Electricity: measuring and testing – Magnetic – With means to create magnetic field to test material
Reexamination Certificate
2000-02-11
2001-09-18
Patidar, Jay (Department: 2862)
Electricity: measuring and testing
Magnetic
With means to create magnetic field to test material
C324S242000, C324S238000, C198S810020
Reexamination Certificate
active
06291991
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a device for continuously monitoring the junction of a conveyor belt made of rubber or a rubber-type material which in particular is provided with embedded strength supports for reinforcing said material.
German laid-open patent specification DE-A-31 31 963 describes a system for monitoring conveyor installations and conveyor belt rollers, specifically in connection with a detection system for detecting mechanical values such as the number of revolutions, the torque, the load acting on the bearings, the temperature, the slack and the tension of the belt, damage to the belt, and oblique run of the belt. Furthermore, patent specification DE-C-195 25 326 introduces a method and an arrangement for monitoring a conveyor belt with the use of transponders. Finally, U.S. Pat. No. 4,020,945 describes a device for continuously monitoring the junction of a conveyor belt. With said device, magnetic areas serving as reference marks are incorporated in the conveyor belt material at the head and at the end of the junction area. The passage of said reference marks is detected by a reference mark detection system, and both the speed of the conveyor belt and the length of the junction area are measured based on the values so detected.
2. The Prior Art
The junctions of conveyor belts are generally viewed as zones of a conveyor belt installation to which special attention needs to be paid with respect to the functionality and durability of such junctions, the reason for this being that the tensile forces change in said zones from the strength support into the rubber material of the junction, and again into the strength support of the following length of the belt. In this process, the force of traction will stress both the rubber with forces of shear and strain the adhesion between the rubber and the strength support. Furthermore, it has to be assumed that the distribution of stress within the junction area and in the areas of transition will not be homogeneous, so that there will be always zones from where failure of the junction can originate after the conveyor belt has been in use for long periods of time.
Such events have to be avoided because failure of a conveyor belt junction poses a very high danger potential and a substantial economical risk. Therefore, operators of conveyor belt installations increasingly request monitoring systems for conveyor belt junctions that alert the operator to any onset of failure in due time, and permit the implementation of repair measures before failure of the junction occurs.
In addition to regular inspections, by which external damage can be detected visually, a possibility available is to continuously and automatically monitor the entire length of the junction or individual discrete zone of the junction. With multistage steel rope-reinforced belt junctions, such zones may be, for example the deflection zones and the so-called guide marks. The starting point in this connection is the idea that under normal operating conditions (but not under extreme overloading conditions), a junction will not fail all of a sudden as a whole, but failure will start gradually from individual zones of the junction. The remaining intact zones are in such a situation subjected to higher stresses, which leads to higher elongation and consequently to an increase in the length of the loaded junction.
The lengths of the junction or reference distances covered and detected in defined sites of the belt installation have to be compared with rated and limit values which, if exceeded, will result in a warning message or even shutdown of the installation.
Adverse influences such as, for example varying load conditions, different measuring sites and temperature changes must, of course, be eliminated by corrective methods of calculation. The length must be detected automatically and continuously with high precision and reliability, which means that the systems to be employed for obtaining the measured values and for the detection have to satisfy extremely strict requirements. This is made even more difficult by the environmental conditions prevailing on site, which may be the environmental conditions of a rough mining operation. It is necessary in this connection to satisfy the conditions of underground pit coal mining just as well as the conditions found in open-pit brown or soft coal mining, or the conditions of ore mining both above-ground and underground. Special requirements have to be met when conveyor belt installations are employed in regions with extreme climatic conditions, for example in desert and tropical zones, in mountain areas, and under arctic conditions.
Since the measurements have to be taken continuously on the operating conveyor belt plant, it is necessary also to take into account the fact that the measuring site not only migrates in the longitudinal direction of the belt at belt speeds reaching up to 8 m/s, but that also displacements of the surface of the conveyor belt of up to ±100 mm take place sideways, and vertical shifts of about ±10 mm may occur in the form of vibrations.
The lengths of the junctions of the conveyor belts comes to between ≦1 m and 8 m depending on which type of belt is employed, as well as on the strength of the belt. The resolution of the measured values and the measuring accuracy should be in the order of magnitude of 1 mm or better.
SUMMARY OF THE INVENTION
The present invention contains
at least two, in particular four reference marks, which are arranged in such a way that at least one reference mark, in particular two reference marks are located both in the zone of the head of the junction area and the end of the junction area, said reference marks being permanently worked into the marginal zone of the top (carrier) side of the conveyor belt, or within the lateral edge zone extending between the bottom and the top sides, whereby the reference marks are stable versus higher thermal and pressure loads as well as versus moisture and other mechanical and chemical stresses.
A reference mark detection system adapted to the type of reference mark used, for the purpose of measuring the speed and also the length of the junction, whereby the reference mark detection system is arranged on the left and/or the right viewed in the direction of movement of the conveyor belt.
A signal processing system for the reference mark detection system based on time measurement, whereby the signals supplied by the reference mark detectors are processed and adapted in such a way that the beginning and the end of the time measurement process can be triggered in a reliable and precise manner.
An identification system that is not depending on the direction of movement of the conveyor belt and comprises the following:
An address for the purpose of identifying the measuring site, said address being located outside of the zone of the junction near the head and/or the end of the junction, whereby the address is arranged on the left and/or the right of the belt viewed in the direction of movement of the conveyor belt, more specifically within the edge area of the bottom and the top sides of the conveyor belt, or within the lateral edge zone extending between the bottom and the top (carrier) sides;
An address detector adapted to the type of address used, said detector being arranged on the left and/or the right viewed in the direction of movement of the conveyor belt as well; and
A reading device for the address, said reading device in turn being connected to the address detector;
a time-measuring member connected with the signal processing system for the reference mark detection system;
a measuring system for determining the temperature of the conveyor belt and the ambient temperature;
another measuring system for determining the tractive force of the belt; as well as
a process computer for evaluating all data, whereby the process computer in turn is connected with a drive control.
REFERENCES:
patent: 4020945 (1977-05-01), Takeno et al.
patent: 4409852 (1983-10-01), Suzuki et
Collar & Roe, P.C.
Patidar Jay
Phoenix Aktiengesellschaft
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