger than the B zone address, the courier
is in the large zone. We will now see how this functions to detect
error.
For purposes of description of error detection, let it be assumed
that the following travel addresses are read by the code
reader:
TRAVEL ADDRESSES READ
Decimal 32 26 40 44 6 14 16 20 (Pin No.) Zone Value 128 64 32 16 8
4 2 1 (Binary)
__________________________________________________________________________
Small 15 0 0 0 0 1 1 1 1 Medium 63 0 0 1 1 1 1 1 1 Large 255 1 1 1
1 1 1 1 1
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Since binary subtraction is performed by inversion of the
subtrahend and adding, this inversion is taken care of by providing
signal values on the above pins of low for "1" and high for "0. "
In other words, the input (read) address is presented to the adder
as inverted.
The sum outputs of the adders are not used, only the carry-out
signals because we wish to determine only if a given input or read
address is equal to or greater than, or less than the A and B
boundary (zone) addresses. From this carry-out signal it is readily
determined which of the zones the courier is in.
To illustrate how the carry-out changes as the input address
changes with respect to the boundary address, let it first be
assumed that the preset (wired in) boundary address is 100 (decimal
4) and that the input (read) address changes from decimal 3 to 4
and to 5. The following table shows the results.
SUBTRACTION TABLE
Input Preset Input Inverted Sum Carry-out
__________________________________________________________________________
100 011 100 000 1 100 100 011 111 0 100 101 010 110 0
__________________________________________________________________________
From this it can be concluded that if the input address is less
than the preset boundary address, the carry-out is "1." If the
input address is equal to or greater than the preset boundary
address, the carry-out is "0. "
Three cases can be tabulated for each adder, where N is the input
address and A and B are the respective preset boundary
addresses:
CARRY-OUT TABLE
A ADDER B ADDER Zone Inputs Carry-out Inputs Carry-out
__________________________________________________________________________
Small N < A 1 N < B 1 Medium N A 0 N < B 1 Large N A 0 N B
0
__________________________________________________________________________
this table shows that the small, medium and large zones can be
defined by carry-out values of 1 and 1, 0 and 1, 0 and 0,
respectively.
Specific error detection will now be described.
STORE MEDIUM PACKAGE IN SMALL BIN
This operation is the detection of the error when an attempt is
made to store a medium size package in a small bin. The result of
this detection is to send the courier back to the pickup station as
hereinafter described.
Four signals are used, namely, medium packages, store mode M-1,
small bin zone and program step 0.
For this purpose, the size of the package has been determined as
hereinbefore described. Being a medium size package, its size is
indicated by the "1" state of flip-flop FF1 as shown in the above
table whereby it applies a high signal to the lower input of logic
AND-5 in FIG. 5d.
The system being in the store mode (M-1), that is, the courier
loaded with a medium size package having arrived in front of a
small bin, a high signal is applied to left-hand terminal 37 in
FIG. 5d that is designated M-1. This high signal goes to the middle
input of logic AND-5.
Let it now be assumed that the code reader has reached the small
bin and has read its travel address shown in the above table and
corresponding to decimal 15. This binary code is applied to the
terminals 20, 16, 14, 6, 44, 40, 26 and 32 at the upper left-hand
portion of FIG. 5d designated MT-1, MT-2, MT-4, MT-8, MT-16, MT-32,
MT-64 and MT-128, respectively. The letter prefix stands for
Maitrol that is the type of code reader used and the suffix number
indicates the binary bit value. A "1" bit low signal will be
applied to terminals MT-1, MT-2, MT-4 and MT-8, and a "0" bit high
signal will be applied to terminals MT-16, MT-32, MT-64 and MT-128.
It will be seen that this binary code comes in inverted form since
subtraction is to be performed by inversion of the subtrahend and
adding.
This binary code 15 that has been read will be applied to both A
and B adders. It will be recalled that the code 31 was wired into
the A adder and the code 127 was wired into the B adder. As
described in connection with the above subtraction table, it will
be apparent that since the read code is smaller than the preset
code, the A adder will provide a carry-out of "1," that is, a high
signal to the upper input of logic AND-5.
The B adder will also provide a carry-out of "1" since the read
code 15 is smaller than the preset code 127 but this will have no
effect at this time since logic AND-7 has not been gated by
flip-flop FF2.
Logic AND-5, having now three high signal inputs, provides a low
signal to logic OR-1, causing it to apply a high signal to the
middle input of logic AND-8.
Since the system is at step 0 of the store program, indicative of
having completed the movement to the front of the bin, high signals
will be present on terminals 38 and 10 designated P-0 and Q-0,
respectively, in FIG. 5d. These high signals go to the upper and
lower inputs of logic AND-8.
To allow operation of flip-flop FF3 by a low signal at its set to
"0" input, a high signal must be present at its set to "1" input.
This is obtained from logic INV-4 which inverts the low signal it
receives from terminal 3 marked GO. This GO signal is low after the
system leaves step O of the pickup program.
With high signals on all three inputs, logic AND-8 applies a low
signal to the set to "0" input of flip-flop FF3 and to output
terminal 36 marked SET S-15 and M-0. This flip-flop applies a low
signal that is inverted in logic INV-5 to a high signal and applied
to terminal 7 designated BIN SELECTION ERROR LIGHT. This high
signal energizes the light to indicate that a bin selection error
has occurred. Also, the low signal at terminal 36 is applied to the
step program flip-flops to set the pair of P flip-flops to "0"
state and to set the pair of Q flip-flops to "0" and "1" states,
respectively, indicative of step 15 as shown on the above step
program table. This low signal at terminal 36 is further applied to
the mode program flip-flops to set the pair of M flip-flops "0"
state, indicative of the pickup program as shown on the above mode
program table. It will now be seen from the flow diagram in FIG. 4
that the system has been changed from step 0 of the store program
to step 15 of the pickup program that causes the courier to move to
the pickup station as indicated by the legend thereon.
STORE LARGE PACKAGE IN NOT LARGE BIN
This operation is the detection of the error when an attempt is
made to store a large package in other than a large bin, that is,
in a small or medium bin. The result of this error detection will
be that the courier will be sent back to the pickup station.
Four signals are used, namely, large package, store mode, not large
bin zone and program step 0.
From the foregoing package sizing description, it will be recalled
that the large package size has been remembered by both flip-flops
FF1 and FF2 in FIG. 5c having been set in their "1" states. The
high signal from flip-flop FF2 to one input of logic AND-7
constitutes the large package indication. Also flip-flop FF1
applies a high signal to logic AND-5 at one input thereof as shown
in FIG. 5d.
A second input of each logic AND-5 and logic AND-7 receives a high
signal from store mode (M-1) terminal 37 as hereinbefore
described.
Now if the courier goes to the small zone so that the read code is
less than 31, both adders A and B will provide a carry-out of 1 as
shown in the above carry-out table. If the courier goes to the
medium zone so that the read code is from 31 through 126, adder B
will provide a carry-out of 1. In the first case, both logics AND-5
and AND-7 will be operated. In the second case, only logic AND-7
will be operated as shown in FIG. 5e. In either case of error, one
or two low signals will be applied to logic OR-1, causing it to
apply a high signal to one input of logic AND-8. This causes the
courier to be moved back to the pickup station and the bin
selection error light to be lit as hereinbefore described.
SHELF ERROR
This operation is the detection of an error when the courier goes
to valid travel (horizontal) address but to an invalid hoist
(vertical) address. This is an error possibility because some of
the small, medium and large bin shelves do not coincide as shown in
FIG. 2.
This error is detected by virtue of a code assigned to each hoist
address that defines the validity of the hoist address for the
various zones of different size bins. These codes are shown at the
right-hand portion of FIG. 2. Since a given hoist address can be
valid for one, two or three zones, a three-position code is used.
As shown in FIG. 2, wherein S, M and L designate small, medium and
large bin zones, respectively, a "1" is placed in the proper
position in the three bit code if the address is valid for the
corresponding zone. For example, an address that is valid for only
the small zone is coded 100, an address valid for only the large
zone is coded 001, and an address that is valid for both small and
medium zones is coded 110, etc.
This code is obtained from three bits added to the hoist address as
read by the magnetic code reader. This code is applied to left-hand
input terminals 25, 18 and 41 in FIG. 5d, these terminals being
designated SMALL BIN SHELF, MEDIUM BIN SHELF, and LARGE BIN SHELF,
respectively. This code is applied in such a manner that a high
signal at the given terminal 25, 18 or 41 means that there is no
bin shelf at that hoist address. A low signal, of course, is the
opposite indication, that is, no error. The code bits can be
applied directly to these terminals if "0" in FIG. 2 is a high
signal and "1" in FIG. 2 is a low signal or inverted if they are
the opposites.
SMALL ZONE AND NOT SMALL BIN SHELF
This operation is the detection of an error when the courier
arrives at a hoist address in the small bin zone and the code read
by the code reader indicates that the hoist address selected is not
valid for that zone.
Four signals are used, namely small bin zone, invalid hoist
address, store or retrieved mode and program step 0.
Let it be again assumed that the courier goes to travel address 15
and that when this is subtracted from the preset address 31 in the
A adder (FIG. 5d), it provides a carry-out of "1" to apply a high
signal to one input of logic AND-9 in FIG. 5f. Since the hoist
address at which the courier stopped is not valid for the small bin
zone, a high signal is applied from terminal 25 to the other input
of logic AND-9. As a result, this logic applies a low signal to
logic OR-2. This logic then applies a high signal to one input of
logic AND-10.
This logic AND-10 will be gated provided the system is in either
the store (M -1) or retrieve (M-2) program. This condition is
indicated by a high signal on terminal 37 or 43, respectively. Such
high signal is inverted in logic INV-6 or INV-7 to a low signal at
one of the inputs of logic OR-3. As a result, this logic applies a
high signal to the other input of logic AND-10 to indicate that the
system is in either the store or retrieve program. Such interlock
limits this shelf error checking to those situations when the table
is about to be extended into the bin.
This causes activation of logic AND-10 to apply a low signal to one
input of logic OR-1, causing it to apply a high signal to one input
of logic AND-8. This logic will now be gated provided the program
is at step 0 whereby high signals appear at terminal 38 (P-0) and
terminal 10 (Q-0). These high signals are applied to the other two
inputs of logic AND-8 to cause it to apply a low signal to the set
to "0" input of flip-flop FF3 and to terminal 36 (SET S-15 and
M-0). The low signal at terminal 3 (GO) is inverted by logic INV-4
to a high signal at the set to "1" input of flip-flop FF3 allowing
the low signal to flop it to its "0" state shown in FIG. 5f. This
causes it to apply a low signal that is inverted by logic INV-5 to
a high signal at terminal 7 to light the bin selection error light.
The low signal at terminal 36 shifts the system back to step 15 of
the pickup mode due to the error as hereinbefore described.
MEDIUM ZONE AND NOT MEDIUM BIN SHELF
This operation is the detection of an error when the courier
arrives at a hoist address in the medium bin zone and the read code
indicates that this hoist address is not valid for that zone.
Five signals are used, namely, not large zone, not small zone,
invalid shelf address, store or retrieve mode and program step
0.
Assuming that the travel address is 63 as shown in the table above,
the B adder (FIG. 5d) provides a carry-out "1" that is applied as a
high signal to one input of logic AND--11 in FIG. 5g. The A adder
doe s not provide a carry-out "1" since 63 is larger than preset
code 31 therein so that its carry-out terminal has a low signal.
This does inverted in logic INV-8 to apply a high signal to another
input of logic AND-11. The third high signal comes to logic AND-11
from terminal 18 marked MEDIUM BIN SHELF since the medium bin zone
does not have a shelf at the hoist level as hereinbefore
described.
This causes logic AND-11 to apply a low signal to logic OR-2 which
in turn applies a high signal to one input of logic AND-10. The
remainder of the operation is similar to that described in the last
section, resulting in a high signal at terminal 7 to ignite the bin
selection error light and further resulting in a low signal at
terminal 36 to shift the program to step 15 in the pickup mode.
This causes the courier to be returned to the pickup station.
LARGE ZONE AND NOT LARGE BIN SHELF
This operation is the detection of an error when the courier
arrives at a hoist address in the large bin zone and the read code
indicates that this address is not valid for that zone.
Four signals are used, namely, large zone, invalid shelf code,
store or retrieve mode and program step 0.
Assuming that the travel address is 255 as shown in the above
table, the B adder (FIG. 5d) does not provide a carry-out "1", so
that a low signal is applied therefrom as shown in FIG. 5h. This is
inverted in logic INV-9 to a high signal and applied to one input
of logic AND-12. The other input of this logic receives a high
signal from terminal 41 designated LARGE BIN SHELF since the large
bin zone does not have a shelf at that hoist level as hereinbefore
described.
This causes logic AND-12 to apply a low signal to logic OR-2 which
in turn applies a high signal to one input of logic AND-10. The
remainder of the operation is similar to that described in the last
two sections, resulting in ignition of the bin selection error
light and return of the courier to the pickup station.
Flip-flop FF3 is reset by the GO signal, a high signal, at terminal
3 of FIGS. 5d-h at the start of the next operation.
INITIAL SIZING PRESET
The purpose of this function is to take care of the situation where
there is a load on the table and there is no way to ascertain its
size in order to direct it to the proper size of bin. In such case,
the system will automatically program for a large bin.
It will be recalled that the load size is normally determined by
scanning the load as it is being retracted to the center of the
courier. Therefore, if there is a load on the table initially when
the power comes on, the scanning action has been skipped. This
creates a potentially dangerous situation in that a load can be
dispatched without any sizing information being present to control
its destination.
This difficulty will actually occur only for one condition, the
initial application of power with a load on the table. Any sizing
information previously obtained will have been lost when the power
was off since the memories of this information are flip-flops FF1
and FF2 in FIG. 5d. The problem then is to protect against bin
selection error when there is no sizing information available.
This is done by forcing the sizing logic to large bin indicative
condition with the initial power-on signal. This makes the system
fail safe. At worst then, there can be only an unnecessary
rejection action such as would occur if the package on the table
was actually small. However, the system is protected against the
attempted storage of a large or medium package in a bin that is too
small for the package. In case of this type of rejection, it is
necessary for the operator manually to control depositing of the
load onto the pickup station. Normal action can then be initiated
in which the load is picked up and scanned for sizing
information.
FORCE TO LARGE INDICATION
Programming for a large bin upon power restoration is done by an
initial power-on signal.
Two signals are used, namely, power-on and not in step 4 of the
program.
This initial power-on is the starting point of the program and
occurs when the power is first applied to the control or when
reapplied after an interruption. The basic signal is provided by a
timing relay with a normally closed contact to a 24 volt source.
This timed signal is converted in a signal board to a high signal
of proper value which is then inverted to a low signal for use in
various parts of the system.
One such use of the initial power-on signal is at the left portion
of FIG. 5j to force flip-flop FF2 to its "1" state, that is, its
large package indication. The initial power-on signal is applied
from terminal 33 to the set to "1" input of flip-flop FF2. To
enable this flip-flop to operate, a high signal must be at its set
to "0" input. In its "1" state, flip-flop FF2 indicates a large
package as described in connection with FIG. 5c.
This high signal is obtained from logic AND-6 which has two low
signals inputs. One of these low signals comes from terminal 11
designated P-3 and the other comes from terminal 21 designated Q-1
when the program leaves step 4. P-3 and Q-1 together indicate step
4 of the program, as shown in the above step program table, which
is used to reset the package sizing flip-flops back to "0" state as
hereinafter described.
From this it will be apparent that flip-flop FF2 can be forced to
large package indication at any step of the program except step 4.
This is because the table is in extended position during step 4 and
size scanning will always occur when it is retracted so that no
forcing of the flip-flop is necessary. Moreover, it is during step
4, just before the table is hoisted or lowered and retracted that
the sizing flip-flops are normally reset. Consequently, forcing the
flip-flops at the same time as they are normally reset is
avoided.
RESET PACKAGE SIZING FLIP-FLOPS
The sizing flip-flops FF1 and FF2 are reset to "0" state at step 4
as follows.
Three signals are used, namely, step 4 of the program, not step 6
of the program and not initial power-on condition.
Referring to the left portion of FIG. 5i, high signals will appear
at terminals 11 and 21 marked P-3 and Q-1 at step 4 of the program.
These high signals are applied to the two inputs of logic AND-6,
causing it to apply a low signal to the set to "0" inputs of both
flip-flops FF1 and FF2. This low signal resets these flip-flops in
view of the following permissive signals appearing at their set to
"1" inputs.
One of these permissive signals is a low signal at terminal 23
marked P-1. This means that the program is not at step 6, retract
operation, during which the flip-flop settings are normally
utilized. This low signal keeps the output of logic AND-4 at a high
signal value that is inverted in logic INV-3 to a low signal and
applied to inputs of logics AND-1 and AND-2. As a result, these two
AND logics apply high signals to the set to "1" inputs of the two
flip-flops to allow resetting of the same.
Another permissive signal is a high signal at terminal 33 marked
INITIAL POWER-ON. This means that the initial power on signal, a
low signal, is absent as it should be at step 4 of the program.
This high signal is applied to the set to "1" input of flip-flop
FF2 to permit resetting of it to "0" state. It will be apparent
that if the initial power-on signal is present on terminal 33, the
flip-flop will be reset after such signal terminates. This may be
done because at step 4 the table is extended and package size will
take place immediately on retraction of the table.
CEILING ERROR
The integrated circuit board shown in FIG. 5d also includes means
for sending the courier back to the pickup station when a ceiling
error signal is received thereby.
It will be recalled from the previous description that the medium
package relay and the large package relay depicted at the lower
right-hand portion of FIG. 5d set up a limit switch circuit when
one of these relays is energized by the package sizing flip-flops.
Such limit switch is arranged to be operated whenever a medium size
package approaches the top of a column of small bins or whenever a
large package approaches the top of a column of either small bins
or medium bins. This occurs during step 15 of the store program
when the courier is moving to the store address and before bin
error or shelf error detection takes place. As will be apparent,
under these error conditions the hoist must be stopped before the
package hits the ceiling of the warehouse.
Such limit switch operation provides an error signal that is
applied to input terminal 9 designated SET M-0-4 in FIG. 5d. This
is a low signal that goes to two places. It first goes to the set
to "0" input of flip-flop FF3 to flop it to its "0" state and
ignite the bin selection error light. This light is lit by a high
signal at terminal 7 that is an inversion by logic INV-5 of the low
signal coming from flip-flop FF3. The M-0-4 error signal also goes
to the mode flip-flop to shift the operation to the pickup mode M-0
while leaving it in step 15. As will be apparent from the flow
diagram in FIG. 4, this causes the hoist to be lowered and the
courier to be returned to the pickup station.
The integrated circuit shown in FIG. 5d is mounted on a plug-in
board and renders the variable bin error control an optional
feature that may be put in or left out of the courier control
system. It is put in by plugging in this board. It is left out by
removing this board. Such removal automatically provides a no error
indication. To this end, the terminal to which error signal output
terminal 36 normally connects will be left floating voltage-wise.
Since a floating condition and a high signal both indicate no error
whereas a low signal indicates bin selection error, the system will
operate as if no error is detected when the boar is left out.
While the apparatus hereinbefore described is effectively adapted
to fulfill the objects stated, it is to be understood that the
invention is not intended to be confined to the particular
preferred embodiment of integrated circuit courier control system
disclosed, inasmuch as it is susceptible of various modifications
without departing from the scope of the invention.
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