Device for monitoring a predetermined level of a liquid in a container

• US 5,836,192 A
• Filed: 10/16/1996
• Issued: 11/17/1998
• Est. Priority Date: 10/17/1995
• Status: Expired due to Fees

• Current Assignee: Endress+Hauser GmbH+Co (ENDRESS)
• Original Assignee: Endress+Hauser GmbH+Co (ENDRESS)
• Inventors: Lopatin, Sergej, Getman, Igor, Muller, Roland
• Primary Examiner(s): Gutierrez, Diego F.F.
• Assistant Examiner(s): HIRSHFELD, ANDREW HOWARD
• Application Number:
  US08/733,099
• Time in Patent Office: 762 Days
• Field of Search: 73/290 V, 73/866.5, 340/618, 340/621, 367/157, 367/159, 367/162, 367/163, 367/165, 367/908, 181/124
• US Class Current: 73/290.00V
• CPC Class Codes: B06B 1/06 operating with piezoelectric effect or with electrostriction piezoelectric or electrostrictive devices per se H10N30/00
• CPC Class Codes: G01F 23/2965 Measuring attenuation of transmitted waves
• CPC Class Codes: G01F 23/2968 Transducers specially adapted for acoustic level indicators
• CPC Class Codes: Y10S 367/908 Material level detection, e.g. liquid level

Abstract

For monitoring a predetermined level of a liquid in a container an ultrasonic transducer is fitted on the outer surface of the container wall at a measurement point situated at the height of the level to be monitored. The ultrasonic transducer contains a piezoelectric element which generates, when excited by an alternating voltage pulse having a given transmission frequency, an ultrasonic transmission pulse which is transferred via a diaphragm to the container wall and which converts ultrasonic vibrations transferred from the container wall to the ultrasonic transducer into electrical reception signals. So that the piezoelectric element for given dimensions can be operated in a large frequency range, and so that a good adaptation to the diaphragm is achieved, the piezoelectric element consists of a porous piezoelectric ceramic having a type 3--3 connectivity.

Claims

1. A device for monitoring a predetermined level of a liquid in a container comprising an ultrasonic transducer fitted on the outer surface of the container wall at a measurement point situated at the height of the level to be monitored and containing a piezoelectric element arranged in a transducer housing, said piezoelectric element generates, when excited by an alternating voltage pulse having a given transmission frequency, an ultrasonic transmission pulse which is transferred via a diaphragm to the container wall and converts ultrasonic vibrations transferred from the container wall to the ultrasonic transducer into electrical reception signals, said piezoelectric element consisting of a porous piezoelectric ceramic having a type 3--3 connectivity, said transducer housing being at least partially filled with a potting compound, an acoustical insulating member being positioned on the side of the piezoelectric element facing away from said diaphragm providing acoustical insulation between said piezoelectric element and said potting compound and preventing contact between said piezoelectric element and said potting compound.

2. The device as set forth in claim 1, wherein said porous piezoelectric ceramic is lead-zirconate titanate (PZT).

3. The device as set forth in claim 1, wherein said acoustical insulating member is a disk of a closed-pore foamed silicone material.

4. The device as set forth in claim 3, comprising a mounting sleeve in which said piezoelectric element together with said acoustical insulating member is installed outside of said transducer housing and which is configured so that after insertion in said transducer housing and prior to filling with said potting compound it maintains said acoustical insulating member in sealing contact with the surface of said piezoelectric element facing away from said diaphragm.

5. The device as set forth in claim 4, wherein between the surfaces of said diaphragm and said piezoelectric element facing each other a hot-curable adhesive is introduced which following insertion of said mounting sleeve in said transducer housing is hardened by being heated.

6. The device as set forth in claim 1, wherein said transducer housing is made of plastics and is pot-shaped, and said piezoelectric element rests on the bottom of said transducer housing which serves as the diaphragm.