ES2339315A1 - System for measurement "in situ" of the resistance to the cutting and the force of friction in soils (Machine-translation by Google Translate, not legally binding) - Google Patents

Abstract

System for the measurement "in situ" of the resistance to the cut and the force of friction in floors. The system defines a team that allows to know the resistance that the floor offers when it is cut, as well as the friction force per unit of surface that exerts the ground on blades (4) and (5) mounted on a frame (1), cutting each blade (4) at a different depth, allowing simultaneous measurement of the cutting force at different depth levels. The cutting blades (4) and friction (5), located behind them, are mounted by an articulated quadrilateral system formed by pairs of vertical bars (9) located on both sides of the blades (4) and (5) ), so that in combination with a load cell associated with each blade (4 or 5), it is possible to separately know the shear strength and friction force of the soil. (Machine-translation by Google Translate, not legally binding)

Description

System for the measurement " in situ " of the resistance to the cut and the force of friction in floors.

Object of the invention

The present invention, as expressed in the statement of this specification, refers to a system of measurement " in situ " of the shear strength and friction force in the floors, intended to operate at different levels of depth by very thin blades, and allow to know the resistance that the soil offers when it is cut, as well as the frictional force per unit of surface that the soil exerts on metal materials.

The system falls within the sector of the measurement instrumentation and soil testing, especially for use agricultural, forestry or livestock, and can also be used in soils for the construction of buildings and works public, and even in the field of agricultural machinery and public works, since it allows to contribute information to improve the designs of machines that work the ground.

Background of the invention

The current farming techniques of precision allow the handling of work floors with greater knowledge of their needs and the consequences of operations carried out. But for this it is necessary to have detailed information for the characterization of the plots of cultivation and to be able to detect in them the areas with more or less need for tillage One of the indicators that best reflect the soil tillage needs is its compaction state, the which has been estimated so far by its resistance to penetration, measured with standard tapered tip penetrometers according to ASABE S313.3. This system requires too much time and effort when the plots to study are large, since the show them are made in discrete points of the plot, therefore they are being replaced by cut resistance meters, that allow the use of self-propelled vehicles and the obtaining georeferenced data in continuous, during Displacement of the measuring device.

Glancey et al. (1989) instrumented a chisel to continuously measure the mechanical resistance of the soil at different depths. To do this, they introduced six load cells mounted directly behind the cutting blade and another six in the back of the chisel at the same depth as the first. In addition, a sensor was installed to measure the vertical forces acting on the chisel.

Adamchuk et al (2001) designed a smooth vertical blade on which they placed a series of load cells at different depths at the back of the blade. A variation of this model was that of Andrade et al. (2001) who designed a sensor that measured the shear resistance of the soil consisting of eight cutting blades that were supported by independent load cells. The sensor measured the resistance along the soil profile to a depth of 60 cm in increments of 7.5 cm.

Sirjacobs et al . (2002) developed and calibrated a sensor inspired by the principle used when tillage implements are instrumented to determine the required traction. It was constituted by a thin blade 27 cm long, 4.5 wide and an angle of 10º from the vertical, which moves horizontally across the ground at constant speed and depth and on which the soil thrust generates horizontal and vertical forces . The arm that supports the blade is attached to the sensitive area which is an octagonal dynamometer, fixed off the ground, just before the tractor. The load cells measure the forces on the blade that produces a 30 cm thick layer of soil and the moment generated at the upper end of the arm that supports it.

Mouazen et al . (2003) were based on a system similar to the previous one to measure in real time the shooting force, 15 cm from the ground surface, with a subsoiler that acted as a compaction sensor. It was composed of a 0.06 m wide chisel and a 0.03 wide blade and an octagonal strain gauge cell. Previously they determined that the angles of 15º for the chisel and 75º for the blade were those that provided the best shot values (Mouazen et al ., 1999) for the application of the theoretical model of finite elements with which to relate the shot (variable dependent) with soil moisture and density and depth of measurements and thus obtain soil compaction maps.

Christenson et al . (2004) designed a sensor composed of cutting edges shaped like triangular prisms of 45º. The prisms transfer the forces of the soil stratum, corresponding to its length, to three discrete points of the blade that supports them. At each of these points a load cell is located that measures the mechanical resistance, so that the second order polynomial equation that represents its variation for the complete soil profile can be obtained. The prisms or cutting edges are designed so that their thickness decreases with depth (to increase the sensitivity in the surface layers, with less mechanical resistance) and is greater than that of the blade (to reduce the effects of soil friction on it ).

Chung et al . (2004) designed a sensor similar to the previous one but replaced the sharp edges with prismatic tips. The system of measurement of horizontal resistance to soil penetration was based on a main blade on which five prismatic tips are placed at different depths. The blade 86 cm long, 18 cm wide and 1.91 cm thick, has a stainless steel sheet cover 0.63 cm thick. Upon entering the ground and advancing the pressure of the latter on the surface of the tips is transmitted through a rod to the corresponding load cell located inside the blade body. The blade is mounted on a structure that in turn hooks on the tractor's tripuntal. Sensor design parameters such as the optimal distance between the tips (10 cm) and the length of the stems (5.1 cm) to the blade edge were optimized, for different speeds and working depths (Chung et al ., 2003).

Sun et al . (2005) designed a continuous measurement sensor of resistance to cutting through a penetration cone that also incorporated a humidity sensor. It operated at a maximum depth of 20 cm. It consists of a horizontal penetrometer that measures the mechanical resistance as the sensor advances introduced into the ground. It has a stem, which joins the penetration cone 20 mm in diameter, with the blade that is 40 cm long and 5 cm wide. Its design ensures that the measurements will be independent of the depth and protects the rest of the elements from the impact of the stones. In turn, the blade is attached to a force lever that is the one that acts on the load cell that is in its upper part, without being introduced into the ground.

This same year, Chukwu and Bowers (2005) designed a sensor that measured at three depths simultaneously. Has three prismatic tips with an angle of 30º that are in contact directly with the ground and that are attached to the load cells by a rod, these elements being inside a housing in wedge shape 30º. The tips are located at a distance of 10.2 cm between them. They used a silicone material to fill the gap that remained inside the housing and prevent the soil particles could enter this area and affect the cell readings.

Hall and Raper (2005) optimize the design of a horizontal penetration resistance sensor, whose main feature is that once introduced on the ground the sensor can be moved up and down allowing Quickly detect the depth of possible work soles. He sensor is based on a patented measurement system (Raper and Hall, 2003) and consists of a single tip embedded in a blade of steel where the force transducer is located. This design It allows the movement of the blade on the vertical at the same time which is advanced without additional vertical forces being supported. The blade length is 90 cm, which allows a depth effective measurement of 60 cm; a width of 15 cm; a thickness of 3.75 cm; the cutting angle is 30º and to facilitate entry into the The ground has a bevel cut of 45º.

Siefken et al . (2005) developed a resistance measurement system based on an independent multi-blade system of the same length, attached to an inclined frame. The blades are made of 1.27 cm thick steel, with a cutting angle of 45º and the design allows each one to measure a 10 cm interval of the soil profile. The inclined frame from which the blades are suspended is located outside the ground and inside the load cells are located: one in the front and one in the back of each blade.

In this list of devices that have been found in the bibliography the following can be indicated inconveniences:

1º.- Those who carry the force sensor for below ground level they need the blades to have a thickness somewhat greater than the thickness of the sensor used, so they are too thick, appreciably altering the structure of the soil, which may not be admissible as occurs for example in comparative studies of tillage and no tillage. They also need Great tensile forces for dragging. Moreover, their Measures are not affected by friction.

2nd.- Those who carry the force sensors above ground level, they need knowledge of the depth at which the resultant forces act to be able to calculate the value of said result using a single value of force measured at a certain distance from that point. They act as a First order lever system, where to know the resistance offered by an extreme we must know the applied force in the other and the length of each arm, being an uncertainty the length of the arm on which the ground resistance acts. In Some models presented take into account this circumstance solving it by using two force sensors for blade, which makes the equipment more expensive by not only double sensor but also double number of conditioning channels and / or registration of The generated signals. Moreover, the effect of the forces of Friction is not taken into account in any of them.

3rd.- The friction force of the soil is not measured on the metal surface of the blades, which is a fact very interesting, not only to correct the sensor reading of force in the case of devices that carry it above the ground level, but also as a reference for the design of machinery that works with tools in contact with the ground.

References cited

Adamchuk , VI, Morgan , MT and Sumali , H., 2001 . Application of a strain gauge array to estimate soil mechanical impedance on-the-go. Transaction of the ASAE 44 (6), 1377-1383.

Andrade , P., Rosa , U., Upadhyaya , S., Jenkins , B., Agüera , J. and Josiah, M., 2001 . Soil profile forced measurements using an instrumented tine. ASAE Meeting Presentation , paper No. 011060. July 28-August 1, Sacramento, California (USA).

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Christenson , PT, Adamchuk , VI and Kocher , MF, 2004 . Instrumented Blade for mapping soil mechanical resistance. ASAE Meeting Presentation paper No. 041038, 1-4 August, Ottawa, Ontario (Canada).

Chukwu , E. and Bowers , CG, 2005 . Instantaneous muítiple-depth soil mechanical impedance sensing from a moving vehicle. Transaction of the ASAE , 48 (3) 885-894.

Chung , S., Sudduth , KA and Hummel , JW, 2003 . On-the-go soil Strength Profile sensor using a load cell array. ASAE Meeting Presentation paper nº 031071, 27-30 July Las Vegas, Nevada (USA).

Chung , S., Sudduthv , KA, Plouffe , C. and Kitchen NR, 2004 . Evaluation of an on-the-go soil strength profile sensor using soil bin and field data. ASAE Meeting Presentation paper No. 041039, 1-4 August, Ottawa, Ontario (Canada).

Glancey , JL, Upadhyaya , SK Chancellor , WJ and Rumsey , JW, 1989 . An instrumented chisel for the study of soil tillage Dynamics. Soil and tillage Research 14, 1-24.

Hall , HE and Raper , RL, 2005 . Development and Concept evaluation of an on-the-go soil strength measurement system. Transaction of the ASAE , 48 (2) 469-477.

Mouazen , AM, Dumont , K., Maertens , K. and Ramón , H., 2003 . Twodmensional prediction of spactial variation in topsoil compaction of a sandy loam field-based on measured horizontal force of compaction sensor, cutting depth and moisture content. Soil and Tillage Research 74, 91-102.

Mouazen , AM, Neményi , M., Schwanghart , H., and Rempfer , M., 1999 . Tillage tool desing by the finite element method: part 2, experimental validation of the finite element results with soil bin test. Journal or Agricultural Engineering Research 72, 53-58.

Raper , RL and Hall , HE, 2003 . Soil strength measurement for site-specific agriculture. US Patent No. 6647799.

Siefken , RJ, Adamchuk , VI, Eisenhauer , DE and Bashford , LL, 2005 . Mapping soil mechanical resistance with a multiple blade system.

Sirjacobs , D., Hanquet , B., Lebeau , F., Destain , MF, 2002 . On-line soil mechanical resistance mapping and correlation soil physical properties for precision agriculture. Soil and Tillage Research 64, 231-242.

Sun , Y., Ma , D., Schulze , P., Schmittmann , O., Rose , M., 2005 . On-the-go measurement of soil water content and mechanical resistance by a combined horizontal penetrometer. Soil and Tillage Research 86 , 209-217.

Description of the invention

The system object of the invention has a series of particularities based on which it is possible to know the resistance that the soil offers when it is cut and, in addition, the frictional force per unit of surface offered by the ground on metallic materials, the cutting force can be measured at different depth levels simultaneously and with the ground in real conditions, without the alterations that the extraction supposes of samples for laboratory analysis.

In that sense, the system of the invention is based on using a plurality of cutting blades and one or more friction blades mounted on a frame and placed a behind the other; with the special feature of using a articulated quadrilateral system for joining each blade to the support frame, allowing to measure directly with a cell of load associated to each blade, the result of the forces horizontal acting on each of said blades, without need to correct the load cell reading to know total soil resistance (cut more friction). I mean, I know avoid the mistake of not knowing precisely the center of application to the corresponding blade, as in the case of lever type systems.

The structure or set of equipment that determines the system can be dragged while cutting by a tractor vehicle or any other self-propelled and suitable vehicle to soils not prepared for transit.

The measurement is carried out by making a cut continuous floor through the different blades located a behind another, cutting each of them to different depths and With a thin cutting width, so that the force you need each of the blades to move sunk in the ground, is the sum of the shear strength plus the friction resistance of soil particles on the faces of the blade. That force resulting is measured with the load cell on which the blade and which is located above ground level, so that eliminate the limitations of placing the sensor force below ground level.

Based on the blade or friction blades is possible to know separately the cutting force and the force of friction, friction blade that does not make any cut but that moves inside the slot previously opened by the cutting blades before it, so it will only be subjected to friction forces, all in such a way that the relationship between the force provided by the load cell of said friction blade and its surface in contact with the ground, results in frictional force per unit of surface, which when multiplied by the surface in contact with the floor of the cutting blades allows to know the strength of friction that is acting on each one of them. If that force is subtracted to the total extent on the cutting blade, it will be taken as result the resistance to the cut that offers the ground to the level of depth at which said blade acts.

The commented value may be applied to cutting blades, taking into account their contact surface, and know so that part of the total force measured by your cell load corresponds to friction and which part corresponds to the cut of the ground.

As for the general structure or equipment in that the system of the invention materializes, it can be said that the blade mounting frame consists of at least a horizontal bar or plate with length and consistency necessary to support the number of blades required. Said frame will incorporate at one of its ends the appropriate means for engaging the corresponding tow vehicle, also ensuring its perfect horizontality during cutting.

On such a frame the different are fixed blades, one behind the other, and at the end of them the blade of friction, so that the lengths of the cutting blades they must be different so that each one makes the cut to a depth different from that of the others, the one being shorter first according to the direction of progress and progressively more long those located behind. The friction blade will not perform cut as previously stated, will have a length less than the one with the longest length of the shear, and will be located in the last place.

Optionally you can mount blades intermediate friction, which will always be of slightly length lower than the cut in front, allowing power have a more precise measure of the friction forces acting on the blades in front of her, avoiding the possible mistakes that can be made when considering that: a) friction on the blades has a uniform distribution in depth and, b) the surface resulting from the cut of the soil entering friction with the faces of the blades is not altered by the step of the successive blades.

The thickness and width of the blades will be the as low as possible to ensure the mechanical strength of the element, but they will be independent of the dimensions of the load cells used, since they will be located on the ground surface. They can take different geometric shapes but in any of the cases will have a bevel on their edge to facilitate cutting, so that the front blade will cut the ground to the first level of depth, so all its leading edge located below ground level will be cut. The one that is located immediately behind the first will make the second cut depth level, so part of its leading edge does not will cut when passing through the strip already cut by the first blade. In the same way will act the blades located behind, with the particularity that the cutting area of the leading edge corresponding to each blade can be oblique, forming a certain angle with the vertical to improve the cutting system.

The horizontal component of the forces that act on each blade is measured by the load cell that acts as the sole support or reaction to this component, which implies that the blade fixing system to the frame should only absorb the vertical components so as not to alter the value of the horizontal component measurement. This is achieved through fixing by an articulated quadrilateral, comprising two bars parallel verticals, one after the other, distributed across the width of the blade and in its upper part, above ground level. Each of these vertical bars is joined by the upper end to the frame and at the lower end of the blade, in both cases through low friction joints, being able to carry bearings

If there is no support on the load cell the blades will have a degree of freedom in their movement, given by the deformation admitted by the articulated quadrilateral formed by the two vertical bars, the blade (forming the side bottom) and the frame (forming the upper side). The cell of load must be supported on the frame and at the same time limit the backward travel of the blade, so as to ensure the verticality of the vertical arms of the quadrilateral.

Brief description of the drawings

To complement the description that then it will be done and in order to help a better understanding of the features of the invention, accompanies the present descriptive memory a set of drawings based on the which innovations and advantages will be more easily understood of the measurement system object of the invention.

Figure 1.- Shows a view according to a general perspective of a preferred embodiment of the equipment that determines the system of the invention.

Figure 2.- Shows a perspective of it equipment represented in the previous figure, with all its components exploding

Description of the preferred embodiment

As you can see in the referred figures, the measuring equipment that materializes, by way of example, the system of the invention, is constituted from a frame formed by two parallel and horizontal plates or bars 1, joined each other using two end plates 2 and 3, the first one as front and will have means for joining the vehicle to be used for dragging while the second plate 3, considered as later, it will allow the extension of the number of cutting blades 4 and friction 5 incorporating the equipment. He number of cutting blades 4 that are mounted will set the number of depth levels whose cut resistance can be measure.

Blades 4 and 5 are affected by two pairs of holes 6 and 7 at different height, those of each couple, corresponding lower holes 7 with respective holes 8 established for this purpose on the side plates 1 of the frame, so that through such holes 7 and 8 are respective interns corresponding articulation bolts pairs of vertical bars 9, each pair placed at either side side of each cutting blade 4 and friction blade 5.

The vertical bars 9 are affected by two holes, one lower 10 for the passage of the articulation pin referred to above, and another superior 11 for the articulation of said vertical bars 9 to the respective blade 4 or 5.

Accordingly, each of the blades 4 and 5 is related to four vertical bars 9, two on each side, to give it greater resistance, forming quadrilaterals articulated

Cutting blades 4 feature all bevel its leading edge 12, the area being cut obliquely 45 ° Shear of each of them. The width of the blades will be preferably 10 cm and each one will cut a depth level 10 cm, so each of these blades must be 10 cm more long than the one immediately before, except the blade of friction 5 which will be 1 cm shorter than the previous one. In position of work, the first cutting blade 4 must be stuck in the ground just to the oblique edge 12 and with the frame perfectly horizontal.

The diameter of the bolts through bottom holes 10 of the vertical bars 9, must match with the diameter of these and of the lower holes 7 of the blades 4 and 5, to ensure articulation without gaps. The length of said bolts must be 1 mm shorter than the separation between the lateral and horizontal plates 1. For their part, the upper holes 11 of the vertical bars 9 of the articulated quadrilaterals, are also of the same diameter, as well as the holes 8 that exist in the horizontal plates 1 of the frame, being crossed by two bolts of equal diameter. Since blades 4 and 5 are continued above the upper ends of the vertical bars 9 of the quadrilaterals articulated, the two holes must be made on them above mentioned above. In this case its diameter should be 5 mm larger than the bolt that crosses it to ensure the quadrilateral joint.

The upper side of blades 4 and 5 is trimmed in the form of step 13, leaving the lowest part of the same, corresponding to the back half of the width of the respective blade, flush with the upper edge of the plates 1 of the frame, while in the highest part, in the first half of the blade width, protrudes 3 cm.

The commented step 13 serves to block the movement of blades 4 and 5 in the opposite direction to that of advance, since the vertical edge of it is supported by the cell of load that in turn is fixed, in each case, to a support rear 14 which is bolted to the frame by means of screws security. If the horizontal force of thrust on the blade exceeds the measurement threshold of the load cell used, the screws will break and the blade will move back until the deformation limit of the articulated quadrilateral, which admits, the 5 mm clearance between the upper bolt and the hole upper blade, which will protect the load cell.

The horizontal result of the forces that act on blades 4 or 5 thus moves to the top Where is it measured? A load cell model is used for this miniaturized strain gauge of 5000 N maximum force, with shape cylindrical, partially introduced into the support by one of its bases, while on the other receives the vertical edge thrust of the upper step 13 of the blade 4 or 5. Using cables suitable drivers the signal is transferred to an electronic device of conditioning, visualization and / or registration that must have so many Input channels such as blades are being used.

Claims (5)

1. System for " in situ " measurement of shear strength and friction force on floors, determining a device that can be dragged by a self-propelled vehicle, and comprising a carrier frame of a plurality of thin blades capable of measuring at different levels deep, it is characterized in that the union of each of the blades (4) and (5) to the frame is carried out by pairs of vertical bars (9) located, each pair, on either side of the corresponding blade (4) and (5), said joint determining an articulated quadrilateral system that allows directly measuring, with a load cell associated with each blade, the result of the horizontal forces acting on each of them, and thereby knowing the total resistance of the soil determined by the sum of the shear strength plus friction resistance. 2. System for the measurement " in situ " of the resistance to the cut and the friction force in floors, according to claim 1, characterized in that it incorporates a plurality of cutting blades (4) located one behind the other, with its leading edge (12) bevelled and oblique, as well as one or more friction blades (5) located behind the last cutting blade (4), or sandwiched between them, each of the cutting blades (4) being provided it has a length greater than the one immediately ahead, while the friction blade (5), lacking a beveled edge, has a length slightly shorter than the cutting blade (4) located immediately ahead of it. 3. System for the measurement " in situ " of the resistance to the cut and the force of friction in floors, according to previous claims, characterized in that the vertical bars (9) of the articulated quadrilateral, have two holes, one inferior (10) and another upper (11), the lower joint being made through a through bolt and adjusted to the holes (8) corresponding to the side plates (1) that form the frame, the blades (4) and (5) and the bars themselves vertical (9) of the articulated quadrilateral, while the upper articulation of said vertical bars (9) to the blades (4) and (5), is made with greater clearance to ensure the articulation of the quadrilateral. 4. System for " in situ " measurement of the shear strength and friction force on floors, according to previous claims, characterized in that the upper edge of the blades (4) and (5) is affected by a step (13) to block the movement in the opposite direction of advance of the blades (4) and (5), the lower and horizontal section being flush with the upper edge of the plates (1) of the frame, with the particularity that the respective cells of load rests on the vertical section of such steps, such load cells being fixed to respective supports (14) joined to the side plates (1) of the frame. 5. System for " in situ " measurement of shear strength and friction force in floors, according to previous claims, characterized in that the faces of the blade or friction blades (5) are in contact with the ground cut by the cutting blades (4) located in front, so that the value obtained as a result of dividing the force measured in said friction blade (5) between its contact surface, makes it possible to know the frictional force acting on each blade of cutting (4), by multiplying said value by the surface in contact with the ground of such cutting blades (4), while the difference between the total force measured in the cutting blades and said friction resulting force, provides the value of the shear resistance offered by the floor at the level of depth at which each cutting blade (4) acts.