Note: Descriptions are shown in the official language in which they were submitted.
CA 02725746 2010-11
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PCT/US2009/003059
Title
Method of Making a Ring
Field of the Invention
The invention relates to a method of making a ring,
and more particularly, to a method of making a ring by
expanding the middle of a slit blank while simultaneously
applying a compressive force to ends of the blank.
F-1
Background of the Invention
Tubular rings are used for many applications in the
industry. Rings can be broached, hobbed, machined,
ground, or used as is for many applications.
Applications include gears, starter gears, clutch hubs,
sprockets, pulleys, crankshaft dampers, and many other
products.
There are many existing arts for manufacturing
tubular rings. Some common methods include making a hoop
from bar stock and welding the joint; making a tube and
cutting it; deep drawing a cup and removing the face of
the cup; expanding a blank in ring rolling, forging,
casting, or spinning a blank from sheet metal.
All of these processes are suitable, but the cost or
quality of the produced ring is always a problem. For
example, welded hoops have problems in the weld area when
the ring is flow formed further to make gears, pulleys,
splined rings, etc. Further, the welding and cleaning the
weld and/or heat treating to normalize the weld area is
costly.
Cut seamless tubes are expensive and making a cup in
a press and removing the face creates excessive waste.
Representative of the art is US patent no. 4,590,780
which discloses a process starting from a pre-heated bar,
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there is sheared-off first a portion (41) which, in a
first forming stage of the machine, is formed into a tier
shaped pressed article. In the second forming stage, the
pressed article is further formed so that it has an inner
ring (J), an outer ring (A) arranged co-axially to this
and a radial annular web (S) connecting the two rings
(J,A). The sheared-off outer ring (44) is therefore
ejected in the next to last stage, while in the last
working stage the inner ring (45) separated from the
r-
lo outer ring is subjected to further working. This last
working stage involves stamping out a waste piece (35)
and shearing-off an annular web (38). It is also possible
to carry out a forming operation in this last working
stage to upset the remaining inner ring (22a). By means
of this process which provides for the elimination of the
finished outer ring (44) in the last working stage, the
radial annular web (38) can be supported over its full
cross-sectional surface during the shearing-off
operation.
What is needed is a method of making a ring by
expanding the middle of a slit blank while simultaneously
applying a compressive force to ends of the blank. The
present invention meets this need.
Summary of the Invention
The primary aspect of the invention is to provide a
method of making a ring by expanding the middle of a slit
blank while simultaneously applying a compressive force
to ends of the blank.
Other aspects of the invention will be pointed out
or made obvious by the following description of the
invention and the accompanying drawings.
The invention comprises a method of making a ring
comprising cutting a raw material stock to a
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predetermined length, cutting a slit through the raw
material stock along its length to form a blank,
inserting the blank into a tool, expanding the middle of
the slit while simultaneously applying a compressive
force to the ends of the blank, and expanding the middle
of the slit until the blank is round.
Brief Description of the Drawings
The accompanying drawings, which are incorporated in
and form a part of the specification, illustrate
preferred embodiments of the present invention, and
together with a description, serve to explain the
principles of the invention.
Fig. 1 is a plan view of a blank.
Fig. 2 is a side of view of the blank in the tooling.
Fig. 3 is a side view of the blank in the tooling.
Fig. 4 is a perspective view of the blank at an
intermediate step.
Fig. 5 is a side view of the blank in the tooling.
Fig. 6 is a perspective view of the finished ring.
Fig. 7 is a top perspective view of a blank in the
tooling.
Fig. 8 is a top perspective view of the tooling.
Fig. 9 is a side perspective view of the tooling.
Detailed Description of the Preferred Embodiment
The invention comprises a process of manufacturing a
tubular ring from bar stock. Although a rectangular bar
stock is preferred, any other configuration (round,
hexagonal, etc.) may also be used.
The manufactured ring may be used in making gears,
pulleys, sprockets, bearing races, one-way clutch races
crankshaft damper inertia rings and similar products.
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Fig. 1 is a plan view of a blank. The
process
starts with a raw material such as a simple bar stock
from which is cut a blank 10 having the desired length
(L) and width (W). Raw materials may comprise other than
bar stock, including flats, rounds, or any other
available form of metal material. For the
purpose of
this example a rectangular bar stock is used. The four
corners 11 at the ends of the cut rectangular blank are
rounded using known processes to facilitate the process
and to give the blank a uniform thickness.
The blank is cut to form a slit 12 in the middle
extending in the longitudinal direction (along its
length). The
slit can be cut using a laser or other
cutting means which include but not limited to: high
pressure water jet, laser, plasma, abrasive cutters,
milling, or other means. At each end of the slit is a
radius 13 to prevent crack formation in the expansion
process and to keep the thickness uniform. The width of
the slit is kept to a minimum to reduce waste.
Fig. 2 is a side of view of the blank in the
tooling. The blank 10 is then introduced into a press.
A contoured thickening and rounding post 20 is pressed
into the blank at the slit which opens and expands the
slit. The post initially contacts the slit in the middle.
End 22 of post 20 comprises a blade which engages
the slit 12. Post 20 is pressed though blank 10 into a
receiving female die 21 using a known hydraulic ram 200.
Use of a lower support die 21 that is as large as
the final size of the ID of the ring, the blank will
expand to a certain extent, about 50%, but it tends to
bend and does not continue to expand in a single plane.
Therefore, in order to have proper support for the blank
as it is being expanded and to prevent it from bending
during forming, either an expandable (sliding) lower
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tooling support tooling or a multi station tooling with
gradually larger lower tooling opening and thicker and
rounder post may be used as described herein.
The maximum outside diameter of the post 20
substantially matches the desired inner diameter of the
finished ring, see Fig. 6, minus any machining that may
be required.
Fig. 3 is a side view of the blank in the tooling.
Since tensile forces are not desirable in metal forming
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and compressive forces are desirable, in order to prevent
pulling the ends apart and causing failure the instant
process pushes, that is, applies a compressive force
simultaneously to the ends of the blank as it is also
being expanded by the post 20.
Applying compressive forces to ends 101, 102 of
blank 10 while driving the post 20 into the slit
gradually forms the blank into a round ring. The
compressive force is applied to ends 101, 102 of the
blank through shoes 23, 24. Shoes 23, 24 are pressed by
known hydraulic rams 201 and 202 in a manner known in the
art.
Fig. 4 is a perspective view of the blank at an
intermediate step. Slit 12
is shown partially opened.
The full diameter of post 20 has not yet engaged the
blank 10 and so it is not yet fully rounded. Shoes 23, 24
engage ends 101, 102 of the blank.
Fig. 5 is a side view of the blank in the tooling.
The full outside diameter of post 20 is shown fully
engaged with the blank 10. Blank 10 is therefore fully
round. Shoes 23, 24 are pressed about blank 10 in order
to control the forming and to avoid "squaring" of the
blank.
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Fig. 6 is a perspective view of the finished ring.
The ID of ring 10 substantially matches the OD of the
post 20.
Once the ring is formed on the post, it is ejected
and it is ready to use. If desired and required it is
ready for final operations, for example, machining,
rolling, spinning, forging, sizing, grinding, etc. The
formed ring can then sized in an ironing die in a press
to obtain a very accurate size and/or a very fine surface
finish.
Yet another version of the method shows that the
blank can be expanded to the somewhat square shape and
then rounded in a simple rotary forging operation. Other
embodiments include taking the square blank and spinning
it into a round ring, or using a ring rolling process to
achieve a round ring.
Further, the ring can either be formed to a round
final shape, or it can be introduced to the press tooling
again for a final sizing and rounding operation. The
need for these additional operations increases as harder
material is used, e.g., alloy steels or high carbon
steels. Harder steels can be formed with the described
press tooling, but, they may require larger diameters at
the end of the inner slit to prevent cracking. They may
also require hot forming (usually 600 to 1100 degrees
Celsius), or warm forming (up to 600 degrees Celsius).
The geometrical aspects of the parent bar stock,
namely the length, radii around the outer edges, the
diameter of the rounded radii at the ends of the slit and
the slit thickness are all relevant variables which can
be easily selected to optimize accuracy with minimum
offal.
The design of the tooling is also relevant to reduce
complexity. The tooling can comprise one long post with
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an expandable lower tooling or a few press stations with
gradually expanding lower tooling and gradually
thickening and rounding upper tooling. Furthermore, to
prevent failure at the ends of the slit for very hard
material, the pre-form blank may be made in a "dog bone"
shape, where very large diameters at the ends of the slit
will allow an easy forming process at the ends of the
slit area.
Fig. 7 is a top perspective view of a blank in the
tooling. Blank 10 is shown staged in collar 25. Collar
25 controls the position of the blank prior to and during
the forming process. Shoes
23, 24 are each shown
withdrawn in order to allow blank 10 to be inserted
between. Members 27, 26 support the blank between shoes
23, 24.
Shoes 23, 24 in Figs. 7, 8, 9 are the same as those
shown in Figs. 2, 3, 5.
Fig. 8 is a top perspective view of the tooling.
Blank 10 is removed to give a better view of the members
26, 27. Members
26, 27 apply a force in a vector
direction normal to the compressive force vector of shoes
23, 24 and simultaneously withdraw, or move apart from
each other in concert with post 20 as post 20 is pressed
through the slit in blank 10. This
provides the
necessary support for blank 10 as it is formed. Put
another way, members 26, 27 support the blank to prevent
an axial deformation that is normal to the direction of
expansion of the slit. This
prevents the blank from
deforming in the direction of movement of post 20. The
movement of post 20 is characterized as movement in an
axial direction.
Fig. 9 is a side perspective view of the tooling.
Post 20 is shown at the beginning of insertion into slit
12. Blade 22 is shown engaged with slit 12. Post 20 is
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pressed into slit 12, thereby expanding the middle of the
slit while shoes 23, 24 simultaneously compress the ends
of the blank. Post 20 is
pressed into the blank 10,
thereby continuing to expand the middle of the slit until
the blank is round. Post 20 is then withdrawn and the
formed ring is ejected.
Although forms of the invention have been described
herein, it will be obvious to those skilled in the art
that variations may be made in the construction and
= 10 relation of parts without departing from the scope of the
invention described herein.
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