FLUID SHUT-OFF VALVE, PROCESS AND A MACHINE TOOL

Abstract: The annular sealing surfaces (16, 20) of a valve body (10) and an associated shutter (12) are constituted by a locus of circles generated by the intersection of the ruled surface of a cone (K) having an elliptical base with planes parallel to one another and normal to a longitudinal axis (A>1<) of the valve. The invention also relates to a process and a machine tool for generating the annular sealing surfaces (16, 20).

Description: FLUID SHUT-OFF VALVE, PROCESS AND A MACHINE TOOL The present invention relates in the first place to a fluid interception valve according to the preamble of Claim 1. The preamble of Claim 1 corresponds to a known butterfly valve of so-called triple eccentric type. In these known valves the annular sealing surfaces of the shutter seat are generated by the intersection of planes normal to the longitudinal axis of the valve with a cone having a circular base and an axis inclined with respect to this longitudinal axis. These annular sealing surfaces thus have a generally elliptical form. The seals utilised with these elliptical surfaces are of the laminated type constituted by a stack of flat metal rings which have been initially worked to an elliptical form at significant cost. In place of these seals constituted by metal rings it is in theory possible to use more economic O ring seals of plastomeric or elastomeric material. In known valves with elliptical sealing surfaces the use of O ring seals is not, however, convenient because such rings, once installed, assume a resiliently stretched form which does not allow them to work in an ideal so-called dynamic, manner, that is to say by adapting themselves to their seat by rolling about the circumferential axis of the torus. A first object of the invention is that of providing a valve according to the preamble of Claim 1 which will not have the above-mentioned disadvantages. According to the invention this object is achieved by means of a fluid interception valve as claimed. In a valve according to the invention the sealing surfaces are all circular, such that, among other things, they permit an O ring seal to be incorporated into the annular surface of the shutter, which seal, when installed, maintains its original circular form and can work in a dynamic manner, that is to say by adapting itself in the seat by rolling about the circular axis of the torus without being subject to stretching and fatiguing by the opening and closing cycles of the valve. The invention is not limited to valves with butterfly shutters and is applicable to rotatable shutter valves of other type, for example so-called poppet valves. The invention also relates to a process and to a machine for machining an annular surface, such as a sealing surface of a valve seat or a valve shutter, according to the preambles of Claims 12 and 14 respectively. The preamble of Claim 12 corresponds to a normal machining process on a known machine tool; the preamble of Claim 14 corresponds to a known machine tool, for example a numerically controlled lathe. As well as a motorised support member, that is to say a workpiece carrier or a tool carrier, and two crossing slides, the process and the machine as claimed make use of a third slide movable along a radial axis with respect to the axis of rotation of the workpiece carrier or tool carrier, which in turn can carry either the tool carrier or the workpiece carrier. The adoption of this third slide makes it possible to generate annular surfaces, for example sealing surfaces having the circular profiles claimed, in a simple manner. The invention also relates to valve bodies and valve shutters intended to form part of a valve as claimed, as well as to workpieces having an annular sealing surface generated using the claimed process. The invention will be more clearly understood from a reading of the detailed description which follows, which is made with reference to the attached drawings given purely by way of non- limitative example, in which: Figure 1 is a front elevation of an interception valve to which the invention has been applied; Figure 2 is a diametral section taken on the line II-II of Figure 1 ; Figure 3 is a diametral section thereof at 90° with respect to the preceding Figure, taken on the line III-III of Figure 1; Figure 4 is a diagram in which the valve is schematically illustrated as in the diametral section of Figure 3 and which serves to clarify the form of the annular sealing surfaces; Figure 5 is a section of a detail on an enlarged scale showing the zone indicated V in Figure 3 ; Figure 6 is a section corresponding to Figure 5, illustrating a modification; and Figures 7, 8 and 9 are very schematic perspective views which illustrate possible corresponding embodiments of machine tools formed according to the invention and usable to perform the process of the invention. Referring now to Figures 1 to 3 , a fluid interception valve of the triple eccentric butterfly type comprises a valve body generally indicated 10 and a rotatable shutter generally indicated 12. The body 10 is of a flat type intended to be interposed between two pipe sections and has, in a known way and, by way of example, a peripheral flange in the form of a ring of ears 14 for flange fixing to corresponding pipe sections. The body 10 has an internal seat with an annular sealing surface 16 (Figures 2 and 3) which will be discussed further below. For now it is sufficient to say that the sealing surface 16 is disposed around a conventional longitudinal axis A- L of the valve which is intended to correspond to the axis of the flow in the pipe. The shutter 12 is carried by an operating shaft 18 mounted rotatably in a known manner in the body 10 and which, outside the body 10, has a stub 20 for coupling to an operating member such as a lever, a handwheel operated manual reduction gear, a geared motor, a fluid actuator etc. The axis of rotation of the shutter 16 and its operating shaft 18 is indicated A 2 . The arrangement of the axis A 2 will be discussed further below. The shutter 12 also has an annular sealing surface 20 (Figures 2 and 3) which, when the valve is closed as in Figures 1 to 3 , mates with the annular surface 16 of the seat . The sealing surface 16 will be also discussed further below. In Figure 3, as well as in Figure 4 to which reference will be made below, Q 2 designates a median plane normal to the longitudinal axis A and which is included in the two annular sealing surfaces 16, 20 when the valve is closed as in Figures 1 to 3. The disposition of the plane Q x has been chosen conventionally for the purpose of facilitating the understanding of the description which will be given below with reference to Figure 4. The axis of rotation A 2 of the shutter 12 extends transversely of the valve assembly along a chord of the opening defined by the sealing surface 16. Moreover, the chordal axis A 2 is offset both with respect to the longitudinal axis A x and with respect to the median plane Q x , according to the known arrangement of triple eccentric valves. Referring to Figure 4 the valve body has again been indicated 10, the shutter 12, the respective annular sealing surfaces 16 and 20, the longitudinal axis A_ , the chordal axis A 2 and the median plane Q x . According to the invention the two mating annular sealing surfaces 16, 20 are generated by a cone K having an elliptical base the apex of which is indicated V. In Figure 4 the axis of the cone K is indicated A 3 . The axis A 3 lies in a longitudinal plane (the plane of the drawing indicated Q 2 in Figure 4) normal to the transverse chordal axis A 2 and containing the longitudinal axis A x of the valve. The chordal transverse axis A 2 and the apex V of the cone K lie on longitudinally opposite sides of the median plane Q x . The arrangement is such that the two annular sealing surfaces 16, 20 are each constituted by a locus of circles generated by the intersection of the ruled surface of the cone with planes parallel to the common median plane Q : . All the circles thus generated have their centres on a central straight line A 4 lying in the said longitudinal plane Q 2 and passing through the apex V of the cone K. To allow the opening of the shutter in the direction of the arrow F of Figure 4 the axis A 3 of the cone K lies between the said central straight line A 4 and the transverse chordal axis Preferably the cone K has a generatrix G lying in the said longitudinal plane Q 2 and situated on the same side of the longitudinal axis A x as the transverse chordal axis A 2 . Preferably the apex angle α of the cone K is of the order of 20-30°. It is also preferred that the said generatrix G diverges from the longitudinal axis A x from the apex V of the cone K to the said median plane Q x , forming a small non-zero internal angle β with the longitudinal axis A x . The internal angle β is also preferably less than 10°. This preferred arrangement serves to facilitate the angular opening and closing movements of the shutter 12 about the axis A 2 entirely avoiding interferences between the two annular surfaces 16 and 20. The generatrix G may also be parallel to the longitudinal axis A- . . Reference will now be made to Figure 5 to describe a preferred embodiment . In Figure 5 the elements which have already been described and illustrated in the preceding Figures have been indicated where possible with the same reference numerals . The annular sealing surface 20 of the shutter 12 has an annular re-entrant portion 22 with circular surfaces concentric with the said straight line A 4 (Figure 4) of the locus of circles. The annular re-entrant portion 22 opens onto a peripheral radial face 24 of the shutter 12 facing towards the apex V of the cone K (Figure 4) . On the radial face 24 is carried an annular shoulder element 26 fixed to the shutter 12 by means of a ring of screws 28. The annular element 26 has, on its side facing the re-entrant portion 22, an annular cavity 32 which, together with the reentrant portion 22 defines an undercut peripheral annular groove 34 opening radially outwardly. The ring 26 finally has a peripheral annular surface 20a which constitutes a continuation of the annular surface 20. Preferably the surface 20a is also constituted by a locus of circles centered, in the same way, on the axis A 4 (Figure 4) and corresponding to that of the principal annular surface 20 of the shutter. Preferably the two annular surfaces 20 and 20a are generated in a single working phase with the ring 26 fixed to the shutter. An O ring seal 36 of plastomeric or elastomeric material is held captive in the groove 34. When the valve is closed the seal 36 is compressed in the manner illustrated in Figure 5 so as to adapt itself to the form of the groove 34 , and squashed against the annular surface 16 of the body 10 to form a perfect seal. In Figure 6 is illustrated a variant intended for a fire safe valve . In Figure 6 the same or similar parts to those of Figure 5 are indicated as far as possible with the same references as Figure 5 and will not be described again. The modification of Figure 6 differs from the embodiment of Figure 5 in that the annular shoulder element, indicated 26a, is retained on the shutter 12 in a floating manner by means of an annular retention element 38 in turn fixed to the shutter 12 by means of a ring of screws 28a. Resilient means in the form of a ring of compression coil springs 40 bias the annular shoulder element 26a away from the peripheral radial f ce 24 of the shutter 12. The reference 34 again indicates the undercut groove defined between the periphery of the shutter 12 and the annular element 26a. An O ring seal 36 is again housed in the groove 34. If the seal 36 becomes damaged or destroyed by an excessive temperature because of a fire in the environment in which the valve is located, the springs 40 guarantee that the peripheral annular surface 20a of the element 26a remains in contact pressed against the annular surface 16 of the body 10, still ensuring a satisfactory seal notwithstanding the destruction or damage of the sealing ring 36. Reference will now be made to Figures 7, 8 and 9 to describe several embodiments of machine tool formed according to the invention to generate the profiles of the inner annular surfaces 16 and the outer annular surfaces 20 on valve elements or even on different workpieces for different purposes . In the three Figures 7, 8 and 9 there have been shown, very schematically, three respective machine tools which have in common the concept of the invention which will be discussed. It is supposed that, as preferred, these machines are numerically controlled and the movements of their movable elements are made under the control of a program of a numerical control unit not shown. In Figures 7 , 8 and 9 the workpiece is indicated P and can for example be the valve body 10 of the preceding Figures the annular sealing surface 16 of which it is desired to work, or else may be the shutter 12 of the preceding Figures of which it is desired to work the annular sealing surface 20, possibly with the surface 22 of the groove 34 and, again, possibly with the sealing surface 20a of the annular retaining element 26 or 26a. A support member for the workpiece P, which will hereinafter be called the workpiece carrier, is indicated C p . A tool intended to generate one of the said annular surfaces is designated T. A support member for the tool T, which hereinafter will be called the tool carrier, is designated C τ . One of the support members, that is to say the tool carrier C τ or the workpiece carrier C p is motorised and is rotatable about a first axis R. A first motorised slide is designated S lr which is movable along a second axis W parallel to the first axis R. A second slide is designated S 2 , which is movable along a third axis perpendicular to the first axis R and to the second axis W. Supposing that the first axis R and the second axis W are horizontal, the third axis may be vertical as in Figures 7 and 9 where it is designated Y, or horizontal as in Figure 8, where it is designated X. According to the invention there is provided a third motorised slide, designated S 3 . This third slide S 3 is movable along a fourth axis U which is always radial with respect to the first axis R. According to the invention it is this third slide S 3 which makes it possible to generate the profiles described above, constituted by a locus of circles generated by the intersection of a ruled surface of a cone having an elliptical base, all as described in more detail above. Figures 7, 8 and 9 illustrate two alternatives, each. In each Figure the parts which the two alternatives have in common are designated with references without parentheses. The parts corresponding only to the first alternative are also indicated in this way with references without parentheses, whilst the parts corresponding only to the second alternative are designated with references in parentheses . In the first alternative of Figure 7 the machine tool comprises a fixed head H x which supports the second slide S 2 movable in the third direction Y. The second slide S 2 carries a motorised platform D rotatable about the first axis R. The platform D in turn carries the third slide S 3 movable in the fourth direction U which is radial with respect to the first direction R. The third slide S 3 in turn carries the tool carrier C τ with the associated tool T. The first slide S x is constituted by a counterhead which is movable in the second direction W parallel to the first direction R. The counterhead or first slide S x carries an angularly fixed workpiece carrier C p in which the workpiece P is fixed. In the second alternative of Figure 7 the first slide, again indicated S l; comprises a movable head which supports the second slide S 2 , the rotating platform D and the third slide S 3 ; the workpiece carrier C p and the workpiece P are, on the other hand, carried by a fixed counterhead H 2 . The two alternatives of Figure 8 differ from those of Figure 7 in that the second direction, indicated X, is horizontal rather than vertical. The parts corresponding to those of Figure 7 are designated with the same references. In the first alternative of Figure 8 the second slide S 2 , movable in the third direction X, is fixed in the second direction W and carries a head H 3 , which in turn carries the motorised platform D rotatable about the first axis R, the associated third slide S 3 movable in the fourth direction U, the associated tool carrier C τ and the associated tool T. As in the first alternative of Figure 7, a counterhead constituting the first slide S x movable in the second direction W carries an angularly fixed workpiece carrier C p and the associated workpiece P. In the second alternative of Figure 8 the slide S 2 is supported by the first slide S x movable in the second direction W, whilst the counterhead H 4 is fixed. In the first alternative of Figure 9 a fixed head H 5 carries a second slide S 2 which is movable vertically in the third direction Y and which in turn carries a motorised workpiece carrier C p rotatable about the first direction R. A first slide S x carries a counterhead H 6 which in turn carries the third slide S 3 . This latter is movable in the fourth direction U which in this case is vertical. The third slide S 3 carries the tool carrier C τ and the associated tool T. In the second alternative of Figure 9 the head itself constitutes the first slide S λ movable in the second direction W, whilst the counterhead, again indicated H 6 , is fixed. It is to be emphasised that it is an essential characteristic of the invention that in each case the fourth direction U is radial with respect to the first direction R about which the workpiece P rotates . Within the scope of the invention the orientations of the various directions indicated above can vary as long as they satisfy the definitions of Claims 12 and 14 which follow.

Claims: CLAIMS 1. An interception valve for fluids, comprising: a valve body (10) with an internal seat having an annular sealing surface (16) disposed about a longitudinal axis (A x ) of the valve, a shutter (12) rotatable in the valve body and having a peripheral annular sealing surface (20) which, when the valve is closed, mates with the annular surface (16) of the seat, the annular sealing surfaces (16, 20) lying in a common median plane (Q x ) normal to the said longitudinal axis (A x ) , when the valve is closed, and in which the two mating annular sealing surfaces (16, 20) are generated by a cone (K) having a ruled surface, the shutter (12) is rotatable about a transverse chordal axis (A 2 ) situated to one side of the longitudinal axis (A x ) , the axis (A 3 ) of the cone (K) lies in a longitudinal plane (Q 2 ) normal to the said transverse chordal axis (A 2 ) and containing the said longitudinal axis (A x ) of the valve, and the transverse chordal axis (A 2 ) and the apex (V) of the cone lie on opposite longitudinal sides of the said common median plane (Q x ) , characterised in that the said cone (K) has an elliptical base, the arrangement is such that the said annular sealing surfaces (16, 20) are constituted by a locus of circles generated by the intersection of the ruled surface of the cone (K) with planes parallel to the said common median plane (Q x ) , all the circles thus generated have their centres on a central straight line (A 4 ) lying in the said longitudinal plane (Q 2 ) and passing through the apex (V) of the cone, and the axis (A 3 ) of the cone (K) lies between the said central straight line (A 4 ) and the said transverse chordal axis (A 2 ) . 2. A valve according to the Claim 1, characterised in that the apex angle (α) of the cone (K) is of the order of 20-30°. 3. A valve according to Claim 1 or Claim 2, characterised in that the cone (K) has a generatrix (G) lying in the said longitudinal plane and situated on the same side of the longitudinal axis (A x ) as the said transverse chordal axis (A 2 ) , which generatrix (G) diverges from the longitudinal axis (A x ) from the apex (V) of the cone (K) to the said median plane (Q- and forms, with the longitudinal axis (A x ) , a nonzero internal angle (β) . 4. A valve according to Claim 3 , characterised in that the said non-zero internal angle (β) is less than 10°. 5. A valve according to Claim 1 or Claim 2, characterised in that the cone (K) has a generatrix (G) lying in the said longitudinal plane and situated on the same side of the longitudinal axis (A x ) as the said transverse chordal axis (A 2 ) , which generatrix (G) is parallel to the longitudinal axis (A . 6. A valve according to any preceding claim, characterised in that the annular sealing surface (20) of the shutter (12) has an annular groove (34) with circular surfaces concentric to the said central straight line (A 4 ) of the locus of circles for housing an O ring seal (36) engageable with the annular sealing surface (16) of the valve body (10) . 7. A valve according to Claim 6 , characterised in that the said annular groove (34) is defined in part by an annular reentrant portion (22) which opens into a radial face (24) of the shutter (12) facing towards the apex (V) of the cone (K) and in part by an annular cavity (32) formed in an annular shoulder element (26; 26a) carried on the shutter (12) and constituting a retaining wall for retaining the seal (38) in the annular groove (34) . 8. A valve according to Claim 7, characterised in that the said annular shoulder element (26; 26a) has a peripheral annular surface (20a) constituted by a locus of circles corresponding to that of the associated annular surface (20) of the shutter (12) . 9. A valve according to Claim 7 or Claim 8 , characterised in that the annular shoulder element (26a) is retained, with respect to the shutter (12) , by an annular retaining element (38) with a clearance with respect to the said radial face (24) of the shutter (12) and is thrust by resilient means (40) in the direction away from this radial face (24) . 10. A valve body having an internal seat with an annular sealing surface (16) according to any of Claims 1 to 4. 11. A valve shutter (12) having a peripheral annular sealing surface (20) according to any of Claims 1 to 9. 12. A process for the machining of an annular surface such as a sealing surface (16; 20) of a valve seat or a valve shutter (12) , on a workpiece (P) fixed on a support member (C p ) , by means of a tool (T) fixed to another support member (C τ ) and in dependence on the control of a motion control unit, in which one of the support members (C p ; C τ ) is motorised and is rotatable about a first axis (R) with respect to the other support member, one of the support members (C p ; C τ ) is supported from a first motorised slide (S^ which is movable along a second axis (W) parallel to the first axis (R) , and one of the support members (C p ; C τ ) is supported from a second motorised slide (S x ) movable along a third axis (X; Y) perpendicular to the first axis (R) and to the second axis (W) , characterised in that to support and displace one of the support members (C p ; C τ ) there is further provided a third motorised slide (S 3 ) movable along a fourth axis (U) which is radial with respect to the first axis (R) , and in that the control unit simultaneously controls the movements of the three motorised slides (S x , S 2 , S 3 ) in a coordinated manner so as to generate on the piece (P) , by means of the tool (T) , an annular surface (16, 20) constituted by a locus of circles generated by the intersection of the ruled surface of a cone (K) of elliptical base with transverse planes (C^) parallel to one another, all the circles thus generated having their centres on a central straight line (A 4 ) passing through the apex (V) of the cone (K) . 13. A workpiece, particularly a valve body (10) or valve shutter (12) having an annular surface, particularly a sealing surface (16, 20) machined with the process according to Claim 11. 14. A machine tool for the machining of an annular workpiece surface (P) such as a sealing surface (16; 20) of a valve seat or a valve shutter (12) , by means of a tool (T) , comprising: a support member (C p ) provided with means for fixing the workpiece (P) and a support member (C τ ) provided with tool fixing means (T) , one of the support members being motorised and rotatable about a first axis (R) with respect to the other of the support members, a first motorised slide (S- movable along a second axis (W) parallel to the first axis (R) and on which one of the support members (C p ; C τ ) is supported, a second motorised slide (S 2 ) movable along a third axis (X; Y) perpendicular to the first axis (R) and to the second axis (W) and on which one of the support members (C p ; C τ ) is supported, and a control unit for controlling the movements of the motorised slides simultaneously in such a way as to generate the annular surface (16; 20) on the workpiece (P) , characterised in that it further comprises: a third motorised slide (S 3 ) which supports one of the support members (C p ; C τ ) and which is movable along a fourth axis (U) radial with respect to the first axis (R) , and in that the control unit is so arranged as to control the movements of the three motorised slides (S 1; S 2 , S 3 ) simultaneously in a coordinated manner so as to generated on the workpiece (P) , by means of the tool (T) , an annular surface (16; 20) constituted by a locus of circles generated by the intersection of the surface of a cone (K) having an elliptical base with transverse planes (Q x ) parallel to one another, all the circles thus generated having their centres on a central straight line (A 4 ) passing through the apex (V) of the cone (K) . 15. A machine tool according to Claim 14, characterised in that the second slide carries a motorised platform (D) rotating about the first axis (R) and along which the third slide (S 3 ) is radially slidable, in that the support member (C p ) for the tool (T) is fixedly connected to the third slide (S 3 ) , and in that the support member (C p ) for the workpiece (P) is fixed against rotation. 16. A machine tool according to Claim 15, characterised in that it comprises a fixed head (H x ) which supports the second slide (S 2 ) , the rotating platform (D) and the third slide (S 3 ) , and a movable counterhead constituting the first slide (S x ) and to which the member (C p ) for supporting the workpiece (P) is fixed. 17. A machine tool according to Claim 15, characterised in that it includes a movable head constituting the first slide (S x ) which supports the second slide (S 2 ) , the rotating platform (D) and the third slide (S 3 ) , and a fixed counterhead (H 2 ) to which the workpiece support member (C p ) is fixed. 18. A machine tool according to Claim 14, characterised in that the workpiece support member (C p ) is in the form of a motorised rotating platform (D) mounted rotatably about the first axis (R) on the second slide (S 2 ) , and in that the support member (C τ ) for the tool (T) is fixed to the third slide (S 3 ) and the third slide (S 3 ) is fixed against rotation. 19. A machine tool according to Claim 18, characterised in that it includes a fixed head (H x ) which carries the second slide (S 2 ) , which in turn carries the rotating platform (D) , and a movable counterhead constituting the first slide (S x ) which in turn carries the third slide (S 3 ) . 20. A machine tool according to Claim 18, characterised in that it includes a head constituting the first slide (S x ) which carries the second slide (S 2 ) which in turn carries the rotating platform (D) , and a fixed counterhead (H 4 ) which carries the third slide. 21. A machine tool according to any of Claims 18 to 20, characterised in that the direction of the fourth axis (U) of movement of the third slide (S 3 ) is parallel to the third axis (Y) of movement of the second slide (S 2 ) . 22. A machine tool according to any of Claims 13 to 20, characterised in that the first and second axes (R; W) are horizontal and the third axis (Y) is vertical. 23. A machine tool according to any of Claims 14 to 21, characterised in that the first, second and third axes (R, W, X) are horizontal.

Inventors: MASSO PAOLO, MASSO, PAOLO
Applicants: MASSO PAOLO, RIZZIO VALVOLE S P A, MASSO, PAOLO, RIZZIO VALVOLE S.P.A.
Application year: 1997
Main classification: B23B5
IPC codes: B23C3, B23Q27, F16K1, G05B19