Measuring and testing – Dynamometers – Responsive to multiple loads or load components
Reexamination Certificate
2001-07-16
2003-04-22
Patel, Harshad (Department: 2855)
Measuring and testing
Dynamometers
Responsive to multiple loads or load components
C073S514260, C250S208600
Reexamination Certificate
active
06550346
ABSTRACT:
BACKGROUND DESCRIPTION
1. Field of the Invention
The invention relates to a means for sensing the relative movements of an object as set forth in the preamble of claim
1
. The invention relates furthermore to possible applications of the means.
2. Prior Art
Known from DE 17 73 870 A1 is a load-sensitive transducer including a deformable intermediate piece disposed between two rigid flanges arranged longitudinally axial, the intermediate piece having the shape of a solid or hollow cylinder and comprising in its interior one or more load-sensitive elements, e.g. electrical strain gages producing a change in the electrical resistance as a function of the deformation of the intermediate piece caused by mechanical stress.
In one achieved embodiment four strain gages are contained in the solid cylindrical intermediate piece in two pairs in parallel, the strain gages of the one pair being arranged parallel to the direction of the exerted load, i.e. axially, whilst the strain gages of the other pair are arranged perpendicular to this direction. The strain gages of each pair are inserted in each diametrically opposed branch of an electric bridge circuit of a measurement device in each case for indicating the direct current of the bridge and thus the load exerted.
In another achieved embodiment only one or two electrical strain gages are inserted in a hollow cylindrical intermediate piece parallel to the exerted load, i.e. axially. In any case the load-sensitive elements, i.e. for example the strain gages are contained in the intermediate piece itself and thus incorporated therein so that the deformation caused by the mechanical stress can be accommodated at all in the intermediate piece.
To ensure that the electrical output values of the strain gages are practically independent of the spatial location of the strain gages in the intermediate piece in each case and that the exerted load is evenly distributed over the cross-section of the deformable intermediate piece, there is additionally inserted between each of the two flanges and the deformable intermediate piece a further body made of an elastomer material, e.g. rubber. The intention of this known arrangement is to measure the mechanical load exerted on the two flanges so that the indication achieved with the aid of the load-sensitive elements, i.e. e.g. the strain gage is substantially independent of the effective line of the load through the intermediate piece.
This known means permits sensing certain relative movements of an object and comprises an input flange securable to the object, a flange rigidly connected to a baseplate, and in the second achieved embodiment in addition a roughly ring-shaped intermediate piece arranged between the two flanges to which it is connected resistant to turning and shifting out of place and is made of an elastomer and including a force-sensing unit in its interior for sensing the movement of each flange relative to the other.
However, this known means permits sensing and measuring substantially only vertical relative movements of an object, but not any side or slanting relative movements and not at all any rotary excursion.
Known from DD 277 330 A1 is an ON/OFF force sensor including a rubber ring mounted on a baseplate, on which a cover plate is located exposed to a force from above as is to be measured. Applied to the inner circumference of the rubber ring, as a connecting part, is an open flexible ring, to the one end of which an electrical springer switch and to the other end of which a set screw is attached which urges the plunger of the springer switch.
Thus, the electrical springer switch is activated by the deformation of the rubber ring caused by the force acting thereon, resulting in a change in the diameter of the flexible ring. The circumference of the flexible ring is accordingly altered by roughly three times which makes for a higher reliability in the response of the springer switch. However, with this known force sensor only the vertical component of a force, i.e. a vertical relative movement of an object can be determined substantially. In this case too, this does not involve a force/moment sensor with which substantially a broad variety of relative movements can be sensed and measured as with the present invention.
Known from DE 39 40 696 C2 is a force sensor producing a practically linear electrical output signal as a function of the active force of the displacement to be sensed, wherein no change in the point at which the force is active occurs, but instead a lengthening of the sensor body in the direction in which the force is active. This force sensor has a folded-type structure and comprises in an effective partial range a mechanical electrical transducer element which is sensitive to the shortening of the surface of the transducer element when the sensor is exposed to tensile loading, this shortening being caused by the bending of the surface about an axis extending parallel to the direction in which the force is effective. This known force sensor too, responds substantially only to relative movement in one direction, in this case in the longitudinal direction of the force sensor.
Suitable for sensing a variety of relative movements are force/moment sensors as known for example from DE 36 11 336 C2 or EP 0 240 023 B1. With the aid of such a force/moment sensor linear displacements and/or rotary excursions can be sensed and converted for example directly into translational and rotational movements in thus permitting the control of automated machines, robotic manipulators or similar systems.
Both the force/moment sensors as cited above as well as all force/moment sensors currently on the market have only a relatively limited stiffness, or, in other words, no high forces or torques can be sensed and processed by these known force/moment sensors. In the case of robotic manipulators, for example, torques of a magnitude in the region of 100 Nm and more may occur at the welding tongs manipulated thereby. Such high torques cannot be sensed and/or processed by force/moment sensors currently available, however.
SUMMARY OF THE INVENTION
It is thus the objective of the invention to provide a means in making use of a force/moment sensor with which the relative movements of objects, especially also of large and correspondingly heavy objects, can be sensed. The intention is to permit sensing and measuring a wide variety of relative movements of an object so that the results can then be analyzed and more particularly made use of for precisely controlling and monitoring the momentary location of the object even when the objects involved are very large and heavy.
In accordance with the invention this objective is achieved by the features in the characterizing clause relating to a means as set forth in the preamble of claim
1
. Advantageous further embodiments and possible applications of the invention are the subject matter of the sub-claims.
Unlike the embodiment of the invention in which the cap of the sensing unit, provided in the internal portion of the intermediate part, is secured to the force/moment sensor in the middle of the input flange to thus totally sense and transduce the translational and rotational movements, in the other embodiment in which the sensing unit with its cap is secured to a connecting part provided in the middle portion of the roughly ring-shaped intermediate part and protruding into the interior thereof, only approximately half of the translational and rotational values are available in each case for analysis.
In accordance with one advantageous aspect of the invention the multiple-piece intermediate part may be formed of approximately ring-shaped sections of approximately rectangular cross-section or also of approximately circularly arranged cuboidal elements. Furthermore, the multiple-piece intermediate part may also be configured of cylindrical elements arranged approximately circularly with a square, rectangular, polygonal and/or circular cross-section.
In accordance with another advantageous aspect of the invention both the approximately circularly conf
Dietrich Johanndes
Gombert Bernd
Senft Volker
Browdy and Neimark , P.L.L.C.
Deutsches Zentrum fur Luft -und Raumfahrt e.V.
Patel Harshad
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