Patent Description:
Leakage of gas from gas installations, pipe lines and their components might be very dangerous for the environment, and human and animal health, especially if the gas is toxic, flammable or corrosive. If such gas leak happens e.g. as an accident, it is important to detect the leak as soon as possible. The leak may also be quantitatively measured to determine if the leak is above certain threshold value for alarm, and also to determine any further steps that should be taken to stop the leak. Therefore, gas detectors may be used in areas where this potential for gas leaks.

Reference may be made to <CIT>, which relates to a sound sensor in the form of a compression assembly for detecting airborne sound, and comprises a piezoelectric crystal transducer, an electrode and a low density environmental seal.

The present invention relates to an ultrasonic gas detector according to claim <NUM> and to a method for forming an ultrasonic gas detector according to claim <NUM>.

Specific embodiments are defined in the dependent claims.

It should be understood at the outset that although illustrative implementations of one or more embodiments are illustrated below, the disclosed systems and methods may be implemented using any number of techniques, whether currently known or not yet in existence. The disclosure should in no way be limited to the illustrative implementations, drawings, and techniques illustrated below, but may be modified within the scope of the appended claims.

Leakage of gas from gas installations, pipe lines and their components might be very dangerous for the environment, as well as human and animal health, especially if the gas is toxic, flammable or corrosive. If such a gas leak happens, for example as an accident, it needs to be detected as soon as possible, and quantitatively measured to determine if the leak of gas is above an alarm threshold value. If the gas is above the threshold, the alarm may sound, allowing for safe evacuation. Additionally, some part of the gas installation may need to be switched off and insulated in order to stop the gas leak.

In some cases, gas leakages from pressurized source produce sound, which typically have frequencies in audible and ultrasonic range. An ultrasonic detector may be capable of detecting this ultrasound (at ultrasonic frequency), and therefore detect the gas leak. An ultrasonic detector would signal the level of this ultrasound, thereby triggering an alarm if the ultrasound level is above certain, preset threshold.

Referring to <FIG>, an ultrasonic detector <NUM> is described. The ultrasonic gas detector <NUM> comprises a piezoelectric element <NUM> operable to convert the pressure of sound waves from mechanical energy into electric signal. The ultrasonic sound waves coming from the environment are illustrated by the arrow <NUM>. The ultrasonic detector <NUM> further comprises a protective cover <NUM>, a hot melt adhesive <NUM> (which may be used as an acoustic filler), one or more perforated metal electrodes <NUM> and <NUM> with openings (holes and slots) <NUM> and <NUM> filled with solder, one or more layers of solder <NUM> and <NUM>, the piezoelectric sensing element <NUM> comprising silver electrodes, and a support <NUM>. The protective cover <NUM> comprises a low density material, such as Polytetrafluoroethylene (PTFE), polyethylene (PE), or another low density material. One or more of the described elements may be attached to one another with adhesive.

The piezoelectric element <NUM> is soldered to the perforated metal electrodes <NUM> and <NUM> that connect it to an electronic circuit. Perforation of the metal electrode(s) <NUM> and <NUM> allows the electrode(s) <NUM> and <NUM> to be attached to the piezoelectric element <NUM> in a way that provides stability for a broad range of temperatures, as these holes <NUM> and <NUM> are filled with solder material. Perforation also simplifies the soldering process, as the solder paste <NUM> and <NUM> penetrates easily through the perforated holes <NUM> and <NUM> and stops the silver electrode(s) of the piezoelectric element <NUM> from being dissolved in the solder during the soldering process. The hot melt adhesive <NUM> is used as acoustic filler for the space between the ultrasound exposed area of the piezoelectric element <NUM> and the protective cover <NUM>. The molten hot melt material solidifies on contact with the piezoelectric element and casing, stopping leakage into the housing while maintaining excellent acoustic and waterproof sealing properties. Hot melt material cools in a matter of minutes allowing for a simpler manufacturing process.

Using the low density material for the protective cover <NUM> for the ultrasonic detector <NUM> is beneficial as it is resistant to many aggressive chemicals in a broad temperature range but allows the ultrasound waves to pass through to the piezoelectric element <NUM>. In other applications, a piezoelectric element may be conductively connected to metal electrodes both with conductive glue and soldering. Applicants have discovered that perforated metal electrodes <NUM> and <NUM> soldered to the piezoelectric element <NUM> can survive multiple temperature shocks, which may relate to or demonstrate aging of device and the influence of the environment on it.

Referring now to <FIG>, two exploded views of an ultrasonic detector <NUM> are shown. The ultrasonic detector <NUM> may be similar to the ultrasonic detector <NUM> of <FIG>, wherein the ultrasonic detector <NUM> may comprise a piezoelectric element <NUM>, a protective cover <NUM>, a hot melt adhesive <NUM> (which may be used as an acoustic filler), one or more perforated metal electrodes <NUM> and <NUM> and a support <NUM>, wherein these elements may be similar to the piezoelectric element <NUM>, protective cover <NUM>, hot melt adhesive <NUM>, perforated metal electrodes <NUM> and <NUM>, and support <NUM> described in <FIG>.

Additionally, the ultrasonic detector <NUM> comprises one or more casing elements <NUM> and <NUM> operable to enclose and house the other elements of the ultrasonic detector <NUM>. In some embodiments, the casing elements <NUM> and <NUM> may comprise a metal material and may be held together by one or more screws <NUM>. In some embodiments, the ultrasonic detector <NUM> may comprise a printed circuit board (PCB) <NUM> operable to receive ultrasonic data from the piezoelectric element <NUM> and electrodes <NUM> and <NUM>, wherein the electrodes <NUM> and <NUM> may connect to, or contact, the PCB <NUM>. The ultrasonic detector <NUM> comprises supporting elements and insulating elements for supporting and insulating the other elements of the ultrasonic detector <NUM>. For example, a foam support <NUM> may be located within the casing elements <NUM> and <NUM>. Additionally, an insulator <NUM> (which may be made of a plastic material) is located in proximity to the electrodes <NUM> and <NUM>, and is operable to prevent shorting between the metal electrodes <NUM> and <NUM> and the metal casing elements <NUM> and <NUM>.

Soldering of the electrode(s) to the piezoelectric element may be done at temperature of +<NUM> degrees Celsius (C) for up to <NUM> seconds. This temperature is beneath the Curie temperature of the piezoelectric material, which is +<NUM> degrees C, and this protects the piezoelectric element from losing its sensitivity.

Using of a low density material as front protective layer of the ultrasonic sensor allows stopping bimetallic corrosion between the metal body of ultrasonic sensor and the metal body of the instrument enclosure, as those two might be made from different metals. The protective cover with an O-ring above it seals the ultrasonic sensor inside the main instrument enclosure.

Some embodiments of the disclosure may include one or more methods for forming an ultrasonic detector. The method may comprise providing a piezoelectric element operable to convert the pressure of sound waves from mechanical energy into electric signal; soldering the piezoelectric element to one or more perforated metal electrodes with holes and slots filled with the solder material; attaching a protective cover comprising a low density material operable to allow sound to pass through to the piezoelectric element; attaching the one or more electrodes to a printed circuit board; and assembling at least some of the above elements within a casing.

Attaching the protective cover comprises attaching a hot melt adhesive between the protective cover and the piezoelectric element. The hot melt adhesive may be used as an acoustic filler. In some embodiments, the method may further comprise providing one or more support elements within the casing for supporting the elements and preventing movement of the elements within the casing. The method further comprises providing one or more insulating elements to insulate the metal electrodes from contacting the casing.

In some embodiments, the ultrasonic detector may further comprise a printed circuit board (PCB) operable to receive ultrasonic data from the piezoelectric element and electrodes, wherein the electrodes connect to, or contact, the PCB.

In some embodiments, the casing elements are held together by one or more screws. The piezoelectric element is soldered to the perforated metal electrodes, and the metal electrodes connect the piezoelectric element to an electronic circuit. In some embodiments, the solder material fills the perforations, holes and slots, of the metal electrodes, allowing the electrodes to be attached to the piezoelectric element in a way that provides stability for a broad range of temperatures. In some embodiments, the hot melt adhesive is used as acoustic filler for the space between the ultrasound exposed area of the piezoelectric element and the protective cover. In some embodiments, the molten hot melt material freezes on contact with the piezoelectric element and casing stopping leakage into the housing while maintain excellent acoustic and waterproof sealing properties. In some embodiments, the protective cover comprises one of Polytetrafluoroethylene (PTFE) and polyethylene (PE). The low density material of the protective cover is resistant to many aggressive chemicals in a broad temperature range but allows the ultrasound waves to pass through to the piezoelectric element. In some embodiments, soldering of the electrode(s) to the piezoelectric element is done at temperature of +<NUM> degrees Celsius (C) for up to <NUM> seconds. The ultrasonic detector further comprises one or more layers of adhesive operable to attach one or more of the above elements.

While various embodiments in accordance with the principles disclosed herein have been shown and described above, modifications thereof may be made by one skilled in the art. The embodiments described herein are representative only and are not intended to be limiting. Many variations, combinations, and modifications are possible and are within the scope of the disclosure. Alternative embodiments that result from combining, integrating, and/or omitting features of the embodiment(s) are also within the scope of the disclosure. Accordingly, the scope of protection is not limited by the description set out above, but is defined by the claims which follow. Furthermore, any advantages and features described above may relate to specific embodiments, but shall not limit the application of such issued claims to processes and structures accomplishing any or all of the above advantages or having any or all of the above features.

Use of broader terms such as comprises, includes, and having should be understood to provide support for narrower terms such as consisting of, consisting essentially of, and comprised substantially of. Use of the term "optionally," "may," "might," "possibly," and the like with respect to any element of an embodiment means that the element is not required, or alternatively, the element is required, both alternatives being within the scope of the embodiment(s). Also, references to examples are merely provided for illustrative purposes, and are not intended to be exclusive.

present examples are to be considered as illustrative and not restrictive, and the intention is not to be limited to the details given herein. For example, the various elements or components may be combined or integrated in another system or certain features may be omitted or not implemented.

Claim 1:
An ultrasonic gas detector (<NUM>) comprising:
a piezoelectric element (<NUM>) configured to convert the pressure of sound waves from mechanical energy into electric signal;
one or more perforated metal electrodes (<NUM> and <NUM>) located proximate to the piezoelectric element (<NUM>);
one or more layers of solder (<NUM> and <NUM>) configured to attach the one or more perforated metal electrodes (<NUM> and <NUM>) to the piezoelectric element (<NUM>);
a protective cover (<NUM>) comprising a low density material, the protective cover located on a first surface of the combined piezoelectric element (<NUM>) and one or more perforated metal electrodes (<NUM> and <NUM>);
a hot melt adhesive (<NUM>) configured to attach the protective cover (<NUM>) to the first surface of the combined piezoelectric element (<NUM>) and one or more perforated metal electrodes (<NUM> and <NUM>);
one or more support elements (<NUM>) located proximate to the combined piezoelectric element (<NUM>) and one or more perforated metal electrodes (<NUM> and <NUM>), wherein the ultrasonic gas detector is configured to detect an ultrasound;
one or more casing elements (<NUM> and <NUM>) operable to enclose and house the other elements of the ultrasonic detector (<NUM>); and
an insulator (<NUM>) located in proximity to the one or more perforated metal electrodes (<NUM> and <NUM>), and operable to prevent shorting between the one or more perforated metal electrodes (<NUM> and <NUM>) and the one or more casing elements (<NUM> and <NUM>).