Expandable lifting devices and valve assemblies for such lifting devices

A valve assembly having a rigid mounting and a valve member located in an opening in the mounting wherein an annular part of the mounting around the opening provides a first valve seat on one side thereof and a second valve seat on the other side; wherein the valve member includes a first head joined to a second head by a neck which extends through the aperture; wherein the first head has a resilient flange which resiliently engages the first valve seat to form a first valve and the second head has a resilient flange which resiliently engages the second seat to form a second valve; and wherein the flange of the second head has an actuator formation thereon which is movable to move at least part of this flange off the second seat whereby, in use, to allow fluid under pressure to flow past this flange into the opening for automatically lifting the flange of the first head off the first seat when the fluid pressure in the opening is greater than the fluid pressure at said one side of the mounting.

Pneumatically inflatable, and hydraulically expandable lifting bags are
 known which bags include air or water inlet valves and/or air or water
 outlet valves for, for example, inflation or expansion of the bags,
 deflation or expansion of the bags, maintaining the bags in an inflated or
 expanded condition, and/or preventing the bags being subjected to
 excessive pressures.
 DE-U-1,897,870 discloses an extendable or inflatable lifting device having
 a pressure release valve assembly; wherein the device comprises an
 enclosure having a first part movable relative to second part by applied
 fluid pressure; wherein the valve assembly is mounted on one of the parts
 and comprises a valve exposed to pressure inside the enclosure and is
 attached to and actuable by an actuating tether which is located in the
 enclosure and is attached to the other of said parts to cause the valve to
 open and release fluid from within the enclosure when the distance between
 the parts reaches a limit determined by the length of the tether.
 Sometimes such valves fail to operate correctly, because of contamination,
 giving rise to operational problems. These problems are particularly
 prevalent in the case of outlet valves such as mechanically actuated
 outlet valves which can fail to close properly giving rise to unwanted
 fluid release, e.g. deflation of the bags, or preventing proper expansion
 or inflation of the bags.
 In order to enable the risk of such problems arising the present invention
 generally provides an extendable or inflatable lifting device having a
 pressure release valve assembly; wherein the device comprises an enclosure
 having a first part movable relative to second part by applied fluid
 pressure; wherein the valve assembly is mounted on one of the parts and
 comprises a valve exposed to pressure inside the enclosure and is attached
 to and actuable by an actuating tether which is located in the enclosure
 and is attached to the other of said parts to cause the valve to open and
 release fluid from within the enclosure when the distance between the
 parts reaches a limit determined by the length of the tether; and
 characterised in that the valve which is actuated by the tether is a
 second valve of the assembly which second valve releases fluid into the
 valve assembly to actuate a first valve which first valve is arranged to
 open automatically only when the pressure within the valve assembly is
 greater than the pressure outside the enclosure.
 In a particular embodiment the invention provides a pneumatically
 inflatable lifting device having an air release valve assembly; wherein
 the valve assembly further comprises a rigid mounting and a valve member
 is located in an opening in the mounting; wherein an annular part of the
 mounting around the opening provides a first valve seat on one side
 thereof and a second valve seat on the other side thereof; wherein the
 valve member comprises a first head joined to a second head by a neck
 which extends through the aperture; wherein the first head has a resilient
 flange which resiliently engages the first valve seat to form said first
 valve and the second head had a resilient flange which resiliently engages
 the second seat to form the second valve; and wherein the flange of the
 second head has an actuator formation thereon which is movable by the
 actuator to move at least part of this flange off the second seat whereby,
 in use, to allow fluid under pressure to flow past this flange into the
 opening for automatically lifting the flange of the first head off the
 first seat when the fluid pressure in the opening is greater than the
 fluid pressure at said one side of the mounting.
 In many instances the enclosure will be a bag having flexible panels, but
 it could, for example, be a bellows having rigid panels.
 The first valve, by opening only when the pressure inside the valve
 assembly is greater than the pressure outside the bag (hereinafter
 referred to as a "positive pressure differential"), ensures that
 contamination cannot enter the valve assembly from outside the device
 irrespective of the operational state of the expansion or inflation
 limiting second valve.
 The valve assembly preferably also serves as an emergency or safety
 pressure release valve in the event of the second valve not functioning,
 e.g. due to the tether breaking, by allowing both valves to be opened
 forcibly by excessive pressure.
 The valve assembly preferably comprises a valve member which is common to
 both valves and provides two independently movable parts, e.g. flanges,
 each of which form a part of one or other of the valves.
 The valve member can preferably be expelled or partially expelled from the
 valve assembly by excessive differential pressure within the enclosure.
 Alternatively, the valve member includes a frangible diaphragm which
 ruptures when subjected to an excessive pressure differential.
 The invention further provides a valve assembly comprising a rigid mounting
 and a valve member located in an opening in the mounting wherein an
 annular part of the mounting around the opening provides a first valve
 seat on one side thereof and a second valve seat on the other side;
 wherein the valve member comprises a first head joined to a second head by
 a neck which extends through the aperture; wherein the first head has a
 resilient flange which resiliently engages the first valve seat to form a
 first valve and the second head has a resilient flange which resiliently
 engages the second seat to form a second valve; and wherein the flange of
 the second head has an actuator formation thereon which is movable to move
 at least part of this flange off the second seat whereby, in use, to allow
 fluid under pressure to flow past this flange into the opening for
 automatically lifting the flange of the first head off the first seat when
 the fluid pressure in the opening is greater than the fluid pressure at
 said one side of the mounting.
 The pressure exerted by the first head on the first seat is preferably
 substantial so that a considerable minimum positive pressure differential
 across the first valve is necessary before the valve will open, and so
 that when the differential falls to or below said minimum positive
 pressure differential said first valve closes automatically to retain
 pressure within the opening (i.e. between the valves) even when the second
 valve is open, whereby to maintain the inflated shape of the bag, and so
 that when a load is applied to the device, the amount of further inflation
 required is reduced.

Referring to FIG. 1, the valve assembly 10 comprises a first valve 12 and a
 second valve 13 having a common rigid mounting 14 and a common elastomeric
 valve member 15.
 The mounting 14 includes an annular part 16 around an opening occupied by a
 neck 17 of the valve member; which annular part 16 is peripherally joined
 to a planar mounting flange 18 by a cylindrical wall 19, and has an
 axially castellated cylindrical inner flange 20 around said opening.
 One side of the annular part 16 provides a seat 21 of the first valve 12,
 and the other side provides a seat 22 for the second valve 13.
 The valve member 15 provides a first, solid, head 23 at one end of the neck
 17, which head has a flange 24 which bears against the seat 21 to form the
 first valve; and a second, hollow head 25 at the other end of the neck,
 which head has a cranked flange 26 which bears against the seat 22 to form
 the second valve 13. The flange 26 has an actuator formation 27 thereon,
 to which tension can be applied to pull the flange off the seat 22.
 The neck 17 is hollow and is radially castellated.
 The valve assembly is intended to be mounted on one of two mutually
 confronting panels 30,31 of a pneumatically inflatable lifting bag (or
 bellows), e.g. as indicated in FIG. 1 in which the flange 18 is bonded to
 the panel 30 around a hole 32 therein. An inelastic flexible tether 33 is
 connected to the other panel 31 and to the formation 27, so that when the
 bag is inflated to separate the panels, the tether becomes taut, and, when
 the tension applied by the tether to the formation 27 is sufficient,
 causes the flange 26 to be, at least partially, pulled away from the seat
 22 to allow air from the bag to enter the valve assembly.
 Initially, when the air enters the valve assembly, the flange 24 will
 resist being forced off its seat 21 by virtue of the valve closing bias
 provided by the inherent resilience of the flange causing the flange to
 forcibly engage the seat. However, as more air enters the valve the
 positive pressure differential will increase to the minimum level required
 to overcome the closing bias and the flange 24 will lift off the seat 21
 allowing air to flow through the second valve, through the spaces 40
 between the castellations in the flange 20, through the spaces 41 between
 the castellations in the neck 17 and out through the first valve. The
 first valve will reclose automatically when the positive pressure
 differential drops below said minimum level, e.g. as the second valve
 closes or the bag pressure falls, well before the positive pressure
 differential ceases to exist, thereby preventing air or contaminants
 entering the valve assembly from outside the bag.
 The flange 26 is cranked and tapers in thickness to provide a well in which
 the lower end of the flange 20 is seated firmly to retain the common valve
 member 15 in the opening against the force exerted on it by the pneumatic
 pressure in the bag. However, said thickness and the form of the flange 26
 are determined so that the flange can yield and be deflected in a radially
 inwards direction so as to pass through the opening in the event of said
 pressure reaching an excessive value because of malfunction of the valve,
 e.g. due to breakage or detachment of the tether.
 Referring to FIG. 2, the lifting device 50 comprises a stack of bags, 51,
 52, 53 and 54 secured together. The top bag 54 has one valve assembly 10
 mounted on its upper panel 30, and further valves 10 are provided within
 the stack at the junctions 55 between adjacent bags to release pressurised
 air from the inferior to the superior bag at each junction. Each of the
 bags 52 to 54 has a manually actuable air valve or vent 58. The bottom bag
 51 has an air inlet 56.
 In use, the valve assemblies automatically ensure sequential inflation of
 the bags in ascending sequence, because, for example, the bag 52 cannot be
 inflated until he bag 51 has been inflated to the extent necessary to
 actuate the second valve and establish the predetermined positive pressure
 differential required to open the first valve of the assembly connecting
 the bags 51 and 52.
 When the device is inflated to reach its maximum height, the valve
 assemblies 10 will retain the pressure in the bags 52 to 54. Pressure in
 the bottom bag may be retained by closing the air supply line to the inlet
 56. If the bottom bag 51 is provided with a non-return valve 57 to prevent
 reverse flow through the inlet 56, and a valve or vent 58 is fitted also
 to the bottom bag to permit deflation of this bag.
 The invention is not confined to details of the foregoing examples, and
 many variations and modifications are possible within the scope of the
 invention. For example, the panels may be linked by internal flexible
 inelastic webs 59 (FIG. 1) to limit the separation thereof.
 The geometrical form of the valve member may be varied to suit any
 appropriate form of manufacture, provided that the modified form provides
 equivalent functions. For example the first head may be hollow and the
 second head solid; and the actuator formation may be attached to the
 latter to displace the flange 26 bodily to open the second valve. The
 actuator formation may be strong enough to pull the entire first head
 through the aperture when the formation is pulled hard enough by over
 expansion of the bag or bags 54.
 The first valves may be varied in stiffness to vary, e.g. reduce, the
 positive pressure differential required to open them, e.g. to minimise the
 differential for opening the valves on bags 51, 52 and 53 leaving the
 uppermost valve on bag 54 only requiring a substantially higher pressure
 differential for opening of its first valve, whereby to minimise the
 pressure differences between the bags at full inflation of the stack.
 The tether 33 of the valve 10 of the top bag 54 may pass through the bags
 53 and 52 and may be attached at its lowest end directly to the bottom of
 the lowermost bag 51, so that only one valve 10 (the uppermost) is
 required to limit the overall height of the stack. Thus the valves of the
 bags 51, 52 and 53 may be omitted leaving air flow ports through which
 said tether 33 extends.
 The invention further provides and includes a valve assembly or a
 pneumatically inflatable lifting device having any novel part, arrangement
 of parts or functional feature disclosed herein or in the accompanying
 drawings, or any mechanical or functional equivalent thereof.