Claims
- 1. The method of forming a perforated concrete casing, comprising the steps of:
- providing a hollow cylindrical canister having a plurality of spaced apart rows of elongated and horizontally disposed openings formed therein,
- positioning movable plates in each of said openings so that said plates extend inwardly into said canister,
- machine positioning a layer of stiff concrete adjacent the inner surface of said canister to form a cylindrical mass so that a cylindrical concrete casing member is created which has the plurality of plates embedded therein.
- removing the plates from the concrete so that a plurality of depressions are created in the concrete which do not extend completely through the casing,
- providing a wedge means comprising a plurality of horizontally disposed and vertically spaced wedge members,
- forcing the wedge members outwardly through the stiff concrete from the interior of the cylindrical casing so that the wedge members register with the said depressions to reshape said depressions and so that the outer ends of said wedge members move into said openings in said canister,
- and removing the wedge members from said concrete so that perforations are formed in the casing.
- 2. The method of claim 1 wherein said wedge members enlarge the said depression.
- 3. The method of claim 2 wherein said wedge members create a tapered perforation.
- 4. The method of claim 2 wherein said wedge members are movably mounted as a unit and wherein said wedge members enlarge all of the depressions in one row of depressions.
BACKGROUND OF THE INVENTION
This is a divisional application on the application Ser. No. 532,763 filed Dec. 24, 1975 now U.S. Pat. No. 5,957,409.
US Referenced Citations (3)
Divisions (1)
|
Number |
Date |
Country |
Parent |
532763 |
Dec 1975 |
|