JP2007244720A - Pc steel wire strand sheath cutter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a PC (Prestressed Concrete) steel wire strand sheath cutter capable of perform stable cutting at all times, since it requires a force of grip even in cutting a thick sheath and held by a holder of the whole form corresponding to a blockout structure. <P>SOLUTION: The sheath cutter comprises a holder part consisting of two facing holder plates, each of which has a narrow part on one side in a longitudinal direction, a wide part on the other side and is formed with a ridge at the center through the narrow and wide parts, and having grip parts extending in a direction opposite to the narrow part on one end side, which is fixed between the wide parts of the two holder plates, and a cutter part having two cutter levers, each of which is pivoted at the narrow part of the holder and attached with a blade on the front end and the rear end extending along the grip part, are symmetrically provided across the ridges. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a sheath cutter for pre-stressed concrete (PC) steel wires, and more particularly to a sheath cutter for PC steel wires that can easily cut a sheath of wire from pre-grout PC steel.

In general, in a prestressed concrete structure by a post-tension method employed in the civil engineering field, a PC steel strand, which is a tension material, is inserted into a sheath, and cement grout is injected into the sheath after the tension is fixed. In recent years, a pre-grout PC steel wire that can omit the injection of the cement grout has been put into practical use. FIG. 5 shows the structure of the wire from the pre-grout PC steel. A flowable curable epoxy resin is applied to the surface of the PC steel wire, and a high-density polyethylene resin is applied to the outer periphery with a thickness of 1.5 to 2.5 mm. And is molded into a shape having irregularities as a sheath.
Since the PC steel strand is constructed, the fixing end and the tension fixing end cannot be hooked by the fixing tool and the jack from the outside of the sheath. Must be exposed.

As a method for cutting the sheath, scissors, nippers and the like have been conventionally used, but there is a problem that when the sheath is thick and hard, it cannot be easily cut. Further, the fixing end of the stranded wire of PC steel often has a so-called box-opening structure in which a recess is formed in a concrete body as shown in FIG. 6, and in this structure, in order to cut the sheath from the side, It took time and effort to draw the wire from the pre-grout PC steel in the construction state, cut it, and return it to its original position after excision.
Conventionally, sheath cutters of Patent Document 1 and Patent Document 2 have been proposed as sheath cutting means in place of the above scissors and nippers. The cutter of Patent Document 1 is composed of a cutter part of a nipper type biting tool and a steel material holding member having a straight pipe or a U-shaped groove for holding a PC steel material, and can be cut in a stable posture, and a blade part It is supposed that there is an effect that can be cut along the position close to the bearing plate. In addition, the sheath cutter disclosed in Patent Document 2 crosses two main materials and is fixed to a shaft, and from one of these two main materials, one side is a cut portion and the other side is a gripped portion, The main material on the cutting portion side is provided with a semicircular cutout portion opposed to each other, and a plurality of disk-shaped blades are arranged so as to surround the cutout portion. The entire circumference of the sheath can be easily cut, and the effect of being able to cut by rotation of about 90 degrees is described.
JP 2000-317157 A JP 2003-134625 A

However, since the sheath cutter disclosed in Patent Document 1 described above is a nipper type cutting of a crossing one-point hinge system, in the case of a thick sheath such as pre-grout PC steel strand, considerable force and time are required for the cutting operation. In addition, in the sheath cutter of Patent Document 2, as in Patent Document 1, since the cutting operation is a type of pushing a lever of a crossing one-point hinge method, it is also very difficult to cut. There was a problem of requiring power and time. In addition, since any type of sheath cutter does not have a structure that stably holds the whole, the cutter operation may be hindered in some cases.
More importantly, the conventional sheath cutter requires a basic structure in which the lever or main material tip is opened and closed in a scissor shape during operation, so when used in the boxing structure shown in FIG. Depending on the size, the sheath cutter cannot be inserted, making it impossible to work, and it is unavoidable to pull out the strands to cut the sheath and then push it back. there were.
The present invention has been made in consideration of the problems and circumstances of such a conventional sheath cutter, and has a structure in which the sheath excision portion keeps the smallest outer diameter as much as possible (does not open outward). Therefore, it can be applied to a narrow box-opening structure, and the sheath can be cut off at the most desirable position, and it is sufficient to cut a thick sheath such as a pre-grout PC steel strand with a normal gripping force. And since the whole is hold | maintained with the holder of the shape corresponding to a boxing structure, it aims at providing the sheath cutter for wires from PC steel which can always perform cutting operation in the stable state.

The PC steel strand sheath cutter according to the present invention for solving the above-mentioned problems has a narrow portion on one end side in the longitudinal direction and a wide portion on the other end side, and is centered through the narrow portion and the wide portion. A holder part formed by fixing two gripping parts that are opposed to the narrow part between the wide parts of the two holder plates, and opposing the two holder plates formed with the protrusions; A cutter part which is provided with two cutter levers that are pivotally supported by the narrow part of the holder and whose blade part is attached to the front end and the rear end extends along the grip part, symmetrically across the protruding part. It is characterized by comprising.
Further, in the above-mentioned sheath cutter, the pipe is fixed along the central ridge portion of the holder plate, and this is used as a wire insertion portion from the PC steel, and further, the shaft fulcrum of the cutter lever with respect to the holder plate. The position or cutting angle of the blade portion with respect to the sheath can be made variable so that the sheath diameter can be changed, and a spring that urges the grip portion and the cutter lever in the direction of expanding both is provided. Is preferred.
In addition, in the sheath cutter of the present invention, the inner surface of the ridge portion at the center of the holder plate or the inner side of the pipe fixed in the ridge portion is peeled so as to contact the sheath cut by the blade portion and pull it out. A mechanism is provided. It is preferable that the peeling mechanism has a shape that does not hinder the insertion of the stranded portion of the PC steel into the ridge portion or the pipe, and is locked to the sheath when pulled out after the sheath cut.

According to the sheath cutter according to the present invention, not the nipper type open and closed cutting, but the cutter part is pivotally supported by the holder part via independent hinges, so the non-expanding type cutting that does not close and open Therefore, it is possible to insert even in a narrow space such as a box shape, and because the sheath is excised with a gripping method that can exert a large gripping force, even a thick sheath of pre-grout PC steel wire It can be easily cut together with the resin part. Moreover, since it is a structure which hold | maintains the whole cutter with the holder part fitted to a box extraction structure, a sheath and a resin part can be excised in the stable state with a construction state. Further, since the cutter blade always enters substantially perpendicular to the sheath, an extra external force is not applied to the blade portion, the service life is prolonged, and there is an advantage that cutting can be performed at an optimum position without leaving the sheath.
Further, according to the sheath cutter of the present invention provided with a mechanism for easily peeling the cut sheath, the sheath after cutting can be easily removed from the line, so that the burden on the blade portion can be reduced. , Contributes to longer life.

The present invention will be described below based on the best embodiment shown in the drawings.
1 is a front view showing a specific example of a sheath cutter according to the present invention, FIG. 2 (a) is a cross-sectional view taken along the line AA 'of FIG. 1, and FIG. 2 (b) is an end view on the left side of FIG. As shown in the figure, the sheath cutter basically includes a holder portion that holds the entire cutter and a cutter portion that is incorporated into the holder portion.
As shown in the drawing, the holder part has a narrow part 1a and a wide part 1b arranged in a substantially T shape via a step part 1c, and a cross-sectional mountain shape in the center through the narrow part 1a and the wide part 1b. The two holder plates (holder main bodies) 1 formed with the protrusions 1d are opposed to each other, and one end side is opposite to the narrow portion 1a between the wide portions 1b of the two holder plates 1. Two extending grips 2 are fixed. The narrow part 1a of the holder plate 1 is a part that enters the boxing fixing structure in an actual sheath excision operation, and has a width and a length that match the boxing dimensions, and the wide part 1b is a boxing fixing. It is a part that goes out of the structure, and the narrow part 1a and the step part 1c of the wide part 1b serve to accurately set the cutter part at a predetermined position when it contacts the concrete end face.
In the illustrated example, the narrow part 1a and the wide part 1b of the holder part are shown in a shape that is clearly separated through the step part 1c. However, in the present invention, the front end side of the holder part can be easily inserted into the box opening structure. Any other shape can be adopted as long as the grip portion 2 is securely attached to the rear end side. For example, the entire holder portion can be formed in a shape similar to a taper shape having no stepped portion.

The grip portion 2 of the holder plate 1 is formed, for example, by fixing a steel pipe between the two holder plates 1 by welding. In addition, a circular pipe (for example, a steel pipe) 3 for inserting a wire from a PC steel covering a sheath portion to be cut is fixed inside the protruding portion 1d. The pipe 3 needs to have a sufficient diameter for insertion of a PC steel strand.
In the example shown in the figure, a case where a steel pipe is separately fixed in the protruding ridge portions 1d of the two holder plates 1 to form a wire insertion portion from PC steel, of course, without providing the steel pipe. The wire insertion portion may be formed from PC steel only by the opposing protruding portion 1d. In this case, the protruding portion 1d may be formed in a cross-sectional arc shape or a polygonal shape.

Next, the cutter part incorporated in the holder is pivotally supported by a hinge 4 serving as a fulcrum at the narrow part 1a of the holder plate 1 and is provided with a blade part (usually a flat part) at the tip part protruding from the narrow part 1a. (Consisting of a blade) 6 is attached, and two cutter levers 5 whose rear end side extends along the grip portion 2 are provided symmetrically with the ridge portion 1d interposed therebetween. The two cutter levers 5 (hereinafter simply referred to as levers) are made of a rigid material (for example, a metal bar) having a rectangular cross section, and the rear end side has a shape that is easy to grip. By moving the rear end portions of these two opposing levers 5 in a direction to open each other, that is, in a direction to bring the lever 5 closer to the grip portion 2, the blade portion 6 on the front end side moves in a direction to close each other. When the lever 5 is bitten into the sheath 9 of the stranded wire 8 (the state of the lower lever and blade portion in FIG. 1) and the lever 5 is moved in the direction to close each other, the blade portion 6 moves in the opening direction (upper side in FIG. 1). Lever and blade state). Such an opening / closing operation of the lever 5 via the hinge 4 is performed when an operator grasps the grip portion 2 of the holder and the lever 5 simultaneously at the time of actual sheath excision.
When the sheath is excised, the grip portion 2 and the lever 5 are gripped together, but after the excision, the lever 5 is automatically returned to the original position so that both are extended between the grip portion 2 and the lever 5. It is preferable to provide a spring 7 for biasing.

The blade portion 6 is preferably attached to the front end surface of the lever 5 with a screw 10 as shown in FIG. The blade portion 6 is replaced when the blade portion is worn or damaged, or for changing the mounting angle so that it always bites into the sheath at a right angle. Further, by setting the hardness of the blade portion 6 to be slightly lower than that of the PC steel wire, it is possible to consider not to damage the wire itself when the sheath is cut.
Furthermore, since the bite depth of the blade 6 can be changed by making the fulcrum position (hinge 4 position) of the lever 5 variable within a certain range, the appropriate bite depth corresponding to the diameter of the sheath to be excised As shown, a plurality of fulcrum positions are provided in advance in the narrow portion 1a of the holder, and the fulcrum positions corresponding to the sheath diameter to be applied are selected in advance and the lever 5 is attached. Further, the fulcrum may be fixed and replaced with a blade portion having an angle corresponding to the sheath diameter.

  In actual use of the sheath cutter according to the present invention, as shown in FIG. 3, the operator holds the two grip portions 2 of the holder portion with both hands, and the pre-grout PC steel strand in the unboxing structure in the construction. After the end of 8 is aligned and inserted into the pipe 3 of the holder part, the blade part 6 comes into contact with the bearing plate, or when the step part 1c of the holder plate 1 hits the concrete 11, the worker By gripping the two pairs of grips 2 and lever 5 with both hands, the blade tip of the blade 6 bites into the sheath 9 of the PC steel wire 8, and pulls forward while rotating around the axis as it is together with the sheath. Excise the curable epoxy resin. It is also possible to provide a separate guide mechanism or the like so that the whole can be easily rotated around the axis.

The cutting and removal of the sheath 9 by the blade portion 6 is difficult when the curable epoxy resin is cured. Therefore, it is desirable that the sheath 9 is not cured, but the sheath cutter shown in FIG. 1 is cut anyway. The removal of the sheath afterward depends on the blade portion (becomes a state where the blade portion is scraped off), and in some cases, a large burden is applied to the blade edge. For this reason, in this invention, the sheath cutter which has a mechanism which does not rely only on a blade part as a removal mechanism (peeling mechanism) of the sheath after a cutting | disconnection is shown as another form example.
That is, as shown in FIGS. 4 (a) and 4 (b), in the example in which the circular pipe 3 is fixed in the projecting ridge portions 1d of the two holder plates 1 to form the wire insertion portion from the PC steel, the pipe 3 includes a fan-shaped presser plate 13 attached to the inner surface of the pipe with one end side in the cutter blade edge direction as a fixed fulcrum 12, and a presser screw 14 capable of pressing the other end side of the presser plate 13 in the pipe radial direction. The peeling mechanism is arranged. The peeling mechanism is preferably provided in a pair as opposed to each other as shown in the drawing, but it is sufficient that at least one peeling mechanism is provided.

The above-mentioned peeling mechanism does not get in the way when the PC steel wire is inserted into the pipe 3, and after the sheath is cut at a predetermined position, the holding plate 13 is pushed by the holding screw 14 to push the tip of the holding plate 13. Enters the rib concave portion of the sheath pipe 9 and is pulled out in this state to remove the sheath portion and expose it. The fan plate of the pressing plate 13 has a shape that matches the circumference of the sheath, and is considered to be as close to the sheath as possible.
The peeling mechanism is not limited to the structure described above. When a pipe is inserted through a stranded wire, the relative movement of the stranded wire and the pipe is not hindered. Any structure and shape may be used as long as the inner surface of the pipe is in a locked state with the sheath of the stranded wire and has a function of pulling out the sheath in the pulling direction.
In order to protect the cutting edge (for situations such as dropping or collision when handling the cutter), a cutting edge guard mechanism smaller than the inner dimension of the box shape, for example, a guard mechanism formed in a cylindrical shape or a polygonal tubular shape is used. It is desirable to put it on the outside.

The performance when the sheath cutter of the present invention is applied under the following conditions in the embodiment shown in FIG. 3 is shown in comparison with the conventional method (Patent Document 1).
[Conditions]
-Boxed structure: depth 180mm, bottom diameter 135mm, top diameter 170mm
-Wire diameter from pre-grout PC steel (sheath covered): 28.6 mm
・ Sheath cutter: 310mm in total length (from the blade part to the rear end of the grip part), 100mm in width of the holder plate narrow part, pipe outer diameter 48.6mm
[Results] (As shown in Table 1)

It is a front view which shows the specific example of the sheath cutter which concerns on this invention. (A) is the sectional view on the AA 'line of FIG. 1, (b) is the left view of FIG. It is explanatory drawing which shows the case where this invention is applied to the actual box extraction fixing structure. (A) is explanatory drawing which shows the example which provided the sheath latching mechanism in the circular pipe for wire insertion from PC steel in the sheath cutter which concerns on this invention, (b) is the sectional side view. (A) is sectional drawing of a pre-grout PC steel strand, (b) is a sheath external view. It is explanatory drawing which shows the box extraction fixing | fixed edge part which constructs a pre-grout PC steel strand.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Holder plate 1a Narrow part 1b Wide part 1c Step part 1d Projection part 2 Grasp part 3 Circular pipe 4 Hinge 5 Cutter lever 6 Blade part 7 Spring 8 PC steel wire 9 Sheath 10 Screw 11 Concrete 12 Holding plate fulcrum 13 Presser Plate 14 holding screw

Claims (6)

  Two holder plates having a narrow portion on one end side in the longitudinal direction and a wide portion on the other end side and having a protrusion formed in the center through the narrow portion and the wide portion are opposed to each other. Between the wide parts of the holder plate, a holder part in which a pair of gripping parts extending in the opposite direction to the narrow part is fixed, and a blade part is attached to the tip end that is pivotally supported by the narrow part of the holder part A PC steel strand sheath cutter, characterized in that the two cutter levers, each having a rear end extending along the inside of the gripping part, are provided with a cutter part sandwiching the protruding part.   The sheath cutter for PC steel strands according to claim 1, wherein a pipe is fixed along a central ridge portion of the holder plate, and this is used as a wire insertion portion from PC steel.   The sheath according to claim 1 or 2, wherein a peeling mechanism for pulling out in contact with the sheath cut by the blade portion is provided on the inner side of the ridge portion or on the inner side of the pipe fixed in the ridge portion. cutter.   The position of the shaft fulcrum with respect to the holder plate of the cutter lever can be made variable, or the cutting angle of the blade portion with respect to the sheath can be made variable, so that the change in the sheath diameter can be dealt with. The sheath cutter for wire from PC steel in any one of 1-3.   The sheath cutter for PC steel strands according to any one of claims 1 to 4, wherein a spring for urging the grip portion and the cutter lever in a direction to spread both is provided.   The sheath cutter for PC steel strands according to any one of claims 1 to 5, wherein a blade portion at the tip of the cutter lever is detachable and can be arbitrarily replaced.

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