Note: Descriptions are shown in the official language in which they were submitted.
CA 02300883 2000-02-18
WO 99/11555 PCT/GB98/02581
- 1 -
H LIFTING CUSHION
The present invention relates to a lifting cushion for
supporting, raising or moving objects.
Lifting cushions of the invention may for example be used
for rescuing people who are trapped by collapsible walls,
girders, concrete slabs or heavy road vehicles.
These lifting cushions can also be used for prising
steering columns, removing windscreens and for forcing
doors. Industrial uses of the lifting cushions include
lifting heavy machinery, rail locomotives and pipelines,
supporting tensioning in mining, splitting slabs in
quarries, and use as compression or spreader elements.
In operation, the lifting cushion in placed in its
flattened condition beneath the object to be raised. The
cushion is then inflated thereby raising the object. If
further lift is required one or more lifting cushions may
be inserted one above the other and subsequently inflated
to provide a required degree of lift of the object.
In order to provide a maximum lifting force the lifting
cushions are generally of rectangular form. With the
previously known lifting cushions the problem arises that
when the cushion is inflated the cushion changes from its
non-inflated flat rectangular form to a form having a
generally oval vertical cross-section. This change in
shape of the cushion considerably reduces the contact
area between the cushion area and the object to be raised
thereby producing a corresponding reduction in the
lifting force that can be applied by the cushion to the
object. There is also a significant risk arising from
the difficulty of calculating the force required to lift
the object from the trapped person or to gain clearance
CA 02300883 2000-02-18
.. ~' , °'
.~ . . ~ : ::
- 2 -
to insert cribbage. It will be appreciated that this
change of shape in the cushions makes it extremely
difficult to provide sufficient stability to be able to
use a plurality of cushions one on top of the other.
W094/26649 (D1) discloses a lifting cushion having an
envelope which includes two rectangular sheets connected
by a plurality of cell structures which extend the length
of the envelope. The sheets are formed of woven
polyaramid cloth or polyaramid cord superimposed with
steel tyre cords. Each cell structure is of rectangular
cross-section and is formed from polyaramid or polyester
sheet material. The end portions of the cell sheet
material overlap at the upper region of each cell. An
important feature of this construction is that each cell
structure is located completely within the space defined
by the envelope sheets.
DE 8506736 (D2) discloses a lifting cushion consisting of
a plurality of individual chambers assembled to form a
lifting cushion. Each chamber comprises lower and upper
rectangular blanks made of coated thread fabric and
_~ connected by spacing threads. Each chamber is closed by
four side strips to be airtight, and an air connection is
provided for each individual chamber.
In D2 the top and bottom panels are connected and
separated solely by spacing threads 2. In consequence
the lifting cushions of D1 and D2 have the above-
mentioned disadvantage that when the cushion is inflated
the cushion changes from its non-inflated rectangular
form to a form having a generally oval cross-section.
In addition, the lifting cushion of D1 has been found
unable to operate at the required standard high pressure.
_..
f~'~.._ ._ _. , .
CA 02300883 2000-02-18
- ' ' < ..
"~ ,~ -_
~ . , . _ ~ . - . ..
t a - -
2a
It is an aim of the invention to alleviate the above-
mentioned disadvantages, and according to one aspect of
the present invention there is provided an inflatable
envelope for a lifting cushion, said envelope comprising
two opposed major members and a plurality of cell
structures extending between and through the said two
members to retain said two major members of the envelope
at a preselected attitude to one another when the
envelope is inflated, in which each cell structure
comprises two opposed generally U-shaped half cell
members with the opposed facing end portions of the two
half cell members connected to the outer surfaces of the
major members.
The length of the mid portion of the half cell members
will define the preselected relative attitude of the two
major members of the envelope, and also the spacing of
these major members, when the envelope is fully inflated.
In one example of the invention, the length of the mid
portion of the half cell members may be 100mm in length
but the invention is not restricted to cell structures of
any specific dimension.
In a preferred embodiment of the invention the two major
members and the half cell members may be constructed of a
polyaramid material such as polyaramid cord, and the
material may be coated on both sides with uncured
neoprene.
. ".:~:v_ _ . ,.. ,.
CA 02300883 2000-02-18
WO 99/11555 PCT/GB98/02581
- 3 -
According to another aspect of the invention there is
provided a lifting cushion comprising the above-mentioned
inflatable envelope and a first layer extending around
the envelope.
The first layer may extend in a first direction, and be
folded around the envelope so as to have folded over
regions.
The invention may include a second layer extending in a
second direction and being folded around the said first
layer to have folded over regions. The folded over
regions of the second layer may be on the opposite side
of the lifting cushion to the folded over regions of the
first layer, and in a preferred embodiment the said first
and second directions are at 90° to one another.
In a construction in which the envelope is rectangular,
the said first and second directions of the layers may
extend parallel to first and second sides of the
rectangular envelope.
In another embodiment of the invention the first layer
comprises two sheet portions which are laid one on each
of the associated major members of the envelope, and
folded over the sides of the envelope.
An embodiment of the invention will now be described by
way of example with reference to the accompanying
drawings in which:-
Figure 1 is a perspective view of an envelope of a
previously proposed lifting cushion,
Figure 2 is a perspective view of the first and second
CA 02300883 2000-02-18
WO 99/11555 PCT/GB98/02581
- 4 -
layers of the cushion of Figure 1,
Figure 3 is a perspective view of a nipple for an air
valve,
Figure 4 is a perspective view of a metallic fitting for
the nipple of Figure 3,
Figure 5 is a diagrammatic side elevation of a double
unit lifting cushion before folding the second layer,
Figure 6 is a diagrammatic side elevation of the lifting
cushion of Figure 5 when the second layer has been
folded, at 90° to the cushion of Figure 5.
Figure 7 is a diagrammatic side elevation of another
previously proposed lifting cushion envelope,
Figure 8 is a diagrammatic side elevation of the lifting
cushion envelope of the invention, and
Figures 9 and 10 are diagrammatic views of parts of
Figure 8.
Referring to the drawings, the previously proposed
lifting cushion comprises an inflatable envelope 2, a
first layer 4 and a second layer 6. The lifting cushion
is manufactured in a press using hot vulcanisation, and
the material of the components of the cushion is
unvulcanised before rot vulcanisation takes place.
Alternatively, the lifting cushion may be hand assembled
prior to hot vulcanisation.
The envelope 2 includes two rectangular sheets 8 and 10
CA 02300883 2000-02-18
WO 99/11555 PCT/GB98/02581
- 5 -
of woven polyaramid cloth or polyaramid cord superimposed
with steel tyre cord. The sheets 8 and 10 are connected
by a very large number of closely adjacent polyaramid
filaments 12, and the length of these filaments defines
the maximum separation distance of the sheets 8 and 10.
In the illustrated embodiment all the filaments are of
equal length to ensure that the sheets 8 and 10 are
parallel to one another when the envelope 2 is fully
inflated. However, different filaments may have
different lengths to enable the sheets 8 and 10 to be
inclined to one another at a required angle when the
envelope 2 is fully inflated. The filaments 12 may have
any desired length in order to provide the required
attitude and spacing of the sheets 8 and l0.
The outer surfaces of the envelope sheets 8 and 10 are
coated with an air retaining rubber compound such as
neoprene thereby enabling the envelope 2 to be vulcanised
to the other components of the lifting cushion. This
coating is spread on the sheets 8 and 10 with rollers.
An air valve for the envelope 2 includes a rubber nipple
14 attached to a nozzle 16, and a metal fitting 18 which
is located in the nozzle 16.
The outer surfaces of the envelope sheets 8 and 10 are
coated with an air retaining rubber compound such as
neoprene thereby enabling the envelope 2 to be vulcanised
to the other components of the lifting cushion. This
coating is spread on the sheets 8 and 10 with rollers.
The first layer 4 consists of a rectangular sheet 20 of
polyaramid which is coated with a neoprene layer on both
the upper and lower surfaces. This sheet 20 has the same
width 24 as the width 25 of the envelope 2, and the
CA 02300883 2000-02-18
WO 99/11555 PCT/GB98/02581
- 6 -
length of the sheet 20 is chosen so that it can be
wrapped round the envelope 2 with the sheet edges 26
overlapping one another in the centre of the lifting
cushion. The direction of reinforcement of the sheet 20
extends in the direction 23.
The second layer 6 consists of a second rectangular sheet
28 which is made of the same material as, and neoprene
coated the same as, the first sheet 20 except that all
its directions and dimensions are rotated through 90°.
The sheet 28 has the same width 29 as the length 31 of
the envelope 2, and the length of the sheet 28 is chosen
so that it can be wrapped round the first layer 4 with
its edges 32 overlapping in the centre of the lifting
cushion. The direction of reinforcement 33 of the sheet
28 runs perpendicularly to the direction of reinforcement
23 of the sheet 20.
During manufacture, the first and second layers 4 and 6
are carefully pressed by a roller in order to prevent air
from being trapped in the two layers. Any such trapped
air would breathe during inflation and evacuation of the
lifting cushion thereby producing unwanted separation of
the components of the cushion.
The envelope 2 is placed in the centre portion of the
laid out first sheet 20. The two outer portions of the
sheet 20 are folded over the envelope 2 so that the two
sheet edges 26 overlap one another. The rubber nipple 14
of the air valve is inserted in one corner of the
envelope 2 with the attached nozzle 16 extending from the
envelope 2.
The sheet 20, envelope 2 and nipple 14 are then heated
and compressed by a platen, and hot vulcanised to secure
CA 02300883 2000-02-18
WO 99/11555 PCT/GB98/02581
these components to one another. The attached sheet 20
and envelope 2 are then placed on the centre portion of
the laid out second sheet 28 which is located at 90° to
the first sheet 20. The two outer portions of the sheet
28 are then folded over the first sheet 20 so that the
two sheet edges 32 overlap one another on the opposite
face of the lifting cushion to the edges 26 of the first
sheet 20. The direction of reinforcement 33 of the sheet
28 runs perpendicularly to the direction of reinforcement
23 of the first sheet 20.
The folded sheet 28 is heated and compressed by a platen
and hot vulcanised to secure the sheet 28 to the sheet 20
and envelope 2. The sheets 20 and 28 are preferably
folded over suitable templates which can be manufactured
from a metal sheet.
Figures 1 to 4 illustrate the components of a single unit
lifting cushion. The invention includes within its scope
a lifting cushion having two or more units. Referring to
Figures 5 and 6, a two unit lifting cushion includes two
units 34 and 36 with each unit constructed as previously
described herein with reference to Figures 2 to 4. This
double unit lifting cushion includes a central hinge
strip 38 extending around a space 40 located between the
two units 34 and 36. This hinge strip is made of a
polyaramid sheet coated on both its surfaces with
neoprene. This strip 38 is folded centrally to form a V
cross-section and each arm of the V is vulcanised to the
adjacent opposed sheets 20 and 28 of the upper and lower
cushion units 34 and 36 which define the upper and lower
surfaces of the space 40. This two unit assembly
requires only a single air valve which is located in
either one of the units. Coaxial central orifices are
made in the envelope sheets 20 and 28 of the first and
CA 02300883 2000-02-18
WO 99/11555 PCT/GB98/02581
_ g _
second layers 4 and 6 adjacent to the space 40 between
the two units to enable air from the air valve to enter
both these units.
A lifting cushion of three or more units can be assembled
in the same way by connecting all adjacent units by a
hinge strip and providing coaxial central orifices
between the sheets of adjacent units.
The lifting cushion of the invention may have any
convenient dimensions. One embodiment of the invention
may have the following dimensions:-
The envelope 2:-
The sheets 8 and 10 are each 510 x 510mm and the
filaments 12 are 100mm in length.
The first layer 4 is 610 x 610mm when folded, and 610 x
1220mm when laid out flat. 5omm is added to the length
for the edge overlap.
The second layer 6 is 610 x 610mm when folded and 610 x
1220mm when laid out flat. 50mm is added to the length
for the edge overlap.
In one example of a double unit lifting cushion of the
invention each unit will have the above dimensions.
The above-mentioned first and second layers 4 and 6 are
larger than the envelope sheets 8 and 10 to allow for the
100mm length of the filaments. When the lifting cushion
is inflated the surface areas of the first and second
layers contract to 510 x 510mm to allow for the fully
stretched filaments 12.
When manufacturing a lifting cushion having two or more
CA 02300883 2000-02-18
WO 99/11555 PCT/GB98/02581
- 9 -
units, each unit may be vulcanised separately and
adjacent units and the connecting hinge assembly then
vulcanised to one another. Alternatively, all the units
and their connecting hinge strips may be secured together
in a single vulcanising operation.
The above-described and illustrated lifting cushion is
designed for an internal working pressure of 800 Kpa when
the filaments 12 are fully extended to their operational
length of 100mm. This enables the lifting cushion to
lift and support a weight of 20,714 kg.
Although the described embodiment includes filaments 12
of polyaramid, the invention includes within its scope a
lifting cushion having filaments of any suitable material
such as, for example, a polyaramid/nylon mixture. The
advantage of polyaramid is that it can sustain a working
pressure greater than some other materials.
The described and illustrated embodiment includes within
its scope a filament density in the range from 230 to
40,000 filaments 12 per square metre.
The important feature of the filaments 12 is that they
retain the envelope sheets 8 and 10 in a preselected
required relative attitude and spacing. It will be
appreciated that the most common relative attitude will
be when the sheets 8 and 10 are parallel to one another
but the invention is not restricted to this
configuration.
Figures 1 to 4 illustrate the components of a single
lifting cushion in which the first layer 4 consists of a
first single rectangular sheet 20, and the second layer 6
consists of a second single rectangular sheet 28. In
CA 02300883 2000-02-18
WO 99/11555 PCT/GB98/02581
- 10 -
another embodiment of the invention the second layer 6 is
not used, and the single sheet 20 of the first layer 4 is
replaced by two half sheets as illustrated in Figure 7.
Referring to Figure 7, another single unit lifting
cushion of the invention includes the inflatable envelope
2 previously described herein and illustrated in Figure
1. The illustrated dimension L of the envelope 2 will be
referred to herein as its length, and the breadth is the
dimension perpendicular to the length.
The first layer 42 of the lifting cushion includes upper
and lower half sheets 44 and 46 of polyaramid which are
coated with a neoprene layer on both their upper and
lower surfaces. Both sheets are rectangular, the same as
the envelope sheets 8 and 10, but the half sheets 44 and
46 have a greater length and breadth than the sheets 8
and 10 in order that.these sheets can cover the sides of
the envelope 2. For example, if the envelope sheets 8
and 10 are held 100 mm apart when the envelope 2 is fully
inflated, then the upper and lower half sheets 44 and 46
would each need to have a length and breadth 100 mm
greater than the length and breadth of the envelope
sheets 8 and 10. As an example, if the envelope sheets 8
and 10 are each 510 mm x 510 mm, then the upper and lower
half sheets 44 and 46 will each be 610 mm x 610 mm.
During manufacture, the upper and lower half sheets 44
and 46 are carefully pressed by a roller in order to
prevent air from being trapped in the two layers.
The envelope 2 is placed centrally on the lower half
sheet 46, and the envelope 2 and half sheet 46 are then
heated and compressed by a platen, and hot vulcanised to
secure these components to one another. The upper half
CA 02300883 2000-02-18
WO 99/11555 PCT/GB98/02581
- 11 -
sheet 44 is then placed centrally on the envelope upper
sheet 8, and the envelope 2 and upper half sheet 44 are
then heated and compressed by a platen and hot vulcanised
to secure the components to one another. A strip 50 is
made of a polyaramid sheet coated on both its surfaces
with neoprene. This strip 50 is folded centrally to form
a V cross-section with the arms of the V extending
inwardly towards the envelope filaments 12 when the V is
in its folded configuration. The strip 50 extends
completely around the sides of the envelope 2, and the
inner surfaces of the V arms are coated with mellamex.
The peripheral portions of the upper and lower half
sheets 44 and 46 are folded over the envelope sides to
form side sheets 52 and 54 which extend around the
envelope 2. A small central gap 56 is left between the
inner edges of the side sheets 52 and 54 which are each
connected to the outer surface of the V strip 50. The
rubber nipple 14 of the air valve is inserted in one
corner of the envelope 2 with the attached nozzle 16
extending from the envelope 2.
The assembly is then hot vulcanised to secure the side
sheets 52 and 54 to their respective arms of the V strip
50. The mellamex coating prevents the V strip 50 from
being vulcanised into the permanently closed position.
When the lifting cushion is inflated the V strip 50 and
the side sheets 52 and 54 adopt the generally straight
configuration illustrated in Figure 7. When the lifting
cushion is deflated the V strip 50 closes inwardly
causing the side sheets 52 and 54 to adopt a V shape with
the point of the V extending outwardly along the
generally central plane of the envelope 2.
Figure 7 illustrates the components of another single
CA 02300883 2000-02-18
WO 99/11555 PCT/GB98/02581
- 12 -
unit lifting cushion. The invention includes within its
scope a lifting cushion having two or more units in which
all or some of the units are as described herein and
illustrated in Figure 7. Such a lifting cushion having
two or more units will be constructed as described and
illustrated in Figures 5 and 6.
Referring to Figure 8, an inflatable envelope 64 of the
invention includes two rectangular sheets 66 and 68 made
of polyaramid cord 70. The sheets 66 and 68 are
connected by a plurality of cell structures 72 which
extend along the length of the envelope 64 in a direction
perpendicular to the plane of Figure 8. The end portions
of the sheets 66 and 68 in the direction perpendicular to
the plane of Figure 8 extend approximately 60mm from each
end of the cell structures 72.
Each cell structure 72 consists of two opposed generally
U-shaped half cell members 74 and 76. Each half cell
member is made of polyaramid cord, and the inner and
outer surfaces of the half cell members and the sheets 66
and 68 are coated with an air retaining rubber compound
such as neoprene.
This coating is spread on the half cell members 74 and 76
with rollers and enable the half cell members 74 and 76
to be hot vulcanised to the other components of the
lifting cushion.
Slits 78 extend through the sheets 66 and 68 in the
direction perpendicular to the plane of Figure 8. These
slits 78 are of the same length as the half cell members
74 and 76 and are located symmetrically in the sheets 66
and 68 so that these slits 78 end at a distance of 60mm
from the adjacent edges of the sheets 66 and 68.
CA 02300883 2000-02-18
WO 99/11555 PCT/GB98/02581
- 13 -
As shown in Figure 8, the two half cell members 74 and 76
of each cell structure 72 are threaded through adjacent
slits 78 in the sheets 66 and 68 so that the end arms 80
and 82 of the two half cell members extend towards one
another to leave a small gap 84 therebetween. Strips of
uncured rubber/neoprene of the width of the whole cell
are positioned under the sheet 66 and over the sheet 68
in each cell. These strips fill in the gaps at the
corners of each cell 72. Strips of melamine or other
suitable barrier material of the width of the whole cell
are laid on the uncured rubber or neoprene strips on the
sheet 68. These strips prevent the sheets 66 and 68 from
sticking together during the hot vulcanising of the
assembly.
The envelope of the invention illustrated in Figure 8 can
be used in place of the envelope 2 in the production of
any of the lifting cushions described in this
specification and illustrated in Figures 1 to 7. When
the assembly is hot vulcanised to produce the finished
lifting cushion, the half cell members 74 and 76 and the
sheets 66 and 68 become homogenous to close the slits 78,
and the half cell members' end arms 80 and 82 of each
cell structure 72 join together to close the gaps 84.
Figures 9 and 10 illustrate the polyaramid cord structure
of the half cell members 74 and 76 in the vertical and
horizontal modes.
