U.S. patent application number 12/315277 was filed with the patent office on 2009-07-02 for sound-damping air-conducting duct and method for the production of a sound-damping air-conducting duct.
Invention is credited to Albert Fendt, Robert Joest, Dimitrios Patsouras.
Application Number | 20090166126 12/315277 |
Document ID | / |
Family ID | 40671525 |
Filed Date | 2009-07-02 |
United States Patent
Application |
20090166126 |
Kind Code |
A1 |
Patsouras; Dimitrios ; et
al. |
July 2, 2009 |
Sound-damping air-conducting duct and method for the production of
a sound-damping air-conducting duct
Abstract
A sound-damping air-conducting duct that has at least one exit
opening for air, and is provided, in the region of the exit
opening, with a lining made of a sound-absorbing material, which
lining is surrounded, at least on its outside, by a wall made of
plastic, provided with holes, and the lining is attached to this
wall, whereby the lining is immediately, preferably directly,
connected with the wall, with material fit and/or shape fit, and/or
is connected with it in a single work step with the wall that is
produced using a primary shaping method. A method for the
production of a sound-absorbing air-conducting duct is also
provided.
Inventors: |
Patsouras; Dimitrios;
(Heppenheim, DE) ; Fendt; Albert; (Ziemetshausen,
DE) ; Joest; Robert; (Worms-Neuhausen, DE) |
Correspondence
Address: |
COLLARD & ROE, P.C.
1077 NORTHERN BOULEVARD
ROSLYN
NY
11576
US
|
Family ID: |
40671525 |
Appl. No.: |
12/315277 |
Filed: |
December 2, 2008 |
Current U.S.
Class: |
181/224 ;
264/35 |
Current CPC
Class: |
B29C 45/14221 20130101;
B60H 2001/006 20130101; B29C 45/14065 20130101; B29C 43/18
20130101; B60H 1/00564 20130101; B29K 2101/12 20130101; B29L
2031/3055 20130101; B29C 45/14786 20130101; B29K 2713/00
20130101 |
Class at
Publication: |
181/224 ;
264/35 |
International
Class: |
E04F 17/04 20060101
E04F017/04; E04B 1/84 20060101 E04B001/84 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 13, 2007 |
DE |
10 2007 060 525.2 |
Claims
1. A sound-damping air-conducting duct for an air conditioning or
ventilation system comprising: (a) at least one exit opening for
air; (b) a lining made of a sound-absorbing material provided near
said at least one exit opening, said lining having an outside
portion; (c) a wall made of plastic attached to said lining and
surrounding at least an outside portion of said lining, said wall
being provided with a plurality of holes at least near said lining;
wherein said lining is immediately connected with the wall with a
material fit or shape fit or is connected with the wall in a single
work step when the wall is formed.
2. The sound-damping air-conducting duct according to claim 1,
wherein the air conditioning or ventilation system is in a vehicle,
said lining comprises a non-woven fabric, said wall forms a
self-supporting line segment, and said lining is directly connected
with the wall.
3. The sound-damping air-conducting duct according to claim 1,
wherein the lining has a profiled surface or a surface provided
with nubs on an inside portion of said lining or on the outside
portion.
4. The sound-damping air-conducting duct according to claim 1,
wherein the plastic is a thermoplastic plastic and the lining is
porous or open-celled at least on the outside portion such that the
thermoplastic plastic of the wall passes through the lining at
least in partial regions of the lining or at least in part.
5. The sound-damping air-conducting duct according to claim 4,
wherein the lining is not completely infiltrated or penetrated by
the thermoplastic plastic of the wall so that the surface of an
inside portion of the lining is essentially free or completely free
of the thermoplastic plastic of the wall.
6. The sound-damping air-conducting duct according to claim 4,
wherein the lining comprises internal material structures and the
thermoplastic plastic of the wall engages behind said internal
material structures.
7. The sound-damping air-conducting duct according to claim 6,
wherein the internal material structures comprise fibers.
8. The sound-damping air-conducting duct according to claim 1,
wherein the lining has a thickness that is less than 1.0 mm.
9. The sound-damping air-conducting duct according to claim 1,
wherein the lining has a thickness of approximately 0.5 mm.
10. The sound-damping air-conducting duct according to claim 1,
wherein the lining has an original thickness and the lining is
compressed to a compressed thickness that amounts to only a
fraction of the original thickness.
11. The sound-damping air-conducting duct according to claim 1,
wherein the holes of the wall comprise passage holes.
12. The sound-damping air-conducting duct according to claim 1,
wherein the holes of the wall have an average diameter or a minimal
diameter of 1 to 3 mm.
13. The sound-damping air-conducting duct according to claim 1,
wherein the holes have an average diameter or a minimal diameter of
1.5 to 2.5 mm.
14. The sound-damping air-conducting duct according to claim 1,
wherein the holes have an average diameter or a minimal diameter of
1.8 to 2.2 mm.
15. The sound-damping air-conducting duct according to claim 1,
wherein the holes of the wall are conical.
16. The sound-damping air-conducting duct according to claim 1,
wherein at least the holes of the wall provided near the lining
narrow in cross-section towards the lining.
17. The sound-damping air-conducting duct according to claim 16,
wherein the holes narrow continuously toward the lining.
18. The sound-damping air-conducting duct according to claim 1,
wherein the holes of the wall provided near the lining are covered
by the lining.
19. The sound-damping air-conducting duct according to claim 18,
wherein the holes are immediately delimited by the lining.
20. A method for producing a sound-damping air conducting duct for
air conditioning or ventilation system comprising the steps of: (a)
producing a wall from thermoplastic using a primary shaping method
selected from the group consisting of an injection-molding method,
a transfer-molding method, and an impact-extrusion method; and (b)
connecting a lining made of sound-absorbing material with the wall
in one work step during formation or shaping of the wall; wherein
the duct has at least one exit opening for air and is provided with
the lining; wherein the lining is surrounded at least on an outside
portion of the lining by the wall; and wherein the wall is provided
with holes.
21. The method accordingly to claim 20, wherein the lining is
immediately connected with the wall with a material fit or a
shape-fit; the air conditioning or ventilation system is in a
vehicle; the lining comprises a non-woven fabric; and the wall
forms a self-supporting line segment.
22. The method according to claim 21, wherein the vehicle is a
motor vehicle and the lining is directly connected with the
wall.
23. The method according to claim 20, wherein the lining has an
original thickness and the lining is compressed to a fraction of
the original thickness before or during the formation or shaping of
the wall, at least in partial regions of the lining.
24. The method according to claim 20, wherein the lining is
compressed by mechanical forces of die structures of a mold die
that determine configuration or shape of the holes of the wall at
local pressure points.
25. The method according to claim 20, wherein during the formation
or shaping of the wall, the thermoplastic plastic is provided in a
molten or viscous state and the lining is compressed during the
formation or shaping of the wall, at least in partial regions by
the internal pressure forces exerted by the thermoplastic plastic
in the molten or viscous state.
26. The method according to claim 20, wherein during the formation
or shaping of the wall, the thermoplastic plastic is provided in a
molten or viscous state and the lining is compressed by mechanical
forces of die structures of a mold die that determine the
configuration or the shape of the holes of the wall, at local
pressure points and, at the same time or subsequently, in regions
disposed adjacent to or between the local pressure points by
internal pressure forces of the thermoplastic plastic in the molten
or viscous state that occur during formation or shaping of the
wall.
27. The method according to claim 20, wherein the lining is
compressed before or during the formation or shaping of the wall,
in such a manner that the holes of the wall of the sound-damping
air-conducting duct in a finished condition are immediately
delimited, at least in part by the lining.
28. The method according to claim 27, wherein the holes of the wall
of the sound-damping air conditioning duct in the finished
condition are immediately delimited essentially by the lining.
29. The method according to claim 24, wherein the lining in the
sound-damping air-conducting duct in a finished condition, near or
at the local pressure points, has a first thickness that
approximately corresponds to a second thickness of the lining in
regions that immediately follow the local pressure points or in
regions disposed adjacent to or between the local pressure
points.
30. The method according to claim 26, wherein the lining in the
sound-damping air-conducting duct in a finished condition, near or
at the local pressure points, has a first thickness that
approximately corresponds to a second thickness of the lining in
regions that immediately follow the local pressure points or in
regions disposed adjacent to or between the local pressure
points.
31. The method according to claim 24, wherein the lining, in the
sound-damping air-conducting duct in a finished condition, near or
at the local pressure points, has a thickness that is different as
compared with adjacent regions of the lining.
32. The method according to claim 26, wherein the lining, in the
sound-damping air-conducting duct in a finished condition, near or
at the local pressure points, has a thickness that is different as
compared with adjacent regions of the lining.
33. The method according to claim 31, wherein the thickness is
smaller as compared with the regions adjacent to the lining.
34. The method according to claim 32, wherein the thickness is
smaller as compared with the regions adjacent to the lining.
35. The method according to claim 20, wherein: (a) the lining is
introduced into an open mold die having a die core; (b) the lining
is held on or on top of the die core, to prevent detachment from
the die core or to prevent displacement relative to the die core by
at least one holding or fixation device; and (c) the plastic
material for the wall is introduced into the open mold die, the
open mold die is subsequently closed, whereby or whereupon the wall
is formed and connected with the lining in one work step, or the
open mold die is closed and the plastic material for the wall is
injected or pressed into the closed mold die, whereby or whereupon
the wall is formed and connected with the lining, in one work step.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] Applicants claim priority under 35 U.S.C. .sctn.119 of
German Application No. 10 2007 060 525.2 filed Dec. 13, 2007.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a sound-damping
air-conducting duct or to an air-conducting duct for air
conditioning and/or ventilation systems, particularly for vehicles
or in a vehicle, preferably for motor vehicles or in a motor
vehicle. The duct has at least one exit opening for air, and is
provided, in the region of the exit opening or in the exit region,
preferably by way of a longitudinal segment, with an at least
partially air-permeable or sound-permeable lining made of a
material that absorbs or damps sound carried in the air, which
lining is surrounded, at least on its outside, by a wall made of
plastic, provided with holes at least in the region of the lining,
preferably forming a self-supporting line segment, and the lining
is attached to this wall.
[0004] 2. The Prior Art
[0005] A sound-damping device for ducts of or in air-conditioning
systems and the like, through which air flows, or which conduct
air, has become known from DE 82 15 489 U1.
[0006] In the case of this sound-damping device, a sound-absorbing
or sound-damping lining, which preferably consists of a foam
material web that has a skin on at least one side, but can also
consist of a non-woven fabric or another sound-absorbing material,
can be surrounded, on the outside, by a carrier that can consist of
a perforated, hard material, for example of plastic, and supports
the lining and forms a self-supporting line segment of the air
duct.
[0007] This sound-absorbing lining can achieve a significant
reduction in the noise level by damping the reflected sound waves
in the exit region of the air duct. The lining is sound-permeable
at least in part, so that sound waves can pass through the lining
and also through the holes of the carrier, without being disruptive
in the space to be air-conditioned, into which the air is passed
from the exit opening of the air duct.
[0008] For the production of this line segment, it is provided to
pre-finish the stiff, perforated carrier, and then to apply the
foam material lining.
[0009] It has also become generally known to produce similar molded
parts that absorb sound carried in air, specifically by means of
multi-step methods, which comprise deforming, cutting to size, and
coating with adhesive, lamination or welding, and subsequent
processing.
[0010] Such production is complicated and expensive. In addition,
detachments of the lining can occur, which can then get into the
space to be ventilated or air-conditioned, and consequently into
the air that is being breathed in, so that they represent a hazard
for life and health.
SUMMARY OF THE INVENTION
[0011] It is an object of the invention to provide a sound-damping
air-conducting duct that can be produced in more cost-advantageous
manner, while providing advantageous possibilities for further
improved noise reduction, and in which detachments of the
sound-absorbing lining are avoided or prevented.
[0012] These and other objects are achieved, according to the
invention, by means of a ventilation duct having the
characteristics mentioned initially, particularly in that the
lining is immediately connected with the wall, with material fit
and/or shape fit, i.e. without any separate connection and adhesion
agents, such as glues, preferably directly, or without any
intermediate layer or without multiple intermediate layers,
particularly without welding, and/or is connected with the wall in
a single work step with the wall that is produced using a primary
shaping method.
[0013] By means of these measures, particularly cost-advantageous
production can be achieved, and the sound-absorbing lining remains
securely connected with the wall of the sound-damping and
air-conducting duct even over an extended period of time. By means
of a suitable layout of the holes of the wall in combination with a
thin lining, it is made possible that noises or sound waves that
are provoked by a fan wheel or the like, or by air that flows in
the shafts of an air-conditioning system, can flow through the
holes of the wall into a cavity, or can be deflected, without being
disruptive in the space to be ventilated or air-conditioned. At the
same time, the air flow can flow through the ventilation channel,
and exit from its exit opening, essentially free of losses, i.e. at
a low flow resistance.
[0014] According to an advantageous embodiment, it can be provided
that the lining has a profiled surface and/or one provided with
nubs, on its inside and/or outside. In this way, the
sound-absorbing effect can be further reinforced and/or in this
way, better adhesion or fixation of the lining to the wall can be
achieved.
[0015] Furthermore, it can be provided that the lining is
configured to be porous and/or open-celled, at least on its
outside, in such a manner that the thermoplastic plastic of the
wall passes through the lining, at least in partial regions or in
part. In this way, an even better connection of the lining to the
wall, secure against detachments, can be achieved.
[0016] Furthermore, it can be provided that the lining is not
completely infiltrated or penetrated by the thermoplastic plastic
of the wall, so that the inner surface or inside of the lining is
essentially free or completely free of the thermoplastic plastic of
the wall. In this way, it can be assured that the air flow through
the air-conducting duct remains essentially uninfluenced by the
lining in the region of the lining, and consequently can be
conducted to the outside through the exit opening with little flow
resistance and minimal noise development.
[0017] Furthermore, the thermoplastic plastic of the wall can
engage behind internal material structures, for example fibers, of
the lining. By these measures, further improved adhesion and
shape-fit attachment of the lining to the wall, and consequently
even greater security against detachment of the lining, can be
achieved.
[0018] In a particularly advantageous embodiment, it can
furthermore be provided that the lining has a thickness that is
less than 1.0 mm, preferably approximately 0.5 mm.
[0019] In a particularly preferred embodiment, it can be provided
that the lining is compressed to a thickness that amounts to a
fraction of its original thickness, and that is less than 1.0 mm,
preferably approximately 0.5 mm.
[0020] Furthermore, it can advantageously be provided that the
holes pass completely through the wall, in other words are
structured as passage holes. In this way, disruptive noises can be
conducted away in particularly advantageous manner.
[0021] According to a particularly preferred embodiment, it can
furthermore be provided, particularly in combination with the above
measures relating to the thickness of the lining, in particularly
advantageous manner, that the holes of the wall have a diameter,
preferably an average diameter, of 1 to 3 mm, preferably of 1.5 to
2.5 mm, particularly of 1.8 to 2.2 mm. By means of these measures,
specifically by means of a lining compressed to a thickness of only
approximately 0.5 mm, which is configured with or is preferably a
non-woven fabric that can have a weight per surface area of about
200 g/m , in combination with opening or hole diameters of 1.8 to 2
mm, increased or maximized sound damping results in that noises or
sound waves penetrate through the holes and can be conducted away.
Furthermore, the use of such a thin, preferably planar lining,
particularly in the form of a non-woven fabric, makes it possible
that no or no noteworthy moisture can collect in it.
[0022] Furthermore, it can be practical that the holes of the wall
are structured conically. Alternatively or additionally, it can be
provided that at least the holes in the wall provided in the region
of the lining narrow in cross-section, preferably continuously,
towards the lining. In this way, problem-free and cost-advantageous
production is made possible, with advantageous sound and noise
absorption.
[0023] Furthermore, it can be provided that the holes of the wall
provided in the region of the lining, preferably all of them, are
covered by the lining, preferably completely, in each instance, and
preferably are immediately delimited by the lining. In this way,
particularly great sound damping or sound absorption can be
achieved, at comparatively simple producibility.
[0024] In another aspect, the above object is also achieved by a
method for the production of a noise-damping air-conducting duct or
an air-conducting duct that absorbs sound carried in air, for air
conditioning and/or ventilation systems, particularly for vehicles,
preferably motor vehicles. To the extent possible, the duct
preferably has the characteristics indicated above, individually or
in any desired combination, and/or the characteristics as discussed
herein and contains at least one exit opening for air, and is
provided, in the region of the. exit opening or in the exit region,
preferably by way of a longitudinal segment, with an at least
partially air-permeable or sound-permeable lining made of a
material that absorbs or damps sound carried in the air, preferably
formed with a or from a non-woven fabric. The lining is surrounded,
at least on its outside, by a wall made of plastic, provided with
holes, at least in the region of the lining, preferably forming a
self-supporting line segment, and the lining is attached to this
wall. According to the invention, the wall is produced from a
thermoplastic plastic, using a primary shaping method, preferably
using an injection-molding and/or transfer-molding method and/or
impact-extrusion method, and the lining is connected with the wall
in a work step during or upon formation or shaping of the wall,
preferably immediately, i.e. without any separate connection or
adhesion means, such as glues, for example, preferably directly,
i.e. without an intermediate layer or without multiple intermediate
layers, particularly without welding, preferably with material fit
and/or shape fit.
[0025] In this manner, the separate handling of the linings and the
walls of the air-conducting ducts to be connected with them, which
was previously necessary, is eliminated. Furthermore, by means of
the production in one work step, in comparison with the previous
production of the wall in a separate work step, and its subsequent
connection with the lining in two separate work steps, significant
time, effort, and costs are saved. Furthermore, additional measures
for attaching the lining to the wall, as they were previously
necessary, for example by means of lamination, particularly by
means of gluing, are eliminated. Furthermore, as a result,
particularly advantageous connection conditions between the lining
and the wall are made possible, so that the risk of detachments of
the wall can be minimized or even entirely precluded. In this
manner, the lining or the acoustically active region formed by the
lining becomes an integral component of the air-conducting duct. No
further components to be handled separately or produced in separate
work steps, and to be connected, such as separate sound-absorbing
material or plates within the duct, or outside walls, such as in
exhaust gas mufflers, are necessary.
[0026] It is particularly advantageous if the lining is compressed
to a fraction of its original thickness before and/or during the
formation or shaping of the wall, at least in partial regions.
[0027] Furthermore, it can be provided that the lining is
mechanically compressed by means of mechanical forces of die
structures that determine the configuration and/or the shape of the
holes of the wall, for example of pins that form hole cores and the
like, a mold die, at local pressure points. Alternatively or
additionally, it can be provided that the lining is compressed upon
or during the formation or shaping of the wall, at least in partial
regions, by means of the internal pressure forces exerted by the
molten or viscous thermoplastic plastic material.
[0028] According to a particularly preferred embodiment, in a first
step, the lining is compressed by mechanical forces of die
structures that determine the configuration and/or the shape of the
holes of the wall, for example by pins that form hole cores, and
the like, a mold die, at local pressure points. At the same time or
subsequently, the lining is compressed in regions disposed adjacent
to and/or between the local pressure points, by the internal
pressure forces of the molten or viscous plastic material that
occur during formation or shaping of the wall.
[0029] In a particularly advantageous further development of the
air-conducting duct and/or of the method for the production of the
or an air-conducting duct, it can be provided that the lining is
compressed before and/or during the formation or shaping of the
wall, in such a manner that the holes of the wall of the finished
air-conducting duct are immediately delimited, at least in part,
preferably essentially, by the lining. In this way, particularly
great sound damping or sound absorption can be achieved, with
comparatively simple producibility.
[0030] Furthermore, the lining, in the finished, compressed state
or in the finished air-conducting duct, in the region of or at the
local pressure points, may have a thickness that approximately
corresponds to the thickness of the lining in the regions that
immediately follow the local pressure points and/or in the regions
disposed adjacent to the local pressure points.
[0031] Alternatively, it can be provided that the lining, in the
finished, compressed state or in the finished air-conducting duct,
in the region of or at the local pressure points, has a thickness
that is different as compared with the regions adjacent to the
lining, particularly smaller.
[0032] In a further preferred embodiment of the method, this can be
characterized by the following steps:
a) The lining is introduced into an open mold die, which has a die
core; b) the lining is held on or on top of the die core, to
prevent detachment from the and/or displacement relative to the die
core, by means of at least one holding and/or fixation means; c)
the plastic material for the wall [0033] is introduced into the
open mold die, which is subsequently closed, whereby and/or
whereupon the wall is formed and connected with the lining, in one
work step, and/or [0034] is injected and/or pressed into the closed
mold die, whereby and/or whereupon the wall is formed and connected
with the lining, in one work step.
[0035] For holding or fixing the lining on or on top of the die
core, the die core can be provided with bores that open on the side
of the die core that lies opposite the lining, and at which a
partial vacuum or vacuum can be applied, in controlled or regulated
manner. In this way, the lining can be held on or on top of the die
core, secured relative to the die core, to prevent detachment
and/or displacement, particularly due to internal pressure forces
that occur during the formation or shaping of the wall. After the
wall has been completely formed or shaped, and firmly connected
with the lining, the partial vacuum or the vacuum can be taken
away. In this way, the finished molded part can subsequently be
removed from the mold die.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] Other objects and features of the present inventions will
become apparent from the following detailed description considered
in connection with the accompanying drawings. It is to be
understood, however, that the drawings are designed as an
illustration only and not as a definition of the limits of the
inventions.
[0037] In the drawings, wherein similar reference characters denote
similar elements throughout the several views:
[0038] FIG. 1 is a longitudinal cross-section of an air-conducting
duct according to an embodiment of the invention;
[0039] FIG. 2 is an enlarged cross-section of the air-conducting
duct along the section lines A-A in FIG. 1, in the region of a
sound-absorbing lining;
[0040] FIG. 3 shows a mold die for the production of an
air-conducting duct according to the invention, having a die core
on which a lining is disposed and held, whereby the die is in a
state in which it is not yet completely closed;
[0041] FIG. 4 is an enlarged view of a section of the mold die for
the production of an air-conducting duct according to the
invention, whereby pins or core disposed at a distance from one
another are provided on a first die half, which determine the holes
to be provided in the wall of the air-conducting duct, whereby the
die is now shown in a closed state, in which the lining disposed on
the die core is mechanically compressed by means of the pins or
cores, at local pressure points, and whereby there is not yet any
plastic material for the formation or shaping of the wall of the
air-conducting duct situated in the region between the pins or
cores.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0042] Referring now in detail to the drawings, the air-conducting
duct 20 shown schematically in longitudinal cross-section in FIG. 1
is configured in tubular shape and has an entry opening 21 for air
and an exit opening 22 for the air that flows through
air-conducting duct 20 in the direction of the arrow 51. Entry
opening 21 can stand in a flow connection with an air transport
device, not shown in the figures, for example with a fan and/or
with an air-conditioning system for conditioning the air. The air
to be conveyed in air-conducting duct 20 in direction 51, if
applicable air-conditioned air, can be transferred to a space or
chamber 50 to be ventilated or to be air-conditioned, out of exit
opening 22. In a region ahead of exit opening 22, air-conducting
duct 20 widens up to exit opening 22, so that the cross-sectional
shape changes in this duct segment region, in the longitudinal
direction of air-conducting duct 20; here, it widens crosswise or
perpendicular to direction 51.
[0043] In this widening end or exit region 23 of air-conducting
duct 20, a lining or inlay 25 is disposed, here in the form of a
non-woven fabric, preferably having a weight per surface area of
about 200 g/m.sup.2. Lining 25 is immediately connected with the
wall 31 of air-conducting duct 20, with material fit and/or shape
fit, i.e. without any separate connection and/or adhesion agents,
such as glues, directly, i.e. without one or more intermediate
layers, and is connected with wall 31 in a single work step with
wall 31 of air-conducting duct 20 produced using a primary shaping
method. Lining 25 consists of sound-absorbing material. It is
surrounded, at least on its outside 26, by a wall 31, and attached
to wall 31. Wall 31 is provided with holes, here passage holes 30,
at least in the region of lining 25, and forms a self-supporting
line segment here. Wall 31 consists of a thermoplastic plastic or
is formed from a thermoplastic plastic. In other words, it can also
have fillers and/or reinforcement substances. The plastic can
preferably be polypropylene.
[0044] Lining 25 extends over a longitudinal segment 24 of the
air-conducting duct 20, which here is essentially delimited with or
by the end region of air-conducting duct 20, which widens outward.
In the region of lining 25, air-conducting duct 20 has an
acoustically optimized region 29. The inside 27 or the inner
surface 28 of lining 25 is preferably disposed in such a manner
that it aligns with the subsequent wall parts of wall 31 of
air-conducting duct 20, so that in the transition region from wall
31 to lining 25, in each instance, essentially no flow losses or
disruptive noises occur.
[0045] In the region of lining 25, a collection chamber 49 is
provided on the outside of air-conducting duct 20, into which part
of the sound waves or noises can be passed in the direction of
arrows 52, which can be caused, for example, by a fan or an
air-conditioning system or the like. For this purpose, the lining
is surrounded on its outside 26 by a wall 31 of air-conducting duct
20 that functions as a carrier for lining 25, which wall supports
the sound-absorbing lining and on which the lining is attached,
secured to prevent detachment.
[0046] Wall 31 of air-conducting duct 20 consists of a
comparatively hard, self-supporting plastic, preferably of
polypropylene. In the region of lining 25, wall 31 has a plurality
of holes 30, which are spaced apart, preferably at regular
intervals. Holes 30 pass through wall 31 completely, in other words
are configured as passage holes. In the region of lining 25, holes
30 are covered completely by lining 25, in each instance, towards
the inside. Holes 30 are preferably configured conically. In other
words the holes preferably have a trapezoid cross-section, whereby
the cross-section of holes 30 narrows towards lining 25, preferably
continuously. It is understood that instead of conical holes, other
hole cross-sections, for example cylindrical holes or holes having
a different cross-section, can also be provided.
[0047] In the exemplary embodiment shown, lining 25 consists of a
non-woven fabric that is formed from fiber-shaped structures. The
non-woven fabric is at least partially air-permeable or
noise-permeable, and is configured with relatively porous or loose
fiber structures. Non-woven fabric 25 is infiltrated, from its
outside 26, by the thermoplastic plastic of wall 31, at least in
part, but not completely to inside 27 or inner surface 28 of lining
25. Consequently, inside 27 or inner surface 28 of lining 25 is
entirely or essentially free of the thermoplastic plastic of wall
31 that supports lining 25.
[0048] The fibers of the lining or of non-woven fabric 25 form
internal material structures behind which the thermoplastic plastic
of wall 31 engages, at least in part, so that lining 25 is
immediately and directly connected with wall 31 or with the
thermoplastic plastic of wall 31, with shape fit. Depending on the
lining material that is used, particularly the fiber materials of
the non-woven fabric, a material-fit connection between wall 31 or
the thermoplastic plastic of wall 31 and lining 25 can also
preferably take place.
[0049] Holes 30 of wall 31 that are provided in the region of
lining 25 have a diameter or average diameter 32 that amounts to
about 1.8 to 2.2 mm here. The lining or non-woven fabric 25 has a
thickness 35, 36 that remains essentially the same in the entire
acoustically optimized region 29, of less than 1.0 mm. Preferably,
the thickness 35, 36 amounts to approximately 0.5 mm. Lining 25 is
compressed to a fraction of its original thickness 34 in the
acoustically optimized region 29, specifically to the thickness 35,
36. In this way, no or essentially no moisture can collect in the
non-woven fabric. Despite the comparatively very thin non-woven
fabric, excellent noise damping can be achieved, surprisingly,
specifically in combination with diameters 32 of holes 30 of wall
31 that are dimensioned in a range of 1.8 to 2.2 mm, whereby the
air flow can flow through air-conducting duct 20 and out of exit
opening 22, uninfluenced or essentially uninfluenced, in loss-free
or essentially loss-free manner.
[0050] Air-conducting duct 20 can be produced, according to the
invention, in that wall 31 that surrounds and supports the lining,
here non-woven fabric 25, is produced from a thermoplastic plastic,
using a primary shaping method, preferably using the
injection-molding method, whereby the wall can alternatively or
additionally be produced using the transfer-molding method and/or
using the impact-extrusion method. Furthermore, lining 25 is
connected with wall 31, according to the invention, in a work step
during or upon formation or shaping of wall 31, preferably
immediately, i.e. without any separate connection or adhesion
means, such as glues, for example, preferably directly, i.e.
without one or more intermediate layers, preferably with material
fit and/or shape fit.
[0051] The production of air-conducting duct 20 using a preferred
injection-molding method is described in greater detail in the
following:
[0052] FIG. 3 shows, in a schematic representation, a mold die 40,
which here has a first or upper die half 41 and a second or lower
die half 42, as well as a central die core 44. Lining 25 is
disposed on die core 44 as an insertion part, and is held there
secured to prevent detachment from and/or displacement relative to
die core 44. For this purpose, holding and/or fixation means that
are not shown in the figures can be provided. Such holding means
can be configured with bores, for example, which are provided in
die core 44. These bores can open towards the die cavity or towards
the cavity 45. In other words the bores can open towards inside 27
or inner surface 28 of lining 25. A partial vacuum or vacuum can be
applied at the bores, in controlled or regulated manner, thereby
causing lining 25 to be drawn against die core 44 and held in place
there.
[0053] The first, here upper die half 41, is provided with a
plurality of conical pins that narrow towards their free end, which
are spaced apart, preferably at the same or regular intervals,
which pins are also referred to as die structures 43 and which form
cores for holes 30 to be provided in wall 31 to be formed. These
die structures 43 determine the configuration and shape of holes 30
of wall 31.
[0054] In FIG. 3, mold die 40 is shown in a position in which it is
not yet completely closed. In this position, the first, here upper
die half 41, is disposed at a distance from die core 44, in such a
manner that the free ends of pins 43 just rest against outside 26
of lining 25, which has a specific original thickness 34. This
starting thickness 34 of lining 25 amounts to about 2 to 3 mm here.
It is also possible to use a very much thicker starting material, 1
to 30 mm, or even more, for the lining. The starting material or
the lining does not have to be a finished non-woven fabric raw
material; it can also be an unfinished non-woven material that has
a cotton-like state, particularly, in other words, is not needled
or consolidated by means of binders.
[0055] Proceeding from the position shown in FIG. 3, mold die 40 is
completely closed, whereby or whereupon molten or viscous
thermoplastic plastic can be injected, under pressure, through the
feed channel or sprue 46 provided in first die half 41 here, for
the purpose of forming and shaping wall 31, and more pressure can
be applied, if necessary.
[0056] In the completely closed state of mold die 40, pins or cores
43 are in a position relative to die core 44 as is evident from
FIG. 4. In this position, lining 25 has been mechanically
compressed by pins or cores 43, at local pressure points 33, to a
thickness 35 that amounts to only a fraction of its original
thickness 34.
[0057] In other words, lining 25, proceeding from the open position
of mold die 40 shown in FIG. 3, and proceeding from its original
thickness 34, is mechanically compressed, in the course of
subsequent closing of mold die 40, by pins or cores 43, in the
region of their free ends, to a thickness 35 that amounts to only a
fraction of this original thickness 34, whereby local pressure
points 33 are formed. The thickness 35 of the compressed lining 25
in the region of the local pressure points 33 preferably amounts to
about 0.5 mm.
[0058] Subsequently, in other words after complete closing of die
40, but possibly also at a point in time at which mold die 40 is
not yet completely closed, molten or viscous thermoplastic plastic
is injected into die cavity 45 or into the cavity of mold die 40,
by way of feed channel or sprue 46, whereby the material flows
around the pins or cores. In the course of injection or transfer of
molten or viscous thermoplastic plastic, which takes place under
elevated hydraulic pressures, internal pressures occur in cavity
45, by means of which lining 25 is compressed, proceeding from its
original thickness 34, to a fraction of this original thickness 34,
also in regions. formed adjacent to and between the local pressure
points 33. Preferably, the lining is compressed, also in these
additional or other regions, to a thickness 36 that approximately
corresponds to the thickness 35 of lining 25 mechanically
compressed by pins or cores 34. In this way, a finished component
is obtained, which is shown in cross-section in FIG. 2, and in
which lining 25 has an approximately uniform thickness 35, 36 in
the acoustically optimized region 29.
[0059] In the case of the method according to the invention, the
internal pressure forces that act on lining 25 by means of the
molten or viscous thermoplastic plastic material during the
formation or shaping of wall 31, act on it essentially only by way
of its outside 26. In the exemplary embodiment, these internal
pressure forces also act on lining 25 by way of its edge or face
surfaces, but not by way of inside 27 of lining 25 that lies
against die core 44.
[0060] Accordingly, although only a few embodiments of the present
invention have been shown and described, it will be apparent that
many changes and modifications may be made thereunto without
departing from the spirit and scope of the invention.
* * * * *