Abstract:
This invention relates to a gyratory shear press of which the compression means are disposed in the lower part of the chassis and of which the gyration means are provided in the upper part of the chassis which is in the form of a casing. The mould is introduced in the casing via an opening provided in the upper wall of the casing and adapted to be closed by a lid. The gyration means comprise two concentric sleeves separated from the casing and the mould by bearings. The inner sleeve is mounted to oscillate in the outer sleeve and is inclined by means of a vernier.

Description:
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 2α 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 α, 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. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be more readily understood on reading the following description given by way of example and with reference to the accompanying drawings, in which: 
     FIG. 1 is a general view in perspective of the gyratory shear press according to the invention. 
     FIG. 2 is an enlarged view of the same machine without the cowling, the switch cabinet, the mould-handling system and the control table. 
     FIG. 3 is a cross-section through the machine along a median vertical plane. 
     FIG. 4 is a cross-section through the upper part of the machine along a median vertical plane represented by line IV—IV of FIG.  5 . 
     FIG. 5 is a cross-section through the upper part of the machine along a vertical plane represented by line V—V of FIG.  4 . 
     FIG. 6 schematically shows the movement of gyration applied to the sample of material. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENT 
     Referring now to the accompanying drawings, the Figures show a gyratory shear press  1  which comprises a chassis  2  whose lower part  3  comprises a lower plate  4  and an upper plate  5  connected by three columns  6  and protected by a cowling  8  and whose upper part  7  is in the form of a hollow rigid casing having a cylindrical peripheral wall  9  of revolution about a vertical axis Y, an upper wall  10  comprising an opening  11  concentric to axis Y and a lower wall  12  fixed on the upper plate  5  and presenting a passage  13  of axis Y. The upper part  7  further comprises a sleeve  14  of axis Y which extends under the upper wall  10  opposite passage  13 . The rigidity of casing  7  is constant over 360°. 
     The opening  11  may be obturated by a lid  15  which serves as bearing for the upper face of an end  16  disposed in the top part of a cylindrical mould  17  of axis X mounted to slide in a cylindrical counter-mould  18 . In the bottom part of the mould  17  there is provided a lower end  19  which may slide in the mould  17 . The space in the mould  17  defined by the upper end  16  and the lower end  19  is filled with a sample  20  of a compaction material, subjected, on the one hand, to an effort or compression F exerted on the lower end  19  in the vertical direction Y, and, on the other hand, to a gyratory movement of axis X about axis Y. 
     The effort of compression F is exerted by the head  21  of a sheath  22  of axis Y which passes through an opening  23  of axis Y made in the upper plate  5 , with the interposition of a bush  24 . A plate  25  made of material with a low coefficient of friction is interposed between the head  21  and the lower face of the lower end  19 . The sheath  22  is driven in vertical translation in the direction of axis Y by an endless screw  26  mounted on the lower plate  4  and disposed inside the sheath  22 , the latter presenting in its lower part an inner thread  27  cooperating with the outer thread of the endless screw. The sheath  22  is, in addition, guided during its vertical translation by rollers  28  which roll on the outer wall of the columns  6 . 
     The endless screw  26  is driven in rotation, by means of pulleys  29 ,  30  and a belt  31 , by a constant-moment servomotor  32  driving a reduction gear  33  on which the pulley  30  is mounted. 
     The servomotor  32  is equipped with an angle encoder  34  of which the measurement is representative of the height of the sample  20  contained in the mould  17 , between the lower end  19  and the upper end  16 . The servomotor  32 /reduction gear  33  assembly is disposed above the lower plate  4 , while the pulleys  29 ,  30  and the belt  31  are disposed beneath the lower plate  4 , the latter comprising a plurality of stands  35 , adjustable in height. 
     The device for gyrating the mould  17  comprises an outer cylindrical sleeve  40  of axis Y mounted to rotate inside the casing  7  by means of a first bearing  41  borne by the sleeve  14  and a second bearing  42  mounted on the periphery of the passage  13  of the lower wall  12 , and an inner cylindrical sleeve  43  which is disposed inside the outer sleeve  41  and mounted thereon so as to be able to oscillate about a horizontal axis Z lying substantially in the plane of the lower face of the upper end  16 , as shown in FIG.  5 . 
     Two bearings  44  and  45  are interposed between the inner cylindrical sleeve  43  and the counter-mould  18 , in order to allow rotation of these two parts with respect to each other, while preventing their relative displacement in the direction of axis X of the mould  17 . 
     A device  50  for adjusting the angle α between the axis X of the mould  17  and the vertical axis Y, is provided in the median vertical plane perpendicular to axis Z. This device  50  is borne by the outer sleeve  40  and cooperates with a screw/nut system  51  fast with the inner sleeve. It comprises a vernier  52  and an effort sensor of which electrical supply and data transmission are ensured by a rotating collector  53 . 
     In order to allow access to the vernier  52  and adjustment of angle α, the peripheral wall  9  of the casing  7  is provided with a door  54  for access. 
     The outer peripheral sleeve  40  is driven in rotation by an electric motor  55   a  driving a synchronous belt  55 . 
     The casing  7  is, in addition, equipped with an inductive detector  56  serving to count the number of revolutions of the outer cylindrical sleeve  40 . 
     The vernier  52  allows a setting of the angle α at 0°, which makes it possible to produce test pieces with parallel faces perpendicular to axis X, to effect controls of the apparatus, and a setting of the same angle α from 30′ to 2° per step of one minute in a very short time, and without control means. 
     On the rear of the lower part  3  of the frame  2 , there is provided a switch cabinet  57  which ensures electrical supply of the drive motors  32  and  55   a  and of the different measuring instruments. 
     To the right of the frame  2  there is fixed, by screws, a panel  60  which comprises the on-off switches  61  of the machine and which supports a microocomputer  62  controlling the machine. There are connected to the microcomputer  62  a keyboard  63  for introducing the characteristics of the materials to be monitored, a screen  64  for displaying the results of each sample and possibly other accessories, such as mouse, data-storage device, etc. . . . The microcomputer  62  is connected to the angle encoder  34  which furnishes the measurement of the height of the sample to the inductive detector  56  and to the effort sensor placed inside the device for adjusting the angle α, in order to allow storage of the data during gyration of the mould  17  and possibly processing thereof. 
     To the left of the casing  7  there may be fixed a bracket  70  which supports an electric winch  71  above the lid  15  for handling the mould  17 . 
     The gyratory shear press described hereinabove operates as follows: 
     A sample  20  of material is disposed in the mould  17  between the two ends  16  and  19 . 
     The mould  17  filled with material is placed in the counter-mould  18  via the upper opening  11 , the head  21  of the sheath  22  in that case being in lower position, i.e. slightly above the upper plate  5 . The lid  15  is then fixed in the opening  11  by screwing. At the beginning of the series of tests, the demi-vertex angle α of the cone of gyration is displaced by means of the vernier  52 . The constant-moment servomotor  32  is switched on, which brings about an increasing vertical effort on the lower end  19  which places the sample  20  in a state of initial compression. When the force of compression attains value F, the motor  55   a  attains its nominal test speed, and therefore generates rotation of axis X of the mould about axis Y, axis X describing a conical surface of which the vertex 0 lies in the middle of the lower face of the upper end  16 . Such gyration provokes shear-kneading of the sample  20 . During gyration of the mould  17 , the upper end  16  and the lower end  19  remain parallel to each other and perpendicular to the vertical axis Y. For the whole duration of the test, the resultant axial force F applied to the ends of the sample  20  and the angle a are maintained constant within standard tolerances.