Agitating – Having specified feed means – Pump forces material through restriction
Reexamination Certificate
1999-07-09
2001-06-12
Soohoo, Tony G. (Department: 1723)
Agitating
Having specified feed means
Pump forces material through restriction
C128S098100, C137S625300, C251S063600
Reexamination Certificate
active
06244739
ABSTRACT:
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 '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.
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Leslie W. Phipps; “Effects of main flow reversal in a simple homogenizing valve”; Journal of Dairy Research; pp 525-528; Mar. 1978.
Jarchau Michael
Korstvedt Harald O.
Potter Blaine
APV North America Inc.
Hamilton Brook Smith & Reynolds P.C.
Soohoo Tony G.
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