U.S. patent application number 10/240064 was filed with the patent office on 2003-03-13 for device for guiding a metal strip on a gas cushion.
Invention is credited to Ebner, Peter.
Application Number | 20030047642 10/240064 |
Document ID | / |
Family ID | 3680989 |
Filed Date | 2003-03-13 |
United States Patent
Application |
20030047642 |
Kind Code |
A1 |
Ebner, Peter |
March 13, 2003 |
Device for guiding a metal strip on a gas cushion
Abstract
An apparatus is described for guiding a metal band (1) on a gas
cushion with blowing boxes (4) which are disposed one after the
other in the longitudinal direction (3) of the band and which
comprise nozzle fields (5) which extend transversally to the
longitudinal direction (3) of the band and comprise hole-type
nozzles (6) distributed over the field surface area. In order to
provide advantageous constructional conditions it is proposed that
the nozzle fields (5) are provided with a convex basic shape
through field sections (1, 3) which slope in at least one end
section at either side transversally to the longitudinal direction
of the band.
Inventors: |
Ebner, Peter; (Leonding,
AT) |
Correspondence
Address: |
Collard & Roe
1077 Northern Boulevard
Roslyn
NY
11576
US
|
Family ID: |
3680989 |
Appl. No.: |
10/240064 |
Filed: |
September 27, 2002 |
PCT Filed: |
April 25, 2001 |
PCT NO: |
PCT/AT01/00160 |
Current U.S.
Class: |
242/615.11 |
Current CPC
Class: |
B21C 47/3475 20130101;
B65H 2406/112 20130101; B65H 23/24 20130101; B21C 47/34 20130101;
C21D 9/63 20130101 |
Class at
Publication: |
242/615.11 |
International
Class: |
B65H 023/24 |
Foreign Application Data
Date |
Code |
Application Number |
May 5, 2000 |
AT |
A 791/200 |
Claims
1. An apparatus for guiding a metal band on a gas cushion with
blowing boxes which are disposed one after the other in the
longitudinal direction of the band and which comprise nozzle fields
which extend transversally to the longitudinal direction of the
band and comprise hole-type nozzles distributed over the field
surface area, characterized in that the nozzle fields (5) are
provided with a convex basic shape through field sections (1, 3)
which slope in at least one end section at either side
transversally to the longitudinal direction of the band.
2. An apparatus as claimed in claim 1, characterized in that the
field sections (2, 3) of the nozzle fields (5) slope increasingly
downwardly to either side.
3. An apparatus as claimed in claim 1 or 2, characterized in that
when providing nozzle fields (5) below and above the metal band (1)
to be guided the upper nozzle fields (5) are provided with a
concave basic shape which is adjusted to the convex basic shape of
the lower nozzle fields (5).
Description
[0001] An apparatus for guiding a metal band on a gas cushion
[0002] The invention relates to an apparatus for guiding a metal
band on a gas cushion with blowing boxes which are disposed one
after the other in the longitudinal direction of the band and which
comprise nozzle fields which extend transversally to the
longitudinal direction of the band and comprise hole-type nozzles
distributed over the field surface area.
[0003] In order to enable the conveyance of a metal band floating
on a gas cushion in the longitudinal direction of the band it is
known (DE 30 26 132 A) to provide blowing boxes which are disposed
one after the other in the longitudinal direction of the band and
whose nozzle fields extend transversally to the longitudinal
direction of the band and comprise hole-type nozzles which are
distributed over the field surface area. The gas flowing through
said hole-type nozzles against the metal band form a supporting air
cushion which is supported by a gas flow from slotted nozzles which
extend transversally to the longitudinal direction of the band and
delimit the field surface forming the hole-type nozzles. Since the
gas cushion is used not only for the contactless guidance of the
metal band but also for heat transmission, it is necessary to
additionally take the heat influences into account for a heat
treatment of the metal band, which lead to the consequence, among
other things, that the metal band arches about a central
longitudinal axis. This means that the distance of the metal band
from the nozzle field is larger than in the zone of the
longitudinal edges of the metal band. Due to said arching of the
band it is necessary to choose the conditions for the supporting
air cushion in such a way that in the middle zone of the metal band
a sufficient distance from the blowing boxes must be ensured in
order to exclude any contacts in the zone of the longitudinal
edges. This necessary increase of the distance in the middle zone
leads to a reduction in the carrying force, which then either
requires the use of thinner metal bands or an increase in the gas
volume flow through the nozzle fields.
[0004] The invention is thus based on the object of providing an
apparatus for guiding a metal band on an air cushion of the kind
mentioned above in such a way that a metal band arching under the
influence of heat can be guided in a contactless manner without
having to take into account any loss in carrying force which is
caused by the arching of the metal band.
[0005] This object is achieved by the invention in such a way that
the nozzle fields are provided with a convex basic shape through
field sections which slope in an end section at either side
transversally to the longitudinal direction of the band.
[0006] As a result of a convex basic shape of the nozzle fields
which is adjusted to the curvature of the metal band, an
approximately even distance between the metal band and the nozzle
fields can be ensured in a simple manner so that the carrying force
of the air cushions as produced by the nozzle fields can be
utilized fully without having to fear that the longitudinal edges
of the band will touch the blowing boxes. The convex basic shape of
the nozzle fields which is adapted to the curvature of the heated
metal band further ensures a substantially vertical flow charging
of the metal bands in the zone of the longitudinal edge, so that
overall favorable carrying conditions can be ensured.
[0007] The continuous progress of the curvature of the metal band
transversally to the longitudinal direction of the band can be
realized in the simplest case by field sections which slope at
either side transversally to the longitudinal direction of the band
in an end section of the nozzle fields. In order to ensure a
further adjustment of the field surface of the nozzle fields to the
curvature of the heated metal band, the field sections of the
nozzle fields can increasingly slope at either side. This condition
can be achieved by longitudinal sections of the nozzle fields which
are combined in a polygon-like way. It is understood that a
continuous curvature of the nozzle fields is possible. This
requires respectively increased manufacturing efforts, however.
[0008] In the heat treatment of metal bands, blowing boxes with
respective nozzle fields are provided both above and below the
metal band to be guided in a contactless manner in order to enable
an even heat treatment from both sides of the metal band. It is
therefore recommended in such a nozzle field arrangement above and
below the metal band to be guided to arrange the upper nozzle
fields with a concave basic shape which is adapted to the convex
basic shape of the lower nozzle fields. Said concave basic shape of
the upper nozzle fields naturally does not have any effect on the
carrying capacity, but instead has a considerable influence on the
even heat transmission, which obviously does not have to be
explained in closer detail here.
[0009] The drawing shows the subject matter of the invention in an
exemplary fashion. An apparatus in accordance with the invention is
shown for guiding a metal band on a gas cushion in sections in a
simplified diagram.
[0010] According to the illustrated embodiment, the apparatus for
guiding a metal band 1 consists of a frame 2 which carries blowing
boxes 4 which are disposed one after the other in the longitudinal
direction 3 of the band and which form nozzle fields 5. Said nozzle
fields 5 extend transversally to the longitudinal direction 3 of
the band and comprise hole-type nozzles 6 which are distributed
over the field surface area and through which gas (e.g. air) is
blown to form a gas cushion against the metal band 1. Along the
edges 7 of the nozzle fields 5 which extend transversally to the
longitudinal direction 3 of the band there are slotted nozzles 8
which delimit the field of the hole-type nozzles 6 and which
support the gas cushion formed by the hole-type nozzles 6 with
their gas jets. The gas flow deflected on the metal band 1 flows
off on the one hand between the two rows of slotted nozzles of each
nozzle field 5 against the longitudinal edges 9 of the metal band 1
and reaches on the other hand between the return flow channels 10
which are formed between the blowing boxes 4 and which expand with
respect to the flow cross section from the longitudinal center of
the metal band 1 against the longitudinal edges 9 as a result of
the frame surfaces 11 which slope downwardly in a roof-like fashion
in order to thus ensure the lowest possible flow speed and thus a
comparably low pressure drop.
[0011] In contrast to conventional nozzle fields, the nozzle fields
5 according to the invention are provided with a convex basic shape
which is adjusted to the curvature of the heated metal band 1 in
order to ensure a distance which remains substantially the same
over the band width between the metal band 1 and the nozzle
surfaces 5. As can be seen in the illustrated embodiment, the
convex basic shape of the blowing boxes 4 is achieved by
longitudinal sections 13 of the field surface which start out from
a middle section 12 and slope increasingly downwardly and are
combined in a polygonal manner in order to enable a sufficient
adjustment to the continuous curvature of the curved metal band 1
with simple constructional means. As a result of this adjustment,
advantageous carrying conditions are obtained without endangering
the contactless guidance of the metal band 1 on the gas cushions of
the nozzle fields 5.
[0012] Since an even heat treatment of a metal band 1 from both
sides requires nozzle fields on both the lower as well as the upper
side of the metal band, the blowing boxes 14 which are disposed
above the metal band 1 and are indicated with the dot-dash line can
also be provided nozzle fields 5 which are adjusted to the
curvature of the metal band 1 and which are then provided with a
respective concave basic shape, so that the distance to the metal
band 1 can be held approximately similarly over the width of the
band.
[0013] It is understood that the invention is not limited to the
illustrated embodiment because it is not the type and arrangement
of the nozzles that is relevant. Instead, it is merely the convex
basic shape of the lower blowing boxes 4 which is adjusted to the
curvature of the heated metal band 1 and possibly also the concave
basic shape of the nozzle fields 5 of the upper blowing boxes 4 in
order to ensure on the one hand advantageous carrying conditions
and on the other hand an even heat treatment of the curved metal
band 1.
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