MXPA99004013A - Bushing-less stem guided control valve - Google Patents

Abstract

A fluid control valve includes a valve bonnet (30) and a packing nut (56) threadably engaging the valve bonnet. A valve stem (26) passes through the valve bonnet and the packing nut in a clearance fit so that there is no engagement therebetween. Two packing sets of V-type PTFE packing (38, 40) are included with each set having a middle virgin PTFE sealing ring (42), a carbon or glass filled PTFE male packing ring (46) on one side and a carbon or glass filled PTFE female ring (44) on the other side. Belleville disk springs (52) are provided intermediate the packing nut and the two packing sets, for supplying live loading to the packing. In an unloaded condition, initially the packing sets both are in a clearance fit with the valve stem. Threadably inserting the packing nut into the valve bonnet until there are no visible threads at the top of the bonnet ensures a sufficient loading to seal the valve stem, seals the inside diameter of the bonnet, and provides a sufficient stem guidance.

Description

VALVE GUIDED BY VASTAGO CONTROL WITHOUT BEARING This invention relates to fluid control valves and in particular to an apparatus for guiding a valve operating member such as a valve rod.

BACKGROUND OF THE INVENTION Reference may be made to the following United States Patents of Interest, all assigned to the same assignee hereof: 4, 886, 241; 5, 056,757; 5, 129.625; and 5,299,812. The aforementioned patents illustrate the intention to use packing material formed of polytetrafluoroethylene (PTFE), and particularly the packet known commally as a "Type V PTFE pack". The above patents also illustrate that in the typical construction for a rod-guided control valve, two separate guide bearings are used in the valve stem to stabilize the valve stem from lateral loads that occur during operation. These bearings are typically made of metal or metal with a PTFE liner, with the packing rings located between them. It is always desired to provide a new device with fewer components than currently available devices, while the new device works well and provides the same advantages as the previous devices. Accordingly, it is desired to provide a fluid control valve that eliminates the usual guide bearings provided in the past to guide the valve stem.

BRIEF DESCRI PC OF THE I NVENC ION In accordance with the principles of the present invention, a fluid control valve without guide bearings is provided and wherein the packing assembly is subjected to a sufficient packing load to provide not only the desired seal around the valve stem. and within the outer diameter of the valve cap hole, although it also provides a sufficient rod guide interference fit to guide the valve stem and to stabilize the valve stem from lateral loads. A fluid control valve is provided having a valve cap with a central hole for containing the package and wherein an elongated packing nut is engaged by screwing into the upper end of the valve cap. A valve stem extends through the packing nut and valve cap. An upper clearance is provided between the packing nut and the valve stem. A lower clearance is provided between the valve cap and the valve stem. In each case, the clearance is such that there is no coupling between the valve stem and either the packing nut or the valve cap. Two packing assemblies are provided surrounding the valve stem and located within the central hole of the valve cap. It is preferred that the type V PTFE packing rings are used in which in each packing assembly there is a medium PTFE sealing ring sandwiched between a filled PTFE male ring (ie PTFE filled with carbon or glass) and a packing ring PTFE filled female formed of PTFE filled with carbon or glass. At each end of each packing assembly is provided an anti-extrusion wiper ring formed of filled PTFE or composition gasket material and a set of disk springs such as Belleville disc springs is mounted between the packing nut and the first of two. Sets of packing rings with rings against extrusion on each end. The adjustment of the packing nut comprises the Belleville disc springs, thereby loading the packing material and compressing the packing rings to create a seal around the valve stem and also on the internal diameter of the cap. The compression of the package assembly eliminates the need for the upper and lower guide bearings typically used in the past in such rod-guided control valves. The Belleville disc springs will maintain the load and compression of the package assembly for an extended period. According to another aspect of the present invention, a visual indication of the proper packing load is obtained by adjusting the packing nut until the threads of the packing nut are flush with the threads on the top of the cap. The preferred embodiment as described above includes the moving load of the package assembly supplied by the Belleville disk washers. In an alternative mode, the Bellevil disc springs can be removed with the load to be supplied by adjusting the packing nut against the packing assembly. However, this is not desirable as the preferred embodiment since it causes the moving load of the Belleville disc springs to have been eliminated, the packing nut would need to be readjusted occasionally.

BRIEF DESCRI PCIÓ N OF THE DI B UJOS The features of this invention that are considered to be novel are set forth with particularity in the appended claims. The invention can be better understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numbers identify similar elements in the different figures and in which: Figure 1 is a sectional elevation view illustrating a fluid control valve without the usual metal guide bearings.

DETAILED DESCRIPTION Figure 1 shows a fluid control valve 10 having a valve body 12 with opposite mounting flanges 14, 16 for mounting the valve 10, for example, in a pipe system. The valve body also includes a fluid inlet 18 and a fluid outlet 20 with a passage 22 communicating therebetween. A seat valve 24 is provided in the passage to control the flow of fluid through the valve in response to the position of an operative valve member such as a valve rod 26 having a valve plunger 28 at one end for sealed coupling with the valve seat 24. A valve cap 30 has a central hole 32 and is securely mounted to the valve body 12 by a series of threaded bolts 34 and mounting nuts 36. Within the central hole 32 are provided two packing assemblies, one upper assembly 38 and one lower assembly 40. Each of the packing assembly assemblies 38, 40 includes the same components, namely, a V-type packing assembly with an average PTFE sealing ring 42 between a filled PTFE female ring 44 and a filled PTFE male ring 46, and with an extrusion ring 48 at each end of the packing assembly. It is preferred that the filled PTFE male and female rings are formed of PTFE filled with carbon or glass, considering that the middle sealing ring 42 is formed of virgin PTFE. The packing assembly assembly 40 is considered to include the same components as described above that are in the packing assembly assembly 38. For proper separation of the components, a pair of spacer rings 50, each formed of metal, is provided. , such as stainless steel. On the upper spacer ring 50, a set of disc springs 52, such as Belleville disc springs, is provided. As shown in Fig. 1, the upper end of the valve cap 30 has internal threads for threadably coupling the threads 54 in a threaded packing nut 56. Furthermore, as shown in Fig. 1, there is illustrated a upper clearance space 58 inside the packing nut 56 so that the inside diameter of the orifice 58 is larger than the external diameter of the valve stem 26. This ensures that as the valve stem operates inside the valve, it does not there is coupling of the valve stem 26 with the packing nut 56. Likewise, a lower clearance hole 60 is provided between the valve stem 26 and the valve cap 30 so that the internal diameter of the hole 60 is larger than the diameter of the orifice 60 is larger than the external diameter of the valve stem 26 to prevent coupling of the valve stem with the valve cap. Similarly, sufficient clearance is provided between the valve stem 26 and the internal diameter of the spacer rings 50 so there is no coupling of the valve stem with the spacer rings. Accordingly, neither the packing nut 56 of the valve cap 30, nor the spacer rings 50 provide any guide to the valve stem 26. While the Belleville disc springs 52 are provided with a narrow tolerance on their outer diameter with the central packing hole 32 within the valve body 30, the inner diameter of the Belleville springs is sufficiently larger than the outer diameter of the valve stem to avoid any coupling therebetween. The anti-extrusion rings 48 have little or no free space on their outer diameter adjacent to the valve cap and also on the internal diameter close to the valve stem. The filled male and female packing rings 46, 44 are provided to return to the virgin PTFE sealing ring 42 and thus hold it in place. In the fastening of the valve components, Fig. 1 shows an unloaded view which can be easily determined by the operator by observing the packing threads visible above the upper part of the valve cap 30. In this discharged condition, all the rings of packing 42, 44, 46 in each of the packing assembly assemblies, 38, 40 are in free space adjustment, ie not in engagement, with the valve stem 26. According to the packing nut 56 threadably engaged within the valve cap 30, a mobile load compression of the disk springs 52 is provided which thereby places a moving load on the packing ring assembly. The operator continues to screw the packing nut 56 into the cap 30 until there are no visible threads 54 on the top of the cap 62. In this packed packing condition, not only the packing rings are compressed sufficiently to create a seal around the rod 26 and also on the inner diameter of the packing hole 38 in the cap, but there is sufficient valve stem guide 26 provided by the loaded packing assembly assemblies 38, 40 so that there is no need for the upper and lower metal guide bearings common in the previous valves. With proper loading in the packing assembly assemblies 38, 40 a rod guiding interference fit of the packing rings 42, 44, 46 in each packing assembly with the valve rod 26 is provided. The rings against extrusion is to prevent the loss of material of the male and female packing rings due to the movement of the valve stem and prolongs its useful life.

The anti-extrusion rings 48 can be removed from the package assembly, although this can reduce the reliable operating life of the package assembly. The above detailed description has been given only for clarity of understanding, and unnecessary limitations should not be understood from it, since the modifications will be obvious to those skilled in the art.

Claims (4)

REIVI NDICATIONS

1 . A fluid control valve comprising: a valve body having a fluid inlet, a fluid outlet, a passage communicating therebetween, and a valve seat in said passage to control fluid flow; a valve cap mounted to the valve body and having a central hole; an elongated valve operating member extending through the central hole of the valve cap with a plunger end for sealingly coupling the valve seat, including a lower clearance hole between the valve cap and the valve member. elongated valve operation so that there is no coupling between them; an elongated packing nut that threadably couples the valve cap, including a valve operating hole between the packing nut and the valve operating member so that there is no coupling therebetween; at least two packing assemblies in said central hole of the valve cap surrounding the valve operation member, each of the packing assemblies of the type V PTFE packing rings including a PTFE seal ring between the rings of filled PTFE male and female; and disc springs surrounding the valve operation member and intermediate assemblies to the packing nut and the two packing assemblies to compress the disk springs and apply a packing load on the two packing assemblies, wherein initially with the non-compressed disc springs there is a clearance adjustment between the two packing assemblies and the valve operating member, and to the additionally threaded coupling of the packing nut on the valve cap, the disc springs are compressed to applying the packing load on the two packing assemblies to provide a guide fit between the two packing assemblies and the valve operating member sufficient to stabilize the valve operating member of the lateral loads applied to the operating member of valve, and to provide a fluid seal around the valve operating member and around the outer diameter of the central hole in the valve cap.

2. A fluid control valve according to claim 1, wherein the filled male and female PTFE packing rings are formed of one filled with carbon and filled with glass. A fluid control valve according to claim 2, including rings against extrusion at each opposite end of said two packing assemblies and encircling the valve operating member with an interference fit with said valve member of said valve member. operation and with the external diameter of the central hole of the valve cap. 4. A fluid control valve according to claim 3, including a first spacer ring between the two packing rings. SUMMARY A fluid control valve that includes a valve cap (30) and a packing nut (56) that threadably couples the valve cap. A valve stem (26) passes through the valve cap and the packing nut in a clearance setting so that there is no coupling between them. Two V-type PTFE packing assemblies (38, 40) are included with each assembly having an intermediate seal PTFE seal ring (42), a PTFE male packing ring filled with carbon or glass (46) in a side and a female PTFE ring filled with carbon or glass (44) on the other side. Belleville disc springs (52) intermediate are provided to the packing nut and the two packing assemblies, to supply mobile load to the package. In a discharged condition, initially the packing assemblies are both in a free space setting with the valve stem. The threaded insertion of the packing nut into the valve cap until there are no taps visible in the upper part of the cap assures a sufficient load to seal the valve stem, seals the internal diameter of the cap, and provides a guide enough rod.