GB2524985A

GB2524985A - Dual valve actuator

Info

Publication number: GB2524985A
Application number: GB1406310.1A
Authority: GB
Inventors: Collin Gibson; Ellis Rowe; Nigel Pennick
Original assignee: GT PREC PRODUCTS Ltd; GT Precision Products Ltd
Current assignee: GT PREC PRODUCTS Ltd; GT Emissions Systems Ltd
Priority date: 2014-04-08
Filing date: 2014-04-08
Publication date: 2015-10-14
Anticipated expiration: 2034-04-08
Also published as: WO2015155528A1; GB201406310D0; GB2524985B; EP3129627A1

Abstract

A linkage for coupling a reciprocal actuator 21 to separate butterfly valves 14, 15, each having an operating lever 28, 29 connected to a spindle pivotable in a housing 11, comprising first and second arms 26, 27 coupled to a pivot at respective first ends, the second ends being respectively pivotably connected to the operating levers, wherein one of the arms includes a spring between its ends permitting relative axial movement of said ends when an axial force transmitted therethrough exceeds a threshold. A bell crank may be coupled to the pivot for attachment to the actuator. The housing preferably has an integral fixed arm 20 on which the actuator is mounted. The actuator may be rotary or linear and can be electric, pneumatic or hydraulic. The linkage may be used with an exhaust brake, an exhaust gas recirculation system or a waste heat recovery system of a vehicle. Using a single actuator to operate parallel valves in two separate ducts ensures an equal degree of throttling in each duct.

Description

Dual Valve Actuator

TECHNICAL FIELD

This invention relates to an actuator for a dual, double or twin valve, in particular to a dual, double or twin butterfly valve having a single actuator for operation thereof

BACKGROUND TO THE INVENTION

Fluid ducts are frequently provided with valves to throttle or close off the flow of fluid therethrough. A typical valve comprises a butterfly disc pivotable in the duct through about 900 between open and closed conditions. Such a valve may be actuated by a linear or rotary actuator, and the actuator may be single or double acting. If single acting, return motion may be provided by a return spring or the like. An actuator may be electric, hydraulic or pneumatic.

In some instances two similar valves are provided for closing respective ducts that are close together. The ducts may for example be the exhaust pipes associated with two sets of engine cylinders of an internal combustion engine (for example in a vee configuration), and the valves may constitute exhaust brakes associated with the exhaust pipes. Exhaust brakes are closable to restrict the flow of exhaust gas from an engine, thereby to provide engine braking to a vehicle. Such valves may also be used as part of an exhaust gas recirculation (EGR) installation of a vehicle engine or as part of a system of recovering heat from the exhaust of a vehide engine. This kind of valve may be termed a thermal management valve, an EGR valve, an EGR bypass valve, an exhaust bypass valve or a waste heat recovery valve.

It is of course desirable that two such valves act simultaneously to provide an equal degree of throttling in each duct. Such valves should close simultaneously, and when closed ensure an effective seal in the duct, Furthermore such valves should both open fully so that an unequal restriction to gas flow is obviated.

Whilst an individual actuator could be provided for each duct, it cannot be ensured that such actuators will act simultaneously because of, for example, manufacturing differences, non-linear deterioration of performance, differential friction and like phenomena.

A single actuator is desirable, but in this case careful adjustable of an operating linkage is required to ensure simultaneous action. In one example, screw threaded parts are provided to permit actuation of at least one valve be progressively ad] ustable to match movement of the other, but continual vigilance is necessary to ensure that valves remain synchronized. Wear in a linkage may make synchronization impossible at both open and closed conditions.

What is required is a solution to this difficulty, which ensures simultaneous activation of two valves from a single actuator, at a relatively low cost, and which accommodates in-service variations between the valves.

SUMIvIARY OF THE INVENTION According to a first aspect of the invention there is provided a linkage for coupling a reciprocal actuator to separate butterfly valves each comprising a spindle pivotable in a valve housing, each spindle having an operating lever coupled thereto, said linkage comprising first and second arms having respective first ends coupled at a first pivot, a second end of the first arm being for pivotal connection to the operating lever of a first spindle, a second end of the second arm being pivotally connected to the operating lever of a second spindle, wherein one of said first and second arms includes a spring between the ends thereof, said spring permitting relative axial movement of said ends when an axial force transmitted therethrough exceeds a threshold.

Such a linkage ensures that relative movement of one of said arms is possible with respect to the other of said arms, to permit full opening and/or full closing of an unsynchronized pair of butterfly valves, The spring is preferably of metal, and may comprise a disc spring (also known as a Belleville washer) or a coil spring. In one embodiment a stack of disc springs is provided -as is well known a stack of such springs can be assembled in many ways to provide variation of rate and pre-load.

In one embodiment the valves are urged closed by tensioning said arms, and preferably said metal spring is compressed upon said threshold being exceeded.

Closing by transmitting actuating force in compression is also possible.

In one embodiment the first and second anns are unequal in length, the ann of variable length being longer in the unstressed condition.

According to a second aspect of the invention, there is provided a linkage for coupling a reciprocal actuator to separate butterfly valves each comprising a spindle pivotable in a valve housing, each spindle having an operating lever coupled thereto, said linkage comprising first and second arms having respective first ends coupled at a first pivot, a second end of the first arm being for pivotal connection to the operating lever of a first spindle, a second end of the second arm being pivotally connected to one end of a third arm, and the other end of the third arm being for pivotal connection to the operating lever of a second spindle, wherein said first and second arms define in use an obtuse angle with respect to the respective lever, and said first pivot is connectable to an actuator whereby said first and second arms are adopted to push and pull in unison.

The linkage of the second aspect allows relative movement between the second and third arms in order to permit both butterfly valves to fully open and/or fully close.

In one embodiment of the second aspect, the first and second arms are substantially equal in length, and the effective length of said third arm is less than said second arm.

In one embodiment the third arm comprises a substantially straight link.

The linkage of the second aspect may include respective operating levers for attachment to spindles of the operating valves, In one embodiment both said levers are straight and comprise elongate members having a pivotal connection at the ends thereof In another embodiment the lever for connection to the third arm comprises an open frame with a connection at one corner for a respective spindle, and a pivotal connection midway along one side for the third arm. The pivotal connection of the third arm to the second arm may be adjacent another corner of the open frame. In one embodiment the open frame is rectangular or rhomboid, The open frame may comprise an abutment of a spring for biasing said third arm about the pivotal connection to the open frame, The spring may be a leaf spring which is tensioned in use at a threshold force corresponding to relative pivoting movement of the second and third arms. This threshold force corresponding to movement of an unsynchronized butterfly valve to the fully open or fully closed condition.

According to a third aspect of the invention there is provided a linkage for coupling a reciprocal actuator to separate butterfly valves each comprising a spindle pivotable in t5 a valve housing, each spindle having an operating lever coupled thereto, said linkage comprising first and second arms having respective first ends coupled at a first pivot, a second end of the first arm being for pivotal connection to the operating lever of a first spindle, and a second end of the second arm being for pivotal connection to the operating lever of a second spindle, wherein said first pivot comprises a pivot pin having a pivot axis, a first swivel joint on said pin for said first arm, a second swivel joint on said pin for said second arm, and a third swivel joint on said pin for connection to a third arm of an actuator, said swivel joints being in side-by-side relationship along said axis, and the inclination of said pin being variable in use.

In this arrangement inclination of the pin may be used to impact movement to one of the first and second arms, whilst the other of said arms remains relatively stationary, The respective swivel joints may be identical, and pemfit such articulation within an angular range of +30° about a mean condition. In the mean condition the pivot axis is substantially perpendicular to the longitudinal axis of the arms, In one embodiment the first and second swivel joints are on either side of the third swivel joint, and the swivel joints are substantially identical, each comprising a part-spherical ball having a bore to receive said pivot pin, and each ball being received in a part-spherical eye of a respective arm.

The linkages of the first, second and third aspects are applicable to a range of butterfly valves.

Typically, the butterfly valves are substantially identical in one embodiment and have respective operating levers of the same effective length; the operating levers may be identical except where a frame is used in the second embodiment.

In one embodiment of the first and second aspects, the first and second arms define an acute angle therebetween, preferably in the angle 20400.

In the third aspect of the invention the first and second arms may be substantially tS aligned, having relative angle of 100 or less between the open and closed conditions.

The butterfly valves may be pivoted in a single housing, or in adjacent separate housings. In one embodiment the actuator is mounted on an arm of the common housing, or on an arm of one of two separate housings. The housing material is typically cast iron, and the arm may be an integral cast arm. Alternatively the arm may be a fabrication, typically formed from sheet material, and attached to a housing by screw-threaded fasteners.

The actuator may be rotary or linear, double or single acting. The actuator may be electric, pneumatic or hydraulic.

The linkage of the invention may be combined with operating levers of the spindles of the butterfly valves, with an actuating arm or lever of an actuator, with the butterfly valves attached to operating levers, and with an actuator to form partial or complete sub-assemblies.

The invention also extends to a vehicle exhaust system incorporating the linkage, butterfly valves and actuator of the invention, to an engine so equipped, and to a vehicle having such an engine. The invention may be incorporated in many kinds of valve associated with an exhaust of a vehicle including exhaust gas recirculation and waste heat recovery.

BRIEF DESCRIPTION OF DRAWINGS

Other features of the invention will be apparent from the following description of several embodiments, illustrated by way of example only in the accompanying drawings in which: Fig. I is a perspective view of a first embodiment of the invention having a rotary actuator, and single valve body; Fig. 2 is a partial plan view corresponding to Fig. 7, and showing the closure valves in cross-section, in a first condition; Fig. 3 corresponds to Fig. 2 and shows the closure valves in a second condition; Fig. 4 is a perspective view of an alternative to the first embodiment, having separate valve bodies; Fig. 5 is a perspective view of another alternative to the first embodiment, having a linear actuator with a single valve body.

Fig. 6 is a partial plan view corresponding Fig. 5, and shows the closure valves in cross-section, in the first condition.

Fig. 7 is a perspective view of yet another embodiment corresponding to Fig. 1, having a linear actuator with separate valve bodies.

Fig. 8 is a perspective view of a second embodiment of the invention, having a rotary actuator, Fig. 9 is a partial plan view corresponding to Fig. 8 and showing the closure valves in the second condition.

Fig. 9a is an illustrative sectional view of a disc spring stack for the embodiment of Fig. 9; Fig. 10 is a perspective view of an alternative second embodiment, with linear actuator.

Fig, ii is a partial plan view corresponding to the embodiment of Fig. 10 with closure valves in the first condition.

Fig. 12 corresponding to Fig. 11 and has closure valves in the second condition.

Fig. 13 is a perspective view of another alternative to the second embodiment, with a rotary actuator and common valve body.

Fig. 14 is a perspective view similar to Fig. 13, but having a linear actuator and separate valve bodies.

Fig. 15 is a perspective view of a third embodiment of the invention with rotary actuator and separate valve bodies.

Fig. 16 is a partial plan view corresponding to Fig. 15 arid showing closure valves in the second condition.

Figs. 17a-17c are partial sectional views showing different conditions of the third embodiment.

Fig. 18 corresponds to Fig. 15 and shows an alternative third embodiment with linear actuator and single valve body.

Fig. 19 is a partial plan view corresponding to Fig. 18 and showing the closure valves in the second condition.

Fig. 20a-20c are partial sectional views showing different conditions of the third embodiment.

Fig. 21 is a perspective view of a fourth embodiment of the invention, with rotary actuator and single valve body.

Fig. 22 is a partial plan view corresponding to Fig. 21 and showing the closure valves in the first condition.

Fig. 23 is a partial plan view corresponding to Fig. 22 and showing the closure valves in the second condition. I5

Fig. 24 is a perspective view of the rhomboid frame and link assembly of Fig. 21.

Fig. 25 is a p'an view of the assembly of Fig. 24.

Fig. 26 is an enlarged cross-section on line 26-26' of Fig. 25.

Fig. 27 is a perspective view of the underside of the link of Fig. 24; and Fig. 28 is an atternative example of the fourth embodiment, with linear actuator.

DESCRIPTION OF EMBODIMENTS

Figs. 1-3 illustrate a first embodiment of the invention.

A twin actuator 10 comprises a cast metal body ii having twin bores 12, 13 within which are mounted respective butterfly valves comprising valve discs 14, 15 each mounted on, and activated via, a respective valve spindle 16, 17. The spindles 16, 17 are journalled in the body 11 at either end and have parallel axes.

Butterfly valves are well known, and the constructional details need not be further described here.

The body 11 is provided with opposed planar faces for attachment of individual flanged pipes, for example vehicle exhaust ducts, via threaded holes 18. The body could also be adapted for direct mounting to other apparatus defining fluid ducts, for example to an exhaust manifold of an internal combustion engine, a waste heat recovery unit or the like.

The body 11 includes an integrally cast arm 20 to which is attached a rotary actuator 21. The rotary actuator 21 may be of any desirable kind (electric, pneumatic or hydraulic) and provides a back and forth rotational output via a spindle 22. A linkage 23 connects the actuator spindle 22 to the valve spindles 16, 17. The actuator spindle may include a return spring to bias the actuator to one or other end condition, and may be double acting.

With reference to Fig. 2, the linkage 23 comprises a bell crank 24 mounted at one end for arcuate movement with the actuator spindle 22. The other end of the bell crank 24 comprises a pivot pin 25 to which are mounted respective ends of actuator arms 26, 27, one above the other. One arm 26 is pivoted at the other end to a lever 28 which is rotationally fixed to the valve spindle 16. A similar lever 29 is provided on the valve spindle 17, and the arm 27 is connected thereto via an intermediate pivoting link 30, and respective spindles, 31, 32. Accordingly the link 30 may in use pivot relative to both the arm 27 and the lever 29.

As illustrated the spindle 32 is retained by a spring clip 33 engaged in a circumferential spindle slot, the clip is of a well-known kind and need not be further described. The arm 27 is freely pivotable with respect to the link 30, and the link 30 is freely pivotable with respect to the lever 29.

Operation of the first embodiment is as follows, In the filly open condition of the valve discs 14, 15 the bell crank 24 is pivoted frilly clockwise by the actuator.

To close the discs 14, 15 in the bores 12, 13, the actuator is operated to rotate the spindle anti-clockwise, as indicated by arrow 34 (Fig. 2). The bell crank 24 pulls the arms 26, 27 to pivot the levers 28, 29 anti-clochvise.

S The linkage 23 is adjusted to ensure that the valve disc 5, associated with the arm 27, closes before the disc N. This condition is illustrated in Fig. 2. The arm 27 may for example be of a length to ensure this condition, or may include a threaded length adjuster (not shown) to enable the condition to be obtained.

From the condition of Fig. 2, further anti-clockwise motion of the spindle 22 causes relative pivoting of the link 30 and lever 29, so that additional movement of the arms 26 and 27 are possible. Since the arm 26 is directly connected to the lever 28, fill closing of the valve disc 14 is assured, as illustrated in Fig. 3; pivoting of link 30 and lever 29 is shown by arrows 35, 36, the additional motion of arm 26 by arrow 37, and tS the additional pivoting of valve disc t4 by arrow 38.

Upon opening of the valve disc 15, for example against a spindle stop (not shown), the link 30 allows reLative motion to permit further movement of the valve disc 14 to a corresponding stop.

Also illustrated in Fig. 1 are individual spiral springs 39 about each valve spindle 16, 17, which operate between the respective lever 28, 29 and the body 11 to provide a respective gas seal against the valve body It.

In the embodiment of Figs. 1-3 the actuator is arranged to tension the arms 26, 27 during closing motion; alternatively the actuator could be arranged to tension the arms during opening motion.

Fig. 4 illustrates an alternative embodiment in which an individual cast body 1 Ia, 1 lb is provided for each butterfly valve. The arm 20 is part of one of the bodies I I a.

Other parts are identical to the embodiment of Fig. I and carry the same reference numerals. Operation of the embodiment of Fig. 4 is as described for Fig. 1.

Figs. 5 and 6 illustrate a pneumatic strut actuator 40 for operating the valve discs of a twin bore valve body 11, of the kind illustrated in Fig. 1. Components common to Fig. I carrying the same reference numeral. The actuator 40 is double acting arid has a body 41 pivoted on an anchor 42 of a cast arm 20a, The actuator ram 43 terminates at a pivot 25a which corresponds to the pivot 25 of Fig. 1; the linkage 23 is of the same kind as illustrated in Fig. 1.

Inward movement of the ram 43 (as illustrated by arrow 44) moves the valve discs 14, in the closing direction, and complete closure of the valve discs is assured by relative motion of the link 30 and lever 29, as previously described. Outward movement of the ram 43 moves the valve discs 14, 15 in the opening direction.

Fig. 7 illustrates an arrangement corresponding to Fig. 4 (with separate valve bodies 1 la, 1 lb), but in association with a pneumatic actuator 40, as illustrated in Figs. 5 and 6. Common parts carrying the same reference numerals, and operation thereof is as previously described.

The linear pneumatic actuator 40 of Figs. 5-7 could be substituted by a linear electric or linear hydraulic actuator of similar form, having a body and a double acting ram, The actuator 40 of Figs. 5-7 is illustrated with inward movement of the ram 41 corresponding to closing movement of the butterfly valves, The actuator could however be arranged in the other sense, so that outward ram movement corresponds to closing movement of the butterfly valves.

The linear actuator could also be single acting against a resilient return force.

Fig. 8 illustrates an alternative embodiment, corresponding closely to the embodiment of Fig. 1, but in which the linkage parts associated with arm 27 are different.

Components common to Fig, I carry the same reference numerals.

As illustrated in Fig. 8, the arm 26 and lever 29 directly actuate valve disc 14, as previously described, The other arm is however comprised of two co-axial parts 27a, 27b between which a stack 27c of disc springs is provided. The respective ends of the arm assembly 27a, 27b, 27c are pivotably connected to the bell crank 24 and lever 29, and it will be observed that the link 3D is omitted.

The arrangement preferably ensures that applying tension to the arm 27a, 27b compresses the disc springs 27c; such an arrangement is illustrated schematically in Fig. 9a, but any suitable mechanism may be employed.

In operation, closure is as previously described, with the valve disc 15 closing before the valve disc 14. At this point compression of the spring stack 27 allows relative separation of the arm parts 27a, 27b, as indicated by arrow 47, to permit further motion of the arm 26, indicated by arrow 48 (Fig. 9). Thus the closure of both butterfly valves is assured.

Fig. 10 illustrates the linkage of Fig. 9 in conjunction with a linear actuator 49 of the kind described in relation to Figs. 5-7. In Fig. 10 the actuator 49 is mounted on a fabricated arm 2Db of sheet steel which is attached to the housing 11 by two screws 50. Operation of Fig. 10 is as previously described, and common parts carry the same reference numerals, In order to provide additional clearance, the arm 26 is distanced from the adjacent end of ram 27a by a tubular spacer 51, and the spindle 25 has a correspondingly increased length. At the body II, a cast boss 52 raises the lever 29, and a correspondingly longer spindle 17 is provided, The principles of the cast boss 52 and spacer 51 may also be applied to the embodiments of Figs. 1-9, as may the use of the fabricated arm 20b. A separate cast arm could of course be attached to the body by fasteners of any suitable kind, for example screws or rivets, and the ann 2Db may be attached to one of two separated bodies, of the kind illustration in Fig. 4.

Figs. and 12 correspond to the arrangement of Fig. ID, and show in Fig. II valve disc 15 only closed, and in Fig, 12 both valve discs N, S closed. In Fig. U the spring stack 27c has compressed to allow further relative movement of the arm 26 (and further inward movement of the actuator ram 53), Figs. 13 and 14 show alternative arrangements corresponding to Figs. 8-12 with a coil spring 54 in place of the spring stack. Other components are as previously described, and as explained above the kind of actuator 21, 40, the kind of support arm 20, 2Db and the kind of valve body I, I Ia, 1 lb are selected according to circumstances of use. Common parts carry the same reference numerals, and operation is as previously described, with the compression spring reducing in length to permit relative separation of the ann parts 27a, 27b.

In the embodiments of Figs. 8-14, the spring stack 27c or compression spring 54 may have pre-tension to ensure a small pre-load or threshold force prior to extension of the arm parts 27a, 27b. In some circumstances it may also be desirable to employ a tension spring in place of a compression spring.

Yet another alternative is illustrated in Figs. 15-17. Separate valve bodies ii a, 1 ib are provided. Again common parts carry the same reference numerals.

In Fig. 15 a rotary actuator has an output arm 24a situated between operating arms 26, 27 of the respective valve discs 14, 15. The pivot pin 25a is coupled to each arm 24a, 26, 27 by a respective swivel joint so that articulation is possible within an angular range permitted by the dimensions selected; the angular range may for example be up to 15° from the orthogonal axis.

As illustrated in Figs. 17a-17c, each swivel joint comprises a part spherical annulus 61a, 61b, 61c having a through bore to closely receive the pivot pin 25. Each annulus is mounted for swivelling in an eye of the corresponding arm 26, 24a, 27. The separation of the arms 26, 27 is accommodated at the connection to the respective lever 28, 29 by placing one arm above and one below, as illustrated in Fig. 15.

The arrangement of Figs. 15-17 allows closure of both valve discs 14, 15 regardless of which disc first reaches the fully closed condition.

If other discs reach the fully closed condition together, the orientation of the pivot pin 25a is on an orthogonal axis 62 (Fig. 17a).

If valve disc 15 reaches the fully closed condition before valve disc 14, continued pivoting of the arm 24a is permitted, and the pivot pin axis 62 inclines progressively until valve disc 14 is fully closed (Fig. 17b -angle 63).

On the other hand, first closing of valve disc 14 causes inclination of the pivot pin axis 62 in the other direction (Fig. 17c -angle 64).

Although relative movement of the arms 26, 27 is somewhat limited, it is in practice sufficient to overcome slight misalignment or maladjustment of the closing position of the valves.

It will also be appreciated that the arrangement of Figs. 15-17 also permits opening of the valves to be equalized, for example by motion of the respective valve discs against a stop. The mechanism allows either disc 14, 15 to reach the fully open condition first, and the other to be given the necessary additional movement, as required.

The wobble' linkage of Figs, S-7 may of course be used with linear and rotary actuators, and with separate or combined valve bodies. Figs. 18-20 show a corresponding arrangement with a linear actuator and combined valve body, common parts carrying common reference numerals.

Yet another embodiment of the invention is illustrated in Figs. 21-27. This embodiment is somewhat similar to Fig. 1, and common parts carry the same reference numeral; a link 30a similar to link 30, is pivoted on a rhomboid frame 70, which in turn constitutes the lever of the valve spindle 17.

The frame 70 has the spindle 17 attached at one corner thereof, and the connection to the operating arm 27 to the link 30a lies over opposite corner, so that the pivoting connection of link 30a to the rhomboid frame is midway along one side thereof The link 30a is biased by a leaf spring 71 in the anti-clockwise direction (as viewed in Fig. 23), the spring being anchored on a mount 72 on another side of the frame 70.

The link 30a lies against the face of the frame 70, and includes a blind track 73 on the underside thereof which is deeper at the ends than in the middle. The track 73 is engaged by a steel ball 74 housed partly within a recess of the rhomboid frame 70, and biased outwardly by a coil compression spring 75, The track is somewhat radiused (Fig. 26) to permit motion of the ball 74 from one end to the other, and the co-operating ball and track define arcuate end positions for the link 30a with respect to the frame 70. The radius of the track tends to urge the ball to one or other end condition.

In use, first closure of the valve disc 15 (Fig. 22) results in relative motion of the link 30a in opposition to the leaf spring 71, to permit further travel of the arm 26 -thereby to allow valve disc 14 to filly close (Fig. 23). t5

Fig. 28 illustrates a variant having a linear actuator 40 and fabricated arm 2Db.

The valves described in relation to Figs. 1-28 may be used as part of an exhaust brake of a vehicle and/or as part of a waste heat recovery system associated with an exhaust of a vehicle and/or with an exhaust gas recirculation system of a vehicle.

Variations and alterations to the invention are envisaged within the scope of the appended claims.

Claims

Claims I. A linkage for coupling a reciprocal actuator to separate butterfly valves each comprising a spindle pivotable in a valve housing, each spindle having an operating S lever coupled thereto, said linkage comprising first and second arms having respective first ends coupled at a first pivot, a second end of the first arm being for pivotal connection to the operating lever of a first spindle, a second end of the second arm being pivotally connected to the operating lever of a second spindle, wherein one of said first and second arms includes a spring between the ends thereof, said spring permitting relative axial movement of said ends when an axial force transmitted therethrough exceeds a threshold.
2. A linkage according to claim 1 wherein said spring is of spring steel.
3. A linkage according to claim 2 wherein said spring comprises a disc spring.
4. A linkage according to claim 3 wherein said spring comprises a plurality of disc springs.
5. A linkage according to claim 2 wherein said spring comprises a coil spring.
6. A linkage according to any preceding claim and further including a bell crank coupled to said pivot for attachment to a rotary actuator.
7. A linkage according to claim 1 or claim 2 wherein said first and second arms are unequal in length.
8. A linkage according to any preceding claim and further including operating levers for attachment to said first and second spindles, said levers being substantially equal in length.
9. A linkage according to claim 8 wherein said levers are identical.
10. A linkage according to any preceding daim wherein said first and second arms define in use an acute angle therebetween.
11. A linkage according to claim 10 wherein said acute angle is in the range 20-4QO
12. A linkage according to any of claims 1-11 and coupled to respective first and second spindles.
13. A linkage according to claim 12 wherein said first and second spindles are mounted in a common valve housing having valve bores for said butterfly valves.
14. A linkage according to claim 13 wherein said housing includes a fixed arm having an actuator mounted thereon, said actuator having an output member connected to said first pivot.
15. A linkage according to claim 14 wherein said fixed arm is integral with said valve housing.
16. A linkage according to claim 14 or claim 15 wherein said actuator is a rotary actuator.
17. A linkage according to claim 14 or claim 15 wherein said actuator is a linear actuator.
18. A linkage according to claim 16 or claim 17 wherein said actuator is one ofan electric, a pneumatic and a hydraulic actuator.
19. A linkage according to any of claims 1-18 applied to parallel butterfly valves associated with one of an exhaust brake of a vehicle, an exhaust gas recirculation system of a vehicle and a waste heat recovery system associated with an exhaust of a vehicle.
20. A twin butterfly valve incorporating the linkage of any of claims 1-18.
21. A vehicle incinding the butterfly valve of claim 20.
22. A linkage substantially as described herein with reference to the accompanying drawings.