Universal holding system for a contoured workpiece

A universal system for supporting and holding a workpiece having a contoured work holding surface is provided with a spaced array of work holding fixtures mounted on a base. Each fixture includes a work engaging head having a vacuum cup and three work engaging projections spaced outwardly from the vacuum cup and disposed in a work contact plane. The work engaging head is supported by a ball joint on a rod mounted for axial movement relative to a base and the ball joint supports the work engaging head for tilting movement about axes orthogonal to each other and to the axis of the rod. The ball joint includes a ball and casing and a ball clamp in the casing with ball clamp operating means for selectively moving the ball clamp means into a ball clamped condition to a ball released condition. A rod clamp means is provided for selectively locking the rod in a rod clamp adjusted position.

RELATED APPLICATIONS 
This application is related to an application of Willy J. Goellner entitled 
"Lockable Ball Joint Apparatus" filed Jun. 2, 1995, Ser. No. 08/460,047, 
now U.S. Pat. No. 5,544,968. 
BACKGROUND OF THE INVENTION 
Apparatus have heretofore been made for supporting and holding large 
workpieces having a contoured holding surface. In general, these apparatus 
include an array of vacuum cups mounted on spindles for adjustment 
relative to a base for holding a workpiece on the upper ends of the 
spindles. In U.S. Pat. No. 4,088,312, vacuum cups are mounted on parallel 
spindles with springs for urging the spindles and vacuum cups to 
individual raised positions and pneumatically actuated clamps for clamping 
the spindles in an adjusted position. In U.S. Pat. No. 4,684,113, a screw 
actuator is provided for adjusting the height of each spindle and a 
pneumatically actuated clamping means for locking the spindles in an 
adjusted position. In the above patents, the holding force generated by 
vacuum cups is generally parallel to the axis of the spindles and the 
vacuum cups are not adequate to effectively resist forces having a 
substantial component in a direction transverse to the spindles. 
U.S. Pat. No. 4,527,783 discloses a plurality of vacuum cups mounted on a 
flexible lattice type spring metal framework that is adjustable relative 
to the base by linear actuators to form a contoured support plane. U.S. 
Pat. No. 4,491,306 discloses a work holding apparatus in which each work 
holder has a cup shaped vacuum chamber which is swivelly supported on an 
upper end of a spindle with a work engaging pin inside the open end of the 
cup shaped vacuum chamber. 
SUMMARY OF THE INVENTION 
In accordance with one aspect of the present invention, a universal system 
for supporting and holding a workpiece having a contoured work holding 
surface is provided with a spaced array of work holding fixtures mounted 
on a base with each fixture including a work engaging head having vacuum 
cup means with a peripheral work contacting rim and three work engaging 
projections spaced outwardly from the vacuum cup means and disposed in a 
work contact plane generally parallel to a plane through the peripheral 
work contact rim of the vacuum cup means. The work engaging head is 
supported by a ball joint on a rod mounted for axial movement relative to 
the base and the ball joint supports the work engaging head for tilting 
movement about second and third axes orthogonal to each other and to the 
axis of movement of the rod. The ball and socket joint includes a ball and 
casing means having a ball receiving cavity and ball clamp means in the 
casing means with a first ball clamp operating means for moving the ball 
clamp means into a ball clamp condition and a second ball clamp operating 
means for moving the ball clamp means to a ball release condition. Rod 
clamp means are provided on the rod mounting means and a first rod clamp 
operating means is provided for moving the rod clamp means into a rod 
clamp condition and a second rod clamp operating means is provided for 
moving the rod clamp means to a rod release condition. 
With the above arrangement, the work engaging head can tilt about second 
and third axes orthogonal to each other and to the axis of movement of the 
rod so that the work contact plane defined by the three work engaging 
projections, can tilt to conform to the work holding surface on the 
workpiece and the vacuum cup tilts with the head to hold the workpiece on 
the work engaging projections. 
In accordance with another aspect of the invention, there is provided a 
ball joint apparatus having an improved arrangement for locking the ball 
joint in adjusted positions. The ball joint includes a casing having ball 
receiving cavity and at least one annular clamp ring in the casing 
extending around the ball, the clamp ring having a spherically concave 
inner clamping surface engaging the outer surface of the ball and a 
frusto-conical outer surface. An annular cam means in the casing extends 
around the clamp ring and has a frusto-conical inner surface engaging the 
frusto-conical outer surface of the clamp ring, and means are provided for 
moving the annular cam means axially in a first direction relative to the 
casing to diametrically compress the clamp ring into clamping engagement 
with the ball, and means are provided for moving the annular clamp means 
axially in a second direction relative to the casing to release the clamp 
ring from clamping engagement with the ball. 
Annular piston means are provided for fluid pressure actuation of the cam 
means in one or both directions. The annular cam means is advantageously 
spring actuated in a direction to diametrically compress the clamp ring to 
normally lock the ball joint against movement, with the piston means 
arranged for actuation by fluid pressure to a release condition. Since the 
axial forces applied to the annular cam ring are effectively amplified by 
the cam action, the annular cam means applies a radial clamping force on 
the clamp ring that is substantially greater than the axial force applied 
to the cam means. Thus, the ball joint can be reliably locked in any 
adjusted position without requiring high actuating forces to move the 
annular cam means.

DETAILED DESCRIPTION 
FIGS. 1-4 illustrate a work holding fixture adapted for use in a universal 
holding system for supporting a large workpiece having a contoured work 
holding surface. The work holding fixture includes a work engaging head 21 
having vacuum cup means 22 with a resilient peripheral work contacting rim 
22a and three rigid work engaging projections 23 spaced outwardly from the 
vacuum cup means and disposed in a plane generally parallel to a plane X 
through the peripheral work contacting rim of the vacuum cup. The plane X 
is preferably disposed slightly below the plane through the peripheral rim 
of the vacuum cup, to assure that the vacuum cup reliably contacts a work 
engaging surface on the workpiece and the vacuum cup is made sufficiently 
resilient and flexible to deform to accommodate workpieces having a 
downwardly facing convex contour when the workpiece is supported on the 
work engaging projections. The work engaging projections 23 are preferably 
angularly spaced 120 degrees apart and at the same radial distance from 
the center of the vacuum cup, as best shown in FIG. 2. 
The work engaging head 21 is mounted by a ball and socket joint 31 on a 
spindle or rod 32 that is mounted by means 33 for axial movement relative 
to a base 34. The ball and socket joint 31 supports the work engaging head 
for tilting or angular movement about axes orthogonal to the axis of the 
rod, and clamp means are provided locking the ball and socket joint in 
angularly adjusted positions. The rod mounting means 33 guidably supports 
the rod for axial movement and rod clamp means 39 are provided on the 
mounting means 33 for locking the rod 32 in axially adjusted positions. 
The ball joint means includes a ball means 44 and ball casing means 41 
defining a ball receiving cavity. In the preferred embodiment illustrated 
in FIGS. 1-4, the ball casing means 41 is fixed to and forms a part of the 
work engaging head 21 as by fasteners 42, and the ball 44 has a stem 44a 
attached to the rod 32. It is deemed apparent that the ball casing means 
could be attached to the rod 32 and the ball 44 attached to a work 
engaging head, if desired. 
The ball receiving cavity has a cylindrical outer wall 43a and annular end 
walls 43b and 43c. In the embodiment of FIGS. 1-4, a pair of clamp rings 
45 and 46 extend around the ball 44 and each having a spherically concave 
inner surface 45a, 46a respectively and a frustoconical outer surface 45b, 
46b respectively. The clamp rings 45 and 46 are disposed at opposite sides 
of a plane through the center C of the ball 44 and a seal ring 49 is 
disposed between adjacent ends of the clamp rings. The outer ends of the 
clamp rings engage the walls 43b and 43c respectively and the inner ends 
of the clamp rings engage opposite ends of the seal ring so that the clamp 
rings are confined against movement in a direction axially of the rings 
while the clamp rings are capable of radially expanding and contracting. 
The clamp rings 45 and 46 are preferably radially slotted part way through 
their length, from one or both ends as indicated at 45c, 46c, to 
facilitate radial expansion and contraction. 
The frusto-conical outer surfaces 45b and 46b are arranged so that they 
taper inwardly in a direction away from a plane through the center of the 
ball, and first and second annular cam means 51 and 52 are formed with a 
frusto-conical inner surface complimentary to the frustoconical outer 
surface of the clamp rings 45 and 46 respectively. The annular cam means 
are mounted for limited axial movement relative to the clamp rings to move 
the latter into clamping engagement with the ball when the cam means is 
moved in one axial direction and to release the clamp rings from the 
clamping engagement with the ball when the cam means is moved in the 
opposite direction. Annular piston means 53 and 54 are provided for fluid 
pressure actuation of the cam means in at least one direction and it is 
contemplated that the piston means may be arranged for selectively 
actuating the cam means in both directions. The annular cam means 51 and 
52 are advantageously formed on the inner periphery of annular pistons 53 
and 54. In the preferred embodiment illustrated in FIGS. 1-4, a plurality 
of compression springs 55 and 56 are disposed between the pistons 53 and 
54 and the adjacent end walls 43b, 43c of the cavity, to yieldably urge 
the pistons and hence the annular cam means 51 and 52 in a direction to 
radially compress the clamp rings and lock the work ,engaging head in an 
angularly adjusted position on the ball. Resilient seals 58 and 59 are 
provided for sealing the pistons to the seal ring 49 and to the outer wall 
43a of the cavity. A passage 61 is provided in the casing 41 and arranged 
to communicate with a chamber between adjacent faces of the pistons, to 
supply and exhaust fluid pressure under the control of valve means 
diagrammatically shown at 61a in FIG. 1. A passage 62 is provided in head 
21 for communicating the vacuum cup 22 with a vacuum source under the 
control of valve means diagrammatically shown at 62a in FIG. 1. As is 
deemed apparent, the fluid may be either a gas or a liquid, but in some 
applications gas such as air is preferred to prevent contamination in the 
event of leakage. 
The ball joint supports the head for tilting movement about the center of 
the ball about axes orthogonal to the axis of the rod 32 and in the 
embodiment illustrated is adapted to allow the head to tilt to an angle of 
up to 45 degrees in any direction from a plane perpendicular to the axis 
of the rod. In some installations it is preferable to prevent turning of 
the head about the axis of the rod. As shown in FIG. 1, a pin 65 on the 
casing 41 extends into a notch 66 in one of the pistons 54 to hold the 
piston against turning relative to the casing. A pin 68 on the seal ring 
49 has one end that extends into a notch 69 in the piston 54 and a second 
end that extends into a groove 70 in the periphery of the ball. The pin 68 
is disposed with its axis in a plane through the center of the ball and 
perpendicular to the axis of the rod 32 and prevents the seal ring from 
turning relative to the piston 54. The groove 70 is disposed in a plane 
that extends radially of the axis of the rod so that the pin 68 prevents 
rotation of the head relative to the ball about the axis of the rod while 
accommodating tilting movement along axes orthogonal to the axis of the 
rod. 
The rod 32 is axially adjustable relative to the base 34 to enable 
adjustment of the spacing of the head relative to the base and the rod 
clamp means 39 is provided for locking the rod and hence the head in an 
adjusted position relative to the base. Any suitable means may be provided 
for guidably supporting and locking the rod in an adjusted position. In 
the embodiment shown in FIG. 1, the rod mounting means 33 includes a head 
74 on an upper end of a cylinder 75 and a piston 76 fixed to a lower end 
of the rod and slidable in the cylinder. The rod clamp means 39 includes 
an annular clamp ring 78 having a cylindrical inner surface that extends 
around the rod and a frustoconical outer surface 78a and slots 78b that 
extend part way through the ring to facilitate radial expansion and 
contraction. The rod clamp also includes an annular cam means 79 having a 
tapered inner surface complimentary to the outer surface of the clamp 
ring. The annular cam means 79 is formed on the inner surface of an 
annular piston 81 slidable on the inner surface 82a of a clamp actuator 
casing 82. The piston is yieldably urged in one direction by springs 83 
and is moved in an opposite direction by fluid pressure introduced through 
a passage 84 into a pressure chamber 85. The rod clamp is preferably of 
the type that is actuated to its clamped condition by springs 83 and 
operated to its release condition by fluid pressure applied to the piston 
chamber 85 under the control of a valve 84a diagrammatically shown in FIG. 
1. In order to prevent turning of the work engaging head about the axis of 
the rod, a pin 86 is mounted on the casing and projects into a 
longitudinally extending groove 87 in the rod. 
FIG. 5 illustrates a modified ball and socket joint for mounting the work 
engaging head 21' for angular adjustment relative to the rod 32. Like 
numerals are used to designate the same parts as in FIG. 1 and like 
numerals followed by the postscript (') are used to designate modified 
parts. In this embodiment, a ball receiving casing means 41' has a cavity 
with cylindrical peripheral wall 43a' and end walls 43b' and 43c'. A 
single clamp ring 45' is provided with a spherically concave inner surface 
45a' and a frusto-conical outer surface 45b'. An annular cam means 51' 
extends around the clamp ring and has a frusto-conical surface 
complimentary to the outer surface of the clamp ring. An annular piston 
54' is provided to enable fluid pressure actuation of the cam means in at 
least one direction and the cam means is preferably formed integrally with 
the annular piston 54'. In the embodiment of FIG. 5, the clamp ring is 
disposed below a plane through the center C of the ball 44 when the head 
is in a horizontal position. The spherically concave inner surface of the 
clamp ring has a major inner diameter at its upper end and the 
frusto-conical outer surface has a major outer diameter at the same end as 
the major inner diameter of the clamp ring. Seals such as 59' and 58' seal 
the piston to the outer wall 43a' of the casing and to a seal ring 49'. 
Means such as springs 55' are provided for yieldably urging the piston and 
the annular cam means in one direction, preferably in a direction to cam 
the clamp ring into clamping engagement with the ball, and passage means 
61' are provided for supplying fluid pressure to a chamber formed between 
the piston and the wall 43c' to move the cam means in an opposite 
direction. In this embodiment, a spherically concave inner surface 46a' is 
provided and arranged to engage the ball at a side opposite the clamp ring 
45'. This arrangement provides firm support for the work engaging head 
when the latter is subjected to heavy loads in a downward direction, that 
is toward the rod 32. 
In the embodiment of FIG. 6, the ball clamp comprises a single clamp ring 
46" arranged to engage the ball 44 at a location that is above a plane 
through the center C of the ball when the head is in a horizontal 
position, and a spherically concave surface 45a" on the casing 41" is 
arranged to engage the ball at a location below a plane through the center 
of the ball when the head is in a horizontal position. The clamp ring 46" 
has a spherically concave inner surface 46a" and a frusto-conical outer 
surface 46b". An annular piston 54" is provided to enable fluid pressure 
actuation of the cam means and annular cam means 52" is formed on the 
annular piston 54". In this embodiment, spring means 56" is provided to 
yieldably urge the piston in a downward direction and fluid under pressure 
is selectively supplied to the head of the piston through a passage 61" to 
move the piston in an upward direction in opposition to the springs 56". 
The work holder is especially adapted for use in a universal work holding 
system for supporting and holding a large workpiece having a contoured 
holding surface. In general, such universal holding systems include a 
spaced array of work holding fixtures mounted on a platform or bed 90 
having indexing or locating bores or grooves such as the work table of a 
machine tool. The work table of a machine tool is commonly horizontal such 
as indicated at 91a but the work holder is also adapted for mounting on 
beds having supports disposed at an angle such as perpendicular to the 
horizontal as indicated at 91b in FIG. 1. The work holding heads 21 of the 
present invention are advantageously arranged such that they can be 
adjusted through an angle of at least 45 degrees in any direction relative 
to the rods 32. Thus, the work holders can be mounted on a horizontal 
surface to support workpieces having a work engaging face that deviates 
between zero and forty-five degrees, and mounted on a vertical surface to 
accommodate portions of the workpiece that extend at an angle of greater 
than forty-five degrees to the horizontal, as shown in FIG. 7. 
FIGS. 10-15 illustrate a method for presetting individual work holders in 
an array to support a large workpiece having a contoured work holding 
surface. As shown in FIG. 10, an adjustable plate Y is first adjusted to 
extend at a preselected angle relative to a vertically movable support Z, 
which angle corresponds to the desired support plane at the preselected 
locus in the array. In step 1 shown in FIG. 10, vacuum to the vacuum cup 
is turned off as indicated by Vo and pressure is supplied to the ball 
clamp and to the rod clamp as indicated by P+ to release the ball and rod. 
The pre-adjusted plate Y is then moved down into engagement with the head 
21 until the plate engages the work engaging projections 23 on the head 
and tilts the head to extend parallel to the plate. In a second step, 
vacuum to the vacuum cup is turned on as indicated by V- in FIG. 11 to 
attach the work engaging head to the plate Y and pressure to the ball 
clamp 31 is turned off as indicated by Po to lock the head in adjusted 
position relative to the rod 32. The plate is then moved upwardly or 
downwardly as shown in FIG. 12 to raise or lower the angularly adjusted 
head to the desired position above the base and pressure to the rod clamp 
is then turned off to lock the head in adjusted positions relative to the 
base. In the step shown in FIG. 13, the pressure supply to the rod clamp 
and the ball clamp is off and the vacuum to the head is turned off so that 
the adjusting plate Y can be separated from the head 21. This sequence of 
steps is continued for each work holder in the array and, after all of the 
work holders in the array are adjusted in the above manner to the desired 
angle and position with respect to the base corresponding to the work 
contour at the locus of the work holders, a workpiece designated WP can be 
lowered onto the work engaging head as shown in FIG. 14 and the vacuum to 
the vacuum cup then turned on as indicated in FIG. 15 to hold the 
workpiece in position on the adjusted work engaging head. 
Alternatively, if a workpiece or model of the workpiece is available, an 
array of the work holders can also be adjusted to conform to the contour 
of a workpiece or model by (1) positioning a workpiece of the desired 
contour over an array of the work holders, (2) raising the work engaging 
heads using means such as springs or fluid pressure to raise the rods 32 
while fluid pressure to the rod clamp and ball clamp for each work holder 
is turned on to unclamp the ball and rod; (3) turning the vacuum to the 
vacuum heads on after the heads contact and conform to the workpiece and 
(4) thereafter turning off pressure to the rod clamps and ball clamps to 
lock the heads in adjusted position while the vacuum to the vacuum cups is 
maintained on to hold the workpiece on the heads.