Home Hydraulic Level Control Pump Protection

Description of application:

The device according to invention for positioning by means of ultrasonic is based on the interruption of the ultrasonic way laterally by the hydraulic piston. The position of the piston in the position between two sensor foils can be formed by computation (evaluation) from the different amplitudes of the sound fields of reflection. A PVDF foil (ultrasonic sensor array) lies (sticks) full-laminar on the cylinder wall. The single sensors of the array are queried over multiplexers lively and. A rough local dissolution takes place already with the 1.Auswertung (wall echo or no wall echo/i.e. piston stands behind it). In a second process step the ultrasonic amplitudes of two (or several) sensors are evaluated. Thus can be made 10 to 20 quantifications (with in each case 5 railways). By the relative evaluation of the amplitudes, do not disturb absorption influences, temperature dependences etc. The measurement of longer procedure distances of the piston is possible by lining up of mehrer sensor arrays. Evaluation electronics (e.g. AD-transducer with microprocessor and multiplexer) is highly integrated. The expenditure of discrete elements is very small. Economical end position switches with redundancy can be developed with a simple sensor array (2-4 sensor ranges). Replacement past mechanical end position switch in hydraulic's applications. The structure height of the sensor amounts to only few millimeters (by the cable connection one determines).

Areas of application:

- Measurement of the piston position for hydraulic cylinders

- Monitoring of end positions

- Retrofit of hydraulic cylinder

Advantages of the procedure:

- Low manufacturing costs
- No moved mechanics
- no complicated construction units are necessary
- independent of shock loads
- Simple retrofit of existing cylinders
- Variable in the length by serial connection
- Bus-able - simple data format
- Small one mechanical dimensions
- Property adaptation to specific tasks
- Squirting and pressure water resist

Procedure principle:

In Fig.1 the arrangement of the ultrasonic sensors in two rows A and B on the cylinder wall of the hydraulic cylinder is represented. The ultrasonic sensors are within that Sensor rows A and B in the direction of motion of the piston in even distances arranged. The position of the piston in the cylinder can be determined by the interruption or weakening of the ultrasonic signal, for example the echo of the cylinder wall with the signal passage by the cylinder. In the pulse response enterprise working ultrasonic sensors receive the echo of the opposite cylinder wall. The piston and the piston rod interrupt the sound passage by that Hydraulic medium. Possible piston positions are represented in Fig.1 and 2. Both sensor rows A and B can be addressed separately or together with the transmit clock. Depending upon kind of the control, the distance between both rows is to be selected. The lines for the signal supply and the signal pick-ups are not here with represented. These lines can be attached on the substrate of the sensor strips. If several devices according to invention in longitudinal direction are to be gereiht together, can take place the interconnection of these devices with well-known and usual contactings (e.g. as when the assembling of SMD). For further signal processing the necessary multiplexers and Demultiplexer are not with represented. For the execution of the procedure according to invention in a first step the piston position is determined. For example if the hydraulic piston is in the piston position after Fig.2, the first process step determines that in sensor row A after all further sensors (e.g. A.10) all are covered to 100% (path length of sound waves to the opposite cylinder wall is not free).
For the sensor row B it is stated that up to the sensor (e.g. B.10) all sensors are covered to 0%. The logical inquiry is here only stated to exemplary. Several criteria can be naturally consulted for the inquiry. So for example: Coverage 0% or more largely, coverage 100% or smaller, coverage 0% or 100%. Also the logic function of several criteria (for example: AND, OR) been suitable (rough) the sensor position is to be specified on or between two sensors. In a second process step the signal amplitudes of the sensors at the piston position are evaluated. The evaluation can take place for example only as pair, Tripel or also as Quadrupel.

The suggestion and evaluation of the ultrasonic signals differ not substantially from the past technology with ceramics transducers. The suggestion for impulse for the sensors is state of the art. The chief work is with the organization of the sensor application. I.e. as the assembly of evaluation electronics takes place (either on the PVDF sensor or on a ceramics carrier). The houses will have to be adapted to that respective application purpose and/or hydraulic cylinder. These questions of the Design are fewer tasks of development, but result from the requirements and desires of the principal clients.

Different linear sensors (concerning length of the sensor array) are essentially equipped with a same, central evaluation unit. The adjustment of the transmitting power and receiver sensitivity to the respective wall thicknesses, infinite cylinders and different hydraulic fluids can be put down in the program. Over interface communication, which is usual with the modern microprocessors, case of application is selected. The number of attached sensor cells is likewise communicated. Thus the number of address lines and the control of the multiplexers are fixed. Also over a Teach in function the adjustment can take place to the hydraulic cylinder. Since the comparison of the sensor amplitudes takes place relatively against each other and is evaluated no absolute measurement, to have fluctuations of the factors of influence on the signal amplitude, no effect on the computed local dissolution between the sensors.

Applications:

Water level sensor for white commodity In the patent specification the
DE 10 2004 042,725 described procedures for the monitoring of hydraulic cylinders is suitable in outstanding for the water level measurement and condition control. The hydraulic cylinder is regarded as perpendicularly standing pipe, its upper end is open and/or represents a communicating system with to supervising container. Without liquid behind the PVDF sensor no sound transmission to the tubing rear wall and concomitantly no echo take place.

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