AU8541791A - Thrust assembly for valve stem - Google Patents

Description

THRUST ASSEMBLY FOR VALVE STEM

This invention relates to a thrust assembly for a valve and in particular to a thrust assembly for a sluice valve.

Sluice valves generally comprise a stem which has a valve element in the form of a wedge ->r the like. The stem is rotatable in a valve body and includes a screw- thread which engages a screw-thread in the wedge. The stem is held fixed in its longitudinal direction by a thrust assembly coupled to a bonnet of the valve. Rotation of the stem therefore causes the wedge to move in the longitudinal direction of the stem to open and close the valve.

The thrust assembly which normally holds the stem in the bonnet is often difficult to assemble and does not allow easy disassembly of the valve if disassembly is at all possible. Furthermore, the thrust assembly may includes glands and the like which are screw-threaded to the bonnet in order to hold the thrust assembly in place. The use of screw-threaded glands may damage a corrosion resistant coating applied to the bonnet. If the coating is worn or damaged by the screw-thread engagement between the gland and the bonnet, this can create problems since valves are often used in corrosive environments and therefore the valve may fail due to corrosion.

The object of this invention is to provide a thrust assembly for a valve which overcomes at least some of the above problems.

The invention provides a thrust assembly for a valve, which has a bonnet and a stem for rotation in said bonnet, a valve element coupled to said stem and which is opened and closed upon rotation of said stem, said thrust assembly comprising first retaining means for engaging said stem and holding said stem substantially fixed in the longitudinal direction of said stem, a locking element for holding said retaining means in place, said locking element having an abutment surface, said bonnet also having an abutment surface, and thrust means for engaging said abutment surface of the locking element and the abutment surface of the bonnet to prevent said locking element from being withdrawn from the bonnet and thereby retaining said retaining means in said bonnet to in turn retain said valve stem in the bonnet when thrust is applied by rotation of said stem.

Since the thrust assembly includes the abutment surfaces and thrust means which prevent the locking element from being withdrawn from the bonnet, the element and retainer are securely fixed in the bonnet to thereby fix the stem in the direction of its longitudinal axis within the bonnet. Since a gland is not required to be screw-threaded onto the bonnet in order to hold the thrust assembly in place the bonnet can be easily coated with a corrosion resistant coating and will not be damaged by a stand. Furthermore, the assembly can be easily disassembled by simply removing the thrust means from the abutment surfaces so that the locking element can be removed from the bonnet to in turn enable the stem and retaining elements to be removed from the bonnet.

The invention also provides a thrust assembly for a valve, which has a bonnet and a stem for rotation in said bonnet, a valve element coupled to said stem and which is opened and closed upon rotation of said stem, said thrust assembly comprising first retaining means for engaging said stem and holding said stem substantially fixed in the longitudinal direction of said stem, a locking element for holding said retaining means in place, said locking element having a groove, a groove in said bonnet which matches the groove in the locking element so that when said locking element is located in said bonnet the groove in the locking element and the groove in the bonnet form a passage, and thrust means for insertion into said passage to prevent said locking element from being withdrawn from the bonnet and thereby retaining said retaining means in said bonnet to in turn retain said valve stem in the bonnet when thrust is applied by rotation of said stem.

Since the thrust assembly includes the grooves which form a passage and thrust means which is inserted into said passage to prevent the locking element from being withdrawn from the bonnet, the element and retainer are securely fixed in the bonnet to thereby fix the stem in the direction of its longitudinal axis within the bonnet. Since a gland is not required to be screw-threaded onto the bonnet in order to hold the thrust assembly in place the bonnet can be easily coated with a corrosion resistant coating and will not be damaged by a stand. Furthermore, the assembly can be easily disassembled by simply removing the thrust means from the passage so that the locking element can be removed from the bonnet to in turn enable the stem and retaining elements to be removed from the bonnet. Preferably the retaining means comprise a pair of semi-circular collets which have an outer tapered surface to match an inner tapered surface in the bonnet, the collets include at least one groove for receiving a rib on said stem for securely retaining said stem to said collets.

Preferably the bonnet includes two bores which are tangential to said passage to enable the thrust means to be inserted through the bores into the passage and, wherein, said passage is a circular passage. The bores can include plugs to close the bores to retain the thrust means in the passage. When it is desired to disassemble the valve the plugs need only be removed by drilling or the like and the thrust means can be pushed out of the passage through one of the bores by inserting a piece of wire or other suitable flexible object into the passage from the other of the bores.

Preferably the thrust means comprise a plurality of short rods having rounded ends.

In a second embodiment of the invention the groove in the bonnet and the groove in the locking element are straight to form a substantially straight passage and said grooves are the continuation of a bore in said bonnet, and wherein said thrust element comprises a thrust pin inserted through said bore and into said passage.

Preferably two said straight passages and two said bores are provided each for receiving a thrust pin. Preferred embodiments of the invention will be described, by way of example, with reference to the accompanying drawings in which:

Figure 1 is a cross-sectional view of a valve including a thrust assembly according to the preferred embodiment of the invention;

Figure 2 is a cross-sectional view along the line II-II of Figure 1;

Figure 3 is an enlarged cross-sectional view of the thrust assembly according to the preferred embodiment of the invention;

Figure 4 is a partly broken away perspective view of the thrust assembly according to the preferred embodiment of the invention; and

Figure 5 is a view similar to figure 2 but showing a second embodiment of the invention.

With reference to Figure 1, the valve including the thrust assembly has a body 1 which is intended to be secured to a pipe or conduit through which a fluid is to flow. A bonnet 3 is connected to the body 1 in the conventional manner and a gasket 11 may be disposed between the body 1 and bonnet 3 in order to seal the bonnet 3 to the body 1. The bonnet 1 is provided with a stem 7 which has a screw-threaded section 7a which engages with a wedge 6 which is provided with a bore having a screw-thread 6a. The wedge 6 is preferably in the form of a casting and is provided with a moulded rubber coat 5. As is conventional, the wedge 6 seals the body 1 when in the position shown in Figure 1 by the rubber coat 5 engaging the inner wall of the body 1 and a step 2 in the body 1.

The bonnet 3 is provided with tapered internal wall portions 20 and a step 22 which receive a pair of semi-circular collets 8. The collets 8 form a retainer for retaining the stem 7 in the bonnet 3. The stem 7 is machined in the vicinity of the collets 20 to provide projecting ribs 24 which are received in grooves 26 formed in the inner surface of the collets 8. The outer surface of the collets 8 are tapered to match the tapered surface 20 of the bonnet 3.

In order to retain the collets 8 in the bonnet a stem seal housing 9 is provided which locks the collets in the bonnet 3. The housing 9 is provided with an annular groove 30 and the internal surface of the bonnet is also provided with an annular groove 32 so that when the housing 9 is inserted into the bonnet and rests on the collets 8 the grooves 30 and 32 match one another to form an annular passage having a generally circular cross- section as is clearly shown in Figures 1 and 2.

The bonnet 3 is provided with two bores 40 and 42 which communicate with the annular passage 33 and are arranged tangentially to the annular passage 33.

Thrust pieces 10 which are preferably in the form of small rods having domed ends are inserted into the annular passage 33 by pushing them into bores 40 in the direction of arrow A. As further pieces are inserted into the bore previous pieces are pushed into the channel 33 and about the channel 33 until the channel 33 has sufficient thrust pieces 10 in order to prevent the housing 9 from being forced out of the bonnet 3. The bores 40 and 42 can be plugged by plugs (not shown) to ensure that the pieces 10 remain within the passage 33 and therefore hold the housing 9 in position to, in turn, lock the collets 8 in position where they hold the valve stem 7 securely within the bonnet 3.

In order to open and close the valve the stem 7 is rotated about its longitudinal axis by a suitable handle (not shown) . The collets 8 securely hold the stem from moving in the direction of its longitudinal axis so that rotation of the stem 7 causes the wedge 6 to move in the direction of double-headed arrow B in Figure 1 to open and close the valve. Thrust applied to the stem 7 during rotation of the stem is transmitted by the collets 8 to the housing 9 and is taken up by the thrust elements 10 which securely hold the housing 9 within the bonnet 3 to in turn hold the collets securely within the bonnet so that the stem 7 cannot move in the longitudinal direction of the stem.

A seal grommet 12 may be located on top of the housing 9 to seal the bonnet and O-rings 14 and 15 can be arranged between the housing 9 and the bonnet 3 and between the housing 9 and the stem 7 to assist in sealing the assembly.

In order to disassemble the valve, the plugs (not show) in the bores 40 and 42 are merely removed by hand or, if necessary, by drilling and a flexible wire or the like is inserted into one of the bores to push against the thrust pieces 10 so that they are pushed around the passage 33 and out of the other of the bore in the direction of arrow C. When al ^'. of the thrust pieces 10 have been removed the housing 9 can be removed from the bonnet (after the grommet 12 is removed) to enable the stem 7 together with the collets 8 to be withdrawn from the bonnet 3 after wedge 6 is removed. Repair or replacement of worn parts can then take place and the valve can be reassembled by relocating the collets 8 about the valve stem 7 and inserting the valve stem 7 with the collets 8 back into the bonnet 3. The wedge 6 can then be resecured to the stem 7 and the bonnet 3 together with the stem 7 can be coupled to the Vc Lve body 1. One of the bores 40 or 42 can then be plugged and the thrust pieces 10 can be reinserted into the passage 33 through the other of the bores 40 or 42. That bore 40 or 42 can then be plugged so that the thrust pieces 10 are securely retained within the passage 33 to take up thrust and prevent the housing 9 from being removed from the bonnet 3.

The thrust pieces 10 have a diameter which closely matches the diameter of the passage 33 and are relatively short .ith domed enαo so that they can easily move about the passage 33. However, in other embodiments it may be possible to use a thrust piece in the form of a single lexible rubber or wire member or the like which is inserted into the passage 33 to prevent removal of the housing 9.

Figure 5 shows a second embodiment of the invention and comprises a view similar to figure 2. In this embodiment the bonnet 3 is provided with two bores 75 which extend into the bonnet 3. Grooves 77 in housing 9 and grooves 79 in the bonnet 3 are an extension of the bores 75.

In this embodiment the bores 75 together with grooves 77 and 79 can be made in a single drilling operation by locating the housing 9 in the bonnet 3 and drilling a bore into the bonnet and also into the housing 9 to form the grooves 77 as well as the grooves 79. Thus, the grooves 77 and 79 and the passage they form together with the bores 75 can be formed by a single drilling operation into the bonnet and housing.

In order to retain the housing 9 in place thrust pins 81 and inserted into the bores 75 and the passage formed by the grooves 79 and 77 so as to lock the housing 9 in place. The bores 75 are provided with a screw-threaded portion 75a which co-operates with a screw thread 81a on the pins 81 to secure the pins in the bores 75 and passages formed by the grooves 77 and 79. As described with reference to the earlier embodiment this in turn locks the collets in place together with the stem 7 (not shown in figure 5) in place.

The preferred embodiment of the invention has the advantage that glands are not required in order to secure the thrust assembly in place and ensure that the valve stem is thereby secured in place. The bonnet can therefore be completely sealed with corrosion resistant coating and the assembly can be assembled and disassembled with relative ease.

Since modifications within the spirit and scope of the invention may readily be effected by persons skilled within the art, it is to be understood that this invention is not limited to the particular embodiment described by way of example hereinabove.

Claims (9)

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A thrust assembly for a valve, which has a bonnet and a stem for rotation in said bonnet, a valve element coupled to said stem and which is opened and closed upon rotation of said stem, said thrust assembly comprising first retaining means for engaging said stem and holding said stem substantially fixed in the longitudinal direction of said stem, a locking element for holding said retaining means in place, said locking element having an abutment surface, said bonnet also having an abutment surface, and thrust means for engaging said abutment surface of the locking element and the abutment surface of the bonnet to prevent said locking element from being withdrawn from the bonnet and thereby retaining said retaining means in said bonnet to in turn retain said valve stem in the bonnet when thr t is applied by rotation of said stem.

2. The thrust assembly of claim 1 wherein the abutment surfaces are formed by grooves in said bonnet and said locking element.

3. A thrust assembly for a valve, which has a bonnet and a stem for rotation in said bonnet, a valve element coupled to said stem and which is opened and closed upon rotation of said stem, said thrust assembly comprising first retaining means for engaging said stem and holding said stem substantially fixed in the longitudinal direction of said stem, a locking element for holding said retaining means in place, said locking element having a groove, a groove in said bonnet which matches the groove in t ^*i locking element so that when said locking element is located in said bonnet the groove in the locking element and the groove in the bonnet form a passage, and thrust means for insertion into said passage to prevent said locking element from being withdrawn from the bonnet and thereby staining said retaining means in said bonnet to in turn retain said valve stem in the bonnet when thrust is applied by rotation of said stem.

4. The thrust assembly according to any one of the preceding claims wherein retaining means comprise a pair of semi-circular collets which have an outer tapered surface to match an inner tapered surface in the bonnet, the collets include at least one groove for receiving a rib on said stem for securely retaining said stem to said collets.

5. The thrust assembly according to claim 3 wherein two bores which are tangential to said passage to enable the thrust means to be inserted through the bores into the passage and, wherein, said passage is a circular passage.

6. The thrust assembly according to any one of the preceding claims wherein the thrust means comprise a plurality of short rods having rounded ends.

7. The thrust assembly according to any one of claims 1 to 4 wherein the groove in the bonnet and the groove in the locking element are straight to form a substantially straight passage and said grooves are the continuation of a bore in said bonnet, and wherein said thrust element comprises a thrust pin inserted through said bore and into said passage.

8. The thrust assembly according to claim 7 wherein two said straight passages and two said bores are provided each for receiving a thrust pin.

9. A thrust assembly for a valve substantially as hereinbefore described with reference to the accompanying drawings.