Patent Application
20130248748
While butterfly valves have been used for many centuries, based primarily on a round disk which is turned by a shaft within a tubular body, more modem versions have only appeared within the past 50 years.
Added features, or improvements, included means to obtain tight shut-off when in the closed position, and ways to reduce dynamic torque created by suction effects on the vane caused by high fluid velocities.
One of the common applications of butterfly valves is in the heating and air-conditioning business, replacing cast iron globe valves with flanged housings and reciprocating valve plugs (the primary throttling element).
Such globe valves are excessively heavy and therefore costly. Another drawback is the installed length of such a valve in a piping system.
Finally, Globe valve actuation requires more mechanical power to lift circular plugs off an orifice against fluid pressure.
This invention overcomes these objections and, in addition, provides important improvements over butterfly valves of prior art. For example, a 4-inch globe valve has a length of 14 inches and a weight of 205 lbs, excluding the actuating device. In contrast, my butterfly valve weighs only 24 lbs and has an installed length of only 2.5 inches, thus offering substantial cost and space savings without compromising performance.
Similar to globe valves, the current invention provides tight shut-off when closed and is able to control fluid flow to less than 2% of the wide-open flow capacity. In addition, it takes less mechanical energy to turn a butterfly vane, resulting in cost savings for the actuating device.
There are prior art devices capable of performing similar functions. However, they do not match the level of sophistication which my invention offers. In order to provide tight shut-off, some devices as in U.S. Pat. No. 4,860,994 employ a spring-loaded, flexible, circular Teflon seal. These seals have to flex into the horizontal direction, in order to conform to the given geometry of the closing vane periphery. This leads to wear and are subject to deformation by high fluid pressures. This invention, on the other hand, employs either a flexible metal ring that can deform only in the radial direction, or, an embedded o-ring seal, which offers an inexpensive way to replace the seal when needed.
In addition, my seal is self-adjusting. It can move radially during assembly, to perfectly match up with the center of the spherical vane rim; thus being immune to machining tolerances.
Other designs, see U.S. Pat. No. 4,489,917 for example, use a rubber-lined housing bore in order to achieve tight contact with the vane, when the latter is squeezed into a closed-position. However, such deformation of the rubber liner creates a substantial amount of radial friction which not only requires extra actuating forces, but also creates hysteresis, very detrimental to automatic control.
This invention, on the other hand employs a right combination of vane eccentricity and the radial dimension of the spherical vane seating periphery, to produce a favorable “Angle of Approach”, which allows a gentle contact with my seals in order to overcome such stickiness.
Other prior art such as U.S. Pat. No. 6,793,197 rely on special geometric contours either on the vane's periphery, or inside the housing bore, in order to obtain a desired mathematical relationship between the degree of vane travel and the percentage of fluid increase. The current invention in contrast relies on the natural distance change between the spherical vane seating surface and the cylindrical housing bore thus obtaining a satisfying fluid increase relationship, while not mathematically correct, nevertheless avoid such complicated machining operations.
In contrast to other prior art devices where the vane is looked onto the stem, my vane is free to slide on a square shaft, thus enabling the vane to self-center onto the seat ring and otherwise avoid the vane's dislocation by thermal expansion differences between shaft and housing.
Finally, since the upper halve of my vane has an area, subjected to fluid pressure, which is larger than that of the lower halve, owing to the eccentric location of the shaft. As a result, there exists a large opening torque when fluid enters the valve from the side of the seal. I have added a lower, semi-circular rim adjacent to the lower sealing edge of my vane to mitigate this dynamic torque effect
Likewise, there is a dynamic torque tending to close the vane, when fluid enters the housing from the side where the shaft is located. Here again, I added a protruding semi-circular ring on the shaft side of the vane's lower periphery. This protrusion provides an impact area for the flowing fluid, again, lowering the total dynamic torque.
These and other benefits and advantages of the invention will be better understood in view of the following description.
Referring to
Hub portions 5 serve to connect said shaft to the vane. Vane 3 furthermore has a circular rim 4, along radius R, originating from the center of opening 2. Said rim 4 interacts with an elastic seal 7 partly embedded in a groove in housing 1 and partly supported by a retaining ring 7a which is forced against a step shoulder 8, in housing 1, by a ring shaped nut 12.
Vane 3 furthermore has a circular recess 19, the depth of which is about 15% of the diameter of the rim 4 and whose purpose is to counteract dynamic fluid induced torque, when the valve is more than 65 degrees open. Such torque reduction is needed when the fluid enters the side located opposite from the shaft.
In addition, vane 3 has an extended rim portion 13 located below the shaft. This extended rim portion, whose width H is typically 53% of the rim radius R. This extension serves as fluid impediment, in order to reduce dynamic torque, whenever the fluid enters from the side where the shaft is located.
Metal seal 9 extends nearly parallel to the curvature of rim radius R, but has itself a smaller, opposite curved, radius, so that only a part of the seal contacts the rim. This will avoid scraping contact of the terminating end of seal 9 against the rim surface 4.
Shaft 6 furthermore has an enlarged rim portion 23, supported by a shoulder of bushing 24 in order to absorb forces created by fluid pressure against the cross-sectional area of the shaft. As shown, vane 3 has two separate hub portions 5 having square openings to pass the square section 14 of the shaft.
Shaft portion 14, features a cross hole 16 containing a pin 17. Pin 17 passes freely through a larger passage 16 in one of the hubs 5, having ample clearance 18 on both sides, in order to compensate against misalignment. This arrangement has the purpose of guarding against the case where flange 26 may be removed accidentally, causing shaft 6 to be propelled out of the valve and cause harm. In such occasion, pin 17 will be retained by the walls of hole 16 and therefore keep shaft 6 from being expelled.
Having shown the invention in a preferred embodiment should nevertheless allow numerous modifications, without departing from the scope of the following claims. For example, it is quite possible to use a multi-splined shaft profile instead of a squared profile. Furthermore, a flanged seat ring retainer could be used instead of the preferred threaded retainer.
