JP4875867B2 - Concrete mixer - Google Patents

Description

  The present invention relates to a concrete mixer for producing ready-mixed concrete by mixing various concrete materials such as gravel, sand, cement, water, and an admixture.

2. Description of the Related Art Conventionally, a vibratory mixer in which kneading is performed while applying vibration to a concrete material in a kneading tank is known. For example, in Patent Document 1 (Japanese Patent Publication No. 53-43257), in a mixer in which a fixed kneading shaft is faced from above in a rotating pan-type kneading tank, a vibrator is provided at the base end of the kneading shaft. A mixer is described in which the kneading shaft at the tip of the kneading shaft and the kneading shaft is vertically vibrated. Patent Document 2 (Japanese Utility Model Laid-Open No. 59-190333) describes a mixer in which a vibrator is attached to the bottom of the kneading tank so that the entire kneading tank is vibrated. In such a vibratory mixer, it is expected that the strength of the concrete after being kneaded is increased by kneading the concrete material put into the kneading tank while giving an appropriate vibration.
Japanese Patent Publication No.53-43257 Japanese Utility Model Publication No.59-190333

  By the way, as the vibration mixer, not only the above-mentioned ones but also various other ones are conceivable, but in any case, those capable of more efficiently applying vibration to the concrete material are required. In consideration of maintenance, it is preferable to consider that the vibration is efficiently transmitted only to the concrete material and not transmitted to the mixer device such as a drive motor as much as possible.

  In view of the above points, an object of the present invention is to provide a concrete mixer that can efficiently vibrate concrete material and is suitable for producing high-quality concrete.

  In order to solve the above problems, the concrete mixer according to claim 1 of the present invention is a concrete mixer for kneading various concrete materials by rotating a kneading shaft disposed in a kneading tank by a kneading shaft driving motor. A shaft body having the same shaft center as that of the kneading shaft is rotatably attached to the shaft end portion of the kneading shaft, a pulley for transmitting a driving force from a shaft body driving motor to the shaft body, a main driving gear, And at least one pair of driven gears along the outer peripheral edge of the main driving gear, and the pair of driven gears are arranged at positions opposed to the shaft body to mesh with the main driving gear, respectively. The unbalanced weight for vibration is fixed to each driven gear, and the positional relationship of the unbalanced weights between the driven gears at the opposite positions is adjusted to be symmetric, and the radial direction with respect to the kneading shaft Vibration is characterized by being configured to grant only the vibration circumferential direction by offsetting.

  The concrete mixer according to claim 2 is characterized by comprising vibration suppressing means for suppressing the vibration to the kneading shaft due to the unbalanced weight from reaching the kneading shaft driving motor side.

  According to the concrete mixer of the first aspect of the present invention, in the concrete mixer for kneading various concrete materials by rotating the kneading shaft disposed in the kneading tank by the kneading shaft driving motor, the shaft end of the kneading shaft A shaft body having the same shaft center as that of the kneading shaft is rotatably attached to the part, and a pulley for transmitting a driving force from the shaft body driving motor and a driving gear are attached to the shaft body, At least one pair or more driven gears are provided along the outer peripheral edge of the main driving gear, and the paired driven gears are arranged at positions opposed to the shaft body to be engaged with the main driving gears respectively. The unbalanced weight for vibration is fixed, and the positional relationship of the unbalanced weights between the driven gears at the opposite positions is adjusted to be symmetric, so that the vibration in the radial direction is canceled with respect to the kneading shaft. Since it is configured to apply vibration only in the circumferential direction, vibration can be efficiently distributed to the concrete material via the kneading shaft and the numerous kneading blades provided for it without applying an excessive load on the kneading shaft. The kneading performance is preferably improved, and high-quality concrete can be obtained.

  In the concrete mixer according to claim 2 of the present invention, since the vibration suppression means for suppressing the vibration to the kneading shaft due to the unbalanced weight from reaching the kneading shaft driving motor side is provided, Failure and damage due to vibration of the drive part can be prevented as much as possible, which is advantageous in terms of maintenance.

  In the concrete mixer according to the first aspect of the present invention, for example, a kneading shaft is disposed horizontally in a kneading tank, and the kneading shaft is rotated by a kneading shaft driving motor to stir and mix various concrete materials. In a forced kneading mixer or the like for mixing and kneading, a shaft body having the same center as the kneading shaft is rotatably attached to the shaft end portion of the kneading shaft. The shaft body is mounted with a pulley that transmits a driving force from a shaft body driving motor provided separately from the kneading shaft driving motor to the shaft body, and a main driving gear that rotates integrally with the shaft body, At least a pair of driven gears are provided along the outer peripheral edge of the main driving gear. The pair of driven gears are arranged at opposing positions with respect to the shaft body and meshed with the main driving gears, respectively, and an unbalanced weight for vibration is fixed to each driven gear, and the driven gears at the opposing positions are fixed. The mounting direction of each weight is adjusted so that the positional relationship of the unbalanced weights between the gears is always symmetrical. With this configuration, when the unbalanced weight of each driven gear rotates with the rotation of the shaft body to generate vibration, the radial vibration of the kneading shaft cancels out, while the kneading shaft circles. Vibrations can be applied in the circumferential direction, that is, the direction in which the kneading shaft is originally rotatable, so that the bearing of the bearing portion of the kneading shaft is not damaged by a load caused by vibration.

  When manufacturing concrete with the mixer, first, the shaft body driving motor is driven to rotate the shaft body, and the main driving gear and the driven gear are rotated accordingly, and the unbalance attached to the driven gear. By rotating the weight, the kneading shaft is caused to vibrate in the circumferential direction. In this state, various concrete materials are sequentially put into the kneading tank while the kneading shaft driving motor is driven to rotate the kneading shaft. The concrete material thrown into the kneading tank is repeatedly stirred and mixed while continuing to receive vibrations from the kneading shaft and a large number of kneading blades, whereby suitable kneading is performed and discharged as high-quality concrete.

  In this way, the concrete material is kneaded while imparting vibrations only in the circumferential direction without imposing an excessive load on the kneading shaft of the concrete mixer. Thus, sufficient vibration can be efficiently distributed to the concrete material via the knives, and the kneading performance can be suitably improved to increase the strength of the concrete after kneading.

  The concrete mixer according to claim 2 of the present invention further includes vibration suppressing means for suppressing vibration of the kneading shaft due to rotation of the unbalanced weight from reaching the kneading shaft driving motor. The vibration suppressing means, for example, loosely fits a sprocket that is rotationally driven by a kneading shaft driving motor on one end side of the kneading shaft, and supports the shaft body rotatably on the shaft end portion of the kneading shaft. A supporting member is mounted, and the supporting member and the sprocket are connected via a spring.

  When manufacturing concrete, the kneading shaft driving motor is driven while generating the vibration by driving the shaft body driving motor and rotating the unbalanced weight in accordance with the rotation of the shaft body. Then, the sprocket is rotated, and the support member is rotated over the spring by the rotation of the sprocket, so that the kneading shaft on which the support member is mounted is finally rotated. At this time, the vibration from the unbalanced weight is directly transmitted to the kneading shaft side through the support member, and the kneading shaft is surely vibrated in the rotating direction, while the sprocket side is greatly influenced by a spring in the middle thereof. The portion is absorbed and weakened, and there is no possibility that vibration is strongly transmitted to the kneading shaft driving motor.

  In this way, vibration is applied to the kneading shaft of the mixer sufficiently and reliably, and vibration is prevented from being transmitted to the motor side that drives the kneading shaft as much as possible. This is advantageous in terms of maintenance.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

  In the figure, reference numeral 1 denotes a biaxial concrete mixer for producing ready-mixed concrete by kneading concrete materials such as gravel, sand, cement, water, and an admixture, and two parallel kneading shafts 3 in a kneading tank 2. And is rotatably supported by a bearing 4 fixed to the kneading tank 2. A large number of arms 5 are radially arranged on the kneading shaft 3 in the radial direction, and kneading blades 6 having an appropriate angle are attached to the tip of the arms 5.

  A sprocket 7 is loosely fitted to one end side of one kneading shaft 3 without being fixed to the kneading shaft 3 as a rotation transmission mechanism, and a kneading shaft driving motor 8 is disposed on the side of the sprocket 7. The sprocket 9 provided in the kneading shaft driving motor 8 and the sprocket 7 loosely fitted to the kneading shaft 3 are connected by a chain 10, and the sprocket 7 is rotated by driving the kneading shaft driving motor 8. Like to do. In the present embodiment, the sprocket 7 and the kneading shaft driving motor 8 are provided only for the one kneading shaft 3. However, both the kneading shafts 3 are each provided with a sprocket and a motor. It may be a thing.

  Further, following the sprocket 7, the gears 11 are loosely fitted to the left and right kneading shafts 3 to be engaged with each other, and the left and right kneading shafts 3 are rotated at a synchronous speed. Further, the gear 11 and the sprocket 7 loosely fitted on the same kneading shaft 3 are integrally fixed so as to rotate together.

  A support member 13 composed of a bearing portion 13a and a flange portion 13b is rotatably supported at a shaft end portion following the gear 11 of the kneading shaft 3 so as to rotatably support a shaft body 12 having the same shaft center as the kneading shaft 3. As shown in FIG. 5, a plurality of fastening pieces 14 and 15 are provided in a substantially concentric manner on each side surface of the support member 13 facing the flange portion 13 b and the gear 11. The fastening pieces 14 and 15 are coupled by being fastened with bolts 17 via a spring 16.

  Accordingly, the driving force for rotating the sprocket 7 by the kneading shaft driving motor 8 is once transmitted from the gear 11 to the support member 13 via the spring 16 and finally transmitted from the support member 13 to the kneading shaft 3. It has become. On the other hand, vibration from an unbalanced weight, which will be described later, which occurs as the shaft body 12 rotates, is directly transmitted to the kneading shaft 3 side via the support member 13, but is not transmitted to the gear 11 and the sprocket 7 side. A vibration suppression mechanism is configured so that most of the vibration is absorbed and weakened by the spring 16 interposed between them and strong vibration is not transmitted to the kneading shaft driving motor 8. As a result, unnecessary vibrations of the drive unit such as the kneading shaft driving motor 8 are suppressed as much as possible, and failure and damage are prevented in advance, which is advantageous in terms of maintenance. Instead of the spring 16, for example, an elastic body such as a disc spring or rubber may be employed.

  A pulley 12 and a main drive gear 19 are mounted on the shaft body 12 rotatably supported by the bearing portion 13a of the support member 13, and a shaft body driving motor is disposed above the shaft body 12. 20, a pulley 21 provided in the shaft body driving motor 20 and the pulley 18 of the shaft body 12 are connected by a belt 22, and the shaft body 12 is driven by driving the shaft body driving motor 20. Is trying to rotate. In addition, a pair of driven gears 23 are arranged at opposite positions with respect to the shaft body 12 along the outer peripheral edge of the main driving gear 19 and meshed with the main driving gear 19 respectively. FIG. 8 shows the positional relationship of the unbalanced weight 25 between the driven gears 23 at the opposing positions. As described above, the mounting directions are adjusted so as to be always symmetrical.

  With this configuration, when the unbalanced weight 25 of each driven gear 23 rotates and generates vibrations as the shaft body 12 rotates, vibrations in the radial direction of the kneading shaft 3 cancel each other. Vibration can be applied in the circumferential direction of the kneading shaft 3, that is, the direction in which the kneading shaft 3 is originally rotatable, and the bearings of the bearing 4 portion of the kneading shaft 3 can be damaged by an unreasonable load due to vibration. I try not to.

  FIG. 8 shows a series of movements of the unbalanced weight 25. First, at the timing (a), a downward exciting force acts from the left unbalanced weight 25 in the figure, and the right unbalanced weight. An upward exciting force is applied from the weight 25, and as a result, an exciting force in the counterclockwise direction around the shaft body 12, that is, the kneading shaft 3 is generated in the support member 13. Next, at the timing (b) showing a state in which each unbalanced weight 25 has rotated about ¼ with the rotation of the shaft body 12, an inward excitation force works from the left unbalanced weight 25. At the same time, an inward excitation force is also exerted from the right unbalance weight 25, and as a result, the excitation force of each unbalance weight 25 cancels out and cancels out, and the support member 13 is applied in any direction. No vibration is generated.

  At the subsequent timing (c), an upward excitation force acts from the left unbalance weight 25 and a downward excitation force acts from the right unbalance weight 25. As a result, the support member 13 An exciting force is generated in the clockwise direction around the shaft body 12, that is, the kneading shaft 3. At the last timing (d), an outward excitation force is applied from the left unbalance weight 25 and an outward excitation force is also applied from the right unbalance weight 25. As a result, The excitation forces of the unbalanced weights 25 cancel each other and cancel each other, and no excitation force is generated in the support member 13 in any direction.

  When the kneading shaft 3 is vibrated through the support member 13 by rotating the unbalanced weights 25 attached to the pair of driven gears 23 in this way, the kneading shaft 3 does not vibrate in the radial direction and does not vibrate. Since it vibrates so as to swing only in the direction, it can be suitably vibrated without applying an excessive load to the bearing of the bearing 4 of the kneading shaft 3. Note that the positional relationship between the left and right unbalanced weights 25 is always symmetrical even in the intermediate state between the steps (a), (b), (c), and (d) not shown in FIG. The fact that vibrations in the radial direction of the kneading shaft 3 always cancel each other out and vibrations are applied only in the circumferential direction remains the same.

  In addition, an opening 26 of a predetermined size is formed in the left and right positions of the bottom surface of the kneading tank 2, and a vibration plate 28 for fixing an electric vibrator 27 is provided so as to close the opening 26. . As shown in FIGS. 6 and 7, the vibration plate 28 to which the vibrator 27 is fixed has its inner surface facing the inside of the kneading tank 2 so as to be flush with the inner wall surface of the kneading tank 2. The periphery of the vibration plate 28 is fastened and fixed to the fixing plate 30 with bolts 31 via vibration-proof rubber 29 which is a vibration-proof material. Further, the fixing plate 30 has its peripheral edge abutted against the outer wall surface of the kneading tank 2 around the opening 26 via a watertight packing 32, and both longitudinal ends of the fixing plate 30 are illustrated in FIG. As shown in FIG. 1, the packing 32 is pressed along a substantially L-shaped fixing piece 33 that is bent into a substantially L-shape and the bent portion projects from the bottom surface of the kneading tank 2. The bolt 34 is fastened and fixed for watertightness.

  Accordingly, when the vibrator 27 is driven, only the vibration plate 28 vibrates strongly, and the vibration force is directly transmitted to the concrete material in the kneading tank 2 facing the vibration plate 28 as it is, but to the kneading tank 2 itself. The vibration isolating rubber 29 absorbs and weakens most of the vibration force, so that strong vibration is not transmitted as it is, and the mixer 1 can be prevented from being broken or damaged by vibration.

  In this embodiment, a pair of vibrators 27 attached to the left and right positions of the bottom surface of the kneading tank 2 is used. However, the present invention is not limited to this. You may make it attach to both a bottom face and a side surface, or various other places. Further, the number of vibrators 27 may be appropriately increased or decreased according to the size of the kneading tank 2, and the size of the vibration plate 28 may be changed as appropriate. Further, as the vibrator 27, a rotary vibrator, a piston vibrator, or the like can be effectively employed.

  Thus, when kneading the ready-mixed concrete using the concrete mixer 1 of the present invention, first, the shaft body driving motor 20 is driven to rotate the shaft body 12, and the unmounted gear 23 attached to the driven gear 23 accordingly. While the kneading shaft 3 is vibrated by rotating the balance weight 25, the kneading shaft driving motor 8 is driven to rotate the two kneading shafts 3 in opposite directions, and the kneading tank 2 is provided. The vibrator 27 is also driven to vibrate the vibration plate 28. At this time, the vibration due to the unbalanced weight 25 is directly transmitted to the kneading shaft 3 side, and is strongly transmitted to a large number of arms 5 and kneading blades 6 provided on the kneading shaft 3, while being transmitted to the driving motor 8 side. Most of the energy is absorbed and weakened by the spring 16 in the middle, and there is no possibility that vibration is transmitted to the driving motor 8 strongly. Further, the vibration by the vibrator 27 is directly transmitted from the vibration plate 28 to the inside of the kneading tank 2, while the kneading tank 2 itself is mostly absorbed and weakened by the anti-vibration rubber 29 interposed therebetween. There is no possibility that the mixer 1 itself vibrates strongly.

  In such a state, various concrete materials are sequentially introduced into the kneading tank 2. The concrete material thrown into the kneading tank 2 is rotated by the kneading shaft 6, rotating constantly while receiving constant vibration from the kneading shaft 3, the numerous arms 5 and the kneading blade 6, and the vibration plate 28 at the bottom of the kneading tank 2. It is repeatedly kneaded and mixed, suitably kneaded, and discharged as high-quality ready-mixed concrete that can be expected to increase in strength.

  As described above, since the vibration is suitably generated with respect to the kneading shaft 3 of the mixer 1, the vibration plate 28 provided in the kneading tank 2, and the like, the corners of the concrete material in the kneading tank 2 are efficiently handled. The vibration can be sufficiently distributed, whereby the kneading performance is improved and the quality of the concrete after kneading can be further improved.

  9 to 15 show another embodiment of the present invention. The parts having the same structure as that of the first embodiment are denoted by the same reference numerals and detailed description thereof is omitted.

  The mixer 1 ′ of this embodiment is a biaxial concrete mixer as in the first embodiment, but includes a pair of kneading shaft driving motors 8, and each of the kneading shaft driving motors 8 provided below the pair of kneading shaft driving motors 8. The input shafts 36 of the speed reducer 35 are connected to each other by a coupling mechanism 37 so as to be synchronized, and the synchronization gear 11 in the first embodiment is unnecessary.

  In addition, a flange 38 is attached to the shaft end of the kneading shaft 3, and a flange 40 is also attached to the output shaft 39 provided in the speed reducer 35. Further, as shown in FIG. 14, a large number of fastening pieces 14, 15 are projected from the respective side surfaces of the flanges 38, 40, and the spring 16 is interposed between the fastening pieces 14, 15. And are connected by fastening with bolts 17.

  Accordingly, the driving force by the kneading shaft driving motor 8 is once transmitted from the flange 40 provided on the output shaft 39 of the speed reducer 35 to the flange 38 provided on the kneading shaft 3 via the spring 16, and finally the kneading shaft 3. It has come to be conveyed to. On the other hand, the vibration from the unbalanced weight 25 provided at the other end of the kneading shaft 3 is directly transmitted to the kneading shaft 3, but a spring interposed between the speed reducer 35 and the kneading shaft driving motor 8 side. The vibration suppressing mechanism similar to that of the first embodiment is configured so that most of the vibration is absorbed and weakened by the screw 16 and the kneading shaft driving motor 8 can be prevented from being damaged or broken without being transmitted to the strong vibration. ing.

  At the other shaft end of the kneading shaft 3, a support member 13 for rotatably supporting a shaft body 12 having the same shaft center as that of the kneading shaft 3 is mounted in the same manner as in the first embodiment. A pulley 18 and a main drive gear 19 are mounted on the shaft body 12 rotatably supported on the support member 13, and a shaft body driving motor 20 is disposed on the side of the shaft body 12. A pulley 21 provided in the shaft body driving motor 20 and a pulley 18 of the shaft body 12 are connected by a belt 22, and the shaft body 12 is rotated by driving the shaft body driving motor 20. I am doing so.

  Further, four pairs of driven gears 23 are provided at equal intervals along the outer peripheral edge of the main driving gear 19, and the paired driven gears 23 are arranged so as to face each other with respect to the shaft body 12. Each driven gear 23 is mounted on another shaft body 24, and unbalanced weights 25 for vibration are fixed to both ends of the shaft body 24, and are opposed to each other. As shown in FIG. 15, the mounting direction is adjusted so that the positional relationship of the unbalanced weights 25 between the driven gears 23 is always symmetrical.

  With this configuration, when the unbalanced weight 25 of each driven gear 23 rotates and generates vibrations as the shaft body 12 rotates, vibrations in the radial direction of the kneading shaft 3 cancel each other. Vibration can be applied in the circumferential direction of the kneading shaft 3, that is, the direction in which the kneading shaft 3 is originally rotatable, and the bearing of the bearing 4 of the kneading shaft 3 is not damaged by an excessive load caused by vibration. I am trying so.

  FIG. 15 shows a series of movements of the unbalanced weights 25. First, at the timing (a), an excitation force in the direction of the arrow acts from each unbalanced weight 25, and the support member 13 An exciting force is generated in the left rotation direction around the shaft body 12, that is, the kneading shaft 3. Next, at the timing of (b) showing a state in which each unbalanced weight 25 has rotated about ¼ with the rotation of the shaft body 12, an inward excitation force works from each unbalanced weight 25. As a result, the excitation forces of the unbalanced weights 25 cancel each other and cancel each other, and no excitation force is generated in the support member 13 in any direction.

  At the subsequent timing (c), an excitation force in the direction of the arrow acts from each unbalanced weight 25, and the support member 13 is excited in the clockwise direction around the shaft body 12, that is, the kneading shaft 3. Power is generated. Then, at the last timing (d), an outward excitation force acts from each unbalanced weight 25, and as a result, the excitation force of each unbalanced weight 25 cancels each other out and cancels out. No exciting force is generated in 13 in any direction.

  As described above, when the unbalanced weights 25 attached to the four pairs of driven gears 23 are rotated to vibrate the kneading shaft 3 via the support member 13, the kneading shaft 3 does not vibrate in the radial direction without being vibrated. Since it vibrates so as to swing only in the circumferential direction, it can be suitably vibrated without applying an excessive load to the bearing of the bearing 4 of the kneading shaft 3. Even in the intermediate state between the steps (a), (b), (c), and (d) not shown in FIG. 15, the positional relationship of the unbalanced weights 25 at the opposing positions is always symmetric. However, the vibration in the radial direction of the kneading shaft 3 always cancels out, and the point that the vibration is applied only in the circumferential direction remains the same. Thus, also in the present embodiment, it can be suitably vibrated as described above, and the quality of the concrete after kneading can be made excellent.

  In the first and second embodiments, the case where the unbalanced weights are one pair and four pairs is described, but two, three pairs, or five or more pairs may be used. Moreover, in Example 2, although the case where a vibrator is not attached to the bottom face of the kneading tank 2 is shown, it goes without saying that it may be attached as in Example 1 if necessary. Also, the mixer itself may be a uniaxial type instead of the biaxial type. Further, in this embodiment, a batch type mixer is employed, but it can also be suitably employed for a continuous type mixer or the like.

1 is a partially cutaway front view showing a first embodiment of a concrete mixer according to the present invention. It is a top view of FIG. It is a left view of FIG. FIG. 3 is an enlarged view of a main part in which a part of FIG. 2 is cut away. It is the AA cross-sectional enlarged view which abbreviate | omitted a part of FIG. It is the BB cross-sectional enlarged view which abbreviate | omitted a part of FIG. It is a principal part enlarged view of FIG. It is explanatory drawing explaining the vibration direction by an unbalanced weight. It is a figure equivalent to FIG. 1 of a 2nd Example. FIG. 10 is a plan view of FIG. 9. FIG. 10 is a left side view of FIG. 9. FIG. 10 is a right side view of FIG. 9. It is the principal part enlarged view which notched a part of FIG. FIG. 10 is an enlarged cross-sectional view taken along the line CC in which a part of FIG. 9 is omitted. It is a figure equivalent to FIG. 8 of a 2nd Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1 '... Concrete mixer 2 ... Kneading tank 3 ... Kneading shaft 5 ... Arm 6 ... Kneading blade 7 ... Sprocket 8 ... Kneading shaft drive motor 11 ... Gear 12 ... Shaft body 13 ... Support member 18 ... Pulley 19 ... Main drive gear DESCRIPTION OF SYMBOLS 20 ... Shaft body drive motor 23 ... Driven gear 25 ... Unbalanced weight 27 ... Vibrator 28 ... Vibration plate

Claims (2)

  In a concrete mixer for kneading various concrete materials by rotating a kneading shaft disposed in a kneading tank by a kneading shaft driving motor, a shaft body having the same center as the kneading shaft is rotated at the shaft end of the kneading shaft. A shaft is freely attached, and a pulley for transmitting a driving force from a shaft body driving motor and a driving gear are attached to the shaft body, and at least a pair of driven gears are disposed along the outer peripheral edge of the driving gear. The paired driven gears are arranged at opposed positions with respect to the shaft body and meshed with the respective driven gears, and each driven gear is fixed with an unbalanced weight for vibration, and The positional relationship of the unbalanced weights between the driven gears is adjusted to be symmetric, and the configuration is such that the vibration in the radial direction is offset with respect to the kneading shaft and the vibration is applied only in the circumferential direction. Features and Concrete mixer that.   2. The concrete mixer according to claim 1, further comprising vibration suppressing means for suppressing vibration of the unbalanced weight to the kneading shaft from reaching the kneading shaft driving motor.

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