GB2192232A - Improvements relating to hydraulically or pneumatically operated lifting bags - Google Patents

Abstract

Present lifting bags are unreliable in their structure due to the relative movement which takes place between the layers of rubber and steel reinforcing cord during the manufacturing process of vulcanization and the adhesion of the inner, opposing faces of the bag. According to the invention such problems are overcome by inserting a sheet of pre-cured rubber or neoprene 3 between the opposing inner faces of a bladder 2 which is made of un-cured rubber. The sheet 3 extends into the extremities of the bladder and fabric strips 4 act as a barrier between the bladder and the outer layers of rubber and reinforcement cord thereby preventing relative movement between the rubber 5 and the steel cording 6. The exterior of the bag has a pattern 7 formed of convex dimples 8 in order to provide a non-slip surface. <IMAGE>

Description

SPECIFICATION Improvements relating to hydraulically or pneumatically operated lifting bags Lifting bags are devices which can be used to raise heavy loads, apply pressure between loads, manoeuvre heavy loads into place, provide a secure anchorage, bursting open cleavages in rocks, etc. in fact the uses to which these bags can be put is limited only by the imagination of the user.

The advantages of using lifting bags in preference are numerous 1. In the deflated condition, the bag is quite thin such that it can be inserted into confined spaces where it would be impossible to insert a conventional mechanical or hydraulic jack.

2. They are much quicker to be raised or inflated than normal jacks thereby increasing the amount of work that can be carried out in a certain period of time.

3. They are silent when being inflated or deflated thereby giving an added advantage when being used to release workmen when trapped in collapsed trenches, buildings, mine roof falls, etc. or when rescuing victims from crashed cars, in these situations it is possible to listen to instructions or for further movement of the entrapping material.

4. They can be inflated by compressed air, pressurised gas from containment cylinders or by fluids which have been pressurised by a pump or in many cases by the "head of pressure" availabie in the local water supply; because of the- very large lifting area offorded by the bags, heavy loads can be raised by the application df a low input pressure.

5. The large bearing area of the bags mean that the- load is evenly spread -over the surrounding surface thereby eliminating high point loading that is associated with conventional jacks, this capability prevents the dis-integration on any friable ground on which the bag may be located or the material which in being lifted.

6. The bags can be operated quite safely even when located on loose, inclined or uneven surfaces.

7. In relation to the heavy lifting duties that the bags can perform, they are light in weight and compact in size thus making them ideal for use in restrictive environments.

8. The bags are anti-static so that no sparks can be created when they are being used in the petro-chemical, mining, gas industries, etc while the bags themselves are fire resistant.

Lifting bags which are capable of performing the above duties are well known, basically, they consist of a rectangular inner bladder made of rubber or neoprene, around this inner bladder, a sheet or sheets of a composite outer skin is folded to form the lifting bag, this outer, composite skin is formed of layers of rubber with parallel strands of steel cord laminated within the thickness of the rubber, if the bag is composed of more than one sheet of the composite skin, then the second skin is folded in such a manner that the parallel strands of steel cord are at right-angles to the first so producing a bag of maximum strength and durability; a valve through which passes the gaseous or fluid inflating medium, is connected from the inner bladder, through the outer skins and protrudes at the corner of the bag.

Once the various components of the bag have been assembed, the whole is placed within a vulcanizing mould in order to produce an aggregate lifting bag, when the lid of the mould is closed, the contents are subjected to heat and pressure thus binding together the layer of rubber and steel cording. During the vulcanizing process, the rubber becomes fluid and is liable to a flowing movement, such movement can lead to problems in the consistancy of the quality of the bags 1. In order to prevent the inner, opposing surfaces of the bladder from being vulcanized together, it is normal to place a layer of some non-bonding material, such as paper, between them to stop them coming into contact.The afore-mentioned flowing movement of the rubber during vulcanization can cause the nonbonding material to tear or disintegrate into holes and so allowing the opposing faces to become vulcanized together, when the bag is in use and is inflated, the bonded together inner faces of are forced apart so pulling away a portion of the rubber of the composite sheet and exposing the steel cording to the corrosive effects of the inflating gas or liquid.

The results of this train of events are not obvious, either during manufacture or while the lifting bag is in use, until at some stage, the bag collapses while it is in use, with dangerous consequences.

2. During the process of vulcanization, as mentioned, the rubber content of the composite skin is liable to fluid movement but the steel cording is resilient to movement, this relevant movement between the two components makes it impossible to guarentee the exact location or depth of the cording, should it be too close to the outer surface of the bag, it has very little protection from the objects being lifted such that if the object is abrasive, the outer surface will wear quickly so exposing the steel cording to corrosive influences and reducing its operational life.The problems of relative movement between the rubber and steel cording of the composite skin are greatly accentuated along the four edges of the rectangular lifting bag, where, during vulcalization, the fluid rubber flows towards the edges of the mould such that the steel cording is no longer equidistant from the edges of the bag such that while in use, the steel cording is subjected to a hinging effect during repeated inflation and deflation so causing the thin layer of rubber to fracture and again exposing the cord to corrosion. Finally, movement of the rubber can create voids within the skin of the bag rendering it weak and vunerable to busting when operating under load.

It is an object of this invention to improve the quality and durability of hydraulic or pneumatic lifting bags by preventing the accidental bonding together of the opposing inner surfaces of the bladder while the enveloping outer layers of composite sheet rubber with inlaid steel cord reinforcement are being vulcanized and at the same time preventing any reiative movement between the rubber and the steel chord whereby the low viscous fluid rubber flows during the process of vulcanisation and leaves the more resiliant steel cord in a position where it is close to the surface and prone to exposure and corrosive effects.

According to the present invention, there is provided a lifting bag of a generally rectangular shape, comprising an inner bladder made of un-cured rubber or neoprene. Placed within this bladder is a flat sheet or former of precured rubber, plastic or some other such material which will not be affected by the vulcanizing process, this former being of such an area and shape that when it is inserted horizontally- into the bladder it will ensure that the periphery will extend into and make contact with the inner edges and corners of the bladder while the general area of the former will prevent any physical contact between the said opposing inner faces of the bladder, even during the process of vulcanisation; at one corner of the bladder is inserted and attached an inlet/outlet valve to which will eventually be connected, via a suitable coupling-to the nose pipe carrying the pressurised inflating gas or liquid. Along the external edges and extending around the periphery of the bladder is attached a strip of fabric which acts as a barrier between the edges of the bladder and the composite sheet or sheets of rubber with steel cord reinforcement which will later be wrapped around it.The bladder is placed upon a sheet of the composite material in which the steel cord is arranged in a horizontal, parallel manner and is spaced equi-distant from both the surfaces of the rubber component of the sheet, this sheet is folded to form an envelope around the bladder, a second sheet of'the composite material is then folded around the first, except that on this occassion the sheet has been touned through an angle of 90 degrees in order to place the steel cord at right-angles to the steel cord in the first sheet thereby attaining a mesh patter and so increasing the strength and- durability of the bag, prior to the folding of the second sheet however, the partly completed bag is turned over such that upon folding, there are the same number of Folds on each side. There is nothing to prevent further counter-layers of the composite material being added.The whole assembly is now placed within a suitable mould and is subjected to heat and pressure of the vulcanizing process, because the former which has been placed within the bladder is made of pre-cured rubber, it will not bond to the un-cured rubber of the bladder thereby acting as a barrier between the inner, opposing faces of the bladder and preventing any attachment taking place, likewise, the edges and corners of the pre-cured rubber former do not become fluid during vulcanization and so it exerts a restraining force on the low viscosity fluidised rubber of the outer composite sheets, thereby preventing movement between the steel cord and the rubber so maintaining the equidistance of the cord from the outer surfaces of the sheet, in a like-manner, the fabric around the periphery of the bladder acts as a barrier between the former and the steel cord and restrains movement, the surface of the second composite sheet which will after folding, be the external surface of the lifting bag, has a pattern of circular pimples of a convex configuration, this pattern is created by a number of indents in the mould and will add a non-slip quality to the bag and provide the extra friction necessary when the bag is being used on a sloping or undulating base.

In order that the invention may be fuily understood and readily carried into effect, a preferred embodiment thereof will now be described by way of example only, with reference to the drawings which accompanying this specification, in which Figure 1 shows a Plan View of the invention.

Figure 2 shows a Sectional View of a corner of the invention as designated AA in the Plan View, as it will appear after the vulcanizing process.

A pneumatic or hydraulic lifting bag 1 of a generally rectangular shape has an inner bladder 2 made of un-cured rubber or neoprene, horizontally placed within the bladder is a flat sheet 3 which may be made of pre-cured rubber, neoprene, plastic or some other material which will remain unaffected during the process of vulcanization, this sheet or former extends across the full internal area of the bladder and extends into the corners and along the edges of the bladder in order to prevent any contact between the opposing inner surfaces of the bladder; around the outer edges of the bladder is placed a strip of fabric 4 which acts as a barrier between the bladder and the composite sheet of rubber and steel reinforcing cord 6, the outer casing of the lifting bag consists of one composite sheet being wrapped or enveloped around the bladder in one direction such that the steel cord 6 is aligned in one direction, the part completed bag is then wrapped in a second composite sheet which in at 90 degrees to the first thereby aligning the second steel cord 6A at right-angles to cord 6, the outer surface of the final composite sheet has a pattern 7 formed of protruding convex dimples 8, at one corner of the bag is fitted an inlet/outlet valve 9 to which may be connected the feed line from the pneumatic or hydraulic supply.

Claims (5)

1. A lifting bag of a generally rectangular shape to be hydraulically or pneumatically activated, comprising an inner bladder of un-cured rubber or neoprene, placed within this bladder is a sheet or former made of pre-cured rubber, neoprene, plastic or other like material which will be unaffected by the rubber vulcanizing process, this former being placed horizontally within the bladder and extending to its inner perimeter and corners.

2. A lifting bag as claimed in claim 1 in which the external of the last envelope of composite rubber inlaid with steel reinforcing cord, has a pattern of circular dimples of a convex configuration.

3. A lifting bag as claimed-in claims 1 and 2 in which the bladder is enveloped in a number of composite sheets of rubber inlaid with strands of steel reinforcing cord and arranged in such a manner that the strands of cord are parallel, each subsequent sheet being enveloped around the first in such a manner that the steel cord is at right-angles to the cord in the first.

4. A lifting bag as claimed in claims 1,2 and 3 in which a strip of fabric is attached around the outer edges of the bladder acting as a barrier between the bladder and and the enveloping composite sheet- at that point.

5. A lifting bag substantially as described herein and as shown in the diagrams which accompanying this specification.