Manhole closure assembly

Claim 2

A manhole closure assembly comprising: A. a retaining ring adapted to be secured within a manhole opening, an inner periphery of said retaining ring defining a central opening therethrough; B. a removable cover plate having opposed upper and lower surfaces, said cover plate being adapted to seat against the retaining ring for sealing off the opening through said retaining ring; C. a handle spaced above the upper surface of the cover plate and connected thereto; D. a pressure-relief passageway extending through the cover plate in alignment with said handle, said passageway providing communication between the upper and lower surfaces of the cover plate; E. a movable valve element including a central stem extending through said passageway, and an enlarged upper section adapted to engage the cover plate to seal off said passageway when the valve element is biased downwardly; and F. a biasing means retained between the handle and the enlarged upper section of the valve element for normally biasing the enlarged upper section of said valve element in a downward direction to seal off said passageway, said valve element being movable in an upward direction against the force of said biasing means when the pressure within the manhole exceeds a predetermined level.

Claim 3

The movable closure assembly according to claim 1, wherein the enlarged upper section extends beyond the entire periphery of said passageway and is adapted to seal off the passageway by engaging the upper surface of the cover plate.

Claim 4

The manhole closure assembly according to claim 1, wherein said movable valve element includes an enlarged lower section overlying the lower surface of the cover plate, whereby an excessive pressure build-up within a manhole will act against said lower section to move the valve element in an upward direction to unseal the passageway.

Claim 5

The manhole closure assembly according to claim 1, wherein said removable cover plate includes a tapered outer periphery which is adapted to frictionally engage a complimentary, tapered inner periphery of the retaining ring to seal off the central opening through the retaining ring.

Claim 6

The manhole closure assembly according to claim 4, including resilient sealing means disposed between the tapered surfaces of the cover plate and retaining ring when the cover plate is positioned to seal off the central opening through the retaining ring.

Claim 7

The manhole cover assembly according to claim 5, including resilient sealing means disposed about the outer periphery of the retaining ring, said resilient sealing means being adapted to frictionally engage peripheral walls defining a manhole opening.

Claim 8

The manhole closure assembly according to claim 5, wherein the outer periphery of the retaining ring is tapered to provide an upwardly directed notch between the periphery of the manhole and the outer periphery of the retaining ring for receiving a sealing material therein to firmly secure the retaining ring within the manhole opening.

Claim 9

The manhole closure assembly according to claim 1, including vertical wall means extending upwardly from the upper surface of the cover plate for providing an upwardly extending compartment which is opened at its upper end and completely surrounds the pressure-relief passageway.

Claim 10

The manhole closure assembly according to claim 1, including a plurality of locking assemblies for locking the removable cover plate to the retaining ring, each locking assembly comprising: A. a rotatable, threaded actuating member extending through an opening in the cover plate adjacent a side margin thereof; B. a laterally extending locking lug retained on a lower section of the actuating member and rotatable with said actuating member, whereby rotation of the actuating member is one direction will cause the locking lug to move from a first position completely underlying the cover plate to a second position in which a section thereof underlies the retaining ring; C. a biasing means disposed between a lower surface of the cover plate and an upper surface of the locking lug to normally bias said locking lug in a downward direction; and D. a stop means for preventing continued rotation of the locking lug when it is in its second position during continued rotation of the actuating member in said one direction, whereby said continued rotation moves the locking lug in an upward, linear direction relative to the actuating member to frictionally seat against a lower surface of the retaining ring to lock the cover plate to said retaining ring.

Claim 11

The manhole closure assembly according to claim 9, including a lug retaining means threaded onto a threaded section of the actuating member beneath the locking lug, whereby the continued rotation of the actuating member in said one direction, after the locking lug is in its second position, will cause the lug retaining means to move upwardly on the threaded lower section of the actuating member to force the locking lug against the lower surface of the retaining ring.

Claim 12

The manhole closure assembly according to claim 9, wherein the threaded actuating member is an allen-head bolt; the head of said bolt being set in a counterbore of the opening through which the bolt extends so that the actuatable head of the bolt is disposed in a plane which is no higher than the plane of the upper surface of the cover plate.

Claim 13

The manhole closure assembly according to claim 9, including a second stop means for preventing continued rotation of the locking lug when it is in its first position completely underlying the cover plate during continued rotation of the actuating member in a second direction opposite to said one direction.

Claim 14

The manhole closure assembly according to claim 12, wherein a lower section of the actuating member below the locking lug is deformed to prevent the locking lug from separating from said actuating member.

Claim 15

The manhole closure assembly comprising: A. a retaining ring adapted to be secured within a manhole opening, an inner periphery of said retaining ring defining a central opening therethrough; B. a removable cover plate having opposed upper and lower surfaces, said cover plate being adapted to seat against the retaining ring for sealing off the opening through said retaining ring; the improvement comprising C. a plurality of locking assemblies for locking the removable cover plate to the retaining ring, each locking assembly comprising: a rotatable, threaded actuating member extending through an opening in the cover plate adjacent a side margin thereof; a laterally extending locking lug retained on a lower section of the actuating member and rotatable with said actuating member, whereby rotation of the actuating member in one direction will cause the locking lug to move from a first position completely underlying the cover plate to a second position in which a section thereof underlies the retaining ring; a biasing means disposed between a lower surface of the cover plate and an upper surface of the locking lug to normally bias said locking lug in a downward direction; and a stop means for preventing continued rotation of the locking lug when it is in its second position during continued rotation of the actuating member in said one direction, whereby said continued rotation moves the locking lug in an upward, linear direction relative to the actuating member to frictionally seat against a lower surface of the retaining ring to lock the cover plate to said retaining ring.

Claim 16

The manhole closure assembly comprising: A. a retaining ring adapted to be secured within a manhole opening, an inner periphery of said retaining ring defining a central opening therethrough; B. a removable cover plate having opposed upper and lower surfaces, said cover plate being adapted to seat against the retaining ring for sealing off the opening through said retaining ring; the improvement comprising C. a plurality of locking assemblies for locking the removable cover plate to the retaining ring, each locking assembly comprising: a rotatable, threaded actuating member extending through an opening in the cover plate adjacent a side margin thereof; a laterally extending locking lug retained on a lower section of the actuating member and rotatable with said actuating member, whereby rotation of the actuating member in one direction will cause the locking lug to move from a first position completely underlying the cover plate to a second position in which a section thereof underlies the retaining ring; a biasing means disposed between a lower surface of the cover plate and an upper surface of the locking lug to normally bias said locking lug in a downward direction; and a stop means for preventing continued rotation of the locking lug when it is in its second position during continued rotation of the actuating member in said one direction, whereby said continued rotation moves the locking lug in an upward, linear direction relative to the actuating member to frictionally seat against a lower surface of the retaining ring to lock the cover plate to said retaining ring.

Claim 17

The manhole closure assembly according to claim 14, including a lug retaining means threaded onto a threaded section of the actuating member beneath the locking lug, whereby the continued rotation of the actuating member in said one direction, after the locking lug is in its second position, will cause the lug retaining means to move upwardly on the threaded lower section of the actuating member to force the locking lug against the lower surface of the retaining ring.

Claim 18

The manhole closure assembly according to claim 14, wherein the threaded actuating member is an allen-head bolt; the head of said bolt being set in a counterbore of the opening through which the bolt extends so that the actuatable head of the bolt is disposed in a plane which is no higher than the plane of the upper surface of the cover plate.

Claim 19

The manhole closure assembly according to claim 14, including a second stop means for preventing continued rotation of the locking lug when it is in its first position completely underlying the cover plate during continued rotation of the actuating member in a second direction opposite to said one direction.

Claim 20

The manhole closure assembly according to claim 17, wherein a lower section of the actuating member below the locking lug is deformed to prevent the locking lug from separating from said actuating member.