ROLL-OVER MECHANISM FOR A PRESSURE RELEASE VALVE

Abstract: A rollover mechanism (3) for a pressure valve (1) is disclosed which is ideally adapted for use on mobile petrol tankers and other tankers for volatile liquids. The valve (1) comprises a valve seat (32) and a sealing means (18) which can be urged against the valve seat (32) to form a seal and prevent any fluid within the tanker from escaping through the valve (1) in the event of a rollover. Such valves (1) allow for pressure release therethrough under normal operating circumstances as fluid within the tanker often evaporates and pressure within said tanker can increase. The inventive valve (1) comprises a pendulum (10) mounted at an intermediate point along its length and having a pendulous weight (8) at one end and an arcuate contact pad (4) at the other. A float arrangement (37) for such a rollover valve (1) is also disclosed wherein a feed tube (36) is connected to the valve (1) beyond the valve seat (32) so that pressure can still be released through the valve (1) even when it is closed as a result of a rollover and the flu id pressure.

Description: Roll-over mechanism for a pressure release valve This invention relates to a roll-over mechanism for a pressure release valve, particularly a roll-over mechanism for a pressure release valve fitted to a tanker. Although this invention refers almost exclusively to a roll-over mechanism for a pressure release valve for a tanker carrying petrol, it will be appreciated by those skilled in the art that the invention could also cover a roll-over mechanism for a tanker involved in the transportation of any fluid or gas. Pressure release valves are commonly employed on the top of tankers used for the transportation of volatile substances, particularly on the top of tankers used for the transportation of petrol. Evaporation of the volatile petrol within the container results in a build up of pressure, which is greater than the ambient pressure external to the tanker. To reduce the risk of explosions due to this pressure build up, the tanker automatically vents its contents at a specified safe pressure via opening of the pressure release valve. Once the pressure inside the tanker has fallen below the specified pressure, the pressure release valve closes, thereby preventing unnecessary release of harmful gases into the environment. Conventionally a pressure release valve comprises a movable first portion which abuts a seat portion, a seal being formed between these components and thus prevent escape of gas from the tanker, and the environment external to the tanker. The first portion is biased towards the seat portion such that sufficient resistance is provided to pressure build ups within the tanker which tend to separate the two valve components. Only when the pressure within the tanker increases to a predetermined level is the biasing force overcome, whereat the two valve portions separate allowing venting of gas from within the container and concomitant pressure release. In the event of an accident wherein a petrol tanker is upturned, gravity or the weight of petrol on the pressure release valve will result in the valve being forced open and the petrol spilling out. It is essential that fluid loss through the valve is prevented in such circumstances as such escape of fluid may have ecological, and environmental consequences, not to mention the possibility of extreme hazard where the fluid carried within the tanker is petrol. To prevent escape of fluid through the valve in the event of an accident, a roll-over mechanism is employed in conjunction with the pressure release valve. Conventionally, roll-over mechanisms comprise a free moving ball disposed between a pair of arcuate valve seats vertically disposed within the valve and defining the ends of a circular cavity within which the ball bearing can move. When the valve is in its conventional vertical orientation, the ball bearing is received in the lower of the two valve seats and forms a seal therewith to prevent fluid within the tanker from passing through the valve as the tanker is vibrated during transportation. In the event of an accident in which the tanker provided with the valve rolls over, the configuration of the ball bearing and the channel in which it moves is such that gravity always acts on the ball to locate same in the valve seat which is beneath the ball. Henceforth the ball will only move between the first seat and the second seat when the channel in which it moves is orientated approximately horizontally. In this orientation, the ball bearing is in neutral equilibrium. Only after the channel is angled with respect to the horizon will the ball bearing move to activate the rollover mechanism and prevent fluid escape. The disadvantage of the conventional roll-over mechanism is that the valve is only completely shut off when the tanker rolls about its longitudinal axis through an angle of more than 90°. In a situation where the tanker rolls about its longitudinal axis through an angle of less than 90°, or the tanker is rotated about an axis different from its longitudinal axis during an accident, the conventional rollover mechanism will no longer function, thereby still resulting in petrol spillage. In addition, the rollover mechanism of the prior art prevents venting of the petrol tanker when activated, and so unacceptable pressure build up within the tanker can still occur. The conventional roll-over mechanism also prevents manual opening once activated, thereby preventing pumping off of the petrol from the tanker before the tanker is returned to its correct orientation. It is therefore an object of the present invention to provide a rollover mechanism incorporated within a pressure release valve which is activated when the tanker is rotated through only a slight angle, for example 10°-20°, thereby preventing spillage of fluid from the tanker. It is further object of the invention to provide a roll-over mechanism which is activated when the tanker is rotated through only a slight angle and about any axis. It is a yet further object of the invention to provide a means allowing venting of a tanker, following an accident wherein the tanker is upturned and the roll-over mechanism of the invention has been activated. According to a first aspect of the invention there is provided a rollover mechanism for a valve, said valve having a movable sealing means which is free to move towards and away from a pressure surface within the valve, said sealing means creating a seal with said pressure surface when adjacent therewith which prevents fluid escape through the valve, characterised in that said roll-over mechanism comprises pendulum means which communicates with the sealing means to urge same towards and ultimately against the pressure surface as gravity acts on the pendulum means to deflect same as the valve rotates about an axis parallel with any axis about which the pendulum means can swing. Preferably, the degree of displacement of the sealing means towards the pressure surface is dependent on the degree of deflection of the pendulum means and therefore with the angle through which the valve is rotated. Preferably the pendulum means includes a profiled end on one side of a pivot about which the pendulum means swings therebeneath, the sealing means resting on said profiled end which urges the sealing means against the pressure surface as it rotates above the pivot with the pendulum means. Preferably the profiled end is at least partially arcuate. Preferably the sealing means is provided with an annular or O-ring seal on the surface of the sealing means adjacent the pressure surface, which is also preferably annular. Preferably the pendulum means is provided with universal joint means in order that said pendulum means can rotate about a plurality of different axes as the valve is rotated about an axis parallel to any of the said plurality of axes.. Preferably the valve is provided on a tanker adapted for carrying volatile fluid, such as petrol. Preferably the valve is further provided with a venting arrangement wherein gaseous pressure above the fluid within the tanker can be vented in the event that the tanker rolls over and the roll-over mechanism is activated, said arrangement comprising a feed tube provided with a float means which floats on the surface of the fluid within the tanker to permit gaseous flow therethrough from above the fluid surface, said float means being provided with an aperture or the like through which gas can pass, characterised in that the said feed tube communicates with a cavity within the valve which allows gaseous venting, said cavity being disposed on the alternate side of the sealing means to that which is adjacent the inside of the tanker. This aspect of the invention constitutes an independent and separately claimable invention in its own right. Preferably the feed tube connected to the float means is flexible and is resistant to corrosion from the fluid. Preferably there is provided movable cover means for float means of the type described above, said cover means being movable between a first position in which it completely covers the aperture of the float means and a second position in which at least a portion of the aperture is uncovered, characterised in that the said cover means moves to cover the aperture when the float means is submerged under fluid and moves to uncover the aperture when the said float means surfaces. Preferably the cover means comprises a collar around the float means. Preferably the sealing means can be manually displaced away from the pressure surface by release means provided in the valve regardless of whether the roll-over mechanism is activated to allow fluid flow through the valve from within the tanker. Preferably the tanker has at least one, and preferably several, pressure release valves with roll-over mechanism and float means. A specific embodiment of the invention will now be described by way of example, with reference to the accompanying drawings wherein; Figure 1. A cross-sectional view of a roll-over mechanism fitted to a pressure release valve for a tanker according to the invention, when said tanker is in an upright position. Figure 2. An enlarged cross-sectional view of a roll-over mechanism for a tanker according to the invention, when said tanker is in an upright position. Figure 3. An enlarged cross-sectional view of a roll-over mechanism for a tanker according to the invention, when said tanker is at an angle. Figure 4a. An enlarged schematic view of the float assembly according to the second aspect of the invention in a venting position. Figure 4b. An enlarged schematic view of the float assembly in the event of the tanker containing a volatile liquid being overturned. Referring firstly to Figure 1 there is illustrated a pressure release valve 1 and a roll-over mechanism 3, which in use is fitted to a tanker carrying petrol, the shell of which is indicated generally at X. The pressure release valve has a cylindrical outer sleeve 2, a plunger 24 sitting on an annular valve seat 32. The plunger 24 comprises a body part 23 and locating sleeve 25, which together provide a pressure resistance against an increasing positive pressure below plunger 24. O rings 31 are provided to create an airtight seal between plunger 24 and valve seat 32, until a point wherein the pressure differential across the plunger 24 is great enough to force the plunger 24 upwards from valve seat 32, thereby breaking the seal and allowing venting of the container. A pressure release valve of this configuration is disclosed in our co-pending application of even date. The outer sleeve 2 has inserted in an uppermost portion, a flame arresting gauze 28 and a retainer ring 30 to maintain the position of the gauze 28 within the outer sleeve 2. Body part 23 of the plunger 24 has a central aperture 19 with a central rod 27 passing through it. A spring 26 is disposed around central rod 27 in the portion above the part 23, and is retained on central rod 27 by means of a circlip 29. A vacuum seal plate 22 is attached to central rod 27. Vacuum seal plate 22 has O rings 5 and sits against the bottom side of part 23 of plunger 24 to form an airtight seal when the plunger 24 forms a seal with valve seat 32. A hollow cylindrical boss 7 provided on a roll-over seal plate 18 receives the free end 20 of the central rod 27 thus preventing the roll-over seal plate 18 from being displaced laterally. Roll-over seal plate 18 has O rings 9 to form an airtight seal with an inner shoulder 33 of the valve. When the tanker is an upright position, the roll-over seal plate sits on a pivot plate 4. Referring to Figures 1 , 2 and 3, there is illustrated a roll-over mechanism 3, comprising the pivot plate 4 rigidly connected to a pendulum shaft 10 with associated weight 8 via a stem section 12. A pivot 6 is disposed on the shaft 10 at any desired point between the weight 8 and the pivot plate 4. The roll-over mechanism 3 is retained within the cavity 100 defined by the walls of the sleeve 2 by means of a pivot pin 14. It will be appreciated by those skilled in the art that the configuration shown in the Figure allows only one degree of freedom in that the pendulum shaft 10 can only rotate in a single plane. It is to be mentioned that a universal joint may be incorporated into the roll-over mechanism 3 to allow 2 degrees of freedom of rotation such any rotation of the valve in toto about an axis not parallel with the longitudinal axis of the valve will cause rotation of the shaft 10 about the pivot and thus cause actuation of the mechanism. When the tanker is in an upright position, the weight 8 hangs in vertically. In the event of an accident wherein the tanker is rolled over, the longitudinal axis of the valve 1 subtends an acute angle θ° from its conventional vertical position but gravitational effects act on the pendulum such that said pendulum always attempts to adopt a vertical attitude. It is to be pointed out that the walls of the sleeve 2 may prevent said pendulum from adopting such vertical attitude in cases where the degree of rotation of the tanker and thus the valve is greater than perhaps 30°, but in any event the roll-over mechanism will have already been actuated. This mode of operation constitutes a significant advantage of the invention in that prior roll-over mechanisms are not generally activated until the tanker has rotated through an angle of 90° or more, after which rotation there may already have been fluid spillage through the valve. Furthermore, prior mechanisms have not previously been capable of preventing spillage through the valve in the event that the tanker is rotated about an axis other than its longitudinal one. As the pendulum shaft 10 swings, the pivot plate 4 also rotates being rigidly connected thereto. As the pivot plate rotates, it urges the roll-over seal plate 18 towards and ultimately against an inner shoulder 33 of outer sleeve 2, thereby forming a seal and blocking off the pressure valve 1 and preventing spillage of petrol from the tanker through the valve. In the event of an accident wherein the roll-over mechanism has been activated, the flame arresting gauze 28 and the retaining ring 30 can be removed and a hose can be fitted over the uppermost portion of outer sleeve 2. The hose is provided with a fitting which pushes down on central rod 27 and spring 26, thereby pushing down vacuum seal plate 22 and roll-over seal plate 18 and breaking the seals between these components and the underside of the plunger 24 and the inner shoulder 33 respectively. This then allows the petrol from within the tanker to be pumped off. Referring now to Figures 4a and 4b, there is illustrated a float assembly 37, the float assembly 37 comprising a main float 38 sitting beneath a secondary float 40 having a collar 48. Under normal circumstances when the tanker is upright, the main float 38 floats on the surface of the petrol 46. A flexible tube 36 has a first end connected between a pressure release valve 1 and roll-over mechanism 3 (not shown) . The said tube 36 is connected to the valve as shown in Figure 1. A second end of flexible tube 36 is connected to the float assembly 37 as shown in Figures 4a, 4b to an apertured pipe 44 which passes through the float assembly 37. Tube 44 has an aperture 42. The main float 38 keeps the aperture 42 above the level of the petrol, thereby allowing venting of the gas and vapour above the petrol 46. In the event of an accident wherein the tanker rolls-over, the main float 38 may be forced below the surface of the petrol 46 as the volume of fuel within the tanker moves under gravity. When the main float 38 is forced below the surface of the petrol 46, the secondary float 40 and collar 48 are forced up the flexible tube to cover the aperture 42 and prevent petrol 46 from escaping along the tube 36 and clogging same. Once the main float rises to the surface of the petrol 46 the secondary float 40 and collar 48 fall below the level of the aperture 42, thereby allowing venting of the tanker even though it is an upturned position. Although the specific embodiments refer exclusively to a tanker transporting petrol, it will be appreciated by those skilled in the art that the invention could also include the transportation of any liquid, or possibly gases.

Claims: CLAIMS 1. A roll-over mechanism for a valve, said valve having a movable sealing means which can move towards and away from a pressure surface within the valve, said sealing means creating a seal with said pressure surface when urged contactingly thereagainst to prevent fluid escape through the valve, characterised in that said roll-over mechanism comprises pendulum means which communicates with the sealing means to urge same towards and ultimately against the pressure surface when gravity acts on the pendulum means to deflect same as the valve rotates about an axis parallel with any axis about which the pendulum means can swing. 2. A mechanism according to claim 1 characterised in that the degree of displacement of the sealing means towards the pressure surface is dependent on the degree of deflection of the pendulum means and thus also on the angle through which the valve is rotated. 3. A mechanism according to any of the preceding claims characterised in that the communication between the pendulum means and the movable sealing means causes axial displacement of said sealing means towards the pressure surface when the pendulum means undergoes angular displacement. 4. A mechanism according to claim 3 characterised in that the pendulum means is pivoted at an intermediate point along its length such that angular displacement of said pendulum means occurs on both sides of said pivot but in substantially opposite directions. 5. A mechanism according to claim 4 characterised in that said pendulum means is provided with a profiled end on one side of the pivot about which the pendulum means swings, said sealing means resting on said profiled end the angular displacement of which axially displaces the sealing means resting thereon against the pressure surface. 6. A mechanism according to claim 6 characterised in that the profiled end is at least partially arcuate. 7. A mechanism according to any of the preceding claims characterised in that the sealing means is provided with an annular seal on the surface thereof and the pressure surface against which said sealing means is urged during operation of the valve, is annular. 8. A mechanism according to any of the preceding claims characterised in that the pendulum means is pivoted at universal joint means to allow for angular displacement of said pendulum means about a plurality of different axes. 9. A mechanism according to any of the preceding claims characterised in that the valve is provided on a tanker adapted for carrying volatile fluid. 10. A mechanism according to any preceding claim characterised in that the sealing means can be manually displaced away from the pressure surface by release means provided in the valve regardless of whether the roll-over mechanism is activated to allow fluid flow through the valve from within the tanker. 1 1. A venting arrangement for a pressure release valve incorporating a roll-over mechanism wherein gaseous pressure above fluid within a tanker can be vented through the valve in the event that the roll-over mechanism is activated, said arrangement comprising a feed tube provided at its free end with float means which floats on the surface of the fluid within the tanker, said free end permitting gaseous flow into the tube from above the fluid surface, characterised in that the said feed tube communicates with a cavity within the valve which allows gaseous venting, said cavity being disposed on the alternate side of the sealing means to that which is adjacent the inside of the tanker. 12. An arrangement according to claim 11 characterised in that the feed tube connected to the float means is flexible and is resistant to corrosion from the fluid. 13. An arrangement according to either claim 1 1 or 12 characterised in that the free end of the feed tube is sealed but provided with a transverse aperture proximate said free end through which gas can flow. 14. An arrangement according to claim 13 characterised in that movable cover means is provided in addition to or in combination with the float means, said cover means being movable over the feed tube between a first position in which it completely covers the aperture of said feed tube and a second position in which said aperture is at least partially uncovered, characterised in that said cover means moves to cover the aperture when the float means is submerged under fluid and moves to uncover the aperture when the said float means surfaces. 15. A arrangement according to claim 14 characterised in that the cover means comprises a collar around the feed tube which can slidingly move thereon.

Inventors: DENBY JAMES EDWARD, DENBY, JAMES, EDWARD
Applicants: DENBY JAMES EDWARD, DENBY, JAMES, EDWARD
Application year: 2000
Main classification: B65D90
IPC codes: B65D90, F16K17