4. DESCRIPTION

Field of Invention

The present invention is directed to resilient seated gate valve, particularly the integration arrangement of wedge nut with wedge and same time ensuring the anti-slippage of the arrangement during the valve operation. The invention directed to elimination of more moving parts and reduction in metal surfaces exposed to fluid and making the design more reliable for drinking water application.

Related Prior Art

The Resilient Seated Gate valve is widely used in pipeline system to open and close the medium (water) flow in the pipeline by means of driving the closing device (wedge) through the stem to move vertically along the seat centre line of the gate valve. Gate Valve is usually applied to a situation where the wedge is remained fully open or fully closed without need to frequently open and close. The advantages of the gate valve are low fluid flow resistance at full open condition, easy to open and close the valve and suitable for bidirectional flow.

The gate valves are majorly classified according to the seat sealing type, Metal Seated and Resilient Seated. In Metal seated gate valve the seat sealing happens by metal seat rings. In resilient sealing gate valve sealing happens by rubber which is encapsulated over the Wedge. As the technology develops, more resilient sealing gate valves are used in the gate valve industry, especially in building services, water supply system, Water treatment plants and low pressure pipeline systems. Also the gate valves can be classified according to stem movement such as non-rising gate Valve (NRS) and Rising Gate Valves (OS&Y).In NRS Gate Valve, drive thread arrangement is at lower end of the stem, and the stem can only rotate but cannot rise or go down. In Outside Spindle and Yoke gate valve (OS&Y) in which drive thread arrangement is at upper end of the stem, the stem can only move up and down but cannot rotate.

Wedges used in gate valves are classified as solid wedge, flexible wedge, split wedge and parallel wedge. Solid wedges, flexible wedges and split wedge are used in valves having inclined seats. Parallel wedges are used in valves having parallel seats. The solid wedge with elastomer encapsulation is used in the resilient seated gate valve.

The traditional Non-Rising Stem Resilient Seated Gate Valve structure and operations are explained below.

The resilient seated gate valve includes a Body, a Bonnet which is fixed to the Body through fasteners, wedge, wedge nut and stem. Gate valve stem is installed in the Bonnet through the Thrust Collar to be relatively rotatable and Thrust Collar positioned by Thrust Collar Nut threaded on the Bonnet, such that stem can only rotate around the vertical axis, rather than vertical translation movement. O-rings are used to achieve the sealing between the stem and bonnet. Wedge nut connects with the thread at the lower end of stem. Wedge nut is assembled to the wedge in bayonet socket type arrangement (like a T slot arrangement). So, the T head portion of the wedge nut carries the wedge during the vertical translation movement. The shape of wedge adapts to the inside cavity of the body to achieve sealing (closing the valve). The outer surface of the wedge is encapsulated with suitable elastomer (such as the rubber) in order to achieve the sealing as resilient sealing.

To operate the valve at works, the stem is rotated by means of a hand wheel. The wedge nut connected at the lower end of the stem will move vertically up and down. The wedge nut carries along with them the wedge during the vertical movement. Thus the wedge opens and closes the fluid flow, achieving the functioning of the valve.

Disadvantages

This traditional resilient sealing gate valve having the loose Wedge Nut has the following disadvantages:

1. The numbers of moving parts are more resulting in reducing the valve reliability.

2. The loose wedge nut sometimes tends to become loose and unthread when in use resulting from vibration and other forces. When the wedge nut unthreads galling of the threads commonly occurs which may make difficult the disassembly of the stern and wedge.

3. It is difficult to vulcanize inside portion of the bayonet socket in the wedge. The loose wedge is influenced by the flow, and the vibration of the wedge will lead to abrasion on the thin rubber portion of the wedge. The rubber layer on the bayonet will wear out easily and corrosion will start occur.

4. A loose wedge nut causes the wedge to have a tendency to "edge" the valve body during high flow velocity. This results in increased friction between the rubber and the inside epoxy coating of the body and hence the operating torque will be increased drastically.

5. In the other designs of integral wedge nut, the interface between wedge nut and wedge is not perfect resulting in galvanic corrosion between the two different materials.

Objective of the invention

The present invention is to solve the above problems by providing better integrated wedge and wedge nut. Thus resulting in a gate valve which has lesser operation torque, sealed reliably, longer service life, and easy to assemble. This present invention applies to all the sizes and ranges of RSGV

Detailed description of the invention

Construction:

The wedge nut is made initially as pre-machined condition. The design of the wedge nut is having ribs on the outside. The main purpose of these ribs is to provide positive locking into wedge during the wedge casting process. The number and size of the ribs vary with respect to the size and range of the gate valve.

This pre-machined wedge nut is used as an insert and positioned in the core of the wedge casting. With this wedge nut as an insert, wedge casting is made.

The integration of wedge nut and wedge happens during the casting process of wedge, eliminating any gap between the two different materials ensuring perfect integration.

The wedge nut in the wedge is machined accurately to the required dimension. The thread formation in the wedge nut is made perfectly, so that the wedge translation movement is happening in the perfect way.
After the wedge nut machining, the integrated wedge is encapsulated with rubber to make it as a finished component. This encapsulation covers all the casting surfaces of wedge and hence covering all the areas that may corrode if it is exposed to media. The wedge nut and wedge integration ensures this rubber encapsulation is done at all the required area, with uniform rubber thickness.

This present invention provides an integrated wedge with wedge nut, with perfect integration design reducing the number of moving parts and increasing the service life of the valve.

Valve arrangement:
As shown in Figure 1, the resilient seated gate valve includes the Body (101), the Bonnet (102) which is fixed to the Body (101) through screws (113), and Wedge with integral nut (103) Stem (104). Gate valve stem (104) is installed in the Bonnet (102) through the Thrust Collar(105) to be relatively rotatable and Thrust Collar(105) positioned by Thrust Collar Nut(106) threaded on the Bonnet(102), such that stem (104) can only rotate around the vertical axis, rather than vertical movement. To achieve the sealing between the gate valve stem (104) and gate valve Bonnet (102), the stem (104) has provided with Bush (108) and 0-rings(lll & 112). Wedge with integral nut (103) connects with the thread at the lower end of stem (104).The shape of wedge (103) adapts to the inside cavity of the Valve Body (101) to open and close the gate valve. The outer surface of the wedge (103) having a coating of elastomer (such as the rubber layer) with a thickness will be provided on the wedge in order to achieve the resilient sealing of valve wedge to the flow medium.

Brief description of the accompanying drawings

Fig-1: The sectional view of gate valve in this invention

Fig-2: Exploded perspective view of the gate valve in this invention

Fig-3: Assembled perspective view of the gate valve in this invention

Fig-4: The Sectional view of Wedge which having integral wedge nut in this invention

Fig-5: The Wedge manufacturing process for this

5. CLAIMS We Claim

1. An integral wedge nut for resilient seated gate valve wherein the wedge nut is premachined having ribs on the outer side

2. An integral wedge nut for resilient seated gate valve as claimed in claim 1, wherein the premachined wedge nut having ribs on the outer side is placed in the core of wedge casting and wedge casting is done with the nut in the core

3. An integral wedge nut for resilient seated gate valve as claimed in claims 1 and 2, wherein the integration of wedge nut and wedge happens during the casting process of wedge.

4. An integral wedge nut for resilient seated gate valve as claimed in claims 1, 2 and 3, wherein after casting, the integral wedge nut is machined for thread formations as per the required dimensions.

5. An integral wedge nut for resilient seated gate valve as claimed in claims 1,2,3 and 4, wherein after the wedge nut is machined, the entire wedge is encapsulated with rubber encapsulation and it covers ail the casting surfaces of wedge and hence covering all the areas that may corrode.

6. An integral wedge nut for resilient seated gate valve substantially described as herein above with reference to the accompanying drawings.