GB2145635A

GB2145635A - An annular trough mixer

Info

Publication number: GB2145635A
Application number: GB08421604A
Authority: GB
Inventors: Rudolf Hagenmuller
Original assignee: TEKA MASCHINENBAU GmbH
Current assignee: TEKA MASCHINENBAU GmbH
Priority date: 1983-08-30
Filing date: 1984-08-24
Publication date: 1985-04-03
Also published as: DE8324853U1; FR2550958A1; GB8421604D0

Abstract

In an annular trough mixer, mixing tools 4 extend downwardly into a stationary annular trough 1. Transducers 6, 6' located in the bottom or walls of the trough 1 measure the moisture content and/or temperature of the material being mixed. A centrally arranged revolving drive 2 for the mixing tools 4 also supports a rotary turbulence creating member 9 extending downwardly into the trough 1. The drive 2 and the associated components mix the material at optimum speed. The transducers 6, 6' are located on the trough 1 in the effective region of the turbulence creating member 9. The mixing tools 4 include a blade positioned within the trough 1 to sweep the surface of the trough containing the transducers 6, 6' so that the surface is not subject to build-up which would interfere with the measuring operation. <IMAGE>

Description

SPECIFICATION An annular trough mixer The present invention concerns an annular trough mixer.

A known annular trough mixer comprises a stationary trough in which rotate mixing tools, such as kneading rods, blades and the like, a dosing device for adding water, steam or heat to the material being mixed, and means for measuring the moisture content or the heat of the material being mixed and arranged for controlling the dosing device. The mixer has a special water spraying device to establish a specific moisture content for the material to be mixed. The water is added uniformly and quickly by adjustable nozzles located in the center of the mixing zone. Accordingly, during the addition of the water, the mixing tools are cleaned at the same time.

If, in addition to moisture, heat is also to be added to the material to be mixed, a vaporization device which injects saturated steam may be used.

To heat the material to be mixed without adding moisture at the same time, a heating device may be arranged on the outside surface of the annular trough.

For the correct control of the addition of water, steam or heat, the moisture content or temperature of the material to be mixed must be continuously measured. Accordingly the use is known of a plurality of transducers located in the bottom or side of the trough or as revolving rod transducers. Each transducer manufacturer sets forth a specific installation position for mounting his transducer, because such installation position presumably affords a maximum and error-free measurement of the actual moisture and temperature in the material to be mixed.

Though the transducers are installed correctly, experience has shown that a considerable period of time is needed until the added amount of moisture or heat is uniformly distributed in the material being mixed. As an example, in the manufacture of concrete, the addition of water must take place in several stages. Initially, the materials to be mixed, such as sand, coarse aggregate and cement are introduced into the annular trough and mixed in the dry state. During this so-called dry mixing time, the moisture of the individual materials is uniformly distributed so that at the end of the dry mixing period the amount of water required has been determined.

The addition of water is carried out in several stages. Initially, there is a so-called coarse dosing.

In the first dosing stage, a large quantity of water is added which, however, is still less than the actual required amount. Subsequently, the mixing operation is carried out until the material being mixed has a uniform moisture content. The moisture content is again measured and then the socalled fine dosing of water takes place. In this subsequent dosing operation, a small amount of water is introduced and subsequently mixed with the materials until the added water is uniformly distributed in the materials being mixed. Again the moisture content is measured and the addition of water is carried out until the desired moisture content is reached.

Such a procedure is relatively time-consuming and, as a consequence, involves higher operating costs. Therefore, the primary object of the present invention is to provide an annular trough mixer of the above type which affords a faster and more uniform distribution as well as a faster measurement of the moisture or heat content of the material being mixed.

The invention provides an annular trough mixer comprising a stationary annular trough disposed around a central axis, one or more mixing tools extending into the annular trough and being movable through the annular trough, a dosing device for the addition of water, or steam or heat to the material to be mixed, and means for measuring the moisture or heat content of the moisture and for controlling the dosing device, wherein a turbulence creating member is located within the annular trough and has an effective region within the trough, and the means for measuring is located in the annular trough adjacent to the effective region of the turbulence creating member.

The use of turbulence creating members which circulate through the trough with the usual mixing tools is known in annular trough mixers. Nevertheless, surprisingly, no such device with an automatic dosing arrangement for water, steam or heat and for simultaneously measuring the moisture content and temperature by means of one or more transducers is known which includes the use of a turbulence creating member for the fast and uniform distribution of moisture and/or heat in the material being mixed.

Preferably, the or each transducer is mounted in the bottom or side of the trough at a location where at least-one blade or the mixing tools keeps the surface within the trough free or clear of the buildup of materials. As a result, the transducer located at the cleared surface is always maintained in contact with the optimally mixed material.

An embodiment of the invention will now be described by way of example, reference being made to the accompanying drawing, which is a partial cross-sectional view of an annular trough mixer.

In the drawing an annular trough 1 is shown, formed of steel plate, and encircling a centrally located driving device 2 for rotating the mixing tools extending into the trough. The driving device 2, which moves the mixing tools through the trough, is actuated by an electric polyphase induction motor, not shown. The centrally arranged driving device 2 supports a series of arms 3, shown only in part, with blade-like mixing tools 4 secured to the lower ends of the arms. The mixing tools 4 which contact the material to be mixed in the annular trough 1 may be selected as to shape and material for the various materials being mixed and their different abrasive properties. The radial angles and the height of the mixing tools are adjustable.

At the upper edge of the side wall of the trough 1, a water spraying device 5 is positioned for intro ducing water into the material to be mixed during the mixing operation. In place of a water spraying device, a steam injection device may be used. Further, heaters or heating means may be provided in the bottom or walls of the mixing trough 1. The top of the trough 1 is closed by a cover 10.

For measuring the moisture content of the materials being mixed, a moisture content transducer 6 or hygrometer is positioned in the bottom of the annular trough. The transducer 6 determines the moisture content, or in the case of a temperature transducer it determines the temperature, of that part of the material being mixed with which it makes contact. Since the entire annular trough 1 is filled with the material to be mixed, however, an adequately long and intensive mixing period is needed for the material being mixed so that the moisture and heat are uniformly distributed throughout the material before the measurement is taken. In the present state of the art, the addition of the required moisture or heat takes place in a number of steps or stages, and after each step a long mixing time must be provided.

In the present invention, however, the known mixing process is accelerated by means of a turbulence creating device. Such a turbulence creating device is formed by a supporting arm 7 mounted on and extending outwardly from the driving device 2 on which the mixing tools 4 are mounted.

The supporting arm 7 mounts a driving motor 8 preferably a hydrostatic motor for a turbulence creating member 9. Below the supporting arm 7, the shaft of the driving motor 8 is attached to the turbulence creating member 9. The turbulence creating member 9 is in the form of rods. The use of a hydrostatic motor 8 permits a continuous adjustment of the speed of the turbulence creating device at a constant torque.

Due to the high speed at which moisture and/or heat is introduced into the material being mixed, the transducer 6, in practice, always displays the average value of moisture or temperature so that the addition of water, steam or heat can be effected in one step up to the desired value. As a result, the entire mixing time is further reduced than is the case for the use of the turbulence creating device alone.

To maintain the active measuring surface of the transducer so that the contact with the material being mixed is maintained at an optimum, preferably at least one of the mixing tools 4 is in the form of a blade which mixes the materials in the region of the transducer 6. Further, the transducer 6 is located on the trough in the region of the turbulence creating device 9.

In closing, it should be noted that the transducers 6 may be not only a bottom electrode but also, in a corresponding adaptation of the mixing tools, it may be a wall electrode 6' or a revolving rod electrode. The arrangement of the transducer as a bottom electrode 6 affords the optimum results at a minimum expenditure.

Claims

1. An annular trough mixer comprising a stationary annular trough disposed around a central axis, one or more mixing tools extending into the annular trough and being movable through the annular trough, a dosing device for the addition of water, or steam or heat to the material to be mixed, and means for measuring the moisture or heat content of the mixture and for controlling the dosing device, wherein a turbulence creating member is located within the annular trough and has an effective region within the trough, and the means for measuring is located in the annular trough adjacent to the effective region of the turbulence creating member.

2. An annular trough mixer as claimed in Claim 1 wherein the means for measuring is a transducer mounted in the bottom or side of the trough.

3. An annular trough mixer as claimed in Claim 2, wherein the or one of the mixing tools includes a blade positioned within the trough and adjacent to the surface of the trough where the transducer is located for maintaining that surface clean.

4. An annular trough mixer as claimed in any preceding claim wherein the dosing device comprises a spraying device located above the side of the trough for spraying downwardly into the trough.

5. An annular trough mixer as claimed in any preceding claim including a central driving device positioned along the central axis of the annular trough for supporting the or each mixing tool and the turbulence creating member for rotating the or each mixing tool and the turbulence creating member through the annular trough.

6. A annular trough mixer as claimed in Claim 5, wherein a support member is mounted on the driving device and extends over the annular trough, a driving motor is mounted on the supporting member, and the turbulence creating member extends downwardly from and is driven by the driving member.

7. An annular trough mixer substantially as herein described with reference to and as shown in the accompanying drawing.