CA1152298A - Method for casting of a concrete base for a column and for stripping the form from said base - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE:

Casting and demolding of a concrete base for a column and for stripping the form from said base. The latter has a base plate, a tubular, upwardly directed portion situated centrally on the base plate and having recesses for forming thin-walled portions, and a plurality of stiffening ribs con-necting the tubular portion to the base plate. The base has an outer, removable form portion defining the outer surfaces of the base plate, the stiffening ribs and the non-recessed parts of the tubular portion, an inner, removable form core defining the inner surface of the tubular portion, and separate form portions defining the recesses in the tubular portion. The form portions are mounted and reinforcement is inserted into the form, which is then placed upside down on a vibrating table, the form is filled with concrete and is vibrated so that the concrete completely fills the form. A flat lid is placed over the form, defining the bottom of the base plate.
The form with the base is lifted, turned right and put down on a suitable support, and the form is stripped on the lid directly after the casting. The inner form core is first with-drawn a short distance, and the form core and the outer form portion are then withdrawn together and returned for erection of the form for the next casting, while the separate form portions for the recesses are left until the concrete of the base has hardened in the required degree.

Description

115Z;~98 The present invention relates to a method for casting of a concrete base foL a column and for stripping the form from said base, said base comprising a base plate, ` a tubular, upwardly directed portion situated centrally on the base plate and having recesses for forming thin-walled portions and a plurality of stiffening ribs or flanges con-necting the tubular portion to the base plate, said base being cast in a form having an outer, removable form por-tion defining the outer surfaces of the base plate, the stiffèning ribs and the non-recessed parts of the tubular portion, an inner, removable form core defining the inner surface of the tubular portion, and separate form portions defining the recesses in the tubular portion, the method comprising the steps that the form portions are mounted and reinforcement is inserted into the form, which then is placed upside down on a vibrating table, that the form i5 filled with fresh concrete and is vibrated by means of the vibrating table, so that the fresh concrete completely fills the form, that a substantially flat lid is placed over the form, said lid defining the bottom of the base plate, that the form with the base is lifted, turned right side up and put down on a suitable support, and that stripping of the form is made on the lid substantially directly after the casting.
In the method described above there is used the so-called direct stripping' i.e. the main portions of the form are removed from the cast ob~ect practically imme-diately after the casting. This is a commonly known method, which often is used in producing pipes and slmilar objects having a simple design. Thereby two different methods for stripping may be used, either that the inner and the outer form portion are removed together or that first one form portion is removed completely, whereafter the other form portion is removed. These methods for stripping function satisfactorily when used for pipes and other similar objects, .. .. _ .

1~5Z298 but they cannot be used for an object having more complicated design, for example a base for a column. One of the reasons for this is that if the method is used for an object of said kind there are yreat risks that the object will be damaged during the stripping, and at the same time there may be de-formations of the object during the hardening after stripping.
The object of the present invention is to pro-vide a method of the above mentioned kind, which method makes it possible to avoid damages on the cast object during strip-ping and the subsequent hardening. This is obtained in thatthe inner form core is first withdrawn a short distance, and in that the form core and the outer form portion are then withdrawn together and returned for erection of the form for the next casting, while the separate form portions for the recesses are left until the concrete of the base has hardened to the degree required.
In the method according to the invention the inner form core is first withdrawn a short distance, whereupon the form core and the outer form portion are withdrawn to-gether. By the first withdrawal of the form core is obtainedthat the core is released from the cast object, which is of great importance, as the force required to release the adhe-sion between the form and the cast object would be too great if both form portions were withdrawn at the same time. By limiting the first withdrawal to a short distance it is at the same time obtained that the inner form core gives satis-factory guidance at the subsequent withdrawal together of the form core and the outer form portion. Thereby the risk for damage is avoided, even if the stripping should be made obliquely and/or if the form is not completely satisfactory.
Further the stripping of the form core and the outer form portion is made in a single operation, which naturally sim-plifies the stripping and further gives a substantial de-crease of the time required. Thereby the capacity of the casting apparatus is naturally increased without the neces-.. . .

sity for increasing the number of forms.
The separate form portions for the recesses areaccording to the invention left until the concrete has hardened to the degree required. The purpose of this is to make direct stripping o the cast object possible. If also the separate form portions were removed directly after the casting there would be great risk that the object would be damaged due to deformations. By leaving the separate form portions for the recesses and by using direct stripping it is possible to release the main form portions, i.e. the~
outer form portion and the form core, for the next casting at a very early stage.

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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method for casting of a concrete base for a column and for stripping the form from said base, said base comprising a base plate, a tubular, upwardly directed portion situated centrally on the base plate and having recesses for forming thin-walled portions, and a plurality of stiffening ribs or flanges connecting the tubular por-tion to the base plate, said base being cast in a form having an outer, removable form portion defining the outer surfaces of the base plate, the stiffening ribs and the non-recessed parts of the tubular portion, an inner, removable form core defining the inner surface of the tubular portion, and separate form portions defining the recesses in the tubular portion, the method comprising the steps that the form por-tions are mounted and reinforcement is inserted into the form, which then is placed upside down on a vribrating table, that the form is filled with fresh concrete and is vibrated by means of the vibrating table, so that the fresh concrete completely fills the form, that a substantially flat lid is placed over the form, said lid defining the bottom of the base plate, that the form with the base is lifted, turned right side up and put down on a suitable support, and that stripping of the form is made on the lid substantially directly after the casting, characterized in that the inner form core is first withdrawn a short distance, and in that the form core and the outer form portion are then withdrawn together and returned for erection of the form for the next casting, while the separate form portions for the recesses are left until the concrete of the base has hardenning to the degree required.