Abstract:
A radial diaphragm valve includes a diaphragm having an elongated stem that is threadably or otherwise installed on an actuator piston. The elongated stem is slideably received in a bore formed in the actuator housing, and includes a circumferential recess that receives a seal. The seal provides a backup seal function separating the process fluid from the interior region of the actuator.

Description:
RELATED APPLICATIONS 
     This application is a continuation-in-part of pending U.S. patent application Ser. No. 10/109,413 filed on Mar. 28, 2002 for SANITARY DIAPHRAGM VALVE, the entire disclosure of which is fully incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     As the need for sanitary valves continues to increase for industries such as semiconductor and biopharmaceutical, radial diaphragm valves are being recognized as highly effective for increased flow, cleanability and low contamination. One such valve is disclosed in U.S. Pat. No. 6,394,417 B1 owned by the assignee of the present invention, the entire disclosure of which is fully incorporated herein by reference. The present invention is directed to additional design options of such a valve. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect of the invention, an alternative design to seal a valve actuator piston and diaphragm is provided. In a preferred embodiment of the invention, the diaphragm includes an elongated stem that is threadably or otherwise installed on an actuator piston. The elongated stem is slideably received in a bore formed in the actuator housing, and includes a circumferential recess that receives a seal. The seal provides a backup seal function separating the process fluid from the interior region of the actuator. In a non-manual actuator the seal separates a pressurized portion of the actuator from the diaphragm. The seal may also function as a guide to facilitate alignment of the diaphragm. In one specific but not required embodiment the seal is an o-ring. 
    
    
     These and other aspects and advantages of the present invention will be apparent to those skilled in the art from the following description of the preferred embodiments in view of the accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWING 
     The drawing is a radial diaphragm valve illustrated in longitudinal cross-section in accordance with the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to the drawing, a radial diaphragm valve  10  in accordance with the invention is illustrated. Many of the features of the valve are similar to the above noted patent and need not be repeated herein. Reference to such patent may be made for a detailed understanding of these common features. Moreover, while the invention is described herein with respect to an exemplary embodiment of a plastic radial diaphragm valve, such description should not be construed in a limiting sense. Those skilled in the art will readily appreciate that the invention may be utilized in many different valve designs including but not limited to weir style valves, metal valves and so on to name a few examples. 
     The valve  10  in this exemplary embodiment includes a valve body A and a valve actuator assembly B mounted thereon by any suitable means such as bolts (not shown). The valve body A includes an inlet C and an outlet D through which the flow of a process fluid, either gas or liquid. The inlet C opens to a valve cavity E at an inlet port F, and the outlet D opens to the valve cavity E at an outlet port G. Fluid flow through the valve is controlled by axial movement of a valve stem H. The valve stem H seals about the inlet port F to close the valve  10 . The drawing illustrates the valve  10  in the open position. 
     The valve stem H is integrally formed with a radial diaphragm I that includes a peripheral rim J and a flexible web K that joins the rim J to the stem H. The rim J is sandwiched between an actuator body L and a counterbore M formed in the valve body A. The rim J thus forms a body seal to prevent the loss of process fluid from the valve cavity. 
     The actuator assembly B in this example is an air actuator, however, other actuator devices and technologies may be alternatively used including but not limited to manual actuators or hydraulic actuators. The actuator assembly B includes an actuator piston N that is slideably received in a piston chamber P. The piston N divides the piston chamber P into an upper section Q and a lower section R. The piston N is translated along the main longitudinal axis X by controlling the pressure differential between the upper and lower sections Q and R, as is known. The piston N includes a central female threaded bore S formed in an actuator stem T. In the exemplary embodiment, the actuator B is of the type that is generally known as a double acting actuator, meaning that air pressure is used to both open and close the valve. Alternatively, a bias element such as a spring (not shown) is appropriately mounted in the actuator to provide either a normally closed valve (the valve is biased closed by the spring) or a normally open valve, as is well known in the art. 
     In accordance with the invention, the diaphragm I includes an upper diaphragm stem portion  20  that, by comparison to the stem in the above incorporated patent, is axially lengthened and extends through and is slideably received in a central bore  30  formed in the actuator body L. The elongated stem  20  includes a male threaded end  25  that threadably mates with the threaded bore S formed in the piston N. Although the diaphragm I is illustrated as being threadably mated with the piston N, those skilled in the art will appreciate that other techniques may be conveniently used to join the parts. In accordance with one aspect of the invention, the diaphragm I may be made of a suitable plastic material such as, for example, PTFE (TEFLON™) or other lubricious -material, thus reducing or eliminating the need for a lubricant between the bore  30  and the upper stem  20 . 
     A circumferential groove  40  is formed in the diaphragm upper stem portion  20  at an axial position such that the groove  40  is substantially contained within the central bore  30  over the entire stroke of the piston N. A seal  50 , in this example an o-ring, is received in the upper stem portion groove  40 . This seal  50  will prevent process fluid from passing into the actuator assembly B in the event that the diaphragm I seal is compromised. In the case where there is fluid pressure in the lower section R of the piston chamber P (for example, in a normally open air actuated valve or a double acting actuator), the seal  50  also isolates this pressure from the diaphragm I. 
     Still further, the seal  50  functions to journal and guide the diaphragm stem  20  within the actuator housing bore  30 . This helps to maintain the diaphragm I in proper alignment for optimum sealing of the inlet port F, particularly when the diaphragm I is installed on the actuator stem T by a bayonet or a floating mount arrangement or other non-threaded mounting arrangement (not shown). 
     The invention has been described with reference to the preferred embodiments. Clearly, modifications and alterations will occur to others upon a reading and understanding of this specification. It is intended to include all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.