Driving mechanism, function part and shut-off valve

The invention relates to a pneumatic, reciprocating rotary driving mechanism unit for operating a shut-off member in a shut-off valve, comprising a substantially closed housing, in which a drive shaft (30) is journalled, a pneumatic control valve (39-42) for controlling said drive shaft and first signal transmitting means (54, 55) for delivering control signals to said pneumatic control valve, wherein the housing consists of a base part (48), in which the drive shaft and the pneumatic control valve are present, and a first function part (53), in which the first signal transmitting means are present, which first function part is detachably and exchangeably connected to said base part so as to make it possible to exchange said first function part for a second function part containing second signal transmitting means of a type for the purpose of changing the manner in which the drive shaft can be controlled.

BACKGROUND OF THE INVENTION

The invention relates to a pneumatic, reciprocating rotary driving mechanism unit for operating a shut-off member in a shut-off valve, comprising a substantially closed housing, in which a drive shaft is journalled which can be connected to said shut-off member, a pneumatic control valve for controlling said drive shaft and first signal transmitting means for delivering control signals to said pneumatic control valve. The driving mechanism as disclosed in Dutch laid-open publication no. 7512312, which is used with peripheral equipment in practice, fits the above description. Such driving mechanisms are generally used for operating butterfly valves, plug valves and ball valves as well as also lamellas in dampers, wherein the angle of rotation of the drive shaft is limited to maximally 180° and usually to 90°. To this end, all kinds of pneumatic components and control equipment are mounted on the outside of the housing, such as the control valve and a signal transmitter.

In a functional situation wherein the drive shaft only needs to be capable of taking up two positions corresponding with an open position and a closed position of the shut-off valve, such peripherals generally comprise a so-called solenoid which is mounted on the outside of the housing, which solenoid converts the electrical control signals from a central electronic control system into pneumatic control signals for operating a pneumatic control valve, which also forms part of the solenoid. A switch box is mounted on to the housing via a bridge, in line with the free end of the drive shaft, which switchbox transmits information about, amongst other things, the actual rotational position of the drive shaft to the central control system, such as a PLC unit. The switch box and the solenoid are interconnected by means of a line outside of the housing for the purpose of exchanging information.

In the functional situation wherein the drive shaft is to be driven in a modulating manner, that is, enabling continuously variable adjustment of the valve between an open position and a closed position, a so-called positioner is mounted on the outside of the housing instead of said solenoid and said switch box, which positioner is capable of continuously variable adjustment of the shut-off member of the shut-off valve between 0-100%, for example by means of a control current of 4-20 mA. Lines are provided outside of the housing for operating the shut-off member.

Units such as a solenoid, a switch box or a positioner must be capable of communication with all kinds of control equipment. This implies that a great many variants of each of the aforesaid components are required. As a result of this it has appeared to be very difficult, costly and time-consuming in practice to change the functionality of a pneumatic driving mechanism. In addition, the driving mechanisms according to the prior art are quite vulnerable, due to the way in which the peripherals are connected to the housing and to each other.

The object of the invention is to provide a solution for the above drawbacks and to meet the aforesaid need. In order to accomplish that objective, the driving mechanism according to the invention is characterized in that the housing consists of a base part, in which the drive shaft and the pneumatic control valve are present, and a first function part, in which the first signal transmitting means are present, which first function part is detachably and exchangeably connected to said base part so as to make it possible to exchange said first function part for a second function part containing second signal transmitting means of a type different from the first signal transmitting means, which first function part is exchanged for the second function part for the purpose of changing the manner in which the drive shaft can be controlled. The invention is based on the insight that some of the components of which the driving mechanism is built up are required for every function that is desired, whilst other components are only required for specific functions. According to the invention, the former components are housed in the base part. By housing the latter components in a specific function part, which is detachably connected to the base part, a simple exchangeability of the function part and thus of the functionality of the pneumatic driving mechanism is effected without any adaptations or the exchange of the base part being required. It is not so much the pneumatic components that make up the difference between the function parts mutually, but rather the electronic components that are present therein, since it is the latter that determine the functionality in question and that can be considered as signal transmitting means. The function part can on the one hand be designed as a black box without control buttons or information panels, but on the other hand it may be designed to comprise sensors, switches, various electrical terminals, manual operation provisions, for example for emergency operation, LED's, LCD's, etc. The integration thereof in the function part obviates the need for additional electrical wiring and/or pneumatic connections.

As an aside it is noted that German utility model DE 298 18075 U1 discloses a fluidic linear actuator comprising a housing in which a piston whose piston rod extends outside the housing is present. Present on the housing is a two-part control housing. A fluidic feed connection is formed in the first part, whilst an electronic control unit is present in the second part, whereby there is an electrical connection between the first part and the second part so as to enable electronic data transfer between the first part and the second part. Present in the first part is a signal transmitting valve, which delivers pneumatic control signals to a pneumatic control valve which is also present in the first part. The actuator disclosed in said publication is only suitable for actuating the piston in one and the same manner, whereby the second part, on the other hand, can be adapted to enable communication with various types of artificial intelligence remote from the actuator.

Advantageously, at least one mechanical portion of a position indicator, which is movable in dependence on the rotation of the drive shaft, is housed in the base part for the purpose of showing and/or transmitting information about the rotational position of the drive shaft. Integration of the position indicator in the base part on the one hand makes it possible to realise a compact and robust construction, whilst on the other hand no vulnerable external lines for the control system are required. By housing the mechanical components of the position indicator at least in part in the base part and housing the electronics in the function part it becomes possible to prevent a situation wherein mechanisms operate between the base part and the function part in a vulnerable manner. In addition, no mechanical adjustment of the position indicator is required when a function part is being connected to a base part. The function part converts the movement or the position of the mechanical part of the position indicator into electronic information for feedback to a control system.

SUMMARY OF THE INVENTION

According to one preferred embodiment, the base part comprises two interconnected housing parts, wherein the drive shaft is present in the first housing part and the second housing part accommodates the control valve. This is advantageous, both as regards the production and as regards the maintenance of the driving mechanism, since the two housing parts are accessible independently of each other in disconnected condition.

According to one preferred embodiment, the mechanical portion of the position indicator is at least partially housed within the second housing part. This makes for a compact construction.

Furthermore it is very advantageous if the first function part is detachably connected to the second housing part, since this makes it possible to use short communication lines between the pneumatic control valve and the signal transmitting means in question, which reduces the vulnerability thereof, whilst furthermore the distance between a mechanical portion of a position indicator in the second housing part and the electronics in the function part that processes information on the position of the position indicator can be small.

The second housing part is preferably disposed outside the central axis of the drive shaft, so that both ends of the drive shaft will be available, for example for the rotary drive of external means or for a visual position indicator.

According to a very advantageous embodiment, the shapes of the base part and the function part are complementary to each other. The absence of connecting pieces, such as bridges, obviates the need to use vulnerable lines via or along such a connecting piece between the base part and the function part. In addition, the driving mechanism, including the base part and the function part, will look as one unit.

If, in accordance with one preferred embodiment of the invention, each function part comprises all function-specific electronics associated with the function of the function part in question, a maximum degree of flexibility is obtained for changing the function of the driving mechanism, if desired. In addition, this obviates the need for electronic signal transmission between the base part and the function part. Such electronic signal transmission is vulnerable and for that reason not sufficiently reliable for certain applications, for example owing to corrosion of the contact points of plugs. In addition to that, only the function part needs to be subjected to a test in the case of safety inspections carried out in connection with the risk of explosion.

In order to enhance safety when using a driving mechanism according to the invention, the electronics are preferably embedded in order to reduce the risk of fire or explosion, because the risk of arcing is eliminated.

A very useful embodiment of a driving mechanism according to the invention is obtained if one of said first function part and said second function part is suitable for positioning the drive shaft in two positions only and the other one of said first function part and said second function part is suitable for positioning the drive shaft in an intermediate position between said two positions as well. Thus it is possible without adapting or exchanging the base part, but only by exchanging the function part, to convert the driving mechanism from a situation wherein the drive shaft can only be placed in two positions corresponding with an open position and a closed position of the shut-off member of a shut-off valve, to a situation wherein the driving mechanism is also suitable for placing the shut-off member in a position between an open position and a closed position, for example in a half-open position. This may be useful, for example, when testing shut-off members in connection with emergency situations. Such shut-off members are sometimes referred to as Emergency Shutdown Valves, whereby it is ascertained annually whether a shut-off member can be opened 10%, which is a clear indication that the valve is satisfactory. Another possible use of the driving mechanism is in the filling of bags with powdery material, wherein a distinction is made between coarse metering and fine metering.

In such a situation it may be very advantageous if the position between an open position and a closed position can be selected at random, thereby creating a modulating situation, to which end the driving mechanism is advantageously characterized in that the other one of the first function part and the second function part is suitable for placing the drive shaft in any desired position between the aforesaid two positions.

Preferably, the control signals from the first signal transmitting means and from the second signal transmitting means are pneumatic signals, which leads to a reduced cost price on the one hand and to greater reliability on the other hand.

Preferably, one of the facing sides of said function part and said base part, or both, is (are) provided with a pattern, as a result of which at least part of the pneumatic circuit for the pneumatic control signals is formed between the function part and the base part in the situation wherein the function part is connected to the base part, all this for the purpose of transmitting pneumatic signals from the signal transmitting means to the pneumatic control valve. Such a configuration is advantageous with regard to obtaining a compact assembly of base part and function part.

In particular in the case of such pneumatic control signals it is advantageous if the first signal transmitting means and the second signal transmitting means each comprise a pneumatic valve for delivering pneumatic control signals to the pneumatic control valve.

In order to obtain an even more compact construction, the function part comprises a mechanical portion of the position indicator, just like the base part, which mechanical portion can be connected to the mechanical part of the position indicator that is housed in the base part.

To this end, the base part is preferably provided with a recess for accommodating the mechanical portion of the position indicator that is present in the function part, as a result of which an optimal screening of the mechanical parts of the position indicator is achieved. Reading of the position indicator is possible, for example, because the mechanical portion of the position indicator that is present in the function part is fitted with a magnet, whose position can be determined by means of a magneto-resistive sensor which is likewise present in the function part.

In view of the inherent exchangeability of the function part, it is of major importance to state that the invention also relates to a function part for use with a driving mechanism according to the above-described invention. Such a function part includes signal transmitting means for converting an electrical control signal into a pneumatic control signal for a pneumatic control valve which is present in a base part of the driving mechanism.

The invention furthermore relates to a shut-off valve comprising a shut-off member, which is provided with a driving mechanism according to the above-described invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1schematically shows a pneumatic driving mechanism1, including the pneumatic components. Driving mechanism1comprises an outgoing drive shaft2, which is rotatably journalled in a cylindrical space3. Space3furthermore accommodates pistons4and5, which are capable of movement towards each other and away from each other, which pistons are provided with projecting racks6and7, respectively, on their sides facing towards each other. Disposed between said racks is the outgoing shaft2, which is circumferentially provided with teeth, so that movement of pistons4and5will result in rotation of outgoing shaft2. Reference is made to Dutch laid-open publication NL 75 12 312 for a more detailed description of such a driving mechanism.

Roughly, such driving mechanisms can be divided into two different types: the single-acting type as shown inFIGS. 1 and 2and the double-acting type as shown inFIGS. 3 and 4.

In the case of the single-acting type, the movement apart is obtained through pressure build-up in the space8between pistons4and5. The movement together of pistons4and5is effected by the spring pressure of springs9and10, which are positioned between the end walls of cylindrical space3and pistons4and5, respectively. The movement together of the pistons takes place upon release of the pressure in space8. Air valve11and vent valve12are provided for the purpose of building-up and releasing the pressure in space8. The two valves11and12are controlled by means of a common pneumatic components control signal13,14from signal transmitting valve15. Signal transmitting valve15is in turn controlled by means of an electric signal (not shown) from an electronic control system. Valves11and15are fed by an external compressor16. In the illustrated situation, signal transmitting valve15has not been excited, as a result of which air valve11and vent valve12are in their inoperative position. There will be no overpressure in space8. Excitation of signal transmitting valve15will cause air valve11to open, whilst vent valve12will close. A pressure build-up will take place in space8, as a result of which cylinders4and5will move apart, thus rotating drive shaft2.

The driving mechanism as described so far does not differ from the prior art. The invention concerns the manner in which the various components of the driving mechanism are arranged. To this end a distinction is made between a base part17and a function part18. Base part17comprises the space3and all the components present therein, as well as air valve11and vent valve12. Function part18comprises a signal transmitting valve15. The lines for pneumatic signals13and14and the pressure line19between compressor16and air valve11connect to each other at the boundary surface between base part17and function part18. Base part17is subdivided into a first base part21and a second base part22, as indicated by means of dotted line20. The two base parts21and22are detachably interconnected, which makes for easy maintenance and manufacture of base part17. The two base parts21and22form one unit, just like base part17and function part18form one unit. Also base part17and function part18are detachably interconnected, like first base part21and base part22. This makes it possible to exchange function part18for another function part.

As already described above, outgoing shaft2can take up two positions when the driving mechanism as shown inFIG. 1is used, resulting in an open position and a closed position of a shut-off valve. When the user of driving mechanism1wishes to upgrade the driving mechanism to obtain a continuously variable driving mechanism, he can do so by exchanging function part18for a function part of a type which is suitable for that purpose. Such a situation is shown in FIG.2. Said figure shows a driving mechanism23comprising a base part17which is completely identical to the base part17as described with reference to FIG.1. In this case, however, a function part24is connected to base part17instead of function part18. Function part24comprises two signal transmitting valves25,26, which are capable of delivering signals27and28, respectively, to air valve11and vent valve12, respectively, independently of each other. The use of valves25and26thus enables a continuously variable operation of the single-acting driving mechanism23, in a manner which is known per se and which will not be explained in more detail herein. A simple exchange of the function part thus suffices to change the functionality of a driving mechanism.

A comparable situation exists for double-acting driving mechanisms as shown inFIGS. 3 and 4. Double-acting driving mechanism29comprises an outgoing drive shaft30, which is rotatably journalled in a cylindrical space31. Furthermore present in space31are pistons32and33, which are provided with racks34and35, respectively. When the double-acting principle is used, pressure build-up can take place not only in the space36between said pistons, but also in the spaces37,38between the end walls of cylindrical space31and pistons32and33, respectively. As is the case with the single-acting principle, the movement apart of pistons32and33is obtained as a result of pressure build-up in the intermediate space36. The movement together of pistons32and33, however, is in this case effected as a result of pressure being built up in spaces37and38and the simultaneous release of pressure in space36. The build-up of pressure in space36is accompanied by the release of pressure in spaces37and38. The build-up and release of pressure in spaces36,37and38takes place by means of air valve39and vent valve40for space36and by means of air valve41and vent valve42for spaces37and38. The operation of valves39and40is similar to that of valves11and12inFIGS. 1 and 2. The same holds for valves41and42, with this understanding that the latter valves are in communication with end spaces37and38instead of with central space36. All four valves39,40,41and42are controlled by a common pneumatic control signal43,44,45and46from signal transmitting valve47. Signal transmitting valve47is in turn controlled by an electrical signal (not shown) from an electronic control system. Since signal transmitting valve47is only capable of joint excitation of valves39,40,41and42, drive shaft30can only take up two positions.

As is the case with the single-acting driving mechanisms1and23that are shown inFIGS. 1 and 2, a distinction can be made as regards the housing of the driving mechanism between a base part48, which is subdivided into a first base part49and a second base part50, and a function part51, which parts are all interconnected in the same way as with driving mechanisms1and23. An upgrade of driving mechanism29to obtain a continuously variable driving mechanism can take place by exchanging function part51for another type of function part, which is shown in FIG.4. Function part53forms the only difference between driving mechanism52and driving mechanism29. Function part53includes two signal transmitting valves54,55. Valve54delivers a common signal43,46to air valve39and vent valve42, respectively. Valve55delivers a common signal44,45to vent valve40and air valve41, respectively. Valves54and55are controlled independently of each other by a control system (not shown). The use of valves54and55makes it possible to set the pressures in space36on the one hand and spaces37and38on the other hand independently of each other, thus enabling a continuously variable setting of drive shaft30. Exchanging function part51inFIG. 3for function part53as shown inFIG. 4makes it possible in a simple manner to convert the driving mechanism29, by means of which only two positions of the drive shaft30can be realised, into a continuously variable driving mechanism52.

InFIGS. 1-4, connection of the driving mechanism in question to the compressor16takes place via the function part. It is also possible to realise the connection via the base part, preferably via the second base part.

FIG. 5is a perspective view of a base part60comprising a first base part61and a second base part62. First base part61is substantially cylindrical in shape. An opening63is formed in the upper side of base part61, in contact surface64thereof, through which opening the hollow end65of the drive shaft is visible. The bottom side of the base part is identical in shape. Said hollow end is internally provided with teeth66, via which a force can be transmitted to a shut-off member of a shut-off valve, or to which a position indicator can be operatively connected, as is shown in FIG.7. Second base part62is substantially block-shaped and is integral with first base part61as regards its shape. Second base part62is fixed to first base part61by means of Allen screws. Internally threaded hollow pins68are provided for fixing a function part to second base part62. Second base part50, and with it the driving mechanism in question, can be connected to a compressor via connection69. Connections70and71function to vent spaces such as spaces36,37and38in FIG.3. Behind screw cap72there is finally located a space in which a speed control valve (not shown) for controlling the speed at which the driving mechanism operates may be present.

FIGS. 6A-6Cshow three different types of function parts75,76and77. Function parts75,76and77are provided with flanges79on their connecting side, via which flanges the function parts can be connected to a second base part. Allen screws79are provided for that purpose. Connections80are used for the electronic transfer of information between a control system and the function part. Function parts75,76and77are identical as regards their shape, with this exception that they are different in length. Function part75is only adapted for opening and closing a shut-off member. Function part76is likewise adapted for opening and closing the shut-off member, but said function part is suitable for digital communication with a control system via a digital bus. Function parts75and76each comprise two control buttons81and three LED indicators82. Function part77is finally adapted for continuously variable adjustment of a shut-off member, wherein digital transfer information likewise takes place via a bus. Furthermore, a more extensive control panel comprising five control buttons83and an LCD display84is present, by means of which a menu-driven control is realised. The function parts and their functions as shown inFIGS. 6A-6Conly form a limited selection of the total amount of possible function parts and functions. It is the electronics that are present in the function part which ultimately determine the function and in part the appearance of the function part. Attention is furthermore drawn in this connection to the possibility of effecting a continuously variable adjustment of a shut-off member by means of an analog signal.

FIG. 7shows the base part60comprising the first base part61and the second base part62that is shown in FIG.5. Connected to second base part62is a function part90similar to the function parts that are shown inFIGS. 6A-6C. The shapes of the two parts at the joining surfaces between the second base part62and function part90are complementary to each other, as a result of which the two parts form one unit. A gasket (not shown) is provided so as to realise a sealed connection between second base part62and function part90. All the required electrical or pneumatic connections between second base part62and function part90take place via the boundary surface between said parts. Mounted on the upper side is a position indicator91, from which the angular position of the drive shaft can be read directly.

FIG. 8is a partially sectional view of a position indicator100for indicating the angular position of drive shaft101, a free end65of which is shown in FIG.5. Said drive shaft is built up of a cylindrical portion102, which is concentric with central axis103, and a cam portion104. A feeler pin106abuts against the surface of cam portion104under the influence of the spring pressure of spring105, which is supported on an inward shoulder122of guide bush107. Feeler pin106is disposed in the interior of guide bush107, which abuts against the cylindrical portion102under the influence of the spring pressure of spring105, which is supported on a fixed edge (not shown) which is present in second base part62. Cam portion104is shaped in such a manner that the degree to which feeler pin106extends outside guide bush107increases along with the angular distortion of drive shaft101within the operating range of 90°. Two magnets109,110are mounted on the end of feeler pin106opposite drive shaft101. Two Reed switches111,112are present opposite and on either side of magnet110. Each Reed switch111,112is capable of taking up an open position and a closed position, in dependence on the translation position of feeler pin106and magnet110. One of the two positions of Reed switch111corresponds to an open position of a shut-off member, whilst one of the two positions of Reed switch112corresponds to a closed position of a shut-off member. Reed switches111,112are capable of driving a solenoid (not shown) either directly or after transformation of the electrical signal from Reed switches111,112by suitable electronics. The spatial orientation of Reed switches111,112can be adjusted by pivoting the arms123,124about pivot points113,114by means of adjusting screws115,116. The Reed switches can thus be calibrated. Adjusting screws115,116are retained in a form-locked manner in the direction of feeler pin106in U-shaped ends of arms123,124extending perpendicularly to the plane of drawing. Reed switches111,112are connected, via flexible bridges117,118in which the pivot points113,114are located, to a frame119which includes a third arm120extending perpendicularly to said feeler pin. A magneto-resistive sensor121, which is known per se, is present on the lower end of said arm, which sensor is capable of delivering signals in dependence on the translation position of feeler pin106on account of the shifting of the lines of flux and the simultaneous changing of the orientation of said lines of flux from magnet109through sensor121. In this way it is possible to derive the angular position between the open position and the closed position of the shut-off member from the translation position of feeler pin106.

The distribution of the various parts of the position indicator over first base part61, second base part62and function part90is schematically illustrated in dotted lines. It is noted that Reed switches111,113extend partially into second base part61with their arms123,124indeed, as does third arm120carrying the magneto-resistive sensor121, but that they are fixedly connected to function part90. The transfer of information between second base part61and function part90takes place entirely without any physical contact.

FIGS. 9A,9B and9C show a second embodiment of a position indicator. As is the case in the situation according toFIG. 8, a drive shaft130is provided, which comprises a curved cam portion131on part of its circumference. The end133of feeler pin134is pushed against cam portion131under the influence of the action of compression spring132, as a result of which the longitudinal position of feeler pin134is indicative of the rotational position of drive shaft130. Feeler pin134is surrounded by a guide bush107, whose function is similar to that of guide bush107of FIG.8. The end136of feeler pin134opposite end133is positioned in a recess137, which is present in the upper side of a run-on shoe138. Feeler pin134extends from cam portion131, via passage139(see FIG.10), into a recessed space140of a second base part141similar to base part62ofFIG. 7, which can be connected, via joining surface142, to a first base part (not shown) similar to first base part61of FIG.7. Function part143is provided with a projecting housing part144, which accommodates run-on shoe138and compression spring132, amongst other parts. In the situation wherein second base part141and function part143are interconnected, projecting housing part143extends within the recessed space140. When said connection is being made, the end136of feeler pin134slides over the sloping surface145of run-on shoe138until the end136slips into recess137, in which situation compression spring132ensures that there is contact between run-on shoe138and the end136of feeler pin134. In this connection it is important to note that while the connection between function part143and second base part141is being made, the longitudinal position of feeler pin134is undefined. In order to be able to make the above-described connection in a sliding manner, a gap146is formed in projecting housing part144, thus enabling relative movement of said end136while the connection is being made. A first end147of guide bush135which, incidentally, has a compound structure, butts against the edges of said gap146. The second end148of guide bush135positioned opposite said first end147butts against the outer circumference of drive shaft130outside cam portion131. This provides compensation for radial movement of the drive shaft130that may occur, for example as a result of play in the bearings in question. A compression spring149is provided for the purpose of effecting a proper contact between guide bush135on the one hand and drive shaft130and the edges of gap146on the other hand, which compression spring is operative between two parts of the projecting part143on either side of a gap150, whose end151functions as a virtual pivot point between the two parts. The projecting part144forms part of a frame152, which is largely positioned within the housing of function part143. All kinds of electronic devices (not shown) required for the proper functioning of the driving mechanism as a whole are mounted on said frame152. Second base part141does not comprise any electronics at all. Present within compression spring132is a pin, which extends from the bottom side of run-on shoe138in line with feeler pin134. A magnet154similar to magnet109is attached to said pin within compression spring132, whilst a magneto-resistive sensor155similar to sensor121inFIG. 8, is present within projecting portion144in the immediate vicinity of the path along which said magnet154can move under the influence of rotation of shaft130. Said magneto-resistive sensor155makes it possible to convert translating movements of magnet154caused by rotation of drive shaft130into electronic signals which can be utilized by the control system of the driving mechanism in question.

As is shown inFIG. 10, the second base part141is provided with a relief pattern153on its side facing towards function part143. The side of the function part143that faces towards second base part141(which is not shown) is substantially flat, as a result of which a pattern of channels is formed between the two facing sides in the situation wherein function part143is connected to second base part141, via which pneumatic control signals from two signal transmitting valves, such as valves54and55inFIG. 4, which are present in function part143can be passed on to a number of air valves, such as valves39,40,41and42inFIG. 4, within second base part141for a correct control of the driving mechanism.