U.S. patent application number 10/181964 was filed with the patent office on 2003-01-30 for method and a press cylinder device for producing a hollow body.
Invention is credited to Rolf, Bernhard.
Application Number | 20030019269 10/181964 |
Document ID | / |
Family ID | 7630258 |
Filed Date | 2003-01-30 |
United States Patent
Application |
20030019269 |
Kind Code |
A1 |
Rolf, Bernhard |
January 30, 2003 |
Method and a press cylinder device for producing a hollow body
Abstract
The invention relates to a flow-forming method and device for
producing a hollow article having a steplike shoulder from a
tubular workpiece. For this purpose on the tubular workpiece is
formed a conical area, which is selectively heated. Then an axial
upsetting force is exerted on the workpiece, so that the heated
conical area is upset and formed to the steplike shoulder. Both the
shaping of the conical area and the upsetting can be performed on
one flow-forming device.
Inventors: |
Rolf, Bernhard;
(Harsewinkel, DE) |
Correspondence
Address: |
OBLON SPIVAK MCCLELLAND MAIER & NEUSTADT PC
FOURTH FLOOR
1755 JEFFERSON DAVIS HIGHWAY
ARLINGTON
VA
22202
US
|
Family ID: |
7630258 |
Appl. No.: |
10/181964 |
Filed: |
August 5, 2002 |
PCT Filed: |
January 16, 2001 |
PCT NO: |
PCT/EP01/00435 |
Current U.S.
Class: |
72/85 |
Current CPC
Class: |
B21K 1/063 20130101;
B21K 1/12 20130101; B21H 1/00 20130101; B21K 21/16 20130101 |
Class at
Publication: |
72/85 |
International
Class: |
B21D 022/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 9, 2000 |
DE |
10005578.8 |
Claims
1. Method for producing a hollow article, particularly a hollow
shaft, with at least one steplike shoulder (20) from a tubular
workpiece (10), in which the tubular workpiece (40) is mounted on a
drivable spindle (60) and is rotated, on the tubular workpiece (10)
is formed a conical area (12), which links a first workpiece
section (14) having a larger diameter with a second workpiece
section (16) having a smaller diameter, and the conical area (12)
is formed to the steplike shoulder (20), charakterized in that
after forming of the conical area (12), it is selectively heated,
by means of a tailstock an axial upsetting force is exerted on the
workpiece (10) and the heated concial area (12) is pushed together
by the axial upsetting force exerted by the tail stock and under
the simultaneous action of at least one spinning roller (42) is
formed to the steplike shoulder (20), the spinning roller (42)
defining the contour of the desired shoulder (20) .
2. Method according to claim 1, characterized in that the conical
area (12) of the tubular workpiece (10) as produced by flow-forming
in a flow-forming machine.
3. Method according to claim 2, characterized in that the heating
and axial upsetting of the conical area (12) in the flow-forming
machine is performed in the same setting as the flow-forming.
4. Method according to one of the claims 1 to 3, characterized in
that a wall thickness increase is formed selectively on the
steplike shoulder (20) during the shaping of the latter.
5. Method according to one of the claims 1 to 4, characterized in
that during the shaping of the steplike shoulder (20) a mandrel
(50) is introduced into the workpiece (10) and predetermines an
inner contour of the shoulder (20).
6. Method according to one of the claims 1 to 5, characterized in
that several steplike shoulders (20) are formed on a workpiece
(10).
7. Flow-forming device, particularly for forming a hollow article
according to one of the claims 1 to 6, having a spindle (60)
drivable in rotary manner, a retaining device (62) fitted thereto
for the non-rotary retention of a tubular workpiece (10) on the
spindle (60), a spinning mandrel (50) with an outer contour adapted
to an inner contour of the workpiece (10) and a tail stock, which
is axially adjustable relative to the spindle (60), Characterized
in that a mechanism (44) is provided for the selective heating of a
workpiece area and the tail stock is constructed for exerting an
axial upsetting force on the workpiece.
8. Flow-forming device according to claim 7, characterized in that
the spinning mandrel (50) is located on the tail stock and a stop
member for transferring the upsetting force is provided on the tail
stock.
9. Flow-forming device according to claim 7 or 8, characterized in
that at its free end the spinning mandrel (50) has a draw-in
mandrel section (72), which is located on the spinning mandrel (50)
accompanied by the formation of a steplike shoulder (74) serving as
a stop.
10. Flow-forming device according to one of the claims 7 to 9,
characterized in that the retaining device (62) has a driving tooth
system (64), in which can be axially formed the workpiece (10) for
producing a non-rotary connection.
Description
[0001] The invention relates to a method for producing a hollow
article, particularly a hollow shaft, with at least one step like
shoulder from a tubular workpiece according to the preamble of
claim 1. The invention also relates to a flow-forming device
according to the preamble of claim 7.
[0002] Such a flow-forming device comprises a spindle drivable in
rotary manner, a retaining device fitted thereto for the non-rotary
retention of a tubular workpiece on the spindle, a spinning mandrel
with an outer contour adapted to an inner contour of the workpiece
and a tail stock, which is axially adjustable relative to the
spindle.
[0003] A method of the related art is described in FR 2 481 273.
According to this known method, the ends of a tubular workpiece are
heated to forging temperature. Afterwards, conical areas are formed
at the tube ends of the rotating workpiece by the infeeding of
friction or roller tools. By the radial infeeding of additional,
specifically shaped friction or roller tools, the inclination angle
of the conical areas is increased until steplike shoulders and
journals have been formed.
[0004] A device of the related art can e.g. be gathered from DE 195
11 963 A1. In this case a tubular starting workpiece is fixed in a
flow-forming machine and radially drawn in by the radial infeeding
of a spinning roller. This method is particularly efficient for
simple parts. On radially drawing in a section of the tubular
starting workpiece, steplike shoulders with radially directed walls
are formed. These radially directed walls can under certain
circumstances be exposed to strong forming forces, which on the one
hand lead to a thinning of walls and on the other to material
embrittlement and incipient cracks on exceeding the forming
capacity.
[0005] A similar problem can arise in the method for producing a
shaft according to DE 197 25 453 A1. In this known method for
weight reduction reasons the shaft is constructed as a hollow
shaft, which has steplike shoulders. During operation relatively
high loads can occur on the steplike shoulders of hollow shafts and
require a correspondingly thick dimensioning of the entire hollow
shaft wall. However, this is contrary to the need for a lightweight
shaft with a low mass moment of inertia.
[0006] The object of the invention is to give a method and a device
with which it is possible to produce a hollow article, particularly
a hollow shaft, with a steplike shoulder in an economic,
weight-saving manner and at the same time high strength is ensured
in the vicinity of the steplike shoulder.
[0007] This object is achieved by a method having the features of
claim 1 and by a flow-forming device having the features of claim
7. Preferred embodiments of the invention are given in the
dependent claims.
[0008] On the tubular workpiece a conical area is formed, which
links a first workpiece section with a larger diameter to a second
workpiece section with a smaller diameter, the conical area is
selectively heated, an axial upsetting force is exerted on the
workpiece and the heated conical area is upset and formed into the
steplike shoulder. As a result of the axial upsetting the tubular
starting workpiece collapses selectively in the heated conical area
and as a result of the material obtained during upsetting, a
steplike shoulder with a high wall thickness and therefore
considerable strength is formed. As a result of the selective
heating in the conical area the material of the workpiece is
influenced in such a way that it is plastically deformable with
respect to adjacent workpiece areas when a desired axial force is
applied. This ensures that even with relatively long workpieces
upsetting only occurs in the desired workpiece area. Heating can be
brought about by a heating device or by friction as a result of
engaging spinning rollers In the latter case, due to the
three-dimensional stress state produced by the spinning rollers, a
relatively limited heating is adequate for upsetting and wall
thickening.
[0009] Fundamentally for the method according to the invention any
tubular workpiece can be used, which is e.g. manufactured by
casting or forging. A particularly reliable construction of the
conical area is achieved in an embodiment of the invention in that
the conical area of the tubular workpiece is constructed by
flow-forming in a flow-forming machine. Thus, a planned wall
thickness reduction in the conical area can for instance be
obtained where, during upsetting, the workpiece bends in in a
clearly defined manner.
[0010] According to a preferred further development of the
invention, the heating and axial upsetting of the conical area is
performed in the flow-forming machine in the same setting as the
flow-forming. This allows a particularly economic manufacture of
the desired cylindrical hollow article.
[0011] During axial upsetting the shape of the steplike shoulder
can be developed freely, without the additional action of tools. If
a particularly precise contour of the steplike shoulder is desired,
it is advantageous according to the invention that during axial
upsetting and during the shaping of the steplike shoulder the
workpiece rotates and the shaping of the steplike shoulder takes
place under the action of at least one spinning roller. Said
spinning roller can be a sizing roller, which precisely
predetermines the contour of the desired shoulder.
[0012] According to a further development of the invention, it is
preferable during the shaping of the steplike shoulder to form in
planned manner a wall thickness increase on the shoulder. This can
in particular be brought about in that on the inside of the hollow
article the material obtained on upsetting freely forms a material
bead.
[0013] However, if a precisely defined inner contour is desired in
the hollow article, according to the invention during the shaping
of the steplike shoulder a mandrel is introduced into the workpiece
and predetermines an inner contour of the shoulder. This inner
contour can be a cylindrical shape with a rectangular shoulder for
receiving a bearing. In this variant with a precisely predetermined
inner contour, preferably a material bead is provided on the
outside of the hollow article, which during a subsequent metal
cutting machining operation, can be worked e.g. for forming a
bearing seat. Thus, it is reliably ensured that even during a
subsequent machining operation, an adequately large wall thickness
and high strength are available in the stepped area.
[0014] Preferably, according to the invention, several steplike
shoulders are formed on a workpiece. First of all, for this purpose
the individual steps can be formed successively, the first conical
area being heated first and then immediately following this the
associated step is formed. These operations are repeated until all
the shoulders have been formed. In another variant the different
conical areas can be simultaneously heated and then the shoulders
are formed in a single, common upsetting process.
[0015] Starting from a flow-forming device according to the
preamble, the object is inventively achieved in that a mechanism is
provided for the selective heating of a workpiece area and that the
tail stock is constructed for exerting an axial upsetting force on
the workpiece. With the flow-forming device according to the
invention, it is possible for the previously described method to be
performed in a single setting on a flow-forming machine.
[0016] On the flow-forming device a suitable mechanism can be
provided for heating the workpiece and can be constituted by an
induction device, a heat radiating means, a laser, a burner,
etc.
[0017] According to a preferred embodiment of the invention, the
spinning mandrel is placed on the tail stock and on the latter is
formed a stop member for the transfer of the upsetting force. It is
possible to set the spinning mandrel on the tail stock initially
for adjusting the wall thickness of the work-piece and for forming
the conical area by flow-forming in the same or opposite
directions. Subsequently by moving the tail stock by means of a
stop member on the latter an axial compressive force can be exerted
on the workpiece in order to form the desired step system. The
spinning mandrel can also remain within the workpiece, so as to
ensure a clearly defined inner contour during upsetting.
[0018] In preferred manner this embodiment is further developed in
that the spinning mandrel has at its free end a draw-in mandrel
section, which is located on the spinning mandrel forming a
steplike collar, which serves as a stop. In said device, after
setting the wall thickness of the workpiece and forming the conical
area, said mandrel is extended with the exception of the draw-in
mandrel section from the tubular workpiece. Then, with a spinning
roller the free end of the workpiece is drawn in against the
draw-in mandrel section, the workpiece diameter being reduced at
the drawn-in section. Thus, the free workpiece end faces the stop,
so that by axially infeeding the tail stock, the desired upsetting
force for forming the steplike shoulder can be transferred.
[0019] According to the invention, a particularly efficient working
of the workpiece is brought about in that the retaining device has
a driving tooth system, in which the workpiece can be axially
shaped for producing a non-rotary connection. After pre-centring on
the mandrel, the workpiece is pressed by the tail stock and/or the
spinning roller under a high axial force against the driving tooth
system, the workpiece being shaped into the driving tooth system
accompanied by the formation of a non-rotary connection.
[0020] The invention is described in greater detail hereinafter
relative to preferred embodiments and the attached diagrammatic
drawings, wherein show:
[0021] FIG. 1 Diagrammatic cross-sectional views of a workpiece
worked according to the invention in different working stages, and
FIG. 2 Diagrammatic cross-sectional views of a workpiece fixed in a
flow-forming device according to the invention in different working
stages.
[0022] FIG. 1a shows a tubular workpiece 10 centrically positioned
on a spinning mandrel 50. The spinning mandrel 50, which is part of
a flow-forming device, has a first cylindrical area 54 and a second
cylindrical area 56 having a smaller diameter, said two areas being
interconnected by a conical area 52.
[0023] By axial and/or radial infeeding of at least one spinning
roller 40, a desired outer contour of the workpiece 10 is set in
contrarotating flow-forming To obtain the shape shown in FIG. 1b
the spinning roller 40 is axially infed to the rotary workpiece 10
and, corresponding to an angle of entry on the spinning roller 40,
the diameter is reduced and the workpiece is simultaneously axially
lengthened. With a clearly defined setting of the forming
parameters, particularly the compressive force and the rotary
speed, contrarotating flow-forming by the roller can be performed
spaced from the mandrel 5Q. The different diameter areas according
to sections d1 and d2 in FIG. 1b are brought about by modifying
said forming parameters and/or the radial infeed position of the
spinning roller 40. The diameter areas d3 and d4 are achieved by a
known ironing flow-forming, in which the spinning roller 40 forms
the material directly cooperating with the spinning mandrel 50. In
the present embodiment a conical area 12 is shaped with a clearly
defined wall thickness, which links a first, larger diameter
workpiece section 14 and a second, smaller diameter workpiece
section 16.
[0024] Subsequently a diagrammatically represented mechanism 44 is
infed at the conical area 12 and as a result the latter is
selectively heated. Preferably a workpiece temperature in this area
is set which is above the recrystallization temperature, so that
the subsequent upsetting process can take place selectively in said
area and without work hardening.
[0025] The axial upsetting process in which a force F is exerted on
the workpiece 10 is illustrated in FIG. 1c. Through the axial force
F the conical area 12 is telescoped, accompanied by the formation
of a steplike shoulder 20. To obtain a clearly defined outer
contour, use is made of a sizing roll 42 with a corresponding
steplike contour, as can be gathered in detail from FIG. 1d. The
upsetting process leads to the production of material, which leads
to a wall thickness increase 22 in the vicinity of the steplike
shoulder 20
[0026] For setting a clearly defined inner contour, as can be
gathered from the upper half of FIG. 1c, the spinning mandrel is
slid into the workpiece 10. Alternatively and according to the
lower half of FIG. 1c, with an internally unsupported workpiece 10
a material head 24 can be formed, which ensures an additional
material reinforcement on the inside of the workpiece 10.
[0027] The thus formed hollow article with the steplike shoulder 20
is shown in FIG. 1e. Said hollow article can optionally be provided
with a further, steplike shoulder, where initially according to
FIG. 1b a further conical area 32 is formed by a correspondingly
shaped draw-in roller. This further conical area 32 can then be
formed in accordance with the previously described method steps by
heating and axial upsetting to give the further steplike shoulder.
Thus, in an efficient and highly precise manner a hollow shaft with
an undercut can be produced, a particularly pronounced material
accumulation occurring at the corresponding steplike shoulders.
[0028] An alternative method performance and a device according to
the invention are shown in FIGS. 2a to 2d. A tubular workpiece 10a
with a solid base area 11 and a centring bore made therein, is
axially pressed against a driving tooth system 64 of a retaining
device 62 by three diagrammatically indicated multipurpose spinning
rollers 46, which have a clearly defined mutual offset in the
circumferential, radial and axial directions in known manner. The
retaining device 62 is linked in non-rotary manner with a spindle
60 of a flow-forming device, whose fundamental construction with
respect to the frame, drive and mounting support of the spinning
rollers is known from the prior art. Between the spindle 60 and the
retaining device 62 is provided a resiliently and axially
displaceably mounted centring pin 61, which for the central
mounting of the workpiece 10a engages in its centring opening.
[0029] According to FIG. 2a, with the multipurpose spinning roller
46 a lengthening of the workpiece 10a by contrarotating
flow-forming is firstly brought about. The thus produced
intermediate product is shown in FIG. 2b. At this time the
multipurpose spinning roller 46 is reset at the free end of
workpiece 10a and simultaneously there is a tilting of the roller
by a tilt angle of e.g. 20.degree.. By adjusting the multipurpose
spinning roller 46, the bead-like projecting draw-in section 48
instead of the entry area 47 used during contrarotating
flow-forming now engages on the workpiece 10a.
[0030] According to FIG. 2c a spinning mandrel 50a inserted in the
workpiece 10a during the contrarotating flow-forming is largely
extended out of the workpiece 10a, so that only a cylindrical
draw-in section 72 located at the free end of the spinning mandrel
50a remains in the workpiece 10a. The draw-in section 72 has a
smaller diameter than the cylindrical spinning mandrel 50a and a
clearly defined collar 74 is formed. This collar 74 serves as an
axial stop through which on the one hand it is possible to limit an
axial lengthening of the workpiece 10a and on the other an axial
upsetting force can be transferred to the workpiece 10a by a tail
stock of the spinning mandrel 50a.
[0031] Through the bead-like draw-in section 48 of the multipurpose
spinning roller 46, the free end of the workpiece 10a is forced
radially inwards against the cylindrical draw-in mandrel section
and a conical area 12a is formed on the workpiece 10a. In
accordance with the description of the method relative to FIG. 2,
said conical area 12a can be shaped to a steplike shoulder. For
further shaping operations the multipurpose spinning roller 46,
which is tilted by an angle a compared with contrarotating
flow-forming, is moved along the outer circumference of the
workpiece 10a in fundamentally known manner.
* * * * *