TECHNICAL FIELD

The present invention relates to a device for a common feed out of from separate containers in a desire mixing ratio, the outlets of the containers being placed abo separate sections of an essentially horizontal conveying screw.

BACKGROUND ART

It has already been suggested, that different bulk material be mixed by means of a conveying screw, which rotates in a s tionary drum, which encloses the conveying screw. DE-B-1 20 788 and FR-A-2 171 055 relate to examples of this techniqu The value of this technique is however limited, since it i either necessary to choose small inlet holes in order to pr vent a clogging of the thread path already by the material which is fed through the inlet hole for the first bulk mate al, a small transport capacity in this way being obtained, or to make the inlet holes larger, said risk of clogging in this case being experienced already from the beginning, no merely a small amount of material being fed through the nex inlet hole, i.e. the desired mixing not taking place or be¬ ing reduced to a great extent. In order to counteract these effects said inlet holes for the different bulk materials have been placed close to each other in the initial end of the conveyor screw, more precisely at a distance of just 1-2 thread turns. Such a construction will of course have a ver minor capacity. It is true that this capacity to some exten can be increased by increasing the rotation speed of the co veying screw, but this of course is also not a satisfactory technical solution.

The above-mentioned problems can be eliminated to some exten by using a so called para screw instead of a normal conveyin screw, i.e. a screw having increasingly deep thread paths in the transportation direction of the screw. NO-C-83 991 shows

an example of this technique. However, the value of the par screw is limited, since it can not be made very long with a maintained reasonable thickness. Thus, it is useful only in smaller units, e.g. for the use described in NO-C-83 991, namely mobile concrete mixers.

BRIEF DISCLOSURE OF THE INVENTION

The object of the present invention is to suggest an improv device of the type set forth in the preamble of the patent claim, which does not have the drawbacks, which devices know in the art have. A particular object is to suggest a device which can feed out and homogenize the bulk materials from s parate containers in a certain mixing ratio with a high acc racy and simultaneously provide a comparatively high feedin capacity. An additional object is to, in an efficient way, able to vary the mixing ratio without also lowering the fee ding capacity.

These and other objects can be attained by a device having the characterizing features set forth in the following pate claims. Additional characterizing features and aspects of t invention are set forth in the following specification, whi relates to two preferred embodiments.

BRIEF DESCRIPTION OF DRAWINGS

In the following description of two preferred embodiments r ference will be made to the accompanying drawings, in which Fig. 1 is a perspective view showing the basic principle of the invention;

Fig. 2 is a sectional side view of the discharge device as well as the containers according to a first embodiment; and Fig. 3 shows in a side view a second embodiment of the dis- charge device.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring firstly to Figs. 1 and 2 a first container is des nated 1 and a second container designated 2. Containers 1 a

2 respectively contain a first bulk material 3 and a seco bulk material 4 respectively, the latter to be mixed with first bulk material in a certain desired mixing proportio Between containers 1 and 2 there is a partition 5.

n Along the bottom of the containers a so called feeder tub extends, common to the two containers, i.e. a bulk mass t port device of the type shown in document SE-C-404 684. F der tube 6 comprises, according to the pricinples known th i.a. this patent specification, a cylindrical drum 7, de¬ signed to rotate about its axis 8, and inside drum 7 a co veying screw 9, coaxially disposed in relation to the dru and its direction of rotation being opposite to the direc tion of rotation of drum 7. Drum 7 is rotated by means of motor 10 and screw 9 is rotated by means of a motor 11, F 2. Feeder tube 6 is, as has been mentioned, disposed in t bottom of containers 1 and 2 and surrounded by bulk mater

3 and 4 respectively along that entire length of the feede tube, which extends through containers 1 and 2, i.e. the d inside those areas where the drum is surrounded by bulk m terials 1 and 2, is exposed to outlets 12 and 13 respecti for bulk materials of the containers. Within these areas, include the main part of the total length of feeder tube 6 drum 7 is provided with a plurality of inlet openings 14 the shape of axial slits, which according to this embodime is evenly distributed on the surface of drum 7, in its axi as well as in its periphery direction. In the outlet end o let holes 15 are placed above a belt conveyor 16. Inspecti holes in the bottom of containers 1,2 are designated.17.

When drum 7 and conveying screw 9 are rotated in opposite rections,bulk materials 3 and 4 fall, into drum 7 through slits 14 along the entire length L. Drum 7 and screw 9 are rotated with such a speed, that the material which is fed to drum 7 will not fill.-.; it to a greater extent than to a tain part of its cross-section. Consequently, the particle in bulk materials 3 and 4 are not stopped by materials, wh have already been fed into drum 7, but are able to fall th

slits 14 with the same ease regardless where they are loca ted along length L of the drum. Thus, in accordance with t known working principle of feeder tube 6, the bulk materia is allowed to be fed into the drum completely uniformly at different locations along length Ll of first container 1 a along length L2 of second container 2 respectively. Howeve the loading speed of the two bulk materials 3 and 4 can be different, depending on the different properties and parti sizes of materials 3 and 4. Thus, in order to obtain the d sired mixing ratio in material 18, which is fed onto belt veyor 16, partition 5 preferably is disposed in such a way that it can be located in different positions along length i.e. for an adjustment of the ratio L-./L-. Through a varia tion of the ratio L ₁ /L_ the mixing ratio.in the discharged material 18 is adjusted.

Fig. 3 shows another particular embodiment of the inventio Those parts of the construction, which are unchanged as co pared to the above described embodiment, have the same ref rence numerals as in Figs. 1 and 2. Thus, information abou these parts is found in the description supra. Thus, e.g. partition 5 preferably can be placed in different positio which, according to this embodiment, can be used to roughl adjust the mixing ratio in the discharged bulk material 18 The novel feature of this embodiment is that the drum has subdivided into two sections 7A and 7B. The two sections 7 and 7B can be rotated independently of each other but are nected to each other through a race bearing 20. Race bear 20 is according to Fig. 3 placed below partition 5 but do not have to be placed in the area of wall 5, which prefer can be placed in different locations along the assembledd 7A/7B. First drum section 7A is driven by means of a moto and second drum section 7B by means of a motor 10. Convey screw 9 s common to the two drum sections 7A and 7B and tends through the two sections. It is driven by motor 11.

By means of motors 21 and 10 drum sections 7A and 7B resp tively can be rotated with different and varying rotation

speeds, and in this way the loading speed of bulk materials 3 and 4 to the assembled drum 7A/7B can be adjusted. This can be utilized to fineadjust the mixing ratio, but it can also be used as the only adjustment instrument, in case par tition 5 is fixedly disposed between containers 1 and 2. Th possibility of influencing the mixing ratio through a varia tion of the absolute and/or relative rotation speeds of dru sections 7A and 7B is of course particularly advantageous, since this adjustment can be done, when containers 1 and 2 already have been filled with bulk materials 3 and 4 respec tively, whereas it is very difficult or impossible to move partition 5 in this situation.

In the described embodiment holes/slits 14 are evenly distr buted on the surface of the drum. However, this does not al ways have to be the case. It is possible to arrange the hol non-uniformly, e.g. use more holes per surface unit in one section of the drum in order to increase the feeding into t section. The drum can also be disposed in such a way, known per se, that it is laterally movable, the drum digging its path through the bulk material. Also, it is possible to use more than two containers and below or in the bottom of thes containers dispose a common feeder tube, in the way describ supra. Thus, the present invention is not limited to the de ribed embodiments, which merely serve as two illustrated em bodiments within the scope of protection of the inventive idea.