GB2351774A

GB2351774A - Inflatable bag

Info

Publication number: GB2351774A
Application number: GB9916023A
Authority: GB
Inventors: Richard Savill Truelove; Ashley William Pugh
Original assignee: Individual
Current assignee: Individual
Priority date: 1999-07-09
Filing date: 1999-07-09
Publication date: 2001-01-10
Anticipated expiration: 2019-07-09
Also published as: GB9916023D0; GB2351774B

Abstract

A composite inflatable bag for use as an air lift jack for motor vehicles comprises an elastic inner inflatable bag (14) inside an inelastic airtight outer bag (12) to which it is joined only at an inflation/deflation valve (36) and a pressure relief valve (34). Constraining outer bag (12) has a top pouch (22) containing a stiff loading plate (24) of tough polypropylene sheet. A bottom panel (18) of the outer bag carries a pouch (28) containing three removable closed cell waterproof compression-resistant polyethylene foam spacer sheets for varying the base thickness of the jack.

Description

2351774 INFLATABLE BAG This invention relates to an inflatable bag which

may be used in any one of a number of different applications. One application is the lifting or tilting of heavy objects. A bag according to the invention may be used as a jack for motor vehicles. The invention also extends to a method of manufacturing such a bag.

Several designs of inflatable bags have been proposed, but there is scope for improvement in terms of stability, control during inflation and deflation, and low pressure operating capability.

According to a first aspect of the present invention, there is provided a composite inflatable bag comprising an inner inflatable bag contained within an outer constraining bag, the inner bag being provided with a gas valve that is accessible through the outer bag, whereby the outer bag may be substantially filled by inflating the inner bag-1 the conformation of the outer bag when filled - the top panel being provided with a including a top panel and a bottom panel, pouch containing a stiff loading plate, and the bottom panel being provided with a pouch containing a removable spacer sheet.

Any convenient gas may be used to inflate the composite bag, by inflating the inner bag. Examples include air, carbon dioxide and vehicle exhaust gas.

The inner inflatable bag is of course desirably entirely gas tight, and may be made of elastic or inelastic material. If the latter, the inner bag should be substantially the same shape and either the same size or marginally smaller than the outer bag. The outer constraining bag is preferably substantially inelastic at operating pressures, to control the shape taken up by the inflated inner bag. The outer constraining bag also performs the functio n of protecting the inner bag, and this protection is enhanced by the loading plate carried by the top panel and the spacer sheet carried by the bottom panel.

The inner bag may be sealingly attached to the outer bag around the gas valve.

This valve may be provided with an inflation stem that is exposed through, and typically projects through, the outer bag. The inner bag may also be provided with a pressure relief valve, which is conveniently arranged to vent gas through the outer constraining bag. The outer bag and inner bag may also be sealingly attached together around such pressure relief valve. Apart from at valves for passing gas into and/or out of the inner bag through the outer constraining bag, the inner bag may be loose within the outer constraining bag, so remaining free to move and adjust its position according to the stresses imposed upon it. In this way, excessive local tension in the skin of the inflatable bag can be relieved by movement, potentially avoiding failure of the bag in some circumstances.

If the inner bag does fail, a substantially airtight outer bag can prevent a catastrophic loss of pressure in the composite bag.

The gas valve is preferably adapted to allow gas out of the bag for deflation purposes when desired. Commercially available valves which can serve for either inflation or deflation at will are well known. Preferred valves have bodies that extend through both the inner inflatable bag and the outer constraining bag, and are adapted to sealingly clamp the materials of the two bags together and to the valve body at that region.

The loading plate in the pouch on the top panel is desirably stiff and tough. Its principal purposes, for which it should be adequate, are to spread a load over the top panel, to protect the top panel of the constraining bag from puncturing, to prevent any sharp object against which the bag is being inflated from deforming the top panel sufficiently, to prejudice the integrity of the inner bag; and to prevent the top of the composite bag from excessive doming. Val4ous plastics materials in particular, especially polypropylene or the like, may b0saitable.

1 Extruded polypropylene sheet 4-30mm thick may be particularly suitable, depending on the application. Tested on 4mm thickness panels, desirable properties are a yield stress of 24-36 N/mm', and elongation at yield stress 6-12%, both tested by DIN 53455, and a notched impact strength of at least 5 KJ/M2, and an unnotched impact strength showing no break, both tested by DIN 53451 The spacer sheet in the pouch on the bottom panel of the outer bag is desirably resiliently cleformable, but quite compression resistant. A closed cell cross- linked polyethylene foam, compressible by 25% under a 25 kPa to 70 kPa loading, is suitable. This allows the base of the composite bag to conform to irregularities in the surface against which it is pressed under load. Such a closed cell foam will not absorb significant water. Preferably, the pouch can contain a plurality of such sheets, so that the user has the option of adding or removing spacer sheets to adjust the total spacer thickness. In this way the thickness of the deflated composite bag can be varied, to minimise the amount of gas that needs to be used to inflate the bag to the desired total height under load.

The spacer sheets may each be from 25mm thick, according to the application. For use of the composite bag for a vehicle jack, up to three sheets each of about 40mm thickness may be suitable.

Each pouch, but especially the bottom pouch, desirably has an open side through which the spacer sheets can be inserted and removed.

According to a further aspect of the invention, there is provided a method of manufacturing a composite inflatable bag of the kind set out above, which comprises partially forming an inner inflatable bag with an opening for a gas valve, partially forming an outer constraining bag with an opening for a gas valve, with a panel for use as the top panel provided with a pouch, and with a panel for use as the bottom panel provided with a pouch, placing the partially formed inner bag within the partially formed constraining bag, aligning the respective valve openings, inserting a valve through the openings and sealing the inner bag and the outer bag to the valve around the valve, closing the inner bag, closing the outer bag over the inner bag, inserting a stiff loading plate into the pouch of the top panel, and inserting a removable spacer sheet into the pouch of the bottom panel.

Other aspects of the method will be set out in the following description of the invention in relation to the accompanying drawings, which illustrate one embodiment, by way of example only.

In the drawings, Figure 1 is a perspective view of a composite bag according to the invention, with one corner and a major part of one adjacent edge of the outer constraining bag cut away to show the inner bag; and Figure 2 is a diagrammatic elevation showing the use of the bag as an air jack to lift one side of a motor vehicle.

As shown in Figure 1, the composite inflatable bag 10 includes an inner inflatable bag 14 contained within an outer constraining bag 12. The composite bag is shown inflated, in which conformation the inner bag substantially fills the outer bag, and the resulting composite bag has six rectangular faces, in the form of a cuboid, although in practice the form will be somewhat distorted owing to the internal gas pressure.

The outer constraining bag is provided with a top panel 16 and a bottom panel 18 immediately outside the top and bottom respectively of the inner bag 14, and it is these panels that constrain the inner bag. For this purpose, the fabric of the outer bag is essentially non-elastic, while the inner inflatable bag can suitably be made of elastic material.

An outer skin 20 overlies the top panel 16, forming a top pouch 22, open at the end visible in Figure 1, containing a stiff loading plate 24. Similarly, a loose outer skin 26, very much looser than outer skin 20 over the top panel, overlies the bottom panel 18, forming a bottom pouch 28 containing three removable spacer sheets 30 which, by removal and/or insertion through the open near end, as shown in Figure 1, of the bottom pouch 28, enable the base thickness of the composite inflatable bag to be varied.

Extending through side panel 32 of the outer bag, and the corresponding side panel 33 of the inner bag, are a pressure relief valve 34 and an inflation valve 36. The pressure relief valve is surrounded by a clamping ring 38, and the inflation valve by a clamping ring 40. Each clamping ring is fast with the body of the corresponding valve, which extends through an opening in both the outer side panel 32 and the corresponding inner bag side panel 33, and on the interior of the inner bag is a further clamping ring, not shown, which screw threadedly engages the corresponding valve body and, on being tightened, sealingly clamps the respective skins of the inner and outer bags to the valve, all around the valve.

The composite bag is manufactured from a plurality of rectangular sheets of different materials, and the two valves, although it will be appreciated that sheets of other shapes could well be used to change the conformation of the composite bag. In this instance, the inner and outer bags are formed respectively from sheets of stretchable polyurethane, and of substantially nonstretchable polyurethane coated woven fabric. These sheets can be joined to themselves by high frequency welding. The inner inflatable bag is partially formed by means of peel welds, leaving one end panel 42 open, and with two pre-cut openings corresponding to the intended positions of valves 34 and 36 cut in side panel 33. The outer constraining bag 12 is likewise partially formed, this time using lap jointing, with pre-c ut openings for the valves in the portion intended for side panel 32, and leaving open the end panel 44. The partially formed inner bag is then placed within the partially formed outer bag, the valve openings aligned, the two valves inserted into their respective openings and the clamping rings tightened to make the necessary airtight seals around each valve. The joints around the end panel of the inner bag are then completed, and finally the joints around the end panel of the outer bag. Thereafter, the loading plate and spacer sheets are inserted into their respective pouches.

Suitable dimensions for the outer constraining bag, excluding the top and bottom pouches, for use as an air lift jack for motor vehicles, may be a height of 36cm, and top and bottom panel dimensions of 48 x 63cm. The inner inflatable bag may suitably be 3cm less in each dimension. The top lifting plate for such a bag may have an area of 38 x 58cm, and the spacer blocks likewise. The top lifting plate may be 12mm thick extruded polypropylene sheet, the spacer blocks of 40mm thick closed cell cross-linked polyethylene foam.

Such a composite bag may be used as a jack as shown in Figure 2. The appropriate number of spacer blocks are inserted into the pouch 28 in order to minimise the amount of pumping required before the vehicle 50 is lifted. Inflation hose 52 is sealingly clamped to the central stem of inflation valve 36, and conducts air under pressure from air compressor or pump 54 into the inflatable inner bag. The structure of the composite lift bag permits the bag to inflate in a relatively uniform manner, whether free standing or under load, to achieve a controllable and stable lift. The pressure relief valve 34 is set to approximately 20 psi (1.4 bar) which allows a potential safe lift of up to 4 tonnes. If the lift bag is rated at a nominal 2 tonnes lifting capacity, the desirable 50% overload tolerance is comfortably accommodated, and the lift capacity is more than adequate to lift one pair of wheels on a typical family car.

When the inner bag is inflated, any air between the inner and outer bags is either compressed automatically to the same pressure as the inner bag, or bleeds away through any small leaks in the outer constraining bag, which is not necessarily made entirely airtight. Desirably there is substantially no air trapped between the inner and outer bags, so that the deflated composite bag can be packed into as small a volume as possible. To deflate the bag, provision may be made, in a known manner, on the inflation valve 36, for example by rotating the central valve stem to a deflation position. Suitable pressure relief valves and inflation/deflation valves for this purpose are available from Honeywell Leafield Ltd.

Claims

1 A composite inflatable bag comprising an inner inflatable bag contained within an outer constraining bag, the inner bag being provided with a gas valve that is accessible through the outer bag, whereby the outer bag may be substantially filled by inflating the inner bag; the conformation of the outer bag when filled including a top panel and a bottom panel; the top panel being provided with a pouch containing a stiff loading plate, and the bottom panel being provided with a pouch containing a removable spacer sheet.

2 A composite inflatable bag according to claim 1 wherein the inner bag is elastic.

3 A composite inflatable bag according to claim 1 or claim 2 wherein the outer bag is substantially inelastic.

4 A composite inflatable bag according to any of the preceding claims wherein the outer bag is substantially airtight.

5 A composite inflatable bag according to any one of the preceding claims wherein the inner bag is sealingly attached to the outer bag around the gas valve.

6 A composite inflatable bag according to any one of the preceding claims wherein the inner bag is provided with a pressure relief valve.

7 A composite inflatable bag according to claim 5 or claim 6 wherein the inner bag is loose within the outer constraining bag, apart from at a valve for passing gas into and/or out of the inner bag through the outer C:\Wpdocs\Clients\TRUELOve\p92777gb\claima.wpd constraining bag.

8 A composite inflatable bag according to any one of the preceding claims wherein the loading plate comprises an extruded polypropylene sheet 4-30mm thick.

9 A composite inflatable bag according to any one of the preceding claims wherein the material of the loading plate has the following properties, when tested in the form of a panel of 4mm thickness:

a yield stress of 24-36 N/mM2 an elongation at yield stress of 6-12% when tested by DIN 53455.

A composite inflatable bag according to any one of the preceding claims wherein the material of the loading plate has the following properties, when tested in the form of a panel of 4mm thickness:

a notched impact strength of at least 5KJ/M2 an unnotched impact strength showing no break when tested by DIN 53453.

11 A composite inflatable bag according to any one of the preceding claims wherein the spacer sheet is resiliently deformable but compression resistant.

12 A composite inflatable bag according to claim 11 wherein the spacer sheet is compressible by 25% under a 25 kPa to 70 kPa loading.

13 A composite inflatable bag according to any one of the preceding claims wherein the spacer sheet comprises a closed cell cross-linked polyethylene foam.

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14 A composite inflatable bag according to any one of the preceding claims wherein the pouch contains a plurality of said spacer sheets, whereby the total spacer thickness can be adjusted by adding or removing spacer sheets.

A composite inflatable bag according to claim 14, wherein each spacer sheet is at least 25mm thick.

16 A composite inflatable bag according to any one of the preceding claims wherein the bottom pouch has an open side through which a spacer sheet can be inserted and removed.

17 An air lift jack substantially as herein described with reference to and as illustrated in the accompanying drawings.

18 A method of manufacturing a composite inflatable bag as claimed in any one of the preceding claims, which comprises partially forming an inner inflatable bag with an opening for a gas valve, partially forming an outer constraining bag with an opening for a gas valve, with a panel for use as the top panel provided with a pouch, and with a panel for use as the bottom panel provided with a pouch, placing the partially formed inner bag within the partially formed constraining bag, aligning the respective valve openings, inserting a valve through the openings and sealing the inner bag and the outer bag to the valve around the valve, closing the inner bag, closing the outer bag over the inner bag, inserting a stiff loading plate into the pouch of the top panel, and inserting a removable spacer sheet into the pouch of the bottom panel.

19 A method according to claim 18 wherein the inner and outer bags are formed from sheets comprising polyurethane which are joined by high frequency welding in forming the inner and outer bags.

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