The invention regards at least one special use of a closable/openable fluid flow valve formed in accordance with the present invention, namely as a modulating valve designed for continuous control of the fluid flow passing through the valve at any time.

Through a method that is also included in the present invention, measures are taken to dampen the final movement of the valve body against the seat when establishing the closed valve position and its opening movement away from the seat, where at the end of the valve body facing the seat, there is provided an annular/sleeve-shaped stopper, and where the inside of the latter end of the valve body is formed with a conical surface for co-operation with a complementary stop face on the stopper.

Fluid that due to the special internal shaping of the valve construction has been guided in between co-operating conical surfaces by one or the other end of the valve body and the seat or the stopper, acts as a damping medium during the final part of the relative movement of the conical surfaces towards each other.

An annulus enclosing the end portion of the valve body closest to the seat may contain a helical compression spring, and will be in fluid communication with fluid located between co-operating conical surfaces at one or the other end of the valve body, depending on whether the valve is about to close or whether the opening movement is about to end.

Said annulus is defined axially between an outward flange of a guide bush that forms a part of the valve housing furthest

away from the seat, and a stepped portion of the valve body, so that the spring in the annulus is compressed axially when the valve body is pulled away from the seat. This annulus acts as a damping chamber during control.

In a referred embodiment, the valve body may have at least one reaction surface facing away from the intended direction of fluid flow, so that the flowing fluid acts on said reaction surface, carrying the valve body towards the seat in order to maintain a closed valve position, provided other forces acting on the valve body in a direction opposite the direction of fluid flow are smaller than the force of the fluid acting on the reaction surface of the valve body.

Advantageously, said other forces are generated by an electromagnetic coil enclosing the valve housing and a portion of the sleeve-shaped valve body acting as magnet armature.

The valve may belong to a valve type that goes by the name "coaxial valves", where the tubular valve housing, a central, perforated circular disc-shaped seat body and a linear, reciprocating sleeve-shaped valve body are arranged coaxially relative to each other, thus having one common rectilinear longitudinal axis.

In one known embodiment of such a coaxial valve designed for concentric mounting in a pipe line in which flows a fluid made up of a gaseous or liquid medium or gelatinous medium, and where the fluid/medium may also be abrasive, aggressive and/or contaminated, the gable face of the sleeve-shaped valve body forms, by the end most proximal to the seat, a flat stop face that is parallel to the opposite circular face

of the seat body, i. e. the stop face of the valve body and opposite face of the seat-forming circular disc are essentially perpendicular on said common rectilinear longitudinal axis.

The fluid/medium that is to be regulated/controlled flows through the valve body and is carried past the valve disc with substantial changes in direction relative to the intended axial direction of flow.

Such coaxial valves are highly versatile and usable, and so have a wide range of applications. They are known for being reliable in operation and ensure high performance. They further distinguish themselves in a favourable respect by being essentially completely balanced with regard to pressure, so that a potential inlet pressure does not have an effect on the opening/closing characteristics of the valve.

The construction of coaxial valves is very simple, and the operation is based on the simplest principles of operation.

However, one serious disadvantage of valve constructions of the type mentioned by way of introduction consists in the fluid flow through the valve being subjected to at least one substantial change in direction of flow as it flows out of the valve body and passes the circular seat. Another serious disadvantage of this known type of valve constructions is that it is necessary to equip the sleeve-shaped valve body with external sliding seals. The construction of the valve requires a plane annular stop face portion on the adjacent end of the valve body in order to ensure a tight seal at the seat when the valve is closed. The outer periphery of said sealing stop face portion of the valve body must reach a

considerable distance outside the orifice-defining, circular inner peripheral edge of the valve body in order to ensure the desired sealing effect with a high degree of reliability.

These requirements concerning the closing characteristics of the valve will inevitably lead to the sleeve-shaped valve body having to be dimensioned so as to give a large wall thickness and a reduced bore diameter, which is highly unfavourable and undesirable in the case of a fluid flow valve of this general type.

Another disadvantage of the coaxial type valve construction mentioned is that the highly simplified design of the valve seat and body makes it difficult (without significant modifications of the structural construction of the valve) to bring about differential choking with a high degree of accuracy. The large deviation in direction of flow at the seat causes undesirable turbulence phenomena, thus affecting the fluid flow in the area of the seat in a negative direction.

A main object of the present invention has therefore been to remedy deficiencies, disadvantages and limitations on use associated with prior art, and also bring about technical benefits in other related respects.

Said object is essentially realised through a device by a closable fluid flow valve designed in accordance with the preamble of claim 1, which also exhibits the distinctive features given in the characterising part of claim 1.

The use and method associated with such a valve construction is characterised by the characteristics given in individual claims.

Advantageous though secondary characteristics of the valve construction appear from the dependent claims, the content of which has a real connection to the invention according to the independent apparatus claim, claim 1.

The seat body is formed as a hollow body with a conically tapering external surface portion facing the valve body, wherein at least two flow orifices terminate, either directly or via a reducing cavity. The conical surface portions enclosing the outer mouths of each flow orifice will essentially be covered under sealing abutment of a complementary, conical, circumferentially extending, non- perforated surface portion formed on the inside of an adjacent end portion of the valve body.

When this end of the valve body, in combination with the seat, is to effect closing of the valve, it is, as a result of the co-operating surface portions that slide into each other, guided in towards a final position in which the now sealingly abutting surface portions displace fluid while dampening the end of the closing.

In a longitudinal plane of symmetry through the valve construction, the outer contour of the seat body will be represented by two diametrically opposed generatrices.

Naturally, the same will hold for an inner contour of the complementary conical cavity of the valve body in the end portion.

The internal conical cavity at the end of the valve body most proximal to the seat will in said axial plane of symmetry be defined by two diametrically opposed generatrices.

Such a generatrix may be imagined to form the hypotenuse in a right triangle, where a leg is assumed to extend at right angles to said plane. It is obvious that the hypotenuse will have a superior longitudinal extent when it comes to covering, during"overlapping", orifices formed in a complementary inclined/conical surface. The internal, effective abutment surface of the valve body has a significantly smaller dimension in a plane perpendicular on said common longitudinal axis.

Thus the sleeve-shaped valve body has a large covering area with regard to closing the orifices in the seat in a sealing manner and in this closed valve position, with a good margin, project outside the mouths of the orifices at the conical seat surface in order to ensure the sealing action. At the same time, the sleeve wall by the valve body may be reduced relative to co-operating abutment surfaces on the seat and on the valve body, where the abutment surfaces run more or less at right angles to the longitudinal axis of the sleeve-shaped valve body. A reduction of the wall thickness of the valve body allows its through bore, through which the fluid flows, to be increased.

In a practical embodiment, the angle at the apex of the cone forming the conical surface portion of the seat body may be e. g. 60°. Due to the risk of the valve body wedging and getting stuck on the outside of the seat body, the amount of taper should not be too small. In an alternative embodiment,

the actual seat surfaces may be arranged radially, perpendicularly on the centre line of the valve, for the purpose of completely avoiding frictional forces arising between the seat body and the valve body.

Conical abutment surfaces on the outside of the seat body and internally of the co-operating end of the valve body have been found to reduce the pull which the electromagnet must provide in order to influence the valve body acting as magnet armature and pull it away from the closed position towards the open position. This favourable feature is caused by the fact that only part of the closing force caused by the differential pressure across the valve multiplied by the orifice area of the valve, acts in the axial direction of the valve. Thus the construction of the valve causes a relatively large orifice area to be uncovered by means of a relatively small axial force.

By connecting the magnet coil to an appropriate control unit, the valve may be used as a modulating valve.

The following describes a non-limiting example of an at present selected, preferred embodiment of a closable fluid flow valve, where the device according to the invention has been realised.

Reference is made to the enclosed drawings, in which: Figure 1 is an axial section through an assembled valve construction according to the invention, shown in the closed position;

Figure 2 shows the same, but with the valve in an intermediate position between the closed and the fully open positions; Figure 3 shows the same, but with the valve in the fully open position; Figure 4 is a side view of an embodiment of a seat body shown separately; Figure 5 is a side view of an alternative embodiment of a seat body; and Figure 6 is a side view of yet another alternative embodiment of a seat body, also showing a section of the valve body.

A principally straight, cylindrical/tubular valve housing generally denoted by reference number 10 is constructed from several screwed/soldered/glued together components with a common longitudinal axis 12.

These components consist of an outlet part 10a, an annular middle part 10b with an outward hexagon nut-shaped end flange lob', a guide bush 10c fixed to the latter, and an inlet part 10d.

A nut 14 is screwed onto the axially outer end of the inlet part 10d, which is formed with threads, which nut abuts the one end face of an electromagnetic coil 18 via a washer 16.

The other end face of the coil 18 abuts the opposite annular end face of the hexagon nut-shaped end flange 10b'on the

annular middle part 10b, which functionally is integral with the guide bush 10c.

The outlet part 10a of the valve housing has, at a certain distance from its outer end, an internal, annular shoulder face 10a'facing away from said outer end and serving as a bearing surface for a specially shaped seat body 20, which through the outside of a radially projecting flange portion 20a abuts the bearing surface 10a', and through an annular portion 20b'engages the bore 22 of the outlet part 10a.

The seat body has a central, solid front portion 20c and an outwardly tapering surface portion 20c located between this and the annular portion 20b, fig. 3, which surface portion is important to the intended function of the present invention.

The conical portion 20c'of the hollow seat body 20, see fig.

4, is formed with through orifices 24, which are given the desired orifice area and number, preferably distributed in an equidistant manner along an imaginary circle perpendicular to the longitudinal axis 12 and positioned approximately in the middle of the length of the cone between the end face 20d and an outer perimeter 20e that is parallel with the circumference of this, which perimeter ends the extent of the conical surface portion in the direction of the outer free end of the outlet part 10a.

The fluid flow orifices 24 of the seat 20 may be formed with quite a considerable individual orifice area, as the mouths of the orifices are located at an inclined/conical surface.

In order to cover these flow orifices 24 in the valve closed- position in a manner so as to achieve simultaneous sealing

covering of a circular, annular orifice mouth-defining surface portion of the conical surface around each orifice 24, use is made of an internal, complementary conical abutment surface portion 26a in the adjacent end portion of a reciprocating valve body 26 that forms the magnet armature of the electromagnetic coil 18.

The complementary conical internal abutment surface 26a of the valve body 26 is designed and dimensioned to allow it to be brought into-predetermined, tight-fitting abutting contact with the conical side face 20c'of the seat body 20, in order to close the valve. The inclined/conical abutment surfaces 26a, 20c'have a certain guiding effect when the valve closed-position is to be established.

It should be mentioned that the real contact surfaces, i. e. a circular orifice edge portion around each orifice 24 as far as the seat body 20 is concerned, and the corresponding abutment surface inside the end portion of the valve body 26, which abutment faces in the closed valve-position come into abutting contact with each other, face against face, do not necessarily have to follow the conical course of the conical outer surface 20c and co-operating inner, complementary surface 26a, but may have another inclined (at a different taper) or straight course relative to the longitudinal axis 12. However, the surface portions of said conical surfaces that enclose said real abutment faces participating actively in the establishment of tightly sealing surface contact, will normally follow the original conical course of the seat body 20 or valve body 26.

The outer end of the outlet part 10a opposite its free outer end, is formed with a radially projecting hexagon nut-shaped flange 10a", which abuts the corresponding flange 10b'on the annular part lOb, which is rigidly mounted to the guide bush lOc.

Between (a) the downstream end lOb" (arrow 28 in fig. 1 shows the direction of fluid flow) of the annular part/portion 10b and (b) a facing annular shoulder surface 26b by a stepped portion formed on the outside of the valve body 26 by its closing end with the internal, complementary conical abutment surface 26a, and between (c) the outside surface of the valve body 26 and the facing (d) inside surface of the reduced wall thickness longitudinal portion of the outlet part 10a, there is formed a longitudinal chamber 30 with an annular cross section (annulus) in which is mounted a helical compression spring 32 that is compressed and tensioned in the axial direction when the valve body/magnet armature 26 of the electromagnetic coil 18 is pulled away from its closing position, fig. 1, towards the open valve position, where figure 2 shows an intermediate position.

Fluid is introduced into the chamber 30, which acts as a damping device during control operations.

When closing the valve, the fluid filled conical space 34, see fig. 2, between the conical surface 20c'of the seat body 20 and the complementary conical surface 26a internally of the downstream end of the valve body 26 also acts as a damping device. A similar but mirror-image space 36 with damping properties due to enclosed fluid with escape possibilities may be found at the upstream end of the valve

body 26, where, during the opening of the valve, it will eventually co-operate with a downstream stop portion 10d'.

The co-operating ends of the valve body 26 and the inlet part 10d with the stop portion 10d'also engage each other with mutually complementary conical end portions that upon a fully open valve position, abut each other in a tight-fitting manner. This end position is shown in figure 3.

With a valve construction of the type shown in the drawings, the valve body 26 may be brought from a position corresponding to an open valve position, fig. 2, towards the position shown in fig. 1, corresponding to the closed valve position, by utilising the fluid flowing in the direction of the arrow 28. When moving the valve body 26 in the opposite direction, use is made of the electromagnetic coil 18.

By ensuring that the two radially projecting hexagon nut- shaped flanges 10a"and 10b'have the same external dimensions and are located in the immediate vicinity of each other, they may advantageously be operated by use of one common device when the need arises.

In an alternative embodiment, see fig. 5, the seat body 20 is equipped with a reducing cavity 20f and an undercut seat portion 20g. The reducing cavity 20f causes the fluid flow into the through orifices 24 to become less turbulent. The reduction of the seat face 20c'by means of the undercut area 20g reduces the area that may be exposed to sticking when the valve is used for certain types of sticky substances.

In a further embodiment, see fig. 6, the sealing surfaces 20c'are constructed perpendicularly in the radial direction

relative to the centre line 12 of the valve. The construction prevents wedging between the seat body 20 and the valve body 26.

When it comes to choice of materials, it is-in the case of the selected pulling-away device for the valve in the form of an electromagnetic coil 18-obviously prerequisite for the sleeve-shaped valve body 26 to consist of a magnetic material such as a material with ferromagnetic properties.

The guide bush 10c should in the case of said embodiment be manufactured from a sintered metal or brass (non-magnetic).