Note: Descriptions are shown in the official language in which they were submitted.
~ ,r~
METHOD OF AND APPAT2ATUS FOR COLD fOf~'2T1VG '.I'OO~I'I~IED Wt-IEELS ,
FROM SHE~'I' METAL
1 BACKGROUND OF THEINVENTION
The invention relates to improvements in methods of
and in apparatus for cold forming toothed wheels from sheet
metal. t4ore particularly, the invention relates to
improvements in methods of and in apparatus for converting
ductile blanks of metallic sheet material into spur gears,
ring gears or analogous gears of the type wherein the
externally toothed rim is of one piece with the hub.
Externally toothed gears of the character to which
the present. invention pertains can be utilized in various
types of transmissions, e.g., in indexing drives, in starters
of engines for motor vehicles, in belt transmissions and for
many other purposes. For example, it is known to construct a
flywheel for use in the starter for the engine of a motor
vehicle in such a way that the central portion or hub is
produced as a discrete or separate first part and the toothed
rim is produced as a discrete or separate second part. The
hub is made of cold formed metallic sheet stock, and the rim
is made from a ring which is provided with teeth as a result
of machining in a material removing tool. The thus finished
ring, i.e., a rim with external teeth formed therein as a
result of material removal, is then welded to the hub. A
drawback of such procedure is that the gear is expensive and,
furthermore, the welding operation is likely to cause highly
unpredictable changes in the material of the hub and/or in
the material of the rim. Moreover, the weight and bulk of
the ultimate product are excessive for many purposes.
European Pat. No. 0 333 917 A2 proposes to reduce
the overall weight of a spur gear, a ring gear or an
analogous gear; iaithout unduly affecting the stability of its
rim and/or hub, by utilizing a preform which is provided with
a relatively thick marginal portion. The relatively thick
marginal portion is obtained by increasing the thickness of
the marginal portion of a circular metallic blank of constant
. thickness so that the cross--sectional area of the thickened
1 marginal portion exceeds the cross-sectional area of a
corresponding length of an annular zone having the thickness
of the blank.
The thickness of the marginal portion of the blank
is increased by resorting to a standard sheet metal treating.
operation, such as upsetting or the like. The treatment
involves pronouced changes in the texture of the material of
the blank. Since a blank of the just outlined character is
normally made of carbon steel, the aforediscussed upsetting
or an analogpus treatment necessarily entails an increase of
hardness which is undesirable in connection with the carrying
out of the next-following steps, i.e., conversion of the
preform into a gear with external teeth. Such conversion
normally involves hammering the thickened marginal portion of
the preform in a well known manner in order to provide the
external surface of the marginal portion with an annulus of
teeth. The method which is produced in European patent No.
0 333 917 A2 exhibits the drawback that the flanks of the
thus obtained teeth are often too weak so that the teeth are
likely to break in response to the application of moderate
stresses: Moreover, the just discussed method involves the
making of external teeth which extend radially outwardly as
well as radially inwardly, i.e., also beyond the internal
surface of the rim to thus impart to the internal surface an
undulate shape which entails the generation of pronounced
noise when the gear is in use.
European Pat. No. 0 140 576 A1 proposes the making
of a flywheel from a pressed article, namely from a so-called
first draw. The patent proposes to roll the teeth into the
peripheral surface of an axially extending portion of the
first draw. The drawing of the patent shows a finished
product which appears to have a smooth internal surface so
that the product is less likely to generate pronounced noise
in actual use. However, this proposal again exhibits another
drawback, namely that a blank must be converted into a first
- 3 -
1 draw in a first operation and the thus obtained first draw
must be transferred into a second machine in order to convert
it into a gear. Furthermore, the thickness of the marginal
portion which is converted into the toothed rim is the same
as that of the hub; this can result in the making of a weak
toothed rim whose teeth are likely to break (if the thickness
of the marginal portion of the preform is insufficient) or in
the making of a heavy and bulky gear if the thickness of the
marginal portion of the preform (and hence the thickness of
the hub) is selected with a view to ensure the making of a
toothed rim which is sufficiently sturdy to avoid the
breaking of its teeth.
Commonly owned German Pat. No. 38 19 957 C1
discloses a method of making a pulley from a circular
metallic blank of constant thickness. The blank is clamped
between two portions of a rotary tool so that its marginal
portion extends beyond the peripheral surface of the tool.
The projecting marginal portion is thereupon flexed by a
second tool to be converted into a flange extending to, one
side of the central portion of the thus deformed blank and
having a concavo-convex crass-sectional outline. Tie flange
is thereafter acted upon by a third tool which flattens the
flange by forcing it into a peripheral recess of the first
tool and thus increases its thickness. The patent discloses
that the external surface of the flattened and thickened
flange can be provided with circumferentially extending
grooves if the thus obtained pulley is to be used in
connection with vee belts, or the external surface of the
flange can be provided with transversely extending teeth for
engagement with the teeth of a toothed belt.
Commonly owned German Pat. No. 39 32 823 C1
discloses a method of making a gear wherein the rim extends
to one side of the hub and is provided with internal as well
_ as with external teeth. The marginal portion of a circular
metallic blank is flexed to one side of the central portion
- 4 -
KlJ 1~ (~ %,,~ '17 l~: c.1
1 of the blank with simultaneous thickening of the marginal
portion and the forming of internal teeth. The thus treated
blank is thereupon acted upon by a different tool which
provides its previously treated marginal portion with
external teeth. The overall axial length of the toothed rim
of the finished product is not predictable because some
material of the blank can flow axially during the making of
internal teeth and again during the making of external teeth.
German patent application Serial No. 40 06 582 A1
of Grob (published September 13, 1990) discloses a method of
making a gear by cold forming a metallic preform having a
marginal portion of U-shaped cross-sectional outline and
extending to one side of the hub. The marginal portion is
provided with external teeth by resorting to a rolling
operation. The internal surface of the externally toothed
rim of the finished product has an undulate shape, and the
material of the rim can flow in the axial direction of the
hub in the course of the rolling operation. ThP marginal
portion must be propped from within while a rotary rolling
tool provides the external surface of the marginal portion
with a set of axially parallel teeth. ,
5
1 OBJECTS OF THE INVENTION
An object of the invention is to provide a method
which renders it possible to convert a blank or a preform
into an externally toothed gear without any, or with
negligible, changes in the texture of the material of the
blank or preform.
Another object of. the invention is to provide a
method of making an externally toothed gear from a blank or
from a preform in such a way that the tYxickness of the
toothed rim of the ultimate product can be increased without
any; or without excessive, changes in the characteristic of
the metallic material of the blank.
A further object of the invention is to provide a
method which renders it possible to increase the thickness of
the marginal portion of a blank ar preform simultaneously
with the making of external teeth therein.
An additional object of the invention is to provide
a novel and improved preform which can be utilized.for the
practice of the above outlined method.
Still another object of the invention is to provide
a method which renders it possible to rapidly convert a
simple circular metallic blank into a gear with an externally
toothed rim having a smooth cylindrical internal surface.
A further object of the invention is to provide a
~ novel and impraved method of making one-piece spur gears,
ring gears or analogous gears in a simple and time-saving
operation.
Another object of the invention is to provide a
method which renders it possible to convert a blank or a
reform into an externally toothed gear with a strong rim
even if the thickness of that portion of the blank or preform
which is converted into the rim is the same as the thickness
of a relatively thin blank or preform of constant thickness.
An additional object of the invention is to provide
,a method which can be practiced to turn out inexpensive but
- 6
"fir ~.'~ ~ ~ ~ '~~'~
1 strong and reliable externally toothed gears for use, for
example, in the starters for the engines of motor vehicles.
Still another object of the invention is to provide
a novel and improved apparatus for the practice of the above
outlined method.
A further object of the invention is to provide the
apparatus with novel and improved means for synchronizing the
movements of various blank- or preform-supporting and
treating tools.
Another abject of the invention is to provide the
apparatus with novel and improved means for transmitting
torque to various rotary parts.
An additional object of the invention is to provide
an apparatus which can treat blanks and/or preforms of
various sizes, thicknesses and/or materials.
sG ad ~ ~'~J ~ L~.
J ,r
1 SUMMARY OF THE INVENTION
One feature of the present invention resides in the
provision of a method of making a rotary member having a hub,
a rim surrounding the hub and external teeth in the rim. The
improved method comprises the steps of mounting a
substantially circular metallic blank of ductile material on
~a first tool having a circumferential recess for a marginal
portion of the blank, deforming the marginal portion of the
blank into or at least close to the recess to convert the
marginal portion into a flange surrounding a central portion
which constitutes the hub of the thus deformed blank, and
cold forming the flange including subjecting the flange to
the deforming action of a rotary tooth forming second tool
having an annulus of teeth in a circumferential recess
adjacent the recess of the first tool to thus transform the
flange of the deformed blank into a rim with external teeth
while the flange is confined in the recesses of the first and
second tools.
The deforming step can include subjecting the
marginal portion of the blank to the cold forming action of a
third tool having a circumferential recess for a portion or
part of the marginal portion of the blank, moving at least
one of the first and third tools toward the other of the
first and third tools, and rotating at least one of the first
and third tools.
The cold forming step can include moving at least
one of the first and second tools toward the other of the
first and second tools and rotating at least one of these
tools.
The deforming step can comprise moving the marginal
portion of the blank in the direction of the axis of the
rotary member and to one side of the central portion of the
blank, i.e., the deforming step can involve a shifting of the
entire marginal portion to one side of the central portion of
the blank, namely of that portion which constitutes the hub
_ g
~~~ ~~ ~ ~'~ ~ ~~ ;~
1 of the deformed blank and of the ultimate product, a.g., a
starter gear for use on a flywheel which is driven by the
output element (e. g., a crankshaft) of the engine in a motor
.vehicle. Otherwise stated, the deforming step can involve
conversion of the marginal portion of the blank into a
flange, and such flange can have a concavo-convex cross-
sectional outline, preferably with a convex external surface
and a concave internal surface.
The deformed blank can constitute a preform having
the aforementioned central portion or hub and a converted
marginal portion in the form of a flange having a
substantially cylindrical first portion which is spaced apart
from the hub and a substantially annular second portion
having a substantially U-shaped cross-sectional outline and
disposed between and of one piece with the hub and the first
portion.
The cold forming step can further include providing
the rim with a smooth substantially cylindrical internal
surface. This cold forming step can involve a movement of
the second tool relative to the first tool, and the cold
forming step can include. increasing the thickness of the rim,
i.e., the rim can be thicker than the marginal portion of the
underformod blank.
Another feature of the invention resides in the
provision of a method of making a rotary member (e. g, a spur
gear, a ring gear or an analogous externally toothed gear)
having a hub, a rim surrounding the hub and external teeth in
the rim. This method comprises the s eps of mounting on a
first tool having a circumferential recess a substantially
circular metallic preform made of a ductile material and
hawing a substantially disc-shaped central portion and a
marginal flange extending to one side of the central portion
and overly ng the circumferential recess of the first tool,
deforming the flange into the recess to convert suoh flange
. into the rim which surrounds the central portzon. the latter
_ g _
1 constituting the hub of the deformed preform, and
simultaneously cold forming the flange including subjecting
the flange to the deforming action of a rotary tooth forming
second tool (e. g., a rolling tool) having an annulus of teeth
in a circumferential recess which is adjacent the recess of
the first tool to thus provide the flange with external teeth
within the recesses of the first and second tools.
The mounting step can include mounting on the first
tool a preform wherein at least a portion of the flange
extends at least.substantially at right angles to the
central portion, and such method can further comprise the
step of forming the preform prior to the mounting step. Such
forming step can include deforming a marginal portion of a
substantially circular metallic blank of ductile material
into the marginal flange of the preform.
The mounting step of the second method can include
mounting on the first tool a preform wherein the flange
includes a cylindrical portion in the recess of the first
tool and a second portion having a substantially U-shaped
cross-sectional outline, extending from the recess of the
first tool, and connecting the first portion with.t,he central
portion of the preform. The cold forming step of such method
can comprise moving the second portion of the flange toward
the recess of the first tool. The cold forming step can
comprise confining the entire flange of the preform in the
recesses of the first and second tools.
As already mentioned above, the second method can
further comprise the step of converting a substantially
circular blank of ductile metallic material into the preform.
A further feature of the present invention resides
in the provision of an apparatus for converting a metallic
blank into an externally toothed rotary member. The
apparatus comprises a blank supporting first rotary tool, a
carriage which is movable substantially radially of the first
. tool, an externally toothed secand tool which is rotatably
- 10 -
1 mounted on the carriage, a chain transmission connecting the
tools for rotation about discrete axes, and means for moving
the carriage relative to the first tool. In accordance with
a presently preferred embodiment of the improved apparatus,
the transmission comprises a first shaft which mounts the
first tool, a first sprocket wheel on the first shaft, a
second shaft provided an the carriage and mounting the second
tool, a second sprocket wheel on the second shaft, at least
one tensioning device, and an endless chain which is trained
over the sprocket wheels and over the at least one tensioning
device. The at least one tensioning device can comprise a
second carriage which is movable substantially radially of
the first tool, at least one additional sprocket wheel
rotatably mounted on the second carriage, and means for
moving the second carriage relative to the first tool. The
means for moving the second carriage can comprise. a fluid-
operated motor (e. g., a hydraulic cylinder-and-piston unit).
The first tool is or can be mounted for rotation
about a fixed axis, and the means for moving the first
carriage relative to the first tool can also comprise a
fluid-operated motor, e.g., a hydraulic cylinder-and-piston
unit.
Still another feature of the present invention
resides in the provision of a method of forming a toothed
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
generally radially outwardly facing control surface means,
and (2) a rotary tooth-forming tool unit having a rotational
axis and a tooth-forming periphery extending annularly about
the rotational axis, the rotary units including a total of
two annular flanges extending outwardly thereof having two
smooth tooth-side forming surface means facing toward one
another spaced apart the aforementioned predetermined
35' distance. This method comprises the steps of cold-forming a
- 11 -
1 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 generally radially inwardly from the outer annular
section toward a preform axis, the outer annular section
having (1) a width greater than the predetermined thickness
but no greater than the predetermined distance, and (2) an
outer periphery which will allow a meshing action with the
tooth-forming periphery of the tooth-forming tool unit,
rotating the rotary holding unit with the preform secured
thereto about the preform axis and with the control surface
means underlying at least a portion 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 their rotational speeds are
synchronized, and while the rotary holding unit with the
preform secured thereto and the tooth-forming tool unit are
in the predetermined rotational relation, effecting a
relative movement between the two units and their axes in a
direction toward one another to engage the tooth-forming
periphery of the tooth-forming tool unit in cooperating
metal-deforming relation with the exterior periphery of the
annular section and deforming the same 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 contact with
the tooth- orming periphery of the tooth-forming tool unit
and portions of the sides of which are smooth and cold-formed
by contact with the smooth tooth-side forming surface means
so that an amount of sheet metal which would otherwise
uncontrollably flow axially outwardly of the smooth tooth-
side forming surface means is concentrated within the teeth
and/or the radially inward back-up therefor.
35. The novel features which are considered as
- 12 _
1 characteristic of the invention are set forth in particular
in the appended claims. The improved apparatus itself,
however, both as to its construction and its mode of
operation, together with additional features and advantages
thereof, will be best understood upon perusal of the
following detailed description of certain presently preferred
specific embodiments with reference to the accompanying
drawings.
1 BRIEF DESCRI~TIOPJ OF THE DR?~WINGS
FIG. 1 is a fragmentary axial sectional view of a
first tool which mounts a circular metallic blank, and a
fragmentary partly elevational arid partly central sectional
view of a tool which serves to deform the marginal portion of
the blank;
FIG. 2 is a similar view of the tools of FIG. 1
but with the marginal portion of the blank in deformed
condition in which it constitutes a flange having a concavo-
convex cross-sectional outline;
FIG. 3 shows the first tool of FIGS. 1 and 2, the
deformed blank of FIG. 2 and an externally toothed tool which
is to convert the deformed marginal portion or flange of the
blank into an externally toothed rim;
FIG. 4 shows the structure of FIG. 3 with the
externally toothed tool in the process of cold forming the
deformed marginal portion or flange of the blank;
FIG. 5 is an axial sectional view of an externally
toothed gear obtained in accordance with the method which can
be carried out with the tools of FIGS. 1 to 4;
FIG. 6 is a fragmentary axzal sectional view of a
tool corresponding to the first tool of FIG. 1 but mounting a
preform having a deformed flange-like marginal portion which
overlies a circumferential recess of the tool, and a partly
elevational and partly axial sectional view of a tool
corresponding to the upper tool shown in FIGS. 3-4 and
serving to convert the flange-like marginal portion of the
preform into an externally toothed rim of the type
corresponding to that forming part of the gear of F3G. 5;
FIG: 7 is aview similar to that of FIG. 6 but
showing a different preform and a tooth forming or rolling
tool constituting a modification of the upper tool which is
shown in FIGS. f, 4 and 6; and
FIG: 8 is a fragmentary schematic partially plan
, and'partly horizontal sectional view of an apparatus which
- 14 -
L
1 can be utilized for the practice of the improved method and
wherein the tooth-farming or rolling tool can be moved
radially of the tool which mounts a blank or a preform.
1 DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows a portion of a circular blank 1 of
ductile metallic material having a central portion clamped
between two coaxial sections 2 and 3 of a rotary tool having
a circumferentially complete peripheral recess 7 between two
radially outwardly extending smooth control surfaces 2A, 3A.
These surfaces are respectively provided on a radially
outwardly extending portion or collar 2B of the section 2,
and on a radially outermost portion 3B of the section 3. The
axis of rotation of the tool including the sections 2, 3 is
denoted by a line X-X or is parallel to and is located below
the level of the line X-X (as viewed in FIG. 1).
The marginal portion lb of the blank 1 extends
radially outwardly well beyond the portions 2B and 3B so that
it can be deformed by a tool 4 into a flange 6 of the type
shown in FIG. 2. The flange 6 extend between the portions
2B, 3B and abuts the control surfaces 2A, 3A. The tool 4 is
rotatable about an axis which is parallel to the axis X-X and
includes two disc-shaped end portions 4a, 4b and an
intermediate or central portion 4c having a concave
peripheral surface 4d extending all the way betweep the end
portions 4a, 4b. The surface 4d converts the radially
outwardly extending marginal portion lb of the blank 1 into
the concavo-convex flange 6 of the deformed blank or preform
lA which is shown in FIG. 2. Such deformation of the
marginal portion lb takes place in response to a reduction of
the distance between the axes of the tool including the
sections 2, 3 and the tool 4. For example, the tool 4 can be
fed toward the axis X-X in the direction of arrow A; at such
time, the radially outermost part o~ the marginal portion lb
slides along the concave peripheral surface 4d of the
intermediate portion 4c of the tool 4.
The deformed blank or preform lA is ready to be
Converted into'an externally toothed gear or wheel of the
type shown in EIG. 5, as at 150 This is achieved by moving
- 16 -
_.
1 the tool including the sections 2, 3 into proper position
relative to a tooth forming tool 5 which is shown in FIGS. 3
and 4, or by repJ.acing the tool 4 with the tool 5 while the
radial and axial positions of the tool including the sections
2, 3 remain unchanged. The tool S has two disc-shaped end
portions 5a, 5b and an intermediate portion or central
portion 5c provided with an annulus of external teeth 9
within a recess 8 between the smooth confronting surfaces 5A,
5B of the end portion 5a, 5b, respectively. The distance
between the surfaces 5A, 5B is the same as that between the
surfaces 2A, 2B (as measured in the direction of the axis
X-X). The tool including the sections 2, 3 and/or the tool 5
is movable radially of the axis X-X in order to flatten the
flange 6, to increase its thickness, and to provide the thus
obtained rim 11 (FIG. S) with external teeth 10 complementary
to the teeth 9 on the tool 5. The arrow B in FIG. 3 denotes
that the tool 5 is movable radially of and toward the axis
X-X. The surfaces 2B, 3B and 5A, 5B cooperate to seal the
peripheral recesses 7 and 8 when the end walls 5a, 5b
respectively abut the portions 2B, 3B of the sections 2, 3 to
thus ensure that the material of the preform lA cannot flow
in an uncontrolled manner, i.e., that the axial length o~ the
rim ll and its teeth matches the distance of the surfaces 2A,,
3A or SA,-5B from each other. The dimensions of the blank 1,
the thickness of this blank, the distance of the surfaces 2A,
3A or SA, 5B from each other, the depths of the recesses 7, 8
and the dimensions of the teeth 9 are selected in such a way
that the recesses 7, 8 and the spaces between the teeth 9 are
filled with the material of the flange 6 when the tool 5
reaches the position of FIG. 4, i.e., when the preform lA is
converted into the rotary externally toothed gear 15 of FIG.
4 or 5. The smooth side surfaces of the rim 11 and its teeth
l0 are shown at l0a and lOb.
The end walls 4a, gb can constitute two separately
35. produced parts which are affixed to the central or
- 17 -
1 intermediate portion 4c of the tool 4 in a manner not forming
part of the present invention. Analogously, the end walls
5a, 5b can constitute separately produced parts which are
affixed to the central or intermediate portion 5c of the tool
5 in any suitable manner not forming part of. the invention.
The specific configuration of the hub 12 of the
gear 15 can be obtained in response to clamping of the blank
1 between the sections 2, 3. Alternatively, a blank having a
central portion corresponding to that of the hub 12 can be
clamped between the sections 2, 3 so that these sections
perform no deforming or shaping action but merely limit the
axial length of the flange 6 (see FIG. 2). The thickness of
the blank 1 can be constant, the same as the thickness a of
the hub 12. The thickness of the rim 11 (as measured in the
radial direction of the gear 15) may but need not be less
than the thickness a; this depends on the selected dimensions
of the recesses 7, 8 and of the spaces between the teeth 9 as
well as on the thickness of the flange 6. It is often
preferred to select the thickness of the rim ll in such a way
that it at least matches the thickness _a of the hub 12. The
internal surface lla of the rim ll is preferably smooth and
is complementary to the smooth surface 7a in the radially
innermost portion of the recess 7.
The gear 15 which is shown in FIG. 5 can constitute .
a spur gear in a starter which is used for the engine of a
motor vehicle. For example, the gear 15 can be welded or
otherwise secured to a flywheel which is mounted on and
receives torque from the crankshaft of an internal combustion
engine.
FIG. 6 shows a tool including the sections 2, 3
which are identical or analogous to the similarly referenced
sections of the tool shown in the lower parts of FIGS. 1 to
:4, and a somewhat modified tool 105 which is used in lieu of
the tool 5 of FIGS. 3~-4. The preform lOlA differs from the
35. preform lA in that its flange 106 merely overlies but does
- 18 -
'~a~~~~i'~j~'~
1 not extend into the recess 7 of the section 2. The preform
lOlA can be obtained from a blank 1 by resorting to a tool
corresponding to the tool 4 in that the tool 4 is not moved
from the position of FIG. 1 and all the way to the position
of FIG. 2. The tool 105 of FIG. 6 performs initially the
function of corwerting the flange 106 into a flange
corresponding to the flange 6 of FIG. 2 or 3, and thereupon
the function of the tool 5, i.e., converting the deformed
flange 106 into an externally toothed rim corresponding to
the part 11 (with teeth 10) shown in FIG. 5. The end
portions 105a, 105b of the tool 105 are provided with
confronting frustoconical smooth internal surfaces 105A,
105B, and the central or intermediate portion 105c of the
tool 105 has an annulus of teeth 109 in a recess 108
extending between the frustoconical surfaces 105A, 105B.
The tool 105 of FIG. 6 can be replaced with the
tool 5 of FIGS. 3-4, or vice versa, without departing from
the spirit of the invention.
FIG. 7 shows a tool including the sections 2 and 3,
a different preform 201A (which can be obtained from a
circular metallic blank 1), and a tool 20 which constitutes a
modification of the tool 105'shown at FIG. 6. The preform
2OlA includes a flange 16 having a cylindrical first portion
18 which is received in the recess 7 and~is normal to the
radially extending central portion 201a, i.e., to the hub of
the finished product. The flange l6 of the preform 20.1A
further includes a second portion l7 which is of one piece
with the central portion 201a and with the cylindrical
portion 18 and has a substantially U-shaped cross-sectional
outline. The portion 17 of the flange 16 extends radially
outwardly from and beyond the recess 7. It will be noted
that, in all illustrated embodiments of the preform or gear,
the flange or the rim is located in its entirety at one side
_ of the central portion or hub.
The tool 20 has a relatively narrow end wall 20b, a
- 19 -
fT
~ l'/, ~ C
1 wider end wall 20a and a central portion 20c with an annulus
of external teeth 9a in a recess 8a between the confronting
smooth frustoconical surfaces 20A, 20B of the respective end
portions 20a, 20b. The teeth 9a serve to cold form teeth
into the portion 17 as well as to force the portion 17 toward
the surface in the radially innermost portion of the recess 7
(when the tool 20 is moved in the direction of arrow B) to
provide the thus obtained rim with a smooth cylindrical
internal surface and with a set of external teeth in that
portion of the rim which constitutes the converted (cold
formed) portion 17 of the flange 16 of the preform 201A. The
cylindrical portion 18 remains, or can remain, at least
substantially unchanged and can be provided (e.g., at the
time of making a blank or at the time of converting such
blank into the preform 201A) with one or more openings which
can constitute so-called pulse openings to permit the .
generation of signals in connection with the use of the gear
in or with a computer-controlled internal combustion engine.
A gear which has openings in the cylindrical portion 18 can .
be used in the starter for a combustion engine.
The method which can be carried out in the
apparatus employing the tools of FIGS. 1 to 4 exhibits the
advantage that a blank 1 which has been clamped between the
sections 2, 3 remains between these sections all the way
until completion of the gear 15. On the other hand, the
apparatus employing the tools of FIG. 6 or 7 exhibits the
advantage that, though it is necessary to shape the preform
lOlA or 201A in a separate machine or in a separate part of a
machine which is designed to make gears in accordance with
the method of the present invention, the gear can be provided
with a rim having an externally toothed portion (namely the
converted flange 106 or the converted portion 17 of the
flange 16) as well as (in FIG. 7) a cylindrical portion 18
which can be provided with the aforediscussed openings.
The end portions 20a, 20b of the tool 20 cooperate
- 20 -
1 with the radially outermost portions 2B, 3B of the sections
2, 3 to prevent any uncontrolled axial flow of the material
of the preform 201A during movement of the tool 20 in the
direction of arrow B. Again, the dimensions of the recesses
7, 8a and of spaces between the teeth 9a are selected with a
view to ensure that a preform 201A matching a standard
preform or norm will be converted into a gear with a rim
having external teeth formed by the teeth 9a and a
cylindrical portion constituted by the portion 18 of the
flange 16 shown in FIG. 7. When the conversion of the flange
16 of the preform 201A into a rim is completed, the recess 7
is preferably completely filled with the metallic maternal to
thus ensure that the rim of the resulting gear will have an
internal surface conforming to the surface in the innermost
portion of the recess 7.
An important advantage of the improved method is
that the making of a flange 6. 106 or 16 merely involves
flexing of the marginal portion of a blank so that the
texture of the material of the marginal portion of the blank
or preform remains at least substantially unchanged. Any
changes in the texture of the material of the blank or
preform, or any pronounced changes of texture, take place
only when the flange 6 or 106 or 16 is acted upon by the tool
5 or 105 or 20, i.e., at the time the blank or preform is
provided with a finished rim having an annulus of external
teeth and preferably a smooth cylindrical internal surface.
Experiments indicate that the improved method
renders it possible to obtain a gear 15 or a similar gear
which has a relatively thin hub 12 arid wherein the thickness
of the rim lI (as measured in the radial direction of the
gear) suffices to ensure the required strength, and the
dimensions of the teeth are also such as to ensure the
required stability and long useful life in actual use in a
motor vehicle or elsewhere. The depth of spaces between the
teeth 10 can be selected practically at will by appropriate
zl
1 selection of the tool 5, 105 or 20 as well as of all other
parameters which influence the dimensions of the teeth at the
exterior of the finished rim 11. The latter can extend
exactly at right angles to the plane of the hub 12.
' FIG. 8 shows a portion of an apparatus which can be
utilized for the practice of the improved method. The
apparatus includes a frame or base 33 supporting a rotary
shaft 22 connected to a sprocket wheel 23 and also carrying '
the tool (for example, a tool including the sections 2, 3)
which mounts the blank 1, the preform lOIA or the preform
201A. A carriage 21 which is reciprocable in the base 33
along tracks 34 radially of the shaft 22 rotatably supports a
second shaft 24 which is parallel to the shaft 22. The shaft
24 is connected with a sprocket wheel 25 and also supports
the tool 4, 5, 105 or 20. The transmission including the
sprocket wheels 23, 25 further comprises an endless chain 26
which is trained over guide wheels 35 adjacent the sprocket
wheel 23 as well as over a chain tensioning unit including a
second caxriage 29 reciprocable in the base 33 radially of
the shaft 22 and supporting two rotary sprocket wheels 27,
28. The carriage 21 is movable toward the shaft 2,2 by a
first motor 36 (e.g., a fluid-operated motor such as a
hydraulic cylinder and piston unit), and the carriage 29 is
reciprocable by a second motor 30, e.g., a fluid-
operated motor including a hydraulic cylinder and piston
unit. It is also possible to provide the apparatus of FIG. 8
with other types of means for moving the carriages 21 and 29;
for example, the means for moving the carriage 21 can
comprise aprime mover and a mechanical power train between
such grime. mover and the carriage 2l. The motor 36 serves to
feed the carriage 21 (and the tool on the shaft 25) toward
the blank or preform mounted in the tool which is carried by
the shaft 22: The carriage 29 is movable by the motor 30 in
order to maintain the chain 26 under requisite tension so
35. that the chain ensures synchronous rotary movements of the ,
- 22
~~8~~~~~
1 shafts 22 and 24, i.e., that blank or preform on the shaft 22
is rotated in synchronism with the tool on the shaft 24. The
reference characters 31 and 32 denote in FIG. 8 bolts or
other adjusting devices which can move the shafts 37, 38 for
the sprocket wheels 27, 28 relative to the carriage 29. The
chain 26 is driven by a motor (not shown) which rotates the
shaft 22 or 24, i.e., a single motor suffices to drive the
blank or preform on the shaft 22 in synchronism with the cold
forming (flange-forming and/or tooth-forming) tool on the
shaft 25. Such synchronism is achieved in spite of
pronounced stresses which develop when the apparatus of FIG.
8 is in use to feed a tool on the shaft 25 toward and against
a blank or against a preform on the shaft 22.
The synchronizing means of the apparatus which is
shown in FIG. 8 has been found to be more reliable and
simpler than heretofore known synchronizing means which rely
on electronic circuita. The main reason for the superiority
of the illustrated apparatus is believed to be that it can
stand pronounced stresses which develop during cold forming
the flange of a blank or preform to convert it into an
externally toothed rim.
23 -
1 Without further analysis, the foregoing will so
fully reveal the gist of the present invention that others
can, by applying current knowledge, readily adapt it for
various applications without omitting features that, from the
standpoint of prior art, fairly constitute essential
characteristics of the generic and specific aspects of my
contribution to the art and, therefore, such adaptations
should and are intended to be comprehended within the meaning
and range, of equivalence of the appended claims.
