Road structure – process – or apparatus – Apparatus – Material distribution means
Patent
1989-02-08
1991-04-23
Britts, Ramon S.
Road structure, process, or apparatus
Apparatus
Material distribution means
404 84, E01C 1918
Patent
active
050095463
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION OF THE STATE OF THE ART
A machine used for laying down layers of materials for paving roads, airports, etc. is commonly called a "road-paver-finisher".
The materials to be laid down (generally mineral aggregates mixed with asphalt, bitumen, cement or other binders to form conglomerates, stabilized soils or the like) must be finished off to form a quite levelled and compacted layer.
To attain the latter object, the "paver-finisher" is usually provided with vibrating or beating ("tamping") members and therefore is often referred as "vibro-finisher" or "vibro-paver".
The function of levelling, compacting, densifying and smoothing the materials to form a layer ("carpet") is of utmost importance. A levelling-tamping member of the paver, called a "screed" performs this function.
Depending on the principle by which the screed provides for minimizing the waves on the finished carpet, the pavers can be divided in two classes, namely pavers with a "semi-floating" screed and pavers with a "full-floating"screed.
The pavers with a semi-floating screed are used in small and medium sized jobs and are therefore highly diffused.
Pavers with a full-floating screed are used on large jobs or in connection with so called "slip-form-paving".
The following description of the invention is referred to pavers with a semi-floating screed, but can as well be adopted on pavers with full-floating screeds.
A paver of the more common type, that is a semi-floating screed paver is formed by the combination of two basic units:
Following the semi-floating principle, the screed is a more or less complicated transverse member that is pulled by two long arms that are pivotally mounted on the tractor unit.
The transverse member itself engages with the material to be laid, "smearing" it on the old road surface, compacting and smoothing it to form an even carpet without waves.
The "tractor unit" is the main body of the paver and comprises many members that are not directly connected with the tractor-unit's main function, that is that of imparting the forward motion to the whole machine and to pull or tow the screed.
Other important functions performed by members belonging to the tractor unit are: order to feed it in the most suitable way to the screed for best levelling and compacting action.
The paver-finishers of known type are described in some of the accompanying drawings, wherein:
FIG. 1 shows a bird's eye view of a typical semi-floating-screed paver having the tractor unit mounted on rubber tired wheels,
FIG. 1a shows a bird's eye view of a typical semi-floating-screed paver having the tractor unit mounted on crawlers,
FIG. 2 shows a side view of the wheel mounted paver of FIG. 1,
FIG. 3 shows the paver of FIG. 2 with detached screed:
The two towing arms of the screed have been disconnected from their mounting on the tractor unit and the whole screed unit has been displaced rearwards to show freely the complete tractor unit.
A "State of the Art" paver-finisher in FIGS. 1, 2 and 3 comprises a tractor unit (10) and a screed (11).
The tractor unit (10) comprises a main frame (12) a hopper (13) for receiving the material mix from rear dump trucks, one or more conveyors (14) and augers (15) providing the adequate flow of material mix towards the screed (11).
The main frame (12) of the tractor unit (10) is provided with traction wheels (12') and with steering wheels (12") (or with crawler tracks (12"') for the purpose of self-propelling the whole machine.
The screed (11) is provided with towing arms (16) that are pivotally mounted at their front end (17) to the main frame (12) of the tractor unit (10).
The geometrical position of the mounting point (18) of the screed arm front end (17) on the tractor unit's main frame (12) is of utmost importance for achieving the best possible levelling action of the screed (11).
In fact, the wheels (12') and (12") of the tractor unit (10) during the forward motion of the paver, are bound to follow the waves of the ground, imparting thus to the whole tractor unit (10) swinging motions that should not
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patent: 4821824 (1989-04-01), Gilbert
patent: 4836564 (1989-06-01), Heims
Domenighetti Domenico
Layton Jack
Britts Ramon S.
Spahn Gay Ann
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