Note: Descriptions are shown in the official language in which they were submitted.
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ORBITAL TABLE FOR ~ACHINE TOOLS
T CHNICAL FIELD
This invention relates generally to an orbital table and to
the mechanism associated therewith which converts rotary motion
input into a planar orbital motion without rotation. More
particularly, this invention relates to a simple, reliable, and
inexpensive orbital table for use on, or in conjunction with, any
application where orbital motion is desired, such as machine
tools where orbital or translational motion of a workpiece,
working tool or both is utilized to produce simple or complex
machined shapes.
BACKGROUND ART
There are a number of metal machining processes where it is
essential that the working tool and/or workpiece follow a defined
by a translational or orbital path as the tool works a given
workpiece surface. For example, jig boring or grinding machines
are well known machine tools where a boring, grinding or
polishing wheel, rotating on its own axis, is further made to
revolve in a planetary or orbital path in the finishing of
circular holes or recesses within metal workpieces. By placing
the workpiece on an orbital table, the combined orbital motions
of the working tool and the workpiece makes possible the working
of complex surfaces other than round.
More recently, orbital grinding machines have come lnto use
which do not utilize rotating grinding wheels, but rather bring a
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tool and workpiece together, at least one of which is orbiting
without rotation against the other. In this application, the
working tool is usually formed of a rather hard material and
typically has a three dimensional configuration in it working
face. By orbiting either the tool or the workpiece, or both,
while the two are in contact and biased against each other, using
a rather small radius of orbit, the negative configuration of the
tool is worked into the workpiece. Because of the orbital motion
of either the tool or workpiece, the resulting machined
configuration in the workpiece cannot be of an identical size to
that of the tool. However, rather complex, intricate and
exacting three dimensional configurations can be produced by
proper allowance for the orbital action between the tool and the
workpiece.
Other recent and advanced machining processes, such as
electrical discharge machining, either sequentially or in
multifunctional singular operations are utilized which in some
applications depend on orbital motion of the work tool and/or
workpiece to machine shapes not attainable in any other practical
way and at levels of finish and accuracy which are exceptional.
The machine tools and techniques mentioned above, usually
utilize conventional X-Y tables which are expensive and tend to
be rather large due to the complex motion creating hardware. The
complex nature of the hardware leads to a rather high power loss
and accuracy factors that are less than desired.
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DISCLOSURE OF TH~ INVENTION
This invention relates to a new simple, reliable and low
cost translational and orbital table for use in any application
where such tables are currently utilized, and in particular for
use on, or in conjunction with, machine tools, to which a
workpiece can be affixed and made to orbit in an orbital path or
otherwise translated without rotation. Because of its low cost,
the orbital table of this invention will find particular utility
in those machining operations where all that is needed is to have
a work table that will orbit in a circular path. In addition to
its being greatly simplified and lower in cost, as compared to
conventional X-Y tables, the orbital or translational table of
this invention provides added advantages of being more accurate,
lighter in weight, capable of being produced at considerable size
reductions with a comparatively low profile form and is
characterized by a lower power loss than conventional prior art
tables. The orbital table of this invention is fabricated to
effect a given movement, and accordingly has no mechanism or
adjustments for changing the movement which will adversely affect
the accuracy of movement. In addition, the orbital table of this
invention does not utilize any sliding linkage as is found in
most X-Y tables, which tend to loosen quickly with use to further
adversely affect the accuracy of the rotation and precision of
control. Accordingly, the orbital table of this invention
provides the added advantage of maintaining the desired fixed
motion without loss in accuracy due to the wearing of sliding
linkage, and without any need for concern that the adjustments
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could be inadvertently moved to unknowingly alter the
movement and therefore without any need to periodically
check the adjustments to assure the proper settings.
Accordingly, it is an object of an aspect of this
invention to provide a new, improved and simplified
translational table for machine tool applications.
It i5 an object of an aspect of this invention to
provide a simple reliable and inexpensive orbital table
having a radius of orbit for the most demanding of
orbital table applications, such as machine tool
applications, and in particular orbital grinding and
polishing machines.
An object of an aspect of this invention is to
provide a new light weight translational and orbital
table for machine tools and other applications, which is
much simpler in construction that the conventional X-Y
tables, does not have any complex mechanism for adjusting
to different orbital motions, and can accordingly be
produced with considerable size reductions and low
profile as compared to conventional X-Y tables.
An object of an aspect of this invention is to
provide an orbital table that will maintain a fixed,
preset radius of orbit which does not utilize any sliding
linkage that will loosen in operation and adversely
affect the accuracy or the orbital motion.
An object of an aspect of this invention is to
provide a translational and orbital table which is
simpler~ more reliable and less expensive that an
conventional X-Y table.
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An object of an aspect of this invention is to
provide a translational and orbital table which exhibits
a lower power loss and an improved accuracy of movement
as compared to prior art X-Y tables.
An aspect of this invention is as follows:
An orbital table assembly having a top plate which
can be made to translate about an axis without rotating,
comprising a fixed base member, a top plate over said
fixed base member, a linkage member interposed between
said base member and said top plate, a rotatable cam
member rotatably secured to said top plate such that
rotation of said cam member will cause said top plate to
orbit in a translational path offset from the axis of
translation, means for rotating said cam member, a first
set of parallel deflecting arms, one end of which are
connected to said linkage member and the other end
connected to said base member at a point opposed on
either side of the axis of translation, a second set of
parallel deflecting arms perpendicular to said first pair
of deflecting arms with one end thereof connected to said
linkage member and the other end connected to said top
plate at a point opposed on either side of the axis of
translation, each pair of said deflecting arms oriented
in a plane perpendicular to the axis of translation and
aligned transversely to said axis, said deflecting arms
thus preventing rotation of said top plate but eflecting
to permit the translational motion thereof.
BR~IEF DESCRIPTION OF_q~HE DRAWINGS
Figure 1 is an isometric view of a preferred
embodiment of this invention illustrating the three major
components of the orbital table in a spaced apart
relationship.
Figure 2 is a sectional side view of the orbital
table illustrated in Figure 1 with the section taken at
line 2-2 depicted in Figure 3.
5a
Figures 3, 4 and 5 are top views of an orbital table
substantially as shown in Figure 1 and 2 illustrating
three different positions of the orbital movement.
Unlike Figure 1 and 2, the base plate in these figures is
made somewhat larger than the tool and linkage plate to
better illustrate the relative displacement of the plates
during operation.
BE8T NODE OF ~ARRYING OUT THE INVENTION
With reference to Figure 1, one of the simplest and
a preferred embodiment of this invention consists merely
of three essential plate components, namely a tool plate
10 at the top, a drive plate 20 at the bottom and a
linkage plate 30 therebetween. Drive plate 20 at the
bottom, forms the base member for the orbital table and
should be secured and fixed as the application dictates.
A rotational drive means, such as an electric motor 4
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is secured to the underside of drive plate 20 with its arbor 6
extending vertically upward through hole 22 in the center of, and
perpendicular to, the the upper surface of drive plate 20. A
drive spindle 24, having a relatively short cylindrical body, is
secured to the motor arbor such that activation of electric motor
4 will cause the rotation of drive spindle 24 in a plane parallel
to and just above the top surface of drive plate 20. A spindle
cam 26 is secured to the top surface of drive spindle 24 with its
axis offset a predetermined distance from the drive spindle axis.
A pair of parallel,link pins 28 are attached to the upper surface
of drive plate 20 diametrically opposed on either side of drive
spindle 24 with their axis perpendicular to the top surface of
drive plate 20 and thus parallel to the axis of rotation of drive
spindle 24.
Linkage plate 30, which may, but not essentially, have the
same peripheral dimensions as drive plate 20, is provided with a
hole 32 through the center thereof, and with a flex-arm 34 on
each side of the four sides of the rectangular plate. As can be
seen from Figure 1, the flex-arms 34 are formed in this
embodiment by cutting slots 36 through plate 30 parallel to each
edge of the plate 30, such that an elongated portion on each edge
of the plate forms a flex-arm 34 which is attached at only one
end of the plate 30 near the corner of thereof. The section of
metal where the flex-arms 34 meet linkage plate 30 must be thin
enough to permit a modest lateral deflection of flex-arms 34
relative to linkage plate 30. Accordingly, two pairs of parallel
flex-arms 34A and 34B are formed on opposite sided of plate 30,
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such that each pair is perpendicular to the other. Each pair of
parallel flex-arms 34A and 34B are diametrically opposed on
either side of hole 32 at an angle of 90 degrees to the other
pair. Each flex-arm 34 is provided with a hole 38 t~rough the
free end thereof perpendicular to the surface of plate 30, with
the axis thereof lying in a vertical plane passing through the
axis of rotation of said drive spindle 24. Flex-arms 34B, and
accordingly linkage plate 30 are attached to drive plate 20 by
fitting the holes 36 therethrough over link pins 28 on drive
plate 20, and accordingly fitting hole 32 over drive spindle 24.
Preferably, link pins 28 should fit into holes 36 as tight as is
necessary to prevent any pivotal action of flex-arms 34B on pins
28. Conversely, hole 32 should be snug but loose enough on drive
spindle 24 to permit rotation of drive spindle 24 without
interference.
Tool plate 10, which is the orbiting plate, and which may,
but not essentially, have the same peripheral dimensions as
plates 20 and 30, is provided with a hole through the center
which in essence forms a spindle cam bearing 12. A pair of
parallel link pins 14 are secured to the underside of tool plate
10 diametrically opposed on either side of spindle cam bearing 12
and spaced so that they will mate with the holes through flex-
arms 34A in linkage plate 30. Accordingly, tool plate 10 is
secured to linkage plate 30 by inserting link pins 12 into holes
34A and such that spindle cam 26 is rotatably fitted into spindle
cam bearing 12. Since spindle cam 26 is not centered on drive
spindle 24 or drive plate 20, one or both pairs of flex-arms 34
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will have to be deflected somewhat in order to get spindle cam
bearing 12 over spindle cam 26. As noted above for flex-arms
34B, flex-arms 34A may be pivotally or securely connected on
link pins 12.
In operation, the above described orbital table is activated
by activating the rotational drive means, e.g. electric motor 4
secured to the bottom of drive plate 20. This of course will
cause rotation of drive spindle 24 on its own axis, while spindle
cam 26, which is offset from the drive spindle axis, will
oscillate in an orbital path around the spindle axis. Since
drive plate 20 is secured in a stationary position, suitable
clearance must be provided at hole 22 to permit the free rotation
of arbor 8 extending therethrough. As noted above, linkage plate
30 is secured to drive plate 20 via link pins 28, so that linkage
plate 30 is likewise not free to rotate. Similarly, tool plate
10 is secured to linkage plate 30 via link pins 14, so that tool
plate 10 cannot rotate either. However, since orbiting spindle
cam 26 is inserted into spindle cam bearing 12 through the center
of tool plate 10, it should be apparent that tool plate 10 will
not remain stationary, but rather must move in unison with the
orbital movement of spindle cam 26. Such an orbital motion
without rotation is permitted by the deflection of flex-arms 34.
As may be apparent from a close look at the linkage of flex-
arms 34, tool plate 10 cannot rotate, but oscillates in an
orbital path as depicted in Figures 3, 4 and 5. ~ith reference
to Figure 3, which is a top view of the orbital table, it can be
seen that when spindle cam 26 is at the twelve O'clock position,
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g
tool plate 10 is positioned as far to the top side as it will go,
that is, top side as viewed in the drawings. To be moved to that
position, link pins 14 will also be moved to the top side along
with tool plate 10 causing flex-arms 34A to be elastically
defle~ted such that the free end thereof is deflected towards the
top by an equal amount. Assuming a clockwise rotation of drive
spindle 24, spindle cam 26 will move from the twelve O'clock
position as shown in Figure 3 by rotating towards the three
O'clock position. Tool plate 10 will of course follow the same
path but without rotating. Accordingly, as spind~e cam 26
rotates from the twelve to the three O'clock position, flex-arms
34A start retracting to their normal undeflected position. The
movement of tool plate 10 to the right, however, as opposed to
top and bottom movement, cannot be accommodated by any deflection
of flex-arms 34A. Instead, link pins 14 will pull the entire
body of linkage plate 30 to the right, and thus flex-arms 34B are
elastically deflected to the left as the body of linkage plate 30
moves to the right~ When spindle cam 26 is in the three O'clock
position, flex-arms 34A will have completely returned to their
normal undeflected position, while flex-arms 34B, will be
elastically deflected to their furthest left position, as both
tool plate 10 and linkage plate 30 are moved to this furthest
right position, as depicted in Figure 4. In a like fashion, as
spindle cam 26 rotates from the three to the six O'clock
position, the following quarter orbital movement of tool plate 10
is permitted by the returning movement of flex-arms 34B to their
undeflected position and the deflection of interaction arms 34A
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in a downward direction. Figure 5 illustrates the relative
positions when spindle cam 26 is in the six O'clock position. It
can be seen that all left and right displacement of tool plate 10
is accommodated by the deflection of flex-arms 34A as tool plate
10 moves left and right with respect to linkage plate 30. On the
other hand, all top and bottom displacement of tool plate 10 is
accommodated by the deflection of link pins 34B as tool plate 10
and linkage plate 30 move jointly towards the top or bottom with
respect to drive plate 20. Since linkage plate 30 does move with
respect to drive plate 20, hole 32 through the center thereof
must be large enough to accommodate such movement without
obstruction. It should be noted that the spindle cam offset as
shown in the drawings was made significantly large so that
relative displacements of the components would be readily
apparent from viewing the drawings. While such displacements
would be within the scope of this invention, smaller offsets
would be more common, particularly in orbital grinding where the
radius of orbits are typically within the range of 0.050 to
0.120-cm.
As previously noted, holes 36 should fit tightly onto link
pins 28 for the purpose of preventing any pivotal rotation of
flex-arms 34 about pins 28. If flex-arms 34 are permitted to
pivot about pins 28, particularly in the embodiment shown in
Figures 1-5l the tool plate 10 will be caused to wabble somewhat
in its orbital path. On the other hand, if the axes of link pins
28 are aligned through the center of flex-arms 34 and such
alignment is perpendicular around the four sides of the table,
then flex-arms 34 can be allowed to pivot on
link pins 28 without causing any wabbling. It should be apparent
that the power loss in operating the table will be a function of
the section of metal "x", as shown in Figure 1. Accordingly, the
thinner that section is, for any given steel plate, the more
easily the flex-arms will be able to be deflected and the lower
the power loss will be.
It should be apparent that the above described embodiment of
this invention is ideal in its simplicity in that the entire unit
is fabricated from simple plate and rod stock with very simple
fabrication and machining requirements. It should be apparent
that a table of very low profile can be produced by minimizing
the thickness the the plate stock used in its manufacture, and
that the absence of complex hardware would readily permit the
other dimensior,s of the table to be reduced or enlarged as
desired. In addition, the power loss can be greatly minimized by
fabricating the plates such that the flex-arm can be easily
deflected, i.e. by minimizing the section thickness where the
flex-arms are deflected. In addition to the above advantages, it
is obvious that numerous modifications and different embodiments
could be utilized without departing from the spirit of the
invention. For example, it should be obvious, of course, that
the preset radius of orbit can be varied from one table to the
next by merely changing the offset distance of spindle cam 26
from the axis of spindle 2~. For added life, it should also be
obvious that spindle cam 26 could be journaled in a ball or
roller bearing instead of the solid bearing 12 as shown. Drive
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plate 20 could also be produced in many different forms depending
on the application where the orbiting table will be utilized, and
could in fact be eliminated provided some sort of base member is
utilized to support the upper two plates 10 and 30, and to
provide a flexible coupling to the free ends of flex-arms 34B to
prevent plate 30 from rotating. Linkage plate 30 could also be
fabricated in many different forms, as could flex-arms 34.
Considerable modifications could be made to the flex-arms 34
which could be separate rod type components pivotally affixed at
both ends with any form of linkage member that will maintain them
in the spaced relationship as shown. In addition, two or more
aligned flex-arms could be utilized in place of each flex-arm 34
as shown. All that is necessary is that the arms or rods be
rigid so as to pxevent rotation of tool plate 10, but yet capable
of readily deflecting or pivoting in the direction perpendicular
thereto to accommodate the orbital motion. On the other hand, it
should be apparent that all that is really necessary is to have a
deflecting means that will secure tool plates 10 to linkage plate
30 and secure linkage plate 30 to base plate 20 sufficiently to
prevent them from rotating but yet will deflect laterally to
allow lateral movement of linkage plate 30 in one direction while
allowing lateral movement of tool plate 10 in a direction
perpendicular to the aforesaid direction.
While tool plate 10 is shown to have a flat upper surface
for simplicity, it is obvious that some sort of machining may be
necessary on the top surface in order to attach some sort of
workpiece holding tool or the like.
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Since the circular path of orbit of tool plate 10 is set
and defined by the circular path of orbit of spindle cam 26 it is
obvious that translational paths other than orbital, such as an
oval path, for example, could be created by providing a spindle
cam which orbits in any such noncircular path. this could be
done by providing a cam which changes its distance from the
spindle axis as the spindle rotates. This could be effected by a
cam which is slideable with respect to the spindle axis and then
providing a stationary template that will guide the cam in a
noncircular path as defined by the template.
