This invention relates to a demountable connecting device for connecting an article to a support member. Although the demountable connecting device is of general applicability it is particularly intended for connecting an article to a handle of a light weight pressure vessel for the storage and transport of a gaseous product under pressure. Such pressure vessels are often referred to as "gas cylinders" but need not be of cylindrical shape.

A gas cylinder typically comprises a thick-walled steel pressure vessel. Such a gas cylinder is heavy and cumbersome. Lighter weight gas cylinders have been introduced in which the pressure vessel is wound with strengthening fibres, thus enabling its walls to be much thinner. In order to protect the vessel, or "liner" as it is sometimes called, and its winding from damage, the vessel is located in an external plastics jacket. The external plastics jacket may be provided with a lid which may have handles that can be employed when manually lifting the gas cylinder. The cylinder may also be provided with a wheel base so that it can be wheeled rather than carried between locations.

We believe it would be desirable to attach various articles to one or both of the handles. To this end the invention provides a demountable connecting device which is of general applicability, not just to gas cylinders.

According to the present invention there is provided A demountable connecting device for connecting an article to a support member, comprising: a first hollow coupling member having a configuration for gripping the support member, and at least one pair of opposed surfaces configured to extend beyond the support member, the surfaces having at least one pair of opposed apertures; a second complementary coupling member having at least one aperture configured to be aligned with the apertures of said first coupling member; and a locking key, configured to engage the apertures of the first coupling member and the second coupling member and hold said members in a locked position; wherein the second coupling member is connectible to or integral with the said article.

In a preferred embodiment, the first coupling member has a substantially U- shaped cross section. The support member may be gripped by the lower (closed) section of the U-shape. An upper portion of the arms may therefore provide said opposing surfaces. The upper section of the U-shape may provide a pair of opposed arms which extend beyond the support member, typically in an upward direction away from a cylinder.

The first coupling member may comprise at least one pair of opposed prongs providing the said at least one pair of opposed surfaces. The second coupling member may comprise a pair of slots or recesses configured to receive the prongs.

The first coupling member and the second coupling member may further comprise mutual engagement features for co-operative engagement. For example, at least one recess may be provided on one of the members which is shaped and dimensioned to mutually engage a protrusion on the other of said members. A pair of mutual engagement features may be provided on opposite sides of the first coupling member and the second coupling members. Typically, the coupling members may be formed from a resilient material (for example a moulded plastic). As such in some embodiments, the first coupling member and second coupling member may be configured to have a "snap fit" engagement.

The locking key typically comprises an elongate member. The locking key may have a proximal handle end, a distal end, and a shaft extending therebetween. The locking key may comprise a retaining feature. The retaining feature is arranged to prevent unintentional removal of the locking key. For example a portion of the distal end of the locking key may comprises at least one radial projection for retaining the key in position. For example, at least one of the said apertures has a complimentary profile such that the key may be rotated after insertion to hold the key in position. Alternatively, the at least one radial projection may be retractable and may be resiliently biased to its extended position such that it extends beyond the width of the aperture after insertion. A button or trigger may be provided to enable retraction of the radial projections.

In a preferred embodiment the second coupling member further comprises a channel configured to receive the key and provide a load transfer surface between the key and the second coupling member. It will therefore be appreciated that a force acting to pull apart the first and second coupling members will be resisted in such an embodiment with the key transferring the load across the channel and the surfaces of the coupling members having the aperture to receive the key. The device may be provided with a tether for connecting the locking key to one of the first or second coupling members. The tether may be permanently attached to one of the coupling devices. The other end of the tether may be permanently attached to the key. The tether may be composed of a flexible elastomer. A flexible elastomer may be attached in a substantially permanent manor by means of elastic deformation. The tether may comprise at least one protrusion shaped and dimensioned to be received and to be force fitted within an opening provided by the coupling member. The second end of the tether may have an opening adapted to receive and engage the proximal handle end of the locking key. A feature may be provided on the handle end over which the tether may stretch during initial assembly but which then retains the tether. The second coupling member may have an endless wall. The endless wall may be integral with a cuff. The cuff may be provided with a flange for connection to a chosen article.

The support may be a handle of lightweight gas cylinder.

In one example, two connecting devices according to the invention are used to connect a table or other horizontal work surface to the handles of a lightweight gas cylinder.

In another example, a single connecting device according to the invention is used to connect, a telescopic handle extension to one handle of a wheeled lightweight gas cylinder. In such an arrangement, the cylinder may be tilted on its wheels and wheeled in the manner of a wheeled travelling case.

The coupling members and the locking key are conveniently made, typically as mouldings, from a resilient plastics material. A connecting device according to the invention will now be described by way of example with reference to the accompanying drawings, in which:

Figure 1 is a schematic perspective view of a lightweight gas cylinder having handles to which a demountable connecting device according to the invention can be attached;

Figure 2 is a schematic exploded perspective view of a demountable connecting device according to the invention; Figure 3 is a schematic perspective view of a demountable connecting device shown in Figure 2 during attachment to the lightweight gas cylinder shown in Figure 1 ; Figures 4A and 4B are schematic perspective views of the demountable connecting device shown in Figure 1 attached to the lightweight gas cylinder shown in Figure 1 ;

Figure 5 is a schematic section through the line A-A in Figure 4A;

The drawings are not to scale.

Like parts in two or more drawings are indicated by the same reference numerals.

Referring to Figure 1 , a pressure vessel 1 (or "gas cylinder") comprises a cylindrical outer protective jacket 3 having an open end and a closed end within which is contained a fibre wound inner pressure vessel (or "liner") (not visible in Figure 1). The inner pressure vessel receives a valve assembly 7 enabling the contents of the inner pressure valve to be controllably

discharged.

The protective jacket 3 is mounted on a wheel base 9 which comprises a main body 1 1 and a pair of wheels 13 attached to an axle (not shown). A lid 17 which comprises a handle assembly is attached to the open end of the protective jacket 3 remote from the wheel base 9.

The protective jacket 3 is mounted on the wheel base 9. The handle assembly on the lid 17 provides a pair of handles 21 which enables the entire pressure vessel 1 to be moved from location to location by being tipped and then pulled to a new position using the handles 21 while the wheels 13 on the wheel base 9 rotate about the axle 15. Additionally, the handles 21 protrude above the valve assembly 7 thereby protecting the valve assembly 7 from being knocked and damaged.

The lid 17 is attached to the protective jacket 3 using a retaining ring 19 which prevents the lid 17 from being removed accidentally but permits the lid 17 to be dismantled when the contents of the inner pressure vessel 5 has been exhausted enabling the inner pressure vessel to be removed from the protective jacket 3 and replaced or refilled. The demountable connecting device 200 according to the invention enables an article to be connected to one or both of the handles 21.

Referring to Figures 2, 3 and 4, a demountable connecting device 200 comprises three principle components, namely a first coupling member 206, a second coupling member 208 (complementary to the first coupling member 206) and a locking key 230. The principle components are all formed of a resilient plastics material such as nylon. The preferred embodiment also comprises a fourth component, a tether 240 which is formed from a flexible material.

The first coupling member 206 is hollow to enable it to fit around a chosen one of the handles 21 of the pressure vessel shown in Figure 1. In the preferred embodiment the coupling member 206 has a substantially U-shaped profile. The first coupling member 206 has an outer wall 214 which (as best seen in Figures 4 and 5) generally conforms to the profile of the handle 21. An opening 212 is provided in the bottom of the first coupling member 206 (as seen in Figure 5) which allows the ergonomic shape of the handle 21 of the pressure vessel to partially protrude through the coupling member 206. The wall 214 further comprises a pair of opposed prongs 210 which extend upward to provide a pair of opposed surfaces which are configured such that, in use, they are positioned above the handle 21. Each prong 210 provides one of a pair of opposed apertures 21 1 which are shaped and dimensioned to receive the locking key 230. The apertures 21 1 are generally cross-shaped. One axis of the cross-shaped aperture 21 1 is shorter in length than the other axis of the cross-shaped aperture therefore matching the profile of the locking key 230 which (as discussed below) has a circular shaft and two opposing projections.

Each prong 210 provides a further aperture 216 to provide a mutual engagement feature for cooperative engagement with a feature on the second coupling member 208. The wall 214 of the coupling member 206 is also provided with two further adjacent, spaced apart apertures 217 each having a circular cross-section for engagement with the tether 240.

The second coupling member 208 has an integral endless wall portion 218 with an external surface which is at least partially complementary to the internal surface of the wall 21 of the first coupling member 206. The wall 214 is connected to a base portion 222 which is profiled (as seen in Figure 5) to conform to the profile of the handle 21. Opposing sides of the endless wall portion 218 are provided with recesses in the form of slots 220. The slots 220 are dimensioned to receive the prongs 210 of the first coupling member 206 when the members are connected together (as will be described in further detail below).

Each slot 220 is provided with an aperture 219 configured to be aligned with the apertures 211 of the prongs 210 of the first coupling member 206 when the members are connected together. The apertures 219 are shaped and dimensioned to receive the locking key 230. The aperture 219 has the same cross-shape as the aperture 21 1 provided by the prongs 210 of the first coupling member 206. Each slot 220 is further provided with a protrusion 221 to provide a mutual engagement feature for cooperative engagement with the aperture 216 of the first coupling member 206. A channel 223 extends between the apertures 219 provided by the slots 220 (see Figure 4B). The channel may be a closed channel but in the present embodiment is an open channel providing a load transfer surface between the lower surface of the locking key 230 and the second coupling member 208 which will help resist a force acting to pull apart the first 206 and second 208 coupling members.

The locking key 230 has an elongate body extending from a proximal handle end 232 to a distal locking end 234. The shaft 236 extending therebetween has a circular cross section (which as will be explained below enables it to be rotated when assembled).

The handle end 232 of the locking key 230 is provided with a shaped profile to enable ease of use and has a retaining feature 233 for connection to the tether 240. The retaining feature 233 comprises a collar which defines a circumferential recess 235 (the function of which is explained in further detail below).

The distal locking end 234 has a retaining feature in the form of two radial protrusions 238 extending perpendicular to the longitudinal axis of the locking key 230 (the operation of which is explained in further detail below).

The tether 240 has a first end 242, a second end 244 and a central portion 246 extending therebetween. The tether is composed of a flexible elastomer. The first end 242 of the tether 240 has a predominantly rectangular cross- section and has two spaced apart protrusions 248 having a circular cross- section extending perpendicular to the longitudinal axis of the tether 240. The prolusions are shaped and dimensioned to be received into the apertures 217 of the first coupling member 206. The central portion 246 has a narrower cross-section than the first and second ends 242, 244 of the tether 240. The second end 244 has a circular cross-section providing an aperture 250. The aperture 250 is shaped and dimensioned to engage the proximal handle end 232 of the key 230.

With particular reference to figures 3 and 4, assembly of the demountable connecting device 200 will now be described. The second coupling member 208 is positioned over the upper portion of the handle 21 (or other support member) and may temporarily be seated on the handle due to the profiling of the base portion 222 matching the profile of the handle 21. The first coupling member 206 is then positioned about the lower portion of the handle and brought into engagement with the second coupling member 208. The two coupling members are arranged to initially "snap fit" together by means of their mutually engagement features. The prongs 210 of the first coupling member 206 slide into the slots 220 provided on the second coupling member 208. The prongs 210 are able to resiliently deflect outwards in order to pass over the protrusions 221 of the second coupling member 208 until they reach the desired alignment and the protrusions are able to "snap" into the aperture 216. In this undeflected position the prongs 2 0 form a substantially flush outer surface with the endless wall 218 of the second coupling member 208 and the wall 214 is substantially flush with the lower extent of the endless wall 218.

The mutual engagement features (protrusions 221 and aperture 216) provide a sufficient force to retain the coupling members 206, 208 in position upon the handle 2 . The mutual engagement features are also arranged to ensure that the apertures 210, 219 of the first 206 and second 208 coupling members are aligned in readiness for the insertion of the locking key 230. As engagement features are provided on both sides of the device the coupling members are held in position on both sides of the handle 21. The distal end 234 of the locking key 230 is inserted through the apertures passing through the aperture 21 1 of the first prong 210, then the aperture 219 in the first of the slots 220, along the channel 223, through the aperture 219 in the opposing slot 220 and finally through aperture 21 1 in the opposing prong 210. When fully inserted (as shown in the cross section of Figure 6) the distal end 234 of the locking key 230 extends past the outer surface of the second prong 2 0. The locking key 230 must be aligned during insertion such that the radial projections 238 pass through the axis of the cross-shaped apertures 211 .

The locking key 230 is placed in a locked position by rotating the locking key 230 by 90 degrees. This rotation prevents removal of the locking key 230 as the radial projections 238 at the distal end 234 of the locking key 230 will abut the outer surface of the prongs 2 0 of the first coupling member 206 as the diameter of the distal end 234 measured between the ends of the radial projections 238 is greater than the smaller axis of the cross-shaped aperture 21 . An interference fit may be provided in the axial direction between the locking key and the outer surface of the prongs 210 such that the action of turning the locking key is against the friction between the radial projections 238 and the surface and therefore the locking key 230 will tend to remain in its locked position.

The tether 240 is press fitted into the first coupling member 206 such that the protrusions 248 of the first end 242 of the tether 240 are force fitted into the spaced apart apertures 217 provided by the first coupling member 206. The protrusions 248 elastically deform as they pass through the apertures 217 and then expand beyond the apertures 217 to provide a substantially permanent attachment. The locking key 230 is secured to the other end 244 of the tether 244 by being received in the aperture 250 which is shaped and dimensioned to be able to receive the locking key 230. The locking key 230 is pushed through the tether aperture 250 and the flexible material allows the aperture 250 to stretch over the retaining collar 233 of the locking key handle end 232. The tether 240 is then retained in the circumferential recess 235 and is therefore substantially permanently attached to the locking key 230 (as shown in the cross section of Figure 6). The connection of the tether 240 and locking key 230 may conveniently be made during initial assembly of the demountable connecting device (which may or may not be during installation onto a support member).

If an axial force is applied to the connecting device which might act to decouple the members 206 and 208, for example when the pressure vessel 1 is lifted, they will not separate. The connecting device 200 is thus able to secure a chosen article firmly to the handle of the pressure vessel. If an axial force is applied, the shaft 236 of the locking key 230 helps to spread the load across the channel 223 of the second coupling member 208.

In order to disassemble the device 200, the locking key 230 is rotated (against any friction force in the case of an interference fit) to an unlocked position, i.e. so that the protrusions 238 are aligned with the axis of the cross-shaped aperture 21 1 and 219 which has the greater length. The locking key 230 is then removed from the device. Axial force is applied by urging the first and second coupling members 206 and 208 in opposite directions to overcome their "snap-fit" engagement. The prongs 210 will be deflected outwardly to allow the protrusions 221 of the second coupling member 208 to disengage the apertures 216 of the first coupling member 206. The coupling members 206, 208 may then be slid out of engagement and removed from the handle 21.

The endless wall portion 218 of the second coupling member 208 is integral with an attachment cuff 226. The cuff 226 may in turn be integral with an article which is to be connected to the handle 21 of the pressure vessel 1 .