Information
-
Patent Grant
-
6776710
-
Patent Number
6,776,710
-
Date Filed
Friday, October 24, 200320 years ago
-
Date Issued
Tuesday, August 17, 200419 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 454 153
- 454 284
- 454 305
- 454 306
- 454 188
- 034 97
-
International Classifications
-
Abstract
A vent structure comprises an inlet-connector section, an outlet section, and a transition section between the inlet-connector section and outlet section. The inlet-connector section is at an inlet end of the vent structure and is adapted for connection with an inlet duct from which the vent structure receives a flow of air. The outlet section is at an outlet end of the vent structure and includes an outlet slot that is adapted to direct the flow of air into a room. The transition section has a flared portion that diverges in cross-sectional area as it extends generally toward the outlet section. The transition section has a constricted portion located between the inlet-connector section and the outlet slot. The constricted portion is also located substantially centrally within a plane that is generally perpendicular to a direction of air flow. The constricted portion is adapted to restrict the flow of air through a central portion of the transition section, thereby restricting the flow of air exiting a corresponding central portion of the outlet slot to provide a more uniform velocity profile of exiting air.
Description
BACKGROUND OF THE INVENTION
The present invention relates to heating, ventilating and air conditioning (HVAC) systems for controlling environmental conditions in a room or space. More particularly, the present invention relates to an HVAC system vent structure, which is configured to provide a uniform velocity profile of exiting air.
In conventional building construction, HVAC ducts are formed of sheet metal and have rectangular cross sections. The ducts and outlet registers have cross sectional areas in the range of tens of square inches. Within conventional stud wall sections, the ducts often occupy most of the space between a pair of adjacent studs. Conventional home environmental systems move heated or cooled air at relatively low velocities.
In some newer ducting designs, cylindrical ducts are used which have much smaller cross sectional areas than more conventional ducts, in the range of less than ten square inches. Airflow through such smaller ducts is at a higher velocity than in conventional ducts to achieve comparable volumetric flow rates and to promote better mixing of conditioned air into the ambient air within a room. These smaller ducts typically have a lower manufacturing cost because less material is used, and because manufacturing labor is reduced. Additional advantages include more convenient installation and higher energy efficiency, because there is less surface area through which heat can be transferred.
A common problem with any vent structure is the generation of audible noise by air flowing through the vent structure and louvers. Airflow noise is generally caused by turbulence resulting from a change in the direction of air flow or a restriction that is too abrupt. Airflow noise can also result from structural components that are vibrated by the flow of air thereover, by natural resonances within the vent structure, and the like. Due to the higher flow velocities in the newer, smaller, cylindrical ducting designs, the potential for generating undesirable noise is increased.
To address this problem, Unico, Inc., assignee of U.S. Pat. No. 6,168,518 and assignee of the present application, developed a novel vent structure that connects between a small-diameter cylindrical airflow duct and a narrow rectangular outlet slot by way of a curved, angularly flared transition section that changes the direction of airflow and transitions from the circular cross section of the duct to the rectangular shape of the outlet slot with a minimum of turbulence and airflow noise. In developing the vent structure disclosed in U.S. Pat. No. 6,168,518, Unico determined that the cross sectional areas of the flared transition section and outlet section, in combination with the gradual curved shape of the flare section, minimized the introduction of turbulence in air flowing therethrough and, thereby, minimized the generation of airflow noise.
The present invention provides further improvements in such vent structures. One drawback to the newer, smaller-diameter, cylindrical ducting designs is that the high velocity flow through the ducts often causes air exiting an outlet vent or louver to be concentrated at a high velocity in a region of the outlet vent that is nearest to or aligned with the cylindrical ducting to which the vent structure is connected. That is, the air being discharged from an outlet vent or louver tends to have a non-uniform velocity profile (see FIG.
6
). Thus, there is a need for a vent structure that is configured to minimize the introduction of turbulence and resulting airflow noise, while providing a more uniform velocity profile of exiting air.
SUMMARY OF THE INVENTION
The present invention provides a vent structure for an HVAC system. In general, the vent structure comprises an inlet-connector section, an outlet section, and a transition section between the inlet-connector section and outlet section. The inlet-connector section is at an inlet end of the vent structure and is adapted for connection with an inlet duct from which the vent structure receives a flow of air. The outlet section is at an outlet end of the vent structure and includes an outlet slot that is adapted to direct the flow of air into a room. The transition section has a flared portion that diverges in cross-sectional area as it extends generally toward the outlet section. The transition section has a constricted portion located between the inlet-connector section and the outlet slot. The constricted portion is also located substantially centrally within a plane that is generally perpendicular to a direction of air flow. The constricted portion is adapted to restrict the flow of air through a central portion of the transition section, thereby restricting the flow of air exiting a corresponding central portion of the outlet slot.
In another aspect of the invention, a vent structure comprises an inlet-connector section, an outlet section, and a transition section. The inlet-connector section is substantially as described above. The outlet section is at an outlet end of the vent structure and includes a generally rectangular outlet slot adapted to direct the flow of air into a room. The outlet slot is defined by left and right end margins and generally parallel upper and lower margins. The upper and lower margins of the slot are longer in dimension than the left and right end margins, such that a width of the outlet slot is greater than a height of the outlet slot. The transition section is located between the inlet-connector section and the outlet section. The transition section has a flared portion that is defined by generally parallel upper and lower walls and left and ride side portions. The left and right side portions of the flared portion are angled relative to one another such that the flared portion diverges in width as it extends toward the outlet section. The upper and lower walls of the flared portion of the transition section are contoured in a manner to define a constricted portion of the transition section. The constricted portion is located generally centrally between the left and right side portions of the flared portion for restricting the flow of air through the constricted portion, and thereby restricting the flow of air exiting a corresponding generally central portion of the outlet slot.
In still another aspect of the invention, a vent structure includes an inlet-connector section, an outlet section, and a transition section, which provides fluid communication between the inlet-connector section and outlet section. The inlet-connector section and outlet section are substantially as described above. The transition section has a flared portion defined by upper and lower walls and left and right side portions. The left and right side portions are angled relative to one another such that the flared portion diverges in width as it extends toward the outlet section. At least one of the upper and lower walls of the flared portion has a protrusion that extends generally toward the other of the upper and lower walls. The protrusion extends in a manner to restrict a part of the flow of air through the flared portion, thereby restricting a corresponding part of the flow of air exiting the outlet slot.
Further objects, features, and advantages of the present invention, as well as the structure and operation of various embodiments of the present invention, are described in detail below with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a perspective view of a vent structure of the present invention;
FIG. 2
is a top plan view of the vent structure of
FIG. 1
;
FIG. 3
is a front elevational view of the vent structure of
FIG. 1
;
FIG. 4
is a side elevational view of the vent structure of
FIG. 1
;
FIG. 5
is a cross-sectional side view of the vent structure taken along the plane of line A—A in
FIG. 2
;
FIG. 6
is a top plan view of a prior art vent structure, including a schematic representation of a velocity profile of air exiting the outlet slot;
FIG. 7
is a top plan view of the vent structure of the present invention similar to
FIG. 2
, but including a schematic representation of a theoretically ideal uniform velocity profile of air exiting the outlet slot; and
FIG. 8
is a graphical representation of the results of one specific application of the present invention, as compared to the prior art.
Reference characters used in these drawings correspond with reference characters used throughout the Detailed Description of the Preferred Embodiments, which follows. These drawings, which are incorporated in and form a part of the specification, illustrate the preferred embodiments of the present invention and, together with the description, serve to explain the principles of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A vent structure of the present invention is represented generally in
FIGS. 1 through 5
by the reference numeral
10
. In general, the vent structure
10
comprises an inlet-connector section
12
, an outlet section
14
, and a transition section
16
located between the inlet-connector section and outlet section.
The inlet-connector section
12
is located at an inlet end
22
of the vent structure, and the outlet section
14
is located at an outlet end of the vent structure
24
. The inlet-connector section is adapted for connection with an inlet duct
26
from which the vent structure
10
receives a flow of air. Preferably, the inlet-connector section
12
is adapted to receive air from the inlet duct
26
generally along an inlet axis A (see FIG.
5
). The inlet duct
26
is supplied with air from an HVAC system (not shown). Preferably, the inlet-connector section
12
is adapted for connection with an inlet duct
26
of the type used the newer, smaller-diameter, cylindrical ducting designs configured for high velocity flow. Thus, preferably, the inlet-connector section
12
has a substantially cylindrical shape adapted to mate with the generally circular cross section of the an inlet duct
26
. Of course, inlet-connector sections and corresponding inlet ducts having different shapes and configurations could be used without departing from the scope of the present invention as claimed.
The outlet section
14
preferably includes a generally rectangular outlet slot
30
, which is adapted to direct the flow of air into a room or other area to be environmentally controlled. The rectangular outlet slot
30
is defined by left and right end margins
32
and
34
and generally parallel upper and lower margins
36
and
38
. The upper and lower margins
36
and
38
of the slot
30
are preferably longer in dimension than the left and right end margins
32
and
34
, such that, as best shown in
FIGS. 1 and 3
, the slot
30
is substantially wider than it is tall. Preferably, the cross-sectional area of the outlet slot
30
is greater than the cross-sectional area of the inlet-connector section
12
, and preferably the width of the outlet slot
30
is greater than the diameter of the cylindrical inlet-connector section
12
. The desirability of these relative dimensions and configurations is discussed below. Of course, outlet sections and outlet slots having different shapes and dimensions could be used without departing from the scope of the present invention as claimed.
As shown in
FIGS. 1
,
2
,
4
and
5
, the transition section
16
is located between the inlet-connector section
12
and outlet section
14
, and is adapted to provide fluid communication therebetween. That is, the transition section
16
is adapted to receive the flow of air from the inlet-connector section
12
and to carry it to the outlet section
14
. Preferably, the transition section
16
has a flared portion
50
, which is defined by generally parallel upper and lower walls
52
and
54
and left a rid right side portions
56
and
58
, which connect the upper and lower walls
52
and
54
to one another. As best shown in
FIGS. 1 and 2
, the left and right side portions
56
and
58
of the flared portion
50
are preferably angled relative to one another such that the flared portion
50
diverges in width as it extends from the inlet-connector section
12
to the outlet section
14
. Again, the upper and lower walls
52
and
54
of the flared portion
50
are preferably generally parallel with one another, so the angled left and right side portions
56
and
58
result in the flared portion
50
also diverging in cross-sectional area as it extends toward the outlet section
14
.
The transitional section
16
of the vent structure of the present invention has many of the same advantages as the vent structure disclosed in U.S. Pat. No. 6,168,518, assigned to Unico, Inc. Both vent structures connect between a small-diameter cylindrical airflow duct and a narrow rectangular outlet slot by way of an angularly flared transition section, which smoothly transitions the air flow from the circular cross section of the inlet duct to the narrow rectangular shape of the outlet slot. By smoothly changing the shape of the air flow (from the cylindrical shape of the inlet duct to the narrow rectangular configuration of the outlet slot) and by providing an outlet section
14
with a greater cross-sectional area than the inlet-connector section
12
, the creation of turbulence with the vent structure
10
, and noise generated thereby, is greatly reduced.
As shown in
FIG. 5
, the inlet-connector section
12
is adapted to receive air from the inlet duct
26
generally along the inlet axis A. Preferably, the transition section
16
and outlet section
14
of the vent structure
10
are configured to maintain the direction of air flow generally along the inlet axis A. Unlike this preferred embodiment of the vent structure
10
of the present invention, the vent structure disclosed in U.S. Pat. No. 6,168,518 has a curved transition section, which changes the direction of air flow so that the air discharged from the outlet slot is substantially perpendicular to the air received from the inlet duct. However, it should be understood that, although the preferred embodiment of the present invention shown in
FIGS. 1-5
does not include such a curved transition section, a curved transition section (having an angle of anywhere between 0 and 180 degrees) could be used with the vent structure
10
of the present invention, without departing from the scope of the invention as claimed.
To this point, the vent structure
10
described is similar to the vent structure disclosed in U.S. Pat. No. 6,168,518. However, a desirable feature of the vent structure
10
of the present invention is a constricted portion
70
of the transition section
16
located between the inlet-connector section
12
and the outlet slot
14
.
As best shown in
FIGS. 3 and 5
, the upper and lower walls
52
and
54
of the flared portion
50
of the transition section
16
are preferably contoured in a manner to define the constricted portion
70
. More specifically, each of the upper and lower walls
52
and
54
of the flared portion
50
includes a depressed section
72
and
74
, which form corresponding protrusions
76
and
78
on the interior surfaces of the upper and lower walls
52
and
54
that extend generally toward one another. Preferably, the constricted portion
70
is located midway between the left and right side portions
56
and
58
of the flared portion
50
for restricting the flow of air through a central portion of the transition section
16
. Stated another way, the constricted portion
70
is preferably located substantially centrally within a plane that is generally perpendicular to a direction of air flow, to thereby restrict the flow of air through the central portion of the transition section
16
. As explained below, this restriction of the flow of air through the central portion of the transition section
16
results in a restriction of the flow of air exiting a corresponding generally central portion of the outlet slot
30
.
Again, the transition section
16
and outlet section
14
of the vent structure
10
are preferably configured to maintain the direction of air flow generally along the inlet axis A. In this preferred embodiment, the constricted portion
70
of the transition section
16
is preferably aligned with the inlet-connector section
12
in a manner so that the constricted portion
70
is located within a central portion of a flow path of air received from the inlet duct
26
, generally along axis A shown in FIG.
5
. However, as noted above, a curved transition section (having an angle of anywhere between 0 and 180 degrees) could be used with the vent structure
10
of the present invention, without departing from the scope of the invention as claimed. In such an alternative embodiment having a curved transition section, the constricted portion
70
is still preferably located relative to the inlet-connector section
12
such that it is within a central portion of a flow path of air received from the inlet duct
26
, though that flow path may be correspondingly curved.
Whether the transition section
16
is curved (as described above) or straight (as shown in the Figures), the constricted portion
70
preferably restricts the flow of air through the central portion of the transition section
16
, which results in a restriction of the flow of air exiting a corresponding generally central portion of the outlet slot
30
. This, in turn, results in a more uniform velocity profile of air flow exiting the outlet slot
30
.
FIG. 6
is a top plan view of a prior art vent structure, including a schematic representation of a velocity profile
90
′ of air exiting the outlet slot As shown in
FIG. 6
, the prior art vent structure
10
′ includes an inlet-connector section
12
′, a transition section
16
′ and an outlet section
14
′ that are all generally aligned with one another so that air flow is generally maintained in the direction of axis A′. Thus, a central portion of the outlet slot is aligned with the inlet-connector section
12
′, which puts it directly in the flow path of air flowing from the inlet-connector section
12
′. While the diverging width of the transition section
16
′ results in some lateral diffusion of the air flowing from the inlet duct, because of the high velocity of the air flow received from the inlet duct, the flow is concentrated at a central portion of the vent structure, generally along axis A′. Consequently, the flow velocity of air exiting the outlet section
14
′ tends to be much greater at a central portion of the outlet section
14
′ adjacent to axis A′ (the higher velocity air is represented by longer arrows X) and flow velocity of exiting air tends to be lower toward left and right side portions
56
′ and
58
′ of the transition section
16
′ (the lower velocity air is represented by shorter arrows Y). Thus, velocity profile
90
′ is not uniform.
FIG. 7
is a top plan view of the vent structure
10
of the present invention, including a schematic representation of a theoretically ideal uniform velocity profile
100
of air exiting the outlet slot
30
. Again, in the preferred embodiment of the invention, the inlet-connector section
12
, transition section
16
and outlet section
14
are all generally aligned with one another, such that a central portion of the outlet slot
30
is aligned with the inlet-connector section
12
. However, the constricted portion (see
FIGS. 3 and 5
) interrupts the flow path of air between the inlet-connector section
12
and outlet section
14
, and thus reduces the velocity of air exiting a generally central portion of the outlet slot
30
. Some of the air flow that would otherwise proceed generally along axis A is diverted laterally (to the left or to the right of axis A as shown in FIG.
7
), thus increasing the velocity of air exiting lateral portions of the outlet section
14
. This, coupled with the diverging width of the transition section
16
, results in a much more uniform velocity profile
100
, with flow velocity of air exiting the outlet section
14
being generally the same at a central portion of the outlet section
14
adjacent to axis A as it is adjacent left and right side portions
56
and
58
of the transition section
16
(the air at uniform flow velocity is represented by arrows Z). Again,
FIG. 7
represents a theoretically ideal uniform velocity profile, with the velocity of air being equal along the entire width of the outlet slot
30
. In practice, such perfect uniformity would be difficult to achieve, and is not necessary to benefit from the improvement provided by the present invention.
FIG. 8
is a graphical representation of one specific application of the present invention to a vent structure that is 8.5 inches wide at a flow rate of 40 cubic feet per minute, and shows exemplary data for a velocity profile
200
produced by a vent structure embodying the present invention, as compared to a velocity profile
202
of a prior art vent structure having no restricted portion. While not perfectly uniform across the width of the vent structure, the profile
200
is substantially more uniform across the width of the outlet slot
30
than the velocity profile
202
of the prior art vent structure. Again, this is one exemplary set of data from a specific application of the present invention to one vent structure, and is not intended to limit the breadth or scope of the present invention, which is defined solely by the claims appended hereto and their equivalents.
As various modifications could be made in the constructions and methods herein described and illustrated without departing from the scope of the invention, it is intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative rather than limiting. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims appended hereto and their equivalents.
Claims
- 1. A vent structure for an air handling system, the vent structure comprising:an inlet-connector section at an inlet end of the vent structure, the inlet-connector section being adapted for connection with an inlet duct from which the vent structure receives a flow of air; an outlet section at an outlet end of the vent structure, the outlet section including an outlet slot adapted to direct the flow of air into a room; and a transition section between the inlet-connector section and outlet section, the transition section having a flared portion that diverges in cross-sectional area as it extends generally toward the outlet section, the transition section having a constricted portion located between the inlet-connector section and the outlet slot and located substantially centrally within a plane that is generally perpendicular to a direction of air flow, the constricted portion being adapted to restrict the flow of air through a central portion of the transition section, thereby restricting the flow of air exiting a corresponding central portion of the outlet slot.
- 2. The vent structure of claim 1 wherein a cross-sectional area of the outlet slot is greater than a cross-sectional area of the inlet connector section.
- 3. The vent structure of claim 1 wherein the inlet-connector section has a substantially cylindrical shape adapted to mate with an inlet duct having a generally circular cross section.
- 4. The vent structure of claim 3 wherein a width of the outlet slot is greater than a diameter of the cylindrical inlet-connector section.
- 5. The vent structure of claim 3 wherein the outlet slot has a generally rectangular configuration and wherein the transition section is shaped and configured to provide a smooth transition between the circular cross section of the inlet duct and the generally rectangular configuration of the outlet slot.
- 6. The vent structure of claim 1 wherein the constricted portion of the transition section is generally aligned with the inlet connector section in a manner so that the constricted portion is located within a central portion of a flow path of air received from the inlet duct.
- 7. The vent structure of claim 1 wherein the inlet-connector section is adapted to receive air from an inlet duct generally along an inlet axis, and wherein the transition and outlet sections of the vent structure are configured to maintain the direction of air flow generally along the inlet axis.
- 8. The vent structure of claim 7 wherein the constricted portion of the transition section lies generally along the inlet axis.
- 9. The vent structure of claim 1 wherein the outlet slot has a generally rectangular configuration defined by left and right end margins and generally parallel upper and lower margins, the upper and lower margins of the slot being longer in dimension than the left and right end margins such that a width of the outlet slot is greater than a height of the outlet slot, and wherein the flared portion of the transition section is defined by generally parallel upper and lower walls and left and right side portions, the left and right side portions being angled relative to one another such that the flared portion diverges in width as it extends toward the outlet section.
- 10. The vent structure of claim 9 wherein the constricted portion of the transition section is defined by the upper and lower walls of the flared portion, which are contoured in a manner to restrict the flow of air through the central portion of the transition section and thereby provide a generally uniform velocity profile of air flow exiting the outlet slot.
- 11. A vent structure for an air handling system, the vent structure comprising:an inlet-connector section at an inlet end of the vent structure, the inlet-connector section being adapted for connection with an inlet duct from which the vent structure receives a flow of air; an outlet section at an outlet end of the vent structure, the outlet section including a generally rectangular outlet slot adapted to direct the flow of air into a room, the outlet slot being defined by left and right end margins and generally parallel upper and lower margins, the upper and lower margins of the slot being longer in dimension than the left and right end margins such that a width of the outlet slot is greater than a height of the outlet slot; and a transition section between the inlet-connector section and outlet section, the transition section having a flared portion defined by generally parallel upper and lower walls and left and right side portions, the left and right side portions of the flared portion being angled relative to one another such that the flared portion diverges in width as it extends toward the outlet section, the upper and lower walls of the flared portion of the transition section being contoured in a manner to define a constricted portion of the transition section located generally centrally between the left and right side portions of the flared portion for restricting the flow of air through the constricted portion, thereby restricting the flow of air exiting a corresponding generally central portion of the outlet slot.
- 12. The vent structure of claim 11 wherein a cross-sectional area of the outlet slot is greater than a cross-sectional area of the inlet connector section.
- 13. The vent structure of claim 11 wherein the inlet-connector section has a substantially cylindrical shape adapted to mate with an inlet duct having a generally circular cross section.
- 14. The vent structure of claim 13 wherein the transition section is shaped and configured to provide a smooth transition between the circular cross section of the inlet duct and the generally rectangular outlet slot.
- 15. The vent structure of claim 11 wherein the constricted portion of the transition section is generally aligned with the inlet-connector section in a manner so that the constricted portion is located within a central portion of a flow path of air received from the inlet duct.
- 16. The vent structure of claim 11 wherein the inlet-connector section is adapted to receive air from an inlet duct generally along an inlet axis, and wherein the transition and outlet sections of the vent structure are configured to maintain a direction of flow generally along the inlet axis.
- 17. The vent structure of claim 16 wherein the constricted portion of the transition section lies generally along the inlet axis.
- 18. A vent structure for an air handling system, the vent structure comprising:an inlet-connector section at an inlet end of the vent structure, the inlet-connector section being adapted for connection with an inlet duct from which the vent structure receives a flow of air; an outlet section at an outlet end of the vent structure, the outlet section including a generally rectangular outlet slot adapted to direct the flow of air into a room, the outlet slot being defined by left and right end margins and generally parallel upper and lower margins, the upper and lower margins of the slot being longer in dimension than the left and right end margins such that a width of the outlet slot is greater than a height of the outlet slot; and a transition section adapted to provide fluid communication between the inlet-connector section and outlet section, the transition section having a flared portion defined by upper and lower walls and left and right side portions, the left and right side portions being angled relative to one another such that the flared portion diverges in width as it extends toward the outlet section, at least one of the upper and lower walls of the flared portion having a protrusion that extends generally toward the other of the upper and lower walls in a manner to restrict a part of the flow of air through the flared portion, thereby restricting a corresponding part of the flow of air exiting the outlet slot.
- 19. The vent structure of claim 18 wherein the protrusion occupies a generally central portion of a flow path of air through the flared portion so that a corresponding central part of the flow of air exiting the outlet slot is restricted, thereby providing a generally uniform velocity profile of air flow exiting the outlet slot.
- 20. The vent structure of claim 18 wherein the inlet-connector section has a substantially cylindrical shape adapted to mate with an inlet duct having a generally circular cross section.
- 21. The vent structure of claim 20 wherein the transition section is shaped and configured to provide a smooth transition between the circular cross section of the inlet duct and the generally rectangular outlet slot.
- 22. The vent structure of claim 18 wherein each of the upper and lower walls of the flared portion includes a protrusion that extends generally toward the other of the upper and lower walls in a manner to restrict the part of the flow of air through the flared portion.
- 23. The vent structure of claim 22 wherein the protrusions are defined by contoured portions of the upper and lower walls of the flared portion, which define a constricted portion of the transition section, which restricts the flow of air passing through the constricted portion, thereby restricting the flow of air exiting a corresponding portion of the outlet slot.
- 24. The vent structure of claim 23 wherein the constricted portion is generally aligned with the inlet-connector section in a manner so that the constricted portion is located generally within a center of the flow path of air received from the inlet duct.
- 25. The vent structure of claim 18 wherein the inlet-connector section is adapted to receive air from an inlet duct generally along an inlet axis, and wherein the transition and outlet sections of the vent structure are configured to maintain a direction of flow generally along the inlet axis.
- 26. The vent structure of claim 25 wherein the constricted portion lies generally along the inlet axis.
US Referenced Citations (12)