Title of Invention	A COMPOSITE MANHOLE COVER
Abstract	A Composite Manhole Cover comprising a FRP skin embedded into the top surface of polymer concrete matrix and wherein the said Polymer Concrete Matrix is provided with a polymer resin saturated glass fibre fabric reinforcement at the bottom surface wherein the said FRP skin has an anti-slip surface on its outer surface.

Full Text

This invention relates to an improved Composite Manhole Cover comprising of a Glassfibre / Fibreglass Reinforced Plastic (GRP / FRP) Skin embedded in Polymer Concrete with polymer resin saturated glass fibre fabric reinforcement. BACKGROUND OF THE INVENTION Manhole covers have to be sufficiently strong to transfer the required load rating efficiently on to the manhole ring frame assembly. They must be highly corrosion resistant, require little or no maintenance and be easy to install. Manhole covers have been traditionally made with Steel, Reinforced Concrete, etc. However, due to corrosion problems and other environmental and installation consideration, new materials like composites are being widely used. Composites manhole covers having a core material and with FRP reinforcement all around and bonded together are disclosed by US Patent No.4726747, US Patent No. 5139845, US Patent No. 5829215, etc. Though these manhole covers are efficient, are difficult to produce and quite expensive. Composite manhole covers using Polymer Concrete reinforced with FRP are now widely used. These manhole covers are efficient and can be designed to meet required load ratings. However, such Polymer Concrete Manholes have certain production and strength considerations and the process requires highly skilled manual labour and suffers from quality and production constraints. In this process, in the first stage onto the bottom half of the mould (mostly comprising of the top surface of the manhole cover) and after lift pins are placed in position, requires a first predetermined quantity of polymer concrete be poured and leveled. Then polymer resin saturated glass fibre fabric reinforcement, is placed in the central area as required manually and then the final pre-determined charge of Polymer Concrete is poured and leveled. Then the final layer of polymer resin saturated glass fibre fabric reinforcement is placed on the leveled Polymer Concrete (bottom surface of the finished manhole cover) and the other half of the mould is clamped and held to cure. After the cure time is over, mould is opened and the component removed / demoulded from the mould. Silicone Rubber Moulds with steel backings are generally used. Silicon Moulds are inexpensive and several moulds can be used, but do not give the required accuracy or high quality and consistent production resulting in rework after mouldings to fit the Manhole Ring Frame Assembly. Metal moulds provide greater dimension stability but requires special anti-slip surface on the mould and as well as requiring additional parting line due to the configuration of the part, thereby increasing the cost of tooling, as several such moulds will be required. SUMMARY OF THE INVENTION This invention envisages the use of a match metal die-moulded FRP skin with an integral anti-slip top surface and with provisions for lift pin arrangements and counter-bore holes for the bolts that lock onto the Manhole Ring Frame Assembly and with provisions for Name Plate. This FRP skin is embedded into the Polymer Concrete matrix with a bottom layer of polymer resin saturated glass fibre fabric reinforcement. In this invention, in the first stage, in the open bottom mould (generally the bottom surface of manhole cover), the polymer resin saturated glass fibre fabric reinforcement is laid onto the mould and the mould is moved to the second stage wherein a pre-determined quantity of Polymer Concrete is poured and leveled. Then, the mould moves to the next stage, wherein the top half of the mould containing the FRP skin is clamped and locked onto the bottom mould and the total clamped assembly moves to the next stage for cure and de-moulding after cure. The whole process can be moved from one stage to another stage without interruption, thereby lending itself to high level of automation and consistency in manufacture. By positioning the polymer resin saturated glass fibre fabric reinforcement in the bottom of mould initially, ensures the fabric reinforcement is perfectly in place before the Polymer Concrete is poured. In the earlier method, as the mould is finally closed over the fabric reinforcement, the fabric reinforcement tend to move away and is difficult to achieve exact reinforcement position, resulting in strength variation, of required load rating. For Manhole Covers requiring larger load rating, after the first stage in the open bottom mould after the polymer resin saturated glass fibre fabric reinforcement is laid and the Polymer Concrete poured, a grid of additional reinforcement (e.g. like honey-comb) can be placed / pushed in position on to the Polymer Concrete and the mould moves to the second stage for clamping and locking the FRP skin into the Polymer Concrete Matrix. This additional grid of reinforcement provides extra strength to meet demanding higher load ratings. FRP skin can be made of sufficient thickness say 3mm to 50mm and can also be provided with deeper ribs below on the bottom surface, if required to meet higher load ratings. The use of FRP skin reduces metal mould cost considerably, as the moulds are simple, only one accurate mould is required to produce the FRP skin's in a high production process, independently. In addition in this invention, if required, the mould can be made such that, after the top mould is closed, the FRP skin alone can be pushed and clamped, which allows dimensional tolerance to be maintained more accurately on the thickness portion with respect to the manhole ring frame assembly. The maximum variation between the FRP skin embedded on the Polymer Concrete matrix can be held between 1 to 2mm, to compensate for the variation in the Polymer Concrete pour quantity consistency, while still maintaining a good compression of the complete matrix under cure. Thereby in addition to the length and width dimensions, which are defined by the bottom mould, the thickness tolerance can also be maintained consistently in this invention. The bottom layer of polymer resin saturated glass fabric reinforcement, which is laid on to the mould initially can be made of a pre-formed reinforcement matrix to the required shape and can be placed into the mould quickly and saturated with polymer resin to increase productivity and to improve consistency. Alternatively, instead of the bottom layer of polymer resin saturated glass fibre fabric reinforcement, a FRP skin made to the bottom mould shape, with suitable thickness to withstand load rating, can be used for high productivity. The FRP skin provided with a ridge all around gets embedded rigidly and mechanically all around with the Polymer Concrete, and the lift pins held at both ends with lift pin anchors also gets embedded to the Polymer Concrete Matrix. In addition, if required more notches can be provided in the FRP skin, at varying locations for increased mechanical bonding to the polymer concrete matrix. The FRP skin can be produced by any suitable high production process using match metal accurate moulds, like hot press moulding using FRP sheet moulding compound method or Glassmat Thermoplastic stamping (GMT) process. A chemical bond can be achieved between the Polymer Concrete and FRP skin by providing a surface treatment on the inside of the FRP skin either by solvent wash, sand blasting, heat treatment, etc. A good mechanical bond occurs due to the shrinkage of Polymer Concrete onto the FRP skin, all round the ridge and at the lift pin positions. In addition, if a chemical bond is also achieved, the composite Manhole Cover can achieve superior mechanical strength. Brief description of the drawings: The accompanying drawings illustrate a preferred embodiment of the invention, and should not be construed as restricting the spirit or scope of the invention in any way: Fig. 1 is a perspective view of Composite Manhole Cover Fig. la is a perspective view of Fig 1 indicating the sections Fig. 2 is a perspective rear view of Fig. 1 Fig. 3 is an exploded view of Fig 1 Fig. 4 is a rear perspective view of FRP skin Fig. 5 is a section at BB of Fig la Fig. 6 is a section at AA of Fig 1 a Fig. 7 is a section at CC of Fig la Fig. 8 is a perspective view at section EE of Fig la Fig. 9 is a section at DD of Fig la Detailed description of the preferred embodiment Fig. 1 is a perspective plan view of the Composite Manhole Cover 1. Fig. la is a perspective view of Fig 1 indicating the sections. Fig. 2 is a perspective rear view of Manhole Cover 1 Fig. 3 is an exploded view of Fig 1 wherein the FRP skin 2 having a ridge 11 all around with pocket for lift pins 7 and nameplate 8 is provided. An anti-slip top surface 9 is provided on top of the FRP skin 2 having counter-bores 10, for bolting the Manhole Cover to the Manhole Ring Frame Assembly. Lift pin 5, are slipped onto the FRP skin 2, at the Lift pin pocket 7. Two Lift Pin Anchors 6 are provided at both ends of lift pin 5, which mechanically bond the FRP skin 2, and lift pin 5, to the Polymer Concrete Matrix 3. At the bottom surface is the layer of polymer resin saturated glass fibre fabric reinforcement 4. Fig. 4 is a rear perspective view of FRP skin 2, wherein ribs 14 are provided on the inside surface 12 of the FRP skin 2, to hold the lift pin anchor in position, and reinforcing ribs 15, are provided for strength. Fig. 5 is a section at BB of Fig. la, wherein the FRP skin 2, is embedded in the Polymer Concrete all around at the ridge 11, and gets anchored through the lift pin anchor 6, at two ends of each lift pin 5. Fig. 6 is a section at AA of Fig la. Fig. 7 shows an alternate view at section CC of fig. 1, having an additional reinforcement grid 13, for increased load ratings of manhole cover 1. Fig. 8 is a section at EE of Fig la, showing lift pin locations, wherein the lift pin 5, and the lift pin anchors 6, are embedded in the Polymer Concrete Matrix 3, to mechanically bond the FRP skin 2, to the Polymer Concrete Matrix 3, reinforced at the bottom by the polymer resin saturated glass fibre fabric reinforcement 4. The ribs 14 are provided on the inside surface of the FRP skin 2, to keep in position the lift pin anchor 6, for good mechanical bond with the Polymer Concrete Matrix 3. The inside surface of FRP skin 12, when provided with surface treatment like solvent wash, sand blasting, heat treatment, etc. provides a good chemical bond with Polymer Concrete Matrix 3, enhancing the strength of the Manhole Cover 1. Fig. 9 is a section at DD of Fig la, showing the counter-bores 10 in FRP skin 2, which are provided to bolt the Manhole Cover 1 to the Manhole Ring Frame Assembly rigidly. As the counter-bores 10 are accurately moulded at required positions in the FRP skin 2, dimensional accuracy of the bolt locations in the Manhole Cover 1 are maintained. The innovative features of this invention are: 1) Use of a FRP skin containing an anti-slip surface on the top side and with provisions for lift pins and a ridge all around, which gets embedded on the Polymer Concrete. The Polymer Concrete shrinks onto the FRP skin all around the ridge and at the lift pin positions giving a good mechanical bond. In addition, if more mechanical bonding is required, provisions can be made available at the inside position of the FRP skin at required locations. 2) In addition to achieving a good mechanical bond by providing special surface treatment like chemical solvent wash, sand blasting, heat treatment, etc at the inside of the FRP skin, can give a good chemical bond between the Polymer Concrete and the FRP skin to enhance the total mechanical strength of the matrix. 3) The use of FRP skin eliminates the need for central polymer resin saturated fabric reinforcement, as the FRP skin provides the required mechanical strength of the central layer of Polymer Concrete with the polymer resin saturated glass fibre fabric reinforcement. 4) The FRP skin and the one pour polymer concrete provision provides automation, high strength and consistent quality standards for the improved Composite Manhole Cover. 5) The FRP skin produced using matched metal moulds in a high production process with integral anti-slip surface, lift pins with pockets, counter-bores, etc. reduces the tooling cost required for production, tool/mould of the Composite Manhole Cover. As will be apparent to those skilled in the art in the light of the foregoing disclosure many alternations and modifications are possible in the practice of this invention without departing from the spirit or scope thereof. Accordingly, the scope of the invention is to be construed in accordance with the substance defined by the following claims. I Claim: 1. A Composite Manhole Cover comprising a FRP skin embedded into the top surface of polymer concrete matrix and wherein the said Polymer Concrete Matrix is provided with a polymer resin saturated glass fibre fabric reinforcement at the bottom surface. 2. A Composite Manhole Cover as claimed in claim 1, wherein the said FRP skin has an anti-slip surface on its outer surface. 3. A Composite Manhole Cover as claimed in claim 1, wherein the said FRP skin has provision of counter-bores for bolting onto the Manhole Ring Frame Assembly. 4. A Composite Manhole Cover as claimed in claim 1, wherein the said FRP skin has provision for pockets for holding lift pins and nameplates. 5. A Composite Manhole Cover as claimed in claim 1, wherein the said FRP skin is made in a high production process using match metal moulds with composite glass-fibre reinforced polymer material. 6. A Composite Manhole Cover as claimed in claim 1, wherein the said FRP skin has a ridge all around for mechanically bonding onto the said Polymer Concrete Matrix. 7. A Composite Manhole Cover as claimed in claim 1, wherein the said FRP skin has a thickness of 3 to 50mm. 8. A Composite Manhole Cover as claimed in claim 1, wherein the said FRP skin has deep ribs provided on the bottom surface. 9. A Composite Manhole Cover as claimed in claim 1, wherein an additional reinforcement grid is placed between the bottom of said FRP skin and said polymer resin saturated glass fibre fabric reinforcement and in the said Polymer Concrete Matrix. 10. A Composite Manhole Cover as claimed in claim 1, wherein the said lift pins have lift pin anchors to mechanically bond the said FRP skin to the said Polymer Concrete matrix. 11. A Composite Manhole Cover as claimed in claim 1, wherein the said polymer resin saturated glass fibre fabric reinforcement is made as a pre-formed reinforcement to required shape and saturated with polymer resin. 12. A Composite Manhole Cover as claimed in claim 1, wherein the said polymer resin saturated glass fibre fabric reinforcement is made of a glass fibre reinforced composite material to the required shape. 13. A Composite Manhole Cover as claimed in any of the above claims, wherein the said FRP skin is provided with treatment on the inside surface to provide a chemical bond with the said Polymer Concrete Matrix, 14. A Composite Manhole Cover as claimed in claim 1, wherein the said FRP skin will be embedded in the said Polymer Concrete Matrix with a tolerance of 2 mm over the said Polymer Concrete Matrix to compensate any inconsistency in the pour volume of the said Polymer Concrete Matrix. DATED THIS 18TH DAY OF APRIL 2006

Documents:

711-che-2006 correspondance others.pdf

711-CHE-2006 CORRESPONDENCE OTHERS.pdf

711-CHE-2006 CORRESPONDENCE PO.pdf

711-che-2006 form-26.pdf

711-che-2006 form-6.pdf

711-CHE-2006 POWER OF ATTORNEY.pdf

711-che-2006-abstract.jpg

711-che-2006-abstract.pdf

711-che-2006-claims.pdf

711-che-2006-correspondence-others.pdf

711-che-2006-correspondence-po.pdf

711-che-2006-description-complete.pdf

711-che-2006-drawings.pdf

711-che-2006-form 1.pdf

711-che-2006-form 18.pdf

711-che-2006-form 3.pdf

711-che-2006-form9.pdf