Note: Descriptions are shown in the official language in which they were submitted.
~L:L97081
"IMPROVED WORKPIECE STORAGE AND
SHUTTLE APPARATUS"
BACK~ROUND OF THE INVE~TION
This invention relates generally to workpiece shuttle
mechanisms such as are four.d on machine tools and more
specifically, this invention relates to an improved work-
- piece shuttle mechanism which is operative to store a
plurality of workpiece carrying pallets and to shuttle
a workpiece carrying pallet then at a selected storage lo-
cation to the worktab~e of a machine tool or to shuttle the
workpiece carrying pallet then on the machine tool to a
storage location.
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As conventional, manually operated, drilling and milling
machines are being superseded by sophisticated computer numeri-
cally controlled machining centers which are capable of auto-
matically performing a sequence of different machining opera-
tions on the workpiece without human intervention, the need torapidly and efficiently shuttle parts onto and off of the ma-
chine tool is becoming increasingly more important. Because
of the relatively large capital cost of such sophisticated nu-
merically controlled machine tools, it is imperative that the
then-completed workpiece on the machine tool table be inter-
changed as quickly as possible with an unfinished workpiece
upon completion of the sequence of machining operations so
that machine idle time can be kept at a minimum. By reducing
machine idle time, machine productivity, that is the number of
parts that can be machined during any given time, is maximized.
In the past, rapid and efficient interchange of workpieces
has been achieved by equipping the computer numerically con-
trolled (CNC) machining center with a workpiece changer or pal-
let shuttle mechanism which automatically interchanges the pal-
let carrying then-completed workpiece with a pallet carrying
an unfinished workpiece after completion of the sequence of
machining operations. Examples of prior art workpiece
changers and shuttle mechanisms may be found in U.S. Patent
3,825,245 issued on July 24, 1974 to John G. Osburn et al
and U.S. Patent 4,133,4~3 issued on January 9, 1979 to Frank
Zankl. Each of the above listed patents describes an apparatus
for completing a single interchange of the workpiece then
on the machine tool table with an unfinished workpiece
stored on a single storage shuttle or table. ~nce an inter-
change has been completed between the then-completed workpiece
on the machine tool table and the unfinished workpiece at the
storage shuttle, then the now-completed workpiece on the stor-
age shuttle must be manually replaced by the operator with an
unfinished workpiece to enable a subsequent exchange by the
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workpiece changer when the now-unfinished workpiece on the ma-
chine tool table is machined.
The obvious draw~ack of such workpiece changer devices is
that only one unfinished workpiece is stored by the workpiece
changer so that even though interchange between a then-completed
workpiece on the machine tool table with an ~nfinished workpiece
on the workpiece changer shuttle can be accomplished quite
rapidly and eEiciently, human effort is still required to load
and unload the workpiece changer shuttle. In an effort to re-
duce the ~requency of manual part loading and unloading to en-
able relatively long periods (8-10 hrs.) of unattended machine
tool operation, a pallet stora~e magazine and associated shuttle
mechanism has been developed to enable multiple storage of
unfinished and finished workpiece carrying pallets. Such ~
pallet storage magazine and shuttle mechanism comprises a con-
veyor which rotates on a base located adjacent to the machine
tool bed. A plurality of pairs of pallet receiving and stor-
age guides are fastened on the conveyor in spaced apart rela-
tionship so that each of the guides of each pair are parallel
to each other. The conveyor rotates about two centrally lo-
cated oppositely extending shuttle arms which are each extend-
ed and retracted by a hydraulic cylinder. Each shuttle arm
has a "T" shaped finger at its distal end for mating with a
complementary slot on each workpiece carrying pallet when, fol-
lowing arm extension, the arm is rocked by a tilting mechanismto locate the finger in the pallet slot.
While the above-described pallet storage magazine and
shuttle mechanism enables multiple pallet storage in contrast
to the prior art workpiece shuttle mechanisms described earlier,
it is nonetheless subject to the disadvantage that two mecha-
nisms must be provided, one to extend and retract each shuttle
arm and the other to rock each shuttle arm to releaseably en-
~age the "T" shaped finger at the distal end of the shuttle
arm in the complementary receiving slot on the pallet. In
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contrast, the present invention concerns an improved workpiece
storage and shuttle mechanism which is not subject to the dis-
advantages of present day pallet storage and shuttle mechanisms.
The principle object of the present invention is to pro-
vide a workpiece storage and shuttle mechanism which employsbut a single mechanism for releaseably en~aging the pallet and
Eor shuttling the workpiece carrying pallet between one of the
several storage locations and the machine tool table. By elimi-
nating the need for separate mechanisms for releaseably engag-
ing the pallet carrying workpiece and for shuttling the work-
piec~ between one of the storage locations and the machine
tool worktable, fabrication can thus be simplified and fabri-
cation costs can be reduced. Another object of the present
invention is to increase the speed at which pallets can be
interchanged. Other objects and advantages of the invention
will become apparent from the detailed description provided
hereinafter.
Brief Summary of the Invention
Briefly, in accordance with the preferred embodiment of
the il~vention, an improved workpiece storage and shuttle mecha-
nism for use on a machine tool for storing both finished and
unfinished workpieces and for exchanging an unfinished one of
the stored workpieces with the finished workpiece then on the
worktable of a machine tool comprises a base located adjacent
to the machine tool bed. A carousel is rotatably journaled
into the base and is precisely indexed by a servo controlled
motor in response to electrical signals generated by the ma-
chine tool control system indicative of the desired carousel
angular orientation. On the carousel is at least one and pre-
3n ferrably two pairs of parallel spaced apart guides, the guidesoE each pair of carousel guides extending out from the center
oE the carousel parallel to a carousel radii to beyond the
periphery of the carousel with the guides of each pair being
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in alignment with, but extending oppositely to, each of the
guides of the other pair of carousel guides. Located about
the orbit of the carousel guides are a plurality of workpiece
storage pe~estals, each in spaced apart relationship with the
others. Each workpiece storage pedestal has a pair of spaced
apart guides thereon which are each parallel to a carousel
radii for slidably receiving and supporting a workpiece car-
rying pallet thereon. ~ workpiece carrying pallet is trans-
~erred between the machine tool worktable and the carousel and
between the carousel and one or the workpiece storage pedestals
by one of a pair of pallet shuttle arm which are each slidably
mounted between the guides of a separate one of each of the
pair of carousel pallet guides for extension out from and ~ith-
drawal into the corresponding carousel guides by a hydraulic
lS cylinder. A workpiece carrying pallet then on the machine
tool table or on one of the workpiece storage pedestals is
transferred onto a pair of carousel guides for subsequent
transfer to a then-empty workpiece storage pedestal or to the
machine tool table, respectively, by first indexing the
carousel so as to position an empty pair of carousel guides
slightly off the axis of the machine tool table or the work-
piece storage pedestal carrying the pallet to be transferred
onto the carousel so that tthe carousel guide shuttle arm may
be fully extended out from the carousel. Once the shuttle
arm is Eully extended, the carousel is rotated to align the
guides on either side of the now-extended shuttle arm with the
~uides of supporting the workpiece carrying pallet to be trans-
~erred onto the carousel, causing a hook on the distal end of
th~ shuttle arm to be brought into engagement with a latch on
3~ the pallet. After the pallet shuttle arm hook engages the
pallet latch, the shuttle arm is retracted to pull the work-
piece onto the carousel guides. Transfer of the workpiece
carrying pallet on the carousel guides is accomplished,
following indexing of the carousel, by extending the shuttle
3~ arm to push the pallet off of the carousel and onto either the
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machine tool table ~r the guides of a workpiece storage pedes-
tal. Disengagement of the shuttle arm from the just-transferred
pallet is accomplished simply by rotating the carousel slightly
off-axis of the just-transferred pallet which allows the now-
extended pallet shuttle arm to be retracted.
Brie_ Description of the Drawings
I'he features of the invention believed to be novel are
set forth with particularity in the appended claims. The in-
vention itself, however, both as to organization and method of
operation, together with further objects and advantages thereof,
may best be understood by reference to the following descrip-
tion taken in conjunction with the accompanying drawings in
which:
Figure 1 is a frontal perspective view of the improved
workpiece storage and shuttle apparatus of the present inven-
tion shown in conjunction with a conventional horizontal
spindle machining center;
Fig. 2 is a top view of the improved workpiece storage
and shuttle apparatus of Fig. 1;
Fig. 3 is an end view of the improved workpiece storage
and shuttle apparatus of Fig. l;
Fig. 4 is an enlarged portion of the improved workpiece
storage and s~uttle apparatus of Fig 2; and
Fig. 5 is a cross sectional view of Fig. 4 taken along
lines 5-5 thereof.
Detailed Descri~tion of the Improved En!bodiment
An improved workpiece storage and shuttle mechanism 10
for use with a numerical control machine tool, such as a hori-
zontal spindle machining center 12, is illustrated in perspec~
tive in Fig. 1 and in top or plan view in Fig. 2. Workpiece
and storage mechanism 10 comprises a base 14 which is located
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adjacent to the bed 16 of machine tool 12 so as to be in align-
ment with the path of travel of the machine tool worktable 18
on machine tool bed 16. In practice, machine tool 12 is pro-
vided with a numerical control system, typically a computer
numerical control system 20 for controlling not only the move-
ment of table 18 on bed 16 but also the movement o~ machine
tool column 22 along bed 16 in a direction perpendicular to the
path of movement of the machine tool table on the machine tool
bed. Further, machine tool control system 20 also controls the
movement of the machine tool spindlehead 24 along machine tool
column, together with the rotational movement of the machine
tool spindle 26 as well as auxiliary machine tool functions
such as the operation of the automatic tool changer 28 and the
operation of workpiece transport and shuttle mechanism 10.
1~ In the present embodiment, base 14 of apparatus 10 has a
carousel 30 rotatably journaled therein for rotation about an
axis parailel to the axis (Fig. 1) along which spindlehead 24
moves on column 22 of the machine tool~ this axis being desig-
nated as the Y axis. Referring now to Fig. 3, which is a cut-
away end view of apparatus 10, it can be seen that carousel
30 is rotatably journaled in base 14 by a bearing 31. Circum-
scribing the inner periphery of the inner race of bearing 31
is a ring gear 32 which is dimensioned to meshingly engage a
gear 35 carried on the output shaft of a right angle gear train
37 secured within the base. The input shaft (not shown) of
gear train 37 is driven by a servo controlled motor 40 having
an internal feedback transducer 41 for generating electrical
signals indicative of motor shaft position. The output signals
from feedback transducer 41 are supplied to machine tool con-
trol system 20 (Figs. 1 and 2) which, in accordance with thefeedback transducer signals, controls the excitation of motor
~0 responsive to numerical control commands indicative of the
desired carousel angular orientation, to achieve precise po-
sitioning of the motor output shaft and hence, precise angular
positioning of carousel 30.
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Extending downwardly from gear train 37 is an auxiliary
output shaft 42 which is coaxial to the gear train output
shaft driving gear 35 and rotates co-jointly therewith. At
the distal end of shaft 42 is a coaxially mounted plate 44
having a pl~rality of dogs 46 disposed through the plate
periphery, the dogs being spaced about the plate at a 45
angle from each other. A proximity detector 48 is secured to
the interior of base 14 so as to be adjacent to plate 44. Each
time one of dogs 46 comes into proximity with detector 48, the
detector provides a pulse to machine tool control system 20.
By knowing the initial position of carousel 30 and by countlng
the number of pulses produced by proximity detector 48 as
carousel 30 is rotated by servo-controlled motor 40, the ma-
chine tool control system can ascertain the approximate angu-
lar orientation of the carousel. The combination of plate 44,dogs 46 and proximity detector 48 serves, in addition to the
feedback transducer 41 within motor 40, to provide an approxi-
mation of the angular orientation of carousel 30 so that in th~
event feedback transducer 41 within motor 40 becomes inopera-
tive, the machine tool control system will still maintain aknowledge of the carousel angular position.
Referring now to Figs. 1-4 jointly, carousel 30 has at
least one and preferrably two pairs of spaced apart guides 50a
and 50b fastened on the top surface thereof, with the guides of
each pair of guides extending outwardly from the center of the
carousel and therebeyond parallel to a carousel radii so as to
overlie base 14. Each of the guides of each pair of carousel
guides is in alignment with, but extends diametrically oppo-
site to, a separate one of the guides of the other pair of
c~ro~lsel guides. The spacing between the guiaes of each pair
oE carousel guides is identical to the spacing in between the
pallet receiving guides (not shown) which are carried on machine
tool table 18 to support a pallet 52 (Figs. 1 and 2) thereon.
As will become better understood hereinafter, by making the
spacing between the guides of each of carousel pallet guides
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identical to the spacing between the machine tool table pallet
guides, a pallet then on the pallet guides on the machine tool
table can be transferred onto an empty one of the two pairs of
carousel pallet guides when the carousel is indexed to align
the empty pair of carousel pallet guides with the machine tool
table pallet guides. Conversely, a pallet then on one of the
pairs of carousel pallet guides can be transferred to the
empty machine tool worktable pallet guides while the carousel
is indexed to align the carousel pallet guides with the ma-
chine tool table pallet guides.
Referring now to Figs. 1 and 2, a plurality of free stand-
ing, fixed height, workpiece supporting pedestals, typically
five in number and each identified by a consecutive one of
reference numerals 54a through 54e, respectively, are located
in semicircular fashion about the arc circumscribed by the tip
of each of the guides of each pair of carousel pallet guide
pairs 50a and 50b. Each workpiece pedestal, such as workpiece
storage pedestal 54a, for e~ample, has a pair of spaced apart
pallet receiving guides 56 thereon, each dimensioned identi-
cally to the guides of carousel pallet guide pairs 50a and50b and each extending across the pedestal parallel to a
carousel radii so as to be adjacent to the arc circumscribed
by the tip of the carousel pallet guides. To facilitate
pallet transfer between carousel 30 and each of workpiece
storage pedestals 54a-54e, the spacing between pallet receiv-
ing guides 56 on each workpiece storage pedestal is identical
to the spacing between the guides of each of carousel pallet
guide pairs 50a and 50b, and the height of each of workpiece
storage pedestals 54a through 54e is such that the guides on
each workpiece storage pedestal lie in the saMe horizontal
plane as the guides of carousel pallet guide pairs 50a and
50b so that when the carousel is indexed to locate each of
the guides of one of pallet guide pairs 50a and 50b in
alignment with each of the pallet receiving guides 56 on one
of workpiece storage pedestals 54a through 54e, a pallet can
be slidably moved off of the workpiece storage pedestal pallet
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guides and onto the carousel pallet guides and vice versa. In
practice, the guides of each of carousel pallet guide pairs 50a
and 50b have replaceable ways fastened thereon (described in
greater detail with respect to Fig. 5) and likewise, guides 56
on each of workpiece storage pedestals 54a 5~e also have re-
placeable ways (not shown) fastened thereon. The addition of
ways on the guides reduces pallet friction as the pallet is
transerred across the guides. Further, the use of ways on
the guides reduces guide maintenance because the ways can be
1~ easily replaced when their surfaces become worn, in contrast to
having to resurface the guides themselves by planing or grinding.
Referring now to Fig. 2 and more particularly to Fig. 4,
which is an enlarged view of a portion of the apparatus illus-
trated in plan view of Fig. 2, transfer of a pallet between
15 one of carousel pallet guide pairs 50a and 50b and one of
workpiece storage pedestals 54a through 54e or between one of
the carousel pallet guide pairs 50a and 50b and the pallet
guides on machine tool worktable 18 is accomplished by one o~
a pair of pallet shuttle arms 57a and 57b which are each
20 slidably mounted between the guides of a separate one of
carousel pallet guide pairs 50a and 50b, respectivelyO The
details of how each shuttle arm is slidably mounted between
the guides of each of carousel pallet guide pairs 50a and
50b are illustrated in Fig. 5 which is a cross sectional
25 view taken along lines 5-5 of Fig. 4. As illustrated, each
of a pair of ways 58 is fastened to each of the guides of
each carousel pallet guide pair, such as carousel pallet
guide pair 50a. Each oE ways 58 has an axially extending
~ongue 59a and an axially extending groove 59b on its inward
30 facing side for each engaging a complementary groove 59b and
a complementary tongue 59a, respectively, on the outward fac-
ing side of each of pallet shuttle arms 57a and 57b, respec-
tively. The top edge of the groove on the outward facing
side of each of the pallet shuttle arms overlies the tongue
35 on a separate one of ways 58. A centrally disposed rib ~0,
located equidistantly between each of the guides of each of
the carousel pallet guide pairs, has an axially extending
tongue on either side thereof for engaging a complementary
groove on the inner side of each of pallet shuttle arms 57a
and 57b so that each pallet shuttle arm is slidably supported
between one of ways 5B and rib 60. Pallet shuttle arms 57a
and 57b are each linked to a separate one of hydraulically
actuated cylinders 62a and 62b, which are each secured between
the guides of a separate carousel pallet guide pair, respec-
tively. Depending on the pressurization of each of cylinders62a and 62b, which is controlled responsive to commands from
machine tool control system 20, a corresponding one of pallet
shuttle arms 57a and 57b, respectively, is either extended
out from or withdrawn into a corresponding one of carousel
pallet guide pairs 50a and 50b, respectively, to push a pal-
let off of the carousel guides or to pull a pallet onto the
carousel guides, respectively.
Referring now to Fig. 4, releaseable engagement between
each of shuttle arms 57a and 57b and the pallet to be pulled
onto or pushed off of the carousel guides by the pallet shuttle
arm is achieved by a pair of hooks 64 which are each carried
on the distal end of a separate one of the pallet shuttle
arms. Each hook 64 has a notch 64a which is dimensioned to
engage a complementary latch 65 carried by each of pallets
52. In practice, the pallet latch consists of a skirt 66
surrounding the periphery of the pallet, the skirt having an
opening 67 therein which is located so as to receive hook 64
when the pallet shuttle arm is extended after the carousel has
been indexed so as to be slightly off the axis (approximately
5) oE the guides on either the workpiece storage pedestal or
on the machine tool table then supporting the pallet. When
carousel 30 is indexed to align each of the carousel pallet
receiving guides on either side of the now extended pal]et
shuttle arm, with the guides supporting the pallet, the notch
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64a of hook 64 engages that portion of pallet skirt 66 con-
tiguous with opening 67 so that the shuttle arm, such as
shuttle arm 57a, is in engagement with the pallet to enable
the pallet to be pulled onto the carousel guides and to be
pushed subsequently oEf of the carousel pallet guides.
Referring back to Fig. 3, a plurality of dogs 68 (only
one of which is shown) are each affixed to the undersurface
of ring gear 32 so as to extend downwardly therefrom. Dogs
68 are spaced about ring gear 32 so that a separate one of
the dogs is in contact with a detector 70, affixed to the
undersurface of base 14 and coupled to the machine tool con-
trol system, when the guides of one of carousel pallet guide
pairs 50a and 50b are in alignment with the guides on one of
workpiece storage pedestals 5~a through 54e. Unless detector
70 is actuated by one of dogs 68, the pallet then on the
guides of the carousel pallet guide pair furthest from ma-
chine tool table 18 is not pushed off of one of carousel
pallet guides while that pair of carousel guides is indexed
between a pair of workpiece storage pedestals, thereby avoid-
ing accidental discharge of the pallet from the ~arousel pal-
let guide pair while the carousel pallet guides are not in
alignment with the guides on one of the workpiece storage
~edestals.
As an additional safety measure, safety mat switches 72
(Figs. 1 and 2) are each placed on either side of the base of
each of workpiece storage pedestals 54a-54e. Each of safety
mat switches 72 is coupled to the machine tool control system
and when any one of the safety mat switches is actuated by an
operator, such as would occur were an operator to stand on
3n either side of a workpiece storage pedestal to load or unload
that pedestal, then, machine tool control system 20 inhibits
servo controlled motor 40, to prevent rotation of carousel
30, thereby virtually eliminating the likelihood of the opera-
tor being struck by one of the carousel pallet guide pairs
SOa and 50b.
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In operation, a pallet is transferred from one of work
piece storage pedestals 54a through 54e to machine tool table
18 as follows.
1. Carousel 30 is indexed to locate an empty
pair of pallet carousel guides slightly off
the axis of the guides of the workpiece
storage pedestal carrying the desired pal-
let to be transferred.
2. Next, the pallet shuttle arm between the
then-empty carousel pallet guide is ex-
tended by appropriate pressurization of
a corresponding one of hydraulic cylinders
62a and 62b so that hook 64 at the end of
the pallet shuttle arm extends through the
opening 67 in the pallet skirt 56.
3. Thereafter, carousel 30 is rotated to
align the carousel pallet guides with the
workpiece storage pedestal pallet guides
which results in the hook a~ the distal
end of the now-extended pallet shuttle
arm being brought into engagement with
the pallet skirt.
4. The hydraulic cylinder associated with the
now-extended pallet shuttle arm is pres-
surized to withdraw the pallet arm into the
9uides so as to pull the pallet off of the
wor~piece storage pedestal and onto the
guides of the carousel pallet guide pair.
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5. Carousel 30 is then indexed to align the
guides of the carousel pallet guide pair
carrying the just-loaded pallet with the
pallet guides on workpiece table 18 which
S had previously been moved so as to now be
adjacent to base 14.
6. Finally, the pallet is pushed off of the
carousel pallet guides and onto the work-
piece table guides by appropriate pressuri-
zation of the pallet shuttle arm cylinder
and then the carousel is indexed to position
the carousel pallet guides slightly off of
the axis of the workpiece table guides to
unlatch hook 64 from the pallet skirt, there-
by enabling the pallet shuttle arm to be
withdrawn into the guides.
Transfer of a workpiece carrying pallet then on the guides of
machine tool table 18 to one of the workpiece storage pedestals
i5 accomplished in a very similar manner.
Although not shown, in certain applications, most particu-
larly where machine tool 12 is part of a flexible manufacturing
system, it might be desirable to interface the flexible manu-
facturing system transport system to workpiece shuttle and
transport mechanism 10 to enable workpiece carrying pallets to
~5 be received from or transferred to other work stations. Such
interfacing could be accomplished by providing a conventional
pallet shuttle mechanism such as are well known in the art be-
tween the distal end of one of the workpiece storage pedestals
30 and the flexible manufacturing system transport mechanism
to transfer pallets onto or off of the guides of the workpiece
storage pedestal.
The foregoing describes a workpiece storage and shuttle
mechanism for storing a plurality of workpieces and for re-
leaseably engaging a workpiece and transporting the workpiece
between a s~orage location and the machine tool worktable.
Although the illustrative embodiment of the invention has
been described in considerable detail for the purpose of fully
disclosing a practical operative structure incorporating the
invention, it is to be understood that the particular apparatus
shown and described is intended to be illustrative only and
that various novel features of the invention may be incorporated
in other structural forms without departing from the spirit and
ln scope of the invention as de~ined in the subjoined claims.
