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Claims  |
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I claim:
1. In a machine tool, in combination:
a traversing work table having a base;
a mounting plate supported on said base for vertical reciprocating movement
and rotary indexing movement;
annular toothed coupling means on the base surrounding the mounting plate;
a pallet seated on the mounting plate, the underside of said pallet having
annular toothed coupling means meshed with the coupling means on the base;
interengaging clamp means on the mounting plate and locking means on the
pallet locking the latter onto the former;
means for elevating the mounting plate to a predetermined level for
disengaging said interengaging means to unlock the pallet from the
mounting plate;
and means for elevating the mounting plate to a first level below said
predetermined level to unmesh the pallet coupling means from the base
coupling means for unitary indexing movement of the mounting plate and the
pallet.
2. The combination of claim 1 which includes driving means operable when
the mounting plate is at said predetermined level to move the clamp means
in one direction to disengage the clamp means from the locking means and
in the opposite direction to engage the clamp means with the locking
means.
3. The combination of claim 2 which includes movable means cooperant with
said clamp means and with the mounting plate to selectively lock the clamp
means to the mounting plate or release it for movement on the mounting
plate, and means for moving said movable means in response to movement of
said mounting plate to said predetermined level to release said clamp
means for movement on the mounting plate.
4. The combination of claim 3 in which the clamp means commprises a clamp
ring rotatably supported in the mounting plate, the movable means
comprises a longitudinally slidable drive pin which impales the mounting
plate and the ring, and the means for moving the movable means comprises a
cam that is contacted by an end of said drive pin as the mounting plate is
elevated to said predetermined level to slide the drive pin out of the
mounting plate.
5. The combination of claim 4 which includes interengaged detent means on
the mounting plate and the underside of the pallet to prevent movement of
the pallet on the plate.
6. The combination of claim 4 in which the annular toothed coupling means
on the base consists of a plurality of arcuate toothed segments separated
from one another by gaps of arcs at least as large as said segments, and
which includes rotatable cover means having peripheral flanges which
normally overlie said gaps, and means for rotating the cover means
simultaneously with rotation of the clamp ring to move said flanges over
the segments when the pallet is disengaged from the mounting plate.
7. The combination of claim 6 in which the drive pin impales the cover
means as it is moved endwise out of the mounting plate to tie the cover
means to the clamp ring.
8. The combination of claim 6 in which the cover means is provided with a
peripheral segment that has lateral teeth, and the driving means engages
said lateral teeth to rotate the cover plate and the clamp ring.
9. The combination of claim 8 which includes a pallet changer with which
the work table may be aligned, longitudinally extensible pallet carrying
rails on the pallet changer for placing pallets on the mounting plate and
removing them therefrom, and in which the driving means comprises a
toothed rack on one of said rails which meshes with said lateral teeth
when the mounting plate is at said predetermined level.
10. The combination of claim 1 which includes a pallet changer adjacent the
work table, said pallet changer having a base, a head rotatably mounted on
said base, first and second pairs of rails movably mounted on said head
for longitudinal reciprocation between an extended position and a
retracted position, said pairs of rails extending in different directions
from the head, means for rotating said head on the base to move either of
said pairs of rails into alignment with the work table so that extension
of the aligned pair of rails moves it to a supporting position beneath the
marginal portions of a pallet on the work table, driving means on a rail
of each pair which operatively connects with the clamp means to disengage
said clamp means from a pallet as said pair of rails is extended with the
mounting plate at said predetermined level and to engage said clamp means
with a pallet as said pair of rails is retracted with said mounting plate
at said predetermined level, and means for causing the apparatus to
function in a pallet changing cycle in which
a. the mounting plate is elevated to said predetermined level,
b. a first, empty, pair of rails is moved to supporting position, thereby
disengaging the clamp means from the pallet,
c. the mounting plate is lowered, leaving the pallet supported on the first
pair of rails,
d. said first pair of rails is retracted, carrying the pallet,
e. the pallet changer head is rotated to align the second pair of rails,
carrying a new pallet, with the work table,
f. said second pair of rails is extended to position said new pallet above
the mounting plate,
g. the mounting plate is elevated to said predetermined level and lifts
said new pallet off the second pair of rails,
h. the second pair of rails is retracted, thereby engaging the clamp means
with the pallet,
i. the mounting plate is lowered.
11. The combination of claim 10 in which the clamp means comprises a clamp
ring rotatably supported in the mounting plate, movable means cooperant
with said clamp ring and with the mounting plate to selectively lock the
clamp ring to the mounting plate or release it for rotation in the
mounting plate, and means for moving said movable means in response to
movement of the mounting plate to the predetermined level to release the
clamp ring for rotation.
12. The combination of claim 11 in which the driving means comprises a rack
on one of the rails of each pair of rails, and in which an arcuate segment
which is operatively connected with the clamp ring has lateral teeth with
which each of said racks meshes when the rails are extended and retracted
with the mounting plate at the predetermined level.
13. The combination of claim 12 in which the annular toothed coupling means
on the base consists of a plurality of arcuate segments separated from one
another by gaps of arcs at least as large as said segments, which includes
rotatable cover means having peripheral flanges which normally overlie
said gaps, and means for selectively tieing the cover means to the clamp
ring when said ring is released from the mounting plate, and in which the
arcuate segment is mounted on the periphery of the cover plate flanges.
14. The combination of claim 13 in which the movable means cooperant with
the clamp ring and mounting plate comprises a longitudinally slidable pin
which impales the mounting plate and the ring, and in which the means for
moving the movable means comprises a cam that is contacted by an end of
said pin as the mounting plate is elevated to said predetermined level to
slide the pin out of the mounting plate and into a hole in the cover
means.
15. In a machine tool, in combination:
a traversing work table having a base with a central vertical opening;
a circular mounting plate supported in said opening for vertical
reciprocating movement and rotary indexing movement;
a clamp ring surrounding and carried by said mounting plate, said clamp
ring being rotatable about the mounting plate;
a radially movable drive pin impaling the clamp ring and extending into a
socket in the plate for selectively locking said ring to the plate or
releasing it for rotation about the plate;
means for moving said drive pin to release the ring in response to upward
movement of the plate and ring to a predetermined level;
annular toothed coupling means on the base surrounding the ring;
a pallet, the underside of said pallet having annular toothed coupling
means meshed with the coupling means on the base, and said underside also
having locking means which is selectively engaged or disengaged by the
clamp ring upon rotation of said ring in opposite directions;
means for elevating the plate to a first level below said predetermined
level to unmesh the pallet coupling means from the base coupling means for
unitary indexing movement of the mounting plate, clamp means and pallet;
means for elevating the plate to said predetermined level to release the
clamp ring for rotation on the plate;
and means operatively connectable with said clamp ring to rotate it for
engaging or disengaging the pallet locking means when the plate is at said
predetermined level.
16. The combination of claim 15 which includes detent means on the plate
and on the underside of the pallet to prevent movement of the pallel on
the plate.
17. The combination of claim 16 which includes a pallet changer adjacent
the work table, a pair of rails on said pallet changer which are adapted
to support a pallet, means for reciprocating said rails longitudinally
between an extended position beneath the marginal portions of a pallet on
the mounting plate and a retracted position, and means on said pair of
rails which operatively connects with the clamp ring to disengage it from
a pallet as the pair of rails is extended with the mounting plate at said
predetermined level and to engage said clamp means with a pallet as the
pair of rails is retracted with said mounting plate in said predetermined
position.
18. In a machine tool, in combination:
a traversing work table having a base;
a mounting plate supported on said base for vertical reciprocating movement
and rotary indexing movement;
annular toothed coupling means on the base surrounding the mounting plate,
said coupling means consisting of a plurality of arcuate toothed segments
separated from one another by gaps of arcs at least at large as said
segments;
a pallet seated on the mounting plate, the underside of said pallet having
annular toothed coupling means meshed with the coupling means on the base;
a clamp ring which is rotatable in the mounting plate and interengaged with
locking means in the bottom of the pallet;
means for elevating the mounting plate to a predetermined level;
means operable when the mounting plate is at said predetermined level to
rotate the clamp ring for disengaging it from the pallet;
and rotatable cover means having peripheral flanges which normally overlie
the gaps in the coupling means on the base, said cover means being
rotatable simultaneously with the clamp ring to move said flanges over the
toothed segments when the pallet is disengaged from the mounting plate.
19. The combination of claim 18 which includes a radially movable drive pin
impaling the clamp ring and extending into a socket in the mounting plate
for selectively locking said ring to the plate or releasing it for
rotation in the mounting plate, an aperture in the cover means aligned
with said drive pin, and means for moving said drive pin in response to
upward movement of the mounting plate and ring to said predetermined level
to move it out of the socket in the mounting plate and into the hole in
the cover means.
20. The combination of claim 19 in which the means operable to rotate the
clamp ring includes an arcuate peripheral toothed segment on the cover
plate and driven rack means drivingly engageable with said toothed segment
when the mounting plate is at the predetermined level.
21. In a machine tool, in combination:
a traversing work table having a base;
a mounting plate supported on said base for vertical reciprocating movement
and rotary indexing movement;
annular toothed coupling means on the base surrounding the mounting plate;
a pallet seated on the mounting plate, the underside of said pallet having
annular toothed coupling means meshed with the coupling means on the base;
interengaging clamp means on the mounting plate and locking means on the
pallet locking the latter onto the former;
and means for elevating the mounting plate to unmesh the pallet coupling
means from the base coupling means. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
Optimum utilization of high capacity machine tools such as milling machines
requires that the work table be provided with interchangeable work
supporting pallets and a pallet changer so that as soon as a machining
operation is completed, a finished work piece fixtured on a pallet may be
removed from the machine and a new work piece fixtured on a second pallet
may be placed in the machine in the shortest possible time.
One of the absolute essentials of a machine tool work table which uses
pallets is that the pallets must be firmly and accurately locked to the
work table; and in the case of an indexing work table it is necessary that
indexing of the table take place without disturbing the orientation of the
pallets on the table. Positive indexing is customarily accomplished by the
use of an annular toothed coupling which is preferably a Curvic coupling
because of the particular tooth conformity of such couplings which causes
a table to assume precisely the same angular and lateral location in spite
of wear in the coupling teeth. The work table is arcuately indexed
relative to the traversing base by elevating it sufficiently to disengage
the coupling teeth and rotating it to the desired extent for the next
operation.
However, where the indexing table carries a pallet, rather than directly
supporting the workpiece, the need for precise positioning of the pallet
with reference to the rotary indexing member has commonly resulted in the
use of two Curvic couplings or suitable equivalents, with a first such
coupling being used to locate the pallet with respect to an indexable
mounting plate, and with the second being used to positively fix the
position of the mounting plate relative to the traversing table base.
By reason of the foregoing structure, it has previously been necessary to
provide two interfaces between the traversing table and the pallet, one
such as a Curvic coupling between a pallet and a mounting plate, and
another between the mounting plate and the work table base. This requires
relatively complex mechanism.
Another problem in the use of Curvic couplings with pallet carrying
indexing type work tables is the protection of the exposed, upwardly open
coupling teeth from the time a pallet is removed until another pallet is
in position and the coupling teeth are meshed.
SUMMARY OF THE INVENTION
In the present apparatus, a traversing work table carries a mounting plate
which is supported for vertical reciprocating movement and rotary indexing
movement. A clamp ring is rotatably supported in the mounting plate so
that it may be turned through an angle of 45.degree. about a vertical axis
to make a bayonet type engagement with the underside of a pallet. Detent
means on the mounting plate and on the underside of the pallet prevent the
pallet from moving with the clamp ring.
The base of the work table has a segmented Curvic coupling which surrounds
the mounting plate. It consists of alternate approximately 30.degree.
toothed segments and 60.degree. gaps. An annular Curvic coupling member on
the underside of the pallet meshes with the coupling segments on the base
when the mounting plate is in a lowermost position which it occupies
during a machining operation. In that position the clamp ring is locked
against rotation in the mounting plate by a radially movable drive pin
which impales the clamp ring and extends into a socket in the mounting
plate.
A cover member which surrounds the clamp ring inwardly of the Curvic
coupling has outwardly extending peripheral flanges which are in the
60.degree. gaps between the toothed segments of the base coupling; and on
the extreme outer periphery of the flanges is an arcuate segment having
laterally extending teeth.
When a pallet is to be changed, the mounting plate is elevated to a
predetermined level, and during this movement the drive pin rides over a
cam surface which disengages it from the socket in the mounting plate and
projects it into an opening in the cover member. This releases the clamp
ring from the mounting plate and drivingly connects it to the cover.
The foregoing operations may occur only when the traversing table is at a
"home" position, where it is aligned with a pallet changer. When the
mounting plate with the pallet on it has reached the predetermined level,
a pair of pallet changer rails is projected to move an empty end portion
of the rails to a position beneath the peripheral portions of the pallet
on the mounting plate; and during this movement a set of rollers on one of
the rails engages with the laterally extending teeth on the cover member
to rotate the cover member and the clamping ring 45.degree.. This moves
the cover flanges to positions overlying the toothed segments of the
Curvic coupling element on the base, and simultaneously disengages the
bayonet connection between the clamp ring and the pallet. Detent means on
the mounting plate and the bottom of the pallet maintain location of the
pallet.
The mounting plate, clamp ring and cover member are then lowered, leaving
the pallet on the change rails, and permitting the cover flanges to rest
upon the toothed segments of the Curvic coupling member on the base. It
also, of course, disengages the laterally extending teeth on the cover
from the rollers on the pallet changer rail so that when the rails are
retracted to remove the pallet the clamp ring and cover member are not
rotated.
After the pallet changer rails are retracted the changer is rotated to
bring the opposite end of the rails, bearing a new pallet carrying a
workpiece, adjacent the mounting plate so that the new pallet may be
positioned above the mounting plate when rails are again extended.
When the new pallet is in position above the mounting plate, the latter is
again elevated to lift the pallet off the rails and engage the laterally
extending teeth on the periphery of the cover member with a set of rollers
on one of the pallet changer rails. The rails are then retracted, and the
rollers rotate the cover member and the clamp ring 45.degree. to their
original positions, thereby interengaging the bayonet connection on the
clamping ring and the fresh pallet and also returning the cover flanges to
a position above the gaps in the Curvic coupling on the base. When the
pallet changer rails are fully retracted, the mounting plate is again
lowered to its original position, and during this movement the radial
drive pin rides off the actuating cam surface so that a drive pin spring
returns the pin to its original position tieing the clamp ring to the
mounting plate and disengaging it from the cover member. The Curvic
coupling element on the bottom of the fresh pallet is engaged with the
coupling segments on the base. This prepares the apparatus to commence a
machining operation on the fresh workpieces.
When indexing of the pallet is required during a machining operation, the
mounting plate is elevated just enough to disengage the Curvic coupling
elements so that the mounting plate, the clamp ring and the pallet may be
rotated as a unit to a new position, after which the mounting plate is
lowered to re-engage the Curvic coupling elements.
The apparatus of the present invention is commonly used with a milling
machine having numerical control which controls pallet indexing and moves
the traversing work table to home position when an operation is completed.
At this point the pallet changing operation may conveniently be carried
out automatically by an electrohydraulic system which carries it through
the entire pallet changing sequence and then reactivates the numerical
control. The pallet changing operation is so described in the following
detailed description; although it is apparent that if desired the pallet
changing steps could be included in the numerical control program.
THE DRAWINGS
FIG. 1 is a perspective view of a multipurpose numerically controlled
machining center with which the apparatus of the present invention is
utilized;
FIG. 2 is a plan view with parts broken away of the traversing work table
and pallet changer in the positions that they occupy immediately prior to
a pallet changing operation;
FIG. 3 is a bottom plan view of a pallet;
FIG. 4 is a fragmentary sectional view on an enlarged scale taken
substantially as indicated along the line 4--4 of FIG. 2;
FIG. 5 is a fragmentary perspective view of the traversing work table in
the position that the pallet carrying piston, mounting plate and
associated parts occupy after a first has been removed and before a second
pallet is mounted;
FIG. 6 is a view similar to FIG. 5 illustrating the components of the
apparatus in the position that they occupy when the piston has been
elevated for removal of a pallet but before the clamping ring has been
rotated;
FIG. 7 is a sectional view an enlarged scale taken substantially as
indicated along the line 7--7 of FIG. 2 with the components in the
position that they occupy when a pallet is clamped for a machining
operation;
FIG. 8 is a sectional view taken substantially as indicated along line 8--8
of FIG. 2;
FIG. 9 is a view similar to FIG. 7 with the parts in the same position as
is illustrated in FIG. 6;
FIG. 10 is a hydraulic circuit and electrical control schematic for the
pallet carrying piston and mounting plate;
FIG. 11 is a pneumatic circuit for a pallet clamping sensor;
FIG. 12 is a pneumatic circuit for a pallet changer brake; and
FIG. 13 is a hydraulic circuit and electrical control schematic for the
pallet changer.
DETAILED DESCRIPTION OF THE INVENTION
I. General Description of a Machining Center Including the Invention
Referring to the drawings in detail, and referring first to FIG. 1, the
invention is illustrated in conjunction with a machining center which
includes a column, indicated generally at C, upon which a spindle head,
indicated generally at S is mounted in ways for vertical movement to
provide the Y-axis stroke of the machine. The column is mounted upon a
wing base, indicated generally at W, providing the Z-axis stroke of the
spindle head S. Adjacent the wing base and the column is a tool storage
center, indicated generally at T; and tool changer means, indicated
generally at TC, provides means for transferring tools between the tool
storage T and the spindle head S.
A table base, indicated generally at B, supports a traversing work table,
indicated generally at 15, which is mounted for movement along the table
base B in front of the wing base W and column C to provide the X-axis, or
table stroke. The traversing work table 15 is constructed to receive a
pallet, indicated generally at P, as will be described in detail
hereafter.
Alongside the table base B, on the side opposite the wing base W, is a
pallet changer, indicated generally at PC, which is constructed and
arranged to remove the pallet P from the work table 15 and place a fresh
pallet P1 in a position to be connected to the work table as will be
described in detail. The pallet changer PC is so located with respect to
the table base B that when the work table 15 is at its home position and
the pallet indexed to its home position, the pallet P is properly aligned
with the pallet changer PC.
II. Detailed Description of the Work Table and Pallet
Referring now particularly to FIGS. 2, and 5 to 7, the work table 15 is
carried upon rails (not shown) on the table base B; and includes a central
pedestal structure, indicated generally at 16, on top of which there is a
base 17.
Referring now particularly to FIGS. 7 to 9, the base 17 is annular and a
cylinder, indicated generally at 18, is rotatably mounted in the central
opening in the base in a ball bearing raceway 19. The cylinder has a
sidewall 20 and a top wall 21 which define a chamber 22, and there is a
central bore 23 in the top wall 21. Embracing the cylinder sidewall 20 is
a gear 24 which is seen in FIG. 8 to be engaged by a worm 25, so that the
cylinder 18 may be rotated in the base 17. A carrier ring 26 is mounted in
the lower end of the central opening of the base and supports an annular
seal 26a; and a seal 27 engages the piston sidewall 20 above the raceway
19.
Mounted in the cylinder chamber 22 is a piston, indicated generally at 28,
which has a lower portion 29 of a first diameter, an intermediate portion
30 which is of larger diameter to make a sliding fit in the chamber 22,
and an upper portion 31 which makes a sliding fit in the bore 23 in the
cylinder top wall 21. A flanged ring 32 makes a snug sliding fit around
the lower portion 29 of the piston 28 and is secured to the cylinder
sidewall 20 by means of bolts such as the bolt 33 seen in FIGS. 7 and 8,
so that it closes the lower end of the cylinder 22 and is externally
sealed by the annular seal 26a. Sealing ring 34 in the flanged ring 32,
sealing ring 35 in the piston portion 30, and sealing ring 36 in cylinder
top wall bore 23 provide a fluid tight seal between the cylinder 18 and
the piston 28. A sealing ring is also provided at the interface of
cylinder sidewall 20 on ring 32.
A vertical bore 37 in the lower end of the piston 28 has a threaded lower
extremity to receive a threaded hollow plug 38 of a hydraulic fitting,
indicated generally at 39. As best seen in FIG. 9, the fitting 39 includes
a tube 40 which is positioned in the bore 37 so as to define with the bore
an annular hydraulic fluid passage which communicates with a transverse
bore 42 that opens exteriorly of the piston portion 29 below the piston
portion 30 so that hydraulic fluid admitted through an inlet passage 43
(FIG. 8) in the lower end portion of the fitting 39 can enter the cylinder
chamber 22 between the flanged ring 32 and the piston portion 30 to
elevate the piston from the position of FIGS. 7 and 8 to the position of
FIG. 9.
The upper end portion of the tube 40 comprises an enlarged head 44 which is
provided with a sealing ring 45 that seals the upper end portion of the
tube in the upper end portion of the bore 37; and the tube 40 communicates
with a lateral bore 46 which is in the upper piston portion 31 above the
enlarged piston portion 30 so that hydraulic fluid admitted through a port
47 in the lower end of the fitting 39 may pass through the bore 46 and
into grooves 21a which are formed in the cylinder top wall 21 so as to
create a hydraulic pressure above the piston portion 30 for the purpose of
returning the piston from the position of FIG. 9 to the position of FIGS.
7 and 8.
The control system for raising and lowering the piston 28 will be described
hereinafter in conjunction with the entire control system for the pallet
changing cycle.
As seen in FIG. 7, the upper end of the piston 28 is provided with vertical
bores to receive machine screws 48 by means of which a circular mounting
plate 49 is affixed to the top of the piston 28 so that functionally the
piston and the mounting plate constitute a unitary structure. The pallet P
is disposed above the mounting plate 49, and as seen in FIG. 8, studs 50
in the mounting plate have tapered portions projecting above the surface
of the plate 49 to loosely engage with mating sockets 51 in the bottom of
the pallet P, thus providing detent means which prevents movement of the
pallet with reference to the mounting plate when those members are not
otherwise locked together.
Referring again to FIGS. 2 and 7, a clamp ring 52 which surrounds the
mounting plate 49 has an internal circumferential shoulder 53 which fits
beneath a step 54 in the mounting plate 49, and a ring 55 which is secured
to the underside of the mounting plate underlies the inner shoulder 53 on
the clamping ring to maintain the ring 52 in its operative relationship
with reference to the plate 49. As seen in FIGS. 7 and 9, at one side of
the ring 55 is a vertical sleeve 56 which makes a friction fit in a hole
in the ring 55 and slidingly receives a connecting pin 57 which is seated
in a socket in an upper end portion of the cylinder sidewall 20, so that
the piston 28 and the mounting plate 49 are tied to the cylinder 18 for
rotation therewith.
The clamp ring 52 is seen in FIGS. 2, 5 and 6 to have four radially
outwardly extending and overhanding clamp lugs 59 which form part of a
bayonet type interconnection, the other part of which consists of radially
inwardly extending locking flanges 60 of a pallet locking ring 61 which is
seen in FIG. 3 to be on the underside of the pallet P. Since the
interconnection between the clamp ring 52 and the pallet P is of the
bayonet type, the flanges 60 are, of course, spaced from the underside of
the pallet and have top surfaces with which the clamp lugs 59 of the clamp
ring 52 are engaged by rotating the clamp ring in the mounting plate 49
when the pallet is seated upon the mounting plate with the detent means 50
and 51 engaged to restrain the pallet from rotating with the clamp ring.
Referring again to FIGS. 7 and 9, the clamp ring 52 is releasably engaged
with the mounting plate 49 for selective rotation with the mounting plate
or independently of the mounting plate. This is provided for by drive pin
means, indicated generally at 62, which includes a radially movable drive
pin 63, a drive pin spring 64, and a drive pin actuating plunger 65. The
drive pin 63 has a shank which impales the clamp ring 52 and an enlarged
head which is at the radially inner end of the shank and extends inwardly
of the clamp ring 52 where it has a frusto conical extremity that seats in
a chamfered recess that forms the outer end portion of a bore which
extends through the clamp ring retainer 55 of the mounting plate 49. The
drive pin actuating plunger 65 is slidably mounted in the last named bore,
and has a rounded inner end that projects from the inner end of said bore.
The drive pin spring 64 surrounds the shank of the drive pin and bears
upon the base of the enlarged drive pin head so that the drive pin is
normally engaged with the chamfered recess in the retaining ring 55,
thereby tieing the clamp ring 52 to the mounting plate for rotary movement
with the mounting plate.
Comparison of FIG. 7 with FIG. 9 shows how the drive pin 63 is disengaged
from the mounting plate 49 when the mounting plate is moved from the
lower, operating position of FIG. 7 to the elevated, pallet changing
position of FIG. 9. Drive pin actuating means comprises a cam pin,
indicated generally at 66, which is slidably mounted in aligned vertical
bores in the mounting plate 49 and the retaining ring 55. The cam pin 66
has a lower end portion which extends into a well in the sidewall 20 of
the hydraulic cylinder 18, and a compression spring 67 which surrounds the
lower end portion of the cam pin 66 is seated against an annular flange at
the top of the well and bears upon a peripheral flange 68 at the lower end
of the cam pin so that the pin remains in a fixed position as the piston
28 and mounting plate 49 are reciprocated vertically. The cam pin 66 has
longitudinal groove 69 which receives the rounded inner end of the drive
pin actuating plunger 65, and at the upper end of the groove 69 is a cam
surface 70 which is seen in FIG. 9 to be contacted by the rounded inner
end of the plunger 65 when the piston and mounting plate have been
elevated to the predetermined level shown in FIG. 9. This moves the drive
pin 63 radially outwardly to disengage its enlarged head from the
chamfered socket in the rataining ring 55, thus disconnecting the clamp
ring 52 from the mounting plate 49 for independent rotation.
Referring now particularly to FIGS. 2, 3, 6 and 9, when the structure is in
the position of FIGS. 7 and 8-- i.e., the operating position which it
occupies during a machining cycle -- the pallet P is supported and firmly
locked to the base 17 by a Curvic coupling means which includes toothed
coupling segments 71 on the base and a mating toothed coupling ring 72 on
the underside of the pallet P; the teeth of the pallet coupling ring 72
being meshed with those of the base coupling segments 71 when the
apparatus is in said operating position. As seen in FIG. 2, each of the
coupling segments 71 occupies an arc of approximately 30.degree., so the
segments are separated by gaps, the angular extent of which is
approximately 60.degree..
The use of coupling segments 71 on base 17 which are separated by gaps that
are as large as the segments, or larger, permit the coupling segments to
be protected when the pallet P is removed from the mounting plate 49 and
the teeth of the segments 71 would otherwise be exposed to possible
contamination by dirt and metal chips. This protecting is accomplished by
cover means, indicated generally at 73 in FIGS. 5 to 9. The cover means 73
comprises a ring 74 which surrounds the clamp ring 52 and is confined by a
laterally extending annular gib plate 75. A thin cover plate 76 extends
radially outwardly from the ring 74 and has circumferentially spaced cover
flanges 77 which extends further radially outwardly and have depending
skirts 78. As seen in FIGS. 2 and 6, when the apparatus is in operating
position the cover flanges 77 occupy positions in the gaps between the
toothed segments 71; whereas, in the pallet changing position seen in FIG.
5 the cover flanges 77 overlie the toothed segments 71 on the base. The
necessary rotary movement of the cover means 73 occurs simultaneously with
rotary movement of the clamp ring 52 in the mounting plate 49, and in fact
the clamp ring is driven by the cover means by reason of the fact that
movement of the drive pin 63 to the position of FIG. 9 not only disengages
it from the chamfered socket in the retaining ring 55, but at the same
time projects the outer end portion of the pin shank into an aligned
opening 79 in the cover means ring 74.
When the drive pin 63 is not engaged in the hole 79 the cover means 73
would be free to rotate relative to the clamp ring 52, due to vibration of
the machine, if it were not a set of four stabilizing pins 80, one of
which is seen in FIG. 8. The pins 80 are mounted in blind bores in the
base 17, and springs 81 urge the pins 80 upwardly so that their upper end
portions 82 are projected out of the base 17 into aligned holes in the
cover means ring 74. The pins 80 are engaged with the holes in the cover
means ring at all times except when the cover means is in the elevated
position of FIG. 9 where, of course, it is prevented from rotating
relative to the clamp ring 52 by the engagement of the drive pin 63 in the
hole 79. III. The Pallet Changer and Its Cooperation with the Traversing
Work Table
As seen in FIGS. 1 and 2, the pallet changer PC consists generally of a
base 83 surmounted by parallel guideways 84 which supports a pair of
pallet carrying rails 85 that | | |
