FOUR-WAY VALVE

Abstract

A four-way valve for use in a regenerative thermal oxidizer (RTO) assembly for alternating between a first cycle with a gas flowing in a first direction and a second cycle with a gas flowing in a second direction. A partition divides the interior of the housing of the valve into an input zone and an output zone. A pivot shaft rotatable about an axis is disposed in the interior of the housing, and a pair of opposing dampers extend radially outwardly on opposite sides of the pivot shaft. A plurality of ducts are disposed in the housing. Each duct engages one of the input and output apertures and extends into one of the input and output zones for engaging the dampers to restrict the flow of gas during the first and second cycles.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a four-way valve for use in a regenerative thermal oxidizer (RTO) assembly and other regenerative heat exchange devices.

2. Description of the Prior Art

RTOs are used in a number of industries to reduce the quantity of contaminants in a contaminated gas. In an RTO, the contaminated gas is routed through a flow path, which includes a combustion chamber for oxidizing the contaminated gas to produce a clean gas. A first recovery chamber is disposed in the flow path on one side of the combustion chamber, and a second recovery chamber is disposed in the flow path on the other side of the combustion chamber. Each of the recovery chambers typically includes a ceramic media. The RTO alternates between a first cycle with the gas flowing in a first direction and a second cycle with the gas flowing in a second direction. While operating in the first cycle, as the high temperature clean gas leaves the combustion chamber, it is routed through the first recovery chamber. In the recovery chamber, heat is transferred from the clean gas to the ceramic media. The flow of the gas is reversed during the second cycle such that the contaminated gas flows through the heated first recovery chamber before entering the combustion chamber. Heat is transferred from the hot ceramic media to the contaminated gas, and consequently, less energy is required to oxidize the contaminated gas in the combustion chamber.

A valve assembly is required to direct the gas in the first direction through the flow path while operating in the first cycle and to direct the gas in a second direction through the flow path while operating in the second cycle. One such valve assembly is shown in FIG. 3 of U.S. Pat. No. 5,515,909, issued to Tanaka on May 14, 1996 (hereinafter referred to as Tanaka '909). Tanaka '909 shows a four-way valve assembly including a housing presenting an open interior and having a front, a back, an input side, and an output side. The input side of the housing defines an intake, and the output side of the housing defines an outlet. A partition is disposed in the open interior to divide the interior into an input zone and an output zone. The housing defines an input aperture and an output aperture. A pivot shaft rotatable about an axis is disposed in the interior of the housing, and a pair of opposing dampers engage the pivot shaft and extend radially outwardly therefrom for rotating with the pivot shaft to restrict the flow of gas through the apertures during the first and second cycles.

SUMMARY OF THE INVENTION AND ADVANTAGES

The invention is for such a four-way valve assembly and including a plurality of ducts disposed in said housing with each duct in fluid communication with one of the input and output apertures and extending into the associated one of the input and output zones for engaging the dampers to restrict the flow of gas during said first and second cycles.

ADVANTAGES OF THE INVENTION

The four-way valve of the subject invention can be assembled more quickly and less expensively than those of the prior art because the dampers directly engage the ducts disposed in the housing during the first and second cycles. In contradistinction, the Takana '909 valve relies on a pair of expensive and specially designed partitions to engage the dampers during the first and second cycles.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a diagram of the subject invention showing the gas flowing through the RTO assembly in a first direction;

FIG. 2 is a diagram of the subject invention showing the gas flowing through the RTO assembly in a second direction;

FIG. 3 is a perspective view of the four-way valve;

FIG. 4 is a cross-sectional view of the four-way valve with the pivot shaft and dampers rotated to engage the first input duct and the second output duct during the first cycle;

FIG. 5 is a cross-sectional view of the four-way valve with the pivot shaft and dampers rotated to engage the second input duct and the first output duct during the second cycle;

FIG. 6 is an exploded and cross-sectional view of the pivot shaft, the dampers, the partition, and the resilient seal;

FIG. 7 is a perspective view of the four-way valve during the first cycle; and

FIG. 8 is a perspective view of the four-way valve during the second cycle.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the Figures, wherein like numerals indicate corresponding parts throughout the several views, the invention is a regenerative thermal oxidizer (RTO) assembly 20, generally shown in FIGS. 1 and 2. It is to be understood that the four-way valve 23 of the present invention is shown for use with an RTO assembly 20, but could be used in any other application, for example with fluids other than gas. The regenerative thermal oxidizer assembly 20 establishes a flow path 22, generally indicated, for cleaning a contaminated fluid (preferably a gas). The assembly 20 alternates between operating in a first cycle, shown in FIG. 1, with the gas flowing in a first direction and a second cycle, shown in FIG. 2, with the gas flowing in a second direction.

A combustion chamber 24 is disposed in the flow path 22 and includes a burner 26 for oxidizing the contaminated gas to produce a clean and heated gas. A first heat recovery chamber 28 and a second heat recovery chamber 30 are disposed in the flow path 22 on either side of the combustion chamber 24. A heat exchange media, typically of ceramic, is disposed in each of the heat recovery chambers 28, 30 for storing and dispensing heat.

The first recovery chamber 28 receives the clean gas from the combustion chamber 24 during the first cycle and dispenses the contaminated gas to the combustion chamber 24 during the second cycle. Heat is transferred from the clean gas to the first recovery chamber 28 during the first cycle, thereby cooling the clean gas and heating the first recovery chamber 28. During the second cycle, heat is transferred from the heated first recovery chamber 28 to the contaminated gas to preheat the contaminated gas, which cools the first recovery chamber 28.

The second recovery chamber 30 receives the clean gas from the combustion chamber 24 during the second cycle and dispenses the contaminated gas to the combustion chamber 24 during the first cycle. Similar to the first recovery chamber 28, heat is transferred from the clean gas to the second recovery chamber 30 during the second cycle, thereby cooling the clean gas and heating the second recovery chamber 30. During the first cycle, heat is transferred from the heated second recovery chamber 30 to the contaminated gas to preheat the contaminated gas and cool the second recovery chamber 30. Together, the first and second recovery chambers 28, 30 preheat all of the contaminated gas before dispensing it to the combustion chamber 24. Preheating the contaminated gas improves the efficiency of the combustion chamber 24 because less energy is required to oxidize the contaminated gas.

A four-way valve 23, generally shown in FIGS. 3-5, is disposed in the flow path 22 for receiving the contaminated gas during both cycles and for directing the contaminated gas to the second recovery chamber 30 during the first cycle and for directing the contaminated gas to the first recovery chamber 28 during the second cycle and for receiving the clean gas from the first recovery chamber 28 during the first cycle and for receiving the clean gas from the second recovery chamber 30 during the second cycle and for dispensing the clean gas out of the flow path 22 during both cycles. A first conduit 34 extends between the four-way valve 23 and the first recovery chamber 28 for conveying the gas therebetween, and a second conduit 36 extends between the four-way valve 23 and the second recovery chamber 30 for conveying the gas therebetween.

The four-way valve 23 includes a housing 38, generally indicated, having a top plate 40, a bottom plate 42, a front plate 44, a back plate 46, an input side plate 48, and an output side plate 50 to define a closed housing 38 having an open interior. The input and output side plates 48, 50 are in spaced and parallel relationship with one another and are disposed on opposite sides of the housing 38. The front and back plates 44, 46 are also in spaced and parallel relationship with one another on opposite sides of the housing 38. Other orientations of the top, bottom, front, back, input side 48, and output side plates 50 is contemplated.

Referring to FIG. 4, a partition 52 is disposed in the interior of the housing 38 and extends in spaced and parallel relationship with the input and output side plates 48, 50 between the front and back plates 44, 46. The partition 52 divides the open interior into an input zone 54 adjacent to the input side plate 48 and an output zone 56 adjacent to the output side plate 50. The input side plate 48 defines an intake 58 for receiving the contaminated gas and for delivering the contaminated gas into the input zone 54 of the housing 38. The output side plate 50 defines an outlet 60 for dispensing the clean gas out of the output zone 56 of the housing 38.

The front plate 44 of the housing 38 defines a first input aperture 62 establishing fluid communication between the first conduit 34 and the input zone 54 of the housing 38. The back plate 46 of the housing 38 defines a second input aperture 64 establishing fluid communication between the second conduit 36 and the input zone 54 of the housing 38 for conveying the contaminated gas from the input zone 54 of the housing 38 to the second recovery chamber 30. The front plate 44 of the housing 38 defines a first output aperture 66 establishing fluid communication between the first conduit 34 and the output zone 56 of the housing 38. The back plate 46 of the housing 38 defines a second output aperture 68 establishing fluid communication between the second conduit 36 and the output zone 56 of the housing 38.

The housing 38 further includes a first input duct 70 disposed in the input zone 54 of the housing 38 and extending inwardly from the first input aperture 62 for channeling the contaminated gas from the input zone 54 of the housing 38 to the first input aperture 62. A second input duct 72 is disposed in the input zone 54 of the housing 38 and extending inwardly from the second input aperture 64 for channeling the contaminated gas from the input zone 54 of the housing 38 to the second input aperture 64. A first output duct 74 is disposed in the output zone 56 of the housing 38 and extends inwardly from the first output aperture 66 for channeling the clean gas from the first output aperture 66 to the output zone 56 of the housing 38. A second output duct 76 is disposed in the output zone 56 of the housing 38 and extends inwardly from the second output aperture 68 for channeling the clean gas from the second output aperture 68 to the output zone 56 of the housing 38.

Each of the ducts 70, 72, 74, 76 is shown as being preferably cylindrically shaped and extending from the associated aperture to a duct end 78. In the exemplary embodiment, the duct end 78 of the first input duct 70 is preferably disposed in substantially the same plane as the duct end 78 of the second output duct 76, and the duct end 78 of the first output duct 74 is preferably disposed in substantially the same plane as the duct end 78 of the second input duct 72. Most preferably, each of the ducts 70, 72, 74, 76 is disposed at the same angle θ of thirty degrees relative to the front and back plates 44, 46, and each of the ducts 70, 72, 74, 76 angles toward the associated one of the input and output side plates 48, 50. In other words, the first and second input ducts 70, 72 angle toward the input side plate 48, and the first and second output ducts 74, 76 angle toward the output side plate 50. It should be appreciated that the ducts 70, 72, 74, 76 do not have to extend at an angle θ into the input and output zones 54, 56 of the housing 38, but could extend perpendicularly to the front and back side plates 48, 50. The duct ends 78 could alternately be cut at an angle θ relative to the front and back side plates 48, 50. The angle θ of the duct ends 78 improves the efficiency of the gas flowing between the ducts 70, 72, 74, 76 and either the intake 58 or the outlet 60 of the four-way valve 23.

Referring to FIG. 6, the partition 52 of the housing 38 presents a gap 80 approximately halfway between the front and back side plates 48, 50. A rotatable pivot shaft 82 is disposed in the gap 80, and the pivot shaft 82 extends along an axis A between the top and bottom plates 40, 42. A gasket 84 is disposed between the partition 52 and the pivot shaft 82. The gasket 84 makes friction contact with the pivot shaft 82 for sealing the partition 52 to the pivot shaft 82 to prevent gas from flowing directly between the input and output zones 54, 56 of the housing 38. The gasket 84 is preferably made of graphite, but any other material suitable for sealing the pivot shaft 82 to the partition 52 is acceptable.

The four-way valve 23 further includes a pair of opposing dampers 86 engaging the pivot shaft 82 and extending radially outwardly therefrom on opposite sides of the pivot shaft 82. The dampers 86 rotate with the pivot shaft 82 to engage the duct end 78 of one of the input ducts 70, 72 and the duct end 78 of one of the output ducts 74, 76 to restrict gas flow through the engaged ducts 70, 72, 74, 76. In other words, the dampers 86 rotate with the pivot shaft 82 to engage and seal the duet ends 78 of one of the input ducts 70, 72 and one of the output ducts 74, 76.

An actuator 88 is operably connected to the pivot shaft 82 and configured to rotate the pivot shaft 82 and the dampers 86 to a first position during the first cycle and a second position during the second cycle. As shown in FIG. 4, in the first position, one of the dampers 86 engages and seals the duct end 78 of the first input duct 70 and the other damper 86 engages and seals the duct end 78 of the second output duct 76. As shown in FIG. 5, in the second position, one of the dampers 86 engages and seals the duct end 78 of the second input duct 72 and the other damper 86 engages and seals the duct end 78 of the first output duct 74.

A seal retaining flange 90 is disposed about each of the ducts 70, 72, 74, 76 and spaced from the duct ends 78. A resilient seal 92 is disposed about each of the ducts 70, 72, 74, 76 and extending past the duct ends 78 for engaging the dampers 86. As shown in FIGS. 4 and 5, when engaging the dampers 86, the resilient seals 92 of the exemplary embodiment compress so that the dampers 86 directly engage the duct ends 78.

The four-way valve 23 functions to switch the assembly 20 between the first and second cycles. During the first cycle, the actuator 88 rotates the pivot shaft 82 and the dampers 86 to the first position shown in FIG. 4. The contaminated gas enters the four-way valve 23 at the intake 58 and is directed through the second input duct 72 to the second conduit 36. As shown in FIG. 1, the second conduit 36 conveys the contaminated gas to the second recovery chamber 30, where the contaminated gas is preheated before entering the combustion chamber 24. After being heated and cleaned in the combustion chamber 24, the heated and cleaned gas flows through the first recovery chamber 28, where it dispenses its heat into the first recovery chamber 28. The gas then flows through the first conduit 34 to the first output duct 74. As shown in FIG. 4, the first output duct 74 conveys the gas into the output zone 56 of the housing 38, where it is directed out of the flow path 22 through the outlet 60 of the four-way valve 23.

During the second cycle, the actuator 88 rotates the pivot shaft 82 and the dampers 86 to the second position shown in FIG. 5. The contaminated gas enters the four-way valve 23 at the intake 58 and is directed through the first input duct 70 to the first conduit 34. As shown in FIG. 2, the first conduit 34 conveys the contaminated gas to the first recovery chamber 28, where the contaminated gas is preheated before entering the combustion chamber 24. After being heated and cleaned in the combustion chamber 24, the heated and cleaned gas flows through the second recovery chamber 30, where it dispenses some of its heat into the second recovery chamber 30. The gas then flows through the second conduit 36 to the second output duct 76. As shown in FIG. 5, the second output duct 76 conveys the gas into the output zone 56 of the housing 38, where it is directed out of the flow path 22 through the outlet 60 of the four-way valve 23.

It is imperative that the actuator 88 rotates the pivot shaft 82 and the dampers 86 between the first and second positions quickly, as some contaminated fluid may escape through the outlet 60 of the housing 38 without being routed through the combustion chamber 24. In the exemplary embodiment, when rotating between the first and second positions, the actuator 88 accelerates the pivot shaft 82 for 0.2 seconds and decelerates the pivot shaft 82 for 0.2 seconds. A sensor (not shown) may be attached to the shaft to dictate when the actuator 88 should switch from accelerating to decelerating the shaft.

It is also very important that the actuator 88 be precisely controlled to prevent the dampers 86 from slamming against the duct ends 78 when switching between the first and second positions. Referring to FIGS. 7 and 8, the actuator 88, generally shown, of the exemplary embodiment includes a motor 94, a rod 96, a loss motion connector 98, and a lever 100. The motor 94 could be an electric motor, a pneumatic actuator, or any other type of actuator capable of rotating the pivot shaft 82 and the dampers 86. The motor 94 is operably connected to the rod 96 for moving the rod 96 in a forward direction (FIG. 7) during the first cycle and for moving the rod 96 in a backward direction during the second cycle. The lever 100 engages the pivot shaft 82 for rotating with the pivot shaft 82. The loss motion connector 98 is operably connected between the rod 96 and the lever 100 for preventing the dampers 86 from slamming against the duct ends 78 and for maintaining a compression seal between the resilient seals 92 and the dampers 86 when the dampers 86 are in the first and second positions.

As shown in FIGS. 7 and 8, the loss motion connector 98, generally indicated, includes a connector plate 102 operably connected to the rod 96 for moving with the rod 96 in the forward direction during the first cycle and for moving with the rod 96 in the backward direction during the second cycle. A pair of spaced connector shafts 104 extend outwardly from the connector plate 102 to connector flanges 106 (shown as washers) at the end of the connector shafts 104. A slider 108 is slidably disposed along the connector shafts 104 between the connector plate 102 and the connector flanges 106. A plurality of front springs 110 are disposed about the shafts 104 and engaging the slider 108 and the connector plate 102, and a plurality of back springs 112 are disposed about the shafts 104 and engaging the slider 108 and the connector flanges 106. The front and back springs 110, 112 bias the slider 108 to a neutral position. The lever 100 attached to the pivot shaft 82 engages the slider 108 of the loss motion connector 98.

In operation, during the first cycle, the motor 94 moves the rod 96 and connector plate 102 forward to the position shown in FIG. 7. The lever 100 stops rotating and the slider 108 stops moving once the pivot shaft 82 and dampers 86 reach the first position. The rod 96 and connector plate 102 continue to move forward so that the back springs 112 maintain a biasing force on the slider 108 and lever 100 to form a compressive seal between the damper 86 and the resilient seal 92.

During the second cycle, the motor 94 moves the rod 96 and connector plate 102 backward to the position shown in FIG. 8. The lever 100 stops rotating once the pivot shaft 82 and dampers 86 reach the second position. The rod 96 and connector plate 102 continue to move backward so that the front springs 110 maintain a biasing force on the slider 108 and lever 100 to form a compressive seal between the dampers 86 and the resilient seals 92.

Obviously, many modifications and variations of the present invention are possible in light of the above teachings and may be practiced otherwise than as specifically described while within the scope of the appended claims. These antecedent recitations should be interpreted to cover any combination in which the inventive novelty exercises its utility. The use of the word “said” in the apparatus claims refers to an antecedent that is a positive recitation meant to be included in the coverage of the claims.

Claims

1. A four-way valve for alternating between a first cycle with a fluid flowing in a first direction and a second cycle with the fluid flowing in a second direction, comprising: a housing having a front and a back and an input side and an output side and defining an open interior,a partition disposed in said interior of said housing to divide said open interior into an input zone adjacent to said input side of said housing and an output zone adjacent to said output side of said housing,said input side of said housing defining an intake for conveying the fluid into said input zone of said housing and said output side of said housing defining an outlet for dispensing the fluid out of said output zone of said housing,said front of said housing defining a first input aperture in fluid communication with said input zone of said housing and said back of said housing defining a second input aperture in fluid communication with said input zone of said housing,said front of said housing defining a first output aperture in fluid communication with said output zone of said housing and said back of said housing defining a second output aperture in fluid communication with said output zone of said housing,a pivot shaft rotatable about an axis and disposed in said interior of said housing,a pair of opposing dampers engaging said pivot shaft and extending radially outwardly therefrom for rotating with said pivot shaft to restrict the flow of fluid through said first input aperture and said second output aperture during said first cycle and for rotating to restrict the flow of fluid through said second input aperture and said first output aperture during said second cycle, anda plurality of ducts disposed in said housing with each duct in fluid communication with one of said input and output apertures and extending into the associated one of said input and output zones for engaging said dampers to restrict the flow of fluid during said first and second cycles.

2. The assembly as set forth in claim 1 wherein the fluid is a gas.

3. The assembly as set forth in claim 2 wherein each of said ducts presents a duct end spaced between said front and back of said housing and disposed at an angle relative to said front and back of said housing and angling toward the associated one of said input and output sides of said housing.

4. The assembly as set forth in claim 3 wherein said plurality of ducts include a first input duct extending into said input zone of said housing from said first input aperture and a second input duct extending into said input zone of said housing from said second input aperture and a first output duct extending into said output zone from said first output aperture and a second output duct extending into said output zone from said second output aperture.

5. The assembly as set forth in claim 4 wherein said duct ends of said first input duct and said second output duct are disposed at the same angle and in substantially the same plane for concurrently engaging said opposing dampers during said first cycle.

6. The assembly as set forth in claim 4 wherein said duct ends of said second input duct and said first output duct are disposed at the same angle and in substantially the same plane for concurrently engaging said opposing dampers during said second cycle.

7. The assembly as set forth in claim 4 wherein each of said duct ends is at an angle of thirty degrees relative to said front and back of said housing.

8. The assembly as set forth in claim 4 wherein each of said ducts is cylindrically shaped and extends at an angle toward the associated one of said input and output sides.

9. The assembly as set forth in claim 2 wherein said partition presents a gap.

10. The assembly as set forth in claim 9 wherein said pivot shaft is disposed in said gap of said partition.

11. The assembly as set forth in claim 10 further including a gasket disposed between and engaging said partition and said pivot shaft for restricting gas flow between said input and output zones of said housing.

12. The assembly as set forth in claim 11 wherein said gasket is of graphite.

13. The assembly as set forth in claim 2 further including a seal of a resilient material disposed on each of said duct ends for sealing said dampers to said ducts to restrict the flow of gas between said ducts engaged with said dampers and the associated one of the input and output zones of the housing.

14. The assembly as set forth in claim 2 further including an actuator operably connected to said pivot shaft and configures to rotate said pivot shaft and said dampers to a first position during said first cycle with one of said dampers engaging said duct end of said first input duct and the other of said dampers engaging said duct end of said second output duct and configured to rotate said pivot shaft and said dampers to a second position during said second cycle with one of said dampers engaging said duct end of said second input duct and the other of said dampers engaging said duct end of said first output duct.

15. The assembly as set forth in claim 2 wherein said four-way valve is in a regenerative thermal oxidizer assembly for cleaning a contaminated gas.

16. The assembly as set forth in claim 15 further including a combustion chamber in said flow path and including a burner for burning contaminants in the contaminated gas to produce a clean gas.

17. The assembly as set forth in claim 16 further including a first recovery chamber in said flow path and in fluid communication with said four-way valve and said combustion chamber for conveying the clean gas from said combustion chamber to said four-way valve during said first cycle and for conveying the contaminated gas from said four-way valve to said combustion chamber during said second cycle and for storing heat from the clean gas during said first cycle and for preheating the contaminated gas during said second cycle.

18. The assembly as set forth in claim 17 further including a second recovery chamber in said flow path and in fluid communication with said four-way valve and said combustion chamber for conveying the clean gas from said combustion chamber to said four-way valve during said second cycle and for conveying the contaminated gas from said four-way valve to said combustion chamber during said first cycle and for storing heat from the clean gas during said second cycle and for preheating the contaminated gas during said first cycle.

19. The assembly as set forth in claim 18 further including a first conduit extending between said four-way valve and said first recovery chamber for conveying the gas therebetween.

20. A regenerative thermal oxidizer assembly establishing a flow path for cleaning a contaminated gas and for alternating between a first cycle with the gas flowing in a first direction and a second cycle with the gas flowing in a second direction, including: a combustion chamber in said flow path and including a burner for burning contaminants in the contaminated gas to produce a clean gas,a first recovery chamber in said flow path and in fluid communication with said combustion chamber for receiving the clean gas from said combustion chamber during said first cycle and for dispensing the contaminated gas to said combustion chamber during said second cycle and for storing heat from said clean gas to preheat the contaminated gas,a second recovery chamber in said flow path and in fluid communication with said combustion chamber for dispensing the contaminated gas to said combustion chamber during said first cycle and for receiving the clean gas from said combustion chamber during said second cycle and for storing heat from said clean gas to preheat the contaminated gas,a four-way valve in said flow path for receiving the contaminated gas during both cycles and for directing the contaminated gas to said second recovery chamber during said first cycle and for directing the contaminated gas to said first recovery chamber during said second cycle and for receiving the clean gas from said first recovery chamber during said first cycle and for receiving the clean gas from said second recovery chamber during said second cycle and for dispensing the clean gas out of said flow path during both cycles,a first conduit extending between said four-way valve and said first recovery chamber for conveying the gas therebetween and a second conduit extending between said four-way valve and said second recovery chamber for conveying the gas therebetween,said four-way valve including a housing having a top plate and a bottom plate and a front plate and a back plate and an input side plate and an output side plate to define a closed housing having an open interior,said input and output side plates being in spaced and parallel relationship with one another and disposed on opposite sides of said housing,a partition disposed in said interior of said housing and extending in spaced and parallel relationship with said input and output side plates between said front and back plates to divide said open interior into an input zone adjacent to said input side plate and an output zone adjacent to said output side plate,said input side plate defining an intake for receiving the contaminated gas and for delivering the contaminated gas to said input zone of said housing,said output side plate defining an outlet for dispensing the clean gas out of said output zone of said housing,said front plate of said housing defining a first input aperture establishing fluid communication between said first conduit and said input zone of said housing,said back plate of said housing defining a second input aperture establishing fluid communication between said second conduit and said input zone of said housing,said front plate of said housing defining a first output aperture establishing fluid communication between said first conduit and said output zone of said housing,said back plate of said housing defining a second output aperture establishing fluid communication between said second conduit and said output zone of said housing,a first input duct disposed in said input zone of said housing and extending inwardly from said first input aperture for channeling the contaminated gas from said input zone of said housing to said first input aperture,a second input duct disposed in said input zone of said housing and extending inwardly from said second input aperture for channeling the contaminated gas from said input zone of said housing to said second input aperture,a first output duct disposed in said output zone of said housing and extending inwardly from said first output aperture for channeling the clean gas from said first output aperture to said output zone of said housing,a second output duct disposed in said output zone of said housing and extending inwardly from said second output aperture for channeling the clean gas from said second output aperture to said output zone of said housing,each of said input and output ducts being disposed at an angle relative to the associated one of said front and back plates and angling toward the associated one of said input and output side plates,each of said input and output ducts extending into inwardly from the associated one of said input and output apertures to a duct end,said duct ends of said first input duct and said second output duct being disposed in substantially the same plane,said duct ends of said second input duct and said first output duct being disposed in substantially the same plane,said partition of said housing presenting a gap between said front and back side plates,a pivot shaft rotatable about an axis and disposed in said gap of said partition and extending axially between said top and bottom plates of said housing,a gasket disposed between and engaging said partition and said pivot shaft for restricting gas flow between said input and output zones of said housing,a pair of opposing dampers engaging said pivot shaft and extending radially outwardly therefrom on opposite sides of said pivot shaft for rotating with said pivot shaft to engage said duct end of one of said input ducts and said duct end of one of said output ducts to restrict gas flow through the engaged ones of said input and output ducts,an actuator operably connected to said pivot shaft and configured to rotate said pivot shaft to a first position during said first cycle with one of said dampers engaging said duct end of said first output duct and the other of said dampers engaging said duct end of said second input duct and configured to rotate said pivot shaft to a second position during said second cycle with one of said dampers engaging said duct end of said first input duct and the other of said dampers engaging said duct end of said second output duct,a seal disposed adjacent to each of said duct ends for engaging said dampers to seal said dampers to said duct ends engaging said dampers, andsaid actuator including a motor and a motion loss connector for operably connected to said motor and said pivot shaft for preventing said dampers from slamming said duct ends and for maintaining a compression seal between said seals and said dampers engaging said seals.