US3557827A

US3557827A - Pressure vessel for water conditioner assembly

Info

Publication number: US3557827A
Application number: US679304A
Authority: US
Inventors: Robert E Marsh
Original assignee: Robert E Marsh
Current assignee: PLASWORLD Inc A CORP OF WISCONSIN
Priority date: 1967-10-31
Filing date: 1967-10-31
Publication date: 1971-01-26
Anticipated expiration: 1988-01-26
Also published as: GB1254868A; GB1254869A

Abstract

A lightweight filament-wound pressure vessel. The vessel includes a central cylindrical shell and a pair of end caps adapted to fit into the opposite ends of the shell. The central shell and cylindrical skirts of the end caps form a smooth external junction. The assembly is overwound with a fiberglass filament to provide the desired bursting strength of the vessel.

Description

United States Patent [72] Inventor Robert E. Marsh 1707 North Prospect 13A, Milwaukee, Wis. 53200 [21] Appl. No. 679,304

[22] Filed Oct. 31, 1967 [45] Patented Jan. 26, 1971 [54] PRESSURE VESSEL FOR WATER CONDITIONER ASSEMBLY 7 Claims, 8 Drawing Figs.

[52] US. Cl 137/590, 210/191, 210/288, 210/456; 220/3, 220/83: 259/18 [51] Int. Cl B01d 2"7/12, B65d 7/42 [50] Field of Search 137/590,

Primary Examiner- Henry T. Klinksiek Attorney Fowler, Knobbe & Martens ABSTRACT: A lightweight filament-wound pressure vessel. The vessel includes a central cylindrical shell and a pair of end caps adapted to fit into the opposite ends of the shell. The central shell and cylindrical skirts of the end caps form a smooth external junction. The assembly is overwound with a fiberglass filament to provide the desired bursting strength of the vessel.

[56] References Cited UNITED STATES PATENTS 3,246,794 4/1966 Marshall 220/3X PATENTED m6 l97| I v sum 1 [IF 3 PRESSURE VESSEL FOR WATER CONDITIONER ASSEMBLY BACKGROUND OF THE INVENTION This invention is directed to pressure vessels made from a lightweight material and adapted to be filament wound. More specifically, this invention is directed to a water conditioner tank having fluid directing vanes integrally mounted on the internal surfaces of the tank for directing fluid flow through the conditioning media therein.

There is a present need for a lightweight, pressure vessel, adapted to be filament wound, which can be molded in several parts, each of which is capable of being inspected for defects or reinforced prior to assembly and filament winding to withstand localized stresses in the assembled vessel. There is also a need for a lightweight pressure vessel which is resistant to corrosion and can be varied in length to accommodate any desired use of the vessel. Such a vessel must be easy to assemble in a fluidtight manner capable of withstanding service pressures and conditions without leakage or failure and must be formed from a liner having a smooth external surface to facilitate filament winding. Additionally, there is a need in the water conditioning field for such a vessel having adequate fluid directing members on the interior surfaces thereof for reducing channeling of the fluids passing through the water conditioning media with either the two-cycle or other multicy cle control valves.

SUMMARY OF INVENTION Basically, this invention comprises a pressure vessel formed from a cylindrical central wall, or shell, and a pair of end caps constructed of a lightweight resilient material. The cylindrical shell is open ended and the end caps are mounted in each end of the shell to form an elongated vessel. Each of the end caps includes a convex, domelike upper portion and a depending cylindrical skirt integrally connected to the upper portion and having substantially the same outer diameter as the central shell. The end caps are connected to the central shell by means which provide a substantially fluidtight seal between the end caps and the shell.

To effect the mounting of the end caps on the central shell, annular lands are connected to the cylindrical skirt of each of the end caps. Each of the annular lands has an outer diameter which is less than the outer diameter of the skirt so that a shoulder is formed at the junction between the land and the skirt. The radial dimension of the shoulder is substantially equal to the thickness of the central shell so that the lands fit snugly within the central shell and the outer surfaces of the skirt and the central shell form a smooth junction for filament overwinding. One of the caps may be provided with an opening for receiving a closure means for the vessel. A filament member may be tightly wound around about the end caps and the central shell to retain the end caps in the central shell and provide an integral, strong, pressure vessel.

The lands may be integrally connected to the end cap skirts or mounted on separate connector rings which are connected to the end caps in a fluidtight manner.

To provide a high strength pressure vessel which is able to withstand high bursting and compressive forces, it has been found that the length of the lands, i.e., the axial distance from the base of the shoulder to the opposite edge of the land should be at least three times the width of the contact between the sealing member and the central shell. Preferably, the sealing member is a resilient O-ring which fits into an annular groove on each land. The outer diameter of the O-ring, in the preferred embodiment, is slightly larger than the outer diameter of the land and the inner diameter of the central shell, so that the O-ring is compressed when the land is inserted within the central shell.

The pressure vessel of this invention is particularly adapted for use as a fluid conditioning tank of the type used for water softeners. These tanks normally contain a central conduit which runs from a flow valve at one end of the tank to a position at substantially the other end of the tank. The portion of the central shell of the tank surrounding the conduit generally contains a fluid conditioning media such as an ion exchange resin. With the pressure vessel of this invention, it is possible to modify the inner surfaces of the end caps or the central shell to provide fluid directing vanes or other structure within the vessel before it is completely assembled. For example, in one embodiment of this invention a plurality of bifurcated fluid directing vanes each having a pair of curved arms are mounted in the end cap nearest the outlet from the conduit so that fluid flowing into the conditioning tank is channeled into a preselected flow pattern which substantially reduces "channeling.

Clearly, with the multipiece assembly of this invention, it is possible to produce vessels of any desired length and to in clude various fluid flow directing structure on the interior surfaces of the vessel. At the same time, the arrangement of the resilient seals on annular lands each having a length three times the axial length of contact between the sealing member and the central shell and having a smooth surface for overwinding provides a lightweight, high strength, pressure vessel.

DESCRIPTION OF THE DRAWINGS The novel features and advantages of the pressure vessel of this invention will become more readily apparent from the appended claims and the detailed description when taken with the accompanying drawings wherein:

FIG. 1 is a side perspective view of the pressure vessel of this invention;

FIG. 2 is an exploded perspective view of one embodiment of the pressure vessel of this invention showing the end cap members and a central cylindrical portion;

FIG. 3 is a longitudinal sectional view of a filament wound pressure vessel of the embodiment shown in FIG. 2;

FIG. 4 is an enlarged sectional view of the pressure vessel end cap and central wall junction of FIG. 3 showing the filament winding on the outer surface thereof;

FIG. 5 is an enlarged plan view of the collector screen of this invention;

FIG. 6 is an enlarged plan view of the lower end cap as shown in FIG. 2;

FIG. 7 is a longitudinal sectional view of a water conditioner assembly using the pressure vessel of this invention; and

FIG. 8 is a longitudinal sectional view of another embodiment of the pressure vessel of this invention.

DETAILED DESCRIPTION OF THE DRAWINGS Referring now to the drawings, FIG. I shows the general construction of the assembled pressure vessel 10 of this invention prior to filament winding. The vessel generally comprises a pair of upper and lower end cap members 12 and I4 fluid tightly mounted on a central elongated cylindrical sidewall or shell 16.

Each of the end caps is of the same general external configuration. They each have a generally convex, dome-shaped end portion 20 integrally connected to a depending cylindrical skirt portion 22 (see FIG. 4). Each of the depending skirt portions 22 terminates in a reduced outer diameter annular land 24. The outer diameter of the land 24 is slightly less than the inner diameter of the shell 16. The junction between the upper portion of the skirt and the land forms a shoulder 26 which is of substantially the same radial length as the thickness of the central shell 16 so that when the end caps are mounted on the shell there is a substantially smooth transition on the external surface of the formed vessel from the end cap to the shell as shown in FIGS. 3 and 4. This provides a smooth surface for applying a filament winding 29 on the vessel.

Annular grooves 30 or other means are provided in each of the lands for receiving resilient sealing members such as the O-rings 32 shown in FIG. 2. The O-rings 32 are of a slightly greater outer diameter than the lands 24 so that when they are placed in the groove in the lands, the surfaces of the O-rings extend radially outwardly of the surface of the lands by few hundredths of an inch. The longitudinal extension of the lands 24 from the shoulders 26 to their opposite ends should be at least three times the width of the resilient sealing contact between the O-ring and the shell 16 and, preferably, is at least seven times the width of the sealing contact to provide a relatively rigid annular support surface for mounting the end caps in the shell 116. The land can be longer than seven times the width of the sealing member, if desired, so long as it provides a good support for attachment of the end caps to the central shell. It has been found that by maintaining the surface area of the land at least three times the area of sealing contact, the pressure vessels are able to withstand very high pressures on the order of 750 p.s.i. after filament winding.

With continued reference to FlG. 4, it can be seen that the lower end of the depending land 24 is internally tapered from a point axially corresponding to the groove 30 for mounting the sealing member, O-ring 32, on the land. This taper provides some flexibility to the lower end of the land for mounting the end caps in the cylindrical shell 16. The lands of both the upper and lower end caps are tapered as shown in FIG.

As best shown in FIG. 3, the upper end cap 12 is provided with an opening 38 which may be internally threaded for receiving a fluid control valve or fitting 40, diagrammatically shown in FIG. 7, or for receiving a pressure cap (not shown).

As shown in FIGS. 2 and 6, the lower end' cap 114 is integrally molded with four upstanding, bifurcated diffuser vanes 42 on its internal surface. The vanes 42 each are formed from two intersecting curved arms and have one end and their lower edge integral with the end cap. They are arranged symmetrically about the axis of the end cap 14 so that the arms extend radially outwardly, as shown in FIG. 6, to form four curved channels 44 extending from the center of the end cap radially outwardly and terminating substantially tangentially to the cylindrical inner periphery of the end cap. The channels 44 decrease in cross-sectional area (see FIG. 6) as they increase in distance from the center of the end cap and empty into four open-topped chambers 46 intermediate the channels. Due to the curvature of the vanes and the convex end wall, the chambers 46 are wider at their outer edges but deeper near the center of the end caps. The upper edges of the vanes 42, as best shown in FIG. 3. are coplanar. The lower edges may be integral with the end cap and each vane is provided with a small diameter through-orifice 48 near the lower edge of the intersection of its arms for connecting the respective chamber to the center of the end cap as shown in FIGS. 2, 3, and 6.

The lower end cap 14 is also provided with a flat annular internal shoulder 50 which is in substantially the same plane as that of the upper edges of the vanes, as best shown in FIG. 2, for mounting a collector screen 52. The shoulder 50 may be machined or molded into the lower end cap. The lower end cap may also be provided externally with an axially extending solid annular overwinding mount 55 as best shown in FIG. 3.

The collector screen 52, as shown in FIGS. 2, 3, and 5, comprises a centrally apertured disc having a downwardly extending annular flange or lip 54 about the central aperture. The collector screen 52 is further provided with concentric circumferentially extending openings or slots 56 at radially spaced locations on the disc to provide paths for fluid flow through the collector screen 52 which vary in capacity in proportion to the distance from the center of the disc. The slots are arranged to be aligned over the four chambers 46 defined by the vanes 42. The collector screen fits tightly on the top of the vanes 42 and may be bonded to the vanes by an appropriate adhesive to make the channels 44 substantially fluidtight and cause fluid to be directed upwardly through the vessel only from the chambers 46. The outermost circumferential slots 56 are larger and have a higher capacity than the innermost since, as shown in FIG. 6, they increase in length corresponding to the increase in width of the chambers 46 as the radial distance from the center of the disc increases.

The end caps 12 and I4 and central shell 16 of the pressure vessel may be constructed of any strong moldablc or machineable material such as the polymeric plastics polyvinyl chloride, high density linear polyethylene or similar polymeric materials or metals such as brass and stainless steels. The preferred materials for use in manufacture of the pressure vessels are the acrylonitrile butadie'ne' styrene resins (ABS resins) and their copolymers which have a tensile strength of about 6,500 p.s.i. at 73 F., a specific gravity of from about 0.99 to 1.05, a water absorption percent increase for a 24-hour period at 73 F. of from 0.2 to 0.4 and a coefficient of linear thermal expansion in in./in./ C. of less than 10.5 X l0*". The resilient seals may be constructed from any flexible, water-resistant material such as neoprene or Teflon. A 40-inch pressure vessel having a diameter of about 8% inches constructed from these materials has a nominal weight of about I I pounds.

The pressure vessel of this invention is assembled by forcing the lands 24 of the end caps 12 and 14 into the cylindrical shell 16 so that the resilient O-rings 32 press tightly against the internal surface of the cylindrical shell (see FIG. 4) and provide a substantially fluidtight vessel. This is accomplished with relative ease due to the small amount of radial flexibility of the tapered portions of the lands and the resiliency of the O-rings. The ends of the shell abut against the shoulders 26 at the junction of the end cap lands 24 and skirt 22 to form a smooth external junction between the end caps and the shell. Any irregularities in the junction can be smoothed with an epoxy resin if necessary.

The vessel is then mounted on a filament-winding machine (not shown) by means of the threaded opening 38 in the end cap 12 and the overwinding mount 55 of the end cap 14. The vessel is then overwound tightly with a polyester resin coated Fiberglas filament to provide a lightweight, unitary, integral pressure vessel capable of withstanding high bursting pressures. As shown in cross-sectional view in FIG. 3, only the threaded opening 38 and the solid overwinding mount 55 are not covered by the filament overwinding. The preferred overwinding material is clear silane glass coated with an isothalic base polyester resin. It has been found that an ABS resin vessel having a shell thickness of from 0.09 to 0.10 inches can be overwound to withstand internal pressures of about 750 p.s.i.a. The ultimate strength of the vessel depends upon its dimensions, the particular materials used to construct the vessel, the type filament with which it is wound and the amount of overwinding. These can be selected to best fit the desired use for the vessel.

In the particular embodiment of the pressure vessel of this invention referred to in'FIG. 2, and further shown in FIG. 7, a flow directing fitting or valve 40 may be mounted in the upper opening of the end cap 12 for regulating fluid flow into the pressure vessel I0. The valve shown is functionally representative of the valves used for water conditioners or softeners for home and industrial service use. The valve has an inlet 57 for raw water from the service line and a valved inlet 58 for brine from a brine tank (not shown). The valve also has a drain line outlet 60 and a service line outlet 62. A central conduit 64 extends from the valve 40 to slightly above the inner surface of the lower end cap in the middle of the juncture of the channels 44 formed by the vanes 42. The entire valve and conduit may be formed from Fiberglas. A water conditioning resin (not shown) such as zeolite is normally contained in the vessel around the conduit.

FIG. 7 shows the valve in the regenerating or brining orientation wherein water enters through the valve inlet 57 on the left side of the valve and circulates past a venturi and the brine line 58 into the conduit 64. As the raw water proceeds past the venturi, a low pressure area is generated which, if the brine valve is open, causes brine to be drawn into the line and down through the central conduit 64 into the pressure vessel 10.

As shown in FIG. 7, the conduit 64 passes through the central aperture of the collector screen 52. Since the collector screen 52 is constructed of a resilient plastic, the flange 54 which extends about the central aperture thereof resiliently engages the outer surface of the cylindrical conduit 64 for maintaining the conduit in substantially fluidtight relationship with the central aperture of the collector screen 52.

During the regeneration cycle of the water conditioner, using the pressure vessel shown in FIG. 7, raw water enters through the water inlet 57 and passes through an inlet chamber and through the venturi causing brine to flow through inlet 58 from a brine tank (not shown) down through the central conduit 64 into the central portion of vanes 42. This raw water-brine mixture is directed out of the central portion of the lower end cap by the vanes 42 through the channels 44. Due to the constriction of the channels, as shown in FIGS. 2 and 6, the fluid is accelerated as it flows radially outwardly through the channels. The mixture, thus, is emitted tangentially into each of the chambers 46 at a relatively high flow rate with a spiraling motion. The outer wall of the end cap and the backs of the vanes 42 at the opposite side of each chamber 46 interrupt fluid flow and cause a high amount of turbulence in the chambers 46. The water-brine mixture under this high turbulence is forced through the openings 56 in the collector disc 52 and injected into the resin. This mixture maintains a high rate of flow and some of its turbulent spiraling motion as it passes upwardly through the resin. Since the capacity of the openings 56 of the outer edges of the disc 52 is greater than at the inner edges of the disc, a greater proportion of the mixture is injected into the resin through these outer openings tending to cause the fluid to move outwardly toward the shell 16 of the vessel. This combined effect of the vanes and collector screen substantially eliminates channeling against the interior conduit 64. The turbulence of the fluid mixture also provides a high amount of interface contact between the water-brine mixture and the ion exchange resin to fully utilize the resin.

As shown in FIG. 7, as the fluid reaches the upper end cap, it is directed inwardly toward the conduit by the end cap and by the channeling effect which occurs at the upper portion of the chamber when the mixture has lost the momentum with which it was injected into the resin. The mixture is then collected around the upper end of the cylindrical conduit and passes out of the vessel through the drain outlet 60. The tapered inner surfaces of the end cap lands 24 assist in directing flow outwardly toward the shell 16.

During the service cycle of the water conditioner of FIG. 7, the water flow pattern is downwardly through the ion exchange resin, through the collector disc 52 on the lower end cap 14 into the chambers 46, through the orifices 48 and upwardly through the central conduit 64 into the service outlet 62. Since the capacity of the openings 56 in the collector disc 52 is greater near the outer periphery of the disc, the path of least resistance to fluid flow is through these radially spaced locations so that channeling is reduced during the service cycle also. The flange 54, by providing a substantially fluidtight fitting with conduit 64 also assists in reducing channeling and permitting full utilization of the resin. The outer edge of the collector disc 52 may be bonded to shoulder 50 by an appropriate bonding material to reduce any tendency of the fluids to flow along the inner surface of the shell 16.

FIG. 8 illustrates another embodiment of the pressure vessel of this invention. In this embodiment, end caps 70 and 71 are each provided with a cylindrical skirt 72 which is of substantially the same thickness as the convex sections of the end caps. The end caps are joined to a cylindrical shell 74 by means of connector rings 76. The connector rings each comprise a central annularly extending shoulder 78 having an external diameter substantially'equal to that of the cylindrical skirts on the end caps. The shoulders 78 of the connector rings are connected to a pair of annular lands 80 which extend in opposite directions from the shoulders as shown in FIG. 8.

Each land is provided with an annular groove 82 or other means for receiving a resilient sealing member such as the 0- rings shown in FIG. 8. The O-rings are of a slightly greater diameter than the depth of the grooves and thus protrude above the lands and must be compressed to fit the connector ring lands into the cylindrical skirts of the end caps and into the central shell of the pressure vessel body.

The internal surface of the connector ring may taper from the outer edge of the lands to a point behind each of the grooves to provide radial flexibility for the lands during insertion into the end caps and cylindrical shell of the vessel.

It has been found that the length of the connector ring lands, in this embodiment of the invention, must still be at least three times the width of the seal-end cap skirt or sealshell interface and preferably should be at least seven times the width of the sealing contact interface to provide the highest bursting pressures for the vessels. The length of each land is measured from the respective radially extending sidewall of the shoulder 78 to that edge of the connector ring. These dimensions have been found to be necessary to enable the pressure vessel to withstand high operating pressures and continue in service over extended periods of time without leakage.

As shown in FIG. 8, the upper end cap is provided with a threaded opening, as discussed with respect to FIGS. 1 through 7, and the lower end cap is provided with an axially extending mounting member for facilitating mounting of the vessel during filament overwinding and for providing a reinforced base for the vessel.

The connector ring 76 shown in FIG. 8 can also be used to vary the length of the vessel by connecting a plurality of cylindrical shells to each other. The same end caps can thus be used with pressure vessels of any desired length. Materials used for constructing the end caps, the cylindrical shells, and the O-rings for the embodiment shown in FIG. 8 are the same as those discussed with respect to FIGS. 1 through 7. The con nector rings may be constructed from the same materials as the end caps and cylindrical shells or similar polymeric resins or lightweight metals.

I claim:

1. A lightweight vessel comprising an elongated cylindrical central wall; a pair of end caps formed from a resilient material and being mounted on the opposite ends of said central wall; each of said end caps comprising a convex, domelike, upper portion and a depending cylindrical skirt integral with said upper portion and of substantially the same outer diameter as said central wall to provide a smooth external junction between each skirt and said central wall; an annular resilient member intermediate said end caps and said central wall providing a substantially fluidtight seal between said end caps and said central wall; and a filament member tightly wound about said end caps and said central wall to provide an integral vessel capable of withstanding high bursting pressures.

2. A light weight vessel comprising an elongated cylindrical central wall; a pair of end caps formed from a resilient material and being mounted on the opposite ends of said central wall; each of said end caps comprising a convex domelike, upper portion and a depending cylindrical skirt integral with said upper portion and of substantially the same outer diameter as said central wall; annular lands connected to said cylindrical skirts of said end caps, said annular lands having an outer diameter less than the outer diameter of said skirts and slightly less than the inner diameter of said central wall and resilient sealing means mounted on said lands and in contact with said central wall for providing a fluidtight seal between said end caps and said central wall, each of said lands being connected to an external shoulder having a radially extending dimension substantially equal to the thickness of said central wall so that said lands fit snugly within said central wall and the outer surfaces of said skirts and said central wall form a substantially smooth abutting junction; and means defining an opening in one of said end caps for receiving a closure means for said vessel, said vessel being adapted to have a filament member tightly wound about said end caps and said central wall to provide an integral vessel capable of withstanding high bursting pressures.

3. A vessel as defined in claim 2 wherein said lands are integrally connected to said depending skirts.

4. A vessel as defined in claim 2 wherein said lands are each connected to an annular connector ring which comprises a central annular shoulder integrally connected to a pair of lands extending axially in opposite directions and each having an annular sealing member thereon, said shoulder extending radially from the outer surface of said lands by a dimension substantially equal to the thickness of said skirt and said central wall; one of said lands being mounted within one of said end caps and the other of said lands being mounted within said central wall.

5. A pressure vessel as defined in claim 2 wherein the length of said lands is at least three times the width of the sealing contact between said sealing means and said central wall.

6. A pressure vessel as defined in claim 2 wherein an annular groove is provided in each of said lands and said resilient sealing means comprise O-rings mounted in said grooves and protruding radially from said grooves so that said O-rings sealingly engage said central wall when said lands are inserted into said central wall.

7. A conditioner tank assembly as defined in claim l wherein said central wall and said end caps are molded from acrylonitrile butadiene styrene resins.

Claims

7. A conditioner tank assembly as defined in claim 1 wherein said central wall and said end caps are molded from acrylonitrile - butadiene - styrene resins.