Agitating – Mortar mixer type – Methods
Reexamination Certificate
2001-01-26
2002-03-12
Soohoo, Tony G. (Department: 1723)
Agitating
Mortar mixer type
Methods
C366S005000, C366S013000, C366S064000, C366S191000
Reexamination Certificate
active
06354726
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a mixing and conveying device for discontinuous mixing interrupted by feeding processes, and subsequent conveying of semifluid materials.
2. The Prior Art
These devices are employed in the construction industry for mixing and conveying semifluid materials, in particular semifluid materials with low water content, for example mortar and flooring concrete. In this process, the components of the semifluid material are typically sand, a binding agent and water. These substances are first loaded into a mixing vessel through a filling opening and subsequently mixed by the agitator gear. The cover of the mixing vessel is closed and compressed air is admitted into the mixing vessel. The semifluid material contains lumps and bubbles of compressed air, and the material pressed through a conveying conduit that is connected to a short outlet pipe located in the lower zone of the mixing vessel. The air bubbles are formed because the blades of the agitator gear, which continue to run, periodically sweep the outlet opening leading into the conveying conduit. To convey the material, additional compressed air is blown in through another conduit feeding into a short outlet pipe. Such mixing and conveying devices are designed with an integrated or a separate compressor.
There are known devices that contain an integrated compressor. Oil-injected rotating compressors are used in such mixing and conveying equipment in most cases. An electric motor or an internal combustion engine drives the compressor element in the rotating compressors either directly or via a belt or toothed gear drive. No switching couplings are employed between the drive motor and the compressor element for cost reasons and because of other engineering drawbacks, i.e. the compressor element is always jointly driven when the drive motor is in operation.
The agitator gear is driven either via a switchable belt drive and a cardan shaft arranged between the drive motor and the agitator gear, or via a hydraulic motor mounted on the agitator gear, and a hydraulic pump attached to the drive motor.
It is cost effective to employ the power output of the drive motor as efficiently as possible, i.e. to achieve the shortest possible mixing and conveying time periods for a defined quantity of the viscous material.
Since the known devices do not contain a switching coupling device between the drive motor and the compressor element, the compressor is driven during the course of the mixing phase. At this stage, no compressed air is required for conveying any material. Therefore, the compressor is running idle, and consumes a notable proportion of the power output of the drive motor that is consequently not available for the mixing process.
The driving torque required for the agitator gear has the highest value at the start of the mixing phase and then drops quickly when the charged material is thoroughly mixed into a pasty compound. Furthermore, the driving torque required for the agitator gear is highly dependent upon the rotational speed of the agitator gear. Reducing the rotational speed of the agitator gear at the start of the mixing phase would reduce the required driving torque and the required driving power output. However, the known mixing and conveying devices do not provide for efficiently reducing the rotational speed of the agitator gear.
The reason for not offering such a reduction, is that transmissions with variable speed ratios between the drive motor and the agitator gear, or controllable hydraulic motors, are not used due to their high cost. A change in the rotational speed of the agitator gear is possible via a change in the rotational speed of the drive motor, in conjunction with hydraulic motors, by means of a bypass control capability with high power output losses. If an internal combustion engine is employed as the drive motor, narrow limits are set for any reduction in the number of revolutions. Moreover, a reduced rotational speed of the drive motor means a reduction in the power output of the motor. When an electric motor is employed as the drive motor, no drives with variable rotational speed are considered due to its high cost.
Therefore, in conjunction with a mixing and conveying device according to the state of the art, the driving power output required for the agitator gear has a maximum output at the start of the mixing phase. The drive motor and the agitator gear have to be coordinated with each other because the motor may otherwise be stalled by the agitator gear. The available power capacity of the drive motor cannot be completely utilized for the mixing process in the course of the mixing phase.
In the conveying phase, a rotational speed that is reduced from the mixing phase would be desirable, i.e. a rotational speed that would be sufficient for thorough mixing and for supporting the formation of lumps. However, in the known mixing and conveying equipment, the agitator gear operates during the conveying phase with an unnecessarily high rotational speed and with an unnecessarily high driving power output, especially if the rotational speed of the drive motor is increased in the course of the conveying phase to generate as much compressed air as possible for the conveying process. The unnecessarily high power requirement of the agitator gear is not available for the generation of compressed air, i.e. for conveying the viscous material.
A further disadvantage of the known mixing and conveying devices equipped with hydraulic pumps and hydraulic motors is the high costs incurred for the additional hydraulic circulation. German Patent DE 42 11 139 A1 discloses the combination of the oil circuit of the rotational compressor and the hydraulic circuit. This system has not been widely accepted until now, presumably because the high air component contained in the compressor oil causes substantial problems in the hydraulic system.
A further disadvantage associated with the known mixing and conveying devices having belt transmissions and cardan shafts are the harmful rotational oscillations of the power or drive train and vibrations resulting therefrom that lead to substantial noise development. Such mixing and conveying devices are described in German Patent DE 42 10 430 A1. This type of drive causes engineering restrictions that have higher manufacturing costs. Furthermore, the switchable belt drive contains a tensioning roller, actuation levers, a cardan shaft, reduction gear used for reducing the number of revolutions, a plurality of bearings, and systems for lubricating the bearings, these components substantially contribute to the high manufacturing costs. Moreover, the high maintenance requirements of the switchable belt drive gear represent another disadvantageous factor.
Known mixing and conveying devices with separate compressors are supplied with compressed air by mobile or transportable compressors set up at the construction site. Typically, an electric motor is employed for driving the agitator gear. The drawback in this case is that these devices are dependent on an additional power connection that is not always available at construction sites.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to improve the known mixing and conveying devices by increasing the output capacity of the drive motor during both the mixing phase and the conveying phase. In addition, the engineering expenditures, the manufacturing costs, and the maintenance for the device of the present invention are reduced. Furthermore, the operating reliability of this a device is increased and its useful life is prolonged.
These and other objects are accomplished by providing the motor drive of the agitator gear with at least one compressed air motor. These motors are supplied with a proportion, preferably with 20% to 100%, of the compressed air generated by the compressor, and have a rotational speed that can be adapted to the various operating phases of the mixing and conveying process to influence the feed of compressed air to the com
Collard & Roe P.C.
Kaeser Compressoren GmbH
Soohoo Tony G.
LandOfFree
Method and device for mixing and conveying concrete does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and device for mixing and conveying concrete, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and device for mixing and conveying concrete will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2871620