JPH0314606B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for demolding a cylindrical concrete molded product formed in a cylindrical form.

(Prior Art) A cylindrical concrete molded product can be obtained by so-called centrifugal force forming, in which a cylindrical mold made of, for example, steel and filled with concrete is rotated around its axis.

Conventionally, a concrete molded product formed in a formwork is thermally expanded by heating the entire formwork from its outer peripheral surface, and during this time, an external force is applied to the concrete molded product for extrusion or pulling out. The mold was removed by doing this.

When heat is applied to the formwork and the formwork expands in its axial and radial directions, the concrete molding has a lower coefficient of thermal expansion than that of the formwork, so there is a gap between the formwork and the concrete molding. A difference in thermal expansion occurs, and this difference in thermal expansion between the two breaks the adhesion between the formwork and the concrete molding created during molding. Therefore, if the external force is applied to the concrete molded product that has been disconnected from the formwork,
Concrete molded products can be smoothly removed from the formwork.

However, according to the conventional demolding method, when the formwork is heated, the concrete molded product is heated by heat transfer to the concrete molded product inside, and expands in its axial and radial directions, causing its expansion. As a result, many cracks occurred in the concrete molded product, and furthermore, a phenomenon called cutting of the concrete molded product occurred.

In addition, in order to separate the concrete molded product from the formwork, it is desirable that there be a relatively large temperature difference between the two, but as mentioned above, the concrete molded product is heated to a relatively high temperature due to heat transfer. The actual situation was that the temperature difference between the two was relatively small.

(Object of the invention) Therefore, an object of the present invention is to provide a method by which a concrete molded product formed in a formwork can be demolded without causing cracks, cuts, etc. in the concrete molded product. do.

(Structure of the Invention) In the demolding method according to the present invention, while pressing the concrete molded product from one end of the formwork toward the other end, the formwork is sequentially removed from the circumferential surface of the formwork from one end to the other end. It is characterized by heating.

(Operations and Effects of the Invention) According to the present invention, by heating the formwork from its periphery from one end to the other end, each part of the formwork from one end to the other end is sequentially expanded,
Correspondingly, the concrete molded product can be peeled off sequentially from one end of the formwork to the other end. At this time, the peeled portion of the concrete molded product tends to thermally expand toward one end of the form because it is heated by heat transfer accompanying heating of the form before peeling. However, since a pressing force is applied to the concrete molded product from one end of the formwork to the other end, the amount of thermal expansion of the peeled portion of the concrete molded product can be reduced or made zero; This makes it possible to prevent cracks from occurring due to expansion of the concrete molded product in the axial direction. Further, the peeled portion further thermally expands in its radial direction, but this expansion is inhibited by the unpeeled portion that continues to the peeled portion. At this time, a tensile force is generated between the peeled portion and the unpeeled portion, but since a part of the tensile force is canceled out by the pressing force, no cracks are caused by the tensile force.

Further, when the pressing force is set to a magnitude that can compress the peeled part between one end of the concrete molded product and the unpeeled part, the peeled part is heated at the heated part of the formwork immediately after the peeled part. It will move relative to the other end of the formwork.
Furthermore, less heat is transferred from the formwork to the peeled portion than when it is not peeled. Therefore, the amount of heat transferred from the formwork can be further reduced. Thereby, the amount of expansion of the concrete molded product can be made relatively small. This further suppresses the temperature rise in the peeled portion, making it possible to demold the concrete molded product while creating a relatively large temperature difference between it and the formwork. .

(Embodiments) The features of the present invention will become clearer from the following description of the illustrated embodiments.

Referring to the drawings, a concrete molded product 12 is formed within a cylindrical steel formwork 10 with both ends open. Hollow concrete molded product 1 having a cylindrical shape
2 can be formed by rotating the formwork 10 filled with concrete around its axis.

The illustrated formwork 10 has a draft angle, and one end 1 of the formwork 10 has a draft angle.
The radius gradually increases from 0a toward the other end 10b.

The formwork 10 has a spigot part 14 and a socket part 16 that respectively define both ends of the concrete molded product 12, and an intermediate part 18 located between these parts and having both ends abutted against the spigot part 14 and the socket part 16. Be prepared. The spigot part 14 and the intermediate part 18, and the socket part 16 and the intermediate part 18,
A bolt 24 is provided with a bolt hole extending parallel to the axis of the intermediate portion, extends through each bolt hole of blocks 20 and 22 fixed to the outer peripheral surface of the intermediate portion 18, and is screwed into the spigot portion 14 and the socket portion 16. , 26, respectively.

The spigot part 14 and the socket part 16 include
Tires 28 and 30, which are placed on rotating rollers (not shown) to apply rotational force to the formwork 10 during concrete molding, are each integrally provided. Incidentally, annular end plates (not shown) are placed in contact with the end surfaces 10a and 10b of the formwork 10, that is, the end surfaces of the spigot portion 14 and the socket portion 16, respectively, during concrete molding.

In the demolding method according to the present invention, while pressing the concrete molded product 12 from one end 10a of the small diameter of the formwork 10 toward the other end 10b of the large diameter,
0 is sequentially heated from its periphery from one end 10a to the other end 10b.

The concrete molded product 12 is pressed by a pressurizing device 31
This can be done using

The pressurizing device 31 includes a hydraulic jack having a plunger 32 and a plurality of arm members 3 each having one end connected to a cylinder (not shown) of the hydraulic jack.
4, and the hook-shaped other end is the spigot part 14.
An arm member 34 that can be locked to the side of the tire 28 of
and has.

With the plunger 32 of the pressurizing device 31 in contact with one end surface 12a of the concrete molded product 12 at one end 10a of the formwork 10, and with the other end of the arm member 34 being locked to the tire 28, the hydraulic jack is turned on. By operating the plunger 32 to extend from the cylinder, the concrete molded product 12 is moved from one end 10a of the formwork 10 to the other end 10a.
It can be pressed towards b.

Further, the formwork 10 can be heated using a heating device 36.

The heating device 36 includes an annular tube 38 that surrounds the formwork 10 at a predetermined distance from the formwork and is movable in the axial direction of the formwork 10, and the pipe is connected to a hose (not shown). The tube 38 is connected to a source of heating medium, such as steam or hot water in the illustrated embodiment, and to a heating medium delivery device (not shown), and the tube 38 also has a A large number of elongated holes 40 are provided at intervals in the circumferential direction of the tube 38 and extend in an arc shape when viewed in a cross section of the tube 38 .

The tube 38 includes an outer tube member 42 having an arc shape as a whole.
partially surrounds tube 38 and
It is slidably attached within a predetermined range along the line in a liquid-tight or air-tight manner.

The tube member 42 has three nozzles 44 (44a, 4
4b, 44c) are provided. These nozzles are arranged at mutually spaced intervals in the circumferential direction of the outer tube member 42 and at mutually spaced intervals in the axial direction of the formwork, that is, at mutually spaced intervals on a spiral. They are each opened on the inner peripheral surface. The interval between the nozzles 44 in the circumferential direction of the tube member 42 is larger than the width dimension of the long hole 40 in the circumferential direction. When the outer tube member 42 is slid along the tube 38, the three nozzles 44 sequentially communicate with the elongated holes 40 of the tube 38, and the tube member 42 allows the nozzles 44 to communicate with the elongated holes 40. It is possible to slide within the range.

When the heating medium supply device is activated to send hot water to the pipe 30, the hot water passes through the elongated hole 40 of the pipe 38 and is discharged from one of the nozzles 44 selected by sliding each outer pipe member 42. The hot water is ejected toward the outer peripheral surface of the mold 10, thereby heating the annular peripheral surface that is a part of the mold 10 onto which the hot water has been sprayed.
The formwork 10 is made by moving the pipe 30 in parallel at a predetermined speed from the one end 10a of the formwork to the other end 10b of the formwork, with the starting point of the hot water spouting destination as the starting point.
can be heated sequentially over its entire length.

The moving speed of the pipe 30 depends on the temperature of the hot water being spouted, the environmental temperature where the formwork 10 is placed (for example, indoor temperature),
Although it varies depending on the thickness of the formwork 10, the material of the formwork 10, etc., when the formwork 10 is heated, the formwork 10 is given a heating temperature sufficient to cause the concrete molded product 12 to peel off from the formwork at the heated location. As you get,
Further, the setting is made so that the concrete molded product 12 will not be tightened due to shrinkage of the heated portion due to a temperature drop after heating the heated portion. For example, in the summer, when demolding a concrete molded product formed in a formwork with a length of 2.5 m, the pipe 30 that spouts hot water at a temperature of 40°C from the start of movement to the end of movement. Travel time is set between 30 and 60 seconds.

Heating of one end 10a of the formwork and its vicinity can be carried out by selecting the nozzle 44a closest to the one end 10a of the formwork among the three nozzles. This nozzle 44a, when the tube 38 is in the position shown,
The direction of the hot water is set so that it is ejected toward the inner peripheral side of the spigot portion 18, that is, the base.By spraying the hot water onto the base of the spigot portion 18, one end 10a of the formwork and its The vicinity can be heated uniformly.

Due to this heating, one end 10a of the mold and its vicinity expand toward the cylinder of the pressurizing device 32 in the axial direction and in the radial direction. Also, due to the heating at this time, one end of the formwork
Heat is transferred to one end 12a of the concrete molded product 12 attached to the inner circumferential surface of the formwork at and near the end 12a of the concrete molded product 12, and this portion thermally expands. However, the thermal expansion of the formwork 12 occurs earlier than that of the concrete molded product 12, and the expansion rate and amount of expansion are much higher than that of the concrete molded product 12, so the formwork 12
After the heating to 0, the state of adhesion that occurred during concrete molding is released within a relatively short time. That is, the adhesion is broken and the portion of the concrete molded product 12 is peeled off from the formwork 10. When the adhesion of said part of the concrete molded article 12 is broken, the amount of heat transferred to said part is lower than if it were in the adhered state.

Since the exfoliated portion of the concrete molded product 12 is subjected to a compressive force in the axial direction by the pressurizing device 31, expansion in the axial direction is restricted or prevented. When the pressing force (compressive force) by the pressurizing device 31 is set to be smaller than the expansion force of the concrete molded product 12 in the axial direction, the expansion can be limited, and the expansion force is equal to or equal to the expansion force. When the expansion force is set larger than the expansion force as in the illustrated example, the expansion can be prevented or not only the expansion can be prevented, but the peeled portion can be compressed between the unpeeled portion and the plunger 32. When the peeled portion is compressed, it is moved a short distance in the axial direction from the spraying location of the heating medium. For this reason, the area of the formwork 10 that receives heat transfer due to the heating becomes smaller than when the peeled portion is not moved, and as a result, the temperature rise and thermal expansion thereof are suppressed.

The peeled portion also expands in its diametrical direction. However, the expansion of the peeled portion in the radial direction is restricted by the unpeeled portion connected thereto, thereby preventing the occurrence of cracks due to thermal expansion in the radial direction. Further, at this time, a tensile force is generated at the boundary between the peeled portion that is about to expand in the radial direction and the unpeeled portion that is not expanded, but this tensile force is partially due to the compressive force caused by the heating device 31. , so that no cracks are generated at the boundary.

The situation during this period is the same when the other portions of the mold 10 are heated subsequent to the heating of one end 10a of the mold and the vicinity thereof.

The heating of the formwork 10 subsequent to the heating of one end 10a of the formwork and its vicinity is carried out through the middle nozzle 44b of the three nozzles, that is, through the nozzle 44b, which is the middle one of the three nozzles, so that the hot water is spouted in a direction perpendicular to the axis of the formwork 10. The heating can be carried out by selecting the nozzle 44b whose direction is set, and furthermore, heating of the other end 10b of the formwork and its vicinity can be performed by using the remaining nozzle 44c, that is, the hot water is heated to the inner peripheral side of the socket part 16, that is, the base part. This can be done by selecting the nozzle 44c whose direction is set so as to eject water toward. However, the spigot part 14 and socket part 1 of the formwork
6 has a larger wall thickness than that in the middle part 18, so when heating the pipe 38, the moving speed of the pipe 38 is made slower than the moving speed with respect to the middle part 18 so that each part is heated to almost the same temperature. It is desirable to provide the spigot portion 14 and the socket portion 16 with an amount of heat of

When the concrete molded product 12 is peeled from the formwork over its entire circumferential surface under the application of the pressing force, the concrete molded product 12 is simultaneously extruded from the other end 10b of the formwork to the outside of the formwork, Demolding is completed.

When the pressing force on the concrete molded product 12 is relatively large, the unpeeled portion is peeled off from the formwork 10 by the pressing force before the heating of the other end 10b of the formwork 10 is completed, and then the concrete molding is performed. The product 12 may be pushed out from the other end 10b of the formwork 10.

In the illustrated example, the tube 38 of the heating device 36 is moved, but alternatively, the formwork 10 can be moved in its axial direction without moving the heating device 36. Alternatively, a number of tubes 38 can be arranged around the formwork in the axial direction thereof, and the heating medium can be jetted out sequentially from the tubes. Furthermore, in addition to the above-mentioned movement of the tube 38 of the heating device 36, the mold 10 can be rotated about its axis in situ, or instead of the rotation of the mold, the tube 38 can be rotated. According to this, more uniform heating of the formwork is possible. Furthermore, by covering the periphery of the tube 38 and the mold, it is possible to reduce the temperature drop after heating the heated area.

Further, although the demolding method of the present invention has been described with respect to a concrete molded product formed in a formwork having a draft angle, the present invention also applies to demolding of a concrete molded product formed in a formwork that does not have a draft angle. Can be applied. Furthermore, the present invention can also be applied to demolding of a concrete molded product formed in a formwork that is not divided into the spigot part, socket part, and cylindrical part.

[Brief explanation of the drawing]

The drawings are longitudinal cross-sectional views of a formwork before demolding, to which equipment for carrying out the present invention is attached, and a concrete molded product formed in the formwork. 10: Formwork, 10a, 10b: One end and the other end of the formwork, 12: Concrete molded product, 31: Pressure device, 36: Heating device.

Claims (1)

[Claims] 1 A method for demolding a cylindrical concrete molded product formed in a cylindrical formwork, the method comprising: removing the molded concrete from the formwork while pressing the concrete molded product from one end of the formwork to the other end; A method for demolding a concrete molded product, characterized by heating the concrete from its surroundings sequentially from one end to the other.