Apparatus and method for manhole collar construction

Manhole slip form apparatus for constructing a manhole collar of concrete comprising:

• an elongated slip form tube, circular in cross-section, and tapering in cross-sectional area from a first end to a second end, for placement within a manhole cone such that said first end and said second end define a top end and a bottom end, respectively, of said placed slip form tube,
• four arms mounted to and radially outwardly extending from said top end of said slip form tube holding said tube at a selected height within said manhole cone by resting said arms upon a support surface, each of said arms provided with a handle for maneuvering of said apparatus, with attached precast manhole ring, into a collar forming position and for lifting said apparatus from said collar forming position;
• and
• fastening means for holding said precast manhole ring about an exterior periphery of said slip form tube during for pouring of concrete about said slip form tube to form said collar extending between said manhole cone and said precast manhole ring and which concrete collar embeds said precast manhole ring at a selected level relative to said support surface and said manhole cone.

A method for constructing a manhole collar upon a manhole cone, utilizing a precast manhole ring, said method comprising the steps of:

• supporting an elongated slip form tube, tapering downwardly in cross-sectional area from a first end to a second end, within a manhole cone by means of at least two arms outwardly extending from said tube and resting upon a support surface, such that said first end and said second end define a top end and a bottom end, respectively, of said supported slip form tube;
• Fastening a precast manhole ring to said tube, about an outer periphery of said tube;
• leveling said tube and said fastened precast manhole ring at a selected height relative to said support surface and said manhole cone;
• pouring concrete about said leveled slip form tube to construct said manhole collar extending between said manhole cone and said precast manhole ring and to embed said precast manhole ring within said concrete collar at said selected height relative to said support surface and said manhole cone;
• loosening said precast manhole ring from said tube;
• and
• removing said slip form tube from said precast manhole ring and from said collar thus formed.