Abstract:
A homogenization valve includes a housing and stacked valve members within the housing. The valve members have central holes therethrough defining a high pressure volume. Each valve member includes a valve seat defining, with a valve surface, gaps through which fluid is expressed radially from an inside high pressure volume to the low pressure volume. The actuator acts on the valve members to control the width of the gaps. The valve member includes circumferentially spaced, compressible spacing elements to maintain the gap. The actuator controls substantially all of the gap widths by compressing the spacing elements. Annular springs are positioned within the high pressure volume in spring-grooves in the valve members to align adjoining pairs of valve members to maintain the stacked member configuration.

Description:
RELATED APPLICATIONS 
     The present application is related to U.S. application Ser. No. 09/351,043 entitled “FORCE ABSORBING HOMOGENIZATION VALVE” by Michael Jarchau and Ser. No. 09/350,503 entitled “HOMOGENIZATION VALVE WITH OUTSIDE HIGH PRESSURE VOLUME” by Michael Jarchau, both applications being filed concurrently with the present application and incorporated herein in their entirety by this reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Homogenization is the process of breaking down and blending components within a fluid. One familiar example is milk homogenization in which milk fat globules are broken-up and distributed into the bulk of the milk. Homogenization is also used to process other emulsions such as silicone oil and process dispersions such as pigments, antacids, and some paper coatings. 
     The most common device for performing homogenization is a homogenization valve. The emulsion or dispersion is introduced under high pressure into the valve, which functions as a flow restrictor to generate intense turbulence. The high pressure fluid is forced out through a usually narrow valve gap into a lower pressure environment. 
     Homogenization occurs in the region surrounding the valve gap. The fluid undergoes rapid acceleration coupled with extreme drops in pressure. Theories have suggested that both turbulence and cavitation in this region are the mechanisms that facilitate the homogenization. 
     Early homogenization valves had a single valve plate that was thrust against a valve seat by some, typically mechanical or hydraulic, actuating system. Milk, for example, was expressed through an annular aperture or valve slit between the valve and the valve seat. 
     While offering the advantage of a relatively simple construction, the early valves could not efficiently handle high milk flow rates. Homogenization occurs most efficiently with comparatively small valve gaps, which limits the milk flow rate for a given pressure. Thus, higher flow rates could only be achieved by increasing the diameter or size of a single homogenizing valve. 
     Newer homogenization valve designs have been more successful at accommodating high flow rates while maintaining near optimal valve gaps. Some of the best examples of these designs are disclosed in U.S. Pat. Nos. 4,352,573 and 4,383,769 to William D. Pandolfe and assigned to the instant assignee, the teachings of these patents being incorporated herein in their entirety by this reference. Multiple annular valve members are stacked one on top of the other. The central holes of the stacked members define a common, high pressure, chamber. Annular grooves are formed on the top and/or bottom surfaces of each valve member, concentric with the central hole. The grooves are in fluid communication with each other via axially directed circular ports that extend through the members, and together the grooves and ports define a second, low pressure, chamber. In each valve member, the wall between the central hole and the grooves is chamfered to provide knife edges. Each knife edge forms a valve seat spaced a small distance from an opposed valve surface on the adjacent valve member. In this design, higher flow rates are accommodated simply by adding more valve members to the stack. 
     SUMMARY OF THE INVENTION 
     Prior art systems have suffered from at least two deficiencies. First, maintaining an optimized distance between substantially all of the valve gaps has not been achieved. For example, as disclosed in the &#39;769 patent, in situations where the valve surface and valve seat wear down due to extended use, the actuator flexes the top valve members to close only a desired number of valve gaps to maintain the pressure differential so that the fluid is properly homogenized. It would be preferable to adjust substantially all of the valve gaps to maintain a predetermined separational distance between the valve seat and valve surface. 
     Second, prior art valves have been prone to noise emissions. It has been found that the noise is attributable, at least in part, to the environment into which the homogenized fluid is expressed. More particularly, the prior valves have expressed the fluid into a relatively closed environment between the valve members. This has been found to cause chattering of the valve members which can damage the valve members, emit noise, and produce other deleterious effects in the operation of the valve. 
     In accordance with one aspect of the invention, a valve member for a stacked valve member homogenizing valve includes a valve seat to define a gap with an opposed valve surface. Fluid is expressed through the gap from a high pressure volume to a low pressure volume. A plurality of gaps are formed between the valve members when stacked on one another. Spacing elements between the valve members are compressed by an actuator to control the width of the gaps. The valve members preferably include circumferentially spaced, compressible spacing elements to maintain the gaps. A housing surrounds the stacked valve members. Preferably, the actuator controls substantially all of the gap widths by compressing the spacing elements. 
     The preferred valve member includes opposite faces. The first face includes the valve seat while the second face includes the valve surface to define respective valve gaps when valve members are stacked on one another. 
     In accordance with other aspects of the present invention, the spacing elements are integral to the valve member and are formed by removing portions of the valve member. Each valve member can include four spacing elements. The spacing elements can be formed from a first material such as stainless steel and the valve seats and valve surfaces can be formed from a second material such as tungsten-carbide. This configuration minimizes wear of the valve seat and surface while allowing compression of the spacing elements to maintain the valve gaps. 
     In accordance with yet another aspect of the present invention, annular springs are positioned within spring-grooves in the valve members to align adjoining pairs of valve members to maintain the stacked member configuration. Preferably, the springs are positioned in the high pressure volume. The ends of the springs can be bent and positioned in notches of adjacent valve members to maintain angular alignment of the valve members. 
     The above and other features of the invention including various novel details of construction and combinations of parts, and other advantages, will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular method and device embodying the invention are shown by way of illustration and not as a limitation of the invention. The principles and features of this invention may be employed in various and numerous embodiments without departing from the scope of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the accompanying drawings, reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale; emphasis has instead been placed upon illustrating the principles of the invention. Of the drawings: 
     FIG. 1 is a cross sectional view of a homogenization valve illustrating prior art valve members on the left side of longitudinal axis A—A and inventive valve members in accordance with the present invention on the right side of the longitudinal axis A—A; 
     FIG. 2 is a cross sectional isometric view of the prior art valve members shown in FIG. 1; 
     FIG. 3 is a cross sectional isometric view of the preferred valve members of the present invention also shown in FIG. 1; 
     FIG. 4 is a plan view of an exemplary valve member with spacer pads in accordance with the present invention; 
     FIG. 5 is a cross sectional view taken along line  5 — 5  of FIG. 4; 
     FIG. 6 is a cross sectional view taken along line  6 — 6  of FIG. 4; 
     FIG. 7 is an enlarged view of the encircled area referenced as “A” of FIG. 6; and 
     FIG. 8 is a cross sectional view of an alternative valve member. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 is a cross sectional view of a primary valve assembly  2  for use in a homogenizing system (complete system not shown). The previous design of valve members is shown on the left side of longitudinal axis A—A while the inventive valve members of the present invention are illustrated on the right side. 
     The prior art valve includes valve members  4  constructed according to the principles disclosed in the &#39;769 patent, many of the details of these members being better understood with reference to FIG.  2 . 
     With reference to both FIGS. 1 and 2, an inlet port  6 , formed in an inlet flange  8 , conveys a high pressure fluid to a valve member stack  10 . The high pressure fluid is introduced into an inner chamber  12  defined by the central holes  14  formed through the generally annular valve members  4 . The high pressure fluid is then expressed through valve gaps  16  into a low pressure chamber  18  that is defined by the axial ports  20  through the valve members  4  and the annular grooves  22  in the valve members  4 . The fluid passing into the low pressure chamber  18  enters a discharge port  24  in a discharge flange assembly  25 . 
     The stack  10  of valve members  4  is sealed against the inlet flange  8  via a base valve member  26  using o-ring  30 . The base valve member  26  is sealed against the housing  28  via o-ring  31 . This base valve member  26  is costly to manufacture because of its complex shape. The top-most valve member  4  engages a top valve plug  32  that seals across the inner chamber  12 . An o-ring  33  provides a fluid seal between the top-most valve member  4  and the top valve plug  32 . This top valve plug  32  is hydraulically or pneumatically urged by actuator assembly  34 , which comprises an actuator body  36  surrounding an actuator piston  38  sealed via an o-ring  40  and a backup o-ring  42 . A vent plug  39  is provided in the actuator body  36  to bleed air from the cavity  48 . 
     The piston  38  is connected to the top plug  32  via an actuator rod  44 . An actuator guide plate  46  sits between the actuator body  36  and the discharge flange assembly  25 . A rod seal  45  provides a fluid seal between the actuator rod  44  and the discharge flange assembly  25 . By varying the pressure of a hydraulic fluid or pneumatically in cavity  48  through a fluid port (not shown), the size of the valve gaps  16  may be modulated by inducing the axial flexing of the valve members  4 . For example, as disclosed in the &#39;769 patent, the downward force flexes the top valve members to close the desired number of valve gaps to adjust the pressure differential. This design has not been able to modulate substantially all of the gaps, which is desirable for optimal performance of the valve. 
     The base valve member  26  and other valve members  4  are aligned with respect to each other and maintained in the stack formation by serpentine valve springs  50  that are confined within cooperating spring-grooves  52 ,  54  formed in the otherwise flat peripheral rim surfaces of each valve member  4 . 
     The inventive valve members  56  of the present invention also form a stack of valve members  58  as illustrated on the right side of the valve of FIG.  1  and FIG.  3 . Generally, as will be described below, the valve members  58  provide improved efficiency and reduced chattering of the stack due to the layout of the valve members. Beneficially, these valve members  58  are configured to be retrofitted within existing assemblies  2 . 
     As illustrated, the valve gaps  60  and valve springs  62  are provided between each valve member pair. The gaps  60  provided between each valve member pair form a restricted passageway through which the emulsion or dispersion is expressed to the low pressure chamber  65 . The gaps  60  can be formed as illustrated in FIG. 3 of the &#39;769 patent. Preferably, the gaps  60  are formed as disclosed in commonly assigned U.S. Pat. No. 5,749,650, filed Mar. 13, 1997, and U.S. Pat. No. 5,899,564 filed May 11, 1998, the contents of both patents being incorporated herein in their entirety by this reference. 
     More specifically, the height of the gap  60  is preferably between 0.0013 and 0.0018 inches, usually about 0.0015 inches, but in any event less than 0.003 inches. This dimension is defined as the vertical distance between the valve seat or land and the opposed, largely flat, valve surface on opposite faces of the valve member. Experimentation has shown that the gap should not be simply increased beyond 0.003 inches to obtain higher flow rates since such increases will lead to lower homogenization efficiencies. 
     In the preferred embodiment, the valve seat is a knife-edge configuration. With reference to FIGS. 5-7, on the upstream, high pressure side of the gap, the valve seat or land  64  is chamfered at 60° angle sloping toward the valve surface  66 . In the gap, the valve seat  64  is flat across a distance of ideally approximately 0.015 to 0.020 inches, but less than 0.06 inches. On the downstream, low pressure side of the gap  60 , the valve seat  64  slopes away from the valve surface  66  at an angle from 5 to 90° or greater, approximately 60° in the illustrated embodiment. The valve surface  66  is similarly constructed. The downstream terminations of valve surfaces overlap valve seats or lands by no more than 0.025 inches. Preferably, the downstream terminations of the valve surfaces  66  overlap the valve seats  64  by at least a height of the valve gaps  60 . It has also been found that no overlap between the valve seats  64  and valve surfaces  66  can be effective as well. 
     It is significant that the valve springs  62  are positioned upstream from the valve gaps  60 , i.e., on the high pressure side of the valve gaps. Prior art designs have expressed the fluid into a closed environment between the valve members. In the present invention, however, the high pressure fluid passes through the spring region before being expressed through the valve gaps  60 . Accordingly, the turbulent expressed fluid is in the open chamber  64  and not over the springs, an arrangement which has been found to reduce chatter of the valve members  56 . Chattering of the valve members  56  is undesirable as such can damage the valve members, emit noise, and produce other deleterious effects in the operation of the valve  2 . 
     It should also be noted that the distance from the center of the high pressure chamber  12  to the valve gaps  16 ,  60  is substantially the same such that the prior art valve members  4  can be replaced by the inventive valve members  56  without any or only minor adjustment to the actuator pressure required to adjust the valve gaps. 
     The inventive valve members  56  include spacing elements or pads which allow the valve members to be compressed by the actuator  34  such that substantially all the valve gaps  60  are adjusted to compensate for wear. This has the advantage of maintaining a separational distance (and often optimized) between the valve seat and valve surface for a preferred pressure despite wear which tends to widen the gaps. 
     FIGS. 3-6 illustrate exemplary spacer pads  68  that form part of valve member  56 . Area  70  is machined off leaving the spacer pads  68 . Valve members  56  are stacked on one another with spacer pads  68  of one valve member contacting the underside  72  of a contiguous valve member to form the valve gaps  60  between the valve seat  64  and opposing valve surface  66 . Alternatively, spacers pads  68  can be a separate element coupled to or positioned adjacent the valve members  56 . The spacer pads  68  are small enough such that they can be compressed by the actuator  34 . In a preferred embodiment of the present invention, each spacer pad  68  has a surface area of approximately 11 mm 2  that touches the underside  72  of a contiguous valve member  56  when assembled. This allows each spacer pad  68  to be compressed up to about 0.002 inches (0.0508 mm). 
     In alternative embodiments, the spacer element can comprise a continuous, relatively thin, annular lip which is compressed to compensate for wear of the valve surfaces and seats. 
     The valve springs  62  help align the stack formation as before. Additionally, the valve spring  62  ends can be bent, for example, 90 degrees, and inserted into machined notches or pockets  74  (see FIGS. 3,  4  and  6 ) in adjacent valve members such that the stack of valve members maintains preferable angular alignment. Such a configuration prevents rotation of the valve members  56  relative to one another. That is to say, the spacer pads  68  are aligned in vertical rows when preferably aligned. 
     Returning to FIG. 1, the base valve member  76  is an improvement over the prior art base valve member  26 . More particularly, the member  76  is similar to the other valve members  56  except that there is no machining on the bottom surface. Thus, an expensive part to machine is beneficially avoided. A valve guide  78  sealed against the housing  28  via o-ring  30  and against the base valve member  76  via gasket  80  is provided to center the base valve member and hence the stack  58  of valve members. Preferably, the valve guide  78  is formed from a less expensive material, such as stainless steel, thereby saving material cost over the prior art base valve member  26 . 
     FIG. 8 illustrates an alternative embodiment of the valve member, designated by reference numeral  56 ′. This valve member  56 ′ illustrates the spacer pads  68  adjacent the high pressure volume  12  and the valve seat  64  and valve surface  66  adjacent the low pressure volume  65 . The valve member  56 ′ is formed from at least two materials: a hard, durable material forming the valve seat and surface to minimize wear thereof and a relatively soft, compressible material forming the spacer pads to allow compression without cracking thereof. Preferably, an inner ring  82  of a relatively soft material, such as stainless steel, is inserted into an outer ring  84  of a harder, more durable material, such as tungsten-carbide. In a preferred embodiment, the hard material has a Rockwell A-scale hardness number of greater than 90 and the compressible material has a Rockwell A-scale hardness number of not greater than 80. The rings  82 ,  84  are maintained in position by an interference fit or other suitable methods, such as welding. 
     It will be understood that the inventive concepts discussed supra can be applied to other homogenizing valve configurations, such as disclosed in U.S. application Ser. No. 09/350,503 entitled “HOMOGENIZATION VALVE WITH OUTSIDE HIGH PRESSURE VOLUME”. More particularly, fluid can be expressed from an outside high pressure volume outside the stacked valve members to a low pressure volume inside the valve members. In that case, preferably the springs are configured to be within the high pressure volume and the spacing elements are adjacent the low pressure volume. 
     While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.