Data processing: measuring – calibrating – or testing – Measurement system – Dimensional determination
Reexamination Certificate
2000-02-02
2002-07-09
Shah, Kamini (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system
Dimensional determination
C701S019000, C700S275000, C191S050000
Reexamination Certificate
active
06418397
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a device for measuring the contact force between a contact wire and a pantograph of an electrically-powered vehicle. More particularly, the present application relates to a device for measuring the contact force between a contact wire and a pantograph of an electrically-powered vehicle, particularly an electrical railway vehicle, with the device having at least one fiber-optic sensor that is suitable for ascertaining the contact force between a contact wire and a contact strip of the pantograph, and a device for sensor control and sensor-signal processing connected to the sensor or sensors for separate-potential signal transmission.
Pantographs of modern high-speed railway vehicles should be embodied as actively-controlled pantographs with respect to the contact force between the contact strip of the pantograph and the contact wire, so that an optimum level of the quality of the energy supply and the wear at the contact point between the contact wire and the contact strip can be found and maintained, regardless of the relative movements between the railway vehicle and the contact wire, the aerodynamic forces on the pantograph components as stipulated by wind and vehicle speed, and the oscillatory behavior of the pantograph, the contact wire and the chain mechanism guiding the wire. While the force component of the true contact force resulting from the vehicle-speed-dependent air flow against the pantograph components can be determined through measurements and established as a parameter function for a control algorithm, the determination of the contact force F resulting from the mechanical action of the pantograph and the overhead-contact system requires a device that determines this contact force as close as possible to the aforementioned contact point, according to its magnitude and its point of entry, and, from the measuring location, which is located at a high-voltage level (e.g., 3 kV DC voltage; 15 kV or 25 kV AC voltage), further conducts contact-pressure-equivalent signals to internal vehicle evaluation devices, which are set at the opposite potential. The term ‘contact force F’ refers hereinafter to this component of the true contact force between the contact wire and the contact strip, as results from the mechanical action of the pantograph and the overhead-contact system.
A generic device for determining the true contact force between a contact wire and a pantograph is described in U.S. Pat. No. 5,115,405 A. Here, a fiber-optic force sensor is mounted to the contact strip, the sensor being connected, via optical fibers (and therefore separated electrically in potential and being extensively independent of electrical and magnetic interference fields), to an internal vehicle device that supplies the sensor with light and receives its contact-force-dependent signal. The force sensor comprises an optical fiber that is clamped in spring-loaded fashion beneath the shoe that is in contact with the contact wire, and between the shoe and its holding device. A contact force that acts on the shoe leads to the deformation and micro-bending of the clamped optical fiber, altering its light-transmitting properties. This device is intended to recognize the overstepping of an upper and/or a lower threshold value of the true contact force between the contact strip and the contact wire, which is dictated, for example, by the impact of wind; the device is further intended to correct the contact force by means of an electronic-pneumatic command device and a pneumatic damping-compensation control element.
This device appears to be well-suited for detecting and signaling the overstepping of contact-force threshold values. This arrangement is, however, completely unsuitable for an effective measurement of a contact force within a specific force range, as is necessary for an active control of the contact force or the true contact force of a pantograph, because the fiber-optic force sensor has a very low signal
oise ratio, and a sufficiently precise, continuous determination of measured values is impossible. This sensor does not permit a determination of the point of entry of the contact force at the contact strip. Because the arrangement extends over the entire length of the shoe, it has a significant spatial expansion and mass, which can have a negative impact on the oscillatory and aerodynamic behavior of the pantograph.
The technical embodiment appears to be too sensitive to the types of stresses that are inevitable in the assembly, maintenance and transport of a pantograph. Because the temperature dependency of the light-transmitting properties changes with the degree of mechanical stress of an optical fiber, an effective compensation of this temperature dependency is scarcely possible. The continuously-changing mechanical stresses and deformities to which the optical fiber of this force sensor is subjected limit the service life of the fiberoptic sensor, thereby offering no guarantee of reliable device operation.
The patent publication EP 0 697 304 A2 discloses a device for measuring the contact force for an actively-controlled pantograph, in which a load recorder that measures in analog fashion and must cooperate with further length-measuring sensors to influence the action of two separately-operating vertical-lifting drives, by way of a control unit, is disposed beneath a pin-type insulator that supports the pantograph head and is disposed on a structure that swings out vertically, or the insulator is associated with the shoe. This load recorder should also be able to be constructed with the use of optical fibers; no further details are offered about the structure, arrangement and function of these fibers. At least in the arrangement of the load recorder beneath the pin-type insulator, considerable difficulties arise with respect to determining the magnitude of the contact force, because wind and mass forces acting between the points of contact and measurement affect the measurement result. It appears that the size of the load recorder, which can be seen from the drawings, makes it impossible to arrange the detector near the shoe, because this would have a negative impact on the oscillatory and aerodynamic behavior of the pantograph. It is not possible to ascertain the point of entry of the contact force at the contact strip using this load recorder.
German Patent Publication DE 195 18 123 C2 discloses a more detailed description of a device having a special optical-fiber sensor, with which mechanical pressure forces can be measured within the scope of rail technology, for example in rail-mounted axle-counting devices. This sensor has an inside tube and an outside tube, which is coaxial to the inside tube, is divided in the longitudinal direction of the tube and forms two contactless half-shells. A glass fiber that conducts light waves is embedded in helical fashion into an elastic mass between the inside tube and the outside-tube shells, and experiences a reversible bending in a certain bending-radius range during a one-sided, mechanical pressure stress of the sensor, in which the two half-shells of the outside shell are moved toward one another; this bending measurably damps an optical signal that passes through the glass fiber. This type of sensor has a complex design. It is only suitable for one stress direction, cannot be integrated as a structurally self-supporting component into the pantograph, and would be destroyed in the event of mechanical overstressing. The variable mechanical stress and deformation of the optical fiber of the sensor reduce the effectiveness of temperature-compensation measures, and likewise lead to a limitation of the service life and operating reliability. Thus, a sensor of this type appears to be unusable for measuring the contact force at a pantograph for the purpose of active pantograph control.
A further device for measuring the contact force for an actively-controllable pantograph is proposed in the German patent publication DE 195 40 913 C1. In this case, a force sensor is intended to be dispos
Blaschko René
Brand Werner
Karguth Andreas
Mollenhauer Olaf
DaimlerChrysler Rail Systems GmbH
Kunitz Norman N.
Shah Kamini
Venable
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