Fluid handling – Line condition change responsive valves – Direct response valves
Reexamination Certificate
2001-09-25
2003-12-09
Rivell, John (Department: 3753)
Fluid handling
Line condition change responsive valves
Direct response valves
C137S527000, C137S271000, C285S004000
Reexamination Certificate
active
06659126
ABSTRACT:
The present invention relates to a backflow preventor and, in particular, to a preventor with a provision for adjusting the outlet direction.
BACKGROUND OF THE INVENTION
Check valves are well known for use in assuring that a flow through a conduit occurs only in a predefined direction. Check valves are used, for example, in backflow prevention assemblies to prevent backflow of one fluid body into another. Back flow prevention is often used in connection with protecting potable water supplies from contaminants which could otherwise be introduced into it via back-siphonage or back-pressure. Many backflow preventors are designed to accommodate pressure commonly encountered in municipal water supplies, such as 150 psi (1030 kPa) or more.
Several factors are important in designing or selecting a backflow preventor for a particular use, including performance (e.g., minimizing pressure drop), serviceability, and ease and cost of installation.
Many backflow preventors are configured such that the direction of inlet and the direction of outlet flow are predetermined. In these devices, when it is desired to provide an outlet flow direction that is different (with respect to the inlet flow direction) from the predetermined direction, additional fittings such as elbows, U-joints, L-joints, T-joints and the like, must be connected. These additional fittings not only add to the cost of parts, labor and design involved in installing these devices, but also contribute to undesirable pressure loss. These additional fittings further take up volume and thus are impractical in applications having close clearances. Such pressure loss can be particularly troublesome in applications where maintenance of pressure is important such as in fire protection systems and high rise buildings.
In previous devices, maximizing serviceability has been incompatible with also maximizing the performance and installation factors. Thus, in past devices, efforts to increase the performance and ease of installation has produced devices with decreased serviceability.
FIG. 6
depicts, schematically, a previous backflow preventor
110
which attempted to provide ease of serviceability by including both valves in
112
a
,
112
b
in a vertical configuration and a cover
114
which, when removed, permits access to the valves
112
a
,
112
b
(e.g., for maintenance purposes) in a vertical direction. The device shown in
FIG. 6
, however, provides a less than optimal performance. This is at least partially because, owing to the orientation of the valves
112
a
,
112
b
with respect to the inlet opening
116
and outlet opening
118
flow through the valve openings
116
,
118
is forced to follow a divergent path (indicated by solid arrow streamlines
120
a
,
120
b
). The blocking action of the valve disks
122
a
,
122
b
, causing this divergent flow
120
a
,
120
b
, provides resistance to flow through the backflow preventor
110
and increases the pressure drop which the backflow preventor produces.
The device depicted in
FIG. 6
also has deficiencies from the point of view of installation. In general terms, the cost of installation is least when the backflow preventor occupies the smallest amount of space. Thus, when a backflow preventor is installed in a building, it is desired to minimize the floor space required for installation. When the backflow preventor is installed outside a building, the expense of installation is related to the size of the enclosure required (e.g., enclosure
132
depicted in FIG.
7
). When the backflow preventor is installed underground, it is desirable to minimize the size of the trench (not shown) required for underground installation.
As seen in
FIG. 6
, the inlet conduit and outlet conduit
124
,
126
occupy a horizontal distance
128
which determines the minimum amount of space theoretically needed for installation of a backflow preventor. The upper portion
134
of the backflow preventor
110
occupies a horizontal extent
136
which is only slightly greater than theoretically minimum horizontal extent
128
required for installation. However, the lower portion
138
has a minimum horizontal extent
142
which is substantially greater, principally because the handle portions
144
a
,
144
b
of the shutoff valves extend outward from the housing
146
in a direction which is parallel to the axis of the conduits
124
,
126
(i.e., parallel to a line passing through the conduits
124
,
126
). Moreover, an even larger horizontal expanse
148
is required to accommodate opening of the shutoff valves since the handles
144
a
,
144
b
move in a direction parallel to the axis of the conduits
124
,
126
.
FIG. 7
depicts another configuration for a backflow preventor which also has certain deficiencies. The axes
152
a
,
152
b
along which the first and second check valves
154
a
,
154
b
extend (defined, for these purposes, as a line passing through the center of the inlet port of the valves
154
a
,
154
b
and parallel to the direction of flow into the valves) are parallel and both extend at an angle of about 45° to vertical. Access for maintenance is obtained by removing covers
156
a
,
156
b
to provide openings. The openings lie in planes
158
a
,
158
b
which are inclined to the horizontal by about 45°. Because neither of the openings lies in a horizontal plane, the device does not provide for access in a vertical direction. This represents a drawback to the serviceability of the device in FIG.
7
.
Installation of the device shown in
FIG. 7
also has certain drawbacks. Installation requires certain additional parts such as 90° elbows
162
a
,
162
b
to change the flow direction from the upward and downward flow of the inlet and outlet conduits
124
,
126
to the horizontal flow direction of a backflow preventor
164
. The size of the enclosure
132
required is relatively large to accommodate the extra parts
162
a
,
162
b
and since the two shutoff valves
166
a
,
166
b
and check valves
154
a
,
154
b
are generally linearly arrayed. Because of the change in flow direction, the flanges
168
a
,
168
b
for installing the backflow preventor
164
are vertically oriented. This requires provision of supports
172
a
,
172
b
for supporting and positioning the backflow preventor
164
at least during installation. As with the device depicted in
FIG. 6
, the check valves
154
a
,
154
b
of the device in
FIG. 7
are of a type requiring that the flow through the valves be divergent
120
a
,
120
b
around the edges of the valve disks.
FIG. 8
depicts another type of previously-provided backflow preventor also having certain deficiencies.
The axes
152
c
,
152
d
, along which the first and second check valves
154
a
,
154
b
extend, are perpendicular and both extend at an angle of 45° to vertical. Covers
156
c
,
156
d
cover access openings which lie in planes
158
c
,
158
d
, neither of which lies in a horizontal plane. Additional parts such as elbows
162
c
,
162
d
are required for installation. The two shutoff valves
166
c
,
166
d
and the two check valves
154
c
,
154
d
are generally linearly arrayed. The means for connection
168
c
,
168
d
of the inlet and outlet of the stop valves
166
c
,
166
d
are vertically oriented. The check valves
154
c
,
154
d
are of a type requiring that the flow through the valves be divergent
120
a
,
120
b
around the edges of the valve disks.
Typically, a check valve is designed to maintain its open configuration as long as there is flow through the valve. Once the flow stops or drops below a predetermined value, the check valve closes. Typically, check valves are designed so that, once the valve is closed, the inlet pressure must exceed a predetermined threshold before the valve will open. Usually, a single structure, typically a spring, is used both to provide the force to hold the valve closed (until the threshold is reached), and to provide the biasing force which moves the valve from the opened to the closed position. Because the biasing device provides some force tending to close the valve, even during normal f
Dunmire Charles W.
Fields Richard D.
Whitelaw Dennis G.
Baker & Hostetler LLP
Rivell John
SPX Corporation
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