WO2017042802A1

WO2017042802A1 - Method for cleaning concrete mixer drum

Info

Publication number: WO2017042802A1
Application number: PCT/IL2016/050974
Authority: WO
Inventors: Gennady Carmi
Original assignee: Flow Industries, Ltd.
Priority date: 2015-09-07
Filing date: 2016-09-04
Publication date: 2017-03-16

Abstract

A method of removing hardened concrete deposits from the interior surfaces of the mixer drum of a concrete mixer truck, the method including at least partially filling the drum with water; submerging a gas impulse generator in the water within the drum; and activating the gas impulse generator within the water to generate shock waves for propagation throughout the drum so as to cause differential elastic distortion of the drum and blade arrangement and of the concrete deposits, consequently causing the concrete to fragment into debris and thus to separate from the surfaces on which it was deposited.

Description

METHOD FOR CLEANING CONCRETE M IXER DRUM

FIELD OF THE INVENTION

The present invention relates to the cleaning of concrete mixer drums, such as of concrete mixer trucks.

BACKGROUND OF THE INVENTION

Concrete trucks transport liquid concrete in rotatable mixer drums. Helical baffles forming a blade arrangement line the interior of the mixer drum and act as an Archimedes' screw so as to force the liquid concrete into the drum and away from the opening when the drum rotates in a first direction, thereby to mix the concrete; and in the opposite direction when the drum rotates in a second direction, thereby to discharge the concrete from the drum through the exit. Concrete residue often remains in the drum after a load of concrete has been discharged, especially on, between or near the baffles. Over time, the build-up of hardened residual concrete adds to the overall weight of the mixer drum so as to require more force in order to rotate it, and also lowers the mixer drum's liquid concrete capacity. In addition, the presence of the hardened residual concrete may also impede the above-described action of the blade arrangement, so also as to make it more difficult to operate the drum and thus increase fuel consumption.

In some cases, in order to remove the hardened concrete an operator enters the interior of the mixer drum and chips the hardened residual concrete so as to remove it. Typically, a jack-hammer is used for this purpose. This is hazardous to the operator due to the large amounts of concrete dust which quickly fill the interior of the drum during this process. Furthermore, an inability to fully control the movement of the jack-hammer movement often results in damage to the drum and baffles.

Some operators rely on the use of high pressure water jets provided by handheld wand- mounted pressurized nozzles to remove residual concrete from the inside of the mixer drum. However, so as to be able to remove the hardened concrete, these devices require very high water pressure (up to 20,000 PSI). Since the distance between the nozzles and the drum surface is usually relatively great (lm or more), the energy of the stream from the nozzle drops sufficiently by the time it reaches the hardened concrete. With the attendant drop in energy of the stream, the nozzle must be directed at the same place for relatively long time to affect the hardened concrete. Furthermore, the process of removal depends on the concrete being cut by the water stream, therefore requiring coverage of all parts of the interior of the drum. It is thus a long and tedious process which is not always fully effective.

There is thus a long felt need for a fast, effective and economical method for cleaning the interior of the mixer drum ensuring thorough residual concrete removal. SUM MARY OF THE INVENTION

There is provided a method of removing hardened concrete deposits from the interior surfaces of the mixer drum of a concrete mixer truck,

the drum having an opening for the intake and exhausting of materials therethrough, and a spiral blade arrangement having a longitudinal axis and arranged within the drum so as to be generally axially aligned with the opening, the drum being rotatable about the axis in a first direction such that the blade arrangement forces the concrete into the interior of the drum away from the opening, and in a second direction, opposite to the first direction, so as to force the concrete out of the drum through the opening, the method including at least partially filling the drum with water; submerging a gas impulse generator in the water within the drum; and activating the gas impulse generator within the water to generate shock waves for propagation throughout the drum so as to cause differential elastic distortion of the drum and blade arrangement and of the concrete deposits, consequently causing the concrete to fragment into debris and thus to separate from the surfaces on which it was deposited.

Preferably, the step of activating includes either or both of operating the gas impulse generator under a working pressure in the range 300 - 3,000 psi and operating the gas impulse generator at a frequency of 16-25 pulses per minute.

Additionally, the gas impulse generator is connected to a source of pressurized gas via a flexible hose, and the step of submerging preferably includes positioning the gas impulse generator in proximity to a baffle portion of the spiral blade arrangement adjacent to the opening; and rotating the drum in the first direction so as to correspondingly rotate the baffle portion so as to cause it to take up the gas impulse generator and force it into the interior of the drum away from the opening.

Further, the step of submerging may include the step of positioning the gas impulse generator within the deepest portion of the water within the drum.

Additionally, the method may also include, after the step of submerging, reversing the direction of rotation of the drum, thereby to force the gas impulse generator to move in reverse, along the length of the blade arrangement towards the opening of the drum, while continuing to operate the gas impulse generator so as continue to generate shock waves as it moves along the interior of the drum.

Further, if the drum has a window, the step of reversing may also include reducing the intensity of the working pressure of the gas impulse generator, as it passes by the window, thereby to avoid damage thereto. BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more fully understood from the following detailed description taken in conjunction with the drawings, in which:

Fig. 1 is a schematic view of a concrete mixer truck and a gas impulse generator for use in the method of the invention;

Fig. 2 is a schematic view of a concrete mixer drum cut away to as to show a spiral blade arrangement therein;

Fig. 3 is a partially cut away schematic view of a concrete mixer drum and the internal blade/baffle arrangement therein at a first stage of the method of the invention; and

Fig. 4 is a partially cut away schematic view of a concrete mixer drum and the internal blade/baffle arrangement therein at a second stage of the method of the invention.

DETAILED DESCRIPTION

Referring now generally to Figs. 1-4, a typical mixer truck 10 includes a drum 12 having an opening 14 (Figs. 3 and 4) for the intake and exhausting of materials therethrough, and a spiral blade arrangement 16 (Figs. 2, 3 and 4). The spiral blade arrangement 16, shown in its entirety in Fig. 2 and cut away in Figs. 3 and 4, has a longitudinal axis 18 and is arranged within the drum 12 so as to be generally axially aligned with the opening 14. When used for making concrete, the drum 12 will normally be filled with cement, gravel, sand and water in selected proportions, with the mixing occurring during transport. Alternatively, the concrete may already have been made before loading into the drum 12 of the mixer truck 10, in which case concrete mixing truck 10 is used to maintain the liquid state of the concrete until the truck 10 reaches the destination, whereat the concrete will be discharged for used.

As seen in Fig. 2, the drum 12 is rotatable about the axis 18 in a first direction, indicated by a first arrow 20, such that, based on the Archimedes' screw principle, the blade arrangement 16 forces the concrete into the interior 22 of the drum 12 away from the opening 14. The drum 12 is further rotatable in a second direction, indicated by a second arrow 24, opposite to the first direction, so as to force the concrete out of the drum 12 through the opening 14.

In order to remove the hardened concrete deposits from the interior surfaces of the drum, including both the interior wall 26 of drum 12 and the baffles 28 of which blade arrangement 16 is comprised, the drum 12 is initially filled with water, at least partially, to a depth generally as indicated in Fig. 1 by dashed line 30.

In accordance with the present invention, the hardened concrete deposits are removed by use of a gas impulse generator 32, as described hereinbelow. A suitable type of gas impulse generator for the present purpose may be, for example, as manufactured by Flow Industries Ltd. of Israel, including any of the AirShock™ Generator models listed at http://www.fjow- industries.com/water- well- rehabilitation/technology . Typically, gas impulse generator 32 is as disclosed in either of the current applicant's US Patents Nos. 6,250,388 or 6,630,032, or any other equivalent model. Gas impulse generator 32 is connected via a suitable flexible hose 34 to a supply of compressed gas, typically air or nitrogen, stored in cylinders 36 connected to a compressor. The supply of compressed gas to the generator 32 is controlled via a suitable gas supply control panel 38, as illustrated schematically in Fig. 1.

As a first step to initiate the cleaning method of the invention, gas impulse generator 32 is submerged in the water within the drum 12. Specifically, as seen in Fig 3, gas impulse generator 32 is positioned in proximity and preferably across a baffle portion 40 of the spiral blade arrangement 16 close to the drum opening 14, and facing into the interior of drum 12 and away from the opening 14. Subsequently, when the drum 12 is rotated in the first direction 20, an end baffle portion 40 (Fig. 3) takes up or pulls the gas impulse generator 32 so that it traverses along the edge 42 of the entire blade arrangement 16, eventually moving it deep into the interior of the drum 12, and preferably, into the deepest part of the water in the drum 12, as seen in Fig. 4.

Once in position, the gas impulse generator 32 is activated so as to generate shock waves which propagate throughout the drum. Typical working conditions of the gas impulse generator 32 are under a working pressure in the range 300 - 3,000 psi or higher, and at a frequency which typically is in the range 16-25 pulses per minute, although this may be either lower or higher.

These shock waves create vibrations and elastic deformation of the drum 12. Drum 12 is made of steel which has far greater elasticity than concrete. The shock waves caused by gas impulse generator 32 cause the drum walls 26 and baffles 28 to vibrate, giving rise to tensile and compressive stresses on and within the concrete. The difference in elastic properties between the hardened concrete on the one hand, and the vibrating elastic steel drum 12 and steel baffles 28 results in the mechanical failure of the concrete, such that it flakes from the steel.

In addition to the above-described flaking mechanism, there exists a further mechanism caused by the shock waves which serves to shatter the concrete, and this is described as follows. As known, plain concrete is a non-homogeneous mixture of coarse aggregate, usually gravel or crushed rock, sand and hydrated cement paste. Accordingly, the above-described tensile loading of the concrete leads to very rapid development of cracks therewithin and a loss of concrete strength. Additionally, the compressive loading that occurs as a result of the shock waves serves to increase the stresses at the edge of the cracks, causing further propagation of the cracks.

It will thus be appreciated that the repeated shock waves give rise to both compression and tension forces on and within the concrete such that in addition to the above-described separation or flaking of the concrete from the inner surface, it shatters, creating debris which can be easily evacuated through the drum opening.

At an appropriate stage during the process of the invention, which may be either immediately after the gas impulse generator 32 has reached the furthest extent inside the drum 12, or at a selected interval thereafter, drum 12 can be rotated in the opposite direction, which is the direction which would normally cause the blade arrangement to discharge the mixed concrete through the opening, for use. In the present situation, in which the gas impulse generator is located in the interior of the drum 12 submerged in water, rotation of the drum 12 in this second, reverse direction, forces the gas impulse generator 32 to move in reverse, along the length of the blade arrangement 16 towards the opening 14 of the drum 12, while continuing to generate shock waves as it moves along the interior of the drum 12. In this manner, even though the drum 12 can be filled only up to the level of the bottom of the opening 14, as the drum is rotated, every portion of the interior, both of the drum wall 26 and of the blade arrangement 16, is repeatedly exposed to high intensity shock waves, thereby separating and fragmenting all of the hardened concrete within the drum 12.

Referring now briefly to Fig. 3 and 4, as seen, there is normally provided an inspection window 44 built into the drum wall 26. In order not to damage the window, when the gas impulse generator 32 is about to pass in proximity to the window 44, the working pressure of the gas impulse generator 32 is reduced, or generator 32 may even be switched off momentarily, in order to avoid damage to the window.

It will be appreciated by persons skilled in the art that the scope of the present invention is not limited to what has been specifically shown and described hereinabove. Rather, the scope of the invention is limited solely by the claims, which follow:

Claims

1. A method for removing hardened concrete deposits from the interior surfaces of the mixer drum of a concrete mixer truck, the drum having an opening for the intake and exhausting of materials therethrough, and a spiral blade arrangement having a longitudinal axis and arranged within the drum so as to be generally axially aligned with the opening, the drum being rotatable about the axis in a first direction such that the blade arrangement forces the concrete into the interior of the drum away from the opening, and in a second direction, opposite to the first direction, so as to force the concrete out of the drum through the opening,

the method including the following steps:

at least partially filling the drum with water;

submerging a gas impulse generator in the water within the drum; and

activating the gas impulse generator within the water to generate shock waves for propagation throughout the drum so as to cause differential elastic distortion of the drum and blade arrangement and of the concrete deposits, consequently causing the concrete to fragment into debris and thus to separate from the surfaces on which it was deposited.

2. A method according to claim 1, wherein the step of activating includes at least one of (i) operating the gas impulse generator under a working pressure in the range 300 - 3,000 psi and (ii) operating the gas impulse generator at a frequency of 16-25 pulses per minute.

3. A method according to claim 1, wherein said gas impulse generator is connected to a source of pressurized gas via a flexible hose, and said step of submerging includes:

positioning the gas impulse generator in proximity to a baffle portion of the spiral blade arrangement adjacent to the opening; and

rotating the drum in the first direction so as to correspondingly rotate the baffle portion so as to cause it to take up the gas impulse generator and force it into the interior of the drum away from the opening.

4. A method according to claim 3, wherein the step of submerging includes the step of positioning the gas impulse generator within the deepest portion of the water within the drum.

5. A method according to claim 3, also including, after the step of submerging, the step of reversing the direction of rotation of the drum, thereby to force the gas impulse generator to move in reverse, along the length of the blade arrangement towards the opening of the drum, while continuing to operate the gas impulse generator so as continue to generate shock waves as it moves along the interior of the drum.

6. A method according to claim 5, the drum also has a window, and in said step of reversing there is also provided the steps of:

sensing proximity of the gas impulse generator to the window; and

at least reducing the intensity of the working pressure of the gas impulse generator, as it passes by the window, thereby to avoid damage thereto.