Patent Description:
A type of commonly used valve system, as shown in <FIG>, comprises a valve body <NUM> housing a plunger <NUM> fixed at one end to a reciprocating valve stem <NUM>. The latter extends at the other end into a top box (not shown) of the valve system. The top box may comprise actuating means for controlling the reciprocating movement of the stem <NUM>.

The valve system further comprises a stuffing box <NUM> fixed to the valve body <NUM> and housing an annular packing <NUM> for sealing the stem <NUM>.

In currently known systems, the stuffing box <NUM>, after being threaded to the valve body <NUM>, forms a visible protrusion P on the outside surface of the valve body <NUM>, where dirt and alike may accumulate, which is not desirable in view of the general requirements of some industries such as the food and hygiene industries.

Furthermore, in known products, a sealing element <NUM> for preventing liquid leakage between the stuffing box and valve body, commonly made of polytetrafluoroethylene (PTFE), is received in an annular cavity <NUM> formed between the stuffing box and the valve body as shown in <FIG>.

In such a construction, the sealing element <NUM> is compressed essentially in the axial direction by the stuffing box <NUM>. This construction requires a relatively high screwing torque for compressing the sealing element <NUM> due to the large contact area between the latter and the stuffing box <NUM>. Furthermore, since the sealing element <NUM> is little compressed or not compressed in the radial direction, the fluid <NUM> is not prevented to enter the space between the sealing element <NUM> and the stuffing box <NUM> on the radially inner side of the sealing element, as shown. Therefore, the pressure of the fluid <NUM> may cause in some situations the sealing element <NUM> to flow into an axial gap <NUM> between the valve body <NUM> and the stuffing box <NUM>. This may lead to a possibility of leakage over a time due to stress relief of the sealing element <NUM> caused by this deformation of the sealing element. The seal relaxation may also result in thread loosening between the stuffing box <NUM> and the valve body <NUM>.

<CIT> discloses a sealing arrangement on a spindle of a valve. The arrangement comprises a stuffing box arranged between a collar threaded thereto and a flange of a valve body. The stuffing box comprises recesses forming respectively with the flange and the collar a cavity for receiving a sealing element. In <CIT>, the cavities also require relatively high screwing torque for compressing the sealing elements due to the large contact area between the latter and the stuffing box.

<CIT>, <CIT>, <CIT> disclose sealing elements for a valve stem.

There exists a need to further improve existing valve systems and to remedy at least in part to the drawbacks mentioned above.

Exemplary embodiments of the present invention relate to a valve system according to claim <NUM>, the valve system comprising a valve body and a stuffing box assembled to the valve body, the valve body having an internal surface defining an annular groove, this annular groove having an upper side, a lower side and a bottom extending axially between the upper and lower sides, the annular groove forming with the stuffing box an annular cavity for receiving a sealing element.

The terms "upper" and "lower" refer to the relative position along a longitudinal axis of the system oriented vertically, with the stuffing box lying above the valve body.

In the present invention, the sealing element is at least partially received in the groove. Accordingly, the part of the sealing element received in the groove is not axially compressed by the stuffing box. Thus, due to the reduced contact area between the stuffing box and the sealing element, the assembly needs lower screwing torque for sealing. In this way, the sealing element may be more easily caused to expend radially against the stuffing box and the valve body and create corresponding sealing surfaces. A flow of fluid at the interface between the sealing element and the stuffing box and over the entire height of the sealing element may be more easily avoided.

The groove may have a depth of at least <NUM>.

A shoulder of the internal surface of the valve body defining the lower side of the groove may come in axial abutment with the stuffing box.

The stuffing box comprises a first and a second shoulder.

The first shoulder comes in axial contact with the sealing element.

The second shoulder may be in axial abutment with the shoulder of the valve body defining the lower side of the groove.

The stuffing box may comprise a surface, preferably cylindrical, extending axially between the first and second shoulders, configured for coming in radial contact with the sealing element.

Preferably, the valve system comprises a plunger housed in the valve body; this plunger may be fixed at one end to a reciprocating valve stem.

The valve may comprise a first interface extending axially between the valve body and the stuffing box, situated axially farther from the plunger than the annular groove. The first interface may be located at a distance from the longitudinal axis of the system, that is smaller than the distance from which the bottom of the groove is spaced from said axis, but preferably larger than the distance by which the surface extending axially between the first and second shoulders is spaced from said axis.

The valve may comprise a second interface extending axially between the valve body and the stuffing box, situated axially closer to the plunger than the annular groove. The second interface may be located at a distance from the longitudinal axis of the system that is smaller than the distance by which the surface extending axially between the first and second shoulders is spaced from said axis.

The stuffing box is preferably assembled to the valve body by screwing and the valve system comprises corresponding threads on the stuffing box and the valve body. The annular cavity is preferably located closer to the plunger than said threads, when observed along a longitudinal axis of the valve system. The sealing element thus avoids the fluid to flow into the threads.

The sealing element may comprise or be composed of PTFE.

The valve system may be a pressure actuated valve system, or motor actuated valve.

Exemplary embodiments of the present invention also relate to a method for assembling a valve body and a stuffing box of a valve system of claim <NUM>, the stuffing box comprising a collar in contact with a top surface of the valve body, the method comprising deforming the stuffing box during assembly thereof to the valve body, preferably by screwing, so that the height by which the collar protrudes is decreased after assembly.

By deforming said collar during assembly, the invention allows forming a smoother surface at the joint line between the stuffing box and the valve body, without leaving any substantial retention area at the joint line.

In particular, the valve system thus obtained may not comprise any acute or right angle between the top surface of the valve body and a top surface of the collar.

Exemplary embodiments of the present invention also relate to a method for assembling a valve body and a stuffing box of a valve system of claim <NUM>, the valve body being assembled to the stuffing box by screwing, the valve body having an internal surface defining an annular groove, this annular groove having an upper side, a lower side and a bottom extending axially between the upper and lower sides, the annular groove forming with the stuffing box an annular cavity for receiving a sealing element, the stuffing box comprising a collar in contact with a top surface of the valve body, the method comprising deforming the stuffing box during assembly thereof to the valve body, so that the height by which the collar protrudes is decreased after assembly.

The valve system obtained after assembly exhibits all or part of the features of the valve system mentioned above.

The method may comprise a first step of positioning the collar of the stuffing box on the top surface of the valve body, while keeping an axial gap between the lower side of the annular groove and the stuffing box, in particular between the lower side of the annular groove and the second shoulder thereof.

The method may comprise a second step of mechanically deforming the collar of the stuffing box, in particular due to screwing during the assembly, until the lower side of the annular groove comes into contact with the stuffing box, in particular until the shoulder of the valve body defining the lower side of the annular groove comes into contact with the second shoulder.

Exemplary embodiments of the present invention also discloses a valve system, comprising a valve body and a stuffing box assembled to the valve body by screwing, the stuffing box comprising a collar in contact with a top surface of the valve body, the collar of the stuffing box being deformed during assembly thereof to the valve body.

Embodiments of the invention will now be described in some further detail with reference to and as illustrated in the accompanying figures. These embodiments are illustrative only, and are not meant to be restrictive of the scope of the invention.

A valve system <NUM> of the invention, as shown in <FIG>, comprises a valve body <NUM> and a top box <NUM>. The valve body <NUM> houses a plunger <NUM> fixed to a reciprocating stem <NUM> at one end. The opposite end of the reciprocating stem <NUM> extends into the top box <NUM>, which comprises an actuator for controlling the up and down movement of the stem <NUM> along the longitudinal axis X of the system, thus the opening and closing of the valve by the plunger <NUM>.

As shown in <FIG>, a stuffing box <NUM> is screwed to the valve body <NUM> via cooperating threads <NUM>, situated respectively on an internal surface <NUM> of the valve body <NUM> and an external surface <NUM> of the stuffing box <NUM>. The stuffing box <NUM> comprises a central bore <NUM> inside which the stem <NUM> may slide.

As can be seen in <FIG>, a top surface <NUM> of the collar <NUM> forms a smooth joint line <NUM> with an adjacent top surface <NUM> of the valve body <NUM>, without the presence of any substantial acute- or right-angle external protrusion between the top surfaces <NUM> and <NUM>. In this way, there is no substantial retention area created at the joint line <NUM>, which helps to avoid accumulation of undesired substances therein.

As shown in <FIG> and <FIG>, the valve body <NUM> comprises an annular groove <NUM> on its internal surface <NUM>. The annular groove <NUM> comprises a bottom <NUM>, an upper side <NUM> and a lower side <NUM>. The bottom <NUM> of the annular groove <NUM> extends axially between the upper and lower sides <NUM>, <NUM>. The lower side <NUM> is defined by a shoulder <NUM> of the valve body.

The annular groove <NUM> preferably has a depth d, measured in a direction parallel to a radial direction of the valve system, which is at least of <NUM>.

The annular groove <NUM> has a height h, measured in a direction parallel to the longitudinal axis X of the valve system, that is preferably of between <NUM> and <NUM>.

The shoulder <NUM> has a width w<NUM> preferably of between <NUM> and <NUM> when measured radially.

The stuffing box <NUM>, as shown in <FIG> and <FIG>, comprises on its external surface <NUM> a first shoulder <NUM> and a second shoulder <NUM>. The first shoulder <NUM> is configured for coming in axial contact with the sealing element <NUM>. The second shoulder <NUM> is in axial abutment with the shoulder <NUM> defining lower side <NUM> of the groove <NUM>.

The first and second shoulders are separated by a cylindrical surface <NUM> extending axially.

The first shoulder <NUM> may have a width w<NUM> of between <NUM> and <NUM>.

The second shoulder <NUM> may have a width w<NUM> of between <NUM> and <NUM>.

In the illustrated embodiment, the annular cavity <NUM> is located closer to the plunger <NUM> than the threads <NUM>, when observed in the longitudinal direction X of the valve system.

The valve system comprises a first interface <NUM> between the stuffing box <NUM> and the valve body <NUM> that is situated farther to the plunger <NUM> than the annular cavity <NUM>. As can be seen in <FIG>, the first interface <NUM> is radially inner to the bottom <NUM> of the groove <NUM>.

The valve system comprises a second interface <NUM> between the stuffing box <NUM> and the valve body <NUM> that is situated axially closer to the plunger <NUM> than the annular cavity <NUM>. The second interface <NUM> is radially inner to the surface <NUM>.

For assembly the valve system, the stuffing box <NUM> is screwed into the valve body until the collar <NUM> comes into abutment with the top surface <NUM> of valve body <NUM>, as shown in <FIG>. As shown in detail in <FIG>, an axial gap <NUM> of a height h' is then existing between the lower side <NUM> of the groove <NUM> and the shoulder <NUM>.

Then, by screwing further the stuffing box <NUM> into the valve body <NUM>, the collar <NUM> is mechanically deformed, leading to the configuration shown in <FIG>.

During this plastic deformation of the collar, the height h by which the collar <NUM> protrudes from the top surface <NUM> is decreased, substantially to a value of less than <NUM>. In this way, there is no pronounced discontinuity between the top surface <NUM> of the valve body <NUM> and the top surface <NUM> of the collar <NUM>, which helps avoid accumulation of undesired material in the zone around the joint line <NUM>.

At the end of the screwing, the shoulder <NUM> of the valve body comes into abutment with the second shoulder <NUM> of the stuffing box <NUM>, so that the sealing element <NUM> is axially compressed by the first shoulder <NUM> and the shoulder <NUM> and expands radially.

Four sealing interfaces are thus formed, respectively between the sealing element <NUM> and the bottom <NUM>, between the sealing element <NUM> and the lower side <NUM>, between the sealing element <NUM> and the cylindrical surface <NUM>, and between the sealing element <NUM> and the first shoulder <NUM>.

The stuffing box <NUM> does not axially compress the sealing element <NUM> on its portion which is received in the annular groove <NUM>.

As shown in <FIG>, after assembly, the first shoulder <NUM> is axially closer to the lower side <NUM> than is the upper side <NUM> of the annular groove <NUM>.

A ratio l/h between the distance l from the first shoulder <NUM> to the lower side <NUM> and the height h of the annular groove <NUM>, is preferably between <NUM> and <NUM>.

The ratio between the depth d of the groove <NUM> and the width w<NUM> of the first shoulder <NUM>, i.e. d/w<NUM> is preferably at least <NUM>.

Claim 1:
A valve system (<NUM>) comprising a valve body (<NUM>), a sealing element (<NUM>) and a stuffing box (<NUM>) assembled to the valve body (<NUM>), the valve body (<NUM>) having an internal surface (<NUM>) defining an annular groove (<NUM>), the annular groove (<NUM>) comprising an upper side (<NUM>), a lower side (<NUM>) and a bottom (<NUM>) extending axially between the upper (<NUM>) and lower (<NUM>) sides, the annular groove (<NUM>) forming with the stuffing box (<NUM>) an annular cavity (<NUM>) for receiving the sealing element (<NUM>), the stuffing box (<NUM>) comprising a first (<NUM>) and a second (<NUM>) shoulder, characterised in that the first shoulder (<NUM>) comes in axial contact with the sealing element (<NUM>).