Manhole infiltration disk and seal assembly
BACKGROUND OF THE INVENTION 
     Manholes are commonly closed by manhole cover assemblies which are placed directly onto the top of the manhole and then embedded in concrete or asphalt. The weight of the manhole assembly is used to hold the manhole cover in position on top of the manhole. No seal is provided other than the weight of the manhole assembly. Over a period of time erosion of the asphalt or concrete will allow water to infiltrate into the manhole through the space between the cover and the top of the manhole. Excessive amounts of water infiltrating the manhole produces an increased burden on the sewer system. 
     SUMMARY OF THE INVENTION 
     The present invention is concerned with an infiltration disk and seal assembly which is used to prevent infiltration of water into the sewer system. The infiltration disk is placed on the manhole and the manhole assembly placed on top of the infiltration disk to produce a seal between the manhole and the manhole cover. Flanges are provided around the inner and outer periphery of the infiltration disk to hold the manhole cover in position on top of the manhole. A seal assembly is used to seal the gap between the manhole and manhole assembly when spacer rings are used to raise the manhole assembly to ground level. 
    
    
     THE DRAWING 
     FIG. 1 is a perspective view of an infiltration disk according to the invention. 
     FIG. 2 is an exploded perspective view of the infiltration disk. 
     FIG. 3 is a section view in elevation showing the infiltration disk placed between the manhole and the manhole cover assembly. 
     FIG. 4 is an enlarged view of a portion of FIG. 3 showing the seal provided by the infiltration disk. 
     FIG. 5 is a view of an infiltration disk used in combination with a seal ring assembly. 
     FIG. 6 is a view in elevation showing the infiltration disk and seal assembly sealing a manhole assembly mounted on spacer rings provided on the top of the manhole. 
     FIG. 7 is an enlarged view of a portion of FIG. 6 showing the seals between spacer rings. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The infiltration disk 10 as seen in FIGS. 1 through 4 is used to seal the space between the top of a manhole 12 and the bottom of a manhole assembly 14 which includes a manhole frame 15 and a cover 17. The infiltration disk generally includes a ring 16 made of 22 gauge iron. Outer peripheral bands 18 are welded to the top and bottom of the disk 16 to form a flange around the outer perimeter of the disk 16. Inner peripheral bands 20 are welded to the top and bottom of the disk to form a flange around the inner perimeter of the disk 16. The disk 16 and flanges 18 and 20 can be coated with a rust protection material such as Ziebart to increase the life of the infiltration disk. 
     Means are provided on the top and bottom of the disk 16 to form a compressible seal when the manhole cover assembly is placed on the manhole. Such means is in the form of a highly refined asphalt strips 22 having a volatile solvent and an inorganic asbestos filler. The strips 22 are placed on the top and the bottom of the infiltration disk. The material for the strips must meet federal specification SS-C-153B and is manufactured by W. R. Meadows, Inc., of Elgin, Ill. under the trademark &#34;Seal Tight.&#34; This material will gradually harden after it has been placed in position to form a tough elastic seal between the infiltration disk 10, the manhole, and the frame 15 of the manhole assembly 14. 
     As seen in FIG. 4, the Seal Tight compound 22 is squeezed by the weight of the manhole cover assembly outwardly toward the flange 18. The Seal Tight compound thus filling the space around the outer periphery of the frame 15 and the manhole 12 to prevent infiltration of water or other contaminants. Means can be provided on the disk to prevent the seal from being squeezed entirely from the disk. Such means is in the form of a number of spacers 23 located on the tops and bottoms of the disk. 
     Referring to FIGS. 5, 6, and 7, another embodiment of the present invention is shown wherein the infiltration disk 10 is used in combination with a seal assembly 24 to seal the spaces between spacer rings 26 and 28 provided between the frame 17 and manhole 12. In this regard whenever the level of the street exceeds the distance between the top of the manhole 12 and the height of the manhole cover assembly 14, spacer rings are used to make up the difference. As seen in FIG. 6, two spacer rings 26 and 28 are shown mounted on the top of the manhole 12. The infiltration disk 10 is positioned on the top of the top spacer ring 26 and the manhole cover assembly 14 placed on the infiltration disk. 
     The spaces between the spacer rings are sealed by means of the assembly 24 which includes a band 30 and a rubber ring 32 and compressible seal strips 34. The strips 34 are placed between the bottom spacer ring 28 and the manhole 12 and the top spacer ring 26 and the bottom spacer ring 28. The rubber ring 32 is placed around the outer periphery of the spacer rings to hold the seal strips in the space between the spacer rings. The band 30 is tightened against the rubber ring 32. When the manhole cover assembly 14 is placed in position on top of the spacer rings, the weight of the manhole cover assembly will squeeze the compressible seal strips 34 outward from the spaces between the rings and the top of the manhole. The seal strips 34 will be retained in the spaces between the spacer rings 26 by the band 32.