Note: Descriptions are shown in the official language in which they were submitted.
7~9
-- 1 --
This invention relates to machine tools with auto-
matic tool changers, and more particularly, to a machine
tool having an internally mounted automatic tool changer.
More especially, the invention is concerned with a counter-
balance system for use with such machine tools.
This application is a division of Canadian Patent
Application S.N. 387,424, filed October 6, 1981.
The advent of automatic tool changers on machine
tools has greatly improved productivity by allowing for
complete automation of machine operation. Exchange of a
cutting tool held by the machine spindle with a new tool,
which previously required the efforts of a human operator,
can now be effectuated automatically by the machine, there-
by permitting unmanned machine tool operation for long
periods of time. The only time it may be necessary for a
human operator to intervene during machine operation is
when a tool must be replaced, due either to wear orbreakage.
Present day automatic tool changing machine tools
include a tool storage magazine located either above,
behind, or to one side of the machine tool spindle.
During a tool change cycle, the tool storage
magazine is rotated to place a selected one of the tool
holding sockets in the tool storage magazine in a ready
position within the reach of a tool transfer arm. The
tool transfer arm, actuated under the command of the
machine tool control system, transfers the tool at the
ready position to the spindle and returns the tool
formerly held in the spindle to the tool storage magazine
at the ready position. Subsequent rotation of the tool
storage magazine p~aces a new tool in the ready position
to facilitate another tool exchange.
Typically, the tool storage magazine carries a
large number of cutting tools, each weighing between 15
and 20 Kg. (30 to 40 lbs.). Because of the weight of the
tools, as well as their size, mounting of the tool stor-
age magazine above, behind, or to the side of the spindle
requires considerable modification of conventional machine
117~'7~
- 2 -
tool designs to avoid interference with machine tool opera-
tions. Further, mounting of the tool storage magazine
above, below, or to the side of the spindle incurs the
disadvantage that mounting of the tool storage magazine
in this manner is likely to expose the cutting tools
carried therein io metal chips and coolants disseminated
during machining operations. Excessive exposure to such
chips and coolant during machining operations can lead to
not only tool damage but also to damage to the tool stor-
age drum itself.
In contrast, the present disclosure concerns amachine tool having a tool storage magazine slidably mounted
within the machine tool upright which permits the tool
storage magazine to be retracted into the recess and away
from the spindle during machining operations thereby
virtually eliminating interference with machine operation,
as well as shielding the cutting tools carried thereon from
disseminated coolant and chips.
The present disclosure seeks to provide a machine
tool having an internally mounted automatic tool changer
retractable into the machine tool upright which virtually
eliminates interference between the tool changer and the
machine tool during machining operations.
The disclosure also seeks to provide a machine
tool having an internally mounted automatic tool changer
retractable into the machine tool upright to shield
cutting tools from metal coolant and chips disseminated
during machining operations.
Still further, the disclosure seeks to provide
a machine tool having an internally mounted automatic
tool changer retractable into the machine tool upright
having reduced complexity and cost in comparison with
other present day automatic tool changers.
In accordance with the invention there is pro-
vided in a counterbalance system for a member that is
movable in a vertical path relative to a fixed base
member of a machine, a piston and cylinder mechanism
having its cylinder secured to one of said members and
11'7~7'~9
-- 3 --
its piston attached to the other of said members; a con-
duit carrying compressed air connected to said cylinder to
produce a force urging said movable member in an upward
direction for counterbalancing its weight, closure means
at the end of said conduit opposite the end connected to
said cylinder for preventing the escape of the compressed
air from the system, and a receiver adapted to contain a
volume of compressed air and being coupled to said conduit
between said cylinder and said closure means and having
sufficient capacity to absorb the compressed air when it is
forced out of said cylinder by the movement of said movable
member in one direction and to return the compressed air to
the system for maintaining the pressure when the compressed
air moves into said cylinder to accommodate the movement of
the movable member in the opposite direction so that the
member is counterbalanced by the uniform pressure in the
closed system as maintained by the operation of saidreciever.
In a particular embodiment, the closure means
comprises a one way valve that admits air into said conduit
but prevents its escape, and including a pressure regulator
coupled between said source of air pressure and said one way
valve for admitting air through said one way valve for
replacing air that may leak out of the system to maintain
the desired air pressure in the system.
In a further particular embodiment, the receiver
may be a sealed space formed in the structure of the machine.
The cylinder may be attached to the base member,
and the piston may include a piston rod extending out of
said cylinder for attachment to said movable member so that
said conduit communicates with said cylinder beneath said
piston so that the air pressure urges said piston upwardly
with sufficient force to counterbalance the weight of the
movable member.
Briefly, in accordance with the preferred embodi-
ment of the inventior., an automatic tool changing machining
center rapidly effectuating exchange of cutting tools with-
out need of a tool transfer arm comprises a worktable for
holding a workpiece which is slidably mounted on the bed
1~7~ 9
-- 4 --
for movement along a first axis.
A vertically extending column or upright is
slidably mounted to the stationary bed for movement along
a second axis perpendicular to the first axis. A spindle-
head, having a rotatably mounted spindle therein, is
slidably mounted on the upright to overlie the table and
is movable on the column along an axis orthogonal to the
first and second axes. Within the column adjacent to the
bed is a recess in which is disposed a tool storage
magazine having a plurality of tool grippers thereon, each
securing a toolholder therein. The tool storage magazine
is slidably mounted on the bed for movement through the
recess along an axis parallel to the first axis.
To exchange a toolholder then held in the spindle
with a toolholder held by one of the tool grippers of the
tool storage magazine, the spindlehead is first moved to a
tool change position. The tool storage magazine then
moves outwardly from the recess so that the empty tool
gripper on the tool storage magazine assigned to the tool-
holder then held in the spindle engages the toolholderheld in the spindle. Thereafter, the toolholder then in
the spindle is unclamped, the spindlehead moves upwardly
to clear toolholder shanks, and then the tool storage drum
is indexed to place a selected one of the toolholders held
therein in a ready position directly beneath the spindle.
Finally, the spindlehead moves downwardly to engage the
spindle with the selected toolholder. Once the spindle
engages the new toolholder, the new toolholder is clamped
therein and the spindlehead returns to the work zone while
the tool storage magazine retracts to its original position
within the recess.
The features of the invention believed to be novel
are set forth with particularity in the appended claims.
However, the invention, itself, both as to organization and
method of operation, together with further objects and ad-
~5~ 117~'7'~9
vantages thereof may best be set forth by reference to the
following description taken in conjunction with the accom-
panying drawings in which:
Figure 1 is a front elevational view of a vertical ma-
chining center in accordance with the preferred embodiment
of the invention;
Fig. 2 is a side elevational view of the vertical ma-
chining center of Fig. l;
Fig. 3 is a cut-away enlarged view of a portion of the
vertical machining center of Fig. 2;
Fig. 4 is a block diagram of the pneumatic system for
counterbalancing the spindlehead of the vertical machining
center of Figs. 1 and 2;
Fig. 4A is a cut-away view of the machine tool upright
of Figs. 1 through 3 illustrating an alternate embodiment
of air receiver employed in the pneumatic system of Fig. 4;
Fig. 5A is a bottom elevational view of a tapered
shank tool gripper comprising a portion of the vertical ma-
chining center of Fig. l;
Fig. 5B is a bottom elevational view of a straight
shank tool gripper comprising a portion of the vertical ma-
chining center of Fig. l;
Fig. 6 is an electrical schematic diagram of the numer-
ical control circuit comprising a portion of the machine
tool of Fig. l; and
Figs. 7A to 7J are schematic sequential illustrations
of the position of the spindlehead and the tool storage
drum of the vertical machining center of Fig. 1 during a
tool change cycle.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Figs. 1 through 3 illustrate the front side and en-
larged cut-away side elevational views, respectively, of
the improved vertical machining center 10 according to the
present invention. Machining center 10 comprises a base or
117~799
--6--
bed 12 mounted to the floor by leveling bolts 13. A pair
of ways 14a and 14b (illustrated in Fig. 2) are mounted on
bed 12 so that each is parallel to a first axis 16 (illus-
trated in Fig. 1). A table 18, for holding a workpiece
thereon, is supported by bearings (not shown) on ways 14a
and 14b for movement therealong. A ball nut 20 (illustra-
ted in Fig. 2) is firmly affixed to the under surface of
table 18 and engages a ball screw (not shown) which is jour-
naled in bed 12 for rotation about axis 16. The ball screw
is driven by a motor 22 (Fig. 1) through combination of pul-
leys 23a and 23b and belt 23c (Fig. 1). Thus, by control-
ling the direction of motor 22 rotation, the position of
table 18 along axis 16 can be controlled accordingly.
A pair of horizontal ways 24a and 24b (best illustra-
ted in Fig. 1) are fastened to bed 12 so as to each be par-
allel to axis 26 (illustrated in Fig. 2), which axis is per-
pendicular to axis 16 (illustrated in Fig. 1). A vertically
extending column or upright 28 is supported by bearings (not
shown) on the ways 24a and 24b for movement therealong. Re-
ferring now to both Figs. 2 and 3, a ball nut 30 is fastenedto the base of upright 28 and threadedly engages a ball
screw 32 which is journaled to bed 12 for rotation about an
axis parallel to axis 26. Ball screw 32 is rotatably driven
by a motor 34 through the combination of pulleys 36a and 36b
and belt 36c (illustrated in Fig. 2). By controlling the
direction of motor 34 rotation, movement of upright 28 on
ways 24a and 24b along axis 26 can be controlled accord-
ingly.
As best illustrated in Fig. 1, a pair of ways 38a and
38b are mounted on the front facing surface of upright 28
parallel to an axis 40, which axis is orthogonal to axes 16
and 26. A spindlehead 42, having a spindle 44 journaled
therein for rotation about axis 40, is slidably mounted to
ways 38a and 38b for movement along axis 40. Referring now
to Fig. 2, a ball nut (not shown) is affixed to spindlehead
42 and engages a ball screw (not shown) journaled to upright
28 for rotation about an axis parallel to axis 40. The ball
117~7'~9
screw is {otatably driven by motor 46 through the combina-
tion of pulleys 48a and 48b and belt 48c. In this manner,
movement of spindlehead 42 along ways 38a and 38b (illus-
trated in Fig. 1) can be controlled by regulating the di-
rection of motor 46 rotation.
To reduce the stress on the spindlehead ball screw and
its support b~arings caused by the downward gravitation
forces on spindlehead 42, a pair of air cylinders 50 (illus-
trated in Figs. 1 and 2) are each mounted between spindle-
head 42 and upright 28 for counterbalancing the spindlehead.Referring now to Fig. 4, which depicts the details of each
of air cylinders 50, it can be seen that each air cylinder
comprises a piston chamber or cylinder 52 having its base
end fastened to machine upright 28. A piston 54, fastened
at its end to spindlehead 42, is vertically reciprocal with-
in piston chamber 52. When spindlehead 42 is moved upwardly,
causing piston 54 to ascend into piston chamber 52, compres-
sed air, admitted into the cylinder through a first port 56
distal from the cylinder base end, fills the expanding pis-
ton chamber volume forcing the piston upwards against thedownward qravitational force, and thus, counterbalancing
spindlehead 42 to prevent undue stress on the spindlehead
ball screw and spindlehead ball screw support bearings. As
piston 54 ascends into piston chamber 52, the air in the
upper end of piston chamber 52 is expelled through a port
58 adjacent to the cylinder upper end. Port 58 also serves
to admit air into piston chamber 52 as piston 54 descends
during downward spindlehead movement.
Port 56, through which compressed air is admitted to
piston chamber 52, is coupled through a line 60 to an air
line 62 which is coupled through a check valve 66 and a pres-
sure regulator 70 to a source of compressed air 72.
Coupled to air line 62 between port 56 and check valve
66 is a receiver 73. Receiver 73 typically takes the form
of a separate stand alone air tank as shown in Fig. 4. Al-
117~7'~9
--8--
ternatively, as illustrated in Fig. 4a, receiver 73 maytake the form of a hollow enclosure within a machine struc-
ture, such as the machine upright 28, having an inlet there-
to connected to air line 62. Referring back to Fig. 4, it
may also be possible for piston chamber 52 itself to func-
tion as the air receiver by extending the piston chamber
lenyth and shortening the piston 54 stroke.
Receiver 73 serves an important role in the operation
of machining center 10 because it reduces the fluctuations
in pressure of compressed air supplied to piston chamber 52
and to the other pneumatic devices represented sche~matically
by a cylinder 74 which is coupled to line 62 by a control
valve 76. To understand how receiver 64 reduces air pres-
sure fluctuations, it will first be necessary to define the
following terms:
Vr = Volume of receiver 73.
Vl = Maximum rod-end volume of piston chamber
52 which occurs when piston 54 is at its
highest vertical position.
V2 = Minimum rod-end volume of piston chamber
52 which occurs when piston 54 is at its
lowest vertical position.
V - Volume contained by all other pneumatic
a devices on machine tool 10 and represen-
ted schematically by the volume of cyl-
inder 74.
A = Piston 54 face area at its rod-end.
Pr = Pressure setting of regulator 70.
PmaX = Maximum system pressure.
Initially, it will be assumed that spindlehead 42,
(illustrated in Figs. 1 to 3) is stationary with air being
admitted into piston chamber 52 through port 56 to force
piston 54 vertically upwards against the downward gravita-
tional force on the spindlehead. After a brief interval,
the system pressure will stablize at Pr and the upward force
ii7~7~9
g
exerted on piston 54, and hence, spindlehead 42 will be
APr. If spindlehead 42 is moved vertically upwards, then
the total pneumatic volume of the system increases because
the rod-end volume of piston chamber 52 will have increased
to Vl. The increase in pneumatic volume causes a corres-
ponding drop in system pressure which regulator 70 immedi-
ately begins to correct by admitting rnore air into receiver
64. Eventually, the system pressure is restored to Pr.
When spindlehead 42 is moved vertically downwards,
total pneumatic volume decreases, owing to the decrease in
piston chamber 52 rod-end volume. Since check valve 66
prohibits reverse air flow, and since there are no relief
valves present, the system pressure rises above Pr. The
maximum system pressure occurs with spindlehead 42 at its
lowest position and can be calculated approximately from:
Pmax Pr (Vr ~ V2 + V )
The ratio of PmaX to Pr can be made smaller by making the
~uantity in parentheses closer to unity. Typically, Va,
Vl and V2 are fixed in accordance with machine require-
ments. Thus, configuring machine 10 with receiver 73 in-
troduces an additional variable Vr into the relationship.
It can readily be observed from the foregoing relationship
that the variation in system air pressure is reduced as Vr
is made larger.
Without the presence of receiver 73, PmaX could become
larger than the maximum allowable system air pressure, and
- the higher pressure might lead to damaging of air cylinders
50, as well as other pneumatic components coupled to line 62.
Although substitution of a relief valve in place of check
valve 66 would prevent system pressure from ever rising
above Pr, employing a relief valve in place of check valve
66 would cause air to be expelled to the atmosphere each
time spindlehead 42 is moved downwardly, obviously a waste-
117~'7~9
--10--
ful practice. In contrast, once receiver 73 is charged,
no additional air need be admitted thereto except to make
up for small leaks and small thermodynamic losses.
It should be noted that although air cylinder 50 has
been illustrated and described with piston chamber 52 af-
fixed to machine upright 28 and piston 54 affixed to spin-
dlehead 42, air cylinder 50 would be equally operative to
counterbalance spindlehead 42 against gravitational force
~f piston chamber 52 were mounted to spindlehead 42 and
piston 54 mounted to machine upright 28. Each air cylinder
50 could also be arranged to push rather than pull spindle-
head 42 upwardly.
Referring back to Figs. 1 through 3, upright 28 in-
cludes a recess 78 therein adjacent to table 18. A pair of
ways 80a and 80b (best illustrated in Fig. 1) are fastened
to bed 12 parallel to axis 26 (illustrated in Fig. 2) so as
to extend into recess 78. As is best illustrated in Figs.
1 and 3, a tool storage magazine 82 is slidably mounted on
ways 80a and 80b for movement therealong. Tool storage
magazine 82 is advanced from or retracted into recess 78
along ways 80a and 80b by an air cylinder 84 (illustrated
in Fig. 3) fastened at one end to bed 12 and at the other
end to the tool storage magazine.
In the presently preferred embodiment, tool storage
magazine 82 takes the form of a drum comprised of a disc
88 (illustrated in Fig. 3) having a plurality of tapered
shank or straight shank tool grippers 90a and 90b, respec-
tively, fastened to disc 88 about the perimeter thereof by
bolts 92 for gripping straight shank and tapered shank tool-
holders 94a and 94b, respectively.
Although disc 88 is depicted in Fig. 3 as having bothtapered and straight shank tool grippers fastened about the
perimeter thereof for the purpose of illustration, in prac-
tice, disk 88 has only one type of tool gripper, either
straight shank or tapered shank, affixed thereto about the
perimeter thereof. This is because the machine tool spin-
ii7~'7~9
--11--
dle is usually configured to receive only one type of tool-
holder such as a tapered shank toolholder and cannot, for
example, without modification, accept a straight shank
toolholder and vice versa.
The details of tapered shank tool gripper 90a are il-
lustrated in Fig. 5a. Tool gripper 90a is comprised of a
strap 95a which is fastened to disc 88 by bolts 92 so as to
extend radially from the disc a short distance therebeyond
for aligning tapered shank toolholder 94a held by the tool
gripper. A pair of substantially V-shaped gripping wires
95b and 95c, respectively, stacked on top of one another,
are each fastened at their closed end to strap 95a by a re-
taining screw 95d. The arms of gripping wires 95b and 95c
are urged toward one another to engage grooves on tapered
shank toolholder 90a by a separate one of a pair of wire re-
tainers, each designated 95f, fastened to disc 88 on either
side of strap 95a. Typically, each of wire retainers 95f is
comprised of an annular collar having a pair of grooves in-
scribed about the circumference thereof for engaging a sep-
arate one of gripping wires 95b and 95c, respectively. Con-
figured in this manner, wire retainers 95f assure firm re-
tention of tapered shank toolholder 90a by gripping wires
95b and 95c, yet, permit release of the toolholder from the
gripping wires once tapered shank toolholder 94 is firmly
engaged in the machine tool spindle and disc 88 is moved
laterally away from the spindle.
Fig. Sb illustrates the details of straight shank tool
gripper 90b. Straight shank tool gripper 90b is comprised
of a strap 95a' which is fastened to disc 88 by bolts 92 so
as to extend radially from disc 88 a short distance there-
beyond. A pair of jaws 95b' are pivotally fastened to the
end of strap 95a' for clamping the shank of straight shank
toolholder 94a. To firmly urge jaws 95b' against the shank
of toolholder 94a, a V-shaped gripping wire 95c' is fastened
at its closed end to strap 95a by a retaining screw 95d' and
117~'7'~9
-12-
is urged at each of its sides against the jaws 95b' to en-
gage a groove therein by a separate one of wire retainers
95f' fastened to disc 88 on either side of strap 95a'.
Typically, each of wire retainers 95f' comprises an annu-
lar collar having a circumferential groove therein for en-
gaging one of the sides of the gripping wire. Jaws 95b',
when urged against one another by gripping wire 95c', firm-
ly secure tool shank 94a, yet, they permit the tool shank
to be disengaged therefrom when the tool shank is firmly
gripped in the spindle and disc 88 is moved laterally from
the spindle during the tool chanse cycle.
Referring back to Fig. 3, disc 88 is carried by a
shaft 96 which is journaled to a housing 97 that is slid-
ably mounted by bearings (not shown) to ways 80a and 80b
for movement therealong. A motor 98 is affixed by plate
99 to housing 97 so that the shaft of motor 98 is parallel
to shaft 96. The shaft of motor 98 is coupled by a chain
or belt tnot shown) to shaft 96 so that shaft 96, and hence,
disc 88, are rotatably driven by motor 98 to rotate a selec-
ted one of the toolholders, held by a separate one of the
tool grippers on disc 88, to a ready position to facilitate
tool exchange. The angular position of disc 88, with re-
spect to a non-rotatable member, such as spindlehead 42, is
determined by an angular position transducer 100, which is
typically a resolver. Resolver 100 is coupled to motor 98
and generates an electrical control signal which varies in
accordance with motor 98 shaft rotation. Since the shaft
rotation of motor 98 is directly related to the rotation of
disc 88, the resolver output signal provides an accurate in-
dication of the position of disc 88 with respect to spindle-
head 42. The output signal of resolver 100 is supplied to
a machine tool numerical control system 101, which controls
motor 98 rotation responsive to the resolver output signal
in accordance with commands from the machine tool control
system (not shown).
The details of the numerical control circuit 101 are
shown schematically in Fig. 6. A controller lOla, typi-
117~7'~9
-13-
cally a programmed electronic data processing device with
internal memory, is coupled to the machine tool control
system (not shown) for receiving commanas therefrom, typi-
cally stored on tape, which specify a particular one of the
tool grippers on the tool storage drum. Controller lOla is
also coupled to resolver 100 to receive feedback informa-
tion indicative of drum motor 98 angular shaft position and
processes the machine tool control system tool storage drum
rotation tape command together with the output signals pro-
'duced by resolver 100, in the manner described hereinafter,
to produce a drum motor command signal for exciting motor
98. During intervals between receipt of successive tool
storage drum rotation tape commands, controller lOla advan-
tageously generates X axis motor command signals to excite
motor 22 (Fig. 1) which drives an associated ball screw to
propel table 18 (Fig. 1) along axis 16 (Fig. 2) in accord-
ance with machine tool control system X axis table movement
tape commands and output signals from a resolver lOlc cou-
pled to motor 22.
The output signal from controller lOla, which is either
a drum motor command signal, or an X axis motor command sig-
nal, depending on whether the machine tool control system
tape commands supplied the controller are tool storage drum
rotation tape commands or X axis table movement tape com-
mands, respectively, is supplied to the input of an ampli-
fier lOld where it is summed with the output signal of a
respective one of tachometers lOle and lOlf which are re-
sponsive to drum motor 98 and motor 22 shaft speed, respec-
tively. Tachometers lOle and lOlf are coupled to the input
of amplifier lOld through a separate one of electronically
actuated switches lOlg and lOlh, respectively, which are
controlled by controller lOla so that when the controller is
generating drum motor command signals, switch 1019 is closed
and switch lOlh is open. During intervals when controller
lOla is yenerating X axis motor command signals, the conduc-
tion state of switches 1019 and lOlh is thus reversed.
1178799
-14-
An electronically actuated switch lOli, responsive to
commands from controller lOla, couples the output of ampli-
fier lOld between drum motor 98 and motor 22 so that only
the drum motor receives drum motor command signals from the
controller, and likewise, only motor 22 receives X axis
motor command signals from the controller.
In operation, when either a machine tool control sys-
tem drum rotation tape command, specifying a particular tool
gripper whose position on the drum is known to the control-
ler, or an X axis table movement tape command, specifyingthe desired X axis coordinate position of table 18, is re-
ceived by controller lOla, the controller references its
internal memory to determine the previous tool storage drum
angular position or X axis table position, re<spectively, and
then generates a drum motor command signal, or an X axis
motor command signal, in accordance with the input tape com-
mand from the machine tool control system, the output signal
of a respective one of resolvers 100 and lOlb, respectively,
and the previously stored position information in internal
memory. The controller output command signal, being either
a drum motor command signal or an X axis motor command sig-
nal, is summed with the output signal of a respective one of
tachometers lOle or lOlf and then amplified before being
supplied to a respective one of motors 98 and 22 to cause
the desired rotation of the tool storage drum or the de-
sired X axis movement of table 18, respectively. By servo
controlling motor 98 in accordance with output signal of
resolver 100, and by servo controlling the motor 22 in ac-
cordance with the output signal of resolver lOlc, accurate
angular positioning of tool storage drum and accurate X axis
positioning of the table is thus assured.
To shield the toolholders, as well as disc 88 and
housing 97 from metal chips and coolant disseminated during
the machining operations, tool storage magazine 82 includes
a cover 102 for substantially sealing the open end of recess
78 adjacent to spindlehead 42. Cover 102 typically consists
11'7~799
-15-
of a pair of quarter-cylindrical sections which are each
mounted to the flanged end of a bushing 104 which rotates
about the end of shaft 96 distal from slides 80a and 80b.
When tool storage magazine 82 is retracted into recess 78,
spring means (not shown) urges the two cylindrical sections
of cover 102 together to shield the tool storage magazine.
Advancing tool storage magazine 82 along ways 80a and 80b
from recess 78 causes a cam 106 on the outer surface of
cover 100 to engage a block 108 fastened ~o the top wall of
recess 78, thereby forcing the two sections of cover 100
apart so that toolholders 94a and 94b on disc 88 may extend
through this opening.
As previously indicated, metal chips and coolant are
disseminated during machining operations. To protect ways
24a and 24b (best illustrated in Fig. 1) from any damage
caused by the disseminated coolant and chips, a rubber cover
109 (shown in Fig. 3) is fastened at one end to the base of
upright 28 adjacent to spindlehead 42 and at the other end
to a spring-wound roller 110 mounted on bed 12 beneath ways
24a and 24b. As upright 28 moves along ways 24a and 24b,
spring-loaded roller 110 (shown in Fig. 3) keeps cover iO9
sufficiently taut so that the cover will not bunch up and
be caught between the upright and w~ys 24a and 24b.
A complete tool change cycle will now be described
with respect to Figs. 7A through 7J, respectively. To sim-
plify discussion of the tool change cycle, it is assumed
that a toolholder is presently secured in the machine tool
spindle and that the machine tool spindle is performing a
designated machining operation, such as drilling, milling,
tapping, or the like. Following completion of the machining
operation, tool exchange is initiated by indexing tool stor-
age magazine 82, that is, rotating disc 88 as illustrated in
Fig. 7A, to place the empty tool gripper 90a on the disc
assigned to the tool then held in the machine tool spindle
to the ready position. Next, spindlehead 42 is moved to a
tool change position, as illustrated in 7B, so as to be ad-
li7~'7'~9
--16--
jacent to the empty tool gripper on disc 88. Once spindle-
head 42 is moved to the tool change position, tool storage
magazine 82 is advanced from the recess in the machine tool
upright, as illustrated in Fig. 7C, so that the empty tool
gripper on disc 88 eng~ges the tool then held in spindle
44. When the empty tool gripper on disc 88 firmly engages
the tool then held in spindle 44, the spindle unclamps the
tool, as illustrated in Fig. 7D, and then, spindlehead 42
is moved upwardly, as depicted diagrammatically in Fig. 7E,
so that spindle 44 can clear the shanks of toolholders 90a
secured to disc 88.
Following upward movement of spindlehead 42, tool stor-
age magazine 82 is indexed to position the selected one of
toolholders 94a directly beneath spindle 44, as illustrated
in Fig. 7F. Next, spindlehead 42 is moved downwardly, as
shown in Fig. 7G, so that spindle 44 engages the tool posi-
tioned directly therebeneath. Once the new tool is firmly
engaged in spindle 44, spindle 44 then clamps the new tool,
as illustrated in Fig. 7~, and thereafter, tool storage mag-
azine 82 is retracted into the recess in the machine toolupright, as illustrated in Fig. 7I. The machine tool change
cycle is completed following movement of spindlehead 42 to
the workpiece, as illustrated in Fig. 7J.
From the foregoing description, it can readily be ob-
served that the present invention provides a vertical machin-
ing center which automatically accomplishes tool exchange
without the necessity of a tool transfer arm. Since tool ex-
change is accomplished in the present invention by moving
both the tool storage magazine and the machine spindlehead,
the need for a transfer arm is thereby obviated, thus redu-
cing machine tool complexity and expense. Although vertical
machining center 10 has been described with a tool storage
magazine 82 slidably mounted on bed 12 for linear movement
in a direction parallel to the direction of linear move-
ment of upright 28, in certain applications it may be desi-
li7~799
-17-
rous to fix the position of tool storage drum 82 so that
it partially extends into recess 78 of the upright. When
tool storage driver 82 is mounted to the bed 12 for rota-
tion about a fixed axis, tool exchange is facilitated by
moving upright 28 to and from the tool storage drum.
While certain features of the invention have been
shown by way of illustration, many modifications and changes
will occur to those skilled in the art. It is, therefore,
to be understood that the appended claims are intended to
cover all such modifications and changes as fall within the
true spirit of the invention.
