JP7511436B2 - Concrete Mixer - Google Patents

Description

The present invention relates to a concrete mixer that produces concrete by mixing various concrete mixing materials such as gravel, sand, cement, water, and admixtures.

Conventionally, in batcher plants for producing concrete, mortar, etc., as shown in FIG. 1, a twin-shaft concrete mixer 101a has been widely used, which is configured in such a way that two parallel mixing shafts 105a, 105b are rotatably supported in a mixing tank 104 consisting of two pairs of mixing drums 102, 103 with a roughly semicircular cross section, and pass through roughly the center of each of the mixing drums 102, 103, and a number of mixing blades 106 are attached around the mixing shafts 105a, 105b.

The twin-shaft concrete mixer 101a is configured so that the rotation trajectories of the mixing blades 106 of the two mixing shafts 105a, 105b intersect in part near the center between the two mixing shafts 105a, 105b in the mixing tank 104, and the mixing shafts 105a, 105b are rotated in the X direction in the figure (hereinafter referred to as "forward rotation") so that when viewed from the lower half of the mixing tank 104, both mixing blades 106 face toward the center of the mixing tank 104, as shown in FIG. 1(a).

The material to be kneaded is fed into the kneading tank 104, and is mixed by flowing (circulating) in a generally circular shape in a plan view throughout the entire area of the kneading tank 104 while applying a shearing action when the kneading blades 106 of the kneading shafts 105a and 105b intersect near the center of the kneading tank 104 (see Patent Document 1).

JP 2010-201835 A

In recent years, there have been increasing opportunities to manufacture not only high-strength concrete, which has a design strength of over 36 N/mm2, but also ultra-high-strength concrete, which has a design strength of over 60 N/mm2, and in some cases, concrete with a strength of about 150 to 200 N/mm2. Such ultra-high-strength concrete has a higher viscosity than normal concrete (concrete with a design strength of 36 N/mm2 or less). In particular, concrete with a strength of about 150 to 200 N/mm2 exhibits a significantly higher viscosity and its fluidity decreases during mixing. For example, when trying to mix such high-viscosity concrete with the conventional biaxial concrete mixer 101a, the circulating flow becomes slow, and in some cases the mixing time tends to be longer.

In view of the above, the present invention aims to provide a concrete mixer that can efficiently mix not only ordinary concrete but also highly viscous concrete such as ultra-high strength concrete.

The inventors conducted extensive research to solve the above problems, focusing on the rotation direction of each mixing shaft 105a, 105b, and came to the conclusion that while, as described above, the rotation direction of each mixing shaft 105a, 105b in the conventional twin-shaft concrete mixer 101a is designed to be exclusively forward rotation, it may not necessarily be necessary to limit it to forward rotation. Based on the above idea, the inventors conducted an experiment in which, as shown in (b) of Figure 1, the mixing shafts 105a, 105b of the concrete mixer 101b were rotated in the Y direction in the figure (hereinafter referred to as "reverse rotation") so that all of the mixing blades 106 faced the left and right side walls 107a, 107b of the mixing tank 104 when viewed from the lower half side of the mixing tank 104, and then mixed highly viscous ultra-high strength concrete.The inventors confirmed that this made it possible to mix the concrete in a relatively short time compared to the conventional concrete mixer 101a in which all of the mixing shafts 105a, 105b rotated forward. This is just a guess, but we think that this is because the conveying surfaces of the kneading blades 106 of the counter-rotating kneading shafts 105a, 105b are able to press the material to be kneaded in the kneading tank 104 strongly against the inner surfaces of the left and right side walls 107a, 107b of the kneading tank 104, effectively applying a compression and shearing action to the material to be kneaded.

However, when both mixing shafts 105a and 105b of the twin-shaft concrete mixer 101b are rotated in the opposite directions, as shown in FIG. 1(b), the material gradually becomes more viscous as it is mixed, and is easily separated and stagnated on the left and right side walls 107a and 107b of the mixing tank 104. As a result, the circulating flow of the material does not improve much, and the mixing blades 106, which rotate from above the center of the mixing tank 104 toward the bottom wall of the mixing tank 104, tend to entrain air, resulting in an increase in entrapped air (air bubbles that are naturally mixed in when the mixer is mixing, and an increase in this leads to a decrease in the strength of the concrete), so there is still room for improvement.

The inventors conducted further research and came to the conclusion that, rather than rotating each of the mixing shafts 105a, 105b in the same direction, it would be better to rotate one mixing shaft 105b of the concrete mixer 101c in the reverse direction and the other mixing shaft 105a in the forward direction, as shown in FIG. 1(c). In other words, by rotating one mixing shaft 105b in the reverse direction, the compression and shearing action on the mixing material caused by the reverse rotation is maintained, while the other mixing shaft 105a rotates forward, which suppresses the fragmentation of the material in the mixing tank 104, enhances the circulating flow, and suppresses the increase in entrapped air, it would be possible to utilize the advantages of both forward and reverse rotation, which they thought would be more preferable.

When the kneading shafts are twin, rotating them as described above would likely cause the material to be concentrated on one side of the kneading tank 104, making it difficult to knead it properly. Therefore, we came to the conclusion that this problem could be eliminated by, for example, dividing each of the two kneading shafts in the middle in the longitudinal direction to make four shafts, and configuring the parallel kneading shafts to rotate in the same direction while the opposing kneading shafts to rotate in opposite directions, thus completing the present invention.

That is, the concrete mixer according to claim 1 of the present invention is characterized in that it is provided with a mixing tank consisting of two pairs of mixing drums with a cross section of a substantially semicircular shape, and four mixing shafts are rotatably supported on the side walls of the mixing tank consisting of a pair of opposing vertical faces so as to pass through the approximately center of each of the mixing drums, and each mixing shaft has a spiral-shaped mixing blade fixed thereto, which rotates along the bottom wall of the mixing drum to continuously deliver the material to be mixed, and the mixing blades of each mixing shaft are of a length such that they do not interfere with the mixing blades of the mixing shafts in the opposing positions, and are formed so that part of the rotation trajectory of the mixing blades of the mixing shafts in the parallel positions intersect, and among the mixing shafts in the parallel positions, the mixing shafts in the parallel positions rotate in the same direction, while the mixing shafts in the opposing positions rotate in opposite directions.

The concrete mixer described in claim 2 is characterized in that the mixing blades are fixed in pairs at opposing positions relative to the axis of the mixing shaft.

The concrete mixer described in claim 3 is characterized in that the mixing blades are long enough that the tips of the mixing blades of the opposing mixing shaft are close to each other.

According to the concrete mixer of the present invention, four mixing shafts are rotatably supported on the side walls of the mixing tank, which are made up of a pair of opposing vertical surfaces, so that they pass through the approximate center of each mixing drum. A spiral mixing blade is fixed to each mixing shaft. The mixing blades of each mixing shaft are of a length that does not interfere with the mixing blades of the mixing shafts in the opposing positions, and are formed so that part of the rotation trajectory intersects with the mixing blades of the mixing shafts in the parallel positions. Among the mixing shafts, the mixing shafts in the parallel positions rotate in the same direction, while the mixing shafts in the opposing positions rotate in opposite directions. Therefore, if the mixing material put into the mixing tank is sent out in the direction of rotation of each mixing blade, the mixing material can be effectively compressed and sheared without impairing the circulating flow of the mixing material, and not only normal concrete but also highly viscous concrete such as ultra-high strength concrete can be efficiently mixed.

In addition, according to the concrete mixer described in claim 2, the mixing blades are fixed in a pair at positions facing each other relative to the axis of the mixing shaft, which enhances the circulating flow of the mixing material and more effectively applies compression and shearing effects to the mixing material, allowing high-viscosity concrete to be mixed more efficiently.

In addition, according to the concrete mixer described in claim 3, the mixing blades are long enough that the tips of the blades of the mixing blades of the opposing mixing shaft are close to each other, so that the mixing material can be sent out more continuously, further enhancing the circulating flow movement, and the shearing action generated between the mixing blades of the opposing mixing shaft can be applied more effectively to the mixing material, allowing high-viscosity concrete to be mixed more efficiently.

FIG. 1 is a cross-sectional view of a mixing tank showing the state in which the materials are mixed when the rotation directions of the mixing shafts of a twin-shaft concrete mixer are all rotating forward (a), both rotating backward (b), and one rotating forward and the other rotating backward (c). 1 is a partially cutaway perspective view showing an embodiment of a concrete mixer according to the present invention; FIG. 3 is a plan view in which a part of FIG. 2 is omitted.

The concrete mixer of the present invention is equipped with a mixing tank consisting of two pairs of mixing barrels with a roughly semicircular cross section, and four mixing shafts are inserted through the side walls of the mixing tank consisting of a pair of opposing vertical faces, passing through roughly the center of each mixing barrel, and are supported so as to be freely rotatable.

A spiral-shaped kneading blade is fixed to each of the kneading shafts, which rotates along the bottom wall of the kneading barrel to continuously deliver the material to be kneaded. The kneading blades of each of the kneading shafts are formed to a length such that they do not interfere with the kneading blades of the opposing kneading shafts, and are formed so that part of the rotation trajectory of the kneading blades of adjacent parallel kneading shafts intersects.

In addition, adjacent kneading shafts in parallel positions rotate in the same direction (one rotates forward and the other rotates backward), while kneading shafts in opposing positions rotate in opposite directions. Note that the kneading shafts in parallel positions rotate in sync with each other, with a phase shift of, for example, about 90 degrees, so as not to interfere with each other in the area where the kneading blades of each kneading shaft intersect, while the kneading shafts in opposing positions are arranged so that there is no interference between the kneading blades of each kneading shaft, so there is no need to synchronize their rotation.

Moreover, preferably, the kneading blades are fixed in a pair at opposing positions relative to the axis of the kneading shaft, which doubles the amount of material fed by the kneading blades when the kneading shaft rotates once, thereby enhancing the circulating flow of the material and providing a configuration that can more effectively apply compression and shearing effects to the material.

More preferably, the kneading blades are long enough that the blade tips of the kneading blades of the opposing kneading shaft are close to each other, which allows the material to be more continuously delivered to the opposing position in the kneading tank, further enhancing the circulating flow of the material to be kneaded, and allowing the shearing action generated between the kneading blades of the opposing kneading shaft to be more effectively applied to the material to be kneaded.

If the spacing between the blades of the opposing mixing shafts is too narrow, the aggregate passing between the blades during mixing may get caught, causing aggregate cracks and placing a high load on the mixer. On the other hand, if the spacing is too wide, the circulating flow of the material in the mixing tank will slow down and the shearing action will be weakened. Therefore, it is preferable to adjust the spacing so that the maximum particle size of the aggregate contained in the concrete being mixed can just pass through (slightly wider than the maximum aggregate diameter).

When mixing high-viscosity concrete such as ultra-high-strength concrete with the concrete mixer, the mixing blades of the mixing shaft on the forward rotation side sequentially deliver the material in the mixing tank to the center between the parallel mixing shafts (hereinafter referred to as the "parallel side center"), while the mixing blades of the mixing shaft on the parallel reverse rotation side take over the material delivered to the parallel side center of the mixing tank and deliver it sequentially to the side wall of the mixing tank, which is downstream in the direction of rotation. At this time, the mixing blades on the forward rotation side and the mixing blades on the parallel reverse rotation side apply a shearing action to the material when they intersect near the parallel side center of the mixing tank, but since the mixing blades move in opposite directions near the parallel side center, a more effective shearing action can be expected. The kneading blade on the reverse rotation side sends the material to be kneaded onto the side wall of the kneading tank, while at the same time strongly pressing the material against the inner surface of the side wall in the direction of travel with the conveying surface of the blade, effectively applying compression and shear forces to the material to be kneaded.

Next, the kneading blades on the reverse rotation side sequentially send out the material pressed against the inner sidewall of the kneading tank in the direction of the kneading axis at the opposing position along the sidewall of the kneading tank, while the kneading blades on the kneading shaft on the forward rotation side at the opposing position take over the sent-out material and, in the same manner as above, send it out sequentially to the center of the parallel side of the kneading tank. At this time, the kneading blades on the kneading shaft on the reverse rotation side and the kneading blades on the kneading shaft on the forward rotation side at the opposing position move in opposite directions even when they take over the material near the center between the kneading shafts (hereinafter referred to as the "center of the opposing side"). This means that, unlike a twin-shaft concrete mixer, a shearing action is effectively applied to the material. As the kneading blades of the four forward and reverse rotating kneading shafts continue the above series of rotations, the material in the kneading tank is circulated and kneaded throughout the entire tank while repeatedly subjected to the shearing action and compression/shearing action.

In this way, four mixing shafts are supported rotatably in the mixing tank, two facing each other, and the parallel mixing shafts rotate in the same direction, while the opposing mixing shafts rotate in opposite directions. This allows the materials in the mixing tank to circulate smoothly throughout the entire tank, and effectively applies shearing and compressive shearing effects to the materials, making it possible to efficiently mix not only ordinary concrete, but also highly viscous concrete such as high-strength concrete and ultra-high-strength concrete.

Below, one embodiment of the present invention will be described with reference to the drawings.

In the figure, 1 is a concrete mixer that produces concrete or mortar by mixing various mixing materials such as gravel, sand, cement, water, and admixtures, and is equipped with a mixing tank 4 consisting of two mixing drums 2 and 3 with a roughly semicircular cross section, each having a material inlet at the top and a discharge gate (not shown) at the bottom.

Of the two pairs of opposing side walls 5a, 5b and 6a, 6b of the kneading tank 4, the four kneading shafts 7a, 7b, 8a, 8b are inserted through the vertical side walls 5a, 5b so as to pass through approximately the center of each of the kneading drums 2, 3, and are supported rotatably and rotated in a predetermined direction by an appropriate drive device (not shown).

A pair of spiral kneading blades 9 are fixed to each of the kneading shafts 7a, 7b, 8a, and 8b at opposing positions relative to the shaft center, and the kneading blades 9 are shaped so that they extend to the vicinity of the center of the opposing side of the kneading tank 4 while rotating (twisting) about 1/4 of a turn in the circumferential direction of the kneading shafts 7a, 7b, 8a, and 8b so as to follow the bottom inner wall surface of the kneading drums 2 and 3. By giving the kneading blades 9 the above shape, it is possible to avoid interference between the kneading blades 9 of the parallel kneading shafts (7a and 7b, and 8a and 8b) while increasing the material delivery capacity as much as possible, which is preferable.

The rotation trajectory of the kneading blade 9 on the kneading shaft 7a and the rotation trajectory of the kneading blade 9 on the parallel kneading shaft 7b are formed so that they partially intersect near the center of the parallel side of the kneading tank 4, and the kneading blade 9 on the kneading shaft 7a and the kneading blade 9 on the kneading shaft 7b are configured to rotate in synchronization with an appropriate synchronization mechanism such as a chain or a synchronization gear after shifting the phase of each other by about 90 degrees so that the blades do not interfere with each other. Also, the kneading blades 9 on the kneading shafts 8a and 8b, which are in a similar positional relationship, are configured to rotate in synchronization with each other after shifting the phase by about 90 degrees as described above. Note that the kneading blades 9 on the kneading shafts 7a and 8b, and the kneading shafts 7b and 8a, which are in opposing positions, are arranged so that there is no interference between the blades, so there is no need to synchronize them when rotating.

The tip of the kneading blade 9 of the kneading shaft 7a (the tip in the axial direction of the kneading shaft 7a) and the tip of the kneading blade 9 of the opposing kneading shaft 8b (the tip in the axial direction of the kneading shaft 8b) are arranged close to each other so that the distance between them is slightly wider than the maximum aggregate diameter of the aggregate contained in the concrete to be mixed (for example, the distance is about 10 mm wider than the maximum aggregate diameter, and if the maximum aggregate diameter is 20 mm, the distance is about 30 mm). This is to prevent the kneading blades 9 from interfering with each other and to prevent defects such as aggregate cracking, while also increasing the circulatory fluidity of the material to be mixed in the kneading tank 4 and the shearing action of the kneading blades 9 of each kneading shaft 7a, 8b as much as possible. The distance between the tips of the kneading blades 9 of the kneading shafts 7b and 8a, which are in the same positional relationship, is also adjusted to be the same as above.

In addition, among the four kneading shafts 7a, 7b, 8a, and 8b in the kneading tank 4, the kneading shafts in parallel positions (7a and 7b, and 8a and 8b) rotate in the same direction, while the kneading shafts in opposing positions (7a and 8b, and 7b and 8a) rotate in opposite directions. Note that the thick arrow X in the figure indicates forward rotation, while the thick arrow Y indicates reverse rotation, indicating that the kneading shafts 7a and 8a rotate forward and the kneading shafts 7b and 8b rotate reversely.

The thick arrows A, B, C, and D in FIG. 2 indicate the direction in which the material to be kneaded in the kneading tank 4 circulates when the kneading shafts 7a and 8a are rotated forward and the kneading shafts 7b and 8b are rotated backward. The shaded area α1 in FIG. 2 indicates the shearing area where the kneading material circulating in the kneading tank 4 is subjected to a shearing action when the kneading blades 9 of the kneading shafts 7a and 7b, and 8a and 8b, which are parallel to each other, cross each other. The shaded area α2 indicates the shearing area where the kneading blades 9 of the kneading shafts 7a and 8b, and 7b and 8a, which are opposed to each other, are subjected to a shearing action due to the difference in the direction of rotation. The shaded area β indicates the compression/shearing area where the kneading blades 9 of the kneading shafts 7b and 8b, which are rotating backward, press the circulating material against the inner surface of the side walls 6a and 6b of the kneading tank 4.

When mixing high-viscosity concrete such as ultra-high strength concrete with the concrete mixer 1 configured as described above, the mixing shafts 7a and 8a are rotated forward while the mixing shafts 7b and 8b are rotated backward. Then, various mixing materials such as gravel, sand, cement, admixtures, and water are added to the mixing tank 4 in predetermined amounts according to the mix ratio. The mixing materials are then sequentially sent out in a predetermined direction (clockwise in plan view in this embodiment) within the mixing tank 4 and circulate.

For example, as shown by the thick arrow A in FIG. 2, the kneading blades 9 of the kneading shaft 7a on the forward rotation side sequentially send the kneading material in the kneading tank 4 to the parallel side center, which is the center between the kneading shaft 7b in the parallel position, while the kneading blades 9 of the kneading shaft 7b on the parallel side take over the kneading material sent to the parallel side center and sequentially send it to the approximately semicircular side wall 6b of the kneading tank 4 downstream in the rotation direction. At this time, the kneading blades 9 of the kneading shaft 7a on the forward rotation side and the kneading blades 9 of the kneading shaft 7b on the parallel side in the reverse rotation side in the parallel position apply a shearing action to the kneading material when they cross in the shearing area α1 near the parallel side center of the kneading tank 4, but since the kneading blades 9 move in the opposite direction near the parallel side center, a more effective shearing action can be expected.

The kneading blade 9 of the kneading shaft 7b on the reverse rotation side sends the material to be kneaded toward the inner surface of the side wall 6b of the kneading tank 4, while at the same time strongly pressing the material against the inner surface of the side wall 6b in the compression/shear region β in the direction of travel on the conveying surface of the kneading blade 9, effectively applying a compression/shear action to the material to be kneaded.

Next, the kneading blades 9 of the kneading shaft 7b on the reverse rotation side sequentially send out the kneading material pressed against the inner surface of the side wall 6b of the kneading tank 4 in the direction of the kneading shaft 8a at the opposing position while keeping it along the inner surface of the side wall 6b, as shown by the thick arrow B in FIG. 2, while the kneading blades 9 of the kneading shaft 8a on the forward rotation side at the opposing position take over the sent-out kneading material and sequentially send it out to the center of the parallel side of the kneading tank 4, as shown by the thick arrow C in FIG. 2. At this time, even when the kneading blades 9 of the kneading shaft 7b on the reverse rotation side and the kneading blades 9 of the kneading shaft 8a on the forward rotation side at the opposing position take over the kneading material in the shear region α2 near the center of the opposing side between the kneading shafts 7b and 8a, the blades do not cross each other, but the kneading blades 9 of the kneading shafts 7b and 8a move in the opposite directions, so that a shearing action can be effectively applied to the kneading material.

The kneading blades 9 of the kneading shaft 8b on the reverse rotation side, which is parallel to the kneading shaft 8a, take over the kneading material sent to the center of the parallel side in the same manner as described above, and send it out sequentially to the approximately semicircular side wall 6a of the kneading tank 4, which is downstream in the direction of rotation, and then send it out sequentially in the direction of the kneading shaft 7a on the forward rotation side, which is opposite to the kneading shaft 8a, as shown by the thick arrow D in Figure 2. At this time, in the shear area α1 between the kneading blades 9 of the kneading shafts 8a and 8b, and the shear area α2 between the kneading blades 9 of the kneading shafts 8b and 7a, a shear action is applied to the kneading material in the same manner as described above, while in the compression/shear area β near the side wall 6a of the kneading tank 4, which is located downstream in the direction of rotation of the kneading blades 9 of the kneading shaft 8b, a compression/shear action is also applied to the kneading material in the same manner as described above. As the kneading blades 9 of the kneading shafts 7a, 7b, 8a, and 8b continue to rotate in the above-mentioned sequence, the material fed into the kneading tank 4 continues to circulate throughout the entire kneading tank 4 while repeatedly undergoing the shearing action and compression/shearing action, and is gradually kneaded.

In this way, the four mixing shafts 7a, 7b, 8a, and 8b are rotatably supported in the mixing tank 4 so that two of them face each other, and the parallel mixing shafts (7a and 7b, and 8a and 8b) rotate in the same direction, while the opposing mixing shafts (7a and 8b, and 7b and 8a) rotate in opposite directions. This allows the materials fed into the mixing tank 4 to circulate smoothly throughout the entire mixing tank 4, and effectively applies shearing and compressive shearing to the materials, making it possible to efficiently mix not only ordinary concrete, but also highly viscous concrete such as high-strength concrete and ultra-high-strength concrete in a relatively short time.

The inventors conducted a comparative mixing experiment of ultra-high strength concrete of 150 N/mm2 using a conventional twin-shaft concrete mixer and the concrete mixer of the present invention, and confirmed that the time required for mixing to be completed with the concrete mixer of the present invention can be reduced by approximately 30% compared to the conventional twin-shaft concrete mixer.

1: concrete mixer 2, 3: kneading drum 4: kneading tank 7a, 7b, 8a, 8b: kneading shaft 9: kneading blade

Claims (3)

A concrete mixer comprising a kneading tank consisting of two pairs of kneading drums with a cross section of a substantially semicircular shape, four kneading shafts rotatably supported on the side walls of the kneading tank consisting of a pair of opposing vertical faces so as to pass through the approximate center of each of the kneading drums, each of the kneading shafts has a spiral-shaped kneading blade fixed thereto, which rotates along the bottom wall of the kneading drum to continuously deliver the material to be mixed, and the kneading blades of each of the kneading shafts are of a length such that they do not interfere with the kneading blades of the kneading shafts in the opposing positions, and are formed so that part of the rotation trajectory of the kneading blades of the kneading shafts in the parallel positions intersect, and the kneading shafts in the parallel positions among the kneading shafts rotate in the same direction, while the kneading shafts in the opposing positions rotate in opposite directions. The concrete mixer according to claim 1, characterized in that the mixing blades are fixed in pairs at opposing positions relative to the axis of the mixing shaft. The concrete mixer according to claim 1 or 2, characterized in that the mixing blades are of a length such that the tips of the mixing blades of the opposing mixing shaft are close to each other.

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