MANHOLE CLOSURE ASSEMBLY WITH VALVE RELIEF MEANS
United States Patent 3712009
Manhole closure assembly primarily prevents drainage and storm water from emptying into manhole leading to sewerage system. Closure assembly comprises cover plate sealing off manhole opening. First valve is secured to cover plate for relieving pressure inside manhole when pressure therein exceeds predetermined amount, and second valve member is secured to cover plate for relieving vacuum inside manhole when vacuum therein exceeds predetermined amount.
US Patent References:
Reel
Kieber - August 1950 - 2518533
Control system
Pfau et al. - September 1928 - 1685750
/1099073.html
Moir - June 1914 - 1099073
Weatherproof sidewalk door
Michelman - December 1931 - 1837916
Support for manhole cover and the like
Hurt, Jr. - March 1967 - 3308727
Reel
Kieber - August 1950 - 2518533
Control system
Pfau et al. - September 1928 - 1685750
/1099073.html
Moir - June 1914 - 1099073
Weatherproof sidewalk door
Michelman - December 1931 - 1837916
Support for manhole cover and the like
Hurt, Jr. - March 1967 - 3308727
Application Number:
05/089301
Publication Date:
01/23/1973
Filing Date:
11/13/1970
View Patent Images:
Export Citation:
Assignee:
Compagna, Benjamin J. (Newark, DE)
, Truono Eugene J. (Wilmington, DE)
, Truono Eugene J. (Wilmington, DE)
Primary Class:
Other Classes:
52/198, 404/25
International Classes:
E02D29/14; E02D29/14
Field of Search:
52/19-21,124,198,302,495 94/34,35,37 137/493.8,541,533.29
US Patent References:
| 2009132 | Manhole construction | July 1935 | Gehris | |
| 1153051 | September 1915 | Fairhurst | ||
| 1630557 | Cover for manholes | May 1927 | Woodrow | |
| 3039232 | Connector for mounting roof forming panels | June 1962 | Dunn | |
| 2599622 | Resilient seal safety valve | July 1952 | Folmsbee | |
| 3267631 | Mounting means for sheet material | August 1966 | Hammitt | |
| 3192671 | Panel structures | July 1965 | Smith | |
| 3001537 | September 1961 | Shepherd | ||
| 3288167 | Relife valve | November 1966 | Gibson |
Primary Examiner:
Abbott, Frank L.
Assistant Examiner:
Braun, Leslie A.
Claims:
What is claimed is
1. The combination of a manhole closure assembly for preventing drainage and storm water from emptying into a manhole opening and an annular manhole frame surrounding the upper portion of the manhole, the manhole frame including an upper lid supporting flange and a lower flange for supporting the manhole closure assembly, and the closure assembly including a cover plate supported by the lower flange of the manhole frame in covering relationship over the manhole opening, the cover plate including a pair of substantially semicircular segments supported along their arcuate edge portions by the lower flange of the manhole frame, means for connecting the semicircular segments together along their diametral edge portions, a first valve member secured to the cover plate constructed and arranged to relieve pressure inside the manhole when the pressure therein exceeds a predetermined amount, and a second valve member secured to the plate constructed and arranged to relieve vacuum inside the manhole when the vacuum therein exceeds a predetermined amount.
2. The combination of claim 1 in which the first and second valve members each comprise a stationary valve body having at least one passageway therein that provides communication between the up side and down side of the cover plate when the valve member is open, and each passageway having a taper with the upper open end thereof smaller than the lower open end thereof.
3. The combination of claim 1 in which the uppermost ends of the first and second valve members are elevated above the cover plate.
4. The combination of claim 1 in which the means for connecting the semicircular segments together includes a connector strip supported at its ends by the lower flange of the manhole frame and securing the semicircular segments together along their diametral edge portions.
1. The combination of a manhole closure assembly for preventing drainage and storm water from emptying into a manhole opening and an annular manhole frame surrounding the upper portion of the manhole, the manhole frame including an upper lid supporting flange and a lower flange for supporting the manhole closure assembly, and the closure assembly including a cover plate supported by the lower flange of the manhole frame in covering relationship over the manhole opening, the cover plate including a pair of substantially semicircular segments supported along their arcuate edge portions by the lower flange of the manhole frame, means for connecting the semicircular segments together along their diametral edge portions, a first valve member secured to the cover plate constructed and arranged to relieve pressure inside the manhole when the pressure therein exceeds a predetermined amount, and a second valve member secured to the plate constructed and arranged to relieve vacuum inside the manhole when the vacuum therein exceeds a predetermined amount.
2. The combination of claim 1 in which the first and second valve members each comprise a stationary valve body having at least one passageway therein that provides communication between the up side and down side of the cover plate when the valve member is open, and each passageway having a taper with the upper open end thereof smaller than the lower open end thereof.
3. The combination of claim 1 in which the uppermost ends of the first and second valve members are elevated above the cover plate.
4. The combination of claim 1 in which the means for connecting the semicircular segments together includes a connector strip supported at its ends by the lower flange of the manhole frame and securing the semicircular segments together along their diametral edge portions.
Description:
BACKGROUND OF THE INVENTION
The present invention relates to a manhole closure assembly, and more particularly to a closure that prevents drainage and storm water from emptying into a manhole that leads to a sewerage system.
The primary reason for segregating sanitary or sewerage systems from systems designed to handle storm and drainage water is an obvious one. Specifically, when drainage and storm water empties into a sanitary system the sewerage treatment plant must necessarily handle the storm water in addition to the sewage material. These conditions place an unnecessary burden on the sewage treatment facility. Standard frames and covers for manholes leading to sanitary or sewerage systems include cover constructions with passageways therein that enable storm water to empty into the sewerage system. The passageways in the standard cover constructions are provided for relieving internal pressure in the sanitary system as well as preventing vacuum build-ups in the system. It is impossible to simply plug up or otherwise eliminate the passageways in these covers since pressure developed inside the sanitary system could easily produce a force sufficient to blow the cover away from its seated position at the manhole opening. Also, unrelieved vacuum can also cause damage to the sanitary systems.
With an over designed sewerage system and/or an over capacity sewerage treatment plant, storm water draining into the sewerage system does not present any significant problems. However, with many systems capacity is now 100 percent, and 40 percent of this capacity is the direct result of storm and drainage water. Storm water volume draining into sewerage systems is much more significant today than it was many years ago, and the key factor is that today there is significantly less impervious area than there was several years ago. This factor is due to larger street areas that collect more drainage water as well as smaller building lots which cut down on the amount of overall impervious area. These factors have significantly contributed to the problem of overtaxing present sanitary systems. By significantly preventing storm and drainage water from emptying into sanitary and sewerage systems, existing systems can easily handle an additional 60 percent sewerage capacity.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a manhole closure assembly that effectively and easily seals off a manhole opening in an efficient and highly economical manner to thereby prevent drainage and storm water from emptying into the manhole.
Another object of the present invention is to provide a highly efficient and easy to follow method for preventing drainage and storm water from emptying into a manhole.
In accordance with the present invention a manhole closure assembly is provided for primarily preventing drainage and storm water from emptying into a manhole opening covered by the closure. The closure assembly comprises a cover plate sealing off the manhole opening with a first valve member secured to the plate arranged to relieve pressure inside the manhole when the pressure therein exceeds a predetermined amount. A second valve member also secured to the plate is arranged to relieve vacuum inside the manhole when the vacuum therein exceeds a predetermined amount.
In one embodiment of the present invention the cover plate comprises a pair of semicircular segments, and a connector strip seals and connects the semicircular segments together along their diametral edges. Preferably, the connector strip has a substantially I-shaped cross section. One valve member is secured to one of the semicircular segments of the cover plate while the other valve member is secured to the second semicircular segment of the plate.
In another aspect of the present invention the manhole closure is in combination with an annular manhole frame surrounding the upper portion of the manhole and anchored thereto. The annular manhole frame has an internal inwardly directed flange that supports the cover plate in sealing relationship over the manhole opening by engaging the arcuate edges of the semicircular segments of the cover plate and the ends of the connector strip. Sealing material is between the inwardly directed supporting flange of the manhole frame and the arcuate edges of the semicircular segments of the cover plate.
Preferably, the valve members of the present invention each comprise a stationary valve body having at least one passageway therein that provides communication between the up side and down side of the cover plate when the valve member is open. Each passageway has a taper with the upper open end thereof smaller than the lower open end thereof. Specifically, each valve member includes a valve body with a seat portion, a movable valve element and stem, and a biasing device between the valve stem and the valve body normally urging the valve element against the seat portion of the valve body. The valve element remains seated until the force acting upon the movable valve element in the direction opposite the force generated by the biasing device is greater than the force of the biasing device. When this condition occurs the movable valve element moves away from the seat portion of the valve body to open the valve member. In one valve member of the present invention the seat portion includes a substantially circular sharpened edge that engages the movable valve element. A ring of resilient material is carried by the movable valve element, and the ring is adapted to be engaged by the sharpened edge of the valve body when the valve member is closed.
The cover plate may comprise a one piece circular segment with a pair of spaced apart housings fixed to the underside thereof. The valve members are secured to the housings with one valve member associated with each housing. Passageways are located in the cover plate directly over each housing for providing communication between the up side of the cover plate and the interior of the housings.
BRIEF DESCRIPTION OF THE DRAWING
Novel features and advantages of the present invention in addition to those mentioned above will become apparent to those skilled in the art from a reading of the following detailed description in conjunction with the accompanying drawing wherein:
FIG. 1 is a top plan view of a manhole closure assembly according to the present invention;
FIG. 2 is a sectional view taken along line 2--2 of FIG. 1;
FIG. 3 is a top plan view of another embodiment of the present invention;
FIG. 4 is a sectional view taken along line 4--4 of FIG. 3;
FIG. 5 is a side elevational view of a valve member according to the present invention;
FIG. 6 is a bottom plan view of the valve member shown in FIG. 5;
FIG. 7 is a sectional view taken along line 7--7 of FIG. 6 with the valve member in its open position;
FIG. 8 is a side elevational view of another valve member according to the present invention with portions broken away to show detail and with the movable valve element shown in its unseated position in phantom outline; and
FIG. 9 is a bottom plan view of the valve member shown in FIG. 8.
DETAILED DESCRIPTION OF THE INVENTION
Referring in more particularity to the drawing, FIGS. 1 and 2 illustrate a manhole closure assembly 10 for primarily preventing drainage and storm water from emptying into a manhole 12 that leads to a sewerage system. As is well known, the upper end of most manhole constructions is surrounded by an annular manhole frame 14 embedded in a road bed 16 or similar surface construction. The annular manhole frame has an upper inwardly directed flange 18 for supporting a standard manhole cover or lid (not shown). The manhole lid has passageways therein, as is well known.
The manhole cover assembly 10 of the present invention comprises a cover plate 20 fabricated from rigid metal or similar material including a pair of semicircular segments 22, 24 and a connector strip or bar 26 that seals, supports and connects the semicircular segments together along their diametral edges 28. The bar 26 may also be constructed of rigid metal and has an I-shaped cross section. As shown in FIG. 2, the annular manhole frame 14 has a lower inwardly directed flange 30 that supports the arcuate edges 32 of the semicircular segments 22, 24 of the cover plate 20. The flange 30 also supports the ends 34 of the connector strip 26. The two piece construction of the cover plate 20 enables the plate to be easily positioned in sealing relationship over the manhole opening. Caulking or other suitable sealing material 36 is located between the flange 30 and the arcuate edges of the cover plate 20. Sealing material is also located at the juncture between the diametral edges 28 and the connector strip 26 to provide an air tight seal of the cover plate over the manhole opening. The weight of the manhole cover assembly is usually sufficient to hold it in place over the manhole opening. However, suitable fastening structure may be provided if a more positive hold down is desired.
A first or pressure relief valve member 38 is secured to the semicircular segment 22 of the cover plate 20 for relieving internal pressure inside the manhole 12. Additionally, a second or vacuum relief valve 40 is secured to the semicircular segment 24 of the cover plate 20 for relieving vacuum that develops inside the manhole 12. As explained more fully below in conjunction with the details of FIGS. 5-7, the valve members 38, 40 function to relieve pressure and vacuum inside the manhole 12 when the pressure therein exceeds a predetermined amount, such as, for example, five pounds per square inch above atmospheric pressure, and also to relieve vacuum in the manhole when it exceeds a predetermined amount, such as, for example, five pounds per square inch below atmospheric pressure.
FIGS. 3 and 4 illustrate another movable closure assembly 50 according to the present invention wherein a standard manhole cover or lid 52 is slightly modified so as to carry a pressure relief valve member 54 and a vacuum relief valve member 56. In this regard, a pair of annular housings 58 are formed on the underside of the cover 52 directly below passageways 60 formed in the cover 52. As is clear from FIGS. 3 and 4, the passageways 60 in the cover 52 provide communication between the up side of the cover 52 and the interior of the annular housings 58. Each housing is sealed off at its lower end by a disc 62 which carries one of the valve members. Suitable fasteners such as 64 are provided for anchoring each disc to its respective annular housing 58. The valve members 54, 56 function to relieve pressure and vacuum inside the manhole 12 when these variables exceed predetermined amounts. The details of the valve members 54, 56 are explained below in conjunction with FIGS. 8 and 9. The manhole cover 52 functions as a cover plate for sealing off the manhole opening. Sealing material or a suitable gasket 66 is located between the lower peripheral edge portion of the cover 52 and the supporting flange 18 of the annular manhole frame 14.
Referring now to FIGS. 5-7, the details of the valve member 38 are shown it being understood that the vacuum relief valve member 40 is substantially the same as valve 38 except that the vacuum valve 40 opens in a downward direction to relieve vacuum while the pressure valve 38 moves in an upward direction to relieve pressure. The pressure valve 38 includes a stationary valve body 70 fabricated from aluminum, for example, having a valve seat portion 72. The valve body 70 is secured to the cover plate 20 by a locking ring arrangement 73. The valve 38 also includes a movable valve element 74 and valve stem 76, and a coil spring 78 that reacts between the valve stem and the stationary valve body 70. Passageways 80 are located in the valve body for providing communication between the up side and down side of the cover plate 20 when the valve is open. The passageways 80 in the pressure relief valve 38 are tapered with an increasing cross sectional area in the downward direction. The tapered passageways provide a self-cleaning function, as explained more fully blow. The movable valve element 74 carries a ring of resilient material 82 which engages the seat portion 72 of the valve body 70 when the valve member is closed. As shown best in FIG. 7, the valve seat portion 72 has a circular sharpened edge 84 that provides an air tight seal with the resilient ring 82 carried by the movable valve element 74 when the valve is closed. Additionally, slit or other material usually accumulates on top of the cover plate 20 and may reach a height close to the height of the valve seat 72. In such instances the sharpened edge 84 cuts through the silt to effectively close the valve when closure of the valve is desired.
Coil spring 78 is designed to hold the movable valve element 74 against the stationary valve body until the force acting upon the underside of the movable valve element is greater than the force of the coil spring 78 which acts in an opposite direction. Thus, when the pressure inside the manhole 12 exceeds 5 pounds per square inch, for example, the force generated by that pressure on the movable valve element 74 is sufficient to urge the valve element in an upward direction to thereby relieve the pressure inside the manhole. When the valve opens water, slit, and silt, foreign material which accumulates on top of the cover plate is flushed through the passageways 80 before the valve 38 closes. The tapered configuration of the passageways 80 functions to assist in maintaining them free of obstructions.
As mentioned above, the vacuum relief valve 40 is practically identical to the pressure relief valve 38 except for its orientation. Additionally, the passageways in the stationary valve body of the vacuum relief valve 40 are tapered in an opposite direction relative to the movable valve element 74. Thus, the vacuum relief valve 40 has the same self-cleaning characteristics as the pressure relief valve even though the vacuum valve is oriented so that the movable valve element 74 is on the down side of the cover plate 20. When the downward pull on the exterior of the movable valve element 74 of the vacuum relief valve 40 exceeds the force generated by the coil spring 78, the valve is pulled open to thereby relieve the vacuum generated inside the manhole 12. When the force of the coil spring exceeds the downward pull on the movable valve element 74 the vacuum relief valve is snapped closed.
The valve members 54, 56 associated with the embodiment of the invention specifically illustrated in FIGS. 3 and 4, are shown in detail in FIGS. 8 and 9. In the manhole closure assembly 50, the pressure relief valve 54 is identical to the vacuum relief valve 56 except that the movable valve element of the pressure relief valve moves in an upward direction when the valve is opened while the valve element of the vacuum relief valve moves in a downward direction when the valve is opened. The valve 54 includes a stationary valve body 90 secured to the disc 62 of the cover plate assembly 50, as shown in FIG. 8. Sealing material 92 provides an air tight seal between the body 90 and the disc 62. Passageways 94 are located in the body 90 for providing communication between the up side and down side of the manhole closure assembly when the valve is opened. A movable valve element 96 secured to a valve stem 98 moves away from the valve seat 100 of the body 90 when the force on the lower surface of the valve element 96 is greater than the force generated by the coil spring 102. As is clear, the coil spring 102 reacts between a stationary spring seat 104 and the movable valve stem 98. The movable valve element 96 carries a ring of resilient material 106 that engages the seat 100 of the valve body 90 when the valve is closed.
Each of the embodiments of the present invention provides a manhole closure assembly for sealing off the opening of a manhole construction that leads to a sewerage system. The closure prevents storm and drainage water from emptying into the manhole. Excessive pressure inside the manhole is readily relieved when it exceeds a predetermined amount. Similarly, vacuum build-ups inside the manhole are relieved by a suitable vacuum relief.
The present invention relates to a manhole closure assembly, and more particularly to a closure that prevents drainage and storm water from emptying into a manhole that leads to a sewerage system.
The primary reason for segregating sanitary or sewerage systems from systems designed to handle storm and drainage water is an obvious one. Specifically, when drainage and storm water empties into a sanitary system the sewerage treatment plant must necessarily handle the storm water in addition to the sewage material. These conditions place an unnecessary burden on the sewage treatment facility. Standard frames and covers for manholes leading to sanitary or sewerage systems include cover constructions with passageways therein that enable storm water to empty into the sewerage system. The passageways in the standard cover constructions are provided for relieving internal pressure in the sanitary system as well as preventing vacuum build-ups in the system. It is impossible to simply plug up or otherwise eliminate the passageways in these covers since pressure developed inside the sanitary system could easily produce a force sufficient to blow the cover away from its seated position at the manhole opening. Also, unrelieved vacuum can also cause damage to the sanitary systems.
With an over designed sewerage system and/or an over capacity sewerage treatment plant, storm water draining into the sewerage system does not present any significant problems. However, with many systems capacity is now 100 percent, and 40 percent of this capacity is the direct result of storm and drainage water. Storm water volume draining into sewerage systems is much more significant today than it was many years ago, and the key factor is that today there is significantly less impervious area than there was several years ago. This factor is due to larger street areas that collect more drainage water as well as smaller building lots which cut down on the amount of overall impervious area. These factors have significantly contributed to the problem of overtaxing present sanitary systems. By significantly preventing storm and drainage water from emptying into sanitary and sewerage systems, existing systems can easily handle an additional 60 percent sewerage capacity.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a manhole closure assembly that effectively and easily seals off a manhole opening in an efficient and highly economical manner to thereby prevent drainage and storm water from emptying into the manhole.
Another object of the present invention is to provide a highly efficient and easy to follow method for preventing drainage and storm water from emptying into a manhole.
In accordance with the present invention a manhole closure assembly is provided for primarily preventing drainage and storm water from emptying into a manhole opening covered by the closure. The closure assembly comprises a cover plate sealing off the manhole opening with a first valve member secured to the plate arranged to relieve pressure inside the manhole when the pressure therein exceeds a predetermined amount. A second valve member also secured to the plate is arranged to relieve vacuum inside the manhole when the vacuum therein exceeds a predetermined amount.
In one embodiment of the present invention the cover plate comprises a pair of semicircular segments, and a connector strip seals and connects the semicircular segments together along their diametral edges. Preferably, the connector strip has a substantially I-shaped cross section. One valve member is secured to one of the semicircular segments of the cover plate while the other valve member is secured to the second semicircular segment of the plate.
In another aspect of the present invention the manhole closure is in combination with an annular manhole frame surrounding the upper portion of the manhole and anchored thereto. The annular manhole frame has an internal inwardly directed flange that supports the cover plate in sealing relationship over the manhole opening by engaging the arcuate edges of the semicircular segments of the cover plate and the ends of the connector strip. Sealing material is between the inwardly directed supporting flange of the manhole frame and the arcuate edges of the semicircular segments of the cover plate.
Preferably, the valve members of the present invention each comprise a stationary valve body having at least one passageway therein that provides communication between the up side and down side of the cover plate when the valve member is open. Each passageway has a taper with the upper open end thereof smaller than the lower open end thereof. Specifically, each valve member includes a valve body with a seat portion, a movable valve element and stem, and a biasing device between the valve stem and the valve body normally urging the valve element against the seat portion of the valve body. The valve element remains seated until the force acting upon the movable valve element in the direction opposite the force generated by the biasing device is greater than the force of the biasing device. When this condition occurs the movable valve element moves away from the seat portion of the valve body to open the valve member. In one valve member of the present invention the seat portion includes a substantially circular sharpened edge that engages the movable valve element. A ring of resilient material is carried by the movable valve element, and the ring is adapted to be engaged by the sharpened edge of the valve body when the valve member is closed.
The cover plate may comprise a one piece circular segment with a pair of spaced apart housings fixed to the underside thereof. The valve members are secured to the housings with one valve member associated with each housing. Passageways are located in the cover plate directly over each housing for providing communication between the up side of the cover plate and the interior of the housings.
BRIEF DESCRIPTION OF THE DRAWING
Novel features and advantages of the present invention in addition to those mentioned above will become apparent to those skilled in the art from a reading of the following detailed description in conjunction with the accompanying drawing wherein:
FIG. 1 is a top plan view of a manhole closure assembly according to the present invention;
FIG. 2 is a sectional view taken along line 2--2 of FIG. 1;
FIG. 3 is a top plan view of another embodiment of the present invention;
FIG. 4 is a sectional view taken along line 4--4 of FIG. 3;
FIG. 5 is a side elevational view of a valve member according to the present invention;
FIG. 6 is a bottom plan view of the valve member shown in FIG. 5;
FIG. 7 is a sectional view taken along line 7--7 of FIG. 6 with the valve member in its open position;
FIG. 8 is a side elevational view of another valve member according to the present invention with portions broken away to show detail and with the movable valve element shown in its unseated position in phantom outline; and
FIG. 9 is a bottom plan view of the valve member shown in FIG. 8.
DETAILED DESCRIPTION OF THE INVENTION
Referring in more particularity to the drawing, FIGS. 1 and 2 illustrate a manhole closure assembly 10 for primarily preventing drainage and storm water from emptying into a manhole 12 that leads to a sewerage system. As is well known, the upper end of most manhole constructions is surrounded by an annular manhole frame 14 embedded in a road bed 16 or similar surface construction. The annular manhole frame has an upper inwardly directed flange 18 for supporting a standard manhole cover or lid (not shown). The manhole lid has passageways therein, as is well known.
The manhole cover assembly 10 of the present invention comprises a cover plate 20 fabricated from rigid metal or similar material including a pair of semicircular segments 22, 24 and a connector strip or bar 26 that seals, supports and connects the semicircular segments together along their diametral edges 28. The bar 26 may also be constructed of rigid metal and has an I-shaped cross section. As shown in FIG. 2, the annular manhole frame 14 has a lower inwardly directed flange 30 that supports the arcuate edges 32 of the semicircular segments 22, 24 of the cover plate 20. The flange 30 also supports the ends 34 of the connector strip 26. The two piece construction of the cover plate 20 enables the plate to be easily positioned in sealing relationship over the manhole opening. Caulking or other suitable sealing material 36 is located between the flange 30 and the arcuate edges of the cover plate 20. Sealing material is also located at the juncture between the diametral edges 28 and the connector strip 26 to provide an air tight seal of the cover plate over the manhole opening. The weight of the manhole cover assembly is usually sufficient to hold it in place over the manhole opening. However, suitable fastening structure may be provided if a more positive hold down is desired.
A first or pressure relief valve member 38 is secured to the semicircular segment 22 of the cover plate 20 for relieving internal pressure inside the manhole 12. Additionally, a second or vacuum relief valve 40 is secured to the semicircular segment 24 of the cover plate 20 for relieving vacuum that develops inside the manhole 12. As explained more fully below in conjunction with the details of FIGS. 5-7, the valve members 38, 40 function to relieve pressure and vacuum inside the manhole 12 when the pressure therein exceeds a predetermined amount, such as, for example, five pounds per square inch above atmospheric pressure, and also to relieve vacuum in the manhole when it exceeds a predetermined amount, such as, for example, five pounds per square inch below atmospheric pressure.
FIGS. 3 and 4 illustrate another movable closure assembly 50 according to the present invention wherein a standard manhole cover or lid 52 is slightly modified so as to carry a pressure relief valve member 54 and a vacuum relief valve member 56. In this regard, a pair of annular housings 58 are formed on the underside of the cover 52 directly below passageways 60 formed in the cover 52. As is clear from FIGS. 3 and 4, the passageways 60 in the cover 52 provide communication between the up side of the cover 52 and the interior of the annular housings 58. Each housing is sealed off at its lower end by a disc 62 which carries one of the valve members. Suitable fasteners such as 64 are provided for anchoring each disc to its respective annular housing 58. The valve members 54, 56 function to relieve pressure and vacuum inside the manhole 12 when these variables exceed predetermined amounts. The details of the valve members 54, 56 are explained below in conjunction with FIGS. 8 and 9. The manhole cover 52 functions as a cover plate for sealing off the manhole opening. Sealing material or a suitable gasket 66 is located between the lower peripheral edge portion of the cover 52 and the supporting flange 18 of the annular manhole frame 14.
Referring now to FIGS. 5-7, the details of the valve member 38 are shown it being understood that the vacuum relief valve member 40 is substantially the same as valve 38 except that the vacuum valve 40 opens in a downward direction to relieve vacuum while the pressure valve 38 moves in an upward direction to relieve pressure. The pressure valve 38 includes a stationary valve body 70 fabricated from aluminum, for example, having a valve seat portion 72. The valve body 70 is secured to the cover plate 20 by a locking ring arrangement 73. The valve 38 also includes a movable valve element 74 and valve stem 76, and a coil spring 78 that reacts between the valve stem and the stationary valve body 70. Passageways 80 are located in the valve body for providing communication between the up side and down side of the cover plate 20 when the valve is open. The passageways 80 in the pressure relief valve 38 are tapered with an increasing cross sectional area in the downward direction. The tapered passageways provide a self-cleaning function, as explained more fully blow. The movable valve element 74 carries a ring of resilient material 82 which engages the seat portion 72 of the valve body 70 when the valve member is closed. As shown best in FIG. 7, the valve seat portion 72 has a circular sharpened edge 84 that provides an air tight seal with the resilient ring 82 carried by the movable valve element 74 when the valve is closed. Additionally, slit or other material usually accumulates on top of the cover plate 20 and may reach a height close to the height of the valve seat 72. In such instances the sharpened edge 84 cuts through the silt to effectively close the valve when closure of the valve is desired.
Coil spring 78 is designed to hold the movable valve element 74 against the stationary valve body until the force acting upon the underside of the movable valve element is greater than the force of the coil spring 78 which acts in an opposite direction. Thus, when the pressure inside the manhole 12 exceeds 5 pounds per square inch, for example, the force generated by that pressure on the movable valve element 74 is sufficient to urge the valve element in an upward direction to thereby relieve the pressure inside the manhole. When the valve opens water, slit, and silt, foreign material which accumulates on top of the cover plate is flushed through the passageways 80 before the valve 38 closes. The tapered configuration of the passageways 80 functions to assist in maintaining them free of obstructions.
As mentioned above, the vacuum relief valve 40 is practically identical to the pressure relief valve 38 except for its orientation. Additionally, the passageways in the stationary valve body of the vacuum relief valve 40 are tapered in an opposite direction relative to the movable valve element 74. Thus, the vacuum relief valve 40 has the same self-cleaning characteristics as the pressure relief valve even though the vacuum valve is oriented so that the movable valve element 74 is on the down side of the cover plate 20. When the downward pull on the exterior of the movable valve element 74 of the vacuum relief valve 40 exceeds the force generated by the coil spring 78, the valve is pulled open to thereby relieve the vacuum generated inside the manhole 12. When the force of the coil spring exceeds the downward pull on the movable valve element 74 the vacuum relief valve is snapped closed.
The valve members 54, 56 associated with the embodiment of the invention specifically illustrated in FIGS. 3 and 4, are shown in detail in FIGS. 8 and 9. In the manhole closure assembly 50, the pressure relief valve 54 is identical to the vacuum relief valve 56 except that the movable valve element of the pressure relief valve moves in an upward direction when the valve is opened while the valve element of the vacuum relief valve moves in a downward direction when the valve is opened. The valve 54 includes a stationary valve body 90 secured to the disc 62 of the cover plate assembly 50, as shown in FIG. 8. Sealing material 92 provides an air tight seal between the body 90 and the disc 62. Passageways 94 are located in the body 90 for providing communication between the up side and down side of the manhole closure assembly when the valve is opened. A movable valve element 96 secured to a valve stem 98 moves away from the valve seat 100 of the body 90 when the force on the lower surface of the valve element 96 is greater than the force generated by the coil spring 102. As is clear, the coil spring 102 reacts between a stationary spring seat 104 and the movable valve stem 98. The movable valve element 96 carries a ring of resilient material 106 that engages the seat 100 of the valve body 90 when the valve is closed.
Each of the embodiments of the present invention provides a manhole closure assembly for sealing off the opening of a manhole construction that leads to a sewerage system. The closure prevents storm and drainage water from emptying into the manhole. Excessive pressure inside the manhole is readily relieved when it exceeds a predetermined amount. Similarly, vacuum build-ups inside the manhole are relieved by a suitable vacuum relief.