GB2312268A

GB2312268A - Valve for gas cylinders

Info

Publication number: GB2312268A
Application number: GB9707541A
Authority: GB
Inventors: Thomas Baker; Jonathan Mark White
Original assignee: Calor Gas Ltd
Current assignee: Calor Gas Ltd
Priority date: 1996-04-15
Filing date: 1997-04-14
Publication date: 1997-10-22
Also published as: GB9707541D0; BR9602643A; BR9701788A; GB9607794D0

Abstract

A valve for a liquefied gas cylinder wherein the valve nipple, engaged in use by a filling nozzle or a regulator nozzle, consists of a threaded spindle part 205b and a cylindrical head 205a. The head has a cavity 241 extending down from the top, and apertures 240 arranged around the side of the head extending into the cavity. During filling, liquefied gas enters the cavity from the top and emerges through the side apertures from the cavity.

Description

Valve Apparatus The present invention relates to valves and more particularly but not exclusively to valves for liquefied petroleum gas cylinders.

Valves for liquefied petroleum gas cylinders are well known in the art.

These valves are designed to open on pressure from filling pipes with bull-nosed nozzles, and once open to allow as large a liquid flow as possible through the valve. The cost of the valve is critical and this is a major consideration in design.

Many valves are therefore designed such that all components are machineable. The valves currently on the market are of various designs, situations which are more safety critical employing valves which are more expensive to manufacture.

A valve currently in wide use is based on the design shown in Figures la and b. Throughout the specification the use of the terms up and down are with reference to the figures and not actual orientation when in use. The valve 100 comprises a brass valve body 101 and a brass retainer 102, arranged to be screwed together to give a coaxial single unit. A gas passageway through the body is blocked by a valve sub-assembly 103, which sits in a cavity defined by upper and lower portions of the valve body. A spring 104 held by the retainer pushes upwards on the valve sub-assembly 103 which is thus held against a down facing surface of the valve body. A valve seal 106 on the valve sub-assembly completely blocks the passage of gas in the absence of any downward force on the valve subassembly.

As shown in Figure ib, when being filled, a filling head 110 is inserted or screwed into the upper portion of the valve body 120, engaging the valve subassembly and forcing it down against the action of the spring. The bull nosed nozzle is limited in being screwed into the valve and at this point is engaging an O-ring 111. This O-ring along with the screw thread, seals the valve body, preventing liquid emerging from the bull-nosed nozzle escaping upward from the valve body.

As shown in the Figure, the filling head 110 has an extrusion 1101 with 3 wings which taper to a blunt point. Liquid flows past the wings and around the valve sub-assembly. The valve sub-assembly comprises three parts, a valve nipple 105 (shown in perspective view in Figure 2), the valve seal 106 and a spindle 107.

The valve nipple screws into the spindle, and the valve seal is then held between lips on both parts. The valve nipple has a groove 141 on its upper surface to allow gas to escape from the bull-nosed nozzle 110. The upper portion of the valve nipple 105 is square in cross-section, thus leaving a gap along the four side faces of the valve nipple between the inner surface of the valve body 250 with its circular cross-section and the valve nipple, as shown most clearly in the overhead view of the prior art valve shown in Figure 3.

When the valve is open, liquid gas flows through the nozzle, through the groove 141, past the gaps down the sides of the upper portion of the nipple, past the valve seal 106, down through the retainer 102 and then into the gas cylinder.

The rate of flow past the valve is therefore restricted by the cross section of the groove 141 on the surface of the valve nipple, and the size of the gaps down the sides of the valve nipple.

As shown in Figure ic, when in use, a bull-nosed nozzle 160 is inserted or screwed into the upper portion of the valve body 120, engaging the valve subassembly and forcing it down against the action of the spring in a similar way to the filling head. This nozzle has a bore down the centre through which gas can escape via the groove 141.

The prior art design described above has various disadvantages. Firstly, the groove 141 in the top of the valve nipple is limited in size by the strength of the brass from which it is made. This in turn limits the volume of the liquid gas that can flow. The shaft 105b bearing the thread that is used in connecting the valve nipple and the spindle is small in diameter, and is subject to breaking. The valve nipple and spindle are thus free to move apart allowing the valve seal to fall free. There is then no seal preventing the gas escaping from the cylinder which will fully discharge, leading to a very hazardous situation.

A further disadvantage of the design of the prior art is that the valve assembly, when there is no nozzle attached to it (ie in its normal state) , has the appearance shown in Figure 3 when looked at from above. What looks like a screw-head groove is presented which might tempt a user to attempt to rotate the valve sub-assembly with a screwdriver. The valve sub-assembly is only designed to cope with compressive forces, and not torque. The torque could lead to the above mentioned breaking of the centre drill shaft causing said hazardous situation.

It is hence an object of the present invention to provide a valve assembly with similar cost characteristics of the prior art design while eliminating the disadvantages mentioned above.

A preferred embodiment of the present invention will now be described with reference to the accompanying drawings in which Figure la shows a cut away view of a valve assembly of the prior art when closed Figure lb shows a cut away view ofthe assembly of the prior art during filling Figure lc shows a cut away view of the assembly of the prior art when in use.

Figure 2 shows a perspective view of the valve nipple of the prior art Figure 3 shows an overhead view of a prior art valve assembly Figure 4a shows a cut away view of a valve assembly according to a first embodiment of the present invention when closed Figure 4b shows a cut away view of the valve assembly according to a first embodiment of the present invention during filling.

Figure 4c shows a cut away view of the valve assembly according to the first embodiment of the present invention during use Figure 5 shows a perspective view of the valve nipple according to a first embodiment of the present invention Figures 6a and b show section views of the valve nipple of the first embodiment.

Figure 7 shows a perspective view of the valve nipple according to a modification of the first embodiment.

Figures 8a and b show section views of the valve nipple of the modification of the first embodiments.

Figure 9 shows a sectional view of a second embodiments of the present invention.

Figures 4a, 4b and 4c show cut away views of the valve assembly of a first embodiment of the present invention when not in use, when being filled, and when in use, respectively. In this embodiment there is provided a valve assembly 200 comprising a brass valve body 201, a plastic retainer 202 also acting as a sediment tube, a valve sub-assembly 203, a spring 204 and an O-ring 211. The valve sub-assembly comprises a valve nipple 205, valve seal 206 and spindle 207.

The valve body 201 is substantially axially symmetric, and has an axial bore formed by first and second cylindrical cavity portions 220 and 224 extending inward from the valve body's upper surface and coaxial with the valve body. The cavity 220 is slightly enlarged around its lower rim so as to hold said O-ring 211.

The majority of the cylindrical surface of said first large cavity portion 220 has a thread 250 to allow engagement of a bull-nosed filling nozzle 210. An annular inward protuberance 221 on the inside of the valve body creates a small cylindrical bore 222, coaxial with, but with substantially smaller radius than the other two cavities, 220 and 224, and which joins the two cavities.

The retainer 202 is also substantially axially symmetric and is arranged to screw into the second large cavity portion 224 of the valve body from below.

The retainer has a cylindrical shaft runing along its axis from its upper surface in which the spring 204 sits. The shaft has substantially the same diameter as a lower portion 207a of the spindle 207 which fits tightly in the shaft and rests on the top of the spring.

The spindle 207 is made from brass and consists of an axially symmetric machined cylinder. The diameter of the lower portion 207a is smaller than that of the upper portion 207b which has a threaded hole drilled into it whose width is as large as possible without deforming the brass. The hole is drilled to a depth slightly above the level where the spindle narrows so that there is a substantially constant thickness of material surrounding the shaft around the bottom corners as well as down the sides. The hole is threaded to approximately three quarters of its depth. The spindle 207 has a flange 207c around its upper surface with a lip 207d which locates the circular valve seal 206. The seal has substantially the same diameter of the inner rim of the lip 207d so as to be held rigidly in place by the lip on the flange.

The shape of the valve nipple 205 is shown more clearly in Figures 5 and 6. It comprises a cylinder, approximately half of the length of which is machined down to generate a shaft 205b approximately 0.7 of the diameter of the unmachined part, hereinafter referred to as the nipple head 205a. The shaft 207b is threaded so as to screw into the hole on the spindle through a hole through the centre of the seal of similar diameter to the thread on the nipple. When fully screwed in, the rim at the top of the shaft is tight against the seal.

The thread on the nipple of this embodiment is substantially greater in diameter than that of the equivalent nipple of the prior art valve described above.

The nipple head has a hole 241 drilled in it and the diameter of the hole 241 is chosen to be the same as or greater than the diameter of the bore of the filling tube.

Two facing radius generated apertures 240 are machined into the cylindrical peripheral sides of the nipple head. the upper edge of which being approximately three tenths of the way down the nipple head, and the lower aperture edge being at substantially the same level as the bottom of the hole drilled in the head. The apertures are machined to subtend an angle of approximately 130 degrees, the remaining head walls thus subtending an angle of 50 degrees. The cross-sections of the walls are therefore fairly equidimensioned and will therefore withstand stresses from a variety of directions.

The machining thus far described leaves an annulus 242 on top of these two walls of approximately square cross section, as best shown in Figure 6b. This annulus, by virtue of its dimensions, has high tensional and compression strength.

When the valve sub-assembly is sitting in the shaft of the retainer resting on the spring with no forces acting on it from above, and when the retainer is fully engaged with the valve body the aperture portion of the valve nipple is surrounded by the cylindrical inside surface of the small cavity of the valve body.

The valve seal is forced up by the spring against a lip on the underside of the annular valve body protuberance creating the small cavity. This seals the valve.

If a filling head is screwed into the valve, as shown in Figure 4b, the nozzle nose pushes down on the valve sub-assembly, which moves downward against the force of the spring. This action releases the valve seal from the lip, and exposes the nipple apertures to the second large cavity of the valve body. A channel is thus created from the nozzle, through the valve nipple annulus, through the exposed portions of the apertures, through the second large cavity, and through a hole running through the retainer, into the liquid gas cylinder below. The plastic retainer is substantially hollow, fins extending from its outer cylindrical surface to hold the shaft which holds the spring. This therefore does not limit the liquid channel.

The filling head has a circular bore running down its centre of similar radius to the inside radius of the nipple annulus. The filling head also has a three winged extrusion which actually engages the nipple head as shown.

The liquid flow is limited by the smallest cross section of this channel.

The cross sections of all portions of this channel are therefore chosen to be as similar as possible. The two combined cross sections of the inside of the apertures according to this design are approximately twice that of the nozzle and therefore do not limit the flow. The main limiting aperture is that defined by the outer circumference of the nipple head apertures and the exposed heights of these apertures. As the radius of the outer edges of the apertures is much larger than the radius of the inside of the nipple annulus 250, the height exposed can be very small and in practice only really needs to be approximately lmm. When the nozzle is fully screwed into place, the valve nozzle is pushed down to an extent where over 2mm of the apertures in height is exposed. As all the apertures are greater than or equal in cross-sectional area to the nozzle, the maximum possible flow is obtained from the nozzle.

When in use, a bull-nosed nozzle 260, shown in Figure 4c is inserted into the upper cavity. The nozzle forces the valve nipple down in a similar way to the filling head and allows gas to escape to escape through the above in the nozzle.

A modification of the valve nipple 205 of the first embodiment of the present invention is shown in Figures 7 (perspective), 8a (cross-section) and 8b (end view).

Recesses 343 are cut into the annulus 342 on the nipple head, in this case arcuate cuts aligned with radius generated apertures 340 and generated with the same tool.

Removing further portions of this aperture increases the size of the flow path when the gas cylinder is being filled as it allows liquid to flow past the outside of the three winged extrusion 2101 on the filling head 210 and past the outside of the annulus 342. In practice this decreases the filling time still further than the embodiment without the modification. The recesses 343 are best located above the aperture 340 so that a continuous flow path is obtained. Having the apertures and recesses diametrically aligned simplifies manufacture as the apertures and recesses can be cut without repositioning the nipple 205.

There is a balance to be struck when deciding on the recess size between increasing the liquid flow and decreasing the mechanical integrity of the nipple.

A second embodiment of the present invention is shown in Figure 9.

The valve body 401 of this embodiment further comprises a relief valve arrangement 470, extending from the side of the valve body. The relief valve arrangement is provided with external apertures 471 allowing gas to flow therethrough when a sufficient pressure is reached to release a relief valve comprising a release valve member 472, a relief valve spring 473 and relief valve seat 474. When not open, the valve seat rests on a valve shoulder 475. The relief valve shoulder surrounds a relief valve hole 475 which opens into the second valve cavity 224.

The valve assembly of this embodiment therefore allows relief of gas when the pressure exceeds a certain level.

The cross section available through the valve of this embodiment is thus several times that obtainable through the valve of the prior art and in practice gives much quicker filling times for the gas cylinders.

In further embodiments of the invention, three or more radius generated apertures are provided on the nipple head.

In yet a further embodiment of the invention, the retainer and valve body are made to the same specification as the aforementioned prior art valve to allow more versatility in replacing parts.

In yet a further embodiment of the invention the apertures in the side of the nipple head extend up to the top of the head such that the nipple head annulus does not in fact exist.

Claims

1. A valve comprising a valve body having first and second portions axially separated by a partition having an aperture therein and a valve member assembly for closing the aperture, the valve member comprising a head portion arranged to be received in the aperture in the partition, said head portion being generally cylindrical with an axial bore and a plurality of apertures in the cylindrical wall of the head which apertures open into the axial bore.

2. A valve according to claim 1, wherein said apertures do not extend to the face of the cylindrical head portion into which the axial bore extends.

3. A valve according to any preceding claim wherein the apertures do not extend to the opposite face of the cylindrical head portion to that into which the axial bore extends.

4. A valve according to any preceding claim wherein the head portion has two apertures in the cylindrical wall.

5. A valve according to any preceding claim wherein the cross-sectional area of the axial bore is at least as large as the smallest cross-section of a pipe through which fluid is applied to the valve.

6. A valve according to any preceding claim wherein the cross-sectional area of said apertures through which the liquid flows when the valve is open is at least as large as the cross-sectional area of the axial bore.