Formwork apparatus and inner formwork for manufacturing precast concrete members having a space extending in a predetermined axial direction

Abstract

The present invention provides a formwork device and an inner formwork that enable the easy manufacture of precast members having a space formed inside that extends in a predetermined axial direction. [Solution] An inner formwork (3) for forming a space extending in a predetermined axial direction (A) in a precast concrete member (30), comprising: a formwork panel (11) having an outer surface and composed of a plurality of panels (16, 17) extending along the axial direction; and a support mechanism (12) for supporting the formwork panel, wherein the formwork panel consists of a plurality of first panels (16) and a plurality of second panels (17) arranged alternately in the circumferential direction; and the support mechanism includes a first support mechanism (18) that supports the plurality of first panels so as to be movable in the radial direction; and a second support mechanism (19) that supports the plurality of second panels so as to be movable in the radial direction.

Description

Technical Field

[0001] The present invention relates to a formwork device and an inner formwork for manufacturing a precast concrete member (hereinafter referred to as "PCa member") having a space extending in a predetermined axial direction.

Background Art

[0002] A PCa member (hereinafter referred to as "PCa member having a space") that extends in a predetermined axial direction and has a space surrounded by concrete on at least three sides is used for constructing columns and beams. A cylindrical PCa member having a hollow portion and a PCa member having a U-shaped cross section are PCa members having a space. When a PCa member having a space is used as a half-precast member, after being placed at a predetermined position at a construction site, concrete is placed in the space of the PCa member.

[0003] For manufacturing a PCa member having a space, an outer formwork and an inner formwork disposed inside the outer formwork are used. Concrete is placed between the outer formwork and the inner formwork to manufacture a PCa member having a space. And, as a technique for manufacturing a PCa member having a space, for example, Patent Document 1 proposes a hollow PC formwork device for manufacturing a cylindrical PCa member having a hollow portion, in which an air tube is used as the inner formwork.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Air tubes are inflated by being filled with compressed air. As a result, air tubes tend to float up in the poured concrete. Also, the shape of the surface of the air tubes is easily altered. Therefore, it is not easy to manufacture multiple precast concrete (PCa) members having the same hollow shape using the hollow PC formwork device described in Patent Document 1. Although it is possible to make the shape of multiple PCa members the same by using formwork panels as inner formwork, assembling the formwork is time-consuming and labor-intensive, and it is difficult to remove the inner formwork when demolding.

[0006] In view of the above background, the present invention aims to facilitate the manufacture of precast members having a space formed inside that extends in a predetermined axial direction. [Means for solving the problem]

[0007] To solve the above problems, one aspect of the present invention provides an inner formwork (3) for forming a space in a precast concrete member (30) that extends in a predetermined axial direction (A), comprising: a formwork panel (11) having an outer surface and composed of a plurality of panels (16, 17) extending along the axial direction; and a support mechanism (12) for supporting the formwork panel, wherein the formwork panel consists of a plurality of first panels (16) and a plurality of second panels (17) arranged alternately in the circumferential direction; and the support mechanism includes a first support mechanism (18) that supports the plurality of first panels so as to be movable in the radial direction; and a second support mechanism (19) that supports the plurality of second panels so as to be movable in the radial direction.

[0008] According to this embodiment, by moving a plurality of first panels and a plurality of second panels radially, the formwork panels can be switched between a state in which they are used as formwork (expanded state) and a state in which they can be removed from the PCa member (retracted state). This makes it possible to easily manufacture PCa members in which a space extending in a predetermined axial direction is formed inside.

[0009] In the above embodiment, it is preferable that at least one of the first panels or at least one of the second panels have a protrusion (17b) on its outer surface.

[0010] According to this embodiment, a recess is formed in the internal space of the PCa member, and a protrusion is formed in the concrete poured into the internal space of the PCa member. As a result, the concrete poured into the internal space of the PCa member is less likely to come out of the internal space of the PCa member.

[0011] In the above embodiment, the support mechanism may have a support tube (21) extending in the axial direction, the first support mechanism may have a first slider (22) extending in the axial direction and supported on the support tube so as to be movable in the axial direction, a plurality of first support arms (23) hinged to each of the plurality of first panels and the support tube, and a plurality of first drive arms (24) each having hinged ends connected to the first slider and the first support arms, and the second support mechanism may have a second slider (25) extending in the axial direction and supported on the support tube so as to be movable in the axial direction, a plurality of second support arms (26) hinged to each of the plurality of second panels and the support tube, and a plurality of second drive arms (27) each having hinged ends connected to the second slider and the second support arms.

[0012] In this embodiment, the first support arm rotates when the first slider is moved in the axial direction, and the second support arm rotates when the second slider is moved in the axial direction. Therefore, the support mechanism can reliably move the multiple first panels and the multiple second panels in the radial direction.

[0013] In the above embodiment, the first slider consists of a tubular first moving tube (22) and is positioned inside the support tube, the second slider consists of a tubular second moving tube (25) and is positioned inside the first moving tube, the support tube has a first elongated hole (21c) through which the first drive arm is inserted and a second elongated hole (21d) through which the second drive arm is inserted, the first moving tube has a third elongated hole (22b) through which the second drive arm is inserted, and the formwork panel may switch between an expanded state in which the plurality of first panels and the plurality of second panels are continuous in the circumferential direction and a contracted state in which the plurality of first panels and the plurality of second panels are positioned inward from their positions in the expanded state, depending on the axial positions of the first and second moving tubes.

[0014] In this embodiment, the support pipe has a first elongated hole and a second elongated hole, the first moving pipe is located inside the support pipe and has a third elongated hole, and the second moving pipe is located inside the first moving pipe. This allows multiple first panels and multiple second panels to be reliably moved in the radial direction.

[0015] In the above embodiment, it is preferable that the support pipe, the first moving pipe, and the second moving pipe are arranged coaxially.

[0016] In this embodiment, the radial relative positions of the support pipe, the first moving pipe, and the second moving pipe do not change. This makes it easy to move the first moving pipe and the second moving pipe in the axial direction relative to the support pipe.

[0017] In the above embodiment, the support mechanism may have a removable fixing pin (20) that pins the first and second movable tubes in the deployed state.

[0018] In this embodiment, the first and second movable tubes are pinned in place by fixing pins when deployed, and become movable when the fixing pins are removed. This makes it easier to maintain the deployed state during the manufacturing of the PCa member.

[0019] In the above embodiment, one of the first panel and the second panel may have an adhesion portion (17c) that adheres to the inner surface of the other panel when unfolded.

[0020] According to this embodiment, in the unfolded state, the contact portion of one of the first panel and the second panel comes into contact with the inner surface of the other of the first panel and the second panel, making it easy to position one of the first panel and the other of the second panel in the appropriate location.

[0021] In the above embodiment, when the formwork panel is in the deployed state, it is preferable that one end of the first and second moving pipes in the axial direction extends outward more than the other end of the first and second moving pipes.

[0022] According to this embodiment, when moving the formwork panel from the deployed state to the retracted state and separating the formwork panel from the PCa member, it becomes easier to move one of the first and second moving pipes. As a result, it becomes easier to move the formwork panel from the deployed state to the retracted state and separate the formwork panel from the PCa member.

[0023] Furthermore, in order to solve the above problems, another aspect of the present invention is a formwork device (1) for manufacturing a precast concrete member (30) having a space extending in a predetermined axial direction (A), comprising an inner formwork (3) as described above, and an outer formwork (2) that defines the outer circumferential surface of the precast concrete member other than the upper surface, wherein the outer formwork comprises a bottom plate (4) that defines the bottom surface of the precast concrete member, a pair of side plates (5) that define a pair of sides of the precast concrete member and are positioned on the bottom plate, and a pair of support jigs (6) that are in close contact with each of the axial ends of the formwork panel of the inner formwork and support the inner formwork.

[0024] According to this embodiment, precast members with appropriately shaped spaces formed inside can be reliably manufactured.

[0025] In the above aspect, the inner formwork is provided, and each of the pair of the support jigs may be fixed to both axial ends of the support pipe of the inner formwork respectively.

[0026] According to this aspect, the support jig can exert a reaction force without being supported by other members against the force received from the placed concrete (that is, the support jig has a self-reaction force). Thereby, it becomes easy to manufacture the PCa member.

[0027] In the above aspect, the precast concrete member has main reinforcement bars (32) extending in the axial direction and protruding at at least one axial end, and at least one of the pair of the support jigs may have main reinforcement holes (6c) through which the main reinforcement bars are inserted.

[0028] According to this aspect, it becomes easy to manufacture the PCa member having main reinforcement bars protruding at at least one axial end.

Advantages of the Invention

[0029] According to the above aspects, it is possible to facilitate the manufacture of the precast member in which a space extending in a predetermined axial direction is formed inside.

Brief Description of the Drawings

[0030] [Figure 1] Side view of the formwork device according to the embodiment [Figure 2] Cross-sectional view of the inner formwork taken along the line II-II in FIG. 1 [Figure 3] Cross-sectional view of the inner formwork taken along the line III-III in FIG. 2 [Figure 4] Cross-sectional view of the inner formwork taken along the line IV-IV in FIG. 2 [Figure 5] Cross-sectional view of the inner formwork in the reduced state [Figure 6] Explanatory drawing for explaining the manufacturing method of the PCa member using the formwork device [Figure 7]Cross-sectional view of the formwork device and PCa member along line VII-VII in Figure 6. [Figure 8] An explanatory diagram illustrating the process of removing the inner formwork from the PCa member. [Figure 9] An explanatory diagram illustrating the process of removing the inner formwork from the PCa member. [Figure 10] This diagram illustrates a method for manufacturing a precast concrete (PCa) member in which multiple main reinforcements each protrude from both ends in the axial direction. [Figure 11] An explanatory diagram illustrating a method for manufacturing U-shaped precast concrete (PCa) members using a formwork device. [Figure 12] Cross-sectional view of the inner formwork relating to the first modified example. [Figure 13] Cross-sectional view of the inner formwork relating to the second modified example. [Figure 14] Cross-sectional view of the inner formwork relating to the third modified example. [Modes for carrying out the invention]

[0031] Hereinafter, several embodiments of the present invention will be described in detail with reference to the drawings. The formwork apparatus according to the embodiment is a formwork apparatus 1 for manufacturing a precast concrete member (hereinafter referred to as "PCa member") having a space extending in a predetermined axial direction.

[0032] <Configuration of formwork device 1> Figure 1 is a side view of a formwork apparatus 1 according to an embodiment. As shown in Figure 1, the formwork apparatus 1 comprises an outer formwork 2 that defines the outer circumferential surface of the PCa member other than the upper surface, and an inner formwork 3 for forming a space in the PCa member that extends in the direction of a predetermined axis A.

[0033] The outer formwork 2 includes a bottom plate 4 that defines the bottom surface of the PCa member to be manufactured, a pair of side plates 5 (see Figure 7) that define a pair of sides of the PCa member, and a pair of support jigs 6 that define both end faces of the PCa member in the direction of axis A. The pair of side plates 5 and the pair of support jigs 6 are placed on the bottom plate 4.

[0034] Each pair of support fixtures 6 comprises a rectangular support plate 6a, a rectangular through-hole 6b provided in the support plate 6a, a plurality of main reinforcement holes 6c provided around the through-hole 6b and passing through the support plate 6a, and two reinforcing beams 6d provided on the outside of the support plate 6a in the direction of axis A and extending vertically. The inner surface of the support plate 6a in the direction of axis A is in close contact with the inner formwork 3 (specifically, the formwork panel 11 described later). In addition, a pair of sides of the support plate 6a are in close contact with a pair of side plates 5. The inner formwork 3 (specifically, the support pipe 21, the first movable pipe 22, and the second movable pipe 25) is inserted through the through-hole 6b. Reinforcing bars (specifically, the main reinforcement bars 32 described later) provided in the PCa member can be inserted through the main reinforcement holes 6c. The inner formwork 3 (specifically the support pipes 21, first movable pipe 22, and second movable pipe 25, which will be described later) is inserted between the two reinforcing beams 6d.

[0035] The inner formwork 3 comprises a formwork panel 11 extending along axis A and a support mechanism 12 that supports the formwork panel 11. When the precast concrete (PCa) member is manufactured, concrete is poured between the outer formwork 2 and the formwork panel 11. The formwork panel 11 has an outer surface that forms the formwork surface for the concrete to be poured.

[0036] Figure 2 is a cross-sectional view of the inner formwork 3 along the line II-II in Figure 1. As shown in Figure 2, the formwork panel 11 consists of a plurality of corner panels 16 (first panels) and a plurality of side panels 17 (second panels) arranged alternately in the circumferential direction. As shown in Figure 1, the corner panels 16 and side panels 17 extend in the direction of axis A. As shown in Figure 2, the corner panel 16 has an L-shaped cross-section. The corner panel 16 has a hinge portion 16a that hinges to the support mechanism 12 (specifically the first support arm 23, which will be described later). The side panel 17 has a main body portion 17a that is in close contact with the adjacent corner panel 16 and has an outer surface, a plurality of protrusions 17b that project radially outward from the main body portion 17a, and a contact portion 17c that protrudes circumferentially on the radially inward side of the main body portion 17a and is in close contact with the inner surface of the corner panel 16. As shown in Figure 1, the protrusions 17b extend in the circumferential direction and are arranged at intervals in the direction of axis A. Alternatively, a recess may be provided on the main body portion 17a instead of the protrusion 17b. Furthermore, a recess may be provided on the main body portion 17a in addition to the protrusion 17b.

[0037] The support mechanism 12 includes a support pipe 21, a first support mechanism 18 that supports a plurality of corner panels 16 so as to be movable in the radial direction, a second support mechanism 19 that supports a plurality of side panels 17 so as to be movable in the radial direction, and a fixing pin 20 (see Figure 1). The first support mechanism 18 includes a first moving pipe 22 (first slider), a first support arm 23, and a first drive arm 24. The second support mechanism 19 includes a second moving pipe 25 (second slider), a second support arm 26, and a second drive arm 27.

[0038] As shown in Figure 1, the support pipe 21, the first movable pipe 22, and the second movable pipe 25 are formed in a tubular shape extending in the direction of axis A, and have female threads at both ends. As shown in Figure 2, the first movable pipe 22 is positioned inside the support pipe 21. The second movable pipe 25 is positioned inside the first movable pipe 22. The support pipe 21, the first movable pipe 22, and the second movable pipe 25 are positioned coaxially. The first movable pipe 22 and the second movable pipe 25 are supported on the support pipe 21 so as to be movable in the direction of axis A. To support the first movable pipe 22 and the second movable pipe 25, a low-friction member such as a ball may be provided between the first movable pipe 22 and the second movable pipe 25, and a low-friction member such as a ball may be provided between the support pipe 21 and the first movable pipe 22.

[0039] The support tube 21 has a first hinge portion 21a (see Figure 3) that hinge-connects to the first support arm 23, a second hinge portion 21b (see Figure 4) that hinge-connects to the second support arm 26, a first elongated hole 21c (see Figure 3) through which the first drive arm 24 is inserted, and a second elongated hole 21d (see Figure 4) through which the second drive arm 27 is inserted.

[0040] Figure 3 is a cross-sectional view of the inner formwork 3 along the line III-III in Figure 2. Figure 3 shows the first support mechanism 18. As shown in Figure 3, the first movable pipe 22 has a hinge portion 22a that hinges to the first support arm 23 and a third elongated hole 22b (see Figure 4) through which the first drive arm 24 is inserted, and is supported on the support pipe 21 so as to be movable in the direction of axis A. One end of the first support arm 23 is hinged to the first hinge portion 21a of the support pipe 21, and the other end is hinged to the hinge portion 16a of the corner panel 16. The first support arm 23 has a hinge portion 23a between the one end and the other end that hinges to the first drive arm 24. As shown in Figure 3, one corner panel 16 has multiple first support arms 23 hinged to each other at intervals in the direction of axis A. As a result, each of the multiple corner panels 16 is supported so that it can move easily in the radial direction. In addition, the multiple first support arms 23 are hinged to each of the multiple corner panels 16 and to the support tube 21.

[0041] The first drive arm 24 has one end hinged to the hinge portion 22a of the first moving pipe 22, and the other end hinged to the hinge portion 23a of the first support arm 23. In other words, each of the multiple first drive arms 24 has both ends hinged to the support pipe 21 and the first support arm 23.

[0042] As shown in Figure 3, as the first movable pipe 22 moves relative to the support pipe 21, and the distance between the first hinge portion 21a of the support pipe 21 and the hinge portion 22a of the first movable pipe 22 increases, the first support arm 23, which is hinged to the first hinge portion 21a of the support pipe 21, rotates together with the first drive arm 24, which is hinged to the hinge portion 22a of the first movable pipe 22. As the first support arm 23 rotates, the corner panel 16, which is hinged to the first support arm 23, receives a radially inward force from the first support arm 23. As a result, the corner panel 16 moves radially inward. Conversely, as the first movable pipe 22 moves relative to the support pipe 21, and the distance between the first hinge portion 21a of the support pipe 21 and the hinge portion 22a of the first movable pipe 22 decreases, the corner panel 16 moves radially outward. In this way, the corner panel 16 moves radially in accordance with the movement of the first moving pipe 22 in the direction of axis A.

[0043] Figure 4 is a cross-sectional view of the inner formwork 3 along the line IV-IV in Figure 2. Figure 4 shows the second support mechanism 19. As shown in Figure 4, the second moving tube 25 has a hinge portion 25a that hinges to the second drive arm 27 and is supported so as to be movable in the direction of axis A. The second support arm 26 has one end hinged to the second hinge portion 21b of the support tube 21 and the other end hinged to the hinge portion 17d of the side panel 17. The second support arm 26 has a hinge portion 26a between its one end and the other that hinges to the second drive arm 27. As shown in Figure 4, one side panel 17 has multiple second support arms 26 hinged to it at intervals in the direction of axis A. This allows each of the multiple side panels 17 to be supported so as to be easily movable in the radial direction. Furthermore, multiple second support arms 26 are hinged to each of the multiple side panels 17 and to the support pipe 21.

[0044] The second drive arm 27 has one end hinged to the hinge portion 25a of the second moving pipe 25, and the other end hinged to the hinge portion 26a of the second support arm 26. In other words, multiple second drive arms 27 each have both ends hinged to the second moving pipe 25 and the second support arm 26.

[0045] As shown in Figure 4, as the second movable pipe 25 moves relative to the support pipe 21, and the distance between the second hinge portion 21b of the support pipe 21 and the hinge portion 25a of the second movable pipe 25 increases, the second support arm 26, which is hinged to the second hinge portion 21b of the support pipe 21, rotates together with the second drive arm 27, which is hinged to the hinge portion 25a of the second movable pipe 25. As the second support arm 26 rotates, the edge panel 17, which is hinged to the second support arm 26, receives a radially inward force from the second support arm 26. As a result, the edge panel 17 moves radially inward. Conversely, as the second movable pipe 25 moves relative to the support pipe 21, and the distance between the second hinge portion 21b of the support pipe 21 and the hinge portion 25a of the second movable pipe 25 decreases, the edge panel 17 moves radially outward. In this way, the edge panel 17 moves radially in accordance with the movement of the second moving pipe 25 in the direction of axis A.

[0046] As described above, the corner panel 16 moves radially in accordance with the movement of the first moving pipe 22 in the direction of axis A (see Figure 3). The edge panel 17 moves radially in accordance with the movement of the second moving pipe 25 in the direction of axis A (see Figure 4). By moving the first moving pipe 22 and the second moving pipe 25, the formwork panel 11 can be transformed into an unfolded state in which multiple corner panels 16 and multiple edge panels 17 are continuous in the circumferential direction (see Figure 2). Furthermore, by moving the first moving pipe 22 and the second moving pipe 25, the formwork panel 11 can be transformed from the unfolded state into a reduced state in which multiple corner panels 16 and multiple edge panels 17 are moved radially inward.

[0047] Figure 5 is a cross-sectional view of the inner formwork 3 in the reduced state. In Figure 5, the outer contour of the formwork panel 11 in the expanded state is shown by a dashed line. The formwork panel 11 can switch between an expanded state in which multiple corner panels 16 and multiple side panels 17 are continuous in the circumferential direction, and a reduced state in which the multiple corner panels 16 and multiple side panels 17 are located inward from their positions in the expanded state, depending on the positions of the first and second moving pipes 22 and 25 along axis A.

[0048] During the fabrication of the PCa members, the formwork panel 11 is unfolded, concrete is poured between the outer formwork 2 and the formwork panel 11, and once the concrete has hardened to a strength that allows for demolding, the formwork panel 11 is retracted. This allows the formwork panel 11 to be removed from the hardened concrete.

[0049] As shown in Figure 1, in order to maintain the deployed state, the support mechanism 12 has removable fixing pins 20 that pin the first movable pipe 22 and the second movable pipe 25 in the deployed state. In addition, the first movable pipe 22 and the second movable pipe 25 are provided with holes through which the fixing pins 20 are inserted so that the fixing pins 20 can pin the first movable pipe 22 and the second movable pipe 25 in the deployed state. When the deployed state is maintained, the fixing pins 20 pin the first movable pipe 22 and the second movable pipe 25, thereby preventing the movement of the first movable pipe 22 and the second movable pipe 25 in the direction of axis A. As a result, the radial inward movement of all corner panels 16 and all side panels 17 is prevented, and the formwork panel 11 is prevented from shrinking from the deployed state.

[0050] As shown in Figure 2, the edge panel 17 has a contact portion 17c that adheres to the inner surface of the corner panel 16 when unfolded. When unfolded, the contact portion 17c of the edge panel 17 adheres to the inner surface of the corner panel 16, making it easy to position the corner panel 16 and the edge panel 17 in the appropriate location. In addition, when unfolded, the edge panel 17 can be moved radially inward. As shown in Figure 4, in order to move the edge panel 17 radially inward, it is necessary to move the second moving pipe 25 in the direction of axis A. As shown in Figure 1, when the formwork panel 11 is unfolded, one end of the second moving pipe 25 in the direction of axis A extends outward from the first moving pipe 22 so that the edge panel 17 can be easily moved radially inward when unfolded.

[0051] <Method for manufacturing precast concrete (PCa) members using formwork device 1> Figure 6 is an explanatory diagram illustrating a method for manufacturing a PCa member 30 using a formwork device 1. Figure 7 is a cross-sectional view of the formwork device 1 and the PCa member 30 along the line VII-VII in Figure 6. As shown in Figure 7, reinforcing bars 31 are embedded in the PCa member 30. The reinforcing bars 31 have a plurality of main bars 32, a plurality of stirrups 33, and a plurality of mechanical connectors 34. The plurality of main bars 32 extend in the direction of axis A (see Figure 6) and protrude from one end of the PCa member 30 in the axial direction. The stirrups 33 intersect the main bars 32 and extend in the circumferential direction. Mechanical connectors 34 are attached to the other end of each of the plurality of main bars 32. Mechanical connectors 34 are, for example, sleeves or couplers. In Figure 6, a coupler is shown as an example of a mechanical connector 34. Also, the illustration of the stirrups 33 is omitted in Figure 6. The reinforcing bars 31 are manufactured in advance before the precast concrete member 30 is fabricated using the formwork device 1.

[0052] The manufacturer moves the inner formwork 3 onto the base plate 4 and reduces the formwork panel 11 of the inner formwork 3. Next, the manufacturer attaches the reinforcing bars 31 around the formwork panel 11. At this point, the reduced state of the formwork panel 11 makes it easier to attach the reinforcing bars 31 around the formwork panel 11. Next, the manufacturer expands the formwork panel 11 of the inner formwork 3. Next, the manufacturer pins the first movable pipe 22 and the second movable pipe 25, which are in the expanded state, to the support pipe 21 with fixing pins 20.

[0053] Next, the manufacturer assembles the formwork device 1 as shown in Figure 6. The manufacturer inserts the support pipe 21, the first movable pipe 22, and the second movable pipe 25 of the inner formwork 3 into the through-hole 6b of one of the support fixtures 6. Next, the manufacturer inserts the end of the main reinforcement bar 32 that does not have the mechanical joint 34 attached into the main reinforcement bar hole 6c of one of the support fixtures 6. Then, the manufacturer temporarily fastens the steel rod 35 to the mechanical joint 34 at the other end of the main reinforcement bar 32. Next, the manufacturer inserts the steel rod 35 into the main reinforcement bar hole 6c of the other support fixture 6, and also inserts the support pipe 21, the first movable pipe 22, and the second movable pipe 25 of the inner formwork 3 into the through-hole 6b of the other support fixture 6.

[0054] Next, the manufacturer attaches a nut 36 to the other end of the support pipe 21 of the inner formwork 3, and attaches a nut 36 and a jack 37 to one end of the support pipe 21. Next, the manufacturer tightens the nuts 36 at the other end and the nuts 36 at the one end of the support pipe 21. This secures each of the pair of support fixtures 6 to both axial ends of the support pipe 21 of the inner formwork 3. Next, the manufacturer attaches the pair of side plates 5 to the pair of support fixtures 6.

[0055] Next, the manufacturer pours concrete between the outer formwork 2 and the formwork panel 11 of the inner formwork 3. Then, the manufacturer waits until the concrete hardens to a strength that allows for demolding. Once the concrete hardens, it becomes a precast concrete member 30. Then, the manufacturer removes the inner formwork 3 from the precast concrete member 30 as follows.

[0056] Figures 8 and 9 are explanatory diagrams illustrating the process of removing the formwork panels 11 of the inner formwork 3 from the PCa member 30. The manufacturer removes the fixing pins 20 from the inner formwork 3. Next, the manufacturer attaches a nut to one end of the second movable pipe 25 (the left end in Figure 6) and moves the second movable pipe 25 with a jack or the like, as shown in Figure 8 (in Figure 8, the second movable pipe 25 is moved to the left). As a result, each of the multiple edge panels 17 moves radially inward and separates from the PCa member 30. Note that, as shown in Figure 6, when the formwork panels 11 are in the unfolded state, one end of the second movable pipe 25 in the direction of axis A extends outward from the first movable pipe 22, so that the second movable pipe 25 can be moved and the edge panels 17 can be moved radially inward.

[0057] Next, the manufacturer attaches a nut to one end of the first movable pipe 22 (the left end in Figure 6) and moves the first movable pipe 22 using a jack or the like, as shown in Figure 9 (in Figure 9, the first movable pipe 22 is moved to the left). As a result, each of the multiple corner panels 16 moves radially inward and separates from the PCa member 30. As a result, the formwork panels 11 are in a reduced state as shown in Figure 5, and the formwork panels 11 of the inner formwork 3 are removed from the PCa member 30.

[0058] Next, the manufacturer removes the nuts 36 and jacks 37 from the support pipes 21 of the inner formwork 3. Then, the manufacturer removes the pair of support jigs 6, the pair of side plates 5, and the inner formwork 3 from the PCa member 30. This removes the formwork device 1 from the PCa member 30.

[0059] As shown in Figure 6, the multiple main reinforcing bars 32 of the PCa member 30 protrude from one end in the axial direction of the PCa member 30 (the left end in Figure 6), and a mechanical joint 34 is attached to the other end. The manufacturer can produce various PCa members 30 using the formwork device 1.

[0060] Figure 10 is an explanatory diagram illustrating a method for manufacturing a PCa member 30 in which each of the multiple main reinforcement bars 32 protrudes from both ends in the axial direction. The difference between the manufacturing method shown in Figure 10 and the manufacturing methods shown in Figures 6 to 9 is that each of the ends of each of the multiple main reinforcement bars 32 is inserted into the corresponding main reinforcement hole 6c of a pair of support jigs 6. A manufacturer can manufacture a PCa member 30 in which each of the multiple main reinforcement bars 32 protrudes from both ends in the axial direction by using a manufacturing method that modifies this point from the above-described method.

[0061] Figure 11 is an explanatory diagram illustrating a method for manufacturing a U-shaped PCa member using the formwork device 1. The manufacturer can produce a U-shaped PCa member by not pouring concrete above the formwork panel 11 of the inner formwork 3 when pouring concrete between the outer formwork 2 and the inner formwork 3. The U-shaped PCa member can be used, for example, as a half-precast member for a beam.

[0062] The operation and effects of the formwork device 1 configured as described above are explained below. The support mechanism 12 includes a first support mechanism 18 that supports a plurality of corner panels 16 so as to be movable in the radial direction, and a second support mechanism 19 that supports a plurality of side panels 17 so as to be movable in the radial direction. Therefore, by moving the plurality of corner panels 16 and the plurality of side panels 17 in the radial direction, the formwork panel 11 can be switched between a state in which it is used as formwork (expanded state) and a state in which the formwork panel 11 can be removed from the PCa member 30 (contracted state). This makes it possible to easily manufacture PCa members in which a space extending in a predetermined axial direction is formed inside.

[0063] Multiple edge panels 17 are provided with protrusions 17b on their outer surfaces. This creates recesses in the internal space of the PCa member 30, and creates protrusions in the concrete poured into the internal space of the PCa member 30. As a result, the concrete poured into the internal space of the PCa member 30 is less likely to detach from the internal space of the PCa member 30.

[0064] The support mechanism 12 includes a support pipe 21, a first moving pipe 22, a first support arm 23, a first drive arm 24, a second moving pipe 25, a second support arm 26, and a second drive arm 27. By moving the first moving pipe 22 (first slider) in the direction of axis A, the first support arm 23 rotates, and by moving the second moving pipe 25 (second slider) in the direction of axis A, the second support arm 26 rotates. As a result, the support mechanism 12 can reliably move multiple corner panels 16 and multiple side panels 17 in the radial direction.

[0065] The support pipe 21 has a first elongated hole 21c and a second elongated hole 21d, the first moving pipe 22 is positioned inside the support pipe 21 and has a third elongated hole 22b, and the second moving pipe 25 is positioned inside the first moving pipe 22. This allows multiple corner panels 16 and multiple side panels 17 to be reliably moved in the radial direction.

[0066] The support pipe 21, the first movable pipe 22, and the second movable pipe 25 are arranged coaxially. This makes it easy to move the first movable pipe 22 and the second movable pipe 25 in the direction of axis A relative to the support pipe 21.

[0067] The support mechanism 12 has a removable fixing pin 20 that pins the first movable tube 22 and the second movable tube 25 in the deployed state. This makes it easy to maintain the deployed state when manufacturing the PCa member.

[0068] The edge panel 17 has an adhesion portion 17c that adheres to the inner surface of the corner panel 16 when unfolded. When unfolded, the adhesion portion 17c of the edge panel 17 adheres to the inner surface of the corner panel 16, making it easy to position the corner panel 16 and the edge panel 17 in the appropriate location.

[0069] When the formwork panel 11 is in the deployed state, one axial end of the second moving pipe 25 extends outward from the first moving pipe 22. This makes it easier to move the second moving pipe 25 when reducing the formwork panel 11 from the deployed state to the retracted state and separating the formwork panel 11 from the PCa member 30. As a result, it becomes easier to reduce the formwork panel 11 from the deployed state to the retracted state and separate the formwork panel 11 from the PCa member 30.

[0070] The formwork apparatus 1 comprises an outer formwork 2 and an inner formwork 3. The outer formwork 2 has a bottom plate 4, a pair of side plates 5, and a pair of support jigs 6. This allows for the reliable production of precast members with appropriately shaped spaces formed inside.

[0071] Each of the pair of support fixtures 6 is fixed to each of the axial ends of the support pipe 21 of the inner formwork 3. As a result, the support fixtures 6 can exert a reaction force against the force received from the poured concrete without being supported by other members (i.e., the support fixtures 6 have their own reaction force). This makes it easier to manufacture the PCa members 30.

[0072] The PCa member 30 has a main reinforcing bar 32 protruding from one end in the direction of axis A, and at least one of the pair of support jigs 6 has a main reinforcing bar hole 6c through which the main reinforcing bar 32 is inserted. This makes it easy to manufacture the PCa member 30 having a main reinforcing bar 32 protruding from one end in the direction of axis A.

[0073] ≪First Variation≫ Figure 12 is a cross-sectional view of the inner formwork 3 according to the first modified example. Elements identical or similar to those in the embodiment are denoted by the same reference numerals, and redundant explanations are omitted. Unless otherwise specified, the same applies to subsequent modified examples. As shown in Figure 12, the inner formwork 3 of the first modified example differs from the inner formwork 3 of the embodiment in that not only the side panels 17 but also the corner panels 16 have protrusions 16b.

[0074] ≪Second variation≫ Figure 13 is a schematic cross-sectional view of the inner formwork 3 according to the second modified example. As shown in Figure 13, the inner formwork 3 of the second modified example differs from the inner formwork 3 of the embodiment in that the side panel 17 does not have a protrusion 17b, while the corner panel 16 has a protrusion 16b.

[0075] ≪Third Variation≫ Figure 14 is a cross-sectional view of the inner formwork 3 according to the third modified example. As shown in Figure 14, the inner formwork 3 of the third modified example has a screw hole in the main body portion 17a of at least one side panel 17, and a pipe 17e that is screwed into the screw hole. When manufacturing the PCa member, concrete is poured up to below the upper end of the pipe 17e. This makes it possible to manufacture a PCa member having a through hole that penetrates radially.

[0076] This concludes the description of specific embodiments, but the present invention is not limited to the above embodiments or modifications and can be broadly modified and implemented. For example, the shape of the PCa member 30 may be cylindrical or U-shaped. The shape of the formwork panel 11 (corner panel 16, edge panel 17) and the configuration of the support mechanism 12 can be appropriately changed according to the shape of the PCa member to be manufactured. For example, if the shape of the PCa member to be manufactured is cylindrical with an equilateral triangle cross-section, the formwork panel 11 may be formed from three corner panels and three edge panels. Also, if the shape of the PCa member to be manufactured is cylindrical, the formwork panel 11 may be formed from panels with an arc-shaped cross-section.

[0077] Furthermore, in the embodiment, the inner formwork 3 has a first slider which is a first movable pipe 22, and a second slider which is a second movable pipe 25. The shapes of the first slider and the second slider can be changed as appropriate. For example, the first slider may have a shape in which each portion of the first movable pipe 22 where a hinge portion 22a is provided is formed into a cylindrical portion where a hinge portion 22a is provided, and each cylindrical portion is connected by a rod. Similarly, the second slider may have a shape in which each portion of the second movable pipe 25 where a hinge portion 25a is provided is formed into a cylindrical portion where a hinge portion 25a is provided, and each cylindrical portion is connected by a rod.

[0078] Furthermore, the outer formwork 2 of the embodiment may have a bottom plate 4 and a pair of side plates 5 formed integrally. In addition, the specific configuration, arrangement, quantity, material, specific work and order of each component and part may be changed as appropriate, as long as it does not depart from the spirit of the present invention. Furthermore, some of the components of the above embodiment may be combined with modified examples. Moreover, not all of the components shown in the above embodiment are essential and can be selected as appropriate. [Explanation of Symbols]

[0079] 1: Formwork equipment 1: Support jig 2: Outer formwork 3: Inner formwork 4: Bottom plate 5: Side panel 6: Support fixture 6c: Main reinforcement hole 11: Formwork Panel 12:Support mechanism 16: Corner panel (an example of the first panel) 16b: Convex part 17: Edge Panel (Example of a second panel) 17b: Convex part 17c: Contact area 18: 1st support mechanism 19:Second support mechanism 20: Fixing pin 21: Support tube 21c: 1st long hole 21d: Second long hole 22: First sliding pipe (an example of the first slider) 22b: 3rd long hole 23: First support arm 24: First drive arm 25: Second sliding pipe (an example of a second slider) 26: Second support arm 27: Second drive arm 30: PCa component 31: Reinforcement bars 32: Main reinforcement A: Axis line

Claims

1. An internal formwork for forming a space extending in a predetermined axial direction in a precast concrete member, A formwork panel having an outer surface and composed of a plurality of panels extending along the axial direction, The formwork panel is supported by a support mechanism, The formwork panel consists of a plurality of first panels and a plurality of second panels arranged alternately in the circumferential direction. The support mechanism includes an inner formwork comprising a first support mechanism for supporting a plurality of first panels so as to be movable in the radial direction, and a second support mechanism for supporting a plurality of second panels so as to be movable in the radial direction.

2. The inner formwork according to claim 1, wherein at least one of the first panels or at least one of the second panels is provided with a protrusion on its outer surface.

3. The aforementioned support mechanism is It has a support pipe that extends in the axial direction, The first support mechanism is, A first slider extending in the axial direction and supported by the support tube so as to be movable in the axial direction, A plurality of first support arms are hinged to each of the plurality of first panels and the support tube, It comprises a plurality of first drive arms, each having hinged connections to the first slider and the first support arm, The second support mechanism is, A second slider extending in the axial direction and supported by the support tube so as to be movable in the axial direction, A plurality of second support arms are hinged to each of the plurality of second panels and the support tube, The inner formwork according to claim 1, further comprising a plurality of second drive arms, each having hinged connections to the second slider and the second support arm.

4. The first slider consists of a tubular first moving tube and is positioned inside the support tube. The second slider consists of a tubular second moving tube and is positioned inside the first moving tube. The support tube has a first elongated hole through which the first drive arm is inserted, and a second elongated hole through which the second drive arm is inserted. The first moving tube has a third elongated hole through which the second drive arm is inserted. The inner formwork according to claim 3, wherein the formwork panel switches between an expanded state in which the plurality of first panels and the plurality of second panels are continuous in the circumferential direction, and a contracted state in which the plurality of first panels and the plurality of second panels are located inward from their positions in the expanded state, depending on the axial positions of the first and second moving pipes.

5. The inner formwork according to claim 4, wherein the support pipe, the first moving pipe, and the second moving pipe are arranged coaxially.

6. The inner formwork according to claim 4, wherein the support mechanism pins the first and second movable tubes in the deployed state and has removable fixing pins.

7. The inner formwork according to claim 4, wherein one of the first panel and the second panel has an adhesion portion that adheres to the inner surface of the other of the first panel and the second panel in the unfolded state.

8. The inner formwork according to claim 7, wherein when the formwork panel is in the deployed state, one axial end of one of the first and second moving pipes extends outward more than the other of the first and second moving pipes.

9. A formwork device for manufacturing a precast concrete member having a space extending in a predetermined axial direction, An inner formwork according to any one of claims 1 to 8, The system comprises an outer formwork that defines the outer surface other than the upper surface of the precast concrete member, The aforementioned outer formwork is A bottom plate that defines the bottom surface of the aforementioned precast concrete member, A pair of side plates are defined on the bottom plate, defining a pair of sides of the precast concrete member, A formwork apparatus comprising a pair of support jigs that are in close contact with each of the axial ends of the formwork panel of the inner formwork and support the inner formwork.

10. The inner formwork is provided as described in claim 3, The formwork apparatus according to claim 9, wherein each of the pair of support jigs is fixed to each of the axial ends of the support pipe of the inner formwork.

11. The precast concrete member extends in the axial direction and has main reinforcement bars protruding from at least one end in the axial direction. The formwork apparatus according to claim 9, wherein at least one of the pair of support jigs has a main reinforcement hole through which the main reinforcement is inserted.

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