EP0245671A1 - Central bolt ultrasonic atomizer - Google Patents

Central bolt ultrasonic atomizer Download PDF

Info

Publication number
EP0245671A1
EP0245671A1 EP87105667A EP87105667A EP0245671A1 EP 0245671 A1 EP0245671 A1 EP 0245671A1 EP 87105667 A EP87105667 A EP 87105667A EP 87105667 A EP87105667 A EP 87105667A EP 0245671 A1 EP0245671 A1 EP 0245671A1
Authority
EP
European Patent Office
Prior art keywords
atomizing
section
passage
cylindrical
transducer assembly
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP87105667A
Other languages
German (de)
French (fr)
Other versions
EP0245671B1 (en
Inventor
Harvey L. Berger
Alan Paul
William J. Broe
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sono Tek Corp
Original Assignee
Sono Tek Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sono Tek Corp filed Critical Sono Tek Corp
Priority to AT87105667T priority Critical patent/ATE71201T1/en
Publication of EP0245671A1 publication Critical patent/EP0245671A1/en
Application granted granted Critical
Publication of EP0245671B1 publication Critical patent/EP0245671B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B05SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05BSPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B17/00Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups
    • B05B17/04Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods
    • B05B17/06Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods using ultrasonic or other kinds of vibrations
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B05SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05BSPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B17/00Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups
    • B05B17/04Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods
    • B05B17/06Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods using ultrasonic or other kinds of vibrations
    • B05B17/0607Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods using ultrasonic or other kinds of vibrations generated by electrical means, e.g. piezoelectric transducers
    • B05B17/0623Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods using ultrasonic or other kinds of vibrations generated by electrical means, e.g. piezoelectric transducers coupled with a vibrating horn
    • B05B17/063Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods using ultrasonic or other kinds of vibrations generated by electrical means, e.g. piezoelectric transducers coupled with a vibrating horn having an internal channel for supplying the liquid or other fluent material
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B05SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05BSPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B17/00Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups
    • B05B17/04Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods
    • B05B17/06Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods using ultrasonic or other kinds of vibrations
    • B05B17/0607Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods using ultrasonic or other kinds of vibrations generated by electrical means, e.g. piezoelectric transducers
    • B05B17/0623Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods using ultrasonic or other kinds of vibrations generated by electrical means, e.g. piezoelectric transducers coupled with a vibrating horn
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B05SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05BSPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B3/00Spraying or sprinkling apparatus with moving outlet elements or moving deflecting elements
    • B05B3/14Spraying or sprinkling apparatus with moving outlet elements or moving deflecting elements with oscillating elements; with intermittent operation
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23DBURNERS
    • F23D11/00Burners using a direct spraying action of liquid droplets or vaporised liquid into the combustion space
    • F23D11/34Burners using a direct spraying action of liquid droplets or vaporised liquid into the combustion space by ultrasonic means or other kinds of vibrations
    • F23D11/345Burners using a direct spraying action of liquid droplets or vaporised liquid into the combustion space by ultrasonic means or other kinds of vibrations with vibrating atomiser surfaces

Definitions

  • the present invention relates to piezoelectric ultrasonic atomizers, particularly of the type having an atomizing surface at a tip of a reduced diameter amplifying probe at one end of a transducer and a coaxial fluid delivery channel extending from the other end of the transducer to the atomizing surface.
  • Piezoelectric ultrasonic atomizers are finding increasing use in industrial applications where liquid materials must be delivered in the form of a very fine spray or mist.
  • the design and construction of such atomizers is described in U.S. Patent No. 4,337,896 of BERGER et al.
  • a typical arrangement is to sandwich a flat electrode between two disks or piezoelectric material, such as lead zirconate titanate, to form a driving element, and then to clamp the driving element between a cylindrical front amplifying horn and a cylindrical rear dummy section.
  • the amplifying horn is provided with a reduced diameter probe having an atomizing surface at its tip.
  • the amplification of vibrational amplitude obtained at the atomizing surface is approximately equal to the ratio between the respective cross-sectional areas of the cylindrical portion of the front horn and of the end of the probe.
  • the clamping flange design has drawbacks, however.
  • the front and rear horns should each be made as a single piece. It is wasteful to have to start with stock having an outer diameter equal to the flange diameter and then machine as much as two-thirds of it away. More importantly, the size of droplets formed by an ultrasonic atomizer varies inversely with the frequency of the unit. To obtain very small particles in the micron range, it is necessary to use very high frequencies, well over 100 kHz. To avoid significant transverse wave motion in the transducer, however, the transverse dimensions of the front and rear sections should be less than one-­quarter wavelength.
  • a quarter wavelength at frequencies above 100 kHz is less than one centimeter.
  • Another object of the invention is to provide external sealing of the piezoelectric elements in an atomizer as characterized above without exially loading the transducer element.
  • an ultrasonic liquid atomizing transducer assembly comprising a driving element including a pair of annular piezoelectric disks and an annular electrode coaxially positioned therebetween; terminal means for feeding ultrasonic frequency electrical energy to said electrode; a cylindrical rear dummy section having a front end contacting one piezoelectric disk of the driving element and a rear end; a front section having a cylindrical portion, the cylindrical portion having a rear end contacting the other piezoelectric disk of the driving element and a front end, and an amplifying portion extending from the front end of the cylindrical portion, the amplifying portion comprising a probe having a tip that forms an atomizing surface, an axial passage being provided through the length of the transducer from the rear end of the rear dummy section to the atomizing surface and a portion of the passage adjacent the driving element in at least one of the front section and the rear dummy section being enlarged and internally threaded; and a tubular central bolt having external threads engaging said internally threade
  • the enlarged internally threaded portion of the passage in the atomizing transducer assembly preferably extends into both the front section and the rear section, and the central bolt comprises a threaded stud engaging the internaly threaded portion in both the front and rear sections, the threaded stud having a front end formed with a smooth sealing surface, and the assembly further includes an annular sealing means disposed between said sealing surface and the axial passage to prevent liquid flowing in the passage from reaching the inner surface of the piezoelectric disks.
  • the assembly may further comprise an enclosed shell surrounding the transducer assembly, the shell having a front end wall provided with an opening that slidably receives the cylindrical portion of the front section and a radially compressed annular sealing means disposed between the opening and the circumference of the cylindrical portion of the front section.
  • the shell further has a rear wall that may be provided with an opening that slidably receives an axial feed tube extending from the rear end of the rear dummy section and a radially compressed annular sealing means disposed between the opening and the feed tube.
  • an ultrasonic atomizing transducer assembly 11 includes a transducer 12 having a driving element 13, a rear dummy section 14, and a front atomizing section 15.
  • the driving element 13 is assembled from a washer-­shaped metal electrode 16 sandwiched between a pair of annular piezoelectric disks 17 and 18.
  • the electrode may be made of copper or any other suitable metal having high electrical conductivity, and it is provided with a terminal 19 for attachment to a source of electrical energy at the resonant frequency of the transducer.
  • the piezoelectric disks are made of any material conventionally used for such service, such as barium titanate or lead zirconate titanate.
  • the rear dummy section 14 is a metal cylinder, preferably titanium, having a length equal to a quarter wavelength at the designed operating frequency of the transducer.
  • a front end 20 of the rear section 14 contacts the rear piezoelectric disk 18, and a rear end 21 of the rear section is free to vibrate as an antinodal plane.
  • the front atomizing section 15 includes a cylindrical portion 22 having a rear end 23 that contacts the front piezoelectric disk 17 and a front end 24 that lies in a nodal plane, the cylindrical portion 22 being designed to be one-half wavelength long at the operating frequency of the transducer. From the front end of the cylindrical portion 22, a quarter wavelength amplifying probe 25 extends to a frustoconical tip 26 having an atomizing surface 27.
  • the front atomizing section preferably is made of the same material as the rear dummy section, although a different material could be used if desired, so long as the appropriate wavelength dimensions were used to match the operating frequency of the rear section.
  • the outer diameter of the transducer is equal to the diameters of the front and rear sections. These sections are clamped against the driving element 13 with a predetermined compressive stress by a central tubular bolt 29 that is formed as an enlarged threaded stud on the end of a liquid feed tube 30.
  • the tubular bolt engages an internally threaded enlarged portion 31 of an axial passage 32 that extends through the transducer from the rear end of the rear dummy secton 14 to open onto the atomizing surface at the tip of the probe 25.
  • an O-­ring seal 33 is provided between a smooth sealing surface 34 machined on the front end of the central bolt 29 and the inner surface of the passage 32.
  • the O-ring is fitted into a circumferential groove machined into the wall of the passage to assure that the O-ring is properly located with respect to the sealing surface 34.
  • the groove could equally well be formed on the end of the bolt, or any other conventional sealing arrangement could be used between the end of the bolt and the inner surface of the passage in the front section.
  • An additional O-ring 35 is provided to seal between the outer circumference of the feed tube 30 and the inner circumference of the axial passage. This second O-ring prevents ingress of moisture from the environment surrounding the atomizer.
  • This shell is in the form of a cylindrical cup 37 having a screw cap 38.
  • the cup 37 has an end wall 39 provided with an opening 40 which receives the cylindrical portion 22 of the front section of the transducer. This opening is sealed by a radially compressed O-ring 41 disposed between the outer circumference of the cylindrical portion 22 and a counterbore 42 in the opening 40.
  • the screw cap 38 has an end wall 43 with a similar but smaller opening 44.
  • O-ring 45 in a counterbore 46 seals this opening in the same way as O-ring 41 seals the front opening. As illustrated, O-ring 45 is radially compressed between the counterbore 46 and a cylindrical collar 47 extending from the end 21 of the rear dummy section.
  • the dimensions of the collar and the counterbore could be revised so that the O-ring 45 could seal radially against the outer periphery of the feed tube 30 and abut against the end of the collar. It is important, however, that there be no axial compression force exerted by the shell against the transducer body via the O-rings 41 and 45.
  • the narrow flange 28 at the rear of the front section serves merely to locate the O-ring 41 as close as possible to the nodal plane defined by the electrode 16. There should be no axial force exerted against this flange by the O-ring since the O-ring 45 at the rear of the shell has room to float axially. Consequently, the transducer is supported in the shell substantially purely radially, with no axial force exerted between the shell and the transducer.
  • the procedure for assembling the transducer is as follows. After the O-ring 33 is installed into its groove in the front section 22, the central bolt is screwed into the front section until it bottoms. The piezoelectric disks and the center electrode are then passed over the bolt. If desired, a sleeve of electrical insulating material (not shown) may be inserted between the bolt and the inner circumferences of the disks and electrode. This will help to center the driving element as well as to prevent a short circuit of the driving element. It also may be desirable to add a second annular electrode (not shown) between the rear piezoelectric disk and the rear dummy section to provide a second terminal to facilitate completing the electrical circuit across the piezoelectric disks.
  • the O-ring 35 is fitted over the feed tube 30, and the rear dummy section is then screwed down against the driving element.
  • the proper compression force is obtained by applying a torque wrench to two diametrically spaced detent holes 48 drilled in the rear end 21 of the rear dummy section.
  • the shell can be mounted by first installing O-ring 45 on the collar 47 (or on the tube 30 in the above-mentioned alternative arrangement) and then sliding the threaded cap 38 over the tube 30 into place over the rear dummy section.
  • a lead wire 49 attached to a hermetically sealed coaxial fitting 50 mounted on the end wall of the cap is then clipped or soldered to terminal 19 of the center electrode 16.
  • a second electrode is provided, as described above, a second lead wire (not shown) from a second coaxial fitting (not shown) should be similarly attached to the second electrode.
  • the O-ring 41 is placed on the cylindrical portion 22 of the front atomizing section, and the cup 37 is slipped onto the cylindrical section 22 and screwed into the cap 38 until it bottoms.
  • the cap can be tightened by means of a spanner wrench fitting the detent holes 51 in the end wall of the cap.
  • the transducer Since the transducer is connected to the shell only radially through the "axially floating" O-rings 41 and 45, the transducer can be mounted by clamping or fastening to the shell in any desired way without adversely affecting either the compression preload on the driving element 13 or the resonant frequency of the transducer.
  • Liquid can be delivered to the rear of the unit via a flexible hose (not shown) connected to the delivery tube 30 by the standard coupling connectors 52 (see Fig. 1).
  • the assembly can be supported by a rigid liquid supply pipe coupled to the delivery tube 30.
  • an atomizing transducer was built and tested.
  • the dimensions were chosen for an operating frequency of about 56 kHz.
  • the front and rear transducer sections were made of titanium and the central bolt was made of 316 stainless steel, to provide corrosion resistance for a wide variety of operating liquids. Due to the relatively low yield strength of this material, however, it is a marginal choice particularly for higher frequencies, because the bolt may have to be torqued beyond its yield point to obtain the required compression on the piezoelectric disks. Thus, in applications where corrosion resistance is not a prime consideration, it may be preferable to use a stronger steel for the central bolt material.
  • the design of the present invention is adapted to provide an ultrasonic atomizing transducer that is simple to manufacture and is completely shielded from damp or hazardous environments, such as explosive atmospheres.
  • the central bolt could be integrally formed as part of the rear or front section in applications where the material of the section is strong enough to carry the necessary tensile stress for preloading the piezoelectric disks.

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Special Spraying Apparatus (AREA)
  • Apparatuses For Generation Of Mechanical Vibrations (AREA)
  • Nozzles (AREA)
  • Catching Or Destruction (AREA)

Abstract

An ultrasonic atomizing transducer assembly (11) includes cylindrical front atomizing and rear dummy sections (14) clamped to a sandwich of an annular electrode (16) between two annular piezoelectric disks (17, 18) by a central tubular bolt (29). Liquid to be atomized enters the rear of the transducer assembly (11) through a feed tube (30) forming a rearward extension of the central bolt (29) and flows through an axial passage to exit onto an atomizing surface (27) on the tip of an amplifying probe (25) extending from the front end of the front cylindrical section. An annular sealing member (33) disposed between a sealing surface (34) at the front end of the bolt (29) and the passage prevents liquid flowing through the passage from contacting the inner surfaces of the piezoelectric disks (17, 18). To protect the outer surfaces of the piezoelectric disks (17, 18), an enclosed shell surrounds and supports the transducer via O-rings loaded purely in radial compression.

Description

    BACKGROUND OF THE INVENTION 1. Technical Field.
  • The present invention relates to piezoelectric ultrasonic atomizers, particularly of the type having an atomizing surface at a tip of a reduced diameter amplifying probe at one end of a transducer and a coaxial fluid delivery channel extending from the other end of the transducer to the atomizing surface.
  • 2. Background Art.
  • Piezoelectric ultrasonic atomizers are finding increasing use in industrial applications where liquid materials must be delivered in the form of a very fine spray or mist. The design and construction of such atomizers is described in U.S. Patent No. 4,337,896 of BERGER et al. A typical arrangement is to sandwich a flat electrode between two disks or piezoelectric material, such as lead zirconate titanate, to form a driving element, and then to clamp the driving element between a cylindrical front amplifying horn and a cylindrical rear dummy section. The amplifying horn is provided with a reduced diameter probe having an atomizing surface at its tip. The amplification of vibrational amplitude obtained at the atomizing surface is approximately equal to the ratio between the respective cross-sectional areas of the cylindrical portion of the front horn and of the end of the probe.
  • In the type of atomizer shown in U.S. Patent No. 4,337,896, the necessary clamping pressure on the driving element is obtained by providing circumferential flanges on the adjacent ends of the front and rear sections and drawing the flanges together with a circle of bolts. The flanges also provide an annular bearing area for compressing an elastomeric gasket ring, to prevent liquid spray from contacting the outer peripheries of the piezoelectric disks. The sealing effectiveness of such a gasket is an important factor in extending the operating life of the atomizer.
  • The clamping flange design has drawbacks, however. To reduce internal losses, the front and rear horns should each be made as a single piece. It is wasteful to have to start with stock having an outer diameter equal to the flange diameter and then machine as much as two-thirds of it away. More importantly, the size of droplets formed by an ultrasonic atomizer varies inversely with the frequency of the unit. To obtain very small particles in the micron range, it is necessary to use very high frequencies, well over 100 kHz. To avoid significant transverse wave motion in the transducer, however, the transverse dimensions of the front and rear sections should be less than one-­quarter wavelength.
  • As an example, in titanium a quarter wavelength at frequencies above 100 kHz is less than one centimeter.
  • It is desirable to have the ratio between cylindrical section diameter and probe tip diameter be as large as possible, for increased amplification. At the same time, the atomizing surface should be large enough to handle a reasonable flow and the probe must be sturdy enough to resist breaking in operation. These factors make it undesirable to use up part of the diametral dimensions for clamping flanges.
  • An alternative arrangement for clamping a cylindrical atomizing transducer and concurrently protecting the piezoelectric elements from liquid contamination is disclosed in U.S. Patent No. 3,861,852 of BERGER. In this arrangement, a cylindrical transducer is inserted into a cup, and the transducer elements are clamped together by force exerted upon a flange on the rear dummy section by a cap threaded into the cup, with the front face of the transducer bearing against the base of the cup. O-rings at the clamping surfaces seal the transducer inside the cup from liquid spray delivered from the tip of a probe extending through an opening in the base of the cup. It is difficult to apply and maintain the proper clamping pressure on the piezoelectric driving element with this arrangement, however, and the end clamping can introduce significant damping and thereby reduce efficiency of the transducer.
  • Although liquid is fed to the above-described atomizers through a radial passage that intersects an axial channel in the front horn of the transducer, it is also known, for example from U.S. Patent No. 4,352,459 of BERGER et al., to feed the liquid axially through the rear section of a flange-clamped transducer. It is necessary in this design, however, to provide an annular sealing gasket between the feed tube and the inner circumferences of the piezoelectric disks, thus reducing the potential cross sectional area of the disks and thereby the available vibrational driving power. It is also known to clamp the driving element of piezoelectric transducer by means of a solid central bolt, as in U.S. Patents No. 3,368,085 of McMASTER et al., No. 3,396,285 of MINCHENKO, No. 3,689,783 of WILLIAMS, and No. 3,694,675 of LOVEDAY. The transducers of these patents are not fluid feed atomizers, however.
  • SUMMARY OF THE INVENTION
  • It is an object of the present invention to provide a piezoelectric atomizer design having a maximum practical amplification and adapted for high frequency operation above 100 kHz.
  • It is another object of the present invention to provide an axial feed piezoelectric atomizer that provides effective internal sealing without reducing the cross-sectional area available for the piezoelectric elements.
  • Another object of the invention is to provide external sealing of the piezoelectric elements in an atomizer as characterized above without exially loading the transducer element.
  • The above and other objects are achieved in an ultrasonic liquid atomizing transducer assembly comprising
    a driving element including a pair of annular piezoelectric disks and an annular electrode coaxially positioned therebetween;
    terminal means for feeding ultrasonic frequency electrical energy to said electrode;
    a cylindrical rear dummy section having a front end contacting one piezoelectric disk of the driving element and a rear end;
    a front section having a cylindrical portion, the cylindrical portion having a rear end contacting the other piezoelectric disk of the driving element and a front end, and an amplifying portion extending from the front end of the cylindrical portion, the amplifying portion comprising a probe having a tip that forms an atomizing surface, an axial passage being provided through the length of the transducer from the rear end of the rear dummy section to the atomizing surface and a portion of the passage adjacent the driving element in at least one of the front section and the rear dummy section being enlarged and internally threaded; and
    a tubular central bolt having external threads engaging said internally threaded portion of the passage and connecting the front section and the rear dummy section under tension to provide a predetermined compressive preload on the driving element.
  • The enlarged internally threaded portion of the passage in the atomizing transducer assembly preferably extends into both the front section and the rear section, and the central bolt comprises a threaded stud engaging the internaly threaded portion in both the front and rear sections, the threaded stud having a front end formed with a smooth sealing surface, and the assembly further includes an annular sealing means disposed between said sealing surface and the axial passage to prevent liquid flowing in the passage from reaching the inner surface of the piezoelectric disks.
  • To prevent liquid contact with the outer surfaces of the piezoelectric disks, the assembly may further comprise an enclosed shell surrounding the transducer assembly, the shell having a front end wall provided with an opening that slidably receives the cylindrical portion of the front section and a radially compressed annular sealing means disposed between the opening and the circumference of the cylindrical portion of the front section. The shell further has a rear wall that may be provided with an opening that slidably receives an axial feed tube extending from the rear end of the rear dummy section and a radially compressed annular sealing means disposed between the opening and the feed tube.
  • The above and other objects, features and advantages of the present invention will be more readily apparent from the following description of the preferred embodiments when considered with the accompanying drawings and the appended claims.
  • BRIEF DESCRIPTION OF THE DRAWINGS
  • The present invention is illustrated by way of example and not limitation in the figures of the accompanying drawing in which like numerals indicate the same or similar parts and in which:
    • Fig. 1 is a partially cut away perspective view of an ultrasonic atomizing transducer assembly according to the invention, and
    • Fig. 2 is a view in longitudinal cross section of the transducer assembly of Fig. 1.
    DESCRIPTION OF THE PREFERRED EMBODIMENT
  • With reference to the figures, a currently preferred embodiment of an ultrasonic atomizing transducer assembly 11 includes a transducer 12 having a driving element 13, a rear dummy section 14, and a front atomizing section 15.
  • The driving element 13 is assembled from a washer-­shaped metal electrode 16 sandwiched between a pair of annular piezoelectric disks 17 and 18. The electrode may be made of copper or any other suitable metal having high electrical conductivity, and it is provided with a terminal 19 for attachment to a source of electrical energy at the resonant frequency of the transducer. The piezoelectric disks are made of any material conventionally used for such service, such as barium titanate or lead zirconate titanate.
  • The rear dummy section 14 is a metal cylinder, preferably titanium, having a length equal to a quarter wavelength at the designed operating frequency of the transducer. A front end 20 of the rear section 14 contacts the rear piezoelectric disk 18, and a rear end 21 of the rear section is free to vibrate as an antinodal plane. The front atomizing section 15 includes a cylindrical portion 22 having a rear end 23 that contacts the front piezoelectric disk 17 and a front end 24 that lies in a nodal plane, the cylindrical portion 22 being designed to be one-half wavelength long at the operating frequency of the transducer. From the front end of the cylindrical portion 22, a quarter wavelength amplifying probe 25 extends to a frustoconical tip 26 having an atomizing surface 27. The front atomizing section preferably is made of the same material as the rear dummy section, although a different material could be used if desired, so long as the appropriate wavelength dimensions were used to match the operating frequency of the rear section.
  • Except for a narrow circumferential flange 28 at the rear end of the front section, the outer diameter of the transducer is equal to the diameters of the front and rear sections. These sections are clamped against the driving element 13 with a predetermined compressive stress by a central tubular bolt 29 that is formed as an enlarged threaded stud on the end of a liquid feed tube 30. The tubular bolt engages an internally threaded enlarged portion 31 of an axial passage 32 that extends through the transducer from the rear end of the rear dummy secton 14 to open onto the atomizing surface at the tip of the probe 25.
  • To prevent liquid flowing through the delivery tube 30 into the passage 32 from penetrating past the threaded portion of the front section and contacting the internal surfaces of the piezoelectric disks, an O-­ring seal 33 is provided between a smooth sealing surface 34 machined on the front end of the central bolt 29 and the inner surface of the passage 32. As illustrated, the O-ring is fitted into a circumferential groove machined into the wall of the passage to assure that the O-ring is properly located with respect to the sealing surface 34. The groove could equally well be formed on the end of the bolt, or any other conventional sealing arrangement could be used between the end of the bolt and the inner surface of the passage in the front section.
  • An additional O-ring 35 is provided to seal between the outer circumference of the feed tube 30 and the inner circumference of the axial passage. This second O-ring prevents ingress of moisture from the environment surrounding the atomizer.
  • Because there are no clamping flanges on the transducer body to provide an annular area for a compressed ring gasket around the outside of the driving element, the outer peripheries of the piezoelectric disks are protected by an enclosed shell 36. This shell is in the form of a cylindrical cup 37 having a screw cap 38. The cup 37 has an end wall 39 provided with an opening 40 which receives the cylindrical portion 22 of the front section of the transducer. This opening is sealed by a radially compressed O-ring 41 disposed between the outer circumference of the cylindrical portion 22 and a counterbore 42 in the opening 40. The screw cap 38 has an end wall 43 with a similar but smaller opening 44. An O-ring 45 in a counterbore 46 seals this opening in the same way as O-ring 41 seals the front opening. As illustrated, O-ring 45 is radially compressed between the counterbore 46 and a cylindrical collar 47 extending from the end 21 of the rear dummy section.
  • Alternatively, the dimensions of the collar and the counterbore could be revised so that the O-ring 45 could seal radially against the outer periphery of the feed tube 30 and abut against the end of the collar. It is important, however, that there be no axial compression force exerted by the shell against the transducer body via the O- rings 41 and 45. In this connection, the narrow flange 28 at the rear of the front section serves merely to locate the O-ring 41 as close as possible to the nodal plane defined by the electrode 16. There should be no axial force exerted against this flange by the O-ring since the O-ring 45 at the rear of the shell has room to float axially. Consequently, the transducer is supported in the shell substantially purely radially, with no axial force exerted between the shell and the transducer.
  • The procedure for assembling the transducer is as follows. After the O-ring 33 is installed into its groove in the front section 22, the central bolt is screwed into the front section until it bottoms. The piezoelectric disks and the center electrode are then passed over the bolt. If desired, a sleeve of electrical insulating material (not shown) may be inserted between the bolt and the inner circumferences of the disks and electrode. This will help to center the driving element as well as to prevent a short circuit of the driving element. It also may be desirable to add a second annular electrode (not shown) between the rear piezoelectric disk and the rear dummy section to provide a second terminal to facilitate completing the electrical circuit across the piezoelectric disks.
  • After the driving element is assembled onto the bolt, the O-ring 35 is fitted over the feed tube 30, and the rear dummy section is then screwed down against the driving element. The proper compression force is obtained by applying a torque wrench to two diametrically spaced detent holes 48 drilled in the rear end 21 of the rear dummy section.
  • Following assembly of the transducer, the shell can be mounted by first installing O-ring 45 on the collar 47 (or on the tube 30 in the above-mentioned alternative arrangement) and then sliding the threaded cap 38 over the tube 30 into place over the rear dummy section. A lead wire 49 attached to a hermetically sealed coaxial fitting 50 mounted on the end wall of the cap is then clipped or soldered to terminal 19 of the center electrode 16. If a second electrode is provided, as described above, a second lead wire (not shown) from a second coaxial fitting (not shown) should be similarly attached to the second electrode. Finally, the O-ring 41 is placed on the cylindrical portion 22 of the front atomizing section, and the cup 37 is slipped onto the cylindrical section 22 and screwed into the cap 38 until it bottoms. The cap can be tightened by means of a spanner wrench fitting the detent holes 51 in the end wall of the cap.
  • Since the transducer is connected to the shell only radially through the "axially floating" O- rings 41 and 45, the transducer can be mounted by clamping or fastening to the shell in any desired way without adversely affecting either the compression preload on the driving element 13 or the resonant frequency of the transducer. Liquid can be delivered to the rear of the unit via a flexible hose (not shown) connected to the delivery tube 30 by the standard coupling connectors 52 (see Fig. 1). Alternatively, the assembly can be supported by a rigid liquid supply pipe coupled to the delivery tube 30.
  • To test the above-described design, an atomizing transducer was built and tested. The dimensions were chosen for an operating frequency of about 56 kHz. The front and rear transducer sections were made of titanium and the central bolt was made of 316 stainless steel, to provide corrosion resistance for a wide variety of operating liquids. Due to the relatively low yield strength of this material, however, it is a marginal choice particularly for higher frequencies, because the bolt may have to be torqued beyond its yield point to obtain the required compression on the piezoelectric disks. Thus, in applications where corrosion resistance is not a prime consideration, it may be preferable to use a stronger steel for the central bolt material.
  • In testing the completed assembly, it was found to be essential to avoid any axial loading on the O-rings of the shell; otherwise, the electrical impedance of the unit would vary over a wide range with time, making it impossible to maintain operation at peak efficiency. With purely radial compression of the O-rings, however, stable operation and repeatable results were easily obtained. The shell was leak-free even when the unit was operated submerged under water.
  • Accordingly, the design of the present invention is adapted to provide an ultrasonic atomizing transducer that is simple to manufacture and is completely shielded from damp or hazardous environments, such as explosive atmospheres. By eliminating the clamping flanges of prior designs, it is possible to obtain a high amplification factor without having the transverse dimensions of the transducer body exceed the practical limit for achieving substantially one-dimensional vibration.
  • Certain changes and modifications of the disclosed embodiment will be readily apparent to those skilled in the art. For example, the central bolt could be integrally formed as part of the rear or front section in applications where the material of the section is strong enough to carry the necessary tensile stress for preloading the piezoelectric disks. In addition, it is possible to provide many different sealing arrangements within the prescribed limitations. It is the applicants' intention, therefore, to claim all those changes and modifications which could be made to the disclosed embodiment without departing from the spirit and scope of the invention.

Claims (9)

1. An ultrasonic liquid atomizing transducer assembly comprising:
a driving element including a pair of annular piezoelectric disks and an annular electrode coaxially positioned therebetween;
terminal means for feeding ultrasonic frequency electrical energy to said electrode;
a cylindrical rear dummy section having a front end contacting one piezoelectric disk of the driving element, a rear end, and a constant outside diameter from the front end to the rear end;
a front section having a cylindrical portion, the cylindrical portion having a rear end contacting the other piezoelectric disk of the driving element and a front end, and an amplifying portion extending from the front end of the cylindrical portion, the amplifying portion comprising a probe having a tip that forms an atomizing surface, an axial passage being provided through the length of the transducer assembly from the rear end of the rear dummy section to the atomizing surface, and a portion of the passage adjacent the driving element in both the front atomizing section and the rear dummy section being enlarged and internally threaded;
a tubular central bolt comprising a hollow stud having external threads engaging said internally threaded portion of the passage in both the front atomizing section and the rear dummy section with sufficient torque to connect the front atomizing section and the rear dummy section under a tension that provides all of a predetermined total compressive preload on the driving element; and
means for sealing the piezoelectric disks from contact with the liquid being atomized, the threaded stud having a front end portion located in the front atomizing section and formed with a smooth cylindrical sealing surface; and wherein the means for sealing the piezoelectric disks comprises an annular sealing member disposed between said sealing surface and the axial passage to prevent liquid flowing in the passage from reaching the inner circumferential surfaces of the piezoelectric disks.
2. An atomizing transducer assembly according to claim 1 wherein the annular sealing member comprises an O-ring.
3. An atomizing transducer assembly according to claim 1 wherein the threaded stud has a rear end located in the rear dummy section, and the tubular central bolt further comprises an integral liquid feed tube having a smooth exterior surface extending axially from the rear end of the threaded stud beyond the rear end of the dummy section.
4. An atomizing transducer assembly according to claim 3 wherein the means for sealing the piezoelectric disks comprises an additional annular sealing member disposed between the smooth exterior surface of said liquid feed tube and the axial passage to prevent moisture in the environment surrounding the transducer assembly from reaching the inner circumferential surfaces of the piezoelectric disks.
5. An atomizing transducer assembly according to claim 4 wherein the additional annular sealing member comprises an O-ring.
6. An atomizing transducer assembly comprising:
a driving element including a pair of annular piezoelectric disks and an annular electrode coaxially positioned therebetween;
terminal means for feeding ultrasonic frequency electrical energy to said electrode;
a cylindrical rear dummy section having a front end contacting one piezoelectric disk of the driving element, a rear end, and a constant outside diameter from the front end to the rear end;
a front section having a cylindrical portion, the cylindrical portion having a rear end contacting the other piezoelectric disk of he driving element and a front end, and an amplifying portion extending from the front end of the cylindrical portion, the amplifying portion comprising a probe having a tip that forms an atomizing surface, an axial passage being provided through the length of the transducer assembly from the rear end of the rear dummy section to the atomizing surface, and a portion of the passage adjacent the driving element in both the front atomizing section and the rear dummy section being enlarged and internally threaded;
a tubular central bolt comprising a hollow stud having external threads engaging said internally threaded portion of the passage in both the front atomizing section and the rear dummy section with sufficient torque to connect the front atomizing section and the rear dummy section under a tension that provides all of a predetermined total compressive preload on the driving element; and
means for sealing the piezoelectric disks from contact with the liquid being atomized, the threaded stud having a front end portion located in the front atomizing section and formed with a smooth cylindrical sealing surface; and wherein the means for sealing the piezoelectric disks comprises an annular sealing member disposed between said sealing surface and the axial passage to prevent liquid flowing in the passage from reaching the inner circumferential surfaces of the piezoelectric disks, and wherein the means for sealing the piezoelectric disks from contact with the liquid being atomized comprises:
an enclosed shell surrounding the transducer assembly, the shell having a front end wall provided with a cylindrical passage that loosely receives the cylindrical portion of the front section and an annular sealing means disposed between the inner surface of the cylindrical passage and the circumference of the cylindrical portion of the front section, the radial spacing between the cylindrical portion of the front section and the cylindrical passage being less than the radial thickness of the annular sealing means when unconstrained, so that the annular sealing means is radially compressed between said passage and said cylindrical portion, and wherein said annular sealing means is unconstrained in the axial direction.
7. An atomizing transducer assembly according to claim 6 wherein the means for sealing the piezoelectric disks from contact with the liquid being atomized further comprises:
the shell further having a rear wall provided with an additional cylindrical passage that loosely receives an axial feed tube extending from the rear end of the rear dummy section and an additional annular sealing means disposed between the additional cylindrical passage and the feed tube, the radial spacing between the additional cylindrical passage and the feed tube being less than the radial thickness of the annular sealing means when unconstrained, so that the annular sealing means is radially compressed betwen said additional passage and said feed tube, and wherein said annular sealing means is unconstrained in the axial direction.
8. An atomizing transducer assembly according to claim 7 wherein said first mentioned and additional radially compressed sealing means comprise O-rings.
9. An atomizing transducer assembly according to claim 8 wherein said enclosed shell comprises a cylindrical cup and a cylindrical cap threadedly fitting on said cup.
EP87105667A 1986-05-09 1987-04-16 Central bolt ultrasonic atomizer Expired - Lifetime EP0245671B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT87105667T ATE71201T1 (en) 1986-05-09 1987-04-16 CENTRALLY BOLTED ULTRASONIC ATOMIZER.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US86151286A 1986-05-09 1986-05-09
US861512 1986-05-09

Publications (2)

Publication Number Publication Date
EP0245671A1 true EP0245671A1 (en) 1987-11-19
EP0245671B1 EP0245671B1 (en) 1992-01-02

Family

ID=25336011

Family Applications (1)

Application Number Title Priority Date Filing Date
EP87105667A Expired - Lifetime EP0245671B1 (en) 1986-05-09 1987-04-16 Central bolt ultrasonic atomizer

Country Status (6)

Country Link
EP (1) EP0245671B1 (en)
JP (1) JPS62273068A (en)
KR (1) KR900003217B1 (en)
AT (1) ATE71201T1 (en)
CA (1) CA1249861A (en)
DE (1) DE3775612D1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114100943A (en) * 2021-12-30 2022-03-01 北京科技大学 Ultrasonic atomizing nozzle for forming fog cone

Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3368085A (en) * 1965-11-19 1968-02-06 Trustees Of The Ohio State Uni Sonic transducer
US3396285A (en) * 1966-08-10 1968-08-06 Trustees Of The Ohio State Uni Electromechanical transducer
US3689783A (en) * 1971-03-11 1972-09-05 David A Williams Ultrasonic transducer with half-wave separator between piezoelectric crystal means
US3694675A (en) * 1971-02-25 1972-09-26 Eastman Kodak Co Cooled ultrasonic transducer
US3861852A (en) * 1974-01-25 1975-01-21 Berger Harvey Fuel burner with improved ultrasonic atomizer
DE2749859A1 (en) * 1976-11-08 1979-05-10 Sono Tek Corp BURNER WITH SPRAYING OF LIQUID FUELS BY MEANS OF ULTRASONIC
FR2465528A1 (en) * 1979-09-26 1981-03-27 Hotchkiss Brandt Sogeme VIBRATION DEVICE WITH PIEZOELECTRIC ELEMENT FOR LIQUID GUNS FOR EYEING HEAD OF A FRAGMENTED LIQUID
US4337896A (en) * 1979-06-08 1982-07-06 Sono-Tek Corporation Ultrasonic fuel atomizer
US4352459A (en) * 1979-11-13 1982-10-05 Sono-Tek Corporation Ultrasonic liquid atomizer having an axially-extending liquid feed passage
DE3244405A1 (en) * 1982-12-01 1984-06-07 Fa. J. Eberspächer, 7300 Esslingen DEVICE FOR MIXTURE TREATMENT IN MOTOR-INDEPENDENT HEATERS

Patent Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3368085A (en) * 1965-11-19 1968-02-06 Trustees Of The Ohio State Uni Sonic transducer
US3396285A (en) * 1966-08-10 1968-08-06 Trustees Of The Ohio State Uni Electromechanical transducer
US3694675A (en) * 1971-02-25 1972-09-26 Eastman Kodak Co Cooled ultrasonic transducer
US3689783A (en) * 1971-03-11 1972-09-05 David A Williams Ultrasonic transducer with half-wave separator between piezoelectric crystal means
US3861852A (en) * 1974-01-25 1975-01-21 Berger Harvey Fuel burner with improved ultrasonic atomizer
DE2749859A1 (en) * 1976-11-08 1979-05-10 Sono Tek Corp BURNER WITH SPRAYING OF LIQUID FUELS BY MEANS OF ULTRASONIC
US4337896A (en) * 1979-06-08 1982-07-06 Sono-Tek Corporation Ultrasonic fuel atomizer
FR2465528A1 (en) * 1979-09-26 1981-03-27 Hotchkiss Brandt Sogeme VIBRATION DEVICE WITH PIEZOELECTRIC ELEMENT FOR LIQUID GUNS FOR EYEING HEAD OF A FRAGMENTED LIQUID
US4352459A (en) * 1979-11-13 1982-10-05 Sono-Tek Corporation Ultrasonic liquid atomizer having an axially-extending liquid feed passage
DE3244405A1 (en) * 1982-12-01 1984-06-07 Fa. J. Eberspächer, 7300 Esslingen DEVICE FOR MIXTURE TREATMENT IN MOTOR-INDEPENDENT HEATERS

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114100943A (en) * 2021-12-30 2022-03-01 北京科技大学 Ultrasonic atomizing nozzle for forming fog cone
CN114100943B (en) * 2021-12-30 2022-12-02 北京科技大学 Ultrasonic atomizing nozzle for forming fog cone

Also Published As

Publication number Publication date
CA1249861A (en) 1989-02-07
KR900003217B1 (en) 1990-05-11
JPH0411268B2 (en) 1992-02-27
EP0245671B1 (en) 1992-01-02
DE3775612D1 (en) 1992-02-13
ATE71201T1 (en) 1992-01-15
KR870010906A (en) 1987-12-18
JPS62273068A (en) 1987-11-27

Similar Documents

Publication Publication Date Title
US4723708A (en) Central bolt ultrasonic atomizer
US4978067A (en) Unitary axial flow tube ultrasonic atomizer with enhanced sealing
US5465468A (en) Method of making an electromechanical transducer device
US4352459A (en) Ultrasonic liquid atomizer having an axially-extending liquid feed passage
US5516043A (en) Ultrasonic atomizing device
US4251031A (en) Vibratory atomizer
US4496101A (en) Ultrasonic metering device and housing assembly
US4893601A (en) Manifold for conveying a high-pressure fuel
US3861852A (en) Fuel burner with improved ultrasonic atomizer
KR970706465A (en) DUAL CONTAINMENT FITTING
JP2726255B2 (en) Device for detecting and / or monitoring a predefined filling surface height in a container
US4918990A (en) Ultrasonic transducer assembly
EP0245671B1 (en) Central bolt ultrasonic atomizer
EP0057466A2 (en) Ultrasonic vibratory atomizer
JP3663411B2 (en) Sealed connection device of cylindrical or spherical tank for injection electromagnetic valve for cleaning sleeve filter
GB2064128A (en) Capacitive level measuring probe
JP2572633B2 (en) Joint for connecting small-diameter piping and connection method
JPS61220756A (en) Ultrasonic wave atomizing device
JPH08326968A (en) Insulated pipe connector
CA1090694A (en) Transducer assembly, ultrasonic atomizer and fuel burner
JPH044853Y2 (en)
JPH0628211Y2 (en) Ultrasonic atomizer
JPH0814504B2 (en) Electrode structure of electromagnetic flowmeter detector
JPS6372371A (en) Method for supporting ultrasonic atomizing apparatus
RU2237982C1 (en) Electroacoustic transducer

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AT BE CH DE ES FR GB GR IT LI LU NL SE

17P Request for examination filed

Effective date: 19880107

17Q First examination report despatched

Effective date: 19890315

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): AT BE CH DE ES FR GB GR IT LI LU NL SE

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GR

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 19920102

REF Corresponds to:

Ref document number: 71201

Country of ref document: AT

Date of ref document: 19920115

Kind code of ref document: T

REF Corresponds to:

Ref document number: 3775612

Country of ref document: DE

Date of ref document: 19920213

ITF It: translation for a ep patent filed
PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: ES

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 19920413

ET Fr: translation filed
PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

26N No opposition filed
PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: SE

Payment date: 19940415

Year of fee payment: 8

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: CH

Payment date: 19940425

Year of fee payment: 8

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: FR

Payment date: 19940426

Year of fee payment: 8

Ref country code: ES

Payment date: 19940426

Year of fee payment: 8

Ref country code: DE

Payment date: 19940426

Year of fee payment: 8

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: AT

Payment date: 19940428

Year of fee payment: 8

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: NL

Payment date: 19940430

Year of fee payment: 8

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: LU

Payment date: 19940531

Year of fee payment: 8

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: BE

Payment date: 19940607

Year of fee payment: 8

EPTA Lu: last paid annual fee
EAL Se: european patent in force in sweden

Ref document number: 87105667.7

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: LU

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 19950416

Ref country code: AT

Effective date: 19950416

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: SE

Effective date: 19950417

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: LI

Effective date: 19950430

Ref country code: CH

Effective date: 19950430

Ref country code: BE

Effective date: 19950430

BERE Be: lapsed

Owner name: SONO-TEK CORP.

Effective date: 19950430

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: NL

Effective date: 19951101

REG Reference to a national code

Ref country code: CH

Ref legal event code: PL

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: FR

Effective date: 19951229

NLV4 Nl: lapsed or anulled due to non-payment of the annual fee

Effective date: 19951101

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DE

Effective date: 19960103

EUG Se: european patent has lapsed

Ref document number: 87105667.7

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: GB

Payment date: 19980518

Year of fee payment: 12

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 19990416

GBPC Gb: european patent ceased through non-payment of renewal fee

Effective date: 19990416

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: IT

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES;WARNING: LAPSES OF ITALIAN PATENTS WITH EFFECTIVE DATE BEFORE 2007 MAY HAVE OCCURRED AT ANY TIME BEFORE 2007. THE CORRECT EFFECTIVE DATE MAY BE DIFFERENT FROM THE ONE RECORDED.

Effective date: 20050416