Method of Aligning and Fixing Valve Components During Valve Assembly

This invention relates to valves or more particularly to butterfly valves. It relates to both the design of the valve and to the method of its manufacture.

Butterfly valves are particularly desirable in a number of applications because of their rapid operation and their relatively high flow capacity. However, to be completely leakproof, especially at high pressures, the valve member must be very accurately positioned with respect to the seal against which it seats. This has required close tolerance machining of not only the valve itself but also of the stem or shaft which mounts the valve and the bearings mounting the shaft. Because these valve housings are sand cast they cannot be cast to the accuracy required for effective operation using conventional valve designs and manufacturing methods.

Because of the access problems inherent in butterfly valve design the tooling for performing the necessary machining is expensive. The fact that machining the valve stem opening necessitates extending the tool from one side of the valve body to the other creates serious difficulty in maintaining accurate alignment, an essential for effective valve operation. If any amount of cut has to be eccentric, this will, unless great care is exercised, cause the tool to wander, resulting in misalignment. Even with expensive and properly operated tooling it is extremely difficulty to consistently maintain accuracy within the tolerances necessary to assure leakproof, high pressure operation of the valves. Further, the machining is very expensive not only because it is demanding of equipment but it is slow and requires very skilled operators. Particularly is this true in the boring and reaming of the valve body to receive the valve stem.

Another problem is that of the high torque required to operate the conventional butterfly valve. If the valve is not equipped with bearings for the valve stem, even the best machining normally results in a valve having excessive torque due to friction between the valve stem and the housing. The addition of bearings normally reduces this high torque, but only to a degree, because of the great difficulty of maintaining highly accurate alignment.

Another factor contributing to high closing torque characteristic of conventional butterfly valves is the amount of compression of the seal by the vane or valve member. The primary area in which leakage is experienced is in the area adjacent the stem. Therefore, a high degree of compression is required in that area. However, further away from the axis of rotation of the valve less seal compression is required to control leakage. However, if the valve and the seal are both circular the amount of compression remains constant entirely around the valve. This contributes substantially to the high torque because of the effect of the moment arm for that portion of the valve which is substantially spaced from the axis of the stem.

The invention eliminates substantially all of the machining and totally eliminates that part of the machining requiring a high degree of accuracy and alignment. The invention provides means for accurately aligning the valve stem bearings by mounting them on a precisely machined replica of the valve and stem and placing them in the unmachined or only rough machined openings in the housing and while so supported in precise alignment on the replica stem locking them in place by injection molding rubber around them. In this manner the bearings are free to float with respect to the stem openings in the valve housing and thus maintain their precise alignment with the stem irrespective of inaccuracies of the stem openings existing in the rough casting either before or after an initial rough machining. The tolerances which can be routinely maintained in sand casting normally do not require any machining when the teachings of this invention are used. Once the injected rubber has cured, the bearings are locked in place and the replica is removed.

The replica not only establishes the alignment of the bearings, it also shapes and defines the inside surface of the seal against which the valve member of the finished valve will seat. By making this replica slightly spheroidal in shape with the greater axis at a right angle to the axis of the stem, the amount of interference and thus of seal compression can be reduced where it is not required. This is a further factor materially contributing to a reduction in the torque necessary to operate the valve.

FIG. 1 is an end elevation view of a valve incorporating this invention with one half of the valve centrally sectioned;

FIG. 2 is a central sectional view taken along the plane II--II of FIG. 1;

FIG. 3 is a sectional view taken along the plane III--III of FIG. 1;

FIG. 4 is an enlarged, fragmentary sectional view taken along the plane IV--IV of FIG. 1;

FIGS. 5 and 5a are enlarged fragmentary sectional view of the engagement of the valve disc with the valve seat;

FIG. 6 is an enlarged fragmentary sectional view of the seal for the stem;

FIG. 7 is a sectional view of the valve and valve seat taken along the same plane as FIG. 3 but with the valve removed;

FIG. 8 is an enlarged fragmentary view of the valve seat;

FIG. 9 is a sectional view of the mold in closed condition for the seal taken along the same plane as FIG. 2;

FIG. 10 is a sectional view of the mold in closed condition for the seal taken along the plane X--X of FIG. 15;

FIG. 11 is a sectional view of one half of the mold taken along the plane X--X of FIG. 9, showing the disc replica in phantom;

FIG. 12 is a sectional view similar to FIG. 11 showing the other half of the mold;

FIG. 13 is a view of the stem replica used with the mold;

FIG. 14 is a view of the inside face of one half of the mold taken along the plane XIII--XIII of FIG. 12;

FIG. 15 is a view of the other half of the mold taken along the plane XV--XV of FIG. 11; and

FIG. 16 is an oblique view of the disc replica.

Referring to FIG. 1, the valve 10 has a housing or body 11 cast of suitable material such as ductile iron. The body is annular having a central passage 12 for fluids. It has a neck extension 13 through which the stem 14 is inserted to mount and actuate the valve member or disc 15. The stem 14 is seated in a stem opening 16 extending diametrically through the disc. Its end opposite from the neck is seated in the blind socket 17 in housing. The stem 14 and disc 15 are rotatable from the closed position illustrated in FIGS. 1 and 2 to an open position turned 90.degree.. The disc 15, in closed position, seats against and forms a seal with the valve seat 18. The valve seat is molded in place within the body 10 of a suitable material such as rubber and bonded to the body. At each end of the valve, the valve seat has a radially outwardly extending lip 19 overlapping the end face of the valve body and surrounding the fluid passage 12. A portion of the lips, in the form of annular beads 20, project axially beyond the end faces of the valve to provide a compressible seal with the ends of the pipes between which the valve will be mounted and clamped when installed.

The valve disc is circular and is supported by the stem 14 which extends diametrically through the disc. The stem 14 is seated in the opening 16 through the valve disc 15 which is centered in an enlarged central boss 21 (FIGS. 3 and 4). Adjacent the neck extension 13 the central opening is circular as at 22 (FIG. 2) and seats relatively closely about the stem 14. Adjacent the blind socket 17 the opening has parallel flat areas forming a non-circular portion 23 which engages the flat surfaces 2 on the stem 14 (FIG. 4). The engagement between these flat areas provides an interference fit (FIGS. 1 and 4) by which rotational motion of the stem 14 is transmitted to the disc 15. Between the portion 22 and the non-circular surfaces 23 the opening 16 is circular and larger than the stem providing clearance 25 between the stem and disc (FIGS. 1 and 3).

The top of the neck 13 is closed by a threaded bushing 26 which centers and supports the end of the stem (FIGS. 2 and 6). The stem extends beyond the bushing to provide means for attaching an actuator such a handle. The bushing has inner and outer O-ring seals 27 and 28, one engaging the stem and the other the housing (FIG. 6). The diameter of the stem 14 is reduced as it passes upwardly through the bushing 26, forming a shoulder 29 which engages the step 29a in the bushing to retain the stem against accidental blow-out.

All of the preceding design and structure is conventional in the butterfly valve art and is state-of-the-art practice. In the valve 10 illustrated in FIG. 1 it will be seen that the stem 14 where it enters the neck 13 from the fluid opening 12 is surrounded by a bushing 30. Also the end of the stem seated in the blind socket 17 is surrounded by a bushing 31. Preferably, the bottom end of the bushing 31 is closed making the seat for the stem 14 a blind socket. While many butterfly valves are constructed with such bushings to reduce torque, in some smaller valves they are omitted. When the conventional practices for machining the openings for these bushings are utilized, the reduction in the torque required to operate the valve is frequently quite minimal because of alignment problems.

In the practice of this invention the valve housing or body 11 is placed in a mold 40 having a pair of halves 40a and 40b which clamp the body 11 between them (FIGS. 9 and 10). The mold halves are clamped tightly against the end faces of the body and have grooves 41 in them to form the beads 20 (FIG. 9). The mold has radially inwardly and convergently inclined annular surfaces 42 and 42a to form the axial outer portions of the seat. The central or valve seating portion of the seat is shaped by a disc replica 43 which is seated in the fluid passageway and is clamped between the mold halves 40a and 40b (FIG. 10). The disc replica 43 is recessed in one face (FIG. 16) creating a cavity 44 into which a mating boss 45 on mold half 40b seats to hold the valve replica properly located within the valve body 11 (FIGS. 10 and 12). The cavity and boss have inclined walls to accurately center the replica. The replica 43 is axially thicker than the valve creating a shallow, annular channel 46 for seating the sealing edge of the disc (FIGS. 3, 5 and 9). The channel is arcuate in cross section and constitutes a narrow, annular segment of a sphere centered about the central axis of the fluid passage 12 as indicated by the phantom line A in FIGS. 5a and 7. However, the fluid passage through the valve seat is not truly circular but rather is slightly spheroidal, having a slightly greater diameter at right angles to the axis of the stem 14 for purposes which will be explained subsequently. For example, if the diameter of the fluid passage along the axis of the stem 14 is 2.00 inches, the diameter of the fluid passage at right angles to the stem will be 2.07 inches. The axial width of the channel 46 is determined by its intersection with the inclined surfaces 42 and 42a which intersection forms a pair of circular, parallel apexes 47 (FIGS. 3-5).

To prepare the valve for molding the valve seat to the valve body 11, the bushings 30 and 31, stem replica 48 and disc replica 43 are first assembled. The bushings 30 and 31 are first placed in their openings and the stem replica inserted through the neck 13. This is done while the valve body is horizontal so that the sleeve bushings will not be biased to slide out of their openings. This is necessary since the bushings are not wedged against the walls of their openings but rather have a limited degree of freedom to float in their openings. As the stem replica is inserted the disc replica 43 is positioned to pass the stem replica through it. In doing this the stem replica is passed through the collars 49s of the disc replica 43 which enclose each end of the stem channel 50 (FIGS. 9 and 16). As the stem replica is assembled to the mold it automatically positions and aligns the bushings 30 and 31. The stem replica has a shoulder 51 which restrains outward axial movement of the neck bushing 30 under the pressure exerted against it by the elastomeric compound during molding (FIGS. 9 and 13).

The stem replica has a spring biased detent 58 which seats in a pocket 58a in the disc replica (FIG. 9). The detent holds the disc replica from rotating around the stem replica while the assembly is being placed in the mold. It also properly locates the disc replica axially of the stem replica.

The valve body and replica assembly are seated against the mold half 40b using the boss 45 and the channel 50a (FIG. 12) for the stem replica to accurately position it. Once the assembly has been properly seated, the other mold half 40a is positioned and the mold is closed. The open end of the neck is closed by a cap 52 which holds the stem replica against accidental discharge during molding. The cap 52, in turn, is secured by wedges 53. A cap screw 54 provides means to grasp and withdraw the stem replica when the molding process is complete.

The stem replica 48 is accurately machined, especially in those portions of the replica that seat the bushings 30 and 31. In the areas seating the bushings the stem replica is preferably machined to a very close tolerance to substantially eliminate differences in bushing position from valve to valve. This is not a costly procedure since the surfaces of the replica are accessible and the replica, once machined satisfactorily, is used for the manufacture of many valves. It will also be recognized that this invention can be practiced with a lower bushing 31 which has no closed end.

It will also be observed in FIGS. 9 and 13 that the stem replica, where it passes through the area where the valve seat is to be formed around it is necked down at 57 and 57a. This results in a valve seat shape which exerts additional sealing pressure against the valve stem, an area prone to leakage in butterfly valves.

The preparation of the body 11 prior to being clamped in the mold 40 is minimal. Except to machine smooth and parallel those of the end faces which must seat tightly against the mold such as at 56 (FIG. 9) and to bore and thread the outer end of the neck 13 to receive the closure bushing 26 (FIG. 2) no other machining is necessary. The neck and socket bushings 30 and 31 are accurately positioned by the stem replica 48 and, prior to molding of the valve seat, are not secured to the housing. They have a clearance fit with the valve body at least sufficient to permit them to be seated in their respective openings in the body 11 as dictated by the stem replica irrespective of the variations in opening size and alignment from casting to casting which are normally found in unmachined sand castings. Thus, using this invention, the bushing position and alignment is entirely controlled by the stem replica 48 rather than the accuracy of the machining performed on the valve body 11 as has heretofore always been the case. Thus, perfect alignment is always achieved and costly machining has also been eliminated.

Before the valve body and replicas are assembled the outer surfaces of the bushings, the walls of the openings into which they are inserted along with all surfaces of the valve body which will be contacted by the elastomeric compound are cleaned with a suitable solvent such as trichloroethane and then coated with a suitable rubber to metal adhesive such as that marketed by Hughson Chemicals, Lord Corporation under the trademark "Chemlok 252". Also before the valve body replica assembly is placed in the mold it is heated to approximately 300.degree. F. to assure adequate flow of the elastomeric compound.

Once the disc replica 43 and stem replica 48 have been locked in place in the closed mold, a rubber or a rubber-like elastomeric compound of suitable composition is injected into the mold under sufficient heat and pressure to fill the cavity in the mold. The composition will vary for several reasons including the expected operating temperatures of the valve and the characteristics of the fluid to be passed through the valve. A suitable elastomer for this purpose is an elastomer-gum sold by E. I. DuPont de Nemoirs & Co. under the trademark "Nordel". The elastomer compound when cured should have a hardness of 70 Shore A.

The injection is done under very high pressure through the gate 60 (FIGS. 9 and 15) and is distributed through the channels 61 (FIGS. 9 and 10). The injected elastomeric compound not only is caused to produce the valve seat 18 in the conventional way, it also is caused to flow around the sleeve bushings 30 and 31 to fill the gap between the bushings and the walls of the openings in which they are seated (FIG. 8). These thin sections of injected compound are indicated at B, C and D in FIG. 8. In fact, as indicated at E in FIG. 8 the rubber or elastomeric material may even fill the void between the end of the sleeve bushing 31 and the bottom of the socket 17. It will be recognized that the thickness of these injected sections has been exaggerated in FIG. 8 to make them more readily visible. It will also be recognized that the thickness of these sections will vary from valve to valve due to normal variations in the body castings. During injection of the elastomeric material the sleeve bushings are held in accurate alignment by the stem replica 48. The sleeve bushings, being mounted on the stem replica 48 with even a closer fit than they may have with the valve stem when it is substituted for the stem replica, will be accurately aligned to receive the valve stem. Because the elastomeric compound will automatically seek these narrow voids and fill them, there is no necessity for machining either the neck opening or the blind socket since the rubber will compensate and permanently fill any gap or void due to misalignment and other inaccuracies normally characteristic of the cast housing 11. In effect, the stem replica with the attached bushings is allowed to float in the rubber and will automatically establish a position where the various forces acting on it equalize. Thus, the bearings, stem replica and disc replica will become stabilized in a position of minimum resistance to subsequent operation of the valve disc after its installation. The cost of the finished valve is materially reduced by the elimination of the costly machining operation and rejects resulting from faulty machining. The thin layers B, C, D and E of elastomeric material which are caused to squeeze between the sleeves and the body are, for all practical purposes, inelastic since there is not enough thickness to permit flexing.

After the elastomeric material has cured the mold is opened, the stem replica removed and the disc replica rotated and then pushed out of the valves ready for reuse to make another valve. Once the replicas have been removed, the actual valve disc 15 can be inserted in the fluid passage with the stem opening aligned with the sleeve bearings 30 and 31. The insertion of the valve disc is facilitated by the bosses 59 and 59a molded into the valve seat at the stem openings (FIG. 8). These bosses are created by the fact that the valve replica 48 is thicker in the area of the valve stem replica changing the slope of the valve seat faces 42 and 42a. The faces have a different inclination at the stem opening (FIGS. 2 and 8) than throughout the rest of the valve seat (FIG. 5). Once the valve disc 15 is positioned and aligned with the stem openings the valve stem 14 can then be inserted through the neck and pushed down through the valve disc to seat in the blind socket 17. It will be noted from FIGS. 1 and 2 that the valve stem 14 does not have the necking of the stem replica and thus has to further compress the valve seat at these points.

The stem opening 16 in the disc, like the valve body, is also not machined except to remove rough burrs and the like except in the area of the key non-circular portion 23. This portion of the stem opening is machined to provide a suitable fit with the stem to reduce the amount of lapse which will be experienced when the valve is operated. This, however, need not be machined to close tolerances, once again eliminating the necessity for costly tooling and the services of highly skilled machinists.

The circumferential edge 62 of the disc is machined to make it truly circular. It is also machined to break or round the edges 63 (FIG. 5a) at the transition between the center portion and the inclined edge portions of the disc. This eliminates any rough, sharp or irregular areas which might cause wear on the elastomer of the valve seat. This machining is relatively simple and inexpensive by comparison with the machining which has heretofore been necessary to properly seat the stem and assembled the stem and disc.

As pointed out earlier, the disc replica 43 is sightly spheroidal in shape with its maximum diameter at a right angle to the stem. Thus the fluid passage through the molded seat normal to the stem is slightly wider than the passage parallel to the stem. This permits the disc to more tightly compress the valve seat in the area adjacent the stem. This is desirable because this is the area where valve leakage most often occurs. Since the disc is machined to accurate circularity of the spheroidal shape of the valve seat reduces the degree of valve seat compression occurring at 90.degree. to the stem where less compression is needed to prevent leakage. The reduction in compression and thus resistance to rotation at a right angle to the axis of the stem significantly reduces the amount of torque necessary to operate the valve since the load at that point is applied at the end of a moment arm representing the radius of the valve. As the diameter of the valve increases, the force necessary to operate it because of resistance at this point increases geometrically. Thus, introduing spheroidal design to the valve seat is a major contribution to reduction of operating torque. Further, this is a factor which can be easily applied in fabrication since the amount of variation from a true spherical shape is proportional to the change in fluid passage diameter. It is comparatively simple and inexpensive to provide the spheroidal shape in the valve seat mold compared to machining the valve disc to a non-circular shape.

Making the cross sectional shape of the channel 46 a segment of a true circle also contributes to the functional characteristics of the valve. This reduces the resistance to opening and closing of the disc. It also eliminates the necessity for exactly positioning the closed valve disc to effect a leakproof closure. Thus, there can be an acceptable degree of lapse in the rotational relationship between the valve disc and the stem. This contributes to the fact that close tolerance machining to effect a fit between these components is no longer necessary. This is also important when the operator is not in a position to physically observe whether or not he has effectively closed the valve.

The invention provides a butterfly valve which can be manufactured at a substantially reduced cost while incorporating a number of significant functional improvements. While a preferred embodiment of the invention in both product and method of manufacture have been described it will be recognized that various modifications can be made without departing from the principles of the invention. Such modifications are to be considered as included in the hereinafter appended claims unless these claims, by their language expressly state otherwise.