U.S. patent application number 09/858726 was filed with the patent office on 2001-10-25 for honeycomb structure and method of manufacturing honeycomb structures.
Invention is credited to Jans, Johannes C., Linders, Petrus W.J., Prins, Menno W.J..
Application Number | 20010033943 09/858726 |
Document ID | / |
Family ID | 26150373 |
Filed Date | 2001-10-25 |
United States Patent
Application |
20010033943 |
Kind Code |
A1 |
Prins, Menno W.J. ; et
al. |
October 25, 2001 |
Honeycomb structure and method of manufacturing honeycomb
structures
Abstract
The invention relates to a method of manufacturing honeycomb
structures in which multiple foils are welded together by means of
thermal compression and the multiple foils form the honeycomb
structure in the expanded condition. The bonding locations, where
the foils are fused together, are defined by inserting a structured
layer between the foils.
Inventors: |
Prins, Menno W.J.;
(Elndhoven, NL) ; Linders, Petrus W.J.;
(Elndhoven, NL) ; Jans, Johannes C.; (Elndhoven,
NL) |
Correspondence
Address: |
Corporate Patent Counsel
U.S. Philips Corporation
580 White Plains Road
Tarrytown
NY
10591
US
|
Family ID: |
26150373 |
Appl. No.: |
09/858726 |
Filed: |
May 16, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09858726 |
May 16, 2001 |
|
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09316779 |
May 21, 1999 |
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Current U.S.
Class: |
428/593 ;
428/594 |
Current CPC
Class: |
B29C 37/0075 20130101;
G21K 1/10 20130101; Y10T 428/1234 20150115; Y10T 156/1003 20150115;
B29D 99/0089 20130101; Y10T 428/24149 20150115; Y10T 428/12347
20150115; Y10T 428/24165 20150115 |
Class at
Publication: |
428/593 ;
428/594 |
International
Class: |
B32B 003/12 |
Foreign Application Data
Date |
Code |
Application Number |
May 22, 1998 |
EP |
98201706.3 |
Nov 25, 1998 |
EP |
98203986.9 |
Claims
1. A method of manufacturing honeycomb structures which includes
the following steps: connecting a plurality of foils to one another
so as to realize a stack of interconnected foils which form a
honeycomb structure in the expanded condition, the foils being
fused at various bonding locations, expanding the stack of foils in
a direction transversely of the surface of the foils in order to
form the honeycomb structure, characterized in that the method
includes a step for: providing a structured separating layer on at
least one side of the foil in order to realize bonding locations on
the foil.
2. A method as claimed in claim 1, characterized in that the step
for realizing the structured separating layer comprises two
sub-steps for: providing a separating layer on the at least one
side of the foil, and providing structures in the separating layer
by the removal of material from the separating layer in order to
realize the bonding locations.
3. A method as claimed in claim 1, characterized in that the method
for interconnecting the foils includes two sub-steps for: stacking
the plurality of foils, and heating the stack to a temperature
beyond the melting point of the foils.
4. A honeycomb structure which includes a plurality of foils which
are fused to one another at various bonding locations,
characterized in that the bonding locations are separated from one
another by a structured separating layer provided on at least one
side of the foil.
5. A honeycomb structure as claimed in claim 4, characterized in
that neighboring foils are locally connected to one another along
bonding seams, the ratio of the width of the individual bonding
seams to the distance between neighboring bonding seams being in
the range of from 0.1 to 0.4 and preferably amounting to
approximately 1/4 or 1/3.
6. A honeycomb structure as claimed in claim 4, characterized in
that the structured separating layer contains a metal having a
thickness in a range of less than 500 nm.
7. A honeycomb structure as claimed in claim 6, characterized in
that the metal contains aluminum.
8. A diagnostic X-ray apparatus provided with an X-ray filter,
characterized in that the X-ray filter includes a honeycomb
structure as claimed in claim 4.
9. A luminary provided with a diffuser, characterized in that the
diffuser includes a honeycomb structure as claimed in claim 4.
Description
[0001] The invention relates to a method of manufacturing honeycomb
structures which includes the following steps:
[0002] connecting a plurality of foils to one another so as to
realize a stack of interconnected foils which form a honeycomb
structure in the expanded condition, the foils being fused at
various bonding locations, and
[0003] expanding the plurality of foils in a direction transversely
of the surface of the foils in order to form the honeycomb
structure.
[0004] The invention also relates to a honeycomb structure which
includes a plurality of foils which are interconnected in different
bonding locations by welding.
[0005] The method and the honeycomb structure of the described kind
are known from international patent application WO 93/01048.
Because of their low weight and unique structural properties,
honeycomb structures are universally used in industrial
applications. Honeycomb structures made of comparatively thin foils
are widely used because of their low weight and ability to
withstand high compression loads. Such honeycomb structures are
used, for example in aircraft components and running shoes.
[0006] Honeycomb structures are also used in, for example an X-ray
examination apparatus. Such an X-ray examination apparatus then
includes an adjustable X-ray filter. The adjustable X-ray filter
includes a bundle of capillary tubes which are formed by the
honeycomb structure. The capillary tubes may be completely or
partly filled with an X-ray absorbing liquid. Furthermore, one end
of the capillary tubes is connected to a reservoir containing an
X-ray absorbing liquid. An electric voltage is applied across the
tubes and the X-ray absorbing liquid in order to fill the capillary
tubes. This enables adjustment of a two-dimensional intensity
profile of an X-ray beam traversing the X-ray filter. Honeycomb
structures are also used as light diffusers in luminaries.
[0007] The known method realizes the honeycomb structure by
expansion of interconnected foils. A stack of foils is formed by
successively arranging first and second foils against one another
and by heating the bonding locations via the second foil, so that
the first and second foils start to melt. When the desired melting
depth has been reached in the first foil, heating is terminated and
the foils are cooled. Subsequently, a next foil is placed on the
stack. The described process steps are repeated until the stack
contains a number of foils which suffices to realize a honeycomb
structure comprising the desired number of channels. After the
plurality of foils has been interconnected in this manner, the
stack of foils is expanded by pulling in order to form the
honeycomb structure.
[0008] It is a drawback of the known process that it is difficult
to apply the appropriate amount of heat to the bonding locations on
the second foils so as to achieve the desired melting depth and to
prevent the foils from being completely connected to one
another.
[0009] It is an object of the invention to provide a method where
the amount of heat to be applied is not critical and the foils are
not completely connected to one another. To achieve this, the
method according to the invention is characterized in that it
includes a step for providing a structured separating layer on at
least one side of the foil in order to realize the bonding
locations on the foil. Other attractive versions of the method
according to the invention are disclosed in the dependent Claims.
The separating layer is structured in such a manner that it
comprises openings which constitute the bonding locations.
Neighboring foils to both sides of the relevant separating layer
can contact one another via the openings. When pressure is exerted
on the stack of foils with the separating layers inserted between
individual foils, the neighboring foils are bonded together at the
areas where they contact one another at the bonding locations in
the separating layers. The separating layers prevent the bonding of
neighboring foils outside the bonding locations. For example, the
bonding locations are formed by narrow strips which form the
bonding seams along which the neighboring foils are fused by
thermal compression so that they are bonded together along said
bonding seams. The insertion of the structured separating layer
also offers the advantage that the process of bonding the foils in
the stack can be accelerated. Furthermore, the structured layer can
be provided, for example by providing a metal layer on the foil and
by locally removing material of the metal layer so as to define the
bonding locations. A further advantage resides in the fact that the
foils to be used may be thin. For example, use is made of foils
having a thickness of approximately 5 .mu.m. Furthermore, it is
advantageous to use foils having a high mechanical strength. It has
been found that polypropylene sulphon (PPS) is a suitable material
for the foils; polyethyleneterephthalate (PETP), polyethylene and
polyesters are also suitable materials for forming the foils.
[0010] The stacked foils are preferably expanded by clamping the
foils transversely of the plane of the foils. As a result,
neighboring foils locally move away from one another at the areas
where they are not interconnected. The expanded, stacked foils can
be maintained in the expanded condition by keeping them
mechanically clamped. The stacked foils can also be maintained in
the expanded condition by drastically reducing the elasticity of
the foils, after clamping, by temporary heating or irradiation by
means of X-rays or ultraviolet radiation. The pattern of
cross-sections of the channels in the honeycomb is determined by
the degree of expansion of the stack of foils transversely of the
foil surface, the spacing of the bonding seams in the direction
parallel to the surface of the foils, the seams along which the
foils are attached to one another, and the width of said bonding
seams. If the width of the bonding seams in a regular pattern
between adjoining foils is approximately three times smaller than
their spacing and if the stack of foils is expanded only slightly,
a more or less eye-shaped pattern will be obtained; if the stack is
expanded further, a hexagonal honeycomb pattern arises and if the
stack is expanded even further, a pattern of rectangles having
slightly rounded corners is obtained. Using a honeycomb pattern it
is achieved notably that the mechanical strength of the expanded
stack of foils is very high. When the width of the bonding seams in
a regular pattern between adjoining foils is approximately two
times smaller than their spacing, a rhombic pattern (with slightly
rounded corners) or a pattern of eyes will be obtained, depending
on whether the stack of foils is expanded more or less. When the
bonding seams are much narrower than their spacing and the stack of
foils is expanded only slightly, an eye-shaped pattern of channel
cross-sections is formed. The directions of the channels in the
expanded foils are dependent on the directions of the bonding seams
relative to one another in the expanded foils. For example, when
straight or curved, mutually parallel bonding seams are used,
straight and curved channels, respectively, are formed and when the
bonding seams are made to converge towards one another, tapered
channels are formed. Furthermore, it is also possible to use
bonding seams which are parallel in pairs while individual pairs of
bonding seams enclose a small angle relative to one another. This
yields filter elements in the form of channels; individual channels
then enclose an angle relative to one another. It is also possible
to realize other shapes by non-parallel expansion of the outermost
foils.
[0011] A special version of the invention is characterized in that
the step for realizing the structured separating layer comprises
two sub-steps: a first sub-step for providing a separating layer on
the at least one side of the foil, and a second sub-step for
providing structures in the separating layer by the removal of
material from the separating layer in order to realize the bonding
locations. The bonding locations on the foils are thus defined.
Material can be removed from the separating layer, for example by
laser ablation.
[0012] A further method according to the invention is characterized
in that it includes two sub-steps: stacking the plurality of foils
and heating the stack to a temperature beyond the melting point of
the foils. The process for realizing the stack of bonded foils can
thus be substantially accelerated, because first all foils are
stacked on one another and subsequently the entire stack of foils
is heated to a temperature beyond the melting point of the foils in
a single further step. Due to the presence of the structured
separating layer, the material of the foils melts only in the bond
locations defined by the structured separating layer.
[0013] The invention also relates to a honeycomb structure which
includes a plurality of foils which are bonded to one another at
various bonding locations by welding. The honeycomb structure
according to the invention is characterized in that the bonding
locations are separated from one another by a structured separating
layer provided on at least one side of the foil.
[0014] A further embodiment of the honeycomb structure according to
the invention is characterized in that the structured separating
layer contains a metal having a thickness in a range of less than
500 nm. An example of such a metal contains aluminum.
[0015] The invention also relates to a diagnostic X-ray apparatus
provided with an X-ray filter. The diagnostic X-ray apparatus
according to the invention is characterized in that the X-ray
filter includes a honeycomb structure as defined in claim 4.
[0016] The invention also relates to a luminary provided with a
diffuser. The luminary according to the invention is characterized
in that the diffuser includes a honeycomb structure as defined in
claim 4.
[0017] The above and other, more detailed aspects of the invention
will be described in detail hereinafter, by way of example, with
reference to the drawing.
[0018] In the drawing:
[0019] FIG. 1 shows a stack of foils,
[0020] FIG. 2 shows a honeycomb structure,
[0021] FIG. 3 shows the use of a honeycomb structure according to
the invention in a luminary, and
[0022] FIG. 4 shows the use of a honeycomb structure according to
the invention in an X-ray filter.
[0023] The method of manufacturing the honeycomb structure will be
described in detail hereinafter with reference to the FIGS. 1 and
2. FIG. 1 is a diagrammatic front and side view of an example of a
stack of foils used to form the honeycomb structure for use in the
X-ray filter. The individual foils 10 in the stack alternate with
structured separating layers 15. The thickness of the foils amounts
to, for example approximately 5 .mu.m. Preferably, the separating
layers 15 are strips of aluminum having a thickness in a range of
from approximately 5 to 500 .mu.m; preferably, aluminum strips
having a thickness of approximately 20 nm are used. When the foils
are heated under pressure to a temperature beyond the melting
point, the neighboring foils are partly fused in bonding locations
where no aluminum is present between the neighboring foils. The
neighboring foils are locally bonded to one another by way of such
a thermal compression treatment. At the areas where a strip of
aluminum is present between neighboring foils, the foils are not
bonded by the thermal compression treatment. It has been found that
foils having a melting point in the range of from 70.degree. to
500.degree. C. are very suitable for carrying out such thermal
compression.
[0024] The honeycomb structure 30 shown in FIG. 2 has been formed
by expanding the stacked foils 10. The stack of foils 10 has been
expanded in the direction of the arrows 20. Expansion is realized,
for example by pulling one or both rigid plates 11 in the direction
of the arrows. Buffer members 12 are provided between the stack of
foils 10 and the respective rigid plates 11. The expansion of the
stack of foils locally creates spaces between neighboring foils,
i.e. at the areas where they are not bonded to one another. When
use is made of parallel separating strips, approximately parallel
bonding seams along which the neighboring foils are bonded to one
another are formed by thermal compression. As a result of such
approximately parallel bonding seams, the spaces between the foils
are shaped as capillary tubes which extend approximately
perpendicularly to the plane of drawing and parallel to the bonding
seams. The degree of expansion of the stack of foils determines, in
conjunction with the dimensions of the bonding seams and the
spacing of the bonding seams, the dimensions of the capillary
tubes. As a result of the expansion in the direction transversely
of the foils, the buffer members 12 are slightly contracted in the
direction parallel to the foils. It is thus achieved that the stack
of foils is expanded mainly transversely of the foils and the size
of the local spaces between the foils is uniform over the honey
comb structure.
[0025] In order to realize the structured separating layer, on one
side of the foils there is provided a metal layer having a
thickness of, for example 20 nm. This metal layer can be deposited,
for example by way of a vapor deposition process. Subsequently, the
metal is removed from the foil at the area of the bonding locations
by means of, for example laser ablation. Other possibilities for
locally removing the material are, for example, wet chemical
etching or the use of a shadow mask vapor deposition method. In
order to make the temperature adjustment even less critical during
the heating and bonding of the stack of foils, preferably both
sides of the foils are provided with the structured separating
layer. FIG. 3 shows the use of the honeycomb structure 30 as a
diffuser in a luminary 31. The luminary 31 includes a housing 32, a
lamp 33, a reflector 34 and a honeycomb structure 30. The lamp 33
is, for example a fluorescent tube. The reflector 34 is shaped, for
example as a parabolic reflector which is arranged in the housing
32 or is integral with the housing. The fluorescent tube 33 is
mounted in the housing 32 near a focal line of the parabolic
reflector 34. The honeycomb structure 30 is provided in a window of
the housing 32 opposite the parabolic reflector 34. The channels 35
of the honeycomb structure 30 are oriented, for example parallel to
one another and in the direction of an object to be illuminated
(not shown). The length of the channels amounts to, for example 2
mm and their diameter is, for example 1 mm. In order to enhance the
efficiency, the inner side of the channels is preferably provided
with a diffusely dispersive reflection layer. A high-efficiency
diffuser is thus obtained. In addition to the described
application, it is also possible to bend the honeycomb structure so
that exit openings of the channels, via which light rays emanate
from the luminary, are directed towards a focal line or a focal
spot.
[0026] FIG. 4 shows an application of a honeycomb structure 30 in
an X-ray filter 45 of an X-ray examination apparatus 40. Such an
X-ray examination apparatus 40 includes an X-ray source 41, an
X-ray detector 42, a power supply unit for delivering a voltage for
the X-ray source 41, a monitor 48, an X-ray filter 45 and a control
unit 47. The object 43 to be examined is arranged between the X-ray
source 41 and the X-ray detector 42. The X-ray detector 42 converts
an X-ray beam 44 having traversed the object 43 into an electric
image signal 49. The image signal 49 is then displayed on a monitor
48. In order to attenuate the X-ray beam 44 locally so as to adjust
a two-dimensional intensity profile, an X-ray filter 45 is arranged
in the X-ray beam 44 between the X-ray source 41 and the object 43.
The X-ray filter 45 comprises a large number of filter elements. A
filter element preferably includes a capillary tube. The capillary
tubes (not shown in FIG. 4) are formed by the honeycomb structure
30. The length of the capillary tubes amounts to, for example 25 mm
and their diameter to, for example 275 .mu.m. The capillary tubes
communicate, by way of a first opening, with a reservoir (not shown
in FIG. 4) which contains an X-ray absorbing liquid, for example an
aqueous solution of a lead salt. The X-ray absorptivity of the
X-ray filter 45 can be adjusted via the control unit 47 by applying
electric voltages across the inner side of the capillary tubes of
the X-ray filter 45 and the X-ray absorbing liquid. This is because
the adhesion of the X-ray absorbing liquid to the inner side of the
capillary tubes is dependent on the electric voltage applied across
the inner side of the capillary tubes and the X-ray absorbing
liquid. The capillary tubes are filled with a given quantity of
X-ray absorbing liquid in dependence on the electric voltage
present across the individual capillary tubes and the X-ray
absorbing liquid. Because the capillary tubes extend approximately
parallel to the X-ray beam, the X-ray absorptivity of the
individual capillary tubes is dependent on the relative quantity of
X-ray absorbing liquid present in the capillary tube.
[0027] Other applications of the honeycomb structure according to
the invention are, for example its use as a collimator for X-rays
in an X-ray examination apparatus. Another application is, for
example its use as an anti-scatter grid in an X-ray examination
apparatus.
* * * * *