Note: Descriptions are shown in the official language in which they were submitted.
2 ~ 6
COLD-FORMING OF TOOT~ED WHEELS FROM SElEhT STE:EL
This invention relates to toothed wheels of the type utilized in motor
vehicles as, for example, in the starter assembly thereof and more particularly to
improvements in the method of making such toothed wheels.
In my prior United States Patent No. 5,152~061, there is disclosed a
method of forming a ~oothed wheel including a series of cold-formed peripheral teeth
having sides spaced apart a predetermined distance utilizing (1) a rotary holding unit
having structure providing a generally radially outwardly facing control surface and
(2) a rotary tooth-forming tool unit having a rotational axis and a tooth-forrning
periphery extending annularly about the rotational axis. One of the rota~y units
includes two annular flanges extending outwardly thereof baving two smooth tooth-
side forming surfaces facing toward one another spaced apart the predetermined
distance. The method of the '061 patent comprises the initial step of cold-forming
a circular piece of sheet metal of predetermined thickness into a preform having an
outer annular section of generally uniform cross-sectional configuration and an
. ~.
, ~ integral sheet metal central wall generally of the predetermined thickness extending
annularly inwardly from the outer annular section toward a pre~orm axis, the outer ;
annular section having (l) a width greater than the
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predetermined thickness but no greater than the
predeterminad distance, and (2) a~ outer periphery
which will allow a ~eshing action with the tooth-
formin~ periphery of the tooth-forming tool unit. The
method of the '061 patent also includes the step
of rotatin~ (1) the rotary holding unit with the
preform secured thereto about the preform axi~ and
: with the control surface underlying at least a portion
10 of the annular section and (2) the tooth-forming tool
unit about the rotational axis thereof in a
predetermined rotational relation wherein the axes are
parallel and the rotational speeds are synchroni~ed.
While the rotary holding unit with th~ preform secured
thereko and the tooth-forming tool unit are in the
predetermined rotational relation, the method of the
'061 patent further includes the ~tep of
affecting a relative movement between the units and
the axes thereof in a direction toward one another to
engage the tooth-formirlq periphery of the tooth-
: forming tool unit in cooperating metal-deforming
relation with the annular section inwardly of the
exterior periphery thereof until the sheet metal of
the annular section is cold-formed into the series of
teeth, the peripheries of which are cold-formed by
rolling contac~ with the tooth-forming periphery of
, . the tooth-forming ~ool unit and portions of the sides
of which are smooth and cold-formed by contact with
the smoo~h too~h-side forming sur~ace so that an
amount of sheet metal which would otherwise
uncontrollably flow axially outwardly of the ~mooth
tooth-side ~orming sur~ace~ i~ conaentrated within the
teeth and/or the radially inward back-up thare~or.
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It has been found that, while the total
confinement o the metal during the cold-forming
operatlon has the advantages stated, there also
existed a tendency to break teeth off of the rotary
tooth-forming tool unit after a period of operation
which, on occasion, would be substantially less than
the normal ~xpected operative life of the tool unit.
The frequency of tooth failure was considered
unexpected particularly in the tool construction where
tha two annular flanges for forming the two ~mooth
tooth sides were integrally interconnected on opposite
side~ of the ~orming teeth.
An object of the present invention is to
overcome the problem of frequency of tooth failure in
the ro~ary tooth ~orming.unit of the above described
method of the '061 patent. In accordance with
the principles of the present invention this objective
is achieved by providing a method of ~orming a one-
piece sheet metal toothed wheel includin~ a central
sheat metal wali of predetermined thickness and a
series of cold-~ormed inteqral teeth on the periphery
of the central wall defined by troughs extending
radially inwardly therebetween to a cylindrical trough
plane concentric with an axis of the central wall, the
series o~ cold~formed integral teeth having an
op~rative width de~ined by spaced tooth side defining
planes. The method utilizes ~1) a rotary holding unit
which in holding operation provides an inner pair of
opposed central wall-engaging surfaces extending
generally radially outwardly to a cylindrical inner
plane ~paced inwardly ~rom an outer cylindrical plane
of a size equal to the trough plane and an outer pair
-- - ., .. .. . . ... .. .. - . ..... . .. . . .... . ... . ..
.:.. - , .: .. ,: :,. , .:,, . : .:: .:.. . . ..... :. :.: . , . ~ :. : ,. :
~0~3~ :
of back-up suraces extending from the inner pair of
opposed central wall-engaging surfaces at the inner
: plan~ to the outer plane where the outer pair of
~urfaces are spaced apart a predetermined distance
which i~ greater than the spacing between the inner
palr of aurfaces so as to define a back~up sp~ce
within an annulus between the inner and outer planes
a~d (2) a rotary tooth-formin~ tool unit having a
rotational axis and a tooth-forming periphery
~o extending annularly about the rotational axi~. The
method c~mprises a combin~tion of steps the initial
one o~ which is cold-forming a circular piece of sheet
metal into a preform having an outer annular section
of generally uniform cross-sectional coniguration and
an integral sheet metal central wall qenerally of the
predetermined thickness extending generally radially
inwardly from tha outer annular section toward a
prerorm axis. The outer annular section has (l) a
width greater than the predetermined thickness but no
greater than the predetermined distance, and (2) an
outer periphery extending beyond the trough plane
which will allow a meshing action with the tooth-
forming periphery o~ the tooth-forming tool unit. The
next step is rotating (1) the rotary holding unit with
the prefor~ secured thereto about the preform axis and
an inner portion of the outer annular section within
the back-up space and an outer portion of the outer
annular section extending radially outwardly o~ the
back-up space, and (2) the tooth-forming tool unit
30 . about the rotational axis thereof in a predetermined
rotational relation wherein the axes are parallel and
the rotational ~peeds are synchronized. ~he third
step is per~ormed while th; rotary holding unit with
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the preform secured thereto and the tooth-forming tool
unit are in the predetermined rotational relation
affecting a relative movement between the uniti and
the axes thereof in a direction toward one another to
engage the tooth-forming periphery of the tooth-
forming tool unit in cooperating metal-deforning
relation with the outer portion of the outer annular
section inwardly of the exterior periphery thereo~
until the sheet metal o~ the outer portion of the
ainnular section is cold formed into the series of
teeth and displaced ~rom the troughs therebetween so
that after the series of teeth are cold-formed the
toothed wheel includes a back-up portion having
- surfaces conforming to an outer extent of each o~ the
outer pair of ~iur~ace defining the back-up space, the
peripheries of the series of teeth being cold-formed
by rolling contact with the tooth-forming periphery of
the tooth-forming tool unit and the sides of the
series of teeth ihcluding portions disposed.outwardly
beyond the spaced tooth side defining planes being
j free formed without surface contact by the axial~y
outward movement of the metal defining the outer
porti~n of the outer annular section.
.. . .
Prefera~ly, the rotary holding tool unit
further provides a pair of cylindrical extarior
peripheral sur~aces extending axially in opposite
directions from the outer pair of surfaces within the
outer plane and the tooth formin~ periphery of the
tooth ~orming tool unit includes trough forming teeth-
like projections having exterior tips which extend toæaid trough plane. Pre~erably, in the third step, at
th~ end of the relative movement between the units
208~3~
, . . .
~owards one another to engaqe the tooth forming
periphery of the ~oo~h forming tool unit in
cooperating relation with the outer portion of the
outer annular section, the tips substantially engage
the exterior periphery sur~aces of the rotary holding
unit.
Preferably, the spaced tooth side def~ning
planes pas~ generally through the outer pair of
surfaces spaced apart within ths outer plane.
Preferably, the method includes a ~ourth step which is
the machinlng of the free-formed portions of the sides
of the series o~ teeth at least along one common side
so that the machined ~ides of the teeth on the one
common ~ide are disposed in a co~mon plane
constituting one of the spaced tooth si~e dePining
planes.
Anoth~r ob~ect of the present invention is
~, to provide a method of cold forming which is cost
effective~
20The~e and other ob~ects of the present
invention will become more apparent during the course
of the following detailed de~cription and appended
claims.
The invention may best be understood with
reference to the accompanying drawings wherein an
illustrative embodiment is shown.
IN THE DRAWINGS:
~0~33~ ~
Figure 1 is a perspective view partly in
solid lines and partly in dotted linas of a starter
gear with an integral pulse ring constructed in
accordance with the method of the pre3ent invention:
S Figure 2 is a fragmentary sectional view of
one-half of a circular piece of sheet ~etal which
constitutes the starting material ~n practicing th~
principles of the present invention:
Figure 3 is a view similar to Figure 2
illu~trating a fir~t step in the process of thP
present invention wherein the circular piece of sheet
metal is cold-formed into a can;
Figure 4 is a Yiew similar to Figurs 3
showing the next step in the method of th~ present
lS invention including the formation of an annular
section from the can;
Figure 5 i8 a view similar to Figure 4
showin~ the next step in the method of the present
invention wherein a ~inal preform is cold-formed by
thickening the annular section:
Figure 6 is a view similar to Figure 5
showing the teeth forming ~tep in the method of the
present invention wherein the th~ckened annular
sectio~ o~ the preform is cold-~ormed into a series of
teeth;
~a~3~
Figure 7 is a sectional view illuætrating
the entire rotary holding unit and rotary tooth
forming unit shown in Figure 6;
Figures 8, 9 and 10 are view8 similar to
Figures 2-6 illustrating steps in performing another
. embodiment of the method of the present invention;
:. Figures 11-13 ar~ views s~milar to Figures
8-10 illustrating steps in still another embodiment of
the method of the present inYention; and
Figures 14-17 are view si~ilar to Figures 2-
6 illustxating steps in still another modificatiun of
the ~ethod of the pr~sent invention.
' Re~rring now more particularly to Figures
1-7, there i~ shown therein a tootAed wheel in the
: 15 form of a starter gear, generally indicated at 10,
. constructed in accordance with the principles of the
present invention. Figures 2-6 illustrate various
steps in the method of making the starter gear 10 in
accordance with one e~bodiment of the methcd of the
' 20 present invention. As shown, the starter gear 10 is
:j made from a single circular pieca of sheet metal, as,
for exampl~, steel capable of being cold-formed. As
best shown in Figure 1, the starter ~ear 10 includes
a central wall 12 of sheet metal having a thickness
generally egual to the predetermined thickness o~ the
sheet metal which forms the starting material. Figure
j 2 illustrates in cross-section one-hal~ o~ a circular
,~ piecQ o~ sheet metal 14 tha ~ormation o~ which
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constitutes a first step in the method of the present
invention.
The starter gear 10 also includes an annular
section formed integrally with the outer periphery o~
the central wall 12, a portion of which is cold-
form2d into a serie~ of g~ar teeth 16 and a portion of
which defines pul~e ring 18 in tha form of an axially
extending cylindrical flange having a series oP
openings 20 extending radially therethrough at regular
intervals. As shown, there are twelve openings 20
equally ~paced annularly sbout the axis o~ the starter
gear 10 with each openin~ 20 being of ~enerally
rectangular configuration.
Referring now more particularly to Figure 2,
th~ circular piece of sheet metal 14 is illustrated
therein to be a separate piece which may be ~tamped
from a continuous sheet of steel. It will be
: undersLood that the separation of the circular
starting piece 14 from a roll or continuous web of
2 0 sheet material need not be accomplished in a ~ingle
step wherein the circular piece 14 i8 produced for
subsequent handling but may be only transitionally
formed as a part of a multi-step sequenc~ in the
~ethod. For example, the circular piece 14 could be
a transitional par~ in the step of cold-forming a can
22. Xowever, as shown in Figure 3, the circular piece
of sheet metal 14 i~ placed over a circular support ~4
and a die 26 having a cylindrical opening 28 therein
is moved axially so as to engage an outer annulus o~
the circul~r pieco 14 and &old-~ora the outer annulus
2~33~ ~
into a flange 30 extending axi~lly ~ro~ the outer
periphery of ~ central wall 12 ~hereof.
Next, as shown in Figure 4, the can 22 i8
placed so that the central wall 12 i~ in abutment with
a support ~2 having an annular reces~ 34 ~berein and
a cantral plunger 36, which has an exterior
cylindrical periphery 38 ~ized to engage within the
axial flange 30 of th~ can 22, i5 moYed toward the
support 3~ 80 as to form the central wall 12 of the
lo can 22 with a central re~ess therein de~ined by an
annular shoulder 400 A second outer annular plunger
42 is then moved toward the ~uppart 32 and tba plunger
~2 has an interior periphery 44 which is of notched
cyl indrical conf iguration so as to engage both the
15 exterior surface and the end surface of the axial
flange 30 of the can 22.
. ~ .
.' During the movement o~ the outer annular
plunger 42 toward the support 32, the portion o~ the
axial flange 30 adjacent the central wall lZ is bulged
20 out so as to form two annular side-by-side wall
port ions 4 6 and 4 8, one of which i8 integral at its
inner periphery with the outer periphery o~ the center
wall 12 and the other of which is integral at its
inner periphery with the adjacent end of the remaining
25 portion of the axial flange 30. The outer periphery
of both annular wall sections 46 and 48 are integrally
interconnected as indicated at 50. ~t the end of
.these procedures, the original circular piece of sheet
metal 14 has now been cold-~ormed into a non-thickened
30 pre~orru which includes the center wall 12 having an
outer annular section integral with the outer
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2~3~
periphery therao~, which ~ncludes the two side by-
side annular wall portions 46 and 48 and the remaining :~
portion of the axial flange 30.
Referring now more particularly to Figure 5,
the u~th~ckened preform is next ~ecured with a rotary
holding un~t, generally indi~ated at 52, which
includes a pair of complementary annular holding
members 54 and 56. As ~hown in Figure 5, the
complementa~y holding members 54 and 56 provide, when
in operative holding relation, an inner pair of
opposed central wall engaging surfaces 58 and 60,
re~pectively, which are spaced axially apart a
; distance equal to the predetermined thickness of the
central wall 12 so as to allow the central wall 12 to
be engaged therebetween. As shown in Figure 5, the
inner pair of opposed surfaces 58 and 60 extend
- generally radially outwardly to an inner cylindrical
plane, indicated by the phantom line ~1 in Figures 5
and 6, which is spaced inwardly from a pair of
exterior peripheral ~ur~aces 6~ and 63 on the holding
members 54 and 56 respectively. ~
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The complementary holding members 54 and 56
also have an outer pair of back-up sur~aces 6~ and 66,
respectively, extending fro~ the inner pair of opposed
. 25 central wall engaging surfa~es 58 and 60 respectively,
to exterior peripheral surfaces 62 and 63,
respectively. The peripheral surfaces 62 and 63 are
coincident with a cylindrical trough plane concentric
with the axis of the central wall 12 which defines the
inner extent oP the troughs to be formed between the
teeth on the preform. The outer extent of the
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2~g3~6
~ surfaces 6~ and 66 extend generally radially to the
; peripheral ~urfaces 62 and 63 in the trough plane in
axially ~paced relation. The axial ~pacing between
the outer pair of surfaces 64 and 66 at the trough
S plane ls a predetermined distance greater than the
predeter~ined thickness of the central wall 14. It
will also be noted that the surfaces 64 and 66 define
a back-up space which is disposed within the annulus
between the inner cylindrical plane 61 and the
cylindrical trough plane.
In the operative sacured relation of the
holding members 5~ and 56 with the non-thic~ene~
preform, the central wall 12 is emgaged between the
inner pair of opposed surfaces 58 and 60 and the
flange 30 i engaged within the back-up space defined
by the surface 66. The non-thickened preform thus
~ecured in the rotary holding unit 52 is then cold-
formed into a final thickened preform by moving a
rotary thickening tool 68 radially inwardly into
engagement with the connection 50 at the outer
periphery o~ the annular wall portions ~6 and 48 of
the non-thickened preform while the rotary holding
unit 52 is rotated to thus cold-form the outer
periphery of the annular section radially inwardly
into a configuration wherein the integral connection
50 between the two annular wall portions 4~ and 4~ are
~hickened as well as the ad~acent portions of the
annular wall portions themselves.
The next cold-forming step in the present
method i8 to cold-form the series of teeth 16 in the
thickened annular section of the final preform while
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it is reta~ned in secured ralation with the rotary?
holding unit 52. Figure 7 illustrates that the rotary
holding unit 52 forms a part of a cold-forming ~achine
capable of cold-forming the series of teeth 16 in the
annular ~ection of the pr~for~. The cold-for~ing of
the series of teeth 16 is accompli~hed by a rotary?
tooth forming tool unit, generally indicated at 70~
having a tooth forming tool structure ~2 on the
exterior periphery? thereof. The rotary tooth forming
unit 70 forms a part of a machine which provides a
means fsr effecting a rotational ~ovement of the
rotary? holding unit 52 and the rotary? tooth ~orming
:tool unit 70 in a predetermined rotational
..relationship wherein the axes are parallel and the
.
rotational speeds are synchronized.
Any suitable motion-transmitting means may
be provided in the machine for effecting the
rotational relationship. For example, as s~own, the
' rotary? holding unit 52 has a tiTning belt pulley 74
:~ 20 fixed to rotate therewith and the rotary tooth forming
tool unit 72 is likewise provided with a timing belt
pulley 76 which rotates therewith. A timing belt 78
is trained about the two timing belt pulleys 74 and 76
and a pair of movable idler pulleys 80 in such a ~ay
that the rotational relationship between the two
` ~ .rotary? units 52 and ? is maintained while permitting
a relative movement between the two units and the axes
thereo~ toward and away from one another. The tlming
belt 78 is of a type which includes ti~ing teeth on
; 30 both the interior and exterior sur~aces thereo~. The
teeth on the interior periphery, as shown, are trained
. about the exterior periphery of the timing belt pulley
13
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2~336
.
76 fixed with respect to the rotary holding unit 52
while the exterior teeth of the timing belt 78 are
trained about the timing belt pulley 76 f~xed to the
rotary tooth forming tool unit 70. The two idler
pulleys 80, which are on opposite sides of a plane
pa~ing through the axes of rotation of the two units,
are movable to take up any belt configuration change
as a result of the relative ~ove~ent o~ the two units
toward and away from one another with the movement of
the idlers 80 being commensurate so as to maintain the
synchronous rotational movement.
In this regard, it will be noted that the
directions of rota~ion of the rotary units 52 and 70
are in opposite directions s~ that the tooth forming
periphery 72 o~ the rotary tool unit 70 can be mo~ed
into meshing relation with the periphery of the
annular section of the preform secured to the rotary
holding unit 52. It will aliso be noted that the
thickness of the annular section is greater than the
predetermined sheet metal thickness and no greater
than the predeter~ined distance between surfaces 64
and 66. More specifically, as shown, the thickness of
the annular section is slightly greater than twice the
predetermined thi.ckness of the sheet metal but less
than the predetermined distance between the tooth side
forming surfaces 64 and 66.
once the predeter~ined rotational
relationship has been established, the two rotary
units 52 and 70 will b~ rotated in the prede~ermined
rotational relationship which, for example, is an
ldentical speed in opposite directions of 150-180
14
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2~8g33G
revolutions per ~inute. with the two rotary units 52
and 70 in the position ~hown in Figur~ 7 and while the
rotational relationship i8 retainsd, a relative
movement between the two rotary units and their
parallel vert.i.cal axes m a direction towards one ano~her is
effected. Preferably, th~ rotary tool unit 70 is
moved while the axis of rotation of the rotary holding
unit 52 i~ held stationary: although both unit~ could
be moved or only the rotary unit 52 could be moved.
An exemplary feed rate o~ the ~ovement of t~e axis of
the rotary tool unit 70 toward the axi~ of the rotary
holding unit 52 is approximately 120 mm. per minute.
As the outer tool forming periphery 7~ of the ~ool
forming tool unit 70 ~o~es to engage the periphery o~
the ~nnular section of the preform in cooperating
metal deforming relation inwardly of the exterior
periphery thereof, the sheet metal of the annular
section is cold-for~ed into a series of teeth.
Preferably, this is accomplished by effecting a
movement o~ the rotary tool unit 70 toward the holder
unit to an extent which equals about four meshing
turns. When this feed movement has been reached, the
drive fox the two units is reversed and then the ~eed
,movement is advanced until ~our more meshing turns are
; 25 acco~plished. These alternative direction feeds are
repeated until the full tooth configuration has been
completed.
Thus, during the i~feed, the peripher~es of
the series of teeth 16 are cold-formed by rolling
contact with the tooth ~orming periphery 72 o~ the
tooth ~or~ing tool unit 70. ~he tooth forming
periphery 72 consists of teeth-like projections with
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2 ~ 3 ~ ~
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trough-like spaces therebetween. The trough-like
spaces form the teeth on the preform and the teeth-
like projections form the troughs between the teeth on
the preform. Ths tips of t~e teeth-like projectionE
form the bottom of the troughs. It is noted that the
width of the teeth-like projections is greater than
the width of the teeth which are formed on the
preform. During the formation of the teeth on the
preform, the preform material which is initially
lo disposed in the spaces where the troughs are finally
provided i6 moved by the teeth-like projections of the
tooth forming periphery 72 either radially inwardly
into the back-up space or axially outwardly. Because
of ~he qreater width of the teeth-like pro~ections,
the axial movement must be accompanied by movements in
opposite circumferential directions. This
circum~erential movement results in a build-up of
material on both sides of the teeth being formed on
the preform. This build-up of the sides of tha teeth
is allowed to take place on a free-~orming basis in
the preferred configuration of the tooth-forming
periphery 72 wherein the teeth-like projections are of
uniform ~ross-sectional configuration across their
entire width. In this pre~erred configuration, there
are no spaced tooth-side defining flanges such as
provided in some of the tooth-forming peripheral
configuration in the '399 application. With the
preferred configuration, the entire sides of the teeth
of the preform are ~ree formed. It i~ within the
contemplation of the present invention to provide
~langes on the tooth-forming periphery 72 at the
posi~ions where it ls desired to ha~e the sides of the
teeth end so long as the flanges are slotted or
16
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208~33~
otherwise relieved 50 as to insure that at least
portion~ o~ the sides of the taeth ar~ free formed.
Tha amount of relief provided should be sufficient to
overcome the problem of premature breakage of the
teeth-like pro~ections of ~he tooth-forming periphery
heretofore experienced as a~oresaid.
In the preferred embodiment ~hown where the
flanges ar~ effectively slotted with a cross-se~tional
configuration the same as the trough-l~ke depressions
of the tooth-forming periphery 72, the desir~d width
of the teeth formed on the pre~orm generally conforms
to axially ~paced planes passing through the juncture
between the peripheral surfa es 62 and 63 with the
outer pair of ~urfaces 64 and 66. Figure 6 shows the
position of the tooth-forminq periphery 72 with
respect to the preform at the end of the relative
movement of ~h~ unit~ toward one another. It will be
noted that the tip o~ the tooth-like projections
extend to the trough plane o~ the ~ormed teeth and
that opposite end portions of the tips are
substantially in engagement with the exterior
peripheral sur~aces 62 and 63. It will also be noted
that the back-up space is filled with preform
material. In this regard, it will be noted that the
portion of surface 66 which extends axially in the
plane 61 l~mits the amount of radially inwardly
movement of preform material which can occur during
the ~ormation of the teeth. Preferably, the
limitation is cnough to fill the entire back-up space
in the areas of the formed teeth as well as the ~ormed
trough shown in the cross~section o~ Figura 6. In its
broadest aspeats, the invention contemplates that some
17
' ' ~. ~::: ~ ::: ~ '' :;'; ~ : ;, ~ ~-,, i, ~ ", " - ,, ::,",,~,, " " ,,, ~"~ ", ;,
2~33~
~oid are~s, as, for example, where the teeth are, can
exist within the back-up space a~ter tooth ~ormation.
With the preferred embodiment as shown in Figure 6,
the ~illing of the back-up space results in the Pree-
forming of the sides of the teeth beyond the desiredwidth of the aforesaid two plane~.
It is great~y preferred that the annular
: section of the preform have an outer peripheral
:dimension which is at least as great as the orest
dimension of the series of teeth and does not exceed
this dimen ion by more than approximat~ly 7% or
fun~tionally an amount which would enable a meshing
relationship between the annular section of the
prefor~ and the perophery oP the tooth ~or~ing tool
unit when initial engagement occurs. This size
relationship insures that it is not necessary to cause
cold flow in a radially outward direction but rather
than the direction of cold ~low of metal ic either
;axially outwardly or radially inwardly or a
combination of both. It will be understaood however
that, in its broadest aspects, the method does
comprehend cold flow radially outwardly.
In its broadest aspects, the present
invention contemplates having the ~ides free-formed,
. 25 however, preferably, the~ method of the present
invention contemplates machining one or both o~ the
sides of the teeth so that the sides are coincident
with the desired spaced planes. In the embodiment
thus far described, only the ~ree~ormed side in
alignment with surface 64 ~ machined and the other is
left free-formed with the flange 30 extending ``
l 18 .
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2~8833~
outwardly thereof. Thi~ rel~tionship is evident from
the perspective view of the completed toothed wheel 10
shown in Fi~ure 1.
As best shown in Figure 1, the central wall
12 is centrally apertured, as indicated ~t 82, which
i8 a cold-forming step that ~ay be accomplished after
the series of teeth 16 are cold-formed or preferably
this opening i~ ~ormed prior there~o. Another cold-
forming step which is made after the ~eries of teeth
16 have been cold-formed is ~he stamping o~ the series
of openings 20 of rectangular configuration at regular
intervals along ~he remaining portion of the axial
flange 30. The exterior surface o~ the remaining
- portion of the axial Plange 30 is pre~erably machined
in a lathe to ~orm the pulse ring 18 with an accurate
-; cylindrical exterior surface ~hich intersects with the
openings 20 to accurately provide signals at regular
intervals which are used to provide computer control
for the engine.
: ; ,
In the case o~ the starter gear 10 made in
accordance with the above procedure, it is desirable
that the f~nal configuration be given a heat treatment
at least in the area of the series of teeth 16.
Pre~erably, the heat treatment is by induction ~eating
~' 25 to a temperature of 850 to 900-C followed by quenching
~ in water to room temperature. Heat treatment is
;i considered desirable in the case of a starting gear
because o~ the severe loads which are imposed along
the volute surfaces of the teeth in operation. With
the pre~ent invention, the teeth can be made to be
~ubstantially solid i~ the aentral area where th~ load
i8 supplied by providing enough material in the
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psrform to ~nsure that the back-up space is ~illed.
However, as previously ~ndicated in its broader
aspects, the back-up space can have void areas. In
~orminq other toothed wheels, such as timing belt
pulleys and pulse rings, the prov~sion of an integral
pulse ring with the series of teeth may be eliminated
and the heat treatments can likewise be eliminated.
Figures 8-10 illustrate additional method
step variations which are within the contemplation of
the present invention. Figure 8 illustrates a
circular piece of sheet metal 114 of predetermined
thickness whioh is secured in a rotary holding unit
152 o~ modified form including first and ~econd
annular holding members ~54 and 156. As sh~wn, the
15holding mambers 154 and 156 are formed with an inner
pair of oppositely facing central wall engaging
surfaces 158 and 160 which are adapted to engage the
central wall 112 when in operative holding relation
therewith. A~ be~ore, the inner pair o~ 6urfaces 158
; 20 and 160 extend outwardly to an inner cylindriaal plane
161 which is inwardly of the trough plane of the
finished toothed wheel. As before, the holding
members 154 and 156 include outwardly facing exterior
peripheral surfaces 162 and 163, respectively, which
are disposed within the trough plane. An outer pair
of surface 164 and 166 respectively extend from the
surfaces 158 and 160 in plane 161 to the surfaces 162
and 163, respectively, so as to define a back-up 6pace
between the plane 161 and the trough plane.
30The holding members 154 and 156 in operative
holding relation cooperate with a rotary preform
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rolling member 168 having a U-shaped groov~ 169 formed
in it~ outer periphery. By advancing the rotary
preform rolling member 168 with respect to the rotary
holding unit 152 in a manner similar to the rotary
member 68 previously described, an outer annulus of
the circular piece 114 extending radlally outwardly
; beyond the surface 162 i~ cold-for~ed into a
peripheral flange extending outwardly and then
downwardly from a curved control port;on so as to
provide a cross sectional configuration which opens
generally radially inwardly. While Pinal
configuration o~ the annular section which is cold-
formed by the preform rolling member 168 could be of
inverted se~i-circular shape, the configuration is
more of an inverted U-shape having a pair o~ side-by-
side annular wall portions 146 and 148 integrally
interconnected by a central arcuate transitional wall
portion 150.
It will be understood that the annular
section provided by wall portions 146, 148, and 150
could be thickened by utilizing a thickening tool
, similar to the tool 68; however, in th~ method
~ according to 8-lO, the next step is to cold-form the
', annular section into a series of teeth. This is
accomplished by a rotary tooth ~orming tool unit 170
which is constructed and operated like the rotary
tooth forming tool unit 70 to include a tooth forming
periphery 172. The tool unit 170 is operated in the
same manner as indicated before with at least portions
of the sides of the teeth being free formed and the
back-up space preferably Pilled with steel material,
~, a8 i8 shown in Figure 10. The finished toothed wheel
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3 3 ~
in this embod~ment i~ prePerably machined along both
of the side defining plane~ which are aligned wi~h
sur~aces 164 and 166 at the trough plane.
Re~erring now more particularly to Figures
11-13, there is shown therein another variation in the
process according to the present invention. Again,
Figure 11 illustrates a starting circular piece o
steel sheet metal 2~4. The circular piece i~ then
secured within a rotary holding unit, generally
indicated at 252, which is constructed like the units
: 52 and 152 previously described. As before, the
rotary holding unit 252 includes two rotary holding
members 254 and 256, having an inner pair o~ central
wall engaging surfaces 258 and 260 extending to an
inner plane 261, a pair of exterior peripheral
surfaces 26~ and 263 and an outer pair of surfaces 264
~nd 266 ext~ndin~ from the surfaces 258 and 260 to the
surfaces 262 and 263 coincident with the tough plane.
.
The circular piece 214 is secured between
20 the members 254 and 256 in an operative relation so
that a central wall 212 is engaged between the
I surfaces 158 and 160. The outer annulus of the
; circular piece 214 extending beyond the inner plane
! 161 is thickened to provide an annular section 246
,25 which together with a portion filling the back-up
`,space constitutes a pre~orm. The cold-forming the
annular section is accomplished by the operation of a
rotary thickening tool 268 having a U-shaped
thickening 810t 269 ~ormed in the exterior periphery
thereo~ outwardly of the back-up 8paae defined by
surfaces 264 and 266.
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By advancing the rotary thickening tool 268
in conjunction with the rotation of the rotary holding
unit 252, the outer annulus of the circular piece 214
i8 thickened into a solid annular sect~on 246 having
a width les~ than the width o~ the teeth to be formed.
It will b~ noted that, during the thicken~ng
operation, the steel cold flows into substantial
filling relation to the back-up space. The outer
~ diameter of the annular section 246 is slightly greater
; 10 than the crest diameter of the teeth to be formed.
.` . .,
A series of teeth are cold formed in the
solid annular section 246 by utilizing the flanged
tooth forming tool unit 170 previously described in
the same manner as previously described. Again both
sides are machined in alignment with the surfaces 264
and 266 at the trough plane.
Referring now more particularly to Figures
14-17, there is shown therein still other
modifications within the principles of the present
invention. Here again, Figure 14 illustrates a
startinq circular piece of steel sheet metal 314. The
circular piece 314 i8 secured with a rotary holding
unit 352 which is similar to the units 52, 152, and
l 252 previously described. As before, the unit 352
i 25 includes t~o rotary holdin~ members 354 and 356. The
holding members 354 and 356 when in operative relation
with the piece 314 include an inner pair of central
wall engaging surfaces 358 and 360 extending to an
inner plane 361, a pair o~ exterior peripharal
30 surfaces 362 and 363 which are wi~hin a trough plane
outwardly o~ the inner plane 361 and an outer pair of
surfaces 364 and 366 which extend from the surfaces
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358 and 3~0 to the surfaces 362 and 363 so as to
define a back-up spaced between the inner plane 361
and the trouqh plane.
As be~orej the circular piece 3~4 i~ secured
in operat~ve relation ~etween the holding members 354
and 356 so as to extend generally axially outwardly
from the inner plane 361 beyond the outer periphery of
. a central portion of the circular piece which
- constitutes a central wall 312. The ~nnulus of the
circular pi~ce 314 is thickened into an initial solid
annular ~ection 348 by utilizin~ an initial thickening
tool 368 in the same manner as the thickening tool
268. Thereafter, a second thickening tool 36g is used
`~ ~n a similar manner to cold-form the initial annular
section 348 into a final ~olid annular section 349
having an axial flange 330 extending therefrom. As
shown, the axial flange 330 is integral with the
central wal} 312 and contacts the ~urface 366 of
holding member 356 along its inner periphery and the
.I 20 outer end thereof. ~he annular section 349 is
integral with the end of the axial flange 330 which $s
integral with the central wall 312. Again, it will be
noted that the annular section 349 has a width greater
than the predetermined sheet steel thickness but lass
than the width of th~ teeth to be formed. Again, the
steel ~aterial of the annular seation 349
.~ubstantially fill~ the back-up space defined by the
; sur~aces 364 and 366. Again, the outer periphery of
the annular section 349 i~ slightly greater than the
crest diam~ter of the teeth to be formed.
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After the pre~orm i~ cold-formed ~ncluding
central wall 312 and tha annular section 349 including
axial flange 330, the port~on of the annular isection
349 outwardly of the back-up ~pace i8 cold-~ormed into
a series of teeth. The teeth are formed by u8ing a
: rotary tooth forming tool unit 370 ~imilar to the
unit~ 70 and 170 in a 6imilar fashion except for one
difference. In all of the embodiment~ hereto~ore
- described, the outer periphery of the tooth-like
projections on the tool periphery 72 or 172 have
engaged or substantially engaged the exterior
peripheral surfaces 62 and 63j 162 and 163, or 262 and
263, however in forming the teeth with the tooth-
forming periphery 372, one side of the outer tips
engages only the sur~ace 362. The other side engagas
the outer surface of the flange 330.
.
This arrangement allows the sides of the
teeth to be free formed as before. Also, as befor~,
the back-up space is generally filled. With the
~` 20 provision of the flanqe 330, the toothed wheel is
IJ finished in the same manner as the wheel 10.
,
It thus will be seen that the obiects of
this invention have been fully and effectively
accomplished. It will be realized, however, that the
foregoing preferred specific embodi~ent has been shown
and described for the purpose of this invention and is
subject to ohange without departure from such
principles. Therefore, this invention includes all
modification~ encompassed within the spirit and scope
o~ the following claims.
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