Note: Descriptions are shown in the official language in which they were submitted.
201755~
ALTERNATING PUSH BACK
SELECTIVE ~ACK STORAGE SYSTEM
Background of the Invention
This invention relates generally to storage systems
and more particularly to a method and apparatus for
facilitating and expediting the flow of packaged goods from
their manufacturers through intermediate storage facilities
at regional distribution centers.
A distributlon center 9tores thou8ands of items in
inventory and attempts to maintain each item at the optimum
minimum inve~ntory level where it will not run out of goods
and generally avoid static inventories which tie up money
in a non-productive mode. Goods are selected for and
shipped to retail outlets according to each outlet' 8 needs.
These needs are based on maintaining flexible but pre-
; established inventory levels to insure meeting and
satisfying the demand of the consuming public serviced by
that retail outlet.
Goods are stored in different areas within the
distribution center depending on the nature of the
products. There is room temperature storage for canned
goods and non-food itemsJ there are refrigerated storage
areas for fruits, vegetables, milk and mllk products, meats
and meat products, floral and garden products~ special
banana rooms for ripening and storing banana frozen
storage areas for ice cream products and for frozen foods;
special enclosed areas for sensitive items such as tobacco
products, photographic supplies, beauty and health aid
items; and isolated storage areas for combustibles and
toxic garden sprays.
The distribution center constantly addresses the
problems of maintaining minimum but adequate inventories,
moving them into and out of storage'quickly and
efficiently, at lowest possible labor cost, holding its
fleets of material handling equipment to barest but
adequate minimums, and is especially concerned with optimum
utilization of available storage space. Furthermore, it is
2017554~
important to store the vast array of goods in such a manner
that each item is readily accessible.
It is also desirable that the products be stored in
such a way that they are removed in inverse order of time
of receipt, that is, items received at a given date move
into the distribution chain before replacement items
received at a subsequent date.
Another important requlrement 18 that items be
warehoused wlthin the distrlbutlon center ln a location
pattern that permits rapid access with minimum labor for
item selection for transfer to an accumulatlon area as a
prelude to loading trucks for transport of these items to
their respective retail outlets.
Present practice to accompli;sh these objectives
includes placing packaged goods on standard sized pallets
and then positioning these pallets on racks so that each
space in the rack holds one pallet. The height of the
racks is limited by the ceiling height of the storage
bullding and by the helght that a orklift can lift a
pallet. Normally, ceiling height is the limiting factor.
In an attempt to achieve the above stated ob~ectives,
a number of known rack type storage sy~tems have been
designed each 9eeking improved eficiencies in performance.
SummarY
It is the primary object of the present invention to
impeove the flexibility of storage and distribution
facilities which will result in savings of storage space,
retrieval time, and labor costs permitting better inventory
control, an enhanced stock rotation capability, and
improved utili~ation of material handling equipment.
It is a further object of the invention to improve the
flow and distribution of all types of packaged goods
originating from the manufacturer through an intermediate
storage center where the packaged goods are broken down
into smaller lots to fill orders from retail outlets for
sale to their customers.
The inventlon comprlses an lmproved plcklng scheme and
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a novel system of different types of racks for use in
distribution centers servicing retail stores with food and
non-food items such as are found in supermarkets. The
inventive method and apparatus can also be used in
distribution system complexes servicing industries other
than retail markets and supermarket chains including but
not limited to hardware, bullding supplies,
pharmaceutlcals, electrl~al and computer aomponents, naval
store~, automotlve supplles, machl~e parts, books and
magazines, etc.
Brief Descrlptlon of the Drawing
The invention will be better understood when
considered in connection with the following drawing Eigures
wherein:
Figure 1 is a perspective view of a single-deep back-
to-back selective container type storage rack according to
the known prior art~
Figure 2 is a qide elevational view of a conventional
double-deep, back-to-back pallet type selective storage
rack~
Figure 3 is a side elevatlonal vlew of a well known
three-deep pallet type storage rack~
Flgure 4 is a side elevational vlew of a slx-deep
pallet type flow-through storage rack al50 known ln the
prlor art~
Figure 5 is a perspective view of a storage rack
system according to one embodiment of the subject
invention~
Figure 6 is a plan view illustrative of a picking
scheme illustrating the method of the subject invention;
Figure 7 is a perspective view of a storage rack
system according to another embodiment of the subject
invention: and
Figure 8 is a plan view illustrative of a picking
scheme further illustrative of the method of the subject
invention.
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Detailed Descriptlon of the Invention
Prior to considering the details of the present
invention, it is desirable to further review and compare
the use of known conventional storage rack systems.
Packaged goods are handled, where possible, on
standardized pallets generally 4B x 40 inches in size and
built for handling by fork lifts or pallet ~ack machlnes.
Stacking pallet loads o product directly one on top
the other can result ln damage to the bottom p~llet load.
This possibllity o damage increases as the number and
height of the pallets increase. Moreover, there is danger
that the pallets will topple as the goods on the bottom
pallet become distorted from the weight of the top pallet
or pallets. Furthermore, if it is desired to access the
bottom pallet in a stack of two or more pallets, it will
require removing the top pallets and then restacking them
after the bottom pallet is accessed. If only part of the
bottom pallet is removed, and a partial layer remains, then
restacking would result in an unstable load space and other
options would have to be exercised ~uch as starting a new
8 tack.
The answer to thls problem ls to stack pallets in
racks where each pallet occupies it5 own rack space and is
lnserted or removed from that space without affectlng other
pallets in that rack. The height of the racks depends upon
ceiling height in the warehouse and the abillty of the
forklift to reach every space in the rack. The racks are
positioned next to each other to form a row of racks, and
the whole distribution center or designated sections of the
distribution center is filled with rows of such racks. The
rows are spaced to permit forklifts to move between the
rows with enough room to access each rack for placing or
removing pallets from any rack space in the rows. In
addition, room is provided at least at one end of each row
in order to permit forklift travel from one row to any
other row in the area. It is also usually desirable to
have a turning space at both ends of each ! OW, otherwlse
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2C)1755~
the forklift will have to back up to the open end of the
row and spend extra time in so doing.
In practice two rows of these racks are normally
placed back-to-back to take advantage of the enhanced
stability resulting from this type configuration. A
typical example of such an arrangement is shown in Figure
1. Moreover, one aisle spacing is saved that would be
needed if the double row of racks were separated into two
single rows. This back-to back rack system i~ cla~sified
as a "Single Deep Selactive Rack Sy~temn. As shown in
Figure 1, pallet loads 10 are placed one deep into each
rack space of two adjacent racks 12 and 14, and only one
single deep rack space is accessible from the aisles 16 and
18 on either side of the rows of racks for stock
replenishing or for order selection.
; The problem with the Single Deep Storage Rack system
is it is wasteful of valuable warehouse space. Efficient
space utilization is not only a function of amount of
warehouse area used for aisles vs. racks, but is also a
function of rack space utilization. For example, when a
truck load of twenty pallets of case goods arrives they
will be stored in twenty rack spaces. Defining a vertical
column of rack spaces in the rack row rom which product i9
picked as a ~facingn, each facing will have room or four
to five pallets set individually one over the other. A
truck load of pallets could use four or five facings. As
order picking progresses, rack spaces become empty and
stand vacant until the next truck load arrives.
Furthermore, in the Single Deep Storage Rack system,
facings used for truckload storage extend linearly along
the row of racks, which means that the order picker must
travel longer distances from item to item if an item
occupies multiple facings than if the item occupied a
single facing. With items requiring multiple facings, one
facing is picked until empty, the others stand static until
this happens.
As orders are picked from these racks, the racks are
2~)1755~
progressiv~ly empt~ed until they are replenished.
Replenishment occurs as inventories drop to predetermined
minimum levels. This happens at different times for
different items within the racks. The overall effect is
that the racks are never completely full with merchandise.
The occupancy rate, or amount of space utilized at any one
time, often exceeds 50~ of available ~pace.
~ "~rive-In ~ack" ~y~tem was then developed whlch not
only re501ved the problem of accessing all our rows o the
Double Deep Standard Rack system, but opened the way to use
multiple rack systems, in excess of four if so desired.
Although not shown, a drive-in rack system involves placing
pallets between uprights on load rails which are
perpendicular to the aisles rather than on load beams
parallel to the aisles. A forklift with a pallet load of
packaged merchandise drives into one of the multiple rack
passageways, positions the pallet in the deepest accessible
pallet space that i~ can reach, then backs out.
In order to improve warehouse space utilization by
increasing space used for racks and decreasing space used
for aisle~, and at the same time reduce statlc storage
facings on the plcklng alsles, a "Double Deep Standard
Rack" system was devised as shown in Figure 2, consisting
of four rows of racks 18, 20, 22 and 24 joined together.
There is an aisle 16 and 18 on both sides of the rack
system from which two-deep rack ~paces 26 and 28 are
accessed from either aisle. A special forklift, not shown,
with a reach mechanism is necessary to reach the inner rack
spaces. In this system, the inner rack is used for static
storage, whereas the outside rack is used for order
picking. The double deep system as well as those described
above use standard rack components for rack construction.
The advantages of the Double Deep ~tandard Rack system
are space saving, improved stàtic storage, improved facing
exposures, and decrease in linear travel for stock
replenishment and for order picking. The disadvantages of
the Double Deep Standard Rack ~ystem are the need fol:
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X01755~
speclal equipped forkllEt~, re~trictlon on ability to reach
into the four aonsolidatea row~ of racks 18,20, 22, 24, bo only
two deep from each aisle, and each set of two deep racks
must hold the same product.
S Disadvantages to thls type of sy~tem are that more
space i~ r~qulred between load~ ~han the s~andatd rack
conelguratlon~ loadlng thQ raaks must occur rom baak to
ront by loading one stack hlgh a~ a tlme startlng from the
floor and progresslng to t~e highest level or vlce versa,
~tartlng from the back of the rack~ and working towards the
front. Once loaded, access to the next row deep must walt
until the entire front "face" 18 removedl and the system
makes it almo~t mandatory that the same product be stored
ii wlthin each passageway, because replenlshlng any level with
a dlfferent product would requlre maklng space available
or forkllft access. Furthermore, when a new shipment
arrlves, it mlght be placed ln front of the re~ldual
prerious ~hlpment which would prevent proper stock rotatlon
according to the prinalple of flrst ln-flr~t out. The
oaaupancy factor, or peroent utllizatlon of ~vallable rack
sp~ae, will ~verage around 50 percen~.
The foregoing type o rack storage, howérer, does not
lend ltself to "family" geoupings, where a group of simiiar
products are combined into classes of product~, like soups,
soaps, breakfast cereals, aOg food, etc. Merchandlse is
usually stored into groups of: (a) bigh movement, (b)
medlum movement, and (c) low movement. Products from
familles may be found in all these three mover categories,
which means that they are spread around the warehouse.
A "Drive-Thru Rack" system was then devl~ed to
increase the flexibllity of the Drlve-In Rack system. This
allows access from either side permitting the two opposlte
faces to be working 'until the immediate front adjoining
stack of pallets are e'mptied or removed. - Both Drive-Thru
.. , .. ~ . . .
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:
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Z01~559c
and Drive-In systems require all vertical stacks of pallets
stored in the same passageway or throughway, to hold the
same product. This applies both to the working faces and
to the static backup stacks positioned within the interior
of the racks.
The disadvantages of the Drive-Thru Rack system are
the same as the Drive-In Rack system discussed above. The
system is still subject to improper stock rotation from
putting fresh ~tock in front of older stock~ but to a
lesser degree, since access for order picking is posslble
from two opposite ace ends. The occupancy factor for the
Drive-Thru Rack system is somewhat better than the Drive-
In Rack system but is still in the order of 50-60%.
The Drive-Thru Rack system, furthermore, does not lend
itself to family grouping of merchandise.
To further increase the flexibility of the compacted
rows of stacks, a "Pallet Flow-Thru System" was next
introduced as sbown in Figure 3, wherein rollers 30 were
placed on load rails 32 which were sloped in such a way
that multi-level pallets 10 placed on the high end would
roll by gravity to the low end where picking takes place.
When one pallet 10 is emptied and removed, the next pallet
10 rolls into place, so that all picking pallets are on the
out8ide and the same side o the rows of racks. The use of
this system permits each level in the stack to carry a
different item if so desired.
Another gravity flow system currently in use is known
as the ~Pallet Push-Back Rack" system and is shown in
Figure 4. There pallets 10 are pushed uphill on sloped
rails 32 from the low side next to aisle 16. When the
lowest pallet 10 is used up and removed, the pallets above
it roll down by gravity to the front on the rack. ~owever,
if product is replenished before all pallet loads move to
the picking face 34, the push back-system places new
product in front of older product and this system as a
consequence loses its flexibility to properly rotate stock
on a ~first in - first out" basis.
20~75591,
While both the Flow-Thru and Push-Back systems have
better occupancy rates, these systems do not lend
themselves to "family" grouping and are best suited for
storage by "movement" categories.
Prior to the subject invention, each row of racks were
configured with the same type rack e.g. Single-Deep Storage
Racks, Double-Deep Storage Racks, Drive-in Racks, Drive-
Thru Racks, Pallet Flow Racks, and Push-Back racks. Use of
two or more different types of racks within a warehouse
require a 9eparate 8et of rack row5 for each sy~tem u~ed.
Each system was designQd to address a particular need~
however, they lacked the flexibility to handle the storage
varlables dictated by consumer demand and reflected in the
rate of consumption quantified by movement values for each
item.
This now leads to a consideration of the subject
invention. Every one of the tens of thousands of items in
a distribution center must be positioned on an outside face
of a rack system to make it readily available to picking
crews for filling orders. Order selection has to be done
in the shortest time possible which is conducive to using
picking crews more efficiently so that the number of order
pickers can be held within realistic limits to hold picking
co~t~ down. To accomplish thi~, the location of the ltems
have to be programmed in such a way as to minimize travel
distance and consequently travel time through the
distribution center complex. Significant savings in time
and labor costs result when this is done properly.
Records are kept of inventory "movements" where a
movement is defined as the ratio of sales over inventory,
and where sales is considered synonymous with movement.
"High movement" items may be picked each time an order
comes through,"medium movement" items are required less
often, and "low movement" items may only be needed
periodically. Some high movement items may require more
storage space because of their higher rate of use. The
frequency of reordering, the amount ordered, whether
2~ i5~
.
truckload lots or split or mixed shipments, and rack space
requirement~ for ~torage and for picking are all
interrelated with each item's inventory and sales
characteristlcs.
Referring now to Figure 6, during order plcking, an
order selector or picker has a set of pre-determlned stop
polnts 34 wheee he ~tops hls truck 36 and walk~ up and down
the ~lsle~ to ~elect ltems as per hi~ order plcklng
document. He caerles them back to h1s truck and dr1ves to
the next stop polnt. He repeats thl8 sequence untll he has
completed hls order selection. Figure 6 further
lllustrates a chart of the stop-polnts ln a hypothetlcal n Z
pick" warehouse situation.
It has been found that by gro;uping storage items
according to their movements, walking dlstances can be
; décreased and tlme for plcking signlflcantly reduced.
It has also been found that grouplng ltems by famlly as
well as by movement that the number of stops may be reduced
and tlme for plcklng signlficantly reduced. Additionally,
it has been found that intermixing the rack systems by type
and by s1ze and by applying the princlples of the invention
descrlbed hereln that the occupancy rate 1~ ~lgnl1cantly
increased resultlng ln ~uperior and more economlcal use of
avallable storage space.
Accordingly, this lnventlon ls directed to a storage
rack conflguration comprised of an lntermix of dlfferent
types of known rack systems in the same row for increasing
the flexibility of storage and retrleval operatlons whlch
results in savings in time and labor costs. Figure 5 shows
one such arrangement of mixed racks utilized, for example,
in the layout depicted in Figure 6.
Referring to Figure 6, there is shown a picking scheme
for three movement frequency levels A, ~ and C which stand
for "high movement", "medium movement" and "low movement",
3~ respectively, and each having its own specific rack type
which is further shown in Figure 6- It can be seen that
there 18 a repetltive set of racks for each truck ~top 34
: " : . ~
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11 .
with a picking range for each stop being defined by the
distance between points 38 and 40. Each distance span
between points 38 and 40 includes the three movement
frequency level rack types which repeats itself. For
example, beginning at point 38 and moving forwardly, there
are three C (low movement) racks followed by three B
(medium movement) racks followed by a slngle A ~hlgh
movement) rack whlch 1~ followed by two C ~low movement)
racks to the polnt 4~. Fur~hermor~, each truck stop 34 18
at the forward end of the A type rack and the first o the
last two C type racks. From this stop point, the operator
carrylng out the order selection thus posltions the length
of his truck immedlately adjacent the hlgh movement A rack
and one or more of the medlum movement ~ rack~, whlch
enables hlm to qulckly and efflciently make the requlred
selectlon of items. It can be seen that the low movement C
racks are located on either side of the high and medlum
movement racks A and B. Accordlngly, as the picker
advances to each stop point 34, he flnds the same
repetitlve grouplng of rack types.
The type of racks employed in the A, ~, and C group as
shown ln Flgure 6 is further shown in Flgure S where the
high movement A and medium movement ~ are comprised of
push-back storage racks and more partlcularly two-deep,
four-hlgh push-back racks 42 whlle the low movement C racks
are comprised of, for example, flve and six.high selective
eacks 44, 46, which face the same aisle. To the rear of
thls rack grouping, one finds A or B type push-back racks
42 behind the C type selective racks 44 and 46, with
selective racks 44 and 46 behlnd the push-back racks 42.
This is the arrangement shown in the plan view of Figure 6.
Figures 7 and 8 are illustrative of a second rack
configuration and are basically the same as that of the
embodiment shown in Figures 5 and 6 with the exception that
periodically a fourth type D rack, comprising a flow-
through rack, is included in the group of A, ~ and C rack
type~.
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12
As shown in Figure 7, a three-deep, four-high flow-
through rack 48 is shown located adjacent an A or B type
push-back rack 42. In the plan view layout of a warehouse
utilizing this arrangement, it can be seen that D type
racks 48 typically appear adjacent alternating locations of
high movement A type racks 42, which due to the back-to-
back configuration, is located adjacent a low movement C
type rack of the next aisle. It should be noted, however,
that when desirable, flow-through D type ràcks 48 can be
selectively intermixed in any required pattern and
therefore the layout shown in Figure 8 is only meant to
disclose a typical example since it is possible to set up
any combination o double deep A or B type push-back racks
and flow-through D type racks, depending upon the needs of
the particular user.
It is further possible to change from one rack type to
another or combinations thereof if and when needed. For
the configuration shown, for example, in Figures 5 and 7,
the time for changeover from one rack type to another can
be made in approximately one hour for a single rack
section. It is also possible to configure more than three
rows of condensed stacks and use the variable stacking
pattern as for the three row configuration as dl~closed.
Having thu~ shown and described what is at present
considered to be the preferred embodiments of the
invention, it should be noted that the same has been made
by way of illustration and not limitation. Accordingly,
all modifications, alterations and changes coming within
the spirit and scope of the invention are herein meant to
be included.
