GB2110794A - Safety valve - Google Patents

Abstract

A closure valve, more particularly but not exclusively for use in the air inlet conduit of an internal combustion engine, comprises a valve member movable from an open position to a closed position and biassed from the open position to the closed position, and holding means to hold the valve member in an open position against the said bias and against up to an additional predetermined fluid pressure on the member towards the closed position, pressure over the said predetermined pressure releasing the valve member from the holding means. An arm 22 fixed to the pivoted valve member (not shown) is rotated, when the valve is set in the open position, to engage behind a spring-biassed pivoted catch 36. When the air pressure acting on the valve member reaches the predetermined value it will cause the arm 22 to rotate, moving the catch 36 against the force of its spring 40. Further means 50 provides retraction of the catch 36 when oil pressure in an engine lubrication system drops. <IMAGE>

Description

SPECIFICATION Closure valve This invention relates to a closure valve, more particularly but not exclusively for use in the air inlet conduit to an internal combustion engine. It is desirable, particularly with compression ignition engines to have a means for stopping the engine other than or in addition to simply shutting down the supply of fuel to the engine. While an engine of this type is running, even after its fuel supply has been stopped it will continue to ingest air through its induction system. If that air contains flammable material, as it might very weli do in the case of engines operated in what would normally be referred to as hazardous environments such as down mines, on oil rigs and in paint and grain stores and the like, the engine may continue to operate effectively using the flammable material as fuel.Likewise of course in similar situations but when the fuel supply has not been cut off, the engine may accelerate with consequent damage not only to the engine itself and its load following overspeeding but also at some risk of explosion.

There is therefore a very real need for a closure valve for an internal combustion engine to ensure that a supply of air and possibly associated flammable matter is denied to the engine when shut down of the engine is required.

Valve devices are known for the control of internal combustion engines whereby the effect of engine overspeed on velocity of air flow into the engine is used to close a valve against a spring biassing force holding the valve away from the closure position. Examples of this type of valve disclosed in U.K.patent specification nos: 1 31 3686 and 1351369 to Esso Research and Engineering Company, the latter being a patent of addition to the former. The Esso patents describe a valve plate mounted to slide into and out of engagement with a valve seat in which position it obstructs air flow through the valve and into the engine, the valve plate being biassed away from the seat by a spring of characteristics such that its biassing force is overcome by the effect on this valve plate of a predetermined velocity of air passing through the valve.In other words, the spring force is in normal operation of the valve sufficiently strong to hold the valve open aginst the flow of air impinging upon it but when the engine starts to run at overspeed the pressure of air on the valve plate increases to the point where it overcomes the spring force and forces the valve shut. A latching arrangement is described for holding the valve in its closed position.

Valves of this type have found fairly widespread application but they suffer from several disadvantages the principal of which are firstly that overspeed of an internal combustion engine is in certain circumstances precluded by the load on that engine irrespective of ingestion of flammable material and secondly that the valve provides no fail safe closure in view of its stable equilibrium position being open.

The present invention seeks to provide a valve overcoming these and other disadvantages and providing further advantages as will become apparent from the following.

According to the present invention a closure valve comprises a valve member movable from an open position to a closed position and biassed from the open position to the closed position, and holding means to hold the valve member in an open position against the said bias and against up to an additional predetermined pressure on the member towards the closed position, pressure over the said predetermined pressure releasing the valve member from the holding means.

The said predetermined pressure is in the particular application of the valve to an internal combustion engine, the pressure caused by impingment on the valve member of air or air and fuel or other flammable material on its path into the engine. The additional predetermined pressure is that at which the operation of the engine is no longer deemed to be safe and can of course be varied depending on the engine its load and other operational circumstances.

The valve member is preferably a valve plate which may be and preferably is disposed substantially parallel to the flow path of fluid through the valve in both its open and closed positions, the connection of the valve member to the valve housing preferably being by an appropriate parallel motion linkage. However in an alternative embodiment the valve plate may move pivotally between its open and closed position, the valve member in both cases engaging a valve seat of complimentary construction and arrangement in the closed position to prevent further flow of fluid through the valve. The valve plate may however be provided with a bleed hole.

The open position of the valve is preferably variable according to the desired predetermined pressure of fluid on the valve member which will release the valve member from the housing means or it may be a static single fully open position governed by appropriate stops and other positioning means.

The bias of the valve member is preferably by spring force, for example by a torsion spring the distal end of which contacts the valve member at one or more points radially spaced from the point at which the valve member is linked to the valve housing. In the case where it is desired that the valve member should move substantially parallel to the direction of fluid flow through the valve and the spring force tends to urge the valve member away from this disposition, appropriate camm ing surfaces may be provided opposite the point or points of contact of the spring to hold the valve member in its appropriate disposition through its movement, the said camming surfaces sliding over one another.

The holding means preferably comprises a spring loaded detent, for example a latch member which in its first position obstructs movement of the valve member, or a member affixed thereto, from an open position to the closed position, and which in its second position allows movement of the valve member to the closed position. The latch member is preferably movable pivotally and biassed to its first position by a spring force, the position of the latch member where it obstructs movement of the valve member and/or magnitude of the spring force being adjustable to permit release of the valve member in accordance with the desired predetermined additional pressure thereupon.

The latch member is preferably located externally of the valve housing and may be provided with further means to bring about movement to its second position, consequent on or responsive to a predetermined change in engine oil pressure or pneumatic or electrical or hydraulic performance of an associated internal combustion engine, temperature changes etc., of an associated internal combustion engine or other integers of the environment in which it works or a host of other variables which may make desirable the shut down of the engine with which the valve is associated. Furthermore the valve may be provided with means whereby the valve member closure arrangement may be overriden to hold the valve in its open condition or alternatively to trip the valve manually to effect its immediate closure.A cable or the like with swaged on stops would be used in one form of the invention to this end. The invention also extends to an internal combustion engine with a valve as defined above in its indication system.

Some specific embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a somewhat schematic view partly in section of a closure valve according to the present invention; Figure 2 is a side view of the closure valve according to Fig. 1 showing its latch or holding mechanism, and Figure 3 is a side view of an alternative latch or holding mechanism for use in connection with the valve of Fig. 1 instead of the latch or holding mechanism of Fig. 2.

Referring to the Fig. 1 of the drawings there is shown generally at 10 a valve housing 1 2 having an inlet side 14 and an outlet side 1 5 the valve 10 being adapted to be affixed in stream in the induction system of an internal combustion engine, the outlet 1 5 being disposed downstream of the inlet 1 4.

Within the valve housing there is a valve plate 1 6 affixed through a stem 1 7 pivotally to a lever 1 8 which lever is rigidly mounted to a shaft at 20 passing through the valve housing 12, the shaft being rigidly affixed at its distal end to an actuation cam 22 (see Fig. 2).

Affixed to the housing 1 2 at 24 is a torsion spring 26 which exerts a strong bias on the plate 1 6 towards the valve seat comprising an annulus as part of the housing 1 2 shown at 30. When the valve plate 1 6 is held by the spring 26 against the annular seat 30, the valve is closed for the passage of air from the inlet 14 to the outlet 1 5.

The valve housing is provided with a flame trap 32 towards its outlet end.

A bleed hole (not shown) may be incorporated in the valve plate to allow vacuum decay more rapidly.

Turning now to Fig. 2 it will be seen that the actuation cam has at its bottom righthand corner a point 32 in contact with a complementary point 34 on a latch cam 36 which latch cam 36 is pivotally mounted on to the valve housing 12 to rotate about its axis 38.

The biassing force from the spring 26 urging the valve plate towards the closure position will it will be seen rotate the lever 1 8 about the axis 20 in a clockwise sense as shown in Fig. 1 and the rigid connection of the lever 1 8 by its shaft 20 to the actuation cam 22 will therefore cause the actuation cam 22 to be biassed to rotate in an anti-clockwise direction as shown in Fig. 2. The bias of the actuation cam 22 is therefore against the latch cam 36, the contact of the point 33 and 34 preventing the valve plate from moving to the closed position engaging the annular valve seat 30.

The latch cam 36 is held in position by a spring 40 having a low spring rate and chosen that it can, through the system of levers represented by the lever 1 8 actuation cam 22 and latch cam 36, hold the actuation cam and therefore the valve member against the force of the spring 26. When air or other fluid passes through the valve in the direction shown by the arrows indicated "air" on the drawings a force will apply itself to the plate 1 6 resulting in part from a pressure difference between the upstream and downstream side of the plate 1 6 and in part from change of gas momentum hitting the plate 16, this force acting to supplement the spring biassing force on the plate 1 6 caused by the spring 26. The action of the mechanism is such that the spring 40 has a high preload the cam 36 therefore does not start to move until the opposing force on the valve plate 1 6 has overcome this pre-load. Once overcome a comparatively small increase in force on plate 1 6 e.g. from a small increase in engine revolutions and cause anti-clockwise movement of the actuation cam 22 which in turn will cause rotation of the latch cam 36. The radial displacement of the point 34 from the axis 38 of the latch cam 36 will precess the point until it no longer obstructs the point 32 of the actuation cam 22 thereby leaving it free to rotate in its anticlockwise sense with the spring force caused by the spring 26 and in consequence allowing the valve plate 1 6 to snap shut into its position engaging the annular valve seat at 30.Thus when the air flow through the valve reaches a predetermined level, that level being essentially determined by the pre-load applied to spring 40 via adjuster 44 the valve will snap shut thus preventing overspeed of an engine for example ingesting flammable matter with its aspirated air. The adjuster 44 provides means to vary the pre-load of spring 40.

It will therefore be seen that the valve may be snapped shut with some degree of sensitivity on increased air flow to the engine to prevent further damage arising. The valve may also be provided with optional additional features as shown on Fig. 2. At 50 there is a plunger system geared to engine oil pressure, the system 50 being connected to the lubrication oil system of an associated internal combustion engine via its port 52. The oil pressure from the engine when running maintains a plunger 56 out of contact with the latch cam 36 but as soon as the oil pressure is released, the plunger will be pulled into the system 50 and by its flared head pull the latch cam 36 in a clockwise direction thereby releasing the actuation cam 22 and the valve plate 1 6 so that the valve may close.

In further embodiments similar arrangements may be made such that pneumatic pressure is used in place of lubricating oil pressure or for example electrical or other senses responsive to other variations in engine performance or the environment in which the engine is working. As an example it may be desirable to trip the latch cam 36 in response to electronic detection of the presence of a flammable gas in the environment in which the engine is working.

Finally the valve may be provided with a cable release arrangement 60 which operates on a Bowden-type cable connected via swaged terminals 62 to the actuation cam coupled with a spring 66 arranged to hold the cable in the position where it does not interfere either way with movement of the actuation cam 22. However if the arrangement of the system 50 is that loss of oil pressure trips the latch cam 36 it will of course be necessary on start up of an engine when there is no oil pressure to hold the actuation cam in position. This can be done with the cable system 60. Likewise should a manual mechanical override be required this can very easily be effected by an operator using the cable system 60. The cable system 60 must of course be provided with suitable "lost motion" so as not to prevent proper automatic closure of the valve mechanism.

Turning now to Fig. 3 of the accompanying drawings there is shown an alternative latching arrangement which will now be described.

The shaft 20 in this embodiment passes through the valve housing as before and is rigidly affixed at its distal end to actuation lever 1 22. At the lower end of the lever 1 22 there is mounted a pin 1 23 on which a trip lever 1 36 is free to rotate within limits. The limit of anti-clockwise motion of the lever 1 36 is the abutment of levers 1 22 and 1 36 at point A. A further attachment point 1 24 forms an anchorage for a tension spring 140 the other end of which is attached via an adjustment point 1 44 to the control lever 1 22 to constrain the lever 4 from moving in a clockwise direction.In an alternative form (not shown) the equivalent force to that provided by the spring 140 is provided by a torsion spring wound around pin 123.

The bias of the valve plate 1 6 to a closed position tends to rotate the shaft 20 and the lever 1 22 in an anti-clockwise direction as shown in Fig. 3, this tendency normally being resisted by the heel 1 50 of the lever 1 36 abutting the end of a piston rod 1 56 which is maintained in an extended position by for example engine lubricating oil pressure via a conduit 1 52. A spring 1 54 biassing the piston 1 56 against the oil pressure force will, upon release of the oil pressure cause the piston 1 56 to retract from abutment of the heel 1 50 of the lever 1 36 thereby allowing movement of the lever 1 22 and closure of the valve itself.

The system of use of a reduction in oil pressure to unlatch the valve may be geared direct to the engine lubricating system or to a system whereby oil pressure is dumped by valves operating on and sensitive to high water temperature or exhaust gas temperature or some other predetermined malfunction.

Where an engine overspeeds, even without the valve being tripped by movement of cylinder 156, excess pneumatic force on the valve 1 6 will cause the lever 1 22 to rotate anticlockwise due to the lever 1 36 overcoming the force of its tension spring 140 so that the heel 1 50 again rides over the piston rod 1 56 to cause closure of the valve and hence engine shutdown. Adjustment of the pre-load of spring 140 at point 1 44 will determine the engine speed at which this occurs.

In the case of an operator being unable to stop the engine to which the valve is attached with normal fuel pump rack control, as in the previous embodiment, an emergency stop facility is provided through a cable arrangement shown generally at 1 60 the cable arrangement being if desired a proprietory item whereby the cable arrangement may be moved a hand set 1 70 in a push or pull mode allowing both for emergency closure of the valve and also re-setting. In this embodiment the cable is attached by a bull joint 1 72 to a stop/reset lever 1 74 which is freely pivoted about the end of the shaft 20.The lever 1 74 has two protrusions or bent over ends so as to make contact with lever 1 22 at either of positions B and C depending on whether the cable is used in the push or pull mode. When it makes contact at position B it will rotate the lever 1 22 anti-clockwise and thus allowing the valve 1 6 to close shutting down the engine.

When the engine is restarted after stopping (whether due to normal shutdown or ioss of oil pressure or overspeed or indeed use of the manual emergency stop override) the valve itself must be reset to the open position and held there until, for example, oil pressure causes the piston rod 1 56 to reset to its fully extended position abutting the heel 1 50. Resetting is accomplished by movement of the cable arrangement 1 60 to pull the cable thus rotating the lever 1 74 clockwise until contact with lever 1 22 occurs at point C thus moving lever 1 22 clockwise to hold the valve open.In the normal running position of the lever 1 22 with the cable arrangement 1 60 at its normal or neutral position there is clearance at both points B and C to give sufficient lost motion to allow the lever 1 22 to move to the shutdown position without having to carry the cable system with it. Furthermore when the shutdown valve has been operated, the valve plate 1 6 may be held in the closed position for some time due to partial vacuum being retained within the engine inlet manifold. To avoid damage of the mechanism by forcible resetting of the cable system 160, a compression spring 1 78 is incorporated in the ball joint assembly 1 72 sufficient to accommodate movement of the reset control system to its neutral position without strain.

In a further embodiment, again not shown, the attachment of the cable system to the lever 1 74 may be reversed so that a push becomes a pull and vice versa, with the spring 1 78 being repositioned appropriately.

In both of the embodiments described the systems indicated at 50 and 1 56 may be dispensed with and replaced by a simple peg arrangement (not shown). In that case the override means for start-up will only be required if the valve has been triggered and closed by engine overspeed.

Claims (14)

1. A closure valve comprising a valve member movable from an open position to a closed position and biassed from the open position to the closed position, and holding means to hold the valve member in an open position against the said bias and against up to an additional predetermined pressure on the member towards the closed position, pressure over the said predetermined pressure releasing the valve member from the holding means.

2. A valve as claimed in Claim 1 in which the member is a valve plate disposed substantially parallel to the flow path of fluid into the valve in both its open and closed positions.

3. A valve as claimed in Claim 1 in which the valve member is a valve plate movable pivotally between its open and closed positions.

4. A valve as claimed in any of the preceding claims in which the bias of the valve member is provided by a spring force.

5. A valve as claimed in Claim 4 wherein the said spring is a torsion spring bearing on the upstream side of the valve member.

6. A valve as claimed in any of the preceding claims wherein the holding means comprises a spring loaded detent.

7. A valve as claimed in any of the preceding claims in which the holding means comprises a latch member which in its first position obstructs movement of the valve member, or a member affixed thereto, from an open position to the closed position and in which in its second position allows movement of the valve member to the closed position.

8. A valve as claimed in Claim 7 in which the latch member is pivotally mounted to the valve housing and is biassed to its first position by a spring force.

9. A valve as claimed in Claim 7 wherein the latch member is pivotally mounted to a member affixed to the valve member and biassed by a spring force to its first position where it obstructs movement of the valve member by abutment against an obstruction.

10. A valve member as claimed in Claim 8 or Claim 9 in which the pre-load on the spring causing the bias in the latch member is adjustable to permit release of the valve member in accordance with the desired predetermined additional pressure thereupon.

11. A valve as claimed in any of the preceding Claims wherein further means are provided to release the valve member from the latch member.

1 2. A valve as claimed in any of the preceding claims wherein means are provided to hold the valve in an open position.

1 3. A valve as claimed in any of the preceding claims having a flame trap.

14. A closure valve substantially as described herein with reference to the accompanying drawings.

1 5. An internal combustion engine fitted with a valve as claimed in any of the preceding claims disposed in its induction system for prevention of fluid flow into the engine when required.