GB2036325A

GB2036325A - Means for detecting liquid levels in a container

Info

Publication number: GB2036325A
Application number: GB7940026A
Authority: GB
Original assignee: Schloemann Siemag AG
Current assignee: SMS Siemag AG
Priority date: 1978-11-20
Filing date: 1979-11-20
Publication date: 1980-06-25
Also published as: JPS5574422A; FR2441837B3; IT7927411A0; DE2850238A1; FR2441837A1; SE7908638L; BR7907482A; GB2036325B; IT1126331B; ES484972A1; IN153398B

Abstract

To detect the liquid level in a container, a plurality of ultrasonic detection units are arranged at various heights on the outside of the container, each unit comprising a transmitter 7, a receiver 8 arranged to receive sound pulses transmitted through the container by the transmitter, and a device 9 for producing the pulses and for converting the signal received by the receiver to an indication of whether liquid is present in the part of the container through which the sound pulses were transmitted. The positions of the detection units are adjustable. The final output from the unit can be used to switch on or off pumps, safety devices or valves controlling the liquid feed to the container. <IMAGE>

Description

SPECIFICATION Means for detecting liquid levels in a container The invention relates to means for detecting liquid levels in a container, for example in pressure fluid containers of pressure storage installations.

Control columns for pressure fluid containers are known in which the switching element of the control column are in direct connection with the liquid medium. In some of the cases the switching elements are in the form of two-armed levers with floats on the one side and with an attached magnet on the other side and are arranged directly in bores of the pressure fluid container, the magnetically actuated mercury switching devices being located outside the pressure fluid container (German Patent Specification No 618 616).

It is also known to arrange these floats in a control column which is constructed as a communicating tube which is connected to the upper and the lower part of the pressure fluid container. In this case, these float switches are provided at the respective filljng level heights which correspond to certain pressures of the pressure fluid (see the book "Hydraulische Schmiedepressen and Kraftwasseranlagen", Ernst Miller, Springer-Verlag, Berlin, 1939, page 68, Figure 68). These communicating tubes are.

connected to the pressure fluid container by way of shutsff valves.

The production and attachment of such communicating tubes, however, is constructionally complicated and expensive. In particular the mechanical parts of the float switch control column, such as the magnetic float, mercury switching tube, the shut-off valves on the water side and on the air side, and the lower connector member with the standpipe require continuous careful servicing, to ensure that the operative reliability and the functioning of the entire installation is in order at all times.

At the same time also constructional limits are set to the switching arrangement by the dimensions of the component parts of the magnetic float. This is an important disadvantage, since a switch spacing, once selected, and thereby also the partial pressure difference of the pressure fluid container cannot be changed at a later date.

The large spacing between the individual magnetic floats of the communicating tube which arises from constructional considerations makes itself felt in a disadvantageous manner in particular during a large and rapid removal of pressure fluid from the pressure fluid container. If the switching points were located more closely together, corresponding pumps for replenishing and maintaining the desired fluid pressure and the quantity of fluid in the pressure fluid container could be switched on earlier during rapid removal.

According to the invention, there is provided means for detecting liquid levels in a container, using ultrasonic sound, said means comprising a plurality of detection units mounted on the outside of the container and spaced over its height, each unit being able to detect the presence or absence of liquid in the container at its own level, each unit comprising a transmitter and receiver arranged so that ultrasonic sound pulses transmitted by the transmitter are received by the receiver, and a device for producing sonic pulses, which device is connected to the transmitter to pass the pulses thereto, and is connected to the receiver to receive and evaluate pulses therefrom, and is arranged to emit a signal indicating the presence or absence of liquid at the level of the unit.

The means according to the invention can therefore be used on a pressure fluid container which does not possess additional bores for the arrangement of a directly controlled contact engagement of a switching element with the pressure fluid in the pressure fluid container, or an indirect contact engagement by means of a communicating tube which in turn again is connected to the pressure fluid container by way of a shut-off valve on the water side and on the air side. Detection of the liquid level of the pressure fluid is effected by means of the sensors without direct contact with the pressure medium, because of the sensors arranged on the outer wall of the pressure fluid container.

Furthermore, because they can be relatively small, the sensors can permit a 'much closer spacing parallel to the filling level height and thereby a faster switching possibility, for example for switching on individual pumps during a large removal of pressure fluid in unit time, than was the case with magnetic floats known heretofore.

A further advantage results if the sensors are attached so that they are adjustable for position parallel to the filling level height. It is possible thereby to attach the sensors within a short period of time at any desired location along the axis of the pressure fluid container without a large technical expenditure of any kind which is further connected with additional loss of time. It thus becomes possible to attain different pressure adjustments of the pressure fluid and thereby also a consumption of pressure fluid which is different per unit time.Also, under certain circumstances, it is possible in this way to save a second pressure fluid container, since as a consequence of the possibility of arranging the sensors at a closer spacing, it is possible to switch the pumps on at an earlier instant and in this way sufficient pressure fluid is available which was not given in the arrangement theretofore by means of the float switches, in consequence of the larger space requirements. In order to be able to remove in unit time larger quantities of pressure fluid with the arrangement known heretofore of magnetic float switches, under certain circumstances a second, extremely expensive, pressure fluid container had to be installed.

The invention will now be further described by way of example, with reference to the accompanying drawings, in which: Figure 1 is a side view of a pressure fluid container including means for detecting liquid levels in the container, Figure 2 is a section on the line I-I of Figure 1, on an enlarged scale, and Figure 3 is an enlarged side view of part of the pressure fluid container.

For the purpose of detecting the presence or absence of liquid at a particular height in the container, a pair of ultrasonic sound sensors 7,8 (transmitter 7 and receiver 8) is attached to the outer wall 6 of a pressure fluid container 1 which is connected at its head portion 2 through a conduit 3 to a source of compressed air (not illustrated), and at its foot portion through a conduit 5 to high pressure fluid pumps (not illustrated). Each pair of sensors 7,8 is associated with a switching device 9 which is connected to the sensor transmitter 7 by means of a cable 10 and to the sensor receiver 3 by means of a cable 1 The device 9 is positioned so that the lengths of cables 1 0 and 11 are as short as possible.In the present example the sensor transmitter 7 and the sensor receiver 8 are attached at mutually opposite positions, with their axes of symmetry in line, to the outer wall 6 of the pressure fluid container 1. The attachment is effected in a mechanical manner. The contact of the sensors 7 and 8 with the pressure flu-id container 1 is obtained by means of an adhesive or binder means.

The sensors 7 and 8 together with the switching device 9 form a so-called ultrasonic sound gate. Dependently upon the presence of liquid in the respective gate region, the corresponding echo pulse is converted to electrical signals by means of a device (not illustrated) located in the switching device 9, whereby a contact previously free of potential is changed and thereby corresponding pumps, safety devices or valves (not illustrated) are switched.

The sound pulses are produced at a certain frequency by means of an oscillator (not illustrated) in the switching device 9. They travel then through the transmitting'sensor 7 and the medium to be sounded into the receiving sensor 8.

In the switching device 9, the arriving pulses are processed to switching signals and used by a relay (likewise not illustrated) for switching control processes.

The switching devices 9 are secured to the pressure fluid container 1 by means of two half shell pipe clips 12, secured by screws 13, which correspond to the outer diameter of the pressure fluid container 1. In contrast the sensors 7 and 8 are attached to the container by a special steel band 14 which may be approximately 0.5 mm thick and which surrounds the periphery of the pressure fluid container 1. In consequence of its elasticity the steel band 14 follows without difficulties in this case the possible elastic expansion of the pressure fluid container 1 owing to changes of its internal pressure. In this case the switching devices 9 are disposed preferably at the same height as the sensors 7 and 8 and at the same spacing therefrom. Thereby the connecting cables 10 and 11 have approximately the same length.The sensors 7 and 8 are provided with protective boxes 15 to prevent them from being damaged.

These so-called ultrasonic sound gates consisting of pairs of sensors 7 and 8 with the switching device 9 are combined to form a socalled "ultrasonic sound control column." For example, a respective ultrasonic sound gate is provided in the region of the highest fluid level HW and of the lowest fluid level NW. Furthermore, an ultrasonic sound gate must be disposed above HW; as a safety device it switches off all the pumps. Likewise for reasons of safety, an ultrasonic sound gate is provided below the lowest fluid level NW; it actuates an acoustic or optical warning signal.

In the space between these sensors, various ultrasonic sound gates may be attached at those levels of the pressure fluid which correspond to a certain desired pressure of the fluid, in order to switch on or off their pumps or valves of any kind.

In contrast to the known magnetic floats which are in contact with the pressure fluid, the sensors 7, 8 and the switching devices 9 are very narrow and moreover are not connected to the fluid through bores or communcating tubes. They control the fluid height in a level dependent manner, but nevertheless in a contact-less manner. Thereby the possibility exists of varying and adjusting the height of the sensors 7 and 8 on the outer wall 6 of the pressure fluid container 1 correspondingly quickly, dependently upon the choice of the pressure or the quantity of the pressure fluid to be consumed in unit time.

In the head portion 2 of the pressure fluid container 1 ,the supply conduit 3 extending from the air supply is constructed in the interior of the pressure fluid container 1 in the form of a nozzle tube 1 6 which ensures the lateral issue of the air and thus prevents disturbance of the liquid surface.

Claims

1. Means for detecting liquid levels in a container, using ulstrasonic sound, said means comprising a plurality of detection units mounted on the outside of the container and spaced over its height, each unit being able to detect the presence or absence of liquid in the container at its own level, each unit comprising a transmitter and receiver arranged so that ultrasonic sound pulses transmitted by the transmitter are received by the receiver, and a device for producing sound pulses, which device is connected to the transmitter to pass the pulses thereto, and is connected to the receiver to receive and evaluate pulses therefrom, and is arranged to emit a signal indicating the presence or absence of liquid at the level of the unit.

2. Means as claimed in claim 1, wherein the detecting units are adjustable in position over the height of the container.

3. Means as claimed in claim 1 or claim 2, wherein the sonic pulse producing devices of the various units emit signals to switch on or off pumps, safety devices or valves.

4. Means for detecting liquid levels in a container, substantially as herein described with reference to and as shown in the accompanying drawings.