Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
  • G01L3/00—Measuring torque, work, mechanical power, or mechanical efficiency, in general
  • G01L3/16—Rotary-absorption dynamometers, e.g. of brake type
  • G01L3/22—Rotary-absorption dynamometers, e.g. of brake type electrically or magnetically actuated
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T403/00—Joints and connections
  • Y10T403/32—Articulated members
  • Y10T403/32549—Articulated members including limit means
  • Y10T403/32557—Articulated members including limit means for pivotal motion

Definitions

• the present invention relates to an elastic joint with a translating spherical hinge and force and moment sensor improved by means of the said joint.
• Rigid sensors can be used, for example, positioned between the elements which exchange forces, or sensors comprising a measuring structure constrained in a statically determined way to the body whose stress is to be measured.
• the sensor consists, for example, of a measuring structure comprising, in the central part, three arms, in which each arm is constrained to the supports con- nected to the body whose stress is to be measured by means of a joint consisting of a spherical translating hinge, i.e. a spherical hinge and a sliding joint.
• a spherical translating hinge i.e. a spherical hinge and a sliding joint.
• Each translating spherical hinge has only two constraint degrees, allowing, in fact, four degrees of freedom, i.e. one degree of freedom for translation in a plane orthogonal to the constraint plane mentioned above, one degree of freedom for torsion and two degrees of freedom with respect to rotations .
• the translating spherical hinges of the known type can, for example, be produced by combining with each other, in series, a spherical joint and a translating sleeve. These hinges however are subject to the friction, due to the use of smooth or ball bearings, which jeopardizes the sensitivity and accuracy of the meas- urements.
• An objective of the present invention is to provide an elastic joint with a translating spherical hinge and a force and moment sensor improved by means of the said joint, which solve the above-mentioned drawbacks.
• Another objective of the present invention is to provide an accurate and sensitive force and moment sensor.
• Yet another objective of the present invention is to provide an elastic joint with a translating spheri- cal hinge and an improved force and moment sensor which is particularly simple and functional, with reduced costs.
• figure 1 shows the mechanical model of an elastic joint with a translating spherical hinge made by means of wires
• figure 2 shows the mechanical model of an elastic joint with translating spherical hinge produced with beams
• figure 3A, 3B and 3C show the functioning principle of an elastic joint with a translating spherical hinge produced with beams
• figure 4 is a perspective view of an embodiment of an elastic joint with a translating spherical hinge, produced with beams, object of the present invention
• figure 5 shows a force and moment sensor improved by means of an elastic joint with a translating spheri- cal hinge object of the present invention
• figures 6A and 6B respectively show an overall design of a further force and moment sensor improved by means of an elastic joint with a translating spheri- cal hinge object of the present invention
• FIG. 1 With reference to the figures 1-3, the functioning mechanical principle of a joint with a translating spherical hinge, according to the present invention, is schematically shown and described.
• a structure can be obtained wherein a vertical rod 14 can translate along its own axis 11 and spherically rotate around the central hinge.
• Horizontal elastic elements 12 are suitably stretched wires, or beams with constraints 15 at the ends, consisting of hinges (generally spherical hinges) .
• This structure is four times unstable and, in addition to the three spatial rotations of the vertical rod 14, it also allows the small movement in a vertical direction of the same vertical rod 14.
• This structure can function with a number of wires or beams 12, higher or equal to three. With two wires or beams 12, in fact, it does not function properly as there is a fragility in the orthogonal direction with respect to the axes of the two beams, or wires 12, and lying in an horizontal plane 13 which contains the two beams or wires 12.
• Figures 4, 5 and 6 illustrate an elastic joint, having a translating spherical hinge, indicated as a whole with 10, and two different embodiments of a force and moment sensor, indicated as a whole with 100, im- proved by means of the said joint 10.
• the elastic joint with a translating spherical hinge 10, or the joint of the type with the spherical hinge with a sliding joint is particularly suitable for being used in the force and moment sensor 100 which, in the example, comprises a three-armed measuring structure 102, connected by means of three joints 10 to a body 101 to which forces and moments to be measured are applied.
• the elastic joint with a translating spherical hinge 10, object of the present invention comprises a series of elastic elements 12, or at least three beams or two elastic laminae 12, positioned in a first horizontal plane with a first end facing so as to form the articulation elastic plane 13.
• the facing ends of the elastic elements 12 are rigidly connected to an axial rod element 14 arranged according to the axis 11 orthogonal to the articulation elastic plane 13. According what is shown in figure 4, a series of beams 12 are uniformly distributed in the horizontal plane 13, equidistanced between each other, or comprising equal angles between each other.
• the beams 12 are connected to a rigid support 16, constrainable to the body 101 by means of a dap joint 15 (figure 5) .
• the beams 12 are flexible in any vertical plane comprising the orthogonal axis 11 and in the horizontal plane 13.
• the articulation of the joint 10 takes place between the axial element 14 and the support 16 and al- lows four degrees of freedom, i.e. the translation of the axial element 14 in the direction of the orthogonal axis 11 and the spatial rotation of the axial element 14, by means of flexure of the elastic elements 12 in any vertical plane comprising the orthogonal axis 11, as well as the torsion of the axial element 14 around the same axis 11, by means of flexure of the elastic elements 12 in the horizontal plane 13, respectively.
• the beams 12 situated in the horizontal plane 13, equidistanced between each other, can consist of two aligned laminae 12, having an extension in the articulation elastic plane 13 much greater than their thickness, as shown in figure 7.
• the elastic elements 12, shown and described, can be made of different materials, for example, the wires 12 in figure 1 can be made with steel wires or Kevlar filaments, or different material, and immersed in a resin matrix.
• the beams or laminae 12 can be made of various materials, such as steel, plastic or composite material. The selection of the material, thickness and width is effected with the intent of optimizing the ra- tio between the rigidities .
• the elastic joint with a translating elastic hinge 10, object of the present invention constrains the axial element 14 and gives it a high rigidity with re- spect to the movements in the plane 13.
• the axial element 14, on the contrary, has an axially pliable behaviour, i.e. in the direction of the axis 11 and, due to the effect of the elastic elements 12, also the possibility of performing a spherical rotation.
• a possible non-exclusive application of the elastic joint with a translating spherical hinge, object of the present invention is the force and moment 100 sensor, shown in figures 5, 6, and 9.
• the sensor 100 comprises the three-arm measuring structure 102 (figure 8) connected to the body 101, to which forces and moments to be measured are applied by means of three elastic joints with a translating spherical hinge 10.
• the measuring structure of figure 8 is assembled as a dynamometric hub centred on a hub 103 of a wheel 101 and the arms, or an extension of the same, represent the axial element 14 of the joint 10.
• the support 16 of the joint 10 is rigidly connected to the body 101, in the example to the wheel rim, by a constraint of the dap joint type 15 .
• Figures 6A and 6B show a further force and moment sensor 100 improved by means of an elastic joint with a translating spherical hinge, object of the pre- sent invention, for use as a static force and moment sensor.
• the sensor 100 of figures 6A and 6B does in fact allow the forces to be measured which are exchanged between a first supporting element 101 to which the joints 10 are constrained and a second axial ele- ment 103, integral with the measuring structure 102.
• the measuring structure 102 is statically determined and is equipped with means for the measuring 104 of six stress magnitudes from which the force and moment vectors acting on the body 101 can be mathematically ob- tained.
• the six magnitudes are revealed on the arms of the measuring structure 102.
• Each arm is in fact subjected to stress along its own length by two orthogonal flex- ing moments.
• the two stress flexures which are exerted by the above two orthogonal flexing moments, can be measured by two pairs of strain gauges applied on opposite sides of the arms themselves, as schematically shown in figure 8, in which Ia, Ib, 2a, 2b, 3a, 3b, 4a, 4b, 5a, 5b, 6a. and 6b indicate six pairs of strain gauges which form an example of possible measuring means .
• the elastic joint with a translating spheri- cal hinge 10 comprises two aligned laminae 12 having extension in the elastic articulation plane 13, according to what is illustrated in figure 7.
• Figure 10 schematically shows the positioning of two pairs of strain gauges l'a, l'b, 2'a, 2'b on the two aligned laminae 12, for measuring the constraint reaction acting in a lateral direction and for measuring the constraint reaction acting in a lon- gitudinal direction on the laminae 12, respectively.
• Other measuring means 104 which can be used for measuring the flexure are, for example, movement sensors which reveal the movements of the laminae 12, directly applied to the laminae 12. From the six measurements, a force vector F is univocally obtained, dissembled into three vectors directed along three coordinated axes and a moment vector T dissembled into three vectors directed along three coordinated axes, i.e. the six generalized forces act- ing on the body.
• Other measuring means 104 which can be used are piezoelectric elements or elements of another kind, not shown, which can be positioned between the end of each of the three arms of the measuring structure 102 and each of the relative joints with a translating spherical hinge 10. These measuring means are capable of measuring two forces orthogonal with respect to the axis 11 and orthogonal with respect to each other and mathematically obtaining the force F and moment T vec- tors acting on the body 101.
• this shows a last embodiment of a force and moment sensor 100 produced as a dynamometric hub, in which each translating spherical hinge 10 is produced integrally with the measuring structure 102 and with the same rim channel 101 as a road or off-road vehicle forming a single structure.
• This rim is extremely economical as it provides localized deformation areas which allow the acting forces and moments to be surveyed, at substantially the same cost as a normal rim.
• the elastic joint with a translating spherical hinge, object of the present invention has the advantage of eliminating the problem of friction.
• the elastic joint with a translating spherical hinge also allows the force and moment sensor to be im- proved, allowing optimum performances, which are more accurate and sensitive, on the part of the sensor, in addition to a relatively economical construction cost .
• the sensor improved by means of the elastic joint with a translating hinge is also suitable for the pro-duction of an extremely precise and low-cost dynamomet- ric hub with the possibility of generalized use on vehicles .
• the elastic joint with a translating spherical hinge and the force and moment sensor improved by means of the said joint thus conceived can undergo numerous modifications and variants, all included in the invention; furthermore, all the details can be substituted by technically equivalent elements.
• the materials used, as also the dimensions, can vary ac- cording to the technical requirements.

Landscapes

• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Force Measurement Appropriate To Specific Purposes (AREA)
• Pivots And Pivotal Connections (AREA)
• Golf Clubs (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (2)

Family

ID=38723673

Family Applications (1)

Country Status (5)

Cited By (5)

Families Citing this family (22)

Family Cites Families (16)

• 2006
  • 2006-05-22 IT IT001000A patent/ITMI20061000A1/it unknown
• 2007
  • 2007-05-16 US US12/227,322 patent/US7779705B2/en active Active
  • 2007-05-16 JP JP2009511600A patent/JP2009537771A/ja active Pending
  • 2007-05-16 EP EP07734641.9A patent/EP2021758B1/en active Active
  • 2007-05-16 WO PCT/IB2007/001335 patent/WO2007135551A2/en not_active Ceased

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