Abstract:
A thermal isolator assembly that provides rigid construction, linearly and rotationally, is presented. The thermal isolator assembly includes a collar and a sleeve that are thermally isolated one from another but held in rigid mechanical relation. When constructed for actuated valves, the collar forms an actuator arm coupling member while the sleeve forms a valve stem coupling member. A pair of thermal isolators provide thermal isolation between these members. A polyphenylene sulfide compound, and preferably a fiberglass reinforced polyphenylene sulfide compound is used because of its high mechanical strength and low thermal conductivity for these thermal isolators.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates generally to thermal isolation assemblies, and more particuarly to a thermal isolator for use with actuator controlled valves.  
         BACKGROUND OF THE INVENTION  
         [0002]    Remote and automatic control mechanisms allow for increased productivity and enhanced safety in many industrial applications. For example, remote or automatic controlled valves may be used to control the flow of hot process fluids and high pressure steam in many industrial and commercial applications. These remote and automatic controllers eliminate the prior need for workers to open and close such flow control valves, thereby removing the possibility of human error, reducing the number of employees needed to operate complex fluid transfer systems, and reducing the possibility that a worker may become injured if a leak or malfunction may occur with the hot process fluid.  
           [0003]    Early remote controlled valves still in use today in many applications utilize a solenoid driven linear actuator to open and close the valves to control the flow of fluid therethrough. The control for such solenoid valves is typically centrally located with power lines being run to each of the solenoids at each of the control valve locations. These valves typically only provide on/off control of the valves.  
           [0004]    To provide variable flow control, the position of the valve stem has to be precisely controlled.  
           [0005]    Such actuators utilize electrical control signals to cause an electric motor to operate, through either gears or a rack and pinion mechanism, to control the valve to open, close, or partially open positions. This allows the valve to control the flow of hot processed fluid, or steam, by way of remotely generated control signals of various magnitudes.  
           [0006]    However, in installations that handle hot process fluid or steam, a considerable amount of heat from the process fluid or steam is conducted from the valve stem to the actuator assembly. Unfortunately, increased heat detrimentally affects the magnetics of the solenoid control mechanism as well as plastic gears and enclosures. As a result, precise control of the valve stem position is difficult. This results from the fact that additional energization current must be supplied to the solenoid as the temperature of the solenoid is increased by this thermal transfer. This precise control problem is exacerbated by the various installation locations and the impedance of the power lines from the central control to each individual solenoid controlled valve location. Likewise, as with the solenoid controlled valves, the increase in heat conducted from the valve stem to the actuator adversely affects the motor&#39;s ability to operate at a controlled level.  
           [0007]    More modern remote and automatic controlled valves include the control electronics at the controlled valve location. Such design overcomes the problems associated with trying to precisely control valve stem position in a widely distributed fluid process control system from a centralized location. While the on-board electronics greatly enhance a valve&#39;s ability to precisely control the flow rate therethrough, electronics&#39; inability to withstand high temperature environments has limited their applicability to process control systems for high temperature process fluids and steam. That is, when valves are used to control hot process fluids or steam, a considerable amount of heat is transferred through the valve stem to the actuator. This is because the moveable portion of the actuator mechanism must be rigidly connected to the valve stem to cause the valve to operate properly. Such heat transfer can be detrimental to sensitive components within the actuator, such as the control circuit electronics, the actuator motor, plastic gears, and the enclosure.  
           [0008]    Therefore, there exists a need in the art for a thermal isolator that rigidly connects a valve actuator to the valve and that will allow proper operation of the actuator/valve combination while preventing unwanted heat from being transferred from the valve into the actuator mechanism.  
         BRIEF SUMMARY OF THE INVENTION  
         [0009]    In view of the above, the present invention provides a new and improved thermal isolator that may be used, for example, to thermally isolate a valve actuator from the valve stem which it controls. More particularly, the present invention provides a new and improved thermal isolator that provides rigid connection between the valve actuator and the valve stem that is in contact with the hot process fluid or steam.  
           [0010]    In a preferred embodiment, the thermal isolator of the present invention includes a valve stem coupling member that attaches to the valve stem, an actuator collar member that attaches to the actuator, and a thermal isolator positioned therebetween to minimize the thermal transfer from the valve stem coupling member to the actuator collar member. To maintain axial rigidity for linearly actuated valves, washers are utilized to allow an increased compression force to be used in the manufacture of the assembly.  
           [0011]    In one embodiment, the valve stem sleeve is threaded to receive a threaded, linearly actuated valve stem. In alternate embodiments, the sleeve is configured to receive the valve stem of rotary actuated valves, such configuration may include geometric shapes, having flat sides to enable rotary actuation of the valve stem. Similarly, the actuator collar member is also configured to receive the actuator, either linear or rotary. In one embodiment the collar member includes pinning holes to allow for pinning to the actuator arm. In other embodiments, the collar may be threaded or surfaced.  
           [0012]    In a preferred embodiment of the present invention, Likewise, as with the solenoid controlled valves, the increase in heat conducted from the valve stem to the actuator adversely affects the motor&#39;s ability to operate at a controlled level. a thermal isolator assembly for use between an actuator arm and a valve stem comprises a first coupling member having a bottom wall having a first aperture. The first coupling member also includes at least one side wall that is adapted to attach to the actuator arm. A second coupling member having a shank portion extends through the first aperture. The shank portion includes a bore that is adapted to receive the valve stem. A pair of thermal isolators are positioned on either side of the bottom wall. Each has an aperture that communicates with the aperture of the first coupling member to form a central passage. The shank portion of the second coupling member is positioned within the central passage and is rigidly affixed therein. The thermal isolators inhibit thermal transfer from the second coupling member to the first coupling member.  
           [0013]    In a preferred embodiment, each of the thermal isolators include a flange of a height approximately equal to one half of a thickness of the bottom wall. The flange is positioned within the first aperture to inhibit thermal transfer from the second coupling member to an interior wall of the first aperture. In one embodiment the first aperture is circular and the flange is annular. In another embodiment, the first aperture is surfaced, and an outer wall of the flange is surfaced to match the surfaced first aperture. Preferably, the second coupling member includes a head portion at an external end of the shank portion having a diameter exceeding a diameter of the shank portion. In this embodiment, a first washer is positioned between the head portion and the thermal isolator. An interior end of the shank portion is rolled over, and a second washer is positioned between the rolled over interior end of the shank portion and the thermal isolator.  
           [0014]    In a further embodiment, an interior surface of the bore is threaded, while in another the interior surface of the bore is surfaced. Preferably, the interior surface of the bore forms a squared “D”. In another embodiment, the side wall includes at least one pinning hole. In one embodiment, the bottom wall is circular, and the side wall forms a cylindrical side wall. Preferably, the first coupling member is steel, the second coupling member is brass, and the thermal isolators are polyphenylene sulfide. The polyphenylene sulfide thermal isolators are preferably fiberglass reinforced; in one embodiment they are 40% fiberglass reinforced.  
           [0015]    In an alternate embodiment of the present invention, a thermal isolator assembly comprises a first coupling member having a cylindrical side wall and a bottom wall including an aperture. A second coupling member has a shank portion positioned through the aperture. The shank portion defines a bore therein. A thermal isolator is positioned between the first coupling member and the second coupling member to inhibit thermal transfer from the second coupling member to the first coupling member. Preferably, the thermal isolator comprises a pair of thermal isolator bodies positioned on either side of the bottom wall of the first coupling member, each having an aperture. The shank portion of the second coupling member is positioned through the apertures. Still further, at least one of the thermal isolator bodies includes an annular flange positioned within the aperture of the bottom wall to inhibit thermal transfer between the second coupling member and a side wall of the aperture in the bottom wall. In one embodiment, the thermal isolator bodies are comprised of Ryton™ R-4. Preferably, the second coupling member includes a head portion having a diameter greater that the aperture in the thermal isolator. An interior end of the shank portion is rolled to form a rigid assembly.  
           [0016]    In a further alternate embodiment of the present invention, a controlled valve comprises a valve body having an inlet, an outlet, and a valve mechanism actuated by a valve stem. An actuator assembly is positioned in proximity to the valve body, and includes an actuator arm. A thermal isolator assembly couples the actuator arm to the valve stem. The thermal isolator assembly comprises a first coupling member having a bottom wall having a first aperture. The first coupling member also includes at least one side wall that is adapted to attach to the actuator arm. A second coupling member having a shank portion extends through the first aperture. The shank portion includes a bore that is adapted to receive the valve stem. A pair of thermal isolators are positioned on either side of the bottom wall. Each has an aperture that communicates with the aperture of the first coupling member to form a central passage. The shank portion of the second coupling member is positioned within the central passage and is rigidly affixed therein. The thermal isolators inhibit thermal transfer from the second coupling member to the first coupling member.  
           [0017]    Other features and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention, and together with the description serve to explain the principals of the invention. In the drawings:  
         [0019]    [0019]FIG. 1 is an exploded isometric view of an embodiment of the thermal isolator of the present invention;  
         [0020]    [0020]FIG. 2 is a perspective view illustration of the thermal isolator assembly of FIG. 1;  
         [0021]    [0021]FIG. 3 is a top perspective view illustration of a partially assembled thermal isolator assembly of the present invention;  
         [0022]    [0022]FIG. 4 is a cross-sectional view of the thermal isolator assembly of FIG. 2;  
         [0023]    [0023]FIG. 5 is a perspective view illustration of a controlled valve utilizing the thermal isolator of the present invention; and  
         [0024]    [0024]FIG. 6 is an exploded isometric view illustrating an alternate embodiment of a thermal isolator assembly constructed in accordance with the teachings of the present invention.  
     
    
       [0025]    While the invention will be described in connection with certain preferred embodiments, there is no intent to limit it to those embodiments. On the contrary, the intent is to cover all alternatives, modifications and equivalents as included within the spirit and scope of the invention as defined by the appended claims.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0026]    Turning now to the drawings there is illustrated in exploded isometric form in FIG. 1 an embodiment of a valve stem thermal isolator  10  constructed in accordance with the teachings of the present invention. This thermal isolator includes an actuator arm coupling member  12  which is adapted to be affixed to the actuator arm of the valve actuator. In one embodiment, this actuator arm coupling member  12  may take the form of a collar that accommodates the driving end of the actuator arm therein. In such an embodiment, the collar  12  may include pinning holes  14  to accommodate pinning of the actuator arm therein. Other attachment mechanisms may also be employed depending on the application and actuator being used including, e.g. threaded attachments, surfaced attachments for rotary actuators, etc.  
         [0027]    The actuator arm coupling member  12  also defines therein an aperture  16  that is sized to accommodate a flange of  19 ,  21  of thermal isolators  18 ,  20  therein. Preferably, each of the thermal isolators  18 ,  20  are of identical configuration so as to reduce the manufacturing cost of the valve stem thermal isolator assembly  10  of the present invention. Each of the thermal isolators  18 ,  20  are made from a material having a low conductivity, and preferably a high compression strength. For example, polyphenylene sulfide resins such as those sold under the trademark Ryton™ by Chevron Phillips Chemical Company, In a preferred embodiment, the particular polyphenylene sulfide resin used to construct the thermal isolators  18 ,  20  is Ryton™ R-4. This material is a 40% fiberglass reinforced polyphenylene sulfide compound having a thermal conductivity of 0.32 W/m·K. As a comparison, the thermal conductivity of steel is 46W/m·K while copper has a coefficient of thermal conductivity of 401 W/m·K.  
         [0028]    In a preferred embodiment, the configuration of the thermal isolators  18 ,  20  are that of a disk having a small annular flange  19 ,  21  of a height approximately equal to one-half of the wall thickness of the actuator arm coupling member  12 . In this way, the two thermal isolators  18 ,  20  may sandwich themselves on either side of the bottom wall  22  of the actuator arm coupling member  12 . In this configuration, each thermal isolator  18 ,  20  provides thermal isolation to both the inside and the outside surfaces of the bottom wall  22 , as well as to the inner wall of aperture  16 .  
         [0029]    A pair of washers  24 ,  26  are preferably used between the thermal isolators and the valve stem coupling member  28 . These washers  24 ,  26  provide some additional thermal isolation, but primarily allow the assembly  10  to be constructed with increased compressive forces so that a very rigid assembly  10  results. In one embodiment, these washers  24 ,  26  are stainless steel. Such rigid assembly  10  is required for high precision linearly actuated valve applications that have a high degree of control flow characteristics. In such applications and in such an embodiment, the linear actuation of the actuator arm correlates directly to a like linear actuation of the valve stem through the valve stem thermal isolator assembly  10 . However, it is noted that other applications may not require such excessive rigidity in a linear direction. In one embodiment of the present invention, the actuator arm coupling member  12  is steel, as are washers  24 ,  26 . Preferably, the valve stem coupling member  28  is made of brass for cost savings, but may more preferably be made of stainless steel.  
         [0030]    In the embodiment illustrated in FIG. 1, this valve stem coupling member  28  is threaded in its interior bore  30  through its shank portion  31  to attach to the valve stem. This configuration is particularly useful for linearly actuated valves. The head portion  29  preferably has a diameter greater than that of the aperture of the washer  24 .  
         [0031]    The completed assembly of the valve stem thermal isolator  10  of the present invention is illustrated in FIG. 2. In this embodiment, a threaded valve stem is received within the threaded bore  30  of the valve stem coupling member  28 . To facilitate a secure connection, the head portion  29  of the valve stem coupling member  28  may include a surfaced exterior to accommodate the use of a wrench to tighten the threaded coupling against the jam nut on the valve stem. Once secure on the valve stem, the actuator arm may be installed into the actuator arm coupling member  12  and pinned in place via pinning holes  14 .  
         [0032]    [0032]FIG. 3 illustrates an internal view of the valve stem thermal isolator assembly  10  of FIG. 2 prior to completing the manufacture of this assembly. As may be seen from this illustration, the shank portion  31  of the valve stem coupling member  28  extends into the interior of the actuator arm coupling member  12 , through the thermal isolator  20  and the washer  26 . This valve stem coupling member  28  may then be secured in place to complete the assembly  10 . While various methods could be used to secure the valve stem coupling member  28  in place, e.g. threading a nut on the end of the valve stem coupling member, a preferred method is to roll the end of the valve stem coupling member  28  in an orbital spin riveter to ensure a rigid construction over the life of the valve stem thermal isolator assembly  10 .  
         [0033]    This preferred method of construction may be seen in the cross-sectional illustration of the valve stem thermal isolator assembly  10  of the present invention in FIG. 4. This cross-sectional illustration also makes clear the cooperating relationship between the two thermal isolators  18 ,  20  as they sandwich within the aperture  16  in the bottom wall  22  of the actuator arm coupling member  12 . The relative thickness of the components of the assembly  10  may be adjusted depending on the application for which the assembly  10  is required and the amount of thermal isolation required.  
         [0034]    [0034]FIG. 5 illustrates an exemplary implementation of the valve stem thermal isolator assembly  10  for a linearly actuated flow control valve. Specifically, the actuator assembly  32  is mounted on top of the flow control valve  34  in a conventional manner. The valve stem thermal isolator assembly  10  is positioned between the actuator  32  and the valve  34 , providing a rigid coupling between the actuator arm  33  and the valve stem  35  while thermally isolating these two components to reduce the amount of heat that is conducted into the actuator  32  from the valve  34 .  
         [0035]    While the preceding embodiments have been particularly useful for application on a linearly actuated flow control valve, the embodiment of the valve stem thermal isolator assembly  10  illustrated in FIG. 6 finds particular applicability for rotary actuated valves. Specifically, in rotary actuated valves the linear rigidity of the assembly  10  is not as important as the rotational rigidity. That is, since rotary actuated valves (for example ball valves, butterfly valves, etc.) operate by rotating their valve stem, the linear position of the valve stem does not change. Instead, the angular rotation determines the amount by which the valve is allowed to open and close. As such, the aperture  16 ′ in the bottom wall  22  of the actuator arm coupling member  12 ′ is modified to have a surfaced wall  36 . Each of the two thermal isolators  18 ′,  20 ′ also utilize a surfaced annular flange  38 ,  40 . In this way, a rigid rotational coupling is maintained between the actuator arm coupling member  12 ′ and the thermal isolators  18 ′,  20 ′. Further, to ensure a rigid rotational coupling between the thermal isolators  18 ′,  20 ′ and the shank portion  31 ′ of the valve stem coupling member  28 ′ the interior aperture walls  42 ,  44  are also surfaced. In a like manner, the exterior walls  46  of the shank portion  31 ′ of the valve stem coupling member  28 ′ is also surfaced. The particular configuration of this surfacing may vary widely depending upon the rotational torque requirements of the particular application for which the valve stem thermal isolator assembly  10 ′ of the present invention is to be applied. The bore  30 ′ of the valve stem coupling member  28 ′ is also surfaced to provide an appropriate rotational coupling to the valve stem. As illustrated in the embodiment of FIG. 6, this bore  30 ′ is in a squared D configuration typical with rotary valve stems. However, this configuration may also vary widely depending upon the valve stem configuration.  
         [0036]    As will be apparent to those skilled in the art, while the foregoing discussion confined itself to the application of the thermal isolator assembly  10  of the present invention to actuated valves, the invention itself is not so limited. Indeed, the thermal isolator assembly  10  of the present invention may find wide application where either linear or rotational couplings are desired, but heat transfer thereacross is not.  
         [0037]    All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.  
         [0038]    The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.  
         [0039]    Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.