Patent Publication Number: US-2009224196-A1

Title: Compact servo poppet valve and pressure relief system employing the same

Description:
TECHNICAL FIELD 
     The present invention relates generally to a poppet valve and, more particularly, to a compact servo poppet valve employing one or more spring washers. 
     BACKGROUND 
     Poppet valves are commonly utilized to regulate the pressure within a pressurized chamber of a hydraulic or pneumatic device. One known servo poppet valve comprises a valve housing having a flow passage therethrough. The flow passage is fluidly coupled between the pressurized chamber of the host device and a low pressure source, which may be, for example, the interior of the device or an ambient air source. A poppet valve element (e.g., a plunger) is disposed within the valve housing and adapted to move between: (i) a closed position wherein the valve element substantially impedes fluid flow through the flow passage, and (ii) an open position wherein the valve element does not substantially impede fluid flow through the flow passage. The poppet valve element is biased toward the closed position by an elongated helical spring (also commonly referred to as a “coil spring”). When the pressure within the pressurized chamber surpasses a predetermined pressure threshold, the force exerted on the exposed area of the poppet valve element exceeds the bias force exerted by the helical spring (and any force exerted on the valve element by the low pressure source). The poppet valve element consequently moves into an open position, and the helical spring is compressed between the poppet valve and an inner wall of the valve housing. When the poppet valve element is in the open position, fluid is permitted to flow from the pressurized chamber, through the poppet valve, and into the low pressure source thus relieving the pressure within the pressurized chamber. The poppet valve element remains in the open position until the pressure of the fluid within the pressurized chamber again falls below the predetermined pressure threshold. 
     Servo poppet valves of the type described above are well-suited for many applications. However, due in large part to the presence of the helical spring, such servo poppet valves may be undesirably heavy and/or bulky for utilization in applications wherein weight and volume are primary drivers. This is especially true when the helical spring employed by the servo poppet valve is characterized by a relatively high spring rate. There thus exists an ongoing need to provide a servo poppet valve that is relatively compact and lightweight. Preferably, such a servo poppet valve would be able to achieve a relatively high spring rate while maintaining the valve&#39;s compact size. Similarly, there exists an ongoing need to provide a pressure relief system employing such a compact servo poppet valve. Other desirable features and characteristics of the present invention will become apparent from the subsequent Detailed Description and the appended claims, taken in conjunction with the accompanying drawings and this Background. 
     BRIEF SUMMARY 
     In a first embodiment, a servo poppet valve is provided that includes a valve housing having a flow passage therethrough, a poppet valve element disposed in the flow passage, and a first spring washer disposed between the valve housing and the poppet valve element. The poppet valve element is movable between an open position and a closed position, and the first spring washer biases the poppet valve element toward the closed position. 
     In a second embodiment, a pressure relief system is provided for fluid communication with a low pressure source. The pressure relief system includes: (i) a system housing having a pressurized chamber therein, and (ii) a servo poppet valve. The servo poppet valve includes a valve housing fixedly coupled to the system housing, a flow passage formed through the valve housing and fluidly coupled between the pressurized chamber and the low pressure source, and a poppet valve element disposed in the flow passage and movable between an open position and a closed position. The poppet valve element permits fluid flow from the pressurized chamber to the low pressure source in the open position. A spring washer is disposed between the valve housing and the poppet valve element and biases the poppet valve element toward the closed position. The poppet valve element normally resides in the closed position and is configured to move into the open position when the pressure of the fluid within the pressurized chamber surpasses a predetermined pressure threshold. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       At least one example of the present invention will hereinafter be described in conjunction with the following figures, wherein like numerals denote like elements, and: 
         FIG. 1  is an isometric cross-sectional view of a compact servo poppet valve employing a stack of bellville washers in accordance with a first exemplary embodiment; 
         FIG. 2  is a high level schematic of an exemplary pressure relief system employing the compact servo poppet valve shown in  FIG. 1 ; and 
         FIG. 3  is an isometric view of a stack of wave springs that may be utilized in place of the stack of bellville washers employed by the compact servo poppet valve shown in  FIG. 1  in accordance with a second exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The following Detailed Description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding Background or the following Detailed Description. 
       FIG. 1  is an isometric cross-sectional view of a compact servo poppet valve  20  in accordance with an exemplary embodiment. Poppet valve  20  comprises a valve housing  22  through which a flow passage  24  is formed. In the illustrated exemplary embodiment, valve housing  22  comprises a main housing body  26  having a housing cap  28  coupled thereto. Housing cap  28  is preferably removably coupled to main housing body  26  by way of a threaded interface, although housing cap  28  may be coupled to main housing body  26  utilizing any suitable attachment means (e.g., via one or more fasteners, such as a snap ring). Flow passage  24  includes at least one inlet  30  and at least one outlet  32 , which may be formed through main housing body  26  and housing cap  28 , respectively. For example, and as indicated in  FIG. 1 , inlet  30  may comprise a single channel that extends through a base wall  33  of main housing body  26 , and outlet  32  may comprise a plurality of channels that extends through an annular sidewall  35  of housing cap  28 . 
     A poppet valve element  34  is disposed between main housing body  26  and housing cap  28 . In the illustrated example, poppet valve element  34  includes a substantially hemi-spherical seating portion  36  and a stemmed portion  38  extending therefrom; however, it will be appreciated that valve element  34  may assume any form suitable for selectively impeding fluid flow through flow passage  24  in the manner described below. Valve element  34  is movable between a closed position (shown in  FIG. 1 ), a fully open position, and various intermediate open positions. When in the closed position ( FIG. 1 ), seating portion  36  of valve element  34  contacts a seating surface  39  provided on main housing body  26  to substantially impeded fluid flow into inlet  30  and through flow passage  24 . Conversely, when valve element  34  moves into an open position, valve element  34  lifts from seating surface  39  and fluid is permitted to flow into inlet  30 , through flow passage  24 , and out of outlets  32 . 
     Compact servo poppet valve  20  further includes one or more spring washers. As used herein, the term “spring washer” is defined to include various low-profile, resilient, compressible elements. A non-exhaustive list of suitable spring washers includes bellville washers, wave springs, and the like. Although compact servo poppet valve  20  may employ a single spring washer, poppet valve  20  preferably comprises multiple spring washers arranged in a stacked configuration. For example, and as shown in  FIG. 1 , compact servo poppet valve may include a plurality of bellville washers  40  arranged in a stacked configuration. Bellville washers  40  are compressed between an end wall  44  of housing cap  28  and poppet valve element  34  and consequently bias poppet valve element  34  toward the closed position shown in  FIG. 1  (i.e., away from end wall  44  of housing cap  28  and toward base wall  33  of main housing body  26 ). By utilizing two or more bellville washers (or other such spring washers) arranged in such a stacked configuration, the tolerance of compact servo poppet valve  20  may be increased. 
     If desired, compact servo poppet valve  20  may also be equipped with an adjustable pre-load mechanism. As indicated in  FIG. 1 , the adjustable pre-load mechanism may comprise, for example, a threaded stop member  42  disposed between end wall  44  of housing cap  28  and bellville washers  40 . Threaded stop member  42  threadably engages an inner annular surface of housing cap  28 . An aperture  46  is provided through housing cap  28  to permit manual access to threaded stop member  42 . A technician may insert a tool (not shown) into aperture  46  to rotate threaded stop member  42  relative to valve housing  22  and thereby adjust the vertical position of threaded stop member  42  relative to end wall  44  of housing cap  28 . In this manner, the compressive pre-load exerted by bellville washers  40  on poppet valve element  34  may be adjusted to preference. This example notwithstanding, alternative embodiments of poppet valve  20  may employ other adjustable pre-load mechanisms, such as a shim stack. 
     To help guide the movement of poppet valve element  34 , compact servo poppet valve  20  may be provided with one or more guide features. In the illustrated exemplary embodiment, compact servo poppet valve  20  includes two such guide features. First, main housing body  26  is provided with an annular collar  48  that extends away from base wall  33 . Notably, annular collar  48  surrounds seating surface  39 , and, when poppet valve element  34  is in the closed position (shown in  FIG. 1 ), poppet valve element  34  resides at least partially within annular collar  48  (e.g., the inner edge of collar  48  may contact an outer circumferential portion of poppet valve element  34 ). In a preferred embodiment, the outer diameter of annular collar  48  is substantially equivalent to an inner diameter of housing cap  28 , and annular collar  48  is substantially co-axial with outlet  30 . As noted above, housing cap  28  may be threadably coupled to an outer annular surface of annular collar  48 . 
     Stemmed portion  38  of poppet valve element  34  serves as a second guide feature of compact servo poppet valve  20 . As shown in  FIG. 1 , stemmed portion  38  extends away from seating portion  36  of valve element  34  and is matingly received by a central opening provided in bellville washers  40 . In this manner, stemmed portion  38  and bellville washers  40  cooperate to help maintain poppet valve element  34  in its proper position. If desired, stemmed portion  38  may be produced by machining (e.g., grinding) an end portion of poppet valve element  34 , which may initially assume the form of a generally spherical body, such as a metal ball. 
     During operation of compact servo poppet valve  20 , poppet valve element  34  normally resides in the closed position shown in  FIG. 1 . When poppet valve element  34  is in the closed position, little to no fluid is permitted to flow into inlet  30  and through flow passage  24 . However, when the pressure exerted by on the area of poppet valve element  34  exposed through inlet  30  exceeds the force exerted on valve element  34  by bellville washers  40  (and, perhaps, by the fluid within flow passage  24 ), poppet valve element  34  transitions into an open position. Bellville washers  40  are consequently compressed between poppet valve element  34  and threaded stop member  42 , and fluid is permitted to flow into inlet  30 , through flow passage  24 , and out of outlets  32 . Poppet valve element  34  remains in an open position until the pressure exerted on poppet valve element  34  by the fluid flowing into inlet  30  is again surpassed by the force exerted on valve element  34  by bellville washers  40  (and any forced exerted on valve element  34  by the fluid within flow passage  24 ). The characteristics of bellville washers  40  and the dimensions of outlet  30  are chosen to yield a desired threshold pressure at which poppet valve element  34  transitions from the closed position (shown in  FIG. 1 ) to an open position. 
     There has thus been provided an exemplary embodiment of a compact servo poppet valve. In the above-described exemplary embodiment, a significant savings in weight and volume of the poppet valve is achieved by utilizing one or more bellville washers as the poppet valve&#39;s main return mechanism. The servo poppet valve&#39;s modest weight and volume is maintained even when employing bellville washers characterized by a relatively high spring rate. The above-described compact servo valve is consequently well-suited for utilization in applications having significant weight and volume constraints. Embodiments of compact servo valve may find use in a variety of pneumatic or hydraulic control circuits, including, for example, various types of pressure relief systems. To further illustrate this point, an exemplary pressure relief system employing compact servo poppet valve  20  will now be described in conjunction with  FIG. 2 . 
       FIG. 2  is a high level schematic of an exemplary pressure relief system  50  employing compact servo poppet valve  20  as a pressure relief valve. In the illustrated example, pressure relief system  50  comprises a system housing  52  containing a pressurized chamber  54  (e.g., a flow passage). Referring collectively to  FIGS. 1 and 2 , servo poppet valve  20  is fixedly coupled to system housing  52  such that flow passage  24  is fluidly coupled between pressurized chamber  54  and a low pressure source  56 . In one embodiment, main housing body  26  ( FIG. 1 ) may be integrally formed with system housing  52 . Low pressure source  56  may comprise any fluid body having a pressure lower than that of the fluid within pressurized chamber  54 . For example, if pressure relief system  50  conducts pressurized air during operation, low pressure source  56  may simply comprise an ambient air source. Alternatively, low pressure source  56  may comprise an internal chamber of the device in which pressure relief system  50  is employed. 
     Pressure relief system  50  is configured to maintain the pressure within pressurized chamber  54  below a predetermined pressure threshold (or possibly below a predetermined pressure differential between pressurized chamber  54  and low pressure source  56 ). As explained above, poppet valve element  34  ( FIG. 1 ) normally resides in the closed position under the bias force of bellville washers  40 . When the pressure within chamber  54  surpasses the predetermined pressure threshold, poppet valve element  34  moves from the closed position to an open position. When poppet valve element  34  is in an open position, fluid is permitted to flow from pressurized chamber  54 , through compact servo poppet valve  20 , and into low pressure source  56  (indicated in  FIG. 2  by arrow  58 ). As a result, the pressure within pressurized chamber  54  is relieved. When the pressure within chamber  54  again falls below the predetermined pressure threshold, poppet valve element  34  returns to the closed position under the force of bellville washers  40  ( FIG. 1 ) and fluid flow through compact servo poppet valve  20  ceases (or is otherwise substantially reduced). 
     Considering the above, it should be appreciated that there has been provided an exemplary embodiment of a relatively compact and lightweight servo poppet valve employing one or more bellville washers, which may be chosen to have a relatively high spring rate, if desired. It should also be appreciated that there has been provided an exemplary embodiment of a pressure relief system employing such a compact servo poppet valve. As previously noted, additional embodiments of compact servo poppet valve may utilize other types of spring washers (e.g., one or more wave springs) in lieu of, or in addition to, one or more bellville washers to bias the poppet valve element toward the closed position. For example, and with reference to  FIG. 3 , compact servo poppet valve  20  ( FIG. 1 ) may employ a stack of wave springs  60  in place of bellville washers  40 . Stack of wave springs  60  may be joined together in either a crest-to-crest configuration (shown in  FIG. 3 ) or a crest-to-valley configuration (not shown). 
     While at least one exemplary embodiment has been presented in the foregoing Detailed Description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing Detailed Description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention. It being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set-forth in the appended claims.