Abstract:
The vane actuator according to the present invention is capable of operating effectively at a working pressure greater than 100 psig. The vane actuator comprises a vane shaft rotatably extending through a casing and a vane disposed within the casing defining a first pressure chamber and a second pressure chamber therein. The casing includes stiffening members for resisting deflection of and maintaining an internal seal within the casing when exposed to a pressure of 150 psig. The stiffening member may be located in the range of about 10° and 20° on either side of a casing centerline to minimize deflection of the casing when exposed to a pressure force.

Description:
BACKGROUND 
     This invention relates to pneumatic and hydraulic actuators of the vane type. This invention further relates to vane type actuators having a clam shaped casing configuration. Actuators are known in the art as the mechanism used to open, close or position valves, dampers, doors, etc. Generally, they may be actuated with a hydraulic fluid or a pneumatic fluid such as air, nitrogen or a process gas. Actuators may be of the on/off variety or my be actuated to a range of positions through the use of a positioner. 
     Many vane actuator manufactures have settled on a casing design having a clam shaped configuration. For example, one of the leading sellers of vane type actuators, Kinetrol Ltd., has manufactured and sold a vane type actuator having a clam shaped configuration. This casing design is an optimal configuration for actuators having internal vanes of the paddle shaped variety. Other manufacturers such as Matryx and FMC have sold vane type actuators having similar configurations. The actuator case comprises case-halves, which are generally secured together with removable fasteners. 
     Actuators of the vane type design are very desirable since they may be designed to have only one moving part. This is accomplished by designing and manufacturing the actuator shaft and vane as a single machined piece. The vane is designed to have a minimal clearance between the internal surfaces of the case-halves. A seal may then be disposed on the peripheral surfaces of the vane to minimize leakage of a process fluid from one side of the vane to the other. The case-halves also include a port through which the shaft may extend. A seal may also be disposed between the shaft and the ports to minimize leakage of fluid. 
     One problem associated with prior art vane actuators is excess leakage of fluid from one side of the vane to the other. This prevents the actuator from maintaining the precise control over the component to be actuated or positioned. In a process plant such as a oil refinery or chemical plant, precise positioning of equipment such as a control valve or damper must be maintained to operate the facility efficiently or to prevent a catastrophic failure. While seal failures are one obvious source of excess leakage, more serious sources of excess leakage include high pressure excursions of the pneumatic or hydraulic fluid as well as expansion or contraction of the casing due to high and low temperatures. These latter sources of excessive leakage are especially notorious since such excursions may permanently damage the actuator often resulting in a loss of containment of the hydraulic or pneumatic fluid. Loss of containment of the pneumatic or hydraulic fluid can cause catastrophic system failures including loss of life and significant property damage. 
     Another problem associated with prior art vane actuators is that heretofore additional appurtenances were required to mount accessories such as solenoids, positioners, and limit switches. While international standards have been established by NAMUR for mounting accessories, vane actuator manufacturers have failed to design an actuator that complies with the NAMUR standards. 
     Therefore there is a need in the art for a vane actuator that reduces or eliminates excessive leakage due to high fluid pressures or excursions. There is a need in the art for a vane actuator that reduces or eliminates excessive leakage due to high or low operating temperatures. There is also a need in the art for a vane type actuator that meets NAMUR standards, thereby allowing accessories such as solenoids, limit switches and positioners of any manufacturer to be mounted directly to the vane actuator casing. A vane actuator which meets the above referenced needs is described herein below. 
     GENERAL DESCRIPTION 
     A vane actuator according to the present invention comprises a case defined by two case-halves having an exterior and/or interior clam shell shape. Each case-half includes a stiffening member positioned along a central region of each case half to resist deflection based on exposure to high pressure as well as high and low temperature conditions. High pressure as used herein shall mean operating pressures above 100 psig. High temperatures as used herein shall mean operating temperatures above 175 F. Low temperatures as used herein shall mean operating temperatures below −50 F. A vane actuator according to the present invention further comprises a pressure enclosure defined by interior surfaces of the respective case-halves. The pressure enclosure is designed to receive a vane, which defines first and second pressure chambers. Each case-half further includes a port to receive a vane shaft for rotating the vane. The vane shaft may be pivoted by causing a pressure difference within regions on either side of the vane. 
     In one embodiment of the present invention, the case further comprises suction and exhaust fluid ports as well as a drain port. Further embodiments of the present invention include integral NAMUR mounting surfaces on the exterior of the case to mount accessories such as solenoids, limit switches and positioners. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES 
     FIG. 1 is a plan view of an actuator in accordance with the present invention; 
     FIG. 2 is a cut away exploded view of an actuator including internal components in accordance with the present invention; 
     FIG. 3 is a side cross-sectional view of an actuator in accordance with the present invention. 
     FIG. 4 is a plan view of the NAMUR and bracket mounting for an actuator in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION 
     Referring to FIGS. 1,  2  and  3 , a vane actuator  100 , according to the present invention, is depicted in a top or plan view. Vane actuator  100  includes case  1 , comprising top case half  10  and bottom case half  50 . Top case half  10  and bottom case half  50  include shaft holes  10   a  and  50   a , respectively. Shaft holes  10   a  and  50   a  allow a shaft  20  to be rotatably inserted there through. Shaft holes  10   a  and  50   a  also include radial bearings  21   a  and  21   b  secured coaxially to radially support the shaft  20  for rotation as well as seals  21   c  and  21   d  to minimize leakage from the case. Top case half  10  and bottom case half  50  form a clam shell configuration, each case half generally being a mirror image of the other with exceptions as noted below. 
     Top case half  10  and bottom case half  50  include top stiffening member  30  and bottom stiffening member  80  respectively. In the preferred embodiment top stiffening member  30  comprises stiffeners  30   a ,  30   b  and  30   c , while bottom stiffening member  80  comprises stiffeners  80   a ,  80   b  and  80   c . The stiffeners and thus the respective stiffening members extend from exterior surfaces  10   b  and  50   b  on case halves  10  and  50 . Stiffeners  30   a  and  80   a  are positioned along the radial centerline of actuator  100 . In the preferred embodiment, the center lines of stiffeners  30   b  and  30   c  are positioned  11 ° on either side of stiffener  30   a  as measured centerline to centerline. Similarly, in the preferred embodiment, the center lines of stiffeners  80   b  and  80   c  are positioned 11° on either side of stiffener  80   a  as measured centerline to centerline. While the preferred embodiment shows 3 stiffeners, one or a plurality of stiffener(s) may be employed within the range noted above on either side of the centerline of actuator  100 . One or more stiffeners may be positioned within the range between about 10° and 20° on either side of the centerline of actuator  100  for the purpose of minimizing deflection of the case when exposed to a working temperature range of −50 F. to 300 F., and/or a maximum working pressure of 150 psig and/or a maximum overload pressure of 220 psig. In the preferred embodiment, each case half comprises a monolithic casting of A380 or A356 grade aluminum. 
     Shaft  20  includes a paddle shaped vane  25  located along the radial center of the shaft  20 . In the preferred embodiment, shaft  20  and vane  25  comprise a monolithic structure machined from a suitable alloy steel. The vane  25  is designed to rotatably travel within a pressure vessel defined by interior surface  10   c  of top case half  10  and interior surface  50   c  of bottom case half  50 . The pressure vessel is divided into two pressurizable sections defined by the vane  25  and shaft  20 . The pressurizable sections may be pressurized and depressurized through ports  5   a  and  5   b  of case half  10  and case half  50  respectively. 
     Leakage between the pressurizable sections is minimized through the use of a seal assembly. To secure the seal assembly, Vane  25  may include integral bolts which may extend through bolt holes in the seal assembly. In the preferred embodiment the vane seal assembly comprises vane seals  40   a  and  40   b , which are made from a durable and flexible material such as a polyurethane or a fluroelastomer. The vane seals  40   a  and  40   b  have exterior wall surfaces which extend away from a flat base surface, which contains bolt holes for receiving the bolts on vane  25 . In the preferred embodiment, a back of the flat base surface is disposed against vane faces of vane  25 . In the preferred embodiment, stainless steel expanders  42   a  and  42   b  are disposed against a front of the flat base surface on the vane seals  40   a  and  40   b . The expanders  42   a  and  42   b  exert a spring type force so as to force the vane seals  40   a  and  40   b  against the interior surfaces  10   c  and  50   c  of the case  1 . Expanders  42   a  and  42   b  also include bolt holes designed to receive the bolts on vane  25 . Side plates  46   a  and  46   b  are disposed against the expanders  42   a  and  42   b  and have bolt holes to receive the vane bolts  25   a  to retain the vane seals  40   a  and  40   b  and the expanders  42   a  and  42   b  against the vane  25 . Finally, nut and washer assemblies  25   b  are threadedly connected to the vane bolts  25   a  to secure the seal assembly. While the preferred embodiment includes the seal assembly as described above, other seal solutions may be envisioned by those skilled in the art. Examples include a system similar to the one described above, but employing the seal assembly only on one face of the vane. Furthermore, a simple o-ring may be disposed within a groove along the peripheral edges of the vane  25  to engage against the interior surfaces  10   c  and  50   c . In a further embodiment, expanders may be located on either side of a T-shaped seal, all of which may be disposed at one end within a slot along the peripheral edges of the vane  25  to engage against the interior surfaces  10   c  and  50   c . In an even further embodiment an expander may be located on one or both sides of an L-shaped seal, and similarly the expander and L-shaped seal may be disposed at one end within a slot along the peripheral edges of the vane  25  to engage against the interior surfaces  10   c  and  50   c.    
     Top case half  10  and bottom case half  50  may be bolted or otherwise secured together such that a seam S is formed there between. The connection of top case half  10  to bottom case half  50  defines a pressure chamber within the actuator case  1 . It can be seen that the manner in which the case halves  10  and  50  are joined together form clam-shell shaped actuator  100 . 
     This clam-shell shaped structure is quite like the clam-shell shaped actuators well known in the art. This configuration readily allows a user to replace the prior art low pressure/low temperature actuators with the high pressure/higher temperature actuators of the present invention, while maintaining substantially the same footprint dimensions of the prior art actuators. This is particularly beneficial to end users since an actuator that is dimensionally different may result in interferences with other pre-existing equipment or structures. 
     In the preferred embodiment, the exterior surfaces  10   b  and  50   b  of the respective case halves  10  and  50  are sloped so as to eliminate pockets or surface cavities, which could be collection points for corrosive fluids. Cavities on the exterior surfaces of prior art case halves are known to be sources for corrosion. Over time, these areas of corrosion can lead to actuator failure and loss of containment of potentially hazardous fluids. In the preferred embodiment, travel stops  11  and  12  extend through side surfaces of case half  10  and case half  50  respectively and into the pressurizable sections to engage against the vane  25  so as to limit the travel of the vane  25  and to protect the case  1  from damage. 
     Referring now to FIGS. 1,  3  and  4 , integral NAMUR VDI/VDE 3845 and bracket mounting surfaces are disclosed for mounting solenoids, positioners and limit switches and brackets for connecting to the component to be actuated, e.g., valve, damper, door, etc. In the preferred embodiment, side surfaces of case half  10  and case half  50  comprise an integral solenoid mounting  15 . Case half  10  further comprises a positioner/limit switch mounting  17 . Case half  50  further comprises a bracket mounting  19  for retaining the actuator  100  to the equipment to be actuated. 
     Techniques and advantages over the prior art apparatus are illustrated in the following non-limiting example: 
     EXAMPLE 1 
     Table 1 includes results from a finite elemental analysis which compares the performance of the prior art Kinetrol actuator with embodiments according to the present invention. The embodiments of the present invention analyzed were Models K1-K6 manufactured by K-Tork International, Inc. Each actuator was computer modeled to conform to the respective actuator specifications. Once modeled each actuator was internally pressured at ambient temperatures to analyze deflections. The overall size, dimensions and torque outputs of the respective actuators were held constant. The results show that the displacement magnitude and maximum displacement for the present invention K-Tork actuators are less than that of the prior art Kinetrol actuator of the same size. The deflections of the K-Tork actuators at 150 psig are less than or equal to the Kinetrol actuator when they were pressurized to 100 psig. The torque outputs (inch-lbs.) for the K-Tork models K1-K6 and the Kinetrol models 01-06 are 1080, 2280, 4992, 12000, 27000, and 60000 respectively. 
     
       
         
               
               
               
             
               
               
               
             
           
               
                   
                 TABLE 1 
               
             
             
               
                   
                   
               
               
                   
                 Displacement Magnitude 
                   
               
             
          
           
               
                 Actuator Type 
                 Maximum 
                 Minimum 
               
               
                   
               
               
                 K-Tork Model K1 
                 8.471 E−04 
                 1.996 E−06 
               
               
                 Kinetrol Model 01 
                 9.201 E−04 
                 6.828 E−06 
               
               
                 K-Tork Model K2 
                 1.036 E−03 
                 1.425 E−06 
               
               
                 Kinetrol Model 02 
                 1.221 E−03 
                 6.280 E−07 
               
               
                 K-Tork Model K3 
                 1.603 E−03 
                 1.641 E−05 
               
               
                 Kinetrol Model 03 
                 2.124 E−03 
                 4.688 E−06 
               
               
                 K-Tork Model K4 
                 2.471 E−03 
                 9.836 E−06 
               
               
                 Kinetrol Model 04 
                 4.575 E−03 
                 4.760 E−06 
               
               
                 K-Tork Model K5 
                 3.070 E−03 
                 1.024 E−03 
               
               
                 Kinetrol Model 05 
                 3.445 E−03 
                 5.363 E−03 
               
               
                 K-Tork Model K6 
                 4.289 E−03 
                 2.824 E−06 
               
               
                 Kinetrol Model 06 
                 5.098 E−03 
                 6.243 E−05 
               
               
                   
               
             
          
         
       
     
     While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof. It is to be understood that all matter herein set forth or shown in the accompanying tables and figures is to be interpreted as illustrative and not in a limiting sense. Accordingly, the foregoing description should be regarded as illustrative of the invention whose full scope is measured by the following claims.