Technical Field

The invention relates to a sliding form for casting columns by placing a dry mix concrete in the form, e.g. about a steel pipe, and whereby the sliding form is preferably to be suspended in a carrying platform dis- placeably situated in a supporting structure, said slid¬ ing form comprising a steel cylinder with vibrators . mounted thereon.

Background Art

It is generally known to use sliding forms (slip form) when casting columns, walls, or other prismatic or cylin¬ drical units of concrete. The sliding form used surrounds the object to be cast and is usually of a dimension of 1 - 1.5 m. The casting is initiated with the form in the bottom position, but after a period of 3 to 4 hours, i.e. when the form is filled with concrete, the raising of the form is started along with the filling in of poured concrete in such a manner that the form is always filled up. The raising speed is typically 30 cm per hour, which in connection with a sliding form height as stated means that as the form is raised the concrete laid open below said form is 4 to 5 hours old and consequently set. The form is usually raised by means of hydraulic jacks with grips "climbing" round bars cast into the concrete. The concrete used is of a plastic consistency, and the neces¬ sary compressing is carried out by means of poker vibra¬ tors put down into the upper 30-40 cm thick layer of poured concrete. The sliding form is mounted so as to allow a "slip", i.e. the form walls are inclined, the lower wall edge being bent 0,5 - 1.0 cm backwards away from the concrete surface produced in order to reduce the friction between the form and the concrete while

said form is sliding upwards.

US patent specification No. 3,468,001 discloses a slid¬ ing form for casting columns and formed as a steel cylin¬ der. The diameter of the steel cylinder is constant to- wards the lower edge, and consequently it allows no slip. A vibrator is mounted on the wall of the form in such a manner that the form can be used for a relatively dry mixture of concrete and run at an increased sliding speed. Such a sliding form for casting columns does not, however, run completely satisfactorily because heavy vibrations arise at the lower edge of the steel cylinder when the vibrator is running, said heavy vibrations causing serious pits in the surface of the concrete immediately below the steel cylinder.

A satisfactory running of the steel cylinder requires a prior displacement (sliding) thereof relative to the concrete when the latter has been set. When the steel cylinder is displaced at a too early stage, the concrete may not be able to retain its shape in spite of the fact that it is of a consistency as moist earth.

Disclos of TnVention

The object of the invention is to provide a sliding form for casting columns of the above type which allows a sliding of the form at a sliding rate many times greater than previously possible.

The sliding form according to the invention is charac¬ terised in that the vibrators are preferably electro-mag¬ netic and situated diametrically opposite one another and furthermore adapted so as to operate in opposition, and that the lower end of the steel cylinder is rela¬ tively rigid, said lower end being provided with a sleeve of vibration-absorbinσ material such as rubber.

In this manner the concrete produced is nondeform imme¬ diately upon the compressing. The reinforcement of the lower end of the steel cylinder implies that the vibra¬ tions at the lower edge of the steel cylinder are so insignificant that they do not damage the shape of the free concrete. The vibration-absorbing sleeve supports the free concrete below the lower edge of the steel cyl¬ inder without transferring the vibrations to the con¬ crete at said edge. As a result the placed concrete is sufficiently vibrated without implying that the vibra¬ tions extend essentially below the lower edge of the steel cylinder where they might cause damages. The sleeve supports the concrete just placed by the steel cylinder and thereby assists the concrete in maintain- ing its shape. The placed concrete is far from being set. Such a procedure allows a sliding rate of the slid¬ ing form which is many times greater than previously possible.

According to the invention the sliding form may be adapfc- ed so as to operate at a sliding rate several times greater than the rate of setting usual for the concrete, which turned out to be particularly advantageous.

Furthermore according to the invention, the two vibra¬ tors operating in opposition may comprise two sets of vibrators situated substantially on the same, preferably horizontal plane and displaced 90 relative to one another. As a result the sliding form is particularly suited for placing concrete about steel pipes as the vibrations are here prevented from being transferred from the concrete to the steel pipe and from said steel pipe to the concrete again. The completed composite object, i.e. the steel pipe and the concrete, can be lifted away relatively quickly from the casting loca¬ tion and moved to the stock without damaging the poured con- crete. Subsequently, the production of the next object can be ini-

tiated. The concrete does not set until it reaches the stock.

Moreover according to the invention the lower edge of the steel cylinder may be provided with a circumferential supporting terminal flange, whereby the lower end of the steel cylinder is supported in a very simple manner.

Furthermore according to the invention the sleeve may be retained between the terminal flange of the steel cylin- - der and a lower steel ring, the terminal flange and.the steel ring for instance being interbolted. In this man- ner the sleeve is retained in a very simple manner as well as it is relatively easily replaceable in case it is worn.

According to the invention the sleeve may be of an axial dimension substantially corresponding to half the length of the steel cylinder, whereby the concrete below the steel cylinder obtains a good side support for a suitable period of time after the steel cylinder has left it.

According to the invention the sleeve may be reinforced by means of at least one substantially circular tension band surrounding the sleeve, said tension band or bands optionally being made extending about a slightly greater or a slightly smaller sleeve diameter, e.g. by means of a tightening device provided with screw bolts. In this manner the diameter of the sleeve is kept unchanged in spite of the pressure of the poured concrete. A suitable adjustment of the tightening device allows a slight extension of the sleeve at the bottom, i.e. it may be frusto-conical.

Moreover according to the invention the sleeve may com- 0 prise more, for instance five reinforcing tension bands arranged substantially in parallel, whereby the con¬ crete is well supported.

According to the invention the sleeve may be of a rela¬ tively small axial dimension, whereby an auxiliary steel cylinder may be mounted below and on the steel ring in connection with the sleeve, said auxiliary steel cylin- der being of a clear substantially corresponding to the clear of the steel cylinder. In this manner the concrete positioned in the area immediately below the lower edge of the steel cylinder is additionally supported to the side.

According to the invention the axial dimension of the auxiliary steel cylinder may correspond substantially to the axial dimension of the steel cylinder, sai di-- mensioning turning out to be advantageous in practice.

Moreover according to the invention the auxiliary steel cylinder may be slotted on the major portion of its length, preferably along four equidistant generatrixes, whereby each of the resulting cylinder parts may be connected to its moving mechanism moving portions of this part away from or towards a central axis in the sliding form, said moving mechanism furthermore being connected to the carrying platform. As a result it is easy to adjust the pressure of the auxiliary steel cyl¬ inder on the concrete, i.e. the side support of the concrete positioned below the lower edge of the steel cylinder. While the form is sliding the parts are abut¬ ting the surface of the concrete, and at the termination of the sliding procedure the lower end of the parts is released from said surface.

Finally according to the invention the moving mechanisms for the parts of the auxiliary steel cylinder may be telescopically formed pull or push rods which are pref¬ erably hydraulicly operated, whereby a simple and very reliable running sliding form is obtained.

Brief Description of Drawings

The invention will be described below with reference to the accompanying drawing, in which

Fig. 1 is a side view of an embodiment of the sliding form according to the invention.

Fig. 2 is a sectional view of the embodiment of Fig, 1 taken along the line II-II of Fig. 1,

Fig. 3 is a vertical sectional view of a vibration-ab¬ sorbing sleeve, and

Fig. 4 is a side view of a second embodiment of the slid¬ ing form according to the invention, whereby an auxiliary steel cylinder is mounted below a lower steel ring and in connection with the sleeve.

Best Mode for Carrying Out the Invention

The sliding form of Fig. 1 is suitable for placing, e.g. about a- steel pipe, a dry mix concrete, i.e. a concrete of a consistency as moist earth. The form is a cylinder 1 of steel plate. Four vibrators 2, cf. Figs. 1 and 2, are mounted on vertical U-irons 3 on the cylinder, said vibrators for instance being electro-magnetic and being situated equidistaπtly along the circumference of the cylinder. A reinforcing terminal flange in the form of a circumferential single iron 4 is welded onto and along the lower edge of the cylinder. Beyond the reinforcing effect this terminal flange retains a vibration-absorb¬ ing sleeve 5, cf. Fig. 3, together with a lower steel ring 14. The sleeve is preferably made of rubber or a rubber-like material. It may optionally be surrounded by substantially circular tension bands 6 ensuring in

the closed position, cf. Fig. 1, that the diameter of the sleeve remains unchanged in spite of the pressure of the poured concrete. As ^' illustrated these tension bands may be secured to a tightening device for instance in the form of two vertical angle irons 7. These angle irons can be turned away from one another by means of a spindle 8, whereby the sleeve 5 is enlarged at the bot¬ tom, i.e. is frusto-conical. The material of the sleeve follows always the extension of the tension bands which allows a mutual movement of the material of the sleeve and the tension bands along the circumference. As a result, the sliding of the form can be terminated with¬ out causing a raising of the uppermost portion of the concrete within the sleeve together with said sleeve. Four angular brackets 9 appear from the top of Fig. 1. These brackets are secured on the steel cylinder 1 and serve to suspend the sliding form on an outer supporting structure not shown and forming part of a production plant.

Fig. 4 illustrates an alternative embodiment of the slid¬ ing form where the sleeve 5a of vibration-absorbing ma¬ terial is of a very short axial length, and where an auxiliary steel cylinder 10 is provided on the underside of the steel ring 14, i.e. in connection with the sleeve and as an extension thereof. This auxiliary steel cylin¬ der is made of steel plate of a suitable thickness and is of a clear substantially corresponding to the clear of the steel cylinder 1. The auxiliary steel cylinder 10 ma for instance be provided on the steel ring 14 by means of four bolts 16 with associated spring washers.

As shown the auxiliary cylinder 10 is for instance of an axial length of about one third of the axial length of the steel cylinder 1. It may, however, also be of an axial length substantially corresponding to the axial length of the steel cylinder 1.

As illustrated, the auxiliary steel cylinder 10 and optionally also the steel ring 14 can be slotted along four equidistant generatrixes, one of said slots 18 ap¬ pearing from Fig. 4. The auxiliary steel cylinder 10 includes consequently four separate cylinder parts, only two parts 10a and 10b being visible. These parts are coherent at the top as the slotting stops about 10 mm from the upper edge of the auxiliary steel cylinder. The above bolts 16 can be centrally mounted on their respec- tive cylinder part. On the outer surface each cylinder part can be connected to a moving mechanism 12, which is diagrammatically shown. This mechanism moves portions of the part away from or towards a central axis of the sliding form and is furthermore connected to a carrying platform not shown. This platform is displaceably situat¬ ed on an outer supporting structure not shown and com¬ prises preferably telescopically formed pull or push rods which for instance are hydraulicly operated. An activation of these pull or push rods allows a moving of. the lower edge of the auxiliary steel cylinder a suitable distance outwards, which is an advantage espe¬ cially at the termination of the sliding movement of the form. While the form is sliding, the-pull or push rods 12 are adjusted in such a manner that the lower edge of the auxiliary steel cylinder is closely abutting the surface of the concrete.

The invention may be varied in many ways without there¬ by deviating from the scope thereof.

Under usual operational conditions the inventive sliding form allows a sliding rate of about 2 m per minute.