Abstract:
This disclosure sets forth a diaphragm valve operative with N ports deployed in an upper head. The ports all connect to a diaphragm having a bead defining a flow path around the diaphragm connecting all the ports. In the cylinder below the upper head, there are upper and lower pistons which are forced apart to define a fluid receiving chamber. The fluid receiving chamber is enlarged on the introduction of fluid above a certain pressure thereby raising half of the piston rods bearing against the diaphragm and reduction of fluid pressure in the chamber lowers those push rods and raises an alternate set of push rods to accomplish diaphragm switching by deformation of the resilient material defining the diaphragm.

Description:
BACKGROUND OF THE DISCLOSURE 
     This disclosure sets forth an improved diaphragm valve. It is a valve which controllably switches a set of multiple ports. Indeed, it can operate with any number of ports, and the typical preferred number is 6, 8, 10 or 12 ports. Examples using many ports will be illustrated further. In operation, it is a valve which switches between two positions where operation changes two sets of ports in timed operation. 
     The valve is constructed with an upper cylinder head, a central cylinder body, and a lower cylinder head. The upper and lower heads are joined to the cylinder body by threaded members which are aligned by threading into a common tapped opening through the cylinder body. This aligns the upper and lower heads with the same or common axis, and it also aligns both heads so that they can be pulled together with independent control of tensioning of the two heads. Pressure responsive pistons are located so that fluid introduced under pressure operates the device. In the preferred version, there are two pistons which are responsive to pressure, the two pistons moving so that the ports are collectively opened and switched dependent on the application of pressure. In that sense, the valve is a binary control device. 
     The valve uses a diaphragm located at one face of the cylinder and upper head, and is switched so that a flow path adjacent to the diaphragm is controlled. The diaphragm is circular with a bead defining a circular flow path when assembled between the head and cylinder. This bead is clamped shut at selected locations by a number of push rods. In this embodiment, the push rods bear against the diaphragm and upper head from the cylinder. Preferably, the push rods are formed of a compressible resilient material so that precise manufacturing of the push rods is not required, thereby accommodating variations in push rod length. Moreover, the push rods bear against the diaphragm so that the diaphragm is compressed ever so slightly to provide the appropriate flow control. Leakage along the face of the diaphragm is prevented by applying an adequate and sufficient sealing force between the upper head and cylinder. This clamps the diaphragm in place and forms a peripheral seal around the diaphragm. It forms a facial seal in the region of the bead also. The bead formed in the diaphragm is confined so that the push rods bear against the diaphragm from the bottom side, thereby closing the bead and switching the fluid path for the ports in the valve. 
     In the preferred embodiment, the device is manufactured with N ports where N is a whole number, even integer. The push rods are divided into two sets and are alternated so that there are N push rods and they are spaced approximately between the two ports nearer to each push rod. This enables them to close the diaphragm flow path as will be defined. Moreover, this enables the push rods to bear against the bottom side of the diaphragm in a timed fashion so that first one set and then a second set of push rods is operated. The push rods are alternated so that proper valving action can be obtained. This involves operating alternate push rods with one piston and the remaining set of push rods with the other piston. More will be noted regarding the push rod operation so that the ports are switched under push rod control. 
     When no pressure is applied to the diaphragm valve, half of the push rods are forced upwardly against the diaphragm. This movement is accomplished by a bias spring. The bias spring is overcome by the application of fluid pressure. This pressure forces a pair of pistons apart, and reverses the state of the push rods so that half the push rods are retracted and the other half are extended. This accomplishes valves switching. As will be understood, push rod travel is relatively short, typically in the range of perhaps 0.002 to about 0.006 inches. Since this range of travel is quite short, the push rods provide sharp movement so that the switching interval is very brief. As one set of rods is retracted, the other is extended against the diaphragm. 
     One advantage of the present apparatus is the incorporation of a single tension point. A threaded bolt is positioned in each head and the bolts are aligned centrally of the cylinder. This is easier to assemble. It does not pose the problem of applying controlled torque to a set of head bolts around the structure. This assures uniform pressure applied around the periphery of the diaphragm and on the face of the diaphragm so that proper sealing is accomplished. Moreover, sealing to close the gap between the head and cylinder is accomplished uniformly when a single centralized bolt is tightened. This mode of assembly is highly desirable and provides the requisite tension for the clamping action on assembly. The device is also adjustable with regard to operating pressure. By utilization of different springs, the operation pressure can be changed. The system typically operates with a control pressure which is quite low such as 5 or 10 psi and a second pressure which is relatively high such as 1000 psi. Again, the gap between the two pressures can be modified, and the maximum pressure can be changed so that switching occurs at some different pressure. 
     Summarizing the present disclosure, it is a diaphragm valve which is assembled with a housing having a central cylindrical body with upper and lower heads attached to it. The body is axially drilled with a threaded passage, and each head is attached by means of a single bolt. The bolts are cut to a length so that they do not jam in the threaded passage. There is sufficient space left between the two bolts to enable threading together with controlled tension in each bolt. The diaphragm is clamped between the upper head and cylinder. In the preferred version, the diaphragm is formed of resilient material and has a shaped bead in it which encircles the ports in the upper head. The bead defines a flow path which connects all the ports on a common header until the spaces between ports are closed by raising a set of push rods. Since the device includes N ports, it also uses N push rods where the push rods are divided into two sets, the two sets of push rods being alternately deployed and alternately operated by a pair of pistons enclosed within the cylinder. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     So that the manner in which the above recited features, advantages and objects of the present invention are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings. 
     It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
     FIG. 1 is a plan view of the diaphragm valve of the present disclosure showing a set of ports in the upper head; 
     FIG. 2 is a sectional view taken along the line  2 — 2  of FIG. 1 showing internal details of construction and further illustrating a single bolt for assembling the upper head and also a single bolt for the lower head to the cylindrical body; and 
     FIG. 3 is a sectional view along the line  3 — 3  of FIG.  1  and at right angles with the sectional view of FIG. 2 which shows a set of push rods operated by a pair of moveable pistons within said cylinder and wherein the push rods are forced upwardly against the diaphragm to control fluid flow between the ports of the valve. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Attention is now directed to FIG. 1 of the drawing, where the numeral  10  identifies the diaphragm valve  10  of the present disclosure. It is constructed with a set of N spaced ports  12  which are deployed in a circle and which are evenly spaced. The ports  12  are formed in the upper head  14 . This head is shown also in FIGS. 2 and 3 as being at the upper end of the structure. The various ports  12  are provided with internally threaded openings  16  to enable easy connection with a set of fluid flow lines. The ports  12  communicate to the bottom face of the head  14  and are constructed with an internal profile as shown in FIG. 2 which enables the device to make threaded connection with suitable fittings. The device is best used in switching small quantities as for example in a control system or alternately in the equipment associated with a HPLC column. Moreover, the ports  16  are threaded so they connect with industry standard Sittings which are mounted on the ends of tubing, the preferred tubing sizes being typically about ¼ or ⅛ inch tubing. 
     Going back to FIG. 1, the head  14  is axially constructed with a central opening which is countersunk to receive the head of a head bolt  20 . The bolt  20  is formed with an opening conforming with all Allen wrench for tightening or fastening. Assembly and disassembly is achieved through the use of a single size Allen wrench as will be clear on describing the lower head and its fastener also. 
     In FIG. 2 of the drawings, the head  14  is constructed with at lower planar face  18  which abuts against the top and conforming planar face  22  of the cylindrical body  24 . The body  24  has all external profile which is a cylinder. It is provided with a planar upper face to thereby enable the two members to abut snugly and thereby capture a sheet diaphragm member  25 . The diaphragm  25  is relatively thin, typically having a thickness in the range of about 2 to 4 mils, and is constructed with a bead in it. The bead is a circular bulge which has a depth of a few mils, al typical depth being about 0.008″ or smaller. The bead has the shape of a centralized, circular flow path which communicates with every port  12 . Each port  12  terminates in a pilot passage  26  which is directed to the bead. The N ports are provided with a pilot passage  26  and all of them are connected in common to the bead so that they communicate together absent the control mechanism which will be described. The bead is a permanent deformation which is formed in the diaphragm  25 . There is a conforming bead in the upper face  22  to receive the diaphragm head on the face of the valve body. The body  24  is thus constructed with a similar bead forming a circle on the exposed upper face. The depth of the bead in the upper face  22  defines the cross-sectional area of the bead so that a flow path of specified cross-sectional area is obtained. 
     The body  24  has a lower face  28  which abuts against the lower head  30 . The head  30  is constructed with a large central passage in it and a suitable shoulder is formed so that it can receive the head of a fastener  32  which again is provided with a central opening suitable for the same size Allen wrench. Through the use of one Allen wrench the bolts  20  and  32  can be tightened or loosened. Both bolts  20  and  32  are provided with threads of a common pitch and construction so that they both thread to the threaded passage  34  in the cylinder body  24 . This passage is centralized and is tapped with threads to receive the two bolts. The two bolts are shortened so that the two bolts can thread into the common passage, one from the top and the other from the bottom. As illustrated, a few threads remain between the ends of the two bolts. This is done to assure that the bolts do not bottom out against the other. They are shortened so that the two bolts thread without bumping and without limiting the necessary range of travel of the two bolts. The bolts are tightened to a desired torque, thereby providing a clamping action of the upper and lower heads on the cylinder  24 . This avoids the problems of tightening excessively on one side of the cylinder. For instance, if three or four head bolts are spaced on a flange around the respective heads, care must be taken to equalize the tightening torque. Care must be taken to assure that the clamping action achieved by the several bolts is evenly applied around the periphery of the diaphragm. Alignment problems are avoided through the use of the centralized single fasteners for the respective upper and lower heads. 
     The body  24  contains a fluid pressure responsive system. Access to it is achieved through a port  40 . Again, this enables connection with industry standard fittings to deliver fluid under pressure. The port  40  in turn connects with a passage  42 . This opens into an area  44  which will be described as the chamber. The chamber is between upper and lower seal rings. The seals  46  are identical and differ only in location. They function as seal rings to define or limit the chamber  44 . The chamber itself is defined by a lower movable piston  48  and a movable upper piston  50 . The pistons  48  and  50  are forced apart upon introduction of an adequate pressure level into the chamber  44 . The chamber  44  is defined on the exterior of a seal ring  52  which is cooperatively clamped between the two pistons. As illustrated, the piston  50  has a larger central opening. It fits on the outside of the seal  52 . The piston  48  supports an upstanding smaller skirt  54  which extends centrally on the interior of the piston  50 . It serves to align both pistons for concentric cooperation and also is a centralizer which surrounds the lower fastener  32 . In this region, the fastener  32  serves in the fashion of a guide post. It assures movement vertically in response to pressure introduced into the chamber  44 . 
     The pistons  48  and  50  are movably mounted with respect to the fastener  32 . The lower head  30  is constructed with an enlarged passage so that a stack of Bellville washers  56  can be positioned in that area. The washers force the lower piston  48  upwardly. The lower piston moves fully upwardly to the limits of travel, jamming against the shoulder  58  which serves as a receptacle for the pair of pistons. This makes assembly much easier. Indeed, the pistons are located in the cylinder  24  and the bolt  32  is then passed through the two pistons for assembly. On tighteninng, the Bellville washers  56  provide the requisite force which is maintained even though no pressure is applied to the chamber  44  between the two pistons. 
     FIG. 3 shows a first push rod  60  extending completely through the body  24  to the diaphragm. A second push rod  62  is also incorporated. While they are structurally identical, they are operated in different manners. Explaining the push rod  60  first, it will be observed in FIG. 3 that it bears against the top face of the piston  50 . The piston  50  is constructed so that it has an internal lip or face bearing against the push rod. The top face  64  extends radially inwardly to be located under the push rod  60 . The piston  50  is forced downwardly by a bias spring  66 . Upward movement of the piston requires overcoming the bias spring. The bias spring  66  moves the piston  50  downwardly to close the chamber  44  when there is no pressure in the chamber  44 . The upper face  64  of the upper piston  50  therefore contacts against the bias spring  66  and also against the push rod  60 . By contrast, the push rod  62  bears against a smaller shoulder  70  which is on the central skirt  54  of the lower piston  48 . The skirt  54  is cylindrical and concentric about the fasteners  20  and  32 . The skirt, however, is notched so that it provides clearance to the push rod  60 . Alternating notches  54 ′ and  50 ′ are deployed around the skirt  54  and the upper face of the piston  50 , respectively. The high surface or face  70  is shown on the left side of FIG.  3  and contacts against the push rod  62 . The push rod  62  is therefore responsive to the position of the lower piston  48 . As illustrated in the drawings, the Bellville washers  56  move the two pistons upwardly together but the motion of the two pistons is transferred from that spring to the push rods  62 . In other words when the piston  48  moves upwardly to its limits of travel, it still does not contact the push rod  60  to force it upwardly. Clearance is left where the skirt  54  is notched in that area. 
     Expanding in some detail on the difference between the push rods  60  and  62 , the push rod  60  moves upwardly only when fluid under pressure is introduced into the chamber  44  and the pressure is sufficient to overcome bias of the spring  66 . In the preferred embodiment, there are typically two or three bias springs. As will be understood, the two sectional views of FIGS. 2 and 3 are taken at right angles so that different components are shown in the different drawings. The springs  66  are replicated at two or three locations. This provides, more or less, an even force applied across the face of the piston  50 . On upward motion of the piston, the springs  66  are compressed and the piston  50  thereby applies a compressive force axially of the push rods  60 . This operates this push rod  60 , it being recalled that alternate push rods are operated by one piston and the remaining and alternating push rods are operated by the other piston. Therefore, the push rod  60  operates out of phase with the push rod  62 . The push rods  60  are closed when the piston  50  is raised in response to hydraulic pressure. 
     In the absence of hydraulic pressure, the chamber  44  is reduced to a minimum capacity. The lower piston  48 , however, is forced upwardly by the bias of the Bellville washers  56 . They force the piston  48  upwardly. This, in turn, prompts the piston  48  to apply a compressive force to the piston rod  62 , thereby closing that piston rod against the diaphragm. 
     The piston rods  60  and  62  are preferably formed of a resilient and deformable plastic material. They are preferably formed to the same length and diameter. Manufacturing tolerances are accommodated by using a somewhat compressible material. Preferably, a relatively hard plastic material is used. It is not necessary to use a rigid material. Indeed, if the rods  60  and  62  were formed of a ferrous metal, there would be severe tolerance requirements on the manufacturer of the two push rods to assure that they were equal in length. This would otherwise cause irregularities in the application of force against the diaphragm and might damage the diaphragm should one rod be longer, and might permit leakage if one were shorter. Extreme manufacturing tolerances are thereby avoided through this approach. In other words, the push rods  60  and  62  are not rigid and are compressible, thereby tolerating differences in compression and length. 
     The two sets of push rods are preferably constructed with larger upper and lower faces, and a somewhat more narrow central portion. The narrow central portion defines a region at which compressive forces find some relief by expanding radially outwardly during compression. If need be, substantial amounts of deformation from compression can be tolerated. It is desirable that the upper ends have a relatively large footprint. For that reason, the push rods  60  and  62  are constructed to the maximum diameter accommodated by the drilled passages in the head for the two sets of push rods. This enables the push rods to deform at central portions thereof, thereby accommodating any manufacturing differences, and also applying adequate forces to the diaphragm  25 . Recall that the diaphragm is constructed with a circular bead. The bead  72  is shown in FIG. 3 of the drawings and protrudes downwardly toward the push rods  60  and  62 . When the rods move downwardly, the bead opens, thereby opening the diaphragm passages between adjacent ports. If, for instance, the plush rod  60  is located between ports  3  and  4 , when it moves upwardly, closure is accomplished between those two ports. When it moves downwardly, the space vacated by the push rod permits the bead to open, thereby reopening the fluid pathway. Moreover, the two rods are deployed in alternating fashion as previously mentioned so that different port connections are achieved. With one set of rods up and the other down, connections are made between ports  1  and  2  and also ports  3  and  4 . When the other set of rods is raised and the first set is lowered, the connection then goes between ports  2  and  3 . Flow between ports  1  and  2  is blocked and flow between ports  3  and  4  is also blocked. This extends all the way around the circle for all the ports  12 . 
     As will be shown in the contrast between the push rods  60  and  62 , they operate in alternating timed sequences and are installed so that the range of travel and compression are equal. This enables construction of the push rods  60  and  62  with equal length. They are deployed in passages which are equal. They are operated in alternating fashion by the pistons  48  and  50 . If N is  12 , then one piston will lift six push rods and the other will lift six. As will be understood, each moves one-half of the push rods. 
     So that proper control of the valving action is correlated with the increase and decrease in pressure in the chamber  44 , it is desirable that the pistons  48  and  50  be assembled at a specified rotational position. While the piston  50  is uniform across its top face, the piston  48  is not because there are notches on it which must be aligned with one-half of the push rods, i.e., the push rods  60  shown at the right side of FIG.  3 . To achieve this at the time of assembly, it is desirable that the lower piston  48  at least be aligned at a specific angle. It is not possible to run a single guide pin through both pistons because it would serve as a leakage path. Therefore, a guide pin  74  anchors the upper piston against rotation. In turn, a second guide pin  76  anchors the lower piston  48  against rotation with respect to the upper piston  50 . The two guide pins together assure proper alignment of the components at the time of assembly. As will be further understood, the guide pin  74  also aligns the upper head  14 . This assures that the ports  12  with their connected pilot passages  26  terminate at proper locations with respect to the push rods. So to speak, the push rods operate best on locating the push rods evenly between the respective ports  12  as viewed in FIG. 1 of the drawings. Each push rod is constructed and arranged so that the width of the push rod is greater than the width of the bead  72  in the diaphragm and yet is smaller than the spacing between adjacent pilot passages  26 . This prevents a push rod from closing a pilot passage by blinding the outlet of the pilot passage  26 . 
     In operation, the diaphragm valve of the present disclosure is installed in a system with any number of leads connected to the ports. If not needed, the ports can be simply plugged by placing a plug in the threaded fittings  16 . A force is selected for the Bellville spring  56  and that size of spring is installed. Typically, the springs  66  do not need to be varied because all that is required of the bias springs is to move the piston away when there is no pressure applied to the system. After Fluid is applied to the system, torque is applied to the fastener  20  which is tightened until leakage is stopped around the diaphragm. This has a most notable benefit. Only one bolt need be tightened; it is not necessary to try to balance a set of head bolts arranged in a circle on a flange. Rather, the device can be assembled rather loosely and tightening continued until leakage around the diaphragm is stopped. In that sense, the diaphragm serves both as a switching element and also as a seal member. Indeed, the bead  72  may typically have a width of only about 0.004 to about 0.0008. With this installation, the diaphragm is clamped on a skirt area (beyond the bead  72 ) of substantial width, typically more than enough to seal against leakage. Indeed, pressures can be switched at 5,000 psi with only modest tightening on the fastener  20  utilizing a valve body of about 2 inches in diameter. Once the tension on the bolt  20  is assured to prevent leakage around the edge of the diaphragm, then a seal is adequate when the leakage is stopped. 
     A pressure is selected for the chamber  44  which overcomes the Bellville washers  56 . A force is created by the washers  56  which is exceeded by the force defined by the pressure in the chamber  44  and the cross-sectional area between the largest seal rings  46  and the smaller seal ring  52 . When that force is achieved by introducing fluid under pressure to the chamber  44  in excess of that pressure, the lower piston  48  is moved downwardly while the upper piston  50  is moved upwardly. When they separate, the chamber  44  is at its maximum capacity. When that pressure is achieved, switching occurs. Switching occurs because both pistons move simultaneously to open the chamber  44 . By contrast, when the pressure is dropped, the chamber  44  is reduced substantially to no volume as the pistons are brought to the closed position. That accomplishes switching in the opposite direction. 
     An important aspect of the present equipment is the compression of the push rods  60  and  62 . Not only do they provide closure, they do not tilt or cant the upper head  14  by applying uneven forces as would occur with steel push rods. Rather, when they operate, they do not cant the head  14  because they are compressible, being formed of a deformable plastic. Preferably, deformation is limited to the elastic range of the material so it is able to be restored to its unloaded shape. 
     While the foregoing is directed to the preferred embodiment of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims which follow.