JP6201278B2 - Fastening device in formwork for centrifugal pile forming - Google Patents

Description

  The present invention relates to a fastening device in a concrete pile centrifugal mold.

  Concrete piles are generally manufactured by centrifugal molding using a formwork. A typical centrifugal mold has a pair of semi-cylindrical upper and lower molds. These upper and lower molds are provided with outward flanges extending in the axial direction of the mold at both ends in the circumferential direction. At the time of centrifugal molding, the upper and lower molds are overlapped with each other, and a fastening device comprising a number of fastening bolts and nuts It is fastened integrally.

  Briefly explaining the manufacturing process of the concrete pile, first, a reinforcing bar is installed in the lower mold on the production line, and the required amount of ready-mixed concrete is filled. After that, the upper mold is placed so as to cover the lower mold, and the flanges of the upper and lower molds are fastened together with a fastening device, and transported onto a centrifugal molding machine and centrifugally molded. After that, the mold pile is artificially cured by steam curing or autoclave, then demolded and naturally cured, and the concrete pile is commercialized.

  The formwork is assembled and demolded every time the concrete pile is molded, and the fastening device is repeatedly fastened and released accordingly. Especially when the fastening device is made of bolts and nuts, the thread of the bolts gradually wears. If the bolts are tightened while the thread is worn, the nuts will be damaged, and the fastening state of the upper and lower molds will eventually deteriorate. Such deterioration of the fastening state leads to deformation of the formwork, occurrence of leakage of concrete paste during centrifugal molding, and accidents of removing the formwork.

  By the way, the flange of the upper mold is provided with a bolt holder for guiding the fastening bolt when the upper and lower molds are fastened, and the fastening bolt is held by the bolt holder even when the mold drawn out from the nut is not fastened. (For example, refer to Patent Document 1). Therefore, the state of the thread of the fastening bolt cannot be confirmed unless the fastening bolt is removed from the holder.

Japanese Utility Model Publication No. 3-87206

  However, there are a large number of fastening bolts per formwork, and the fastening bolt and the bolt holder are provided with a retaining mechanism for preventing the fastening bolt from coming out of the holder. For this reason, it is not easy to check the screw thread by releasing the fastening bolts one by one from the bolt holder after releasing the retaining mechanism.

  For this reason, conventionally, the confirmation of the wear state of the fastening bolt has relied on the feel of the operator's hand and the sound entering the ear during fastening. However, such a confirmation method requires skill.

The present invention has been made based on the technical background as described above, and achieves the following object.
An object of the present invention is to provide a fastening device in a concrete pile centrifugal mold that can easily confirm the state of a screw thread regardless of the skill of an operator.

The present invention employs the following means in order to achieve the above object.
That is, the present invention is a mold for centrifugally forming a concrete pile, and has a pair of semi-cylindrical upper and lower molds, and the molds at both circumferential ends of the upper and lower molds. An outward flange extending along the axial direction of the frame is provided, the flanges of the upper and lower molds are overlapped, and a number of fastening bolts that penetrate these flanges from the flange side of the upper mold and the lower mold The upper and lower molds are fastened to each other by nuts provided on the upper mold, and the fastening bolts are guided to the flanges of the upper mold when the upper and lower molds are fastened and are held when not fastened. In a formwork in which a large number of cylindrical bolt holders are provided at intervals in the axial direction of the formwork,
The bolt holder is fixed to the upper surface of the flange of the upper mold frame by welding,
An opening through which the threaded portion of the fastening bolt can be seen is provided in the peripheral wall of the bolt holder, and the opening is provided by cutting out the peripheral wall from the lower end of the bolt holder to the axial middle portion. > It is in the fastening device in the form for concrete pile centrifugal forming characterized by the above.

  More specifically, a coil spring that biases the fastening bolt upward is disposed between the head of the fastening bolt and the bolt holder. In this case, an annular step portion may be provided on the outer periphery of the bolt holder at a position above the upper end of the opening, and the lower end of the coil spring may be locked to the step portion.

  According to the present invention, the state of the thread can be easily visually confirmed regardless of the skill of the operator.

BRIEF DESCRIPTION OF THE DRAWINGS It is a front view which shows 1st Embodiment of this invention and shows the mold for centrifugal forming of a concrete pile partially. It is an expanded sectional view by the AA arrow of FIG. It is a front view by the BB line arrow of FIG. It is a bottom view by the CC arrow of FIG. It is sectional drawing which shows the fastening state of a formwork. It is sectional drawing which shows 2nd Embodiment of this invention. It is sectional drawing which shows 3rd Embodiment of this invention. It is sectional drawing which shows 4th Embodiment of this invention. The other example of opening is shown, (a) is a front view, (b) is sectional drawing. Another example of opening is shown, (a) is a front view, (b) is sectional drawing. Another example of opening is shown, (a) is a front view, (b) is sectional drawing.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a front view showing a first embodiment of the present invention and partially showing a formwork for centrifugal forming of a concrete pile (hereinafter simply referred to as a formwork). The mold 1 has a pair of semi-cylindrical upper mold 1a and lower mold 1b installed sideways. These upper and lower molds 1a and 1b are made of steel, and are reinforced by ribs 2 and 3 provided in the axial direction and the circumferential direction of the mold 1, respectively.

  At both ends in the circumferential direction of the upper and lower molds 1a and 1b (only one is shown in FIG. 1), outward flanges 4a and 4b extending in the axial direction of the mold 1 are provided. A large number of bolt holders 5 are provided on the upper surface of a flange (hereinafter referred to as an upper flange) 4 a of the upper mold 1 a at intervals in the axial direction of the mold 1. These bolt holders 5 hold fastening bolts 6.

  On the other hand, a nut case 7 is provided at a position corresponding to the bolt holder 5 on the lower surface of a flange (hereinafter referred to as a lower flange) 4b of the lower mold 1b. The upper and lower molds 1 a and 1 b are fastened to each other by fastening fastening bolts 6 to nuts (described later) housed in these nut cases 7. Thereby, the formwork 1 becomes a substantially cylindrical shape as a whole.

  FIG. 2 is an enlarged cross-sectional view taken along line AA in FIG. 3 is a front view taken along the line BB in FIG. 2, and FIG. 4 is a bottom view taken along the line CC in FIG. The upper flange 4a is fixed to the end of the upper mold 1a in the circumferential direction by welding so that approximately half of the flange thickness protrudes from the end. On the other hand, the lower flange 4b is fixed to the end of the lower mold 1b in the circumferential direction by welding so that approximately half of the flange thickness is retracted from the end.

  That is, a deviation (step) in the circumferential direction of the mold is generated between the abutting surface 8 by the circumferential end surfaces of the upper and lower molds 1a and 1b and the overlapping surface 9 of the upper and lower flanges 4a and 4b. A packing 10 is provided at the inner end of the lower flange 4b. By adopting such a structure, the concrete paste is prevented from leaking during centrifugal forming of the concrete pile.

  The upper and lower flanges 4a and 4b are provided with holes 11a and 11b, respectively, through which the fastening bolts 6 are passed. The bolt holder 5 is fixed to the periphery of the hole 11a on the upper surface of the upper flange 4a by welding. The bolt holder 5 is cylindrical and has a flange 12 at the lower end. The fastening bolt 6 to be inserted into the bolt holder 5 has a threaded portion 6b formed at the tip of the shaft portion 6a. The bolt holder 5 has a height dimension that is somewhat larger than the length dimension of the threaded portion 6b.

  A coil spring 14 is disposed between the head 6 c of the fastening bolt 6 and the bolt holder 5. Specifically, the coil spring 14 is disposed between the washer 13 fitted to the shaft portion 6 a of the fastening bolt 6 and the flange 12 of the bolt holder 5 so as to surround the fastening bolt 6. The fastening bolt 6 is always urged upward by the coil spring 14, that is, in a direction of coming out of the bolt holder 5, and when the mold 1 is not fastened, the tip surface of the threaded portion 6b of the fastening bolt 6 is the top surface of the upper flange 4a. It becomes almost the same. An annular groove 15 is formed in the upper inner periphery of the bolt holder 5, and a stopper 16 made of a C-shaped ring spring is fitted into the annular groove 15. On the other hand, a flange 17 is provided immediately above the threaded portion 6 b of the fastening bolt 6, and the flange 17 is locked to the stopper 16, thereby preventing the fastening bolt 6 from coming out of the bolt holder 5. The retaining mechanism for the fastening bolt 6 is constituted by the stopper 16 and the flange 17.

  The nut case 7 is fixed to the periphery of the hole 11b on the lower surface of the lower flange 4b by welding. A nut 19 to which the screw portion 6 b of the fastening bolt 6 is screwed is accommodated in the nut case 7. The nut case 7 is provided with a pair of split pins 18 that penetrate the peripheral wall at two locations and pass through the inside of the case 7, and the nut 19 is supported by these split pins 18.

  2 and 3 show a state when the mold 1 is not fastened. In order to fasten the mold 1 from this state, the fastening bolt 6 is guided against the urging force of the coil spring 14 to guide the bolt holder 5. Rotate while descending. Thereby, the threaded portion 6b of the fastening bolt 6 is screwed to the nut 19 through the holes 11a and 11b, and the washer 13 is locked to the upper surface of the bolt holder 5 (see FIG. 5). Even in the fastening state of the mold 1, the urging force of the coil spring 14 acts and is added as a fastening force between the screw portion 6 b and the nut 19.

  Here, the centrifugal forming of the concrete pile will be schematically described. After the reinforcing bar is set on the lower mold 1b, concrete is placed on the lower mold 1b. Next, the upper mold 1a is placed on the lower mold 1b, and the upper and lower flanges 4a and 4b are overlapped. Then, the upper and lower molds 1 a and 1 b are fastened by the fastening bolt 6, that is, the mold 1 is fastened. After the mold 1 is fastened, the mold 1 is set in a centrifuge and the concrete is compacted by rotating at high speed. Next, solidification of the concrete is promoted in the steam curing room. After the concrete is solidified, the fastening bolt 6 is extracted from the nut 19 and the fastening of the mold 1 is released. And the upper mold 1a is removed from the lower mold 1b (demolding), and the finished concrete pile is taken out from the lower mold 1b.

  In this way, the mold 1 is assembled and demolded every time the concrete pile is manufactured, and the screwing and unloading of the fastening bolt 6 to and from the nut 19 is repeated accordingly. It will wear out.

  Therefore, in the present invention, the opening 20 is provided in the peripheral wall of the bolt holder 5 so that the screw portion 6b can be seen. The opening 20 is provided so as to face outward in the radial direction of the mold 1. In this embodiment, the opening 20 is a notched opening provided by notching a peripheral wall from the lower end of the bolt holder 5 to its middle portion in the axial direction.

  As for the screw part 6b, it has been empirically found that the second to fourth thread from the tip of the fastening bolt 6 is severely damaged by wear. Therefore, the opening 20 has a height dimension H in which these threads can be visually observed. Further, if the width dimension W of the opening 20 is too large, not only the function of the bolt holder 5 guiding the fastening bolt 6 is impaired, but also the compressive strength of the bolt holder 5 is reduced, so that the outer diameter of the screw portion 6b. Is also small. Even if the width dimension W is reduced, the entire circumference of the threaded portion 6b can be visually observed by rotating the fastening bolt 6.

  By providing the opening 20 as described above, the state of the thread of the screw portion 6b can be easily confirmed when the mold 1 is not fastened. As a result, the wear damage of the screw thread can be detected at an early stage, and the fastening bolt 6 can be replaced without delay. Therefore, it is possible to prevent leakage of the concrete paste due to poor tightening of the formwork, and a defective product of the manufactured concrete pile. It is possible to reduce the occurrence of. In addition, it is possible to prevent the occurrence of an accident in which the formwork is removed.

  FIG. 6 is a sectional view showing a second embodiment of the present invention. In this embodiment, a coil spring 24 that biases the fastening bolt 6 is disposed between a flange 6 d provided immediately below the head of the fastening bolt 6 and the upper end surface of the bolt holder 5. Both the coil spring 14 shown in the first embodiment and the coil spring 24 shown in the second embodiment have a relatively wide winding interval, and the openings 20 are arranged as shown in the first embodiment. Although the screw thread is sufficiently visible through the opening 20, the opening 20 is not covered by the coil spring 24 by the arrangement as in the second embodiment, so that the worn state of the screw thread can be surely seen.

  In the second embodiment, the winding 24a of the coil spring 24 has a rectangular cross section. If the winding has a circular cross section, when the coil spring 24 is compressed, slipping occurs between the upper and lower windings and the winding is disturbed. As a result, the tightening force is not transmitted to the upper and lower flanges 4a and 4b. Such a problem can be avoided by using the winding 24a having a rectangular cross section. Other configurations are the same as those of the first embodiment.

  7 and 8 are cross-sectional views showing third and fourth embodiments of the present invention, respectively. In these embodiments, an annular step 25 is provided on the outer periphery of the bolt holder 5 so that the lower end of the coil spring 14 is locked. In the third embodiment shown in FIG. 7, the annular step portion 25 is formed by a flange provided on the outer periphery of the bolt holder 5. In the third embodiment shown in FIG. 8, the annular step portion 25 is formed by cutting the outer periphery of the upper portion of the bolt holder 5 to reduce the outer diameter. In both the third and fourth embodiments, the annular step portion 25 is provided above the upper end of the opening 20. Other configurations are the same as those of the first embodiment.

  According to the third and fourth embodiments, when the coil spring 14 is compressed, the washer 13 abuts against the upper end surface of the bolt holder 5, so that the load that causes the coil winding of the coil spring 14 to slip. Therefore, there is no problem that a winding having a circular cross section is used. Further, since the opening 20 is not covered by the coil spring 14, the wear state of the thread can be surely visually observed.

  In each of the above embodiments, the number of openings is one. However, the number of openings is not limited to this. Also, the shape of the opening can take various forms. FIGS. 9-11 shows another example of opening, in each figure, (a) is a front view of the bolt holder 5, (b) is an axial sectional view.

  In the example shown in FIG. 9, the opening 30 is a notch opening as in the above embodiment, and the upper peripheral surface of the opening 30 is a tapered surface 30 a that expands inward of the bolt holder 5. By doing in this way, the visible range of the screw part 6b can be enlarged.

  In the example shown in FIG. 10, the opening 40 is a circular hole, and the entire peripheral surface of the opening 40 is a tapered surface 40 a that expands inward of the bolt holder 5. Also in this example, the visible range of the screw portion 6b can be increased.

  In the example shown in FIG. 11, the opening 50 is an oval hole along the circumferential direction of the bolt holder 5, and the upper and lower peripheral surfaces of the opening 50 are tapered surfaces 50 a and 50 b that expand toward the inside of the bolt holder 5. Is. Also in this example, the visible range of the screw portion 6b can be increased.

1 Formwork 1a Upper formwork 1b Lower formwork 4a Upper flange 4b Lower flange 5 Bolt holder 6 Fastening bolt 6a Shaft part 6b Screw part 7 Nut case 14 Coil spring 19 Nut 18 Split pin 20 Opening

Claims (3)

A mold for centrifugally forming a concrete pile, having a pair of semi-cylindrical upper and lower molds, along the axial direction of the mold at both circumferential ends of the upper and lower molds The flanges of the upper and lower molds are overlapped, and a plurality of fastening bolts penetrating these flanges from the flange side of the upper mold and the nuts provided on the lower mold are provided. The upper and lower molds are fastened to each other, and a cylindrical bolt holder is provided on the flange of the upper mold to guide the fastening bolts when the upper and lower molds are fastened and to hold the fastening bolts when not fastened. In the mold provided with a large number of intervals in the axial direction of the mold,
The bolt holder is fixed to the upper surface of the flange of the upper mold frame by welding,
An opening through which the threaded portion of the fastening bolt can be seen is provided in the peripheral wall of the bolt holder, and the opening is provided by cutting out the peripheral wall from the lower end of the bolt holder to the axial middle portion. > A fastening device for a formwork for centrifugal forming of concrete piles.   2. The fastening in a concrete pile centrifugal mold according to claim 1, wherein a coil spring for biasing the fastening bolt upward is disposed between a head of the fastening bolt and the bolt holder. apparatus.   3. The concrete pile centrifugal machine according to claim 2, wherein an annular step portion is provided on an outer periphery of the bolt holder at a position above the upper end of the opening, and a lower end of the coil spring is locked to the step portion. Fastening device in the mold for molding.

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