Note: Descriptions are shown in the official language in which they were submitted.
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The invention relates to a body of resilient foam
material, such as a buffer, a seat cushion or mattress of foam
rubber or synthetic foam material, which body at a plurality spaced
apart locations has been provided with compressible spring elements
in incisions of the foam body.
A body of this kind in the form of a mattress is known
from published German specification 2,324,101. In this known
mattress which has been divided into blocks by longitudinally and
transversely extending incisions, each block has been provided with
a cylindrical slit within which a conical helical spring has been
placed which has been compressed to one half of its length and
accordingly is pretensioned and which compresses the core in radial
direction. This spring is not in contact with the outer wall of
the cylindrical slit.
With that known mattress one aims, when use is made-of
foam material of small density or specific mass, to give the
mattress additional rigidity by means of the pretensioned springs
which are placed in the slits to enable the mattress to support a
body and to make sure that after compression of parts of the
mattress recovery of the shape can take place quickly when the load
is removed. Pretensioned springs of this kind in a foam body of
small specific mass and accordingly great softness are felt as hard
cores, which in particular is undesirable in the application as a
mattress. The same of course holds true for seat cushions whereas
with the application in buffers or for packaging the springs also
form hard places. A pretensioned spring only becomes compressible
and accordingly only operates as a spring when the load becomes
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equal to the pretensioning force.
It is a known fact, that the rigidity of a mattress
cushion, seat or the like, of Eoam rubber or synthetic foam falls
off after some time of use. This has as a consequence that, as a
rule, one cannot make use of a foam material which is relatively
soft and accordingly not of foam material which delivers a soft
mattress or cushion with high comfortability because after some
time they become too soft and offer too little support due to the
decrease in the rigidity. This of course holds true as well for
buffers because after some time their ability to take up blows
decreases so much that they become unfit for use. If one makes use
of the above known pretensioned conical helical springs said
springs certainly give some compensation for the reduction of the
rigidity but in certain applications, such as seat cushions and
mattresses, the springs then are locations which are inconveniently
perceptible and accordingly useless.
In the past many proposals already have been made to
place helical springs and the like in a mattress. Thus from the
published Netherlands patent application 7808781 a mattress is
known in which a plurality of cylindrical holes are made in the
main body of foam material which holes extend transversely through
the main body and within which helical springs are placed. Said
helical springs are enclosed in the h~'es by attaching, e.g. by
glueing, plates of foam material against the underside and upon the
upper side of the main body. Comparable proposals are found as
well in Swiss patent specification 452824, Australian patent
specification 450041 and United States patent specification
2,540,441.
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From French patent specification 1,110,462 a mattress is
known as well comprising two layers of foam material having
recesses in each layer which only form part of the thickness of the
layer and which are in line with each other when the layers are
placed upon each other, helical springs being enclosed within said
recesses. According to the proposals no slits are made in the foam
body, but chambers. These chambers form large hollow spaces within
which, apart from the helical spring, as a rule also air is present.
The homogeneous character of the isolating properties is disturbed
therewith because each hollow space with the spring placed in it
forms a cold bridge. Moreover the hollow spaces disturb the entire
spring characteristic of the foam body which then in a positive
sense is influenced by the helical springs placed in the chambers.
Another objection of helical springs placed in hollow
chambers is that they can tilt, which means take up a position in
which they partly extend transversely or curved inside the hollow
space and then they no longer can operate properly.
With modern mattress support structures having a head
portion and a foot portion respectively which can swing upwardly
the foam mattress must be flexible. A normally interconnected
mattress with inner springs cannot do this. The spring frame with
interconnected springs will kink upon bending at each location
where the springs are interconnected. The mattresses according to
the above-mentioned known proposals with helical springs placed in
hollow spaces as a rule can be bent, but the risk is increased that
the spring inside the hollow space will take up an incorrect posi-
tion.
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The manufacturing of hollow spaces can take place by
punching them as through holes out of the massive material. How-
ever, it then is not easy to obtain a pure cylindrical opening. If
discontinuous recesses are used then the manufacturing is compli-
cated because the recesses have to be made by means of cores to be
placed in the mould in which foaming takes place at the locations
where the recesses are to be made.
Each hollow space obtained by cutting away material means
loss of material.
From French patent specification 1,552,214, in particular
Figure 2, it is known to surround the helical spring elements com-
pletely by the foam material. To this end, however, it is necessary
to place the spring elements in a mould within which the foaming
takes place and this makes manufacturing complicated and expensive.
Manufacturing a slit, as is known does not lead to any
loss of material, and can be done in a relatively simple way by
means of a cutting device making a cut without removing material.
The purpose of the invention is to provide a body of
resilient foam material which is suitable for many purposes, can be
manufactured in a simple way, maintains its rigidity without the
spring elements used for that purpose becoming perceptible.
The invention provides in a support device including a
body formed from a flexible resilient material and having a plur-
ality of spaced apart chambers formed therein, said body provided
with compressible spring elements within said chambers, the
improvement comprising said flexible resilient material and said
spring elements having substantially the same spring rates and said
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spring elements being in an unstressed state when said structure
is in an unloaded state.
Each spring element over its entire length is in contact
in a non-shiftable manner with the one and/or the other wall of
the slit defining the chamber. In the loaded condition the spring
element over the entire length is in contact with the two walls of
the slit and between the spring element containing slits the foam
body is unin-terrupted.
Accordingly the spring elements are not pretensioned and
immediately come into operation as soon as a load occurs.
Due to the fact that the spring elements are enclosed
over the entire length such that they always are in contact with
one wall of the slit and upon being loaded always with both walls
of the slit, no shifting whatsoever of parts of the spring elements
with respect to the walls of the slit takes place. The spring
elements are not perceptible but ensure maintenance of the rigidity.
With the measure according to the invention in a simple way it has
been achieved that the resilient foam body always maintains its
properties. The foam body with the exception of the slits within
which the spring elements are present is not interrupted by other
incisions, slots or the like between the spring elements. In other
words large portions of the foam body each comprising a plurality
of spring elements can be considered as one block or plate.
The spring elements enclosed in this way cannot tilt or
bend if loaded at only one side.
Preferably cylindrical slits are used within which a
cylindrical helical spring is placed. The spring elements can be
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formed by a wire the thickness of which is larger than the width
of the slit. The spring elements are then enclosed completely
invisibly and from the very beginning, even in unloaded condition,
are completely enclosed. It is also possible, however, to give
the slits a width which is larger than the thickness of the wire
of the spring element, so that this spring element in unloaded con-
dition is spaced from one of the walls of the slit. In loaded con-
dition the foam material is displaced and immediately encloses the
spring element completely.
Instead of cylindrical slits rectilinear slits can be
made in the form of parallel rows with or without staggered
relationship and extending transversely and/or longitudinally of
the body.
Such rectilinear slits have the advantage that the spring
elements can easily be placed because one only needs to place the
body on a curved surface to be able to insert the spring elements
in the then opened slits. It is conceivable as well to apply zig-
zag shaped slits having a separate spring element in each part of
the zig-zag or interconnected spring elements extending over the
entire length of the zig-zag line.
Instead of spring elements made from spring steel sprin~
elements of another resilient material such as synthetic material,
foam material, rubber and the like could be used.
With mattresses one preferably makes the slits in planes
extending perpendicular to the main plane of the mattress because
the mattress is loaded in a direction perpendicular to that plane.
With cushions such as cushions which rest against a curved back or
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supporting plate, it can be useful for the axis or planes of the
slits in the direction of compressibility of the spring elements
to extend at different angles with respect to each other. The slits
can also extend perpendicular to two or more planes of the body.
Accordingly one can manufacture blocks which can take up loads in
different directions. Thus with a cup-shaped chair e.g. a bucket
seat of a vehicle, the supporting function, apart from by the shape
of the cup also can be defined by the direction within which the
spring elements are directed so that at the edges of the cup forces
in transverse direction can be taken up as well.
It is observed that from published Netherlands patent
application 7007648 a resilient covering system is known suitable
for use in beds, seat cushions, back supports and like objects
comprising a foam material which surrounds a plurality of adjacent
helical springs in the form of interconnected bags which specifica-
tion also states that the resilient foam material can be a
resilient urethane foam having a low specific weight because the
foam material need not add anything to the function of the spring.
Here, however, one has to deal with a resilient support of a con-
struction such that the helical springs have to be placed first inthe mould in which the foam material that has to surround the
springs is foamed. This is a very complicated expensive manner of
manufacturing which does not allow foam layers to be cut from a
large prefabricated block. It is observed further that from
British patent specification 493,356 buffers are known having spring
elements which are prepared with a vulcanizable material and are
placed in a mould within which the rubber is fed. In this way a
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complete enclosure of the spring elements is obtained. This
manner of manufacturing is complicated and expensive as well.
The principle underlying the invention, i.e. the complete
enclosure of spring elements which in unloaded condition are free
of tension and which have a spring characteristic comparable with
that of the foam material, can be applied in many ways. Thus it
can in principle be applied with each type of cushion such as loose
cushions for furniture but also for fixed coverings of furniture,
vehicle seats, in particular bucket seats, air plane seats and the
like. Application is conceivable with bump free safety layers such
as e.g. the dash board and the roof coverings of vehicles. Indus-
trial applications are possible such as packaging materials, e.g.
with the inner coating of a box or case and with supporting cushions
for vibration-free support of machines or apparatuses. Conceivable
as well is an application in children's playgrounds, such as in the
form of play blocks and bump free coatings of floor or wall.
The principle according to the invention in particular
is suitable for the application on mattresses.
With all applications of foam materials according to the
known proposals, to obtain the required rigidity and the required
capacity to absorb shocks and loads respectively, one had to make
use of foam materials having a relatively high specific mass and
this entails a cost factor which is prohibitive for many applica-
tions. This is the reason that in the older proposals some, such
as the earlier mentioned German specification 2,324,101 use a foam
material of low specific mass which are given a spring character-
istic by enclosing spring elements therein. One, however did not
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understand that by placing and enclosing the correct spring
elements according to the proposal of the present invention, even
with bodies of resilient synthetic material having a low specific
mass the decrease in rigidity can be obviated.
The invention now will be further elucidated, by way of
example only, with reference to the drawings, wherein:-
Figure 1 shows in cross section a first embodiment of a
part of a mattress according to the invention;
Figure 2 in the same way shows a cross section through
another embodiment;
Figure 3 shows a third embodiment in cross section;
Figure 4 shows a fourth embodiment in cross section;
Figure 5 shows a fifth embodiment in cross section;
Figure 6 shows a sixth embodiment in cross section;
Figure 7 shows a seventh embodiment in cross section;
Figures 8 and 9 show in top view schematically the
locations where the slits can be made;
Figures 10, 11 and 12 show different possibilities of
forms of slit for receiving a spring element;
Figure 13 in side view shows a spring element which can be
used with the possibilities shown in Figures 10 to 12 inclusive;
Figure 14 shows still another embodiment;
Figure 15 is a perspective view of a block of foam mater-
ial having spring elements in two perpendicular directions;
Figure 16 shows a cross section through a back support;
and
Figure 17 shows an application in the form of a support
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cushion e.g. for the vibration-free mounting of some apparatus.
The mattress shown in Figure 1 comprises a main body 1
having a cylindrical incision 2 which extends through a part of
the thickness of the main body 1. A helical spring 3 has been
placed in the incision. The helical springs are retained within
their slits covering layer 4. In the embodiment of Figure 2 the
incision 5 has the same depth as in Figure 1. The helical spring
3 in unloaded condition engages the core 6 of the material of the
mattress 1, which core has been left in place in the same way as
with the embodiment of Figure 1.
The incision 5 has a width such that in unloaded condition
the spring is not in contact with the outer wall 7 of the incision.
In loaded condition this outer wall, however, will move inwardly
and engage the helical spring.
With the embodiment of Figure 3 the incision 8 is made
with the same small width as in Figure 1, however, the incision 8
now extends through the entire thickness of the mattress body 1.
The core 9 thus separated, however, is placed together with the
helical spring 3 in the opening obtained. Enclosure again takes
place by means of the top covering layer 4 and an additional
bottom covering layer 10.
With the embodiment of Figure 4, the mattress comprises
two layers 11 and 12. Incisions 13 and 14 respectively are made in
the two layers with a depth which is less than the thickness of
the corresponding layer 11, 12 so that the cores 15 and 16 remain.
One single helical spring 3 is placed in the two incisions 13 and
14.
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The embodiment of Figure 5 is similar to Figure 4 with
the difference, that the incision 17 is made with a larger width
comparable to the width shown in E'igure 2.
In the embodiment of Figure 6 the mattress comprises a
thick layer 18 and a thinner layer 19. Helical springs may be
placed in the thick layer as shown at 20 and e.g. by means of an
incision of the type shown in Figures 1, 3 and 4. Furthermore the
two layers 18 and 19 can have incisions 21 and 22 respectively of
a larger width comparable to the embodiment shown in Figure 5, the
helical spring 23 surrounding both cores 24 and 25.
Figure 7 shows a mattress having an incision 26 in the
main body 1, the incision 26 having a width of the type shown in
Figures 2 and 5. The difference with the other embodiments, how-
ever, is that the helical spring does not engage the core but
engages the outer wall of the incision 26.
In Figures 8 and 9 top views are shown of mattresses and
each circle shown represents an incision in which a helical spring
is placed.
Instead of cylindrical metal helical springs, it is con-
ceivable to use another circumferential shape. Instead of metal
spring elements it is possible to use spring elements of other
material such as synthetic material or rubber.
Figure 10 shows in top view a mattress 30 having longitu-
dinally extending parallel rows of incisions 31 which do not extend
through the entire thickness. In the transverse direction incisions
32 are provided.
Figure 11 shows a mattress 33 also provided with rows of
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incisions 34 extending parallel to the longitudinal direction,
which incisions, however, are staggered from row to row whereas in
Figure 10 the incisions of adjacent rows are aligned in the trans-
verse direction.
The incisions 35 shown in Figure 11 and extending in
transverse direction lie between the incisions 34.
Figure 12 shows two possibilities of zig~zag shaped
incisions namely a zig-zag of rectangular angles as shown at 36 and
a V-shaped zig-zag as shown at 37.
Spring elements as shown in principle in Figure 13 can be
placed in the rectilinear incisions of all embodiments shown in
Figures 10 to 12 inclusive, such spring elements comprising a wire
or strip of spring steel 38 bent in a zig-zag and lying in a flat
plane, the lower leg 39 of the spring being shorter than the upper
leg 40 to facilitate insertion.
Such a spring can be manufactured in unrestricted lengths
as indicated by the interrupted lines 41 and in this way one can
manufacture a strip of spring elements which by bending can be
adapted to the zig-zag shaped path of the incision made.
Figure 14 shows a mattress 1 of the type shown in Figure
1 but upside-down and without a covering layer 4.
The mattress shown in Figure 14 comprises exclusively a
layer 1 of foam material having incisions 2 into which springs 3
are placed. The incisions are made in the bottom surface which
lies upon a perforated plate 43 which is supported by lath 44 of
a frame. Any other forrn of underbed is possible as well.
Figure 15 in a perspective view shows a block 47 in which
a plurality of spaced parallel cylindrically shaped incisions 48
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are made, in such incisions helical springs 49 being placed.
Between the incisions 48 and in a direction perpendicular thereto
there are incisions 50 having helical springs 51. This block 47
accordingly can take up loads in two perpendicular directions. The
incisions 48 need not, as shown, extend through the entire thick-
ness of the material.
Figure 16 shows a curved plate 52 which may be the back
of a chair and on this plate is attached a foam layer 53 into which
a plurality of incisions are made e.g. of the same type as shown in
the preceding figures and within which are helical springs 54. In
the central area of the foam layer 53 the axis of the helical
springs are in principle perpendicular to the plate 52. The more
outwardly located helical springs 55, 56 extend at an angle to the
perpendicular and due to this also give support in the transverse
direction.
Figure 17 shows a supporting surface 57 having a recess
58 into which a block 59 of foam material is placed, having spring
elements comparable to the embodiment of Figure 14, namely springs
60, compressible in the vertical direction and springs 61 which
are compressible in the horizontal direction. This is of importance
for a block 59 the width of which is larger than the width of the
recess 58 so that the foam material can be under pretension in the
recess. Such a support can be useful for the vibration free mount-
ing of measuring devices, laboratory apparatus, and also of machines.
Many other applications are possible on a large or small
scale. Small scale is any relatively thin coating layer suitable
for taking up bumps. Large scale is a cushion having a thickness
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of at least one meter, e.g. for sports such as high jumping or
for safety purposes.
