U.S. patent application number 11/873656 was filed with the patent office on 2008-04-17 for dimpled sheet.
This patent application is currently assigned to EWALD DORKEN AG. Invention is credited to Heinz-Peter Raidt, Jorn Schroer.
Application Number | 20080086958 11/873656 |
Document ID | / |
Family ID | 38820247 |
Filed Date | 2008-04-17 |
United States Patent
Application |
20080086958 |
Kind Code |
A1 |
Schroer; Jorn ; et
al. |
April 17, 2008 |
DIMPLED SHEET
Abstract
A dimpled sheet, with a flat area and a plurality of dimples
protruding over the flat area, each having a dimple casing and a
dimple cover, wherein contact surfaces for placement of the dimpled
sheet against a subsurface are formed on the side of the dimples by
the outer sides of the dimple covers. The proportion of the total
contact surface of all dimples of the total surface of the dimpled
sheet is greater than 35%, with the base surface of the dimpled
sheet being formed from the flat area and the base surface of all
dimples at the level of the flat area. The dimpled sheet has a
protection coefficient (PC) of more than 10.000, whereby the PC is:
PC=(CS).sup.2.times.DH with CS=total contact surface of all dimples
in [%] of the total base surface of the dimpled sheet DH=dimple
height [min].
Inventors: |
Schroer; Jorn; (Herdecke,
DE) ; Raidt; Heinz-Peter; (Dortmund, DE) |
Correspondence
Address: |
Jason H. Vick;Sheridan Ross, PC
Suite # 1200, 1560 Broadway
Denver
CO
80202
US
|
Assignee: |
EWALD DORKEN AG
Herdecke
DE
|
Family ID: |
38820247 |
Appl. No.: |
11/873656 |
Filed: |
October 17, 2007 |
Current U.S.
Class: |
52/169.14 ;
52/302.6; 52/403.1 |
Current CPC
Class: |
E02D 31/02 20130101 |
Class at
Publication: |
52/169.14 ;
52/302.6; 52/403.1 |
International
Class: |
E02D 19/00 20060101
E02D019/00; E04B 1/70 20060101 E04B001/70; E04F 15/22 20060101
E04F015/22 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 17, 2006 |
DE |
10 2006 049 450.4 |
Nov 3, 2006 |
DE |
10 2006 052 257.5 |
Claims
1. Dimpled sheet, particularly for construction purposes and
preferably for use as foundation wall protection or drainage
sheeting, with a flat area and a plurality of dimples protruding
over the flat area, each having a dimple casing and a dimple cover,
wherein contact surfaces for placement of the dimpled sheet against
a subsurface are formed on the side of the dimples by the outer
sides of the dimple covers, wherein the proportion of the total
contact surface of all dimples of the total surface of the dimpled
sheet is greater than 35%, wherein the base surface of the dimpled
sheet is formed from the flat area, having a protection coefficient
(PC) of more than 10.000, whereby the protection coefficient (PC)
is defined by the formula PC=(CS).sup.2.times.DH with CS=total
contact surface of all dimples in [%] of the total base surface of
the dimpled sheet DH=dimple height in [min]
2. Dimpled sheet as set forth in claim 1, wherein the protection
coefficient (PC) is more than 12.000 and especially more than
16.000,00.
3. Dimpled sheet as set forth in claim 1, wherein a compressive
strength per DIN 53454 of between 50 to 1500 kPa, preferably
between 150 to 1000 kPa, and particularly between 300 to 700 kPa is
provided.
4. Dimpled sheet as set forth in claim 1, wherein an sd value per
EN 1931 of greater than 2 m, preferably greater than 50 m and
especially preferably greater than 100 m and particularly greater
than 500 m is provided.
5. Dimpled sheet as set forth in claim 1, wherein the total contact
surface of all dimples is up to 80% of the base surface of the
dimpled sheet, preferably between 40 and 70% and particularly
between 45 and 60%.
6. Dimpled sheet as set forth in claim 1, wherein the free volume
between the dimples lies in the range between 500 to 10,000
mm.sup.3/m.sup.2, preferably between 1000 to 7000 mm.sup.3/m.sup.2
and particularly between 1500 and 4000 mm.sup.3/m.sup.2.
7. Dimpled sheet as set forth in claim 1, wherein dimples each with
a first contact surface and other dimples each with another contact
surface deviating from the first contact surface are provided and
that the dimples and the other dimples have contact surfaces of
different shapes and/or sizes.
8. Dimpled sheet as set forth in claim 1, wherein the dimples and
the other dimples are arranged alternatingly next to each other, in
each case at least with respect to the level of the contact
surfaces.
9. Dimpled sheet as set forth in claim 1, wherein the dimples are
arranged in a regular raster and that the other dimples are
provided in empty spaces of the raster, in each case at least with
respect to the level of the contact surfaces.
10. Dimpled sheet as set forth in claim 1, wherein the dimples are
framed by the other dimples, in each case at least with respect to
the level of the contact surfaces.
11. Dimpled sheet as set forth in claim 1, wherein the dimples with
respectively circular contact surfaces and other dimples are each
provided with an n-cornered contact surface.
12. Dimpled sheet as set forth in claim 1, wherein the dimples and
neighboring other dimples have contact surfaces which are
complementary to each other at least in sections.
13. Dimpled sheet as set forth in claim 1, wherein the dimples are
each provided with an ellipsoid contact surface and that each
contact surface preferably has a narrowing in its middle area.
14. Dimpled sheet as set forth in claim 1, wherein the dimple
height is between 3 to 15 mm, particularly between 3 to 10 mm, more
particularly between 3 to 7 mm.
15. Dimpled sheet as set forth in claim 1, wherein the contact
surfaces have an edge length or a diameter of 3 to 30 mm.
16. Dimpled sheet as set forth in claim 1, wherein the wall
thickness of the dimples is between 0.1 to 1.0 mm, particularly
between 0.3 to 0.6 mm.
Description
[0001] The invention relates to a dimpled sheet, particularly for
construction purposes and preferably for use as foundation wall
protection or drainage sheeting, with a flat area and a plurality
of dimples protruding over the flat area, each having a dimple
casing and a dimple cover, wherein contact surfaces for placement
of the dimpled sheet against a subsurface are formed on the side of
the dimples by the outer sides of the dimple covers.
[0002] Plastic dimpled sheets are used as foundation wall
protection from surfaces in contact with soil. The known dimpled
sheets consist of an impact-resistant and rigid plastic,
particularly HDPE and PP, with the dimpled sheets lying flush in
the installed state on the respective waterproofing and protecting
them against mechanical damage during the filling of the pit by
virtue of their cushioning characteristics. In the known dimpled
sheets, in their installed state, the total contact surface of the
dimples against the subsurface or against waterproofing is
generally between 10 to 20% of the total surface of the dimpled
sheet. Dimpled sheets of the type described in the foregoing are
known, for example, as foundation wall protection sheets under the
commercial name DELTA-MS or as drainage and protective sheets under
the commercial name DELTA-GEO-DRAIN QUATTRO of the Dorrken
Company.
[0003] Dimpled sheets with cup-shaped indentations in the form of
truncated cones or truncated pyramids which serve to protect
foundation walls are known, for example, from DE 33 02 244 A1.
Moreover, a dimpled sheet is described in WO 82/03099 A1 wherein
the stiffness of the dimples is increased through crater-shaped
recesses in the center of the dimples. At the same time, very
small, annular contact surfaces are formed by crater-shaped
recesses on the dimple side of the dimpled sheet.
[0004] In higher-quality waterproofing materials made of bitumen,
the punctiform transfer of the soil pressure via the dimples can
have a negative effect on a bitumen sheet. As a result of the
constantly acting soil pressure, the dimples sink with the contact
surfaces into the 4 to 5 mm thick bitumen sheets. This can lead to
damage to the seal. For this reason, dimpled sheets are put in
place in part with the back side, i.e. with the side of the dimpled
sheet facing away from the dimples, onto the waterproofing. It is
disadvantageous here that the dimples facing outwardly toward the
pit with respect to the building wall form a large contact surface
for the soil to be filled in. There is the danger that, during the
filling of the pit, the dimpled sheet will be torn at least
partially from the waterproofing or will be shifted at least
partially downward. In addition, the protective effect for the
building is greatly reduced if the dimpled sheet is installed with
the back side on the waterproofing, and the total contact surface
of the dimples to the filled soil is merely 10 to 20% of the total
surface of the dimpled sheet, so that stones impinging on the
building wall and large particles in the filled soil can only be
repelled to a small extent.
[0005] Moreover, with the back-side laying of the dimpled sheet on
the waterproofing, it is disadvantageous that water transport
cannot take place between the waterproofing and the dimpled sheet.
Driving rain that flows down on the facade of a building wall can
collect between the waterproofing and the dimpled sheet, which is a
disadvantage. What is more, the heat-insulating effect of the
dimpled sheet is reduced considerably with back-side installation
compared to installation of the sheet with dimples facing the
waterproofing. In this context, it also has to be considered that,
during the laying of the dimpled sheet with dimples facing the
waterproofing, a sufficiently large vapor pressure compensation
layer is formed by the dimple gaps, hence permitting the transport
of material by diffusion.
SUMMARY
[0006] It is the object of the present invention to make available
a dimpled sheet of the type mentioned at the outset in which damage
to the waterproofing cannot occur in the installed state in the
event of installation with dimples facing inwardly towards the
waterproofing, with the dimpled sheet also being intended to ensure
a high level of insulation and a sufficient transport of material
through the dimple gaps.
[0007] The aforementioned object is achieved in a dimpled sheet of
the type mentioned at the outset by means of the features of claim
1.
[0008] The invention is based on the fundamental idea of enlarging
the total contact surface of the dimpled sheet with the subsurface
on the dimpled side such that damage to the waterproofing,
particularly damage to bitumen sheets, through sinking-in of the
dimples into the waterproofing under a soil pressure load is
reduced considerably. Another contributing factor to this is,
finally, that the contact surface between the dimpled sheet and the
bitumen sheet is distributed relatively evenly by virtue of the
inventive arrangement in order to reduce to the greatest extent
possible excessive localized loads and a consequent sinking-in.
Here it is especially advantageous if the total contact surface of
the dimpled sheet is at least 45 to 50% of the total base area of
the dimpled sheet. However, total contact surfaces between 50% and
70% are also very advantageous, whereby every single value within
the interval between 36% and 70% is possible, that means 36%, 37%,
. . . 69%, 70% including all decimal values within this interval.
The total contact surface of the dimpled sheet is formed here by
the contact surfaces of all dimples or by the areas of the dimple
covers of all dimples of the sheet that come into contact with the
subsurface during installation of the sheet according to the
invention. In connection with the present invention, it has also
been discovered that a sufficiently large vapor pressure
compensation layer is produced even with the enlarged contact
surface, so that sufficient transport of material is ensured.
[0009] To provide the protection of the sealing or waterproofing
and to provide the drain or drainage as well as the areation
function, the dimpled sheet is characterized in a protection
coefficient PC of more than 10.000. Preferred are PC-values of more
than 12.000, especially of more than 16.000 and more preferrably of
more than 20.000, whereby every single value of more than 10.000 is
possible (that means 10.001, 10.002 . . . ) including all decimal
values, although if these values are not mentioned explicitly. The
protection coefficient PC is defined by the formula
PC=(CS).sup.2.times.DH
with [0010] CS=total contact surface of all dimples in [%] in
relation to the total base surface of the dimpled sheet [0011]
DH=dimple height in [min]
[0012] The total contact surface or area results from the sum of
the upper surfaces or contact areas of the respective dimples over
the total base surface or area of the dimpled sheet. The higher the
total contact surface is the lower, is the sinking-in of the
dimpled sheet in the ground and the better is the drain function.
Further, the higher the dimples are, the better is the protection
of the sheet against any soil or filling material like rocks, which
might come in contact with the dimpled sheet. Surprisingly, it has
been found out that the dimpled sheet has a very good function to
solve the mentioned object if the protection coefficient PC has a
value of more than 10.000 and especially in the range of the values
mentioned before.
[0013] To prevent the dimple from collapsing under the soil load, a
sufficient compressive strength per DIN 53454 is required. It has
been observed in experiments that the compressive strength of the
dimpled sheet or of the dimple should lie in the range of between
50 and 1500 kPa, and particularly between 150 and 1000 kPa. As will
readily be understood, every intermediate value and every
intermediate interval within the aforementioned limits is possible
even if this is not mentioned in detail. In order to minimize the
penetration of moisture through the sheet here, the dimpled sheet
according to the invention should have a certain level of water
vapor permeability. The sd value per EN 1931 should in any case be
greater than 2 m, preferably greater than 50 m and especially
preferably greater than 100 m. In order to have as little moisture
penetration as possible, the sd value should be even greater than
500 m.
[0014] In order to be able to ensure sufficient drainage capacity
as well as sufficient air compensation, the free volume between the
dimples lies in the range between 500 to 10,000 mm.sup.3/m.sup.2,
preferably between 1000 and 7000 mm.sup.3/m.sup.2. Especially
preferred values lie between 1500 and 4000 mm.sup.3/m.sup.2. Here,
the free volume is measured between the flat area of the dimpled
sheet and the level of the contact surface.
[0015] Moreover, the dimpled sheet can be embodied such that the
following features are realized alone or in any combination with
each other, namely [0016] that the dimples at the level of the
contact surfaces are equally spaced apart from each other in all
directions of the dimpled sheet, [0017] that dimples with
respective square contact surfaces are provided, with the edge
length of the contact surface preferably being approx. 11 mm and
the distance between neighboring contact surfaces being approx. 4
mm in all directions, [0018] that dimples with respective
rectangular contact surfaces are provided, [0019] that a plurality
of rows of dimples arranged perpendicularly to each other and
having a plurality of dimples is provided, with all dimples of a
row of dimples preferably being arranged axially to the middle
longitudinal axis of the row of dimples, and [0020] that the
dimples of a first row of dimples and the dimples of at least one
other neighboring row of dimples running parallel to the first row
of dimples are arranged in the direction of the middle longitudinal
axes of the neighboring rows of dimples in a staggered manner with
respect to each other.
[0021] When arranging the dimples, care should be taken that a
minimum height be provided so that the air permeability is
maintained on the dimple side even if the dimples should sink in
slightly or be compressed by the soil pressure. With slope angles
of the individual dimples of less than 90.degree., the distance
between the dimples at the level of the dimple covers and the
distance between the neighboring contact surfaces increases as the
dimple height increases, which limits the reliable dimple height
given the large total contact surface required. The dimple height
should therefore preferably be 3 to 15 mm, particularly between 4
to 10 mm, more particularly 6, 8 and 10 mm. The wall thickness of
the dimples can lie between 0.1 to 1.0 mm, particularly between 0.3
to 0.6 mm. A sufficient strength of the dimpled sheet can be
ensured in this way.
[0022] In this connection it should be pointed out that the
cross-sectional size and/or the cross-sectional shape of the
dimples at the level of the dimple covers ends up determining the
contour of the contact surface of a dimple. In this context, the
dimple cover can have a square or circular or preferably level
surface and an edge length or diameter of 3 to 30 mm. If smaller
dimples and larger dimples are provided on the dimpled sheet, then
the smaller dimples can particularly have an edge length or
diameter of 3 to 15 mm and the larger dimples an edge length or
diameter of 10 to 30 mm, in each case with respect to the contact
surfaces of the individual dimples formed by the dimple covers.
[0023] Thermoforming or injection molding methods can be used to
manufacture the dimpled sheet according to the invention. The
dimpled sheet according to the invention can be manufactured from
plastic, preferably from PE, PP, ABS, PS and/or PA and, optionally,
at least one additive, particularly at least one thermostabilizer.
The abovementioned materials are characterized by a high pressure
load capacity as well as a high impact resistance. Moreover, the
materials are resistant to bitumen and have a high stress crack
resistance. If thermostabilizers are used as additives, the stress
crack resistance and/or the resistance to ageing of the dimpled
sheet according to the invention can be increased further.
[0024] With respect to information given in ranges and intervals
above, in the following and in the claims, it goes without saying
that every single value within an interval or range is comprised by
the present invention and regarded as essential to the invention,
even if concrete individual values are not mentioned in detail.
[0025] Particularly, there are a number of possibilities of
embodying and modifying the dimpled sheet according to the
invention, in light of which we refer to the dependent claims on
the one hand and to the following description of preferred sample
embodiments of the invention with reference to the drawing on the
other hand. Moreover, the invention permits a combination as needed
of the features disclosed and described in the following in the
claims and/or on the basis of the drawing, even if this is not
described in detail.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 shows a section from a cross-sectional view of a
dimpled sheet, and
[0027] FIGS. 2-23 show sections of top views of the contact
surfaces of dimpled sheets according to the invention formed by the
dimple covers of the dimples, each in schematic representation.
DETAILED DESCRIPTION
[0028] The dimpled sheet 1 has a flat area 2 and a plurality of
dimples 5 protruding over the flat area 2 and each having a dimple
casing 3 and a dimple cover 4. On the side of the dimples 5,
contact surfaces for placement of the dimpled sheet 1 against a
bitumen sheet 6 are formed by the outer side A of the dimple covers
4, with said bitumen sheet 6 being applied to the outside of a
building wall 7. The outer side A is the outer contact surface of a
dimple cover.
[0029] In the dimpled sheet 1 depicted in FIG. 1, the dimples 5
have a truncated cone shape and have a substantially level dimple
cover 4. The dimples 5 can also have the shape of a truncated
pyramid, a cone, a cylinder or a rectangle. As will readily be
understood, the dimple cover 4 can also have recesses in order to
increase the rigidity of a dimple 5. For example, in this
connection, the dimple cover 4 can have a circular or annular or
even an n-cornered contact surface, with the contact surface of a
dimple 5 being formed by the surface components of the dimple cover
4 acting against the bitumen sheet 6.
[0030] In the dimpled sheet 1 depicted in FIG. 1, a provision is
made that the proportion of the total contact surface that is
formed by the dimple covers 4 of all dimples 5 lying against the
bitumen wall 6 is greater than 35%, preferably between at least 45
to 50%, of the base surface of the dimpled sheet 1, with the base
surface of the dimpled sheet 1 being formed by the flat area 2 and
the base surface of all dimples 5 at the level of the flat area 2.
In this connection, the flat area 2 describes the entire surface of
the level areas of the dimpled sheet 1 arranged between the dimples
5. As a result, the dimpled sheet 1 illustrated in FIG. 1 has a
relatively large total contact surface to the subsurface. This
makes it possible to ensure that, after the filling of a
construction pit with fill dirt 8, either no or only slight
penetration of the dimples 5 into the bitumen sheet 6 can occur due
to the fill pressure brought about by the fill dirt 8. The danger
of damaging the bitumen sheet 6 is hence reduced considerably. At
the same time, it is ensured by the inwardly oriented dimples 5
that the dimpled sheet 1 is torn off or partially shifted downward
during filling of the fill dirt 8 into a pit (not depicted)
adjacent to the building wall 7. Moreover, the removal of water
through the hollow spaces 9 arranged between the dimples 5 is
ensured by the inwardly oriented dimples 5, with the hollow spaces
9 forming air cushions which have a heat-insulating effect and
permit vapor pressure compensation. In addition, the individual
hollow spaces of the dimpled sheets are connected to each other,
although it is also possible in principle that a plurality of
hollow spaces that are separated from each other can be
provided.
[0031] In FIGS. 2 to 23, contact surfaces of dimpled sheets 1 for
one cross-section of the respective dimpled sheet 1 are
respectively depicted for the sake of example, with the contact
surfaces being formed by outer sides of dimple covers 4 of a
plurality of dimples 5. The base or cross-sectional surfaces of the
dimples 5 at the level of the flat area 2 are not shown. Here it is
possible that the dimples 5 have the same cross-section over the
entire dimple height, as is the case in cylindrical or rectangular
dimples 5, for example. As will be readily understood, the dimples
5 can also have a cross-section which changes over the dimple
height, as can be the case with truncated cone- or truncated
pyramid-shaped dimples 5.
[0032] In the embodiment of a dimpled sheet 1 depicted in FIG. 2,
the formed contact surfaces are preferably spaced equally apart
from each other in all directions of the dimpled sheet 1. Here,
according to FIG. 2, the dimples 5 have square contact surfaces,
and the dimples 5 as such can be shaped in the form of a truncated
pyramid or be rectangular. In dimples 5 with square contact
surfaces, a proportion of the total contact surface of greater than
50% of the total surface of the dimpled sheet 1 is achieved, for
example, if every dimple cover 4 has an edge length of approx. 11
mm, with a distance between neighboring dimple covers 4 of approx.
4 mm, respectively.
[0033] In the embodiment shown in FIG. 3, the contact surfaces of
the dimples 5, in turn, have the same spacing from each other in
all directions of the dimpled sheet 1 at least at the level of the
dimple covers 4, with the dimples 5 having rectangular contact
surfaces. In this way, the total contact surface can be increased
further while maintaining the intermediate spacing of approx. 4
mm.
[0034] Moreover, in the dimpled sheet 1 depicted in FIG. 3, a
plurality of rows of dimples 10, 11 are provided which are arranged
perpendicularly to each other and each having a plurality of
dimples 5, with the dimples 5 of a row of dimples 10, 11 being
respectively arranged axially on the middle longitudinal axis of
the respective row of dimples 10, 11. In the embodiment portrayed
in FIG. 3, a raster- or lattice-like arrangement of the dimples 5
on the dimpled sheet 1 is further provided. By contrast, the
embodiment shown in FIG. 4 is such that the dimples 5 of a first
row of dimples 10 and the dimples 5 of at least one other adjacent
row of dimples 10a running parallel to the first row of dimples 10
are arranged in a staggered manner with respect to each other in
the direction of the middle longitudinal axis of the neighboring
row of dimples 10, 10a.
[0035] In the dimpled sheets 1 depicted in FIG. 3 and FIG. 4, the
longitudinal and transverse sides of the dimple covers 4 are
oriented parallel to the longitudinal and transverse sides of the
dimpled sheet 1. It goes without saying that it is of course also
possible to embody the longitudinal and transverse sides of the
dimple covers 4 and hence the contact surfaces of the dimpled sheet
1 such that they run perpendicularly to the longitudinal and
transverse sides of the dimpled sheet 1.
[0036] Since, as the size of the dimples 5 or of the contact
surfaces increases, their compressive strength decreases, dimples
5, 5a, 5b can be arranged regularly, particularly alternatingly,
next to each other with different-sized contact surfaces and/or
different shapes of the contact surfaces. This is shown, for
example, in FIGS. 5 to 7. For example, a provision is made in FIG.
5 to arrange dimples 5 with larger contact surfaces and dimples 5a
with relatively smaller contact surfaces next to each other, with
the dimples 5 each having dimple covers 4 with a square contact
surface and the dimples 5a each having dimple covers 4 with a
rectangular contact surface. Here, the contact surface of a dimple
5a is approx. 50% of the contact surface of a dimple 5.
[0037] In FIG. 6 and FIG. 7, other dimpled sheets 1 are depicted
which show the possible combinations of larger dimples 5 with
smaller dimples 5a, 5b. The illustrated embodiments show that
dimples 5 can be respectively provided with a first contact surface
and other dimples 5a, 5b can be respectively provided with another
contact surface deviating from the first contact surface in order
to enlarge the total contact surface of the dimpled sheet 1, with
the dimples 5 and the other dimples 5a, 5b having contact surfaces
of different shapes and/or sizes. As a result, two, three or even
more types of dimple of different shapes and/or sizes can be
provided in order to make available a comparatively larger total
contact surface of the dimpled sheet 1 to the subsurface.
[0038] In principle, a total contact surface proportion of greater
than 50% of the base surface of the dimpled sheet 1 can also be
ensured with dimples 5 that have circular contact surfaces, with
cylindrical dimples 5 having a higher load capacity than dimples 5
of an n-cornered shape. One possible sample embodiment of a dimpled
sheet 1 with dimples 5 that have circular dimple covers 4 is shown
in FIG. 8, for example. In the dimpled sheet 1 depicted in FIG. 8,
the condition indicated below must preferably be met in order to
ensure a sufficient total contact surface proportion of greater
than 50%:
[.pi.d.sup.2/4]/[(d+a.sub.1)(d+a.sub.2)]>0,5
[0039] Even with dimples 5 with circular contact surfaces, an
increase of the load capacity of the dimpled sheet 1 can be
achieved by having larger dimples 5 arranged adjacent to smaller
dimples 5a, each with respect to the size of the contact surfaces
or the size of the dimple covers 4. This is shown, for example, in
FIGS. 9 and 10. As also follows from FIGS. 9 and 10, the larger
dimples 5 can be arranged in a regular raster, with the other,
smaller dimples 5a being disposed in empty spaces of the
raster.
[0040] Moreover, dimples 5 that have contact surfaces having one
shape and/or size can have other dimples 5a that have contact
surfaces having another shape and/or size arranged peripherally in
the manner of a frame. This is shown, for example, in FIGS. 9 and
11.
[0041] In the dimpled sheet 1 depicted in FIG. 11, dimples 5 with
dimple covers 4 are provided which form square contact surfaces.
The dimples 5 are arranged here in the manner of a frame about a
dimple 5a whose dimple cover 4 forms a circular contact surface.
The combination of dimples 5, 5a with different contact surfaces is
advantageous, since dimples 5 with an n-cornered contact surface
ensure a larger surface utilization and dimples 5a with circular
contact surface ensure a greater pressure load capacity. Further
examples of embodiments of dimpled sheets 1 having dimples 5, 5a,
5b with contact surfaces of different sizes and/or shapes or
contours are shown in FIGS. 12 to 20. In the dimpled sheet 1
depicted in FIG. 20, the condition indicated below must preferably
be met in order to ensure a sufficient total contact surface
proportion of greater than 50%:
[.pi.d.sup.2/4+4x.sub.1x.sub.2]/[(x.sub.2+2a.sub.1+x.sub.1)(x.sub.2+2a.s-
ub.2+x.sub.1)]>0,5
[0042] Dimpled sheets 1 are shown in FIGS. 13 and 16, each with 3
different types of dimples, with the types of dimple differing in
terms of the size and shape of the contact surfaces formed by the
dimple covers 4.
[0043] In another embodiment of a dimpled sheet 1, a provision can
be made that the contact surfaces of neighboring dimples 5a, 5b
formed by the dimple covers 4 have contours that are complementary
to each other, at least in sections. For example, according to FIG.
21, three different types of dimple are provided in dimples 5, 5a,
5b, with one dimple 5b being framed by a circular contact surface
of four dimples 5a, each having contact surfaces with inwardly
curved longitudinal sides 12. This results in an annular space 13
which is bounded toward the inside by the outer edge of the dimple
cover 4 of the dimple 5b and toward the outside by the inwardly
curved longitudinal sides 12 of the dimple covers 4 of the
neighboring dimples 5a. By virtue of the mutually complementary
contact surfaces of the dimples 5a, 5b, an even greater surface
utilization can be ensured.
[0044] Another possibility for enlarging the total contact surface
of the dimpled sheet 1 consists in providing dimples 5 with oval or
ellipsoid contact surfaces, with the contact surfaces each
preferably being narrowed in the middle area and the dimples 5
being arranged such that neighboring contact surfaces, in turn,
have a complementary contour to each other at least in sections.
This is shown, for example, in FIG. 22. A combination of the
dimples 5 shown in FIG. 22 with other dimples 5a having circular
contact surfaces is also possible and contributes to the
enlargement of the total contact surface. This is illustrated in
FIG. 23.
[0045] It is not shown that the dimple covers 4 can also have an
n-cornered shape, for example as a hexagon, octagon or dodecagon.
Moreover, as will readily be understood, the dimple covers 4 of the
dimples 5, 5a, 5b can also have recesses, resulting in annular
contact surfaces, for example.
[0046] Finally, it should be pointed out that dimples with
different extensions in the longitudinal and transverse direction
can also be arranged such that they have reciprocal directional
preferences, which is shown in FIGS. 6, 20 and 21, for example. By
reciprocal directional preferences is meant, for example, that
rectangular dimples can be arranged both standing and lying. This
can also be the case, for example, in the embodiments shown in
FIGS. 3, 4, 5, 7, 18, 19 and 23.
[0047] At a preferred embodiment of the present invention the total
contact surface CS has 36% and the dimple height DH is 8,2 mm. With
these values the protection coefficient PC has an amount of
10.627,2.
* * * * *