FURLANI, Michele (Via Zambelli 24, Verona, I-37121, IT)
| CLAIMS A planetary mixer for the production of concrete at construction sites or similar and at the sites of the manufacturers of prefabricated elements, where the mixer comprises a tank (21) fitted with a fixed reduction gear unit (22) carrying the mixing means and their actuating components and where the upper central part of the fixed body (22) has a feeder unit (24), characterised in that the system for distributing water, cement and additives (24) is fixed to the fixed reduction gear body (22) and comprises a series of concentric pipes where the first, innermost pipe (33) is for the passage of cement, the outer concentric pipe (34) is for dust extraction and which, being concentric with the cement pipe, limits the formation of cement dusts, and the last, outermost concentric pipe (35) which is used for feeding in water and which thanks to a sector (36) with a cone-shaped lower edge, distributes an umbrella-like shower of water and additives radially over the entire surface of the tank through the openings (37) located at regular intervals; additives enter the water pipe through the connectors (17). The planetary mixer for the production of concrete according to the foregoing claim, where the mixer comprises a tank (21) , characterised in that the tank is constructed from sector modules (41, 42), fixed to each other with bolts and designed to facilitate variations in the position and number of the unloading doors (32) being bolted to each other or to support columns . The planetary mixer for the production of concrete according to the foregoing claim, characterised in that the mixing elements inside the tank comprise a plurality of mixer paddles (25) and scraper paddles (26) actuated by a transmission system where planetary gear motors (23) , flanged to the upper part of the mixer reduction gear body (22) , transmit drive power to a ring gear (27) which powers the lower part (39) of the reduction gear body which acts as a planet carrier, in such a way that the rotary body of the reduction gear box transmits drive power to the scraper paddles (26) . The planetary mixer for the production of concrete according to one of the foregoing claims, characterised in that the mixer paddles (25) are driven by a sun gear (28) which meshes with a fixed, toothed crown wheel (29) . The planetary mixer for the production of concrete according to one of the foregoing claims, characterised in that the coupling between the ' mixer planet and the sun gear shaft comprises splining designed to make timing easier and to exclude the stress concentration factors otherwise found in keyed applications . The planetary mixer for the production of concrete according to one of the foregoing claims, characterised in that the lower part (39) of the reduction gear body houses a rotary seal (30) mounted in a open groove, to facilitate maintenance, protected by containing sectors. The planetary mixer for the production of concrete according to one of the foregoing claims, characterised in that the inside parts of the mixing tank in contact with the material are completely lined with interchangeable anti-wear panels (31) made from high-abrasion resistant steel. The planetary mixer for the production of concrete according to one of the foregoing claims, characterised in that the mixer paddles (25) are made from cast iron castings or made from high abrasion resistant steel or coated with wearproof rubber and also characterised in that all the paddles are shaped to optimise the flow of material during mixing and to minimise friction and therefore abrasion wear caused by the aggregates. |
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TECHNICAL FIELD
The present invention relates to a planetary mixer for the production of concrete at construction sites or similar and at the sites of the manufacturers of prefabricated elements.
In particular the present invention relates to a family of planetary mixers in which the part comprising the mixing tank is constructed from modular elements connected to each other by bolted joints, which facilitate the easy and rapid configuration of the position' and number of unloading doors with which the mixer is to be fitted. The upper part comprises a fixed reduction gear body which can be fitted with inspection doors or aggregate feed doors also in a modular fashion, and a corresponding rotary body which via an epicyclic gear mechanism transmits motion to the mixer and scraper paddles .
The drive unit rather than being concentrated in a single large gear motor is decentralised to one or more gear motors which transmit motion to a ring gear with the advantage of distributing the load to the teeth of the gearing at multiple points and thereby enabling an improved distribution of power.
This leaves the centre of the mixer free and available for housing a radial distribution system for distributing the ingredients needed to make the concrete. This system is the most important feature of the innovation and enables greater uniformity in the distribution of the ingredients.
The present invention applies to the industrial sector for the production of concrete using both fixed and mobile plant for the production of concrete.
BACKGROUND ART
It is well known that the equipment for the production of concrete comprises an aggregate storage unit, a mixing unit for receiving, measuring and dosing the aggregates, the water and the cement, a loading system for transferring the aggregates from the storage unit to the mixing unit and silos containing the cement; the silos are usually fitted with feed screws for conveying the cement to the mixing unit.
At the present time according to known technology, mixing is undoubtedly the most critical step in the concrete making process, so much so that the quality of concrete depends largely on the type of mixer used.
Vertical axis mixers are available in a variety of constructional variants. The most widely used have a central drive unit with the aggregate, cement and water feeds being mounted on the sides; this limits the space available for maintenance and cleaning.
The upper part has a substantially conical shape whereas the mixing tank is cylindrical and has one or more unloading doors. There are versions with twin drive units where the feed system is also centrally located.
There are mixers where the upper part is not conical but consists of a vertical extension of the cylindrical tank. In this case the covers do not open at the top but open at the sides; this feature makes efficient washing and cleaning more difficult.
Usually these mixers comprise a one-piece mixing tank with one or more unloading doors and with the epicyclic reduction unit mounted on top.
On many models the drive transmission system consists of gearing or a toothed crown wheel driven by a gear motor which has a drive pinion meshing with the transmission gearing.
On other models the drive is transmitted to the lower part of the reduction unit by a rack or a toothed bearing .
On some models where the drive transmission is a ring gear, the free central space is used for loading aggregates but the infeeds for cement, water and additives remain at the side.
The known method for water distribution usually consists of piping feeding water into the mixer on one side of the mixer rather than radially; this means that the water is not distributed uniformly to the mix.
In other applications the water is distributed by nozzles mounted on uprights on the upper part of the mixer, that is, on the arms supporting the main reduction gear and the drive motor; here there are only three or four water distribution points depending on the size of the mixer.
All these systems have the drawback that the water is not distributed uniformly with the result that the product obtained is of a low quality; this lack of uniformity can derive from the side mounting of the water distribution components.
DESCRIPTION OF THE INVENTION
The present invention provides a modular planetary mixer for the production of concrete which eliminates or at least reduces the shortcomings described above.
This is achieved by a concrete mixing system which can be transported on trucks or similar vehicles and whose characteristics are described in the main claim. The dependent claims describe advantageous embodiments of the present invention.
In order to solve the drawbacks described above, the present invention uses the central part for feeding the concrete components such as water, cement and additives and at the same time provides a concentric feed system which optimises component distribution and reduces the effects of a lack of uniformity deriving from the side feeding of these components .
The present invention provides a concrete mixing system comprising modular tank elements where the mixing tank comprises sectors which can be fastened to each other in the configuration required and with the possibility of choosing, even at a later date, the position of the concrete unloading doors and the number of doors installed.
The modular construction can also be applied to the upper part of the mixer and to the installation of the inspection doors and the aggregate feeding door. The concentric design of the central system for distributing cement, water and additives enables the distribution and uniform mixing of the components on the entire mix being mixed.
In one embodiment of the invention, the outermost concentric pipe is connected at the bottom to a cone which forms an umbrella-like shower of water distributing the water radially over the entire surface.
This pipe has rectangular slits to prevent the formation of deposits in cases where dirty water is used.
The embodiment also comprises a sliding ring which partially covers the slits thereby regulating the flow of water . BRIEF DESCRIPTION OF THE DRAWINGS
Further features and advantages of the invention will become apparent from the description of an example embodiment which follows with reference to the annexed drawings, given purely by way of a non-limiting example, in which:
Figure 1 shows an overview of the entire plant which includes the planetary mixer for the production of concrete at construction sites or similar and at the sites of the manufacturers of prefabricated elements .
Figure 2 is a front, partially cut-away view of the plant .
Figure 3 is a view of the plant seen from above.
- Figure 4 shows a cross-section, side view of the plant .
Figures 5 to 9 show various views of the plant according to the present invention; some of the figures show the plant partially exploded.
- Figure 10 shows diagrammatic views of the material and water feeding units and the dust extraction unit .
Figure 11 shows a perspective view of the feed and extraction unit according to the present invention.
DESCRIPTION OF AN EXAMPLE EMBODIMENT
With reference to the annexed drawings, the plant according to the present invention substantially comprises a body 20 with a rounded shape which at the bottom has a tank 21, defined by sector modules and which at the top has a fixed body 22 or mixer carrying vertical-axis ring gear motors 23. The fixed reduction gear body 22 in turn comprises a series of mixer elements operating inside the tank 21 while the central upper part of the fixed body is fitted with a feeder unit 24 used to feed water, cement and additives into the tank 21.
The mixer elements located inside the tank comprise a plurality of mixer paddles 25 and scraper paddles 26 actuated by a transmission system where generously overdimensioned planetary gear motors 23, flanged to the upper part of the mixer reduction gear body 22, transmit drive power to a strong ring gear 27 which powers the lower part 39 of the reduction gear body which acts as a planet carrier in such a way that the rotary body of the reduction gear box transmits drive power to the scraper paddles 26.
The mixer paddles 25 are driven by a sun gear 28 which meshes with a fixed, toothed crown wheel 29.
The coupling between the mixer planet, which drives the two or three mixer paddles, and the transmission shaft (38) driving the sun gear consists of splining; splines make timing easier and, above all, exclude the stress concentration factors otherwise found in keyed applications. This has the effect of making the transmission stronger and more resistant to the fatigue stresses to which mixers are subject.
The lower part 39 of the reduction gear body 22 houses a rotary seal 30 which has a twin purpose: to stop dust and contaminants entering into the reduction gear box 22 and to stop the leakage of lubricant from the reduction gear. The seal is mounted in a open groove to facilitate maintenance and is protected by containing sectors .
The inside parts of the mixing tank 21 in contact with the material are completely lined with interchangeable anti-wear panels 31 made from high abrasion resistant steel; for special applications a lining made from wearproof rubber can also be used.
The mixer paddles 25 are made from cast iron castings; variants made from high abrasion resistant steel or coated with wearproof rubber could also be used.
All the paddles are shaped to optimise the flow of material during mixing and to minimise friction and therefore the abrasion wear caused by aggregates.
Special hydrodynamic profiles were designed for the central paddles, for the peripheral scraper paddles and for the paddle support arms.
The tank 21 is constructed using sector modules 41, 42, fixed to each other with bolts and designed to facilitate variations in the position and number of the unloading doors 32. In cases where it necessary to add unloading doors it is sufficient to substitute a fixed sector with a sector fitted with a door. This is made possible by the design of the bolted joints on the mixer.
The main innovative feature of the present invention is the water, cement and additive distribution system, indicated in its entirety by the numeral 24. This is fixed to the fixed part of the reduction gear body 22 and comprises a series of concentric pipes visible in Figure 10.
The first, innermost pipe 33 is designed for the passage of cement given that the central distribution of cement together with the centrifuging of the aggregates in the tank is the ideal way of obtaining uniform distribution, reducing mixing times and improving the mechanical performance of concrete.
The outer concentric pipe 34 is designed to extract dust and being concentric with the cement pipe limits the deposits of unused cement dust on the inside walls of the mixer; this pipe forms an annular screen which extracts dust radially from the entire volume of the tank.
The last, outermost concentric pipe 35 is used for feeding in water and, thanks to a sector 36 with a cone- shaped lower edge, distributes an umbrella-like shower of water and additives radially over the entire surface of the tank through the openings 37 located at regular intervals. This radially distributed shower of water forms a barrier which also damps down the dust caused by the entry of the cement being fed in through a pipe which is concentric to the dust extraction pipe and the water pipe .
The additives enter the water pipe through the connectors (17).
Thanks to the efficiency of the forced mixing method used, the mixer in the present invention meets the technical requirements of a wide range of production processes and applications including the following: plant for loading truck-mounted concrete mixers; prefabricated concrete production facilities; mobile plant; construction site applications; special mixing process (for dusts, binders, industrial waste treatment and treatment of chemical materials) .
The mixing flow is highly efficient thanks to centrifugal effect of the orbiting central planets (one or more depending on the capacity of the mixer model) combined with the centripetal effect of the perimeter scraper paddles.
The advantage of using multiple gear motors (23) (the number depends on the size of the mixer) is an improved distribution of torque to the ring gear 27 so that the toothing of the rack is less stressed in comparison with a rack driven by a single gear motor and therefore has greater fatigue resistance and a longer life.
The entire perimeter of the mixing tanks is fitted with steel panels 40, which can be opened a section at a time and which facilitate easy access to the mixing components. The mixer is fitted with inspection hatches and safety limit switches in compliance with the most stringent accident prevention regulations .
The invention as described above refers to a preferred embodiment. Naturally, while the principle of the invention remains the same, the details of construction and the embodiments may widely vary with respect to what has been described and illustrated purely by way of the example, without departing from the scope of the present invention.