Patent Description:
Check valves are valves that allow fluid flow in one direction therethrough and prevent flow in the opposite direction. They are widely used in a range of applications, for example, check valves may be used in an air distribution system to vent or control an amount of air that flows from one portion of an aircraft to another.

With reference to <FIG>, a conventional check valve <NUM> includes a pair of flappers <NUM> located at an opening <NUM> in a valve housing <NUM>. The flappers <NUM> are hingedly supported on a pin <NUM> mounted across (e.g. through the centre of) the opening <NUM> for rotation between an open position and a closed position. In the closed position they lie across and close the opening <NUM>, preventing fluid flow through the opening <NUM>. In the open position, and under the pressure of a fluid (gas or liquid) on one side of the check valve, the flappers <NUM> rotate from their closed position so as to allow the fluid to flow through the valve.

Ordinarily, as illustrated in <FIG>, a cylindrical pin <NUM> is provided to limit the rotational movement of the flapper elements <NUM> as they open. Typically, the pin <NUM> is mounted in a pair of mounting posts <NUM> that extend upwardly from the valve housing <NUM> and space the pin <NUM> from the opening <NUM>. Accordingly, when the flappers <NUM> open, they engage the stop pin <NUM> and are prevented from contacting each other. The stop pin <NUM> is typically quite narrow, its size being minimised so as to ensure a maximised open area when the flappers <NUM> are in the open position.

Thus, a very narrow contact area <NUM> is typically present between the cylindrical surface of the stop pin <NUM> and the surface of the flapper <NUM>, and a high level of stress is experienced by both the stop pin <NUM> and flapper <NUM> in this contact area <NUM>. This can lead to a gradual wear down <NUM> of either or both of the flapper <NUM> surface or cylindrical surface of the stop pin <NUM>, resulting in a change in the performance of the check valve <NUM>. The displacement of the flapper <NUM> relative to the stop pin <NUM> caused by this wear down <NUM> can also accelerate the wear of the associated hinge pin <NUM> to an unsatisfactory level, as illustrated in <FIG>.

Generally, flapper-type check valve <NUM> components are made of metallic materials. These metallic materials are relatively heavy, and may undesirably increase the weight of an aircraft when implemented therein. Additionally, metallic check valves may produce relatively loud noises during check valve operation (e.g. the opening and closing, or a fluttering of the flappers).

In a conventional check valve arrangement, as in <CIT>, each flapper (or alternatively the stop pin) comprises an elastomeric protrusion configured to contact the stop pin (or flapper) when the flapper is in the open position. The elastomeric protrusions are provided to cushion contact between flappers and stop pin in order to minimise noise.

However, though such resilient arrangements may help to reduce unwanted noise, they present significant drawbacks as, for example, they do not serve to prevent the cause of the fluttering.

Further, such resilient arrangements allow the flappers to move against the resilient elements (e.g. a vibratory movement) when in the open position in response to, for example, fluctuations in forces created by high pressure, eddies or other turbulent flow regimes through the check valve.

This fluttering and/or vibratory movement can also contribute to the significant wear to the hinge pin <NUM> illustrated in <FIG>, and reduce the operational lifetime of the check valve <NUM>. Further example prior art valves are provided by <CIT>, <CIT>, <CIT>, <CIT>, <CIT> and <CIT>. <CIT> discloses a prior art check valve according to the preamble of claim <NUM>.

The present disclosure aims to provide a check valve of this general construction, whilst having an improved stop arrangement that solves the above problems.

In an aspect of the invention there is provided a check valve according to claim <NUM>.

The relatively large contact areas due to the provision of conformal contact surfaces allow for the even distribution of stress between the flappers and stop elements, for example, due to the percussive opening of the valve. This can greatly reduce the wear exhibited by these components locally (e.g. at the contact surface). The bumpers and the adjacent openings serve to facilitate smooth opening and closing of the valve by allowing the passage of air, thereby reducing fluttering and percussive opening events. This reduces wear on the contact surfaces associated with impact events between the contact surfaces, and vibrationary wear on the pin of the hinge. Further, the provision of a static stop element with contact surfaces configured to be stationary (e.g. non-resilient) can prevent positional fluctuations of the flapper when in the open position further reducing wear at the pin onto which the flappers are pivotly mounted (and, also locally on the contact surfaces). Moreover, a synergistic effect is provided by the provision of each of the conformal contact surfaces, the bumpers and associated openings, and stop element surfaces which are configured to remain stationary (rather than bend or flex in use). Indeed the aforementioned prevention of wear on the contact surface prevents wear on the pin, and the aforementioned prevention of wear on the pin prevents wear on the contact surfaces.

The contact surfaces on the flappers and the contact areas of the stop elements may be planar. In other words, and more generally the contact surfaces (<NUM>) of the flappers (<NUM>) and opposing portions of the stop element (<NUM>) are planar.

The pair of valve openings may define a plane. The stop element comprises a strip of material. The strip of material may be oriented parallel to the plane. The use of a strip of material may increase the ease of manufacture and reduce the weight of the valve.

The strip of material may be substantially flat and may comprise a thickness selected such that a superficial contact width between the contact surfaces of the flappers and contact areas of the stop elements is equivalent. This matching of thicknesses allows for the minimisation of excess weight, which is particularly important when such valves are employed in the aviation industry.

The contact areas of the stop element may be inclined relative to each other. In other words, the static, opposing portions of the stop element may define planar surfaces that converge towards each other in the direction of the valve openings. This facilitates easy tailoring of the conformal contact surfaces. For example, the contact surfaces of the flappers may be flat (i.e. parallel to a major surface of the flappers), and only the stop element may be tailored (e.g. cut or machined) to be conformal to the flappers. In this way the same flappers may be used on different check valves, for example, check valves configured for different fluids and which may require valves with different (smaller or larger) opening angles for smooth operation.

The stop element may comprise one or more apertures configured to allow the passage of fluid. These apertures, when provided, may further facilitate a reduction in fluttering, by facilitating the passage of fluid from the cavity.

The one or more bumpers may be configured to evenly distribute stress (e.g., evenly) around the flappers and/or distribute stress (e.g., evenly) along the pin.

Each of the flappers may comprise two or more knuckles configured to contact the pin. At least one of the one or more bumpers (or contact surfaces of the flapper) may be aligned to one of the knuckles. This allows for even distribution of stress through the pin.

The flappers and/or stop surfaces may be asymmetric relative to the pin such that, when in the open position, the openings of one of the flappers are offset from the openings of the other of the flappers. This can more evenly distribute fluid flow through the cavity and prevent high and low velocity regions of flow which can fluctuations in pressure and lead to valve fluttering.

The valve comprises a pair of mounting posts for supporting the pin and/or the stop element. According to the invention, the mounting posts and the stop element are formed of a single strip of material. This reduces manufacturing complexity and the overall mass of the valve.

Each flapper may comprise a length along which the one or more bumpers (or contact surfaces of the flapper) may extend in a direction substantially parallel to the pin. The one or more bumpers (or contact surfaces of the flapper) may extend across at least <NUM>% of the length. The one or more bumpers (or contact surfaces of the flapper) may extend across at least <NUM>% of the length. The provision of such relatively long bumpers, or with such large coverage can not only increase the contact surface area for stress distribution, but can also increase the area of the flapper around which the stress may be distributed. This again reduces wear on both the pin and the contact surfaces.

The provision of a unitary mounting post and stop element arrangement greatly simplifies the manufacturing process and allows for rapid replacement and repair of the entire support and stop structure. It also allows the valve to be easily reconfigured (e.g. to modify the opening angle of the flappers). Further, the simple strip of material configuration drastically reduced the overall weight of the check valve.

Each of the flappers comprises one or more contact surfaces configured to contact the stop element when in the open position. The stop element comprises pair of stop surfaces, comprising respective contact areas configured to oppose and abut the contact surfaces of the flappers when the flappers are in the open position. The contact areas may be configured to remain stationary. At least one of the contact surfaces of the flappers and contact areas may be formed on one or more bumpers disposed on a respective at least one of the flappers and stop surfaces. The provision of bumpers can facilitate a flow of fluid from a cavity formed between the bumpers and the stop element when the valve is in the open position, thereby preventing fluttering of the various valve elements.

The contact areas are configured to be conformal to the contact surfaces of the flappers when the flappers are in the open position.

In another aspect a method of manufacturing a check valve is provided according to claim <NUM>, the method comprising forming a stop element and a pair of mounting posts from a single flat piece of metal. This allows for simple mass manufacture of the valve elements, e.g. by machining, pressing or cutting multifaceted components of the valve.

The method may further comprise selecting a thickness of the flat piece of metal such that a superficial contact width between contact surfaces of the flappers and contact areas is equivalent. This minimises the weight of the valve.

With reference to <FIG>, various embodiments of a check valve <NUM> in accordance with this disclosure are herewith described.

The check valve <NUM> comprises a housing <NUM>. The valve housing <NUM> is a generally planar annular element which may be mounted in a pipe, duct or the like. The valve housing <NUM> comprises a pair of generally D-shaped valve openings <NUM> which are separated by a central web <NUM> of the valve housing <NUM>.

A pair of mounting posts <NUM> extend upwardly from the valve housing <NUM>. The mounting posts <NUM> may be integrally formed in place, for example cast, with the valve housing <NUM>. Alternatively, the mounting posts <NUM> may be separately formed from the valve housing <NUM> and mounted thereto by suitable means, for example, welded thereto, or attached by bolts or other fasteners (not shown).

A pin <NUM> is mounted between the mounting posts <NUM> above the central web <NUM>. The pin <NUM> may be a unitary structure, or may be constituted from two or more sections. The pin <NUM> may be mounted through pin apertures <NUM> in the mounting posts <NUM>. Thus, the pin <NUM> may be installed in sections between mounting posts <NUM> already in place, or a unitary pin <NUM> may be installed, e.g., from one side through apertures <NUM> in the side of the posts. Alternatively, a pin <NUM> (e.g. a unitary pin) may be installed between the mounting posts before they are in place (i.e. before their mounting to the housing <NUM> as discussed below).

A stop element <NUM> (e.g. a rigid stop element) abridges the mounting posts <NUM>, and is positioned above the pin <NUM>.

A pair of generally D-shaped flappers <NUM> are pivotally mounted to the pin <NUM> and each flapper <NUM> interacts with a respective valve opening <NUM> to selectively close it. As is known in the art, the flappers <NUM> are pivotally mounted to the pin <NUM> by a hinge mechanism including respective mounting lugs or knuckles <NUM>, and are pivotable between an open position and a closed position. In the closed position they close the valve openings <NUM>, thereby preventing flow through the check valve, and in the open position the flappers <NUM> permit fluid to pass through the valve openings <NUM> in a flow direction <NUM> from a pressure side <NUM> of the valve <NUM> to a suction side <NUM> of the valve <NUM>.

<FIG> and <FIG> show a check valve <NUM> wherein, for illustrative purposes to show both positions, one of the flappers 30a is disposed in the closed position, whilst the other flapper 30b is disposed in the open position. In the open position the flappers <NUM> engage the stop element <NUM> and define an opening angle α.

In normal operation, and when a pressure difference exists between the pressure side <NUM> and the suction side <NUM>, a fluid exerts a force F on the flappers <NUM>. This serves to move the flappers <NUM> from the closed position to the open position when the pressure difference exceeds a threshold pressure. The force is generally exerted on a flapper surface <NUM> (e.g. the pressure side surface). Thus, the magnitude of the force F on the flapper is reduced as the opening angle α is increased and the direction of fluid flow becomes more perpendicular to the surface <NUM>.

In this context, and contrary to established principles for ensuring a maximised opening <NUM> area for maximised fluid flow <NUM>, it has been found that a smaller opening angle α may reduce fluttering. This is because a larger force F is maintained against the flapper surface <NUM>, relative to a smaller force which is present when a large opening angle α is employed.

However, maintaining a larger force F can also increase stress and associated wear (e.g., the wear down <NUM> of either or both of the flapper <NUM> surface or cylindrical surface of the stop pin <NUM> illustrated in <FIG>). Consequently, reducing fluttering in this way may lead to unintended knock-on effects which reduce the lifetime of the valve.

Advantageously, it has been found that a relatively large contact surface area <NUM>, 44a between the flappers <NUM> and the stop element <NUM> may help to more evenly distribute stress across the flapper <NUM> and reduce wear on both the flapper <NUM> and the stop element <NUM>. The even distribution of stresses and the reduction of wear of the flapper <NUM> and stop element <NUM> can also subsequently result in reduced stress and wear on the pin <NUM>. It has therefore been found to be desirable to maximise the surface area of the contact surfaces between the flapper and stop element.

In accordance with the invention, and with continued reference to <FIG>, the stop element <NUM> is shaped so as to present a surface <NUM> which is complementary or conformal to the flappers <NUM> in their open position. According to the invention, the stop element <NUM> comprises a contact surface or area 44a which is conformal to the contact surface <NUM> of the respective flappers <NUM>. For example, both the contact areas 44a on the stop element <NUM>, and contact surfaces <NUM> on the flapper <NUM> may be flat (in contrast, for example, to established flat flapper and round stop pin arrangements). Either or both respective contact surfaces or areas <NUM>, 44a may also be angled (e.g. inclined such that they are not parallel or perpendicular to a major surface thereof) in order to be complimentary to the angle of the other respective contact surface or area <NUM>, 44a when the valve <NUM> is in the open position. In this way, the contact surface area between the flappers <NUM> and stop element <NUM> may be maximised.

With reference to <FIG>, it has also been found that, during operation, a portion of fluid <NUM> may pass through the hinge mechanism (e.g. through gaps in the knuckles <NUM>) and enter a cavity <NUM> formed between the flappers <NUM> and stop element <NUM> when in the open position. A build of pressure P resulting from this passage of fluid may oppose the force F from the fluid flow <NUM> and push the flappers <NUM> towards the closed position to allow the pressure build up to escape, thereby causing the flappers <NUM> to flutter.

Such fluttering can be present even in the absence of this passage of fluid (for example, when the hinge mechanism is sealed to prevent the passage of fluid to the cavity). With reference to <FIG>, it is believed that a high pressure fluid flow <NUM> through the valve opening <NUM> can cause local pressure fluctuations on the exposed surface of the flapper (e.g. the pressure side surface) which leads to the fluttering. Further, the fluid flow <NUM> over the tips of the flappers <NUM> can create eddies (turbulence) in the vacant space behind the flappers <NUM> (e.g. on the suction side) which, again, results in the fluttering of the flappers <NUM>.

It has been found to be highly beneficial to provide clearances or openings <NUM> between the flappers <NUM> and the stop element <NUM> (when the flappers <NUM> are in the closed position), to not only allow the escape of fluid in the cavity <NUM>, but to facilitate a fluid flow <NUM> therethrough such that the formation of eddies are prevented, thereby ensuring lower stress laminar flow regimes (see <FIG>).

There are therefore potentially conflicting requirements for maximising the contact area <NUM> between the flappers <NUM> and stop element <NUM> whilst simultaneously facilitating a flow of fluid between the flappers <NUM> and stop element <NUM>.

In accordance with embodiments, and with reference to <FIG>, it has been found beneficial to create a contact area <NUM> between each flapper <NUM> and the stop element <NUM> which extends across at least <NUM>% of the length L of the flapper <NUM> (e.g. the superficial length L which would be in contact with the stop element <NUM> in the absence of any further surface features), whilst at the same time providing openings <NUM>, clearances or vacancies along the same length L. The contact area between each flapper <NUM> and the stop element <NUM> may extend also across at least <NUM>% of the length L of the flapper <NUM>.

The contact area between flappers <NUM> and stop element <NUM> is facilitated by one or more bumpers <NUM> (e.g. non-resilient or rigid bumpers which are substantially solid, hard, made of non-resilient materials and/or devoid of cushioning or resilient features, etc.) provided on either or both of the flappers <NUM> (see <FIG>). Additionally or alternatively, such bumpers may be provided on the stop element, e.g. on opposing lateral stop surfaces <NUM> thereof (not shown), such that the contact areas 44a of the stop element <NUM> are provided on the bumpers. The bumpers <NUM> may extend over a length L of the flapper (or a length of the stop element). In embodiments, the bumpers may cumulatively extend across at least <NUM>% of the length L of the flapper <NUM> or across at least <NUM>% of the length L of the flapper <NUM> or stop element <NUM>.

Accordign to the invention, the openings <NUM> are provided adjacent to the bumpers <NUM>. In these embodiments a height of the bumpers may be regulated so as to control the size of the openings <NUM>.

Further, to ensure a maximised contact area (and optimise the weight of the check valve <NUM>, as discussed below), a width W of each of the bumpers <NUM> may be controlled so as to match (and, thus, be complimentary to) a superficial contact width W of the stop element <NUM> (see <FIG> and <FIG>).

With a view to further facilitating flow through the cavity <NUM>, and in accordance with some embodiments, the stop element <NUM> itself may comprise openings or apertures <NUM> configured to allow the passage of air from the cavity <NUM> (see <FIG>). Such apertures <NUM> may be provided in addition to, or as an alternative to, the previously described openings <NUM> between flapper and stop element.

In order to harmonise fluid flow through the cavity, it has been found to be beneficial to offset the bumpers <NUM> on one flapper <NUM> from the bumpers <NUM> on the other flapper <NUM>. Accordingly, in embodiments, the bumpers <NUM> of the respective flappers are positioned asymmetrically to each other with respect to (on either side of) the centrally positioned pin <NUM> of the hinge mechanism.

With a view to more evenly distributing stresses along the pin <NUM>, it has also been found to be beneficial to substantially align one or more of the bumpers <NUM> with the knuckles <NUM>. Accordingly, in some embodiments, at least one bumper <NUM> of the one or more bumpers <NUM> on each flapper <NUM> is aligned with one of the knuckles <NUM> (i.e. aligned with respect to pin <NUM>).

As discussed above, the opening angle α impacts the force F exerted on the flappers <NUM> in the open position. With a view to ensuring a more stable operation (e.g. to prevent fluttering and the associated wear), it is advantageous to limit the opening angle α in order to maintain a higher force F for steadily holding the flappers in the open position. For example, in some embodiments the opening angle α between the flappers <NUM> and the openings <NUM> may be less than <NUM> degrees. Limiting the opening angle may be achieved by providing a stop element with a larger separation between its sides.

However, the provision of ever larger stop pins (in the established cylindrical form) can exponentially increase the weight of the check valve as a whole. Such an increase in weight is highly undesirable, particularly in applications within the field of aerospace.

Thus, in embodiments, the stop element <NUM> is advantageously not cylindrical, or not substantially cylindrical in form. Instead the stop element <NUM> is provided as (comprises or consists of) a substantially flat, e.g. bar-shaped, strip of material. For example, the stop element <NUM> may comprise a rectangular, or trapezoid cross-section as it extends from one mounting post <NUM> to the other. In this form the breadth of the stop element <NUM> (i.e. the separation between opposing lateral sides <NUM> or contact areas 44a thereof) may be easily controlled without substantially affecting the overall mass of the check valve <NUM>. Thus, the opening angle α of the check valve <NUM> may be optimised without adversely affecting the weight. The provision of the flat shape also allows thickness thereof to be more easily tailored. For example, the thickness of the stop element may be provided to as to exactly match a superficial contact thickness or width W of the bumpers <NUM>. In this way the mass of the check valve may be minimised, and indeed reduced below current standards. Apertures <NUM>, where provided, are easier to install and tailor as well.

Further, in embodiments, the stop element <NUM> is a non-resilient or rigid stop element <NUM> (i.e. substantially solid, hard, made of non-resilient materials and/or devoid of cushioning or resilient features, etc.). As such, the contact areas 44a of the stop element <NUM> may be configured to remain stationary, even when subject to the opening and closing or percussion of the flappers <NUM>. Advantageously, the absence of any resilient or cushioning features (i.e. the provision of stationary stop contact surfaces or areas) helps to prevent vibratory movements in the flappers <NUM>, thereby preventing increased wear on the pin of the hinge mechanism (see, for example, <FIG>).

The stop element <NUM> and the mounting posts <NUM> form a unitary or continuous bridge structure extending from one side of the housing <NUM> to the other (according to the invention, a single strip of material). According to the invention, the bridge structure simultaneously performs the functions of supporting the pin <NUM>, supporting the stop element <NUM> and serving as the stop element <NUM>. The bridge structure may advantageously comprise a substantially uniform thickness along its entire build (i.e. the mounting posts <NUM>, stop element <NUM> and any intervening sections may be substantially the same thickness and/or have substantially the same cross-section). The bridge structure may be formed of a single, bent piece of material of uniform thickness (e.g. sheet metal) which is shaped to form the mounting posts <NUM>, the stop element <NUM>, and/or pin apertures <NUM> for supporting the pin <NUM>. Alternatively, the bridge structure may be cast, either independently, or integrally to the housing <NUM>. In cases of bridge structure being formed separate from the housing, the bridge structure may be deformed along its axis to facilitate installation of the pin <NUM> (e.g. a unitary hinge pin) between the mounting posts <NUM>. The bridge structure and pin may then be mounted to the housing <NUM> by the mounting posts <NUM> thereof by any suitable means (as discussed above).

Regardless of how the bridge structure is formed (e.g. from a sheet of metal, or by casting, separately or as part of the housing <NUM>), the simplified design thereof (e.g. its substantially uniform thickness and/or its continuous design) may significantly improve the ease of its manufacture (e.g. by being stamped from sheet metal, or by greatly reducing the complexity of a mould needed for casting).

Claim 1:
A check valve comprising:
a housing (<NUM>) defining a pair of valve openings (<NUM>);
a pair of flappers (<NUM>, 30a, 30b) pivotably mounted to a pin (<NUM>) and such that they are configured to rotate relative to the housing (<NUM>) between an open position in which they permit fluid flow through the valve openings (<NUM>) and a closed position in which they prevent fluid flow through the valve openings (<NUM>); and
a stop element (<NUM>) configured to stop and hold the flappers (<NUM>) in the open position, wherein a cavity (<NUM>) is formed between the pair of flappers and the stop element (<NUM>) when the flappers are in the open position (30b),
wherein the check valve further comprises:
a pair of mounting posts (<NUM>) for supporting the pin (<NUM>) and the stop element (<NUM>),
wherein each of the flappers (<NUM>) comprises one or more contact surfaces (<NUM>) configured to engage and contact a respective static, opposing portion of the stop element (<NUM>), the stop element comprising a pair of stop surfaces (<NUM>), each comprising respective contact areas (44a) configured to oppose and abut the contact surfaces (<NUM>) of the flappers (<NUM>) when the flappers (<NUM>) contact the stop element (<NUM>) in the open position,
wherein at least one of the contact surfaces (<NUM>) of the flappers (<NUM>) and contact areas (44a) of the stop element (<NUM>) are formed on one or more bumpers (<NUM>) disposed on a respective one of the flappers (<NUM>) and/or stop surfaces (<NUM>) such that one or more openings (<NUM>) are formed between each of the pair of flappers (<NUM>) and the stop element (<NUM>) adjacent to the one or more bumpers (<NUM>) when the flappers (<NUM>) contact the stop element (<NUM>) in the open position to ensure fluid is able to flow therebetween,
wherein each of the contact areas (44a) of the stop element (<NUM>) are configured to be conformal to the contact surface (<NUM>) of a respective flapper (<NUM>) when the flappers contact the stop element (<NUM>) in the open position,
characterized in that
the mounting posts (<NUM>) and the stop element (<NUM>) are formed of a single strip of material.