CA1146527A - Gate valve - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE.

In this gate valve, two semi-seal lines between the closure member and the seat cross at the level of the flow axis through the valve. In this way, the overall axial size and the force for operating the valve are reduced.

Description

6S2~

DESCRIPTIoN

n GA~E V~,VE ~I
Ihe present invention relates to a gate valve of the type comprising a body having a cylin~rical flow pipe assumed to be horizontal and defining a seat surface,an~ a ~losure member ,~r~vided with a seal rib of elastomer anl guided in vertical translation, said rib being applied against the seat surface of the body and having the same general shape as the seat.
oonventional gate valves of this type have a seal line having the general shape of a wedge. m ey must have an axial dimension which is compa~;hle with the required distances between the flanges of piping and th~y must ensure a reduced w~r of the elastomer seal when repeatedly opening and closing the valve.
Now, these two conditions oppose each other. In order to decrease the wear of the seal the friction of this seal against its seat requ~red in order to achieve the desired ccmpression of the elastarer must be decreased and consequently the travel of the gate at each point of the latter mllst be decreased b~
the m~nent the seal touches the seat and the. ~r~nent the considered ccnpression is achieved. For this purpose, the angle between the seat surface and the direction of displac~nent of the gate =t be increased, but, unfortunately, this in~rease increases the overall axial size of the gate valve.
The Applicant has prcposed a solut:ion to this problem in French patent N 71 16057 and the carresponding certificate of addition N 72 11641 published under Ns 2 139 616 and 2 178 457 respectively.

652~

Indeed, the seat and the closure.~emker have in these documents, on each side of a plane of symmetry containing the axis of the operating rod and perpendicular to the axis of the flow tube, tw~ continuous closed conjugate surfaces which gradually vary in a sinuous manner.
In the various embodlments of this patented gate valve, each ruied surface fcrming a seat on each side of said plane of symmetry oomprises an upper curved portion roughly transverse to the axis of flow, a lower curved-pcrtion coinciding with the inner cylindrical flo~ surface, and therebetwe~n, above an~
kelow a diametral zone represented in projection by the flow axis, an inter~ediate roughly helicoidal transition portion in the shape of a rotating ra~p which connects said upper and lower portions by extending around the cylindrical flow surface as lS close as possible to the latter.
Ihis ruled surface, i.e. surface formed by rectilinear generatrices, has a mEan seal line which is a closed c w e. At each point of this seal line, the plane tangent to the surface forming the seat ~plane formed by the rectilinear generatrix and by the tangent to the seal line at this point) makes an angle which is at least equal to a predetermined angle which is, for example, 20, with the direction of translation of the closure member or the axis of the operating rod.
Along a seal zone exbendin3 over more than one half of the seal line, the angle between the plane tan~ent at e~ch point to the seal line and the axis of the operating rod is roughly constant.

~ he low~r generatrices of the flow tube may be rectilinear or have a deviation formlng a hollow or a projection against whlch the lower part of the closure me~ber is a~Dlied.
0wing to this arrangement, the sealing contact between the S seat and the closure member through the r~bber seal element ls completely contLnuous throughcut the closed contour of the seat so that the gate valve is absolutely fluidtight in the closed positian thereof, even and in particular in said Lnt O te portiGn of transition of the seal surface.
Further, owing to the afore~enticned mlnimun angle of 20, the sliding of the seal on the seat when closing the gate is substant~ally r~duced with respect to that which occurs in prior gate valves. Cooseqyently, there is less wear of the sealing element on the olosure member.
An object of the invention is to provide another soluticn co~patibie with the foregoling solutio~ an~ m,ore advantageous from the point of view of the force required for opening the closure n~er.
~ar t~ s purpose, the invention provides a gate valve of the aforementioned type wherein the seal 11nP of the ~oat,seen in a direction perpendicular to the axis of the flcw pipe, has the general sh~pe of an X and is obtained, throughout or substantially throughout ~ts length, by translation of tWD half seal lines towands each other along said axis, said half seal lines having together the g~neral shape of a w~dge.
In an advantageous embod~ment, which ensures a minImum of axial c~erall size, each half seal surface is such zs that defined in French patent N 71 16057 or ln the corresponding certificate of addition N 72 11641 briefly mentioned hereinbefore.
In thls case, and in order to s~mplify manufacture, the part of each half seal surface located abcve the zane of the flow axis may be replaced by two portions of a plane converyent towards said axis and extended by curved surfaces for connection to the surfaces located below said zone.
When, in the lower pcrtion of the seat, the angle between the axis of the cperating rod and the plane t~ngent to the seal surface varies, advantageously the crest line of the seal bead is defined in such manner as to meet sim~ltaneously the seat surface at all points thereof except in the lower portion of ~;d surface where, up~n this first contact, there is a radial clearance which progressively increases on each side to the lower point of the flow cavity. In this way the uniformlty of the cxushing of the bead is improved.
~ hus, during the closure member closin~ stage,once the seal contact between the closure member and the seat has been achieved on the major part of the seal bead, except in said lower part, the gaps - between the seal bead and the s~at, which increase in the lower loops of each seal line in the ~rection away from the diametral plane of the flow tube, are progressively reduced and the seal contact is achieved progressively followed also ~y a progressive compression of the seal element. This l~k of simul-taneousness of the se~l contact throughout the periphery of theseal line and this progressivity of the coming into contact with the seat anl of the radial or perpendicular compression of the K$~7 _ 5 bead or of the seal element at l~.qt partly compensate,~n respect of the uniformity of the crushing of the bead at the end of the closLng travel of the valve me~ber, for the varlation in the angle c~ between the axis of the operating rod and the plane tangent S to the seal surface alQng its mean line in the lower portiQn of the seat surface.
A complete or practically complete uniformity of the crushing of the bead can be obtained when said clearance varies in accordanoe with a law of the type :
j = a sin o~ - b ln which a and b are constants. This may be simply achieved in the case of a flow tube having a cir~ular section-by giving the Jower part of the bead, when viewed along the axis of flow, a circular shape having a radius exceeding that of the flow cavity.
In or &r to t~ke into account manufacturing requirements it may be desirable to arrange that-the crossing points of the X
be replaced by flat surfaces on the seat surface and on the seal line by segments of a straight line which are roughly vertical when seen in side elevation.
In the case where the flcw tube has in the region of the clo-sure nEmber an inner or outer projecting regian, the lower part of the seat surface is modificd in a corresponding manner with surfaces which merge into the remainder of this surface.
r~he invention will be described in more detail with reference to the accompanying drawings which shaw solely some entDdiments of the invention. In the drawings :
Fig. 1 is a longitudinal sectional view of a yate valve according to the invention withits closure me~ber in the closing position and shcwn in side elevatian, the upper part of the gate valve not being shown ;
Fig. 2 is a cross-sectional view, taken on line 2-2 of Fig. 1, i.e. in the transverse plane of symmetry of the gate valve ;
Fig. 3 is a longitudinal sectiQnal view similar to Fig. 1 of the gate valve without its valve member, said view illustrating the seat ;
Fig. 4 is a cross-sectional view taken on line 4-4 of Fig. 3 ;
Figs. 5 to 8 are views s~ilar to Figs. 1 b~ 4 of a second embodlment of the gate valve according to the invention ;
Fig. 9 is a sectional view taken on line 9-9 of Fig. 5 with a part cut away ;
Fig. 10 is a sectional view of the closure mmber taken on line 10-10 of Fig. 6 ;
Fig. 11 is a diagrammatic perspective view of the closure nE~ber of the embod1ment shown in Figs~ 4 to 10 ;
Fig. 12 is a p~rspective view of the seal lin~ according to this seoand embodiment ;
Figs. 13 and 14, Qne one hand, and 15 and 16, on the other, are partial sectianal views taken in a diametral plane containing the flow axis and illustrating tw~ manners of assembling according to the invention two se~d-closure members S3 as to for~ a single clo-su~e member, these Figures illustrating in section the assemblinymeans and the lower part of the seal el~m~nt ;
Fig. 17 is a partial sectional view taken in a horizontal ~4~5~27 plane located a little below the flow axis and shcwing the configu-ration of the semi-cLosure members ;
Fig. 18 is a diagram in cross-section illustrating the angle ~e planes t~ngent to the seal surface make with the direction of the cperating rod in the lower part of the co~nection with the cylindrical flow surface shown by a circle ;
Fig. 19 is a diagram in elevation and in plane illustrating the seal line of a gate valve according to the French patent N 71 16057 of the Applicant ;
Figs. 20 and 21 are diagrams similar to ~ig. 19 showing, for purposes of comparison, the seal lines of two embodlments of the present invention ;
Fig. 22 is a longitu~inal sectional vicw of a modificati~n of the body of the g~te valve according to the invention in the case where the flow tube includes a hollow cavity with vertical walls in the lower part of the travel of theclosure mem~er ;
Figs. 23 and 24 are respectively half-sectional views taken along lines 23-23 of Fig. 22 and Fig. 24-24 of Fig. 23 ;
Fig. 25 is a longitudinal sectional view of another modi-fication si~ilar to that of Fig. 22 -but in which the hollow cavity is connected to the flow tube by inclined walls instead of being connecb~d to the flow tube by vertical walls ;
Figs. 26 and 27 are half-sectional views ~aken:~espectively along lines 26-26 of Fig. 25 and 27-27 of Fiy. 26 ;
Fig. 28 is a longitudinal sectional view of another mcdifi-- cation similar to that of Fig. 22 but in which the lower generatrices of the flow tube have a deviation formung a projection inside this ~

tube ;
Figs. 29 and 30 are half-sectional views taken respectively alony lines 29-29 of Fig. 28 and 30-30 of Fig. 29 ;
Figs. 31 to 34 are views similar to Figs. 5 to 8 respecti-vely rel~ting to a mLdification of the second enbcdim nt of the invention ;
Fig. 35 is a partial longitu~inal sectional view of anot~er enbodiment of the gate valve ac~ording to the invention ;
Fig. 36 is a sectional view taken on line 36-36 of Fig. 35 of this gate valve ;
Fig. 37 illustrates, in longitudinal section of the bead, the first ccntact of the latter with the seat ;
Fig. 38 is a sectional view taken on line 38-38 of Fig. 37 ;
F$g. 39 is a view s~milar to Fig. 38 but corresFonding to the camplete closure of the closure member ;
Fig. 40 shows, in cross-sec~ion of the bead, the contact ~ of the l~tter with the seat in the lower point of the flow tube ; Fig. 41 is a view similar to Fig. 40 but corresponding to the oomplete closure of the closure member.
Ihe gate valve illustrated in Figs. 1 to 4 com~rises a T-shaped body 1 which is moulded from cast iron or some other metal alloy or from a plastics material. me body 1 has a tube or pipe 2 haviny an axis X-X for the entry and exit of the fluid passing thrcugh the valve, this tube 2 being adapted to be oonnectE~, for example hy flanges, to piping (not sh~wn), and a tubu-lar housing 3 having an axis Y-Y perpendicular to the axis X-X
and forming the stem of the T. For the purposes of the description, L6S~7 g it will be assumed that the axis X-X is horizontal, and the axis Y-Y vextical,the housing3 extending uF~ y from the tube 2.
Only the lcwer part of the tubular housing 3 ha~ been shcwn and it~
other part comprises in the known nanner a cap which closes the body and acts as a liquidtight guide for the cFerating rod of the closure nEmber.
The tube ~ has a cylindrical inner cavity 4 of circul~r sectional shape and the tubular hsusing 3 has an inner cavity 5 of axis Y-Y which is also cylindrical but has a roughly elliptical sectional shape. ~he cavit~ 4 is interrupted in the extension of the housing 3 by a seat surface 6 of special sha~e described hereinafter.
A closure me~ber or gate 7 operated by a screwthreaded operating rod 8 of axis Y-Y is adapted to be applied against the seat 6 by translation between an up~er cpen position and a lower closed posltion. The upper end of the screwthreaded rod is nounted to be rotatable but prevented from m~ving in translation in the upper cap of the body 1 and its lower end cooperates with an operating nut (not shown) which is trapped in an upFer case 9 of the closure member. Ihe closure member 7 has, ln the s~me way as the body 1, planes of symmetry, namely the vertical plane g cantaining the axes X-X and Y-Y and the veItical plane P
contaIning the axis Y-Y and perpendicular to the axis X-X.
Ihe closure member 7, which will be described hereinafter, may be made fram any suit~ble material, such as grey cast iron, spheroidal graphite cast iran, steel, a ccpper alloy, a plas~ics material, and may be manufactured by any suitable method (precision ~65;~:7 mculding, die casting, machi~LLng, etc..). In the presently-descri-bed embod1ment, the closure member is hollow and consists of two semi-closure nembers 7a and 7b which are assembled in the manner described hereinafter and completely ccvered with ruhber.
The closure m~mber 7 has the general shape of a pl~te pirpendicular to the axis X-X and adapked to the dimensions of thz cylindrical cavity 4 of the flow tube 2 and to the shapes of the se~t 6 so as to be i~serted b etwee n the tw~ halves of the tube 2 and be applied in a fluidtight manner against the seat 6. It has in its upper part, apart from the case 9 containing the nut of the - operating rod 8, tw~ pairs of lateral guide ribs or ears 10 which are parallel to the axis Y-Y and located on each side of the vertical plane Q.
The guide ribs 10 cocperate w~ith tw~ vertical guide ribs 11 contained in the plane of symmetry P of the gate valve inside the housing 3 and projecting fro~ the cavity 5 of the latter.
Two embodiments of the surface of the seat 6 and of the closure nember 7 will now be described.
First embod1~ent of the soat and closure member (Figs. 1 to ;.
4 and 20).
The shape of the seat 6 is directly derived from that described in the aforementioned French patent N 71 16C57 of the Appli~ant, as can be seen from a ccmparison of the diagrams of Figs.l9 and 20.
A~cording to said French patent N 71 16057 and as gecme-trically illustrated in Fig. 19, the transverse profile of the seat, or more precisely the projection of the curved and continuous - ~46S27 seal llne on the plane of symmetry Q, is represented ~y the line A B D C and Al Bl Dl, Cl. Ihis profile comprises two curves which are symmetrical with respect to the plane P and has the general shape of a boat hlll. mere will be recognized the upper curve portions A, E, and Al, El which ~re transverse with respect to the flow axis X-X, i.e. substantially vertical, the . .
lower curve port1ons D, C, and D , C which colnclde Wlth the line representing the plane P and are wholly located on the cylindrical flow cavity A,and the intermediate ~ransition portions E, B, D
and El, Bl, Dl which are heliooidal and intersect the axis X-X
at B and gl and which connect the upper transverse portions to ; the lower portions of each semi-seal line. The lines ~, B, D, C, and Al, Bl, Dl, ~ are the projections of the mean line of the seat 6 w.hich comprises two ruled surfaces whose generatrices are perpendicular to the axis X-X in the upper portions A, E, and Al, El, parallel to the axis X-X in the coinciding lower portions B, C, and Bl, Cl, and have an ev~lutive orientation between perpendicularity and parallelism in ~he manner of the steps of a spiral staircase in the intermediate portions E, B, D, and El sl Dl ~;
It will be n~reover recalled that the seal lines A, E, B, D, ; and Al~ El, Bl, Dl, have at every point a plane tangent to the seat surf~e 6 which forms with the axis Y-Y an angle 0~ which is : roughly eqyal to a predetermined value, for example 20~ (tangent planes indicated by lines Kl, T and K2, T in Fig. 18). Between D and C and Dl and Cl, the angle o~ gradually changes from the minimum value 20 to 90.

The upper part of the diagram of Fig. 20 is the projection on the same plane Q of the seal line of a valve according to the present invention. The curves A, E, B~ D, C an~ A2, E2, B2, D2, c2 are respectively identical to the curves A, E, B, D, C and Al, El, Bl, S Dl, Cl of Fig. 19 and oomprise the same upper p~rtions A, E, A2, ~ , lower p~rtions D, C and D2, C , and intermediate transition and oonnectLn7 portions E, B, D, and E2, B2, D2 between the up~er portions and the lcwer portions and satisfy the same geametric definitions and the same is true of the oo.nditions concerning the planes tangent to the seat surface along these.twD curves.
But, in order to reduce the longitudinal overall size of the seat (distance A~ A and A, A2 of Flgs. 19 and 20), the tw~
sy~metrical curves have been mDved together by translation in ~.
... a direction parallel to the axis X-X so that they cross at B or B2 (Fig, 2) on the axis X~X. Consequently~ the nE~u~lm longitudi-nal overA11 size A, A2 relative to the axis X-X is less than the p~eceding overall size A, Al, the decrease in the overall ~! size being equal to the extent of the considere~ translation~
Cbnsequently, the seal surface 6 has a mean seal l~ne 61 ~hich oonstitutes, in projection on the pl~ne Q, Al~ of the . curves A, E, B, D, C and A2, E2, B2, D2, C2. The seal line 61 is illustrated in Figs. 3 and 4 by a dot~dash line on the seat surfaoe 6 and is embodied by the crest 71 of an elastic seal bead 12 carried by the closure member 7, this crest having exactly the same shape. The line 61 is formed by both the tWD lines which cross at the ends of the hDrizontal diameter of the tube 2 on the axis X-X. The p~rtions of each half of the seal surface 6

2~

are oor.respondingly : -two upper partions 62 located roughly in a transverse plane rel~tive bo the flow axis X~X corresponding, for the seal line, to ~ E, and A ~
two upper inte ~ ate porti~n~ of transition 63 which are helicoidal and located above the diametral zone of the flow axis oorrespondlng to E, B and E2, B2 ;
t~o lcwer intermediate portions oi transitian 64 ~hich a,re h~rizontal and Joca ~ below the:d1ametral zone of ~he fl~w axis X-~ and on the other side of the vertical plane P with . respect to the'preceding, correspondlng to B, D, and B2, D2, and . two c~lindrical l.ower'portions 65 which ooincide with : the flow cavity 4 and are parallel bo the flow axis X-X, oorres-p~nding to D, C and D2, C2, , 15 All these surf~Ge portions are oontinuously connected to each oth~ and. oor.responding t~ these surace portions on the se~t a~e sea~ line po~tions 72 to 75 respe~tively on the seal bead 12 of the closure member 7~
, The seal l~,ne 61 of the seat.6 an~ 71 of the.closure member 7 have conseguRntly a gene~ally X shape when viewed in side ele-vation~ Each semi-line located on one slde of the plane P has a tUXnin~ back polnt B at each end o the horizontal diamete~ of the flow, tube 2. ~n the'same way there are obtained seal surfaces which cross on the dlametral zone o the flow axis X-X. Eelow th~s diametral zone, thR surfaces whlch diverge in the upper part CDnVerge toward the dlametral zone of the axis X-X~ Below this diametral zOnR~ the seal surfaces are convergent frcm the lower part ~65Z7 boward the diametral zone of the axis X-X.
In other words, the surface portions located above the dlame-tral zone of the axis X-X anl on one side of the plane of symmetry P are extended belcw this dlametral zone and on the other side of said plane of symmetry P~ It is thls extension which p¢Dvides the oontinuity, notwithstan~ing the gea~etric discontinulty indi-~ cated by the turning back point B, fo~ the sealing surface portions ; located on the same side o~ the plane of symmetry P, . As shown in perspective i~ Fig. 12 in xesPect ~f a ~bdi~ica-ti,on ~escribed hereinafter, the seal line 61, 71 is in fact a closed curve ex~ending round the entire periphery of the seal su~faces a,nd therefoxe surrcunding the cylindrical flow cavit~ 4, ~with two turn-back points 8, B2 which are symmetrioal .with respect to the plane of symne*ry Q containing the axes X-X and Y-Y (plane shown in Figs. 1~ 3 and 20). The.lines 61 and. 71 coincide Ln the closed po~ition of the ga,te valve~
~ n the clo2ure mem~er 7 (Fig. 11) the seal bea,d 12,which has a roughly circular cross-section, extends aroun~ a closure plate 76 whose mean plane is the pLane Q and oomprises a lower portion 77 having a ~hickness (i.e. dimension in the direction of axis X-X) and a semi-cylindrical sha~e, the horizontal diameter thereof being located akove the flow axis X-X, then a parallelepi-pedic intermediate portion 78 of the same thlckness a~d then an upper portion 79 having a wedge shape whose edge crosses the . 2S axis X-X at a right an~le and which diverges upwardly up to the upp~r loops of the seal line 71~ The wedge shape has ln its upper part a dimension in the direction of axis X-X which ls ~L6527 greater than that of the intermediate and lower portions of the plate 76. m e lateral guide ears 10 project from the wedge 79 on each side of the plane P.
The seal rib 12 extends along the entire edge o the wedge 79 and the lower portion of the semi-cylindrical region 77 at each axial end of the latter, m enceforth, the two lower curved por,tions o the'seal surface unite at the apices of the wedge shape 79 and converge toward the'diametral zone of axis X-X.
According to Figs. 2 and 4, sho~lng the'cl~sure member and the seat taken in the'transverse plane of symmetry P, the diffe-rent p~rtions of the seal suraces extend symmetrically with respect to the'plane Q in the plane P along arcs having the following approxImate values on each si1e of the plane of symmetry P, which must therefore be c~unted twice :
a) 62-72 : about 60 ;
b~ 63-73 ; about 30Q 7 c~ 64~74 ; about 30 d) 65~75 : about 60.
m e ehtcdlment of-the closure member 7 ~hich i5 oommon to the first a~d seoond embod1ment will be sh~wn subsequently.
Second embodLment (Figs. 5 to 12 and 19) In order to understand the structure of the second embodiment as cqmpared to the first embodiment the diagrams of Figs. 20 and 21 will be ccmpared.
Z5 While the principle of crossing sea~ lines and surfaces has been retained, for the purpose of simplification,the portions 62-72 and 63-73 (or A, E, B, and A2, E2, B2) located abcve the 1~65Z7 diametral zone of axis X-X, i.e. the upper p~rtions and upper intenmediate portions having a continuous curvature and extendin~
helically,' have been replaced by two convergent planes shown by the rectilinear line A3, F, B and A4, ~ , B2 (Fig. 21), the se~i-angle at the apex oc being greater than or equal to 20 relative bD the'axis Y-Y.
Eelow the diametral zone of axis X-X, the seal surfaces and - lines of the'first embodlm~nt ha,Ye been retained, It can be seen that this simplification in the upper zone of the seal surfaces an~ iines'is obtai,ned at the cost of a slight increase in the maxim~m longitudinal overall,size for a given angle cC , since the distance ~3, ~4 of Fig~ 21 is greater than the di,stance A, A2 of Fig. 20. But this n~xim~m longitudinal overall size nonetheless remains for a giVen angle o~ less than that of the prior gate valve (A, Al ~f Fig. 19).
Mbre precisely, in this e~bodi~ent, the upper portion 62 of the seat is formed ky :
tw~ semi-ellipkical pl~nar surfaces 62a whlch are the intersect~Qns of tw~ convergent planes symmetrical with respect to the plane P with the wall of the tube 2. These semi-elliptical surfaces exten~ from the junction between the tubular houslng 3 and the tube 2 to a zone located roughly mid-way ketween the horizontal diametral plane containlng the axis X-X and the junction ketween the tukular housing 3 and the tube 2 (segments ~3, F and A4, ~ of Fig. 21) ;
two ~ntermediate r,uled helicoidal surfaces 63a which extend to the aforementioned diametral plane,corresponding b~ the ~65Z7 portions F, B and Fl, B2 of Fig. 21. m ese surfaces 63a ensure the progressive transition with the two lower transition surfaces 64.
The tWD lower transition surfaces 64 are, as in the first embodiment, twisted surfaces which extend fram a zone located at the level of the axis X-X to about half-way between the axis X-X
and the lower generatrix of the cavity 4. It concerns twisted surfaces in the shape of turning ram~s, i.e. ruled helicoidal surfaces generated by generatrioes based on a curve of intersection of the surface 6 with the cylindrical flow cavity 4. m e surfaces 64 gradhally change in rotating about a vertical axis when their curve of intersection with the cylindrical cavity is followed. The surfaces 63a and 64 are such that a tangent plane at all points of the median line or seal line 61 makes a mdnim~m angle of 20 with the axis Y-Y~ this angle gradually increasing to 90~ in the lower part where the surf~ces 64 are connected to the surfaces 65 ~oinciding with the ca~ity 4.
The median seal line 64 of the seat surface 6 is,as before, formed by two lines which are symmetrical with respect to the plane of symmetry P of the gate valve~ These two lines appear in the plan view of Fig. 9 and on the lower part of Fig. 21. They are closed and continuous but have large changes in ~1rection or line (turn-back points) on the line corresponding to plane P. The line 61 is also represented in perspective in Fig. 12, As beore, it is ~5 along this seal line 61, oOmmDn to the seat 6 and the closure member 7 (identical line 71),that the seal element of the closure member 7 bears against the se~t 6.

S2~

In projection on the plane Q (Figs. 5 and 7), the line 61 forms an X consisting of a V, whose apex points downwards,superimr posed on a lower inverted U. In the first embodiment,the upper V is replaced by an up~er U.
In the plane of projection P,which is that of Fig. 6, the seal bead 12 and the seal line 71 only aF~ear in the upper seal portion 62, 72 in the form of a seml-ellipse in a Fortion of the intermediate zone 63, 73 and in the lower portion 65, 75, whereas they are hidden in the pcrtion 64, 74.
The two parts 7a, 7b of the closure member 7 in the tw~ fore-going embol~m=nts have a construction which will now be descrIbed.
These tWD parts 7a, 7b are formed by thin shells (Fig. 13)which are reinforced, i~e. thickened at 13,on each side of the closure member in the region of the axis X-X, so as to include at these places asse~bly means formed by a pair of conical studs 14 which p~ject from a semd-closure member (for example 7a) and are fitted in corresponding conical cavities 15 o~ the other semi-closure member (7b). Also provided are inner projections 16 which bear against each other (Fig~ 17) and are disposed on both the semi-closure nembers 7a and 7b and constitute spacer members which preclude the crushing of the thin walls of the closure member 7 when a rubber cover or fitting 17 is applied on the cl~sure member by a mDulding operation, i.e. is injected under pressure in a mould containing the closure me~ber.
Further, as can be seen in Fig. 10, the tWD parts 7a, 7b include internally two inner lugs 18 which extend from a part 7a and bear against the upper horizontal inner wall of the other part 7b, ana vice-versa, just below the nut case 9,-the~e lugs 1~L6527 extending across the joint plane P. These lugs preclude any sepa-ration of the parts 7a,~7b by a shear movement thereof when closing the valve,should any foreign kody create an obstacle on one side of the plane of symmetry P.
m e seal element of elastcmer 17 having a variable thicXness is thickened so as to form the seal bead or crest 12 whlch e~bodies the cpal line '61 and is thinne~ do~n in the plane o~ symmetry p-p or the asse~bly plane of the parts 7a, 7b, The two parts 7a, 7b axe oov,er~d in~ependently of each other throughout their surface intem 3lly ,a~d, extexnally, including the bearing prDjections 16 ,an~ the'studs 17, by the seal element 17. m ey are rendered rigid with each other by means of an adhesive product and conseguently without screws, Only the end of the studs 14 and the botbam of the cayities 15 are de~Did o~ the cqVer 17.
~5 gwin~ t~ theix $hape~ each of the parts 7a~ 7b constitutes a~ Qbject W~thQUt undercuts and oonsequently mouldable withDut a oore, It Will be obse~ved~ in oom~arin~ Figs~ 13-14 and Fiqs. 15-16, that the c~est 12 of the seal element 17 may be divided into tWD
symmetrical parts on each part 7a, 7b (Figs. 13-14) or it may exl5t only on a single closure member part, for example 7b, the other part 7a being oorrespondingly truncated (Figs. 15-16), so that the assembly joint for~s in this region a ~iqht-angled labyrinth which opposes poss~ble entry of fluid between the t~D parts of the closure member.
It will be further observed, in comparing the section of Fig. 17 to that of Figs. 13 to 16, that in the u~Fer seal portion / ~
~6SZ7 and belcw the diametral zone of axis X-X, the cP~l bead 12 has a different orientation to that of the bead 12 located in the lower portion ; in the latter, the bead 12 bears against a - surface which is closely si~ilar to or coincides with the cylin-drical caVity 4, whereas, in the upper levels~ it bears against a s~rface which becomes roughly transverse to the axis X-X, as descrih~ hereinbefore~ Thus the bead 12 is thr~ughout d;rected toward the surface 6.
Ih~ closure member 7 formed by the adhered assembly of the parts 7a, 7b, oomprises on the periphery thereof,convex surfaces which corresoond to concave surfaces forming the seat 6.
By way of a m~dification, the closure member 7 may be in a single piece,but its moulding is m~re difficult than when it is in two parts.
There will now be considered the horizontal projections of the seal lines of the gate valve according to the invention (Figs.
20 and 21) and of the gate valve of French patent N 71 16057.
Under the effect of the upstrean or dbwnatream pressure of the oonveyed fluid, the closure ~ember 7 in its closing position is applied against the part of the seat 6 which is opposed to th~ pressure, and the seal line 61 is A! B, c2 (Figs. 20 and 21) in projection on the plane ~ of the section of Fig. 5.
, If this seal line is ~rojected onto the diametral plane containing the axis X-X and perpendicular to the axis Y-Y, there is obtained for the second embodlment of the invention the crescent-shaped crosshatched area of the lower part of Fig. 21.
This area represents the surface on which a force must be exerted ~6~i27 ~ 21 -in ord~er to open the closure me~ber and overoome the pressure that the fluid exerts thereon. The resistance to overcome for opening the closure member 7 is termed the bottom effect. This resistance or bottcm effect is the product of the pressure to be overccme by the projected crosshatched area of Fig. 21. Thus it can be seen that this bottom effect or this resistance to be overocme is the greater, for a given pressure to be overoome, as the prDjected~area is larger.
It can be seen, by oo~parison, that the projected area of Fig. 20 in respect of the closure member 7 of the s~cond embodi-ment of the invention, is substantially reduced relative to that of the closure member of the French patent ~ 71 16057 of the Applicant (the seal line and the crosshatched projected area of Fig. 19) for a given diame~r of the flow tube 4.
Numerical example.
In respect of an inside diameter of the flow cavity 4 of ,~ 150 mm and for a pressure of 16 bars to be overoome when opening the closure member, the projected area (Fig. 19) of a closure member of said prior patent of the Applicant was 2S0 sq.cn and the opening force or bottom effect was 4 000 kg.
In respect of a closure m~mber according to the second en~cdiment of the invention, the projected area is re~uced bo 50 sq.cm (Fig. 20) and the force to overcome when opening the valve is reduced to 800 kg.
It will be observed in Fig. 20 (projecte~ area in respect of first e~todiment) that the projected area is stlll smaller than that of Fig. 21 and o~nsequently smaller than that of Fig. 19 5~7 corres~onding to the prior gate valve.
Owing to this substantial reduction in the botbom effect, an actuator of lower power and smaller overall size may be employed with the gate valve according to the invention.
Fhrther, the upper part of the diagrams of Figs. 19 to 21 illustrates the re~uction in the longitudinal overall size, i.e.
the distance ketween the flanges of the tube 2 measured parallel to the axis X-X, for a given diameter of the cavity 4, relative to a gate valve in accordance with the prior patent N 71 16057 of the Applicant for a given minimun angle between the axis X-X and the plane tangent to the seal surface along th~ seal line.
The closure member of the invention retains, owing to the shape of the seat 6 and the corresponding shape of the parts 7a and 7b of the closure memker 7, the advantage of approaching or moving away from the seat 6 with a minimum of friction, since the surfaces which must be applied against each other for achieving the seal move with respect to each other practically without slidLng.
The advantageous result is that the seal element 17 of elastomer, and in particular its seal bead 12,is subjected to the n~ll m~n amDunt of wear.
.~Ddifications of the two foregoing embodime~ts will ncw be described~ These modifications concern only the lcwer part of the seal surface 6 and relate to the case where the flow tube 2 has an inner or outRr prDjection.
Mbdificat on of Figs. 22 to 24.
The tubular body 1 has a transverse chamker 20 on each side of the transverse plane P and oonsequently around the axis Y-~

~4~527 resulting in an outer enlargement or projection from the lcwer generatrices of the tube 2. The chamber 20 acts a~ a housing for the lower part of the closure member at the end of its valve-closing travel.
This chamber hasthe shape of a cylindrical rule~ surface whose generatrices are parallel to those of the cylindrical cavity 4 and are connected to the latter by walls parallel to the plane P. Conse~uently, the seal surface of the seat of the closure nfmber is simply modified by replacing the lower cylindrical part 65 by a lower cylindrical p~rt 66 ~hich coincides both with a part of the cylindrical cavity 4 and wqth the chamber 20. Conse-quently, the lower portion 66 is a ruled surface which is partly cylindrical and partly of a shape which is dbwnNardly elongated beyDnd the cyli~rical shape so that the rectilinear generatrices ~5 thereof gr~ y change from those of the cavity 4 to those of the chamber 20 with which latter they finally ooincide.
Mbdification of Figs. 25 to 27~
rrhe tlibular body 1 has, as before, a transverse cha~r-21 ~hich projects outwardly from the tube 2, but this cha~ber is connected to the cavity 4 by chamfers 22. The lower portion 65 of the seal surface is r~placed by a lower portion 67 and has rec-tilinear generatrices which gr~ ly change between those of the cylindrical cavity 4 and those of t~e chambers 22.
Mbdification of Figs. 28 to 30.
The tubular body 1 has an inner projectlon 23 on each side of the transverse plane P. This projection 23 is a ruled surface forming a cylindrical thickening whose axis is p~rallel to the .

axis X-X and whose radius ls larger than the radius of the cavity 4. It is oonnected to the latter by circular chlmfers 24.
The lcwer portlon of the closure member 7 must bear in a fluidti~ht manner against the inner projection 23 and in parti-cular against the circular chamfers 24. Consequently, the sealsurface of the seat of the closure member is mDdified by replacing the lower cylindrical portion 65 by a lower portion 68 which has rule~ surface the generatrices of which gradually changefrom the generatrices of the cavity 4,which are par~llel to the axis X-X, to those of the chamfers 24.
-In each of the foregoing three m~difications, the lower portion of the closure member 7, and in particular of its seal line 71, is of oourse modified in the same way as the seat surface.
; ~orew er, it will be understood that the same mDdifications may be envisaged far the first ~m}odiment of the invention.
In the mPdlfications of Figs. 25 to 27 and 28 to 30, it is essential to note that the angle that the plane tangent to the bearing surface 22 or 24 along the seal line makes with the axis Y-Y i5 at least e~al to the m~nin~ angle oc of 20. Thlls 20 a constant angle of at least 20 is obtained throughalt the length of the seal line. The advantage of this is that, throughout the periphery of the seat, the elastic seal element 17 operates ur~ler the sam~ conditions. T}~s the cc~pression of the seal element, .~nsidered perper~icularly to the beariny surface, is oonstant 25 throughout the periphery of the seat in respect of a given penetra-tion of the closure m~nber. If the penetration of ~he closure m~er is modifie~, this cc~npression changes its value but ret~ns , . .

~46527 the new value uniformly throughout the periphery of the seat.
Another advantage of these tw3 mcdificatlons ls that the closure me~ber is guided and supported in the lower part thereof at the end of the closure. This is an advantage which is of particular interest when it is ccnsidered that the be~ring and guiding surface of the ears 10 of the closure mfmker on the guides 11 of the body is of limited height.
M~dification of Figs. 31 to 34.
_ It will be observed that in the tw~ embodiments of Figs. 1 to 4 and Figs. 5 to 8, there is on the seal line a critical crossing point B, B2 which must coincide on the seat and on the ~A~l element li of the closure member 7.
If the manufacturing tolerances of the seat and of the closure member are too wide, there is a risk of a slight offset between -~5 this crossing point on the seat and on the closure mem~er andaonsequently a risk of a defective seal.
This is why, in the case where wide manufachlring tolerances are employed, it is advisable to replace this critical crossing point by a short ~P~l line 80 forming a ccnnectlon line in vertical lateral projection onto the plane Q. This line 80 is embodied by a crest line 81 on the closure member on each side of the diametral plane having the axis X-X and in the vicinity of the latter, this crest line being located on a small straight segment 82 of the seal rib of the closure menber (Fig. 31), and by a flat face 83 interconnecting the surfaces 63 and 64 on the seat (Fig. 33).
mus a slight offset to one side or the other of the plane of ~4~52'7 ~ymmetry P-P is possible between the seat and the closure member since there will always exist a sealing contact between the seal crest 81 of the straight segment 82 and the corresponding flat face 83 of the seat.
The gate valve shcwn in Figs. 35 and 36 has a ~ody 1 identi-cal to that of Figs, 31 to 34, The closure member or gate is generally similar to the closure m~mber 7 of Figs. 31 and 32. The sole difference is in the shape of the crest line 171 of its seal bead 112.
Indee~, in the upper and intermediate portions of the bead 112, i.e., in following on each side of the plane of symmetry P, the path AECDEFG, the crest line 171 has the same shape as the seal line 61 of the seat but is slightly expanded, i.e. offset at each point a constant distance or interference i perpendicularly to the seat surface 6.
In the lcwer portion of the bead 112 between the two points G which are the upper limits of the portion of the surface 6 coinciding with the cavity 4 of the flow tube 2, the shape of the crest line 171 ls on the other hand set back relative to that of the seal line 61. Mbre precisely, when viewed along the axis X-X (Fig. 35), the lower portion of the line 171 has the shape of an arc of a circle whose radius is slightly larger than the radius of the cavity 4 of the flow tube.
When the closure member 107 descends for closin~ the flow cavity 4, a m~ment ~ is reache~ at which all the points of the line 171 located above the two points G, namely all the points such as A, B, C, D, E, F an~ G, come simultaneously ~6~27 in oontact with the line 61 of the seat (Figs. 41 and 42). At the sa~e ~Pment ~ , a radial clearance i exists below the tw~ points Gr and this clea~ance gradually increase5 from a zero value at the F~int5 G to a n~ximun value iM at the lower point H in the plane 5 . of sycnetry P on the axis Y-~. .
When the closure membe~ 107 continues to descend in the vertl-C3~ travel s to its fully closed position, in the'upper and inter-~diate regions of the bead 112~ i.e~ abcve the tw~ Points G, ~hi,s bea~ is Ero~r.essi,vel,y cr~shed on the su2face 6 With~ut slid-~ng,or substantially with wt sliding,on this surface! to ac~ushed o~ interference value i (Fig~ 43? . As in ~11 these regionS A~ Br C~ D, E, F~ G~ the plane ta,ngent to the:surface 6 al~ng the line 61 ~akes an angle which is roughly constant with the directi,on Y-Y of displacem.ent, this angle being for exa~ple 20 o~ 30, we have at all points i = s . sin CX O =
c~nstant = lo, Eelcw the two poin~s G, in the preceding embDd1ments, the co~tArt 71-61 oocu~s sim~tane~usly at.the t~me ~ as akcve the po,ints G. As in this ~egio-n the angle ~ varies ~nom oY o, to 90~ the i.nterference i = s . sinCX varies from one point to the other fram s , sin o~ O at the point G to g , sin 90 _ s at the point H.
On the other hRnd~ in Figs. 35 and 36r w~e have below the poir.ts G : i = s ~ sin ~ - j, so that it is sufficient to choose j _ s . sin c~ - io = S (sin c~ - sin CX O) (I) at each point so that the inte~f,erence i be still equal to io in this lcwer, region. The formula (I~ is thus of the tyEe j = a sin - b, with a = s and b = s . sin 0.
~ y way of example, ~ith c~0 = 30, the interferences i at the Points A and ~ at the time t2 of complete fluidtight closure, after ~ travel s of 2 m~ from the t~ne ~ and a S clearance at the po~nt H of ~ m~ at the t~me ~ ,are calculated in the following manner with the fornula (I) : -fron the po~nt A tQ the point G :
io - 2 x sin 30 - 1 m~
at the point H (j = 1 nP~ ;
i - 2 x sin 90- - 1 = 1 mm at an intermediate point K below G and a ~ ly spaced 30 .
frQ~ e have d - 60 an~ a r ~ clea~ance 0~732 m~ nust be prcvided in order to obtain the same . ~nterfer.ence ;
i _ 2 x sin 60 - 0,732 - 2 x 0.866 - 0,732 = 1 mm In this way there is obtained an interference or a crushing i which is constant and equal to io throughout the periphery of the sea~ be~d, ThiS property is of interest and advantageous~ sin~e an insufficlent interference at cert2ins points is liable to result in a defective seal whereas an excessive interference results in in great wear of the seal head, The fo~egoing formula (0 t namely j = s . sin c~ - io =
s (sin ~ - sin c~ 0), gives the contour of the c~est line 171 providing a uniform value lo of i throughout its periphe~y. In practice, there may be adopted below the tw~ points G a shape of an arc of a circle of radius Rl for the line 171 slightly greater than the radius R of the cavity 4 with ;

~6S;~7 Rl = R + lo It will be understood that in the completely closed positicn of, the valve, the mean line ~71~ of the cxushed surface 17Ib of th,e'kead 171 coincides ~ith the'se~ ~ine 61 of the seat 6, ~ eas S in the p~eceding embcdi~ents, it waS the'crest line 71 whic~ ooin-cided wi.th thi~ line 61 at tl~e tl, The aXrangement described ~ith xefe.r.ence to Figs~ 35 an~ 36 m~y be applied bo all the prese~ing enbodlnents in Which the angle between the'tan~ent pl,an~ and the axis Y.-Y varies in the ~cWer, part of the se~t, i.e. in al~ the pr,~rC~ing eTb~diments except those of Fi~s. 25 ba 27 an~ 28 t~ 30. When the cr~ssing ~f the seml-seal lines. ls at a point (F~gs, 1 bo 30?, the'inter-section point replaces the yertical section C, D, ~ of Figs.
1 an~ 2! but the rem~in,d,er o~ the.'bead ~s ~s def i d hereinbefore.
It m~st be unde~st~od that th.e express,ion "crest line"
employed herei,nbefore mu,st be.understqod in the broadest sense~
since this line ~ay be ln so~e cases a 5urface of sm~ll width in the case o~ a seal bead, having a rec ~ r, trapezoidal or a half-moon shape~ ' . 20 ~ ughout the foregoing description it has been assu~e~ that the axis X-X is horizontal and the axis Y-Y is vertical. However, it must be undersbood that the gate valYe accordi~g to the invention may be employed in any des~,red orienta,tion, for example w~th the flc~ axis X-X vertical or inclined.

': ;

.

Claims (14)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A gate valve of the type comprising a body having a horizontal cylindrical flow tube which defines a seat surface, and a closure member provided with a seal bead of elastomer and guided in vertical translation, said bead bearing on the seat surface of the body and having the same general shape as the seat, wherein the seal line of the seat has, when viewed in a d direction perpendicular to the axis of the flow tube, a generally X-shape and is obtained, throughout or substantially throughout its length, by the translation of two semi-seal lines in a direction toward each other along said axis, said semi-seal lines having together the general shape of a wedge.

2. A gate valve according to claim 1, wherein the two semi-seal lines cross roughly in the horizontal diametral plane of the flow tube.

3. A gate valve according to claim 1, wherein each semi-seal surface is a ruled surface which comprises an upper curved portion which is roughly transverse to the flow axis, a lower curved portion which coincides with the inner cylindrical flow surface and, between said two portions, above and below a diametral zone represented in projection by the flow axis, an intermediate roughly helicoidal transition portion in the shape of a turning ramp which interconnects said upper and lower portions by turning around the cylindrical flow surface as close as possible to said flow surface.

4. A gate valve according to claim 3, wherein the portion of each semi-seal surface located above the zone of the flow axis is replaced by two portions of a plane which converge toward said axis and are extended by curved surfaces of connection to the surfaces located below said zone.

5. A gate valve according to any one of the claims 1 to 3, wherein the crossing points of the X-shape are replaced by flat faces on the seat surface and, in respect of the seal bead, by segments of a straight line which is roughly vertical when viewed in side elevation.

6, A gate valve according to any one of the claims 1 to 3, wherein the seal bead follows along the periphery of a plate formed by a cylindrical lower portion having an axis parallel to the flow axis, a parallelepipedic intermediate portion and an upper wedge shaped portion whose apex is horizontal and perpendicular to the flow axis.

7. A gate valve according to any one of the claims 1, wherein the closure member comprises two semi-closure members which are assembled on a vertical joint plane which is perpendicular to the flow axis, each semi-closure member being a thin shell provided with reinforcing means and positioning means for positioning it with respect by the other semi-closure member.

8. A gate valve according to claim 7, wherein each semi-closure member comprises an inner projection which bears against a horizon-tal end surface of the other semi-closure member.

9. A gate valve according to any one of the claim 8, wherein the seal bead is formed by a thicknening of a cover element which covers the whole of the closure member.

10. A gate valve according to claim 9, wherein each semi-closure member is covered with said cover element on the inner and outer surfaces thereof.

11. A gate valve according to any one of the claims 1 to 3, wherein the flow tube has in the region of the closure member an inner or outer projecting region and the lower portion of the seat surface is modified accordingly with surfaces for gradually connect-ing it to the remainder of said surface.

12. A gate valve according to claims 3, wherein, the lower portion, the angle that the axis of the operating rod makes with the plane tangent to the seal surface varies, the rest line of the seal bead vein defined in such manner as to simultaneously meet the seat surface at all points except in the lower portion of said surface where, upon said first contact, there remains a radial clearance which progressively increases on each side to the lower point of the flow cavity.

13. A gate valve according to claim 12, wherein said clearance is obtained by giving the lower portion of the bead, wherein viewed in the direction of the flow axis, a radius of curvature greater than the radius of curvature of the flow cavity.

14. A gate valve according to claim 12 or 13, wherein, if .alpha. designates the angle that the axis of the operating rod makes with the plane tangent to the seal surface along its mean line, said clearance varies in accordance with a law of the type j = a sin .alpha. - b, where a and b are constants.