JP3405459B2 - Head structure for concrete spraying machine - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a head structure for a concrete spraying machine for lining concrete or the like on an inner wall of a tunnel or the like used in civil engineering work or the like.

[0002]

2. Description of the Related Art As a means for lining the inner walls of tunnels, tunnels, cable ducts, etc. with concrete or mortar, an air sprayer schematically shown in FIG. 5 has been conventionally used. This air spraying machine has a nozzle connected to a concrete pump and an air pressure source, and sprays concrete or the like from the nozzle with a large amount of compressed air and sprays it on the inner wall of the tunnel or the like.

However, since such an air spraying machine uses a large amount of compressed air, not only the power of the wind pressure source increases, but also dust containing fine concrete and the like is diffused by the large amount of compressed air and pollutes the surroundings. Therefore, there is a problem that the working environment becomes extremely bad, and the worker has to wear a dust mask or the like to perform the work.

In order to solve this problem, for example, a concrete spraying machine, such as the "concrete spraying machine" of Japanese Patent Laid-Open No. 11-71997, which can be lined without using compressed air, has been proposed.

FIG. 6 shows the principle of the head structure of this concrete spraying machine. It should be noted that description of the ejection of the quick-setting admixture in the configuration of the present invention is omitted.

As shown in FIG. 6, a head structure 50 of this concrete spraying machine has an impeller 51 that rotates at a high speed around an axis, a casing 52 that surrounds the impeller and has a circular inner peripheral surface, and a casing 52 inside the casing. A concrete supply pipe 53 communicating with the inside of the casing for supplying concrete toward the impeller, and a concrete discharge pipe 54 provided in the casing adjacent to the concrete supply pipe.
And an impeller blade 5 for hitting the concrete supplied from the concrete supply pipe by its rotation and projecting it from the concrete discharge pipe.
5 are provided. Here, the impeller has a structure in which an impeller blade is sandwiched between two circular impeller side plates 56.

The concrete injected from the concrete supply pipe toward the impeller in the casing is projected by being hit by an impeller blade provided on the impeller rotating at high speed, and the concrete is discharged from the concrete discharge pipe to a desired wall surface or the like. To be sprayed.

[0008]

The concrete poured into the casing from the concrete supply pipe is hit by an impeller blade provided on an impeller rotating at a high speed inside the casing, and solid such as gravel which is a coarse aggregate. The component is projected tangentially to the rotation of the impeller blade upon impact. On the other hand, since the paste component containing fine aggregate has a relatively high viscosity, it once diffuses over the entire blade striking surface at the moment of impact, and the centrifugal force generated by the rotation of the impeller acts on the outer periphery of the impeller blade and the impeller. After moving to the inner surface side outer periphery of the side plate, the impeller blade and the impeller side plate are projected in the radial direction of rotation.

Therefore, the projection timing of the paste component is delayed as compared with the solid component, but the paste component diffused to the outer peripheral side of the impeller blade requires almost no time to move to the outer periphery, and the impeller blade immediately rotates. By being projected in the radial direction of, the projected paste component can be directed to the concrete discharge pipe.
On the other hand, the paste component diffused to the impeller blade shaft center side and the impeller side plate side is projected in the radial direction after being moved to the outer periphery by the action of centrifugal force, so that the paste component is diffused to the outer periphery side of the impeller blade than the diffused component. The projection is delayed by the time, and it is projected on the inner peripheral surface of the casing at a position displaced from the direction of the concrete discharge pipe. That is, the projection timing of the paste component is delayed as the spread of the paste component on the blade surface due to the impact of the impeller blade progresses deeper in the axial direction of the impeller. The paste component projected on the inner peripheral surface of the casing gradually accumulates, and when it reaches a certain amount, the paste component orbits in the casing as the impeller rotates.

Further, in order to improve the spot property of the concrete in the projection direction, it is necessary to reduce the radius of the concrete discharge pipe. In such a case, the concrete or concrete that does not project from the concrete discharge pipe and circulates in the casing. The concrete that droops from the discharge port (dripping) without being projected onto the desired wall surface from the discharge pipe is further increased.

Since this orbiting concrete acts as a load on the rotation of the impeller, it impedes the smooth rotation of the impeller, and it causes friction between the impeller and the casing, and this friction causes the impeller and the like to wear out violently. This has caused the product life to be significantly shortened.

Further, at the moment of hitting with the impeller blade, the paste component diffuses over the entire striking face, but since the paste component diffused in the width direction of the impeller is stopped by the impeller side plates on both sides, as a result, the paste diffuses over the striking face. The component was increased as it was closer to the impeller side plate. The bias of the paste components disturbs the projection flow of concrete and causes the spot projection property to deteriorate.

Further, the impact surface of the impeller blade is the part that is most worn by the impact of the injected concrete. In the conventional concrete spraying machine, the impeller blade is formed integrally with the impeller and only the impeller blade is replaced. However, even if the impeller blade can be replaced, it is necessary to replace the entire impeller blade including the part that is not worn.

The present invention was devised to solve these various problems. That is, the present invention, by suppressing the generation of the orbiting concrete, smooth the rotation of the impeller in the casing by removing the load that the orbiting concrete exerts on the rotation of the impeller, reduce the friction generated between the impeller and the like. The first purpose is to suppress wear and extend the life of the product. In addition, the second object is to make the projection flow of the concrete uniform by making the diffusion of the paste component to the impeller blade uniform, and to improve the projection efficiency and the spot projection property. Furthermore, a third object is to provide a head structure for a concrete spraying machine, in which the abrasion resistance of the striking portion of the impeller blade is strengthened, and even when the impeller blade is worn, only the worn portion can be easily replaced. And

[0015]

According to the present invention, an impeller (22) that rotates at high speed around an axis (20), and a casing (23) that surrounds the impeller and has an inner peripheral surface of a circular shape (23). A concrete supply pipe (21) communicating with the inside of the casing for supplying concrete toward the impeller, and a concrete discharge pipe (24) provided in the casing so as to be adjacent to the concrete supply pipe.
The impeller is provided with at least two impeller blades (25) having an axis as a center for projecting concrete supplied from the concrete supply pipe from the concrete discharge pipe, and the impeller blade is provided with An L-shaped concrete contact portion (28) formed of a striking portion (27) extending in the radial direction of the impeller and a receiving jaw portion (26) extending in the rotational direction of the impeller from one end located in the axial direction of the striking portion. ) Is provided, the head structure for a concrete spraying machine is provided.

According to the head for a concrete spraying machine of the present invention described above, the solid component of the concrete injected into the casing from the concrete supply pipe is supplied by the impeller blades provided on the impeller rotating at high speed inside the casing. It is struck and is projected in the tangential direction of the rotation of the impeller blade at the same time as it is struck. On the other hand, the paste component once diffuses to the striking surface at the moment of striking, but since the impeller has a receiving jaw portion extending in the rotation direction of the impeller at one end located in the axial direction of the striking portion of the impeller blade, Immediately after the impact, the paste component is captured near the outer circumference of the impeller blade and the receiving jaw, that is, the concrete contact portion, does not diffuse near the axis, and is immediately projected in the radial direction by the action of centrifugal force. That is, by delaying the projection timing to a minimum by capturing the paste component diffused by impact on the outer periphery of the impeller blade and the receiving jaw, it is possible to project most of the paste component in the discharge pipe direction, The occurrence of can be drastically reduced.

Further, the impeller blade (25) may be provided with a separating plate (30) located at the center of the striking portion (27) in the width direction and projecting parallel to the impeller side plate (29). preferable.

When most of the components of the concrete fed from the concrete supply pipe are paste components, a separator plate is provided so that the paste components diffused into the striking part are made uniform and the projection flow is made uniform. be able to.

That is, the paste component that diffuses on the striking surface at the moment of striking tends to spread over a wide area, but since the impeller side plates are located on both sides of the striking part, the paste component is dammed up here, resulting in striking part. In this case, more paste components spread as they approach the impeller side plate. Therefore, by providing a separating plate projecting parallel to the impeller side plate in the widthwise center of the striking part, the paste component diffused into the striking surface is divided into two parts, and the bias of the paste component in the impeller side plate direction is suppressed, It is possible to make the diffusion of the paste component on the part uniform.

Conventionally, the diffusion of the paste component has occurred in one space between the side plates of the impeller blades. Therefore, immediately after the impact, the amount of the paste components is small near the center of the impact portion, and the impeller side plates near the impeller side plates are mostly used to prevent them. Of the paste component was present and the paste component was unevenly distributed on the hitting part. Therefore, by providing a separation plate, this space is divided into two, the paste component is diffused in the two spaces between the impeller side plate and the separation plate, and the diffusion of the paste component is stopped not only by the impeller side plate but also by the separation plate. By this, it is possible to diffuse the paste component on the hitting portion relatively uniformly. When the paste component is uniformly diffused on the striking portion, the projection flow of the paste component that is projected by the rotation of the impeller is also uniform, so that it is possible to improve the projection efficiency and improve the spot projection property.

On the other hand, the impeller blade (25) has two dam walls (41) located on both sides in the width direction of the striking portion (27) and projecting parallel to the impeller side plate (29) and facing each other. The U-shaped part (4
2) is formed, and the U-shaped portion has an impeller (2
The inner diameter (D) of the concrete supply pipe (21) is the same between the opposing weir walls so that it comes to a position corresponding to the concrete supply port (21a) in the casing (23) with the rotation of 2). It is also preferable to make it slightly larger.

When a large amount of coarse aggregate (solid component) such as gravel is included in the components of the concrete which is put into the casing from the concrete supply pipe, the above-mentioned separation plate is provided and the tip portion of the separation plate is provided. Since the coarse aggregate that has been hit is irregularly reflected, the projection flow is disturbed. Therefore, when using concrete containing coarse aggregate or the like, it is not always appropriate to provide the separating plate. So in the impeller blade,
By forming U-shaped portions provided on both sides in the width direction of the striking portion and facing each other that project in parallel to the impeller side plate, the U-shaped portion is formed in the direction of the impeller side plate when striking concrete. It is possible to suppress the diffusion of the paste component and control the bias of the paste component in the impeller width direction.

At this time, the U-shaped portion is provided between the opposing dam walls so that the U-shaped portion comes to a position corresponding to the opening in the casing of the concrete supply pipe as the impeller rotates. It must be the same as or slightly larger than the inner diameter (D).

It is assumed that the U-shaped portion comes to a position corresponding to the opening in the casing of the concrete supply pipe with the rotation of the impeller, and the distance between the opposing dam walls is the inner diameter (D) of the concrete supply pipe. By making it almost the same as, concrete injected from the concrete supply pipe can hardly diffuse in the U-shaped portion. for that reason,
The occurrence of unevenness of the paste components is suppressed, the projection flow is made uniform, and as a result, the spot projection property is improved.

The distance between the opposing weir walls may be set to be slightly wider than the inner diameter (D) of the concrete supply pipe because the distance between the opposing weir walls is equal to the inner diameter (D) of the concrete supply pipe. ) By making the width wider, it is possible to reliably capture the poured concrete at the hitting portion. Here, it is not appropriate to make the distance between the opposing dam walls wider than the inner diameter (D) of the concrete supply pipe. If the distance between the weir walls is much wider than the inner diameter of the concrete supply pipe, the injected concrete will spread over a wide area of the U-shaped part and will be dammed by the weir wall. This is because the paste components are unevenly distributed.

Further, a curved surface portion (43) for connecting the striking portion and the receiving jaw portion may be formed at a joint portion of the striking portion (27) with the receiving jaw portion (26). preferable.

The paste component of concrete introduced from the concrete supply pipe tends to diffuse in all directions on the striking surface by striking with an impeller blade rotating at high speed in the casing. Here, for example, when the striking part and the receiving jaw are joined at a right angle, the paste component that diffuses in the axial direction on the striking surface is dammed in the receiving jaw, and as a result, the striking part and the receiving jaw. A paste component accumulation occurs at the joint portion with the portion. In order to obtain a uniform blast flow, it is ideally necessary that the paste components are uniformly diffused on the striking surface, so that such a paste component accumulation is not desirable.

Therefore, by forming a curved surface portion for connecting the striking portion and the receiving jaw portion at a joint portion of the striking portion with the receiving jaw portion, the paste which spreads in the axial direction on the striking surface. The components are dammed in the receiving jaws, and the paste components can smoothly flow into the receiving jaws without forming a pool of paste components in the joint portion. Therefore, the paste component can be spread almost uniformly on the striking surface,
This makes it possible to obtain a uniform projection flow.

Further, the striking part (27) is provided with an impeller blade cemented carbide (33) which is detachable by being inserted into and engaged with the impeller blade (25) from the rotational axis direction of the impeller (22). It is also preferable that

By providing a removable impeller blade carbide on the striking surface of the impeller blade which strikes the injected concrete and projects it in the direction of the concrete discharge pipe, it is possible to suppress the abrasion of the most worn portion by performing the striking action. In addition, even when worn, only the impeller blade cemented carbide, which is the worn portion, can be replaced, so that the operating cost of the equipment can be reduced.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described below with reference to the drawings. In addition, in each figure, the common part is denoted by the same reference numeral, and the duplicated description will be omitted.

FIG. 1 is a view showing a state of use of a concrete spraying machine using the head structure for a concrete spraying machine of the present invention. In this figure, reference numeral 4 is a main engine, which has a traveling portion 4a and a concrete pump 4b provided on the rear side. A robot arm mechanism 5 is provided on the front side of the main machine 4. In this example, the robot arm mechanism 5 includes a main beam 5a, a swing cylinder 5c provided on the telescopic rod 5b of the main beam 5a, a linear cylinder 5d, a base 5e provided at the rod tip of the linear cylinder 5d, and the like. Therefore, the head portion 10 can be moved to any position and direction, and concrete can be sprayed on a desired wall surface.

FIG. 2 is a schematic view showing the internal structure of the concrete sprayer head of the present invention. As shown in the figure, the concrete spraying machine head 2 according to the present invention is
A concrete supply pipe 21 is communicated with, and a head portion thereof has an impeller 22 which is rotated at a high speed by, for example, a hydraulic motor (not shown) about an axis, and a casing 23 which surrounds the impeller 22 and has an inner peripheral surface of a circular shape. And a concrete discharge pipe 24 provided in the casing adjacent to the concrete supply pipe 21.

The impeller 22 has a concrete supply pipe 2
The concrete supplied from No. 1 is hit by its rotation, and four impeller blades 25 for projecting from the concrete discharge pipe 24 are provided.
Is an inverted L-shaped concrete contact portion formed by a striking portion 27 extending in the radial direction of the impeller 22 and a receiving jaw portion 26 extending in the rotation direction of the impeller 22 from one end located in the axial direction of the striking portion 27. 28 is provided.

Here, the impeller blades 25 are arranged at equal intervals in a concentric circle between the two impeller side plates 29 forming both sides of the impeller with a constant interval from the center thereof. In addition, the two impeller side plates are, for example, four impeller blades as pillars, which are sandwiched and screwed together to form a structure in which they can be separated from each other.

The concrete pumped by the concrete pump is sent to the head portion through the concrete supply pipe 21 and put into the concrete spraying machine head 2. An impeller 22 that rotates counterclockwise at a high speed is provided inside the head portion, and the solid component in the poured concrete is struck by the impeller blade 25 and is projected in the Z-axis direction by the urging force given by the collision. Projected concrete is concrete discharge pipe 24
It is projected toward a desired wall surface or the like.

On the other hand, the paste component of the poured concrete is the moment of impact by the impeller blade 25,
It diffuses into the striking part 27 and the receiving jaw part 26. Here, a large centrifugal force acts on the paste component diffused in the striking portion 27 so that the paste component immediately moves to the outer circumference of the impeller blade and is then projected in the radial direction without delay. Further, the paste component received by the receiving jaw 26 is also directly projected in the radial direction by the action of centrifugal force. Here, the paste component has a slightly delayed projection timing as compared with the solid component, but it can be directed to the concrete discharge pipe by being projected in the radial direction.

Further, as shown in FIG. 3, the impeller blade 25 is provided with a separating plate 30 which is located at the center of the striking portion 27 in the width direction and which projects in parallel with the impeller side plate 29. Therefore, the paste component that diffuses into the striking part and the receiving jaw at the moment of striking with the impeller blade is divided into two parts by the separating plate, and the paste component spreads relatively evenly over the entire surface of the striking part etc. without being biased only near the impeller side plate. It will be. When the paste component is uniformly diffused, the flow of the paste component projected by the rotation of the impeller also becomes uniform, so that the projection efficiency is improved and the spot projection property is improved.

Further, as shown in FIG. 3, impeller blade cemented carbide 33
Is provided. This is because the impact of concrete is mainly on the radial surface of the impeller of the impeller blade 25, so that the life of the product is extended by providing a cemented carbide material in the part that is most worn by the collision with concrete. It is intended for.

This impeller blade cemented carbide 33 is provided with a convex portion 34 on one side in the radial direction of the impeller.
Is attached by being inserted into the recess 35 provided on one side of the impeller blade 25 in the radial direction of the impeller from the direction of the rotation axis of the impeller. The protrusion of the convex portion 34 has a taper shape that slightly expands toward the outside, and the recess of the concave portion 35 has a taper shape that slightly expands toward the inside. With such a mounting structure, the both are fixed without using a screw or the like, and the convex portion 34 of the impeller blade cemented carbide 33 and the recessed portion 35 of the impeller blade 25 can be inserted and fitted, whereby the impeller blade cemented carbide 33 can be easily fitted. Can be exchanged. Here, the impeller blade cemented carbide and the separating plate 30 are integrally formed. For the impeller blade cemented carbide 33, a metal material having excellent wear resistance such as JIS E4 is used. Further, since the impeller blade 25 itself is also fixed to the impeller by the screw 36, it can be replaced if necessary.

The casing 23 surrounding the impeller 22 consists of two casing members which are separated from each other by a diametrical joining line passing through the center of the impeller, each casing member being outside the casing 23 and on the extension of said joining line. It is mounted so as to be rotatable around a common axis located at. As a result, the two casing members can be rotated in opposite directions to completely open the inside.

By adopting this mechanism, the impeller can be exposed by removing one piece of the casing member, and the maintenance work such as internal inspection and cleaning, and replacement of the impeller blade and the cemented carbide can be facilitated. it can.

FIG. 4 illustrates an impeller blade of a concrete spraying machine head structure of another embodiment. Note that this embodiment differs from the above-described embodiments only in the portion related to the shape of the impeller blades, and thus duplicate description of other portions will be omitted.

The impeller blade 25 is provided with two dam walls 41 located on both sides of the striking portion 27 in the width direction and opposed to each other and projecting in parallel to the impeller side plate 29, thereby forming a U-shaped portion 42. The U-shaped portion 42 is positioned between the opposing dam walls 41 of the concrete supply pipe 21 so that the U-shaped portion 42 comes to a position corresponding to the concrete supply port 21a in the casing 23 as the impeller 22 rotates. It is slightly larger than the inner diameter (D).

The impeller blade of this embodiment is mainly used when coarse aggregate (solid component) such as gravel is contained in the components of the concrete which is put into the casing from the concrete supply pipe. When using an impeller blade provided with a separation plate like the above-mentioned example in concrete containing a large amount of coarse aggregate, the turbulence of the projection flow occurs because the coarse aggregate hit at the tip of the separation plate reflects irregularly . Therefore, without providing a separating plate on the impeller blade, instead of having two separating walls located on both sides in the width direction of the striking portion and facing each other protruding in parallel to the impeller side plate, the U-shaped portion is provided. To form a U-shaped portion at a position corresponding to the opening in the casing of the concrete supply pipe with the rotation of the impeller, and between the opposing dam walls of the concrete supply pipe. By making the diameter slightly larger than the inner diameter (D), the concrete injected from the concrete supply pipe is immediately hit with almost no diffusion in the hit part. Therefore, it is possible to suppress the occurrence of the bias of the paste component, uniformize the projection flow, and improve the spot projection property.

Further, since the weir wall functions as a concrete guide rail which is hit and projected, and a certain distance is formed between the weir wall and the impeller side plate, the paste component projected by the impeller blades is radiated. Even when spread and projected onto the inner surface of the casing or concrete discharge pipe can be reduced, suppress the occurrence of the surrounding concrete and the occurrence of the drool, projection efficiency It is possible to improve.

The reason why the distance between the opposing dam walls is made slightly larger than the inner diameter (D) of the concrete supply pipe is to ensure that the concrete injected from the concrete supply pipe is caught by the U-shaped portion. . Here, a little is about 1
A few millimeters.

A curved surface portion 43 for connecting the striking portion and the receiving jaw portion is formed by a smooth curved surface at the joint portion of the striking portion 27 with the receiving jaw portion 26.

The coarse bone component of the concrete charged from the concrete supply pipe is immediately projected by the impact of the impeller blade rotating at high speed in the casing. On the other hand, the paste component diffuses in all directions on the striking surface at the moment of striking. At that time, the paste component that diffuses in the axial direction flows along the curved surface portion and changes the diffusion direction, so that it smoothly flows into the receiving jaw and there is no paste accumulation at the joint between the striking portion and the receiving jaw. . A uniform projection flow can be obtained by spreading the paste components almost uniformly on the striking surface.

[0050]

As described above, according to the head structure for a concrete spraying machine of the present invention, by suppressing the generation of the circulating concrete, the load exerted by the circulating concrete on the rotation of the impeller is removed and the rotation of the impeller is reduced. The concrete is sprayed efficiently by performing the above, or the product life is extended by reducing the friction generated between the concrete and the impeller and suppressing the wear of the impeller and the like. More preferably, by equipping the striking part with a separating plate or a dam wall, the diffusion of the paste component to the striking part is equalized, and when the impeller blade is worn, only the impeller blade can be easily replaced. Thus, the operating cost of the equipment can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic view showing a general use state of a concrete spraying machine.

FIG. 2 is a schematic view showing a concrete sprayer head structure according to the present invention.

FIG. 3 is a schematic view showing a structure of an impeller blade according to one embodiment. Here, (A) is a side perspective view,
(B) is a Y direction arrow view of (A).

FIG. 4 is a schematic view showing a structure of an impeller blade according to another embodiment. Here, (A) is a side perspective view,
(B) is a Y'direction arrow view of (A).

FIG. 5 is a schematic view of a conventional air spraying machine.

FIG. 6 is a schematic view showing a structure of a head portion for a concrete spraying machine using a conventional impeller.

[Explanation of symbols]

2 Head for concrete spraying machine 3 impeller blade 4 main engine 5 Robot arm mechanism 10 head 20 axis 21 Concrete supply pipe 21a Concrete supply port 22 Impeller 23 casing 24 Concrete discharge pipe 25 Impeller blade 26 Receiving jaw 27 Strike part 28 Concrete contact part 29 Impeller side plate 30 Separation plate 33 Impeller blade Carbide 34 Convex part 35 recess 41 Weir wall 42 U-shaped part 43 curved surface 50 head structure 51 impeller 52 casing 53 Concrete supply pipe 54 Concrete discharge pipe 55 Impeller blade 56 Impeller side plate

Claims (5)

(57) [Claims] 1. An impeller (22) rotating at a high speed around an axis (20), a casing (23) surrounding the impeller and having a circular inner peripheral surface, and for supplying concrete to the impeller. Concrete supply pipe (21) communicating with the inside of the casing
And a concrete discharge pipe (24) provided in the casing so as to be adjacent to the concrete supply pipe, wherein the impeller has a shaft for projecting concrete supplied from the concrete supply pipe from the concrete discharge pipe. At least two impeller blades (2
5) is provided, and the impeller blade is formed from a striking portion (27) extending in the radial direction of the impeller and a receiving jaw portion (26) extending from one end located in the axial direction of the striking portion in the rotational direction of the impeller. A head structure for a concrete spraying machine, characterized in that an L-shaped concrete contact portion (28) is provided. 2. The impeller blade (25) is provided with a separating plate (30) located in the center of the striking portion (27) in the width direction and projecting parallel to the impeller side plate (29). The head structure for a concrete spraying machine according to claim 1, which is characterized in that. 3. The impeller blade (25) has two dam walls (41) located on both sides in the width direction of the striking portion (27) and projecting parallel to the impeller side plate (29) and facing each other. The U-shaped portion (42) is formed by the provision of the above, and the U-shaped portion corresponds to the concrete supply port (21a) in the casing (23) as the impeller (22) rotates. The concrete spraying machine according to claim 1, characterized in that the distance between the opposing dams is equal to or slightly larger than the inner diameter (D) of the concrete supply pipe (21) so as to come to the position. Head structure. 4. The receiving jaw (2) of the striking part (27).
The head structure for a concrete spraying machine according to claim 1, wherein a curved surface portion (43) that connects the striking portion and the receiving jaw portion is formed at a joint portion with 6). . 5. The impact portion (27) is provided with an impeller blade cemented carbide (33) which is detachable by being inserted into and engaged with the impeller blade (25) from a rotation axis direction of the impeller (22). The head structure for a concrete spraying machine according to any one of claims 1 to 4, wherein: