Agitating – Mortar mixer type – Gravity type
Patent
1987-09-11
1989-05-23
Hornsby, Harvey C.
Agitating
Mortar mixer type
Gravity type
366 2, 366 34, 366 37, 366 40, 366337, B01F 314, B01F 524
Patent
active
048324973
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method and an apparatus for mixing gravel materials with liquid bitumen, for example in the form of an emulsion, for the purpose of using the mixed mass in road coatings or the like, the bitumen acting as a binding agent for the gravel material. The gravel material consists of particles of varying size, and the smallest particles tend to absorb a major part of the bitumen, leaving the larger particles insufficiently coated. Therefore a very thorough mixing is needed to obtain masses of sufficient quality.
Such masses are usually mixed in oil gravel works, socalled cold mixing works, with rotating mixing means mounted on horizontally extending shafts in a mixing trough. Owing to the capacities required from a such work its size and weight is considerable so that it is rather immobile. Also, high investment and production costs are involved resulting in an expensive mixture. As an example of such prior art Swedish patent No. 377 820 may be mentioned.
The object of the present invention is to provide a more simple, cheap and effective mixing system than those conventionally used, and this is achieved through a method and an apparatus as defined in the appending patent claims.
Admittedly, Swedish patent No. 427 328 discloses a method and an apparatus for continuous mixing a liquid into a pulverous material, in which the liquid is sprayed onto the pulverous materiale when the latter, in the form of a hollow cylindrical flow, is falling freely from a cone spreader, the liquid being ejected from nozzles located below the spreader. A such technique could also be contemplated for mixing bitumen emulsion into gravel, but this would not result in a sufficient mixing of the materials. An effective and sufficient mixing of the bitumen and gravel materials is obtained, however, by employing the novel features according to the present invention, i.e. initial separation of the gravel material into a coarse and a fine particle flow, and, after separately spraying bitumen emulsion onto the two gravel flows, final reunification and intermixing of the gravel flows by means of oppositely inclined baffles. In addition to securing an effective penetration and intermixing of the bitumen in the gravel materials the invention makes it possible to vary the amount of bitumen added to the coarse and fine particle flows respectively. Since the coarse particles generally requires considerably less bitumen than the fine particles, the above variation possibility may result in considerable savings in the consumption of bitumen which by far is the most expensive component of the mixture.
The invention is described more fully below with reference to the drawing in which:
FIG. 1 is a schematic side view of a preferred embodiment of an apparatus according to the invention, with side cover removed, and
FIG. 2 is a front view of the apparatus, i.e. seen in the direction of the arrow II in FIG. 1, with some parts removed.
On the drawing the apparatus according to the invention is generally denoted by numeral 2. It consists of a plate housing or frame 4 of substantially rectangular crossection pivotably suspended at its upper end directly below the outlet end of a belt conveyor 6, for example by means of an upper through going shaft or bolt 8 and a lower threaded adjustment bolt 10 which is connected to the belt conveyor support (not shown).
In frame 4 there are mounted a number of components which will be described below in connection with the operation of the apparatus.
The gravel material to be mixed with bitumen is metered from a calibrated feed station (not shown) onto the belt conveyor 6. From the outlet end of the belt conveyor the material falls down onto a grading device in the form of an inclined screen 12 adapted to separate coarser gravel particles from finer ones. The screen 12 may for example be adapted to let through fine gravel particles "g" smaller than 8 mm while coarse gravel particles "G" larger than 8 mm slide along the upper side of the inclined screen and continue as a free fall flow separ
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patent: 1056590 (1913-03-01), Sayers
patent: 1109725 (1914-09-01), Whitney
patent: 2064807 (1936-12-01), Barber
patent: 3129779 (1964-04-01), Clements
patent: 4096588 (1978-06-01), Mendenhall
patent: 4322288 (1982-03-01), Schmidt
patent: 4387996 (1983-06-01), Mendenhall
Haugland Scott J.
Hornsby Harvey C.
Nodest Vei A/S
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