Measuring and testing – Specimen stress or strain – or testing by stress or strain... – By loading of specimen
Reexamination Certificate
1999-07-11
2001-03-27
Noori, Max (Department: 2855)
Measuring and testing
Specimen stress or strain, or testing by stress or strain...
By loading of specimen
C073S813000, C073S818000
Reexamination Certificate
active
06205864
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a gyratory shear press for compacting samples of compaction materials.
It concerns more especially a press intended for studies of formulation of granular mixtures, for the development of new formulae and for research concerning the process of compacting materials used for road surfacings, in order to determine the behaviour of bituminous mixtures with respect to compaction and that of materials other than those treated with bituminous binding agents.
BACKGROUND OF THE INVENTION
In this type of press, compaction of the material is obtained by kneading, under low static compression, a sample of material contained in a cylindrical mould limited by parallel ends and maintained at constant temperature, to within standardized temperature tolerances.
Kneading by shearing action is provoked by the movement of the axis of the mould which generates a conical surface of revolution with vertex angle 2&agr; while the ends remain at all times perpendicular to the axis of the conical surface.
The resultant axial force F applied to the ends of the sample, the temperature of the mould and the angle &agr;, are maintained constant for the whole duration of the test. The cross-section and mass of the sample do not vary during the test, but the height reduces continually.
For each sample, the height and the shearing force are measured and memorized as a function of the number of gyrations.
U.S. Pat. No. 5,275,056 and WO 95/22751 disclose gyratory shear presses in which the mould comprises a peripheral ring extending outwardly and maintained between rollers disposed at different levels and driven in rotation about a vertical axis and which ensure tilting of the mould. In these two documents, the means for compressing the material of the sample are arranged above the mould and the latter rests on a fixed table. These arrangements bring about difficulties for replacing a mould containing one sample by a second mould containing another sample, and for making checks on several samples with different parameters, as it is difficult and long to check and change the angle a.
U.S. Pat. No. 5,323,655 discloses a gyratory shear press in which the compression means are likewise arranged above the mould, the latter resting on a rotating table mounted out-of-center on a rotating plate. Here, it is necessary to ensure a relative movement between the lower end of the mould and the rotating table. This is effected by a ceramic disc interposed between the lower end and the rotating table.
In all these documents, the means for compressing the sample contained in the mould are arranged in the upper part of the apparatus, which increases the volume and consequently the mass of the apparatus, and brings about difficulties in positioning the mould before the test and for removing the sample after compaction.
It is an object of the present invention to propose a gyratory shear press which overcomes these drawbacks.
SUMMARY OF THE INVENTION
To that end, the invention relates to a gyratory shear press for compacting samples of compaction materials, comprising:
a chassis
a cylindrical mould of axis X adapted to receive a sample interposed between an upper end and a lower end, maintained parallel to each other;
means for compressing the sample, borne by said chassis and adapted to apply a constant effort on one of said ends along an axis Y perpendicular to said ends;
means for inclining axis X of the mould with respect to axis Y;
gyration means adapted to impart a gyratory movement of axis X about axis Y;
means for controlling the compression means and the gyration means; and
means for measuring the heights of the sample between the ends and the shearing efforts of the sample as a function of the number of gyrations of axis X.
The invention attains its object in that:
a) the chassis comprises in its upper part a casing whose rigidity is constant over 360° and which presents, in its upper wall, an opening adapted to be closed by a lid intended to serve as bearing for the upper end, and, in its lower wall, an orifice for the passage of a mobile element of the compression means, which is in abutment on the lower end;
b) the gyration means comprise an outer cylindrical sleeve of axis Y mounted to rotate in the casing via bearings, an inner cylindrical sleeve of axis X mounted to rotate about a counter-mould of axis X intended to receive the mould, via bearings, and means for driving the outer cylindrical sleeve in rotation, said drive means being borne by the casing; the inner cylindrical sleeve being disposed inside the outer cylindrical sleeve and being mounted to oscillate thereon so as to be able to pivot about an axis Z perpendicular to axes X and Y and lying substantially in the plane of the upper end;
c) the means for inclining axis X of the mould with respect to axis Y comprise an angle-adjusting system interposed between the outer cylindrical sleeve and the inner cylindrical sleeve and lying in the median plane perpendicular to axis Z.
The following advantageous arrangements are furthermore adopted:
The lower part of the chassis comprises a lower plate, an upper plate on which the casing is fixed, and a plurality of columns parallel to axis Y and connecting the lower plate to the upper plate, the lower plate supporting the compression means.
The compression means comprise an endless screw driven by second drive means and a sheath driven in translation along axis Y by the endless screw, and whose head is in abutment on the lower end, said sheath being guided along axis Y by rollers cooperating with the columns and traversing an opening made in the upper plate with interposition of a bearing bush. A plate with a low coefficient of friction is interposed between the head of the sheath and the lower end. The second drive means comprise an electric servomotor with reduction gear and a displacement encoder.
The angle-adjusting system is provided with a vernier and a door is arranged in the peripheral wall of the casing in order to access the vernier. The means for measuring the shearing efforts comprise a shear sensor placed inside the angle-adjusting system. Electrical supply of the shear sensor and transmission of the data picked up by the sensor are ensured by a rotating collector.
The casing comprises an inductive detector for counting the number of revolutions of the outer cylindrical sleeve.
The press according to the invention advantageously further comprises a mould-handling system, comprising a bracket disposed above the upper wall of the casing and a winch disposed above the lid and supported by the bracket.
REFERENCES:
patent: 5275056 (1994-01-01), Hamilton et al.
patent: 5323655 (1994-06-01), Eagan et al.
patent: 5456118 (1995-10-01), Hines et al.
patent: 5606133 (1997-02-01), Hines et al.
patent: 5817946 (1998-10-01), Brovold
patent: 5824913 (1998-10-01), Pyle
patent: 5939642 (1999-08-01), King et al.
patent: 6026692 (2000-02-01), Brovold
patent: 911155 (1962-11-01), None
Gallier Sylvain
Gaschet Jacky
Moutier Francis
Vialletel Hugues
Laboratoire Central des Ponts et Chayssees
Noori Max
Wolf Greenfield & Sacks P.C.
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