Adsorber Switching Valve

This invention relates generally to multi-line switching valves. Protection of combat vehicle crews against chemical warfare agents requires that air entering the vehicle be purified before it enters the crew compartment. Present technology utilizes Whetlerite charcoal to purify the air by adsorption. The Whetlerite charcoal process has numerous disadvantages. One of the most significant of these is that the charcoal bed must be replaced when the charcoal becomes saturated. This places a great logistical burden on military supply lines. To reduce this burden, regenerative air purification technologies have been developed using multiple adsorber beds. Air entering the vehicle is purified by one adsorber bed while other adsorber beds are being regenerated by outgassing by heating or pressure differential techniques. As each bed becomes saturated, a switching valve switches the flow of air to a fresh bed, at the same time switching the contaminated bed to an outlet line in a regeneration configuration. The leading regenerable purification technologies are of the class called regenerative adsorption technologies which include temperature swing adsorption and pressure swing adsorption. Temperature swing adsorption, utilizing below ambient temperatures, is presently a leading technology for advanced collective protection systems for military vehicles.

A problem with regenerative adsorption systems is that they have complicated valving arrangements. A two-bed system requires four valves on the inlet side. These valves allow the inlet process stream to be directed to the proper bed while shutting off the regeneration back flush outlet line. It is known in the art to provide four shutoff valves at the outlet and to simplify the system by utilizing four check valves. An arrangement using two four-way valves is the previous best state-of-the-art. However, controls are still needed to coordinate the action of the two valves. In such a two-valve system, the two valves must act simultaneously to maintain a flow of purified air to the crew compartment. Failure of the two valves to act simultaneously may result in the death of the crew. The objective of the present invention is to remove this safety hazard by providing one multiple switching valve which switches all the bed inlet and outlet lines simultaneously. This significantly increases safety and reliability while decreasing the complexity of the required control logic. It may also reduce the overall weight, power and volume requirements.

It is therefore a principal object of this invention to provide an 8-way switching valve that is capable of handling bed inlet and outlet air streams with a single valve that switches all the lines simultaneously.

Another object of the invention is to provide a switching valve that is more reliable and therefore safer in operation than previously available valves.

A further object of the invention is to decrease the complexity of the controls necessary to operate the switching system.

A still further object of the invention is to reduce the weight, power and volume requirements of the valve system.

FIG. 1 is an exploded view of the preferred embodiment of the adsorber switching valve according to the present invention;

FIG. 2 is a sectional view of a second embodiment of the invention in which several valve housings are stacked;

FIG. 3 is a sectional view of a third embodiment of the invention in which the valve housing is split.

FIG. 4 is an isometric view of the assembled switching valve.

Referring to FIG. 1, the adsorber switching valve in its preferred embodiment comprises two valve housings 2, 3, two valve spools 4, 5, colinearly axially disposed with respect to each other, a spool drive shaft 6 having an upper end and a lower end, axially disposed with respect to the valve spools 4, 5; a drive mechanism 7 having a drive shaft, not shown, sealing means 8 and a valve position sensing means, not shown. The driving mechanism may be a high torque 28 VDC motor. Cover plates 9, 10 close off the housings. A valve spool separator 11 is interposed between the cover plates 9, 10 and axially disposed with respect to the spool drive shaft 6. The valve spools 4, 5 are fixed to the spool drive shaft 6. Gears 12a, 12b rotatably mesh with each other. Gear 12a is mounted on the drive shaft of the drive meohanism 7. Gear 12b is axially mounted on the lower end of the spool drive shaft 6. Operation of the drive mechanism 7 rotates the spool drive shaft 6 axially through the action of the gears 12a, 12b, rotating the valve spools 4, 5. The gears are covered by a gear cover plate 13 and a motor frame/gear housing 14.

The valve spools 4, 5 contain through ports 16, circular in cross section. The through ports 16 are passageways for fluid, the fluid being air when the invention is used in the preferred embodiment. Each passageway through a valve spool 4, 5 makes a right-angle turn in direction through the valve spool 4 or 5 and opens out of the valve spool at a point 90 degrees around the circumference of the valve spool. The through ports 16 are preferentially made to the full bore dimension of the openings 20 on the valve housing 2, 3, that is, the through ports 16 and the openings 20 are of the same shape and cross sectional area throughout, so as to minimize pressure drop. Notches 17 may be fabricated into the valve spools 4, 5 to reduce weight. The openings 20 on the valve housings 2, 3 are located opposite the locations of the through ports 16 in the valve spools 4, 5. A quarter turn of the valve spools 4, 5 switches each through port 16 to a position aligned opposite an opening 20 located one quarter of the way cicumferentially around the housing 2, 3. The openings 20 in the housing 2, 3 communicate to piping 21 leading to the adsorber beds, not shown, and to inlet and outlet piping, also not shown. The piping may contain flexible parts or bellows to compensate for thermal expansion.

The two-bed system has four inlet streams and four outlet streams. Each spool has two inlets and two outlets. The top spool, 5, processes contaminated air. Its first inlet takes in the outside air. Its outlet goes to one of the adsorber beds. Its second inlet takes the contaminated air from the other adsorber bed and discharges that air to outside the vehicle. Thus, spool 5 processes contaminated air. At the same time, the bottom spool, 4, is configured so that its first inlet takes air from the adsorber bed and sends it to the crew compartment and the regeneration heater. The second inlet of spool 4 takes air from the regeneration air heater and sends it to the other adsorber bed. This air is used to regenerate the second bed. In this configuration Bed One purifies the inlet air while Bed Two is being regenerated. When Bed One reaches saturation, the valve spools are rotated 90 degrees to a second position in which the inlet stream is now directed to Bed Two and then to the crew compartment while the outlet stream is directed to Bed One and then to the atmosphere. In this second configuration Bed Two purifies the inlet air while Bed One is being regenerated.

The collinear axial spool drive shaft 6 connects the valve spools 4, 5. Bearings 19 are preferentially located at every point where the spcol drive shaft 6 is supported at the valve housing 2, 3 or the valve housing cover plates 9, 10. The spool drive shaft 6 may be a single piece or, for ease of assembly, may be made of multiple pieces connected by couplings. One such coupling may be a flexible shaft 18 as shown in FIG. 1. The flexibility of the shaft reduces the starting torque necessary to turn the valve and compensates for slight misalignment of the valve spools 4, 5, thus avoiding excess bearing 19 wear. A shear key, not shown, is provided at the connection between the spool drive shaft 6 and the drive mechanism 7. The spool drive shaft 6 is fastened to the flexible shaft 18 by a set screw 25. A hole 26 appropriately located in the valve spool separator 11 allows access to the set. screw 25 for screwdriving means.

The junction between the through ports 16 and the openings 20 are sealed by sealing means comprising 0-rings 8 mounted in 0-ring grooves 23 in the valve spools in the preferred embodiment. The 0-rings should be 70 durometer or higher.

The valve housings 2, 3 and valve spools 4, 5 may be fabricated of stainless steel or any other suitable metal, plastic, or chemically resistant material. For use with high regeneration temperatures the valve housings 2, 3 and valve spools 4, 5 may be fabricated from or coated with Polytetrafluoroethylene (PTFE).

RIG. 4 shows an exterior view of the assembled switching valve.

Multiple valve housings 2, 2a, 2b, 2c may be stacked one next to another as shown in FIG. 2 and fastened in place with through bolts 15 or other fastening means. This provides maximum economy of space for a multiple spool valve when using multiple beds.

An alternative multi-spool design comprises a multi-spool split housing 22 as shown in FIG. 3. The split housing 22 would be utilized for six adsorption beds. However, an advantage of separating the valve housings in the manner shown in FIG. 1 as opposed to stacking the housings as shown in FIGS. 2 and 3, is that spatially separating the housings as in FIG. 1 provides absolute protection against cross contamination when the valve spools rotate. It also provides protection against contamination in the event of seal failure in the housings. This absolute protection is obtained as long as all spools are operating above ambient pressure.

Another way of minimizing cross contamination is by venting each housing 2, 3 to the atmosphere. For industrial uses, where hazardous gases or liquids are being handled, the vents may be piped either to a safe location or to a flare line or other safe collection point.

The spool drive shaft may be directly coupled to the drive mechanism instead of being driven through gears. A brake may be provided to assist the stopping of the valve spool rotation.

Although the preferred embodiment of this invention has been described in detail it is recognized that the invention is not limited to the precise form and structure described and various modifications and rearrangements as will occur to those skilled in the art upon full comprehension of this invention may be resorted to without departing from the scope of the invention as defined in the claims.