Ball valve

An improved ball valve is disclosed, which is particularly adapted for use with pipelines of large diameter, possibly of the kind intended to convey toxic or dangerous fluids and for which a virtually perfect seal is required, said valve having a control mechanism which comprises sequentially acting linkages and preloaded resilient means in order that the valve shutter is always in an accurate central position as to its axis of rotation and the approach of the shutter to the seat takes place only once that the rotation of 90.degree. has been completed, in order that a uniform and intense pressural action of the shutter on the seat may be obtained. Alternative embodiments within the scope of the invention are shown and described.

This invention relates to a ball valve of an improved type, having one or 
two shutter members, for stopping the flow in large-diameter pipings, in 
which the closure is effected by a twofold movement of the shutter(s), 
said movement being composed of a 90-degree rotation about the axle of the 
ball which is perpendicular to the axis of the stream and a subsequent 
advance towards the seat. 
More detailedly, the invention relates to a novel type of linkage which 
effects both these movements of the shutter(s) and which thus permits the 
achievement of a fully satisfactory seal when the valve is closed. 
The state of the art has already disclosed a number of types of ball 
valves, but all of these types of conventional make use, for moving the 
shutter(s), of linkages which are both extremely intricate in construction 
and unreliable in operation. 
According to a conventional embodiment, in fact, independent members are 
provided for effecting the shutter rotation step and that of final 
advance, and the latter step is performed by two intricate systems which 
are equal to one another and act resiliently upon both sides of the 
shutter rotation axle and shift said axle of rotation towards the valve 
seat. 
It is apparent, now, that such an approach cannot absolutely afford a 
uniform pressure of the shutter against its seat so that the achievement 
of a full seal is at least questionable. 
According to another known approach, moreover, a single linkage is adopted 
for effecting both movements of the shutter, the seal being entrusted to 
the elastic deformation of two flexible arms; these are affixed to the 
sides of the shutter and mounted eccentrically on the rotation shaft, to 
press the shutter during the rotation of the latter, within guideways 
provided in the seat in cooperation with a thrust member which causes the 
shutter to be tilted forward. 
However, not even the latter approach is such as to provide an even 
pressure of the shutter against its seat and, in addition, due to the 
continuous elastic deformations to which the two flexible arms are 
subjected, an adequately long and satisfactory service life of the valve 
is not warranted at all. 
An object of this invention is to do away with such shortcomings by 
providing a ball valve in which both the movements of the shutter are 
effected by a single simple and reliable linkage which ensures the 
obtaining and the maintenance of a perfect seal in spite of the lapse of 
time. 
This object is achieved, according to a feature of the invention, by a 
shutter which is resiliently connected to a yoke, the two ends of which 
are hinged to two levers which embody a toggle system with two cranks 
integrally fulcrumed to the two sides of an internal rotation shaft, the 
latter being arranged perpendicularly to the direction of the flow and 
rotated by a servomotor with the intermediary of a leverage system placed 
laterally and externally of the valve body, said yoke having its ends 
inserted in straight guideways formed in a rigid guiding structure having 
substantially the shape of a U and mounted idly on said internal rotation 
shaft, said guiding structure supporting the shutter, the central hub of 
which is inserted in a bore formed in correspondence with the axis of 
symmetry of such U-shaped structure and the rotation of said hub is 
confined to an angle of 90 degrees by arresting planes which are supported 
by the valve body aforesaid. 
By so doing, in fact, a first 90-degree rotation of the internal rotation 
shaft, as obtained through said servomotor, entails a like rotation of the 
assembly shutter-yoke-guiding structure and brings the shutter in 
confronting relationship with its seat while the guiding structure goes to 
abut said arresting planes. At this stage, an additional rotation of the 
shaft, still by the instrumentality of the servomotor, will involve only a 
straightening of the toggle systems formed by two connecting rods and two 
cranks since the assembly shutter-yoke-guiding structure cannot be rotated 
due to the presence of the arresting planes, so that the yoke will be 
pushed forward and the same shutter will do and will rest pressurally 
against its seat. On the other hand, since the forward movement of the 
yoke and the shutter is guided by the rectilinear guideways of the rigid 
guiding structure which is idly mounted on the internal rotation shaft, it 
is warranted that the displacements of the shutter will always take place 
in the radial direction, that is to say in such a way that the central 
axis of the shutter will always contain the center of the valve and the 
shutter is always centered relative to its seat, just as must be in order 
that an efficient seal may be achieved. 
Definitely, a feature of the present invention is the fact that the linkage 
for the rotation of the shutter and the subsequent advance thereof towards 
its scat is formed by an internal rotation shaft, arranged perpendicularly 
to the direction of the stream to be stopped and rotated by a servomotor 
through a system of leverages placed laterally and externally of the valve 
body, at both sides of which are affixed two cranks which make up a toggle 
assembly with two levers which are respectively fulcrumed to the two ends 
of a yoke and are inserted in rectilinear guideways borne by a rigid 
guiding structure shaped substantially in the form of a U, said structure 
being mounted idly on the internal rotation shaft and supports the 
shutter: the central hub of the shutter is inserted in a bore formed in 
registry with the axis of symmetry of the U-shaped structure and is 
resiliently connected with said yoke, the rotation of the rigid guiding 
structure being limited to an angle of 90 degrees by arresting planes 
which are supported by the valve body aforesaid. 
According to another feature of the present invention, the central hub and 
thus the shutter, are resiliently connected to the yoke by two preloaded 
cup spring systems, the first system acting between the rigid guiding 
structure and a projection of the hub, the second system acting between 
said projection and said yoke to which the hub is movably and axially 
connected by a through-screw, said second spring system being preloaded to 
a preselected sealing value while the first spring system is preloaded to 
a lighter value. 
By so doing, the twofold result is achieved that, in the valve-opening 
stage, both spring systems withdraw the shutter from its seat and 
automatically restore the angle between the cranks and the connecting rods 
of the two toggle systems, whereas the tight seal of the valve is obtained 
with a first stage of approach of the shutter to its seat via the 
comparatively small force applied by the first spring system and a 
subsequent stage of sealing proper through the preselected intense force 
as displayed by said second spring system. 
Actually, as the two toggle systems are straightened and thrust both the 
yoke and the shutter forward, the spring of the first system is compressed 
at the outset, whereby the shutter is pressed against its seat with a 
comparatively small force and this fact makes possible the setting 
movements, if any, of the shutter on the seat, and only thereafter the 
spring of the second spring system is compressed and transfers the 
preselected load by which the shutter must be pressed against the seat to 
achieve the desired sealing force. 
However, in the embodiment as described hereinbefore, the ball valve is 
always fitted with an internal rotation shaft which, when the valve is 
open, dips in the flowing stream. 
Since the existence of such a shaft might originate in certain cases 
pressure drops which are inadmissible, in order to effect such a 
shortcoming and according to a characteristic modification of the present 
invention, the linkage for the rotation of the shutter and the subsequent 
advance thereof towards its seat, is composed of an annular structure 
which is pivoted to the valve body by the agency of two diametrically 
opposite rotation pins, either of which is controlled by the servomotor 
aforementioned, the annular structure having pivoted thereon, 
eccentrically relative to the rotation pins, two connecting rods the heads 
of which are, respectively, pivoted to the end of a yoke which centrally 
bears the shutter through a cup-spring system, the yoke ends being, in 
addition, integral with two guiding arms which are inserted in a groove of 
two grooved pins which are idly supported by said rotation pins, 
respectively, and the rotations of which are limited to an angle of 90 
degrees by arresting planes supported by the valve body. 
It is apparent that such a linkage is substantially akin to that described 
hereinabove, As a matter of fact, also in this case, there is a double 
toggle-system formed by two connecting rods and by two cranks, but now the 
two cranks are an entity with the annular structure aforesaid and the 
toggle effect is provided by the eccentrical pivoting of the two 
connecting rods. In addition, even if the rigid guiding structure has been 
omitted, also in this case the yoke and thus the shutter must always be 
displaced radially, their axis of symmetry being always maintained as 
passing through the valve center by virtue of the action exerted by the 
guiding arms. 
However, the absence of a rigid guiding structure in the valve embodiment 
just now described, by its permitting relative movements of the 
yoke-shutter assembly with respect to the annular structure, may 
originate, during the open-valve operation or during the closing stage, 
that is when the shutter is being rotated, detrimental vibrations of the 
yoke-shutter assembly. 
In order that such a drawback may be offset and that any movement of the 
yoke-shutter assembly may be prevented prior that the shutter has brought 
about the sealing action, and thus, summing up, in order to lock the 
yoke-shutter assembly to the annular structure in the open-valve situation 
and during the closing stage, according to another modification of the 
present invention, such an annular structure is equipped with two conical 
latching dowels which are inserted into corresponding seats formed through 
said yoke, the unlatching taking place spontaneously as a result of the 
valve-closing operation itself. 
As a matter of fact, as soon as, upon a 90-degree rotation of the annular 
structure, the guiding arms integral with the yoke abutthe respective 
arresting planes and cannot consequently be rotated any wider, the further 
rotation of the annular structure to straighten the levers of the toggle 
systems and thus to effect the valve-closing step, will do nothing else 
than automatically unlatching the conical dowels integral with the annular 
structure which rotates from the seats to the yoke, the latter remaining 
at standstill, so that the yoke itself is disengaged. 
Moreover, in order to improve the latching of the yoke-shutter assembly to 
the annular structure still better in the open-valve operation and during 
the closing stage, according to a further characteristic of the present 
invention, there are pivoted onto the annular structure two gripping hooks 
which are respectively urged by recoiling springs towards becoming hooked 
to gripping planes tendered by the guiding arms, the hooks being equipped 
with rolling followers which cooperate with the arresting planes, 
respectively, for releasing said hooks. 
Lastly, it must be borne in mind that, in order that the pressure drops of 
the valve may be further reduced, the annular structure can be affixed to 
a pipe section which is, when the valve is open, an extension of the 
pipeline in the valve interior, so that the fluid fillets undergo no 
deflection at all. On the other hand, it is likewise apparent that the 
invention can be applied also to a ball-valve having two shutters, it 
being only necessary to adopt two linkages of the kind referred to above 
to actuate both shutters. 
The invention is now better illustrated with reference to the accompanying 
drawings which show preferential embodiments of a practical nature which 
have been indicated by way of example only and without any limitation: 
technical or constructional modifications and changes may be introduced 
without departing from the scope of the invention.

Having now reference to the drawings, in which like members are connoted by 
like numerals, at 1 is shown the spherical valve body, at 2 the seat for a 
shutter 3, and at 4 a lever which, installed laterally and externally of 
the valve body 1 on the rotation member of the shutter 3, is intended to 
transfer to the rotation member, via a connecting rod 5, the drive of a 
servo-motor 6 (best seen in FIG. 5). 
Now, the linkage for the rotation of the shutter 3 and for the subsequent 
advance of the latter towards its seat 2, comprises, according to the 
invention, an internal rotation shaft 7 (best seen in FIGS. 1 to 4) which, 
arranged perpendicularly to the direction of flow 8, is supported for 
rotation by the valve body 1 and, emerging by either end from the valve 
body, is made fast to the lever 4. At the two ends of the shaft there are, 
solidly therewith, two cranks 9 and 10 and these are pivoted by two 
respective pins 11 to two levers 12 and 13. Levers 12 and 13, in their 
turn, are pivoted to the ends 14 and 15, of a yoke 16. The two cranks 9 
and 10 and the respective levers 12 and 13 are arranged at an angle 
relative to one another (best seen in FIG. 2) so as to make up a toggle 
system. 
On the other hand, the two ends 14 and 15 of the yoke 16 are inserted, 
respectively, in rectilinear guideways 17 and 18 formed on the wings of a 
rigid guiding structure 19: the latter has substantially the shape of a U 
and is idly mounted on the internal rotation shaft 7. 
The rigid structure 19, has, in addition and in correspondence with its 
axis of symmetry, a bore 20 within which the central hub 21 of the shutter 
3 is inserted for being supported thereby. Hub 21 is resiliently connected 
to the yoke 16 by the through-screw 22 and the two cup spring systems 23 
and 24, the springs of which are preloaded: more detailedly, the first 
system 23 is preloaded at a comparatively low load, is caused to act 
between the rigid guiding structure 19 and an embossment 25 on hub 21, and 
the second spring system 24: is pre-loaded, conversely, to the preselected 
value of the seaming pressure and acts between the embossment 25 and a 
shoulder 26, integral with the yoke 16. 
Eventually, the rotation of 19 about the shaft 7 and thus the rotation of 
16 and the shutter 3, are limited to an angle of 90.degree. by arresting 
planes 27 which are borne by the valve body 1: thus there is the assurance 
that the shutter 3, when the valve is open, lies in the position shown in 
phantom at 3' in FIG. 2 and is always perfectly centered, during its 
rotation, relatively to its seat 2. 
According to the modification of the invention shown in FIGS. from 5 to 9 
inclusive, conversely, the linkage is composed by an annular structure 28, 
which is supported for rotation by the valve body 1, through the two 
rotation pins 29 and 30: these are fastened to the grooved blocks 31 and 
32, respectively, and the latter blocks are screwably affixed to the 
annular structure 28 in central and diametrically opposite locations. In 
the drawings the annular structure 28 is shown integral with a pipe 
section 33. Section 33 is, when the valve is open, nothing but an 
extension of the pipeline concerned in the valve interior, as best seen in 
FIG. 6. In addition, the rotation pin 29, is fastened to the lever 4 
aforementioned. To the annular structure 28 are then pivoted, 
eccentrically relative to the rotation pins 29 and 30, by the agency of 
the pivots 34 and 35, respectively, two connecting rods 36 and 37: these 
are hinged to the ends 38 and 39, respectively, of a yoke 40 which 
centrally bears the shutter 3 with the intermediary of a system of cup 
springs 41. The ends 38 and 39 of the yoke 40, moreover, are made integral 
with either end of two guiding blocks 42 and 43, respectively: the other 
ends of the blocks are tapered and pass through the grooves of the grooved 
blocks 31 and 32 and are inserted into, and remain in, the grooves of two 
grooved pins 44 and 45, respectively: these are supported for rotation in 
the interior of the blocks 31 and 32 in a position which is coaxial with 
the rotation pins 29 and 30. On the other hand, the rotation of the 
guiding arms 42 and 43 and thus also that of the yoke-shutter assembly 
integral with such arms, is limited to an angle of 90.degree. by arresting 
planes 46 and 47, the latter being supported by the valve body 1. The 
annular structure 28 has, furthermore, a cantilevering plate 48 to which 
two conical latching dowels, 49 and 50, are affixed: these are inserted in 
corresponding seats 51 formed through the yoke 40. Unlatching takes place 
automatically as can be both seen and clearly understood in FIG. 8. 
Lastly, to the annular structure 28 are also pivoted, via pins 52, two 
gripping hooks, 53 and 54; these are biased by recoil springs 55 to become 
hooked to gripping planes 56 as borne by the guiding arms 42 and 43. 
The gripping hooks 53 and 54 are also equipped with rolling followers 57 
which cooperate with their respective arresting planes 46 and 47 to 
release the hooks 53 and 54: all this can clearly be seen in FIGS. 7 and 8 
.