JPS5911212A - Manufacture of non-circular pipe and formwork used for the manufacture - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] The present invention relates to a method of manufacturing a pipe by tightening a material using centrifugal force, such as a Huyum pipe (centrifugal force reinforced concrete pipe), and a formwork used therein. Specifically, the present invention relates to a method for casting a non-circular tube with a circular cross-sectional shape and a non-circular cross-sectional shape by centrifugal molding, and a formwork thereof.

A centrifugal reinforced concrete pipe, so-called a Huum pipe, is produced by pouring fresh concrete into a cylindrical formwork in which reinforcing bars have been assembled and arranged in advance, and rotating this formwork a with a rotating wheel as shown in Figure 1. The centrifugal force generated by this rotation compacts and shapes the concrete. Therefore, all of them have a hollow circular cross section and can be formed into pipes with high material density, and are used in a wide range of areas such as water supply and sewerage, agricultural canals, and industrial canals.

However, the biggest problem with such a pipe with a circular cross section is that the flow velocity decreases significantly as the flow rate decreases. In other words, in a pipe with a circular cross section, when the flow rate decreases, the contact area between the water and the pipe wall becomes larger than the cross-sectional area of the flowing water (8), so the flow velocity rapidly decreases due to the influence of frictional resistance on the pipe wall. do.

This point becomes particularly serious as the pipe diameter increases; in a wide-diameter pipe, when the flow rate decreases, the water depth becomes extremely shallow, and the contact area increases significantly compared to the cross-sectional area of the flowing water.

Therefore, in order to overcome the drawbacks of tubes with circular cross sections, tubes with special cross sections have been devised. For example, a pipe with an oval cross section is an example of such a pipe, so that even if the flow rate decreases, the contact area does not increase relative to the cross-sectional area of the flowing water.
The lower part of the tube has a special shape that differs from the circular cross section. However, a problem with such non-circular pipes is the manufacturing method (casting method). That is, if a non-circular pipe is cast using the centrifugal forming method described above, the material in a plastic state will be shifted to a position far from the center of rotation, making it impossible to form a pipe of the desired shape. For this reason, non-circular pipes have so far been exclusively compacted by methods other than the above (4), such as vibration compaction.

However, with this method, it is not possible to apply steady stress in the radial direction of the pipe during pouring;
- It has the drawback that sufficient density cannot be obtained in the curve direction, and the mechanical properties are inferior to that of the casting method using centrifugal molding.

This invention was made as a result of studies in view of the conventional problems, and its primary purpose is to provide a method for easily centrifugally molding even non-circular tubes. The second purpose is to provide information. That is, in the method according to the present invention, a gap corresponding to the wall thickness of the tube is formed between the outer frame and the inner frame in the portion corresponding to the non-circular portion of the tube, and a gap corresponding to the wall thickness of the tube is formed in the portion corresponding to the circular portion of the tube. forming a circular hollow material input port corresponding to the input port, and inputting the material in a plastic state through the input port, and rotating the outer frame and the inner frame integrally about the central axis of the circular portion; The first objective is achieved by forming a layer of the above material inside the outer frame, curing and hardening it, and then casting a non-circular pipe.

Further, in the formwork according to the present invention, the inner surface shape of the outer frame corresponds to the outer surface shape of the pipe to be poured, and the outer surface shape of the inner frame is made to correspond to the inner surface shape of the non-circular portion of the pipe, and a circular surface having a diameter equal to the inner diameter of the circular portion, an inner frame being disposed inside the outer frame, and a non-circular surface of the inner frame facing the non-circular portion of the outer frame to form a gap therebetween; The circular surface of the inner frame faces the circular part of the outer frame, a material input port is formed between them, and the outer frame and inner frame are fixed to each other in this state.
This aims to achieve the second objective mentioned above. Hereinafter, this invention will be explained in detail based on the drawings.

1 to 8 show an example in which the present invention is applied to the manufacture of a concrete pipe having a so-called oval cross section. As shown in these drawings, the formwork according to the present invention includes an outer frame 10, an inner frame 20, and a means for fixing these in one body.
For example, it consists of 7 lunges and 80.

The outer frame 10 has an internal cross-sectional shape corresponding to the external shape of the pipe A to be cast (in the case shown, a so-called oval cross section), and this internal cross-sectional shape corresponds to the external shape of the pipe A to be cast, as shown in FIG. In the case of a so-called A-shaped pipe, which has a uniform cross-sectional shape in the axial direction, the cross-sectional shape is uniform in the axial direction, and the cross-sectional shape changes in the axial direction, as shown in Figure 4. In the case of a so-called B-shaped tube, the cross-sectional shape changes continuously in the axial direction. In the illustrated outer frame 10, the joint 13°1
4 as a border, a constant radius R-)T from a constant central axis O
(However, T is the wall thickness of the pipe to be cast. The same applies hereinafter.) It is divided into a circular part 11 left, which has a circular inner surface, and a non-circular part 12, which has an inner surface without a fixed radius of curvature. The inner surface of the circular portion 12 is made up of a continuous curved surface with a radius Rz+T and a flat surface. On the other hand, the inner frame 20 has a non-circular surface 22 corresponding to the inner surface shape of the non-circular portion a of the tube A, and a non-circular surface 22 corresponding to the inner surface shape of the non-circular portion a of the tube A.
It has a cross-sectional outer shape consisting of a circular surface 21 having a radius R equal to the inner diameter of the circular portion B, and the non-circular surface 2 shown in the figure.
2 is formed from a plurality of curved surfaces having different radii of curvature.

In the curved pipe shown in Fig. 4, a step is provided on the inner periphery of the end surface of the pipe A, but in this case, the inner frame 2o has a uniform cross-sectional shape in the axial direction from the viewpoint of the removal work of the pipe 1, which will be described later. On the other hand, it is appropriate to extend a collar 81ti as a core from the seventh flange 8o and use this as an inner mold to form the step.

To assemble this formwork, first, as shown in Figure 2, the outer frame 1
By joining the circular part 11 of 0 and the non-circular part 12 at the joint 18° 14 and fixing this with bolts, nuts, etc., it is assembled as a cylindrical body having an inner surface corresponding to the outer shape of the pipe A to be cast. . The number of joints, that is, the parts where the outer frame 10 is divided, is usually two, but if the shape of the pipe is complex, this may be eight or more. Sometimes things are in one place. Furthermore, this assembled outer frame 10 is fixed between two or more seven flange 80. Next, the inner frame 20 is inserted into the outer frame 10, and the inner frame 20 is fixed to the 7 flange 80 via the joint 28°88. In this way, the outer frame 10 and the inner frame 20 are fixed to each other. At this time, the non-circular surface 22 of the inner frame 20 is made to face the non-circular part 12 of the outer frame 10, and the wall thickness T of the pipe A is While forming a corresponding gap, the circular surface 21 of the inner frame 20 is made to face the circular part 11 of the outer frame 10, and a circular hollow material input port 15 corresponding to the inner diameter of the circular part B of the pipe A is formed therebetween. . Note that in many cases, pre-assembled reinforcing bars are inserted inside the outer frame 10.

The formwork assembled in this way is rotated around the central axis 0 of the circular portion B of the pipe A after inputting materials in a plastic state such as fresh concrete, ductile, asbestos, and plastic through the material input port 8. .

Then, the material first gathers at the farthest position from the central axis 0, which is the center of rotation (lowest part in Figure 2), and then gradually fills the gap between the outer frame 10 and the inner frame 20, where a certain amount of material When this is filled, the material also wraps around the circular part 11 side of the outer frame 10, and finally a uniform layer of material corresponding to the shape of the tube A is formed. In this state, the formwork is initially rotated at a low speed, and then the rotation is increased to a high speed in the middle, so that the material is gradually compacted and excess moisture contained in the material is removed. When the 7 langes 80 are used as the formwork fixing means, the 7 langes 80 are rotated.
A rotary wheel S is applied to the mold and rotated once, but in addition to this method using a friction wheel, a method of applying rotation directly to the formwork may also be adopted. In addition, in this invention, since the formwork and tube A are not circular, there will be an imbalance with respect to the central axis 0, which is the center of rotation, but this point will be balanced on an appropriate position)
16.16 is attached to adjust the dynamic balance.

Once the material is sufficiently compacted by such rotation, it is cured and hardened, but before this, the inner frame 20 is rotated in its longitudinal direction as shown by the two-dot button line in Figures 3 and 4. Pull it out and disassemble it. However, this is a disassembly method when the inner frame 20 is formed as one piece, and if the inner frame 20 is divided along diagonal lines in FIG. 2, it can also be disassembled after curing. Curing is usually accelerated at a temperature of around 60° C. After curing, the outer frame 10 is disassembled to obtain the non-circular tube A.

When the egg-shaped concrete pipe manufactured by the method according to the present invention was compared with the same type of pipe manufactured by the conventional vibration casting method, both the density and strength of the material were extremely good. In particular, in actual use, the strength of the non-circular portion C in the lower part of Figure 2, where the highest internal pressure is said to be, is excellent, and in that sense, its mechanical properties are comparable to conventional circular tubes formed by centrifugation. I was able to get more than that.

As described above, according to the method of the present invention, a tube with excellent mechanical properties can be manufactured by centrifugal molding of a non-circular tube, which has been considered difficult in the past. Further, according to the formwork according to the present invention, pipes of complicated shapes can be centrifugally formed with simple operations, and there is an advantage that the number of operations does not increase compared to the conventional casting method using vibration.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a conventional method for centrifugally forming a circular tube, FIG. 2 is a longitudinal sectional front view showing an embodiment of a mold according to the present invention, and FIGS. 8 and 4 are illustrations of tubes of different shapes. FIG. 10... Outer frame 11... 4-frame circular part 12
...Non-circular part of the outer frame 15...Input port 20...Inner frame 21...Circular part of the inner frame 22...Non-circular part 80 of the inner frame...Fixing means 7 Lunge included...Pipe B...Circular part of the pipe C...
・Patent applicant for non-circular part of pipe Patent attorney Kazuyoshi Hojo, representative of Tomoe Iron Works Co., Ltd.

Claims (1)

[Scope of Claims] In a method for manufacturing a non-circular tube having circular and non-circular sections in the cross-sectional shapes of the inner and outer surfaces, a tube is provided between the outer frame and the inner frame in the portion corresponding to the non-circular section of the tube. A gap corresponding to the wall thickness of the tube is formed, and a circular hollow material input port corresponding to the inner diameter of the pipe is formed in a portion corresponding to the circular portion of the tube, and the material in a plastic state is inputted from this input port. , the outer frame and the inner frame are rotated integrally around the central axis of the circular part, a layer of the material is formed inside the outer frame, this is cured and hardened, and a non-circular pipe is cast. A method for manufacturing a non-circular tube, characterized in that: 2. The manufacturing method according to claim 1, wherein the inner frame is pulled out from inside the outer frame in the longitudinal direction before curing the two materials. a) In a formwork consisting of an outer frame, an inner frame, and a fixing means for fixing these together, the inner surface shape of the outer frame is made to correspond to the outer surface shape of the pipe to be cast, and the outer surface shape of the inner frame is made to correspond to the outer surface shape of the pipe to be cast. It is formed from a non-circular surface corresponding to the inner surface shape of the non-circular portion and a circular surface having a diameter equal to the inner diameter of the circular portion of the tube, the inner frame is arranged inside the outer frame, and the non-circular surface of the inner frame is arranged outside. The non-circular part of the frame is made to face each other to form a gap therebetween, the circular surface of the inner frame is made to face the circular part of the outer frame to form a material input port therebetween, and in this state, the outer frame and the inner frame are connected to each other. Fixed non-circular pipe casting #I
Formwork. 9. The formwork according to claim 8, wherein the inner frame has a uniform cross section along its longitudinal direction.