U.S. patent application number 10/415026 was filed with the patent office on 2004-02-12 for endless yarn tensioning strip and method for producing the same.
Invention is credited to Jacobsson, Kurt Arne Gunnar, Ohlson, Per.
Application Number | 20040026562 10/415026 |
Document ID | / |
Family ID | 7662522 |
Filed Date | 2004-02-12 |
United States Patent
Application |
20040026562 |
Kind Code |
A1 |
Jacobsson, Kurt Arne Gunnar ;
et al. |
February 12, 2004 |
Endless yarn tensioning strip and method for producing the same
Abstract
An endless yarn braking strip for a yarn tensioning device
consists of precipitation hardened stainless steel (S). The endless
yarn braking strip is produced by first manufacturing an endless
blank from a sheet of precipitation hardening steel, shaping the
blank into a truncated cone in its endless form, and then hardening
the strip by precipitation hardening.
Inventors: |
Jacobsson, Kurt Arne Gunnar;
(Ulriceham, SE) ; Ohlson, Per; (Tvaerred,
SE) |
Correspondence
Address: |
Flynn Thiel Boutell & Tanis
2026 Rambling Road
Kalamazoo
MI
49008-1631
US
|
Family ID: |
7662522 |
Appl. No.: |
10/415026 |
Filed: |
August 11, 2003 |
PCT Filed: |
November 7, 2001 |
PCT NO: |
PCT/EP01/12881 |
Current U.S.
Class: |
242/615 ; 29/557;
428/596 |
Current CPC
Class: |
B65H 2601/121 20130101;
C21D 6/02 20130101; Y10T 29/49995 20150115; C21D 6/04 20130101;
B65H 2404/522 20130101; Y10T 428/12361 20150115; D03D 47/366
20130101; C21D 8/0205 20130101; C21D 6/004 20130101 |
Class at
Publication: |
242/615 ; 29/557;
428/596 |
International
Class: |
B23P 013/00; B65H
057/06 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 8, 2000 |
DE |
100 55 275.7 |
Claims
1. Endless braking strip (B) for a yarn brake, the braking strip
having the shape of a frustocone coat produced by cold deformation
of a flat blank (Z) made from thin metal sheet (M), characterised
in that the braking strip (B) consists of precipitation hardened
stainless steel (S) of the class "Precipitation Hardening Stainless
Steel" containing chromium and nickel as main alloy
ingredients.
2. Method for manufacturing an endless braking strip for a yarn
brake according to claim 1, wherein the method comprises the
following sequential method steps, cutting the endless flat blank
(Z) from the sheet metal (M), cold forming of the blank (Z) into
the shape of a frustocone, precipitation hardening of the
frustoconical blank (Z1).
3. Method as in claim 2, characterised by stamping the blank (Z),
deep drawing the stamped blank (Z) into the frustoconical shape,
and precipitation hardening of the deep drawn blank (Z1) an in an
austenite conditioning step (I), a subsequent
austenite-martensite-transforming step (II) and a final
precipitation hardening step (III) .
4. Method as in claim 2, characterised by heating the deep drawn
blank (Z1) to slightly below 1000.degree. C., preferably to
955.degree. C., and maintaining this temperature for about ten
minutes, and cooling down in ambient air to ambient temperature
(RT) during the austenite conditioning step (I), cooling the blank
(Z1) subsequently within one hour to about -73.degree. C.,
maintaining this cooling temperature over about eight hours during
the austenite-martensite-transforming step (II), and warming in
ambient air to ambient temperature, and heating the blank to
somewhat above 500.degree. C., preferably 510.degree. C.,
maintaining this temperature over about ninety minutes, and cooling
down in ambient air to ambient temperature (RT) during the
precipitation hardening step (III).
5. Method as in claim 2, characterised by stamping the blank (Z) as
a flat annulus with over dimensions in radial direction and cutting
the blank in radial direction to the target dimensions (di, da)
first after the deep drawing and prior to the precipitation
hardening process.
6. Method as in claim 2, characterised by stamping the blank (Z) as
a flat annulus with over dimensions in radial direction and cutting
the blank in radial direction to the target dimensions (di, da)
first after the precipitation hardening step.
7. Method as in claim 2, characterised by deep drawing the blank
into a uniform wall thickness within a range (y) between 0.01 mm
and 0.5 mm, preferably between 0.05 mm and 0.3 mm.
8. Method as in at least one of claims 2 to 7, characterised by
annealing the sheet metal (M) prior to stamping the blank (Z).
Description
[0001] The invention relates to an endless yarn braking strip
according to the preamble part of claim 1 and to a method for
manufacturing an endless yarn braking strip according to the
preamble part of claim 2.
[0002] In a yarn brake comprising a frustoconical, endless braking
strip the inner surface of the braking strip is pressed coaxially
against a yarn withdrawal surface of e.g. a storage body, the yarn
withdrawal surface in most cases being rounded. In this way a
contact area is created between the inner surface of the braking
band and the yarn withdrawal surface which contact area is used as
a braking zone. The yarn is stored on the storage body in the form
of windings and is withdrawn from the windings overhead of the
storage body and below the braking strip. The yarn passes the
contact area between the braking band and the withdrawal rim in
order to be braked, or to create a substantially uniform yarn
tension, respectively. By the withdrawal of the windings an
orbiting rotation of the withdrawn yarn is generated similar to the
motion of the hand of a clock. The braking strip undergoes a
deformation following the orbiting motion. The yarn rubs at the
braking strip. The storage body and the braking strip are
maintained substantially stationarily. For this reason the braking
strip needs to have flexibility, good spring property and high wear
resistance against the friction load of the respective yarn
material and against the friction load at the withdrawal surface
defining the braking zone together with the braking strip, which
withdrawal surface in most cases is metallic.
[0003] A frustoconical endless braking strip is known from WO
98/23520. The braking strip consists of a metal or a metal alloy.
In this case beryllium-copper is mentioned as an example.
Beryllium-copper is a material which needs extreme care during
machining. In case of certain operation conditions or for certain
yarn qualities the braking strip, however, may become worn out
relatively rapidly and markedly.
[0004] U.S. Pat. No. 5,546,994 discloses a braking strip consisting
of a metal sheet with a thickness of 0.1 mm or less and which is
produced by stamping and deep drawing. The braking strip is
described as being flexible.
[0005] U.S. Pat. No. 5,678,779 discloses an endless braking strip
of this kind consisting of a metal alloy.
[0006] U.S. Pat. No. 5,409,043 discloses such a braking strip which
is provided in the form of a very thin metallic layer at the inner
side of an outer Kevlar carrier cone. The braking strip,
alternatively, may consist of a steel sheet of a thickness of 0.05
to 0.1 mm. The active surface of the strip may be chromium plated
or nickel plated, respectively.
[0007] The braking strip has to be endless, springy, smooth despite
the small thickness and wearproof at its active surface for a
proper performance. The spring property and the wearproofness could
be achieved by hardened conventional steel types. However, hardened
conventional steel normally cannot be formed anymore. On the other
hand, hardening of prior deformed conventional steel hardly could
be carried out until now. Hardening of conventional steel types
after the forming process could result in form deficiencies of the
frustocone in case of such thin wall thicknesses (maximum a few
tenths of a millimetre) which form deficiencies destroy the
necessary evenness of the braking strip at the active surface and
which do not allow to achieve a homogeneous deformation performance
of the braking strip in operation. For those reasons such yarn
braking strips until now were produced from other metallic
materials.
[0008] A flexible yarn guiding sleeve known from U.S. Pat. No.
2,218,976 A consists of steel. For improving the wear resistance
only a free end section of the yarn guiding sleeve is hardened by a
heat treatment with subsequent quenching.
[0009] The article W. T. LANKFORD, Jr. & AL.: "The Making,
Shaping and Treating of Steel" 1985, HERBICK & HELD,
PITTSBURGH, Pa. XPOO2193211, pages 1335, 1339, 1344, 1345 discusses
the compositions of steels having high amounts of Cr-Ni of the
class "Precipitation Hardening Stainless Steel" as well as method
steps carried out during precipitation hardening of those steel
classes.
[0010] The section Beitz, K: H: Grote, Dubbel: "Taschenbuch fur den
Maschinenbau", 19 Edition, Springer Verlag, Berlin, 1997, ISBN
3-540-62467-8, E37-E39, discloses steel hardening processes for
different steel classes, the consequences of the hardening
processes and several application examples for the hardened
steels.
[0011] It is an object of the invention to provide a yarn braking
strip of the kind as mentioned at the beginning as well as a method
for manufacturing of such a yarn braking strip which allow to
fulfil the requirements of wearproofness, uniform surface
smoothness, uniform spring property and industrial large series
production in a cost effective way.
[0012] The object can be achieved by the features of claim 1 and in
terms of the method by the features of claim 2.
[0013] Precipitation hardened stainless steel containing a high
Cr-Ni amount of the class "Precipitation Hardening Stainless Steel"
as is normally used for constructing aircrafts unexpectedly
precisely fulfils the requirements which are valid for a braking
strip of a yarn brake. That is, the steel can be formed comfortably
prior to the hardening process in order to form the frustoconical
shape of the braking strip from a flat blank without form
deficiencies and then can be hardened such that it has the required
springiness, the smooth surface and mainly the wear resistancy at
the active surface. Precipitation hardening stainless steel is
available in the desired thicknesses for fair costs, and can be
simply machined mechanically and hardened comfortably.
[0014] In terms of the method the deformability of the
precipitation hardenable stainless steel is used in order to form
first the frustoconical shape of the braking strip from the flat
blank. Then the good hardening property is used in view to high
springiness and good wearproofness at the active surface. In this
case it astonishingly has been found out that the hardening process
can be carried out despite the thin wall thickness such that a
smooth surface results and such that no form deficiencies of the
frustocone of the yarn braking strip occur.
[0015] The flat blank, expediently, is formed by stamping. This
allows to achieve a high production rate with sufficient
preciseness. The cold deformation into the form of the frustocone
coat is expediently carried out by deep drawing in a tool. The
hardening process is carried out in three steps, namely in an
austenite conditioning step, a subsequent
austenite-martensite-transforming step and finally in an ultimate
precipitation hardening step.
[0016] During the austenite conditioning step the cold deformed
blank is heated to about 955.degree. C. and is then maintained
about ten minutes at this temperature. Thereafter the blank is
cooled down in ambient air to ambient temperature. Before an hour
has expired the cooled down, cold deformed blank is cooled down to
about -73.degree. C. and is maintained at this temperature for
eight hours. Then the blank is allowed to warm in ambient air again
to ambient temperature (transformation step). Ultimately the blank
is heated to about 510.degree. C., is maintained at this
temperature for about 90 minutes, and finally is cooled down in
ambient air to ambient temperature. By this the precipitation
hardening is terminated. The braking strip then can undergo further
conventional machining steps or may be directly integrated into the
yarn brake, respectively.
[0017] In view to precise dimensions and homogeneous properties of
the braking strip, it may be expedient, to stamp the blank as a
flat annulus over-dimensioned in radial direction and to cut the
blank only after the cold deformation and prior to the hardening
process to the target dimensions.
[0018] The material provided in radial direction in the
over-dimensions is expedient to compensate for material
displacements occurring during the stretching process accompanying
the cold deformation. As a result of the subsequent cutting then
uniform properties will be achieved in the yarn braking strip up to
the final cutting edges.
[0019] Alternatively, the final cutting even may be carried out
after the hardening process.
[0020] During the cold deformation, expediently, a uniform wall
thickness is set between 0.01 mm to 0.5 mm. A thickness range of
about 0.05 mm to about 0.3 mm is of particular advantage for such
yarn braking strips made from this precipitation hardened
steel.
[0021] In order to avoid corrosion during storing and
transportation or the like which corrosion might disturb during the
machining of the steel, and to achieve a better machinability, the
blank ought to be stamped from an annealed sheet metal. The term
"annealed" is to be understood as a corrosion protection measure
already employed by the sheet metal producer. This may, e.g.,
comprise a state which is called "Mill Annealed", i.e., a state
achieved by a treatment called "Solution Heat Treated And Rapid
Cooled".
[0022] The invention will be explained with the help of the
drawing. In the drawing is:
[0023] FIG. 1 a perspective view of an endless braking strip for a
yarn brake,
[0024] FIG. 2 the step of manufacturing a flat blank, in a vertical
section,
[0025] FIG. 3 schematically the cold deformation of the flat blank
of FIG. 2 into the shape of a frustocone, including a subsequent
cutting of the blank into the final dimensions, and
[0026] FIG. 4 a vertical section of the braking strip, including
indications to the carried out annealing or hardening steps.
[0027] An endless braking strip B has in FIG. 1 the shape of a
frustocone coat with a smaller diameter di and a larger diameter
da, a height h in the direction of the cone axis X, a strip width b
in the direction of the generatrice, and a wall thickness y. The
wall thickness y lies between about 0.01 mm and 0.5 mm and is
uniform within the entire braking strip B. The braking strip B
consists of a precipitation hardened stainless steel S
(precipitation
[0028] An endless braking strip B has in FIG. 1 the shape of a
frustocone coat with a smaller diameter di and a larger diameter
da, a height h in the direction of the cone axis X, a strip width b
in the direction of the generatrice, and a wall thickness y. The
wall thickness y lies between about 0.01 mm and 0.5 mm and is
uniform within the entire braking strip B. The braking strip B
consists of a precipitation hardened stainless steel S of the class
"Precipitation Hardening Stainless Steel". A good operation
performance can be achieved with the wall thickness of 0.08 mm,
e.g. in case of a yarn braking strip having an outer diameter of
about 110 mm, and inner diameter of about 85 mm, and a cone apex
angle between about 90.degree. and 120.degree..
[0029] The inner surface of the braking strip B is the active
braking surface which has to be smooth and wear resistant.
Furthermore, the strip has to be unstretchable but must be
deformable in radial direction or must be springy in radial
direction.
[0030] For manufacturing the braking strip B of FIG. 1 the
following steps are carried out:
[0031] According to FIG. 2 first an annular flat blank Z is formed
from a flat sheet metal M, e.g. by stamping. The inner diameter of
the annulus is smaller than the target inner diameter di of the
braking strip. The outer diameter of the blank is larger than the
target outer diameter da of the braking strip B.
[0032] According to FIG. 3 the flat blank Z is brought to the shape
of the frustocone or of a frustoconical intermediate product Z1 in
a tool W, e.g. by deep drawing. Since unavoidably material
displacements occur during a deep drawing process the blank Z is
oversized in radial direction. The over dimensions then will be
used during the deformation step of FIG. 3 in order to allow a cold
flow of the material. After the deformation steps the blank is cut
such that the target diameters di and da result.
[0033] The blank Z1 now having already the final dimensions then is
treated as follows:
[0034] During an austenite conditioning step I the blank Z1 first
is heated to e.g. 955.degree. C. and is maintained for about ten
minutes at this temperature. Then the blank is allowed to cool down
in ambient air again to ambient temperature RT.
[0035] In a second austenite-martensite-transforming step II which
starts within one hour after the first step I the blank Z1 is
cooled down to about -73.degree. C. and is then maintained at this
temperature for about eight hours before the blank is allowed to
again warm in ambient air to ambient temperature RT.
[0036] In a subsequent precipitation hardening step III blank Z1
again is heated, optionally to about 510.degree. C., is maintained
for ninety minutes at this temperature, and then is allowed to cool
down in ambient air to ambient temperature RT. Then the braking
strip B consisting of the precipitation hardened stainless steel S
is manufactured.
[0037] A subsequent machining is not necessary, however, may
occasionally be carried out.
[0038] Among other ingredients precipitation hardenable stainless
steel of the class "Precipitation Hardening Stainless Steel"
contains chromium and nickel as main alloy ingredients. This steel
type per se is intended for manufacturing springs, clips, frame
structures in aircrafts and pressure tanks. For such applications
the wear resistance of this steel is of secondary importance.
According to the invention to the contrary, mainly the wear
resistance of the precipitation hardenable steel is used as an
extremely favourable side effect for braking yarns.
* * * * *